Similarity transformations for the axisymmetric Boussinesque's problem

Summary Lie's infinitesimal transformation groups, which leave the basic equations of axially symmetric problems of classical elasticity invariant, are constructed. For the case of the axisymmetric Boussinesque's problem of an elastic semi-space subjected to a point force applied normal to its surface, the invariance of boundary and boundary conditions leads to the explicit form of similarity transformations which are used to solve the problem. Expressions for the displacements and stresses derived by this approach, which is believed to be new, are found to agree with the known results.     

Effect of filler content on mechanical strength in bis-GMA-based resins with urethane linkages

Bis-GMA-based visible-light-cured resins containing urethane linkages exhibited improved hardness and strength by addition of filler to the unfilled resins. The urethane monomers in the resins strengthened the resin matrix, exhibiting an increased Shore hardness value. Urethane monomer derived from 2HEMA and N3500 was more effective than that from 2HEMA and HT. The increased strength in the resin matrix occurred after storage in water at 37°C. Addition of filler to bis-GMA-based resins increased compressive strength (110 MPa as the maximum), while diametral strength values of 20 MPa were obtained.     

The effects of pressure and temperature on the catalytic oxidation of hydrogen sulfide in natural gas and regeneration of the catalyst to recover the sulfur produced

The influence of pressure up to 5600 kPa and temperature up to 175 °C on the oxidation of low concentrations of H₂S in natural gas was studied in a fixed bed reactor over an activated carbon catalyst. Operation of this system at 5600 kPa provides higher catalyst activity (virtually 100% H₂S conversion) over a longer period of time and with lower selectivity to SO₂ than when operated at atmospheric pressure. The desorption of sulfur from a loaded catalyst occurs first from the macropores (> 100 nm) of the catalyst which contain a substantial portion of the sulfur load and then from the micropores (< 100 nm). This study also indicated that the sulfur recovery process is both rapid and effective at 327°C.     

Groundwater management and development by integrated remote sensing and geographic information systems: prospects and constraints

Groundwater is one of the most valuable natural resources, which supports human health, economic development and ecological diversity. Overexploitation and unabated pollution of this vital resource is threatening our ecosystems and even the life of future generations. With the advent of powerful personal computers and the advances in space technology, efficient techniques for land and water management have evolved of which RS (remote sensing) and GIS (geographic information system) are of great significance. These techniques have fundamentally changed our thoughts and ways to manage natural resources in general and water resources in particular. The main intent of the present paper is to highlight RS and GIS technologies and to present a comprehensive review on their applications to groundwater hydrology. A detailed survey of literature revealed six major areas of RS and GIS applications in groundwater hydrology: (i) exploration and assessment of groundwater resources, (ii) selection of artificial recharge sites, (iii) GIS-based subsurface flow and pollution modeling, (iv) groundwater-pollution hazard assessment and protection planning, (v) estimation of natural recharge distribution, and (vi) hydrogeologic data analysis and process monitoring. Although the use of these techniques in groundwater studies has rapidly increased since early nineties, the success rate is very limited and most applications are still in their infancy. Based on this review, salient areas in need of further research and development are discussed, together with the constraints for RS and GIS applications in developing nations. More and more RS- and GIS-based groundwater studies are recommended to be carried out in conjunction with field investigations to effectively exploit the expanding potential of RS and GIS technologies, which will perfect and standardize current applications as well as evolve new approaches and applications. It is concluded that both the RS and GIS technologies have great potential to revolutionize the monitoring and management of vital groundwater resources in the future, though some challenges are daunting before hydrogeologists/hydrologists.     

A discrete-sectional model for particle growth in aerosol reactor: Application to titania particles

A one-dimensional discrete-sectional model has been developed to simulate particle growth in aerosol reactors. Two sets of differential equations for volume and surface area, respectively, were solved simultaneously to determine the size distributions of agglomerates and primary particles. The surface area equations were derived in such a way that the coagulation integrals calculated for the volume equations could be used for the surface area equations as well, which is new in this model. The model was applied to a production of TiO₂ particles by oxidation of titanium tetrachloride. Model predictions were compared with experimental data and those of a two-dimensional sectional model. Good agreement was shown in calculated particle size distributions between the present model and the two-dimensional model, which is more rigorous but demands a large amount of computer time and memory. Compared to experimental data, the primary particle size calculated by the model was more sensitive to the variation of reactor temperature.     

