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Biomedical subjects

C B Carter

Publications and source records attributed to C B Carter.

18 recordsLinked to original sources
PubMed2004

Self-assembly via adsorbate-driven dislocation reactions.

Deposition of S onto a monolayer of Ag/Ru(0001) transforms the herringbone pattern of the clean Ag film into a strikingly regular array of 2D-vacancy islands [Nature (London) 397, 238 (1999)]]. Time-resolved scanning tunneling microscopy reveals that this nanometer-scale restructuring occurs by a cooperative mechanism involving the sequential formation of triangular regions with fcc and hcp stacking. Using a 2D Frenkel-Kontorova model, we can simulate the creation of these triangular building blocks via basic dislocation motions and reactions.

Journal Article↗
PubMed2004

Stented Lich-Gregoir ureteroneocystostomy: case series report and cost-effectiveness analysis.

UNLABELLED: Extravesical ureteroneocystostomy to reestablish urinary tract continuity in renal transplantation has been examined through a meta-analysis of more than 14,000 kidney transplants leading to the finding that stented anastomosis was associated with a lower urologic complication rate compared with nonstented anastomoses. Fourteen stents must be used to prevent one urologic complication. We now report the urologic complication rate in our case series in which a stented Lich-Gregoir anastomosis was routinely utilized. We present a cost-effectiveness analysis regarding the usage of ureteral stents. METHODS: The records of 395 consecutive renal transplants were reviewed. Minimum follow-up time was 6 months. The standard anastomosis was a Lich-Gregoir with a 6- or 8-F 12- or 14-cm J-J stent. Monitored urologic complications included postoperative vesicoureteral leak or ureteral necrosis, obstruction or stricture, or clinically significant hematuria. Charges in 2004 US dollars were reported by the hospital accounting office. RESULTS: Four urologic complications were noted-three leaks and one stricture (complication rate of 1.0%). There were no stent-related complications requiring reoperation. There were no cases in which the urologic complication led to graft loss or patient death. Total charges associated with stent use were $1,087 per patient, or $15,218 per urologic complication prevented. CONCLUSIONS: The urologic complication rate in this case series is similar to the five previously published randomized trials, as well as our previously published meta-analysis. These results support the routine use of a ureteral stent. Our analysis suggests that stent use is cost effective.

Anastomosis, Surgical↗
PubMed2004

Using the FIB to characterize nanoparticle materials.

In the 1-100-nm size regime, the properties of materials can differ significantly from those of their bulk counterparts. The present study applies the focused ion beam (FIB) tool to the characterization of nanoscale structures for scanning and transmission electron microscopy. The strength of this method is its ability to manufacture samples that cannot be produced using traditional means. The films of nanoparticles examined here are examples of such systems; the films are found to be not fully dense, composed of chemically heterogeneous areas and mechanically different from the substrate. Distinct advantages of the application of the FIB for characterization of nanoscale structures are highlighted for several nanoparticle structures. This successful application of FIB techniques provides a pathway to integrate the study of nanoscale production techniques and their resulting structure-property relationships.

Journal Article↗
PubMed2004

A method for determining void arrangements in inverse opals.

The periodic arrangement of voids in ceramic materials templated by colloidal crystal arrays (inverse opals) has been analysed by transmission electron microscopy. Individual particles consisting of an approximately spherical array of at least 100 voids were tilted through 90 degrees along a single axis within the transmission electron microscope. The bright-field images of these particles at high-symmetry points, their diffractograms calculated by fast Fourier transforms, and the transmission electron microscope goniometer angles were compared with model face-centred cubic, body-centred cubic, hexagonal close-packed, and simple cubic lattices in real and reciprocal space. The spatial periodicities were calculated for two-dimensional projections. The systematic absences in these diffractograms differed from those found in diffraction patterns from three-dimensional objects. The experimental data matched only the model face-centred cubic lattice, so it was concluded that the packing of the voids (and, thus, the polymer spheres that composed the original colloidal crystals) was face-centred cubic. In face-centred cubic structures, the stacking-fault displacement vector is a/6<211> . No stacking faults were observed when viewing the inverse opal structure along the orthogonal <110>-type directions, eliminating the possibility of a random hexagonally close-packed structure for the particles observed. This technique complements synchrotron X-ray scattering work on colloidal crystals by allowing both real-space and reciprocal-space analysis to be carried out on a smaller cross-sectional area.

Ceramics↗
PubMed2002

Structure of the (110) antiphase boundary in gallium phosphide.

