bluuebunny/crossref_metadata_2025 huggingface dataset:
The thymic theme of acetylcholinesterase splice variants in myasthenia gravis
Authors: Gilboa-Geffen Adi , Lacoste Paul P. , Soreq Lilach , Cizeron-Clairac Geraldine , Le Panse Rozen , Truffault Frederique , Shaked Iftach , Soreq Hermona , Berrih-Aknin Sonia
Published: February 2007

Cholinergic signaling and acetylcholinesterase (AChE) influence immune response and inflammation. Autoimmune myasthenia gravis (MG) is mediated by antibodies to the acetylcholine receptor and current therapy is based on anti-AChE drugs. MG is associated with thymic hyperplasia, showing signs of inflammation. The objectives of this study were to analyze the involvement of AChE variants in thymic hyperplasia. We found lower hydrolytic activities in the MG thymus compared with adult controls, accompanied by translocation of AChE-R from the cytoplasm to the membrane and increased expression of the signaling protein kinase PKC-βII. To explore possible causal association of AChE-R changes with thymic composition and function, we used an AChE-R transgenic model and showed smaller thymic medulla compared with strain-matched controls, indicating that AChE-R overexpression interferes with thymic differentiation mechanisms. Interestingly, AChE-R transgenic mice showed increased numbers of CD4+CD8+ cells that were considerably more resistant in vitro to apoptosis than normal thymocytes, suggesting possibly altered positive selection. We further analyzed microarray data of MG thymic hyperplasia compared with healthy controls and found continuous and discrete changes in AChE-annotated GO categories. Together, these findings show that modified AChE gene expression and properties are causally involved in thymic function and development.
Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse eosinophils
Authors: Zhang Mai , Angata Takashi , Cho Jae Youn , Miller Marina , Broide David H. , Varki Ajit
Published: February 2007

CD33-related Siglecs (CD33rSiglecs) are a family of sialic acid–recognizing lectins on immune cells whose biologic functions are unknown. We studied in vivo functions of Siglec-F, the CD33rSiglec expressed on mouse eosinophils, which are prominent in allergic processes. Induction of allergic lung inflammation in mice caused up-regulation of Siglec-F on blood and bone marrow eosinophils, accompanied by newly induced expression on some CD4+ cells, as well as quantitative up-regulation of endogenous Siglec-F ligands in the lung tissue and airways. Taken together with the tyrosine-based inhibitory motif in the cytosolic tail of Siglec-F, the data suggested a negative feedback loop, controlling allergic responses of eosinophils and helper T cells, via Siglec-F and Siglec-F ligands. To pursue this hypothesis, we created Siglec-F–null mice. Allergen-challenged null mice showed increased lung eosinophil infiltration, enhanced bone marrow and blood eosinophilia, delayed resolution of lung eosinophilia, and reduced peribronchial-cell apoptosis. Anti–Siglec-F antibody cross-linking also enhanced eosinophil apoptosis in vitro. These data support the proposed negative feedback role for Siglec-F, represent the first in vivo demonstration of biologic functions for any CD33rSiglec, and predict a role for human Siglec-8 (the isofunctional paralog of mouse Siglec-F) in regulating the pathogenesis of human eosinophil-mediated disorders.
Human bone marrow mesenchymal stromal cells express the neural ganglioside GD2: a novel surface marker for the identification of MSCs
Authors: Martinez Caridad , Hofmann Ted J. , Marino Roberta , Dominici Massimo , Horwitz Edwin M.
Published: February 2007

Mesenchymal stromal cells (MSCs) have enormous potential for the regeneration of bone, cartilage, and other tissues derived from primitive mesoderm. Despite extensive research, there is still no single marker that reliably identifies MSCs within the bone marrow. Using immunocytochemistry and flow cytometry, we demonstrate here that the neural ganglioside GD2 is expressed by MSCs either newly isolated from bone marrow or expanded in tissue culture; this finding was supported by reverse transcriptase–polymerase chain reaction (RT-PCR) analysis showing expression of the mRNA for GD2 synthase, an essential enzyme for GD2 biosynthesis. GD2 was also expressed on MSCs isolated from adipose tissue, but not on foreskin fibroblasts. Importantly, MSCs were the only cells within normal marrow that expressed this marker. Thus, GD2 appears to be the first reported single surface marker that uniquely distinguishes MSCs from other marrow elements. GD2 may prove valuable to study MSC biology and for the preparation of MSCs for clinical applications.
Computed Tomography Coronary Angiography for Rapid Disposition of Low‐risk Emergency Department Patients with Chest Pain Syndromes
Authors: Hollander Judd E. , Litt Harold I. , Chase Maureen , Brown Aaron M. , Kim Woojin , Baxt William G.
Published: February 2007

Background

Patients with recent normal cardiac catheterization are at low risk for complications of ischemic chest pain. Computed tomography (CT) coronary angiography has high correlation with cardiac catheterization for detection of coronary stenosis. Therefore, the investigators' emergency department (ED) incorporated CT coronary angiography into the evaluation of low‐risk patients with chest pain.

Objectives

To report on the 30‐day cardiovascular event rates of the first 54 patients evaluated by this strategy.

