Charged particle and neutron backgrounds in an e-e- interaction region at the NLC (open access)

Charged particle and neutron backgrounds in an e-e- interaction region at the NLC

We compare the detector background situation in an e{sup -} e{sup -} interaction region at the NLC with previous studies done of the NLC e{sup +} e{sup -} interaction region. We note from previous studies that the dominant source of detector backgrounds are the beamstrahlung pairs. Since these scale with luminosity, the reduction in luminosity in e{sup -} e{sup -} collisions leads to a reduction in detector backgrounds compared to the e{sup +} e{sup -} situation.
Date: March 6, 2000
Creator: Gronberg, J
System: The UNT Digital Library
Confocal Imaging of Biological Tissues Using Second Harmonic Generation (open access)

Confocal Imaging of Biological Tissues Using Second Harmonic Generation

A confocal microscopy imaging system was devised to selectively detect Second harmonic signals generated by biological tissues. Several types of biological tissues were examined using this imaging system, including human teeth, bovine blood vessels, and chicken skin. All these tissues generated strong second harmonic signals. There is considerable evidence that the source of these signals in tissue is collagen. Collagen, the predominant component of most tissues, is known to have second order nonlinear susceptibility. This technique may have diagnostic usefulness in pathophysiological conditions characterized by changes in collagen structure including malignant transformation of nevi, progression of diabetic complications, and abnormalities in wound healing.
Date: March 6, 2000
Creator: Kim, B. M.; Stoller, P.; Reiser, K.; Eichler, J.; Yan, M.; Rubenchik, A. et al.
System: The UNT Digital Library
Femtosecond Laser Materials Processing (open access)

Femtosecond Laser Materials Processing

The use of femtosecond lasers allows materials processing of practically any material with extremely high precision and minimal collateral damage. Advantages over conventional laser machining (using pulses longer than a few tens of picoseconds) are realized by depositing the laser energy into the electrons of the material on a time scale short compared to the transfer time of this energy to the bulk of the material, resulting in increased ablation efficiency and negligible shock or thermal stress. The improvement in the morphology by using femtosecond pulses rather than nanosecond pulses has been studied in numerous materials from biologic materials to dielectrics to metals. During the drilling process, we have observed the onset of small channels which drill faster than the surrounding material.
Date: March 6, 2000
Creator: Banks, P. S.; Stuart, B. C.; Komashko, A. M.; Feit, M. D.; Rubenchik, A. M. & Perry, M. D.
System: The UNT Digital Library
High molecular orientation in mono- and tri-layer polydiacetylene films imaged by atomic force microscopy (open access)

High molecular orientation in mono- and tri-layer polydiacetylene films imaged by atomic force microscopy

Atomically flat monolayer and trilayer films of polydiacetylenes have been prepared on mica and silicon using a horizontal deposition technique from a pure water subphase. Langmuir films of 10,12-pentacosadiynoic acid (I) and N-(2-ethanol)-10,12-pentacosadiynamide (II) were compressed to 20 mN/m and subsequently polymerized by UV irradiation at the air-water interface. Blue and red forms of the films were prepared by varying exposure times and incident power. Polymerization to the blue-phase films produced slight contractions in the film of 2 and 5% for the films of II and I, respectively. Longer UV exposures yielded red-phase films with dramatic film contraction of 15 and 32% for II and I, respectively. The horizontal deposition technique provided transfer ratios of unity with minimal film stress or structure modification. Atomic force microscopy images revealed nearly complete coverage of the substrate with atomically flat films. Crystalline domains of up to 100 microns of highly oriented polydiacetylene molecules were observed. The results reported herein provided insight into the roles of molecular packing and chain orientations in converting the monomeric film to the polymerized blue- and red-phases.
Date: March 6, 2000
Creator: SASAKI,DARRYL Y.; CARPICK,ROBERT W. & BURNS,ALAN R.
System: The UNT Digital Library
A nonplanar porphyrin-based receptor molecule for chiral amine ligands (open access)

