Impact of orientation and water depth on productivity of single-basin dual-slope solar still with Al2O3 and CuO nanoparticles

Journal of Thermal Analysis and Calorimetry - The thermal performance of solar still can be enhanced by means of nanoparticles. The core aim of the present work is to identify the influence of...     

Arbitrage without borrowing or short selling?

We show that a trader, who starts with no initial wealth and is not allowed to borrow money or short sell assets, is theoretically able to attain positive wealth by continuous trading, provided that she has perfect foresight of future asset prices, given by a continuous semimartingale. Such an arbitrage strategy can be constructed as a process of finite variation that satisfies a seemingly innocuous self-financing condition, formulated using a pathwise Riemann–Stieltjes integral. Our result exemplifies the potential intricacies of formulating economically meaningful self-financing conditions in continuous time, when one leaves the conventional arbitrage-free framework.     

Schatten class Toeplitz operators on generalized Fock spaces

In this paper we characterize the Schatten p   class membership of Toeplitz operators with positive measure symbols acting on generalized Fock spaces for the full range 0<p<∞$0<p<\infty$.     

Monitoring bisphenol A and estrogenic chemicals in thermal paper with yeast-based bioreporter assay

Bioluminescent Saccharomyces cerevisiae yeast-based bioreporters were used to monitor bisphenol A and other estrogenic chemicals in thermal paper samples collected mainly from Finland on two occasions in 2010/2011, and 2013. The bisphenol A-targeted (BPA-R) and the human oestrogen receptor (hERα) bioreporters were applied to analyse both non-treated and extracted paper samples. Bisphenol A was readily bioavailable to the yeast bioreporters on the non-treated paper samples without any pre-treatment. Detected concentrations ranged from a detection limit of 9–142 μg/g to over 20 mg/g of bisphenol A equivalents in the thermal papers. Low bisphenol A like activities were detected in many samples, and were considered to be caused by residual bisphenol A or other types of bisphenols, such as bisphenol S. Most of the thermal paper samples were toxic to the yeast bioreporters. The toxicity did not, however, depend on the bisphenol A concentration of the samples. The yeast bioreporters were demonstrated to be a robust and cost-efficient method to monitor thermal paper samples for their bisphenol A content and estrogenicity. Thermal paper was considered as a potential BPA source for both human exposure and environmental emission.     

Elastic properties of GaxIn1−xP semiconductor

A theoretical procedure is presented for the study of elastic properties of the ternary alloy Ga_xIn_1−xP. The calculations are based on the pseudopotential formalism in which local potential coupled with the virtual crystal approximation (VCA) is applied to evaluate elastic constants c₁₁, c₁₂ and c₄₄, bulk modulus, shear modulus, Young's modulus and Poisson's ratio for the entire range of the alloy composition x of the ternary alloy Ga_xIn_1−xP. The effect of compositional disorder is included. Our results for parent compounds are compared to experimental and other theoretical calculations and showed generally good agreement. The inclusion of compositional disorder increases values of all elastic constants. During the present study it is found that elastic constant c₁₁ is largely influenced by compositional disorder.     

Physical characterization of a new composition of oxidized zirconium-2.5 wt% niobium produced using a two step process for biomedical applications

Zirconium and particularly Zr-2.5 wt%Nb (Zr2.5Nb) alloy are useful for engineering bearing applications because they can be oxidized in air to form a hard surface ceramic. Oxidized zirconium (OxZr) due to its abrasion resistant ceramic surface and biocompatible substrate alloy has been used as a bearing surface in total joint arthroplasty for several years. OxZr is characterized by hard zirconium oxide (oxide) formed on Zr2.5Nb using one step thermal oxidation carried out in air. Because the oxide is only at the surface, the bulk material behaves like a metal, with high toughness. The oxide, furthermore, exhibits high adhesion to the substrate because of an oxygen-rich diffusion hardened zone (DHZ) interposing between the oxide and the substrate.In this study, we demonstrate a two step process that forms a thicker DHZ and thus increased depth of hardening than that can be obtained using a one step oxidation process. The first step is thermal oxidation in air and the second step is a heat treatment in vacuum. The second step drives oxygen from the oxide formed in the first step deeper into the substrate to form a thicker DHZ. During the process only a portion of the oxide is dissolved. This new composition (DHOxZr) has approximately 4-6 μm oxide similar to that of OxZr. The nano-hardness of the oxide is similar but the DHZ is approximately 10 times thicker. The stoichiometry of the oxide is similar and a secondary phase rich in oxygen is present through the entire thickness. Due to the increased depth of hardening, the critical load required for the onset of oxide cracking is approximately 1.6 times more than that of the oxide of OxZr. This new composition has a potential to be used as a bearing surface in applications where greater depth of hardening is required.     

Conserving approximations for response functions of the Fermi gas in a random potential

One- and two-electron Green functions are simultaneously needed to determine the responsefunctions of the electron gas in a random potential. Reliable approximations must retainconsistency between the two types of Green functions expressed via Ward identities so thattheir output is compliant with macroscopic symmetries and conservation laws. Such aconsistency is not directly guaranteed when summing nonlocal corrections to the local(dynamical) mean field. We analyze the reasons for this failure and show how the full Wardidentity can generically be implemented in the diagrammatic approach to the vertexfunctions without breaking the analytic properties of the self-energy. We use thelow-energy asymptotics of the conserving two-particle vertex determining the singular partof response and correlation functions to derive an exact representation of the diffusionconstant in terms of Green functions of the perturbation theory. We then calculateexplicitly the leading vertex corrections to the mean-field diffusion constant due tomaximally-crossed diagrams.