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1.
We report spectroscopic ellipsometry studies in the energy range of 0.5-5 eV on samples of 1-10 bilayers of polymer and HgTe nanocrystals, which exhibit strong transitions at higher critical points in the dispersion relation. We show that the dispersion relation for nanocrystals can be modelled with the same concepts for critical points as used in semiconductor bulk optics. We find an energy shift of up to 0.4 eV of the critical points to higher energies compared to the HgTe bulk properties, caused by quantum confinement in the nanocrystals, which increases with decreasing nanocrystal size. 相似文献
2.
3.
Kurt Schütte 《Archive for Mathematical Logic》1988,27(1):85-99
Summary This paper gives a recursive generalization of a strong notation system of ordinals, which was devellopped by Jäger [3]. The generalized systemT(V) is based on a hierarchy of Veblen-functions for inaccessible ordinals. The definition ofT(V) assumes the existence of a weak Mahlo-ordinal. The wellordering ofT(V) is provable in a formal system of second order arithmetic with the axiom schema of
2
1
-comprehension in a similar way, as it is proved in [6] for the weaker notation systemT(V). 相似文献
4.
The racemic cis-anti-trans-steroids 9 to 11 have been synthesized in a highly stereoselective manner starting from 4-methoxybenzocyclobutene carboxylic acid via the key step 8 → 9 . (cf. Scheme 2). 相似文献
5.
Kurt Girstmair 《Monatshefte für Mathematik》1987,104(2):109-118
Letk, n be relatively prime integers, 1k<n. The numbersB
k
m
=m(i/2)
m
cot(m–1)(k/n),m2, belong to then-th cyclotomic field. They occur as values of certain simple Dirichlet series at integral arguments and have a natural interpretation as generalized Bernoulli numbers. Therefore the arithmetic properties of these numbers arouse some interest. Ifn is not a prime power,B
k
m
/m is an algebraic integer. In the other case, i.e.n=p
e
,p prime, the fractional part ofB
k
m
/m resp.B
k
m
is determined in this paper. It is periodic modulop–1 and exhibits a connection between these Bernoulli numbers and the Stirling numbers of the second kind. 相似文献
6.
Kurt Rüfenacht 《Helvetica chimica acta》1975,58(6):1521-1527
Aza-analogues of the known pesticidal dithiophosphates 2, 4 and 5 have been prepared by replacing the phthalimide, benzotriazole and 1,2,3-benzotriazin-4(3H)-one moieties resp. in 2 by those of quinolinic acid imide (6), cinchomeronic acid imide (7) and pyrazine-2,3-dicarboxylic acid imide (12), in 4 by 1H-v-triazolo[4,5-b]pyridine (15) and in 5 by pyrido[2,3-e]1,2,3-triazin-4(3H)-one (21). Compared to the known compounds the new esters are less or at best equally pesticidal with an equal or even higher mammalian toxicity. 相似文献
7.
The synthesis of endo- and exo-13-oxo-4b, 5, 12, 12a-tetrahydro-5, 12-ethanoindeno[2,3-b]anthracene ( 23 ; Schemes 1 and 2), exo- and endo-11-oxo-4b, 5, 10, 10a-tetrahydro-5, 10-ethano-indeno[2,3-b]naphthalene ( 31 ; Scheme 3), 1,2,3,4,4a,9a-hexahydro?1,4-(peri-naphthaleno)-fluoren-9-one (36; Scheme 4), and the corresponding hydrocarbons of the stereoisomeric ketone pairs 23 and 36 , is described. 相似文献
8.
Mathematische Semesterberichte - Nicolaus Cusanus’ Beiträge zur Mathematik des 15. Jahrhunderts betreffen hauptsächlich Kreisquadraturen. Wir besprechen seinen... 相似文献
9.
Kurt Günther Reinhold Carle Ilona Fleischhauer Stefan Merget 《Fresenius' Journal of Analytical Chemistry》1993,345(12):787-790
Summary A semi-preparative low-pressure liquid-chromatographic procedure using tribenzoylcellulose has been developed for the separation and isolation of the four -bisabolol stereoisomers. Stereochemical assignments were made by HPLC-polarimeter coupling and by using the authentical isomers. This method can be applied to the quality control of chamomile preparations, as it allows the detection of adulterations resulting from admixtures of synthetic -bisabolol. In addition, the isolation of all four -bisabolol stereoisomers from commercially available synthetic -bisabolol has been made possible. 相似文献
10.
The literature data on heteropolar and homopolar 2-center bond dissociation energies in organic molecules in the gas phase and the corresponding heats of formation of radicals and ions have been critically evaluated. Data for more than 500 bonds are represented in tabular form together with the pertinent literature references. Selected electron affinities and π-bond dissociation energies have also been incorporated. The follow-up paper will discuss some empirical general aspects of these data particularly regarding the effect of structure on the bond dissociation energies. 相似文献