Why Nations Become Wealthy: The Effects of Adult Longevity on Saving

Many countries experienced a rema rkable increase in life expectancy during the 20th century, but the development implications have received only modest attention. We analyze steady state and out-of-steady-state effects of the transition in adult longevity on the national saving rate using an overlapping generations model. We show that the national saving rate depends on both the level and rate of change in adult survival. Countries with rapid transitions have particularly elevated saving rates. Empirical evidence is drawn from two sources: long-term historical trends for a small number of countries and world panel data for 1960-95. Two important conclusions are supported by the empirical analysis. First, the demographic transition had a large positive effect on aggregate saving, but over three-quarters of the gain was due to improvements in old-age survival rather than declines in youth dependency. Second, population aging will not lead to a decline in aggregate saving rates. The compositional effect – lower saving rates among the elderly – is dominated by the behavioral effect – individuals will save more to provide for a longer old age.

ASCA Observation of the Crab-Like Supernova Remnant 3C58

We present here the X-ray observation of a Crab-like supernova remnant (SNR) 3C58 with ASCA. We find that the integrated energy spectrum over the nebula is consistent with previous results, showing a power-law spectrum with the photon index $\gamma = 2.2-2.4$ modified by interstellar absorption of about $(3-4)\times 10^{21}{\rm cm^{-2}}$. Inclusion of a blackbody component which is attributable to the central compact source significantly improves the spectral fit. Stringent upper limits for any line emitting thin hot plasma are established. We find for the first time that the nebular spectrum is harder in the central part of the SNR, becoming softer toward the periphery, while the absorption column is uniform across the nebula. Correspondingly, the nebular size decreases with increasing photon energy which is a steeper function of radius than that of the Crab nebula. The results are compared with synchrotron energy loss models and the nature of the putative pulsar is discussed. Timing analysis was performed to search for pulsed X-ray emission from the central compact source. No significant pulsations are observed, and we present the upper limit for the pulsed fraction.Comment: 27 pages, 7 figures, to appear in PAS

Interaponeurosis shear strain modulates behavior of myotendinous junction of the human triceps surae.

Muscle fascicles insert into a sheet-like aponeurosis. Adjacent aponeuroses are structurally in contact with each other, and ultimately merge into a common tendon. Consequently, fascicle shortening in planes of tissue layers in adjacent compartments must cause sliding between aponeuroses parallel to the acting forces. In this study, we used velocity-encoded, phase-contrast, and water-saturated spin-lattice relaxation time-weighted imaging to identify and track fascicle and aponeurosis behaviors of human medial gastrocnemius (MG) and soleus (Sol) during 15° dorsiflexion to 30° plantarflexion contractions of the ankle. Interaponeurosis shear strain, which was defined as the relative displacement of the aponeurosis at the fascicle end points (insertion) of the MG and Sol, was an average of 1.35 ± 0.27% (range 1.12 ∼ 1.87%), indicating that the strain is greater in the aponeurosis of MG fascicle insertion than the Sol. The myotendinous junction (MTJ) displacement increased significantly with decreasing interaponeurosis shear strain (P < 0.05). The magnitude of interaponeurosis shear strain had significant correlation with the temporal difference between the time at which the peak aponeurosis displacement of the MG and Sol occurred (P < 0.05). Our model also indicated that theoretical MTJ displacement varies in relation to temporal difference: no temporal difference caused the largest MTJ displacement and presence of temporal differences indicated a reduction in MTJ displacement. Therefore, we concluded that interaponeurosis shear strain is a mechanism enabling individual muscle contraction and thus specific loading of the tendon and joint

Thermal X-Ray Emission from Shocked Ejecta in Type Ia Supernova Remnants II: Parameters Affecting the Spectrum

The supernova remnants left behind by Type Ia supernovae provide an excellent opportunity for the study of these enigmatic objects. In a previous work, we showed that it is possible to use the X-ray spectra of young Type Ia supernova remnants to explore the physics of Type Ia supernovae and identify the relevant mechanism underlying these explosions. Our simulation technique is based on hydrodynamic and nonequilibrium ionization calculations of the interaction of a grid of Type Ia explosion models with the surrounding ambient medium, coupled to an X-ray spectral code. In this work we explore the influence of two key parameters on the shape of the X-ray spectrum of the ejecta: the density of the ambient medium around the supernova progenitor and the efficiency of collisionless electron heating at the reverse shock. We also discuss the performance of recent 3D simulations of Type Ia SN explosions in the context of the X-ray spectra of young SNRs. We find a better agreement with the observations for Type Ia supernova models with stratified ejecta than for 3D deflagration models with well mixed ejecta. We conclude that our grid of Type Ia supernova remnant models can improve our understanding of these objects and their relationship to the supernovae that originated them.Comment: Accepted for publication in Ap

Depopulation and importance of agriculture in Japan: Implications from the overlapping generations and general equilibrium growth accounting model

