Pointing calibration of the MKIVA DSN antennas Voyager 2 Uranus encounter operations support

The MKIVA DSN introduced significant changes to the pointing systems of the 34-meter and 64-meter diameter antennas. To support the Voyager 2 Uranus Encounter, the systems had to be accurately calibrated. Reliable techniques for use of the calibrations during intense mission support activity had to be provided. This article describes the techniques used to make the antenna pointing calibrations and to demonstrate their operational use. The results of the calibrations are summarized

ANALYSING THE LOW ADOPTION OF WATER CONSERVATION TECHNOLOGIES BY SMALLHOLDER FARMERS IN SOUTHERN AFRICA

Natural resource degradation and water scarcity are a global concern, which typically threatens the sustainability of smallholder farmers' livelihoods in semi-arid developing areas. As part of research efforts, a number of water-conservation technologies (WCT) have been developed, yet with low adoption rates in smallholder farming environments. This paper discusses the concepts of adoption and innovation, comparing the perspectives of research operators to the ones of smallholder farmers. Discrepancies are highlighted and ultimately explain low uptake of technologies by farmer. Then it addresses socio-economic factors affecting such adoption. It is argued that WCT show specific traits: (1) diversity and applicability to different time and spatial scales; (2) hence, the dependency upon a context. These traits influence dissemination and adoption of WCT, and should not be ignored, from the early stage of technology development. It is shown that adoption does not only depend on individual farmers willingness, but also upon the role of property rights on resources, and collective action at community level. Other specific issues and factors like the demand for WCT, the role of public sector and research, and related biases are also discusses. It finally draws some recommendations towards rural livelihoods that are more sustainable. Farmers' participation in technology development, taking account of local indigenous knowledge and sound institutional arrangements are among other the pathways that are suggested towards a better integration of technology development and innovation processes.adoption, innovation, water conservation, technologies, collective action, property rights, sustainability, livelihoods, Resource /Energy Economics and Policy,

Probing the wind-wind collision in Gamma Velorum with high-resolution Chandra X-ray spectroscopy: evidence for sudden radiative braking and non-equilibrium ionization

We present a new analysis of an archived Chandra HETGS X-ray spectrum of the WR+O colliding wind binary Gamma Velorum. The spectrum is dominated by emission lines from astrophysically abundant elements: Ne, Mg, Si, S and Fe. From a combination of broad-band spectral analysis and an analysis of line flux ratios we infer a wide range of temperatures in the X-ray emitting plasma (~4-40 MK). As in the previously published analysis, we find the X-ray emission lines are essentially unshifted, with a mean FWHM of 1240 +/- 30 km/s. Calculations of line profiles based on hydrodynamical simulations of the wind-wind collision predict lines that are blueshifted by a few hundred km/s. The lack of any observed shift in the lines may be evidence of a large shock-cone opening half-angle (> 85 degrees), and we suggest this may be evidence of sudden radiative braking. From the R and G ratios measured from He-like forbidden-intercombination-resonance triplets we find evidence that the Mg XI emission originates from hotter gas closer to the O star than the Si XIII emission, which suggests that non-equilibrium ionization may be present.Comment: 22 pages, 14 figures. Accepted for publication in MNRA

Introduction to floriculture

This bulletin is to provide a basic understanding of the principles and practices of commercial flower production, from which further studies can be undertaken as required. A complete study of floriculture is beyond the objectives and resources of this course because of the complexity of the flowering process and its control in plants. These notes are to be supplemented by lectures, slides, demonstrations and field studies

Differential Relationship between Physical Activity and Intake of Added Sugar and Nutrient-Dense Foods: A Cross-Sectional Analysis

A curvilinear relationship exists between physical activity (PA) and dietary energy intake (EI), which is reduced in moderately active when compared to inactive and highly active individuals, but the impact of PA on eating patterns remains poorly understood. Our goal was to establish the relationship between PA and intake of foods with varying energy and nutrient density. Data from the 2009–2010 United States National Health and Nutrition Examination Survey were used to include a Dietary Screener Questionnaire for estimated intakes of added sugar, fruits and vegetables, whole grains, fiber, and dairy. Participants (n = 4766; 49.7% women) were divided into sex-specific quintiles based on their habitual PA. After adjustment for age, body mass index, household income, and education, intakes were compared between PA quartiles, using the lowest activity quintile (Q1) as reference. Women in the second to fourth quintile (Q2-Q4) consumed less added sugar from sugary foods (+2 tsp/day) and from sweetened beverages (+2 tsp/day; all p \u3c 0.05 vs. Q1). In men, added sugar intake was elevated in the highest activity quintile (Q5: +3 ± 1 tsp/day, p = 0.007 vs. Q1). Fruit and vegetable intake increased (women: Q1-Q4 +0.3 ± 0.1 cup eq/day; p \u3c 0.001; men: Q1-Q3 +0.3 ± 0.1 cup eq/day, p = 0.002) and stagnated in higher quintiles. Dairy intake increased with PA only in men (Q5: +0.3 ± 0.1 cup eq/day, p \u3c 0.001 vs. Q1). Results demonstrate a differential relationship between habitual PA and dietary intakes, whereby moderate but not necessarily highest PA levels are associated with reduced added sugar and increased nutrient-dense food consumption. Future research should examine specific mechanisms of food choices at various PA levels to ensure dietary behaviors (i.e., increased sugary food intake) do not negate positive effects of PA

