bluuebunny/crossref_metadata_2025 huggingface dataset:
Ab initio molecular orbital study of structures and energetics of Si3H2, Si3H2+, and Si3H2−
Authors: Ikuta Shigeru , Wakamatsu Souichi
Published: May 2004

The geometric structures, isomeric stabilities, and potential energy profiles of various isomers and transition states in Si3H2 neutral, cation and anion are investigated at the coupled-cluster singles, doubles (triples) level of theory. For the geometrical survey, the basis sets used are of the Dunning’s correlation consistent basis sets of triple-zeta quality (cc-pVTZ) for the neutral and cation and the Dunning’s correlation consistent basis sets of double-zeta quality with diffuse functions (aug-cc-pVDZ) for the anion. For the final energy calculations, the aug-cc-pVTZ: Dunning’s correlation consistent basis sets of triple-zeta quality with diffuse functions and cc-pVQZ: Dunning’s correlation consistent basis sets of quadruple-zeta quality basis sets are used for the neutral and the aug-cc-pVTZ ones for the cation and anion. The global minimum neutral (I-1: A11) has the same framework as that (cyclopropenylidene) of the C3H2 molecule. Other low-lying three isomers (I-2, I-3, and I-4) are also predicted to be within 20 kJ/mol. Five transition states are optimized and their energy relationships with the isomers are clarified. The geometric structure of the global minimum cation (C-1: A12) has the same framework as that of the neutral, but that of the anion (A-1: A′2) differs very much from those of the neutral and cation. The calculated vertical and adiabatic ionization potentials from the global minimum neutral (I-1) are 7.85 and 7.77 eV, respectively. The adiabatic electron affinity of the neutral I-1 and the electron detachment energy of the global minimum anion (A-1) are predicted to be 1.21 and 1.92 eV, respectively. The two-electron three-centered bond is widely observed in the present Si3H2 neutral, cation, and anion. The contour plots of their localized molecular orbitals clearly show the existence of such nonclassical chemical bonds.
Estimating the Lyapunov exponents of discrete systems
Authors: Li Changpin , Chen Guanrong
Published: May 2004

In the present paper, our aim is to determine both upper and lower bounds for all the Lyapunov exponents of a given finite-dimensional discrete map. To show the efficiency of the proposed estimation method, two examples are given, including the well-known Hénon map and a coupled map lattice.
A Bohmian total potential view to quantum effects. I. Methodology and simple model systems
Authors: González Javier , Bofill Josep Maria , Giménez Xavier
Published: May 2004

The coherent-state wave packet dynamics of several model systems is analyzed in terms of Bohm’s total potential. The quantum dynamics has been obtained by solving the time-dependent Schrödinger equation, and a method for obtaining the total potential from it, involving just matrix algebra, has been proposed. Contrary to what one may expect, it is shown that the time- and state-dependent features of the total potential admit a rationale, classical-like description of quantum effects, leading to a unified picture of them, which is not critically dependent, as for the key features, on the classical potential. An outstanding feature is found to be the relation of the state system’s density amplitude and sharpness (in its dependence with position) with quantum effects. Sharp density profiles and low densities cause the total potential to strongly depart from the classical value, in both time regimes and position ranges, which provide a clearer, more deterministic view to quantum dynamics. Free motion as well as scattering processes by square and Eckart barriers have been analyzed by means of careful inspection of several time dependent snapshots. The result is an insightful picture of processes involving tunneling and antitunneling, including their dynamical variants, as well as resonances and quantization.
TiC–diamond composite disk-heater cell assembly to generate temperature of 2000 °C in a large-volume belt-type high-pressure apparatus at 10 GPa
Authors: Taniguchi Takashi , Akaishi Minoru , Kanke Yasushi , Yamaoka Shinobu
Published: May 2004

A TiC–diamond composite was prepared for the heater of a large-volume belt type high-pressure apparatus. Graphite has conventionally been used for the heater in high-pressure studies, but it cannot be used at pressure higher than 10 GPa and above 1500 °C because of the problem associated with the graphite-to-diamond phase transformation. New TiC–diamond heater overcomes this problem and achieves stable temperature generation by using a belt-type high-pressure apparatus. The composite was fabricated by heat-treatment of a mixture of diamond and TiC0.8 with nonstoichiometric composition at ambient pressure. By optimizing the preparation conditions, we obtained TiC–diamond composites that exhibited mechanical and electrical properties suitable for a heater material without any volatile component such as resin. Since reported conventional TiC–diamond composite heaters include epoxy resin as binder, volatile components arise from decomposition of the resin at high temperature preventing stable high-pressure/high-temperature experiment above 2000 °C. Attainment of reproducible temperature-generation efficiency in the present heater makes it possible to perform stable experiments at high temperature and pressure, i.e., in the region of 2000 °C and 10 GPa.
32-channel arbitrary waveform generator for bistable nematic devices
Authors: Lombardo Giuseppe , Malara Manuela , Barberi Riccardo , Rudin John C.
Published: May 2004

