bluuebunny/crossref_metadata_2025 huggingface dataset:
Capsular glucan and intracellular glycogen of Mycobacterium tuberculosis: biosynthesis and impact on the persistence in mice
Authors: Sambou Tounkang , Dinadayala Premkumar , Stadthagen Gustavo , Barilone Nathalie , Bordat Yann , Constant Patricia , Levillain Florence , Neyrolles Olivier , Gicquel Brigitte , Lemassu Anne , Daffé Mamadou , Jackson Mary
Published: September 2008

Mycobacterium tuberculosis and other pathogenic mycobacterial species produce large amounts of a glycogen‐like α‐glucan that represents the major polysaccharide of their outermost capsular layer. To determine the role of the surface‐exposed glucan in the physiology and virulence of these bacteria, orthologues of the glg genes involved in the biosynthesis of glycogen in Escherichia coli were identified in M. tuberculosis H37Rv and inactivated by allelic replacement. Biochemical analyses of the mutants and complemented strains indicated that the synthesis of glucan and glycogen involves the α‐1,4‐glucosyltransferases Rv3032 and GlgA (Rv1212c), the ADP‐glucose pyrophosphorylase GlgC (Rv1213) and the branching enzyme GlgB (Rv1326c). Disruption of glgC reduced by half the glucan and glycogen contents of M. tuberculosis, whereas the inactivation of glgA and Rv3032 affected the production of capsular glucan and glycogen, respectively. Attempts to disrupt Rv3032 in the glgA mutant were unsuccessful, suggesting that a functional copy of at least one of the two α‐1,4‐glucosyltransferases is required for growth. Importantly, the glgA mutant was impaired in its ability to persist in mice, suggesting a role for the capsular glucan in the persistence phase of infection. Unexpectedly, GlgB was found to be an essential enzyme.
Placental invasiveness and brain–body allometry in eutherian mammals
Authors: ELLIOT M. G. , CRESPI B. J.
Published: September 2008

Brain growth is a key trait in the evolution of mammalian life history. Brain development should be mediated by placentation, which determines patterns of resource transfer from mothers to fetal offspring. Eutherian placentation varies in the extent to which a maternal barrier separates fetal tissues from maternal blood. We demonstrate here that more invasive forms of placentation are associated with substantially steeper brain–body allometry, faster prenatal brain growth and slower prenatal body growth. On the basis of the physiological literature we suggest a simple mechanism for these differences: in species with invasive placentation, where the placenta is bathed directly in maternal blood, fatty acids essential for brain development can be readily extracted by the fetus, but in species with less invasive placentation they must be synthesized by the fetus. Hence, with regard to brain–body allometry and prenatal growth patterns, eutherian mammals are structured into distinct groups differing in placental invasiveness.
Characteristics of pediatric‐onset spinal cord injury
Authors: Lee Jung H. , Sung In Y. , Kang Jin Y. , Park Song R.
Published: September 2008

Background:  Although children rarely experience spinal cord injuries (SCI), those who do are subject to various lifelong disabilities and morbidities. The aim of the present study was to retrospectively assess the characteristics of pediatric onset SCI patients and their differences among age groups.

Methods:  Clinical characteristics were compared in 48 patients who experienced SCI during childhood and adolescence and who underwent rehabilitation treatment. Clinical characteristics were compared in patients under 4 years old (group A), 4–12 years old (group B), and 13–18 years old (group C) at SCI onset. Radiological findings were compared in 20 patients who were examined on both plain radiograph and computed tomography.

Results:  The overall male : female ratio was 3:2, with SCI due to non‐traumatic causes more frequent overall. Of traumatic causes of SCI, vehicle accident was the most frequent. Of non‐traumatic causes, congenital anomaly was most frequent in group A, but tumors became dominant as age increased. Overall, thoracic cord level of injury was most frequent. SCI without radiologic abnormalities (SCIWORA) was predominant in group A, but none was observed in group C. Spinal fractures with or without subluxation accounted for >60% of group C SCI.

Conclusions:  Non‐traumatic, thoracic cord injury was frequent in the pediatric SCI population. SCIWORA was predominant in younger children.
Epidemiology of neonatal sepsis in South Korea
Authors: Shin Youn‐Jeong , Ki Moran , Foxman Betsy
Published: September 2008

Background:  Neonatal sepsis is a severe clinical syndrome characterized by systemic signs of infection, shock and system organ failure; diagnosis is confirmed on positive culture from a normally sterile site(s). There are few reports comparing incidence, mortality, and risk factors between clinically diagnosed sepsis and that confirmed by culture.

Methods:  All infants diagnosed with early‐ (within first 72 h after birth) or late‐onset (72 h–4 weeks after birth) neonatal sepsis between 1997 and 1999 from four neonatal centers in South Korea, were investigated.

