Contraction Stress Research Articles

Assessment of antioxidant activity of Ocimum sanctum in healing of thermal burn wound with and without supportive treatment of silver sulfadiazine in rabbits

Background: Burns remain a major public health issue all over the world, especially in developing countries. Pseudomonas aeruginosa is a major cause of infection and death in patients with severe burns. So, there is a need to develop drugs which will decrease complications and prevent infections more effectively than the presently used drugs.Methods: Ocimum sanctum, ointment silver sulfadiazine and 24 Rabbits were used in this study. Animals were acclimatized and divided randomly into 04 groups of 06 animals each. After producing partial thickness burn wound ointment silver sulfadiazine was applied daily on the burn wound and Ocimum sanctum was administered orally once daily. Healing was assessed by wound contraction and Oxidative stress and Antioxidant Activity were measured by Malondialdehyde and Superoxide dismutase respectively. Results were analysed by student’s ‘t’ test, one way ANOVA followed by Dennett’s test. P values <0.05 were considered statistically significant.Results: At the end of treatment (After 28th Day) Group treated with ointment silver sulfadiazine+Ocimum sanctum showed maximum Percentage of wound contraction (93.17±4.34), maximum decrease of MDA percentage (0.30±0.02 nmol/ml) and maximum increase of SOD percentage (0.0045±0.0002 IU/gm of Hb).Conclusions: Most effective treatment for burn wound healing in this study was ointment silver sulfadiazine+Ocimum sanctum.

Mechanical analysis of intestinal contractility in a neonatal maternal deprivation irritable bowel syndrome rat model

The aims of the present study are to investigate biomechanical properties and provide mechanical analysis of contractility in ileum and colon in a neonatal maternal deprivation (NMD) irritable bowel syndrome (IBS) rat model. Mechanical testing was done on segments from ileum and colon in 25 IBS rats and 13 Control rats. Morphometric data were obtained from digitized images of the segments at no-load and zero-stress states. Pressure and diameter changes were measured during flow and ramp distensions under active and passive experimental conditions. Circumferential stresses (force per area) and strains (deformation) were computed with referenced to the zero-stress state. The contraction frequency was analyzed. Contraction thresholds and maximum contraction amplitude were calculated in terms of mechanical stress and strain. Compared with controls, the IBS rats had lower body weight (P < 0.01), smaller colonic opening angle (P < 0.05), higher colonic contraction frequency (P < 0.05 and P < 0.01) and lower contraction thresholds of pressure, stress and strain in both ileum and colon (P < 0.05 and P < 0.01). The maximum contraction pressure, stress and strain did not differ between IBS and Control groups (P > 0.05). In conclusion, the pressure, stress, and strain to evoke contractility in ileum and colon were lower whereas the frequency of induced colon contractions was higher in NMD IBS rats compared to normal rats. Furthermore, zero-stress state remodeling occur in colon in NMD IBS rats. Further studies on the association between intestinal biomechanical properties, hypersensitivity and afferent signaling in the IBS animal models are warranted.

Relationships between psychological contract violation, stress and well-being in firefighters

Purpose Negative emotions resulting from the broken promises by the organisation or employers, as perceived by an employee are called psychological contract (PC) violation. The purpose of this paper is to examine the relationships between perceived feelings of violation, work-related stress, anxiety and depression. Fairness and self-efficacy are used as mediators to understand the underlying mechanism of associations. Design/methodology/approach In total, 97 firefighters completed an online-survey and structural equation modelling was used to examine the multiple mediation models. Findings PC violation was positively associated with occupational stress and job-related well-being. Together, fairness and self-efficacy mediated the relationship between feelings of violation and job-related depression. Therefore, the results partially supported the hypotheses. Originality/value As the first quantitative study of its kind, this study makes an important contribution to the firefighters literature by investigating the potential influence of PC violation on their work-related stress and well-being. Also, previous studies have failed to identify fairness and self-efficacy as potential mediators of the PC violation.

