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Applications of X-ray absorption spectroscopy and low temperature XMCD to metalloproteins

Description: The author has used the extended X-ray absorption fine structure (EXAFS) and ultra-low temperature X-ray magnetic circular dichroism (XMCD) to study the environments of the metal sites in metalloproteins. EXAFS has been used to study the Zn site in spinach carbonic anhydrase. The EXAFS, in parallel with site directed mutagenesis studies, indicate that the active site Zn is in a cys-cys-his-H{sub 2}O environment, very different from the mammalian carbonic anhydrase active site. Nitrogenase, the primary enzyme in biological nitrogen fixation, contains two complex metal clusters of unique structure. EXAFS studies at the Fe and Mo K-edges of nitrogenase solutions and crystals yielded information about the various metal-metal distances in these two clusters. The author assigned 4 Fe and 3 Mo interactions >4 {angstrom}. Single crystal Mo K-edge EXAFS then found a very long Fe-Fe distance of {approximately}5.1 {angstrom}. These distances were then used to further refine the proposed crystallographic models to their highest accuracy yet. Studies were carried further by examining nitrogenas in oxidized and reduced forms--states for which there is no crystallographic information. Small structural changes were observed and an EXAFS model was put forth that attempts to deconvolute the EXAFS distances of the two metal clusters. Nitrogenase Apo I, a genetic mutant of nitrogenase which is though to contain only one of the two different metal clusters, was also examined using EXAFS. These studies showed results consistent with current models, yet the metal clusters were very disordered. Finally, ultra-low temperature methods were used to further the development of XMCD as a technique for studying biological systems. Experiments were performed on the copper in plastocyanin. Data was collected that definitively proves that the sample surface was at 0.55 {+-} 0.05 K. This result opens the door to further study of more complex biological metal clusters.
Date: January 1996
Creator: Christiansen, J. H.
Partner: UNT Libraries Government Documents Department

You Won`t Find These Leaks with a Blower Door: The Latest in "Leaking Electricity" in Homes

Description: Leaking electricity is the energy consumed by appliances when they are switched off or not performing their principal functions. Field measurements in Florida, California, and Japan show that leaking electricity represents 50 to 100 Watts in typical homes, corresponding to about 5 GW of total electricity demand in the United States. There are three strategies to reduce leaking electricity: eliminate leakage entirely, eliminate constant leakage and replace with intermittent charge plus storage, and improve efficiency of conversion. These options are constrained by the low value of energy savings-less than $5 per saved Watt. Some technical and lifestyle solutions are proposed. 13 refs., 1 fig., 2 tabs.
Date: August 1996
Creator: Rainer, L.; Greenberg, S. & Meier, A.
Partner: UNT Libraries Government Documents Department

Guidelines for sustainable building design: Recommendations from the Presidio of San Francisco energy efficiency design charrette

Description: In 1994, the Bay Chapter of the Association of Energy Engineers{reg_sign} organized a two-day design charrette for energy-efficient redevelopment of buildings by the National Park Services (NPS) at the Presidio of San Francisco. This event brought together engineers, researchers, architects, government officials, and students in a participatory environment to apply their experience to create guidelines for the sustainable redesign of Presidio buildings. The venue for the charrette was a representative barracks building located at the Main Post of the Presidio. Examination of this building allowed for the development of design recommendations, both for the building and for the remainder of the facilities. The charrette was organized into a committee structure consisting of: steering, measurement and monitoring, modeling, building envelope and historic preservation (architectural), HVAC and controls, lighting, and presentation. Prior to the charrette itself, the modeling and measurement/monitoring committees developed substantial baseline data for the other committees during the charrette. An integrated design approach was initiated through interaction between the committees during the charrette. Later, committee reports were cross-referenced to emphasize whole building design and systems integration.
Date: May 1996
Creator: Brown, K.; Sartor, D. & Greenberg, S.
Partner: UNT Libraries Government Documents Department