Methods

Low‐risk chest pain patients (Thrombolysis In Myocardial Infarction [TIMI] score of 2 or less) without acute ischemia on an electrocardiogram had CT coronary angiography performed in the ED. If the CT coronary angiography was negative, the patient was discharged home. The main outcomes were death and myocardial infarction within 30 days of ED discharge, as determined by telephone follow up and record review. Data are presented as percentage frequency of occurrence with 95% confidence intervals (CIs).

Results

Of the 54 patients evaluated, after CT coronary angiography, 46 patients (85%) were immediately released from the ED, and none had cardiovascular complications within 30 days. Eight patients were admitted after CT coronary angiography: one had >70% stenosis, five patients had 50%–69% stenosis, and two had 0–49% stenosis. Three patients had further noninvasive testing; one had reversible ischemia, and catheterization confirmed the results of CT coronary angiography. All patients were followed for 30 days, and none (0; 95% CI = 0 to 6.6%) had an adverse event during index hospitalization or at 30‐day follow up.

Conclusions

When used in the clinical setting for the evaluation of ED patients with low‐risk chest pain, CT coronary angiography may safely allow rapid discharge of patients with negative studies. Further study to conclusively determine the safety and cost effectiveness of this approach is warranted.
Sexual dimorphism of extensor carpi radialis muscle size, isometric force, relaxation rate and stamina during the breeding season of the frogRana temporariaLinnaeus 1758
Authors: Navas Carlos A. , James Rob S.
Published: February 2007

Mating success of individual male frogs within explosive breeding species can depend on their ability to compete for a mate and to hold onto that mate during amplexus. Such importance of amplexus has resulted in the evolution of sexual dimorphism in the morphology and contractile characteristics of the anuran forelimb muscles used during amplexus. The aims of our study were to use an explosive breeding frog (Rana temporaria) during the breeding season to compare extensor carpi radialis (ECR) muscle length, mass, isometric activation times, relaxation times, absolute force, relative force (stress)and fatigue between male and female frogs. We found that ECR muscle mass and length were greater (tenfold and 1.4-fold, respectively), absolute tetanic muscle force and relative tetanic force (stress) were greater (16-fold and 2.2-fold, respectively) and relaxation times were slower in males than in females. Male ECR muscles incompletely relaxed during fatigue tests and showed less fatigue than female muscles. These sex differences are likely to be beneficial to the male frogs in allowing them to produce relatively high absolute muscle forces for prolonged periods of time to hold onto their mate during amplexus.
Acquiring, retaining and integrating memories of the outbound distance in the Australian desert ant Melophorus bagoti
Authors: Narendra Ajay , Cheng Ken , Wehner Rüdiger
Published: February 2007

Estimation of distance travelled (odometry) forms a vital part of navigation for solitarily foraging ants. In this study we investigated the properties of odometric memory in the Australian desert ant Melophorus bagoti. Ants were trained to travel in linear channels to a feeder placed at 6 m or 12 m from the nest. We determined if the ability to estimate distances accurately increased with experience. We also determined the delay at which the odometric memory started to decay at both these distances. Ants with six trials of experience did not get better at estimating distances and the odometric memory decayed after a 24 h delay. We then determined if ants integrated their latest odometric memory with their previous memories. We did this by training two groups of ants for five trials, one group to 6 m and another to 12 m, and then halving or doubling the outbound distance on their sixth trip, respectively. The ant's estimate was noted when the ants were released either immediately or after a 24 h delay. Ants always estimated their last outbound distance when released immediately. However, they switched to route-based navigation rather than estimating distances after a 24 h delay (at which time their odometric memory would have decayed).
Assessing the Impact of a School Subsidy Program in Mexico: Using a Social Experiment to Validate a Dynamic Behavioral Model of Child Schooling and Fertility
Authors: Todd Petra E , Wolpin Kenneth I
Published: February 2007

This paper uses data from a randomized social experiment in Mexico to estimate and validate a dynamic behavioral model of parental decisions about fertility and child schooling, to evaluate the effects of the PROGRESA school subsidy program, and to perform a variety of counterfactual experiments of policy alternatives. Our method of validation estimates the model without using post-program data and then compares the model's predictions about program impacts to the experimental impact estimates. The results show that the model's predicted program impacts track the experimental results. Our analysis of counterfactual policies reveals an alternative subsidy schedule that would induce a greater impact on average school attainment at similar cost to the existing program.
Storable Good Monopoly: The Role of Commitment
Authors: Dudine Paolo , Hendel Igal , Lizzeri Alessandro
Published: February 2007

We study dynamic monopoly pricing of storable goods in an environment where demand changes over time. The literature on durables has focused on incentives to delay purchases. Our analysis focuses on a different intertemporal demand incentive. The key force on the consumer side is advance purchases or stockpiling. In the case of storable goods, the stockpiling motive has recently been documented empirically. We show that, in this environment, if the monopolist cannot commit, then prices are higher in all periods, and social welfare is lower, than in the case in which the monopolist can commit. This is in contrast with the analysis in the literature on the Coase conjecture.
A New Method of Estimating Risk Aversion
Authors: Chetty Raj
Published: February 2007

