bluuebunny/crossref_metadata_2025 huggingface dataset:
Water transport by Na+‐coupled cotransporters of glucose (SGLT1) and of iodide (NIS). The dependence of substrate size studied at high resolution
Authors: Zeuthen* Thomas , Belhage Bo , Zeuthen Emil
Published: December 2005

The relation between substrate and water transport was studied in Na+‐coupled cotransporters of glucose (SGLT1) and of iodide (NIS) expressed in Xenopus oocytes. The water transport was monitored from changes in oocyte volume at a resolution of 20 pl, more than one order of magnitude better than previous investigations. The rate of cotransport was monitored as the clamp current obtained from two‐electrode voltage clamp. The high resolution data demonstrated a fixed ratio between the turn‐over of the cotransporter and the rate of water transport. This applied to experiments in which the rate of cotransport was changed by isosmotic application of substrate, by rapid changes in clamp voltage, or by poisoning. Transport of larger substrates gave rise to less water transport. For the rabbit SGLT1, 378 ± 20 (n = 18 oocytes) water molecules were cotransported along with the 2 Na+ ions and the glucose‐analogue α‐MDG (MW 194); using the larger sugar arbutin (MW 272) this number was reduced by a factor of at least 0.86 ± 0.03 (15). For the human SGLT1 the respective numbers were 234 ± 12 (18) and 0.85 ± 0.8 (7). For NIS, 253 ± 16 (12) water molecules were cotransported for each 2 Na+ and 1 thiocyanate (SCN−, MW 58), with I− as anion (MW 127) only 162 ± 11 (19) water molecules were cotransported. The effect of substrate size suggests a molecular mechanism for water cotransport and is opposite to what would be expected from unstirred layer effects. Data were analysed by a model which combined cotransport and osmosis at the membrane with diffusion in the cytoplasm. The combination of high resolution measurements and precise modelling showed that water transport across the membrane can be explained by cotransport of water in the membrane proteins and that intracellular unstirred layers effects are minute.
Neutral Instability and Optimum Convective Mode in a Fluid Layer with PCM Particles
Authors: Dai Chuanshan , Inaba Hideo
Published: December 2005

Linear stability analysis is performed to determine the critical Rayleigh number for the onset of convection in a fluid layer with phase-change-material particles. Sine and Gaussian functions are used for describing the large variation of apparent specific heat in a narrow phase changing temperature range. The critical conditions are numerically obtained using the fourth order Runge-Kutta-Gill finite difference method with Newton-Raphson iteration. The critical eigenfunctions of temperature and velocity perturbations are obtained. The results show that the critical Rayleigh number decreases monotonically with the amplitude of Sine or Gaussian function. There is a minimum critical Rayleigh number while the phase angle is between π∕2 and π, which corresponds to the optimum experimental convective mode.
Exchanger
Performance Behavior Through Irreversibility Analysis for 1-2 TEMA G Heat
Exchangers
Authors: Shah Ramesh
K. , Skiepko Teodor
Published: December 2005

The objective of this paper is to illustrate, discuss, and explain the interrelationship between the temperature difference irreversibility and heat exchanger effectiveness to clarify the performance trends of exchangers with some complex flow arrangements. This is because there is no physical explanation provided for the following results presented by Shah and Skiepko (ASME J. Heat Transfer, 126, pp. 994–1002, 2004): the heat exchanger effectiveness can be maximum, having an intermediate value or minimum at the maximum irreversibility operating point depending upon the flow arrangement of two fluids; similarly, the heat exchanger effectiveness can be minimum or maximum at the minimum irreversibility operating point. The analysis of such complex performance behavior is presented in this paper with an example of overall parallelflow and counterflow 1-2 TEMA G exchangers. This is accomplished by the decomposition of complex flow arrangements into simple subexchangers, and then the overall irreversibility trends for the exchangers are explained by irreversibilities produced due to temperature difference and fluid mixing in component subexchangers. It is shown for 1-2 TEMA G exchangers that the temperature difference irreversibility for a pure parallelflow subexchanger passes through a maximum at finite value of NTU1, and then approaches 0 when NTU1→∞. On the contrary, the irreversibility for a pure counterflow subexchanger attains a minimum value at finite NTU1 and then increases with NTU1 and approaches maximum at NTU1→∞ for 1–2 TEMA G exchangers. This is because the temperatures at the inlet of the subexchangers are variable and dependent on the exit temperatures from the preceding subexchangers. Detailed exchanger effectivenesses and temperature ratios are presented as a function of NTU1 for the explanation.
Heat Transfer Enhancement by Acoustic Streaming in an Enclosure
Authors: Aktas Murat K. , Farouk Bakhtier , Lin Yiqiang
Published: December 2005

Thermal convection in a differentially heated shallow enclosure due to acoustic excitations induced by the vibration of a vertical side wall is investigated numerically. The fully compressible form of the Navier-Stokes equations is considered and an explicit time-marching algorithm is used to track the acoustic waves. Numerical solutions are obtained by employing a highly accurate flux corrected transport algorithm. The frequency of the wall vibration is chosen such that an acoustic standing wave forms in the enclosure. The interaction of the acoustic standing waves and the fluid properties trigger steady secondary streaming flows in the enclosure. Simulations were also carried out for “off-design” vibration frequency where no standing waves were formed. The effects of steady second order acoustic streaming structures are found to be more significant than the main oscillatory flow field on the heat transfer rates. The model developed can be used for the analysis of flow and temperature fields driven by acoustic transducers and in the design of high performance resonators for acoustic compressors.
Steady Laminar Convective Flow with Variable Properties Due to a Porous Rotating Disk
Authors: Maleque Kh. Abdul , Sattar Md. Abdus
Published: December 2005

