bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress relaxation behavior of glass fiber‐reinforced polyester composites prepared by the newly proposed rubber pressure molding
Authors: Kar Kamal K. , Sharma S.D. , Kumar Prashant , Mohanty Akash
Published: April 2008

Stress‐relaxation behavior of glass fiber‐reinforced polyester composites, prepared by a recently developed manufacturing method called rubber pressure molding (RPM), is investigated with special reference to the effect of environmental temperature (−70°C to +100°C), fiber volume fraction (30–60%), and initial load level (1–5 kN). It is found that the stress‐relaxation rate decreases with an increase in the applied load of composites and a decrease in temperature. Below glass transition temperature, the rate of stress relaxation increases with an increase in volume fraction of fibers in the composites, whereas above glass transition temperature, it increases with a decrease in the volume fraction of fibers. The experimental results for a given composites are summarized by four values, the slopes of the two straight lines (two separate relaxation processes), and their intercepts upon the stress axis. Both the slopes are dependent upon the applied load, temperature, and volume fraction of fibers in the composites. Relaxation times in both primary and secondary are calculated over the wide range of temperatures, loads, and volume fraction of fibers in the composites. It depends strongly on the temperature, but does not depend strongly on the applied load and volume fraction of fibers. The performances of the composites are also evaluated through conventional compression‐molding process. The rate of stress relaxation is small when the composites are made of newly proposed RPM technique when compared with the conventional process. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
An homogenization procedure for the description of pre‐ and post‐yielding stages of isotropic polymer composites
Authors: Pandermarakis Z.G. , Spathis G.
Published: April 2008

There will be integrated and provided a complete set of relations for an exact description of the whole mechanical behavior of a composite, i.e. from low to high deformations and stresses. The results from an extended homogenization procedure will be presented here, starting from the fact that the basic material—polymer matrix—presents viscoelastic and viscoplastic response. Analyzing the results from a unidirectional compression loading of an isotropic polymer composite, we found a characteristic enhancement of yield stress and also a distinct hardening stage: Features that generally are absent from similar test sets of unidirectional tension loading. The need for a more systematic study of this loading case in order to explain and describe correctly this inversion/asymmetry in relation to tension reference case, led us to the identification of a yielding stress impetus quantity: k = τ/(s + a · p), a critical stressed area, and to a true strain rate of loading matrix and reinforcement. We found that only by knowing the interaction between them and the entire equations set that controls the corresponding quantities, we will be able to describe correctly the real behavior of composites, i.e. their viscoelastic, viscoplastic, strain softening, and strain hardening response. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Influence of concentration, temperature and humidity on the toxicity of phosphine to the strongly phosphine‐resistant psocid Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae)
Authors: Nayak Manoj K , Collins Patrick J
Published: April 2008

BACKGROUND: The psocid Liposcelis bostrychophila Badonnel, is a widespread, significant pest of stored commodities, has developed strong resistance to phosphine, the major grain disinfestant. The aim was to develop effective fumigation protocols to control this resistant pest.

RESULTS: Time to population extinction of all life stages (TPE) in days was evaluated at a series of phosphine concentrations and temperatures at two relative humidities. Regression analysis showed that temperature, concentration and relative humidity all contributed significantly to describing TPE (P < 0.001, R2 = 0.95), with temperature being the dominant variable, accounting for 74.4% of the variation. Irrespective of phosphine concentration, TPE was longer at lower temperatures and high humidity (70% RH) and shorter at higher temperatures and low humidity (55% RH). At any concentration of phosphine, a combination of higher temperature and lower humidity provides the shortest fumigation period to control resistant L. bostrychophila. For example, 19 and 11 days of fumigation are required at 15 °C and 70% RH at 0.1 and 1.0 mg L−1 of phosphine respectively, whereas only 4 and 2 days are required at 35 °C and 55% RH for the same respective concentrations.

CONCLUSIONS: The developed fumigation protocols will provide industry with flexibility in application of phosphine. Copyright © The State of Queensland (through the Department of Primary Industries and Fisheries) 2008.
Structural and functional changes of tropical riffle macroinvertebrate communities associated with stream flow withdrawal
Authors: McIntosh Mollie D. , Schmitz Jennifer A. , Benbow M. Eric , Burky Albert J.
Published: April 2008

Tropical island streams worldwide are threatened by existing or proposed dams and diversions that remove freshwater for human use; yet, there have been few studies that address the effects on aquatic communities. The objective of this study was to quantify changes in tropical macroinvertebrate communities associated with stream flow withdrawal. Benthic macroinvertebrates were collected from riffle habitats located above and below a stream diversion on Maui, Hawaii, from June to August 2000. Native and introduced taxa were identified from both locations. The most dominant taxon was midges (Diptera: Chironomidae) followed by two introduced caddisflies, Cheumatopsyche analis (Banks) (Trichoptera: Hydropsychidae) and Hydroptila potosina (Buenoa‐Soria) (Trichoptera: Hydroptilidae). A native shrimp, Atyoida bisulcata, and beach fly, Procanace sp. (Diptera: Canacidae), were either eliminated from or significantly reduced below the diversion. Mean total macroinvertebrate densities were greater above (13 357 individuals/m2) the diversion compared to below (10 360 individuals/m2). Mean total macroinvertebrate biomass was significantly reduced by 60 per cent below the diversion, but specific taxa did not show this effect. These results suggest that diverted stream flow limited macroinvertebrate colonization and growth, expressed as reduced community density and biomass, which may alter the structure and function of other trophic levels within tropical stream food webs. Copyright © 2008 John Wiley & Sons, Ltd.
The influence of sensation seeking in the heritability of entrepreneurship
Authors: Nicolaou Nicos , Shane Scott , Cherkas Lynn , Spector Tim D.
Published: April 2008

