bluuebunny/crossref_metadata_2025 huggingface dataset:
Premature Graying, Balding, and Low Bone Mineral Density in Older Women and Men
Authors: Morton Deborah J. , Kritz-Silverstein Donna , Riley Donna J. , Barrett-Connor Elizabeth L. , Wingard Deborah L.
Published: April 2007

Objective: The authors report the association of balding or graying with BMD in older adults. Method: BMD was measured at the spine, hip, and total body in 1,207 participants. Of these, 508 women and 380 men responded to a 1986 survey about balding patterns; in 1994, all participants answered questions about graying. Results: Among men, 10.7% reported graying, and 51.1%, balding; 9.9% of women reported graying, and 9.5%, balding. Models were adjusted for age, body mass index, alcohol consumption, smoking, exercise, calcium supplements, diuretics, glucocorticoids, thyroid hormone, and estrogen. Conclusion: Graying was not significantly associated with BMD in either group. Balding men averaged 5% lower total body BMD ( p ≤ 0.05), and balding women had ~24% higher mean hip BMD (p ≤ 0.05). Graying and balding women reported a higher proportion of current estrogen use; balding women reported more use of glucocorticosteroids. Balding women using estrogen may explain the higher BMD.
How Managers Can Retain Qualified In-Home Caregivers in a Competitive Job Market
Authors: Froymovich Etelka
Published: April 2007

This article addresses how home health care managers can improve employee retention at their respective agencies. It begins by discussing the growing shortage of nurses, certified nursing assistants (CNAs), and home health aides and continues by identifying several key factors that can have a dramatic effect on an in-home caregiver's morale and job loyalty. The article provides the home health care manager with a number of steps that can be taken to manage these factors in such a way as to create a pleasant working experience for these employees, thus decreasing employee turnover.
Liquid composite moulding of fibre nanocomposites
Authors: Lekakou C. , Hearn A. , Murugesh A. K. , Le Page B.
Published: April 2007

Two liquid composite moulding techniques have been investigated in this study, resin transfer moulding (RTM) and resin infusion under flexible tool (RIFT) for the processing of glass fabric–epoxy laminates with 5% nanoaggregates of silica nanoparticles in the epoxy matrix. It has been found that the high fibre fraction reinforcement ( Vf=0·50) filters the silica nanoaggregates resulting in stopping the in plane resin infiltration in RTM right at the beginning of the filling stage. Laminates of lower fibre fraction ( Vf=0·40) were produced successfully by RIFT. Dynamic mechanical thermal analysis (DMTA) and three point bend tests showed that fibre–silica–epoxy composites, processed by RIFT, had higher elastic shear modulus and interlaminar shear strength than conventional fibre–epoxy composites manufactured by the same RIFT process.
Kinetics of spherodisation, coalescence and coarsening of lead inclusions in aluminium
Authors: Jones H.
Published: April 2007

Reported measurements of the kinetics of spherodisation, coalescence and coarsening (ripening) of liquid and solid lead inclusions in aluminium are compared with theoretical predictions. The experimental results for spherodisation and coarsening of liquid inclusions above the Al–Pb eutectic temperature are in reasonable accord with predictions assuming control by diffusion of aluminium in liquid lead while those for coarsening of liquid lead spheres lie some six orders of magnitude above predictions assuming control by diffusion of lead through the aluminium matrix.
Analysis of solidification in Bridgman furnace as simulation of DC casting of aluminium alloy slabs
Authors: Jaradeh M. , Carlberg T.
Published: April 2007

The vertical Bridgman directional solidification equipment has been used in several investigations to simulate direct chill casting of wrought aluminium alloys. As a basis for such investigations and alloy developments, it is important to have an understanding of the performance of the furnace used during simulation of the casting conditions. In this investigation the thermal conditions in the furnace have been analysed in detail, both by measurements and by mathematical modelling. The growth characteristics of the furnace, such as gradient, growth rates and cooling rates have been compared to conditions in large ingots. The direct chill casting conditions, which the simulations have been compared to, are casting of slabs of 330 and 600 mm thickness of an aluminium AA3003 type alloy. The results show that the experiments are able to simulate the cooling conditions in the ingots except from the surface zone. Comparisons of the microstructures have been made and a good agreement has been obtained for structure parameters such as grain size and DAS.
Effect of Nb on dynamic strain induced austenite to ferrite transformation
Authors: Rios P. R. , de S. Bott I. , Santos D. B. , de Melo T. M. F. , Ferreira J. L.
Published: April 2007

Dynamic strain induced transformation (DSIT) is an interesting processing route to obtain ultrafine ferrite grains. In the present work, the effect of Nb on DSIT was investigated. Samples of low C–Mn steels, with and without Nb, were intensively deformed in hot torsion, aiming at the production of ultrafine ferrite grains. After soaking at 1200°C, the samples were cooled to 1100°C, submitted to hot torsion deformation to decrease the grain size and then cooled to 900, 850 or 800°C for further hot torsion deformation. In the steel without Nb, recrystallisation took place before enough deformation could be accumulated to induce ferrite formation, so DSIT would only take place at the lowest temperature investigated, 800°C. In the Nb steel, Nb addition delayed austenite recrystallisation, allowing DSIT ferrite to form at higher temperature than in the steel without Nb, 850°C.
Novel sloping plate process for semisolid metal forming
Authors: Guan R.-G. , Wang C. , Xing Z.-H. , Lee C.S. , Hu F.-Y.
Published: April 2007

