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  • 1
    Electronic Resource
    Electronic Resource
    Two novel transferable extended-spectrum β-lactamases from Klebsiella pneumoniae in Tunisia (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 67 (1990), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two novel β-lactamases conferring multiresistance to antibiotics including oxyimino β-lactams have been identified in two nosocomial K. pneumoniae strains isolated in Tunis in 1986 and 1988. Both enzymes were encoded by ca. 150-kilobase plasmids. Donor and transconjugant strains producing these enzymes exhibited highly similar pattern of resistance (CTX phenotype) to β-lactams including penicillins and oxyimino β-lactams e.g. cefotaxime, ceftriaxone, ceftazidime, and aztreonam. High and variable synergy (16 to 1066-fold) was obtained when combined to 0.1 μg/ml of clavulance (β-lactamase inhibitor). The isoelectric points of these two enzymes were 5.4 and 6.4. These β-lactamases differed from TEM types by hydrolysis for cefotaxime or ceftriaxone but were inhibited by clavulanate and cloxacillin. DNA hybridization studies suggested that the genes of these enzymes may be derived from genes encoding TEM-type enzymes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb13831.x
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  • 2
    Electronic Resource
    Electronic Resource
    Beam divergence effects on nonlinear frequency mixing (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1091-1101 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of the beam divergence of the input pump laser beams on the nonlinear frequency mixing process in a dielectric medium is discussed. The divergent laser beams have finite angular spreads so that all of the interactions between the two input beams can never satisfy the phase-matching condition exactly. A numerical model is developed to investigate the effects of input beam divergence on conversion efficiency. The angular spread of each of the input beams is represented by a set of plane waves having a distribution of propagation directions. Each of the plane-wave components from one input beam is allowed to interact with all the plane-wave components of the second input beam. This model is applicable to processes such as sum frequency generation, difference frequency generation, and optical parametric amplification. Second-harmonic generations as a special case of sum frequency generation is used as an example in the numerical studies. Results indicate that the conversion efficiency is dependent on the amount of beam divergence, the input intensity, and the length of the nonlinear medium. These parameters must be optimized with respect to one another to maximize the conversion. The optimization is especially critical in high-power systems where high conversion efficiency is sought.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351272
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  • 3
    Electronic Resource
    Electronic Resource
    ECR ion and free radical sources for MBE applications : International conference on ion sources (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 282-284 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A small 2.45 GHz ion/free radical source that has been specifically designed for MBE applications is described. The overall outside diameter of this cylindrical source is 5.8 cm (includes magnets and applicator) and the length is less than 15 cm. Thus, it fits through vacuum ports on existing MBE machines and can be placed near the substrate. The microwave discharge, which is created within a cylindrical quartz tube, is surrounded by rare-earth magnets and a tunable coaxial cavity applicator. Single or double accelerating grids can be placed on the 3.75-cm-diam discharge output producing an ion beam, or the discharge can be freely exhausted into the vacuum allowing the charged and excited species to diffuse onto the substrate for plasma and/or free radical processing. This device can operate at pressures as low as 10−5 Torr with A, O2, and N2 gases using only 50–150 W of incident power. The detailed description and the preliminary experimental test of this source is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141322
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  • 4
    Electronic Resource
    Electronic Resource
    Two variants of transferrable extended-spectrum TEM-β-lactamase successively isolated from a clinical Escherichia coli isolate (1992)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 93 (1992), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract In a leukaemic patient presenting a septicaemia treated with ceftrazidime and amikacin, two clinical Escherichia coli isolates distinguished by their level of resistance to oxyimino-β-lactams were isolated at an interval of 24 h. The isolates were identified by biotyping and esterase electrophoretic typing and the two host strains were shown to be identical. However, each of these strains exhibited a different transferrable extended-spectrum β-lactamase. These enzymes had different pl values (5.25 and 5.58), but were both blaTEM-1 mutants. The enzyme with pI 5.25 was identical to TEM-101 (TEM-12) (serine 162 substitution). The enzyme with pI 5.58 showed an additional amino acid substitution (lysine residue instead of an arginine at position 237) and was denominated TEM-23. These data indicate that point-mutations can be successively cumulated in vivo by blaTEM mutants, leading to expression of β-lactamases with increased hydrolysis rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1992.tb05083.x