The present paper investigates the effects of variable properties (density (ρ), viscosity (μ), and thermal conductivity (κ)) on steady laminar flow and heat transfer for a viscous fluid due to an impulsively started rotating porous infinite disk. These properties ρ, μ and κ are taken to be the functions of temperature. The system of axisymmetric nonlinear partial differential equations governing the steady flow and heat transfer are written in cylindrical polar coordinates and are reduced to nonlinear ordinary differential equations by introducing suitable similarity parameters. The resulting steady equations are solved numerically by using Runge-Kutta and Shooting methods, and the effects of the relative temperature difference and suction/injection parameters are examined.
Correlations for the Onset of Instabilities of Spherical Laminar Premixed Flames
Authors: Haq M. Z.
Published: December 2005

A spherically expanding flame in a quiescent premixture is a bifurcation phenomenon, in which the flame becomes unstable at a radius, greater than some critical value, while remaining stable below that critical radius. Beyond this critical radius, developing instabilities are initiated by propagating cracks to form a coherent structure covering the entire flame surface and the flame accelerates. The present paper reports a Schlieren photographic study of spherical flame propagation in methane—air, iso-octane—air and n-heptane—air premixtures at different initial conditions where the onset of instability and the flame acceleration are clearly perceived. Critical size and corresponding elapsed time for the development of such instability are measured and these values are correlated with the appropriate flame parameter.
Cooling of a Finned Cylinder by a Jet Flow of Air
Authors: Gori F. , Borgia M. , Altan A. Doro , Mascia M. , Petracci I.
Published: December 2005

A submerged slot jet of air is used to cool an externally finned cylinder, heated by electric current. The cylinder ensemble is made of a stainless steel finned tube and a Teflon bar core inside. Five thermocouples, pressed inside the steel tube by the Teflon bar, measure the wall temperature to determine local and mean convective heat transfer coefficients. The local Nusselt number has the maximum on the impinging point and the minimum on the rear point. The variation of local and mean Nusselt numbers with the distance from the slot exit is investigated. Empirical expressions are proposed to correlate the experimental data. The cooling of a finned cylinder with a jet flow realizes a higher heat transfer as compared to a smooth cylinder.
A Review of Heat Transfer Issues in Hydrogen Storage Technologies
Authors: Zhang Jinsong , Fisher Timothy S. , Ramachandran P. Veeraraghavan , Gore Jay P. , Mudawar Issam
Published: December 2005

Significant heat transfer issues associated with four alternative hydrogen storage methods are identified and discussed, with particular emphasis on technologies for vehicle applications. For compressed hydrogen storage, efficient heat transfer during compression and intercooling decreases compression work. In addition, enhanced heat transfer inside the tank during the fueling process can minimize additional compression work. For liquid hydrogen storage, improved thermal insulation of cryogenic tanks can significantly reduce energy loss caused by liquid boil-off. For storage systems using metal hydrides, enhanced heat transfer is essential because of the low effective thermal conductivity of particle beds. Enhanced heat transfer is also necessary to ensure that both hydriding and dehydriding processes achieve completion and to prevent hydride bed meltdown. For hydrogen storage in the form of chemical hydrides, innovative vehicle cooling design will be needed to enable their acceptance.
Energy and Exergy Balance in the Process of Pulverized Coal Combustion in a Tubular Combustor
Authors: Som S. K. , Mondal S. S. , Dash S. K.
Published: December 2005

A theoretical model of exergy balance, based on availability transfer and flow availability, in the process of pulverized coal combustion in a tubular air-coal combustor has been developed to evaluate the total thermodynamic irreversibility and second law efficiency of the process at various operating conditions. The velocity, temperature, and concentration fields required for the evaluation of flow availability have been computed numerically from a two-phase separated flow model on a Eulerian-Lagrangian frame in the process of combustion of pulverized coal particles in air. The total thermodynamic irreversibility in the process has been determined from the difference in the flow availability at the inlet and outlet of the combustor. A comparative picture of the variations of combustion efficiency and second law efficiency at different operating conditions, such as inlet pressure and temperature of air, total air flow rate and inlet air swirl, initial mean particle diameter, and length of the combustor, has been provided to shed light on the trade-off between the effectiveness of combustion and the lost work in the process of pulverized coal combustion in a tubular combustor.
Racial differences in child safety restraint use in Tennessee
Authors: Gunn V L , Phillippi R M , Cooper W O
Published: December 2005

Objectives:To evaluate the appropriate use of child safety restraints (CSR) in black and white children.

Design:Cross sectional, observational study of drivers of children age 0–10 years involving an on-site vehicle and CSR inspection and brief driver interview.

