Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e., the natural particle found inside the plant, at air/aqueous interfaces, and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film. Oil in water (O/W) emulsions can be stabilized by adsorbing particles at the oil/water interfaces, i.e., the so-called Pickering type emulsions  are efficiently packed in the plant cells into semi-crystalline starch granules. Starch granules (referred to as “starch particles” from here on) can be isolated from a variety of plants, mainly from tubers and cereals. They have a considerable natural variation with respect to granule size (0.5 to 100 μm), shape  and composition  depending on its botanical origin  modified starch (OSA starch) is obtained from the esterification reaction between the hydroxyl (OH) groups on starch and octenylsuccinic anhydride, see Figure The physical properties of OSA modified starch particles affect their ability to effectively stabilize O/W emulsions. The effect of the OSA modification on the physical properties of starch particles has been studied. The hydrophobicity of a starch particle is reported to increase after the OSA modification. This modification not only increases the amphiphilicity of the starch particle, but also weakens the internal hydrogen bonding of the starch particle /hydrophilic (aqueous) interface and the effect of the OSA modification of starch particles is less understood. Studies have shown that the degree of modification of the starch particle, the weight percent of particles used in the system, and the size of the starch particles can affect the surface coverage of the oil/water interface by the particles and the stability of the droplet  of the air/aqueous interface can be systematically studied. Here, we used a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus (MPIA) , sodium chloride , and ethanol . The water used in this study was ultrapure water , which had a specific resistivity of 18.2 MΩ cm.The materials in this experiment were chloroform . Afterwards, the protein and the fiber were separated from the starch by repeated centrifugation (decanter) and wet-sieving (vibration sieve) steps. Finally, the starch suspension was neutralized and spray dried using a spray dryer   and rice starch particles modified by OSA to different degrees were used in this study. The rice starch particles were modified with OSA to give surface hydrophobized starches with a modification level of 0.46 ± 0.01, 0.97 ± 0.03, 1.40 ± 0.05, 1.90 ± 0.05, 2.36 ± 0.02% OSA by mass in dry matter of the sample. These values correspond to degrees of substitution (DS) of 0.0036, 0.0077, 0.0108, 0.0149, and 0.0186, respectively  was used to prepare the films of starch particles at the air/aqueous interface. The surface pressure was measured using a Wilhelmy plate of wet filter paper . A time of 10 min was allowed for the ethanol to evaporate. The particle films were then compressed with a speed of 80 cmAstarch) isotherms so as to enable the isotherms of the different starch particle types to be directly compared. This was necessary, as different volumes of spreading solutions needed to be spread to the air/aqueous interfaces for the different particle types, so as to measure both the loose packing and tight packing regions in each film. The area values were converted to area per starch particle (Astarch) values by calculating the number of starch particles spread at the air/aqueous interface (Nstarch). This was achieved by usingThe surface pressure (∏)-area isotherms were converted to ∏-area per starch particle , respectively. Wstarch is the mass of one particle and was calculated usingThe parameters ρstarch is the density of starch, approximated by the standard value of 1.5 g/cm3  with mean starch size was calculated usingThe maximum volume fraction of close-packed spheres is reported to be 0.74  with an epoxy resin .The colloid probes to be used in the MPIA measurements were prepared by using a light microscope  and a micro-manipulator  to attach a rice starch particle (native or OSA modified) to a gold-plated SiThe MPIA was used to measure the forces between a film of starch particles at an air/aqueous interface and the colloid probe in the water. The MPIA is comprised of a force measurement unit that is attached to a Langmuir trough . Detailed information about the MPIA can be found elsewhere  was required to convert the raw force curves (force [V] vs. piezo position [nm] curves) to the calibrated force curves (force [nN] vs. piezo position [nm] curves). This was achieved by measuring the force curves between the probe and a clean mica substrate that was placed across the edges of the Langmuir trough filled with water. CFmica was obtained from the constant compliance region (the region where the probe was in contact with the mica substrate) of these force curves. The water in the trough was removed after the calibration. The solution to be used as the subphase was then added to the trough, and that surface cleaned. The particle in ethanol spreading solution was next spread at the air/aqueous interface, after which 10 min was allowed for the ethanol to evaporate. The films were then compressed to a certain surface pressure, and the forces measured between that film and the same probe that was used to measure CFmica. A minimum of 50 force curves was recorded at each surface pressure. CFmica was used to convert the raw force curves (force [V] vs. piezo position [nm] curves) measured between the film of starch particles at the air/aqueous interface and the probe in the aqueous phase to the calibrated force curves (force [nN] vs. piezo position [nm] curves). Zero force was defined at large probe-film separations, where no surface forces acted on the cantilever. Zero distance was defined at the onset of the linear contact region in the force curves; the contact region was defined as the area where the probe was in contact with the particle film at the air/aqueous interface.The MPIA was used in the following way. First, the Langmuir trough was cleaned using chloroform and ethanol. Any remaining solvent was eliminated from the trough by adding water to the trough and then by removing it. The colloid probe was next inserted into the MPIA cantilever holder and the cantilever holder attached to the MPIA. Water was then added to the trough and its surface suctioned cleaned. The temperature of the subphase was maintained at 20.0 ± 0.1°C by running thermostated water through the base of the trough by using a circulation system . A calibration factor (CFFad) was calculated by fitting a Gaussian curve to a histogram of the adhesive forces that were calculated from the measured force curves taken at the same conditions . The effective stiffness (SN)  by the slope of the linear contact region of the force curves measured between the same probe and the mica substrate in water (S2).The magnitude of the adhesive force between the probe and the film of starch particles at the air/aqueous interface was obtained from the force curve minimum that was measured in the retraction force curves. The average adhesion force  values of the starch particles were measured with a Zetasizer  by preparing a 1,000 ppm concentration of native or modified starches dispersed in water or aqueous solutions containing NaCl. Briefly, the electrophoretic mobility was measured for each sample five times. These values were then converted into zeta potential values by using the Helmholtz-Smoluchowski approximation, assuming that the particles were spherical and large compared to the Debye length of the system. The zeta potential values of each sample type were then averaged.Astarch) isotherms, see Figure Astarch values < ~120 μm2. The surface pressure increased gradually with an Astarch decrease, suggesting a loose particle packing in the film of the NRS particles at the air/water interface. OSA modification of the rice particles caused the isotherms to shift to lower Astarch values than those measured with the NRS particles, when the same surface pressure values were compared. The isotherms also showed a change in slope from a flatter to a steeper isotherm as the particles were compressed. These two slope regions are thought to indicate films of loose packing and tight packing, respectively. The Astarch values where the phase transition from loose to tight packing films occurred moved to higher values as the degree of modification of the rice particles increased. A change in the inter-particle interactions and therefore the particle packing at the air/water interface may explain this shift in the critical Astarch values and this change in the particle packing ability.The effect of modifying the structure of rice starch on its ability to form films of starch particles at air/water interfaces was firstly investigated by spreading native rice starch particles (NRS) and OSA modified rice starch particles at air/water interfaces and then by measuring their surface pressure-area per rice starch particles (hex) was calculated using equation 4 and is shown in Figure Astarch isotherms of the native rice starch and the OSA modified rice particles are to the left of this line, then some of the particles may have been lost from the air/water interface to the subphase. The Astarch corresponding to the commencement of the tight packing region for the films of NRS, 0.6RS and 1.2RS particles were less than the Ahex value. The 1.8RS, 2.4RS, and 3.0RS particles gave films, where the Astarch corresponding to the commencement of the tight packing region was larger than Ahex. Thus, the NRS, 0.6RS and 1.2RS particles are thought to have been less stable at the air/water interface than the 1.8RS, 2.4RS, and 3.0RS particles.The area expected for a hexagonal packed layer of particles with a mean starch size (A5 show the images of the Langmuir films of the native starch particles (NRS), and the OSA modified starch particles  at air/water interfaces, when the films were compressed to surface pressure values of 5, 15, and 25 mN/m, respectively. These values were chosen as the surface pressure-Astarch isotherms indicated that these three values should allow the different packing densities to be studied. The NRS particles can be seen to aggregate to give large, 3-dimensional types of aggregates at the air/water interface, regardless of the surface pressure . These aggregates were compressed as the film was compressed, resulting in a surface pressure increase with an Astarch decrease. A closely packed film of particles without holes could therefore not be formed at the air/water interface with the NRS particles due to this aggregation. This inability to form a closely packed film of particles may also be related to a loss of material to the subphase, due to the hydrophilicity of the native starch particles. In