A three-dimensional analysis of marine radar images for the determination of ocean wave directionality and surface currents

A series of spatial wave images recorded by a conventional marine radar is analyzed to determine the three-dimensional E(kx, ky, ω) spectrum. In the absence of a surface current the spectral energy in this three-dimensional wave number frequency space will lie on a shell defined by the dispersion relationship. Any deviation from the expected dispersion relationship can be interpreted as being due to a current induced Doppler shift of the wave frequency. A least squares curve fitting technique is used to determine the surface current required to account for the observed Doppler shift. A comparison of the radar determined spectra and surface currents with ground truth data indicates that the radar system and analysis technique produces results consistent with conventional instrumentation

A Flattened Protostellar Envelope in Absorption around L1157

Deep Spitzer IRAC images of L1157 reveal many of the details of the outflow and the circumstellar environment of this Class 0 protostar. In IRAC band 4, 8 microns, there is a flattened structure seen in absorption against the background emission. The structure is perpendicular to the outflow and is extended to a diameter of 2 arcminutes. This structure is the first clear detection of a flattened circumstellar envelope or pseudo-disk around a Class 0 protostar. Such a flattened morphology is an expected outcome for many collapse theories that include magnetic fields or rotation. We construct an extinction model for a power-law density profile, but we do not constrain the density power-law index.Comment: ApJL accepte

Can skills assessment on a virtual reality trainer predict a surgical trainee's talent in laparoscopic surgery?

Background: A number of studies have investigated several aspects of feasibility and validity of performance assessments with virtual reality surgical simulators. However, the validity of performance assessments is limited by the reliability of such measurements, and some issues of reliability still need to be addressed. This study aimed to evaluate the hypothesis that test subjects show logarithmic performance curves on repetitive trials for a component task of laparoscopic cholecystectomy on a virtual reality simulator, and that interindividual differences in performance after considerable training are significant. According to kinesiologic theory, logarithmic performance curves are expected and an individual's learning capacity for a specific task can be extrapolated, allowing quantification of a person's innate ability to develop task-specific skills. Methods: In this study, 20 medical students at the University of Basel Medical School performed five trials of a standardized task on the LS 500 virtual reality simulator for laparoscopic surgery. Task completion time, number of errors, economy of instrument movements, and maximum speed of instrument movements were measured. Results: The hypothesis was confirmed by the fact that the performance curves for some of the simulator measurements were very close to logarithmic curves, and there were significant interindividual differences in performance at the end of the repetitive trials. Conclusions: Assessment of perceptual motor skills and the innate ability of an individual with no prior experience in laparoscopic surgery to develop such skills using the LS 500 VR surgical simulator is feasible and reliabl

The Role of Canids in Ritual and Domestic Contexts: New Ancient DNA Insights from Complex Hunter-Gatherer Sites in Prehistoric Central California

This study explores the interrelationship between the genus Canis and hunter–gatherers through a case study of prehistoric Native Americans in the San Francisco Bay-Sacramento Delta area. A distinctive aspect of the region\u27s prehistoric record is the interment of canids, variously classified as coyotes, dogs, and wolves. Since these species are difficult to distinguish based solely on morphology, ancient DNA analysis was employed to distinguish species. The DNA study results, the first on canids from archaeological sites in California, are entirely represented by domesticated dogs (including both interments and disarticulated samples from midden deposits). These results, buttressed by stable isotope analyses, provide new insight into the complex interrelationship between humans and canids in both ritual and prosaic contexts, and reveal a more prominent role for dogs than previously envisioned

Pouvoir et propriété dans l'entreprise: Pour une histoire internationale des sociétés à responsabilité limitée

Une longue tradition admet la supériorité de la société anonyme comme forme d'organisation. Une autre, plus récente, estime que les systèmes juridiques anglo-américains donnent aux investisseurs une meilleure protection que les systèmes de droit civil. Cet article remet en cause ces deux idées. Il s'intéresse à l'introduction des sociétés à responsabilité limitée en France, en Allemagne, au Royaume-Uni et aux États-Unis à la fin du XIXe siècle et au XXe siècle. Ces sociétés combinent les avantages de la personnalité juridique et de la société par actions avec des règles de gouvernance interne flexibles. Sont ainsi évités la menace de dissolution inhérente aux sociétés en partenariat et le danger propre aux sociétés anonymes d'une oppression des minoritaires. La SARL fut introduite avec succès d'abord en Allemagne, régie par un code juridique, et en dernier lieu seulement aux États-Unis, pays où domine la common law. La SARL fut partout privilégiée par les sociétés petites et moyennes, même dans les pays où les sociétés anonymes étaient faciles et peu coûteuses à créer et où les règles juridiques les régissant étaient assez légères. A long tradition in the economics, corporate law, and corporate finance literatures presumes the general superiority of the corporation as a form of business organization. A more recent tradition claims that countries with Anglo-American legal systems afford investors greater protection than countries with civil-law systems. This article challenges both claims. We focus on the introduction of the private limited-liability company (the PLLC) in France, Germany, the United Kingdom, and the United States in the late nineteenth and twentieth centuries. The PLLC combined the advantages of legal personhood and joint stock with flexible internal governance rules. It allowed business people to avoid the threat of untimely dissolution inherent in partnerships without taking on the full danger of minority oppression that came with the corporation. The PLLC was successfully introduced first in Germany, a code country, and last in the US, a common-law country whose courts had effectively killed earlier attempts to enact the form. Using data on the number of firms organized under various enterprise forms, we show that the PLLC became the form of choice for small- and medium-size enterprises wherever it was introduced, even in countries where incorporation was cheap and easy and the regulatory burden on corporations was light

Epstein-Barr virus infections and DNA hybridization studies in posttransplantation lymphoma and lymphoproliferative lesions: The role of primary infection

Fourteen patients who developed B cell lymphomas or lymphoproliferative lesions after kidney, liver, heart, or heart-lung transplantation in Pittsburgh during 1981-1983 had active infection with Epstein-Barr virus (EBV)of the primary (six patients), reactivated (seven patients), or chronic (one patient) type. In transplant patients without tumors, the incidence of EBV infection was 30% (39 of 128). Only three of these patients had primary infections. Thus the frequency of active infection was significantly higher in patients with tumors, and patients with primary infections were at greater risk of developing tumors. Five of 13 tumors tested contained EBV nuclear antigen (EBNA) and nine of 11 contained EBV genomes detected by DNA-DNA hybridization with BamHI K, BamHI W, or EcoRI B cloned probes. All EBNA-positive tumors, except one, were also positive by hybridization. Only one tumor was negative for both EBNA and EBV DNA. These data suggest that EBV plays an etiologic role in the development of these lesions. © 1985 by The University of Chicago

Canadian and U.S. Antitrust Law--Areas of Overlap between Anitrust and Import Relief Laws

Competition and Dispute Resolution in the North American Context and antitrust and free trade zone