All commercially available liquid crystal nematic displays use cells with strong surface anchoring conditions and under field bulk monostable texture distortions. About ten years ago, a technological research line started to study liquid crystal nematic displays with intrinsic bistable textures. It implies pixels with two distinct stable states in the absence of field, but electrically switchable. Bistability allows infinite multiplexing for passive matrix displays: It suppresses the need of refreshing permanent informations. At present, commercial active matrix displays behave like bistable displays by means of electronic elements (TFT or diodes), one for each pixel. This is not an intrinsic bistability, because it is due to external active devices placed on the screen surface. The aim of the present research is to design a suitable and flexible experimental setup to create addressing waveforms for passive electro-optical intrinsically bistable devices.
Millikelvin scanned probe for measurement of nanostructures
Authors: Brown K. R. , Sun L. , Kane B. E.
Published: May 2004

We demonstrate a scanning force microscope, based upon a quartz tuning fork, that operates below 100 mK and in magnetic fields up to 6 T. The microscope has a conducting tip for electrical probing of nanostructures of interest, and it incorporates a low noise cryogenic amplifier to measure both the vibrations of the tuning fork and the electrical signals from the nanostructures. At millikelvin temperatures, the imaging resolution is below 1 μm in a 22 μm×22 μm range, and a coarse motion provides translations of a few mm. This scanned probe is useful for high bandwidth measurement of many high impedance nanostructures on a single sample. We show data locating a single electron transistor within an array and measure its Coulomb blockade with a sensitivity of 2.6×10−5 e/Hz.
3-geometries and the Hamilton–Jacobi equation
Authors: Garcı́a-Godı́nez Patricia , Newman Ezra Ted , Silva-Ortigoza Gilberto
Published: May 2004

In the first part of this work we show that on the space of solutions of a certain class of systems of three second-order PDE’s, uαα=Υ(α,β,u,uα,uβ), uββ=Ψ(α,β,u,uα,uβ) and uαβ=Ω(α,β,u,uα,uβ), a three-dimensional definite or indefinite metric, gab, can be constructed such that the three-dimensional Hamilton–Jacobi equation, gabu,au,b=1 holds. Furthermore, we remark that this structure is invariant under a subset of contact transformations. In the second part, we obtain analogous results for a certain class of third-order ordinary differential equation (ODE’s), u′′′=Λ(s,u,u′,u″). In both cases, we apply our general results to the cental force problem.
Liquid helium cryostat with internal fluorescence detection for x-ray absorption studies in the 2–6 keV energy region
Authors: McFarlane Holman Karen L. , Latimer Matthew J. , Yachandra Vittal K.
Published: May 2004

X-ray absorption spectroscopy (XAS) in the intermediate x-ray region (2–6 keV) for dilute biological samples has been limited because of detector/flux limitations and inadequate cryogenic instrumentation. We have designed and constructed a new tailpiece/sample chamber for a commercially available liquid helium cooled cryostat which overcomes difficulties related to low fluorescence signals by using thin window materials and incorporating an internal photodiode detector. With the apparatus, XAS data at the Cl, S, and Ca K edges have been collected on frozen solutions and biological samples at temperatures down to 60 K. A separate chamber has been incorporated for collecting room-temperature spectra of standard compounds (for energy calibration purposes) which prevents contamination of the cryostat chamber and allows the sample to remain undisturbed, both important concerns for studying dilute and radiation-sensitive samples.
Remote sensing instrument for solid samples based on open-path atomic emission spectrometry
Authors: Palanco Santiago , Laserna Javier
Published: May 2004

Design considerations and development steps towards the construction of an open-path laser-induced plasma spectrometer for remote elemental measurements are presented and the main variables influencing the analytical signal discussed. The instrument is based on a coaxial optical design where the interrogating laser beam and the returning plasma light share the same optical axis. This scheme allows both tight focusing of the infrared laser radiation to induce a plasma on a remote sample surface and collection of the ultraviolet-visible plasma emission through the same open air path. The selection of the optical scheme and the different components of the instrument are discussed on the basis of the measurement range, the light throughput and signal-to-noise ratio considerations. The results presented demonstrate the feasibility of the open-path laser-induced plasma spectrometry approach to remote atomic-emission spectrometry in the hundred meters range. Based on these results, additional estimations evidence the potential of the technique for measurements in the thousand meters range.
Application of a tunnel diode oscillator to noncontact resistivity measurement in pulsed magnetic fields
Authors: Ohmichi E. , Komatsu E. , Osada T.
Published: May 2004

We have developed a noncontact technique of resistivity measurement in pulsed high magnetic fields of up to 40 T with use of a tunnel diode oscillator. An LC tank circuit powered by a tunnel diode oscillates at frequency of f∼1/LC, which is typically in a megahertz range. A sample is placed in the tank coil, and a small change in the resonant frequency f of the circuit is measured. For metals, the frequency change is related to the change in skin depth, which is converted to resistivity via δ=ρ/πμf. In order to read out the frequency change from frequency modulated (FM) signals in a short time, we utilize an integrated circuit of portable FM radio as FM demodulator. This FM demodulator is found to be highly sensitive and useful for highly conducting samples of the order of milliohms. We will show some examples of resistivity measurements applied to oxide and organic metals in pulsed magnetic fields of up to 40 T.
Simultaneous determination of ultra-shallow junction depth and abruptness using thermal wave technique
Authors: Salnick Alex , Nicolaides Lena , Opsal Jon , Jain Amitabh , Rogers Duncan , Robertson Lance
Published: May 2004