We investigate the effects of demographic change on agriculture and nonagriculture in Japan while considering capital accumulation and total population and labour. Combining the overlapping generations model with the three generations and general equilibrium growth accounting models, we simulate the effect of demographic change on agricultural and nonagricultural inputs and outputs. Our simulation analyses show that demographic change greatly influenced agriculture and nonagriculture through capital accumulation although the influences of total population and labour were not negligible. Remarkable demographic dividends like the decline of young dependents and increase of adult longevity greatly influenced capital accumulation in Japan in the 1950s to the 1990s, which decreased the importance of agriculture. In the future, aggregate capital in Japan will presumably decrease due to a decline of the working age population, which may result in the disappearance of the advantages of nonagriculture and an increase of the importance of agriculture

Mechanisms of Glomerular Albumin Filtration and Tubular Reabsorption

Albumin is filtered through the glomerulus with a sieving coefficient of 0.00062, which results in approximately 3.3 g of albumin filtered daily in human kidneys. The proximal convoluted tubule reabsorbs 71%, the loop of Henle and distal tubule 23%, and collecting duct 3% of the glomerular filtered albumin, thus indicating that the kidney plays an important role in protein metabolism. Dysfunction of albumin reabsorption in the proximal tubules, due to reduced megalin expression, may explain the microalbuminuria in early-stage diabetes. Meanwhile, massive nonselective proteinuria is ascribed to various disorders of the glomerular filtration barrier, including podocyte detachment, glomerular basement membrane rupture, and slit diaphragm dysfunction in focal segmental glomerulosclerosis, membranous nephropathy, and other glomerulonephritis. Selective albuminuria associated with foot process effacement and tight junction-like slit alteration is observed in the patients with minimal-change nephrotic syndrome, and the albumin uptake is enhanced in the podocyte cell body, possibly mediated by albumin receptors in the low-dose puromycin model. The role of enhanced podocyte albumin transport needs to be investigated to elucidate the mechanism of the selective albuminuria in minimal-change disease

Ionization States and Plasma Structures of Mixed-morphology SNRs Observed with ASCA

We present the results of a systematic study using ASCA of the ionization state for six ``mixed-morphology'' supernova emnants (MMSNRs): IC 443, W49B, W28, W44, 3C391, and Kes 27. MMSNRs show centrally filled thermal X-ray emission, which contrasts to shell-like radio morphology, a set of haracteristics at odds with the standard model of SNR evolution (e.g., the Sedov model). We have therefore studied the evolution of the MMSNRs from the ionization conditions inferred from the X-ray spectra, independent of X-ray morphology. We find highly ionized plasmas approaching ionization equilibrium in all the mmsnrs. The degree of ionization is systematically higher than the plasma usually seen in shell-like SNRs. Radial temperature gradients are also observed in five remnants, with cooler plasma toward the limb. In IC 443 and W49B, we find a plasma structure consistent with shell-like SNRs, suggesting that at least some MMSNRs have experienced similar evolution to shell-like SNRs. In addition to the results above, we have discovered an ``overionized'' ionization state in W49B, in addition to that previously found in IC 443. Thermal conduction can cause the hot interior plasma to become overionized by reducing the temperature and density gradients, leading to an interior density increase and temperature decrease. Therefore, we suggest that the ``center-filled'' X-ray morphology develops as the result of thermal conduction, and should arise in all SNRs. This is consistent with the results that MMSNRs are near collisional ionization equilibrium since the conduction timescale is roughly similar to the ionization timescale. Hence, we conclude that MMSNRs are those that have evolved over$\sim10^4$ yr. We call this phase as the ``conduction phase.''Comment: 34 pages, 20 figures, 9 tables, accepted for publication in The Astrophysical Journa

The Kinematics of Kepler's Supernova Remnant as revealed by Chandra

I determine the expansion of the supernova remnant of SN1604 (Kepler's supernova) based on archival Chandra ACIS-S observations made in 2000 and 2006. The measurements were done in several distinct energy bands, and were made for the remnant as a whole, and for six individual sectors. The average expansion parameter indicates that the remnant expands as $r \propto t^{0.5}$, but there are significant differences in different parts of the remnant: the bright northwestern part expands as $r \propto t^{0.35}$, whereas the rest of the remnant's expansion shows an expansion $r \propto t^{0.6}$. The latter is consistent with an explosion in which the outer part of the ejecta has a negative power law slope for density ($\rho \propto v^{-n}$) of $n=7$, or with an exponential density profile($\rho \propto \exp(-v/v_e)$). The expansion parameter in the southern region, in conjunction with the shock radius, indicate a rather low value (<5E50 erg) for the explosion energy of SN1604 for a distance of 4 kpc. An higher explosion energy is consistent with the results, if the distance is larger. The filament in the eastern part of the remnant, which is dominated by X-ray synchrotron radiation seems to mark a region with a fast shock speed $r \propto t^{0.7}$, corresponding to a shock velocity of v= 4200 km/s, for a distance to SN1604 of 4 kpc. This is consistent with the idea that X-ray synchrotron emission requires shock velocities in excess of ~2000 km/s. The X-ray based expansion measurements reported are consistent with results based on optical and radio measurements, but disagree with previous X-ray measurements based on ROSAT and Einstein observations.Comment: Accepted for publication in ApJ. This new version is the accepted version, which differs mainly in the discussion sectio