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Hydrogen Production by the Cyanobacterium Plectonema Boryanum: Effects of Initial Nitrate Concentration, Light Intensity, and Inhibition of Photosystem II by DCMU (open access)

Hydrogen Production by the Cyanobacterium Plectonema Boryanum: Effects of Initial Nitrate Concentration, Light Intensity, and Inhibition of Photosystem II by DCMU

The alarming rate at which atmospheric carbon dioxide levels are increasing due to the burning of fossil fuels will have incalculable consequences if disregarded. Fuel cells, a source of energy that does not add to carbon dioxide emissions, have become an important topic of study. Although signifi cant advances have been made related to fuel cells, the problem of cheap and renewable hydrogen production still remains. The cyanobacterium Plectonema boryanum has demonstrated potential as a resolution to this problem by producing hydrogen under nitrogen defi cient growing conditions. Plectonema boryanum cultures were tested in a series of experiments to determine the effects of light intensity, initial nitrate concentration, and photosystem II inhibitor DCMU (3-(3,4- dichlorophenyl)-1,1-dimethylurea) upon hydrogen production. Cultures were grown in sterile Chu. No. 10 medium within photobioreactors constantly illuminated by halogen lights. Because the enzyme responsible for hydrogen production is sensitive to oxygen, the medium was continuously sparged with argon/CO2 (99.7%/0.3% vol/vol) by gas dispersion tubes immersed in the culture. Hydrogen production was monitored by using a gas chromatograph equipped with a thermal conductivity detector. In the initial experiment, the effects of initial nitrate concentration were tested and results revealed cumulative hydrogen production was maximum at an initial …
Date: January 1, 2008
Creator: Carter, B. & Huesemann, M.
Object Type: Article
System: The UNT Digital Library
An improved Neutrino Oscillations Analysis of the MiniBooNE Data (open access)

An improved Neutrino Oscillations Analysis of the MiniBooNE Data

We calculate the exclusion region in the parameter space of {nu}{sub {mu}} {yields} {nu}{sub e} oscillations of the LSND type using a combined fit to the reconstructed energy distributions of neutrino candidate samples from the MiniBooNE data obtained with two different particle identification methods. The two {nu}{sub e} candidate samples are included together with a high statistics sample of {nu}{sub {mu}} events in the definition of a {chi}{sup 2} statistic which includes the correlations between the energy intervals of all three samples and handles the event overlap between the {nu}{sub e} samples. The {nu}{sub {mu}} sample is introduced to constrain the effect of systematic uncertainties. This analysis increases the exclusion limit in the region {Delta}m{sup 2} {approx}< 1eV{sup 2} when compared with the result previously published by the collaboration, which used a different technique.
Date: January 1, 2008
Creator: Aguilar-Arevalo, Alexis Armando
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Improving the reliability of the jpHMM recombination prediction in HIV (open access)

Improving the reliability of the jpHMM recombination prediction in HIV

Accurate classification of HIV and the identification of recombinants, including precise breakpoint definitions, is of crucial importance for epidemiological monitoring and the design of potential drugs. Recently we developed jpHMM, a new method to detect recombinations in HIV-l genomes. jpHMM predicts phylogenetic recombination breakpoints in a query sequence and assigns to each segment of the sequence one of the major HIV-l subtypes. For the user the reliability of the predicted breakpoint positions and parental subtypes is most important. For this reason we extended the output of jpHMM to include the information on regions where the model is 'uncertain' about the parental subtype and an interval estimate of the breakpoint. This information is determined using the posterior probabilities of the subtypes at each query sequence position.
Date: January 1, 2008
Creator: Zhang, Ming; Letiner, Thomas K & Korber, Bette T
Object Type: Article
System: The UNT Digital Library
Inclusive jet production at the Tevatron using the D0 experiment (open access)

