Electrical properties of Zn+-doped (AlGa)As prepared by molecular beam epitaxy and its use in shallow junction solar cells

In conventional molecular beam epitaxy the p-type dopant zinc cannot be incorporated into GaAs because of its high vapour pressure. In the present work, zinc atoms were ionized to increase the sticking coefficient and zinc-doped p-type (AlGa)As was prepared by molecular beam epitaxy for the first time. The p-type layer with hole concentrations of $\text{10}{}^{16}\text{?10}{}^{19}\text{cm}{}^{\mathrm{?3}}$ is readily produced by this technique. Measurements of the Hall effect, the impurity distribution profile and the photoluminescence showed that Zn⁺-doped GaAs and (AlGa)As layers have a good quality comparable with that of layers doped with other impurities such as magnesium and beryllium. The epitaxial p-GaAs thin films were used to prepare shallow junction solar cells. The electrical characteristics showed a reduction of the surface recombination effect, and an energy conversion efficiency of up to 12.6% was obtained.     

Phase separation structure in poly(vinyl alcohol)/silk fibroin blend films

Blend films of a commercial poly(vinyl alcohol) (a-PVA) derived from vinyl acetate and silk fibroin (SF) obtained from degummed silk were prepared by mixing the aqueous solutions of both samples. A plain weave structure was recognized only in the blend films, whereas no structure was found for the superimposed films of both samples. The phase separation structure of the blend films was examined by microscopic observations elongation, tensile tests, and IR measurements. The microphase separation region increased with increase in the degree of polymerization of the PVA. In the IR spectra of the blend films with high PVA contents cast under certain conditions, the absorption peak attributed to the cross-β-form conformation of SF appeared strongly. Gelatin, a water-soluble and natural polymer, was also used for comparison with SF. The ternary phase diagram in an a-PVA/gelatin/H₂O system was obtained experimentally and the critical point was used to estimate the interaction parameter between PVA and gelatin molecules. The phase separation structure and the interaction between PVA and SF molecules were also discussed taking into consideration the results of the a-PVA/gelatin system. © 1998 SCI.     

变压吸附技术的发展

介绍了变压吸附作为一种新型的气体分离技术的发展及其应用。同时与传统的气体分离方法相比较，指出了变压吸附技术具有能耗低，投资省，易操作等显著特点，极富有市场竞争力。最后介绍了变压吸附与其它几种气体分离纯化方法相结合在工业中的应用。     

磁性材料在低温技术中的新应用

研究了Ｅｒ（ＮｉＣｏ）＿２系新型磁性蓄冷材料的制备和材料的比热等物理性能，并且将该材料用于Ｖ－Ｍ制冷机进行了制冷实验。结果表明，Ｅｒ（ＮｉＣＯ）＿２系材料在２０Ｋ以下的比热远大于传统蓄冷材料铅，该材料作为蓄冷材料使用时，明显提高了制冷机的效率。     

Analysis of in-plane transonically propagating interface crack with a finite contact zone

The report of Lambros and Rosakis [(1995) J Mech Phys Solids 43(2): 169–188] has focused attention on steady-state transonic interfacial crack growth accounting for the phenomenon of crack face contact in elastic/rigid bimaterial but could not handle issues relating to energy transmission across the interface. The present paper attempts to provide a complete explicit expression of the asymptotic fields induced by transonically propagating interfacial crack in elastic/elastic bimaterial for in-plane case. The energy distribution on the contact area, crack tip and two singular characteristic lines is analysed thoroughly and compared with the dynamic separated J-integrals. The length of the contact zone is also discussed briefly by establishing energy fracture criterion that satisfies contact condition. The two-dimensional in-plane asymptotic deformation field surrounding the contact area of a crack propagating transonically along an elastic/elastic bimaterial interface is observed and discussed thoroughly.     

Finite element method for unbounded field problems and application to two-dimensional taper

Treatment of the finite element method for an unbounded field problem was proposed by McDonald and Wexler in 1972. Their method is superior to others, because it can exclude the singularities of Green's functions. This paper explains the treatment of the method in our 1979 letter which had some revisions of McDonald and Wexler's and calculated the time-harmonic field problems. Examples presented are electromagnetic fields of two-dimensional tapers which are open-ended. Electromagnetic waves propagate in the taper and radiate from the taper to free space. In this case, the exact solutions for radiation from tapers are not available because of the complicated shape, and so the finite element method is useful in solving these problems. Electromagnetic fields of tapers involving dielectric slabs are also calculated as examples of inhomogeneous problems.     

A novel flavin adenine dinucleotide (FAD) containing d-lactate dehydrogenase from the thermoacidophilic crenarchaeota Sulfolobus tokodaii strain 7: purification, characterization and expression in Escherichia coli

Dye-linked D-lactate dehydrogenase activity was found in the crude extract of a continental thermoacidophilic crenarchaeota, Sulfolobus tokodaii strain 7, and was purified 375-fold through four sequential chromatography steps. With a molecular mass of about 93 kDa, this enzyme was a homodimer comprised of identical subunits with molecular masses of about 48 kDa. The enzyme retained its full activity after incubation at 80 degrees C for 10 min and after incubation at pHs ranging from 6.5 to 10.0 for 30 min at 50 degrees C. The preferred substrate for this enzyme was D-lactate, with 2,6-dichloroindophenol serving as the electron acceptor. Using high-performance liquid chromatography (HPLC), the enzyme's prosthetic group was determined to be flavin adenine dinucleotide (FAD). Its N-terminal amino acid sequence was MLEGIEYSQGEEREDFVGFKIKPKI. Using that sequence and previously reported genome information, the gene encoding the enzyme (ST0649) was identified. It was subsequently cloned and expressed in Escherichia coli and found to encode a polypeptide of 440 amino acids with a calculated molecular weight of 49,715. The amino acid sequence of this dye-linked D-lactate dehydrogenase showed higher homology (39% identity) with that of a glycolate oxidase subunit homologue from Archaeoglobus fulgidus, but less similarity (32% identity) to D-lactate dehydrogenase from A. fulgidus. Taken together, our findings indicate that the dye-linked D-lactate dehydrogenase from S. tokodaii is a novel type of FAD containing D-lactate dehydrogenase.     

Measurement of radon concentration in water using the portable radon survey meter

A measurement method for measuring radon in water using the portable radon survey meter (RnSM) was developed. The container with propeller was used to stir the water samples and release radon from the water into the air in a sample box of the RnSM. In this method, the measurement of error would be <20 %, when the radon concentration in the mineral water was >20 Bq l(-1).     

Minor actinides incineration by loading moderated targets in fast reactor

The effect of contained hydrogen and loaded mass of minor actinides (MAs) in the target on the core performance and MAs transmutation characteristic was analyzed. An optimum core was proposed which has MAs pin cells per assembly of 38 with the composition ratio U/MA/Zr/H of 1/4/10/50. This optimum core can offer good core characteristics and transmute MAs very effectively by about 67% (93kg) and incinerate (transmute by fission) MAs by about 35% (489kg) through 3 years of reactor operation. It is about 2–3 times larger than the current transmutation method which loads MAs homogeneously in the PWR and FR.