Results:  The estimated incidence rate of neonatal sepsis during the 3 years was 30.5 per 1000 live births for clinical sepsis and 6.1 per 1000 live births for sepsis with positive culture, with case‐fatality rates of 4.7% and 2.2%, respectively. When only early‐onset sepsis was considered, the incidence and fatality rates were 25.1 per 1000 live births and 6.1% for clinical sepsis, and 4.3 per 1000 live births and 2.5% for culture‐confirmed sepsis, respectively. For the 179 patients (185 causative organisms) of proven sepsis, Staphylococcus spp. including S. aureus were the most frequent isolates. In early‐onset clinical sepsis, having very low birthweight (≤1500 g), a low Apgar score at 5 min (≤7), and being male were related to higher rates of case‐fatality (relative risk: 11.3, 6.8 and 2.5, respectively)

Conclusions:  Clinical sepsis was more common than culture‐confirmed sepsis and had a higher case‐fatality rate. It seems prudent to take rapid and decisive steps toward better management of the high‐risk group whether the sepsis is clinically diagnosed or culture confirmed.
Lancashire, India, and shifting competitive advantage in cotton textiles, 1700–1850: the neglected role of factor prices1
Authors: BROADBERRY STEPHEN , GUPTA BISHNUPRIYA
Published: September 2008

In the early eighteenth century, wages in Britain were more than four times as high as in India, the world's major exporter of cotton textiles. This induced the adoption of more capital‐intensive production methods in Britain and a faster rate of technological progress, so that competitive advantage had begun to shift in Britain's favour by the late eighteenth century. However, the completion of the process was delayed until after the Napoleonic Wars by increasing raw cotton costs, before supply adjusted to the major increase in demand for inputs.
Pregnancy may be followed by an inflexion of the immune reconstitution in HIV‐infected women who receive antiretroviral drugs before conception
Authors: Le Moing V , Taïeb A , Longuet P , Lewden C , Delcey V , Drobacheff MC Thiebaut , Chêne G , Leport C ,   the ANRS CO8 (APROCO‐COPILOTE) study group
Published: September 2008

Background

Whether pregnancy has an impact on the evolution of CD4 cell counts in women treated with highly potent antiretrovirals before conception remains largely unknown.

Methods

Among patients enrolled in the ANRS CO8 (APROCO/COPILOTE) cohort, we selected all women aged between 18 and 50 years at initiation of combination antiretroviral therapy (cART). Slopes of CD4 cell counts during follow‐up were estimated using mixed longitudinal models with time‐dependent indicators for pregnancy and delivery.

Results

Of the 260 selected HIV‐infected women, a pregnancy occurred in 39 women in a median follow‐up time of 66 months. Women who became pregnant had higher CD4 cell count at baseline but this difference progressively lessened during follow‐up because they had a slower increase than women who did not become pregnant. The estimated slope of CD4 cell count decreased significantly from +2.3 cells/μL/month before pregnancy and in women who did not become pregnant to −0.04 cells/μL/month after delivery (P=0.0003).

Conclusion

A significant increase in CD4 cell count may be preferable before pregnancy in women treated with cART, in order to overcome the evolution observed after pregnancy.
The dynamics of the nurse–patient relationship: introduction of a synthesized theory from the patient’s perspective
Authors: Halldorsdottir Sigridur
Published: September 2008

The nurse–patient relationship is by many considered the core of nursing. In this paper, a synthesized theory on the dynamics of that relationship is introduced from the patient’s perspective. It is described as a dynamic lived reality characterized by a sense of spiritual connection which is experienced as a bond of energy. The highest quality of this connection is the life‐giving nurse–patient relationship which is greatly empowering for the patient. The prerequisites for the development of the nurse–patient relationship are perceived nurse caring, wisdom and competence in connecting with people. The dialectic nature of this relationship is discussed as well as the six main phases in the nurse–patient relationship development.
The incomprehensible injury – interpretations of patients’ narratives concerning experiences with an acute and dramatic spinal cord injury
Authors: Lohne Vibeke
Published: September 2008

Spinal cord injury is one of the most devastating incidents that can occur to an individual as it results in life being suddenly, dramatically, radically and long lastingly changed. Different studies show that a spinal cord injury is a stressful event, leading to physiological dependence, psychological and social illness and suffering, although the situation tends to improve over time. This study is a part of a larger longitudinal study. The aim of this study was to explore and interpret 10 individuals’ experiences in connection with their acute and unexpected spinal cord injury. This qualitative study has a descriptive and explorative design and is a part of a larger study. A phenomenological hermeneutic approach inspired by Ricoeur was used to extract the meaningful content of the patients’ narratives. In this study, the findings revealed three main themes: (I) ‘the incomprehensible shock’, (II) ‘brave survivors’ and (III) ‘miracles, luck or coincidences?’ The incomprehensible spinal cord injury was often experienced as a dramatic and unexpected shock in the middle of a pleasant occasion, and every participant felt immediately overwhelmed by emotional suffering, such as despair and panic, but also anxiety, confusion, sorrow, guilt, shame, fear, aggression or depression at the moment of injury. Some individuals immediately understood that they had become completely paralysed and that something was seriously wrong with their body. Many also experienced guilt or shame because of choices or decisions made immediately before the injury. Several of the narratives were illuminating participants that had been brave survivors and heroes and saved others (passengers or friends) during the injury, by preventing the car form driving out or by softening the fall of co‐passengers, which also entailed more serious injuries to themselves. However, the fact of having survived was experienced as ‘being lucky, after all’. They all repeatedly reflected on the accident, and their individual understanding of it changed over time, from, on the whole, as a perspective of a ‘miracle’ to ‘just luck’ or a coincidence’ which also reflected the meaning and significance of what the injury really meant to their body and to their lives. And these reflections gave rise to different ways; they later on learned to live with their new lives. These important aspects, narrated by the brave survivors, have not been reported in the research literature earlier.
Development of professional knowledge in action: experiences from an action science design focusing on acknowledging communication in mental health
Authors: Vatne Solfrid , Bjornerem Heidi , Hoem Elisabeth
Published: September 2008

