A study of the thermal conductivity of alumina/glass dispersed composites

The thermal diffusivity of five groups of alumina/glass composite systems has been measured at room temperature using a laser flash system. These data have been used, in conjunction with specific heat and density measurements, to calculate the effective thermal conductivity of these composites. In each of the five groups a systematic variation in glass concentration was made, and each group represents systematic variations in glass and alumina particle sizes. The thermal conductivities calculated are compared with those predicted by four models. It is apparent from these comparisons that the geometry and orientation of porosity within the sample measured are a key factor in determining which of these models (if any) is appropriate for describing the thermal conductivity of these composites.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

CD4 is a critical component of the receptor for human herpesvirus 7: interference with human immunodeficiency virus

In this study, we demonstrate that the glycoprotein CD4, a member of the immunoglobulin superfamily, is a critical component of the receptor for human herpesvirus 7 (HHV-7), a recently discovered T-lymphotropic human herpesvirus. A selective and progressive downregulation of the surface membrane expression of CD4 was observed in human CD4+ T cells in the course of HHV-7 infection. Various murine monoclonal antibodies to CD4 and the recombinant soluble form of human CD4 caused a dose-dependent inhibition of HHV-7 infection in primary CD4+ T lymphocytes. Moreover, radiolabeled HHV-7 specifically bound to cervical carcinoma cells (HeLa) expressing human CD4. A marked carcinoma cells (HeLa) expressing human CD4. A marked reciprocal interference was observed between HHV-7 and human immunodeficiency virus (HIV), the retrovirus that causes the acquired immunodeficiency syndrome and also uses CD4 as a receptor. Previous exposure of CD4+ T cells to HHV-7 dramatically interfered with infection by both primary and in vitro-passaged HIV-1 isolates. Reciprocally, persistent infection with HIV-1 or treatment with the soluble form of gp120, the CD4-binding envelope glycoprotein of HIV-1, rendered CD4+ T cells resistant to HHV-7 infection. These data indicate that CD4 is critically involved in the receptor mechanism for HHV-7. The antagonistic effect between HHV-7 and HIV could be exploited to devise therapeutic approaches to AIDS.     

Water purification from organic pollutants by optimized micelle-clay systems

Removal of anionic pollutants (imazaquin, sulfentrazone, sulfosulfuron) and neutral pollutants (alachlor, acetochlor, chlorotoluron, bromacil) from water by micelles preadsorbed on montmorillonite was studied. Micelles of octadecyltrimethylammonium and benzyldimethylhexadecylammonium (BDMHDA) were used. The micelle-clay systems (1% w/w) removed 87-99% of the pollutants from their water solutions containing 1-33 mg/L of herbicide. The nature of the headgroup of the organic cation, which forms the micelles, is critical. Desorption of imazaquin and acetochlor from 0.3% (w/w) suspension of BDMHDA-clay complex after 24 h was around 7% in the range of adsorbed amounts from 0.6 to 15.3 mg/g. These results indicate rather slow rates and small extents of release of pollutants from micelle-clay complexes. Column filters (25 cm) made of a mixture of quartz sand and BDMHDA micelle-clay complex at 100:1 w/w ratio removed at least 99% of above pollutants from initial solutions containing 10 mg/L; 99.5 and 97% of sulfosulfuron and alachlor were removed from their initial solutions containing 200 and 5 microg/L, respectively. These data indicate that micelle-clay complexes are very efficient for water purification from organic contaminants.     

Quantitative mapping of arid alluvial fan surfaces using field spectrometer and hyperspectral remote sensing

Mapping and dating of arid and semi-arid alluvial fans are of great importance in many Quaternary studies. Yet the most common mapping method of these features is based on visual, qualitative interpretation of air-photos. In this study we examine the feasibility of mapping arid alluvial surfaces by using airborne hyperspectral reflective remote sensing methodology. This technique was tested on Late Pleistocene to Holocene alluvial fan surfaces located in the hyperarid southern Arava valley, Israel. Results of spectral field measurements showed that the surface reflectance is controlled by two main surficial processes, which are used as relative age criteria: the degree of desert pavement development (gravel coverage %) controls the absorption feature depths, while the rock coating development influences significantly the overall reflectance of the surface, but its effect on the absorption feature depths is limited. We show that as the percent of the surface covered by gravels increases, the absorption feature depth of the common gravels, in this case carbonate at 2.33 μm, increases as well; whereas the absorption features depth of the fine particle in-between the gravels, decrease (hydroxyl and ferric absorption features at 2.21 μm, and 0.87 μm, respectively), as the fines are removed from the surface. Using these correlations we were able to map the surface gravel coverage (%) on the entire alluvial fan, by calculating the gravel coverage (%) in each pixel of the hyperspectral image. The prediction of gravel coverage (%) is with accuracy of ± 15% (e.g. gravel coverage of 50% can be predicted to be 35% to 65%). Using extensive accuracy assessment data, we show that the spectral based mapping maintained high accuracy degree (R² = 0.57 to 0.83). The quantitative methodology developed in this study for mapping alluvial surfaces can be adapted for other surfaces and piedmonts throughout the arid regions of the world.     

Performance evaluation of polyamide nanofiltration membranes for phosphorus removal process and their stability against strong acid/alkali solution

In this study,a quantitative performance of three commercial polyamide nanofiltration(NF) membranes(i.e.,NF,NF90,and NF270) for phosphorus removal under different feed conditions was investigated.The experiments were conducted at different feed phosphorus concentrations(2.5,5,10,and 15 mg·L~(-1)) and elevated pHs(pH 1.5,5,10,and 13.5) at a constant feed pressure of 1 MPa using a dead-end filtration cell.Membrane rejection against total phosphorus generally increased with increasing phosphorus concentration regardless of membrane type.In contrast,the permeate flux for all the membranes only decreased slightly with increasing phosphorus concentration.The results also showed that the phosphorus rejections improved while water flux remained almost unchanged with increasing feed solution pH.When the three membranes were exposed to strong pHs(pH 1.5 and 13.5) for a longer duration(up to 6 weeks)it was found that the rejection capability and water flux of the membranes remained very similar throughout the duration,except for NF membrane with marginal decrement in phosphorus rejection.Adsorption study also revealed that more phosphorus was adsorbed onto the membrane structure at alkaline conditions(pH 10 and 13.5) compared to the same membranes tested at lower pHs(pH 1.5 and 5).In eonelusion,NF270 membrane outperformed Nf and NF90 membranes owing to its desirable performance of water flux and phosphorus rejection particularly under strong alkali solution.The NF270 membrane achieved 14.0 L·m~(-2)·h~(-1) and 96.5% rejection against 10 mg·L~(-1) phosphorus solution with a pH value of 13.5 at the applied pressure of 1 MPa.     

Feasible Formation of Coalitions Among Autonomous Agents in Nonsuperadditive Environments

Cooperating and sharing resources by creating coalitions of agents are important ways for autonomous agents to execute tasks and to maximize payoff. Such coalitions will form only if each member of a coalition gains more by joining the coalition than it could gain otherwise. There are several ways of creating such coalitions and dividing the joint payoff among the members. In this paper we present algorithms for coalition formation and payoff distribution in nonsuperadditive environments. We focus on a low-complexity kernel-oriented coalition formation algorithm. The properties of this algorithm were examined via simulations. These have shown that the model increases the benefits of the agents within a reasonable time period, and more coalition formations provide more benefits to the agents.