bluuebunny/crossref_metadata_2025 huggingface dataset:
Viral Evolution and Interferon Resistance of Hepatitis C Virus RNA Replication in a Cell Culture Model
Authors: Sumpter Rhea , Wang Chunfu , Foy Eileen , Loo Yueh-Ming , Gale Michael
Published: October 2004

Hepatitis C virus (HCV) replicates through an error-prone process that may support the evolution of genetic variants resistant to the host cell antiviral response and interferon (IFN)-based therapy. We evaluated HCV-IFN interactions within a long-term culture system of Huh7 cell lines harboring different variants of an HCV type 1b subgenomic RNA replicon that differed at only two sites within the NS5A-encoding region. A replicon with a K insertion at HCV codon 2040 replicated efficiently and exhibited sequence stability in the absence of host antiviral pressure. In contrast, a replicon with an L2198S point mutation replicated poorly and triggered a cellular response characterized by IFN-β production and low-level IFN-stimulated gene (ISG) expression. When maintained in long term-culture, the L2198S RNA evolved into a stable high-passage (HP) variant with six additional point mutations throughout the HCV protein-encoding region that enhanced viral replication. The HP RNA transduced Huh7 cells with more than 1,000-fold greater efficiency than its L2198S progenitor or the K2040 sequence. Replication of the HP RNA resisted suppression by IFN-α treatment and was associated with virus-directed reduction in host cell expression of ISG56, an antagonist of HCV RNA translation. Accordingly, the HP RNA was retained within polyribosome complexes in vivo that were refractory to IFN-induced disassembly. These results identify ISG56 as a translational control effector of the host response to HCV and provide direct evidence to link this response to viral sequence evolution, ISG regulation, and selection of the IFN-resistant viral phenotype.
Differential Effects on Human Immunodeficiency Virus Type 1 Replication by α-Defensins with Comparable Bactericidal Activities
Authors: Tanabe Hiroki , Ouellette Andre J. , Cocco Melanie J. , Robinson W. Edward
Published: October 2004

In addition to their antibacterial activities, certain antimicrobial peptides inactivate enveloped viruses, including the human immunodeficiency virus (HIV). To determine whether peptide bactericidal activities are predictive of antiviral activity, the anti-HIV properties of recombinant human α-defensin 5, mouse α-defensins, cryptdins (Crp) 3 and 4, and rhesus macaque myeloid α-defensins (RMADs) 3 and 4 were determined in vitro. The peptides, purified to homogeneity, had equivalent bactericidal activities that were similar to those of the native molecules. Nuclear magnetic resonance spectroscopy showed RMAD-4 and Crp3 had characteristic α-defensin tridisulfide arrays. Of the peptides analyzed, only RMAD-4 inhibited HIV infectivity at 150 μg/ml, and Crp3 unexpectedly increased HIV replication. Quantitative real-time PCRs for minus-strand strong stop DNA and complete viral cDNA synthesis were used to distinguish between preentry and postentry anti-HIV effects by RMAD-4. Viral exposure to RMAD-4 for 1 h prior to infection reduced HIV minus-strand strong stop DNA and HIV cDNA by 4- to 20-fold during the first round of replication, showing that RMAD-4-exposed virions were not entering cells during the first 24 h. On the other hand, when RMAD-4 was added coincident with HIV inoculation, no anti-HIV activity was detected. Viral exposure to Crp3 resulted in a threefold increase in both HIV minus-strand strong stop DNA and HIV cDNA over the first round of replication. Therefore, two α-defensins, RMAD-4 and Crp3, inhibit or augment HIV replication, respectively, by mechanisms that precede reverse transcription.
Genome-Wide Analyses of Avian Sarcoma Virus Integration Sites
Authors: Narezkina Anna , Taganov Konstantin D. , Litwin Samuel , Stoyanova Radka , Hayashi Junpei , Seeger Christoph , Skalka Anna Marie , Katz Richard A.
Published: October 2004

The chromosomal features that influence retroviral integration site selection are not well understood. Here, we report the mapping of 226 avian sarcoma virus (ASV) integration sites in the human genome. The results show that the sites are distributed over all chromosomes, and no global bias for integration site selection was detected. However, RNA polymerase II transcription units (protein-encoding genes) appear to be favored targets of ASV integration. The integration frequency within genes is similar to that previously described for murine leukemia virus but distinct from the higher frequency observed with human immunodeficiency virus type 1. We found no evidence for preferred ASV integration sites over the length of genes and immediate flanking regions. Microarray analysis of uninfected HeLa cells revealed that the expression levels of ASV target genes were similar to the median level for all genes represented in the array. Although expressed genes were targets for integration, we found no preference for integration into highly expressed genes. Our results provide a more detailed description of the chromosomal features that may influence ASV integration and support the idea that distinct, virus-specific mechanisms mediate integration site selection. Such differences may be relevant to viral pathogenesis and provide utility in retroviral vector design.
A Novel Approach for Producing Lentiviruses That Are Limited to a Single Cycle of Infection
Authors: Evans David T. , Bricker Jennifer E. , Desrosiers Ronald C.
Published: October 2004

