Good Ohmic contacts to P−doped and undoped p−type CdTe have been obtained by evaporating Au or Pt on the surfaces in high vacuum (p<1×10−6 Torr) and firing these in a H2 atmosphere. This contact has been used on the crystals having carrier concentrations between 3×1014 and 3×1017 cm−3 and stayed nearly Ohmic down to 4 °K. Consequently, temperature dependences of Hall coefficients and resistivities have been measured and an impurity conduction has been found in the P−doped CdTe.

The effects of combinations of 13-lactams with two P-lactamase inhibitors, sulbactam and clavulanic acid, were determined in vitro against 22 clinical isolates of methicillin-resistant Staphylococcus aureus. Combinations of cefpirome, cefotaxime, and cefazolin with sulbactam (10 ,ug/ml) showed synergistic effects against more than 70% of the strains. Combinations of methicillin and penicillin G with sulbactam also showed synergistic effects against 50 and 68% of the strains, respectively, while cefotiam, moxalactam, flomoxef, and cefmetazole in combination with sulbactam showed such effects against only 40% or fewer. Clavulanic acid was synergistic only when combined with penicillin G, the effect probably being due to the 1-lactamase inhibition by the inhibitor. Sulbactam did not improve the antimicrobial activities of the 1-lactams against methicillinsusceptible S. aureus strains. At 42°C the MICs of cefotaxime, methicillin, and flomoxef alone were markedly decreased from the values at 35°C, and no synergy between these P-lactams and sulbactam appeared. The resistance to penicillin G was not inhibited by incubation at 42°C, and combinations of penicillin G with sulbactam and clavulanic acid showed synergy. The amounts of 13-lactamase produced were not related to the decreases in the MICs of the I-lactams, except for penicillin G combined with sulbactam. Clavulanic acid showed slightly stronger ,3-lactamase-inhibiting activity than sulbactam did. These results suggest that the synergy between sulbactam and the 13-lactams, except for penicillin G, may not be due to 13-lactamase inhibition but to suppression of the methicillin-resistant S. aureus-specific resistance based on other factors.Recently, reports have been made on the isolation of and infections with methicillin-resistant Staphylococcus aureus (MRSA) (1,5,9,25,26). The resistance of these strains is associated with the presence of a low-affinity penicillinbinding protein, PBP 2' (23) or PBP 2a (10), and the protein has been suggested to be inducible by ,-lactams (7, 18, 22). The role of ,B-lactamase in the resistance has also been examined with the ,B-lactamase inhibitors clavulanic acid (17, 18) and sulbactam (3,8), and it has been reported that staphylococcal P-lactamase may be the cause of decreased antimicrobial activities of drugs such as penicillin G and cefazolin, which are relatively susceptible to 1-lactamase hydrolysis (4, 15). There has also been a report that drug inactivation by penicillinase is the main possible mechanism of resistance to cefazolin, cephaloridine, and cephalothin in S. aureus (14).To determine the role of ,-lactamase in the resistance to more antimicrobial agents, we determined the effects of combinations of nine 3-lactams with the two 3-lactamase inhibitors in vitro against clinically isolated MRSA strains. The ,B-lactams examined were cefpirome (20) and flomoxef (21), which have strong antimicrobial activities against S. aureus as well as gram-negative bacteria; five other cephalosporins (cefotaxime, moxalactam, cefmetazo...

A new ,-lactamase assay method with agar plates containing pyridinium-2-azo-p-dimethylaniline chromophore (PADAC) (50 ,uM), a ,-lactamase-labile, chromogenic cephalosporin, was examined. On the PADAC plates inoculated with 3-lactamase-producing gram-negative bacteria (104 CFU per spot) and incubated at 37°C, a yellow zone showing hydrolysis of PADAC by I-lactamase was formed around the colony. The zone diameter increased with incubation time. Examination with Enterobacter cloacae GN7471 revealed that ,-lactamase activity was present in the agar around the colony, decreasing exponentially with increasing distance from the colonial margin; this suggests that the PADAC hydrolysis zone is formed by an extracellular enzyme. At 18 h, significant correlations were obtained between the zone diameters of the 10 species (clinical isolates) examined and their periplasmic P-lactamase activities determined spectrophotometrically. The addition of clavulanic acid (0.5 to 10 ,ug/ml) inhibited zone formation on the PADAC plates inoculated with type lIla, Va, Vb, PSE-1, and Ic ,-lactamase producers. When the clinical isolates were tested on plates with clavulanic acid (2 ,ug/ml), inhibition was observed in 41 to 58% of the Escherichia coli, Serratia marcescens, and Pseudomonas aeruginosa isolates and in all isolates of Klebsiella pneumoniae, Klebsiella oxytoca, and Proteus vulgaris. Thus, the use of the inhibitor made it possible to detect penicillinase or type Ic cephalosporinase producers. These results proved that the PADAC plate might be a useful tool permitting easy, semiquantitative determination of ,-lactamase activity.The clinical use of many ,-lactams is associated with the emergence of resistant strains, and their resistance, mainly caused by 1-lactamase production (7), has long been an issue to resolve in the clinical field. Various methods for rapidly detecting P-lactamase have been devised. A typical detection method is the test based on a change of color following hydrolysis of a chromogenic cephalosporin in the disk or solution containing the bacterial colony (2,4,6,8). However, this is a qualitative means of enzyme detection and seems to be less practical for use in the clinic than expected.The quantitative assay for P-lactamase activity requires laborious procedures, including enzyme isolation and purification (plus extracellular release of the enzyme by ultrasonic or other treatment in the case of gram-negative bacteria) and spectrophotometric determination.We have searched for a new simple method to assay ,-lactamase and found that on agar containing pyridinium-2-azo-p-dimethylaniline chromophore (PADAC), one of the chromogenic cephalosporins used conventionally for qualitative detection of ,B-lactamase (2), a yellow zone showing enzyme hydrolysis of PADAC (PADAC hydrolysis zone) is formed around the colony of P-lactamase-producing, gramnegative bacteria, giving semiquantitative results of enzyme activity. This paper describes a new method of estimating ,-lactamase with PADAC agar. MATERIALS AND METHODSBacteria...

An adaptation of the Monch and Galster specimen form to the biaxial tensile testing of paper is described. This form gives a known, uniform, biaxial stress field. A versatile test instrument for use with such specimens, as well as with wet or dry uniaxial ones, is also described. Poisson's ratio values of well-bonded, isotropic handsheets measured in the elastic region with this equipment are closer to the expected value of approximately one-third than earlier measurements made on equipment using other specimen shapes. Good agreement is observed among Poisson's ratio measurements made biaxially and those made uniaxially on the same specimens. Also, agreement is reasonable with measurements made with an ultrasonic technique.

Very high-resistivity (I 01l_10 12 n em at 300 OK) layers have been obtained by AI vapor diffusion into ZnTe using iodine as a carrier gas under a Zn atmosphere without surface erosion. Avalanching MIS electroluminescent diodes were fabricated using this technique. Spectral outputs of the diodes are yellow at 300 oK and green or yellow-green at 77 oK. The external quantum efficiencies are 0.1 '" 0.2% in the yellow, 10% in the green, and 20% in the yellow-green. The yellow and the green electroluminescence appear to be due to an acceptor-donor pair consisting of the doubly ionizable Zn vacancy and an unknown donor, whereas the yellow-green is characteristic of AI-doped ZnTe.