Effective Bi–Sb Crystals for Thermoelectric Cooling at Temperatures of T ≲ 180 K

Semiconductors - Extrusion methods have become widespread in the fabrication technology of thermoelectric materials with high strength characteristics. The extrusion method of thermoelectric...     

Feasibility of high performance in p-type Ge1−xBixTe materials for thermoelectric modules

GeTe is a promising candidate for the fabrication of high-temperature segments for p-type thermoelectric (TE) legs. The main restriction for the widespread use of this material in TE devices is high carrier concentration (up to ∼ 10²¹ cm⁻³), which causes the low Seebeck coefficient and high electronic component of thermal conductivity. In this work, the band structure diagram and phase equilibria data have been effectively used to attune the carrier concentration and to obtain the high TE performance. The Ge_1−xBi_xTe (x = 0.04) material prepared by the Spark plasma sintering (SPS) technique demonstrates a high power factor accompanied by moderate thermal conductivity. As a result, a significantly higher dimensionless TE figure of merit ZT = 2.0 has been obtained at ∼ 800 K. Moreover, we are the first to propose that application of the developed Ge_1−xBi_xTe (x = 0.04) material in the TE unicouple should be accompanied by SnTe and CoGe₂ transition layers. Only such a unique solution for the TE unicouple makes it possible to prevent the negative effects of high contact resistance and chemical diffusion between the segments at high temperatures.     

Photoconductivity of PbTe:In films with variable microstructure

It is shown that the microstructure and features of formation of surface states in nanocrystalline and polycrystalline PbTe:In films most significantly affect the character of photoconductivity in the spectral range of 1–2.5 THz. We present the results of a study and comparative analysis of the character of conductivity of PbTe:In films in the temperature range from 4.2 to 300 K in a static mode and in variable electric fields with a frequency of up to 1 MHz with illumination with white light and under the effect of high-power terahertz laser pulses with a wavelength of up to 280 μm.     

New developments in fire retardant non‐halogen aromatic phosphates

Akzo Nobel Chemicals has recently introduced on the market an aromatic oligomeric phosphate (BDP) based on Bisphenol A. This product shows higher thermal and hydrolytic stability than other aryl phosphates. It provides similar or better fire retardant performance than an oligomeric phosphate (RDP) based on resorcinol. Fire retardant formulations with BDP based on polycarbonate/ABS plastic (PC/ABS) blend, polyphenylene oxide/high impact polystyrene (PPO/HIPS) blend, and HIPS alone show similar or better physical properties than those obtained with RDP. Upon thermal decomposition of the fire retarded polymers containing BDP, phosphorus tends to accumulate in the solid residue, a result which indicates that the primary fire retardant action of BDP is likely to occur in the condensed phase.     

Combining check-reading accuracy and quantitative information in a space-saving display.

An experiment investigated the possibilities that a check-reading display could be designed to yield quantitative information, and that a more compact format could be used, saving space while preserving information content. The commonly used 4 X 4 display matrix and 0.50 sec. exposure time were used. Application of Gestalt principles proved advantageous. In an earlier study the principle of continuity was found highly efficient for qualitative readout. In this case, the principle of similarity of form was found to allow quantitative readout with little or no loss of check-reading efficiencies, which ranged between 94% and 98% correct detection of errors. Compressing the display by use of semicircular, rather than circular, dials improved performance even beyond its earliest, almost perfect, level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral treatment of chronic insomnia in psychiatrically ill patients

BACKGROUND: Psychiatric patients often have residual intractable insomnia as a serious problem. METHOD: Forty-eight psychiatrically ill patients (DSM-IV diagnoses) who had failed to respond to medicinal treatment for chronic insomnia were referred for and completed behavioral therapy as an adjunct to the pharmacologic treatment of their insomnia. The behavioral treatments included structured sleep hygiene, progressive muscle relaxation, stimulus control, and sleep restriction. The treatment program was accomplished in 6 sessions over 2 months. Follow-up evaluations were completed at 2, 6, and 12 months from the beginning of the treatment program. The outcome of the treatment program was evaluated in terms of the change in (1) self-reported specific sleep parameters, (2) self-ratings of sleep-related day-time state, (3) self-rating of quality of sleep, (4) the use of sleep medication, and (5) the therapist's global rating of improvement. RESULTS: There was a statistically significant change from the baseline in all self-reported specific sleep parameters after 2 months that was sustained after 6 and 12 months. Sleep-related characteristics of daytime state showed statistically significant changes after 2 and 6 months that were maintained after 12 months. Sleep quality had a statistically significant change after 2 months, continued to improve statistically after 6 months, and was maximum after 12 months. Over half the patients (52.7%; 20 of 38) either reduced their sleep medication by half or stopped it completely. The therapist's global rating showed an improvement in 29.2% (N = 14) of patients after 2 months, 56.2% (N = 27) after 6 months, and 68.7% (N = 33) after 12 months. CONCLUSION: The use of concomitant behavioral and pharmacologic treatment of chronic insomnia in psychiatrically ill patients results in improving sleep and sleep-related state and reduces the risk of return of insomnia for 10 months after finishing active treatment.     

