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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

The ion-channel laser

Description: A relativistic electron beam propagating through a plasma in the ion-focused regime exhibits an electromagnetic instability at a resonant frequency {omega} {approximately} 2{gamma}{sup 2} {omega}{sub {beta}}. Growth is enhanced by optical guiding in the ion channel, which acts as dielectric waveguide, with fiber parameter V {approximately} 2 (I/I{sub A}){sup 1/2}. A 1-D theory for such an ion-channel laser'' is formulated, scaling laws are derived and numerical examples are given. Possible experimental evidence is noted. 23 refs., 1 fig., 1 tab.
Date: January 1, 1990
Creator: Whittum, D.H.; Sessler, A.M. (Lawrence Berkeley Lab., CA (USA)) & Dawson, J.M. (California Univ., Los Angeles, CA (USA). Dept. of Physics)
Partner: UNT Libraries Government Documents Department

Pion correlations in relativistic heavy ion collisions at Heavy Ion Spectrometer Systems (HISS)

Description: This thesis contains the setup, analysis and results of experiment E684H Multi-Pion Correlations in Relativistic Heavy Ion Collisions''. The goals of the original proposal were: (1) To initiate the use of the HISS facility in the study of central Relativistic Heavy Ion Collisions (RHIC). (2) To perform a second generation experiment for the detailed study of the pion source in RHIC. The first generation experiments, implied by the second goal above, refer to pion correlation studies which the Riverside group had performed at the LBL streamer chamber. The major advantage offered by moving the pion correlation studies to HISS is that, being an electronic detector system, as opposed to the Streamer Chamber which is a visual detector, one can greatly increase the statistics for a study of this sort. An additional advantage is that once one has written the necessary detector and physics analysis code to do a particular type of study, the study may be extended to investigate the systematics, with much less effort and in a relatively short time. This paper discusses the Physics motivation for this experiment, the experimental setup and detectors used, the pion correlation analysis, the results, and the conclusions possible future directions for pion studies at HISS. If one is not interested in all the details of the experiment, I believe that by reading the sections on intensity interferometry, the section the fitting of the correlation function and the systematic corrections applied, and the results section, one will get a fairly complete synopsis of the experiment.
Date: May 1, 1990
Creator: Christie, W.B. Jr.
Partner: UNT Libraries Government Documents Department

Stochastic ion heating by lower hybrid turbulence

Description: The motion of an ion in a spectrum of lower hybrid waves propagating across a constant magnetic field is examined. In particular, numerical simulation is used to determine the extent to which a turbulent spectrum of these electrostatic waves may accelerate thermal ions (T < 1 eV). The significance of stochastic web development in this heating process is also discussed. 20 refs., 31 figs.
Date: May 1, 1990
Creator: Candy, J.
Partner: UNT Libraries Government Documents Department

Prospects for research with radioactive beams and targets

Description: Research with heavy ion (HI) beams has become a major field of physics. Nuclei of all naturally occuring elements and isotopes can be accelerated to energies as high as 2 GeV/A with even higher energies expected in the future. With the advent of relativistic heavy ion accelerators and the development of high intensity on-line isotope separators it has now become possible to explore a new dimension in nuclear physics based on the production and application of radioactive ion beams (RIB). More than 1400 unstable nuclei with half lives of more than 1 ..mu..s are known and could potentially serve as projectiles in RIB experiments. The purpose of this paper is firstly to point out that there are now several promising possibilities to obtain RIB's of acceptable intensity and that secondly a large variety of scientific questions can be addressed should such beams become routinely available. The discussion of the production of RIB's is divided into methods where the radioactive species are stopped and reaccelerated, and methods where the RIB emerges as a secondary beam from a suitable nuclear reation. A third section is devoted to the far reaching experimental possibilities related to accumulator and storage rings. The chapters on research will cover the application of RIB's to the synthesis of exotic nuclei, astrophysics, reaction mechanisms, nuclear structure, atomic- and solid-state physics, bio-medicine, and physics related to the special characteristics of storage rings.
Date: June 1, 1984
Creator: Nitschke, J.M.
Partner: UNT Libraries Government Documents Department

