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Modeling pollutant penetration across building envelopes

Description: As air infiltrates through unintentional openings in building envelopes, pollutants may interact with adjacent surfaces. Such interactions can alter human exposure to air pollutants of outdoor origin. We present modeling explorations of the proportion of particles and reactive gases (e.g., ozone) that penetrate building envelopes as air enters through cracks and wall cavities. Calculations were performed for idealized rectangular cracks, assuming regular geometry, smooth inner crack surface and steady airflow. Particles of 0.1-1.0 {micro}m diameter are predicted to have the highest penetration efficiency, nearly unity for crack heights of 0.25 mm or larger, assuming a pressure difference of 4 Pa or greater and a flow path length of 3 cm or less. Supermicron and ultrafine particles are significantly removed by means of gravitational settling and Brownian diffusion, respectively. In addition to crack geometry, ozone penetration depends on its reactivity with crack surfaces, as parameterized by the reaction probability. For reaction probabilities less than {approx}10{sup -5}, penetration is complete for cracks heights greater than 1 mm. However, penetration through mm scale cracks is small if the reaction probability is {approx}10{sup -4} or greater. For wall cavities, fiberglass insulation is an efficient particle filter, but particles would penetrate efficiently through uninsulated wall cavities or through insulated cavities with significant airflow bypass. The ozone reaction probability on fiberglass fibers was measured to be 10{sup -7} for fibers previously exposed to high ozone levels and 6 x 10{sup -6} for unexposed fibers. Over this range, ozone penetration through fiberglass insulation would vary from >90% to {approx}10-40%. Thus, under many conditions penetration is high; however, there are realistic circumstances in which building envelopes can provide substantial pollutant removal. Not enough is yet known about the detailed nature of pollutant penetration leakage paths to reliably predict infiltration into real buildings.
Date: April 1, 2001
Creator: Liu, De-Ling & Nazaroff, William W.
Partner: UNT Libraries Government Documents Department

Benefits of microscopy with super resolution

Description: Transmission Electron Microscopy developed from an imagingtool into a quantitative electron beam characterization tool that locallyaccesses structure, chemistry, and bonding in materials with sub Angstromresolution. Experiments utilize coherently and incoherently scatteredelectrons. In this contribution, the interface between gallium nitrideand sapphire as well as thin silicon gate oxides are studied tounderstand underlying physical processes and the strength of thedifferent microscopy techniques. An investigation of the GaN/sapphireinterface benefits largely from the application of phase contrastmicroscopy that makes it possible to visualize dislocation corestructures and single columns of oxygen and nitrogen at a closest spacingof 85 pm. In contrast, it is adequate to investigate Si/SiOxNy/poly-Siinterfaces with incoherently scattered electrons and electronspectroscopy because amorphous and poly crystalline materials areinvolved. Here, it is demonstrated that the SiOxNy/poly-Si interface isrougher than the Si/SiOx interface, that desirable nitrogen diffusiongradients can be introduced into the gate oxide, and that a nitridationcoupled with annealing increases its physical width while reducing theequivalent electrical oxide thickness to values approaching 1.2 nm.Therefore, an amorphous SiNxOy gate dielectric seems to be a suitablesubstitute for traditional gate oxides to further increase device speedby reducing dimensions in Si technology.
Date: July 9, 2001
Creator: Kisielowski, C.; Principe, E.; Freitag, B. & Hubert, D.
Partner: UNT Libraries Government Documents Department

Experiments and evaluation of chaotic behavior of dripping waterin fracture models