The HLA A1-B8 haplotype extends 6 Mb beyond HLA-A: associations between HLA-A, B, F and 15 microsatellite markers

Ornithodoros (Alectorobius) amblus Chamberlin 1920 specimens were collected from a seagull (Larus spp.) nest in northern Chile. This reports the occurrence of this species outside Peru. The biology of 79 specimens reared under laboratory conditions at 27 degrees C, 75-80% RH, and total darkness was determined. A 13% mortality rate from larval to adult was observed. Larval ticks were fed on chicks, Gallus gallus domesticus; and nymphs and adults were fed on chickens. We recorded the number of eggs per female per gonotrophic cycle and the mean duration of the periods of preoviposition, oviposition, and incubation. The total duration of their life cycle ranged from 111 to 239 d, depending on the number of molts. Males were found after the 4th molt, and after the 5th molt the proportion of females was greater than that of males or remaining nymphs. The feeding period of larvae was 4-6 d, N1 nymphs do not feed. The N2-N6 nymphs, males and females, had a 10- to 60-min feeding period. From N2 on, there was emission of coxal fluid while on the host and during or immediately after feeding.     

Neuropathology of bovine herpesvirus type 5 (BHV-5) meningo-encephalitis in a rabbit seizure model

CI-994 (acetyldinaline) is an orally active anticancer drug currently in Phase 1 clinical trials. To assess its preclinical toxicity, CI-994 was administered orally as suspensions to Wistar rats (10/sex/dose) and in capsules to beagle dogs (3/sex/dose) once daily for two weeks. Doses were 1.5, 5, and 15 mg/kg for rats (9, 30, and 90 mg/m2, respectively), and 0.5, 2, and 5 mg/kg for dogs (10, 40, and 100 mg/m2, respectively). Systemic exposure was dose-proportional based on toxicokinetic analysis in dogs. Severe clinical signs and mortality occurred at the highest dose in both species beginning on Day 10. Neutropenia, lymphocytopenia, thrombocytopenia, lymphoid depletion, bone marrow hypocellularity, and testicular degeneration were observed in both species, primarily at the mid- and high-doses. Despite continued treatment, neutrophil counts in dogs returned to control levels in Week 2. Other microscopic findings in rats included splenic hematopoietic depletion at all doses and epithelial cell necrosis in various tissues at 15 mg/kg. Additional bone marrow changes in dogs involved myeloid and megakaryocyte hyperplasia at 2 mg/kg and abnormal myeloid and megakaryocyte maturation at 2 and 5 mg/kg. Except for the testicular effects in both species, all changes were reversible within a 4-week (rat) or 9-week (dog) recovery period. The results of these studies show that target organ effects of CI-994 principally involve tissues with rapidly dividing cell populations and that bone marrow suppression is the dose-limiting toxicity. CI-994 also seems to interfere with the release and/or maturation of cells in the bone marrow.     

X gene and precore region mutations in the hepatitis B virus genome in persons positive for antibody to hepatitis B e antigen: comparison between asymptomatic "healthy" carriers and patients with severe chronic active hepatitis

Hepatitis B virus (HBV) carriers with antibody to hepatitis e antigen comprise asymptomatic carriers (ASCs), who have low replication levels of HBV, and patients with chronic active hepatitis (CAH), who have high levels of viral replication. To investigate whether defects in the X protein might be responsible for this difference in the level of viral replication, nucleotide sequences of X and precore gene regions in serum HBV were analyzed in 19 ASCs and 9 CAH patients. All patients had a point mutation creating a stop codon in the precore region. Seventeen ASCs (87.3%) had identical mutations consisting of 4 noncontiguous 1-bp deletions or an 8-bp deletion, both of which truncate the normal X protein, whereas no CAH patient had an X gene mutation (P < .001). Thus, deletion of the X protein might be responsible for the low levels of viral replication in ASCs.