bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Phylogeny of the Psittacid Herpesviruses Causing Pacheco's Disease: Correlation of Genotype with Phenotypic Expression
Authors: Tomaszewski Elizabeth K. , Kaleta Erhard F. , Phalen David N. 
Published: September 2003

ABSTRACTFragments of 419 bp of the UL16 open reading frame from 73 psittacid herpesviruses (PsHVs) from the United States and Europe were sequenced. All viruses caused Pacheco's disease, and serotypes of the European isolates were known. A phylogenetic tree derived from these sequences demonstrated that the PsHVs that cause Pacheco's disease comprised four major genotypes, with each genotype including between two and four variants. With the exception of two viruses, the serotypes of the virus isolates could be predicted by the genotypes. Genotypes 1 and 4 corresponded to serotype 1 isolates, genotype 2 corresponded to serotype 2 isolates, and genotype 3 corresponded to serotype 3 isolates. The single serotype 4 virus mapped to genotype 4. DNA from a virus with a unique serotype could not be amplified with primers that amplified DNA from all other PsHVs, and its classification remains unknown. Viruses representing all four genotypes were found in both the United States and Europe, and it was therefore predicted that serotypes 1, 2, and 3 were present in the United States. Serotype 4 was represented by a single European isolate that could not be genetically distinguished from serotype 1 viruses; therefore, the presence of serotype 4 in the United States could not be predicted. Viruses of genotype 4 were found to be the most commonly associated with Pacheco's disease in macaws and conures and were least likely to be isolated in chicken embryo fibroblasts in the United States. All four genotypes caused deaths in Amazon parrots, but genotype 4 was associated with Pacheco's disease only in Amazons in Europe. Genotypes 2, 3, and 4, but not 1, were found in African grey parrots. Although parrots from the Pacific distribution represent a relatively small percentage of the total number of birds with Pacheco's disease, all four genotypes were found to cause disease in these species.
Characterization of Endogenous Retroviruses in Sheep
Authors: Klymiuk Nikolai , Müller Mathias , Brem Gottfried , Aigner Bernhard 
Published: September 2003

ABSTRACT

Endogenous retrovirus (ERV) sequences have been found in all mammals. In vitro and in vivo experiments revealed ERV activation and cross-species infection in several species. Sheep (
Ovis aries
) are used for various biotechnological purposes; however, they have not yet been comprehensively screened for ERV sequences. Therefore, the aim of the study was to classify the ERV sequences in the ovine genome (OERV) by analyzing the retroviral
pro
-
pol
sequences. Three OERV β families and nine OERV γ families were revealed. Novel open reading frames (ORF) in the amplified proviral fragment were found in one OERV β family and two OERV γ families. Hybrid OERV produced by putative recombination events were not detected. Quantitative analysis of the OERV sequences in the ovine genome revealed no relevant variations in the endogenous retroviral loads of different breeds. Expression analysis of different tissues from fetal and pregnant sheep detected mRNA from both gammaretrovirus families, showing ORF fragments. Thus, the release of retroviruses from sheep cells cannot be excluded.
Dissemination of Rat Cytomegalovirus through Infected Granulocytes and Monocytes In Vitro and In Vivo
Authors: van der Strate B. W. A. , Hillebrands J. L. , Lycklama à Nijeholt S. S. , Beljaars L. , Bruggeman C. A. , van Luyn M. J. A. , Rozing J. , The T. H. , Meijer D. K. F. , Molema G. , Harmsen M. C. 
Published: September 2003

ABSTRACTThe role of leukocytes in the in vivo dissemination of cytomegalovirus was studied in this experiment. Rat cytomegalovirus (RCMV) could be transferred to rat granulocytes and monocytes by cocultivation with RCMV-infected fibroblasts in vitro. Intravenous injection of purified infected granulocytes or monocytes resulted in a systemic infection in rats, indicating that our model is a powerful tool to gain further insight into CMV dissemination and the development of new antivirals.
Molecular Dissection of the Vaccinia Virus I7L Core Protein Proteinase
Authors: Byrd Chelsea M. , Bolken Tove' C. , Hruby Dennis E. 
Published: September 2003

