15,890 research outputs found

    Southern California marine sport fishing from privately-owned boats: catch and effort for October-December 1981

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    The catch landed and effort expended by private-boat sport fishermen were studied in southern California between October and December 1981, in order to determine the impact of one segment of the sport fishery on local marine resources. Fishermen returning from fishing trips were interviewed at launch ramps, hoists, and boat-rental facilities. This report contains quantitative data and statistical estimates of total effort, total catch, catch of preferred species, and length frequencies for those species whose catches are regulated by minimum size limits. An estimated 208,000 organisms were landed by 54,000 anglers and 4,500 divers. The major components of the catch were Pacific mackerel, Scomber japonicus, 50,200 landed; white croaker, Genyonemus lineatus, 35,000 landed, and Pacific bonito, Sarda chiliensis, 27,000 landed. Together, these three species made up over half of the total catch. Most of the size limit regulations were closely observed by anglers; the one exception was that of California halibut, Paralichthys californicus, of which only 65% met legal size requirements. Regarding invertebrates landed by divers, size limit compliance was 90% for red abalone, Haliotis rufescens, and 95% for spiny lobster, Panulirus interruptus. (28pp.

    Southern California marine sport fishing from privately owned boats: catch and effort for October-December 1982

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    The catch landed and effort expended by private-boat sport fishermen were studied in southern California marine waters between October and December 1982, to determine the impact of one segment of the sport fishery on local marine resources. Fishermen returning from fishing trips were interviewed at launch ramps, hoists, and boat-rental facilities. This report contains quantitative data and statistical estimates of total effort, total catch, catch of preferred species, and length frequencies for those species whose catches are regulated by minimum size limits. An estimated 157,000 organisms were landed by 57,700 anglers and 4800 divers. The major components of the angler catch were Pacific mackerel, Scomber japonicus (28,700 estimated catch): white croaker, Genyonemus lineatus (24,000 estimated catch); and Pacific bonito, Sarda chiliensis (16,700 estimated catch). These three species represented almost half the total estimated angler catch. Rockfishes, Sebastes spp: were a major catch component; the 35 rockfish species landed made up 24% of the estimated catch. Divers landed an estimated 14,700 fishes and invertebrates. Chief among these were abalone, Haliotis spp. (4200 estimated catch); rock scallop, Hinnites rugosus (3600 estimated catch); and California spiny lobster, Panulirus interruptus (2500 estimated catch). Angler and diver compliance with size-limit regulations was generally favorable, with diver compliance being particularly scrupulous, especially with invertebrate species. The compliance rate for California halibut, Paralichthys californicus, showed a drop from the previous quarter (July - September 1982) from 70 to 59% legal. During the same time period, size-limit compliance rose from 4 to 20% for Pacific bonito, a species with a tolerance allowing the take of some under-sized fish. (28p.

    Flexible control of the Peierls transition in metallic C60_{60} polymers

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    The metal-semiconductor transition of peanut-shaped fullerene (C60_{60}) polymers is clarified by considering the electron-phonon coupling in the uneven structure of the polymers. We established a theory that accounts for the transition temperature TcT_c reported in a recent experiment and also suggests that TcT_c is considerably lowered by electron doping or prolonged irradiation during synthesis. The decrease in TcT_c is an appealing phenomenon with regard to realizing high-conductivity C60_{60}-based nanowires even at low temperatures.Comment: 3 pages, 3 figure

    Antisymmetrized molecular dynamics with quantum branching processes for collisions of heavy nuclei

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    Antisymmetrized molecular dynamics (AMD) with quantum branching processes is reformulated so that it can be applicable to the collisions of heavy nuclei such as Au + Au multifragmentation reactions. The quantum branching process due to the wave packet diffusion effect is treated as a random term in a Langevin-type equation of motion, whose numerical treatment is much easier than the method of the previous papers. Furthermore a new approximation formula, called the triple-loop approximation, is introduced in order to evaluate the Hamiltonian in the equation of motion with much less computation time than the exact calculation. A calculation is performed for the Au + Au central collisions at 150 MeV/nucleon. The result shows that AMD almost reproduces the copious fragment formation in this reaction.Comment: 24 pages, 5 figures embedde

    Short timescale behavior of colliding heavy nuclei at intermediate energies

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    An Antisymmetrized Molecular Dynamics model is used to explore the collision of 114^{114}Cd projectiles with 92^{92}Mo target nuclei at E/A=50 MeV over a broad range in impact parameter. The atomic number (Z), velocity, and emission pattern of the reaction products are examined as a function of the impact parameter and the cluster recognition time. The non-central collisions are found to be essentially binary in character resulting in the formation of an excited projectile-like fragment (PLF∗^*) and target-like fragment (TLF∗^*). The decay of these fragments occurs on a short timescale, 100≤\let≤\le300 fm/c. The average excitation energy deduced for the PLF∗^* and TLF∗^* `saturates for mid-central collisions, 3.5≤\leb≤\le6 fm, with its magnitude depending on the cluster recognition time. For short cluster recognition times (t=150 fm/c), an average excitation energy as high as ≈\approx6 MeV is predicted. Short timescale emission leads to a loss of initial correlations and results in features such as an anisotropic emission pattern of both IMFs and alpha particles emitted from the PLF∗^* and TLF∗^* in peripheral collisions.Comment: 19 pages, 17 figure

    Antisymmetrized molecular dynamics of wave packets with stochastic incorporation of Vlasov equation

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    On the basis of the antisymmetrized molecular dynamics (AMD) of wave packets for the quantum system, a novel model (called AMD-V) is constructed by the stochastic incorporation of the diffusion and the deformation of wave packets which is calculated by Vlasov equation without any restriction on the one-body distribution. In other words, the stochastic branching process in molecular dynamics is formulated so that the instantaneous time evolution of the averaged one-body distribution is essentially equivalent to the solution of Vlasov equation. Furthermore, as usual molecular dynamics, AMD-V keeps the many-body correlation and can naturally describe the fluctuation among many channels of the reaction. It is demonstrated that the newly introduced process of AMD-V has drastic effects in heavy ion collisions of 40Ca + 40Ca at 35 MeV/nucleon, especially on the fragmentation mechanism, and AMD-V reproduces the fragmentation data very well. Discussions are given on the interrelation among the frameworks of AMD, AMD-V and other microscopic models developed for the nuclear dynamics.Comment: 26 pages, LaTeX with revtex and epsf, embedded postscript figure

    Two mechanisms of pseudogap formation in Bi-2201: Evidence from the c-axis magnetoresistance

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    Measurements of the c-axis resistivity and magnetoresistance have been used to investigate the pseudogap (PG) behavior in Bi_{2+z}Sr_{2-x-z}La_xCuO_y (Bi-2201) crystals at various hole densities. While the PG opening temperature T* increases with decreasing hole doping, the magnetic-field sensitivity of the PG is found to have a very different trend: it appears at lower temperatures in more underdoped samples and vanishes in non-superconducting samples. These data suggest that besides the field-insensitive pseudogap emerging at T*, a distinct one is formed above T_c as a precursor to superconductivity.Comment: 7 pages, 6 figures, accepted for publication in Europhysics Letters (initially submitted to PRL on 14 June 2000
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