Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2009

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 661 - 690 of 7616

Full-Text Articles in Physical Sciences and Mathematics

Bayesian Analysis Of Evidence From Studies Of Warfarin V Aspirin For Symptomatic Intracranial Stenosis, Vicki Hertzberg, Barney Stern, Karen Johnston Nov 2009

Bayesian Analysis Of Evidence From Studies Of Warfarin V Aspirin For Symptomatic Intracranial Stenosis, Vicki Hertzberg, Barney Stern, Karen Johnston

Journal of Modern Applied Statistical Methods

Bayesian analyses of symptomatic intracranial stenosis studies were conducted to compare the benefits of long-term therapy with warfarin to aspirin. The synthesis of evidence of effect from previous nonrandomized studies in monitoring a randomized clinical trial was of particular interest. Sequential Bayesian learning analysis was conducted and Bayesian hierarchical random effects models were used to incorporate variability between studies. The posterior point estimates for the risk rate ratio (RRR) were similar between analyses, although the interval estimates resulting from the hierarchical analyses are larger than the corresponding Bayesian learning analyses. This demonstrated the difference between these methods in accounting for …

Go to article

A Maximum Test For The Analysis Of Ordered Categorical Data, Markus Neuhäeuser Nov 2009

A Maximum Test For The Analysis Of Ordered Categorical Data, Markus Neuhäeuser

Journal of Modern Applied Statistical Methods

Different scoring schemes are possible when performing exact tests using scores on ordered categorical data. The standard scheme is based on integer scores, but non-integer scores were proposed to increase power (Ivanova & Berger, 2001). However, different non-integer scores exist and the question arises as to which of the non-integer schemes should be chosen. To solve this problem, a maximum test is proposed. To be precise, the maximum of the competing statistics is used as the new test statistic, rather than arbitrarily choosing one single test statistic.

Go to article

An Inductive Approach To Calculate The Mle For The Double Exponential Distribution, W. J. Hurley Nov 2009

An Inductive Approach To Calculate The Mle For The Double Exponential Distribution, W. J. Hurley

Journal of Modern Applied Statistical Methods

Norton (1984) presented a calculation of the MLE for the parameter of the double exponential distribution based on the calculus. An inductive approach is presented here.

Go to article

New Effect Size Rules Of Thumb, Shlomo S. Sawilowsky Nov 2009

New Effect Size Rules Of Thumb, Shlomo S. Sawilowsky

Journal of Modern Applied Statistical Methods

Recommendations to expand Cohen’s (1988) rules of thumb for interpreting effect sizes are given to include very small, very large, and huge effect sizes. The reasons for the expansion, and implications for designing Monte Carlo studies, are discussed.

Go to article

Multiple Search Paths And The General-To-Specific Methodology, Paul Turner Nov 2009

Multiple Search Paths And The General-To-Specific Methodology, Paul Turner

Journal of Modern Applied Statistical Methods

Increased interest in computer automation of the general-to-specific methodology has resulted from research by Hoover and Perez (1999) and Krolzig and Hendry (2001). This article presents simulation results for a multiple search path algorithm that has better properties than those generated by a single search path. The most noticeable improvements occur when the data contain unit roots.

Go to article

Intermediate R Values For Use In The Fleishman Power Method, Julie M. Smith Nov 2009

Intermediate R Values For Use In The Fleishman Power Method, Julie M. Smith

Journal of Modern Applied Statistical Methods

Several intermediate r values are calculated at three different correlations for use in the Fleishman Power Method for generating correlated data from normal and non-normal populations.

Go to article

Ordinal Regression Analysis: Fitting The Proportional Odds Model Using Stata, Sas And Spss, Xing Liu Nov 2009

Ordinal Regression Analysis: Fitting The Proportional Odds Model Using Stata, Sas And Spss, Xing Liu

Journal of Modern Applied Statistical Methods

Researchers have a variety of options when choosing statistical software packages that can perform ordinal logistic regression analyses. However, statistical software, such as Stata, SAS, and SPSS, may use different techniques to estimate the parameters. The purpose of this article is to (1) illustrate the use of Stata, SAS and SPSS to fit proportional odds models using educational data; and (2) compare the features and results for fitting the proportional odds model using Stata OLOGIT, SAS PROC LOGISTIC (ascending and descending), and SPSS PLUM. The assumption of the proportional odds was tested, and the results of the fitted models were …

Go to article

Generating And Comparing Aggregate Variables For Use Across Datasets In Multilevel Analysis, James Chowhan, Laura Duncan Nov 2009

Generating And Comparing Aggregate Variables For Use Across Datasets In Multilevel Analysis, James Chowhan, Laura Duncan

Journal of Modern Applied Statistical Methods

This article examines the creation of contextual aggregate variables from one dataset for use with another dataset in multilevel analysis. The process of generating aggregate variables and methods of assessing the validity of the constructed aggregates are presented, together with the difficulties that this approach presents.

Go to article

Jmasm28: Gibbs Sampling For 2pno Multi-Unidimensional Item Response Theory Models (Fortran), Yanyan Sheng, Todd C. Headrick Nov 2009

Jmasm28: Gibbs Sampling For 2pno Multi-Unidimensional Item Response Theory Models (Fortran), Yanyan Sheng, Todd C. Headrick

Journal of Modern Applied Statistical Methods

A Fortran 77 subroutine is provided for implementing the Gibbs sampling procedure to a multiunidimensional IRT model for binary item response data with the choice of uniform and normal prior distributions for item parameters. In addition to posterior estimates of the model parameters and their Monte Carlo standard errors, the algorithm also estimates the correlations between distinct latent traits. The subroutine requires the user to have access to the IMSL library. The source code is available at http://www.siuc.edu/~epse1/sheng/Fortran/MUIRT/GSMU2.FOR. An executable file is also provided for download at http://www.siuc.edu/~epse1/sheng/Fortran/MUIRT/EXAMPLE.zip to demonstrate the implementation of the algorithm on simulated data.

