bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative evaluation of the lengths of homobifunctional protein cross‐linking reagents used as molecular rulers
Authors: Green Nora S. , Reisler Emil , Houk K.N. 
Published: July 2002

AbstractHomobifunctional chemical cross‐linking reagents are important tools for functional and structural characterization of proteins. Accurate measures of the lengths of these molecules currently are not available, despite their widespread use. Stochastic dynamics calculations now provide quantitative measures of the lengths, and length dispersions, of 32 widely used molecular rulers. Significant differences from published data have been found.
Some Plastic Deformation Modes for Indentation of Half Space by a
Rigid Body With Serrated Surface as a Model of Roughness Transfer in Metal
Forming
Authors: Shi Jingyu , McElwain D. L. S. , Domanti S. A. 
Published: July 2002

Abstract
This paper is concerned with the plastic deformation modes of the free surface of the half space between the teeth on the serrated surface of a rigid body. The rigid body indents the half space perpendicularly and the material of the half space is assumed to be elastic/rigid perfectly plastic. Plane-strain conditions are assumed. The emphasis in this paper is on the profile left on the surfaces of the material when the indentation proceeds to some depth and then the indenter is removed. Based on the observations from finite element results, slip line fields for the plastic deformation regions at various stages of indentation are proposed and the corresponding hodographs for the velocity field are presented. This has application in roughness transfer of final metal forming process.
Exact Solution for Determination of the Maximum Sublimation Rate in a
Porous Medium
Authors: Lin Sui 
Published: July 2002

Abstract
The optimum condition for the sublimation process taking place in a porous half space are determined in this paper. The vapor mass concentration at the surface of the porous medium and the initial frozen mass concentration in the frozen region are predetermined. The optimum condition is found by determining the vapor mass concentration at the sublimation front between the vapor and frozen phases, that yields the maximum flux of the vapor mass at the sublimation front. Exact solutions of the temperature and vapor mass concentration as well as the location of the moving sublimation front are obtained. The surface temperature used as the thermal controller is also determined to match the optimum sublimation condition.
Stagnation Line Heat Transfer Augmentation Due to Freestream
Vortical Structures and Vorticity
Authors: Oo Aung N. , Ching Chan Y. 
Published: July 2002

Abstract
An experimental study has been performed to investigate the effect of freestream vortical structures and vorticity on stagnation region heat transfer. A heat transfer model with a cylindrical leading edge was tested in a wind tunnel at Reynolds numbers ranging from 67,750 to 142,250 based on leading edge diameter of the model. Grids of parallel rods were placed at several locations upstream of the heat transfer model in orientations where the rods were perpendicular and parallel to the stagnation line to generate freestream turbulence with distinct vortical structures. All three components of turbulence intensity, integral length scale and the spanwise and transverse vorticity were measured to characterize the freestream turbulence. The measured heat transfer data and freestream turbulence characteristics were compared with existing empirical models for the stagnation line heat transfer. A new correlation for the stagnation line heat transfer has been developed that includes the spanwise fluctuating vorticity components.
Critical Heat Flux During Natural Circulation Boiling of Saturated
Liquid in Annulus With Uniformly Heated Outer Tube
Authors: Monde M. , Mitsutake Y. 
Published: July 2002

Abstract
Critical heat flux has been measured during natural circulation boiling of water and R113 on a uniformly heated outer tube in a vertical annular tube. The experiment was carried out using water at atmospheric pressure and R113 at a pressure of 0.1–0.4 MPa for the annular gap width of S=1.0-4.0 mm, the heated tube diameter of 9–17 mm, and the annular tube length of 100–1000 mm. The similarity of critical heat flux between annular configurations of either inner or outer heated tubes and a simple heated tube can be clearly elucidated based on the characteristics of the heated equivalent diameter. The critical heat flux measured for S=1 mm can be predicted accurately by existing correlation for the annular tube and for clearance larger than S=4 mm by existing correlation for the single tube. A new correlation for medium clearances from S=1 to 4 mm has been developed to connect between both the existing correlations. [S0022-1481(00)01901-0]
Reliability Analysis of Pipelines During Laying, Considering Ultimate
Strength Under Combined Loads
Authors: Igland Ragnar T. , Moan Torgeir 
Published: July 2002

