bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibitors of Human Immunodeficiency Virus Type 1 Reverse Transcriptase Target Distinct Phases of Early Reverse Transcription
Authors: Hooker C. William , Lott William B. , Harrich David
Published: July 2002

Early HIV-1 reverse transcription can be separated into initiation and elongation phases. Here we show, using PCR analysis of negative-strand strong-stop DNA [(−)ssDNA] synthesis in intact virus, that different reverse transcriptase (RT) inhibitors affect distinct phases of early natural endogenous reverse transcription (NERT). The effects of nevirapine on NERT were consistent with a mechanism of action including both specific and nonspecific binding events. The nonspecific component of this inhibition targeted the elongation reaction, whereas the specific effect seemed principally to be directed at very early events (initiation or the initiation-elongation switch). In contrast, foscarnet and the nucleoside analog ddATP inhibited both early and late (−)ssDNA synthesis in a similar manner. We also examined compounds that targeted other viral proteins and found that Ro24-7429 (a Tat antagonist) and rosmarinic acid (an integrase inhibitor) also directly inhibited RT. Our results indicate that NERT can be used to identify and evaluate compounds that directly target the reverse transcription complex.
Human Papillomavirus Type 6b Virus-Like Particles Are Able To Activate the Ras-MAP Kinase Pathway and Induce Cell Proliferation
Authors: Payne Elizabeth , Bowles Mark R. , Don Alistair , Hancock John F. , McMillan Nigel A. J.
Published: July 2002

The initial step in viral infection is the attachment of the virus to the host cell via an interaction with its receptor. We have previously shown that a receptor for human papillomavirus is the α6 integrin. The α6 integrin is involved in the attachment of epithelial cells with the basement membrane, but recent evidence suggests that ligation of many integrins results in intracellular signaling events that influence cell proliferation. Here we present evidence that exposure of A431 human epithelial cells to human papillomavirus type 6b L1 virus-like particles (VLPs) results in a dose-dependent increase in cell proliferation, as measured by bromodeoxyuridine incorporation. This proliferation is lost if VLPs are first denatured or incubated with a monoclonal antibody against L1 protein. The MEK1 inhibitor PB98059 inhibits the VLP-mediated increase in cell proliferation, suggesting involvement of the Ras-MAP kinase pathway. Indeed, VLP binding results in rapid phosphorylation of the β4 integrin upon tyrosine residues and subsequent recruitment of the adapter protein Shc to β4. Within 30 min, the activation of Ras, Raf, and Erk2 was observed. Finally, the upregulation of c-
myc
mRNA was observed at 60 min. These data indicate that human papillomavirus type 6b is able to signal cells via the Ras-MAP kinase pathway to induce cell proliferation. We hypothesize that such a mechanism would allow papillomaviruses to infect hosts more successfully by increasing the potential pool of cells they are able to infect via the initiation of proliferation in resting keratinocyte stem and suprabasal cells.
Rotavirus Genome Segment 7 (NSP3) Is a Determinant of Extraintestinal Spread in the Neonatal Mouse
Authors: Mossel Eric C. , Ramig Robert F.
Published: July 2002

We used the neonatal mouse model of rotavirus infection to study extraintestinal spread following oral inoculation. Five-day-old pups were inoculated with either SA11-Cl3, SA11-Cl4, SA11-4F, RRV, or B223. By using virus detection in the liver as a proxy determination for extraintestinal spread, rotavirus strains capable of extraintestinal spread at high frequency (rhesus rotavirus [RRV]) and very low frequency (SA11-Cl4) were identified. Both strains productively infected the gastrointestinal tract. Oral inoculation of mice with RRV/ SA11-Cl4 reassortants and determination of virus titers in the gut and liver revealed that the extraintestinal spread phenotype segregated with RRV genome segment 7 to a high level of significance (
P
= 10
−3
). RRV segment 7 also segregated with the growth of virus in the gut (
P
= 10
−5
). Although infection of the gut was clearly required for tropism to the liver, there was no correlation between virus titers in the gut and detection of virus in the liver. Five days after intraperitoneal administration to bypass the gut barrier to virus spread, RRV and SA11-Cl4 both were recovered in the liver. However, only RRV was found in the liver following subcutaneous inoculation, suggesting that this peripheral site presented a similar barrier to virus spread as the gut. Sequence analysis of segment 7 from parental RRV and SA11-Cl4 and selected reassortants showed that (i) amino acid differences were distributed throughout the coding sequences and not concentrated in any particular functional motif and (ii) parental sequence was preserved in reassortants. These data support the hypothesis that NSP3, coded for by genome segment 7, plays a significant role in viral growth in the gut and spread to peripheral sites. The mechanism of NSP3-mediated tropism is under investigation.
Alternative Fates of Keratinocytes Transduced by Human Papillomavirus Type 18 E7 during Squamous Differentiation
Authors: Chien Wei-Ming , Noya Francisco , Benedict-Hamilton Heather M. , Broker Thomas R. , Chow Louise T.
Published: July 2002