Thermal wave (TW) studies of ultra-shallow junctions (USJ) formed by ion implantation into a semiconductor wafer followed by rapid thermal annealing (RTP) are described. It is shown that using the TW technique allows for a simultaneous determination of the most important USJ parameters—depth and profile abruptness. In a TW-based system, the USJ depth is obtained using the quadrature component of the TW signal while determination of USJ profile abruptness is based on the analysis of the TW quadrature and in-phase components measured at two different pump-probe beam offsets. Experimental results for junction depth and abruptness obtained on a set of B+-implanted, RTP-annealed USJ samples show better than 0.99 correlations to the corresponding secondary ion mass spectroscopy data.
Enhanced mass sensing using torsional and lateral resonances in microcantilevers
Authors: Sharos L. B. , Raman A. , Crittenden S. , Reifenberger R.
Published: May 2004

We present a method to detect, with enhanced sensitivity, a target mass particle attached eccentrically to a microcantilever by measuring multiple three-dimensional modes in the microcantilever vibration spectrum. Peaks in the spectrum reveal a complex coupling between the bending, torsional, and lateral motions and detailed finite element models assist in their interpretation. The mass sensitivities of the torsional and lateral mode frequencies are an order of magnitude greater, and their Q factors significantly higher, than that of the conventionally used fundamental bending mode. These modes offer significantly enhanced mass sensing capabilities within the realm of existing microcantilever technology.
Facile Synthesis of Azo Compounds from Aromatic Nitro Compounds using Magnesium and Triethylammonium Formate
Authors: Srinivasa G. R. , Abiraj K. , Gowda D. Channe
Published: May 2004

Magnesium/triethylammonium formate is a convenient reagent for the reduction of aromatic nitro compounds to corresponding symmetrically substituted azo compounds. Various azo compounds containing additional reducible substituents, including halogen, nitrile, acid, phenol, ester, and methoxy functions, have been synthesized in a single step by the use of this reagent. The conversion is reasonably fast, clean, high yielding, and occurs at room temperature in methanol.
Diazacoronand-Linked α- and β-Cyclodextrin Dimer Complexes of the Brilliant Yellow Tetraanion
Authors: Wyness Oska , May Bruce L. , Clements Philip , Lincoln Stephen F. , Easton Christopher J.
Published: May 2004

Complexation of the Brilliant Yellow tetraanion, 14–, by the new coronand-linked α- and β-cyclodextrin (αCD and βCD) dimers 4,13-bis(6 A-deoxy-α-cyclodextrin-6 A-ylamidomethyl)-4,13-diaza-1,7,10-trioxacyclodecapentane and 4,13-bis(6 A-deoxy-β-cyclodextrin-6 A-ylamidomethyl)-4,13-diaza-1,7,10-trioxacyclodecapentane, 2 and 3, respectively, has been studied in aqueous solution. The complexation constants for 2 · 14– and 3 · 14– are K1 = (3.20 ± 0.05) × 105 and (2.76 ± 0.09) × 104 dm3 mol–1, respectively, at 298.2 K, pH 10.0, and I 0.10 mol dm–3 (NEt4ClO4). The pK a values of 2 · H22+ are 6.57 ± 0.04 and 5.88 ± 0.05, and of 3 · H22+ are 6.70 ± 0.03 and 6.08 ± 0.02. Complexation of the alkaline earth metal ions by 2 is characterized by complexation constants (2.73 ± 0.51) × 102, (1.52 ± 0.36) × 105, (1.49 ± 0.03) × 105, and (4.28 ± 0.07) × 104 dm3 mol–1 for Mg2+, Ca2+, Sr2+, and Ba2+, respectively. These data are compared with those reported for analogous coronand-linked βCD dimer complexes to establish the hierarchy of the factors determining the stability of such complexes.
Synthesis and Antiviral Activity of Dimeric Capsid-Binding Inhibitors of Human Rhinovirus (HRV)
Authors: Krippner Guy Y. , Chalmers David K. , Stanislawski Pauline C. , Tucker Simon P. , Watson Keith G.
Published: May 2004

A set of dimeric analogues of known rhinovirus capsid-binders Pleconaril 1 and Pirodavir 55 has been synthesized and tested against two representative human rhinovirus (HRV) strains. Dimers with linker lengths ranging from five atoms up to approximately 60 atoms were prepared by coupling various functionalized monomeric precursors. Many of the dimers showed activity against HRV, with the most active compounds being those with the shorter linking groups. The lower activity of all the dimers relative to similar monomeric compounds, and especially the low activity of the longest dimers, suggests that cooperative bivalent binding is not occurring with any of these compounds.
Leukocyte-Endothelium Interactions during Permanent Focal Cerebral Ischemia in Mice
Authors: Kataoka Hiroharu , Kim Seong-Woong , Plesnila Nikolaus
Published: May 2004

The contribution of leukocyte infiltration to brain damage after permanent focal cerebral ischemia and the underlying molecular mechanisms are still unclear. Therefore, the aim of this study was to establish a mouse model for the visualization of leukocytes in the cerebral microcirculation in vivo and to investigate leukocyte-endothelial interaction (LEI) after permanent middle cerebral artery occlusion (MCAO). Sham-operated 129/Sv mice showed physiologic LEI in pial venules as observed by intravital fluorescent microscopy. Permanent focal cerebral ischemia induced a significant increase of LEI predominantly in pial venules. The number of rolling and adherent leukocytes reached 36.5 ± 13.2/100 μm × min and 22.5 ± 7.9/100 μm × min, respectively at 120 minutes after MCAO ( P = 0.016 vs. control). Of note, rolling and adherent leukocytes were also observed in arterioles of ischemic animals (7.3 ± 3.0/100 μm × min rolling and 3.0 ± 3.6/100 μm × min adherent). Capillary density was not different between groups. These results demonstrate that leukocytes accumulate in the brain not only after transient but also after permanent focal cerebral ischemia and may therefore contribute to brain damage after stroke without reperfusion.
Similarity Indices for Spatia I Ecological Data
Authors: Fewster R. M. , Buckland S. T.
Published: May 2004