Inclusive jet production at the Tevatron using the D0 experiment

A preliminary measurement is presented of the inclusive jet production cross section in p{bar p} collisions at a center-of-mass energy of {radical}s = 1960GeV: The data was taken with the D0 detector and represents an integrated luminosity of {approx} 900 pb{sup -1} of Tevatron RunII data. The cross section is studied as a function of jet transverse momentum (p{sub T}) and rapidity (y) and compared to perturbative QCD predictions in next-to-leading order including two-loop threshold corrections.
Date: January 1, 2008
Creator: Hegeman, J. & /NIKHEF, Amsterdam /Fermilab
Object Type: Article
System: The UNT Digital Library
Incommensurate Spin Resonance in URu2Si2 (open access)

Incommensurate Spin Resonance in URu2Si2

We propose to search for the spin resonance in URu{sub 2}Si{sub 2} at {omega}{sub res} = 4-6meV at the incommensurate wavector Q* = (1 {+-} 0.4, 0, 0). We expect that this spin resonance will set in at temperatures below HO transition and the intensity of this peak will scale as {approx} {Delta}{sub HO} {approx} (T{sub HO} - T). The resonance peak is know to occur in the states with superconducting gap and results in the gapping of the electronic spectrum add ref on SrruO and cel 15. In the case of HO the gap {Delta}{sub HO} results in the partially gapped electron spectrum. That appears to be a sufficient condition, as shown by Wiebe et al to produce a gap in spin excitation spectrum. In addition, we predict a peak in the spin excitation spectrum, as spectral weight redistribution produces the resonance feature. To the best of our knowledge, if the predicted resonance peak indeed occurs, it would be the first case where the spin resonance occurs at an incommensurate vector Q*.
Date: January 1, 2008
Creator: Balatsky, A. V.; Chantis, A.; Dahal, Hari; Zhu, J. X. & Parker, David
Object Type: Article
System: The UNT Digital Library
Industrial Energy Efficiency Cooperative Partnership (Chinese/English) (open access)

Industrial Energy Efficiency Cooperative Partnership (Chinese/English)

Chinese/English brochure on the Save Energy Now process for DOE Industrial Energy Efficiency Partnership with China.
Date: January 1, 2008
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Infinitely many kinds of quantum channels (open access)

Infinitely many kinds of quantum channels

We define the ability of a quantum channel to simulate another by means of suitable encoding and decoding operations. While classical channels have only two equivalence classes under simulation (channels with non-vanishing capacity and those with vanishing capacity), we show that there are an uncountable infinity of different equivalence classes of quantum channels using the example of the quantum erasure channel. Our results also imply a kind of 'Matthew principle' for error correction on certain channels.
Date: January 1, 2008
Creator: Hastings, Matthew B
Object Type: Article
System: The UNT Digital Library
Initial Market Assessment for Small-Scale Biomass-Based CHP (open access)

Initial Market Assessment for Small-Scale Biomass-Based CHP

The purpose of this report is to reexamine the energy generation market opportunities for biomass CHP applications smaller than 20 MW. This paper provides an overview of the benefits of and challenges for biomass CHP in terms of policy, including a discussion of the drivers behind, and constraints on, the biomass CHP market. The report provides a summary discussion of the available biomass supply types and technologies that could be used to feed the market. Two primary markets are outlined--rural/agricultural and urban--for small-scale biomass CHP, and illustrate the primary intersections of supply and demand for those markets. The paper concludes by summarizing the potential markets and suggests next steps for identifying and utilizing small-scale biomass.
Date: January 1, 2008
Creator: Brown, E. & Mann, M.
Object Type: Report
System: The UNT Digital Library
Inkjet Printing of Nickel and Silver Metal Solar Cell Contacts (open access)