The human papillomavirus type 18 (HPV-18) E7 protein promotes S-phase reentry in postmitotic, differentiated keratinocytes in squamous epithelium to facilitate vegetative viral DNA amplification. To examine the nature and fate of the differentiated cells that reenter S phase, organotypic cultures of primary human keratinocytes transduced with HPV-18 E7 were pulse-chase-pulse-labeled with
3
H-thymidine (
3
H-TdR) and bromodeoxyuridine (BrdU). The kinetics of the appearance of doubly labeled suprabasal cells demonstrate that E7 expression did not promote prolonged S phase. Rather, there was a considerable lag before a small percentage of the cells reentered another round of S phase. Fluorescence in situ hybridization analysis, indeed, revealed a small fraction of the cells with more than 4n chromosomes in the differentiated strata. Differentiated cells positive for
3
H-TdR, BrdU, or both often had enlarged nuclei or were binucleated. These results suggest that S phase is not followed by cell division, although nuclear division may occur. Interestingly, a significant fraction of differentiated cells that entered S phase subsequently accumulated p27kip1 protein with a kinetics preceding the accumulation of cyclin E. We conclude that E7-transduced, differentiated keratinocytes that enter S phase have two alternative fates: (i) a low percentage of cells undergoes endoreduplication, achieving higher than 4n ploidy, and (ii) a high percentage of cells accumulates the p27kip1, cyclin E, and p21cip1 proteins, resulting in arrest and preventing further S-phase reentry.
Viable Human Cytomegalovirus Recombinant Virus with an Internal Deletion of the IE2 86 Gene Affects Late Stages of Viral Replication
Authors: Sanchez Veronica , Clark Charles L. , Yen Judy Y. , Dwarakanath Roopashree , Spector Deborah H.
Published: July 2002

Using bacterial artificial chromosome (BAC) technology, we have constructed and characterized a human cytomegalovirus recombinant virus with a mutation in the exon specific for the major immediate-early region 2 (IE2) gene product. The resulting IE2 86-kDa protein (IE2 86) has an internal deletion of amino acids 136 to 290 and is fused at the carboxy terminus to enhanced green fluorescent protein (EGFP). The deletion also removes the promoter and initiator methionine for the p40 form of IE2 and initiator methionine for the p60 form of the protein, and therefore, these late gene products are not produced. The mutant virus IE2 86ΔSX-EGFP is viable but exhibits altered growth characteristics in tissue culture compared with a full-length wild-type (wt) IE2 86-EGFP virus or a revertant virus. When cells are infected with the mutant virus at a low multiplicity of infection (MOI), there is a marked delay in the production of infectious virus. This is associated with slower cell-to-cell spread of the virus. By immunofluorescence and Western blot analyses, we show that the early steps in the replication of the mutant virus are comparable to those for the wt. Although there is significantly less IE2 protein in the cells infected with the mutant, there is only a modest lag in the initial accumulation of IE1 72 and viral early proteins, and viral DNA replication proceeds normally. The mutation also has only a small effect on the synthesis of the viral major capsid protein. The most notable molecular defect in the mutant virus infection is that the steady-state levels of the pp65 (UL83) and pp28 (UL99) matrix proteins are greatly reduced. In the case of UL83, but not UL99, there is also a corresponding decrease in the amount of mRNA present in cells infected with the mutant virus.
Cyclophilin A Plays Distinct Roles in Human Immunodeficiency Virus Type 1 Entry and Postentry Events, as Revealed by Spinoculation
Authors: Saphire Andrew C. S. , Bobardt Michael D. , Gallay Philippe A.
Published: July 2002

Cyclophilin A (CypA) is necessary for effective human immunodeficiency virus type 1 (HIV-1) replication. However, the functions of CypA and the precise steps at which CypA acts in the HIV-1 life cycle remain to be determined. By using a methodology that bypasses the need for attachment factors—spinoculation—we present evidence that CypA participates in both entry and postentry events.
The Structure of Bis(isopropylxanthato)nickel(II)
Authors: Trávníček Zdeněk , Pastorek Richard , Marek Jaromír
Published: July 2002

The structure of [Ni(i-PrXa)2] (i-Pr = i-C3H7, Xa = S2CO-) was solved by the heavy-atom method and refined anisotropically to R = 0.044 for 985 unique observed reflections. The compound crystallizes in the P21/c space group with a = 8.879(2), b = 6.086(1), c = 13.203(3) Å, β = 94.74(3)°, V = 711.0(3) Å3, T = 296 K, Z = 2. The molecule contains the NiS4 chromophore with an approximately planar configuration of the four sulfur atoms around the Ni(II). The Ni atom is located in the centre of symmetry.
Surface Studies and Nature of Active Sites of Supported Heteropolyacids as Catalysts in Methanol Dehydration
Authors: Anwar Amin , Abdel-Ghaffar Ali , Aboul-Fotouh Sameh , Fikry Ebeid
Published: July 2002

Different amounts of molybdo- and tungstophosphoric acids were supported on α-Al2O3 to get information about their surface and catalytic properties. The surface study revealed that surface area, total pore volume and the mean pore radius decreased as the acid content increased. X-Ray diffraction analysis showed that there is no interaction between the acid and α-Al2O3. Using a continuous flow system, methanol transformation was carried out under atmospheric pressure. Some experiments were made to determine the nature of active centers and reaction mechanism.
Time Dependence of Immunoresponse of Different Epitopes of gp41 and Its Relation to the Structure of Short Peptide Fragments of gp41
Authors: Štys Dalibor , Novák Ján , Krchňák Viktor , Vágner Josef , Štrop Petr , Buděšínský Miloš
Published: July 2002

Twenty amino acid residues peptides derived from the N-terminal domain of glycoprotein gp41 exhibit four different types of reactivity with human sera in the course of seroconversion. The differences in the accessibility of the peptide by immune apparatus can result from different binding of the knobs formed by trimers of glycoprotein gp120 to the surface of the viral particle. The region covered with peptides of higher immunoresponse may be involved in binding of knobs to the viral surface. The loss of knobs during ageing is probably the source of differences in the time-dependence of immunoresponse of different epitopes. Peptide fragments covering amino acids 580-588 and 592-612 have been already studied in detail from the point of view of their reactivity with sera and structure. Here we describe new reactive region between the residues 612-629. The structure features of corresponding peptide in solution (studied by 1H NMR spectroscopy) are different from those previously reported. In this particular case peptides corresponding to different regions of gp41 differ also in their structures in solution prior to the binding to the antibody.
Quantum Chemical Study of Thermal Dehydrochlorination of Poly(vinyl chloride) Containing Aldehyde Groups
Authors: Burda Jaroslav
Published: July 2002

