National Emission Standards for Hazardous Air Pollutants - Radionuclide Emissions Calendar Year 2009 (open access)

National Emission Standards for Hazardous Air Pollutants - Radionuclide Emissions Calendar Year 2009

The U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office operates the Nevada Test Site (NTS) and North Las Vegas Facility (NLVF). From 1951 through 1992, the NTS was the continental testing location for U.S. nuclear weapons. The release of radionuclides from NTS activities has been monitored since the initiation of atmospheric testing. Limitation to underground detonations after 1962 greatly reduced radiation exposure to the public surrounding the NTS. After nuclear testing ended in 1992, NTS radiation monitoring focused on detecting airborne radionuclides from historically contaminated soils. These radionuclides are derived from re-suspension of soil (primarily by wind) and emission of tritium-contaminated soil moisture through evapotranspiration. Low amounts of tritium were also emitted to air at the NLVF, an NTS support complex in North Las Vegas. To protect the public from harmful levels of man-made radiation, the Clean Air Act, National Emission Standards for Hazardous Air Pollutants (NESHAP) (Title 40 Code of Federal Regulations [CFR] Part 61 Subpart H) limits the release of radioactivity from a U.S. Department of Energy facility to 10 millirem per year (mrem/yr) effective dose equivalent to any member of the public. This limit does not include radiation not related to NTS activities. Unrelated …
Date: June 11, 2010
Creator: Monitoring, NSTec Ecological and Environmental
Object Type: Report
System: The UNT Digital Library
YALINA-booster Subcritical Assembly Pulsed-Neutron Experiments : Data Processing and Spatial Corrections. (open access)

YALINA-booster Subcritical Assembly Pulsed-Neutron Experiments : Data Processing and Spatial Corrections.

The YALINA-Booster experiments and analyses are part of the collaboration between Argonne National Laboratory of USA and the Joint Institute for Power & Nuclear Research - SOSNY of Belarus for studying the physics of accelerator driven systems for nuclear energy applications using low enriched uranium. The YALINA-Booster subcritical assembly is utilized for studying the kinetics of accelerator driven systems with its highly intensive D-T or D-D pulsed neutron source. In particular, the pulsed neutron methods are used to determine the reactivity of the subcritical system. This report examines the pulsed-neutron experiments performed in the YALINA-Booster facility with different configurations for the subcritical assembly. The 1141 configuration with 90% U-235 fuel and the 1185 configuration with 36% or 21% U-235 fuel are examined. The Sjoestrand area-ratio method is utilized to determine the reactivities of the different configurations. The linear regression method is applied to obtain the prompt neutron decay constants from the pulsed-neutron experimental data. The reactivity values obtained from the experimental data are shown to be dependent on the detector locations inside the subcritical assembly and the types of detector used for the measurements. In this report, Bell's spatial correction factors are calculated based on a Monte Carlo model to …
Date: October 11, 2010
Creator: Cao, Y.; Gohar, Y. & Division, Nuclear Engineering
Object Type: Report
System: The UNT Digital Library
Finding the Higgs boson of the standard model in the channel ZH → e<sup>+</sup>e<sup>-</sup>b$\bar{b}$ with the D0 detector at the Tevatron; Recherche du boson de Higgs du nideke standard dans le canal ZH → e<sup>+</sup>e<sup>-</sup>b$\bar{b}$ Avec le Detecteur DØ Aupres du Tevatron (open access)

Finding the Higgs boson of the standard model in the channel ZH → e<sup>+</sup>e<sup>-</sup>b$\bar{b}$ with the D0 detector at the Tevatron; Recherche du boson de Higgs du nideke standard dans le canal ZH → e<sup>+</sup>e<sup>-</sup>b$\bar{b}$ Avec le Detecteur DØ Aupres du Tevatron

