22,034,675 research outputs found

    "You Can't Study if you're Hungry" Report of a Parliamentary Delegation to Tanzania\ud

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    Confirmation of the detection of B-modes in the Planck polarization maps

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    One of the main problems for extracting the Cosmic Microwave Background (CMB) from submm/mm observations is to correct for the Galactic components, mainly synchrotron, free - free and thermal dust emission with the required accuracy. Through a series of papers, it has been demonstrated that this task can be fulfilled by means of simple neural networks with high confidence. The main purpose of this paper is to demonstrate that the CMB BB power spectrum detected in the Planck 2015 polarization maps is present in the improved Planck 2017 maps with higher signal-to-noise ratio. Two features have been detected in the EB power spectrum in the new data set, both with S/N ∟\sim4 . The origin of these features is most likely leakage from E to B with a level of about 1 per cent. This leakage gives no significant contribution to the detected BB power spectrum. The TB power spectrum is consistent with a zero signal. Altogether, the BB power spectrum is not consistent with the 'canonical' tensor-to-scalar models combined with gravitational lensing spectra. These results will give additional strong arguments for support to the proposed polarization satellite projects to follow up on the Planck mission .Comment: accepted for puplication in Astronomical Note

    Kinetics of exciton photoluminescence in type-II semiconductor superlattices

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    The exciton decay rate at a rough interface in type-II semiconductor superlattices is investigated. It is shown that the possibility of recombination of indirect excitons at a plane interface essentially affects kinetics of the exciton photoluminescence at a rough interface. This happens because of strong correlation between the exciton recombination at the plane interface and at the roughness. Expressions that relate the parameters of the luminescence kinetics with statistical characteristics of the rough interface are obtained. The mean height and length of roughnesses in GaAs/AlAs superlattices are estimated from the experimental data.Comment: 3 PostScript figure

    Reviewing science and technology in the context of the Biological Weapons Convention

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    There is evidence of the emergence of a consensus amongst a number of States Parties to the BWC and NGOs on the principle of changing the process of S&T review as part of the wider quinquennial review process of the BWC. However, there is little evidence of agreement on the details of what needs to be done, how, by whom and to what end. Wrestling with these questions will be essential if state parties wish to capitalise on the momentum that has built up around changing S&T reviews and convert this into an evolution of the practice. With the review conference less than a year away, thinking needs to begin sooner, rather than later

    Using Evaluation to Improve and Promote America Reads

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    This report covers: Project Objectives; Collecting Data; Sample Instruments; Analyzing Data; and Using Evaluation Findings

    An Estimation of the Gamma-Ray Burst Afterglow Apparent Optical Brightness Distribution Function

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    By using recent publicly available observational data obtained in conjunction with the NASA Swift gamma-ray burst mission and a novel data analysis technique, we have been able to make some rough estimates of the GRB afterglow apparent optical brightness distribution function. The results suggest that 71% of all burst afterglows have optical magnitudes with mR < 22.1 at 1000 seconds after the burst onset, the dimmest detected object in the data sample. There is a strong indication that the apparent optical magnitude distribution function peaks at mR ~ 19.5. Such estimates may prove useful in guiding future plans to improve GRB counterpart observation programs. The employed numerical techniques might find application in a variety of other data analysis problems in which the intrinsic distributions must be inferred from a heterogeneous sample.Comment: 15 pages including 2 tables and 7 figures, accepted for publication in Ap

    What works for Nutrition? Stories of success from Vietnam, Uganda and Kenya

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    This report discusses the drivers of progress in tackling multiple forms of malnutrition in these three countries: Vietnam, Uganda, and Kenya. It also identifies some of the challenges which pose as barriers to sustaining progress. Finally, it makes recommendations for key stakeholders such as governments of high burden countries, donor governments, development partners, and civil society, on their role to promote further success

    The Intrinsically X-ray Weak Quasar PHL 1811. I. X-ray Observations and Spectral Energy Distribution

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    This is the first of two papers reporting observations and analysis of the unusually bright (m_b=14.4), luminous (M_B=-25.5), nearby (z=0.192) narrow-line quasar PHL 1811, focusing on the X-ray properties and the spectral energy distribution. Two Chandra observations reveal a weak X-ray source with a steep spectrum. Variability by a factor of 4 between the two observations separated by 12 days suggest that the X-rays are not scattered emission. The XMM-Newton spectra are modelled in the 0.3--5 keV band by a steep power law with \Gamma = 2.3\pm 0.1, and the upper limit on intrinsic absorption is 8.7 x 10^{20} cm^{-2}. The spectral slopes are consistent with power law indices commonly observed in NLS1s, and it appears that we observe the central engine X-rays directly. Including two recent Swift ToO snapshots, a factor of ~5 variability was observed among the five X-ray observations reported here. In contrast, the UV photometry obtained by the XMM-Newton OM and Swift UVOT, and the HST spectrum reveal no significant UV variability. The \alpha_{ox} inferred from the Chandra and contemporaneous HST spectrum is -2.3 \pm 0.1, significantly steeper than observed from other quasars of the same optical luminosity. The steep, canonical X-ray spectra, lack of absorption, and significant X-ray variability lead us to conclude that PHL 1811 is intrinsically X-ray weak. We also discuss an accretion disk model, and the host galaxy of PHL 1811.Comment: 45 pages, 9 figures, accepted for publication in Ap
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