Experimental evidence for thermal generation of interstitials in a metallic crystal near the melting temperature.

The only intrinsic point defects of simple crystalline metals known from solid state physics are vacancies and interstitials. It is widely believed that while vacancies play a major role in crystal properties and their concentration reaches relatively big values near the melting temperature T m, interstitials essentially do not occur in thermodynamic equilibrium and their influence on properties is minor. Here, taking aluminum single crystals as an example, we present compelling experimental evidence for rapid thermoactivated growth of interstitial concentration upon approaching T m. Using high precision measurements of the shear modulus we found a diaelastic effect of up to [Formula: see text] near T m. It is argued that this effect is mostly due to the generation of dumbbell (split) interstitials. The interstitial concentration c i rapidly increases upon approaching T m and becomes only 2-3 times smaller than that of vacancies just below T m. The reason for this c i -increase is conditioned by a decrease of the Gibbs free energy with temperature, which in turn originates from the high formation entropy of dumbbell interstitials and a decrease of their formation enthalpy at high c i . Special molecular dynamic simulation confirmed all basic aspects of the proposed interpretation. The results obtained (i) demonstrate the significance of interstitial concentration near T m that could lead to the revaluation of vacancy concentration at high temperatures, (ii) suggest that dumbbell interstitials play a major role in the melting mechanism of monatomic metallic crystals and (iii) support a new avenue for in-depth understanding of glassy metals.

[Effect of toxins of cyanobacteria of the Microcystis genus from the Shershnevo Reservoir on DNA, cell cycle, and apoptosis of bone marrow cells in CBA mice].

The effect of toxins of a Cyanobacterium sample of the Shershnevo Reservoir on DNA, which was presented by cyanobacteria of the Microcystis genera, on the bone marrow of male CBA mice (whose age was 3 months and weight 24 g) was evaluated. With intraperitoneal administration, LD50 and LD16 of this sample for male CBA mice were 48.4 and 42.1 mg/kg, respectively. Administration of Microcystis cyanobacterial sample from the Shershnevo Reservoir in doses of 1/10 of LD16 and 1/2 of LD16, and LD16 was found to cause a dose-dependent reduction in the number of bone marrow nucleated cells, a dose-dependent increase in the rate of cell apoptotic death, a reduction in the duration of a cell cycle (within the first 12 hours), which gave way to an increase in the duration of the cycle 24 hours after administration, a dose-dependent increase in the frequency of micronuclei in the murine bone marrow eryphrocytes, and a dose-dependent decrease in the polychromatophil/normochromatophil ratio in the murine bone marrow.

[Evaluation of the toxic properties of cyanobacteriae of the Shershnevo water storage basin in the Chelyabinsk Region].

The toxic properties of cyanobacteriae of the Shershnevo water storage basin have been studied. Over almost the whole vegetative period of 2005, the cyanobacteriae of the Shershnevo water storage basin may be characterized as high toxic (when intraperitoneally injected to male CBA mice, LD50 was less than 100 mg/kg). There were no interspecific differences between the noninbred animals in cyanotoxin susceptibility. Gender differences were revealed in cyanotoxin susceptibility in CBA and noninbred albino mice: quantitative differences in LD50 (males/females) were 1.34 in CBA mice and 1.3 times in noninbred albino mice. The cyanobacteriae of the Shershnevo water storage basin were found to have an irritating effect on the skin and ocular mucosa. It is suggested that the toxins of Shershnevo water storage basin cyanobacteriae may have a damaging effect on human beings.

[Preliminary data on combined assessment of tolerance to exercise, left ventricular contractile function in ischemic heart disease patients taking bradycardic agents]. / Predvaritel'nye dannye o kombinirovannoi otsenke tolerantnosti k fizicheskoi nagruzke, perfuzii miokarda i sokratitelnoi funktsii levogo zheludochka u bol'nykh ishemicheskoi bolezn'iu serdtsa na fone priema preparatov s bardikardicheskim deistviem.

AIM: To study effects of bradicardia induced by atenolol, diltiazem and ivabradin on exercise tolerance, myocardial perfusion and left ventricular contractile function in patients with stable angina pectoris. MATERIAL AND METHODS: The trial included 7 male patients aged 57 +/- 2.6 years with coronary heart disease, stable angina of functional class II free of cardiac failure and severe arterial hypertension, with a positive and reproducible VEM test after therapy discontinuation. For 10 consecutive days with 5-day intervals, all the patients received atenolol, diltiazem, ivabradin in doses lowering heart rate at rest by 20% from the initial level. Before the treatment all the patients were studied with VEM test, perfusion synchronized single-photon emission computerized tomoscintigraphy of the myocardium (PSSPECT) at rest and exercise. On day 10 of each drug intake PSSPECT and VEM test were performed if the expected heart rate was achieved. RESULTS: Each of the studied drugs resulted in a 22-24% reduction in the heart rate at rest accompanied by a significant rise in exercise tolerance, improvement of performance and myocardial perfusion. There were no significant changes in left ventricular contractility. CONCLUSION: A 20% reduction in resting heart rate due to monotherapy with drugs having a bradicardic effect leads to positive changes in exercise tolerance and myocardial perfusion.

[Atenolol induced bradycardia in patients with stable angina: effects on exercise tolerance, myocardial perfusion and left ventricular contractility]. / Vliianie bradikardii pri monoterapii atenololom na tolerantnost' k fizicheskoi nagruzke, perfuziiu miokarda i sokratitel'nuiu sposobnost' levogo zheludochka u bol'nykh so stabil'noi stenokardiei.

AIM: To assess effects of atenolol-induced heart rate decrease on myocardial perfusion, left ventricular contractility and tolerance to exercise in patients with chronic coronary artery disease. MATERIAL AND METHODS: Twenty eight men (mean age 54,5-/+9,2 years) with stable class I-III angina and positive reproducible result of bicycle exercise test underwent rest/stress 99mTc-MIIBI gated single-photon emission computed tomography (SPECT) before and after 10 days of administration of atenolol (20 patients) or placebo (8 patients). Dose of atenolol was titrated to achieve at least 15% decrease of heart rate from baseline. RESULTS: After 10 days of treatment with atenolol heart rate decreased from 78-/+3.1 to 59-/+1.1 bpm (p=0.01), whereas in placebo group there were no significant changes. Compared with placebo, treatment with atenolol was associated with significant decreases in extent and severity of perfusion defects, ischemic score and number of ischemic segments. No significant changes of parameters of left ventricular contractility occurred. Treatment with atenolol was associated with symptomatic improvement and increase of the total exercise time. CONCLUSION: Heart rate lowering during monotherapy with atenolol was associated with improvement of myocardial perfusion and tolerance to exercise.