We have devised a novel approach for producing simian immunodeficiency virus (SIV) strains and, potentially, human immunodeficiency virus type 1 (HIV-1) strains that are limited to a single cycle of infection. Unlike previous lentiviral vectors, our single-cycle SIV is capable of expressing eight of the nine viral gene products and infected cells release immature virus particles that are unable to complete subsequent rounds of infection. Single-cycle SIV (scSIV) was produced by using a two-plasmid system specifically designed to minimize the possibility of generating replication-competent virus by recombination or nucleotide reversion. One plasmid carried a full-length SIV genome with three nucleotide substitutions in the
gag-pol
frameshift site to inactivate Pol expression. To ensure inactivation of Pol and to prevent the recovery of wild-type virus by nucleotide reversion, deletions were also introduced into the viral
pol
gene. In order to provide Gag-Pol in
trans
, a Gag-Pol-complementing plasmid that included a single nucleotide insertion to permanently place
gag
and
pol
in the same reading frame was constructed. We also mutated the frameshift site of this Gag-Pol expression construct so that any recombinants between the two plasmids would remain defective for replication. Cotransfection of both plasmids into 293T cells resulted in the release of Gag-Pol-complemented virus that was capable of one round of infection and one round of viral gene expression but was unable to propagate a spreading infection. The infectivity of scSIV was limited by the amount of Gag-Pol provided in
trans
and was dependent on the incorporation of a functional integrase. Single-cycle SIV produced by this approach will be useful for addressing questions relating to viral dynamics and viral pathogenesis and for evaluation as an experimental AIDS vaccine in rhesus macaques.
Functional Analysis of the Noncoding Regions of the Uukuniemi Virus (
Bunyaviridae
) RNA Segments
Authors: Flick Kirsten , Katz Anna , Överby Anna , Feldmann Heinz , Pettersson Ralf F. , Flick Ramon
Published: October 2004

The role of the variable portion of the noncoding regions (NCRs) of the three
Bunyaviridae
RNA segments (L, M, S) in transcription, replication, and packaging was studied using the recently developed plasmid-driven RNA polymerase I minigenome system for
Uukuniemi
(UUK)
virus
, genus
Phlebovirus
(11), as a model. Comparison of the different segments showed that all NCRs were sufficient to mediate transcription/replication of a minigenome but demonstrated decreased promoter strength in the order M > L > S. Chimeric minigenomes with flanking NCRs from different genome segments revealed that the number of total base pairs within the inverted, partially complementary ends was important for transcription and replication. Point mutations increasing the base-pairing potential produced increased reporter expression, indicating that complementarity between the 5′ and 3′ ends is crucial for promoter activity. The role of the intergenic region (IGR) located between the two open reading frames of the ambisense UUK virus S segment was analyzed by inserting this sequence element downstream of the reporter genes. The presence of the IGR was found to enhance reporter expression, demonstrating that efficient transcription termination, regulated by the IGR, is important for optimal minigenome mRNA translation. Finally, genome packaging efficacy varied for different NCRs and was strongest for L followed by M and S. Strong reporter gene activity was still observed after seven consecutive cell culture passages, indicating a selective rather than random genome-packaging mechanism. In summary, our results demonstrate that the NCRs from all three segments contain the necessary signals to initiate transcription and replication as well as packaging. Based on promoter strength, M-segment NCRs may be the preferred choice for the development of reverse genetics and minigenome rescue systems for bunyaviruses.
Translation of Duck Hepatitis B Virus Reverse Transcriptase by Ribosomal Shunting
Authors: Sen Nandini , Cao Feng , Tavis John E.
Published: October 2004

The duck hepatitis B virus (DHBV) polymerase (P) is translated by de novo initiation from a downstream open reading frame (ORF) that partially overlaps the core (C) ORF on the bicistronic pregenomic RNA (pgRNA). The DHBV P AUG is in a poor context for translational initiation and is preceded by 14 AUGs that could intercept scanning ribosomes, yet P translation is unanticipatedly rapid. Therefore, we assessed C and P translation in the context of the pgRNA. Mutating the upstream C ORF revealed that P translation was inversely related to C translation, primarily due to occlusion of P translation by ribosomes translating C. Translation of the pgRNA was found to be cap dependent, because inserting a stem-loop (BamHI-SL) that blocked >90% of scanning ribosomes at the 5′ end of the pgRNA greatly inhibited C and P synthesis. Neither mutating AUGs between the C and P start sites in contexts similar to that of the P AUG nor blocking ribosomal scanning by inserting the BamHI-SL between the C and P start codons greatly altered P translation, indicating that most ribosomes that translate P do not scan through these sequences. Finally, optimizing the P AUG context did not increase P translation. Therefore, the majority of the ribosomes that translate P are shunted from a donor region near the 5′ end of the pgRNA to an acceptor site at or near the P AUG, and the shunt acceptor sequences may augment initiation at the P AUG.
Influence of
gag
on Human Immunodeficiency Virus Type 1 Species-Specific Tropism
Authors: Ikeda Yasuhiro , Ylinen Laura M. J. , Kahar-Bador Maria , Towers Greg J.
Published: October 2004

The narrow host range of human immunodeficiency virus type 1 (HIV-1) is due in part to dominant acting restriction factors in humans (Ref1) and monkeys (Lv1). Here we show that
gag
encodes determinants of species-specific lentiviral infection, related in part to such restriction factors. Interaction between capsid and host cyclophilin A (CypA) protects HIV-1 from restriction in human cells but is essential for maximal restriction in simian cells. We show that sequence variation between HIV-1 isolates leads to variation in sensitivity to restriction factors in human and simian cells. We present further evidence for the importance of target cell CypA over CypA packaged in virions, specifically in the context of gp160 pseudotyped HIV-1 vectors. We also show that sensitivity to restriction is controlled by an H87Q mutation in the capsid, implicated in the immune control of HIV-1, possibly linking immune and innate control of HIV-1 infection.
The Putative Zinc Finger of the Human Cytomegalovirus IE2 86-Kilodalton Protein Is Dispensable for DNA Binding and Autorepression, Thereby Demarcating a Concise Core Domain in the C Terminus of the Protein
Authors: Asmar Jasmin , Wiebusch Lüder , Truss Matthias , Hagemeier Christian
Published: October 2004

