bluuebunny/crossref_metadata_2025_split huggingface dataset:
pH‐induced conformational transitions of a molten–globule–like state of the inhibitory prodomain of furin: Implications for zymogen activation
Authors: Bhattacharjya Surajit , Xu Ping , Xiang Hui , Chrétien Michel , Seidah Nabil G. , Ni Feng 
Published: July 2002

AbstractThe endoprotease furin, which belongs to the family of mammalian proprotein convertase (PC), is synthesized as a zymogen with an N‐terminal, 81‐residue inhibitory prodomain. It has been shown that the proenzyme form of furin undergoes a multistep ‘autocatalytic’ removal of the prodomain at the C‐terminal side of the two consensus sites, R78‐T‐K‐R81∼ and R44‐G‐V‐T‐K‐R49∼. The furin‐mediated cleavage at R44‐G‐V‐T‐K‐R49∼, in particular, is significantly accelerated in an ‘acidic’ environment. Here, we show that under neutral pH conditions, the inhibitory prodomain of furin is partially folded and undergoes conformational exchanges as indicated by extensive broadening of the NMR spectra. Presence of many ring‐current shifted methyl resonances suggests that the partially folded state of the prodomain may still possess a ‘semirigid’ protein core with specific packing interactions among amino acid side chains. Measurements of the hydrodynamic radii and compaction factors indicate that this partially folded state is significantly more compact than a random chain. The conformational stability of the prodomain appears to be pH sensitive, in that the prodomain undergoes an unfolding transition towards acidic conditions. Our NMR analyses establish that the acid‐induced unfolding is mainly experienced by the residues from the C‐terminal half of the prodomain (residues R44–R81) that contains the two furin cleavage sites. A 38‐residue peptide fragment derived from the entire pH‐sensitive C‐terminal region (residues R44–R81) does not exhibit any exchange‐induced line broadening and adopts flexible conformations. We propose that at neutral pH, the cleavage site R44‐G‐V‐T‐K‐R49∼ is buried within the protein core that is formed in part by residues from the N‐terminal region, and that the cleavage site becomes exposed under acidic conditions, leading to a facile cleavage by the furin enzyme.
CFD Predictions and Field Measurements of NOx
Emissions From LM1600 Gas Turbine During Part Load Operation
Authors: Price G. R. , Botros K. K. , Goldin G. M. 
Published: July 2002

Abstract
CFD simulations of the combustion process and formation of emissions in an industrial GE LM1600 gas turbine have been performed over a range of unit loads. Two combustion models were considered here to characterize the combustion process, the chemical equilibrium model and the nonequilibrium laminar flamelet model. The flamelet model predictions of nitric oxide concentration demonstrated much closer agreement with field measurements of continuous emission monitoring systems, due to accurate modeling of the oxygen radial concentration. The predictions made with this model are within 15 percent at maximum load and considerably better at lower loads. Field measurements also showed that nitric oxide constitutes about 95 percent of the total NOx measured. Unburnt hydrocarbons and carbon monoxide emissions are significantly overpredicted, however, arguably as a result of neglecting their oxidation in the high temperature, fuel-lean environment of the turbine and exhaust stack downstream of the combustor.
Damage Zone Around Tip of an Interface Crack Between Rubber-Modified
Epoxy Resin and Aluminum
Authors: Lee Deok-Bo , Ikeda Toru , Miyazaki Noriyuki , Choi Nak-Sam 
Published: July 2002

Abstract
The fracture behavior of an interface crack tip has significant influence on the structural integrity of an adhesive joint. We investigate a damage zone and the deformation of rubber particles around a tip of an interface crack between rubber-modified epoxy resin and aluminum. They are compared with those around a crack tip in homogeneous rubber-modified epoxy resin. Cavitations in rubber particles are observed around a damaged crack tip in homogeneous resin but not around a damaged interface crack tip. Rubber particles around an interface crack tip are deformed ellipsoidally due to the residual stress even before being damaged, and interfaces between rubber particles and epoxy resin around an interface crack tip are debonded after being damaged.
Analysis of the Heat Transfer Mechanism in High-Temperature
Circulating Fluidized Beds by a Numerical Model
Authors: He Qiao , Winter Franz , Lu Ji-Dong 
Published: July 2002

