bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser excited fluorescence and self-absorption in LaF3:Nd3+
Authors: Kumar U. Vignaneswara , Rao D. Ramachandra , Venkateswarlu Putcha
Published: February 2003

Fluorescence of LaF3:Nd3+ has been observed at 77 °K and at room temperature in the region 5170–9020 Å using the Ar+, 5145 Å laser excitation. The fluorescence at 77 °K consists of lines orginating in the E,D, and R levels of Nd3+ as well as in the K and L levels which are probably reached as a result of a two photon excitation of Nd3+. The S and A levels are also found to fluoresce at room temperature, and it is suggested that thermally assisted ion pair processes may be responsible for the population buildup in these levels at high temperatures. Transitions from the R (4F3/2) levels to the ground state Z1 and first excited state Z2 (45 cm−1) showed self-reversal at 77 °K. Owing to the simple geometry of laser excitation, the degree of self-reversal could be directly related to the oscillator strength of the transitions. This enabled an evaluation of the total f number of the Z–R transitions which could be compared with an earlier value obtained from direct absorption measurements.
Quenching of N2(A 3Σ+u) by I2
Authors: Mandl A. , Ewing J. J.
Published: February 2003

Production and decay of N2(A 3Σ+u) (v=0, 1, 2) states were monitored photoelectrically from the sensitized fluorescence of NO γ bands. These states were produced by collisional transfer from excited Xe (1S4) which in turn was produced by radiative energy transfer via resonance radiation (147 nm) from a closely coupled Xe flash lamp. The rate coefficient for the deactivation of N2(A 3Σ+u) by I2 was measured as kI2= 6.9±1.9×10−12 cm3/sec. The deactivation by NO itself was measured as kNO=4.5±0.5×10−11 cm3/sec.
Information theory for marginal distributions: Application to energy disposal in an exothermic reaction
Authors: Arnold Graham S. , Kinsey James L.
Published: February 2003

Information theory is used to make the best estimate of a multi-variable probability distribution from one of its marginal distributions. The method developed is used to examine the relationship between the distributions of available energy over two different degrees of freedom of the products of the reaction of H+NO2→OH+NO. It is ascertained that a molecular beam experiment to measure the product translational energy distribution and experiments whereby the internal energy distribution in OH are determined from infrared chemiluminescence and laser-induced fluorescence are not redundant.
Deconvolution of differential cross sections obtained from molecular beam experiments
Authors: Shapiro M. , Gerber R. B. , Buck U. , Schleusener J.
Published: February 2003

A method is given for the deconvolution of measured differential cross sections to yield the correct center-of-mass cross sections, free of laboratory averaging. An input showing well-resolved oscillations, as observed in diffraction scattering of light atoms, is assumed. Both velocity and angular experimental averaging are allowed for. To deconvolute energy-fixed data a ’’scaling law’’ for the differential cross section is used. A method for the extraction of a sufficiently accurate scaling relation from experiment is described. Several numerical illustrations of the scheme are given, including the deconvolution of the elastic cross section for the Ne+D2 system.
Molecular dynamics studies of Lennard-Jones liquid mixtures. II. Mass and size dependence in the behavior of one different particle
Authors: Toukubo Kazuo , Nakanishi Koichiro , Watanabe Nobuatsu
Published: February 2003

Molecular dynamics calculations have been made for Lennard-Jones liquid mixtures consisting of 107 solvents and one solute. In order to examine the effects of mass and size of solute on the solvent structure around the solute and on the motion of solute, the mass or σ value of the Lennard-Jones potential assigned for a solute was chosen as either twice or half that for solvent, while the ε value for all solutes was assumed to be the same as that for solvent. Thermodynamic quantities, radial distribution functions, velocity autocorrelation functions, and self-diffusion coefficients were obtained. They were compared with those for the corresponding hard sphere system calculated by Alder et al. In some respects, characteristic behaviors of LJ solute were found to be different from those of the hard sphere. In contrast with the case of the hard sphere, the first peak of g12 becomes higher as the size of the solute decreases. The rate of increase in the self-diffusion of LJ solute with decrease in the size of the solute is not so large as that of hard sphere solute.
Hartree–Fock equations for open shell states
Authors: Silverstone Harris J.
Published: February 2003

Fock equations are derived for multideterminantal single configuration states with any number of open shells of any symmetry. New operators, ’’projection–transition’’ operators and ’’off-diagonal’’ Coulomb and exchange operators, are required for cases that do not fit a Roothaan-like mold.
A mean-field approximation for multicomponent solid solutions of molecular crystals with orientational and substitutional disorder
Authors: Govers H. A. J.
Published: February 2003

A mean-field model is proposed for the calculation of thermodynamic properties and order parameters of multicomponent solid solutions of molecular crystals with orientational and substitutional disorder. Intermolecular interaction in a static lattice is calculated using the atom–atom approximation. Lattice state probabilities are supposed to be those of an ensemble of noninteracting particles. Absence of correlation between the order parameters is assumed. The expression for the lattice entropy at partial order is chosen to be similar to the one at complete disorder. The number of order parameters is reduced with the help of symmetry relations between them, which can be chosen in accordance with computational capacity. Order parameters and lattice (free) energy are found by minimization of the expectation value of the lattice free energy. High temperature and lower temperature expressions are derived. The model is illustrated by four simple examples, in which reasonable values are predicted for the order parameters.
Second-order nuclear quadrupole coupling in the Br− ion
Authors: Stuart S. N.
Published: February 2003