This article reports a multi‐professional development project that was based on an action science design. The purpose was to develop ‘acknowledging communication’ in a psychiatric department for young people, and the objective to study the staffs’ experiences of participating in the project. The professional part of the project has its foundation in Schibbye’s treatment theory of inter‐subjective understanding of relationships, and involves three main approaches from her theory: self‐reflection, self‐delimitation and emotional presence. The article presents the specific action design used, where reflection processes were developed in three different arenas: multidisciplinary Reflection groups, a Leader support group for the group leaders of the Reflection groups and collective Project seminars for all employees. A formal study programme designed to increase professional expertise, 15 European Credit Transfer System (ECTS), was also offered. The research methods included the researcher’s process notes taken during the process, field notes from participating in the Leader support group, and qualitative interviews of eight informants participating in the various reflection arenas. The article presents and discusses the experiences evolved from the methods that were developed during the professional action science project: reflection on specific situations of interaction with patients in the form of oral/written narratives and the development of video presentations in combination with ‘reflective teams’. The study showed that to facilitate change in the role of staff members, it is important to combine several reflection arenas where theoretical principles can be converted into practical action. By drawing data from only one study site, the study has a limited transferability, but should be of interest for professionals working with clinical change processes.
Risky Business: Perceived Behavior of Local Scientists and Community Support for Their Research
Authors: McComas Katherine A. , Besley John C. , Yang Zheng
Published: September 2008

Attracting new technologies to a region can mean significant economic growth, so understanding why some communities may not favor becoming “the next Silicon Valley” merits consideration. This study investigates the relationship among the perceived behavior of local scientists and community members' attitudes toward their research. Drawing on theories from organizational justice, it hypothesizes that when local residents consider scientists as more just in their behavior, they will also have more favorable attitudes toward the scientists and their research. Just, in this sense, refers to whether scientists are perceived as fair in terms of outcomes, procedures, interpersonal treatment, and explanations in their dealings with the community. Favorable attitudes are measured in terms of concern about new technologies and satisfaction with research. Data were collected via a mail survey of residents in two upstate New York counties (N= 1,306) that host substantial technology research facilities. Controlling for demographics, media use, basic science knowledge, and technology awareness, the results show that distributive justice (i.e., fairness of outcomes) had a consistent, negative relationship with technology concern. In comparison, all four justice variables were positively related with research satisfaction. The findings suggest that the perceived behavior of local scientists may indeed impact community support for their research.
The Effect of Feeding Enrichment upon Reported Working Ability and Behavior of Kenneled Working Dogs
Authors: Gaines Samantha A. , Rooney Nicola J. , Bradshaw John W.S.
Published: September 2008

Abstract: It is widely recommended that kenneled dogs are provided with environmental enrichment such as toys or feeding devices. However, the adoption of enrichment for military working dogs is impeded by a widespread belief that it reduces their motivation to work. Handlers of 22 working German Shepherd dogs were asked to rate their dogs on 11 attributes pertaining to working ability, related behavioral traits, and health. Eight of the dogs were then provided with daily feeding enrichment for 4 months, while the remainder were given equivalent human attention. The same 11 traits were scored again following the enrichment period: 10 changed little over the period while handlers’ reports of their dogs’Ability to learn from being rewardedincreased significantly. Changes for all attributes were virtually identical in enriched and control dogs. We conclude that if correctly managed, feeding enrichment can be introduced to kenneled working dogs without any reported detrimental effects upon working ability, health, or behavior.
Extraction, Derivatization, and Analysis of Vegetable Oils from Fire Debris
Authors: Gambrel Abby K. , Reardon Michelle R.
Published: September 2008

Abstract:  Vegetable oils have the ability to spontaneously heat under certain conditions, which may lead to spontaneous ignition. While the oils are not often encountered in forensic casework, they may be suspected in some fire cases. As these oils are not effectively analyzed using traditional fire debris analysis methods, a protocol must be established for extracting vegetable oils from fire debris. In this study, a protocol was developed for the extraction, derivatization, and analysis of vegetable oils from fire debris. Three derivatization methods were compared to establish an optimal derivatization procedure to convert the fatty acids found in vegetable oils to the fatty acid methyl esters (FAMEs) used in analysis. Three different gas chromatograph columns and programs were examined to determine which was best suited for the separation and analysis of FAMEs. The procedure was tested and refined using a variety of neat and burned vegetable oils, in addition to extractions from oils burned on commonly encountered fire debris materials. The findings of this research will serve as a starting point for further understanding and research of vegetable oils in fire debris.
Wound dressing components degrade proteins detrimental to wound healing
Authors: Baskovich Brett , Sampson Edith M , Schultz Gregory S , Parnell Laura KS
Published: September 2008

