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Microcomputer-based pellet trajectory guidance system for the Baseball II-T experiment

Description: In the Baseball II-T experiment a pellet generation and injection system was employed to place frozen ammonia pellets at the focus of a laser beam. The original trajectory guidance system suffered a number of problems that limited its accuracy and complicated the operation of the system. These problems were related to variable charge-to-mass ratios, timing, pellet discrimination, and computer speed. The original system design was improved by changes to the sensing components, microcomputer, and… more
Date: October 15, 1977
Creator: Mortensen, W.K.
Partner: UNT Libraries Government Documents Department
open access

Safety questions relevant to nuclear thermal propulsion

Description: Nuclear propulsion is necessary for successful Mars exploration to enhance crew safety and reduce mission costs. Safety concerns are considered by some to be an implements to the use of nuclear thermal rockets for these missions. Therefore, an assessment was made of the various types of possible accident conditions that might occur and whether design or operational solutions exist. With the previous work on the NERVA nuclear rocket, most of the issues have been addressed in some detail. Thus, a… more
Date: October 15, 1991
Creator: Buden, D.
Partner: UNT Libraries Government Documents Department
open access

Increasing FTIR spectromicroscopy speed and resolution through compressive imaging

Description: At the Advanced Light Source at Lawrence Berkeley National Laboratory, we are investigating how to increase both the speed and resolution of synchrotron infrared imaging. Synchrotron infrared beamlines have diffraction-limited spot sizes and high signal to noise, however spectral images must be obtained one point at a time and the spatial resolution is limited by the effects of diffraction. One technique to assist in speeding up spectral image acquisition is described here and uses compressive … more
Date: October 15, 2007
Creator: Gallet, Julien; Riley, Michael; Hao, Zhao & Martin, Michael C
Partner: UNT Libraries Government Documents Department
open access

Spatial resolution limits for synchrotron-based infrared spectromicroscopy

Description: Detailed spatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source synchrotron facility in Berkeley, CA. The high-brightness synchrotron source is coupled at this beamline to a Thermo-Electron Continumum XL infrared microscope. Two types of resolution tests in both the mid-IR (using a KBr beamsplitter and an MCT-A* detector) and in the near-IR (using a CaF2 beamsplitter and an InGaAS detector) were performed and compared to a simple diffraction-limited spot size mod… more
Date: October 15, 2007
Creator: Levenson, Erika; Lerch, Philippe & Martin, Michael C.
Partner: UNT Libraries Government Documents Department
open access

Analysis of Non-Enzymatically Glycated Peptides: Neutral-Loss Triggered MS3 Versus Multi-Stage Activation Tandem Mass Spectrometry

Description: Non-enzymatic glycation of tissue proteins has important implications in the development of complications of diabetes mellitus. While electron transfer dissociation (ETD) has been shown to outperform collision-induced dissociation (CID) in sequencing glycated peptides by tandem mass spectrometry, ETD instrumentation is not yet available in all laboratories. In this study, we evaluated different advanced CID techniques (i.e., neutral-loss triggered MS3 and multi-stage activation) during LC-MSn a… more
Date: October 15, 2008
Creator: Zhang, Qibin; Petyuk, Vladislav A.; Schepmoes, Athena A.; Orton, Daniel J.; Monroe, Matthew E.; Yang, Feng et al.
Partner: UNT Libraries Government Documents Department
open access

Detection of low energy single ion impacts in micron scaletransistors at room temperature

Description: We report the detection of single ion impacts throughmonitoring of changes in the source-drain currents of field effecttransistors (FET) at room temperature. Implant apertures are formed inthe interlayer dielectrics and gate electrodes of planar, micro-scaleFETs by electron beam assisted etching. FET currents increase due to thegeneration of positively charged defects in gate oxides when ions(121Sb12+, 14+, Xe6+; 50 to 70 keV) impinge into channel regions. Implantdamage is repaired by rapid the… more
Date: October 15, 2007
Creator: Batra, A.; Weis, C. D.; Reijonen, J.; Persaud, A.; Schenkel, T.; Cabrini, S. et al.
Partner: UNT Libraries Government Documents Department
open access

John Pendry: His Contributions to the Development of LEED Surface Crystallography

Description: In this paper we discuss the pivotal role played by Sir John Pendry in the development of Low Energy Electron Diffraction (LEED) during the past three decades; the earliest understanding on the physics of LEED to the development of sophisticated methods for the structural solution of complex surfaces.
Date: October 15, 2007
Creator: Somorjai, Gabor A. & Rous, P. J.
Partner: UNT Libraries Government Documents Department
open access

The National Ignition Facility: The world's largest optical system

Description: The National Ignition Facility (NIF), a 192-beam fusion laser, is presently under construction at the Lawrence Livermore National Laboratory with an expected completion in 2008. The facility contains 7,456 meter-scale optics for amplification, beam steering, vacuum barriers, focusing, polarization rotation, and wavelength conversion. A multiphase program was put in place to increase the monthly optical manufacturing rate by up to 20x while simultaneously reducing cost by up to 3x through a sub-… more
Date: October 15, 2007
Creator: Stolz, C J
Partner: UNT Libraries Government Documents Department
open access

