bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic divergence predicts reproductive isolation in damselflies
Authors: Sánchez‐Guillén R. A. , Córdoba‐Aguilar A. , Cordero‐Rivera A. , Wellenreuther M.
Published: November 2013

Reproductive isolation is the defining characteristic of a biological species, and a common, but often untested prediction is a positive correlation between reproductive isolation and genetic divergence. Here, we test for this correlation in odonates, an order characterized by strong sexual selection. First, we measure reproductive isolation and genetic divergence in eight damselfly genera (30 species pairs) and test for a positive correlation. Second, we estimate the genetic threshold preventing hybrid formation and empirically test this threshold using wild populations of species within theIschnuragenus. Our results indicate a positive and strong correlation between reproductive isolation and genetic distance using both mitochondrial and nuclear genes cytochrome oxidaseII(COII:r = 0.781 and 18S–28S:r = 0.658). Hybridization thresholds range from −0.43 to 1.78% forCOIIand −0.052–0.71% for 18S–28S, and both F1‐hybrids and backcrosses were detected in wild populations of two pairs ofIschnuraspecies with overlapping thresholds. Our study suggests that threshold values are suitable to identify species prone to hybridization and that positive isolation–divergence relationships are taxonomically widespread.
First Report of Anthracnose of Ledebouriella seseloides Caused by Colletotrichum gloeosporioides in Korea
Authors: Lee Jung Han , Kwak Youn‐Sig
Published: November 2013

In 2012, dark brown spots were observed on leaves of Ledebouriella seseloides (Fang Feng) in several research plots located at the Goseong Agricultural Research Extension services in Gyeongam Province, Republic of Korea. A fungus was isolated from the infected plants which produced pink‐coloured spores in mucilage on PDA and conidial morphology suggested that the causal agent was Colletotrichum gloeosporioides. Internal transcribed spacer sequences of the pathogen showed 99% identity to those of C. gloeosporioides. Pathogenicity of the isolate was proved by Koch's postulates. This is the first report of anthracnose in L. seseloides caused by C. gloeosporioides.
Differential impact of the Bisphosphonate Alendronate on undifferentiated and terminally differentiated human myogenic cells
Authors: Shiomi Kosuke , Nagata Yuki , Kiyono Tohru , Harada Atsushi , Hashimoto Naohiro
Published: November 2013

Objectives

Alendronate, a nitrogen-containing bisphosphonate, is well established as a treatment for osteoporosis through regulation of osteoclast activity. Previously, the pharmacological effects of bisphosphonates on cells outside the bone environment have been considered irrelevant because of the bone-targeting property of bisphosphonates. However, the chronic effects of bisphosphonates on tissue-neighbouring bone, in particular skeletal muscles, should not be ignored because patients are treated with bisphosphonates for long periods.

Methods

Here, we show that the impact of alendronate on immortalized human myogenic cells depends on growth and differentiation-inducing conditions.

Key findings

Alendronate disrupted cytoskeletal structures and prevented migration, proliferation and differentiation of undifferentiated human myogenic cells that are involved in muscle regeneration. In contrast, alendronate did not affect the morphology, gene expression or survival of terminally differentiated human myotubes.

Conclusions

The present results suggest that the muscle regeneration capacity of osteoporosis patients treated with bisphosphonates for long periods may be attenuated. The present research on the pharmacological effects of alendronate on cultured human myogenic cells will contribute to improvement of therapeutic strategies and optimization of rehabilitation programmes for locomotive activity in osteoporosis patients treated with bisphosphonates.
Dialectical behaviour therapy (DBT) in the treatment of borderline personality disorder
Authors: O'Connell B. , Dowling M.
Published: November 2013

Accessible summary

Borderline Personality Disorder (BPD) is a complex disorder that is difficult to treat. Five psychotherapeutic approaches are used in the management of BPD. These include cognitive behavioural therapy, mentalization‐based therapy, schema‐focused therapy, transference‐focused therapy and dialectical behaviour therapy (DBT). Of the five approaches used to manage BPD, DBT has been studied the most extensively.

Dialectical behaviour therapy (DBT) is a multi‐pronged approach comprising of skills‐based training, individual psychotherapy, telephone calls and consultation team meetings.

DBT can have a positive effect on therapists, shifting therapeutic pessimism towards one of optimism with DBT therapists also describing personal changes resulting from their work with clients.

A considerable number of trials have been conducted as DBT was developed in the early 1990s, and most support the usefulness of BPD in the treatment of BPD. However, two Cochrane reviews conclude that more research is needed to provide stronger evidence in support of DBT for the management of BPD.

Borderline personality disorder (BPD) is a complex disorder that is difficult to treat. However, dialectical behaviour therapy (DBT), developed by Dr. Marsha Linehan in the early 1990s, has emerged as a promising treatment option for those diagnosed with BPD. DBT is a multi‐pronged treatment approach delivered normally in outpatient settings over 12 months and requires highly skilled and trained therapists. Many trials have provided evidence to support the use of DBT in the treatment of BPD. However, outcome measures vary and are mostly limited to measurable behavioural outcomes such as incidences of deliberate self‐harm or suicidal thoughts. Two recent Cochrane reviews conclude that DBT does benefit those with BPD, but more robust evidence is needed. DBT training for health care professionals also has the potential to shift health care professionals' attitudes from one of therapeutic pessimism to one of optimism.
Patient Satisfaction with Testosterone Replacement Therapies: The Reasons Behind the Choices
Authors: Kovac Jason R. , Rajanahally Saneal , Smith Ryan P. , Coward Robert M. , Lamb Dolores J. , Lipshultz Larry I.
Published: November 2013

Introduction

Testosterone replacement therapy (TRT) for male hypogonadism is rapidly gaining popularity and acceptance. Options include gels, injections, and implantable subcutaneous pellets.

