bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal-Fluid Interactions of Neighboring Components on Air-Cooled Circuit Boards
Authors: Manno V. P. , Azar K.
Published: April 2008

The effects of neighboring components on the thermal performance of air-cooled electronic circuit boards are reviewed using a four part framework—identification, anticipation, quantification and optimization. Interactions are categorized as either isothermal fluid flow or thermal-fluid phenomena. Fluid flow phenomena include multi-dimensional, laminar and transitional flow which can have large spatial influences and exhibit unsteady behavior. The importance of all heat transfer mechanisms is demonstrated and the inadequacy of isolated component thermal characterization is illustrated. Effective thermal proximity of a neighboring component is discussed. Current achievements and inadequacies of experimental characterization and predictive models are described. Finally, proactive optimization strategies based upon circuit board layout and exploitation of unsteady flow effects are considered.
Modeling and Performance Analysis of a Flexible PCB Assembly Station Using Petri Nets
Authors: Zhou MengChu , Leu Ming C.
Published: April 2008

This paper presents Petri net modeling and performance analysis of a flexible workstation for automatic assembly of printed circuit boards. Concentrating on the operational aspects, we construct ordinary and temporal Petri net models for an existing flexible workstation (AT&T FWS-200). These models enable designers to have better understanding of concurrency, synchronization, mutual exclusion, and sequential relations involved in the system control from the graphical representations of Petri nets. From the models the performance analysis of system operations under different settings can be conducted, with the results used to help designers choose the best operational setting based on system parameters such as component insertion time and robot failure rate. We focus our performance analysis on two cases: one is the Petri net with parallel mutual exclusion based control structure, and the other is the control structure based on the marked graph. The analysis results lead to the conclusion that the former structure has better performance in terms of throughput and equipment utilization. The approaches as presented in this paper can be generalized and applied to many other applications of multi-robot assembly systems.
Nickel Fiber Silicone-Matrix Composites as Resilient Electrical Conductors
Authors: Zhu Mingguang , Chung D. D. L.
Published: April 2008

Short nickel fiber silicone-matrix composites containing 3–12 vol. percent fibers were fabricated by the impregnation of silicone into a nickel fiber perform. The composites exhibited volume electrical resistivity ranging from 4.5 × 10−4 to 2.8 × 10−3 ohm.cm, contact electrical resistivity (with copper at a pressure > 0.1 MPa) ranging from 0.0090 to 0.0155 ohm.cm2, permanent set one percent after compression to a stress of 0.4 MPa and a strain up to 13.5 percent for 7 days, and electromagnetic interference (EMI) shielding effectiveness > 50 dB at 1.0–2.0 GHz. The volume and contact resistivities were essentially not affected after heating in air at 130–150°C for 7 days. The coefficient of thermal expansion was 27.5 × 10−6 °C−1 for a composite containing 8.2 vol. percent nickel fibers. These resilient electrically conducting composites are useful for electrical contacts and for gaskets for EMI shielding.
An Improved Procedure for the Determination of the Elastic Constants of Component-Lead-Board Assemblies
Authors: Chang T. S. , Magrab Edward B.
Published: April 2008

An improved means of obtaining the elastic constants of component-lead-board assemblages from two three-point bending tests and one four-point torsion test is proposed. The suggested method models the three-point bending test as an orthotropic plate and uses the experimentally obtained bending and torsion results in a standard nonlinear least square procedure to determine the rigidities in the x and y directions and the Poisson’s ratios directly. Numerical simulation of the method indicates that the beam model overestimates the elastic modulii by 4 to 7 percent and the corresponding rigidities by 7 to 13 percent.
A New Model for Accelerated Thermal Cycle Testing With Application to TAB Leads and PCB PTHs
Authors: Bayer R. G.
Published: April 2008

A model for thermal fatigue that accounts for both plastic and elastic strains and a mean strain is developed. The model is based on a combination of the generalized Coffin-Manson Equation and the Goodman diagram for fatigue. This model was applied to two accelerated thermal cycling tests—one was for TAB leads; the other, unfilled PTHs at TCM sites in PC boards. Good agreement between the model and data was found. In addition, an existing industry model, which is based solely on plastic strain, is compared to the proposed model and the observed behavior in these two tests. It was concluded that both the effects of elastic and plastic strains and a mean strain are needed to explain the results of these evaluations.
Study of an Air Cooling Scheme for 3-D Packaging
Authors: Xie H. , Lee Y. C.
Published: April 2008

An air cooling scheme is proposed for 3-D packaging. It consists of converging, impinging, and diverging flows among stacked circuit packs. Its cooling concept is demonstrated by experimental studies. Using a small Muffin fan (Flight-80 series), the scheme can cool a very compact system, 8 cm × 8 cm × 12 cm, with 56 Watts power dissipation. The maximum temperature difference between the circuit packs and the air is under 50°C, without the use of heat sinks. The flow and heat transfer behaviors of the system are then characterized and optimized by numerical simulation. The sizes and locations of the plates’ openings for the flow passage are identified as the most effective parameters. The optimization adjusts these parameters or power dissipation levels to achieve a uniform distribution of plate temperatures. The uniform plate temperature distribution results in a higher system cooling capability, e.g., 71 Watts, and lower levels of temperature-gradient related problems. The improved cooling capability can be estimated by a simple formula derived by a linear relationship between the plate’s temperature rise and its power dissipation level. The scheme can be applied to higher-power systems by adding more cooling surfaces and a more powerful fan.
The Thermal Wake Function for Rectangular Electronic Modules
Authors: Kang S. S.
Published: April 2008

