2,621 research outputs found
Year-class formation in Pacific herring (Clupea pallasi) estimated from spawning-date distributions of juveniles in San Francisco Bay, California
Inter and intra-annual variation in year-class strength was analyzed for San Francisco Bay Pacific herring (Clupea pallasi) by using otoliths of juveniles. Juvenile herring
were collected from March through June in 1999 and 2000 and otoliths from subsamples of these collections were aged by daily otolith increment analysis. The composition of the year classes in 1999 and 2000 were determined by back-calculating the birth date distribution for surviving juvenile herring. In 2000, 729% more juveniles were captured than in 1999, even though an estimated 12% fewer
eggs were spawned in 2000. Spawning-date distributions show that survival for the 2000 year class was exceptionally good for a short (approximately 1 month) period of spawning,
resulting in a large abundance of juvenile recruits. Analysis of age at size shows that growth rate increased
significantly as the spawning season progressed both in 1999 and 2000. However, only in 2000 were the bulk of surviving juveniles a product of the fast growth period. In the two years examined, year-class strength was not predicted by the estimated number of eggs spawned, but rather appeared to depend on survival of eggs or larvae (or both) through the juvenile stage. Fast growth through the larval stage may have little effect on year-class strength if mortality during the egg stage is high and few larvae are available
Structure and dynamics of colloidal depletion gels: coincidence of transitions and heterogeneity
Transitions in structural heterogeneity of colloidal depletion gels formed
through short-range attractive interactions are correlated with their dynamical
arrest. The system is a density and refractive index matched suspension of 0.20
volume fraction poly(methyl methacyrlate) colloids with the non-adsorbing
depletant polystyrene added at a size ratio of depletant to colloid of 0.043.
As the strength of the short-range attractive interaction is increased,
clusters become increasingly structurally heterogeneous, as characterized by
number-density fluctuations, and dynamically immobilized, as characterized by
the single-particle mean-squared displacement. The number of free colloids in
the suspension also progressively declines. As an immobile cluster to gel
transition is traversed, structural heterogeneity abruptly decreases.
Simultaneously, the mean single-particle dynamics saturates at a localization
length on the order of the short-range attractive potential range. Both
immobile cluster and gel regimes show dynamical heterogeneity. Non-Gaussian
distributions of single particle displacements reveal enhanced populations of
dynamical trajectories localized on two different length scales. Similar
dependencies of number density fluctuations, free particle number and dynamical
length scales on the order of the range of short-range attraction suggests a
collective structural origin of dynamic heterogeneity in colloidal gels.Comment: 14 pages, 10 figure
Velocity-resolved observations of water in Comet Halley
High resolution (lambda/delta lambda approx. = 3 x 10 to the 5th power) near-infrared observations of H2O emission from Comet Halley were acquired at the time of maximum post-perihelion geocentric Doppler shift. The observed widths and absolute positions of the H2O line profiles reveal characteristics of the molecular velocity field in the coma. These results support H2O outflow from a Sun-lit hemisphere or the entire nucleus, but not from a single, narrow jet emanating from the nucleus. The measured pre- and post-perihelion outflow velocities were 0.9 + or - 0.2 and 1.4 + or - 0.2 km/s, respectively. Temporal variations in the kinematic properties of the outflow were inferred from changes in the spectral line shapes. These results are consistent with the release of H2O into the coma from multiple jets
Report to the California Public Utilities Commission Regarding Ex Parte Communications and Related Practices
Part I contains the analysis of existing law. We review the statutes and regulations governing ex parte communications before the CPUC, examine corresponding laws of other jurisdictions, and compare the CPUC statutes and regulations with those of the other jurisdictions. In Part II we examine actual ex parte practices before the CPUC. Based on data obtained from notices filed on the Commission’s website by parties to rate-setting cases, we provide a quantitative characterization of the extent and nature of noticed ex parte communications over the past roughly 22 years. We then place ex parte communications within the context of the CPUC’s proceedings. Part III provides the results of an interview process we undertook to hear the experiences and opinions of people with a stake or an interest in CPUC decision-making, including representatives of regulated utilities, intervenor groups who generally (but not always) appear in CPUC rate-setting cases in opposition to the positions of utilities, companies and industry groups who generally oppose specific utilities’ positions, legislators and legislative staff, public critics of CPUC ex parte practices, CPUC staff (administrative law judges (ALJs), attorneys, and technical staff), and the CPUC Commissioners and their staffs. Then, in Part IV, we present our analysis of this information and our recommendations for changes to statutes, CPUC rules, and Commission practices
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