bluuebunny/crossref_metadata_2025 huggingface dataset:
A General Approach to Perturbation Theoretic Analysis in Nonlinear Optics and its Application to Ferroelectrics and Antiferroelectrics
Authors: Webb J. F.
Published: October 2003

Perturbation analysis in which the time variation of an electric field applied to a dielectric is treated as inducing a weakly nonlinear response expressed as a Taylor series expansion, is a standard technique for deriving the nonlinear susceptibility coefficients that relate the applied electric field to the polarization in the dielectric. In this paper a generalized method incorporating Fourier analysis is employed to treat a one-dimensional dynamical system subject to a time dependent driving force consisting of a superposition of monochromatic plane waves. It is then shown how this method can be applied to the calculation of nonlinear susceptibility coefficients, of any order, in bulk ferroelectric and antiferroelectric materials.
Preservation of Femoral Head Blood Circulation with Lovastatin in Steroid Treated Rabbits
Authors: Atsumi Takashi , Shen Wun-Jer , Wang Gwo-Jaw
Published: October 2003

To better understand the etiology of steroid-induced osteonecrosis, microangiographs of the femur were made in rabbits receiving either methylprednisolone alone or methylprednisolone plus the lipid clearing agent, lovastatin. Administration of steroid caused a rapid elevation in serum cholesterol. Changes in the vascularity of the femur were evident by three weeks, particularly in the femoral head and neck region. A staging system was developed based on changes in the microangiographic pattern. All rabbits showed progressive deterioration; co-administration of lovastatin delayed the loss of vascularity for a limited period of time.

Clinical relevance: Lipid clearing agents may delay the onset of osteonecrosis in patients receiving steroids.
Soluble Factors from Human Saos-2 Osteosarcoma Cells Induce Ectopic Bone Formation and Osteoblastic Differentiation of Cultured Mesenchymal Cells
Authors: Laitinen Minna , Jortikka Leena , Halttunen Tuula , Böhling Tom , Marttinen Aulis , Lindholm T. Sam
Published: October 2003

Freeze-dried cells of the human osteosarcoma cell line Saos-2 have the capacity to induce bone formation. We studied the bone-inductive capacity of factors expressed by Saos-2 cells and secreted to a growth medium. When lyophilized Saos-2-conditioned medium was implanted in a mouse hamstring muscle pouch, new bone formation was observed. Unlike the radially symmetric cartilage usually seen in induced ossicles, an asymmetric morphology of the newly formed bone was observed, with hyaline cartilage on one side and fibrocartilage on the other side. The new bone area resembled histologically osteochondroma, a benign bone tumor, with flat chondrocyte-like cells arranged in rows, endochondral ossification and red bone marrow. Osteoinductivity was further confirmed in in vitro tests with mesenchymal cell lines. A serum-free ten-fold concentrated Saos-2 growth medium increased mineralization, measured as 45Ca incorporation, and also stimulated alkaline phosphatase activity in cultured rat myoblasts and mouse embryo cells. These in vitro results indicate that Saos-2 cells secrete factors, among which is BMP-2/4, which stimulate mesenchymal cell differentiation to osteoblastic lineage.
Evolving Ant Colony Optimization
Authors: Botee Hozefa M. , Bonabeau Eric
Published: October 2003

Ant Colony Optimization (ACO) is a promising new approach to combinatorial optimization. Here ACO is applied to the traveling salesman problem (TSP). Using a genetic algorithm (GA) to find the best set of parameters, we demonstrate the good performance of ACO in finding good solutions to the TSP.
All-frequency shadows using non-linear wavelet lighting approximation
Authors: Ng Ren , Ramamoorthi Ravi , Hanrahan Pat
Published: October 2003

We present a method, based on pre-computed light transport, for real-time rendering of objects under all-frequency, time-varying illumination represented as a high-resolution environment map. Current techniques are limited to small area lights, with sharp shadows, or large low-frequency lights, with very soft shadows. Our main contribution is to approximate the environment map in a wavelet basis, keeping only the largest terms (this is known as a
non-linear approximation
). We obtain further compression by encoding the light transport matrix sparsely but accurately in the same basis. Rendering is performed by multiplying a sparse light vector by a sparse transport matrix, which is very fast. For accurate rendering, using non-linear wavelets is an order of magnitude faster than using linear spherical harmonics, the current best technique.
Multi-level partition of unity implicits
Authors: Ohtake Yutaka , Belyaev Alexander , Alexa Marc , Turk Greg , Seidel Hans-Peter
Published: October 2003

We present a new shape representation, the
multi-level partition of unity
implicit surface, that allows us to construct surface models from very large sets of points. There are three key ingredients to our approach: 1) piecewise quadratic functions that capture the local shape of the surface, 2) weighting functions (the partitions of unity) that blend together these local shape functions, and 3) an octree subdivision method that adapts to variations in the complexity of the local shape.Our approach gives us considerable flexibility in the choice of local shape functions, and in particular we can accurately represent sharp features such as edges and corners by selecting appropriate shape functions. An error-controlled subdivision leads to an adaptive approximation whose time and memory consumption depends on the required accuracy. Due to the separation of local approximation and local blending, the representation is not global and can be created and evaluated rapidly. Because our surfaces are described using implicit functions, operations such as shape blending, offsets, deformations and CSG are simple to perform.
Billboard clouds for extreme model simplification
Authors: Décoret Xavier , Durand Frédo , Sillion François X. , Dorsey Julie
Published: October 2003

