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This paper has two principal aims: (1) to analyze and measure how the demographic variables-mortality, fertility, and immigration- affect the cost of education; (2) to evaluate what possibilities developing countries, such as those of Latin America, have for a rapid educational improvement. The paper relates demographic and educational variables of three different populations: Sweden, 1840-1965; the United States, 1850-1960; and Latin America, 1930-2000. Three educational variables are also cone sidered: (a) school attendance rates by sex and age; (b) distribution of students of same age by grade; and (c) cost of student by grade. Demographic changes in countries such as Sweden and the United States were favorable for the development of education. For the future, unless an increase of fertility occurs, mortality and fertility changes will not have a significant effect on the cost of education in these countries. In current less developed countries the demographic changes during the past were less favorable to educational development. A future reduction of fertility will significantly help them to achieve a higher educational level. [ABSTRACT FROM AUTHOR]

Using an ecological perspective, one aspect of the relationship of social distance and physical distance is analyzed in the three largest cities in Israel. The principal aim of the paper is to examine ethnic (country of origin) residential segregation as an indicator of social patterning within the society. Despite the different demographic, topographical and functional characteristics of the three cities, fairly similar patterns of ethnic segregation are found using the technique of Smallest Space Analysis (SSA-I) to analyze index of dissimilarity matrices. Patterns of ethnic segregation are then related to the SES of sub-quarters to determine the nature of the internal structure of the cities. It is suggested that ethnicity is an important variable in the process of social stratification in urban Israel, at least insofar as ecological relationships are concerned. [ABSTRACT FROM AUTHOR]

We have determined unidirectional influxes by measuring rate of uptake between 0.5 and 1.0 min of incubation in 5 mm galactose.H-inulin was used to correct for galactose in residual mucosal solution. Influx was greatly depressed by removing Na from or adding 10 m phlorizin to the incubation medium. Influx was also greatly depressed by making the mucosal solution anaerobic during a 10-min preincubation period. The same severe inhibition of galactose influx by mucosal anaerobiosis also occurrend under conditions in which the epithelial cells did not gain Na. After taking into account the effect of the mucosal unstirred water layer, influxes could be normalized to a concentration of 1.0 mm at the membrane surface. It was estimated that at 1.0 mm the phlorizin-sensitive component of galactose influx was reduced 93% by 10 min of mucosal anaerobiosis. Unidirectional effluxes were estimated by subtracting steady-state downhill mucosal-to-serosal flux from influx. The ease of efflux was apparently augmented 2.8-fold by mucosal anaerobiosis. After 10 min of mucosal anaerobiosis, there was no longer any directional preference for movement of galactose across the brush border and there was no uphill transport, in spite of the persistence of a large Na gradient. These results provide strong evidence against the theory that ion gradients provide the major source of energy for directional preference and uphill transport. [ABSTRACT FROM AUTHOR]

Ionophoric material isolated by tryptic digestion of (Na+K)-ATPase containing electroplax membranes shows fluctuating discrete current levels in oxidized cholesterol membranes with conductance amplitudes ranging from 10 to 10 mhos, suggesting pore formation. The rate of pore formation is dependent on the imposed voltage. If the voltage is maintained for a short time (5 to 10 sec), pore formation is reversible, whereas permanent pores are formed when the voltage is maintained for more than 10 sec. At pH=7 the permeability ratio for sodium versus chloride is 5 and for potassium versus sodium, 1.7. The permeability of the ionophoric material is dependent on pH. At pH=6 a conversion takes place from more cation-permeable to more anionpermeable pores, suggesting that histidine plays a role in the permeation mechanism. A model is proposed to account for the observed ionophoric properties. [ABSTRACT FROM AUTHOR]