ABSTRACT
The vaccinia virus I7L gene product is predicted to be a cysteine proteinase and is demonstrated in this study to be responsible for cleavage of each of the three major core protein precursors (P4a, P4b, and P25K) in vivo. Mutagenesis of the putative catalytic triad of I7L or of the cleavage sites in the core protein precursors inhibits processing. A truncated protein lost the ability to cleave the core protein precursors.
The 5′ Untranslated Region of Alfalfa Mosaic Virus RNA 1 Is Involved in Negative-Strand RNA Synthesis
Authors: Vlot A. Corina , Bol John F. 
Published: September 2003

ABSTRACT
The three genomic RNAs of alfalfa mosaic virus each contain a unique 5′ untranslated region (5′ UTR). Replacement of the 5′ UTR of RNA 1 by that of RNA 2 or 3 yielded infectious replicons. The sequence of a putative 5′ stem-loop structure in RNA 1 was found to be required for negative-strand RNA synthesis. A similar putative 5′ stem-loop structure is present in RNA 2 but not in RNA 3.
Recovery of Infectious Foot-and-Mouth Disease Virus from Suckling Mice after Direct Inoculation with In Vitro-Transcribed RNA
Authors: Baranowski Eric , Molina Nicolás , Núñez José Ignacio , Sobrino Francisco , Sáiz Margarita 
Published: September 2003

ABSTRACT
We assayed the infectivity of naked foot-and-mouth disease virus (FMDV) RNA by direct inoculation of suckling mice. Our results demonstrate that transcripts generated from full-length cDNA clones were infectious, as was virion-extracted RNA. Interestingly, infectious virus could be recovered from a mutant transcript encoding amino acid substitution L-147→P in capsid protein VP1, known to be noninfectious for BHK-21 cells. The model described here provides a useful tool for virulence studies in vivo, bypassing possible selection of variants during viral replication in cell culture.
Patterns of Intra- and Interhost Nonsynonymous Variation Reveal Strong Purifying Selection in Dengue Virus
Authors: Holmes Edward C. 
Published: September 2003

ABSTRACT
Considerable uncertainty surrounds the evolutionary rates of and selection pressures acting on arthropod-borne RNA viruses (arboviruses). In particular, it is unclear why arboviruses such as dengue virus show substantial genetic variation within individual humans and mosquitoes yet low long-term rates of amino acid substitution. To address this question, I compared patterns of nonsynonymous variation in populations of dengue virus sampled at different levels of evolutionary divergence. Although nonsynonymous variation was abundant in viral populations within individual humans, there was a marked reduction in the frequency of nonsynonymous mutations in interhost comparisons. Moreover, intrahost genetic variation corresponded to a random pattern of mutation, and most of the sites that exhibited nonsynonymous variation within hosts were invariant at deeper phylogenetic levels. This loss of long-term nonsynonymous variation is the signature of extensive purifying selection such that more than 90% of all nonsynonymous mutations are deleterious. Consequently, although arboviruses are able to successfully adapt to diverse cell types, they are characterized by a high rate of deleterious mutation.
Impedance Study of Adsorption of Chloride Ions in Ethanol on Bi(001) Single Crystal Plane
Authors: Väärtnõu Mart , Lust Enn 
Published: September 2003

The impedance spectra for Bi(001) single crystal plane in 0.1, 0.02 and 0.003 M LiCl solutions in ethanol have been measured. It was found that reproducible experimental data for Bi electrode in ethanol solutions could be obtained at ac frequencies between 0.1 and 10 000 Hz and electrode potentials from -1.6 to -0.2 V (vs saturated calomel electrode). Outside this potential region, faradaic processes were detected. By fitting the experimental data to various equivalent circuits it was found that the Frumkin-Melik-Gaikazyan model yields good fit in almost the whole potential range studied. Using this model the dependences of "true" and adsorption capacitance as well as diffusion resistance on electrode potential have been obtained. The ionic charge due to the specific adsorption has been obtained using the mixed-electrolyte method for both electrode charge and electrode potential as the independent electric variables. The Gibbs energy of adsorption of Cl- ions has been calculated using a simple virial adsorption isotherm. It was found that the adsorption of Cl- anion increases in the order methanol < ethanol < propan-2-ol. It was found that on the Bi(001) plane the electrosorption valency has a constant value in the potential range studied. It was concluded that the formed effective surface dipole is significantly screened by the solvent molecules and the metal electron gas.
YANGIAN DEFORMATION OF THE LIE ALGEBRA dĩff(T2)
Authors: LIPIŃSKI Z. 
Published: September 2003