I show existing evidence on labor supply behavior places an upper bound on risk aversion in the expected utility model. I derive a formula for the coefficient of relative risk aversion (γ) in terms of the ratio of the income elasticity of labor supply to wage elasticity and degree of complementarity between consumption and labor. I bound the degree of complementarity using data on consumption choices when labor supply varies across states. Using labor supply elasticity estimates, I find a mean estimate of [Formula: see text], then show generating γ > 2 requires that wage increases cause sharper labor supply reductions.
Economics and the Biologists: A Review of Geerat J. Vermeij's Nature: An Economic History
Authors: Mokyr Joel
Published: February 2007

This essay reviews and criticizes Vermeij's Nature: An Economic History and places it in the context of evolutionary economics. Vermeij presents a natural history written in what he considers economic terms and argues that biologists should know more about economics. While the exchanges between economics and biology can sometimes be hazardous and misleading, quite a bit could be learned by economists from reading this book.
Regulating Infrastructure: The Impact on Risk and Investment
Authors: Guthrie Graeme
Published: February 2007

The last thirty years have witnessed a fundamental change in the regulation of infrastructure industries. Whereas firms were subject to rate of return regulation and protected from entry in the past, they now face various forms of incentive regulation, competition is actively promoted by many regulators, and both regulators and the firms they regulate must often confront rapid technological progress. This paper surveys the literature on the investment implications of different regulatory schemes, highlighting the relevance of modern investment theory, which puts risk and intertemporal issues, such as the irreversibility of much infrastructure investment, center stage. It discusses the impact on regulated monopolists' investment behavior of key regulatory characteristics, namely the price flexibility allowed by the regulator, the length of the regulatory cycle, and the costs the regulator will allow the firm to recover at future regulatory hearings. It also considers the impact of competition, especially the situation where a vertically integrated firm has its operation of a bottleneck asset regulated, on investment by regulated firms and their competitors.
Domestic dogs and human health: An overview
Authors: Wells Deborah L.
Published: February 2007

Purpose. The domestic dog is one of the most commonly owned, and widely utilized, animals in today's society. This paper provides an overview of research that has explored the relationship between the domestic dog and human well‐being.

Methods. The article initially concentrates on the value of dogs for physical health in humans, exploring the evidence that this species can prevent us from becoming ill, facilitate our recovery from ill‐health, and even serve as an early warning system for certain types of underlying ailment including cancer, oncoming seizures and hypoglycaemia. The paper then examines the relationship between dogs and psychological health in humans, exploring the ability of this species to aid the disabled and serve as a therapist to those in institutional settings such as hospitals, residential homes and prisons. Weaknesses in the existing research in this area are highlighted throughout the article.

Conclusion. Taken together, the studies reviewed suggest that dogs can have prophylactic and therapeutic value for people.
Physical and psychological sequelae of critical illness
Authors: Sukantarat Kannika , Greer Steven , Brett Stephen , Williamson Robin
Published: February 2007

Objectives. To measure levels of anxiety, depression and post‐traumatic stress among survivors of a critical illness and to relate these symptoms to general health parameters.

Design. A prospective study of patients who had spent a minimum 3 days (median 9 days) in a general intensive care unit (ICU). Of these patients, 51 were interviewed 3 months after discharge and 45 of them were reviewed at 9 months.

Methods. General health was assessed by a physical symptom score, the EuroQol ‘thermometer’ and the Short Form 36 (SF‐36) questionnaire. Physical and mental component summary measures (PCS, MCS) were calculated from the SF‐36 data. Psychological health was assessed using both the Hospital Anxiety and Depression Scale and the Impact of Events Scale.

Results. At both 3 and 9 months after ICU discharge 24% of patients qualified as a ‘case’ of anxiety, while similar figures were seen for intrusion (24 and 20%). The incidence of depression (35 and 47%) and avoidance (36 and 38%) was higher on each occasion. Four of the eight SF‐36 domains improved with time, as did PCS (from 29.0 to 35.4), but there was no significant difference in physical symptom score, EuroQol value or MCS. Strong correlations were seen between the physical and psychological parameters at each time point.

Conclusion. A substantial proportion of patients who survive a critical illness show evidence of anxiety and depression up to 9 months later, and most of them also have symptoms indicative of post‐traumatic stress. Delayed physical recovery may contribute to this psychological morbidity. ICU follow‐up clinics should be able to detect patients suitable for psychological intervention.
Predicting stress in pre‐registration nursing students
Authors: Pryjmachuk Steven , Richards David A.
Published: February 2007

Objectives. To determine which variables from a pool of potential predictors predict General Health Questionnaire ‘caseness’ in pre‐registration nursing students.

Design. Cross‐sectional survey, utilizing self‐report measures of sources of stress, stress (psychological distress) and coping, together with pertinent demographic measures such as sex, ethnicity, educational programme and nursing specialty being pursued, and age, social class and highest qualifications on entry to the programme.

Methods. Questionnaire packs were distributed to all pre‐registration nursing students (N = 1,362) in a large English university. Completed packs were coded, entered into statistical software and subjected to a series of logistic regression analyses.