A nonplanar porphyrin-based receptor molecule for chiral amine ligands

A novel porphyrin-based receptor molecule for chiral amine ligands is described in which nonplanarity of the porphyrin macrocycle is used to orient the ligand and to enhance porphyrin-ligand interactions. The porphyrin macrocycle provides a versatile platform upon which to build elaborate superstructures, and this feature coupled with a rich and well-developed synthetic chemistry has led to the synthesis of many elegant models of heme protein active sites and numerous porphyrin-based receptor molecules. One design feature which is not usually considered in the design of porphyrin-based receptor molecules is nonplanarity of the porphyrin ring, although there are a few systems such as the pyridine sensitive Venus Flytrap and the chirality-memory molecule which illustrate that nonplanar porphyrin-based receptors can display unique and interesting behavior. Given the novel properties of these receptors and the continuing interest in the effects of nonplanarity on the properties of porphyrins the authors decided to investigate in more detail the potential applications of nonplanarity in the design of porphyrin-based receptors. Herein, they describe the design, synthesis, and characterization of a new kind of nonplanar porphyrin-based receptor molecule for chiral amines.
Date: March 6, 2000
Creator: Muzzi, Cinzia M.; Medforth, Craig J.; Smith, Kevin M.; Jia,Song-Ling & Shelnutt, John A.
System: The UNT Digital Library
Surface Intensive Materials Processing for Multi-Functional Purposes (open access)

Surface Intensive Materials Processing for Multi-Functional Purposes

We have chosen silicon carbide (SiC) as a multi-functional material to demonstrate the application of surface intensive processing for device fabrication. We will highlight two devices which are produced in house at the Center for Irradiation of materials of Alabama A and M university: (A) High temperature electronic gas sensor, (B) High temperature optical properties/sensor.
Date: March 6, 2000
Creator: Ila, D.; Williams, E. K.; Muntele, C. I.; George, M. A.; Poker, D. B.; Hensley, D. K. et al.
System: The UNT Digital Library
Synthesis and unusual properties of the first 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraalkylporphyrin (open access)

Synthesis and unusual properties of the first 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraalkylporphyrin

The new perhalogenated porphyrin 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(trifluoromethyl)porphinato-nickel(II) exhibits several striking features, including an extremely ruffled macrocycle with a very short Ni-N distance, an unusually red-shifted optical spectrum, and, surprisingly, hindered rotation of the meso-trifluoromethyl substituents ({Delta}G{sub 278}{sup +} = 47 kJ/mol).
Date: March 6, 2000
Creator: Nelson, Nora Y.; Medforth, Craig J.; Nurco, Daniel J.; Jia, Song-Ling; Shelnutt, John A. & Smith, Kevin M.
System: The UNT Digital Library
Ultrathin aluminum oxide films: Al-sublattice structure and the effect of substrate on ad-metal adhesion (open access)

Ultrathin aluminum oxide films: Al-sublattice structure and the effect of substrate on ad-metal adhesion

First principles density-functional slab calculations are used to study 5 {angstrom} (two O-layer) Al{sub 2}O{sub 3} films on Ru(0001) and Al(111). Using larger unit cells than in a recent study, it is found that the lowest energy stable film has an even mix of tetrahedral (t) and octahedral (o) site Al ions, and thus most closely resembles the {kappa}-phase of bulk alumina. Here, alternating zig-zag rows of t and o occur within the surface plane, resulting in a greater average lateral separation of the Al-ions than with pure t or o. A second structure with an even mix of t and o has also been found, consisting of alternating stripes. These patterns mix easily, can exist in three equivalent directions on basal substrates, and can also be displaced laterally, suggesting a mechanism for a loss of long-range order in the Al-sublattice. While the latter would cause the film to appear amorphous in diffraction experiments, local coordination and film density are little affected. On a film supported by rigid Ru(0001), overlayers of Cu, Pd, and Pt bind similarly as on bulk truncated {alpha}-Al{sub 2}O{sub 3}(0001). However, when the film is supported by soft Al(111), the adhesion of Cu, Pd, and Pt …
Date: March 6, 2000
Creator: Jennison, Dwight R. & Bogicevic, Alexander
System: The UNT Digital Library
You catch more flies with sugar...marketing RIM (open access)

