8,202 research outputs found
Chasing the second gamma-ray bright isolated neutron star: 3EG J1835+5918/RX J1836.2+5925
The EGRET telescope aboard NASAs Compton GRO has repeatedly detected 3EG
J1835+5918, a bright and steady source of high-energy gamma-ray emission with
no identification suggested until recently. The long absence of any likely
counterpart for a bright gamma-ray source located 25 degrees off the Galactic
plane initiated several attempts of deep observations at other wavelengths. We
report on counterparts in X-rays on a basis of a 60 ksec ROSAT HRI image. In
order to conclude on the plausibility of the X-ray counterparts, we reanalyzed
data from EGRET at energies above 100 MeV and above 1 GeV, including data up to
CGRO observation cycle 7. The gamma-ray source location represents the latest
and probably the final positional assessment based on EGRET data. The X-ray
counterparts were studied during follow-up optical identification campaigns,
leaving only one object to be likely associated with the gamma-ray source 3EG
J1835+5918. This object, RX J1836.2+5925, has the characteristics of an
isolated neutron star and possibly of a radio-quiet pulsar.Comment: 5 pages, 3 figures. To appear in the Proceedings of the 270.
WE-Heraeus Seminar on Neutron Stars, Pulsars and Supernova Remnants, Jan.
21-25, 2002, Physikzentrum Bad Honnef, eds W. Becker, H. Lesch & J. Truemper.
Proceedings are available as MPE-Report 27
A note on behaviour at an isotropic singularity
The behaviour of Jacobi fields along a time-like geodesic running into an
isotropic singularity is studied. It is shown that the Jacobi fields are
crushed to zero length at a rate which is the same in every direction
orthogonal to the geodesic. We show by means of a counter-example that this
crushing effect depends crucially on a technicality of the definition of
isotropic singularities, and not just on the uniform degeneracy of the metric
at the singularity.Comment: 13 pp. plain latex. To appear in Classical and Quantum Gravit
Pengaruh Kualitas Ransum Dna Temperatur Lingkungan
Penelitian untuk mengetahui pengaruh ransum dan suhu lingkungan terhadap karakteristik karkas dan daging telah dilakukan dengan menggunakan 16 ekor domba persilangan Border Leicester x Merino jantan kastrasi, umur 7 bulan, bobot 33.0+1.49 kg. Domba-bomba tersebut dialokasikan secara acak pada perlakuan dalam rancangan acak kelompok dengan struktur faktorial 2 x 2. Perlakuan yang diterapkan adalah suhu lingkungan (20° and 30°C) dan ransum (RPTS: rendah protein tinggi serat, dan TPRS: tinggi protein rendah serat). Ransum TPRS memberikan hasil persentase karkas dan ketebalan lemak punggung yang lebih tinggi daripada ransum RPTS (49.7 vs 44.4 % dan 14.2 vs 6.8 mm berturutan), tetapi tidak terdapat pengaruh nyata suhu terhadap karakteristik karkas. Terdapat interaksi nyata antara suhu dan ransum pada otot mata rusuk. Pada domba yang mendapat ransum RPTS, suhu berpengaruh nyata, sementara pada domba yang mendapat TPRS, suhu tidak berpengaruh nyata. Daging domba yang diberi RPTS mempunyai rasa yang lebih enak daripada domba yang dib,_.i TPRS. Suhu tidak berpengaruh nyata terhadap aroma daging. Baik suhu maupun ransum tidak berpengaruh nyata pada pH, warna maupun keempukan daging.
