Escherichia coli and one Pseudomonas putida strains. Each gate shows seven different dynamic behaviours, depending on the context. That is, gates can be fine-tuned by changing only contextual parameters, thus improving the compatibility between gates. Finally, we analyse portability by measuring, scoring, and comparing gate performance across contexts. Rather than being a limitation, we argue that the effect of the genetic background on synthetic constructs expands functionality, and advocate for considering context as a fundamental design parameter.The implementation of Boolean logic circuits in cells have become a very active field within synthetic biology. Although these are mostly focussed on the genetic components alone, the context in which the circuit performs is crucial for its outcome. We characterise 20 genetic NOT logic gates in up to 7 bacterial-based contexts each, to generate 135 different functions. The contexts we focus on are combinations of four plasmid backbones and three hosts, two  Genetic circuits can be engineered to generate predefined outcomes, however host context is a crucial factor in performance. Here the authors characterise twenty NOT gates in seven different bacteria to understand and predict interoperability and portability across hosts. Such devices result from assembling two or more genetic logic gates2—the basic unit for processing information in genetic circuits based on Boolean logic. A core objective of synthetic biology3 is the building of new regulatory circuits to compute inputs into outputs according to predefined logical functions4, which are then used in a number of applications, ranging from bioproduction5 to medical diagnosis6. Although this approach has been relatively successful, genetic logic gates are far more fragile and less reliable than their electronic counterparts as their signals are rarely constant and often fluctuate over time8. Consequently, the large-scale control of gene regulation based on Boolean logic alone is challenging. The central underlying issue is that a number of features intrinsic to biological systems, such as gene expression noise, analogue signalling9 and evolutionary dynamics10, make the intracellular environment an unsuitable domain for engineering idealised Boolean logic11.The abstraction of gene regulatory signals into on (high) and off (low) values allows for the design and implementation of genetic Boolean circuits12. Our results here suggest that, rather than being antagonistic, incorporating context into the design of biological circuits can actually provide advantages by enlarging the available design space. Both the burden imposed by synthetic constructs on the host14 and the impact of context on genetic activity15, have phenotypic implications that cannot be predicted from a gene-centric standpoint. A common strategy seen in nature is to achieve a similar outcome using a different pathway in different organisms, rather than normalising pathways across all organism. For instance, E. coli solves energy requirements through the EMP metabolic pathway, while P. putida does it via the ED pathway. The function is the same: glucose as input and energy as output, but the circuitry is not normalised. Rather, it depends on the context. Recently, the term host-awareness17 has been coined to bring attention to this problem, which is at the core of the lack of part interoperability18 . Here, we propose to utilise a strategy that is inspired by nature, and includes context as a parameter in the design of optimal genetic circuits.A fundamental challenge for the design of robust synthetic circuits, which underpins this work, is the oversimplified model that assumes DNA elements  alone explain the performance of genetic circuits. Based on this assumption, the host chassis (the cell that receives a specific genetic construct) is generally ignored and the interplay of a genetic circuit with the host context is most often overlooked in the bottom-up design process—an issue that has been identified as essential for the predictability of synthetic biology devices19. For instance, circuit-constructs optimised in Escherichia coli for rapid prototyping, might be implanted into Pseudomonas putida for a bioremediation application20 or into Geobacter sulfurreducens for bioelectricity production21. However, circuit performance will likely differ in different chassis, gene dosages and vectors, highlighting the importance of context in host-circuit design. As a result, the performance of a given genetic logic device would not only be a consequence of its DNA sequence but also would be influenced by its context. Within this scenario, modifying the context could fine-tune the performance of logic gates, thus engineering reconfigurable genetic logic devices which share the same sequences but exhibit different behaviours22. In the work presented below we inspect these scenarios by analysing quantitatively the behaviour of a collection of genetic inverters in different strains of the same species, in other species and in either case with the same devices borne by low, medium and high-copy-number vectors. The results illustrate that playing with these biological backgrounds expands the range of parameters that rule the behaviour of each construct. On this basis, we consider that context variability could be an advantage for circuit design rather than being seen as problematic.While most synthetic biology efforts make use of only one host chassis to develop and characterise genetic constructs, potential applications may require the same genetic devices to work with different cell typesE. coli1 and then recloned in broad host range vectors of different copy numbers for delivery to different types Gram-negative hosts23. The logic function (NOT or inverter) corresponds to a genetic device that reverses the incoming signal (i.e. output high to input low and vice versa). The inverters used are pairs of a specific regulator (repressor) and its cognate promoter  generated by specific concentration of regulator (input). In order to manipulate the expression level of the regulator, its coding sequence was placed under the control of a lac promoter, which was externally induced by IPTG. For gates characterisation, these were transformed into a bacterial host, which was then used to measure the NOT function , medium  and high  copy numbers. This contextual feature accounted for dynamics generated by circuit burden25, since more copies of the same gate would increase the cost (of running it) to the cellular machinery. Regarding the chassis, we used two Escherichia coli (DH5α and CC118λpir) strains that are evolutionary relatively close and one Pseudomonas putida (KT2440) strain that is an evolutionary distant host to the other two. Combinations of these resulted in a library of gate-backbone-host devices  its logic function. Moreover, context-dependent changes of qualitative behaviour imply that the dynamics of the interplay between context and construct are nonlinear. That is, a given pair of gates may suffer similar modifications in one context but very different in another.When a genetic logic gate is either passed onto another organism, or carried by a different backbone, the interplay between itself and the context changesE. coli DH5α, the backbone (either pAN or pSEVA221) seems to play a key role in the logic outcome of PhlF-P2, which becomes more step-like with pSEVA221 (i.e. sharper transition from on to off). In contrast to this, gate PsrA-R1 does not follow that trend and remains qualitatively unchanged, although absolute expression values drop. Using the same backbone (pSEVA221) we then tested the context impact of varying the E. coli strain. Whilst the performance of PhlF-P2 is qualitatively the same , PsrA-R1 shows a qualitative change, becoming more step-like, thus showing more desirable behaviour than in other contexts. These inconsistencies in changes of qualitative behaviour of gates highlight the difficulty of compensating for such effects in order to engineer context-independent circuits26. However, there are also more predictable contextual changes in which that strategy may work well. For example, when both gates are hosted by E. coli CC118λpir, changing the backbone from pSEVA221 to pSEVA231 (that only differ in the origin of replication) generates almost the exact same phenotypic modification. Finally, a marked difference occurs when the gates are hosted by P. putida KT2240. In these contexts, the gates lose their NOT logic, regardless of choice of backbone . The characterisation of the full library (20 gates) is shown in Supplementary Information Tables For example, PsrA-R1 and PhlF-P2 show these effects Fig. . When boE. coli DH5α (pSEVA221), based on gate performance in E. coli CC118λpir (pSEVA221) failed. The prediction was based on applying an optimised linear transformation to the gates transfer function. No linear transformation that performed consistently well could be found using this procedure, suggesting that a nonlinear transformation may be required. In this case, the optimisation was done using the AmtR-A1 gate, and the predictions tested on other gates in the library. As expected, some of the gates showed a relatively good prediction (good candidates for portability applications), but that was not the case for all of the constructs. Although predictable, gate portability is highlighted as an open problem and contextual dependencies offer a unique opportunity for fine-tuning gate performance, which we carefully analysed as explained next.The issue of inter-context predictions arose as a formidable challenge. For example, in Fig. 28. This is one of the major bottlenecks that restrict the depth of genetic logic circuits and limit scalability, since not every gate within a library will be compatible with another. The analysis of inter-gate compatibility is therefore fundamental for circuit design and is an integral part of current synthetic biology Computer Aided Design tools29. However, knowledge about the effect of context on gate compatibility has until now been lacking.Building a genetic circuit by coupling genetic logic gates requires an assessment of their compatibility, to determine which gates can be connected. In order to connect two gates, the output levels of one must match the input levels for the other. If not, it may result in failure of the overall circuit logicIn order to tackle this issue, we first scored the matching of all the gate pairs in the library according to their input and output thresholds Fig. . The incE. coli DH5α (pAN::PsrA-R1) or E. coli DH5α (pSEVA221::PsrA-R1), rather than individual gates alone (e.g. PsrA-R1) so that results account for the performance of a gate in a given context. We consider that high numbers of compatible pairs in a library are a desirable trait, and examine the impact of the two contextual features we focus on (backbone and host) on this metric, both independently and together. As a general trend, relaxation of the contextual parameters of backbone and host results in an increase in compatible pairings. More importantly, this increase is made up of not only new pairings within the additional contexts, but also additional pairings between gates in different contexts. In the example shown in Fig. In this analysis, constructs were considered as gate-context entities (e.g. E. coli DH5α and the latter by E. coli CC118λpir. This suggests that taking a multicellular (distributed) computing approach33 will be required to couple the functions of these two constructs. In multicellular computations, a predefined function is distributed across different engineered bacterial strains (or species), which are connected in such a way that the output of one cell is the input of another one. Therefore, considering the host of a genetic construct within circuit design will allow for building both intra- and inter-cellular computations11.Due to the consideration of contextual dependencies of host and backbone, the original gate library of only 20 genetic devices was increased to 135 different functions. Therefore, there were many more options to evaluate and more compatible pairs found. However, some of these pairs correspond to gates that are compatible only if they are inside different hosts. For example, the gates HIyIIR-H1 and AmeR-F1 can only be matched  if the former is hosted by 34. The fact that genetic constructs show different dynamics depending on their context is not necessarily a disadvantage for predefined circuit design—could we rationally use such variability? To begin to address this question, we carried out computations in order to identify the maximum circuit depth  that could be achieved by connecting gates within our library, and assessed the impact of contextual effects in such a chain  increases the maximum depth to 5. This can be further improved upon by allowing freedom in the choice of host, for a total of 7 contexts  in order to link genotype to phenotype—an oversimplified reductionist approach. The comfortable, yet error-prone, assumption that engineered parts alone can ultimately explain phenotypic performance needs to be expanded upon12. This leads us to consider what has been termed genetic background15 and host-aware16 dynamics: cellular features and constraints that have an impact on circuit performance but are not captured by the DNA sequences of the construct. In recent years, several of these features have been analysed: the impact of having limited cellular resources37 (e.g. ribosomes) to “spend” on synthetic constructs, the effects of placing DNA parts in different genomic locations39, the role played by metabolism in genetic control41, or even genetic stability42 due to evolution over time. All these effects turn the portability of genetic circuits into an overarching challenge—the fine-tuning of a circuit to work inside a different host  is still a major task26. Furthermore, it limits the scope of biological circuits by solely using a DNA-insert toolbox for designing circuits.A fundamental driving force for synthetic biology23.Here, we use the word “context” to refer to the molecular background of the cell beyond genes and analyse how such context can be used for improving