This study examined the influence of genetic factors on the tendency to engage in entrepreneurship. We found that, in the particular sample we examined, between 37 and 42 percent of the variance in the tendency of people to engage in entrepreneurship is accounted for by genetic factors. A substantial part of this variance was mediated by the psychological trait of sensation seeking, suggesting that genes affect the tendency of people to engage in entrepreneurship by affecting the distribution of sensation seeking across people. Copyright © 2008 Strategic Management Society.
New look at creativity in the entrepreneurial process
Authors: Zhou Jing
Published: April 2008

In this article I provide brief review and comments on three articles presented at the Strategic Entrepreneurship Journal's Launch Conference and published in this issue of the Journal. Arguing that creativity plays an important role in the entire entrepreneurial process and that contemporary research on creativity has much to offer in advancing our understanding of entrepreneurship, I suggest four new research directions that would expand the scope of entrepreneurship research. Copyright © 2008 Strategic Management Society.
Entrepreneurship, subjectivism, and the resource‐based view: toward a new synthesis
Authors: Foss Nicolai J. , Klein Peter G. , Kor Yasemin Y. , Mahoney Joseph T.
Published: April 2008

This article maintains that the consistent application of subjectivism helps reconcile contemporary entrepreneurship theory with the strategic management literature, particularly the resource‐based view of the firm. The article synthesizes theoretical insights from Austrian economics, Penrose's (1959) resources approach, and modern resource‐based theory, focusing on the essential subjectivity of the entrepreneurial process. This new synthesis describes entrepreneurship as a creative team act in which heterogeneous managerial mental models interact to create and arrange resources to produce a collective output that is creatively superior to individual output. Copyright © 2008 Strategic Management Society.
Question: How Should Middle East Studies Address the Issues of Academic Freedom and Academic Boycotts?
Authors: Brand Laurie A.
Published: April 2008

Challenges to academic freedom have been much in the news of late, with coverage and interest extending well beyond college newspapers and the publications of our profession.

In the United States, there is no question that members of the Middle East studies community have been disproportionately targeted. A number of our colleagues have been victims of ugly smear campaigns regarding their scholarship; several tenure cases have triggered vicious, high-profile “extramural” attacks against junior faculty; and, in a handful of cases, our colleagues have been barred from giving talks or participating in educational events, owing to their political positions on Middle East-related issues. Others from outside this community who have also ventured to engage key regional issues in critical ways have had their invitations to give presentations in policy or academic forums rescinded.
WHEN MEMORY REPEATS ITSELF: THE POLITICS OF HERITAGE IN POST CIVIL WAR LEBANON
Authors: Volk Lucia
Published: April 2008

On 4 August 2005 the Lebanese English-language paper theDaily Starreported that Lebanon's ancient inscriptions at Nahr al-Kalb had been accepted into the United Nations Educational, Scientific and Cultural Organization's (UNESCO’s) collection of “worldwide rare documents” through its Memory of the World Programme. UNESCO established the Memory of the World Programme in 1992, after realizing that its World Heritage Programme, which seeks to protect historic landscapes and architectural landmarks, did not safeguard a category of less visible, yet equally important, documents of the past: texts. The Memory of the World Programme made the preservation of “documentary heritage [which] reflects the diversity of languages, peoples and cultures” its goal, hoping that its work would help prevent “collective amnesia.” An eight-member Lebanese national committee made up of cultural and political elites affiliated with Lebanon's Ministry of Culture and Lebanese University, the country's largest public university, submitted a unanimous proposal to UNESCO's International Advisory Committee (IAC) to include Nahr al-Kalb in its collection of “documentary heritage.” The IAC reviewed and accepted the proposal in June 2005, placing the inscriptions along the river of Nahr al-Kalb in the company of 156 other universally memorable texts from around the world.
Analyzing kinematics and solving active/constrained forces of a 4-dof 3SPS+SP parallel manipulator
Authors: Lu Yi , Hu Bo
Published: April 2008

A novel 3SPS+SP parallel manipulator (PM) with 4-dof is proposed. Its kinematics and statics are analyzed systematically. The analytic formulae for solving the displacement, velocity, acceleration, workspace, active forces and constrained force are derived. The analytic results are verified by using a simulation mechanism of the 3SPS+SP PM.
History, An Exit Strategy: The RetroFuture Fabulations of kara lynch
Authors: OUZOUNIAN GASCIA
Published: April 2008