We introduce
billboard clouds
-- a new approach for extreme simplification in the context of real-time rendering. 3D models are simplified onto a set of planes with texture and transparency maps. We present an optimization approach to build a billboard cloud given a geometric error threshold. After computing an appropriate density function in plane space, a greedy approach is used to select suitable representative planes. A good surface approximation is ensured by favoring planes that are "nearly tangent" to the model. This method does not require connectivity information, but instead avoids cracks by projecting primitives onto multiple planes when needed. For extreme simplification, our approach combines the strengths of mesh decimation and image-based impostors. We demonstrate our technique on a large class of models, including smooth manifolds and composite objects.
Flows on surfaces of arbitrary topology
Authors: Stam Jos
Published: October 2003

In this paper we introduce a method to simulate fluid flows on smooth surfaces of arbitrary topology: an effect never seen before. We achieve this by combining a two-dimensional stable fluid solver with an atlas of parametrizations of a Catmull-Clark surface. The contributions of this paper are: (i) an extension of the Stable Fluids solver to arbitrary curvilinear coordinates, (ii) an elegant method to handle cross-patch boundary conditions and (iii) a set of new external forces custom tailored for surface flows. Our techniques can also be generalized to handle other types of processes on surfaces modeled by partial differential equations, such as reaction-diffusion. Some of our simulations allow a user to interactively place densities and apply forces to the surface, then watch their effects in real-time. We have also computed higher resolution animations of surface flows off-line.
Adaptive grid-based document layout
Authors: Jacobs Charles , Li Wilmot , Schrier Evan , Bargeron David , Salesin David
Published: October 2003

Grid-based page designs are ubiquitous in commercially printed publications, such as newspapers and magazines. Yet, to date, no one has invented a good way to easily and automatically adapt such designs to arbitrarily-sized electronic displays. The difficulty of generalizing grid-based designs explains the generally inferior nature of on-screen layouts when compared to their printed counterparts, and is arguably one of the greatest remaining impediments to creating on-line reading experiences that rival those of ink on paper. In this work, we present a new approach to adaptive grid-based document layout, which attempts to bridge this gap. In our approach, an adaptive layout style is encoded as a set of grid-based templates that know how to adapt to a range of page sizes and other viewing conditions. These templates include various types of layout elements (such as text, figures, etc.) and define, through constraint-based relationships, just how these elements are to be laid out together as a function of both the properties of the content itself, such as a figure's size and aspect ratio, and the properties of the viewing conditions under which the content is being displayed. We describe an XML-based representation for our templates and content, which maintains a clean separation between the two. We also describe the various parts of our research prototype system: a layout engine for formatting the page; a paginator for determining a globally optimal allocation of content amongst the pages, as well as an optimal pairing of templates with content; and a graphical user interface for interactively creating adaptive templates. We also provide numerous examples demonstrating the capabilities of this prototype, including this paper, itself, which has been laid out with our system.
Nonconvex rigid bodies with stacking
Authors: Guendelman Eran , Bridson Robert , Fedkiw Ronald
Published: October 2003

We consider the simulation of nonconvex rigid bodies focusing on interactions such as collision, contact, friction (kinetic, static, rolling and spinning) and stacking. We advocate representing the geometry with both a triangulated surface and a signed distance function defined on a grid, and this dual representation is shown to have many advantages. We propose a novel approach to time integration merging it with the collision and contact processing algorithms in a fashion that obviates the need for
ad hoc
threshold velocities. We show that this approach matches the theoretical solution for blocks sliding and stopping on inclined planes with friction. We also present a new shock propagation algorithm that allows for efficient use of the propagation (as opposed to the simultaneous) method for treating contact. These new techniques are demonstrated on a variety of problems ranging from simple test cases to stacking problems with as many as 1000 nonconvex rigid bodies with friction as shown in Figure 1.
Cg
Authors: Mark William R. , Glanville R. Steven , Akeley Kurt , Kilgard Mark J.
Published: October 2003

The latest real-time graphics architectures include programmable floating-point vertex and fragment processors, with support for data-dependent control flow in the vertex processor. We present a programming language and a supporting system that are designed for programming these stream processors. The language follows the philosophy of C, in that it is a hardware-oriented, general-purpose language, rather than an application-specific shading language. The language includes a variety of facilities designed to support the key architectural features of programmable graphics processors, and is designed to support multiple generations of graphics architectures with different levels of functionality. The system supports both of the major 3D graphics APIs: OpenGL and Direct3D. This paper identifies many of the choices that we faced as we designed the system, and explains why we made the decisions that we did.
Why math?
Authors: Bruce Kim B. , Drysdale Robert L. Scot , Kelemen Charles , Tucker Allen
Published: October 2003

The mathematical thinking, as well as the mathematics, in a computer science education prepares students for all stages of system development, from design to the correctness of the final implementation.
Automatic testing equivalence verification of spi calculus specifications
Authors: Durante Luca , Sisto Riccardo , Valenzano Adriano
Published: October 2003