biocircuit design. By “dependencies”, we mean the constraints imposed by the context on a given genetic construct. Therefore, genetic logic gates are exposed to contextual dependencies that influence their phenotypic behaviour. In the extreme case, these constraints can even result in unviability of the cellular host, for example, during the conversion to pSEVA broad host range backbones, five of the genetic inverters were not functional when cloned into a high-copy plasmid (pSEVA251), perhaps due to overload in the allocation of cellular resources resulting in toxicity43 already, we entertain here a new one that we consider to provide a useful conceptual frame: the use of contextual dependencies as in a software engineering problem. Any piece of software, or program, must run inside a specific environment (e.g. operating system) and software engineers usually face the problem of adapting it to the particular dependencies of the environment/context at stake. Under this metaphor, genetic circuits are considered software (instead of hardware44) whose performance is deeply linked to context-specific dependencies, which can allow designers to access functions that could not be coded otherwise. In this paper, we propose that contextual dependencies are important parameters for circuit design, and focus on [i] backbone carrying the construct, and [ii] cellular host in which the construct performs.Although synthetic biology is a field full of metaphors46 in order to connect logic gates in different hosts. These connections could be established by using orthogonal quorum sensing (QS) systems48. In order to prevent the number of orthogonal QS systems from being a limiting factor, paths should be selected that minimise these inter-host connections—therefore maximising the number of gates per host. Secondly, linking gates inside a host requires using repressor molecules for signalling, which must also be orthogonal to ensure correct gate operation. Since the library of repressors would also be limited, the adoption of multicellular approaches offers an important advantage: the re-usability of parts i.e. a repressor that is used in one host may be reused in another. This second rule may be used to distribute circuit burden across different strains. Finally, plasmid backbones can coexist inside the same host as long as their origins of replication are different—otherwise, some plasmids may be lost during the process. Altogether, these guidelines establish a rational criteria for the selection of context-dependent circuitry components from a bottom-up design.In this work, we exploited a library of 20 genetic inverters (NOT logic gates), which are combined with four different backbones and three cellular strains to give a total of 135 gate-context constructs. In this regard, the number of functions exposed by the library increases by 675% due to the addition of these two contextual dependencies. With this new library we carried out experiments in order to assess the implications of adding context to the context-free initial collection of NOT gates. First, the characterisation of the constructs showed how gate behaviour changed across contexts in a nonlinear fashion. That is, the phenotypic modifications in the performance of one gate across two contexts may not match those of another gate under the same contextual transformations. This has major implications for the portability of genetic devices, since not all genetic components may be affected in the same way upon host change—thus building complex portable devices will become difficult (if not entirely impossible). Second, our experiments suggested that the compatibility of gates  does not only depend on selected genetic inserts, but also on their context. While only 67 compatible pairs were found in the original library of 20 inverters, the number increased to 697 in the new library. For instance, by allowing gates to be carried by four different backbones, the computational algorithm was able to evaluate the compatibility of four functions instead of 1 and return not only the name of the compatible gate but also the name of the backbone to use for carrying it. This allows reconfiguration of genetic constructs, since the same piece of DNA-insert can have different behaviours depending on rationally selected contextual dependencies. Finally, the use of the cellular host as a separate design parameter allowed identification of gate pairs that were only compatible if connected gates were located in different strains/species. Consideration of different contextual dependencies was found to increase the theoretical maximum circuit depth from 3 to 12, as shown in Fig. 11—therefore more robust, reliable, predictable and reproducible.In a similar way to living systems that use a number of mechanisms to go from genotype to phenotype, we advocate for the development of genetic circuits by considering whole-cell dynamics—including contextual dependencies. Although in this work we have considered backbones and strains as the contextual dependencies, this library could be extended by adding other contextual parameters such as other promoters, context-specific genetic parts, or substrates. This will result in the design of biological circuits that are closer to the internal workings of natural systemsE. coli CC118λpir. Primers are ordered from Merck Sigma Aldrich, Inc. The repressible and inducible systems were previously described by Voigt Lab and acquired by the courtesy of Voigt Laboratory in MIT (USA). Description of the 20 different NOT gates moved into broad host range pSEVA backbones are described in Tas et al.23. Components of the original inverters, like terminators, RBSs and insulators were kept the same during the SEVA conversion. SEVA backbones have two terminators, T0 and T1 which are important to lower potential leakages. Required oligo list can be found in the Supplementary Information , 125 μl of 1% Thiamine, 2.5 ml of 1% Casamino acids and milliQ-H2O up to 250 ml. The concentration of kanamycin used is 50 µg ml−1 in the experimentation procedures. IPTG was used as inducer for pTac/LacI inducible system in 12 different concentrations diluted from 1 M stock concentration that are 0, 5, 10, 20, 30, 40, 50, 70, 100, 150, 200, 500 and 1000 μM. For synchronising the cells in the experimental procedure, cultures are started from a single colony picked from LB agar plate which is each time freshly prepared from −80C glycerol stock by inoculating it O/N in 1 ml M9 minimal medium. O/N cultures after saturation were diluted by ~666 times to inoculate 200 μl M9 minimal medium in 96 well plate for 24 h, which is enough to reach to 0.2 - 0.3 OD in 96 well plate after which for halting the growth cells were kept on cold platform during the measurements.In all experiments (unless stated otherwise) M9 minimal medium for Miltenyi Biotec MACS flow cytometer at channel B1 with an excitation of 488 nm and emission of 525/50 nm was used for measuring YFP fluorescence distribution of each sample. 30000 events were defined as the statistically sufficient amount under singlet gating for each sample. Calibration of the flow cytometer was done daily by using MACSQuant Calibration Beads. Throughout flow cytometer measurements samples were always kept on cold 96 well plate platforms. For the analysis of the data FlowJo software was used. In the analysis, gating was done via the usage of auto-option and allowing to cover at least 50% of the whole events run while Forward and Side scatters were plotted, and the same gating conditions were kept for all samples in the same group.In order to unify fluorescence measures between and within flow cytometry experiments, we analysed fluorescence and scattering values. Variation in cell size across experiments showed that median fluorescence values were decisively affected, therefore inaccurate for the sake of comparison. To compare between experiments, we took the distribution of fluorescence for single scattering values. A full description of this process is detailed in Supplementary Information.yfp expression under the pLacI constitutive promoter. In order to derive relative promoter units (RPU), the following equation was applied:autofluorescence is the median fluorescence value of the autofluorescence plasmid, <YPF>standardisation indicates the median fluorescence value from the standardisation plasmid. RPU values were calculated in transfer function plots for different data points using at least 6 inducer levels covering the range of induction up to saturation.Two extra plasmids were used for measurements, the autofluorescence plasmid (Backbone::1201), and the reference standard plasmid (Backbone::1717) that triggers The pre-filtered experimental data were fitted to a 4-parameter hill equation of the form1, where it is used to describe the input–output relationship of genetic inverters (NOT gates). In this study, we consider only NOT gates, for other types of gate, other models should be selectedThis model is often used to relate gene expression levels to the concentration of a repressive transcription factor, most notably inymin and ymax were set to the minimum and maximum of the corrected experimental data. The values for k and n were then fitted using the least squares method from the scipy.optimize Python package49, with logarithmic residuals.The parameter values for Fits were obtained for all gates presented in this paper. The fitted parameters are shown in tables in the Supplementary Materials. However, for many gates, it was found that the model was a poor fit to the data. In this case, the gate cannot be considered an example of a NOT gate and should not be used as parts in circuit design. In particular, the criteria for valid inverters as described below should omit these poorly behaved gates.ymin and half of ymax, respectively. IL and IH are the values of x for which the output of the fitted hill function is equal to OL and OH, respectively. Accordingly, the values of IL and IH were calculated with the following formulae:Thresholds OL, OH, IL and IH were computed from the parameters of the fitted hill curves according to the definitions given in [1]. OL and OH are twice Inverters were considered operational under the condition that OH>OL and IH>IL for their fitted hill curve.For a pair of operational inverters, A and B, their compatibility score was defined asA positive score indicates that a high(low) output from A will also be interpreted as high(low) by B, because IL(IH) of B is greater(less) than OL(OH) of A. From this we imply that inverter A can be connected as input to inverter B, if and only if their compatibility score is positive.Chains of compatible inverters were found by creating a table of compatibility between available inverters, for which the entry for a compatible pair was 1, and all other entries were 0. This table was then treated as the adjacency matrix of the graph of all possible connections, and the longest paths were enumerated using a depth-first search of the graph. Paths in which the same repressor was used more than once were excluded from the results, thus imposing an upper bound of 12 on path length.50 was used to measure similarity of the shapes of two experimental curves, after first log transforming and min-max normalisation of the data along both axes. The Frechet distance was then subtracted from 1 in order to produce a metric that increases as the shape of the curves becomes more similar. The discrete Frechet distance was computed using the ‘similarity measures’ Python package51.The discrete Frechet distance49 is used to compute a linear transformation matrix, which when applied to the source characterisation, minimises the L1Loss between the transformed characterisation and the target’s true characterisation. Predictions for other gates in the library are then made by applying the same transformation to their characterisation in the source context.The goal of the prediction is to transform the characterisation of gates in a source context, to a characterisation in the target context. A single operable gate was selected arbitrarily upon which to base the prediction. The ‘scipy.optimise’ Python packageFurther information on research design is available in the Supplementary InformationPeer Review FileReporting Summary


