The History, Present Condition, and Future of the Molluscan Fisheries of North and Central America and Europe: Volume 2, Pacific Coast and Supplemental Topics

Over 100 molluscan species are landed in Mexico. About 30% are harvested on the Pacific coast and 70% on the Atlantic coast. Clams, scallops, and squid predominate on the Pacific coast (abalone, limpets, and mussels are landed there exclusively). Conchs and oysters predominate on the Atlantic coast. In 1988, some 95,000 metric tons (t) of mollusks were landed, with a value of $33 million. Mollusks were used extensively in prehispanic Mexico as food, tools, and jewelry. Their use as food and jewelry continues. Except in the States of Baja California and Baja California Sur, where abalone, clams, and scallops provide fishermen with year-round employment, mollusk fishing is done part time. On both the Pacific and Atlantic coasts, many fishermen are nomads, harvesting mollusks wherever they find abundant stocks. Upon finding such beds, they build camps, begin harvesting, and continue until the mollusks become so scarce that it no longer pays to continue. They then look for productive beds in other areas and rebuild their camps. Fishermen harvest abalones, mussels, scallops, and clams by free-diving and using scuba and hooka. Landings of clams and cockles have been growing, and 22,000 t were landed in 1988. Fishermen harvest intertidal clams by hand at wading depths, finding them with their feet. In waters up to 5 m, they harvest them by free-diving. In deeper water, they use scuba and hooka. Many species of gastropods have commercial importance on both coasts. All species with a large detachable muscle are sold as scallops. On the Pacific coast, hatchery culture of oysters prevails. Oyster culture in Atlantic coast lagoons began in the 1950's, when beds were enhanced by spreading shells as cultch for spat. (PDF file contains 228 pages.

The History, Present Condition, and Future of the Molluscan Fisheries of North and Central American and Europe: Volume 1, Atlantic and Gulf Coasts

This three-volume monograph represents the first major attempt in over a century to provide, on regional bases, broad surveys of the history, present condition, and future of the important shellfisheries of North and Central America and Europe. It was about 100 years ago that Ernest Ingersoll wrote extensively about several molluscan fisheries of North America (1881, 1887) and about 100 years ago that Bashford Dean wrote comprehensively about methods of oyster culture in Europe (1893). Since those were published, several reports, books, and pamphlets have been written about the biology and management of individual species or groups ofclosely related mollusk species (Galtsoff, 1964; Korringa, 1976 a, b, c; Lutz, 1980; Manzi and Castagna, 1989; Shumway, 1991). However, nothing has been written during the past century that is comparable to the approach used by Ingersoll in describing the molluscan fisheries as they existed in his day in North America or, for that matter, in Europe. (PDF file contains 224 pages.

A multiple scales approach to crack front waves

Perturbation of a propagating crack with a straight edge is solved using the method of matched asymptotic expansions (MAE). This provides a simplified analysis in which the inner and outer solutions are governed by distinct mechanics. The inner solution contains the explicit perturbation and is governed by a quasi-static equation. The outer solution determines the radiation of energy away from the tip, and requires solving dynamic equations in the unperturbed configuration. The outer and inner expansions are matched via the small parameter L/l defined by the disparate length scales: the crack perturbation length L and the outer length scale l associated with the loading. The method is first illustrated for a scalar crack model and then applied to the elastodynamic mode I problem. The dispersion relation for crack front waves is found by requiring that the energy release rate is unaltered under perturbation. The wave speed is calculated as a function of the nondimensional parameter kl where k is the crack front wavenumber, and dispersive properties of the crack front wave speed are described for the first time. The example problems considered here demonstrate that the potential of using MAE for moving boundary value problems with multiple scales.Comment: 25 pages, 5 figure

The History, Present Condition, and Future of the Molluscan Fisheries of North and Central America and Europe: Volume 3, Europe

(PDF file contains 248 pages.

Gas core rocket reactors - A new look

Feasibility analysis of open-cycle gas-core nuclear rocket engin

Strain gradient plasticity: energetic or dissipative?

It has been established by computation, and confirmed by analysis, for an infinite slab of strain-gradient sensitive material subjected to plane-strain tensile loading, that passivation of the lateral boundaries at some stage of loading inhibits plastic deformation upon further loading. This result is not surprising in itself except that, remarkably, if the gradient terms contribute to the dissipation, the plastic deformation is switched off completely, and only resumes at a clearly-defined higher load, corresponding to a total strain ε_c say. The analysis presented in this paper confirms the delay of plastic deformation following passivation and determines the exact manner in which the plastic flow resumes. The plastic strain-rate is continuous at the exact point ε_c of resumption of plastic flow and, for the first small increment Δε = ε − ε_c in the imposed total strain, the corresponding increment in plastic strain, Δε^p, is proportional to (Δε)^2. The constant A in the relation Δε^p(0) = A(Δε)^2, where Δε^p(0) denotes the plastic strain increment at the centre of the slab, has been determined explicitly; it depends on the hardening modulus of the material. The presence of energetic gradient terms has no effect on the value of ε_c unless the dissipative terms are absent, in which case passivation reduces the rate of plastic deformation but introduces no delay. This qualitative effect of dissipative gradient terms opens the possibility of experimental discrimination of their presence or absence. The analysis employs an incremental variational formulation that is likely to find use in other problems.This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/10.1007/s10409-015-0468-

Imputing historical statistics, soils information, and other land-use data to crop area

In foreign crop condition monitoring, satellite acquired imagery is routinely used. To facilitate interpretation of this imagery, it is advantageous to have estimates of the crop types and their extent for small area units, i.e., grid cells on a map represent, at 60 deg latitude, an area nominally 25 by 25 nautical miles in size. The feasibility of imputing historical crop statistics, soils information, and other ancillary data to crop area for a province in Argentina is studied

The effective non-linear properties of a composite coating and a composite sandwich layer

Hashin-Shtrikman based bounds and estimates are obtained for the linear and non-linear effective properties of composites in the form of a thin coating or sandwich layer. It is assumed that the thickness of the layer is of the same order of magnitude as the correlation length between phases, and size effects thereby result. Boundary layers exist within the coating adjacent to the substrate and to the free surface (in the case of a coating). Attention is focused on two-dimensional problems by considering anti-plane shear of an isotropic 2-phase composite on a single-phase substrate, with microstructure prismatic along the direction of anti-plane shear.NAF is grateful for financial support in the form of an ERC MULTILAT grant 669764, and to the US ONR (N62909-14-1-N232, project manager, Dr. Dave Shifler).This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.euromechsol.2016.02.00