Measures of tuna abundance from purse-seine operations in the Eastern Pacific Ocean, adjusted for fleet-wide evolution of increased fishing power, 1960-1971

ENGLISH: The fishing power of the tuna purse-seine fleet of the eastern Pacific Ocean has increased since the early 1960's. Because the entire fleet seems to have adopted equipment and techniques to increase its efficiency in capturing tunas, traditional methods of adjusting catch rates to a reference vessel type of fixed efficiency to index tuna abundance from fishing success are inapplicable. Instead, a methodology for such adjustment based on a mathematical representation of purse seining activities is developed. Observed changes in efficiency in subprocesses of purse seining are then used to adjust catch rates when computing abundance histories for yellowfin and skipjack in large regions of the eastern Pacific Ocean. SPANISH: La eficacia de pesca de la flota de cerco atunera en el Océano Pacífico oriental ha aumentado desde el comienzo del decenio de 1960. Como toda la flota parece haber adoptado equipo y métodos para incrementar su eficaciaen capturar atunes, no se pueden aplicar los métodos tradicionales de ajustar los índices de captura a un tipo normalizado de barco (es decir de eficacia fija) para indicar la abundancia del atún según los resultados de pesca. En su lugar se ha desarrollado un método para realizar tal ajuste basado en una representación matemática de las actividades de las embarcaciones de cerco. Cuando se calcula la abundancia histórica del atún aleta amarilla y barrilete en grandes regiones del Océano Pacífico oriental, se usan entonces los cambios observados en la eficacia de los subprocesos cerqueros para ajustar los índices de captura. (PDF contains 120 pages.

Effects of hydroperiod on metamorphosis in \u3ci\u3eRana sphenocephala\u3c/i\u3e

Hydroperiod, the time a temporary pond holds water, is an important factor influencing recruitment in amphibian populations and structuring amphibian communities. We conducted an experiment to test the effect of hydroperiod on metamorphic traits of the southern leopard frog (Rana sphenocephala), a common amphibian in the southeastern United States. We reared larval R. sphenocephala in artificial ponds at a density of 32 larvae per tank (initial volume = approximately 650 liter). We dried the tanks according to natural patterns, using three different hydroperiods (60, 75 and 90 d). Experimental hydroperiods had a significant effect on the number of metamorphs and the length of the larval period, but not on overall survival (larvae + metamorphs) nor size at metamorphosis. Our findings confirm a pattern observed in field studies and are similar to results of experimental investigations of closely related ranid frogs. Our results demonstrate that relatively small differences in hydroperiod length (i.e., as little as 15 d) may have large effects on juvenile recruitment in R. sphenocephala

Anomalies, Chern-Simons Terms and Chiral Delocalization in Extra Dimensions

Gauge invariant topological interactions, such as the D=5 Chern-Simons terms, are required in models in extra dimensions that split anomaly free representations. The Chern-Simons term is necessary to maintain the overall anomaly cancellations of the theory, but it can have significant, observable, physical effects. The CS-term locks the KK-mode parity to the parity of space-time, leaving a single parity symmetry. It leads to new processes amongst KK-modes, eg, the decay of a KK-mode to a 2-body final state of KK-modes. A formalism for the effective interaction amongst KK-modes is constructed, and the decay of a KK-mode to KK-mode plus zero mode is analyzed as an example. We elaborate the general KK-mode current and anomaly structure of these theories. This includes a detailed study of the triangle diagrams and the associated ``consistent anomalies'' for Weyl spinors on the boundary branes. We also develop the non-abelian formalism. We illustrate this by showing in a simple way how a D=5 Yang-Mills ``quark flavor'' symmetry leads to the D=4 chiral lagrangian of mesons and the quantized Wess-Zumino-Witten term.Comment: 51 pages, 3 figures; Corrected typos, amplified discussio

T-Parity Violation by Anomalies

Little Higgs theories often rely on an internal parity ("T-parity'') to suppress non-standard electroweak effects or to provide a dark matter candidate. We show that such a symmetry is generally broken by anomalies, as described by the Wess-Zumino-Witten term. We study a simple SU(3) x SU(3)/SU(3) Little Higgs scheme where we obtain a minimal form for the topological interactions of a single Higgs field. The results apply to more general models, including [SU(3) x SU(3)/SU(3)]^4, SU(5)/SO(5), and SU(6)/Sp(6).Comment: 17 page