You catch more flies with sugar...marketing RIM

There is a difference between marketing and selling. Marketing is finding out what the customer wants and/or needs and showing that customer how a product meets those needs. Modifying or repackaging the product may be required to make its utility clear to the customer. When it is, they'll buy because they, on their own, want it. Selling is pushing a product on the customer for reasons of profit, compliance, the way things have always been done here, or any others. When one markets, a relationship is built. This isn't about a one-time sale, it's about getting those records into safekeeping and customers trusting us to give them back, retrieve them, the way that customer needs them, when and how that customer needs them. This is a trust building exercise that has long-term as well as short-term actions and reactions all aligned toward that interdependent relationship between customers and us, the recorded information managers. Marketing works better than selling because human beings don't like to be pushed...think door-to-door sales people and evaluate emotions. Are they positive? Go a step further. No one likes to be told to do what's good for you? Which brings us to the fundamental marketing, as opposed …
Date: March 6, 2000
Creator: KEENEN,MARTHA JANE
System: The UNT Digital Library
Absorption of Bound States in Hot, Dense Matter (open access)

Absorption of Bound States in Hot, Dense Matter

Preliminary experiments using a long pulse laser generated X-ray source to back-light a short pulse laser heated thin foil have been performed at the Laboratoire pour l'Utilisation des Lasers Intenses (LULI) at Ecole Polytechnique in France. In this experiment, a 2 J, 300 ps, 532 nm laser was used to create the X-ray back-lighter. The primary diagnostic was a von Hamos spectrograph coupled to a 500 fs X-ray streak camera (TREX-VHS) developed at LLNL. This diagnostic combines high collection efficiency ({approx} 10{sup -4} steradians) with fast temporal response ({approx} 500 fs), allowing resolution of extremely transient spectral variations. The TREX-VHS was used to determine the time history, intensity, and spectral content of the back-lighter. The second diagnostic, Fourier Domain Interferometry (FDI), provides information about the position of the critical density of the target and thus the expansion hydrodynamics, laying the ground work for the plasma characterization. The plasmas were determined to be moderately to strongly coupled, resulting in absorption measurements that provide insight into bound states under such conditions.
Date: March 6, 2001
Creator: Shepherd, R.; Audebert, P.; Chenais-Popovics, C.; Geindre, J. P.; Fajardo, M.; Iglesias, C. et al.
System: The UNT Digital Library
A control-theoretic formulation of the bunch train cavity interaction. (open access)

A control-theoretic formulation of the bunch train cavity interaction.

The bunch train cavity interaction is an accelerator physics problem, for which a system-theoretic model is lacking. Modal analysis has been used to characterize the system dynamics, exploiting the system's symmetry. Correspondingly, control design has been done using classical frequency-domain-based control. Several shortcomings of these methods are highlighted, all of which are remedied by a new time-domain, system-theoretic model presented herein. The new formulation is a periodic, discrete-time system, amenable to state-space control-design methods.
Date: March 6, 2001
Creator: Schwartz, C.; Haddad, H. & Nassiri, A.
System: The UNT Digital Library
Observations of microstructural coarsening in micro flip-chip solder joints (open access)

Observations of microstructural coarsening in micro flip-chip solder joints

Coarsening of solder microstructures dramatically affects fatigue lifetimes. This paper presents a study of microstructural evolution due to thermal cycling and aging of small solder joints.
Date: March 6, 2001
Creator: Barney, Monica M. & Morris, John W., Jr.
System: The UNT Digital Library
Relative Advantages of Direct and Indirect Drive for an Inertial Fusion Energy Power Plant Driven by a Diode-Pumped Solid-State Laser (open access)

Relative Advantages of Direct and Indirect Drive for an Inertial Fusion Energy Power Plant Driven by a Diode-Pumped Solid-State Laser