Summary. We present a method for assessing similarity between species maps of presence and absence or abundance that emphasizes global features while ignoring minor local dissimilarities. The method arranges sites into small groups, or cliques, and allows controlled changes to be made within cliques to reduce the influence of local discrepancies. Resulting measures of similarity are visually more satisfactory than traditional indices. We show that the similarity indices are useful for model selection by comparing observed spatial patterns with those predicted by different fitted models. Examples are provided for spatial distributions of oribatid mites (Acari, Oribatei), woodlarks (Lullula arborea), and red deer (Genius elaphus).
Modeling and Optimization in Early Detection Programs with a Single Exam
Authors: Parmigiani Giovanni , Skates Steven , Zelen Marvin
Published: May 2004

Summary. The choice of timing of screening examinations is an important element in determining the efficacy of strategies for the early detection of occult disease. In this article, we describe a flexible decision‐making framework for the design of early detection programs, and we investigate the choice of timing when each individual in the screening program is examined only once. We focus on the theoretical relation between the optimal examination time and the distributions of sojourn times in health‐related states. Specifically, we derive closed‐form solutions of the optimal age using two specifications of utility functions, discuss the effects of natural history and utility specifications on the optimal solution, and present an application to early detection of colorectal cancer by once‐only sigmoidoscopy or colonoscopy.
The Use of Frailty Hazard Models for Unrecognized Heterogeneity That Interacts with Treatment: Considerations of Efficiency and Power
Authors: Li Yi , Betensky Rebecca A. , Louis David N. , Cairncross J. Gregory
Published: May 2004

Summary. Increasingly, genetic studies of tumors of the same histologic diagnosis are elucidating subtypes that are distinct with respect to clinical endpoints such as response to treatment and survival. This raises concerns about the efficiency of using the simple log‐rank test for analysis of treatment effect on survival in studies of possibly heterogeneous tumors. Furthermore, such studies, designed under the assumption of homogeneity, may be severely underpowered. We derive analytic approximations for the asymptotic relative efficiency of the simple log‐rank test relative to the optimally weighted log‐rank test and for the power of the simple log‐rank test when applied to subjects with unobserved heterogeneity, as reflected in a continuous frailty, that may interact with treatment. Numerical studies demonstrate that the simple log‐rank test may be quite inefficient if the frailty interacts with treatment. Further, there may be a substantial loss of power in the presence of the frailty with or without an interaction with treatment.
Moderated histogram equalization, an automatic means of enhancing the contrast in digital light micrographs reversibly
Authors: ENTWISTLE A.
Published: May 2004

A means for improving the contrast in the images produced from digital light micrographs is described that requires no intervention by the experimenter: zero‐order, scaling, tonally independent, moderated histogram equalization. It is based upon histogram equalization, which often results in digital light micrographs that contain regions that appear to be saturated, negatively biased or very grainy. Here a non‐decreasing monotonic function is introduced into the process, which moderates the changes in contrast that are generated. This method is highly effective for all three of the main types of contrast found in digital light micrography: bright objects viewed against a dark background, e.g. fluorescence and dark‐ground or dark‐field image data sets; bright and dark objects sets against a grey background, e.g. image data sets collected with phase or Nomarski differential interference contrast optics; and darker objects set against a light background, e.g. views of absorbing specimens. Moreover, it is demonstrated that there is a single fixed moderating function, whose actions are independent of the number of elements of image data, which works well with all types of digital light micrographs, including multimodal or multidimensional image data sets. The use of this fixed function is very robust as the appearance of the final image is not altered discernibly when it is applied repeatedly to an image data set. Consequently, moderated histogram equalization can be applied to digital light micrographs as a push‐button solution, thereby eliminating biases that those undertaking the processing might have introduced during manual processing. Finally, moderated histogram equalization yields a mapping function and so, through the use of look‐up tables, indexes or palettes, the information present in the original data file can be preserved while an image with the improved contrast is displayed on the monitor screen.
Is Your Perinatal Practice Mother‐Friendly? A Strategy for Improving Maternity Care
Authors: Hotelling Barbara A
Published: May 2004

Abstract:  The purpose of the questionnaire, “Is Your Perinatal Practice Mother‐Friendly?” is to provide health practitioners with an evidence‐based tool that can be used to improve maternity care. The Mother‐Friendly Childbirth Initiative is a consensus document promoting a wellness model of maternity care that was developed by the Coalition for Improving Maternity Services (CIMS) and ratified by major childbirth organizations and leading authorities in maternity care. By complying with the “Ten Steps of Mother‐Friendly Care,” a hospital or practice can be designated as “mother‐friendly.” The questionnaire enables health care providers to apply the Ten Steps to their maternity practice or services.
Mantle‐like Sr–Nd isotope composition of Fe–K subalkaline granites: the Peneda–Gerês Variscan massif (NW Iberian Peninsula)
Authors: Mendes A. C. , Dias G.
Published: May 2004

