bluuebunny/crossref_metadata_2025 huggingface dataset:
Neutron-Mapping Polymer Flow: Scattering, Flow Visualization, and Molecular Theory
Authors: Bent J. , Hutchings L. R. , Richards R. W. , Gough T. , Spares R. , Coates P. D. , Grillo I. , Harlen O. G. , Read D. J. , Graham R. S. , Likhtman A. E. , Groves D. J. , Nicholson T. M. , McLeish T. C. B.
Published: September 2003

Flows of complex fluids need to be understood at both macroscopic and molecular scales, because it is the macroscopic response that controls the fluid behavior, but the molecular scale that ultimately gives rise to rheological and solid-state properties. Here the flow field of an entangled polymer melt through an extended contraction, typical of many polymer processes, is imaged optically and by small-angle neutron scattering. The dual-probe technique samples both the macroscopic stress field in the flow and the microscopic configuration of the polymer molecules at selected points. The results are compared with a recent “tube model” molecular theory of entangled melt flow that is able to calculate both the stress and the single-chain structure factor from first principles. The combined action of the three fundamental entangled processes of reptation, contour length fluctuation, and convective constraint release is essential to account quantitatively for the rich rheological behavior. The multiscale approach unearths a new feature: Orientation at the length scale of the entire chain decays considerably more slowly than at the smaller entanglement length.
Ultrafast Hydrogen-Bond Dynamics in the Infrared Spectroscopy of Water
Authors: Fecko C. J. , Eaves J. D. , Loparo J. J. , Tokmakoff A. , Geissler P. L.
Published: September 2003

We investigated rearrangements of the hydrogen-bond network in water by measuring fluctuations in the OH-stretching frequency of HOD in liquid D
2
O with femtosecond infrared spectroscopy. Using simulations of an atomistic model of water, we relate these frequency fluctuations to intermolecular dynamics. The model reveals that OH frequency shifts arise from changes in the molecular electric field that acts on the proton. At short times, vibrational dephasing reflects an underdamped oscillation of the hydrogen bond with a period of 170 femtoseconds. At longer times, vibrational correlations decay on a 1.2-picosecond time scale because of collective structural reorganizations.
A Seven-Transmembrane RGS Protein That Modulates Plant Cell Proliferation
Authors: Chen Jin-Gui , Willard Francis S. , Huang Jirong , Liang Jiansheng , Chasse Scott A. , Jones Alan M. , Siderovski David P.
Published: September 2003

G protein–coupled receptors (GPCRs) at the cell surface activate heterotrimeric G proteins by inducing the G protein alpha (Gα) subunit to exchange guanosine diphosphate for guanosine triphosphate. Regulators of G protein signaling (RGS) proteins accelerate the deactivation of Gα subunits to reduce GPCR signaling. Here we identified an RGS protein (AtRGS1) in
Arabidopsis
that has a predicted structure similar to a GPCR as well as an RGS box with GTPase accelerating activity. Expression of AtRGS1 complemented the pheromone supersensitivity phenotype of a yeast RGS mutant,
sst2
Δ. Loss of AtRGS1 increased the activity of the
Arabidopsis
Gα subunit, resulting in increased cell elongation in hypocotyls in darkness and increased cell production in roots grown in light. These findings suggest that AtRGS1 is a critical modulator of plant cell proliferation.
Island Biology and Ecosystem Functioning in Epiphytic Soil Communities
Authors: Wardle David A. , Yeates Gregor W. , Barker Gary M. , Bellingham Peter J. , Bonner Karen I. , Williamson Wendy M.
Published: September 2003

Although island attributes such as size and accessibility to colonizing organisms can influence community structure, the consequences of these for ecosystem functioning are little understood. A study of the suspended soils of spatially discrete epiphytes or treetop “islands” in the canopies of New Zealand rainforest trees revealed that different components of the decomposer community responded either positively or negatively to island size, as well as to the tree species that the islands occurred in. This in turn led to important differences between islands in the rates of ecosystem processes driven by the decomposer biota. This system serves as a model for better understanding how attributes of both real and habitat islands may affect key ecosystem functions through determining the community structure of organisms that drive these functions.
Cerebellar LTD and Learning-Dependent Timing of Conditioned Eyelid Responses
Authors: Koekkoek S. K. E. , Hulscher H. C. , Dortland B. R. , Hensbroek R. A. , Elgersma Y. , Ruigrok T. J. H. , De Zeeuw C. I.
Published: September 2003

Mammals can be trained to make a conditioned movement at a precise time, which is correlated to the interval between the conditioned stimulus and unconditioned stimulus during the learning. This learning-dependent timing has been shown to depend on an intact cerebellar cortex, but which cellular process is responsible for this form of learning remains to be demonstrated. Here, we show that protein kinase C–dependent long-term depression in Purkinje cells is necessary for learning-dependent timing of Pavlovian-conditioned eyeblink responses.
Generation of Megawatt Optical Solitons in Hollow-Core Photonic Band-Gap Fibers
Authors: Ouzounov Dimitre G. , Ahmad Faisal R. , Müller Dirk , Venkataraman Natesan , Gallagher Michael T. , Thomas Malcolm G. , Silcox John , Koch Karl W. , Gaeta Alexander L.
Published: September 2003

