bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECT OF SOCIAL INFLUENCE ON MARKET INEQUALITIES IN THE MOTION PICTURE INDUSTRY
Authors: DELRE SEBASTIANO A. , BROEKHUIZEN THIJS L. J. , JAGER WANDER
Published: May 2008

In this paper we investigate the degree to which two social influences, namely imitation and coordinated consumption, effectuate inequalities in the motion picture industry. We develop an agent-based model based on micro movie visitors' decision-making that generates the observed macro market outcomes. The simulation model makes use of the findings of an empirical survey amongst 1112 cinema visitors. We find that social influences explain market inequalities and that the impact of coordinated consumption on market inequalities is stronger than the impact of imitation.
PRIOR KNOWLEDGE VERSUS CONSTRUCTED KNOWLEDGE: WHAT IMPACT ON LEARNING?
Authors: GUECHTOULI WIDAD
Published: May 2008

The aim of this paper is to model the process of learning within a social network and compare the levels of learning in two different situations: one where individuals know others' competencies as given data and interact on this basis; and one where individuals know nothing about others' competencies but rather build this knowledge over time, according to their past interactions. For this purpose, we build an agent-based model, and model these two scenarios of simulations. Results are partly studied using network analysis, and they show that in the second type of simulations agents are able to identify the most competent agents in the network and increase their competencies. Results also show that learning is easier when there is no prior knowledge of others' competencies. Otherwise, agents deal with a congestion effect that slows down the learning process.
AFFYGCQC: A WEB-BASED INTERFACE TO DETECT OUTLYING GENECHIPS WITH EXTREME STUDENTIZED DEVIATE TESTS
Authors: OSORIO Y FORTÉA JOSÉ , PRINA ÉRIC , LANG THIERRY , MILON GENEVIÈVE , DAVORY CLARISSE , COPPÉE JEAN-YVES , REGNAULT BÉATRICE
Published: May 2008

Affymetrix GeneChip®oligonucleotide arrays are dedicated to analyzing gene expression differences across distinct experimental conditions. Data production for such arrays is an elaborate process with many potential sources of variability unrelated to biologically relevant gene expression variations. Therefore, rigorous data quality assessment is fundamental throughout the process for downstream biologically meaningful analyses. We have developed a program named AffyGCQC, which is the acronym for a bioinformatics tool designed to perform Affymetrix GeneChip Quality Control. This program implements a graphical representation of QC metrics recommended by Affymetrix for GeneChip oligonucleotide array technology. Most importantly, it performs extreme studentized deviate statistical tests for the set of arrays being compared in a given experiment, thus providing an objective measure for outlier detection. AffyGCQC has been designed as an easy-to-use Web-based interface (online supplementary information: ; contact: affygcqc@biologie.ens.fr).
A DIFFERENT LOOK AT THE QUALITY OF MODELED THREE-DIMENSIONAL PROTEIN STRUCTURES
Authors: POLEKSIC ALEKSANDAR , FIENUP MARK , DANZER JOSEPH F. , DEBE DEREK A.
Published: May 2008

Measuring the accuracy of protein three-dimensional structures is one of the most important problems in protein structure prediction. For structure-based drug design, the accuracy of the binding site is far more important than the accuracy of any other region of the protein. We have developed an automated method for assessing the quality of a protein model by focusing on the set of residues in the small molecule binding site. Small molecule binding sites typically involve multiple regions of the protein coming together in space, and their accuracy has been observed to be sensitive to even small alignment errors. In addition, ligand binding sites contain the critical information required for drug design, making their accuracy particularly important. We analyzed the accuracy of the binding sites on two sets of protein models: the predictions submitted by the top-performing CASP7 groups, and the models generated by four widely used homology modeling packages. The results of our CASP7 analysis significantly differ from the previous findings, implying that the binding site measure does not correlate with the traditional model quality measures used in the structure prediction benchmarks. For the modeling programs, the resolution of binding sites is extremely sensitive to the degree of sequence homology between the query and the template, even when the most accurate alignments are used in the homology modeling process.
Optical Probes for Molecular Processes in Live Cells
Authors: Umezawa Yoshio
Published: May 2008

In this review, I summarize the development over the past several years of fluorescent and/or bioluminescent indicators to pinpoint cellular processes in living cells. These processes involve second messengers, protein phosphorylations, protein-protein interactions, protein-ligand interactions, nuclear receptor–coregulator interactions, nucleocytoplasmic trafficking of functional proteins, and protein localization.
Matrix-Assisted Laser Desorption/Ionization Imaging Mass Spectrometry for the Investigation of Proteins and Peptides
Authors: Burnum Kristin E. , Frappier Sara L. , Caprioli Richard M.
Published: May 2008

Mass spectrometry (MS) is an excellent technology for molecular imaging because of its high data dimensionality. MS can monitor thousands of individual molecular data channels measured as mass-to-charge (m/z). We describe the use of matrix-assisted laser desorption/ionization (MALDI) MS for the image analysis of proteins, peptides, lipids, drugs, and metabolites in tissues. We discuss the basic instrumentation and sample preparation methods needed to produce high-resolution images and high image reproducibility. Matrix-addition protocols are briefly discussed along with normal operating procedures, and selected biological and medical applications of MALDI imaging MS are described. We give examples of both two- and three-dimensional imaging, including normal mouse embryo implantation, sperm maturation in mouse epididymis, protein distributions in brain sections, protein alterations as a result of drug administration, and protein changes in brain due to neurodegeneration and tumor formation. Advantages of this technology and future challenges for its improvement are discussed.
Combining Self-Assembled Monolayers and Mass Spectrometry for Applications in Biochips
Authors: Gurard-Levin Zachary A. , Mrksich Milan
Published: May 2008

