How much do helioseismological inferences depend upon the assumed reference model?

We investigate systematic uncertainties in determining the profiles of the solar sound speed, density, and adiabatic index by helioseismological techniques. We find that rms uncertainties-averaged over the sun of ~ 0.2%-0.4% are contributed to the sound speed profile by each of three sources: 1)the choice of assumed reference model, 2) the width of the inversion kernel, and 3) the measurements errors. The density profile is about an order of magnitude less well determined by the helioseismological measurements. The profile of the adiabatic index is determined to an accuracy of about 0.2% . We find that even relatively crude reference models yield reasonably accurate solar parameters.Comment: Accepted for publication in ApJ . Related material at http://www.sns.ias.edu/~jn

Limfangiektazija jajovoda kao posljedica leiomioma mezosalpinksa u kokoši (Gallus gallus domesticus)

A rare case of oviductal lymphangiectasia was described in a 73-week old Nera-black layer, brought from a farm in the western part of Nigeria with a capacity of 41,000 birds. The layer was found dead inside the cage, without premonitory signs. Necropsy examination revealed marked oedema of the oviduct, with prominent mucosal folds. The dorsal ligament showed prominent and markedly dilated lymphatic vessels, having a discrete, soft but fi rm, pouch-like appearance and a centrally located oval-shaped, solid encapsulated tumorous mass. Histologically, there was severe oedema of the lamina propria, submucosa and muscularis of the oviduct, with ballooning dilatation of their lymphatic vessels and those of the dorsal ligament, which contained deeply eosinophilic proteinaceous fl uid and moderate mononuclear cells, mostly lymphocytes and macrophages. The tumorous mass revealed interlacing bundles of elongated cells that showed eosinophilic cytoplasm and oval to cigar-shaped nuclei. The tumorous mass was positive with Van Gieson stain. This is the fi rst reported case of oviductal lymphangiectasia secondary to mesosalphinx leiomyoma in a domestic chicken.Rijedak slučaj limfangiektazije jajovoda opisan je u 73 tjedna stare nesilice podrijetlom s farme od 41000 ptica u zapadnom dijelu Nigerije. Nesilica je nađena uginula bez prethodnih znakova bolesti. Pri razudbi je ustanovljen edem jajovoda s izraženim sluzničnim naborima. Na dorzalnom ligamentu isticale su se znatno proširene limfne žile s mekanom, ali čvrstom vrećastom tvorevinom u čijem se središtu nalazila jajasta, solidna, učahurena tumorska masa. Histološki je ustanovljen jak edem lamine proprije te submukoze i mišićnice jajovoda s balonskim proširenjem njegovih limfnih žila i onih na dorzalnom ligamentu koje su sadržavale bjelančevinsku tekućinu i eozinofile te nešto mononuklearnih stanica, pretežito limfocita i makrofaga. Tumorska masa sastojala se od isprepletenih snopića izduženih stanica koje su imale eozinofilnu citoplazmu s jezgrama jajastoga do cigarastoga oblika. Tumorska masa bila je pozitivna bojenjem po Van Giesonu. To je prvi opisani slučaj limfangiektazije jajovoda kao posljedice leiomioma mezosalpinksa u domaće kokoši

Writing biology, assessing biology: The nature and effects of variation in terminology

There has been substantial research into terminology as an issue in learning science, especially against the backdrop of concerns over school literacy in science and as sometimes reflected in the poor performance of high school students in assessment tasks. Relevant research has emphasized issues such as lexical load, complexity and metaphor. Variation in the use of terminology has, however, been relatively under researched, although there is evidence that terminology use does vary within and across high school textbooks of science. Drawing on an eclectic theoretical framework comprising transitivity analysis (Halliday 1994), legitimation code theory semantics (Maton 2013a), and the context-specific term model (Gerzymisch-Arbogast 2008), this article identifies and classifies variations in the terminology employed in three high school textbooks of biology in Nigeria. It then determines what impact assessment tasks which use terms that differ from those employed in students’ study materials have on students. Examples are found of variant terminology impeding science literacy and task performance, even though there is reason to suspect such variation might in fact have been leveraged to enhance cognition

Changes in Solar Dynamics from 1995 to 2002

Data obtained by the GONG and MDI instruments over the last seven years are used to study how solar dynamics -- both rotation and other large scale flows -- have changed with time. In addition to the well known phenomenon of bands of faster and slower rotation moving towards the equator and pole, we find that the zonal flow pattern rises upwards with time. Like the zonal flows, the meridional flows also show distinct solar activity related changes. In particular, the anti-symmetric component of the meridional flow shows a decrease in speed with activity. We do not see any significant temporal variations in the dynamics of the tachocline region where the solar dynamo is believed to be operating.Comment: To appear in ApJ, March 1 200

OPserver: interactive online-computations of opacities and radiative accelerations