A point heat source model is employed to study the thermal wake function for an array of rectangular electronic modules situated in a uniform flow stream. For the particular case of in-line modules, a simple equation for the wake function is developed in terms of a modified Peclet number. The length scale for the Peclet number is the square of the module width divided by the streamwise spacing of the modules. The downstream decay of the wake function is shown to be well represented by a power law. Sample calculations using the present model are shown to compare well with experimental data for laminar as well as turbulent flows.
A Preliminary Investigation of the Cooling of Electronic Components With Flat Plate Heat Sinks
Authors: Ahmed I. , Krane R. J. , Parsons J. R.
Published: April 2008

Flat rectangular plate heat sinks are often used to cool large electronic components by the combined effects of natural convection and thermal radiation. There is, however, a paucity of rational design techniques for these devices. Thus, a systematic program to investigate the use of flat, rectangular plate heat sinks with surface coatings to enhance the net radiative exchange with the surroundings has been undertaken. The preliminary results of this program are presented in this work. A two-dimensional numerical model of a single electronic component mounted on a vertically oriented, flat rectangular plate heat sink that is located immediately above an upward-facing, horizontal component board was developed for this investigation. This model, which is solved using a control volume method based on the SIMPLER algorithm, accounts for the fully-coupled natural convection, conduction and radiative heat transfer processes that occur in the two-dimensional heat sink configuration described above. The results of a parametric study performed with the numerical model confirm the necessity of employing a heat sink, since for the ranges of values investigated, from 64 to 88 percent of the energy dissipated in the component is transferred to the surroundings from the heat sink. The parametric study examines the effects of component power, heat sink size (height), the thickness and emissivity of the heat sink, the vertical location of the component on the heat sink, and the temperature of the horizontal component board on the temperature of the component mounted on the heat sink.
Immersion-Cooled Standard Electronic Clamshell Module: A Building Block for Future High-Flux Avionic Systems
Authors: Mudawar Issam , Jimenez Peter E. , Morgan Robert E.
Published: April 2008

An 820-Watt clamshell module was fabricated and tested in order to assess the feasibility of cooling future high heat flux avionic hardware via subcooled phase change. One half of the module was constructed from aluminum 7075-T6 and populated with 16 heat sources simulating microelectronic chips. The other half was substituted with a transparent plastic cover to facilitate optical access to the boiling taking place in the module cavity. A dielectric coolant, Fluorinert FC-72, was supplied to, and rejected from the module via sleeveless quick connection couplers. Tests were performed with an inlet coolant pressure of 1.52 bar (22 psia) and inlet temperatures ranging from 27 to 47°C. These tests yielded power dissipation exceeding 410 W per half module for coolant flow rates and pressure drops as small as 0.023 kg/s (0.221 gpm) and 0.149 bar (2.16 psia), respectively, and the device and rib guide temperatures were maintained below 80 and 60°C, respectively. The pressure drop remained constant with increasing module power proving, as was confirmed visually, it is possible to condensate all the vapor within the module cavity, allowing only liquid to exit the module. Thus, coolant conditioning external to the module can be greatly simplified by employing a simple single-phase liquid flow loop.
Crack Propagation in Solder Joints During Thermal-Mechanical Cycling
Authors: Ross Ronald G. , Wen Liang-chi
Published: April 2008

Differential expansion induced creep-fatigue resulting from temperature cycling is an important cause of solder joint failure. The deterioration of solder joint integrity typically involves a sequential development of local stressing, microcracks, crack initiation and crack propagation, ultimately resulting in electrical open-circuiting by total joint separation from the PWB footprint. To better understand the failure process, a series of combined analytical and experimental investigations have been performed on flat-pack parts with gull-wing leads ranging in height from 9 to 56 mils. JPL’s special purpose nonlinear finite element computer program has been modified to dynamically simulate the crack propagation process. Solder creep properties, including the effect of grain growth, are also incorporated into the model. Depending upon the system geometry and materials properties, the combination of crack development and grain growth may have either a positive or negative effect on the rate of cracking of the solder elements. Consequently, the crack propagation process may accelerate or decelerate as cycles progress. Sensitivity studies are used to highlight the individual effects of crack propagation and grain growth and compare the failure prediction results with those obtained using conventional finite element techniques. The analytical results are corroborated using visual observations obtained using SEM photography of test samples exposed to the thermal-cycle environment used in the analysis.
Effects of Solder Joint Voiding and Seating Plane Stability on Surface Mount Lead Standoff
Authors: Schwiebert M. K.
Published: April 2008

This study considers the influence of solder joint voiding and seating plane stability on the lead standoffs of surface mount technology (SMT) solder joints. A model is presented for approximating the reaction force generated by a gas-filled void in molten solder which is compressed under an SMT lead. Seating plane stability is defined with a simple model. The lead standoffs of a component with an unstable seating plane are sensitive to small forces. For some SMT components, the reaction force generated by compressed voids in molten solder can tilt or rock a component, resulting in lead standoffs much greater than the measured lead coplanarity.
Moire´ Interferometry Analysis of Laser Weld Induced Thermal Strain
Authors: Kowalski V. T. , Voloshin A. S.
Published: April 2008