Results. Of the questionnaire packs 1,005 (74%) were returned, of which up to 973 were available for the regression analyses undertaken. Four logistic regression models were considered and, on the principle of parsimony, a single model was chosen for discussion. This model suggested that the key predictors of caseness in the population studied were self‐report of pressure, whether or not respondents had children (specifically, whether these children were pre‐school or school‐age), scores on a ‘personal problems’ scale and the type of coping employed. The overall caseness rate among the population was around one‐third.

Conclusion. Since self‐report and personal, rather than academic, concerns predict stress, personal teachers need to play a key role in supporting students through ‘active listening’, especially when students self‐report high levels of stress and where personal/social problems are evident. The work‐life balance of students, especially those with child‐care responsibilities, should be a central tenet in curriculum design in nurse education (and, indeed, the education of other professional and occupational groups). There may be some benefit in offering stress management (coping skills) training to nursing students and, indeed, students of other disciplines.
Natural products with taxol-like anti-tumor activity: Synthetic approaches to eleutherobin and dictyostatin
Authors: Gennari Cesare , Castoldi Damiano , Sharon Ofer
Published: February 2007

Eleutherobin and dictyostatin are antimitotic compounds which exert their cytotoxic activity by a taxol-like mode of action, i.e., hypernucleating tubulin assembly and interfering with the dynamic instability of the cytoskeleton during mitosis. A formal total synthesis of eleutherobin was accomplished by accessing a key intermediate reported by Danishefsky and coworkers in their 1998 synthesis of the natural product. The key step of our strategy, used for obtaining the [8.4.0] fused bicyclic ring system, is a ring-closing metathesis (RCM) reaction of a densely functionalized diene under forcing conditions, using Grubbs' second-generation catalyst. Synthetic approaches to dictyostatin are also described, and in particular the preparation of the C15-C23 fragment of the macrolide, containing 5 of its 11 stereocenters.
Functional phosphorus-based π-conjugated systems: Structural diversity without multistep synthesis
Authors: Hissler Muriel , Lescop Christophe , Réau Régis
Published: February 2007

The synthesis and properties of linear π-conjugated systems incorporating phosphole rings are described. Their supramolecular organization in the solid state can be controlled either by chemical modifications or coordination to transition metals of the phosphorus atom. Furthermore, chemical transformations of the phosphole ring allow organizing these P-chromophores in 3D assemblies exhibiting σ-π conjugation or in organometallic ferrocene-like derivatives. Phosphole-pyridine-containing π-conjugated chromophores act as P,N-chelates toward transition-metal ions, giving rise to mono- and di-nuclear complexes. The specific properties of these complexes make them valuable materials for organic light-emitting diodes (OLEDs) and interesting building blocks for the tailoring of π-conjugated systems.
Effects of α-Tocopherol and Mixed Tocopherol Supplementation on Markers of Oxidative Stress and Inflammation in Type 2 Diabetes
Authors: Wu Jason HY , Ward Natalie C , Indrawan Adeline P , Almeida Coral-Ann , Hodgson Jonathan M , Proudfoot Julie M , Puddey Ian B , Croft Kevin D
Published: February 2007

Background: Vitamin E isomers may protect against atherosclerosis. The aim of this study was to compare the effects of supplementation with either α-tocopherol (αT) or mixed tocopherols rich in γ-tocopherol (γT) on markers of oxidative stress and inflammation in patients with type 2 diabetes.

Methods: In a double-blind, placebo-controlled trial, 55 patients with type 2 diabetes were randomly assigned to receive (500 mg/day) (a) αT, (b) mixed tocopherols, or (c) placebo for 6 weeks. Cellular tocopherols, plasma and urine F2-isoprostanes, erythrocyte antioxidant enzyme activities, plasma inflammatory markers, and ex vivo assessment of eicosanoid synthesis were analyzed pre- and postsupplementation.

Results: Neutrophil αT and γT increased (both P <0.001) with mixed tocopherol supplementation, whereas αT (P <0.001) increased and γT decreased (P <0.005) after αT supplementation. Both αT and mixed tocopherol supplementation resulted in reduced plasma F2-isoprostanes (P <0.001 and P = 0.001, respectively) but did not affect 24-h urinary F2-isoprostanes or erythrocyte antioxidant enzyme activities. Neither αT nor mixed tocopherol supplementation affected plasma C-reactive protein, interleukin 6, tumor necrosis factor-α, or monocyte chemoattractant protein-1. Stimulated neutrophil leukotriene B4 production decreased significantly in the mixed tocopherol group (P = 0.02) but not in the αT group (P = 0.15).