Testing equivalence is a powerful means for expressing the security properties of cryptographic protocols, but its formal verification is a difficult task because of the quantification over contexts on which it is based. Previous articles have provided insights into using theorem-proving for the verification of testing equivalence of spi calculus specifications. This article addresses the same verification problem, but uses a state exploration approach. The verification technique is based on the definition of an environment-sensitive, labeled transition system representing a spi calculus specification. Trace equivalence defined on such a transition system coincides with testing equivalence. Symbolic techniques are used to keep the set of traces finite. If a difference in the traces of two spi descriptions (typically a specification and the corresponding implementation of a protocol) is found, it can be used to automatically build the spi calculus description of an intruder process that can exploit the difference.
Multimode scan
Authors: Singh Adit D. , Seuring Markus , Gössel Michael , Sogomonyan Egor S.
Published: October 2003

Built-in self-test (BIST) is an attractive design-for-test methodology for core-based SoC design because of the minimal need for test access when tests are generated and evaluated within the core itself. However, the scan based logic BIST approach being widely considered for this application suffers from two significant weaknesses: slow test-per-scan execution, and a limited capability for detecting realistic timing and delay faults, critical in deep submicron technologies. The new multimode scan based approach presented here supports test-per-clock BIST, which runs orders of magnitude faster, and also provides significantly better delay fault coverage.
Lightweight probabilistic broadcast
Authors: Eugster P. Th. , Guerraoui R. , Handurukande S. B. , Kouznetsov P. , Kermarrec A.-M.
Published: October 2003

Gossip-based broadcast algorithms, a family of probabilistic broadcast algorithms, trade reliability guarantees against "scalability" properties. Scalability in this context has usually been expressed in terms of message throughput and delivery latency, but there has been little work on how to reduce the memory consumption for membership management and message buffering at large scale.This paper presents lightweight probabilistic broadcast (
lpbcast
), a novel gossip-based broadcast algorithm, which complements the inherent throughput scalability of traditional probabilistic broadcast algorithms with a scalable memory management technique. Our algorithm is completely decentralized and based only on local information: in particular, every process only knows a fixed subset of processes in the system and only buffers fixed "most suitable" subsets of messages. We analyze our broadcast algorithm stochastically and compare the analytical results both with simulations and concrete implementation measurements.
Dose Equivalency Evaluation of Major Corticosteroids: Pharmacokinetics and Cell Trafficking and Cortisol Dynamics
Authors: Mager Donald E. , Lin Sheren X. , Blum Robert A. , Lates Christian D. , Jusko William J.
Published: October 2003

The integrity of current corticosteroid dose equivalency tables, as assessed by mechanistic models for cell trafficking and cortisol dynamics, was investigated in this study. Single, presumably equivalent, doses of intravenous hydrocortisone, methylprednisolone, dexamethasone, and oral prednisolone were given to 5 white men, according to total body weight, in a 5‐way crossover, placebo‐controlled study. Pharmacodynamic (PD) response‐time profiles for T helper cells, T suppressor cells, neutrophils, and adrenal suppression were evaluated by extended indirect response models. For adrenal suppression, prednisolone appears to be less potent than methylprednisolone or dexamethasone. A good correlation was found between the estimated in vivo EC50 values and relative receptor affinity (equilibrium dissociation constants normalized to dexamethasone). Area under the effect curves of all PD responses was calculated using a linear‐trapezoidal method. Although T helper cell trafficking and adrenal suppression achieved significant differences by repeated‐measures ANOVA (p = 0.014 and 0.022), post hoc analysis using the Bonferroni method revealed no difference between treatments. Although limited by the use of single doses and a relatively small sample size, this study applies mechanistic models for several biomarkers showing that currently used dosing tables reflect reasonable dose equivalency relationships for four corticosteroids.
Plasma Kinetics, Metabolism, and Urinary Excretion of Alpha‐Lipoic Acid following Oral Administration in Healthy Volunteers
Authors: Teichert Jens , Hermann Robert , Ruus Peter , Preiss Rainer
Published: October 2003

R(+)‐alpha‐lipoic acid is a natural occurring compound that acts as an essential cofactor for certain dehydrogenase complexes. The redox couple alpha‐lipoic acid/dihydrolipoic acid possesses potent antioxidant activity. Exogenous racemic alpha‐lipoic acid orally administered for the symptomatic treatment of diabetic polyneuropathy is readily and nearly completely absorbed, with a limited absolute bioavailability of about 30% caused by high hepatic extraction. Although the pharmacokinetics of the parent drug have been well characterized in humans, relatively little is known regarding the excretion of alpha‐lipoic acid and the pharmacokinetics of any metabolites in humans. In the present study, plasma concentration‐time courses, urinary excreted amounts, and pharmacokinetic parameters of alpha‐lipoic acid metabolites were evaluated in 9 healthy volunteers after multiple once‐daily oral administration of 600 mg racemic alpha‐lipoic acid. The primary metabolic pathways of alpha‐lipoic acid in man, S‐methylation and β‐oxidation, were quantitatively confirmed by an HPLC‐electrochemical assay newly established prior to the beginning of this study. Major circulating metabolites were the S‐methylated β‐oxidation products 4,6‐bismethylthio‐hexanoic acid and 2,4‐bismethylthio‐butanoic acid, whereas its conjugated forms accounted for the major portion excreted in urine. There was no statistically significant difference in the pharmacokinetic parameters Cmax, AUC, and tmax between day 1 and day 4. Despite the prolonged half‐lives of the major metabolites compared to the parent drug, no evidence of accumulation was found. Mean values of 12.4% of the administered dose were recovered in the urine after 24 hours as the sum of alpha‐lipoic acid and its metabolites. The results of the present study revealed that urinary excretion of alpha‐lipoic acid and five of its main metabolites does not play a significant role in the elimination of alpha‐lipoic acid. Therefore, biliary excretion, further electrochemically inactive degradation products, and complete utilization of alpha‐lipoic acid as a primary substrate in the endogenous metabolism should be considered.
Trends in Survival Rates After Allogeneic Hematopoietic Stem-Cell Transplantation for Acute and Chronic Leukemia by Ethnicity in the United States and Canada
Authors: Serna Derek S. , Lee Stephanie J. , Zhang Mei-jie , Baker K. Scott , Eapen Mary , Horowitz Mary M. , Klein John P. , Rizzo J. Douglas , Loberiza Fausto R.
Published: October 2003

