Occultation studies of planets and satellites: The occultation of epsilon Geminorum by Mars

The occultation of epsilon Geminorum by Mars on 1976 April 8 was observed at three wavelengths and 4 ms time resolution with the 91 cm telescope. Temperature, pressure, and number density profiles of the Martian atmosphere were obtained for both the immersion and emersion events. Within the altitude range of 50 to 80 km above the mean surface, the mean temperature is 145 K, and the profiles exhibit wavelike structures with a peak to peak amplitude of 35 K and a vertical scale of about 20 km. The ratio of the refractivity of the atmosphere at 4500 A and 7500 A, determined from the time shift of the light curves for these wavelengths, is consistent with the atmospheric composition measured by Viking 1, 15 weeks later. From the central flash - a bright feature in the light curve midway between immersion and emersion - an optical depth is found at 4500 A of 3.3 plus or minus 1.7 per km atm (about 0.23 per equivalent Martian air mass) for the atmosphere about 25 km above the mean surface, near the south polar region. This large value and its weak wavelength dependence rule out Rayleigh scattering as the principal cause of the observed extinction

Scintillation Caustics in Planetary Occultation Light Curves

We revisit the GSC5249-01240 light curve obtained during its occultation by Saturn's North polar region. In addition to refractive scintillations, the power spectrum of intensity fluctuations shows an enhancement of power between refractive and diffractive regimes. We identify this excess power as due to high amplitude spikes in the light curve and suggest that these spikes are due to caustics associated with ray crossing situations. The flux variation in individual spikes follows the expected caustic behavior, including diffraction fringes which we have observed for the first time in a planetary occultation light curve. The presence of caustics in scintillation light curves require an inner scale cut off to the power spectrum of underlying density fluctuations associated with turbulence. Another possibility is the presence of gravity waves in the atmosphere. While occultation light curves previously showed the existence of refractive scintillations, a combination of small projected stellar size and a low relative velocity during the event have allowed us to identify caustics in this occultation. This has led us to re-examine previous data sets, in which we have also found likely examples of caustics.Comment: 4 pages, 3 figures; ApJL submitte

Comparative Analysis of the Major Polypeptides from Liver Gap Junctions and Lens Fiber Junctions

Gap junctions from rat liver and fiber junctions from bovine lens have similar septilaminar profiles when examined by thin-section electron microscopy and differ only slightly with respect to the packing of intramembrane particles in freeze-fracture images. These similarities have often led to lens fiber junctions being referred to as gap junctions. Junctions from both sources were isolated as enriched subcellular fractions and their major polypeptide components compared biochemically and immunochemically. The major liver gap junction polypeptide has an apparent molecular weight of 27,000, while a 25,000-dalton polypeptide is the major component of lens fiber junctions. The two polypeptides are not homologous when compared by partial peptide mapping in SDS. In addition, there is not detectable antigenic similarity between the two polypeptides by immunochemical criteria using antibodies to the 25,000-dalton lens fiber junction polypeptide. Thus, in spite of the ultrastructural similarities, the gap junction and the lens fiber junction are comprised of distinctly different polypeptides, suggesting that the lens fiber junction contains a unique gene product and potentially different physiological properties

Achievement goals, self-handicapping, and performance: A 2 × 2 achievement goal perspective

Elliot and colleagues (2006) examined the effects of experimentally induced achievement goals, proposed by the trichotomous model, on self-handicapping and performance in physical education. Our study replicated and extended the work of Elliot et al. by experimentally promoting all four goals proposed by the 262 model (Elliot & McGregor, 2001), measuring the participants’ own situational achievement goals, using a relatively novel task, and testing the participants in a group setting. We used a randomized experimental design with four conditions that aimed to induce one of the four goals advanced by the 262 model. The participants (n¼138) were undergraduates who engaged in a dart-throwing task. The results pertaining to self-handicapping partly replicated Elliot and colleagues’ findings by showing that experimentally promoted performance-avoidance goals resulted in less practice. In contrast, the promotion of mastery-avoidance goals did not result in less practice compared with either of the approach goals. Dart-throwing performance did not differ among the four goal conditions. Personal achievement goals did not moderate the effects of experimentally induced goals on selfhandicapping and performance. The extent to which mastery-avoidance goals are maladaptive is discussed, as well as the interplay between personal and experimentally induced goals

Studies of planetary upper atmospheres through occultations

The structure, composition, dynamics and energy balance of planetary upper atmospheres through interpretation of steller occultation data from Uranus is discussed. The wave-optical problem of modelling strong scintillation for arbitrary turbulent atmospheres is studied, as well as influence of turbulence. It was concluded that quasi-global features of atmospheric structure are accurately determined by numerical inversion. Horizontally inhomogeneous structures are filtered out and have little effect on temperature profiles

