Multicomputers: message-passing concurrent computers

A status report is provided on the architecture and programming of a family of concurrent computers that are organized as ensembles of small programmable computers called nodes, connected by a message-passing network, each with its own private memory. The architecture of the multicomputer is described and contrasted with that of the shared-memory multiprocessor, and the concept of grain size (which depends on the size of the individual memories) is explained. Medium-grain and fine-grain multicomputers, with nodes containing megabytes and tens of kilobytes of memory, respectively, are examined, and their programming is discussed     

Stereoisomers of cyclic urea HIV-1 protease inhibitors: synthesis and binding affinities

We have synthesized stereoisomers of cyclic urea HIV-1 protease inhibitors to study the effect of varying configurations on binding affinities. Four different synthetic approaches were used to prepare the desired cyclic urea stereoisomers. The original cyclic urea synthesis using amino acid starting materials was used to prepare three isomers. Three additional isomers were prepared by synthetic routes utilizing L-tartaric acid and D-sorbitol as chiral starting materials. A stereoselective hydroxyl inversion of the cyclic urea trans-diol was used to prepare three additional isomers. In all 9 of the 10 possible cyclic urea stereoisomers were prepared, and their binding affinities are described.     

Thermal conductivity of R134a and R141b within the temperature range 240–307 K at the saturation vapor pressure

New, absolute values of the thermal conductivity of two refrigerants, R134a and R141b, in the liquid phase at saturation are reported. The measurements have been performed in transient hot-wire instruments making use of electrically insulated tantalum wires within the temperature range 240–307 K. The results are estimated to have an accuracy of ±1%.     

A tube in the pharynx for emergency ventilation

BACKGROUND: If the endotracheal placement of a nasal advanced tube fails, ventilation via this tube could bridge the time until a fibreoptic bronchoscope is available. This study investigates the efficiency of ventilation via a tube resting with its tip in the pharynx near the glottis. METHODS: In 20 patients respiratory data during ventilation via a pharyngeally placed tube were recorded by means of pulse oximetry, capnometry and side-stream spirometry. Results were compared with those measured previously in the same patients during conventional facemask ventilation. RESULTS: Oxygen saturation and end-tidal carbon dioxide concentration remained unchanged using ventilation via facemask (SO2 98.5 +/- 0.9%, FECO2 4.5 +/- 0.7 vol%) or pharyngeal tube (SO2 98.6 +/- 0.7%, FECO2 4.8 +/- 0.4 vol%). No significant differences were found between the two groups with regard to peak airway pressure, tidal volume leakage, compliance and resistance of the respiratory system. CONCLUSIONS: Our results suggest an effective ventilation and oxygenation via a tube placed with its tip in the pharynx. This technique may be helpful during difficult and prolonged nasal intubation.     

Immune responses induced by intramuscular or gene gun injection of protective deoxyribonucleic acid vaccines that express the circumsporozoite protein from Plasmodium berghei malaria parasites

The circumsporozoite protein (CSP) is a target for effector Ab and cell mediated immunity against malaria parasites; DNA vaccination can induce both types of effector response. The immunogenicity and efficacy of two DNA plasmids expressing different amounts of Plasmodium berghei CSP were evaluated by immunizing BALB/c mice i.m. or epidermally and by varying the number of immunizations (one to three doses) and the interval between immunizations. Expanding the interval gave the strongest effect, increasing efficacy and antibody boosting, and, in the case of epidermal vaccination, promoting a switch in CSP-specific IgG isotypes from IgG1 to a balance with IgG2a. The strongest humoral immune response and the greatest level of protection were induced by vaccinating epidermally with high expresser plasmid, using a gene gun to administer three doses at 6-wk intervals. For this group, the mean, repeat-specific, prechallenge antibody titer among mice not infected after challenge was significantly higher than that in infected mice, but the mean prechallenge titers for antibody reactive with whole sporozoites were not significantly different. The interval-dependent induction of IgG2a antibodies by epidermal vaccination contradicts the widely held belief that antibody responses induced by this method are restricted to those that are Th2 dependent.     

Instructive induction of prostate growth and differentiation by a defined urogenital sinus mesenchyme

Instructive influences of fetal mesenchyme were examined in heterotypic tissue recombinants consisting of urogenital sinus mesenchyme (UGM) from male and female rats and distal ductal tips from adult rat prostate. Tissues were grown under the renal capsule of male hosts for periods up to 28 days. Resultant growths exhibited typical prostate histology. Expression of lobe-specific proteins for the ventral (prostatic steroid binding protein [PSBP]) lateral (seminal vesicle secretion II [SVS II]), and dorsal prostate (secretory transglutaminase [TGase]) were examined by immunocytochemistry. Male or female UGM combined with terminal segments of the ventral or dorsal prostate and immunolabeled with antibodies to lobe-specific proteins demonstrated expression of all three secretory products. The pattern of staining was consistent with a compound inductive response from the UGM. Unique to this study was our ability to use a defined mesenchymal tissue (female ventral mesenchymal pad [VMP]). This tissue is specifically associated with ductal branching morphogenesis and cytodifferentiation of the ventral prostate. Distal ductal tips from the dorsal lobe of the adult male prostate when recombined with female VMP and grown in vivo exhibited transformation of secretory phenotype, and the epithelium expressed mRNAs for PSBP. Immunocytochemistry of serial sections did not demonstrate labeling for TGase in the new epithelial growth. Ultrastructural analysis of the heterotypic recombinants indicated that the epithelium had similar characteristics to those of normal ventral prostate. Early stages of the mesenchymal-epithelial interactions resulted in dedifferentiation of the adult epithelium to solid cords of stratified cells. These findings illustrate the potent instructive capacity of a defined fetal UGM to influence development and cytodifferentiation of adult prostate epithelium.     

Comparison of the Corrosion Behavior of Coated and Uncoated Magnesium Alloys in an In Vitro Corrosion Environment

The in vitro degradation of magnesium alloys with various alloying elements, the effect of coatings, and the impact of an altered experimental environment are investigated. LANd442 and Nd2 alloys are subjected to a continuously moving environment during an immersion test allowing flowing SBF. Applying an MgF₂ coating to the alloys increases the corrosion resistance of LANd442 but has no effect on the corrosion rate of Nd2 within the period of investigation. It leads to a more‐even degradation with less pitting corrosion in the early stages of corrosion. A bioglass coating on Nd2 increases the corrosion rate. The mass loss, volume loss, and loss in maximum force all show the same trends as the specimens degrade over time.