New solution of a classical Yang–Baxter equation on a loop extended, "modified" Lie algebra of a diffeomorphism group of a torus dĩff(T2)[λ]is given. Lie bialgebra structure on dĩff(T2)[λ] is defined. By quantization of a defined Lie bialgebra, a Yangian algebra Y(dĩff(T2)) is obtained. Existence of a quantum double and a quantum R-matrix for Y(dĩff(T2)) is considered.
NEGATIVE ENERGIES AND THE LIMIT OF CLASSICAL SPACE–TIME
Authors: HELFER ADAM D. 
Published: September 2003

Relativistic quantum field theories predict negative energy densities, contravening a basic tenet of classical physics and a fundamental hypothesis of the deepest results in classical general relativity. These densities may be sources for exotic general relativistic effects, and may also lead to pathologies. Combining Ford's "quantum inequality" with quantum restrictions on measuring devices, we present an argument that these densities nevertheless satisfy a sort of "operational" positivity: the energy in a region, plus the energy of an isolated device designed to detect or trap the exotic energy, must be non-negative. This will suppress at least some pathological effects. If we suppose also that Einstein's field equation holds, then no local observer can measure the geometry of a negative energy density regime accurately enough to infer a negative energy density form the curvature. This means that the physics of a negative energy regime cannot be adequately modeled by a classical space–time.
ON MIXING ANGLES AND MAGNETIC MOMENT OF HEAVY TAU NEUTRINO
Authors: GNINENKO S. N. 
Published: September 2003

If the magnetic moment of unstable tau neutrinos with the mass of 0(MeV) is in the region of 10-8μB≲ μντ≲ 10-6μB, it is compatible with the present experimental and cosmological bounds. We point out that if the tau neutrino has such a large magnetic moment and can oscillate into a neutrino of another flavor, the results from νe scattering experiment at LAMPF constrain the tau neutrino mixing angles to sin 2 2θeτ≲ 2 × 10-6-2 × 10-2 and sin 2 2θμτ ≲ 10-6-10-2 depending on the magnetic moment value in the allowed region.
ESTIMATION OF $\bar p/p$ FLUX RATIO FROM LEAKY BOX AND CLOSED GALAXY MODELS USING CERN ACCELERATOR RESULTS ON $\bar p$ PRODUCTION
Authors: SAHA R. K. , MAJUMDAR R. , PAL P. , BHATTACHARYYA D. P. 
Published: September 2003

Using steady state leaky box and closed galaxy models and the latest primary proton spectrum based on the directly measured data along with the accelerator data on [Formula: see text] production, the [Formula: see text] flux ratio in the interstellar medium has been estimated in the spectral range from 6 to 100 GeV/n. The derived result is in approximate agreement with the balloon borne calorimeter data of Golden et al. We have closed galaxy model for the estimation of the old component and young component of primary proton spectrum from the composite primary proton spectrum obtained from the recent experiments performed by Menn et al., Webber et al., Seo et al., JACEE and others. The derived results differ slightly from the results of Protheroe, Pal and Bhattacharyya.
SCALAR NEUTRINOS AND HIGGS BOSONS PRODUCTION WITH PHOTONS AT LEPTON–ANTILEPTON COLLIDERS
Authors: ALANAKYAN R. A. 
Published: September 2003

Scalar and pseudoscalar neutral Higgs bosons production with photons μ+μ-→H0γ is considered in model independent way in the tree approximation. Under some conditions the tree contributions to this process may exceed loop contribution. Also the related processes of scalar neutrinos production with photons in e+e-, μ+μ-, [Formula: see text] are considered in the framework of supersymmetric models with R-parity violation. Our results are also applicable for flavor changing scalars and pseudoscalars production with photons.
A Note on the Determination of the Type of Communication Areas
Authors: Jansen Wolfgang 
Published: September 2003

The paper presents a method that determines, by standard numerical means, the type of mutual relations of fold and flip bifurcations (configured as a so-called communication area) of a map. Equation systems are developed for the computation of points where a transition between areas of different types occurs. Furthermore, it is shown that saddle area↔spring area transitions can exist which have not yet been considered in the literature. Analytical conditions of that transition are derived.
Symmetry of Generic Bifurcations in Cubic Domains
Authors: Gabriela M. , Gomes M. , Stewart Ian 
Published: September 2003