A novel sloping plate with wavelike surface was used to prepare semisolid alloy. Semisolid billets and slurries have been prepared by cooling or preheating the sloping plate. During preparation of the semisolid alloy by the proposed process, seed crystals derive from burst nucleation and breaking of dendrite and the coaction causes fine spherical microstructure formation. Casting temperature, sloping plate length, degree of cooling sloping angle are the main factors influencing the microstructure. Under current experimental conditions, in order to prepare good quality semisolid billets, proper casting temperature ranges of 660–690°C for Al–3 wt-%Mg alloy and 660–680°C for Al–6Si–2Mg (wt-%) alloy are suggested. The reasonable technological conditions for preparing Al–6Si–2Mg (wt-%) slurry are also proposed: the sloping plate preheating temperature is 300°C, and the casting temperature is 680°C. The optimum conditions for preparing semisolid billet of 1Cr–18Ni–9Ti stainless steel were obtained: the sloping plate length is 640 mm, and the casting temperature is 1600°C.
Dual phase versus TRIP strip steels: Comparison of dynamic properties for automotive crash performance
Authors: Oliver S. , Jones T. B. , Fourlaris G.
Published: April 2007

The need to simultaneously reduce vehicle emissions and increase the safety of passengers is encouraging the automotive industry to incorporate new technologies and materials into today's vehicles. To remain competitive, the steel industry has developed steel grades with increased energy absorbing properties allowing down gauging of body in white components to address the competition from alternative materials such as aluminium alloys and composites. Two of the more important developments are the introduction of dual phase (DP) and transformation induced plasticity (TRIP) grades for the automotive industry. These grades offer superior strength/formability and work hardening properties compared to conventional high strength grades of similar tensile strength. Utilising thinner gauge components with increased energy absorbing properties would permit addressing the mass/safety issues by the automotive industry. This paper relates the crash performance of a range of both commercial and experimental DP and TRIP grades. Dynamic tensile testing was performed at low and very high strain rates within the range of 0·001–200 s−1, to allow an extensive analysis of the effect of strain rate on the material properties. Crash testing was also performed on closed top hat sections at low, medium and high strain rates and the results compared to the dynamically tested tensile specimens. This study helped clarify the enhanced performance offered by high strength DP and TRIP strip steel grades during dynamic tensile testing and impact loading conditions. This advantageous behaviour is attributed to the favourable microconstituents present in these novel grades and their deformation characteristics. This paper concentrates only on the crash properties measured from dynamic tensile tests. The microstructural analysis is presented in a separate publication.
Determination of mechanical adhesion energy of thermal oxide scales on AISI 430Ti alloy using tensile test
Authors: Chandra-Ambhorn S. , Roussel-Dherbey F. , Toscan F. , Wouters Y. , Galerie A. , Dupeux M.
Published: April 2007

The present paper deals with mechanical adhesion energy determination of thermal oxide scales on metallic alloys. AISI 430Ti alloy (Fe–18Cr–0·4Ti–0·5Si, wt-%) was isothermally oxidised at 900°C in Ar–20%O2 atmosphere to grow thermal oxide scales of various thickness. These oxide/metal systems were subjected to room temperature in situ tensile test in the SEM chamber allowing continuous observation of surface failure during the test. Characteristic observations were oxide transverse cracking and scale spallation. A theoretical model was developed to quantify stress and strain evolution in oxide during the test, allowing to derive adhesion energy from strain and stress values at spallation onset. It was found that oxide scales on AISI 430Ti exhibited high mechanical adhesion energy, decreasing from 163 to 38 J m−2 with increasing oxide thickness in the range from 0·3 to 2·2 μm. Excellent agreement was observed with adhesion energy values obtained using the inverted blister test on the same alloy.
Formation of microstructure in Ag–In–Sn solder alloys
Authors: Snugovsky L. , Snugovsky P. , Perovic D. D. , Rutter J. W.
Published: April 2007

A metallographic study is reported of the phases and reactions that occur in Ag–In–Sn (Pb-free) solder alloys containing approximately 3 wt-%Ag and up to 10 wt-%In. Specimens were prepared by very slow unidirectional solidification and as small castings. Three different intermetallic compound phases and two different matrix phases were observed, depending on the In content of the alloy. The probable reactions that produce these phases are discussed and compared with data from the published ternary liquidus projection. This study was carried out in the Department of Materials Science and Engineering, University of Toronto, as part of the CMAP program.
Development of biodegradable scaffolds for tissue engineering: A perspective on emerging technology
Authors: Liu C. Z. , Czernuszka J. T.
Published: April 2007

