Somatic diversification and affinity maturation of IgM and IgG anti-DNA antibodies in murine lupus

Molecular events occurring during the process of generation of pathogenic immunoglobulin (Ig)G anti-DNA antibodies in systemic lupus erythematosus (SLE) were studied using a newly established method. We analyzed the Ig variable (V) region gene sequence and DNA-binding activity of IgM and IgG anti-DNA monoclonal antibodies (mAb) from individual SLE-prone (NZB x NZW) F1 mice. The first event appeared to be clonal selection and expansion of IgM anti-DNA clones, in which several clones had intraclonal V gene mutations. Although the number of mutations was small, the mutated IgM clones were associated with an increase in DNA-binding activity. The somatic mutations located in complementarity-determining regions (CDR) and in framework regions (FR) of V genes were apparently related to changes in DNA-binding activity. IgG anti-DNA clones that progressively increased in number with aging had numerous somatic mutations in the V region genes and there was a pair of clones which showed an intraclonal accumulation of mutations, in association with increase in the DNA-binding activity. All these findings show that somatic mutations associated with affinity maturation of the V region begin immediately before isotype-switching from IgM to IgG of the clones that have been selected and expanded, in an antigen-driven manner and/or by other forces. We propose that further accumulations of intraclonal somatic hypermutation, in association with selection and expansion of high affinity IgG clones, may lead to formation of highly pathogenic anti-DNA antibodies.     

Characteristics of germanium thin film thermometers for use at low temperatures

Germanium, thin films to be used as resistance thermometers have been tested at liquid helium temperature. Germanium is deposited in vacuum on insulated substrates and then silver is deposited onto the germanium films as ohmic contacts. Thermometers with desired resistances and suitable sensitivities can be easily fabricated by choosing proper deposition conditions. These thermometers have a quick response time and can be used to measure rapidly changing surface temperatures.The film resistance can be expressed as a function of temperature by a simple correlation, log R = C₀ + C₁ log T, between 4.2 K and 20 K. The sensitivity is approximately 20 Ω/K^?1 at 4.2 K. After 50 thermal cycles, the resistance at liquid helium temperature increased slightly, but is reproducible to within 0.8%. An estimated heat capacity of the germanium film is 2 × 10^?8 J K^?1, and a thermal relaxation time is of the order of 10^?12 s at 4.2 K.A stainless steel ribbon with the thermometers deposited on its surfaces is heated by a direct current in a liquid helium pool, and the surface temperature is measured. Large temperature oscillations due to occasional liquid solid contacts are observed.     

Thermal performance test of the hot gas ducts of HENDEL

A hot gas duct provided with internal thermal insulation is to be used for high-temperature gas-cooled reactors (HTGR). This type of hot gas duct has not been used so far in industrial facilities, and only a couple of tests on such a large-scale model of a hot gas duct have been conducted. The present report deals with the results of the thermal performance of the single tube type hot gas ducts which are installed as parts of a helium engineering demonstration loop (HENDEL).Uniform temperature and heat flux distribution at the surface of the duct were observed, the experimental correlations being obtained for the effective thermal conductivity of the internal thermal insulation layer. The measured temperature distribution of the pressure tube was in good agreement with the calculation by a TRUMP heat transfer computer code. The temperature distribution of the inner tube of the co-axial hot gas duct was evaluated and no hot spot was detected.These results would be very valuable for the design and development of HTGR.     

Stress analysis of core support post in a very high-temperature reactor

A very high-temperature gas-cooled reactor (VHTR) has been developed by Japan Atomic Energy Research Institute and its core consists of so-called fuel blocks, removable reflector blocks and so on. These graphite blocks are supported by thin cylindrical graphite bars called support posts. These posts are in contact with the blocks through hemispherical seats to absorb the relative displacement of blocks by small inclination or rotation of the posts.Stress distributions and stress concentration coefficients of the support post under the reactor core weight are analysed by means of photoelastic experiment and compared with two-dimensional calculation by using the finite element method.

The following are the conclusions we have derived:

1. (1) Stress concentration coefficients of the post are expressed uniquely as a function of regardless of the shapes of model and material properties.

2. (2) Inclination of the post caused by small rotation has little effect on the stress concentration coefficients.

Characterization of the extracts and residues from CS2-N-methyl-2-pyrrolidinone mixed solvent extraction

The extracts and residues obtained by extraction of five bituminous coals with CS₂-N-methyl-2-pyrrolidinone mixed solvent (1:1 by volume) were characterized at room temperature. The extraction yields were 31.1–63.0% (daf) and the extracts were fractionated into acetone soluble (AS), acetone insoluble-pyridine soluble (PS) and pyridine insoluble-mixed solvent soluble (MS) fractions. The MS fraction, which was the heaviest fraction examined, had higher values of % oxygen, f_a, molecular weight and spin concentration than the corresponding AS and PS fractions, but a similar degree of aromatic condensation. The quantities of volatile matter (daf) in the residues were similar or slightly less than those in the extracts.