251 - 275 of 7,174
Number of results to display per page
251 Davidson, Diane W.Experimental study of diffuse competition in harvester antsExperiments carried out over a 5-yr period in the Chihuahuan Desert support the a priori prediction of diffuse competition between two species of harvester ants. Despite dietary overlap between a large species {Pogonomyrmex rugosus) and a small species (Pheidole xerophila), the large species facilit...Chihuahuan Desert; Ants; Facilitation; Resource allocation; Granivory1985
252 Gerton, JordanNanoscale fluorescence microscopy using carbon nanotubesWe demonstrate the first reported use of single-walled carbon nanotubes as nano-optical probes in apertureless nearfield fluorescence microscopy. We show that, in contrast to silicon probes, carbon nanotubes always cause strong fluorescence quenching when used to image dye-doped polystyrene spheres...2008
253 Miller, Joel Steven; Epstein, Arthur J.Optical properties of the 1:2 compound of dimethylferrocenium with tetracyanoquinodimethanide: [(Me2Fc)(TCNQ)2]We present the results of a study of the room-temperature polarized reflectance of (1:2) 1,1'-dimethylferrocenium ditetracyanoquinodimethanide [(Me2Fc)(TCNQ)2] over the range between the far infrared and the near ultraviolet. Kramers-Kronig analysis of the reflectance is used to determine the optica...Reflectance; Electrons ; Molecules1987
254 Cates, Joshua E.; Whitaker, Ross T.; Jones, Greg M.Case study: an evaluation of user-assisted hierarchical watershed segmentationWhile level sets have demonstrated a great potential for 3D medical image segmentation, their usefulness has been limited by two problems. First, 3D level sets are relatively slow to compute. Second, their formulation usually entails several free parameters which can be very difficult to correctl...Watershed segmentation; Brain tumor imaging2004-02-27
255 Greenfield, HarveySimulation of arbitrary shaped boundaries for hemodynamic studies1973
256 Bastiani, MichaelGuidance of neuronal growth cones in the grasshopper embryo. I. Recognition of a specific axonal pathway by the pCC neuronThe selective affinities that growth cones display for specific axonal surfaces give rise to stereotyped patterns of selective fasciculation. Previous studies on cell recognition by neuronal growth cones in the grasshopper embryo led to the proposal and initial experimental testing of the labeled-p...Fascicle; Axon; Affinity1986
257 Christensen, Douglas A.Laser diode coherence length variation with drive current: a tool for dispersion measurementsA visible light (670nm) laser diode was used as a variable coherence length source to measure dispersion characteristics in single-mode fibers. The diode's spectral width, measured against increasing drive current, was found to change from about 16 nanometers to less than 0.2 nanometer. The corresp...Laser diode; Fiber interferometry1992
258 Liu, FengSimple theory of the electronic structure: clusters to crystalsA simple scheme based upon a cross between the molecular clusters and the tight-binding theory has been developed to calculate the electronic structure of a large class of systems ranging from molecules to solids. The method is applied to study the variations in the magnetic moments of Fe and Ni for...Clusters; Tight-binding theory; Magnetic moment1988-09
259 Capecchi, Mario R.Gene targeting. How efficient can you get?With targeting in Leishmania and Trypanosoma, there are now greater incentives to develop the technology in organisms of intermediate complexity such as Caenorhabditis elegans and Drosophila. The ratio of homologous to nonhomologus recombination in these organisms might prove to be greater than in m...Animals; DNA Mutational Analysis; Recombination, Genetic1990-11-08
260 DeTar, CarletonMomentum spectrum of hadronic secondaries in the multiperipheral modelMotivated by a simplified multiperipheral model, we formulate a general qualitative description of the momentum spectrum of secondaries, resulting from a collision of two hadrons at high energies. Arguing from two fundamental multiperipheral concepts, (a) that transverse momenta are limited and (b...Secondaries; Multiperipheral model; Fireballs1971-01
261 Organick, Elliott I.Transformation of Ada program units into silicon (Fourth Semiannual technical report 83 Apr 1 - 83 Nov 15)This report, augmented with several appended papers and supplementary reports describes the most recent six months of work on the research project, "Transformation of Ada Programs into Silicon". This report is also the last of the series to be rendered under the current contact.Transformation; Ada program units; Silicon1983
262 Armentrout, Peter B.Guided ion-beam studies of the reactions of Con + (n=2-20) with O2: cobalt cluster-oxide and -dioxide bond energiesThe kinetic-energy dependence for the reactions of Con + (n=2-20) with O2 is measured as a function of kinetic energy over a range of 0 to 10 eV in a guided ion-beam tandem mass spectrometer. A variety of Com+ , ComO+, and ComO2 + (mMetal clusters; Cobalt ions; Collision-induced dissociation; Bond energies; Exothermic reactions; Endothermic reactions2005
263 Olivera, Baldomero M.Poly(ADP-ribosylation) of DNA topoisomerase I from calf thymusWe demonstrate that the activity of the major DNA topoisomerase I from calf thymus is severely inhibited after modification by purified poly(ADP-ribose) synthetase. Polymeric chains of poly(ADP-ribose) are covalently attached to DNA topoisomerase I. These observations with highly purified enzymes ...ADP-ribosylation; Poly(ADP-ribose) synthetase1984