The organization of this thesis consists of three main ideas: the first presents the theoretical framework and experimental, as well as objects used in the analysis and the second relates to the various work tasks of service that I performed on the calorimeter, and the third is the search for the Higgs boson in the channel ZH → e<sup>+</sup>e<sup>-</sup>b$\bar{b}$. Thus, this thesis has the following structure: Chapter 1 is an introduction to the standard model of particle physics and the Higgs mechanism; Chapter 2 is an overview of the complex and the acceleration of the Tevatron at Fermilab DØ detector; Chapter 3 is an introduction to physical objects used in this thesis; Chapter 4 presents the study made on correcting the energy measured in the calorimeter; Chapter 5 describes the study of certification of electrons in the calorimeter; Chapter 6 describes the study of certification of electrons in the intercryostat region of calorimeter; Chapter 7 Detailed analysis on the search for Higgs production in the channel ZH → e<sup>+</sup>e<sup>-</sup>b$\bar{b}$; and Chapter 8 presents the final results of the calculations of upper limits to the production cross section of the Higgs boson on a range of low masses.
Date: June 11, 2010
Creator: Calpas, Betty Constante
Object Type: Thesis or Dissertation
System: The UNT Digital Library
YALINA-booster Subcritical Assembly Pulsed-Neutron E Xperiments: Detector Dead Time and Apatial Corrections. (open access)

YALINA-booster Subcritical Assembly Pulsed-Neutron E Xperiments: Detector Dead Time and Apatial Corrections.

In almost every detector counting system, a minimal dead time is required to record two successive events as two separated pulses. Due to the random nature of neutron interactions in the subcritical assembly, there is always some probability that a true neutron event will not be recorded because it occurs too close to the preceding event. These losses may become rather severe for counting systems with high counting rates, and should be corrected before any utilization of the experimental data. This report examines the dead time effects for the pulsed neutron experiments of the YALINA-Booster subcritical assembly. The nonparalyzable model is utilized to correct the experimental data due to dead time. Overall, the reactivity values are increased by 0.19$ and 0.32$ after the spatial corrections for the YALINA-Booster 36% and 21% configurations respectively. The differences of the reactivities obtained with He-3 long or short detectors at the same detector channel diminish after the dead time corrections of the experimental data for the 36% YALINA-Booster configuration. In addition, better agreements between reactivities obtained from different experimental data sets are also observed after the dead time corrections for the 21% YALINA-Booster configuration.
Date: October 11, 2010
Creator: Cao, Y.; Gohar, Y. & Division, Nuclear Engineering
Object Type: Report
System: The UNT Digital Library
Large Angular Jump Mechanism Observed for Hydrogen Bond Exchange in Aqueous Perchlorate Solution (open access)

Large Angular Jump Mechanism Observed for Hydrogen Bond Exchange in Aqueous Perchlorate Solution

The mechanism for hydrogen bond (H-bond) switching in solution has remained subject to debate despite extensive experimental and theoretical studies. We have applied polarization-selective multidimensional vibrational spectroscopy to investigate the H-bond exchange mechanism in aqueous NaClO{sub 4} solution. The results show that a water molecule shifts its donated H-bonds between water and perchlorate acceptors by means of large, prompt angular rotation. Using a jump-exchange kinetic model, we extract an average jump angle of 49 {+-} 4{sup o}, in qualitative agreement with the jump angle observed in molecular dynamics simulations of the same aqueous NaClO{sub 4} solution.
Date: June 11, 2010
Creator: Ji, Minbiao; /SLAC, PULSE /Stanford U., Phys. Dept.; Odelius3, Michael; U., /Stockholm; Gaffney1, K.J. & /aff SLAC, PULSE
Object Type: Article
System: The UNT Digital Library
Internal Energies of Ion-Sputtered Neutral Tryptophan and Thymine Molecules Determined by Vacuum Ultraviolet Photoionization (open access)

Internal Energies of Ion-Sputtered Neutral Tryptophan and Thymine Molecules Determined by Vacuum Ultraviolet Photoionization

