Physical Sciences and Mathematics Commons^™

Stability Of A Pivoting Strategy For Parallel Gaussian Elimination, Jodi Mead, R. Renaud, B. Welfert

Jodi Mead

Gaussian elimination with partial pivoting achieved by adding the pivot row to the kth row at step k, was introduced by Onaga and Takechi in 1986 as means for reducing communications in parallel implementations. In this paper it is shown that the growth factor of this partial pivoting algorithm is bounded above by n <#60; 3 n–1, as compared to 2 n–1 for the standard partial pivoting. This bound n, close to 3 n–2, is attainable for class of near-singular matrices. Moreover, for the same matrices the growth factor is small under partial pivoting.

Kinetics Of Substitution Of Weakly Coordinating Nitrate By Chloride In (Η5-Cp)Ru(Co)(Er3)Ono2 (Er3 = Asph3, Pph3, P(P-Anisyl)3, Pph2(O-Anisyl), P(Oph)3) In Dichloromethane., Minhton Cao, Liem Do, Norris Hoffman, Man Lung Kwan, Julie Little, J. Mcgilvray, Christopher Morris, Bjorn Söderberg, Andrzej Wierzbicki, Thomas Cundari, Charles Lake, Edward Valente

Man Lung Desmond Kwan

The d6 complexes of formula (η5-Cp)Ru(CO)(ER3)ONO2, where ER3 = AsPh3, PPh3, P(p-anisyl)3, PPh2(o-anisyl), and P(OPh)3, were prepared by reaction of their chloro analogues with AgNO3 in CH2Cl2. They underwent moderately slow substitution of the relatively weakly coordinating nitrate by chloride in dry CH2Cl2 in the presence of excess [N(PPh3)2+]Cl-. A kinetics study showed the reaction to be first order in nitrato complex and independent of chloride salt concentration under pseudo-first-order conditions. First-order rate constants for nitrate metathesis follow the trend P(OPh)3 < PPh3 < P(p-anisyl)3 < AsPh3 PPh2(o-anisyl), with k1 at 25 °C for the first four in the series from 1.4 to 4.4 × 10-5 s-1. Activation parameters for conversion of (η5-Cp)Ru(CO)(AsPh3)ONO2 to its chloride are ΔH‡ = 17(2) kcal/mol and ΔS‡ = −21(5) eu. Even use of a slightly moist solvent increased the rate of nitrate metathesis by 20−30% without changing the form of the rate law. The complex containing PPh2(o-anisyl) was approximately 2 orders of magnitude more reactive (k1 = 4.9 × 10-3 s-1). A likely explanation is stabilization of a coordinatively unsaturated intermediate by weak coordination of the potentially chelating o-OMe group. A mechanism entailing rate-limiting conversion of the neutral nitrato complex into a coordinatively unsaturated ion-paired species is consistent with this set of data. Semiempirical calculations (PM3(tm)), which model the structures of complexes in these systems quite well, supported such behavior. X-ray crystal structures were determined for the AsPh3 nitrato and chloro complexes and for the PPh3 chloro complex.

Investigation Of The Structure Of T He Ternary Cluster Of Aniline−Water−Tetrahydrofuran And Its Cation By Infrared Depletion Spectroscopy, Taisuke Nakanaga, Naveed Piracha, Fumiyuki Ito

Naveed K. Piracha

No abstract provided.

Environmental Justice And Southern California's “Riskscape” The Distribution Of Air Toxics Exposures And Health Risks Among Diverse Communities, James Sadd

James Sadd

Past research on “environmental justice” has often failed to systematically link hazard proximity with quantifiable health risks. The authors employ recent advances in air emissions inventories and modeling techniques to consider a broad range of outdoor air toxics in Southern California and to calculate the potential lifetime cancer risks associated with these pollutants. They find that such risks are attributable mostly to transportation and small-area sources and not the usually targeted large-facility pollution emissions. Multivariate regression suggests that race plays an explanatory role in risk distribution even after controlling for other economic, land-use, and population factors. This pattern suggests the …