Influence of Al addition on solidification path and hot tearing susceptibility of Mg–2Zn–(3 + 0.5x)Y–xAl alloys

Abstract Hot tearing susceptibility (HTS) of Mg–2Zn–(3 + 0.5x)Y–xAl (x = 0, 2 and 3 at%) alloys is predicted by using modified Clyne–Davies’ model (CSC*). The solidification path, solidification characteristic temperatures and dendritic coherency solid fraction have been studied by double-thermocouple thermal analysis. The solidification contraction stress vs. temperature (and time) curves are measured by using a “T” type hot tearing permanent-mold. The results reveal that the CSC* prediction values are in good agreement with the experimental results. Moreover, Al2Y phase acts as the heterogeneous nucleation core of α-Mg and significantly influences the grain size. It has been observed that minimum grain size, optimal dendritic coherency and minimum HTS are exhibited by Mg–2Zn–(3 + 0.5x)Y–xAl alloy (x = 2). Furthermore, when Al content was increased to 3 at%, Al2Y phase exhibited a peritectic reaction and transformed into a mixed structure of Al2Y and Al + Al3Y phases, which increased the HTS of the alloy due to reduced fine-grained Al2Y content.

Different depth-related polymerization kinetics of dual-cure, bulk-fill composites

ObjectiveThe aim of this study was to evaluate the polymerization kinetics qualitatively and quantitatively for dual-cure bulk-fill composites in comparison with light-cure bulk-fill and traditional incremental composites at two clinically relevant depths. MethodsFive commercial dental composites were evaluated, including three dual-cure bulk-fill composites (BulkEZ, HyperFIL and Injectafil), one light-cure bulk-fill composite Filtek Bulk Fill Flowable (FBF) and one traditional incremental composite Filtek Z250 (Z250) as controls. Specimens were prepared in two different depths (0.5 mm and 5 mm) for 20 s light irradiation. Self-cure was also evaluated for the three dual-cure composites. The polymerization kinetics were measured continuously in real-time for at least 10 min using a Fourier-transform infrared spectroscopy (FTIR) with an attenuated total reflectance (ATR) accessory. The experimental kinetic data were fitted using two mathematical models — a sigmoidal function and a superposition of two exponential functions characterizing the gel phase and glass phase. The degree of conversion (DC) and the rate of polymerization were calculated for all test conditions. ResultsBoth experimental FTIR measurements and mathematical modeling revealed distinct depth-related polymerization kinetics for BulkEZ compared to the other two dual-cure composites. Specifically, BulkEZ exhibited moderately-paced polymerization kinetics at both depths while HyperFIL and Injectafil exhibited faster polymerization at 0.5 mm and slower polymerization at 5 mm. The bulk-fill FBF and incremental Z250 exhibited relatively fast polymerization at both depths, a characteristic for light-cure. The DC values at the two depths were not significantly different for BulkEZ, but significantly higher at 0.5 mm than at 5 mm for the other four composites (α = 0.05). SignificancePolymerization kinetics and their depth variation for dual-cure bulk-fill composites are material dependent. The distinct depth-related polymerization kinetics revealed for BulkEZ compared to other composites may affect their contraction stress and clinical performance.

Outcrop evidence of polygonal faulting in Ypresian marine clays (Southern North Sea Basin) leads to a new synthesis

Layer-bound, polygonal fault systems (PFS) in marine, fine-grained sediments have been documented with seismic data over large areas in over 100 basins. The questions of how, when and how fast these muds broke without tectonic stress were still open. This study covered the missing observational length scales from 100 m to μms with a continuous range of outcrop observations and related lab results from two quarries in Ypresian marine unlithified swelling clays in the Belgian part of the North Sea Basin.The observed coeval dilatant hydrofractures and folded faults imply highly unstable and transitional tensile fracturing behaviour under shallow overpressure. The random fault plane orientations, radial striation vectors and conal micro-faults exclude far-field stress and slope instability as the driving force, and show that gravity was the major principal stress. A contributing driving force was overpressure in the oxidising fluviatile and lagoonal sands below, which further weakened its clayey caprock and supplied at least part of the water evacuating through it. This fracture water flow eroded and oxidised bits of wall clay and tell-tale microfossil mixtures along the way up. The sharp contrast of black gouge against barely stained wall clays implies that such dilatant fracture and fault growth was almost instantaneous. This resulted in winner-takes-all shear localisation along often razor-thin, slickensided fault mirrors. Faults that locked-up by different degrees of compaction folding and local rotational flow imply: 1) that this clayey mud was still an underconsolidated viscoplastic gel just prior to plastic faulting, capable of syneresis and therefore capable of supplying isotropic contractional stress; 2) not episodic growth but episodic nucleation of additional fractures and faults and punctuated dewatering along them, until the clayey gel matrix and the overpressure in it were fully deflated.

