The Rise and Fall of Pentaquarks in Experiments

Experimental evidence for and against the existence of pentaquarks has accumulated rapidly in the last three years. If they exist, they would be dramatic examples of hadronic states beyond our well-tested and successful particle models. The positive evidence suggests existence of baryonic objects with widths of at most a few MeV, some displaying exotic quantum numbers, such as baryons with strangeness $S = +1$. The non-observations of these states have often come from reaction channels very different from the positive evidence channels, making comparisons difficult. The situation has now been largely clarified, however, by high-statistics repetitions of the positive sightings, with the result that none of the positive sightings have been convincingly reproduced. The most recent unconfirmed positive sightings suffer again from low statistics and large backgrounds. It seems that a kind of ``bandwagon'' effect led to the overly-optimistic interpretation of numerous experiments in the earlier reports of exotic pentaquarks.Comment: Presented at Particles and Nuclei International Conference (PANIC'05), Santa Fe, N.M. October 28, 2005; 9 pages, 1 figur

A Comparison of Airport Risks: Unmanned Aircraft Systems (UAS) Sightings, Wildlife Strikes, and Runway Incursions

To provide a context for the potential threat of unmanned aircraft systems (UAS) sightings on airport operations, this paper compares the characteristics of UAS sightings with two common airport threats: wildlife strikes and runway incursions. This study analyzed over 60,000 events in a three-year period (September 2016 to August 2019), including 6,551 UAS sightings from the Federal Aviation Administration (FAA) UAS Sightings Report database, 47,574 wildlife strikes from the FAA Wildlife Strike database, and 6,041 runway incursions from the FAA Runway Safety database. The results suggest both similarities and differences among the airport threats. Both UAS sightings and wildlife strikes vary by time of year and time of day. UAS sightings and wildlife strikes farther from the airport occur at higher altitudes than sightings and strikes occurring close to the airport. However, UAS sightings are reported at higher altitudes than wildlife strikes, and the distance of UAS sightings from the airport is farther than that of wildlife strikes, in general. The severities of UAS sightings and runway incursions are similar. Pilots take evasive actions in three percent of UAS sightings, and runway incursions of severity A and B are also rare. Pilots of general aviation (GA) aircraft reported the most UAS sightings, and GA operations are also involved in more runway incursions. Considering the kind of airport affected, UAS sightings and wildlife strikes are more common at primary airports, notably large and medium hub airports, whereas runway incursions are more common at reliever airports. Generally, UAS have had a minimal impact on airport operations despite their growing prevalence, which reflects the overall success of integrating this new airspace user into the national airspace system

Distribution and density of harbour popoises in Dutch North Sea waters

Aerial surveys were conducted to investigate harbour porpoise density and distribution in Dutch waters. Surveys were conducted following standard line transect distance sampling methodology on tracklines providing a representative coverage of the study area which ranged from the Dutch coast to about 120 km offshore thus covering about half of the Dutch EEZ. Within this overall study area two sub-areas were defined. One sub-area (from Texel to the German border) was covered in on 29 November 2008 and 3 April 2009. Density was 1.02 animals per km² during the November survey and 0.52 animals per km² during the April survey. An overall survey, covering both sub-areas, was conducted on 3 February, 18 March and 3 April 2009. The resulting density was 1.12 animals per km². This corresponds to an estimate of harbour porpoise abundance for this study area of 36 825 animals (95% C.I. 19 090 – 68 130; 0.33 C.V.). Distribution patterns of porpoises in the surveys waters were patchy and seemed variable between surveys. Applying this abundance estimate, a range of potential mortality limits were calculated for the Dutch harbour porpoises

Event-based personal retrieval

People who work in a research, academic or business environment often have personal information collections which are large enough to need retrieval aids. A major difference between personal information retrieval and normal document retrieval is that the items to be retrieved are often associated with events in the searcher's life and can be retrieved by their relationship to other events as well as by content. This paper describes some of the background to event-based retrieval and then describes a prototype graphical event-based retrieval system

Soundings: the Newsletter of the Monterey Bay Chapter of the American Cetacean Society. 2006

(PDF contains 88 pages.

Soundings: the Newsletter of the Monterey Bay Chapter of the American Cetacean Society. 1996

(PDF contains 96 pages.

Phantom German Air Raids on Canada: War Hysteria in Quebec and Ontario during the First World War

In late August of 1914, Canada entered the First World War following the unanimous vote of a special session of Parliament. This event occurred amid great exuberance and unanimity, and was marked by parades, decorations, cheering crowds and patriotic speeches. Canada was situated far from the European front lines, and its distant, vast land mass and cold climate also contributed to a feeling of insulation from attack or invasion. However, despite a general feeling of distance from the war\u27s unfolding events, there was a rapidly growing realization that German sympathizers and enemy agents might pose a more immediate threat