Conclusions: The ability of tocopherols to reduce systemic oxidative stress suggests potential benefits of vitamin E supplementation in patients with type 2 diabetes. In populations with well-controlled type 2 diabetes, supplementation with either αT or mixed tocopherols rich in γT is unlikely to confer further benefits in reducing inflammation.
Virtual Cities: Redefining the Urban Experience in the Physical and the Virtual at the Turn of the Millennium
Authors: Hales Peter Bacon
Published: February 2007

The end of the nineteenth century and the first decades of the twentieth brought Chicago to the front of the list of great urban centres across the globe. This rapid elevation was the result of a concordance of circumstances which themselves represented new forms of urban conceptualism.
Today we find ourselves in a position similar to that experienced by the denizens of Chicago at the turn of the century; on a global scale, we have found new technologies of representation at precisely the moment that significant new forms of urban space and urbanity are emerging. But to see
these as unconnected would be to miss the lessons of a century ago. New Internet technologies offer forms of representation that promise universal applicability but in fact reinflect information about the city in both blatant and subtle ways. Here and now, again, we find older systems of representation
still holding out against the promises of new technologies, even as the new technologies have begun to transform our systems of imagining urban space.
Literature America Power: The Professionalization of American Literature
Authors: Isernhagen Hartwig
Published: February 2007

In the discipline of American Literature (and perhaps to a lesser degree in the humanities in general) the last few decades have seen an ever more strongly developed feedback relation between definitions of professionalism and the discourses of the discipline(s). Terms such as creative
destruction embody a naturalizing view of cultural processes that validates the position of the professional in society and generates sets of uncritically affirmative ways of reading literary (and other) texts. In so far as both the central terms and the view of culture are axiomatically associated
with a hegemonic view of America that in its turn centralizes the notion of pre-emption of dissent, literature, the academy, and the critic, in this perspective, have to give up all pretensions to any type of adversarialism. A reorientation in terms of an adversarial definition of the intellectual
might open up new horizons and incidentally realign the two central terms in late twentieth-century criticism: politics and aesthetics. It might also reverse the Americanization of the globalized academy.
Would'st thou be in a dream: John Bunyan's The Pilgrim's Progress and Kurt Vonnegut's Slaughterhouse-Five
Authors: Hinchcliffe Richard
Published: February 2007

This article establishes intertextual connections between Kurt Vonnegut's Slaughterhouse-Five and John Bunyan's The Pilgrim's Progress and describes how the Puritan conversion narrative form and the pilgrim narrative play a major part in Vonnegut's canonical anti-war novel.
The protagonist Billy Pilgrim is seen as a modern personification of the Protestant work ethic, a successful, wealthy and hardworking businessman. He blithely espouses white Anglo-Saxon Protestant attitudes but becomes an evangelist for his science-fiction fantasies, which appear constructed
from the religious materials around him and in his past. The narrative of Slaughterhouse-Five, like Tralfamadorian time, tries to destabilize the dominant Western master narrative typified by the linearity of The Pilgrim's Progress. If Dresden is seen as an inversion of Bunyan's
Celestial City then its destruction is an indictment of capitalist progress born from pilgrim and conversion narratives.
Two doctors and one cause: Len Crome and Reginald Saxton in the International Brigades
Authors: Preston Paul
Published: February 2007

One of the most impressive, lasting and least known features of the International Brigades was the contribution of their medical services. Impressive, because not all health professionals take their Hippocratic oath seriously, and the doctors and nurses of the International Brigades
not only made the same gestures of courage and solidarity as the other volunteers but also left behind them professional careers that were unforgiving of long absences. Lasting, because the contributions of the various Spanish and foreign doctors, from the Catalans Josep Trueta and Moiss Broggi,
the famous Canadian Norman Bethune, the New Zealander Douglas Jolly and the Englishmen Len Crome and Reggie Saxton, were of a colossal importance in the later development of traumatalogical medicine in both war and peacetime. Unknown, for the obvious reason that the tireless abnegation, behind
the lines, of ambulance drivers, nurses and doctors have attracted far less attention from journalists, writers and historians than the struggle of front-line combatants. In recent times, there has been a growth of interest in this aspect of the history of the International Brigades, and what
follows a study of two doctors whose work in Spain had a later impact during the Second World War aims to make a small contribution to that history. Although of widely differing origins, Crome from Russia, Saxton from imperial Britain, they were both typical of volunteers within the Brigades
medical services. Their similarities were even more typical their selfless dedication to the struggle against fascism and their later service in the Second World War. Like other doctors in the Spanish Civil War, Broggi, Trueta, Bethune, Jolly, both made medical advances that would be of considerable
use thereafter. This could have been the story of other doctors who were equally courageous, idealistic and professional in their service with the International Brigades. Nonetheless, these two men were both exemplary and representative of so many others. Their stories go some way to giving
some notion of the dedication and sacrifice that characterized the men and women of the International Brigades medical services.
Las desapariciones infantiles durante el franquismo y sus consecuencias
Authors: Vinyes Ricardo
Published: February 2007

This paper examines the magnitude and consequences of children's placements in institutions and disappearances during the dictatorship of Francisco Franco. The article analyses the nature of these disappearances, arguing that their origins were to be found in the regeneration of the
Spanish race as defined by Antonio Vallejo Ngera. The article explores the different strategies implemented by the Francoist state and the Falange in order to ensure the annihilation of dissidence in the immediate postwar period, and to consolidate the dominance of the State the victors by
segregating, institutionalising and re-educating the children of the vanquished of the Spanish Civil War.
The Critical Role of Locomotion Mechanics in Decoding Sensory Systems
Authors: Cowan Noah J. , Fortune Eric S.
Published: February 2007

