Impact of Paternal Temporary Absence on Children Left Behind

Using the first two waves of the Vietnam Living Standards Survey, we investigate how a father's temporary absence affects children left behind in terms of their school attendance, household expenditures on education, and nonhousework labor supply in the 1990s. The estimating subsample is children aged 7-18 in households in which both parents usually coreside and the mother has not been absent. Our results indicate that paternal temporary absence increases nonhousework labor supply by his son. The longer the absence of the father, the larger the impact. One additional month of paternal temporary absence increases a son's nonhousework labor supply by approximately one week. However, a daughter's nonhousework labor supply is not affected. We find no evidence that paternal temporary absence influences his children in terms of school attendance or education-related household expenditures.parental absence, temporary migration, schooling, human capital investment, child labor, Vietnam, VLSS

Analysis of quantum conductance of carbon nanotube junctions by the effective mass approximation

The electron transport through the nanotube junctions which connect the different metallic nanotubes by a pair of a pentagonal defect and a heptagonal defect is investigated by Landauer's formula and the effective mass approximation. From our previous calculations based on the tight binding model, it has been known that the conductance is determined almost only by two parameters,i.e., the energy in the unit of the onset energy of more than two channels and the ratio of the radii of the two nanotubes. The conductance is calculated again by the effective mass theory in this paper and a simple analytical form of the conductance is obtained considering a special boundary conditions of the envelop wavefunctions. The two scaling parameters appear naturally in this treatment. The results by this formula coincide fairly well with those of the tight binding model. The physical origin of the scaling law is clarified by this approach.Comment: RevTe

Factor Returns, Institutions, and Geography: A View From Trade

We examine the importance of institutions and geography for determining workers' wages and the return to capital. These returns to labor and capital are examined through the lens of labor and capital's productivities, which are directly related to the factors' returns. We estimate productivities of labor and capital based on trade flows across countries and present statistical evidence that these productivities are related to total factor productivities which rationalize output differences across countries. We examine whether these labor and capital productivities are related to countries' political institutions and geography. Protection of property rights is the dominant influence on both labor and capital productivity. There is some evidence that a democratic government affects productivity, but once property rights are included in the analysis, the overall democracy index has little influence on factor productivity.. Geography is only important in terms of distance to a large market. Factors such as the incidence of malaria are relatively unimportant. The unimportance of geography is not only statistical. For example, if the Philippines kept its geography but had the United Kingdom 's institutions, the Philippines ' labor productivity would increase from seven percent to 75 percent of the U.S. 's and capital productivity would increase from 25 percent to 58 percent of the U.S. 's. On the other hand, if the Philippines were to keep its institutions and were magically more to the United Kingdom 's geographic location, labor productivity would increase only from seven percent to 28 percent and capital productivity would increase from 25 percent to 26 percent.

How important are capital and total factor productivity for economic growth?

The authors examine the relative importance of the growth of physical and human capital and the growth of total factor productivity (TFP) using newly organized data on 145 countries that span more than one hundred years for twenty-four of these countries. For all countries, only 3 percent of average output growth per worker is associated with TFP growth. This world average masks interesting variations across countries and regions. Of the nine regions, TFP growth accounts for about twenty percent of average output growth in three regions and between ten and zero percent in the other three regions. In three regions, TFP growth is negative on average. The authors use priors from theories to construct estimates of the relative importance of the variances of aggregate input growth and TFP growth for the variance of output growth across countries. Across all countries, variation in aggregate input growth per worker could account for as much as 35 percent of the variance of the growth of output per worker across countries, and variation in TFP growth could account for as much as 87 percent of that variance. Much of the importance of the variance of TFP growth appears to be associated with negative TFP growth.Productivity ; Economic development ; Capital ; Industrial productivity

Band structures of periodic carbon nanotube junctions and their symmetries analyzed by the effective mass approximation

The band structures of the periodic nanotube junctions are investigated by the effective mass theory and the tight binding model. The periodic junctions are constructed by introducing pairs of a pentagonal defect and a heptagonal defect periodically in the carbon nanotube. We treat the periodic junctions whose unit cell is composed by two kinds of metallic nanotubes with almost same radii, the ratio of which is between 0.7 and 1 . The discussed energy region is near the undoped Fermi level where the channel number is kept to two, so there are two bands. The energy bands are expressed with closed analytical forms by the effective mass theory with some assumptions, and they coincide well with the numerical results by the tight binding model. Differences between the two methods are also discussed. Origin of correspondence between the band structures and the phason pattern discussed in Phys. Rev. B {\bf 53}, 2114, is clarified. The width of the gap and the band are in inverse proportion to the length of the unit cell, which is the sum of the lengths measured along the tube axis in each tube part and along 'radial' direction in the junction part. The degeneracy and repulsion between the two bands are determined only from symmetries.Comment: RevTeX, gif fil

