5,504 research outputs found
Age and growth estimates of the winter skate (Leucoraja ocellata) in the western Gulf of Maine
Age and growth estimates for the winter skate (Leucoraja ocellata) were estimated from vertebral band counts on 209 fish ranging in size from 145 to 940 mm total length (TL). An index of average percent error (IAPE) of 5.8% suggests that our aging method represents a precise approach to the age assessment of L. ocellata. Marginal increments were significantly different between months (Kruskal-Wallis P<0.001) and a distinct trend of increasing monthly increment growth began in July. Estimates of von Bertalanffy growth parameters suggest that females attain a slightly larger asymptotic TL (L∞=1374 mm) than males (L∞=1218 mm) and grow more slowly (k=0.059 and 0.074, respectively). The oldest ages obtained for the winter skate were 19 years for males and 18 years for females, which corresponded to total lengths of 932 mm and 940 mm, respectively. The results indicate that the winter skate exhibits the characteristics that have made other elasmobranch populations highly susceptible to exploitation by commercial fisheries
Energy exchange during stimulated Raman scattering of a relativistic laser in a plasma
Energy exchange between pump and daughter waves during the stimulated Raman scattering process in a plasma is investigated, including the effect of a damping coefficient of electron-ion collision at different initial three-wave phases. To obey the energy and momentum conservations, the resonance conditions are satisfied at an optimal initial phase difference between the interacting waves. The amplitudes of the interacting waves exhibit behaviors such as a parametric oscillator. The variations in initial three-wave phase difference generate a phase mismatch, which enhances the rate of the amplitude variations of the interacting waves. The relativistic mass effect modifies the dispersion relations of the interacting waves, and consequently the energy exchange during the stimulated Raman scattering is affected. The collisional damping in the plasma is shown to have an important effect on the evolution of the interacting waves.open91
Fouling and performance of outer selective hollow fiber membrane in osmotic membrane bioreactor: Cross flow and air scouring effects
© 2019 Elsevier Ltd This study assessed impacts of cross-flow velocity (CFV) and air scouring on the performance and membrane fouling mitigation of a side-stream module containing outer-selective hollow fiber thin film composite forward osmosis membrane in osmosis membrane bioreactor (OMBR) system for urban wastewater treatment. CFV of draw solution was optimized, followed by the impact assessment of three CFVs on feed solution (FS) stream and periodic injection of air scouring into the side-stream module. Overall, the OMBR system exhibited high and stable performance with initial water flux of approximately 15 LMH, high removal efficiencies of bulk organic matter and nutrients. While FS's CFVs insignificantly affected the performance and membrane fouling, regular air scouring showed substantial impact with better performance and high efficiency in mitigating membrane fouling. These results indicated that periodic air scouring can be applied into the side-stream membrane module for efficient fouling mitigation without interruption the operation of the OMBR system
Scaling analysis of a model Hamiltonian for Ce impurity in a cubic metal
We introduce various exchange interactions in a model Hamiltonian for
Ce ions in cubic symmetry with three configurations (,,).
With the impurity pseudo spin , our Hamiltonian includes: (i)
One-channel Anderson model; (ii) Two-channel Anderson
model; (iii) An unforseen one-channel Anderson model with a
non-trivial fixed point; (iv) Mixing exchange interaction between the
and the conduction electron partial wave states; (v)
Multiple conduction electron partial wave states. Using the third-order scaling
(perturbative renormalization group) analysis, we study stability of various
fixed points relevant to various exchange interactions for Ce ions in
cubic symmetry.Comment: 68 pages. 4 figures are available upon request from
[email protected] (revised
Triangle-Free Penny Graphs: Degeneracy, Choosability, and Edge Count
We show that triangle-free penny graphs have degeneracy at most two, list
coloring number (choosability) at most three, diameter , and
at most edges.Comment: 10 pages, 2 figures. To appear at the 25th International Symposium on
Graph Drawing and Network Visualization (GD 2017
Comment on ???Electron acceleration by a chirped Gaussian laser pulse in vacuum??? [Phys. Plasmas13, 123108 (2006)]
Sohbatzadeh [Phys. Plasmas 13, 123108 (2006)] have presented a scheme of vacuum electron acceleration by using a chirped Gaussian laser pulse. They assume a linear polarization of the laser pulse in this scheme. We point out that this might be an important assumption in their work and it can seriously influence the electron energy gain during laser acceleration. In this Comment, the circular polarization of a chirped laser pulse is employed and our results show higher electron energy gainsclose4
