bluuebunny/crossref_metadata_2025 huggingface dataset:
EXPERIMENT STUDY ON DYNAMIC STRENGTH OF LOESS UNDER REPEATED LOAD
Authors: XIAO ZHENGHUA , HAN BO , LIAO HONGJIAN , TUOHUTI AKENJIANG
Published: March 2009

A series of dynamic triaxial tests are performed on normal anisotropic consolidation and over anisotropic consolidation specimens of loess. Based on the test results, the variable regularity of dynamic shear stress, axial strain and pore water pressure of loess under dynamic loading are measured and analyzed. The influences of the dynamic shear strength and pore water pressure at different over consolidation ratio are analyzed. The relationship between dynamic shear strength and over consolidation ratio of loess is obtained. The evaluating standard of dynamic shear strength of loess is discussed. Meanwhile, how to determine the effective dynamic shear strength index of normal anisotropic consolidated loess is also discussed in this paper. Several obtained conclusions can be referenced for studying the dynamic shear strength of loess foundation.
STUDY ON STRESS-STRAIN RELATIONSHIP OF LOESS BASED ON TWIN SHEAR UNIFIED DAMAGE CONSTITUTIVE MODEL
Authors: HAN BO , LI HANGZHOU , LIAO HONG-JIAN , XIAO ZHENGHUA
Published: March 2009

To investigate the change of loess stress state, a series of triaxial shear tests were performed on normal consolidation and over consolidation loess. From the test results, the stress-strain relationships of loess were obtained and discussed. Based on unified strength theory, the statistical damage constitutive equation was obtained under triaxial stress state assuming distribution statistical probability of micro-units strength. Then the proposed formulation was adopted to study on stress-strain constitutive relationships of loess and to simulate consolidation undrained triaxial test and consolidation drained triaxial test for normal consolidated and over-consolidated specimens. Compared between experimental and theoretical results, it was shown that the proposed constitutive model can well describe stress-strain relationship of loess, whatever the characteristic of strain softening or stain hardening.
THE STUDY ON THE GAS PERMEABILITIES OF THE ETHYLENE/1-HEXENE COPOLYMER BY MOLECULAR DYNAMICS SIMULATION
Authors: WU SIZHU , YI JUN , ZHANG LISHU , ZHANG LIQUN , MARK JAMES E.
Published: March 2009

In this research, molecular dynamics(MD) simulations were used to study the transport properties of small gas molecules in poly(ethylene-co-1-hexene) copolymer. The condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS) forcefield was applied. The diffusion coefficients were obtained from MD (NVT ensemble). The results indicated that the diffusion coefficient of oxygen increased with increasing 1-hexene content in copolymer membrane.
ENERGY OF ARMCHAIR NANOTUBE USING THE MODIFIED CAUCHY-BORN RULE
Authors: LU S. , CHO C.D. , SONG L.
Published: March 2009

Due to the difference of nanotube diameters, the single-walled carbon nanotubes (SWCNTs) show the different energy and mechanical properties. In order to take the effect of the curvature of nanotubes into account in the modeling of those structures, the present paper proposes an atomistic based continuum model with using a type of modified Cauchy-Born to link the continuum strain energy to the interatomic potential. This modified Cauchy-Born is developed by incorporating the concept of differential mean value theorem into the standard Cauchy-Born rule. The present model not only can bridge the microscopic and macroscopic length scales, but also can investigate the curvature effect of a single layer film on the continuum level. Application of the current model to armchair carbon nanotubes and graphite shows an excellent prediction of the size dependent strain energy which are compared in a good agreement with the existing experimental and theoretical results.
EFFECT OF TRANSFORMATION VOLUME STRAIN ON THE SPHERICAL INDENTATION OF SHAPE MEMORY ALLOYS
Authors: YAN WENYI , SUN QINGPING , LIU HONG-YUAN
Published: March 2009

The mechanical response of spherical indentation of superelastic shape memory alloys (SMAs) was theoretically studied in this paper. Firstly, the friction effect was examined. It was found that the friction influence is negligibly small. Secondly, the influence of the elasticity of the indenter was investigated. Numerical results indicate that this influence can not be neglected as long as the indentation depth is not very small. After that, this paper focused on the effect of transformation volume contraction. Our results show that the transformation volume contraction due to forward martensitic transformation can reduce the maximum indentation force and the spherical indentation hardness. These research results enhance our understanding of the spherical indentation responses, including the hardness of the smart material SMAs.
TEXTURES OF EQUAL CHANNEL ANGULAR PRESSED 1050 ALUMINUM ALLOY STRIPS
Authors: PARK JAE YEOL , HONG SEUNG-HYUN , LEE DONG NYUNG
Published: March 2009

In order to improve the deep drawability of aluminum and aluminum alloy sheets, it is desirable to increase the ND//<111> component in their textures. The ND//<111> component is known to develop in shear-deformed fcc alloy sheets. The equal-channel angular pressing (ECAP) is a process in which materials undergo approximately simple shear deformation. The deformation texture of ECAPed strips can change depending on process variables such as the texture of starting strips, the oblique angle, the number of pressing passes, and the shear direction. The deformation and deformation texture have been analyzed.
FLD OF AZ31 SHEET UNDER WARM STRETCHING AND ITS PREDICTION
Authors: NAKA TETSUO , NAKAYAMA YASUHIDE , UEMORI TAKESHI , HINO RYUTARO , YOSHIDA FUSAHITO , KOHZU MASAHIDE , HIGASHI KENJI
Published: March 2009