Thermal dehydrochlorination of syndiotactic oligomeric models of PVC with aldehyde groups is studied using semiempirical quantum chemical methods AM1 and MNDO. The possibility of both radical and ionic mechanism of HCl elimination is examined. From the results it follows that the homolytic detachment of chlorine from the carbon in β-position to the aldehyde group is preferred, followed by hydrogen splitting off. Hydrogen atom detachment from the carbon in α-position to the aldehyde group as the first step is found energetically less convenient. The dehydrochlorination of aldehyde-containing PVC model, especially of the first molecule from the chain, is remarkably easier in comparison with regular PVC model. However, the energetical preference is smaller for further HCl splitting off and, from the kinetic point of view, this process seems to be slower. The influence of the aldehyde group inductive effect on the driving force potential m(Ca-Cw) is apparent from the partial charge distributions.
Phase Separation in Liquid-Crystalline Copolymer/Poly(methyl methacrylate) Blends
Authors: Nesterov Anatoly E. , Lipatov Yuri S. , Horichko Vitaly V.
Published: July 2002

The phase separation in the blends of poly(methyl methacrylate) and liquid-crystalline polymer (copolymer of ethylene terephthalate and p-hydroxybenzoic acid) has been studied by the light scattering method and the cloud point curves have been obtained. Simultaneously some morphological features of the blends have been observed. It was found that the initial blends are in the state of forced compatibility and that thermally induced phase separation occurs by the mechanism of spinodal decomposition but presumably in the non-linear regime.
Anharmonic Oscillations and Tg, Tm Transitions
Authors: Hlaváček Bořivoj , Khünová Viera , Večeřa Miroslav
Published: July 2002

A working hypothesis has been developed to account for a change in character of thermal motion at glass transition. According to this hypothesis the pronounced onset of anharmonic vibrations is responsible for a stepwise increase in the thermal expansion coefficient alpha as well as in the similar temperature change in specific heat coefficient cp. In this paper the both transitions (the first order transition at melting point and the second order transition at Tg) are investigated on the basis of the viewpoint connected with the change in characteristics of motion of the particles, so typical for an onset of a liquid state. At present, two different definitions for the coefficient of thermal expansion are used. One is usually adopted in polymer physics, where also the statistical approach to polymer chains configurations plays the major role in Tg definition. However, the statistical configurational approach of polymer physics cannot be applied directly to the inorganic glasses and also does not provide any explanation of relatively small changes in cp values at melting point transition which sometime occur. Using the interpretation of solid state physics, the present paper intends to make a first step and bridge over the gap between these two approaches and to explain the Tg transition in dynamic terms, common to the polymers as well as to the low molecular weight substances.
Principal Component Regression with Chemical Shift Increments. I. p-Disubstituted Benzenes and 2-Naphthyl Derivatives
Authors: Holík Miroslav
Published: July 2002

Prediction of 13C substituent chemical shifts in 14 series of para-disubstituted benzenes and in 2-substituted naphthalenes was based on principal component regression with chemical shift increments for the ipso, ortho, meta and para position of monosubstituted benzenes. Mean-centered matrix of shift increments was submitted to singular value decomposition and principal component regression was used for the projection of the investigated substituent chemical shifts and for the calculation of regression coefficients. Residual standard deviation between experimental and fitted values in para-disubstituted benzenes was in agreement with absolute values of "an electron demand" of substituents. Inspection of the regression parameters revealed that for the prediction of chemical shifts in 2-substituted naphthalenes the combination of chemical shift increments was better than the use of single increments. It is believed that the presented procedure is general and can be used for other aromatic or heteroaromatic systems.
Adsorption and Diffusion of Carbon Dioxide in Phenolic Resin Carbonizates
Authors: Kolář František , Fott Pavel , Svítilová Jaroslava
Published: July 2002

The adsorption and diffusion of CO2 in phenolic resin carbonizates prepared at final carbonization temperatures of 500, 600, and 700 °C were investigated at 20 °C and pressures of 6 to 130 kPa. The experimental data were compared with theoretical dependences obtained by numerical solution of differential equations set up based on the occluded gas model and on the model of diffusion through a pore network. The former model, which assumes that the diffusion is driven by the concentration gradient of the gas dissolved in the solid, was found to fit the experimental data better than the latter model.
Proton-Sponge-Initiated Reactions of 6,8-Dicarba-arachno-nonaborane(13) and 6,7-Dicarba-arachno-nonaborane(13) with Methyl Propynoate: One-Step Syntheses of the 6-(MeOOCCH2)-5,6,7-Tricarba-arachno-decaborane(12) and 6-(MeOOCCH2)-5,6,10-Tricarba-nido-decaborane(10) Tricarbaboranes
Authors: Wille Andrew E. , Sneddon Larry G.
Published: July 2002

