Negation is widely present in human communication, yet it is largely neglected in the research on conversational agents based on neural network architectures. Cognitive studies show that a supportive visual context makes the processing of negation easier. We take GuessWhat?!, a referential visually grounded guessing game, as test-bed and evaluate to which extent guessers based on pre-trained language models profit from negatively answered polar questions. Moreover, to get a better grasp of models' results, we select a controlled sample of games and run a crowdsourcing experiment with subjects. We evaluate models and humans against the same settings and use the comparison to better interpret the models' results. We show that while humans profit from negatively answered questions to solve the task, models struggle in grounding negation, and some of them barely use it; however, when the language signal is poorly informative, visual features help encoding the negative information. Finally, the experiments with human subjects put us in the position of comparing humans and models' predictions and get a grasp about which models make errors that are more human-like and as such more plausible. Negation is often neglected by computational studies of natural language understanding, in particular when using the successful neural network models. Very recently, a series of work have highlighted that negation is under-represented in existing natural language inference benchmarks  negation and that the data we collected through our online experiment and its annotation will be a valuable contribution to such research direction.Sankar et al.  study hoKaushik and Lipton  show thaInteresting exploratory analysis has been carried out to understand Visual Question Answering (VQA) systems and highlight their strengths and weaknesses  contain in the last turn a question answered positively (resp. negatively). From these games, we randomly select 300 games  from the Yes- and No- test sets (150 each). In this way, we obtain a subset balanced also with respect of the polarity of the last question. We believe games in this sample set are equally difficult, considering the criteria discussed above.Following, Greco et al. , all theAs in de Vries et al. , the repBASE which has been pre-trained on 160GB of English text trained for 500K steps to perform masked language modeling. RoBERTa was pretrained on several text corpora containing rather long utterances: BookCorpus , against its counterpart trained from scratch only on the game (RoBERTa-S).In the architecture of the model described above, we replace the LSTM with a robustly-optimized version of BERT  and the one trained from scratch (LXMERT-S).To evaluate the performance of a universal multimodal encoder, we employ LXMERT   when receiving only the questions from the dialogues (without the answers). Moreover, as commented above, the last turn in the Yes-set vs. No-set is expected to play a rather different role. In particular, already alone a positively answered question in the last turn is expected to be rather informative whereas a last turn answered negatively is not. On the other hand, last turns containing a negative answer are expected to enrich the dialogue history and help to guess the target. Hence, in the following, we evaluate models aiming to understand the role of the last turn.We evaluate models when receiving dialogues containing only the questions.We now investigate how the polarity of the final answer in the dialogue affects the performance in the guessing task. Models reach a rather lower accuracy on the No-set, suggesting that models have harder time interpreting dialogues ending with a negative answer . DiffereTo analyse the role of the last turn, we compute models' accuracy when receiving the dialogues without the last turn or with only the last turn. The drop obtained from the setting in which models have access to the full dialogue quantifies the role of the last turn. First of all, as shown in To validate our findings about the comparison between RoBERTa and LXMERT, we have run the McNemar's test with a significance level of 0.05. We use an asterisk to signal scores whose differences is not significant , 3.P(o) changes after each turn (P(o)Ti+i−P(o)Ti) and compare turns Ti with a Yes, No or N/A answer. We expect it is easier to use the Yes-turns than the No ones, but we hope models are able to benefit from the questions answered negatively more than those answered by N/A. Moreover, we focus on the games in which the Guesser succeeds to select the target object, and quantify the effect of the last turn on the probability assigned to the target. We expect the change in the last turn of the No-set to be much higher than No-turns in average, whereas this should not happen with last turn in the Yes-set.We now analyze how the guesser module assigns probabilities to the target object across the turns to understand better the role of positive and negative answers at a more fine-grained level. We compute how the probability assigned by the Guesser to the target object Although the average probability assigned to the target is similar before a Yes-turn and a No-tun for all models,In short, the experiments run so far show that all models take the answer of the asymmetric GuessWhat?! dialogues into account. The pre-trained encoders are the best models over all games and are on par with one another in processing positively answered questions. But, the results on the Yes-set when removing the last turn or when giving only the last turn shows that LXMERT profits from the last Yes-turn more than RoBERTa. We conjecture this is due to the fact that LXMERT has a harder time encoding the dialogue history. The overall accuracy obtained on the No-set suggests that RoBERTa encodes the negatively answered questions better than LXMERT. However, an in-depth analysis of the Guesser probability distribution shows that the Guesser profits from the last turn in the No-set more when it is based on LXMERT than on RoBERTa. From the analyses presented so far, it emerges that the models we considered have different strengths and weaknesses, depending on many factors. To establish an upper-bound for models' performance and to assess the severity of the errors made by the models, in the following we present an in-depth analysis we carried out with human annotators playing the same guessing task of the models.In order to interpret models' performance on encoding Yes/No-turns, we evaluated humans' performance on the controlled games sample described in section 3. These results set an upper-bound for model performance, and give us a powerful tool to better scrutinize our results.We asked human annotators to perform the GuessWhat?! guessing task on a controlled sample of test set games. Similarly to what discussed in section 5, we evaluate several settings: we provide annotators with the full dialogue, the dialogue without the last turns, or only the last turn. Moreover, to check the average informativeness of Yes- No-turns, we add the setting in which we remove from the dialogues all turns of the same polarity.Through Prolific,Participants were given an image with bounding boxes associated with each candidate object, together with a progressive ID number, as illustrated in As we did in the previous section, we validate the accuracy results by running a McNemar's test with a significance level of 0.05 , 7. TablAs mentioned above, we focus on games on which human players have been successful in guessing the target object. It has to be noted that during the GuessWhat?! data collection, each game was played only once and the target object was guessed by the same player who asked the questions. Hence we do not know whether the same dialogue-image would be equally informative for another player to succeed in the game neither we know the level of uncertainty behind the choice made by the successful player. With these questions in mind, in Given that we are working with games on which GuessWhat?! human players succeed guessing the target, the fact we do not obtain 100% accuracy in the group D  is by itself interesting. The difference between the two schema shows that, also in the games successfully solved by human players in the GuessWhat?! dataset, there is a margin of uncertainty. As we see from the p < 0.05), this might be due to what observed above, namely the last Yes-turn summarizes the salient information collected till that point and hence speeds up the choice. Whereas the negative answer in the last turn brings a boost in performance, it does not affect significantly the time taken by human annotators to process the dialogue . These results show that the time taken by human participants to solve the game mirrors the processing cost of negation, which is also influenced by the context  in which it appears.To measure the processing cost of negative turns, we have analyzed the average time taken by human to correctly solve games belonging to the four categories we discussed so far. We now evaluate the models on the same controlled sample of games we used with human annotators. In In the following, we run an error analysis by comparing models and humans on their failures. We expect that a model that properly grounds the dialogues is likely to make human-like mistakes. To this end, among the games failed by a model, we check how many of them have been failed by at least one human annotator ; moreoveIn The evaluation of models on the controlled sample confirms that RoBERTa and LXMERT behave rather similarly on the Yes-set across all settings. More interestingly, it shows that in the No-set LXMERT is closer to humans than RoBERTa considering the accuracy in the task. LXMERT seems to be failing in the integration of the last No-turn with the dialogue history: its accuracy is similar to humans in the settings without last and only last turn, but it is far from them when the whole dialogue is given. Moreover, visual features seem to be of more help in the No-set than in the Yes-set: in the Yes-set across the controlled groups, the blind models do better or similar to their multimodal counterpart, whereas on the No-set the opposite holds. Finally, our error analysis reveals that RoBERTa is the model whose predictions are most human-like when it fails to identify the target object.In the current AI research, driven by the success of language models and neural network architectures, negation is under-studied. Dialogue history and visual context have been shown to facilitate the processing of negation in humans. Hence, we took negation in visual dialogues as our object of investigation and studied how SOTA multimodal models profit from negatively answered questions (No-turns) in the GuessWhat?! game. Such negative information is informative for humans to succeed in the game, and this holds in particular when the No-turn occurs as the last one of a game in which the human player has been successful in guessing the target. Therefore, we focus attention on the subset of dialogues ending with a No-turn and compare them with those ending with a Yes-turn. Our results show that SOTA models' performances on these two sub-sets is rather different, e.g., LXMERT obtains 71.9 vs. 50.9% accuracy in the Yes- vs. No-set, respectively . To bettOur findings can help design models which could ground negation better than current SOTA models. First of all, our comparison between the accuracy obtained by LXMERT and RoBERTa in the various settings , 3, 8 suThe results we obtain do not always provide conclusive answers, but we believe they convincingly show the weakness of current multimodal encoders in processing negation and represent a starting point toward future research. We started from the observation that dialogue history and visual context makes the processing of negation easier for humans. To fully understand whether this can be the case for models too, a comparison on processing negation in language-only vs. multimodal settings should be carried out. To this end, the study could be extended to other dasests in which the visual input is not shared or only partially shared by the agents, such as VisDial, PhotoBook and Meet up! , human data collection and analysis (Section 6), and writing. CG: design of computational experiments, model implementation, and evaluation (Section 5.1), The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The composite films were successfully fabricated by constructing a series of PI-based hybrid aerogels