bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Measurement of the Poisson’s Ratio of Human Patella Cartilage in Tension
Authors: Elliott Dawn M. , Narmoneva Daria A. , Setton Lori A. 
Published: July 2002

AbstractArticular cartilage has been shown to exhibit large transverse contractions when loaded in tension, suggesting the existence of large values for the Poisson’s ratio. Previous studies have suggested that this effect is dependent on amplitude of applied strain, so that a single Poisson’s ratio may not be sufficient to describe cartilage behavior. In this study, the Poisson’s ratio (ν), toe region modulus Eo, and linear region modulus E of human patellar articular cartilage were calculated in simple tension tests from optical analysis of the two-dimensional strain fields at equilibrium. The Poisson’s ratio was found to be independent of strain due to the absence of viscoelastic effects during testing. The Poisson’s ratio was found to be significantly higher in the surface zone (1.87±1.11, p&lt;0.01) than in the middle zone (0.62±0.23), with no significant correlation of ν with age of the cartilage. In general, values for Poisson’s ratio were greater than 0.5, suggesting cartilage behavior in tension deviates from isotropy. Reported values for the Poisson’s ratio of cartilage in compression have been much lower than values measured here in tension, reflecting a mechanical contribution of the collagen fibers to anisotropy in tension but not compression. The toe-region modulus Eo was significantly higher in the surface zone (4.51±2.78 MPa, n=8) compared to the middle zone (2.51±1.93 MPa, n=10). In addition, the linear-region modulus E in the surface zone, but not middle zone (3.42±2.17 MPa, n=10), was found to correlate with age R=0.97,p&lt;0.02 with values of surface zone E equal to 23.92±12.29 MPa n=5 for subjects under 70 yr of age, and 4.27±2.89 MPa n=3 for subjects over 70 yr. Moduli values and trends with depth were consistent with previous studies of human and animal cartilage. From direct measures of two independent material properties, ν and E, we calculated a shear modulus, G, which had not been previously reported for cartilage from tensile testing. Calculated values for surface zone G were 3.64±1.80 MPa for subjects under 70 yr old and 0.96±0.69 MPa for subjects over 70 yr old, and were significantly higher in the surface zone than in the middle zone (1.10±0.78 MPa). This study provides an intrinsic measure for the Poisson’s ratio of articular cartilage and its dependence on depth which will be important in understanding the nonlinear tension-compression and anisotropic behaviors of articular cartilage.
Fundamental Design Issues of Brush Seals for Industrial Applications
Authors: Dinc Saim , Demiroglu Mehmet , Turnquist Norman , Mortzheim Jason , Goetze Gayle , Maupin John , Hopkins James , Wolfe Christopher , Florin Mark 
Published: July 2002

Abstract
Advanced seals have been applied to numerous turbine machines over the last decade to improve the performance and output. Industrial experiences have shown that significant benefits can be attained if the seals are designed and applied properly. On the other hand, penalties can be expected if brush seals are not designed correctly. In recent years, attempts have been made to apply brush seals to more challenging locations with high speed (&gt;400 m/s), high temperature (&gt;650 °C), and discontinuous contact surfaces, such as blade tips in a turbine. Various failure modes of a brush seal can be activated under these conditions. It becomes crucial to understand the physical behavior of a brush seal under the operating conditions, and to be capable of quantifying seal life and performance as functions of both operating parameters and seal design parameters. Design criteria are required for different failure modes such as stress, fatigue, creep, wear, oxidation etc. This paper illustrates some of the most important brush seal design criteria and the trade-off of different design approaches.
Heat Transfer From a Moving Surface Due to Impinging Slot Jets
Authors: Chattopadhyay H. , Biswas G. , Mitra N. K. 
Published: July 2002

Abstract
Turbulent flow field and heat transfer in an array of slot jets impinging on a moving surface have been numerically investigated by Large-eddy Simulation (LES) technique in the range of Reynolds numbers between 500 and 3000. The surface velocity, directed perpendicular to the jet, is varied up to two times the jet velocity at the nozzle exit. The Nusselt number distributions for various surface velocities are presented. It has been observed that on one hand increasing velocity of the impingement plate reduces heat transfer, while on the other hand distribution of Nusselt number over the impingement surface becomes more uniform with the increased surface velocity.
Fluorocarbon high-density plasmas. I. Fluorocarbon film deposition and etching using CF4 and CHF3
Authors: Oehrlein G. S. , Zhang Y. , Vender D. , Haverlag M. 
Published: July 2002