The reaction of arachno-6,8-C2B7H13 (1) with methyl propynoate in the presence of only 0.1 equivalent of 1,8-bis(dimethylamino)naphthalene (Proton Sponge®, PS) results in the one-step formation of the neutral tricarbaborane 6-(MeOOCCH2)-arachno-5,6,7-C3B7H12 (2). Similarly, only 0.1 equivalent of PS initiates the reaction of the isomeric arachno-6,7-C2B7H13 (3) carborane with methyl propynoate to yield the new tricarbaborane, 6-(MeOOCCH2)-nido-5,6,10-C3B7H10 (4). These results suggest a cyclic reaction sequence involving initial deprotonation of the starting dicarbaborane by PS, followed by reaction of the resulting anion with methyl propynoate to produce a new anion. Protonation of this second anion by another equivalent of the starting dicarbaborane then produces the final neutral tricarbaborane product and the cycle begins again. While 4 is unreactive toward NaH or KH, it readily added n-BuLi to give, following acidification with HCl-Et2O, a new product tentatively identified as 6-(MeOOCCH2)-Bu-arachno-5,6,10-C3B7H11 (6). The proposed structures of 4 and 6 are strongly supported by ab initio/IGLO nuclear shielding calculations.
Effect of Kinetic Parameters on the Dynamicsof Continuous Crystallizers
Authors: Nývlt Jaroslav
Published: July 2002

Continuous crystallizers can exhibit periodic cycles of supersaturation, production rate, suspension concentration, crystal size and related quantities. These cycles are most pronounced at the beginning of the crystallization process and depend on the value of kinetic parameters whether they are damped during the run time. Apparently, the cycling behaviour of the crystallizing system depends on the value of ratio of the nucleation and growth exponents n/g. The higher the value of this ratio, the more pronounced is the instability of the system. Admixtures that have a significant effect on the kinetic parameters can dramatically affect the dynamic behaviour of crystallizers so that the steady state may not be established at all.
Configuration and Conformation Study of S-Allyl O-Methyl N-(2- and 4-Substituted Acridin-9-yl)thiocarbonimidates in Relation to Their [3,3] Sigmatropic Rearrangement
Authors: Danihel Ivan , Pihlaja Kalevi , Imrich Ján , Suchár Gejza , Kristian Pavol , Böhm Stanislav , Hočová Slávka
Published: July 2002

Configuration and conformations of S-allyl O-methyl N-(2- and 4-substituted acridin-9-yl)thiocarbonimidates were studied by means of NMR spectroscopy, dipole moments and quantum chemical calculations. The E configuration was proved for the unsubstituted and 2-chloro derivatives from the NOE-difference spectra. Experimental values of dipole moments were related to those obtained from vector addition. Quantum chemical calculations pointed to the chair conformation of these compounds in transition state for above-mentioned rearrangement.
On the Influence of Fluctuating Flow Rate Upon the Performance and Behaviour of Isothermal Reacting Systems
Authors: Trnka Otakar , Hartman Miloslav
Published: July 2002

Three simple computational techniques are proposed and employed to demonstrate the effect of fluctuating flow rate of feed on the behaviour and performance of an isothermal, continuous stirred tank reactor (CSTR). A fluidized bed reactor (FBR), in which a non-catalytic gas-solid reaction occurs, is also considered. The influence of amplitude and frequency of gas flow rate fluctuations on reactant concentrations at the exit of the CSTR is shown in four different situations.
Synthesis of (8E,10Z)-Tetradeca-8,10-dienal, Sex Pheromone of Horse Chestnut Leafminer (Cameraria ohridella), and All Its Geometrical Isomers
Authors: Hoskovec Michal , Šaman David , Svatoš Aleš
Published: July 2002

(8E,10Z)-Tetradeca-8,10-dienal (1a), sex pheromone of the horse chestnut leafminer (Cameraria ohridella; Lepidoptera, Gracillariidae), and its geometrical isomers (1b-1d) were efficiently synthesized using tetrakis(triphenylphosphine)palladium catalyzed cross-coupling reactions of alk-1-ynes or alkenyl alanes with corresponding vinyl iodides. The stereoisomeric purity of obtained tetradecadienals1a-1dwas higher than 95% (GC). Relative electroantennographic (EAG) activities of the prepared compounds1a-1delicited on male antennae supported the previously published identification of theC. ohridellasex pheromone.
Numerical Simulation of Alternating Current Linear Sweep Voltammetry at Microdisc Electrodes
Authors: Gavaghan David J. , Elton Darrell M. , Bond Alan M.
Published: July 2002

We extend our earlier work on the numerical simulation of ac linear sweep voltammetry at macroelectrodes to the case of microdisc electrodes. This requires the solution of the underlying diffusional transport equations in two dimensions, rather than one, using a cylindrical coordinate system. We use the two-dimensional FIRM algorithm combined with a specially designed exponentially expanding mesh. We examine the ac response as a function of the frequency and amplitude of the ac signal, and as a function of the non-dimensional parameter p = (nFa2v/RTD)1/2, where a is electrode radius, v the sweep rate, and D the diffusion coefficient. Results are analysed using Fast Fourier Transform (FFT) methods. We are able to derive a range of conditions under which radial diffusion has only a minor effect on the ac response of the system. The analytical results available for macroelectrodes therefore carry through to the microelectrode case for many practical ranges of system parameters (electrode size, dc sweep rate and diffusion coefficient). Experimental results are given which show good agreement with the numerical simulations.
DC Polarographic and UV Spectrometric Studies of Substituted Furo[3,2-b]- and Furo[2,3-b]pyrroles
Authors: Romanová Darina , Vachálková Anna , Horváthová Katarína , Krutošíková Alžbeta
Published: July 2002

The aim of the synthesis of substituted furo[3,2-b]- and furo[2,3-b]pyrroles was to discover biologically active compounds. On that account, their potential carcinogenicity was tested by DC polarographic assay in the presence of α-lipoic acid. Only one of the studied compounds showed a marginal carcinogenic activity, the other exhibited only a negligible carcinogenic potential under the conditions studied. Their apparent ionization constants, determined by spectrometric titration, were correlated with their structure. The results confirm that the presence of methyl, furyl and/or phenyl groups affects the ionization.
An aggressive intrasinusoidal lymphoma presenting with marked systemic disturbance but normal imaging studies
Authors: Camidge Ross , Ong Edmund , Lucraft Helen
Published: July 2002

