Feasibility Study of Fish Passage Facilities In the James River, Richmond, Virginia

This is a feasibility study on the construction and maintenance of fish passage facilities in the Richmond area of the James River

Communication and control system for a 15-channel hermetic retinal prosthesis

A small, hermetic, wirelessly-controlled retinal prosthesis has been developed for pre-clinical studies in Yucatan minipigs. The device was attached conformally to the outside of the eye in the socket and received both power and data wirelessly from external sources. Based on the received image data, the prosthesis drove a subretinal thin-film polyimide array of sputtered iridium oxide stimulating electrodes. The implanted device included a hermetic titanium case containing a 15-channel stimulator and receiver chip and discrete circuit components. Feedthroughs in the hermetic case connected the chip to secondary power- and data-receiving coils, which coupled to corresponding external power and data coils driven by power amplifiers. Power was delivered by a 125 kHz carrier, and data were delivered by amplitude shift keying of a 15.5 MHz carrier at 100 kbps. Stimulation pulse strength, duration and frequency were programmed wirelessly from an external computer system. The final assembly was tested in vitro in physiological saline and in vivo in two minipigs for up to five and a half months by measuring stimulus artifacts generated by the implant's current drivers.United States. Dept. of Veteran AffairsUnited states. Dept. of Veterans Affairs. Boston Healthcare SystemNational Institutes of Health (U.S.)United States. Dept. of DefenseMassachusetts Lions Foundatio

Thresholds for Activation of Rabbit Retinal Ganglion Cells with an Ultrafine, Extracellular Microelectrode

PURPOSE. To determine electrical thresholds required for extracellular activation of retinal ganglion cells as part of a project to develop an epiretinal prosthesis. METHODS. Retinal ganglion cells were recorded extracellularly in retinas isolated from adult New Zealand White rabbits. Electrical current pulses of 100-s duration were delivered to the inner surface of the retina from a 5-m long electrode. In about half of the cells, the point of lowest threshold was found by searching with anodal current pulses; in the other cells, cathodal current pulses were used. RESULTS. Threshold measurements were obtained near the cell bodies of 20 ganglion cells and near the axons of 19 ganglion cells. Both cathodal and anodal stimuli evoked a neural response in the ganglion cells that consisted of a single action potential of near-constant latency that persisted when retinal synaptic transmission was blocked with cadmium chloride. For cell bodies, but not axons, thresholds for both cathodal and anodal stimulation were dependent on the search method used to find the point of lowest threshold. With search and stimulation of matching polarity, cathodal stimuli evoked a ganglion cell response at lower currents (approximately one seventh to one tenth axonal threshold) than did anodal stimuli for both cell bodies and axons. With cathodal search and stimulation, cell body median thresholds were somewhat lower (approximately one half) than the axonal median thresholds. With anodal search and stimulation, cell body median thresholds were approximately the same as axonal median thresholds. CONCLUSIONS. The results suggest that cathodal stimulation should produce lower thresholds, more localized stimulation, and somewhat better selectivity for cell bodies over axons than would anodal stimulation. (Invest Ophthalmol Vis Sci. 2003; 