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Fission Product Gamma-Ray Line Pairs Sensitive to Fissile Material and Neutron Energy (open access)

Fission Product Gamma-Ray Line Pairs Sensitive to Fissile Material and Neutron Energy

The beta-delayed gamma-ray spectra from the fission of {sup 235}U, {sup 238}U, and {sup 239}Pu by thermal and near-14-MeV neutrons have been measured for delay times ranging from 1 minute to 14 hours. Spectra at all delay times contain sets of prominent gamma-ray lines with intensity ratios that identify the fissile material and distinguish between fission induced by low-energy or high-energy neutrons.
Date: November 15, 2007
Creator: Marrs, R. E.; Norman, E. B.; Burke, J. T.; Macri, R. A.; Shugart, H. A.; Browne, E. et al.
System: The UNT Digital Library
The histone H3K9 methylation and RNAi pathways regulate normalnucleolar and repeated DNA organization by inhibiting formation ofextrachromosomal DNAs (open access)

The histone H3K9 methylation and RNAi pathways regulate normalnucleolar and repeated DNA organization by inhibiting formation ofextrachromosomal DNAs

In order to identify regulators of nuclear organization, Drosophila mutants in the Su(var)3-9 histone H3K9 methyltransferase, RNAi pathway components, and other regulators of heterochromatin-mediated gene silencing were examined for altered nucleoli and positioning of repeated DNAs. Animals lacking components of the H3K9 methylation and RNAi pathways contained disorganized nucleoli, ribosomal DNA (rDNA) and satellite DNAs. The levels of H3K9 dimethylation (H3K9me2) in chromatin associated with repeated DNAs decreased dramatically in Su(var)3-9 and dcr-2 (dicer-2) mutant tissues compared to wild type. We also observed a substantial increase in extrachromosomal repeated DNAs in mutant tissues. The disorganized nucleolus phenotype depends on the presence of Ligase 4 (Lig4), and ecc DNA formation is not induced by removal of cohesin. We conclude that H3K9 methylation of rDNA and satellites, maintained by Su(var)3-9, HP1, and the RNAi pathway, is necessary for the structural stability of repeated DNAs, which is mediated through suppression of non-homologous end joining (NHEJ). These results suggest a mechanism for how local chromatin structure can regulate genome stability, and the organization of chromosomal elements and nuclear organelles.
Date: June 15, 2006
Creator: Peng, Jamy C. & Karpen, Gary H.
System: The UNT Digital Library
The Life-cycle of Operons (open access)

The Life-cycle of Operons

Operons are a major feature of all prokaryotic genomes, buthow and why operon structures vary is not well understood. To elucidatethe life-cycle of operons, we compared gene order between Escherichiacoli K12 and its relatives and identified the recently formed anddestroyed operons in E. coli. This allowed us to determine how operonsform, how they become closely spaced, and how they die. Our findingssuggest that operon evolution may be driven by selection on geneexpression patterns. First, both operon creation and operon destructionlead to large changes in gene expression patterns. For example, theremoval of lysA and ruvA from ancestral operons that contained essentialgenes allowed their expression to respond to lysine levels and DNAdamage, respectively. Second, some operons have undergone acceleratedevolution, with multiple new genes being added during a brief period.Third, although genes within operons are usually closely spaced becauseof a neutral bias toward deletion and because of selection against largeoverlaps, genes in highly expressed operons tend to be widely spacedbecause of regulatory fine-tuning by intervening sequences. Althoughoperon evolution may be adaptive, it need not be optimal: new operonsoften comprise functionally unrelated genes that were already inproximity before the operon formed.
Date: March 15, 2007
Creator: Price, Morgan N.; Arkin, Adam P. & Alm, Eric J.
System: The UNT Digital Library
Shear-slip analysis in multiphase fluid-flow reservoir engineeringap plications using TOUGH-FLAC (open access)