A patient with an aggressive intrasinusoidal non-Hodgkins lymphoma, presenting with marked systemic disturbance but only a mildly raised alkaline phosphatase as a localising sign is described. All imaging studies of the liver were normal and the diagnosis was delayed until a percutaneous liver biopsy was performed. Once diagnosed, the patient responded extremely well to conventional anti-lymphoma chemotherapy.
Fulminant ischaemic colitis with atypical clinical features complicating sickle cell disease
Authors: Karim A , Ahmed S , Rossoff L J , Siddiqui R , Fuchs A , Multz A S
Published: July 2002

Clinically significant ischaemic bowel injury is an exceedingly rare complication of sickle cell disease. It manifests as acute surgical abdomen and may respond to conservative treatment. An unusual fatal case of ischaemic colitis with minimal abdominal findings in a young male during a sickle cell vaso-occlusive pain crisis is described. This case demonstrates that an acute surgical abdomen should be considered in such patients who fail to respond to conservative management as untreated this condition may be fatal.
Synthesis of a hexasaccharide fragment of the capsular polysaccharide of Streptococcus pneumoniae type 3
Authors: Lefeber Dirk J , Arévalo Eneko Aldaba , Kamerling Johannis P , Vliegenthart Johannes FG
Published: July 2002

In the framework of the development of a new generation of neoglycoconjugate vaccines against Streptococcus pneumoniae, the synthesis is described of a spacer-containing hexasaccharide fragment related to the capsular polysaccharide of S. pneumoniae type 3. Hexasaccharide β-D-GlcpA-(1[Formula: see text]4)-β-D-Glcp-(1[Formula: see text]3)-β-D-GlcpA-(1[Formula: see text]4)-β-D- Glcp-(1[Formula: see text]3)-β-D-GlcpA-(1[Formula: see text]4)-β-D-Glcp-(1[Formula: see text]O-(CH2)3NH2) (1), comprised of three repeating units, was synthesized via a blockwise strategy employing suitably protected disaccharide building blocks. Carboxylic groups were introduced by selective oxidation with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) in the last reaction steps. Deprotection afforded target hexasaccharide 1.Key words: oligosaccharide synthesis, Streptococcus pneumoniae type 3, TEMPO oxidation.
Combination IK1 and IKr channel blockade: no additive lowering of the defibrillation threshold
Authors: Varma Pryamvada , Qi Xiangqian , Newman David , Dorian Paul
Published: July 2002

Selective blockade of the inward rectifier potassium channel IK1 by barium, or of the rapidly activating delayed rectifier potassium channel IKr by D,L-sotalol, prolongs repolarization and reduces the defibrillation threshold (DFT). This study hypothesized that combination IK1 and IKr channel block would produce concentration-dependent additive effects on DFT and ventricular refractoriness. A range of barium and D,L-sotalol concentrations, alone and in combination, were examined with respect to DFT, ventricular effective refractory period (VERP), and ventricular fibrillation cycle length (VFCL) in 133 Langendorff-perfused rabbit hearts. Barium produced a concentration-dependent reduction of DFT (49 ± 4%), with concentration-dependent increases in VERP (26 ± 6%) and VFCL (42 ± 18%). D,L-Sotalol produced a concentration-dependent lowering of DFT (53 ± 6%) with a concentration-dependent increase in VFCL (34 ± 8%) but not VERP. Low (1.6 µM), intermediate (3.1 µM), and high (12.5 µM) barium concentrations combined with varying D,L-sotalol concentrations produced equal or smaller decreases in DFT compared with corresponding doses of barium or D,L-sotalol alone. Except at the lowest concentrations of barium (1.6 and 3.1 µM) (p < 0.05), there was no significant additive interaction between barium and D,L-sotalol on VERP or VFCL. Combination IK1 and IKr channel block by barium and D,L-sotalol does not produce additive reduction of DFT.Key words: antiarrhythmic drugs, defibrillation, K+ channel, refractory period, ventricular fibrillation.
ON THE ROUTING NUMBER OF COMPLETE d-ARY TREES
Authors: ROBERTS ALAN , SYMVONIS ANTONIOS
Published: July 2002

We consider the routing number of trees, denoted by rt(), with respect to the matching routing model. For an arbitrary n-node tree T, it is known that rt(T) < 3n/2 + O( log n). In this paper, by providing a recursive off-line permutation routing algorithm, we show that the routing number of an n-node complete d-ary tree of height h(T) > 1 is bounded from above by n + o(n). This is near optimal since, for an n-node complete d-ary tree T of height h(T) > 1 it holds that rt(T) ≥ n.
WALKING IN A TRIANGULATION
Authors: DEVILLERS OLIVIER , PION SYLVAIN , TEILLAUD MONIQUE
Published: July 2002

Given a triangulation in the plane or a tetrahedralization in 3-space, we investigate the efficiency of locating a point by walking in the structure with different strategies.
SYMMETRICAL TREATMENT OF ELECTRON AND NUCLEAR MOTIONS IN M. BORN’S THEORY OF IDEAL CRYSTALS
Authors: BERGMANN OTTO , RAYCHOWDHURY P.N.
Published: July 2002

