Improved Spatial Resolution in Thick, Fully-Depleted CCDs withEnhanced Red Sensitivity (open access)

Improved Spatial Resolution in Thick, Fully-Depleted CCDs withEnhanced Red Sensitivity

The point spread function (PSF) is an important measure of spatial resolution in CCDs for point-like objects, since it affects image quality and spectroscopic resolution. We present new data and theoretical developments for lateral charge diffusion in thick, fully-depleted charge-coupled devices (CCDs) developed at Lawrence Berkeley National Laboratory (LBNL). Because they can be over-depleted, the LBNL devices have no field-free region and diffusion is controlled through the application of an external bias voltage. We give results for a 3512 x 3512 format, 10.5 {micro}m pixel back-illuminated p-channel CCD developed for the SuperNova/Acceleration Probe (SNAP), a proposed satellite-based experiment designed to study dark energy. The PSF was measured at substrate bias voltages between 3 V and 115 V. At a bias voltage of 115 V, we measure an rms diffusion of 3.7 {+-} 0.2 {micro}m. Lateral charge diffusion in LBNL CCDs will meet the SNAP requirements.
Date: March 9, 2006
Creator: Fairfield, Jessamyn A.; Groom, Donald E.; Bailey, Stephen J.; Bebek, Christopher J.; Holland, Stephen E.; Karcher, Armin et al.
System: The UNT Digital Library
Charge-State-Resolved Ion Energy Distribution Functions ofCathodic Vacuum Arcs: A Study Involving the Plasma Potential and BiasedPlasmas (open access)

Charge-State-Resolved Ion Energy Distribution Functions ofCathodic Vacuum Arcs: A Study Involving the Plasma Potential and BiasedPlasmas

There are divergent results in the literature on the(in)dependence of the ion velocity distribution functions on the ioncharge states. Apparently, most time-of-flight methods of measurementsindicate independence whereas most measurements with electrostaticanalyzers state the opposite. It is shown here that this grouping iscoincidental with investigations of pulsed and continuous arcs. Allresults can be consolidated by taking ion-neutral interaction intoaccount, especially charge exchange collisions with the metal neutralsproduced by the arc itself. The velocity distribution functions areindependent of charge state when produced at cathode spots but becomecharge-state dependent when the plasma interacts withneutrals.
Date: March 9, 2006
Creator: Anders, Andre & Oks, Efim
System: The UNT Digital Library
The 4He Total Photo-Absorption Cross Section With Two- Plus Three-Nucleon Interactions From Chiral Effective Field Theory (open access)

The 4He Total Photo-Absorption Cross Section With Two- Plus Three-Nucleon Interactions From Chiral Effective Field Theory

The total photo-absorption cross section of {sup 4}He is evaluated microscopically using two- (NN) and three-nucleon (NNN) interactions based upon chiral effective field theory ({chi}EFT). The calculation is performed using the Lorentz integral transform method along with the ab initio no-core shell model approach. An important feature of the present study is the consistency of the NN and NNN interactions and also, through the Siegert theorem, of the two- and three-body current operators. This is due to the application of the {chi}EFT framework. The inclusion of the NNN interaction produces a suppression of the peak height and enhancement of the tail of the cross section. We compare to calculations obtained using other interactions and to representative experiments. The rather confused experimental situation in the giant resonance region prevents discrimination among different interaction models.
Date: March 9, 2007
Creator: Quaglioni, S & Navratil, P
System: The UNT Digital Library
Investigating the Affinities and Persistence of VX Nerve Agent in Environmental Matrices (open access)

Investigating the Affinities and Persistence of VX Nerve Agent in Environmental Matrices

Laboratory experiments were conducted to determine environmental variables that affect the affinities and persistence of the nerve agent O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothiolate (VX) at dilute concentrations in environmental matrices. Quantitative analyses of VX and its degradation products were performed using LC-MS. Batch hydrolysis experiments demonstrated an increasing hydrolysis rate as pH increased, as shown in previous studies, but also indicated that dissolved aqueous constituents can cause significant differences in the absolute hydrolysis rate. Adsorption isotherms from batch aqueous experiments revealed that VX has a high affinity for hydrophobic organics, a moderate affinity for montmorillonite clay, and a very low affinity for an iron-oxyhydroxide soil mineral, goethite. The adsorption on goethite was increased with the presence of dissolved organic matter in solution. VX degraded rapidly when dried onto goethite, when an inner-sphere complex was forced. No enhanced degradation occurred with goethite in small amounts water. These results suggest that aqueous conditions have important controls on VX adsorption and degradation in the environment and a more mechanistic understanding of these controls is needed in order to enable accurate predictions of its long-term fate and persistence.
Date: March 9, 2004
Creator: Love, A H; Vance, A L; Reynolds, J G & Davisson, M L
System: The UNT Digital Library
Normalized Texture Motifs and Their Application to Statistical Object Modeling (open access)