the case of the modified starch particles, films with holes were seen at Π = 5 mN/m. An increase in the degree of modification of the starch particles improved the packing of the particles in the film and consequently decreased the size of these holes seen in the film. The dark colored patches  of the film of particles at the air/water interface was calculated from the slope of this region. An increase in the slope of this region indicates an increase in the interface stiffness. The retract force curves (not shown) showed an adhesion, the strength of this adhesion was calculated to give the adhesive force (Fad).The difference in the physical properties of the films of the native and modified starch particles at the air/water interface was further investigated by measuring the force-distance curves between a starch particle attached to an AFM cantilever (probe) in the water phase and a film of starch particles at the air/water interface. The same starch particle type that was used to form the film of particles was used as the probe. Forces were measured for the NRS, 0.6RS, and 3.0RS systems, in order to determine the effect of modifying the rice starch structure and the degree of modification. Figures Fad) measured between a rice starch particle in the water phase and the film of particles at the air/water interface. The adhesive force tended to decrease with an increase in the degree of modification of the rice starch particles and with an increase in the surface pressure of the film of particles at the air/water interface. A decrease in the adhesive force indicates that the attractive forces between two starch particles separated by water have decreased. The introduction of an inter-particle electrostatic repulsion could explain this decrease in the adhesive force. The increase in number of charged octenyl succcinate derivatives on the rice starch particles with an increased degree of modification of the rice starch particles could cause this increase in the electrostatic repulsion between two rice starch particles. Additionally, compressing the film, i.e., decreasing the separation distance between the particles in the film, would increase the charge density of the film, causing the magnitude of the electrostatic repulsion to increase. The surface pressure was observed to increase with the film compression. Thus, the adhesive force may also have decreased with a surface pressure increase, due to this increased electrostatic repulsion.Figure SN) of the film of particles at the air/water interface. There was only a small change in the measured surface stiffness between systems formed using the NRS, 0.6RS, and 3.0RS particles, when the same surface pressure values were compared. The stiffness of the films of 0.6RS particles was seen to be a little less than that of the film formed by the NRS particles. The stiffness of the film of 3.0RS particles was, however, a little greater than that of the films of NRS or 0.6RS particles. The lack of change in the stiffness for the particle types is thought to be related to the surface pressures used in the MPIA experiments. If the interface was held at a high enough surface pressure, then there would have been little flexibility in the interface. The forces measured would then have been dominated by the probe particle and the immediate particle in the interface that it contacts. This would have caused the influence of the surrounding network to be reduced.Figure Figure The stiffness of a film of particles at the air/water interface is controlled by the surface tension of the interface, the stiffness of the particles, and continuity or integrity of the film. The stiffness of an interface decreases with the surface tension (or increased surface pressure) of the film. A film of loosely packed particles would contain areas of air/water interface that are bare and areas that are covered by particles. The size of the area of the air/water interface that is bare and therefore not covered by particles decreases with an increase in the particle packing density. As the surface tension of a bare air/water interface is higher than the surface tension of an air/water interface with adsorbed matter, the surface tension of a film of particles at the air/water interface would decrease with a surface pressure increase. This would cause the stiffness of the air/water interface with the particles to decrease with a surface pressure increase. The stiffness of an interface would also increase with an increased stiffness or hardness of the material adsorbed at the air/water interface. A change in the stiffness of the particles with the modification of the starch particles would therefore also affect the stiffness of the film of particles at the air/water interface. Starch gels made from OSA starch are reported to be softer than starch gels made from native starch , i.e., highly compressed films.The effect of adding salt to water on which the particles formed the films was firstly investigated by measuring the surface pressure-l Figure . The isoThe surface tension of air/aqueous solutions containing NaCl can be calculated to increase by 0.28% when the concentration of NaCl was increased from 0.1 to 100 mM, if the values of the apparent relative surface tensions of air/NaCl aqueous solutions are compared (Jones and Ray, Astarch values with a salt concentration increase was obtained by using an optical microscope to observe the films of 3.0RS particles at the different subphases. Figure Astarch values with a salt concentration increase can be explained by the presence of these holes.Information as to why the isotherms shift to larger The effect of the presence of the holes formed at higher ionic strength of the aqueous subphase on the stiffness of the films of particles was next investigated. The force curves between a 3.0RS particle in the subphase and films of 3.0RS particle compressed to 10 mN/m at air/aqueous interfaces were recorded with 0, 1, 10, and 100 mM NaCl in the subphase Figure . The surThe stiffness values obtained from the slope of the linear contact area of the approach force curves were calculated and are shown in Figure In general, the stiffness of the film of particles tended to decrease with an increase in the number and size of holes in the film of particles. The decreased stiffness can be explained by an increased discontinuity in the particle film, due to the presence of the holes.Previous studies investigating the physical properties of a monolayer of charged surfactants at air/aqueous interfaces showed that the addition of salt to the water subphase changed the packing of the monolayer and caused the stiffness of the interface to increase with high NaCl concentrations (McNamee et al., The formation of holes due to the increased aggregation of particles within the films at the air/aqueous interface with a salt concentration increase can be explained by a decrease in the magnitude of the inter-particle electrostatic repulsions. The electrostatic repulsion between two charged surfaces separated by an aqueous solution decreases with an ionic strength increase due to an increase in the screening of the charged surfaces (Israelachvili, The force acting between two particles is the resultant of the attractive and repulsive forces. The effect of the inter-particle attractive forces would therefore be more prevalent in the total forces acting between the two particles in the presence of salt. Other studies have also shown that the addition of salt to starch granule stabilized emulsions for starch modified with OSA to 4.66% increased the size of the droplet, which was explained by an increased droplet aggregation (Rayner et al., Modification of the rice starch particles caused octenyl succcinate derivatives to be introduced on the starch particle, which contained both charge and hydrophobicity. In the absence of salt in the water subphase, the presence of the charge reduced the aggregation of the particles at the air/aqueous interface. This was explained by the inhibition of the inter-particle hydrophobic attractions resulting from the charge of the octenyl succcinate derivatives. The addition of salt to the water subphase caused these charges to be screened. As a result, the hydrophobic octenyl succcinate derivatives could have come into contact closer, causing the strength of the inter-particle hydrophobic attractions to increase. These attractions would have caused the particles to aggregate and form islands at the air/aqueous interface. Holes would be present in the film of particles, when the particles are not compressed enough to remove the spaces between the islands. The stiffness of the film of particles with holes is lower than one without holes. It would therefore be necessary to compress the films to higher amounts in order to achieve a dense packing density, if a stiff and strong film of particles is required with OSA modified starch particles used at air/aqueous interfaces containing salts.Native rice starch particles formed large aggregates at air/water interfaces. A two-dimensional film of particles could not be formed with these particles at an air/water interface. The modification of the rice starches particles decreased the aggregation of the starch particles, due to the introduction of a charged group on the starch particle. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the increase in the magnitude of the inter-particle electrostatic interactions arising from the greater number of charged groups on the particles. The stiffness of the film also increased with the degree of modification, due to this improved particle packing. Introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to screening of the charged groups on the starch particles. The presence of these holes decreased the stiffness of the films.The packing and stiffness of films of starch particles formed at hydrophobic/hydrophilic interfaces in the absence of salt can be improved by increasing the degree of modification of the starch particles. In the presence of salt, the films of particles must be compressed to give a high packing density, in order to remove holes in the films of the particles. Such holes would decrease the stiffness of the films.CM: Designed the study, performed the research, wrote the manuscript; YS and IF: Performed the research; MK: Provided new methods; BW: Prepared the starch particles; TN, MR, and AM: Designed the study and wrote the manuscript; and all authors approved the revisions.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.


The affiliation for the sixth author is incomplete. Hanna S. Rode is affiliated with Department of Veterinary Clinical Sciences, Royal Veterinary College, London, United Kingdom and Institute of Veterinary Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, Germany.


