646 research outputs found
The Discovery of Two Lyman Emitters Beyond Redshift 6 in the Subaru Deep Field
We have performed a deep optical imaging survey using a narrowband filter
() centered at 9196 \AA ~ together with and
broadband filters covering an 814 arcmin area of the Subaru Deep
Field. We obtained a sample of 73 strong -excess objects based on the
following two color criteria; and . We then obtained optical spectroscopy of nine objects in our
-excess sample, and identified at least two Ly emitters
at and , each of which shows the
characteristic sharp cutoff together with the continuum depression at
wavelengths shortward of the line peak. The latter object is more distant than
HCM-6A at and thus this is the most distant known object found so far.
These new data allow us to estimate the first meaningful lower limit of the
star formation rate density beyond redshift 6; yr Mpc. Since it is expected that the actual
density is higher by a factor of several than this value, our new observation
reveals that a moderately high level of star formation activity already
occurred at 6.6.Comment: 13 pages, 3 figures. PASJ (Letters), 55, vol.2, in pres
Luminosity versus Phase-Space-Density Relation of Galaxies Revisited
We reexamined the correlation between the B-T magnitude and the phase-space-density parameter w = (D-2(25) v(o))(-1) of galaxies for the Virgo, the Coma, the Fornax, and the Perseus clusters in an effort to better understand the physical underpinning of the fundamental plane. A tight correlation (B-T = a log w + b) common to different morphological types of galaxies (E, S0, S) was found for the Virgo and the Coma clusters, with a = 1.87 +/- 0.10 and 1.33 +/- 0.11, respectively. An investigation using only E galaxies was made for the four clusters. The results indicated that the empirical linear relation might be common among the Coma, the Fornax, and the Perseus clusters, with the Virgo Cluster showing deviation. This relation, which is another way to project the fundamental plane, has an expression insensitive to the morphology and may be suitable for treating galaxies of different morphological types collectively.ArticleThe Astrophysical Journal. 531:665-675 (2000)journal articl
Unusually Large Fluctuations in the Statistics of Galaxy Formation at High Redshift
We show that various milestones of high-redshift galaxy formation, such as
the formation of the first stars or the complete reionization of the
intergalactic medium, occurred at different times in different regions of the
universe. The predicted spread in redshift, caused by large-scale fluctuations
in the number density of galaxies, is at least an order of magnitude larger
than previous expectations that argued for a sharp end to reionization. This
cosmic scatter in the abundance of galaxies introduces new features that affect
the nature of reionization and the expectations for future probes of
reionization, and may help explain the present properties of dwarf galaxies in
different environments. The predictions can be tested by future numerical
simulations and may be verified by upcoming observations. Current simulations,
limited to relatively small volumes and periodic boundary conditions, largely
omit cosmic scatter and its consequences. In particular, they artificially
produce a sudden end to reionization, and they underestimate the number of
galaxies by up to an order of magnitude at redshift 20.Comment: 8 ApJ pages, 4 figures, ApJ. Minor changes in revised version.
Originally first submitted for publication on Aug. 29, 200
A_{LT} in the Nucleon-Nucleon Polarized Drell-Yan Process
We present a leading order (LO) estimate for the longitidinal-transverse spin
asymmetry (A_{LT}) in the nucleon-nucleon polarized Drell-Yan process at RHIC
and HERA- energies in comparison with A_{LL} and A_{TT}. A_{LT}
receives contribution from g_1, the transversity ditribution h_1, and the
twist-3 distributions g_T and h_L. For the twist-3 contribution we use the bag
model prediction evolved to a high energy scale by the large-N_c evolution
equation. We found that A_{LT} (normalized by the asymmetry in the parton
level) is much smaller than the corresponding A_{TT}. Twist-3 contribution
given by the bag model also turned out to be negligible.Comment: Talk presented at the KEK-Tanashi International Conference "Physics
of Hadrons and Nuclei", Dec. 14-17, 1998, Tokyo. 4 pages in Latex. 1 figure
included as eps files using epsbox.st
Peripheral nerve involvement in primary systemic AL amyloidosis: a clinical and electrophysiological study
Background: Involvement of visceral organs usually dominates the clinical picture of primary systemic AL amyloidosis, but some patients suffer from serious peripheral neuropathy. The aim of this study is to clinically and electrophysiologically investigate peripheral nerve involvement in AL amyloidosis patients. Patients and methods: We reviewed clinical manifestations, electrophysiological findings including nerve conduction velocities and treatments in 43 consecutive patients. Twenty age-matched healthy subjects were employed as controls. Results: Fifteen patients (34.9%) showed apparent neuropathic symptoms, which consisted of polyneuropathy in 11 (25.6%), bilateral carpal tunnel syndrome in 4 (9.3%), and autonomic dysfunction in 8 (18.6%). Polyneuropathy in this disease was characterized by symmetrical and sensory-dominant impairment, early involvement of the lower limbs, loss of all sensations, rarity of