The measured dispersion of a low-loss, hollow-core photonic band-gap fiber is anomalous throughout most of the transmission band, and its variation with wavelength is large compared with that of a conventional step-index fiber. For an air-filled fiber, femtosecond self-frequency–shifted fundamental solitons with peak powers greater than 2megawatts can be supported. For Xe-filled fibers, nonfrequency-shifted temporal solitons with peak powers greater than 5.5 megawatts can be generated, representing an increase in the power that can be propagated in an optical fiber of two orders of magnitude. The results demonstrate a unique capability to deliver high-power pulses in a single spatial mode over distances exceeding 200 meters.
Soliton Self-Frequency Shift Cancellation in Photonic Crystal Fibers
Authors: Skryabin D. V. , Luan F. , Knight J. C. , Russell P. St. J.
Published: September 2003

We report the cancellation of the soliton self-frequency shift in a silica-core photonic crystal fiber with a negative dispersion slope. Numerical and experimental results show that stabilization of the soliton wavelength is accompanied by exponential amplification of the red-shifted Cherenkov radiation emitted by the soliton. The spectral recoil from the radiation acts on the soliton to compensate for the Raman frequency shift. This phenomenon may find applications in the development of a family of optical parametric amplifiers.
Insightful Storytelling on Geodynamics
Authors: Stevenson David J.
Published: September 2003

The Dynamic Structure of the Deep Earth
An Interdisciplinary Approach. by Shun-ichiro Karato. Princeton University Press, Princeton, NJ, 2003. 253 pp. $35, £24.95. ISBN 0-691-09511-6.

Karato integrates findings from mineral physics, seismology, and geodynamics to provide a graduate text on Earth's deep interior.
Erythrocyte G Protein-Coupled Receptor Signaling in Malarial Infection
Authors: Harrison Travis , Samuel Benjamin U. , Akompong Thomas , Hamm Heidi , Mohandas Narla , Lomasney Jon W. , Haldar Kasturi
Published: September 2003

Erythrocytic mechanisms involved in malarial infection are poorly understood. We have found that signaling via the erythrocyte β2-adrenergic receptor and heterotrimeric guanine nucleotide–binding protein (Gαs) regulated the entry of the human malaria parasite
Plasmodium falciparum
. Agonists that stimulate cyclic adenosine 3′,5′-monophosphate production led to an increase in malarial infection that could be blocked by specific receptor antagonists. Moreover, peptides designed to inhibit Gαs protein function reduced parasitemia in
P. falciparum
cultures in vitro, and β-antagonists reduced parasitemia of
P. berghei
infections in an in vivo mouse model. Thus, signaling via the erythrocyte β2-adrenergic receptor and Gαs may regulate malarial infection across parasite species.
The Anatomy of the World's Largest Extinct Rodent
Authors: Sánchez-Villagra Marcelo R. , Aguilera Orangel , Horovitz Inés
Published: September 2003

Phoberomys
is reported to be the largest rodent that ever existed, although it has been known only from isolated teeth and fragmentary postcranial bones. An exceptionally complete skeleton of
Phoberomys pattersoni
was discovered in a rich locality of fossil vertebrates in the Upper Miocene of Venezuela. Reliable body mass estimates yield ∼700 kilograms, more than 10 times the mass of the largest living rodent, the capybara. With
Phoberomys
, Rodentia becomes one of the mammalian orders with the largest size range, second only to diprotodontian marsupials. Several postcranial features support an evolutionary relationship of
Phoberomys
with pakaranas from the South American rodent radiation. The associated fossil fauna is diverse and suggests that
Phoberomys
lived in marginal lagoons and wetlands.
Dreams That Stuff Is Made Of
Authors: Robinson Spider
Published: September 2003

Where Stuff Comes From
How Toasters, Toilets, Cars, Computers, and Many Other Things Come to Be As They Are. by Harvey Molotch. Routledge, New York, 2003. 336 pp. $24.95, C$34.95. ISBN 0-415-94400-7.

Molotch explores the web of interactions (including social, cultural, and economic factors) that determine how everyday objects are designed, manufactured, distributed, and used.
A CASE FOR SINGLE SYSTEM IMAGE CLUSTER OPERATING SYSTEMS: THE KERRIGHED APPROACH
Authors: VALLÉE GEOFFROY , LOTTIAUX RENAUD , RILLING LOUIS , BERTHOU JEAN-YVES , MALHEN IVAN DUTKA , MORIN CHRISTINE
Published: September 2003

In this paper, we present fundamental mechanisms for global process and memory management in an efficient single system image cluster operating system designed to execute workloads composed of high performance sequential and parallel applications. Their implementation in Kerrighed, our proposed distributed operating system, is composed of a set of Linux modules and a patch of less than 200 lines of code to the Linux kernel. Kerrighed is a unique single system image cluster operating system providing the standard Unix interface as well as distributed OS mechanisms such as load balancing on all cluster nodes. Our support for standard Unix interface includes support for multi-threaded applications and a checkpointing facility for both sequential and shared memory parallel applications. We present an experimental evaluation of the Kerrighed system and demonstrate the feasibility of the single system image approach at the kernel level.
VISUALIZATION SERVICES ON THE GRID: THE GRID VISUALIZATION KERNEL
Authors: HEINZLREITER PAUL , KRANZLMÜLLER DIETER
Published: September 2003