Biochip arrays have enabled the massively parallel analysis of genomic DNA and hold great promise for application to the analysis of proteins, carbohydrates, and small molecules. Surface chemistry plays an intrinsic role in the preparation and analysis of biochips by providing functional groups for immobilization of ligands, providing an environment that maintains activity of the immobilized molecules, controlling nonspecific interactions of analytes with the surface, and enabling detection methods. This review describes recent advances in surface chemistry that enable quantitative assays of a broad range of biochemical activities. The discussion emphasizes the use of self-assembled monolayers of alkanethiolates on gold as a structurally well-defined and synthetically flexible platform for controlling the immobilization and activity of molecules in an array. The review also surveys recent methods of performing label-free assays, and emphasizes the use of matrix-assisted laser desorption/ionization mass spectrometry to directly observe molecules attached to the self-assembled monolayers.
Ion Chemistry in the Interstellar Medium
Authors: Snow Theodore P. , Bierbaum Veronica M.
Published: May 2008

We present an overview of the interstellar medium, including physical and chemical conditions, spectroscopic observations, and current challenges in characterizing interstellar chemistry. Laboratory studies of ion-atom reactions, including experimental approaches and instrumentation, are described. We also tabulate and discuss comprehensive summaries of ion-neutral reactions involving hydrogen, nitrogen, and oxygen atoms that have been studied since Sablier and Rolando's 1993 review.
Applications of Ultrafast Lasers for Optical Measurements in Combusting Flows
Authors: Gord James R. , Meyer Terrence R. , Roy Sukesh
Published: May 2008

Optical measurement techniques are powerful tools for the detailed study of combustion chemistry and physics. Although traditional combustion diagnostics based on continuous-wave and nanosecond-pulsed lasers continue to dominate fundamental combustion studies and applications in reacting flows, revolutionary advances in the science and engineering of ultrafast (picosecond- and femtosecond-pulsed) lasers are driving the enhancement of existing diagnostic techniques and enabling the development of new measurement approaches. The ultrashort pulses afforded by these new laser systems provide unprecedented temporal resolution for studies of chemical kinetics and dynamics, freedom from collisional-quenching effects, and tremendous peak powers for broad spectral coverage and nonlinear signal generation. The high pulse-repetition rates of ultrafast oscillators and amplifiers allow previously unachievable data-acquisition bandwidths for the study of turbulence and combustion instabilities. We review applications of ultrafast lasers for optical measurements in combusting flows and sprays, emphasizing recent achievements and future opportunities.
Biomolecule Analysis by Ion Mobility Spectrometry
Authors: Bohrer Brian C. , Merenbloom Samuel I. , Koeniger Stormy L. , Hilderbrand Amy E. , Clemmer David E.
Published: May 2008

Although nonnative protein conformations, including intermediates along the folding pathway and kinetically trapped misfolded species that disfavor the native state, are rarely isolated in the solution phase, they are often stable in the gas phase, where macromolecular ions from electrospray ionization can exist in varying charge states. Differences in the structures of nonnative conformations in the gas phase are often large enough to allow different shapes and charge states to be separated because of differences in their mobilities through a gas. Moreover, gentle collisional activation can be used to induce structural transformations. These new structures often have different mobilities. Thus, there is the possibility of developing a multidimensional separation that takes advantage of structural differences of multiple stable states. This review discusses how nonnative states differ in the gas phase compared with solution and presents an overview of early attempts to utilize and manipulate structures in order to develop ion mobility spectrometry as a rapid and sensitive technique for separating complex mixtures of biomolecules prior to mass spectrometry.
In Vitro Electrochemistry of Biological Systems
Authors: Adams Kelly L. , Puchades Maja , Ewing Andrew G.
Published: May 2008

This article reviews recent work involving electrochemical methods for in vitro analysis of biomolecules, with an emphasis on detection and manipulation at and of single cells and cultures of cells. The techniques discussed include constant potential amperometry, chronoamperometry, cellular electroporation, scanning electrochemical microscopy, and microfluidic platforms integrated with electrochemical detection. The principles of these methods are briefly described, followed in most cases with a short description of an analytical or biological application and its significance. The use of electrochemical methods to examine specific mechanistic issues in exocytosis is highlighted, as a great deal of recent work has been devoted to this application.
Quantitative Imaging of Musculoskeletal Tissue
Authors: Augat Peter , Eckstein Felix
Published: May 2008

Quantitative imaging of musculoskeletal tissue, including radiography, computed tomography (CT), and magnetic resonance imaging (MRI), has become the essential methodology in clinical practice for diagnosis and monitoring of various musculoskeletal conditions. Furthermore, quantitative imaging technologies have become indispensable for research and development in diseases of the human skeleton. Standardized methods of image analysis have been developed through the years to quantify measurements on bone and cartilage with high precision and accuracy. Key areas of musculoskeletal disease where quantitative imaging is currently employed are osteoporosis and arthritis.
Human Telomere Structure and Biology
Authors: Riethman Harold
Published: May 2008