Abstract
Structural reliability methods are applied to establish a measure of safety for pipelines during laying, and especially to calibrate semi-probabilistic ultimate limit state criteria based on measures of uncertainty, method of reliability, and a given target level. Ultimate collapse of thick tubes under combined external pressure, tension, and bending loads are studied applying the finite element method. Nonlinear effects of large deformations, effects of initial ovality, residual stresses, strain-hardening, yield anisotropy, and loading paths were accounted for in the analysis. A set of interaction equations is proposed. Load effects in the pipelines during installation by the S-lay method are studied. The effects of uncertainties in yield stress, mass, stiffness of the stinger, response amplitude operator and peak period for the wave spectrum were accounted for in the analysis. The major factors affecting strain concentration due to concrete coating are taken into account. A combination of design point calculation and importance sampling procedure is used to calculate the probability of failure. The study includes calibration of partial safety factors for the design format selected. The most important random variable is the model uncertainty for bending capacity, while the uncertainty of the load effect has minor importance for the probability of failure. The system effect is taken into account considering the correlation along the pipeline. The probability of failure is referred both to the total laying period as well as a 3-h period demonstrating that the target level needs to be defined in view of the reference time period. [S0892-7219(00)01501-6]
Titanium Drilling Risers—Application and Qualification
Authors: Salama Mamdouh M. , Murali Jagannathan , Joosten Mike W. 
Published: July 2002

Abstract
Titanium alloy Ti-6AI-4V ELI is selected for a high-pressure drilling riser application due to its high specific strength, corrosion resistance, and favorable elastic properties. The qualification of this titanium alloy requires assessing its resistance to hydrogen embrittlement and stress corrosion cracking due to seawater with/without cathodic protection, evaluating its wear resistance against a rotating steel drill string, and studying the influence of service-induced defects on fatigue and crack growth behavior when subjected to the operating environment. The paper presents an overview of the design requirements for a titanium drilling riser, and the material properties of the Ti-6AI-4V ELI alloy proposed for this application. The paper also highlights recent efforts to merge titanium and composite technologies to develop cost-effective drilling risers. [S0892-7219(00)01001-3]
Comparative Assessment of Hydrodynamic Models in Slow-Motion Mooring
Dynamics
Authors: Matsuura João Paulo J. , Nishimoto Kazuo , Bernitsas Michael M. , Garza-Rios Luis O. 
Published: July 2002

Abstract
The slow-motion dynamics of a turret mooring system is analyzed and compared for four of the most commonly used ship hydrodynamic maneuvering models. Each of those utilizes a different approach to model and then to calculate or measure the hydrodynamic forces and moment acting on the vessel. The four hydrodynamic maneuvering models are studied first by a physics-based analysis of each model and then by numerically comparing their prediction of equilibria, nonlinear stability analysis, bifurcation sequences, and morphogeneses of turret mooring systems. Catastrophe sets are constructed in two-dimensional parametric design spaces to determine the qualitative behavior of the system, and nonlinear time simulations are used to assess its quantitative properties. Static bifurcations of the principal equilibrium are compared to determine the nature of alternate equilibria. A turret-moored tanker is modeled with anchored catenaries, including nonlinear drag. External excitation is time independent, and for the numerical applications it is limited to steady current. Of the four models used, the Abkowitz and Takashina models show similar qualitative dynamics. The Obokata and Short-Wing models are also qualitatively similar, but very different from the first group. Limited sensitivity analysis pinpoints the source of discrepancy between the two schools of thought. [S0892-7219(00)01401-1]
Assessment and Repair of Offshore Platform Applications to Bay of
Campeche Facilities
Authors: Bayazitoglu Yildirim O. 
Published: July 2002

Abstract
In 1995 hurricanes Opal and Roxanne passed through Bay of Campeche (BOC). Opal did not cause any noticeable damage. Roxanne, on the other hand, was the most severe hurricane recorded in the Bay of Campeche in this century. Its anomalous behavior and the resulting extreme environmental conditions did considerable damage. PEMEX implemented a rapid repair program and was able to bring tile production back to its normal levels within two months. Subsequently, PEMEX, jointly with Instituto Mexicano del Petro´leo (IMP), launched an extensive program to inspect, assess, and repair the facilities. Results of the initial assessments indicated that the assessment parameters, as well as the metocean criteria utilized, were not suitable for Bay of Campeche. A detailed risk study considering the site-specific conditions and requirements was performed. Utilizing probability-based risk assessment techniques, a new criteria, known as the “transitory criteria,” was developed. The transitory criteria was then used to reassess the platforms and pipelines in the southwest marine region of BOC. Critically damaged platforms were identified for repair. The scope of repairs included jacket structural members and support framing for deck facilities. An overview of various techniques used for repairs of the underwater jacket structural members and joints is given. Different underwater repair methods are discussed. Repairs of both jacket and deck damages caused by hurricane Roxanne are presented as examples. The repair methods used are based on currently available technology and they will provide practical examples for economical platform repair in shallow, warm water environments. [S0892-7219(00)01101-8]
Pharmacokinetics of Tobramycin in Adults with Cystic Fibrosis: Implications for Once-Daily Administration
Authors: Beringer P. M. , Vinks A. A. T. M. M. , Jelliffe R. W. , Shapiro B. J. 
Published: July 2002