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  • 5
    Electronic Resource
    Electronic Resource
    Almost periodic weak solutions to forced pendulum type equations without friction (1992)
    Springer
    Aequationes mathematicae 43 (1992), S. 313-313 
    Details
    ISSN: 1420-8903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01835716
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  • 6
    Electronic Resource
    Electronic Resource
    Almost periodic weak solutions to forced pendulum type equations without friction (1992)
    Springer
    Aequationes mathematicae 44 (1992), S. 100-108 
    Details
    ISSN: 1420-8903
    Keywords: Primary 34C27 ; Secondary 34C15
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary We obtain sufficient conditions for the existence of almost periodic weak solutions to equations of the frictionless pendulum type with forcing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01834208
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  • 7
    Electronic Resource
    Electronic Resource
    Captopril induces correction of postrenal transplant erythremia (1990)
    Springer
    Transplant international 3 (1990), S. 222-225 
    Details
    ISSN: 1432-2277
    Keywords: Erythremia, post-transplantation ; Captopril, erythremia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Kidney transplant patients may develop post-transplant erythremia (PTE), and in order to avoid thromboembolism venesection, anticoagulation and native kidney removal have been suggested. We propose captopril as an alternative therapy for PTE. Seven hypertensive PTE patients, aged 42±10 years with stable renal function, were investigated to exclude primary or secondary polycythemia. All patients manifested true erythrocytosis [red blood cells (RBC) mass〉20% of predicted level] with concomitant increases in hematocrit and hemoglobin levels. Captopril was introduced in gradually increasing doses up to 75 mg/day under careful monitoring of blood pressure and renal function. Weekly follow-up was arranged to evaluate drug efficacy. After captopril, a significant reduction with normalization of the RBC mass (42±4 vs 31±5 ml/kg; P〈0.005) was observed. The RBC counts and hematocrit and hemoglobin levels also decreased. One patient had recurrent erythrocytosis after captopril withdrawal. Captopril may be a simple, effective, and non aggressive treatment for postrenal transplant erythremia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366970
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  • 8
    Electronic Resource
    Electronic Resource
    Outbreak of nosocomial infections due toKlebsiella pneumoniae producing SHV-4 beta-lactamase (1990)
    Springer
    European journal of clinical microbiology & infectious diseases 9 (1990), S. 797-803 
    Details
    ISSN: 1435-4373
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract One hundred and fifty-four clinical isolates ofKlebsiella pneumoniae resistant to broad-spectrum cephalosporins, aztreonam and amikacin were responsible for an outbreak of nosocomial infections lasting eight months in a university hospital in Paris. This outbreak occurred in the intensive care unit (39 patients), haematology units (8 patients) and surgical and medical units (11 patients). Antibiotic resistant strains were isolated from the urinary tract (48 %), wound and drainage fluids (21 %), respiratory tract (14 %), blood (12 %) and stools (5 %). High resistance to oxyimino-beta-lactams was mediated by a plasmid-encoded beta-lactamase with an isoelectric point of 7.8 (SHV-4). This CAZ-type enzyme conferred a higher level of resistance to ceftazidime and aztreonam (geometric mean MIC 135 mg/l) than to cefotaxime (geometric mean MIC 14 mg/l). All isolates were of the same biotype (weakly urease positive and no sucrose fermentation). EightKlebsiella pneumoniae strains isolated in different units and at different times of the outbreak were of the same serotype, had common plasmid patterns and harboured a large self-transferable plasmid of about 180 kilobases encoding resistance to penicillins, oxyimino-beta-lactams, aminoglycosides, tetracycline and trimethoprim. These eight large plasmids had indistinguishableEcoRI restriction patterns. These results suggest that a single strain ofKlebsiella pneumoniae was responsible for this outbreak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01967377
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  • 9
    Electronic Resource
    Electronic Resource
    On the convergence of the projected gradient method (1993)
    Springer
    Journal of optimization theory and applications 77 (1993), S. 197-208 
    Details
    ISSN: 1573-2878
    Keywords: Nonlinear optimization ; convergence of ascent methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We study the projected gradient algorithm for linearly constrained optimization. Wolfe (Ref. 1) has produced a counterexample to show that this algorithm can jam. However, his counterexample is only ℒ1(ℝ n ), and it is conjectured that the algorithm is convergent for ℒ2-functions. We show that this conjecture is partly right. We also show that one needs more assumptions to prove convergence, since we present a family of counterexamples. We finally give a demonstration that no jamming can occur for quadratic objective functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00940786
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