Results:Data were obtained on 244 white and 204 black children; results were stratified by race due to effect modification of race on driver restraint use and CSR use. Twenty four percent of black and 13% of white child passengers aged 4–10 years were completely unrestrained (p = 0.003). Of the 168 black and 220 white child passengers aged 0–10 years who were restrained, 64% of black and 58% of white children had inappropriate restraint use. Appropriate CSR use was significantly lower in 4–8 year old passengers compared with appropriately restrained children aged <4 years and 9–10 years (p<0.0001 for both black and white child passengers).

Conclusions:Black child passengers and all child passengers aged 4–8 years are at increased risk of being inappropriately restrained. Educational efforts should address specific barriers to booster seat use in these populations.
Deaths from international terrorism compared with road crash deaths in OECD countries: Table 1
Authors: Wilson N , Thomson G
Published: December 2005

Objective:To estimate the relative number of deaths in member countries of the Organisation for Economic Co-operation and Development (OECD) from international terrorism and road crashes.

Methods:Data on deaths from international terrorism (US State Department database) were collated (1994–2003) and compared to the road injury deaths (year 2000 and 2001 data) from the OECD International Road Transport Accident Database.

Results:In the 29 OECD countries for which comparable data were available, the annual average death rate from road injury was approximately 390 times that from international terrorism. The ratio of annual road to international terrorism deaths (averaged over 10 years) was lowest for the United States at 142 times. In 2001, road crash deaths in the US were equal to those from a September 11 attack every 26 days.

Conclusions:There is a large difference in the magnitude of these two causes of deaths from injury. Policy makers need to be aware of this when allocating resources to preventing these two avoidable causes of mortality.
Injury prevention education in medical schools: an international survey of medical students
Authors: Villaveces A , Kammeyer J A , Bencevic H
Published: December 2005

Background:Injuries account for an estimated 9% of global mortality. Health professionals worldwide receive little formal injury prevention training, especially in developing countries.

Objective:To identify injury prevention training topics taught in a sample of medical schools throughout the world.

Design and setting:Cross sectional survey of 82 medical schools from 31 countries. Based on a convenience sample, respondents recalled the injury prevention concepts they were taught, estimated the time dedicated to these topics, specified the courses and rotations where these concepts were taught, and noted whether they were compulsory or elective sessions.

Participants:Medical students in their last year of medical training.

Main exposure measures:Student recall of classes and rotations where topics of injury prevention and control were discussed.

Results:Basic injury prevention concepts including risk factors for injuries and injury classification systems were not covered in 60% of medical schools. Concepts related to child abuse and neglect and emergency care were more commonly taught than others such as traffic injury prevention and youth violence prevention. In general, injury prevention and control concepts were less frequently taught in Middle Eastern and African universities compared with other regions and some topics such as violence prevention were more frequently taught in medical schools in the Americas. Injury prevention concepts were taught most frequently in preventive medicine, forensic medicine, emergency medicine, surgery and pediatrics courses, and rotations.

Conclusions:Injury prevention and control education is infrequent and fragmented in medical schools around the world. Inclusion or further development of curricula on this subject could benefit prevention and control efforts.
Severity of playground fractures: play equipment versus standing height falls
Authors: Fiissel D , Pattison G , Howard A
Published: December 2005

Aim:To compare the severity of fractures from playground equipment falls to the severity of fractures from standing height falls occurring on the playground.

Methods:This case control study used data on all children presenting to the Hospital for Sick Children (Toronto) from 1995 to 2002 with a fracture due to a playground fall. Cases were children who fell from a height off playground equipment. Controls were children who fell from standing height on a playground. Fractures were major if they required reduction and minor if they did not.

Results:Fractures from equipment falls were 3.91 (95% CI 2.76 to 5.54) times more likely to require reduction than were fractures from standing height falls.

Conclusions:Major fractures were strongly associated with falls from playground equipment, whereas minor fractures came from both play equipment and standing height falls. Efforts to prevent major fractures should target playground equipment and the impact absorbing surface beneath it.
A SIMPLE LOSSLESS COMPRESSION HEURISTIC FOR GREY SCALE IMAGES
Authors: CINQUE LUIGI , DE AGOSTINO SERGIO , LIBERATI FRANCO , WESTGEEST BART
Published: December 2005

In this paper, we show a simple lossless compression heuristic for gray scale images. The main advantage of this approach is that it provides a highly parallelizable compressor and decompressor. In fact, it can be applied independently to each block of 8×8 pixels, achieving 80 percent of the compression obtained with LOCO-I (JPEG-LS), the current lossless standard in low-complexity applications. The compressed form of each block employs a header and a fixed length code, and the sequential implementations of the encoder and decoder are 50 to 60 percent faster than LOCO-I.
SORTING SUFFIXES OF TWO-PATTERN STRINGS
Authors: FRANEK FRANTISEK , SMYTH W. F.
Published: December 2005

Recently, several authors presented linear recursive algorithms for sorting suffixes of a string. All these algorithms employ a similar three-step approach, based on an initial division of the suffixes of x into two sets: Step 1 sorts the first set using recursive reduction of the problem, Step 2 determines the order of the suffixes in the second set based on the order of the suffixes in the first set, and Step 3 merges the two sets together. To optimize such an algorithm either for space or time, it may not be sufficient to optimize one of the three steps, since in doing so, one might increase the resources required for the others to an unacceptable extent.