Purpose: Differences in survival among ethnic groups in the United States are reported in numerous diseases and treatment strategies. Whether survival after allogeneic hematopoietic stem-cell transplantation (HSCT) differs by ethnicity is uncertain.

Patients and Methods: Patients (n = 6,443) receiving HLA-identical sibling HSCT for acute or chronic leukemia in the United States or Canada between 1985 and 1999 and reported to the International Bone Marrow Transplant Registry were included. The survival of recipients reported as white, black, Hispanic, or Asian was compared using Cox proportional hazards regression adjusting for other clinical factors. Three 5-year periods were studied to evaluate changes over time.

Results: Hispanics compared with whites had lower 1-year (53% v 65%; P < .001) and 3-year adjusted survival rates (38% v 53%; P < .001) between 1995 and 1999, the most recent period studied. We failed to find significant differences in survival rates comparing whites with blacks or with Asians in any of the time periods. Overall survival for the entire cohort improved over time, from 56% to 63% at 1 year and from 43% to 51% at 3 years, with greater improvements noted among blacks (45% to 61% at 1 year and 34% to 48% at 3 years).

Conclusion: Disparities remain in survival rates between whites and Hispanics despite adjustment for clinical factors. Factors not accounted for in this analysis, such as comorbid disease, socioeconomic status, healthcare access and delivery, and psychosocial and cultural variables, require further prospective study.
Exposure to ultraviolet radiation causes apoptosis in developing sea urchin embryos
Authors: Lesser Michael P. , Kruse Valerie A. , Barry Thomas M.
Published: October 2003

Laboratory exposures of embryos from the sea urchin Strongylocentrotus droebachiensis to ultraviolet B radiation (UV-B, 290-320 nm), equivalent to a depth of 1-3 m in the Gulf of Maine, resulted in significant damage to DNA measured as cyclobutane pyrimidine dimer formation. Cells with DNA damage caused by ultraviolet radiation (UVR, 290-400 nm) and oxidative stress can survive, but are often retained in the G1/S phase of the cell cycle to repair DNA as a result of the expression of cell cycle genes such as p53 and p21, and the subsequent inhibition of the activity of cyclin-dependent kinases such as cdc2; if DNA cannot be repaired it can lead to programmed cell death or apoptosis. Sea urchin embryos exposed to UV-B radiation exhibit significantly higher protein concentrations of the antioxidant enzyme superoxide dismutase, and the transcriptional activators p53 and p21. The downstream activator of the cell cycle,cdc2, showed significantly lower protein concentrations with exposure to increasingly shorter wavelengths of UVR. Decreases in cdc2 could have been caused directly by exposure to UV-B or as a result of downregulation via the p53, p21 cascade, or both. These cellular events lead to apoptosis, as shown by the significant increase in DNA strand breaks observed in the nuclei of developing embryos exposed to UVR using the TUNEL assay. Cellular death, and a decrease in sea urchin embryo survivorship,are caused by the indirect and direct effects of exposure to UVR that leads to apoptosis in these laboratory experiments.
Short-term transformation and long-term replacement of branchial chloride cells in killifish transferred from seawater to freshwater, revealed by morphofunctional observations and a newly established `time-differential double fluorescent staining' technique
Authors: Katoh Fumi , Kaneko Toyoji
Published: October 2003

Short- and long-term responses to direct transfer from seawater to freshwater were examined in gill chloride cells of killifish, which developed distinct freshwater- and seawater-type chloride cells in the respective environments. In a short-term response within 24 h after transfer,seawater-type chloride cells forming a pit structure on the apical surface were transformed into freshwater-type cells equipped with developed microvilli on the flat or projecting apical membrane, via the intermediate type. The transformation process was accompanied by the disappearance of apically located Cl- channel (cystic fibrosis transmembrane conductance regulator) and neighboring accessory cells. Chloride cell replacement was also examined as a long-term adaptation to freshwater transfer, using a newly established `time-differential double fluorescent staining (TDS)' technique. In the TDS technique, in vivo labeling of chloride cells was performed on two separate days, using two distinguishable mitochondria-specific fluorescent probes. For 3 days after freshwater transfer, 14.7% of seawater-type cells were replaced with newly differentiated freshwater-type cells, whereas these ratios of chloride cell replacement were much lower (1.2% and 1.8%) in seawater- and freshwater-maintained groups,respectively. In consequence, following direct transfer of killifish from seawater to freshwater, seawater-type chloride cells were transformed morphologically and functionally into freshwater-type cells as a short-term response, followed by the promotion of chloride cell replacement as a long-term response.
Leadership Development: A Collaborative Approach
Authors: Carroll Constance M. , Gandert Romero Martha
Published: October 2003

