3,662 research outputs found
A role for glyceraldehyde-3-phosphate dehydrogenase in the development of thermotolerance in Xenopus laevis embryos
During heat shock, Xenopus laevis embryos exhibit an increase in the rate of accumulation of lactate and a loss of ATP relative to non-heat- shocked control embryos. These results suggest that heat shock stimulates a shift in energy metabolism to anaerobic glycolysis while at the same time causing an increase in the demand for ATP. We have evidence indicating that the embryo may meet such demands placed on it by increasing the levels of some glycolytic enzymes. In this report, we show that heat shock stimulates increases in the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase [( EC 1.2.1.12] GAPDH). The specific activity of GAPDH shows a significant increase after heat shock, which correlates with the accumulation of GAPDH in heat-shocked embryos as detected by immunoblotting. Increases in GAPDH-specific activity are variable, however, and are inversely proportional to the levels of specific activity in control embryos; i.e., constitutive enzyme activity. We further analyzed the heat-enhanced accumulation of GAPDH by electrophoretically separating GAPDH isozymes on nondenaturing polyacrylamide gels. Control embryos exhibit a single isozyme of GAPDH, whereas heat-shocked embryos exhibit two isozymes of GAPDH. When these isozymes are labeled with [35S]methionine, separated by nondenaturing gel electrophoresis, and analyzed by fluorography, a heat-shock protein is found to comigrate with the isozyme unique to the heat-shocked sample. Enzyme activity assays at different temperatures suggest that this isozyme has optimum enzymatic activity only at heat-shock temperatures. We have correlated a 35-kD heat-shock protein (hsp35) with GAPDH using the following evidence: this hsp comigrates with GAPDH on one-dimensional SDS polyacrylamide gels; heat-enhanced increases in GAPDH specific activity correlate with hsp35 synthesis; and hsp35 and GAPDH have similar peptide maps. This relationship also provides a compelling explanation for the restriction of hsp35 synthesis to the vegetal hemisphere cells of heat-shocked early gastrulae reported previously (Nickells, R. W., and L. W. Browder. 1985. Dev. Biol. 112:391-395)
A subalgebra of the Hardy algebra relevant in control theory and its algebraic-analytic properties
We denote by A_0+AP_+ the Banach algebra of all complex-valued functions f
defined in the closed right half plane, such that f is the sum of a holomorphic
function vanishing at infinity and a ``causal'' almost periodic function. We
give a complete description of the maximum ideal space M(A_0+AP_+) of A_0+AP_+.
Using this description, we also establish the following results:
(1) The corona theorem for A_0+AP_+.
(2) M(A_0+AP_+) is contractible (which implies that A_0+AP_+ is a projective
free ring).
(3) A_0+AP_+ is not a GCD domain.
(4) A_0+AP_+ is not a pre-Bezout domain.
(5) A_0+AP_+ is not a coherent ring.
The study of the above algebraic-anlaytic properties is motivated by
applications in the frequency domain approach to linear control theory, where
they play an important role in the stabilization problem.Comment: 17 page
Results of a fish health survey of North Biscayne Bay, June 1976-June 1977
Fish were collected weekly in Biscayne Bay using a monofilament gill net set from a small skiff during 20-30 minute intervals. Although weekly sampling took place for 2.5 years, only the data from samples collected from June 1976 to June 1977 were used in this document. Abnormal external conditions of fins and body were observed on each fish and recorded. Fish were returned immediately to their habitats. Fish collected in the time period for this study numbered 3,765 and included 32 species. Of these, 16 species, totaling 3,556 fish, were caught in sufficient numbers (20 or more) to warrant data analysis. Only 3 of the 16 species could be considered relatively unafflicted: Aetobatus narinari (spotted eagle ray), Diodon hystrix (porcupinefish), and Selene vomer (lookdown). More than 80% of the examined specimens of these three species were unaffected. Less than 20% of the specimens of Diapterus plumieri (striped mojarra), Micropogonias undulatus (Atlantic croaker), and Pogonias cromis (black drum) displayed normal conditions. The three most afflicted species were Diapterus plumieri, striped mojarra; Micropogonias undulatus, Atlantic croaker; and Pogonias cromis, black drum. Only 7, 3, and 7% respectively showed no external evidence of disease. Data described in this document were originally tabulated in the mid-1970s, remained unpublished, and are no longer available. This document was based on archived unpublished text, a data summary table, and figures. Most of the text and cited references were the ones used in the original manuscript and no attempt was made to update them. (PDF contains 44 pages
Precision Flavour Physics with and
We show that a combined analysis of and
allows for new physics tests practically free of form factor uncertainties.