Forming Limit Diagrams (FLDs) of a magnesium alloy (AZ31) sheet at various forming speeds (3 to 300 mm·mm-1) at several temperatures of 100-250°C were investigated by performing a punch stretch-forming test. The forming limit strains increased with temperature rise and with decreasing forming speed, where the effect of forming speed was stronger at higher temperatures. To describe such a characteristic of FLD of AZ31, the Marciniak-Kucznski type forming limit analysis was conducted using the Backofen-type constitutive equation (c = Cεnεm). In this analysis, the damage evolution in the necking zone was taken into account based on Oyane's ductile fracture criterion. The numerical results of the FLD show a good agreement with the corresponding experimental observations.
EFFECT OF INITIAL MICROSTRUCTURE ON HOT FORGING OF MG ALLOYS
Authors: KWON Y. , LEE Y. , KIM S. , LEE J.
Published: March 2009

Magnesium alloys still have a lot of technical challenges to be solved for more applications. There have been many research activities to enhance formability of magnesium alloys. One is to design new alloy composition having better formability. Also, low formability of wrought alloys can be improved by optimizing the processing variables. In the present study, effect of process variables such as forging temperature and forging speed were investigated to forgeability of three different magnesium alloys such as AZ31, AZ61 and ZK60. To understand the effect of process variables more specifically, both numerical and experimental works have been carried out on the model which contains both upsetting and extrusion geometries. Forgeability of magnesium alloys was found to depend more on the forging speed rather than temperature. Forged sample showed a significant activity of twinning, which was found to be closely related with flow uniformity.
THE UNLOADING MODULUS OF AKDQ STEEL AFTER UNIAXIAL AND NEAR PLANE-STRAIN PLASTIC DEFORMATION
Authors: PAVLINA E. J. , LEVY B. S. , VAN TYNE C. J. , KWON S. O. , MOON Y. H.
Published: March 2009

Springback is a problem in the manufacture of a variety of automotive components. To determine springback, it is necessary to know the strength of the material after plastic deformation and the slope of the unloading curve (i.e. the unloading modulus). Prior investigations have shown that the unloading modulus for steels after plastic deformation has a slope that is lower than the normally accepted value for Young's modulus. Previous studies on the slope of the unloading curve were after uniaxial tensile plastic deformation. In the present study, the unloading modulus for an aluminum killed drawing quality (AKDQ) steel was evaluated after both uniaxial and near plane strain deformation. A tube hydroforming system was used for near plane-strain deformation. The average unloading modulus following uniaxial deformation for the AKDQ steel is approximately 168 GPa. The average unloading modulus for the circumferential stress component after near plane-strain deformation is lower than after uniaxial deformation. For a given amount of overall plastic deformation, the axial component of the unloading modulus is greater than the circumferential component, and with increased plastic strain, the unloading modulus for both components decreases. These results demonstrate that the components of the unloading modulus are dependent on the strain path of the prior plastic deformation.
SPRING-BACK CHARACTERISTICS OF GRAIN-REFINED MAGNESIUM ALLOY ZK60 SHEET
Authors: KANG SEONG-HOON , LEE YOUNG-SEON , LEE JUNG-HWAN
Published: March 2009

In this work, the effect of grain size on the spring-back characteristic was investigated by carrying out air-bending test using magnesium alloy ZK60 sheet with thickness of 0.5 mm at the various temperatures from room temperature to 300 °C. The angles of the bent specimen before and after unloading were measured in order to quantify spring-back amount. It was found out from the bending tests that when the specimens with grain sizes of 14.66 and 60.71 µm were bent by 90°, the amount of spring-back was relatively small at the testing temperature range and was in the range between -2.5° and 2.5°. On the other hand, the spring-back amount dramatically increased at room temperature and phenomenon of spring-go was observed at high temperature when the specimen with submicro grain size of 0.98 µm was bent by 90°. From this finding, it was confirmed that the different spring-back characteristics according to the grain size takes place and thus the grain size of material is one of the important factors which have an effect on the spring-back.
INFLUENCE OF BILLET SIZE ON THE DEFORMATION INHOMOGENEITY OF MATERIAL PROCESSED BY EQUAL CHANNEL ANGULAR PRESSING
Authors: SUO TAO , LI YULONG , ZHAO FENG
Published: March 2009

Equal channel angular pressing provides a convenient procedure for introducing an ultrafine grained microstructure into materials. In this paper, the deformation distribution of cylindrical billet with different diameters during equal channel angular pressing (ECAP) was simulated using 3D finite element models. The plastic strains in three perpendicular planes of the billet are predicted. And the influence of the friction between billet and channel on the equivalent plastic strain is also determined. The results show that the equivalent plastic strains are inhomogeneous in three directions and the inhomogeneity of the strain distribution inside ECAPed materials is slightly related to their diameters, which means larger scale UFG materials can be achieved via ECAP process.
COMPARING SLIDING-WEAR CHARACTERISTICS OF THE ELECTRO-PRESSURE SINTERED AND WROUGHT COBALT
Authors: LEE J. E. , KIM Y. S. , KIM T. W.
Published: March 2009