Aims

The aim of this study was to determine rates of patient satisfaction and reasons for patient preferences in hypogonadal men on TRT.

Methods

An anonymous, prospective survey was distributed to men presenting for TRT at an academic urology clinic. The survey was organized into multiple domains including patient satisfaction and treatment motivation.

Main Outcome Measures

Patient satisfaction responses obtained via anonymous survey.

Results

Average patient age was 49 ± 0.7 years (n = 382). Injectable testosterone was chosen by 53%, gel-based regimens by 31%, and pellets by 17%. Overall, 70% of patients were satisfied with their TRT and 14% reported dissatisfaction. Satisfaction rates were similar between gels (68%), injections (73%), and implantable pellets (70%). Doctor recommendation was the sole significant reason for patients preferring gel-based TRT (66% vs. 37% injection users vs. 31% pellet users). Injectable TRT was favored because of lower cost (35% vs. 21% gel users vs. 19% pellet users). Pellets were favored for ease of use (64% vs. 44% injection users vs. 43% gel users) and convenience (58% vs. 26% injection users vs. 19% gel users). Pellets had increased rates of satisfaction within the first 12 months. Improvements in concentration and mood occurred at higher percentages in satisfied patients.

Conclusions

Patients are satisfied with TRT. Lower costs are important to patients on injections. Convenience and ease of use are central in choosing pellet therapy. Men on TRT should be questioned about mood and concentration because these factors exhibited the greatest improvements in satisfied patients.
The Use and Effectiveness of a Question Exploration Routine in Secondary‐Level English Language Arts Classrooms
Authors: Bulgren Janis A. , Marquis Janet G. , Deshler Donald D. , Lenz B. Keith , Schumaker Jean B.
Published: November 2013

This purpose of the study was to determine the effects of teachers using the Question Exploration Routine (QER) in regularly scheduled secondary‐level English Language Arts classes to help students answer questions about the development and use of main ideas in Shakespeare's Romeo and Juliet. Questions were posed in both multiple‐choice and written formats. On average, students representing diverse groups who received instruction with the QER correctly answered a significantly higher percentage of total questions than students receiving traditional lecture‐discussion instruction (effect sizes were very large). Results are reported for total scores, subscores of multiple‐choice and written responses, and for responses of subgroups of students. Students’ mean satisfaction and confidence responses are reported.
Long‐distance dispersal maximizes evolutionary potential during rapid geographic range expansion
Authors: Berthouly‐Salazar Cécile , Hui Cang , Blackburn Tim M. , Gaboriaud Coline , van Rensburg Berndt J. , van Vuuren Bettine Jansen , Le Roux Johannes J.
Published: November 2013

Conventional wisdom predicts that sequential founder events will cause genetic diversity to erode in species with expanding geographic ranges, limiting evolutionary potential at the range margin. Here, we show that invasive European starlings (Sturnus vulgaris) in South Africa preserve genetic diversity during range expansion, possibly as a result of frequent long‐distance dispersal events. We further show that unfavourable environmental conditions trigger enhanced dispersal, as indicated by signatures of selection detected across the expanding range. This brings genetic variation to the expansion front, counterbalancing the cumulative effects of sequential founding events and optimizing standing genetic diversity and thus evolutionary potential at range margins during spread. Therefore, dispersal strategies should be highlighted as key determinants of the ecological and evolutionary performances of species in novel environments and in response to global environmental change.
Long‐period Positions in Multi‐sectoral Cobb–Douglas Economies
Authors: Eichert Wolfgang
Published: November 2013

The present paper considers a constant returns to scale non‐joint production economy with one primary factor (labour). It follows from the non‐substitution theorem that macroeconomic variables are completely determined by the wage–profit distribution in a long‐period position. We investigate the special case in which production in each sector as well as consumption are characterized by means of Cobb–Douglas functions. Despite the non‐linearity, this parametrization allows us to compute sectoral and macroeconomic variables in simple and intuitive equations. As noted in earlier literature, many variables behave differently than would be expected on basis of a one‐sectoral Solow growth model.
A divergent Pseudomonas aeruginosa palmitoyltransferase essential for cystic fibrosis‐specific lipid A
Authors: Thaipisuttikul Iyarit , Hittle Lauren E. , Chandra Ramesh , Zangari Daniel , Dixon Charneal L. , Garrett Teresa A. , Rasko David A. , Dasgupta Nandini , Moskowitz Samuel M. , Malmström Lars , Goodlett David R. , Miller Samuel I. , Bishop Russell E. , Ernst Robert K.
Published: November 2013