The IE2 86-kDa gene product is an essential regulatory protein of human cytomegalovirus (HCMV) with several functions, including transactivation, negative autoregulation, and cell cycle regulation. In order to understand the physiological significance of each of the IE2 functions, discriminating mutants of IE2 are required that can be tested in a viral background. However, no such mutants of IE2 are available, possibly reflecting structural peculiarities of the large and ill-defined C-terminal domain of IE2. Here, we revisited the C-terminal domain by analyzing IE2 mutants for transactivation, DNA binding, autoregulation, and cell cycle regulation in parallel. We found it to contain an unexpectedly concise core domain (amino acids 450 to 544) that is defined by its absolute sensitivity to any kind of mutation. In contrast, the region adjacent to the core (amino acids 290 to 449) generally tolerates mutations much better. Although it contributes more specific sequence information to distinct IE2 activities, none of the mutations analyzed abolished any particular function. The core is demarcated from the adjacent region by the putative zinc finger region (amino acids 428 to 452). Surprisingly, the deletion of the putative zinc finger region from IE2 revealed that this region is entirely dispensable for any of the IE2 functions tested here in transfection assays. Our work supports the view that the 100 amino acids of the core domain hold the key to most functions of IE2. A systematic, high-density mutational analysis of this region may identify informative mutants discriminating between various IE2 functions that can then be tested in a viral background.
Endocytic Host Cell Machinery Plays a Dominant Role in Intracellular Trafficking of Incoming Human Immunodeficiency Virus Type 1 in Human Placental Trophoblasts
Authors: Vidricaire Gaël , Imbeault Michael , Tremblay Michel J.
Published: October 2004

Vertical transmission of human immunodeficiency virus type 1 (HIV-1) is the primary cause of infection by this retrovirus in infants. In this study, we report for the first time that there is a correlation between endocytic uptake of HIV-1 and virus gene expression in polarized trophoblasts. To shed light on the relationship between endocytosis and the fate of HIV-1 in polarized trophoblasts, the step-by-step movements of HIV-1 within the endocytic compartments were tracked by confocal imaging. Incoming virions were initially located in early endosomes. As time progressed, virions accumulated in late endosomes. HIV-1 was also found in apical recycling endosomes and at the basolateral pole. Experiments performed with indicator cells revealed that HIV-1 is recycled and transcytosed. These data indicate that the intracellular trafficking of HIV-1 upon entry into polarized human trophoblasts is a complex process which requires the active participation of the endocytic host cell machinery.
Transmission Study of Andes Hantavirus Infection in Wild Sigmodontine Rodents
Authors: Padula P. , Figueroa R. , Navarrete M. , Pizarro E. , Cadiz R. , Bellomo C. , Jofre C. , Zaror L. , Rodriguez E. , Murúa R.
Published: October 2004

Our study was designed to contribute to an understanding of the timing and conditions under which transmission of Andes hantavirus in
Oligoryzomys longicaudatus
reservoir populations takes place. Mice were caged in test habitats consisting of steel drums containing holding cages, where seronegative rodents were exposed to wild seropositive individuals by freely sharing the same cage or being separated by a wire mesh. Tests were also performed for potential viral transmission to mice from excrement-tainted bedding in the cages. Andes virus transmitted efficiently; from 130 attempts with direct contact, 12.3% resulted in virus transmission. However, if we consider only those rodents that proved to be infectious, from 93 attempts we obtained 16 infected animals (17.2%). Twelve of them resulted from intraspecies
O. longicaudatus
encounters where male mice were differentially affected and 4 resulted from
O. longicaudatus
to
Abrothrix olivaceus
. Experiments using
Abrothrix longipilis
as receptors were not successful. Transmission was not observed between wire mesh-separated animals, and mice were not infected from excrement-tainted bedding. Bites seemed not to be a requisite for oral transmission. Genomic viral RNA was amplified in two out of three saliva samples from seropositive rodents, but it was not detected in urine samples obtained by vesicle puncture from two other infected rodents. Immunohistochemistry, using antibodies against Andes (AND) hantavirus proteins, revealed strong reactions in the lung and salivary glands, supporting the possibility of oral transmission. Our study suggests that AND hantavirus may be principally transmitted via saliva or saliva aerosols rather than via feces and urine.
Infection of Specific Dendritic Cells by CCR5-Tropic Human Immunodeficiency Virus Type 1 Promotes Cell-Mediated Transmission of Virus Resistant to Broadly Neutralizing Antibodies
Authors: Ganesh Lakshmanan , Leung Kwanyee , Loré Karin , Levin Reuven , Panet Amos , Schwartz Owen , Koup Richard A. , Nabel Gary J.
Published: October 2004