Two important tools of today's science and engineering are computational grids and visualization. While grid infrastructures offer a means to process large amounts of data across different, possibly distant resources, visualization aids in understanding the meaning of data. The Grid Visualization Kernel (GVK) addresses the connection of grid applications and visualization clients on the grid. The visualization capabilities of GVK are provided as flexible grid services via dedicated interfaces and protocols, while GVK itself relies on Globus services to implement the functionality of the visualization pipeline. This paper describes the concept of GVK and its core functionality for grid visualization services, and discusses how to use visualization in the grid environment.
TOWARDS THE DESIGN OF A HIGH PERFORMANCE ACTIVE NODE
Authors: GELAS JEAN-PATRICK , EL HADRI SAAD , LEFÈVRE LAURENT
Published: September 2003

Achieving high performance in active networks is one of the most challenging task. In this paper, we propose an architecture for the design of next generation gigabit active routers . This original architecture allows service deployment of 4 levels: inside network cards, in kernel space, in user space and on distributed computing resources. We deploy and validate this architecture within the Tamanoir execution environment. First experiments on gigabit network platforms are described.
AUTOMATIC PERFORMANCE ANALYSIS AND DYNAMIC TUNING OF DISTRIBUTED APPLICATIONS
Authors: MORAJKO ANNA , MORAJKO OLEG , JORBA JOSEP , MARGALEF TOMÀS , LUQUE EMILIO
Published: September 2003

The classical way of tuning parallel/distributed applications is based on the analysis of the monitoring information obtained from an execution of the application. However, this "measure and modify" approach is not feasible when the applications have a dynamic behavior. In this case, another approach is required to accomplish performance expectations. This paper presents a solution based on the dynamic tuning approach that addresses these issues. In this approach, an application is monitored, its performance bottlenecks are detected and the application is modified automatically during the execution, without stopping, recompiling or re-running it. The introduced modifications adapt the behavior of the application to dynamic variations.
USABILITY ISSUES IN DEVELOPING TOOLS FOR THE GRID — AND HOW VISUAL REPRESENTATIONS CAN HELP
Authors: PANCAKE CHERRI M.
Published: September 2003

Initial tools developed for grid administrators and users have built on the technology and representational techniques of large parallel systems. Like their predecessors, grid tools must cope with extreme variations in scale, rapidly evolving hardware and software environments, and the competing demands of operating systems and middleware. Computational grids present several unique challenges, however, that go well beyond the lessons we have learned from parallel and distributed tools: the volatile nature of grid resources, their extreme heterogeneity, and the lack of coordinated management. Because they define a new and unfamiliar computing environment, there is a significant human challenge as well. Grid users will be extremely diverse, including resource providers, resource managers, users of data and derived data products, etc., as well as application developers. The future usability of the grid will depend on how well grid tools can capture information on grid resources and synthesize a higher-level perspective that helps users make sense of this complex new environment.

This article identifies the tool requirements that will have most impact on the usability. It then explores recent advances in information visualization, demonstrating that many of the techniques grid tools will need already exist in preliminary form. A series of examples illustrates how those techniques can be applied to portray grid landscapes (graphical representations of grid resources, activities, behavior, costs, etc.) in useful and meaningful ways.
ALGORITHMS FOR HIGH PERFORMANCE, WIDE-AREA DISTRIBUTED FILE DOWNLOADS
Authors: PLANK JAMES S. , ATCHLEY SCOTT , DING YING , BECK MICAH
Published: September 2003

As peer-to-peer and wide-area storage systems become in vogue, the issue of delivering content that is cached, partitioned and replicated in the wide area, with high performance, becomes of great importance. This paper explores three algorithms for such downloads. The storage model is based on the Network Storage Stack, which allows for flexible sharing and utilization of writable storage as a network resource. The algorithms assume that data is replicated in various storage depots in the wide area, and the data must be delivered to the client either as a downloaded file or as a stream to be consumed by an application, such as a media player. The algorithms are threaded and adaptive, attempting to get good performance from nearby replicas, while still utilizing the faraway replicas. After defining the algorithms, we explore their performance downloading a 50 MB file replicated on six storage depots in the U.S., Europe and Asia, to two clients in different parts of the U.S. One algorithm, called progress-driven redundancy, exhibits excellent performance characteristics for both file and streaming downloads.
SCHEDULING STRATEGIES FOR MIXED DATA AND TASK PARALLELISM ON HETEROGENEOUS CLUSTERS
Authors: BEAUMONT O. , LEGRAND A. , MARCHAL L. , ROBERT Y.
Published: September 2003

We consider the execution of a complex application on a heterogeneous "grid" computing platform. The complex application consists of a suite of identical, independent problems to be solved. In turn, each problem consists of a set of tasks. There are dependences (precedence constraints) between these tasks and these dependences are organized as a tree. A typical example is the repeated execution of the same algorithm on several distinct data samples. We use a non-oriented graph to model the grid platform, where resources have different speeds of computation and communication. We show how to determine the optimal steady-state scheduling strategy for each processor (the fraction of time spent computing and the fraction of time spent communicating with each neighbor). This result holds for a quite general framework, allowing for cycles and multiple paths in the platform graph.
DATABASE SUPPORT FOR DATA-DRIVEN SCIENTIFIC APPLICATIONS IN THE GRID
Authors: NARAYANAN SIVARAMAKRISHNAN , KURC TAHSIN , CATALYUREK UMIT , SALTZ JOEL
Published: September 2003

