Search

The predominant narrative of covid-19 emphasizes its unpredictable origins, virulence, human targets, and spatial targets. Its international spread may be erratic, but at the regional level, diffus...

In this study, grounded in the literature on transnational migration, a theory of transnational social gravity is developed in which economic, social, and psychological dimensions of transn...

This exercise introduces students to the observation that warming is unequal at the level of regions and countries, helps them analyze why this is so, and encourages reflection on actions by specif...

1. The possibility that infectious bronchitis virus (IBV) variants isolated from broilers with enteric and respiratory problems have a different tropism and pathological outcome from those IBV strains causing classical respiratory disease was investigated. 2. IBV variants were isolated from broiler flocks with enteric and respiratory problems in two regions of Brazil. The USP-10 isolate, of enteric origin, was inoculated via the oral oroculonasal routes into IBV-antibody-free broilers and specific pathogen-free (SPF) chickens to determine tissue tropism and pathogenicity and compared with an IBV variant (USP-50) isolated from chickens showing signs of respiratory disease only. 3. Both USP-10 and USP-50 strains caused similar pathological patterns by either route of inoculation. Both variants were detected in respiratory and non-respiratory tissues, including the kidney, intestine and testis. 4. Broilers were more susceptible to infection than SPF chickens, and seroconversion was detected in all of the chicks.

A three-stage diffusion model of international migration and inequality posits that household income inequality first increases, then decreases, and finally increases again as a community's migration experience deepens. Analysis of data from a survey of 417 households in the Valle Alto region of Bolivia supports this model. Concomitant with the region's overall position in the middle stage, the results indicate that income inequality among active migrant households is less than that of non-migrant households, suggesting that migration reduces inequality. Furthermore, income inequality between urban and rural areas is diminished by migration. Individual towns in the region, however, illustrate all three stages of the diffusion model. The study supports other research showing that the middle stage of migration generates the most remittances, the highest commitment of resources to the home community, and the lowest inequalities among households.

1. The use of vaccines is the main approach to control of the economically important poultry viral respiratory diseases infectious laryngotracheitis (ILT), avian metapneumovirus (aMPV) infections and infectious bronchitis (IB). This paper appraises the current methods of vaccine control in the light of the nature of each virus and epidemiological factors associated with each disease. 2. Infectious laryngotracheitis virus (ILTV) exists as a single type with a wide range of disease severity. It is a serious disease in certain regions of the world. Recent work has distinguished molecular differences between vaccine and field strains and vaccine virus can be a cause of disease. Vaccines have remained unaltered for many years but new ones are being developed to counter vaccine side effects and reversion and reactivation of latent virus. 3. Avian metapneumoviruses, the cause of turkey rhinotracheitis and respiratory disease in chickens exists as 4 subtypes, A, B, C and D. A and B are widespread and vaccines work well provided that accurate doses are given. Newer vaccine developments are designed to eliminate reversion and possibly counter the appearance of newer field strains which may break through established vaccine coverage. 4. IB presents the biggest problem of the three. Being an unstable RNA virus, part of the viral genome that codes for the S1 spike gene can undergo mutation and recombination so that important antigenic variants can appear irregularly which may evade existing vaccine protection. While conventional vaccines work well against homologous types, new strategies are needed to counter this instability. Molecular approaches involving tailoring viruses to suit field challenges are in progress. However, the simple use of two genetically different vaccines to protect against a wide range of heterologous types is now a widespread practice that is very effective. 5. None of the three diseases described can claim to be satisfactorily controlled and it remains to be seen whether the newer generations of vaccines will be more efficacious and cost effective. The importance of constant surveillance is emphasised and the testing of novel vaccines cannot be achieved without the use of vaccine-challenge experiments in poultry.