Porphyrin-Based Photocatalytic Lithography

Description: Photocatalytic lithography is an emerging technique that couples light with coated mask materials in order to pattern surface chemistry. We excite porphyrins to create radical species that photocatalytically oxidize, and thereby pattern, chemistries in the local vicinity. The technique advantageously does not necessitate mass transport or specified substrates, it is fast and robust and the wavelength of light does not limit the resolution of patterned features. We have patterned proteins and ce… more
Date: October 15, 2007
Creator: Bearinger, J.; Stone, G.; Christian, A.; Dugan, L.; Hiddessen, A.; Wu, K. J. et al.
Partner: UNT Libraries Government Documents Department
open access

Water adsorption on O(2x2)/Ru(0001) from STM experiments andfirst-principles calculations

Description: We present a combined theoretical and experimental study of water adsorption on Ru(0001) pre-covered with 0.25 monolayers (ML) of oxygen forming a (2 x 2) structure. Several structures were analyzed by means of Density Functional Theory calculations for which STM simulations were performed and compared with experimental data. Up to 0.25 monolayers the molecules bind to the exposed Ru atoms of the 2 x 2 unit cell via the lone pair orbitals. The molecular plane is almost parallel to the surface w… more
Date: October 15, 2007
Creator: Cabrera-Sanfelix, P.; Sanchez-Portal, D.; Mugarza, A.; Shimizu,T.K.; Salmeron, M. & Arnau, A.
Partner: UNT Libraries Government Documents Department
open access

Simulations of plasma confinement in an antihydrogen trap

Description: The three-dimensional particle-in-cell (3-D PIC) simulation code WARP is used to study positron confinement in antihydrogen traps. The magnetic geometry is close to that of a UC Berkeley experiment conducted, with electrons, as part of the ALPHA collaboration (W. Bertsche et al., AIP Conf. Proc. 796, 301 (2005)). In order to trap antihydrogen atoms, multipole magnetic fields are added to a conventional Malmberg-Penning trap. These multipole fields must be strong enough to confine the antihydrog… more
Date: October 15, 2007
Creator: Gomberoff, K.; Fajans, J.; Friedman, A.; Grote, D.; Vay, J. L. & Wurtele, J. S.
Partner: UNT Libraries Government Documents Department
open access

Shotgun Metaproteomics of the Human Distal Gut Microbiota

Description: The human gut contains a dense, complex and diverse microbial community, comprising the gut microbiome. Metagenomics has recently revealed the composition of genes in the gut microbiome, but provides no direct information about which genes are expressed or functioning. Therefore, our goal was to develop a novel approach to directly identify microbial proteins in fecal samples to gain information about the genes expressed and about key microbial functions in the human gut. We used a non-targeted… more
Date: October 15, 2008
Creator: VerBerkmoes, N. C.; Russell, A. L.; Shah, M.; Godzik, A.; Rosenquist, M.; Halfvarsson, J. et al.
Partner: UNT Libraries Government Documents Department
open access

Six-week time series of eddy covariance CO2 flux at Mammoth Mountain, California: performance evaluation and role of meteorological forcing

Description: CO{sub 2} and heat fluxes were measured over a six-week period (09/08/2006 to 10/24/2006) by the eddy covariance (EC) technique at the Horseshoe Lake tree kill (HLTK), Mammoth Mountain, CA, a site with complex terrain and high, spatially heterogeneous CO{sub 2} emission rates. EC CO{sub 2} fluxes ranged from 218 to 3500 g m{sup -2} d{sup -1} (mean = 1346 g m{sup -2} d{sup -1}). Using footprint modeling, EC CO{sub 2} fluxes were compared to CO{sub 2} fluxes measured by the chamber method on a gr… more
Date: October 15, 2007
Creator: Lewicki, Jennifer; Lewicki, J. L.; Fischer, M. L. & Hilley, G. E.
Partner: UNT Libraries Government Documents Department
open access

Simple Models and Methods for Estimating the UltrasonicReflectivity of Spot Welds

Description: This paper describes models and methods for estimating theacoustic reflectivity of the welded interfaces between spot-welded sheetsfrom normal-incidence pulse-echo ultrasound signals. The simple geometryof the problem allows an abstraction that does not resort to complex waveequations. Instead, a reflectivity model predicts the timing andamplitude of the echoes arriving at the probe. This reflectivity model isnested in a signal processing model; recovering reflectivity firstrequires deconvoluti… more
Date: October 15, 2006
Creator: Davis, William B.
Partner: UNT Libraries Government Documents Department
open access

Decisive role of the energetics of dissociation products in the adsorption of water on O/Ru(0001)

