Near-Infrared Spectroscopy of Very Low-Luminosity Young Stellar Objects in the Taurus Molecular Cloud

We have carried out near-infrared spectroscopic observations of 23 very low-luminosity young stellar object (YSO) candidates and 5 their companions in Heiles Cloud 2, one of the densest parts of the Taurus molecular cloud. Twelve objects were confirmed as YSOs by Br gamma feature. The effective temperatures of the YSOs and of the companions are estimated from the 2.26 micron feature, the 2.21 micron feature, and the H2O band strengths. Detailed comparisons of our photometric and spectroscopic observations with evolutionary tracks on the HR diagram suggest some objects to be very low-mass YSOs.Comment: 15 pages, 19 figures. PASJ accepte

Fertility decline, baby boom and economic growth

We present new data documenting the secular decline in fertility in the states of the United States, the dramatic convergence in fertility, child schooling, parental schooling, survival probabilities. In addition we document the disparate nature of the Baby Boom in the United States. There were two different regimes, a large Baby Boom and a Small Baby Boom. The large Baby Boom regions also had the smallest increase in child schooling, whereas the small Baby Boom regions had the largest increase in child schooling. We present suggestive evidence that falling mortality risk is strongly positively correlated with falling fertility, rising education levels of parents is strongly negatively related to fetility, and that population density is negatively related to fertility. Finally we show the robust negative correlation of mortality risk on child schooling attainment, and positve correlation of population density and child schooling attainment.mortality; density; fertility decline; baby boom; economic growth

Observational Test of Environmental Effects on The Local Group Dwarf Spheroidal Galaxies

In this paper, we examine whether tidal forces exerted by the Galaxy or M31 have an influence on the Local Group dwarf spheroidal galaxies (dSphs) which are their companions. We focus on the surface brightness profiles of the dSphs, especially their core radii because it is suggested based on the numerical simulations that tidal disturbance can make core radii extended. We examine the correlation for the dSphs between the distances from their parent galaxy (the Galaxy or M31) and the compactnesses of their surface brightness profiles by using a parameter ``C'' defined newly in this paper. Consequently, we find no significant correlation. We make some remarks on the origin of this result by considering three possible scenarios; tidal picture, dark matter picture, and heterogeneity of the group of dSphs, each of which has been often discussed to understand fundamental properties and formation processes of dSphs.Comment: 14 pages LaTeX, 2 PostScript figures, to appear in ApJ Letter

Severe acute maternal morbidity and associated deaths in conflict and post-conflict settings in Africa

SETTING:  Five hospitals in four conflict and post-conflict countries (Democratic Republic of Congo, Somaliland, Sierra Leone and Burundi). OBJECTIVES:  To report among hospital deliveries: 1) the proportion of severe acute maternal morbidity (SAMM), 2) the pattern of SAMM, and 3) maternal deaths according to type of SAMM. METHODS:  An audit of data from a standardised database implemented in all the sites in the study. RESULTS:  Of the 18 675 deliveries, there were 6314 (34%) known SAMM cases with 63 associated deaths, implying that for every 100 SAMM cases there was one maternal death. In descending order, the death-to-SAMM ratios per 1000 deliveries were: 1:7 for sepsis, 6 for haemorrhage 1:70 for hypertensive disorder and 1:398 for obstructed labour. A substantial proportion of deaths (38%) that occurred in hospitals could not be categorised into the standardised SAMM conditions available in the database. CONCLUSION:  As this is the first study using multi-centre data from conflict and post-conflict countries, these findings are relevant to improving maternal health in such settings. Findings, implications and possible ways forward in addressing various challenges are discussed

Strong Magnetization Measured in the Cool Cores of Galaxy Clusters

Tangential discontinuities, seen as X-ray edges known as cold fronts (CFs), are ubiquitous in cool-core galaxy clusters. We analyze all 17 deprojected CF thermal profiles found in the literature, including three new CFs we tentatively identify (in clusters A2204 and 2A0335). We discover small but significant thermal pressure drops below all nonmerger CFs, and argue that they arise from strong magnetic fields below and parallel to the discontinuity, carrying 10%-20% of the pressure. Such magnetization can stabilize the CFs, and explain the CF-radio minihalo connection.Comment: PRL accepted, additional control tests adde

Human Capital, Fertility, and Economic Growth

Our model of growth departs from both the Malthusian and neoclassical approaches by including investments in human capital. We assume, crucially, that rates of return on human capital investments rise, rather than, decline, as the stock of human capital increases, until the stock becomes large. This arises because the education sector uses human capital note intensively than either the capital producing sector of the goods producing sector. This produces multiple steady scares: an undeveloped steady stare with little human capital, low rates of return on human capital investments and high fertility, and a developed steady stats with higher rates of return a large, and, perhaps, growing stock of human capital and low fertility. Multiple steady states mean that history and luck are critical determinants of a country's growth experience.

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