A cartographer constructs a map of an individual creative history, that of the American artist kara lynch, as it emerges in connection to a collective history of African American cultural expression. Positioning history as complex, dynamic systems of interwoven memory networks, the map follows lynch's traversals through various “zones of cultural haunting”: places where collective memories made invisible through systematic processes of cultural erasure may be recovered and revived. Through these traversals, which are inspired by lynch's “forever project”Invisible, the map covers such terrains as haunted narratives, mechanisms of abstraction and coding within African American media production, water as an informational technology, the distribution of memory in blood, the dialectics of materiality and immateriality that frame considerations of black subjectivity, and the possibility that place of music might not be the site of sound but instead the social production of memory.
Dislocation models of interseismic deformation in the western United States
Authors: Pollitz Fred F. , McCrory Patricia , Svarc Jerry , Murray Jessica
Published: April 2008

The GPS‐derived crustal velocity field of the western United States is used to construct dislocation models in a viscoelastic medium of interseismic crustal deformation. The interseismic velocity field is constrained by 1052 GPS velocity vectors spanning the ∼2500‐km‐long plate boundary zone adjacent to the San Andreas fault and Cascadia subduction zone and extending ∼1000 km into the plate interior. The GPS data set is compiled from U.S. Geological Survey campaign data, Plate Boundary Observatory data, and the Western U.S. Cordillera velocity field of Bennett et al. (1999). In the context of viscoelastic cycle models of postearthquake deformation, the interseismic velocity field is modeled with a combination of earthquake sources on ∼100 known faults plus broadly distributed sources. Models that best explain the observed interseismic velocity field include the contributions of viscoelastic relaxation from faulting near the major plate margins, viscoelastic relaxation from distributed faulting in the plate interior, as well as lateral variations in depth‐averaged rigidity in the elastic lithosphere. Resulting rigidity variations are consistent with reduced effective elastic plate thickness in a zone a few tens of kilometers wide surrounding the San Andreas fault (SAF) system. Primary deformation characteristics are captured along the entire SAF system, Eastern California Shear Zone, Walker Lane, the Mendocino triple junction, the Cascadia margin, and the plate interior up to ∼1000 km from the major plate boundaries.
Remote sensing of hydrologic recharge in the Peace‐Athabasca Delta, Canada
Authors: Pavelsky Tamlin M. , Smith Laurence C.
Published: April 2008

Northern wetlands like Canada's Peace‐Athabasca Delta (PAD) have global environmental significance, yet fundamental processes of hydrologic recharge critical to their functionality remain poorly understood. We use in situ water level and MODIS satellite data to examine how main‐stem river level fluctuations drive inundation across the delta. Temporal covariance between the two datasets allows inference of hydrologic connectivity processes, not just inundation extent. A strong contrast is found between hydrologic connectivity properties in a high‐water (2007) vs. low‐water year (2006). Results suggest that existing theoretical models of floodplain recharge fail to capture observed patterns of inundation in the PAD. Instead, we find a dichotomy between the distributary channel network, which responds to summer high‐water events, and floodplain lakes and wetlands, which do not. The latter occurs even where hydrologic connections do exist between the two. Results have strong management implications for the impact of proposed up‐river water diversion on PAD hydrology.
Humoral immunity to commensal oral bacteria in human infants: evidence that Streptococcus mitis biovar 1 colonization induces strain-specific salivary immunoglobulin A antibodies
Authors: Wirth Katherine A , Bowden George H , Kirchherr Jennifer L , Richmond Dorothy A , Sheridan Michael J , Cole Michael F
Published: April 2008

To define the relationship between salivary SIgA antibodies and commensal oral bacteria, we examined the reactivity of SIgA antibodies from the saliva of four infants with their own colonizing Streptococcus mitis biovar 1 (S. mitis bv 1) clones (ribotypes). Immunoblot analysis was used to examine reactivity of these antibodies with persistent ribotypes isolated from the mouths of the infants over the first year postpartum. Results showed that the pattern of SIgA antibody reactivity with the majority of clones increased in complexity after colonization but that most additional bands were common to other clones, indicating that they represented shared antigens. However, unique bands were identified in 75% of the selected persistent clones. We hypothesized that if strain-specific SIgA antibody was induced in response to colonization of a particular clone and contributed to its elimination from the mouth, then the appearance of unique bands would immediately precede the disappearance of the strain. Seventy-three percent of all unique bands identified in the study fulfilled this criterion. Because the mouth is an open, dynamic environment and multiple factors are believed to play a role in the immune response at mucosal surfaces, it may not be possible to conclusively define the relationship between SIgA antibody and commensal bacteria. However, our data provide evidence that SIgA antibody, reactive with unique antigens of their own colonizing strains, is produced in infants and may point to a role of this antibody in regulating colonization by S. mitis bv 1.
Contribution of Midparental BMI and Other Determinants of Obesity in Adult Offspring
Authors: Abu‐Rmeileh Niveen M.E. , Hart Carole L. , McConnachie Alex , Upton Mark N. , Lean Michael E.J. , Watt Graham C.M.
Published: April 2008

