Disorders and oxygen vacancies in p-type Sn2B2O7 (B = Nb,Ta): Role of the B-site element

Sn₂Nb_2−xTa_xO₇ (x = 0.0–2.0) with pyrochlore structure is a promising material for p-type oxide semiconductors. A systematic study of its Nb/Ta ratio indicated that the hole–generation efficiency of the Nb end (Sn₂Nb₂O₇) was an order of magnitude lower than that of the Ta end (Sn₂Ta₂O₇). Although this occurs due to differences in oxygen-vacancy formation, the origins of the hole–generation efficiencies remain unclear due to limited information on local and global crystal-structure disorders in pyrochlore Sn₂Nb₂O₇ and Sn₂Ta₂O₇. In this study, the crystal structures of Sn₂B₂O₇ (B = Nb, Ta), composed of BO₆ octahedra and Sn₄O tetrahedra, were investigated using X-ray absorption spectroscopy and X-ray diffraction. A detailed investigation of the local and global crystal structures indicated a larger amount of disorder in the Sn₄O tetrahedra in Sn₂Nb₂O₇ compared to Sn₂Ta₂O₇; disorder in the BO₆ octahedra occurred only in Sn₂Ta₂O₇. This study indicates that an appropriate selection of the B-site element is vital for suppressing defect and disorder formation in Sn₄O tetrahedra and subsequently improving the hole–carrier–generation efficiency.     

Measurement of residual stresses in injection‐molded polymer parts by time‐resolved fluorescence

Time‐resolved fluorescence properties of 9‐methylanthracene (9MAn) dispersed in film of polyvinylchloride (PVC) containing carbon black were studied under tensile loadings. The fluorescence lifetime of 9MAn decreased from 5.70 to 5.55 ns, whereas the stresses acting on the films increased from 0 to 3 MPa. The change in fluorescence lifetimes of 9MAn during the stress relaxation process showed that the fluorescence lifetimes were correlated with the stresses, not with the strains. The results suggest that 9MAn is a useful probe for monitoring stresses acting on the matrix. With the use of the fluorescence properties of 9MAn, the residual tensile stresses on the skin‐layer of PVC injection‐molded test pieces were estimated. The estimated residual stresses were about ～ 1 MPa. The residual stresses were relaxed to 0 MPa with annealing at 100°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2600–2603, 2002     

Fluorescence EXAFS analysis of ErP grown on InP by organometallic vapor phase epitaxy using a new organometal Er(EtCp)3

We have investigated local structures of ErP grown by organometallic vapor phase epitaxy Er source: tris(ethylcyclopentadienyl)erbium (Er(EtCp)₃ by extended X-ray absorption fine structure (EXAFS) measurement. The EXAFS analysis revealed that NaCl-type ErP and Er–O(–C) compounds coexisted in the case of ErP growth by using Er(EtCp)₃. The NaCl-type ErP was preferentially formed on InP(1 1 1)A compared with InP(0 0 1) and InP(1 1 1)B. It is considered that formation of unexpected Er–O(–C) compounds is due to low but significant concentration of residual O and/or C in Er(EtCp)₃.     

Synthesis of polypropylene oligomer—clay intercalation compounds

The synthesis of polypropylene (PP) oligomer—clay intercalation compounds was studied by using three kinds of PP oligomers and organophylic clay. PP oligomers were two types of maleic-anhydride-modified PP oligomers containing different amount of maleic anhydride groups and one type of hydroxy modified PP oligomer. Organophylic clay was sodium-ion-exchanged montmorillonite with octadecylammonium ion (C18—Mt). PP oligomer was mixed with C18—Mt at 200°C. Maleic-anhydride-modified PP oligomer, which was of high acid value type, and hydroxy-modified PP oligomer were intercalated between silicate layers of clay; and PP oligomer—clay intercalation compounds were synthesized successfully. But maleic-anhydride-modified PP oligomer, which was of low acid value type, was not intercalated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1781–1785, 1997     

Measurement of internal stresses in coatings using time resolved fluorescence

This paper describes a new nondestructive technique for detecting internal stresses in coatings using time resolved fluorescence. The measurement principle is based upon an experimental result that the decay time of fluorescence from poly(3-octylthiophene), P3OT, dispersed in uniaxially-stretched polymer films decreases with increasing tensile stress acting on the films. Internal stresses in the clear coat and in the base coat of a multilayer structure, which was composed of electrodeposited coat, surface coat, base coat, and clear coat, were estimated from the decay time of fluorescence from P3OT in both coats. The order of internal stresses in the clear coat and base coat of the multilayer system was 1 MPa. When the coatings were piled up, the internal stress decreased as the distance from a metal substrate was increased. It was found that moisture and temperature influenced internal stresses in the clear coat rather than in the base coat. Internal stress in the clear coat, which was one layer coated on a metal substrate, was measured by the traditional bimetallic method or by the time resolved fluorescence technique. Comparing both methods, it was concluded that the time resolved fluorescence technique gave reliable values for internal stresses in coatings.     

