scholarly journals On the development of instabilities in an annulus and a shell composed of a poro-hyperelastic material

2018 ◽  
Vol 474 (2218) ◽  
pp. 20180239 ◽  
Author(s):  
A. P. S. Selvadurai ◽  
A. P. Suvorov
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Numerical Solutions ◽  
Pore Space ◽  
Stability Loss ◽  
Computational Approach ◽  
Hyperelastic Material ◽  
Porous Skeleton ◽  
Internal Pressures

The paper investigates the development of instability in an internally pressurized annulus of a poro-hyperelastic material. The theory of poro-hyperelasticity is proposed as an approach for modelling the mechanical behaviour of highly deformable elastic materials, the pore space of which is saturated with a fluid. The consideration of coupling between the mechanical response of the hyperelastic porous skeleton and the pore fluid is important when applying the developments to soft tissues encountered in biomechanical applications. The paper examines the development of an instability in a poro-hyperelastic annulus subjected to internal pressure. Using a computational approach, numerical solutions are obtained for the internal pressures that promote either short-term or long-term instability in a poro-hyperelastic annulus and a poro-hyperelastic shell. In addition, time-dependent effects of stability loss are examined. The analytical solutions are used to benchmark the accuracy of the computational approach.

Infections and use of antibiotics in residents of long-term care facilities in Hungary

2014 ◽  
Vol 155 (23) ◽  
pp. 911-917 ◽  
Author(s):  
Rita Szabó ◽  
Karolina Böröcz
Keyword(s):  
Urinary Tract ◽  
Long Term Care ◽  
Soft Tissues ◽  
Good Practice ◽  
Antibiotic Use ◽  
Prevalence Survey ◽  
Term Care ◽  
Care Facilities ◽  
Tract Infections

Introduction: Healthcare associated infections and antimicrobial use are common among residents of long-term care facilities. Faced to the lack of standardized data, the European Centre for Disease Prevention and Control funded a project with the aim of estimating prevalence of infections and antibiotic use in European long-term care facilities. Aim: The aim of the authors was to present the results of the European survey which were obtained in Hungary. Method: In Hungary, 91 long-term care facilities with 11,823 residents participated in the point-prevalence survey in May, 2013. Results: The prevalence of infections was 2.1%. Skin and soft tissues infections were the most frequent (36%), followed by infections of the respiratory (30%) and urinary tract (21%). Antimicrobials were mostly prescribed for urinary tract infections (40.3%), respiratory tract infections (38.4%) and skin and soft tissue infections (13.2%). The most common antimicrobials (97.5%) belonged to the ATC J01 class of “antibacterials for systemic use”. Conclusions: The results emphasise the need for a national guideline and education for good practice in long-term care facilities. Orv. Hetil., 2014, 155(23), 911–917.

CHANGES IN BLOOD PROTEOME OF COSMONAUTS WITH MICRO- AND MACROVASCULAR INJURIES DUE TO G-LOADS AT THE FINAL STAGE OF LONG-DURATION SPACE MISSIONS

2020 ◽  
Vol 54 (5) ◽  
pp. 5-14
Author(s):  
L.Kh. Pastushkova ◽  
◽  
K.S. Kireev ◽  
I.M. Larina ◽  
◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Soft Tissues ◽  
Blood Rheology ◽  
Landing Site ◽  
Space Missions ◽  
Vascular Injuries ◽  
New Approach ◽  
Long Duration ◽  
Integrated Response

The integrated response of the human proteome to re-entry g-loads following long-term space missions was studied in 13 male cosmonauts at the age of 44 ± 6 years. Examination at the landing site discovered local petechial hemorrhages into soft tissues of the back and lower legs. The paper presents a new approach to evaluation of petechia and soft tissue hemorrhages in cosmonauts on return to Earth. Proteomic analysis was performed with the use of LC-MS. Bioinformation analysis was made using Perseus, PubMed, Uniprot and ANDSystem software. Nine out of 19 significantly different (p < 0.05) proteins were related to vascular injuries directly. We described proteins with a primarily protecting effect against endothelial cells apoptosis and augmentation of vascular permeability, proteins that are responsible for blood rheology and proteins antagonistic to the main triggers of ischeamia-reperfusion injuries of the lungs, liver and other parenchymal organs.