First metatarsophalangeal joint (MTPJ) mobility is commonly assessed by its angular displacement (joint angle) or subjectively rated as ‘hypermobile’, ‘normal’ or ‘stiff’ by a clinician. Neither of these methods is ideal because displacement alone does not take into account the force required to displace the joint and subjective evaluation is not always reliable. This study presented a novel method to determine the passive quasi-stiffness of the first MTPJ. The reliability of the proposed method was also assessed. The first MTPJ passive quasi-stiffness of 13 healthy subjects were measured at two occasions, 7 days apart, by two testers (experienced and inexperienced). A tactile pressure sensing system was used to measure the force applied to dorsiflex the first toe by the testers. The torque (in Nmm) about the first MTPJ was calculated as the applied force (in N) multiplied by a moment arm (in mm), where moment arm was the length of the first proximal phalanx. A video camera recorded the motion of the first MTPJ, simultaneously with force measurements, to determine the joint angular displacement (in degrees) using the Dartfish software. The quasi-stiffness (in Nmm/degrees) was calculated as the slope of a graph where torque was plotted against first MTPJ angular displacement. Descriptive statistics of the first MTPJ quasi-stiffness were calculated. Intra-rater and inter-rater reliability were assessed using Bland and Altman plot, intraclass correlation coefficients (ICC), and standard error of measurement (SEM).First MTPJ quasi-stiffness of the subjects ranged widely from 0.66 to 53.4 Nmm/degrees. Intra-rater reliability for experienced tester was moderate . Inter-rater reliability between experienced (12.6 ± 8.4 Nmm/degrees) and non-experienced (19.9 ± 9.2 Nmm/degrees) testers was poor .First MTPJ passive quasi-stiffness can be quantified from torque and angular displacement measurements using simple equipment in a clinical setting. The tester’s experience affected the consistency in joint quasi-stiffness measurements.The online version of this article (doi:10.1186/s13047-016-0173-2) contains supplementary material, which is available to authorized users. The first metatarsophalangeal joint (MTPJ) is the articulating joint between the first metatarsal and the proximal phalanx of the big toe. It is classified as a single synovial joint that allows motion in the sagittal and transverse planes, with sagittal plane dorsiflexion being the joint’s primary movement in gait. Approximately 65 to 75 degrees of dorsiflexion is considered necessary to enable efficient forward transfer of bodyweight during the propulsive phase of gait , 2. RestThere are no standardised methods for measuring first MTPJ mobility. A common practice is to subjectively “feel” how easily the first MTPJ moves through its range of motion , 11. TheQuasi-stiffness, which is the resistance of a joint to an external force, may be a better alternative to assess the first MTPJ mobility. Quasi-stiffness is often determined experimentally as the derivative of the torque-angle relationship , 19. AltQuantifying first MTPJ quasi-stiffness can be useful in clinical assessment as well as informing orthotic prescription. With quasi-stiffness measurements, joint mobility can be assessed in an objective manner instead of relying on subjective descriptions such as “excessive excursion with soft end-point” . For exaThis study aimed to present a novel method incorporating joint range of motion and force applied to displace the first MTPJ, in order to measure passive quasi-stiffness of the first MTPJ. The intra-rater and inter-rater reliability of the proposed method were also assessed.SD) age = 24.4 (5.0) years, body mass = 63.3 (15.1) kg, height = 1.67 (0.11) m] were recruited for this study. All participants had no joint conditions (such as inflammatory arthritis and osteoarthritis), had no previous foot surgeries or trauma, and were free from foot pain and injuries at the time of study. They were informed of the nature, benefits, and risks of the study, and provided their written consent for participation. Ethical approval was received from the Nanyang Technological University Institutional Review Board (IRB/2013/08/18).Thirteen healthy participants  before returning the big toe to its neutral position; and d). This process was repeated three times providing a total of nine data points  to plot a torque-angular displacement graph  The first MTPJ was moved into maximal dorsiflexion passively by the tester; this data point was excluded in the analysis because joint quasi-stiffness close to the end range cannot be assumed linear ; b) The T2,θ2), T,θ3] befoThe quasi-stiffness (k) of the first MTPJ joint can be calculated based on the following equation:lot Fig. .Statistical analysis was performed using IBM SPSS Statistics 21  and Microsoft Excel. The first MTPJ quasi-stiffness was the only dependent variable. Descriptive statistics were used to summarise the group data in means and standard deviations. Repeated measurements which were performed twice by the experienced tester were used to assess between-day intra-rater reliability using the Bland and Altman plot and intra-class correlation coefficient [ICC ]. The ICCs were interpreted as slight (<.20), fair (.21–.40), moderate (.41–.60), substantial (.61–.80), and almost perfect (> .80) . The sta1, …,θ9) used to plot the torque-angular displacement graphs ranged between 3.2 to 47 degrees (median = 24 degrees). Table First MTPJ dorsiflexion angles θ, …,θ9 usWhen comparing the MTPJ quasi-stiffness measurements between the experienced and inexperienced testers, the inter-rater reliability was poor Table . The pooThis study reported a novel method to quantify first MTPJ quasi-stiffness in a clinical setting using pressure sensors and video analysis. The between-day intra-rater reliability was moderate for the experienced tester but the inter-rater reliability was poor between the experienced and inexperienced testers.Given that our study is the first to measure first MTPJ passive quasi-stiffness, there are no available data for direct comparison in the literature. Thus, the study findings will be discussed in reference to relevant studies on the stiffness of other foot joints including the first ray  and anklIn the study by Glasoe et al , the firIn studies examining passive ankle stiffness, the torque versus angular displacement plots were non-linear throughout the measured range , 30. As The novel method presented in this study was developed for use in a clinical setting. The Finger TPS system and camera were portable and easy to be placed next to an examination table. This set-up does not interfere with the space required in normal clinical assessments: the camera is small and mounted on a tripod, while the pressure sensor is worn on the tester’s thumb and linked to the laptop via wireless receiver. The time required for data collection from each participant was about 10 minutes, inclusive of preparation and explanation. Analysis was performed offline after the participant has left. Digitisation of video recordings to determine angular displacement and extraction of corresponding force data from the software took about 10 minutes per participant. All equipment and software used are commercially available, with a total cost of approximately USD 7500.The reliability of measuring first MTPJ passive quasi-stiffness using the methods described in this study appears unsatisfactory. Measurement errors were, at best, moderate even for the experienced tester, with a large SEM of 7.71 Nmm/degree . This is likely due to the lower proficiency in securing the foot joints and manipulating the toe movement. Comparing the outcomes between the inexperienced tester to experienced tester, we speculated that the differences were observed because the experienced tester is able to better control the amount of force applied to the joint. This allows the experienced tester to manipulate the joint movements within the ‘working range’ where the quasi-stiffness is assumed to be linear and less variable. The inexperienced tester, who may have difficulty in controlling such fine movements, may have over-displaced the joint near the end range where quasi-stiffness becomes non-linear and highly variable . OverallTo overcome the issues associated with clinical experience and human error, it will be necessary to develop a device that can quantify first MTPJ quasi-stiffness. Future directions for development can consider the following stages: (i) Technology for accurate quantification of foot joint quasi-stiffness in a clinical setting, (ii) commercialisation of equipment, (iii) gathering normative data to determine cut-off values for diagnoses for hallux conditions associated with joint quasi-stiffness, and (iv) targeted, precision treatment based on objective measurements.Current subjective evaluation methods used by clinicians are unreliable . In its With future population level studies and normative data, classification of pathological foot conditions is recommended. There is potential for advancing care to enable early intervention in conditions associated with abnormal joint quasi-stiffness. Currently, objective measurement as a method of assessing possible early pathological first MTPJ conditions does not exist. For instance, hallux valgus (bunions) is diagnosed after joint deformation has occurred, described as “medial slant of first metatarsal” .Interventions for joint hypermobility can be more specific and targeted. Currently, the orthotic stiffness required to control for hypermobile joints in the foot is estimated by clinicians based on their experience. With objective measurements, deviations from normal joint quasi-stiffness may be corrected with corresponding material stiffness.This study provided preliminary results that first MTPJ passive quasi-stiffness can be quantified from torque and angular displacement measurements using simple equipment in clinical settings. The tester’s experience affects the consistency in joint quasi-stiffness measurements. Future studies can aim at refining the measurement protocol, and to develop instrumentation that can accurately quantify foot joint quasi-stiffness.


International Journal of Molecular Sciences [The authors would like to indicate that Dr. Angeles Cancino-Rodezno and Leidy P. Bedoya-Pérez participated equally in their paper published in the Sciences . For thiThe changes do not affect the scientific results. The manuscript will be updated and the original will remain online on the article webpage.