Shear-slip analysis in multiphase fluid-flow reservoir engineeringap plications using TOUGH-FLAC

This paper describes and demonstrates the use of the coupledTOUGH-FLAC simulator for geomechanical shear-slip (failure) analysis inmultiphase fluid-flow reservoir-engineering applications. Two approachesfor analyzing shear-slip are described, one using continuum stress-strainanalysis and another using discrete fault analysis. The use of shear-slipanalysis in TOUGH-FLAC is demonstrated on application examples related toCO2 sequestration and geothermal energy extraction. In the case of CO2sequestration, the shear-slip analysis is used to evaluate maximumsustainable CO2-injection pressure under increasing reservoir pressure,whereas in the case of geothermal energy extraction, the shear-slipanalysis is used to study induced seismicity during steam productionunder decreasing reservoir pressure and temperature.
Date: January 15, 2006
Creator: Rutqvist, Jonny; Birkholzer, Jens; Cappa, Frederic; Oldenburg,Curt & Tsang, Chin-Fu
System: The UNT Digital Library
Japan's Residential Energy Demand Outlook to 2030 Considering Energy Efficiency Standards"Top-Runner Approach" (open access)

Japan's Residential Energy Demand Outlook to 2030 Considering Energy Efficiency Standards"Top-Runner Approach"

As one of the measures to achieve the reduction in greenhouse gas emissions agreed to in the"Kyoto Protocol," an institutional scheme for determining energy efficiency standards for energy-consuming appliances, called the"Top-Runner Approach," was developed by the Japanese government. Its goal is to strengthen the legal underpinnings of various energy conservation measures. Particularly in Japan's residential sector, where energy demand has grown vigorously so far, this efficiency standard is expected to play a key role in mitigating both energy demand growth and the associated CO2 emissions. This paper presents an outlook of Japan's residential energy demand, developed by a stochastic econometric model for the purpose of analyzing the impacts of the Japan's energy efficiency standards, as well as the future stochastic behavior of income growth, demography, energy prices, and climate on the future energy demand growth to 2030. In this analysis, we attempt to explicitly take into consideration more than 30 kinds of electricity uses, heating, cooling and hot water appliances in order to comprehensively capture the progress of energy efficiency in residential energy end-use equipment. Since electricity demand, is projected to exhibit astonishing growth in Japan's residential sector due to universal increasing ownership of electric and other appliances, it is …
Date: May 15, 2008
Creator: Lacommare, Kristina S H; Komiyama, Ryoichi & Marnay, Chris
System: The UNT Digital Library
Analysis of Non-Enzymatically Glycated Peptides: Neutral-Loss Triggered MS3 Versus Multi-Stage Activation Tandem Mass Spectrometry (open access)

Analysis of Non-Enzymatically Glycated Peptides: Neutral-Loss Triggered MS3 Versus Multi-Stage Activation Tandem Mass Spectrometry

Non-enzymatic glycation of tissue proteins has important implications in the development of complications of diabetes mellitus. While electron transfer dissociation (ETD) has been shown to outperform collision-induced dissociation (CID) in sequencing glycated peptides by tandem mass spectrometry, ETD instrumentation is not yet available in all laboratories. In this study, we evaluated different advanced CID techniques (i.e., neutral-loss triggered MS3 and multi-stage activation) during LC-MSn analyses of Amadori-modified peptides enriched from human serum glycated in vitro. During neutral-loss triggered MS3 experiments, MS3 scans triggered by neutral-losses of 3 H2O or 3 H2O + HCHO produced similar results in terms of glycated peptide identifications. However, neutral losses of 3 H2O resulted in significantly more glycated peptide identifications during multi-stage activation experiments. Overall, the multi-stage activation approach produced more glycated peptide identifications, while the neutral-loss triggered MS3 approach resulted in much higher specificity. Both techniques offer a viable alternative to ETD for identifying glycated peptides when that method is unavailable.
Date: October 15, 2008
Creator: Zhang, Qibin; Petyuk, Vladislav A.; Schepmoes, Athena A.; Orton, Daniel J.; Monroe, Matthew E.; Yang, Feng et al.
System: The UNT Digital Library
Optimal Technology Selection and Operation of Microgrids inCommercial Buildings (open access)