This paper reviews our current understanding of the relative advantages of direct drive (DD) and indirect drive (ID) for a 1 GWe inertial fusion energy (IFE) power plant driven by a diode-pumped solid-state laser (DPSSL). This comparison is motivated by a recent study (1) that shows that the projected cost of electricity (COE) for DD is actually about the same as that for ID even though the target gain for DD can be much larger. We can therefore no longer assume that DD is the ultimate targeting scenario for IFE, and must begin a more rigorous comparison of these two drive options. The comparison begun here shows that ID may actually end up being preferred, but the uncertainties are still rather large.
Date: March 6, 2001
Creator: Orth, C D
System: The UNT Digital Library
Relative Advantages of Direct and Indirect Drive for an Inertial Fusion Energy Power Plant Driven by a Diode-Pumped Solid-State Laser (open access)

Relative Advantages of Direct and Indirect Drive for an Inertial Fusion Energy Power Plant Driven by a Diode-Pumped Solid-State Laser

This paper reviews our current understanding of the relative advantages of direct drive (DD) and indirect drive (ID) for a 1 GWe inertial fusion energy (IFE) power plant driven by a diode-pumped solid-state laser (DPSSL). This comparison is motivated by a recent study (1) that shows that the projected cost of electricity (COE) for DD is actually about the same as that for ID even though the target gain for DD can be much larger. We can therefore no longer assume that DD is the ultimate targeting scenario for IFE, and must begin a more rigorous comparison of these two drive options. The comparison begun here shows that ID may actually end up being preferred, but the uncertainties are still rather large.
Date: March 6, 2001
Creator: Orth, C.D.
System: The UNT Digital Library
The interplay of matrix metalloproteinases, morphogens and growth factors is necessary for branching of mammary epithelial cells (open access)

The interplay of matrix metalloproteinases, morphogens and growth factors is necessary for branching of mammary epithelial cells

The mammary gland develops its adult form by a process referred to as branching morphogenesis. Many factors have been reported to affect this process. We have used cultured primary mammary epithelial organoids and mammary epithelial cell lines in three-dimensional collagen gels to elucidate which growth factors, matrix metalloproteinases (MMPs) and mammary morphogens interact in branching morphogenesis. Branching stimulated by stromal fibroblasts, epidermal growth factor, fibroblast growth factor 7, fibroblast growth factor 2 and hepatocyte growth factor was strongly reduced by inhibitors of MMPs, indicating the requirement of MMPs for three-dimensional growth involved in morphogenesis. Recombinant stromelysin 1/MMP-3 alone was sufficient to drive branching in the absence of growth factors in the organoids. Plasmin also stimulated branching; however, plasmin-dependent branching was abolished by both inhibitors of plasmin and MMPs, suggesting that plasmin activates MMPs. To differentiate between signals for proliferation and morphogenesis, we used a cloned mammary epithelial cell line that lacks epimorphin, an essential mammary morphogen. Both epimorphin and MMPs were required for morphogenesis, but neither was required for epithelial cell proliferation. These results provide direct evidence for a critical role of MMPs in branching in mammary epithelium and suggest that, in addition to epimorphin, MMP activity is a minimum …
Date: March 6, 2002
Creator: Simian, M.; Harail, Y.; Navre, M.; Werb, Z.; Lochter, A. & Bissell, M.J.
System: The UNT Digital Library
Liquid metal flows in circular insulated ducts in nonuniform magnetic fields. (open access)

Liquid metal flows in circular insulated ducts in nonuniform magnetic fields.

Magnetohydrodynamic flows in insulated circular ducts in nonuniform magnetic fields are studied with reference to liquid metal blankets and divertors of fusion reactors. Particular emphasis is made on C-MOD. The ducts are supposed to be straight, while the gradient of the magnetic field to be inclined by an angle {alpha} to the duct axis. The results are presented for the values of the Hartmann numbers, Ha, of 1000 and 100. Three-dimensional pressure drop, development length, three-dimensional length and nonuniformities of the velocity profiles have been evaluated. It has been shown that for Ha = 1000 the three-dimensional effects are of considerable importance, while for Ha = 100 they may be neglected.
Date: March 6, 2002
Creator: Molokov, S.
System: The UNT Digital Library
MACHO Project Analysis of the Galactic Bulge Microlensing Events with Clump Giants as Sources (open access)