This paper describes a theoretical treatment of the second-order Stark effect on the nuclear quadrupole interaction of a closed-shell atomic system. A method of calculation is presented which applies a dipolar perturbation in the uncoupled Hartree approximation. It is suggested in the context of ionic solids that the unperturbed anion be represented by Hartree–Fock wavefunctions appropriate to the free neutral atom rather than by the more extended free-ion functions. The first-order perturbation to the wavefunction is obtained by numerical solution of a differential equation (the method of Kotani and Sternheimer), and the second-order perturbation is approximated by projecting it onto the unperturbed wavefunction. The Br− ion is considered in detail and it is shown that, in the strong electrostatic fields to be found in ionic solids, the second-order nuclear quadrupole coupling can be considerable. The calculation yields a dipolarizability of 6.19 Å3, a dipole shielding factor of 4.45, a second-order Stark quadrupolarizability of 0.544 Å5 V−1, and a second-order Stark effect on the field gradient of γ24=−3.23 V−1. The second-order response is smaller in this case than in the free Cl− ion of earlier, variational calculations.
Thermodynamics of internal variables in the context of the absolute reaction rate theory
Authors: Valanis K. C. , Lalwani S.
Published: February 2003

In this paper we present a nonlinear internal constitutive equation which we have obtained by unifying the theory of ’’The Thermodynamics of Internal Variables’’ and a modified version, presented here, of ’’The Theory of Absolute Reaction Rates’’. The chief characteristic of this equation is the explicit form of the nonlinear relation between the internal forces and the rates of change of the internal variables. In addition, we have given the internal variables a precise physical interpretation. An internal variable in effect represents the average displacement of a group of atoms whose motion is impeded by a potential energy barrier of a specific height. As a consequence, the microforce encountered in the Eyring theory is identified as the free energy gradient causing the displacement of this particular group; the precise relationship between the microforce and the externally applied force field is also established. It is deduced that the single-well model, characteristic of theories with one internal variable, represents the mechanical response of a perfect crystal to externally applied force fields. The theory developed, herein, is anticipated to have wide applicability in the mathematical representation of the rate dependent behavior of metals and other materials.
Phase transitions of (1:1) alkaline salts of TCNQ as studied by vibronic intensity enhancement in the infrared spectra
Authors: Bozio Renato , Pecile Cesare
Published: February 2003

The results of a study of the temperature dependence of the infrared absorption spectra of M+TCNQ− (M+=Na+, K+, Rb+, Cs+, and NH4+) salts are reported and exemplified in detail for the case of triclinic RbTCNQ(II). On lowering the temperature, the infared absorptions which have already been recognized as due to vibronic activation of the totally symmetric modes of the TCNQ anion display a striking intensity enhancement. The plot of the vibronic band intensities against temperature displays an abrupt variation at nearly the same transition temperatures reported in the literature and determined by magnetic susceptibility and dc conductivity measurements. This result suggests that the vibronic intensity enhancement follows the distortion of the regular TCNQ anion stacks in the high temperature phases to alternating stacks in the low temperature ones.
On the equivalence between the space fixed and the body fixed formulations of the j
z-conserving approximation
Authors: Khare V.
Published: February 2003

It is shown that space fixed and the body fixed formulations of the jz-conserving approximation are equivalent if the partial wave parameter ? is chosen equal to the final orbitral angular momentum l′. We also examine the replacement of ? by l, the initial orbital angular momentum in the space fixed formulation. Only these two choices of ? give simple expressions for the scattering amplitude.
Septins, under Cla4p Regulation, and the Chitin Ring Are Required for Neck Integrity in Budding Yeast
Authors: Schmidt Martin , Varma Archana , Drgon Tomás , Bowers Blair , Cabib Enrico
Published: February 2003

CLA4, encoding a protein kinase of the PAK type, and CDC11, encoding a septin, were isolated in a screen for synthetic lethality with CHS3, which encodes the chitin synthase III catalytic moiety. Although Ste20p shares some essential function with Cla4p, it did not show synthetic lethality with Chs3p. cla4 and cdc11 mutants exhibited similar morphological and septin localization defects, including aberrant and ectopic septa. Myo1p, which requires septins for localization, formed abnormally wide rings in cla4 mutants. In cultures started with unbudded cells, an inhibitor of Chs3p activity, nikkomycin Z, aggravated the abnormalities of cla4 and cdc11 mutants and gave rise to enlarged necks at the mother-bud junction, leading to cell death. It is concluded that Cla4p is required for the correct localization and/or assembly of the septin ring and that both the septin ring and the Chs3p-requiring chitin ring at the mother-bud neck cooperate in maintaining the neck constricted throughout the cell cycle, a vital function in budding yeast.
COPI Recruitment Is Modulated by a Rab1b-dependent Mechanism
Authors: Alvarez Cecilia , Garcia-Mata Rafael , Brandon Elizabeth , Sztul Elizabeth
Published: February 2003