Human telomeric DNA is complex and highly variable. Subterminal sequences are associated with cis-acting determinants of allele-specific (TTAGGG)n tract length regulation and may modulate susceptibility of (TTAGGG)n tracts to rapid deletion events. More extensive subtelomeric DNA tracts are filled with segmental duplications and segments that vary in copy number, leading to highly variable subtelomeric allele structures in the human population. RNA transcripts encoded in telomere regions include multicopy protein-encoding gene families and a variety of noncoding RNAs. One recently described family of (UUAGGG)n-containing subterminal RNAs appears to be critical for telomere integrity; these RNAs associate with telomeric chromatin and are regulated by RNA surveillance factors including human homologs of the yeast Est1p protein. An increasingly detailed and complete picture of telomeric DNA sequence organization and structural variation is essential for understanding and tracking allele-specific subterminal and subtelomeric features critical for human biology.
Dynamics of Wetting from an Experimental Point of View
Authors: Ralston John , Popescu Mihail , Sedev Rossen
Published: May 2008

This review critically examines the experimental aspects of dynamic wetting, considering extant data for different geometries. Both partial wetting and complete wetting are considered for cases that include droplets, fibers, tubes, and plates. The wetting of porous materials is also considered, along with the new field of micro- and nanofluidics.
Recent Developments in Irradiation-Resistant Steels
Authors: Odette G.R. , Alinger M.J. , Wirth B.D.
Published: May 2008

Advanced fission and future fusion energy will require new high-performance structural alloys with outstanding properties that are sustained under long-term service in ultrasevere environments, including neutron damage producing up to 200 atomic displacements per atom and, for fusion, 2000 appm of He. Following a brief description of irradiation damage and damage resistance, we focus on an emerging class of nanostructured ferritic alloys (NFAs) that show promise for meeting these challenges. NFAs contain an ultrahigh density of Y-Ti-O-enriched dispersion-strengthening nanofeatures (NFs) that, along with fine grains and high dislocation densities, provide remarkably high tensile, creep, and fatigue strength. The NFs are stable under irradiation up to 800°C and trap He in fine-scale bubbles, suppressing void swelling and fast fracture embrittlement at lower temperatures and creep rupture embrittlement at high temperatures. The current state of the development and understanding of NFAs is described, along with some significant outstanding challenges.
Wetting and Prewetting on Ceramic Surfaces
Authors: Luo Jian , Chiang Yet-Ming
Published: May 2008

The stabilization of nanoscale surficial amorphous films (SAFs) for Bi2O3 on ZnO, VOx on TiO2, SiOx on Si, and several other oxide systems provides evidence for the existence of prewetting phenomena with analogies in water and other simple systems, as well as the stabilization of intergranular amorphous films in ceramics. Experimental results show that in the subeutectic regime, the equilibrium film thickness decreases monotonically with decreasing temperature until it vanishes at a dewetting (prewetting) temperature. With increasing temperatures, nanometer-thick SAFs persist into a solid-liquid coexistence regime, in equilibrium with partial-wetting drops, with a gradual decrease in the macroscopic contact angle upon heating. The presence of an attractive dispersion force can significantly delay or inhibit the (otherwise expected) occurrence of complete wetting at higher temperatures. The equilibrium thickness of SAFs is explained from a balance between several interfacial interactions, including dispersion forces, short-range forces of structural or chemical origins, volumetric free-energy terms, and electrostatic interactions. In a generalized Cahn critical-point wetting model, these SAFs are alternatively considered to be disordered multilayer adsorbates formed from coupled prewetting and premelting transitions.
Interfacial Segregation Effects in Wetting Phenomena
Authors: Wynblatt Paul
Published: May 2008

Wetting generally involves three phases and is controlled by the energies of the three interfaces that separate each of the three pairs of phases. Because interfacial segregation can significantly modify interfacial energies, it plays an important role in wetting phenomena. This paper is divided into two principal parts. The first part describes the effects of interfacial energy anisotropy in wetting equilibrium, the thermodynamics of segregation and its effects on interfacial energies, and the interaction of segregation and wetting. The second part reviews some experimental approaches for controlling and monitoring interfacial segregation in wetting studies and summarizes examples of wetting experiments in which such approaches have been used effectively to understand the impact of segregation effects.
Wetting Phenomena in Nanofluidics
Authors: Rauscher M. , Dietrich S.
Published: May 2008

We focus on the dynamical aspects of wetting phenomena on the nanoscale for which bulk hydrodynamic equations become invalid. At the nanoscale, phenomena that are irrelevant on the micrometer scale and larger, or that can be summarily incorporated in terms of boundary conditions, become important. Among these features are long-ranged molecular interactions such as dispersion forces, thermal fluctuations, hydrodynamic slip, segregation of mixtures and solutions at walls, and electrical double layers.
Adiponectin is expressed by skeletal muscle fibers and influences muscle phenotype and function
Authors: Krause Matthew P. , Liu Ying , Vu Vivian , Chan Lawrence , Xu Aimin , Riddell Michael C. , Sweeney Gary , Hawke Thomas J.
Published: May 2008

