Redistribution of alloy elements in aging of austenitic chrome-manganese steel containing nitrogen

Conclusions In interrupted decomposition of the austenite of chrome-manganese steel containing nitrogen in the 600–900°C range the alloy element content in the nitride phase formed changes. The quantity of chromium increases while that of iron decreases significantly. The manganese content in the nitride is low and remains approximately constant.The residual austenite in the grains which have undergone interrupted decomposition is gradually depleted of chromium and nitrogen.The growth of pearlitelike colonies consisting of transformed austenite and type M₂N nitride is controlled simultaneously by the mechanisms of grain-boundary and three-dimensional diffusion.Institute of Metallurgy and Metals Technology, Sofiya, Peoples Republic of Bulgaria. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 60–61, November, 1988.     

BINARY CONTROL OF FERMENTATION PROCESSES

In this paper a binary control for nonlinear and uncertain systems is proposed. In particular, continuous fermentation processes are considered. The control design is carried out with the direct use of a nonlinear model, expert knowledge, and an on-line measurement of output variable only. Asymptotic stability of the closed-loop systems in the presence of parameter uncertainties and external disturbances is guaranteed. Simulation investigations are performed. The results obtained prove that the designed binary control is especially suitable for the stabilization of nonlinear and uncertain fermentation processes.     

Secondary amyloidosis in Hodgkin's disease

One case with secondary amyloidosis is described, manifested by a nephrotic syndrome, 13 years after the establishment of lymphogranulomatosis in a male, ages 46. Amyloidosis diagnosis with biopsy, after a long-term remission in a patient with a relatively restricted lymphogranulomatosis is of certain interest. The diagnostic difficulties of secondary amyloidosis in Hodgkin disease are discussed as well as the mechanism origination and the role of certain medicaments in amyloidosis origination and treatment.     

Improvement of lipoprotein lipid composition in type II diabetic patients with concomitant hyperlipoproteinemia by acipimox treatment. Results of a multicenter trial

OBJECTIVE: To study the tolerability and efficacy of acipimox on hyperlipidemia and diabetes compensation in patients with NIDDM under conditions of a routine clinical practice. RESEARCH DESIGN AND METHODS: We recruited 121 patients (60 men and 61 women) from 10 participating clinical centers. They were randomly divided into two groups and treated for 3 mo either with acipimox (250 mg three times a day) or placebo, using an open study design. RESULTS: Acipimox treatment led to a significant drop in fasting serum total triglyceride levels (by 28%) after 1 mo of drug administration. This decrease prevailed up to the end of the 3-mo study. Serum total cholesterol levels declined by 14%, and high-density lipoprotein tended to rise in acipimox-treated patients. These changes in lipid metabolism were not accompanied by any adverse effects of acipimox on glucose metabolism as judged by HbA1c measurements and the oral glucose tolerance test. Eight patients (out of 82 treated with acipimox) reported moderate adverse events of transient character, such as skin reactions and gastric disturbances. CONCLUSIONS: Acipimox seems to be a useful agent for treatment of diabetic dyslipidemia and does not deteriorate glycemic control.     

Resonant Raman and micro-Raman scattering from Si matrix with unburied beta-FeSi2 nanolayers

Samples, representing Si matrix with nanolayers of the semiconducting beta-FeSi2 silicide are studied by Raman scattering. The unpolarized Raman spectra of the samples are measured in two different configurations. It is found that the characteristic beta-FeSi2 Raman modes are seen in the spectra, taken at incident angle of about 45 degrees , while only comparatively intensive broad feature is detected in a back-scattering geometry. The difference in the spectra is interpreted with the appearance of surface polariton modes of the optical phonons in the nanosized layers in near back-scattering geometry. The resonant Raman scattering is investigated at incident light angle of about 45 degrees and the energies of the interband transitions in the investigated energy range are determined. It is known that the resonant Raman scattering appears to be even more precise method for the determination of the interband transitions energies than the modulation spectroscopy. Thus we claim that the energies determined here are firstly determined with such a precision.     

Structure and properties of thermoluminescent calcium fluoride glass-ceramic materials

New types of material for use inγ-dosimetry described here are glass-ceramics and silicate glass-ceramic enamels with thermoluminescent properties containing up to 30 wt% CaF₂ doped with MnO₂ and rare earth oxides. The structure and thermoluminescent properties of these materials have been investigated by applying a variety of complementary methods: X-ray analysis, electron microscopy, differential thermal analysis, electron paramagnetic resonance measurements and volume dilatometry. Thermal history, i.e. phase composition and degree of crystallinity, largely determines the thermoluminescent properties of the vitro-crystalline materials investigated. Optimal heat treatment favouring appropriate crystallization leads to a maximum in thermoluminescent intensity. Completely amorphous materials containing 20 to 30 wt% CaF₂ in the form of a glassy solution are devoid of any thermoluminescence. The thermoluminescent properties of natural fluorite are compared with those of synthetic materials.     

Raman scattering of Si matrix with randomly distributed nanoparticles of semiconducting silicides

Samples, representing Si matrix with nanoformations of the semiconducting silicides beta-FeSi2 and Mg2Si are studied by Raman scattering. The unpolarized Raman spectra of the samples are interpreted in the framework of the appearance of interface-phonon polaritons. The theoretical dispersion relations of the interface-phonon polaritons in the system Si/silicide/Si are obtained from the Maxwell equations. The correspondence of the theoretical calculations and the experimental observations appeared to be sufficiently good. An evolution of the features in the Raman spectra on the experimental conditions is observed.     

The kinetics and mechanism of crystallization in enstatite-type glass-ceramic materials

The general crystallization behaviour of a model glass-forming melt having a composition (wt%) 7.5 SiO₂ · 1.0 Al₂O₃ · 1.0 MgO · 1.5 CaO + 10 TiO₂ is investigated. The composition and the morphology of the crystalline phases formed in the system and the structure of the resulting glass-ceramic material are examined by X-ray diffraction, electron microscopy and DTA. Detailed kinetic measurements indicate that the process of nucleation of the initially formed anosovite-type phase may be described from the viewpoint of the non-steady state theory of nucleation. It is also demonstrated that the crystal growth of the spherulites in this phase is diffusion-limited. The role played by TiO₂ in the system under investigation and in similar glass-forming melts is also discussed.