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Abstract: Proposed mathematical and software analysis of reactor experiments allowed interpretation of the experimental results of a tritium release study. Tritium was continuously generated by the reaction of lithium-6 with thermal neutrons for various thermal conditions of lithium metatitanate (Li2TiO3). The main gas release parameters were calculated in order to assess the potential use of lithium metatitanate in tritium breeders. These parameters were: gas release rate, tritium retention, retention time, activation energy for thermal desorption as HT, activation energy for volume diffusion as Т+, and the corresponding pre-exponential (frequency) indexes. [Copyright &y& Elsevier]

The background for the modelling of radon diffusion release from disordered solids is given and used for the simulation of emanation thermal analysis results characterizing the annealing of structural irregularities that serve as radon diffusion paths in the solids. [ABSTRACT FROM AUTHOR]

A hybridoma (FMC4) has been derived which secretes antibody showing selective reaction with human B lymphocytes. monocytes and some null lymphocytes. Few, if any, T lymphocytes in normal blood are stained, although stimulation of lymphocytes with PHA leads to an increase in the proportion of cells reacting with the hybridoma antibody. The antibody reacts with B and null lymphoblastoid cell lines but not with T cell lines. B chronic lymphocytic leukaemia (CLL) cells but not T-CLLs are stained and null-type acute lymphoblastic leukaemia (ALL) cells but not T-type ALL also react. Normal blood myeloid cells do not react with FMC4 supernatant whilst some myeloid leukaemias do. The expression of the antigen reacting with FMC4 supernatant suggests that FMC4 may secrete an antibody against the human equivalent of the la antigen. [ABSTRACT FROM AUTHOR]

A hybridoma has been isolated from the products of fusion of a myeloma cell line with spleen cells from mice immunized with a human B cell line. After cloning, the hybridoma secretes antibody with the following properties: (i) Human B-lymphohlastoid cell lines react with the antibody while T and null cell lines do not. (ii) The antibody reacts with the majority of leucocytes in the blood of patients with CLL, but with a minority of cells in the blood of patients with A ML or ALL of the null or T type, (iii) The antibody reacts with 9-21% of mononuclear cells in normal peripheral blood. The reacting cells are not T cells and overlap extensively with cells identified as B cells by other markers. The antigen identified by this antibody appears to be distinct from known B cell markers, and is put forward as a new B cell marker with diagnostic potential. [ABSTRACT FROM AUTHOR]

It is well documented that the proliferative capacity of T cells declines with advancing age. There are, however, conflicting data as to the role of the accessory cell and whether or not this loss in responsiveness extends to all T-cell stimuli and to all T cells. We report here on the capacity of subpopulations of peripheral blood CD4+ T cells from the healthy aged to proliferate in response to anti-CD2 receptor-induced activation in the complete absence of accessory cells by using various exogenous cofactors as second signals. These costimulatory factors included phorbol 12-myristate 13-acetate (PMA), interleukin (IL)-1, IL-2, IL-6 and IL-7 and the monoclonal antibodies, anti-CD28 and anti-CD44. Under these conditions, the proliferative responsiveness of CD4+CD45RO+ T cells from the aged was found to be comparable to young control cells for all stimuli tested, except anti-CD2 plus IL-7. This suggests that signal transduction pathways involving CD2, except IL-7-mediated events, are essentially intact in 'old' memory CD4+ T cells. On the other hand, several cofactors, namely IL-2, IL-6, IL-7 and to a lesser extent IL-1β and PMA, failed to support adequately CD2-induced activation in 'old' CD4+CD45RA+ T cells suggesting severe and multiple signalling deficiencies in this subset. [ABSTRACT FROM AUTHOR]

Triggering of the T-cell receptor by anti-CD3 monoclonal antibodies (mAb), for example OKT3, induces accessory cell (AC)-dependent interleukin-2 (IL-2) and IL-2 receptor synthesis, and ultimately, T-celI proliferation. We report on the ability of a HLA-class I specific monomorphic mAb, namely FMC16, to inhibit OKT3-driven T-cell mitogenesis. FMC16 was apparently selective for OKT3 because it did not block Concanavalin A (Con A) or mAb Leu-4 induced proliferation. Moreover, this effect was not due to non-specific toxicity nor interference with OKT3 binding. Kinetic analysis showed that FMC16 was inhibitory when added up to 24 hr after initiation of culture. FMC16 drastically reduced both IL-2 production and IL-2 receptor expression, but did not interfere with IL-2 responsiveness. The inhibitory effects were not altered by the addition of exogenous IL-2 if FMC16 was present at the beginning of culture; however, 11-2 did restore proliferation if FMCI6 was not added until 3 to 6 hr after initiation of culture. This coincided exactly with an IL-2 mediated increase in the level of TAC-positive cells. Furthermore, T-cell activation triggered by the synergistic action of OKT3 and a phorbol ester (TM) in the absence of AC was also blocked by FMC16, suggesting that inhibition was not AC-dependent. Taken together, these results indicate that FMC16 interferes with early signals leading to IL-2 production and IL-2 receptor expression and suggest that HLA-class I determinants play an early role in T-cell activation. [ABSTRACT FROM AUTHOR]