The small GTPase Rab1b is essential for endoplasmic reticulum (ER) to Golgi transport, but its exact function remains unclear. We have examined the effects of wild-type and three mutant forms of Rab1b in vivo. We show that the inactive form of Rab1b (the N121I mutant with impaired guanine nucleotide binding) blocks forward transport of cargo and induces Golgi disruption. The phenotype is analogous to that induced by brefeldin A (BFA): it causes resident Golgi proteins to relocate to the ER and induces redistribution of ER-Golgi intermediate compartment proteins to punctate structures. The COPII exit machinery seems to be functional in cells expressing the N121I mutant, but COPI is compromised, as shown by the release of β-COP into the cytosol. Our results suggest that Rab1b function influences COPI recruitment. In support of this, we show that the disruptive effects of N121I can be reversed by expressing known mediators of COPI recruitment, the GTPase ARF1 and its guanine nucleotide exchange factor GBF1. Further evidence is provided by the finding that cells expressing the active form of Rab1b (the Q67L mutant with impaired GTPase activity) are resistant to BFA. Our data suggest a novel role for Rab1b in ARF1- and GBF1-mediated COPI recruitment pathway.
Dual Prenylation Is Required for Rab Protein Localization and Function
Authors: Calero Monica , Chen Catherine Z. , Zhu Wenyan , Winand Nena , Havas Karyn A. , Gilbert Penny M. , Burd Christopher G. , Collins Ruth N.
Published: February 2003

The majority of Rab proteins are posttranslationally modified with two geranylgeranyl lipid moieties that enable their stable association with membranes. In this study, we present evidence to demonstrate that there is a specific lipid requirement for Rab protein localization and function. Substitution of different prenyl anchors on Rab GTPases does not lead to correct function. In the case of YPT1 and SEC4, two essential Rab genes in Saccharomyces cerevisiae, alternative lipid tails cannot support life when present as the sole source of YPT1 and SEC4. Furthermore, our data suggest that double geranyl-geranyl groups are required for Rab proteins to correctly localize to their characteristic organelle membrane. We have identified a factor, Yip1p that specifically binds the di-geranylgeranylated Rab and does not interact with mono-prenylated Rab proteins. This is the first demonstration that the double prenylation modification of Rab proteins is an important feature in the function of this small GTPase family and adds specific prenylation to the already known determinants of Rab localization.
The analysis of creep data for solder alloys
Authors: Plumbridge W.J.
Published: February 2003

With the continued miniaturisation of electronics equipment, a more detailed examination of the mechanical behaviour of solders is required to ensure reliability in performance. The paper reviews various aspects of the interpretation of the creep response of lead‐containing and lead‐free alloys. It demonstrates the necessity of acquiring stress‐rupture data over as long a period as possible to avoid non‐conservative extrapolation. For example, at 75°C, the transition in slope of the applied stress vs time to rupture plot occurs after about 1,000 h for Sn‐37Pb, although for the lead‐free alloys examined no such transition is observed within this timescale. Sometimes, deformation may be a more appropriate failure criterion than rupture, and it is shown that for Sn‐37Pb this may result in substantially shorter failure times than utilising a rupture criterion. The quality of life estimation methods then depends upon the extent of this stage when the creep rate is a minimum. The Y factor (tm : tr) where tm is the time spent in steady state or within 10 per cent of the minimum creep rate, for all the solders examined at 75°C generally falls into the 20‐30 per cent range. Estimations of creep life may substantially under predict because of this.
Retail exchanges: a research agenda
Authors: Sparks Leigh , Wagner Beverly A.
Published: February 2003

The nature of logistics and supply chain management has dramatically changed as a result of new information technology. Information is now critical in supply systems and information technology has allowed companies to transform their dealings with customers and suppliers. The development of retail exchanges is stimulating further change in supply chains and buyer‐supplier relationships in the retail sector. This paper briefly considers concepts such as QR, ECR and CPFR utilised by the retail sector to promote supply‐chain efficiencies. It then goes on to explore the impact of retail exchanges and outlines progress so far. Finally, research issues arising from the retail exchanges are set in the context of research questions and propositions to further understanding of the impact of retail exchanges on supply chain management and the retail industry as a whole.
Human Parvovirus B19 Nonstructural Protein (NS1) Induces Cell Cycle Arrest at G
1
Phase
Authors: Morita Eiji , Nakashima Akitoshi , Asao Hironobu , Sato Hiroyuki , Sugamura Kazuo
Published: February 2003

Human parvovirus B19 infects predominantly erythroid precursor cells, leading to inhibition of erythropoiesis. This erythroid cell damage is mediated by the viral nonstructural protein 1 (NS1) through an apoptotic mechanism. We previously demonstrated that B19 virus infection induces G
2
arrest in erythroid UT7/Epo-S1 cells; however, the role of NS1 in regulating cell cycle arrest is unknown. In this report, by using paclitaxel, a mitotic inhibitor, we show that B19 virus infection induces not only G
2
arrest but also G
1
arrest. Interestingly, UV-irradiated B19 virus, which has inactivated the expression of NS1, still harbors the ability to induce G
2
arrest but not G
1
arrest. Furthermore, treatment with caffeine, a G
2
checkpoint inhibitor, abrogated the B19 virus-induced G
2
arrest despite expression of NS1. These results suggest that the B19 virus-induced G
2
arrest is not mediated by NS1 expression. We also found that NS1-transfected UT7/Epo-S1 and 293T cells induced cell cycle arrest at the G
1
phase. These results indicate that NS1 expression plays a critical role in G
1
arrest induced by B19 virus. Furthermore, NS1 expression significantly increased p21/WAF1 expression, a cyclin-dependent kinase inhibitor that induces G
1
arrest. Thus, G
1
arrest mediated by NS1 may be a prerequisite for the apoptotic damage of erythroid progenitor cells upon B19 virus infection.
Persistent Replication of Hepatitis C Virus Replicons Expressing the β-Lactamase Reporter in Subpopulations of Highly Permissive Huh7 Cells
Authors: Murray Edward M. , Grobler Jay A. , Markel Eric J. , Pagnoni Marco F. , Paonessa Giacomo , Simon Adam J. , Flores Osvaldo A.
Published: February 2003

