6,864 research outputs found
Observational tests for oscillating expansion rate of the Universe
We investigate the observational constraints on the oscillating scalar field
model using data from type Ia supernovae, cosmic microwave background
anisotropies, and baryon acoustic oscillations. According to a Fourier
analysis, the galaxy number count from redshift data indicates that
galaxies have preferred periodic redshift spacings. We fix the mass of the
scalar field as such that the scalar
field model can account for the redshift spacings, and we constrain the other
basic parameters by comparing the model with accurate observational data. We
obtain the following constraints: (95% C.L.),
(95% C.L.) (in the range
). The best fit values of the energy density parameter of the scalar
field and the coupling constant are and ,
respectively. The value of is close to but not equal to .
Hence, in the scalar field model, the amplitude of the galaxy number count
cannot be large. However, because the best fit values of and
are not , the scalar field model has the possibility of accounting for
the periodic structure in the -- relation of galaxies. The variation of
the effective gravitational constant in the scalar field model is not
inconsistent with the bound from observation.Comment: 9 pages, 11 figures, 1 table, Accepted for publication in Physical
Review
Janus within Janus
We found a simple and interesting generalization of the non-supersymmetric
Janus solution in type IIB string theory. The Janus solution can be thought of
as a thick AdS_d-sliced domain wall in AdS_{d+1} space. It turns out that the
AdS_d-sliced domain wall can support its own AdS_{d-1}-sliced domain wall
within it. Indeed this pattern persists further until it reaches the
AdS_2-slice of the domain wall within self-similar AdS_{p (2<p\le d)}-sliced
domain walls. In other words the solution represents a sequence of little Janus
nested in the interface of the parent Janus according to a remarkably simple
``nesting'' rule. Via the AdS/CFT duality, the dual gauge theory description is
in general an interface CFT of higher codimensions.Comment: 15 pages, 6 figures, v2 references added. v3 eq.(3.33) correcte
CGC, Hydrodynamics, and the Parton Energy Loss
Hadron spectra in Au+Au collisions at RHIC are calculated by hydrodynamics
with initial conditions from the Color Glass Condensate (CGC). Minijet
components with parton energy loss in medium are also taken into account by
using parton density obtained from hydrodynamical simulations. We found that
CGC provides a good initial condition for hydrodynamics in Au+Au collisions at
RHIC.Comment: Quark Matter 2004 contribution, 4 pages, 2 figure
Flounder metamorphosis: its regulation by various hormones
The elongation and shortening of the flounder fin rays during its metamorphosis may be parallel to the appearance and resorption of the tadpole tail during amphibian metamorphosis. The dorsal fin rays of the Japanese flounder (Paralichthys olivaceus) elongate during the time when thyroid hormone levels are low and are resorbed during climax of metamorphosis when thyroid levels are elevated. Using an in vitro system for culture of isolated flounder fin rays, we examined how various hormones affect the process of resorption. Both T4 and T3 directly stimulated fin ray shortening, T3 being more potent than T4. Other hormones did not directly affect the resorption process but modified the tissue's response to thyroid hormones. Cortisol enhanced the stimulatory effects of both T4 and T3. On the other hand, estradiol and testosterone were inhibitory. Ovine prolactin (oPRL) also diminished the effect of T3 while ovine growth hormone (oGH) was without effect. Similar observations were observed from the in vivo studies.