Franek, Lu, and Smyth introduced two-pattern strings as a generalization of Sturmian strings. Like Sturmian strings, two-pattern strings are generated by iterated morphisms, but they exhibit a much richer structure. In this paper we show that the suffixes of two-pattern strings can be sorted in linear time using a variant of the three-step approach outlined above, but without the need for recursion. It turns out that, given the order of the suffixes in a two-pattern string, one can almost directly list in linear time all the suffixes of its expansion under a two-pattern morphism.
A FULLY COMPRESSED PATTERN MATCHING ALGORITHM FOR SIMPLE COLLAGE SYSTEMS
Authors: INENAGA SHUNSUKE , SHINOHARA AYUMI , TAKEDA MASAYUKI
Published: December 2005

We study the fully compressed pattern matching problem (FCPM problem): Given [Formula: see text] and [Formula: see text] which are descriptions of text T and pattern P respectively, find the occurrences of P in Twithout decompressing[Formula: see text]or[Formula: see text]. This problem is rather challenging since patterns are also given in a compressed form. In this paper we present an FCPM algorithm for simple collage systems. Collage systems are a general framework representing various kinds of dictionary-based compressions in a uniform way, and simple collage systems are a subclass that includes LZW and LZ78 compressions. Collage systems are of the form [Formula: see text], where [Formula: see text] is a dictionary and [Formula: see text] is a sequence of variables from [Formula: see text]. Our FCPM algorithm performs in [Formula: see text] time, where [Formula: see text] and [Formula: see text]. This is faster than the previous best result of O(m2n2) time.
A FRAMEWORK FOR THE DYNAMIC IMPLEMENTATION OF FINITE AUTOMATA FOR PERFORMANCE ENHANCEMENT
Authors: NGASSAM ERNEST KETCHA , WATSON BRUCE W. , KOURIE DERRICK G.
Published: December 2005

The aim of this work is to provide a model for the dynamic implementation of finite automata for enhanced performance. Investigations have shown that hardcoded finite automata outperforms the traditional table-driven implementation up to some threshold. Moreover, the kind of string being recognized plays a major role in the overall processing speed of the string recognizer. Various experiments are depicted to show when the advantages of using hardcoding as basis for implementing finite automata (instead of using the classical table-driven approach) become manifest. The model, a dynamic algorithm that combines both hardcoding and table-driven is introduced.
CONDITIONAL INEQUALITIES AND THE SHORTEST COMMON SUPERSTRING PROBLEM
Authors: Laube Uli , Weinard Maik
Published: December 2005

We investigate the shortest common superstring problem (SCSSP). As SCSSP is APX-complete it cannot be approximated within an arbitrarily small performance ratio. One heuristic that is widely used is the notorious greedy heuristic. It is known, that the performance ratio of this heuristic is at least 2 and not worse than 4. It is conjectured that the greedy heuristic's performance ratio is in fact 2 (the greedy conjecture). Even the best algorithms introduced for SCSSP can only guarantee an upper bound of 2.5. In [11] an even stronger version of the greedy conjecture is proven for a restricted class of orders in which strings are merged. We extend these results by broadening the class for which this stronger version can be established. We also show that the Triple inequality, introduced in [11] and crucial for their results, is inherently insufficient to carry the proof for the greedy conjecture in the general case. Finally we describe how linear programming can be used to support research along this line.
ENUMERATING NONDETERMINISTIC AUTOMATA FOR A GIVEN LANGUAGE WITHOUT CONSTRUCTING THE CANONICAL AUTOMATON
Authors: CHAMPARNAUD J.-M. , COULON F.
Published: December 2005

Our aim is to enumerate all NFAs (nondeterministic finite automata) that recognize a given regular language [Formula: see text]. More precisely, we produce a set 𝔸 of automata such that each automaton A recognizing [Formula: see text] appears in 𝔸 up to the merging of some states and the addition of some transitions, that is, there is a surjective morphism that maps A onto an automaton of 𝔸. We provide a common theoretical framework, based on morphism properties, to previous works of Kameda and Weiner (1970), and of Sengoku (1992), whose issue is the minimization of NFAs. Our paper gives two incomparable enumeration techniques. Both proceed by enumerating a specific class of grid covers of the automaton map. The first one is related to the canonical automaton introduced by Carrez. The second one is based on new outcomes related to the relationship between grid covers and their projections.
NONDETERMINISTIC CIRCUIT MINIMIZATION PROBLEM AND DERANDOMIZING ARTHUR-MERLIN GAMES
Authors: VINODCHANDRAN N. V.
Published: December 2005

We investigate the complexity of strong nondeterministic circuit minimization problem (SNCMP in short) in relation to derandomizing Arthur-Merlin games. We show derandomization results for Arthur-Merlin games under both easiness and hardness assumptions about the complexity of SNCMP. Assuming SNCMP is non-uniformly easy, we present derandomization of Arthur-Merlin games using weaker hardness assumptions than what is currently known. On the other hand, we show that establishing SNCMP is hard for SAT or Graph Isomorphism problem under certain natural reductions will show that Graph Nonisomorphism problem has subexponential proofs of membership. We combine known constructions of pseudorandom and hitting set generators to prove our results.
DYNAMIC POWER MANAGEMENT IN AN EMBEDDED SYSTEM FOR MULTIPLE SERVICE REQUESTS
Authors: VISWANATHAN LAKSHMI PRABHA , MONIE ELWIN CHANDRA
Published: December 2005