Progress toward development of better therapies for the treatment of hepatitis C virus (HCV) infection has been hampered by poor understanding of HCV biology and the lack of biological assays suitable for drug screening. Here we describe a powerful HCV replication system that employs HCV replicons expressing the β-lactamase reporter (
bla
replicons) and subpopulations of Huh7 cells that are more permissive (or “enhanced”) to HCV replication than naïve Huh7 cells. Enhanced cells represent a small fraction of permissive cells present among naïve Huh7 cells that is enriched during selection with replicons expressing the neomycin phosphotransferase gene (
neo
replicons). The level of permissiveness of cell lines harboring
neo
replicons can vary greatly, and the enhanced phenotype is usually revealed upon removal of the
neo
replicon with inhibitors of HCV replication. Replicon removal is responsible for increased permissiveness, since this effect could be reproduced either with alpha interferon or with an HCV NS5B inhibitor. Moreover, adaptive mutations present in the replicon genome used during selection do not influence the permissiveness of the resulting enhanced-cell population, suggesting that the mechanisms governing the permissiveness of enhanced cells are independent from viral adaptation. Because the β-lactamase reporter allows simultaneous quantitation of replicon-harboring cells and reporter activity, it was possible to investigate the relationship between genome replication activity and the frequency with which transfected genomes can establish persistent replication. Our study demonstrates that differences in the replication potential of the viral genome are manifested primarily in the frequency with which persistent replication is established but modestly affect the number of replicons observed per replicon-harboring cell. Replicon copy number was found to vary over a narrow range that may be defined by a minimal number required for persistent maintenance and a maximum that is limited by the availability of essential host factors.
Role of the 5′-Proximal Stem-Loop Structure of the 5′ Untranslated Region in Replication and Translation of Hepatitis C Virus RNA
Authors: Luo Guangxiang , Xin Shaojie , Cai Zhaohui
Published: February 2003

Sequences of the untranslated regions at the 5′ and 3′ ends (5′UTR and 3′UTR) of the hepatitis C virus (HCV) RNA genome are highly conserved and contain
cis
-acting RNA elements for HCV RNA replication. The HCV 5′UTR consists of two distinct RNA elements, a short 5′-proximal stem-loop RNA element (nucleotides 1 to 43) and a longer element of internal ribosome entry site. To determine the sequence and structural requirements of the 5′-proximal stem-loop RNA element in HCV RNA replication and translation, a mutagenesis analysis was preformed by nucleotide deletions and substitutions. Effects of mutations in the 5′-proximal stem-loop RNA element on HCV RNA replication were determined by using a cell-based HCV replicon replication system. Deletion of the first 20 nucleotides from the 5′ end resulted in elimination of cell colony formation. Likewise, disruption of the 5′-proximal stem-loop by nucleotide substitutions abolished the ability of HCV RNA to induce cell colony formation. However, restoration of the 5′-proximal stem-loop by compensatory mutations with different nucleotides rescued the ability of the subgenomic HCV RNA to replicate in Huh7 cells. In addition, deletion and nucleotide substitutions of the 5′-proximal stem-loop structure, including the restored stem-loop by compensatory mutations, all resulted in reduction of translation by two- to fivefold, suggesting that the 5′-proximal stem-loop RNA element also modulates HCV RNA translation. These findings demonstrate that the 5′-proximal stem-loop of the HCV RNA is a
cis
-acting RNA element that regulates HCV RNA replication and translation.
The Structure of Mammalian Cyclooxygenases
Authors: Garavito R. Michael , Mulichak Anne M.
Published: February 2003

▪ Abstract  Cyclooxygenases-1 and -2 (COX-1 and COX-2, also known as prostaglandin H2synthases-1 and -2) catalyze the committed step in prostaglandin synthesis. COX-1 and -2 are of particular interest because they are the major targets of nonsteroidal antiinflammatory drugs (NSAIDs) including aspirin, ibuprofen, and the new COX-2-selective inhibitors. Inhibition of the COXs with NSAIDs acutely reduces inflammation, pain, and fever, and long-term use of these drugs reduces the incidence of fatal thrombotic events, as well as the development of colon cancer and Alzheimer's disease. In this review, we examine how the structures of COXs relate mechanistically to cyclooxygenase and peroxidase catalysis and how alternative fatty acid substrates bind within the COX active site. We further examine how NSAIDs interact with COXs and how differences in the structure of COX-2 result in enhanced selectivity toward COX-2 inhibitors.
Nuclear localization of cyclin B1 regulates DNA damage–induced apoptosis
Authors: Porter Lisa A. , Cukier I. Howard , Lee Jonathan M.
Published: February 2003

