414 research outputs found
Effect of Primordial Magnetic Field on Seeds for Large Scale Structure
Magnetic field plays a very important role in many astronomical phenomena at
various scales of the universe. It is no exception in the early universe.
Since the energy density, pressure, and tension of the primordial magnetic
field affect gravitational collapses of plasma, the formation of seeds for
large scale structures should be influenced by them. Here we numerically
investigate the effects of stochastic primordial magnetic field on the seeds of
large scale structures in the universe in detail. We found that the amplitude
ratio between the density spectra with and without PMF ( at
Mpc) lies between 75% and 130% at present for the range of PMF
strengths 0.5 nG nG, depending on the spectral index of PMF
and the correlation between the matter density and the PMF distributions.Comment: 20 pages, 5 figures, submitted to PRD 23 Jan 2006, Revised 02 Oct
2006, accepted for publication in PR
Fuzzy control applied to an electrical power generation system mounted on tractors for driving of agricultural implements
CAPES - COORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL DE NĂVEL SUPERIORThe demand of the agricultural sector for more operationally efficient machines and implements motivated the development of alternatives for driving of this equipment. Aiming an electrical supply to apply in agricultural implements, this study proposes a system that uses the tractor power take off to activate a synchronous generator, using a fuzzy logic controller designed to regulate the generated voltage level. Different control architectures were tested and evaluated by simulations. In the initial stage were evaluated fuzzy PI, fuzzy PD and fuzzy PID controllers of multiple inputs and single output (MISO) and the error of the generated voltage as state variable. Subsequently, it was evaluated a fuzzy PI controller of single input and multiple outputs (SIMO) with a modified rule base for the system. In the final stage, the angular drive speed was included as state variable of the controller. The behavior of each architecture was analyzed by means of performance indexes. The results show that among the tested controllers, the modified fuzzy PI SIMO presented the best performance values while maintaining the operating variables within the established limits.The demand of the agricultural sector for more operationally efficient machines and implements motivated the development of alternatives for driving of this equipment. Aiming an electrical supply to apply in agricultural implements, this study proposes a365846857CAPES - COORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL DE NĂVEL SUPERIORCAPES - COORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL DE NĂVEL SUPERIORsem informaçã
Fuzzy control applied to an electrical power generation system mounted on tractors for driving of agricultural implements
Observational Constraints on Accelerating Brane Cosmology with Exchange between the Bulk and Brane
We explore observational constraints on a cosmological brane-world scenario
in which the bulk is not empty. Rather, exchange of mass-energy between the
bulk and the bane is allowed. The evolution of matter fields to an observer on
the brane is then modified due to new terms in the energy momentum tensor
describing this exchange. We investigate the constraints from various
cosmological observations on the flow of matter from the bulk into the brane.
Interestingly, we show that it is possible to have a cosmology to
an observer in the brane which satisfies standard cosmological constraints
including the CMB temperature fluctuations, Type Ia supernovae at high
redshift, and the matter power spectrum. This model even accounts for the
observed suppression of the CMB power spectrum at low multipoles. In this
cosmology, the observed cosmic acceleration is attributable to the flow of
matter from the bulk to the brane. A peculiar aspect of this cosmology is that
the present dark-matter content of the universe may be significantly larger
than that of a CDM cosmology. Its influence, however, is offset by the
dark-radiation term. Possible additional observational tests of this new
cosmological paradigm are suggested.Comment: 11 pages, 5 figures, 1 tabl
Endometrial Carcinoma: A Review of Chemotherapy, Drug Resistance, and the Search for New Agents
The article examines current treatment options in patients with endometrial carcinoma, the role of drug resistance, and the rationale for the use of epothilones in treating this disease
Super-acceleration on the Brane by Energy Flow from the Bulk
We consider a brane cosmological model with energy exchange between brane and
bulk. Parameterizing the energy exchange term by the scale factor and Hubble
parameter, we are able to exactly solve the modified Friedmann equation on the