Description: Using density-functional theory they found that, depending on coverage, coadsorbed oxygen can act both as a promoter and as an inhibitor of the dissociation of water on Ru(0001), the transition between these two behaviors occurring at (0.2 M). The key factor that determines this transition is the adsorption energy of the reaction products, OH in particular. The chemistry of this coadsorbed system is dictated by the effective coordination of the Ru atoms that participate in the bonding of the di… more
Date: October 15, 2008
Creator: Cabrera-Sanfelix, Pepa; Arnau, Andres; Mugarza, Aitor; Shimizu, Tomoko K.; Salmeron, Miquel & Sánchez-Portal, Daniel
Partner: UNT Libraries Government Documents Department
open access

Realization of a Custom Designed FPGA Based Embedded Controller

Description: As part of the Low Level RF (LLRF) upgrade project at Brookhaven National Laboratory's Collider-Accelerator Department (BNL C-AD), we have recently developed and tested a prototype high performance embedded controller. This controller is a custom designed PMC module employing a Xilinx V4FX60 FPGA with a PowerPC405 embedded processor, and a wide variety of on board peripherals (DDR2 SDRAM, FLASH, Ethernet, PCI, multi-gigabit serial transceivers, etc.). The controller is capable of running either… more
Date: October 15, 2007
Creator: Severino, F.; Harvey, M.; Hayes, T.; Hoff, L.; Oddo, P. & Smith, K. S.
Partner: UNT Libraries Government Documents Department
open access

Space nuclear power requirements for ozone layer modification

Description: This work estimates the power requirements for using photochemical processes driven by space nuclear power to counteract the Earth's ozone layer depletion. The total quantity of ozone (O{sub 3}) in the Earth's atmosphere is estimated to be about 4.7 {times} 10{sup 37} molecules. The ozone production and destruction rates in the stratosphere are both on the order of 4.9 {times} 10{sup 31} molecules/s, differing by a small fraction so that the net depletion rate is about 0.16 to 0.26% per year. T… more
Date: October 15, 1991
Creator: Dolan, T.J.
Partner: UNT Libraries Government Documents Department
open access

Predictions for nuclear properties along the r-process path

Description: The uniformity of different nuclear regions as a function of the number of valence protons and neutrons (counted from the nearest closed shell) has been exploited for the parameterization of calculations for nuclei far from stability within the IBA model. Predictions are given for low lying levels, E2 transition rates, and binding energies for nuclei in the r-process path in the A = 150 and A = 190 mass regions. 6 refs., 6 figs.
Date: October 15, 1987
Creator: Aprahamian, A.
Partner: UNT Libraries Government Documents Department
open access

On the spurious pressures generated by certain GFEM solutions of the incompressible Navier-Stokes equations

Description: The spurious pressures and acceptable velocities generated when using certain combinations of velocity and pressure approximations in a Galerkin finite element discretization of the primitive variable form of the incompressible Navier-Stokes equations are analyzed both theoretically and numerically for grids composed of quadrilateral finite elements. Schemes for obtaining usable pressure fields from the spurious numerical results are presented for certain cases.
Date: October 15, 1979
Creator: Sani, R. L.; Gresho, P. M. & Lee, R. L.
Partner: UNT Libraries Government Documents Department
open access

Picosecond x-ray measurements from 100 eV to 30 keV

Description: Picosecond x-ray measurements relevant to the Livermore Laser Fusion Program are reviewed. Resolved to 15 picoseconds, streak camera detection capabilities extend from 100 eV to higher than 30 keV, with synchronous capabilities in the visible, near infrared, and ultraviolet. Capabilities include automated data retrieval using charge coupled devices (CCD's), absolute x-ray intensity levels, novel cathodes, x-ray mirror/reflector combinations, and a variety of x-ray imaging devices.
Date: October 15, 1980
Creator: Attwood, D.T.; Kauffman, R.L. & Stradling, G.L.
Partner: UNT Libraries Government Documents Department
open access

Fermilab Physics Program for the 1990's

Description: Following a brief introduction to Fermilab facilities and a review of the accelerator status and plans, the physics potential for the Fermilab III upgrade program is discussed for both the fixed target and collider modes.
Date: October 15, 1990
Creator: Stanfield, K. C.
Partner: UNT Libraries Government Documents Department
open access

Numerical determination of injector design for high beam quality

Description: The performance of a free electron laser strongly depends on the electron beam quality or brightness. The electron beam is transported into the free electron laser after it has been accelerated to the desired energy. Typically the maximum beam brightness produced by an accelerator is constrained by the beam brightness deliverd by the accelerator injector. Thus it is important to design the accelerator injector to yield the required electron beam brightness. The DPC (Darwin Particle Code) comput… more
Date: October 15, 1985
Creator: Boyd, J.K.
Partner: UNT Libraries Government Documents Department
open access

Optimum ranges for x-ray thickness measurements

Description: Film thicknesses can be measured by two x-ray methods: x-ray absorption (gauging or radiography) and x-ray fluorescence. Optimization of both methods is discussed.
Date: October 15, 1985
Creator: Ryon, R.W.
Partner: UNT Libraries Government Documents Department
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