Vacuum ultraviolet photoionization coupled to secondary neutral mass spectrometry (VUV-SNMS) of deposited tryptophan and thymine films are performed at the Chemical Dynamics Beamline. The resulting mass spectra show that while the intensity of the VUV-SNMS signal is lower than the corresponding secondary ion mass spectroscopy (SIMS) signal, the mass spectra are significantly simplified in VUV-SNMS. A detailed examination of tryptophan and thymine neutral molecules sputtered by 25 keV Bi3 + indicates that the ion-sputtered parent molecules have ~;;2.5 eV of internal energy. While this internal energy shifts the appearance energy of the photofragment ions for both tryptophan and thymine, it does not change the characteristic photoionizaton efficiency (PIE) curves of thymine versus photon energy. Further analysis of the mass spectral signals indicate that approximately 80 neutral thymine molecules and 400 tryptophan molecules are sputtered per incident Bi3 + ion. The simplified mass spectra and significant characteristic ion contributions to the VUV-SNMS spectra indicate the potential power of the technique for organic molecule surface analysis.
Date: March 11, 2010
Creator: Zhou, Jia; Takahashi, Lynelle; Wilson, Kevin R.; Leone, Stephen R. & Ahmed, Musahid
Object Type: Article
System: The UNT Digital Library
The Role of INSPIRE in HEP Data Preservation Efforts (open access)

The Role of INSPIRE in HEP Data Preservation Efforts

INSPIRE is a new community resource for HEP literature and associated information. It is based on the combination of SPIRES content and features and the powerful Invenio software developed at CERN. The INSPIRE service will come online in fall of 2009, and be run by CERN, DESY, Fermilab and SLAC. Data preservation, to be successful, must not only preserve the data, but must also organize it and allow it to be found by those who would make use of it, and resources such as INSPIRE are ideally positioned and ready to provide this organization and context. In addition, INSPIRE will soon be ready to provide storage of smaller datasets, such as high-level analysis objects, as stand-alone objects placed in the repository or as objects associated with an analysis paper. This small project could pave the way towards the context and organization which is one piece of the infrastructure needed for all levels of data preservation.
Date: June 11, 2010
Creator: Brooks, Travis C.
Object Type: Article
System: The UNT Digital Library
Verification of an IGBT Fusing Switch for Over-current Protection of the SNS HVCM (open access)

Verification of an IGBT Fusing Switch for Over-current Protection of the SNS HVCM

An IGBT based over-current protection system has been developed to detect faults and limit the damage caused by faults in high voltage converter modulators. During normal operation, an IGBT enables energy to be transferred from storage capacitors to a H-bridge. When a fault occurs, the over-current protection system detects the fault, limits the fault current and opens the IGBT to isolate the remaining stored energy from the fault. This paper presents an experimental verification of the over-current protection system under applicable conditions.
Date: June 11, 2010
Creator: Benwell, Andrew; Kemp, Mark; Burkhart, Craig & Nguyen, Minh
Object Type: Article
System: The UNT Digital Library
The Influence of Cloud Microphysics and Radiation on the Response of Water Vapor and Clouds to Climate Change (open access)

The Influence of Cloud Microphysics and Radiation on the Response of Water Vapor and Clouds to Climate Change

Uncertainties in representing the atmospheric water cycle are major obstacles to the accurate prediction of future climate. This project focused on addressing some of these uncertainties by implementing new physics for convection and radiation into the NCAR Community Atmosphere Model (CAM). To better understand and eventually better represent these processes in this major national climate model, we modified CAM3.5 to use the convection and cloud schemes developed by the Massachusetts Institute of Technology (MIT) and the RRTMG rapid radiation code for global climate models developed by Atmospheric and Environmental Research, Inc. (AER). The impact of the new physics on the CAM3.5 simulation of convection on diurnal and intra-seasonal scales, on intra-seasonal oscillations and on the distribution of water vapor has been investigated. In addition, the MIT and AER physics packages have been incorporated and tested in combination within the Weather Research and Forecasting (WRF) regional forecast model for the purpose of evaluating and improving convective and radiative processes on time scales appropriate to weather simulations. It has been found that the application of the AER radiation and MIT convection produces significant improvements in the modeled diurnal cycle of convection, especially over land, in the NCAR climate model. However, both the …
Date: November 11, 2010
Creator: Emanuel, Kerry & Iacono, Michael J.
Object Type: Report
System: The UNT Digital Library
Longitudinal Diagnostics for Short Electron Beam Bunches (open access)