Finishing store lambs from organic hill and upland farms OF0119

1. The aim of this study was to assess the economics and constraints associated with home finishing lambs on a range of organic hill and upland farms in England and Wales, and to evaluate the potential for further finishing on registered farms in the lowlands. 2. The current state of the organic sheep sector is briefly reviewed. This identifies problems of scale, limited premia and uneveness of supply as limiting factors to more rapid development of the market and associated production systems. 3. To quanitfy the effect of organic management on financial performance, hill and upland farms were classified under four typical systems, depending on the degree of intensification. 4. Without a sizeable area of improved ground, to which fertiliser and other inputs could have been applied conventionally, flocks based on high hill or marginal hill systems were least affected by switching to organic management. Flock Gross Margin on the marginal hill declined by approximately 7%. 5. On more intensive farms, typified by Welsh hill or upland farming systems, there is greater potential to finish lambs at higher stocking rates under conventional management, and the consequences of changing to organic management are greatly increased. Assuming a 10% premium for fnished organic lambs, deviating from convetional practice to produce store lambs or finish lambs at higher production cost, reduced flock Gross Margin by approximately 12-15%. Without a premium, this deficit increased to 15-20%. 6. The Organic Aid Scheme can make good the likely income loss during the first two years after conversion, when the highest rates are payable. However, in the long-term organic flocks must compete solely on the basis os a premium paid for finished, and ideally, for store lambs. 7. Physical and financial constraints were identified as t wy systems had not developed linking potential production of store lambs in the hills/uplands with finishing on organic farms in the lowlands. These were mainly scale and infrastructure, availability of suitable feeds and the likely level of return to the lowland farmer from a store lamb finishing enterprise. Potential sources of feed for finishing organic lambs were assessed. These include permanent pasture, short-term leys, catch crops, grazed set-aside land and conserved fodder. 8. Integration with existing organic systems of all types was estimated to have the potential to finish an extra 10-15,000 lambs per annum, equivalent to the number of lambs currently receiving an organic premium. 9. Further opportunities to expand finishing capacity on lowland farms were examined. Mixed organic farms are likely to have little or no capacity to finish bought in store lambs, except where overall stocking rates are constrained by insufficient ewe/suckler cow quota, or where catch crops are added to the rotation. 10. The addition of a store lamb enterprise to lowland systems was calculated to increase farm Gross MArgin by 2-3%, depending on the type of farm (dairy, stockless arable, or mixed). This represented a marginal return on capital invested in a store lamb finishing enterprise of 9-24%. 1. The financial risks involved, the availability of suitable labour and fixed equipment, and reluctance to vary arable rotations, make store lamb finishing enterprises less attractive to the lowland farmer. 12. Beyond the capacity to increase the number of certified lambs currently offered by up to 50%, greater opportunities are only likely to develop, when there is a significant increase in land (particularly on arable farms) entering conversion

The Hubble Space Telescope high speed photometer

The Hubble Space Telescope will provide the opportunity to perform precise astronomical photometry above the disturbing effects of the atmosphere. The High Speed Photometer is designed to provide the observatory with a stable, precise photometer with wide dynamic range, broad wavelenth coverage, time resolution in the microsecond region, and polarimetric capability. Here, the scientific requirements for the instrument are examined, the unique design features of the photometer are explored, and the improvements to be expected over the performance of ground-based instruments are projected

Density waves theory of the capsid structure of small icosahedral viruses

We apply Landau theory of crystallization to explain and to classify the capsid structures of small viruses with spherical topology and icosahedral symmetry. We develop an explicit method which predicts the positions of centers of mass for the proteins constituting viral capsid shell. Corresponding density distribution function which generates the positions has universal form without any fitting parameter. The theory describes in a uniform way both the structures satisfying the well-known Caspar and Klug geometrical model for capsid construction and those violating it. The quasiequivalence of protein environments in viral capsid and peculiarities of the assembly thermodynamics are also discussed.Comment: 8 pages, 3 figur

Examining the Effect of Pore Size Distribution and Shape on Flow through Unsaturated Peat using Computer Tomography

The hydraulic conductivity of unsaturated peat soil is controlled by the air-filled porosity, pore size and geometric distribution as well as other physical properties of peat materials. This study investigates how the size and shape of pores affects the flow of water through peat soils. In this study we used X-ray Computed Tomography (CT), at 45μm resolution under 5 specific soil-water pressure head levels to provide 3-D, high-resolution images that were used to detect the inner pore structure of peat samples under a changing water regime. Pore structure and configuration were found to be irregular, which affected the rate of water transmission through peat soils. The 3-D analysis suggested that pore distribution is dominated by a single large pore-space. At low pressure head, this single large air-filled pore imparted a more effective flowpath compared to smaller pores. Smaller pores were disconnected and the flowpath was more tortuous than in the single large air-filled pore, and their contribution to flow was negligible when the single large pore was active. We quantify the pore structure of peat soil that affects the hydraulic conductivity in the unsaturated condition, and demonstrate the validity of our estimation of peat unsaturated hydraulic conductivity by making a comparison with a standard permeameter-based method. Estimates of unsaturated hydraulic conductivities were made for the purpose of testing the sensitivity of pore shape and geometry parameters on the hydraulic properties of peats and how to evaluate the structure of the peat and its affects on parameterization. We also studied the ability to quantify these factors for different soil moisture contents in order to define how the factors controlling the shape coefficient vary with changes in soil water pressure head. The relation between measured and estimated unsaturated hydraulic conductivity at various heads shows that rapid initial drainage, that changes the air-filled pore properties, creates a sharp decline in hydraulic conductivity. This is because the large pores readily lose water, the peat rapidly becomes less conductive and the flow path among pores, more tortuous