Optimal Technology Selection and Operation of Microgrids inCommercial Buildings

The deployment of small (<1-2 MW) clusters of generators,heat and electrical storage, efficiency investments, and combined heatand power (CHP) applications (particularly involving heat activatedcooling) in commercial buildings promises significant benefits but posesmany technical and financial challenges, both in system choice and itsoperation; if successful, such systems may be precursors to widespreadmicrogrid deployment. The presented optimization approach to choosingsuch systems and their operating schedules uses Berkeley Lab'sDistributed Energy Resources Customer Adoption Model [DER-CAM], extendedto incorporate electrical storage options. DER-CAM chooses annual energybill minimizing systems in a fully technology-neutral manner. Anillustrative example for a San Francisco hotel is reported. The chosensystem includes two engines and an absorption chiller, providing anestimated 11 percent cost savings and 10 percent carbon emissionreductions, under idealized circumstances.
Date: January 15, 2007
Creator: Marnay, Chris; Venkataramanan, Giri; Stadler, Michael; Siddiqui,Afzal; Firestone, Ryan & Chandran, Bala
System: The UNT Digital Library
Searches for Fractionally Charged Particles: What Should Be Done Next? (open access)

Searches for Fractionally Charged Particles: What Should Be Done Next?

Since the initial measurements of the electron charge a century ago, experimenters have faced the persistent question as to whether elementary particles exist that have charges that are fractional multiples of the electron charge. I concisely review the results of the last 50 years of searching for fractional charge particles with no confirmed positive results. I discuss the question of whether more searching is worthwhile?
Date: January 15, 2009
Creator: Perl, Martin L.
System: The UNT Digital Library
Specific interactions between arbuscular mycorrhizal fungi and plant growth-promoting bacteria--as revealed by different combinations (open access)

Specific interactions between arbuscular mycorrhizal fungi and plant growth-promoting bacteria--as revealed by different combinations

The interactions between two plant growth promoting rhizobacteria (PGPR), Pseudomonas fluorescens SBW25 and Paenibacillus brasilensis PB177, two arbuscular mycorrhizal (AM) fungi (Glomus mosseae and G. intraradices) and one pathogenic fungus (Microdochium nivale) were investigated on winter wheat (Triticum aestivum cultivar Tarso) in a greenhouse trial. PB177, but not SBW25, had strong inhibitory effects on M. nivale in dual culture plate assays. The results from the greenhouse experiment show very specific interactions; e.g. the two AM fungi react differently when interacting with the same bacteria on plants. G. intraradices (single inoculation or together with SBW25) increased plant dry weight on M. nivale infested plants, suggesting that the pathogenic fungus is counteracted by G. intraradices, but PB177 inhibited this positive effect. This is an example of two completely different reactions between the same AM fungus and two species of bacteria, previously known to enhance plant growth and inhibit pathogens. When searching for plant growth promoting microorganisms it is therefore important to test for the most suitable combination of plant, bacteria and fungi in order to get satisfactory plant growth benefits.
Date: May 15, 2008
Creator: Jaderlund, Lotta; Arthurson, Veronica; Granhall, Ulf & Jansson, Janet K.
System: The UNT Digital Library
UXO detection and identification based on intrinsic target polarizabilities: A case history (open access)

UXO detection and identification based on intrinsic target polarizabilities: A case history