Inkjet Printing of Nickel and Silver Metal Solar Cell Contacts

With about 125,000 terawatts of solar power striking the earth at any given moment, solar energy may be the only renewable energy resource with enough capacity to meet a major portion of our future energy needs. Thin-fi lm technologies and solution deposition processes seek to reduce manufacturing costs in order to compete with conventional coal-based electricity. Inkjet printing, as a derivative of the direct-write process, offers the potential for low-cost, material-effi cient deposition of the metals for photovoltaic contacts. Advances in contact metallizations are important because they can be employed on existing silicon technology and in future-generation devices. We report on the atmospheric, non-contact deposition of nickel (Ni) and silver (Ag) metal patterns on glass, Si, and ZnO substrates at 180–220°C from metal-organic precursor inks using a Dimatix inkjet printer. Near-bulk conductivity Ag contacts were successfully printed up to 4.5 μm thick and 130 μm wide on the silicon nitride antirefl ective coating of silicon solar cells. Thin, high-resolution Ni adhesion-layer lines were printed on glass and zinc oxide at 80 μm wide and 55 nm thick with a conductivity two orders of magnitude less than the bulk metal. Additionally, the ability to print multi-layered metallizations (Ag on Ni) on …
Date: January 1, 2008
Creator: Pasquarelli, R.; Curtis, C. & van Hest, M.
Object Type: Article
System: The UNT Digital Library
Integrated NEMS and optoelectronics for sensor applications. (open access)

Integrated NEMS and optoelectronics for sensor applications.

This work utilized advanced engineering in several fields to find solutions to the challenges presented by the integration of MEMS/NEMS with optoelectronics to realize a compact sensor system, comprised of a microfabricated sensor, VCSEL, and photodiode. By utilizing microfabrication techniques in the realization of the MEMS/NEMS component, the VCSEL and the photodiode, the system would be small in size and require less power than a macro-sized component. The work focused on two technologies, accelerometers and microphones, leveraged from other LDRD programs. The first technology was the nano-g accelerometer using a nanophotonic motion detection system (67023). This accelerometer had measured sensitivity of approximately 10 nano-g. The Integrated NEMS and optoelectronics LDRD supported the nano-g accelerometer LDRD by providing advanced designs for the accelerometers, packaging, and a detection scheme to encapsulate the accelerometer, furthering the testing capabilities beyond bench-top tests. A fully packaged and tested die was never realized, but significant packaging issues were addressed and many resolved. The second technology supported by this work was the ultrasensitive directional microphone arrays for military operations in urban terrain and future combat systems (93518). This application utilized a diffraction-based sensing technique with different optical component placement and a different detection scheme from the nano-g …
Date: January 1, 2008
Creator: Czaplewski, David A.; Serkland, Darwin Keith; Olsson, Roy H., III; Bogart, Gregory R. (Symphony Acoustics, Rio Rancho, NM); Krishnamoorthy, Uma; Warren, Mial E. et al.
Object Type: Report
System: The UNT Digital Library
Integrated optical MEMS using through-wafer vias and bump-bonding. (open access)

Integrated optical MEMS using through-wafer vias and bump-bonding.

This LDRD began as a three year program to integrate through-wafer vias, micro-mirrors and control electronics with high-voltage capability to yield a 64 by 64 array of individually controllable micro-mirrors on 125 or 250 micron pitch with piston, tip and tilt movement. The effort was a mix of R&D and application. Care was taken to create SUMMiT{trademark} (Sandia's ultraplanar, multilevel MEMS technology) compatible via and mirror processes, and the ultimate goal was to mate this MEMS fabrication product to a complementary metal-oxide semiconductor (CMOS) electronics substrate. Significant progress was made on the via and mirror fabrication and design, the attach process development as well as the electronics high voltage (30 volt) and control designs. After approximately 22 months, the program was ready to proceed with fabrication and integration of the electronics, final mirror array, and through wafer vias to create a high resolution OMEMS array with individual mirror electronic control. At this point, however, mission alignment and budget constraints reduced the last year program funding and redirected the program to help support the through-silicon via work in the Hyper-Temporal Sensors (HTS) Grand Challenge (GC) LDRD. Several months of investigation and discussion with the HTS team resulted in a revised plan …
Date: January 1, 2008
Creator: McCormick, Frederick Bossert & Frederick, Scott K.
Object Type: Report
System: The UNT Digital Library
Integrated Status and Effectiveness Monitoring Program - Entiat River Snorkel Surveys and Rotary Screw Trap, 2007. (open access)

Integrated Status and Effectiveness Monitoring Program - Entiat River Snorkel Surveys and Rotary Screw Trap, 2007.