In this paper we describe a services oriented software system to provide basic database support for efficient execution of applications that make use of scientific datasets in the Grid. This system supports two core operations: efficient selection of the data of interest from distributed databases and efficient transfer of data from storage nodes to compute nodes for processing. We present its overall architecture and main components and describe preliminary experimental results.
TOWARDS SELF-ORGANIZING DISTRIBUTED COMPUTING FRAMEWORKS: THE H2O APPROACH
Authors: KURZYNIEC DAWID , WRZOSEK TOMASZ , DRZEWIECKI DOMINIK , SUNDERAM VAIDY
Published: September 2003

A novel component-based, service-oriented framework for distributed metacomputing is described. Adopting a provider-centric view of resource sharing, this framework emphasizes lightweight software infrastructures that maintain minimal state, and interface to current and emerging distributed computing standards. In this model, resource owners host a software backplane onto which owners, clients, or third-party resellers may load components or component-suites that deliver value added services without compromising owner security or control. Standards-based descriptions of services facilitate publication and discovery via established schemes. The architecture of the container framework, design of components, security and access control schemes, and preliminary experiences are described in this paper.
SRS: A FRAMEWORK FOR DEVELOPING MALLEABLE AND MIGRATABLE PARALLEL APPLICATIONS FOR DISTRIBUTED SYSTEMS
Authors: VADHIYAR SATHISH S. , DONGARRA JACK J.
Published: September 2003

The ability to produce malleable parallel applications that can be stopped and reconfigured during the execution can offer attractive benefits for both the system and the applications. The reconfiguration can be in terms of varying the parallelism for the applications, changing the data distributions during the executions or dynamically changing the software components involved in the application execution. In distributed and Grid computing systems, migration and reconfiguration of such malleable applications across distributed heterogeneous sites which do not share common file systems provides flexibility for scheduling and resource management in such distributed environments. The present reconfiguration systems do not support migration of parallel applications to distributed locations. In this paper, we discuss a framework for developing malleable and migratable MPI message-passing parallel applications for distributed systems. The framework includes a user-level checkpointing library called SRS and a runtime support system that manages the checkpointed data for distribution to distributed locations. Our experiments and results indicate that the parallel applications, with instrumentation to SRS library, were able to achieve reconfigurability incurring about 15-35% overhead.
First Principles Investigations of Diamond Ultrananocrystals
Authors: Barnard A. S. , Russo S. P. , Snook I. K.
Published: September 2003

Presented here are results of ab initio Density Functional Theory (DFT) structural relaxations performed on dehydrogenated and monohydrogenated nanocrystalline diamond structures of octahedral {111} and cuboctahedral morphologies, up to approximately 2 nm in diameter. Our results in this size range show an inward transition of dehydrogenated nanodiamond clusters into carbon onion-like structures, with preferential exfoliation of the (111) surfaces, in agreement with experimental observations. However, we have found that this transition may be prevented by monohydrogenation of the surfaces. Bonding of atoms in the surface layers of the relaxed structures, and interlayer bonding has been investigated using the electron charge density.
The Influence of Heat Treatment on Electric Properties of Bulk (Bi,Pb):2223 Superconductor
Authors: Pop V.
Published: September 2003

The (Bi,Pb)(Sr,Ba) :2223 samples were prepared using different sintering temperatures. The electrical properties were investigated by electrical resistance and V–I characteristics measurements. The increase of sintering temperature induces the decrease of transition width and the increase of intergranular critical current density Jcj and phase purity. The critical current density from electrical measurement agrees with the results obtained from complex magnetic susceptibility measurements function of temperature and AC field amplitude.
MgB2: Superconductivity and Pressure
Authors: Islam A. K. M. A. , Islam F. N.
Published: September 2003

The present work is an overview of the properties of the newly discovered MgB 2 carried out by us using first-principles density functional calculations as implemented in a program package, not used by other workers. Structural, bonding and elastic properties, phonon coupling, transition temperature, electronic band structure, density of states, charge-density and chemical bonding, electric field gradient are all considered for the new material at ambient and at higher pressures. New and interesting aspects including the pressure-induced structural phase transition in MgB 2 are also discussed. The calculations are compared with the available results and their implications are discussed which may help in understanding some key issues.
Low Field Second Harmonic Response and AC Susceptibility of (Bi,Pb)-2223 Pellet in a Generalized Critical State Model
Authors: Ray A. , Dey T. K. , Ghatak S. K.
Published: September 2003

The AC susceptibility and second harmonic response of bulk high Tc superconductor (Bi,Pb) -2223 is measured in presence of small AC field excitation and DC magnetic field superimposed on it. This response increases with the increase in DC field whereas decreases at a higher excitation amplitude. Critical state models are used to explain the nonlinear magnetic response in HTSCs. With a generalized field dependence of critical current Jc : Jc(B) = J0/(1 + B/B0)n, the fundamental AC susceptibility and low field second harmonics response are calculated for different n values. It is found that the theoretical consideration adopted here explains the observed AC susceptibility and low field second harmonic response qualitatively reasonably well within the Anderson–Kim regime (n = 1).
Dielectric Behavior and Impedance Spectroscopy of Bi2Sr2GdCu2Oy
Authors: Chandrasekhar M.
Published: September 2003

