1,266 research outputs found
Ecology of Juvenile Walleye Pollock, Theragra chalcogramma: Papers from the workshop "The Importance of Prerecruit Walleye Pollock to the Bering Sea and North Pacific Ecosystems" Seattle, Washington, 28-30 October 1993
The Alaska Fisheries Science Center (AFSC), National
Marine Fisheries Service (NMFS), hosted an international
workshop, 'The Importance of Prerecruit Walleye Pollock to the Bering Sea and North Pacific Ecosystems," from 28 to 30 October 1993. This workshop was held in conjunction with the annual International North Pacific Marine Science Organization (PICES) meeting held in Seattle. Nearly 100 representatives from government agencies, universities, and the fishing industry in Canada, Japan, the People's Republic of China, Russia, and the United States took part in the workshop to review and discuss current knowledge on juvenile pollock from the postlarval period to the time they recruit to the fisheries. In addition to its importance to humans as a major commercial species, pollock also serves as a major forage species for many marine fishes, birds, and mammals in the North Pacific region.
(PDF file contains 236 pages.
Control of the Onset of Filamentation in Condensed Media
Propagation of intense, ultrashort laser pulses through condensed media like
crystals of BaF and sapphire results in the formation of filaments. We
demonstrate that the onset of filamentation may be controlled by rotating the
plane of polarization of incident light. We directly visualize filamentation in
BaF_2 via six-photon absorption-induced fluorescence and, concomitantly, by
probing the spectral and spatial properties of white light that is generated.Comment: To appear in Phys. Rev.
Erythropoietin/erythropoietin receptor system is involved in angiogenesis in human neuroblastoma
Ribatti D, Poliani P L, Longo V, Mangieri D, Nico B & Vacca A (2007) Histopathology50, 636â641 Erythropoietin/erythropoietin receptor system is involved in angiogenesis in human neuroblastom
Trapped-ion decay spectroscopy towards the determination of ground-state components of double-beta decay matrix elements
A new technique has been developed at TRIUMF's TITAN facility to perform
in-trap decay spectroscopy. The aim of this technique is to eventually measure
weak electron capture branching ratios (ECBRs) and by this to consequently
determine GT matrix elements of decaying nuclei. These branching
ratios provide important input to the theoretical description of these decays.
The feasibility and power of the technique is demonstrated by measuring the
ECBR of Cs.Comment: 9 pages, 9 figure
Precision mass measurements on neutron-rich rare-earth isotopes at JYFLTRAP - reduced neutron pairing and implications for the -process calculations
The rare-earth peak in the -process abundance pattern depends sensitively
on both the astrophysical conditions and subtle changes in nuclear structure in
the region. This work takes an important step elucidating the nuclear structure
and reducing the uncertainties in -process calculations via precise atomic
mass measurements at the JYFLTRAP double Penning trap. Nd, Pm,
Sm, and Gd have been measured for the first time and the
precisions for Nd, Pm, Eu, Gd, and
Tb have been improved considerably. Nuclear structure has been probed
via two-neutron separation energies and neutron pairing energy metrics
. The data do not support the existence of a subshell closure at .
Neutron pairing has been found to be weaker than predicted by theoretical mass
models. The impact on the calculated -process abundances has been studied.
