bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and functional characterization of the periplasmic N‐terminal polypeptide domain of the sugar‐specific ion channel protein (ScrY porin)
Authors: Michels Jenny , Geyer Armin , Mocanu Viorel , Welte Wolfram , Burlingame Alma L. , Przybylski Michael 
Published: July 2002

AbstractThe structure of the sucrose‐specific porin (ScrY) from Salmonella typhimurium has been elucidated by X‐ray crystallography to consist of 18 antiparallel β‐strands, associated as a trimer complex similar to ion‐transport channels. However, the 71‐amino‐acid‐residue N‐terminal periplasmic domain was not determined from the crystal structure due to the absence of sufficient electron density. The N‐terminal polypeptide contains a coiled‐coil structural motif and has been assumed to play a role in the sugar binding of ScrY porin. In this study the proteolytic stability and a specific proteolytic truncation site at the N‐terminal domain were identified by the complete primary structure characterization of ScrY porin, using MALDI mass spectrometry and post‐source‐decay fragmentation. The secondary structure and supramolecular association of the coiled‐coil N‐terminal domain were determined by chemical synthesis of the complete N‐terminal polypeptide and several partial sequences and their spectroscopic, biophysical, and mass spectrometric characterization. Circular dichroism spectra revealed predominant α‐helical conformation for the putative coiled‐coil domain comprising residues 4–46. Specific association to both dimer and trimer complexes was identified by electrospray ionization mass spectra and was ascertained by dynamic light scattering and electrophoresis data. The role of the N‐terminal domain in sugar binding was examined by comparative TR‐NOE‐NMR spectroscopy of the complete ScrY porin and a recombinant mutant, ScrY(Δ1–62), lacking the N‐terminal polypeptide. The TR‐NOE‐NMR data showed a strong influence of ScrY porin on the sugar‐binding affinity and suggested a possible function of the periplasmic N terminus for supramolecular stabilization and low‐affinity sugar binding.
Physicochemical consequences of the perdeuteriation of glutathione S‐transferase from S. japonicum
Authors: Brockwell David , Yu Lu , Cooper Serena , Mccleland Steven , Cooper Alan , Attwood David , Gaskell Simon J. , Barber Jill 
Published: July 2002

AbstractGlutathione S‐transferase (GST) from Schistosoma japonicum has been prepared in both normal protiated (pGST) and fully deuteriated (dGST) form by recombinant DNA technology. Electrospray mass spectrometry showed that the level of deuteriation in dGST was 96% and was homogeneous across the sample. This result is attributed to the use of a deuterium‐tolerant host Escherichia coli strain in the preparation of the protein. 10 heteroatom‐bound deuteriums (in addition to the carbon‐bound deuteriums) were resistant to exchange when dGST was incubated in protiated buffer. The physicochemical and biological properties of the two proteins were compared. dGST was relatively less stable to heat denaturation and to proteolytic cleavage than was pGST. The midpoint transition temperature for pGST was 54.9°C, whereas that for dGST was 51.0°C. Static light‐scattering measurements revealed that the association behavior of dGST is also different from that of pGST. The perdeuteriated enzyme shows a tendency to associate into dimers of the fundamental dimer. This is in contrast with results that have been obtained for other perdeuteriated proteins in which perdeuteriation has been shown to promote dissociation of aggregates. dGST showed a similar Km to pGST; similar results had been obtained previously with bacterial alkaline phosphatase. However, whereas the alkaline phosphatase showed a reduced rate of catalysis on deuteriation, dGST exhibited a slightly higher rate of catalysis than pGST. It is clear that the bulk substitution of deuterium for protium has significant effects on the properties of proteins. Until many more examples have been studied, it will be difficult to predict these effects for any given protein. Nevertheless, deuteriation represents an intriguing method of preparing functional analogs of recombinant proteins.
The Flexural Response of a Submarine Pipeline to an Underwater
Explosion Bubble
Authors: Zong Z. , Lam K. Y. 
Published: July 2002