Lightweight concrete has a history of more than two-thousand years and its technical development is still proceeding. This review starts with a retrospective that gives an idea of the wide range of applications covered by lightweight concrete during the last century. Although lightweight concrete is well known and has proven its technical potential in a wide range of applications over the past decades, there are still hesitations and uncertainties in practice. For that reason, lightweight aggregate properties and the various types of lightweight concrete are discussed in detail with a special focus on current standards. The review is based on a background of 25 years of practical and theoretical experience in this field. One of the main challenges in designing lightweight concrete is to adapt most of design, production and execution rules since they often deviate from normal weight concrete. Therefore, aspects are highlighted that often are the cause of misunderstandings, such as nomenclature or the informational value of certain tests. Frequently occurring problems regarding the mix design and production of lightweight concrete are addressed and the unintended consequences are described. A critical view is provided on some information given in existing European concrete standards regarding the mechanical properties of structural lightweight concrete. Finally, the latest stage of development of very light lightweight concretes is presented. Infra-lightweight concrete is introduced as an innovative approach for further extending the range of applications of lightweight concrete by providing background knowledge and experiences from case records. Lightweight concretes are not a modern achievement of concrete technology. They have been known since ancient times and are basically the predecessors of today’s concrete. The first European references of lightweight concrete were built two thousand years ago during the early Roman Empire. The Pantheon in Rome, Italy, was built ca. 128 A.D. and can be cited as one of the best-known examples. It has amazed engineers from various disciplines over hundreds of years and has impressively demonstrated the systematic use of various natural lightweight aggregates in opus caementitium . Initially, the use of the expanded aggregates was reserved for the Navy of the United States of America. The associated U.S. Emergency Fleet Building Corporation established a shipbuilding program with the U.S. entry into World War I. In 1918, Atlantis was the first ship to emerge from this program and fourteen lightweight concrete ship hulls were built in total. During World War II, these early experiences led to the deployment of 104 supply ships, with cargo capacities ranging from 3200 to 140,000 tons  of 100-mm cores drilled from LAC elements. LAC is used for structural elements like loadbearing walls, roof elements, slabs and beams, and for non-structural components like noise barriers. Some properties of LAC can be improved significantly when the open structure is filled with a porous matrix (aerated cement paste) [Lightweight aggregate concrete with open structure (LAC) differs significantly from the aforementioned lightweight concrete (LC). Its properties are defined in EN 1520 . The dryt paste) . Figure t paste) . Hence, 3. Its compressive strength is less or equal than LC8/9 [A recent kind of lightweight concrete was developed initially for an application outside building industry. This very light lightweight concrete was intended for sandwich ship hulls. The underlying concept for design of ships and marine structures was developed by using sandwich plates composed of steel skins with a very low density lightweight concrete as core material . Schlaican LC8/9 ,48. ILC an LC8/9 ,38 have New approaches are now initiated at Universität der Bundeswehr München in cooperation with several industrial partners. The basic idea is combining the initial design concept of ILC with the technical regulations laid down in EN 1520 . The actMost LC use a combination of lightweight coarse aggregate and normal weight sand. The decision depends among others on the requirements regarding specified strength and density, thermal conductivity and the market price of the aggregates. The quality and availability of LWA gradings are further factors that influence the optimum ratio of normal weight aggregate and LWA. Especially fine LWA often are available as crushed material only, resulting in a high water demand and affecting workability characteristics. The requirements for normal weight sand are the same as for their use in NC. LC can be produced with any cement available. For LC made with LWA it is highly recommended to use a cement with a modest specific heat release, like blast furnace cement, or cements in combination with fly ash, calcined clay, granulated blast furnace slag or limestone. These LC have a low thermal conductivity which could lead to high temperatures in the core of the construction element  during hAny kind of water used in normal concrete production can be used for LC as well. This includes recycling water .Any admixture used in normal concrete production can be used for LC as well. The compatibility with the binder and LWA used should be checked beforehand, as for NC. This holds especially for LWA that may have different surface charges compared to normal weight aggregate. Initially dry or only prewetted LWA will absorb parts of liquid admixtures if these are added too early to the mix see . ACI 3043. At the same time, compressive strength is lowered as well depending on the type of lightweight sand selected. The mix design for LC differs fundamentally from NC due to the dominant impact of the LWA used ,60,61,6260 value indicates the water absorbed by coarse LWA within 60 minutes and is a common parameter in practice [Mix design of LC should always disclose the water added to account for the water absorption of the LWA, although the water will not increase the LC volume ,67. The practice . This expractice ,69,70. Ipractice  and mustpractice  which repractice . This tepractice .Any mix design for LC must be given in dm³/m³ based on volumetric share of the constituents. The weight is an inaccurate measure for LC. Nevertheless, this weight information shall be provided together with the particle densities used in the mix design. By doing so, the air void content must be given as well. It is often missing in mix designs. Measurements of the air void content following ASTM C 173  and the The dosage of the LWA should be volumetric wherever possible. Since in most concrete plants gravimetric weighing is available only, the moisture content and absorption of the LWA  as well During mixing, the LWA are filled in first. Up to two thirds of the required mixing water and the water compensating the absorption are added to the running mixer and mixed in for about 30 seconds. This is particularly important when lightweight sand is used as it absorbs a relatively large amount of water. If LWA is prewetted, it should be as uniform as possible . Next, tStructural lightweight concrete is preferably produced in a compulsory mixer. If possible, the mixer blades should have a plastic lining in order to avoid unnecessary crushing of the LWA, especially in the case of very light LWA. In concrete plants, up to 5–10% of the very light coarse LWA can be crushed. In the laboratory, this grain fragmentation is between 3% and 5%, in some laboratory mixers also significantly higher. Water absorption of LWA and LC density both rise due to the LWA fragmentation. Workability will be reduced due to the higher water absorption of the crushed LWA.The fresh LC should be checked for unit weight and yield . One optAs a result of the water absorption of the lightweight aggregates, the duration of transport and placing has a greater impact on the workability of LC than on that of NC. The degree of compactability  should bStructural lightweight concrete does require the same placing techniques as used for NC . LC is mWhen pumping LC with non-water saturated LWA, the water in cement paste is pressed out by the pumping pressure and ingresses together with fine particles into the pores of air-filled LWA . This, iEven if the pumping of LC has been successful, it may have negatively affected the quality of the hardened concrete . The cauInfra-lightweight concrete combines LC with several ideas used for LAC with a porous matrix. Thus, the mix design approach is similar as for LC. In order to reduce density and thermal conductivity, the air void content exceeds the limitation of 10% by volume for LC . The necThe LWA absorbs water during mixing. Together with the mixing water, parts of the binder components infiltrate the porous LWA. The hydration products therefore do not only grow towards the outer LWA surface, but also to a limited extent towards the inside of the LWA . The res2AS), on the outer shell of the coarse aggregate. These LWA can therefore react with the binder components to a limited extent [Some expanded clays exhibit reactive clinker phases, such as Gehlenite  around the aggregate ,82. In cThe absence of a pronounced ITZ affects load-bearing behavior and durability ,91,92,93The strength of the mortar matrix determines the strength of NC. Therefore, a uniform relationship between the concrete and matrix compressive strength can be established. Mortar strength is characterized by the w/c ratio and the standard compressive strength of the cement.In the case of LC, the LWA are often less solid and less stiff than the matrix, depending on the density of the LWA. The LWA is therefore decisive for the strength of the lightweight concrete structure. As a result, the concrete strength may lag behind the compressive strength of the matrix ,98.At young age, the strength of LC and NC initially develops simultaneously ,100. Undlc,lim) [As hydration progresses, the stiffness and strength of the matrix can exceed that of the LWA. In this case, the internal flow of forces changes ,100. Thelc,lim) .s ~ 350 kg/m3 and “lightweight aggregate 2” an expanded clay with ρs ~ 600 kg/m3.Up to a level, which dependents on the strength capacity of the LWA, strength of LC does more or less coincide with the matrix strength to a certain level. Above this level, the strength of LC increases disproportionately less with an increase in matrix strength ,103. In Since the lightweight aggregates contribute increasingly less to the load transfer above the limit strength, the matrix strength must be drastically enhanced to further increase the concrete strength. This procedure is not economically meaningful and it is better to select a stronger LWA instead. The ultimate LC strength depends on the LWA used: The stronger the LWA, the higher the ultimate strength of the LC. For a mortar strength below the limit strength, the strength of LC differs only slightly from the matrix strength, i.e., it corresponds approximately with that of a NC of the same strength. This is important with respect to strength classes and conversion factors see . The ultlc,lim). For economic reasons, most LC in practice will have a design strength below flc,lim. Thus, their behavior is dominated by the matrix as it is the case for NC and the conversion factors between different specimen sizes are expected to be the same for LC and NC. This was confirmed in a series of tests involving more than 200 mix designs with various types of LWA, covering the strength range between 15 and 70 MPa and densities between 950 and 1700 kg/m3 [The load bearing behavior of LC has an impact on conversion factors applied for different specimen shapes and sizes ,105,106.00 kg/m3 ,114. Fig00 kg/m3  cast sev00 kg/m3 ,38 for L00 kg/m3 ,114.3 is aimed for highly stressed facades of office buildings with many and wide window and door openings. They demand for a higher compressive strength in combination with a reduced thermal conductivity of the LC.A concrete dry density in the range between 1.3 and 1.6 kg/dm3. These walls often have a thickness of 50 cm in order to fulfill legal requirements regarding building physics.Less stressed facades with higher requirements regarding thermal insulation are built with LC densities in the range between 1.0 and 1.3 kg/dmThe third field of LC with a dry density < 1.0 kg/dm³ represents the most innovative part these days in central Europe. These very light LC offer the best thermal insulation for monolithic concrete and are increasingly used for exclusive private houses. The architect Gartmann developed a fair faced LC for the monolithic exterior walls of his private house . His ideLC is suitable for a wide range of applications due to its versatility. Much information is available for LC made with coarse LWA and normal weight sand since it is quite common worldwide. The most interesting and challenging LC structures are bridges ,128,129 3 and thus are no longer covered by existing LC standards [A new approach is needed since building physics requirements ask for thermal insulation properties, which cannot be accomplished within the limits defined in the standards for structural lightweight concrete. Some ILC exhibit a dry concrete density below 800 kg/mtandards . Schlaictandards ,138,139.3. At the same time, mean strength can be reduced to less than 4 MPa which corresponds with strength class LAC 2 [3 and less on site and strength values suitable for LAC 4 [Recently, another approach to extend the application range of ILC was started at Universität der Bundeswehr München, Germany. Since the mix design of ILC is rather close to LAC, due to the high air void content see , it was ss LAC 2 . Figure ss LAC 2 ,48. It sss LAC 2 . The firor LAC 4 . 3 is given in [The new LAC based approach is very successful with respect to the thermal insulation properties of the LAC based ILC. given in .Another very important challenge for ILC is maintaining the appearance of a fair faced concrete which is mandatory for meeting the expectations of future house owners and architects. It is not possible to classify the surface quality according to the same technical and design criteria as applied for NC, such as defined in . AlthougCurrently there are two deviating ILC approaches under investigation in close cooperation with concrete producers. The first one is a conventional course of action: the ILC is produced in a concrete plant, delivered in a conventional mixing truck and placed on site with a concrete bucket. Quite often, architects who are interested in using ILC for their projects fail finding a concrete producer willing or capable to provide ILC. Since the request for LC is low in most regions, common concrete plants are not equipped for the production of LC or even ILC or suffer from a lack of silo capacity. Both dilemma can be solved with the second approach: the ILC is produced under controlled conditions on site by means of a tailored truck-mounted concrete plant .Despite the lack of a basis for production and execution rules for lightweight concretes below a dry density of 800 kg/m³, the increased interest of clients and architects has led to the construction of various single and multi-family houses. Lightweight concrete is an extremely versatile material, which can be used for a wide range of applications. Although lightweight concrete has been in use for two millennia, there are still uncertainties, which were addressed in this review paper. Clear definitions were given for the different types of lightweight concrete and information was provided about crucial topics regarding lightweight aggregate properties as well as mix design, testing and classification of structural lightweight concrete. Several issues represent key information in the state-of-the-art of lightweight concrete. Infra-lightweight concretes (ILC) constitute an innovative development with very low dry densities (<800 kg/m³) and respectable thermal insulation properties. ILC is the answer to a new and unexploited area of application. Future research is an essential precondition for the development of a reliable design and construction methodology to ensure production quality and to prepare a European standardization concept.