The tropism of human immunodeficiency virus type 1 for chemokine receptors plays an important role in the transmission of AIDS. Although CXCR4-tropic virus is more cytopathic for T cells, CCR5-tropic strains are transmitted more frequently in humans for reasons that are not understood. Phenotypically immature myeloid dendritic cells (mDCs) are preferentially infected by CCR5-tropic virus, in contrast to mature mDCs, which are not susceptible to infection but instead internalize virus into a protected intracellular compartment and enhance the infection of T cells. Here, we define a mechanism to explain preferential transmission of CCR5-tropic viruses based on their interaction with mDCs and sensitivity to neutralizing antibodies. Infected immature mDCs differentiated normally and were found to enhance CCR5-tropic but not CXCR4-tropic virus infection of T cells even in the continuous presence of neutralizing antibodies. Infectious synapses also formed normally in the presence of such antibodies. Infection of immature mDCs by CCR5-tropic virus can therefore establish a pool of infected cells that can efficiently transfer virus at the same time that they protect virus from antibody neutralization. This property of DCs may enhance infection, contribute to immune evasion, and could provide a selective advantage for CCR5-tropic virus transmission.
Amino Acid Insertions near Gag Cleavage Sites Restore the Otherwise Compromised Replication of Human Immunodeficiency Virus Type 1 Variants Resistant to Protease Inhibitors
Authors: Tamiya Sadahiro , Mardy Sek , Kavlick Mark F. , Yoshimura Kazuhisa , Mistuya Hiroaki
Published: October 2004

A variety of amino acid substitutions in the protease and Gag proteins have been reported to contribute to the development of human immunodeficiency virus type 1 (HIV-1) resistance to protease inhibitors. In the present study, full-length molecular infectious HIV-1 clones were generated by using HIV-1 variants isolated from heavily drug-experienced and therapy-failed AIDS patients. Of six full-length infectious clones generated, four were found to have unique insertions (TGNS, SQVN, AQQA, SRPE, APP, and/or PTAPPA) near the p17/p24 and p1/p6 Gag cleavage sites, in addition to the known resistance-related multiple amino acid substitutions within the protease. The addition of such Gag inserts mostly compromised the replication of wild-type HIV-1, whereas the primary multidrug-resistant HIV infectious clones containing inserts replicated significantly better than those modified to lack the inserts. Western blot analyses revealed that the processing of Gag proteins by wild-type protease was impaired by the presence of the inserts, whereas that by mutant protease was substantially improved. The present study represents the first report clearly demonstrating that the inserts seen in the proximity of the Gag cleavage sites in highly multi-PI resistant HIV-1 variants restore the otherwise compromised enzymatic activity of mutant protease, enabling the multi-PI-resistant HIV-1 variants to remain replication competent.
The Ability of Chloroquine To Prevent Tat-Induced Cytokine Secretion by Monocytes Is Implicated in Its In Vivo Anti-Human Immunodeficiency Virus Type 1 Activity
Authors: Rayne Fabienne , Vendeville Agnès , Bonhoure Anne , Beaumelle Bruno
Published: October 2004

Hydroxychloroquine at 1 μM reduces the load of human immunodeficiency virus type 1 (HIV-1) in patients, whereas chloroquine (CQ) concentrations above 3 μM are required for inhibition of HIV-1 replication in peripheral blood mononuclear cells. Exogenous HIV-1 Tat reaches the cytosol of T cells by using low endosomal pH, and endosome neutralization by CQ prevents Tat from entering and affecting T cells. We show here that 0.6 μM CQ inhibits cytokine secretion induced by Tat in monocytes without affecting lipopolysaccharide-triggered cytokine release. This finding suggests that the in vivo anti-HIV-1 effect of CQ results not from a direct effect on the infected cell but rather from the capacity of CQ to prevent Tat from perturbing the cytokine balance.
Selection for Loss of Ref1 Activity in Human Cells Releases Human Immunodeficiency Virus Type 1 from Cyclophilin A Dependence during Infection
Authors: Sayah David M. , Luban Jeremy
Published: October 2004

Capsid (CA)-specific restrictions are determinants of retroviral tropism in mammalian cells. One such restriction, human Ref1, targets strains of murine leukemia virus bearing an arginine at CA residue 110 (N-MLV), resulting in decreased accumulation of viral cDNA. The cellular factors accounting for Ref1 activity are unknown. As
2
O
3
increases N-MLV titer in Ref1-positive cells, possibly by counteracting Ref1. Restriction factor saturation experiments suggest that Ref1 may also target human immunodeficiency virus type 1 (HIV-1), but only if its CA is not bound to the cellular protein cyclophilin A (CypA). As a step towards understanding the genetic determinants of Ref1, we subjected Ref1-positive TE671 cells to three sequential rounds of selection with N-MLV reporter viruses. We isolated a subclone, 17H1, that was permissive for N-MLV infection and therefore deficient in Ref1 activity. Stimulation of N-MLV replication by As
2
O
3
was attenuated in 17H1, confirming that the drug acts by overcoming Ref1 activity. HIV-1 infection of 17H1 cells was resistant to disruption of the CA-CypA interaction, demonstrating that Ref1 restricts CypA-free HIV-1. Our results suggest that interaction with CypA evolved to protect HIV-1 from this human antiviral activity.
EXTREMA OF FRACTAL RANDOM WATER WAVES
Authors: WEST BRUCE J.
Published: October 2004

Herein we review the statistical properties of the visibly random behavior of sea waves and the resulting stochastic forces loading off-shore structures and ships. The traditional assumption is that the statistics of the sea surface displacement produced by waves is Gaussian, or equivalently that the statistics of the wave amplitudes are Rayleigh. We examine this and a more general statistical hypothesis in this review, that being that the statistics of surface waves are Lévy stable, and investigate the response of dynamical models of off-shore structures to such stochastic forcing. We find that such familiar results as the Weibull distribution for the failure of a dynamical system may be a consequence of the statistics of the driver rather than any nonlinearity in the structure response.
DESTRUCTION OF MAGNETOPHONON RESONANCE IN HIGH MAGNETIC FIELDS FROM IMPURITY AND PHONON SCATTERING IN HETEROJUNCTIONS
Authors: XU W. , PEETERS F.M. , DEVREESE J.T. , LEADLEY D.R. , NICHOLAS R.J.
Published: October 2004