The Peneda–Gerês massif is one of the most representative NW Iberian late‐ to post‐orogenic Variscan granitic plutons. It resulted essentially from the subsynchronous emplacement, at 290–296 Ma, of two granitic magmas of Fe–K subalkaline affinity, with primitive isotopic composition: Sri = 0.703–0.707 and εNdi=−1.5 to −2.4. An origin by mantle input followed by mantle–crust interactions is proposed, implying the contribution of a less enriched mantle component than that involved in the genesis of synorogenic hybrid granitoids of Mg–K subalkaline affinity. A less voluminous aluminopotassic and isotopically more evolved magma (Sri=0.708–0.709 and εNdi=−3.5 to −3.9) with little or no mantle input was also generated, suggesting the involvement of lower crust materials. Therefore, this study suggests an input of juvenile magmas in late Variscan times, the mantle‐like isotope signature of Fe–K granitic magmatism being clearly related to a geodynamic setting of extensional processes, large‐scale uplift and thinning.
Neogene tectono‐sedimentary development of the western margin of the Çankırı Basin, central Turkey: reply to the comment of Kaymakçı 2003
Authors: Seyitoğlu G. , Kazancı N. , Karadenizli L. , Şen Ş. , Varol B. , Saraç G.
Published: May 2004

The Neogene succession in the western margin of Çankırı Basin is fragmented by a NNE‐trending tectonic sliver having normal faulted western and thrusted eastern margins. This newly recognized E‐vergent sliver was created by the NW–SE compression due to the North Anatolian and Kırıkkale–Erbaa Fault zones following late Pliocene, accommodating the internal deformation of the Anatolian plate. Determinations of the Kılçak, Kumartaş and Hançili formations on both sides of this tectonic sliver invalidate the stratigraphical, structural and basin evolution models previously proposed by Kaymakçı.
Practical methods for estimating the infection rate of Quercus robur acorn seedlots by Ciboria batschiana
Authors: Schröder T. , Kehr R. , Procházková Z. , Sutherland J. R.
Published: May 2004

The pathogenic fungus, Ciboria batschiana infects acorns prior to fall collection and if they are not freed of the fungus by thermotherapy seedlots can suffer serious losses during subsequent storage. However, since thermotherapy is time‐consuming and expensive, and sometimes has undesirable side‐effects, its use is not justified without knowing if and how intensively a seedlot is infected. It is demonstrated here that typical lesions on the surface of the cotyledons are a reliable indicator of infection by C. batschiana and that a method based on mycelium development on incubated cotyledons allows C. batschiana infection levels to be determined within 1–2 weeks. There were no significant differences in estimated C. batschiana infection levels between the visual assessment of the lesions before the incubation and the visual assessment of outgrowing mycelium from these lesions after the incubation. Using one or both of the described methods a decision can be made on the necessity for thermotherapy of acorn seedlots, i.e. before nursery sowing or long‐term, cold storage. The test based on mycelium development on incubated cotyledons can also be used for quality control following thermotherapy.
The Magnitude of the Association between Fluoroquinolone Use and Quinolone-Resistant
Escherichia coli
and
Klebsiella pneumoniae
May Be Lower than Previously Reported
Authors: Bolon Maureen K. , Wright Sharon B. , Gold Howard S. , Carmeli Yehuda
Published: May 2004

Case-control analyses of resistant versus susceptible isolates have implicated fluoroquinolone exposure as a strong risk factor for fluoroquinolone-resistant isolates of
Enterobacteriaceae
. We suspect that such methodology may overestimate this association. A total of 84 cases with fluoroquinolone-resistant isolates and 578 cases with fluoroquinolone-susceptible isolates of
Escherichia coli
or
Klebsiella pneumoniae
were compared with 608 hospitalized controls in parallel multivariable analyses. For comparison of previous estimates, the results of 10 published case-control studies of risk for fluoroquinolone resistance in isolates of
Enterobacteriaceae
were pooled by using a random-effects model. Exposure to fluoroquinolones was significantly positively associated with fluoroquinolone resistance (odds ratio [OR], 3.17) and negatively associated with fluoroquinolone susceptibility (OR, 0.18). Multivariable analyses yielded similar estimates (ORs, 2.04 and 0.10, respectively). As data on antibiotic exposure were limited to inpatient prescriptions, misclassification of fluoroquinolone exposure in persons who received fluoroquinolones as outpatients may have led to an underestimation of the true effect size. Pooling the results of previously published studies in which a direct comparison of fluoroquinolone-resistant and fluoroquinolone-susceptible cases was used resulted in a markedly higher effect estimate (OR, 18.7). Had we directly compared resistant and susceptible cases, our univariate OR for the association between fluoroquinolone use and the isolation of resistant
Enterobacteriaceae
would have been 19.3, and the multivariate OR would have been 16.5. Fluoroquinolone use is significantly associated with the isolation of fluoroquinolone-resistant
Enterobacteriaceae
; however, previous studies likely exaggerated the magnitude of this association.
Genetic Environments of the
rmtA
Gene in
Pseudomonas aeruginosa
Clinical Isolates
Authors: Yamane Kunikazu , Doi Yohei , Yokoyama Keiko , Yagi Tetsuya , Kurokawa Hiroshi , Shibata Naohiro , Shibayama Keigo , Kato Haru , Arakawa Yoshichika
Published: May 2004