44:3533-3543) DOI:10.1167/iovs.02-1041 O ur ultimate goal is to develop an implantable retinal prosthesis that electrically stimulates the retina to provide some functional vision to patients with advanced retinitis pigmentosa or age-related macular degeneration. Retinitis pigmentosa and age-related macular degeneration are forms of blindness that result in substantial loss of photoreceptors. Although physiological and morphologic changes may take place in the inner retinas of affected patients, 1-5 the opportunity exists for direct electrical excitation of the residual neurons as a means of restoring vision. Stimulation possibilities are either epiretinal (the stimulating points are on the inner surface of the retina) or subretinal (the stimulating points are on the outer surface of the retina, between the neural retina and the underlying pigment epithelium). The goal of the present study was to determine current threshold and increase in threshold with electrode displacement for epiretinal stimulation of retinal ganglion cells. The former can be used to judge the power requirements of a functioning prosthesis and the potential for electrochemical toxicity that occurs as current passes through the metal electrode. The latter can be used to guide the choice of interelectrode spacing and estimate the potential spatial resolution that could be derived from a prosthesis. Another motivation is the desire to achieve selective stimulation of ganglion cell bodies rather than axons en passage, which would presumably enhance the quality of perceptions induced by a retinal prosthesis. Only a few studies 6 -8 have been reported in which the currents needed to stimulate individual ganglion cells in the retina with an epiretinal electrode were investigated, and in none of these studies was the current thresholds of axons compared with cell bodies or the current thresholds measured as a function of electrode distance from the site of activation. Also, with the exception of Grumet et al., 8 relatively large microelectrodes have been used in these studies. A small microelectrode was used in the present study to enable a more precise study of threshold variation with electrode position near a cell body or axon of a ganglion cell. Preliminary portions of this work have been presented elsewhere 9 (Wyatt JL, et al. IOVS 1994;35:ARVO Abstract 593; Rizzo JF, et al. IOVS 1997;38:ARVO Abstract 182). MATERIALS AND METHODS Thirty-two adult New Zealand White rabbits (2-2.5 kg) were used in this study. All experimental procedures were in accordance with institutional guidelines and conformed to the guidelines of the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. Retinal Preparation The rabbits were sedated by an intraperitoneal injection of urethane (1.6 g/kg) and then received an intravenous injection of pentobarbital sodium (20 mg/kg) for deep anesthesia. Under normal room lighting, an eye was enucleated and hemisected, and the vitreous humor was removed with gentle suction applied to the back of a Pasteur pipet. A strip (Ϸ1 ϫ 2 cm) of inferior retina and attached sclera including the optic nerve head was removed and laid flat, ganglion cell side up, on a 10°inclined platform. The retinal strip was superfused with a solution of 8.9 g/L Ames medium (Sigma-Aldrich, St. Louis, MO), 1.9 g/L NaHCO 3 , and 0.8 g/L D-glucose and saturated with 95% O 2 -5% CO 2 . The solution flowed by gravity over the surface of the retina at a rate of 1.4 to 1.7 mL/min. The temperature of the solution on the retina was maintained at 34°C to 36°C. Diffuse background light (Ϸ1 W/cm 2 at the retina) was present throughout the experiments