To meet the unprecedented demand for well‐prepared leaders, a regional approach can be helpful that draws on a range of providers, offering a variety of development opportunities for aspiring and practicing leaders.
In‐House Leadership Development: Placing the Colleges Squarely in the Middle
Authors: Piland William E. , Wolf David B.
Published: October 2003

The traditional means of preparing community college leaders are disjointed and in many cases ill suited to meet the challenges leaders will face through the beginning decades of the twenty‐first century. Community colleges must take a proactive role in the development of their future leaders.
Efficient Transport of Saccharides through a Liquid Membrane Mediated by a Cyclodextrin Dimer
Authors: Ikeda Hiroshi , Matsuhisa Akiyuki , Ueno Akihiko
Published: October 2003

A new efficient system for transporting saccharides through a liquid membrane has been constructed. The transport rates of saccharides were accelerated greatly by the cyclodextrin dimer 2; by contrast, the corresponding cyclodextrin monomer 1 was not effective at mediating saccharide transport. The transport rate of D‐ribose through a chloroform liquid membrane was 17 times faster when the cyclodextrin dimer 2 was used as the transporter than when the cyclodextrin monomer 1 was used. Similarly the transport rate of methyl D‐galactopyranoside was 16 times faster by 2 than by 1.
Bisporphyrins with Bischlorin Features Obtained by Direct Anodic Coupling of Porphyrins
Authors: Ruhlmann Laurent , Gross Maurice , Giraudeau Alain
Published: October 2003

The proximity of two or more porphyrin or chlorin‐like structures has been shown to be crucial in numerous biological processes, such as electron transfers. The one‐pot electrochemical synthesis of a dimeric tetraphenylporphyrin with one 1,2‐(diphenylphosphonium)benzene as a spacer and of its porphyrin‐monomer precursor are reported. These new compounds have been characterized by 1H and 31P NMR, ESR, and UV‐visible spectroscopy and microanalysis. Electrochemical data are reported, and the redox behavior is analyzed for the monomers and the dimers. Important interactions between the two chromophores and a phosphonium–phosphonium interaction have been observed. UV‐visible and 1H NMR data along with electrochemical behavior suggest that the positive charge carried by the two phosphonium units is in part delocalized onto the π system of the porphyrins, this gives an unexpected bis‐porphyrin with bischlorin spectroscopic features.
Formation of Quaternary Stereocenters by Copper‐Catalyzed Michael Reactions with L‐Valine Amides as Auxiliaries
Authors: Christoffers Jens
Published: October 2003

Extensive investigations of chiral auxiliaries and active metals for Michael addition of 1,3‐dicarbonyl compounds with vinyl ketones are summarized. Our efforts result in a widely applicable auxiliary‐mediated, copper(II) acetate‐catalyzed procedure. For these purposes, L‐valine diethylamide is an optimal chiral auxiliary giving quaternary stereocenters with up to 99 % ee at ambient temperature. No inert or anhydrous conditions are required, the solvent is simply acetone, and the auxiliary can be recovered almost quantitatively after workup.
The Evolution of [{Ph2P(CH2)nPPh2}Pt(μ‐S)2Pt{Ph2P(CH2)nPPh2}] (n=2, 3) Metalloligands in Protic Acids: A Cascade of Sequential Reactions
Authors: Mas‐Ballesté Rubén , Aullón Gabriel , Champkin Paul A. , Clegg William , Mégret Claire , González‐Duarte Pilar , Lledós Agustí
Published: October 2003

Given the nucleophilicity of the {Pt2S2} ring, the evolution of [Pt2(μ‐S)2(P∩P)2] (P∩P=1,2‐bis(diphenylphosphino)ethane (dppe), 1,3‐bis(diphenylphosphino)propane (dppp)) metalloligands in the presence of the simplest electrophilic species, the proton, has been studied. Combined use of experimental and theoretical data has allowed the whole set of reactions ensuing the protonation of the {Pt2S2} core to be established. The titration of [Pt2(μ‐S)2(P∩P)2] with HCl or HClO4 was monitored mainly by 31P{1H} NMR and mass techniques. Characterization of all the species involved was completed with the determination of the crystal structure of [Pt(SH)2(P∩P)], for dppe and dppp, and [Pt3(μ3‐S)2(dppp)3](PF6)2. The first protonation step of the {Pt2S2} core leads to the stable [Pt2(μ‐S)(μ‐SH)(P∩P)2]+ complex, but the second step implies disintegration of the ring, thus giving rise to various mononuclear species. The subsequent evolution of some of these species allows regeneration of [Pt2(μ‐S)(μ‐SH)(P∩P)2]+, evidencing the cyclic nature of this process. Whereas the reaction pathway is essentially common for both phosphine ligands, dppe and dppp, the different coordinating ability of Cl− or ClO4− determines the nature of the final products, [PtCl2(P∩P)], [Pt3(μ3‐S)2(P∩P)3]Cl2 or [Pt3(μ3‐S)2(P∩P)3](ClO4)2. DFT calculations have corroborated the thermodynamic feasibility of the reactions proposed on the basis of experimental data.
Correlation effects in low dimensional electron systems: the electron‐hole bilayer
Authors: Senatore G. , De Palo S.
Published: October 2003

