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

Two dimensional pattern formation in a chemotactic system

Chemotaxis is known to be important in cell aggregation in a variety of contexts. We propose a simple partial differential equation model for a chemotactic system of two species, a population of cells and a chemoattractant to which cells respond. Linear analysis shows that there exists the possibility of spatially inhomogeneous solutions to the model equations for suitable choices of parameters. We solve the full nonlinear steady state equations numerically on a two dimensional rectangular domain. By using mode selection from the linear analysis we produce simple pattern elements such as stripes and regular spots. More complex patterns evolve from these simple solutions as parameter values or domain shape change continuously. An example bifurcation diagram is calculated using the chemotactic response of the cells as the bifurcation parameter. These numerical solutions suggest that a chemotactic mechanism can produce a rich variety of complex patterns

Transient inactivation of perirhinal cortex disrupts encoding, retrieval, and consolidation of object recognition memory.

Damage to perirhinal cortex (PRh) impairs object recognition memory in humans, monkeys, and rats when tested in tasks such as delayed nonmatching to sample, visual paired comparison, and its rodent analog, the spontaneous object recognition task. In the present study, we have capitalized on the discrete one-trial nature of the spontaneous object recognition task to investigate the role of PRh in several distinct stages of object recognition memory. In a series of experiments, transient inactivation of PRh was accomplished with bilateral infusions of lidocaine directly into PRh immediately before the sample phase (encoding), immediately before the choice phase (retrieval), or within the retention delay after the sample phase (storage-consolidation). Compared with performance on trials in which they received saline infusions, rats were significantly impaired when lidocaine was infused before the sample phase, regardless of the length of the retention delay. Similarly, delay-independent deficits were observed after immediate pre-choice infusions of lidocaine. Finally, PRh inactivation immediately and 20 min after the sample phase, but not 40, 60, or 80 min after, also disrupted subsequent object recognition when the retention delay was sufficiently long to ensure the dissipation of the actions of lidocaine during the choice phase. The effects of pre-sample and pre-choice inactivation indicate involvement of PRh in encoding and retrieval stages of object recognition, and the time course of post-sample inactivation effects suggests a role for PRh in the maintenance of the object trace during memory consolidation

Glutamate receptors in perirhinal cortex mediate encoding, retrieval, and consolidation of object recognition memory.

Object recognition is consistently impaired in human amnesia and animal models thereof. Results from subjects with permanent brain damage have revealed the importance of the perirhinal cortex to object recognition memory. Here, we report evidence from rats for interdependent but distinct stages in object recognition memory (encoding, retrieval, and consolidation), which require glutamate receptor activity within perirhinal cortex. Transient blockade of AMPA receptor-mediated synaptic transmission within perirhinal cortex disrupted encoding for short- and long-term memory as well as retrieval and consolidation. In contrast, transient NMDA receptor blockade during encoding affected only long-term object recognition memory; NMDA receptor activity was also necessary for consolidation but not retrieval. These results further demonstrate the importance of perirhinal cortex for object recognition memory and suggest that, as in the hippocampus, AMPA and NMDA receptors mediate synaptic transmission and activity-dependent synaptic plasticity, respectively, in several stages of memory processing

The COBE DIRBE Point Source Catalog

We present the COBE DIRBE Point Source Catalog, an all-sky catalog containing infrared photometry in 10 bands from 1.25 microns to 240 microns for 11,788 of the brightest near and mid-infrared point sources in the sky. Since DIRBE had excellent temporal coverage (100 - 1900 independent measurements per object during the 10 month cryogenic mission), the Catalog also contains information about variability at each wavelength, including amplitudes of variation observed during the mission. Since the DIRBE spatial resolution is relatively poor (0.7 degrees), we have carefully investigated the question of confusion, and have flagged sources with infrared-bright companions within the DIRBE beam. In addition, we filtered the DIRBE light curves for data points affected by companions outside of the main DIRBE beam but within the `sky' portion of the scan. At high Galactic latitudes (|b| > 5 degrees), the Catalog contains essentially all of the unconfused sources with flux densities greater than 90, 60, 60, 50, 90, and 165 Jy at 1.25, 2.2, 3.5, 4.9, 12, and 25 microns, respectively, corresponding to magnitude limits of approximately 3.1, 2.6, 1.7, 1.3, -1.3, and -3.5. At longer wavelengths and in the Galactic Plane, the completeness is less certain because of the large DIRBE beam and possible contributions from extended emission. The Catalog also contains the names of the sources in other catalogs, their spectral types, variability types, and whether or not the sources are known OH/IR stars. We discuss a few remarkable objects in the Catalog. [abridged]Comment: Accepted for publication in the Astrophysical Journal Supplement. The full tables are available at http://www.etsu.edu/physics/bsmith/dirbe

