Modeling of Diffusion in Capillary Porous Materials During the Drying Process

This paper presents a model of heterogenous diffusion in capillary porous materials during the process of drying. The governing heat and mass transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by considering the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the moisture and temperature dependent thermophysical properties of the product. All equations have been established in spherical coordinates but the programme written for the purpose of calculations can be used for other geometries also. Numerical calculations have been performed for gas concrete and tiles using model 1, while model 2 has been used for gas concrete only because of the lack of data for thermophysical properties of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions of the drying process were reasonably accurate.     

Polymer networks based on α,ω-methacrylate-terminated poly(1,3-dioxolane)

α,ω-Methacrylate-terminated poly(1,3-dioxolane)s (polyDXL) were synthesized by cationic ring-opening polymerization of DXL in the presence of methylene-bis(oxyethylmethacrylate) as transfer agent. If the initiator concentration is small compared with the transfer agent concentration, the molecular weights of the polymers are governed by the ratio of the reacted monomer to the reacted transfer agent. The α,ω-methacrylate-terminated polyDXLs obtained undergo free radical polymerization with formation of polyacetal networks. The properties of the networks as function of the molecular weight of the corresponding prepolymers are reported.     

Chemistry of the pyrrolo[1,2-alpha]benzimidazole antitumor agents: influence of the 7-substituent on the ability to alkylate DNA and inhibit topoisomerase II

This study addresses the influence the 7-substituent on the cytotoxicity of pyrrolo[1,2-alpha]-benzimidazole quinones possessing a 6-aziridinyl group (PBIs) and a 6-acetamido group (APBIs). Reduction of a PBI to the aziridinyl hydroquinone results in both nucleophile trapping (alkylation) and 1,5-sigmatropic shift reactions. The latter process is essentially an internal redox reaction wherein the hydroquinone causes reductive opening of the aziridinyl ring. The 7-substituent controls the fate of the aziridinyl ring by means of steric and electronic effects. An electron-rich 7-substituent favors the 1,5-sigmatropic shift reaction. If the 7-substituent distorts the 6-aziridinyl group from the conformation required for the 1,5-sigmatropic shift, then nucleophile trapping occurs. The 7-methyl substituent results in significant nucleophilic trapping, and the 7-unsubstituted and 7-methoxy substituents favor the 1,5-sigmatropic reaction. Thus, the 7-methyl PBIs show the most cytotoxicity of the analogues studied. The APBIs are cytotoxic only as quinones, and reduction to the hydroquinone results in loss of activity. Consistent with this observation, the change from 7-methyl to the more electron-rich 7-methoxy results in a substantial loss of APBI cytotoxicity as well as decreased topoisomerase II inhibition. The mechanism of inhibition is thought to involve the interacalation of only electron deficient APBIs into DNA.     

The effects of growth hormone in children with a GH deficiency: a report of 5 cases

The authors describe 5 cases, 3 boys and 2 girls, with idiopathic growth hormone deficiency in prepubertal age, treated with human growth hormone. In four of five cases the response to treatment with GH was relevant. Only in one case (F1) the response was negative. The results of this study confirm that rhGH is a safe and effective therapy in children with GHD.     

Low-temperature phase transformation in Li-10 at. % Mg

It is not known whether impaired hematopoiesis noted during human immunodeficiency virus (HIV) infection results from infection of stem/progenitor cells or of cells of the bone marrow microenvironment. Normal adherent primary stromal layers were exposed to HIV to determine which of this mixture of endothelial cells, fibroblasts, and macrophages are susceptible to the virus. Viral p24 in supernatants was noted with monocytotropic HIV-1Ada, HIV-1Ba-L, and HIV-1JR-FL but not with lymphotropic HIV-1LAI nor HIV-1MN strain, and only stromal macrophages expressed the viral antigens. Coculture of the layers with PHA-activated normal lymphocytes failed to rescue lymphotropic virus. No p24 was produced when macrophage-depleted stromal cells were exposed to either HIV-1Ba-L or HIV-1LAI; proviral DNA was then amplified by PCR in cells exposed to either virus, though coculture with lymphocytes rescued only HIV-1Ba-L. Altogether, these data indicate that macrophages are the major targets of HIV in cultured stromal layers. As virus replication in macrophages did not affect the profile of major cytokines involved in regulating hematopoiesis, HIV infection could alter hematopoiesis by other as yet unspecified mechanisms.     

Increasing the interference immunity of broadband systems for measuring and transmitting information by utilizing nonlinear signal processing methods

A method is considered for increasing the immunity from interference of broadband systems for measuring and transmitting information. It is based on utilizing nonlinear methods to process spread-spectrum signals. The possibility is investigated of using a quasioptimal receiving device which can be implemented in practice. It is shown that the proposed method makes it possible to solve the rejection problem at the physical level. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 13–15, November, 1996.     