The USFWS Mid-Columbia River Fishery Resource Office conducted snorkel surveys at 24 sites during the summer and fall periods of 2006 survey periods as part of the Integrated Status and Effectiveness Monitoring Program in the Entiat River. A total of 37,938 fish from 15 species/genera and an unknown category were enumerated. Chinook salmon were the overall most common fish observed and comprised 15% of fish enumerated followed by rainbow trout (10%) and mountain whitefish (7%). Day surveys were conducted during the summer period 2007 (August), while night surveys were conducted during the fall 2007 (October) surveys. The USFWS Mid-Columbia River Fishery Resource Office (MCFRO) operated two rotary screw traps on the Entiat River as part of the Integrated Status and Effectiveness Monitoring Program (ISEMP) program from August through November of 2007. Along with the smolt traps, juvenile emigrants were also captured at remote locations throughout the Entiat watershed and its major tributary, the Mad River. A total of 999 wild Oncorhynchus mykiss and 5,107 wild run O. tshawytscha were PIT tagged during the study period. Rotary screw trap efficiencies averaged 22.3% for juvenile O. tshawytscha and 9.0% for juvenile O. mykiss. Rotary screw traps operated 7 days a week and …
Date: January 1, 2008
Creator: Nelle, R.D.
Object Type: Report
System: The UNT Digital Library
Interactions of Jet Fuels with Nitrile O-Rings: Petroleum-Derived versus Synthetic Fuels (open access)

Interactions of Jet Fuels with Nitrile O-Rings: Petroleum-Derived versus Synthetic Fuels

A transition from petroleum-derived jet fuels to blends with Fischer-Tropsch (F-T) fuels, and ultimately fully synthetic hydro-isomerized F-T fuels has raised concern about the fate of plasticizers in nitrile-butadiene rubber o-rings that are contacted by the fuels as this transition occurs. The partitioning of plasticizers and fuel molecules between nitrile o-rings and petroleum-derived, synthetic, and additized-synthetic jet fuels has been measured. Thermal desorption of o-rings soaked in the various jet fuels followed by gas chromatographic analysis with a mass spectrometric detector showed many of the plasticizer and stabilizer compounds were removed from the o-rings regardless of the contact fuel. Fuel molecules were observed to migrate into the o-rings for the petroleum-derived fuel as did both the fuel and additive for a synthetic F-T jet fuel additized with benzyl alcohol, but less for the unadditized synthetic fuel. The specific compounds or classes of compounds involved in the partitioning were identified and a semiquantitative comparison of relative partitioning of the compounds of interest was made. The results provide another step forward in improving the confidence level of using additized, fuIly synthetic jet fuel in the place of petroleum-derived fueL
Date: January 1, 2008
Creator: Gormley, R. J.; Link, D. D.; Baltrus, J. P. & Zandhuis, P. H.
Object Type: Article
System: The UNT Digital Library
Interplay of metal-allyl and metal-metal bonding in dimolybdenum allyl complexes (open access)

Interplay of metal-allyl and metal-metal bonding in dimolybdenum allyl complexes

Addition of PMe{sub 3} to Mo{sub 2}(allyl){sub 4} afforded Mo{sub 2}(allyl){sub 4}(PMe{sub 3}){sub 2}, in which two of the allyl groups adopt an unprecedented {mu}{sub 2{sup -}}{eta}{sup 1}, {eta}{sup 3} bonding mode; theoretical studies elucidate the role sof the {sigma}- and {pi}-donor ligands in the interplay of metal-allyl and metal-metal bonding.
Date: January 1, 2008
Creator: John, Kevin D.; Martin, Richard L.; Obrey, Steven J. & Scott, Brian L.
Object Type: Article
System: The UNT Digital Library
Investigation of gas hydrate-bearing sandstone reservoirs at the "Mount Elbert" stratigraphic test well, Milne Point, Alaska (open access)

Investigation of gas hydrate-bearing sandstone reservoirs at the "Mount Elbert" stratigraphic test well, Milne Point, Alaska

