Progesterone bioconversion by microalgal cultures

Ten different strains of unicellular microalgae have been used in the bioconversion of progesterone. Regio and stereoselective reduction and hydroxylation of the title compound were induced. A 9,10-seco derivative was obtained in high yield by using Scenedesmus quadricauda.     

Zollinger-Ellison syndrome and antral G-cell hyperfunction in patients with resistant duodenal ulcer disease

We measured basal and pentagastrin-stimulated acid secretion, as well as basal and meal-stimulated plasma gastrin concentration to determine, in 67 patients affected by resistant duodenal ulcer, whether their condition could be related to gastric acid secretion and/or gastrin-related syndromes. We then compared them to 46 duodenal ulcer control patients. The outpatients were investigated consecutively. The resistant duodenal ulcer patients differed from the controls only in their higher complication rates (bleeding or perforation, P < 0.05). We identified five patients in the resistant duodenal ulcer group with Zollinger-Ellison syndrome and 12 with antral G cell hyperfunction, whereas in the control group only one patient was affected by antral G cell hyperfunction. IgG anti-Helicobacter pylori antibodies were positive for the presence of infection in 7 of the hypergastrinaemic patients. When Zollinger-Ellison syndrome or antral G cell hyperfunction were excluded, no differences could be found in gastric acid secretion, or basal and meal-stimulated plasma gastrin levels, between the resistant and control duodenal ulcer patients, except for basal acid hypersecretion (resistant duodenal ulcer 16% vs duodenal ulcer 2% P = 0.0144). In the presence of duodenal ulcer disease resistant to H2-blockers, it is mandatory to measure basal plasma gastrin concentration since it was possible to diagnose the gastrin-related syndromes, Zollinger-Ellison syndrome and antral G cell hyperfunction, in 26% of this group of patients.     

Inhibitory effect of 9-(2-phosphonylmethoxyethyl)adenine on visna virus infection in lambs: a model for in vivo testing of candidate anti-human immunodeficiency virus drugs

The acyclic nucleoside phosphonate analog 9-(2-phosphonylmethoxyethyl)adenine (PMEA) was recently found to be effective as an inhibitor of visna virus replication and cytopathic effect in sheep choroid plexus cultures. To study whether PMEA also affects visna virus infection in sheep, two groups of four lambs each were inoculated intracerebrally with 10(6.3) TCID50 of visna virus strain KV1772 and treated subcutaneously three times a week with PMEA at 10 and 25 mg/kg, respectively. The treatment was begun on the day of virus inoculation and continued for 6 weeks. A group of four lambs were infected in the same way but were not treated. The lambs were bled weekly or biweekly and the leukocytes were tested for virus. At 7 weeks after infection, the animals were sacrificed, and cerebrospinal fluid (CSF) and samples of tissue from various areas of the brain and from lungs, spleen, and lymph nodes were collected for isolation of virus and for histopathologic examination. The PMEA treatment had a striking effect on visna virus infection, which was similar for both doses of the drug. Thus, the frequency of virus isolations was much lower in PMEA-treated than in untreated lambs. The difference was particularly pronounced in the blood, CSF, and brain tissue. Furthermore, CSF cell counts were much lower and inflammatory lesions in the brain were much less severe in the treated lambs than in the untreated controls. The results indicate that PMEA inhibits the propagation and spread of visna virus in infected lambs and prevents brain lesions, at least during early infection. The drug caused no noticeable side effects during the 6 weeks of treatment.     

Self-calibration techniques for a second-order multibit sigma-deltamodulator

Design techniques for self-calibration of the digital-to-analog converter DAC in a multibit sigma-delta modulator are described. When used in conjunction with dynamic element matching, self-calibration provides linearity performance suitable for digital audio applications. The dynamic element matching circuitry provides the mechanism of determining device mismatch for self-calibration. Practical circuit details and an effective calibration method are discussed. Test results from a l-μm CMOS test chip are presented. In this test system, a second-order loop with a 3-b quantizer achieves an 89-dB dynamic range and -91-dB harmonic distortion after calibration. In addition, a new method of detecting the presence of tones is described, using the entropy of the spectrum of the decimation filter output     

Study on phase behavior–impact strength relationship of unsaturated polyester/polyurethane hybrid polymer network

The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties.     

Six Synthesis Methods for Reversible Logic

The (2 ^w )! reversible transformations on w wires, i.e. reversible logic circuits with w inputs and w outputs, together with the action of cascading, form a group, isomorphic to the symmetric group S ₂ ^w . Therefore, we investigate the group S _n as well as one of its subgroups isomorphic to S _n/2 × S _n/2. We then consider the left cosets, the right cosets, and the double cosets generated by the subgroup. Each element of a coset can function as the representative of the coset. The coset can then be considered as the set of all group elements that differ from the representative by merely multiplying (either to the left or to the right or to both sides) by an arbitrary element of the subgroup. Different choices of the coset space and different choices of the coset representatives lead to six different syntheses for implementing an arbitrary reversible logic operation into hardware. Evaluation of all six methods, by means of three different cost functions (gate cost, switch cost, and quantum cost), leads to a best choice.     

单片机在超声测距系统中的一种应用

为提高人们在测量距离时的方便性和准确性,现介绍一种基于单片机控制的超声测距系统的构成、工作原理和硬软件设计,利用该系统及其设计方法可以作为机器人的辅助视觉系统,也可用于其他的检测系统中.     

Dental caries in nineteenth century upper Canada

This study examines the presence of dental caries in a large sample of adult skeletons from the 19th century cemetery of St. Thomas' Anglican Church in Belleville, Ontario. The cemetery was used from 1821 to 1874. Caries prevalence and frequencies of diseased and missing teeth were calculated both by observing summary statistics of individual rates and by the total sample of teeth. Postmortem tooth loss is low in this sample and antemortem tooth loss is highest in first mandibular molars, all other molars and then premolars. Age at death, but not sex, was found to be significantly related to the overall Caries Rate while both age and sex were significantly associated with the Diseased-Missing Index. The increase in diseased and missing teeth in older individuals is expected while the sex difference is not explained by simple dietary factors. When compared to reports on British and American samples, caries and antemortem tooth loss in the St. Thomas' sample is most similar to a pre-1850 British group and higher than American samples. Although there is undoubtedly a complex of factors contributing to caries prevalence in this sample, more data are required from large historic samples, particularly from the American northeast and late 19th century Britain, to have a clearer understanding of the influence of diet, cultural, and environmental factors affecting caries rates in historic populations.