Description: Laboratory experiments of water seepage in smooth and rough-walled, inclined fracture models were performed and the monitoring data analyzed for evidence of chaos. One fracture model consisted of smooth, parallel glass plates separated by 0.36 mm. The second model was made with textured glass plates. The fracture model was inclined 60{sup o} from the horizontal. Water was delivered to the fracture model through a capillary tube in contact with the top fracture edge at constant flow rates. Three types of capillary tubes were used: (1) a stainless steel blunt needle of 0.18 mm ID for flow rates of 0.25 to 4 mL/hr, (2) a nylon tube of 0.8 mm ID for flow rates of 0.25 to 10 mL/hr, and (3) a glass tube of 0.75 mm ID for flow rates of 0.5 to 20 mL/hr. Liquid pressure was monitored upstream of the capillary tube. Visual observations showed that water seeped through the fracture models in discrete channels that underwent cycles of snapping and reforming. Observations also showed that liquid segments, or drips, detached at different points along the water channel. The measured liquid pressure responded to the growth and detachment of drips. Separate experiments were carried out to measure pressure time-trends for dripping into open air to compare these data with those obtained in fracture models. Analysis of the pressure time-trends included determination of the time lag from the minimum of the average mutual information function, the local and global embedding dimensions, Lyapunov exponents and the Lyapunov dimension, the Hurst exponent and the entropy as a function of the embedding dimension for each data set. Most of the water pressure data contain oscillations exhibiting chaotic behavior, with local embedding dimensions ranging from 3 to 10, and global embedding dimensions one to two units higher. The higher dimensionality of some of ...
Date: June 1, 2001
Creator: Geller, Jil T.; Borglin, Sharon E. & Faybishenko, Boris A.
Partner: UNT Libraries Government Documents Department

Effects of buoyancy on the flowfields of lean premixed turbulentv-flames

Description: Open laboratory turbulent flames used for investigating fundament flame turbulence interactions are greatly affected by buoyancy. Though much of our current knowledge is based on observations made in these open flames, the effects of buoyancy are usually not included in data interpretation, numerical analysis or theories. This inconsistency remains an obstacle to merging experimental observations and theoretical predictions. To better understanding the effects of buoyancy, our research focuses on steady lean premixed flames propagating in fully developed turbulence. We hypothesize that the most significant role of buoyancy forces on these flames is to influence their flowfields through a coupling with mean and fluctuating pressure fields. Changes in flow pattern alter the mean aerodynamic stretch and in turn affect turbulence fluctuation intensities both upstream and downstream of the flame zone. Consequently, flame stabilization, reaction rates, and turbulent flame processes are all affected. This coupling relates to the elliptical problem that emphasizes the importance of the upstream, wall and downstream boundary conditions in determining all aspects of flame propagation. Therefore, buoyancy has the same significance as other parameters such as flow configuration, flame geometry, means of flame stabilization, flame shape, enclosure size, mixture conditions, and flow conditions.
Date: March 1, 2001
Creator: Cheng, R.K.; Bedat, B.; Yegian, D.T. & Greenberg, P.
Partner: UNT Libraries Government Documents Department

Characteristics of laser-driven electron acceleration invacuum

Description: The interaction of free electrons with intense laser beamsin vacuum is studied using a 3D test particle simulation model thatsolves the relativistic Newton-Lorentz equations of motion inanalytically specified laser fields. Recently, a group of solutions wasfound for very intense laser fields that show interesting and unusualcharacteristics. In particular, it was found that an electron can becaptured within the high-intensity laser region, rather than expelledfrom it, and the captured electron can be accelerated to GeV energieswith acceleration gradients on the order of tens of GeV/cm. Thisphenomenon is termed the capture and acceleration scenario (CAS) and isstudied in detail in this paper. The maximum net energy exchange by theCAS mechanism is found to be approximately proportional to a 2_o, in theregime where a_o>100, where a_o = eE_o/m_ewc is a dimensionlessparameter specifying the magnitude of the laser field. The acceleratedGeV electron bunch is a macro-pulse, with duration equal or less thanthat of the laser pulse, which is composed of many micro-pulses that areperiodic at the laser frequency. The energy spectrum of the CAS electronbunch is presented. The dependence of the energy exchange in the CAS onvarious parameters, e.g., a 2_o (laser intensity), w_o (laser radius atfocus), tao (laser pulse duration), b_o (the impact parameter), andtheta_i (the injection angle with respect to the laser propagationdirection), are explored in detail. A comparison with diverse theoreticalmodels is also presented, including a classical model based on phasevelocities and a quantum model based on nonlinear Comptonscattering.
Date: November 1, 2001
Creator: Wang, P.X.; Ho, Y.K.; Yuan, X.Q.; Kong, Q.; Sessler, A.M.; Esarey, E. et al.
Partner: UNT Libraries Government Documents Department

The farthest known supernova: Support for an accelerating universeand a glimpse of the epoch of deceleration

