AME - Asteroseismology Made Easy. Estimating stellar properties by use of scaled models

We present a new method to obtain stellar properties for stars exhibiting solar-like oscillations in an easy, fast, and transparent way. The method, called Asteroseismology Made Easy (AME), can determine stellar masses, mean-densities, radii, and surface gravities, as well as estimate ages. In this writing we present AME as a visual and powerful tool which could be useful; in particular in the light of the large number of exoplanets being found. AME consists of a set of figures from which the stellar parameters are deduced. These figures are made from a grid of stellar evolutionary models that cover masses ranging from 0.7 Msun to 1.6 Msun in steps of 0.1 Msun and metallicities in the interval -0.3 dex <= [Fe/H] <= +0.3 dex in increments of 0.1 dex. The stellar evolutionary models are computed using the Modules for Experiments in Stellar Astrophysics (MESA) code with simple input physics. We have compared the results from AME with results for three groups of stars; stars with radii determined from interferometry (and measured parallaxes), stars with radii determined from measurements of their parallaxes (and calculated angular diameters), and stars with results based on the modelling of their individual oscillation frequencies. We find that a comparison of the radii from interferometry to those from AME yield a weighted mean of the fractional differences of just 2%. This is also the level of deviation that we find when we compare the parallax-based radii to the radii determined from AME. The comparison between independently determined stellar parameters and those found using AME show that our method can provide reliable stellar masses, radii, and ages, with median uncertainties in the order of 4%, 2%, and 25% respectively.Comment: 18 pages, 25 figures. To be published in Astronomy & Astrophysic

Electron degeneracy and intrinsic magnetic properties of epitaxial Nb:SrTiO3_3 thin-films controlled by defects

We report thermoelectric power experiments in e-doped thin films of SrTiO$_3$ (STO) which demonstrate that the electronic band degeneracy can be lifted through defect management during growth. We show that even small amounts of cationic vacancies, combined with epitaxial stress, produce a homogeneous tetragonal distortion of the films, resulting in a Kondo-like resistance upturn at low temperature, large anisotropic magnetoresistance, and non-linear Hall effect. Ab-initio calculations confirm a different occupation of each band depending on the degree of tetragonal distortion. The phenomenology reported in this paper for tetragonally distorted e-doped STO thin films, is similarto that observed in LaAlO$_3$/STO interfaces and magnetic STO quantum wells.Comment: 5 pages, 5 figure

Landau parameters for isospin asymmetric nuclear matter based on a relativistic model of composite and finite extension nucleons

We study the properties of cold asymmetric nuclear matter at high density, applying the quark meson coupling model with excluded volume corrections in the framework of the Landau theory of relativistic Fermi liquids. We discuss the role of the finite spatial extension of composite baryons on dynamical and statistical properties such as the Landau parameters, the compressibility, and the symmetry energy. We have also calculated the low lying collective eigenfrequencies arising from the collisionless quasiparticle transport equation, considering both unstable and stable modes. An overall analysis of the excluded volume correlations on the collective properties is performed.Comment: 24 pages, 6 figure

Spin Seebeck effect in Y-type hexagonal ferrite thin films

Spin Seebeck effect (SSE) has been investigated in thin films of two Y-hexagonal ferrites Ba$_2$Zn$_{2}$Fe$_{12}$O$_{22}$ (Zn2Y) and Ba$_2$Co$_{2}$Fe$_{12}$O$_{22}$ (Co2Y) deposited by a spin-coating method on SrTiO$_3$(111) substrate. The selected hexagonal ferrites are both ferrimagnetic with similar magnetic moments at room temperature and both exhibit easy magnetization plane normal to $c$-axis. Despite that, SSE signal was only observed for Zn2Y, whereas no significant SSE signal was detected for Co2Y. We tentatively explain this different behavior by a presence of two different magnetic ions in Co2Y, whose random distribution over octahedral sites interferes the long range ordering and enhances the Gilbert damping constant. The temperature dependence of SSE for Zn2Y was measured and analyzed with regard to the heat flux and temperature gradient relevant to the SSE signal.Comment: 7 pages, 9 figure

Does tutor subject-matter expertise influence student achievement in the problem based learning curriculum at UNITRA medical school?

Objective. To establish whether or not tutor subject-matter expertise influences student achievement in content-based examinations in the problem-based learning (PBL) curriculum at the University of Transkei (UNITRA) Medical School.Design. A retrospective study of MB ChB III student achievement in end-of-block modified essay questions (MEQ) examinations in microbiology, pathology and pharmacology for the years 1994 - 1999, inclusive. Pooled scores from the expert-tutored groups were compared with those from the groups tutored by non-experts using analysis of variance (ANOVA) or t-test. Subject expert tutors were those with postgraduate specialisation in the given discipline.Setting. The Medical School, Faculty of Health Sciences, UNITRA, Umtata.Outcome measures. Whether pooled mean MEQ scores in end-of-block examinations for microbiology, pathology or pharmacology differ according to the subject-matter expertise of the tutor.Results. There were no significant differences in mean scores obtained for pharmacology (51.1 ± 0.6 versus 52.6 ± 0.7, P = 0.109) and pathology (49.8 ± 0.6 versus 49.9 ± 0.8, P = 0.919). The difference between the scores in microbiology was small (3 percentage points) but statistically significant, with the groups tutored by microbiologists scoring higher than those tutored by pathologists or pharmacologists (54.1 ± 1.0 versus 51.2 ± 0.8, P = 0.032).Conclusions. These data demonstrate that in the UNITRA Medical School PBL curriculum tutor subject-matter expertise has little or no influence on student achievement in the discrete areas of tutor expertise