containing different contents of graphene nanosheets and Fe3O4 nanoparticles through prepolymerizaton, film casting, freeze-drying, and thermal imidization, followed by loading molten PEG through vacuum impregnation. The construction of PI/graphene/Fe3O4 hybrid aerogel films provides a robust, flexible, and microwave-absorption-functionalized support material for PEG. The resultant multifunctional composite films not only exhibit high microwave absorption effectiveness across a broad frequency range, but also show a good ability to implement thermal management and temperature regulation under a high latent-heat capacity of over 158 J/g. Most of all, the multifunctional composite films present a wideband absorption capability at 7.0–16.5 GHz and a minimum reflection loss of −38.5 dB. This results in excellent EM and IR bi-stealth performance through the effective wideband microwave absorption of graphene/Fe3O4 component and the thermal buffer of PEG. This study offers a new strategy for the design and development of high-performance and lightweight EM–IR bi-stealth materials to meet the requirement of stealth and camouflage applications in military equipment and defense engineering.Electromagnetic (EM) and infrared (IR) stealth play an important role in the development of military technology and the defense industry. This study focused on developing a new type of multifunctional composite film based on polyimide (PI)/graphene/Fe Stealth technologies are a combination of technologies that attempt to make military equipment and vehicles, mostly aircraft, less visible or ideally invisible to radar, infrared, sonar, and other detection methods, leading to a practical form of active camouflage . Stealth0.5Sr0.5CoO3 perovskites decorated with carbon nanotubes (CNTs) and found that the resultant composites exhibited a remarkable enhanced microwave absorption property along with low IR emissivity compared to pure perovskites. Chu et al. [A literature survey indicates that there have been many efforts so far made to develop multifunctional materials synchronously with EM and IR stealth capabilities. The traditional method to realize EM and IR bi-stealth is mainly to adopt the microwave absorbers coated by metallic particles with high reflectivity in IR frequencies. Chen et al.  reportedu et al.  fabricatu et al.  designedu et al.  construcu et al.  develope3O4 hybrid aerogel and polyethylene glycol (PEG) as a phase change material (PCM) for EM and IR bi-stealth. Phase change materials (PCMs) are a class of latent-heat materials that can offer an order of magnitude increase in heat capacity with very small or negligible temperature change compared to traditional sensible heat-storage materials [3O4 nanoparticles is able to generate prominent microwave-absorption effectiveness because both of them contribute to the attenuation of EM waves through microwave absorption and reflection loss [3O4 nanoparticles into the PI aerogel not only can provide an ultralight, flexible and robust support material for PEG but also can impart excellent microwave absorption and thermal insulating effectiveness to the resultant multifunctional films. It is expected that an innovative integration of PI/graphene/Fe3O4 hybrid aerogel and PCM can endow the resultant composite material with superior microwave absorption and thermal buffering effectiveness. Furthermore, the EM and IR stealth effectiveness can be further enhanced through flexible and rational configuration of PI/graphene/Fe3O4 hybrid aerogel films and PI/graphene/Fe3O4 aerogel/PEG composite films into a multilayer film, extending the application range of this type of multifunctional composite films in practice accordingly. Herein, the fabrication method and formation mechanism of the multifunctional composite films are described in detail, and their microstructure and comprehensive performance are investigated extensively. With an enhanced IR-EM bi-stealth capability, the multifunctional composite films developed in this work are expected to have potential applications for military aircraft, helicopters, surface ships, ground weapons, and other military equipment. This study not only opens a door for the utilization of PCMs in the IR stealth, but also provides a new strategy for the design and development of ultralight, flexible, robust, and high-performance EM-IR bi-stealth functional materials to meet the requirement for the high-efficient EM-IR bi-stealth-compatible applications.In this study, we designed and fabricated a novel type of multifunctional composite film based on the polyimide (PI)/graphene/Featerials ,18. Theyaterials . Based oaterials . PCMs araterials . Therefoion loss . Multipoion loss . IntegraN,N′-dimethylacetamide (DMAc), graphene nanosheets, Ferrous chloride tetrahydrate (FeCl2·4H2O) and ferric chloride hexahydrate (FeCl3·6H2O), and triethylamine (TEA) were commercially supplied by Aladdin Reagent Co., Ltd., Shanghai, China. PEG, used as a solid–liquid PCM, was purchased from Tianjin Fuchen Chemical Reagent Co., Ltd., Tianjin, China, and it has a number-average molecular weight of 6000 g/mol and a polydispersity index of 1.79. Ethanol and acetone were purchased from Beijing Chemical Factory Co., Ltd., Beijing, China. All of the chemicals were of analytic grade and used as received without further purification.Pyromellitic dianhydride (PMDA), 4,4′-diaminodiphenyl ether (ODA), Poly(amic acid) ammonium salt (PAAs) as a water-soluble PI precursor was first synthesized through polycondensation of PMDA and ODA, followed by neutralization with TEA. 3O4 nanoparticles (hereafter graphene/Fe3O4 hybrid) were prepared through in situ hybridization. In a typical procedure, graphene nanosheets (0.19 g) were dispersed in deionized water (100 mL) under ultrasonication. FeCl2·4H2O (0.16 g) and FeCl3·6H2O (0.43 g) were added into the graphene dispersion with mechanical agitation at 50 °C for 20 min under a nitrogen atmosphere. Then, an ammonium hydroxide solution (3.0 mL) was added dropwise into the mixture to maintain the basicity of the aqueous solution at pH 11, and the resulting mixture was stirred for 20 min. Following the completion of co-precipitation, the black precipitate in the solution was collected by a magnet and washed with deionized water several times to obtain the graphene/Fe3O4 hybrid for future use.The graphene nanosheets loaded with Fe3O4 hybrid as a functional filler, a series of PI/graphene/Fe3O4 hybrid aerogel films with a graphene content of 5 wt% and different contents of Fe3O4 nanoparticles at 0, 2, 4, 6, and 8 wt% were prepared through the freeze-drying and thermal imidization processes as depicted in 3O4 hybrid  was then added into the flask with continuous stirring for 6 h under a nitrogen atmosphere to obtain a homogeneous PAA/graphene/Fe3O4 dispersion. The resulting dispersion was cast on a glass plate to form a thin film with a thickness of around 0.5 mm and then subjected to freeze-drying in a lyophilizer  at −80 °C for 12 h to obtain a PAA/graphene/Fe3O4 hybrid aerogel film. The thermal imidization procedure was further conducted in nitrogen to obtain a PI/graphene/Fe3O4 hybrid aerogel film with graphene and Fe3O4 loadings of 5 and 6 wt%, respectively, according to a standard two-stage imidization technique reported in the literature [Following the formation of PAAs as a water-soluble polyimide precursor and the graphene/Feterature ,24. The 3O4 aerogel/PEG composite films with a graphene content of 5 wt% and different Fe3O4 contents of 0, 2, 4, 6, and 8 wt% as well as a PI aerogel/PEG composite film as a control was prepared through a vacuum impregnation method according to the fabrication method shown in 3O4 aerogel film was immersed into molten PEG at 100 °C for 5 h under vacuum. The molten PEG can easily permeate into the aerogel film through the interconnected channels in the aerogel under the vacuum condition due to its extremely low viscosity at a high temperature of 100 °C. The resultant composite film was immediately wiped with a filter paper to erase the excessive PEG on the film surface. A clean and smooth PI/graphene/Fe3O4 aerogel/PEG composite film with a thickness of 0.7 mm was finally obtained for future use. In addition, the loading amounts of PEG in the composite films were determined to be 88–90 wt% according to the following equation:wcomposite and waerogel are the weights of the PI/graphene/Fe3O4 aerogel/PEG composite film and PI/graphene/Fe3O4 hybrid aerogel, respectively.A series of PI/graphene/Fe3O4 hybrids using a JEM 2100 high-resolution transmission electron microscope  at an acceleration voltage of 100 kV. Atomic force microscopy (AFM) was performed to detect the topology of graphene/Fe3O4 hybrids using a Dimension ICON atomic force microscope . Raman spectra were recorded on an inVia confocal Raman microscope  equipped with an argon ion laser at an excitation wavelength of 514.5 nm. X-ray powder diffraction (XRD) patterns were recorded on a D/max 2500VB2+/PC X-ray diffractometer  using a Cu–Kα radiation source. X-ray photoelectron (XPS) spectroscopy was performed to carry out the surface elemental and chemical state analysis of composite films using an ESCALAB–250 XPS spectrometer  equipped with a focused monochromatized Al–Kα radiation source. Fourier-transform infrared (FTIR) spectra were recorded on a Nicolet iS5 infrared spectrometer  in the wavelength range of 400–4000 cm−1 at a resolution of 2 cm−1. A PPMS-9 vibrating sample magnetometer  was used to analyze the magnetic properties of graphene/Fe3O4 hybrids under an applied field of −30,000–30,000 Oe. The magnetization saturation, magnetic retentivity and coercivity were derived from the resultant comparative magnetic hysteresis loops. Mercury intrusion porosimetry was carried out to measure the pore size and volume of aerogel films using an AutoPore V 9600 mercury porosimeter  in the pressure range of 0.5–62354.60 Psia.Scanning electron microscopy (SEM) was conducted to observe the morphology and microstructure of composite films using a SUPRA™ 55 scanning electron microscope  at an acceleration voltage of 20 kV. Energy-dispersive X-ray (EDX) spectroscopy was performed to analyze the surface elemental compositions and distributions of composite films using a INCAX-Act EDX spectrometer . Transmission electron microscopy (TEM) was performed to characterize the morphology and microstructure of graphene/Fe™ 875–1i IR thermal imaging camera . Their surface temperatures were recorded as a function of time as determined from the IR thermographic analysis using the Testo™ ComSoft Basic software. IR stealth and thermal camouflage behaviors were examined on different high-temperature targets covered with the aerogel/PEG composite films developed in this work using the same IR thermal imaging camera. The electromagnetic measurements were performed using a PNA-N5244A vector network analyzer  in the frequency range of 2–18 GHz. In a typical procedure, the composite film was tailored into several pieces and then mixed with paraffin at a mass ratio of 2:1. The as-prepared mixture was compressed into a toroidal shape with an outer diameter of 7.0 mm, an inner diameter of 3.0 mm, and a thickness of about 1.5 mm to fit the sample holder in the instrument. A transmission/reflection method was adopted to measure the electromagnetic parameters using the vector network analyzer, and the permittivity and permeability of the sample were determined from the obtained electromagnetic parameters.Tensile measurements were carried out using a CMT–4101 electronic universal materials testing machine  at a tensile loading rate of 1 mm/min. Differential scanning calorimetry (DSC) was conducted under nitrogen flux using a Q20 differential scanning calorimeter  with a ramp rate of 10 °C/min. Indium was used as a standard to calibrate the deflections of phase-change temperature and enthalpy. Thermogravimetric analysis (TGA) was carried out using a Q50 thermogravimetric analyzer  with a ramp rate of 10 °C/min under a nitrogen atmosphere. A high-temperature heat impact experiment was carried out to evaluate the shape/form stability and leakage prevention performance of composite films with isothermal heating at 120 °C on a high-precision electronic hot plate, and the aspects of specimens were monitored in real-time using a digital camera . IR thermography was adopted to characterize the thermal regulation performance of composite films during the isothermal heating and natural cooling processes using a Testo3O4 hybrid as a microwave absorbing filler was obtained from decorating graphene nanosheets with Fe3O4 nanoparticles using an in situ hybridization method. 