We review recent progress in the area of low‐dimensional electrons, which has been made possible mainly by the use of quantum simulations. We focus on DMC results for a symmetric electron‐hole bilayer, which we analyze in some detail. We also contrast the results of simulations with (i) the predictions of a mean field treatments and (ii) the results of approaches based on the dielectric formalism, such as the STLS and qSTLS schemes. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of inverse solution in two‐dimensional heat conduction problem using Laplace transformation
Authors: Monde Masanori , Hammad J. A. , Arima Hirofumi , Mitsutake Yuhichi
Published: October 2003

An inverse solution has been explicitly derived for two‐dimensional heat conduction in cylindrical coordinates using the Laplace transformation. The applicability of the inverse solution is checked using the numerical temperatures with a normal random error calculated from the corresponding direct solution. For a gradual temperature change in a solid, the surface heat flux and temperature can be satisfactorily predicted, while for a rapid change in the temperature this method needs the help of a time partition method, in which the entire measurement time is split into several partitions. The solution with the time partitions is found to make an improvement in the prediction of the surface heat flux and temperature. It is found that the solution can be applied to experimental data, leading to good prediction. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(7): 602–617, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10115
Improvement of inverse heat conduction solution using Laplace transformation: Method of partial division of time
Authors: Monde Masanori , Liu Wei , Arima Hirofumi , Mitsutake Yuhichi , Hammad J.A.
Published: October 2003

Any solution for an inverse heat conduction problem makes the estimation of surface temperature and surface heat flux worsen in the case where these values behave like a triangular shape change with time. In order to compensate for this defect, Monde and colleagues, who succeeded in obtaining analytical inverse solutions using the Laplace transform technique, introduce a new idea where these changes over the entire measurement time can be split into several parts depending on the behavior. Therefore, an approximate equation to trace the measured temperature change can be derived, resulting in good estimation of surface temperature and surface heat flux even in the case of the triangular shape change and sharp change. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(7): 630–638, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10117
Hohe Lebensdauer, niedriger Verschleiß
Authors: Dobler K. , Schöfer J. , Meyer K. , Dornhöfer G.
Published: October 2003

Aufgrund steigender Anforderungen an Qualität und Lebensdauer moderner mechanischer Systeme ist die tribologische Forschung ein wichtiger Bestandteil des industriellen Entwicklungsprozesses. Neben Schadensanalysen gewinnt hier die Erarbeitung von produktbezogenem Wissen zunehmend an Bedeutung. Die Robert Bosch GmbH setzt daher seit Jahren modernste Analysetools wie das Focused Ion Beam System ein, mit dem sich kleinste Gefügeveränderungen nachweisen und so Verschleißentwicklungen dokumentieren lassen. Im Bereich der Kraftstoffeinspritzung erfordern neue Umweltgesetze die Entwicklung direkteinspritzender Systeme, die in der Lage sind, immer höhere Einspritzdrücke zu realisieren. Da die meisten dieser Systeme auf einer Kraftstoffschmierung basieren, ist die Gewährleistung der Systemfunktion über die gesamte Lebensdauer abhängig von einer ausreichenden Schmierfähigkeit der Otto‐ und Dieselkraftstoffe. Um diese sicherzustellen, ist eine permanente Erweiterung der bestehenden Wissensbasis und der tribologischen Prüfmethodik notwendig. Bei Produkten ohne funktionsbedingte Anwesenheit von Schmiermedien ist das zusätzliche Einbringen eines flüssigen oder konsistenten Schmierstoffes oft unverzichtbar. Bei der Robert Bosch GmbH wird daher die Entwicklung spezieller Hochleistungsschmierstoffe intensiv vorangetrieben.
Microstructural changes in the wear surface of high strength stainless austenitic steels
Authors: Berns H. , Gavriljuk V. G. , Petrov Y. N. , Schmalt F. , Tyshchenko A.
Published: October 2003

High strength CrMn steels alloyed with C or N or C+N were subjected to grooving or impact wear. The interstitial content ranged from 0.44 to 0.87 mass%. The bulk structure was characterized by internal friction and TEM, while the wear surface was inspected by TEM, XRD and magnetic response. The bulk is fully austenitic and the Snoek‐like relaxation reveals a “frozen splitting” caused by interstitial / substitutional complexes. Deformation induced ε‐martensite is found in the grooving wear surface, but traces of α‐martensite are present only in the specimen of lowest interstial content corresponding to the lowest stability of austenite. Neither XRD nor the magnetic response give evidence of α‐martensite in the impact wear surface.
Multiorgan transplantation with a new organ‐chip technique in mice: Preliminary histological data
Authors: Brath Endre , Miko Iren , Kovacs Judit , Toth Ferenc F. , Fachet Jozsef , Furka Istvan
Published: October 2003

A simple model was developed for multiorgan liver‐kidney‐spleen‐intestine transplantation on 108 inbred mice. Donor operations included hepatectomy, nephrectomy, splenectomy, and jejunum segment resection. Following removal of the organ, small slices or abdominal organ “chips” were prepared. During multiorgan recipient operations, chips from each of these organs were transplanted into the omentum; in the control single‐organ groups, only 1 organ was transplanted. All animals survived. Biopsies were taken for histology after 6 weeks. All organs were found to have developed a blood supply. In the liver chips, hypertrophied cells could be detected. In the margin of the kidney tissue, both the glomeruli and tubules were preserved. Lymphoid zone and red pulp were intact in spleen chips. All layers of the intestinal chips were identifiable and contained intraluminal mucinous substances. This model is a simple surgical intervention with the possibility of the investigation of 4 organs.