Description: We present photometric observations of an apparent Type Iasupernova (SN Ia) at a redshift of approximately 1.7, the farthest SNobserved to date. The supernova, SN 1997, was discovered in a repeatobservation by the Hubble Space Telescope (HST) of the Hubble DeepField{North (HDF-N), and serendipitously monitored with NICMOS on HSTthroughout the Thompson et al. GTO campaign. The SN type can bedetermined from the host galaxy type: an evolved, red elliptical lackingenough recent star formation to provide a significant population ofcore-collapse supernovae. The classification is further supported bydiagnostics available from the observed colors and temporal behavior ofthe SN, both of which match a typical SN Ia. The photometric record ofthe SN includes a dozen flux measurements in the I, J, and H bandsspanning 35 days in the observed frame. The redshift derived from the SNphotometry, z = 1:7 plus or minus 0:1, is in excellent agreement with theredshift estimate of z = 1:65 plus or minus 0:15 derived from the U_300B_450 V_-606 I_814 J_110 J_125 H_160 H_165 K_s photometry of the galaxy.Optical and near-infrared spectra of the host provide a very tentativespectroscopic redshift of 1.755. Fits to observations of the SN provideconstraints for the redshift-distance relation of SNe Ia and a powerfultest of the current accelerating Universe hypothesis. The apparent SNbrightness is consistent with that expected in the decelerating phase ofthe preferred cosmological model, Omega_M approximately equal to 1/3;Omega_Lambda approximately equal to 2/3. It is inconsistent with greydust or simple luminosity evolution, candidate astrophysical effectswhich could mimic previous evidence for an accelerating Universe from SNeIa at z approximately equal to 0:5. We consider several sources ofpotential systematic error including gravitational lensing, supernovamisclassification, sample selection bias, and luminosity calibrationerrors. Currently, none of these effects alone appears likely tochallenge our conclusions. Additional SNe Ia at z>1 will be requiredto test more exotic alternatives to ...
Date: April 1, 2001
Creator: Riess, Adam G.; Nugent, Peter E.; Schmidt, Brian P.; Tonry, John; Dickinson, Mark; Gilliland, Ronald L. et al.
Partner: UNT Libraries Government Documents Department

In/Si(111): Self-assembled one and two-dimensional electrongases

Description: We present angle-resolved photoemission measurements forultrathin In films on Si(111). Depending on the coverage, this systemself-organizes into a metallic monolayer with either 4x1 or sqrt7 x sqrt3symmetry relative to the substrate. Electronically, they behave likeideal one- and two-dimensional electron gases (1DEG and 2DEG),respectively. The 4x1 system has atomic chains of In whose energy bandsdisperse only parallel to the chains, while for the sqrt7 x sqrt3 system,the dominant reciprocal space features (in both diffraction andbandstructure) resemble a pseudo-square lattice with only weakersecondary features relating to the sqrt7 x sqrt3 periodicity. In bothmaterials the electrons show coupling to the structure. The 1DEG couplesstrongly to phonons of momentum 2kF, leading to an 8x"2" Peierls-likeinsulating ground state. The 2DEG appears to be partially stabilized byelectron gap formation at the sqrt 7 x sqrt3 zone boundary.
Date: January 22, 2001
Creator: Rotenberg, Eli; Yeom, H.W.; Takeda, S.; Matsuda, I.; Horikoshi,K.; Schaefer, J. et al.
Partner: UNT Libraries Government Documents Department

The use of a permanent magnet for water content measurements ofwood chips

Description: The Lawrence Berkeley National Laboratory has developed a device that measures the water content of wood chips, pulp and brown stock for the paper industry. This device employs a permanent magnet as the central part of a NMR measurement system. This report describes the magnet and the NMR measurement system. The results of water content measurements in wood chips in a magnetic field of 0.47 T are presented.
Date: September 20, 2001
Creator: Barale, P.J.; Fong, C.G.; Green, M.A.; Luft, P.A.; McInturff,A.D.; Reimer, J.A. et al.
Partner: UNT Libraries Government Documents Department

Optimization of signal extraction and front-end design in a fast,multigap ionization chamber

