Linear and non-linear conduction regimes in broken down gate oxides

We have investigated conduction properties of gate oxides in metal-oxide–semiconductor structures in which dielectric breakdown has occurred. The measurements were performed on p- and n-type substrate samples with oxide thickness ranging from 2.0 to 13.5 nm. It is shown that the post-breakdown differential conductance has two typical modes, which, in terms of the physics of mesoscopic conducting systems, are referred to as linear and non-linear conduction regimes. In this work, we propose an analytic model for the conductance based on the electron transmission properties of quantum point contacts, which captures the essential features and consistently explains both breakdown modes.     

The single facility location problem with average-distances

This paper considers a location problem in ℝ ⁿ , where the demand is not necessarily concentrated at points but it is distributed in hypercubes following a Uniform probability distribution. The goal is to locate a service facility minimizing the weighted sum of average distances (measured with ℓ _p norms) to these demand hypercubes. In order to do that, we present an iterative scheme that provides a sequence converging to an optimal solution of the problem for p∈[1,2]. For the planar case, analytical expressions of this iterative procedure are obtained for p=2 and p=1, where two different approaches are proposed. The paper ends with a computational analysis of the proposed methodology, comparing its efficiency with a standard minimizer.      

Photophysics and Photochemistry of z‐Chlorprothixene in Acetonitrile†

Chlorprothixene (CPTX, Taractan^®) is a low potency antipsychotic mainly used for the treatment of psychotic disorders (e.g. schizophrenia) and acute mania occurring as part of bipolar disorders. As in the case of other numerous drugs used in the treatment of psychiatric disorders, CPTX presents geometric isomerism. Therefore, in vitro irradiation induces a rapid Z/E isomerization, which can affect its pharmacokinetic properties. This photoisomerization is not dependent on the oxygen concentration. The Z/E quantum yields determined for zCPTX in acetonitrile are 0.22 and 0.21 in anaerobic and aerobic environments, respectively. In the presence of water, both isomers decompose to produce 2‐chlorothioxanthone (CTX) after prolonged irradiation. This process strongly depends on the water concentration and the irradiation time, i.e. it is autocatalyzed by the CTX through a triplet‐energy transfer mechanism. The protonation state of the terminal amino group, on the other hand, has no effect on the isomerization process, but inhibits the formation of CTX. These results indicate that the phototoxicity of zCPTX is somehow affected by the formation of CTX.     

Characterization of complex networks by higher order neighborhood properties

A concept of higher order neighborhood in complex networks, introduced previously [Phys. Rev. E 73, 046101 (2006)], is systematically explored to investigate larger scale structures in complex networks. The basic idea is to consider each higher order neighborhood as a network in itself, represented by a corresponding adjacency matrix, and to settle a plenty of new parameters in order to obtain a best characterization of the whole network. Usual network indices are then used to evaluate the properties of each neighborhood. The identification of high order neighborhoods is also regarded as intermediary step towards the evaluation of global network properties, like the diameter, average shortest path between node, and network fractal dimension. Results for a large number of typical networks are presented and discussed.     

Determination of non-steroidal anti-inflammatory drugs in wastewaters by magnetic matrix solid phase dispersion-HPLC

A series of supports functionalized with different alkyl chains and covered with magnetite were synthesized, characterized and applied in the sample pre-concentration of four non-steroidal anti-inflammatory drugs (acetaminophen, naproxen, diclofenac and ibuprofen) contained in wastewater samples. The general methodology involved magnetic solid phase dispersion followed by the analysis by high-performance liquid chromatography with ultraviolet detection. The magnetic supports were initially dispersed in the samples with the aid of Triton X-100, then supports were magnetically isolated and the analytes were eluted with methanol. Finally the extract was injected into the HPLC system. The highest recovery percentage (>90%) was obtained with the support containing octyl chains (C8) at pH 3. The lowest limits of detection achieved ranged within 1-2 μg L⁻¹ with repeatability (expressed as RSD) below 5% in all cases. The method was applied in the analysis of wastewater samples.     

Combined effects of electric field and hydrostatic pressure on electron states in asymmetric GaAs/(Ga,Al) triple quantum dots

The combined effects of an in-growth direction applied electric field and hydrostatic pressure on the exciton binding energy and photoluminescence energy transitions are reported in this work for triple vertically coupled quantum dots. The calculations have been carried out within the effective mass approximation, and using a variational procedure. The results show that the exciton binding energy and the photoluminescence energy transitions are functions of external probes like the hydrostatic pressure and the applied electric field.     

Decision making with imprecise probabilities and utilities by means of statistical preference and stochastic dominance

A problem of decision making under uncertainty in which the choice must be made between two sets of alternatives instead of two single ones is considered. A number of choice rules are proposed and their main properties are investigated, focusing particularly on the generalizations of stochastic dominance and statistical preference. The particular cases where imprecision is present in the utilities or in the beliefs associated to two alternatives are considered.     

Study of prehispanic wall paintings from Xochicalco, Mexico, using PIXE, XRD, SEM and FTIR

The characterization of samples of painted plasters obtained from the archaeological site of Xochicalco, in Central Mexico, is presented. Elemental concentrations of the painted layers were obtained by using proton induced X-ray emission (PIXE). The main crystalline structures of the samples are identified with the help of X-ray diffraction (XRD), while the microstructure is studied by scanning electron microscopy (SEM). The information resulting from the application of these three techniques is used to achieve more accurate values for the elemental concentrations. Additional data regarding organic components of the paintings was obtained through Fourier transform infrared spectrometry (FTIR). Although the latter results only provided reliable data on inorganic components, they help to clarify the results from XRD and confirm those of SEM.