3,086 research outputs found
Tissue holder for experimental and Demonstration Surgery
Development of device for holding anatomical tissues during operations is discussed. Device consists of plastic dish with hemispherical recess in center to hold excised eyes. Low vacuum applied to underside of recess insures holding of part
Novel designs for Penning ion traps
We present a number of alternative designs for Penning ion traps suitable for
quantum information processing (QIP) applications with atomic ions. The first
trap design is a simple array of long straight wires which allows easy optical
access. A prototype of this trap has been built to trap Ca+ and a simple
electronic detection scheme has been employed to demonstrate the operation of
the trap. Another trap design consists of a conducting plate with a hole in it
situated above a continuous conducting plane. The final trap design is based on
an array of pad electrodes. Although this trap design lacks the open geometry
of the traps described above, the pad design may prove useful in a hybrid
scheme in which information processing and qubit storage take place in
different types of trap. The behaviour of the pad traps is simulated
numerically and techniques for moving ions rapidly between traps are discussed.
Future experiments with these various designs are discussed. All of the designs
lend themselves to the construction of multiple trap arrays, as required for
scalable ion trap QIP.Comment: 11 pages, 10 figure
Substrate-Dependent Activation of Polyphenol Oxidase in Red Clover
Polyphenol oxidases (PPO) are copper metaloproteins that catalyse the oxidation of o-diphenols to quinones, highly reactive molecules which readily bind to nucleophilic sites on cellular components and proteins. Red clover protein, due to this enzyme is resistant to protease degradation during. Theses enzymes (circa. 60-65 kDa) are located in the thylakoid lumen and can be converted to a 40-45 kDa form by proteolysis both in vitro and in vivo (Gelder et al., 1997). Conversion to the smaller form has been demonstrated to confer activity at neutral pH. Other treatments, such as the presence of lipids or detergents eg. SDS, can also confer activity at pH7 (Gelder et al., 1997). Here we describe studies on treatments that affect red clover PPO activity at neutral pH, which is equivalent to the physiological pH of macerated/homogenised leaf extracts
Reduced-Complexity Transmit/Receive-Diversity Systems
We consider wireless systems with transmit and receive diversity. For reduction of complexity, we propose to use hybrid selection/maximal ratio transmission at one link end, choosing L out of N antennas. We analyze the performance of such systems, giving analytical bounds and comparing them to computer simulations. Outage probability, symbol error probability, and capacity are shown. We demonstrate that in typical cases, a small number of used antennas L is sufficient to achieve considerable performance gains. We also analyze the infuence of the number of base station antennas, of fading correlation and channel estimation errors. The simulation results confirm that the proposed scheme is effective in a variety of environments
Synthesis and biodistribution of immunoconjugates of a human IgM and polymeric drug carriers
The synthesis and purification of radiolabelled immunoconjugates, composed of a human IgM monoclonal antibody directed against an intracellular tumour-associated antigen and either poly (alpha-L-glutamic acid) (PGA) or poly[N5-(2-hydroxyethyl)-L-glutamine] (PHEG) is described. Coupling of polymers to the antibody was performed through disulfide bond formation involving a single thiol group at the C-terminus of the polymer chain and 2-pyridyldisulfide groups introduced onto the antibody. The antibody was iodinated with 131I before conjugation. The polymers contained tyrosinamide in a low degree of substitution and were radiolabelled with 125I. 125I-labelled PGA and PHEG were found to be stable for at least 3 days in murine and human plasma. The biodistribution in mice of the doubly labelled immunoconjugates was studied and was compared with the pharmacokinetics of the individual components.\ud
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PHEG showed a relatively slow blood clearance, the half-life being approximately 10 h with low uptake in liver, kidneys and spleen. PGA was rapidly cleared from the circulation and was significantly taken up in liver, kidneys and spleen. The biodistribution of both immunoconjugates was indistinguishable from that of the IgM proper, with plasma half-lives of approximately 6 h, indicating that the pharmacokinetic properties of the immunoconjugates are largely determined by the antibody part
Methane hydrate formation in partially water-saturated Ottawa sand
This paper is not subject to U.S. copyright. The definitive version was published in American Mineralogist 89 (2004): 1202-1207.Bulk properties of gas hydrate-bearing sediment strongly depend on whether hydrate forms primarily
in the pore fluid, becomes a load-bearing member of the sediment matrix, or cements sediment
grains. Our compressional wave speed measurements through partially water-saturated, methane
hydrate-bearing Ottawa sands suggest hydrate surrounds and cements sediment grains. The three
Ottawa sand packs tested in the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI)
contain 38(1)% porosity, initially with distilled water saturating 58, 31, and 16% of that pore space,
respectively. From the volume of methane gas produced during hydrate dissociation, we calculated
the hydrate concentration in the pore space to be 70, 37, and 20% respectively. Based on these hydrate
concentrations and our measured compressional wave speeds, we used a rock physics model to differentiate
between potential pore-space hydrate distributions. Model results suggest methane hydrate
cements unconsolidated sediment when forming in systems containing an abundant gas phase.This work was supported by the U.S. Geological Surveyʼs Coastal and Marine
Geology and Eastern Region Gas Hydrate Programs, in addition to DOE contract
DE-AI21-92MC29214
Electron dynamics in a plasma focus
Results are presented of a numerical integration of the three-dimensional relativistic equations of motion of electrons subject to given electric and magnetic fields deduced from experiments. Fields due to two different models are investigated. For the first model, the fields are those due to a circular distribution of axial current filaments. As the current filaments collapse toward the axis, large azimuthal magnetic and axial electric fields are induced. These fields effectively heat the electrons to a temperature of approximately 8 keV and accelerate electrons within the radius of the filaments to high axial velocities. Similar results are obtained for the current-reduction phase of focus formation. For the second model, the fields are those due to a uniform current distribution. Both the current-reduction and the compression phases were studied. These is little heating or acceleration of electrons during the compression phase because the electrons are tied to the magnetic field. However, during the current-reduction phase, electrons near the axis are accelerated toward the center electrode and reach energies of 100 keV. A criterion is obtained which limits the runaway electron current to about 400 A
The geometry of the close environment of SV Psc as probed by VLTI/MIDI
Context. SV Psc is an asymptotic giant branch (AGB) star surrounded by an
oxygen-rich dust envelope. The mm-CO line profile of the object's outflow shows
a clear double-component structure. Because of the high angular resolution,
mid-IR interferometry may give strong constraints on the origin of this
composite profile.
Aims. The aim of this work is to investigate the morphology of the
environment around SV Psc using high-angular resolution interferometry
observations in the mid-IR with the Very Large Telescope MID-infrared
Interferometric instrument (VLTI/MIDI).
Methods. Interferometric data in the N-band taken at different baseline
lengths (ranging from 32-64 m) and position angles (73- 142{\deg}) allow a
study of the morphology of the circumstellar environment close to the star. The
data are interpreted on the basis of 2-dimensional, chromatic geometrical
models using the fitting software tool GEM-FIND developed for this purpose.
Results. The results favor two scenarios: (i) the presence of a highly
inclined, optically thin, dusty disk surrounding the central star; (ii) the
presence of an unresolved binary companion at a separation of 13.7 AU and a
position angle of 121.8{\deg} NE. The derived orbital period of the binary is
38.1 yr. This detection is in good agreement with hydrodynamic simulations
showing that a close companion could be responsible for the entrainment of the
gas and dust into a circumbinary structure.Comment: 10 pages, 12 figure
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