Entanglement witnesses arising from Choi type positive linear maps

We construct optimal PPTES witnesses to detect $3\otimes 3$ PPT entangled edge states of type $(6,8)$ constructed recently \cite{kye_osaka}. To do this, we consider positive linear maps which are variants of the Choi type map involving complex numbers, and examine several notions related to optimality for those entanglement witnesses. Through the discussion, we suggest a method to check the optimality of entanglement witnesses without the spanning property.Comment: 18 pages, 4 figures, 1 tabl

Kolmogorov-Smirnov method for the determination of signal time-shifts

A new method for the determination of electric signal time-shifts is introduced. As the Kolmogorov-Smirnov test, it is based on the comparison of the cumulative distribution functions of the reference signal with the test signal. This method is very fast and thus well suited for on-line applications. It is robust to noise and its performances in terms of precision are excellent for time-shifts ranging from a fraction to several sample durations. PACS. 29.40.Gx (Tracking and position-sensitive detectors), 29.30.Kv (X- and -ray spectroscopy), 07.50.Qx (Signal processing electronics)Comment: 8 pages, 7 figure

Then You Fall Off : Youth Experiences and Responses to Transitioning to Homelessness

Introduction: This study aims to broaden our understanding of the experience of homelessness and unstable housing in youth. While quantitative research highlights risk factors associated with experiencing homelessness as a youth, little qualitative research has been conducted to explore the lived experience of this transition to homelessness or unstable housing and how youth respond to becoming homeless. This study utilizes data from youth descriptions of their experiences to understand the context of the transition to homelessness and how youth manage this transition. Methods: A qualitative study with a quantitative component was conducted with a nonprobability sample of homeless youth aged 14-24 recruited from shelters, drop-in centers, and magnet events in a large urban area in the Southwest. Four qualitative researchers used content analysis to assess themes that emerged related to transitions to homelessness. Results: A predominately minority (88%) sample of sheltered (67%) and unsheltered (33%) youth (n=64) described their experience of and responses to transitioning to homelessness. Three main themes emerged relating to transitioning to homelessness; family homelessness, histories of foster care, and non-supportive family processes. Youth described how these experiences manifested and influenced their transition into homelessness. In response to homelessness three dominant themes emerged; self-reliance, hope, and resilience. Discussion: The data highlight the unique issues of homeless youth and how they respond to circumstantial challenges. While homeless youth experience lifetime adversities that lead to homelessness, they respond to these circumstantial challenges with self-reliance, hope, and maintaining resilience. Interventions aiming to facilitate health behaviors and improve self-sufficiency in homeless youth should tap into these positive responses to improve self-care strategies, service utilization, and help homeless youth reduce risk behaviors

Interplay of charge, spin and lattice degrees of freedom on the spectral properties of the one-dimensional Hubbard-Holstein model

We calculate the spectral function of the one dimensional Hubbard-Holstein model using the time dependent Density Matrix Renormalization Group (tDMRG), focusing on the regime of large local Coulomb repulsion, and away from electronic half-filling. We argue that, from weak to intermediate electron-phonon coupling, phonons interact only with the electronic charge, and not with the spin degrees of freedom. For strong electron-phonon interaction, spinon and holon bands are not discernible anymore and the system is well described by a spinless polaronic liquid. In this regime, we observe multiple peaks in the spectrum with an energy separation corresponding to the energy of the lattice vibrations (i.e., phonons). We support the numerical results by introducing a well controlled analytical approach based on Ogata-Shiba's factorized wave-function, showing that the spectrum can be understood as a convolution of three contributions, originating from charge, spin, and lattice sectors. We recognize and interpret these signatures in the spectral properties and discuss the experimental implications.Comment: 8 pages, 7 figure

Fast analytical methods for the correction of signal random time-shifts and application to segmented HPGe detectors

Detection systems rely more and more on on-line or off-line comparison of detected signals with basis signals in order to determine the characteristics of the impinging particles. Unfortunately, these comparisons are very sensitive to the random time shifts that may alter the signal delivered by the detectors. We present two fast algebraic methods to determine the value of the time shift and to enhance the reliability of the comparison to the basis signals.Comment: 13 pages, 8 figure