Dry sliding wear tests of hot-pressure sintered and wrought cobalt were carried out to compare their wear characteristics. Cobalt powders with average size of 1.5µm were electro-pressure sintered to make sintered-cobalt disk wear specimens. A vacuum-induction melted cobalt ingot was hot-rolled at 800°C to a plate, from which wrought-cobalt disk specimens were machined. The specimens were heat treated at various temperatures to vary grain size and phase fraction. Wear tests of the cobalt specimens were carried out using a pin-on-disk wear tester against a glass (83% SiO 2) bead at 100N with the constant sliding speed and distance of 0.36m/s and 600m, respectively. Worn surfaces, their cross sections, and wear debris were examined by an SEM. The wear of the cobalt was found to be strongly influenced by the strain-induced phase transformation of ε- Co ( hcp ) to α- Co ( fcc ). The sintered cobalt had smaller uniform grain size and showed higher wear rate than the wrought cobalt. The higher wear rate of the sintered cobalt was explained by the more active deformation-induced phase transformation than in the wrought cobalt with larger irregular grains.
MULTI-SCALE CREEP ANALYSIS OF PLAIN-WOVEN LAMINATES USING TIME-DEPENDENT HOMOGENIZATION THEORY: EFFECTS OF LAMINATE CONFIGURATION
Authors: NAKATA K. , MATSUDA T. , KAWAI M.
Published: March 2009

In this study, multi-scale creep analysis of plain-woven GFRP laminates is performed using the time-dependent homogenization theory developed by the present authors. First, point-symmetry of internal structures of plain-woven laminates is utilized for a boundary condition of unit cell problems, reducing the domain of analysis to 1/4 and 1/8 for in-phase and out-of-phase laminate configurations, respectively. The time-dependent homogenization theory is then reconstructed for these domains of analysis. Using the present method, in-plane creep behavior of plain-woven glass fiber/epoxy laminates subjected to a constant stress is analyzed. The results are summarized as follows: (1) The in-plane creep behavior of the plain-woven GFRP laminates exhibits marked anisotropy. (2) The laminate configurations considerably affect the creep behavior of the laminates.
LOAD-CARRYING CAPACITIES FOR CIRCULAR METAL FOAM CORE SANDWICH PANELS AT LARGE DEFLECTION
Authors: HOU W. , WANG Z. , ZHAO L. , LU G. , SHU D.
Published: March 2009

This paper is concerned with the load-carrying capacities of a circular sandwich panel with metallic foam core subjected to quasi-static pressure loading. The analysis is performed with a newly developed yield criterion for the sandwich cross section. The large deflection response is estimated by assuming a velocity field, which is defined based on the initial velocity field and the boundary condition. A finite element simulation has been performed to validate the analytical solution for the simply supported cases. Good agreement is found between the theoretical and finite element predictions for the load-deflection response.
ANALYSIS OF ELASTO-PLASTIC STRESS WAVES BY A TIME-DISCONTINUOUS VARIATIONAL INTEGRATOR OF HAMILTONIAN
Authors: CHO SANG-SOON , HUH HOON , PARK KWANG-CHUN
Published: March 2009

This paper proposes a numerical algorithm of a time-discontinuous variational integrator based on the Hamiltonian in order to obtain more accurate results in the analysis of elasto-plastic stress wave. The algorithm proposed adopts both a time-discontinuous variational integrator and space-continuous Hamiltonian so as to capture discontinuities of stress waves. The algorithm also adopts the limited kinetic energy to enhance the stability of the numerical algorithm so as to solve the discontinuities such as elastic unloading and internal reflection in plastic deformation. Finite element analysis of one dimensional elasto-plastic stress waves is carried out in order to demonstrate the accuracy of the algorithm proposed.
VISCO-ELASTIC AND PLASTIC SINGULAR BEHAVIORS OF AN INTERFACE CORNER IN ELECTRONIC PACKAGES
Authors: XU JIN-QUAN , ZHENG HUIMIAO , ZHU HONGLAI
Published: March 2009

Failure of an electronic package generally initiates from the interface corners, due to the stress and strain singular behaviors near the corners. Since the solder materials are viscous elastic and even maybe viscous plastic, the singular behavior near the solder joint corner is thereby time-dependent, and is quite different from that of an elastic one. It is necessary to clarify such a singular behavior for the strength and life evaluation of an electronic package. This paper firstly has deduced the approximated viscous elastic singular fields theoretically based on the principle of correspondence and the Laplace transformation techniques, and secondly has investigated the viscous plastic singular behavior of an elastic-plastic interface corner by the analogue method; finally the numerical analysis of an electronic package has been carried out to show the details of the singular behaviors.
ENTANGLEMENT DIVERSION BETWEEN TWO PAIRS OF ENTANGLED COHERENT STATES: FIDELITY AND DECOHERENCE
Authors: PRAKASH H. , CHANDRA N. , PRAKASH R. , KUMAR SHIVANI A.
Published: March 2009

We consider the scheme for entanglement diversion proposed by Xin-Hua with our suggested modification (in press, issue 1 Jan 2009) and discuss the effect of decoherence on fidelity in such entanglement diversion. For odd photon counts, the fidelity decreases with increase in |α|2 for low noise but in the case of high noise, it increases, attains a maximum value and then decreases with |α|2. However, for nonzero even photon counts, the case is reversed. For this case, fidelity decreases with increase in |α|2 for high noise but in the case of low noise, it increases, attains a maximum value and then decreases with |α|2.
THE MULTI-SOLITON SOLUTIONS FOR THE NON-ISOSPECTRAL mKdV–SINE-GORDON EQUATION
Authors: ZHAO SONG-LIN , HAO HONG-HAI , ZHANG DA-JUN
Published: March 2009

