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131.
Trends in location, labor force, and procurement practices in maquiladoras are examined using recent data sources. A growing proportion of maquiladoras are selecting interior locations, south of the borderlands. Once dominated by young women, the labor force is rapidly approaching gender parity. While far below prevailing rates in the United States, maquiladora wages are comparable with equivalent manufacturing sectors in Mexico. Majority ownership of maquiladoras is split almost evenly between Mexico and the U.S., however, maquiladoras have failed to develop domestic sources of materials and parts and remain dependent on imported material inputs. As the North American Free Trade Agreement is phased in, the regulatory environment of maquiladoras will change but their role as low cost assembly specialists will persist. 相似文献
132.
133.
Andrew Harrison Phil Puxley Adrian Russell & Peter Brand 《Monthly notices of the Royal Astronomical Society》1998,297(2):624-632
We present measurements of several near-infrared emission lines from the nearby galaxy NGC 253. We have been able to measure four H2 lines across the circumnuclear starburst, from which we estimate the ortho- to para- ratio of excited H2 to be ∼2. This indicates that the bulk of the H2 emission arises from photodissociation regions (PDRs), rather than from shocks. This is the case across the entire region of active star formation.
As the H2 emission arises from PDRs, it is likely that the ratio of H2 to Brγ (the bright hydrogen recombination line) is a measure of the relative geometry of O and B stars and PDRs. Towards the nucleus of NGC 253 the geometry is deduced to be tightly clustered O and B stars in a few giant H II regions that are encompassed by PDRs. Away from the nuclear region, the geometry becomes that of PDRs bathed in a relatively diffuse ultraviolet radiation field.
The rotation curves of 1–0 S(1) and Brγ suggest that the ionized gas is tracing a kinetic system different from that of the molecular gas in NGC 253, particularly away from the nucleus. 相似文献
As the H
The rotation curves of 1–0 S(1) and Brγ suggest that the ionized gas is tracing a kinetic system different from that of the molecular gas in NGC 253, particularly away from the nucleus. 相似文献
134.
135.
A compact, spheroidal Type B inclusion in Allende contains melilite laths that project radially inward from the inclusion edge which show interference growth textures. The combined textural and chemical features of this object cannot be explained by independent vapor-solid condensation of grains in space, followed by random aggregation of these grains into an inclusion. Rather, it probably formed from a once-molten droplet that crystallized in response to radiative cooling from its outer surface. The crystallization sequence in this and another similar inclusion in which oxygen isotopes have been measured is: melilite-spinel-anorthite-fassaite. This sequence supports the idea that oxygen isotopic heterogeneities in coarse-grained inclusions were formed after complete solidification of these objects by partial exchange with a less16O-rich gas, and not during or before a melting event. 相似文献
136.
The oxygen isotope composition of calcite veins and vugs in basalts from a drill site on the island of Sao Miguel show near-equilibration with fresh water at observed temperatures only at a depth of 600–700 m. This is interpreted to mean that the greatest flow of hot water may be occurring in this depth interval. 相似文献
137.
James I. Drever James R. Lawrence Ronald C. Antweiler 《Earth and Planetary Science Letters》1979,42(1):98-102
Gypsum and halite crystals, together with saponite and phillipsite, were found in a vein in a basalt sill 625 m below the sea floor at DSDP Site 395A, located 190 km west of the crest of the Mid-Atlantic Ridge. The δ34S value of the gypsum (+19.4‰) indicates a seawater source for the sulfate. The δ18O values of the saponite (+19.9‰) and phillipsite (+18.1‰) indicate either formation from normal seawater at about 55°C or formation from18O-depleted seawater at a lower temperature.The gypsum (which could be secondary after anhydrite) was formed by reaction between Ca2+ released from basalt and SO42? in circulating seawater. The halite could have formed when water was consumed by hydration of basalt under conditions of extremely restricted circulation. A more probable mechanism is that the gypsum was originally precipitated as anhydrite at temperatures above 60°C. As the temperature dropped the anhydrite converted to gypsum. The conversion would consume water, which could cause halite precipitation, and would cause an increase in the volume of solids, which would plug the vein and prevent subsequent dissolution of the halite. 相似文献
138.
Lawrence Grossman John M. Allen Glenn J. MacPherson 《Geochimica et cosmochimica acta》1980,44(2):211-216
The black inclusion from the Krymka LL3 chondrite previously found to contain ‘mysterite’ by Lewiset al. (1979) belongs to a hitherto unknown class of carbonaceous chondrites. Its olivine and pyroxene compositions. Fo 97–99 and En 96, respectively, are characteristic of carbonaceous chondrites and its plagioclase composition. An 100, is characteristic of C3's. It contains a peculiar group of Co-, Cr-rich metal grains whose compositions are similar, but not identical, to those in C2 chondrites and which also bear some similarities to those in Renazzo. Its weight ratios of total and are 0.74 and 1.43, respectively, and its atomic ratio of is 10.7, exactly the same as in carbonaceous chondrites. Its bulk chemical composition is very close to that of the Murchison C2 chondrite. The association of mysterite with a special type of carbonaceous chondrite material suggests that mysterite formed by low-temperature condensation in a different region of the nebula from other carbonaceous chondrites. 相似文献
139.
E. Bonatti J.R. Lawrence P.R. Hamlyn D. Breger 《Geochimica et cosmochimica acta》1980,44(8):1207-1214
Aragonite mineralization was observed in serpentinized peridotites from the Romanche and Vema Fracture Zones in the Atlantic and the Owen Fracture Zone in the Indian Ocean, either in veins or as radial aggregates in cavities within the serpentinites. Evidence of incipient dissolution of the aragonite crystals was observed in one case. The aragonites tend to have lower Mg content (< 0.03%) and higher Sr content (> 0.95%) relative to other marine aragonites. Their , and isotopic ratios suggest the aragonite was deposited at ocean floor temperatures from solutions derived from sea water circulating in fissures and fractures within the ultramafic rocks. The ratios of the serpentines indicate serpentinization occurred at higher temperatures, probably deeper in the crust. Low-T reactions between circulating seawater and Mg-silicates (primarily serpentine and pyroxenes) caused high pH and enrichment of Mg and Ca in the solution, conditions favoring carbonate precipitation. Aragonite was formed rather than calcite presumably because the high Mg2+ concentration in the solution inhibited calcite precipitation. The high Sr content of the aragonites is probably related, at least in part, to their low temperature of formation. Opaque mineral grains containing over 8% NiO and over 40% MnO were observed concentrated along the margins of some of the aragonite veins, suggesting that Ni is one of the elements mobilized during reactions between ultramafic rocks and circulating seawater. 相似文献
140.