Nine
Pseudomonas aeruginosa
strains showing very high levels of resistance to various aminoglycosides have been isolated from clinical specimens in seven separate Japanese hospitals in five prefectures since 1997. These strains harbor the newly identified 16S rRNA methylase gene (
rmtA
). When an
rmtA
gene probe was hybridized with genomic DNAs of the nine strains digested with EcoRI, two distinct patterns were observed. The 11.1- and 15.8-kb regions containing the
rmtA
genes of strains AR-2 and AR-11, respectively, were sequenced and compared. In strain AR-2, a transposase gene-like sequence (sequence 1) and a probable tRNA ribosyltransferase gene (
orfA
) were located upstream of
rmtA
, and a Na
+
/H
+
antiporter gene-like sequence (sequence 2) was identified downstream of
rmtA
. This 6.2-kbp insert (the
rmtA
locus) was flanked by 262-bp κγ elements. Part of the
orfQ
gene adjacent to an inverted repeat was found outside of the
rmtA
locus. In strain AR-11, the
rmtA
gene and sequence 2 were found, but the 5′ end of the
orfA
gene was truncated and replaced with IS
6100
. An
orfQ-orfI
region was present on each side of the
rmtA
gene in strain AR-11. The G+C content of the
rmtA
gene was about 55%, and since the newly identified
rmtA
gene may well be mediated by some mobile genetic elements such as Tn
5041
, further dissemination of the
rmtA
gene could become an actual clinical problem in the near future.
Interactions between Atazanavir-Ritonavir and Tenofovir in Heavily Pretreated Human Immunodeficiency Virus-Infected Patients
Authors: Taburet Anne-Marie , Piketty Christophe , Chazallon Corine , Vincent Isabelle , Gérard Laurence , Calvez Vincent , Clavel Francois , Aboulker Jean-Pierre , Girard Pierre-Marie
Published: May 2004

The aim of the present study was to assess the pharmacokinetic behavior of atazanavir-ritonavir when it is coadministered with tenofovir disoproxil fumarate (DF) in human immunodeficiency virus (HIV)-infected patients. Eleven patients enrolled in Agence Nationale de Recherche sur le SIDA (National Agency for AIDS Research, Paris, France) trial 107 were included in this pharmacokinetic study. They received atazanavir at 300 mg and ritonavir at 100 mg once a day (QD) from day 1 to the end of study. For the first 2 weeks, their nucleoside analog reverse transcriptase inhibitor (NRTI) treatments remained unchanged. Tenofovir DF was administered QD from day 15 to the end of the study. Ongoing NRTIs were selected according to the reverse transcriptase genotype of the HIV isolates from each patient. The values of the pharmacokinetic parameters for atazanavir and ritonavir were measured before (day 14 [week 2]) and after (day 42 [week 6]) initiation of tenofovir DF and are reported for the 10 patients who completed the study. There was a significant decrease in the area under the concentration-time curve from 0 to 24 h (AUC
0-24
) for atazanavir with the addition of tenofovir DF (AUC
0-24
ratio, 0.75; 90% confidence interval, 0.58 to 0.97;
P
= 0.05). There was a trend for a decrease in the minimum concentrations of atazanavir and ritonavir in plasma when they were combined with tenofovir, but none of the differences reached statistical significance. The median decreases in the HIV RNA loads at week 2 and week 6 were 0.1 and 0.2 log copies/ml, respectively. In summary, our data are consistent with the existence of a significant interaction between atazanavir and tenofovir DF.
Ciprofloxacin Dimers Target Gyrase in
Streptococcus pneumoniae
Authors: Gould Katherine A. , Pan Xiao-Su , Kerns Robert J. , Fisher L. Mark
Published: May 2004

We have examined the antipneumococcal activities of novel quinolone dimers in which ciprofloxacin was tethered to itself or to pipemidic acid by linkage of C-7 piperazinyl rings. Symmetric 2,6-lutidinyl- and
trans
-butenyl-linked ciprofloxacin dimers (dimers 1 and 2, respectively) and a pipemidic acid-ciprofloxacin dimer (dimer 3) had activities against
Streptococcus pneumoniae
strain 7785 that were comparable to that of ciprofloxacin, i.e., MICs of 2, 1, and 4 to 8 μg/ml versus an MIC of 1 to 2 μg/ml, respectively. Surprisingly, unlike ciprofloxacin (which targets topoisomerase IV), several lines of evidence revealed that the dimers act through gyrase in
S. pneumoniae
. First, ciprofloxacin-resistant
parC
mutants of strain 7785 remained susceptible to dimers 1 to 3, whereas a
gyrA
mutation conferred a four- to eightfold increase in the dimer MIC but had little effect on ciprofloxacin activity. Second, dimer 1 selected first-step
gyrA
(S81Y or S81F) mutants (MICs, 8 to 16 μg/ml) that carried wild-type topoisomerase IV
parE-parC
genes. Third, dimers 1 and 2 promoted comparable DNA cleavage by
S. pneumoniae
gyrase and topoisomerase IV, whereas ciprofloxacin-mediated cleavage was 10-fold more efficient with topoisomerase IV than with gyrase. Fourth, the GyrA S81F and ParC S79F enzymes were resistant to dimers, confirming that the resistance phenotype is largely silent in
parC
mutants. Although a dimer molecule could bind very tightly by bridging quinolone binding sites in the enzyme-DNA complex, the greater potency of ciprofloxacin against gyrase and topoisomerase IV suggests that dimers 1 to 3 bind in a monomeric fashion. The bulky C-7 side chain may explain dimer targeting of gyrase and activity against efflux mutants. Tethered quinolones have potential as mechanistic tools and as novel antimicrobial agents.
Efficacy of Cidofovir in a Murine Model of Disseminated Progressive Vaccinia
Authors: Neyts Johan , Leyssen Pieter , Verbeken Erik , De Clercq Erik
Published: May 2004

