Outer planets probe testing

An atmospheric entry Probe is being developed by NASA Ames Research Center (ARC) to conduct in situ scientific investigations of the outer planets' atmospheres. A full scale engineering model of an MDAC-E Probe configuration, was fabricated by NASA ARC. Proof-of-concept test validation of the structural and thermal design is being obtained at NASA ARC. The model was successfully tested for shock and dynamic loading and is currently in thermal vacuum testing

Would You Choose to be Happy? Tradeoffs Between Happiness and the Other Dimensions of Life in a Large Population Survey

A large literature documents the correlates and causes of subjective well-being, or happiness. But few studies have investigated whether people choose happiness. Is happiness all that people want from life, or are they willing to sacrifice it for other attributes, such as income and health? Tackling this question has largely been the preserve of philosophers. In this article, we find out just how much happiness matters to ordinary citizens. Our sample consists of nearly 13,000 members of the UK and US general populations. We ask them to choose between, and make judgments over, lives that are high (or low) in different types of happiness and low (or high) in income, physical health, family, career success, or education. We find that people by and large choose the life that is highest in happiness but health is by far the most important other concern, with considerable numbers of people choosing to be healthy rather than happy. We discuss some possible reasons for this preference

Extension of MAD Version 8 to include beam acceleration

In this paper, we describe modifications to MAD version 8.23 to include linear accelerator cavities and beam acceleration An additional energy variable has been added which is modified as the beam passes through LCAV elements (linear accelerator cavities) and can be used as a constraint in matching commands. The calculation of the beta functions and phase advance is consistent with that in other codes that treat acceleration such as TRANSPORT or DIMAD. These modifications allow this version of MAD to be used for the design and modeling of linacs and we present examples from the Next Linear Collider design as well as a muon acceleration complex. The code is available from CERN or SLAC

Nutrient flows in agricultural production and international trade: Ecological and policy issues

This paper addresses the issue of environmental and ecological impacts of nutrient flows within and between countries by reviewing and presenting data on nutrient balances and global nutrient movements. The results for nutrient depletion in agricultural soils during 1996-1999 show that in most countries in Africa and Latin America and the Caribbean rates of depletion are so high that current land use is not sustainable. At the other end of the scale, nutrient surplus derived from agriculture is most serious in the USA and industrialized countries of Europe, but also occurs in some densely populated areas of countries such as India and China. International net flows of NPK in traded agricultural commodities were estimated to total 4.8 Tg in 1997 and predicted to increase to 8.8 Tg in 2020. Flows vary widely across regions. Major net importers of NPK are West Asia/North Africa and China. Although soils in countries of Sub-Saharan Africa are widely known to be heavily degraded due to nutrient depletion, this region is nevertheless a net importer of NPK in agricultural commodities. However, the nutrients imported in food and feed commodities to Sub-Saharan countries are commonly concentrated in the cities creating waste disposal problems rather than alleviating deficiencies in rural soils. Countries with a net loss of NPK in agricultural commodities are the major food exporting countries the United States, Australia, and some countries of Latin America. A wide range of policy measures influence agricultural trade, nutrient flows and balances. The effects of agricultural trade liberalization and the reduction of production subsidies are briefly described, as well as more direct environmental policies like nutrient accounting schemes, eco-labeling, and nutrient trading. Our study highlights the need for environmental costs to be factored into the debate on nutrient management and advocates more interdisciplinary research on these important problems

A controllability method for Maxwell's equations

We propose a controllability method for the numerical solution of time-harmonic Maxwell's equations in their first-order formulation. By minimizing a quadratic cost functional, which measures the deviation from periodicity, the controllability method determines iteratively a periodic solution in the time domain. At each conjugate gradient iteration, the gradient of the cost functional is simply computed by running any time-dependent simulation code forward and backward for one period, thus leading to a non-intrusive implementation easily integrated into existing software. Moreover, the proposed algorithm automatically inherits the parallelism, scalability, and low memory footprint of the underlying time-domain solver. Since the time-periodic solution obtained by minimization is not necessarily unique, we apply a cheap post-processing filtering procedure which recovers the time-harmonic solution from any minimizer. Finally, we present a series of numerical examples which show that our algorithm greatly speeds up the convergence towards the desired time-harmonic solution when compared to simply running the time-marching code until the time-harmonic regime is eventually reached

