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Articles 15691 - 15720 of 16838

Full-Text Articles in Physical Sciences and Mathematics

The Conspicuous Absence Of X-Ray Emission From Carbon-Enriched Wolf-Rayet Stars., L. M. Oskinova, R. Ignace, W.-R. Hamann, A. M. T. Pollock, J. C. Brown Apr 2003

The Conspicuous Absence Of X-Ray Emission From Carbon-Enriched Wolf-Rayet Stars., L. M. Oskinova, R. Ignace, W.-R. Hamann, A. M. T. Pollock, J. C. Brown

Richard Ignace

The carbon-rich WC5 star WR 114 was not detected during a 15.9 ksec XMM-Newton observation, implying an upper limit to the X-ray luminosity of L-X less than or similar to 2.5 x 10(30) erg s(-1) and to the X-ray to bolometric luminosity ratio of L-X/L(bo)l less than or similar to 4 x 10(-9). This confirms indications from earlier less sensitive measurements that there has been no convincing X-ray detection of any single WC star. This lack of detections is reinforced by XMM-Newton and Chandra observations of WC stars. Thus the conclusion has to be drawn that the stars with radiatively-driven …


Three-Dimensional Quantitative Structure−Property Relationship (3d-Qspr) Models For Prediction Of Thermodynamic Properties Of Polychlorinated Biphenyls (Pcbs): Enthalpies Of Fusion And Their Application To Estimates Of Enthalpies Of Sublimation And Aqueous Solubilities, Swati Puri, James S. Chickos, William J. Welsh Apr 2003

Three-Dimensional Quantitative Structure−Property Relationship (3d-Qspr) Models For Prediction Of Thermodynamic Properties Of Polychlorinated Biphenyls (Pcbs): Enthalpies Of Fusion And Their Application To Estimates Of Enthalpies Of Sublimation And Aqueous Solubilities, Swati Puri, James S. Chickos, William J. Welsh

James Chickos

No abstract provided.


Effect Of Sn Substituting For Sb On The Low-Temperature Transport Properties Of Ytterbium-Filled Skutterudites, J. Yang, D. Morelli, G. Meisner, W. Chen, Jeffrey Dyck, C. Uher Apr 2003

Effect Of Sn Substituting For Sb On The Low-Temperature Transport Properties Of Ytterbium-Filled Skutterudites, J. Yang, D. Morelli, G. Meisner, W. Chen, Jeffrey Dyck, C. Uher

Jeffrey Dyck

We examine the effect of alloying Sn on the Sb site of ytterbium-filled skutterudites, a promising class of thermoelectric materials. We report measurements of the Hall effect, electrical resistivity, Seebeck coefficient, and thermal conductivity between 2 and 300 K on two series of samples having different ytterbium filling fractions: Yb0.19Co4Sb12-xSnx, with x=0, 0.05, 0.1, and 0.2, and Yb0.5Co4Sb12-xSnx, with x=0.5, 0.6, 0.8, 0.83, and 0.9. We find that the substitution of Sn does not lower the electron concentration of these samples, but rather gives rise to a p-type carrier. Hall measurement data for Yb0.5Co4Sb11.17Sn0.83 can be understood in the context …


Waves And Current, Christopher Roman Mar 2003

Waves And Current, Christopher Roman

Christopher N. Roman

Article that appeared in Sail magazine (ISSN: 0036-2700).


A New Class Of Entropy Estimators For Multi-Dimensional Densities, Erik G. Learned-Miller Mar 2003

A New Class Of Entropy Estimators For Multi-Dimensional Densities, Erik G. Learned-Miller

Erik G Learned-Miller

We present a new class of estimators for approximating the entropy of multi-dimensional probability densities based on a sample of the density. These estimators extend the classic "m-spacing" estimators of Vasicek (1976) and others for estimating entropies of one-dimensional probability densities. Unlike plug-in estimators of entropy, which first estimate a probability density and then compute its entropy. our estimators avoid the difficult intermediate step of density estimation. For fixed dimension. the estimators an polynomial in the sample size. Similarities to consistent and asymptotically efficient one-dimensional estimators of entropy suggest that our estimators may sham these properties.


Development Of A Regression Model For Estimating The Effects Of Assumption Violations On Type I Error Rates In The Student's T Test: Implications For Practitioners, John Fraas, Isadore Newman, Rosalie J. Hall Mar 2003

Development Of A Regression Model For Estimating The Effects Of Assumption Violations On Type I Error Rates In The Student's T Test: Implications For Practitioners, John Fraas, Isadore Newman, Rosalie J. Hall

John W. Fraas

No abstract provided.