We present a detailed theoretical calculation to explain the collapse of the magnetophonon resonance (MPR) effect in high magnetic fields in certain high mobility AlGaAs/GaAs heterojunction samples. The magnetoresistivity (ρxx) and the density of states (DOS) are calculated self-consistently. We include the interaction of electrons with background and remote impurities, with acoustic-phonons via deformation potential and piezoelectric coupling, and with optic (LO) phonons. We find that: (i) the DOS is modified strongly by both elastic and inelastic scattering; (ii) the Landau-level (LL) width oscillates with magnetic fields commensurate with the MPR oscillations in ρxx; and (iii) strong impurity scattering leads to a shift of the DOS peaks to lower energy. An increase in LL width will reduce the additional resonant LO-phonon scattering, but also decrease the contribution to ρxx from all scattering mechanisms due to the reduction in DOS. Near the MPR condition there are thus two competing processes: ρxx increases due to LO-phonon scattering; but this increases the LL width and so reduces the contribution to ρxx from elastic scattering. In certain samples we found that the two effects balanced at high magnetic fields resulting in the disappearance of MPR oscillations from ρxx.
CHIRALITY CORRELATION OF SPIN SOLITONS: BLOCH WALLS, SPIN-½ SOLITONS AND HOLES IN A 2D ANTIFERROMAGNETIC BACKGROUND
Authors: BRAUN HANS-BENJAMIN , LOSS DANIEL
Published: October 2004

We consider the quantum dynamics of spin solitons in a variety of low-dimensional magnetic systems in the semiclassical and the extreme quantum limit. Introducing the concept of chirality of the soliton we derive the dispersion of spin solitons moving through a periodic pinning potential and show that for half-odd integer spin the topological part of the Berry phase induces a halving of the Brillouin zone as well as chirality correlations between subsequent band minima. We demonstrate that these chirality and spin parity effects are universal by considering quasi-one-dimensional ferromagnets and antiferromagnets with local anisotropies and large spins, as well as spin-½ ferromagnetic and antiferromagnetic Heisenberg chains in the Ising limit. For large spin systems, the tunneling rate between states of opposite chiralities is derived and shown to provide a novel scenario for macroscopic quantum phenomena. The results are extended to solitons moving as holes in a two-dimensional antiferromagnetic background, leading to a hole spectrum which is in remarkable agreement with recent ARPES measurements on high-Tc compounds.
A NEW SOLVABLE 3D MODEL OF STATISTICAL MECHANICS: THE FREE-FERMION SOLUTION
Authors: BOROVICK A.E. , KULINICH S.I. , POPKOV V. Yu. , STRZHEMECHNY Yu. M.
Published: October 2004

We obtain a new exactly solvable K-plane vertex model. This 3D model is one wih real Boltzmann weights and nearest neighbor interactions. The corresponding Yang-Baxter equation is proved. The Bethe ansatz has also been found, enabling us to completely investigate the phase diagram in the “free fermions” case.
ASPECTS OF 3He AND THE STANDARD ELECTROWEAK MODEL
Authors: VOLOVIK G. E. , VACHASPATI TANMAY
Published: October 2004

We describe certain aspects of 3 He and compare them to related aspects of the standard electroweak model of particle physics. We note various similarities in the order parameter structure, defect structure, interactions with fermions and anomalies in the two systems. Many issues in the condensed matter literature that are often confusing to the particle physics reader and vice versa are clarified.
THERMODYNAMICS OF q-MODIFIED BOSONS
Authors: SWAMY P. NARAYANA
Published: October 2004

Based on a recent study of the statistical mechanical properties of the q-modified boson oscillators, we develop the statistical mechanics of the q-modified boson gas, in particular the Grand Partition Function. We derive the various thermodynamic functions for the q-boson gas including the entropy, pressure and specific heat. We demonstrate that the gas exhibits a phase transition analogous to ordinary bose condensation. We derive the equation of state and develop the virial expansion for the equation of state. Several interesting properties of the q-boson gas are derived and compared with those of the ordinary boson which may point to the physical relevance of such systems.
MANY-BODY EFFECT IN ELECTRORHEOLOGICAL RESPONSES
Authors: WANG ZUOWEI , LIN ZHIFANG , TAO RUIBAO
Published: October 2004

The many-body effect in the kinetic responses of ER fluids is studied by a moleculardynamic simulation method. The mutual polarization effects of the particles are considered by self-consistently calculating the dipole strength on each particle according to the external field and the dipole field due to all the other particles in the fluids. The many-body effect is found to increase with the enhancement of the particle concentration and the permittivity ratio between the solvent and the particles. The calculated response times are shorter than that predicted with the ‘point-dipole’ model and agree very well with experimental results. The many-body effect enhances the shear stresses of the fluids by several times. But they are not proportional to the many-body correction factor λ as expected. This is due to the fact that larger interaction forces between the particles lead to coarsening of the fibers formed in the suspensions. The results show that the many-body and multipolar interaction between the particles must be treated comprehensively in the simulations in order to get more reliable results.
THEORY OF THE MAGNETIC FORM FACTOR IN REDUCED-MOMENT KONDO SYSTEMS
Authors: PAVARINI EVA , ANDREANI LUCIO CLAUDIO , AMORETTI GIUSEPPE
Published: October 2004

