Isochoric cooling of air in the University Physics laboratory

In this paper an alternative way of conducting the physics laboratory exercise for determining the adiabatic index of air using the Clement -- Desormes method is proposed. The process of isochoric cooling of air has been studied in terms of the dependence of pressure on time, and hence temperature on time, since it is proportional to pressure at a constant volume and mass of air. A theoretical model of the considered process was also made. The experimental results were processed statistically. The coefficient of determination $R^2$ and the F-test statistic were calculated and their values indicate a very good agreement between theory and experiment. The analysis of the residuals, however, implies that the model could be further improved through the inclusion of higher order terms.Comment: Accepted for publication in Romanian Reports in Physics, https://rrp.nipne.ro/inpress.htm

Chemical composition of the brown alga Padina pavonia (L.) Gaill. from the adriatic sea

The chemical composition of the brown alga Padina pavonia (L.) Gaill. from the southern Adriatic Sea was investigated. Twelve sterols were identified in the sterol fraction, the main ones being cholesterol and fucosterol. The main fatty acids in the lipids were also identified.The most abundant fatty acid was palmitic acid, followed by oleic and myristic acids.The concentration of polyunsaturated fatty acids was unusually low for a marine alga. By GC/MS analysis of the volatile and polar fractions, 40 compounds were identified. Some of them probably possess defensive functions. In the volatile fraction free fatty acids, aromatic esters, benzyl alcohol and benzaldehyde predominated. Low concentrations of terpenoids, phenols and sulfur containing compounds were also identified.The nbutanol extract contained mainly fatty acids and polyols. Some of the extracts had an antibacterial activity

The Response to a Perturbation in the Reflection Amplitude

We apply inverse scattering theory to calculate the functional derivative of the potential $V(x)$ and wave function $\psi(x,k)$ of a one-dimensional Schr\"odinger operator with respect to the reflection amplitude $r(k)$.Comment: 16 pages, no figure

Multiple-relay selection in amplify-and-forward cooperative wireless networks with multiple source nodes

In this article, we propose multiple-relay selection schemes for multiple source nodes in amplify-and-forward wireless relay networks based on the sum capacity maximization criterion. Both optimal and sub-optimal relay selection criteria are discussed, considering that sub-optimal approaches demonstrate advantages in reduced computational complexity. Using semi-definite programming convex optimization, we present computationally efficient algorithms for multiple-source multiple-relay selection (MSMRS) with both fixed number and varied number of relays. Finally, numerical results are provided to illustrate the comparisons between different relay selection criteria. It isdemonstrated that optimal varied number MSMRS outperforms optimal fixed number MSMRS under the same power constraints.publisher versio