Energy effectiveness of duct sealing and insulation in two multifamily buildings

Description: Energy losses from forced air distribution systems have a significant impact on the energy efficiency of buildings. Little work has been done to quantify these losses in apartment buildings. In this paper the authors will discuss field measurements made on four forced air heating systems to evaluate the duct system energy losses to unconditioned basements. The apartments were heated by natural gas furnaces located in the basements. The systems had bare sheet metal ductwork exposed to the basement conditions. The pre-retrofit measurements were made on the systems after sealing large easily visible leaks. The post-retrofit measurements were made after wrapping the ducts in foil backed glass fiber insulation and additional leak sealing. Only the sections of duct exposed to the basement were retrofitted because only these sections were accessible. This study examines the potential energy savings for this type of limited retrofit. The energy losses were separated into leakage and conduction terms. Leakage measurements were made using register flowhood techniques. Conduction losses were estimated by measuring temperatures in the plenums and at the registers. Analysis of the measurements has shown typical reduction in leakage flow due to duct sealing of about 40%. The reduction in leakage translated into a reduction in energy consumption of about 10%.
Date: August 1996
Creator: Walker, I. S.; Modera, M. P.; Tuluca, A. & Graham, I.
Partner: UNT Libraries Government Documents Department

Decision making through use of interoperable simulation software

Description: Many building simulation computer programs, originally developed on mainframe computers for research purposes, can now run on the powerful workstation and personal computers that are available to most architectural and engineering firms. Major efforts have been underway during the last decade to compile these programs on personal computers and make them available to a wider range of building professionals. However, even with the addition of user-friendly front- and back-ends, their use is still limited to a small number of specialized consultants. Considering the tremendous benefits of informed decisions that these programs can support, it is critical to address and resolve the issues that are associated with their limited acceptance. In this paper, the authors report on their research and development efforts to better understand decision-making and develop computer tools that will facilitate the use of simulation software during the building design process. They present a brief analysis of decision-making and then describe how they try to address it in building design through the development of the Building Design Advisor (BDA). Moreover, the authors elaborate on the major issues that they have encountered, discuss lessons learned, and offer recommendations for short- and long-term developments in this area.
Date: March 1997
Creator: Papamichael, K.; La Porta, J. & Chauvet, H.
Partner: UNT Libraries Government Documents Department

Bipolar pulsed reset for AC coupled charge-sensitive preamplifiers

Description: A new type of charge restoration is described for use particularly in germanium gamma-ray spectrometers for accelerator and space physics applications. A bipolar pulsed reset technique is applied to these applications for the first time. This technique overcomes the problems introduced by the need to AC couple detectors and the fact that very large energy depositions occur due to charged particles present in substantial fluxes, particularly in space. The circuit is described and experimental results are presented and discussed.
Date: July 1, 1997
Creator: Landis, D. A.; Madden, N. M. & Goulding, F. S.
Partner: UNT Libraries Government Documents Department

Electrochromic lithium nickel oxide thin film by pulsed laser deposition

Description: * Thin films of lithium nickel oxide were deposited by pulsed laser deposition (PLD) from targets of pressed LiNiO{sub 2} powder with layered structure. The composition, structure and surface air sensitivity of these films were analyzed using a variety of techniques, such as nuclear reaction analysis, Rutherford backscattering spectrometry (RBS), x-ray diffraction, infrared spectroscopy, and atomic force microscopy. Optical properties were measured using a combination of variable angle spectroscopic ellipsometry and IP spectroradiometry. Crystalline structure, surface morphology and chemical composition of Li{sub x}Ni{sub 1-x}O thin films depend strongly on deposition oxygen pressure, temperature as well as substrate target distance. The films produced at temperatures lower than 600 degrees C spontaneously absorb CO{sub 2} and H{sub 2}O at their surface once they are exposed to the air. The films deposited at 600 degrees C proved to be stable in air over a long period. Even when deposited at room temperature the PLD films are denser and more stable than sputtered films. RBS determined that the best electrochromic films had the stoichiometric composition L{sub 0.5}Ni{sub 0.5}O when deposited at 60 mTorr O{sub 2} pressure. Electrochemical tests show that the films exhibit excellent reversibility in the range 1.0 V to 3.4 V versus lithium and long cyclic life stability in a liquid electrolyte half cell. Electrochemical formatting which is used to develop electrochromism in other films and nickel oxide films is not needed for these stoichiometric films. The optical transmission range is almost 70% at 550 nm for 120 nm thick films.
Date: October 1996
Creator: Wen, S. J.; von Rottkay, K. & Rubin, M.
Partner: UNT Libraries Government Documents Department