The magnetic form factor in Kondo systems, as measured by polarized neutron elastic scattering, is uniformly reduced (with respect to the atomic form factor in the crystal field) due to the Kondo effect, and moreover it shows deviations at small scattering vector due to a spin polarization of conduction electrons: the sign of the deviations in Ce compounds is positive, which is opposite to what is observed in normal rare earths of the first half of the series, and expected from the s-f exchange Hamiltonian. In the present work the above two anomalies are interpreted within a theory for the magnetic form factor in Kondo systems. The uniform reduction of the form factor follows from a variational calculation for the one-impurity Anderson model in an effective magnetic field: Kondo reduction of the localized moment is distinguished here from the presence of a screening cloud, which cannot be observed by neutron scattering. The conduction electron polarization is first studied for the Coqblin-Schrieffer Hamiltonian, which we find to lead again to negative deviations of the form factor. Within the Anderson impurity model, the conduction electron contribution to the form factor is found to be the sum of two terms: a negative RKKY-like polarization, and a positive superexchange term, which is nonzero even for a filled (or empty) band. Dominance of the superexchange polarization could explain the observed sign of the deviations in Ce compounds. A variational basis which describes both Kondo reduction and conduction electron polarization effects is studied: the two effects are clearly separated, since they appear in different orders of the calculations. The conduction electron polarization is shown to be reduced due to the Kondo effect by the same spin-fluctuation factor which reduces the localized moment.
WEAK ITINERANT ANTIFERROMAGNETISM: TWO-BAND NESTING MODEL AND EFFECT OF SPIN FLUCTUATIONS
Authors: LIKHACHEV D.V. , POVZNER A.A.
Published: October 2004

In this work we calculate the effect of spin fluctuations on a weak itinerant antiferromagnetism of transition metals alloys described by a nesting model with the presence of both the nesting parts at the Fermi surface and the so-called “electron reservoir”. It is shown that the presence of “electron reservoir” with the large exchange enhancement factor of spin fluctuations leads to a decrease of the Néel temperature as compared to its value estimated in the mean-field approximation. A mechanism of magnetic order destruction, which is not associated with the scattering of the nesting parts electronic states on the “electron reservoir” spin fluctuations, is discussed. An extensive discussion of the thermophysical properties for this model, and of the physical and experimental implications of the results are presented.
DECAY OF METASTABLE STATES IN SPATIALLY EXTENDED REACTION-DIFFUSION SYSTEMS: ITS DEPENDENCE ON PARTIALLY REFLECTING BOUNDARY CONDITIONS
Authors: IZÚS G. , WIO H.S. , DE RUEDA J. REYES , RAMÍREZ O. , DEZA R.
Published: October 2004

We study a piecewise linear version of a one-component, two-dimensional reaction-diffusion bistable model with partially reflecting boundary conditions, with the aim of analyzing the decay of metastable states in spatially extended systems. We have studied the dependence of systems’ Lyapunov functional in terms of a control parameter: the reflectivity at the boundary. Through the knowledge of this functional, we have computed the mean first-passage time for the decay of metastable nonhomogeneous stationary states, providing in this way dynamical information on the changes of the relative stability between attractors.
NUMERICAL STOCHASTIC METHODS IN STATISTICAL MECHANICS
Authors: DE OLIVEIRA MÁRIO J.
Published: October 2004

We review the numerical stochastic methods used in statistical mechanics with emphasis on the Langevin and Monte Carlo methods. We point out the role of microscopic reversibility in setting up the stochastic dynamics associated to the methods. We also present a Monte Carlo method which allows the calculation of the ground state properties of quantum spin systems.
A VARIATIONAL GROUND-STATE FOR THE ν=2/3 FRACTIONAL QUANTUM HALL REGIME
Authors: MEIR YIGAL
Published: October 2004

A variational ν=2/3 state, which unifies the sharp edge picture of MacDonald with the soft edge picture of Chang and of Beenakker is presented and studied in detail. Using an exact relation between correlation functions of this state and those of the Laughlin ν=1/3 wavefunction, the correlation functions of the ν=2/3 state are determined via a classical Monte Carlo calculation, for systems up to 50 electrons. It is found that as a function of the slope of the confining potential there is a sharp transition of the ground state from one description to the other. This transition should be observable in tunneling experiments through quantum dots.
ISOLATION AND EXPULSION OF DIVERGENCES IN QUANTUM FIELD THEORY
Authors: KLAUDER JOHN R.
Published: October 2004

Divergences that arise in the quantization of scalar quantum field models by means of a lattice-space functional integration may be attributed to a single integration variable, and this fact is demonstrated by showing that if the integrand for that single integration variable is appropriately changed, then a perturbation expansion becomes order-by-order finite and divergence free. The paper concludes with a brief review of a current proposal of how an auxiliary, nonclassical potential added to the lattice action of a relativistic scalar field quantization may automatically render an analogous change of the integrand, and thus may lead, as well, to nontrivial and divergence-free results.
HOW HOT IS THE DE SITTER SPACE?
Authors: NARNHOFER H. , PETER I. , THIRRING W.
Published: October 2004

We show that the unique invariant locally Minkowskian state of quantum fields in de Sitter space M has for an observer moving along with a Killing vector field a temperature [Formula: see text] where R is the radius of M and a his acceleration. States with another temperature cannot be locally Minkowskian all over M.
DOUBLE RESONANCES AND JORDAN BLOCK SPECTRA
Authors: BHAMATHI G. , SUDARSHAN E.C.G.
Published: October 2004