Thyroid hormone levels, especially T4, were low during premetamorphosis, increased during prometamorphosis, to peak levels during metamorphic climax, and declined in the juveniles. The changes in whole body concentrations of Cortisol paralleled the changes in thyroid hormone concentrations. On the other hand, whole body estradiol and testosterone concentrations did not show significant change and remained low throughout the larval period. The expression of GH and PRLmRNA, as assessed by in situ hybridization using cDNA for flounder PRL and GH also increased during the metamorphosis. However, the increase in the expression of GH and PRL genes was observed later than the increases in tissue levels of thyroid hormones and Cortisol. At late climax, the flounder larvae have undergone considerable transformation, presumably triggered by both hormones, hence the increase in PRL could hardly be antimetamorphic but may have other physiological implications
ISWI remodeling complexes in Xenopus egg extracts: Identification as major chromosomal components that are regulated by INCENP-aurora B
We previously characterized major components of mitotic chromosomes assembled in Xenopus laevis egg extracts and collectively referred to them as Xenopuschromosome–associated polypeptides (XCAPs). They included five subunits of the condensin complex essential for chromosome condensation. In an effort to identify novel proteins involved in this process, we have isolated XCAP-F and found it to be theXenopus ortholog of ISWI, a chromatin remodeling ATPase. ISWI exists in two major complexes in Xenopus egg extracts. The first complex contains ACF1 and two low-molecular-weight subunits, most likely corresponding to Xenopus CHRAC. The second complex is a novel one that contains theXenopus ortholog of the human Williams syndrome transcription factor (WSTF). In the absence of the ISWI complexes, the deposition of histones onto DNA is apparently normal, but the spacing of nucleosomes is greatly disturbed. Despite the poor spacing of nucleosomes, ISWI depletion has little effect on DNA replication, chromosome condensation or sister chromatid cohesion in the cell-free extracts. The association of ISWI with chromatin is cell cycle regulated and is under the control of the INCENP-aurora B kinase complex that phosphorylates histone H3 during mitosis. Apparently contradictory to the generally accepted model, we find that neither chromosome condensation nor chromosomal targeting of condensin is compromised when H3 phosphorylation is drastically reduced by depletion of INCENP-aurora B
Elliptic flow of thermal dileptons as a probe of QCD matter
We study the variation of elliptic flow of thermal dileptons with transverse
momentum and invariant mass of the pairs for Pb+Pb collisions at
= 2.76 TeV. The dilepton productions from quark gluon plasma
(QGP) and hot hadrons have been considered including the spectral change of
light vector mesons in the thermal bath. The space time evolution has been
carried out within the frame work of 2+1 dimensional ideal hydrodynamics with
lattice+hadron resonance gas equation of state. We find that a judicious
selection of invariant mass(M) and transverse momentum (p_T) windows can be
used to extract the collective properties of quark matter, hadronic matter and
also get a distinct signature of medium effects on vector mesons. Our results
indicate a reduction of elliptic flow (v_2) for M beyond phi mass, which if
observed experimentally would give the measure of v_2 of the partonic phase.Comment: To appear in Phys. Rev. C (Rapid Comm.
THE EXPRESSION OF HLA-G ANTIGEN IN DIFFERENT HUMAN TISSUES AND PLACENTAS AT DIFFERENT STAGES OF PREGNANCY
The distribution of HLA-G antigens in human tissues including placents was examined by immunohistochemical methods, using monoclonal antibody (Mab) specific to HLA-G antigen (87 G). Comparatively, class â… specific Mab, W 6/32 was also employed for the detection of the antigen. W 6/32 reacted with a wide variety of cells and tissues throughout the body, whereas Mab 87 G did not react at all with these W 6/32 reactive cells except for those of placental tissues. Mab 87 G reacted with extravillous cytotrophoblast cells such as cytotrophoblastic cell columns, cytotrophoblastic shell and
invasive cytotrophoblast but not other parts of placentas throughout the pregnant periods.
Essentially the same results were obtained with W 6/32 staining in placentas. These results indicate that HLA-G antigens are exclusively expressed in extravillous cytotrophoblast cells although we cannot rule out the possibility that undetectable amounts of the HLA-G antigen or its isoforms which cannot be recognized by the Mabs used in this study are synthesized in some other tissues
Theoretical Study of Friction: A Case of One-Dimensional Clean Surfaces
A new method has been proposed to evaluate the frictional force in the
stationary state. This method is applied to the 1-dimensional model of clean
surfaces. The kinetic frictional force is seen to depend on velocity in
general, but the dependence becomes weaker as the maximum static frictional
force increases and in the limiting case the kinetic friction gets only weakly
dependent on velocity as described by one of the laws of friction. It is also
shown that there is a phase transition between state with vanishing maximum
static frictional force and that with finite one. The role of randomness at the
interface and the relation to the impurity pinning of the sliding
Charge-Density-Wave are discussed. to appear in Phys.Rev.B. abstract only. Full
text is available upon request. E-mail: [email protected]: 2 pages, Plain TEX, OUCMT-94-
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