Norms and inequalities for condition numbers, III

AbstractThe main results provide comparisons between condition numbers (based on unitarily invariant norms) of (i) positive definite (Hermitian) matrices A, B and of A + B, (ii) a positive definite matrix and its principal submatrix, and (iii) a matrix and an augmented form of the matrix

The superwind mass-loss rate of the metal-poor carbon star LI-LMC 1813 in the LMC cluster KMHK 1603

LI-LMC 1813 is a dust-enshrouded Asymptotic Giant Branch (AGB) star, located in the small open cluster KMHK 1603 near the rim of the Large Magellanic Cloud (LMC). Optical and infrared photometry between 0.5 and 60 micron is obtained to constrain the spectral energy distribution of LI-LMC 1813. Near-infrared spectra unambiguously show it to be a carbon star. Modelling with the radiation transfer code Dusty yields accurate values for the bolometric luminosity, L=1.5 x 10^4 Lsun, and mass-loss rate, Mdot=3.7(+/-1.2) x 10^-5 Msun/yr. On the basis of colour-magnitude diagrams, the age of the cluster KMHK 1603 is estimated to be t=0.9-1.0 Gyr, which implies a Zero-Age Main Sequence mass for LI-LMC 1813 of M(ZAMS)=2.2+/-0.1 Msun. This makes LI-LMC 1813 arguably the object with the most accurately and reliably determined (circum)stellar parameters amongst all carbon stars in the superwind phase.Comment: Accepted for publication in MNRAS (better quality figure 1 on request from jacco

Does having highly educated adult children reduce mortality risks for parents with low educational attainment in Europe?

This work was supported by the ESRC Centre for Population Change (grant number ES/K007394/1); and the University of St Andrews.It is known that the education of significant others may affect an individual’s mortality. This paper extends an emerging body of research by investigating the effect of having highly educated adult children on the longevity of older parents in Europe, especially parents with low educational attainment. Using a sample of 15,015 individuals (6,620 fathers and 8,395 mothers) aged 50 and above, with 1,847 recorded deaths, over a mean follow-up period of 10.9 years from the Survey of Health, Ageing and Retirement in Europe (SHARE), we examine whether the well-established socioeconomic gradient in mortality among parents is modified when their adult children have higher educational attainment than their parents. We find that having highly educated adult children is associated with reduced mortality risks for fathers and mothers with low educational attainment, compared to their counterparts whose adult children have only compulsory education. The association is stronger in early older age (ages 50 to 74) than in later older age (ages 75 and over). Part of the association appears to be explained by health behaviours (physical (in)activity) and health status (self-rated health). Our findings suggest that the socioeconomic-mortality gradient among older parents might be better captured using an intergenerational approach that recognises the advantage of having highly educated adult children, especially for fathers and mothers with only compulsory education.Publisher PDFPeer reviewe

Forecasting temporal dynamics of cutaneous leishmaniasis in Northeast Brazil.

IntroductionCutaneous leishmaniasis (CL) is a vector-borne disease of increasing importance in northeastern Brazil. It is known that sandflies, which spread the causative parasites, have weather-dependent population dynamics. Routinely-gathered weather data may be useful for anticipating disease risk and planning interventions.Methodology/principal findingsWe fit time series models using meteorological covariates to predict CL cases in a rural region of Bahía, Brazil from 1994 to 2004. We used the models to forecast CL cases for the period 2005 to 2008. Models accounting for meteorological predictors reduced mean squared error in one, two, and three month-ahead forecasts by up to 16% relative to forecasts from a null model accounting only for temporal autocorrelation.SignificanceThese outcomes suggest CL risk in northeastern Brazil might be partially dependent on weather. Responses to forecasted CL epidemics may include bolstering clinical capacity and disease surveillance in at-risk areas. Ecological mechanisms by which weather influences CL risk merit future research attention as public health intervention targets

Farm tenure in Iowa: V. Some legal aspects of landlord-tenant relationships

The present Iowa laws pertaining to landlord-tenant relationships do not distinguish between urban and agricultural conditions, with only two exceptions: The agricultural landlord’s lien and the termination of indefinite agricultural leases. This lien applies to the total crop and to all personal property of the tenant, except to the property exempted from execution. In addition, leases usually contain a provision in which the tenant waives his exemption rights. In periods of excessive price decline or crop failure, and if production credit is sought by the tenant, the landlord’s lien may work serious hardship. As a possible corrective, placing of certain limitations on the landlord’s lien, and declaring invalid any waivers of exemption rights might be considered. An Iowa statute provides that any lease with a fixed date of termination shall expire without notice and that only 1 month’s notice is necessary to terminate an indefinite tenancy. The old common law rule provided for a 6 months’ period of notice for termination of leases without a definite expiration date. It was changed by legislation in order to accommodate urban tenants and landlords. A statute requiring a 6 months’ notice for the termination of any farm lease would be better adapted to agricultural needs

NASA/DOE/DOD nuclear propulsion technology planning: Summary of FY 1991 interagency panel results

Interagency (NASA/DOE/DOD) technical panels worked in 1991 to evaluate critical nuclear propulsion issues, compare nuclear propulsion concepts for a manned Mars mission on a consistent basis, and to continue planning a technology development project for the Space Exploration Initiative (SEI). Panels were formed to address mission analysis, nuclear facilities, safety policy, nuclear fuels and materials, nuclear electric propulsion technology, and nuclear thermal propulsion technology. A summary of the results and recommendations of the panels is presented

On the Nonexistence of Singular Equilibria in the Four-vortex Problem

In this paper we provide a partial answer to a question recently posed by Hassan Aref et. al. in their article Vortex Crystals, namely whether there are certain singular equilibria of point vortices. We prove that there are no such equilibria in the four-vortex case

RSMASS: A Preliminary Reactor/Shield Mass Model for SDI Applications

A simple mathematical model (RSMASS) has been developed to provide rapid estimates of reactor and shield masses for space-based reactor power systems. Approximations are used rather than correlations or detailed calculations to estimate the reactor fuel mass and the masses of the moderator, structure, reflector, pressure vessel, miscellaneous components, and the reactor shield. The fuel mass is determined either by neutronics limits, specific power limits, or fuel burnup limits - whichever yields the largest mass. RSMASS requires the reactor power and energy, 24 reactor parameters, and 20 shield parameters to be specified. This parametric approach should provide good mass estimates for a very broad range of reactor types. Reactor and shield masses calculated by RSMASS were found to be in good agreement with the masses obtained from detailed calculations