排序方式: 共有49条查询结果,搜索用时 46 毫秒
21.
A. Péter G. Török G. Tóth W. Van Den Nest G. Laus D. Tourwé D. W. Armstrong 《Chromatographia》1998,48(1-2):53-58
Summary High-performance liquid chromatographic and gas chromatographic methods were developed for the separation of unusual secondary
aromatic amino acids. Amino acids containing 1,2,3,4-tetrahydroisoquinoline, 1,2,3,4-tetrahydronorharmane-1-carboxylic acid
and 1,2,3,4-tetrahydro-3-carboxy-2-carboline moieties were synthetized in racemic or chiral forms. The high-performance liquid
chromatography was carried out either on a teicoplanin-containing chiral stationary phase or on an achiral C18 column. In the latter case the diastereomers of the amino acids formed by precolumn derivatization with the chiral reagents
2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate or 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide were separated. The gas chromatographic
analyses were based on separation on a Chirasil-L-Val column.
Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997 相似文献
22.
Immunological and chemical studies of cell surfaces from normal and transformed BALB/c fibroblasts have shown alterations associated with transformation. The cells studied include normal lines which do not cause tumors when injected into BALB/c mice, viral transformants, and spontaneous transformants which cause tumors that either regress or grow progressively, killing the host. The spontaneously transformed progressors include cell lines which are immunogenic and nonimmunogenic as determined by the ability of tumor excision to protect an animal from subsequent rechallenge by tumor cells. Tumor-bearing mice produce lymphocytes which are nonspecifically cytotoxic for all the normal and transformed lines. Some of the cell lines induce specific antibody formation in BALB/hosts. Antisera have been prepared in rabbits which are specific for the transformed cell lines. These antisera can be used to determine specific surface changes on the transformed cells. Chemical studies have shown glycolipid alterations between the normal cells and some, but not all, of the transformants. Glycoproteins labeled by lactoperoxidase-125I or [3H] glucosamine were compared by SDS gel electrophoresis. Results from these studies do not show changes associated with malignancy. Individual glycoprotein regions from gels were treated with pronase, and the glycopeptides compared by Sephadex G50 chromatography. Alterations in glycopeptides from several cellular glycoproteins are the only changes which appear to be associated with malignancy. 相似文献
23.
In this Letter, we discuss problems that can arise in the interpretation of results obtained by quantum dynamical simulations with the multi-configuration time-dependent Hartree–Fock (MCTDHF) method. In particular, we show that an effect, which can be seen as the time-dependent version of the state averaging known from standard quantum chemistry, can modify the electronic structure as derived from such a simulation. We illustrate our findings with numerical calculations for the laser excitation of a water molecule, with a Gaussian Type Orbital basis set. 相似文献
24.
25.
We discuss a topological method to quantize closed surfaces. 相似文献
26.
We introduce the notion of a strict quantization of a symplectic manifold and show its existence under a topological condition. 相似文献
27.
The main result of the present paper is an analogue of Kontsevich formality theorem in the context of the deformation theory of gerbes. We construct an L∞ deformation of the Schouten algebra of multi-vectors which controls the deformation theory of a gerbe. 相似文献
28.
Bergfinnur Durhuus Thordur Jonsson Ryszard Nest 《Communications in Mathematical Physics》2003,233(1):49-78
We establish existence and stability results for solitons in noncommutative scalar field theories in even space dimension
2d. In particular, for any finite rank spectral projection P of the number operator 𝒩 of the d-dimensional harmonic oscillator and sufficiently large noncommutativity parameter θ we prove the existence of a rotationally
invariant soliton which depends smoothly on θ and converges to a multiple of P as θ→∞.
In the two-dimensional case we prove that these solitons are stable at large θ, if P=P
N
, where P
N
projects onto the space spanned by the N+1 lowest eigenstates of 𝒩, and otherwise they are unstable. We also discuss the generalisation of the stability results
to higher dimensions. In particular, we prove stability of the soliton corresponding to P=P
0
for all θ in its domain of existence.
Finally, for arbitrary d and small values of θ, we prove without assuming rotational invariance that there do not exist any solitons depending smoothly
on θ.
Received: 13 July 2001 / Accepted: 9 July 2002 Published online: 10 January 2003 相似文献
29.
We establish a connection between ground states of local quantum Hamiltonians and thermal states of classical spin systems. For any discrete classical statistical mechanical model in any spatial dimension, we find an associated quantum state such that the reduced density operator behaves as the thermal state of the classical system. We show that all these quantum states are unique ground states of a universal 5-body local quantum Hamiltonian acting on a (polynomially enlarged) qubit system on a 2D lattice. The only free parameters of the quantum Hamiltonian are coupling strengths of two-body interactions, which allow one to choose the type and dimension of the classical model as well as the interaction strength and temperature. This opens the possibility to study and simulate classical spin models in arbitrary dimension using a 2D quantum system. 相似文献
30.
Several macromolecular networks, based on nitrocellulose and polyethers such as polyethylene and polypropylene oxide, were prepared by cross/linking following typical polyurethane preparations. These materials, charged with sodium salts such as sodium tetraphenyl boride, display ionic conductivity, which was studied as a function of various parameters viz. temperature, nitrocellulose content, molecular weight of the polyether and cross-linking agent. Membranes with 8% nitrocellulose give conductivities exceeding 10?5 Ω?1 cm?1 at 100. 相似文献