The equilibrium positions of the nuclei in an ideal crystal can be determined by thermal averages, as suggested by Max Born many years ago. We derive these equations without appealing to Born’s second condition which relates the proper frequencies to the statistical operator. We obtain these frequencies directly from the action principle and develop a perturbation theory including all the parity-violating terms (under reflection of generalized, proper coordinates). The equation which determines the equilibrium positions allows us to derive a system of differential equations for the derivatives of these positions with respect to the temperature.
THE LARGE DEVIATION PRINCIPLE FOR MEASURES WITH RANDOM WEIGHTS
Authors: ELLIS R. S. , GOUGH J. , PULÉ J. V.
Published: July 2002

In this paper, we study the problem of large deviations for measures with random weights. We are motivated by previous work dealing with the special case occuring in the statistical mechanics of the Bose gas. We study the problem in an abstract setting, isolating what is general from what is dependent on Bose statistics. We succeed in proving the large deviation principle for a large class of measures with random weights and obtaining the corresponding rate function in an explicit form. In particular, our results are applicable to the Fermi gas and the spherical model.
GLOBAL SMOOTH SOLUTION AND UNIFORM RATE OF DECAY IN NONLINEAR VISCOELASTICITY
Authors: RIVERA JAIME E. MUÑOZ
Published: July 2002

We prove a global existence theorem for the nonlinear viscoelastic equation for small data in H2. Moreover we prove that the solution decays exponentially in bounded domains when t goes to infinity.
A Modified Approach to the Doplicher/Roberts Theorem on the Construction of the Field Algebra and the Symmetry Group in Superselection Theory
Authors: Baumgärtel H.
Published: July 2002

Let [Formula: see text] be a unital C*-algebra with trivial center [Formula: see text]. Let [Formula: see text] denote a tensorial category of unital endomorphisms of [Formula: see text] equipped with several properties to be explained in the text.

Doplicher and Roberts have shown, among other things, that there is a C*-algebra [Formula: see text] and a compact group [Formula: see text] of automorphisms of ℱ such that ℱ is a Hilbert C*-system over [Formula: see text] w.r.t. [Formula: see text], where [Formula: see text] is the fixed point algebra w.r.t. [Formula: see text], [Formula: see text] and the objects [Formula: see text] are characterized as the canonical endomorphisms of certain algebraic [Formula: see text]-invariant Hilbert spaces ℋρ⊂ℱ, see Doplicher/Roberts [1, 2, 3].

The starting point of the approach presented in this paper to point out the mentioned result is an [Formula: see text]-leftmodule ℱ0:={∑ρ,jAρ,jΦρ,j}. ρ runs through a full system of irreducible and mutually disjoint objects of [Formula: see text], j=1,2,…,d(ρ), where d(ρ) denotes the statistical dimension of [Formula: see text] is an orthonormal basis of a d(ρ)-dimensional Hilbert space. The system {Φρj}ρj forms a leftmodule basis of ℱ0, the coefficients Aρj are members of [Formula: see text]. The strategy is to equip successively ℱ0 with a bimodule structure, a product and a *-structure and finally with a C*-norm ||.||*. The symmetry group [Formula: see text] appears as the group of all automorphisms of the *-algebra ℱ0 leaving the [Formula: see text]-scalar product [Formula: see text] invariant, where F=∑ρ,jAρjΦρj, G=∑ρ,jBρjΦρj. The field algebra is then given by ℱ:= clo ||.||*ℱ0.
Determinants, Pfaffians and Quasi-Free Representations of the CAR Algebra
Authors: Spera Mauro , Wurzbacher Tilmann
Published: July 2002

In this paper we apply the theory of quasi-free states of CAR algebras and Bogolubov automorphisms to give an alternative C*-algebraic construction of the Determinant and Pfaffian line bundles discussed by Pressley and Segal and by Borthwick. The basic property of the Pfaffian of being the holomorphic square root of the Determinant line bundle (after restriction from the Hilbert space Grassmannian to the Siegel manifold, or isotropic Grassmannian, consisting of all complex structures on an associated Hilbert space) is derived from a Fock–anti-Fock correspondence and an application of the Powers–Størmer purification procedure. A Borel–Weil type description of the infinite dimensional Spin c- representation is obtained, via a Shale–Stinespring implementation of Bogolubov transformations.
A CLOSURE OPERATION IN RINGS
Authors: ARA PERE , PEDERSEN GERT K. , PERERA FRANCESC
Published: July 2002

We study the operation E → cl (E) defined on subsets E of a unital ring R, where x ∈ cl (E) if (x + Rb) ∩ E ≠ ∅ for each b in R such that Rx + Rb = R. This operation, which strongly resembles a closure, originates in algebraic K-theory. For any left ideal L we show that cl (L) equals the intersection of the maximal left ideals of R containing L. Moreover, cl (Re) = Re + rad (R) if e is an idempotent in R, and cl (I) = I for a two-sided ideal I precisely when I is semi-primitive in R (i.e. rad (R/I) = 0).

We then explore a special class of von Neumann regular elements in R, called persistently regular and characterized by forming an "open" subset Rpr in R, i.e. cl (R\Rpr) = R\Rpr. In fact, R\Rpr = cl (R\Rr), so that Rpr is the "algebraic interior" of the set Rr of regular elements. We show that a regular element x with partial inverse y is persistently regular, if and only if the skew corner (1 - xy)R(1 - yx) is contained in Rr. If I reg (R) denotes the maximal regular ideal in R and [Formula: see text] the set of quasi-invertible elements, defined and studied in [4], we prove that [Formula: see text].

