Search

We have measured sputtering yields of H2O films with 19F ions at bombarding energies from 1.6 to 25 MeV. The sputtering yield was found to be very sensitive to the incident charge state of the beam, and insensitive to the thickness of the ice film for thicknesses ranging from approximately 20 to 80×l016H2O/cm2. The yield was independent of the target substrate temperature from 10 to 60 K and independent of the F beam current density from < 1 to approximately 5.5 particle nanoamps/mm2. There are several models proposed to explain enhanced sputtering of dielectrics; we have discussed their relevance to our data.

A case is presented in which yeastlike cells resembling the yeast phase of Paracoccidioides brasiliensis were observed by microscopic examination of a urine sample. A mold identified as Mucor circinelloides was isolated from the specimen. It was converted to the yeast form by cultivation on Sabouraud agar incubated in a GasPak jar at 37 ° C. The isolate was eventually shown not to be related to the patient's illness; however, the superficial resemblance of the yeast phase to P. brasiliensis caused some confusion in making a correct diagnosis.

Sputtering yields of solid SO2 by high energy ions were measured in order to study the mechanism for sputtering dielectrics with ions in the electronic stopping power region. The incident ions were helium and fluorine with energies ranging from 1.5 MeV to 25 MeV. Yields as high as 7000 SO2 molecules/incident F ion were measured; the 1.5 MeV 4He beam had a sputtering yield of 50. The data are compared to yield measurements made on UF4 and H2O targets. There is a striking similarity in the yield as a function of the incident F energy for all three targets. The data compare favorably with theoretical yield curves based on a new model for the sputtering which considers the electronic excitations induced in the target by the incident beam. Measurements and calculations of this sort are also useful in understanding processes which occur on the surface of Jupiter's satellite Io, which is covered with SO2 frost and bombarded by energetic ions trapped in the Jovian magnetosphere.

The precision, accuracy, and other performance characteristics of the MS-2 (Abbott Laboratories, Diagnostic Division, Dallas, Tex.) system for the identification of Enterobacteriaceae were evaluated in a collaborative study involving three clinical laboratories. When identifying 150 unknown, coded organisms, the MS-2 system was 97%, 98%, and 93% accurate, respectively, in three laboratories. The system showed an overall accuracy of 94% when compared with conventional manual tube methods in identifying 1,154 clinical isolates of 26 species of Enterobacteriaceae. Discrepancies between automated and conventional methods were chiefly caused by biochemical variants, especially among Enterobacter species. The MS-2 system was rapid and simple to operate and produced printed results of bacterial identification in 5 h. The cost of disposable components compared favorably with commercial, visually read systems for identifying Enterobacteriaceae.

The results of over 400 tests for identification of clinical yeast isolates as to species using the Uni-Yeast-Tek (UYT) system in comparison with a more conventional system are reported. The conventional system utilized a total of 23 individual tests, including both fermentation and assimilation tests, whereas the UYT system included only 11 separate tests. In the initial phase of the study, coded unknown isolates were evaluated by each of two technologists using both methods independently. After this initial evaluation, the two methods were used in parallel for routine testing of yeast isolates as they were obtained from clinical specimens. A further evaluation of the UYT system was carried out by retrospectively analyzing the species reported from a clinical mycology laboratory during two separate time periods in which different approaches to yeast identification were employed. A total of 92% of the isolates tested with the UYT system were correctly reported within 72 h, 96% were correctly named after 1 week of incubation, and 97% were correctly reported after 2 weeks of incubation of UYT plates at 30°C when results of the two phases of the study were analyzed together. With the conventional system, 88% of the isolates were correctly reported at 72 h, 96% at 1 week, and 98% after 2 weeks of incubation of biochemical tests. Retrospective analysis of laboratory records revealed no major changes in species reported after adoption of the UYT system for routine testing of clinical isolates. The data presented in this report suggest that the UYT system can be expected to yield rapid presumptive identification of clinical yeast isolates with reasonable confidence when certain minor limitations that are discussed in the text are taken into account.