Internal Structures and Growth Style of a Quaternary Subaerial Rhyodacite Cryptodome at Ogariyama, Usu Volcano, Hokkaido, Japan

This paper describes internal structures of a Quaternary subaerial rhyodacite cryptodome at Usu volcano, Japan, and examines the textural differences between subaerial and subaqueous cryptodomes. Ogariyama dome is one of the youngest subaerial cryptodomes in the world (<0.4 ka). The cross-section of this young cryptodome is visible because a vertical fault formed during the 1977–1978 eruption and cut through the center of the cryptodome, exposing its interior. The morphology of the cryptodome is scalene triangular in shape, with rounded corners in cross-section, and it is 150 m across and 80 m high. The internal structure of the dome is concentrically zoned, with a massive core, jointed rim, and brecciated border, all of which are composed of uniform, feldspar-phyric rhyodacite (SiO2 = 71–72 wt.%). The massive core (130 m across) consists of coherent rhyodacite that has indistinct, large-scale flow banding and rectangular joints that are spaced 50–200 cm apart. The jointed rim (8–12 m wide) surrounds the massive core and consists of coherent rhyodacite that is characterized by distinct rectangular joints that are 30–80 cm apart and radiate outward. The outermost brecciated border (7–10 m wide) comprises monolithological breccia, consisting of angular rhyodacite clasts (5–30 cm across) and a cogenetic matrix. These internal structures suggest that Ogariyama dome was formed by endogenous growth, involving continuous magma supply during a single intrusive event and simple expansion from its interior. The massive core formed by slow cooling of homogeneous rhyodacite magma. The jointed rim formed by fracturing of solidifying rhyodacite magma in response to cooling–contraction and dynamic stress driven by continued movement of the less viscous core. The brecciated border formed by fragmentation of the solidified rim of the dome in response to dynamic stress. The growth style of Ogariyama dome closely resembles that of subaqueous cryptodomes. However, the morphology and internal structures of Ogariyama dome differ from those of subaqueous cryptodomes, given its asymmetric morphology and absence of radial columnar joints and large-scale flow banding. These differences might reflect the well-consolidated and non-homogeneous physical properties of host sediment, slow cooling rate, and high viscosity of the Ogariyama dome.

Beef tenderness and intramuscular fat proteomic biomarkers: Effect of gender and rearing practices

This study analyzed the effect of gender on the abundances of 20 protein biomarkers of tenderness and/or intramuscular fat content in five muscles: Longissimus thoracis, previously identified as biomarkers of tenderness and/or intramuscular Semimembranosus, Rectus abdominis, Triceps brachii and Semitendinosus, from cows and steers of the Protected Designation Origin Maine Anjou. The protein abundances were quantified using Reverse Phase Protein Array with specific validated antibodies. Among the 20 studied proteins, the abundance of 8 biomarkers involved in energetic metabolism, contraction and cellular stress, was different according to gender. The gender effect was different depending on the muscle type with greater abundances in Semitendinosus, Rectus abdominis and Longissimus thoracis muscles. On the basis of animal characteristics and rearing factors, three rearing practices classes were identified for cows. Among the factors, fattening duration modified the abundance of 12 proteins mainly in Triceps brachii muscle. A positive correlation between the abundance of the small HSP20 and slaughter age was observed in the 5 muscles. Two proteins, Four and a half LIM domains 1 (FHL1) and Glycogen phosphorylase (PYGB) appeared to be muscle, gender and rearing practices independent. These results constitute valuable data to understand how to manage beef quality by controlling these different factors. SignificanceThis study is the first to compare the relative abundance of 20 proteins previously identified as biomarkers of tenderness and/or intramuscular fat (IMF) content of beef meat between cows and steers among 5 different muscles. Its originality is in the use of Reverse Phase Protein Array for fast quantification of the proteins and the integration of data from rearing factors, carcass characteristics and biomarkers of meat qualities. The findings provide evidence for modulating biomarker levels by controlling the choice of animal type and rearing factors according to the type of muscle that would produce animals with the desired meat qualities.

