Showing papers by "Pacific Northwest National Laboratory published in 1996"

Economic and environmental choices in the stabilization of atmospheric CO2concentrations

Abstract: THE ultimate goal of the UN Framework Convention on Climate Change is to achieve "stabilization of greenhouse-gas concentrations at a level that would prevent dangerous anthropogenic interference with the climate system". With the concentration targets yet to be determined, Working Group I of the Intergovernmental Panel on Climate Change developed a set of illustrative pathways for stabilizing the atmospheric CO2 concentration at 350, 450, 550, 650 and 750 p.p.m.v. over the next few hundred years1,2. But no attempt was made to determine whether the implied emissions might constitute a realistic transition away from the current heavy dependence on fossil fuels. Here we devise new stabilization profiles that explicitly (albeit qualitatively) incorporate considerations of the global economic system, estimate the corresponding anthropogenic emissions requirements, and assess the significance of the profiles in terms of global-mean temperature and sea level changes. Our findings raise a number of important issues for those engaged in climate-change policy making, particularly with regard to the optimal timing of mitigation measures.

Electrochemical Properties of Mixed Conducting Perovskites La1 − x M x Co1 − y Fe y O 3 − δ (M = Sr, Ba, Ca)

Abstract: Perovskite compositions in the system La{sub 1{minus}x}M{sub x}Co{sub 1{minus}y}Fe{sub y}O{sub 3{minus}{delta}} (M = Sr, Ba, Ca) exhibited high electronic and ionic conductivity. Substantial reversible weight loss was observed at elevated temperatures as the materials became increasingly oxygen deficient. This loss of lattice oxygen at high temperatures, which tended to increase with increasing acceptor content, resulted in a decrease in the electronic conductivity. In an oxygen partial pressure gradient, oxygen flux through dense sintered membranes of these materials was highly dependent on composition and increased with increasing temperature. The increase in oxygen flux with increasing temperature was attributed to increases in the mobility and concentration of lattice oxygen vacancies. The calculated ionic conductivities of some compositions exceeded that of yttria-stabilized zirconia. This material is an attractive candidate for several important applications, including solid oxide fuel cell cathodes.

Biodiversity and application of microalgae

Abstract: The algae are a polyphyletic, artificial assemblage of O2-evolving, photosynthetic organisms (and secondarily nonphotosynthetic evolutionary descendants) that includes seaweeds (macroalgae) and a highly diverse group of microorganisms known as microalgae. Phycology, the study of algae, developed historically as a discipline focused on the morphological, physiological and ecological similarities of the subject organisms, including the prokaryotic bluegreen algae (cyanobacteria) and prochlorophytes. Eukaryotic algal groups represent at least five distinct evolutionary lineages, some of which include protists traditionally recognized as fungi and protozoa. Ubiquitous in marine, freshwater and terrestrial habitats and possessing broad biochemical diversity, the number of algal species has been estimated at between one and ten million, most of which are microalgae. The implied biochemical diversity is the basis for many biotechnological and industrial applications.

Global arrays: a nonuniform memory access programming model for high-performance computers

Abstract: Portability, efficiency, and ease of coding are all important considerations in choosing the programming model for a scalable parallel application. The message-passing programming model is widely used because of its portability, yet some applications are too complex to code in it while also trying to maintain a balanced computation load and avoid redundant computations. The shared-memory programming model simplifies coding, but it is not portable and often provides little control over interprocessor data transfer costs. This paper describes an approach, called Global Arrays (GAs), that combines the better features of both other models, leading to both simple coding and efficient execution. The key concept of GAs is that they provide a portable interface through which each process in a MIMD parallel program can asynchronously access logical blocks of physically distributed matrices, with no need for explicit cooperation by other processes. We have implemented the GA library on a variety of computer systems, including the Intel Delta and Paragon, the IBM SP-1 and SP-2 (all message passers), the Kendall Square Research KSR-1/2 and the Convex SPP-1200 (nonuniform access shared-memory machines), the CRAY T3D (a globally addressable distributed-memory computer), and networks of UNIX workstations. We discuss the design and implementation of these libraries, report their performance, illustrate the use of GAs in the context of computational chemistry applications, and describe the use of a GA performance visualization tool.

Collaboratories: doing science on the Internet

Abstract: The success of many complex scientific investigations hinges on bringing the capabilities of diverse individuals from multiple institutions together with state-of-the-art instrumentation. Computer scientists working with domain specialists have made progress on several fronts to create and integrate the tools required for Internet-based scientific collaboration. However, both technical and sociological challenges remain. The tools of computer-supported cooperative work are now being applied to such collaborations. Through immersive electronic interaction, team members distributed across a widespread area can collaborate, using the newest instruments and computing resources. The paper discusses some collaboratory prototypes and considers the sociology of collaboration.