The IgG4/IgG-positive cell ratio was significantly higher in the IgG4-RD group (p < 0.001). The IgA-positive cell count and IL-6 expression intensity were higher in the PC-iMCD group than in the IgG4-RD group (p < 0.001). Based on these findings, we proposed a new diagnostic approach to differentiate lung lesions of PC-iMCD and IgG4-RD. Our approach can be utilized to stratify patients with suspected lung-dominant PC-iMCD to identify candidates for strong immunosuppressive treatment, including IL-6 blockade, at an early stage.Plasma cell type idiopathic multicentric Castleman disease (PC-iMCD) occasionally manifests as parenchymal lung disease. This study aimed to elucidate the detailed clinicopathological features of lung lesions in PC-iMCD and compare the findings with those in immunoglobulin (Ig) G4-related disease (IgG4-RD), the most difficult differential diagnosis of PC-iMCD. We analyzed the clinicopathological findings and immunohistochemical expression patterns of interleukin-6 (IL-6) and Igs in lung specimens from 16 patients with PC-iMCD and 7 patients with IgG4-RD. Histologically, pulmonary PC-iMCD could not be differentiated from IgG4-RD based on lesion distribution patterns, the number of lymphoid follicles and obliterative vasculitis, or fibrosis types. The eosinophil count was higher in the IgG4-RD group than in the PC-iMCD group ( Castleman disease (CD) was originally described by Castleman et al. in 1956 . The etiImmunoglobulin (Ig) G4-related disease (IgG4-RD) is a systemic immune-mediated disorder characterized by elevated serum IgG4 levels and mass-forming lesions . This coiMCD is a heterogeneous disease that exhibits clinicopathological overlap with other conditions, such as autoimmune disorders, infectious diseases, and IgG4-RD ,15. BecaIncreasing difficulties are encountered in differentiating lung lesions due to PC-iMCD from those due to IgG4-RD. To date, only two studies have investigated the clinical and histological differences between lung lesions of PC-iMCD and IgG4-RD ,20. HistHere, we present detailed clinical and histological analyses of the lung lesions associated with PC-iMCD and IgG4-RD, with particular reference to the expression patterns of various markers, including IgA and IL-6, and propose a new diagnostic approach for lung PC-iMCD. Twenty-three Japanese patients with lung lesions caused by either PC-iMCD (n = 16) or IgG4-RD (n = 7) were included in this study. All 23 cases were retrieved from surgical pathology consultation files from the Department of Pathology, Okayama University Hospital. All patients underwent surgical lung resection by video-assisted thoracic surgery except for one patient with IgG4-RD who was autopsied.Patient data were retrospectively reviewed to determine if they were compatible with the latest criteria of either PC-iMCD or IgG4-RD ,21. iMCDAll patients with IgG4-RD met both the 2019 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) Classification Criteria for IgG4-Related Disease  and the Electronic medical records and consultation files of the study subjects were reviewed for age, sex, symptoms, affected organs, laboratory data (white blood cells (WBCs), hemoglobin (Hb), platelets (Plts), albumin (Alb), C-reactive protein (CRP), Igs , and IL-6), as well as a treatment course. Lymph node involvement and the affected organs were clinically determined by physical examination and CT imaging at the time of surgical biopsy. Radiologists evaluated the chest CT findings obtained from each institution. Using imaging reports and radiologists’ remarks, we collected information related to the localization, distribution patterns, presence of ground-glass opacity (GGO), nodular shadows, pleural effusions, and differential diagnoses. All lung specimens were fixed with 10% formaldehyde and embedded in paraffin. These paraffin-embedded tissue blocks were sliced into 4-µm-thick sections, which were stained with hematoxylin and eosin and either Elastica-Masson Goldner or Elastica-van Gieson (EVG) stains. Lesion distribution patterns (bronchovascular bundles (BvBs), interlobular septal, and alveolar interstitial), fibrosis types, number of lymphoid follicles and eosinophils, and the presence of hemosiderin-laden macrophages, as well as obliterative vasculitis determined by elastic staining with either Elastica-Masson Goldner or EVG staining, were histologically examined. The numbers of lymphoid follicles and obliterative vasculitis per slide were determined. The number of eosinophils in areas with the highest density of eosinophils was counted in three different HPFs , and average values were calculated. Immunohistochemistry was performed using an automated Bond-III instrument  with the following primary antibodies: IL-6 ; IgG4 ; IgG ; polyclonal IgA .The number of IgG4-positive cells and IgG-positive cells was estimated in areas with the highest density of IgG4-positive cells. As stipulated in the consensus statement of the pathology of IgG4-RD published in 2012 , three dp < 0.05. All statistical analyses were performed using SPSS software, version 24 .Statistical analyses were conducted using the Mann–Whitney U test or Fisher’s exact test. Statistical significance was set at The study protocol was approved by the Institutional Review Board of Okayama University, Okayama, Japan . The study wasperformed in accordance with the ethical standards laid down in the Declaration of Helsinki. Informed consent was obtained for all subjects in the form of opt-out on the website. The demographics, clinical and laboratory findings of the patients are summarized in p = 0.018). With respect to comorbidities, patients with PC-iMCD had IgA nephropathy related to CD , asthma , emphysema , chronic hepatitis B , type 2 diabetes mellitus , and hyperthyroidism . Patients with IgG4-RD had asthma , type 2 diabetes mellitus , allergic rhinitis , hypertension , chronic kidney disease , previous history of lung cancer , and old myocardial infarction . Six of the seven (85.7%) patients with IgG4-RD suffered from allergic diseases, including asthma or allergic rhinitis, whereas two of the sixteen (12.5%) patients with PC-iMCD had allergic diseases (p = 0.002). Seven of the sixteen patients with PC-iMCD (43.8%) had constitutional symptoms such as general fatigue or fever, whereas no patients with IgG4-RD presented with these symptoms (p = 0.057). Among patients with PC-iMCD, there were seven men and nine women aged 26–73 years with a median age of 49.5 years. All patients with IgG4-RD were men aged 39–77 years with a median age of 70.0 years. Patients with PC-iMCD were significantly younger than those with IgG4-RD . In the PC-iMCD group, the involvement of extranodal organs including the skin, spleen, and liver were observed. By contrast, no patients in the IgG4-RD group had skin rash or hepatosplenomegaly. Instead, six of the seven (85.7%) patients with IgG4-RD had typical extrapulmonary lesions in at least one of the following: the salivary glands, lacrimal glands, pancreas, bile duct, and aorta. Particularly, the pancreas and salivary glands were more frequently affected in patients with IgG4-RD than those with PC-iMCD (All the patients with PC-iMCD showed lymph node enlargement (short-axis diameter > 1 cm) in ≥2 lymph node stations in the chest CT images. In four (25.0%) patients, the extent of lymph node enlargement was limited to the hilar and mediastinal regions. Eight patients (50%) showed evidence of PC-iMCD in the lymph nodes. In these patients, the following lymph nodes were biopsied: mediastinal (five patients), inguinal (two patients), and axillary (one patient). Notably, in one patient with PC-iMCD, lung lesions preceded cervical, mediastinal, and hilar lymph node swelling. Another patient initially exhibited only lung lesions and submandibular lymphadenopathy, and inguinal lymphadenopathy resulted over time. No patients in the IgG4-RD group exhibited systemic lymph node enlargement, while five (71.4%) showed localized lymph node swelling. The affected lymph nodes were limited to the submandibular, mediastinal, or hilar lymph nodes. One patient with IgG4-RD had preceding lung lesions. The patient presented with the submandibular, pancreas, and periaortic lesions approximately two years after the emergence of lung lesions and surgical lung