Some cells undergo apoptosis in response to DNA damage, whereas others do not. To understand the biochemical pathways controlling this differential response, we have studied the intracellular localization of cyclin B1 in cell types sensitive or resistant to apoptosis induced by DNA damage. We found that cyclin B1 protein accumulates in the nucleus of cells that are sensitive to γ radiation–induced apoptosis (thymocytes, lymphoid cell lines), but remains cytoplasmic in apoptosis-resistant cells (primary and transformed fibroblasts). Treatment of both cell types with leptomycin B, an inhibitor of CRM1-dependent cyclin B1 nuclear export, induces apoptosis. Furthermore, ectopic expression of cyclin B1-5xE, a protein that preferentially localizes to the nucleus, is sufficient to trigger apoptosis. Conversely, expression of cyclin B1-5xA, a predominantly cytoplasmic protein, fails to induce apoptosis. This suggests that nuclear accumulation is necessary for cyclin B1–dependent apoptosis. Our observations are consistent with the idea that localization of cyclin B1 is among the factors determining the cellular decision to undergo apoptosis in response to DNA damage.
Prognostic value of angiogenesis in solitary bone plasmacytoma
Authors: Kumar Shaji , Fonseca Rafael , Dispenzieri Angela , Lacy Martha Q. , Lust John A. , Wellik Linda , Witzig Thomas E. , Gertz Morie A. , Kyle Robert A. , Greipp Philip R. , Rajkumar S. Vincent
Published: February 2003

Angiogenesis plays an important role in the biology of multiple myeloma (MM) and has prognostic importance in this disease. Solitary plasmacytoma is a localized plasma cell malignancy that progresses to MM in a significant number of patients. We examined if angiogenesis is increased in solitary plasmacytoma and if it can help identify patients likely to progress to myeloma. We studied angiogenesis in plasmacytoma biopsy samples and bone marrow biopsies from 25 patients. High-grade angiogenesis was present in 64% of plasmacytomas. In contrast, bone marrow angiogenesis was low in all patients. Patients with high-grade angiogenesis in the plasmacytoma sample were more likely to progress to myeloma and had a shorter progression-free survival compared with patients with low-grade angiogenesis (P = .02). Angiogenesis is increased in solitary plasmacytoma and is a significant predictor of progression to myeloma and provides further evidence of its importance in the pathogenesis of myeloma.
Circulation is established in a stepwise pattern in the mammalian embryo
Authors: McGrath Kathleen E. , Koniski Anne D. , Malik Jeffrey , Palis James
Published: February 2003

To better understand the relationship between the embryonic hematopoietic and vascular systems, we investigated the establishment of circulation in mouse embryos by examining the redistribution of yolk sac–derived primitive erythroblasts and definitive hematopoietic progenitors. Our studies revealed that small numbers of erythroblasts first enter the embryo proper at 4 to 8 somite pairs (sp) (embryonic day 8.25 [E8.25]), concomitant with the proposed onset of cardiac function. Hours later (E8.5), most red cells remained in the yolk sac. Although the number of red cells expanded rapidly in the embryo proper, a steady state of approximately 40% red cells was not reached until 26 to 30 sp (E10). Additionally, erythroblasts were unevenly distributed within the embryo's vasculature before 35 sp. These data suggest that fully functional circulation is established after E10. This timing correlated with vascular remodeling, suggesting that vessel arborization, smooth muscle recruitment, or both are required. We also examined the distribution of committed hematopoietic progenitors during early embryogenesis. Before E8.0, all progenitors were found in the yolk sac. When normalized to circulating erythroblasts, there was a significant enrichment (20- to 5-fold) of progenitors in the yolk sac compared with the embryo proper from E9.5 to E10.5. These results indicated that the yolk sac vascular network remains a site of progenitor production and preferential adhesion even as the fetal liver becomes a hematopoietic organ. We conclude that a functional vascular system develops gradually and that specialized vascular–hematopoietic environments exist after circulation becomes fully established.
Simian immunodeficiency virus dramatically alters expression of homeostatic chemokines and dendritic cell markers during infection in vivo
Authors: Choi Yang Kyu , Fallert Beth A. , Murphey-Corb Michael A. , Reinhart Todd A.
Published: February 2003

Dendritic cells (DCs) are potent antigen-presenting cells that likely play multiple roles in human immunodeficiency virus type 1 (HIV-1) pathogenesis. We used the simian immunodeficiency virus (SIV)/macaque model to study the effects of infection on homeostatic chemokine expression and DC localization directly in secondary lymphoid tissues. SIV infection altered the expression of chemokines (CCL19/MIP-3β, CCL21/ 6Ckine, and CCL20/MIP-3α) and of chemokine receptors (CCR7 and CCR6) that drive DC trafficking. CCL19/MIP-3β, CCL20/MIP-3α, CCR6, and CCR7 expression increased in lymph nodes during the early systemic burst of viral replication (acute infection), whereas CCL21/6Ckine expression progressively decreased throughout disease to AIDS. Parallel with the SIV-induced perturbations in chemokine expression were changes in the expression of the DC-associated markers, DC-SIGN, DC-LAMP, and DECTIN-1. During AIDS, DC-LAMP mRNA expression levels were significantly reduced in lymph nodes and spleen, and DC-SIGN levels were significantly reduced in spleen. These findings suggest that the disruption of homeostatic chemokine expression is responsible, in part, for alterations in the networks of antigen-presenting cells in lymphoid tissues, ultimately contributing to systemic immunodeficiency.
Determination of fluoxetine and norfluoxetine in rat plasma by HPLC with pre‐column derivatization and fluorescence detection
Authors: Guo Xingjie , Fukushima Takeshi , Li Famei , Imai Kazuhiro
Published: February 2003