A new model for the emplacement of Columbia River basalts as large, inflated Pahoehoe Lava Flow Fields

Abstract: Extensive flows of the Columbia River Basalt (CRB) Group in Washington, Oregon, and Idaho are dominantly inflated compound pahoehoe sheet lavas. Early studies recognized that CRB lavas are compound pahoehoe flows, with textures suggesting low flow velocities, but it was thought that the great thickness and extent of the major flows required very rapid emplacement as turbulent floods of lava over a period of days or weeks. However, small volume (< 1 km³) compound pahoehoe flows on Kilauea, Hawai'i, demonstrate that such flows can thicken by at least an order of magnitude through gradual inflation and the same mechanism has been proposed for larger (10–20 km3) pahoehoe flows in Iceland. The vertical distribution of vesicles and other morphologic features within CRB lava flows indicate that they grew similarly by inflation. Small pahoehoe lobes at the base and top of many CRB pahoehoe lava flows indicate emplacement in a gradual, piecemeal manner rather than as a single flood. We propose that each thick CRB sheet flow was active for months to years and that each group of flows produced by a single eruption (a flow field) was emplaced slowly over many years.

The evaporation rate, free energy, and entropy of amorphous water at 150 K

Abstract: Measurement of the rates of evaporation of amorphous water (a) and ice (i) near 150 K can be interpreted as giving a measure of their free energy difference, ΔaiG (150 K)=1100±100 J/mol, which, together with the known enthalpy difference and heat capacity data, suggests a residual entropy difference of ΔaiS (0)=−0.7±2.2 J/(K mol) at absolute zero. Previous theoretical estimates of ΔaiS (0), which are much larger, did not allow the amorph to be connected with normal liquid water by a reversible thermodynamic path at atmospheric pressure. The present value allows such a connection.

The melatonin hypothesis: electric power and breast cancer.

Abstract: Breast cancer is a disease of modern life As societies industrialize, risk increases, yet it is unclear which of the myriad changes coming with industrialization drives this increase One importan

Comparison of perturbative and multiconfigurational electron propagator methods

Abstract: Ionization energies below 20 eV of 10 molecules calculated with electron propagator techniques employing Hartree-Fock orbitals and multiconfigurational self-consistent field orbitals are compared. Diagonal and nondiagonal self-energy approximations are used in the perturbative formalism. Three diagonal methods based on second- and third-order self-energy terms, all known as the outer valence Green's function, are discussed. A procedure for selecting the most reliable of these three versions for a given calculation is tested. Results with a polarized, triple ζ basis produce root mean square errors with respect to experiment of approximately 0.3 eV. Use of the selection procedure has a slight influence on the quality of the results. A related, nondiagonal method, known as ADC(3), performs infinite-order summations on several types of self-energy contributions, is complete through third-order, and produces similar accuracy. These results are compared to ionization energies calculated with the multiconfigurational spin-tensor electron propagator method. Complete active space wave functions or close approximations constitute the reference states. Simple field operators and transfer operators pertaining to the active space define the operator manifold. With the same basis sets, these methods produce ionization energies with accuracy that is comparable to that of the perturbative techniques. © 1996 John Wiley & Sons, Inc.

Nucleophilic displacements in mixed self-assembled monolayers

Abstract: Synthetic elaboration of self-assembled monolayers (SAMs) provides a powerful method for the preparation of smooth, ordered surfaces with carefully controlled functionality. Chemically rugged siloxane-based SAMs have been employed as a foundation for the preparation of a variety of functionalized surfaces. Nucleophilic displacements are described between halide-terminated SAMs and anionic nucleophiles (e.g. azide, thiocyanate, thiolate). Problems were encountered due to the steric congestion surrounding the terminal bromomethylene carbon. The concept of trajectory control is applied to these displacement reactions. In addition, reactions between ester-terminated SAMs and neutral nucleophiles (e.g. amines, hydrazine, hydroxylamine) are described. Evidence is presented suggesting that a modest amount of cross-linking (i.e. imide formation) takes place in the amidation reactions, while reaction stoichiometry indicates that cross-linking is virtually complete for the bifunctional nucleophiles. These synthetic elaborations were also carried out on mixed monolayers to create functionalized SAMs with systematically varied loading densities. Linear correlation (or lack thereof) of elemental composition to predicted functional composition is used to provide an estimation of reaction efficiency. 66 refs., 11 figs.

