Quantum criticality in a generalized Dicke model

We employ a generalized Dicke model to study theoretically the quantum criticality of an extended two-level atomic ensemble interacting with a single-mode quantized light field. Effective Hamiltonians are derived and diagonalized to investigate numerically their eigenfrequencies for different quantum phases in the system. Based on the analysis of the eigenfrequencies, an intriguing quantum-phase transition from a normal phase to a superradiant phase is revealed clearly, which is quite different from that observed with a standard Dicke model.Comment: 6 pages, 3 figure

Keys to academic success for under-represented minority young investigators: recommendations from the Research in Academic Pediatrics Initiative on Diversity (RAPID) National Advisory Committee.

BackgroundAlthough Latinos, African-Americans, and American Indians/Alaska Natives comprise 34% of Americans, these under-represented minorities (URMs) account for only 7% of US medical-school faculty. Even when URMs become faculty, they face many substantial challenges to success. Little has been published, however, on keys to academic success for URM young faculty investigators.MethodsThe Research in Academic Pediatrics Initiative on Diversity (RAPID) goal is to enhance the professional advancement of URM junior faculty pursuing research careers in general academic pediatrics. One important RAPID component is the annual mentoring/career-development conference, which targets URM residents, fellows, and junior faculty, and has included 62 URM participants since its 2013 inception. A conference highlight is the panel discussion on keys to academic success for URM young investigators, conducted by the RAPID National Advisory Committee, a diverse group of leading senior researchers. The article aim was to provide a guide to academic success for URM young investigators using the 2018 RAPID Conference panel discussion. A modified Delphi technique was used to provide a systematic approach to obtaining answers to six key questions using an expert panel: the single most important key to success for URM young investigators; ensuring optimal mentorship; how to respond when patients/families say, "I don't want you to see my child because you are ____"; best strategies for maximizing funding success; how to balance serving on time-consuming committees with enough time to advance research/career objectives; and the single thing you wish someone had told you which would have substantially enhanced your success early on.Results/conclusionsThis is the first published practical guide on keys to academic success for URM young investigators. Identified keys to success included having multiple mentors, writing prolifically, being tenaciously persistent, having mentors who are invested in you, dealing with families who do not want you to care for their child because of your race/ethnicity by seeking to understand the reasons and debriefing with colleagues, seeking non-traditional funding streams, balancing committee work with having enough time to advance one's research and career by using these opportunities to generate scholarly products, and asking for all needed resources when negotiating for new jobs

Undecidable properties of self-affine sets and multi-tape automata

We study the decidability of the topological properties of some objects coming from fractal geometry. We prove that having empty interior is undecidable for the sets defined by two-dimensional graph-directed iterated function systems. These results are obtained by studying a particular class of self-affine sets associated with multi-tape automata. We first establish the undecidability of some language-theoretical properties of such automata, which then translate into undecidability results about their associated self-affine sets.Comment: 10 pages, v2 includes some corrections to match the published versio

Systems intervention to promote colon cancer screening in safety net settings: Protocol for a community-based participatory randomized controlled trial

BACKGROUND: Colorectal cancer is a leading cause of cancer mortality. Screening can be effective but is underutilized. System- or multi-level interventions could be effective at increasing screening, but most have been implemented and evaluated in higher-resource settings such as health maintenance organizations. Given the disparities evident for colorectal cancer and the potential for screening to improve outcomes, there is a need to expand this work to include diverse settings, including those who treat economically disadvantaged patients. This paper describes the study protocol for a trial designed to increase colorectal cancer screening in those ‘safety-net’ health centers that serve underinsured and uninsured patients. This trial was designed and is being implemented using a community-based participatory approach. METHODS/DESIGN: We developed a practical clinical cluster-randomized controlled trial. We will recruit 16 community health centers to this trial. This systems-level intervention consists of a menu of evidence-based implementation strategies for increasing colorectal cancer screening. Health centers in the intervention arm then collaborate with the study team to tailor strategies to their own setting in order to maximize fit and acceptability. Data are collected at the organizational level through interviews, and at the provider and patient levels through surveys. Patients complete a survey about their healthcare and screening utilization at baseline, six months, and twelve months. OUTCOMES: The primary outcome is colorectal cancer screening by patient self-report, supplemented by a chart-audit in a subsample of patients. Implementation outcomes informed by the Reach, Efficacy/Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) conceptual framework will be measured at patient, provider, and practice levels. DISCUSSION: Our study is one of the first to integrate community participatory strategies to a randomized controlled trial in a healthcare setting. The multi-level approach will support the ability of the intervention to affect screening through multiple avenues. The participatory approach will strengthen the chance that implementation strategies will be maintained after study completion and, supports external validity by increasing health center interest and willingness to participate. TRIAL REGISTRATION: NCT0129949