The morphology of antiphase boundaries in GaP films grown by molecular beam epitaxy on Si (001) has been studied by transmission electron microscopy. The inversion of the crystal polarity between antiphase domains was confirmed by convergent-beam electron diffraction. The APBs were often found to facet parallel to [110] planes. Strong-beam alpha-fringe contrast observed along the (110) facets indicates that adjacent antiphase domains are related by an additional rigid-body lattice translation. Diffraction-contrast analysis shows that this R corresponds to a shear parallel to the [001] direction and a small expansion. The magnitude of the translation was inferred, quantitatively, through a comparison between energy-filtered zero-loss images of the alpha-fringe contrast with numerical calculations. The components of the rigid-body lattice translation were determined to be 0.023 +/- 0.0033 nm in the [001] direction and 0.005 +/- 0.002 nm in the 0 direction. Based upon a geometric model of the [110] antiphase boundary, the lengths of the Ga and P antisite bonds were calculated to be 254 +/- 2 pm and 227 +/- 4 pm, respectively.

Journal Article↗
PubMed2001

Direct observation of misfit dislocation glide on surfaces.

Using scanning tunneling microscopy we have observed thermally induced dislocation glide in monolayer Cu films on Ru(0001) at room temperature. The motion is governed by a Peierls barrier that depends on the detailed structure of the dislocations, in particular upon whether the threading dislocations that terminate them are dissociated or not. Calculations based on the Frenkel-Kontorova model reproduce the threading dislocation structure and provide estimates of the Peierls barrier and dislocation stiffness which are consistent with experiment.

Journal Article↗
PubMed2000

Risk of early renal allograft failure is increased for patients with antiphospholipid antibodies.

Renal allograft thrombosis can cause transplant failure. Because antiphospholipid antibodies (aPA) are associated with thrombosis, we investigated pretransplant sera from patients with early renal allograft failure to determine if aPA were present. Fifty-six final cross-match (FxM) sera from patients whose transplant failed within 16 days were compared to FxM sera from the next sequential transplant patients. The sera were tested for IgG, IgM, and IgA antibodies to cardiolipin, phosphatidylserine, and phosphatidylethanolamine. aPA were identified in 57% of FxM sera from patients with early non-function versus 35% of FxM sera from patients with functioning grafts (P = 0.02). Historical sera from 11 aPA-positive patients contained aPA up to 18 months prior to transplantation. Since aPA were present in historical sera, testing for aPA can identify certain patients at risk for early allograft failure. The involvement of aPA in early allograft loss is supported by studies demonstrating aPA recovery from an explanted failed transplant.

Antibodies, Antiphospholipid↗
PubMed1996

Cholesterol embolization in renal allografts.

Renal cholesterol embolization has been well described for many years. It has only been reported in a small number of renal transplant recipients, however. Two instances of primary renal allograft nonfunction because of cholesterol embolization are reported. The source of the emboli was believed to be the donor's aorta. Cholesterol embolization must be considered in the differential diagnosis of primary renal allograft dysfunction. Additionally, care must be taken during evaluation and procurement procedures to help avoid this complication.

Adult↗
PubMed1991

A computer program for many-beam image simulation of amplitude-contrast images.

A computer program for the simulation of amplitude-contrast electron micrographs is described. The program is based on the n-beam dynamical theory of diffraction contrast as described by Howie and Whelan (see Howie, A., and Whelan, M.J. (1961) Proc. R. Soc. Lond. [Biol]). The displacement fields associated with crystal lattice defects are calculated using linear anisotropic elasticity. The program can be used to simulate images of crystals containing line or planar defects or combinations of these defects. The line defects can be oriented freely within the foil, and are not restricted to being mutually parallel, but must be straight. Different techniques available for solving the diffraction problem, with or without the column approximation, are discussed.

Crystallization↗
PubMed1988

Structure of superconducting thin films of YBa2Cu3O7-x grown on SrTiO3 and cubic zirconia.

Thin films of the superconductive oxide YBa2Cu3O7-x have been made by electron-beam coevaporation of the metals in an oxygen atmosphere onto single-crystal [001]-oriented SrTiO3 and yttria-stabilized zirconia (YSZ) substrates. The oxide films were superconducting in the as-deposited state (Tc = 81-83K, Jc = 10(6) A/cm2 at 4.2K). Bright-field imaging, selected-area diffraction (SAD), and high-resolution imaging in the transmission electron microscope were used to characterize the microstructure of these films. All of the films were polycrystalline. On SrTiO3 the films were oriented, for the most part, with [110] parallel to the substrate surface. On YSZ, two microstructures were observed: one with smaller rectangular grains oriented with (100) or (010) parallel to the substrate surface and the other with (001) parallel to the surface (i.e., c-axis up).

Computer Simulation↗