Polyaniline nanotubes: conditions of formation

The courses of aniline oxidation with ammonium peroxydisulfate in aqueous solutions of strong (sulfuric) and in weak (acetic) acids, followed by temperature and acidity changes, are different. In solutions of sulfuric acid, granular polyaniline (PANI) was produced; in solutions of acetic acid, PANI nanotubes were obtained. The external diameter of the nanotubes was 100–300 nm, the internal cavity 20–100 nm, and the length extended to several micrometres. The morphology of PANI, granular or tubular, depends on the acidity conditions during the reaction rather than on the chemical nature of the acid. PANI nanotubes were also produced when aniline was oxidized in the absence of any acid. The bulk conductivity of PANI prepared in solutions of acetic acid was 0.08–0.27 S cm^?1, depending on the acid concentration. Protonated PANI prepared in sulfuric and acetic acids were deprotonated with ammonium hydroxide to obtain PANI bases and the ammonium salt of the protonating acid. FTIR spectroscopy showed the differences in the molecular structure of the PANI bases. Irrespective of whether the polymerization was performed in solutions of sulfuric or acetic acid, PANI had hydrogen sulfate counter‐ions only. The PANI morphology is thus not controlled by the nature of counter‐ions. The acidity of the reaction medium determines the protonation of monomer, oligomer and polymer species. The chemistry of aniline oxidation is likely to be affected especially by the protonation of an intermediate in the pernigraniline form. It is proposed that, in the course of aniline oxidation, pH‐dependent self‐assembly of aniline oligomers predetermines the final PANI morphology. Copyright © 2005 Society of Chemical Industry     

Overview: Signal production and detection.

Studies of signal production and detection are complicated by the diverse modalities used by animals, constraints of human signal perception, and limitations of a controlled laboratory environment. These complications can be addressed by creative approaches to studying anatomical adaptations for signal production and detection, innovative technology, and careful studies of signal production and detection in the field. These solutions should overcome the perceptual limitations of researchers as they explore Umwelten in other species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Standby supply voltage minimization for deep sub-micron SRAM

Suppressing the leakage current in memories is critical in low-power design. By reducing the standby supply voltage (V_DD) to its limit, which is the data retention voltage (DRV), leakage power can be substantially reduced. This paper models the DRV of a standard low leakage SRAM module as a function of process and design parameters, and analyzes the SRAM cell stability when V_DD approaches DRV. The DRV model is verified using simulations as well as measurements from a 4 KB SRAM chip in a 0.13 μm technology. Due to a large on-chip variation, DRV of the 4 KB SRAM module ranges between 60 and 390 mV. Measurements taken at 100 mV above the worst-case DRV show that reducing the SRAM standby V_DD to a safe level of 490 mV saves 85% leakage power. Further savings can be achieved by applying DRV-aware SRAM optimization techniques, which are discussed at the end of this paper.     

Safety-relevant mode confusions—modelling and reducing them

Mode confusions are a significant safety concern in safety-critical systems, for example in aircraft. A mode confusion occurs when the observed behaviour of a technical system is out of sync with the user's mental model of its behaviour. But the notion is described only informally in the literature. We present a rigorous way of modelling the user and the machine in a shared-control system. This enables us to propose precise definitions of ‘mode’ and ‘mode confusion’ for safety-critical systems. We then validate these definitions against the informal notions in the literature. A new classification of mode confusions by cause leads to a number of design recommendations for shared-control systems. These help in avoiding mode confusion problems. Our approach supports the automated detection of remaining mode confusion problems. We apply our approach practically to a wheelchair robot.     

Stress singularities in a periodically layered composite near interface crack tips

The paper deals with the asymptotic analysis of stresses near interface crack tips in the periodically two-layered elastic composites. The problem is investigated for the plane state of strain within the framework of the homogenized model with microlocal parameters. The angular dependence of stresses at the crack tip is presented for different mechanical and geometrical properties of the composite.     