Description: This paper discusses the criteria that have been adopted tooptimize the signal processing in a shower detector to be employed as LHCbeam luminosity monitor. The original aspect ofthis instrument is itsablility to operate on a bunch-by-bunch basis. This means that it mustperform accurate charge measurements at a repetition rate of 40 MHz. Thedetector must withstand an integrated dose of 100 Grad, that is, two tothree orders of magnitude beyond those expected in the experiments. Tomeet the above requirements, an ionization chamber consisting of severalgaps of thickness 0.5 mm, filled with a gas that is expected to beradiation resistant, has been designed. Crucial in the development of thesystem is the signal processing, as the electronic noise may set thedominant limitation to the accuracy of the measurement. This is relatedto two aspects. One is the short time available for the chargemeasurement. The second one is the presence of a few meter cable betweenthe detector and the preamplifier, as this must be located out of theregion of highest radiation field. Therefore the optimization of thesignal-to-noise ratio requires that the best configuration of the chambergaps be determined under the constraint of the presence of a cable ofnon-negligible length between detector and preamplifier. The remoteplacement of the amplifying electronics will require that the front-endelectronics be radiation hard although to a lesser extent than thedetector.
Date: November 5, 2001
Creator: Datte, P.S.; Manfredi, P.F.; Millaud, J.E.; Placidi, M.; Ratti,L.; Speziali, V. et al.
Partner: UNT Libraries Government Documents Department

Interfacial segregation, pore formation and scale adhesion on NiAlalloys

Description: Alloys of commercial grades that do not contain a reactive element, such as yttrium, often develop pores at the scale/alloy interface. The accumulation and growth of these pores greatly weaken scale adhesion. The purpose of this study is to evaluate pore development in Fe-40at%Al and determine the change in pore volume with oxidation time. Experimental results are then compared to a theoretical calculation where all vacancies are allowed to condense as voids. After removing the oxide scales that formed after various times of oxidation at 1000 C in oxygen, the alloy surface was analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM) to determine the size and depth of interfacial pores. Results are discussed in light of possible mechanisms involved in pore formation at scale/alloy interfaces.
Date: October 9, 2001
Creator: Hou, Peggy Y. & Priimak, K.
Partner: UNT Libraries Government Documents Department

Investigations of silica alcogel aging using coherent light

Description: Light scattering methods have previously been used to monitor the formation of gels. In this report we present new light scattering techniques to study the properties of silica alcogels during the aging process. Monitoring one particular polarization transformation of scattered light with time reveals a clear increase in internal strain in standing alcogels with time. The stress birefringence coefficient of an acid-catalyzed SiO{sub 2} gel was found to be 3.4 x 10{sup 12} Brewsters. Additionally, the evolution of the stiffness of alcogels was investigated using laser speckle methods. Specifically, image analysis of specklegrams obtained during multi-frequency acoustic excitation of aging gels was used to non-destructively measure the hardening of alcogels. For an acid catalyzed gel with a theoretical density of {approx}0.05 g/cm{sup 3} SiO{sub 2}, the rate of hardening is found to be greatest between gelation and 2X the gel time, and drops considerably thereafter. The Young's modulus of the gel can be monitored over time with this method and was found to range from 6.2 x 10{sup 3} N/m{sup 2} after 6 hours to 2.2 x 10{sup 5} N/m{sup 2} after 24 hours for acid-catalyzed silica gels.
Date: June 1, 2001
Creator: Hunt, Arlon J. & Ayers, Michael R.
Partner: UNT Libraries Government Documents Department

Multiple Peaks in the Angular Power Spectrum of the CosmicMicrowave Background: Significance and Consequences for Cosmology