Fluorocarbon film deposition in discharges used for oxide etching plays a key role in determining the profile shape of contact holes and the etch selectivity with respect to the mask and the underlayer. For low-density capacitatively coupled rf discharges this deposition is due to neutral radicals. We report a study of fluorocarbon film deposition and etching phenomena in electron cyclotron resonance (ECR) discharges of CF4 and CHF3. Plasma operation without rf sample bias in the pressure range below 10 mTorr results in the deposition of fluorocarbon films for both gases, with the highest deposition rate in each case at 2 mTorr (≂120 nm/min for a 1000 W CF4 plasma and ≂180 nm/min for CHF3 using the same conditions). For CF4 this behavior differs dramatically from that seen for conventional rf diode plasmas where no deposition occurs. The deposition is due to the more efficient breakdown and ionization of CF4 and CHF3 in the ECR discharge and the lack of energetic ion bombardment of the substrate as compared to capacitatively coupled rf diode plasmas. We have used a double grid ion energy analyzer in front of a silicon wafer being ellipsometrically sampled to unambiguously demonstrate that in these high-density discharges, fluorocarbon deposition is primarily due to bombardment with low energy ions. The fluorocarbon growth rate dropped by a factor of 5 if positive biasing of the grid prevented ions from reaching the fluorocarbon film surface in a CHF3 plasma at 2 mTorr.
The energy distribution of the ions which may be obtained from these data is in good agreement with measurements of the plasma potential. The ion fluxes for CF4 are ≂4–5 times greater than the fluorine and carbon atom fluxes required to explain the deposition rates (assuming a sticking coefficient of 1). Film-growth due to direct ion incorporation rather than ion enhancement can explain the experimental results. For CHF3 plasmas the deposition rates are ≂100 nm/min greater than for CF4 for all conditions. This suggests that neutrals contribute strongly to fluorocarbon film growth for CHF3 since the ion currents are nearly the same as for CF4. The ion enhancement effect of film growth rate decreases at higher pressure and lower microwave powers and mirrors the behavior of the ion current. This finding has important implications for etch selectivity, etching profiles, and the slow-down of the SiO2 etch rates in high-aspect ratio contact holes. Biasing the substrate reduces the net fluorocarbon deposition rate for low rf bias values. At higher rf bias values, etching of the initially deposited film takes place. These threshold voltages for etching are higher for CHF3 than CF4, e.g., 55 versus 35 V for 1 mTorr operation. Oxide etching can only take place for rf bias values equal or greater than these threshold voltages.
Evernimicin (SCH27899) Inhibits a Novel Ribosome Target Site: Analysis of 23S Ribosomal DNA Mutants
Authors: Adrian Peter V. , Mendrick Cara , Loebenberg David , McNicholas Paul , Shaw Karen J. , Klugman Keith P. , Hare Roberta S. , Black Todd A. 
Published: July 2002

ABSTRACT

Spontaneous mutants of susceptible clinical and laboratory isolates of
Streptococcus pneumoniae
exhibiting reduced susceptibility to evernimicin (SCH27899; MIC, 0.5 to 4.0 mg/liter) were selected on plates containing evernimicin. Four isolates that did not harbor mutations in
rplP
(which encodes ribosomal protein L16) were further analyzed. Whole chromosomal DNA or PCR products of the 23S ribosomal DNA (rDNA) operons from these mutants could be used to transform the susceptible
S. pneumoniae
strain R6 to resistance at frequencies of 10
−5
and 10
−4
, respectively, rates 10- to 100-fold lower than that for a single-allele chromosomal marker. The transformants appeared slowly (48 to 72 h) on selective medium, and primary transformants passaged on nonselective medium produced single colonies that displayed heterogeneous susceptibilities to evernimicin. A single passage on selective medium of colonies derived from a single primary transformant homogenized the resistance phenotype. Sequence analysis of the 23S rDNA and rRNA from the resistant mutants revealed single, unique mutations in each isolate at the equivalent
Escherichia coli
positions 2469 (A → C), 2480 (C → T), 2535 (G → A), and 2536 (G → C). The mutations map within two different stems of the peptidyltransferase region of domain V. Because multiple copies of rDNA are present in the chromosome, gene conversion between mutant and wild-type 23S rDNA alleles may be necessary for stable resistance. Additionally, none of the characterized mutants showed cross-resistance to any of a spectrum of protein synthesis inhibitors, suggesting that the target site of evernimicin may be unique.
Mutant Prevention Concentration as a Measure of Fluoroquinolone Potency against Mycobacteria
Authors: Sindelar Georg , Zhao Xilin , Liew Anthony , Dong Yuzhi , Lu Tao , Zhou Jianfeng , Domagala John , Drlica Karl 
Published: July 2002