Abstract
The flexural response of a submarine pipeline to an underwater explosion bubble is studied in this paper. A simple model for estimating bubble evolution with time and predicting bubble-induced pressure is introduced. A detailed analysis is given to estimate the fluid force acting on the pipeline. Finally, the fluid-structure interaction equation is given and an approximate solution is found using modal superposition method. The response features are discussed. The relation between pipeline length and maximum stresses is investigated. [S0892-7219(00)00303-4]
Transient Coupled Radiation and Conduction in a Three-Layer Composite
With Semitransparent Specular Interfaces and Surfaces
Authors: Tan He-Ping , Luo Jian-Feng , Xia Xin-Lin 
Published: July 2002

Abstract
Transient coupled radiative and conductive heat transfer in a three-layer absorbing and isotropically scattering composite with semitransparent specular interfaces and surfaces is investigated. The transient energy equation is solved by the full implicit control-volume method in combination with spectral band model. The radiative heat source term is calculated by the radiative transfer coefficients (RTCs), which are deduced by the ray tracing method in combination with Hottel and Sarofim’s zonal method (Hottel H. C., and Sarofim A. F., 1967, Radiative Transfer, McGraw-Hill Book Company, New York). The effects of extinction coefficient, refractive index, and scattering albedo etc., on coupled heat transfer are studied under radiative and convective boundary conditions. The effect of isolating space on coupled heat transfer and the appearance of temperature peaks within the composite are investigated. It is found that temperature peaks also appear in the inner parts of an inhomogeneous semitransparent medium layer even though there is no convection cooling on the surfaces. This occurs when the absorbing coefficient of inner parts is higher than that of the parts close to the surfaces, and the two surfaces are semitransparent and subjected to an external radiation.
A Test Rig for Frictionally Damped Bladed Segments
Authors: Berruti T. , Filippi S. , Goglio L. , Gola M. M. , Salvano S. 
Published: July 2002

Abstract
The paper describes the development of an instrumented test rig suitable to carry out vibration testing of the bladed segments of a turbine (belonging to a stator low pressure stage) in which the friction occurring at the contact of neighboring segments is used in service to damp the vibrations. The system is able to assign the desired preload to the segment and to measure the forces exerted in the contact and the relative displacements due to slipping. The main results that can be obtained concern the type of motion that takes place (stick/slip) and the effect of the interlocking on it, the friction coefficients, the contact tangential stiffness, and, more generally, the frequency response.
Flexible Bearing Supports, Using Experimental Data
Authors: Vázquez J. A. , Barrett L. E. , Flack R. D. 
Published: July 2002

Abstract
A laboratory rotor, representing a scaled-down model of a three-stage compressor supported by fluid film bearings on anisotropic flexible supports was analyzed. The support characteristics were measured at the bearing locations by exciting the bearing housings with electromechanical shakers and measuring the acceleration. Direct, cross-coupled, and cross-talk accelerance between supports were measured. Unbalance response and stability analyses of the rotor were performed using polynomial transfer functions extracted from the measured accelarance data. The predicted critical speeds and instability threshold agree with measured data. Predictions using other support models are included to show the effectiveness of this method.
Relationship Between Rockwell C Hardness and Inelastic Material
Constants
Authors: Hirano Akihiko , Sakane Masao , Hamada Naomi 
Published: July 2002

Abstract
This paper describes the relationship between Rockwell C hardness and elastic-plastic material constants by using finite element analyses. Finite element Rockwell C hardness analyses were carried out to study the effects of friction coefficient and elastic-plastic material constants on the hardness. The friction coefficient and Young’s modulus had no influence on the hardness but the inelastic materials constants, yield stress, and strain hardening coefficient and exponent, had a significant influence on the hardness. A new equation for predicting the hardness was proposed as a function of yield stress and strain hardening coefficient and exponent. The equation evaluated the hardness within a ±5% difference for all the finite element and experimental results. The critical thickness of specimen and critical distance from specimen edge in the hardness testing was also discussed in connection with JIS and ISO standards.
Application of a Unified Viscoplastic Model With Mixed Hardening to
Ionic Solids and Metallic Alloys
Authors: Yahya O. M. L. , Aubertin M. 
Published: July 2002

