Results of the jack mackerel subpopulation discrimination feasibility study

A report is made on the feasibility of discriminating subpopulations of jack mackerel, Trachurus symmetricus, off of the southern California and Baja California coast. Histochemical, morphometric, and meristic characters are compared from four samples of approximately 200 fish each taken from three areas. The data are analyzed for homogeneity by chi-square tests. Heterogeneity was found only in anal fin ray counts. Recommendations for a comprehensive study are made. (16pp.

Results of Jack Mackerel tagging study, 1971-75

Methods and materials used to tag and recapture jack mackerel, Trachurus symmetricus, off the coast of southern Ca1ifornia and Baja California, Mexico, are described. Tagging, recapture, and movement data resulting from this program are reported. Analysis of these data indicates substantial movement of jack mackerel within the range of the California fishery and suggests a seasonal inshore-offshore movement pattern. (13pp.

Forced to Be Rich? Returns to Compulsory Schooling in Britain

Do students benefit from compulsory schooling? Researchers using changes in compulsory schooling laws as instruments have typically estimated very high returns to additional schooling that are greater than the corresponding OLS estimates and concluded that the group of individuals who are influenced by the law change have particularly high returns to education. That is, the Local Average Treatment Effect (LATE) is larger than the average treatment effect (ATE). However, studies of a 1947 British compulsory schooling law change that impacted about half the relevant population have also found very high instrumental variables returns to schooling (about 15%), suggesting that the ATE of schooling is also very high and higher than OLS estimates suggest. We utilize the New Earnings Survey Panel Data-set (NESPD), that has superior earnings information compared to the datasets previously used and find instrumental variable estimates that are small and much lower than OLS. In fact, there is no evidence of any positive return for women and the return for men is in the 4-7% range. These estimates provide no evidence that the ATE of schooling is very high.compulsory schooling, return to education

A Good Time to Stay Out? Strikes and the Business Cycle

In this paper, we compile a unique historical dataset that records strike activity in the British engineering industry from 1920 to 1970. These data have the advantage of containing a fairly homogenous set of companies and workers, covering a long period with varying labour market conditions, including information that enables the addition of union and company fixed effects, and providing geographical detail that allows a district-level analysis that controls for year and seasonal effects. We study the cyclicality of strike durations, strike incidence, and strike outcomes and distinguish between pay and non-pay strikes. Like the previous literature, we find evidence that strikes over pay have countercyclical durations. However, in the post-war period, the magnitude of this effect is much reduced when union and firm fixed effects are included. These findings suggest that it is important when studying strike durations to take account of differences in the composition of companies and unions that are involved in strikes at different points of the business cycle. We also find that strike outcomes tend to be more favourable to unions when the national unemployment rate is lower.incidence, duration, cyclicality, strikes, outcome

Wright-Fisher diffusion bridges

{\bf Abstract} The trajectory of the frequency of an allele which begins at $x$ at time $0$ and is known to have frequency $z$ at time $T$ can be modelled by the bridge process of the Wright-Fisher diffusion. Bridges when $x=z=0$ are particularly interesting because they model the trajectory of the frequency of an allele which appears at a time, then is lost by random drift or mutation after a time $T$. The coalescent genealogy back in time of a population in a neutral Wright-Fisher diffusion process is well understood. In this paper we obtain a new interpretation of the coalescent genealogy of the population in a bridge from a time $t\in (0,T)$. In a bridge with allele frequencies of 0 at times 0 and $T$ the coalescence structure is that the population coalesces in two directions from $t$ to $0$ and $t$ to $T$ such that there is just one lineage of the allele under consideration at times $0$ and $T$. The genealogy in Wright-Fisher diffusion bridges with selection is more complex than in the neutral model, but still with the property of the population branching and coalescing in two directions from time $t\in (0,T)$. The density of the frequency of an allele at time $t$ is expressed in a way that shows coalescence in the two directions. A new algorithm for exact simulation of a neutral Wright-Fisher bridge is derived. This follows from knowing the density of the frequency in a bridge and exact simulation from the Wright-Fisher diffusion. The genealogy of the neutral Wright-Fisher bridge is also modelled by branching P\'olya urns, extending a representation in a Wright-Fisher diffusion. This is a new very interesting representation that relates Wright-Fisher bridges to classical urn models in a Bayesian setting

Direct emissivity measurements on liquids and corrections to multi-color pyrometers

Optical pyrometry provides a means for non-contact temperature measurements whose accuracy depends on the accuracy with which specimen emittance is known. Two methods for obtaining the required emittance data are discussed in which the emittance is determined from measurements of the wavelength or polarization dependence of light emitted by the specimen. The spectral technique, multi-color pyrometry, yields apparent values for specimen emittance and temperature from emitted intensity measurements at two or more wavelengths. Emittance corrections cannot be eliminated by increasing the number of spectral intensity measurements required by an n-color pyrometer. Even if this were possible, the accuracy of temperature measurements by n-color pyrometry decreases with n such that pyrometers that require four intensity measurements would be impractical. In contrast, emittance values and corrections for one-color pyrometers can be accurately measured by the polarized light technique. The polarized light technique involves measurement of the degree of polarization for light emitted at an angle of 45 deg to the specimen normal. The reflectivities (r) for light polarized parallel (p) and normal (n) to the plane of emission are related by r(p) = r(n) squared. This leads to a simple relation between the intensity ratio for light emitted in the two polarized states and the emittance, i.e., e(n) = 2 - I(p)/I(n). The true specimen temperature is also obtained if absolute intensities are measured. Delvelopment of the polarized light technique in combination with one-color optical pyrometry is recommended to achieve accurate non-contact temperature measurements on liquids

Forced to be Rich? Returns to Compulsory Schooling in Britain

Do students benefit from compulsory schooling? In an important article, Oreopoulos (2006) studied the 1947 British compulsory schooling law change and found large returns to schooling of about 15% using the General Household Survey (GHS). Reanalysing this dataset, we find much smaller returns of about 3% on average with no evidence of any positive return for women and a return for men of 4-7%. Additionally, we utilize the New Earnings Survey Panel Data-set (NESPD) that has earnings information superior to that in the GHS and find similar estimates: zero returns for women and returns of 3 to 4% for men.Compulsory Schooling, Returns to Education

The absorption and emission spectrum of radiative cooling galactic fountain gas

We have calculated the time-dependent, nonequilibrium thermal and ionization history of gas cooling radiatively from 10(exp 6) K in a one-dimensional, planar, steady-state flow model of the galactic fountain, including the effects of radiative transfer. Our previous optically thin calculations explored the effects of photoionization on such a flow and demonstrated that self-ionization was sufficient to cause the flow to match the observed galactic halo column densities of C 4, Si 4, and N 5 and UV emission from C 4 and O 3 in the constant density (isochoric) limit, which corresponded to cooling regions homogeneous on scales D less than or approximately equal to 1 kpc. Our new calculations which take full account of radiative transfer confirm the importance of self-ionization in enabling such a flow to match the data but allow a much larger range for cooling region sizes, i.e. D(sub 0) greater than or approximately equal to 15 pc. For an initial flow velocity v(sub 0) approximately equal to 100 km/s, comparable to the sound speed of a 10(exp 6) K gas, the initial density is found to be n(sub h,0) is approximately 2 x 10(exp -2) cm(exp -3), in reasonable agreement with other observation estimates, and D(sub 0) is approximately equal to 40 pc. We also compare predicted H(alpha) fluxes, UV line emission, and broadband x-ray fluxes with observed values. One dimensional numerical hydrodynamical calculations including the effects of radiative cooling are also presented