The scaffold, a three-dimensional (3D) substrate that serves as a template for tissue regeneration, plays an essential role in tissue engineering. The ideal scaffold should have surface chemistry and microstructure tailored to facilitate cellular attachment, proliferation and differentiation; adequate mechanical strength for handling; and an appropriate biodegradation rate without undesirable byproducts. Research on biopolymer formulation and scaffold fabrication has been intense over the past 10 years. A perspective is provided of important issues related to scaffold development from biodegradable polymers. The mechanical properties and biocompatibility (including biodegradability and bioresorptability) of commonly used biopolymers are reviewed. Scaffold design and fabrication techniques are assessed and compared. Scaffold architecture, including pore size and size distribution, and its effects on cell growth are discussed. The importance of structural hierarchy over a range of length scales is highlighted. Unfortunately, conventional processing techniques cannot yet control both scaffold architecture and surface chemistry. An emerging scaffold fabricating technique using solid free form fabrication (SFF), although currently restricted to relatively symmetrical structures, has been shown to be highly effective in integrating structural architecture with changes in surface chemistry of the scaffolds, and integration of growth factors. Several examples of the application of SFF are presented.
Chemokine and chemoattractant receptor expression: post-transcriptional regulation
Authors: Hamilton Thomas A , Novotny Michael , Datta Shyamasree , Mandal Palash , Hartupee Justin , Tebo Julie , Li Xiaoxia
Published: April 2007

The magnitude and character of the inflammatory process are determined in part via the trafficking of leukocytes into sites of injury and infection, and this process depends on proper control of the expression of genes encoding chemoattractant peptides and their receptors. Although these controls operate at multiple mechanistic levels, recent evidence indicates that post-transcriptional events governing the half-life of select mRNAs are important determinants. Adenine-uridine rich elements (AREs) located within 3′ untranslated regions (UTRs) confer constitutive mRNA instability and in some cases, stabilization following stimulation by ligands of the Toll-IL-1 receptor (TIR) family. Although the importance of AREs in determining activity and mRNA half-life is well-recognized, the mechanistic scope and diversity remain poorly understood. Using the mouse KC or CXCL1 gene as a model, we have demonstrated that the abundance of mRNA and protein produced during an inflammatory response depends on multiple mechanistically distinct AREs present in the 3′ UTR of the mRNA. The mRNA encoding the receptor for N-terminal formyl-methionine-containing peptides is also unstable and subject to stabilization in response to TIR ligands. These two models can, however, be readily distinguished from one another on the basis of specific stimulus sensitivity and the signaling pathways, through which such stimuli couple to the control of mRNA decay. These models demonstrate the substantial diversity operative in the post-transcriptional regulation of inflammatory gene expression.
Various Dendritic Abnormalities Are Associated with Fibrillar Amyloid Deposits in Alzheimer's Disease
Authors: GRUTZENDLER JAIME , HELMIN KATHRYN , TSAI JULIA , GAN WEN‐BIAO
Published: April 2007

Abstract:  Dystrophic neurites are associated with fibrillar amyloid deposition in Alzheimer's disease (AD), but the frequency and types of changes in synaptic structures near amyloid deposits have not been well characterized. Using high‐resolution confocal microscopy to image lipophilic dye‐labeled dendrites and thioflavin‐S‐labeled amyloid plaques, we systematically analyzed the structural changes of dendrites associated with amyloid deposition in both a transgenic mouse model of AD (PSAPP) and in human postmortem brain. We found that in PSAPP mice, dendritic branches passing through or within 40 μm from amyloid deposits displayed various dendritic abnormalities such as loss of dendritic spines, shaft atrophy, bending, abrupt branch endings, varicosity formation, and sprouting. Similar structural alterations of dendrites were seen in postmortem human AD tissue, with spine loss as the most common abnormality in both PSAPP mice and human AD brains. These results demonstrate that fibrillar amyloid deposits and their surrounding microenvironment are toxic to dendrites and likely contribute to significant disruption of neuronal circuits in AD.
Anatomical and Functional Phenotyping of Mice Models of Alzheimer's Disease by MR Microscopy
Authors: BENVENISTE HELENE , MA YU , DHAWAN JASBEER , GIFFORD ANDREW , SMITH S. DAVID , FEINSTEIN IGOR , DU CONGWU , GRANT SAMUEL C. , HOF PATRICK R.
Published: April 2007