We derive multi-soliton solutions for a non-isospectral mKdV–sine-Gordon equation by means of a bilinear approach. Solutions are given in both Hirota's form and Wronskian form. This non-isospectral equation is a generic one which is related to a time-dependent spectral parameter with time evolution [Formula: see text].
EXACT SOLUTIONS OF THE SCHRÖDINGER EQUATION WITH THE SECOND PÖSCHL–TELLER-LIKE POTENTIAL
Authors: DONG SHI-HAI , GARCIA-RAVELO J.
Published: March 2009

The exact solutions of the Schrödinger equation with the second Pöschl–Teller-like potential are presented. Two special cases are studied briefly.
SIMULATION OF TURBULENT FLOW IN A COMPLEX PASSAGE WITH A VIBRATING STRUCTURE BY FINITE ELEMENT FORMULATIONS
Authors: ZHANG L. X. , GUO Y.
Published: March 2009

A modeling of the turbulent flow in a complex passage with dynamical fluid-structure interaction (FSI) is established on the generalized variational principle. A monolithic coupling method on the finite element formulations (FEM) is used to realize numerical computation of the flow with dynamical FSI. The comparisons with LES show that the results on the FEM formulations suggested in this paper are favorable, and the computing effort is economical.
GHOST-CELL METHOD FOR INVISCID THREE-DIMENSIONAL FLOWS WITH MOVING BODY ON CARTESIAN GRIDS
Authors: LIU JIANMING , ZHAO NING , HU OU
Published: March 2009

This paper depicts a ghost cell method to solve the three dimensional compressible time-dependent Euler equations using Cartesian grids for static or moving bodies. In this method, there is no need for special treatment corresponding to cut cells, which complicate other Cartesian mesh methods, and the method avoids the small cell problem. As an application, we present some numerical results for a special moving body using this method, which demonstrates the efficiency of the proposed method.
NUMERICAL SIMULATION OF HIGH-TEMPERATURE IONIZED AIR RADIATION ON UNSTRUCTURED GRIDS
Authors: LIU XUEQIANG , WANG YIBIN , WU YIZHAO
Published: March 2009

A numerical method which is based on unstructured grids to compute high-temperature ionized air radiation is described. The multi-species N-S equations are used and the chemical model includes 11 species ( O 2, N 2, O , N , NO , NO +, N +, O +, N +2, O +2, e -) and 20 reactions. For simulating thermal non-equilibrium effect, the two-temperature model is considered. The finite volume method (FVM) is used for spatial and directional discretization for the RTE on unstructured grids. The code can deal with different kinds of species and radiative bands. Particularly, the Delta, Epsilon, Beta prime and Gamma prime bands of NO are considered in this paper. The numerical results of MESES-C for hypersonic flow with high-temperature ionized radiation are shown, and compared well with the reference data and experimental data.
THERMAL CHARACTERISTICS OF FOAMS AND DISCHARGE FROM FIRE-EXTINGUISHMENT FOAM SPRAY NOZZLE
Authors: KIM YOUN-JEA , PYO JIN-SOO
Published: March 2009

To evaluate the performance of discharged foam agents used to protect structures from heat and fire damages, the thermal characteristics of fire-extinguishment foams were experimentally investigated. Especially, two different parameters of a spray nozzle, that is, the number of air holes and the orifice diameter, were considered. A simple repeatable test for fire-extinguishment foams subjected to fire radiation was performed. Experimental results showed that the expansion ratio of the discharged foam with the small orifice throat ( d 0= 9.5 mm ) and opened air hole ( N h =9) was large. Results also showed that although the temperature gradient in the foam increased as the foam expansion ratio is increased, it remained constant as the intensity of heat flux increased.
PIV MEASUREMENTS OF DUAL SYNTHETIC JETS ACTUATOR DRIVEN BY ELECTRICAL FACTORS
Authors: LUO ZHEN-BING , XIA ZHI-XUN , LIU BING , WANG DE-QUAN , HU JIAN-XIN , WANG LIN
Published: March 2009

A dual synthetic jets actuator driven by different electrical factors was investigated using particle image velocimetry (PIV). A transfer-phase and sub-frequency technique was provided to capture the arbitrary phase of the dual synthetic jets, and a transfer-phase to equal technique was provided to determine the phase of the dual synthetic jets. The results show that both the amplitude and frequency of the electrical forcing voltages vastly affect the flow-field of the dual synthetic jets actuator. Both the forcing frequency and the driving voltage amplitudes contribute to the pressure difference and the area of the lower pressure, which determines the interactions of dual synthetic jets. The dual synthetic jet actuator exits a circumscription of electrical factors in which the actuator works efficiently.
AEROELASTIC PHENOMENA OF FLIGHT VEHICLES IN TRANSONIC REGION
Authors: LEE IN , KIM JONG-YUN , KIM KYUNG-SEOK , LIM IN-GYU
Published: March 2009