Adiponectin (Ad) is linked to various disease states and mediates antidiabetic and anti-inflammatory effects. While it was originally thought that Ad expression was limited to adipocytes, we demonstrate here that Ad is expressed in mouse skeletal muscles and within differentiated L6 myotubes, as assessed by RT-PCR, Western blot, and immunohistochemical analyses. Serial muscle sections stained for fiber type, lipid content, and Ad revealed that muscle fibers with elevated intramyocellular Ad expression were consistently type IIA and IID fibers with detectably higher intramyocellular lipid (IMCL) content. To determine the effect of Ad on muscle phenotype and function, we used an Ad-null [knockout (KO)] mouse model. Body mass increased significantly in 24-wk-old KO mice [+5.5 ± 3% relative to wild-type mice (WT)], with no change in muscle mass observed. IMCL content was significantly increased (+75.1 ± 25%), whereas epididymal fat mass, although elevated, was not different in the KO mice compared with WT (+35.1 ± 23%; P = 0.16). Fiber-type composition was unaltered, although type IIB fiber area was increased in KO mice (+25.5 ± 6%). In situ muscle stimulation revealed lower peak tetanic forces in KO mice relative to WT (−47.5 ± 6%), with no change in low-frequency fatigue rates. These data demonstrate that the absence of Ad expression causes contractile dysfunction and phenotypical changes in skeletal muscle. Furthermore, we demonstrate that Ad is expressed in skeletal muscle and that its intramyocellular localization is associated with elevated IMCL, particularly in type IIA/D fibers.
Regulation of the voltage-gated K+channels KCNQ2/3 and KCNQ3/5 by serum- and glucocorticoid-regulated kinase-1
Authors: Schuetz Friderike , Kumar Sharad , Poronnik Philip , Adams David J.
Published: May 2008

The voltage-gated KCNQ2/3 and KCNQ3/5 K+channels regulate neuronal excitability. We recently showed that KCNQ2/3 and KCNQ3/5 channels are regulated by the ubiquitin ligase Nedd4-2. Serum- and glucocorticoid-regulated kinase-1 (SGK-1) plays an important role in regulation of epithelial ion transport. SGK-1 phosphorylation of Nedd4-2 decreases the ability of Nedd4-2 to ubiquitinate the epithelial Na+channel, which increases the abundance of channel protein in the cell membrane. In this study, we investigated the mechanism(s) of SGK-1 regulation of M-type KCNQ channels expressed in Xenopus oocytes. SGK-1 significantly upregulated the K+current amplitudes of KCNQ2/3 and KCNQ3/5 channels ∼1.4- and ∼1.7-fold, respectively, whereas the kinase-inactive SGK-1 mutant had no effect. The cell surface levels of KCNQ2-hemagglutinin/3 were also increased by SGK-1. Deletion of the KCNQ3 channel COOH terminus in the presence of SGK-1 did not affect the K+current amplitude of KCNQ2/3/5-mediated currents. Coexpression of Nedd4-2 and SGK-1 with KCNQ2/3 or KCNQ3/5 channels did not significantly alter K+current amplitudes. Only the Nedd4-2 mutantS448ANedd4-2 exhibited a significant downregulation of the KCNQ2/3/5 K+current amplitudes. Taken together, these results demonstrate a potential mechanism for regulation of KCNQ2/3 and KCNQ3/5 channels by SGK-1 regulation of the activity of the ubiquitin ligase Nedd4-2.
O2-sensing signal cascade: clamping of O2 respiration, reduced ATP utilization, and inducible fumarate respiration
Authors: Sridharan Vijayalakshmi , Guichard Jason , Li Chuan-Yuan , Muise-Helmericks Robin , Beeson Craig Cano , Wright Gary L.
Published: May 2008

These studies explore the consequences of activating the prolyl hydroxylase (PHD) O2-sensing pathway in spontaneously twitching neonatal cardiomyocytes. Full activation of the PHD pathway was achieved using the broad-spectrum PHD inhibitor (PHI) dimethyloxaloylglycine (DMOG). PHI treatment of cardiomyocytes caused an 85% decrease in O2 consumption and a 300% increase in lactic acid production under basal conditions. This indicates a ∼75% decrease in ATP turnover rate, inasmuch as the increased ATP generation by glycolysis is inadequate to compensate for the lower respiration. To determine the extent to which decreased ATP turnover underlies the suppressed O2 consumption, mitochondria were uncoupled with 2,4-dinitrophenol. We were surprised to find that 2,4-dinitrophenol failed to increase O2 consumption by PHI-treated cells, indicating that electron transport chain activity, rather than ATP turnover rate, limits respiration in PHI-treated cardiomyocytes. Silencing of hypoxia-inducible factor-1α (HIF-1α) expression restored the ability of uncoupled PHI-treated myocytes to increase O2 consumption; however, basal O2 uptake rates remained low because of the unabated suppression of cellular ATP consumption. Thus it appears that respiration is actively “clamped” through an HIF-dependent mechanism, whereas HIF-independent mechanisms are responsible for downregulation of ATP consumption. In addition, we find that PHD pathway activation enables mitochondria to utilize fumarate as a terminal electron acceptor when cytochrome c oxidase is inactive. The source of fumarate for this unusual respiration is derived from aspartate via the purine nucleotide cycle. In sum, these studies show that the O2-sensing pathway is sufficient to actively “clamp” O2 consumption and independently suppress cellular ATP consumption. The PHD pathway also enables the mitochondria to utilize fumarate for respiration.
Rho-ROCK signaling differentially regulates chondrocyte spreading on fibronectin and bone sialoprotein
Authors: Gill Kamal S. , Beier Frank , Goldberg Harvey A.
Published: May 2008

