Shallow Surveying in Hazardous Waters

Of order one importance to any study of nearshore processes is knowledge of the bathymetry in shallow water. This is true for studies on open coast sandy beaches where surf zone dynamics drive the system, inlet environments where bathymetric evolution can rapidly change navigation channels, and in more benign, lower-energy coastal environments that evolve slowly over 10’s to 100’s of years. Difficulties in obtaining shallow bathymetry where depth-limited wave breaking occurs, submerged hazards are present, or other harsh environments has led to the development of survey systems on highly maneuverable personal watercraft (Beach, et al., 1994; Cote, 1999; Dugan, et al., 1999; MacMahan, 2001). In this work we discuss shallow water surveying from the Coastal Bathymetry Survey System (CBASS), a Yamaha Waverunner equipped with differential GPS, single-beam 192 KHz acoustic echo-sounder, and onboard navigation system. Data obtained with the CBASS in three regions will be discussed, including an energetic surf zone located in southern California during the 2003 Nearshore Canyon Experiment (NCEX), on Lake Erie in 2002 (and compared with historical surveys dating back 150 years), and around Piscataqua River Inlet, NH, in 2007. Estimated accuracy (for sandy bottoms) in water depths ranging 1–10 m are 0.07-0.10 m in the vertical, and on the order of 0.1-1 m horizontally depending on water depth and bottom slope. The high maneuverability of the personal watercraft makes very shallow water bathymetric surveys possible with acoustic altimeters, particularly in regions where airborne remote sensing systems fail (owing to water clarity issues) or where repeated high resolution surveys are required (e.g., where an erodible bottom is rapidly evolving)

High-resolution X-ray Spectra Of The Symbiotic Star SS73 17

SS73 17 was an innocuous Mira-type symbiotic star until Integral and Swift discovered its bright hard X-ray emission, adding it to the small class of "hard X-ray emitting symbiotics." Suzaku observations in 2006 then showed it emits three bright iron lines as well, with little to no emission in the 0.3-2 keV bandpass. We present here followup observations with the Chandra HETG and Suzaku that confirm the earlier detection of strong emission lines of Fe Kalpha fluorescence, Fe XXV and Fe XXVI but also show significantly more soft X-ray emission. The high resolution spectrum also shows emission lines of other highly ionized ions as Si XIV and possibly S XVI. In addition, a reanalysis of the 2006 Suzaku data using the latest calibration shows that the hard (15-50 keV) X-ray emission is brighter than previously thought and remains constant in both the 2006 and 2008 data. The G ratio calculated from the Fe XXV lines shows that these lines are thermal, not photoionized, in origin. With the exception of the hard X-ray emission, the spectra from both epochs can be fit using thermal radiation assuming a differential emission measure based on a cooling flow model combined with a full and partial absorber. We show that acceptable fits can be obtained for all the data in the 1-10 keV band varying only the partial absorber. Based on the temperature and accretion rate, the thermal emission appears to be arising from the boundary layer between the accreting white dwarf and the accretion disk.Comment: 7 pages, 5 figures. Accepted by the Astrophysical Journa

Grindr Users Take More Risks, but Are More Open to Human Immunodeficiency Virus (HIV) Pre-exposure Prophylaxis: Could This Dating App Provide a Platform for HIV Prevention Outreach?