ABSTRACT

Mutant prevention concentration (MPC) has been proposed as a new measure of antibiotic potency by which the ability to restrict selection of resistant mutants is evaluated. To determine whether MPC provides potency information unavailable from the more customary measurement of the MIC, 18 fluoroquinolones were examined for their ability to block the growth of
Mycobacterium smegmatis
and to select resistant mutants from wild-type populations. Both MPC and MIC were affected by changes in the moiety at the fluoroquinolone C-8 position and in alkyl groups attached to the C-7 piperazinyl ring. When eight resistant mutants, altered in the gyrase A protein, were tested with fluoroquinolones having either a methoxy or a hydrogen at the C-8 position, the MIC for the most resistant mutant correlated better with the MPC than did the MIC for wild-type cells. For C-8-fluorine derivatives, which were generally less active than the C-8-methoxy compounds but which were more active than C-8-hydrogen derivatives, the MICs for both the mutant and the wild type correlated well with the MPCs. Thus, measurement of the MICs for wild-type cells can reflect the ability of a quinolone to restrict the selection of resistance, but often it does not. With the present series of compounds, the most potent contained a C-8-methoxy and a small group attached to the C-7 ring.
Flow Cytometric Investigation of Filamentation, Membrane Patency, and Membrane Potential in
Escherichia coli
following Ciprofloxacin Exposure
Authors: Wickens H. J. , Pinney R. J. , Mason D. J. , Gant V. A. 
Published: July 2002

ABSTRACT

Ninety-eight percent of the cells in a population of
Escherichia coli
in log-phase growth lost colony-forming ability after being exposed for 3 h to the quinolone antibiotic ciprofloxacin at four times the MIC in nutrient broth, a concentration easily reached in vivo. Flow cytometric analysis, however, demonstrated that only 68% of this bacterial population had lost membrane potential, as judged by the membrane potential-sensitive dye bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC
4
(3)], and only 30% could no longer exclude the nucleic acid-binding dye propidium iodide (PI), reflecting lost membrane integrity, efflux mechanisms, or both. Subsequent removal of ciprofloxacin and resuspension in nutrient broth resulted in renewed cell division after 2 h, with a calculated postantibiotic effect (PAE) time of 57 min. The proportion of DiBAC- and PI-fluorescent cells in this recovering population remained stable for more than 4 h after antibiotic removal. Eighty percent of cells present at drug removal were filamentous. Their number subsequently decreased with time, and the increase in particle count seen at the end of the PAE resulted from the division of short cells. Exposure to ciprofloxacin in the presence of the protein synthesis inhibitor chloramphenicol increased colony-forming ability to 60% of starting population numbers. In contrast to ciprofloxacin alone, this antibiotic combination resulted in insignificant filamentation and no dye uptake. Subsequent drug removal and resuspension in nutrient broth resulted in the appearance of filaments within 1 h, with 69% of the population forming filaments at 3 h. Dye uptake was also seen, with 20% of the population fluorescing with either dye after 4 h. We were unable to relate dye uptake to the viable count. Cell division resumed 240 min after removal of both drugs, yielding a PAE calculated at 186 min. Inhibition of protein synthesis with chloramphenicol prevented ciprofloxacin-induced changes in bacterial morphology, cell membrane potential, and ability to exclude nucleic acid-binding dye. These changes persisted beyond the end of the classically defined PAE and were not a definite indicator of cell death as defined by loss of colony formation, which related at least in part to filamentation.
Risk Factors for Recovery of Ampicillin-Sulbactam-Resistant
Escherichia coli
in Hospitalized Patients
Authors: Kaye Keith S. , Harris Anthony D. , Gold Howard , Carmeli Yehuda 
Published: July 2002