Strains of Pseudomonas aeruginosa (PA) isolated from the airways of cystic fibrosis patients constitutively add palmitate to lipid A, the membrane anchor of lipopolysaccharide. The PhoPQ regulated enzyme PagP is responsible for the transfer of palmitate from outer membrane phospholipids to lipid A. This enzyme had previously been identified in many pathogenic Gram‐negative bacteria, but in PA had remained elusive, despite abundant evidence that its lipid A contains palmitate. Using a combined genetic and biochemical approach, we identified PA1343 as the PA gene encoding PagP. Although PA1343 lacks obvious primary structural similarity with known PagP enzymes, the β‐barrel tertiary structure with an interior hydrocarbon ruler appears to be conserved. PA PagP transfers palmitate to the 3′ position of lipid A, in contrast to the 2 position seen with the enterobacterial PagP. Palmitoylated PA lipid A alters host innate immune responses, including increased resistance to some antimicrobial peptides and an elevated pro‐inflammatory response, consistent with the synthesis of a hexa‐acylated structure preferentially recognized by the TLR4/MD2 complex. Palmitoylation commonly confers resistance to cationic antimicrobial peptides, however, increased cytokine production resulting in inflammation is not seen with other palmitoylated lipid A, indicating a unique role for this modification in PA pathogenesis.
Distribution and spread of pyrethroid and DDT resistance among the Anopheles gambiae complex in Tanzania
Authors: KABULA B. , TUNGU P. , MALIMA R. , ROWLAND M. , MINJA J. , WILILO R. , RAMSAN M. , MCELROY P. D. , KAFUKO J. , KULKARNI M. , PROTOPOPOFF N. , MAGESA S. , MOSHA F. , KISINZA W.
Published: November 2013

The development of insecticide resistance is a threat to the control of malaria in Africa. We report the findings of a national survey carried out in Tanzania in 2011 to monitor the susceptibility of malaria vectors to pyrethroid, organophosphate, carbamate and DDT insecticides, and compare these findings with those identified in 2004 and 2010. Standard World Health Organization (WHO) methods were used to detect knock‐down and mortality rates in wild female Anopheles gambiae s.l. (Diptera: Culicidae) collected from 14 sentinel districts. Diagnostic doses of the pyrethroids deltamethrin, lambdacyhalothrin and permethrin, the carbamate propoxur, the organophosphate fenitrothion and the organochlorine DDT were used. Anopheles gambiae s.l. was resistant to permethrin in Muleba, where a mortality rate of 11% [95% confidence interval (CI) 6–19%] was recorded, Muheza (mortality rate of 75%, 95% CI 66–83%), Moshi and Arumeru (mortality rates of 74% in both). Similarly, resistance was reported to lambdacyhalothrin in Muleba, Muheza, Moshi and Arumeru (mortality rates of 31–82%), and to deltamethrin in Muleba, Moshi and Muheza (mortality rates of 28–75%). Resistance to DDT was reported in Muleba. No resistance to the carbamate propoxur or the organophosphate fenitrothion was observed. Anopheles gambiae s.l. is becoming resistant to pyrethoids and DDT in several parts of Tanzania. This has coincided with the scaling up of vector control measures. Resistance may impair the effectiveness of these interventions and therefore demands close monitoring and the adoption of a resistance management strategy.
Urban legend series: mucous membrane pemphigoid
Authors: Di Zenzo G , Carrozzo M , Chan LS
Published: November 2013

Mucous membrane pemphigoid (MMP) is a heterogeneous group of autoimmune subepithelial blistering diseases affecting primarily mucous membranes showing marked degree of clinical and immunological variability. We investigated four controversial topics: (i) Does oral pemphigoid (OP) really exist as a separate entity? (ii) Is mucous membrane pemphigoid curable? (iii) What is the best therapeutic option for MMP? (iv) Does exclusive oral IgA dermatitis exist as a distinct entity from MMP? Results from extensive literature searches suggested that (i) it is still unclear whether patients with OP could be considered as a distinct subset of MMP with specific clinical and immunological features; (ii) it is uncertain whether treatment regimens that get MMP under control can be eliminated to allow patients to be in drug‐free remission or they should be continuously administered in some capacities; (iii) there is a concerning paucity of good‐quality trials on MMP and available recommendations are solely based on generally small patients' cohorts or case series. Some of the 2002 consensus experts' opinions should be possibly updated, particularly regarding the safety of sulfa drugs; (iv) we did not find any strong evidence to support an exclusive oral (and perhaps also mucosal) form of LAD as a separate entity.
Prevalence of IgE sensitization in Danish children with suspected asthma
Authors: Hoffmann‐Petersen Benjamin , Høst Arne , Toksvig Larsen Kirsten , Ryttov Bergstein Katrine , Løgtholt Thomsen Martin , Brændholt Vagn , Halken Susanne
Published: November 2013

Objective

The aim of this article was to estimate the prevalence of IgE sensitization in Danish children with suspected asthma and to characterize the pattern of sensitization.

Study design

We performed a cross‐sectional study including 1744 children from 0 to 15 yr suspected of asthma who were referred to pediatric outpatient clinics in the region of southern Denmark from 2003 to 2005. The children were subjected to an extensive questionnaire‐based interview, clinical examination, and both skin prick testing (SPT) and IgE measurements for 17 allergens.