The partition of alkali cations and anions between an aqueous and an immiscible organic phase has been studied in the absence and presence of neutral and carboxylic ionophores of the valinomycin and nigericin types, respectively. Cation extraction into the organic phase was augmented considerably by the ionophores, and a cation specificity of K≧Rb>Cs≫Na was found for all the neutral ionophores tested. Evidence is given that the actual values of ion specificity are a function of the solvent polarity, especially for valinomycin where an inversion of the K/Rb specificity was observed. The ionophores examined have the following rank order of effectiveness for K extraction into a standard organic phase consisting of 70% toluene-30% n-butanol: valinomycin>18-crown-6≫trinactin>enniatin B≈dinactin>monactin>nonactin. The ion affinity and selectivity data thus obtained have been compared with data previously reported. In a toluene-butanol solvent, extraction of cations in the absence of ionophores occurs as ion pairs. On the other hand, the neutral ionophores extract the cations by the mechanism of complexation, with the lipophilic anions coextracted as free gegenionic species at lower ionophore complex concentrations. When the concentration of extracted cations exceeds 1×10 m, ion pairing between the ionophore complex and the anion occurs, and this tendency increases with increasing concentration and decreasing polarity of the organic phase. Anion pairing with the complexed cations is much less than for the free cations and this effect appears to be due to the larger distance of closest approach of the anion for the complexed cation. [ABSTRACT FROM AUTHOR]

The cation selectivity and its relation to the inward-going rectification of the immature egg cell membrane of a starfish, Nordora punctiformis, were studied and the following results were obtained. (1) When the external saline contains usual ion species the cell membrane at rest is predominantly permeable to K ions. The K chord conductance g depends on the electrochemical potential of K ions, Δ V=V−E and the external K concentration [K] by $$(\Delta V_h \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ \doteq } - 15mV,\upsilon \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ \doteq } 7mV)$$ . (2) The permeability sequence of monovalent cations and the permeability ratios P/P of the cell membrane at rest obtained with membrane tpotential measurements are, T1 (1.5)>K(1.0)>Rb(0.3 to 0.4)>NH(0.03 to 0.04)>Na, Cs. (3) Current-voltage relations obtained when the external solution contains Rb, Cs or T1 in addition to K show: (a) Rb and Cs decrease the K conductance and the rate of decrease becomes greater with an increasing hyperpolarization, thereby the inward-going rectification is reduced; (b) the membrane conductance shows an 'anomalous mole fraction dependence' in Tl-K media, i.e., the conductance becomes minimum at a certain mole fraction; and (c) the current-voltage relation often shows a transitiontype behavior suggesting that the membrane undergoes metastable states during an ncrease of hyperpolarization. [ABSTRACT FROM AUTHOR]

The turnover numbers of the ionophores valinomycin, the macrolide actins, enniatin B and dicyclohexyl 18-crown-6 for translocation of cations through the mitochondrial membrane have been compared quantitatively. The rank order of decreasing maximum turnover number for K transport calculated on the basis of the ionophore concentration within the membrane is trinactin>dinactin∼monactin∼ valinomycin>nonactin>18-crown-6>enniatin B. The strength of binding of the ionophores to the mitochondria has the following rank order: valinomycin>macrolide actins>enniatin B>18-crown-6. A rough proportionality was observed between the transport rate of K, Rb, Cs or Na with a given ionophore and the heterogeneous complexation constant of the corresponding ionophore-cation pair in two-phase extraction experiments. However, the proportionality constants between transport and the heterogeneous complexation constant differ between the ionophores. These comparisons indicate that valinomycin and enniatin B transport cations about 10 times slower than would be expected from their two-phase complexation behavior, using the complexation and transport reactions of the macrolide actins as a basis for comparison. Transport with 18-crown-6 was about 1,000 times slower than predicted. These observations are discussed in terms of partitioning of the ionophores between various regions of the mitochondrial membrane. The data are discussed in terms of a carrier model involving hydrophilic complexes on the membrane surface in addition to hydrophobic complexes which cross the membrane. [ABSTRACT FROM AUTHOR]