Screening derivatized peptide libraries for tight binding inhibitors to carbonic anhydrase II by electrospray ionization-mass spectrometry.

Abstract: This paper describes the use of electrospray ionization-mass spectrometry (ESI-MS) to screen two libraries of soluble compounds to search for tight binding inhibitors for carbonic anhydrase II (EC 4.2.1.1). The two libraries, H2NO2SC6H4C(O)NH-AA1-AA2-C(O)NHCH2CH2CO2H (1), where AA1 and AA2 are l-amino acids (library size: 289 compounds) or d-amino acids (256 compounds), were constructed by attaching tripeptides to the carboxyl group of 4-carboxybenzenesulfonamide. Screening of both libraries yielded, as the tightest binding inhibitor, compound 1 (AA1 = AA2 = l-Leu; binding constant Kb = 1.4 × 108 M-1). The ability of ESI-MS to estimate simultaneously the relative binding affinities of a protein to soluble ligands in a library, if general, should be useful in drug development.

A Case Study of the Great Plains Low-Level Jet Using Wind Profiler Network Data and a High-Resolution Mesoscale Model

Abstract: A detailed case study of one complete episode of a typical summertime Great Plains low-level jet (LLJ) using data collected by the NOAA wind profiler demonstration network is presented. The high temporal and spatial resolution of the data from the profiler network permits a much more detailed picture of the Great Plains LLJ than is possible from previous studies of this phenomenon. A three-dimensional mesoscale numerical model is also used to simulate the episode and to provide information on the physical mechanisms responsible for the initiation, evolution, maintenance, and decay of the LLJ. The position and width of the jet core, as well as the diurnal variation of wind speed and direction inside the jet core are well predicted by the model. The analysis and modeling suggest that the diurnal oscillation of horizontal pressure gradient over sloping terrain is secondary to the inertial oscillation mechanism resulting from the release of frictional constraint in the evening and throughout the nigh...

Direct Modeling of EXAFS Spectra from Molecular Dynamics Simulations

Abstract: A method for generating extended X-ray absorption fine-structure (EXAFS) spectra directly from molecular dynamics trajectories is described. Conventional molecular dynamics trajectories are run, and configurations from the trajectory are saved at periodic intervals. Clusters containing the EXAFS atom at the center are extracted from the configurations and used as input to the multiple scattering code FEFF6, which produces an EXAFS spectrum for each cluster. The separate spectra for the individual clusters are then averaged together to get a configurationally averaged EXAFS spectrum that can be compared directly with experiment. The method is tested on strontium chloride solutions and compared with recent experimental results on strontium nitrate solutions at both standard and supercritical conditions.

Surface‐induced mineralization: A new method for producing calcium phosphate coatings

Abstract: Calcium phosphate coatings were nucleated and grown from aqueous solution onto titanium metal substrates via surface-induced mineralization (SIM) processing techniques. This process is based on the observation that in nature organisms use biopolymers to produce ceramic composites, such as teeth, bones, and shells. The SIM process involves modification of a surface to introduce surface functionalization followed by immersion in aqueous supersaturated calcium phosphate solutions. This low-temperature process (< 100 degrees C) has advantages over conventional methods of calcium phosphate deposition in that uniform coatings are produced onto complex-shaped and/or microporous samples. Additionally, because it is a low-temperature process, control of the phase and crystallinity of the deposited material can be maintained.

Theoretical analysis of magnetic field interactions with aortic blood flow.

Abstract: The flow of blood in the presence of a magnetic field gives rise to induced voltages in the major arteries of the central circulatory system. Under certain simplifying conditions, such as the assumption that the length of major arteries (e.g., the aorta) is infinite and that the vessel walls are not electrically conductive, the distribution of induced voltages and currents within these blood vessels can be calculated with reasonable precision. However, the propagation of magnetically induced voltages and currents from the aorta into neighboring tissue structures such as the sinuatrial node of the heart has not been previously determined by any experimental or theoretical technique. In the analysis presented in this paper, a solution of the complete Navier-Stokes equation was obtained by the finite element technique for blood flow through the ascending and descending aortic vessels in the presence of a uniform static magnetic field. Spatial distributions of the magnetically induced voltage and current were obtained for the aortic vessel and surrounding tissues under the assumption that the wall of the aorta is electrically conductive. Results are presented for the calculated values of magnetically induced voltages and current densities in the aorta and surrounding tissue structures, including the sinuatrial node, and for their field-strength dependence. In addition, an analysis is presented of magnetohydrodynamic interactions that lead to a small reduction of blood volume flow at high field levels above approximately 10 tesla (T). Quantitative results are presented on the offsetting effects of oppositely directed blood flows in the ascending and descending aortic segments, and a quantitative estimate is made of the effects of assuming an infinite vs. a finite length of the aortic vessel in calculating the magnetically induced voltage and current density distribution in tissue. © 1996 Wiley-Liss, Inc.