An experimental method is presented to study laser weld induced thermal strain using digital image analysis enhanced moire´ interferometry. A phenomenon that occurs in the assembly of optical components is that the final optimum coupled power will randomly change upon completion of the laser weld process. The change in power is due to residual thermal stresses being generated in the welded components. For single mode devices, relative motions of the components in the order of 1 μm could result in a 1 dB degradation of coupled power. The behavior of thermal strain is unpredictable since the relative orientation of the optical components at the optimum alignment is random. The goal of this investigation was to perform a baseline study of parameters affecting laser weld thermal strain. The first phase of the work was to study thermal strain induced by a single weld on a flat Kovar plate. The results show that thermal strain is independent of material inhomogeneity. However, this investigation did reveal asymmetry of the power distribution in the weld laser with a principal axes offset +30 deg from horizontal. The second phase of the experiment was to characterize thermal strain resulting from welding on an interface of two Kovar plates. The results indicate that thermal strain at the center of two welds is not affected by welds that are greater than 1 mm apart. Also, thermal strain levels at locations adjacent to the weld are not significantly affected by weld separation distance. This study successfully demonstrated that digital image analysis enhanced moire´ interferometry can be used in the study of laser weld induced thermal strain. Digital image processing, fractional fringe analysis, and high frequency specimen gratings increase sensitivity levels to enable the technique to be used to characterize submicron thermal distortions.
Influence of Polymer Viscoelasticity on a Bending Bilayer
Authors: Harper B. D.
Published: April 2008

The bending bilayer technique is commonly employed to provide an empirical assessment of the often significant thermal stresses that develop in thin polymer films used in microelectronic packaging. Polymers are known to exhibit time-dependent (viscoelastic) behavior that is greatly accelerated at elevated temperatures. The solution for a bilayer beam with a linear viscoelastic, thermorheologically simple film bonded to a linear elastic substrate is developed. A wide variety of assumed viscoelastic material properties are considered along with properties for several specific electronic polymers in order to illustrate the general effects of polymer viscoelasticity upon the thermal stress in a polymer film. Practical methods for deducing the relative significance of polymer viscoelasticity from empirical bending bilayer results are emphasized. Comparisons with experimental data for two polymides and one epoxy molding compound are also provided.
Heat Conduction in Concentric Cylinders: An Application to Electronic Packages
Authors: Sathe Sanjeev
Published: April 2008

A numerical analysis on the heat conduction characteristics of concentric cylinders is presented. The study is relevant to heat transfer in electronic equipment wherein cylindrical electrical conductors or thermal vias (typically characterized by high thermal conductivities) are surrounded by electrical insulators having a different thermal conductivity. The heat conduction equation is solved using a control-volume finite-difference technique. Results are presented in terms of the thermal spreading resistance, the heat removal contribution of the inner cylinder (pin) and the heat spreading contribution of the surrounding material for a wide range of governing parameters. In particular, the effects of the thermal conductivities of the cylinders and the geometric dimensions on the heat spreading characteristics are investigated. It is shown that there is no spreading when the ratio of the conductivity of the pin to the conductivity of the surrounding material (k/K) is larger than about 1000; as found in copper pins surrounded by Teflon or Fr-4 type of a dielectric material. Substantial reduction in the overall thermal resistance is obtained with k/K less than 10, which could be practically achieved by using silicon carbide or aluminum nitride as the surrounding material.
Advantages and Disadvantages of Thin Small Outline Packages (TSOP) With Copper Gull-Wing Leads
Authors: Lau John , Golwalkar Suresh , Erasmus Steve
Published: April 2008

In this paper, the advantage of TSOP with copper leads is shown by comparing: (1) the calculated stress and strain in the solder joints with that of the TSOP with Alloy 42 lead frames (Lau et al., 1992), and (2) the experimental thermal life distribution with that of the TSOP with Alloy 42 leads (Lau et al., 1993). The disadvantage of TSOP with copper leads is shown by considering the technology limitations and manufacturing constraints.
A Finite Element Study of Factors Affecting Fatigue Life of Solder Joints
Authors: Paydar N. , Tong Y. , Akay H. U.
Published: April 2008

The elastic-plastic-creep characteristics of solder joints are implemented in a nonlinear finite element program ABAQUS by developing user defined material subroutines. An eutectic Pb-Sn solder joint of a resistor carrier under thermal cycling between 125°C and −55°C is modeled, and the effect of various parameters on the solder joint cycle life is evaluated. The strain range of the solder joint under thermal cycling loads is calculated, which is then converted into solder joint cycle life through a fatigue-life relationship proposed by Engelmaier (1983). The parameters studied include: ramp time, hold time, grain size, initial temperature, constitutive equations, material properties for solder alloys, and mesh refinement. The effects of these variations on the fatigue life of solder joints are illustrated. The described method can serve as a tool in the design and manufacturing of surface-mount (SMT) assemblies.
Methodology for Automated Design of Microelectronic Packages
Authors: Rajan S. D. , Sarihan V. , Mahalingam M.
Published: April 2008

A general design methodology for the optimal design of electronic packages is presented. The design problem is cast as a nonlinear programming (NLP) problem. Design for critical packaging issues such as thermal and mechanical performance, is automated by combining thermal and mechanical finite element analysis with an NLP optimizer. The major issues such as design problem formulation, model generation or preprocessing, nonlinear finite element analysis, design variable identification, design sensitivity analysis and software implementation are addressed. A case study involving the design of an RF packaging component in communication products illustrates the design methodology implemented in the Automated Design of Electronic Packaging (ADEP) software system.
Two-Phase Electronic Cooling Using Mini-Channel and Micro-Channel Heat Sinks: Part 1—Design Criteria and Heat Diffusion Constraints
Authors: Bowers Morris B. , Mudawar Issam
Published: April 2008