Longitudinal Diagnostics for Short Electron Beam Bunches

Single-pass free electron lasers require high peak currents from ultra-short electron bunches to reach saturation and an accurate measurement of bunch length and longitudinal bunch profile is necessary to control the bunch compression process from low to high beam energy. The various state-of-the-art diagnostics methods from ps to fs time scales using coherent radiation detection, RF deflection, and other techniques are presented. The use of linear accelerators as drivers for free electron lasers (FEL) and the advent of single-pass (SASE) FELs has driven the development of a wide range of diagnostic techniques for measuring the length and longitudinal distribution of short and ultra-short electron bunches. For SASE FELs the radiation power and the length of the undulator needed to achieve saturation depend strongly on the charge density of the electron beam. In the case of X-ray FELs, this requires the accelerator to produce ultra-high brightness beams with micron size transverse normalized emittances and peak currents of several kA through several stages of magnetic bunch compression. Different longitudinal diagnostics are employed to measure the peak current and bunch profile along these stages. The measurement techniques can be distinguished into different classes. Coherent methods detect the light emitted from the beam by …
Date: June 11, 2010
Creator: Loos, H.
Object Type: Article
System: The UNT Digital Library
100-N Area Strontium-90 Treatability Demonstration Project: Phytoextraction Along the 100-N Columbia River Riparian Zone – Field Treatability Study (open access)

100-N Area Strontium-90 Treatability Demonstration Project: Phytoextraction Along the 100-N Columbia River Riparian Zone – Field Treatability Study

Strontium-90 (90Sr) is present both in the aquifer near the river and in the vadose and riparian zones of the river’s shore at 100-NR-2. Phytoextraction of 90Sr is being considered as a potential remediation system along the riparian zone of the Columbia River. Phytoextraction would employ coyote willow (Salix exigua). Past studies have shown that willow roots share uptake mechanisms for Sr with Ca, a plant macronutrient as well as no discrimination between Sr and 90Sr. Willow 90Sr concentration ratios [CR’s; (pCi 90Sr/g dry wt. of new growth tissue)/(pCi 90Sr/g soil porewater)] were consistently greater than 65 with three-quarters of the assimilated label partitioned into the above ground shoot. Insect herbivore experiments also demonstrated no significant potential for bioaccumulation or food chain transfer from their natural activities. The objectives of this field study were three-fold: (1) to demonstrate that a viable, “managed” plot of coyote willows can be established on the shoreline of the Columbia River that would survive the same microenvironment to be encountered at the 100-NR-2 shoreline; (2) to show through engineered barriers that large and small animal herbivores can be prevented from feeding on these plants; and (3) to show that once established, the plants will provide …
Date: January 11, 2010
Creator: Fellows, Robert J.; Fruchter, Jonathan S.; Driver, Crystal J. & Ainsworth, Calvin C.
Object Type: Report
System: The UNT Digital Library
Methodology Development and Applications of Proliferation Resistance and Physical Protection Evaluation. (open access)

Methodology Development and Applications of Proliferation Resistance and Physical Protection Evaluation.

We present an overview of the program on the evaluation methodology for proliferation resistance and physical protection (PR&amp;PP) of advanced nuclear energy systems (NESs) sponsored by the Generation IV International Forum (GIF). For a proposed NES design, the methodology defines a set of challenges, analyzes system response to these challenges, and assesses outcomes. The challenges to the NES are the threats posed by potential actors (proliferant States or sub-national adversaries). The characteristics of Generation IV systems, both technical and institutional, are used to evaluate the response of the system and to determine its resistance against proliferation threats and robustness against sabotage and terrorism threats. The outcomes of the system response are expressed in terms of a set of measures, which are the high-level PR&amp;PP characteristics of the NES. The methodology is organized to allow evaluations to be performed at the earliest stages of system design and to become more detailed and more representative as the design progresses. It can thus be used to enable a program in safeguards by design or to enhance the conceptual design process of an NES with regard to intrinsic features for PR&amp;PP.
Date: April 11, 2010
Creator: Bari, R. A.; Peterson, P. F.; Whitlock, J. J. & Therios, I. U.
Object Type: Article
System: The UNT Digital Library
A Permanent-Magnet Microwave Ion Source for a Compact High-Yield Neutron Generator (open access)