biopsy. p < 0.001, p < 0.001, p = 0.033, p < 0.001, respectively). By contrast, albumin, serum IgG4, and the serum IgG4/IgG ratio were significantly higher in the IgG4-RD group . Importantly, all patients with PC-iMCD for whom serum IgG4 levels were available (15 cases) had elevated serum IgG4 level (>135 mg/dL). There were no significant differences in serum IgE levels between the two groups (p = 1.000). The serum IL-6 levels were elevated (>4 pg/mL) in all patients with PC-iMCD, whereas IL-6 data were not available for evaluation in the IgG4-RD group.Laboratory findings indicated that the levels of Plts, CRP, serum IgG, and serum IgA were significantly elevated in the PC-iMCD group compared to those in the IgG4-RD group (The CT findings of PC-iMCD and IgG4-RD groups are shown in Representative pictures of lung lesions in patients with PC-iMCD and IgG4-RD are shown in p = 0.027). In patients with IgG4-RD, a mixed infiltrate of immature (plasmablast-like cells with dispersed chromatin and a single prominent nucleolus) to mature plasma cells, small lymphocytes, and eosinophils were observed. Disease distribution patterns in both groups mainly exhibited lymphangitic spread, including BvBs, interlobular septa, and pleura. Additionally, 7/16 (43.8%) patients with PC-iMCD and 3/7 (42.9%) patients with IgG4-RD displayed alveolar interstitial involvement. Nodular patterns were seen in areas of marked inflammation. There was no significant difference in the number of lymphoid follicles between the two groups (p = 0.053). Patients in both groups exhibited fibrosis to varying degrees, and there was no difference in the types of fibrosis between the two groups. Typical storiform fibrosis was seen only in one patient with PC-iMCD (p = 0.892). Only two patients with PC-iMCD exhibited the presence of hemosiderin-laden macrophages, while none were observed in the IgG4-RD group did. Eosinophil infiltration was significantly greater in the IgG4-RD group (p = 0.004). Based on the number of eosinophils/HPF, a receiver operating characteristic (ROC) curve differentiating PC-iMCD from IgG4-RD was generated. The area under the curve (AUC) was 0.875. The curve had a cut-off value of 19.5/HPF, as determined using the Youden index (sensitivity + specificity − 1); this value was associated with a sensitivity of 75.0% and a specificity of 100%.In both groups, histological features of lung lesions were associated with plasma cell and lymphocyte infiltration. The sheet-like proliferation of mature plasma cells was more frequently confirmed in patients with PC-iMCD than those with IgG4-RD ( PC-iMCD . Obliterp = 0.867). The IgG4/IgG-positive cell ratio was significantly higher in the IgG4-RD group (p < 0.001). In the IgG4-RD groups, the ratio was approximately 100% in all patients, with the highest percentage of 124%. A comparison of immunohistochemical findings is shown in p < 0.001) (The number of IgA-positive cells was significantly higher in the PC-iMCD group than that in the IgG4-RD group (< 0.001) .Based on the IgG4/IgG-positive cell ratio (%) and the number of IgA-positive cells/HPF, ROC curves, which differentiated PC-iMCD from IgG4-RD, were generated. With respect to the IgG4/IgG-positive cell ratio, the AUC was estimated to be 0.982, and the curve had a cut-off value of 89.2%; the value was associated with a sensitivity and specificity of 93.8% and 100%, respectively. The AUC for the number of IgA-positive cells/HPF was 0.982, the-cut off value was 23.7/HPF, and this value was associated with 97.5% sensitivity and 100% specificity.p < 0.001, p = 0.002, respectively; IL-6 expression via immunohistochemistry in both groups is shown in Clinical courses for the patients, except two patients in the PC-iMCD group for whom the data were unavailable, are summarized in Diagnosing lung-dominant PC-iMCD is challenging for both clinicians and pathologists. From a clinical perspective, because of the non-specificity of radiological findings of iMCD , imagingAll 16 patients with PC-iMCD in our study showed enlarged lymph nodes in at least two lymph node stations. However, 8 of 16 (50%) patients did not receive a histological diagnosis based on lymph node specimens because of inaccessibility caused by anatomical factors, as described above. Although these eight patients did not fully meet the consensus criteria for iMCD  without IgG4-RD is the most challenging differential diagnosis of PC-iMCD because of the similarities in the histological features and lack of specific biomarkers. As both PC-iMCD and IgG4-RD are rare, only two studies have previously investigated the clinicopathological differences between the lung lesions in these two diseases ,20. One In this study, we compared the clinicopathological findings associated with the lung lesions of PC-iMCD and IgG4-RD. To our knowledge, this is the first study to immunohistochemically assess the expression patterns of IL-6 and IgA in the lung lesions of both diseases, specifically to improve diagnostic utility.To develop comprehensive clinical perspectives, we detailed the patient demographics and laboratory findings and summarized the findings. Clinically, the median value for age; involvement of the pancreas or salivary gland; serum levels of Plts, Alb, CRP, IgG, and IgG4; and IgG4/IgG ratio, significantly differed between the two groups, as previously reported ,15,26, sp = 0.027 and p = 0.004, respectively). Although a previous study suggested that the degree of active fibrosis and the number of obliterative vasculitis were significantly different between iMCD and IgG4-RD groups [p = 0.124 and p = 0.892, respectively). This may be because we comprehensively evaluated entire sections, whereas the previous study evaluated values in three randomly selected visual fields. Furthermore, although one study suggested that hemosiderin-laden lesions in lymph node specimens can be used to distinguish iMCD from IgG4-RD [Histologically, there were significant differences in the presence of sheet-like plasmacytosis and the number of eosinophils between the patients of PC-iMCD and IgG4-RD . The number of IgA-positive cells was higher in the PC-iMCD group (p < 0.001). A previous study suggested that IgA immunohistochemistry findings can be used to distinguish lymph node lesions of PC-iMCD from those of IgG4-RD [Immunohistochemically, the following three measurements are considered particularly important: (1) the IgG4/IgG-positive cell ratio; (2) IgA-positive cells; (3) IL-6 expression intensity. The IgG4/IgG-positive cell ratio was significantly higher in the IgG4-RD group than in the PC-iMCD group . One study that performed immunostaining on lymph node specimens reported that plasma cells in PC-type CD cases showed significantly increased IL-6 expression compared to those in reactive lymph nodes [In IL-6 immunostaining, the intensity scores for interfollicular plasma cells and cells of the germinal center area were significantly higher in the PC-iMCD group than in the IgG4-RD group (ph nodes , supportBased on our clinicopathological findings, we propose a new differential diagnostic approach for PC-iMCD compared with IgG4-RD in the lungs . With reOur study had several limitations. First, this was a retrospective study with relatively small sample size. Because of the rarity of lung involvement in PC-iMCD and IgG4-RD, selection bias may be involved. Second, IL-6 immunostaining patterns in other hyper IL-6 syndromes were not investigated in this study. As these syndromes also involve abundant IgG4-positive cells , such diIn conclusion, we investigated the detailed clinicopathological features of lung lesions in PC-iMCD and compared the findings with those in IgG4-RD. The usefulness of immunostaining was highlighted, with specific reference to IL-6, IgA, and the IgG4/IgG-positive cell ratio. The differential diagnostic approach proposed in this study may be useful for accurately distinguishing lung lesions of PC-iMCD from those of IgG4-RD at an early stage, particularly in lung-dominant PC-iMCD where excisional lymph node biopsy is not feasible. Future studies using a larger patient sample size are needed to investigate the clinicopathological findings of lung lesions in other PC-iMCD mimickers, including hyper-IL-6 syndromes, to establish lung-specific criteria for PC-iMCD.