Metastable states are associated with discrete complex eigenvalues of the Hamiltonian in the analytically continued spaces of quantum mechanics formulated in dual spaces. The necessary modifications when two resonances approach each other and coincide are discussed and illustrated in some exactly soluble models. The Hamiltonian no longer can be diagonalized completely but can be reduced to a Jordan block form. The duals are identified and a resolution of unity established. Some remarks are made about secular terms in the survival amplitude.
UNITARILY INEQUIVALENT CLASSES OF MINIMUM UNCERTAINTY STATES OF SU(1, 1)
Authors: PURI R.R. , AGARWAL G.S.
Published: October 2004

The notion of the minimum uncertainty states (MUS) of a Lie algebra is discussed. That is used to obtain the MUS of SU(1, 1) algebra. Those states fall in two classes. One is the class of the states obtained by the SU(1, 1) group transformation on the MUS of the pair of its noncompact hermitian generators and the other is obtained by that on the MUS of the pair of a compact and a noncomp]act generator.
MANY-PARTICLE QUANTUM STATISTICS AND CO-ALGEBRA
Authors: CELEGHINI ENRICO , RASETTI MARIO
Published: October 2004

Duplication of the space of states, peculiar of Thermo-field Dynamics, is related to fundamental physical concepts such as the idea of “isolated system”. By a correct mathematical description of such doubling of the Fock space in terms of co-algebra, the algebra h(1) and its quantum deformation hq(1) are shown to pertain to classical objects rather than to bosons, which are instead properly described by su(1, 1). In addition new statistics are introduced, connected to the graded algebra osp(1|2) and the q-algebras suq(1, 1) and ospq(1|2).
SCHRÖDINGER OPERATORS FOR PLEKTONS
Authors: DELL’ANTONIO GIANFAUSTO
Published: October 2004

The way statistics can be introduced for identical quantum particles constrained in a two-dimensional space, and how the corresponding Schrödinger operator can be constructed are discussed. Statistics is related to a representation of the braid group and the operator construction is done through Dirichlet forms. A connection with the Bohm-Aharanov problem is briefly discussed. The results outlined here stem from a collaboration with R. Figari and A. Teta. A complete presentation will be the content of a forthcoming joint paper.
FROM CONSCIOUS EXPERIENCE TO MEMORY STORAGE AND RETRIEVAL: THE ROLE OF QUANTUM BRAIN DYNAMICS AND BOSON CONDENSATION OF EVANESCENT PHOTONS
Authors: JIBU MARI , PRIBRAM KARL H. , YASUE KUNIO
Published: October 2004

A quantum field theoretical formulation of an interaction between the radiation field and the electric dipole field of intracellular and extracellular water in perimembranous dendritic compartments is proposed. The intercellular spaces filled mostly with water are shown to be not just a filler but a proper substrate for dendritic processing composed of a boson condensation of evanescent photons. Macroscopic ordered dynamics of the electric dipoles of water in the perimembranous region immediately adjacent to dendritic membranes provides interactions with the radiation field to produce evanescent photons that ensure that the critical temperature of the boson condensation can be higher than the body temperature. Thus, superconducting phenomena can take place. Such a high-temperature boson condensate of evanescent photons can be understood as a physical substrate for distributed saltatory processing in dendritic arborizations. Memory storage can be understood in terms of processing involving the ionic coating of the dynamically ordered structure of water facilitated by the boson condensate of evanescent photons.
ON THE MEISSNER EFFECT AND THE HIGGS-LIKE MECHANISM IN ANYON SUPERCONDUCTORS
Authors: BUJKIEWICZ L. , JACAK L. , RADOSZ A. , SITKO P.
Published: October 2004

The problem of the Meissner effect in the exotic anyon superconductor is rediscussed from the point of view of the spontaneous breaking of symmetry and the Higgs mechanism idea. It is shown that the inclusion of electromagnetic interactions leads to the typical Higgs mechanism only in the case of the two-dimensional Coulomb interaction. The qualitative difference between anyon superconductivity—where the Meissner effect and the Higgs mechanism are independent—and ordinary BCS superconductivity is underlined.
ADIABATIC EFFECTIVE ACTION FOR VORTICES IN NEUTRAL AND CHARGED SUPERFLUIDS
Authors: HATSUDA M. , SATO M. , YAHIKOZAWA S. , HATSUDA T.
Published: October 2004

Adiabatic effective action for vortices in neutral and charged superfluids at zero temperature are calculated using the topological Landau-Ginzburg theory recently proposed by Hatsuda, Yahikozawa, Ao and Thouless, and vortex dynamics are examined. The Berry phase term arising in the effective action naturally yields the Magnus force in both neutral and charged superfluids. It is shown that in neutral superfluid there is only one degree of freedom, namely the center of vorticities, and the vortex energy is proportional to the sum of all vorticities so that it is finite only for the vanishing total vorticity of the system. On the other hand the effective mass and the vortex energy for a vortex in charged superfluids are defined individually as expected. The effects of the vortex core on these quantities are also estimated. The possible depinning scenario which is governed by the Magnus force and the inertial mass is also discussed.
DISTRIBUTION FUNCTION FOR SHOT NOISE IN WIGNER-DYSON ENSEMBLES
Authors: MUTTALIB K.A. , CHEN Y.
Published: October 2004

