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R. Bruce Merrifield and Solid-Phase Peptide Synthesis: A Historical Assessment

Description: Bruce Merrifield, trained as a biochemist, had to address three major challenges related to the development and acceptance of solid-phase peptide synthesis (SPPS). The challenges were (1) to reduce the concept of peptide synthesis on a insoluble support to practice, (2) overcome the resistance of synthetic chemists to this novel approach, and (3) establish that a biochemist had the scientific credentials to effect the proposed revolutionary change in chemical synthesis. How these challenges wer… more
Date: December 4, 2007
Creator: Mitchell, A R
Partner: UNT Libraries Government Documents Department
open access

Radioactive Elements in the Standard Atomic Weights Table.

Description: In the 1949 Report of the Atomic Weights Commission, a series of new elements were added to the Atomic Weights Table. Since these elements had been produced in the laboratory and were not discovered in nature, the atomic weight value of these artificial products would depend upon the production method. Since atomic weight is a property of an element as it occurs in nature, it would be incorrect to assign an atomic weight value to that element. As a result of that discussion, the Commission deci… more
Date: August 4, 2007
Creator: Holden, N. E.
Partner: UNT Libraries Government Documents Department
open access

Measurement of the B to Xs gammaBranching Fraction and Photon Energy Spectrum usingthe Recoil Method

Description: We present a measurement of the branching fraction and photon energy spectrum for the decay B {yields} X{sub s}{gamma} using data from the BABAR experiment. The data sample corresponds to an integrated luminosity of 210 fb{sup -1}, from which approximately 680,000 B{bar B} events are tagged by a fully reconstructed hadronic decay of one of the B mesons. In the decay of the second B meson, an isolated high-energy photon is identified. We measure {Beta}(B {yields} X{sub s}{gamma}) = (3.66 {+-} 0.… more
Date: December 4, 2007
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department
open access

Recovering the Elemental Composition of Comet Wild 2 Dust in Five Stardust Impact Tracks and Terminal Particles in Aerogel

Description: The elemental (non-volatile) composition of five Stardust impact tracks and terminal particles left from capture of Comet 81P/Wild 2 dust were mapped in a synchrotron x-ray scanning microprobe with full fluorescence spectra at each pixel. Because aerogel includes background levels of several elements of interest, we employ a novel 'dual threshold' approach to discriminate against background contaminants: an upper threshold, above which a spectrum contains cometary material plus aerogel and a lo… more
Date: January 4, 2007
Creator: Ishii, H. A.; Brennan, S.; Bradley, J. P.; Luening, K.; Ignatyev, K. & Pianetta, P.
Partner: UNT Libraries Government Documents Department
open access

Electrons in a positive-ion beam with solenoid or quadrupole magnetic transport

Description: The High Current Experiment (HCX) is used to study beam transport and accumulation of electrons in quadrupole magnets and the Neutralized Drift-Compression Experiment (NDCX) to study beam transport through and accumulation of electrons in magnetic solenoids. We find that both clearing and suppressor electrodes perform as intended, enabling electron cloud densities to be minimized. Then, the measured beam envelopes in both quadrupoles and solenoids agree with simulations, indicating that theoret… more
Date: June 4, 2007
Creator: Molvik, A. W.; Kireeff Covo, M.; Cohen, R.; Coleman, J.; Sharp, W.; Bieniosek, F. et al.
Partner: UNT Libraries Government Documents Department
open access

Generalization of the ERIT principle and method.