Ep/Ei and certain radius of PTD, where Ep is the PTD modulus and Ei is the intertubular dentine modulus. So in order to ensure the whole dentinal equivalent stiffness is not loss, the porosity should get some value while the Ep/Ei is certain. Thus, PTD prevents the stress concentration around DTs and reduces the risk of DTs failure. Mechanically, the overall role of PTD appears to enhance the stiffness of the dentine composite structure. These results provide some new and significant insights into the biological evolution of the optimal design for the porous dentine microstructure. These findings on the biological microstructure design of dentine materials are applicable to other engineering structural designs aimed at increasing the overall structural strength.In the current study, we evaluate the equivalent stiffness of peritubular reinforcement effect (PRE) of porous dentine optimized by the thickness of peritubular dentine (PTD). Few studies to date have evaluated or quantitated the effect of PRE on composite dentine. The miscrostructure of porous dentine is captured by scanning electron microscope images, and then finite element modeling is used to quantitate the deformation and stiffness of the porous dentine structure. By optimizing the radius of PTD and dentine tubule (DT), the proposed FE model is able to demonstrate the effect of peritubular reinforcement on porous dentine stiffness. It is concluded that the dentinal equivalent stiffness is reduced and degraded with the increase of the radius of DT  in the certain ratio value of  Dentine, as measured by either weight or volume, is the major component in individual teeth and exhibits a complex hierarchical structure with both organic and inorganic components . AssemenSince dentine is the irregular and porous material microstructure, it leads that the micromechanical modeling of porous dentine is complicated. Dentine also can be considered as a composite material structure. It mainly contains three hierarchical phases such as intertubular inclusion, bonding matrix, and water. In the analysis of dentine configuration, the dentine is regarded as two-phase composite material. One is the dentine tubules which are considered as defects in composite material. The other is the peritubular dentine which is considered as the reinforcement phase, and it is used to compensate the losing stiffness.Our studies show that the peritubular dentine around DTs has interesting effects on the stiffness of composite dentine structure. Biologically, the porosity associates with the presence of the DTs can serve as a path for neural conduction. However, mechanically, the potential impact of this porosity is still unclear. In addition, the attribution for the complexity and great thickness of the PTD microstructure also remains unclear. Therefore, the main prurpose of this study is to further evaluate the mechanical and structural properties of PTD to gain insight into its biological function.All the experimental procedures involving human tooth were approved by the Medical Ethics Committee of Stomatology Hospital of College of Medicine, Xi'an Jiaotong University. All patients provided written informed consent.in-situ scanning electron microscope (SEM). The SEM images were obtained which provided the modeling data and served for the following finite element model. The micro-structural evolution were recorded under different compression loading to verify the finite element analysis results about the PTD function. After compression loading, the compression stiffness also could been calculated by each load-displacement curve. The compression stiffness is considered as the verification results to finite element analysis results.The compression experiment test was performed using 3 as shown in Five non-carious third molars were used for testing, the samples were discard material and thus exempt from the need for Institutional Review Board approval. Teeth were extracted from healthy male and female patients between the ages of 20–40. Because the third posterior molars had to suffer the bite force in general. It had higher requirement in strength property which had more suitable for our study. After extraction, the teeth were kept in normal saline solution at 4°C°C. Before cutting, the tooth was embedded in epoxy resin. The long axis of the teeth was parallel to the mold, and the collisional surface was exposed. The samples were sectioned by a low-speed precision cutting machine  with water cooling. The five samples were sectioned at a specific location in the teeth with cubic dimensions of 1.5 mmEach sample surface was polished in multiple steps using an automatic polishing machine . The samples were polished with a series of SiC abrasive papers down to 4000 mesh and finally with 9 μm, 3 μm, and 1 μm diamond suspensions . The surface morphology was assessed (Keyence Japan) and the zone in which the tubules were arranged perpendicular to the surface was chosen as the compression surface contacted with the cross-header of the machine.in-situ by SEM.The MTEST-5000-situ loading machine  was equipped with a loading station, displacement sensor, force sensor, propeller lever and software control system. In the loading process, the control system regulated the propeller lever movement, then the displacement and force datas were recorded. Meanwhile, the micro-structure of the sample surface could be observed in-situ changes in the surface morphology could be observed. Loading direction was perpendicular to the DT direction. With loading held at 200 N, 400 N, 600 N, 800 N, and 1000 N, SEM photographs were recorded in Dentine samples were carefully placed into the scanning electron microscope chamber  after being coated with metal . To obtain a high quality image, the conducting resin was placed lateral to the sample. Compression loading was set at the rate of 0.1 mm / min so that Dentine can be modeled as a continuous reinforcement composite. This model includes peritubular dentine, intertubular dentine, and dentinal tubules as shown in Due to the complicated topological structure of dentine and the uncertainty distribution of DTs, we introduce more than one of its components into an analytical model leads to intractable solutions, however methods such as the finite element method (FEM) offer an alternative approach –13. The The equivalent stiffness of the dentine is defined to describe the dentine mechanics. When dentine is compressed, internal pressure is increasing in an enclosed cavity. It causes the compression of internal fluids in DTs which accelerates fluid to flow to the dental pulp. Then it stimulates the dental pulp nerve of the teeth root. In the end, the neuronal signaling is increased until it tranmits to the brain. For modeling purpose, dentine stiffness is correlated with flow rate and nerve stimulations, which could then be studied by FEM under the given dentine configuration.We use the Image-Pro Plus (IPP) software to create the FE model. The IPP software could read and write image data in all the standard image files formats including the scanning electron microscope image. It could trace and count objects manually or automatically. Measure object attributes such as: area, angle, perimeter, diameter, roundness and aspect ratio. Based on IPP feature, we obtain the location, count, and diameter of PTD and DTs using the original SEM image. The IPP software could also calculate the mean diameter of object. As the PTD and DTs are not totally regularity and PTD is not uniformly distributed around DTs, the mean diameters of PTD and DTs are required to analyze the model correctly. After obtaining the coordinate and mean diameter of PTD and DTs, the model is created and used to perform the finite element analysis.So just one clear image is needed to create the basic FE model. Based on the above results, we modify the base model like decrease or increase the radius of PTD and DTs by manually to create models with different porosities. The compression stiffness in experiment and the equivalent stiffness in finite element analysis (FEA) are the same description about dentine strength.x axis as shown in x and y directions. The boundary conditions: the middle points of left and right sides are fixed in y direction, and middle points of top and bottom sides are fixed in x direction. After solving, the data could obtain in post-processing. The data mainly contains the displacement of the two loading sides. Then the strain is acquired. According to the experiment compression loading and the loading area of sample, the compression pressure is calculated about 100 MPa. So the equivalent stiffness is defined as the compression pressure divided by the strain. The compression stiffness is considered as the verification results to finite element analysis results. The material parameters of dentine model and the comparison results under 1000 N as the following ANSYS software is used to analysis. The finite element package is used to calculate the dentine equivalent stiffness. In finite element analysis, compression loading is set at both sides along the Ep is the modulus of PTD, Ei is the modulus of ITD and the dimensionless parameter m is the ratio of RPTD to RDT. The stiffness relative error between the experiment and FEA is about 0.80%. Therefore, the results show that the FE model in our present study is effective. And it provides the basis for the subsequent topological structure study. So in the following study, the different FE models are determined from manually assigned. In other words, we just increase or decrease the radius of PTD and DTs by manually assigned.where the In order to study the effect of PTD on stress and deformation distribution in dentine, two different scenarios are modeled: with and without PTD in the structure. The boundary conditions and the distribution of DTs are just the same, the only different from the two kinds of models is the PTD. The FEA results are plotted in From the results of Ep to Ei, porosity and the ratio of RPTD to RDT which influence the equivalent stiffness are discussed. Where Ep and Ei are the elastic modulus of PTD and ITD, respectively. And RPTD and RDT are the radius of PTD and DT. The δ is the porosity, which is defined as the percentage of the area of DTs to the entire force area. The thickness of PTD is just calculated by RPTD subtract RDT. The change in equivalent stiffness is observed under restrictions. The numerical simulations and boundary conditions are the same with In this section, the ratio of It is known that, the greater of porosity, the greater effect on equivalent stiffness , 16. We Ep/Ei is used to compare the equivalent stiffness and obtain the optimized ratio of RPTD to RDT. Kinney et al [Ep to Ei is calculated as 2, 1.73 and 1.The modulus of PTD and ITD are influenced by many factors, and the measured modulus varies in published literature. To better describe the effect of PTD and ITD on equivalent stiffness, ey et al , used aney et al , calculaEff, δ and Ep/Ei when RPTD is kept the same, Ei is defined as 15 GPa presented in the dotted line. When the RPTD is kept