Topological Physics of Little Higgs Bosons

Topological interactions will generally occur in composite Higgs or Little Higgs theories, extra-dimensional gauge theories in which A_5 plays the role of a Higgs boson, and amongst the pNGB's of technicolor. This phenomena arises from the chiral and anomaly structure of the underlying UV completion theory, and/or through chiral delocalization in higher dimensions. These effects are described by a full Wess-Zumino-Witten term involving gauge fields and pNGB's. We give a general discussion of these interactions, some of which may have novel signatures at future colliders, such as the LHC and ILC.Comment: 22 page

Atypical Work and Employment Continuity

Atypical employment arrangements such as agency temporary work and contracting have long been criticized as offering more precarious and unstable work than regular employment. Using data from two datasets Ð the CAEAS and the NLSY79 Ð we determine whether workers who take such jobs rather than regular employment, or the alternative of continued job search, subsequently experience greater or lesser employment continuity. Observed differences between the various working arrangements are starkest when we do not account for unobserved individual heterogeneity. Controlling for the latter, we report that the advantage of regular work over atypical work and atypical work over continued joblessness dissipates.atypical work, open-ended work, employment continuity, unemployment, inactivity

The Cost of Caring for Young Children

This study examines the "cost burden" of child care, defined as day care expenses divided by after-tax income. Data are from the wave 10 core and child care topical modules to the 1996 Survey of Income and Program Participation. We estimate that the average child under six years of age lives in a family that spends 4.9 percent of after-tax income on day care. However, this conceals wide variation: 63 percent of such children reside in families with no child care expenses and 10 percent are in families where the cost burden exceeds 16 percent. The burden is typically greater in single-parent than married-couple families but is not systematically related to a measure of socioeconomic status that we construct. One reason for this is that disadvantaged families use lower cost modes and pay less per hour for given types of care. The cost burden would be much less equal without low cost (presumably subsidized) formal care focused on needy families, as well as government tax and transfer policies that redistribute income towards them.

Atypical Work and Employment Continuity

Atypical employment arrangements such as agency temporary work and contracting have long been criticized as offering more precarious and unstable work than regular employment. Using data from two datasets – the CAEAS and the NLSY79 – we determine whether workers who take such jobs rather than regular employment, or the alternative of continued job search, subsequently experience greater or lesser employment continuity. Observed differences between the various working arrangements are starkest when we do not account for unobserved individual heterogeneity. Controlling for the latter, we report that the advantage of regular work over atypical work and atypical work over continued joblessness dissipates.employment continuity, open-ended work, atypical work, unemployment, inactivity

‘Atypical Work’ and Compensation

Atypical work, or alternative work arrangements in U.S. parlance, has long been criticized in popular debate as providing poorly-compensated employment. Although the early U.S. literature seemed to confirm this perception, more recent cet. par. analysis has offered a partial but somewhat more optimistic evaluation. The present paper builds on the latter body of research with a view to providing improved estimates of the effect of the full range alternative work arrangements on worker compensation. The improvements are basically two-fold. First, we account for the skewness in atypical worker earnings while retaining the Mincerian human capital earnings function. Second, we deploy additional waves of the main dataset on atypical workers (the CAEAS), while supplementing this cross-section analysis with longitudinal data from the NLSY. Our analysis covers earnings and (access to) health benefits. We report that although one group of atypical workers (contractors) seems to enjoy a wage premium, cross-section results from the CPS and NLSY for the better-known category of temporary workers point to a negative wage differential of some 6-15 percent. It emerges that much of the disparity stems from unobserved worker heterogeneity, accounting for which still supports a wage advantage for contracting work. As far as fringes are concerned, the appearance in cross section of a potentially large deficit in access to health benefits is again reduced after accounting for the permanent unobserved individual heterogeneity, although in this case the attenuation is much more modest.atypical/contingent work, alternative work arrangements, wage differentials, employer-related health insurance

Evaluating Pooled Evidence from the Reemployment Bonus Experiments

Social experiments conducted in Pennsylvania and Washington tested the effect of offering Unemployment Insurance (UI) claimants a cash bonus for rapid reemployment. This paper combines data from the two experiments and uses a consistent framework to evaluate the experiments and determine with greater certainty the extent to which a reemployment bonus can affect economic outcomes. Bonus offers in each of the experiments generated statistically significant but relatively modest reductions in UI receipt. Since the estimated impacts on UI receipt were modest, the reemployment bonuses did not generate the UI savings necessary to pay for administering and paying the bonuses. Hence, contrary to earlier findings from a bonus experiment conducted in Illinois, findings from the Pennsylvania and Washington experiments strongly suggest that a reemployment bonus is not a cost-effective method of speeding the reemployment of UI claimants.unemployment, insurance, bonus, experiments, O'Leary, Decker