BackgroundTechnology has changed the way that men who have sex with men (MSM) seek sex. More than 60% of MSM in the United States use the internet and/or smartphone-based geospatial networking apps to find sex partners. We correlated use of the most popular app (Grindr) with sexual risk and prevention behavior among MSM.MethodsA nested cohort study was conducted between September 2018 and June 2019 among MSM receiving community-based human immunodeficiency virus (HIV) and sexually transmitted infection (STI) screening in central San Diego. During the testing encounter, participants were surveyed for demographics, substance use, risk behavior (previous 3 months), HIV pre-exposure prophylaxis (PrEP) use, and Grindr usage. Participants who tested negative for HIV and who were not on PrEP were offered immediate PrEP.ResultsThe study included 1256 MSM, 1090 of whom (86.8%) were not taking PrEP. Overall, 580 of 1256 (46%) participants indicated that they used Grindr in the previous 7 days. Grindr users reported significantly higher risk behavior (greater number of male partners and condomless sex) and were more likely to test positive for chlamydia or gonorrhea (8.6% vs 4.7% of nonusers; P = .005). Grindr users were also more likely to be on PrEP (18.7% vs 8.7% of nonusers; P < .001) and had fewer newly diagnosed HIV infections (9 vs 26 among nonusers; P = .014). Grindr users were also nearly twice as likely as nonusers to initiate PrEP (24.6% vs 14%; P < .001).ConclusionsGiven the higher risk behavior and greater acceptance of PrEP among MSM who used Grindr, Grindr may provide a useful platform to promote HIV and STI testing and increase PrEP uptake

The Effect of Stainless Steel 304 Surface Roughness on Ice Adhesion Shear Strength of Accreted Impact Ice

Aircraft in-flight icing is problematic due to the ad-verse effect on vehicle performance. It occurs when supercooled water droplets (SCWD) present in clouds, under the appropriate environmental conditions, col-lide with the aircraft surface resulting in accretion of ice (i.e., impact icing). Impact ice can range from clear/glaze to rime or a combination of the two (i.e., mixed) with the type determined by the air temperature (0 to -20C), liquid water content (LWC, 0.3-0.6 g/cu.m), and droplet size [median volumetric diameter (MVD) of 15-40 m] present during accretion.1 These impact icing events generally occur at temperatures ranging from 0 to -20C. Below -20C, ice crystals dominate the environment and typically do not adhere to the aircraft surface. A main difference between an impact icing occurrence and a slow growth icing (i.e., freezer ice) one is the speed of the icing event. Besides environmental conditions, ice adhesion strength (IAS) to a metallic substrate depends upon surface roughness. It is known that increasing surface roughness and decreasing temperature lead to in-creases in IAS

Characterization of a Double Mesospheric Bore Over Europe

Observations of a pair of mesospheric bore disturbances that propagated through the nighttime mesosphere over Europe are presented. The observations were made at the Padua Observatory, Asiago (45.9\ub0N, 11.5\ub0E), by the Boston University all-sky imager on 11 March 2013. The bores appeared over the northwest horizon, approximately 30 min apart, and propagated toward the southeast. Using additional satellite and radar data, we present evidence indicating the bores originated in the mesosphere from a single, larger-scale mesospheric disturbance propagating through the mesopause region. Furthermore, the large-scale mesospheric disturbance appeared to be associated with an intense weather disturbance that moved southeastward over the United Kingdom and western Europe during 10 and 11 March

An Extensive Collection of Stellar Wind X-ray Source Region Emission Line Parameters,Temperatures, Velocities, and Their Radial Distributions as Obtained from Chandra Observations of 17 OB Stars

Chandra high energy resolution observations have now been obtained from numerous non-peculiar O and early B stars. The observed X-ray emission line properties differ from pre-launch predictions, and the interpretations are still problematic. We present a straightforward analysis of a broad collection of OB stellar line profile data to search for morphological trends. X-ray line emission parameters and the spatial distributions of derived quantities are examined with respect to luminosity class. The X-ray source locations and their corresponding temperatures are extracted by using the He-like f/i line ratios and the H-like to He-like line ratios respectively. Our luminosity class study reveals line widths increasing with luminosity. Although the majority of the OB emission lines are found to be symmetric, with little central line displacement, there is evidence for small, but finite, blue-ward line-shifts that also increase with luminosity. The spatial X-ray temperature distributions indicate that the highest temperatures occur near the star and steadily decrease outward. This trend is most pronounced in the OB supergiants. For the lower density wind stars, both high and low X-ray source temperatures exist near the star. However, we find no evidence of any high temperature X-ray emission in the outer wind regions for any OB star. Since the temperature distributions are counter to basic shock model predictions, we call this the "near-star high-ion problem" for OB stars. By invoking the traditional OB stellar mass loss rates, we find a good correlation between the fir-inferred radii and their associated X-ray continuum optical depth unity radii. We conclude by presenting some possible explanations to the X-ray source problems that have been revealed by this study.Comment: Published in 2007, ApJ, 668, 456. An Erratum scheduled for publication in 2008, ApJ, 680, is included as an Appendix. The Erratum corrects some tabulated data in 5 tables and 2 figure