Excessive levels of matrix metalloproteinases (MMPs) are present in chronic wounds preventing wound closure. Reducing detrimental components may be key in healing chronic wounds. Elta Protease‐containing wound dressings have been observed clinically to resolve inflammation and appear to aid healing in acute and chronic recalcitrant wounds. To investigate possible mechanisms of action, in vitro tests, zymography, collagenase assays and enzyme‐linked immunosorbent assays (ELISAs), were performed to evaluate the effect of the dressing proteases on detrimental and beneficial wound healing components such as MMPs, Tissue Inhibitor of Matrix Metalloproteinases (TIMPs), cytokines and growth factors. Standards of pro‐ and active MMP‐2, MMP‐9 and chronic wound fluid (CWF) were prepared. Degradation of target proteins was enhanced by increased Elta Protease concentration, temperature and incubation time. Incubation with serial dilutions of the Elta Proteases resulted in nearly complete degradation of all MMP standards. After a 30‐minute incubation, twofold diluted Elta Proteases degraded >90% of the gelatinases in CWF. ELISAs showed that Elta Proteases effectively degraded MMP‐9 and tumour necrosis factor (TNF‐α). In contrast, Platelet Derived Growth Factor (PDGF) and interleukin 1β were resistant to degradation by Elta Proteases. These results suggest that Elta Protease dressings appear to deactivate detrimental components in CWF, which may reduce wound bed contact with harmful proteins.
Pressure transduction to the thoracic cavity during topical negative pressure therapy of a sternotomy wound
Authors: Torbrand Christian , Ingemansson Richard , Gustafsson Lotta , Paulsson Per , Malmsjö Malin
Published: September 2008

The present study was performed to examine pressure transduction to the thoracic cavity during topical negative pressure (TNP) therapy of a sternotomy wound. Seven pigs underwent median sternotomy. Pressure transduction catheters were placed on the anterior surface of the heart (under the foam), in the pericardium (under the heart), in the left pleura and in the oesophagus at the level of the heart. The wound was sealed as for TNP therapy. The vacuum source was set to deliver negative pressures between −50 and −200 mmHg. The pressure on the anterior surface of the heart changed in a linear relationship with the applied negative pressure and was slightly lower than the applied negative pressure (−102 ± 9 mmHg at delivered −125 mmHg). Further down in the thoracic cavity, in the pericardium (under the heart), in the left pleura and in the oesophagus, the wound pressure was only slightly affected by TNP therapy. In conclusion during TNP therapy, negative pressure is effectively transmitted to anterior portions of the heart. This may explain our recent findings that TNP increases microvascular blood flow in the myocardium. The pressure difference between the anterior and the posterior portions of the heart causes the right ventricle to be sucked up towards the posterior parts of the sternum, where it might be exposed to the sharp edges of the sternal bone, which may result in heart injury.
Telemedicine in wound care
Authors: Chanussot‐Deprez Caroline , Contreras‐Ruiz José
Published: September 2008

Telemedical wound care is one of the applications of teledermatology. We present our experience using telemedicine in the successful assessment and treatment of three patients with hard‐to‐heal ulcers. Three patients were seen at the PEMEX General Hospital in Veracruz, Mexico. The first patient was a 53‐year‐old man with hypertension, morbid obesity, chronic venous insufficiency, recurrent erysipelas, leg ulcers and lymphoedema. There was one ulcer on his left lower leg (20 × 10 cm) and one on his right leg (9 × 7 cm). The second patient was a 73‐year‐old woman with class III obesity and ulcers in her right leg, secondary to surgical debridement of bullous erysipelas. The third patient was a 51‐year‐old female with rheumatoid arthritis with one ulcer on each leg and chronic lymphostasis. Photographs with a digital camera were taken and sent weekly via email to a wound care specialist in Mexico City. The photographs allowed the expert to diagnose and evaluate the chronic wounds periodically. In the present cases, telemedicine allowed us to have a rapid evaluation, diagnosis and treatment. The images were of enough quality to be useful and small enough to be sent via regular email to the remote physician who immediately gave his feedback. The expert was confident to give therapeutic recommendations in this way, and we considered this method to be very cost‐effective, saving the patient and the health care system, especially in transportation.
The expression patterns of Pax7 in satellite cells during overload‐induced rat adult skeletal muscle hypertrophy
Authors: Ishido M. , Uda M. , Kasuga N. , Masuhara M.
Published: September 2008

Aim:  Activated satellite cells (SCs) have the ability to reacquire a quiescent, undifferentiated state. Pax7 plays a crucial role in allowing activated SCs to undergo self‐renewal. Because the increase in the SC population is induced during overload‐induced skeletal muscle hypertrophy, it is possible that Pax7‐regulated SC self‐renewal is involved in the modulation of the SC population during the functional overload of skeletal muscles. However, the characteristics of the expression patterns of Pax7 in SCs during the functional overload of adult skeletal muscles are poorly understood.

