679 research outputs found
Cosmic microwave background: polarization and temperature anisotropies from symmetric structures
I consider the case of anisotropies in the Cosmic Microwave Background (CMB)
from one single ordered perturbation source, or seed, existing well before
decoupling between matter and radiation. Such structures could have been left
by high energy symmetries breaking in the early universe.
I focus on the cases of spherical and cylindrical symmetry of the seed. I
give general analytic expressions for the polarization and temperature linear
perturbations, factoring out of the Fourier integral the dependence on the
photon propagation direction and on the geometric coordinates describing the
seed. I show how the CMB perturbations manifestly reflect the symmetries of
their seeds. CMB anisotropies are obtained with a line of sight integration.
This treatment highlights the undulatory properties of the CMB. I show with
numerical examples how the polarization and temperature perturbations propagate
beyond the size of their seeds, reaching the CMB sound horizon at the time
considered. Just like the waves from a pebble thrown in a pond, CMB anisotropy
from a seed intersecting the last scattering surface appears as a series of
temperature and polarization waves surrounding the seed, extending on the scale
of the CMB sound horizon at decoupling, roughly in the sky. Each wave
is characterized by its own value of the CMB perturbation, with the same mean
amplitude of the signal coming from the seed interior.
These waves could allow to distinguish relics from high energy processes of
the early universe from point-like astrophysical sources, because of their
angular extension and amplitude. Also, the marked analogy between polarization
and temperature signals offers cross correlation possibilities for the future
Planck Surveyor observations.Comment: 21 pages, seven postscript figures, final version accepted for
publication in Phys.Rev.
Blackbody Radiation and the Scaling Symmetry of Relativistic Classical Electron Theory with Classical Electromagnetic Zero-Point Radiation
It is pointed out that relativistic classical electron theory with classical
electromagnetic zero-point radiation has a scaling symmetry which is suitable
for understanding the equilibrium behavior of classical thermal radiation at a
spectrum other than the Rayleigh-Jeans spectrum. In relativistic classical
electron theory, the masses of the particles are the only scale-giving
parameters associated with mechanics while the action-angle variables are scale
invariant. The theory thus separates the interaction of the action variables of
matter and radiation from the scale-giving parameters. Classical zero-point
radiation is invariant under scattering by the charged particles of
relativistic classical electron theory. The basic ideas of the matter
-radiation interaction are illustrated in a simple relativistic classical
electromagnetic example.Comment: 18 page
Voltage-programmable liquid optical interface
Recently, there has been intense interest in photonic devices based on microfluidics, including displays and refractive tunable microlenses and optical beamsteerers, that work using the principle of electrowetting. Here, we report a novel approach to optical devices in which static wrinkles are produced at the surface of a thin film of oil as a result of dielectrophoretic forces. We have demonstrated this voltage-programmable surface wrinkling effect in periodic devices with pitch lengths of between 20 and 240 µm and with response times of less than 40 µs. By a careful choice of oils, it is possible to optimize either for high-amplitude sinusoidal wrinkles at micrometre-scale pitches or more complex non-sinusoidal profiles with higher Fourier components at longer pitches. This opens up the possibility of developing rapidly responsive voltage-programmable, polarization-insensitive transmission and reflection diffraction devices and arbitrary surface profile optical devices
Bohr's Correspondence Principle and The Area Spectrum of Quantum Black Holes
During the last twenty-five years evidence has been mounting that a
black-hole surface area has a {\it discrete} spectrum. Moreover, it is widely
believed that area eigenvalues are {\it uniformally} spaced. There is, however,
no general agreement on the {\it spacing} of the levels. In this letter we use
Bohr's correspondence principle to provide this missing link. We conclude that
the area spacing of a black-hole is . This is the unique spacing
consistent both with the area-entropy {\it thermodynamic} relation for black
holes, with Boltzmann-Einstein formula in {\it statistical physics} and with
{\it Bohr's correspondence principle}.Comment: 10 page
Exploring the conformational dynamics of alanine dipeptide in solution subjected to an external electric field: A nonequilibrium molecular dynamics simulation
In this paper, we investigate the conformational dynamics of alanine
dipeptide under an external electric field by nonequilibrium molecular dynamics
simulation. We consider the case of a constant and of an oscillatory field. In
this context we propose a procedure to implement the temperature control, which
removes the irrelevant thermal effects of the field. For the constant field
different time-scales are identified in the conformational, dipole moment, and
orientational dynamics. Moreover, we prove that the solvent structure only
marginally changes when the external field is switched on. In the case of
oscillatory field, the conformational changes are shown to be as strong as in
the previous case, and non-trivial nonequilibrium circular paths in the
conformation space are revealed by calculating the integrated net probability
fluxes.Comment: 23 pages, 12 figure
Transcriptional portrait of M. bovis BCG during biofilm production shows genes differentially expressed during intercellular aggregation and substrate attachment.