Electromagnetic induction data parameterized in time dependent object intrinsic polarizabilities allow discrimination of unexploded ordnance (UXO) from false targets (scrap metal). Data from a cart-mounted system designed for discrimination of UXO with 20 mm to 155 mm diameters are used. Discrimination of UXO from irregular scrap metal is based on the principal dipole polarizabilities of a target. A near-intact UXO displays a single major polarizability coincident with the long axis of the object and two equal smaller transverse polarizabilities, whereas metal scraps have distinct polarizability signatures that rarely mimic those of elongated symmetric bodies. Based on a training data set of known targets, object identification was made by estimating the probability that an object is a single UXO. Our test survey took place on a military base where both 4.2-inch mortar shells and scrap metal were present. The results show that we detected and discriminated correctly all 4.2-inch mortars, and in that process we added 7%, and 17%, respectively, of dry holes (digging scrap) to the total number of excavations in two different survey modes. We also demonstrated a mode of operation that might be more cost effective than the current practice.
Date: July 15, 2008
Creator: Gasperikova, E.; Smith, J.T.; Morrison, H.F.; Becker, A. & Kappler, K.
System: The UNT Digital Library
The Education and Outreach Project of ATLAS - A New Participant inPhysics Education (open access)

The Education and Outreach Project of ATLAS - A New Participant inPhysics Education

The ATLAS experiment at the Large Hadron Collider at CERN has a substantial collaborative Education and Outreach project. This article describes its activities and how it promotes physics to students around the world. With the extraordinary possibility to make groundbreaking discoveries, the ATLAS Experiment [1] at the Large Hadron Collider at CERN can play an important role in promoting contemporary physics at school. For many years ATLAS has had a substantial collaborative Education and Outreach (E&amp;O) project in which physicists from various parts of the world take part. When the experiment begins in 2007, students from around the world will be analyzing data using cutting-edge technology. The unprecedented collision energies of the Large Hadron Collider allow ATLAS to decode the 'events' that unfold after the head-on collisions of protons (Fig. 1). The scientific results from these events will reveal much about the basic nature of matter, energy, space, and time. Students and others will be excited as they try to find events that may be signs for dark matter, extra dimensions of space, mini-black holes, string theory, and other fundamental discoveries. Science education and outreach and the promotion of awareness and appreciation of physics research have become important tasks for …
Date: April 15, 2006
Creator: Barnett, R. Michael & Johansson, K. Erik
System: The UNT Digital Library
Poroelastic modeling of fracture-seismic wave interaction (open access)

Poroelastic modeling of fracture-seismic wave interaction

Rock containing a compliant, fluid-filled fracture can be viewed as one case of heterogeneous poroelastic media. When this fracture is subjected to seismic waves, a strong contrast in the elastic stiffness between the fracture itself and the background can result in enhanced grain-scale local fluid flow. Because this flow--relaxing the pressure building up within the fracture--can increase the dynamic compliance of the fracture and change energy dissipation (attenuation), the scattering of seismic waves can be enhanced. Previously, for a flat, infinite fracture, we derived poroelastic seismic boundary conditions that describe the relationship between a finite jump in the stress and displacement across a fracture, expressed as a function of the stress and displacement at the boundaries. In this paper, we use these boundary conditions to determine frequency-dependent seismic wave transmission and reflection coefficients. Fluid-filled fractures with a range of mechanical and hydraulic properties are examined. From parametric studies, we found that the hydraulic permeability of a fracture fully saturated with water has little impact on seismic wave scattering. In contrast, the seismic response of a partially water-saturated fracture and a heterogeneous fracture filled with compliant liquid (e.g., supercritical CO{sub 2}) depended on the fracture permeability.
Date: August 15, 2008
Creator: Nakagawa, Seiji
System: The UNT Digital Library
Extension of the operating parameters of the two stage light gas gun to velocities below 2 km/sec. (open access)

Extension of the operating parameters of the two stage light gas gun to velocities below 2 km/sec.

