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41.
We communicate on an unusual feature of the DLTS spectrum of plastically deformed n-type silicon. In the cooling mode the DLTS signal at 240 K suddenly jumps nearly to zero. We interpret this effect as an entropy driven metastability of the deepest deformation-induced electron trap.Dedicated to H.-J. Queisser on the occasion of his 60th birthday 相似文献
42.
Penicillin -cyanosulphoximines are obtained by permanganate oxidation of the sulphilimines. Phthalimidosulphoximines are obtained from penicillin or cephalosporin sulphoxides are phthalimidonitrene (from -aminophthalimide with lead tetraacetate). 相似文献
43.
The isomeric structures of oximes, nitrones and nitroso compounds may be readily differentiated on the basis of their nitrogen chemical shifts. The tautomeric equilibria present in oximenitroso systems are easily observed by means of 14N NMR spectroscopy. An explanation of the range of chemical shifts found within the oxime and nitrone groups of compounds is presented, based upon the average excitation energy approximation to the paramagnetic term in the nuclear screening tensor. The increase in screening of the nitrogen found upon protonation of an oxime is analogous to that observed for pyridine-type structures and their N-oxides. 相似文献
44.
R. Ahmad M. Zia-ul-Haq H. Duddeck L. Stefaniak J. Sitkowski 《Monatshefte für Chemie / Chemical Monthly》1997,128(6-7):633-640
Summary Variable temperature1H NMR experiments of 2-(2-hydroxyphenyl)-4-phenyl-3H-1,5-benzodiazepine (5a) and its derivatives5d and5e were carried out in order to investigate the conformational behaviour of these compounds. The G* values for the ring inversion barriers of5a and5d areca. 52 kJ/mol,i.e. they do not differ significantly as compared to analogous compounds without phenolic OH group(s). This indicates that the hydrogen bond has not to be opened during the inversion process. In5e the barrier is about 2–3 kJ/mol higher which can be explained by steric interference between the additional methoxy group and the H-3 atoms during ring inversion.15N NMR data which can be discussed in terms of hydrogen bond strength support this interpretation.
Untersuchung des Konformationsgleichgewichtes einiger 2-(2-Hydroxyphenyl)-4-aryl-3H-1,5-benzodiazepine mit Hilfe der1H- und15N-NMR-Spektroskopie
Zusammenfassung Es wurden1H-NMR-Experimente mit 2-(2-Hydroxyphenyl)-4-aryl-3H-1,5-benzodiazepin (5a) und seinen Derivaten5d und5e bei unterschiedlichen Temperaturen durchgeführt. Die G*-Werte für die Ring-Inversion von5a und5d betragenca. 52 kJ/mol, d.h. sie sind gegenüber Verbindungen ohne eine phenolische OH-Gruppe kaum verändert. Das zeigt an, daß die Wasserstoffbrückenbindung während der Inversion nicht geöffnet werden muß. In5e ist die Barriere um ungefähr 2–3 kJ/mol höher, was durch eine sterische Wechselwirkung zwischen der zusätzlichen Methoxygruppe und den H-3-Atomen während der Inversion erklärt werden kann.15N-NMR-Daten können als Hinweise auf die Stärke der Wasserstoffbrückenbindung interpretiert werden.相似文献
45.
46.
Stefaniak AB Turk GC Dickerson RM Hoover MD 《Analytical and bioanalytical chemistry》2008,391(6):2071-2077
Owing to the absence of readily available certified particulate reference materials (RMs), most analytical methods used to determine particulate contaminant levels in workplace or other environments are validated using solution RMs, which do not assess the robustness of the digestion step for all forms and sizes of particles in a sample. A library of particulate RMs having a range of chemical forms and particle sizes is needed to support a shift in method evaluation strategies to include both solution and particulate RMs. In support of creating this library, we characterized bulk and physically size separated fractions of beryllium oxide (BeO) particles recovered from the machining fluid sludge of an industrial ceramic products grinding operation. Particles were large agglomerates of compact, crystalline BeO primary particles having diameters on the order of several micrometers. As expected, the particle surface area was independent of sieve size, with a range from 3.61 m(2)/g (53-63-microm fraction) to 4.82 m(2)/g (355-600-microm fraction). The density was near the theoretical value (3.01 g/cm(3)). The data support more detailed characterization of the sludge materials for use as size-selective RMs. This work illustrates an approach that can be used to develop RMs that are difficult to digest. 相似文献
47.