We obtain the generating function for shot noise through a random multi-channel system in the zero temperature quantum regime using a random matrix model. The generating function is a product statistic as opposed to a linear one, and we develop a general method to obtain fluctuation properties of such product statistics within a random matrix framework.
A QUANTUM MODEL FOR THE GIANT MAGNETORESISTANCE EFFECT
Authors: ZHOU LEI , TAO RUIBAO
Published: October 2004

A quantum explanation based on the previous semi-classical theory has been presented for the giant magnetoresistance (GMR) effect in this letter. A simple model Hamiltonian has been proposed for the conduction electrons in the magnetic layered structures in which the interaction of the conduction electrons with the local spins and the spin-dependent scattering potential have been considered, then an analytical expression of the effective electric conductivity is derived after some simplifying procedures. The main feature of the GMR effect may be explained by this simple model qualitatively.
BOSONIZATION AND THE EIKONAL EXPANSION: SIMILARITIES AND DIFFERENCES
Authors: KOPIETZ PETER
Published: October 2004

We compare two non-perturbative techniques for calculating the single-particle Green’s function of interacting Fermi systems with dominant forward scattering: our recently developed functional integral approach to bosonization in arbitrary dimensions, and the eikonal expansion. In both methods the Green’s function is first calculated for a fixed configuration of a background field, and then averaged with respect to a suitably defined effective action. We show that, after linearization of the energy dispersion at the Fermi surface, both methods yield for Fermi liquids exactly the same non-perturbative expression for the quasi-particle residue. However, in the case of non-Fermi liquid behavior the low-energy behavior of the Green’s function predicted by the eikonal method can be erroneous. In particular, for the Tomonaga-Luttinger model the eikonal method neither reproduces the correct scaling behavior of the spectral function, nor predicts the correct location of its singularities.
THEORY OF RANDOM ADVECTION IN TWO DIMENSIONS
Authors: CHERTKOV M. , FALKOVICH G. , KOLOKOLOV I. , LEBEDEV V.
Published: October 2004

The steady statistics of a passive scalar advected by a random two-dimensional flow of an incompressible fluid is described at scales less than the correlation length of the flow and larger than the diffusion scale. The probability distribution of the scalar is expressed via the probability distribution of the line stretching rate. The description of the line stretching can be reduced to the classical problem of studying the product of many matrices with a unit determinant. We found a change of variables which allows one to map the matrix problem into a scalar one and to prove thus a central limit theorem for the statistics of the stretching rate. The proof is valid for any finite correlation time of the velocity field. Whatever be the statistics of the velocity field, the statistics of the passive scalar in the inertial interval of scales is shown to approach Gaussianity as one increases the Peclet number Pe (the ratio of the pumping scale to the diffusion one). The first n < ln (Pe) simultaneous correlation functions are expressed via the flux of the squared scalar and only one unknown factor depending on the velocity field: the mean stretching rate. That factor can be calculated analytically for the limiting cases. The non-Gaussian tails of the probability distributions at finite Pe are found to be exponential.
TUNNELING AND MAGNETIC RELAXATION IN MESOSCOPIC MOLECULES
Authors: HARTMANN-BOUTRON FRANÇOISE , POLITI PAOLO , VILLAIN JACQUES
Published: October 2004

The relaxation of the magnetization in big molecular groups embedded in crystals is studied and compared with experimental data on Mn 12 O 12. At sufficiently high temperatures (T > 2 K in Mn 12 O 12) the relaxation is thermally activated, and the exchange of energy with phonons produces relaxation through a cascade of elementary transitions where the component Sz of the spin along the tetragonal axis changes by δm = ±1 or ±2. At lower temperatures, tunneling occurs, but energy conservation requires exchange of energy with nuclear spins in very low magnetic fields (smaller than the hyperfine field), or with phonons in higher field. The phonon assisted tunneling rate 1/τ is proportional to H 3 for weak fields H(H < 2 Tesla ). A minimum of τ is expected when the field is of the order of magnitude of the maximum hyperfine field. The theoretically predicted minimum is sharper and should occur at a field value four times as small than experimentally observed.
COMPUTER SIMULATION STUDY OF A CLASSICAL HEISENBERG MODEL IN TWO DIMENSIONS WITH LONG-RANGE FERROMAGNETIC INTERACTIONS ISOTROPIC IN SPIN SPACE
Authors: ROMANO S.
Published: October 2004

We have considered a classical spin system, consisting of 3-component unit vectors, associated with a two-dimensional lattice {uk, k ∈ Z2}, and interacting via a translationally and rotationally invariant pair potential, of the long-range ferromagnetic form [Formula: see text] Here ∊ is a positive constant setting energy and temperature scales (i.e. T* = k B T/∊), and xj denotes dimensionless coordinates of the lattice sites. This potential model is known rigorously to possess an ordering transition at finite temperature, and has been characterized quantitatively by Monte Carlo simulation, whose results suggest a continuous transition taking place at [Formula: see text]; comparison is also reported with other theoretical treatments, such as Spherical Model, Molecular Field and Two Site Cluster approximations.
DYNAMICAL STRUCTURE FACTOR FOR s - f MODEL WITH SPIN-PHONON INTERACTION
Authors: WESSELINOWA J. M. , APOSTOLOV A. T.
Published: October 2004

A Green's function technique is used to study the effects of spin–phonon interaction in ferromagnetic semiconductors based on the s - f model. The spin wave energy and the damping are evaluated for the first time beyond the RPA and numerically calculated. They increase with increasing spin–phonon interaction. The dependence of the dynamical structure factor on temperature and on spin–phonon interaction is discussed. At fixed T with increasing spin–phonon interaction the peak height decreases, the half-width increases, whereas the peak shifts to higher energy values.