It is now well known that bifurcation problems arising from elliptic PDEs on finite domains may possess translational symmetries, even though translations cannot leave a finite domain invariant. These "hidden symmetries" are well understood when the domain is a multidimensional rectangle, a square, and a hemisphere. Hidden symmetries have two effects: they extend the symmetries of known solutions, and they make it possible to prove the existence of solutions that were not previously known. We determine the appropriate group action, which depends upon the mode numbers of the bifurcating solution. Throughout we consider only single modes (supported by absolutely irreducible representations). The group theory is considerably richer than for rectangular domains, because a cubic domain is invariant under the group Sn of all permutations of the coordinate axes. We specialize our results to the cases n = 1, 2, 3. When n = 2 we establish a conjecture of Crawford, made in the context of the Faraday experiment, by using hidden symmetries to predict the unexpected branches that he found. We also show that all such branches are pitchforks. The analysis of the case n = 3 is extensive and we find many new branches by using group elements that do not leave the appropriate fixed-point space invariant to define one-dimensional fixed-point spaces and applying the equivariant branching lemma. We illustrate sample planforms for these solutions when the mode numbers are (15, 6, 10), (42, 15, 35) and (21, 15, 35), the smallest numbers for which all pairs have a nontrivial common factor. Finally we observe that generic normal forms must vary wildly with the mode numbers, unlike the situation for rectangles. We briefly describe an algorithm to find normal forms in any specific case.
Complexity and Predictability of the Heartbeat Time Series in Transplanted Subjects
Authors: Balocchi Rita , Barbi Michele , Carpeggiani Clara , Chillemi Santi , Di Garbo Angelo , Michelassi Claudio 
Published: September 2003

Physiological fluctuations in heart rate, known as "sinus arrhythmia", are due to the influence of the autonomic nervous system on the sinus node, modulated by baroreceptor activity and respiration. Reduction in heart rate variability (HRV) correlated to age or disease has been reported by several investigators, together with its importance as prognostic indicator in pathophysiological situations. In this paper the heart rhythm is investigated in heart transplanted subjects, an apparently opposite condition with respect to normal hearts as for the influence of the autonomic system. Selected segments of the (first difference) interbeat interval time series are analyzed with an efficient approach [Sugihara, 1994] able to evaluate both the short term predictability and the nonlinearity of these data. Moreover, other more qualitative methods are used to better characterize the experimental sequences. The results indicate that these time series only occasionally exhibit some degree of predictability, as assessed by this metric. A careful examination of the predictability behavior, by means of surrogate data, reveals that it cannot be interpreted as evidence of nonlinearity. Rather, a stochastic-like dynamics seems to characterize the transplanted hearts.
Diffusive Interaction Leading to Dephasing of Coupled Neural Oscillators
Authors: Han Seung Kee , Kurrer Christian , Kuramoto Yoshiki 
Published: September 2003

It is usually believed that strong diffusive coupling in one of the dynamical variables is well-suited for imposing synchronization of oscillators. But it was recently shown that weak diffusive coupling, counter-intuitively, can lead to dephasing of coupled neural oscillators. In this paper, we investigate how diffusively coupled oscillators become dephasing. For this we study a system of coupled neural oscillators on a limit cycle generated through a homoclinic bifurcation. We examine the asymptotic behavior of diffusive coupling as the control parameter approaches the critical value for which the homoclinic bifurcation occurs. In this study, we show that the gradient of phase velocity near the limit cycle is essential in generating dephasing through diffusive interaction.
Chaotic Bursting Behavior of Coupled Neural Oscillators
Authors: Han Seung Kee , Park Seon Hee , Yim Tae Gyu , Kim Seunghwan , Kim Seunghwan 
Published: September 2003

Recently it was shown that dephasing of diffusively coupled neural oscillators leads to a new class of bursting phenomena, where neural oscillators switch between high and low oscillation amplitudes. To analyze this behavior we study a system of three-coupled neurons, which is the most simple one that shows chaotic bursting behavior. For the intermediate values of coupling constant kc, the chaotic bursting behavior occurs. For a quantitative analysis of chaotic bursting, we introduce three mean activities of oscillators. From the Poincaré sections we find a period-doubling route to chaos. We illustrate the busting behavior in terms of competition of the single oscillator behavior with the collective one arising from the diffusive coupling of oscillators.
Links and Bifurcations in Nonsingular Morse–Smale Systems
Authors: Campos B. , Alfaro J. Martínez , Vindel P. 
Published: September 2003