the same but with increasing porosity, which means the RDT increases, the results of Eff with different Ep/Ei are plotted in Ep/Ei = 1 is used as the reference, we found that Eff decreases with increasing porosity. When Ep/Ei = 2 and δ = 5.43%, Eff would be 15GPa which is also the modulus of the matrix ITD. When Ep/Ei = 1.73 and δ = 4.44%, Eff would almost 15GPa. So when RPTD is confirmed, with the decreases of Ep/Ei, the Eff is decreasing. These will also results in decreased porosity to achieve the strength and stiffness requirement. Thus, in order to get the modulus of the matrix at least, the different Ep/Ei corresponds to different porosity. Examining from a different perspective, the presence of porosity which is considered as the pore defects could be compensated by adjusting the thickness or the radius of PTD to ensure preserved stiffness in the porous dentine.Further in the discussion of Ep/Ei is 1.73. Basing on the above discussion, we would expect the porosity to be 4.44% in order to avoid reduction in dentine stiffness. In fact, our calculated porosity based on the SEM image is 4.38%, which is very close to the FEA result. So these results could confirm the reliability of our FEA results.In our experiment model, the PTD thickness is known to vary between individuals and with age . The lowRPTD subtract RDT. Then, the question is how much would PTD thickness need to vary to ‘compensate’ the decreasing stiffness which associates with DTs. We introduce the dimensionless parameter m, which is defined as the ratio of RPTD to RDT, to describe the relationship between the equivalent stiffness and PTD thickness. The underlying hypothesis is that PTD evolves around DTs to enhance the dentine stiffness.In this study, the thickness of PTD is just calculated by From the SEM images, we found that the PTD do not overlap with each other. Then the maximum and minimum porosities are obtained. In our experiment, the porosity which we statistics is about 3~6%. In our FE models, we calculate the two different results when the porosities are 3.74% and 4.44%, respectively. The results are shown in m increases, which means the radius of PTD or the thickness of PTD is increasing, the variation trends of Eff are plotted in Ep/Ei is 2, 1.73, 1. When the ratio of Ep to Ei is greater than 1, the Eff increases. When the value of Ep/Ei gets closer to 1, the variation trends are not obvious. When Ep/Ei = 2 and m = 2.07, the Eff could get 15 GPa which is the modulus of the matrix ITD. When Ep/Ei = 1.73 and m = 2.33, the Eff could also get 15 GPa. The same situation happens in Ep/Ei = 2 and m = 2.07, the Eff could get the modulus of the matrix. When Ep/Ei = 1.73 and m = 2.33, the Eff could also get the modulus of the matrix 15 GPa.If the porosity is kept at 3.74% while m is evaluated using different porosities .To verify the above two results, numerical calculation about rosities . The matEp/Ei is determined, regardless of the porosity, the m is unchanged. So we could obtain the thickness of PTD basing on the value of m to achieve the objective of preventing reduction in stiffness. Therefore, in order to ensure that the stiffness of the composite structure is not lower than the matrix stiffness, once the porosity and Ep, Ei or Ep/Ei is confirmed, the thickness of PTD is also confirmed. This would avoid the loss of stiffness and ensure the stiffness of the dentine composite structure. It also would explain the biologically optimized microstructure basing on the existence of porous dentine.The above results show that once the -1 [There are thousands of dentine tubules extend from the inner pulp space to the outer surface. This structure determines the dentine is a permeable mineralized tissue. Their densities in dentine are about 10,000 to 96,000 mm-1 . Based o-1 . This is-1 . The mer-1 . In orde-1 . And the-1  found th-1 . Within -1 , 29. WitIn dentine, the mineral constituents contribute the stiffness of dentine, and the high mineralization with high elastic modulus and static strength but low strain energy and stiffness . The orgAlthough there are many studies examining PTD and DTs, few examine PTD thickness and porosity in relation to the strength and stiffness of the composite dentine structure. It is difficult however to understand the function for the PTD, although its porosity does provide means for the transport of ions and other components between the odontoblast processes and the dentine matrix.In classical mechanics, DTs are considered as defects or voids in dentine which result in the loss of equivalent stiffness of dentine. In order to improve the dentine stiffness, the PTD plays an important role in enhancing the equivalent stiffness of dentine. Mechanically, the modulus of PTD is much larger than ITD; thus, PTD is considered as the peritubular reinforcement phase. On the other hand, the biological functional of the dentine structure is not only to make sure that the DTs transport nutrients normally, but also to sustain the strength of the composite dentine structure for daily function, such as chewing. In the current manuscript, we perform numerical modeling for the optimal microstructure based on a biologicaly porous dentine, which mainly aims to explain the optimized development of porous dentine with the PRE on dentine biomedical porous materials.Our approach involves an analysis of the effects of PTD thickness and radius on dentine stiffness. This is done by comparing the models with and without the PTD based on the IPP software, and vertifying the FEA results with experiment. The measured radius and location of the PTD and DTs corresponded well with our FEM estimate. So we believe that this approach has wide potential application.RPTD and RDT to accord with the dentine models as soon as possible meanwhile ensure the continuity of models and results. And the FEA could calculate different dentine models correctly. First, we just consider the peritubular phase effect on equivalent stiffness of dentine model by finite element analysis. Its try to use the simple model to solve the complex problem. So the 2D FE model is totally could solve these dentine models. Besides, the characteristic length of microstructure is negligible compared to the thickness of the dentine tubules. Therefore, the 2D plane strain is assumed in the FEA which can be used to study the stiffness property. In other words, the 2D plane strain FE model is suitable to represent the approximate a 3D dentine structure.Finite element analysis is an analytical method for better to study the dentine microstructure properties. As we discuss different models in this study. However, we could not test so many dentine specimens to create the models. So we regulate the ratio of m. In other words, the different stiffness for corresponding models are calculated just by changing the radius of PTD and DT of Ep/Ei, the compensate porosity is given which could ensure that the whole equivalent stiffness wouldn’t decrease. The thickness of PTD is proportional to the equivalent stiffness. It is shown in m (ratio of RPTD and RDT) discussion, increasing m means increasing the radius of PTD while the radius of DT or the porosity remains the same. So in this parts’ discussion, it mainly adjusts the radius of PTD. In Ep/Ei, the compensate m is given which could ensure that the whole equivalent stiffness wouldn’t decrease. In the end, we take multi-factor, porosity and m, into comprehensively considering to discuss the relationship among the porosity, m and the whole equivalent stiffness of dentine. And the porosity and m are two factors which all have relation with peritubular thickness. The results are shown in The manually assigned parameters mainly contain the porosity and Ep/Ei and porosity, the m (RPTD/RDT) is different. So the relation between the radius of PTD and DT can be calculated. In our 72 DTs’ experimental configuration, the modulus of PTD and ITD is 26 GPa and 15 GPa, respectively. So Ep/Ei is about 1.73 and the porosity is about 4.38%. From the above results like m is about 2.33 which means the RPTD/RDT is about 2.33. We found that the mean value of RPTD/RDT in our dentinal configuration is about 2.32 which corresponds well with our findings in Our results demonstrate that the PTD appear thicker around the smaller DTs. This is in accord with other reports of stiffening and strengthening of the dentine microstructure  which caMechanical properties of dentine with age have largely been attributed to the increase in mineralization due to filling of the dentine tubules. Human teeth undergoes changes with increasing age, there are difference in mechanical properties, such as an increase in elastic modulus and hardness, a decrease in strength. Besides, the increase in mineralization of the dentine tubules which could cause some trouble in modeling and the statistics porosities of dentine. For example, the dim boundary between PTD and DT. Therefore, the age has a great effect on stiffness property and microstructure of dentine. We have noticed these characteristics. However, we mainly pay attention to the equivalent stiffness of young people dentine in order to decrease or eliminate the affection of other factors. The present method is suitable to study the mechanical properties of teeth in a large range of age.There are variations in composition in restorative materials between anterior and posterior teeth. However, aesthetics factor should be considered in restorative materials of anterior teeth firstly. It mainly includes such as color, gloss and permeability. Whereas the function of posterior teeth is chewing. So the restorative materials of posterior teeth should consider the mechanical property (strength and stiffness) which could bear the bite force. Therefore, the third molars are chose to test. And the SEM image of the third molars specimen is regarded as the basic FE model.Porous material are widely used in clinical and engineering structures although the porosity results in decreasing the material strength. In engineering, material stiffness of porous material can be reinforced by adding the reinforcement materials around the porosity. Our present findings suggest that with the dentine structures evolving, they came up with this same biological solution. Thus, these findings are also broadly applicable to other biomaterials and to the engineering of porous materials.In this study, we develop a mechanical model to simulate peritubular reinforcement effect of porous dentine tubules. We report that increasing PTD thickness could result in improving the composite dentine stiffness. The biological significance is that the existence of the PTD reduces the stress concentration around DTs and the destruction of the DTs. Particually, the PTD strengthens the stiffness of the composite dentinal structure. And it is the “biological solution” which is utilized by this microstructure to compensate the stiffness of porous dentine. These results are applicable to other porous materials in engineering which could use this method to strengthen the structure by adding the reinforcement materials around the porosities.