In February 2007, the U.S. Department of Energy, BP Exploration (Alaska), Inc., and the U.S. Geological Survey conducted an extensive data collection effort at the "Mount Elbert #1" gas hydrates stratigraphic test well on the Alaska North Slope (ANS). The 22-day field program acquired significant gas hydrate-bearing reservoir data, including a full suite of open-hole well logs, over 500 feet of continuous core, and open-hole formation pressure response tests. Hole conditions, and therefore log data quality, were excellent due largely to the use of chilled oil-based drilling fluids. The logging program confirmed the existence of approximately 30 m of gashydrate saturated, fine-grained sand reservoir. Gas hydrate saturations were observed to range from 60% to 75% largely as a function of reservoir quality. Continuous wire-line coring operations (the first conducted on the ANS) achieved 85% recovery through 153 meters of section, providing more than 250 subsamples for analysis. The "Mount Elbert" data collection program culminated with open-hole tests of reservoir flow and pressure responses, as well as gas and water sample collection, using Schlumberger's Modular Formation Dynamics Tester (MDT) wireline tool. Four such tests, ranging from six to twelve hours duration, were conducted. This field program demonstrated the ability to safely …
Date: January 1, 2008
Creator: Boswell, Ray M.; Hunter, Robert; Collett, Timothy; Digert, Scott; Hancock, Steve & Weeks, Micaela
Object Type: Article
System: The UNT Digital Library
Journal of Undergraduate Research, Volume 8, 2008 (open access)

Journal of Undergraduate Research, Volume 8, 2008

None
Date: January 1, 2008
Creator: Stiner, K.S.; Graham, S.; Khan, M.; Dilks, J. & Mayer, D.
Object Type: Journal/Magazine/Newsletter
System: The UNT Digital Library
JV Task 109 - Risk Assessment and Feasibility of Remedial Alternatives for Coal Seam at Garrison, North Dakota (open access)

JV Task 109 - Risk Assessment and Feasibility of Remedial Alternatives for Coal Seam at Garrison, North Dakota

The Energy & Environmental Research Center (EERC) conducted an evaluation of alternative technologies for remediation of hydrocarbon-contaminated coal seam, including impacted soils and groundwater in Garrison, North Dakota. Geotechnical characteristics of the impacted fractured coal seam provide for rapid off-site contaminant transport, with the currently identified impacted zone covering an area of about 40 acres. Regardless of the exposure mechanism (free, dissolved, or vapor phase), results of laboratory tests confirmed secondary release of gasoline-based compounds from contaminated coal to water reaching concentrations documented from the impacted areas. Coal laboratory tests confirmed low risks associated with spontaneous ignition of gasoline-contaminated coal. High contaminant recovery efficiency for the vacuum-enhanced recovery pilot tests conducted at three selected locations confirmed its feasibility for full-scale remediation. A total of 3500 gallons (13.3 m{sup 3}) of contaminated groundwater and over 430,000 ft{sup 3} (12,200 m{sup 3}) of soil vapor were extracted during vacuum-enhanced recovery testing conducted July 17-24, 2007, resulting in the removal of about 1330 lb (603 kg) of hydrocarbons, an equivalent of about 213 gallons of product. The summary of project activities is as follows: (1) Groundwater and vapor monitoring for existing wells, including domestic wells, conducted on a monthly basis from December 12, …
Date: January 1, 2008
Creator: Solc, Jarda
Object Type: Text
System: The UNT Digital Library
Large Scale Production, Purification, and 65cu Solid State NMR of Azurin (open access)

Large Scale Production, Purification, and 65cu Solid State NMR of Azurin

This paper details a way to produce azurin with an effi ciency over 10 times greater than previously described and demonstrates the fi rst solid state nuclear magnetic resonance spectrum of 65Cu(I) in a metalloprotein. A synthetic gene for azurin based upon the DNA sequence from Pseudomonas aeruginosa including the periplasmic targeting sequence was subcloned into a T7 overexpression vector to create the plasmid pGS-azurin, which was transformed into BL21 (DE3) competent cells. The leader sequence on the expressed protein causes it to be exported to the periplasmic space of Escherichia coli. Bacteria grown in a fermentation unit were induced to overexpress the azurin, which was subsequently purifi ed through an endosmotic shock procedure followed by high performance liquid chromatography (HPLC). 1,500 mg of azurin were purifi ed per liter of culture. 65Cu(II) was added to apo-azurin and then reduced. The 65Cu metal cofactor in azurin was observed with solid state nuclear magnetic resonance (NMR) to determine any structural variations that accompanied copper reduction. This is the fi rst solid state NMR spectra of a copper(I) metalloprotein. Analysis of the NMR spectra is being used to complement hypotheses set forth by x-ray diffraction and computational calculations of electron transfer mechanisms …
Date: January 1, 2008
Creator: Gao, A. & Heck, R.W.
Object Type: Article
System: The UNT Digital Library
Local and bulk melting of Cu at grain boundaries (open access)