Samples with the nominal composition Bi 2 Sr 2 GdCu 2 O y in Bi -2212 where Gd replaces Ca as well as samples without Gd were prepared by solid-state reaction method. From the room temperature X-ray diffraction data, the samples were found to be similar to the single phase Bi -2212 structure. Impedance studies were performed from room temperature to 423 K at different frequencies in the range of 10 to 700 KHz. The AC conductivity increases with temperature and frequency, exhibiting frequency dispersion at low temperature region. The activation energy from AC conductivity in the high temperature region is found to be 0.432 eV. The permitivity increases with the increase in temperature and at 373 K it shows a maximum value exhibiting a dielectric loss. Complex impedance spectra are analyzed in terms of bulk relaxation and interfacial effects. The activation energy of the dipoles involved in the relaxation was estimated to be 0.482 eV. The universal power law of Jonscher is verified in the present system.
Stripe Phase: Analytical Results for Weakly Coupled Repulsive Hubbard Model
Authors: Mukhin S. I. , Matveenko S. I.
Published: September 2003

Motivated by the stripe developments in cuprates, we review analytical results for the spin-charge solitonic superstructures derived in the framework of the Hubbard model in our studies of weakly coupled (quasi) one-dimensional repulsive electron systems on a lattice. These results demonstrate that close to half filling, in the high temperature regime above the mean field transition temperature, short range repulsions favor charge density fluctuations with wavevectors bearing special relations with those of the spin density fluctuations. In the low temperature regime, besides the wavevectors, mutual phases of the charge and spin densities also become coupled due to a quantum interference phenomenon, leading to the stripe phase instability. It is shown that away from half filling, periodic lattice potential causes cooperative condensation of the spin and charge superlattices. "Switching off" this potential leads to the vanishing of the stripe order. The leading spin-charge coupling term in the effective Landau functional is derived microscopically. Results of the 1D renormalization group ("parquet") analysis away from half filling are also presented. They reveal transient-scale correlations resembling the mean-field pattern. Possible correspondence of our theory with the experimental data on stripe phase in high Tc cuprates is discussed.
A Dendrite with "Sierpinski Gasket" Fractal Morphology in Matt Glaze of LiAlSiO4-SiO2 System
Authors: Zhao Shanrong , Tan Jin , Wang Jiyang , Xu Xiaohong , Liu Hong
Published: September 2003

In this paper, we introduce a dendritic crystal, formed in matt glaze of LiAlSiO 4- SiO 2, having "Sierpinski gasket" fractal morphology. The crystal structure of this "Sierpinski gasket" dendrite is β-quartz. β-quartz can grow two kinds of fractal patterns: snow-shaped dendrite and "Sierpinski gasket" dendrite, depending on different supercooling conditions. These two kinds of fractals can develop together in one dendritic crystal. The evolution of the boundary morphologies between these two kinds of fractal dendrites can be described by another fractal — Koch curve. The "Sierpinski gasket" dendrite is a rather new fractal growth pattern which can introduce new opportunities to fractal growth research of nonlinear sciences.
Marginal Distribution of Stationary Multifractal Measures and Their Haar Wavelet Coefficients
Authors: Veneziano Daniele , Furcolo Pierluigi
Published: September 2003

Let X be a stationary multifractal measure in the unit cube S0of Rdand Xr= X(S0/r), r ≥ 1, be the measure in a smaller cube. We develop methods to calculate the marginal distributions of Xrand the coefficients Cj,iof the Haar wavelet representation of X. The methods are exact for discrete cascades and approximate for continuous-scaling multifractal measures. In the small scale limit r → ∞, the distribution of log [Xr] or log [Xr|Xr> 0] converges under renormalization to one of three different distribution types: normal, stable non-normal, or non-stable of a particular type. The normal distribution has the largest domain of attraction. The distribution of the absolute wavelet coefficients |Cj,i| at level j has similar asymptotic properties as j → ∞. We also develop a way to directly obtain the integer moments of Xrand Cj,iwithout preliminary calculation of the marginal distributions. Using the marginal distribution of the measure density εr= rdXr, we assess the accuracy for finite r of the asymptotic scaling relation P[εr> rγ] ~ r-c(γ), where c(γ) is the co-dimension function of X.
On a Generalized Fatou-Julia Theorem
Authors: Rochon Dominic
Published: September 2003

In this article, we continue to explore some specific results in bicomplex dynamics. In particular, we give a bicomplex version of the so-called Fatou-Julia theorem. In fact, we give a complete topological characterization in ℝ4 of the bicomplex filled-Julia set for a quadratic polynomial in bicomplex numbers of the form w2 + c.
Self-Similar Criticality
Authors: Tebbens Sarah F. , Burroughs Stephen M.
Published: September 2003

Cumulative frequency-size distributions associated with many natural phenomena follow a power law. Self-organized criticality (SOC) models have been used to model characteristics associated with these natural systems. As originally proposed, SOC models generate event frequency-size distributions that follow a power law with a single scaling exponent. Natural systems often exhibit power law frequency-size distributions with a range of scaling exponents. We modify the forest fire SOC model to produce a range of scaling exponents. In our model, uniform energy (material) input produces events initiated on a self-similar distribution of critical grid cells. An event occurs when material is added to a critical cell, causing that material and all material in occupied non-diagonal adjacent cells to leave the grid. The scaling exponent of the resulting cumulative frequency-size distribution depends on the fractal dimension of the critical cells. Since events occur on a self-similar distribution of critical cells, we call this model Self-Similar Criticality (SSC). The SSC model may provide a link between fractal geometry in nature and observed power law frequency-size distributions for many natural systems.
Hidden Variable Bivariate Fractal Interpolation Surfaces
Authors: Chand A. K. B. , Kapoor G. P.
Published: September 2003