A Permanent-Magnet Microwave Ion Source for a Compact High-Yield Neutron Generator

We present recent work on the development of a microwave ion source that will be used in a high-yield compact neutron generator for active interrogation applications. The sealed tube generator will be capable of producing high neutron yields, 5x1011 n/s for D-T and ~;;1x1010 n/s for D-D reactions, while remaining transportable. We constructed a microwave ion source (2.45 GHz) with permanent magnets to provide the magnetic field strength of 87.5 mT necessary for satisfying the electron cyclotron resonance (ECR) condition. Microwave ion sources can produce high extracted beam currents at the low gas pressures required for sealed tube operation and at lower power levels than previously used RF-driven ion sources. A 100 mA deuterium/tritium beam will be extracted through a large slit (60x6 mm2) to spread the beam power over a larger target area. This paper describes the design of the permanent-magnet microwave ion source and discusses the impact of the magnetic field design on the source performance. The required equivalent proton beam current density of 40 mA/cm2 was extracted at a moderate microwave power of 400 W with an optimized magnetic field.
Date: October 11, 2010
Creator: Waldmann, Ole & Ludewigt, Bernhard
Object Type: Article
System: The UNT Digital Library
Low Prevalence of Chronic Beryllium Disease among Workers at a Nuclear Weapons Research and Development Facility (open access)

Low Prevalence of Chronic Beryllium Disease among Workers at a Nuclear Weapons Research and Development Facility

To study the prevalence of beryllium sensitization (BeS) and chronic beryllium disease (CBD) in a cohort of workers from a nuclear weapons research and development facility. We evaluated 50 workers with BeS with medical and occupational histories, physical examination, chest imaging with HRCT (N=49), and pulmonary function testing. Forty of these workers also underwent bronchoscopy for bronchoalveolar lavage (BAL) and transbronchial biopsies. The mean duration of employment at the facility was 18 yrs and the mean latency (from first possible exposure) to time of evaluation was 32 yrs. Five of the workers had CBD at the time of evaluation (based on histology or HRCT); three others had evidence of probable CBD. These workers with BeS, characterized by a long duration of potential Be exposure and a long latency, had a low prevalence of CBD.
Date: January 11, 2010
Creator: Arjomandi, M; Seward, J P; Gotway, M B; Nishimura, S; Fulton, G P; Thundiyil, J et al.
Object Type: Article
System: The UNT Digital Library
Compression and strong rarefaction in high power impulse magnetron sputtering discharges (open access)

Compression and strong rarefaction in high power impulse magnetron sputtering discharges

Gas compression and strong rarefaction have been observed for high power impulse magnetron sputtering (HIPIMS) discharges using a copper target in argon. Time-resolved ion saturation currents of 35 probes were simultaneously recorded for HIPIMS discharges operating far above the self-sputtering runaway threshold. The argon background pressure was a parameter for the evaluation of the spatial and temporal development of the plasma density distribution. The data can be interpreted by a massive onset of the sputtering flux (sputter wind) that causes a transient densification of the gas, followed by rarefaction and the replacement of gas plasma by the metal plasma of sustained self-sputtering. The plasma density pulse follows closely the power pulse at low pressure. At high pressure, the relatively remote probes recorded a density peak only after the discharge pulse, indicative for slow, diffusive ion transport.
Date: November 11, 2010
Creator: Horwat, David & Anders, Andre
Object Type: Article
System: The UNT Digital Library
Search for a Lorentz-violating sidereal signal with atmospheric neutrinos in IceCube (open access)

Search for a Lorentz-violating sidereal signal with atmospheric neutrinos in IceCube