Power is increasingly becoming a design constraint for embedded systems. Dynamic Power Management algorithms enable optimal utilization of hardware at runtime. The present work attempts to arrive at an optimal policy to reduce the energy consumption at system level, by selectively placing components into low power states. A new, simple algorithm for power management systems involving multiple requests and services, proposed here, has been obtained from stochastic queuing models. The proposed policy is event driven and based on a Deterministic Markov Nonstationary Policy model (DMNSP). The proposed policy has been tested using a Java-based event driven simulator. The test results show that there is about 23% minimum power saving over the existing schemes with less impact on performance or reliability.
DISCRETE TIME-DOMAIN ANALYSIS OF NONUNIFORM LOSSLESS COUPLED TRANSMISSION LINES
Authors: REZAI-RAD GHOLAMALI , CHELDAVI AHMAD
Published: December 2005

In this paper, a discrete time-domain method to analyze multiple coupled nonuniform lossless transmission lines has been presented. The solution is based on the steplines approximation of the nonuniform transmission lines and quasi-TEM assumptions. Using steplines approximation, the system of coupled nonuniform transmission lines is decomposed into a large number of coupled steplines with different characteristics. Then, using modal decomposition method, the system of coupled partial differential equations for each step is decomposed to a set of uncoupled ordinary wave equation. Using time-domain approach and invoking the boundary condition at the discontinuities of the adjacent steps, each step is modeled as continuous time linear filter characterized by a time-domain transfer matrix. Finally, this continuous time linear filter (for band limited input signal), is modeled as a discrete time-domain linear filter with constant matrix coefficients using sampling theorem. The method proposed here can be implemented using general purpose software packages like MATLAB.
THE PROPER USE OF RISK MEASURES IN PORTFOLIO THEORY
Authors: ORTOBELLI SERGIO , RACHEV SVETLOZAR T. , STOYANOV STOYAN , FABOZZI FRANK J. , BIGLOVA ALMIRA
Published: December 2005

This paper discusses and analyzes risk measure properties in order to understand how a risk measure has to be used to optimize the investor's portfolio choices. In particular, we distinguish between two admissible classes of risk measures proposed in the portfolio literature: safety-risk measures and dispersion measures. We study and describe how the risk could depend on other distributional parameters. Then, we examine and discuss the differences between statistical parametric models and linear fund separation ones. Finally, we propose an empirical comparison among three different portfolio choice models which depend on the mean, on a risk measure, and on a skewness parameter. Thus, we assess and value the impact on the investor's preferences of three different risk measures even considering some derivative assets among the possible choices.
SECOND-ORDER ANALYSIS AND DESIGN OF CABLES AND CABLE-FRAMES
Authors: SHU GANPING , CHAN SIU LAI , LÜ ZHITAO
Published: December 2005

Cable structures are lightweighted, simple to fabricate and reusable. They provide effective solutions for large-span structures. Analysis of cables is complex because of their highly geometrically nonlinear behavior. Based on the Lagrangian formulation and a fourth-order polynomial displacement function, the tangent stiffness matrix for a five-node curved cable element is derived and statically condensed to a simple form readily for incorporation into a frame analysis computer program. The program uses the pointwise–equilibrium–polynomial (PEP) element with initial imperfection and the "Nonlinear Integrated Design and Analysis (NIDA)" method for design and nonlinear analysis of cabled structures. Numerical examples demonstrate the robustness and practicality of the proposed method.
STABILITY AND VIBRATION ANALYSIS OF NON-PRISMATIC THIN-WALLED COMPOSITE SPATIAL MEMBERS OF GENERIC SECTION
Authors: RAJASEKARAN S. , NALINAA K.
Published: December 2005

This paper presents a detailed treatment of the formulation of static, bucking and vibration analysis of non-prismatic thin-walled composite spatial members of generic section. The theory is limited to small strains, moderate deflections and small rotations. The torsional shear strain on the middle surface of the beam wall is zero for an open contour while it corresponds to constant shear flow for a closed contour. Rigorous expressions for strains based on membrane theory of shells are obtained through which the effect of nonlinear tapering is considered. Solutions for classical buckling and vibration analysis by the finite element method are discussed. Numerical integration by using Gaussian quadrature on the cross-sections for the computation of sectorial properties and stress resultants and over the length for the computation of flexural, geometric and mass matrices is suggested. Some examples are solved and critical bucking loads, natural frequencies and the corresponding buckled and mode shapes are obtained by the Jacobi iteration procedure.
CONTINUUM MODEL FOR STABILITY ANALYSIS OF CARBON NANOTUBES UNDER INITIAL BEND
Authors: WANG Q. , XU F. , ZHOU G. Y.
Published: December 2005

