Influence of ionizing radiation on the spectral properties of photo-thermo-refractive glass containing silver nanoparticles

Experimental results on the investigation into the influence of ultraviolet, X-ray, and γ-radiation on the absorption spectra of photo-thermo-refractive glass containing silver nanoparticles have been presented. It is established that the peak position of the silver plasmon absorption band shifts depending on the ionizing radiation type. The observed changes are explained by changes in the particle size and refraction index of the layer surrounding the nanoparticles.     

H3+ cooling in primordial gas

Simulations of the thermal and dynamical evolution of primordial gas typically focus on the role played by H2 cooling. H2 is the dominant coolant in low-density primordial gas and it is usually assumed that it remains dominant at high densities. However, H2 is not an effective coolant at high densities, owing to the low critical density at which it reaches local thermodynamic equilibrium and to the large opacities that develop in its emission lines. It is therefore important to quantify the contribution made to the cooling rate by emission from the other molecules and ions present in the gas. A particularly interesting candidate is the H3+ ion, which is known to be an effective coolant at high densities in planetary atmospheres. In this paper, we present results from simulations of the thermal and chemical evolution of gravitationally collapsing primordial gas, which include a detailed treatment of H3+ chemistry and an approximate treatment of H3+ cooling. We show that in most cases, the contribution from H3+ is too small to be important, but if a sufficiently strong ionizing background is present, then H3+ cooling may become significant.     

Low incidence of myocardial recovery after left ventricular assist device implantation in patients with chronic heart failure

BACKGROUND: Mechanical, histological, and biochemical improvement has been described in patients after left ventricular assist device (LVAD) support. Explantation of the LVADs without heart transplantation has been described in selected patients who received this therapy as a bridge to transplantation. METHODS AND RESULTS: A retrospective review of patients receiving a mechanical bridge to transplantation at Columbia Presbyterian Hospital after July 21, 1991, was performed to determine the incidence of patients in whom the device was successfully explanted. From August 1, 1996, to February 1, 1998, we prospectively attempted to identify potential explant candidates by the use of exercise testing. During this time, we recruited 39 consecutive patients after insertion of the Thermo Cardiosystems vented electric device to participate in the following study. Approximately 3 months after device implantation, a maximal exercise test with hemodynamic monitoring and respiratory gas analysis was performed with the LVAD in the automated mode. The electric device was interfaced with a pneumatic console such that the rate could be decreased to 20 cycles/min. Hemodynamic measurements were recorded as the device rate was decreased. A repeat exercise test was then performed if the patient remained hemodynamically stable. A retrospective chart review of 111 LVAD recipients at our institution identified only 5 successful explant patients. Eighteen of the 39 patients were studied. Fifteen patients exercised with maximal device support. At peak exercise, VO2 averaged 14.5+/-3.6 mL. kg-1. min-1; LVAD flow, 8.0+/-1.3 L/min; Fick cardiac output, 11.4+/-3.3 L/min; and pulmonary capillary wedge pressure, 13+/-4 mm Hg. Seven patients remained normotensive and could exercise at a fixed rate of 20 cycles/min. In these patients, peak VO2 declined from 17.3+/-3.9 to 13.0+/-6.1 mL. kg-1. min-1. In one of these patients, the device was explanted. CONCLUSIONS: Significant myocardial recovery after LVAD therapy in patients with end-stage congestive heart failure occurs in a small percentage of patients. Most of these patients have dilated cardiomyopathy. Exercise testing may be a useful modality to identify those patients in whom the device can be explanted.     

Equation of pressing of nickel powders

Conclusions It was shown experimentally that compaction of different nickel powders during pressing in the 29–490 MN/m² range cannot be described by any one of the investigated equations of pressing.In this pressure range pressing of carbonyl powder is described by Lipson's Eq. (4), whereas pressing of enlarged carbonyl and spherical electrolytic powders in the 98–490 MN/m² is described by a polytropic type Eq. (1). The constants involved in these equations were found.Translated from Poroshkovaya Metallurgiya, No. 2 (74), pp. 11–14, February, 1969.     

Epileptogenesis due to glia-mediated synaptic scaling

Homeostatic regulation of neuronal activity is fundamental for the stable functioning of the cerebral cortex. One form of homeostatic synaptic scaling has been recently shown to be mediated by glial cells that interact with neurons through the diffusible messenger tumour necrosis factor-α (TNF-α). Interestingly, TNF-α is also used by the immune system as a pro-inflammatory messenger, suggesting potential interactions between immune system signalling and the homeostatic regulation of neuronal activity. We present the first computational model of neuron–glia interaction in TNF-α-mediated synaptic scaling. The model shows how under normal conditions the homeostatic mechanism is effective in balancing network activity. After chronic immune activation or TNF-α overexpression by glia, however, the network develops seizure-like activity patterns. This may explain why under certain conditions brain inflammation increases the risk of seizures. Additionally, the model shows that TNF-α diffusion may be responsible for epileptogenesis after localized brain lesions.     

Method for Assessing the Structural Stability of Refractory Nickel Alloys Based on Determination of Parameter PS of Phase Stability

Metal Science and Heat Treatment - Anew method for assessing the structural stability of nickel-base refractory alloys is suggested. The method is based on determination of the parameter of phase...