Polarized Redundant-Baseline Calibration for 21 cm Cosmology Without Adding Spectral Structure

21 cm cosmology is a promising new probe of the evolution of visible matter in our universe, especially during the poorly-constrained Cosmic Dawn and Epoch of Reionization. However, in order to separate the 21 cm signal from bright astrophysical foregrounds, we need an exquisite understanding of our telescopes so as to avoid adding spectral structure to spectrally-smooth foregrounds. One powerful calibration method relies on repeated simultaneous measurements of the same interferometric baseline to solve for the sky signal and for instrumental parameters simultaneously. However, certain degrees of freedom are not constrained by asserting internal consistency between redundant measurements. In this paper, we review the origin of these "degeneracies" of redundant-baseline calibration and demonstrate how they can source unwanted spectral structure in our measurement and show how to eliminate that additional, artificial structure. We also generalize redundant calibration to dual-polarization instruments, derive the degeneracy structure, and explore the unique challenges to calibration and preserving spectral smoothness presented by a polarized measurement.Comment: 12 pages, 3 figures, updated to match the published MNRAS versio

Flight representative positive isolation disconnect

Resolutions were developed for each problem encountered and a tradeoff analysis was performed to select a final configuration for a flight representative PID (Positive Isolation Disconnect) that is reduced in size and comparable in weight and pressure drop to the developmental PID. A 6.35 mm (1/4-inch) line size PID was fabricated and tested. The flight representative PID consists of two coupled disconnect halves, each capable of fluid isolation with essentially zero clearance between them for zero leakage upon disconnect half disengagement. An interlocking foolproofing technique prevents uncoupling of disconnect halves prior to fluid isolation. Future development efforts for the Space Shuttle subsystems that would benefit from the use of the positive isolation disconnect are also recommended. Customary units were utilized for principal measurements and calculations with conversion factors being inserted in equations to convert the results to the international system of units

Targeting the poor and smallholder farmers: empirical evidence from Malawi

This paper develops low cost, reasonably accurate, and simple models for improving the targeting efficiency of development policies in Malawi. Using a stepwise logistic regression (weighted) along with other techniques applied in credit scoring, the research identifies a set of easily observable and verifiable indicators for correctly predicting whether a household is poor or not, based on the 2004-05 Malawi Integrated Household Survey data. The predictive power of the models is assessed using out-of-sample validation tests and receiver operating characteristic curves, whereas the model’s robustness is evaluated by bootstrap simulation methods. Finally, sensitivity analyses are performed using the international and extreme poverty lines. The models developed have proven their validity in an independent sample derived from the same population. Findings suggest that the rural model calibrated to the national poverty line correctly predicts the status of about 69% of poor households when applied to an independent subset of surveyed households, whereas the urban model correctly identifies 64% of poor households. Increasing the poverty line improves the model’s targeting performances, while reducing the poverty line does the opposite. In terms of robustness, the rural model yields a more robust result with a prediction margin ±10% points compared to the urban model. While the best indicator sets can potentially yield a sizable impact on poverty if used in combination with a direct transfer program, some non-poor households would also be targeted as the result of model’s leakage. One major feature of the models is that household score can be easily and quickly computed in the field. Overall, the models developed can be potential policy tools for Malawi.Malawi, poverty targeting, proxy means tests, out-of-sample tests, bootstrap, Food Security and Poverty, Research Methods/ Statistical Methods, I32, C15,

Debating Targeting Methods for Cash Transfers: A Multidimensional Index vs. an Income Proxy for Paraguay?s Tekoporã Programme

There is a lively global debate on how to target beneficiaries of Conditional Cash Transfer (CCT) programmes. In this Evaluation Note we analyze alternative targeting methods for Paraguay?s CCT programme, Tekoporã. The major practical choice for Paraguay is between a multidimensional quality-of-life index and a proxy-means test for income. We focus on the efficiency and efficacy of these approaches by examining primarily the trade-off between leakage and coverage. Tekoporã is a CCT programme that is being scaled up in Paraguay. Like other recent CCT programmes, it was designed in the context of a national strategy for combating poverty, as part of the general effort to achieve the Millennium Development Goals (MDGs). Its pilot started in August 2005, covering 4,500 households in five districts of two departments. Tekoporã is gradually expanding and intends to cover 35 districts by 2008. These districts were selected from the pool of 66 districts that had been judged to have the most vulnerable populations, according to a scoring system based on a Geographical Prioritization Index (IPG). Tekoporã?s objective is to break the intergenerational transmission of poverty by means of the cash transfer and follow-up activities for beneficiary households. This follow-up consists of the monitoring of co-responsibilities (between beneficiaries and the programme) with regard to the supply and use of health and education facilities and the development of related family-support activities. (...)Debating Targeting Methods for Cash Transfers: A Multidimensional Index vs. an Income Proxy for Paraguay?s Tekoporã Programme