868 research outputs found

    Description of embryonic development of Atka mackerel (Pleurogrammus monopterygius)

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    Atka mackerel (Pleurogrammus monopterygius) is hexagrammid fish that inhabits the temperate and subarctic North Pacific Ocean and neighboring seas (Fig. 1). This highly abundant fish is a critically important prey species (Sinclair and Zeppelin, 2002; Zenger, 2004) that supports a directed commercial trawl fishery (Lowe et al., 2006). Atka mackerel is a demersal spawner and males provide parental care to eggs (Zolotov, 1993). During breeding periods, sexually mature males aggregate on the bottom at nesting sites where they establish territories (Lauth et al., in press). Sexually mature females periodically visit male nesting territories from July to October to spawn batches of demersal egg masses (McDermott and Lowe, 1997; McDermott et al., 2007). Individual nests may consist of multiple egg masses deposited by different females, and males defend nesting territories for a protracted period lasting from the time territories are being established until all eggs within the territory are completely hatched (Lauth et al., 2007). Knowledge about the timing of the reproductive cycle and the use of spawning habitat are important for understanding population structure and the dynamics of stock recruitment, which in turn are important factors in the management of Atka mackerel populations

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

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    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.

    Tlingit Women in Leadership: One Culture, Two Worlds

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    This project has been completed through a multi-level stage using the following applications: examination of comprehensive examination of gender equality in Tlingit society (traditional and contemporary) using historical and descriptive research. The Tlingit tribe continues the custom of matrilineal descent (familial lineage is determined through mother) decided clan affiliation, inheritance and disbursal of wealth, tribal and clan leadership. Tlingit culture still continues to be divided into two matrilineal moieties, Raven and Eagle (Wolf). Throughout traditional into present-day Tlingit culture, both men and women continue to be treated equally. The role of Tlingit women include are educating the young, conducting business in the tribal and public sectors and lastly, working to change public policy at the local, state and federal levels of government. Seven Tlingit women leaders (ages from 26 to 87 years old) participated in this qualitative study, which examined influences, challenges and experiences they encountered during their lifetimes. The intent of this researcher focused in the qualities of leadership developed in each participant. Through the use of a questionnaire and a semi-structured interview from each participant resulted in a collection of data. Examination of each participant â„¢s family histories and personal experiences has influenced who they are. This study has focused on how these Tlingit women â„¢s experiences of family/tribal roles, education and life, opportunities as well as barriers, their role models and/or mentors who have shaped their lives. Last to be examined was the participants â„¢ own definition of leadership and their personal and social concerns (specifically role of education, land and cultural preservation, tribal autonomy). These Tlingit women are well-known and respected for their involvement in numerous areas of Business, Management, Politics (at local, state and federal levels). The data collected from these seven participants â„¢ revealed commonalities and how they have shaped their leadership qualities

    Precision Measurement of the First Ionization Potential of Nobelium

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    One of the most important atomic properties governing an element’s chemical behavior is the energy required to remove its least-bound electron, referred to as the first ionization potential. For the heaviest elements, this fundamental quantity is strongly influenced by relativistic effects which lead to unique chemical properties. Laser spectroscopy on an atom-at-a-time scale was developed and applied to probe the optical spectrum of neutral nobelium near the ionization threshold. The first ionization potential of nobelium is determined here with a very high precision from the convergence of measured Rydberg series to be 6.626   21 ± 0.000   05     eV . This work provides a stringent benchmark for state-of-the-art many-body atomic modeling that considers relativistic and quantum electrodynamic effects and paves the way for high-precision measurements of atomic properties of elements only available from heavy-ion accelerator facilities

    Developments for resonance ionization laser spectroscopy of the heaviest elements at SHIP

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    The experimental determination of atomic levels and the first ionization potential of the heaviest elements (Z >= 100) is key to challenge theoretical predictions and to reveal changes in the atomic shell structure. These elements are only artificially produced in complete-fusion evaporation reactions at on-line facilities such as the GSI in Darmstadt at a rate of, at most, a few atoms per second. Hence, highly sensitive spectroscopic methods are required. Laser spectroscopy is one of the most powerful and valuable tools to investigate atomic properties. In combination with a buffer-gas filled stopping cell, the Radiation Detected Resonance Ionization Spectroscopy (RADRIS) technique provides the highest sensitivity for laser spectroscopy on the heaviest elements. The RADRIS setup, as well as the measurement procedure, have been optimized and characterized using the a-emitter 155Yb in on-line conditions, resulting in an overall efficiency well above 1%. This paves the way for a successful search of excited atomic levels in nobelium and heavier elements.publisher: Elsevier articletitle: Developments for resonance ionization laser spectroscopy of the heaviest elements at SHIP journaltitle: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms articlelink: http://dx.doi.org/10.1016/j.nimb.2016.06.001 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved.status: publishe
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