Flight vehicles experience aeroelastic problems due to the interaction between structures and aerodynamic forces. Aeroelastic instability is usually a critical problem in transonic and lower supersonic regions. In present study, the aeroelastic analyses of several flight vehicles have been performed using the coupled techniques of computational fluid dynamics (CFD) and computational structural dynamics (CSD). The aeroelastic characteristics based on several aircraft models are investigated using the developed aeroelastic analysis system. On the other hand, structural nonlinearities always exist in flight vehicles. Structural nonlinearities such as freeplay and large deformation effects are considered in the present aeroelastic analysis system. Finally, aeroelastic characteristics of several flight vehicles will be explained considering both aerodynamic and structural nonlinearities.
THE TECHNIQUE OF THE IMMERSED BOUNDARY METHOD: APPLICATIONS TO THE NUMERICAL SOLUTIONS OF IMCOMPRESSIBLE FLOWS AND WAVE SCATTERING
Authors: CHEN HONGQUAN , RAO LING
Published: March 2009

A fictitious domain method, in which the Dirichlet boundary conditions are treated using boundary supported Lagrangian multipliers, is considered. The technique of the immersed boundary method is incorporated into the framework of the fictitious domain method. Contrary to conventional methods, it does not make use of the finite element discretization. It has a simpler structure and is easily programmable. The numerical simulation of two-dimensional incompressible inviscid uniform flows over a circular cylinder validates the methodology and the numerical procedure. The numerical simulation of propagation phenomena for time harmonic electromagnetic waves by methods combining controllability and fictitious domain techniques is also presented. Using distributed Lagrangian multipliers, the propagation of the wave can be simulated on an obstacle free computational region with regular finite element meshes essentially independent of the geometry of the obstacle and by a controllability formulation which leads to algorithms with good convergence properties for time-periodic solutions. The numerical results presented are in good agreement with those in the literature using obstacle fitted meshes.
A TIME-DOMAIN METHOD FOR TRANSONIC FLUTTER ANALYSIS WITH MULTIDIRECTIONAL COUPLED VIBRATIONS
Authors: GUO TONGQING , LU ZHILIANG , WU YONGJIAN
Published: March 2009

Gridgen is employed for static multi-block grid generation. A rapid deforming technique is employed for dynamic grids. Flutters are numerically analyzed in the time domain with a coupled solution of unsteady Euler equations and structural equations of motion. Based on variable stiffness method of transonic flutter analysis, a time-domain method of transonic flutter analysis with multi-directional coupled vibrations is develpoed. For completeness, flutter characteristics of a wing model with winglets and an aircraft model with external stores are numerically analyzed.
TRANSONIC AEROELASTIC ANALYSIS OF AIRCRAFT WINGS CONSIDERING THE BOUNDARY-LAYER EFFECTS
Authors: KIM JONG-YUN , KIM KYUNG-SEOK , LEE SEUNG-JUN , LEE IN
Published: March 2009

Aerodynamic solver using the transonic small-disturbance (TSD) equation has frequently been used to perform practical aeroelastic analysis for many aircraft models. In the present study, the more accurate aeroelastic analysis solver using the TSD equation was developed by considering the viscous effects of the boundary-layer. The viscous effects were considered using Green's lag-entrainment equations and an inverse boundary-layer method. Through aerodynamic analyses for several aircraft wings, the viscous-inviscid interaction approach could improve the accuracy of the aerodynamic computation using the TSD equation. Finally, the aeroelastic characteristics were investigated using comparisons of the time responses between the inviscid and viscous flows.
LEAST SQUARE ANALYSIS OF ERROR-COMPONENTS MODEL FOR THE STUDY OF PROVINCIAL ECONOMIC PERFORMANCE
Authors: WU LIHUA
Published: March 2009

The pattern of provincial economic integration in a country can be well measured by the error-components model, which enables us to attribute the variation of real output growth to factors that are industry specific and those that are province specific. Usually, the error-components model equation is solved by the dummy variable regression method. This paper presents an alternative approach, that is, the least square method, which can solve the error components model equation effectively. The presented approach is validated by its application to study the pattern of provincial economic integration in China for the period 1996-2004.
SALINITY BUILD-UP DUE TO BRINE DISCHARGES INTO SHALLOW COASTAL WATERS
Authors: SHAO DONGDONG , LAW ADRIAN WING-KEUNG
Published: March 2009

A two-dimensional mathematical model simulating the long-term build-up of salinity around the brine outfall is developed in this paper. A flat seabed and steady longshore current are assumed as a first step towards modelling the actual scenario. Transient and steady-state analytical solutions for continuous point source condition are derived. These solutions are then applied to assess shoreline/offshore discharge. Characteristic features such as the temporal buildup of salinity excess and the variation of the shoreline salinity with respect to time and outfall location are investigated. The effect of the advection-to-diffusion ratio ν in the modelling results is also discussed.
Aldosterone in the brain
Authors: Geerling Joel C. , Loewy Arthur D.
Published: March 2009

Pharmacological and physiological phenomena suggest that cells somewhere inside the central nervous system are responsive to aldosterone. Here, we present the fundamental physiological limitations for aldosterone action in the brain, including its limited blood-brain barrier penetration and its substantial competition from glucocorticoids. Recently, a small group of neurons with unusual sensitivity to circulating aldosterone were identified in the nucleus of the solitary tract. We review the discovery and characterization of these neurons, which express the enzyme 11β-hydroxysteroid dehydrogenase type 2, and consider alternative proposals regarding sites and mechanisms for mineralocorticoid action within the brain.
Sensory Signals of Unloading in One Leg Follow Stance Onset in Another Leg: Transfer of Load and Emergent Coordination in Cockroach Walking
Authors: Zill Sasha N. , Keller Bridget R. , Duke Elizabeth R.
Published: March 2009

