Two-nucleon momentum distributions measured in 3He(e,e'pp)n

We have measured the 3He(e,e'pp)n reaction at 2.2 GeV over a wide kinematic range. The kinetic energy distribution for "fast" nucleons (p>250 MeV/c) peaks where two nucleons each have 20% or less, and the third nucleon has most of the transferred energy. These fast pp and pn pairs are back to back with little momentum along the three-momentum transfer, indicating that they are spectators. Calculations by Sargsian and by Laget also indicate that we have measured distorted two-nucleon momentum distributions by striking one nucleon and detecting the spectator correlated pair.     

Observation of an exotic S = +1 baryon in exclusive photoproduction from the deuteron

In an exclusive measurement of the reaction gammad-->K(+)K(-)pn, a narrow peak that can be attributed to an exotic baryon with strangeness S=+1 is seen in the K(+)n invariant mass spectrum. The peak is at 1.542+/-0.005 GeV/c(2) with a measured width of 0.021 GeV/c(2) FWHM, which is largely determined by experimental mass resolution. The statistical significance of the peak is (5.2+/-0.6)sigma. The mass and width of the observed peak are consistent with recent reports of a narrow S=+1 baryon by other experimental groups.     

First measurement of transferred polarization in the exclusive ep-->e'K+Lambda--> reaction

The first measurements of the transferred polarization for the exclusive e-->p-->e(')K+Lambda--> reaction have been performed at Jefferson Laboratory using the CLAS spectrometer. A 2.567 GeV beam was used to measure the hyperon polarization over Q2 from 0.3 to 1.5 (GeV/c)(2), W from 1.6 to 2.15 GeV, and over the full K+ center-of-mass angular range. Comparison with predictions of hadrodynamic models indicates strong sensitivity to the underlying resonance contributions. A nonrelativistic quark-model interpretation of our data suggests that the ssmacr; quark pair is produced with spins predominantly antialigned. Implications for the validity of the most widely used quark-pair creation operator are discussed.     

Morphometry of the corneal endothelium in glassblowers compared to non-glassblowers

Acute exposure to high levels of IR radiation (IRR) can damage the endothelial cell layer of the human cornea, but the impact of chronic lower-dose exposure has not been assessed objectively. The corneal endothelium of 10 individuals who had occupational exposure to IRR as glassblowers (average 16 years) was examined by photo-slitlamp biomicroscopy, the endothelial mosaic assessed by morphometry, and compared to 10 non-glassblowers (controls). The analyses reveal the glassblowers to have higher than expected endothelial cell density (ECD, average 3371+/-304 cells/mm(2) compared to a control value of 3072+/-198 cells/mm(2)), a higher variance in cell area, and a lower percentage of the most-prevalent cell type, i.e. the six-sided cells (average 52.0+/-12.2%, compared to controls of 64.1+/-6.6%). Analyses of the sizes of different cell types (four-, five-, six-sided, etc.) indicate that the cells in both groups are proportionately larger as the number of sides increases, but that this area-side relationship is different in the glassblowers, who had both smaller and larger cells compared to controls. Two other cases had even higher cell density values (>5000 cells/mm(2)) and <50% six-sided cells. Occupational exposure to a mixture of IRR, perhaps some UVR as well as thermal convection effects, can apparently result in morphological changes in the human corneal endothelium. These may be the result of IRR-stimulated cell division.     

Investigation of CO<Subscript>2</Subscript> Plume Behavior for a Large-Scale Pilot Test of Geologic Carbon Storage in a Saline Formation

The hydrodynamic behavior of carbon dioxide (CO₂) injected into a deep saline formation is investigated, focusing on trapping mechanisms that lead to CO₂ plume stabilization. A numerical model of the subsurface at a proposed power plant with CO₂ capture is developed to simulate a planned pilot test, in which 1,000,000 metric tons of CO₂ is injected over a 4-year period, and the subsequent evolution of the CO₂ plume for hundreds of years. Key measures are plume migration distance and the time evolution of the partitioning of CO₂ between dissolved, immobile free-phase, and mobile free-phase forms. Model results indicate that the injected CO₂ plume is effectively immobilized at 25 years. At that time, 38% of the CO₂ is in dissolved form, 59% is immobile free phase, and 3% is mobile free phase. The plume footprint is roughly elliptical, and extends much farther up-dip of the injection well than down-dip. The pressure increase extends far beyond the plume footprint, but the pressure response decreases rapidly with distance from the injection well, and decays rapidly in time once injection ceases. Sensitivity studies that were carried out to investigate the effect of poorly constrained model parameters permeability, permeability anisotropy, and residual CO₂ saturation indicate that small changes in properties can have a large impact on plume evolution, causing significant trade-offs between different trapping mechanisms.     

The application of molecular modelling to the interpretation of inverse gas chromatography data

The use of molecular modelling in the interpretation of inverse gas chromatography data is discussed. Crystal faces can be visualised and likely cleavage planes calculated using the surface attachment energies. Assuming that the preferred cleavage plane is the crystal face with the smallest attachment energy then the predominant crystal faces of a crystalline particle can be predicted. Surface adsorption can be modelled using Van der Waals and electrostatic interactions to evaluate the interaction energies between individual atoms of the probe molecule and atoms of the test molecule orientated as in the surface. Using examples of pharmaceutical materials, modelling has been shown to be successful in the understanding of changes in the surface energetics.     

LONG-TERM EFFECTS OF A SINGLE DOSE OF ULTRAVIOLET-B ON ALBINO RABBIT CORNEA–II. DETURGESCENCE and FLUID PUMP ASSESSED in vitro

Both eyes of female albino rabbits (1.9 kg: 9-10 wk old) were exposed to a single dose of UV-B (300 +/- 9 nm; 0.125 J/cm2 total dose) between 13.30 and 15.00 h. At various time periods thereafter (every 12 h for 3 days, 6, 7, 14, 28, 42, 56, 112, 224 and 336 days post-irradiation), animals were sacrificed, samples of aqueous humor taken for analysis and stroma-endothelium preparations obtained from the corneas. Following such threshold irradiation, small increases in aqueous humor tonicity and protein levels were observed. The preparations were mounted in a specular microscope assembly (for measuring the rate and magnitude of corneal deturgescence) or between two half chambers (for measuring fluid pump) and equilibrated for 2 h with a CO2-equilibrated glucose-adenosine-glutathione-supplemented Ringer solution at 37 degrees C and a hydrostatic pressure of 20 cm H2O. After equilibration the stromal thickness showed large variation with large reductions in both the rate and amplitude of deturgescence function observed by 36 h. Large reductions in fluid pump activity were also observed by 36 h. The magnitude of the effects on fluid pump were somewhat greater than the effects on deturgescence. Both functions recovered to pre-irradiation levels by 112 days post-irradiation.