Dimensional Instability of Doped Lanthanum Chromite

Abstract: Lattice expansion phase stability, and dimensional stability of doped lanthanum chromites have been examined over a wide range of temperatures and oxygen partial pressures. Reduction of doped lanthanum chromite resulted in a linear expansion of the sample that was dependent on the acceptor (Sr, Ca) concentration, temperature, oxygen partial pressure, and oxygen content within the sample. Additional doping with aliovalent B-site additives significantly reduced lattice expansion in reducing environments. The lattice expansion in reducing environments was directly related to the loss of lattice oxygen and the simultaneous reduction of Cr{sup 4+} to Cr{sup 3+} to maintain electroneutrality.

Ultrahigh-Speed Calculation of Isotope Distributions

Abstract: This paper introduces an ultrahigh-speed algorithm for calculating isotope distributions from molecular formulas, elemental isotopic masses, and elemental isotopic abundances. For a given set of input data (molecular formula, elemental isotopic masses, and elemental isotopic abundances), and assuming round-off error to be negilgible, the new algorithm rigorously produces isotope distributions whose mean and standard deviation are “correct” in the sense that an error-free algorithm would produce a distribution having the same mean and standard deviation. The peak heights are also “correct” in the sense that the height of each nominal isotope peak from the ultrahigh-speed calculation equals the integrated peak area of the corresponding nominal isotope peak from an exact calculation. As a consequence of these properties, the algorithm generally places isotope peaks within millidaltons of their true centroids. The method uses Fourier transform methods and relates closely to two other recently introduced algor...

A Molecular Dynamics and Quantum Mechanics Analysis of the Effect of DMSO on Enzyme Structure and Dynamics: Subtilisin

Abstract: This report describes a 745-ps molecular dynamics simulation of the enzyme subtilisin Carlsberg in a periodic box of dimethyl sulfoxide (DMSO). The starting coordinates for subtilisin and crystallographic waters were taken from the aqueous X-ray crystal structure. Although the overall structure of subtilisin is stable throughout the simulation, some structural perturbations are observed. The five N-terminal residues of the protein migrate away from the rest of the protein; whether this movement is the start of partial unfolding in DMSO is unclear. We compare these findings with recent simulations of this enzyme in CCl4, acetonitrile, and water. The simulation results indicate that DMSO is capable of stripping waters and metal ions away from the protein surface. The total number of intraprotein hydrogen bonds is increased in DMSO compared to in water. Eighteen DMSO binding sites were identified based on root-mean-square fluctuations, most of which were hydrogen bonded to a protein amide hydrogen atom. Quan...

Climate Change Impacts on U.S. Commercial Building Energy Consumption: An Analysis Using Sample Survey Data

Abstract: Although much of the commercial sector infrastructure for the next century is currently under construction or is in the planning stages, little has been done in communicating how potential global warming might change the energy consumption characteristics of the building stock. The research discussed in this article advances the literature on how climate change affects commercial sector energy demand systems. It projects the effects of climate change on commercial energy demand in the United States at the national level. The article relies heavily on time-series regressions of monthly energy consumption by building on monthly heating and cooling degree days. It provides empirical results for the effects of climate on a projected building stock in the year 2030 and examines the prospects for saving energy with advanced building designs in the context of potential global warming.

Density and Temperature Effects on the Hydrogen Bond Structure of Liquid Methanol

Abstract: The hydrogen bond structure of liquid methanol was investigated as a function of pressure and temperature up to 2.8 kbar and from 297 to 413 K. Chemical shifts of the CH3 and OH groups were monitored throughout this pressure and temperature regime, and the chemical shift difference between these two groups was used to describe changes of the hydrogen bond network in methanol. The hydrogen bond equilibrium was investigated using molecular dynamics simulations and a phenomenological model describing clustering in liquid methanol. Results are presented concerning the size and distribution of hydrogen-bonded clusters in methanol as a function of pressure and temperature. The results indicate that the extent of hydrogen bonding decreases upon an increase in temperature. The results for pressure are equivocal, the phenomenological model suggests that hydrogen bonding decreases with increasing pressure, which supports earlier interpretations regarding the measured self-diffusion coefficients in deuterated methan...