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91.
Calderbank AR; Cameron PJ; Kantor WM; Seidel JJ 《Proceedings London Mathematical Society》1997,75(2):436-480
When m is odd, spreads in an orthogonal vector space of type+(2m + 2,2) are related to binary Kerdock codes and extremalline-sets in 2m + 1 with prescribed angles. Spreads in a 2m-dimensionalbinary symplectic vector space are related to Kerdock codesover Z4 and extremal line-sets in with prescribed angles. These connections involve binary, realand complex geometry associated with extraspecial 2-groups.A geometric map from symplectic to orthogonal spreads is shownto induce the Gray map from a corresponding Z4-Kerdock codeto its binary image. These geometric considerations lead tothe construction, for any odd composite m, of large numbersof Z4-Kerdock codes. They also produce new Z4-linear Kerdockand Preparata codes. 1991 Mathematics Subject Classification:primary 94B60; secondary 51M15, 20C99. 相似文献
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93.
De Muynck H Madder A Farcy N De Clercq PJ Pérez-Payán MN Öhberg LM Davis AP 《Angewandte Chemie (International ed. in English)》2000,39(1):145-148
Recursive deconvolution of a 729-membered peptide library has identified three active sequences, in which both Ser and His are present in one of the two tripeptidic chains generated on a steroidal scaffold (see structural formula), for the cleavage of an activated p-nitrophenyl ester. This combinatorial approach aims at searching for serine-protease-like activity. 相似文献
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This paper will review the dramatic increase in our knowledge of one and two proton unbound nuclei [1] such as recoil decay
tagging [2] are revealing unique insights into the structure of nuclei beyond the proton drip-line. These studies of excited
states provide complementary information to proton radioactivity studies, particularly regarding the role of deformation [3].
Radioactive beams are being used to study two-proton unbound resonances and to study explosive nuclear astrophysical reactions
in the region of the proton drip-line. 相似文献
98.
Vincent Porte Giovanni Di Mauro Manuel Schupp Dr. Daniel Kaiser Prof. Dr. Nuno Maulide 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(67):15509-15512
A synthetically convenient approach for the direct α-deuteration of amides is reported. This mechanistically unusual process relies on a retro-ene-type process, triggered by the addition of deuterated dimethyl sulfoxide to a keteniminium intermediate, generated through electrophilic amide activation. The transformation displays broad functional-group tolerance and high deuterium incorporation. 相似文献
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100.
We have carried out numerous experiments with supersources having intensities in the 100 Curie range. These sources usually require massive shielding, and are not easily moved to carry out Mössbauer spectroscopy. Several of these sources can be used with microfoil conversion electron (MICE) detectors, but they cannot be moved easily either because of the delicate microfoils used, which ideally have thicknesses less than the range of the internally converted electrons. Here, we describe a technique for doing Mössbauer spectroscopy by oscillating a monochromating crystal parallel to the reciprocal lattice vector of the Bragg reflection, this being used to filter out extraneous photons from the beam. Specifically, an LiF crystal is used in diffraction experiments as a filter to scatter the 46.5-keV Mössbauer gamma rays from183Ta by setting it at the (200) Bragg reflection. In the present measurements, the LiF crystal was mounted in the transmission mode and oscillated with a crank along the scattering vectorQ to produce the velocity modulation, with the source, sample and absorber all at rest. The velocity components of the filtering crystal along the incident and scattered beams cause the measured linewidth to be equal to the usual Mössbauer width divided by 2 sin, where is the Bragg angle. Measured widths for the (200), (400), (600) and (800) Bragg reflections agreed with the calculated values of 12.08, 6.04, 4.03 and 3.02 cm/s, within our experimental uncertainties. The technique could have applications not only to MICE detectors, but also to very narrow resonances such as67Zn, where the increased velocities required for small Bragg angles could be an advantage and lead to enhanced resolution. 相似文献