An animal model that mimics progressive disseminated vaccinia was elaborated. To this end nude (athymic) mice were inoculated intracutaneously with vaccinia virus in the lumbosacral area. Viral replication (DNA) in the skin was detected as early as day 2 postinfection (p.i.). Mice developed typical vaccinia lesions at the site of inoculation by day 4 to 6 p.i. By about 2 weeks p.i., the infection had spread all over the body, a situation reminiscent of disseminated vaccinia in humans. The infection resulted in viremia and spread of the virus to visceral organs, as well as to the brain. Topical treatment with cidofovir, initiated at the day of infection or at day 1 p.i., completely protected against virus-induced cutaneous lesions and against associated mortality. When treatment was initiated at a later time (day 2 to 5 p.i.), a partial but marked protective effect was noted, which can be explained by the fact that by that time, the virus had spread from the skin to the visceral organs. Next, infected animals were left untreated until the time (∼2 weeks p.i.) at which disseminated vaccinia had developed. When systemic treatment with cidofovir was initiated at that time, it caused lesions to heal and regress. In most of these animals, lesions had completely (or almost completely) disappeared by day 10 to 15 after the start of therapy. The observation that cidofovir is able to cause healing of disseminated vaccinia lesions in animals should have implications for the therapy of complications of vaccination against smallpox.
In Vitro Activity of OPT-80 against
Clostridium difficile
Authors: Ackermann Grit , Löffler Birgit , Adler Daniela , Rodloff Arne C.
Published: May 2004

Clostridium difficile
remains the major cause of nosocomial diarrhea. Reports on impaired susceptibility of
C. difficile
to metronidazole and vancomycin and frequent relapses of patients after therapy necessitate the search for new substances. With this study, the activity of OPT-80, a new macrocycle, against 207
C. difficile
strains and against other obligately anaerobic bacteria was tested. OPT-80 showed high in vitro activity against all
C. difficile
strains tested.
Genetic Basis of Erythromycin Resistance in Oral Bacteria
Authors: Villedieu A. , Diaz-Torres M. L. , Roberts A. P. , Hunt N. , McNab R. , Spratt D. A. , Wilson M. , Mullany P.
Published: May 2004

We determined the prevalence of erythromycin-resistant bacteria in the oral cavity and identified
mef
and
erm
(B) as the most common resistance determinants. In addition, we demonstrate the genetic linkage, on various Tn
1545
-like conjugative transposons, between erythromycin and tetracycline resistance in a number of isolates.
Mountaineer’s heel
Authors: Strauss R M
Published: May 2004

Mountaineers are at risk of skin lesions caused by constant boot friction. This is the case of a 35 year old mountaineer who presented with large and deeply ulcerated lesions over the medial aspects of both heels after a two and a half day climb using crampons. A number of factors such as the length of the climb in cold and thin air and the impossibility of removal of the footwear to allow rapid rewarming may have contributed to a more acute presentation of these lesions.
Statistical procedures for determining the extent of cognitive change following concussion
Authors: Collie A , Maruff P , Makdissi M , McStephen M , Darby D G , McCrory P
Published: May 2004

Neuropsychological (NP) testing is now often used to help to determine if the cognitive function of a concussed athlete has declined. The NP test score after concussion is compared with the baseline test score. Many clinicians simply subtract one from the other and make a clinical decision about the significance or otherwise of the resulting “difference score”. Such techniques are inadequate, as they fail to account for the many factors that may confound interpretation of serially acquired cognitive test scores. This is a review of a number of alternative approaches used in other areas of medicine for differentiating “true” changes from changes caused by these confounding factors. A case example is used to illustrate the effect that the statistical approach may have on clinical decision making.
The management of facial injuries in rugby union
Authors: Hayton M J , Stevenson H I , Jones C D , Frostick S P
Published: May 2004

Background:There are as yet no guidelines in rugby union for the management of facial lacerations which account for one-third of total injuries sustained by players.

Method:We devised a questionnaire to establish the current standards in rugby union clubs in England. The questionnaire covered such issues as inadequate wound cleansing, inappropriate suture material, the use of sterile suture equipment, and advice required for suture removal.

Results:We recommend that a dedicated medical room should be available in all clubs, the doctor should always wear gloves, and local anaesthetic and sterile suture packs and instruments should be provided.
A punch drunk jockey?
Authors: McCrory P , Turner M , Murray J
Published: May 2004

The case is reported of a retired professional jockey with progressive memory loss. The concern is that he may be suffering from chronic traumatic encephalopathy or the “punch drunk syndrome”.
ON THE FORMULATION OF THE GENERIC SUPERSYMMETRIC STANDARD MODEL (OR SUPERSYMMETRY WITHOUT R PARITY)
Authors: KONG OTTO C. W.
Published: May 2004

