Study of the acoustic signature of UHE neutrino interactions in water and ice

The production of acoustic signals from the interactions of ultra-high energy (UHE) cosmic ray neutrinos in water and ice has been studied. A new computationally fast and efficient method of deriving the signal is presented. This method allows the implementation of up to date parameterisations of acoustic attenuation in sea water and ice that now includes the effects of complex attenuation, where appropriate. The methods presented here have been used to compute and study the properties of the acoustic signals which would be expected from such interactions. A matrix method of parameterising the signals, which includes the expected fluctuations, is also presented. These methods are used to generate the expected signals that would be detected in acoustic UHE neutrino telescopes.Comment: 21 pages and 13 figure

Dihydrolipoic acid reduces cytochrome b561 proteins.

Cytochrome b561 (Cyt-b561) proteins constitute a family of trans-membrane proteins that are present in a wide variety of organisms. Two of their characteristic properties are the reducibility by ascorbate (ASC) and the presence of two distinct b-type hemes localized on two opposite sides of the membrane. Here we show that the tonoplast-localized and the putative tumor suppressor Cyt-b561 proteins can be reduced by other reductants than ASC and dithionite. A detailed spectral analysis of the ASC-dependent and dihydrolipoic acid (DHLA)-dependent reduction of these two Cyt-b561 proteins is also presented. Our results are discussed in relation to the known antioxidant capability of DHLA as well as its role in the regeneration of other antioxidant compounds of cells. These results allow us to speculate on new biological functions for the trans-membrane Cyt-b561 proteins

A stacked search for intermediate-mass black holes in 337 extragalactic star clusters

Forbes et al. recently used the Hubble Space Telescope to localize hundreds of candidate star clusters in NGC 1023, an early-type galaxy at a distance of 11.1 Mpc. Old stars dominate the light of 92% of the clusters and intermediate-age stars dominate the light of the remaining 8%. Theory predicts that clusters with such ages can host intermediate-mass black holes (IMBHs) with masses M_BH \lesssim 10^5 M_sun. To investigate this prediction, we used 264 s of 5.5 GHz data from the Karl G. Jansky Very Large Array (VLA) to search for the radiative signatures of IMBH accretion from 337 candidate clusters in an image spanning 492 arcsec (26 kpc) with a resolution of 0.40 arcsec (22 pc). None of the individual clusters are detected, nor are weighted-mean image stacks of the 311 old clusters, the 26 intermediate-age clusters, and the 20 clusters with stellar masses M_star \gtrsim 7.5 x 10^5 M_sun. The clusters thus lack radio analogs of HLX-1, a strong IMBH candidate in a cluster in the early-type galaxy ESO 243-49. This suggests that HLX-1 is accreting gas related to its cluster's light-dominating young stars. Alternatively, the HLX-1 phenomenon could be so rare that no radio analog is expected in NGC 1023. Also, using a formalism heretofore applied to star clusters in the Milky Way, the radio-luminosity upper limit for the massive-cluster stack corresponds to a mean 3$\sigma$ IMBH mass of M_BH(massive) < 2.3 x 10^5 M_sun, suggesting mean black-hole mass fractions of M_BH(massive)/M_star < 0.05-0.29.Comment: 19 pages; 6 figures; accepted by A