The aim of this study was to evaluate short-term patency of the new prosthetic graft and its structural changes after explantation. The study team developed a three-layer conduit composed of a scaffold made from polyester coated with collagen from the inner and outer side with an internal diameter of 6 mm. The conduit was implanted as a bilateral bypass to the carotid artery in 7 sheep and stenosis was created in selected animals. After a period of 161 days, the explants were evaluated as gross and microscopic specimens. The initial flow rate (median ± IQR) in grafts with and without artificial stenosis was 120 ± 79 ml/min and 255 ± 255 ml/min, respectively. Graft occlusion occurred after 99 days in one of 13 conduits (patency rate: 92%). Wall-adherent thrombi occurred only in sharp curvatures in two grafts. Microscopic evaluation showed good engraftment and preserved structure in seven conduits; inflammatory changes with foci of bleeding, necrosis, and disintegration in four conduits; and narrowing of the graft due to thickening of the wall with multifocal separation of the outer layer in two conduits. This study demonstrates good short-term patency rates of a newly designed three-layer vascular graft even in low-flow conditions in a sheep model. Long-term patency of bypass reconstructions connected to crural or femoral arteries is jeopardized by low flow and small distal outflow beds. Specifically, prosthetic grafts are known to have a poor performance compared to autologous (venous) grafts with primary patency rates as low as 50–60% in three years in pedal bypass , 2.Prosthetic bypass grafts used for revascularization of the lower limbs have undergone development, from single cast polytetrafluorethylene (PTFE) to covered mesh grafts including coating of the inner surface with heparin, collagen, sirolimus, or fibronectin to reduce the risk of early thrombosis, restenosis, and intimal hyperplasia and improve cell attachment and coating of the inner layer –6. New tAdditionally, the mismatch between the mechanical behavior of prosthetic grafts and natural arteries including transduction of the pulse wave and adjustment to pressure changes has been discussed and researched , 9, 10. Our research team has designed, developed, and tested a new three-layer collagen-based vascular graft primarily designed to withstand the adverse low-flow conditions in reconstructions of small arteries, which currently is in patent proceedings .The aim of this study was to evaluate short-term patency of the new prosthetic graft and its structural changes after explantation.This prospective study was approved by the Institutional Animal Care and Use Committee and was conducted in accordance with national Act number 246/1992 Coll. as amended on the protection of animals against cruelty, which is harmonized with the legislation of EU.In this study, we tested the performance of a newly developed prosthetic graft constructed for low-flow conditions between 100 and 200 ml/min intended for peripheral vascular reconstructions in a sheep. The study involved (1) implantation of the graft connected end-to-end or end-to-side in the carotid artery and adjustment of its flow, (2) follow-up by Duplex ultrasound, and (3) explantation of the graft with macroscopic and microscopic analysis.2 at 120 mmHg) with collagen from the inner and outer side with an internal diameter of 6 mm  domestic sheep, 10 to 48 months old, weighing 49 ± 14 kg . The freThe procedure was performed in the supine position after induction of general anesthesia with propofol (1-2 mg/kg) and morphine (0.1 mg/kg) as a bolus, placement of the endotracheal tube, and continuous monitoring of vital signs . Baseline blood flow was recorded using Duplex ultrasound after shaving the anterior side of the neck and its disinfection. Then two board-certified cardiovascular surgeons exposed both carotid arteries and preformed resection of one carotid artery with end-to-end bridging by the vascular graft on one side and its closure by ligation and bypassing by the graft connected end-to-side on the other side, at least 65 mm in length on both sides. Sheep #1 had one end-to-end graft only due to technical complications with the graft. When constructing the proximal anastomosis, the inner collagen layer was damaged. This resulted in formation of intramural hematoma after placing a clamp on the graft. The grafts were connected using a continuous 6.0 prolene suture. Blood flow in the vascular graft was measured using a perivascular transient-time ultrasonic probe . Mean flow velocity was calculated using the continuity equation. In selected animals, a lace was tied around the inflow or outflow artery, or on the graft to narrow the segment by about 70% . The bypOn the first postoperative day, the animals received morphine (2 mg/kg) s.c. and NSAIDs (meloxicam 1 mg/kg) for the first three days or longer as required. Acetylsalicylic acid  was given for the first seven days. Patency of the grafts was evaluated by ultrasound on a biweekly basis , the grafts were exposed, blood flow in the vascular graft was measured using a perivascular transient-time ultrasonic probe, and the grafts were explanted . Gross sP value below 0.05 was considered significant.Statistical tests were performed using GraphPad Prism 5.0 . Normality of the data was tested with the Kolmogorov-Smirnov test. Wilcoxon matched pairs test was used to test for statistical significance due to the nonnormal distribution of the data. A P = 1.00) and 172 ± 80 ml/min , respectively. Graft occlusion occurred in one conduit in animal #4 after 99 days. The rest remained patent (12 of 13 grafts) for the whole study period. Patency rate of the graft was 92% at a median follow-up of 161 days. Macroscopic appearance of the inner layer was excellent . Despite minimal flow before explantation, there was no apparent thrombosis  up to 90° because the grafts were oversized. This resulted in turbulent flow and formation of an island with wall-adherent thrombi . In sheerombosis .The histopathological features of the grafts could be accommodated in three groups.Type 1. Sheep #1 sin. (379 days), #3 sin. and dx. (308 days), #4 sin. and dx. (99 days), and #5 sin. and dx. (211 days): the three layers were clearly visible. There was an occasional thin layer of fibrin on the inner layer with flat cellular elements, acellular and avascular inner layer, large cell reaction in the middle layer, and vascularization of the middle and outer layers with good engraftment (raftment .Type 2. Sheep #7 sin. and dx. (161 days) and #6 sin. and dx. (160 days): there were inflammatory changes in the middle layer of the graft with foci of bleeding and disintegration of the middle layer which was followed by focal necrosis and detachment of the inner layer with deposits of fibrin and inflammatory cells. Vascularization of the outer layer with good engraftment was present ( present .Type 3. Sheep #2 sin. and dx. (53 days): the graft was narrowed due to thickening of the wall with the multifocal separation of the outer layer; the inner surface was uneven with occasional small wall-adherent thrombi ( thrombi .In this in vivo study, we have demonstrated good performance of a newly designed three-layer collagen-based vascular graft designed for low-flow vascular reconstructions, with a patency rate of 92% with a median follow-up of 161 days in a sheep model. Compared to patients with critical limb ischemia with patency rates varying between 50 and 78% depending on concomitant treatment, this is a favorable outcome considering that the animals were not receiving any antiplatelet or anticoagulant after the first postoperative week .Although autologous grafts from the great saphenous vein should be preferred to PTFE grafts whenever possible due to their superior patency rates , 14, thiMechanical properties of the fabric of prosthetic vascular grafts are of importance. High porosity of the inner layer reduces graft compliance due to fibrovascular infiltration of the wall and low porosity impedes formation of the neointimal lining , 7. In oThe outer layer showed neovascularization in 9 grafts which is a favorable process that ensures nutrition of the wall and its integration into the body metabolism. This process had probably been facilitated by high permeability of the outer layer of the graft and infiltration of the middle layer with large cells consistent with a reaction to foreign bodies . AlthougFlow velocity in a vascular graft is one of the key determinants of its durability , 21. LowThis study has several limitations. Firstly, the immune reaction to the graft wall may be different between sheep and humans. Secondly, all patients with vascular grafts require lifelong antiplatelet therapy, which we gave to the animals during the first postoperative week only. Thirdly, we did not fully appreciate the fact that the reaction to the changes in circulation in a sheep is much more dynamic than in humans. The target flow rate around 100 ml/min achieved by placing a sling increased after several days in most of the grafts. Fortunately, it remained below 200 ml/min for all the animals. Lastly, the location of the sling was not held constant among the study animals. We became aware of the fact that the placement of the sling before or on the graft would induce turbulent flow that might affect patency of the graft on its own. Therefore, we modified the protocol and placed the sling in the outflow segment.This study demonstrates good patency rates of a newly designed three-layer vascular graft even in low-flow conditions in a sheep model. The differences in cellular reaction to the graft among the animals represent various degrees of immune reaction and need to be addressed in further research.