The generic supersymmetric version of the Standard Model would have the minimal list of superfields incorporating the Standard Model particles, and a Lagrangian dictated by the Standard Model gauge symmetries. To be phenomenologically viable, soft supersymmetry breaking terms have to be included. In the most popular version of the supersymmetric Standard Model, an ad hoc discrete symmetry, called R parity, is added in by hand. While there has been a lot of various kinds of R-parity violation studies in the literature, the complete version of supersymmetry without R parity is not popularly appreciated. In this article, we present a pedagogical review of the formulation of this generic supersymmetric Standard Model and give a detailed discussion on the basic conceptual issues involved. Unfortunately, there are quite some confusing, or even plainly wrong, statements on the issues within the literature of R-parity violations. We aim at clarifying these issues here. We will first discuss our formulation, about which readers are urged to read without bias from previous acquired perspectives on the topic. Based on the formulation, we will then address the various issues. In relation to phenomenology, our review here will not go beyond tree-level mass matrices. But we will give a careful discussion of mass matrices of all the matter fields involved. Useful expressions for perturbative diagonalizations of the mass matrices at the phenomenologically interesting limit of corresponds to small neutrino masses are derived. All these expressions are given in the fully generic setting, with information on complex phases of parameters retained. Such expressions have been shown to be useful in the analyses of various phenomenological features.
NONCOMMUTATIVE DE RHAM COHOMOLOGY OF FINITE GROUPS
Authors: CASTELLANI L. , CATENACCI R. , DEBERNARDI M. , PAGANI C.
Published: May 2004

We study de Rham cohomology for various differential calculi on finite groups G up to order 8. These include the permutation group S3, the dihedral group D4 and the quaternion group Q. Poincaré duality holds in every case, and under some assumptions (essentially the existence of a top form) we find that it must hold in general.

A short review of the bicovariant (noncommutative) differential calculus on finite G is given for selfconsistency. Exterior derivative, exterior product, metric, Hodge dual, connections, torsion, curvature, and biinvariant integration can be defined algebraically. A projector decomposition of the braiding operator is found, and used in constructing the projector on the space of two-forms. By means of the braiding operator and the metric a knot invariant is defined for any finite group.
Wavelength Translation in WDM Networks: Optimization Models and Solution Procedures
Authors: Kennington Jeffery L. , Olinick Eli V.
Published: May 2004

Wavelength-division multiplexing (WDM) is the best technology currently available to handle the rapidly increasing demand for bandwidth in fiber-optical telecommunications networks. In a WDM wavelength-routed network, end users communicate with one another using all-optical channels called lightpaths. Such lightpaths are used to support point-to-point connections and may span multiple fiber links. In the absence of wavelength translators, a lightpath must use the same wavelengths from origin to destination along each fiber span. Translators located at nodes permit wavelength translation within a lightpath. This investigation presents an empirical study comparing solutions that forbid translation with those that permit translation. For our 20 test problems, the extreme cases of no translation and translation at every node are solvable using CPLEX. For the more difficult intermediate cases, a special tabu search heuristic was developed. For those difficult cases, the tabu search procedure ran approximately 25 times faster than CPLEX using the default settings and in 78% of the problem instances found solutions that were as good as or better than those found by CPLEX.
Effect of Diuresis on P‐Wave Duration and Dispersion
Authors: Song Jessica , Kalus James S. , Caron Michael F. , Kluger Jeffrey , White C. Michael
Published: May 2004

Study Objective. To evaluate the effects of changing volume status on P‐wave duration and dispersion in patients with decompensated heart failure.

Design. Prospective analysis.

Setting. Hospital cardiology unit.

Patients. Twenty‐one patients with symptoms of decompensated heart failure who were treated with diuretics on admission.

Intervention. Twelve‐lead electrocardiograms were obtained at baseline and after diuresis. Average, minimum, and maximum P‐wave duration and P‐wave dispersion (minimum minus maximum duration) were determined.

Measurements and Main Results. P‐wave duration was measured manually in all 12 leads by using a 0.5‐mm‐scale precision ruler and magnifying lens. After 40 ± 23 hours of diuresis, 3 ± 1 L of fluid was removed. A significant correlation was found between average P‐wave duration and amount of fluid removed (r = −0.59, p=0.015). Also, average and maximum P‐wave duration were significantly decreased with diuresis (p=0.001 and 0.022, respectively). No other P‐wave variables were significantly affected.

Conclusions. Diuresis may attenuate electrophysiologic changes caused by fluid overload.
Oral Anticoagulant Drug Interactions with Statins: Case Report of Fluvastatin and Review of the Literature
Authors: Andrus Miranda R.
Published: May 2004

A 67‐year‐old man receiving a stable maintenance dosage of warfarin experienced an increased international normalized ratio (INR) without bleeding when his atorvastatin therapy was switched to fluvastatin. His warfarin dosage was reduced and his INR stabilized. The fluvastatin was switched back to atorvastatin, and the warfarin dosage was increased to maintain the patient's goal INR. The literature supports a drug interaction between warfarin and fluvastatin due to the strong affinity of fluvastatin for the cytochrome P450 enzyme 2D6. This interaction has not been seen with atorvastatin. Lovastatin also reportedly has caused increases in INR when coadministered with warfarin. It is unclear whether simvastatin interacts with warfarin, but it may increase INRs slightly or increase serum simvastatin levels. One case report describes an interaction between simvastatin and the anticoagulant acenocoumarol, which resulted in an elevated INR. Pravastatin does not appear to interact with warfarin but has caused an increased INR when combined with the anticoagulant fluindione. Thus, until more definitive data are available, clinicians should monitor the INR closely after starting statin therapy in any patient receiving anticoagulation therapy.