Specializing to C*-algebras we prove that cl (E) coincides with the norm closure of E, when E is one of the five interesting sets R-1, [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], and that Rpr coincides with the topological interior of Rr. We also show that the operation cl respects boundedness, self-adjointness and positivity.
MIXING DRIVEN BY RAYLEIGH–TAYLOR INSTABILITY IN THE MESOSCALE MODELED WITH DISSIPATIVE PARTICLE DYNAMICS
Authors: DZWINEL WITOLD , YUEN DAVID A.
Published: July 2002

In the mesoscale, mixing dynamics involving immiscible fluids is truly an outstanding problem in many fields, ranging from biology to geology, because of the multiscale nature which causes severe difficulties for conventional methods using partial differential equations. The existing macroscopic models incorporating the two microstructural mechanisms of breakup and coalescence do not have the necessary physical ingredients for feedback dynamics. We demonstrate here that the approach of dissipative particle dynamics (DPD) does include the feedback mechanism and thus can yield much deeper insight into the nature of immiscible mixing. We have employed the DPD method for simulating numerically the highly nonlinear aspects of the Rayleigh–Taylor (R–T) instability developed over the mesoscale for viscous, immiscible, elastically compressible fluids. In the initial stages, we encounter the spontaneous, vertical oscillations in the incipient period of mixing. The long-term dynamics are controlled by the initial breakup and the subsequent coalescence of the microstructures and the termination of the chaotic stage in the development of the R–T instability. In the regime with high capillary number, breakup plays a dominant role in the mixing whereas in the low capillary number regime, the flow decelerates and coalescence takes over and causes a more rapid turnover. The speed of mixing and the turnover depend on the immiscibility factor which results from microscopic interactions between the binary fluid components. Both the speed of mixing and the overturn dynamics depend not only on the mascrocopic fluid properties but also on the breakup and coalescent patterns, and most importantly on the nonlinear interactions between the microstructural dynamics and the large-scale flow.
CROSSOVER TO GAUSSIAN BEHAVIOR IN HERDING MARKET MODELS
Authors: KULLMANN L. , KERTÉSZ J.
Published: July 2002

We have analyzed possible mechanisms of the crossover to the Gaussian distribution of the logarithmic returns in the Cont–Bouchaud herding model of the stock market. Either the underlying cluster distribution is not in the Lévy attraction regime, or a cut-off effect is responsible for the crossover. The cut-off can be due to the finite size of the system, where clusters are created. If such finite size effects are responsible for the crossover, a delicate interplay between the size dependence of the deviation from the Gaussian and of the number of values to be summed up in one step may result in a size-independent crossover value of the activity. It is shown that this is the case for percolation clusters in spatial dimensions from 2 to 6. A further origin of the cut-off can be the limited number of clusters taken into account.
STORING PATTERNS IN HAMILTONIAN NEURAL NETWORKS
Authors: POTAPOV ALEXEI B. , ALI M. K.
Published: July 2002

We consider a number of techniques for storing patterns in orthogonal normal modes of a Hamiltonian system. Such techniques, along with the method of selecting the most excited mode, enable us to introduce a new class of pattern recognition systems that we call Hamiltonian neural networks. In contrast to all traditional neural networks, our Hamiltonian neural networks are nondissipative. Quantization of the Hamiltonian of our network is expected to serve as a means for future work on quantum analogs of classical information processing.
THE DYNAMICAL MODELS AND THE $Z \rightarrow b\bar{b}$ ASYMMETRY
Authors: YUE CHONGXING , DAI YUANBEN , LI HONG
Published: July 2002

Motivated by the 3.2σ(1.4σ) deviations between the recent experimental value for [Formula: see text] and the standard model (SM) prediction, we examine the effect of new physics (NP) on the [Formula: see text] couplings [Formula: see text] and [Formula: see text]. First we focus our attention on the dynamical models. Then, using effective Lagrangian techniques, we discuss the corrections of NP to [Formula: see text] and [Formula: see text]. We find some kinds of NP which might explain the recently experimental data about Rb and [Formula: see text]. However, the free parameters of these kinds of NP must be severely constrained.
T-DUALITY AND NONCOMMUTATIVE DBI ACTION
Authors: KAMANI DAVOUD
Published: July 2002

In this paper we study the noncommutative description of the DBI Lagrangian and its T-dual counterpart. We restrict the freedoms of the noncommutativity parameters of these Lagrangians. Therefore the noncommutativity parameter, the effective metric, the effective coupling constant of the string and the extra modulus [Formula: see text] of the effective T-dual theory, can be expressed in terms of the closed string variables g, B, gs and the noncommutativity parameter of the effective theory of open string.
THE COSMOLOGICAL TESTS
Authors: PEEBLES P. J. E.
Published: July 2002

Recent observational advances have considerably improved the cosmological tests, adding to the lines of evidence, and showing that some issues under discussion just a few years ago may now be considered resolved or irrelevant. Other issues remain, however, and await resolution before the great program of testing the relativistic Friedmann–Lemaître model, that commenced in the 1930s, may at last be considered complete.
THE PULSATING UNIVERSE: REVIEW AND LATEST DEVELOPMENTS
Authors: Tangherlini F. R.
Published: July 2002

The pulsating model is briefly reviewed. The main idea is that a new tensor is introduced as a replacement for the cosmological term. The model predicts that the universe cannot be presently accelerating, and hence is in disagreement with the Type Ia supernovae results.
LATTICE SUPERSYMMETRY WITH DOMAIN WALL FERMIONS
Authors: FLEMING GEORGE T.
Published: July 2002

Supersymmetry, like Poincaré symmetry, is softly broken at finite lattice spacing provided the gaugino mass term is strongly suppressed. Domain wall fermions provide the mechanism for suppressing this term by approximately imposing chiral symmetry. We present the first numerical simulations of [Formula: see text] supersymmetric SU(2) Yang-Mills on the lattice in d=4 dimensions using domain wall fermions.
PROPERTIES OF GLUONS IN COLOR SUPERCONDUCTORS
Authors: RISCHKE DIRK H.
Published: July 2002