MACHO Project Analysis of the Galactic Bulge Microlensing Events with Clump Giants as Sources

We present preliminary results of the analysis of 5 years of MACHO data on the Galactic bulge microlensing events with clump giants as sources. This class of events allows one to obtain robust conclusions because relatively bright clump stars are not strongly affected by blending. We discuss: (1) the selection of ''giant'' events, (2) the distribution of event durations, (3) the anomalous character of event durations and optical depth in the MACHO field 104 centered on (l,b) = (3{sup o}.1,-3{sup o}.0). We report the preliminary average optical depth of {tau} = (2.0 {+-} 0.4) x10{sup -6} (internal) at (l,b) = (3{sup o}.9, -3{sup o}.8), and present a map of the spatial distribution of the optical depth. When field 104 is removed from the sample, the optical depth drops to {tau} = (1.4 {+-} 0.3) x 10{sup -6}, which is in excellent agreement with infrared-based models of the central Galactic region.
Date: March 6, 2002
Creator: Popowski, P.; Vandehei, T.; Griest, K.; Alcock, C.; Alves, D. R.; Allsman, R. A. et al.
System: The UNT Digital Library
Building a Successful Machine Safeguarding Program (open access)

Building a Successful Machine Safeguarding Program

Safeguarding hazards associated with machines is a goal common to all health and safety professionals. Whether the individual is new to the safety field or has held associated responsibilities for a period of time, safeguarding personnel who work with or around machine tools and equipment should be considered an important aspect of the job. Although significant progress has been made in terms of safeguarding machines since the era prior to the organized safety movement, companies continue to be cited by the Occupational Safety and Health Administration (OSHA) and workers continue to be injured, even killed by machine tools and equipment. In the early 1900s, it was common practice to operate transmission machinery (gears, belts, pulleys, shafting, etc.) completely unguarded. At that time, the countersunk set screw used on shafting had not been invented and projecting set screws were involved in many horrific accidents. Manufacturers built machines with little regard for worker safety. Workers were killed or seriously injured before definitive actions were taken to improve safety in the workplace. Many states adopted legislation aimed at requiring machine guarding and improved injury reduction. The first patent for a machine safeguard was issued in 1868 for a mechanical interlock. Other patents followed. …
Date: March 6, 2003
Creator: McConnell, S
System: The UNT Digital Library
["On Same-Sex Marriage, Bush Failed the Public and Himself" article, March 6, 2004] (open access)

["On Same-Sex Marriage, Bush Failed the Public and Himself" article, March 6, 2004]

An article written by Jonathan Rauch for the National Journal magazine about Bush's stance against gay marriage. The piece assesses Bush's actions treatment of the issue and how his policy negatively affects citizens.
Date: March 6, 2004
Creator: Rauch, Jonathan
System: The UNT Digital Library
Beam Energy Scaling of Ion-Induced Electron Yield from K+ Impact on Stainless Steel (open access)

Beam Energy Scaling of Ion-Induced Electron Yield from K+ Impact on Stainless Steel

Electron clouds limit the performance of many major accelerators and storage rings. Significant quantities of electrons result when halo ions are lost to beam tubes, generating gas which can be ionized and ion-induced electrons that can multiply and accumulate, causing degradation or loss of the ion beam. In order to understand the physical mechanisms of ion-induced electron production, experiments studied the impact of 50 to 400 keV K{sup +} ions on stainless steel surfaces near grazing incidence, using the 500 kV Ion Source Test Stand (STS-500) at LLNL. The experimental electron yield scales with the electronic component (dE{sub e}/dx) of the stopping power and its angular dependence does not follow l/cos({theta}). A theoretical model is developed, using TRIM code to evaluate dE{sub e}/dx at several depths in the target, to estimate the electron yield, which is compared with the experimental results. The experiment extends the range of energy from previous works and the model reproduces the angular dependence and magnitude of the electron yield.
Date: March 6, 2006
Creator: Covo, M K; Molvik, A; Friedman, A; Westenskow, G; Barnard, J J; Cohen, R et al.
System: The UNT Digital Library
Detailed Simulations of Atmospheric Flow and Dispersion in Urban Downtown Areas by Computational Fluid Dynamics (CFD) Models - An Application of Five CFD Models to Manhattan (open access)