The transfer of load from one leg to another is an essential component in walking, but sense organs that signal this process have rarely been identified. We used high-speed digital imaging and neurophysiological recordings to characterize activities of tibial campaniform sensilla, receptors that detect forces via cuticular strains, in the middle legs of cockroaches during walking. Previous studies demonstrated that the distal tibial sensilla discharge when body load is suddenly decreased in freely standing animals. Sensory recordings during walking showed that distal receptors in the middle leg fired an intense burst near the end of the stance phase. We tested the hypothesis that initiation of distal firing resulted from the action of other legs entering stance. Analysis of leg movements in slow walking showed that sensory bursts in the middle leg closely followed stance onset of the ipsilateral hind leg while the ipsilateral front leg entered stance earlier in phase. Similar phases of leg movement were found in slow walking in experiments in which animals had no implanted recording wires. Those studies also demonstrated that the opposite middle leg entered stance earlier in phase. Measurements of leg positions in walking showed that the hind leg tarsus was placed closest to the middle leg, in keeping with a “targeting” strategy. Triggering of distal bursts in the middle leg by mechanical action of the hind leg could facilitate the onset of swing in the middle leg through local reflex effects and contribute to emergent coordination of leg movements in metachronal gaits.
Neural Control of Visual Search by Frontal Eye Field: Effects of Unexpected Target Displacement on Visual Selection and Saccade Preparation
Authors: Murthy Aditya , Ray Supriya , Shorter Stephanie M. , Schall Jeffrey D. , Thompson Kirk G.
Published: March 2009

The dynamics of visual selection and saccade preparation by the frontal eye field was investigated in macaque monkeys performing a search-step task combining the classic double-step saccade task with visual search. Reward was earned for producing a saccade to a color singleton. On random trials the target and one distractor swapped locations before the saccade and monkeys were rewarded for shifting gaze to the new singleton location. A race model accounts for the probabilities and latencies of saccades to the initial and final singleton locations and provides a measure of the duration of a covert compensation process—target-step reaction time. When the target stepped out of a movement field, noncompensated saccades to the original location were produced when movement-related activity grew rapidly to a threshold. Compensated saccades to the final location were produced when the growth of the original movement-related activity was interrupted within target-step reaction time and was replaced by activation of other neurons producing the compensated saccade. When the target stepped into a receptive field, visual neurons selected the new target location regardless of the monkeys’ response. When the target stepped out of a receptive field most visual neurons maintained the representation of the original target location, but a minority of visual neurons showed reduced activity. Chronometric analyses of the neural responses to the target step revealed that the modulation of visually responsive neurons and movement-related neurons occurred early enough to shift attention and saccade preparation from the old to the new target location. These findings indicate that visual activity in the frontal eye field signals the location of targets for orienting, whereas movement-related activity instantiates saccade preparation.
A 6-Month, Office-Based, Low-Carbohydrate Diet Intervention in Obese Teens
Authors: Siegel Robert M. , Rich Whitney , Joseph Evelyn C. , Linhardt Joan , Knight Jamie , Khoury Jane , Daniels Stephen R.
Published: March 2009

Background. Previous studies have shown the success of a low-carbohydrate diet (LCD) in adults. In one study, the LCD has also been shown as safe and effective in teens, the study period was only 12 weeks. Furthermore, there is no information on whether the LCD is a practical intervention in a pediatric office setting. Objective. The object of this study was to demonstrate the effectiveness of a LCD in obese children in a primary care pediatric setting. Design/Methods . The study was done in 11 community pediatric practices. Children ages 12 to 18 years with a body mass index (BMI) greater than 95th percentile were put on a LCD of less than 50 grams of carbohydrate daily. Results . A total of 38 of the 63 teens finished the 6-month study and 32 (84%) lost weight (range from a gain of 5.5 kg to a loss of 23.9 kg). There was also a significant decrease in mean BMI (34.9 to 32.5). Conclusions. The LCD appears to an effective and practical office-based intervention in obese teenagers.
Effect of an Anterior Glenoid Defect on Anterior Shoulder Stability
Authors: Yamamoto Nobuyuki , Itoi Eiji , Abe Hidekazu , Kikuchi Kazuma , Seki Nobutoshi , Minagawa Hiroshi , Tuoheti Yilihamu
Published: March 2009

Background

There have been few biomechanical studies to clarify which size of a glenoid defect is critical. However, those studies have assumed that the defect occurred anteroinferiorly. Recent studies have reported that the defect is located anteriorly rather than anteroinferiorly. Therefore, the effect of the anterior, not anteroinferior, glenoid defect on shoulder stability needs to be investigated.

Hypothesis

The anterior glenoid defect would have a similar effect on anterior shoulder stability as that of the anteroinferior glenoid defect.

Study Design

Controlled laboratory study.

Methods

Eight fresh-frozen cadaveric shoulders were used (mean age, 74 years). The specimen was attached to a shoulder-testing device with the arm in abduction and external rotation. An osseous defect was created stepwise with a 2-mm increment of the defect width. The stability ratio was used to evaluate joint stability. With a 50-N axial force, the translational force applied to the humeral head was measured by a force transducer.

Results

The stability ratio without a defect (32% ± 6%) significantly decreased after creating a 6-mm defect (17% ± 5%; P = .0001), which was equivalent to 20% of the glenoid length.

Conclusion

An osseous defect at 3 o'clock with a width that was equal to or greater than 20% of the glenoid length significantly decreased anterior stability.