Nutrient flows in agricultural production and international trade : Ecology and policy issues

This paper addresses the issue of environmental and ecological impacts of nutrient flows within and between countries by reviewing and presenting data on nutrient balances and global nutrient movements. The results for nutrient depletion in agricultural soils during 1996-1999 show that in most countries in Africa and Latin America and the Caribbean rates of depletion are so high that current land use is not sustainable. At the other end of the scale, nutrient surplus derived from agriculture is most serious in the USA and industrialized countries of Europe, but also occurs in some densely populated areas of countries such as India and China. International net flows of NPK in traded agricultural commodities were estimated to total 4.8 Tg in 1997 and predicted to increase to 8.8 Tg in 2020. Flows vary widely across regions. Major net importers of NPK are West Asia/North Africa and China. Although soils in countries of Sub-Saharan Africa are widely known to be heavily degraded due to nutrient depletion, this region is nevertheless a net importer of NPK in agricultural commodities. However, the nutrients imported in food and feed commodities to Sub-Saharan countries are commonly concentrated in the cities creating waste disposal problems rather than alleviating deficiencies in rural soils. Countries with a net loss of NPK in agricultural commodities are the major food exporting countries – the United States, Australia, and some countries of Latin America. A wide range of policy measures influence agricultural trade, nutrient flows and balances. The effects of agricultural trade liberalization and the reduction of production subsidies are briefly described, as well as more direct environmental policies like nutrient accounting schemes, eco-labeling, and nutrient trading. Our study highlights the need for environmental costs to be factored into the debate on nutrient management and advocates more inter- disciplinary research on these important problems

Renormalization approach to many-particle systems

This paper presents a renormalization approach to many-particle systems. By starting from a bare Hamiltonian ${\cal H}= {\cal H}_0 +{\cal H}_1$ with an unperturbed part ${\cal H}_0$ and a perturbation ${\cal H}_1$,we define an effective Hamiltonian which has a band-diagonal shape with respect to the eigenbasis of ${\cal H}_0$. This means that all transition matrix elements are suppressed which have energy differences larger than a given cutoff $\lambda$ that is smaller than the cutoff $\Lambda$ of the original Hamiltonian. This property resembles a recent flow equation approach on the basis of continuous unitary transformations. For demonstration of the method we discuss an exact solvable model, as well as the Anderson-lattice model where the well-known quasiparticle behavior of heavy fermions is derived.Comment: 11 pages, final version, to be published in Phys. Rev.

Characterization of Soil Water Content Variability and Soil Texture Using GPR Groundwave Techniques

Accurate characterization of near-surface soil water content is vital for guiding agricultural management decisions and for reducing the potential negative environmental impacts of agriculture. Characterizing the near-surface soil water content can be difficult, as this parameter is often both spatially and temporally variable, and obtaining sufficient measurements to describe the heterogeneity can be prohibitively expensive. Understanding the spatial correlation of near-surface soil water content can help optimize data acquisition and improve understanding of the processes controlling soil water content at the field scale. In this study, ground penetrating radar (GPR) methods were used to characterize the spatial correlation of water content in a three acre field as a function of sampling depth, season, vegetation, and soil texture. GPR data were acquired with 450 MHz and 900 MHz antennas, and measurements of the GPR groundwave were used to estimate soil water content at four different times. Additional water content estimates were obtained using time domain reflectometry measurements, and soil texture measurements were also acquired. Variograms were calculated for each set of measurements, and comparison of these variograms showed that the horizontal spatial correlation was greater for deeper water content measurements than for shallower measurements. Precipitation and irrigation were both shown to increase the spatial variability of water content, while shallowly-rooted vegetation decreased the variability. Comparison of the variograms of water content and soil texture showed that soil texture generally had greater small-scale spatial correlation than water content, and that the variability of water content in deeper soil layers was more closely correlated to soil texture than were shallower water content measurements. Lastly, cross-variograms of soil texture and water content were calculated, and co-kriging of water content estimates and soil texture measurements showed that geophysically-derived estimates of soil water content could be used to improve spatial estimation of soil texture