Performance of the SERT 2 spacecraft after 4 and one-half years in space

The SERT 2 satellite, launched in February, 1970, has recently been reactivated after being dormant for a year. The satellite orientation was changed to spin stabilization in 1973 and the satellite is now coning such that the active side of the solar arrays move into and out of the sun every 23 days. There is sufficient power to operate the ion thrusters for seven days of this cycle. The 2 ion thruster system was successfully operated; the electrical short in the accelerating grids had cleared during the year long dormant phase

Paths to accuracy for radiation parameterizations in atmospheric models

Radiative transfer is sufficiently well understood that its parameterization in atmospheric models is primarily an effort to balance computational cost and accuracy. The most common approach is to compute radiative transfer with the highest practical spectral accuracy but infrequently in time and/or space, though errors introduced by this approximation are difficult to quantify. An alternative is to perform spectrally sparse calculations frequently in time using randomly chosen spectral quadrature points. Here we show that purely random quadrature points, though effective in some large-eddy simulations, are not a good choice for models in which the land surface responds to radiative fluxes because surface temperature perturbations can be large enough, and persistent long enough, to affect model evolution. These errors may be mitigated by choosing teams of spectral points designed to limit the maximum surface flux error; teams, rather than individual quadrature points, are then chosen randomly. The approach is implemented in the ECHAM6 global model and the results are examined using “perfect-model” experiments on time scales ranging from a day to a month. In this application the approach introduces errors commensurate with the infrequent calculation of broadband calculations for the same computational cost. But because teams need not increase with size, and indeed may become better and more balanced with increased spectral density, improvements in radiative transfer may not need to be traded off against spatiotemporal sampling

Neutron scattering measurements of phonons in nickel at elevated temperatures

Measurements of elastic and inelastic neutron scatterings from elemental nickel were made at 10, 300, 575, 875, and 1275 K. The phonon densities of states (DOSs) were calculated from the inelastic scattering and were fit with Born–von Kármán models of the lattice dynamics. With ancillary data on thermal expansion and elastic moduli, we found a small, negative anharmonic contribution to the phonon entropy at high temperature. We used this to place bounds on the magnetic entropy of nickel. A significant broadening of the phonon DOS at elevated temperatures, another indication of anharmonicity, was also measured and quantified

A two Turbulence Kinetic Energy model as a scale-adaptive approach to modeling the planetary boundary layer

A two Turbulence Kinetic Energy (2TKE) model is developed to address the boundary layer “grey zone” problem. The model combines ideas from local and nonlocal models into a single energetically consistent framework. By applying the Reynolds averaging to the large eddy simulation (LES) equations that employ Deardorff's subgrid TKE, we arrive at a system of equations for the boundary layer quantities and two turbulence kinetic energies: one which encapsulates the TKE of large boundary-layer-scale eddies and another which represents the energy of eddies subgrid to the vertical grid size of a typical large-scale model. These two energies are linked via the turbulent cascade of energy from larger to smaller scales and are used to model the mixing in the boundary layer. The model is evaluated for three dry test cases and found to compare favorably to large eddy simulations. The usage of two TKEs for mixing helps reduce the dependency of the model on the vertical grid scale as well as on the free tropospheric stability and facilitates a smoother transition from convective to stable regimes. The usage of two TKEs representing two ranges of scales satisfies the prerequisite for modeling the boundary layer in the “grey zone”: an idea that is explored further in a companion paper

Absolute Calibration of the Radio Astronomy Flux Density Scale at 22 to 43 GHz Using Planck

The Planck mission detected thousands of extragalactic radio sources at frequencies from 28 to 857 GHz. Planck's calibration is absolute (in the sense that it is based on the satellite's annual motion around the Sun and the temperature of the cosmic microwave background), and its beams are well characterized at sub-percent levels. Thus Planck's flux density measurements of compact sources are absolute in the same sense. We have made coordinated VLA and ATCA observations of 65 strong, unresolved Planck sources in order to transfer Planck's calibration to ground-based instruments at 22, 28, and 43 GHz. The results are compared to microwave flux density scales currently based on planetary observations. Despite the scatter introduced by the variability of many of the sources, the flux density scales are determined to 1-2% accuracy. At 28 GHz, the flux density scale used by the VLA runs 3.6% +- 1.0% below Planck values; at 43 GHz, the discrepancy increases to 6.2% +- 1.4% for both ATCA and the VLA.Comment: 16 pages, 4 figures and 4 table