Local and bulk melting of Cu at grain boundaries

We investigate gain boundary (GB) melting using molecular dynamics simulations on face-centered-cubic Cu bicrystals with symmetric {l_angle}110{r_angle} tilt grain boundaries. Two representative types of GBs are explored: {Sigma} = 11/(113)/50.48{sup o} (low GB energy) and {Sigma} = 27/(552)/148.41{sup o} (high GB energy). The temperature and temporal evolutions of the Cu bicrystals under stepped heating are characterized in terms of order parameters and diffusion coefficients, as ell as the nucleation and growth of melt. Within the GB region, continuous local melting precedes discontinuous bulk melting, while continuous solid state disordering may precede local melting. Premelting may occur for local melting but not for bulk melting. For {Sigma} = 11/(113)/50.48{sup o}, premelting of the GB region is negligible, and local melting occurs near the thermodynamic melting temperature. The GB region as a whole is superheated by about 13% before its bulk melting. In the case of {Sigma} = 27/(552)/148.41, considerable premelting is observed for local melting, while the bulk melting occurs with negligible superheating. The exact melting behavior of a general GB depends on the GB energy, but is likely bracketed within these two cases.
Date: January 1, 2008
Creator: Luo, Shengnian; Han, Li - Bo; An, Qi; Fu, Rong - Shan & Zheng, Lianqing
Object Type: Article
System: The UNT Digital Library
Local structure of La1-xSrxCoO3 determined from EXAFS and neutron PDF studies (open access)

Local structure of La1-xSrxCoO3 determined from EXAFS and neutron PDF studies

The combined local structure techniques, extended X-ray absorption fine struture (EXAFS) and neutron pair distribution function (PDF) analysis, have been used for temperatures 4 {<=} T {<=} 330 K to rule out a large Jahn-Teller (J-T) distortion of the Co-O bond in La{sub 1-x}Sr{sub x}CoO{sub 3} for a significant fraction of Co sites (x {<=} 0.35), indicating few, if any, J-T active, single-occupied e{sub g} Co sites exist.
Date: January 1, 2008
Creator: Proffen, Thomas; Sundaram, Nalini; Jiang, Y; Anderson, Ingrid; Belanger, D P; Booth, C H et al.
Object Type: Article
System: The UNT Digital Library
Localized ferromagnetic resonance force microscopy of permalloy-cobalt films (open access)

Localized ferromagnetic resonance force microscopy of permalloy-cobalt films

We report the Ferromagnetic Resonance Force Microscopy (FMRFM) experiments on a combined permalloy-cobalt continuous film. Our studies demonstrate the capability of FMRFM to perform local spectroscopy of different ferromagnetic materials. Theoretical analysis of the uniform resonance mode at the edge of the film provides good quantitative agreement with the experimental data. Our experiments demonstrate the micron scale lateral resolution and allow to extract local magnetic properties in continuous ferromagnetic samples.
Date: January 1, 2008
Creator: Nazaretski, Evgueni; Movshovich, Roman; Martin, Ivar; Cha, Kitty V; Akhadov, Elshan A; Obukhov, Yu et al.
Object Type: Article
System: The UNT Digital Library
Long-wavelength magnetic excitations in multiferroic BiFeO3 (open access)

