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101.
Let be a simplicial model category and J : a simplicial coaugmented functor. Given an object X, the assignment nJn+1X defines a cofacial resolution (an augmented cosimplicial space without its codegeneracy maps). Following Bousfield and Kan we define JsX = tots([n] Jn+1X). An object X is called J-injective if it is a retract of JX in Ho() via the natural map. We show that certain homotopy limits of J-injective objects are Js-injective. Our method is to use the notion of pro-weak equivalences which was first introduced in a different language and context by David Edwards and Harold Hastings. The key observation is that a cofacial resolution X (-1) X which admits a left contraction gives rise to a pro-weak equivalence of towers {X(-1)}s0{totSX}s 0.The first author was supported in part by National Science Foundation grant DMS-0296117 相似文献
102.
J. Andrzejewski N. A. Gundorin I. L. Karpikhin L. Lason G. A. Lobov D. V. Matveev L. B. Pikelner 《Physics of Atomic Nuclei》2004,67(7):1233-1238
The effect of parity violation in the interaction of thermal neutrons with lead was discovered in a number of studies. According to the existing theory, this effect is explained by the mixing of compound states characterized by different parities (s-and p-wave resonances). In view of the absence of a p-wave resonance in the region of thermal neutron energies, it is of importance to reveal a level below the neutron binding energy, a so-called negative resonance. The energy dependence of the cross section for radiative neutron capture on lead was measured in the present study, and it is shown that, for the 207Pb isotope, the results of this measurement deviate from the \({1 \mathord{\left/ {\vphantom {1 {\sqrt E }}} \right. \kern-\nulldelimiterspace} {\sqrt E }}\) law, thereby suggesting the presence of a strong negative resonance. The parameters of this resonance are estimated. 相似文献
103.
Dutka M Gurbiel RJ Kozioł J Froncisz W 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,170(2):5786-227
Applicability of continuous wave multiquantum EPR methods to study relaxation times at X-band is examined. Multiquantum transitions excited in a two-level system by tetrachromatic irradiation are used for these studies. The Bloch equation model is applied to simulate lineshapes of the three quantum transitions as a function of frequency difference between exciting fields. The dependence of multiquantum transition signals on relaxation times and microwave amplitude is shown. On this basis a method of deducing relaxation times from these signals is formulated. The case of a homogeneously and inhomogeneously broadened resonance line is considered. Two experimental methods are used to verify the proposed hypothesis: the X-band continuous wave multiquantum EPR with four frequencies microwave field and saturation recovery EPR. The values of T1 obtained from CW MQ EPR and SR EPR are compared. 相似文献
104.
Pisula W Kastler M Wasserfallen D Pakula T Müllen K 《Journal of the American Chemical Society》2004,126(26):8074-8075
The substitution of a hexa-peri-hexabenzocoronene by bulky, space-demanding, 2-decyltetradecyl side chains proved to be an effective procedure to influence the thermal and self-aggregation behavior. The extremely large steric requirement of the introduced side chains modulated the aggregation and resulted in a dramatic lowering of the isotropization temperature and a higher solubility. As an additional consequence of the exceptional, long-range self-aggregation of the discotic molecule, spherulite formation was observed during crystallization by polarized light microscopy. Macroscopic self-assembly was induced by zone crystallization of the material, leading to aligned columnar superstructures as revealed by 2D-WAXS experiments. These extraordinary properties have not yet been reported for a discotic columnar material, making this compound very promising for application in electronic devices. 相似文献
105.
D'Amelio N Gaggelli E Gaggelli N Molteni E Baratto MC Valensin G Jezowska-Bojczuk M Szczepanik W 《Dalton transactions (Cambridge, England : 2003)》2004,(3):363-368
The complexes formed by kanamycin A at three different pH values (5.5, 7.4 and 12.0) were investigated by NMR and EPR spectroscopy. Paramagnetic relaxation contributions to proton relaxation rates were measured using a combination of the TOCSY sequence with the inversion recovery experiment in order to gain signal resolution in the bulk region. Measured contributions were converted into distances and used for structural determination by restrained simulated annealing where all possible chair and boat conformations of the rings were taken into account. The interaction of the Cu(II) ion with the nitrogen of the C ring is apparent at all pH values. At higher pH also the amino group of ring A starts to be involved in the metal coordination sphere. This is accompanied by a switch in conformation of ring C. Structures are consistent with the involvement in the coordination sphere either of the 2' or 4' hydroxyl oxygens at pH 5.5 and the 5 and the 6' hydroxyl oxygens (or the ring oxygen) at pH 12.0. 相似文献
106.