We construct hidden variable bivariate fractal interpolation surfaces (FIS). The vector valued iterated function system (IFS) is constructed in ℝ4 and its projection in ℝ3 is taken. The extra degree of freedom coming from ℝ4 provides hidden variable, which is an important factor for flexibility and diversity in the interpolated surface. In the present paper, we construct an IFS that generates both self-similar and non-self-similar FIS simultaneously and show that the hidden variable fractal surface may be self-similar under certain conditions.
Smoothing Before Estimating Uncertainty, Scaling and Intermittency: Application to Short Heart Rate Signals
Authors: Bickel David R.
Published: September 2003

Three aspects of time series are uncertainty (dispersion at a given time scale), scaling (time-scale dependence) and intermittency (inclination to change dynamics). Simple measures of dispersion are the mean absolute deviation and the standard deviation; scaling exponents describe how dispersions change with the time scale. Intermittency has been defined as a difference between two scaling exponents. After taking a moving average, these measures give descriptive information, even for short heart rate records. For this data, dispersion and intermittency perform better than scaling exponents.
Symbolic Analysis of Swimming Trajectories Reveals Scale Invariance and Provides a Model for Fish Locomotion
Authors: Faure Philippe , Neumeister Heike , Faber Donald S. , Korn Henri
Published: September 2003

We have questioned whether a complex behavior, such as fish swimming, can be better described quantitatively as a sequence of discrete events or states than with classical kinematic measures which can be compromised by inherent variability. Here, the different states, expressed as combinations of symbols, were defined on the basis of the animal's location (A: periphery, and B: inner part of the aquarium) and speed (Fast and Slow). We observed that the distributions of time intervals spent in the successive states were not gaussian. Rather, they were fit by power laws associated with an underlying Lévy-like process which has more long intervals, primarily due to prolonged periods of relative inactivity. Furthermore, our data suggest that the swimming behavior can be attributed to interactions between two intrinsic systems. One is represented by the matrix of transition of probabilities between states and controls their sequential organization while the second, which is defined by interval distributions, determines the time spent in each state. This kinetic model detects subtle effects of low doses of neuroactive compounds, and identifies their specific locus of action. We propose that this paradigm can be applied to characterize normal behavior and its modifications by genetic or pharmacological manipulations.
Power-Spectrum Behavior of Yearly Mean Grain Yields
Authors: Valdez-Cepeda Ricardo D. , Mendoza Blanca , Díaz-Sandoval Rosa , Valdés-Galicia José , López-Martínez José D. , de Celis Enrique Martínez-Rubín
Published: September 2003

Advanced statistical approaches have been applied to determine the temporal scaling-invariance laws in annual mean yields registered in Mexico during the period 1897–1999. When the maize, bean, wheat and rice series are treated as self-affine profiles through power spectrum analysis, the temporal fluctuation f-β is detected in each case for time scales of 2 to 103 years. β values (p < 0.0001) of -1.84 ± 0.15, -1.71 ± 0.218, -1.62 ± 0.194 and -1.7 ± 0.139 for maize, bean, wheat and rice profiles, respectively, suggest that short-term variation is important and are influencing the dynamic evolution of the yearly mean yields. Thus, in addition to the linear trends driven by endogenous factors of agricultural systems, grain yield variation may be due to external forcings such as climatic oscillations and/or solar signals. Through the spectral analysis using the maximum entropy method, the influence of external forcings on the behavior of the annual mean yields in all four crops was evidenced. The detected main external forcings are: a 6- to 8-year political oscillation, the magnetic and sunspot cycles of the Sun, and El Niño Southern Oscillation (ENSO). Taking into account the number of significant periodicities, the order of annual mean yield series' sensitivity to external forcings influencing their short-term variation is as follows: maize < wheat < rice < bean.
Antiarrhythmic Drug Target Choices and Screening
Authors: Sanguinetti Michael C. , Bennett Paul B.
Published: September 2003

Most antiarrhythmic drugs are ion channel blockers, and to date, those tested in large randomized placebo-controlled clinical trials have shown no decrease in mortality outcome. This apparent lack of survival benefit may result from the significant liabilities associated with these agents that offset any long-term benefit. Despite the current success of implantable defibrillators and the future promise of gene therapy, there is still a pressing need for new antiarrhythmic drugs. An improved understanding of cardiac ion channels and novel approaches to target selection and compound screening will provide new opportunities for drug discovery in the near future. Here, we briefly review the multiple mechanisms of arrhythmia, the history of drug failures, and the possibilities that evolving technologies may provide in the search for more efficacious and safer antiarrhythmic drugs.
Early decompressive craniectomy and duraplasty for refractory intracranial hypertension in children: results of a pilot study
Authors: Ruf Bettina , Heckmann Matthias , Schroth Ilona , Hügens-Penzel Monika , Reiss Irwin , Borkhardt Arndt , Gortner Ludwig , Jödicke Andreas
Published: September 2003

Introduction

Severe traumatic brain injury (TBI) in childhood is associated with a high mortality and morbidity. Decompressive craniectomy has regained therapeutic interest during past years; however, treatment guidelines consider it a last resort treatment strategy for use only after failure of conservative therapy.