I argue that a reliable computation of the color-superconducting gap parameter in cold, dense quark matter requires knowledge of the gluon self-energy in a color superconductor. As a first step to determine the gluon self-energy, I report calculations of the Debye and Meissner masses in two- and three-flavor color superconductors.
DUALITY TRANSFORMATION FOR (3+1)-DIMENSIONAL YANG–MILLS THEORY
Authors: MAJUMDAR PUSHAN , SHARATCHANDRA H. S.
Published: July 2002

A dual form of (3+1)-dimensional Yang–Mills theory is obtained as another SO(3) gauge theory. Duality transformation is realized as a canonical transformation. The non-Abelian Gauss law implies the corresponding Gauss law for the dual theory. The dual theory is nonlocal. There is a nonlocal version of Yang–Mills theory which is self-dual.
EXPLICIT N = 2 SUPERSYMMETRY FOR HIGHER-SPIN FIELDS IN D = 4 AdS SUPERSPACE
Authors: SEGAL A. YU. , SIBIRYAKOV A. G.
Published: July 2002

We develop two N = 2 superfield formulations of free equations of motion for the joint model of all D = 4 massless higher-superspin fields. The explicit Osp (2|4) supersymmetry is achieved without exploiting the harmonic superspace, and with adding no auxiliary component fields to those of N = 1 superfields. The formulations are developed in two different Osp (2|4) homogeneous superspaces which have a structure of a fibre bundle over the standard D = 4 AdS superspace, with dimensions (7|4) and (7|8). The N = 2 covariant derivatives in these spaces are expressed in terms of N = 1 ones which give simple rules for component analysis.
2D DILATON GRAVITY AND REGULAR HORIZONS AWAY FROM THE HAWKING TEMPERATURE
Authors: ZASLAVSKII O. B.
Published: July 2002

Static solutions with a finite curvature at the horizon may exist in dilaton gravity at temperatures T ≠ TH (including T = 0) where TH is the Hawking temperature. In so doing, regular geometries are compatible with infinite quantum stresses. This phenomenon cannot be obtained within the perturbative scheme. It occurs in the weak-coupling regime between gravitation and dilaton and enables us to obtain well-defined entropy of extremal horizons S = 0 on the semiclassical level.
STRIPES IN MANGANITES
Authors: Hotta Takashi , Dagotto Elbio , Koizumi Hiroyasu , Takada Yasutami
Published: July 2002

Topological aspects of the stripe structure in manganese oxides are discussed in terms of the "winding number" w associated with the Berry-phase conncection for e g orbitals acquired by the parallel transport through the periodic array of Jahn-Teller centers. For La 1-x Ca x MnO 3, w is shown to characterize both the three-dimensional spin-charge-orbital structures in the antiferromagnetic phase for x≥1/2 and the charge-orbital stripes in the two-dimensional ferromagnetic phase for <1/2.
DYNAMICAL CHAOS AND NONEQUILIBRIUM STATISTICAL MECHANICS
Authors: GASPARD PIERRE
Published: July 2002

Chaos in the motion of atoms and molecules composing fluids is a new topic in nonequilibrium physics. Relationships have been established between the characteristic quantities of chaos and the transport coefficients thanks to the concept of fractal repeller and the escape-rate formalism. Moreover, the hydrodynamic modes of relaxation to the thermodynamic equilibrium as well as the nonequilibrium stationary states have turned out to be described by fractal-like singular distributions. This singular character explains the second law of thermodynamics as an emergent property of large chaotic systems. These and other results show the growing importance of ephemeral phenomena in modern physics.
UNIVERSAL DIAMAGNETISM: EXACT RESULTS AND APPLICATIONS
Authors: JANA DEBNARAYAN
Published: July 2002

Diamagnetism is a universal pheneomenon of spinless boson system at any finite temperature regardless of their interactions. We present here the exact, non-perturbative results of universal diamagnetism of charged scalar fields at any finite temperature. As an application, we study the effect of anisotropy of two coherence lengths on diamagnetic susceptibility of Cooper pairs in an arbitrary d-dimensions above the transition temperature.
CONSTRAINT AND CONFINEMENT IN STRONGLY CORRELATED FERMION SYSTEMS
Authors: NG T.-K.
Published: July 2002

We discuss in this paper the low energy properties of a liquid of fermions coupling to a U(1) gauge field at wavevectors q<Λ≪k F at dimensions larger than one, where Λ≪k F is a high momentum cutoff and k F is the Fermi wave vector. In particular, we shall consider the e2→∞ limit where charge and current fluctuations at wave vectors q<Λ are forbidden, and the problem reduces to the problem of imposing constraint that no charge and current fluctuations are allowed in the liquid of fermions. Within a bosonization approximation, we show that the low energy properties of the system can be described as a Fermi liquid of chargeless quasiparticles which has vanishing wavefunction overlap with the bare fermion's in the system. The case of a two component system (t–J model) will also be discussed.
STATICS AND DYNAMICS OF COUPLED ELECTRON–PHONON SYSTEMS
Authors: TRUGMAN S. A. , BONČA J. , KU LI-CHUNG
Published: July 2002

We review recent variational methods that provide extremely accurate solutions for the problem of one and two electrons coupled to dynamical, quantum phonons, including retardation effects. The dynamics of these systems far from equilibrium is explored, including the dynamics of polaron formation after electron injection by an STM. An examination of three-point functions suggests a qualitative modification of the traditional picture of a polaron. Long-range electron–phonon interactions are studied in some generality, including vector and frustrated Fröhlich models, and bounds are obtained on the possible mass enhancement.