Exclusive Production of Higgs Bosons in Hadron Colliders

We study the exclusive, double--diffractive production of the Standard Model Higgs particle in hadronic collisions at LHC and FNAL (upgraded) energies. Such a mechanism would provide an exceptionally clean signal for experimental detection in which the usual penalty for triggering on the rare decays of the Higgs could be avoided. In addition, because of the color singlet nature of the hard interaction, factorization is expected to be preserved, allowing the cross--section to be related to similar hard--diffractive events at HERA. Starting from a Fock state expansion in perturbative QCD, we obtain an estimate for the cross section in terms of the gluon structure functions squared of the colliding hadrons. Unfortunately, our estimates yield a production rate well below what is likely to be experimentally feasible.Comment: 17 pages, RevTeX file, four uufiled PostScript figures. UMPP #94-177. (Revised version. Some mistakenly missing Feynman diagrams are now added. Results do not change qualitatively. Paper reorganized.

Identification of KIF21A mutations as a rare cause of congenital fibrosis of the extraocular muscles type 3 (CFEOM3).

PURPOSE. Three congenital fibrosis of the extraocular muscles phenotypes (CFEOM1-3) have been identified. Each represents a specific form of paralytic strabismus characterized by congenital restrictive ophthalmoplegia, often with accompanying ptosis. It has been demonstrated that CFEOM1 results from mutations in KIF21A and CFEOM2 from mutations in PHOX2A. This study was conducted to determine the incidence of KIF21A and PHOX2A mutations among individuals with the third CFEOM phenotype, CFEOM3. METHODS. All pedigrees and sporadic individuals with CFEOM3 in the authors' database were identified, whether the pedigrees were linked or consistent with linkage to the FEOM1, FEOM2, and/or FEOM3 loci was determined, and the appropriate pedigrees and the sporadic individuals were screened for mutations in KIF21A and PHOX2A. RESULTS. Twelve CFEOM3 pedigrees and 10 CFEOM3 sporadic individuals were identified in the database. The structures of eight of the pedigrees permitted the generation of meaningful linkage data. KIF21A was screened in 17 probands, and mutations were identified in two CFEOM3 pedigrees. One pedigree harbored a novel mutation (2841G-->A, M947I) and one harbored the most common and recurrent of the CFEOM1 mutations identified previously (2860C-->T, R954W). None of CFEOM3 pedigrees or sporadic individuals harbored mutations in PHOX2A. CONCLUSIONS. The results demonstrate that KIF21A mutations are a rare cause of CFEOM3 and that KIF21A mutations can be nonpenetrant. Although KIF21A is the first gene to be associated with CFEOM3, the results imply that mutations in the unidentified FEOM3 gene are the more common cause of this phenotype

Calibration and Characterization of the IceCube Photomultiplier Tube

Over 5,000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-inch diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts.Comment: 40 pages, 12 figure

Limits on the high-energy gamma and neutrino fluxes from the SGR 1806-20 giant flare of December 27th, 2004 with the AMANDA-II detector

On December 27th 2004, a giant gamma flare from the Soft Gamma-ray Repeater 1806-20 saturated many satellite gamma-ray detectors. This event was by more than two orders of magnitude the brightest cosmic transient ever observed. If the gamma emission extends up to TeV energies with a hard power law energy spectrum, photo-produced muons could be observed in surface and underground arrays. Moreover, high-energy neutrinos could have been produced during the SGR giant flare if there were substantial baryonic outflow from the magnetar. These high-energy neutrinos would have also produced muons in an underground array. AMANDA-II was used to search for downgoing muons indicative of high-energy gammas and/or neutrinos. The data revealed no significant signal. The upper limit on the gamma flux at 90% CL is dN/dE < 0.05 (0.5) TeV^-1 m^-2 s^-1 for gamma=-1.47 (-2). Similarly, we set limits on the normalization constant of the high-energy neutrino emission of 0.4 (6.1) TeV^-1 m^-2 s^-1 for gamma=-1.47 (-2).Comment: 14 pages, 3 figure

Detection of Atmospheric Muon Neutrinos with the IceCube 9-String Detector

The IceCube neutrino detector is a cubic kilometer TeV to PeV neutrino detector under construction at the geographic South Pole. The dominant population of neutrinos detected in IceCube is due to meson decay in cosmic-ray air showers. These atmospheric neutrinos are relatively well-understood and serve as a calibration and verification tool for the new detector. In 2006, the detector was approximately 10% completed, and we report on data acquired from the detector in this configuration. We observe an atmospheric neutrino signal consistent with expectations, demonstrating that the IceCube detector is capable of identifying neutrino events. In the first 137.4 days of livetime, 234 neutrino candidates were selected with an expectation of 211 +/- 76.1(syst.) +/- 14.5(stat.) events from atmospheric neutrinos

On the selection of AGN neutrino source candidates for a source stacking analysis with neutrino telescopes

The sensitivity of a search for sources of TeV neutrinos can be improved by grouping potential sources together into generic classes in a procedure that is known as source stacking. In this paper, we define catalogs of Active Galactic Nuclei (AGN) and use them to perform a source stacking analysis. The grouping of AGN into classes is done in two steps: first, AGN classes are defined, then, sources to be stacked are selected assuming that a potential neutrino flux is linearly correlated with the photon luminosity in a certain energy band (radio, IR, optical, keV, GeV, TeV). Lacking any secure detailed knowledge on neutrino production in AGN, this correlation is motivated by hadronic AGN models, as briefly reviewed in this paper. The source stacking search for neutrinos from generic AGN classes is illustrated using the data collected by the AMANDA-II high energy neutrino detector during the year 2000. No significant excess for any of the suggested groups was found.Comment: 43 pages, 12 figures, accepted by Astroparticle Physic