Abstract
The mechanical behavior of different types of polycrystalline materials shows many common features in the ductile inelastic flow regime. It is typically controlled by dislocations motion, which involves the competitive action of hardening and recovery processes that induces a strong dependency upon mechanical history. The object of this paper is to show how a constitutive model, named SUVIC, can be used to describe and predict in a unified manner the inelastic response of various types of materials. For that purpose, the authors use laboratory test results obtained on alkali halides (NaCl) and on metallic alloys (Inconel 738LC and A508 steel) at different homologous temperatures.
Multi-State Transient Rotor Vibration Control Using Sampled Harmonics
Authors: Keogh P. S. , Cole M. O. T , Burrows C. R. 
Published: July 2002

Abstract
A technique is introduced to achieve transient vibration attenuation in a multi-input, multi-output flexible rotor/magnetic bearing system. The strategy employs feedback control of measured harmonic components of rotor vibration. Whereas previous harmonic controllers have been based only on steady state vibration characteristics, the new controller also incorporates the transient dynamics. The controller may still be designed from measured data and is determined from target transient vibrational responses arising from step changes in particular disturbances. Account is taken of delays arising from evaluation of harmonic components. Furthermore, stability boundaries for the controller are shown to have significant tolerance to measurement error. The controller is validated experimentally in a flexible rotor/magnetic bearing system and mass loss tests are used to demonstrate rapid decrease in vibration levels with near elimination of transient overshoot.
An Analysis of Turbulent Shear Stresses in Leakage Flow Through a Bileaflet Mechanical Prostheses
Authors: Travis Brandon R. , Leo Hwa L. , Shah Parina A. , Frakes David H. , Yoganathan Ajit P. 
Published: July 2002

AbstractIn this work, estimates of turbulence were made from pulsatile flow laser Doppler velocimetry measurements using traditional phase averaging and averaging after the removal of cyclic variation. These estimates were compared with estimates obtained from steady leakage flow LDV measurements and an analytical method. The results of these studies indicate that leakage jets which are free and planar in shape may be more unstable than other leakage jets, and that cyclic variation does not cause a gross overestimation of the Reynolds stresses at large distances from the leakage jet orifice.
Vibration Behavior and Simplified Design of Thick Rectangular Plates
With Variable Thickness
Authors: Sasajima M. , Kakudate T. , Narita Y. 
Published: July 2002

Abstract
A free vibration analysis and an optimal design approach have been presented for thick isotropic rectangular plates with varying thickness under general edge conditions. First, the analysis is developed for vibrating rectangular plates by using the Mindlin plate theory and an eigenvalue problem is formulated by extending a method of Ritz to arbitrary sets of standard boundary conditions. The classical plate theory is also used to derive the frequency equation for comparison purpose. Secondly, a simplified optimal design approach is proposed to maximize the fundamental frequency of the plates. In applying this approach, the thickness variation is assumed to be linear in one direction and a taper ratio is chosen to be a design variable that represents the whole plate design. This approach significantly reduces the process for obtaining optimal or nearly optimal design under constraint of the constant plate volume. Numerical results are presented for various sets of boundary conditions, thickness ratio and two different plate theories, and their effects on the optimal taper ratio and its corresponding maximized fundamental frequency are discussed.
Combined Free and Forced Convection Film Condensation on a
Finite-Size Horizontal Wavy Plate
Authors: Wang Chi-Chang , Chen Cha'o-Kuang 
Published: July 2002

Abstract
Mixed-convection film condensation with downward flowing vapors onto a finite-size horizontal wavy plate is studied by a simple mathematical model and the spline alternating-direction implicit method. Effects of the wavy geometry, the interfacial vapor shear and the pressure gradient on the local condensate film thickness and the heat transfer characteristics have been studied independently. Results show that the pressure gradient tends to increase the heat transfer rate and to decrease the influence of the wavy amplitude. The appropriate wave number which can enhance the maximum condensation heat transfer rate is found in the neighborhood of lunder all circumstances.
Flow Visualizations and Transient Temperature Measurements in an
Axisymmetric Impinging Jet Rapid Thermal Chemical Vapor Deposition Reactor
Authors: Mathews A. G. , Peterson J. E. 
Published: July 2002