brane. In this model, the equation of state for the effective dark energy has a
transition behavior changing from to , while
the equation of state for the dark energy on the brane has . Fitting data
from type Ia supernova, Sloan Digital Sky Survey and Wilkinson Microwave
Anisotropy Probe, our universe is predicted now in the state of
super-acceleration with .Comment: Revtex, 11 pages including 2 figures,v2: tpos fixed, references
added, to appear in JCA
Restoring New Agegraphic Dark Energy in RS II Braneworld
Motivated by recent works [1,2], we investigate new agegraphic model of dark
energy in the framework of RS II braneworld. We also include the case of
variable gravitational constant in our model. Furthermore, we establish
correspondence between the new agegraphic dark energy with other dark energy
candidates based on scalar fields.Comment: 13 pages, accepted for publication in IJT
Multinucleation followed by an acytokinetic cell division in myxofibrosarcoma with giant cell proliferation
<p>Abstract</p> <p>Background</p> <p>Multinucleated cells are frequently seen in association with a malignant neoplasm. Some of these multinucleated cells are considered to be neoplastic. The mechanism of neoplastic multinucleation remains unknown, but is considered to be induced by either cell-cell fusion or acytokinetic cell division. Myxofibrosarcoma consists of spindled and pleomorphic tumor cells and bizarre multinucleated giant cells. Some of these multinucleated cells are considered to be neoplastic.</p> <p>Methods</p> <p>We studied the mitotic activity of the multinucleated cells by Ki-67 immunohistochemistry, and the dynamics and differentiation by live-cell video microscopy in the two myxofibrosarcoma cell lines to determine whether the mechanism of multinucleation is cell-cell fusion or acytokinetic cell division</p> <p>Results</p> <p>A Ki-67 immunohistochemical analysis revealed a high positive rate of multinucleated cells, as well as mononuclear cells, and mitotic ability was shown in the multinucleated cells. In live-cell video microscopy, most of the multinucleated cells were induced via the process of acytokinetic cell division.</p> <p>Conclusion</p> <p>The current study indicates that a vulnerability of the cytoskeleton components, such as the contractile ring, causes multinucleation to occur from the telophase to the cytokinesis of the cell cycle.</p
Non-minimally coupled canonical, phantom and quintom models of holographic dark energy
We investigate canonical, phantom and quintom models, with the various fields
being non-minimally coupled to gravity, in the framework of holographic dark
energy. We classify them and we discuss their cosmological implications. In
particular, we examine the present value of the dark energy equation-of-state
parameter and the crossing through the phantom divide, and we extract the
conditions for a future cosmological singularity. The combined scenarios are in
agreement with observations and reveal interesting cosmological behaviors.Comment: 9 pages, 5 figures, version published in Phys. Lett.
Dimensionless cosmology
Although it is well known that any consideration of the variations of
fundamental constants should be restricted to their dimensionless combinations,
the literature on variations of the gravitational constant is entirely
dimensionful. To illustrate applications of this to cosmology, we explicitly
give a dimensionless version of the parameters of the standard cosmological
model, and describe the physics of Big Bang Neucleosynthesis and recombination
in a dimensionless manner. The issue that appears to have been missed in many
studies is that in cosmology the strength of gravity is bound up in the
cosmological equations, and the epoch at which we live is a crucial part of the
model. We argue that it is useful to consider the hypothetical situation of
communicating with another civilization (with entirely different units),
comparing only dimensionless constants, in order to decide if we live in a
Universe governed by precisely the same physical laws. In this thought
experiment, we would also have to compare epochs, which can be defined by
giving the value of any {\it one} of the evolving cosmological parameters. By
setting things up carefully in this way one can avoid inconsistent results when
considering variable constants, caused by effectively fixing more than one
parameter today. We show examples of this effect by considering microwave
background anisotropies, being careful to maintain dimensionlessness
throughout. We present Fisher matrix calculations to estimate how well the fine
structure constants for electromagnetism and gravity can be determined with
future microwave background experiments. We highlight how one can be misled by
simply adding to the usual cosmological parameter set
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