Abstract
A general numerical model is presented here to describe the complex fluid dynamics and the heat transfer process in high-temperature circulating fluidized beds (CFBs). The core-wall concept is used to describe the gas-solid flow in the dilute phase section of CFBs. The variation of the thickness of the wall layer along the height direction is considered in the fluid dynamic model in order to approach the practical conditions. Three components of heat transfer, i.e., the particle-convective heat transfer, the gas-convective heat transfer, and the radiative heat transfer, and their contributions to the total heat transfer coefficient are investigated. The influences of some operating parameters on the total heat transfer and its components are predicted. Detailed information about the mechanism of heat transfer is discussed. The radiative heat transfer accounts for about 30∼60% of the total heat transfer in high temperature CFBs. It gradually increases along the height direction of the furnace. When the contribution of particle convection increases, the contribution of gas convection decreases, and vice versa. Particle size shows a significant effect on the radiative heat transfer and the convective heat transfer. High bed and wall temperatures will primarily increase the radiative heat transfer.
A Recuperated Gas Turbine Incorporating External Heat Sources in the
Combined Gas-Steam Cycle
Authors: Chodkiewicz R. , Krysinski J. , Porochnicki J. 
Published: July 2002

Abstract
The recuperation by means of external waste heat sources, as opposed to the recuperation of the turbine exhaust gases (to preheat the compressed air), allows one to utilize the hot exhaust gases of the gas turbine in the bottoming steam cycle to produce steam in order to generate additional power. Such a combined gas/steam energy system, closely integrated with the industrial process, can produce electric power (and useful heat) with high efficiency and very low atmospheric air pollution. In the present paper two examples of applications of this new technology have been analyzed from the economic and ecological viewpoint.
Thermal Field and Flow Visualization Within the Stagnation Region of
a Film-Cooled Turbine Vane
Authors: Cutbirth J. Michael , Bogard David G. 
Published: July 2002

Abstract
To develop quality computational codes for the film cooling of a turbine vane, a detailed understanding is needed of the physical mechanisms of the mainstream-coolant interactions. In this study flow visualization, thermal profiles, and laser Doppler velocimetry measurements were used to define the thermal and velocity fields of the film cooled showerhead region of a turbine vane. The showerhead consisted of six rows of spanwise oriented coolant holes, and blowing ratios ranged from 0.5 to 2.0. Performances with low and high mainstream turbulence levels were tested. Coolant jets from the showerhead were completely separated from the surface even at relatively low blowing ratios. However, the interaction of the coolant jets from laterally adjacent holes created a barrier to the mainstream flow, resulting in relatively high adiabatic effectiveness.
Experimental Investigation of Convective Melting of Granular Packed
Bed Under Microgravity
Authors: Jiang J. , Hao Y. , Tao Y.-X. 
Published: July 2002

Abstract
To improve the understanding of convective melting of packed solid particles in a fluid, an experimental investigation is conducted to study the melting characteristics of a packed bed by unmasking the buoyancy forces due to the density difference between the melt and solid particles. A close-loop apparatus, named the particle-melting-in-flow (PMF) module, is designed to allow a steady-state liquid flow at a specified temperature. The module is installed onboard NASA’s KC-135 reduced gravity aircraft using ice particles of desired sizes and water as the test media. Experimentally determined melting rates are presented as a function of upstream flow velocity, temperature and initial average particle size of the packed bed. It is found that the melting rate is influenced mainly by the ratio of the Reynolds number (Re, based on the initial particle diameter) to the square of the Froude number (Fr), and the Stefan number (Ste). In general, the dimensionless melting rate decreases as Re/Fr2 increases and increases as Ste increases. With the absence of gravity, i.e., as the Froude number approaches infinity, a maximum melting rate can be achieved. The increase in the melting rate proportional to the Stefan number also becomes more pronounced under the zero gravity condition. The trend of average and local Nusselt number of the melting packed bed under microgravity, as a function of Reynolds number and Prandtl number, is discussed and compared with the case of nonmelting packed bed.
Average Boiling and Condensation Heat Transfer Coefficients of the
Zeotropic Refrigerant Mixture R22/R142b in a Coaxial Tube-in-Tube Heat Exchanger
Authors: Meyer J. P. , Bukasa J. M. , Kebonte S. A. 
Published: July 2002