The mammalian growth plate is a dynamic structure rich in extracellular matrix (ECM). Interactions of growth plate chondrocytes with ECM proteins regulate cell behavior. In this study, we compared chondrocyte adhesion and spreading dynamics on fibronectin (FN) and bone sialoprotein (BSP). Chondrocyte adhesion and spreading were also compared with fibroblasts to analyze potential cell-type-specific effects. Chondrocyte adhesion to BSP is independent of posttranslational modifications but is dependent on the RGD sequence in BSP. Whereas chondrocytes and fibroblasts adhered at similar levels on FN and BSP, cells displayed more actin-dependent spread on FN despite a 16× molar excess of BSP adsorbed to plastic. To identify intracellular mediators responsible for this difference in spreading, we investigated focal adhesion kinase (FAK)-Src and Rho-Rho kinase (ROCK) signaling. Although activated FAK localized to the vertices of adhered chondrocytes, levels of FAK activation did not correlate with the extent of spreading. Furthermore, Src inhibition reduced chondrocyte spreading on both FN and BSP, suggesting that FAK-Src signaling is not responsible for less cell spreading on BSP. In contrast, inhibition of Rho and ROCK in chondrocytes increased cell spreading on BSP and membrane protrusiveness on FN but did not affect cell adhesion. In fibroblasts, Rho inhibition increased fibroblast spreading on BSP while ROCK inhibition changed membrane protrusiveness of FN and BSP. In summary, we identify a novel role for Rho-ROCK signaling in regulating chondrocyte spreading and demonstrate both cell- and matrix molecule-specific mechanisms controlling cell spreading.
Induction of oscillatory ventilation pattern using dynamic modulation of heart rate through a pacemaker
Authors: Manisty Charlotte H. , Willson Keith , Davies Justin E. R. , Whinnett Zachary I. , Baruah Resham , Mebrate Yoseph , Kanagaratnam Prapa , Peters Nicholas S. , Hughes Alun D. , Mayet Jamil , Francis Darrel P.
Published: May 2008

For disease states characterized by oscillatory ventilation, an ideal dynamic therapy would apply a counteracting oscillation in ventilation. Modulating respiratory gas transport through the circulation might allow this. We explore the ability of repetitive alternations in heart rate, using a cardiac pacemaker, to elicit oscillations in respiratory variables and discuss the potential for therapeutic exploitation. By incorporating acute cardiac output manipulations into an integrated mathematical model, we observed that a rise in cardiac output should yield a gradual rise in end-tidal CO2 and, subsequently, ventilation. An alternating pattern of cardiac output might, therefore, create oscillations in CO2 and ventilation. We studied the effect of repeated alternations in heart rate of 30 beats/min with periodicity of 60 s, on cardiac output, respiratory gases, and ventilation in 22 subjects with implanted cardiac pacemakers and stable breathing patterns. End-tidal CO2 and ventilation developed consistent oscillations with a period of 60 s during the heart rate alternations, with mean peak-to-trough relative excursions of 8.4 ± 5.0% ( P < 0.0001) and 24.4 ± 18.8% ( P < 0.0001), respectively. Furthermore, we verified the mathematical prediction that the amplitude of these oscillations would depend on those in cardiac output ( r = 0.59, P = 0.001). Repetitive alternations in heart rate can elicit reproducible oscillations in end-tidal CO2 and ventilation. The size of this effect depends on the magnitude of the cardiac output response. Harnessed and timed appropriately, this cardiorespiratory mechanism might be exploited to create an active dynamic responsive pacing algorithm to counteract spontaneous respiratory oscillations, such as those causing apneic breathing disorders.
Upregulation of AT2 receptor and iNOS impairs angiotensin II-induced contraction without endothelium influence in young normotensive diabetic rats
Authors: Lee Jin Hee , Xia Shichao , Ragolia Louis
Published: May 2008

Diabetes and insulin resistance are associated with an increased risk of hypertension and cardiovascular disease. Recent evidence demonstrates that AT2 receptors (AT2R) play an important role in the hemodynamic control of hypertension by vasodilation. The quantitative significance of AT2R in the establishment of diabetic vascular dysfunction, however, is not well defined and needs further investigation. Goto-Kakizaki (GK) rats, a polygenic model of spontaneous normotensive type 2 diabetes, were used to examine any abnormalities in cardiovascular function associated with AT2R at the early stage of the disease without endothelium influence. Using a myograph to measure the isometric force, we observed that ANG II-induced contraction was impaired in denuded GK aorta compared with control Wistar-Kyoto (WKY) aorta and exhibited a retarded AT1R antagonist response and enhanced Rho kinase signaling. When AT1R were blocked, ANG II induced a significant vasodilation of precontracted GK aorta via AT2R. The protein and mRNA of AT2R were increased in diabetic GK denuded aorta. Blocking AT2R restored the ANG II-induced contraction in the GK vasculature to control levels, demonstrating a counteractive role for AT2R in AT1R-induced contraction. Inhibition of inducible nitric oxide synthase (iNOS) by NG-monomethyl-l-arginine mimicked AT2R inhibition in denuded GK aorta, suggesting that AT2R-induced vasodilation was dependent on iNOS/NO generation. The protein and mRNA of iNOS were also increased in GK aorta. In conclusion, these results clearly demonstrate that enhanced AT2R and iNOS-induced, NO-mediated vasodilation impair ANG II-induced contraction in an endothelium-independent manner at the early stage of type 2 diabetes.
Aldosterone induces mesangial cell apoptosis both in vivo and in vitro
Authors: Mathew Jayant T. , Patni Hitesh , Chaudhary Ahmad N. , Liang Wei , Gupta Aakriti , Chander Praveen N. , Ding Guohua , Singhal Pravin C.
Published: May 2008