How do neural systems process sensory information to control locomotion? The weakly electric knifefishEigenmannia, an ideal model for studying sensorimotor control, swims to stabilize the sensory image of a sinusoidally moving refuge. Tracking performance is best at stimulus frequencies less than ∼1 Hz. Kinematic analysis, which is widely used in the study of neural control of movement, predicts commensurately low-pass sensory processing for control. The inclusion of Newtonian mechanics in the analysis of the behavior, however, categorically shifts the prediction: this analysis predicts that sensory processing is high pass. The counterintuitive prediction that a low-pass behavior is controlled by a high-pass neural filter nevertheless matches previously reported but poorly understood high-pass filtering seen in electrosensory afferents and downstream neurons. Furthermore, a model incorporating the high-pass controller matches animal behavior, whereas the model with the low-pass controller does not and is unstable. Because locomotor mechanics are similar in a wide array of animals, these data suggest that such high-pass sensory filters may be a general mechanism used for task-level locomotion control. Furthermore, these data highlight the critical role of mechanical analyses in addition to widely used kinematic analyses in the study of neural control systems.
Prenatal Alcohol Exposure and Gender Differences in Childhood Mental Health Problems: A Longitudinal Population-Based Study
Authors: Sayal Kapil , Heron Jon , Golding Jean , Emond Alan
Published: February 2007

OBJECTIVES. High levels of alcohol use during pregnancy can lead to adverse physical and neurodevelopmental outcomes in children. It remains uncertain whether there is a safe level of drinking during pregnancy. In this study we investigate whether very low levels of alcohol consumption (<1 drink per week) are independently associated with childhood mental health problems (assessed at 3 time points between ages 4 and 8 years) and whether these effects are moderated by gender. We expected that only higher levels of alcohol consumption would be associated with later mental health problems and that any associations might be more readily detectable in boys.

METHODS. This prospective, population-based study used data from the Avon Longitudinal Study of Parents and Children. We investigated the relationship between self-reports of the amount and frequency of alcohol use in the first trimester and the presence of clinically significant mental health (behavioral and emotional) problems at 47 and 81 months (parental report: n = 9086 and 8046, respectively) and at 93 to 108 months (teacher report: n = 5648).

RESULTS. After controlling for a range of prenatal and postnatal factors, the consumption of <1 drink per week during the first trimester was independently associated with clinically significant mental health problems in girls at 47 months. This gender-specific association persisted at 81 months and was confirmed by later teacher ratings.

CONCLUSIONS. Very low levels of alcohol consumption during early pregnancy may have a negative and persistent effect on mental health outcomes. Given the lack of a clear dose-response relationship and unexpected gender effects, these findings should be considered preliminary and need additional investigation.
The Impact of Placement Stability on Behavioral Well-being for Children in Foster Care
Authors: Rubin David M. , O'Reilly Amanda L.R. , Luan Xianqun , Localio A. Russell
Published: February 2007

OBJECTIVE. The problems children have upon entering foster care can potentially explain prior research findings that frequent placement changes are associated with poor outcomes. This study sought to disentangle this cascading relationship in order to identify the independent impact of placement stability on behavioral outcomes downstream.

DESIGN/METHODS. Placement stability over the first 18 months in out-of-home care for 729 children from the National Survey of Child and Adolescent Well-being was categorized as early stability (stable placement within 45 days), late stability (stable placement beyond 45 days), or unstable (never achieving stability). Propensity scores predicting placement instability based on baseline attributes were divided into risk categories and added to a logistic regression model to examine the independent association between placement stability and behavioral well-being using the Child Behavior Checklist and temperament scores from the National Longitudinal Survey of Youth.

RESULTS. Half (52%) of the children achieved early stability, 19% achieved later stability, and 28% remained unstable. Early stabilizers were more likely to be young, have normal baseline behavior, have no prior history with child welfare, and have birth parents without mental health problems. After accounting for baseline attributes, stability remained an important predictor of well-being at 18 months. Unstable children were more likely to have behavior problems than children who achieved early stability across every level of risk for instability. Among low-risk children, the probability of behavioral problems among early stabilizers was 22%, compared to 36% among unstable children, showing a 63% increase in behavior problems due to instability alone.

CONCLUSIONS. Children in foster care experience placement instability unrelated to their baseline problems, and this instability has a significant impact on their behavioral well-being. This finding would support the development of interventions that promote placement stability as a means to improve outcomes among youth entering care.
Children's Mental Health and Family Functioning in Rhode Island
Authors: Kim Hyun (Hanna) K. , Viner-Brown Samara I. , Garcia Jorge
Published: February 2007

OBJECTIVES. Our objectives were to (a) estimate the prevalence of children's mental health problems, (b) assess family functioning, and (c) investigate the relationship between children's mental health and family functioning in Rhode Island.

METHODS. From the 2003 National Survey of Children's Health, Rhode Island data for children 6 to 17 years of age were used for the analyses (N = 1326). Two aspects of family functioning measures, parental stress and parental involvement, were constructed and were examined by children's mental health problems, as well as other child and family characteristics (child's age, gender, race/ethnicity, special needs, parent's education, income, employment, family structure, number of children, and mother's general and mental health). Bivariate analyses and multivariate logistic regression were used to investigate the relationship.