The operation of a seven-compartment model is described with respect to flows of Na within and across this system, simulating published results obtained on frog skin. The seven compartments represent: one outside and one inside solution compartment; the subcorneal space; the first reacting cell layer (1. RCL); the remaining cell compartment; the non-, or slowly exchangeable Na compartment; the extracellular space. Assuming reasonable volumes for the epidermal compartments and further chosing, by trial and error, appropriate rate constants, a set of seven simultaneous linear differential equations was solved by the application of the Continuous System Modeling Program (CSMP), using an IBM 1130 computer. Initial conditions for influx, backflux and net flux were taken which correspond to [Na]; [Na]=115 mm. Print-out data were obtained at 0.5-min intervals for 30 min, when steady states were obtained in 13 models studied, varying certain k's thus simulating actions of chemical agents (hormones; drugs). Simulation was achieved with regard to rate of influx, backflux and net flux, steady-state time (30 min), and electrical potentials. In addition, this approach gave detailed information on Na pool sizes and their variations with changes in k's. These results are compared to published data on frog skin and good agreement between operation of skin epidermis and model was found. [ABSTRACT FROM AUTHOR]

The role played by transmembrane K gradients in providing an energy input for Na-dependent monosaccharide transport systems was evaluated with the use of isolated intestinal epithelial cells. Experimentally imposing a K gradient in a sense reversed from normal did not lead to extrusion of sugar from cells which had been pre-equilibrated withC-3-OMG, even in situations where a reversed Na gradient was also imposed. Furthermore, cells preloaded with K have no better ability to accumulate 3-OMG than do cells depleted of K, when the two populations are compared under identical incubation conditions. Fluxes of K associated with the sugar carrier could not be detected in terms of suspected sensitivity to agents which immobilize the sugar carrier. In addition, fluxes of sugar in response to imposed K gradients were not demonstrable in cells de-energized by preincubation with DNP, no matter in which direction the K gradient was imposed. Finally, the severe inhibitory effects of K on Na-dependent sugar transport by the cells disappears in de-energized cells, despite the fact that Na-dependent carrier-mediated sugar entry still occurs. All of these facts are difficult to reconcile with a significant role for cellular K gradients in supporting active sugar transport as envisioned by the ion gradient hypothesis. We have suggested instead a fundamental Na-dependent energy transductive event which depends on ATP, and which can generate a membrane-bound energized intermediate which serves to support a variety of active transport events. An analogy is drawn between this concept for animal cell plasma membranes and the better documented phosphotransferase system for sugar transport described for certain microorganisms. [ABSTRACT FROM AUTHOR]

The concept that interaction between sodium-dependent transport systems represents competition for energy inherent in the transmembrane sodium gradient was examined with the use of isolated intestinal epithelial cells. The isolated cells exhibit transport interactions which are more significant in magnitude than those which have been described for intact tissue preparations. Accumulation of 1 mm valine is inhibited 60% by 10 mm 3-OMG. Conversely, uptake of 1 mm 3-OMG is inhibited only 20% by 10 mm valine. These data suggest that 3-OMG must discharge the cellular Na gradient more effectively than valine, if Na gradient dissipation can be taken as a basis for the inhibitory interaction. However, entry of 10 mm 3-OMG is significantly slower than the entry of 10 mm valine. Even if appropriate corrections are made for passive substrate entry and for differences in Na/substrate entry stoichiometry, it appears that valine should be somewhat more effective than 3-OMG in discharging the Na gradient. In light of these facts, it seems unlikely that the mechanistic basis for interaction between sugar and amino acid transport systems can be related to concomitant co-entry of Na. It is suggested that the interaction results instead from competition for energized intermediates generated at limited rates by basic energy transduction events associated with the cell membrane which serve in support of a variety of active transport systems. [ABSTRACT FROM AUTHOR]

