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101.
102.
103.
Ulrich Huckenbeck 《manuscripta mathematica》1987,59(2):147-173
In this paper we prove the following theorem: Suppose that n≥3 and 1≤jn $$(\forall a,b) d(a,b) : = \sum\limits_{\nu = 1}^j { (a_\nu - b_\nu )^2 - \sum\limits_{\nu = j + 1}^n { (a_\nu - b_\nu )^2 .} }$$ If a function f:?n→?n satisfies the condition: (*) $$(\forall x,y \in \mathbb{R}^n ) d(f(x),f(y)) = 0 \Leftrightarrow d(x,y) = 0,$$ then f is affine. Moreover, f preserves distances up to a constant factor C≠0, i.e. d(f(x),f(y))=C·d(x,y) for every x,y. In contrast to Alexandrov's result [1] we do not assume that f is bijective, and we also do not assume that j=n?1. A very important part of our proof will be the discussion of a functional equation. 相似文献
104.
Ulrich Dierkes 《manuscripta mathematica》1986,56(3):313-331
Plateau's problem for surfaces of prescribed mean curvature will be considered in regions which are not necessarily H-convex. 相似文献
105.
Ulrich Schafft 《manuscripta mathematica》1986,57(1):33-48
It is shown that the third Chern-number of a semistable Rk-3-vector bundle on a smooth hypersurface of degree 3 in 4 can be bounded by the first and the second Chern-number of the bundle. 相似文献
106.
The decays of3 S 1 quarkonia into a photon and a scalar or pseudoscalar Higgs particle are examined, taking into account the bound-state dynamics in the framework of a nonrelativistic potential model. We find that for realistic quark potentials the naive calculation [1] overestimates the scalar rate. Numerical results are obtained for the \(\bar bb\) and \(\bar tt\) quark systems. 相似文献
107.
[reaction: see text] The fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by nucleotides has been studied. The quenching mechanism was analyzed on the basis of deuterium isotope effects, tendencies for exciplex formation, and the quenching efficiency in the presence of a molecular container (cucurbit[7]uril). Exciplex-induced quenching appears to prevail for adenosine, cytidine, and uridine, while hydrogen abstraction becomes competitive for thymidine and guanosine. Compared to other fluorescent probes, DBO responds very selectively to the type of nucleotide. 相似文献
108.
The reaction of C5H5Rh(CO)(PiPr3) (1] which is prepared from C5H5Rh(CO)2 and neat P1Pr3, with the nitriloxides 2-RC6H4CNO (R = H, Cl) leads to the formation of the metallaheterocycles C5H5(P1Pr3)
) (2, 3) in 90–95% yield. Compound 1 reacts with tosylazide to give the C,N-bound isocyanate complex C5 H5(PiPr3)Rh(η2-TosN=C=O) (6). Analogously, on treatment of C5Me5Co(CO)(PMe3) with phenylazide the phenylisocyanate derivative C5Me5(PMe3)Co(η2-PhN=C=O) (7) is formed. Protonation of 7 with CF3CO 2H affords the non-ionic carbamoylcobalt complex C5Me5(PMe3)Co[C(O)NHPh](O2CCF3) (8). The X-ray structural analysis of 2 reveals the presence of an almost planar
heterocycle in which the two Rh-C distances differ by 0.045 Å 相似文献
109.
Summary Coordination compounds of the S2N2 molecule including methods for their preparation, reactivities, i.r. data, structures, and aspects of chemical bonding are reviewed. Methods of synthesis include reactions of S2N2, S4N4 or (NSCl)3 with metal halides, metal complexes such as carbonyls, or even metals themselves. In all cases, the planar S2N2 ring is coordinated, usuallyvia both, of its nitrogen atoms so that S2N2 acts as a bridging ligand between two metal centres; short contact distances imply that halogen atoms linked to the metal atoms show some interaction with the sulphur atoms. The stability of S2N2 is greatly enhanced by coordination. In the i.r. spectra, two characteristic S2N2 vibrations assist identification of the S2N2 species, a ring stretching mode being observable atca. 850 cm–1 and the out-of-plane deformation at 450–490 cm–1. 相似文献
110.
Five different structures of CH5
+ and one structure of CH5
– are calculated using a gaussian basis both in the SCF approximation and with the inclusion of electron correlation in the independent electron pair approximation (IEPA). While on SCF level the C
sstructure of CH5
+ has to lowest energy, the energy difference between the C
sand C
2vstructures becomes negligible if correlation is included. In contrast to this the approach of a proton to CH4 at large and intermediate distances is most favorable towards a corner of the CH4 tetrahedron which means a structure. The decomposition of CH5
+ into CH3
+ and H2 requires 20kcal/mol on SCF level and 40 kcal/mol if correlation is included. 相似文献