Influence of stress concentrators on the temperature dependence of the liquid metal embrittlement of Armco iron

We study temperature dependences of the effects of liquid indium and lead-bismuth eutectics on the ultimate strength and tensile elongation of Armco iron. Tests were performed on Armco iron cylindrical specimens with stress concentrators and with square cross section under active strain with a rate of 8.3 · 10^–4 s^–1. It was found that, under identical test conditions, the decrease in the ultimate strength of the specimens with concentrators caused by the effect of melts occurs in a broader temperature range than the embrittlement of specimens without concentrators. The effect of liquid metal also depends on the size of the grains in iron (26 – 110 µm) but its character is different for specimens with and without concentrators.Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 29, No. 5, pp. 65–72, September–October, 1993.     

X-Ray luminescence of polycrystalline TbO<Subscript>2</Subscript>-doped Li<Subscript>2</Subscript>B<Subscript>4</Subscript>O<Subscript>7</Subscript>

This paper examines the effect of doping level on the X-ray luminescence of TbO₂-doped polycrystalline lithium tetraborate. It is shown that, when interpreting such spectra, it is convenient to proceed from the terms of free activator and constituent ions. We demonstrate that the emission lines of Tb³⁺ in doped polycrystalline lithium tetraborate are effectively excited in the band between 350 and 650 nm, which is predominantly due to electron transitions from the ⁵ D ₃ and ⁵ D ₄ excited states to spin-orbital levels of the ⁷ F _J ground multiplet. The emission lines of lithium and boron in single-crystal and polycrystalline undoped lithium tetraborate are effectively excited in the band between 274 and 550 nm.     

Influence of Microstructure on the Strength and Cyclic Crack Resistance of Cast Irons

We study the influence of microstructure of high-strength cast irons of ferritic, ferritic-pearlitic, and pearlitic classes on the characteristics of strength and cyclic crack resistance and establish the relationship between the characteristics of strength and cyclic crack resistance and the chemical composition and microstructural parameters of the matrix and graphite inclusions of high-strength cast irons. Indeed, the ultimate strength _u = 750–850 MPa, fatigue threshold K _th = 8–10 MPa , and cyclic fracture toughness K _fc = 50–60 MPa are guaranteed by the pearlitic matrix and the following parameters of the graphite phase: the content of graphite f _p 10%, the degree of its spheroidization of about 95%, the size of globules d _gl 20–50 m, and the distance between them 40–70 m, obtained in high-strength cast irons containing (wt.%): 3.2–3.5 C, 1.9–2.5 Si, 0.35–0.4 Mn, and 0.05 Mg.     

Demand-controlled desynchronization of oscillatory networks by means of a multisite delayed feedback stimulation

We study the potential of delayed feedback stimulation administered via multiple sites to control the synchronization and the spatio-temporal activity pattern within a network of oscillators. Two models with different levels of complexity are investigated: an ensemble of phase oscillators is used to study and analyze the effects of the stimulation in detail and a microscopic model is presented to exemplify the effectiveness of the method in terms of a stable desynchronization continuously maintained under realistic conditions. The investigation shows that depending on the spatial stimulation profile a multi-cluster state or a fully desynchronized state results. Both states are characterized by a strong suppression of the first order parameter indicating a strong desynchronization. Multisite delayed feedback stimulation realizes a demand-controlled stimulation which stabilizes the desired desynchronized state while the used stimulation current is minimized. We propose the method to be tested as a therapy of diseases characterized by pathological synchronization and for the therapy of defective neuronal pattern generators.     

Wounds of the heart

The frequency of wounds of the heart as the cause of lethal outcomes on the battle-field practically has not changed during the recent 50 years and is equal to 80%. At the same time, the danger of such complications as infectious endocarditis has increased. The author's experience with surgical treatment of gunshot wounds of the heart makes 85 cases. Symptoms of intracardiac infection were detected in 74% of the wounded, 52 of them having the septic form. Operations were performed under artificial circulation. They included the extraction of foreign bodies, complex sanitation of the heart chambers and recovery of intracardiac hemodynamics. There were no lethal outcomes in the nearest postoperative period. Success of the treatment depends on terms of delivery of the patient to the hospital, quickness of surgical intervention and adequate intensive therapy.     

The debatable aspects of the adhesive syndrome

The commissural intestinal obstruction and commissural disease are two variants of the commissural syndrome characterized by a complete or partial disturbance of the intestinal transit. The data of 390 clinical observations have shown that choice of methods of treatment must be based on the topical diagnosis of the syndrome such as the establishment of the place of obstruction and assessment of the degree of the intestinal transit disturbance. In the both cases a new roentgenological technique of investigation can be used with contrast labels. The new approaches to medical tactics allowed the time of diagnosing the commissural syndrome to become shorter and to considerably improve the direct results of the operative procedures.     

Optical-luminescence properties of ZnO and TiO2 nanopowders obtained by pulsed laser reactive ablation

Journal of Materials Science: Materials in Electronics - The ZnO and TiO2 nanopowders have been prepared by means of the pulsed laser reactive ablation of metallic (Zn, Ti) targets. The Structural,...