Effects of Gear Modifications on the Trawl Performance and Catching Efficiency of the West Coast Upper Continental Slope Groundfish Survey Trawl

Since 1984, annual bottom trawl surveys of the west coast (California–Washington) upper continental slope (WCUCS) have provided information on the abundance, distribution, and biological characteristics of groundfish resources. Slope species of the deep-water complex (DWC) are of particular importance and include Dover sole, Microstomus pacificus; sablefish, Anoplopoma fimbria; shortspine thornyhead, Sebastolobus alascanus; and longspine thornyhead, S. altivelis. In the fall of 1994, we conducted an experimental gear research cruise in lieu of our normal survey because of concerns about the performance of the survey trawl. The experiment was conducted on a soft mud bottom at depths of 460–490 m off the central Oregon coast. Treatments included different combinations of door-bridle rigging, groundgear weight, and scope length. The experimental design was a 2 ´ 2 ´ 2 factorial within a randomized complete-block. Analysis of variance was used to examine the effects of gear modifications on the engineering performance of the trawl (i.e. trawl dimensions, variation in trawl dimensions, and door attitude) and to determine if catch rates in terms of weight and number of DWC species and invertebrates were affected by the gear modifications. Trawl performance was highly variable for the historically used standard trawl configuration. Improvements were observed with the addition of either a 2-bridle door or lighter ground gear. Changes in scope length had relatively little effect on trawl performance. The interaction of door bridle and ground gear weight had the most effect on trawl performance. In spite of the standard trawl’s erratic performance, catch rates of all four DWC species and invertebrates were not significantly different than the 2-bridle/heavy combination, which did the best in terms of engineering performance. The most important factor affecting DWC catch rates was ground gear. Scope length and the type of door bridle had little effect on DWC catch rates. Subsequent revisions to survey gear and towing protocol and their impact on the continuity of the slope survey time series are discussed

Attention Deficit Disorder and Memory Capacity in Language-impaired and Inconspicuous Children

Ausgehend von der Hypothese einer geringeren Gedächtnisfähigkeit sprachauffälliger Kinder wurden 110 sprachauffällige und 123 sprachunauffällige Kinder im Grundschulalter (Altersdurchschnitt 10;0 Jahre) untersucht. Die Kinder absolvierten jeweils einzeln einen verbalen Gedächtnistest sowie einen Test zur Problemlösereflexivität. Ferner beurteilten die Lehrer ihre Schüler im Hinblick auf Aufmerksamkeitsstörungen und Aufmerksamkeitsverhalten. Im Ergebnis zeigen sich signifikante Unterschiede zwischen beiden Gruppen in bezug auf die Gedächtnisfähigkeit und die Anzahl der Fehler. Den sprachauffälligen Schülern gelingt es weniger gut, Wortlisten zu lernen und den Lerngewinn gegen eine Ablenkung aufrechtzuerhalten. Sie weisen eine signifikant geringere Behaltensstabilität auf. Die Gedächtnisfähigkeit ist ferner weitgehend unabhängig von der Problemlösereflexivität und dem im Lehrerurteil festgehaltenen Aufmerksamkeitsverhalten. Es wird geschlossen, daß sprachauffällige Kinder sowohl Schwierigkeiten bei der Informationsaufnahme als auch Einschränkungen der Gedächtniskapazität haben. Die unterschiedliche Gedächtnisfähigkeit von sprachauffälligen und sprachunauffälligen Kindern ist am ehesten durch die (meta)kognitiven Kompetenzen der Kinder erklärbar.(DIPF/Orig.)In order to investigate the hypothesis that language-impaired children also show deficits in memory, 110 language-impaired and 123 children showing no such impairments (average age 10;0 yrs.) were tested for verbal memory and selecting attention through a matching familiar figures test. As an additional measure, teachers assessed the children, using DSM criteria, for both general attentivenesse and attention deficit disorder. The results revealed significant differences between both groups concerning their ability to memorise word lists and difficulties resisting distractions. They also show a significantly diminished stability regarding the retention of memories. Furthermore, the ability to memorise has proved to be greatly independent of both selective attention and the rated attentiveness in class. It is therefore concluded that language-impaired children have difficulties in acquiring information as well as a limited capacity to memorise. These differences in ability to memorise between language-impaired children and children with no impairments are most likely attributable to the meta-cognitive competence of the child.(DIPF/Orig.

X-ray emission from a crystal undulator—Experimental results at channeling of electrons

Experiments have been performed at the Mainz Microtron MAMI to explore the radiation emission from a 4-period epitaxially grown strained layer Si1−xGex undulator with a period length λu = 9.9 μm. Electron energies of 270 and 855MeV have been chosen. In comparison with a flat silicon reference crystal, a broad excess yield around the theoretically expected photon energies of 0.069 and 0.637 MeV, respectively, has been observed for channeling at the undulating (110) planes. The results are discussed within the framework of the classical undulator theory

Design considerations for table-top, laser-based VUV and X-ray free electron lasers

A recent breakthrough in laser-plasma accelerators, based upon ultrashort high-intensity lasers, demonstrated the generation of quasi-monoenergetic GeV-electrons. With future Petawatt lasers ultra-high beam currents of ~100 kA in ~10 fs can be expected, allowing for drastic reduction in the undulator length of free-electron-lasers (FELs). We present a discussion of the key aspects of a table-top FEL design, including energy loss and chirps induced by space-charge and wakefields. These effects become important for an optimized table-top FEL operation. A first proof-of-principle VUV case is considered as well as a table-top X-ray-FEL which may open a brilliant light source also for new ways in clinical diagnostics.Comment: 6 pages, 4 figures; accepted for publication in Appl. Phys.