Description: The paper describes the generalization of the method to produce secondary particles with a low-energy and low-intensity primary beam circulating in a Storage Ring with the Emittance-Recovery by Internal-Target (ERIT).
Date: November 4, 2007
Creator: Ruggiero, A. G.
Partner: UNT Libraries Government Documents Department
open access

Electron-Cloud Build-up in the FNAL Main Injector

Description: We present a summary on ongoing simulation results for the electron-cloud buildup in the context of the proposed FNAL Main Injector (MI) intensity upgrade [1] in a fieldfree region at the location of the RFA electron detector [2]. By combining our simulated results for the electron flux at the vacuum chamber wall with the corresponding measurements obtained with the RFA we infer that the peak secondary electron yield (SEY) {delta}{sub max} is {approx}> 1.4, and the average electron density i… more
Date: June 4, 2007
Creator: Furman, M. A.
Partner: UNT Libraries Government Documents Department
open access

Development of an Immersed Boundary Method to Resolve Complex Terrain in the Weather Research and Forecasting Model

Description: Flow and dispersion processes in urban areas are profoundly influenced by the presence of buildings which divert mean flow, affect surface heating and cooling, and alter the structure of turbulence in the lower atmosphere. Accurate prediction of velocity, temperature, and turbulent kinetic energy fields are necessary for determining the transport and dispersion of scalars. Correct predictions of scalar concentrations are vital in densely populated urban areas where they are used to aid in emerg… more
Date: September 4, 2007
Creator: Lunquist, K A; Chow, F K; Lundquist, J K & Mirocha, J D
Partner: UNT Libraries Government Documents Department
open access

Isochoric Implosions for Fast Ignition

Description: Various gain models have shown the potentially great advantages of Fast Ignition (FI) Inertial Confinement Fusion (ICF) over its conventional hot spot ignition counterpart [e.g., S. Atzeni, Phys. Plasmas 6, 3316 (1999); M. Tabak et al., Fusion Sci. & Technology 49, 254 (2006)]. These gain models, however, all assume nearly uniform-density fuel assemblies. In contrast, conventional ICF implosions yield hollowed fuel assemblies with a high-density shell of fuel surrounding a low-density, high-pre… more
Date: April 4, 2007
Creator: Clark, D S & Tabak, M
Partner: UNT Libraries Government Documents Department
open access

Laser heating of solid matter by light pressure-driven shocks

Description: Heating by irradiation of a solid surface in vacuum with 5 x 10{sup 20} W cm{sup -2}, 0.8 ps, 1.05 {micro}m wavelength laser light is studied by x-ray spectroscopy of the K-shell emission from thin layers of Ni, Mo and V. A surface layer is heated to {approx} 5 keV with an axial temperature gradient of 0.6 {micro}m scale length. Images of Ni Ly{sub {alpha}} show the hot region has a {approx} 25 {micro}m diameter, much smaller than {approx} 70 {micro}m region of K{sub {alpha}} emission. 2D parti… more
Date: May 4, 2007
Creator: Akli, K.; Hansen, S. B.; Kemp, A. J.; Freeman, R. R.; Beg, F. N.; Clark, D. et al.
Partner: UNT Libraries Government Documents Department
open access

CHARACTERIZATION OF SPATIAL HETEROGENIETIES IN DETECTOR GRADE CDZNTE

Description: Synthetic Cd{sub 1-x}Zn{sub x}Te or 'CZT' crystals are highly suitable for the room temperature-based spectroscopy of gamma radiation. Structural/morphological heterogeneities within CZT, such as secondary phases that are thought to consist of Te metal and have detrimental impacts on detector performance. In this study, we used electron and X-ray-based imaging techniques to examine heterogeneous properties of detector grade CZT. Using experimental analytical techniques rather than arbitrary the… more
Date: December 4, 2007
Creator: Duff, M
Partner: UNT Libraries Government Documents Department
open access

Emergence of Strong Exchange Interaction in the Actinide Series: The Driving Force for Magnetic Stabilization of Curium

Description: Using electron energy-loss spectroscopy in a transmission electron microscope, many-electron atomic spectral calculations and density functional theory, we examine the electronic and magnetic structure of Cm metal. We show that angular momentum coupling in the 5f states plays a decisive role in the formation of the magnetic moment. The 5f states of Cm in intermediate coupling are strongly shifted towards the LS coupling limit due to exchange interaction, unlike most actinide elements where the … more
Date: January 4, 2007
Creator: Moore, K; der Laan, G v; Haire, D; Wall, M; Schwartz, A & Soderlind, P
Partner: UNT Libraries Government Documents Department
open access