The aim of this study was to evaluate midparental BMI among intergenerational factors associated with obesity in adult offspring. The data was from an unusual two‐generational observational design of 1,477 married couples from Renfrew and Paisley in Scotland who were aged 45–64 years when screened in 1972–1976, and 1,040 sons and 1,298 daughters aged 30–59 years when screened in 1996. BMI was categorized as normal (<25 kg/m2), overweight (25–29.9 kg/m2), and obese (≥30 kg/m2) in offspring and parents. Midparental BMI was defined as the mean of the mother's and father's BMI. Low physical activity, nonsmoking status, higher cholesterol level, and manual social class were all associated with increased BMI in offspring. The effect of reported dietary intake was less clear. Offspring of obese parents (defined by midparental BMI) were over four times more likely to be obese than offspring of normal weight parents. Midparental BMI had a strong effect on offspring BMI, independent of social class, smoking habit, physical activity, and reported dietary intake. Adding midparental BMI to the regression model more than doubled the explained variation of offspring BMI from 7.7 to 17%. Every 1 kg/m2 increment in midparental BMI was associated with a BMI greater by 0.51 kg/m2 in offspring. We conclude that midparental BMI is a useful simple tool to predict offspring BMI. Whether it represents genetic or environmental family effects, it is easily ascertained by the individual and could be used in health promotion and clinical settings to target individuals who are at increased risk of becoming obese.
Calcium and Dairy Product Modulation of Lipid Utilization and Energy Expenditure
Authors: Teegarden Dorothy , White Kimberly M. , Lyle Roseann M. , Zemel Michael B. , Van Loan Marta D. , Matkovic Velimir , Craig Bruce A. , Schoeller Dale A.
Published: April 2008

Objective: The purpose of this study was to investigate the impact of dietary calcium or dairy product intake on total energy expenditure (TEE), fat oxidation, and thermic effect of a meal (TEM) during a weight loss trial.

Methods and Procedures: The intervention included a prescribed 500‐kcal deficit diet in a randomized placebo‐controlled calcium or dairy product intervention employing twenty‐four 18 to 31‐year‐old (22.2 ± 3.1 years, mean ± s.d.) overweight women (75.5 ± 9.6 kg). TEM and fat oxidation were measured using respiratory gas exchange after a meal challenge, and TEE was measured by doubly labeled water. Fat mass (FM) and lean mass (fat‐free mass (FFM)) were measured by dual‐energy X‐ray absorptiometry. Subjects were randomized into one of these three intervention groups: (i) placebo (<800 mg/day calcium intake); (ii) 900 mg/day calcium supplement; (iii) three servings of dairy products/day to achieve an additional 900 mg/day.

Results: There were no group effects observed in change in TEE; however, a group effect was observed for fat oxidation after adjusting for FFM (P = 0.02). The treatment effect was due to an increase in fat oxidation in the calcium‐supplemented group of 1.5 ± 0.6 g/h, P = 0.02. Baseline 25‐hydroxyvitamin D (25OHD) was positively correlated with TEM (R = 0.31, P = 0.004), and trended toward a correlation with fat oxidation (P = 0.06), independent of group assignment. Finally, the change in log parathyroid hormone (PTH) was positively correlated with the change in trunk FM (R = 0.27, P = 0.03).

Discussion: These results support that calcium intake increases fat oxidation, but does not change TEE and that adequate vitamin D status may enhance TEM and fat oxidation.
Genome‐wide Linkage Scan for the Metabolic Syndrome: The GENNID Study
Authors: Edwards Karen L. , Hutter Carolyn M. , Wan Jia Yin , Kim Helen , Monks Stephanie A.
Published: April 2008

In the United States, the metabolic syndrome (MetS) constitutes a major public health problem with over 47 million persons meeting clinical criteria for MetS. Numerous studies have suggested genetic susceptibility to MetS. The goals of this study were (i) to identify susceptibility loci for MetS in well‐characterized families with type 2 diabetes (T2D) in four ethnic groups and (ii) to determine whether evidence for linkage varies across the four groups. The GENNID study (Genetics of NIDDM) is a multicenter study established by the American Diabetes Association in 1993 and comprises a comprehensive, well‐characterized resource of T2D families from four ethnic groups (whites, Mexican Americans, African Americans, and Japanese Americans). Principal component factor analysis (PCFA) was used to define quantitative phenotypes of the MetS. Variance components linkage analysis was conducted using microsatellite markers from a 10‐cM genome‐wide linkage scan, separately in each of the four ethnic groups. Three quantitative MetS factors were identified by PCFA and used as phenotypes for MetS: (i) a weight/waist factor, (ii) a blood pressure factor, and (iii) a lipid factor. Evidence for linkage to each of these factors was observed. For each ethnic group, our results suggest that several regions harbor susceptibility genes for the MetS. The strongest evidence for linkage for MetS phenotypes was observed on chromosome 2 (2q12.1–2q13) in the white sample and on chromosome 3 (3q26.1–3q29) in the Mexican‐American sample. In conclusion, the results suggest that several regions harbor MetS susceptibility genes and that heterogeneity may exist across groups.
Childhood Obesity: Genetic and Environmental Overlap With Normal‐range BMI
Authors: Haworth Claire M.A. , Plomin Robert , Carnell Susan , Wardle Jane
Published: April 2008

Objective: To understand the overlap between the etiology of obesity and normal variation in BMI in children.