RESULTS. Among Rhode Island children, nearly 1 (19.0%) in 5 had mental health problems, 1 (15.6%) in 6 lived with a highly stressed parent, and one third (32.7%) had parents with low involvement. Bivariate analyses showed that high parental stress and low parental involvement were higher among parents of children with mental health problems than parents of children without those problems (33.2% vs 11.0% and 41.0% vs 30.3%, respectively). In multivariate logistic regression, parents of children with mental health problems had nearly 4 times the odds of high stress compared with parents of children without those problems. When children's mental health problems were severe, the odds of high parental stress were elevated. However, children's mental health was not associated with parental involvement.

CONCLUSIONS. Children's mental health was strongly associated with parental stress, but it was not associated with parental involvement. The findings indicate that when examining the mental health issues of children, parental mental health and stress must be considered.
Factors Associated With Not Having a Personal Health Care Provider for Children in Florida
Authors: Zeni Mary Beth , Sappenfield William , Thompson Dan , Chen Hailin
Published: February 2007

OBJECTIVE. National recommendations by the American Academy of Pediatrics and the National Association of Pediatric Nurse Practitioners promote that all children obtain quality primary care through a consistent medical provider who can better assess, diagnose, and monitor a child's health. The purpose of this article was to identify characteristics of children in Florida without a personal health care provider.

METHODS. Florida data (N = 2116) from the 2003 National Survey of Children's Health were analyzed by using bivariate and multivariate methods. The dependent, or outcome, variable was a personal health care provider, defined in the National Survey of Children's Health as a personal doctor or nurse.

RESULTS. In Florida, 20.1% of children (0–17 years of age) do not have a personal health care provider compared with 16.7% in the United States. Children at greatest risk are those without health insurance. Other significant risk factors include family poverty up to 100% of federal poverty level, poverty level 100% to 199%, poverty level unknown, poverty level 200% to 399%, children aged 5 to 12 years, children aged 13 to 17 years, and Hispanic ethnicity. All the factors in the Florida model were also significant in the national model.

CONCLUSIONS. Lack of a personal health care provider is driven by larger community issues of health insurance, socioeconomic status, and ethnicity, including race, on a national level. To achieve the goal of a personal health care provider for children, a multifaceted approach needs to be considered. Knowing which children are without a personal health care provider provides valuable information for state policy-makers, program planners, and evaluators.
Persistent Diastolic Flow Reversal in Abdominal Aortic Doppler-Flow Profiles Is Associated With an Increased Risk of Necrotizing Enterocolitis in Term Infants With Congenital Heart Disease
Authors: Carlo Waldemar F. , Kimball Thomas R. , Michelfelder Erik C. , Border William L.
Published: February 2007

OBJECTIVE. Diastolic runoff in the abdominal aorta, with subsequent circulatory mesenteric insufficiency, has been postulated as a cause of necrotizing enterocolitis in term infants with congenital heart disease. With this study we sought to determine whether Doppler-flow characteristics in the abdominal aorta can predict which infants are at specific risk, independent of gestational age and type of congenital heart disease.

PATIENTS AND METHODS. We conducted a case-control study of term infants with congenital heart disease and proven necrotizing enterocolitis (n = 18) compared with gestational age–matched and diagnosis-matched control subjects (n = 20). Abdominal aortic Doppler velocities, time intervals, and reversals were analyzed. Groups were compared, and independent risk factors for necrotizing enterocolitis were determined.

RESULTS. The groups were similar with regard to weight, pulse pressure, use of prostaglandins or inotropes, presence of a patent ductus arteriosus, and systolic function. However, 47% of the case subjects with necrotizing enterocolitis had persistent retrograde diastolic flow in the abdominal aorta compared with 15% of the control subjects. When adjusting for multiple risk factors, persistent diastolic flow reversal remained the only factor significantly associated with necrotizing enterocolitis.

CONCLUSION. Persistent diastolic flow reversal in the abdominal aortic Doppler profile is associated with an increased risk of necrotizing enterocolitis in term infants with congenital heart disease irrespective of gestational age or anatomic type of congenital heart disease.
Chill-cast in situ composites in the pseudo-ternary Mg–(Cu,Ni)–Y glass-forming system: Microstructure and compressive properties
Authors: Ma Han , Shi Ling-Ling , Xu Jian , Ma En
Published: February 2007

Starting with a bulk metallic glass-forming alloy Mg65Cu18Ni6Y11, we prepared in situ composites by increasing the Mg content in a series of alloys, Mgx(Cu0.51Ni0.17Y0.32)100−x (65 ≤ x ≤ 90), via copper mold casting of rods 4 mm in diameter. The fully glassy alloy at x = 65 showed a compressive fracture strength of 755 MPa but no observable macroscopic plasticity prior to failure. Metallic glass-based composites were formed when the Mg content was increased. For x > 80, the glassy phase no longer existed in the as-cast rods. In the composition range of 80 ≤ x ≤ 85, needle-shaped Mg solution with a 14H-type long period stacking (LPS) structure appeared as the primary phase in the as-cast microstructure. On further increase of the Mg content up to x = 90, the solidified primary phase became 2H-Mg, coexisting with the remaining eutectic structure. The best combination of mechanical properties was obtained for the alloy at x = 81.5, which showed a fracture strength of 665 MPa and a compressive plastic strain of 11.6%. The specific strength of this alloy was 2.8 × 105 N m kg−1, much higher than conventional cast magnesium alloys. The mechanical properties are discussed in light of the phase selection and microstructural features uncovered in microscopy examinations.
Mechanical behavior of a Zr-based bulk metallic glass and its composite at cryogenic temperatures
Authors: Fan Cang , Gao Y.F. , Li H.Q. , Choo H. , Liaw P.K. , Inoue A. , Liu C.T.
Published: February 2007