Abstract:  The wide variety of transgenic mouse models of Alzheimer's disease (AD) reflects the search for specific genes that influence AD pathology and the drive to create a clinically relevant animal model. An ideal AD mouse model must display hallmark AD pathology such as amyloid plaques, neurofibrillary tangles, reactive gliosis, dystrophic neurites, neuron and synapse loss, and brain atrophy and in parallel behaviorally mimic the cognitive decline observed in humans. Magnetic resonance (MR) microscopy (MRM) can detect amyloid plaque load, development of brain atrophy, and acute neurodegeneration
. MRM examples of AD pathology will be presented and discussed. What has lagged behind in preclinical research using transgenic AD mouse models is functional phenotyping of the brain; in other words, the ability to correlate a specific genotype with potential aberrant brain activation patterns. This lack of information is caused by the technical challenges involved in performing functional MRI (fMRI) in mice including the effects of anesthetic agents and the lack of relevant “cognitive” paradigms. An alternative approach to classical fMRI using external stimuli as triggers of brain activation in rodents is to electrically or pharmacologically stimulate regions directly while simultaneously locally tracking the activated interconnected regions of rodents using, for example, the manganese‐enhanced MRI (MEMRI) technique. Finally, transgenic mouse models, MRM, and future AD research would be strengthened by the ability to screen for AD‐like pathology in other non‐AD transgenic mouse models. For example, molecular biologists may focus on cardiac or pulmonary pathologies in transgenic mice models and as an incidental finding discover behavioral AD phenotypes. We will present MRM data of brain and cardiac phenotyping in transgenic mouse models with behavioral deficits.
Tracking Alzheimer's Disease
Authors: THOMPSON PAUL M. , HAYASHI KIRALEE M. , DUTTON REBECCA A. , CHIANG MING‐CHANG , LEOW ALEX D. , SOWELL ELIZABETH R. , DE ZUBICARAY GREIG , BECKER JAMES T. , LOPEZ OSCAR L. , AIZENSTEIN HOWARD J. , TOGA ARTHUR W.
Published: April 2007

Abstract: Population‐based brain mapping provides great insight into the trajectory of aging and dementia, as well as brain changes that normally occur over the human life span. We describe three novel brain mapping techniques,cortical thickness mapping,tensor‐based morphometry (TBM), andhippocampal surface modeling, which offer enormous power for measuring disease progression in drug trials, and shed light on the neuroscience of brain degeneration in Alzheimer's disease (AD) and mild cognitive impairment (MCI). We report the first time‐lapse maps of cortical atrophy spreading dynamically in the living brain, based on averaging data from populations of subjects with Alzheimer's disease and normal subjects imaged longitudinally with MRI. These dynamic sequences show a rapidly advancing wave of cortical atrophy sweeping from limbic and temporal cortices into higher‐order association and ultimately primary sensorimotor areas, in a pattern that correlates with cognitive decline. A complementary technique, TBM, reveals the 3D profile of atrophic rates, at each point in the brain. A third technique,hippocampal surface modeling, plots the profile of shape alterations across the hippocampal surface. The three techniques provide moderate to highly automated analyses of images, have been validated on hundreds of scans, and are sensitive to clinically relevant changes in individual patients and groups undergoing different drug treatments. We compare time‐lapse maps of AD, MCI, and other dementias, correlate these changes with cognition, and relate them to similar time‐lapse maps of childhood development, schizophrenia, and HIV‐associated brain degeneration. Strengths and weaknesses of these different imaging measures for basic neuroscience and drug trials are discussed.
Fibrillar and Oligomeric β‐Amyloid as Distinct Local Biomarkers for Alzheimer's Disease
Authors: MONTALTO MICHAEL C. , FARRAR GILL , HEHIR CRISTINA TAN
Published: April 2007

Abstract:  β‐amyloid is a key component of Alzheimer's disease (AD) pathology. Researchers in both academic and industry are actively pursuing the development of imaging tracers and techniques to noninvasively measure local levels of β‐amyloid in the Alzheimer's brain. This presentation summarizes recent data and discusses the opportunities and challenges of imaging plaques containing fibrillar β‐amyloid for the early diagnosis and therapeutic monitoring of amyloid targeted therapies. Further, the value and feasibility of measuring the recently described soluble oligomeric form of β‐amyloid as an alternative noninvasive biomarker is also discussed.
Magnetic Resonance Spectroscopy and Environmental Toxicant Exposure
Authors: WEISSKOPF MARC G.
Published: April 2007

Abstract:  The study of neurological impacts of toxicants has emphasized neuropsychological tests as important outcome variables. Direct assessment of neural substrates of environmental impacts could offer many advantages. I discuss our use of magnetic resonance spectroscopy (MRS) in the neurological assessment of adult lead poisoning of monozygotic twins as an example. Cognitive testing showed frontal lobe dysfunction in both twins, and more dramatic hippocampal dysfunction in the twin with higher lead exposure (JG). MRS showed lower N‐acetylaspartate/creatine ratios in JG. The findings illustrate the potential utility of MRS in assessing impacts of not only lead, but other toxicants as well.
Protease nexin 1 and its receptor LRP modulate SHH signalling during cerebellar development
Authors: Vaillant Catherine , Michos Odyssé , Orolicki Slobodanka , Brellier Florence , Taieb Sabrina , Moreno Eliza , Té Hélène , Zeller Rolf , Monard Denis
Published: April 2007