Mini-channel (D = 2.54 mm) and micro-channel (D = 510 μm) heat sinks with a 1-cm2 heated surface were tested for their high heat flux performance with flow boiling of R-113. Experimental results yielded CHF values in excess of 200 W cm−2 for flow rates less than 95 ml min−1 (0.025 gpm) over a range of inlet subcooling from 10 to 32°C. Heat diffusion within the heat sink was analyzed to ascertain the optimum heat sink geometry in terms of channel spacing and overall thickness. A heat sink thickness to channel diameter ratio of 1.2 provided a good compromise between minimizing overall thermal resistance and structural integrity. A ratio of channel pitch to diameter of less than two produced negligible surface temperature gradients even with a surface heat flux of 200 W cm−2. To further aid in determining channel diameter for a specific cooling application, a pressure drop model was developed, which is presented in the second part of the study.
TWISTED ALEXANDER POLYNOMIAL OF LINKS IN THE PROJECTIVE SPACE
Authors: HUYNH VU Q. , LE THANG T. Q.
Published: April 2008

We use Reidemeister torsion to study a twisted Alexander polynomial, as defined by Turaev, for links in the projective space. Using sign-refined torsion, we derive a skein relation for a normalized form of this polynomial.
DETERMINING THE THIRD-HARMONIC SUSCEPTIBILITY BY FOURIER ANALYSIS
Authors: YANG PAO-KENG
Published: April 2008

A novel analyzing procedure was introduced to extract the third-harmonic susceptibility from the measured third-harmonic-generation fringe obtained by translating a wedged liquid cell along the direction perpendicular to the propagating direction of the incident fundamental beam. By Fourier transform, we can easily separate the Fourier component purely contributed by the liquid/window interface from those involving the air contribution. Comparing this spectral component with that from a reference sample with known third-harmonic susceptibility and coherence length, we can determine the third-harmonic susceptibility and coherence length of the liquid under test. Finally, Fourier analysis was used to determine the third-harmonic susceptibility and coherent length of pure water using ethanol as the reference sample and the results have shown the feasibility of the proposed procedure.
ROTATIONAL SYMMETRY OF TRANSMISSION PATTERNS AND ORDERING OF OPAL PHOTONIC CRYSTALS
Authors: KHUNSIN W. , ROMANOV S. G. , TORRES C. M. SOTOMAYOR
Published: April 2008

A novel approach to the quantitative characterization of the regularity of the opal photonic crystal lattice based on a Fourier transform analysis of the azimuth rotational symmetry of the optical transmission is proposed. The magnitudes of three harmonics in the Fourier transform related to the two-, six- and twelvefold rotational symmetry of the transmission pattern have been suggested for quantification of the lattice ordering. The specific composition of these harmonics has been observed for the transmission attenuation at different lattice planes. The diffraction at (220) and (200) families of crystal planes has been identified as the most sensitive to the crystallinity of the opal lattice. The transmission pattern obtained in the s-polarized light is recommended for comparison.
DETERMINISTIC DIFFERENTIAL GAMES UNDER PROBABILITY KNOWLEDGE OF INITIAL CONDITION
Authors: CARDALIAGUET P. , QUINCAMPOIX M.
Published: April 2008

We study a zero-sum differential game where the players have only an unperfect information on the state of the system. In the beginning of the game only a random distribution on the initial state is available. The main result of the paper is the existence of the value obtained through an uniqueness result for Hamilton-Jacobi-Isaacs equations stated on the space of measure in ℝn. This result is the first step for future work on differential games with lack of information.
FINDING NORMALIZED EQUILIBRIUM IN CONVEX-CONCAVE GAMES
Authors: FLÅM S. D. , RUSZCZYŃSKI A.
Published: April 2008

This paper considers a fairly large class of noncooperative games in which strategies are jointly constrained. When what is called the Ky Fan or Nikaidô-Isoda function is convex-concave, selected Nash equilibria correspond to diagonal saddle points of that function. This feature is exploited to design computational algorithms for finding such equilibria.

To comply with some freedom of individual choice the algorithms developed here are fairly decentralized. However, since coupling constraints must be enforced, repeated coordination is needed while underway towards equilibrium.

Particular instances include zero-sum, two-person games — or minimax problems — that are convex-concave and involve convex coupling constraints.
FRIENDLINESS AND RECIPROCITY IN EQUILIBRIUM SELECTION
Authors: DE MARCO GIUSEPPE , MORGAN JACQUELINE
Published: April 2008

A concept of altruistic behavior (called friendly behavior) has been defined and used for equilibrium selection in some bargaining models in Rusinowska (2002), "Refinements of Nash Equilibria in view of Jealous and Friendly Behavior of Players", International Game Theory Review, 4, 281–299.

