Unusual superconducting behavior in HfV2Ga4

Bulk superconductivity in HfV₂Ga₄ with critical temperature close to 4.1 K was determined via magnetic susceptibility, electrical resistivity and specific heat measurements. Both the upper and lower critical field dependence with reduced temperature ($T/T_c$) exhibit non-conventional behavior. The electronic component of specific heat shows a double-jump, the first close to $T_c$ and the other close to $0.75T_c$. We speculate about the nature of the douple jump observed in specific heat considering two plausable scenarios: bulk inhomogeneities and the existence of a second gap.     

Correlation among the effective mass (m⁎), λab and Tc of superconducting cuprates in a Casimir energy scenario

The relevance of the Casimir effect, discovered in 1948, has recently been pointed out in studies on materials such as graphene and high-temperature superconducting cuprates. In particular, the relationship between Casimir energy and the energy of a superconducting condensate with anisotropy characterized by high bidimensionality has already been discussed in certain theoretical scenarios. Using this proposal, this work describes the relationship between the effective mass of the charge carriers ($m^{?}=\alpha m_e$) and the macroscopic parameters characteristic of several families of high-$T_c$ superconducting cuprates (Cu-HTSC) that have copper and oxygen superconducting planes (Cu-O). We have verified that an expression exists that correlates the effective mass, the London penetration length in the plane ${\lambda }_{ab}$, the critical temperature $T_c$ and the distance d between the equivalent superconducting planes of Cu-HTSC. This study revealed that the intersection between the asymptotic behavior of α as a function of $T_c$ and the line describing the optimal value of $\alpha ?2$ ($m^{?}?2m_e$) indicates that a nonadiabatic region exists, which implies a carrier-lattice interaction and where the critical temperature can have its highest value in Cu-HTSC.     

Synthesis and properties of Sn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> nanoparticles obtained by a proteic sol–gel method

Iron-doped SnO₂ nanoparticles with chemical formula Sn_1?xFe_xO_2?y (x =?0.02, 0.05 and 0.10 at%) were successfully produced by a proteic sol–gel method. Thermogravimetric analysis and differential scanning calorimetry were performed to investigate the thermal behavior of the precursor powders as well as to select the appropriate calcination temperatures for oxide formation. X-ray absorption near-edge spectroscopy studies were carried out to determine the valence state of the transition metal used as dopant. Structural, morphological, and optical properties of the synthesized materials were studied by X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, and ultraviolet-visible spectroscopy. The results confirmed the formation of nanometric spherical particles of single-phased SnO₂ with rutile-type tetragonal structure. Iron doping was accomplished in the form of Fe³⁺ substituting for Sn⁴⁺ in the SnO₂ matrix, with the creation of oxygen vacancies to achieve charge balance. Band gaps of SnO₂ were found to be unaffected by the introduction of iron.     

Constructal Design Applied to the Geometric Evaluation of an Oscillating Water Column Wave Energy Converter Considering Different Real Scale Wave Periods

The present work presents numerical study of the influence of geometry on the performance of an oscillating water column (OWC) wave energy converter by means of a constructal design. The main purpose is to maximize the root mean square hydrodynamic power of device, (P_hyd)_RMS, subject to several real scale waves with different periods. The problem has two constraints: hydropneumatic chamber volume (V _HC ) and total OWC volume (V _T ), and two degrees of freedom: H₁/L (ratio of height to length of the hydropneumatic chamber) and H₃ (OWC submergence). For the numerical solution it was used a computational fluid dynamic (CFD) code, based on the finite volume method (FVM). The multiphasic volume of fluid (VOF) model is applied to tackle with the water–air interaction. The results led to important theoretical recommendations about the design of OWC device. For instance, the best shape for OWC chamber, which maximizes the (P_hyd)_RMS, was achieved when the ratio (H₁/L) was four times higher than the ratio of height to length of incident wave (H/λ), (H₁/L) _o = 4(H/λ). Moreover, the optimal submergence (H₃) was achieved as a function of wave height (H) and water depth (h), more precisely given by the following relation: h ? (3H/4) ≤ (H₃) _o ≤ h.     