Microlensing Of Circumstellar Envelopes Ii. Emission Lines From Radial And Azimuthal Flow During Fold Caustic Crossings., H. M. Bryce, R. Ignace, M. A. Hendry Mar 2003

Microlensing Of Circumstellar Envelopes Ii. Emission Lines From Radial And Azimuthal Flow During Fold Caustic Crossings., H. M. Bryce, R. Ignace, M. A. Hendry

Richard Ignace

This paper examines the line profile evolution due to bulk motion in circumstellar envelopes during microlensing fold caustic crossing events. These events have recently been shown to be a sensitive probe of stellar surface brightness profiles, thus providing a means - through both photometric and spectroscopic observations - to constrain and test stellar atmosphere models. Here it is demonstrated, through the examination of simplified line profiles, that spectroscopic studies of fold caustic crossings could also prove to be a powerful diagnostic of bulk motion in circumstellar envelopes.


Electrochemical Detection Of Oxidative Stress, Alice Harper, Mark Anderson Mar 2003

Electrochemical Detection Of Oxidative Stress, Alice Harper, Mark Anderson

Mark R. Anderson

No abstract is currently available.


Studies Of Monolayer Films As Adhesion Promoters, Huimin Li, Mark Anderson Mar 2003

Studies Of Monolayer Films As Adhesion Promoters, Huimin Li, Mark Anderson

Mark R. Anderson

No abstract is currently available.


Capillary Electrophoresis To Determine Oxidative Stress, Stephanie Hooper, Mark Anderson Mar 2003

Capillary Electrophoresis To Determine Oxidative Stress, Stephanie Hooper, Mark Anderson

Mark R. Anderson

No abstract is currently available.


Raman Spectroscopy Of Rhombohedral P4o10, Sean J. Gilliam, Scott Kirkby, Clifton N. Merrow, Daniel Zeroka, Ajit Banerjee, James O. Jensen Mar 2003

Raman Spectroscopy Of Rhombohedral P4o10, Sean J. Gilliam, Scott Kirkby, Clifton N. Merrow, Daniel Zeroka, Ajit Banerjee, James O. Jensen

Scott J. Kirkby

A complete Raman vibrational analysis has been performed on phase-pure rhombohedral phosphorus pentoxide (P4O10) at room temperature. The “molecular” Td symmetry is reduced to C3v symmetry when bound in the rhombohedral crystalline lattice. Therefore, the 15 fundamental modes of vibration irreducibly represented as Γvib = 3A1 + 3E + 3T1 + 6T2 reduce to 21 fundamental modes with a factor group analysis resulting in Γvib = 9A1 + 12E for the irreducible representation, all of which are Raman active. Complete vibrational assignments and relative intensities, including all T2 to E and A1 splittings, are reported. Five new E fundamentals (262, …


Global Challenges Show, Nat Quansah Feb 2003

Global Challenges Show, Nat Quansah

Nat Quansah

No abstract provided.


Enabling Predictable Assembly, Scott A. Hissam, Gabriel A. Moreno, Judith Stafford, Kurt C. Wallnau Feb 2003

Enabling Predictable Assembly, Scott A. Hissam, Gabriel A. Moreno, Judith Stafford, Kurt C. Wallnau

Gabriel A. Moreno

Demands for increased functionality, better quality, and faster time-to-market in software products continue to increase. Component-based development is the software industry’s response to these demands. The industry has developed technologies such as EJB and CORBA to assemble components that are created in isolation. Component technologies available today allow designers to plug components together, but do little to allow the developer to reason about how well they will play together. Predictable assembly focuses on issues related to assembling component-based systems that predictably meet their quality attribute requirements. This paper introduces prediction-enabled component technology (PECT) as a means of packaging predictable assembly …


Benefits Of A Comprehensive Undergraduate Teaching Assistant Program, Christopher Goff, Brigitte Lahme Feb 2003

Benefits Of A Comprehensive Undergraduate Teaching Assistant Program, Christopher Goff, Brigitte Lahme

Christopher Goff

The Undergraduate Teaching Assistant (UTA) Program at the University of Arizona exposes students to many different aspects of teaching an undergraduate mathematics course. The program's breadth generates various qualitative and quantitative benefits. Some of these benefits are that the UTAs improve their mathematics and communications skills, instructors have additional support both inside and outside the classroom, and mathematics students in classes with UTAs enjoy their mathematics classes more than students in similar classes without UTAs.


Using Scienti, Elizabeth Shoop, P. Wagner, J.V. Carlis Jan 2003

Using Scienti, Elizabeth Shoop, P. Wagner, J.V. Carlis

Elizabeth Shoop

No abstract provided.


The Mysterious Marine Layer, Christopher Roman Jan 2003

The Mysterious Marine Layer, Christopher Roman

Christopher N. Roman

Article that appeared in Sail magazine (ISSN: 0036-2700).