Both fluoxetine (FLX) and its N‐demethylated metabolite, norfluoxetine (NFLX), have been reported to be potent serotonin‐reuptake inhibitors. A sensitive and reliable method that allows simultaneous quantification of their plasma levels would be valuable and was developed in this work. The procedure included extraction of FLX and NFLX from plasma, fluorescence derivatization with 4‐(N‐chloroformylmethyl‐N‐methyl) amino‐7‐nitro‐2,1,3‐benzoxadiazole (NBD‐COCl), separation of the derivatives on an octadecylsilica column with acetonitrile–water (55:45,v/v) as mobile phase and fluorescence detection with emission at 537 nm and excitation at 478 nm. The calibration curves were linear for FLX and NFLX concentration over the range of 10–1000 nM (r = 0.9992 and r = 0.9997) and the limits of quantitation were 10 nM in 100 µL of plasma. Precision of intra‐ and inter‐day RSD of less than 12% and accuracy of intra‐ and inter‐day RE within −6.0–13% were achieved. The method described was applied to analysis of the plasma samples from rats treated with FLX hydrochloride and to the pharmacokinetic study. Copyright © 2002 John Wiley & Sons, Ltd.
Re‐Based Heterogeneous Catalysts for Olefin Metathesis Prepared by Surface Organometallic Chemistry: Reactivity and Selectivity
Authors: Chabanas Mathieu , Copéret Christophe , Basset Jean‐Marie
Published: February 2003

Herein we describe the catalytic activity of 1, a well‐defined Re alkylidene complex supported silica, in the reaction of olefin metathesis. This system is highly active for terminal and internal olefins with initial rates up to 0.7 mol per mol Re per s. It also catalyses the self‐metathesis of methyl oleate (MO) without the need of co‐catalysts. The turnover numbers can reach up to 900 for MO, which is unprecedented for a heterogeneous Re‐based catalyst. Moreover the use of silica as a support can bring major advantages, such as the possibility to use branched olefins like isobutene, which are usually incompatible with alumina‐based supports; therefore, the formation of isoamylene from the cross‐metathesis of propene and isobutene can be performed. All these results are in sharp contrast to what has been found for other silica‐ or alumina‐supported rhenium oxide systems, which are either completely inactive (silica system) or typically need co‐catalysts when functionalised olefins are used. Finally the initiation step corresponds to a cross‐metathesis reaction to give a 3:1 mixture of 3,3‐dimethylbutene and trans‐4,4‐dimethylpent‐2‐ene, and make this catalyst the first generation of well‐defined Re‐based heterogeneous catalysts.
Metal Nanowire Arrays by Electrodeposition
Authors: Walter Erich C. , Zach Michael P. , Favier Frédéric , Murray Benjamin J. , Inazu Koji , Hemminger John C. , Penner Reginald M.
Published: February 2003

We describe two related methods for preparing arrays of nanowires composed of molybdenum, copper, nickel, gold, and palladium. Nanowires were obtained by selectively electrodepositing either a metal oxide or a metal at the step edges present on the basal plane of highly oriented pyrolytic graphite (HOPG) electrodes. If a metal oxide was electrodeposited, then nanowires of the parent metal were obtained by reduction at elevated temperature in hydrogen. The resulting nanowires were organized in parallel arrays of 100–1000 wires. These nanowires were long (some >500 μm), polycrystalline, and approximately hemicylindrical in cross‐section. The nanowire arrays prepared by electrodeposition were also “portable”: After embedding the nanowires in a polymer or cyanoacrylate film, arrays of nanowires could be lifted off the graphite surface thereby facilitating the incorporation of metal nanowire arrays into devices such as sensors.
Dynamics of Full Fusion During Vesicular Exocytotic Events: Release of Adrenaline by Chromaffin Cells
Authors: Amatore Christian , Arbault Stéphane , Bonifas Imelda , Bouret Yann , Erard Marie , Guille Manon
Published: February 2003

Vesicular exocytosis is important in the communication between cells in complex organisms. It controls the release of specific chemical or biochemical messengers stored in the emitting cell, which elicit a response upon detection by the target cells. Secretion of a messenger molecule (a neurotransmitter) was measured electrochemically, which allowed the quantification of cellular events and the validation of current physicochemical models. This model led us to formulate predictions about the occurrence and kinetics of vesicular exocytotic events based on the physicochemical meaning of its key parameters. These predictions were tested successfully through a series of experiments on chromaffin cells, involving changes of osmotic conditions, presence of trivalent ions and cholesterol‐induced structuring of the cell plasmic membrane.
Regular Irregularity in the Transfer of Anionic Surfactant across the Liquid/Liquid Interface
Authors: Kakiuchi Takashi , Nishi Naoya , Kasahara Takuya , Chiba Minako
Published: February 2003

Irregular current spikes and other anomalies seen in voltammetry of the transfer of anionic surfactants, alkyl sulfonates, and alkyl sulfates across the 1,2‐dichloroethane/water (DCE/W) interface are reproducible. The anomalies have a certain regularity that is predicted by a recently proposed concept, the electrochemical instability. Irregular current spikes follow after the augmentation of the current induced when the phase‐boundary potential is brought close to the mid‐point potential of the transferring surfactant ions. Potential‐step chronoamperometry clearly demonstrates the presence of the instability window, that is, the potential region where the interface becomes unstable only in the limited range of the phase‐boundary potential.
An Olefin Metathesis/Double Bond Isomerization Sequence Catalyzed by an In Situ Generated Ruthenium Hydride Species
Authors: Schmidt Bernd
Published: February 2003