This study analyzes the effect of conditional mediation of environment-absorptive capacity in international entrepreneurial orientation of family businesses. Results involve data from 218 Spanish family businesses, analyzed with SmartPLS 3.2.7 software. This paper presents a relevant contribution both to the academic field and the performance of family firms, helping to understand the process of transforming international entrepreneurial orientation into a better international performance through absorptive capacity while family businesses invest their efforts in aligning international entrepreneurial orientation and absorptive capacity with international results, bearing in mind the positive moderator effect of environment. The most relevant contribution of this work is to integrate in the same model the mediating effect of the absorption capacity and the moderating effect of the environment: the effect of the international entrepreneurial orientation on the international performance of family businesses improves with the mediation of the absorptive capacity  and the moderation of the environment . In the past few years, entrepreneurial orientation, internationalization (IEO), absorptive capacity (ACAP), and environment (ENV) have drawn much academic and business interest. This study attempts to address the above concerns by checking how these concepts relate to each other. The first two concepts can be related through what has come to be known as “international entrepreneurial orientation.” It is an emerging area of research that seeks to analyze the innovative, risky and proactive behaviors of companies with international activity . The participation in the study was voluntary and participants were advised of the anonymity of their answers. Participants were sent a letter presenting the research and its purpose. Research Ethics Committee must not intervene in this type of studies like our research work in Spain. The questionnaire involves Likert-type questions 1–5). The sample consists of 1,045 family businesses registered in the IEF, who produced 218 responses, which represents 20.86%. Fieldwork was conducted between June to November 2016 . This is done using the G. This isThis variable was measured according to the scale proposed by Miller  and thenMeasurement of ACAP uses a four-dimension scale validated by Flatten et al. , who evaIn the present work, international performance is measured according to a multi-item scale based on exporting intensity, which was included as a measure of international performance by some authors such as Zahra et al.  and MorgScales proposed by Robertson and Chetty , BalabanThe control variables under study are: size (number of employees), age (years of service since start-up) and activity sector (industry and services) of the family business. These variables are often used in studies on family business  method, a structural equation multivariate quantitative method. The PLS method allows addressing the research questions, due to its predictive nature . There is discriminant validity when the resulting interval contains values lower than 1. This is the case of this study  . Of the model it appears that the IEO explains 32.5% of the international performance variance of family businesses.First, the direct effect between IEO and international performance of family businesses was analyzed. To do so, the value of the path coefficient was checked, along with its significance . The effect is positive and significant  H2a: β = 0.696; p < 0.001; and between ACAP and international performance H2b: β = 0.439; p < 0.001). The mediating effect completely eliminates the direct effect, since the direct relationship between the IEO and the international performance of family businesses has a β = −0.093 and is not significant.The second step was to include the effect of the mediating variable (ACAP). As observed in Figure 11). Therefore, this study has proven the mediation between ACAP in relation to IEO and international performance of family businesses. Additionally, this mediating effect is a total effect, as it removes the direct effect  and ACAP vs. international performance . Moreover, this moderator effect increases explained the variance of international performance almost in 8%, from 40.6 to 45.3%, confirming the double moderator effect of ENV of the proposed model  and a result of 0.24 for the second moderator effect of environment .Third step consists on introducing moderator effect of ENV when comparing IEO vs. ACAP (first moderator effect) as well as in the relation between ACAP and international performance (second moderator effect). As we can see, moderator effect of ENV is present both in the relation IEO vs. ACAP  (see Table None of the control variables has an influence that may be considered relevant (the path coefficients are less than 0.2) and are not significant  is improvedThe first conclusion of this model is that the dimensions used to measure the different variables and the variables themselves have values of reliability and convergent and discriminant validity above the thresholds established by the literature (Fornell and Larcker, The second conclusion of this study is that international performance of family businesses can be explained to a great extent by IEO. This result is consistent with previous studies (Miller and Friesen, The third ACAP is demonstrated: it can have a direct role (e.g., Liao et al., Finally, the ENV acts as a positive moderator in the mediation model of the ACAP between the IEO and the international performance of family firm. In our case, the consideration of the ENVsupposes to improve the explanation of the variance of the international performance of the family firms up to 45.3%. This study confirms the moderating effect of the environment, and also confirms that in turbulent environments, ACAP becomes an essential part of improving EO (Todorova and Durisin, The implications of this study in relation to family business management are as follows:Entrepreneurial behavior is an important factor in the international performance of family businesses (in line with Hernández-Perlines et al., IEO acts as a background for ACAP (in line with Wales et al., Taking into account ACAP will allow family businesses to improve their international profits [in similar terms with what stated by Yeoh ].Family businesses can use the mediation of ACAP to improve their international profits through IEO, as a mediating variable.As for limitations of the study, the first limitation is using a single informant in Likert-type scales. To overcome this limitation, the study follows recommendations by Rong and Wilkinson , WoodsidAs future research lines, this study suggests conducting longitudinal studies to analyze the effect of time or the presence of family members in business management, or the generational level. Also, comparative studies with other firms/countries are suggested, in order to check for significant differences. Finally, this study suggests analyzing the mediating effect of ACAP by taking into account both its potential and realized dimensions (Zahra and George, Ethics approval for this research was not required as per institutional and national guidelines. Consent from all research participants was obtained by virtue of survey completion.All authors listed, have made substantial, direct and intellectual contribution to the work, and approved it for publication.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.


This paper presents new findings concerning a hand-held stiffness probe for the medical diagnosis of abnormalities during palpation of soft-tissue. Palpation is recognized by the medical community as an essential and low-cost method to detect and diagnose disease in soft-tissue. However, differences are often subtle and clinicians need to train for many years before they can conduct a reliable diagnosis. The probe presented here fills this gap providing a means to easily obtain stiffness values of soft tissue during a palpation procedure. Our stiffness sensor is equipped with a multi degree of freedom (DoF) Aurora magnetic tracker, allowing us to track and record the 3D position of the probe whilst examining a tissue area, and generate a 3D stiffness map in real-time. The stiffness probe was integrated in a robotic arm and tested in an artificial environment representing a good model of soft tissue organs; the results show that the sensor can accurately measure and map the stiffness of a silicon phantom embedded with areas of varying stiffness. Palpation is frequently used in medical practice and plays an important role in physical diagnosis . A palpaIt is reported that the sensitivity of palpation procedures, i.e., the clinician’s ability to correctly identify a tumour, is subjective and highly dependent upon the skill and experience of the practitioner—a skill often difficult to master ,5,6. InaIn this paper, we propose a vision-based multi-directional stiffness sensor, as shown in Early diagnosis, during the first stage of cancer development, leads to a precocious therapeutic strategy, with high chances of recovery or prolongation of the patient’s life expectancy. Changes in tissue stiffness may be an indication that cancer is present and thus one of the points of interest within the robotics and haptics research community has been the development of methods for tissue elasticity measurement. Therefore, starting from the early 1990s, in order to enhance the outcome of physical examinations, different instruments and technologies have been developed and explored. Indentation is one of the most exploited diagnostic techniques used to measure reaction forces as well as stiffness of a probed tissue . GeneralFurther investigation of the influence of the inclination of the probe on the computation of the stiffness.Generation of a colour-coded stiffness map using a magnetic tracking mechanism.Evaluation of the sensor performance in robotic palpation.In previous works, the authors proposed a single axis force sensor device using a vision system to “view” the deformation of the sensing element for minimally invasive surgery (MIS) . The senThe proposed stiffness probe is composed of four indenters, each of which is connected to a spring and a spherical feature, and a standard USB camera tightly assembled in a 3D printed shell. The USB camera has an outer diameter of dilate and erode are applied to eliminate the bias and reduce the noise. The sliding movements of the feature’s centroid along the horizontal axis are then tracked using the image moment. A Kalman filter is applied to robustly track the features, and the position of each centroid is mapped in a fixed reference system with its origin at the sensor. The mapping between the movements of the feature’s centroid in the image, in The image processing algorithm consists mainly of the detection and tracking of coloured spheres in an image. In order to compute the intrinsic parameters of the camera and eliminate distortions of the lens, the camera calibration toolbox in the robot operating system (ROS), was used. The algorithm involves different steps: image-filtering in the HSV  color space to detect the coloured feature; in the obtained greyscale image, four Regions of Interest (RoIs) are selected. Each RoI contains a section of the image that is related to the full range of motion of one spherical feature. In each RoI, the morphological operators x–z plane of the local reference system on the probe and the position of the indenters is expressed in this frame. As the springs are compressed or decompressed, the indenters are sliding, changing their z-position in the local reference frame; consequently, the spherical features are moving, changing their x-position in the image plane. The relationship between the springs, the indenter and the spherical features allow mapping the variation in position of the centroids, to the change in depth of the indenters.A local reference system was chosen on the stiffness probe as shown in The mapping between the position of the spherical features in the image and the position of the indenters is used to characterise the interaction between our device and the probed tissue. The sliding motion of the three indenters placed on the vertices of the triangle make use of the same type of spring, while the indenter in the centre is connected to a spring with a higher spring constant, thus it moves less during the interaction with the soft tissue. The stiffness of the surface in contact can be computed using the forces applied by the harder indenter placed in the barycentre of the triangle and the three softer indenters . In our Seven parameters are sufficient to fully characterise a palpation procedure with the proposed stiffness probe: the stiffness of the soft tissue, ith sphere, ith and jth sphere in the reference system of the sensor. In Equation , dxi is applied here to solve Equation . This alIn order to be able to find a solution to the unknown parameters and to compute the stiffness in real time, in the implemented algorithm, the threshold Algorithm 1 Iterative procedure solving Equations  is fixed to an allocated position on the stiffness probe, as shown in To evaluate the performance of the vision-based stiffness sensing mechanism in medical robotics applications, the stiffness probe is fixed to the end-effector of the Lightweight 6 degrees of freedom (DOF) robot arm LWA 4P by SCHUNK GmbH & Co. KG  . A multi-axis ATI force/torque sensor by ATI Technologies Inc. , is attached to the end-effector of the robotic arm and the stiffness sensor is fixed to the front plate to palpate silicone phantoms as shown in 06z-axis. The transformation matrix that expresses the local frame with origin on the stiffness probe into the base frame is:Given the six joint values, [Different experiments were carried out to analyse the performance of the proposed stiffness probe. The proposed algorithm runs at the same rate of the USB camera embedded in the device, i.e., The linear elastic model was used here to mimic human soft tissue. In this model, the tissue is considered as a homogeneous, linear elastic material; the stress/strain relationship is assumed to be linear too. Although biological tissues are much more complex, this behaviour was found coherent for a relative strain under 10 to 15% . Under t15% . Therefo15%  can be u15% . Each saThe hand-held stiffness probe is equipped with the Aurora reference disk tracker, as shown in Evaluation tests have been performed using the SCHUNK Lightweight Arm LWA 4P, as shown in The value of the parameter found was A customised phantom presenting areas of different stiffness values as shown in In this paper, further investigation on the multi-directional capability of the hand-held stiffness probe for medical palpation developed in our previous work  has beenReferences