Mycobacterium tuberculosis and M. smegmatis form drug-tolerant biofilms through dedicated genetic programs. In support of a stepwise process regulating biofilm production in mycobacteria, it was shown elsewhere that lsr2 participates in intercellular aggregation, while groEL1 was required for biofilm maturation in M. smegmatis. Here, by means of RNA-Seq, we monitored the early steps of biofilm production in M. bovis BCG, to distinguish intercellular aggregation from attachment to a surface. Genes encoding for the transcriptional regulators dosR and BCG0114 (Rv0081) were significantly regulated and responded differently to intercellular aggregation and surface attachment. Moreover, a M. tuberculosis H37Rv deletion mutant in the Rv3134c-dosS-dosR regulon, formed less biofilm than wild type M. tuberculosis, a phenotype reverted upon reintroduction of this operon into the mutant. Combining RT-qPCR with microbiological assays (colony and surface pellicle morphologies, biofilm quantification, Ziehl-Neelsen staining, growth curve and replication of planktonic cells), we found that BCG0642c affected biofilm production and replication of planktonic BCG, whereas ethR affected only phenotypes linked to planktonic cells despite its downregulation at the intercellular aggregation step. Our results provide evidence for a stage-dependent expression of genes that contribute to biofilm production in slow-growing mycobacteria
"Fresnel light drag in a coherently driven moving medium"
We theoretically study how the phase of a light plane wave propagating in a resonant medium under electromagnetically induced transparency (EIT) is affected by the uniform motion of the medium. For cuprous oxide (Cu2O), where EIT can be implemented through a typical pump-probe configuration, the resonant probe beam experiences a phase shift (Fresnel-Fizeau effect) that may vary over a wide range of values, positive or negative, and even vanishing, due to the combined effects of the strong frequency dispersion and anisotropy both induced by the pump. The use of such a coherently driven dragging medium may improve by at least 1 order of magnitude the sensitivity at low velocity in optical drag experiments
Imaging the Impact of Chemically Inducible Proteins on Cellular Dynamics In Vivo
The analysis of dynamic events in the tumor microenvironment during cancer progression is limited by the complexity of current in vivo imaging models. This is coupled with an inability to rapidly modulate and visualize protein activity in real time and to understand the consequence of these perturbations in vivo. We developed an intravital imaging approach that allows the rapid induction and subsequent depletion of target protein levels within human cancer xenografts while assessing the impact on cell behavior and morphology in real time. A conditionally stabilized fluorescent E-cadherin chimera was expressed in metastatic breast cancer cells, and the impact of E-cadherin induction and depletion was visualized using real-time confocal microscopy in a xenograft avian embryo model. We demonstrate the assessment of protein localization, cell morphology and migration in cells undergoing epithelial-mesenchymal and mesenchymal-epithelial transitions in breast tumors. This technique allows for precise control over protein activity in vivo while permitting the temporal analysis of dynamic biophysical parameters
Primary aldosteronism: A Japanese perspective
Primary aldosteronism (PA) is the most common cause of secondary hypertension, accounting for 10% of all hypertension. Far from being benign, hypertension due to PA is associated with high cardiovascular morbidity and mortality. However, PA is still underdiagnosed in general practice. Recent reports strongly recommend that identifying patients with PA is cost-beneficial based on improved cardiovascular outcomes afforded by specific surgical and medical treatment. This review provides an update of PA including controversial aspects of diagnosis and treatment
Implications For The Origin Of GRB 051103 From LIGO Observations
We present the results of a LIGO search for gravitational waves (GWs)
associated with GRB 051103, a short-duration hard-spectrum gamma-ray burst
(GRB) whose electromagnetically determined sky position is coincident with the
spiral galaxy M81, which is 3.6 Mpc from Earth. Possible progenitors for
short-hard GRBs include compact object mergers and soft gamma repeater (SGR)
giant flares. A merger progenitor would produce a characteristic GW signal that
should be detectable at the distance of M81, while GW emission from an SGR is
not expected to be detectable at that distance. We found no evidence of a GW
signal associated with GRB 051103. Assuming weakly beamed gamma-ray emission
with a jet semi-angle of 30 deg we exclude a binary neutron star merger in M81
as the progenitor with a confidence of 98%. Neutron star-black hole mergers are
excluded with > 99% confidence. If the event occurred in M81 our findings
support the the hypothesis that GRB 051103 was due to an SGR giant flare,
making it the most distant extragalactic magnetar observed to date.Comment: 8 pages, 3 figures. For a repository of data used in the publication,
go to: https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=15166 . Also see
the announcement for this paper on ligo.org at:
http://www.ligo.org/science/Publication-GRB051103/index.ph
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