Residual theory errors are at the level of several percent. Our study
underlines the excellent motivation for measuring these modes at a Super
Flavour Factory.Comment: 26 pages, 2 figure
Prospects for Direct CP Violaton in Exclusive and Inclusive Charmless B decays
Within the Standard Model, CP rate asymmetries for could
reach 10%. With strong final state phases, they could go up to 20--30%, even
for mode which would have opposite sign. We can account for
, and rate data with new physics enhanced
color dipole coupling and destructive interference. Asymmetries could reach
40--60% for and modes and are all of the same sign. We are
unable to account for rate. Our inclusive study supports our
exclusive results.Comment: Minor changes, correct a small bug in Fig. 1(b). Version to appear in
Phys. Rev. Let
An imaging time-of-propagation system for charged particle identification at a super B factory
Super B factories that will further probe the flavor sector of the Standard
Model and physics beyond will demand excellent charged particle identification
(PID), particularly K/pi separation, for momenta up to 4 GeV/c, as well as the
ability to operate under beam backgrounds significantly higher than current B
factory experiments. We describe an Imaging Time-of-Propagation (iTOP) detector
which shows significant potential to meet these requirements. Photons emitted
from charged particle interactions in a Cerenkov radiator bar are internally
reflected to the end of the bar, where they are collected on a compact image
plane using photodetectors with fine spatial segmentation in two dimensions.
Precision measurements of photon arrival time are used to enhance the two
dimensional imaging, allowing the system to provide excellent PID capabilities
within a reduced detector envelope. Results of the ongoing optimization of the
geometric and physical properties of such a detector are presented, as well as
simulated PID performance. Validation of simulations is being performed using a
prototype in a cosmic ray test stand at the University of Hawaii.Comment: 3 pages, 5 figures, submitted to TIPP09 proceeding
B-> K photon photon via intermediate eta'
We examine our previous conjecture that the eta' intermediate resonance has
the dominant role in the long distance contributions to B decay into two
photons and a strange final state hadron. We calculate the branching ratio of
the exclusive B-> K eta'-> K photon photon decay using the nonspectator
mechanism for eta' production in charmless hadronic B decays. It is shown that
the obtained branching ratio B^eta'(B-> K\gamma\gamma)~ 8.7 X 10^{-7} is more
than twice as large as the eta_c contribution to this decay mode.Comment: 6 pages, latex, no figure
Model-independent analysis of \bbox{B}-\bbox{\bar B} mixing and \bbox{CP} violation in \bbox{B} decays
We present a framework to analyze effects of new physics beyond the standard
model on - mixing and violation in decays in a
model-independent manner. Assuming that tree level decay amplitudes are
dominated by the standard model ones, new physics contribution to the - mixing can be extracted from several measurements at factories. Using
this framework, we show the present constraint on new physics contribution to
the - mixing, and illustrate constraints expected to be given by
future experiments at factories. We also point out a possibility that
asymmetries in , , and modes look consistent with the standard model, even if a large new physics
contribution is present in the - mixing.Comment: 11 pages, 3 Postscript figures, also available via anonymous ftp at
ftp://ftp.kek.jp/kek/preprints/TH/TH-44
Heavy-Quark Symmetry and the Electromagnetic Decays of Excited Charmed Strange Mesons
Heavy-hadron chiral perturbation theory (HHPT) is applied to the decays
of the even-parity charmed strange mesons, D_{s0}(2317) and D_{s1}(2460).
Heavy-quark spin symmetry predicts the branching fractions for the three
electromagnetic decays of these states to the ground states D_s and D_s^* in
terms of a single parameter. The resulting predictions for two of the branching
fractions are significantly higher than current upper limits from the CLEO
experiment. Leading corrections to the branching ratios from chiral loop
diagrams and spin-symmetry violating operators in the HHPT Lagrangian can
naturally account for this discrepancy. Finally the proposal that the
D_{s0}(2317) (D_{s1}(2460)) is a hadronic bound state of a D (D^*) meson and a
kaon is considered. Leading order predictions for electromagnetic branching
ratios in this molecular scenario are in very poor agreement with existing
data.Comment: 25 pages, 3 figure
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