Kísérletünk célja új, multiorgan máj‐vese‐lép‐vékonybél chip‐transzplantációs modell kidolgozása volt egerekben. Kísérletünkhöz 108 beltenyésztett egeret használtunk. Donor műtétek: hepatectomia, nephrectomia, splenectomia, és jejunum segment resectio. Az eltávolított szervekből kis szeleteket, “chip”‐eket alakítottunk ki. A multiorgan recipiens műtétek: minden szervből darabokat transzplantáltunk a csepleszbe, míg kontrollba csak egy szerv került. Minden állat túlélt: 6 hét múlva szövettani mintavétel történt. A chip‐vérellátás jól követhető volt. A máj “chip”‐ekben hipertrophiás sejteket találtunk. A vese darabok széli részén a glomerolusok és tubulusok megőrízték szerkezetüket. Jól körülírt lép fészkeket detektáltunk lympoid zónával és vörös pulpával. A bél falának minden rétegét, és mucin termelést sikerült azonosítani. A modell technikailag egyszerűen kivitelezhetü, előnye, hogy egyszerre 4 szerv vizsgálatára van lehetőség. © 2003 Wiley‐Liss, Inc. MICROSURGERY 23:466–469 2003
High‐efficiency doped polymeric organic light‐emitting diodes
Authors: Vaeth Kathleen M. , DiCillo John
Published: October 2003

Fabrication of polymer light‐emitting diodes based on emission from the phosphorescent molecule fac‐tris(2‐phenylpyridine) iridium doped into a poly(N‐vinyl carbazole) host are reported. For single‐layered devices with magnesium‐silver cathodes, the luminance efficiency at 20 mA/cm2 was measured as 8.7 cd/A. This efficiency could be increased by over a factor of two by incorporation of evaporated small‐molecule layers into the device structure. Significant increases in device efficiency were also obtained without these evaporated layers by modification of the electrodes. Incorporation of 3,4‐poly(ethylene dioxythiophene):poly(styrene sulfonate) at the anode improved the device efficiency but had little impact on drive voltage. Insertion of lithium fluoride at the cathode resulted in no improvement in performance for magnesium‐silver and aluminum cathodes, but a significant improvement was realized in efficiency and drive voltage for calcium‐aluminum cathodes. Excellent device performance was observed for all three cathode metals used in conjunction with cesium fluoride. Through optimization of the electrodes and emitter‐layer thickness, devices exhibiting efficiencies as high as 37.3 cd/A are realized. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2715–2725, 2003
Peeling the onion: NMDA dysfunction as a unifying model in schizophrenia
Authors: Javitt Daniel C.
Published: October 2003

N-methyl-d-aspartate receptor (NMDAR) dysfunction plays a crucial role in schizophrenia, leading to impairments in cognitive coordination. NMDAR agonists (e.g., glycine) ameliorate negative and cognitive symptoms, consistent with NMDAR models. However, not all types of cognitive coordination use NMDAR. Further, not all aspects of cognitive coordination are impaired in schizophrenia, suggesting the need for specificity in applying the cognitive coordination construct.
Why do schizophrenic patients hallucinate?
Authors: Roelfsema Pieter R. , Supèr Hans
Published: October 2003

Phillips & Silverstein argue that schizophrenia is a result of a deficit of the contextual coordination of neuronal responses. The authors propose that NMDA-receptors control these modulatory effects. However, hallucinations, which are among the principle symptoms of schizophrenia, imply a flaw in the interactions between neurons that is more fundamental than just a general weakness of contextual modulation.
What can be done for the elderly patient who is incontinent of
urine&?
Authors: Wynne Hilary A
Published: October 2003

Urinary incontinence has been defined by the International
Continence Society as ‘the involuntary loss of urine, which is a
social and hygienic problem and can be objectively demonstrated’.
This is a useful definition, although due to the subjective component,
prevalence can only be estimated.
Hierarchical Structures in Spatially Extended Systems
Authors: Liu Jian , She Zhen-Su , Ouyang Qi , He X. T.
Published: October 2003

Hierarchical Structure (HS) analysis is applied to numerical solutions of two-dimensional complex Ginzberg–Landau equation (CGLE). We show that both the ordered spiral waves and the spatiotemporal chaotic states of the CGLE satisfy the She-Leveque hierarchical symmetry [She and Leveque, Phys. Rev. Lett.72, 336 (1994)]. The HS parameter β is measured for the CGLE solutions, which characterizes the statistical similarity between fluctuation structures of different intensities at different scales. The value of β is consistent with that recently obtained from an analysis of experimental spatiotemporal fluctuations. The analysis is able to reveal two different mechanisms of breaking-up: far-field and core breaking-up in the developement of spatiotemporal chaos.
Pseudochaotic Systems and Their Fractional Kinetics
Authors: Lyubomudrov O. , Edelman M. , Zaslavsky G. M.
Published: October 2003