Blacks are more likely than whites to have unwanted births. A common explanation for that difference is that blacks use less effective contraceptive methods, use contraception less effectively, and use contraception less often than whites. Analysis of data from 17 cities in our family planning evaluation project suggested that, among women living in low-income neighborhoods, the black-white difference in unwanted births was not due to (1) blacks reaching desired completed parity at younger ages than whites, (2) differences in age or parity in our black and white samples, (3) black-white differences in current use of physician-administered contraception, or (4) blacks being more likely than whites to adopt physician-administered contraception after having an unwanted birth. Black-white differences which might have contributed to relatively more unwanted births among blacks were (1) blacks desired fewer children, (2) blacks were less likely than whites to use nonphysician-administered methods and more likely than whites to use no contraception, and (3) blacks had higher failure rates than whites subsequent to the adoption of physician-administered methods and when not using those methods. Comparisons are made with the 1965 and 1970 National Fertility Studies, and program implications of the findings discussed. [ABSTRACT FROM AUTHOR]

The effects of education on current migration propensities in the United States are examined for each age group, and an estimate is made of how these age-specific differentials cumulate over a lifetime in determining the number of times that individuals at different educational levels can expect to move over the course of their lives. The independent effects of age, education, and occupation are also examined. Two other sections investigate trends in educational selectivity of migration in the United States and international comparisons of occupational differences in migration. [ABSTRACT FROM AUTHOR]

Differences in the distribution of population within and across metropolitan areas are seen as a product of the development of the metropolis during different transportation epochs. Age cohorts of census tracts in Cleveland, Ohio, may be split into three groups of development patterns based on the time of their early development: (1) before the development of the automobile, (2) during the early period of the auto's diffusion to the population, and (3) during the period of the mass diffusion of the auto. Patterns of population concentration and congestion across metropolitan areas are heavily selective of places with large population growth before the development of the streetcar and the automobile. More recent population growth has had little effect on population congestion but has led to a deconcentrated metropolis. [ABSTRACT FROM AUTHOR]

An attempt is made to investigate the educational differentials between various types of interdivisional migrants and nonmigrants in selected Standard Metropolitan Statistical Areas (SMSA's) of the United States. The analysis is carried out for four color-sex groups standardized for age. We have been able to identify three distinct patterns of migration differentials by education, that is, the J-shaped, the U-shaped, and the reverse J-shaped distributions. The tendency for migrants to be better educated than nonmigrants, by and large, has received support from the data we have analyzed. Wherever this tendency has not been confirmed, the main factors which, we believe, have influenced the differentials are the proportion of foreign-born whites, the geographic location of the places of origin and destination, and the differences in levels of educational attainment. [ABSTRACT FROM AUTHOR]

There was an impressive increase between 1965 and 1970 in the prevalence of contraceptive sterilization, an increase that accelerated in the later years of the period and was shared in by virtually all subgroups considered, Among couples in 1970 for whom sterilization had been an option (recognizing that it is a terminal method), about one of every five had chosen this method of contraception. About half of all sterilizations were vasectomies, though vasectomies have outnumbered tubal ligations in recent years. Differentials in prevalence and in increases during 1965-1970 are reported for a number of life-cycle and social variables. In addition, a profile of the contraceptive sterile is presented for recent sterilizations. Significant proportions are relatively young and, of low parity at the time of sterilization. In the context of the continued diffusion of the pill and IUD and increases in legal abortion, the net demographic effect of increasing sterilization is regarded as low, though sterilization is an important component of an effective fertility control regime. [ABSTRACT FROM AUTHOR]

Between 1960 and 1970 blacks, as well as whites, improved their socioeconomic status. Among both races, educational attainment increased, the occupational distribution was upgraded, and real purchasing power rose markedly. In almost every comparison, the gains were somewhat greater among blacks than among whites and thus most indicators of racial differentiation declined. Nevertheless, the changes of this decade failed to eliminate racial differences with regard to socioeconomic status. In all comparisons, except for the income of certain groups of women, blacks were at a disadvantage when compared to whites both at the start and at the end of this decade, and very large racial differences remain. Further socio- economic progress by blacks during the 1970s will probably not eliminate racial differences. The article concludes by relating the socioeconomic trends to such other aspects of race relations as integration, governmental policy, and the attitudes of whites and blacks. [ABSTRACT FROM AUTHOR]