Long-wavelength magnetic excitations in multiferroic BiFeO3

Colossal magnetoresistance manganites have been subjected to extensive research due to their unique magnetic and electrical properties. The physical origin of this phenomenon has been attributed to the double-exchange model. However, this double-exchange mechanism of carriers between Mn{sup 2+} and Mn{sup 3+} ions alone cannot account for all the observed changes such as metal-insulator transition in these materials. Other factors include the highly correlated nature of the spin, lattice, charge and orbital degrees of freedom. Ultrafast optical techniques are powerful probes for investigating the quasi-particle and spin relaxation dynamics in these strongly correlated systems. Recently, Zhao et. al. reported a re-entrant metal insulator (M-I) transition in single crystals of Cu-doped manganites La{sub 1-x}Pb{sub x}MnO{sub 3} (x = 0.14). The re-entrant M-I transition at low temperatures was observed in samples with Cu-doping (y {>=} 0.02) and was attributed to the charge carrier localization due to lattice distortion caused by Cu doping at Mn sites. However, there have been no reports on the effects of Cu-doping on the spin-lattice interaction in these materials. In this work, we investigate the spin-lattice relaxation and photo-induced magnetization dynamics in single crystals of La{sub 1-x}Pb{sub x}Mn{sub 1-y-z}Cu{sub y}O{sub 3} (x = 0.14, y = 0,0.01,0.02,0.04,0.06 and …
Date: January 1, 2008
Creator: Talbayev, Diyar & Taylor, Antoinette J
Object Type: Article
System: The UNT Digital Library
Low dose rectal inoculation of rhesus macaques by SIV smE660 or SIVmac251 recapitulates (open access)

Low dose rectal inoculation of rhesus macaques by SIV smE660 or SIVmac251 recapitulates

We recently developed a novel strategy to identify transmitted HIV-1 genomes in acutely infected humans using single-genome amplification and a model of random virus evolution. Here, we used this approach to determine the molecular features of simian immunodeficiency virus (SIV) transmission in 18 experimentally infected Indian rhesus macaques. Animals were inoculated intrarectally (i.r.) or intravenously (i.v.) with stocks of SIVmac251 or SIVsmE660 that exhibited sequence diversity typical of early-chronic HIV-1 infection. 987 full-length SIV env sequences (median of 48 per animal) were determined from plasma virion RNA 1--5 wk after infection. i.r. inoculation was followed by productive infection by one or a few viruses (median 1; range 1--5) that diversified randomly with near starlike phylogeny and a Poisson distribution of mutations. Consensus viral sequences from ramp-up and peak viremia were identical to viruses found in the inocula or differed from them by only one or a few nucleotides, providing direct evidence that early plasma viral sequences coalesce to transmitted/founder viruses. i.v. infection was >2,000-fold more efficient than i.r. infection, and viruses transmitted by either route represented the full genetic spectra of the inocula. These findings identify key similarities in mucosal transmission and early diversification between SIV and HIV-1, and thus …
Date: January 1, 2008
Creator: Hraber, Peter; Giorgi, Elena E; Keele, Brandon; Li, Hui & Learn, Gerald
Object Type: Article
System: The UNT Digital Library
Making almost commuting matrices commute (open access)

Making almost commuting matrices commute

Suppose two Hermitian matrices A, B almost commute ({parallel}[A,B]{parallel} {<=} {delta}). Are they close to a commuting pair of Hermitian matrices, A', B', with {parallel}A-A'{parallel},{parallel}B-B'{parallel} {<=} {epsilon}? A theorem of H. Lin shows that this is uniformly true, in that for every {epsilon} > 0 there exists a {delta} > 0, independent of the size N of the matrices, for which almost commuting implies being close to a commuting pair. However, this theorem does not specifiy how {delta} depends on {epsilon}. We give uniform bounds relating {delta} and {epsilon}. The proof is constructive, giving an explicit algorithm to construct A' and B'. We provide tighter bounds in the case of block tridiagonal and tridiagnonal matrices. Within the context of quantum measurement, this implies an algorithm to construct a basis in which we can make a projective measurement that approximately measures two approximately commuting operators simultaneously. Finally, we comment briefly on the case of approximately measuring three or more approximately commuting operators using POVMs (positive operator-valued measures) instead of projective measurements.
Date: January 1, 2008
Creator: Hastings, Matthew B
Object Type: Article
System: The UNT Digital Library