Agnieszka Łupicka-Słowik Mateusz Psurski Renata Grzywa Kamila Bobrek Patrycja Smok Maciej Walczak Andrzej Gaweł Tadeusz Stefaniak Józef Oleksyszyn Marcin Sieńczyk 《Applied biochemistry and biotechnology》2018,184(4):1358-1374
Adenosine deaminase (ADA) is currently used as a diagnostic marker for tuberculous pleuritis. Although ADA has been suggested as a potential marker for several types of cancer, the importance of each of ADA isoforms as well as their levels and enzymatic activities in tumors need to be further investigated. Herein we developed avian immunoglobulin Y highly specific to human ADA via hens immunization with calf adenosine deaminase. The obtained antibodies were used for the development of a sensitive double-egg yolk immunoglobulin (IgY) sandwich ELISA assay with an ADA detection limit of 0.5 ng/ml and a linearity range of up to 10 ng/ml. Specific, affinity-purified IgYs were able to recognize human recombinant ADA and ADA present in human cancer cell lines. In addition, antigen-specific IgY antibodies were able to inhibit catalytic activity of calf ADA with an IC50 value of 47.48 nM. We showed that generated IgY antibodies may be useful for ADA detection, thus acting as a diagnostic agent in immunoenzymatic assays. 相似文献
48.
Janusz Lipkowski Roman Luboradzki Lech Stefaniak Jacek Wójcik 《Journal of chemical crystallography》1995,25(6):299-308
X-ray diffraction studies are reported for six indolinones. The results show that two different types of associates are present in the crystal state of the compounds having an NH group. The indolinone molecules without any substituents form cyclic dimers while those with one or two methyl groups attached to the C3 atom of the lactam ring form infinite hydrogen bonded chains. It is confirmed that the lactam moiety forms a typical planar amide structure with no sign of the enol form present. 相似文献
49.
J. Goworek A. Kierys M. Iwan W. Stefaniak 《Journal of Thermal Analysis and Calorimetry》2007,87(1):165-169
Mesoporous materials MCM-41 with the hexagonal arrangement of pores
were obtained using dodecyltrimethylammonium bromide and octadecyltrimethylammonium
bromide as templating surfactants. Adsorption of toluene and propan-1-ol on
the as-synthesized MCM-41 silica samples was investigated using the TG-DTG,
DTA and DSC techniques. The sorption mechanism of used adsorptives is discussed
in terms of hydrophobicity of pore interior filled with template as well as
pore dimensions. 相似文献
50.
Philip Bechtle Sven Heinemeyer Oscar Stål Tim Stefaniak Georg Weiglein 《The European Physical Journal C - Particles and Fields》2014,74(2):1-40
HiggsSignals is a Fortran90 computer code that allows to test the compatibility of Higgs sector predictions against Higgs rates and masses measured at the LHC or the Tevatron. Arbitrary models with any number of Higgs bosons can be investigated using a model-independent input scheme based on HiggsBounds. The test is based on the calculation of a $\chi ^2$ measure from the predictions and the measured Higgs rates and masses, with the ability of fully taking into account systematics and correlations for the signal rate predictions, luminosity and Higgs mass predictions. It features two complementary methods for the test. First, the peak-centered method, in which each observable is defined by a Higgs signal rate measured at a specific hypothetical Higgs mass, corresponding to a tentative Higgs signal. Second, the mass-centered method, where the test is evaluated by comparing the signal rate measurement to the theory prediction at the Higgs mass predicted by the model. The program allows for the simultaneous use of both methods, which is useful in testing models with multiple Higgs bosons. The code automatically combines the signal rates of multiple Higgs bosons if their signals cannot be resolved by the experimental analysis. We compare results obtained with HiggsSignals to official ATLAS and CMS results for various examples of Higgs property determinations and find very good agreement. A few examples of HiggsSignals applications are provided, going beyond the scenarios investigated by the LHC collaborations. For models with more than one Higgs boson we recommend to use HiggsSignals and HiggsBounds in parallel to exploit the full constraining power of Higgs search exclusion limits and the measurements of the signal seen at $m_H\approx 125.5$ GeV. 相似文献