A search for sidereal modulation in the flux of atmospheric muon neutrinos in IceCube was performed. Such a signal could be an indication of Lorentz-violating physics. Neutrino oscillationmodels, derivable from extensions to the Standard Model, allow for neutrino oscillations that depend on the neutrino's direction of propagation. No such direction-dependent variation was found. Adiscrete Fourier transform method was used to constrain the Lorentz and CPT-violating coefficients in one of these models. Due to the unique high energy reach of IceCube, it was possible to improveconstraints on certain Lorentz-violating oscillations by three orders of magnitude with respect to limits set by other experiments.
Date: November 11, 2010
Creator: IceCube & etal, Abbasi, R,
Object Type: Article
System: The UNT Digital Library
Field Summary Report for Remedial Investigation of Hanford Site Releases to the Columbia River, Hanford Site, Washington (open access)

Field Summary Report for Remedial Investigation of Hanford Site Releases to the Columbia River, Hanford Site, Washington

This report summarizes field sampling activities conducted in support of WCH’s Remedial Investigation of Hanford Site Releases to the Columbia River. This work was conducted form 2008 through 2010. The work included preliminary mapping and measurement of Hanford Site contaminants in sediment, pore water, and surface water located in areas where groundwater upwelling were found.
Date: August 11, 2010
Creator: Hulstrom, L. C.
Object Type: Report
System: The UNT Digital Library

Effect of System and Air Contaminants on PEMFC Performance and Durability

This presentation summarizes Effect of System and Air Contaminants on PEMFC Performance and Durability.
Date: June 11, 2010
Creator: Dinh, H.
Object Type: Presentation
System: The UNT Digital Library
Equal Access Initiative HIV/AIDS Information Resources from NLM (open access)

Equal Access Initiative HIV/AIDS Information Resources from NLM

The Equal Access Initiative: HIV/AIDS Information Resources from the National Library of Medicine training is designed specifically for the National Minority AIDS Council 2010 Equal Access Initiative (EAI) Computer Grants Program awardees to provide valuable health information resources from the National Library of Medicine and other reliable sources to increase awareness of the wealth of treatment information and educational materials that are available on the Internet and to improve prevention and treatment education for their clients. These resources will also meet the needs of community-based
Date: September 11, 2010
Creator: Dancy, Templin-Branner W. and N.
Object Type: Book
System: The UNT Digital Library
PACE Status Update (open access)

PACE Status Update

The Federal Housing Finance Agency (FHFA) regulates Fannie Mae, Freddie Mac, and the 12 Federal Home Loan Banks (the government-sponsored enterprises - GSEs). On July 6, 2010, FHFA and the Office of the Comptroller of the Currency (OCC) concluded that Property Assessed Clean Energy (PACE) programs 'present significant safety and soundness concerns' to the housing finance industry. This statement came after a year of discussions with state and federal agencies in which PACE, a novel mechanism for financing energy efficiency and renewable energy improvements, has gone from receiving support from the White House, canonization as one of Scientific American's 'World Changing Ideas' and legislative adoption in 24 states to questionable relevance, at least in the residential sector. Whether PACE resumes its expansion as an innovative tool for financing energy efficiency and clean generation depends on outcomes in each of the three branches of government - discussions on a PACE pilot phase among federal agencies, litigation in federal court, and legislation in Congress - all highly uncertain. This policy brief addresses the practical impacts of these possible outcomes on existing and emerging PACE programs across the United States and potential paths forward.
Date: August 11, 2010
Creator: M., Zimring,; Hoffman, I. & Fuller, M.
Object Type: Report
System: The UNT Digital Library
Reducing variance in batch partitioning measurements (open access)

Reducing variance in batch partitioning measurements

The partitioning experiment is commonly performed with little or no attention to reducing measurement variance. Batch test procedures such as those used to measure K{sub d} values (e.g., ASTM D 4646 and EPA402 -R-99-004A) do not explain how to evaluate measurement uncertainty nor how to minimize measurement variance. In fact, ASTM D 4646 prescribes a sorbent:water ratio that prevents variance minimization. Consequently, the variance of a set of partitioning measurements can be extreme and even absurd. Such data sets, which are commonplace, hamper probabilistic modeling efforts. An error-savvy design requires adjustment of the solution:sorbent ratio so that approximately half of the sorbate partitions to the sorbent. Results of Monte Carlo simulations indicate that this simple step can markedly improve the precision and statistical characterization of partitioning uncertainty.
Date: August 11, 2010
Creator: Mariner, Paul E.
Object Type: Article
System: The UNT Digital Library
Ecloud Build-Up Simulations for the FNAL MI for a Mixed Fill Pattern: Dependence on Peak SEY and Pulse Intensity During the Ramp (open access)