USING WET AIR OXIDATION TECHNOLOGY TO DESTROY TETRAPHENYLBORATE

Description: A bench-scale feasibility study on the use of a Wet Air Oxidation (WAO) process to destroy a slurry laden with tetraphenylborate (TPB) compounds has been undertaken. WAO is an aqueous phase process in which soluble and/or insoluble waste constituents are oxidized using oxygen or oxygen in air at elevated temperatures and pressures ranging from 150 C and 1 MPa to 320 C and 22 MPa. The products of the reaction are CO{sub 2}, H{sub 2}O, and low molecular weight oxygenated organics (e.g. acetate, o… more
Date: April 4, 2007
Creator: Adu-Wusu, K; Daniel McCabe, D & Bill Wilmarth, B
Partner: UNT Libraries Government Documents Department
open access

Age validation of canary rockfish (Sebastes pinniger) using two independent otolith techniques: lead-radium and bomb radiocarbon dating.

Description: Canary rockfish (Sebastes pinniger) have long been an important part of recreational and commercial rockfish fishing from southeast Alaska to southern California, but localized stock abundances have declined considerably. Based on age estimates from otoliths and other structures, lifespan estimates vary from about 20 years to over 80 years. For the purpose of monitoring stocks, age composition is routinely estimated by counting growth zones in otoliths; however, age estimation procedures and li… more
Date: November 4, 2007
Creator: Andrews, A H; Kerr, L A; Cailliet, G M; Brown, T A; Lundstrom, C C & Stanley, R D
Partner: UNT Libraries Government Documents Department
open access

An Improved WRF for Urban-Scale and Complex-Terrain Applications

Description: Simulations of atmospheric flow through urban areas must account for a wide range of physical phenomena including both mesoscale and urban processes. Numerical weather prediction models, such as the Weather and Research Forecasting model (WRF), excel at predicting synoptic and mesoscale phenomena. With grid spacings of less than 1 km (as is required for complex heterogeneous urban areas), however, the limits of WRF's terrain capabilities and subfilter scale (SFS) turbulence parameterizations ar… more
Date: September 4, 2007
Creator: Lundquist, J K; Chow, F K; Mirocha, J D & Lundquist, K A
Partner: UNT Libraries Government Documents Department
open access

FutureGen: Pathway to Near-Zero Emissions and Sustainable Energy

Description: This presentation will highlight the U.S. Department of Energy’s (DOE) FutureGen project − a $1 billion government-industry partnership to design, build, and operate a near-zero emissions coal-fueled power plant. The lead organization for the FutureGen initiative is the National Energy Technology Laboratory (NETL), a multi-purpose laboratory operated by the U.S. DOE’s Office of Fossil Energy. NETL has a mission to conduct R&D from fundamental science to technology demonstration for resolving th… more
Date: November 4, 2007
Creator: Zitney, S. E. & Sarkus, T. A
Partner: UNT Libraries Government Documents Department
open access

Debris and Shrapnel Mitigation Procedure for NIF Experiments

Description: All experiments at the National Ignition Facility (NIF) will produce debris and shrapnel from vaporized, melted, or fragmented target/diagnostics components. For some experiments mitigation is needed to reduce the impact of debris and shrapnel on optics and diagnostics. The final optics, e.g., wedge focus lens, are protected by two layers of debris shields. There are 192 relatively thin (1-3 mm) disposable debris shields (DDS's) located in front of an equal number of thicker (10 mm) main debris… more
Date: September 4, 2007
Creator: Eder, D.; Koniges, A.; Landen, O.; Masters, N.; Fisher, A.; Jones, O. et al.
Partner: UNT Libraries Government Documents Department
open access

Scientific Computing Kernels on the Cell Processor

Description: The slowing pace of commodity microprocessor performance improvements combined with ever-increasing chip power demands has become of utmost concern to computational scientists. As a result, the high performance computing community is examining alternative architectures that address the limitations of modern cache-based designs. In this work, we examine the potential of using the recently-released STI Cell processor as a building block for future high-end computing systems. Our work contains sev… more
Date: April 4, 2007
Creator: Williams, Samuel W.; Shalf, John; Oliker, Leonid; Kamil, Shoaib; Husbands, Parry & Yelick, Katherine
Partner: UNT Libraries Government Documents Department
open access