Abstracts
Carrier gas flow in a rapid thermal chemical vapor deposition (RTCVD) reactor was studied using flow visualization and laser induced Rayleigh light scattering (RLS). The flow field consists of a downward axisymmetric jet of carrier gas impinging on a wafer which undergoes transient heating. Flow visualization results showed three stable flow regimes as the surface rose from ambient to high temperature: momentum dominated, buoyancy dominated, and a second momentum dominated regime at high temperature; each separated by unstable, chaotic flows. RLS temperature measurements provided transient gas temperature histories, documenting flow visualization results. Regions of momentum dominated, buoyancy dominated, and unstable flows were defined as a function of Grashof number, Reynolds number, pressure, and wafer temperature.
Flammability Measurements of Difluoromethane
Authors: Grosshandler W. L. , Donnelly M. K. , Womeldorf C. 
Published: July 2002

Abstract
Difluoromethane (CH2F2, or R-32) is a candidate to replace ozone-depleting chlorofluorocarbon refrigerants. Because CH2F2 is flammable, it is necessary to assess the hazard posed by a leak in a refrigeration machine. The currently accepted method for determining flammability, ASTM E 681 has difficulty discerning the flammability boundary for weak fuels such as CH2F2. This article describes an alternative approach to identify the limits of flammability, using a twin, premixed counterflow flame. By using the extinction of an already established flame, the point dividing flammable from nonflammable becomes unambiguous. The limiting extinction mixture changes with stretch rate, so it is convenient to report the flammability limit as the value extrapolated to a zero stretch condition. In the burner, contoured nozzles with outlet diameters of 12 mm are aligned counter to each other and spaced 12 mm apart. The lean flammability limit of CH2F2 in dry air at room temperature was previously reported by the authors to be a mole fraction of 0.14, using the twin counterflow flame method. In the current study, relative humidity was not found to affect the lean limit. Increasing the temperature of the premixed fuel and air to 100°C is shown to extend the flammability limit in the lean direction to 0.13. The rich limit of CH2F2 found using the counterflow method is around 0.27. The uncertainties of the measurements are presented and the results compared to data in the literature. [S0022-1481(00)02501-9]
Analysis of the Two-Flux Model for Predicting Water Spray Transmittance in Fire Protection Application
Authors: Dembele S. , Wen J. X. , Sacadura J. F. 
Published: July 2002

AbstractAn investigation is carried out to assess the two-flux model for evaluating the attenuation ability of a water spray curtain in fire protection. Transmittances calculated with this model are compared with the “exact” discrete ordinates solutions for a range of water curtains under practical conditions. The results show the unsuitability of the two-flux method under a collimated incidence boundary condition, even if some improvements could be expected with very small droplets. Whereas the diffuse incidence type provides relatively better results, it is more reliable for transmittance calculations. [S0022-1481(00)00101-8]
Abstract: Computer analysis of FIM diffusion studies
Authors: Reed D. A. , Ehrlich Gert 
Published: July 2002