Patients

We report on the clinical course of six children treated with decompressive craniectomy after TBI at a pediatric intensive care unit. The standard protocol of intensive care treatment included continuous intracranial pressure (ICP) monitoring, sedation and muscle relaxation, normothermia, mild hyperventilation and catecholamines to maintain an adequate cerebral perfusion pressure. Decompressive craniectomy including dura opening was initiated in cases of a sustained increase in ICP > 20 mmHg for > 30 min despite maximally intensified conservative therapy (optimized sedation and ventilation, barbiturates or mannitol).

Results

In all cases, the ICP normalized immediately after craniectomy. At discharge, three children were without disability, two children had a mild arm-focused hemiparesis (one with a verbal impairment), and one child had a spastic hemiparesis and verbal impairment. This spastic hemiparesis improved within 6 months follow-up (no motor deficit, increased muscle tone), and all others remained unchanged.

Conclusion

These observational pilot data indicate feasibility and efficacy of decompressive craniectomy in malignant ICP rise secondary to TBI. Further controlled trials are necessary to evaluate the indication and standardization of early decompressive craniectomy as a 'second tier' standard therapy in pediatric severe head injury.
Voluntary Medication Error Reporting Program in a Japanese National University Hospital
Authors: Furukawa Hiroyuki , Bunko Hisashi , Tsuchiya Fumito , Miyamoto Ken-ichi
Published: September 2003

BACKGROUND:

In Japan, as in other countries, medical accidents arising from human error can seriously damage public confidence in medical services, as well as being intrinsically undesirable.

OBJECTIVE:

Errors voluntarily reported by the healthcare practitioners in our institution (Kanazawa University Hospital) were considered to assess the contributory factors by using the accumulated error database in the hospital information system.

METHODS:

Medical errors in our institution during the period from July 1, 2000, to June 30, 2002, were counted using the error reporting system database and were classified.

RESULTS:

The number of errors reported during the investigation period was 1378, of which 78% were reported by nursing staff. Medication errors involving administration of injectable or oral drugs to inpatients, dispensing, and prescription accounted for about 50% of that number. Among dispensing errors, 53% were detected by patients or their families and 36% by nurses.

CONCLUSIONS:

The best method of error prevention is to learn from previous errors. For this purpose, the error reporting program is effective. In patient safety management, it is important to take into account the potential risks of future errors, as well as to capture information about errors that have already happened. For safety management, adoption of appropriate information technology (e.g., implementation of a prescription order entry system) is effective in reducing medication errors. However, it is important to note that serious errors can also arise in computer-based systems.
Allopurinol as a Cardioprotectant during Coronary Artery Bypass Graft Surgery
Authors: Weimert Nicole A , Tanke William F , Sims J Jason
Published: September 2003

OBJECTIVE:

To examine the role of allopurinol as a cardioprotectant during coronary artery bypass graft (CABG) surgery.

DATA SOURCES:

A search of MEDLINE (1966–October 2002) was performed using the following terms: allopurinol, xanthine oxidase, oxygen free radical, and coronary artery bypass. References evaluated were limited to English-language and human studies, yielding 41 citations, 13 of which were found suitable. The 5 largest studies are discussed.

DATA SYNTHESIS:

Multiple studies with various doses have evaluated the effects of allopurinol on outcomes in CABG patients. These studies found that allopurinol can reduce in hospital mortality, improve cardiac performance, reduce incidence of arrhythmias, reduce markers of ischemia and free-radical generation, and reduce the need for inotropic support. However, these findings were not consistent between all studies.

CONCLUSIONS:

Allopurinol may reduce the incidence of CABG complications. Although the optimal dose has not been determined, reviewed literature suggests that patients should receive at least 600 mg one day prior to surgery, as well as at least 600 mg on the day of surgery.
Evaluation of HIV Drug Interaction Web Sites
Authors: Sheehan Nancy L , Kelly Deborah V , Tseng Alice L , van Heeswijk Rolf PG , Béïque Lizanne C , Hughes Christine A
Published: September 2003

BACKGROUND:

Clinicians frequently consult HIV drug interaction Web sites of unknown quality.

OBJECTIVE:

To systematically review and identify HIV drug interaction Web sites of high quality and usefulness for healthcare professionals.

METHODS:

Relevant Web sites were identified through a structured search on commonly used search engines. An assessment tool containing 4 domains (content, reliability, access restrictions, ease of navigation) was developed. English and French Web sites were selected for review if they included HIV drug interaction information directed to healthcare professionals. Web sites were excluded if antiretroviral interaction data were not available or were out of date. Commercial online databases and sites that required payment were not included. Seventeen HIV pharmacists from across Canada participated in the review. The Web sites were ranked with total mean scores. Mean scores for each domain were then analyzed. Interrater agreement and ANOVA using the rater as a covariate were determined.