In this paper, the situation in which every player has friendly behavior is incorporated into the general context of normal form games by introducing a new refinement concept (called friendliness equilibrium). Existence, properties and connections with another refinement concept, introduced by the authors in a previous paper and which captures an idea of reciprocal altruism, are investigated. Examples and counterexamples are given illustrating concepts, results and links with other classical refinement concepts.
RECURSIVE SEQUENCES IDENTIFYING THE NUMBER OF EMBEDDED COALITIONS
Authors: YEUNG DAVID W. K.
Published: April 2008

Strategic behaviors of players depend crucially on the coalition structures of a game. A recursive sequence identifying the number of embedded coalitions in a n-player game is derived. The paper also derives a recursive sequence identifying the number of embedded coalitions in a n-player game where the position of the individual player in a partition counts.
DISCRETE CONCAVITY FOR POTENTIAL GAMES
Authors: UI TAKASHI
Published: April 2008

This paper proposes a discrete analogue of concavity appropriate for potential games with discrete strategy sets. It guarantees that every Nash equilibrium maximizes a potential function.
COSTANDARD MODULES OVER SCHUR SUPERALGEBRAS IN CHARACTERISTIC p
Authors: SCALA ROBERTO LA , ZUBKOV ALEXANDER
Published: April 2008

In this paper we consider the problem of describing the costandard modules ∇(λ) of a Schur superalgebra S(m|n,r) over a base field K of arbitrary characteristic. Precisely, if G = GL(m|n) is a general linear supergroup and Dist (G) its distribution superalgebra we compute the images of the Kostant ℤ-form under the epimorphism Dist (G) → S(m|n,r). Then, we describe ∇(λ) as the null-space of some set of superderivations and we obtain an isomorphism ∇(λ) ≈ ∇(λ+|0) ⊗ ∇(0|λ-) assuming that λ = (λ+|λ-) and λm = 0. If char (K) = p we give a Frobenius isomorphism ∇(0|pμ) ≈ ∇(μ)p where ∇(μ) is a costandard module of the ordinary Schur algebra S(n,r). Finally we provide a characteristic free linear basis for ∇(λ|0) which is parametrized by a set of superstandard tableaux.
FREE ROTA–BAXTER ALGEBRAS AND ROOTED TREES
Authors: EBRAHIMI-FARD KURUSCH , GUO LI
Published: April 2008

A Rota–Baxter algebra, also known as a Baxter algebra, is an algebra with a linear operator satisfying a relation, called the Rota–Baxter relation, that generalizes the integration by parts formula. Most of the studies on Rota–Baxter algebras have been for commutative algebras. Two constructions of free commutative Rota–Baxter algebras were obtained by Rota and Cartier in the 1970s and a third one by Keigher and one of the authors in the 1990s in terms of mixable shuffles. Recently, noncommutative Rota–Baxter algebras have appeared both in physics in connection with the work of Connes and Kreimer on renormalization in perturbative quantum field theory, and in mathematics related to the work of Loday and Ronco on dendriform dialgebras and trialgebras.

This paper uses rooted trees and forests to give explicit constructions of free noncommutative Rota–Baxter algebras on modules and sets. This highlights the combinatorial nature of Rota–Baxter algebras and facilitates their further study. As an application, we obtain the unitarization of Rota–Baxter algebras.
CLEAN CLASSICAL RINGS OF QUOTIENTS OF COMMUTATIVE RINGS, WITH APPLICATIONS TO C(X)
Authors: BURGESS W. D. , RAPHAEL R.
Published: April 2008

Commutative clean rings and related rings have received much recent attention. A ring R is clean if each r ∈ R can be written r = u + e, where u is a unit and e an idempotent. This article deals mostly with the question: When is the classical ring of quotients of a commutative ring clean? After some general results, the article focuses on C(X) to characterize spaces X when Qcl(X) is clean. Such spaces include cozero complemented, strongly 0-dimensional and more spaces. Along the way, other extensions of rings are studied: directed limits and extensions by idempotents.
ON ORE EXTENSIONS OF QUASI-BAER RINGS
Authors: NASR-ISFAHANI A. R. , MOUSSAVI A.
Published: April 2008

A ring R is called (right principally) quasi-Baer if the right annihilator of every (principal right) ideal of R is generated by an idempotent. We study on the relationship between the quasi-Baer and p.q.-Baer property of a ring R and these of the Ore extension R[x; α, δ] for any automorphism α and α-derivation δ of R.
A POLYNOMIAL INVARIANT OF FINITE QUANDLES
Authors: NELSON SAM
Published: April 2008

We define a two-variable polynomial invariant of finite quandles. In many cases this invariant completely determines the algebraic structure of the quandle up to isomorphism. We use this polynomial to define a family of link invariants which generalize the quandle counting invariant.
Optical and SKP Studies of Corrosion-Driven Delamination Inhibition by Polyaniline Solid Films on Iron
Authors: Bennett Andrew R. , McMurray H. N. , Williams Geraint
Published: April 2008

This paper describes systematic optical and Scanning Kelvin Probe (SKP) studies of homogeneous solid films of polyaniline emeraldine salt (PAni-ES) as it effects corrosion driven cathodic disbondment on iron substrates. The effects of varying PAni-ES coating thickness are fully described in terms of optically and spatially resolved PAni-ES speciation, intact coating potentials (Eintact) and resulting atmospheric delamination kinetics. A kinetic and mechanistic comparison of these PAni-ES solid film studies is made between the results of previous studies in which PAni-ES is used as a pigment dispersion within a non-conducting resin.
AFM Study of the Corrosion of Pipeline Steel in Organic Compounds Extracted from Soil
Authors: Yasakau Kyril A. , Weber Cristina Rejane , Rodrigues Luciana M. , Zheludkevich Mikhail , Ferreira Mario Guereiro , Dick Luís Frederico P.
Published: April 2008