Results

Asthma was confirmed in 1024 of the 1744 children. Among the children in whom the asthma diagnosis was confirmed, sensitization to one or more of the 17 allergens tested was found in 67.5% by either SPT or s‐IgE ≥ class 2. Sensitization to any food allergen was found in 31.1%, to any outdoor allergen in 36.2%, and to any indoor allergen in 51.8%. Sensitization to cockroach and latex was rare. We found a weak correlation between SPT and s‐IgE among food allergens and a more distinct correlation among inhalant allergens. Surprisingly, 30.1% of children in whom the asthma diagnosis was disproven used inhaled corticosteroids (ICS). On the contrary, 32.5% of the children for whom the asthma diagnosis was verified were not treated with ICS.

Conclusion

We have found a high prevalence of sensitization among children with verified asthma. Our study supports relevant allergy testing in all children with verified asthma and emphasizes the importance of a thorough asthma diagnosis before prescribing continuous inhaled corticosteroids to children.
An Ecological Model for Quantitative Risk Assessment for Schistosomiasis: The Case of a Patchy Environment in the Coastal Tropical Area of Northeastern Brazil
Authors: de Oliveira Duarte Heitor , Droguett Enrique Lopez , Moura Márcio das Chagas , de Souza Gomes Elainne Christine , Barbosa Constança , Barbosa Verônica , Araújo Moacyr
Published: November 2013

We developed a stochastic model for quantitative risk assessment for theSchistosoma mansoni(SM) parasite, which causes an endemic disease of public concern. The model provides answers in a useful format for public health decisions, uses data and expert opinion, and can be applied to any landscape where the snailBiomphalaria glabratais the main intermediate host (South and Central America, the Caribbean, and Africa). It incorporates several realistic and case‐specific features: stage‐structured parasite populations, periodic praziquantel (PZQ) drug treatment for humans, density dependence, extreme events (prolonged rainfall), site‐specific sanitation quality, environmental stochasticity, monthly rainfall variation, uncertainty in parameters, and spatial dynamics. We parameterize the model through a real‐world application in the district of Porto de Galinhas (PG), one of the main touristic destinations in Brazil, where previous studies identified four parasite populations within the metapopulation. The results provide a good approximation of the dynamics of the system and are in agreement with our field observations, i.e., the lack of basic infrastructure (sanitation level and health programs) makes PG a suitable habitat for the persistence and growth of a parasite metapopulation. We quantify the risk of SM metapopulation explosion and quasi‐extinction and the time to metapopulation explosion and quasi‐extinction. We evaluate the sensitivity of the results under varying scenarios of future periodic PZQ treatment (based on the Brazilian Ministry of Health's plan) and sanitation quality. We conclude that the plan might be useful to slow SM metapopulation growth but not to control it. Additional investments in better sanitation are necessary.
Decomposing Vulnerability to Poverty
Authors: Celidoni Martina
Published: November 2013

This paper applies the decomposition of the Foster–Greer–Thorbecke poverty index to the measurement of individual vulnerability to poverty. I highlight that poverty risk can be expressed as a function of expected incidence, expected intensity, and expected variability below the poverty line, three essential aspects for improving the design of appropriate risk‐management policies. An empirical illustration is provided using the British Household Panel Survey and the Italian Survey on Household Income and Wealth.
Modelling Menstrual Cycle Length and Variability at the Approach of Menopause by Using Hierarchical Change Point Models
Authors: Huang Xiaobi , Elliott Michael R. , Harlow Siobán D.
Published: November 2013

As women approach menopause, the patterns of their menstrual cycle lengths change. To study these changes, we need to model jointly both the mean and the variability of cycle length. Our proposed model incorporates separate mean and variance change points for each woman and a hierarchical model to link them together, along with regression components to include predictors of menopausal onset such as age at menarche and parity. Additional complexity arises from the fact that the calendar data have substantial missingness due to hormone use, surgery and failure to report. We integrate multiple imputation and time-to-event modelling in a Bayesian estimation framework to deal with different forms of the missingness. Posterior predictive model checks are applied to evaluate the model fit. Our method successfully models patterns of women's menstrual cycle trajectories throughout their late reproductive life and identifies change points for mean and variability of segment length, providing insight into the menopausal process. More generally, our model points the way towards increasing use of joint mean–variance models to predict health outcomes and to understand disease processes better.
Fibrinogen recovery and changes in fibrin‐based clot firmness after cryoprecipitate administration in patients undergoing aortic surgery involving deep hypothermic circulatory arrest
Authors: Lee Sang Hyun , Lee Sangmin M. , Kim Chung Su , Cho Hyun Sung , Lee Jong‐Hwan , Lee Cheol Hee , Kim Eunhee , Sung Kiick , Solomon Cristina , Kang Jingu , Kim Young Ri
Published: November 2013

Background

Cryoprecipitate may be used to treat bleeding in cardiac surgery. Its effects on plasma fibrinogen and fibrin clotting in this setting are poorly defined.

Study Design And Methods

Patients undergoing on‐pump aortic surgery with deep hypothermic circulatory arrest (DHCA) were recruited prospectively. After protamine reversal, cryoprecipitate was administered to patients with bleeding, and fibrin deficit was indicated by thromboelastometry (ROTEM)‐based FIBTEM test. Coagulation was assessed using ROTEM‐based tests and standard laboratory tests before and after cryoprecipitate.