Stereoselective One-Pot Synthesis Of Vinylsilanes From Aromatic Aldehydes, Man Lung Kwan, Chiu Yeung, Kerry Breno, Kenneth Doxsee

Man Lung Desmond Kwan

Vinylsilanes serve as convenient vinyl anion equivalents, but procedures for their stereoselective synthesis from aldehydes are scarce. A variety of aromatic aldehydes are converted to the corresponding vinylsilanes in a one-pot procedure involving the addition of (trimethylsilylmethyl)lithium to the aldehyde followed by treatment with Cp2TiCH2·AlMe2Cl (‘Tebbe's reagent’). Halide and alkoxide substituents are tolerated, and (E)-vinylsilanes are formed exclusively in good yield.

A2bi8se1 3 (A = Rb, Cs), Csbi3.67se6, And Babi2< /Inf>Se4: New Ternary Semiconducting Bismuth Selenides, Lykourgis Iordanidis, Paul Brazis, Theodora Kyratsi, John Irel, Melissa Lane, Carl Kannewurf, Wei Chen, Jeffrey Dyck, Ctirad Uher, Nishant Ghelani, Tim Hogan, Mercouri Kanatzidis

Jeffrey Dyck

No abstract provided.

The Y-Triangle Move Does Not Preserve Intrinsic Knottedness, Ramin Naimi, Erica Flapan

Ramin Naimi

We answer the question "Does the Y-triangle move preserve intrinsic knottedness?" in the negative by giving an example of a graph that is obtained from the intrinsically knotted graph K_7 by triangle-Y and Y-triangle moves but is not intrinsically knotted.

The Influence Of Ni On The Transport Properties Of Cosb3, C. Uher, Jeffrey Dyck, W. Chen, G. Meisner, J. Yang

Jeffrey Dyck

The effect of Ni doping on the Co site of the binary skutterudite CoSb3 is investigated. We measured resistivity, Hall effect, magnetoresistance, thermopower, thermal conductivity, and magnetization of a series of samples of the form Co1-xNixSb3 with x in the range x=0 to x=0.01. We find that Ni takes the tetravalent state Ni4+, assumes the d6 electronic configuration for the lower energy non-bonding orbitals, and gives an electron to the conduction band. Ni doping dramatically suppresses the thermal conductivity, changes the temperature dependence of the thermopower, and increases the carrier concentration. Low temperature anomalies in thermopower, Hall coefficient and magnetoresistance …

Low Temperature Thermoelectric Properties Of Ni Doped N-Type Filled Skutterudites Ba0.3co4sb12 ., W. Chen, Jeffrey Dyck, C. Uher, L. Chen, X. Tang, T. Hirai

Jeffrey Dyck

n-type Ba filled skutterudites doped with Ni, Ba0.3Ni xCo4-xSb12 with 0⩽x⩽0.2, have been synthesized and the Seebeck coefficient, thermal conductivity, electrical resistivity and Hall coefficient have been measured. ZT of 1.2 has been achieved at 800 K with x=0.05. The thermal conductivity data are fitted and the rattling effect of the Ba atoms is identified through a resonance scattering term. The Hall mobility is studied and a mixed scattering mechanism of acoustic phonons and ionized impurities based on a single, rigid band picture is presented. The role of Ni atoms in enhancing the thermoelectric performance is discussed

Multi-Filling Approach For The Improvement Of Thermoelectric Properties Of Skutterudites., L. Chen, X. Tang, T. Kawahara, Jeffrey Dyck

Jeffrey Dyck

Several skutterudite antimonides filled with atoms of different kinds, (Ba, M)yCo4Sb12 (M=Ce, La, Sr), have been synthesized by the combination of solid state reaction and melting methods. Thermal conductivity of (Ba,Sr)yCo4 Sb12 samples shows a behavior similar to that of BayCo4Sb12. Adding a small amount of Ce or La to the BayCo4Sb12 system is effective in further reducing the lattice thermal conductivity. The difference in the ionic radii of the two co-filler atoms is the most sensitive factor for scattering of phonons. The multi-filled (Ba, M)yCo4Sb12 (M=Sr, Ce, La) show lower Seebeck coefficients as compared to the single-filled BayCo 4Sb12 …