ABSTRACTOnce-daily administration of aminoglycosides is routinely used in many institutions. However, comparative efficacy data for patients with cystic fibrosis (CF) are lacking. The purpose of the present study was to compare the predicted pharmacodynamic activity of tobramycin at 10 mg/kg of body weight/day administered every 24 h (q24h), q12h, and q8h. Pharmacokinetic (PK) data were derived from analysis of data on the drug concentration in sera from 60 adult CF patients. Individual maximum a posteriori probability Bayesian PK parameter values were used to construct serum concentration-versus-time curves and to determine various indices (peak concentration/MIC ratio [peak/MIC], area under the concentration-time curve/MIC ratio [AUC/MIC], and time that the concentration was less than the MIC [T<MIC]) for the three regimens described above. MICs of 1, 2, and 4 μg/ml forPseudomonas aeruginosawere assumed in the simulations. Irrespective of the MIC, significantly lower peak/MIC but shorterT<MIC were noted when regimens of q8h versus q12h (P< 0.001), q8h versus q24h (P< 0.001), and q12h versus q24h (P< 0.001) were compared. This analysis suggests that the potential benefit of achieving a greater peak/MIC with once-daily aminoglycoside administration may be offset by the significantly greaterT<MIC in CF patients compared with that achieved with multiple-daily-dosing regimens. Clinical trials are necessary to determine if once daily aminoglycoside administration is efficacious in the CF population before its routine use can be recommended.
Macrolide Resistance Genes in
Enterococcus
spp
Authors: Portillo Aránzazu , Ruiz-Larrea Fernanda , Zarazaga Myriam , Alonso Ana , Martinez Jose Luis , Torres Carmen 
Published: July 2002

ABSTRACT

Seventy-eight isolates of different
Enterococcus
species (
E. faecalis
,
n
= 27;
E. faecium
,
n
= 23;
E. durans
,
n
= 8;
E. avium
,
n
= 6;
E. hirae
,
n
= 9;
E. gallinarum
,
n
= 3; and
E. casseliflavus
,
n
= 2) with a variety of erythromycin resistance phenotypes were examined for the presence of macrolide resistance genes (
ermA
,
ermB
,
ermC
,
ermTR
,
mefA/E
, and
msrA
). Positive PCR amplifications of
ermB
were obtained for 39 of 40 highly erythromycin-resistant
Enterococcus
isolates (MICs, >128 μg/ml) of different species; the remaining highly resistant
E. faecium
isolate was positive for PCR amplification of
ermA
but was negative for PCR amplification of the
ermB
and
ermC
genes. For all enterococcal strains for which erythromycin MICs were ≤32 μg/ml PCRs were negative for
erm
methylase genes. For all
E. faecium
isolates PCR amplified products of the expected size of 400 bp were obtained when
msrA
primers were used, with the results being independent of the erythromycin resistance phenotype. All the other enterococcal species gave negative results by
msrA
PCRs. Sequencing of the
msrA
PCR products from either erythromycin-susceptible, low-level-resistant, or highly resistant
E. faecium
strains showed that the amplicons did not correspond to the
msrA
gene described for
Staphylococcus epidermidis
but corresponded to a new putative efflux determinant, which showed 62% identity with the
msrA
gene at the DNA level and 72% similarity at the amino acid level. This new gene was named
msrC
.
Experimental Induction of Fluconazole Resistance in
Candida tropicalis
ATCC 750
Authors: Barchiesi Francesco , Calabrese David , Sanglard Dominique , Falconi Di Francesco Luigi , Caselli Francesca , Giannini Daniele , Giacometti Andrea , Gavaudan Stefano , Scalise Giorgio 
Published: July 2002

