7,217 research outputs found
Increased concentration of an apparently identical cellular protein in cells transformed by either Abelson murine leukemia virus or other transforming agents
Abelson murine leukemia virus (A-MuLV)-transformed cells, simian virus 40 (SV40)-transformed cells, and chemically transformed cells all have increased levels of a 50,000-molecular-weight host cell protein. The protein was detected with sera raised to the A-MuLV-transformed and chemically transformed cells and was tightly bound to T-antigen in extracts of SV40-transformed cells. Partial protease digests showed that the proteins from all three sources were indistinguishable. The three proteins were phosphorylated in cells, and the linkage of phosphate to the A-MuLV-associated P50 was to a serine residue. By immunofluorescence methods, P50-related protein was found on the surface of both normal lymphoid cells and A-MuLV-transformed lymphoid cells, but cell fractionation showed that the majority of P50 was free in the cytoplasm of the transformed cells. Immunofluorescence also showed that P50 was found in granules in the cytoplasm of both untransformed and SV40-transformed fibroblasts. Other cells gave indistinct patterns. Cocapping experiments showed that the A-MuLV-specified P120 protein is weakly associated with the surface P50-related protein of lymphoid cells, but no association of P120 and P50 could be demonstrated by immunoprecipitation methods. Although a monoclonal antiserum to P50 was used in many of these studies, the identity of the bulk P50 protein with the molecules that are reactive at the cell surface requires further study
Influence of branch points in the complex plane on the transmission through double quantum dots
We consider single-channel transmission through a double quantum dot system
consisting of two single dots that are connected by a wire and coupled each to
one lead. The system is described in the framework of the S-matrix theory by
using the effective Hamiltonian of the open quantum system. It consists of the
Hamiltonian of the closed system (without attached leads) and a term that
accounts for the coupling of the states via the continuum of propagating modes
in the leads. This model allows to study the physical meaning of branch points
in the complex plane. They are points of coalesced eigenvalues and separate the
two scenarios with avoided level crossings and without any crossings in the
complex plane. They influence strongly the features of transmission through
double quantum dots.Comment: 30 pages, 14 figure
Double Exchange model for nanoscopic clusters
We solve the double exchange model on nanoscopic clusters exactly, and
specifically consider a six-site benzene-like nanocluster. This simple model is
an ideal testbed for studying magnetism in nanoclusters and for validating
approximations such as the dynamical mean field theory (DMFT). Non-local
correlations arise between neighboring localized spins due to the Hund's rule
coupling, favoring a short-range magnetic order of ferro- or antiferromagnetic
type. For a geometry with more neighboring sites or a sufficiently strong
hybridization between leads and the nanocluster, these non-local correlations
are less relevant, and DMFT can be applied reliably.Comment: 9 pages, 9 figures, 1 tabl
The brachistochrone problem in open quantum systems
Recently, the quantum brachistochrone problem is discussed in the literature
by using non-Hermitian Hamilton operators of different type. Here, it is
demonstrated that the passage time is tunable in realistic open quantum systems
due to the biorthogonality of the eigenfunctions of the non-Hermitian Hamilton
operator. As an example, the numerical results obtained by Bulgakov et al. for
the transmission through microwave cavities of different shape are analyzed
from the point of view of the brachistochrone problem. The passage time is
shortened in the crossover from the weak-coupling to the strong-coupling regime
where the resonance states overlap and many branch points (exceptional points)
in the complex plane exist. The effect can {\it not} be described in the
framework of standard quantum mechanics with Hermitian Hamilton operator and
consideration of matrix poles.Comment: 18 page
Suppression of Magnetic Order by Pressure in BaFe2As2
We performed the dc resistivity and the ZF 75As-NMR measurement of BaFe2As2
under high pressure. The T-P phase diagram of BaFe2As2 determined from
resistivity anomalies and the ZF 75As-NMR clearly revealed that the SDW anomaly
is quite robust against P.Comment: 2 pages, 2 figure
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