The direct conversion of allyl ethers to cyclic enol ethers using an olefin metathesis/double bond migration sequence is described. Ruthenium carbene complexes were activated to catalyze the double bond migration step by addition of hydride sources, such as NaH or NaBH4. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Imprinted Polymer – Modified Hanging Mercury Drop Electrode for Differential Pulse Adsorptive Stripping Voltammetric Analysis of a Diquat Herbicide
Authors: Prasad Bhim Bali , Arora Bhavana
Published: February 2003

An imprinted polymer modified hanging mercury drop electrode (HMDE) in Model 303A system in conjunction with a PAR Model 264A Polarographic Analyzer/Stripping Voltammeter has been used for the selective analysis of a diquat herbicide viz., 5,6‐dihydropyrazino[1,2,3,4‐[lmn]‐1,10‐phenanthrolinium dichlorides in differential pulse cathodic stripping voltammetry mode. Complex aqueous samples (drinking water and agricultural soil suspension), spiked with a diquat herbicide, were directly analyzed by the adsorptive accumulation of the analyte over the working electrode (accumulation potential −0.8 V (vs. Ag/AgCl), accumulation time 120 s, pH 7.0, supporting electrolyte 0.1 M KCl, scan rate 10 mV s−1, pulse amplitude 25 mV). The limit of detection for diquat herbicide was found to be 0.34 nmol L−1 (0.1 ppb, RSD 2%, S/N=2).
Voltammetric Behavior of MoS$\rm{ {_{4}^{2-}}}$ and SbS$\rm{ {_{4}^{3-}}}$ as Possible Components of “Dissolved Sulfide” in Oxic Natural Waters
Authors: Ciglenečki Irena , Helz George R.
Published: February 2003

Nanomolar concentrations of dissolved sulfide have been observed in O2‐ bearing natural waters. The sulfide consists of oxidation‐resistant, unknown chemical components that might include metal‐sulfide complexes, elemental sulfur in various forms or organic sulfur compounds. Here we show that thioanions are also plausible components. Tetrathiomolybdate and tetrathioantimonate ions deposit respectively 3 and 4 equivalents of HgS at mercury electrodes. In cathodic stripping voltammetry, a common method to quantify nanomolar sulfide in nature, MoS$\rm{ {_{4}^{2-}}}$ and SbS$\rm{ {_{4}^{3-}}}$ would therefore contribute to “total dissolved sulfide.” Limited evidence suggests that thioanions may be powerful complexing agents that would be capable of affecting trace metal speciation and bioavailability in natural waters.
Modelling nonlinear dynamics of shape‐memory‐alloys with approximate models of coupled thermoelasticity
Authors: Melnik R.V.N. , Roberts A.J.
Published: February 2003

We present a general methodology for constructing approximate models describing shape memory alloys dynamics. We base our discussion on a general three‐dimensional model and the Falk‐Konopka representation for the free energy function. By considering a one‐dimensional counterpart of that model, we show that with little computational efforts we can reproduce successfully phase transition phenomena with our numerical scheme. The same scheme is applied in our code for the general case. Then, we describe a systematic approach to modelling SMA materials, and demonstrate that approach in deriving a centre‐manifold‐based low‐dimensional model from the general three‐dimensional model, preserving all main features of the dynamics. Computer algebra technique allows us to derive such models efficiently and with arbitrary degree of accuracy.
On the j
z-conserving coupled states approximation: Magnetic transitions and angular distributions in rotating and fixed frames
Authors: Kouri Donald J. , Shimoni Yair
Published: February 2003

Recently Shimoni and Kouri have pointed out that a careful treatment of the jz-conserving coupled states (CS) approximation results in a body frame T-matrix TJ(jλ‖j0λ0) which is not diagonal in λ,λ0. In addition they have shown that previous investigations of the CS did not optimally identify the body frame T-matrix. In this paper, we explore the consequences of these observations. The exact T-matrix is obtained in the R13- and P-helicity frames, as well as in an uncoupled spaceframe (USF) representation. The resulting exact expressions for these T-matrices are in terms of certain integrals, IJl(jλ‖j0λ0), introduced earlier by Shimoni and Kouri. By obtaining the CS approximation to these integrals, we are able to derive the preferred CS approximation in the R- and P-helicity and USF representations. We then employ the resulting CS T-matrices to derive the differential scattering amplitude and cross section in the various possible reference frames. The result is a unified treatment of these quantities. We are then able to demonstrate the equivalence of the CS approximation to the R- and P-helicity amplitudes. In addition, we show explicitly that the CS approximate degeneracy averaged differential cross section is frame independent. The CS approximation to the USF equation provides a rigorous basis for the original derivation of the CS method as given by McGuire and Kouri. In particular, our treatment shows that when the L2 operator is approximated by an eigenvalue form l (l+1) h/2 (as was suggested first by McGuire and Kouri), there is no longer any difference between the BF and USF in the dynamical equations (for the wavefunction or amplitude density). Any differences are strictly kinematic in origin, and are the source of the λ transitions which occur in the BF CS approximation. In the USF, since there are no rotational kinematic effects, there are no magnetic transitions in the CS approximation. Thus, the name jz-conserving coupled states is appropriate in two senses. First, in the USF, jz is conserved in the CS approximation. Second, even though jz is not conserved in the BF CS-approximation T-matrices, jz-conservation does occur so far as the dynamics are concerned; i.e., the BF amplitude density and wavefunction both conserve jz in the CS approximation.
Static and dynamic light scattering studies of critical phenomena. I. Upper and lower consolute points of 3-methylpyridine–D2O
Authors: Harker George G. , Schmidt Raymond L.
Published: February 2003