Results

Thirteen patients were included. Cryoprecipitate significantly elevated EXTEM A10 from (mean ± standard deviation) 29.4 ± 5.8 to 34.8 ± 5.9 mm (p = 0.01), FIBTEM A10 from 3.5 ± 0.9 to 5.8 ± 1.7 mm (p = 0.04), and plasma fibrinogen concentration from 154.2 ± 25.6 to 193.4 ± 30.5 mg/dL (p = 0.01). EXTEM clot elasticity at 10 minutes (CE10) increased from 42.5 ± 12.0 to 54.7 ± 14.9 mm after cryoprecipitate (30.0% increase). FIBTEM CE10 increased from 3.7 ± 0.9 to 6.2 ± 2.0 mm (53.0% increase). A fibrinogen dose of 13.2 ± 5.2 mg/kg was required to increase FIBTEM A10 by 1 mm. In vivo recovery of fibrinogen was 61.6 ± 31.2%.

Conclusions

Cryoprecipitate increased plasma fibrinogen levels and fibrin‐based clotting in bleeding patients undergoing aortic surgery with DHCA. In vivo recovery of fibrinogen was considerably below 100% and fibrinogen content varied between cryoprecipitate units. Trials are needed to assess whether cryoprecipitate impacts clinical outcomes and to evaluate its safety.
An Experimental Study on Smoke Reduction Effect of Post Injection in Combination With Pilot Injection for a Diesel Engine
Authors: Liu Long , Horibe Naoto , Komizo Tatsuya , Tamura Issei , Ishiyama Takuji
Published: November 2013

With the universal utilization of the common-rail injection system in automotive diesel engines, the multistage injection strategies have become typical approaches to satisfy the increasingly stringent emission regulations, and especially the post injection has received considerable attention as an effective way for reducing the smoke emissions. Normally the post injection is applied in combination with the pilot injection to restrain the NOx emissions, smoke emissions, and combustion noise simultaneously, and the pilot injection condition affects the combustion process of the main injection and might affect the smoke reduction effect of the post injection. Thus this study aims at obtaining the post injection strategy to reduce smoke emissions in a diesel engine, where post injection is employed in combination with pilot injection. The experiments were performed using a single-cylinder diesel engine under various conditions of pilot and post injection with a constant load at an IMEP of 1.01 MPa, fixed speed of 1500 rpm, and NOx emissions concentration of 150 ± 5 ppm that was maintained by adjusting the EGR ratio. The injection pressure was set at 90 MPa at first, and then it was varied to 125 MPa to evaluate the effects of post injection on the smoke reduction in the case of higher injection pressure. The experimental results show that small post injection quantity with a short interval from the end of main injection causes less smoke emissions. And larger pilot injection quantity and later pilot injection timing lead to higher smoke emissions. And then, to explore and interpret the smoke emissions tendencies with varying pilot and post injection conditions, the experimental results of three-stage injection conditions were compared to those of two reference cases, which only included the pilot and main injection, and the interaction between main spray flames and post sprays was applied for analysis. Based on the comparative analysis, the larger smoke reduction effect of post injection was observed with the larger pilot injection quantity, while it is not greatly influenced by pilot injection timing. In addition, the smoke emissions can be reduced considerably by increasing the injection pressure, however the smoke reduction effect of post injection was attenuated. And all of these tendencies were able to be interpreted by considering the intensity variation of the interaction between main spray flames and post sprays.
Nonisothermal Hydrodynamic Modeling of the Flowing Electrolyte Channel in a Flowing Electrolyte–Direct Methanol Fuel Cell
Authors: Duivesteyn Eric , Cruickshank Cynthia A. , Matida Edgar
Published: November 2013

The performance of a direct methanol fuel cell (DMFC) can be significantly reduced by methanol crossover. One method to reduce methanol crossover is to utilize a flowing electrolyte channel. This is known as a flowing electrolyte–direct methanol fuel cell (FE–DMFC). In this study, recommendations for the improvement of the flowing electrolyte channel design and operating conditions are made using previous modeling studies on the fluid dynamics in the porous domain of the flowing electrolyte channel and on the performance of a 1D isothermal FE-DMFC incorporating multiphase flow, in addition to modeling of the nonisothermal effects on the fluid dynamics of the FE-DMFC flowing electrolyte channel. The results of this study indicate that temperature difference between flowing electrolyte inflow and the fuel cell have negligible hydrodynamic implications, except that higher fuel-cell temperatures reduce pressure drop. Reducing porosity and increasing permeability is recommended, with a porosity of around 0.4 and a porous-material microstructure typical dimension around 60–70 μm being potentially suitable values for achieving these goals.
Step-to-Step Variability in Tibiofemoral Contact Force During Walking Measured by an Instrumented Knee Implant
Authors: Scanlan Sean F. , D’Lima Darryl D. , Colwell Clifford W. , Andriacchi Thomas P.
Published: November 2013

Understanding the dynamic loading at the knee can provide critical information for characterizing normal as well as pathologic conditions. However, measuring or predicting this loading from extrinsic measurement remains an unmet challenge. Part of the complexity of generalizing the tibiofemoral loading is that contact force patterns are largely subject specific and vary within subjects based on the activity performed and the specific muscle activation patterns exhibited [1]. While several studies have quantified the intra-subject variability in extrinsic knee kinematics and kinetics during repetitive activities of daily living [2,3], changes in patterns of muscle contraction can yield substantial step-to-step variability in tibiofemoral contact force with minimal changes in extrinsic kinetics due to the potential influence of muscle co-contraction. Knowledge of this step-to-step tibiofemoral loading variability could play an integral role in improving the interpretation of analytical contact force predictions.
Correlation Between Aortic Motion and Vessel Bulging in a Murine Aneurysm Model Using Small Animal Magnetic Resonance Imaging
Authors: Goergen Craig J. , Choi Gilwoo , Hedehus Maj , Taylor Charles A. , Tsao Philip S. , Greve Joan M.
Published: November 2013

