1,408 research outputs found
Exact Eigenfunctions of -Body system with Quadratic Pair Potential
We obtain all the exact eigenvalues and the corresponding eigenfunctions of
-body Bose and Fermi systems with Quadratic Pair Potentials in one
dimension. The originally existed first excited state level is missing in one
dimension, which results from the operation of symmetry or antisymmetry of
identical particles. In two and higher dimensions, we give all the eigenvalues
and the analytical ground state wave functions and the number of degeneracy.
Through the comparison with Avinash Khare's results, we have perfected his
results.Comment: 7 pages,1 figur
Diffuse interstitial and multiple cavitary lung lesions due to Talaromyces marneffei infection in a non-HIV patient
AbstractA 57-year-old man presented with unproductive cough and dyspnea for 6 months in Fujian Province, China. His misuse of a large amount of steroids (accumulated dose equivalent to 3530Â mg prednisolone) resulted in Talaromyces marneffei infection. Chest computed tomographic scan revealed diffuse interstitial and multiple cavitary lung lesions. Treatment with amphotericin B combined with itraconazole resulted in total recovery, with marked regression of lung lesions
Identification of essential cysteine residues in 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Corynebacterium glutamicum
To ascertain the functional role of cysteine residue in 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase from Corynebacterium glutamicum, site-directed mutagenesis was performed to change each of the three residues to serine. Plasmids were constructed for high-level overproduction and one-step purification of histidine-tagged DAHP synthase. Analysis of the purified wild-type and mutant enzymes by SDS-polyacrylamide gel electrophoresis showed an apparent protein band with a molecular mass of approximately 45 kDa. Cys(145)Ser mutant retained about 16% of the enzyme activity, while DAHP synthase activity was abolished in Cys(67)Ser mutant. Kinetic analysis of Cys(145)Ser mutant with PEP as a substrate revealed a marked increase in K-m with significant change in k(cat), resulting in a 13.6-fold decrease in k(cat)/K-m(PEP). Cys(334) was found to be nonessential for catalytic activity, although it is highly conserved in DAHP synthases. From these studies, Cys(67) appears important for synthase activity, while Cys(145) plays a crucial role in the catalytic efficiency through affecting the mode of substrate binding
Serine 187 is a crucial residue for allosteric regulation of Corynebacterium glutamicum 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase
Corynebacterium glutamicum 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase is sensitive to feedback inhibition by tyrosine. One feedback-insensitive mutant was obtained by in vitro chemical mutagenesis and the mutation was identified as a C-->G mutation at nucleotide 560 causing a Ser(187) to Cys(187) substitution. Replacing Ser(187) with cysteine, tyrosine or phenylalanine by site-directed mutagenesis not only reduced the enzymatic activity but also relieved its feedback inhibition by tyrosine, while Ser(187)Ala exhibited a comparable activity to that of wild-type enzyme and sensitized to allosteric regulation. The His(6)-tagged enzymes were expressed in Escherichia coli and purified to homogeneity by immobilized nickel-ion affinity chromatography. Kinetic analysis showed that tyrosine is a competitive inhibitor of phosphoenol pyruvate, one of the precursors for DAHP biosynthesis. (C) 2001 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved
The role of a conserved histidine residue, His324, in Trigonopsis variabilis D-amino acid oxidase
To investigate the functional role of an invariant histidine residue in Trigonopsis variabilis D-amino acid oxidase (DAAO), a set of mutant enzymes with replacement of the histidine residue at position 324 was constructed and their enzymatic properties were examined, Wild-type and mutant enzymes have been purified to homogeneity using the His-bound column and the molecular masses were determined to be 39.2 kDa. Western blot analysis revealed that the in vivo synthesized mutant enzymes are immune-identical with that of the wild-type DAAO. The His324Asn and His324Gln mutants displayed comparable enzymatic activity to that of the wild-type enzyme, while the other mutant DAAOs showed markedly decreased or no detectable activity. The mutants, His324/Asn/Gln/Ala/Tyr/Glu, exhibited 38-181% increase in K-m and a 2-10-fold reduction in k(cat)/K-m. Based on the crystal structure of a homologous protein, pig kidney DAAO, it is suggested that His324 might play a structural role for proper catalytic function of T. variabilis DAAO. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved
Dynamics of Baryons from String Theory and Vector Dominance
We consider a holographic model of QCD from string theory, a la Sakai and
Sugimoto, and study baryons. In this model, mesons are collectively realized as
a five-dimensional \ Yang-Mills field and baryons
are classically identified as solitons with a unit Pontryagin number
and electric charges. The soliton is shown to be very small in the large
't Hooft coupling limit, allowing us to introduce an effective field . Its coupling to the mesons are dictated by the soliton structure, and
consists of a direct magnetic coupling to the field strength as well
as a minimal coupling to the gauge field. Upon the dimensional
reduction, this effective action reproduces all interaction terms between
nucleons and an infinite tower of mesons in a manner consistent with the large
expansion. We further find that all electromagnetic interactions, as
inferred from the same effective action via a holographic prescription, are
mediated by an infinite tower of vector mesons, rendering the baryon
electromagnetic form factors completely vector-dominated as well. We estimate
nucleon-meson couplings and also the anomalous magnetic moments, which compare
well with nature.Comment: 65pages, 3 figures, vector mesons and axial-vector mesons are now
canonically normalized (comparisons with data and conclusions unaffected
Torus knots and mirror symmetry
We propose a spectral curve describing torus knots and links in the B-model.
In particular, the application of the topological recursion to this curve
generates all their colored HOMFLY invariants. The curve is obtained by
exploiting the full Sl(2, Z) symmetry of the spectral curve of the resolved
conifold, and should be regarded as the mirror of the topological D-brane
associated to torus knots in the large N Gopakumar-Vafa duality. Moreover, we
derive the curve as the large N limit of the matrix model computing torus knot
invariants.Comment: 30 pages + appendix, 3 figure
Ownership and control in a competitive industry
We study a differentiated product market in which an investor initially owns a controlling stake in one of two competing firms and may acquire a non-controlling or a controlling stake in a competitor, either directly using her own assets, or indirectly via the controlled firm. While industry profits are maximized within a symmetric two product monopoly, the investor attains this only in exceptional cases. Instead, she sometimes acquires a noncontrolling stake. Or she invests asymmetrically rather than pursuing a full takeover if she acquires a controlling one. Generally, she invests indirectly if she only wants to affect the product market outcome, and directly if acquiring shares is profitable per se. --differentiated products,separation of ownership and control,private benefits of control
Physics of Solar Prominences: II - Magnetic Structure and Dynamics
Observations and models of solar prominences are reviewed. We focus on
non-eruptive prominences, and describe recent progress in four areas of
prominence research: (1) magnetic structure deduced from observations and
models, (2) the dynamics of prominence plasmas (formation and flows), (3)
Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and
large-scale patterns of the filament channels in which prominences are located.
Finally, several outstanding issues in prominence research are discussed, along
with observations and models required to resolve them.Comment: 75 pages, 31 pictures, review pape
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