Codes to compute mean opacities and radiative accelerations for arbitrary chemical mixtures using the Opacity Project recently revised data have been restructured in a client--server architecture and transcribed as a subroutine library. This implementation increases efficiency in stellar modelling where element stratification due to diffusion processes is depth dependent, and thus requires repeated fast opacity reestimates. Three user modes are provided to fit different computing environments, namely a web browser, a local workstation and a distributed grid.Comment: 5 pages, 1 figur

Solar Models: current epoch and time dependences, neutrinos, and helioseismological properties

We calculate accurate solar models and report the detailed time dependences of important solar quantities. We use helioseismology to constrain the luminosity evolution of the sun and report the discovery of semi-convection in evolved solar models that include diffusion. In addition, we compare the computed sound speeds with the results of p-mode observations by BiSON, GOLF, GONG, LOWL, and MDI instruments. We contrast the neutrino predictions from a set of eight standard-like solar models and four deviant (or deficient) solar models with the results of solar neutrino experiments. For solar neutrino and for helioseismological applications, we present present-epoch numerical tabulations of characteristics of the standard solar model as a function of solar radius, including the principal physical and composition variables, sound speeds, neutrino fluxes, and functions needed for calculating solar neutrino oscillations.Comment: Accepted ApJ. Have used refined satellite value for solar luminosity. Changes slightly best neutrino fluxes. Include new references, number density of scatterers of sterile neutrinos, some additional helioseismological predictions. 70 pages, 16 figures, additional material at http://www.sns.ias.edu/~jn

Presupernova Evolution of Rotating Massive Stars I: Numerical Method and Evolution of the Internal Stellar Structure

The evolution of rotating stars with zero-age main sequence (ZAMS) masses in the range 8 to 25 M_sun is followed through all stages of stable evolution. The initial angular momentum is chosen such that the star's equatorial rotational velocity on the ZAMS ranges from zero to ~ 70 % of break-up. Redistribution of angular momentum and chemical species are then followed as a consequence of rotationally induced circulation and instablities. The effects of the centrifugal force on the stellar structure are included. Uncertain mixing efficiencies are gauged by observations. We find, as noted in previous work, that rotation increases the helium core masses and enriches the stellar envelopes with products of hydrogen burning. We determine, for the first time, the angular momentum distribution in typical presupernova stars along with their detailed chemical structure. Angular momentum loss due to (non-magnetic) stellar winds and the redistribution of angular momentum during core hydrogen burning are of crucial importance for the specific angular momentum of the core. Neglecting magnetic fields, we find angular momentum transport from the core to the envelope to be unimportant after core helium burning. We obtain specific angular momenta for the iron core and overlaying material of 1E16...1E17 erg s. These values are insensitive to the initial angular momentum. They are small enough to avoid triaxial deformations of the iron core before it collapses, but could lead to neutron stars which rotate close to break-up. They are also in the range required for the collapsar model of gamma-ray bursts. The apparent discrepancy with the measured rotation rates of young pulsars is discussed.Comment: 62 pages, including 7 tables and 19 figures. Accepted by Ap

Can three-flavor oscillations solve the solar neutrino problem?

The most promising solution to the solar neutrino problem are neutrino oscillations, which usually are analyzed within the reduced 2-flavor scheme, because the solutions found therein reasonably well reproduce the recent data of Super-Kamiokande about the recoil-electron energy spectrum, zenith-angle and seasonal variations, and the event rate data of all the neutrino detectors. In this work, however, a survey of the complete parameter space of 3-flavor oscillations is performed. Basically eight new additional solutions could be identified, where the best one with \Delta m(12)^2=2.7x10^(-10) eV^2, \Delta m(13)^2=1.0x10^(-5) eV^2, \Theta(12)=23, and \Theta(13)=1.3 (denoted SVO) is slightly more probable than any 2-flavor solution. However, including the results of the atmospheric neutrino problem excludes all 3-flavour solutions apart from the SLMA-solution (\Delta m(12)^2=7.9x10^(-6) eV^2, \Delta m(13)^2=2.5x10^(-4) eV^2, \Theta(12)=1.4, and \Theta(13)=20). Besides, the ability of SNO and Borexino to discriminate the various 2- and 3-flavor solutions is investigated. Only with very good statistics in these experiments the correct solution to the solar neutrino problem can be identified unambiguously.Comment: 22 pages, 19 figures, REVTeX, submitted to Phys.Rev.D, article with better resolved figures available under http://www.mpa-garching.mpg.de/~schlattl/public.htm

Astrophysical turbulence modeling

The role of turbulence in various astrophysical settings is reviewed. Among the differences to laboratory and atmospheric turbulence we highlight the ubiquitous presence of magnetic fields that are generally produced and maintained by dynamo action. The extreme temperature and density contrasts and stratifications are emphasized in connection with turbulence in the interstellar medium and in stars with outer convection zones, respectively. In many cases turbulence plays an essential role in facilitating enhanced transport of mass, momentum, energy, and magnetic fields in terms of the corresponding coarse-grained mean fields. Those transport properties are usually strongly modified by anisotropies and often completely new effects emerge in such a description that have no correspondence in terms of the original (non coarse-grained) fields.Comment: 88 pages, 26 figures, published in Reports on Progress in Physic