22,430 research outputs found
Nonaxisymmetric MHD instabilities of Chandrasekhar states in Taylor-Couette geometry
We consider axially periodic Taylor-Couette geometry with insulating boundary
conditions. The imposed basic states are so-called Chandrasekhar states, where
the azimuthal flow and magnetic field have the same radial
profiles. Mainly three particular profiles are considered: the Rayleigh limit,
quasi-Keplerian, and solid-body rotation. In each case we begin by computing
linear instability curves and their dependence on the magnetic Prandtl number
Pm. For the azimuthal wavenumber m=1 modes, the instability curves always scale
with the Reynolds number and the Hartmann number. For sufficiently small Pm
these modes therefore only become unstable for magnetic Mach numbers less than
unity, and are thus not relevant for most astrophysical applications. However,
modes with m>10 can behave very differently. For sufficiently flat profiles,
they scale with the magnetic Reynolds number and the Lundquist number, thereby
allowing instability also for the large magnetic Mach numbers of astrophysical
objects. We further compute fully nonlinear, three-dimensional equilibration of
these instabilities, and investigate how the energy is distributed among the
azimuthal (m) and axial (k) wavenumbers. In comparison spectra become steeper
for large m, reflecting the smoothing action of shear. On the other hand
kinetic and magnetic energy spectra exhibit similar behavior: if several
azimuthal modes are already linearly unstable they are relatively flat, but for
the rigidly rotating case where m=1 is the only unstable mode they are so steep
that neither Kolmogorov nor Iroshnikov-Kraichnan spectra fit the results. The
total magnetic energy exceeds the kinetic energy only for large magnetic
Reynolds numbers Rm>100.Comment: 12 pages, 14 figures, submitted to Ap
CSIC Abierto 5
12 páginas, imágenes.La revista "CSIC Abierto" está dividida en 2 partes, una primera que informa sobre noticias varias de Digital.CSIC y da a conocer las investigaciones científicas depositadas en la plataforma así como las comunidades científica y bibliotecaria de los respectivos centros y una segunda parte que difunde recursos de interés y novedades en el contexto general del acceso abierto.Noticias de Digital.CSIC: La investigación del CSIC en abierto: 1. la Escuela de Estudios Árabes (EEA). 2. El Instituto de Recursos Naturales y Agrobiología (IRNASA).-- Novedades en Digital.CSIC: 3.Tiempo para nuevos modelos de comunicación y difusión de la ciencia. 4. Twitter de Digital.CSIC. 5. Los handles de las noticias. --Noticias y recursos de interés: 6. LiquidPub, un proyecto europeo de acceso abierto con participación CSIC. 7. ¿Qué porcentaje de revistas científicas permiten el auto-archivo?. 8. ¿Es inevitable la gratuitidad en la comunicación científica?Peer reviewe
State education as high-yield investment: human capital theory in European policy discourse
Human Capital Theory has been an increasingly important phenomenon in economic thought over the last 50 years. The central role it affords to education has become even more marked in recent years as the concept of the ‘knowledge economy’ has become a global concern. In this paper, the prevalence of Human Capital Theory within European educational policy discourse is explored. The paper examines a selection of policy documents from a number of disparate European national contexts and considers the extent to which the ideas of Human Capital Theory can be seen to be influential. In the second part of the paper, the implications of Human Capital Theory for education are considered, with a particular focus on the possible ramifications at a time of economic austerity. The paper argues that Human Capital Theory risks offering a diminished view of the person, a diminished view of education, but that with its sole focus on economic goals leaves room for educationists and others to argue for the educational, social, and moral values it ignores, and for the conception of the good life and good society it fails to mention
The role of carbon for superconductivity in MgCNi from specific heat
The influence of carbon deficiency on superconductivity of MgCNi is
investigated by specific heat measurements in the normal and superconducting
state. In order to perform a detailed analysis of the normal state specific
heat, a computer code is developed which allows for an instantaneous estimate
of the main features of the lattice dynamics. By analyzing the evolution of the
lattice vibrations within the series and simultaneously considering the visible
mass enhancement, the loss in the electron-phonon coupling can be attributed to
significant changes of the prominent Ni vibrations. The present data well
supports the recently established picture of strong electron-phonon coupling
and ferromagnetic spin fluctuations in this compound.Comment: 4 pages, latex, corrections to the text, one reference added, one
figure correcte
How to make a blastocyst.
Several of the new reproductive technologies have been cultivated from our current understanding of the genetic programming and cellular processes that are involved in the major morphogenetic events of mammalian preimplantation development. Research directed at characterizing the patterns of gene expression during early development has shown that the embryo is initially under maternal control and later superseded by new transcriptional activity provided by the activation of the embryonic genome. Several embryonic transcripts encoding: (i) growth factors, (ii) cell junctions, (iii) plasma membrane ion transporters, and (iv) cell adhesion molecules have been identified as contributing directly to the progression of the embryo through the preimplantation interval of development. In this brief review, we have outlined the patterns of expression and the integral roles that these gene families play in the morphogenetic events of compaction and cavitation. Research of this type has greatly facilitate our understanding of the control processes that underlie preimplantation development and represent but one area of this exciting and vigorous field of research
Variations in swine prices within Iowa including a study in statistical procedure
Iowa\u27s agriculture is chiefly corn-hog farming. Corn, which is produced in abundance, provides the raw material upon which the gigantic livestock industry depends. The sale of swine is the most important source of income of the state.
Profound changes have taken place in the economics of hog marketing during the last decade. Three-fifths of Iowa hogs are today sold direct to packers; receipts at public stockyards have declined accordingly. Concentration points have been established throughout the hog producing area. Order buying has become well developed. Add to these the improvements in rural transportation, better market news facilities, standardization of hog grades and the comparatively large scale country buying that is practiced today and it becomes apparent that the machinery for marketing hogs is strikingly different from that which served producers only a few years ago
Rugged Metropolis Sampling with Simultaneous Updating of Two Dynamical Variables
The Rugged Metropolis (RM) algorithm is a biased updating scheme, which aims
at directly hitting the most likely configurations in a rugged free energy
landscape. Details of the one-variable (RM) implementation of this
algorithm are presented. This is followed by an extension to simultaneous
updating of two dynamical variables (RM). In a test with Met-Enkephalin in
vacuum RM improves conventional Metropolis simulations by a factor of about
four. Correlations between three or more dihedral angles appear to prevent
larger improvements at low temperatures. We also investigate a multi-hit
Metropolis scheme, which spends more CPU time on variables with large
autocorrelation times.Comment: 8 pages, 5 figures. Revisions after referee reports. Additional
simulations for temperatures down to 220
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