3O4 hybrid. Pristine graphene nanosheets show an ultrathin layered structure with crumpled and rippled textures and curled edges. The thickness of graphene nanosheets was determined to be 2.5–3 nm according to the AFM analysis as seen in 3O4 nanoparticles can be clearly distinguished from the surface of graphene nanosheets as observed in 3O4 nanoparticles are well dispersed on the graphene surface without any agglomerations, indicating that the graphene nanosheets act as a framework and network to support and separate the loaded Fe3O4 nanoparticles. 3O4 hybrid. Both of them were found to exhibit typical graphene characteristic bands by showing the C–OH, C–O–C, C=O absorption peaks in their FTIR spectra. It is worth noting that the IR spectrum of graphene/Fe3O4 hybrid shows a new Fe–O characteristic absorption peak at 584 cm−1 compared to that of pristine graphene nanosheets, indicating the presence of Fe3O4 nanoparticles on the graphene nanosheets [3O4 hybrid and pristine graphene nanosheets. Only an intensive diffraction peak was observed at 2θ = 26.7° assigned to the (002) plane of graphene from the XRD pattern of pristine graphene nanosheets. However, the XRD pattern of graphene/Fe3O4 hybrid not only shows a diffraction peak for the (002) reflection of graphene but also exhibit a set of diffraction peaks at 2θ = 30.4°, 35.8°, 43.2°, 54.1°, 57.5°, and 63.1° assigned to the (220), (311), (400), (422), (511), and (440) reflections of Fe3O4 nanoparticles, respectively, according to the standard JCPDS No. 19-0629 [−1 corresponding to the D, G, and 2D vibrational modes of graphene nanosheets, respectively. In contrast, the Raman spectrum of the graphene/Fe3O4 hybrid shows the extra Raman peaks at 218.9, 280.3, 389.1, 590.9, and 480.1 cm−1 associated with the A1g, Eg, and T2g vibrational modes of Fe3O4 nanoparticles in addition to the Raman peaks of graphene nanosheets [3O4 hybrid with an ultrathin laminar structure and small lateral dimensions. 3O4 nanoparticles and a graphene/Fe3O4 hybrid as well as pristine graphene nanosheets as a control. Pristine graphene nanosheets show no magnetic response, whereas Fe3O4 nanoparticles exhibit a typical magnetic hysteresis behavior with a saturation magnetic moment of 63.9 emu/g under the applied magnetic field. Furthermore, Fe3O4 nanoparticles present extremely low magnetic retentivity and coercivity according to the magnetization result, indicating a superparamagnetic feature. It is of importance to note that the graphene/Fe3O4 hybrid shows a similar magnetic hysteresis behavior to the Fe3O4 nanoparticles, and their saturation magnetic moment decreases to 27.1 emu/g in the presence of diamagnetic graphene nanosheets. Nevertheless, the negligible coercivity and remanent magnetization reveal that the graphene/Fe3O4 hybrid is superparamagnetic. In addition, the graphene/Fe3O4 hybrid is easily dispersed in water to form an aqueous suspension through ultrasonication, and it can be attracted onto the beaker wall using a magnet as observed from the insert in 3O4 hybrid is ready for use in the PI-based hybrid aerogels as a microwave absorbing filler.The graphene/Fenosheets . Figure nosheets . These r3O4 hybrid aerogel films with a graphene content of 5 wt% and different Fe3O4 content were prepared through polycondensation of PAAs as a water-soluble PI precursor, premixing of PAAs with the graphene/Fe3O4 hybrid, film casting, freeze-drying, and thermal imidization according to the fabrication method shown in 3O4 hybrid aerogel films with different loadings of graphene/Fe3O4 hybrid. As seen in 3O4 hybrid. Moreover, it is observed from the close-up SEM images in 3O4 hybrid can be clearly distinguished as small particles from the cell wall as seen in A series of PI/graphene/Fe3O4 hybrid aerogel films were characterized with EDX, FTIR, XRD, and XPS using the hybrid aerogel film containing 5 wt% of graphene nanosheets and 6 wt% of Fe3O4 nanoparticles as a representative. As observed from the EDX spectrum in −1 (C=O), 1494 cm−1 (C=C in benzene ring), 1374 cm−1 (C–N), 1231 cm−1 (C–O), 827 cm−1 (C–H), and 585 cm−1 (Fe–O), corresponding to PI and graphene/Fe3O4 hybrid as marked in 3O4 nanoparticles affects the chemical structure of the PI matrix as observed from the FTIR spectrum of the hybrid aerogel film in 3O4 nanoparticles were identified in the XRD pattern of the hybrid aerogel film. In addition, the XPS survey spectrum of the hybrid aerogel film in 3O4 hybrid for the hybrid aerogel films. These results confirm the successful fabrication of PI/graphene/Fe3O4 hybrid aerogel films with the desired morphology, microstructure, and chemical structure.The elemental distribution and chemical structure of the PI/graphene/Fe3O4 hybrid aerogel films were investigated by mercury intrusion porosimetry, and the resultant mercury intrusion and pore size distribution curves are shown in 3O4 hybrid aerogel film exhibit a fast increase in the total volume of mercury intrusion at a pore size larger than 40 μm, indicating a macroporous feature of the aerogel films. These macropores also show a wide size distribution ranging from 10 to 100 μm. It should be noted that there is a slight decrease in the mean pore diameter and total immersion volume of the hybrid aerogel films with the addition of the graphene/Fe3O4 hybrid as observed in 3O4 content. This may be due to the nucleation effect of Fe3O4 nanoparticles in the process of cell formation, resulting in smaller cells [3O4 nanoparticles as well as graphene nanosheets as inorganic fillers improves the viscosity of the PAAs costing solution, restricting the coalescence and growth of cells [3O4 hybrid. In summary, these porosity characteristics maximize the volume capacity of the hybrid aerogel films to load a great quantity of PEG and meanwhile minimize the leakage of PEG in the molten state.The porosity characteristics of pure PI aerogel film and PI/graphene/Feer cells . Furtherof cells . However3O4 aerogel/PEG composite films were fabricated using a simple vacuum impregnation method as depicted in 3O4 aerogel/PEG films with a graphene content of 5 wt% and different Fe3O4 contents. It is of importance to note that all composite films have been fully impregnated with PEG in their cellular framework, and almost no void is observed. The loading amount of PEG in these composite films were determined to be 88–90 wt%, indicating an extremely high loading of PEG in the PI-based aerogel composite system. Such a high loading quantity can be attributed to a huge pore volume and a large specific surface of the aerogel films, generating a capillary force to anchor PEG macromolecules in the pores together with the hydrogen bond from the cell wall [PI/graphene/Feell wall .3O4 hybrid aerogel films were characterized with EDX, FTIR, and XRD using the hybrid aerogel film containing 5 wt% of graphene nanosheets and 6 wt% of Fe3O4 nanoparticles as a representative. −1 for the O–H bond, 2884, 1466, 1342, 961 and 844 cm−1 for the C–H bond, and 1097 and 1145 cm−1 for the C–O–C bond. These IR characteristic bands are derived from the PEG loaded in the hybrid aerogel film [θ = 19.2° and 23.4° assigned to (120) and (132) planes of PEG  of 183.6 J/g at a crystallization peak temperature (Tc) of 35.7 °C a fusion enthalpy (ΔHm) of 188.7 J/g at a melting peak temperature (Tm) of 61.4 °C. These results indicate that PEG possesses a high latent-heat capacity as an organic PCM. It is of importance to note a slight decrease in Tc but a slight increase in Tm taking place in the hybrid aerogel/PEG composite films. The decrease of Tc can be ascribed to the capillary effect generated by the PI-based framework. Under a capillary force, the motion of PEG macromolecular chains is greatly restricted during the crystallization process, resulting in a higher temperature required for the crystallization of PEG [Tc’s of the hybrid aerogel/PEG composite films tend to decrease with an increase in the Fe3O4 content. This may be due to the reduction of cell volume in the hybrid aerogel, resulting in more serious geometric confinement. On the other hand, the Tm’s of the hybrid aerogel/PEG composite films were also found to increase with an increase in the Fe3O4 content. This can be explained by the fact that the presence of the PI-based framework postpones the heat transfer of the composite system, delaying the melting process of the PEG loaded in the aerogel. Accordingly, a delayed thermal response occurs in the loaded PEG during the heating process, resulting in an increase in Tm [Hc and ΔHm. This indicates that there is a high mass fraction of PEG loaded in the aerogel system, imparting a high latent-heat capacity of approximately 159 J/g to the hybrid aerogel/PEG composite films. Such a high heat storage capacity is adequate for practical use in IR stealth and thermal camouflage.Phase-change behavior plays an important role in heat energy absorption, storage, and release of a PCM at the desired temperature, speed, and quantity for practical use. The phase-change behavior and thermal performance of PI/graphene/Fen of PEG ,38. It ise in Tm . It is w3O4 aerogel/PEG composite films were investigated through a thermal cycling experiment with consecutive heating-cooling cycles between 0 and 100 °C for 500 cycles. DSC measurements were conducted for the samples after every 50 thermal cycles. The phase-change durability and long-term heat energy storage-release stability of the PI/graphene/Fe3O4 aerogel/PEG composite films were investigated using TGA, and pure PEG and the PI/PEG composite film were also examined as controls. Tmax) is generally used as an indicator to reflect the thermal stability of the polymeric material [Tmax’s of all samples were determined from the peak temperatures of their DTG curves as shown in Tmax’s than pure PEG. It is also noted in The thermal stability of the PI/graphene/Fematerial . The Tma3O4 aerogel/PEG composite films were evaluated through an isothermal heat-impact experiment, with pure PEG and the PI/aerogel/PEG composite film examined as controls. In this experiment, all samples were cut into square chips and then subjected to an isothermal heat impact on the hot plate at 120 °C, and their appearances were monitored using a digital camera during the isothermal heating process. The shape stability and heat-impact resistance of the PI/graphene/Fe3O4 aerogel/PEG composite film, PI aerogel/PEG composite film, and PI/graphene/Fe3O4 hybrid aerogel film were investigated comparatively using a facile IR thermographic method. These three samples were subjected to heating up to 90 °C using a hot plate as a heat source and then natural cooling down to room temperature. Their surface temperatures as well as the background temperature were monitored using an IR thermal imaging camera during the heating and cooling processes. 3O4 hybrid aerogel film shows a visible color change from dark blue through light purple to yellow during the heating process, representing a rapid rise in surface temperature. An opposite phenomenon can be observed from the hybrid aerogel film in the natural cooling process, reflecting a drastic decrease in surface temperature without a discernible delay. These results can be confirmed by its temperature evolutions with heating and cooling time derived from IR thermographic analysis. Both the PI aerogel/PEG and the hybrid aerogel/PEG composite films were found to exhibit a lower color change than the PI/graphene/Fe3O4 hybrid aerogel film during the heating and cooling processes, indicating a delayed temperature change with regard to the hybrid aerogel film. The plots of temperature evolution with time clearly show two temperature hysteresis regions appearing in the heating and cooling processes as observed from The thermal buffering and temperature-regulating behaviors of the PI/graphene/Fe3O4 aerogel/PEG composite films. In general, the latent heat resulting from a phase transition in the physical states is many times greater than the sensible heat required to raise a solid or liquid to its melting or boiling temperature. Therefore, such a huge amount of latent heat adsorbed or released can lead to a tardy response to background temperature, generating an extra thermal buffering effect on the composite film. However, the total quantity of thermal energy absorbed or released by the PI/graphene/Fe3O4 hybrid aerogel film is only dominated by sensible heat energy in the absence of PCM, resulting in a continuous process in the temperature evolution without any hysteresis. It is noteworthy that the PI/graphene/Fe3O4 aerogel/PEG composite film exhibits a slower temperature evolution and more significant temperature hysteresis compared to the PI aerogel/PEG one as seen in As reported in the literature, the total quantity of heat energy absorbed or released by a material is normally determined by two forms of energy, i.e., sensible heat and latent heat. Sensible heat energy describes the energy exchange between a system and its surroundings, whereas latent heat represents the changes in the internal heat energy of a system . As an o3O4 hybrid aerogel film and hybrid aerogel/PEG composite film were investigated through infrared thermographic detection using a hot plate at 90 °C as a simulated high-temperature target. 