11,830 research outputs found
Exploration of Lorentz violation in neutral-kaon decay
The KLOE collaboration recently reported bounds on the directional dependence
of the lifetime of the short-lived neutral kaon with respect to the
dipole anisotropy of the cosmic microwave background. We interpret their
results in an effective field theory framework developed to probe the violation
of Lorentz invariance in the weak interaction and previously applied to
semileptonic processes, in particular decay. In this approach a general
Lorentz-violating tensor is added to the standard propagator of
the boson. We perform an exploratory study of the prospects to search for
Lorentz violation in nonleptonic decays. For the kaon, we find that the
sensitivity to Lorentz violation is limited by the velocity of the kaons and by
the extent to which hadronic effects can be calculated. In a simple model we
derive the decay rate and calculate the asymmetry for the lifetime.
Using the KLOE data, limits on the values of are determined.Comment: accepted for publication in Physics Letters
The orbits of subdwarf-B + main-sequence binaries. II. Three eccentric systems; BD+29 3070, BD +34 1543 and Feige 87
The predicted orbital-period distribution of the subdwarf-B (sdB) population
is bi-modal with a peak at short ( 250 days) periods.
Observationally, many short-period sdB systems are known, but the predicted
long period peak is missing as orbits have only been determined for a few
long-period systems. As these predictions are based on poorly understood
binary-interaction processes, it is of prime importance to confront the
predictions with reliable observational data. We therefore initiated a
monitoring program to find and characterize long-period sdB stars. In this
paper we aim to determine the orbital parameters of the three long-period
sdB+MS binaries BD+29 3070, BD+34 1543 and Feige 87, to constrain their
absolute dimensions and the physical parameters of the components.
High-resolution spectroscopic time series were obtained with HERMES at the
Mercator telescope on La Palma, and analyzed to determine the radial velocities
of both the sdB and MS components. Photometry from the literature was used to
construct the spectral-energy distribution (SED) of the binaries. Atmosphere
models were used to fit these SEDs and to determine the surface gravities and
temperatures of both components of all systems. Spectral analysis was used to
check the results of the SEDs. An orbital period of 1283 +- 63 d, a mass ratio
of q = 0.39 +- 0.04 and a significant non-zero eccentricity of e = 0.15 +- 0.01
were found for BD+29 3070. For BD+34 1543 we determined P = 972 +- 2 d, q =
0.57 +- 0.01 and again a clear non-zero eccentricity of e = 0.16 +- 0.01. Last,
for Feige 87 we found P = 936 +- 2 d, q = 0.55 +- 0.01 and e = 0.11 +- 0.01.
BD+29 3070, BD+34 1543 and Feige 87 are long period sdB + MS binaries on
clearly eccentric orbits. These results are in conflict with the predictions of
stable Roche-lobe overflow models.Comment: 15 pages, 6 figures, Accepted by A&
Scattering Lens Resolves sub-100 nm Structures with Visible Light
The smallest structures that conventional lenses are able to optically
resolve are of the order of 200 nm. We introduce a new type of lens that
exploits multiple scattering of light to generate a scanning nano-sized optical
focus. With an experimental realization of this lens in gallium phosphide we
have succeeded to image gold nanoparticles at 97 nm optical resolution. Our
work is the first lens that provides a resolution in the nanometer regime at
visible wavelengths.Comment: 4 pages, 3 figure
Protein Homeostasis in Amyotrophic Lateral Sclerosis: Therapeutic Opportunities?
Protein homeostasis (proteostasis), the correct balance between production and degradation of proteins, is essential for the health and survival of cells. Proteostasis requires an intricate network of protein quality control pathways (the proteostasis network) that work to prevent protein aggregation and maintain proteome health throughout the lifespan of the cell. Collapse of proteostasis has been implicated in the etiology of a number of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), the most common adult onset motor neuron disorder. Here, we review the evidence linking dysfunctional proteostasis to the etiology of ALS and discuss how ALS-associated insults affect the proteostasis network. Finally, we discuss the potential therapeutic benefit of proteostasis network modulation in ALS
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