Substantial changes resulting in a smoother abundance distribution and a better
agreement with the solar -process abundances are observed.Comment: 8 pages, 4 figures, accepted for publication in Physical Review
Letter
First direct mass-measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He
The first direct mass-measurement of He has been performed with the
TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the
mass of He was determined with improved precision over our previous
measurement. The obtained masses are (He) = 6.018 885 883(57) u and
(He) = 8.033 934 44(11) u. The He value shows a deviation from
the literature of 4. With these new mass values and the previously
measured atomic isotope shifts we obtain charge radii of 2.060(8) fm and
1.959(16) fm for He and He respectively. We present a detailed
comparison to nuclear theory for He, including new hyperspherical harmonics
results. A correlation plot of the point-proton radius with the two-neutron
separation energy demonstrates clearly the importance of three-nucleon forces.Comment: 4 pages, 2 figure
Breakdown of the Isobaric Multiplet Mass Equation for the A = 20 and 21 Multiplets
Using the Penning trap mass spectrometer TITAN, we performed the first direct
mass measurements of 20,21Mg, isotopes that are the most proton-rich members of
the A = 20 and A = 21 isospin multiplets. These measurements were possible
through the use of a unique ion-guide laser ion source, a development that
suppressed isobaric contamination by six orders of magnitude. Compared to the
latest atomic mass evaluation, we find that the mass of 21Mg is in good
agreement but that the mass of 20Mg deviates by 3{\sigma}. These measurements
reduce the uncertainties in the masses of 20,21Mg by 15 and 22 times,
respectively, resulting in a significant departure from the expected behavior
of the isobaric multiplet mass equation in both the A = 20 and A = 21
multiplets. This presents a challenge to shell model calculations using either
the isospin non-conserving USDA/B Hamiltonians or isospin non-conserving
interactions based on chiral two- and three-nucleon forces.Comment: 5 pages, 2 figure
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Warming Ocean Conditions Relate to Increased Trophic Requirements of Threatened and Endangered Salmon
The trophic habits, size and condition of yearling Chinook salmon (Oncorhynchus tshawytscha) caught early in their marine residence were examined during 19 survey years (1981â1985; 1998â2011). Juvenile salmon consumed distinct highly piscivorous diets in cold and warm ocean regimes with major differences between ocean regimes driven by changes in consumption of juvenile rockfishes, followed by several other fish prey, adult euphausiids and decapod larvae. Notable, Chinook salmon consumed 30% more food in the warm versus cold ocean regime in both May and June. Additionally, there were about 30% fewer empty stomachs in the warm ocean regime in May, and 10% fewer in warm June periods. The total prey energy density consumed during the warmer ocean regime was also significantly higher than in cold. Chinook salmon had lower condition factor and were smaller in fork length during the warm ocean regime, and were longer and heavier for their size during the cold ocean regime. The significant increase in foraging during the warm ocean regime occurred concurrently with lower available prey biomass. Adult return rates of juvenile Chinook salmon that entered the ocean during a warm ocean regime were lower. Notably, our long term data set contradicts the long held assertion that juvenile salmon eat less in a warm ocean regime when low growth and survival is observed, and when available prey are reduced. Comparing diet changes between decades under variable ocean conditions may assist us in understanding the effects of projected warming ocean regimes on juvenile Chinook salmon and their survival in the ocean environment. Bioenergetically, the salmon appear to require more food resources during warm ocean regimes
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Influence of a Coastal Riverine Plume on the Cross-shelf Variability in Hydrography, Zooplankton, and Juvenile Salmon Diets
Riverine plumes in nearshore coastal waters are areas of enhanced production and accumulation of prey and may increase availability of food during a critical period of juvenile salmon survival and hence serve as a nursery area for these juveniles. Physical and biological sampling was conducted along a cross-shelf transect through the Columbia River plume during May 1999. Based on cluster analyses of physical variables, stations considered to be within the core of the plume, at 27.8â46.3 km from shore, were distinct from inshore (7.4â18.5 km) and offshore (55.6â92.7 km) stations. Five variables (temperature at 10 m, salinity at 3 and 10 m, silicate, and chlorophyll) accounted for 92 % of this difference. Both surface neuston and subsurface plankton tows revealed differences in plankton composition at the plume core stations compared to non-plume stations. However, stomach contents of juvenile Chinook salmon were not significantly different inside and outside the plume core. Comparison of similarity indices showed that the stomach composition was more similar to the catch composition in the neuston than the meter net. Fishes, decapod larvae, and hyperiid amphipods occurred in greater proportions and copepods and euphausiids in lesser proportions in the stomachs than in the plankton. There appeared to be a distinctive plume signal, evident in both the physical environment and zooplankton resources sampled inside and outside the plume core, but the plume signature was not as evident in the salmon diets, possibly due to their higher mobility and shorter residence time within the plume.Keywords: Habitat, Oceanography, Riverine plume, Feeding habits, Juvenile salmon, Zooplankto
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