3O4 hybrid aerogel film can generate a partial IR stealth effect through heat insulation to block IR emission from the high-temperature target. The PI/graphene/Fe3O4 aerogel/PEG composite film was found to exhibit a better IR stealth effect than the hybrid aerogel film by showing a target color closer to the background as seen in 3O4 aerogel/PEG composite film and a lower PI/graphene/Fe3O4 hybrid aerogel film is applied to the high-temperature target  and complex permeability (μr = μ′ − jμ″), the real parts, ε′ and μ′, represent the storage capability of electric and magnetic energy, respectively, whereas the imaginary parts, ε″ and μ″, reflect the dissipation ability of electric and magnetic energy, respectively [3O4 nanoparticles. In general, the dielectric loss of a material is related to the polarization relaxation and/or conductive loss, and it can be used to identify the EM energy dissipation ability of a material [3O4 nanoparticles compared to the PI/graphene/Fe3O4 hybrid aerogel/PEG composite films as shown in Microwave absorption plays a critical role in the realization of EM stealth because RADAR is the use of reflected EM waves in the microwave part of the spectrum to detect targets or map landscapes. EM stealth requires that a target-like craft absorbs incident RADAR pulses, actively cancels them by emitting inverse waveforms, deflects them away from receiving antennas, or all of the above. Both absorption and deflection are the most important prerequisites of EM stealth . In the ectively ,46. It cmaterial . The PI/material . The lowmaterial . However3O4 hybrid aerogel/PEG composite films exhibit significantly enhanced real parts and imaginary parts of their complex permeability along with an improvement in the dielectric loss. Their real parts and imaginary parts were found to continuously increase with an increase in the Fe3O4 content, followed by an increasing improvement in dielectric loss as seen in 3O4 content, resulting in an increase in magnetic loss [3O4 nanoparticles generates a synergistic enhancement effect on dielectric and magnetic losses. According to the electromagnetic theory, the dielectric and magnetic losses of the hybrid aerogel/PEG composite films may be attributed to natural resonance, Debye dipolar relaxation, and electron polarization relaxation as well as the interfacial polarization resulting from their multiporous structure and multiple interfaces [3O4 hybrid aerogel films. As depicted in 3O4 nanoparticles attenuates microwave energy through both dielectric loss and magnetic loss. The interfaces between the graphene nanosheets and Fe3O4 nanoparticles also generate multiple scattering and interfacial polarization, consequently increasing the microwave absorption [3O4 nanoparticles not only changes the graphene lamellar structure but also acts as polarized centers to facilitate the electromagnetic energy absorption. Furthermore, both the dielectric and the magnetic losses exhibit dependence on frequency, and they decrease with an increase in frequency [3O4 hybrid aerogel/PEG composite films have a good microwave absorption ability to meet the requirement of EM stealth applications.It is worth noting that the PI/graphene/Fetic loss . Moreoveterfaces . Figure sorption . Thereforequency . This marequency . However3O4 hybrid aerogel/PEG composite films, the reflection loss (RL) could be determined according to the transmit-line theory and calculated using the following equations [Zin is the input impedance of the composite films, Z0 is the impedance in free space, c is the velocity of light, f is the frequency of EM wave, εr and μr are the complex permittivity and complex permeability, respectively, and d is the thickness of the composite film. In general, a higher absolute value of RL reflects a stronger ability to absorb EM waves. 3O4 hybrid aerogel/PEG composite film through calculation with Equations (2) and (3). It can be seen in 3O4 hybrid aerogel/PEG composite film, its minimum reflection loss was found to reach −38.5 dB at a frequency of 13.5 GHz and a thickness of 2.8 RL(d 2.8 see c. The ba3O4 hybrid aerogel and PEG for EM and IR bi-stealth applications. A series of PI/graphene/Fe3O4 hybrid aerogel films were first constructed through prepolymerizaton, film casting, freeze-drying, and thermal imidization, and then PEG as a PCM was impregnated into the aerogel framework under a vacuum condition. The resultant hybrid aerogel films not only showed ultralight, robust foldable, and flexible characteristics but also achieved a good microwave absorption capability as a result of the introduction of the broad-band EM-absorbing materials, i.e., graphene nanosheets and Fe3O4 nanoparticles. The hybrid aerogel films also exhibit a high PEG loading of near 90 wt% thanks to their macroporous structure and large pore volume. The resultant hybrid aerogel/PEG composite films gained a good thermal management capability to implement temperature regulation through thermal energy absorption and release under a latent-heat capacity of over 158 J/g. These multifunctional composite films also exhibit high heat-impact resistance and good thermal cycle stability to meet the requirement of long-term use for EM and IR bi-stealth applications. More importantly, the multifunctional composite films present a wideband absorption capability at 7.0–16.5 GHz and a minimum reflection loss of −38.5 dB. This results in excellent EM and IR bi-stealth performance through the effective wideband microwave absorption of graphene/Fe3O4 component and the thermal buffer of PEG. Through an innovative integration of PI-based functionalized multiporous materials and PCMs, the resultant multifunctional composite films gained a superior ability to implement EM and IR bi-stealth. This study offers a new strategy for the design and development of high-performance and lightweight EM–IR bi-stealth materials to meet the requirement of stealth and camouflage applications in military equipment and defense engineering.In summary, we have developed a novel type of multifunctional phase-change composite films based on PI/graphene/Fe


CTD-2528L19.6, which was up-regulated in early-stage IPF compared to normal lung tissue, and subsequently down-regulated during advanced-stage IPF. CTD-2528L19.6 was indicated to regulate fibroblast activation in IPF progression by mediating the expression of fibrosis related genes LRRC8C, DDIT4, THBS1, S100A8 and TLR7 et al. Further studies showed that silencing of CTD-2528L19.6 increases the expression of Fn1 and Collagen I both at mRNA and protein levels, promoted the transition of fibroblasts into myofibroblasts and accelerated the migration and proliferation of MRC-5 cells. In contrast, CTD-2528L19.6 overexpression alleviated fibroblast activation in MRC-5 cells induced by TGF-β1. LncRNA CTD-2528L19.6 inhibited fibroblast activation through regulating the expression of LRRC8C in vitro assays. Our results suggest that CTD-2528L19.6 may prevent the progression of IPF from early-stage and alleviate fibroblast activation during the advanced-stage of IPF. Thus, exploring the regulatory effect of lncRNA CTD-2528L19.6 may provide new sights for the prevention and treatment of IPF.Long non-coding RNAs (lncRNAs) have emerged as critical factors for regulating multiple biological processes during organ fibrosis. However, the mechanism of lncRNAs in idiopathic pulmonary fibrosis (IPF) remains incompletely understood. In the present study, two sets of lncRNAs were defined: IPF pathogenic lncRNAs and IPF progression lncRNAs. IPF pathogenic and progression lncRNAs-mRNAs co-expression networks were constructed to identify essential lncRNAs. Network analysis revealed a key lncRNA  IPF is likely driven by abnormal epithelium and propagated by dysregulated overabundant, heterogeneous fibroblast population in various states of activation5. It has been reported that transforming growth factor-β1 (TGF-β1) plays a key role in the development of IPF and TGF-β1 gene polymorphisms may affect disease progression in patients with IPF6. Survival rate of the advanced-stage IPF patients at 5 years is much lower than that of early-stage IPF7. Although emerging evidence indicates that genetic studies may hold promise in the connections between early-stage and advanced-stage disease8, no special study focuses on analyzing the difference of gene expression during different stages of IPF. Thus, a comprehensive understanding of the pathogenesis and progression mechanisms involved in IPF remains elusive.Idiopathic Pulmonary Fibrosis (IPF) is a progressive and chronic disorder that has been characterized by excessive wound repair and fibrosing interstitial pneumonia of unknown etiology11. Some studies developed IPF signatures based on lncRNAs expression analysis. For example, lncRNA H19 functions as a molecular sponge of miR-196a, which provides a novel therapeutic target for IPF14. LncRNA MALAT1, E2F1, and YBX1 may be key regulators for the pathogenesis of IPF, in the peripheral blood of IPF patients15. LncRNA sirt1 antisense was reported to inhibit TGF-β1-mediated epithelial-mesenchymal transition in vitro and alleviate the progression of IPF in vivo16. Crosstalk among non-coding RNAs plays a crucial regulatory role in the progression of IPF17. Savary et al. demonstrated that lncRNA DNM3OS regulates myofibroblast activation by giving rise to profibrotic mature miRNAs, such as miR-199a-5p/3p and miR-214-3p18. Interfering with DNM3OS function not only prevents lung fibrosis but also improves established pulmonary fibrosis. LncRNA ZFAS1 promotes the progression of pulmonary fibrosis and facilitates the proliferation and phenotypic differentiation of fibroblasts into myofibroblasts via functioning as a ceRNA19, and lncRNA Hoxaas3 promotes lung fibroblast activation and fibrosis by targeting miR-450b-5p to regulate Runx120. Huang et al. demonstrated that lncRNA FENDRR exhibits anti-fibrotic activity in pulmonary fibrosis21. Recently, we have reported several functional lncRNAs as targets for the treatment of fibrosis, and designated three pulmonary fibrosis regulatory associated lncRNAs  that promote lung fibrosis by competitively binding miRNA24.Long non-coding RNAs (lncRNAs) are one type of non-coding RNAs with lengths greater than 200 nucleotides. The aberrant expression of lncRNAs has been linked to multiple biological processes involved in IPF26. The changes in lncRNAs expression may affect the stability and translation of genes involved in lung fibrosis26. Hao et al. reported that lncRNA AP003419.16 regulates its adjacent gene RPS6KB2, which regulates the process of IPF27. Increasing studies suggest new theories for the pathogenesis and treatments of IPF25. Thus, systematically exploring the deregulation mechanism between lncRNAs and mRNAs in different stages of IPF will enhance our understanding of the progression of IPF.Previous studies provided insights into the crosstalk between mRNAs and lncRNAs to explore the regulatory mechanism in pulmonary fibrosisCTD-2528L19.6, which was up-regulated in the early-stage of IPF patients but down-regulated in advanced-stage IPF patients. In vitro assays, consistent with bioinformatics analysis of IPF progression in context: CTD-2528L19.6 was proven to alleviate fibroblast activation by regulating LRRC8C in MRC-5 cells and the silencing CTD-2528L19.6 promoted pulmonary fibrosis. In summary, our study highlighted that CTD-2528L19.6 may prevent the progression of IPF by alleviating fibroblast activation.In this study, we identified IPF pathogenic and progression related mRNAs and