ABSTRACT

Ampicillin-sulbactam resistance in
Escherichia coli
is an emerging problem. This study determined risk factors for the recovery of ampicillin-sulbactam-resistant
E. coli
in hospitalized patients. A case-control design was used to compare two groups of case patients with control patients. The first group of case patients consisted of patients from whom nosocomially acquired ampicillin-sulbactam-resistant
E. coli
strains were isolated, and the second group of case patients consisted of patients from whom ampicillin-sulbactam-susceptible
E. coli
strains were isolated. Control patients were a random selection among 5% of all patients admitted during the same time period. Risk factors analyzed included antimicrobial drug exposure, comorbid conditions, and demographics. Univariate and multivariate analyses were performed. Ampicillin-sulbactam-resistant
E. coli
strains were isolated from 175 patients, and ampicillin-sulbactam-susceptible
E. coli
strains were isolated from 577 patients. Nine hundred thirty-four control patients were selected. Exposure to penicillin antibiotics as a class and to ampicillin and ampicillin-sulbactam individually were the only significant, independent risk factors associated with the isolation of ampicillin-sulbactam-resistant
E. coli
(odds ratio [OR] = 2.32 [
P
< 0.001], OR = 3.04 [
P
= 0.02], and OR = 1.72 [
P
= 0.04], respectively), but they were not associated with the isolation of ampicillin-sulbactam-susceptible
E. coli
. Interestingly, exposure to piperacillin-tazobactam tended to protect against the isolation of
E. coli
strains resistant to ampicillin-sulbactam, but this did not reach statistical significance (OR = 0.13;
P
= 0.11).
Non-Target Gene Mutations in the Development of Fluoroquinolone Resistance in
Escherichia coli
Authors: Kern W. V. , Oethinger M. , Jellen-Ritter A. S. , Levy S. B. 
Published: July 2002

ABSTRACT

Mutations in loci other than genes for the target topoisomerases of fluoroquinolones,
gyrA
and
parC
, may play a role in the development of fluoroquinolone resistance in
Escherichia coli
. A series of mutants with increasing resistance to ofloxacin was obtained from an
E. coli
K-12 strain and five clinical isolates. First-step mutants acquired a
gyrA
mutation. Second-step mutants reproducibly acquired a phenotype of multiple antibiotic resistance (Mar) and organic solvent tolerance and showed enhanced fluoroquinolone efflux. None of the second-step mutants showed additional topoisomerase mutations. All second-step mutants showed constitutive expression of
marA
and/or overexpressed
soxS
. In some third-step mutants, fluoroquinolone efflux was further enhanced compared to that for second-step mutants, even when the mutant had acquired additional topoisomerase mutations. Attempts to circumvent the second-step Mar mutation by induction of the
mar
locus with sodium salicylate and thus to select for pure topoisomerase mutants at the second step were not successful. At least in vitro, non-target gene mutations accumulate in second- and third-step mutants upon exposure to a fluoroquinolone and typically include, but do not appear to be limited to, mutations in the
mar
or
sox
regulons with consequent increased drug efflux.
A between-Species Comparison of Antimicrobial Resistance in Enterobacteria in Fecal Flora
Authors: Österblad Monica , Hakanen Antti , Manninen Raija , Leistevuo Tiina , Peltonen Reijo , Meurman Olli , Huovinen Pentti , Kotilainen Pirkko 
Published: July 2002

ABSTRACT

Enterobacteria in fecal flora are often reported to be highly resistant.
Escherichia coli
is the main species; resistance data on other species are rare. To assess the effect of the host's environment, antimicrobial resistance was determined in fecal species of the family
Enterobacteriaceae
from three populations: healthy people (HP)(
n
= 125) with no exposure to antimicrobials for 3 months preceding sampling, university hospital patients (UP) (
n
= 159) from wards where the antibiotic use was 112 defined daily doses (DDD)/bed/month, and geriatric long-term patients (LTP) (
n
= 74) who used 1.8 DDD/bed/month. The mean length of hospital stay was 5 days for the UP and 22 months for the LTP. The isolates were identified to at least genus level, and MICs of 16 antimicrobials were determined. From the university hospital, resistance data on clinical
Enterobacteriaceae
isolates were also collected. Resistance data for on average two different isolates per sample (range, 1 to 5) were analyzed: 471
E. coli
isolates and 261 other
Enterobacteriaceae
spp. Resistance was mainly found among
E. coli
; even in HP, 18% of
E. coli
isolates were resistant to two or more antimicrobial groups, with MIC patterns indicative of transferable resistance. Other fecal enterobacteria were generally susceptible, with little typically transferable multiresistance. Clinical
Klebsiella
and
Enterobacter
isolates were significantly more resistant than fecal isolates. The resistance patterns at both hospitals mirrored the patterns of antibiotic use, but LTP
E. coli
isolates were significantly more resistant than those from UP. Conditions permitting an efficient spread may have been more important in sustaining high resistance levels in the LTP.
E. coli
was the main carrier of antimicrobial resistance in fecal flora; resistance in other species was rare in the absence of antimicrobial selection.
Combination Antifungal Therapy in Treatment of Murine Pulmonary Mucormycosis: Roles of Quinolones and Azoles
Authors: Sugar Alan M. , Liu Xiu-Ping 
Published: July 2002