Sterile stainless-steel electrodes implanted in blood culture bottles and monitored electronically were used to detect growth of microorganisms. Each blood culture bottle contained 100 ml of medium and was inoculated with 10 ml of blood seeded with either 300 or 50 colony-forming units of one of several bacterial or yeast species that are commonly isolated from clinical blood cultures. Growth was indicated by a voltage change of at least 0.1 mV/min with an increasing slope over at least three consecutive 15-min intervals. This method was compared to the conventional visual method for detecting microbial growth in broth. Growth detection by both techniques was confirmed by subculture to solid media. Of the 163 cultures seeded with the high inoculum (300 colony-forming units) and confirmed as being positive, 148 (90.8%) were positive by the electronic detection system (EDS). At the lower inoculum (50 colony-forming units), 47 of 53 (88.7%) positive cultures were detected by EDS. Twelve of the 21 false-negatives by the EDS were cultures seeded with Cryptococcus neoformans. Excluding C. neoformans, the rate of detection of growth was 96.0%. Microbial growth was detected an average of 18 h earlier by EDS than by the conventional system in 176 (90.2%) of the cultures. Also examined were 156 patient blood cultures: 13 were positive both by EDS and by conventional methods.

The Abbott yeast identification system (Abbott Laboratories, Diagnostics Division, Irving, Tex.) is a 24-h, instrumental method for identifying medically important yeasts, based on matrix analysis of 19 biochemical reactions and the germ tube test. The system was evaluated in two clinical laboratories by using 179 coded isolates, which included a high percentage of the less frequently encountered species. Based upon results with these coded isolates and from previously obtained laboratory data, the system software was adjusted and accuracy of the yeast identification system was further evaluated with 378 isolates from clinical sources. Of the 378 clinical yeast isolates tested, 364 (96%) were correctly identified with the Abbott system. Isolates were deliberately selected so that germ tube-positive isolates made up less than 10% of the clinical isolates tested.

The new API 20C yeast identification system together with appropriate microscopic morphology determinations achieved a 97% correlation with a rapid conventional method. Whereas a group composed of Candida, Torulopsis, Saccharomyces, and Rhodotorula was identified with ease (98% overall correlation), a second group, containing Cryptococcus, Trichosporon, and Geotrichum species, appeared to give the system the most difficulty (90% correlation). Within this group particular difficulty was encountered in identifying varieties of Cryptococcus albidus, C. terreus, C. laurentii, Trichosporon beigelli, and Geotrichum spp. as to species. The API 20C system should be incubated the full 72 h prescribed by the manufacturer. However, when used in conjunction with appropriate morphological tests, presumptive identifications of some Candida and Torulopsis species may be made at 24 to 48 h. To facilitate identifications of the more difficult group of yeasts, ancillary tests for determining nitrate reductase, urease, and phenol oxidase activities should be considered as additions to the strip. Incorporating the phenol oxidase test would be especially important for identification of Cryptococcus neoformans, a yeast which should be identified as quickly and as accurately as possible. The API 20C system with computer assistance has proved to be an easy-to-inoculate, versatile, and fairly rapid method of yeast identification, giving results comparable to those obtained by conventional methodologies.

The capability of the Abbott Avantage system to identify 10 species of commonly isolated glucose nonfermentative or oxidase-positive gram-negative bacilli in a 5-h test period was evaluated in a collaborative study. The Avantage nonenteric data base uses 20 biochemical test reactions performed in an expanded Abbott bacterial identification cartridge plus the results of a manual oxidase test. The species included in the Avantage data base are Acinetobacter anitratus, Acinetobacter Iwoffi, Aeromonas hydrophila, Flavobacterium meningosepticum-IIb group, Pseudomonas aeruginosa, Pseudomonas cepacia, Pseudomonas fluorescens-putida group, Pseudomonas maltophilia, Pasteurella multocida, and Plesiomonas shigelloides. The collaborative study included the testing of 200 coded challenge strains in all three laboratories and the subsequent testing of an additional group of 100 to 200 clinical isolates recovered independently by each laboratory. Reference identifications for all isolates were determined by conventional biochemical test reactions. The overall accuracy of identification of the coded challenge strains for the three laboratories was 97%, whereas 95% of 437 clinical isolates and selected stock cultures of clinical derivation were identified correctly.