Over-prescribing and inappropriate use of antibiotics contributes to the emergence of antimicrobial resistance (AMR). Few studies in low and middle-income settings have employed qualitative approaches to examine the drivers of antibiotic sale and dispensing across the full range of healthcare providers (HCPs). We aimed to explore understandings of the use and functions of antibiotics; awareness of AMR and perceived patient or customer demand and adherence among HCPs for human and animal medicine in Bangladesh.We used an ethnographic approach to conduct face-to-face, in-depth interviews with 46 community HCPs in one urban and one rural area (Gazipur and Mirzapur districts respectively). We purposefully selected participants from four categories of provider in human and veterinary medicine: qualified; semi-qualified; auxiliary and unqualified. Using a grounded theory approach, thematic analysis was conducted using a framework method.Antibiotics were considered a medicine of power that gives quick results and works against almost all diseases, including viruses. The price of antibiotics was equated with power such that expensive antibiotics were considered the most powerful medicines. Antibiotics were also seen as preventative medicines. While some providers were well informed about antibiotic resistance and its causes, others were completely unaware. Many providers mistook antibiotic resistance as the side effects of antibiotics, both in human and animal medicine. Despite varied knowledge, providers showed concern about antibiotic resistance but responsibility for inappropriate antibiotic use was shifted to the patients and clients including owners of livestock and animals.Misconceptions and misinformation led to a wide range of inappropriate uses of antibiotics across the different categories of human and animal healthcare providers. Low awareness of antibiotic action and antibiotic resistance were apparent among healthcare providers, particularly those with little or no training and those in rural areas. Specific and targeted interventions to address AMR in Bangladesh should include educational messages on the rational use of antibiotics and how they work, targeting all types of healthcare providers. While tailored training for providers may increase understanding of antibiotic action and improve practices, more far-reaching structural changes are required to influence and increase responsibility for optimising antibiotic dispensing among all HCPs. Global resistance to antibiotics among clinically important and commensal bacteria is increasing at an alarming rate, thereby threatening the effective treatment of infectious diseases , 2. AntiIn many South and Southeast Asian countries, antimicrobials are widely available as over-the-counter drugs purchased without prescription from registered or unregistered retail drug outlets. Excess use of antibiotics in livestock, poultry, and aquaculture is a further driver of antimicrobial resistance , 7. A stIn Bangladesh, the scale of over-the-counter sales combined with the high number of retail outlets poses a considerable burden on regulatory authorities. Similarly, the limitations in human, technical and logistic capacity of the state render regulatory enforcement relatively weak. The presence of unregulated drug shops and a ‘pluralistic’ health system  compound this complexity . In urbaSurvey-based studies in Bangladesh among both qualified and unqualified healthcare providers (HCPs) show complex prescribing behaviours characterized by polypharmacy, high use of antimicrobials and almost non-existent generic prescribing –14. NatiDespite meeting or exceeding millennium development goals in maternal and child mortality, universal immunisation and community-based health provision , the burProgress against targets set in the National Action Plan on AMR is hampered by a lack of information on the socio-cultural dimensions of antibiotic prescription and use. There is a significant gap in knowledge around the dispensing behaviours of qualified and unqualified HCPs for antibiotics in low resource settings, both in humans and in livestock or animals. Humans and animals have closely shared environments in Bangladesh and the division between healthcare provision for humans and animals is less distinct, with some providers serving both sectors . This stThis study aimed to explore healthcare providers’ understandings of the use and functions of antibiotics; awareness of AMR, and perceived patient demand and adherence in urban and rural Bangladesh employing a One Health approach.upazila) and in the urban town centre of Tongi in Gazipur district from July 2017 to January 2018. The study adopted a One Health approach by examining providers for both human and animal care including registered doctors and veterinarians; qualified healthcare practitioners, and providers with no formal qualifications. HCPs were identified who dispense or prescribe allopathic medicine (biomedicines) across the human and animal sectors. Considering the context of medical pluralism within the biomedical sector in South Asia  antibiotics children get well quickly. Mothers want their child's quick recovery, that’s why we give them.” .In contrast to the other groups, the qualified providers generally had a good understanding of the use, appropriate dose and actions of antibiotics. As one qualified provider for animals said:If, for example, I diagnose that the animal disease is Black Quarter, I know that this disease is occurring by the infection of a Gram-positive bacteria; in that case, I can easily choose to prescribe penicillin. Again, if I diagnose a Gram-negative bacteria infected disease then I try to give treatment with the gentamicin group of antibiotics or specific drugs which will respond to the Gram-positive and negative bacteria."“On the other hand, even though qualified providers for animals had knowledge about the generation of antibiotics, they did not always prescribe these rationally. As one qualified urban animal health provider said without much consideration that he immediately prescribes third generation antibiotics:“Antibiotics work against Gram-positive organisms, gangrene and mastitis diseases. Most of the time I prescribe third generation antibiotics straight away and I mix a combination of antibiotics for cattle”.Misconceptions about the use, appropriate dose and function of antibiotics particularly among unqualified, semi-qualified and auxiliary providers seem to be similarly prevalent in rural and urban settings.Although the informal providers did not have a full understanding of the generations of antibiotics, they figured this out through other means. Many a time they did this through the difference in price; learning by prescribing as mentioned earlier or by following a doctor’s prescription. Whatever the means of identifying antibiotic generations, it was evident that providers had a tendency to prescribe antibiotics of advanced generation. An urban semi-qualified provider for humans said,An important component of this study was to explore the understanding among providers about antimicrobial resistance. Providers of antibiotics for humans in rural areas showed a varying degree of knowledge about resistance, with variation within and between different categories of providers. Among unqualified, semi-qualified and auxiliary providers some were well informed about the term and causes of antibiotic resistance whilst others were completely unaware.I have not heard about resistance. But, I think that if someone does not take antibiotics correctly, then the disease condition will get worse day by day.”“One auxiliary provider also had vague ideas about resistance and said,“Sometimes the antibiotic’s power gets diluted in the body then it does not work against the disease. Then the patient keeps on suffering from the disease. Then we need to give more powerful antibiotics”.One rural unqualified provider for humans said,One striking finding was that many providers, when asked about antibiotic resistance, mistook this as the side effect of antibiotics. One semi-qualified provider said, antibiotics can be harmful to teeth in growing children. Another one said antibiotics can damage children’s cartilage.“After having Azithromycin, a few patients complained that they had swelling in the body. Although I did not find any reactions in any other antibiotics like this.”One urban auxiliary provider for humans mentioned antibiotics can cause allergy and scabies as a side effect. When asked about resistance one urban unqualified provider said,“Sometimes after having antibiotics, swelling or infection appears on the whole body and the cow can’t stand up and feels a headache. That is resistance”. .Similarly, a semi-qualified provider for animals talked about the side effects of antibiotics for animals when asked about resistance:Antibiotics are harmful medicines. If anyone does not take the full course of medicine, then it will not be working exactly. For that reason, diseases may increase more in future. Suppose in the future a patient may not be able to walk, talk or take food properly (meaning disabled) due to taking irregular antibiotics”. .A respondent said, “If any patient doesn’t complete the full courses of antibiotics, then in future the medicines will not work accordingly. I always tell the patients ‘if you do not face any problem then still please don’t stop it after consuming one or two days later’. Because if someone doesn’t complete the antibiotic course properly over several occasions then that drug becomes resistant.”“However, the providers who were informed and aware of AMR related it to irregular consumption, incomplete doses, or the overuse of antibiotics. An auxiliary urban provider for humans also pointed out the dangers of inappropriate use of antibiotics,“Antibiotics are a dangerous medicine. If someone does not complete the full course, it will not work properly. In which case, the disease may become even more severe.”One rural semi-qualified provider for humans also mentioned how failing to comply with the appropriate dose of antibiotic can cause serious consequences,Our human body is like a battlefield, antibiotics are the main missiles. When we invent any new drugs, it is like we invented a new missile against the germs. If the opposition party gets any information before then they will create a protection system like anti-missiles. So, when antibiotics are not used fully then bacteria will create an antibody against antibiotics and it will not work against that disease or germs. These are all antibiotic resistance mechanisms”. The qualified provider points out how overuse of antibiotics can cause resistance.“A qualified provider for humans used a metaphor to explain resistance. He said,“Number one would be that without a prescription no pharmacy outlet should be allowed to sell their drugs. Without a doctor’s consultation, no one should take medicines, we should follow these two steps then resistance will stop. Rural practitioners [‘Unqualified providers’] should stop their practice because they have training for only two months and become doctors who give the wrong treatment to the patients. You will see that they prescribe third or fourth generation antibiotics like cefuroxime, for any diseases, they use all broad-spectrum antibiotics that we keep as a reserve for later use.” .Despite the varied knowledge of AMR, all providers showed concern about antibiotic resistance. When asked about how to prevent this risk the providers usually shifted the responsibility to one other. For example, a qualified provider thought that to prevent antibiotic resistance all practices by the unqualified providers should be stopped because they are incompetent:a farmer depends on the doctor and the doctor has a liaison with pharmaceutical companies who push them to sell antibiotics, so a policy should be there to control the qualified doctors and pharmaceutical companies in their control of the overuse of antibiotics or drugs.” .“.....On the other hand, a rural unqualified provider for animals saw the problem within the qualified providers, who he thinks should be controlled.Patients do not complete the course. They take an incomplete dose and become resistant. They take it for one day or two days only”. . Also, “If you count it then you will find only 20% to 30% of people follow the instructions, the majority do not follow the instruction and do not consume it [antibiotics] properly.” .“All categories of providers, irrespective of their location, blamed patients for contributing to antibiotic resistance by not following instructions and failing to adhere to the course of drugs as directed.