lncRNAs by constructing a pathogenic network and two dynamic progression networks for IPF. Our study revealed a core IPF regulatory sub-network centered on the lncRNA vs. normal; (2) advanced-stage IPF vs. normal; (3) advanced-stage IPF vs. early-stage IPF. The methodological workflow for this study is summarized in Supplementary Fig. SP < 0.01, Student’s t-test, Fig. CTD-2528L19.6, NR2F1-AS1 were significantly up-regulated in early-stage of IPF compared with normal lung and then down-regulated in advanced-stage of IPF  genes (DEGs) for the following three comparisons: 1) early-stage IPF  early-stThen, 43 DE lncRNAs and 835 DE mRNAs that were differentially expressed in both early-stage and advanced-stage IPF compared to normal samples, were defined as IPF pathogenic signatures. IPF pathogenic lncRNAs and mRNAs showed consistently up-regulated or down-regulated expression in both early-stage and advanced-stage IPF compared with normal samples Fig. . A similFDR < 0.05, Hypergeometric test, Supplementary Fig. SFDR < 0.05, Hypergeometric test, Supplementary Fig. S29.Additionally, we performed pathway enrichment analyses to investigate the potential functional mechanisms involved in pathogenesis and progression of IPF. IPF pathogenic mRNAs participated in pathways related to immune system and inflammation, including “Phagosome”, “Antigen processing and presentation”, “Cell adhesion molecules (CAMs)”, “Focal adhesion” and “ECM-receptor interaction”   Fig. . The lncst) Fig. . A sub-nR2 = 0.99, P < 0.01, Goodness of fit test, Fig. CTD-2528L19.6 was co-expressed with 15 mRNAs in this network  and TLR7  that co-expressed with CTD-2528L19.6 have been reported to be novel biomarkers of IPF fibrosis32. DDIT4, whose expression was significantly positively co-expressed with CTD-2528L19.6 , was contained in 42% of fibrosis related gene sets, which were annotated in the MSigDB database  and CTD-2528L19.6 . THBS1, which showed significant positive co-expression with CTD-2528L19.6 , was contained in 84% fibrosis related gene sets  showed significantly up-regulation in advanced-stage of IPF and the other two makers  were marginally significantly up-expressed in advanced-stage of IPF compared with early-stage of IPF . FISH results showed that CTD-2528L19.6 was expressed in both the nucleus and the cytoplasm  to explore the effects of CTD-2528L19.6 knockdown on the proliferation, migration and trans-differentiation of MRC-5 cells  against CTD-2528L19.6 in IPF. We demonstrated that lncRNA CTD-2528L19.6 participates in the pathogenesis and progression of IPF in different stages with different mechanisms. In MRC-5 cells, up-regulation of CTD-2528L19.6 prevented the fibrosis progression of IPF by alleviating fibroblast activation. LncRNA CTD-2528L19.6 inhibited fibroblast activation through regulating the expression of LRRC8C in vitro assays. Silencing of CTD-2528L19.6 promoted fibroblast activation, which may be a novel biomarker for IPF.In this study, by systematical analysis of transcriptome profile, we revealed a set of differentially expressed lncRNAs in IPF compared with normal lung tissues. Interestingly, some lncRNAs were up-regulated in the transition from normal lung to early-stage IPF, subsequently down-regulated during the transition to advanced-stage IPF. The lncRNA-mRNA co-expression network-based transcriptome analysis revealed a key fibrosis regulator lncRNA CTD-2528L19.6 was increased in early-stage of IPF and decreased in advanced-stage IPF. The dysregulation and effect of CTD-2528L19.6 in IPF is similar to the MMP13, whose expression is up-regulated during two stages after fibrosis whereas knockdown of MMP13 could aggravate the progression of lung fibrosis35. Thus, we inferred that, at the early-stage of IPF, the adaptive up-regulating CTD-2528L19.6 is sufficiently to partially offset the activation of fibroblasts. However, with long-term stress, a sustained increase of the fibroblasts beyond a certain threshold could counteract the function of CTD-2528L19.6 up-regulation, leading to the development of fibroblast activation. Also, the biological experiments in our work revealed that enhanced expression of lncRNA CTD-2528L19.6 prevents the activation of fibroblast, which confirmed our hypothesis.Expression of CTD-2528L19.6 may prevent the progression of IPF and exhibit anti-fibrotic activity by regulating the expression of fibrosis associated mRNAs. In IPF pathogenesis network, mRNA DCLRE1C is a member of the non-homologous end joining pathways, and deleterious mutations which can cause severe combined immunodeficiency36. In early-stage IPF progression networks, mRNA S100A8 has been reported in bronchoalveolar lavage fluid as a biomarker of IPF fibrosis31. In advanced-stage IPF progression network, mRNA THBS1 is co-expressed with CTD-2528L19.6, which activates the reproduction of fibroblast cells in mice37. TLR7 has been revealed to be a novel IPF associated gene and biomarker32, and is dysregulated in IPF pathogenesis38. In IPF progression network, genes S100A8 and TLR7, which were positively correlated with the expression of CTD-2528L19.6, act as immune cell markers32. The crosstalk analysis between mRNAs and lncRNAs highlights the important role of immune regulation in IPF, which warrants further detail in vitro or in vivo biological experiments. The functional relationship between LRRC8C and CTD-2528L19.6 in fibrosis was proved in vitro assays. LncRNA CTD-2528L19.6 inhibited fibroblast activation through regulating the expression of LRRC8C. Limited by the sample amount of IPF data set, we did not control the FDR when performing differential expression analysis. However, the roles of CTD-2528L19.6 in IPF predicted by bioinformatics analysis could be validated by cellular experiments and some correlated genes were proved to be involved in IPF by functional annotation. Another key lncRNA NR2F1-AS1 with many transcripts was not tested in this study, which is worthy of our follow-up in-depth research. Notably, the lncRNA TP53TG1, which is most frequently co-expressed with mRNAs in IPF pathogenesis network, also deserves our following study.CTD-2528L19.6 was captured to regulate the pathogenesis and progression of IPF as a potential biomarker. CTD-2528L19.6 may regulate fibroblast activation in IPF progression by mediating the expression of some mRNAs, such as LRRC8C, DDIT4, THBS1, S100A8 and TLR7. Our results suggest that during early-stage, CTD-2528L19.6 was up-regulated to prevent IPF, while CTD-2528L19.6 was down-regulated to promote fibroblast activation from early-stage to advanced-stage transition. This finding provides a framework for designing interventions that could prevent the development or progression of fibrosis at various stages of IPF development. The present research also reveals some lncRNAs as potential IPF biomarkers.Overall, we predicted IPF pathogenic and progression related lncRNAs and mRNAs through analyzing transcriptional profile, then constructed an IPF pathogenic lncRNA-mRNA co-expression network and dynamic IPF progression networks. A key lncRNA 39, with 17 IPF (8 early-stage IPF and 9 advanced-stage IPF) and 6 normal lung tissues, was downloaded from the Gene Expression Omnibus  https://www.ncbi.nlm.nih.gov/sra/).GSE10667 and GSE73854 were collected from the GEO and SRP10849 was download from The Sequence Read Archive  early-stage IPF vs. normal; (2) advanced-stage IPF vs. normal; (3) advanced-stage IPF vs. early-stage IPF. We selected genes with P < 0.01 as DEGs, including DE lncRNAs and DE mRNAs. The DEGs derived from both (1) and (2) were defined as IPF pathogenic signatures. And, the DEGs detected from both (1) and (3) were defined as IPF progression signatures, as showed in Supplementary Fig. SWe performed three comparisons using Student’s r > 0.8 and P-value < 0.01 were included in the co-expression network.Pearson correlation test was used to test the expression correlation between differential expressed lncRNAs and mRNAs. The lncRNA-mRNA pairs with the absolute value of correlation coefficient Then, a pathogenic co-expression network between IPF pathogenic lncRNAs and mRNAs was constructed in IPF samples. Two IPF progression co-expression networks between IPF progression lncRNAs and mRNAs were constructed in early-stage IPF and advanced-stage IPF samples, respectively , including fibroblast related gene sets. These annotated sets of genes involved in fibrosis related biochemical pathways, signaling cascades, expression profiles from research publications, and other biological concepts41. IPF cell markers  were collected from the CellMarker database (http://biocc.hrbmu.edu.cn/CellMarker/)42.Fibrosis related gene sets were collected from the Molecular Signatures Database , consists of six top categories (09100 to 09160) for KEGG pathway maps. The hypergeometric distribution model was used to test whether KEGG pathways were enriched with genes in the co-expression network. The P-value was adjusted by the Benjamini-Hochberg (BH) procedure. The pathways with a false discovery rate (FDR) less than 0.05 were considered to be significant.Pathway information was downloaded from Kyoto Encyclopedia of Genes and Genomes (KEGG) on August 17, 2017 (2. PCR was used to synthesize the full-length of lncRNA CTD-2528L19.6 and inserted into the pcDNA3.1 vector. pcDNA3.1 empty vector was used as control. LncRNA smart silencer SSi-CTD/SSi-NC (negative control) was constructed by RiboBio Tech . CTD-2528L19.6 plasmid or SSi-CTD/SSi-NC and Lipofectamine 2000  transfection reagents were mixed with Opti-MEM  in serum-free medium, respectively. Then incubated for 5 min and protected from the light. Mixed two liquids and placed for 15 min at room temperature, then added to the cell plate and cultured in incubator. After transfection 6 h replaced with a normal culture medium. After cells were cultured with 10 ng/ml TGF-β1  for 48 h and prepared for further analysis  containing 10% FBS  and 1% Penicillin-Streptomycin-Amphotericin B  then plated in a standard humidity incubator at 37 °C with 5% COFluorescence in situ hybridization (FISH) was performed using the lncRNA FISH Probe Mix kit . MRC-5 cells were fixed in 4% paraformaldehyde  for 10 min and then added 1 ml precooling permeable solution (5 μl Triton-X + 1 ml PBS) for 5 min at 4 °C. Added 200 μl pre-hybridization buffer into each well then incubated at 37 °C for 30 min. Then discarded the pre-hybridization buffer and added 150 μl hybridization buffer with lncRNA FISH Probe Mix, hybridized overnight at 37 °C. Later washed with buffer I (4x SSC), buffer II (2x SSC) and buffer III (1x SSC) at 42 °C. The nuclei were stained with DAPI . The images were taken under the inverted fluorescence microscope .The total RNA of cells was extracted with TRIzol reagent. The concentration and purity of extracted RNA were determined by NanoDrop 8000 . RNA reverse transcription for cDNA by using 5× All-in-One RT Master Mix. cDNA was used to detect the relative expression of mRNA by real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) in the presence of SYBR Green fluorescent dye . The relative expression level was calculated based on the Ct values and GAPDH was used as a normalized control.Total proteins of MRC-5 cells were extracted and lysed with RIPA buffer  containing protease inhibitor. Protein samples were separated on 8% sodium dodecyl sulfate-polyacrylamide gel and transferred to pure nitrocellulose  after electrophoresis. The membranes were probed with primary antibodies against β-actin , Fn1  and Collagen I . The protein expression levels were detected by the Odyssey Infrared Imaging System .After transfected and treated with TGF-β1, MRC-5 cells were fixed by 4% paraformaldehyde at room temperature for 30 min, and then permeabilized with 0.1% Triton X-100. Then, the cells were blocked with 50% goat serum and incubated with anti-Rabbit α-SMA antibody . Finally, cells were incubated with anti-rabbit IgG (H + L) (Alexa Fluor 488 Conjugate) . Nuclei were stained with DAPI. Immunofluorescence images were photographed under fluorescence microscope.According to the Cell-Light EdU DNA cell proliferation kit  instructions, the cells were incubated with 200 μl, 50 μM EdU solution. The cells were fixed with 4% paraformaldehyde and incubated in a 2 mg/ml glycine shaker. Afterwards, cells were stained with Apollo solution staining for proliferating cells. Nuclei were stained by DAPI. Images were finally photographed under the inverted fluorescence microscope.24. MRC-5 cells were seeded in 6-well plates and grown until formation of confluent monolayer. Then cells were gently scratched with a 10 μl pipette tip. The scratch healing areas were observed and photographed under microscope (×20 objective). Afterwards, the cells were transfected and added with TGF-β1. The images were taken by the Nikon Ts100 microscope  and analyzed by using Image-J. First, the images resolution was changed to 8-bit and adjust the contrast of the enhanced image. After that, smoothed the scratch edge then found edge again. Finally, set the appropriate image threshold and measured the scratch area. Wound healing rate (%)= 1-(24 h or 48 h scratch area /0 h scratch area)*100.Wound-healing migration assay was performed as previously describedt-test was used for statistical analysis between two groups. The fitting regression was constructed to modeling the relationship between CTD-2528L19.6 and IPF cell markers with linear fitting using formula = y~x with method = “lm” in R package ggplot2. All bioinformatics analyses were carried out using R software version 3.6.0 (http://www.r-project.org/). Cytoscape software (version 3.6.0) was used to visualize the lncRNA-mRNA co-expression networks. All experimental data were presented as mean ± SEM. One-way analysis of variance (ANOVA) was used to determine the statistically significant differences among multiple groups. Statistical analyses were carried out using GraphPad Prism 8.0.Student’s supplement file


