Southern California partyboat sampling study Quarterly Report no. 8

Between April 1 and June 30, 1977, 125 trips were sampled aboard southern California partyboats by Department personnel. A total of 14,842 fishes belonging to 72 species was identified and measured. Otoliths were removed from 134 rockfish carcasses representing 20 species for age deterination studies. The 10 most common species sampled during the quarter accounted for 76.9% of the catch. Individually, the most common were Pacific mackerel, Scomber japonicus (16.9%); kelp bass, Paralabrax clathratus (14.5%); bocaccio, Sebastes paucispinis (11.4%); Pacific bonito, Sarda chiliensis (10.3%); barred sand bass, Paralabrax nebulifer (5.6%); olive rockfish, Sebastes serranoides (5.3%); chilipepper, S. goodei (4.0%); California barracuda, Sphyraena argentea (2.9%); and ocean whitefish, Caulolatilus princeps (2.8%). Fishing effort switched from "rockcod" to surface activity as it did during the second quarter of 1976 (26pp.

Two tone response of radiofrequency signals using the voltage output of a Superconducting Quantum Interference Filter

In the presence of weak time harmonic electromagnetic fields, Superconducting Quantum Interference Filters (SQIFs) show the typical behavior of non linear mixers. The SQIFs are manufactured from high-T_c grain boundary Josephson junctions and operated in active microcooler. The dependence of dc voltage output V_dc vs. static external magnetic field B is non-periodic and consists of a well pronounced unique dip at zero field, with marginal side modulations at higher fields. We have successfully exploited the parabolic shape of the voltage dip around B=0 to mix quadratically two external time harmonic rf-signals, at frequencies f_1 and f_2 below the Josephson frequency f_J, and detect the corresponding mixing signal at f_1-f_2. When the mixing takes place on the SQIF current-voltage characteristics the component at 2f_2 - f_1 is present. The experiments suggest potential applications of a SQIF as a non-linear mixing device, capable to operate at frequencies from dc to few GHz with a large dynamic range.Comment: 10 pages, 3 Figures, submitted to J. Supercond. (as proceeding of the HTSHFF Symposium, June 2006, Cardiff

The identification of outliers in exponential samples

In this paper, the task of identifying outliers in exponential samples is treated conceptionally in the sense of Davies and Gather (1989, 1993) by means of a so-called outlier region. In case of an exponential distribution, an empirical approximation of such a region - also called an outlier identifier - is mainly dependent on some estimator of the unknown scale parameter. The worst-case behaviour of several reasonable outlier identifiers is investigated thoroughly and it is shown that only robust estimators of scale should be used to construct reliable identifiers. These fifindings lead to the recommendation of an outlier identifier that is based on a standardized version of the sample median

Identification of outliers in exponential samples with stepwise procedures

In this paper we consider the problem of identifying outliers in exponential samples with stepwise procedures, namely inward and outward testing procedures. We treat outliers in the spirit of Davies and Gather (1993) as points which for given alpha > 0 lie in a certain alpha-outlier region and focus especially on the worst-case be-haviour of the identification rules. Best results yield stepwise procedures which use test statistics based on a standardized version of the sample median

Enhancement of the ferromagnetic order of graphite after sulphuric acid treatment

We have studied the changes in the ferromagnetic behavior of graphite powder and graphite flakes after treatment with diluted sulphuric acid. We show that this kind of acid treatment enhances substantially the ferromagnetic magnetization of virgin graphite micrometer size powder as well as in graphite flakes. The anisotropic magnetoresistance (AMR) amplitude at 300 K measured in a micrometer size thin graphite flake after acid treatment reaches values comparable to polycrystalline cobalt.Comment: 3.2 pages, 4 figure

Increased Mixing and Turbulence in the Wake of Offshore Wind Farm Foundations

The addition of offshore wind farms (OWFs) to stratified regions of shelf seas poses an anthropogenic source of turbulence, in which the foundation structures remove power from the oceanic flow that is fed into turbulent mixing in the wake downstream. The loss of stratification within the wake of a single OWF structure is observed for the first time by means of field observations, which enable a qualitative characterization of the disturbed flow downstream. These results are complemented with high-resolution large eddy simulations of four different stratification strengths that allow for a quantification of turbulence and mixing quantities in the wake of a foundation structure. The turbulent wake of a structure is narrow and highly energetic within the first 100 m, with the dissipation of turbulent kinetic energy well above background levels downstream of the structure. A single monopile is responsible for 7–10% additional mixing to that of the bottom mixed layer, whereby ∼10% of the turbulent kinetic energy generated by the structure is used in mixing. Although the effect of a single turbine on stratification is relatively low, large-scale OWFs could significantly affect the vertical structure of a weakly stratified water column. Further, rough estimates show that the rate of formation of stratification in the study area is of the same order of magnitude as the additional mixing promoted by the structures, thus OWFs could modify the stratification regime and water column dynamics on a seasonal scale, depending on local conditions and farm geometries