Patterns of family size, family stability, and timing of family formation characteristic of Mexican-Americans are contrasted with those of Japanese-Americans, and consequences of their demographic differences for group achievement are explored. Mexican-Americans are found to have a demographic system marked by young ages at marriage, young ages at beginning of childbearing, high rates of reproduction, and high rates of marital instability. Japanese-Americans display just the opposite pattern of behavior on each of these variables. Using existing research on determinants of individual achievement, reasons are then suggested why the demographic environment encountered by Japanese-American youth is more conducive to educational and economic achievement than is that encountered by Mexican-American youth. [ABSTRACT FROM AUTHOR]

In terms of quantitative comparative data Middle Eastern countries report systematically the lowest female participation rates in economic activities outside of agriculture. This behavior represents a deviation from the current experience of other developing nations and from the historical experience of the now-industrialized West. Using comparative data on female employment patterns in Latin American countries which are at roughly a similar stage of economic development, it is shown that the low level and particular character of women's involvement in the work force in the Middle East can be explained by institutional arrangements contingent upon aspects of social structure. Five countries are selected for intensive analysis: Chile, Mexico, Egypt, Morocco and Pakistan. One major aspect of social organization and its cultural adjuncts is emphasized: The interplay between the volitional avoidance by women of certain occupational sectors because of the social stigmatizing aspect and the prohibition of occupational opportunities imposed by males. The combined effects of this tradition of female seclusion and exclusion are confirmed by the detailed analysis of the structure of the non-agricultural labor force: Middle Eastern women are absent systematically from occupational and industrial sectors of employment which involve public activity and presuppose contact with males. [ABSTRACT FROM AUTHOR]

This study empirically investigates the relationship between the economic structure of populations and their level of fertility, using data from censuses recently conducted in some 50 nations. Findings show that high rates of female labor force participation outside the home and low rates of economic activity of children depress a society's fertility level, as measured by the crude birth rate or the child-woman ratio. It is also hypothesized, but not confirmed, that the per cent of unpaid family work- ers in a society is positively related to its fertility level. A model is presented that treats these three components of economic structure as intervening variables through which the exogenous variables, urbanization, industrialization, and education, operate in influencing the fertility level of a society. [ABSTRACT FROM AUTHOR]

The primary objective of this study is to present an explanation of the interstate migratory movements of white and nonwhite persons which occurred over the period 1955-1960. The study is similar to several other recent studies in that we estimate the magnitudes in which various factors have influenced interstate or interregional migration in the United States. It differs from earlier studies in two important respects. First, we estimate and compare the magnitudes in which certain factors have influenced both white and nonwhite interstate migration. Second, unlike previous studies, many of which have made "country-wide" estimates of the determinants of migration, we have disaggregated data to the state level and obtained white and nonwhite "migration elasticities" for every state. These elasticities are in turn used to test several additional hypotheses relating to racial and regional differences in the elasticities themselves. We argue that discrimination against nonwhites and/or differences in "social milieu" between South and nonsouth provide a unifying explanation for most of the observed differences in white and nonwhite migration elasticities. [ABSTRACT FROM AUTHOR]

A method to compare fertility sequences, each of which represents a cyclical fluctuation around an underlying trend, is presented. Each fertility sequence is viewed as composed of a time trend in childspacing pattern and a corresponding trend in terminal fertility rate. The procedure involved in comparing each component of one fertility sequence with the corresponding component of another is described and illustrated. Using hypothetical data it is shown, among other things, that if A and B are two cyclical fluctuations in fertility such that (i) the cycles in both are of the same length, (ii) the terminal fertility components of the two are identical, and (iii) the trend in the mean age at childbirth associated with A is higher than the corresponding trend associated with B, then, replacing B with A need not necessarily result in lowering the long-run rates of increase in the birth sequence. [ABSTRACT FROM AUTHOR]

Presents information on a study regarding giardia lamblia found in small intestines of children. Elements that were compared in order to estimate morphologic alterations; Comparative analysis between giardiasis and malabsorption syndrome; Criteria for the selection of patients to be included in the study.