Equivalence of two approaches for the inhomogeneous density in the canonical ensemble

In this article we show that the inhomogeneous density obtained from a density-functional theory of classical fluids in the canonical ensemble (CE), recently presented by White et al [Phys. Rev. Lett. 84 (2000) 1220], is equivalent to first order to the result of the series expansion of the CE inhomogeneous density introduced by Gonzalez et al [Phys. Rev. Lett. 79 (1997) 2466].Comment: 6 pages, RevTe

APOCALYPSE NO: Population Aging and the Future of Health Care Systems

Illness increases with age. All else equal, an older population has greater needs for health care. This logic has led to dire predictions of skyrocketing costs-- "apocalyptic demography". Yet numerous studies have shown that aging effects are relatively small, and all else is not equal. Cost projections rest on specific assumptions about trends in age- specific morbidity and health care use that are far from self-evident. Sharply contrasting assumptions, for example, are made by Fries, who foresees a "compression of morbidity" and falling needs. Long term trends in health care use in British Columbia show minimal effects of population aging, but major effects, up and down, from changes in age- specific use patterns. Why then is the demographic apocalypse story so persistent, despite numerous contrary studies? It serves identifiable economic interests.aging, health care utilization, demography, health care financing

Evaluating the surface irrigation soil loss (SISL) model

Although the percentage of surface irrigated land in the United States is declining, it is still used on 43% of the irrigated land, and 51% of the surface irrigated land is irrigated down furrows or rows (USDA, 2004). Water flowing in irrigation furrows often detaches and transports soil, reducing crop productivity and impairing off-site water quality. Crop yields were at least 25% less on fields eroded from over 80 years of furrow irrigation in south-central Idaho (Carter et al., 1985). Measured soil loss from furrow irrigated fields in this area varied from 1 to 141 Mg ha-1 annually (Berg and Carter, 1980) while the annual average soil loss from the entire irrigated tract was 0.46 Mg ha-1 in 1971 (Brown et al, 1974). This soil, and associated nutrients, is transported with irrigation water as it returns to the Snake River. The Natural Resources Conservation Service (NRCS) and other land planning agencies need a tool to predict furrow irrigation erosion to assess the extent of the problem and to compare conservation practices applied to irrigated land. An evaluation of the Water Erosion Prediction Project (WEPP) model indicated that it could not be used to predict furrow irrigation erosion without substantially adjusting erodibility parameter values (Bjorneberg et al., 1999). The model also over-predicted sediment transport capacity resulting in no predicted sediment deposition on the lower end of fields, although data and observations document much on-field deposition (Bjorneberg et al., 1999). The Idaho NRCS, in consultation with scientists and engineers at the Northwest Irrigation and Soils Research Laboratory, Kimberly, Idaho, developed a simple empirical model for estimating annual irrigation-induced soil loss from furrow irrigated fields. The SISL (surface irrigation soil loss) model was developed in 1991 based on over 200 field-years of data from southern Idaho. This model estimates soil loss at the end of the furrow and does not account for deposition or additional erosion that may occur in the drainage ditch at the end of the field. The only published documentation of this model is Idaho NRCS Agronomy Technical Note No. 32. Idaho NRCS uses this model to assess benefits of conservation practices, such as converting from furrow to sprinkler irrigation, but this model has not been independently evaluated. Therefore, the objective of this study was to compare the SISL model with erosion data collected from furrow irrigated fields near Kimberly, Idaho and Prosser, Washington

Irrigation Management

Competition for limited water supplies continues to restrict water available for irrigation. Irrigated agricultural must continually improve irrigation management to continue producing food, fiber and fuel for a growing world population. Precision irrigation is the process of applying the right amount of water at the right time and place to obtain the best use of available water. Precision irrigation management is needed on large irrigation projects so water delivery matches irrigation needs and on individual fields to apply the right amount of water at the right time and place. Technology is commercially available to precisely apply water when and where it is needed by crops, however, user-friendly decision tools are still needed to quantify specific irrigation needs and control water application within fields. Integrating information from various sensors and systems into a decision support program will be critical to highly managed, spatially varied irrigation

Risk homeostasis theory - A study of intrinsic compensation

Risk homeostasis theory (RHT) suggests that changes made to the intrinsic risk of environments are negated in one of three ways: behavioural adjustments within the environment, mode migration, and avoidance of the physical risk. To date, this three-way model of RHT has little empirical support, whilst research findings on RHT have at times been diametrically opposed. A reconciliation of apparently opposing findings might be possible by suggesting that extrinsic compensation fails to restore previously existing levels of actual risk in cases where behavioural adjustments within the environment are incapable of negating intrinsic risk changes. This paper reports a study in which behavioural adjustments within the physical risk-taking environment are capable of reconciling target with actual risk. The results provide positive support for RHT in the form of overcompensation for the intrinsic risk change on specific driver behaviours

Multiple pulse sheath acceleration : an optical approach to spectral control

Recent experimental results have shown that it is possible to produce laser-accelerated proton and ion beams with distinct quasi-monoenergetic features in the energy spectrum [1, 2]. As short-pulse ultraintense laser intensities exceed 1021Wcm−2, it may be possible to produce quasi-monoenergetic proton bunches with energies in the range of 100-200 MeV. This opens up the prospect of a new route to developing medical ion accelerators for oncology. In this paper we will briefly report on some of our recent work [3]. This showed that it is theoretically possible to produce laser-accelerated proton/ion beams with distinct spectral peaks by irradiating a solid target with two laser pulses that arrive in rapid succession. No special target composition or structure is required, unlike the other schemes that have been proposed [1, 2]. This may be advantageous for certain applications

Micro-computed tomographic analysis of the radial geometry of intrarenal artery-vein pairs in rats and rabbits: Comparison with light microscopy

We assessed the utility of synchrotron-radiation micro-computed tomography (micro-CT) for quantification of the radial geometry of the renal cortical vasculature. The kidneys of nine rats and six rabbits were perfusion fixed and the renal circulation filled with Microfil. In order to assess shrinkage of Microfil, rat kidneys were imaged at the Australian Synchrotron immediately upon tissue preparation and then post fixed in paraformaldehyde and reimaged 24 hours later. The Microfil shrank only 2-5% over the 24 hour period. All subsequent micro-CT imaging was completed within 24 hours of sample preparation. After micro-CT imaging, the kidneys were processed for histological analysis. In both rat and rabbit kidneys, vascular structures identified in histological sections could be identified in two-dimensional (2D) micro-CT images from the original kidney. Vascular morphology was similar in the two sets of images. Radial geometry quantified by manual analysis of 2D images from micro-CT was consistent with corresponding data generated by light microscopy. However, due to limited spatial resolution when imaging a whole organ using contrast-enhanced micro-CT, only arteries ≥100 and ≥60 μm in diameter, for the rat and rabbit respectively, could be assessed. We conclude that it is feasible and valid to use micro-CT to quantify vascular geometry of the renal cortical circulation in both the rat and rabbit. However, a combination of light microscopic and micro-CT approaches are required to evaluate the spatial relationships between intrarenal arteries and veins over an extensive range of vessel size