Normalized Texture Motifs and Their Application to Statistical Object Modeling

A fundamental challenge in applying texture features to statistical object modeling is recognizing differently oriented spatial patterns. Rows of moored boats in remote sensed images of harbors should be consistently labeled regardless of the orientation of the harbors, or of the boats within the harbors. This is not straightforward to do, however, when using anisotropic texture features to characterize the spatial patterns. We here propose an elegant solution, termed normalized texture motifs, that uses a parametric statistical model to characterize the patterns regardless of their orientation. The models are learned in an unsupervised fashion from arbitrarily orientated training samples. The proposed approach is general enough to be used with a large category of orientation-selective texture features.
Date: March 9, 2004
Creator: Newsam, S D
System: The UNT Digital Library
A technique for accelerating the convergence of restarted GMRES (open access)

A technique for accelerating the convergence of restarted GMRES

We have observed that the residual vectors at the end of each restart cycle of restarted GMRES often alternate direction in a cyclic fashion, thereby slowing convergence. We present a new technique for accelerating the convergence of restarted GMRES by disrupting this alternating pattern. The new algorithm resembles a full conjugate gradient method with polynomial preconditioning, and its implementation requires minimal changes to the standard restarted GMRES algorithm.
Date: March 9, 2004
Creator: Baker, A H; Jessup, E R & Manteuffel, T
System: The UNT Digital Library
DIFFUSION OF H THROUGH PD MEMBRANES EFFECTS OF NON-IDEALITY ON DH AND ED (open access)

DIFFUSION OF H THROUGH PD MEMBRANES EFFECTS OF NON-IDEALITY ON DH AND ED

H diffusion constants, D{sub H}, have been obtained from steady-state fluxes across Pd membranes with the downstream side maintained at p{sub H2} {approx} 0. Good linearity of plots of H flux versus (1/d), where d is the thickness, attests to the H permeation being bulk diffusion controlled in this temperature (423 to 523K) and p{sub H2} range ({le} 0.2 MPa). D{sub H} values have been determined at constant p{sub up} and also at constant (H/Pd)=r conditions. H fluxes through Pd membranes with three different surface treatments have been investigated (polished (un-oxidized), oxidized, and palladized) in order to determine the effects of these pretreatments. The palladized and oxidized membranes give similar D{sub H} values but the polished membranes give values about 12% lower. For diffusion in a concentration gradient D{sub H}*(c{sub H}/RT)(d{mu}{sub H}/dx) is the more proper description, where c{sub H} is the H concentration, rather than D{sub H}(dc{sub H}/dx) where D{sub H} and D{sub H}* are the concentration-dependent and independent diffusion constants. D{sub H}* can be obtained from D{sub H} using the thermodynamic factor, D{sub H}(r) = D{sub H}*({partial_derivative}lnp{sub H2}{sup 1/2}/{partial_derivative}lnr){sub T} = D{sub H}*f(r). In the commonly employed situation where there is a large difference in concentrations between the …
Date: March 9, 2007
Creator: Shanahan, K
System: The UNT Digital Library
Atomistic modeling of shock-induced void collapse in copper (open access)

Atomistic modeling of shock-induced void collapse in copper

Nonequilibrium molecular dynamics (MD) simulations show that shock-induced void collapse in copper occurs by emission of shear loops. These loops carry away the vacancies which comprise the void. The growth of the loops continues even after they collide and form sessile junctions, creating a hardened region around the collapsing void. The scenario seen in our simulations differs from current models that assume that prismatic loop emission is responsible for void collapse. We propose a new dislocation-based model that gives excellent agreement with the stress threshold found in the MD simulations for void collapse as a function of void radius.
Date: March 9, 2005
Creator: Davila, L P; Erhart, P; Bringa, E M; Meyers, M A; Lubarda, V A; Schneider, M S et al.
System: The UNT Digital Library
Exploiting Data Parallelism in the Image Content Engine (open access)