Wada's theorem classifies the set of periodic orbits in NMS systems on S3 as links, that can be written in terms of six operations. This characterization allows us to study the topological restrictions that links require to suffer a given codimension one bifurcation. Moreover, these results are reproduced in the case of NMS systems with rotational symmetries, introducing new geometrical tools.
Nonlinear Computation
Authors: Seydel Rüdiger 
Published: September 2003

Nonlinear Computation will provide a framework for the computational science and engineering of the future. Topics such as bifurcation and chaos, and methods such as continuation and branch switching, and features such as stability and sensitivity are basic ingredients in the attempt to understand our world. Nonlinear Computation is indispensable when we try to predict and simulate the dynamics of states in the biological systems we consist of, in the ecological and economical systems we live in, and in the technical systems we make use of. This paper essentially consists of three parts. The first part (Sec. 1) explains what nonlinear computation means. The second part (Secs. 2–5) presents a survey on nonlinear phenomena, and on the methods of nonlinear computation. The final part (Secs. 6 and 7) will speculate on visions and trends for the next decades.
Real Perturbation of Complex Analytic Families: Points to Regions
Authors: Peckham Bruce B. 
Published: September 2003

This study provides some connections between bifurcations of one-complex-parameter complex analytic families of maps of the complex plane C and bifurcations of more general two-real-parameter families of real analytic (or Ck or C∞) maps of the real plane ℛ2. We perform a numerical study of local bifurcations in the families of maps of the plane given by [Formula: see text] where z is a complex dynamic (phase) variable, [Formula: see text] its complex conjugate, C is a complex parameter, and α is a real parameter. For α=0, the resulting family is the familiar complex quadratic family. For α≠ 0, the map fails to be complex analytic, but is still analytic (quadratic) when viewed as a map of ℛ2. We treat α in this family as a perturbing parameter and ask how the two-parameter bifurcation diagrams in the C parameter plane change as the perturbing parameter α is varied. The most striking phenomenon that appears as α is varied is that bifurcation points in the C plane for the quadratic family (α=0) evolve into fascinating bifurcation regions in the C plane for nonzero α. Such points are the cusp of the main cardioid of the Mandelbrot set and contact points between "bulbs" of the Mandelbrot set. Arnold resonance tongues are part of the evolved scenario. We also provide sufficient conditions for more general perturbations of complex analytic maps of the plane of the form: [Formula: see text] to have bifurcation points for α=0 which evolve into nontrivial bifurcation regions as α grows from zero.
An Algorithm for the Computation of Preimages in Noninvertible Mappings
Authors: Nien Chia-Hsing , Wicklin Frederick J. 
Published: September 2003

For discrete dynamical systems generated by iterating a diffeomorphism, every point in the phase space has a unique preimage and it is straightforward to compute geometric structures such as inverse orbits and one-dimensional stable manifolds of periodic points. For noninvertible mappings, however, some points have multiple preimages; others may have no preimages. This makes the computation of inverse orbits difficult, because accurate computations require global knowledge about the way the mapping folds and pleats phase space. In this article we use ideas from singularity theory to examine the geometry of noninvertible mappings. We use the geometry to derive a computational algorithm for efficiently computing preimages in noninvertible mappings.
Chaotic Vibrations of the One-Dimensional Wave Equation due to a Self-Excitation Boundary Condition.
Authors: Chen Goong , Hsu Sze-Bi , Zhou Jianxin 
Published: September 2003

The nonlinear reflection curve due to a van der Pol type boundary condition at the right end becomes a multivalued relation when one of the parameters (α) exceeds the characteristic impedance value (α=1). From stability and continuity considerations, we prescribe kinematic admissibility and define hysteresis iterations with memory effects, whose dynamical behavior is herein investigated. Assume first that the left end boundary condition is fixed. We show that asymptotically there are two types of stable periodic solutions: (i) a single period-2k orbit, or (ii) coexistence of a period-2k and a period-2(k+1) orbits, where as the parameter α increases, k will also increase and assume all positive integral values. Even though unstable periodic solutions do appear, there is obviously no chaos. When the left end boundary condition is energy-injecting, however, we show that for a certain parameter range a shift sequence of subintervals of an invariant interval can be constructed and, therefore, chaos appears. Numerical simulations of chaotic and nonchaotic phenomena are also illustrated.