CO and HI observations of an enigmatic cloud

An isolated HI cloud with peculiar properties has recently been discovered by Dedes, Dedes, & Kalberla (2008, A&A, 491, L45) with the 300-m Arecibo telescope, and subsequently imaged with the VLA. It has an angular size of ~6', and the HI emission has a narrow line profile of width ~ 3 km/s. We explore the possibility that this cloud could be associated with a circumstellar envelope ejected by an evolved star. Observations were made in the rotational lines of CO with the IRAM-30m telescope, on three positions in the cloud, and a total-power mapping in the HI line was obtained with the Nancay Radio Telescope. CO was not detected and seems too underabundant in this cloud to be a classical late-type star circumstellar envelope. On the other hand, the HI emission is compatible with the detached-shell model that we developed for representing the external environments of AGB stars. We propose that this cloud could be a fossil circumstellar shell left over from a system that is now in a post-planetary-nebula phase. Nevertheless, we cannot rule out that it is a Galactic cloud or a member of the Local Group, although the narrow line profile would be atypical in both cases.Comment: Accepted for publication in Astronomy and Astrophysic

The core structure of presolar graphite onions

Of the ``presolar particles'' extracted from carbonaceous chondrite dissolution residues, i.e. of those particles which show isotopic evidence of solidification in the neighborhood of other stars prior to the origin of our solar system, one subset has an interesting concentric graphite-rim/graphene-core structure. We show here that single graphene sheet defects in the onion cores (e.g. cyclopentane loops) may be observable edge-on by HREM. This could allow a closer look at models for their formation, and in particular strengthen the possibility that growth of these assemblages proceeds atom-by-atom with the aid of such in-plane defects, under conditions of growth (e.g. radiation fluxes or grain temperature) which discourage the graphite layering that dominates subsequent formation of the rim.Comment: 4 pages, 7 figures, 11 refs, see also http://www.umsl.edu/~fraundor/isocore.htm

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

Circumstellar HI and CO around the carbon stars V1942 Sgr and V CrB

Context. The majority of stars that leave the main sequence are undergoing extensive mass loss, in particular during the asymptotic giant branch (AGB) phase of evolution. Observations show that the rate at which this phenomenon develops differs highly from source to source, so that the time-integrated mass loss as a function of the initial conditions (mass, metallicity, etc.) and of the stage of evolution is presently not well understood. Aims. We are investigating the mass loss history of AGB stars by observing the molecular and atomic emissions of their circumstellar envelopes. Methods. In this work we have selected two stars that are on the thermally pulsing phase of the AGB (TP-AGB) and for which high quality data in the CO rotation lines and in the atomic hydrogen line at 21 cm could be obained. Results. V1942 Sgr, a carbon star of the Irregular variability type, shows a complex CO line profile that may originate from a long-lived wind at a rate of ~ 10^-7 Msol/yr, and from a young (< 10^4 years) fast outflow at a rate of ~ 5 10^-7 Msol/yr. Intense HI emission indicates a detached shell with 0.044 Msol of hydrogen. This shell probably results from the slowing-down, by surrounding matter, of the same long-lived wind observed in CO that has been active during ~ 6 10^5 years. On the other hand, the carbon Mira V CrB is presently undergoing mass loss at a rate of 2 10^-7 Msol/yr, but was not detected in HI. The wind is mostly molecular, and was active for at most 3 10^4 years, with an integrated mass loss of at most 6.5 10^-3 Msol. Conclusions. Although both sources are carbon stars on the TP-AGB, they appear to develop mass loss under very different conditions, and a high rate of mass loss may not imply a high integrated mass loss.Comment: Accepted for publication in Astron. Astrophy

The Structure of Urinary Catheter Encrusting Bacterial Biofilms

A major complication of long-term urethral catheterization is catheter blockage by encrustation. We have examined 20 encrusted catheters and in each case crystal formation was associated with the presence of bacterial biofilms on the luminal surfaces. Scanning electron microscopy and X-ray microanalysis indicated the presence of struvite and hydroxyapatite in the biofilms. Urease producing bacteria were colonizing 16 of the catheters. Proteus mirabilis was the commonest species being recovered from ten of the catheters. These results support the hypothesis that catheter encrustation has a similar etiology to that of infection-induced urinary stones and confirm that the important target for any attempt to control catheter encrustations is Pr. mirabilis