Abstract
Average boiling and condensation heat transfer coefficients were determined experimentally for a coaxial tube-in-tube heat exchanger used in hot water heat pumps. During manufacturing, the heat exchanger geometry used for the experiments changed from round tubes to elliptical tubes as no spacers were used to keep the inner tube from touching the outer tube. The refrigerant used was two different mixtures of R22 with R142b in mass ratios of 80 percent/20 percent and 60 percent/40 percent. The results were compared to theoretical results for straight tubes. It was concluded that the theoretical modes do not predict the heat transfer coefficients very well in coaxial tube-in-tube heat exchangers where the annulus touches the inside of the outer tube. [S0022-1481(00)01001-X]
Hydrodynamic Coefficient Estimation for TLP and Spar Structures
Authors: Lake Matthew , He Haiping , Troesch Armin W. , Perlin Marc , Thiagarajan Krish P. 
Published: July 2002

Abstract
Research papers at previous OMAE conferences by Thiagarajan and Troesch 45 described forced oscillation model tests using a 0.45-m-dia cylinder and a 0.6-m-disk appended to the cylinder base for drag augmentation. Scaling laws were proposed based on a component scaling concept for extrapolation of full-scale added mass and damping coefficients. The present work further verifies the scaling methodology by presenting and discussing results on smaller models—cylinder and disk of diameters 0.15 m and 0.19 m, respectively. The dimensions of the smaller models are typical of more complex offshore platform models tested in scale 1:50 to 1:75 design sea states. The hydrodynamic coefficients of the cylinder and of the disk are estimated individually, and component-scaling methodology is examined. Physics-based arguments for the differences in force coefficients of the configurations are discussed: flow around the cylinder, flow around the disk, and flow around the composite structure. The analysis results from force measurements and flow visualization conducted during forced oscillation experiments. Further, difficulties in maintaining accuracy with the smaller models are examined. [S0892-7219(00)00202-8]
Abstract: Characterization of multilayer thin films using secondary ion mass spectrometry and improvement of the analytical techniques
Authors: Lewis R. K. 
Published: July 2002

Secondary ion mass spectrometry (SIMS) has been shown to be a highly sensitive analytical technique for characterizing thin films. 1 In depth analysis results because of the inherent nature of the sputtering process. With the more sophisticated SIMS instruments an imaging mode is provided which also gives a spatial distribution analysis. When this spatial information is combined with depth analysis a truly three−dimensional characterization results. It has been shown that this combined analysis can prevent confusing variations in spatial distribution with uniform depth gradients in depth profile analysis.
The most important advantage the SIMS technique has over other analytical techniques with good depth profiling capability (e.g.: Auger electron spectroscopy, AES) is that a much higher sensitivity can be achieved with SIMS. In favorable cases where the ion yield is high and large areas (diam ≳ 50 μ) are available this sensitivity has been shown to be 104 to 105 times higher than any other analytical techniques applicable to depth profiling.
The depth profiles described in this paper have been obtained with a specific SIMS instrument. This is the direct imaging mass analyzer developed by Cameca following the original concepts of Slodzian and Castaing. 2,3 This instrument has been shown to be well suited to the depth profile analysis of multilayer thin films. The principal advantages and disadvantages of the SIMS technique are the following: Advantages: (1) A very high gram detection sensitivity (10−15−10−19 g) can be achieved. (2) Rapid depth profiling is possible (up to 500 Å/sec). (3) All elements can be detected (inert gases excepted). (4) A very high detection sensitivity occurs for the very light elements. (5) Surface into bulk analysis can be performed in the same experiment. Disadvantages: (1) Many polyatomic cluster ions are generated by the sputtering process which produce serious mass interferences, particularly at higher masses. (2) Secondary ion yield enhancement effects from the presence of reactive elements seriously interfere with quantitation. (3) Sputtering artifacts can limit depth resolution. (4) The destructive nature of sputtering limits certain types of analysis.
These points are illustrated in the study of a series of multilayer thin films which have undergone various heat treatments producing interdiffusion. The principle limitation of SIMS depth profiling (item 1 above) is mass interference. This problem is considerably minimized when high mass resolution (m/Δm≳3000) is available. Recently an electrostatic analyzer has been integrated into the Cameca IMS 300 design which converts the geometry into a Neir Johnson type configuration. 4 This design allows a mass resolution up to 5000 to be achieved which greatly increases the applicability of the instrument for depth profiling and other microanalytical applications.
0.1 μm x-ray mask replication
Authors: Gentili M. , Kumar R. , Luciani L. , Grella L. , Plumb D. , Leonard Q. 
Published: July 2002