Ultrafast negative thermal expansion driven by spin disorder

We measure the transient strain profile in a nanoscale multilayer system composed of Yttrium, Holmium and Niobium after laser excitation using ultrafast X-ray diffraction. The strain propagation through each layer is determined by transient changes of the material-specific Bragg angles. We experimentally derive the exponentially decreasing stress profile driving the strain wave and show that it closely matches the optical penetration depth. Below the Neel temperature of Ho, the optical excitation triggers negative thermal expansion, which is induced by a quasi-instantaneous contractive stress, and a second contractive stress contribution rising on a 12 ps timescale. These two timescales have recently been measured for the spin-disordering in Ho [Rettig et al, PRL 116, 257202 (2016)]. As a consequence we observe an unconventional bipolar strain pulse with an inverted sign travelling through the heterostructure.

A simple mechanochemical model for calcium signalling in embryonic epithelial cells

Calcium signalling is one of the most important mechanisms of information propagation in the body. In embryogenesis the interplay between calcium signalling and mechanical forces is critical to the healthy development of an embryo but poorly understood. Several types of embryonic cells exhibit calcium-induced contractions and many experiments indicate that calcium signals and contractions are coupled via a two-way mechanochemical feedback mechanism. We present a new analysis of experimental data that supports the existence of this coupling during apical constriction. We then propose a simple mechanochemical model, building on early models that couple calcium dynamics to the cell mechanics and we replace the hypothetical bistable calcium release with modern, experimentally validated calcium dynamics. We assume that the cell is a linear, viscoelastic material and we model the calcium-induced contraction stress with a Hill function, i.e. saturating at high calcium levels. We also express, for the first time, the “stretch-activation” calcium flux in the early mechanochemical models as a bottom-up contribution from stretch-sensitive calcium channels on the cell membrane. We reduce the model to three ordinary differential equations and analyse its bifurcation structure semi-analytically as two bifurcation parameters vary—the textit{IP}_3 concentration, and the “strength” of stretch activation, lambda . The calcium system (lambda =0, no mechanics) exhibits relaxation oscillations for a certain range of textit{IP}_3 values. As lambda is increased the range of textit{IP}_3 values decreases and oscillations eventually vanish at a sufficiently high value of lambda . This result agrees with experimental evidence in embryonic cells which also links the loss of calcium oscillations to embryo abnormalities. Furthermore, as lambda is increased the oscillation amplitude decreases but the frequency increases. Finally, we also identify the parameter range for oscillations as the mechanical responsiveness factor of the cytosol increases. This work addresses a very important and not well studied question regarding the coupling between chemical and mechanical signalling in embryogenesis.

Physical Model for Cell Migration Guided by Elastic Properties of the Substrate

During annual fish epiboly, between the egg yolk and the enveloping layer cells (EVL),there is a group of deep cells that move in contact with EVL layer. It is experimentally observed that these cells migrate toward the EVL borders and move freely on them. Apparently,the phenomenon is due to elastic properties of the EVLs: either a difference in the Young modulus on the border or a stress gradient inside the cell. In this work,a model is developed to elucidate how this kind of migration works and what are sensing the cells. It considers a cell modelled as a circle with four contacts on a thin elastic membrane,representing the EVL layer. Each of the four contacts simulates a random protrusion which elongates their end out of the center of the cell,attach rigidly to the substrate, and contracts without gliding. We study the elastic response of the substrate and its implications in the cell dynamics when it has different stiffness and when it is under internal tensions. In the first case, the substrate has a stiffer strip which simulates the EVL border which in theory has a higher Young modulus. In this case,the results do not show the expected durotaxis effect. In fact, the cell shows a random walk movement added to a slight repulsion generated by the border so that a stiffer strip on a thin plate is not enough to reproduce the phenomenon. In the second case,when the substrate is under internal applied tensions,the results show that in a substrate with circular geometry,if the contractive circumferential stress component increases with the radial distance,the cell migrates and reproduce experimental observations. We conclude that cell migration could be due to differences in internal tensions instead of thickness or stiffness differences.

