Biology and pathology of Schistosoma mansoni and Schistosoma japonicum infections in several strains of nude mice

Schistosoma mansoni and S. japonicum infections in nude mice (nu/nu) were compared with infections in nu/+ heterozygotes or intact mice. Seven to 12 weeks after exposure to S. mansoni, the responses of Swiss NCR, C3H, BALB/c and C57B1/6 nude mice did not differ substantially. Nude mice of all these strains showed minute granulomas around eggs in the liver and minimal hepatic fibrosis. Microvesicular and necrotizing changes in hepatocytes were similar in all mouse strains, and S. mansoni infections were frequently lethal to nude, but not to intact mice between the seventh and ninth weeks of infection. Nude mice that survived the ninth week of infection generally lived until the 12th week. The number of eggs per mature worm pair in the tissues of S. mansoni-infected nude mice was similar to the number in intact mice, but nude mice passed fewer eggs in the feces. Nude mice that received serum from infected intact mice excreted eggs in the stool in numbers equivalent to intact mice, but continued to form minute granulomas around S. mansoni eggs. Reconstitution with fetal thymus or with splenocytes from normal or S. mansoni-infected mice partially or completely restored hepatic granuloma size, granuloma eosinophils, hepatic fibrosis, and excretion of eggs in the feces. In contrast to S. mansoni infection, S. japonicum infections in nude mice did not cause necrosis of hepatocytes or excessive mortality, and S. japonicum eggs were passed in the feces in numbers equivalent to those passed by infected intact mice.     

Public participation in radiological surveillance

In 1989, Pacific Northwest National Laboratory developed a program, for the U.S. Department of Energy, to involve local citizens in environmental surveillance at the Hanford Site. The Community-Operated Environmental Surveillance Program was patterned after similar community-involvement efforts at the Nevada Test Site and the Three Mile Island nuclear facility. Its purpose is to increase the flow of information to the public, thereby enhancing the public's awareness and understanding of surveillance activities. The program consists of two components: radiological air monitoring at nine offsite locations and agricultural product sampling at selected locations near the site. At each air-monitoring station, two local school teachers collect air particulate samples and operate equipment to monitor ambient radiation levels. Atmospheric tritium samples (as water vapor) are also collected at some locations. Four of the air-monitoring stations include large, colorful informational displays for public viewing. These displays provide details on station equipment, sample types, and sampling purposes. Instruments in the displays also monitor, record, and show real-time ambient radiation readings (measured with a pressurized ionization chamber) and meteorological conditions. Agricultural products, grown primarily by middle-school-aged students, are obtained from areas downwind of the site. Following analysis of these samples, environmental surveillance staff visit the schools to discuss the results with the students and their teachers. The data collected by these air and agricultural sampling efforts are summarized with other routinely collected sitewide surveillance data and reported annually in the Hanford Site environmental report.     

Low-temperature CV dispersion in MOS devices

A study is reported of the dispersion seen in the accumulation and depletion regions, of the C-V curve in n-channel MOS devices in the temperature range 30-45 K. It is concluded that the dispersion observed in these experiments is caused by time-constant effects, due to the substrate resistance and not caused by dopant atom emission time constant effects. From the measured admittance as a function of temperature and frequency, the acceptor energy level is determined to within ±0.4 meV     

Importance of the Arg-Gly-Asp triplet in human thrombin for maintenance of structure and function

Site-directed mutagenesis was employed to assess the importance of the Arg-Gly-Asp triplet that comprises residues 197 to 199 in the B-chain of thrombin. Properties of the R197E and the D199E variants were compared with those of zeta-thrombin and the inactive S205A variant wherein the active site Ser is replaced by Ala. Relative to zeta-thrombin, the R197E thrombin variant under the assay conditions used exhibits 26% activity toward a small chromogenic substrate, 13% activity in the activation of protein C in the presence of thrombomodulin, < 3% activity in processing fibrinogen, and 1% activity in inducing platelet activation. Thus, the substrate specificity of thrombin was altered by the R197-->E replacement. The D199E variant was essentially inactive. It exhibited only 0.02% of the activity of thrombin toward the chromogenic substrate and its reactivity toward the active site-directed alkylating agent D-Phe-Pro-Arg-CH2Cl was 10,000-fold lower than that of thrombin. Like the inactive S205A thrombin variant, the D199E variant antagonized the interactions of thrombin with hirudin and thrombomodulin, but was a less effective antagonist. The dependence of the antagonism of the thrombin-thrombomodulin interaction on the concentration of D199E thrombin variant provided evidence suggesting the presence of two or more domains in thrombin that independently interact with their counterparts in thrombomodulin. Although the S205A thrombin variant antagonized the action of thrombin on platelets no such activity could be demonstrated for the D199E variant in the concentration range studied (< 800 nm). Comparison of the circular dichroism spectra of zeta-thrombin, the D199E, R197E, and S205A variants indicated that subtle differences in conformation exist between the D199E variant and the other thrombins. These differences in conformation might well account for the altered behavior of the D199E variant with respect to its interactions toward thrombomodulin, hirudin, and platelets.     