Possible large phase in psi(2S) -> 1-0- Decays

The strong and the electromagnetic amplitudes are analyzed on the basis of the measurements of J/psi, psi(2S) -> 1-0- in e+e- experiments. The currently available experimental information is revised with inclusion of the contribution from e+e- -> gamma * -> 1-0- . The study shows that a large phase around minus 90 degree between the strong and the electromagnetic amplitudes could not be ruled out by the experimental data for psi(2S).Comment: 4 page

Test structure, circuits and extraction methods to determine the radius of infuence of STI and polysilicon pattern density

Advanced CMOS processes need new methodologies to extract, characterize and model process variations and their sources. Most prior studies have focused on understanding the effect of local layout features on transistor performance; limited work has been done to characterize medium-range (≈ 10μm to 2mm) pattern density effects. We propose a new methodology to extract the radius of influence, or the range of neighboring layout that should be taken into account in determining transistor characteristics, for shallow trench isolation (STI) and polysilicon pattern density. A test chip, with 130k devices under test (DUTs) and step-like pattern density layout changes, is designed in 65nm bulk CMOS technology as a case study. The extraction result of the measured data suggests that the local layout geometry, within the DUT cell size of 6μm × 8μm, is the dominant contributor to systematic device variation. Across-die medium-range layout pattern densities are found to have a statistically significant and detectable effect, but this effect is small and contributes only 2-5% of the total variation in this technology

Annihilation emission from young supernova remnants

A promising source of the positrons that contribute through annihilation to the diffuse Galactic 511keV emission is the beta-decay of unstable nuclei like 56Ni and 44Ti synthesised by massive stars and supernovae. Although a large fraction of these positrons annihilate in the ejecta of SNe/SNRs, no point-source of annihilation radiation appears in the INTEGRAL/SPI map of the 511keV emission. We exploit the absence of detectable annihilation emission from young local SNe/SNRs to derive constraints on the transport of MeV positrons inside SN/SNR ejecta and their escape into the CSM/ISM, both aspects being crucial to the understanding of the observed Galactic 511keV emission. We simulated 511keV lightcurves resulting from the annihilation of the decay positrons of 56Ni and 44Ti in SNe/SNRs and their surroundings using a simple model. We computed specific 511keV lightcurves for Cas A, Tycho, Kepler, SN1006, G1.9+0.3 and SN1987A, and compared these to the upper-limits derived from INTEGRAL/SPI observations. The predicted 511keV signals from positrons annihilating in the ejecta are below the sensitivity of the SPI instrument by several orders of magnitude, but the predicted 511keV signals for positrons escaping the ejecta and annihilating in the surrounding medium allowed to derive upper-limits on the positron escape fraction of ~13% for Cas A, ~12% for Tycho, ~30% for Kepler and ~33% for SN1006. The transport of ~MeV positrons inside SNe/SNRs cannot be constrained from current observations of the 511keV emission from these objects, but the limits obtained on their escape fraction are consistent with a nucleosynthesis origin of the positrons that give rise to the diffuse Galactic 511keV emission.Comment: 15 pages, 11 figures, accepted for publication in A&