264 Vardeny, Zeev Valentine; Gellermann, WernerTwo-photon absorption measured in the presence of strong one-photon saturation in cumulene-containing polymerThe Z-scan technique is used to extract the real and imaginary third order nonlinear susceptibilities, Rex(3) and Imx(3), respectively. A series of Z scans were conducted at 590 nm (near one-photon resonance) on a cumulene-containing polymer, poly(p-phenylene-l,4-diphenyl-l,2,3-butatriene) or PPC3, ...Molecular second hyperpolarizability; One-photon saturation; Polymer solution; Chain length1997
265 Ogburn, Joyce L.Bit by bit: communicating voucher information to the accounting department from automated library systems(pt. 2)Bit by Bit column: "This is the second of a two-part article. Part 1 (ATG Feb. 1991) presented some general considerations about the value of the automation process, the time and effort saved and the improved accuracy achieved by eliminating redundant data entry. Part II will present the rudiments o...Library automation; Library information systems; Library acquisitions1991-06
266 DeTar, CarletonFinite temperature lattice QCD with clover fermionsWe report on our simulation of finite temperature lattice QCD with two flavors of O(a) Symanzik-improved fermions and O(a2) Symanzik-improved glue. Our thermodynamic simulations were performed on an 83 × 4 lattice, and we have performed complementary zero temperature simulations on an 83 × 16 la...Wilson quarks; Clover fermions1997-02
267 Morse, Michael DavidThe ground state and excited ?-hole states of CuAuResonant two-photon ionization spectroscopy has been applied to jet-cooled diatomic CuAu. Eight band systems have been observed, rotationally resolved, and analyzed. The ground state is X??+ in symmetry, deriving from the 3d??Cu 5d??Au, ?? molecular configuration. Its bond length has been determined...1991
268 Miller, Joel StevenZero field splitting, field-dependent magnetization of mixed-valent S = 3/2 Diruthenium(II,III) tetracarboxylatesThe 2 K field-dependent magnetization, M(H), of S = 3/2 [RunII/III2(OAc)4]+ was studied. [RuII/III 2(OAc)4]+ exhibits an unusually low magnetization with respect to that predicted by the classical Brillouin function. This reduced value is a consequence of the large anisotropy arising from the large ...Spin; Coupling; Expressions2004
269 Mathews, V. JohnLattice algorithms for recursive least squares adaptive second-order volterra filteringThis paper presents two computationally efficient recursive least-square (RLS) lattice algorithms for adaptive nonlinear filtering based on a truncated second-order Volterra system model. The lattice formulation transforms the nonlinear filtering problem into an equivalent multichannel, linear filte...1994
270 Couldwell, William T.Practicing neurosurgery in the United StatesCompared with other developed countries, the U.S. spends a high percentage of its gross domestic product on healthcare: 16 percent in 2005, up from 15 percent in 2004. This is far and away the greatest percentage of GDP spent on healthcare of any nation for which such data is collected. However,...2008-01-01
271 Boll, Steven F.; Done, William JohnNoise suppression methods for robust speech processing (1 Oct. 1978- 31 Mar. 1981)Robust speech processing in practical operating environments requires effective environmental and processor noise suppression. This report describes the technical findings and accomplishments during this reporting period for period for research program funded to develop real time, compressed speech ...Noise suppression; Compressed speech analysis-synthesis algorithms; Signal contamination1978
272 Stang, Peter J.Supramolecular chemistry and molecular design: self-assembly of molecular squaresModem supramolecular chemistry has been described as organized polymolecular systems held together by noncovalent interactions and represents one of the major frontiers in the chemical sciences.'-' At present the field is dominated by the hydrogen bonding motif that mimics biological systems and th...Molecular design; Molecular squares1997
273 Dailey, Andrew T.Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 11: interbody techniques for lumbar fusionStandards. There is insufficient evidence to recommend a treatment standard. Guidelines. In the context of a single-level stand-alone ALIF or ALIF with posterior instrumentation, the addition of a PLF is not recommended as it increases operating room time and blood loss without influencing the like...Fusion; Lumbar spine; Degenerative disease; Lumbar fusion; Interbody techniques2005
274 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Linear and nonlinear photoexcitation dynamics in ∏-conjugated polymersLinear and nonlinear recombination kinetics with various lifetime distributions were identified for long-lived photoexcitations in a series of rr-conjugated polymer films using modulation frequency and excitation intensity dependencies of the photoinduced absorption. This includes monomolecular, bim...Linear photoexcitation; Nonlinear photoexcitation; pi-conjugated polymers; Recombination kinetics2003-01
275 Harrison, Reid R.Polymer based thin film coils as a power module of wireless neural interfacesFor the conventional Utah Electrode Array (UEA) to be able to function without transcutaneous wire connections, a kind of power source is needed in an integrated form with the UEA. To develop such wireless neural interfaces, inductive coupling between two coils was used to deliver power to the integ...Wireless; Neural interfaces; Thin film coils; Utah Electrode Array2006
251 - 275 of 7,174