Solar heat gain coefficient of complex fenestrations with a venetian blind for differing slat tilt angles

Description: Measured bidirectional transmittances and reflectances of a buff-colored venetian blind together with a layer calculation scheme developed in previous publications are utilized to produce directional-hemispherical properties for the venetian blind layer and solar heat gain coefficients for the blind in combination with clear double glazing. Results are presented for three blind slat tilt angles and for the blind mounted either interior to the double glazing or between the glass panes. Implications of the results for solar heat gain calculations are discussed in the context of sun positions for St. Louis, MO.
Date: August 1996
Creator: Klems, J. H. & Warner, J. L.
Partner: UNT Libraries Government Documents Department

A comparison between calculated and measured SHGC for complex fenestration systems

Description: Calorimetric measurements of dynamic net heat flow through a complex fenestration system consisting of a buff venetian blind inside clear double glazing are used to derive the direction-dependent beam SHGC (solar heat gain coefficient) of the fenestration. The data are compared with calculations according to a proposed general method for deriving complex fenestration system SHGC`s from bidirectional layer optical properties and generic calorimetric properties. Previously published optical data for the same venetian blind and generic inward-flowing fraction measurements are used in the calculation. Satisfactory agreement is found between SHGC measurements and calculation. Significant dependence on incident angle was found in the measured SHGC`s. Profile angle was not found to be a useful variable in characterizing the system performance. Predicted SHGC was found to be inherently dependent on two angles, although only the incident angle variations were observable under test conditions.
Date: September 1995
Creator: Klems, J. H.; Warner, J. L. & Kelley, G. O.
Partner: UNT Libraries Government Documents Department

A field test of permeation grouting in heterogeneous soils using a new generation of barrier liquids

Description: A field demonstration of permeation grouting was conducted at a gravel quarry near Los Banos, California, with the purpose of demonstrating the feasibility of the concept. Two grouts were used: a form of colloidal silica that gels after the addition of a gelling agent, and a polysiloxane that polymerizes after the addition of a catalyst. Both create relatively impermeable barriers in response to the large increase in viscosity during gelation or polymerization, respectively. The grouts were successfully injected at a depth between 10 and 14ft. Subsequent exhumation of the injected gravels revealed that both grouts produced relatively uniform bulbs. Laboratory measurements of the grouted material retrieved from the field showed at least a four order of magnitude reduction in permeability over the ungrouted material.
Date: August 1995
Creator: Moridis, G. J.; Persoff, P.; Apps, J. A.; Myer, L.; Pruess, K. & Yen, P.
Partner: UNT Libraries Government Documents Department

The {alpha}-induced thick-target {gamma}-ray yield from light elements

Description: The {alpha}-induced thick-target {gamma}-ray yield from light elements has been measured in the energy range 5.6 MeV {le} E{sub {alpha}} {le} 10 MeV. The {gamma}-ray yield for > 2.1 MeV from thick targets of beryllium, boron nitride, sodium fluoride, magnesium, aluminum and silicon were measured using the {alpha}-particle beam from the Lawrence Berkeley Laboratories 88 in. cyclotron. The elemental yields from this experiment were used to construct the {alpha}-induced direct production {gamma}-ray spectrum from materials in the SNO detector, a large volume ultra-low background neutrino detector located in the Creighton mine near Sudbury, Canada. This background source was an order of magnitude lower than predicted by previous calculations. These measurements are in good agreement with theoretical calculations of this spectrum based on a statistical nuclear model of the reaction, with the gross high energy spectrum structure being reproduced to within a factor of two. Detailed comparison of experimental and theoretical excitation population distribution of several residual nuclei indicate the same level of agreement within experimental uncertainties.
Date: October 1994
Creator: Heaton, R. K.
Partner: UNT Libraries Government Documents Department