Methods and Procedures: Height and weight data were available from a large UK representative sample of twins: 2,342 same‐sex pairs at 7 years and 3,526 same‐sex pairs at 10 years. The twin method and model‐fitting techniques were used to estimate genetic and environmental contributions to BMI. DeFries‐Fulker (DF) extremes analysis was used to investigate genetic and environmental influences on the mean difference between obese and normal‐weight children. Obesity was classified using the International Obesity Task Force (IOTF) criteria.

Results: At both ages, BMI and obesity were highly heritable (0.60–0.74) and only modestly influenced by shared environmental factors (0.12–0.22). Extremes analyses indicated that genetic and environmental influences on obesity are quantitatively and qualitatively similar to those operating across the range of BMI.

Discussion: Obesity is the extreme of the same genetic and environmental factors responsible for variation throughout the distribution of BMI. This finding implies that genes that influence obesity will also be associated with BMI in the normal range, and similar environmental influences will affect BMI in the clinical and normal range. Knowing that obesity is influenced by the same genetic and environmental factors that affect weight at all levels has implications for investigating the mechanisms for weight gain and developing interventions for weight control.
B2FH, the Cosmic Microwave Background and Cosmology
Authors: Burbidge G.
Published: April 2008

In this talk I shall start by describing how we set about and carried out the work that led to the publication of Burbidge et al. (1957, hereafter B2FH). I then shall try and relate this work and the circumstances that surrounded it to the larger problem of the origin and formation of the universe. Here it is necessary to look back at the way that ideas developed and how, in many situations, astronomers went astray. Of course this is a personal view, though I very strongly believe that if he were still here, it is the approach that Fred Hoyle would take.

I start by describing the problems originally encountered by Gamow and his associates in trying to decide where the helium was made. This leads me to a modern discussion of the origin of 2D, 3He, 4He and 7Li, originally described by B2FH as due to the x-process. While it is generally argued, following Gamow, Alpher, and Herman, that these isotopes were synthesised in a big bang I shall show that it is equally likely that these isotopes were made in active galactic nuclei, as was the cosmic microwave background (CMB), in a cyclic universe model. The key piece of observational evidence is that the amount of energy released in the conversion of hydrogen to helium in the universe is very close to the energy carried by the CMB, namely ∼4.5 × 10−13 erg cm−3.
Nuclear Physics of thesProcess
Authors: Dillmann I. , Pardo C. Domingo , Käppeler F. , Mengoni A. , Sonnabend K.
Published: April 2008

Starting from a sketch of thes-process concept formulated 50 years ago, the nuclear physics data fors-process calculations are briefly reviewed with emphasis on the status of neutron capture cross sections and beta decay rates. Accurate and comprehensive experimental data are mandatory as direct input fors-process calculations as well as for improving the complementary information from nuclear theory. The current challenges of the field are discussed in the light of new or optimized methods and state-of-the-art facilities, indicating the potential for accurate measurements and the possibility to study cross sections of radioactive isotopes. These opportunities will be considerably enriched by the enormous improvements provided by new facilities.
Adsorption and desorption of phosphate on Fe2O3: effect of fulvic acid and pH
Authors: Tongesayi Tsanangurayi , Byam Eric J. , Keysper Sarah B. , Crounce Michael J.
Published: April 2008

Environmental context. Adsorption controls the mobility of chemical species like nutrients in the soil and water environments and forms the basis for some of the methods of treating contaminated waters. Nutrients are introduced into environments where there are large quantities of humic substances adsorbed onto mineral oxides in the soil and sediments but no work has specifically focussed on the effect of adsorbed and free humic substances on the mobility of nutrients, and their adsorption and desorption mechanism on surface sites covered with adsorbed humic substances is still obscure. We believe that our findings and the proposed adsorption mechanism will help advance the technologies and methodologies for the removal of nutrients from wastewater.
Abstract. The main objective of the present study was to evaluate the effect of adsorbed fulvic acid (FA) on the mobility of phosphate (Pi) using Fe2O3 as the soil or sediment model. The study showed that adsorbed FA increased the amount of adsorbed Pi as a function of time and pH without it being remobilised. We envisage that Pi adsorbs onto both residual cationic surface sites and onto the adsorbed FA and that additional Pi loads onto the adsorption surface as FA–Pi precipitate. Addition of FA to Fe2O3 with adsorbed Pi resulted in the remobilisation of Pi as FA got adsorbed at pH 5.30 and 6.30. At pH 8.30, FA adsorbed without remobilising Pi. FA is a stronger base than the Pi species at pH 5.30 and 6.30 and should adsorb more strongly. At pH 8.30, FA is thought to bind onto adsorbed Pi. The experimental isotherm data could not be completely fitted into the Freundlich equation. This could be due to the complex adsorption mechanism.
A liquid-crystal model for friction
Authors: Cheng C. H. A. , Kellogg L. H. , Shkoller S. , Turcotte D. L.
Published: April 2008