At the same time that the Third World has become more dependent on international wage-labor migration, developed countries have become less hospitable to this migration. This inhospitality is beginning to have negative repercussions on rural sending regions such as north-central Mexico. This study is based on a survey of a stratified random sample of households in Villanueva municipio (county), Zacatecas, in 1988 and again in 2002, employing the same questions and methodology. The results suggest that restrictive U.S. border policies over this period have had a negative impact on village economies in the municipio. Although migrant families continued to hold a distinctive edge on nonmigrant families in terms of possessions and productive investments, there was a decline overall in levels of investment and remittances in the municipio. In the latter year, Villanueva had more nonmigrant families as well as more families with permanent migrants—both trends leading to less money remitted to rural families and...

The traditional spatial assimilation model, though still operative, has proven inadequate to explain new trends in urban residential location in which, for example, disadvantaged and newly arrived groups move directly to the suburbs where they may re-segregate rather than disperse. Understanding residential patterns after 1990 often benefits from a micro-level approach, looking at specific cities and disaggregating traditional measures (e.g., the dissimilarity index) to examine changes within areas and neighborhoods of the city. This study takes such an approach. It analyzes segregation by means of the residential micro-patterns that give rise to it, and examines their relationship to suburbanization and immigration in greater San Antonio (Bexar County) during the 1990s for four ethnic groups: Hispanics, Blacks, non-Hispanic Whites, and Latino immigrants. The results reveal that segregation patterns in San Antonio have deep historic roots—the result of ongoing processes of urban job and housing availabili...

This study examines the factors that influence the residential segregation and spatial patterns of twenty-seven ancestry groups in San Antonio (Bexar County), Texas, in 2000. It is hypothesized that the residential segregation of an ancestry group (measured by its dissimilarity index at census tract level) is positively related to the recency of the group's arrival, its identification with a non-European culture, and its tendency to exhibit either high or low (as opposed to average) educational attainment. It is also hypothesized that later-arriving groups will be found located closer to the city center; and that groups which entered the city from its regional hinterland will be disproportionately represented today in the directional sectors of their original entry into the city. Census data support the segregation hypotheses. There is no necessary relationship between distance from the central city and the time of arrival of a group; however, there is ample evidence that those groups who moved into the c...

Despite some evidence for the economic advancement and suburbanization of urban-bound immigrants in the United States, the preponderance of evidence points to increasing residential segregation of these groups in ethnic enclaves in U.S. cities. In this study, based on an extensive literature review, the segregation of an ancestry group is tied to the group’s SES, recency, physical and cultural distinctiveness, and social distance as judged by the majority population. The dissimilarity index (DI) is calculated for each of 28 ancestry groups in San Antonio, based on the 1990 U.S. Census, and related to explanatory indicators from various sources. The socio-economic status of a group is found to exert a non-linear influence on segregation—reducing it for below-average SES groups (the traditional immigrant assimilation model), while increasing it for above-average SES groups (a new pluralism model, reflecting the decisions of professional and entrepreneurial immigrants). The recency of an ancestry’s entry; whether it is non-European versus European; and (especially) the magnitude of its social distance rating, all play significant supplementary roles in its segregation.

The high costs of rapid growth in the fragile environment of the Middle Rio Grande Valley of Texas and Mexico have become more evident in recent years. This study investigates the relationships between selected diseases and a wide range of site and situational factors for 2,140 households located in the environmentally strained colonias of Laredo-Nuevo Laredo, Eagle Pass-Piedras Negras, and Del Rio-Ciudad Acuna. The results suggest that gastrointestinal and neurological/degenerative diseases are related to situational factors, such as family behavior and family size, as well as proximity to polluted watercourses, industry, and agriculture. Policy implications include the separation of residences from pollution sources (in Mexico), and the improvement of public health and drainage (in the United States).