The mechanical behavior of Zr-Cu-Al bulk metallic glasses (BMGs) and in situ Ta-particle-containing composites (BMGCs) was investigated at 77 K. Their strengths increased significantly whereas the plastic strains remained at comparable levels, when compared to that at 298 K. The interaction between shear bands and particles shows that shear extension in particles has limited penetration, and shear bands build up around particles. Pair distribution functions (PDFs), which carried out at cryogenic and ambient temperatures on the as-cast Zr-Cu-Al bulk metallic glasses, were studied, and simulations with reverse Monte Carlo (RMC) were performed by combining icosahedral and cubic structures as the initial structures. Based on the studies of the pair distribution functions and the Reverse Monte Carlo simulations, the concept of free volume was defined—spaces between clusters with longer bond lengths of atom pairs; the structural model of BMGs was proposed—the strongly bonded clusters correlated with each other and separated by free volume. An attempt has been made to connect the relationship between amorphous structures and their mechanical properties.
Nanocrystalline coating enhanced ductility in a Zr-based bulk metallic glass
Authors: Li Hongqi , Li Li , Fan Cang , Choo Hahn , Liaw Peter K.
Published: February 2007

Compression tests were conducted on the as-cast Zr58Ni13.6Cu18Al10.4 metallic glass at room temperature. The effect of nanocrystalline Ni-15%Fe coating (mean grain size: ∼10 nm) on mechanical properties was investigated. The results demonstrate that the strength, elastic limit, Young’s modulus, and fracture geometry and morphology are not affected by this nanostructured coating. However, the compressive plastic strain increased noticeably when the specimens were coated with a layer of nanocrystal, which is attributed to the increased shear band density. The high shear band density is suggested to be due to the inhibition of shear band operation by nanocrystalline coating. The significance of this study is that a new strategy was developed to improve the ductility of bulk metallic glasses.
Indentation plasticity of amorphous and partially crystallized metallic glasses
Authors: Charleux L. , Gravier S. , Verdier M. , Fivel M. , Blandin J.J.
Published: February 2007

Plastic behavior at room temperature of amorphous, partially crystallized, and fully crystallized Zr41.25Ti13.75Cu12.5Ni10Be22.5 Vitreloy 1 samples was investigated using instrumented indentation. Residual imprints were imaged using atomic force microscopy (AFM). Young’s modulus and hardness were estimated using the contact area derived from AFM imaging. It has been shown that the postmortem area measurement is useful to take into account the pileup effect. Indentation experiments performed with a conical tip were associated with parametric two-dimensional axisymmetric finite element modeling using a pressure-sensitive yield criterion. A two-parameter reverse analysis algorithm was used to probe both yield stress and pressure angle. Results showed that the amorphous alloy exhibits a yield stress and pressure angle in good agreement with literature and compressive tests, and that crystallization affects the pressure angle.
Resonant vibration analysis for temperature dependence of elastic properties of bulk metallic glass
Authors: Bossuyt Sven , Giménez Sixto , Schroers Jan
Published: February 2007

The variation of a Zr57Nb5Cu15Ni13Al10 bulk metallic glass’s elastic constants with temperature and thermal history was investigated, using an impulse excitation technique for resonant vibration analysis. The Young’s modulus at 550 K is 78 GPa with a slope of −17 MPa/K in the glass as-produced and increases to 80 GPa with a slope of −26 MPa/K upon annealing. The modulus of the supercooled liquid at 700 K is 74 GPa with a slope of −90 MPa/K, whereas for the crystallized material E = 100 GPa with a slope of −15 MPa/K. These results are interpreted in terms of the vibrational and configurational contributions to the temperature dependence and compared with calorimetry data.
Pseudo-binary phase diagram for Zr-based in situ β phase composites
Authors: Lee S.Y. , Kim C.P. , Almer J.D. , Lienert U. , Ustundag E. , Johnson W.L.
Published: February 2007

The pseudo-binary (quasi-equilibrium) phase diagram for Zr-based bulk metallic glasses with crystalline in situ precipitates (β phase) has been constructed from high-temperature phase information and chemical composition analysis. The phase evolution was detected in situ by high-energy synchrotron x-ray diffraction followed by Rietveld analysis of the data for volume fraction estimation. The phase diagram delineates phase fields and allows the control of phase fractions. Combined with related previous work by the authors, this diagram offers a unique opportunity to control both the morphology and volume of the dendritic β phase precipitates to enhance the properties of the composites.