Clinical Relevance

The results suggest that reconstruction of the glenoid concavity might be necessary in shoulders with an anterior glenoid defect of at least 20% of the glenoid length.
Dextropropoxyphene Poisoning: Problems with Interpretation of Analytical Data
Authors: Buckley B.M. , Vale J.A.
Published: March 2009

1 Difficulties in the estimation and interpretation of dextropropoxyphene and norpropoxyphene analyses have added to the controversy concerning the toxicity of these compounds.

2 Poor performance in external proficiency assessment trials reflects the unsatisfactory state of many dextropropoxyphene and norpropoxyphene analyses in general use.

3 There is substantial overlap between blood concentrations of dextropropoxyphene and norpropoxyphene encountered in chronic therapeutic dose and those associated with acute toxicity.

4 As dextropropoxyphene and norpropoxyphene are often taken in overdose with other drugs, their blood concentrations must be interpreted in the context of careful identification and quantitation of such agents.

5 The present availability of accurate methods for measurement of parent drug and metabolite should now make anecdotal reports unsupported by analytical data entirely superfluous.
Mechanisms of action of mycophenolate mofetil
Authors: Allison AC
Published: March 2009

Mycophenolate mofetil (MMF, CellCept®) is a prodrug of mycophenolic acid (MPA), an inhibitor of inosine-5′‘monophosphate dehydrogenase. MPA depletes guanosine nucleotides preferentially in T and B lymphocytes and inhibits their proliferation, thereby suppressing cell-mediated immune responses and antibody formation. MPA also inhibits the glycosylation and expression of adhesion molecules, and the recruitment of lymphocytes and monocytes into sites of inflammation. MPA depletes tetrahydrobiopterin and decreases the production of nitric oxide by inducible NO synthase without affecting the activity of constitutive NO synthases. Activated macrophages produce NO and superoxide, which combine to generate tissue-damaging peroxynitrite. By these two mechanisms MMF exerts anti-inflammatory activity. Unlike calcineurin inhibitors, MMF is not nephrotoxic and does not induce the production of TGF β, which is fibrogenic. MMF does not increase blood pressure, cholesterol levels or triglyceride levels in recipients. MMF reduces acute and chronic rejection in allograft recipients and is efficacious in some nephropathies. Evidence is accumulating that MMF may have clinical utility in some autoimmune disorders.
Lupus Nephritis: Induction Therapy
Authors: Chan TM
Published: March 2009

Effective induction therapy is of pivotal importance in minimizing renal parenchymal damage by the active immune-mediated inflammatory processes in severe proliferative lupus nephritis. Preservation of nephron mass is prerequisite to long-term renal survival. Data from US-based studies have shown improved efficacy with induction treatment comprising corticosteroid and cyclophosphamide, compared with corticosteroid treatment alone. Data from European studies have shown similar efficacy with a modified treatment regimen, in which smaller doses of cyclophosphamide were given at weekly or fortnightly intervals over a shortened treatment duration, and the treatment related adverse effects appeared less frequent with the reduced-dose regimen. We have also reported that sequential immunosuppression with prednisolone and oral cyclophosphamide as induction followed by azathioprine maintenance was associated with a high incidence of remission and relatively favourable long-term renal outcome in Chinese patients. However, cyclophosphamide treatment is associated with considerable adverse effects, which could be potentially fatal. Mycophenolate mofetil selectively inhibits lymphocyte proliferation, and thus targets an instrumental step in the pathogenesis of systemic lupus erythematosus. There is accumulating evidence that the combined use of mycophenolate mofetil and corticosteroid presents an effective treatment for severe proliferative lupus nephritis in different ethnic groups, and is associated with much fewer adverse effects compared with cyclophosphamide-based regimens. Recent data from our group also demonstrate the long-term efficacy of mycophenolate mofetil in preserving renal survival, when used continuously as both induction and maintenance therapy.
MMF and Eye Disease
Authors: Zierhut M , StüBiger N , Siepmann K , Deuter CME
Published: March 2009

Immunosuppressive treatment has shown to be effective in various ocular inflammatory disorders. Factors limiting their use are the individual response and the rate of side effects. This report summarizes our knowledge about the use of mycophenolate mofetil (MMF) in the treatment of ocular cicatricial pemphigoid (OCP), uveitis, atopic keratoconjunctivitis (AKC), prevention of graft rejection after penetrating keratoplasty (PK) and scleritis. Controlled studies have been performed for prevention of graft rejection after PK, showing MMF as effective in the prevention of graft rejection as cyclosporine A. In experimental uveitis, MMF has been demonstrated to be highly effective in prevention of retinal destruction. A number of studies have now shown that MMF also seems effective in uveitis. There are also studies with smaller patient groups which point out the effectiveness of MMF in OCP, AKC, and scleritis. In most of the studies, the spectrum of side effects was small, compared to other immunosuppressives.
Mycophenolate mofetil in systemic vasculitis
Authors: D'cruz DP
Published: March 2009

The systemic vasculitides are a group of potentially life-threatening multi-system autoimmune connective tissue diseases characterized by vascular inflammation. The gold standard therapies include corticosteroids and cyclophosphamide as induction therapy and other agents such as azathioprine and methotrexate to maintain remission. Mycophenolate mofetil (MMF) is increasingly being used in autoimmune disorders and this article reviews the use of this agent in the systemic vasculitides.
Interstitial Inflammatory and Chronic Tubulointerstitial Lesions in Lupus Nephritis: Comparison with those in IgA Nephropathy
Authors: Yamamoto Tatsuo , Nagase Mitsumasa , Hishida Akira , Honda Nishio
Published: March 2009