Rate-and-state friction is an empirical approach to the behavior of a frictional surface. We use a nematic liquid crystal in a channel between two parallel planes to model frictional sliding. Nematic liquid crystals model a wide variety of physical phenomena in systems that rapidly switch between states; they are well studied and interesting examples of anisotropic non-Newtonian fluids, characterized by the orientational order of a director fieldd⃗(x⃗,t) interacting with the the velocity fieldu⃗(x⃗,t). To model frictional sliding, we introduce a nonlinear viscosity that changes as a function of the director field orientation; the specific choice of viscosity function determines the behavior of the system. In response to sliding of the top moving plane, the fluid undergoes a rapid increase in resistance followed by relaxation. Strain is localized within the channel. The director field plays a role analogous to the state variable in rate-and-state friction.
An Unsettling Integration: Immigrant Lives and Work in Palermo
Authors: Booth Sally S. , Cole Jeffrey E.
Published: April 2008

This article, based on ethnographic research, describes the precarious integration of Africans, Asians and others in the Sicilian city of Palermo. Most newcomers perform low-status jobs (particularly domestic work), have little access to state-sponsored services, lack political representation and suffer from derogatory stereotypes of non-whites and non-Westerners. In this context, immigrants express frustration at their marginality and they obtain jobs, housing, information and mutual aid from family and co-national networks that span the city, Italy itself and international borders.
Constitutive phosphorylation of MDC1 physically links the MRE11–RAD50–NBS1 complex to damaged chromatin
Authors: Spycher Christoph , Miller Edward S. , Townsend Kelly , Pavic Lucijana , Morrice Nicholas A. , Janscak Pavel , Stewart Grant S. , Stucki Manuel
Published: April 2008

The MRE11–RAD50–Nijmegen breakage syndrome 1 (NBS1 [MRN]) complex accumulates at sites of DNA double-strand breaks (DSBs) in microscopically discernible nuclear foci. Focus formation by the MRN complex is dependent on MDC1, a large nuclear protein that directly interacts with phosphorylated H2AX. In this study, we identified a region in MDC1 that is essential for the focal accumulation of the MRN complex at sites of DNA damage. This region contains multiple conserved acidic sequence motifs that are constitutively phosphorylated in vivo. We show that these motifs are efficiently phosphorylated by caseine kinase 2 (CK2) in vitro and directly interact with the N-terminal forkhead-associated domain of NBS1 in a phosphorylation-dependent manner. Mutation of these conserved motifs in MDC1 or depletion of CK2 by small interfering RNA disrupts the interaction between MDC1 and NBS1 and abrogates accumulation of the MRN complex at sites of DNA DSBs in vivo. Thus, our data reveal the mechanism by which MDC1 physically couples the MRN complex to damaged chromatin.
Glypican-1 Regulates Anaphase Promoting Complex/Cyclosome Substrates and Cell Cycle Progression in Endothelial Cells
Authors: Qiao Dianhua , Yang Xinhai , Meyer Kristy , Friedl Andreas
Published: April 2008

Glypican-1 (GPC1), a member of the mammalian glypican family of heparan sulfate proteoglycans, is highly expressed in glioma blood vessel endothelial cells (ECs). In this study, we investigated the role of GPC1 in EC replication by manipulating GPC1 expression in cultured mouse brain ECs. Moderate GPC1 overexpression stimulates EC growth, but proliferation is significantly suppressed when GPC1 expression is either knocked down or the molecule is highly overexpressed. Flow cytometric and biochemical analyses show that high or low expression of GPC1 causes cell cycle arrest at mitosis or the G2 phase of the cell cycle, accompanied by endoreduplication and consequently polyploidization. We further show that GPC1 inhibits the anaphase-promoting complex/cyclosome (APC/C)–mediated degradation of mitotic cyclins and securin. High levels of GPC1 induce metaphase arrest and centrosome overproduction, alterations that are mimicked by overexpression of cyclin B1 and cyclin A, respectively. These observations suggest that GPC1 regulates EC cell cycle progression at least partially by modulating APC/C-mediated degradation of mitotic cyclins and securin.
The Rho GDI Rdi1 Regulates Rho GTPases by Distinct Mechanisms
Authors: Tiedje Christopher , Sakwa Imme , Just Ursula , Höfken Thomas
Published: April 2008

The small guanosine triphosphate (GTP)-binding proteins of the Rho family are implicated in various cell functions, including establishment and maintenance of cell polarity. Activity of Rho guanosine triphosphatases (GTPases) is not only regulated by guanine nucleotide exchange factors and GTPase-activating proteins but also by guanine nucleotide dissociation inhibitors (GDIs). These proteins have the ability to extract Rho proteins from membranes and keep them in an inactive cytosolic complex. Here, we show that Rdi1, the sole Rho GDI of the yeast Saccharomyces cerevisiae, contributes to pseudohyphal growth and mitotic exit. Rdi1 interacts only with Cdc42, Rho1, and Rho4, and it regulates these Rho GTPases by distinct mechanisms. Binding between Rdi1 and Cdc42 as well as Rho1 is modulated by the Cdc42 effector and p21-activated kinase Cla4. After membrane extraction mediated by Rdi1, Rho4 is degraded by a novel mechanism, which includes the glycogen synthase kinase 3β homologue Ygk3, vacuolar proteases, and the proteasome. Together, these results indicate that Rdi1 uses distinct modes of regulation for different Rho GTPases.
IDMap: facilitating the detection of potential leads with therapeutic targets
Authors: Ha Soyang , Seo Young-Ju , Kwon Min-Seok , Chang Byung-Ha , Han Cheol-Kyu , Yoon Jeong-Hyeok
Published: April 2008

Summary: Pharmaceutical industry has been striving to reduce the costs of drug development and increase productivity. Among the many different attempts, drug repositioning (retargeting existing drugs) comes into the spotlight because of its financial efficiency. We introduce IDMap which predicts novel relationships between targets and chemicals and thus is capable of repositioning the marketed drugs by using text mining and chemical structure information. Also capable of mapping commercial chemicals to possible drug targets and vice versa, IDMap creates convenient environments for identifying the potential lead and its targets, especially in the field of drug repositioning.