Some new approaches to semiclassical and quantum transition state theory

Description: Semiclassical and quantum mechanical transition state theory is reviewed and two new approaches described. One is general implementation of a semiclassical rate expression that involves the good'' action-angle variables associated with the saddle point (i.e., transition state) of a potential energy surface. The other is an evaluation of a formally exact quantum expression for the rate in terms of Siegert eigenvalues associated with the transition state. Siegert eigenvalues are usually associated with scattering resonances, so their identification with the saddle point of a potential surface, and the expression for the reaction rate in terms of them, is quite an unexpected and novel development. 14 refs.
Date: October 1, 1990
Creator: Miller, W.H.
Partner: UNT Libraries Government Documents Department

Strangeness production in nucleus-nucleus collisions: An experimental review

Description: In experiments with oxygen (60 and 200 GeV/N) and sulphur (200 GeV/N) ions at CERNSPS, large energy densities of the order of 2--3 GeV/fm{sub 3} have been observed, which according to QCD calculations, satisfy necessary conditions for the formation of a quark gluon plasma (QGP) phase. Under such conditions, colour would no longer be confined to hadronic dimensions, and quarks and gluons will propagate freely throughout an extended volume. Somehow lower energy densities, of the order of 0.7--1 GeV/fm{sub 3}, were observed in AGS experiments with 15 GeV/N silicon beams and heavy targets. These energy densities might be adequate for investigations of the pre-equilibrium stage, during which the momentum space distribution has been degradated from its initial value but is not yet thermal. First experimental results, available now, show promise of seeing signs of a new phase of matter. In this review the current status of the selective experimental results on strange-particle production, which are relevant to equilibration and QGP formation in nucleus-nucleus collisions, is presented.
Date: December 1, 1990
Creator: Odyniec, G.
Partner: UNT Libraries Government Documents Department

Experience with the EM-60 electromagnetic system for geothermal exploration in Nevada

Description: Lawrence Berkeley Laboratory (LBL) conducted controlled-source electromagnetic (EM) surveys at three geothermal prospects in northern Nevada. Over 40 soundings were made in Panther Canyon (Grass Valley), near Winnemucca; Soda Lakes, near Fallon; and McCoy, west of Austin, to test and demonstrate the applicability of LBL's EM-60 system to geothermal exploration. The EM-60 is a frequency-domain system using three-component magnetic detection. Typically, +-65 A is applied to an 100-m-diameter four-turn horizontal loop, generating a dipole moment >10/sup 6/ MKS over the frequency range 10/sup -3/ to 10/sup -3/ Hz. With such a source loop, soundings were made, at transmitter-receiver separations of up to 4 km, providing a maximum depth of penetration of 4 km.
Date: September 1, 1981
Creator: Wilt, M.; Goldstein, N.E.; Stark, M.; Haught, J.R. & Morrison, H.F.
Partner: UNT Libraries Government Documents Department

Excitation functions and isomer ratio measurements for the reaction /sup 41/K(/sup 6/Li,p2n)/sup 44/Sc/sup m/,/sup 44/Sc/sup q/. [14. 4, 23. 4, 32. 0, and 41. 5 MeV]