The aim of this study is to characterize the microstructure and high temperature induced structural changes within fiber reinforced silicon carbide (SiC/SiC) composites by means of non-destructive techniques. In order to understand their properties, the characterization of the microstructure of SiC/SiC composites is the crucial issue. Porosity within composites is unavoidable with currently available manufacturing processes, and reduces significantly the life time and performance of the composites under harsh environments. Moreover, the internal pores, created in the manufacturing process cause the degradation most of the outstanding properties such as thermal conductivity, mechanical properties at high temperature, and radiation stability. Cold neutron tomography and diffusion structural diagnostic techniques were applied in the investigation of the microstructure of SiC/SiC composites to gain complementary information. One of the main obstacles to using these composites in fusion technology and other applications are a change of the porous structure and a swelling at high temperatures and in a severe radiation environment. Cold neutron tomography enables visualization of the microstructure of the composite and consequently the pore distributions within the SiC/SiC composite were observed with a suitable resolution. The diffusion structural diagnostic technique was used to characterize the thermal behavior of SiC/SiC composites on heating up to 1300 °C. [ABSTRACT FROM AUTHOR]

Vascular damage, initiated by host inflammatory cells, is a component of the pathophysiology of many acute and chronic inflammatory disorders. Neutrophil-mediated tissue damage is mediated primarily hyproteinases, particularly elastase and cathepsin G. In this study we have identified endothelial binding of two key serine proteinase inhibitors (serpins), α1-antitrypsin, the inhibitor of elastase, and α1-antichymotrypsin, the inhibitor of cathepsin G. These serpins are shed from the endothelium into the supernatant when neutrophils adherent to the endothelium are activated. Endothelium activated by lipopolysaccharide (LPS) augments this process, Serpin-proteinase complexes activate neutrophils and induce further cytokine release, thereby amplifying inflammatory processes. Strategies aimed at preventing endothelial serpin depletion may help minimize vascular damage during inflammation. [ABSTRACT FROM AUTHOR]

The method of emanation thermal analysis (ETA), based on the measurement of radon release from samples, has been used in the investigation of the tricalcium-silicate (CaSiO) to characterize the microstructure development during the sample hydration. Results of the ETA made it possible to obtain the diffusion structural diagnostics of the material under in situ conditions of it is hydration. The influence of temperature and surface area of the tricalcium-silicate sample on kinetics of the sample hydration was characterized. Computer modeling of time dependences of radon release rate during hydration of tricalcium-silicate was carried out. A good agreement of the numerical model with the experimental results of the radon release was found. [ABSTRACT FROM AUTHOR]

Portland cement hydration has been investigated by emanation thermal analysis (ETA), based on the application of radon atoms as radioactive indicators. This method enabled us to characterize continuously changes in the microstructure of the cement paste at selected temperatures. The numerical simulation of time dependences of the emanating rate during cement hydration was carried out. An agreement between the mathematical model and experimental results of the ETA was obtained. [ABSTRACT FROM AUTHOR]

Brannerite based ceramics, designed as a matrix for immobilization of high level radioactive waste (HLW), was investigated from the viewpoint of microstructure changes and atomic transport properties caused by leaching of the ceramics at pH 2 and 11, respectively. Scanning electron microscopy (SEM) and emanation thermal analysis (ETA) techniques were used for this purpose. Surface morphology, microstructure changes and transport properties of both ‘as-leached’ and ‘as-prepared’ samples were compared and the effect of leaching on the thermal behavior of the ceramics samples heated in the temperature range from 20 to 1250°C was characterized. The mobility of radon in the brannerite ceramics was evaluated by mathematical modeling from ETA results. The thermal behavior of the non-leached brannerite ceramics sample and its natural analogue brannerite mineral was compared using the ETA. [ABSTRACT FROM AUTHOR]

Thermal behavior of talc samples (from locality Puebla de Lillo, Spain) were characterized by emanation thermal analysis (ETA), DTA and TG. The ETA, based on the measurement of radon release rate from samples, revealed a closing up of surface micro-cracks and annealing of microstructure irregularities of the talc samples on heating in the range 200–500°C. For ground talc sample a crystallization of non-crystalline phase formed by grinding, into orthorhombic enstatite was characterized as a decrease of radon mobility in the range 785–825°C and by a DTA exothermal effect with the maximum at 830°C. ETA results characterized the microstructure development of the talc samples on heating and served to evaluate their radon mobility and transport properties on heating and cooling. Transport properties of the talc samples were evaluated by using ETA experimental data measured during heating to 600 and 1300°C, respectively, and subsequent cooling to room temperature. [ABSTRACT FROM AUTHOR]

Emanation thermal analysis (ETA) was used to characterize thermal behaviour of the perovskite ceramics designed as a matrix for the encapsulation of high level radioactive waste. The perovskite ceramics (composition CaTiO3 where small admixtures of Nd and Ce simulated the radioactive elements Cm and Pu, respectively) was prepared from sol-gel precursors by hot pressing at 1250°C/29 MPa for 2 h. The chemical durability of the ceramics was tested by leaching in the solution with pH 2 at 90°C/2 months. ETA results of ‘as-leached’ and ‘as-prepared’ perovskite ceramics samples were compared and evaluated by means of a mathematical model. Three temperature ranges of the annealing of structure defects in the ‘as-prepared’ sample were determined from the decrease of radon release rate in the ranges 280-560, 800-960 and 960-1200°C, respectively. One annealing step was determined for the ‘as-leached’ sample from the decrease of radon release rate in the range of 800-950°C. [ABSTRACT FROM AUTHOR]