In a series of experiments, we investigate issues of absorber thickness increase (contrast amplification) and resolution capabilities of an x-ray mask copying process utilizing x-ray lithography. Two types of high resolution master masks were patterned using e-beam lithography and gold electroplating deposition and then replicated using x-ray lithography. The print quality and feature linewidths of each replica were then evaluated using a scanning electron microscope. The production of ULSI masks for x-ray lithography can be simplified if the necessary step of electron beam patterning can be performed in a thin resist layer, reducing the complexity of subsequent processing procedures and enhancing e-beam capabilities. When working with a thin resist, however, plated absorber thicknesses are small and the resulting mask contrast is limited. For x-ray lithography, Au absorber thicknesses on the order of 0.6 μm are required to ensure sufficient mask contrast when using synchrotron radiation (SR) sources (λ=0.1–1.2 nm). This implies than an aspect ratio of 3:1 is needed to print 0.2 μm features, and a ratio greater than 6:1 is necessary for sub-100 nm features.
A promising approach to achieving greater absorber thickness in x-ray masks is based on a mask replication process utilizing x-ray lithography. The large depth of focus and wide process latitude offered by x-ray lithography (XRL) permit exposure into thicker resist layers, and consequently, greater absorber thicknesses can be produced via direct metallization of the printed image. This technique also has the advantage of reducing e-beam time requirements, since many x-ray mask replicas can be produced from a single e-beam master mask. Two types of master x-ray masks were used in our evaluation. The first was a 2-μm-thick SiNx membrane with sub-100-nm Au features, and the second was a 2-μm-thick Si membrane with Au features down to 250 nm. Using the SiNx master mask, sub-100-nm resist features were successfully printed in 600 nm of resist on base plated wafers, using x-ray lithography. Subsequent electroplating of these samples yielded sub-100 nm features with Au absorber thicknesses of 450 nm. These results demonstrate successful mask contrast amplification (from 6 dB for the master to 15 dB for the copy), and show that high resolution, high contrast masks can be fabricated using this replication process.
Activity of ABT-773 against
Mycobacterium avium
Complex in the Beige Mouse Model
Authors: Cynamon M. H. , Carter J. L. , Shoen C. M. 
Published: July 2002

ABSTRACT

ABT-773, a new ketolide antimicrobial agent, was evaluated in comparison to clarithromycin (CLA) in vitro against
Mycobacterium avium
complex (MAC) and in a beige mouse model of disseminated MAC infection. The MICs at which 50 and 90% of the isolates tested were inhibited were 2 and 4 μg/ml, respectively, for CLA and 8 and 16 μg/ml, respectively, for ABT-773. Eight CLA-resistant isolates were found to be resistant to ABT-773 (MICs > 64 μg/ml). In the in vivo study mice were treated with ABT-773 (50, 100, and 200 mg/kg of body weight) or CLA (200 mg/kg). Both ABT-773 (100 and 200 mg/kg) and CLA significantly decreased the viable cell counts in spleens and lungs. ABT-773 (200 mg/kg) and CLA had similar activities in lungs, but the former was more active in spleens.
In Vitro Activity of the New Ketolide Telithromycin Compared with Those of Macrolides against
Streptococcus pyogenes
: Influences of Resistance Mechanisms and Methodological Factors
Authors: Bemer-Melchior Pascale , Juvin Marie-Emmanuelle , Tassin Sandrine , Bryskier Andre , Schito Gian Carlo , Drugeon Henri-B. 
Published: July 2002