Availability: IDMap executable and its user manual including color images are freely available to non-commercial users at http://www.equispharm.com/idmap

Contact:  idmap@equispharm.com
Part Task and Variable Priority Training in First-year Anesthesia Resident Education
Authors: Johnson Ken B. , Syroid Noah D. , Drews Frank A. , Ogden L Lazarre , Strayer David L. , Pace Nathan L. , Tyler Diane L. , White Julia L. , Westenskow Dwayne R.
Published: April 2008

Background

Part task training (PTT) focuses on dividing complex tasks into components followed by intensive concentrated training on individual components. Variable priority training (VPT) focuses on optimal distribution of attention when performing multiple tasks simultaneously with the goal of flexible allocation of attention. This study explored how principles of PTT and VPT adapted to anesthesia training would improve first-year anesthesiology residents' management of simulated adverse airway and respiratory events. The authors hypothesized that participants with PTT and VPT would perform better than those with standard training.

Methods

Twenty-two first-year anesthesia residents were randomly divided into two groups and trained over 12 months. The control group received standard didactic and simulation-based training. The experimental group received similar training but with emphasis on PTT and VPT techniques. Participant ability to manage seven adverse airway and respiratory events were assessed before and after the training period. Performance was measured by the number of correct tasks, making a correct diagnosis, assessment of perceived workload, and an assessment of scenario comprehension.

Results

Participants in both groups exhibited significant improvement in all metrics after a year of training. Participants in the experimental group were able to complete more tasks and answered more comprehension questions correctly. There was no difference in perceived workload or the number of correct diagnoses between groups.

Conclusion

This study in part confirmed the study hypotheses. The results suggest that VPT and PTT are promising adjuncts to didactic and simulation-based training for management of adverse airway and respiratory events.
Sevoflurane Concentrations Required to Block Autonomic Hyperreflexia during Transurethral Litholapaxy in Patients with Complete Spinal Cord Injury
Authors: Yoo Kyung Y. , Jeong Cheol W. , Kim Seok J. , Chung Sung T. , Bae Hong B. , Oh Kyung J. , Lee JongUn
Published: April 2008

Background

Autonomic hyperreflexia (AHR) is a potentially life-threatening hypertensive condition that occurs in patients with high spinal cord injury (SCI). The current study was aimed to determine sevoflurane concentrations that block AHR in SCI patients.

Methods

The study involved 28 patients with chronic, complete SCI scheduled to undergo transurethral litholapaxy during general anesthesia. Nine patients without SCI served as controls post hoc. Anesthesia was induced with thiopental, and sevoflurane concentrations in 50% nitrous oxide were adjusted to maintain a Bispectral Index of 40-50. When a patient developed AHR during bladder distension, the target sevoflurane concentration was maintained for at least 10 min, and then the procedure was resumed. Systolic blood pressure, heart rate, and Bispectral Index as well as plasma concentrations of catecholamines and arginine vasopressin were measured before and during the bladder distension. Each target concentration was determined by the up-and-down method based on changes (15% increase or more) of systolic blood pressure in response to bladder distension.

Results

In SCI, systolic pressure increased by 67 +/- 33 mmHg, whereas heart rate decreased by 13 +/- 8 beats/min during the first trial (P < 0.01). The hypertensive event was associated with increases of norepinephrine concentrations, but not of epinephrine or vasopressin concentrations. Systolic pressure, heart rate, and norepinephrine concentrations did not change significantly in the control patients. The end-tidal concentrations of sevoflurane to prevent AHR were EC50 of 3.12% and EC95 of 3.83%.

Conclusion

The EC95 for sevoflurane in 50% nitrous oxide to block AHR during transurethral litholapaxy in patients with SCI was 3.83%.
Hypertonic Resuscitation Improves Neuronal and Behavioral Outcomes after Traumatic Brain Injury plus Hemorrhage
Authors: Sell Stacy L. , Avila Marcela A. , Yu Guangxiang , Vergara Leoncio , Prough Donald S. , Grady James J. , DeWitt Douglas S.
Published: April 2008

Background

: Resuscitation with hypertonic saline or hypertonic saline plus l-arginine acutely improves cerebral blood flow after traumatic brain injury (TBI) followed by hemorrhagic hypotension. The authors investigated whether hypertonic saline or hypertonic l-arginine would improve long-term neuronal survival and behavioral outcomes 15 days after TBI and hemorrhagic hypotension.