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Date: October 15, 2007
Creator: Thoe, R S
System: The UNT Digital Library
Microwave Ion Source and Beam Injection for an Accelerator-drivenNeutron Source (open access)

Microwave Ion Source and Beam Injection for an Accelerator-drivenNeutron Source

An over-dense microwave driven ion source capable ofproducing deuterium (or hydrogen) beams at 100-200 mA/cm2 and with atomicfraction>90 percent was designed and tested with an electrostaticlow energy beam transport section (LEBT). This ion source wasincorporatedinto the design of an Accelerator Driven Neutron Source(ADNS). The other key components in the ADNS include a 6 MeV RFQaccelerator, a beam bending and scanning system, and a deuterium gastarget. In this design a 40 mA D+ beam is produced from a 6 mm diameteraperture using a 60 kV extraction voltage. The LEBT section consists of 5electrodes arranged to form 2 Einzel lenses that focus the beam into theRFQ entrance. To create the ECR condition, 2 induction coils are used tocreate ~; 875 Gauss on axis inside the source chamber. To prevent HVbreakdown in the LEBT a magnetic field clamp is necessary to minimize thefield in this region. Matching of the microwave power from the waveguideto the plasma is done by an autotuner. We observed significantimprovement of the beam quality after installing a boron nitride linerinside the ion source. The measured emittance data are compared withPBGUNS simulations.
Date: February 15, 2007
Creator: Vainionpaa, J. H.; Gough, R.; Hoff, M.; Kwan, J. W.; Ludewigt, B. A.; Regis, M. J. et al.
System: The UNT Digital Library
Characterization of Surplus Plutonium for Disposition Options (open access)

Characterization of Surplus Plutonium for Disposition Options

The United States (U.S.) has identified 61.5 metric tons (MT) of plutonium that is permanently excess to use in nuclear weapons programs, including 47.2 MT of weapons-grade plutonium. Except for materials that remain in use for programs outside of national defense, including programs for nuclear-energy development, the surplus inventories will be stored safely by the Department of Energy (DOE) and then transferred to facilities that will prepare the plutonium for permanent disposition. Some items will be disposed as transuranic waste, low-level waste, or spent fuel. The remaining surplus plutonium will be managed through: (1) the Mixed Oxide (MOX) Fuel Fabrication Facility (FFF), to be constructed at the Savannah River Site (SRS), where the plutonium will be converted to fuel that will be irradiated in civilian power reactors and later disposed to a high-level waste (HLW) repository as spent fuel; (2) the SRS H-Area facilities, by dissolving and transfer to HLW systems, also for disposal to the repository; or (3) alternative immobilization techniques that would provide durable and secure disposal. From the beginning of the U.S. program for surplus plutonium disposition, DOE has sponsored research to characterize the surplus materials and to judge their suitability for planned disposition options. Because many …
Date: July 15, 2008
Creator: Allender, Jeffrey S.; Moore, Edwin N. & Davies, Scott H.
System: The UNT Digital Library
Correlations and Fluctuations: Status and Perspectives (open access)

Correlations and Fluctuations: Status and Perspectives

We will provide an overview of the physics which can be addressed by studying fluctuations and correlations in heavy ion collisions. Observables, which have been discussed in the literature will be briefly reviewed and put in context with experiment and information from Lattice QCD. Special attention will be given to the QCD critical point and the first order co-existence region.
Date: April 15, 2008
Creator: Koch, Volker & Koch, Volker
System: The UNT Digital Library
Test of the consistency of various linearized semiclassical initial value time correlation functions in application to inelastic neutron scattering from liquid para-hydrogen (open access)

Test of the consistency of various linearized semiclassical initial value time correlation functions in application to inelastic neutron scattering from liquid para-hydrogen