The Equivalence Principle in the Non-baryonic Regime

We consider the empirical validity of the equivalence principle for non-baryonic matter. Working in the context of the TH\epsilon\mu formalism, we evaluate the constraints experiments place on parameters associated with violation of the equivalence principle (EVPs) over as wide a sector of the standard model as possible. Specific examples include new parameter constraints which arise from torsion balance experiments, gravitational red shift, variation of the fine structure constant, time-dilation measurements, and matter/antimatter experiments. We find several new bounds on EVPs in the leptonic and kaon sectors.Comment: 22 pages, late

Rank-(n – 1) convexity and quasiconvexity for divergence free fields

The CAST experiment at CERN (European Organization of Nuclear Research) searches for axions from the sun. The axion is a pseudoscalar particle that was motivated by theory thirty years ago, with the intention to solve the strong CP problem. Together with the neutralino, the axion is one of the most promising dark matter candidates. The CAST experiment has been taking data during the last two years, setting an upper limit on the coupling of axions to photons more restrictive than from any other solar axion search in the mass range below 0.1 eV. In 2005 CAST will enter a new experimental phase extending the sensitivity of the experiment to higher axion masses. The CAST experiment strongly profits from technology developed for high energy physics and for X-ray astronomy: A superconducting prototype LHC magnet is used to convert potential axions to detectable X-rays in the 1-10 keV range via the inverse Primakoff effect. The most sensitive detector system of CAST is a spin-off from space technology, a Wolter I type X-ray optics in combination with a prototype pn-CCD developed for ESA's XMM-Newton mission. As in other rare event searches, background suppression and a thorough shielding concept is essential to improve the sensitivity of the experiment to the best possible. In this context CAST offers the opportunity to study the background of pn-CCDs and its long term behavior in a terrestrial environment with possible implications for future space applications. We will present a systematic study of the detector background of the pn-CCD of CAST based on the data acquired since 2002 including preliminary results of our background simulations.Comment: 11 pages, 8 figures, to appear in Proc. SPIE 5898, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XI

Cellular Dynamical Mean Field Approach to Strongly Correlated Systems

We propose a cellular version of dynamical-mean field theory which gives a natural generalization of its original single-site construction and is formulated in different sets of variables. We show how non-orthogonality of the tight-binding basis sets enters the problem and prove that the resulting equations lead to manifestly causal self energies.Comment: RevTex, 4 pages, 1 embedded figur

Perceiving ‘capability’ within dynamic capabilities: the role of owner-manager self-efficacy

This article combines two popular, yet separate concepts, dynamic capabilities and self-efficacy. Both are concerned with ability / capability and offer potentially valuable synergies. As such, our in-depth qualitative study based in three micro-enterprises in the United Kingdom (UK), investigated, ‘what role(s) may owner-manager perceived self-efficacy play as a micro-foundation of dynamic capabilities in micro-enterprises?’ Our findings show that perceived self-efficacy can influence dynamic capability enactment in multifaceted ways and even suggest that in some cases, perceived self-efficacy is a crucial component of dynamic capabilities, without which there may be no such capability. These insights help open up the black box of dynamic capabilities by contributing important knowledge to the growing body of research into the micro-foundations of such capabilities. Furthermore, our study illuminates the importance of idiosyncratic micro-foundations of dynamic capabilities in micro-enterprises and expands extant knowledge of the potential effects of self-efficacy in the small business and entrepreneurship domain