Neural auto-regressive sequence-to-sequence models have been dominant in text generation tasks, especially the question generation task. However, neural generation models suffer from the global and local semantic semantic drift problems. Hence, we propose the hierarchical encoding–decoding mechanism that aims at encoding rich structure information of the input passages and reducing the variance in the decoding phase. In the encoder, we hierarchically encode the input passages according to its structure at four granularity-levels: -level. Second, we progressively select the context vector from the document-level representations to the word-level representations at each decoding time step. At each time-step in the decoding phase, we progressively select the context vector from the document-level representations to word-level. We also propose the context switch mechanism that enables the decoder to use the context vector from the last step when generating the current word at each time-step.It provides a means of improving the stability of the text generation process during the decoding phase when generating a set of consecutive words. Additionally, we inject syntactic parsing knowledge to enrich the word representations. Experimental results show that our proposed model substantially improves the performance and outperforms previous baselines according to both automatic and human evaluation. Besides, we implement a deep and comprehensive analysis of generated questions based on their types. Question generation (QG) aims to generate appropriate questions for the given passages, it is an important task in natural language processing (NLP) research, QG has many applications for various NLP tasks. For example, QG can be used to augment a question answering (QA) dataset that is expensive to obtain, construct a synthetic QA dataset and facilitate a dialogue system by controlling conversation flow through generating questions. Besides, QG can be used for an educational purpose as it can improve and enhance children’s comprehension and retention by proposing questions based on textbook passages ,2,3,4. EQG has attracted researchers’ interests for many years. In the early years, rule/template-based methods were the mainstream models for the QG task. For example, a rule-based approach was proposed to transform a declarative sentence into its interrogative counterparts, and a statistical ranker was then invoked to select the most appropriate questions and discard those of low quality . Howeversemantic drift .https://www.mturk.com/ accessed on 11 October 2021), and we ask human workers to evaluate the performances of seven models, including the previous six QG models and an extra model, Gold, for which the outputs consist of the reference questions.Since the popular automatic metrics appear to not agree with each other, we additionally examine the human evaluation as a means of further investigating the performances of these QG models. We conduct the crowd-sourcing experiment on Amazon Mechanical Turk —are better than the other five QG models, when other models are only deemed to be good (4–5).The result of human evaluation is reported in What, Which, Who, How, Where, When and Other (questions without specific interrogative words), and analyze how the QG models prefer to to generate questions of a certain type from these types. What questions, while GPT-2 generates 10% less What questions than the dataset. Among these models, RNN is the only model that generates no Where question.We split the questions into seven types: To take a closer look at the quality of question types, we investigate the overall scores of human evaluation on different types of generated questions. According to the results of Other, Semantic-Graph and Semantic-Graph* achieve the best quality on Where and When. However, our proposed model with the dictionary (model-2) is able to generate What, Which, Who, and How questions with the best quality among all models. According to human evaluation, our model-2 outperforms the other question generation models on What, Who and Other questions, especially on Other questions. It warrants noting that the vanilla RNN model achieves the highest performance on Which, How and When questions. For Where questions, our model-2 and RNN get no human score because no question of this type is evaluated.With respect to ROUGE-L scores shown in Which, How and When questions. Hence, how to incorporate more information in contextual encoding and decoding will be the future direction to be explored.Although our model achieves a superior performance over other baseline models, there is still room for improvement, as Besides, current QG models mainly focus on generating questions based on textual input, but the usage of input in other formats  receives less attention. For example, visual QG is a QG problem that takes images as the input, and its applications are also useful for the educational purpose, including child education and interactive lectures . Our furIn this paper, we propose a novel question generation model incorporating the hierarchical encoding–decoding structure in order to inject the structural information of input documents, and a context switch mechanism for the purpose of stabilizing the decoding and making the generation process more consistent. The automatic metric results in The data presented in this study are available in the


The need for photodetectors in various fields has gradually emerged, and several studies in this area are therefore being conducted. For photodetectors to be used in various environments, their transparency, flexibility, and durability must be ensured. However, the development of flexible photodetectors based on the current measurement techniques of conventional photodetectors has been difficult owing to the limitations of semiconductor materials. In this study, a new type of flexible and transparent capacitive photodetector was fabricated to address the shortcomings of conventional photodetectors. In addition, by introducing graphene electrodes to a new type of manufactured photodetector, devices with excellent overall chemical, thermal, and mechanical durability have been developed. Compared to photodetectors based on pristine Ag nanowire (AgNW) electrodes, AgNW/graphene hybrid electrode-based photodetectors exhibit a 20% higher photosensitivity. Also, the hybrid AgNW/graphene electrode on the dielectric layer exhibited low sheet resistance (~ 8 Ω/sq) and relatively high transmittance (~ 45%). For wide applicability, a photodetector must have good durability in various environments. For example, mechanical durability is fundamental, and the properties of the photodetector must be maintained even in extreme environments such as under high temperature or chemical penetration. To realize flexible and durable photodetectors and other electronic devices, the electrodes that make up the device must also be flexible and durable. In particular, in the case of the photodetector, as mentioned above, the durability of the electrode is of paramount importance because it is a device that converts applied light into an electrical signal and measures it.A photodetector operates through a mechanism that converts photons into measurable electrical signals. Photodetectors are employed in daily applications such as optical telecommunications, imaging, and biomedical sensing3, graphene8, metal nanowires10, metal nanogrids12, and thin films13. Among these alternatives, one-dimensional (1D) metal networks, such as metal nanowires and metal fiber electrodes, have been extensively studied. Numerous studies on metal networks have been conducted, and they have been actively applied owing to their low sheet resistance (10 Ω/sq), high optical transmittance (approximately 90%), and high strain value (approximately 11%)14. In particular, among these 1D metal network electrodes, AgNWs do not require a high vacuum or high-temperature deposition process and can be developed via roll-to-roll manufacturing15. For this reason, studies using AgNWs are being actively conducted.In this regard, various flexible and conductive electrodes for photodetectors have been studied, such as carbon nanotubes (CNTs)18. Typical AgNWs exhibit a diameter of ~ 40 nm, a length of ~ 120 µm, and an aspect ratio of up to 250019. Because AgNWs have an extremely small length, a large amount of AgNWs must be coated to exhibit sufficient electrical characteristics, that is, to achieve a low percolation threshold. As more AgNWs are coated, the electrical properties are improved; however, the transmittance decreases. As a result, AgNWs do not have sufficient properties to be used as a transparent electrode20. In addition, because AgNWs are manufactured based on a spin-coating process, high surface roughness is exhibited at the junction where the nanowires overlap. Finally, to solve the structural problems of AgNW, the fabrication of a gas- and thermal-stable, conductive, and flexible buffer layer for the AgNW electrodes is required, which can improve the non-uniform current flow caused by the network structure while maintaining the durability of the AgNW electrodes.However, AgNWs have fatal disadvantages as electrodes, such as low adhesiveness, high surface roughness, and low durability, a common disadvantage of metal electrodes22. Based on a previous study23, graphene was transferred to the top surface of the AgNW electrodes to improve the chemical and thermal durability while fabricating an AgNW-based photodetector.Graphene represents a two-dimensional (2D) graphite structure and is considered the most promising material with outstanding electrical, optical, and thermal properties because it can prevent the penetration of small molecules thanks to its unique honeycomb structure28. At this time, a photocurrent is produced as electrons move to the conduction band and holes to the valence band. A photodetector employing such a current measurement method is difficult to develop into a flexible and highly durable device. Most highly efficient thin-film semiconductor materials are highly brittle; hence, it is extremely difficult to fabricate them using flexible photodetectors. Through neutral plane engineering, slightly flexible photodetectors have been developed; however, the process is somewhat difficult and inefficient.In this study, the fabricated photodetectors are capacitance-based photodetectors rather than conventional ones representing a current measurement base. Conventional photodetectors are based on the principle that an electron–hole pair is generated when photons of the same or higher energy are received in an active layer made of a semiconductor having a specific bandgap31. The fabricated device is based on a structure wherein ZnS:Cu particles are dispersed in a polymer film and transparent electrodes, which are AgNWs formed on both surfaces of a composite film. By dispersing the particulate semiconductors into a flexible polymer rather than forming a thin film, the problem of easily