On the dynamic stress intensity factors in finite cracked bodies under harmonic loading

A method of computing stress intensity factors under harmonic loading is suggested. The method is based on the representation of the stress intensity factors in form of superposition of the modal stress intensity factors corresponding to the normalized free vibration modes with some weight coefficients. The motion equations are built with the help of the finite element method. The singularity of stresses in the crack tip is taken into account using special finite elements. To demonstrate the accuracy and possibilities of the method, the dependence of the stress intensity factors of the first and second kind on frequency in square plate with inclined central crack under harmonic extension-compression was calculated.     

Thermoelectric Properties of (Pb,Sn,Ge)Te-Based Alloys

The search for alternative energy sources is presently at the forefront of␣applied research. In this context, thermoelectricity for direct energy conversion from thermal to electrical energy plays an important role. This␣paper is␣concerned with the development of highly efficient p-type [(PbTe)(SnTe)(Bi₂Te₃)] _x (GeTe)_1−x alloys for thermoelectric applications using spark plasma sintering (SPS). Varying the carrier concentration of GeTe was achieved by alloying of PbTe, SnTe, and/or Bi₂Te₃. The rhombohedral to cubic phase transition temperature, T _c, was found to be sensitive to the degree of alloying. Highest power factor values (P ≤ 33 μW/cm K²) were obtained for (GeTe)_0.95(Bi₂Te₃)_0.05 composition.     

Effect of oxidation on the conductivity of nanocrystalline PbTe:In films in an alternating electric field

Temperature and frequency dependences of components of complex impedance for nanocrystalline PbTe:In films in the temperature range of 4.2–300 K and the frequency range from 20 Hz to 1 MHz have been studied. The films were deposited onto a cooled glass substrate and then annealed in an oxygen atmosphere at temperatures of 300 and 350°C. The charge-carrier transport in the studied films is controlled by charge transport over inversion channels at the surface of grains and by transitions through barriers at the grain boundaries. Parameters (resistance and capacitance) corresponding to each of above-mentioned mechanisms were determined. Dominant contribution to conductance of the film annealed at 350°C is made by inversion channels. It is shown that the transport of charge carriers over inversion channels in the region of low temperatures is realized by hopping conductivity.

     

In vitro and in vivo performance of a multiparticulate pulsatile drug delivery system

The objective of this study was to investigate the in vitro and in vivo drug release performance of a rupturable multiparticulate pulsatile system, coated with aqueous polymer dispersion Aquacoat® ECD. Acetaminophen was used as a model drug, because in vivo performance can be monitored by measuring its concentration in saliva. Drug release was typical pulsatile, characterized by lag time, followed by fast drug release. Increasing the coating level of outer membrane lag time was clearly delayed. In vitro the lag time in 0.1 N HCl was longer, compared to phosphate buffer pH 7.4 because of ionisable ingredients present in the formulation (crosscarmelose sodium and sodium dodecyl sulphate). In vitro release was also longer in medium with higher ion concentration (0.9% NaCl solution compared to purified water); but independent of paddle rotation speed (50 vs.100 rpm). Macroscopically observation of the pellets during release experiment confirms that the rupturing of outer membrane was the main trigger for the onset of release. At the end of release outer membrane of all pellets was destructed and the content completely released.

However, pellets with higher coating level and correspondingly longer lag time showed decreased bioavailability of acetaminophen. This phenomenon was described previously and explained by decreased liquid flow in the lower part of intestine. This disadvantage can be considered as a limitation for drugs (like acetaminophen) with high dose and moderate solubility; however, it should not diminish performance of the investigated system in principle.