Aiming to simulate the external corrosion of pipelines, the first stages of the inclusion attack and nucleation of pits were studied by AFM on the API 5LX56 steel in pure 10mM Na2SO4 solution and with additions of HA or FA, both extracted from a Brazilian peat soil. For this, selected inclusions were first marked with micro indentations, viewed in the SEM in the backscattering mode and chemically mapped with EDS. Pit formation was then investigated by scanning Kelvin probe force microscopy (SKPFM). The SKPFM evidenced that HA added to sulfate solutions promotes the fast dissolution of the sulfides of complex inclusions, resulting in pit nucleation, while FA additions slow this attack, acting as a natural corrosion inhibitor.
Crosslinked Sulfonated Poly(arylene ether sulfone) Membranes as Candidate for PEMs
Authors: Paul Mou , Roy Abhishek , Riffle Judy , McGrath James E. E.
Published: April 2008

A series of controlled molecular weight, phenoxide-endcapped, 50% disulfonated BPS 50 copolymers was synthesized. The terminal phenoxide groups were reacted with glycidyl methacrylate via nucleophilic aromatic substitution to produce GMA-BPS 50 copolymers endcapped with crosslinkable glycidyl methacrylate moieties. Various blend compositions in varying weight percents of GMA-BPS 50-5k and 15k copolymers were made and thermally cured in presence of benzoyl peroxide initiator at 90-95 degree C. The cured copolymers were characterized in terms of water uptake,proton conductivity and self-diffusion coefficient of water.
Significance of Additive Content on the Properties of Electrodeposited Ni-Al2O3 Nanocomposite Coatings
Authors: Injeti Gurrappa , Jitendra Verma , Rama Krishna Vemula
Published: April 2008

The present paper explains the efforts made in synthesizing Ni- Al2O3 nonocomposite coatings with enhanced properties by varying the additive concentration systematically. Microstructural, morphological and microhardness measurements revealed that the optimized additive concentration helped in improving the coatings properties considerably. The ceramic particles were distributed uniformly over nanocrystalline nickel matrix for the optimized additive concentration as evidenced from different characterization techniques. It was stressed that the addition of optimum content of additive is highly essential in order to obtain nanocomposite coatings with enhanced properties. Finally, the mechanism involved in improving the enhanced properties of nanocomposite coatings was described.
Ascaris lumbricoides: A Review of Its Epidemiology and Relationship to Other Infections
Authors: Scott Marilyn E.
Published: April 2008

This review highlights advances made since 2004 in understanding the epidemiology of infection and the interactions between Ascarislumbricoides and other concurrent infections. As water scarcity increases, untreated wastewater is increasingly used to irrigate crops, thus increasing the risk of transmission. New methods to detect and inactivate Ascaris eggs in water, soil and food are described. The association between pig ownership and Ascaris infection in humans may represent cross-transmission as hybridization among the pig and human ascarids occurs more frequently than previously believed. Geospatial analyses have successfully predicted infection levels both at a regional level (based on vegetation indices, temperature and humidity) and within communities (based on social and environmental factors). The interpretation of antibody and cytokine responses to Ascaris is becoming clearer, as researchers recognize the role of antigen type, age, the history of Ascaris and other infections. The considerable interest emerging on the interactions between Ascaris and other infections (helminths, malaria, HIV, tuberculosis) and allergy is explored. The impact of concurrent infection on the design of control strategies is discussed including the benefits arising from combination therapies and the evidence that intestinal nematodes impair the efficacy of childhood vaccines. Finally, recommended areas for future research are identified.
Giardiasis: Modern Concepts in Control and Management
Authors: Thompson R.C. Andrew
Published: April 2008

Giardia is the most common enteric protozoan pathogen of humans, domestic animals and wildlife. Children are at the most risk from the clinical consequences of Giardia infection, particularly those in developing countries and living in disadvantaged community settings. Molecular epidemiological studies have helped to elucidate sources of infection and the public health significance of animal reservoirs. Although aspects of the pathogenesis of Giardia infection are now understood, we are still a long way from understanding the factors that predispose to clinical disease. Effective drugs are available to treat giardial infections but can serve only as an adjunct to traditional public health approaches in endemic settings where children are commonly infected.
Nitric Oxide Synthase Inhibitor (MTR-105) during Open-Heart Surgery
Authors: Sasson Lior , Ureche Andrei , Manolache Gheorghe , Ciubotaru Anatol , Borer Jeffrey S. , Schachner Arie
Published: April 2008

Objectives: Hypotension is common immediately following cardiopulmonary bypass. Experimentally, MTR-105 (S-ethylisothiuronium diethylphosphate), a fast-acting synthetic nitric oxide synthase inhibitor, rapidly increases blood pressure. The purpose of the current study was to assess the influence of MTR-105 on hemodynamics early after cardiopulmonary bypass in patients undergoing open-heart surgery. Methods:Thirty-six patients with an ejection fraction >50% undergoing open-heart surgery were randomly assigned to either 50 µg kg–1 min–1 MTR-105 (M50, n = 12), 10 µg kg–1 min–1 MTR-105 (M10, n = 12) or buffered phosphate solution (placebo control, n = 12). Half suffered from atrial fibrillation and 75% had severe tricuspid regurgitation. Patients received the drug for 6 h after cross-clamp removal. Hemodynamic variables were measured before drug administration until 24 h after operation. Adverse events were recorded from study drug initiation through 30 days after the operation. Results:Compared with control, both MTR-105 doses were associated with an immediate increase in systemic blood pressure (16%) and systemic vascular resistance and a decrease in cardiac index. Half-life time of MTR-105 was calculated to be 4.1 ± 0.8 h (M10) and 4.45 ± 0.92 h (M50). Three patients died during hospitalization, unrelated to the study medication. Conclusions:At the doses employed, MTR-105 appears hemodynamically active in increasing both blood pressures.
Involvement of Retinal Neurons and Pigment Epithelial Cells in a Murine Model of Sandhoff Disease
Authors: Sango Kazunori , Yamanaka Shoji , Ajiki Kyoko , Arai Nobutaka , Takano Masahiko
Published: April 2008