Exploiting Data Parallelism in the Image Content Engine

The Image Content Engine (ICE) is a framework of software and underlying mathematical and physical models that enable scientists and analysts to extract features from Terabytes of imagery and search the extracted features for content relevant to their problem domain. The ICE team has developed a set of tools for feature extraction and analysis of image data, primarily based on the image content. The scale and volume of imagery that must be searched presents a formidable computation and data bandwidth challenge, and a search of moderate to large scale imagery quickly becomes intractable without exploiting high degrees of data parallelism in the feature extraction engine. In this paper we describe the software and hardware architecture developed to build a data parallel processing engine for ICE. We discuss our highly tunable parallel process and job scheduling subsystem, remote procedure invocation, parallel I/O strategy, and our experience in running ICE on a 16 node, 32 processing element (CPU) Linux Cluster. We present performance and benchmark results, and describe how we obtain excellent speedup for the imagery searches in our test-bed prototype.
Date: March 9, 2006
Creator: Miller, W M; Garlick, J E; Weinert, G F & Abdulla, G M
System: The UNT Digital Library
Of extracellular matrix, scaffolds, and signaling: Tissuearchitectureregulates development, homeostasis, and cancer (open access)

Of extracellular matrix, scaffolds, and signaling: Tissuearchitectureregulates development, homeostasis, and cancer

The microenvironment surrounding cells influences gene expression, such that a cell's behavior is largely determined by its interactions with the extracellular matrix, neighboring cells, and soluble cues released locally or by distant tissues. We describe the essential role of context and organ structure in directing mammary gland development and differentiated function, and in determining response to oncogenic insults including mutations. We expand on the concept of 'dynamic reciprocity' to present an integrated view of development, cancer, and aging, and posit that genes are like piano keys: while essential, it is the context that makes the music.
Date: March 9, 2006
Creator: Nelson, Celeste M. & Bissell, Mina J.
System: The UNT Digital Library
A Consistent Prescription for the Production Involving MassiveQuarks in Hadron Collisions (open access)

A Consistent Prescription for the Production Involving MassiveQuarks in Hadron Collisions

This paper addresses the issue of production of charm orbottom quarks in association with a high pT process in hadron hadroncollision. These quarks can be produced either as part of the hardscattering process or as a remnant from the structure functions. Thelatter sums terms of the type (alpha_s log(pT/mq))n. If structurefunctions of charm or bottom quarks are used together with a hard processwhich also allows production of these quarks double counting occurs. Thispaper describes the correct procedure and provides two examples of itsimplimentation in single top and Drell-Yan at the LHC.
Date: March 9, 2006
Creator: Kersevan, Borut Paul & Hinchliffe, Ian
System: The UNT Digital Library
An IR-Selected Galaxy Cluster at Z=1.41 (open access)

An IR-Selected Galaxy Cluster at Z=1.41

We report the discovery of a galaxy cluster at z = 1.41. ISCS J143809+341419 was found in the Spitzer/IRAC Shallow Survey of the Bootes field in the NOAO Deep Wide-Field Survey carried out by IRAC. The cluster candidate was initially identified as a high density region of objects with photometric redshifts in the range 1.3 < z < 1.5. Optical spectroscopy of a limited number of objects in the region shows that 5 galaxies within a {approx}120 arcsec diameter region lie at z = 1.41 {+-} 0.01. Most of these member galaxies have broad-band colors consistent with the expected spectral energy distribution of a passively-evolving elliptical galaxy formed at high redshift. The redshift of ISCS J143809+341419 is the highest currently known for a spectroscopically-confirmed cluster of galaxies.
Date: March 9, 2006
Creator: Stanford, S. A.; Eisenhardt, P. R.; Brodwin, M.; Gonzalez, A. H.; Stern, D.; Jannuzi, B. et al.
System: The UNT Digital Library
High-resolution, high-transmission soft x-ray spectrometer for the study of biological samples (open access)

High-resolution, high-transmission soft x-ray spectrometer for the study of biological samples

We present a variable line-space grating spectrometer for soft x-rays that covers the photon energy range between 130 and 650 eV. The optical design is based on the Hettrick-Underwood principle and tailored to synchrotron-based studies of radiation-sensitive biological samples. The spectrometer is able to record the entire spectral range in one shot, i.e., without any mechanical motion, at a resolving power of 1200 or better. Despite its slitless design, such a resolving power can be achieved for a source spot as large as 30x3000 mu m2, which is important for keeping beam damage effects in radiation-sensitive samples low. The high spectrometer efficiency allows recording of comprehensive two-dimensional resonant inelastic soft x-ray scattering (RIXS) maps with good statistics within several minutes. This is exemplarily demonstrated for a RIXS map of highly oriented pyrolytic graphite, which was taken within 10 min.
Date: March 9, 2009
Creator: Fuchs, Oliver; Weinhardt, L.; Blum, M.; Weigand, M.; Umbach, E.; Bar, M. et al.
System: The UNT Digital Library
Luminosity and Redshift dependence of quasar spectral properties (open access)