Field ion microscopy has made it possible to observe the diffusion of single atoms or atom clusters at a surface and to examine the interactions between individual atoms. There are two main problems associated with such studies: (1) Only a small number of adatom positions can be recorded per observation, so that statistical fluctuations have a profound effect on the data. (2) The available planes are no larger than 100 Å in diameter, and the effects of the plane boundaries may be significant.
We have performed computer simulations1 of the diffusion of one and two adatoms over a surface, both to determine the magnitude of the statistical errors in such experiments and to ascertain the optimal conditions for data collection. In the usual expression for the diffusion coefficient, D= D0 exp(−VD/kT), the activation energy VD can be obtained to ±8%, and the prefactor D0 to an order of magnitude, provided M, the number of diffusion intervals in the Arrhenius plot, amounts to 300. The statistical error in VD can be reduced to 5% with 750 measurements; the error in the prefactor is similarly lowered to a factor of 5. Further increases in M yield only minimal reductions of the statistical error.
Simulations were also carried out in order to determine corrections to compensate for the presence of boundaries. The effect of boundaries on the measured values of the mean-square displacement 〈R2〉 is generally approximated by the expression
〈R2〉=2Dτ[1−(4/3a) (4Dτ/π)1/2],
which relates the mean-square displacement, executed during an interval τ on a line of length a, to the diffusion coefficient. This is found to be adequate, unless displacements of only one or two steps per diffusion interval predominate. On a plane bounded by a circle of diameter d, this relation becomes
〈R2〉=4Dτ[1−(16/3πd) (4Dτ/π)1/2]. Interactions between adatoms can be deduced from the distribution function governing the distance between two atoms on a surface. Accurate distance measurements on two-dimensional surfaces are difficult. However, for atoms in adjacent one-dimensional channels no such limitation operates. From Monte Carlo simulations it appears that interaction energies can be derived with a standard error of kT/4 provided ?50 pairs per distance are available over the distance range of interest. The most important factor in such measurements is adequate equilibration between observations; atoms should make at least 5 jumps between determinations of interatomic distances to insure meaningful results. These estimates are applied to an analysis of experimental measurements on diffusion and interaction of W2,3 and Ir adatoms4 on the (211) plane of W.
Zidovudine Phosphorylation Determined Sequentially over 12 Months in Human Immunodeficiency Virus-Infected Patients with or without Previous Exposure to Antiretroviral Agents
Authors: Hoggard Patrick G. , Lloyd Judy , Khoo Save H. , Barry Michael G. , Dann Louise , Gibbons Sara E. , Wilkins Edmund G. , Loveday Clive , Back David J. 
Published: July 2002

ABSTRACT

We sought to determine whether the intracellular activation of zidovudine (ZDV) varied over time and with previous antiretroviral exposure in human immunodeficiency virus-infected individuals and to examine whether there is an association between virological responses and intracellular phosphorylation. A total of 23 patients (12 treatment naı̈ve, 11 previously treated with ZDV) who commenced ZDV as part of dual nucleoside therapy were prospectively monitored for 12 months or until withdrawal from the study. No association was observed between virological responses at 2 weeks and 3 months and ZDV phosphorylation. The mean intracellular concentrations of ZDV mono-, di-, and triphosphates did not change significantly over time or with previous ZDV exposure. The rate of formation of total ZDV phosphates was increased in patients with CD4 counts <100 cells/mm
3
. Previous reports from in vitro cell culture experiments or cross-sectional cohort studies suggesting alterations of ZDV phosphorylation over time are not confirmed by this longitudinal study.
Mupirocin Prophylaxis against Methicillin-Susceptible, Methicillin-Resistant, or Vancomycin-Intermediate
Staphylococcus epidermidis
Vascular-Graft Infection
Authors: Giacometti A. , Cirioni O. , Ghiselli R. , Goffi L. , Viticchi C. , Mocchegiani F. , Riva A. , Orlando F. , Saba V. , Scalise G. 
Published: July 2002

ABSTRACT

A rat model was used to investigate the efficacy of mupirocin in the prevention of vascular prosthetic graft infection due to
Staphylococcus epidermidis
strains with different susceptibility patterns (methicillin susceptible, methicillin resistant, and with intermediate resistance to vancomycin). The effect of mupirocin-soaked Dacron was compared to that of perioperative intraperitoneal prophylaxis with vancomycin. Graft infections were established in the back subcutaneous tissue of adult male Wistar rats by implantation of Dacron prostheses (1 cm
2
) followed by topical inoculation with 5 × 10
7
CFU of one staphylococcal strain. The study included a control group (no graft contamination), three contaminated groups that did not receive any antibiotic prophylaxis, three contaminated groups that received mupirocin-soaked grafts, three contaminated groups in which perioperative intraperitoneal vancomycin prophylaxis (10 mg/kg of body weight) was administered, and three contaminated groups that received mupirocin-soaked grafts and perioperative intraperitoneal vancomycin prophylaxis (10 mg/kg). The grafts were sterilely removed 7 days after implantation, and the infection was evaluated by using sonication and quantitative agar culture. Data analysis showed the efficacy of mupirocin against all three strains, with growth of the strains in treated rats significantly different than that in the untreated control. In addition, mupirocin was more effective than vancomycin against the strain with intermediate susceptibility to the glycopeptide. Finally, the combination of mupirocin and vancomycin produced complete suppression of the growth of all of the strains.