The linearized approximation to the semiclassical initial value representation (LSC-IVR) is used to calculate time correlation functions relevant to the incoherent dynamic structure factor for inelastic neutron scattering from liquid para-hydrogen at 14 K. Various time correlations functions were used which, if evaluated exactly, would give identical results, but they do not because the LSC-IVR is approximate. Some of the correlation functions involve only linear operators, and others involve non-linear operators. The consistency of the results obtained with the various time correlation functions thus provides a useful test of the accuracy of the LSC-IVR approximation and its ability to treat correlation functions involving both linear and nonlinear operators in realistic anharmonic systems. The good agreement of the results obtained from different correlation functions, their excellent behavior in the spectral moment tests based on the exact moment constraints, and their semi-quantitative agreement with the inelastic neutron scattering experimental data all suggest that the LSC-IVR is indeed a good short-time approximation for quantum mechanical correlation functions.
Date: March 15, 2008
Creator: Miller, William; Liu, Jian & Miller, William H.
System: The UNT Digital Library
Indoor Thermal Comfort, an Evolutionary Biology Perspective (open access)

Indoor Thermal Comfort, an Evolutionary Biology Perspective

As is becoming increasingly clear, the human species evolvedin the East African savannah. Details of the precise evolutionary chainremain unresolved however it appears that the process lasted severalmillion years, culminating with the emergence of modern Homo sapiensroughly 200,000 years ago. Following that final evolutionary developmentmodern Homo sapiens relatively quickly populated the entire world.Clearly modern Homo sapiens is a successful, resourceful and adaptablespecies. In the developed societies, modern humans live an existence farremoved from our evolutionary ancestors. As we have learned over the lastcentury, this "new" lifestyle can often result in unintendedconsequences. Clearly, our modern access to food, shelter, transportationand healthcare has resulted in greatly expanded expected lifespan butthis new lifestyle can also result in the emergence of different kinds ofdiseases and health problems. The environment in modern buildings haslittle resemblance to the environment of the savannah. We strive tocreate environments with little temperature, air movement and lightvariation. Building occupants often express great dissatisfaction withthese modern created environments and a significant fraction even developsomething akin to allergies to specific buildings (sick buildingsyndrome). Are the indoor environments we are creating fundamentallyunhealthy -- when examined from an evolutionary perspective?
Date: April 15, 2006
Creator: Stoops, John L.
System: The UNT Digital Library
Baryon Triality And Neutrino Masses From An Anomalous FlavorU(1) (open access)

Baryon Triality And Neutrino Masses From An Anomalous FlavorU(1)

We construct a concise U(1){sub X} Froggatt-Nielsen model in which baryon triality, a discrete gauge Z{sub 3}-symmetry, arises from U(1){sub X} breaking. The proton is thus stable, however, R-parity is violated. With the proper choice of U(1){sub X} charges we can obtain neutrino masses and mixings consistent with an explanation of the atmospheric and solar neutrino anomalies in terms of neutrino oscillations, with no right-handed neutrinos required. The only mass scale apart from M{sub grav} is m{sub soft}.
Date: August 15, 2007
Creator: Dreiner, Herbi K.; Luhn, Christoph; Murayama, Hitoshi & Thormeier,Marc
System: The UNT Digital Library
Detection of low energy single ion impacts in micron scaletransistors at room temperature (open access)

Detection of low energy single ion impacts in micron scaletransistors at room temperature

We report the detection of single ion impacts throughmonitoring of changes in the source-drain currents of field effecttransistors (FET) at room temperature. Implant apertures are formed inthe interlayer dielectrics and gate electrodes of planar, micro-scaleFETs by electron beam assisted etching. FET currents increase due to thegeneration of positively charged defects in gate oxides when ions(121Sb12+, 14+, Xe6+; 50 to 70 keV) impinge into channel regions. Implantdamage is repaired by rapid thermal annealing, enabling iterative cyclesof device doping and electrical characterization for development ofsingle atom devices and studies of dopant fluctuationeffects.
Date: October 15, 2007
Creator: Batra, A.; Weis, C. D.; Reijonen, J.; Persaud, A.; Schenkel, T.; Cabrini, S. et al.
System: The UNT Digital Library
Health, Safety, and Environmental Screening and Ranking Frameworkfor Geologic CO2 Storage Site Selection (open access)