Encapsulation of Local Anesthetic Bupivacaine in Biodegradable Poly(DL-lactide-co-glycolide) Nanospheres: Factorial Design,Characterization and Cytotoxicity Studies

Summary: Local anesthetic agents cause temporary blockade of nerve impulses productiong insensitivity to painful stimuli in the area supplied by that nerve. Bupivacaine (BVC) is an amide-type local anesthetic widely used in surgery and obstetrics for sustained peripheral and central nerve blockade. In this study, we prepared and characterized nanosphere formulations containing BVC. To achieve these goals, BVC loaded poly(DL-lactide-co-glycolide) (PLGA) nanospheres (NS) were prepared by nanopreciptation and characterized with regard to size distribution, drug loading and cytotoxicity assays. The 2^3-1 factorial experimental design was used to study the influence of three different independent variables on nanoparticle drug loading. BVC was assayed by HPLC, the particle size and zeta potential were determined by dynamic light scattering. BVC was determined using a combined ultrafiltration-centrifugation technique. The results of optimized formulations showed a narrow size distribution with a polydispersivity of 0.05%, an average diameter of 236.7 ± 2.6 nm and the zeta potential −2.93 ± 1,10 mV. In toxicity studies with fibroblast 3T3 cells, BVC loaded-PLGA-NS increased cell viability, in comparison with the effect produced by free BVC. In this way, BVC-loaded PLGA-NS decreased BVC toxicity. The development of BVC formulations in carriers such as nanospheres could offer the possibility of controlling drug delivery in biological systems, prolonging the anesthetic effect and reducing toxicity.     

Skew‐normal linear calibration: a Bayesian perspective

In this paper, we present a Bayesian approach for estimation in the skew‐normal calibration model, as well as the conditional posterior distributions which are useful for implementing the Gibbs sampler. Data transformation is thus avoided by using the methodology proposed. Model fitting is implemented by proposing the asymmetric deviance information criterion, ADIC, a modification of the ordinary DIC. We also report an application of the model studied by using a real data set, related to the relationship between the resistance and the elasticity of a sample of concrete beams. Copyright © 2008 John Wiley & Sons, Ltd.     

A Note on Truncated Long-Range Percolation with Heavy Tails on Oriented Graphs

We consider oriented long-range percolation on a graph with vertex set \({\mathbb {Z}}^d \times {\mathbb {Z}}_+\) and directed edges of the form \(\langle (x,t), (x+y,t+1)\rangle \), for x, y in \({\mathbb {Z}}^d\) and \(t \in {\mathbb {Z}}_+\). Any edge of this form is open with probability \(p_y\), independently for all edges. Under the assumption that the values \(p_y\) do not vanish at infinity, we show that there is percolation even if all edges of length more than k are deleted, for k large enough. We also state the analogous result for a long-range contact process on \({\mathbb {Z}}^d\).     

Generic Hamiltonian Dynamics

In this paper we contribute to the generic theory of Hamiltonians by proving that there is a \(C^2\)-residual \({\mathcal {R}}\) in the set of \(C^2\) Hamiltonians on a closed symplectic manifold \(M\), such that, for any \(H\in {\mathcal {R}}\), there is a full measure subset of energies \(e\) in \(H(M)\) such that the Hamiltonian level \((H,e)\) is topologically mixing; moreover these level sets are homoclinic classes.     

Calculation of the permeability and apparent permeability of three-dimensional porous media

In this study, creeping and inertial incompressible fluid flows through three-dimensional porous media are considered, and an analytical–numerical approach is employed to calculate the associated permeability and apparent permeability. The multiscale homogenization method for periodic structures is applied to the Stokes and Navier–Stokes equations (aided by a control-volume type argument in the latter case), to derive the appropriate cell problems and effective properties. Numerical solutions are then obtained through Galerkin finite-element formulations. The implementations are validated, and results are presented for flows through cubic lattices of cylinders, and through the dendritic zone found at the solid–liquid interface during solidification of metals. For the interdendritic flow problem, a geometric configuration for the periodic cell is built by the approximate matching of experimental and numerical results for the creeping-flow problem; inertial effects are then quantified upon solution of the inertial-flow problem. Finally, the functional behavior of the apparent permeability results is analyzed in the light of existing macroscopic seepage laws. The findings contribute to the (numerical) verification of the validity of such laws.