Functional Characterization of 3-Aminobenzoic Acid Adenylation Enzyme PctU and UDP-N-Acetyl-d-Glucosamine: 3-Aminobenzoyl-ACP Glycosyltransferase PctL in Pactamycin Biosynthesis

Pactamycin is an antibiotic produced by Streptomyces pactum with antitumor and antimalarial properties. Pactamycin has a unique aminocyclitol core that is decorated with 3-aminoacetophenone, 6-methylsaliciate, and an N,N-dimethylcarbamoyl group. Herein, we show that the adenylation enzyme PctU activates 3-aminobenzoic acid (3ABA) with adenosine triphosphate and ligates it to the holo form of the discrete acyl carrier protein PctK to yield 3ABA-PctK. Then, 3ABA-PctK is N-glycosylated with uridine diphosphate-N-acetyl-d -glucosamine (UDP-GlcNAc) by the glycosyltransferase PctL to yield GlcNAc-3ABA-PctK. Because 3ABA is known to be a precursor of the 3-aminoacetophenone moiety, PctU appears to be a gatekeeper that selects the appropriate 3-aminobenzoate starter unit. Overall, we propose that acyl carrier protein-bound glycosylated 3ABA derivatives are biosynthetic intermediates of pactamycin biosynthesis.     

Konzept einer autarken elektrischen und thermischen Energieversorgung auf Basis von Photovoltaik

A photovoltaic system could supply a single-family house with electrical power, warm water, and room heat if the energy would be distributed over the year to suit the load profile. However, storage systems for this are not state of the art yet. A concrete example is used to estimate which parameters such a power storage system should have. A suitable electrochemical reaction system based on inorganic salt mixtures is proposed. The German Federal Ministry of Education and Research is currently funding the development of a world storage facility based on the same reaction system.     

Using nitrogen isotope fractionation to assess abiotic reduction of nitroaromatic compounds

Compound-specific isotope analysis (CSIA) is an increasingly important tool for the qualitative and quantitative assessment of transformations of organic compounds in contaminated environments. To date, the use of CSIA has been mainly restricted to the elements C and H, although Nconstitutes a very important reactive centerfor many priority contaminants. To evaluate the potential use of N isotope effects in the fate assessment of organic contaminants, we investigated the N isotope enrichment during the abiotic reduction of 4 substituted nitroaromatic compounds (NACs), using two abiotic model reductants, namely Fe(ll) sorbed to goethite (alpha-FeOOH) and juglone (8-hydroxy-1,4-naphthoquinone) in the presence of H2S. Substantial and virtually identical isotope enrichment factors, EpsilonN, of about -30%, indicative of the breaking of one N-O bond, were found for all NACs, regardless of the reductant involved and the substitution of the NAC. These results indicate that the EpsilonN-values determined in our study could be representative for the reduction of aromatic NO2-groups and thus be used to assess the abiotic transformation of NACs qualitatively and quantitatively in complex anoxic environments.     

Possible action of vasohibin-1 as an inhibitor in the regulation of vascularization of the bovine corpus luteum

The development of the corpus luteum (CL), which secretes large amounts of progesterone to establish pregnancy, is accompanied by active angiogenesis, vascularization, and lymphangiogenesis. Negative feedback regulation is a critical physiological mechanism. Vasohibin-1 (VASH1) was recently discovered as a novel endothelium-derived negative feedback regulator of vascularization. We therefore investigated the expression of VASH1 in the bovine CL. Expression of VASH1 mRNA and protein was predominantly localized to luteal endothelial cells (LECs). VASH1 expression in the CL was constant through the early to late luteal phases and decreased during CL regression relating with the action of luteolytic prostaglandin F(2)(α) in vivo. To investigate the role of VASH1, we determined whether VASH1 treatment affects angiogenesis and/or lymphangiogenesis using LECs and lymphatic endothelial cells (LyECs) in vitro. Vascular endothelial growth factor A (VEGFA) stimulated the expression of VASH1 in LECs but not in LyECs, and VASH1 completely blocked VEGFA-induced formation of capillary-like tube structures of LECs and LyECs in vitro. In summary, VASH1 is predominantly located on LECs in the bovine CL and inhibits the angiogenic and lymphangiogenic actions of VEGFA. Bovine CL therefore has a VEGFA-VASH1 system that may be involved in regulation of luteal function, especially in the development of the CL. The results indicate that VASH1 has the potential to act as a negative feedback regulator of angiogenesis and lymphangiogenesis in the CL in cows.