Processes of growth of disordered semiconductors in the context of self-organiziation theory

The possibility of applying the concepts and methods of self-organization theory to the growth of disordered semiconductors is justified. A basic method for analyzing the dynamics of complex systems is described. The invariants of random dynamics are considered in the context of the processes involved in material growth. New principles for the construction of technological systems are stated.     

Relaxation of light-induced metastable state of boron-doped p-type a-Si:H

Relaxation of the dark conductivity of boron-doped a-Si: H films after illumination in the temperature range 360–470 K has been studied. It is shown that the measuring conductivity relaxation after illumination under different conditions (illumination time and temperature) makes it possible to separately investigate relaxation of the concentration of light-induced metastable defects of the “dangling-bonds” type and relaxation of the concentration of metastable states associated with impurity atoms. In both cases the relaxation obeys a stretched-exponential law. The main parameters of both relaxations and their temperature dependence have been measured. The experimental results can be explained within the framework of a model of the annealing activation energy distribution for light-induced metastable states. Fiz. Tekh. Poluprovodn. 32, 117–120 (January 1998)     

Gas-phase epoxidation of butadiene: Effect of the concentration and distribution of cesium on the properties of the Ag/α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst

Using the well-known patent methods, we have synthesized 1,3-butadiene epoxidation α-Al₂O₃ supported catalysts containing 15 wt % of Ag and 250–1500 ppm of Cs (Johnson Matthey, H16P07). The physicochemical properties of samples are systematically studied by varying the dispersion of supported silver, the amount of an introduced promoter, and its distribution over the surface of a catalyst. Catalytic tests of samples show that the optimum amount of a promoter depends directly on the surface of a catalyst. With optimum promotion, the steady-state activity of catalysts is determined by the dispersion of supported silver. In the course of catalytic tests, it is established that the shape of kinetic curves is governed by the excess or lack of Cs in a catalyst, thus providing a method for optimizing the concentration of the promoter. An analysis of the energy dispersion spectra (EDS) is applied for the first time to study the distribution of Cs over the surface of promoted catalysts. It is shown that thermal treatment favors the uniform distribution of a promoter over the surface of a catalyst and shortens the time required to attain its steady-state activity in catalytic tests. In our work, the steady-state productivity of catalysts reaches 0.5 g of 3,4-epoxy-1-butene per gram of the catalyst per hour, thus exceeding the claimed patent values.     

The antidyslipoproteinemic activity of ufibrate in patients with non-insulin-dependent diabetes mellitus

Ufibrate (150 mg daily) was found to have a beneficial effect on main parameters characterizing lipid metabolism, with no effect being exerted on carbohydrate metabolism, as evidenced by three months' follow-up of 24 patients aged 42 to 65 presenting with insulin-nondependent type II diabetes mellitus and hyperlipidemia. Ufibrate appeared to be a most efficacious long-term drug treatment option, particularly so in those patients presenting with initially high blood levels of a great many of lipid fractions.     

Tunnel kiln for firing large refractory products

Conclusions A tunnel kiln has been put into operation for firing large products in which cycles were worked out for firing blocks for the glass industry. When these products are being fired in the tunnel kiln loss is reduced by a factor of 10 compared with loss obtained when firing them in round furnaces. There are appreciable reductions in labor expenditure, and the working conditions are improved. Setting and unloading are mechanized.Location of the kiln under an open roof hinders operations.Translated from Ogneupory, No, 5, pp. 7–10, May, 1969.     