Methods:  Using immunohistochemical approaches, we examined the temporal and spatial expression patterns of Pax7 expressed in SCs during the functional overloading of rat skeletal muscles.

Results:  The time course of Pax7 expression in SCs was similar to that of the expression of the differentiation regulatory factor myogenin during the early stage of functional overload. However, the percentage of SCs that expressed Pax7 was markedly higher than that of the SCs that expressed myogenin. Coexpression of Pax7 and myogenin was not detected in SCs. In addition, the expression of cyclin‐dependent kinase inhibitor p21, which regulates cell cycle arrest and differentiation, was not detected in Pax7‐positive SCs.

Conclusion:  These results suggest that Pax7‐regulated self‐renewal of SCs may be induced during the early stage of functional overload and may contribute to modulating the SC population in hypertrophied muscles. Furthermore, it was suggested that the numbers of SCs which underwent self‐renewal may be higher than that of SCs which were provided as the additional myonuclei for hypertrophying myofibres.
Dark adaptation recovery of human rod bipolar cell response kinetics estimated from scotopic b‐wave measurements
Authors: Cameron A. M. , Miao L. , Ruseckaite R. , Pianta M. J. , Lamb T. D.
Published: September 2008

We recorded ganzfeld scotopic ERGs to examine the responses of human rod bipolar cells in vivo, during dark adaptation recovery following bleaching exposures, as well as during adaptation to steady background lights. In order to be able to record responses at relatively early times in recovery, we utilized a ‘criterion response amplitude’ protocol in which the test flash strength was adjusted to elicit responses of nearly constant amplitude. In order to provide accurate and unbiased measures of response kinetics, we utilized a curve‐fitting procedure to fit a smooth function to the measured responses in the vicinity of the peak, thereby extracting both the time‐to‐peak and the amplitude of the responses. Following bleaching exposures, the responses exhibited both desensitization and accelerated kinetics. During early post‐bleach recovery, the flash sensitivity and time‐to‐peak varied according to a power‐law expression (with an exponent of 6), as found in the presence of steady background light. This light‐like phenomenon, however, appeared to be set against the backdrop of a second, more slowly recovering ‘pure’ desensitization, most clearly evident at late post‐bleach times. The post‐bleach ‘equivalent background intensity’ derived from measurements of flash sensitivity faded initially with an S2 slope of ∼0.24 decades min−1, and later as a gentle S3 tail. When calculated from kinetics, the results displayed only the S2 slope. While the recovery of rod bipolar cell response kinetics can be described accurately by a declining level of opsin in the rods, the sensitivity of these cells is reduced further than expected by this mechanism alone.
Voltage‐gated proton channels: what's next?
Authors: DeCoursey Thomas E.
Published: September 2008

This review is an attempt to identify and place in context some of the many questions about voltage‐gated proton channels that remain unsolved. As the gene was identified only 2 years ago, the situation is very different than in fields where the gene has been known for decades. For the proton channel, most of the obvious and less obvious structure–function questions are still wide open. Remarkably, the proton channel protein strongly resembles the voltage‐sensing domain of many voltage‐gated ion channels, and thus offers a novel approach to study gating mechanisms. Another surprise is that the proton channel appears to function as a dimer, with two separate conduction pathways. A number of significant biological questions remain in dispute, unanswered, or in some cases, not yet asked. This latter deficit is ascribable to the intrinsic difficulty in evaluating the importance of one component in a complex system, and in addition, to the lack, until recently, of a means of performing an unambiguous lesion experiment, that is, of selectively eliminating the molecule in question. We still lack a potent, selective pharmacological inhibitor, but the identification of the gene has allowed the development of powerful new tools including proton channel antibodies, siRNA and knockout mice.
Fluid and Thermal Dynamics of Cryogen Sprays Impinging on a Human Tissue Phantom
Authors: Franco Walfre , Vu Henry , Jia Wangcun , Nelson J. Stuart , Aguilar Guillermo
Published: September 2008

Cryogen spray cooling (CSC) protects the epidermis from unintended heating during cutaneous laser surgery. The present work investigated the time-dependent flow characteristics of cryogen sprays and correspondent thermal dynamics at the surface of a human tissue phantom. First, a numerical analysis was carried out to evaluate an epoxy block substrate as a human tissue phantom. Next, the velocity and diameter of cryogen droplets were measured simultaneously and correlated with surface temperature of the human tissue phantom during CSC. Finally, velocity and diameter measurements were used to compute the spray number, mass, and kinetic energy fluxes, and temperature measurements were used to compute the surface heat flux. Numerical modeling showed that the thermal response of our phantom was qualitatively similar to that of human stratum corneum and epidermis; quantitatively, thermal responses differed. A simple transformation to map the temperature response of the phantom to that of tissue was derived. Despite the relatively short spurt durations (10ms, 30ms, and 50ms), cryogen delivery is mostly a steady state process with initial and final fluid transients mainly due to the valve dynamics. Thermal transients (16ms) are longer than fluid transients (4ms) due to the low thermal diffusivity of human tissues; steady states are comparable in duration (≈10ms, 30ms, and 50ms) although there is an inherent thermal delay (≈12ms). Steady state temperatures are the lowest surface temperatures experienced by the substrate, independent of spurt duration; hence, longer spurt durations result in larger exposures of the tissue surface to the same lower, steady state temperature as in shorter spurts. Temperatures in human tissue during CSC for the spray system and parameters used herein are estimated to be ≈−19°C at the stratum corneum surface and >0°C across the epidermis.
Frictional Characteristics of Erythrocytes on Coated Glass Plates Subject to Inclined Centrifugal Forces
Authors: Kandori Takashi , Hayase Toshiyuki , Inoue Kousuke , Funamoto Kenichi , Takeno Takanori , Ohta Makoto , Takeda Motohiro , Shirai Atsushi
Published: September 2008

