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121.
A planar-chiral DMAP derivative catalyzes an intriguing [3 + 2] annulation reaction of silylated indenes to produce diquinanes that bear three contiguous stereocenters (one quaternary and two tertiary). 相似文献
122.
123.
Michael Steffens Jakob Penner Hassan Kamleh Reiner Vianden 《Hyperfine Interactions》2010,195(1-3):167-171
Cr has been added to FeCo substituting 10 at.% of Co or Fe in the alloy. The alloys Fe50Co40Cr10, Fe40Co50Cr10 and Fe50Co50 were prepared by mechanical alloying for 2, 5, 10, 20, 40 and 60 h. The formation of the alloy and the incorporation of the elements have been followed by X-Ray Diffraction (XRD) and Mössbauer Spectroscopy. The kinetics of mixing occurs by incorporation of Co and Cr into the Fe structure. After prolonged milling it seems that Cr incorporates itself into both $\upalpha $ -Fe and $\upalpha $ -FeCo structures and a mixture of FeCoCr rich in Cr and FeCoCr rich in Co solid solutions is obtained. 相似文献
124.
We prove a theorem unifying three results from combinatorial homological and commutative algebra, characterizing the Koszul property for incidence algebras of posets and affine semigroup rings, and characterizing linear resolutions of squarefree monomial ideals. The characterization in the graded setting is via the Cohen-Macaulay property of certain posets or simplicial complexes, and in the more general nongraded setting, via the sequential Cohen-Macaulay property. 相似文献
125.
Reiner Michael Schätzle 《Mathematische Zeitschrift》2013,274(3-4):1341-1383
We prove for closed, orientable surfaces in $\ \mathbb{R }^3\ $ with Willmore energy less that $\ 8 \pi - \delta \ $ and whose conformal structures are compactly contained in moduli space that after applying appropriate Möbius transformations the conformal factors between the induced metrics and conformal metrics of constant curvature are uniformly bounded by constants depending only on $\ \delta > 0,$ the genus of the surfaces and the compact subset of the moduli space. Secondly, for a given sequence of closed, orientable surfaces as above, we prove that the conformal factor remains bounded without applying Möbius transformations if and only if no topology is lost. Similar estimates hold in higher codimension. 相似文献
126.
The possible presence of a large magnetic field due to spin polarization of a Cd nucleus (decay product of 111In) at an Al substitutional site in AlN is investigated with perturbed angular correlation (PAC) spectroscopy. The PAC spectra of 111In/111Cd in AlN show two probe environments: a weak quadrupole interaction (quadrupole interaction constant, $\nu _{\rm Q}^{\,\,\,\rm lattice} = 30$ MHz) due to 111In probes at a defect free Al substitutional site and an unknown large interaction ( $\nu _{\rm Q}^{\,\,\,\rm complex} = 300$ MHz) tentatively attributed to a nearest neighbour pair between 111In and a nitrogen vacancy (VN) aligned along the c-axis. Surprisingly, in density functional theory (DFT) calculations, such a large electric field gradient (EFG) could not be reproduced. However, an inclusion of spin polarization in the calculations indicates a strong magnetic field at ~50 % of the 111In/111Cd site. An attempt to verify the presence of the strong magnetic field and to explain the origin of the strong interaction is made. Orientation measurements show, the large interaction is not characterised by a magnetic interaction and is predominantly due to the EFG. However, in the presence of an external magnetic field, the strong interaction probe environment becomes more uniform and the EFG increases by ~10 %. This definitely hints towards some sort of magnetic interaction at the strong interaction probe site. 相似文献
127.
Zusammenfassung Die Ausscheidung des Globulins w?hrend der Elektrodialyse h?ngt in einer zun?chst noch unübersichtlichen Weise von den Beziehungen
zwischen Schutzstoff und Globulin und von der Beeinflussung dieser durch Aenderung der H+Konzentration und Entsalzungsgeschwindigkeit ab. Es ist auffallend, da? unter den untersuchten, gegen Ausflockung schützenden
Stoffen solche am wirksamsten sind, die-auch die Gerinnung hemmen. Unter diesen kommt m?glicherweise unter physiologischen
Verh?ltnissen das Heparin in Betracht. Die Wirkung dieser Stoffe besteht in der Verschiebung des isoelektrischen Punktes nach
der sauren Seite, was eine st?rkere Aufladung bei neutraler Reaktion nach sich zieht.
Im Gegensatze zu den Behauptungen von Ettisch und Ewig wird festgestellt, da? die von Reiner benützten, mit Eiwei? beladenen
Kolloidmembranen bei der Elektrodialyse sehr gute Dienste leisten.
Es wird die Entstehung einer elektrischen Polarisation in Kolloidmembranen beschrieben, die bei der Elektrodialyse zu beobachten
war. 相似文献
128.
Small sample sizes are very common in multivariate analysis. Sample sizes of 10–100 statistically independent objects (rejects
from processes or loading dock analysis, or patients with a rare disease), each with hundreds of data points, cause unstable
models with poor predictive quality. Model stability is assessed by comparing models that were built using slightly varying
training data. Iterated k-fold cross-validation is used for this purpose. Aggregation stabilizes models. It is possible to
assess the quality of the aggregated model without calculating further models. The validation and aggregation methods investigated
in this study apply to regression as well as to classification. These techniques are useful for analyzing data with large
numbers of variates, e.g., any spectral data like FT-IR, Raman, UV/VIS, fluorescence, AAS, and MS. FT-IR images of tumor tissue
were used in this study. Some tissue types occur frequently, while some are very rare. They are classified using LDA. Initial
models were severely unstable. Aggregation stabilizes the predictions. The hit rate increased from 67% to 82%. 相似文献
129.
Liu Q Meermann C Görlitzer HW Runte O Herdtweck E Sirsch P Törnroos KW Anwander R 《Dalton transactions (Cambridge, England : 2003)》2008,(44):6170-6178
Complexes (Salpren(tBu,tBu))Y[N(SiHMe2)2](thf) and (SALEN(tBu,tBu))La[N(SiHMe2)2](thf) (SALEN(tBu,tBu) = Salcyc(tBu,tBu) and Salpren(tBu,tBu)) were prepared from Ln[N(SiHMe2)2]3(thf)2 and H2SALEN(tBu,tBu). The yttrium complex was characterized by X-ray crystallography revealing intrinsic solid-state structural features: the metal centre is displaced by 1.05 angstroms from the [N2O2] least squares plane of a highly bent Salpren(tBu,tBu) ligand (angle(Ph,Ph) dihedral angle of 80.4(1) degrees ) and is coordinated asymmetrically by the silylamide ligand exhibiting one significant Y---(HSi) beta-agostic interaction (Y-N1-Si1, 106.90(9) degrees; Y---Si1, 3.2317(6) angstroms). Complexes (SALEN(tBu,tBu))Ln[N(SiHMe2)2](thf)n (n = 1, Sc; n = 2, Y, La) react with ammonium tetraphenylborate to form the ion pairs [(SALEN(tBu,tBu))Ln(thf)n][BPh4]. The cationisation was proven by X-ray crystal structure analyses of [(Salpren(tBu,tBu))Sc(thf)2][B(C6H5)4].2(thf) and [(Salpren(tBu,tBu))Ln(thf)3][B(C6H5)4].4(thf) (Ln = Y, La), showing an octahedral and pentagonal-bipyramidal coordination geometry, respectively. 相似文献
130.