Background/Aims: To investigate the effects of deficient degradation of glycolipids on the morphological appearance of all retinal cells in a murine model of GM2 gangliosidosis (Sandhoff disease). Methods: The morphological appearance of the retina in Sandhoff mice at symptomatic stages (3 and 4 months of age) was examined by immunohistochemistry, lectin histochemistry and electron microscopy. Results: Under a light microscope, intense immunoreactivity for GM2 ganglioside was observed in the ganglion cell, inner plexiform, and inner nuclear layers in the Sandhoff mice. The ganglion cell layers and retinal pigment epithelium in the Sandhoff mice were stained intensely withconcanavalin A agglutinin and succinylated wheat germ agglutinin. Ultrastructural studies revealed numerous inclusions in the cytoplasm of retinal ganglion cells and other neuronal cells (particularly amacrine cells), whereas we failed to detect apparent involvement of photoreceptor cells. In addition to the cytoplasmic inclusions in the retinal neurons, vacuolation was evident in the retinal pigment epithelium. Conclusion: These findings suggest that neuronal cells and pigment epithelial cells are more vulnerable to the deficient ganglioside degradation than other retinal cells in Sandhoff mice.
Clinical Evaluation of Succinylated Collagen Bandage Lenses for Ophthalmic Applications
Authors: Hadassah J. , Prakash D. , Sehgal P.K. , Agarwal A. , Bhuvaneshwari N.
Published: April 2008

Aim: To study whether succinylated collagen bandage lenses (SCBL) prepared from modified bovine collagen (succinylated collagen) can replace other bandage lenses presently employed to treat various corneal conditions like filamentary keratitis, dry eyes, recurrent corneal erosions, foreign body removal and epithelial trauma. Methods: This observational case study included 32 patients (22 female and 10 male): 8 patients for filamentary keratitis (25%), 10 patients for dry eyes (31%), 4 patients for recurrent corneal erosions (13%), 7 patients for foreign body removal (22%) and 3 patients for epithelial trauma (9%). Their eyes were evaluated for biocompatibility, in vivo transparency, patient comfort, corneal fit, best corrected visual acuity (BCVA), tear fluid level and dissolution rate of SCBL. This was carried out over a 24-hour period of time. Results: SCBL exhibited good transparency and remained transparent throughout the period of study (between 0 and 24 h) in the eyes of patients. SCBL did not cause any irritation, discomfort and foreign body sensation in the eye and eyes remained comfortable throughout the experiment. BCVA in the control group of patients was 1.00 (20/20). Mean (±SD) BCVA before inserting SCBL (in decimal equivalent) was 0.31 (20/60) ± 0.18 (range 0.1– 0.66). BCVA (±SD) changed to 0.25 (20/80) ± 0.18 4 h after the application of SCBL and 0.27 (20/70) ± 0.18 24 h after the application of SCBL, with a safety index of 1.20. The mean (±SD) tear fluid level before application of SCBL was 11.9 ± 5.39 h (range 3–24 mm) and changed to 13.9 ± 5.68 h (range 5–28 mm) after 4 h of application of SCBL and 15.9 ± 5.72 h (range 7–30 mm) after 24 h with a safety index of 13 mm. The mean (±SD) dissolution rate of SCBL in the control group of patients was 17.8 ± 8.65 h (range 10–24 h) and the mean (±SD) dissolution rate in the experimental group was 22.2 ± 9.29 h (range 10–24 h). We report the use of SCBL in various corneal conditions. Conclusion: The present study showed that SCBL has complete corneal fit and good comfort in human eyes. Transparency was maintained for a longer period along with fair visual acuity and improvement in tear fluid levels. The disadvantages of other bandage lenses presently used to treat various corneal conditions could be overcome by the use of SCBL lenses.
Effect of Febuxostat on the Progression of Renal Disease in 5/6 Nephrectomy Rats with and without Hyperuricemia
Authors: Sánchez-Lozada Laura G. , Tapia Edilia , Soto Virgilia , Ávila-Casado Carmen , Franco Martha , Wessale Jerry L. , Zhao Lin , Johnson Richard J.
Published: April 2008

Background/Aims: The effect of febuxostat (Fx), a non-purine and selective xanthine oxidase inhibitor, on glomerular microcirculatory changes in 5/6 nephrectomy (5/6 Nx) Wistar rats with and without oxonic acid (OA)-induced hyperuricemia was evaluated. Methods: Four groups were studied: 5/6 Nx+vehicle (V)+placebo (P) (n = 7); 5/6 Nx+V+Fx (n = 8); 5/6 Nx+OA+P (n = 6) and 5/6 Nx+OA+Fx (n = 10). OA (750 mg/kg/day, oral gavage) and Fx (3–4 mg/kg/day, drinking water) were administered for 4 weeks. Systolic blood pressure, proteinuria and plasma uric acid were measured at baseline and at the end of 4 weeks. Measurement of glomerular hemodynamics and evaluation of histology were performed at the end of 4 weeks. Results: 5/6 Nx+OA+P rats developed hyperuricemia, renal vasoconstriction and glomerular hypertension in association with further aggravation of afferent arteriolopathy compared to 5/6 Nx+V+P. Fx prevented hyperuricemia in 5/6 Nx+OA+Fx rats and ameliorated proteinuria, preserved renal function and prevented glomerular hypertension in both 5/6 Nx+V+Fx and 5/6 Nx+OA+Fx groups. Functional improvement was accompanied by preservation of afferent arteriolar morphology and reduced tubulointerstitial fibrosis. Conclusion: Fx prevented renal injury in 5/6 Nx rats with and without coexisting hyperuricemia. Because Fx helped to preserve preglomerular vessel morphology, normal glomerular pressure was maintained even in the presence of systemic hypertension.
The Lesion Patterns and Mechanisms of Ischemic Stroke Contralateral to the Internal Carotid Artery Occlusive Disease
Authors: Lee Seung-Jae , Lee Kwang-Soo , An Jae-Young , Kim Woo-Jun , Kim Yeong-In , Kim Bum-Soo , Chung So-Ryoung , Kim Joong-Seok
Published: April 2008