Probing Internal Pressures and Long-Term Stability of Nanobubbles in Water

Langmuir ◽  
2021 ◽  
Vol 37 (7) ◽  
pp. 2514-2522
Author(s):  
Xiaonan Shi ◽  
Shan Xue ◽  
Taha Marhaba ◽  
Wen Zhang
Keyword(s):  
Term Stability ◽  
Long Term Stability ◽  
Internal Pressures

Dynamic Performance of Neck Protection Devices: Performance Analysis Based on a Simplified Multibody Model of the Human Neck

2012 ◽  
Author(s):  
Massimiliano Gobbi ◽  
Gianpiero Mastinu ◽  
Giorgio Previati ◽  
Ermes Tarallo
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Dynamic Performance ◽  
Safety Devices ◽  
Anatomy And Physiology ◽  
Multibody Model ◽  
Impulsive Loads ◽  
Protection Devices ◽  
Safety Systems ◽  
Deformation System

This work is focused on the evaluation of the dynamic performance of different neck protection devices. In order to evaluate the mechanical response of the safety devices, a multibody model of the human neck has been developed in Matlab™ SimMechanics™. The mechanical behavior of the neck is described in the paper and different injury indices are presented and compared. The information about anatomy and physiology of the cervical spine of the neck has been collected from the literature, with particular focus on the mechanism of damage of vertebrae, disks and soft tissues. The multibody model has been validated against experimental data available in the literature concerning impulsive loads representative of crash phenomena. By means of the presented model, some relevant injury indices are computed for an accident involving a motorcyclist. Since the focus has been set on mild injuries of the neck, the simulated crash should cause a high probability of injuries of the neck together with a low probability of damages of the head while wearing a standard helmet. The performance of neck safety devices that link the helmet with the thoracic-shield are evaluated and compared. For sake of clearness, three types of neck safety devices are considered referencing to US patents: an airbag jacket, a 3D cushion wrapping the motorcyclist’s neck, and a “spring and dampers” system. The airbag jacket has been modeled as a high stiffness and low deformation system by considering the airbag in its fully deployed configuration and by neglecting its dynamic performance during inflation phase. The other safety devices have been modeled as lumped parameters spring-damper systems. A sensitivity analysis on the injury indexes has been performed by changing the stiffness and the damping parameters of these safety systems. The injury indexes collected by simulating the different neck safety systems have been compared.

scholarly journals Perturbation of eigenvalues due to gaps in two-dimensional boundaries

2006 ◽  
Vol 463 (2079) ◽  
pp. 759-786 ◽  
Author(s):  
Anthony M.J Davis ◽  
Stefan G Llewellyn Smith
Keyword(s):  
Eigenvalue Problems ◽  
Numerical Solutions ◽  
Neumann Boundary ◽  
Diffusion Problem ◽  
Length Scale ◽  
Two Dimensional ◽  
Constructive Approach ◽  
Term Outcome ◽  
Long Term Outcome

Motivated by problems involving diffusion through small gaps, we revisit two-dimensional eigenvalue problems with localized perturbations to Neumann boundary conditions. We recover the known result that the gravest eigenvalue is O (|ln  ϵ | −1 ), where ϵ is the ratio of the size of the hole to the length-scale of the domain, and provide a simple and constructive approach for summing the inverse logarithm terms and obtaining further corrections. Comparisons with numerical solutions obtained for special geometries, both for the Dirichlet ‘patch problem’ where the perturbation to the boundary consists of a different boundary condition and for the gap problem, confirm that this approach is a simple way of obtaining an accurate value for the gravest eigenvalue and hence the long-term outcome of the underlying diffusion problem.

Frequency selectivity, multistability, and oscillations emerge from models of genetic regulatory systems

1998 ◽  
Vol 274 (2) ◽  
pp. C531-C542 ◽  
Author(s):  
Paul Smolen ◽  
Douglas A. Baxter ◽  
John H. Byrne
Keyword(s):  
Cellular Response ◽  
Cultured Cells ◽  
Computational Approach ◽  
Long Term Memory ◽  
Mrna Levels ◽  
Complex Dynamic ◽  
Dynamic Activity ◽  
Regulatory Systems ◽  
Complex Models

To examine the capability of genetic regulatory systems for complex dynamic activity, we developed simple kinetic models that incorporate known features of these systems. These include autoregulation and stimulus-dependent phosphorylation of transcription factors (TFs), dimerization of TFs, crosstalk, and feedback. The simplest model manifested multiple stable steady states, and brief perturbations could switch the model between these states. Such transitions might explain, for example, how a brief pulse of hormone or neurotransmitter could elicit a long-lasting cellular response. In slightly more complex models, oscillatory regimes were identified. The addition of competition between activating and repressing TFs provided a plausible explanation for optimal stimulus frequencies that give maximal transcription. Such optimal frequencies are suggested by recent experiments comparing training paradigms for long-term memory formation and examining changes in mRNA levels in repetitively stimulated cultured cells. In general, the computational approach illustrated here, combined with appropriate experiments, provides a conceptual framework for investigating the function of genetic regulatory systems.