Modern economic growth and recent stagnation

During the past 200 years, most countries have entered a period of modern economic growth-consistent increases in output, input, and productivity per worker that were rare in previous centuries. Even so, a few regions of the world have experienced stagnant or falling living standards in recent years, which some have interpreted as typical of modern economic growth in the last two centuries. ; Using data for most countries in the world since the 1800s and early 1900s, the authors find that (1) economic growth has improved the lives of people all around the world compared to those of their ancestors and (2) the economic stagnation or decline in some parts of the world in recent decades is unusual in the broader context of the history of the world since 1800. ; The authors find that economic growth had become nearly global by the 1950s, and the recent economic declines in four regions in recent decades are atypical. Decreases in income and productivity are likely to be transitory in Central and Eastern Europe but may be longer lasting in the Middle East and Latin America. While modern economic growth may never have begun in Sub-Saharan Africa, government policies in that region have done more to throttle economic growth than to encourage it.Economic history ; Economic development

Backward diode composed of a metallic and semiconducting nanotube

The conditions necessary for a nanotube junction connecting a metallic and semiconducting nanotube to rectify the current are theoretically investigated. A tight binding model is used for the analysis, which includes the Hartree-Fock approximation and the Green's function method. It is found that the junction has a behavior similar to the backward diode if the gate electrode is located nearby and the Fermi level of the semiconducting tube is near the gap. Such a junction would be advantageous since the required length for the rectification could be reduced.Comment: 4 pages, RevTeX, uses epsf.st

Epithelial integrin alpha 6 beta 4: complete primary structure of alpha 6 and variant forms of beta 4.

The integrin alpha 6 beta 4 is a heterodimer predominantly expressed by epithelia. While no definite receptor function has yet been assigned to it, this integrin may mediate adhesive and/or migratory functions of epithelial cells. We have determined the complete primary structure of both the alpha 6 and beta 4 subunits from cDNA clones isolated from pancreatic carcinoma cell line libraries. The deduced amino acid sequence of alpha 6 is homologous to other integrin alpha chains (18-26% identity). Antibodies to an alpha 6 carboxy terminus peptide immunoprecipitated alpha 6 beta 4 complexes from carcinoma cells and alpha 6 beta 1 complexes from platelets, providing further evidence for the association of alpha 6 with more than one beta subunit. The deduced amino acid sequence of beta 4 predicts an extracellular portion homologous to other integrin beta chains, and a unique cytoplasmic domain comprised of greater than 1,000 residues. This agrees with the structures of the beta 4 cDNAs from normal epithelial cells (Suzuki, S., and Y. Naitoh. 1990. EMBO [Eur. Mol. Biol. Organ.] J. 9:757-763; Hogervost, F., I. Kuikman, A. E. G. Kr. von dem Borne, and A. Sonnenberg. 1990. EMBO [Eur. Mol. Biol. Organ.] J. 9:765-770). Compared to these structures, however, the beta 4 cDNAs that we have cloned from carcinoma cells contain extra sequences. One of these is located in the 5'-untranslated region, and may encode regulatory sequences. Another specifies a segment of 70 amino acids in the cytoplasmic tail. Amplification by reverse transcription-polymerase chain reaction of mRNA indicated that multiple forms of beta 4 may exist, possibly due to cell-type specific alternative splicing. The unique structure of beta 4 suggests its involvement in novel cytoskeletal interactions. Consistent with this possibility, alpha 6 beta 4 is mostly concentrated on the basal surface of epithelial cells, but does not colocalize with components of adhesion plaques

Phonon Transmission Rate, Fluctuations, and Localization in Random Semiconductor Superlattices: Green's Function Approach

We analytically study phonon transmission and localization in random superlattices by using a Green's function approach. We derive expressions for the average transmission rate and localization length, or Lyapunov exponent, in terms of the superlattice structure factor. This is done by considering the backscattering of phonons, due to the complex mass density fluctuations, which incorporates all of the forward scattering processes. These analytical results are applied to two types of random superlattices and compared with numerical simulations based on the transfer matrix method. Our analytical results show excellent agreement with the numerical data. A universal relation for the transmission fluctuations versus the average transmission is derived explicitly, and independently confirmed by numerical simulations. The transient of the distribution of transmission to the log-normal distribution for the localized phonons is also studied.Comment: 36 pages, Late