ABSTRACT

Candida tropicalis
is less commonly isolated from clinical specimens than
Candida albicans
. Unlike
C. albicans
, which can be occasionally found as a commensal,
C. tropicalis
is almost always associated with the development of fungal infections. In addition,
C. tropicalis
has been reported to be resistant to fluconazole (FLC). To analyze the development of FLC resistance in
C. tropicalis
, an FLC-susceptible strain (ATCC 750) (MIC = 1.0 μg/ml) was cultured in liquid medium containing increasing FLC concentrations from 8.0 to 128 μg/ml. The strain developed variable degrees of FLC resistance which paralleled the concentrations of FLC used in the medium. The highest MICs of FLC were 16, 256, and 512 μg/ml for strains grown in medium with 8.0, 32, and 128 μg of FLC per ml, respectively. Development of resistance was rapid and could be observed already after a single subculture in azole-containing medium. The resistant strains were cross-resistant to itraconazole (MIC > 1.0 μg/ml) and terbinafine (MIC > 512 μg/ml) but not to amphotericin B. Isolates grown in FLC at concentrations of 8.0 and 32 μg/ml reverted to low MICs (1.0 μg/ml) after 12 and 11 passages in FLC-free medium, respectively. The MIC for one isolate grown in FLC (128 μg/ml) (128 R) reverted to 16 μg/ml but remained stable over 60 passages in FLC-free medium. Azole-resistant isolates revealed upregulation of two different multidrug efflux transporter genes: the major facilitators gene
MDR1
and the ATP-binding cassette transporter
CDR1
. The development of FLC resistance in vitro correlated well with the results obtained in an experimental model of disseminated candidiasis. While FLC given at 10 mg/kg of body weight/day was effective in reducing the fungal burden of mice infected with the parent strain, the same dosing regimen was ineffective in mice infected with strain 128 R. Finally, the acquisition of in vitro FLC resistance in strain 128 R was related to a loss of virulence. The results of our study elucidate important characteristics and potential mechanisms of FLC resistance in
C. tropicalis
.
Peptide Deformylase in
Staphylococcus aureus
: Resistance to Inhibition Is Mediated by Mutations in the Formyltransferase Gene
Authors: Margolis Peter S. , Hackbarth Corinne J. , Young Dennis C. , Wang Wen , Chen Dawn , Yuan Zhengyu , White Richard , Trias Joaquim 
Published: July 2002

ABSTRACT

Peptide deformylase, a bacterial enzyme, represents a novel target for antibiotic discovery. Two deformylase homologs,
defA
and
defB
, were identified in
Staphylococcus aureus
. The
defA
homolog, located upstream of the transformylase gene, was identified by genomic analysis and was cloned from chromosomal DNA by PCR. A distinct homolog,
defB
, was cloned from an
S. aureus
genomic library by complementation of the arabinose-dependent phenotype of a P

BAD

-def Escherichia coli
strain grown under arabinose-limiting conditions. Overexpression in
E. coli
of
defB
, but not
defA
, correlated to increased deformylase activity and decreased susceptibility to actinonin, a deformylase-specific inhibitor. The
defB
gene could not be disrupted in wild-type
S. aureus
, suggesting that this gene, which encodes a functional deformylase, is essential. In contrast, the
defA
gene could be inactivated; the function of this gene is unknown. Actinonin-resistant mutants grew slowly in vitro and did not show cross-resistance to other classes of antibiotics. When compared to the parent, an actinonin-resistant strain produced an attenuated infection in a murine abscess model, indicating that this strain also has a growth disadvantage in vivo. Sequence analysis of the actinonin-resistant mutants revealed that each harbors a loss-of-function mutation in the
fmt
gene. Susceptibility to actinonin was restored when the wild-type
fmt
gene was introduced into these mutant strains. An
S. aureus
Δ
fmt
strain was also resistant to actinonin, suggesting that a functional deformylase activity is not required in a strain that lacks formyltransferase activity. Accordingly, the
defB
gene could be disrupted in an
fmt
mutant.
Effect of Polygodial on the Mitochondrial ATPase of
Saccharomyces cerevisiae
Authors: Lunde Christopher S. , Kubo Isao 
Published: July 2002