Stability analysis of carbon nanotubes (CNT) under initial bend is conducted using continuum elastic beam models for both single wall nanotube (SWNT) and double wall nanotube (DWNT). A discrete beam model is proposed for simulating the mechanism of kink instability, a local buckling phenomenon, of CNTs. Theoretical analysis of the critical axial load for kink instability is carried out with the elastic beam model. Based on the theoretical analysis, the size effect of CNTs on the critical axial force is studied. By setting the initial bend to be zero, the current model can be used to predict the buckling load of a straight CNT as well.
PARAMETRIC COMBINATION RESONANCE CHARACTERISTICS OF DOUBLY CURVED PANELS SUBJECTED TO NON-UNIFORM HARMONIC EDGE LOADING
Authors: UDAR RATNAKAR S. , DATTA P. K.
Published: December 2005

This paper is concerned with the problem of occurrence of combination resonances in parametrically excited doubly curved panels. The dynamic instability of doubly curved panels, subjected to non-uniform in-plane harmonic loading is investigated. Sander's first-order shear deformation theory is used to model the doubly curved panels, considering the effects of transverse shear deformation and rotary inertia. The theory can be reduced to Love's and Donnell's theories by means of tracers. Analytical expressions for the instability regions are obtained at Ω = ωm+ ωn(Ω is the excitation frequency and ωmand ωnare the natural frequencies of the system), by using the method of multiple scales. It is shown that besides the principal instability region at Ω =2ω1, where ω1is the fundamental frequency, other cases of Ω = ωm+ ωnwhich are related to other modes, can be of major importance and yield a significantly enlarged instability region. The results show that under localized edge loading, combination resonance zones are as important as simple resonance zones. The effects of edge loading, curvature, shallowness ratio, edge length to thickness ratio, aspect ratio, boundary conditions and the static load factor on dynamic instability regions are considered.
Balance of bacterial pro- and anti-inflammatory mediators dictates net effect of enteropathogenicEscherichia colion intestinal epithelial cells
Authors: Sharma Rachna , Tesfay Samuel , Tomson Farol L. , Kanteti Rajani P. , Viswanathan V. K. , Hecht Gail
Published: December 2005

Enteropathogenic Escherichia coli (EPEC) virulence requires a type III secretion system (TTSS) to deliver effector molecules in host cells. Although the TTSS is crucial to EPEC pathogenesis, its function in EPEC-induced inflammation is not known. The aim of this study was to investigate the role of the TTSS in EPEC-induced inflammation. HT-29 intestinal epithelial cells were infected with wild-type (WT) EPEC or select mutant strains or exposed to corresponding filter-sterilized supernatants (SN), and interleukin-8 (IL-8) secretion was determined by ELISA. EPEC SN stimulated significantly greater IL-8 production than EPEC organisms. Flagellin, as well as a TTSS-independent >50-kDa nonflagellin protein, was found to significantly contribute to this response. Dose-response studies showed that increasing concentrations of WT SN proportionally increased IL-8, whereas increasing multiplicity of infection of EPEC inversely correlated with IL-8 secretion, suggesting that EPEC dampens this host response. Infection with Δ escN (nonfunctional TTSS) markedly increased IL-8 compared with WT, indicating that a functional TTSS is required for this anti-inflammatory property; complementation of escN restored the attenuated response. Mutation of espB also enhanced the IL-8 response, and complementation returned IL-8 to near WT levels, suggesting involvement of this effector. The anti-inflammatory effect extends to both bacterial and host-derived proinflammatory stimuli, since prior infection with EPEC suppressed the IL-8 response to tumor necrosis factor-α, IL-1β, and enterohemorrhagic E. coli flagellin. These findings indicate that EPEC-induced inflammation is a balance between pro- and anti-inflammatory proteins; extracellular factors, including flagellin and an unidentified TTSS-independent, >50-kDa protein, trigger inflammation while intracellular TTSS-dependent factors, including EspB, attenuate this response.
Inhibition of human pancreatic and biliary output but not intestinal motility by physiological intraileal lipid loads
Authors: Keller Jutta , Holst Jens Juul , Layer Peter
Published: December 2005

Lipid perfusion into the distal ileal lumen at supraphysiological loads inhibits pancreatic exocrine secretion and gastrointestinal motility in humans. In the present study, we sought to determine the effects of physiological postprandial intraileal lipid concentrations on endogenously stimulated pancreaticobiliary secretion, intestinal motility, and release of regulatory mediators. Eight healthy volunteers were intubated with an oroileal multilumen tube for continuous duodenal perfusion of essential amino acids (450 μmol/min), ileal perfusion of graded doses of lipids (0, 50 and 100 mg/min, each dose for 90–120 min), aspiration of duodenal and ileal chyme, and intestinal manometry. Venous blood samples were obtained for measurement of GLP-1 and PYY. Ileal lipid perfusion dose dependently decreased endogenously stimulated trypsin [262 ± 59 vs. 154 ± 42 vs. 92 ± 20 U/min ( P < 0.05)] and bile acid output [18.6 ± 1.9 vs. 8.4 ± 2.8 vs. 3.0 ± 1.0 μmol/min ( P < 0.05)]. Duodenal motor activity was not inhibited by either lipid dose. Trypsin and bile acid output correlated inversely with the release of GLP-1 and PYY (absolute value of R > 0.84; P < 0.05), whereas the motility index did not. Physiological postprandial ileal lipid concentrations dose dependently inhibited human digestive pancreatic protease and bile acid output, but not intestinal motor activity. Thus physiological postprandial ileal nutrient exposure may be of importance for the termination of digestive secretory responses. Ileocolonic release of GLP-1 and PYY appears to participate in mediating these effects.
Hedgehog signaling maintains resident hepatic progenitors throughout life
Authors: Sicklick Jason K. , Li Yin-Xiong , Melhem Alaa , Schmelzer Eva , Zdanowicz Marzena , Huang Jiawen , Caballero Montserrat , Fair Jeff H. , Ludlow John W. , McClelland Randall E. , Reid Lola M. , Diehl Anna Mae
Published: December 2005