In the United States as well as in Western Europe, a combination of recession, nativist popular attitudes, and trade liberalization since 1980 has been accompanied by increasing immigration restrictions. This paper poses a singular question: Has the stiffening of U.S. immigration policy [by the Immigration Reform and Control Act of 1986 (IRCA), and subsequent policy decisions] reduced the volume and changed the composition and origins of Mexican undocumented migrants?Studies of national data show a reduction in such migration after IRCA. Using INS data on undocumeted entrants to South Texas, this paper documents Post-IRCA increases in the proportions of migrants that are young, single, and male from metropolitan areas and from south central Mexico. These suggest that IRCA has served as a barrier inducing demographically selective migration and that changes in the Mexican economy since 1980 have favored the north versus the south–creating a “neo-employment frontier” in the northeastern border stat...

The purpose of this study is to conceptualize the different dimensions of access to higher education, and to examine the nature of current spatial access to comprehensive universities in Texas (i.e., those offering multiple doctorates and awarding at least 10 doctorate degrees per year). We conclude that the Border Region of Texas is an especially deprived area in this regard. The average Border student must travel five times as far to the closest comprehensive in-state university, as the average student from elsewhere in the state. Furthermore, this inaccessibility is associated, at the country level, with a relatively low percentage of college students actually attending a comprehensive university. Finally, the impact of distance on attendance is stronger for Hispanic than for Anglo students. This is because their lower incomes, lack of transportation, and family responsibilities make it very difficult for them to leave their region to attend a far-away university.

The neighborhood supermarket shopping center is an increasingly important element of the suburban retail landscape. An analysis of patronage differentials for such centers in San Antonio, TX, reveals that both competitive share and retail mix factors are important. Correlation analysis of a patronage density index with locational and management variables indicates that center and store visibility, distance from a regional mall, retail mix (offering of goods appropriate to a small center), and size of center (smaller is better) were the most important explanatory factors in center viability.

The purpose of this study is to analyze the differences in the economic bases of two small towns, each tributary to nearby metropolitan areas, on either side of the U.S.-Mexico border. Thus, it combines the policy concerns of small town economic development (Alguire et al. 1987) with a social scientific interest in cross-cultural differences. Small towns face certain common problems independent of which side of the border they are on - social stratification, limited shopping opportunities, non-dynamic leaders (more ambitious residents have frequently invested their talents elsewhere), limited employment opportunities and anemic tax bases. Nevertheless, the international border does impose cultural and structural differences which are reflected in differences in the flows of capital, labor and consumption expenses. For example, Mexican rural society is poorer, less residentially mobile, less diurnally mobile and more socially tied to the local community than is the case in the U.S. Also, jobs in government service and income from transfer payments are less available in the average Mexican town than in the average U.S. town. Because of these differences people in the Mexican town are likely to purchase lower-order goods and services, spend more money locally and be less directly dependent on the government or on private pensions, for their livelihood, than their counterparts in the U.S. town. Understanding the fundamental patterns of income flows into and out of the community is a task that economic base analysis is uniquely designed to meet. Here, a modified form of the Tiebout (1962) procedure will be used to trace the basic income flow into and out of establishments and households. A town's economic viability will depend on the magnitude of the difference between the inward and outward flows. The study will analyze a town in south Texas and a town of similar characteristics in northern Coahuila. Economic base analysis in this study will refer both to the study of such exogenous income, and to the study of household and establishment expenditure patterns which determine the degree of income recycling within the local region (the multiplier).

Although undocumented Mexican immigrants in the United States are highly concentrated in California and Texas their locations have become increasingly dispersed in recent years. The most rapid growth in apprehensions by U.S. authorities is now occurring outside the Southwest. Furthermore the already-dispersed patterns of migrant origins in Mexico are becoming more so over time. Thus the phenomenon of undocumented flows is spreading spatially in both the U.S. and Mexico. Historic factors promoting migrant channelization are being supplanted by factors promoting dispersion: increased migrant job awareness and capability a liberalization of U.S. immigration enforcement and generally worsening conditions in rural Mexico. (EXCERPT)

An analysis of illegal migration between Mexico and Texas is presented using data from the U.S. Immigration and Naturalization Services I-213 form on deportable aliens. Consideration is given to migrant characteristics and to origins of migrants in Mexico. (ANNOTATION)