Both clinical and experimental reports indicate that aldosterone contributes to the progression of renal failure independent of its hemodynamic effects. In the present study, we evaluated effect of aldosterone on human mesangial cell (MC) growth. Aldosterone induced apoptotic and mitogenic effects on MCs. Aldosterone promoted MC apoptosis in a dose- and time-dependent manner. Spironolactone, a mineralocorticoid receptor antagonist, inhibited aldosterone-induced MC apoptosis. Similarly, antioxidants and free radical scavengers partially attenuated proapoaptotic effects of aldosterone. Aldosterone also enhanced dephosphorylation of phospho-Bad and accumulation of cytosolic cytochrome c in MCs. In in vivo studies, rats were randomly assigned to receive normal saline, aldosterone, or eplerenone + aldosterone for 28 days. Systolic blood pressure, urinary albumin excretion rate, serum creatinine, and aldosterone were measured. Aldosterone-infused rats developed elevated systolic blood pressure and albuminuria when compared with control rats. Aldosterone-treated rats also showed greater numbers of apoptosed MCs. This proapoptotic effect of aldosterone was inhibited by eplerenone, a selective aldosterone antagonist. These findings suggest that aldosterone, besides its hemodynamic effects, may also directly contribute to the occurrence of MC apoptosis.
MiRP3 acts as an accessory subunit with the BK potassium channel
Authors: Levy Daniel I. , Wanderling Sherry , Biemesderfer Daniel , Goldstein Steve A. N.
Published: May 2008

MinK-related peptides (MiRPs) are single-span membrane proteins that assemble with specific voltage-gated K+(Kv) channel α-subunits to establish gating kinetics, unitary conductance, expression level, and pharmacology of the mixed complex. MiRP3 (encoded by the KCNE4 gene) has been shown to alter the behavior of some Kv α-subunits in vitro but its natural partners and physiologic functions are unknown. Seeking in vivo partners for MiRP3, immunohistochemistry was used to localize its expression to a unique subcellular site, the apical membrane of renal intercalated cells, where one potassium channel type has been recorded, the calcium- and voltage-gated channel BK. Overlapping staining of these two proteins was found in rabbit intercalated cells, and MiRP3 and BK subunits expressed in tissue culture cells were found to form detergent-stable complexes. Electrophysiologic and biochemical evaluation showed MiRP3 to act on BK to reduce current density in two fashions: shifting the current-voltage relationship to more depolarized voltages in a calcium-dependent fashion (∼10 mV at normal intracellular calcium levels) and accelerating degradation of MiRP3-BK complexes. The findings suggest a role for MiRP3 modulation of BK-dependent urinary potassium excretion.
Regulation of middle cerebral artery blood velocity during dynamic exercise in humans: influence of aging
Authors: Fisher James P. , Ogoh Shigehiko , Young Colin N. , Raven Peter B. , Fadel Paul J.
Published: May 2008

Although cerebral autoregulation (CA) appears well maintained during mild to moderate intensity dynamic exercise in young subjects, it is presently unclear how aging influences the regulation of cerebral blood flow during physical activity. Therefore, to address this question, middle cerebral artery blood velocity (MCA V), mean arterial pressure (MAP), and the partial pressure of arterial carbon dioxide (PaCO2) were assessed at rest and during steady-state cycling at 30% and 50% heart rate reserve (HRR) in 9 young (24 ± 3 yr; mean ± SD) and 10 older middle-aged (57 ± 7 yr) subjects. Transfer function analysis between changes in MAP and mean MCA V (MCA Vmean) in the low-frequency (LF) range were used to assess dynamic CA. No age-group differences were found in PaCO2 at rest or during cycling. Exercise-induced increases in MAP were greater in older subjects, while changes in MCA Vmean were similar between groups. The cerebral vascular conductance index (MCA Vmean/MAP) was not different at rest (young 0.66 ± 0.04 cm·s−1·mmHg−1 vs. older 0.67 ± 0.03 cm·s−1·mmHg−1; mean ± SE) or during 30% HRR cycling between groups but was reduced in older subjects during 50% HRR cycling (young 0.67 ± 0.03 cm·s−1·mmHg−1 vs. older 0.56 ± 0.02 cm·s−1·mmHg−1; P < 0.05). LF transfer function gain and phase between MAP and MCA Vmean was not different between groups at rest (LF gain: young 0.95 ± 0.05 cm·s−1·mmHg−1 vs. older 0.88 ± 0.06 cm·s−1·mmHg−1; P > 0.05) or during exercise (LF gain: young 0.80 ± 0.05 cm·s−1·mmHg−1 vs. older 0.72 ± 0.07 cm·s−1·mmHg−1 at 50% HRR; P > 0.05). We conclude that despite greater increases in MAP, the regulation of MCA Vmean is well maintained during dynamic exercise in healthy older middle-aged subjects.
Unsupervised Whisker Tracking in Unrestrained Behaving Animals
Authors: Voigts Jakob , Sakmann Bert , Celikel Tansu
Published: May 2008