Hedgehog signaling through its receptor, Patched, activates transcription of genes, including Patched, that regulate the fate of various progenitors. Although Hedgehog signaling is required for endodermal commitment and hepatogenesis, the possibility that it regulates liver turnover in adults had not been considered because mature liver epithelial cells lack Hedgehog signaling. Herein, we show that this pathway is essential throughout life for maintaining hepatic progenitors. Patched-expressing cells have been identified among endodermally lineage-restricted, murine embryonic stem cells as well as in livers of fetal and adult Ptc-lacZ mice. An adult-derived, murine hepatic progenitor cell line expresses Patched, and Hedgehog-responsive cells exist in stem cell compartments of fetal and adult human livers. In both species, manipulation of Hedgehog activity influences hepatic progenitor cell survival. Therefore, Hedgehog signaling is conserved in hepatic progenitors from fetal development through adulthood and may be a new therapeutic target in patients with liver damage.
Distribution and function of muscarinic receptor subtypes in the ovine submandibular gland
Authors: Tobin G. , Ryberg A. T. , Gentle S. , Edwards A. V.
Published: December 2005

The effects of muscarinic receptor antagonists on responses to electrical stimulation of the chorda-lingual nerve were determined in pentobarbitone-anesthetized sheep and correlated to the morphology of tissue specimens. Stimulation at 2 Hz continuously, or in bursts of 1 s at 20 Hz every 10 s, for 10 min induced similar submandibular fluid responses (19 ± 3 vs. 21 ± 3 μl·min−1·g gland−1), whereas vasodilatation was greater during stimulation in bursts (−52 ± 4 vs. −43 ± 5%; P < 0.01). Continuous stimulation at 8 Hz induced substantially greater responses (66 ± 9 μl·min−1·g gland−1and −77 ± 3%). While atropine (0.5 mg/kg iv) abolished the secretory response at 2 and 20 Hz (1:10 s), a small response persisted at 8 Hz (<5%). The “M1-selective” antagonist pirenzepine (40 μg/kg iv) reduced the fluid response at all frequencies tested ( P < 0.05–0.01), most conspicuously at 2 Hz (reduced by 69%). Methoctramine (“M2/M4-selective”; 100 μg/kg iv; n = 5) had no effect on fluid or the vascular responses but increased the protein output at 2 (+90%, P < 0.05) and 8 Hz (+45%, P < 0.05). The immunoblotting showed distinct bands for muscarinic M1, M3, M4, and M5 receptors, and immunohistochemistry showed muscarinic M1 and M3 receptors to occur in the parenchyma. Thus muscarinic M1 receptors contribute to the secretory response to parasympathetic stimulation but have little effect on the vasodilatation in the ovine submandibular gland. Increased transmitter release caused by blockade of neuronal inhibitory receptors of the M4 subtype would explain the increase in protein output.
A novel method for using accelerometer data to predict energy expenditure
Authors: Crouter Scott E. , Clowers Kurt G. , Bassett David R.
Published: December 2005

The purpose of this study was to develop a new two-regression model relating Actigraph activity counts to energy expenditure over a wide range of physical activities. Forty-eight participants [age 35 yr (11.4)] performed various activities chosen to represent sedentary, light, moderate, and vigorous intensities. Eighteen activities were split into three routines with each routine being performed by 20 individuals, for a total of 60 tests. Forty-five tests were randomly selected for the development of the new equation, and 15 tests were used to cross-validate the new equation and compare it against already existing equations. During each routine, the participant wore an Actigraph accelerometer on the hip, and oxygen consumption was simultaneously measured by a portable metabolic system. For each activity, the coefficient of variation (CV) for the counts per 10 s was calculated to determine whether the activity was walking/running or some other activity. If the CV was ≤10, then a walk/run regression equation was used, whereas if the CV was >10, a lifestyle/leisure time physical activity regression was used. In the cross-validation group, the mean estimates using the new algorithm (2-regression model with an inactivity threshold) were within 0.75 metabolic equivalents (METs) of measured METs for each of the activities performed ( P ≥ 0.05), which was a substantial improvement over the single-regression models. The new algorithm is more accurate for the prediction of energy expenditure than currently published regression equations using the Actigraph accelerometer.
Stretch-shortening cycle exercises: an effective training paradigm to enhance power output of human single muscle fibers
Authors: Malisoux Laurent , Francaux Marc , Nielens Henri , Theisen Daniel
Published: December 2005