motor weakness, and painful paresthesia in the legs predominant at an early stage. Autonomic dysfunction including orthostatic hypotension was frequently associated with polyneuropathy at an advanced stage. On electrophysiological studies, motor conduction velocity and compound muscle action potential of both median and tibial nerves were significantly decreased in the patients with polyneuropathy but also in those without any signs of neuropathy. Only four of 15 patients with neuropathy were able to receive intensive but promising chemotherapy with a large dose of melphalan for plasma cell dyscrasia. Conclusions: Peripheral nerves in primary systemic AL amyloidosis patients seem to be involved more extensively than clinical manifestations might suggest. The clinical picture of polyneuropathy in this disease closely resembles that in transthyretin-type familial amyloid polyneuropathy patients with a late age at onset, particularly those originating from sporadic kindreds.ArticleEUROPEAN JOURNAL OF NEUROLOGY. 18(4):604-610 (2011)journal articl
Right Handed Weak Currents in Sum Rules for Axialvector Constant Renormalization
The recent experimental results on deep inelastic polarized lepton scattering
off proton, deuteron and He together with polari% zed neutron
-decay data are analyzed. It is shown that the problem of Ellis-Jaffe
and Bjorken sum rules deficiency and the neutron paradox could be solved
simultaneously by assuming the small right handed current (RHC) admixture in
the weak interaction Lagrangian. The possible RHC impact on pion-nucleon
-term and Gamow-Teller sum rule for nuclear reactions is
pointed out.Comment: to be published in Phys. Rev. Lett. LaTeX, 8 pages, 21 k
One-Loop Factorization of the Nucleon g_2-Structure Function in the Non-Singlet Case
We consider the one-loop factorization of the simplest twist-three process:
inclusive deep-inelastic scattering of longitudinally-polarized leptons on a
transversely-polarized nucleon target. By studying the Compton amplitudes for
certain quark and gluon states at one loop, we find the coefficient functions
for the non-singlet twist-three distributions in the factorization formula of
g_2(x_B,Q^2). The result marks the first step towards a next-to-leading order
(NLO) formalism for this transverse-spin-dependent structure function of the
nucleon.Comment: 14 pages, revtex4, four figures included, minor change
Knots, Braids and BPS States in M-Theory
In previous work we considered M-theory five branes wrapped on elliptic
Calabi-Yau threefold near the smooth part of the discriminant curve. In this
paper, we extend that work to compute the light states on the worldvolume of
five-branes wrapped on fibers near certain singular loci of the discriminant.
We regulate the singular behavior near these loci by deforming the discriminant
curve and expressing the singularity in terms of knots and their associated
braids. There braids allow us to compute the appropriate string junction
lattice for the singularity and,hence to determine the spectrum of light BPS
states. We find that these techniques are valid near singular points with N=2
supersymmetry.Comment: 38 page
Hyperkahler Metrics from Periodic Monopoles
Relative moduli spaces of periodic monopoles provide novel examples of
Asymptotically Locally Flat hyperkahler manifolds. By considering the
interactions between well-separated periodic monopoles, we infer the asymptotic
behavior of their metrics. When the monopole moduli space is four-dimensional,
this construction yields interesting examples of metrics with self-dual
curvature (gravitational instantons). We discuss their topology and complex
geometry. An alternative construction of these gravitational instantons using
moduli spaces of Hitchin equations is also described.Comment: 23 pages, latex. v2: an erroneous formula is corrected, and its
derivation is given. v3 (published version): references adde
Purification and characterization of UDP-glucose: hydroxycoumarin 7-O-glucosyltransferase, with broad substrate specificity from tobacco cultured cells
The enzyme UDP-glucose: hydroxycoumarin 7-O-glucosyltransferase (CGTase), which catalyzes the formation of scopolin from scopoletin, was purified approximately 1200-fold from a culture of 2,4-D-treated tobacco cells (Nicotiana tabacum L. cv. Bright Yellow T-13) with a yield of 7%. Purification to apparent homogeneity, as judged by SDS-PAGE, was achieved by sequential anion-exchange chromatography, hydroxyapatite chromatography, gel filtration, a second round of anion-exchange chromatography, and affinity chromatography on UDP-glucuronic acid agarose. The purified enzyme had a pH optimum of 7.5, an isoelectric point (pI) of 5.0, and a molecular mass of 49 kDa. The enzyme did not require metal cofactors for activity. Its activity was inhibited by Zn2+, Co2+ and Cu2+ ions, as well as by SH-blocking reagents. The K-m values for UDP-glucose, scopoletin and esculetin were 43, 150 and 25 mu M. respectively. A study of the initial rate of the reaction suggested that the reaction proceeded via a sequential mechanism. The purified enzyme preferred hydroxycoumarins as substrates but also exhibited significant activity with flavonoids. A database search using the amino terminus amino acid sequence of CGTase revealed strong homology to the amino acid sequences of other glucosyltransferases in plants.ArticlePlant Science. 157(1):105-112 (2000)journal articl
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