Abdominal aortic aneurysm (AAA), defined as a 1.5-fold or greater increase in vessel diameter, leads to approximately 15,000 deaths per year in the United States. While the clinical morbidities are well-known, a detailed understanding of the underlying mechanisms that lead to initiation of the disease and progressive expansion of the vessel remain elusive. Murine AAA models have been developed to aid in better understanding the condition in humans. However, aneurysm research in mice to date has been limited to assessment of vessel growth by invasive or 2D ultrasound methods and has not considered wall dynamics. Thus, the purpose of this study was to characterize wall motion and aortic displacement in mouse aortas by developing high spatial and temporal resolution MR imaging and vessel quantification methods, with the goal of comparing the motion of healthy vasculature to the direction of AAA bulging.
A Two-Dimensional Model of Particle Motion in Ureteral Peristaltic Flow
Authors: Jiménez-Lozano Joel , Sen Mihir , Dunn Patrick
Published: November 2013

Physiological fluids in human or animals are, in general, propelled by the continuous periodic muscular contraction or expansion (or both) of the ducts through which the fluids pass, a phenomenon known as peristalsis. Peristaltic mechanisms may be involved in the swallowing of food through the esophagus, vasomotion of small blood vessels, spermatic flows in the ductus efferentes, embryo transport in the uterus, and transport of urine through the ureters, among others [1]. Peristaltic fluid flow can be accompanied by solid particles. In this work the Basset-Boussinesq-Oseen (BBO) equation will be employed to analyze particle motion in peristaltic fluid flow, this model considers motion of a small spherical particle suspended in a nonuniform fluid flow and diverse forces are considered. In ureteral peristaltic flow, fluid being transported is essentially Newtonian and incompressible. Ureteral peristaltic flow is sometimes accompanied by particles such as stones or bacteria. In the present study, the geometrical form of the peristaltic wave will be taken to be sinusoidal. The governing equations are Navier-Stokes for the fluid and momentum for the particle (BBO equation). A regular perturbation series in which the variables are expanded in a power series of the wavenumber (ε = πRw/λ) is used to solve the fluid problem. One-way coupling between the fluid and particles is assumed.
Use of Design of Experiment Approach to Predict Force-Displacement Relationship for the Knee Joint and Menisci in a Multi-Body Dynamic Knee Model
Authors: Kia Mohammad , Guess Trent M.
Published: November 2013

The multi-body method can provide computationally efficient simulations of muscle and tissue interactions. A limitation of the multi-body approach is in the functional representation of soft tissues such as articular cartilage and the menisci. In previous work, a deformable contact with constant coefficients was applied to a subject-specific multi-body knee model to define the contact force between patella, femur, and tibia articular cartilage [1, 2]. Hertzian contact theory was used to determine the parameters of the compliant contact force model based on cartilage material properties and contact geometry. To improve upon the Hertzian theory formulation of contact parameters, a design of experiments approach was used to find prediction equations to determine parameters for a compliant contact and multi-body meniscus model. Solutions for the prediction equations can come from either finite element or experimental solutions.
Articular Cartilage and Meniscal Fibrocartilage Mechanics: Evidence for Differences in Ultrastructure and Function of Proteoglycans
Authors: Nguyen An M. , Levenston Marc E.
Published: November 2013

The organization and function of proteoglycans have been extensively studied in articular cartilage. Proteoglycans are widely dispersed throughout articular cartilage [1] and resist compressive as well as shear loads through high hydrostatic pressures, low fluid permeability and stiffening of the collagen network [2]. Few studies have investigated the organization and function of proteoglycans in meniscal fibrocartilage. Previous studies have shown PG degradation leads to decreased meniscal fibrocartilage mechanics [3,4]. In contrast to articular cartilage, meniscal fibrocartilage PGs are concentrated around circumferential collagen fibers [2]. To better understand the role of proteoglycans in meniscal fibrocartilage, the proteoglycan interactions within the tissue can be manipulated without extracellular matrix degradation. The goal of this study was to compare the effects of osmotic swelling stress on articular cartilage and meniscal fibrocartilage mechanics by varying osmotic strength and tissue compressive offset.
Isolation, Loading and Estimating the Poroelastic Properties of a Single Osteon
Authors: Gailani Gaffar , Benalla Mohammed , Mahamud Rashal , Cowin Stephen , Cardoso Luis
Published: November 2013

Determining the poroelastic properties of osteons is critical to better understand the role of fluid flow in the nutrition, mechanotransduction, remodeling, homeostasis and loss of bone. The permeability of single osteons is among the key properties that may influence these phenomena. The measurement of permeability of a single osteon remains one of the most demanding tasks in bone mechanics to be developed. Two associated challenges are the size of the osteon and the absence of appropriate tools and methods to perform such measurement. In this communication, we present the development of a new procedure to isolate osteons, the design of a mechanism for loading an osteon and the comparison of the stress relaxation test in unconfined compression experiment with the analytical results for a compressible transverse isotropy model that we previously reported in Gailani and Cowin [1]. These experimentally determined values of permeability and mechanical properties have shown reasonable agreement with the previously reported experimentally and theoretically estimated values.
Anatomical and Surgical Risk Factors Affecting the Internal Mechanical Conditions in the Transtibial Residuum
Authors: Portnoy Sigal , Yizhar Ziva , Shabshin Noga , Itzchak Yaakov , Kristal Anat , Siev-Ner Itzhak , Gefen Amit
Published: November 2013

