799 research outputs found
Do the Herschel cold clouds in the Galactic halo embody its dark matter?
Recent Herschel/SPIRE maps of the Small and Large Magellanic Clouds (SMC,
LMC) exhibit in each thousands of clouds. Observed at 250 microns, they must be
cold, T ~ 15 K, hence the name "Herschel cold clouds" (HCCs). From the observed
rotational velocity profile and the assumption of spherical symmetry, the
Galactic mass density is modeled in a form close to that of an isothermal
sphere. If the HCCs constitute a certain fraction of it, their angular size
distribution has a specified shape. A fit to the data deduced from the SMC/LMC
maps supports this and yields for their radius 2.5 pc, with a small change when
allowing for a spread in HCC radii. There are so many HCCs that they will make
up all the missing Halo mass density if there is spherical symmetry and their
average mass is of order 15,000 Mo. This compares well with the Jeans mass of
circa 40,000 Mo and puts forward that the HCCs are in fact Jeans clusters,
constituting all the Galactic dark matter and much of its missing baryons, a
conclusion deduced before from a different field of the sky (Nieuwenhuizen,
Schild and Gibson 2011). A preliminary analysis of the intensities yields that
the Jeans clusters themselves may consist of some billion MACHOs of a few dozen
Earth masses. With a size of dozens of solar radii, they would mostly obscure
stars in the LMC, SMC and towards the Galactic center, and may thus have been
overlooked in microlensing.Comment: Revised and corrected version, matches published version. Conclusions
unchange
Analisis Produksi dan Pendapatan USAhatani Kacang Tanah di Kabupaten Tapanuli Utara (Studi Kasus: Desa Banuaji IV, Kecamatan Adiankoting)
Penelitian ini bertujuan untuk mengetahui sistem USAhatani kacang tanah, tingkat produksi kacang tanah, faktor-faktor yang mempengaruhi tingkat produksi dan pendapatan USAhatani kacang tanah, serta layak atau tidaknya USAhatani kacang tanah dikembangkan di Desa Banuaji IV, Kecamatan Adiankoting, Kabupaten Tapanuli Utara. Pengambilan sampel dilakukan secara simple random sampling dengan jumlah sampel 30 KK berasal dari 255 KK. Metode penelitian yang digunakan adalah: skoring; analisis data deskriptif; Fungsi produksi Cobb-Douglass dan regresi linear berganda ; Analisis Usahatani rasio R/C. Hasil penelitian menunjukkan sistem USAhatani kacang tanah belum sesuai dengan sistem USAhatani anjuran, tingkat produksi kacang tanah tergolong rendah, faktor-faktor produksi yang mempengaruhi tingkat produksi kacang tanah adalah pupuk Phonska, TSP dan jumlah tenaga kerja, sementara faktor biaya produksi yang berpengarh nyata terhadap pendapatan USAhatani kacang tanah adalah biaya penyusutan peralatan, USAhatani kacang tanah layak dikembangkan di lokasi penelitian
Happiness, environmental protection and market economy
The manufacturing sector is leaving the West for Asiaâs low wages and good working culture. Europe would be better off keeping these manufacturing activities, slowing down wage inflation and what is more, letting a young, cheaper workforce from the East settle down within their borders. This would aid in preserving the diverse economic structure which has been characteristic for Europe.Beside the economic growth there are two more concepts which have turned into the âholy cowsâ of economics during the last fifty years. One is the need to constantly improve labor productivity and the other is increasing competitiveness of nations. The high labor productivity of some countries, induces severe unemployment in the globalized world. In the other hand it is high time we understood that it is not competition, but cooperation that brings more happiness to humanity.Should we still opt for âhappinessâ and âsanityâ, it is quite obvious that we all should, in economistsâ terms, define our individual welfare functions corresponding to our own set of values, staying free from the influence of media, advertisements and fashion. The cornerstone to all this is the intelligent citizen who prefers local goods and services
Simulation of the hydrogen ground state in Stochastic Electrodynamics
Stochastic electrodynamics is a classical theory which assumes that the
physical vacuum consists of classical stochastic fields with average energy
in each mode, i.e., the zero-point Planck spectrum.