Ecloud Build-Up Simulations for the FNAL MI for a Mixed Fill Pattern: Dependence on Peak SEY and Pulse Intensity During the Ramp

We present simulation results of the build-up of the electron-cloud density n{sub e} in three regions of the FNAL Main Injector (MI) for a beam fill pattern made up of 5 double booster batches followed by a 6th single batch. We vary the pulse intensity in the range N{sub t} = (2-5) x 10{sup 13}, and the beam kinetic energy in the range E{sub k} = 8-120 GeV. We assume a secondary electron emission model qualitatively corresponding to TiN, except that we let the peak value of the secondary electron yield (SEY) {delta}{sub max} vary as a free parameter in a fairly broad range. Our main conclusions are: (1) At fixed N{sub t} there is a clear threshold behavior of n{sub e} as a function of {delta}{sub max} in the range {approx} 1.1-1.3. (2) At fixed {delta}{sub max}, there is a threshold behavior of n{sub e} as a function of N{sub t} provided {delta}{sub max} is sufficiently high; the threshold value of N{sub t} is a function of the characteristics of the region being simulated. (3) The dependence on E{sub k} is weak except possibly at transition energy. Most of these results were informally presented to the relevant MI personnel …
Date: December 11, 2010
Creator: Furman, M. A.
Object Type: Report
System: The UNT Digital Library
Real time in situ detection of organic nitrates in atmospheric aerosols (open access)

Real time in situ detection of organic nitrates in atmospheric aerosols

A new field instrument is described that quantifies total particle phase organic nitrates. The instrument is based on the thermal dissociation laser induced fluorescence (TD-LIF) method that thermally converts nitrates to NO2 which is then detected by LIF. This instrument is unique in its ability to provide fast sensitive measurements of particle phase organic nitrates, without interference from inorganic nitrate. Here we use it to quantify organic nitrates in SOA generated from high-NOx photooxidation of limonene, a-pinene, D-3-carene, and tridecane. In these experiments the organic nitrate moiety is observed to be 6-15percent of the total SOA mass, depending on the organic precursor.
Date: June 11, 2010
Creator: Rollins, Andrew W.; Smith, Jared D.; Wilson, Kevin R. & Cohen, Ronald C.
Object Type: Article
System: The UNT Digital Library
Investigation of anti-Relaxation coatings for alkali-metal vapor cells using surface science techniques (open access)

Investigation of anti-Relaxation coatings for alkali-metal vapor cells using surface science techniques

Many technologies based on cells containing alkali-metal atomic vapor benefit from the use of antirelaxation surface coatings in order to preserve atomic spin polarization. In particular, paraffin has been used for this purpose for several decades and has been demonstrated to allow an atom to experience up to 10?000 collisions with the walls of its container without depolarizing, but the details of its operation remain poorly understood. We apply modern surface and bulk techniques to the study of paraffin coatings in order to characterize the properties that enable the effective preservation of alkali spin polarization. These methods include Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, near-edge x-ray absorption fine structure spectroscopy, and x-ray photoelectron spectroscopy. We also compare the light-induced atomic desorption yields of several different paraffin materials. Experimental results include the determination that crystallinity of the coating material is unnecessary, and the detection of C=C double bonds present within a particular class of effective paraffin coatings. Further study should lead to the development of more robust paraffin antirelaxation coatings, as well as the design and synthesis of new classes of coating materials.
Date: October 11, 2010
Creator: Seltzer, S. J.; Michalak, D. J.; Donaldson, M. H.; Balabas, M. V.; Barber, S. K.; Bernasek, S. L. et al.
Object Type: Article
System: The UNT Digital Library