High-Temperature Thermoelectric Properties Of N-Type Baynixco4-Xsb12., X. Tang, L. Zhang, R. Yuan, L. Chen, T. Goto, T. Hirai, Jeffrey Dyck, W. Chen, C. Uher

Jeffrey Dyck

Effects of Ba filling fraction and Ni content on the thermoelectric properties of n-type BayNixCo4-xSb12 (x = 0-0.1, y = 0.-0.4) were investigated at temperature range of 300 to 900 K. Thermal conductivity decreased with increasing Ba filling fraction and temperature. When y was fixed at 0.3, thermal conductivity decreased with increasing Ni content and reached a minimum value at about x = 0.05. Lattice thermal conductivity decreased with increasing Ni content, monotonously (y ≤ 0.1). Electron concentration and electrical conductivity increased with increasing Ba filling fraction and Ni content. Seebeck coefficient increased with increasing temperature and decreased with increasing …

Femtosecond Polarization Detection Using High-Speed Pulse Shaping, D. Keusters, Peifang Tian, W. Warren

Peifang Tian

This book presents the latest advances in ultrafast science, including ultrafast laser and measurement technology as well as studies of ultrafast phenomena. Pico- and femtosecond processes relevant in physics, chemistry, biology and engineering are presented. Ultrafast technology has had a profound impact in a wide range of applications, among them imaging, material diagnostics and transformation and high-speed optoelectronics. This book summarizes the results presented at the 12th Ultrafast Phenomena Conference and reviews the state of the art of this important and rapidly advancing field.

Preparation And Some Physical Properties Of Tetradymite-Type Sb2te3 Single Crystals Doped With Cds., P. LošŤÁK, Č. Drašar, A. Krejc ̆ Ova, L. Beneš, Jeffrey Dyck, W. Chen, C. Uher

Jeffrey Dyck

Single crystals of Sb2Te3 doped with CdS were prepared by a modified Bridgman method from the elements Sb and Te of 5N purity and the CdS compound of 4.5N purity. Samples were characterized by X-ray diffraction and by measurement of reflectance in the plasma resonance frequency region at room temperature. Furthermore, we made measurements of temperature dependence of the electrical resistivity, Hall and Seebeck coefficients, and thermal conductivity in the temperature range of 4.2–300K. In the process of crystal growth, CdS dissociated and it was assumed that the Cd-atoms formed substitutional defects in the Sb-sublattice (CdSb′) while the S-atoms formed …

Ima Journal Of Management Mathematics,, Ron Buckmire, David Edwards

Ron Buckmire

No abstract provided.

Synthesis And High Temperature Thermoelectric Properties Of N-Type Baynixco4-Xsb12., X. Tang, L. Chen, T. Goto, Jeffrey Dyck

Jeffrey Dyck

Single-phase filled skutterudite compounds BayNx Co4-xSb12 (x=0-0.1, y=0-0.4) were synthesized by a two-step solid state reaction. Effects of Ba filling fraction and Ni content on the thermoelectric properties of n-type Ba yNixCo4-xSb12 were investigated. Thermal conductivity decreased with increasing Ba filling fraction and temperature. When barium filling fraction (y) was fixed at 0.3, the thermal conductivity decreased with increasing Ni content, and reached a minimum value at about x=0.05. Electron concentration and electrical conductivity increased with increasing Ba filling fraction and Ni content. Seebeck coefficient increased with increasing temperature, and decreased with increasing Ba filling fraction and Ni content. A …

Thermoelectric Properties Of Yb-Filled And Sn-Compensated Skutterudites ., Jihui Yang, Gregory Meisner, Wei Chen, Jeffrey Dyck, Ctirad Uher

