15,628 research outputs found
The Ritter-Kolb Catalogue and its Impact on Research into CVs, LMXBs and related Objects
In the first part of this paper, the Ritter-Kolb catalogue (RKcat for short), its history and a few examples of its application to research in the field of cataclysmic variables are briefly described. In a second part we look forward to possible future applications of RKcat for the study of cataclysmic variables, low-mass X-ray binaries and related objects. Last but not least we also briefly comment on the future of the RKcat service itself
Vision to reality: From Robert R. Wilson's frontier to Leon M. Lederman's Fermilab
This paper examines the roles of vision and leadership in creating and
directing Fermi National Accelerator Laboratory from the late 1960s through the
1980s. The story divides into two administrations having different problems and
accomplishments, that of Robert R. Wilson (1967-1978), which saw the
transformation from cornfield to frontier physics facility, and that of Leon
Max Lederman (1979-1989), in which the laboratory evolved into one of the
world's major high-energy facilities. Lederman's pragmatic vision of a
user-based experimental community helped him to convert the pioneering facility
that Wilson had built frugally into a laboratory with a stable scientific,
cultural, and funding environment
Regulation of 92-kD gelatinase release in HL-60 leukemia cells
Matrix metalloproteinase 9 (MMP-9), also known as 92-kD type IV collagenase/gelatinase, is believed to play a critical role in tumor invasion and metastasis. Here, we report that MMP-9 was constitutively released from the human promyelocytic cell line HL-60 as determined by zymographic analysis. Tumor necrosis factor-alpha (TNF-alpha) enhanced the enzyme release threefold to fourfold and the protein kinase C (PKC) activator and differentiation inducer 12-O-tetradecanoylphorbol-13- acetate (TPA) eightfold to ninefold. Gelatinase induction by TNF-alpha and TPA was inhibited by actinomycin D or cycloheximide, indicating that de novo protein synthesis was required. Neutralizing monoclonal antibodies to TNF-alpha (anti-TNF-alpha) decreased the basal MMP-9 release of these cells. In addition, these antibodies also significantly interfered with the TPA-induced enzyme release. Agents that inhibit TNF-alpha expression in HL-60 cells, such as pentoxifylline and dexamethasone, completely abrogated both the constitutive and TPA-evoked MMP-9 release. Diethyldithiocarbamate, which is known to stimulate TNF-alpha production in HL-60 cells, exerted a positive effect on MMP-9 release in untreated cells but was inhibitory in TPA-treated HL-60 cells. The PKC inhibitor staurosporine at low concentrations (100 ng/mL) caused a significant augmentation of MMP-9 release in untreated cultures that was blocked by the addition of anti-TNF-alpha. High concentrations (2 mumol/L) of staurosporine completely abolished the extracellular enzyme activity both in untreated and TPA-stimulated cells. These results suggest, that TNF- alpha is required for basal and PKC-mediated MMP-9 release in HL-60 leukemia cells. Thus, MMP-9 secretion may be regulated by TNF-alpha not only in a paracrine but also in an autocrine fashion. This may potentiate the matrix degradative capacity of immature leukemic cells in the processes of bone marrow egress and the evasion of these cells into peripheral tissue
Cosmic Microwave Background Observations as a Way to Discriminate Among Inflation Models
The upcoming satellite missions MAP and Planck will measure the spectrum of
fluctuations in the Cosmic Microwave Background with unprecedented accuracy. We
discuss the prospect of using these observations to distinguish among proposed
models of inflationary cosmology.Comment: To appear in the proceedings of the XXXIIIrd Rencontres de Moriond,
"Fundamental Parameters in Cosmology", 17-24 January, Les Arcs, France. 6
Pages, 2 figures, uses moriond.st
Non-critical String Cosmologies
Non-critical String Cosmologies are offered as an alternative to Standard Big
Bang Cosmology. The new features encompassed within the dilaton dependent
non-critical terms affect the dynamics of the Universe\'s evolution in an
unconventional manner being in agreement with the cosmological data.
Non-criticality is responsible for a late transition to acceleration at
redshifts z=0.2. The role of the uncoupled rolling dilaton to relic abundance
calculations is discussed. The uncoupled rolling dilaton dilutes the neutralino
relic densities in supersymmetric theories by factors of ten, relaxing
considerably the severe WMAP Dark Matter constraints, while at the same time
leaves almost unaffected the baryon density in agreement with primordial
Nucleosynthesis.Comment: 16 pages, 7 figures, conference tal
Elliptic Flow from a Transversally Thermalized Fireball
The agreement of elliptic flow data at RHIC at central rapidity with the
hydrodynamic model has led to the conclusion of very rapid thermalization. This
conclusion is based on the intuitive argument that hydrodynamics, which assumes
instantaneous local thermalization, produces the largest possible elliptic flow
values and that the data seem to saturate this limit. We here investigate the
question whether incompletely thermalized viscous systems may actually produce
more elliptic flow than ideal hydrodynamics. Motivated by the extremely fast
primordial longitudinal expansion of the reaction zone, we investigate a toy
model which exhibits thermalization only in the transverse directions but
undergoes collisionless free-streaming expansion in the longitudinal direction.
For collisions at RHIC energies, elliptic flow results from the model are
compared with those from hydrodynamics. With the final particle yield and
\kt-distribution fixed, the transversally thermalized model is shown not to
be able to produce the measured amount of elliptic flow. This investigation
provides further support for very rapid local kinetic equilibration at RHIC. It
also yields interesting novel results for the elliptic flow of massless
particles such as direct photons.Comment: revtex4, 15 pages + 10 embedded EPS figure
A Note on Gravitational Baryogenesis
The coupling between Ricci scalar curvature and the baryon number current
dynamically breaks CPT in an expanding universe and leads to baryon asymmetry.
We study the effect of time dependence of equation of state parameter of the
FRW universe on this asymmetry.Comment: 10 pages, accepted for publication in Physical Review
Multicomponent solution in modified theory of gravity in the early universe
We study the modified theory of gravity in Friedmann Robertson Walker
universe composed of several perfect fluids. We consider the power law
inflation and determine the equation of state parameters in terms of the
parameters of modified gravity's Lagrangian in the early universe. We also
discuss briefly the gravitational baryogenesis in this model.Comment: 9 pages, accepted for publication in Physical Review
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