Does habituation play a role in drug habit? Comment on McSweeney, Murphy, and Kowal (2005).

Comment on the article, "Regulation of Drug Taking by Sensitization and Habituation," by McSweeney, et al (see record 2005-10634-001). McSweeney, Murphy, and Kowal offer the intriguing suggestion that the basic behavioral processes of habituation and sensitization play an important role in drug taking, specifically, repeated drug taking. The suggestion is noteworthy because, if correct, it, as the authors point out, could lead to new approaches to prevention and treatment, approaches that involve the use of environmental variables that are relatively accessible. I think their exposition raises several issues. A number of these questions are related to the phenomenon of drug tolerance, an outcome that can be understood as either an instance of or deriving from the process of habituation. The presentation also contains passages in which the logic is not fully clear. Another issue I have with the article is the overall logic approach on the basis of features of drug addiction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A sensitivity study for an indoor channel

The context of this paper is the 3D wave propagation simulation with a software based on a ray tracing technique in typical indoor environments. The presented works are complementary to these of the literature which propose the validation of a propagation model in comparison with measurements. Indeed, the presented study consists of a sensitivity analysis of an already validated propagation model. The considered parameters are electromagnetic, geometric and electric; they directly intervene in the two parts of a simulation: the modelling of the wave propagation and of the environment. The aim of this study is to contribute to the setting up of parameterisation rules of a simulation software according to two criteria: the accuracy and the compromise between accuracy and computation time.     

Digital Rights Management

This article presents a selection of Internet links which provide a sound introduction to Digital Rights Management Systems (DRMS). First, links to scientific papers, information portals, organizations companies and consortia are presented to give a general view about DRMS. Then, various aspects about DRMS are presented with a special focus on legal, technological and economical aspect. For each of those further information and links are provided in order to give a better understanding about this topic.     

Theory of Seepage into an Auger Hole in a Confined Aquifer

A steady-state theory is presented for predicting flow into an auger hole partially penetrating a homogeneous and anisotropic confined aquifer that is underlain by an impermeable layer. The developed equations can be directly applied (i.e., without resorting to a coordinate transformation) to translate the rate of rise of the water in a pumped auger hole into directional conductivities of soil. The study shows that the conductivity values calculated by neglecting the confining pressure of an artesian aquifer (i.e., by applying the existing unconfined auger-hole seepage theories to experimental auger data obtained from a confined aquifer) may lead to serious error; hence, the confining head of an aquifer must be considered while the conductivity values are computed. Further, the distance of the outer layer also plays an important role in determining the flow to an auger hole penetrating a confined aquifer, and this parameter must therefore be included in the theoretical analysis of the problem. The validity of the proposed theory is checked by comparing a few results obtained from the theory with corresponding results obtained from numerical and analytical works. The developed theory is an addition to already existing auger-hole seepage theories for water-table aquifers; together with the available theories, the proposed solution is expected to cover the most commonly encountered auger hole experimental flow situations in the field.     

Computerized indoor radio channel estimation using ray tracing

This paper describes a computer tool for site specific indoor radio channel characterization. The behavior of the electromagnetic fields associated with a base station and a portable radio unit is simulated by combining approximate geometric optics and ray tracing techniques. Given a building plan and the transmitter/receiver locations, the set of all[attenuation / time delay /phase] vectors, each representing an electromagnetic propagation path between transmitter and receiver, is computed using ray shooting techniques to generate the channel wideband impulse response. The model takes into account specular reflection and transmission. Linear polarization and various antenna patterns can be simulated as well. The simulated results are shown to correlate well with experimental data. The computer tool can be used to provide estimates of the coverage of a base station and of the channel quality.     

Derivatisation of 4-nonylphenol and bisphenol A with halogenated anhydrides.

The aim of this work is to synthesize and characterise the halogenated derivatives of the endocrine disrupting compounds (EDCs) 4-nonylphenol (4-NP) and bisphenol A (BPA). Characterisation was performed after gas chromatographic (GC) separation on-line coupled to mass spectrometric (MS) detector and a Fourier Transform Infrared (FTIR) spectroscopic detector. Further structure elucidation was done applying Nuclear Magnetic Resonance spectroscopy (NMR). Two different approaches for the preparation of derivatives were evaluated. At first trifluoroacetyl derivatives were synthesized by the reaction of trifluoroacetic acid (TFA) anhydride and the EDCs in acetonitrile at a temperature of 50 degrees C for 30 minutes. In a second step the 4-NP was derivatised using trichloroacetic acid anhydride and triethylamine in diethyl ether at 20 degrees C for 30 minutes. After synthesis the halogenated NP and BPA derivatives were characterised applying GC/MS, GC/FTIR and NMR. Three indices for a successful derivatisation were observed: El-GC/MS proved a complete derivatisation presenting a characteristic fragmentation pattern for each derivative. The IR spectra obtained by GC/FTIR after derivatisation and separation confirmed the loss of the phenolic O-H stretching vibration at 3,600 cm(-1) while typical absorptions for halogenated compounds now were observed. The NMR-spectra contained the predicted resonance signals.     

Guidance of eye movements during conjunctive visual search: The distractor-ratio effect.

The distractor-ratio effect refers to the finding that search performance in a conjunctive visual search task depends on the relative frequency of two types or subsets of distractors when the total number of items in a display is fixed. Previously, Shen, Reingold, and Pomplun (2000) examined participants' patterns of eye movements in a distractor-ratio paradigm and demonstrated that on any given trial saccadic endpoints were biased towards the smaller subset of distractors and participants flexibly switched between different subsets across trials. The current study explored the boundary conditions of this tendency to flexibly search through a smaller subset of distractors by examining the influence of several manipulations known to modulate search efficiency, including stimulus discriminability (Experiment 1), within-dimension versus cross-dimension conjunction search and distractor heterogeneity (Experiment 2). The results indicated that the flexibility of visual guidance and saccadic bias exemplified by the distractor-ratio effect is a robust phenomenon that mediates search efficiency by adapting to changes in the relative informativeness of stimulus dimensions and features. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A stochastic continuation approach to piecewise constant reconstruction.

We address the problem of reconstructing a piecewise constant 3-D object from a few noisy 2-D line-integral projections. More generally, the theory developed here readily applies to the recovery of an ideal n-D signal (n > or =1) from indirect measurements corrupted by noise. Stabilization of this ill-conditioned inverse problem is achieved with the Potts prior model, which leads to a challenging optimization task. To overcome this difficulty, we introduce a new class of hybrid algorithms that combines simulated annealing with deterministic continuation. We call this class of algorithms stochastic continuation (SC). We first prove that, under mild assumptions, SC inherits the finite-time convergence properties of generalized simulated annealing. Then, we show that SC can be successfully applied to our reconstruction problem. In addition, we look into the concave distortion acceleration method introduced for standard simulated annealing and we derive an explicit formula for choosing the free parameter of the cost function. Numerical experiments using both synthetic data and real radiographic testing data show that SC outperforms standard simulated annealing.