Inelastic relaxation and noise temperature in S/N/S junctions

We studied electronic relaxation in long diffusive superconductor / normal metal / superconductor (S/N/S) junctions by means of current noise and transport measurements down to very low temperature (100mK). Samples with normal metal lengths of 4, 10 and 60 micrometer have been investigated. In all samples the shot noise increases very rapidly with the voltage. This is interpreted in terms of enhanced heating of the electron gas confined between the two S/N interfaces. Experimental results are analyzed quantitatively taking into account electron-phonon interaction and heat transfer through the S/N interfaces. Transport measurements reveal that in all samples the two S/N interfaces are connected incoherently, as shown by the reentrance of the resistance at low temperature. The complementarity of noise and transport measurements allows us to show that the energy dependence of the reentrance at low voltage is essentially due to the increasing effective temperature of the quasiparticles in the normal metal.Comment: 5 pages, 4 figures, to be published in EPJ

A Simple Data-Adaptive Probabilistic Variant Calling Model

Background: Several sources of noise obfuscate the identification of single nucleotide variation (SNV) in next generation sequencing data. For instance, errors may be introduced during library construction and sequencing steps. In addition, the reference genome and the algorithms used for the alignment of the reads are further critical factors determining the efficacy of variant calling methods. It is crucial to account for these factors in individual sequencing experiments. Results: We introduce a simple data-adaptive model for variant calling. This model automatically adjusts to specific factors such as alignment errors. To achieve this, several characteristics are sampled from sites with low mismatch rates, and these are used to estimate empirical log-likelihoods. These likelihoods are then combined to a score that typically gives rise to a mixture distribution. From these we determine a decision threshold to separate potentially variant sites from the noisy background. Conclusions: In simulations we show that our simple proposed model is competitive with frequently used much more complex SNV calling algorithms in terms of sensitivity and specificity. It performs specifically well in cases with low allele frequencies. The application to next-generation sequencing data reveals stark differences of the score distributions indicating a strong influence of data specific sources of noise. The proposed model is specifically designed to adjust to these differences.Comment: 19 pages, 6 figure

SiO overcoating and polishing of CFRP telescope panels

Development of carbon fiber reinforces plastic (CFRP) panel overcoating and polishing is structured in two parts. The first part utilized a short series of experiments to determine the feasibility of overcoating and polishing CFRP panels, and the second part employes a systematic approach to optimize techniques learned. Questions which required answers in the initial investigation are summarized. Tests were performedin the Steward Observatory's 2.2 Meter Vacuum Coating Chamber and began with 3 cm square pieces of CFRP facesheet material. Next, a 10 cm square and one-inch-thick CFPR-Aluminum core panel was tested. Tests were then conducted on a 0.5-meter-square Dornier panel (QUAD 4) with CFRP facesheets on two-inch aluminum Flexcore. To complete the initial study, a previously characterized 0.5 m Dornier panel (QUAD 23) was coated and hand polished. The mirror's optical performance was not affected by the SiO coating

The 100 micron surveys in the Northern and Southern Hemispheres

Partial surveys in the far infrared in the Northern and Southern Hemispheres have covered 40% of the galactic equator and assorted regions away from the galactic plane. Approximately 120 100-micron objects are known. These are distributed extensively in galactic longitude and concentrated within + or - two degrees in galactic latitude. From this information, some general conclusions can be drawn about the sensitivity and coverage required for a general sky survey in the far infrared

Mesoscopic transition in the shot noise of diffusive S/N/S junctions

We experimentally investigated the current noise in diffusive Superconductor/Normal metal/Superconductor junctions with lengths between the superconducting coherence length xi_Delta and the phase coherence length L_Phi of the normal metal (xi_Delta < L < L_Phi). We measured the shot noise over a large range of energy covering both the regimes of coherent and incoherent multiple Andreev reflections. The transition between these two regimes occurs at the Thouless energy where a pronounced minimum in the current noise density is observed. Above the Thouless energy, in the regime of incoherent multiple Andreev reflections, the noise is strongly enhanced compared to a normal junction and grows linearly with the bias voltage. Semi-classical theory describes the experimental results accurately, when taking into account the voltage dependence of the resistance which reflects the proximity effect. Below the Thouless energy, the shot noise diverges with decreasing voltage which may indicate the coherent transfer of multiple charges.Comment: 5 pages, 5 figures, accepted for publication in Phys. Rev. B, Rapid Communicatio

Low temperature optical testing of CFRP telescope panels

Since 1984, low temperature optical tests were made of very lightweight mirror panels for use in balloon and space infrared and submillimeter telescopes. In order to accomplish this testing, an ambient pressure 0.5 meter test chamber operating from 20 to -80 C, developed techniques for measuring non-optical quality mirrors with phase modulation 10.6 micron interferometry, and created the interferogram reduction program. During the course of the program, nineteen mirrors from four manufactures were tested: carbon fiber reinforced plastic (CFRP) aluminum honeycomb sandwich panel mirrors, a CFRP sandwich panel with an added glass facesheet, and carbon fiber reinforced glass panels. The results of the panel development and test program are summarized

A genetic algorithm for the design of a fuzzy controller for active queue management

Active queue management (AQM) policies are those policies of router queue management that allow for the detection of network congestion, the notification of such occurrences to the hosts on the network borders, and the adoption of a suitable control policy. This paper proposes the adoption of a fuzzy proportional integral (FPI) controller as an active queue manager for Internet routers. The analytical design of the proposed FPI controller is carried out in analogy with a proportional integral (PI) controller, which recently has been proposed for AQM. A genetic algorithm is proposed for tuning of the FPI controller parameters with respect to optimal disturbance rejection. In the paper the FPI controller design metodology is described and the results of the comparison with random early detection (RED), tail drop, and PI controller are presented