Ordinary Least Squares Regression, Discriminant Analysis,And Logisitic Regression: Questions Researchers And Practioners Should Address When Selecting An Analytic Technique, John Fraas, Isadore Newman Jan 2003

Ordinary Least Squares Regression, Discriminant Analysis,And Logisitic Regression: Questions Researchers And Practioners Should Address When Selecting An Analytic Technique, John Fraas, Isadore Newman

John W. Fraas

No abstract provided.


Evolution Of Microstructure And Phase In Amorphous, Protocrystalline, And Microcrystalline Silicon Studied By Real Time Spectroscopic Ellipsometry, R. W. Collins, A. S. Ferlauto, G. M. Ferreira, Chi Chen, Joohyun Koh, R. J. Koval, Joshua M. Pearce, C. R. Wronski Jan 2003

Evolution Of Microstructure And Phase In Amorphous, Protocrystalline, And Microcrystalline Silicon Studied By Real Time Spectroscopic Ellipsometry, R. W. Collins, A. S. Ferlauto, G. M. Ferreira, Chi Chen, Joohyun Koh, R. J. Koval, Joshua M. Pearce, C. R. Wronski

Joshua M. Pearce

Real time spectroscopic ellipsometry has been applied to develop deposition phase diagrams that can guide the fabrication of hydrogenated silicon (Si:H) thin films at low temperatures (<300°C) for highest performance electronic devices such as solar cells. The simplest phase diagrams incorporate a single transition from the amorphous growth regime to the mixed-phase (amorphous+microcrystalline) growth regime versus accumulated film thickness [the a ͢(a+µc) transition]. These phase diagrams have shown that optimization of amorphous silicon (a-Si:H) intrinsic layers by RF plasma-enhanced chemical vapor deposition (PECVD) at low rates is achieved using the maximum possible flow ratio of H₂ to SiH₄ that can …


Implications Of Distributed Crustal Deformation For Exhumation In A Portion Of A Transpressional Plate Boundary, Western Transverse Ranges, Southern California, Andrew Meigs, Dong Yule, Ann Blythe, Doug Burbank Jan 2003

Implications Of Distributed Crustal Deformation For Exhumation In A Portion Of A Transpressional Plate Boundary, Western Transverse Ranges, Southern California, Andrew Meigs, Dong Yule, Ann Blythe, Doug Burbank

Ann Blythe

Spatial and temporal patterns of exhumation are inextricably linked to patterns of crustal deformation because crustal deformation drives rock uplift. A new interpretation of a segment of the Pacific-North America transpressional plate boundary in southern California is analyzed in the context of crustal shortening, rock uplift, and exhumation. Deformation is partitioned between two structural anticlinoria formed above thrust faults that root into a mid-crustal décollement. The southern anticlinorium began growing after 5 Ma and is characterized by almost no topographic expression, rock uplift of ∼3 km, and exhumation of <1.2 km. Deposition in the Los Angeles basin on the south generally kept pace with growth of this anticlinorium. In contrast, the northern anticlinorium is younger, has a significant topographic expression, rock uplift of 2.5–4.0 km, and exhumation of ∼1.5–2 km. On-going surface uplift above the northern anticlinorium is suggested by the mismatch between the magnitude of rock uplift relative to the exhumation. These data emphasize that the distribution of deformation between faults in the upper and middle crust, crustal root formation in the lower crust, and flexural subsidence are primary controls of patterns of exhumation, which together dictate net surface uplift in active orogenic belts.


Heat Capacities Of Thiane Sulfones And Thiane Sulfoxide: Refining Of Cp Group Values For Organosulfur Compounds And Their Oxides, Marı́A Victoria Roux, Manuel Temprado, Pilar Jiménez, Ramón Guzmán-Mejı́A, Eusebio Juaristi, James S. Chickos Jan 2003

Heat Capacities Of Thiane Sulfones And Thiane Sulfoxide: Refining Of Cp Group Values For Organosulfur Compounds And Their Oxides, Marı́A Victoria Roux, Manuel Temprado, Pilar Jiménez, Ramón Guzmán-Mejı́A, Eusebio Juaristi, James S. Chickos

James Chickos

No abstract provided.


Enthalpies Of Vaporization Of Organic And Organometallic Compounds, 1880-2002, James S. Chickos, William E. Acree Jan 2003

Enthalpies Of Vaporization Of Organic And Organometallic Compounds, 1880-2002, James S. Chickos, William E. Acree

James Chickos

No abstract provided.


