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The Murchison Widefield Array (MWA) is an open access telescope dedicated to studying the low-frequency (80–300 MHz) southern sky. Since beginning operations in mid-2013, the MWA has opened a new observational window in the southern hemisphere enabling many science areas. The driving science objectives of the original design were to observe 21 cm radiation from the Epoch of Reionisation (EoR), explore the radio time domain, perform Galactic and extragalactic surveys, and monitor solar, heliospheric, and ionospheric phenomena. All together
programs recorded 20 000 h producing 146 papers to date. In 2016, the telescope underwent a major upgrade resulting in alternating compact and extended configurations. Other upgrades, including digital back-ends and a rapid-response triggering system, have been developed since the original array was commissioned. In this paper, we review the major results from the prior operation of the MWA and then discuss the new science paths enabled by the improved capabilities. We group these science opportunities by the four original science themes but also include ideas for directions outside these categories.
Various silicon carbide polytypes, such as 4H-, 6H- and 3C-SiC are clearly distinguished by the magnitude and rotational anisotropy of their optical second-harmonic (SH) response. The large dynamic range of the SH response of more than two orders of magnitude between these polytypes allows a fast and non-invasive mapping of 3C-SiC micron areas in 4H - and 6H-SiC epilayers. 3C-Microcrystallites of different oricutations are identified from SH rotational anisotropy scans.
This paper examines the impact of domestic and foreign macroeconomic variables on U.S. meat exports, including beef, pork, turkey, and chicken, in the context of an open economy. The results show that foreign macroeconomic variables exert more significant and persistent effects on U.S. meat exports than domestic macroeconomic variables. The implication is that the U.S. can increase its meat exports more effectively by expending efforts on international macroeconomic policy coordination rather than on domestic sectoral policy. The results also suggest that macroeconomic models of the agricultural sector should include foreign variables and should not be limited only to domestic ones.
Lung cancer in either smokers or in uranium miners exposed to radon occurs preferentially in the epithelium of the bronchi (airway generations 2 to 6). Accurate carcinogenesis risk/dose modeling requires quantitative data on normal bronchial epithelial parameters including: (a) the average number and volume densities (VD) of the nuclei of the possible target cell types and (b) the distances to the free surface of the nuclei of each type. Current dose models use data from an inadequate 1972 light microscopic study. Since smoking and radon effects may be synergistic, these parameters of the bronchi of smokers and non-smokers should be compared.
Human bronchial specimens (72) dissected by airway generation were obtained from non-involved areas of lungs/lobes removed for various pathologies (16 smokers, 8 non-smokers). Samples were fixed with 2% glutaraldehyde, 0.1 M cacodylate, 0.1M sucrose for routine TEM (graded ethanols, Epon embedding, lead and uranyl staining) and sections were examined on a JEOL 1200 EX at l,000x at 60 KV.
We have developed an apparatus that provides a high flux, low energy, monoenergetic positron beam to investigate various processes which occur when a positron beam impinges on a metal surface, including annihilation at the surface, trapping in vacancies, and the emission of both fast and thermally desorbed positronium. We report here the first angular correlation of annihilation gamma-rays measurements and positronium time of flight experiments at a material surface. We applied a simple free electron model which explains the general trend of the data but differences due to the surface specific properties and the deviation from a free electron metal are evident.
The cornerstone of the 1977 and 1981 Farm Bills for crops is a buffer stock-supply management program involving the farmer-owned reserve and acreage adjustment instruments. Among the several reasons normally cited for adopting this type program is price and income stability. However, recent swings in commodity prices, net farm income and government program costs have stimulated widespread interest in farm program redesign and modification in 1985.
The Commodity Credit Corporation (CCC), established by Executive Order in 1933 and granted a federal charter in 1948, is authorized to extend nonrecourse loans to farmers who use agricultural commodities from the most recent harvest as collateral. The loan program was designed to foster a more orderly marketing procedure and stabilize agricultural prices and income, but farmers also use this program as both a residual market and a speculation and marketing aid. The amount loaned to a farmer equals the quantity of the commodity pledged as collateral times a fixed per unit value (loan rate) which is announced prior to the production period. Eligibility of a farmer for a CCC loan may require compliance with USDA allotment or set-aside programs and storage of the commodity in a CCC approved facility. The CCC's commodity demand via the loan program is perfectly elastic at the loan rate and farmers can supply as much as they desire. When the loan matures the farmer can either repay it with interest or default on both principal and interest, in which case the CCC assumes ownership of the pledged commodity.