X-ray absorption near edge spectroscopy with a superconducting detector for nitrogen dopants in SiC.

Fluorescence-yield X-ray absorption fine structure (FY-XAFS) is extensively used for investigating atomic-scale local structures around specific elements in functional materials. However, conventional FY-XAFS instruments frequently cannot cover trace light elements, for example dopants in wide gap semiconductors, because of insufficient energy resolution of semiconductor X-ray detectors. Here we introduce a superconducting XAFS (SC-XAFS) apparatus to measure X-ray absorption near-edge structure (XANES) of n-type dopant N atoms (4 ×10(19) cm(-3)) implanted at 500°C into 4H-SiC substrates annealed subsequently. The XANES spectra and ab initio multiple scattering calculations indicate that the N atoms almost completely substitute for the C sites, associated with a possible existence of local CN regions, in the as-implanted state. This is a reason why hot implantation is necessary for dopant activation in ion implantation. The SC-XAFS apparatus may play an important role in improving doping processes for energy-saving wide-gap semiconductors and other functional materials.

Yersinia pseudotuberculosis infection in breeding monkeys: detection and analysis of strain diversity by PCR.

In the last three decades, several monkeys reared in outdoor/indoor-outdoor breeding colonies and cages of the Primate Research Institute, Kyoto University, died of yersiniosis caused by Yersinia pseudotuberculosis, necessitating introduction of a method to detect the bacteria rapidly and thus allow preventive measures to be undertaken. A rapid nested polymerase chain reaction (PCR) method for identification of Y. pseudotuberculosis in fecal samples and a random amplified polymorphic DNA (RAPD)-PCR approach for distinguishing between bacterial strains were therefore developed. Yersinia pseudotuberculosis isolates from monkey specimens were found to be classifiable into several types. To determine the source of infection, hundreds of fecal samples of wild rats, pigeons, and sparrows were collected from around the breeding colonies and cages, and subjected to PCR analyses. Yersinia pseudotuberculosis was detected in 1.7% of the fecal samples of wild rats. The DNA fingerprints of the bacteria revealed by RAPD-PCR were the same as that of one strain isolated from macaques, suggesting the wild rat to be a possible source of infection.

Synchronous scanning of undulator gap and monochromator for XAFS measurements in soft x-ray region.

Synchronous scanning of the undulator gap and a monochromator was done to obtain smooth profiles of incident x-rays that are suitable for XAFS measurements. By changing the gap from 150 mm(B=0.12 T) to 140 mm (B=0.15 T) with the use of the 3rd to 11th harmonic peaks, soft x-rays with energy from 200 eV to 1200 eV were obtained. The smooth profile of the incident x-rays provided high-quality measurement of XANES and EXAFS spectra in the soft x-ray region. Issues that would improve the synchronous scanning system are discussed.

In situ XAFS analysis system for high-pressure catalytic reactions and its application to CO2 hydrogenation over a Rh/Y-zeolite catalyst.

An in-situ XAFS cell was developed and used for the structural analysis of a Rh ion-exchanged zeolite catalyst during high-pressure hydrogenation of carbon dioxide. The in-situ cell enabled analyses of the catalyst structures that changed with the reaction atmosphere and elapsed time; the peak assigned to Rh-O scattering changed to that assigned to Rh-Rh scattering at 404 K during the pretreatment by hydrogen. After 30 min. of the carbon dioxide hydrogenation reaction, the peak intensity assigned to Rh-Rh scattering increased corresponding to the increase in the catalytic activity.

Multi-component fitting XAFS analysis of molybdate species during catalyst preparation ration by the molten salt method.

The goal of the present study was to elucidate the formation mechanisms of highly dispersed catalysts by the molten salt method. For this purpose, multi-component fitting Mo K-edge EXAFS analysis was applied to the structure of molybdate catalysts prepared in KNO3 and NaNO3. The analysis revealed that MoO3 dissolved in molten salts was at first transformed into polymolybdate anions and finally into MoO(4)2- anions. The transformation into MoO(4)2- anions took place at a lower temperature when NaNO3 was used as molten salt than KNO3. In contrast, polymolybdate anions were stable even at higher temperature when ZrO2 was added as a support of molybdate.

XAFS study on the sulfidation mechanisms of Co-Mo catalysts supported on activated carbon and alumina: effect of complexing agent.