ABSTRACT

One hundred and seven clinical isolates of
Streptococcus pyogenes
, 80 susceptible to macrolides and 27 resistant to erythromycin A (MIC >0.5 μg/ml), were examined. The erythromycin A-lincomycin double-disk test assigned 7 resistant strains to the M-phenotype, 8 to the inducible macrolide, lincosamide, and streptogramin B resistance (iMLS
B
) phenotype, and 12 to the constitutive MLS
B
resistance (cMLS
B
) phenotype. MICs of erythromycin A, clarithromycin, azithromycin, roxithromycin, and clindamycin were determined by a broth microdilution method. MICs of telithromycin were determined by three different methods (broth microdilution, agar dilution, and E-test methods) in an ambient air atmosphere and in a 5 to 6% CO
2
atmosphere. Erythromycin A resistance genes were investigated by PCR in the 27 erythromycin A-resistant isolates. MICs of erythromycin A and clindamycin showed six groups of resistant strains, groups A to F. iMLS
B
strains (A, B, and D groups) are characterized by two distinct patterns of resistance correlated with genotypic results. A- and B-group strains were moderately resistant to 14- and 15-membered ring macrolides and highly susceptible to telithromycin. All A- and B-group isolates harbored
erm TR
gene, D-group strains, highly resistant to macrolides and intermediately resistant to telithromycin (MICs, 1 to 16 μg/ml), were all characterized by having the
ermB
gene. All M-phenotype isolates (C group), resistant to 14- and 15-membered ring macrolides and susceptible to clindamycin and telithromycin, harbored the
mefA
gene. All cMLS
B
strains (E and F groups) with high level of resistance to macrolides, lincosamide, and telithromycin had the
ermB
gene. The effect of 5 to 6% CO
2
was remarkable on resistant strains, by increasing MICs of telithromycin from 1 to 6 twofold dilutions against D-E- and F-group isolates.
Mechanisms and Frequency of Resistance to Premafloxacin in
Staphylococcus aureus
: Novel Mutations Suggest Novel Drug-Target Interactions
Authors: Ince Dilek , Hooper David C. 
Published: July 2002

ABSTRACT

Premafloxacin is a novel 8-methoxy fluoroquinolone with enhanced activity against
Staphylococcus aureus
. We found premafloxacin to be 32-fold more active than ciprofloxacin against wild-type
S. aureus
. Single mutations in either subunit of topoisomerase IV caused a four- to eightfold increase in the MICs of both quinolones. A double mutation (
gyrA
and either
grlA
or
grlB
) caused a 32-fold increase in the MIC of premafloxacin, while the MIC of ciprofloxacin increased 128-fold. Premafloxacin appeared to be a poor substrate for NorA, with NorA overexpression causing an increase of twofold or less in the MIC of premafloxacin in comparison to a fourfold increase in the MIC of ciprofloxacin. The frequency of selection of resistant mutants was 6.4 × 10
−10
to 4.0 × 10
−7
at twofold the MIC of premafloxacin, 2 to 4 log
10
less than that with ciprofloxacin. Single-step mutants could not be selected at higher concentrations of premafloxacin. In five single-step mutants, only one previously described uncommon mutation (Ala116Glu), and four novel mutations (Arg43Cys, Asp69Tyr, Ala176Thr, and Pro157Leu), three of which were outside the quinolone resistance-determining region (QRDR) were found. Genetic linkage studies, in which incross of
grlA
+
and outcross of mutations were performed, showed a high correlation between the mutations and the resistance phenotypes, and allelic exchange experiments confirmed the role of the novel mutations in
grlA
in resistance. Our results suggest that although topoisomerase IV is the primary target of premafloxacin, premafloxacin appears to interact with topoisomerase IV in a manner different from that of other quinolones and that the range of the QRDR of
grlA
should be expanded.