Transtibial amputation (TTA) patients face ongoing morphological changes in their residual limb. The residuum volume changes due to weight gain or loss, diurnal edema, and muscle atrophy. Consequently, the TTA prosthetic-user is fitted with a new prosthetic socket approximately every four years. Despite new innovations in socket and liner materials and design, contemporary prosthetics are not yet equipped to confront these changes. The TTA residual limb is therefore subjected to high superficial and internal stresses which may cause injury. Appending the hazardous condition of natural volume change of the residuum is the initial geometrical state of the truncated bones. The primary surgical considerations in TTA are the tibial length, the bevelment of the distal end of the tibia and the location of the surgical scar. These risk factors may significantly affect the well being of the TTA residuum. Previous studies assumed that the criteria for a well-fitted socket were low interface stresses. However, while interface stress measurements may help prevent superficial skin damage, knowledge of the internal stress distribution can prevent the formation of deep tissue injury (DTI) [1]. While superficial pressure ulcers are visually detected, DTI is concealed under the skin and spreads to its surroundings in the soft tissues of the residuum. If this latent wound is ignored, the skin will rupture to reveal a massive injury to skin, fat and muscle tissues, clinically termed as a type IV pressure ulcer. Our purpose was to evaluate the effect of the following risk factors on the internal mechanical condition of the TTA residuum: shorter tibial lengths (thicker muscle flap tissue), milder tibial end bevelments, different mechanical properties of the muscle flap (simulating both variance between patients or flaccid versus contracted muscle) and superficial scarring in inferior and anterior locations on the skin.
Reduction in the Medial Compartment Force Correlates With the Reduction in Knee Adduction Moment Using a Variable-Stiffness Shoe With an Instrumented Knee
Authors: Erhart Jennifer C. , Dyrby Chris , D’Lima Darryl D. , Colwell Clifford W. , Andriacchi Thomas P.
Published: November 2013

Osteoarthritis (OA) of the knee affects an estimated 20–40% of individuals over the age of 65 [1], and is nearly 10 times more common in the medial compartment than the lateral compartment [2]. Many studies have reported the effectiveness of footwear modifications using laterally-wedged insoles [3,4] and more recently, variable-stiffness soles [5] in reducing the adduction moment at the knee in patients with medial compartment knee OA. The adduction moment is known to be associated with the progression [6] and treatment outcome [7] of medial compartment knee OA, and has been shown to be correlated with medial compartment joint loading [8]. However, the exact changes in medial compartment joint loading in vivo with the variable-stiffness shoe remain unknown. The development of an instrumented total knee implant which has the ability to directly measure tibial forces, and can differentiate between medial and lateral joint loads in vivo during walking [9], allows the testing of changes in the medial compartment loading with an intervention shoe.
Simultaneous Determination of E, G and ν of Soft Hydrogels Using Theory of Elasticity
Authors: Chippada Uday , Jiang Xue , Li Lulu , Schloss Rene , Yurke Bernard , Langrana Noshir
Published: November 2013

Hydrogels have been used as substrates by many researchers in the study of cellular processes. The mechanical properties of these gels play a significant role in the growth of the cells. Significant research using several methods like compression, indentation, atomic force microscopy and manipulation of beads has been performed in the past to characterize the stiffness of these substrates. However, most of the methods employed assume the gel to be incompressible, with a Poisson’s ratio of 0.5. However, Poisson’s ratio can differ from 0.5. Hence, a more complete characterization of the elastic properties of hydrogels requires that one experimentally obtain the value of at least two of the three quantities: Poisson’s ratio, shear modulus, and elastic modulus.
Computation of Blast-Induced Traumatic Brain Injury
Authors: Chafi M. S. , Karami G. , Ziejewski M.
Published: November 2013

In this paper, an integrated numerical approach is introduced to determine the human brain responses when the head is exposed to blast explosions. The procedure is based on a 3D non-linear finite element method (FEM) that implements a simultaneous conduction of explosive detonation, shock wave propagation, and blast-brain interaction of the confronting human head. Due to the fact that there is no reported experimental data on blast-head interactions, several important checkpoints should be made before trusting the brain responses resulting from the blast modeling. These checkpoints include; a) a validated human head FEM subjected to impact loading; b) a validated air-free blast propagation model; and c) the verified blast waves-solid interactions. The simulations presented in this paper satisfy the above-mentioned requirements and checkpoints. The head model employed here has been validated again impact loadings. In this respect, Chafi et al. [1] have examined the head model against the brain intracranial pressure, and brain’s strains under different impact loadings of cadaveric experimental tests of Hardy et al. [2]. In another report, Chafi et al. [3] has examined the air-blast and blast-object simulations using Arbitrary Lagrangian Eulerian (ALE) multi-material and Fluid-Solid Interaction (FSI) formulations. The predicted results of blast propagation matched very well with those of experimental data proving that this computational solid-fluid algorithm is able to accurately predict the blast wave propagation in the medium and the response of the structure to blast loading. Various aspects of blast wave propagations in air as well as when barriers such as solid walls are encountered have been studied. With the head model included, different scenarios have been assumed to capture an appropriate picture of the brain response at a constant stand-off distance of nearly 80cm (2.62 feet) from the explosion core. The impact of brain response due to severity of the blast under different amounts of the explosive material, TNT (0.0838, 0.205, and 0.5lb) is examined. The accuracy of the modeling can provide the information to design protection facilities for human head for the hostile environments.
The Effect of Polyethylene Cup Penetration on Acetabular Cement Fatigue Life
Authors: Coultrup Oliver J. , Hunt Chris , Taylor Mark
Published: November 2013