RESULTS:

Nine Web sites met the criteria for review. Web sites from Toronto General Hospital (Canada), HIVinSite (beta version) (US), and the University of Liverpool (UK) ranked highest for total mean scores and for content. Other Web sites were found to be reliable, accessible, and easy to navigate; however, they did not consistently include unpublished data or data on herbal preparations, recreational drugs, or multiple interactions.

CONCLUSIONS:

Three HIV interaction Web sites of high quality were identified that can be valuable tools for HIV and non-HIV healthcare professionals. Regular reviews are necessary in order to keep pace with the growing body of HIV interaction data and the constant evolution of Web sites.
Drug-Induced Esophageal Injuries and Dysphagia
Authors: O'Neill Jessica L , Remington Tami L
Published: September 2003

OBJECTIVE:

To review and analyze medical literature documenting drug-induced esophageal injury and dysphagia and to formulate strategies to enhance pharmacists' prevention, detection, and treatment of these iatrogenic complications.

DATA SOURCES:

A MEDLINE search (1966–April 2002) was conducted to identify primary and secondary literature using variable combinations of the following search terms: pill-induced, drug-induced, or iatrogenic with esophageal injury, esophageal damage, or dysphagia. Bibliographies were also reviewed to identify additional relevant references.

STUDY SELECTION AND DATA EXTRACTION:

All case reports, reviews, and clinical studies relating to drug-induced esophageal injury or swallowing dysfunction were evaluated.

DATA SYNTHESIS:

Drug-induced esophageal injury may be under-recognized. Several drugs have been associated with physical or chemically mediated injuries. Risk factors for injury have been identified and preventive and treatment strategies have been successful in limiting esophageal injury. Drug-induced dysphagia can have serious complications and is most often associated with typical neuroleptics such as haloperidol.

CONCLUSIONS:

Pharmacists can play a pivotal role in proactively identifying situations where there is a higher likelihood of drug-induced esophageal injury or dysphagia. They can recommend preventive strategies to promote safe medication use, help identify iatrogenic complications when they occur, and assist in formulation of appropriate treatment strategies.
Causes and Management of Hyponatremia
Authors: Palmer Biff F , Gates John R , Lader Malcolm
Published: September 2003

OBJECTIVE:

To review clinical information on the incidence and causes of hyponatremia (defined as a serum sodium level <130 mEq/L), the most common electrolyte abnormality seen in general hospital patients, and to discuss the diagnosis and treatment of hyponatremia in relation to these factors.

DATA SOURCES:

Primary sources and review articles were identified via MEDLINE (1981–July 2003) for entries on hyponatremia. We limited the search to specific topics including incidence, risk factors, diagnosis, treatment, and clinical disorders and medications associated with hypotonic hyponatremia.

STUDY SELECTION AND DATA EXTRACTION:

All of the articles identified were evaluated, and relevant and representative information was included in this review.

DATA SYNTHESIS:

Hyponatremia can result from several disease states, injury, surgery, physical exercise, or the administration of certain drugs (e.g., antidepressants, antiepileptics) and is associated with advanced age. Drug-induced hyponatremia is often asymptomatic and usually resolves following water restriction and monitoring of medication. Symptoms of hyponatremia are primarily neurologic; the principal danger of hyponatremia relates to effects on central nervous system function due to changes in brain size.

CONCLUSIONS:

Although hyponatremia can be a serious condition, appropriate measures for the management of at-risk and affected patients will lead to full recovery in most cases.
Venlafaxine Treatment of Fibromyalgia
Authors: Sayar Kemal , Aksu Gokhan , Ak Ismail , Tosun Mehmet
Published: September 2003

BACKGROUND:

Although the pathophysiology of fibromyalgia is unknown, central monoaminergic transmission may play a role. Antidepressants have proved to be successful in alleviating symptoms of fibromyalgia. Medications that act on multiple neurotransmitters may be more effective in symptom management.

OBJECTIVE:

To assess the efficacy of venlafaxine, a potent inhibitor of both norepinephrine and serotonin reuptake, in the treatment of patients with fibromyalgia.

METHODS:

Fifteen patients with fibromyalgia were assessed prior to and after treatment with fixed-dose venlafaxine 75 mg/d. Before initiation of pharmacotherapy, patients were interviewed with the Structured Clinical Interview for Axis I disorders in the Diagnostic and Statistical Manual of Mental Disorders, 4th edition. The study lasted for 12 weeks, and patients were evaluated in weeks 6 and 12. The primary outcome measures were the Fibromyalgia Impact Questionnaire (FIQ) total score and pain score. The anxiety and depression levels of the patients were measured with the Beck Depression, the Beck Anxiety, the Hamilton Anxiety, and the Hamilton Depression scales.

RESULTS:

There was a significant improvement in the mean intensity of pain (F = 14.3; p = 0.0001) and in the disability caused by fibromyalgia (F = 42.7; p = 0.0001) from baseline to week 12 of treatment. The depression and anxiety scores also decreased significantly from baseline to week 12. The improvement in the FIQ scores did not correlate with the decrease of scores in both patient- and physician-rated depression and anxiety inventories. Change in pain scores also was not correlated with the change in depression and anxiety scores.

CONCLUSIONS:

Venlafaxine was quite promising in alleviating the pain and disability associated with fibromyalgia. This effect seems to be independent of its anxiolytic and antidepressant properties. Blockade of both norepinephrine and serotonin reuptake might be more effective than blockade of either neurotransmitter alone in the treatment of fibromyalgia.