Understanding how whisker-based tactile information is represented in the nervous system requires quantification of sensory input and observation of neural activity during whisking and whisker touch. Chronic electrophysiological methods have long been available to study neural responses in awake and behaving animals; however, methods to quantify the sensory input on whiskers have not yet been developed. Here we describe an unsupervised algorithm to track whisker movements in high-speed video recordings and to quantify the statistics of the tactile information on whiskers in freely behaving animals during haptic object exploration. The algorithm does not require human identification of whiskers, nor does it assume the shape, location, orientation, length of whiskers, or direction of the whisker movements. The algorithm performs well on temporary loss of whisker visibility and under low-light/low-contrast conditions even with inherent anisotropic noise and non-Gaussian variability in the signal. Using this algorithm, we define the speed [protraction (P), 1,081 ± 322; retraction (R), 1,564 ± 549 °/s], duration (P, 34 ± 10; R, 24 ± 8 ms), amplitude (P = R, 40 ± 13°), and frequency (19 ± 7 Hz) of active whisking in freely behaving mice. We furthermore quantify whisker deflection induced changes in whisking kinematics and calculate the statistics (i.e., speed, amplitude and duration) of whisker touch and finally show that whisker deprivation does not alter whisking kinematics during haptic exploration.
Amplitude Cancellation of Motor-Unit Action Potentials in the Surface Electromyogram Can Be Estimated With Spike-Triggered Averaging
Authors: Farina Dario , Cescon Corrado , Negro Francesco , Enoka Roger M.
Published: May 2008

The study presents analytical, simulation, and experimental analyses of amplitude cancellation of motor-unit action potentials (APs) in the interference electromyogram (EMG) and its relation to the size of the spike-triggered average (STA) EMG. The amount of cancellation of motor-unit APs decreases monotonically as a function of the ratio between the root mean square (RMS) of the motor-unit AP and the RMS of the interference EMG signal. The theoretical derivation of this association indicates a method to measure cancellation in individual motor units by STA of the interference and squared EMGs. The theoretical relation was examined in both simulated EMG signals generated by populations of 200 motor units and experimental recordings of 492 and 184 motor-unit APs in the vastus medialis and abductor digiti minimi muscles, respectively. Although the theoretical relation predicted ( R2 = 0.95; P < 0.001) the amount of cancellation in the simulated EMGs, the presence of motor-unit synchronization decreased the strength of the association for small APs. The decrease in size of the STA obtained from the squared EMG relative to that extracted from the interference EMG was predicted by the experimental measure of cancellation ( R2 = 0.65; P < 0.001, for vastus medialis; R2 = 0.26; P < 0.05, for abductor digiti minimi). The results indicate that cancellation of APs in the interference EMG can be analytically predicted and experimentally measured with STA from the discharge times of the motor units into the surface EMG.
Impact Fracture of Composite and Homogeneous Nanoagglomerates
Authors: Antony S. J. , Moreno-Atanasio R. , Musadaidzwa J. , Williams R. A.
Published: May 2008

It is not yet clear on whether the fracture characteristics of structured composite capsules and homogeneous nanoagglomerates differ significantly under impact loading conditions. Experimental measurement of impact fracture properties of such small agglomerates is difficult, due to the length and time scales associated with this problem. Using computer simulations, here we show that nanoagglomerates are subjected to normal impact loading fracture within a few nanoseconds in a brittle manner. The restitution coefficient of the nanoagglomerates varies nonlinearly with initial kinetic energy. The fracture of nanoagglomerates does not always happen at the moment when they experience the maximum wall force, but occurs after a time lag of a few nanoseconds as characterised by impact survival time
(IST) and IST index. IST is dependant on the initial kinetic energy, mechanical and geometric properties of the nanoagglomerates. For identical geometries of the capsules, IST index is higher for capsules with a soft shell than for these with a hard shell, an indication of the enhanced ability of the soft nanocapsules to dissipate impact energy. The DEM simulations reported here based on theories of contact mechanics provide fundamental insights on the fracture behaviour of agglomerates–‐at nanoscale, the structure of the agglomerates significantly influences their breakage behaviour.
Design of Short Synchronization Codes for Use in Future GNSS System
Authors: Shanmugam Surendran K. , Mongrédien Cécile , Nielsen John , Lachapelle Gérard
Published: May 2008

The prolific growth in civilian GNSS market initiated the modernization of GPS and the GLONASS systems in addition to the potential deployment of Galileo and Compass GNSS system. The modernization efforts include numerous signal structure innovations to ensure better performances over legacy GNSS system. The adoption of secondary short synchronization codes is one among these innovations that play an important role in spectral separation, bit synchronization, and narrowband interference protection. In this paper, we present a short synchronization code design based on the optimization of judiciously selected performance criteria. The new synchronization codes were obtained for lengths up to 30 bits through exhaustive search and are characterized by optimal periodic correlation. More importantly, the presence of better synchronization codes over standardized GPS and Galileo codes corroborates the benefits and the need for short synchronization code design.
On the Evection Resonance and Its Connection to the Stability of Outer Satellites
Authors: Yokoyama Tadashi , Vieira Neto Ernesto , Winter Othon Cabo , Sanchez Diogo Merguizo , Brasil Pedro Ivo de Oliveira
Published: May 2008

In terms of stability around the primary, it is widely known that the semimajor axis of the retrograde satellites is much larger than the corresponding semimajor axis of the prograde satellites. Usually this conclusion is obtained numerically, since precise analytical derivation is far from being easy, especially, in the case of two or more disturbers. Following the seminal idea that what is unstable in the restricted three‐body problem is also unstable in the general N‐body problem, we present a simplified model which allows us to derive interesting resonant configurations. These configurations are responsible for cumulative perturbations which can give birth to strong instability that may cause the ejection of the satellite. Then we obtain, analytically, approximate bounds of the stability of prograde and retrograde satellites. Although we recover quite well previous results of other authors, we comment very briefly some weakness of these bounds.
Statistical Analysis of Weighted Networks
Authors: Antoniou I. E. , Tsompa E. T.
Published: May 2008