breaking semiconductor-based photodetectors has been solved. In addition, inspired by the fact that the dielectric properties of composite films, including semiconductor particles, change upon light irradiation, it is possible to measure the capacitance generated in the composite film by using surface electrodes. In this study, for the transparent electrodes formed on both surfaces of the film, AgNWs and AgNW/graphene electrodes are used. Owing to the AgNW/graphene electrode used on the top surface of the film, the overall durability of the photodetector was further improved. A new type of next-generation flexible and durable photodetectors can be realized by introducing a graphene electrode to a capacitive photodetector whose manufacturing process is extremely simple and measurement method and principle are intuitive.In our previous study, a new type of capacitive photodetector was introduced that didn’t exist beforeN,N-dimethylformamide , Butvar  was immersed in acetone, methanol, and deionized (DI) water and washed for 10 min each time through ultrasonication. In addition, 1.0 wt% of AgNWs  in isopropanol was spin-coated on the glass at 500 rpm for 30 s and dried for 1 min at 100 °C. The prepared ZnS:Cu-PVB solution was then spin-coated on the AgNW-coated glass at 500 rpm and baked for more than 2 h at 85 °C. For the top electrode of the photodetector, AgNWs were spin coated onto the glass after the PVB solution was baked. To safely peel them off the preliminary glass substrate, the prepared samples were then soaked in DI water for 2 h to induce hygroscopic swelling of the composite film. Finally, to ensure the durability of the manufactured photodetector, graphene was transferred onto the composite film. The graphene monolayer was transferred using a poly (methyl methacrylate) (PMMA)-based wet-transfer technique . The detailed fabrication process is described in our previous paper23. An inductance–capacitance–resistance (LCR) meter  was used to measure the sample capacitance upon light irradiation31.A four-probe system comprising equal tip spacing was used to measure the sheet resistance over randomly selected points of each sample and estimate the electrical properties of the AgNW/graphene hybrid electrodes. AgNW/graphene hybrid electrodes based a capacitive photodetector were analyzed using a field emission scanning electron microscope , and the optical properties were measured using a Cary 5000 UV–visible spectrophotometer (Varian/Agilent). A cyclic bending test was conducted using a bending tester  with a digital multimeter to determine the real-time line resistance. To investigate the chemical stability, pH solutions were prepared by mixing a solution of hydrochloric acid (HCl) and sodium hydroxide (NaOH) with deionized water34. The MWS effect is known to occur in the heterojunction structures owing to the accumulation of charges at the interfaces as well as the formation of dipoles on particles or clusters. In the heterostructures, additional charge accumulations occur at the particle boundaries under an external electric field owing to the differences in dielectric characteristics (ability to hold charges) and electrical conductivity35. It is well known that the huge difference in the conductivity of the particles and polymers will lead to a large charge accumulation at the interface because the current cannot flow freely across it. The accumulated charges are directly proportional to the difference between the two conductivities, and the interface behaves like a nanocapacitor33. Thus, the assembled movements of the interfacial dipoles at the interfaces amplify the response to the incoming electromagnetic field and thus enhance the microwave absorbing capability. Based on these theories, in this study, a composite film was fabricated by dispersing ZnS:Cu particles in polyvinyl butyral (PVB), a flexible free-standing polymer. The fabricated devices were mechanically flexible and able to withstand bending with a curvature radius of several millimeters.The increase in the dielectric permittivity of the semiconductor with particle-polymer composites upon irradiation of light with a specific wavelength changes the capacitance of the composite sandwiched between the two facing electrodes. Two physical theories of “interfacial polarization” and the “Maxwell–Wagner-Sillars (MWS) effect” at particle–polymer interfaces can explain these changes in the dielectric response of the composites upon light irradiationFigure Figure By transferring graphene to the top of the AgNWs, adhesion of the upper AgNWs can be increased, and an additional current path can be formed. The average sheet resistances of the AgNW electrodes obtained at the ZnS:Cu ratios of 0.3, 0.5, 0.7, and 0.9 wt% in PVB were 8.516, 9.09, 10.864, and 12.076 Ω/sq, respectively, as shown in Fig. Here, for both AgNW electrodes and AgNW/graphene hybrid electrodes, the sheet resistance of the substrate increased as the ratio of ZnS:Cu particles in PVB increased. As the number of particles increases, the density of particles inside the thin polymer layer increases. This increases the roughness of the polymer layer, resulting in an increase in resistance.Compared to those of the AgNW electrodes, the sheet resistance of the AgNW/graphene hybrid electrodes was lower, which suggests that the AgNW/graphene hybrid electrodes delivered a better electrical performance than the AgNW electrodes. This is because, as the AgNW electrodes feature a network form, there are void spaces where the electrodes are not present, which eventually leads to an open-circuit fault. In addition, AgNWs are known to have a large surface roughness, which can easily penetrate the thin film layers. For the AgNW/graphene hybrid electrodes, the CVD graphene layer covered the entire AgNW electrodes, and the current flowed throughout all non-empty spaces. In addition, covering the CVD graphene layer has the advantage of solving the problem of the large surface roughness of the AgNWs.To investigate the optical properties of the AgNW/graphene capacitive photodetector, the transmittance, reflectance and absorption were measured depending on the ZnS:Cu particle ratio in PVB Fig. a–c. Over29. From this perspective, the AgNWs concentration should be lowered to increase the transmittance and sensitivity; however, in this study, the device was fabricated using a 1.0 wt% dispersion, which represents a relatively high density of AgNWs, to enhance the flexibility of the device. It is well known that the resistance of the AgNW electrodes is increased via repeated bending owing to the decreased number of conduction paths made by AgNWs33. When a photodetector is manufactured with low-concentration-based AgNWs, the resistance increases rapidly upon mechanical stress, and an excessively large increase in resistance hinders the transfer of charges from the power source to the dielectric, which can cause the capacitance to decrease. In conclusion, photodetectors fabricated with a 1.0 wt% AgNWs dispersion with graphene exhibited a transmittance of approximately 45% of incident light with a 550-nm wavelength.The measured transmittance of the photodetector can be evaluated as relatively low, and this is because the photodetectors were manufactured using 1.0 wt% of AgNWs. As the concentration of AgNWs increases, the overall device transmittance decreases, and the sensitivity decreasesIn addition, we can see distinctive aspects depicted in Fig. 31.The absorption spectra of different ZnS:Cu particle ratios are depicted in Fig. 2 was employed to test the photoresponsivity of the photodetectors. The photoresponsive capacitance was measured under ambient conditions using a two-probe method and a 50-kHz signal. The ZnS:Cu particle ratio-dependent photoresponsivities of the AgNW-based photodetector and that of the AgNW/graphene-based photodetector are shown in Fig. Based on the calculated ZnS:Cu-PVB composite bandgap energy, a lighting source with a wavelength of 420 nm and a power of 1.2 mW/cm36. From Fig. To measure the photoresponsivities of the fabricated photodetectors, capacitances at different wavelengths were also observed, as shown in Fig. As mentioned earlier, as the thickness of the electrodes increases, the overall device transmittance decreases, and the sensitivity decreases. This is because as the thickness of the electrode increases, the light transmitted through the ZnS:Cu-PVB composite film decreases, and the amount of charge to be transferred decreases. In the case of the AgNW/graphene photodetector, compared to the AgNW electrode-based photodetector, because the thickness of the electrode becomes thicker owing to the additional graphene electrode, it can be predicted that the photoresponsivity will be relatively lower. In addition, the result indicates that the transmittance of the AgNW/graphene photodetector is approximately 4% lower than that of the AgNW electrode-based photodetector. Nevertheless, it can be seen that the measured photoresponsivity of both photodetectors shows little difference. It can be confirmed that the lowered transmittance, which is a disadvantage caused by the additional use of the graphene electrode, does not significantly affect the photoresponsivity of the photodetectors.rb) or rolled and subsequently unrolled at a bending radius of 5 mm at a speed of 3 mm s−1. The sheet resistance of each photodetector was compared to its initial value . The tensile strain applied to the bent substrate was estimated using37The fabricated AgNW/graphene-based photodetectors exhibited a superior mechanical flexibility, which is essential for emerging flexible optoelectronic devices. A repetitive bending test was conducted to investigate their mechanical durability. During the test, photodetectors based on AgNW and AgNW/graphene electrodes were rolled at various bending radii (b). The AgNW-based photodetector exhibited changes in resistance of more than 100% at above rb = 6 mm and finally reached 700% of the initial resistance. This is because the polyvinyl pyrrolidone (PVP) on the surface of the nanowires generated during the manufacturing process weakens the adhesion to the substrate38, and as the bending radius decreases, the AgNWs at the top of the composite layer fall off. By contrast, there was little change in the resistance of the AgNW/graphene photodetector. Figure In Fig. To further evaluate whether the graphene layer acted as a protective layer against the AgNW electrodes, various solutions with pH values ranging from 2 to 12 were prepared. The AgNW and AgNW/graphene electrode-based photodetectors were then covered at each pH for 20 min. As shown in Fig. Finally, to further evaluate the thermal stability of the AgNW/graphene-based photodetector through the thermal stability of the graphene protection layer, the photodetectors based on AgNWs and AgNW/graphene were annealed on a hot plate at 160 °C for 120 h. The variations in resistance were measured every 24 h. As shown in Fig. Overall, the fabricated AgNW/graphene hybrid electrode-based photodetector exhibited an excellent performance, compared to the AgNW electrode-based photodetector, and presented stable photoswitching responsivity without being affected by the surrounding environment, that is, it was unaffected by chemicals or temperature changes. The overall results suggest that the AgNW/graphene hybrid electrode-based photodetector is expected to be used in various next-generation optoelectronic devices.We fabricated a highly stable and flexible AgNW/graphene hybrid electrode-based capacitive photodetector by wet-transferring CVD-grown monolayer graphene onto AgNW electrodes. The fabricated photodetector was inspired by the fact that the dielectric permittivity of a given semiconductor increases upon irradiation by photons with an energy equal to or higher than the semiconductor band-gap energy. The simple structure of the photodetector is composed of embedded AgNWs underneath the composite layer and another layer of AgNWs deposited on the opposite side of the composite layer, and graphene is additionally transferred to increase the adhesion of the AgNWs. Because the CVD graphene layer acts as both an excellent gas-barrier layer and a flexible buffer layer simultaneously, the AgNW/graphene hybrid electrode-based photodetector exhibits excellent chemical, thermal, and mechanical flexibility. We anticipate that this unconventional technology will advance the development of various wearable devices for next-generation electronics.