Strong terahertz emission from electromagnetic diffusion near cutoff in plasma
Anew mechanism for electromagnetic emission in the terahertz (THz) frequency regime from laser-plasma interactions is described. A localized and long-lasting transverse current is produced by two counter-propagating short laser pulses in weakly magnetized plasma. We show that the electromagnetic wave radiating from this current source, even though its frequency is close to cut-off of the ambient plasma, grows and diffuses towards the plasma-vacuum boundary, emitting a strong monochromatic THz wave. With driving laser pulses of moderate power, the THz wave has a field strength of tens of MV m(-1), a frequency of a few THz and a quasi-continuous power that exceeds all previous monochromatic THz sources. The novelty of the mechanism lies in a diffusing electromagnetic wave close to cut-off, which is modelled by a continuously driven complex diffusion equationopen
Theory of One-Channel vs. Multi-Channel Kondo Effects for Ce Impurities
We introduce a model for Ce impurities in cubic metals which exhibits
competition between the Fermi-liquid fixed point of the single channel Kondo
model and the non-Fermi-liquid fixed point of the two- and three-channel Kondo
models. Using the non-crossing approximation and scaling theory, we find: (i) A
possible three-channel Kondo effect between the one- and two-channel regimes in
parameter space. (ii) The sign of the thermopower is a fixed point diagnostic.
(iii) Our results will likely survive the introduction of additional and
conduction states. We apply this model to interpret the non-Fermi liquid alloy
LaCeCuSi.Comment: 13 pages, Revtex, To appear in Phys. Rev. Let
The H Beta Index as an Age Indicator of Old Stellar Systems: The Effects of Horizontal-Branch Stars
The strength of the H index has been computed for the integrated
spectra of model globular clusters from the evolutionary population synthesis.
These models take into account, for the first time, the detailed systematic
variation of horizontal-branch (HB) morphology with age and metallicity. Our
models show that the H index is significantly affected by the presence
of blue HB stars. Because of the contribution from blue HB stars, the H
does not monotonically decrease as metallicity increases at a given age.
Instead, it reaches a maximum strength when the distribution of HB stars is
centered around 9500 K, the temperature where the H index becomes
strongest. Our models indicate that the strength of the H index
increases as much as 0.75 {\AA} due to the presence of blue HB stars.
The comparison of the recent Keck observations of the globular cluster system
in the Milky Way Galaxy with those in giant elliptical galaxies, NGC 1399 and
M87, shows a systematic shift in the H against metallicity plane. Our
models suggest that this systematic difference is understood if the globular
cluster systems in giant elliptical galaxies are several billion years older,
in the mean, than the Galactic counterpart. Further observations of globular
cluster systems in the external galaxies from the large ground-based telescopes
and space UV facilities will enable to clarify whether this difference is
indeed due to the age difference or other explanations are also possible.Comment: 21 pages, 8 figures, Accepted for publication in the Astronomical
Journal, August 2000 issue, Postscript files are available at
http://csaweb.yonsei.ac.kr/~hclee/Hbet
Even-odd parity effects in conductance and shot noise of metal-atomic wire-metal(superconducting) junctions
In this paper, we study the conductance and shot noise in transport through a
multi-site system in a two terminal configuration. The dependence of the
transport on the number of atoms in the atomic wire is investigated using a
tight-binding Hamiltonian and the nonequilibrium Green's function method. In
addition to reproducing the even-odd behavior in the transmission probability
at the Fermi energy or the linear response conductance in the normal-atomic
wire-normal metallic(NAN) junctions, we find the following: (i) The shot noise
is larger in the even-numbered atomic wire than in the odd-numbered wire. (ii)
The Andreev conductance displays the same even-odd parity effects in the
normal-atomic wire-superconducting(NAS) junctions. In general, the conductance
is higher in the odd-numbered atomic wire than in the even-numbered wire. When
the number of sites () is odd and the atomic wire is mirror symmetric with
respect to the center of the atomic wire, the conductance does not depend on
the details of the hopping matrices in the atomic wire, but is solely
determined by the coupling strength to the two leads. When is even, the
conductance is sensitive to the values of the hopping matrices.Comment: 12 pages, 9 figure
- …