Jeffrey Dyck

The effect of alloying tin on the antimony site of ytterbium-filled skutterudites is examined. We performed measurements of Hall effect, electrical resistivity, Seebeck coefficient and thermal conductivity on the series Yb0.5Co4Sb12-x Snx, with x=0.5, 0.6, 0.8 and 0.83. We find that the substitution of tin does not alter the position of the Fermi level with respect to the conduction band of these heavily doped semiconducting samples, but rather it gives rise to a p-type band. Experimental data for x=0.83 can be understood in the context of a two-carrier electrical conduction. Thermal conductivity of these ytterbium-filled skutterudites is significantly suppressed with …

Geomagnetic Field Behavior Before And After The Kauai Reverse-Normal Polarity Transition, Scott Bogue

Scott Bogue

New paleomagnetic results from 4 m.y. old lava flows from Kauai, Hawaii, suggest that strong poloidal field is associated with an unusual state of the geodynamo that follows attempts at polarity reversal (successful or not). The new data comprise 50 paleomagnetic sites from superposed lava flows occurring just below and above the Kauai reverse-normal polarity transition. A composite record of 45 distinct field determinations was constructed by combining sites that record similar ancient field and correlating them to previously published results from Kauai. Of the 45 data, 25 include paleointensity estimates derived from double-heating experiments. A comparison of the composite …

Transport And Magnetic Properties Of Co1-Xnixsb3 With X Less Than 0.01, Jeffrey Dyck, W. Chen, Y. Yang, G. Meisner, C. Uher

Jeffrey Dyck

The filled skutterudite compounds based on the binary skutterudite CoSb3 are currently being investigated for their potential application as thermoelectric materials. One route to optimization of these compounds is by doping on the Co site. An obvious candidate for an n-type dopant is Ni, because it has one more electron in its valence shell than Co. We present electrical resistivity, thermopower, Hall effect and magnetic susceptibility measurements on polycrystalline, n-type Co1-xNixSb3 with x less than 0.01. A model which takes into account conduction of electrons residing in the conduction band in addition to hopping conduction within an impurity "band" formed …

Weak-Singlet Fermions: Models And Constraints, Marko Popovic, Elizabeth Simmons

Marko B. Popovic

We employ data from precision electroweak tests and collider searches to derive constraints on the possibility that weak-singlet fermions mix with the ordinary standard model fermions. Our findings are presented within the context of a theory with weak-singlet partners for all ordinary fermions and theories in which only third-generation fermions mix with weak singlets. In addition, we indicate how our results can be applied more widely in theories containing exotic fermions.

Fuzzy Neural Network Models For Classification, Arun D. Kulkarni, Charles D. Cavanaugh

Arun Kulkarni

The Spectral Function Of A Composite From Reflectance Data., Anthony Day, M. Thorpe, A. Grant, A. Sievers

Anthony Roy Day

In the Bergman-Milton spectral representation for the effective dielectric constant of a composite all relevant geometric information is captured in a spectral function that is independent of material properties. We present numerical simulations of the reflectance of a model two component composite, where both components have temperature-dependant dielectric resonances, and show that the spectral function can be extracted from the data. The same spectral function is obtained from simulation data corresponding to different temperatures but the resolution depends on the width of the resonance line and is greatest at low-temperatures.

Infrared Spectro-Electrochemistry, Mark Anderson, C. Douglas Taylor

Mark R. Anderson

The combination of infrared (IR) spectroscopy and electrochemistry in a single measurement has been an area of active research interest since the late 1960s. IR spectroelectrochemical experiments provide insight about interfacial electrochemical phenomena and/or oxidation–reduction reaction mechanisms that cannot be obtained using either technique individually. The power of the measurement is in the complementary nature of the spectroscopic and electrochemical information available when obtained simultaneously. The combination of measurements, however, requires compromise between the IR spectroscopy and the electrochemistry because of their different sampling requirements. The need for compromise illustrates the unique strengths and weaknesses of the combined spectroelectrochemical measurement. …

Interactive Real Analysis. / Glossary, Bert Wachsmuth

Bert Wachsmuth

No abstract provided.