scholarly journals Simulation of long-term thermo-mechanical response of clay using an advanced constitutive model

2018 ◽  
Vol 14 (2) ◽  
pp. 295-311 ◽  
Author(s):  
Despina M. Zymnis ◽  
Andrew J. Whittle ◽  
Xiaohui Cheng
Keyword(s):  
Constitutive Model ◽  
Mechanical Response

The effect of the length and severity of feed restriction on weight, carcass measurements and body composition of goats

1996 ◽  
Vol 127 (4) ◽  
pp. 549-553 ◽  
Author(s):  
O. Mora ◽  
A. Shimada ◽  
F. J. Ruiz
Keyword(s):  
Body Condition ◽  
Dry Matter ◽  
Soft Tissues ◽  
Experimental Period ◽  
Feed Restriction ◽  
Tissue Composition ◽  
Female Adult ◽  
Adaptation Capacity ◽  
Stabilization Period

SUMMARYTwo experiments were done in Mexico (1992–93) to determine the response of goats to different periods of feed restriction on liveweight, organ weights and tissue composition. In each, the weight, body condition and daily dry matter intake (DM1) of two groups of 12 female, adult, non-lactating, non-pregnant, Nubian crossbred goats were recorded for 7 weeks (stabilization period; SP), to allow the animals to reach and maintain their liveweight and body condition. At the end of the SP the animals in Expt 1 (RP1) were feed restricted for 18 weeks and for 36 weeks in Expt 2 (RP2). Animals were divided into three groups receiving either 100 (FL1), 80 (FL2) or 60% (FL3) of the levels of DM1 previously observed. At the end of each experimental period all animals were slaughtered, carcass weights were recorded and viscerae were weighed.A sample of the soft tissues was chemically analysed. There were no significant changes in body condition in either experiment (P > 0·05). None of the feeding levels had an effect on carcass weight or the chemical composition of soft tissues (P > 0·05). Liver weights (as a proportion of slaughter weight) were significantly different among goats fed at different feeding levels in both experiments. The results of this study show the adaptation capacity of adult goats to medium and long term malnutrition, and the importance of the liver as a source for the generation of energy and for sustaining protein turnover. This could be especially important for goats grazing in arid and semiarid zones where dry periods can last for months and feed availability is therefore sometimes limited.

Deconstructing the Anterior Cruciate Ligament: What We Know and Do Not Know About Function, Material Properties, and Injury Mechanics

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Scott G. McLean ◽  
Kaitlyn F. Mallett ◽  
Ellen M. Arruda
Keyword(s):  
Anterior Cruciate Ligament ◽  
Knee Joint ◽  
Mechanical Response ◽  
Cruciate Ligament ◽  
Complex Structure ◽  
Acute Injury ◽  
Research Attention ◽  
Increased Risk ◽  
Anterior Cruciate

Anterior cruciate ligament (ACL) injury is a common and potentially catastrophic knee joint injury, afflicting a large number of males and particularly females annually. Apart from the obvious acute injury events, it also presents with significant long-term morbidities, in which osteoarthritis (OA) is a frequent and debilitative outcome. With these facts in mind, a vast amount of research has been undertaken over the past five decades geared toward characterizing the structural and mechanical behaviors of the native ACL tissue under various external load applications. While these efforts have afforded important insights, both in terms of understanding treating and rehabilitating ACL injuries; injury rates, their well-established sex-based disparity, and long-term sequelae have endured. In reviewing the expanse of literature conducted to date in this area, this paper identifies important knowledge gaps that contribute directly to this long-standing clinical dilemma. In particular, the following limitations remain. First, minimal data exist that accurately describe native ACL mechanics under the extreme loading rates synonymous with actual injury. Second, current ACL mechanical data are typically derived from isolated and oversimplified strain estimates that fail to adequately capture the true 3D mechanical response of this anatomically complex structure. Third, graft tissues commonly chosen to reconstruct the ruptured ACL are mechanically suboptimal, being overdesigned for stiffness compared to the native tissue. The net result is an increased risk of rerupture and a modified and potentially hazardous habitual joint contact profile. These major limitations appear to warrant explicit research attention moving forward in order to successfully maintain/restore optimal knee joint function and long-term life quality in a large number of otherwise healthy individuals.

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