New trends in solar photovoltaics: From physics to chemistry

The paper briefly discusses the current situation in the field of traditional and unconventional photovoltaic materials and solar cells. It emphasizes the fact that the main basic achievements in the field of solid-state solar photovoltaics were gained at least two decades ago and the further progress focused on the improvement of cell parameters and technological aspects. Finally, the article concludes that this scientific area has nearly fulfilled its historical task. Indeed, the last decade has brought many new achievements in the field of the alternative, molecular-based materials. The future of solar energy conversion seems to be mainly connected with chemistry, chemical physics and chemical engineering but not with solid-state physics as in the twentieth century. The paper gives also a short over-view of some promising organic semiconductors, fullerenes and TiO₂ nanocrystalline structures used now in a new generation of molecular solar cells. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University     

A new approach for design of organic electrochromic devices with inter-digitated electrode structure

We present a new approach for design of organic electrochromic devices (ECD) with inter-digitated electrode (IDE) structure and three-electrode dynamic operation. The advantages of the IDE design include the ability to produce fast and homogenous color change over large areas. In addition, it enables fabrication of multi-color devices. Our method involves photolithographic etching of ITO followed by electrophoretic deposition (EPD) and mechanical compression of porous titania to produce finely patterned electrodes with high surface area. The titania layer is chemically modified by new stable and reversible electrochromic viologen derivatives involving phenylphosphonic acid anchoring moiety. The new device demonstrates reversible and strong color change from colorless to deep blue and yellow.     

Synthesis,electronic state,and particle size stabilization of nanoparticulate [Co(OH)<Subscript>2</Subscript>(H<Subscript>3</Subscript>O)<Stack><Subscript>δ</Subscript><Superscript>+</Superscript></Stack>]<Superscript>δ+</Superscript>

We have synthesized nanoparticulate cobalt(II) hydroxide containing Co²⁺ in tetrahedral oxygen coordination (Co _Td ²⁺ ), atypical of such systems: nano- [Co(OH)₂(H₃O) _δ ⁺ ]^δ+. The (Co _Td ²⁺ ) coordination in the hydroxide is inferred from its electronic diffuse reflectance spectrum, which shows a multiplet of strong absorption bands at 14500, 15000, and 16000 cm^?1 (⁴ A ₂(F)-⁴ T ₁(P) transition). Nanoparticulate cobalt(II) hydroxide forms in a weakly acidic medium under essentially nonequilibrium conditions due to supersaturation (by three to four orders of magnitude) with the starting reagents (CoCl₂ and LiOH) at the instant of the formation of the poorly soluble phase Co(OH)₂. Presumably, colloidal particles of nanoparticulate cobalt(II) hydroxide in a weakly acidic aqueous medium have a positive surface charge, compensated by a counter-ion (Cl^?) layer: nano-[Co(OH)₂(H₃O) _δ ⁺ ]^δ+ · δCl^?. The XRD patterns of pastes (gels) containing this hydroxide show three broad-ened lines with d = 5.31 (2θ = 16.7°), 2.77 (2θ = 32.3°), and 2.32 Å (2θ = 38.8°). According to small-angle X-ray scattering data, nano-[Co(OH)₂(H₃O) _δ ⁺ ]^δ+ has a narrow particle size distribution (1.0–2.0 nm). Synthesis and storage conditions are identified which ensure stabilization of the electronic state and particle size of nano-[Co(OH)₂(H₃O) _δ ⁺ ]^δ+ for a long time.     

Optoacoustic technique for noninvasive monitoring of blood oxygenation: a feasibility study

Replacement of invasive monitoring of cerebral venous oxygenation with noninvasive techniques offers great promise in the management of life-threatening neurologic illnesses including traumatic brain injury. We developed and built an optoacoustic system to noninvasively monitor cerebral venous oxygenation; the system includes a nanosecond Nd:YAG laser and a specially designed optoacoustic probe. We tested the system in vitro in sheep blood with experimentally varied oxygenation. Our results demonstrated that (1) the amplitude and temporal profile of the optoacoustic waves increase with blood oxygenation in the range from 24% to 92%, (2) optoacoustic signals can be detected despite optical and acoustic attenuation by thick bone, and (3) the system is capable of real-time and continuous measurements. These results suggest that the optoacoustic technique is technically feasible for continuous, noninvasive monitoring of cerebral venous oxygenation.