8,674 research outputs found
PSR J0737-3039B: A probe of radio pulsar emission heights
In the double pulsar system PSR J0737-3039A/B the strong wind produced by
pulsar A distorts the magnetosphere of pulsar B. The influence of these
distortions on the orbital-dependent emission properties of pulsar B can be
used to determine the location of the coherent radio emission generation region
in the pulsar magnetosphere. Using a model of the wind-distorted magnetosphere
of pulsar B and the well defined geometrical parameters of the system, we
determine the minimum emission height to be ~ 20 neutron star radii in the two
bright orbital longitude regions. We can determine the maximum emission height
by accounting for the amount of deflection of the polar field line with respect
to the magnetic axis using the analytical magnetic reconnection model of Dungey
and the semi-empirical numerical model of Tsyganenko. Both of these models
estimate the maximum emission height to be ~ 2500 neutron star radii. The
minimum and maximum emission heights we calculate are consistent with those
estimated for normal isolated pulsars.Comment: 29 pages, 14 figures, Accepted by ApJ on 3 March 201
DETERMINANTS OF ENTREPRENEURIAL INTENTIONS: TECHNICAL VOCATIONAL EDUCATION AND TRAINING (TVET) IN SRI LANKA
Purpose of the study: This study is focused to investigate the determinants of the entrepreneurial intention of Technical Vocational Education and Training (TVET) students in Sri Lanka.
Methodology: The research model comprises seven independent variables i.e. entrepreneurial attitude, perceived self-efficacy, social capital, demographic factors, perceived financial support, perceived regulatory support, perceived technical vocational education, and training and dependent variables of entrepreneurial intention. The primary data was collected through administering structured questionnaires among a hundred and twenty-eight TVET students represented by three TVET sector institutions in Sri Lanka. Linear regression was applied to test the hypotheses.
Main Findings: The findings of the study revealed a positive and significant impact of the variables of entrepreneurial attitudes and perceived technical vocational education and training on entrepreneurial intention of TVET students of Sri Lanka. TVET student attitudes pertaining to entrepreneurship intention are positive since they perceive that TVET enhances their entrepreneurship education and this is very important to the policymakers in entrepreneurship development to initiate effective strategies to foster entrepreneurship for TVET students.
Implications: This research study provides an academic contribution to enhance the entrepreneurial intention among the TVET students in Sri Lanka
Macropolyhedral boron-containing cluster chemistry. Ligand-induced two-electron variations of intercluster bonding intimacy. Structures of nineteen-vertex[(eta(5)-C5Me5) HIrB18H19(PMe2Ph)] and the related carbene complex [(eta(5)-C5Me5)HIrB18H19{C(NHMe)(2)}]
Addition of PMe2Ph to fused-cluster syn-[(η5-C5Me5)IrB18H20] 1 to give [(η5-C5Me5)HIrB18H19(PMe2Ph)] 3 entails a diminution in the degree of intimacy of the intercluster fusion, rather than retention of inter-subcluster binding intimacy and a nido → arachno conversion of the character of either of the subclusters. Reaction with MeNC gives [(η5-C5Me5)HIrB18H19{C(NHMe)2}] 4 which has a similar structure, but with the ligand now being the carbene {:C(NHMe)2}, resulting from a reductive assembly reaction involving two MeNC residues and the loss of a carbon atom
Macropolyhedral boron-containing cluster chemistry: two-electron variations in intercluster bonding intimacy. Contrasting structures of 19-vertex [(eta(5)-C5Me5)HIrB18H19(PHPh2)] and [(eta(5) -C5Me5)IrB18H18(PH2Ph)]
Fused double-cluster [(5-C5Me5)IrB18H18(PH2Ph)]8, from syn-[(5-C5Me5)IrB18H20] 1 and PH2Ph, retains the three-atoms-in-common cluster fusion intimacy of 1, in contrast to [(5-C5Me5)HIrB18H19(PHPh2)]6, from PHPh2 with 1, which exhibits an opening to a two atoms-in-common cluster fusion intimacy. Compound 8 forms via spontaneous dihydrogen loss from its precursor [(5-C5Me5)HIrB18H19(PH2Ph)]7, which has two-atoms-in-common cluster-fusion intimacy and is structurally analogous to 6
Modeling the non-recycled Fermi gamma-ray pulsar population
We use Fermi Gamma-ray Space Telescope detections and upper limits on
non-recycled pulsars obtained from the Large Area Telescope (LAT) to constrain
how the gamma-ray luminosity L depends on the period P and the period
derivative \dot{P}. We use a Bayesian analysis to calculate a best-fit
luminosity law, or dependence of L on P and \dot{P}, including different
methods for modeling the beaming factor. An outer gap (OG) magnetosphere
geometry provides the best-fit model, which is L \propto P^{-a} \dot{P}^{b}
where a=1.36\pm0.03 and b=0.44\pm0.02, similar to but not identical to the
commonly assumed L \propto \sqrt{\dot{E}} \propto P^{-1.5} \dot{P}^{0.5}. Given
upper limits on gamma-ray fluxes of currently known radio pulsars and using the
OG model, we find that about 92% of the radio-detected pulsars have gamma-ray
beams that intersect our line of sight. By modeling the misalignment of radio
and gamma-ray beams of these pulsars, we find an average gamma-ray beaming
solid angle of about 3.7{\pi} for the OG model, assuming a uniform beam. Using
LAT-measured diffuse fluxes, we place a 2{\sigma} upper limit on the average
braking index and a 2{\sigma} lower limit on the average surface magnetic field
strength of the pulsar population of 3.8 and 3.2 X 10^{10} G, respectively. We
then predict the number of non-recycled pulsars detectable by the LAT based on
our population model. Using the two-year sensitivity, we find that the LAT is
capable of detecting emission from about 380 non-recycled pulsars, including
150 currently identified radio pulsars. Using the expected five-year
sensitivity, about 620 non-recycled pulsars are detectable, including about 220
currently identified radio pulsars. We note that these predictions
significantly depend on our model assumptions.Comment: 26 pages, 10 figures, Accepted by ApJ on 8 September 201
The International Pulsar Timing Array: second data release
In this paper, we describe the International Pulsar Timing Array second data release, which includes recent pulsar timing data obtained by three regional consortia: the European Pulsar Timing Array, the North American Nanohertz Observatory for Gravitational Waves, and the Parkes Pulsar Timing Array. We analyse and where possible combine high-precision timing data for 65 millisecond pulsars which are regularly observed by these groups. A basic noise analysis, including the processes which are both correlated and uncorrelated in time, provides noise models and timing ephemerides for the pulsars. We find that the timing precisions of pulsars are generally improved compared to the previous data release, mainly due to the addition of new data in the combination. The main purpose of this work is to create the most up-to-date IPTA data release. These data are publicly available for searches for low-frequency gravitational waves and other pulsar science
Levantamento da comunidade de macroinvertebrados bentĂ´nicos em lavouras de arroz irrigado.
bitstream/item/67320/1/Boletim-148-corrigido.pd
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