The purpose of this paper is to assess the statistical characterization of weighted networks in terms of the generalization of the relevant parameters, namely, average path length, degree distribution, and clustering coefficient. Although the degree distribution and the average path length admit straightforward generalizations, for the clustering coefficient several different definitions have been proposed in the literature. We examined the different definitions and identified the similarities and differences between them. In order to elucidate the significance of different definitions of the weighted clustering coefficient, we studied their dependence on the weights of the connections. For this purpose, we introduce the relative perturbation norm of the weights as an index to assess the weight distribution. This study revealed new interesting statistical regularities in terms of the relative perturbation norm useful for the statistical characterization of weighted graphs.
The Distribution of Path Losses for Uniformly Distributed Nodes in a Circle
Authors: Bharucha Zubin , Haas Harald
Published: May 2008

When simulating a wireless network, users/nodes are usually assumed to be distributed uniformly in space. Path losses between nodes in a simulated network are generally calculated by determining the distance between every pair of nodes and applying a suitable path loss model as a function of this distance (power of distance with an environment‐specific path loss exponent) and adding a random component to represent the log‐normal shadowing. A network with N nodes consists of N(N − 1)/2 path loss values. In order to generate statistically significant results for system‐level simulations, Monte Carlo simulations must be performed where the nodes are randomly distributed at the start of every run. This is a time‐consuming operation which need not be carried out if the distribution of path losses between the nodes is known. The probability density function (pdf) of the path loss between the centre of a circle and a node distributed uniformly within a the circle is derived in this work.
Models of Function Type for Commutative Symmetric Operator Families in Krein Spaces
Authors: Strauss Vladimir
Published: May 2008

Commutative symmetric operator families of the so‐called ‐class are considered in Krein spaces. It is proved that the restriction of a family of this type on a special kind of invariant subspace is similar to a family of operators adjoint to multiplication operators by scalar functions acting on a suitable function space.
Laparoscopic Cholecystectomy for Severe Acute Cholecystitis in a Patient with Situs Inversus Totalis and Posterior Cystic Artery
Authors: Pavlidis Theodoros E. , Psarras Kyriakos , Triantafyllou Apostolos , Marakis Georgios N. , Sakantamis Athanasios K.
Published: May 2008

Situs inversus totalis is an inherited condition characterized
by a mirror-image transposition of thoracic and abdominal organs. It often coexists
with other anatomical variations. Transposition of the organs imposes special demands
on the diagnostic and surgical skills of the surgeon. We report a case of a 34-year-old
female patient presented with left upper quadrant pain, signs of acute abdomen, and
unknown situs inversus totalis. Severe acute cholecystitis was diagnosed,
and an uneventful laparoscopic cholecystectomy was performed. A posterior cystic
artery was identified and ligated. Laparoscopic cholecystectomy is feasible in patients
with severe acute calculus cholecystitis and situs inversus totalis; however,
the surgeon should be alert of possible anatomic variations.
Cord Blood Ischemia‐Modified Albumin Levels in Normal and Intrauterine Growth Restricted Pregnancies
Authors: Iacovidou Nicoletta , Briana Despina D. , Boutsikou Maria , Liosi Sophia , Baka Stavroula , Boutsikou Theodora , Hassiakos Demetrios , Malamitsi-Puchner Ariadne
Published: May 2008

Ischemia‐modified albumin (IMA) is a sensitive biomarker of cardiac
ischemia. Intrauterine growth restriction (IUGR) may imply fetal hypoxia,
resulting in blood flow centralization in favour of vital organs (brain, heart,
adrenals—‘‘brain sparing effect’’). Based on the latter, we
hypothesized that cord blood IMA levels should not differ between IUGR and
appropriate‐for‐gestational‐age (AGA) full‐term pregnancies. IMA was measured
in blood samples from doubly‐clamped umbilical cords of 110 AGA and 57
asymmetric IUGR pregnancies. No significant differences in IMA levels
were documented between AGA and IUGR groups. IMA levels were elevated in
cases of elective cesarean section (P = .035), and offspring of
multigravidas (P = .021). In conclusion, ‘‘brain
sparing effect’’ is possibly responsible for the lack of differences in
cord blood IMA levels at term, between IUGR and AGA groups. Furthermore, higher
oxidative stress could account for the elevated IMA levels in cases of elective
cesarean section, and offspring of multigravidas.
Inverse Parameter Identification Technique Using PSO Algorithm Applied to Geotechnical Modeling
Authors: Meier Joerg , Schaedler Winfried , Borgatti Lisa , Corsini Alessandro , Schanz Tom
Published: May 2008

This paper presents a concept for the application of particle swarm optimization in geotechnical engineering. For the calculation of deformations in soil or rock, numerical simulations based on continuum methods are widely used. The material behavior is modeled using constitutive relations that require sets of material parameters to be specified. We present an inverse parameter identification technique, based on statistical analyses and a particle swarm optimization algorithm, to be used in the calibration process of geomechanical models. Its application is demonstrated with typical examples from the fields of soil mechanics and engineering geology. The results for two different laboratory tests and a natural slope clearly show that particle swarms are an efficient and fast tool for finding improved parameter sets to represent the measured reference data.