Nitric oxide reduction and carbon monoxide oxidation over carbon-supported copper-chromium catalysts

Carbon supported copper-chromium catalysts are shown to be very active for both the reduction of nitric oxide with carbon monoxide and the oxidation of carbon monoxide with oxygen. Mixed copper-chromium oxide active phases have good activity in the simultaneous removal of nitric oxide and carbon monoxide from exhaust gases. The influence of several catalyst variables has been investigated. The activity per volume of catalyst increases with increasing loading, while the intrinsic activity shows a maximum around C/M=100−50. An optimum catalyst for nitric oxide reduction and carbon monoxide oxidation has a copper/chromium ratio of 2/1. The apparent activation energy for the carbon monoxide oxidation over carbon supported copper-chromium catalysts is 77 kJ/mol, suggesting that the Cu---O bond rupture is the rate-limiting process. The reduction of nitric oxide takes place at higher temperatures. Since all catalysts have a low selectivity for molecular nitrogen formation at lower temperatures, the dissociation of nitric oxide is probably rate determining, resulting in a slightly reduced catalyst system. In an excess of carbon monoxide the reaction is first-order in nitric oxide and zero-order in carbon monoxide. Moisture inhibits the reaction by reversible competitive adsorption, whereas carbon dioxide does not. Oxygen completely inhibits the reduction of nitric oxide due to the more rapid reoxidation of the catalytic sites compared to nitric oxide. Therefore, the reduction of nitric oxide takes place only when all oxygen has been converted and, hence, is shifted to higher temperatures. As a possible consequence, the production of nitrous oxide is reduced. Nitric oxide and molecular oxygen react preferentially with carbon monoxide, so, in an excess of oxidizing component, gasification of the carbon support occurs at higher temperatures after carbon monoxide has been completely consumed.     

Health promotion and empowerment: reflections on professional practice

Recent reformulations of health promotion focus on empowerment as both a means and an end in health promotion practice. Both concepts, however, are rarely examined for their assumptions about social change processes or the potential of community groups, professionals, and institutions to create healthier living situations. This article attends to some of these assumptions, expressing ideas generated during 6 years of professional training workshops with over 2,500 community health practitioners in Canada, New Zealand, and Australia. The article first argues that health promotion is not a social movement but a professional and bureaucratic response to the new knowledge challenges of social movements. As such, it has both empowering and disempowering aspects. The article analyzes empowerment as a dialectical relation in which power is simultaneously given and taken, and illustrates this in the context of health promotion programs. A model of an empowering professional (institutional) health promotion practice is presented, in which linkages among personal services, small group supports, community organizing, coalition advocacy, and political action are made explicit. Practice examples are provided to illustrate each level of the empowering relation, and the article concludes with a brief discussion of the model's educational and organizational utility.     

Predictive equation for acquisition of hepatitis B in hospital workers in a general hospital

A cross-sectional study was performed to obtain risk factors for hepatitis B disease, HBsAg carriers and immunised personnel, among 2470 workers in a general hospital in Madrid, Spain. The data obtained were analyzed with multiple logistic regression to obtain beta coefficients for variables. The results of the analysis show that being a nurse or being regularly exposed to blood are the most important risk factors for hepatitis B acquisition. The length of time working at the same job activity was also a risk factor. The resulting beta coefficients allow the construction for a hepatitis non-immunised, HBsAg carrier and immunised HBV status, which can select subjects for a hepatitis B vaccination program.     

Radon as a risk factor for extra-pulmonary tumours

Most divers and diving medicine specialists know that application of normobaric oxygen as first aid after a bubble disease incident is highly effective. However, as yet technical difficulties acted as a deterrent to using normobaric oxygen at the diving site. This can now be overcome by a newer technique. To be efficient, any therapy of bubble disease should follow three main principles: maximal partial pressure of inhaled oxygen (i.e. 100 kpa in normobaric, and 280 kpa in hyperbaric conditions); minimal partial pressure of inhaled nitrogen, which should ideally be near zero; immediate start of therapy, if possible at the diving site, but not later than 2 hours after the onset of the first symptoms. However, it has to be borne in mind that for an efficient normobaric oxygenation (100%), the standard apparatus design without oxygen reservoir is obsolete, for it offers at most 40% oxygen to the lungs. Currently the following technical approaches for an efficient normobaric oxygenation are available: open one-way systems with tightly fitting mask and oxygen reservoir bag (type Ambu or Leardal, etc.); open systems with on-demand regulation and tightly fitting mouth piece (type SCUBA, or Bird-respirator); closed systems with CO2 absorber (type oxygen rebreathing diving gear). The closed system is a genuine technical advance, because it needs 15 times less oxygen than open systems (about 90 liters oxygen for a 3-hours oxygenation run). Such an apparatus is thus of light weight, far less cumbersome, and nevertheless highly efficient. The therapy should start immediately at the site of the mishap and be maintained during the transport to the next HBO-unit (usually 3 to 6 hours).(ABSTRACT TRUNCATED AT 250 WORDS)