To further probe the ’’universality’’ ideas of critical phenomena, the turbidity, light scattering intensity, and Rayleigh linewidth have been measured for the 3-methylpyridine–D2O binary liquid system in the region of both the entropy-driven lower (LCST) and the enthalpy-driven upper (UCST) critical solution temperatures. The LCST was found to be 38.240 °C at XD2O=0.923 and the UCST was 115.440 °C at XD2O=0.9005, both under a nitrogen atmosphere in a sealed cell. In addition to being the first complete light scattering study of two critical points in a single system, the UCST is the highest temperature attempted for such investigations and the LCST study is only the second complete LCST study that has been reported. For the LCST mixture, γ=1.27±0.03 and ν=0.65±0.03; for the UCST system, γ=1.27±0.03 and ν=0.61±0.02. Some deviations from OZ behavior were noted which are related to multiple scattering effects. The critical linewidth data, ranging from the hydrodynamic region (Kξ≪1) to the critical region (Kξ≫1), were compared to the original Kawasaki expression. Deviations similar to those previously reported for other critical systems were observed which resulted from the constant viscosity assumption. Kawasaki viscosities η* at given ΔT values were determined semiquantitatively to infer the different nature of the viscosity anomaly in the UCST and LCST regions. Analysis of the linewidth data also yielded the ’’apparent’’ exponent ν* describing the behavior of the diffusion coefficient. For the LCST system, ν* =0.61±02; for the UCST system, ν*=0.62±02.
Statistical mechanics of helical wormlike chains. V. Distribution functions
Authors: Shimada Jiro , Yamakawa Hiromi
Published: February 2003

By an application of the operational method, general expressions are derived for the Daniels-type and moment-based trivariate distribution functions of the end-to-end vector, the unit tangent vector, and the unit curvature vector for the helical wormlike chain. Some numerical results are presented for the distribution function of the end-to-end vector alone, the mean reciprocal distance, and the ring closure probability to examine the convergence. For chains of strong helical nature, the Hermite series truncated at terms including the second to sixth even moments give rather good approximations. For such chains, the mean reciprocal distance and the ring closure probability as functions of chain length are also shown to exhibit damped oscillatory behavior.
Lattice dynamics and phase transition in sodium azidea)
Authors: Kanney L. B. , Gillis N. S. , Raich J. C.
Published: February 2003

Within the context of the quasiharmonic theory of lattice dynamics, the zone center frequencies, dispersion curves, and frequency distribution of sodium azide are calculated using two potential models. Good agreement is obtained between the calculated zone center frequencies and the available Raman data. In particular, the calculated temperature dependence of the splitting of the Eg librational mode in the β phase into Ag and Bg modes in the α phase is in excellent agreement with experiment.
Optical spectra of molecular aggregates near the strong coupling limit
Authors: Hemenger R. P.
Published: February 2003

It is shown that the Green function operator for the electronic excited states of an arbitrary aggregate of identical monomers can be expanded in a series of terms in which the first represents the strong coupling (exciton) limit. Higher terms in this series successively improve the exciton limit by bringing in the effects of vibrational structure of the monomers. By evaluating the contribution to optical spectra of three terms in this series explicit expressions are found for the intensities, positions, and widths of individual exciton peaks near the strong coupling limit. It is shown for example that each exciton peak is narrowed with respect to the monomer band width at most by a factor of M−1/2 where M is the number of monomers in the aggregate. An approximate expression for optical absorption by molecular aggregates (DGS model) derived earlier is shown to satisfy the relations derived here.
Relaxation of nuclear magnetization at low densities
Authors: Sanctuary B. C.
Published: February 2003

In a recent paper, Tenti and McCourt [J. Chem. Phys. 65, 623 (1976)] presented theoretical evidence for the existence of a minimum in the transverse relaxation time T2 of the nuclear magnetization in dilute gases. Here the transverse relaxation rate is reexamined and it is shown that in the low density regime it is impossible to define a T2. Moreover, the slowing down of the relaxation rate at low densities is due to a decreasing collision rate and not to a dynamical shift as reported by Tenti and McCourt. It is found that the transverse magnetization behaves as a damped oscillator below a certain critical density. Explicit calculations are presented for H2 gas and for this system the T2 description breaks down below 0.02 Torr.
Response to ’’Comment on ’Probability of escaping neutralization when the mobility is field dependent’ ’’
Authors: Mozumder A.
Published: February 2003

The field dependence of the electron mobility in dielectric liquid media is discussed.(AIP)
Molecular hydrodynamics of the partially rough sphere fluid
Authors: Montgomery John A. , Berne Bruce J.
Published: February 2003

Molecular hydrodynamics is used to theoretically describe recent computer experiments on rough and partially rough sphere fluids. Agreement with the experimental translational and rotational diffusion coefficients may be obtained when the macroscopic boundary conditions of the hydrodynamics are made to depend on the microscopic boundary conditions of the collision dynamics. An attempt to extend the treatment to a self-consistent theory of the linear and angular velocity correlation functions (VCF and AVCF) fails, due to the unphysical short time behavior of the hydrodynamic VCF. The hydrodynamic AVCF appears to reproduce the structure due to changes in microscopic roughness, although quantitative agreement is not found at all densities. The long time behavior of the hydrodynamic AVCF is discussed.