Description: Three peaks and two dips have been detected in the power spectrum of the cosmic microwave background from the BOOMERANG experiment, at {ell} {approx} 210, 540, 840 and {ell} {approx} 420, 750, respectively. Using model-independent analyses, we find that all five features are statistically significant and we measure their location and amplitude. These are consistent with the adiabatic inflationary model. We also calculate the mean and variance of the peak and dip locations and amplitudes in a large 7-dimensional parameter space of such models, which gives good agreement with the model-independent estimates, and forecast where the next few peaks and dips should be found if the basic paradigm is correct. We test the robustness of our results by comparing Bayesian marginalization techniques on this space with likelihood maximization techniques applied to a second 7-dimensional cosmological parameter space, using an independent computational pipeline, and find excellent agreement: {Omega}{sub tot} = 1.02{sub -0.05}{sup +0.06} vs. 1.04 {+-} 0.05, {Omega}{sub b}h{sup 2} = 0.022{sub -0.003}{sup +0.004} vs. 0.019{sub -0.004}{sup +0.005}, and n{sub s} = 0.96{sub -0.09}{sup +0.10} vs. 0.90 {+-} 0.08. The deviation in primordial spectral index n{sub s} is a consequence of the strong correlation with the optical depth.
Date: May 17, 2001
Creator: de Bernardis, P.; Ade, P.A.R.; Bock, J.J.; Bond, J.R.; Borrill,J.; Boscaleri, A. et al.
Partner: UNT Libraries Government Documents Department

Synthesis and properties of Chitosan-silica hybrid aerogels

Description: Chitosan, a polymer that is soluble in dilute aqueous acid, is derived from chitin, a natural polyglucosamide. Aquagels where the solid phase consists of both chitosan and silica can be easily prepared by using an acidic solution of chitosan to catalyze the hydrolysis and condensation of tetraethylorthosilicate. Gels with chitosan/TEOS mass ratios of 0.1-1.1 have been prepared by this method. Standard drying processes using CO{sub 2} give the corresponding aerogels. The amount of chitosan in the gel plays a role in the shrinkage of the aerogel during drying. Gels with the lowest chitosan/silica ratios show the most linear shrinkage, up to 24%, while those with the highest ratios show only a 7% linear shrinkage. Pyrolysis at 700 C under nitrogen produces a darkened aerogel due to the thermal decomposition of the chitosan, however, the aerogel retains its monolithic form. The pyrolyzed aerogels absorb slightly more infrared radiation in the 2-5 {micro}m region than the original aerogels. B.E.T. surface areas of these aerogels range from 470-750 m{sup 2}/g. Biocompatibility screening of this material shows a very high value for hemolysis, but a low value for cytotoxicity.
Date: June 1, 2001
Creator: Ayers, Michael R. & Hunt, Arlon J.
Partner: UNT Libraries Government Documents Department

A triple-continuum approach for modeling flow and transportprocesses in fractured rock

Description: This paper presents a triple-continuum conceptual model forsimulating flow and transport processes in fractured rock. Field datacollected from the unsaturated zone of Yucca Mountain, a repository siteof high-level nuclear waste, show a large number of small-scalefractures. The effect of these small fractures has not been considered inprevious modeling investigations within the context of a continuumapproach. A new triple-continuum model (consisting of matrix,small-fracture, and large-fracture continua) has been developed toinvestigate the effect of these small fractures. This paper derives themodel formulation and discusses the basic triple-continuum behavior offlow and transport processes under different conditions, using bothanalytical solutions and numerical approaches. The simulation resultsfrom the site-scale model of the unsaturated zone of Yucca Mountainindicate that these small fractures may have an important effect onradionuclide transport within the mountain
Date: August 31, 2001
Creator: Wu, Yu-Shu; Liu, H.H.; Bodvarsson, G.S & Zellmer, K .E.
Partner: UNT Libraries Government Documents Department

Reanalysis of the Schwertmannite structure and the incorporationof SO42- groups: An IR, XAS, WAXS and simulation study

Description: Schwertmannite is a poorly crystallized iron oxyhydroxidewith essential structural sulfate that can be a major component in acidmine drainage environments. Original characterization work concluded thatthe sulfate was largely contained within tunnels of an orderedakaganeite-like structure based on powder XRD, analysis of IR spectra,and sulfate extraction procedures [1]. Since the original description,problems have emerged with the nature of the tunnel sulfate, and with theinterpretation of the IR spectra. Other related work has shown that it isnow possible to determine sulfate-iron oxide inner sphere bindingunambiguously from the S K-edge XANES spectrum. Hence a reassessment ofthe evidence for the original schwertmannite structure was deemednecessary and timely.
Date: May 5, 2001
Creator: Waychunas, G.A.; Myneni, S.C.B.; Traina, S.J.; Bigham, J.M.; Fuller, C.C. & Davis, J.A.
Partner: UNT Libraries Government Documents Department

