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排序方式: 共有49条查询结果,搜索用时 15 毫秒
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2.
Wolf Dietrich Krautgartner Ljubomir Vitkov Matthias Hannig Klaus Pelz Walter Stoiber 《Microscopy and microanalysis》2005,11(1):2-8
To examine new cytochemical aspects of the bacterial adhesion, a strain 41452/01 of the oral commensal Streptococcus sanguis and a wild strain of Staphylococcus aureus were grown with and without sucrose supplementation for 6 days. Osmiumtetraoxyde (OsO4), uranyl acetate (UA), ruthenium red (RR), cupromeronic blue (CB) staining with critical electrolytic concentrations (CECs), and the tannic acid-metal salt technique (TAMST) were applied for electron microscopy. Cytochemically, only RR-positive fimbriae in S. sanguis were visualized. By contrast, some types of fimbriae staining were observed in S. aureus glycocalyx: RR-positive, OsO4-positive, tannophilic and CB-positive with ceasing point at 0.3 M MgCl2. The CB staining with CEC, used for the first time for visualization of glycoproteins of bacterial glycocalyx, also reveals intacellular CB-positive substances-probably the monomeric molecules, that is, subunits forming the fimbriae via extracellular assembly. Thus, glycosylated components of the biofilm matrix can be reliably related to single cells. The visualization of intracellular components by CB with CEC enables clear distinction between S. aureus and other bacteria, which do not produce CB-positive substances. The small quantities of tannophilic substances found in S. aureus makes the use of TAMST for the same purpose difficult. The present work protocol enables, for the first time, a partial cytochemical differentiation of the bacterial glycocalyx. 相似文献
3.
A method for the quantitative analysis of individual hydrocarbons in the C1-C8 range emitted in engine exhaust gases is described. The procedure provides base-line or near base-line resolution of C4 components including 1,3-butadiene. With a run time of less than 50 min, the light aromatics (benzene, toluene, ethyl benzene, p- and m-xylene, and o-xylene) are resolved during the same analysis as aliphatic hydrocarbons in the C1-C8 range. It is shown that typical 1,3-butadiene levels in engine exhaust are about 5 ppm at each of two engine conditions. Aromatic hydrocarbon levels show a dependence on engine operating conditions, benzene being about 20 ppm at high speed and about 40 ppm at idle. 相似文献
4.
A. Eremin S. Diele G. Pelzl L. Kovalenko K. Pelz W. Weissflog 《Liquid crystals》2013,40(10):1451-1461
New homologous symmetric dimers are presented in which two-ring monomers are connected by a flexible spacer and perfluorinated chains are introduced in terminal positions. The mesophase behaviour depends on the length and structure of the spacer and on the length of the terminal chains. The most interesting finding is the occurrence of dimorphic SmA phases in the longer chain homologues with odd-numbered spacer. The transition between the dimorphic SmA phases is accompanied by a relatively high enthalpy. Considering the results of XRD measurements and computer simulations, structural models are proposed, based on different conformations of the molecules. 相似文献
5.
Model metal-semiconductor nanostructure Schottky nanocontacts were made on cleaved heterostructures containing GaAs quantum wells (QWs) of varying width and were locally probed by ballistic electron emission microscopy. The local Schottky barrier was found to increase by approximately 0.140 eV as the QW width was systematically decreased from 15 to 1 nm, due mostly to a large (approximately 0.200 eV) quantum-confinement increase to the QW conduction band. The measured barrier increase over the full 1 to 15 nm QW range was quantitatively explained when local "interface pinning" and image force lowering effects are also considered. 相似文献
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Kojic acid was used to synthesize bent-core mesogens. Antiferroelectric polar smectic mesophases, an oblique and a rectangular columnar mesophase were found. The mesophases were characterized by X-ray scattering, electro-optical measurements, polarizing microscopy and DSC. On the base of these measurements, models of the mesophases are proposed. 相似文献
8.
W. Ebert P. Hecking K. Pelz S. G. Steadman P. Winkler 《Zeitschrift für Physik A Hadrons and Nuclei》1973,263(3):191-200
TheE4 transition matrix element from the ground state to the 4+ state has been measured in152Sm and154Sm, by comparing relative thick targetγ-ray intensities following Coulomb excitation with 12 MeV4He, 24–30 MeV16O, and 35–40 MeV32S projectiles. Values for 〈0+∥?(E4)∥4+〉 of (+0.31 ?0.20 +0.12 ) barn in152Sm and (+0.50 ?0.12 +0.09 ) barn in154Sm are found. 相似文献
9.
Chiral allyl vinyl boronates are generated by catalytic enantioselective diboration of prochiral allenes. They may then be reacted, in situ, with a hydroborating reagent to form a novel triboron intermediate. The least hindered and most reactive C-B bond then participates in cross-coupling wherein the coupling is brought about by the same catalyst as that which catalyzed the diboration reaction. The remaining C-B bonds are then oxidized in the reaction workup, thereby allowing for the modular synthesis of chiral diols in a concise single-pot fashion. 相似文献
10.
O. Pelz C. Hesse M. Tesar R. B. Coffin W.-R. Abraham 《Isotopes in environmental and health studies》2013,49(1-2):131-144
Abstract The δ13C value of bacterial carbon is an important parameter in microbial ecology for studying the carbon flow within a microbial community and for the identification of ecological important strains involved in the mineralization of certain carbon pools in the environment. In our study, biomarkers were isolated from bacteria from a microbial consortium derived from two chemostats and δ13C values were measured. Similar isotope ratios between biomarkers such as fatty acids and outer membrane protein, biomass and substrate were observed. The δ13C analyses of outer membrane protein F of Pseudomonas and biomarker fatty acids were combined to follow bacterial assimilation of 13C labelled 4-chlorocatechol. This new approach was also used in the environment where soil samples were cultivated with different 13C traced substrates. The isotopic analyses of bacterial biomarkers indicated that carbons of histidine were widely incorporated into bacterial biomarkers, in contrast to 4-chlorocatechol which was less often used as a substrate. Results indicate that by isolating bacterial biomarkers and measuring their δ13C values, activities of microbial communities in a complex environmental sample can be determined. This new method has the potential to elucidate individual carbon sources for individual bacterial taxa in microbial ecology. 相似文献