Breaking the Buildup-time Limit of sensitivity in Avalanche Photodiodes by Dynamic Biasing

Avalanche photodiodes (APDs) are the preferred photodetectors for direct-detection, high data-rate long-haul optical telecommunications. APDs can detect low-level optical signals due to their internal amplification of the photon-generated electrical current, which is attributable to the avalanche of electron and hole impact ionizations. Despite recent advances in APDs aimed at reducing the average avalanche-buildup time, which causes intersymbol interference and compromises receiver sensitivity at high data rates, operable speeds of commercially available APDs have been limited to 10Gbps. We report the first demonstration of a dynamically biased APD that breaks the traditional sensitivity-versus-speed limit by employing a data-synchronous sinusoidal reverse-bias that drastically suppresses the average avalanche-buildup time. Compared with traditional DC biasing, the sensitivity of germanium APDs at 3Gbps is improved by 4.3 dB, which is equivalent to a 3,500-fold reduction in the bit-error rate. The method is APD-type agnostic and it promises to enable operation at rates of 25Gbps and beyond

Recognizing greenway network for quantifying students experience on campus-based universities : assessing the campus outdoor spaces at San Diego State University

This paper evaluates the potential of creating a green infrastructure – more specifically, an urban greenway – and its contribution the students’ campus experience, with emphasis on the outdoor university activities. To achieve best value for money – particularly in the current financial climate, with severe budget cuts constraining universities – justifying investments on campus outdoor spaces such as greenways, relies on a clear demonstration of their link to the overall success of the campus. Attempts of quantify the benefits from investments on such spaces are challenged by the scarcity of studies on the relationship between students’ experience and design (and related cost) of different types of campus landscape settings. This paper fills this gap by offering a thorough examination of a variety of extant campus developments and by measuring the performance of some selected open spaces against a ‘price-tag’ mechanism. The case study of the San Diego State University has been chosen as core case study and supplemented by 16 sub-cases across California State. The assessment has been conducted through three steps. First, a site inventory of the physical characteristics and landscape features has been conducted, focusing on 7 typologies of campus outdoor spaces (COS). Second, four main use patterns (Individual-customized, Group-social, Programmed-scheduled, and Active experiences) have been assessed by calculating the intensity of use (function of the frequency and duration of use) for each of them. The data collected was based on syntax observation methods with photos and maps of COS as prompts. Third, a Campus-Experience-Score (C-E-C) has been calculated and normalized to the size and population of the university, matching it against the actual development costs of each COS setting. The C-E-C allows measuring the link between types and features of COS and related students’ experience. Findings were discussed and verified through six in-depth interviews with local and international academics and developers/practitioners. This paper offers valuable benchmark to designers and planners seeking to maximize the value for money of investments on COS such as greenways

Fast rotating stars resulting from binary evolution will often appear to be single

Rapidly rotating stars are readily produced in binary systems. An accreting star in a binary system can be spun up by mass accretion and quickly approach the break-up limit. Mergers between two stars in a binary are expected to result in massive, fast rotating stars. These rapid rotators may appear as Be or Oe stars or at low metallicity they may be progenitors of long gamma-ray bursts. Given the high frequency of massive stars in close binaries it seems likely that a large fraction of rapidly rotating stars result from binary interaction. It is not straightforward to distinguish a a fast rotator that was born as a rapidly rotating single star from a fast rotator that resulted from some kind of binary interaction. Rapidly rotating stars resulting from binary interaction will often appear to be single because the companion tends to be a low mass, low luminosity star in a wide orbit. Alternatively, they became single stars after a merger or disruption of the binary system during the supernova explosion of the primary. The absence of evidence for a companion does not guarantee that the system did not experience binary interaction in the past. If binary interaction is one of the main causes of high stellar rotation rates, the binary fraction is expected to be smaller among fast rotators. How this prediction depend on uncertainties in the physics of the binary interactions requires further investigation.Comment: 2 pages, 1 figure, to be published in the proceedings of IAU 272 "Active OB stars: structure, evolution, mass loss and critical limit", Paris 19-23 July 201