Development of Aluminum LEKIDs for Balloon-Borne Far-IR Spectroscopy

We are developing lumped-element kinetic inductance detectors (LEKIDs) designed to achieve background-limited sensitivity for far-infrared (FIR) spectroscopy on a stratospheric balloon. The Spectroscopic Terahertz Airborne Receiver for Far-InfraRed Exploration (STARFIRE) will study the evolution of dusty galaxies with observations of the [CII] 158 $\mu$m and other atomic fine-structure transitions at $z=0.5-1.5$, both through direct observations of individual luminous infrared galaxies, and in blind surveys using the technique of line intensity mapping. The spectrometer will require large format ($\sim$1800 detectors) arrays of dual-polarization sensitive detectors with NEPs of $1 \times 10^{-17}$ W Hz$^{-1/2}$. The low-volume LEKIDs are fabricated with a single layer of aluminum (20 nm thick) deposited on a crystalline silicon wafer, with resonance frequencies of $100-250$ MHz. The inductor is a single meander with a linewidth of 0.4 $\mu$m, patterned in a grid to absorb optical power in both polarizations. The meander is coupled to a circular waveguide, fed by a conical feedhorn. Initial testing of a small array prototype has demonstrated good yield, and a median NEP of $4 \times 10^{-18}$ W Hz$^{-1/2}$.Comment: accepted for publication in Journal of Low Temperature Physic

Observation of huge thermal spin currents in magnetic multilayers

Thermal spin pumping constitutes a novel mechanism for generation of spin currents; however their weak intensity constitutes a major roadblock for its usefulness. We report a phenomenon that produces a huge spin current in the central region of a multilayer system, resulting in a giant spin Seebeck effect in a structure formed by repetition of ferromagnet/metal bilayers. The result is a consequence of the interconversion of magnon and electron spin currents at the multiple interfaces. This work opens the possibility to design thin film heterostructures that may boost the application of thermal spin currents in spintronics

Survival Rate and Morphological Growth Patterns of Five Populations of \u3cem\u3eFestuca dolichophylla\u3c/em\u3e Under Similar Conditions

The majority of the natural grasslands of Perú are located in the Puna region; they are the only source of feed for raising animals in this area, and they also protect the soil from erosion. Festuca dolichophylla is a representative species with high productivity in this ecosystem. The aim of this study was to evaluate survival rate and morphological growth patterns of five populations of Festuca dolichophylla under similar conditions. Five accessions were obtained from each population: Pastales Huando Peasant Community - Huancavelica (CCPH), Lachocc South American Camelids Research and Development Center of the National University of Huancavelica (CIDCSL), Junin, Pasco, and Puno. Six cuttings were obtained from each accession. They were planted in a block design in a uniform soil in the CCPH. After twelve months of establishment all plants were cut to five cm in height and survival rate was estimated. Plant height, number of stems, and leaf number were monitored twice a month; growth rate, stem emergence rate, and leaf emergence rate were calculated and data was analyzed for each month. Accessions from Puno had a 96.67% survival rate, which was significantly higher (p\u3c0.05) than accessions from CIDCSL (43.33% survival) but similar to accessions from the other populations. The morphological growth patterns showed differences between populations and high variability along the evaluation period; this variability and differences are likely due to the genetic constitution of each accession since the environment was similar. This information is crucial for further genetic breeding programs; however, first a morphologic and genetic characterization is necessary. We also observed an orderly growth of this species; first, the plants grow in size, then they increase their stem number, and finally the number of leaves increases. To our knowledge this is the first study that compares morphological growth patterns in different populations of Festuca dolichophylla under similar conditions

Detecting periodicity in experimental data using linear modeling techniques

Fourier spectral estimates and, to a lesser extent, the autocorrelation function are the primary tools to detect periodicities in experimental data in the physical and biological sciences. We propose a new method which is more reliable than traditional techniques, and is able to make clear identification of periodic behavior when traditional techniques do not. This technique is based on an information theoretic reduction of linear (autoregressive) models so that only the essential features of an autoregressive model are retained. These models we call reduced autoregressive models (RARM). The essential features of reduced autoregressive models include any periodicity present in the data. We provide theoretical and numerical evidence from both experimental and artificial data, to demonstrate that this technique will reliably detect periodicities if and only if they are present in the data. There are strong information theoretic arguments to support the statement that RARM detects periodicities if they are present. Surrogate data techniques are used to ensure the converse. Furthermore, our calculations demonstrate that RARM is more robust, more accurate, and more sensitive, than traditional spectral techniques.Comment: 10 pages (revtex) and 6 figures. To appear in Phys Rev E. Modified styl