Sexual fantasies of child molesters.

Investigated the mood accompanying sexual fantasies, and the way in which the other person in the fantasy was perceived, by 21 child molesters, 19 rapists, and 19 non-sexual offenders. Child molesters did not differ from other Ss in their perceptions of adults in their fantasies, and the adult fantasy was perceived more positively than the child fantasy. Child molesters were more likely to fantasize about children when in a negative emotional state than when in a positive mood, and these fantasies were likely to produce a negative mood state. Child molesters may fantasize about a child as an inappropriate way of coping with dysphoric moods, thus enhancing that dysphoria and leading to further inappropriate fantasies. Results suggest that sexual fantasy monitoring should become an important component in the treatment of child molesters. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the operational and manufacturing tolerances of GaAs-AlAs MQWmodulators

We approach the question of optimization of surface-normal p-i(multiquantum-well, MQW)-n modulators from the viewpoint of investigating their tolerance to variations in wavelength and temperature and errors in manufacture. The reflection characteristics of two high-quality samples are carefully processed to eliminate Fabry-Perot fringes, and then their spectra at any bias are characterized with six phenomenological parameters which depend on λ₀, the zero-field exciton position. The two GaAs-AlAs samples have λ₀'s of 833.8 and 842.3 nm, and so cover a range useful for modulators designed to operate near 850 nm in the normally reflecting condition, i.e., reflection decreases with field. A linear interpolation of the parameters of these two samples is used to predict the behavior of MQW diodes with λ₀'s around this range, and so a fully comprehensive examination of normally reflecting MQW modulators is performed. The performance aspect that is examined is contrast ratio as a function of nonuniformities in the devices or operating conditions given a voltage swing of 3 V. There are two operational modes discussed. If the voltage offset of the bias is allowed to vary via a feedback circuit, a contrast of 2:1 may be maintained over an operating wavelength change (Δλ) of 17 nm with local variations of wavelength of ±1 nm, which corresponds to a temperature variation of 60°C while allowing for variations of laser driver wavelength of ±1 nm. If feedback Is not permitted, we determine that, given tolerances to manufacturing errors, a contrast of 1.5:1 may be maintained over a wavelength range of ~5 nm by either using stacked diode designs or extremely shallow quantum wells     

Modelling of selective catalytic denox reactors – strategy for replacing deactivated catalyst elements

A simulation model for denox reactors (high dust) containing honeycomb catalysts and operating at temperatures between 300 and 400 °C has been developed. The model predicts the NO_x reduction as a function of process variables (temperature, gas velocity, NO_x concentration, NH₃/NO_x ratio) as well as a function of reactor and catalyst geometry (pitch diameter, length of catalyst layer, number of layers). Model parameters such as the rate constant and the adsorption equilibrium constant of NH₃ on the catalyst surface were determined by curve fitting of experimental data obtained in a pilot test unit. Based on model calculations, it is shown that the effect of catalyst poisoning (deactivation) on NO_x reduction is not the same for every catalyst layer. The lifetimes of catalyst elements located at the inlet to the reactor appear shorter than those of the elements positioned at the outlet from the reactor. Experimental verification of this theoretical finding is required.     

Primary coexistent adenocarcinoma and choriocarcinoma of the stomach. A case report and review of the literature

We report a case of primary gastric choriocarcinoma with liver metastasis. The mixed histologic patterns included adenocarcinoma, undifferentiated carcinoma, and choriocarcinoma. Immunohistologic staining for the beta-subunit of human chorionic gonadotrophin (beta-HCG) showed positive results in the choriocarcinoma, adenocarcinoma, and normal mucosal gland. However, positive HCG cells were present at different intensities in the choriocarcinoma, adenocarcinoma, and normal mucosal gland. The level of HCG was significantly increased in serum. This unusual tumor probably resulted from dedifferentiation of a primary adenocarcinoma or developed directly from the mucosal glands.