Limitations of science and adaptive management

Description: Adaptive management consists in patterning human sustenancewithin the constraints of Earth and biological systems whose behavior isinherently uncertain and difficult to control. For successful adaptivemanagement, a mind-set recognizing the limitations of science isneeded.
Date: December 20, 2001
Creator: Narasimhan, T.N.
Partner: UNT Libraries Government Documents Department

Nb3Sn Quadrupole Magnets for the LHC IR

Description: The development of insertion quadrupoles with 205 T/m gradient and 90 mm bore represents a promising strategy to achieve the ultimate luminosity goal of 2.5 x 10{sup 34} cm{sup -2}s{sup -1} at the Large Hadron Collider (LHC). At present, Nb{sub 3}Sn is the only practical conductor which can meet these requirements. Since Nb{sub 3}Sn is brittle, and considerably more strain sensitive than NbTi, the design concepts and fabrication techniques developed for NbTi magnets need to be modified appropriately. In addition, IR magnets must provide high field quality and operate reliably under severe radiation loads. The results of conceptual design studies addressing these issues are presented.
Date: August 1, 2001
Creator: Sabbi, G.; Caspi, S.; Chiesa, L.; Coccoli, M.; Dietderich, D.r.; Ferracin, P. et al.
Partner: UNT Libraries Government Documents Department

Magnet options for sensors for the pulp and paper industry

Description: The Lawrence Berkeley National Laboratory (LBNL) has been developing sensors for the pulp and paper industry that uses a magnetic field. The applications for magnetic sensors that have studied include (1) sensors for the measurement of the water and ice content of wood chips entering the pulping mill, (2) sensors for measuring the water content and other constituents of the black liquor leaving the paper digester, and (3) sensors for measuring paper thickness and water content as the paper is being processed. These tasks can be done using nuclear magnetic resonance (NMR). The magnetic field used for doing the NMR can come from either permanent magnets or superconducting magnets. The choice of the magnet is dependent on a number of factors, which include the size of the sample and field strength needed to do the sensing task at hand. This paper describes some superconducting magnet options that can be used in the pulp and paper industry.
Date: May 5, 2001
Creator: Green, M.A.; Barale, P.J.; Fong, C.G.; Luft, P.A.; Reimer, J.A. & Yahnke, M.S.
Partner: UNT Libraries Government Documents Department

Fabrication and test results of a high field, Nb3Sn superconducting racetrack dipole magnet

Description: The LBNL Superconducting Magnet Program is extending accelerator magnet technology to the highest possible fields. A 1 meter long, racetrack dipole magnet, utilizing state-of-the-art Nb{sub 3}Sn superconductor, has been built and tested. A record dipole filed of 14.7 Tesla has been achieved. Relevant features of the final assembly and tested results are discussed.
Date: June 15, 2001
Creator: Benjegerdes, R.; Bish, P.; Byford, D.; Caspi, S.; Dietderich, D.R.; Gourlay, S.A. et al.
Partner: UNT Libraries Government Documents Department

MCF-10A-NeoST: A New Cell System for Studying Cell-ECM and Cell-Cell Interactions in Breast Cancer

Description: There is a continuing need for genetically matched cell systems to model cellular behaviors that are frequently observed in aggressive breast cancers. We report here the isolation and initial characterization of a spontaneously arising variant of MCF-10A cells, NeoST, which provides a new model to study cell adhesion and signal transduction in breast cancer. NeoST cells recapitulate important biological and biochemical features of metastatic breast cancer, including anchorage-independent growth, invasiveness in threedimensional reconstituted membranes, loss of E-cadherin expression, and increased tyrosine kinase activity. A comprehensive analysis of tyrosine kinase expression revealed overexpression or functional activation of the Axl, FAK, and EphA2 tyrosine kinases in transformed MCF-10A cells. MCF-10A and these new derivatives provide a genetically matched model to study defects in cell adhesion and signaling that are relevant to cellular behaviors that often typify aggressive breast cancer cells.
Date: August 22, 2001
Creator: Zantek, Nicole Dodge; Walker-Daniels, Jennifer; Stewart, Jane; Hansen, Rhonda K.; Robinson, Daniel; Miao, Hui et al.
Partner: UNT Libraries Government Documents Department