Development of the postnatal cerebellum relies on the tight regulation of cell number by morphogens that control the balance between cell proliferation,survival and differentiation. Here, we analyze the role of the serine-protease inhibitor protease nexin 1 (PN-1; SERPINE2) in the proliferation and differentiation of cerebellar granular neuron precursors (CGNPs) via the modulation of their main mitogenic factor, sonic hedgehog (SHH). Our studies show that PN-1 interacts with low-density lipoprotein receptor-related proteins (LRPs) to antagonize SHH-induced CGNP proliferation and that it inhibits the activity of the SHH transcriptional target GLI1. The binding of PN-1 to LRPs interferes with SHH-induced cyclin D1 expression. CGNPs isolated from Pn-1-deficient mice exhibit enhanced basal proliferation rates due to overactivation of the SHH pathway and show higher sensitivity to exogenous SHH. In vivo, the Pn-1 deficiency alters the expression of SHH target genes. In addition, the onset of CGNP differentiation is delayed,which results in an enlarged outer external granular layer. Furthermore, the Pn-1 deficiency leads to an overproduction of CGNPs and to enlargement of the internal granular layer in a subset of cerebellar lobes during late development and adulthood. We propose that PN-1 contributes to shaping the cerebellum by promoting cell cycle exit.
Analysis of actin filament network organization in lamellipodia by comparing experimental and simulated images
Authors: Schaub Sébastien , Meister Jean-Jacques , Verkhovsky Alexander B.
Published: March 2007

Protrusion of lamellipodia during cell migration depends on the assembly of actin network. The assembly mechanism, based on dendritic filament branching, has been investigated in reconstituted in vitro systems, but little is known about the dynamical and structural properties of the actin network in the lamellipodia of migrating cells. The length and orientation of filaments are difficult to measure directly in either optical or electron microscopy images because of the high filament density and overlapping of individual filaments. Here, we use the non-uniformity of optical images of the lamellipodia to extract information about the structural and dynamical properties of the underlying actin network. To determine the relationship between the image features and the properties of the network, we performed simulations of actin network assembly, based on the hypothesis of stochastic branching and capping of filaments, and produced computed `fluorescence' and `electron microscopy' images of the simulated network. By varying simulation parameters, in particular the actin filament density, length and orientation, we closely reproduced the contrast and the characteristic diagonal criss-cross pattern observed in the experimental optical images. Thus, matching the images of the simulated network to the experimental images allowed us to estimate parameters of actin filament network in lamellipodia.
The urinary bladder as a physiological reservoir that moderates dehydration in a large desert lizard, the Gila monsterHeloderma suspectum
Authors: Davis Jon R. , DeNardo Dale F.
Published: March 2007

Animals inhabiting xeric environments use a variety of behavioral and physiological strategies to balance water budgets. We studied the potential contribution of the urinary bladder to osmoregulation in a large desert lizard, the Gila monster Heloderma suspectum. Here we present results of a series of in vivo laboratory experiments which tested the hypothesis that the Gila monster urinary bladder serves as a physiological reservoir, as in amphibians and chelonians, providing water that buffers increases in plasma osmolality when food and water are unavailable. Adult Gila monsters absorbed water from the urinary bladder into circulation and absorption of water from the urinary bladder and drinking water provided similar osmoregulatory benefits within 24 h, although drinking water provided a more immediate osmotic benefit. During food and water deprivation, plasma osmolality increased 2.5 times faster in lizards with an empty urinary bladder compared with those with a full bladder. During rehydration, stereotyped binge drinking behavior increased body mass nearly 22%, which resulted in a 24%reduction in plasma osmolality and a substantial increase in bladder water within 24 h. These results support our hypothesis and demonstrate for the first time in an adult lizard that the urinary bladder can function as a long-term physiological water reservoir. This trait can provide a critical benefit to osmoregulation during the 2- to 3-month summer dry season characteristic of the deserts that Gila monsters inhabit.
Osmoregulation, ionoregulation and acid–base regulation by the gastrointestinal tract after feeding in the elasmobranch (Squalus acanthias)
Authors: Wood Chris M. , Kajimura Makiko , Bucking Carol , Walsh Patrick J.
Published: March 2007

In order to study the physiological consequences of voluntary feeding in the gastrointestinal tract of a ureotelic marine elasmobranch, dogfish (fasted for 96 h) were sampled at various times up to 360 h after consuming a 5–6% ration of teleost fish (hake) under natural feeding conditions. Digestion and absorption were completed between 120 and 360 h post-feeding. The tissue masses of different segments of the gastrointestinal tract increased and decreased markedly as the chyme moved through, mainly because of fluid engorgement rather than hyperplasia. In fasted dogfish, the cardiac and pyloric stomachs contained only small volumes of highly acidic fluid (pH 1.77±1.12, 2.05±0.08) similar in composition to seawater. Feeding resulted in gastric pHs of 3.20±0.31 and 3.95±0.40 at 6 h, followed by slow declines through 60 h. An alkaline tide in the blood also occurred at 6 h. In the face of large changing masses of highly acidic chyme in the stomachs, the pH (6.50±0.10), ionic composition and volume of chyme in the intestine (spiral valve) were precisely regulated from 6 to 60 h post-feeding at very different values from those in the stomachs, and intestinal HCO –3 remained low (5.12±0.83 mmol l–1). The colon was usually empty and its pH constant at 7.20±0.16 at all times. Despite the ingestion of strongly hypo-osmotic teleost tissue, the osmolality of the chyme remained in equilibrium with that of the blood plasma in all segments at all times after feeding. Much of the osmotic equilibration was because of the secretion of urea into the chyme,particularly in the intestine. After feeding, gastric fluid concentrations of Na+ and Mg2+ declined, K+ and Ca2+increased, whereas Cl– exhibited little change, indicating that additional drinking of seawater was minimal. Na+,K+, water and especially Cl– were absorbed in the intestine, whereas Mg2+ and Ca2+ were largely excluded. Our results illustrate the complex integration of digestive and ionoregulatory function in the elasmobranch digestive tract, and marked differences from the teleost pattern.
Spectral properties of identified polarized-light sensitive interneurons in the brain of the desert locustSchistocerca gregaria
Authors: Kinoshita Michiyo , Pfeiffer Keram , Homberg Uwe
Published: March 2007

