Strong Quasiparticle Trapping In A 6x6 Array Of Vanadium-Aluminum Superconducting Tunnel Junctions

A 6x6 array of symmetrical V/Al/AlOx/Al/V Superconducting Tunnel Junctions (STJs) was fabricated. The base electrode is a high quality epitaxial film with a residual resistance ratio (RRR) of ~30. The top film is polycrystalline with an RRR of ~10. The leakage currents of the 25x25 mm^2 junctions are of the order of 0.5 pA/mm^2 at a bias voltage of 100 mV, which corresponds to a dynamical resistance of ~ 3 10^5 ohms. When the array was illuminated by 6 keV X-ray photons from a 55Fe radioactive source the single photon charge output was found to be low and strongly dependent on the temperature of the devices. This temperature dependence at X-ray energies can be explained by the existence of a very large number of quasiparticle (QP) traps in the Vanadium. QPs are confined in these traps, having a lower energy gap than the surrounding material, and are therefore not available for tunneling. The number of traps can be derived from the energy dependence of the responsivity of the devices (charge output per electron volt of photon input energy).Comment: 4 pages. presented at Low Temperature Detectors-

First results of a cryogenic optical photon counting imaging spectrometer using a DROID array

Context. In this paper we present the first system test in which we demonstrate the concept of using an array of Distributed Read Out Imaging Devices (DROIDs) for optical photon detection. Aims. After the successful S-Cam 3 detector the next step in the development of a cryogenic optical photon counting imaging spectrometer under the S-Cam project is to increase the field of view using DROIDs. With this modification the field of view of the camera has been increased by a factor of 5 in area, while keeping the number of readout channels the same. Methods. The test has been performed using the flexible S-Cam 3 system and exchanging the 10x12 Superconducting Tunnel Junction array for a 3x20 DROID array. The extra data reduction needed with DROIDs is performed offline. Results. We show that, although the responsivity (number of tunnelled quasiparticles per unit of absorbed photon energy, e- /eV) of the current array is too low for direct astronomical applications, the imaging quality is already good enough for pattern detection, and will improve further with increasing responsivity. Conclusions. The obtained knowledge can be used to optimise the system for the use of DROIDs.Comment: 7 pages, 9 figures, accepted for publicaiton in A&

E-ASTROGAM: A space mission for MeV-GeV gamma-ray astrophysics

e-ASTROGAM is an observatory space mission dedicated to the study of the gamma radiation in the range from 0.3 MeV to 3 GeV. The detector is composed by a Silicon tracker, a calorimeter, and an anticoincidence system. The mission is based on an advanced space-proven detector technology, with unprecedented sensitivity, angular and energy resolution, combined with polarimetric capability. Thanks to its performance in the MeV-GeV domain, substantially improving its predecessors, eASTROGAM will open a new window on the non-thermal Universe. In particular it will determine the origin of key isotopes fundamental for the understanding of supernova explosions and the chemical evolution of our Galaxy. It will also shed light on the processes behind the acceleration of cosmic rays in our Galaxy

Sheep α-globin gene sequences: Implications for their concerted evolution and for the down-regulation of the 3' genes

In sheep as in man and most other mammals, there are two α-globin genes (Iα and IIα), which are expressed at different levels, the upstream gene being the most efficient. In α-globin gene triplication and quadruplication, this trend is confirmed, i.e., the α-chain output of the downstream genes progressively decreases. In this study, we have determined the complete sequence of the cDNAs and of both the introns in a triple-α haplotype in which each gene could be recognized for the presence of distinct alleles. The sequence analysis reveals that the bodies of the three α-globin genes are essentially identical (99.9% homology) and moreover indicates that the down-regulation of additional α-globin genes in sheep is not the effect of sequence variation from the Cap to the Poly(A) addition sites. This striking similarity among α-genes is higher than that seen in other mammals and is probably sustained by particularly efficient mechanisms of gene conversion and cross-over fixation

Novel technique for monitoring the performance of the LAT instrument on board the GLAST satellite

The Gamma-ray Large Area Space Telescope (GLAST) is an observatory designed to perform gamma-ray astronomy in the energy range 20 MeV to 300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. GLAST will be launched at the end of 2007, opening a new and important window on a wide variety of high energy astrophysical phenomena . The main instrument of GLAST is the Large Area Telescope (LAT), which provides break-through high-energy measurements using techniques typically used in particle detectors for collider experiments. The LAT consists of 16 identical towers in a four-by-four grid, each one containing a pair conversion tracker and a hodoscopic crystal calorimeter, all covered by a segmented plastic scintillator anti-coincidence shield. The scientific return of the instrument depends very much on how accurately we know its performance, and how well we can monitor it and correct potential problems promptly. We report on a novel technique that we are developing to help in the characterization and monitoring of LAT by using the power of classification trees to pinpoint in a short time potential problems in the recorded data. The same technique could also be used to evaluate the effect on the overall LAT performance produced by potential instrumental problems.Comment: 2 pages, 1 figure, manuscript submitted on behalf of the GLAST/LAT collaboration to First GLAST symposium proceeding