“Suppose we have prescribed medicines for ten days but many patients consume it just for five days because they do not have enough money to buy the full course.”Reasons for non-compliance by the patients were explained as the inability to afford the full course of medicine; illiteracy and ignorance of the patients or stopping the medication due to feeling better. One qualified provider for humans said,… sometimes poor men such as rickshaw pullers visit me with a severe fever for over 7 days, since they cannot afford to visit the private and qualified (MBBS) practitioners. Then, as per their request, I prescribe them a few antibiotic capsules.” .“Considering the patients’ ability to afford medicines the unqualified providers sometimes deliberately gave a partial dose of antibiotics instead of the full course.Many of them (patients) don’t understand that they are taking antibiotic due to lack of education. Even here in this slum many of them are illiterate, I mean, they are all slum dwellers. They are not conscious and maybe they don’t know what an antibiotic is”. .“The providers thought patients do not adhere to antibiotic courses in some cases because they do not understand the instructions from the providers or read the instructions written on the medicine packet due to their illiteracy.“Sometimes it is seen that after getting some antibiotics, the cattle become healthy. Then they do not provide any medicine to their cattle. But it has been observed that the disease appears again. ... “. . Also,While they consume (antibiotics) if they feel vomiting or swelling then they do not continue the drugs. Sometimes they stop antibiotics suddenly due to some side effects, but they do not understand why it is happening. A person may feel unwell by consuming another drug that they may be taking but their first action is to stop the antibiotics.” .“Some providers stated that patients do not continue medicine once they or their animal start feeling better or if they experience any side effects.In our country we have two popular media, television and radio, for building mass awareness - we can use these two media. In every hospital, we need a counsellor who will give advice to the patients about drug adherence.” .The providers emphasized the need to educate patients through various means. For example, a qualified provider suggested using mass media to raise awareness:It is interesting to note that the providers do not take any responsibility for creating the problem of antibiotic resistance.This study provides novel insights into the supply side of antibiotics at the community level in rural and urban Bangladesh. Antibiotics were considered powerful medicines that give quick results and work against almost all diseases including viruses. Awareness and understanding about antibiotics and resistance among providers reflected the varying level of qualifications as well as the location of practice . Urban providers tended to have a better understanding of the correct course duration and generations of antibiotics than their rural counterparts. Urban providers were also better informed about the function of antibiotics. While several factors could contribute to this difference, we found that providers in urban areas had greater exposure to, and interaction with, medical representatives from pharmaceutical companies compared to providers in rural areas which could be one contributing factor. Pharmaceutical company representatives have been highlighted as important sources of knowledge on antibiotics among informal providers in India  and are The price of antibiotics was equated with power such that expensive antibiotics were considered the most powerful medicines. Antibiotics were also seen as preventative medicines. The semi-qualified, unqualified and auxiliary providers in the study showed some gross misconceptions about the use, function and appropriate dose and duration of antibiotics. Although auxiliary providers would be expected to have fewer misconceptions than semi-qualified or unqualified providers, they too demonstrated vague knowledge about antibiotics and AMR. This important group of healthcare providers may have been overlooked in efforts to improve antibiotic stewardship .While some providers were well informed about antibiotic resistance and its causes, others were completely unaware. Among providers who claimed that they were aware, many mistook antibiotic resistance as the side effects of antibiotics, both in human and animal medicine. Qualified providers had good awareness and understanding of antibiotic resistance, yet some were found to prescribe antibiotics irrationally, for example, by providing third-generation antibiotics as first-line therapy. A quantitative study in India also demonstrated a dissonance between knowledge and practice with qualified providers . Mixed pAll providers who showed awareness of antibiotic resistance thought this was a concern, but they considered that this was due to irresponsible antibiotic use among patients and customers, including the owners of livestock and animals. Most strikingly, none of the HCPs from the formal or informal sectors acknowledged that their behaviour may contribute to AMR, in keeping with other studies . All blaA potential limitation of this study is that we focused on biomedicine providers and did not include traditional medicine providers or healers who may have added further perspectives on antibiotic understandings and use. Strengths of the study include the perspectives gained from a wide range of providers, especially unqualified providers who play a key role in antibiotic access. Potential bias within the study was addressed using qualitative methods of triangulation across the different data sources and methods of collection . Qualitahuman resources for health is the key to understanding the supply-side factors driving AMR. The pluralistic health service provision and weak regulation of prescription-only medicines, coupled with poor awareness of AMR among providers, greatly hampers the supply-side competency of Bangladesh health services. Of note, however, the providers themselves did not relate the problem of antimicrobial resistance to competency within the supply side. Rather, interviewees placed blame on other types of HCPs or on the demand side, which they characterised as misconceptions and non-compliance among the patients. This study reveals how multiple stakeholders from the supply and demand side influence the provision of antibiotics. This echoes previous work highlighting that antibiotic prescribing is a complex process influenced by factors affecting all the actors involved: physicians, other healthcare providers, the healthcare system, patients and the general public [The emergence of antibiotic resistance can be examined according to the factors determining antibiotic use, overuse, and misuse , 36. Ourl public .Interestingly, household interviews revealed a heavy reliance of patients and consumers on unregulated retail drug outlets for both antibiotics and healthcare advice . Retail The Bangladesh NAP  includesThe study reveals that misconceptions and misinformation lead to a wide range of inappropriate uses of antibiotics across different categories of human and animal healthcare providers. We highlight important areas for reducing misconceptions around antibiotics among the key actors in healthcare provision. Our findings suggest that specific and targeted interventions to address AMR in Bangladesh should include educational messages on the rational use of antibiotics and how they work. Providers and consumers should be informed that antibiotics do not work for all diseases. Awareness raising around antimicrobial resistance needs to create a better understanding of both antibiotics, and resistance to antibiotics. Such interventions need to target qualified and unqualified providers across human and animal healthcare.More far-reaching structural changes within the health system are required to influence and increase responsibility for optimising antibiotic dispensing among all HCPs. This paper has clear policy implications that demonstrate the need for the National Action Plan on AMR to increase advocacy around appropriate antibiotic prescribing particularly among less qualified and unqualified providers.


N-[(heptaisobutyl-POSS)propyl]-3,5-diaminobenzamide (DABA-POSS). Subsequently, the effects of the molecular structures on the thermal, tensile, optical, and especially the AO-erosion behaviors of the POSS-PI films were investigated. The incorporation of the latent POSS substituents decreased the thermal stability and the high-temperature dimensional stability of the pristine PI-0 (PMDA-ODA) film. For instance, the PI-30 film with the DABA-POSS content of 30 wt% in the film exhibited a 5% weight loss temperature (T5%) of 512 °C and a coefficient of linear thermal expansion (CTE) of 54.6 × 10−6/K in the temperature range of 50–250 °C, respectively, which were all inferior to those of the PI-0 film . In addition, the tensile properties of the POSS-containing PI films were also deteriorated, to some extent, due to the incorporation of the DABA-POSS components. The tensile strength (TS) of the POSS-PI films decreased with the order of PI-0 > PI-10 > PI-15 > PI-20 > PI-25 > PI-30, and so did the tensile modulus (TM) and the elongations at break (Eb). PI-30 showed the TS, TM, and Eb values of 75.0 MPa, 1.55 GPa, and 16.1%, respectively, which were all lower than those of the PI-0 film . Nevertheless, the incorporation of POSS components obviously increased the AO resistance of the PI films. All of the POSS-PI films survived from the AO exposure with the total fluence of 2.16 × 1021 atoms/cm2, while PI-0 was totally eroded under the same circumstance. The PI-30 film showed an AO erosion yield (sE) of 1.1 × 10−25 cm3/atom, which was approximately 3.67% of the PI-0 film (sE = 3.0 × 10−24 cm3/atom). Inert silica or silicate passivation layers were detected on the surface of the POSS-PI films after AO exposure, which efficiently prevented the further erosion of the under-layer materials.The relatively poor atomic-oxygen (AO) resistance of the standard polyimide (PI) films greatly limits the wide applications in low earth orbit (LEO) environments. The introduction of polyhedral oligomeric silsesquioxane (POSS) units into the molecular structures of the PI films has been proven to be an effective procedure for enhancing the AO resistance of the PI films. In the current work, a series of POSS-substituted poly  (PMDA-ODA) films (POSS-PI) with different POSS contents were synthesized via a POSS-containing diamine,  The influence of the latent POSS substituents on the thermal, tensile, optical, and especially the AO resistant properties of the films were investigated in detail.In the current work, as one of our continuous work developing high-performance PI films with excellent AO resistance , a serieN-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), and other solvents were obtained from Beijing Innochem Science & Technology Co., Ltd.  and then purified by distillation prior to use.Sublimation-purified pyromellitic dianhydride (PMDA) was purchased from Shijiazhuang HOPE Chem. Co. Ltd.  and then dried at 180 °C in vacuum for 24 h prior to use. 4,4′-Oxydianline (ODA) was purchased from Tokyo Chemical Industry (TCI) Co., Ltd.  and purified by sublimation under reduced pressure. Aminopropylisobutyl POSS was purchased from Hybrid Plastics Co. Ltd.  (Product code: AM0265) and used as received. 3,5-Dinitrobenzyl chloride (DNBC) was purchased from TCI  and used as received. nM) and weight average molecular weight (wM) of the PAAs were measured using a gel permeation chromatography (GPC) system  with a LC-20AD dual-plunger parallel-flow pumps (D1-LC), a SIL-20A is a total-volume injection-type auto-sampler, a CTO-20A column oven, and a RID-20A detector. HPLC grade NMP was used as the mobile phase at a flow rate of 1.0 mL/min. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of the PI films were recorded on a Iraffinity-1S FT-IR spectrometer . Nuclear magnetic resonances (1H-NMR) of the DABA-POSS diamine were performed on an AV 400 spectrometer  operating at 400 MHz in CDCl3. Ultraviolet-visible (UV-Vis) spectra were recorded on a Hitachi U-3210 spectrophotometer  at room temperature. Wide-angle X-ray diffraction (XRD) was conducted on a Rigaku D/max-2500 X-ray diffractometer  with Cu-Kα1 radiation, operating at 40 kV and 200 mA. X-ray photoelectron spectroscopy (XPS) data were obtained with an ESCALab220i-XL electron spectrometer  while using 300 W of MgKα radiation. The base pressure was 3 × 10−9 mbar. The binding energies were referenced to the C1s line at 284.8 eV from the adventitious carbon. Field emission scanning electron microscopy (FE-SEM) was carried out using a Technex Lab Tiny-SEM 1540  with an accelerating voltage of 15 KV for imaging. Pt/Pd was sputtered on each film in advance of the SEM measurements.The inherent viscosity of the PI precursors, poly (amic acid) (PAA) was measured while using an Ubbelohde viscometer  with a 0.5 g/dL NMP solution at 25 °C. The number average molecular weight  values of the POSS-PI films were measured using an X-rite color i7 spectrophotometer  with PI samples at a thickness of 25 μm in accordance with the procedure that is described in ASTM D1925. The color parameters were recorded according to a CIE Lab equation. Thermo-gravimetric analysis (TGA) was performed on a TA-Q50 thermal analysis system  at a heating rate of 20 °C/min. in nitrogen. Differential scanning calorimetry (DSC) was recorded on a TA-Q100 thermal analysis system  at a heating rate of 10 °C/min. in nitrogen. Dynamic mechanical analysis (DMA) was recorded on a TA-Q800 thermal analysis system  in nitrogen at a frequency of 1 Hz and heating rate of 5 °C /min. Thermomechanical analysis (TMA) was recorded on a TA-Q400 thermal analysis system  in nitrogen at a heating rate of 10 °C/min.3 samples in accordance with GB/T 1040.3-2006 at a drawing rate of 2.0 mm/min. At least six test samples were tested for each PI film and the results were averaged.The tensile properties were performed on an Instron 3365 Tensile Apparatus  with 80 × 10 × 0.05 mm® exposed to AO characterizes the AO flux. The facility produces an AO flux at a magnitude of 1015 atoms/cm2/s and the total AO exposure dose is 2.16 × 10 21 atoms/cm2 in the current work. The average kinetic energy of AO beam falls in the range of 3~8 eV. The AO exposure was performed on square POSS-PI film samples with the size of 20 (length) × 20 (width) × 0.05 (thickness) mm3. The films were exposed to AO at a fluence of 2.1 × 1021 atoms/cm2 and the mass loss was determined. The erosion yield of the sample, sE, is calculated through the following Equation (1) -3,5-diaminobenzamide (DABA-POSS) was synthesized in our laboratory according to a modified procedure that is reported in the literature [N-[(heptaisobutyl-POSS)propyl]-3,5-dinitrobenzamide (DNBA-POSS), was performed under the reduction of hydrazine monohydrate with the palladium on activated carbon (Pd/C) catalyst instead of the platinum oxide/hydrogen (PtO2/H2) system.terature . The hyd−1): 3444, 3356, 2955, 2872, 1626, 1597, 1527, 1466, 1365, 1333, 1230, 1111, 839, and 742. 1H-NMR : 6.45 , 6.12 , 5.96 , 3.67 , 3.41–3.39 , 1.85 , 1.67 , 0.97 , and 0.68-0.61 . Elemental analysis: C38H77N3O13Si8: Cald. C, 45.25%, H, 7.69%, N, 4.17%; Found: C, 45.01%, H, 7.71%, and N, 4.26%.Yield: 93.2%. Purity: 99.5% . Melting point: 202.5 °C (DSC peak temperature). FT-IR  was added into a 500 mL three-necked flask equipped with a mechanical stirrer, a cold-water bath, and a nitrogen inlet and the reaction system was filled with the continuous nitrogen flow. Subsequently, ODA  and DABA-POSS  were added and the reaction system was cooled to −5–0 °C. The diamine solution with the deep pink color was obtained after stirring for 10 min. under the flow of nitrogen. Subsequently, PMDA  was added to the solution together with an additional DMAc (164.0 g). The solid content of the reaction system was controlled to be 20 wt%. The reaction mixture was stirred for 1h and then the cold-water bath was removed. The reaction was prolonged for another 20 h at room temperature. Afterwards, the viscous brown-yellow solution was obtained, which was purified by filtration through a 2.0 μm polytetrafluoroethylene (PTFE) filter in order to afford the PAA-20 solution.The purified PAA-20 solution was cast on a clean glass substrate with a scraper blade. The thickness of the wet PAA-20 film was adjusted by regulating the slit height of the scraper blade. Subsequently, the PI-20 films with different controlled thicknesses were obtained by thermally baking the PAA-20 solution in an oven with nitrogen gas flow, according to the following procedure: 80 °C/3 h, 150 °C/1 h, 180 °C/1 h, 250 °C/1 h, and 300 °C/1 h.The other PAA solutions and the corresponding PI films, including PI-10, PI-15, PI-25, and PI-30 films, were prepared according to a similar procedure mentioned above. The PI-0 (PMDA-ODA) film without POSS components was also prepared for comparison.N-[(-heptaisobutyl-POSS)propyl]-3,5-dinitrobenzamide (DNBA-POSS), was prepared from the starting DNBC and aminopropylisobutyl POSS (AM0265) with dichloromethane as the solvent and triethylamine as the acid absorbent. The reaction was performed at the temperature below 0 °C in order to avoid the occurrence of side reactions. Subsequently, the dinitro compounds were catalytically hydrogenated with hydrazine monohydrate to afford the target DABA-POSS compound. The total yield was about 93.2%. The highly pure DABA-POSS diamine was obtained as colorless crystals with the sharp endothermic melting peak at 202.5 °C in the DSC measurement. The light-sensitive DABA-POSS diamine was easily to be oxidized in air and the color turned from colorlessness to pinkness during storage.1H-NMR, and elemental analysis measurements. 1H-NMR spectra of DABA-POSS diamine together with its dinitro precursor. It could be clearly observed that the protons in the POSS side chains (H5~H10) revealed absorptions at the farthest upfield region in the spectra. On the country, the protons in the benzene units  showed absorptions at the farthest downfield region in the spectra, although the chemical shifts were not the same for DABA-POSS and DNBA-POSS. Proton H7 that was attached with the silicon elements exhibited the signals with the lowest chemical shift values in both of the spectra for DABA-POSS and DNBA-POSS. For DABA-POSS, clear absorption for the amino hydrogen protons was detected at 3.67 ppm, as in The chemical structure of the DABA-POSS diamine was identified the FT-IR, η]inh) and molecular weights, including the number average molecular weight (Mn), weight average molecular weight (Mw), and the polydispersity index (PDI) of the PAA varnishes. The [η]inh and molecular weights of the PAA varnishes gradually decreased with the increasing contents of the POSS diamine in the systems. For example, PAA-30, with the highest POSS diamine content in the systems, exhibited the [η]inh and Mn values of 0.93 dL/g and 7.43 × 104 g/mol, respectively, which are apparently lower than those of the pristine PAA-0 without POSS component . This decreasing trend in the molecular weights of the PAA varnishes is mainly attributed to the relatively lower polymerization reactivity of the POSS diamine when compared to that of ODA. Nevertheless, the current level of the molecular weights of the PAA varnishes could guarantee the film-forming ability and good mechanical properties of the derived PI films.A series of PAA varnishes, a total of six samples, including one system without POSS component, PI-0 (PMDA-ODA) and five copolymers with different DABA-POSS contents, PI-10, PI-15, PI-20, PI-25, and PI-30 , were prepared, respectively, with the procedure that is shown in A series of PI films were prepared from the corresponding PAA varnishes according to the procedure that is shown in −1 that were assigned to the asymmetrical carbonyl stretching vibrations, at 1723 cm−1 assigned to the symmetrical carbonyl stretching vibrations, at 1373 cm−1 for the C–N stretching vibrations, and at 724 cm−1 for the carbonyl out-of-plane bending vibrations were all clearly observed. The characteristic absorptions of the saturated C-H bonds at 2955 cm−1 and the Si-O-Si stretching vibrations at 1130 cm−1 were only observed in the spectra of PI-10~PI-30, which indicated the successful introduction of the POSS units in the PI films.b*) and haze values of the PI films increased with the increasing contents of POSS units. For example, the PI-30 film showed the b* and haze values of 96.42 and 31.70%, respectively, which are obviously higher than those of the pristine PI-0 film . It is the phase separation instead of the crystallization of the molecular chains that caused the opaque appearance of the PI films with high POSS units. This could be confirmed by the XRD measurement that is shown in Although the POSS components were successfully introduced into the molecular structures of the PI films via copolymerization instead of external adding as fillers, obvious phase separation was still observed with the increasing contents of DABA-POSS. This could be indirectly confirmed by the change of the optical parameters of the films. T5%) in the range of 512–574 °C. At the end of the TGA measurement, the PI films left approximately 57–60% of their original weights at 750 °C. The incorporation of the POSS units into the PI films decreased the initial thermal decomposition temperatures of the PI films; however, it slightly increased the values of residual weight ratio at 750 °C (Rw750). For instance, the PI-30 film showed the T5% and Rw750 values of 506 °C and 59.3%, respectively. The former value is 68 °C lower than that of the pristine PI-0 film (T5% = 574 °C) and the latter value is slightly higher than that of the pristine PI-0 film (Rw750 = 57.4%). The decrease of the T5% values of the POSS-PI films is mainly due to the thermal unstable nature of the isobutyl groups in the POSS units, while the slight increase of the Rw750 values might be attributed to the formation of heat-resistant silicon oxide at elevated temperatures, due to the oxidation reaction of the silicone elements with the trace amount of oxygen in the gas.The effects of the POSS units on the thermal properties and high-temperature dimensional stability of the PI films were investigated by TGA and TMA, respectively. −6/K, which is obviously higher than that of the pristine PI-0 film (CTE = 28.9 × 10−6/K). This might be due to the internal plasticization effects of the latent POSS units in the PIs. In addition, all the POSS-PI films did not show clear glass transitions in the differential scanning calorimetry (DSC) measurement in the temperature range of 30 to 400 °C. In the TMA measurement, PI-0 showed clear glass transition in the temperature range of 300 to 350 °C. However, the POSS-PI films did not show an obvious glass transition before 320 °C. This phenomenon indicates that the incorporation of POSS units might delay the softening of the PI films; that is increasing the glass transition temperatures (Tg) of the PI films, although the CTE values increased at the same time. This result agreed well with the POSS-containing PI films that are reported in the literature [Subsequently, the high-temperature dimensional stability of the PI films was investigated by the TMA measurements and the CTE values of the PI films in the temperature range of 50–250 °C were recorded in the TMA plots that are shown in terature .TS), tensile modulus (TM), and elongations at breaks (Eb) values of the PI films decreased with the increasing contents of the POSS units in the polymers. For example, the PI-30 film showed the TS, TM, and Eb values of 75.0 MPa, 1.55 GPa, and 16.1%, respectively. These values are obviously lower than those of the PI-0 film . This result is in good consistence with the analogous POSS-containing PI films that are reported in the literature [The influence of the POSS units on the tensile properties of the PI films was investigated and the tensile data are summarized in terature . The det21 atoms/cm2. The AO-resistant ability of the PI films was justified by the weight loss during the AO exposure, which was recorded in sE) of the PI films were calculated according to equation (2) in ® reference. It can be clearly observed that the incorporation of POSS components obviously increased the AO resistance of the PI films. All of the POSS-PI films survived from the AO exposure. The sE values of the PI films decreased with the increasing contents of the POSS components in the films. The PI-30 film showed an sE value of 1.1 × 10−25 cm3/atom, which was approximately 3.67% of the Kapton® film (sE = 3.0 × 10−24 cm3/atom).The AO erosion behaviors of the current PI films were investigated in the ground-simulated facility with the total AO dose of 2.16 × 10In order to reveal the mechanism for the enhancement of the AO resistance of the PI films via incorporation of POSS units, the surface chemical compositions and the micro-morphologies of the films were investigated, respectively. First, T5% of 526 °C, the CTE of 56.1 × 10−6/K, the TS of 97.6 MPa, the TM of 1.69 GPa, the Eb of 28.0%, and AO erosion yield of 1.7 × 10−25 cm3/atom. For such series of POSS-containing PI films, the relatively high CTE and low tensile modulus might be the weakness for future practical applications. How to enhance the high-temperature dimensional stability (CTE ≤ 40 ×10−6/K) and modulus (TM ≥ 3.0 GPa) of these PI films will be the main challenges to face in the future research work. Related research is now under investigation in our laboratory.A series of POSS-containing PI films were prepared in order to enhance the AO resistance of the common PI (PMDA-ODA) film. The purpose was successfully achieved, although the incorporation of POSS units deteriorated the thermal and tensile properties of the PI films to some extent. Overall, it is more optimal to control the proportion of POSS diamine unit in the PI film at 20 wt%. The derived PI-20 film possessed the best combined properties in the series, including the