Background: In previous studies on unilateral internal carotid artery (ICA) occlusive disease, contralateral strokes have been ignored or excluded, probably because of their heterogeneity in etiology. The purpose of this study was to analyze the acute ischemic lesions contralateral to ICA occlusive disease and characterize the patterns and mechanisms of these strokes. Methods: Eight patients, who had an acute ischemic stroke contralateral to the ICA occlusion, were enrolled. All patients underwent routine clinical evaluation including history and physical examination, laboratory tests and magnetic resonance imaging (MRI). Both magnetic resonance angiography and digital subtraction cerebral angiography, along with carotid duplex sonography, transcranial Doppler sonography, electrocardiography and echocardiography were performed to confirm the stroke subtypes. Results: There were three distinctive stroke lesion patterns: (1) multiple infarcts in the border zone with or without a territorial lesion (4 patients), (2) multiple infarcts in the arterial territories sparing the border zone (2 patients), and (3) a small (<15 mm in MRI) single infarct in the internal border zone (2 patients). Overall, the patterns of ischemic lesions contralateral to the ICA occlusion were multiple and had a border zone distribution. Conclusion: These results suggest that the pathogenic mechanisms underlying these strokes could be the synergistic effects of both the embolism and a low flow state.
The Effect of Lipoproteins on the Development and Progression of Renal Disease
Authors: Dalrymple Lorien S. , Kaysen George A.
Published: April 2008

The field of research examining how lipoproteins may contribute to the development and/or progression of renal disease has rapidly expanded over the last 25 years. In animal models, lipoproteins and lipids have been associated with both the initiation and progression of renal disease. Numerous potential mechanisms of lipoprotein-induced renal injury have been identified by utilizing animal models and tissue-culture experiments. However, with the exception of rare genetic mutations, the association between lipoproteins and human renal disease is less clear. In humans, the evidence that lipid-lowering therapy delays renal progression is limited. The purpose of this paper is to review the current literature on lipoprotein abnormalities and the development or progression of renal disease.
Electronegative LDL and Lipid Abnormalities in Patients Undergoing Hemodialysis and Peritoneal Dialysis
Authors: Lobo J. , Santos F. , Grosso D. , Lima R. , Barreira A.L. , Leite, Jr. M. , Mafra D. , Abdalla D.S.P.
Published: April 2008

Background: Oxidative modification of low-density lipoprotein (LDL) has been demonstrated in patients with end-stage renal disease, where it is associated with oxidative stress and plays a key role in the pathogenesis of atherosclerosis. In this context, the generation of minimally oxidized LDL, also called electronegative LDL [LDL(–)], has been associated with active disease, and is a detectable sign of atherogenic tendencies. The purpose of this study was to evaluate serum LDL(–) levels and anti-LDL(–) IgG autoantibodies in end-stage renal disease patients on dialysis, comparing patients on hemodialysis (HD), peritoneal dialysis (PD) and a control group. In addition, the serum lipid profile, nutritional status, biochemical data and parameters of mineral metabolism were also evaluated. Methods: The serum levels of LDL(–) and anti-LDL(–) IgG autoantibodies were measured in 25 patients undergoing HD and 11 patients undergoing PD at the Centro Integrado de Nefrologia, Rio de Janeiro, Brazil. Ten healthy subjects served as a control group. Serum levels of albumin, total cholesterol, triglycerides and lipoproteins were measured. Calculations of subjects’ body mass index and measurements of waist circumference, triceps skin fold and arm muscle area were performed. Measurements of hematocrit, serum blood urea nitrogen, creatinine, parathyroid hormone, phosphorus and calcium were taken. Results: Levels of LDL(–) were higher in HD patients (575.6 ± 233.1 µg/ml) as compared to PD patients (223.4 ± 117.5 µg/ml, p < 0.05), which in turn were higher than in the control group (54.9 ± 33.3 µg/ml, p < 0.01). The anti-LDL(–) IgG autoantibodies were increased in controls (0.36 ± 0.09 µg/ml) as compared to PD (0.28 ± 0.12 µg/ml, p < 0.001) and HD patients (0.2 ± 0.1 µg/ml, p < 0.001). The mean values of total cholesterol and LDL were considered high in the PD group, whereas the mean triceps skin fold was significantly lower in the HD group. Conclusion: Levels of LDL(–) are higher in renal patients on dialysis than in normal individuals, and are reciprocally related to IgG autoantibodies. LDL(–) may be a useful marker of oxidative stress, and this study suggests that HD patients are more susceptible to cardiovascular risk due to this condition. Moreover, autoantibodies reactive to LDL(–) may have protective effects in chronic kidney disease.