Aseptic loosening in the acetabular component is the most prevalent cause of failure in cemented total hip arthroplasty (THA) [1]. There is clinical evidence of high polyethylene cup wear accompanying acetabular aseptic loosening [2]. One such study discriminated between cups experiencing low and high wear, showing the revision rate in the high-wear group was approximately eight times that of the low-wear group after seventeen years in vivo, and could not be linked to osteolysis [2]. In the present study a finite element (FE) model was used to simulate aseptic loosening in THA acetabular components with different rates of polyethylene cup penetration to measure the effect on cement fatigue life.
Design and Development of Silicone Rubbers for Use in the Experimental Modelling of Abdominal Aortic Aneurysms
Authors: Doyle Barry J. , Corbett Timothy J. , Vorp David A. , McGloughlin Timothy M.
Published: November 2013

Silicone is a synthetic polymer consisting of a linear backbone of repeating, alternating silicone and oxygen atoms. Each silicone atom has two groups attached to it, referred to as R groups, representing any organic group that may be attached to the backbone. These rubbers can therefore undergo large recoverable deformations, hence the wide use of silicone rubbers as material analogues in the study of arterial vessels [1,2] and other soft tissues. Abdominal aortic aneurysms (AAAs) are permanent irreversible dilations of the infrarenal section of the aorta that will eventually expand to the point of rupture if left untreated. Many previous studies have focussed on the numerical prediction of wall stresses and ultimately rupture prediction of AAAs [3,4]. However, there have been limited reports as to how these aneurysms behave experimentally [2,5]. Also, previous experimental work has employed the use of a single material to represent the AAA wall, even though it is known that a realistic AAA may have differing materials properties at various locations throughout the aneurysm [6].
Derivation of Surrogate Variables to Assess Pathological Conditions Using a 3D Model of the Aortic Valve
Authors: Nobari Soroush , Mongrain Rosaire , Campbell Ian , Leask Richard , Cartier Raymond
Published: November 2013

The aortic valve has received much attention in the biomedical research community during recent years. As a critical part of the cardiovascular system, any alteration in its structure or in the surrounding area directly or because of pathologies would change the flow pattern of that region as a consequence. Numerous studies have been done and regardless of the approach, the aim of all these studies is the same: to understand the intricacies of the healthy aortic valve and, perhaps, to mimic it in the realm of prosthetics.
Traumatic Anterior Cruciate Ligament Tear and Its Implications on Meniscal Degradation: A Preliminary Novel Lapine Osteoarthritis Model
Authors: Killian Megan L. , Isaac Dan , Haut Roger C. , Dejardin Loic M. , Leetun Darin , Haut Donahue T. L.
Published: November 2013

The meniscus plays a crucial role in the dynamics of the knee. Damage to the meniscus can influence proprioception, stability, and mobility of the knee [1]. Risk factors of meniscal tears include prolonged or repeated deep knee bending, obesity, and sporting injuries [2]. Acute injury, as seen in alpine sports, involves complex dynamics which can damage singular or multiple tissue structures of the knee [2]. It is not uncommon for meniscal injuries to occur in conjunction with ACL lesions, and the loading imbalance that results in ACL lesions may also initiate meniscal tears [3, 4]. Investigations of meniscal tears following ACL rupture have indicated chronic damage to medial menisci more so than lateral menisci [5]. However, experimental studies of acute damage following ACL transection are not consistent, with some showing more lateral damage acutely and some showing equality between medial and lateral meniscal damage [5].
Computational Biomechanical Analysis of Fixation Performance and Bone Resorption of Tibial Prosthesis Implantation
Authors: Chong Desmond Y. R. , Hansen Ulrich N. , Amis Andrew A.
Published: November 2013

Long-term survivorship of total knee replacement (TKR) relies on the periprosthetic bone strength and its initial fixation stability. Aseptic loosening caused by mechanical factors is a recognised failure mode for knee prostheses. Bone resorption due to “stress-shielding” of the stiff stemmed implants will potentially lead to weakened bone strength, and also presents a challenge for revision surgery. While the bone cement is commonly used to provide mechanical attachment of the prosthesis to the bone, cement fatigue and bone-cement interface failures would eventually lead to component migration and aseptic loosening of the tibial components. The cementless fixation relies on bony ingrowth into the porous surfaces of the prosthesis thereby providing a biological attachment. Its fixation strength would depend largely on the initial stability of the fixation, where excessive bone-prosthesis relative motion (>50μm) would inhibit the osseointegration process [1]. The above are caused partly by a lack of knowledge of the optimum implant design and fixation technique factors.