Migrant worker centers: contending with downgrading in the low-wage labor market     

Nina Martin  Sandra Morales  Nik Theodore 《GeoJournal》2007,68(2-3):155-165

Mass migration to major USA cities is reworking patterns of ethnic jobholding and labor market segmentation. Employers in a variety of industries have turned to recent migrants, many of whom are not authorized to work in the USA, as a stable labor supply for low-wage jobs. As a result, many migrant workers enter urban economies through precarious jobs in low-wage industries and the informal economy where they often endure routine violations of labor and employment laws. This paper examines the activities of a “migrant worker center” in improving wages and working conditions in migrant labor markets. Through a case study of a worker center located in a port-of-entry immigrant neighborhood on Chicago’s Southwest Side, we examine the geographies of the low-wage labor market and the problems that have arisen for workers who hold jobs that effectively exist beyond the reach of government regulation. We argue that migrant worker centers will likely emerge as a key resource for workers who are drawn to global cities by the promise of economic opportunity yet confront harsh conditions in the local labor markets in which they are employed.  相似文献   

Well productivity controlling factors in crystalline terrains of southeastern Brazil   总被引：1，自引：0，他引：1  

Mirna A. Neves  Norberto Morales 《Hydrogeology Journal》2007,15(3):471-482

Over the last decades, increasing water demands have fostered research to obtain high well yields in crystalline terrains where, besides the intrinsic properties of rocks, the groundwater flow depends on several factors. The depth of the wells, the lithotypes, the presence and thickness of sedimentary coverings and weathered layers, the landforms, the geological structures, and the effects of tectonic stresses are among the most investigated factors considered as determinant of well productivity. The influence of these factors on productivity of wells that exploit the Crystalline Aquifer System in the Jundiaí River Catchment, southeastern Brazil, is investigated in this work. The largest region of the studied area is located on the Precambrian Basement, partially covered by sedimentary deposits. The results show that the sedimentary deposits and the weathered layer are important for high well yield, but it also depends on the existence of a net of open fractures, in order to maintain high productivity. The sites that have more possibility of occurrence of such structures are the regional shear and fault zones and other minor structures with NW–SE and E–W directions, which characterize areas subjected to transtensional stress related to the neotectonics.  相似文献   

Historical landslides in Nicaragua—collection and analysis of data   总被引：2，自引：0，他引：2  

Graziella Devoli  Alejandro Morales  Kaare Høeg 《Landslides》2007,4(1):5-18

  相似文献   

Spectrum of the Extreme Ultraviolet Nightglow as Measured by EURD     

José J. López-Moreno  Carmen Morales  José F. Gómez  Joaquín Trapero  Stuart Bowyer  Jerry Edelstein  Eric Korpela  Michael Lampton 《Astrophysics and Space Science》2001,276(1):211-217

After 2 years of operation onboard the Spanish satellite MINISAT, EURDhas achieved an unprecedented success in the observation of the terrestrialnightglow in the EUV, covering a range of 350-1100 Å EURD hasprovided a total of more than 543 hours ofintegration in the long wavelength spectrometer and more than898 hours in the short wavelength one, allowing the achievement of the most detailed atlas of the terrestrial EUV nightglow ever obtained. We present here the spectra obtained, together with the identification of the lines, some of themdetected for the first time in the nightglow. These spectrarepresent an improvement in sensitivity of several orders of magnitude with respect to previous observations. It has beenpossible, for the first time, to identify the complete Lymanseries of atomic hydrogen, resolving up to Lyman-. It hasalso been possible to identify the helium Lyman- line at 537 Å andto detect other lines of the blended Lyman series of helium, at 515 and522 Å. The spectra clearly show the presenceof the OII lines at 617, 644, 673, and 718 Å, previouslyobserved in the dayglow but seen here for the first time in thenightglow. In addition to the recombination continuum of the atomicoxygen at 911 Å, two features of OI have been detected in thenightglow: the 3s ³D_o transition at 989 Å, previouslyobserved by Chakrabarti (1984) and the 2p³4s³S^o transition at 1040 Å, partially overlapped with Lyman , but clearly distinguishable from it. This feature has been seen for the first timein the terrestrial nightglow. The radiative recombination continuum of atomic oxygen at 911 Å, that wasabsent in the observations of the first year of operation of EURD,is now clearly visible. The reasons of the absence of the OIfeature during the first year of operation are still unknown.Anderson et al. (1976) also noticed a strong variation with time of this 911 Å emission.  相似文献   