Detailed Simulations of Atmospheric Flow and Dispersion in Urban Downtown Areas by Computational Fluid Dynamics (CFD) Models - An Application of Five CFD Models to Manhattan

Computational Fluid Dynamics (CFD) model simulations of urban boundary layers have improved so that they are useful in many types of flow and dispersion analyses. The study described here is intended to assist in planning emergency response activities related to releases of chemical or biological agents into the atmosphere in large cities such as New York City. Five CFD models (CFD-Urban, FLACS, FEM3MP, FEFLO-Urban, and Fluent-Urban) have been applied by five independent groups to the same 3-D building data and geographic domain in Manhattan, using approximately the same wind input conditions. Wind flow observations are available from the Madison Square Garden March 2005 (MSG05) field experiment. It is seen from the many side-by-side comparison plots that the CFD models simulations of near-surface wind fields generally agree with each other and with field observations, within typical atmospheric uncertainties of a factor of two. The qualitative results shown here suggest, for example, that transport of a release at street level in a large city could reach a few blocks in the upwind and crosswind directions. There are still key differences seen among the models for certain parts of the domain. Further quantitative examinations of differences among the models and the observations are …
Date: March 6, 2006
Creator: Hanna, S. R.; Brown, M. J.; Camelli, F. E.; Chan, S. T.; Coirier, W. J.; Hansen, O. R. et al.
System: The UNT Digital Library
Development of Ultra-Fast Silicon Switches for Active X-Band High Power RF Compression Systems (open access)

Development of Ultra-Fast Silicon Switches for Active X-Band High Power RF Compression Systems

We present the recent results of our research on the high power ultra-fast silicon RF switches. This switch is composed of a group of PIN diodes on a high purity silicon wafer. The wafer is inserted into a cylindrical waveguide under TE{sub 01} mode, performing switching by injecting carriers into the bulk silicon. Our current design uses a CMOS compatible process and the device was fabricated at SNF (Stanford Nanofabrication Facility). 300 ns switching time has been observed, while the switching speed can be improved further with 3-D device structure and faster driving circuit. Power handling capacity of the switch is at the level of 10 MW. The switch was designed for active X-band RF pulse compression systems--especially for NLC, but it is also possible to be modified for other applications and other frequencies.
Date: March 6, 2006
Creator: Guo, Ji-Quan & Tantawi, S.
System: The UNT Digital Library
Dynamic Program Phase Detection in Distributed Shared-Memory Multiprocessors (open access)

Dynamic Program Phase Detection in Distributed Shared-Memory Multiprocessors

We present a novel hardware mechanism for dynamic program phase detection in distributed shared-memory (DSM) multiprocessors. We show that successful hardware mechanisms for phase detection in uniprocessors do not necessarily work well in DSM systems, since they lack the ability to incorporate the parallel application's global execution information and memory access behavior based on data distribution. We then propose a hardware extension to a well-known uniprocessor mechanism that significantly improves phase detection in the context of DSM multiprocessors. The resulting mechanism is modest in size and complexity, and is transparent to the parallel application.
Date: March 6, 2006
Creator: Ipek, E; Martinez, J F; de Supinski, B R; McKee, S A & Schulz, M
System: The UNT Digital Library
From Non-Hermitian Effective Operators to Large-Scale No-Core Shell Model Calculations for Light Nuclei (open access)

From Non-Hermitian Effective Operators to Large-Scale No-Core Shell Model Calculations for Light Nuclei

No-core shell model (NCSM) calculations using ab initio effective interactions are very successful in reproducing experimental nuclear spectra. The main theoretical approach is the use of effective operators, which include correlations left out by the truncation of the model space to a numerically tractable size. We review recent applications of the effective operator approach, within a NCSM framework, to the renormalization of the nucleon-nucleon interaction, as well as scalar and tensor operators.
Date: March 6, 2006
Creator: Barrett, B R; Stetcu, I; Navratil, P & Vary, J P
System: The UNT Digital Library