ABSTRACT

The fungicidal mechanism of a naturally occurring sesquiterpene dialdehyde, polygodial, was investigated in
Saccharomyces cerevisiae
. In an acidification assay, polygodial completely suppressed the glucose-induced decrease in external pH at 3.13 μg/ml, the same as the fungicidal concentration. Acidification occurs primarily through the proton-pumping action of the plasma membrane ATPase, Pma1p. Surprisingly, this ATPase was not directly inhibited by polygodial. In contrast, the two other membrane-bound ATPases in yeast were found to be susceptible to the compound. The mitochondrial ATPase was inhibited by polygodial in a dose-dependent manner at concentrations similar to the fungicidal concentration, whereas the vacuolar ATPase was only slightly inhibited. Cytoplasmic petite mutants, which lack mitochondrial DNA and are respiration deficient, were significantly less susceptible to polygodial than the wild type, as was shown in time-kill curves. A
pet9
mutant which lacks a functional ADP-ATP translocator and is therefore respiration dependent was rapidly inhibited by polygodial. The results of these susceptibility assays link enzyme inhibition to physiological effect. Previous studies have reported that plasma membrane disruption is the mechanism of polygodial-induced cell death; however, these results support a more complex picture of its effect. A major target of polygodial in yeast is mitochondrial ATP synthase. Reduction of the ATP supply leads to a suppression of Pma1 ATPase activity and impairs adaptive responses to other facets of polygodial's cellular inhibition.
Ofloxacin-Loaded Liposomes: In Vitro Activity and Drug Accumulation in Bacteria
Authors: Furneri Pio M. , Fresta Massimo , Puglisi Giovanni , Tempera Gianna 
Published: July 2002

ABSTRACT

Different ofloxacin-loaded unilamellar vesicles were prepared by the extrusion technique, and their antimicrobial activities were determined in comparison to those of the free drug by means of MIC determinations with both American Type Culture Collection standards and wild-type bacterial strains (six strains of
Enterococcus faecalis
, seven strains of
Escherichia coli
, six strains of
Staphylococcus aureus
, and six strains of
Pseudomonas aeruginosa
). The accumulation of ofloxacin and liposome-ofloxacin was measured by determining the amount of the drug inside the bacteria as a function of time. Encapsulated fluoroquinolone yielded MICs which were at least twofold lower than those obtained with the free drug. In particular, liposomes made up of dimyristoylphosphatidylcholine-cholesterol-dipalmitoylphosphatidylserine and dimyristoylphosphatidylcholine-cholesterol-dihexadecylphosphate (4:3:4 molar ratio) provided the best improvement in antimicrobial activity against the various bacterial strains investigated. The liposome formulation produced higher intracellular fluoroquinolone concentrations than those achieved simultaneously with the free drug in both
E. coli
and
P. aeruginosa
.
Trends in Antifungal Drug Susceptibility of
Cryptococcus neoformans
Isolates in the United States: 1992 to 1994 and 1996 to 1998
Authors: Brandt Mary E. , Pfaller Michael A. , Hajjeh Rana A. , Hamill Richard J. , Pappas Peter G. , Reingold Arthur L. , Rimland David , Warnock David W. 
Published: July 2002

ABSTRACT

The antifungal drug susceptibilities of two collections of
Cryptococcus neoformans
isolates obtained through active laboratory-based surveillance from 1992 to 1994 (368 isolates) and 1996 to 1998 (364 isolates) were determined. The MICs of fluconazole, itraconazole, and flucytosine were determined by the National Committee for Clinical Laboratory Standards broth microdilution method; amphotericin B MICs were determined by the E-test. Our results showed that the MIC ranges, the MICs at which 50% of isolates are inhibited (MIC
50
s), and the MIC
90
s of these four antifungal agents did not change from 1992 to 1998. In addition, very small numbers of isolates showed elevated MICs suggestive of in vitro resistance. The MICs of amphotericin B were elevated (≥2 μg/ml) for 2 isolates, and the MICs of flucytosine were elevated (≥32 μg/ml) for 14 isolates. Among the azoles, the fluconazole MIC was elevated (≥64 μg/ml) for 8 isolates and the itraconazole MIC (≥1 μg/ml) was elevated for 45 isolates. Analysis of 172 serial isolates from 71 patients showed little change in the fluconazole MIC over time. For isolates from 58 patients (82% of serial cases) there was either no change or a twofold change in the fluconazole MIC. In contrast, for isolates from seven patients (12% of serial cases) the increase in the MIC was at least fourfold. For isolates from another patient there was a 32-fold decrease in the fluconazole MIC over a 1-month period. We conclude that in vitro resistance to antifungal agents remains uncommon in
C. neoformans
and has not significantly changed with time during the past decade.