The effect of nitrilotriacetic acid (NTA) as a complexing agent on the sulfidation mechanisms of Co-Mo catalysts supported on activated carbon and alumina was examined by the XAFS technique. The XAFS results revealed that NTA interacted with Co atoms and formed the Co-NTA interaction, while it showed almost no influence on the local structures around Mo atoms. The Co-NTA interaction suppressed the aggregation of cobalt atoms and the interaction between cobalt and alumina during sulfiding, and consequently promoted the formation of the Co-Mo-S phase.

The influence of rearing conditions on the physical growth of captive Japanese macaques (Macaca fuscata).

To clarify the influence of rearing conditions on the growth of various body parts of Japanese macaques (Macaca fuscata), two groups reared under different conditions, i.e., a group born and reared in open enclosures (Enclosure group) and another consisting of macaques born and reared in cages (Caged group), were somatometrically analyzed. Somatometric data on 36 measures of various body parts were collected from 77 males and 92 females. Growth in many body parts was smaller in the Caged group than in the Enclosure group. Body parts that exhibited large incremental increases were more sensitive to differences in rearing space at the infantile growth stage in both sexes. Recovery from delayed growth at the pubertal growth stage was found in many body parts. However, the size of some locomotor elements such as the wrist and hand, and ankle and foot strongly reflected limitations of space and changes due to this were irreversible. Females were more sensitive than males to such differences in rearing conditions. We conclude that open enclosures with ample rearing space are necessary for the innate growth of Japanese macaques to occur.

High prevalence of infection with Entamoeba dispar, but not E. histolytica, in captive macaques.

A total of 268 nonhuman primates (20 species) kept in the Primate Research Institute, Kyoto University, Japan, were surveyed for intestinal amebas. Total positive rates as based on the presence of cysts in the stool following formalin-ether sedimentation were as follows: Entamoeba histolytica/E. dispar, 53%; E. coli, 34%; E. hartmanni, 34%; Iodamoeba buetschlii, 25%; Endolimax nana, 8%; and E. chattoni, 3%. Positive rates were higher in Old World monkeys and lower in New World monkeys. All the 141 E. histolytica/E. dispar-positive animals were Macaca monkeys. The E. histolytica/E. dispar-positive samples were analyzed by polymerase chain reaction (PCR) for identification of E. histolytica and E. dispar. E. dispar DNA was detected in 137 samples, whereas no E. histolytica DNA was seen. Zymodeme analysis and reactivity to monoclonal antibodies of cultured trophozoites also supported the presence of E. dispar and the absence of E. histolytica. When the sera of 93 macaques were examined by an indirect fluorescent antibody test, only 3 animals proved to be positive for E. histolytica, showing the lowest titer. These results demonstrate that infection with E. dispar, but not E. histolytica, is predominant in macaques.

Detection of congenital malaria by polymerase-chain-reaction methodology in Dar es Salaam, Tanzania.

The examination of congenital malaria was performed by Giemsa staining and polymerase-chain-reaction (PCR) methodology. We randomly selected 298 neonates who had been admitted to Muhimbili Medical Center (MMC) at Dar es Salaam, Tanzania. One baby among all the enrolled neonates was recognized as having a congenital malaria infection, which gave a prevalence of 0.33%. The present result was 5-fold the clinically recognized prevalence of congenital infection with malaria in the ward. The PCR method identified two cases, one of which was negative as determined by the Giemsa-staining method. Therefore, the PCR method was useful for the detection of scant amounts of malarial parasites in numerous blood samples. The screening of malaria by a sensitive PCR method contributes to reduce the mortality of asymptotic neonates in particular.

Diagnosis of bacterial enteric infections in children in Zambia.

BACKGROUND: The bacterial pathogens commonly responsible for diarrhea in children under the age of 5 in Zambia were identified and the most effective methods of diagnosis of such infections in laboratories with limited resources, such as those in developing countries, are recommended. METHODS: Stool samples were collected from children under the age of 5 years who visited the Diarrhoea Training Unit (DTU) of Zambia University Teaching Hospital in Lusaka, Zambia, between May 1992 and May 1993. A total of 639 children were evaluated for the presence of bacterial infection using standard culture media. The prevalence of bacterial pathogens was compared with that reported from other developing countries. RESULTS: Pathogenic strains of Escherichia coli were isolated from 95 (14.9%) children, Shigella species from 65 (10.2%) children, and Vibrio cholerae from 21 (3.3%) children. The presence of visible blood in the feces was an early indicator of the presence of shigellosis. CONCLUSIONS: E. coli, Shigella species and Vibrio cholerae were the major causes of bacterial diarrhea in the Zambian children studied. Research is required to determine the prevalence of such enteropathogenic strains. The use of adequate diagnostic procedures is indispensable to appropriate management. The recommendations have been prepared as a manual for the identification of enteropathogenic bacteria to be used in laboratories with limited resources, such as in developing countries.