ABSTRACT
Amphotericin B is the only recognized antifungal used in the treatment of mucormycosis. In this study, we evaluated various combinations of amphotericin B, fluconazole, and trovafloxacin or ciprofloxacin in the treatment of murine pulmonary mucormycosis. The combination of fluconazole and a quinolone has a marked effect on the outcome of murine pulmonary mucormycosis. Even though we did not optimize therapy with the drugs, these experiments suggest that azoles, especially fluconazole, in combination with either trovafloxacin or ciprofloxacin were effective in the treatment of this aggressive mycosis in the mouse model.
Saccharomicins, Novel Heptadecaglycoside Antibiotics Produced by
Saccharothrix espanaensis
: Antibacterial and Mechanistic Activities
Authors: Singh M. P. , Petersen P. J. , Weiss W. J. , Kong F. , Greenstein M. 
Published: July 2002

ABSTRACT

Saccharomicins A and B, two new heptadecaglycoside antibiotics, were isolated from the fermentation broth of the rare actinomycete
Saccharothrix espanaensis
. They represent a novel class of bactericidal antibiotics that are active both in vitro and in vivo against bacteria and yeast (MICs:
Staphylococcus aureus
, <0.12 to 0.5; vancomycin-resistant enterococci, 0.25 to 16; gram-negative bacteria, 0.25 to >128; and yeast, >128 μg/ml), including multiply resistant strains. Saccharomicins protected mice from lethal challenges by staphylococci (subcutaneous 50% effective dose range of 0.06 to 2.6 mg/kg of body weight, depending on the
S. aureus
strain). The 50% lethal dose by the subcutaneous route was 16 mg/kg. Mechanistic studies with
Escherichia coli imp
and
Bacillus subtilis
suggested complete, nonspecific inhibition of DNA, RNA, and protein biosynthesis within 10 min of drug treatment. Microscopic examination of drug-treated cells also suggested cell lysis. These data are consistent with a strong membrane-disruptive activity. The antibacterial activities of the saccharomicins against gram-positive bacteria were unaffected by the presence of Ca
2+
or Mg
2+
, but activity against gram-negative bacteria was substantially reduced.
Congeners of SMAP29 Kill Ovine Pathogens and Induce Ultrastructural Damage in Bacterial Cells
Authors: Kalfa V. C. , Jia H. P. , Kunkle R. A. , McCray P. B. , Tack B. F. , Brogden K. A. 
Published: July 2002

ABSTRACT

SMAP29, an ovine cathelicidin, was systematically altered to create a family of 23 related peptides for MIC and minimum bactericidal concentration determinations. SMAP28, SMAP29, and a derivative of SMAP29 called ovispirin were all antimicrobial. However, many congeners of SMAP29 and ovispirin were not as active as the parent molecules. With immunoelectron microscopy, SMAP29 was seen on membranes and within the cytoplasm of
Pseudomonas aeruginosa
PAO1.
Antimicrobial Susceptibilities of Group B Streptococci Isolated from Patients with Invasive Disease: 10-Year Perspective
Authors: Murdoch David R. , Reller L. Barth 
Published: July 2002

ABSTRACT
Antimicrobial susceptibility testing of 192 group B streptococcal isolates from patients with invasive disease demonstrated that 31 (16%) were resistant to erythromycin and 17 (9%) were resistant to clindamycin. One isolate demonstrated high-level resistance to streptomycin, but none was highly resistant to gentamicin. Erythromycin and clindamycin are no longer reliable empirical alternatives to penicillin for the treatment and prevention of group B streptococcal infections.
The AbcA Transporter of
Staphylococcus aureus
Affects Cell Autolysis
Authors: Schrader-Fischer Gesine , Berger-Bächi Brigitte 
Published: July 2002

ABSTRACT

Increased production of penicillin-binding protein PBP 4 is known to increase peptidoglycan cross-linking and contributes to methicillin resistance in
Staphylococcus aureus
. The
pbp4
gene shares a 400-nucleotide intercistronic region with the divergently transcribed
abcA
gene, encoding an ATP-binding cassette transporter of unknown function. Our study revealed that methicillin stimulated
abcA
transcription but had no effects on
pbp4
transcription. Analysis of
abcA
expression in mutants defective for global regulators showed that
abcA
is under the control of
agr
. Insertional inactivation of
abcA
by an erythromycin resistance determinant did not influence
pbp4
transcription, nor did it alter resistance to methicillin and other cell wall-directed antibiotics. However,
abcA
mutants showed spontaneous partial lysis on plates containing subinhibitory concentrations of methicillin due to increased spontaneous autolysis. Since the autolytic zymograms of cell extracts were identical in mutants and parental strains, we postulate an indirect role of AbcA in control of autolytic activities and in protection of the cells against methicillin.