We describe a wide class of systems, which corresponds to the random non-chaotic dynamics with zero Lyapunov exponents. We call this type of dynamics pseudochaos and show that the corresponding kinetic description of such systems can be developed in the frame of the so-called fractional kinetics with space-time self-similarity. Numerous simulations and some analytical predictions display unusual features of the pseudochaos.
Variational Path-Integral Study on a Bipolaron in a Parabolic Quantum Wire or Well
Authors: Ruan Yong-Hong , Chen Qing-Hu , Jiao Zheng-Kuan
Published: October 2003

The expression of the ground-state energy of a bipolaron in a parabolic quantum wire or well is derived within the framework of Feynman variational path-integral theory. We obtain a general result with arbitrary electron-phonon coupling constant, confining potential strength, and ratio of dielectric constants, which could be used for further numerical calculation of bipolaron properties. Moreover, it is shown that all previous path-integral formula for a bipolaron in a parabolic quantum wire, quantum well or quantum dot can be recovered in the present formalism.
A Study of the Effective Properties of Complex Scatterers Using Multiresolution Decomposition
Authors: Steinberg Ben Zion , McCoy John J.
Published: October 2003

A systematic study of the across scale coupling phenomenology in scattering problems is addressed using the theory of multiresolution decomposition and orthogonal wavelets. By projecting an integral equation formulation of the scattering problem onto a set of sub-spaces that constitutes a multiresolution decomposition of L2(R), one can derive two coupled formulations. The first governs the macroscale response, and the second governs the microscale response. By substituting the formal solution of the latter into the former, a new self consistent formulation that governs the macroscale response component is obtained. This formulation is written on a macroscale grid, where the effects of the microscale heterogeneity is expressed via an across scale coupling operator. This operator can also be interpreted as representing the effective properties of the microstructure. We study the properties of this operator versus the characteristics of the Green function, and the microstructure for various structural acoustics problems using general asymptotic considerations. Specific examples of scattering from a thin, linearly elastic, fluid-loaded plate with surface mass density, or bending stiffness variations, are provided. We show that mass microscale variation has virtually no effect on the macroscale response, and stiffness microscale variations can significantly affect the macroscale response. Classes of stiffness variations that have an identical macroscale response are derived using a one dimensional local constitutive relation developed to govern the macroscale field components. The results are supported by numerical examples.
Multiresolution Reproducing Kernel Particle Methods in Acoustics
Authors: Uras R. A. , Chang C.-T. , Chen Y. , Liu W. K.
Published: October 2003

In the analysis of complex phenomena of acoustic systems, the computational modeling requires special attention in order to give a realistic representation of the physics. As a powerful tool, the finite element method has been widely used in the study of complex systems. In order to capture the important physical phenomena, p-finite elements and/or hp-finite elements are employed. The Reproducing Kernel Particle Methods (RKPM) are emerging as an effective alternative due to the absence of a mesh and the ability to analyze a specific frequency range. In this study, a wavelet particle method based on the multiresolution analysis encountered in signal processing has been developed. The interpolation functions consist of spline functions with a built-in window which permits translation as well as dilation. A variation in the size of the window implies a geometrical refinement and allows the filtering of the desired frequency range. An adaptivity similar to hp-finite element method is obtained through the choice of an optimal dilation parameter. The analysis of the wave equation shows the effectiveness of this approach. The frequency/wave number relationship of the continuum case can be closely simulated by using the reproducing kernel particle methods. A similar methodology is also developed for the Timoshenko beam.
A Time-Domain Implementation of Surface Acoustic Impedance Condition with and Without Flow
Authors: Özyörük Yusuf , Long Lyle N.
Published: October 2003

The impedance condition in computational aeroacoustic applications is required in order to model acoustically treated walls. The application of this condition in time-domain methods, however, is extremely difficult because of the convolutions involved. In this paper, a time-domain method is developed which overcomes the computational difficulties associated with these convolutions. This method builds on the z-transform from control and signal processing theory and the z-domain model of the impedance. The idea of using the z-domain operations originates from the computational electromagnetics community. When the impedance is expressed in the z-domain with a rational function, the inverse z-transform of the impedance condition results in only infinite impulse response type, digital, recursive filter operations. These operations, unlike convolutions, require only limited past-time knowledge of the acoustic pressures and velocities on the surface. Examples of one- and two-dimensional problems with and without flow indicate that the method promises success in aeroacoustic applications.
Random Walks, Fractals and the Origins of Rainforest Diversity
Authors: Solé Ricard V. , Alonso David
Published: October 2003

Rainforests are legendary because their extreme species richness. In the richest rain forests every second tree on a hectare is a differnt species. As a consequence, most species are rare. Using field data from studies in dfiferent parts of the world, we show that species-rich plots often display a distribution of number of species Ns(I) represented by I individuals with a power-law shape Ns(I)∝I-β with β≈1.5. Power laws are characteristic (but not exclusive) of systems poised close to critical points and this is supported by the analysis of the gap distribution over space in the Barro Colorado Island forest, which has been shown to be fractal. Here we propose a new model of rainforest dynamics which is able to account for a wide set of observations, strongly suggesting that indeed rainforests would be organized close to instability points, showing strongly path-dependent dynamics.