Design philosophy for high-resolution rate and throughput spectroscopy systems

Description: The paper describes the philosophy behind the design of a pulse processing system used in a semiconductor detector x-ray spectrometer to be used for plasma diagnostics at the Princeton TFTR facility. This application presents the unusual problems of very high counting rates and a high-energy neutron background while still requiring excellent resolution. To meet these requirements three specific new advances are included in the design: (i) A symmetrical triangular pulse shape is employed in the main pulse-processing channel. A new simple method of generating a close approximation to the symmetrical triangle has been developed. (ii) To cope with the very wide dynamic range of signals while maintaining a constant fast resolving time, approximately symmetical triangular pulse shaping is also used in the fast pulse pile-up inspection channel. (iii) The demand for high throughput has resulted in a re-examination of the operation of pile-up rejectors and pulse stretchers. As a result a technique has been developed that, for a given total pulse shaping time, permits approximately a 40% increase in throughput in the system. Performance results obtained using the new techniques are presented.
Date: May 1, 1982
Creator: Goulding, F.S.; Landis, D.A. & Madden, N.W.
Partner: UNT Libraries Government Documents Department

High-resolution results from the LBL 55-meter SGM (Spherical Grating Monochromator) at SSRL (Stanford Synchrotron Radiation Laboratory) near the K-edge of carbon and nitrogen

Description: The performance of a 55-meter Spherical Grating Monochromator (SGM) is described. A resolution of 60 MeV has been achieved at 400 eV, inferred from the linewidths of the nitrogen 1s-{pi}* resonance. With 0.5 eV resolution, a photon flux of 4 {times} 10{sup 10} photons/sec has been observed at 440 eV. An initial experiment has studied the core-shell resonances of gas-phase ethylene, C{sub 2}H{sub 4}. Vibrational fine structure was resolved both for the carbon 1s-{pi}* and carbon 1s-Rydberg excitations. Comparison with the vibrational frequencies of ground state ethylene implies that the {nu}{sub 1} (C-H stretch) and {nu}{sub 2} (C-C stretch) or {nu}{sub 3} (H-C-H bend) are excited. It is suggested that the lower Rydberg orbitals, 3s and 3p{sigma}, have molecular, anti-bonding character. 13 refs., 6 figs.
Date: July 1, 1989
Creator: Heimann, P.A.; McKinney, W.; Howells, M.; van Zee, R.D.; Medhurst, L.J.; Lauritzen, T. et al.
Partner: UNT Libraries Government Documents Department

Quantum noise in Josephson junctions and squids

Description: A theory for noise in the resistively shunted Josephson junction in the quantum limit is outlined and extended to the dc SQUID. Experimental results for both the single junction and the SQUID are reported.
Date: April 1, 1981
Creator: Koch, R.H.; Van Harlingen, D.J. & Clarke, J.
Partner: UNT Libraries Government Documents Department

Multiple dissociation of /sup 16/O, /sup 14/N, and /sup 12/C at 32. 5 MeV/nucleon

Description: An array of 34 fast/slow plastic scintillators has been used to identify fragments from the breakup of /sup 16/O, /sup 14/N, and /sup 12/C projectiles at 32.5 MeV/nucleon, scattered by a Au target. The dissociation of /sup 16/O into as many as five charged particles has been observed. The yields of the different channels correlate approximately with the threshold energy for separation of the projectile into the observed fragments. The excitation spectrum of the primary projectile fragment was deduced from the measured positions and kinetic energies of the individual fragments. These spectra show that, although most of the decomposition proceeds through excitation energies within /approximately/20 MeV of the lower particle-decay thresholds, excitation energies extending up to /approximately/80 MeV can be produced in the primary stage of the reaction. This represents a significant acquisition of energy by the projectile. Calculations of the yields based on a sequence of binary decays have been presented. Reactions in which one or two units of charge are acquired by the projectile were also observed. 25 refs., 10 figs.
Date: September 1, 1988
Creator: Stokstad, R.G.; Chan, Y.D.; Dacal, A.; DiGregorio, D.E.; Harmon, B.A.; Knop, R. et al.
Partner: UNT Libraries Government Documents Department