Description: For the purpose of eventually determining how population distributions of /sup 44/Sc* in the E-J plane affect resulting isomer ratios in /sup 44/Sc, excitation functions and isomer ratios in the reaction /sup 41/K(/sup 6/Li,p2n)/sup 44/Sc/sup m/,/sup 44/Sc/sup q/ were measured. Preliminary results seem to indicate, as expected, a very weak compound nucleus reaction component of the reaction cross section.
Date: October 1, 1981
Creator: Nguyen, H.D.; Trinh, H.N.; Le, H.D.; Moody, K.J.; Groening, H. & Seaborg, G.T.
Partner: UNT Libraries Government Documents Department

Experience with measuring magnetic moments of permanent magnet blocks at Lawrence Berkeley Laboratory

Description: Since May 1985, The Magnetic Measurements Engineering Group at LBL has measured and sorted a total of 3834 permanent magnet blocks. These magnetic blocks have been used in the construction of various successful beam-line elements including dipoles, quadrupoles, and wigglers. We report on observed variations in magnetic moments among blocks supplied by five manufacturers, describe the operational capabilities (accuracy, precision, and resolution) of the LBL Magnetic-moment Measurement and Sorting System (MMSS), cite the results of comparative calibrations by permanent-magnet manufacturers and other National Laboratories, and suggest criteria for automating the MMSS for measuring the large number of permanent-magnet blocks required for the insertion devices for the projected LBL 1-2 GeV Synchrotron Radiation Source. 14 refs., 2 figs., 2 tabs.
Date: September 1, 1987
Creator: Nelson, D.H.; Barale, P.J.; Green, M.I. & Van Dyke, D.A.
Partner: UNT Libraries Government Documents Department

Exact Monte Carlo for molecules

Description: A brief summary of the fixed-node quantum Monte Carlo method is presented. Results obtained for binding energies, the classical barrier height for H + H2, and the singlet-triplet splitting in methylene are presented and discussed. 17 refs.
Date: March 1, 1985
Creator: Lester, W.A. Jr. & Reynolds, P.J.
Partner: UNT Libraries Government Documents Department

Excitation cross sections of hydrogen relevant to neutral-beam diagnostics

Description: Data were measured for the excitation of H atom projectiles, dissociation of H/sub 2//sup +/ and H/sub 3//sup +/ projectiles into the 3p or 3d states of the H atom, and the collisional destruction cross section for the n = 3 levels in the energy range between 40 and 120 keV.
Date: September 1, 1981
Creator: Bae, Y.K.; Burrell, C.F. & MacFarland, R.H.
Partner: UNT Libraries Government Documents Department

Excitation and multiple dissociation of projectiles at intermediate energy

Description: Cross sections for the multiple breakup of /sup 16/O, /sup 14/N and /sup 12/C projectiles scattered by a Au target were measured with an array of 34 phoswich detectors. The dissociation of the projectiles into as many as five charged particles has been observed. The yields of different exit channels correlate approximately with the threshold energy for separation of the projectile into the observed fragments. The excitation spectrum of the primary projectile-like nucleus was reconstructed from the measured positions and kinetic energies of the individual fragments. The energy sharing between projectile and target is consistent with a fast excitation mechanism in which differential increases in projectile excitation energy appear to be accompanied by comparable increases in target excitation. Calculations of the yields based on a sequence of binary decays are presented. The question of prompt or sequential decay is also considered by examining the directional correlations of the particles. 19 refs., 8 figs.
Date: April 1, 1989
Creator: Pouliot, J.; Chan, Y.; Dacal, A.; DiGregorio, D.E.; Harmon, B.A.; Knop, R. et al.
Partner: UNT Libraries Government Documents Department