We have measured sputtering yields of H2O films with 19F ions at bombarding energies from 1.6 to 25 MeV. The sputtering yield was found to be very sensitive to the incident charge state of the beam, and insensitive to the thickness of the ice film for thicknesses ranging from approximately 20 to 80×l016H2O/cm2. The yield was independent of the target substrate temperature from 10 to 60 K and independent of the F beam current density from < 1 to approximately 5.5 particle nanoamps/mm2. There are several models proposed to explain enhanced sputtering of dielectrics; we have discussed their relevance to our data. [ABSTRACT FROM PUBLISHER]

Sputtering yields of solid SO2 by high energy ions were measured in order to study the mechanism for sputtering dielectrics with ions in the electronic stopping power region. The incident ions were helium and fluorine with energies ranging from 1.5 MeV to 25 MeV. Yields as high as 7000 SO2 molecules/incident F ion were measured; the 1.5 MeV 4He beam had a sputtering yield of 50. The data are compared to yield measurements made on UF4 and H2O targets. There is a striking similarity in the yield as a function of the incident F energy for all three targets. The data compare favorably with theoretical yield curves based on a new model for the sputtering which considers the electronic excitations induced in the target by the incident beam. Measurements and calculations of this sort are also useful in understanding processes which occur on the surface of Jupiter's satellite Io, which is covered with SO2 frost and bombarded by energetic ions trapped in the Jovian magnetosphere. [ABSTRACT FROM PUBLISHER]

The hyphal septa of 3 chromomycosis agents, Phialophora pedrosoi, Phialophora verrucosa, and Cladosporium carrionii were investigated ultrastructurally. Single pores were observed in the septa of all 3 species. Conspicuous bodies consistent in appearance with previous descriptions of Woronin bodies were also observed. These observations suggest an ascomycetous affinity for these imperfect dematiaceous fungi.

Chemical analyses demonstrated the similar compositions of hyphal walls isolated from the chromomycosis agents Phialophora verrucosa, P. pedrosoi and Cladosporium carrionii. Unfractionated walls of each species consisted of large amounts of glucose (17-31%) and protein components (29-42%) and smaller amounts of mannose (8-14%) and glucosamine (6-8%). Alkali-soluble wall fractions consisted predominantly of glucose and mannose, while alkali-insoluble wall fractions consisted predominately of glucosamine and protein components. Chitin was identified as a wall component by release of N-acetylglucosamine during enzymatic digestions of the walls with Streptomyces griseus chitinase. The presence of chitin in the walls and alkali-insoluble residues was confirmed by X-ray powder analysis. The suggestion is made that the hyphal forms of human pathogenic fungi have wall compositions intermediate between those of euascomycetes and hemiascomycetes.

The antigenic relationships among Phialophora verrucosa, Fonsecaea pedrosoi, and Cladosporium carrionii were studied by comparing water soluble antigens extracted from mycelia and extra-cellular antigens from culture filtrates. Immunodiffusion and immunoelectrophoresis tests detected common antigens among all 3 species, as well as antigens which appeared to be either genus or species-specific. Each test revealed more common antigens between P. verrucosa and C. carrionii than between either species and F. pedrosoi, indicating that P. verrucosa and C. carrionii are more closely related to one another than they are to F. pedrosoi. These findings provide justification for the retention of F. pedrosoi in the genus Fonsecaea.

Results obtained with 433 yeast isolates indicated that the CN screen medium could be used with confidence for presumptive identification of Cryptococcus neoformans. Of 49 C. neoformans isolates tested, only four stock isolates yielded false-negative results upon initial testing. After repeated subculturing on Sabouraud agar and retesting, these four isolates yielded correct results. Essentially, no false-positive results were obtained, and the data suggested that false-negative results could be eliminated by using fresh isolates of C. neoformans preincubated at 25 degrees C on Sabouraud glucose agar.

Test for the ability of yeasts isolated from clinical specimens to utilize protocatechuic acid and p-hydroxybenzoic acid were carried out by using techniques that are commonly employed to test assimilation of carbon sources. A total of 60 isolates of Candida parapsilosis and 5 isolates of Candida humicola readily assimilated these two phenolic acids, whereas other Candida species gave uniformly negative results. Cryptococcus albidus, Cryptococcus terreus, and some isolates of Cryptococcus laurentii also assimilated protocatechuate and p-hydroxybenzoate, whereas Cryptococcus neoformans did not. Results of these tests suggest that assimilation of protocatechuate and p-hydroxybenzoate may be a useful characteristic, when used in conjunction with traditional tests, for identifying C. parapsilosis and C. albidus.