Many migrating animals employ a celestial compass mechanism for spatial navigation. Behavioral experiments in bees and ants have shown that sun compass navigation may rely on the spectral gradient in the sky as well as on the pattern of sky polarization. While polarized-light sensitive interneurons(POL neurons) have been identified in the brain of several insect species,there are at present no data on the neural basis of coding the spectral gradient of the sky. In the present study we have analyzed the chromatic properties of two identified POL neurons in the brain of the desert locust. Both neurons, termed TuTu1 and LoTu1, arborize in the anterior optic tubercle and respond to unpolarized light as well as to polarized light. We show here that the polarized-light response of both types of neuron relies on blue-sensitive photoreceptors. Responses to unpolarized light depended on stimulus position and wavelength. Dorsal unpolarized blue light inhibited the neurons, while stimulation from the ipsilateral side resulted in opponent responses to UV light and green light. While LoTu1 was inhibited by UV light and was excited by green light, one subtype of TuTu1 was excited by UV and inhibited by green light. In LoTu1 the sensitivity to polarized light was at least 2 log units higher than the response to unpolarized light stimuli. Taken together, the spatial and chromatic properties of the neurons may be suited to signal azimuthal directions based on a combination of the spectral gradient and the polarization pattern of the sky.
Neuroprotection from secondary injury by polyethylene glycol requires its internalization
Authors: Liu-Snyder Peishan , Logan Melissa Peasley , Shi Riyi , Smith Daniel T. , Borgens Richard Ben
Published: March 2007

Polyethylene glycol (PEG) is well known to both fuse and repair cell membranes. This capability has been exploited for such diverse usages as the construction of hybridomas and as a reparative agent following neurotrauma. The latter development has proceeded through preclinical testing in cases of naturally induced paraplegia in dogs. The mechanisms of action of polymer-mediated neurorepair/neuroprotection are still under investigation. It is likely that the unique interaction of hydrophilic polymers with the mechanical properties of cell membranes in concert with an ability to interfere with mechanisms of secondary injury such as the production of highly reactive oxygen species (ROS or `free radicals') is the basis for neuroprotection by polymers.

Here we provide further evidence that the ability of PEG to reduce or limit secondary injury and/or lipid peroxidation (LPO) of membranes requires entry of PEG into the cytosol, further suggesting a physical interaction with the membranes of organelles such as mitochondria as the initial event leading to neurorepair/neuroprotection.

We have evaluated this relationship in vitro using acrolein, a potent endogenous toxin that is a product of LPO. Acrolein can pass through cell membranes with ease, inducing progressive LPO in `bystander' cells, and the production of even more acrolein by inducing its own production. Immediate application of PEG (10 mmol l–1, 2000 Da) to poisoned neurons in vitro was unable to rescue them from necrosis and death. Furthermore, three-dimensional confocal microscopy of fluorescently decorated PEG shows that it does not enter these cells for up to 2 h after application. By this time the mechanisms of necrosis are likely irreversible. Additionally,severe oxygen and or glucose deprivation of spinal cord white matter in vitro also initiates LPO. Addition of potent free radical scavengers such as ascorbic acid or superoxide dismutase (SOD) is able to interfere with this process, but PEG is not. Taken together, these data are consistent with the hypothesis that PEG is able to rescue mechanically damaged cells, based on a restructuring of the damaged plasmalemma. Furthermore, in compromised cells with an intact cell membrane, PEG must first gain access to the cytosol where this same capability may be useful in restoring the integrity of cellular organelles such as mitochondria, though the intracellular concentration of the polymer must be significant relative to the concentration of toxins produced by LPO in order to rescue the cell.
Just drop it and run: the effect of limb autotomy on running distance and locomotion energetics of field crickets (Gryllus bimaculatus)
Authors: Fleming Patricia A. , Bateman Philip W.
Published: March 2007

This is the first study to examine the direct metabolic costs of autotomy,the voluntary shedding of an appendage as an escape mechanism, in invertebrates. We investigated the effects of limb autotomy upon endurance and metabolic cost of locomotion in the field cricket Gryllus bimaculatus. Compared with control (intact) crickets, animals that had autotomised a single hindlimb were slower, stopped more often, moved a shorter distance and expended more energy doing so. Both the cost of locomotion (COT)and minimal cost of locomotion (MCOT) were significantly higher for autotomised animals. We compare these data with locomotion energetics of 36 other invertebrate species, and discuss the results in terms of the biomechanics of walking in crickets.
Physical distribution activities and vehicle routing problems in logistics management: A case study
Authors: Güneri A F
Published: April 2007