(Kata kunci: Domba jantan kastrasi, Cekaman panas, Karkas, Daging)
Solving the time-dependent Schr\"odinger equation with absorbing boundary conditions and source terms in Mathematica 6.0
In recent decades a lot of research has been done on the numerical solution
of the time-dependent Schr\"odinger equation. On the one hand, some of the
proposed numerical methods do not need any kind of matrix inversion, but source
terms cannot be easily implemented into this schemes; on the other, some
methods involving matrix inversion can implement source terms in a natural way,
but are not easy to implement into some computational software programs widely
used by non-experts in programming (e.g. Mathematica). We present a simple
method to solve the time-dependent Schr\"odinger equation by using a standard
Crank-Nicholson method together with a Cayley's form for the finite-difference
representation of evolution operator. Here, such standard numerical scheme has
been simplified by inverting analytically the matrix of the evolution operator
in position representation. The analytical inversion of the N x N matrix let us
easily and fully implement the numerical method, with or without source terms,
into Mathematica or even into any numerical computing language or computational
software used for scientific computing.Comment: 15 pages, 7 figure
Patient reactions to a web-based cardiovascular risk calculator in type 2 diabetes: a qualitative study in primary care.
Use of risk calculators for specific diseases is increasing, with an underlying assumption that they promote risk reduction as users become better informed and motivated to take preventive action. Empirical data to support this are, however, sparse and contradictory
Forecasting GDP Growth using Disaggregated GDP Revisions
This paper investigates the informational content of regular revisions to real GDP growth and its components. We perform a real-time forecasting exercise for the advance estimate of real GDP growth using dynamic regression models that include revisions to GDP and its components. Echoing other work in the literature, we find little evidence that including aggregate GDP growth revisions improves forecast accuracy relative to an AR(1) baseline model; however, models that include revisions to components of GDP improve forecast accuracy. The first revision to consumption is particularly relevant in that every model that includes the revision outperforms the baseline model. Measured by root mean squared forecasting error (RMSFE), improvements are quite sizable, with many models increasing forecasting performance by 5% or more, and with top-performing models forecasting 0.24 percentage points closer to the advance estimate of growth. We use Bayesian model averaging to underscore that our results are driven by the informational content of revisions. The posterior probability of models with the first revision to consumption is significantly higher than our baseline model, despite strong priors that the latter should be the preferred forecasting model
Cooperative solar radiation data collection program, Fort Collins, Colorado, June 1985-May 1986
September 1986.Funding shared by the Colorado Agricultural Experiment Station and Fort Collins Light and Power
Goodness-of-Fit Tests for Symmetric Stable Distributions -- Empirical Characteristic Function Approach
We consider goodness-of-fit tests of symmetric stable distributions based on
weighted integrals of the squared distance between the empirical characteristic
function of the standardized data and the characteristic function of the
standard symmetric stable distribution with the characteristic exponent
estimated from the data. We treat as an unknown parameter,
but for theoretical simplicity we also consider the case that is
fixed. For estimation of parameters and the standardization of data we use
maximum likelihood estimator (MLE) and an equivariant integrated squared error
estimator (EISE) which minimizes the weighted integral. We derive the
asymptotic covariance function of the characteristic function process with
parameters estimated by MLE and EISE. For the case of MLE, the eigenvalues of
the covariance function are numerically evaluated and asymptotic distribution
of the test statistic is obtained using complex integration. Simulation studies
show that the asymptotic distribution of the test statistics is very accurate.
We also present a formula of the asymptotic covariance function of the
characteristic function process with parameters estimated by an efficient
estimator for general distributions
Endothelial progenitor cells control the angiogenic switch in mouse lung metastasis
Angiogenesis-mediated progression of micrometastasis to lethal macrometastasis is the major cause of death in cancer patients. Here, using mouse models of pulmonary metastasis, we identify bone marrow (BM)-derived endothelial progenitor cells (EPCs) as critical regulators of this angiogenic switch. We show that tumors induce expression of the transcription factor Id1 in the EPCs and that suppression of Id1 after metastatic colonization blocked EPC mobilization, caused angiogenesis inhibition, impaired pulmonary macrometastases, and increased survival of tumor-bearing animals. These findings establish the role of EPCs in metastatic progression in preclinical models and suggest that selective targeting of EPCs may merit investigation as a therapy for cancer patients with lung metastases
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