Health, Safety, and Environmental Screening and Ranking Frameworkfor Geologic CO2 Storage Site Selection

This report describes a screening and ranking framework(SRF) developed to evaluate potential geologic carbon dioxide (CO2)storage sites on the basis of health, safety, and environmental (HSE)risk arising from possible CO2 leakage. The approach is based on theassumption that HSE risk due to CO2 leakage is dependent on three basiccharacteristics of a geologic CO2 storage site: (1) the potential forprimary containment by the target formation, (2) the potential forsecondary containment if the primary formation leaks, and (3) thepotential for attenuation and dispersion of leaking CO2 if the primaryformation leaks and secondary containment fails. The framework isimplemented in a spreadsheet in which users enter numerical scoresrepresenting expert opinions or general information available frompublished materials along with estimates of uncertainty to evaluate thethree basic characteristics in order to screen and rank candidate sites.Application of the framework to the Rio Vista Gas Field, Ventura OilField, and Mammoth Mountain demonstrates the approach. Refinements andextensions are possible through the use of more detailed data or modelresults in place of property proxies. Revisions and extensions to improvethe approach are anticipated in the near future as it is used and testedby colleagues and collaborators.
Date: March 15, 2006
Creator: Oldenburg, Curtis M.
System: The UNT Digital Library
John Pendry: His Contributions to the Development of LEED Surface Crystallography (open access)

John Pendry: His Contributions to the Development of LEED Surface Crystallography

In this paper we discuss the pivotal role played by Sir John Pendry in the development of Low Energy Electron Diffraction (LEED) during the past three decades; the earliest understanding on the physics of LEED to the development of sophisticated methods for the structural solution of complex surfaces.
Date: October 15, 2007
Creator: Somorjai, Gabor A. & Rous, P. J.
System: The UNT Digital Library
The National Ignition Facility: The world's largest optical system (open access)

The National Ignition Facility: The world's largest optical system

The National Ignition Facility (NIF), a 192-beam fusion laser, is presently under construction at the Lawrence Livermore National Laboratory with an expected completion in 2008. The facility contains 7,456 meter-scale optics for amplification, beam steering, vacuum barriers, focusing, polarization rotation, and wavelength conversion. A multiphase program was put in place to increase the monthly optical manufacturing rate by up to 20x while simultaneously reducing cost by up to 3x through a sub-scale development, full-scale facilitization, and a pilot production phase. Currently 80% of the optics are complete with over 50% installed. In order to manufacture the high quality optics at desired manufacturing rate of over 100 precision optics per month, new more deterministic advanced fabrication technologies had to be employed over those used to manufacture previous fusion lasers.
Date: October 15, 2007
Creator: Stolz, C J
System: The UNT Digital Library
Temperature dependence of the interface moments in Co2MnSi thin films (open access)

Temperature dependence of the interface moments in Co2MnSi thin films

X-ray magnetic circular dichroism (XMCD) is utilized to explore the temperature dependence of the interface moments in Co{sub 2}MnSi (CMS) thin films capped with aluminium. By increasing the thickness of the capping layer we demonstrate enhanced interface sensitivity of the measurements and the existence of a thin Mn oxide layer at the CMS/Al interface even when a thick capping layer is used. We show that for well ordered L2{sub 1} CMS films there is no significant variation in either the Co or Mn interface moments as a function of temperature. However, a dramatic reduction in the interface moments at low temperature is observed in a disordered CMS film that is likely to be caused by increased Mn-Mn antiferromagnetic coupling. It is suggested that for ordered L2{sub 1} CMS films the temperature dependence of the tunneling magnetoresistance is not related to changes in the interface moments. However, the existence of residual Mn oxide at the CMS/barrier interface could be a contributing factor.
Date: March 15, 2008
Creator: Arenholz, Elke; Telling, N.; Keatley, P.; Shelford, L.; Arenholz, E.; van der Laan, G. et al.
System: The UNT Digital Library