The vehicle routing path (VRP) is non-deterministic polynomial-time hard (NP-hard) and therefore difficult to solve. The fact that VRP is both of theoretical and practical interest (owing to its real-world applications), explains the amount of attention given to the VRP by researchers during past years. Research on the development of heuristics for the VRP has made considerable progress since the first algorithms were proposed in the early 1960s. Several families of heuristics have been proposed for the VRP. The purpose of this paper is to review some of the most important families of heuristics for the VRP. At the end, the survey presents the solution method used for a small-scale case study in a logistic company in Turkey.
Monitoring the dynamic displacements of railway track
Authors: Bowness D , Lock A C , Powrie W , Priest J A , Richards D J
Published: April 2007

This paper reports the development and testing of two independent, innovative techniques for measuring rail displacements. One system combines remote video monitoring with particle image velocimetry, using a webcam and a small telescope. The second uses sleeper mounted geophones that give a voltage output proportional to the velocity of motion, which can be filtered and integrated to calculate displacements. Laboratory validation tests show that the video monitoring system can measure peak-to-peak displacements to within 0.04 mm from a distance of 15 m for frequencies less than 4 Hz. The geophones measure peak-to-peak displacements to within 0.07 mm for frequencies as low as 1 Hz. Data from three different standards of railway track and/or train speeds are used to explore and quantify the limitations of each system in the field.
International railway comparisons
Authors: Hatano L , Smith R A , Hillmansen S
Published: April 2007

This technical note presents data on international railway comparisons. It is intended as a general introduction to some of the main themes and problems of international comparisons. The authors provide a selection of time series data for a set of countries and an extensive collection of reference sources on international rail statistics. Interesting general conclusions on first-order comparisons are highlighted. Key economics-based references for those wishing to study the subject in depth are provided at the end.
Friction of plasticity: Application of the dynamic friction model
Authors: Tan X
Published: April 2007

There have not been any suitable friction models to properly solve plasticity problems yet. Most recently, a new dynamic friction model merging the definition expression of the viscosity with the Amontons-Coulomb friction model suggested by the author has been successfully applied in axisymmetric upsetting to predict the contact stresses. In this paper, the dynamic friction model is further used for resolving the problem of plane-strain compression. With element-equilibrium approach, contact stresses in plane-strain compression have been derived. The mathematical expressions of these contact stresses are verified by the previous experimental data with various ratios of instant length to instant height of workpiece and different lubrications. The curves obtained from the dynamic friction model agree with these experimental results very well, not only for contribution of the normal pressure, mean normal pressure, but also for contribution of the friction stress. Comparisons of results of the dynamic friction model, the Amontons-Coulomb friction model, and the constant friction model with the experimental data are also made. It is seen that the predictions by the dynamic friction model show much better solutions to the practical plasticity problems. It is believed that the dynamic friction model could extensively be used to plasticity problems of solids.
Study of the effect of transverse and longitudinal surface patterns on drag-reduction in shear-thinning fluid
Authors: Chen H , Li J , Chen D , Wang J
Published: April 2007

To investigate the effect of surface pattern on drag reduction in non-Newtonian fluid, a pin-disc lubrication experiment is performed with a universal microtribotester system. In the experiment, polyoxyethylene water solution is used as the lubricant, and the longitudinal and transverse grooves are etched on the disc surface as different surface patterns. The experimental results show that the drag force on the pattern is not always higher than that on a smooth surface. The drag reduction effect caused by the surface pattern occurs in the Newtonian field of the fluid, not in the shear-thinning field, as shown by the numerical results based on the CFD method. The drag on side walls of the transverse and grooves longitudinal cannot totally compensate the loss of drag on the bottom walls of the grooves: then the drag reduction occurs on surface patterns. On the other hand, the drag reduction effect caused by the surface pattern is weakened by the shear-thinning viscosity of the fluid.
Intermediate tyre model for vehicle handling simulation
Authors: Blundell M V , Harty D
Published: April 2007

The work presented in this article describes a new mathematical model of the force and moment components generated in a tyre to road surface contact patch. The model has been implemented with the industry standard multi-body systems program MSC.ADAMS™ and is intended for use in computer simulations of proving ground-test manoeuvres used to evaluate vehicle handling performance. The proposed model uses a small set of model parameters that can be obtained without recourse to special software and can be easily manipulated to fit the model to tyre test data. The model has been exercised and compared with two existing tyre models using a multibody computer model of a tyre test machine and has been shown to produce reliable predictions of the important forces and moments generated in a tyre contact patch. The tyre test data and model parameters used are provided here. The evaluation at this stage is related to the tyre characteristics needed to simulate vehicle braking and cornering manoeuvres.
The identifying extended Kalman filter: Parametric system identification of a vehicle handling model
Authors: Best M C , Newton A P , Tuplin S
Published: April 2007

This article considers a novel method for estimating parameters in a vehicle-handling dynamic model using a recursive filter. The well-known extended Kalman filter - which is widely used for real-time state estimation of vehicle dynamics - is used here in an unorthodox fashion; a model is prescribed for the sensors alone, and the state vector is replaced by a set of unknown model parameters. With the aid of two simple tuning parameters, the system self-regulates its estimates of parameter and sensor errors, and hence smoothly identifies optimal parameter choices.