Reducing musculoskeletal disorder (MSD) risk of wiring harness workstation using workplace ergonomic risk assessment (WERA) method

Bureau of Labor Statistics in Indonesia notes that musculoskeletal disorder (MSD) is the main category of injury causes in workplaces leading to 30% compensation costs. The purpose of this paper was to know the risk of work position of wire harness companies using workplace ergonomic risk assessment (WERA) for basic workstation improvements. The first step of this research was studying the literature of MSD, work posture, work position, and WERA. It subsequently proceeded with the identification and assessment process using WERA on each type of wiring harness activity. From the research results, it was obtained three jobs indicated causing muscle injury and soreness namely torque job, grommet job, and offline job. Moreover, the problem was supported by complaints from most workers known by using a discomfort survey. Based on the problem, this research was conducted to find out the action levels with WERA method and give improvement recommendation to overcome the problem of musculoskeletal disorders. The results of WERA showed that torque, grommet, and offl ine jobs needed further investigation and improvement with the scores of 31.23, 28.87, and 30.9. Recommendations were then given in the form of personal protective equipment (PPE) to reduce the risk factor scores on contract stress, to provide a new workstation design of torque job, and to add aids for solving other pain problems.

A Contraction Stress Model of Hypertrophic Cardiomyopathy due to Sarcomere Mutations.

SummaryThick-filament sarcomere mutations are a common cause of hypertrophic cardiomyopathy (HCM), a disorder of heart muscle thickening associated with sudden cardiac death and heart failure, with unclear mechanisms. We engineered four isogenic induced pluripotent stem cell (iPSC) models of β-myosin heavy chain and myosin-binding protein C3 mutations, and studied iPSC-derived cardiomyocytes in cardiac microtissue assays that resemble cardiac architecture and biomechanics. All HCM mutations resulted in hypercontractility with prolonged relaxation kinetics in proportion to mutation pathogenicity, but not changes in calcium handling. RNA sequencing and expression studies of HCM models identified p53 activation, oxidative stress, and cytotoxicity induced by metabolic stress that can be reversed by p53 genetic ablation. Our findings implicate hypercontractility as a direct consequence of thick-filament mutations, irrespective of mutation localization, and the p53 pathway as a molecular marker of contraction stress and candidate therapeutic target for HCM patients.

Influence of Secondary Dendrite Orientation on the Evolution of Misorientation in the Platform Region of Single Crystal Superalloy Turbine Blades

In the castings of Ni‐base single crystal superalloys, misorientation defects are detrimental to mechanical performance at high temperatures. In this study, combined seeding‐grain selection technique is used to study the effects of secondary dendrite orientation and withdrawal rate on dendrite growth and the associated evolution of misorientation in the platform region of single crystal superalloy turbine blades. It is observed that the rapid growth of dendrite arms near the platform edge induces a long secondary dendrite arm and the convergent boundary of dendrite arms (CBDA), and the misorientation angle along the CBDA monotonically increases. Furthermore, with the decrease in misorientation angle of the &lt;001&gt; SX orientation from the platform edge, the growth trace of dendrite arms required to cover CBDA increases, and the long secondary dendrite arm becomes more vulnerable to the contraction stress around platform edge, which leads to increased misorientation angle.