Using Non-Invasive Multi-Spectral Imaging to Quantitatively Assess Tissue Vasculature

Description: This research describes a non-invasive, non-contact method used to quantitatively analyze the functional characteristics of tissue. Multi-spectral images collected at several near-infrared wavelengths are input into a mathematical optical skin model that considers the contributions from different analytes in the epidermis and dermis skin layers. Through a reconstruction algorithm, we can quantify the percent of blood in a given area of tissue and the fraction of that blood that is oxygenated. I… more
Date: October 4, 2007
Creator: Vogel, A; Chernomordik, V; Riley, J; Hassan, M; Amyot, F; Dasgeb, B et al.
Partner: UNT Libraries Government Documents Department
open access

Photoionization Dynamics in Pure Helium Droplets

Description: The photoionization and photoelectron spectroscopy of pure He droplets are investigated at photon energies between 24.6 eV (the ionization energy of He) and 28 eV. Time-of-flight mass spectra and photoelectron images were obtained at a series of molecular beam source temperatures and pressures to assess the effect of droplet size on the photoionization dynamics. At source temperatures below 16 K, the photoelectron images are dominated by fast electrons produced via direct ionization of He atoms… more
Date: February 4, 2007
Creator: Peterka, Darcy S.; Kim, Jeong Hyun; Wang, Chia C.; Poisson, Lionel & Neumark, Daniel M.
Partner: UNT Libraries Government Documents Department
open access

Charmless Hadronic B Decays at BaBar

Description: We report recent measurements for the branching fractions of charmless hadronic B decays obtained from data collected by the BABAR detector at the PEP-II asymmetric-energy collider at the Stanford Linear Accelerator Center.
Date: December 4, 2007
Creator: Burke, James P.
Partner: UNT Libraries Government Documents Department
open access

Observation of Y(3940) to J/psi omega in B to J/psi omega K at BABAR

Description: The authors report the results of a study of the decays B{sup +} {yields} J/{psi}{omega}K{sup +} and B{sup 0} {yields} J/{psi}{omega}K{sub S}{sup 0} using 383 million B{bar B} events from {Upsilon}(4S) decays with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage rings. They observe evidence for Y(3940) {yields} J/{psi}{omega} with product branching fractions {Beta}(B{sup +} {yields} Y K{sup +}, Y {yields} J/{psi}{omega}) = (4.9 {+-} 1.0(stat) {+-} 0.5(syst)) x 10{sup … more
Date: December 4, 2007
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department
open access

Topological Strings And (Almost) Modular Forms

Description: The B-model topological string theory on a Calabi-Yau threefold X has a symmetry group {Lambda}, generated by monodromies of the periods of X. This acts on the topological string wave function in a natural way, governed by the quantum mechanics of the phase space H{sup 3}(X). We show that, depending on the choice of polarization, the genus g topological string amplitude is either a holomorphic quasi-modular form or an almost holomorphic modular form of weight 0 under {Lambda}. Moreover, at each… more
Date: May 4, 2007
Creator: Aganagic, Mina; Bouchard, Vincent & Klemm, Albrecht
Partner: UNT Libraries Government Documents Department
open access

Waveforms Measured in Confined Thermobaric Explosion

Description: Experiments with 1.5-g Shock-Dispersed-Fuel (SDF) charges have been conducted in six different chambers. Both flake Aluminum and TNT were used as the fuel. Static pressure gauges on the chamber wall were the main diagnostic. Waveforms for explosions in air were significantly larger than those in nitrogen - thereby demonstrating a strong thermobaric (combustion) effect. This effect increases as the confinement volume decreases and the mixture richness approaches 1.
Date: May 4, 2007
Creator: Reichenbach, H; Neuwald, P & Kuhl, A L
Partner: UNT Libraries Government Documents Department
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