Methods

: Mean arterial pressure, arterial blood gases, pH, plasma glucose, hematocrit, and hemoglobin were measured in male Sprague-Dawley rats before and after moderate (2.0 atm) fluid percussion TBI. Rats were assigned to one of six groups: (1) sham TBI, (2) hemorrhage only, (3) TBI only, (4) TBI plus hemorrhage and resuscitation with 0.9% saline, (5) TBI plus hemorrhage and resuscitation with hypertonic saline (7.5%), or (6) TBI plus hemorrhage and resuscitation with l-arginine (100 mg/kg) in hypertonic saline. On postinjury days 1-5, vestibulomotor function was assessed using beam balance and beam walking tasks. On postinjury days 11-15, spatial memory function was assessed using the Morris water maze. After behavioral testing, neuronal counting was performed bilaterally on specific hippocampal regions.

Results

: Groups receiving hypertonic saline (P < 0.05, day 15 vs. day 11) or hypertonic l-arginine (P < 0.05, days 13-15 vs. day 11) showed improved performance over time on the Morris water maze, as well as significantly improved neuronal survival in the contralateral hippocampus (P < 0.05, hypertonic saline or hypertonic l-arginine vs. normal saline) compared with untreated TBI or normal saline-treated TBI plus hemorrhage groups.

Conclusions

: Hypertonic saline and hypertonic l-arginine were both effective at promoting long-term neuronal survival and behavioral recovery. The slightly earlier improvement in Morris water maze performance in the hypertonic l-arginine group warrants further studies to determine whether higher doses of l-arginine provide additional improvement. This study supports the therapeutic benefits of hypertonic resuscitation after TBI plus hemorrhagic hypotension.
Effect of Disrupting N -Methyl-d-aspartate Receptor–Postsynaptic Density Protein-95 Interactions on the Threshold for Halothane Anesthesia in Mice
Authors: Tao Feng , Johns Roger A.
Published: April 2008

Background

The authors' previous studies have shown that clinically relevant concentrations of inhalational anesthetics dose-dependently and specifically inhibit the PSD-95, Dlg, and ZO-1 (PDZ) domain-mediated protein interactions between postsynaptic density protein 95 (PSD-95) and N-methyl-d-aspartate receptors, and that the knockdown of spinal PSD-95 by intrathecal injection of PSD-95 antisense oligodeoxynucleotide significantly reduces the minimum alveolar anesthetic concentration for isoflurane in rats.

Methods

The authors constructed a fusion peptide, Tat-PSD-95 PDZ2, comprising the second PDZ domain of PSD-95, which can specifically disrupt PSD-95 PDZ2-mediated protein interactions by binding to its interaction partner. By intraperitoneal injection of this fusion peptide into mice, the authors investigated the effect of disrupting the PSD-95 PDZ2-mediated protein interactions on the threshold for halothane anesthesia.

Results

Systemically injected fusion peptide Tat-PSD-95 PDZ2 was delivered into the central nervous system, disrupted the protein-protein interactions between N-methyl-d-aspartate receptor NR2 subunits and PSD-95, and significantly reduced the minimum alveolar anesthetic concentration and righting reflex EC50 for halothane.

Conclusions

By disrupting PSD-95 PDZ2 domain-mediated protein interactions, intraperitoneal injection of cell-permeant fusion peptide Tat-PSD-95 PDZ2 dose-dependently reduces the threshold for halothane anesthesia. These results suggest that PDZ domain-mediated protein interactions at synapses in the central nervous system might play an important role in the molecular mechanisms of halothane anesthesia.
STOP Questionnaire
Authors: Chung Frances , Yegneswaran Balaji , Liao Pu , Chung Sharon A. , Vairavanathan Santhira , Islam Sazzadul , Khajehdehi Ali , Shapiro Colin M.
Published: April 2008

Background

Obstructive sleep apnea (OSA) is a major risk factor for perioperative adverse events. However, no screening tool for OSA has been validated in surgical patients. This study was conducted to develop and validate a concise and easy-to-use questionnaire for OSA screening in surgical patients.

Methods

After hospital ethics approval, preoperative patients aged 18 yr or older and without previously diagnosed OSA were recruited. After a factor analysis, reliability check, and pilot study; four yes/no questions were used to develop this screening tool. The four questions were respectively related to snoring, tiredness during daytime, observed apnea, and high blood pressure (STOP). For validation, the score from the STOP questionnaire was evaluated versus the apnea-hypopnea index from monitored polysomnography.

Results

The STOP questionnaire was given to 2,467 patients, 27.5% classified as being at high risk of OSA. Two hundred eleven patients underwent polysomnography, 34 for the pilot test and 177 for validation. In the validation group, the apnea-hypopnea index was 20 +/- 6. The sensitivities of the STOP questionnaire with apnea-hypopnea index greater than 5, greater than 15, and greater than 30 as cutoffs were 65.6, 74.3, and 79.5%, respectively. When incorporating body mass index, age, neck circumference, and gender into the STOP questionnaire, sensitivities were increased to 83.6, 92.9, and 100% with the same apnea-hypopnea index cutoffs.

Conclusions

The STOP questionnaire is a concise and easy-to-use screening tool for OSA. It has been developed and validated in surgical patients at preoperative clinics. Combined with body mass index, age, neck size, and gender, it had a high sensitivity, especially for patients with moderate to severe OSA.