Clusterin Is An Atp-Independent Chaperone With Very Broad Substrate Specificity That Stabilizes Stressed Proteins In A Folding-Competent State, Stephen Poon, Simon Easterbrook-Smith, Mark Rybchyn, John Carver, Mark Wilson

Mark R Wilson

We recently reported that the ubiquitous, secreted protein clusterin has chaperone activity in vitro [Humphreys et al. (1999) J. Biol. Chem. 274, 6875−6881]. In this study, we demonstrate that clusterin (i) inhibits stress-induced precipitation of a very broad range of structurally divergent protein substrates, (ii) binds irreversibly via an ATP-independent mechanism to stressed proteins to form solubilized high molecular weight complexes, (iii) lacks detectable ATPase activity, (iv) when acting alone, does not effect refolding of stressed proteins in vitro, and (v) stabilizes stressed proteins in a state competent for refolding by heat shock protein 70 (HSP70). Furthermore, we show that, …

Making Connections Between Metallofullerenes And Fullerenes: Electrochemical Investigations, Mark Anderson, Harry Dorn, Steven Stevenson

Mark R. Anderson

The square-wave voltammetry for a series of related fullerenes and metallofullerenes measured in pyridine solutions containing 0.10 M tetra-n-butylammonium perchlorate is reported. Several dimetallic metallofullerenes, M2@Cx (where M=Sc or Er, and x=82 or 84), are found to have similar voltammetric responses regardless of metal identity or carbon number. Assignment of formal charges to the fullerene cage suggests that these metallofullerenes are isoelectronic and have related molecular orbital structures. The voltammetry of the empty C82 and D2d-C84 cages are also alike, but are different from the square-wave voltammetry of the C60, C70, and D2-C84. The similarity of the voltammetry for C82 …

Structural And Topographic Evolution Of The Central Transverse Ranges, California, From Apatite Fission- Track, (U-Th)/He And Digital Elevation Model Analyses, Ann Blythe, D Burbank, K Farley, E Fielding

Ann Blythe

No abstract provided.

Logic-Based Methods For Optimization: Combining Optimization And Constraint Satisfaction, John Hooker

John Hooker

No abstract provided.

Internal Waves Revealed By Synthetic Aperture Radar (Sar) Imagery In The Vicinity Of The Eastern Cretan Arc Straits (Eastern Mediterranean), Adonis Velegrakis, E. Oikonomou, A. Theocharis, M Collins, H Kontoyannis, V Papadopoulos, George Voulgaris, T. Wells, E. Balopoulos

George Voulgaris

Internal waves have been detected on ERS-1 SAR images obtained during late summer over the eastern Cretan Straits, an area characterised by complex regional physiography, bottom topography, flow regime and stratification patterns of the upper part of the water column. Analysis of the imaged characteristics of the internal waves has revealed a strong diversity in form, propagation direction and type of sea surface modulation, which indicates various mechanisms of generation. Analysis of the currents recorded over the area shows that, although semi-diurnal tidal currents are present, these are of low magnitude in comparison with the overall flow and, therefore, tidal …

Fuzzy Neural Network Models For Supervised Classification: Multispectral Image Analysis, Arun D. Kulkarni, Kamlesh Lulla

Arun Kulkarni

No abstract provided.

Phase Imaging: Deep Or Superficial?, Nancy Burnham, O Behrend, L Odoni, J Loubet

Nancy A. Burnham

Phase images acquired while intermittently contacting a sample surface with the tip of an atomic force microscope cantilever are not easy to relate to material properties. We have simulated dynamic force curves and compared simulated with experimental results. For some cantilever–sample combinations, the interaction remains a surface effect, whereas for others, the tip penetrates the sample significantly. Height artifacts in the “topography” images, and the role of the sample stiffness, work of adhesion, damping, and topography in the cantilever response manifest themselves to different extents depending on the indentation depth.