Cahill MA Wozny W Schwall G Schroer K Hölzer K Poznanovic S Hunzinger C Vogt JA Stegmann W Matthies H Schrattenholz A 《Rapid communications in mass spectrometry : RCM》2003,17(12):1283-1290
The new method of analysis of relative isotopologue abundances (ARIA) applied here is based on the evaluation of total isotope patterns of tryptic protein fragments measured by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) to calculate the mixing ratios of composites consisting of stable isotope labelled and isotopically natural (unlabelled) proteins, as described in an accompanying paper in this issue. Recently, Sechi (Rapid Commun. Mass Spectrom. 2002; 16: 1416-1424) and Gehanne et al. (Rapid Commun. Mass Spectrom. 2002; 16: 1692-1698) introduced the use of differential quantitative mass analysis by MALDI-TOFMS using mixtures of standard proteins alkylated prior to two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) with either acrylamide (AA) or deuterium-labelled [2,3,3'-D(3)]-acrylamide (D3AA). In the present study we validate the AA/D3AA system, firstly by measuring the yield of proteins alkylated with AA, and secondly by using differential radioactive labels ((125)I and (131)I) to quantitatively establish that non-comigration in 2D-PAGE is negligible. ARIA is then applied to quantitatively estimate the relative proportions of peptides labelled with AA or D3AA in the validated system, using typical silver-stained 2D-PAGE protein spots from 2D gels loaded with 150 microg of total liver protein. The precision and limitations of ARIA quantification of peptides differentially alkylated with isotopomeric reagents are discussed. 相似文献
107.
GSH and L-His are abundant biomolecules and likely biological ligands for Zn(II) under certain conditions. Potentiometric titrations provide evidence of formation of ternary Zn(II) complexes with GSH and L-His or D-His with slight stereoselectivity in favour of L-His (ca. 1 log unit of stability constant). The solution structure of the ZnH(GSH)(L-His)(H2O) complex at pH 6.8, determined by NMR, includes tridentate L-His, monodentate (sulfur) GSH, and weak interligand interactions. Calculations of competitivity of this complex for Zn(II) binding at pH 7.4 indicate that it is likely to be formed in vivo under conditions of GSH depletion. Otherwise, GSH alone emerges as a likely Zn(II) carrier. 相似文献
108.
A. Pautrat A. Daignere C. Goupil Ch. Simon B. Andrzejewski A.I. Rykov S. Tajima 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):279-284
We report complex impedance measurements in an untwinned YBaCuO crystal. Our broad frequency range covers both the quasi static
response and the resistive response of the vortex lattice. It allow us to characterize the irreversibility line without the
need of any frequency dependent pinning parameters. We confirm the validity of the two modes model of vortex dynamic, and
extract both the surface critical current and the flux flow resistivity around the first order transition Tm. This latter is identified by the abrupt loss of pinning and by an unexpected step of (T) at Tm.
Received 22 November 2002 / Received in final form 17 February 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: alain.pautrat@ismra.fr
RID="b"
ID="b"UMR 6508 associée au CNRS 相似文献
109.
John?J.?BenedettoEmail author Wojciech?Czaja Przemystaw?Gadziński Alexander?M.?Powell 《Journal of Geometric Analysis》2003,13(2):239-254
For any positive real numbers A, B, and d satisfying the conditions
, d>2, we construct a Gabor orthonormal basis for L2(ℝ), such that the generating function g∈L2(ℝ) satisfies the condition:∫ℝ|g(x)|2(1+|x|
A
)/log
d
(2+|x|)dx < ∞ and
. 相似文献
110.
Wojciech Gajda 《K-Theory》2001,23(4):323-343
We apply the recently proven compatibility of Beilinson and Soulé elements in K-theory to investigate density of rational primes p, for which the reduction map K
2n+1() K{2n+1}(Fp)is nontrivial. Here n is an even, positive integer and Fp denotes the field of p elements. In the proof we use arithmetic of cyclotomic numbers which come from Soulé elements. Divisibility properties of the numbers are related to the Vandiver conjecture on the class group of cyclotomic fields. Using the K-theory of the integers, we compute an upper bound on the divisibility of these cyclotomic numbers. 相似文献