In recent years a diamond-like carbon (DLC) film and a 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer have attracted attention as coating materials for implantable artificial organs or devices. When these materials are coated on vascular devices, compatibility to blood is an important problem. The present paper focuses on friction characteristics of erythrocytes to these coating materials in a medium. With an inclined centrifuge microscope developed by the authors, observation was made for erythrocytes moving on flat glass plates with and without coating in a medium of plasma or saline under the effect of inclined centrifugal force. Friction characteristics of erythrocytes with respect to these coating materials were then measured and compared to each other to characterize DLC and MPC as coating materials. The friction characteristics of erythrocytes in plasma using the DLC-coated and noncoated glass plates are similar, changing approximately proportional to the 0.5th power of the cell velocity. The cells stick to these plates in saline as well, implying the influence of plasma protein. The results using the MPC-coated plate in plasma are similar to those of the other plates for large cell velocities, but deviate from the other results with decreased cell velocity. The results change nearly proportional to the 0.75th power of the cell velocity in the range of small velocities. The results for the MPC-coated plate in saline are similar to that in plasma but somewhat smaller, implying that the friction characteristics for the MPC-coated plate are essentially independent of plasma protein.
Validation of Finite Element Predictions of Cartilage Contact Pressure in the Human Hip Joint
Authors: Anderson Andrew E. , Ellis Benjamin J. , Maas Steve A. , Peters Christopher L. , Weiss Jeffrey A.
Published: September 2008

Methods to predict contact stresses in the hip can provide an improved understanding of load distribution in the normal and pathologic joint. The objectives of this study were to develop and validate a three-dimensional finite element (FE) model for predicting cartilage contact stresses in the human hip using subject-specific geometry from computed tomography image data, and to assess the sensitivity of model predictions to boundary conditions, cartilage geometry, and cartilage material properties. Loads based on in vivo data were applied to a cadaveric hip joint to simulate walking, descending stairs, and stair-climbing. Contact pressures and areas were measured using pressure sensitive film. CT image data were segmented and discretized into FE meshes of bone and cartilage. FE boundary and loading conditions mimicked the experimental testing. Fair to good qualitative correspondence was obtained between FE predictions and experimental measurements for simulated walking and descending stairs, while excellent agreement was obtained for stair-climbing. Experimental peak pressures, average pressures, and contact areas were 10.0MPa (limit of film detection), 4.4–5.0MPa, and 321.9–425.1mm2, respectively, while FE-predicted peak pressures, average pressures, and contact areas were 10.8–12.7MPa, 5.1–6.2MPa, and 304.2–366.1mm2, respectively. Misalignment errors, determined as the difference in root mean squared error before and after alignment of FE results, were less than 10%. Magnitude errors, determined as the residual error following alignment, were approximately 30% but decreased to 10–15% when the regions of highest pressure were compared. Alterations to the cartilage shear modulus, bulk modulus, or thickness resulted in ±25% change in peak pressures, while changes in average pressures and contact areas were minor (±10%). When the pelvis and proximal femur were represented as rigid, there were large changes, but the effect depended on the particular loading scenario. Overall, the subject-specific FE predictions compared favorably with pressure film measurements and were in good agreement with published experimental data. The validated modeling framework provides a foundation for development of patient-specific FE models to investigate the mechanics of normal and pathological hips.
Numerical Simulations of Flow in Cerebral Aneurysms: Comparison of CFD Results and In Vivo MRI Measurements
Authors: Rayz Vitaliy L. , Boussel Loic , Acevedo-Bolton Gabriel , Martin Alastair J. , Young William L. , Lawton Michael T. , Higashida Randall , Saloner David
Published: September 2008