Functional performance of lower limb muscles and contractile properties of chemically skinned single muscle fibers were evaluated before and after 8 wk of maximal effort stretch-shortening cycle (SSC) exercise training. Muscle biopsies were obtained from the vastus lateralis of eight men before and after the training period. Fibers were evaluated regarding their mechanical properties and subsequently classified according to their myosin heavy chain content (SDS-PAGE). After training, maximal leg extensor muscle force and vertical jump performance were improved 12% ( P < 0.01) and 13% ( P < 0.001), respectively. Single-fiber cross-sectional area increased 23% in type I ( P < 0.01), 22% in type IIa ( P < 0.001), and 30% in type IIa/IIx fibers ( P < 0.001). Peak force increased 19% in type I ( P < 0.01), 15% in type IIa ( P < 0.001), and 16% in type IIa/IIx fibers ( P < 0.001). When peak force was normalized with cross-sectional area, no changes were found for any fiber type. Maximal shortening velocity was increased 18, 29, and 22% in type I, IIa, and hybrid IIa/IIx fibers, respectively ( P < 0.001). Peak power was enhanced in all fiber types, and normalized peak power improved 9% in type IIa fibers ( P < 0.05). Fiber tension on passive stretch increased in IIa/IIx fibers only ( P < 0.05). In conclusion, short-term SSC exercise training enhanced single-fiber contraction performance via force and contraction velocity in type I, IIa, and IIa/IIx fibers. These results suggest that SSC exercises are an effective training approach to improve fiber force, contraction velocity, and therefore power.
Effects of LPS stimulation on the expression of prostaglandin carriers in the cells of the blood-brain and blood-cerebrospinal fluid barriers
Authors: Kis Bela , Isse Toyohi , Snipes James A. , Chen Lei , Yamashita Hiroshi , Ueta Yoichi , Busija David W.
Published: December 2005

Prostaglandins produced in cerebral endothelial cells (CECs) are the final signal transduction mediators from the periphery to the brain during fever response. However, prostaglandins are organic anions at physiological pH, and they enter cells poorly using simple diffusion. Several transporters have been described that specifically transport prostaglandins across cell membranes. We examined the expression of the two principal prostaglandin carriers, prostaglandin transporter (PGT), and multidrug resistance-associated protein 4 (MRP4) in cells of the blood-brain barrier and in choroid epithelial cells in vitro as well as in vivo in rat brain in control conditions and after lipopolysaccharide (LPS) challenge. We detected PGT in primary cultures of rat CECs, astrocytes, pericytes, and choroid epithelial cells. LPS stimulation had no effect on the expression level of PGT in these cells; however, after LPS stimulation the polarized, dominantly luminal, expression pattern of PGT significantly changed. MRP4 is also expressed in CECs, and its level was not influenced by LPS treatment. In rat brain, PGT was highly expressed in the supraoptic and paraventricular nuclei of the hypothalamus, in the ependymal cell layer of the third ventricle, and in the choroid plexus. LPS treatment increased the expression of PGT in the supraoptic and paraventricular nuclei. Our results suggest that PGT and MRP4 likely play a role in transporting prostaglandins through the blood-brain and blood-cerebrospinal fluid barriers and may be involved in the maintenance of prostaglandin homeostasis in the brain and in the initiation of fever response.
Prawns Masquerading as Endobronchial Tumours
Authors: Sharma M. , Lewis C. , Lewis M.E. , Marzouk J.F.K.
Published: December 2005

This report details the events surrounding the case of an 89-year-old woman referred for surgery with a suspected endobronchial tumour. At rigid bronchoscopy she was found to have inspissated sputum within which the remains of organic foreign bodies (king prawns) were found obstructing the left main and left upper lobe bronchi. We outline her presentation, initial diagnosis and eventual outcome, and re-emphasise the importance of bronchoscopy as a vital tool in the assessment of any endoluminal lesion of the airway.
Influence of Cardiovascular Risk Factors on Endothelial Progenitor Cells
Authors: Werner Nikos , Nickenig Georg
Published: December 2005

The ideal way to prevent and cure atherosclerosis and the subsequent end organ damage is to restore and rejuvenate the dysfunctional vasculature and the damaged organs. Various studies have underlined the important role of bone marrow–derived endothelial progenitor cells (EPCs) in vasculogenesis and angiogenesis of ischemic tissue, but only a few studies have concentrated on the role of EPCs in the prevention and therapy of atherosclerosis. Extended endothelial cell damage by cardiovascular risk factors can result in endothelial cell apoptosis with loss of the integrity of the endothelium. The consequences are an increased vascular permeability of the endothelium followed by facilitated migration of monocytes and vascular smooth muscle cell proliferation, resulting in the premature manifestation of an atherosclerotic lesion. A growing body of evidence suggests that circulating EPCs play an important role in endothelial cell regeneration. Systemic transfusion or intrinsic mobilization of EPCs enhances the restoration of the endothelium after focal endothelial denudation, resulting in a diminished neointima formation. In mice with atherosclerotic lesions, bone-marrow–derived stem cells are able to reduce atherosclerotic plaque size. However, various studies have demonstrated that in humans, cardiovascular risk factors impair number and function of EPCs, potentially restricting the therapeutic potential of progenitor cells. The current review focuses on the role of cardiovascular risk factors on endothelial cell apoptosis and EPCs with its pathophysiological consequences for atherogenesis and a regenerative therapy approach and will highlight the role of EPCs as a marker for cardiovascular mortality and morbidity.