The method makes one contentious assumption that vehicle lateral velocity (or body sideslip angle) is available as a measurement, along with the more conventionally available yaw velocity state. However, the article demonstrates that by using the new generation of combined GPS/inertial body motion measurement systems, a suitable lateral velocity signal is indeed measurable. The system identification is thus demonstrated in simulation, and also proved by successful parametrization of a model, using test vehicle data. The identifying extended Kalman filter has applications in model validation - for example, acting as a reference between vehicle behaviour and higher-order multi-body models - and it could also be operated in a real-time capacity to adapt parameters in model-based vehicle control applications.
Simulation model of an aircraft landing gear considering elastic properties of the shock absorber
Authors: Lernbeiss R , Plöchl M
Published: April 2007

For the investigation of elastic bending of the landing gear shock absorber of an aircraft under dynamic loads upon landing and subsequent braking during roll out, an MBS-based model of the landing gear is introduced. To separate effects of the elastic bending of the main landing gear the fuselage is considered rigid. After performing a flare with subsequent landing, the aircraft is stopped by means of an antiskid system. For comparison, an analytical-numerical study of a finite-element model of the main landing gear shock strut components is done for simple static and dynamic loads considering Bernoulli's hypothesis. Simulation of a rough-landing manoeuvre reveals that vibrations due to the elastic properties of the shock absorber not only increase loads on the components but significantly affect the braking process as well.
Multi-body co-simulation of semi-active suspension systems
Authors: Levesley M C , Ramli R , Stembridge N , Crolla D A
Published: April 2007

This paper describes the development and use of a multi-body co-simulation approach for predicting the dynamic response of a vehicle containing magnetorheological (MR) semi-active dampers. The approach is used to investigate the effects of various local and global control strategies on the load histories of suspension components for the purpose of assessing their likely impact on fatigue life. The approach adopted aims to exploit the capability of a multi-body system (MBS) code and a mathematical simulation code, by integrating the MBS vehicle models with selected semi-active damper/controller models. Various MBS vehicle models are developed of increasing complexity using MSC.visualNastran, which are linked to three local, two-state switchable, control algorithms and also two global controllers, each developed in MATLAB/Simulink. The control strategies are implemented within the vehicle model using an MR damper model derived from experimental test data. Road inputs, including both bump/pothole and random road excitation, and the tyre model are also implemented within MATLAB/Simulink. Ultimately, the aim is to develop an approach which would allow concurrent structural optimization and controller optimization to enable lighter and more durable suspension components to be produced.
Integrated optimization of system design and spare parts allocation by means of multiobjective genetic algorithms and Monte Carlo simulation
Authors: Zio E , Podofillini L
Published: April 2007

In this paper, the issue of the combined optimization of system design and spare parts allocation is addressed from a methodological point of view. The problem is framed as a typical optimization problem with multiple choices of component types and number of spares available for each component category. The component types differ with respect to their availability and cost characteristics. The optimization variables are then the type of components (both principal and spare) to be allocated for each category and the number of spare parts to be allocated for each component category in the operating system. The optimization is carried out according to a multiobjective perspective, with the aim of identifying optimal compromising solutions characterized by both high system availability and revenues. The optimization problem is solved by means of an approach that effectively combines genetic algorithms, as the multiobjective search engine of the optimal solution for the system design and spare parts allocation, and Monte Carlo simulation, as the evaluation engine of the system solution performance with respect to the availability and revenue objectives (the fitness functions of the genetic search algorithm). The approach has been previously introduced in works coauthored by the first author of this paper and demonstrated to achieve statistically accurate estimates of the fitness functions for the potentially optimal solutions, without wasting computational resources on solutions with low potential for optimality. Two numerical examples are presented.
Joint modelling and optimization of monitoring and maintenance performance for a two-unit parallel system
Authors: Barros A , Grall A , Berenguer C
Published: April 2007

This paper proposes a new methodology for optimizing maintenance and monitoring performance. The performance of the monitoring device is modelled classically by receiver operating characteristic (ROC) curves. From a practical point of view, this approach leads to a very simple optimization scheme in which the optimal monitoring technology or structure can be chosen among a finite set of possible ones, on the basis of their impact on the maintenance performance and their own cost. At the same time, the maintenance parameters are optimally tuned to adapt to the current monitoring quality level. Compared with previous work on the subject, this work allows the assessment of a more realistic integration between maintenance or reliability concerns and monitoring ones, owing to comprehensive reliability/maintenance/monitoring performance modelling.