Inhibition of experimental autoimmune orchitis by fossil diatoms     

Oscar D. Bustuoabad  Roberto P. Meiss  Alfredo R. Molinolo  Alejandro M. S. Mayer 《中国海洋湖沼学报》1985,3(1):23-29

Experimental autoimmune orchitis (EAO) induced in Swiss mice could be reduced by means of the utilization of micronized frustules of fossil diatoms (DS) containing 54% of SiO₂. Experimental mice were sensitized with testicular Antigen (Ag) in Complete Freund’s Adjuvant (CFA) inoculated twice, on day 0 and day 21. 100 μg of DS suspension was inoculated into sensitized mice 10 times, once every 4 days, subcutaneously, starting on day 7 after the first Ag inoculation. Mice receiving the DS treatment showed a diminution of the delayed hypersensitivity reaction, lower antibody titer and decreased incidence of testicular injury as well as reduced grade and extension of the lesions. Possible explanation of these results would suggest alteration of monocyte and/or macrophage normal behaviour as well as alteration of antibody synthesis by different mechanisms.  相似文献   

Effects of the Magnetic Field on the Hα Emission from Jets     

Fabio de Colle  Alejandro Raga 《Astrophysics and Space Science》2004,293(1-2):173-180

We present results of MHD axisymmetrical cylindrical simulations performed to study Hα emission maps from jets, with a toroidal field geometry for the magnetic field. Our code uses a linear Riemann solver, integrates equations in 2.5 dimensions and includes the calculation of the ionization fraction and the effects of the emission due to the collisional excitation of [O I] and [O II] lines, radiative recombination of H and the collisional ionization of H and excitation of Lyman-α. The simulations with variable ejection velocities show that the magnetic field produces an increase in the emission from all of the knots except for the first bow shock.  相似文献   

Geomechanical characterisation of rock masses in Alpine regions: the Basque Arc (Basque-Cantabrian basin, Northern Spain)   总被引：1，自引：0，他引：1  

Toms Morales  Gorka Uribe-Etxebarria  Jesús A. Uriarte  Iigo Fernndez de Valderrama 《Engineering Geology》2004,71(3-4):343-362

The geomechanical characterisation of rock masses in Alpine regions is one of the main challenges currently facing rock mechanics. These rock masses, made up of very different materials and frequently tectonically disturbed, are affected by engineering works, giving rise to potentially important problems. Thus, in the Basque Country, these materials are at the cause of important fatalities occurring in recent years. In this context, we aim at characterising these materials with the ultimate purpose of predicting their behaviour. The characterisation is initially approached based on the GSI, m_i and σ_ci parameters, following the Hoek-Brown failure criterion. This information is supplemented with field and laboratory measurements, and by obtaining the RQD and RMR indices. Using the information obtained from 99 metering stations, we develop a graphic classification procedure, which allows us to distinguish materials based on their characteristics, behaviour, type and degree of associated problems, and type and effectiveness of solutions provided. Eight classes of material are established.  相似文献   

Wavelet methods: application to the study of the stable atmospheric boundary layer under non-stationary conditions   总被引：1，自引：0，他引：1  

E. Terradellas  G. Morales  J. Cuxart  C. Yagüe   《Dynamics of Atmospheres and Oceans》2001,34(2-4)

In this work, some wavelet methods are introduced to study the atmospheric boundary layer under stable conditions, where intermittent events and non-stationary turbulence take place. Such behavior makes classical methods, based on Fourier transform, difficult to use or even of no application.The wavelet transform is used to detect and characterize some structures in the stable atmospheric boundary layer. First, a wave-like event with a 16 min period is detected and analyzed in a wind record. The sum of some Morlet wavelets is proposed as a model for the oscillations. Afterwards, the wavelet transform is introduced to the study of non-stationary small scale turbulence. It provides the time evolution of the energy and a good location in time of the spots of turbulence. Finally, some wavelet tools are used to characterize a traveling structure, provided that it is simultaneously detected at different locations. The phase differences in the wavelet transform give the wavelength and the phase speed of the oscillations, whereas a double transform method is introduced to estimate the group velocity of the structure.  相似文献   