The significance of interstitial inflammatory and chronic tubulointerstitial lesions was studied in relation to the severity of glomerular lesions in 62 patients with lupus nephritis and 88 with IgA nephropathy. Severe interstitial inflammatory and chronic tubulointerstitial lesions were found in patients with severe glomerular lesions in both lupus nephritis and IgA nephropathy. In such cases, the serum creatinine levels at biopsy were high and the renal prognosis was poor regardless of the underlying disease (lupus nephritis or IgA nephropathy). No IgA nephropathy patients with nil or mild glomerular lesions had moderate or severe interstitial inflammatory and/or chronic tubulointerstitial lesions. In contrast, predominantly severe interstitial inflammatory lesions were found in 36% of lupus nephritis patients with nil or mild glomerular lesions. The prevalence of interstitial immune complexes deposition was markedly high in those with predominant interstitial inflammatory lesions. However, the severity of chronic tubulointerstitial lesions was mild and renal function did not deteriorate in the mean follow-up periods of 68.6 months. It is suggested that, besides the tubulointerstitial lesions attributable to the severe concomitant glomerular damage, the interstitial deposition of immune complexes per se plays a pathogenic role in the interstitial inflammatory lesions in lupus nephritis. Its prognostic significance, however, was considered to be minor.
Amaurosis fugax, Crohn's Disease and the Anticardiolipin Antibody
Authors: Greenfield S.M. , Teare J.P. , Whitehead M.W. , Thompson R.P.H.
Published: March 2009

Crohn's disease is associated with a hypercoagulable state due to platelet or clotting abnormalities which may be responsible for the thromboembolic episodes seen in this condition. We report the occurrence of anticardiolipin antibodies in a patient with Crohn's disease who presented with Amaurosis fugax and suggest that these antibodies may be a further cause of the hypercoagulable state of Crohn's disease in some patients.
Lupus anticoagulant antibodies: Recognition of phospholipid-binding protein complexes
Authors: Rauch J
Published: March 2009

Lupus anticoagulant antibodies form a heterogeneous group of antiphospholipid antibodies with rather poorly defined antigens. The role that phospholipid-binding proteins play in lupus anticoagulant antibody activity is a subject of current investigation. Several candidate proteins have been proposed, including β2-glycoprotein I (β2GPI), prothrombin, and annexin V. As β2GPI-dependent lupus anticoagulants will be reviewed elsewhere in this issue, this paper will focus on the involvement of prothrombin and annexin V in lupus anticoagulant activity. Evidence for a role for these proteins in the reactivity and induction of lupus anticoagulant antibodies will be discussed, as well as an apparent requirement for both phospholipid and phospholipid-binding protein. The data presented here suggest that some lupus anticoagulant antibodies recognize and may be induced by complexes of phospholipid and phospholipid-binding proteins, in particular, phospholipid and prothrombin or annexin V.
Diagnosis of the antiphospholipid syndrome: A proposal for use of laboratory tests
Authors: Harris EN , Pierangeli SS , Gharavi AE
Published: March 2009

The presence of antiphospholipid (aPL) antibodies has been associated with thrombosis, pregnancy loss and thrombocytopenia in the antiphospholipid syndrome (APS). The anticardiolipin and the lupus anticoagulant tests are frequently used to detect aPL antibodies. The anticardiolipin ELISA utilizes cardiolipin coated on polystyrene plates as antigen and is a very sensitive test but lacks specificity, since it can be positive in a number of infectious (such as syphilis, HIV) and autoimmune diseases other than APS. In an effort to improve specificity, new ELISA techniques that employ alternative antigens (such as β2-glycoprotein 1, particularly when coated onto oxidized microtiter plates or mixture of phospholipids) have been developed. Several investigators have reported that these new assays enable more specific determination of aPL antibodies and thus can be used more reliably for the diagnosis and confirmation of APS. This article examines the results of those studies, including data that shows correlations of these assays with clinical manifestations of APS, and proposes a new protocol for the use of laboratory tests in the diagnosis of APS.
Lessons from experimental APS models
Authors: Shoenfeld Y , Ziporen L
Published: March 2009

Several animal models for antiphospholipid syndrome (APS) have been reported in the literature. These experimental models have contributed significantly in resolving enigmas in this multisystemic disease. We, and others have previously shown the pathogenicity of anticardiolipin (aCL) antibodies in pregnancy outcome. We have expanded our studies to show the pathogenicity of aCL antibodies in renal dysfunction and neurological and behavioral impairments in animals with experimental APS. Animals immunized with aCL or with the cofactor β2GPI developed clinical manifestations of APS, including fetal loss, thrombocytopenia and neurological and behavioral dysfunction, along with elevated levels of aPL antibodies. In another animal model, peripheral blood lymphocytes (PBLs) derived from APS patients could initiate APS manifestations with renal dysfunction in SCID mice. A unique in vivo model for thrombus formation was recently established to show the pathogenicity of aPL in thrombosis associated with APS. Histological evaluation of affected tissues derived from animals or from patients with APS have pointed to common mechanisms underlying APS, showing mainly thrombotic changes accompanied by mild inflammatory reaction.