The mixed chimerism approach is an exceptionally potent strategy for the induction of donor-specific tolerance in organ transplantation and so far the only one that was demonstrated to work in the clinical setting. Regulatory T cells (Tregs) have been shown to improve chimerism induction in experimental animal models. This review summarizes the development of innovative BMT protocols using therapeutic Treg transfer for tolerance induction.Treg cell therapy promotes BM engraftment in reduced conditioning protocols in both, mice and non-human primates. In mice, transfer of polyclonal recipient Tregs was sufficient to substitute cytotoxic recipient conditioning. Treg therapy prevented chronic rejection of skin and heart allografts related to tissue-specific antigen disparities, in part by promoting intragraft Treg accumulation.Adoptive Treg transfer is remarkably effective in facilitating BM engraftment in reduced-intensity protocols in mice and non-human primates. Furthermore, it promotes regulatory mechanisms that prevent chronic rejection. The age-long history of organ transplantation is a story of miracles, myths, and science fiction until six decades ago, when the first successful kidney transplant was performed between identical twins . Some yeRegulatory T cells (Tregs) are not only the key mediators of self-tolerance, preventing fatal autoimmunity , but areTolerance per se is defined by as immunological non-reactivity to a specific antigen while maintaining reactivity to others, in the field of transplantation this means “the absence of graft rejection without the (chronic) use of immunosuppressive drugs” . ExtensiAlthough mouse models have been an invaluable tool for uncovering the basic principles of allorecognition and defined strain combinations as well as genetically modified mice allowed dissection of individual pathways in transplantation immunology, there are major limitations when it comes to translation from mice to men . A majorClinicalTrials.gov Identifier: NCT01780844). Currently, next-generation anti-CD40L mAbs devoid of the Fc-mediated toxicity are under development and offer promise for clinical application [Another barrier for translation of tolerance approaches from mice to humans is the limited availability of pharmaceuticals. Blockade of the CD40:CD40L pathway using an anti-CD40L mAb (MR1) was the most successful and promising approach in murine models. It is the backbone of many non-myeloablative mixed chimerism protocols, obviating the need for global T cell depletion and thymic irradiation . A clinilication .Preclinical animal studies using knockout, immunodeficient, or TCR transgenic strains are definitely important for mechanistic understanding of allorecognition and signaling pathways. However, for the development of tolerance strategies, more realistic approaches using stringent strain combinations including minor antigen disparities, housing in non-SPF environment and clinically available pharmaceuticals are warranted.Mixed chimerism denotes a state of co-existence of donor and recipient hematopoietic cells after allogeneic BMT in a pre-conditioned recipient . InductiAs current clinical protocols for HLA-mismatched BMT are not ready for widespread clinical application for non-life-threatening diseases due to the toxicity related to recipient pre-conditioning and the risk of GVHD, a lot of effort has been made to develop “safer” BMT protocols. Considering the importance of regulatory mechanisms and the potency of Tregs to suppress allo-reactivity, adoptive Treg transfer has emerged as attractive possibility that might be the key to translating murine chimerism-based tolerance protocols to the clinic.+CD25+ Tregs, even in the presence of hematopoietic donor cells. However, neither regulation through Tregs nor classical anergy appear crucial several months after BMT for the maintenance of tolerance in established chimeras [Physiological self-tolerance not only involves central deletion but also critically requires non-deletional mechanisms  in order to maintain peripheral tolerance as autoreactive clones can escape negative selection. Deficits in central or peripheral tolerance cause autoimmune disease or in terms of transplantation tolerance result in graft rejection. In protocols using myeloablative and T cell depleting conditioning regimens, non-deletional tolerance mechanisms play a minor or even dispensable role likely due to the fact that potentially allo-reactive T cells are destroyed at the time of BMT and high levels of intrathymic chimerism retain central deletion of newly developing allo-reactive T cells. Experiments employing reduced intensity BMT protocols have revealed the importance for regulatory mechanisms in the induction phase of tolerance when deletion of allo-reactive T cell clones is still incomplete . Toleranchimeras . In sharchimeras ••, 31. Achimeras , 33, modchimeras , or adopchimeras . Chimerichimeras ••, 36 anchimeras •. This rchimeras –41. The chimeras  and it wchimeras .The original observation that the chimerism approach is successful in the clinical setting derives from numerous case reports in which conventional BMT recipients  subsequently received an organ from the same donor for unrelated treatment of organ failure . In suchThe MGH approach is based on decade-long studies in mice and NHPs and initially tested in patient who suffered from coincidental multiple myeloma and end-stage kidney disease, legitimating BMT and cytotoxic recipient conditioning –59. The In contrast, in murine models, stable macrochimerism and sustained presence of discrete populations of donor APCs in the thymus is a pre-requisite for durable tolerance as it ensures intrathymic deletion of alloreactive T cells. Nevertheless, high levels of chimerism do not necessarily predict long-term allograft survival and donor T cell engraftment was shown to be critical for long-term tolerance . Dissoci+CD25+FoxP3+ Tregs for tolerance induction have been envisioned since the (re)discovery of these powerful suppressor cells more than two decades ago [onestudy.org).Cell therapy approaches using CD4ades ago  and is cThe therapeutic potential of Tregs was underlined by numerous reports, showing potent effects in pre-clinical autoimmune and allo-transplantation models; however, in these reports, the use of lymphopenic hosts , 70 or TAlthough the hype has stagnated a little bit during the last years due to the realization of several hurdles associated with adoptive Treg therapy , a recenGiven the potency of both approaches, combination of the mixed chimerism approach and adoptive Treg transfer seems to be the next logical step on the search for the holy grail of tolerance . The pro6 which corresponds to ≈ 1 × 109 cells/kg). Recipient preconditioning was non-myeloablative and consisted mostly of mild doses of irradiation and/or costimulation blockade targeting the CD40:CD40L or CD28:B7 pathway. Notably, Treg transfer was capable of obviating the need for recipient irradiation (or cytotoxic drug treatment), allowing for the first time engraftment of fully mismatched BM without myelosuppression [6 cells. The most interesting and critical question is the source of Tregs (donor- vs recipient- vs third party-derived) and the need for specificity . Several groups reported that antigen-specific Tregs are more potent compared to a polyclonal Treg population in models with [Most of the protocols with combined Treg and BMT are employing clinically achievable doses of allogeneic BM immune responses is recognized as a complex network of multiple regulatory cell types, CD4


European Journal of Psychotraumatology is proud to announce its first special issue focusing on the neurobiology of posttraumatic stress disorder (PTSD). Since its inception, the journal has published a number of papers on the neural mechanisms underlying PTSD, including review articles on the biological correlates of complex PTSD  by studying brain activation patterns during traumatic memory recall with and without eye movements (Thomaes, Engelhard, Sijbrandij, Cath, & Van den Heuvel, European Journal of Psychotraumatology.In summary, we have received a range of articles focusing on key emerging neurobiological and clinical concepts in PTSD. We look forward to receiving more papers focusing on the neurobiology underlying trauma-related disorders in order to make this area an integral part of the


I thank Editor Peter Almond for inviting me to write this Editorial for the second issue of the Journal of Applied Clinical Medical Physics (JACMP). This gives me the opportunity to be one of the first to congratulate Professor Almond, his Advisory and Editorial Boards, and the American College of Medical Physics (ACMP) on their outstanding new contribution. I especially want to recognize the contributions of Associate Editor Mike Mills. It was Mike who first thought of this journal several years ago, and without Mike's foresight, enthusiasm, and persistence, it is unlikely that this journal would have made it to our desktops today.What impresses me most about the JACMP is its professional, polished appearance. You would never know it is a brand new journal. Much of this is due to the inspired selection of the AIP as the publisher. The American Institute of Physics (AIP) has considerable experience with putting journals online, including our other journal, Medical Physics. I am especially pleased that the formats of our two online journals are so similar. There is considerable overlap in our readership so it is appropriate that readers who become familiar with maneuvering through one journal will find it seamless (and painless) to move through the other. When the JACMP was first proposed, many of us feared that it might be envisioned as a rival to Medical Physics. The last thing we needed was another scientific journal of medical physics. With this in mind, it was decided that the JACMP would concentrate on publication of clinical, professional, and educational articles, as opposed to the research manuscripts and extensive reports published in Medical Physics. In my mind, there is no question: the JACMP complements rather than competes with Medical Physics. Indeed, for the past six months‐or‐so, the Associate Editors of Medical Physics and I have frequently recommended that some of the manuscripts submitted to Medical Physics would be better off published in the JACMP. This is often done before extensive review, which would otherwise delay submission to the JACMP. Our new journal is clearly of benefit to authors and readers alike and, as an Editor, I can attest that it is also of benefit to me. I have often felt dejected because I have had to inform an author of the rejection of a well‐written article just because it was out of the scope of Medical Physics, especially when there was no suitable alternative journal to which to refer it. This is no longer the case.I am especially interested in the fully online nature of this journal: online submission, online review, and online publication. I have no doubt that this is the way journal publications will have to go in the near future. Indeed, I am already watching the progress of the JACMP with the intention of using many of the online features for Medical Physics.Congratulations Peter on an excellent start to an outstanding journal. With your leadership, I am confident that the JACMP will soon become a major player in the medical physics publication arena.Colin G. Orton, Ph.D.Editor, Medical Physics