Proteomic Analysis of the Myocardium in Hypertrophic Obstructive Cardiomyopathy

Background: Hypertrophic cardiomyopathy (HCM) is characterized by a complex phenotype that is only partly explained by the biological effects of individual genetic variants. The aim of this study was to use proteomic analysis of myocardial tissue to explore the postgenomic phenotype. Methods: Label-free proteomic analysis was used initially to compare protein profiles in myocardial samples from 11 patients with HCM undergoing surgical myectomy with control samples from 6 healthy unused donor hearts. Differentially expressed proteins of interest were validated in myocardial samples from 65 unrelated individuals (HCM [n=51], controls [n=7], and aortic stenosis [n=7]) by the development and use of targeted multiple reaction monitoring-based triple quadrupole mass spectrometry. Results: In this exploratory study, 1586 proteins were identified with 151 proteins differentially expressed in HCM samples compared with controls ( P &lt;0.05). Protein expression profiling showed that many proteins identified in the initial discovery study were associated with metabolism, muscle contraction, calcium regulation, and oxidative stress. Proteins downregulated in HCM versus controls included creatine kinase M-type, fructose-bisphosphate aldolase A, and phosphoglycerate mutase ( P &lt;0.001). Proteins upregulated in HCM included lumican, carbonic anhydrase 3, desmin, α-actin skeletal, and FHL1 (four and a half LIM domain protein 1; P &lt;0.01). Myocardial lumican concentration correlated with the left atrial area (ρ=0.34, P =0.015), late gadolinium enhancement on cardiac magnetic resonance imaging ( P =0.03) and the presence of a pathogenic sarcomere mutation ( P =0.04). Conclusions: The myocardial proteome of HCM provides supporting evidence for dysregulation of metabolic and structural proteins. The finding that lumican is raised in HCM hearts provides insight into the myocardial fibrosis that characterizes this disease.

Proteomic Analysis of the Myocardium in Hypertrophic Obstructive Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is characterized by a complex phenotype that is only partly explained by the biological effects of individual genetic variants. The aim of this study was to use proteomic analysis of myocardial tissue to explore the postgenomic phenotype. Label-free proteomic analysis was used initially to compare protein profiles in myocardial samples from 11 patients with HCM undergoing surgical myectomy with control samples from 6 healthy unused donor hearts. Differentially expressed proteins of interest were validated in myocardial samples from 65 unrelated individuals (HCM [n=51], controls [n=7], and aortic stenosis [n=7]) by the development and use of targeted multiple reaction monitoring-based triple quadrupole mass spectrometry. In this exploratory study, 1586 proteins were identified with 151 proteins differentially expressed in HCM samples compared with controls ( P<0.05). Protein expression profiling showed that many proteins identified in the initial discovery study were associated with metabolism, muscle contraction, calcium regulation, and oxidative stress. Proteins downregulated in HCM versus controls included creatine kinase M-type, fructose-bisphosphate aldolase A, and phosphoglycerate mutase ( P<0.001). Proteins upregulated in HCM included lumican, carbonic anhydrase 3, desmin, α-actin skeletal, and FHL1 (four and a half LIM domain protein 1; P<0.01). Myocardial lumican concentration correlated with the left atrial area (ρ=0.34, P=0.015), late gadolinium enhancement on cardiac magnetic resonance imaging ( P=0.03) and the presence of a pathogenic sarcomere mutation ( P=0.04). The myocardial proteome of HCM provides supporting evidence for dysregulation of metabolic and structural proteins. The finding that lumican is raised in HCM hearts provides insight into the myocardial fibrosis that characterizes this disease.

CdS sensitized sol-gel derived thin films of self-patterned micro-blocks of closely-packed SnO2 nanoparticles as high-performance photoanodes in alkaline solution of methanol

Materials with patterned micro-/nano-structures fabricated via self-organization for the conversion and utilization of solar energy are attractive. Thin films of self-patterned irregular micro-blocks of closely packed SnO2 nanoparticles have been achieved here as photoanodes in photoelectrochemical cells for the first time, which are accomplished facilely by annealing SnO2 gel coatings on conducting glass substrates at 500 °C. During the annealing, the gel coating evolves into closely packed SnO2 nanoparticles. They self-assemble into irregular micro-blocks (mostly about 10 μm in size), generating dense network micro-cracks (∼2 μm wide in average) around the micro-blocks and nano-cracks embedded in the micro-blocks due to the thermal contraction stress that the SnO2 nanocrystallization and self-assembly induce. Optimally, the self-patterned SnO2 film is well sensitized with nanolayers of CdS nanoparticles by successive ionic layer adsorption and reactions for six cycles. Under optimized conditions, the prepared SnO2/CdS film demonstrates an apparent anodic photocurrent density as high as 10 mA cm−2 while holding the potential at 0 V (vs. SMSE) in a photoelectrochemical cell with 2 M NaOH +1 M methanol under visible light illumination of 100 mW cm−2, which is among the highest record for SnO2/CdS photoanodes. We ascribe its high performance not only to the patterned micro/nano-structure and the type-II energy level alignments of the SnO2/CdS photoanode, but also to the photo-electro synergistic catalyses in methanol oxidation reaction.