Computational fluid dynamics (CFD) methods can be used to compute the velocity field in patient-specific vascular geometries for pulsatile physiological flow. Those simulations require geometric and hemodynamic boundary values. The purpose of this study is to demonstrate that CFD models constructed from patient-specific magnetic resonance (MR) angiography and velocimetry data predict flow fields that are in good agreement with in vivo measurements and therefore can provide valuable information for clinicians. The effect of the inlet flow rate conditions on calculated velocity fields was investigated. We assessed the internal consistency of our approach by comparing CFD predictions of the in-plane velocity field to the corresponding in vivo MR velocimetry measurements. Patient-specific surface models of four basilar artery aneurysms were constructed from contrast-enhanced MR angiography data. CFD simulations were carried out in those models using patient-specific flow conditions extracted from MR velocity measurements of flow in the inlet vessels. The simulation results computed for slices through the vasculature of interest were compared with in-plane velocity measurements acquired with phase-contrast MR imaging in vivo. The sensitivity of the flow fields to inlet flow ratio variations was assessed by simulating five different inlet flow scenarios for each of the basilar aneurysm models. In the majority of cases, altering the inlet flow ratio caused major changes in the flow fields predicted in the aneurysm. A good agreement was found between the flow fields measured in vivo using the in-plane MR velocimetry technique and those predicted with CFD simulations. The study serves to demonstrate the consistency and reliability of both MR imaging and numerical modeling methods. The results demonstrate the clinical relevance of computational models and suggest that realistic patient-specific flow conditions are required for numerical simulations of the flow in aneurysmal blood vessels.
Computational Mechanobiology to Study the Effect of Surface Geometry on Peri-Implant Tissue Differentiation
Authors: Andreykiv A. , van Keulen F. , Prendergast P. J.
Published: September 2008

The geometry of an implant surface to best promote osseointegration has been the subject of several experimental studies, with porous beads and woven mesh surfaces being among the options available. Furthermore, it is unlikely that one surface geometry is optimal for all loading conditions. In this paper, a computational method is used to simulate tissue differentiation and osseointegration on a smooth surface, a surface covered with sintered beads (this simulated the experiment (Simmons, C., and Pilliar, R., 2000, Biomechanical Study of Early Tissue Formation Around Bone-Interface Implants: The Effects of Implant Surface Geometry,” Bone Engineering, J. E. Davies, ed., Emsquared, Chap. A, pp. 369–379) and established that the method gives realistic results) and a surface covered by porous tantalum. The computational method assumes differentiation of mesenchymal stem cells in response to fluid flow and shear strain and models cell migration and proliferation as continuum processes. The results of the simulation show a higher rate of bone ingrowth into the surfaces with porous coatings as compared with the smooth surface. It is also shown that a thicker interface does not increase the chance of fixation failure.
Improvement of Formability and Spring-Back of AA5052-H32 Sheets Based on Surface Friction Stir Method
Authors: Park Sangjoon , Lee Chang Gil , Kim Junehyung , Han Heung Nam , Kim Sung-Joon , Chung Kwansoo
Published: September 2008

A process to improve formability and spring-back was developed for AA5xxx-H temper sheets based on the surface friction stir (SFS) method. In the SFS method, a rotating probe stirs the sheet surface so that material flow and heat, which result from plastic deformation and friction, change the microstructure and macroscopic mechanical properties of the stirred zone and therefore, ultimately, the formability and spring-back performances of the whole sheet. When applied to AA5052-H32 sheets, the process improved formability and spring-back, as experimentally and numerically confirmed in the limit dome height and unconstrained bending tests.
Effect of Shape of the Tip in Determining Interphase Properties in Fiber Reinforced Plastic Composites Using Nanoindentation
Authors: Yedla S. B. , Kalukanimuttam M. , Winter R. M. , Khanna Sanjeev K.
Published: September 2008

Fiber reinforced polymer composites are two component material systems in which fibers are embedded in a polymer matrix. Such a system inherently has an interface where the two components meet. Adjacent to the interface extending beyond the fiber surface is the “interphase region.” Properties within the interphase vary due to variations in the chemistry. The study of mechanical property variations with changing chemistry will help in better understanding and tailoring of the composite properties. The present work concentrates on the investigation of nanomechanical properties within the interphase of a glass fiber embedded in polyester matrix system. The glass fibers were coated with two types of silanes to produce a strong and a weak bond at the fiber-matrix interface. Nanoindentation techniques coupled with atomic force microscopy imaging capabilities have been used for this investigation. Two different tips were employed for indenting, one being a Berkovich diamond tip supplied by Hysitron, Inc., Minneapolis, MN and another being a parabolic tungsten tip, which was made in the laboratory. Indentations were performed within the interphase region, also in the bulk matrix, and on the glass fiber. The variation in mechanical properties such as modulus, stiffness, hardness, and penetration depth were obtained within the interphase by indenting at the fiber surface outward. Variations of the elastic modulus in the interphase region and its relation to the chemistry are presented. The results obtained using two different tip shapes have been compared. Phase imaging was performed using tapping mode atomic force microscopy to qualitatively identify the presence of an interphase near the glass fiber-polyester interface. These experiments show that when no coupling agent is used the interphase thickness is less than 0.1 μm, and its exact determination is limited by the spatial resolution of the tips employed and the process of indentation. Phase imaging results with composite samples made of coated glass fibers corroborate the results obtained from nanoindentation experiments.
Modifying a Tilting Disk Mechanical Heart Valve Design to Improve Closing Dynamics
Authors: Herbertson Luke H. , Deutsch Steven , Manning Keefe B.
Published: September 2008