While this classical theory explains many quantum phenomena related to harmonic
oscillator problems, hard results on nonlinear systems are still lacking. In
this work the hydrogen ground state is studied by numerically solving the
Abraham -- Lorentz equation in the dipole approximation. First the stochastic
Gaussian field is represented by a sum over Gaussian frequency components, next
the dynamics is solved numerically using OpenCL. The approach improves on work
by Cole and Zou 2003 by treating the full problem and reaching longer
simulation times. The results are compared with a conjecture for the ground
state phase space density. Though short time results suggest a trend towards
confirmation, in all attempted modelings the atom ionises at longer times.Comment: 20 pages, 9 figures. Published version, minor change
OPE statistics from higher-point crossing
We present new asymptotic formulas for the distribution of OPE coefficients in conformal field theories. These formulas involve products of four or more coefficients and include light-light-heavy as well as heavy-heavy-heavy contributions. They are derived from crossing symmetry of the six and higher point functions on the plane and should be interpreted as non-Gaussianities in the statistical distribution of the OPE coefficients. We begin with a formula for arbitrary operator exchanges (not necessarily primary) valid in any dimension. This is the first asymptotic formula constraining heavy-heavy-heavy OPE coefficients in d > 2. For two-dimensional CFTs, we present refined asymptotic formulas stemming from exchanges of quasi-primaries as well as Virasoro primaries.We present new asymptotic formulas for the distribution of OPE coefficients in conformal field theories. These formulas involve products of four or more coefficients and include light-light-heavy as well as heavy-heavy-heavy contributions. They are derived from crossing symmetry of the six and higher point functions on the plane and should be interpreted as non-Gaussianities in the statistical distribution of the OPE coefficients. We begin with a formula for arbitrary operator exchanges (not necessarily primary) valid in any dimension. This is the first asymptotic formula constraining heavy-heavy-heavy OPE coefficients in . For two-dimensional CFTs, we present refined asymptotic formulas stemming from exchanges of quasi-primaries as well as Virasoro primaries
Potential Vorticity Evolution of a Protoplanetary Disk with An Embedded Protoplanet
We present two-dimensional inviscid hydrodynamic simulations of a
protoplanetary disk with an embedded planet, emphasizing the evolution of
potential vorticity (the ratio of vorticity to density) and its dependence on
numerical resolutions. By analyzing the structure of spiral shocks made by the
planet, we show that progressive changes of the potential vorticity caused by
spiral shocks ultimately lead to the excitation of a secondary instability. We
also demonstrate that very high numerical resolution is required to both follow
the potential vorticity changes and identify the location where the secondary
instability is first excited. Low-resolution results are shown to give the
wrong location. We establish the robustness of a secondary instability and its
impact on the torque onto the planet. After the saturation of the instability,
the disk shows large-scale non-axisymmetry, causing the torque on the planet to
oscillate with large amplitude. The impact of the oscillating torque on the
protoplanet's migration remains to be investigated.Comment: 17 pages total with 9 figures (Fig.4,5,9 are in .jpg), accepted to
Ap
Fish schooling as a basis for vertical axis wind turbine farm design
Most wind farms consist of horizontal axis wind turbines (HAWTs) due to the
high power coefficient (mechanical power output divided by the power of the
free-stream air through the turbine cross-sectional area) of an isolated
turbine. However when in close proximity to neighbouring turbines, HAWTs suffer
from a reduced power coefficient. In contrast, previous research on vertical
axis wind turbines (VAWTs) suggests that closely-spaced VAWTs may experience
only small decreases (or even increases) in an individual turbine's power
coefficient when placed in close proximity to neighbours, thus yielding much
higher power outputs for a given area of land. A potential flow model of
inter-VAWT interactions is developed to investigate the effect of changes in
VAWT spatial arrangement on the array performance coefficient, which compares
the expected average power coefficient of turbines in an array to a
spatially-isolated turbine. A geometric arrangement based on the configuration
of shed vortices in the wake of schooling fish is shown to significantly
increase the array performance coefficient based upon an array of 16x16 wind
turbines. Results suggest increases in power output of over one order of
magnitude for a given area of land as compared to HAWTs.Comment: Submitted for publication in BioInspiration and Biomimetics. Note:
The technology described in this paper is protected under both US and
international pending patents filed by the California Institute of Technolog
TFLink: an integrated gateway to access transcription factor-target gene interactions for multiple species
Analysis of transcriptional regulatory interactions and their comparisons across multiple species are crucial for progress in various fields in biology, from functional genomics to the evolution of signal transduction pathways. However, despite the rapidly growing body of data on regulatory interactions in several eukaryotes, no databases exist to provide curated high-quality information on transcription factor-target gene interactions for multiple species. Here, we address this gap by introducing the TFLink gateway, which uniquely provides experimentally explored and highly accurate information on transcription factor-target gene interactions (âŒ12 million), nucleotide sequences and genomic locations of transcription factor binding sites (âŒ9 million) for human and six model organisms: mouse, rat, zebrafish, fruit fly, worm and yeast by integrating 10 resources. TFLink provides user-friendly access to data on transcription factor-target gene interactions, interactive network visualizations and transcription factor binding sites, with cross-links to several other databases. Besides containing accurate information on transcription factors, with a clear labelling of the type/volume of the experiments (small-scale or high-throughput), the source database and the original publications, TFLink also provides a wealth of standardized regulatory data available for download in multiple formats. The database offers easy access to high-quality data for wet-lab researchers, supplies data for gene set enrichment analyses and facilitates systems biology and comparative gene regulation studies. Database URL https://tflink.net/
- âŠ