7,925 research outputs found
Recommended from our members
Editorial: Innovative Technologies and Clinical Applications for Invasive and Non-invasive Neuromodulation: From the Workbench to the Bedside.
Foreground removal requirements for measuring large-scale CMB B-modes in light of BICEP2
The most convincing confirmation that the B-mode polarization signal detected
at degree scales by BICEP2 is due to the Cosmic Microwave Background (CMB)
would be the measurement of its large-scale counterpart. We assess the
requirements for diffuse component separation accuracy over large portions of
the sky in order to measure the large-scale B-mode signal corresponding to a
tensor to scalar ratio of r=0.1-0.2.
We use the method proposed by Bonaldi & Ricciardi (2011) to forecast the
performances of different simulated experiments taking into account noise and
foreground removal issues. We do not consider instrumental systematics, and we
implicitly assume that they are not the dominant source of error. If this is
the case, the confirmation of an r=0.1-0.2 signal is achievable by Planck even
for conservative assumptions regarding the accuracy of foreground cleaning. Our
forecasts suggest that the combination of this experiment with BICEP2 will lead
to an improvement of 25-45% in the constraint on r.
A next-generation CMB polarization satellite, represented in this work by the
COrE experiment, can reduce dramatically (by almost another order of magnitude)
the uncertainty on r. In this case, however, the accuracy of foreground removal
becomes critical to fully benefit from the increase in sensitivity.Comment: 8 pages, 3 figures, 1 table. Accepted by MNRA
A stochastic model for the stepwise motion in actomyosin dynamics
A jump-diffusion process is proposed to describe the displacements performed
by single myosin heads along actin filaments during the rising phases. The
process consists of the superposition of a Wiener and a jump process, with
jumps originated by sequences of Poisson-distributed energy-supplying pulses.
In a previous paper, the amplitude of the jumps was described by a mixture of
two Gaussian distributions. To embody the effects of ATP hydrolysis, we now
refine such a model by assuming that the jumps' amplitude is described by a
mixture of three Gaussian distributions. This model has been inspired by the
experimental data of T. Yanagida and his co-workers concerning observations at
single molecule processes level.Comment: 9 pages, 4 figure
A chemically driven fluctuating ratchet model for actomyosin interaction
With reference to the experimental observations by T. Yanagida and his
co-workers on actomyosin interaction, a Brownian motor of fluctuating ratchet
kind is designed with the aim to describe the interaction between a Myosin II
head and a neighboring actin filament. Our motor combines the dynamics of the
myosin head with a chemical external system related to the ATP cycle, whose
role is to provide the energy supply necessary to bias the motion. Analytical
expressions for the duration of the ATP cycle, for the Gibbs free energy and
for the net displacement of the myosin head are obtained. Finally, by
exploiting a method due to Sekimoto (1997, J. Phys. Soc. Jpn., 66, 1234), a
formula is worked out for the amount of energy consumed during the ATP cycle.Comment: 15 pages. 1 figur
Towards the Modeling of Neuronal Firing by Gaussian Processes
This paper focuses on the outline of some computational methods for the
approximate solution of the integral equations for the neuronal firing
probability density and an algorithm for the generation of sample-paths in
order to construct histograms estimating the firing densities. Our results
originate from the study of non-Markov stationary Gaussian neuronal models with
the aim to determine the neuron's firing probability density function. A
parallel algorithm has been implemented in order to simulate large numbers of
sample paths of Gaussian processes characterized by damped oscillatory
covariances in the presence of time dependent boundaries. The analysis based on
the simulation procedure provides an alternative research tool when closed-form
results or analytic evaluation of the neuronal firing densities are not
available.Comment: 10 pages, 3 figures, to be published in Scientiae Mathematicae
Japonica
Biological aspects of mTOR in leukemia
The mammalian target of rapamycin (mTOR) is a central processor of intra-and extracellular signals, regulating many fundamental cellular processes such as metabolism, growth, proliferation, and survival. Strong evidences have indicated that mTOR dysregulation is deeply implicated in leukemogenesis. This has led to growing interest in the development of modulators of its activity for leukemia treatment. This review intends to provide an outline of the principal biological and molecular functions of mTOR. We summarize the current understanding of how mTOR interacts with microRNAs, with components of cell metabolism, and with controllers of apoptotic machinery. Lastly, from a clinical/translational perspective, we recapitulate the therapeutic results in leukemia, obtained by using mTOR inhibitors as single agents and in combination with other compounds
Dispersion of longitudinal momentum distributions induced in fragmentation reactions
On the basis of systematic measurements of fragmentation reactions, which
provide a detailed overview on the velocity distributions of residual nuclei,
an improved description of the kinematical properties of the fragmentation
residues is established. This work is dedicated to the fluctuations of their
momentum distributions. In contrast to previous investigations, limited to
close-to-projectile fragments, we extended our study to the entire production
range, down to the lightest observed fragments. In this context, beside the
contribution of abrasion and evaporation processes, we considered the effect of
the thermal break-up on the width of the momentum distributions. Using
approximated theoretical descriptions of the different reaction stages, a new
analytical formula for the variance of the momentum distribution is derived,
which is well adapted to technical applications.Comment: 14 pages, 3 figures, background info. at
http://www-wnt.gsi.de/charms
On Myosin II dynamics in the presence of external loads
We address the controversial hot question concerning the validity of the
loose coupling versus the lever-arm theories in the actomyosin dynamics by
re-interpreting and extending the phenomenological washboard potential model
proposed by some of us in a previous paper. In this new model a Brownian motion
harnessing thermal energy is assumed to co-exist with the deterministic swing
of the lever-arm, to yield an excellent fit of the set of data obtained by some
of us on the sliding of Myosin II heads on immobilized actin filaments under
various load conditions. Our theoretical arguments are complemented by accurate
numerical simulations, and the robustness of the model is tested via different
choices of parameters and potential profiles.Comment: 6 figures, 8 tables, to appear on Biosystem
- …