Influence of volcanic activity on spring water chemistry at Popocatepetl Volcano, Mexico     

A. L. Martin-Del Pozzo  F. Aceves  R. Espinasa  A. Aguayo  S. Inguaggiato  P. Morales  E. Cienfuegos 《Chemical Geology》2002,190(1-4):207-229

The results of the 7 years (1994–2000) of monthly monitoring of spring water before and during eruptions show response to volcanic activity. Low salinity and temperature characterize most of the springs, which are located on the flanks of Popocatepetl Volcano. The pH ranges from 5.8 to 7.8 and temperature from 3 to 36 °C. Oxygen and hydrogen isotopic data show that the water is of meteoric origin, but SO₄²⁻, Cl⁻, F⁻, HCO₃⁻, B, and SO₄²⁻/Cl⁻ variations precede main eruptive activity, which is considered linked to influx of magmatic gases and acid fluids that react with sublimates and host rock and mix with the large water system. Na⁺, Ca²⁺, SiO₂ and Mg²⁺ concentrations in the water also increased before eruptive activity. The computed partial pressure of CO₂ in equilibrium with spring waters shows values higher than air-saturated water (ASW), with the highest values up to 0.73 bar of pCO₂. Boron is detected in the water only preceding the larger eruptions. When present, boron concentration is normally under health standard limits, but in two cases the concentration was slightly above. Other components are within health standard limits, except for F⁻ in one spring.  相似文献   

Neoformation of Ni phyllosilicate upon Ni uptake on montmorillonite: A kinetics study by powder and polarized extended X-ray absorption fine structure spectroscopy     

Rainer Dähn  André M ScheideggerAlain Manceau  Michel L Schlegel  Bart BaeyensMichael H Bradbury  Magali Morales 《Geochimica et cosmochimica acta》2002,66(13):2335-2347

Wet chemistry kinetics and powder and polarized extended X-ray absorption fine structure (EXAFS and P-EXAFS) spectroscopy were combined to investigate the mechanism of Ni uptake on montmorillonite, at pH 8, high ionic strength (0.2 M Ca(NO₃)₂), initial Ni concentration of 660 μM, and solid concentration of 5.3 g/L. Approximately 20% of Ni sorbed within the first 24 h; thereafter, the Ni uptake rate slowed, and 12% of the initial Ni concentration remained in solution after 206 d of reaction time. Powder EXAFS spectra collected on wet pastes at 1, 14, 90, and 206 d showed the presence of Ni-Ni pairs at ∼3.08 Å in an amount that gradually increased with time. Results were interpreted by the nucleation of a Ni phase having either an α-Ni-hydroxide- or a Ni-phyllosilicate-like local structure. The latter possibility was confirmed by recording P-EXAFS spectra of a highly textured, self-supporting montmorillonite film prepared in the same conditions as the wet samples and equilibrated for 14 d. The orientation distribution of the c*-axes of individual clay particles off the film plane, as measured by quantitative texture analysis, was 32.8° full width at half maximum, and this value was used to correct from texture effect the effective numbers of Ni and Si nearest neighbors determined by P-EXAFS. Ni atoms were found to be surrounded by 2.6 ± 0.5 Ni atoms at 3.08 Å in the in-plane direction and by 4.2 ± 0.5 Si atoms at 3.26 Å in the out-of-plane direction. These structural parameters, but also the orientation and angular dependence of the Ni and Si shells, strongly support the formation of a Ni phyllosilicate having its layers parallel to the montmorillonite layers. The neoformation of a phyllosilicate on metal uptake on montmorillonite, documented herein for the first time, has important geochemical implications because this dioctahedral smectite is overwhelmingly present in the environment. The resulting sequestration of sorbed trace metals in sparingly soluble phyllosilicate structure may durably decrease their migration and bioavailability at the Earth’s surface and near surface.  相似文献