Evaluation of hot hardness and creep of a 350 grade commercial maraging steel

The hardening response and the indentation creep of a 350 grade commercial maraging steel were evaluated using a hot hardness tester. The hardness versus temperature plot exhibited three distinct regions. Hardness response was noted between 500–800 K. The unusually high values of activation energy and stress exponent obtained during the creep experiment could be rationalized by a novel concept of introducing a back stress term in the indentation creep relation. The corrected value of the activation energy was found to be reasonably in agreement with the activation energy for diffusion of Ni in iron. Results are supplemented with microstructural observation.     

Peritoneal dialysis in children under 5 years of age

The aim of this study was to examine the effect of intensive practice in table tennis on perceptual coincident timing. The main question was whether the perceptual demands encountered in fast ball sports produce modifications of the perceptual visual system. Expert table tennis players and novices were compared in a perceptual task which consisted of estimating, by pressing a key, the arrival of a moving stimulus at a target. The stimulus, which was presented either at constant velocity or at constant deceleration, reproduced as closely as possible the natural visual demands encountered in table tennis. The difference between the time of response and the time of arrival of the stimulus at a target position was measured over 40 trials for each of the 16 participants. The results showed no effect of expertise under the constant-velocity condition but an effect under the decelerative condition, indicating that experts were less trajectory-dependent than novices. This result was interpreted as reflecting a better adaptation of the perceptual system of experts to the constraints encountered during table tennis and specifically to the perceptual demands resulting from varied and decelerated ball trajectories. Finally, some limitations of the coincidence anticipation procedure are highlighted, concerning its use in practical settings for evaluating athletes or detecting sport talents, and the need for the simulation conditions during testing to reproduce as closely as possible the perceptual demands of real life is discussed.     

CMOS scaling into the nanometer regime

Starting with a brief review on 0.1-μm (100 nm) CMOS status, this paper addresses the key challenges in further scaling of CMOS technology into the nanometer (sub-100 nm) regime in light of fundamental physical effects and practical considerations. Among the issues discussed are: lithography, power supply and threshold voltage, short-channel effect, gate oxide, high-field effects, dopant number fluctuations and interconnect delays. The last part of the paper discusses several alternative or unconventional device structures, including silicon-on-insulator (SOI), SiGe MOSFET's, low-temperature CMOS, and double-gate MOSFET's, which may lead to the outermost limits of silicon scaling     

Evaluation of effect of hydrogen on toughness of Zircaloy-2 by instrumented drop weight impact testing

Hydride-assisted degradation in fracture toughness of Zircaloy-2 was evaluated by carrying out instrumented drop-weight tests on curved Charpy specimens fabricated from virgin pressure tube. Samples were charged to 60 ppm and 225 ppm hydrogen. Ductile-to-brittle-transition behaviour was exhibited by as-received and hydrided samples. The onset of ductile-to-brittle-transition was at about 130 °C for hydrided samples, irrespective of their hydrogen content. Dynamic fracture toughness (K_ID) was estimated based on linear elastic fracture mechanics (LEFM) approach. For fractures occurring after general yielding, the fracture toughness was derived based on equivalent energy criterion. Results are supplemented with fractography. This simple procedure of impact testing appears to be promising for monitoring service-induced degradation in fracture toughness of pressure tubes.     

Use of the cell division protein FtsZ as a means of differentiating among Bartonella species

Genes coding for homologs of the highly conserved cell division protein FtsZ were isolated from Bartonella henselae and Bartonella quintana, the causative agents of cat scratch disease and trench fever, respectively. DNA fragments coding for the ftsZ open reading frames (ORFs) were cloned into Escherichia coli following PCR amplification with primers based on the ftsZ sequence of the closely related species Bartonella bacilliformis. The amino acid sequences predicted from the cloned B. henselae and B. quintana ftsZ ORFs are 81 to 83% identical to the corresponding protein in B. bacilliformis. Like the FtsZ protein of B. bacilliformis, the B. henselae and B. quintana homologs are about twice as large as the FtsZ proteins reported in most other organisms. Localized sequence differences within the C-terminal coding regions of the Bartonella ftsZ genes were used as the basis for species-specific identification of these organisms at both the DNA and protein levels. Oligonucleotide primers which permit the amplification of an ftsZ fragment from each of the Bartonella species without amplifying DNA from the other two species were designed. Anti-FtsZ antisera raised in rabbits against synthetic peptides corresponding to the relatively divergent C-terminal regions were shown via Western blot analysis to react only with the FtsZ protein from the cognate Bartonella species. These observations raise the possibility that the differences in ftsZ sequences can be used as the basis for diagnostic tests to differentiate among these closely related pathogens.