Graphene is known as an atomically thin, transparent, highly electrically and thermally conductive, light-weight, and the strongest 2D material. We investigate disruptive application of graphene as a target of laser-driven ion acceleration. We develop large-area suspended graphene (LSG) and by transferring graphene layer by layer we control the thickness with precision down to a single atomic layer. Direct irradiations of the LSG targets generate MeV protons and carbons from sub-relativistic to relativistic laser intensities from low contrast to high contrast conditions without plasma mirror, evidently showing the durability of graphene. Recent developments of laser technologies allow us to access radiation regime5 of laser ion acceleration with relatively thin targets11. However, the thinner target is the less durable and can be easily broken by the pedestal or prepulse through impact and heating prior to the main laser arrival13. One of the solutions to avoid this is plasma mirror, which is a surface plasma created by the foot of the laser pulse on an optically transparent material working as an effective mirror only for the main laser. So far, the ion acceleration in extremely thin target regime  to realize energetic ion generation11. The combinations of relatively thin targets and plasma mirrors have been successful and the proton energies are approaching 100 MeV9. However, it is costly to make thin and flat targets using conventional 3D materials, and installing and operating plasma mirrors at high repetition rate is also costly.Laser driven ion sources have been widely investigated for pure science, plasma diagnostics, medical and engineering applications15. In such small laser facilities, the radiations from the laser matter interactions by shooting 16, it is not practical for such small laser facilities. Constructing the radiation shielding is also practical unavoidable issue since the massive lead normally used for radiation shield might exceed the acceptable floor strength in such small facilities. We have to suppress the radiation itself by reducing the number of encounters of relativistic electrons with atomic nuclei in the target. To this end we have to develop a thin and strong, low Z material, reasonable to fabricate, that is, graphene. Graphene is stronger than diamond at extremely thin regime17, and much more reasonable for mass-production. Graphene has several unique features suitable for laser ion acceleration, i.e., the thinnest, lightest, transparent and the strongest material at this regime18. Direct irradiations of the LSG targets from non-relativistic to relativistic laser intensities without plasma mirror generating MeV carbons and protons evidently show the durability of graphene. We further demonstrate the durability of graphene with low contrast laser condition with We have developed large-area suspended graphene (LSG) for proton radiography intended to use laboratory astrophysics experiments with a relatively small laser facility, where no plasma mirror is equipped19. Figure 21. The small peak next to the 2D peak comes from the tiny curvature of LSG due to the large aspect ration of LSG. Note that the ideal LSG is 0.34 nm, while the obtained transferring graphene is close to 1 nm due to molecular adsorption on the surface15. By transferring graphene layer by layer, we control the target thickness at 1 nm accuracy15.The experiments are performed with the J-KAREN-P laser at the short-F chamber, Kansai Photon Science Institute in JapanBy irradiating the LSGs with the intense laser, energetic ion beams are produced. The ion diagnostics are stack detector composed of radiochromic films  and solid state nuclear track detectors  as shown in Fig. Z carbons , the carbon energies measured with the TPS in Fig. –94 MeV, 19. For reference, we also plot the first ionization threshold of carbon assuming the field ionization by laser24. The carbon ionization potential is obtained from the NIST Atomic Spectra Database25, and is plotted against charge state in Fig. 24. We do not consider here the graphene structure but just carbon atom. Nevertheless, the graphene will be destroy even one electron is kicked out by laser. In the low contrast experiment, there is a big hump of the contrast level Figure 10 all utilize the single or double plasma mirrors to suppress the pre-pulse and pedestal to realize the energetic ion acceleration. Even with such the large pre-pulse, the double-layer LSG generates MeV protons without plasma mirror. The 2 nm thick target is the thinnest target ever generated MeV protons; it is hard make 3D material as thin as this.Figure The low contrast shots with single-digit-nanometer thick LSGs are unstable; some show just proton as in Fig. 26. Measuring the laser powers at the position 1, the transmission rate T can be calculated by dividing the results with and without graphene on the hole, and thus, most reliable and the error is also small as shown in Fig. R, the optical properties of the beam splitter  and reflection rates (R), and obtain the absorption rate (A) by Figure 27, where 28. We plot the 97.7% transmission (dotted line) and 2.3% absorption (dashed line) per layer for reference in Fig. 29, and thus, the heat can diffuse quicker than other materials within the layer, but not for interlayers. As discussed above, the high contrast measurement in Fig. It is known that a single atomic layer graphene absorbs white light entclass1pt{minima30. The simulation details are given in “x direction. The laser pedestal and pre-pulse are not taken into account. We estimate the total number of electrons from LSG including water contaminations, and then replace the oxygen with carbon for simplicity; the major component of heavy ions are essentially from graphene carbons as shown in Supplementary Fig. We perform 2D particle-in-cell (PIC) simulations with an open code EPOCH33.The numerical obtained maximum ion energies are factor two larger than those in the experimental results in Fig. Another possibility account for the lower experimental results is that the LSG optical properties show in Fig. 15, where graphene is the thinnest, lightest, transparent, and strongest 2D material18. By transferring graphene layer by layer, we control the target thickness by 1 nm accuracy. We measured the LSG transmission, reflection, and absorption rates, where the transmission and reflection deviate from the theoretical prediction, however, the absorption rate is nearly identical to the theoretical expectation of 2.3% per layer, which is determined from the fine structure constant27. By irradiating the LSGs with J-KAREN laser from non-relativistic to relativistic intensities with high and low contrast conditions without plasma mirror, we successfully observe the MeV protons and carbons. With the high contrast condition, we have 16 effective shots in total and the MeV protons and carbons are stably generated in all the shots as shown in Figs. We have developed an extremely thin target, large-area suspended graphene (LSG)We also perform 2D PIC simulations with various conditions. Although the target seems ionized prior to the main laser peak, the factor two difference from the ideal simulation without considering any pre-pulse and pedestal is already significant; there is no experimental report on the energetic ion production without plasma mirror at a few nanometer thickness with other materials. This clearly shows that, even though the graphene is melted by pre-pulse, it can keep the critical density until the main laser arrival without plasma mirror. In order to understand the interactions between graphene and pre-pulse, we need molecular dynamic simulation with time dependent density functional theory, where the unique graphene properties taken into account, for instance, the absorption property of 2.3% determined with the fine structure constant and high thermal and electrical conductivities within a layer but not inter layers, together with the PIC simulations. Note that there is no comprehensive numerical code that includes the ab-initio quantum theory together with the corrective plasma dynamics. Our results imply the necessity of such code. This will be discussed elsewhere in the future.In PIC simulations, unless we use a code taking the molecular and atomic structures properly included such as the time-dependent density functional theory based molecular dynamic code, there is no difference between amorphous carbon and graphene. We take into account the ionization of carbon atoms in Fig. Our experimental and numerical results show that the target thickness is still too thin, and also that we do not need that high laser intensity to produce several MeV ions. As shown in Fig. The J-KAREN-P laser is focused with an F/1.3 off-axis parabolic mirror (OAP) on the LSG without plasma mirror. The pulse energy, duration, focal spot, and the intensity are 30. We fix the laser parameters based on the experimental conditions, and linearly polarized Gaussian beam in simulation plane. We consider the target ionization with the laser electric field via barrier suppression, tunneling, and multi photon ionization processes with a standard option of EPOCH. Ionization thresholds of atoms are cited from Atomic Spectra Database25.We perform 2D PIC simulations for the J-KAREN-P experiment using an open simulation code EPOCHx axis, we have to resolve the target in the y direction as well as the x direction.The areal density of graphene is entclass1pt{minimaSupplementary Information.