Luminosity and Redshift dependence of quasar spectral properties

Using a large sample of quasar spectra from the SDSS, we examine the composite spectral trends of quasars as functions of both redshift and luminosity, independently of one another. Aside from the well known Baldwin effect (BE)--the decrease of line equivalent width with luminosity--the average spectral properties are remarkably similar. Host galaxy contamination and the BE are the primary causes for apparent changes in the average spectral slope of the quasars. The BE is detected for most emission lines, including the Balmer lines, but with several exceptions including NV1240A. Emission line shifts of several lines are associated with the BE. The BE is mainly a function of luminosity, but also partly a function of redshift in that line equivalent widths become stronger with redshift. Some of the complex iron features change with redshift, particularly near the small blue bump region.
Date: March 9, 2004
Creator: al., Daniel E. Vanden Berk et
System: The UNT Digital Library
Summary of the 2003 Moriond Workshop on electroweak interactions and unified theories (open access)

Summary of the 2003 Moriond Workshop on electroweak interactions and unified theories

The 2003 Moriond Workshop on Electroweak Interactions and Unified Theories covered a very rich, diverse array of recent results concerning neutrinos, astrophysics and cosmology, searches for new particles, Higgs physics, precision low-energy measurements, quark flavor physics, CP violation, and electroweak interactions. In this summary, we recapitulate some of the highlights. We update many of the results reported at the Workshop to include newer findings reported during Summer, 2003. In this report, We recount some of the highlights of the 2003 Moriond Workshop on Electroweak Interactions and Unified Theories.
Date: March 9, 2004
Creator: Kayser, Boris
System: The UNT Digital Library
Cancelling tow ship noise using an adaptive model-based approach (open access)

Cancelling tow ship noise using an adaptive model-based approach

None
Date: March 9, 2005
Creator: Candy, J. V. & Sullivan, E. J.
System: The UNT Digital Library
Model-Based Acoustic Array Processing (open access)

Model-Based Acoustic Array Processing

None
Date: March 9, 2005
Creator: Sullivan, E. J.; Candy, J. V. & Persson, L.
System: The UNT Digital Library
Recent results in high pT physics from CDF (open access)

Recent results in high pT physics from CDF

The authors present the most recent high p{sub T} results from the CDF experiment using p{bar p} collisions at {radical}s = 1.96 TeV produced at the Tevatron Collider at Fermilab. They summarize results in electroweak physics, top physics and searches for physics beyond the Standard Model. Many measurements of important signals like W boson, Z boson, and the top quark have been reestablished. Taking advantage of the increase in energy and detector upgrades, these measurements already begin to be competitive with previous results.
Date: March 9, 2004
Creator: Veramendi, G.
System: The UNT Digital Library
A Cryogenic test stand for LHC quadrupole magnets (open access)

A Cryogenic test stand for LHC quadrupole magnets

A new test stand for testing LHC interaction region (IR) quadrupole magnets at the Fermilab Magnet Test Facility has been designed and operated. The test stand uses a double bath system with a lambda plate to provide the magnet with a stagnant bath of pressurized He II at 1.9 K and 0.13 MPa. A cryostated magnet 0.91 m in diameter and up to 13 m in length can be accommodated. This paper describes the system design and operation. Issues related to both 4.5 K and 1.9 K operations and magnet quenching are highlighted. An overview of the data acquisition and cryogenics controls systems is also included.
Date: March 9, 2004
Creator: al., R. J. Rabehl et
System: The UNT Digital Library
Hydrodynamic Simulations of Tilted Thick-Disk Accretion onto a Kerr Black Hole (open access)

Hydrodynamic Simulations of Tilted Thick-Disk Accretion onto a Kerr Black Hole

None
Date: March 9, 2005
Creator: Fragile, P C & Anninos, P
System: The UNT Digital Library
Anisotropic flow in the forward directions at {radical}s{sub NN} = 200 GeV (open access)