The closing behavior of mechanical heart valves is dependent on the design of the valve and its housing, the valve composition, and the environment in which the valve is placed. One innovative approach for improving the closure dynamics of tilting disk valves is introduced here. We transformed a normal Delrin occluder into one containing a ”dynamic liquid core” to resist acceleration and reduce the moment of inertia, closing velocity, and impact forces of the valve during closure. The modified occluder was studied in the mitral position of a simulation chamber under the physiologic and elevated closing conditions of 2500 mm Hg/s and 4500 mm Hg/s, respectively. Cavitation energy, detected as high-frequency pressure transients with a hydrophone, was the measure used to compare the modified valve with its unaltered counterpart. The cavitation potential of tilting disk valves is indicative of the extent of blood damage occurring during valve closure. Initial findings suggest that changes to the structure or physical properties of well established mechanical valves, such as the one described here, can reduce closure induced hemolysis by minimizing cavitation. Compared with a normal valve, the cavitation intensity associated with our modified valve was reduced by more than 66% at the higher load. Furthermore, the modified valve took longer to completely close than did the standard tilting disk valve, indicating a dampened impact and rebound of the occluder with its housing.
Lumped Flow Modeling in Dynamically Loaded Coronary Vessels
Authors: Jacobs J. , Algranati D. , Lanir Y.
Published: September 2008

Most of the myriad (order of 109) interconnected coronary vessels interact nonlinearly with their embedding contracting myocardium. Their dynamic flow can be simulated based on a nonlinear distributive segmental flow model involving highly nonlinear partial differential equations. Such network flow analysis, although of high accuracy, is computationally excessively complex. On the other hand, a corresponding nonlinear lumped analysis is significantly less demanding since it involves ordinary differential equations. This is, however, at the detriment of accuracy. In the present technical report, a nonlinear lumped representation of coronary segmental flow is presented and tested against predictions of the corresponding distributive analysis. The results suggest that under physiological conditions, the proposed lumped model achieves similar accuracy to the distributive one, yet with considerably higher computational speed.
Experimental study of transient paths to the extinction in sonoluminescence
Authors: Urteaga Raúl , Dellavale Damián , Puente Gabriela F. , Bonetto Fabián J.
Published: September 2008

An experimental study of the extinction threshold of single bubble sonoluminescence in an air-water system is presented. Different runs from 5% to 100% of air concentrations were performed at room pressure and temperature. The intensity of sonoluminescence (SL) and time of collapse (tc) with respect to the driving were measured while the acoustic pressure was linearly increased from the onset of SL until the bubble extinction. The experimental data were compared with theoretical predictions for shape and position instability thresholds. It was found that the extinction of the bubble is determined by different mechanisms depending on the air concentration. For concentrations greater than ∼30%–40% with respect to the saturation, the parametric instability limits the maximum value of R0 that can be reached. On the other hand, for lower concentrations, the extinction appears as a limitation in the time of collapse. Two different mechanisms emerge in this range, i.e., the Bjerknes force and the Rayleigh–Taylor instability. The bubble acoustic emission produces backreaction on the bubble itself. This effect occurs in both mechanisms and is essential for the correct prediction of the extinction threshold in the case of low air dissolved concentration.
A 2D fast near-field method for calculating near-field pressures generated by apodized rectangular pistons
Authors: Chen Duo , McGough Robert J.
Published: September 2008

Analytical two-dimensional (2D) integral expressions are derived for fast calculations of time-harmonic and transient near-field pressures generated by apodized rectangular pistons. These 2D expressions represent an extension of the fast near-field method (FNM) for uniformly excited pistons. After subdividing the rectangular piston into smaller rectangles, the pressure produced by each of the smaller rectangles is calculated using the uniformly excited FNM expression for a rectangular piston, and the total pressure generated by an apodized rectangular piston is the superposition of the pressures produced by all of the subdivided rectangles. By exchanging summation variables and performing integration by parts, a 2D apodized FNM expression is obtained, and the resulting expression eliminates the numerical singularities that are otherwise present in numerical models of pressure fields generated by apodized rectangular pistons. A simplified time space decomposition method is also described, and this method further reduces the computation time for transient pressure fields. The results are compared with the Rayleigh–Sommerfeld integral and the FIELD II program for a rectangular source with each side equal to four wavelengths. For time-harmonic calculations with a 0.1 normalized root mean square error (NRMSE), the apodized FNM is 4.14 times faster than the Rayleigh–Sommerfeld integral and 59.43 times faster than the FIELD II program, and for a 0.01 NRMSE, the apodized FNM is 12.50 times faster than the Rayleigh–Sommerfeld integral and 155.06 times faster than the FIELD II program. For transient calculations with a 0.1 NRMSE, the apodized FNM is 2.31 times faster than the Rayleigh–Sommerfeld integral and 4.66 times faster than the FIELD II program, and for a 0.01 NRMSE, the apodized FNM is 11.90 times faster than the Rayleigh–Sommerfeld integral and 24.04 times faster than the FIELD II program. Thus, the 2D apodized FNM is ideal for fast pressure calculations and for accurate reference calculations in the near-field region.