Contraction and Hydroscopic Expansion Stress of Dental Ion-Releasing Polymeric Materials.

Ion-releasing polymeric restorative materials seem to be promising solutions, due to their possible anticaries effect. However, acid functional groups (monomers) and glass filler increase hydrophilicity and, supposedly, water sorption. The purpose of the study was to evaluate the influence of water sorption of polymeric materials on the stress state at the restoration-tooth interface. Beautifil Bulk Fill Flow, Beautifil Flow Plus F00, Beautifil Flow F02, Dyract eXtra, Compoglass Flow, Ionosit, Glasiosite, TwinkiStar, Ionolux and Fuji II LC were used for the study. The stress state was measured using photoelastic analysis after: 0.5, 24, 72, 96, 168, 240, 336, 504, 672, 1344 and 2016 h. Moreover, water sorption, solubility and absorption dynamic were assessed. The water sorption, solubility and absorption dynamic of ion-releasing restorative materials are material dependent properties. The overall results indicated that the tested restorative materials showed significant stress decrease. The total reduction in contraction stress and water expansion stress was not observed for materials with low value of water sorption (Beautifil Bulk Fill, Dyract eXtra, Glasionosit and Twinky Star). The photoelastic method turned out to be inadequate to evaluate stress changes of resin modified glass-ionomer cement (RMGI, Fuji II LC and Ionolux).

The influence of filler amount on selected properties of new experimental resin dental composite

Abstract Aim of the study was to evaluate the influence of filler amounts on mechanical properties and contraction stress of light-curing experimental composite. Hardness, flexural strength, diametral tensile strength of material filled with 40, 50 or 60 wt. % of silanized silica were tested. The contraction stress was measured after 24 h by means of photoelastic study. The addition of 40-60 wt. % filler to composite caused significant increase in hardness, Young’s modulus and flexural strength. The DTS, after incorporating filler into polymer matrix, was valued at ~26 MPa. The composite containing 40 wt. % of filler demonstrated significantly lower contraction stress in comparison to neat resin and filled &gt; 50 wt. % of silica.

A Multiphysics Biventricular Cardiac Model: Simulations With a Left-Ventricular Assist Device.

Computational models have become essential in predicting medical device efficacy prior to clinical studies. To investigate the performance of a left-ventricular assist device (LVAD), a fully-coupled cardiac fluid-electromechanics finite element model was developed, incorporating electrical activation, passive and active myocardial mechanics, as well as blood hemodynamics solved simultaneously in an idealized biventricular geometry. Electrical activation was initiated using a simplified Purkinje network with one-way coupling to the surrounding myocardium. Phenomenological action potential and excitation-contraction equations were adapted to trigger myocardial contraction. Action potential propagation was formulated within a material frame to emulate gap junction-controlled propagation, such that the activation sequence was independent of myocardial deformation. Passive cardiac mechanics were governed by a transverse isotropic hyperelastic constitutive formulation. Blood velocity and pressure were determined by the incompressible Navier-Stokes formulations with a closed-loop Windkessel circuit governing the circulatory load. To investigate heart-LVAD interaction, we reduced the left ventricular (LV) contraction stress to mimic a failing heart, and inserted a LVAD cannula at the LV apex with continuous flow governing the outflow rate. A proportional controller was implemented to determine the pump motor voltage whilst maintaining pump motor speed. Following LVAD insertion, the model revealed a change in the LV pressure-volume loop shape from rectangular to triangular. At higher pump speeds, aortic ejection ceased and the LV decompressed to smaller end diastolic volumes. After multiple cycles, the LV cavity gradually collapsed along with a drop in pump motor current. The model was therefore able to predict ventricular collapse, indicating its utility for future development of control algorithms and pre-clinical testing of LVADs to avoid LV collapse in recipients.