A Concept for an STJ-based Spectrograph

We describe a multi-order spectrograph concept suitable for 8m-class telescopes, using the intrinsic spectral resolution of Superconducting Tunneling Junction detectors to sort the spectral orders. The spectrograph works at low orders, 1-5 or 1-6, and provides spectral coverage with a resolving power of R~8000 from the atmospheric cutoff at 320 nm to the long wavelength end of the infrared H or K band at 1800 nm or 2400 nm. We calculate that the spectrograph would provide substantial throughput and wavelength coverage, together with high time resolution and sufficient dynamic range. The concept uses currently available technology, or technologies with short development horizons, restricting the spatial sampling to two linear arrays; however an upgrade path to provide more spatial sampling is identified. All of the other challenging aspects of the concept - the cryogenics, thermal baffling and magnetic field biasing - are identified as being feasible.Comment: Accepted in Monthly Notices of the Royal Astronomical Society, 12 pages with 10 figure

Analogs of farnesylcysteine induce apoptosis in HL-60 cells

AbstractS-Farnesyl-thioacetic acid (FTA), a competitive inhibitor of isoprenylated protein methyltransferase, potently suppressed the growth of HL-60 cells and induced apoptosis, as evidenced by the development of increased annexin-V binding, decreased binding of DNA dyes and internucleosomal DNA degradation. FTA did not impair the membrane association of ras proteins, conversely, it brought about a decrease in the proportion of ras present in the cytosolic fraction. Farnesylated molecules which are weak inhibitors of the methyltransferase also induced DNA laddering and reduced the proportion of cytosolic ras. These findings suggest that neither inhibition of isoprenylated protein methylation nor impairment of ras membrane association are essential for apoptosis induced by farnesylcysteine analogs

Aquafeed production from fermented fish waste and lemon peel

In order to obtain a high-protein-content supplement for aquaculture feeds, rich in healthy microorganisms, in this study, Saccharomyces cerevisiae American Type Culture Collection (ATCC) 4126 and Lactobacillus reuteri ATCC 53608 strains were used as starters for fermenting fish waste supplemented with lemon peel as a prebiotic source and filler. Fermentation tests were carried out for 120 h until no further growth of the selected microorganisms was observed and the pH value became stable. All the samples were tested for proteins, crude lipids, and ash determination, and submitted for fatty acid analysis. Moreover, microbiological analyses for coliform bacteria identification were carried out. At the end of the fermentation period, the substrate reached a concentration in protein and in crude lipids of 48.55 ± 1.15% and 15.25 ± 0.80%, respectively, representing adequate levels for the resulting aquafeed, whereas the ash percentage was 0.66 ± 0.03. The main fatty acids detected were palmitic, oleic, and linoleic acids. Saturated fatty acids concentration was not affected by the fermentation process, whereas monounsaturated and polyunsaturated ones showed an opposite trend, increasing and decreasing, respectively, during the process. Coliform bacteria were not detected in the media at the end of the fermentation, whereas the amount of S. cerevisiae and L. reuteri were around 1011 and 1012 cells per g, respectively

Open Collaboration: A Problem Solving Strategy That Is Redefining NASA's Innovative Spirit

In 2010, NASA?s Space Life Sciences Directorate announced the successful results from pilot experiments with open innovation methodologies. Specifically, utilization of internet based external crowd sourcing platforms to solve challenging problems in human health and performance related to the future of spaceflight. The follow-up to this success was an internal crowd sourcing pilot program entitled NASA@work, which was supported by the InnoCentive@work software platform. The objective of the NASA@work pilot was to connect the collective knowledge of individuals from all areas within the NASA organization via a private web based environment. The platform provided a venue for NASA Challenge Owners, those looking for solutions or new ideas, to pose challenges to internal solvers, those within NASA with the skill and desire to create solutions. The pilot was launched in 57 days, a record for InnoCentive and NASA, and ran for three months with a total of 20 challenges posted Agency wide. The NASA@work pilot attracted over 6000 participants throughout NASA with a total of 183 contributing solvers for the 20 challenges posted. At the time of the pilot?s closure, solvers provided viable solutions and ideas for 17 of the 20 posted challenges. The solver community provided feedback on the pilot describing it as a barrier breaking activity, conveying that there was a satisfaction associated with helping co-workers, that it was "fun" to think about problems outside normal work boundaries, and it was nice to learn what challenges others were facing across the agency. The results and the feedback from the solver community have demonstrated the power and utility of an internal collaboration tool, such as NASA@work