First in-beam. gamma. -ray study of sup 67 As

Description: Excited states of the neutron-deficient nucleus {sup 67}As were populated using the {sup 40}Ca({sup 32}S,{alpha}p){sup 67}As and the {sup 40}Ca({sup 33}S,{alpha}pn){sup 67}As reactions at bombarding energies between 95 and 110 MeV. We present a tentative level scheme for {sup 67}As, derived from {gamma}-{gamma} coincidence studies in conjunction with measurement of evaporated charged particles and neutrons.
Date: January 1, 1990
Creator: Lang, T.F.; Moltz, D.M.; Reiff, J.E.; Batchelder, J.C.; Ognibene, T.J.; Cerny, J. et al.
Partner: UNT Libraries Government Documents Department

First-order kinetics-controlled multiple species reactive transport of dissolved organic compounds in groundwater: Development and application of a numerical model

Description: Reactive chemical transport models developed over the past decade have generally relied on the assumption that local thermodynamic equilibrium is achieved at all times between aqueous species in a given system. Consequently, homogeneous aqueous systems characterized by a number of kinetically slow reactions, particularly problems involving organic species, cannot be satisfactorily modeled. In this study, we present a prototype computer model, KINETRAN, which is designed to handle kinetically-controlled homogeneous reactions in the aqueous phase, along with the transport of the various species involved, through geologic media. 31 refs., 53 figs., 10 tabs.
Date: May 1, 1990
Creator: McNab, W.W. Jr.
Partner: UNT Libraries Government Documents Department

PEP liquid level system

Description: A liquid level system has been installed in the accelerator housing of the PEP storage ring. This instrument spans the entire 2.2 km circumference of the PEP project, and over one hundred readouts provide reference elevations which are used for the accurate alignment of accelerator components. The liquid level has proven to be extremely precise (+-0.10 mm) and quick to use, and it has contributed to the accurate alignment of PEP before beam turn-on. Since the liquid level readouts are rigidly attached to the accelerator housing, the liquid level has been a convenient means to monitor the settling of the accelerator housing.
Date: March 1, 1981
Creator: Lauritzen, T. & Sah, R.C.
Partner: UNT Libraries Government Documents Department

Multiple beam induction linac research at LBL

Description: We present results of progress on the LBL multiple beam induction linac experiment (MBE-4). This machine models the accelerator physics of the electric-focused portion of a driver for heavy ion inertial confinement fusion. Four beams of cesium ions are accelerated in common through twenty four induction gaps while being separately focused in individual electrostatic AG focusing channels. Early experiments have demonstrated current amplification in the linac, from 10 mA to 90 mA per beam. This is achieved both by acceleration (from 200 keV to 1 MeV) and by carefully controlled bunch compression. Recent experiments have concentrated on studies of beams extracted from an ion source which produces 5 mA cesium beams at emittances near 0.03 {pi} mm-mrad (normalized). Experiments and theory show a growth of emittance (by about a factor of 2) as these beams are accelerated through the linac. Results of recent measurements of the transverse emittance behavior of these strongly space-charge-dominated ion beams are reviewed and compared with theory. 9 refs., 3 figs.
Date: June 1, 1990
Creator: Garvey, T.; Eylon, S.; Fessenden, T.J.; Hahn, K.; Henestroza, E. & Keefe, D.
Partner: UNT Libraries Government Documents Department