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101.
Ogino I Nigra MM Hwang SJ Ha JM Rea T Zones SI Katz A 《Journal of the American Chemical Society》2011,133(10):3288-3291
New material UCB-1 is synthesized via the delamination of zeolite precursor MCM-22 (P) at pH 9 using an aqueous solution of cetyltrimethylammonium bromide, tetrabutylammonium fluoride, and tetrabutylammonium chloride at 353 K. Characterization by powder X-ray diffraction, transmission electron microscopy, and nitrogen physisorption at 77 K indicates the same degree of delamination in UCB-1 as previously reported for delaminated zeolite precursors, which require a pH of greater than 13.5 and sonication in order to achieve exfoliation. UCB-1 consists of a high degree of structural integrity via (29)Si MAS NMR and Fourier transform infrared spectroscopies, and no detectable formation of amorphous silica phase via transmission electron microscopy. Porosimetry measurements demonstrate a lack of hysteresis in the N(2) adsorption/desorption isotherms and macroporosity in UCB-1. The new method is generalizable to a variety of Si:Al ratios and leads to delaminated zeolite precursor materials lacking amorphization. 相似文献
102.
Gromov’s celebrated systolic inequality from ’83 is a universal volume lower bound in terms of the least length of a noncontractible
loop in M. His proof passes via a strongly isometric imbedding called the Kuratowski imbedding, into the Banach space of bounded functions
on M. We show that the imbedding admits an approximation by a (1+e){(1+\epsilon)}-bi-Lipschitz (onto its image), finite-dimensional imbedding for every ${\epsilon > 0}${\epsilon > 0}, using the first variation formula and the mean value theorem. 相似文献
103.
Li Z Rosenbaum MA Venkataraman A Tam TK Katz E Angenent LT 《Chemical communications (Cambridge, England)》2011,47(11):3060-3062
We developed a bacteria-based AND logic gate using a Pseudomonas aeruginosa lasI/rhlI double mutant with two quorum-sensing signaling molecules as the input signals. We showed a distinct electrical output signal, despite the complexity and continuous regulation of metabolic reactions of living cells. 相似文献
104.
Measurements of the tip leakage vortex structures and turbulence in the meridional plane of an axial water-jet pump 总被引:2,自引:0,他引:2
Particle image velocimetry (PIV) measurements at varying resolutions focus on the flow structures in the tip region of a water-jet
pump rotor, including the tip-clearance flow and the rollup process of a tip leakage vortex (TLV). Unobstructed views of these
regions are facilitated by matching the optical refractive index of the transparent pump with that of the fluid. High-magnification
data reveal the flow non-uniformities and associated turbulence within the tip gap. Instantaneous data and statistics of spatial
distributions and strength of vortices in the rotor passage reveal that the leakage flow emerges as a wall jet with a shear
layer containing a train of vortex filaments extending from the tip of the blade. These vortices are entrained into the TLV,
but do not have time to merge. TLV breakdown in the aft part of the blade passage further fragments these structures, increasing
their number and reducing their size. Analogy is made between the circumferential development of the TLV in the blade passage
and that of the starting jet vortex ring rollup. Subject to several assumptions, these flows display similar trends, including
conditions for TLV separation from the shear layer feeding vorticity into it. 相似文献
105.
106.
107.
108.
109.
We consider equilibrium configurations ofn identical particles in three dimensions interacting via two-body potentials depending only on the distance. The symmetry group of a given configuration is defined as the subgroup of isometries which leaves it invariant, up to permutations of the particles. We prove the stability of the symmetry in the following sense: the symmetry group of an equilibrium configuration is the same for the neighboring equilibria arising from any small enough perturbation of the initial potential. Furthermore, for a large class of realistic potentials, the existence of nontrivial symmetries is proved, thus giving a completely geometrical, although partial, approach to the classical crystal problem. 相似文献
110.
Moshe Katz 《Israel Journal of Mathematics》1971,9(1):53-72
Let ℬ(m) be the set of all then-square (0–1) matrices containingm ones andn
2−m zeros, 0<m<n
2. The problem of finding the maximum ofs(A
2) over this set, wheres(A
2) is the sum of the entries ofA
2,A ∈ ℬ (m) is considered. This problem is solved in the particular casesm=n
2 −k
2 andm=k
2,k
2>(n
2/2).
This paper forms part of a thesis in partial fulfillment of the requirements for the degree of Doctor of Science at the Technion-Israel
Institute of Technology. The author wishes to thank Professor B. Schwarz and Dr. D. London for their help in the preparation
of this paper. 相似文献