Fabrication and measurement of high T sub c superconducting microbolometers

Description: We have fabricated and measured the performance of antenna-coupled microbolometers based on the resistive transition of a high {Tc} superconducting film for use as detectors of far-infrared and millimeter waves. A planar lithographed antenna (log-periodic or log-spiral) is used to couple the radiation to a thin YBCO film with dimensions ({approx}6 {times} 13 {mu}m{sup 2}) which are smaller than the wavelength to be measured. This film acts both as the resistor to thermalize the rf currents and as a transition edge thermometer to measure the resulting temperature rise. Because of its small size, both the thermal conductance from the film into the bulk of the substrate and the heat capacity of the thermally active region are small. Consequently, the microbolometer has low noise, fast response and a high voltage responsivity. We have measured a phonon limited electrical NEP of 4.5 {times} 10{sup {minus}12} WHz{sup {minus}{1/2}} at 10 kHz modulation frequency and a responsivity of 478 V/W at a bias of 550 {mu}A. Measurements of the optical efficiency are in progress and will be discussed. 12 refs., 6 figs.
Date: September 1, 1990
Creator: Nahum, M.; Hu, Qing; Richards, P.L. (Lawrence Berkeley Lab., CA (USA)); Sachtjen, S.A.; Newman, N. & Cole, B.F. (Conductus, Inc., Sunnyvale, CA (USA))
Partner: UNT Libraries Government Documents Department

Very hot nuclear systems and their binary and multifragment decay

Description: Compound emission of complex fragments in the reaction {sup 63}Cu + {sup 12}C is used to determine the associated ridge-line potential. Compound binary emission of complex fragments at higher energies is illustrated for a variety of reactions. Complex fragment emission from 18, 26, 31, 35, 45 and 55 MeV/N {sup 139}La/{sup 129}Xe + {sup 12}C, {sup 27}Al, {sup 40}Ca, {sup 51}V, {sup nat}Cu and {sup 139}La reactions has been studied. Multifragment events from these reactions were assigned to sources characterized by their energy and mass through the incomplete-fusion-model kinematics. Excitation functions for the various multifragment channels appear to be nearly independent of the system and bombarding energy. Preliminary comparisons of the data with sequential-statistical-decay calculations are discussed. 16 refs., 9 figs.
Date: October 1, 1990
Creator: Moretto, L.G.; Blumenfeld, Y.; Delis, D. & Wozniak, G.J.
Partner: UNT Libraries Government Documents Department

Research opportunities at the advanced light source

Description: The Advanced Light Source (ALS), now under construction at the Lawrence Berkeley Laboratory, is a third-generation synchrotron radiation facility based on a low-emittance, 1.5-GeV electron storage ring with 10 long straight sections available for insertion devices and, initially, 24 bend-magnet ports. Undulators will provide high-brightness radiation at photon energies from below 10 eV to above 2 keV; wiggler and bend-magnet radiation will extend the spectral coverage with high fluxes to above 10 keV. Scheduled to begin operations as a US Department of Energy national user facility in the spring of 1993, the ALS will support an extensive research program in which soft x-ray and ultraviolet radiation is used to study matter in all its varied gaseous, liquid, and solid forms. Participating research teams to implement the initial scientific program have been selected. 13 refs., 3 figs., 2 tabs.
Date: September 26, 1990
Creator: Robinson, A.L. & Schlachter, A.S.
Partner: UNT Libraries Government Documents Department

Hydrogenated amorphous silicon radiation detectors: Material parameters, radiation hardness, charge collection

Description: For nearly two decades now hydrogenated amorphous silicon has generated considerable interest for its potential use in various device applications namely, solar cells, electrolithography, large-area electronics etc. The development of efficient and economic solar cells has been on the forefront of this research. This interest in hydrogenated amorphous silicon has been motivated by the fact that amorphous silicon can be deposited over a large area at relatively low cost compared to crystalline silicon. Hydrogenated amorphous silicon, frequently abbreviated as a-Si:H, used in solar-cell applications is a micron or less thick. The basic device structure is a p-i-n diode where the i layer is the active layer for radiation to interact. This is so because intrinsic a-Si:H has superior electrical properties in comparison to doped a-Si:H which serves the purpose of forming a potential barrier on either end of the i layer. The research presented in this dissertation was undertaken to study the properties of a-Si:H for radiation detection applications in physics and medicine.
Date: January 1, 1991
Creator: Qureshi, S.
Partner: UNT Libraries Government Documents Department