Anisotropic flow in the forward directions at {radical}s{sub NN} = 200 GeV

The addition of the two Forward TPCs to the STAR detector allows one to measure anisotropic flow at forward pseudorapidities. This made possible the first measurement of directed flow at collision energies of {radical}s{sub NN} = 200 GeV. PHOBOS' results on elliptic flow at forward rapidities were confirmed, and the sign of v{sub 2} was determined to be positive for the first time at RHIC energies. The higher harmonic, v{sub 4}, is consistent with the recently suggested v{sub 2}2 scaling behavior.
Date: March 9, 2004
Creator: Oldenburg, Markus D.
System: The UNT Digital Library
Bioorganometallic chemistry: biocatalytic oxidation reactions with biomimetic nad+/nadh co-factors and [cp*rh(bpy)h]+ for selective organic synthesis (open access)

Bioorganometallic chemistry: biocatalytic oxidation reactions with biomimetic nad+/nadh co-factors and [cp*rh(bpy)h]+ for selective organic synthesis

The biocatalytic, regioselective hydroxylation of 2-hydroxybiphenyl to the corresponding catechol was accomplished utilizing the monooxygenase 2-hydroxybiphenyl 3-monooxygenase (HbpA). The necessary natural nicotinamide adenine dinucleotide (NAD{sup +}) co-factor for this biocatalytic process was replaced by a biomimetic co-factor, N-benzylnicotinamide bromide, 1a. The interaction between the flavin (FAD) containing HbpA enzyme and the corresponding biomimetic NADH compound, N-benzyl-1,4-dihdronicotinamide, 1b, for hydride transfers, was shown to readily occur. The in situ recycling of the reduced NADH biomimic 1b from 1a was accomplished with [Cp*Rh(bpy)H](Cl); however, productive coupling of this regeneration reaction to the enzymatic hydroxylation reaction was not totally successful, due to a deactivation process concerning the HbpA enzyme peripheral groups; i.e., -SH or -NH{sub 2} possibly reacting with the precatalyst, [Cp*Rh(bpy)(H{sub 2}O)](Cl){sub 2}, and thus inhibiting the co-factor regeneration process. The deactivation mechanism was studied, and a promising strategy of derivatizing these peripheral -SH or -NH{sub 2} groups with a polymer containing epoxide was successful in circumventing the undesired interaction between HbpA and the precatalyst. This latter strategy allowed tandem co-factor regeneration using 1a or 2a, [Cp*Rh(bpy)(H2O)](Cl){sub 2}, and formate ion, in conjunction with the polymer bound, FAD containing HbpA enzyme to provide the catechol product.
Date: March 9, 2004
Creator: Lutz, Jochen; Hollman, Frank; Ho, The Vinh; Schnyder, Adrian; Fish, Richard H. & Schmid, Andreas
System: The UNT Digital Library
www.fermiqcd.net (open access)

www.fermiqcd.net

FermiQCD is a C++ library for fast development of parallel lattice QCD applications. The expression FermiQCD Collaboration is used as a collective name to indicate both the users of the software and its contributors. One of the main differences between FermiQCD and libraries developed by other collaborations is that it follows an object oriented design as opposed to a procedural design. FermiQCD should not be identified exclusively with the implementation of the algorithms but, rather, with the strict specifications that define its Application Program Interface. One should think of FermiQCD as a language on its own (a superset of the C++ language), designed to describe Lattice QCD algorithms. The objects of the language include complex numbers (mdp-complex), matrices (mdp-matrix), lattices (mdp-lattice), fields (gauge-field, fermi-field, staggered-field), propagators (fermi-propagator) and actions. Algorithms written in terms of these objects are automatically parallel.
Date: March 9, 2004
Creator: al., Massino Di Pierro et
System: The UNT Digital Library
First upper limits from LIGO on gravitational wave bursts (open access)

First upper limits from LIGO on gravitational wave bursts

We report on a search for gravitational wave bursts using data from the first science run of the LIGO detectors. Our search focuses on bursts with durations ranging from 4 ms to 100 ms, and with significant power in the LIGO sensitivity band of 150 to 3000 Hz. We bound the rate for such detected bursts at less than 1.6 events per day at 90% confidence level. This result is interpreted in terms of the detection efficiency for ad hoc waveforms (Gaussians and sine-Gaussians) as a function of their root-sum-square strain h{sub rss}; typical sensitivities lie in the range h{sub rss} {approx} 10{sup -19} - 10{sup -17} strain/{radical}Hz, depending on waveform. We discuss improvements in the search method that will be applied to future science data from LIGO and other gravitational wave detectors.
Date: March 9, 2004
Creator: al., B. Abbott et
System: The UNT Digital Library