Ionic Strength Effects On Hexadecane Contact Angles On A Gold-Coated Glass Surface In Ionic Surfactant Solutions, A. Davis, Samuel Morton, R. Counce, D. Depaoli, M. Hu Dec 2002

Ionic Strength Effects On Hexadecane Contact Angles On A Gold-Coated Glass Surface In Ionic Surfactant Solutions, A. Davis, Samuel Morton, R. Counce, D. Depaoli, M. Hu

Samuel A Morton

No abstract provided.


An Insider's View Of Cmm(R) Level 5, Robert Yacobellis Dec 2002

An Insider's View Of Cmm(R) Level 5, Robert Yacobellis

Robert H Yacobellis

No abstract provided.


Mockup-Driven Fast-Prototyping Methodology For Web Application Development, Jia Zhang, Jen-Yao Chung Dec 2002

Mockup-Driven Fast-Prototyping Methodology For Web Application Development, Jia Zhang, Jen-Yao Chung

Jia Zhang

No abstract provided.


Inverting For Heterogeneous Slip On Three-Dimensional Fault Systems; A First Step Toward Understanding Fault Mechanics, Phillip Resor, D Pollard, F Maerten Dec 2002

Inverting For Heterogeneous Slip On Three-Dimensional Fault Systems; A First Step Toward Understanding Fault Mechanics, Phillip Resor, D Pollard, F Maerten

Phillip G Resor

Many studies of earthquake triggering and fault interaction have relied on highly-idealized fault geometries and slip distributions. Geological and geophysical observations, however, reveal that faults typically are not single planar surfaces with uniform slip bounded by rectangular tiplines, but are composed of multiple curved surfaces with curved tiplines and heterogeneous slip distributions. The segments typically are organized into echelon, conjugate, and intersecting patterns. The discontinuities, bends, intersections, and slip heterogeneities generate stress concentrations that may promote or inhibit slip on nearby faults and thus play an important role in the mechanics of fault systems. It is therefore important to incorporate …


Bayesian Modelling And Forecasting Of Intra-Day Electricity Load, Remy Cottet, Michael Smith Dec 2002

Bayesian Modelling And Forecasting Of Intra-Day Electricity Load, Remy Cottet, Michael Smith

Michael Stanley Smith

With the advent of wholesale electricity markets there has been renewed focus on intra-day electricity load forecasting. This paper employs a multi-equation regression model with a diagonal first order stationary vector autoregresson (VAR) for modeling and forecasting intra-day electricity load. The correlation structure of the disturbances to the VAR and the appropriate subset of regressors are explored using Bayesian model selection methodology. The full spectrum of finite sample inference is obtained using a Bayesian Markov chain Monte Carlo sampling scheme. This includes the predictive distribution of load and the distribution of the time and level of daily peak load, something …


Geochemistry Of Kauai Shield-Stage Lavas: Implications For The Chemical Evolution Of The Hawaiian Plume, Scott Bogue, S. Mukhopadhyay, J.C. Lassiter, K.A. Farley Dec 2002

Geochemistry Of Kauai Shield-Stage Lavas: Implications For The Chemical Evolution Of The Hawaiian Plume, Scott Bogue, S. Mukhopadhyay, J.C. Lassiter, K.A. Farley

Scott Bogue

We measured He, Sr, Nd, Pb, and Os isotope ratios and major and trace element concentrations in stratigraphically and paleomagnetically controlled shield-stage lavas from Kauai, Hawaii. The range of 3He/4He ratios (17–28 RA) from Kauai is similar to that reported from Loihi and thus challenges the prevailing notion that high 3He/4He ratios are restricted to the preshield stage of Hawaiian magmatism. 3He/4He ratios vary erratically with stratigraphic position, and chronostratigraphic control from paleomagnetic data indicates very rapid changes in the 3He/4He ratios (up to 8 RA in ∼102 years). These variations in helium isotopic ratios are correlated with variations in …


Working Across Cultures, John Hooker Dec 2002

Working Across Cultures, John Hooker

John Hooker

No abstract provided.


Graphs Of Essentially Equivalent Lattice Paths, Lara Pudwell, Marjorie Brewer, Adam Hughes Dec 2002

Graphs Of Essentially Equivalent Lattice Paths, Lara Pudwell, Marjorie Brewer, Adam Hughes

Lara K. Pudwell

No abstract provided.


Classifying Instantaneous Cognitive States From Fmri Data, Tom Mitchell, Rebecca Hutchinson, Marcel Just, Radu Niculescu, Francisco Pereira, Xuerui Wang Dec 2002

Classifying Instantaneous Cognitive States From Fmri Data, Tom Mitchell, Rebecca Hutchinson, Marcel Just, Radu Niculescu, Francisco Pereira, Xuerui Wang

Marcel Adam Just

No abstract provided.