Rotavirus gastro-enteritis in hospitalized children with acute diarrhoea in Zambia.

The clinical and epidemiological aspects of rotavirus diarrhoea were studied in hospitalized children with acute diarrhoea in Lusaka, Zambia. Two hundred and fifty-six (24.0%) of 1069 children admitted to the study were shedding rotavirus. The rotavirus-positive rate was highest in children less than 1 year of age (37.0%) and it was also high in those less than 6 months old. Rotavirus diarrhoea was seen throughout the year with a higher rotavirus-positive rate in the dry season. In rotavirus-positive diarrhoea patients, more children were dehydrated (82.4%) than in the rotavirus-negative group (56.2%). Rotavirus infection was more common in the children with normal nutritional status (27.6%, 162/588) than in those with malnutrition (19.3%, 93/482). The associated case fatality rate in the rotavirus-positive group was 6.4%, significantly less than in the rotavirus-negative group (OR 0.44, 95% CI 0.24-0.79), and mortality cases were seen only in children less than 2 years old.

Association of rotavirus and human immunodeficiency virus infection in children hospitalized with acute diarrhea, Lusaka, Zambia.

In Lusaka, Zambia, rotavirus (RV) and human immunodeficiency virus (HIV) infection commonly coexist; 132 (25%) of 537 consecutively studied infants < 5 years old hospitalized with diarrhea were positive for both viral infections. Infants with RV infection were younger than those who were RV-negative (P > .05), and infants with both viruses more frequently experienced dehydration (P < .05). HIV-infected children more often exhibited respiratory symptoms on admission to the study (P < .0001) and were more frequently underweight (P < .0001) than were HIV-negative children, independent of RV infection. The mortality rate was highest in HIV-positive infants (P < .05), and coinfection with RV did not increase the risk of fatality. This study demonstrates that while RV and HIV infections commonly coexist in one region of Africa, RV infection is no more common nor is the illness more severe in HIV-positive infants.

Prevalence of antibodies to five selected zoonosis agents in monkeys.

The prevalence of antibodies against 5 zoonosis agents was determined in serum samples of 443 breeding monkeys. Of the monkeys, 296 were bred or kept for a long time at R institute, and the remaining 147 were newly imported from the Philippines and kept at S institute for quarantine. Antibodies to simian virus 40 were highly prevalent at 89.1% among monkeys of R institute, whereas no antibody could be detected in those of S institute. Antibodies to Chlamydia psittaci and Yersinia pseudotuberculosis were detected in 14.4 and 11.6% at R institute, and in 9.0 and 3.5% at S institute, respectively, evidencing a significant difference (P less than 0.05) between those of the two institutes for both agents. Antibodies to Toxoplasma gondii and Leptospira interrogans were found in 3.6 and 2.9% of the overall, respectively, showing no difference in positive rates in relation to breeding place. Even in cases positive to the latter 4 zoonosis agents, the antibody titers were low. The results obtained suggest that all zoonoses tested do not seem to be so serious diseases among monkeys at the present time except simian virus 40 infection, which is highly prevalent among breeding monkeys in Japan.

A serological survey of simian virus 40 in monkeys.

A serological survey of simian virus 40 (SV 40) was conducted by an immune adherence hemagglutination (IAHA) test in breeding monkeys. Of a total of 356 monkeys tested, 168 (47.2%) were seropositive. All 168 seropositive monkeys were detected from 224 monkeys which were bred or kept in Japan for a long time. In contrast, none of the 132 monkeys which were newly imported from Southeast Asia was seropositive. If a comparison was made in the same breeding place, the positive rate of 80.4% (111/138) of Japanese monkeys was significantly (P less than 0.01) higher than the 59.5% (25/42) among rhesus monkeys. The positive rate and the IAHA titers were higher in older age group (greater than 5 years) but similar in male and female. These results indicated that SV 40 was highly prevalent among breeding monkeys in Japan.