Go to article

Presence Of A Long-Term Lithospheric Thermal Anomaly: Evidence From Apatite Fission-Track Analysis In Northern New England, Mary K. Roden-Tice, David P. West Jr., Jaime K. Potter, Sarah M. Raymond, Jenny L. Winch Nov 2009

Presence Of A Long-Term Lithospheric Thermal Anomaly: Evidence From Apatite Fission-Track Analysis In Northern New England, Mary K. Roden-Tice, David P. West Jr., Jaime K. Potter, Sarah M. Raymond, Jenny L. Winch

Mary K. Roden-Tice

Apatite fission-track (AFT) ages from 56 samples of Paleozoic and Mesozoic crystalline rocks in New Hampshire, northeastern Vermont, and western Maine range from 70 to 140 Ma and reflect widespread Early to Late Cretaceous cooling. The regional AFT age distributions determined in this study suggest that reactivation of preexisting orogen-parallel faults and the presence of a long-lived thermal anomaly in the lithospheric mantle controlled the late unroofing history of this part of the northern Appalachians. A northeast-trending zone of young, dominantly Late Cretaceous AFT ages (70-118 Ma) extends from southwestern New Hampshire through the central White Mountain region and continues …

Go to article

The Symmetric Positive Solutions Of Four-Point Problems For Nonlinear Boundary Value Second-Order Differential Equations, Qu Haidong Nov 2009

The Symmetric Positive Solutions Of Four-Point Problems For Nonlinear Boundary Value Second-Order Differential Equations, Qu Haidong

qu haidong

In this paper, we are concerned with the existence of symmetric positive solutions for second-order differential equations. Under the suitable conditions, the existence and symmetric positive solutions are established by using Krasnoselskii’s fixed-point theorems.

Go to article

Bipolar Electrode Focusing: The Effect Of Current And Electric Field On Concentration Enrichment, Robbyn K. Perdue, Derek R. Laws, Dzmitry Hlushkou, Ulrich Tallarek, Richard M. Crooks Nov 2009

Bipolar Electrode Focusing: The Effect Of Current And Electric Field On Concentration Enrichment, Robbyn K. Perdue, Derek R. Laws, Dzmitry Hlushkou, Ulrich Tallarek, Richard M. Crooks

Robbyn Anand

Bipolar electrode focusing at discontinuous bipolar electrodes (BPEs) provides new insight into the faradaic current and electric field characteristics associated with the technique and allows for the controlled transport of a focused anionic tracer in a microfluidic channel. The findings corroborate our previously reported simulation results, which describe the formation of an extended electric field gradient leading to concentration enrichment. This gradient has been attributed to the passage of faradaic current through a BPE affixed to the floor of the microchannel. Our results demonstrate that the onset of faradaic current is coincident with the onset of concentration enrichment. Utilizing an …

Go to article

High-Dimensional Software Engineering Data And Feature Selection, Huanjing Wang, Taghi M. Khoshgoftaar, Kehan Gao Nov 2009

High-Dimensional Software Engineering Data And Feature Selection, Huanjing Wang, Taghi M. Khoshgoftaar, Kehan Gao

Dr. Huanjing Wang

Software metrics collected during project development play a critical role in software quality assurance. A software practitioner is very keen on learning which software metrics to focus on for software quality prediction. While a concise set of software metrics is often desired, a typical project collects a very large number of metrics. Minimal attention has been devoted to finding the minimum set of software metrics that have the same predictive capability as a larger set of metrics – we strive to answer that question in this paper. We present a comprehensive comparison between seven commonly-used filter-based feature ranking techniques (FRT) …

Go to article

Insights And Opportunities: Technologies, Policies, And Markets For Clean Energy Solutions, Douglas J. Arent Nov 2009

Insights And Opportunities: Technologies, Policies, And Markets For Clean Energy Solutions, Douglas J. Arent

Publications (E)

A presentation highlighting how strategic energy analysis can affect technologies, policies, and markets for clean energy solutions. This includes an overview of some of NREL's models and tools as well as results from laboratory analysis.

Go to article

Synthesis And Evaluation Of Some Steroidal Oximes As Cytotoxic Agents: Structure/Activity Studies (Ii), Jianguo Cui, Lei Fan, Yanmin Huang, Yi Xin, Aimin Zhou Nov 2009

Synthesis And Evaluation Of Some Steroidal Oximes As Cytotoxic Agents: Structure/Activity Studies (Ii), Jianguo Cui, Lei Fan, Yanmin Huang, Yi Xin, Aimin Zhou

Chemistry Faculty Publications

Hydroximinosteroids isolated from marine sponges display a variety of biological functions including cytotoxicity and anti-virus. In this study, we synthesized a series of hydroximinosteroid derivatives with a different functional group on the ring A or B and various side chains at position 17, and analyzed the cytotoxicity of these compounds against sk-Hep-1, H-292, PC-3 and Hey-1B cancer cells. Our results revealed that although a cholesterol-type side chain at position 17 is required for the biological activity of the compounds as we previously confirmed, elimination of the 4,5-double bond augmented the cytotoxic activity for the steroidal oximes. In addition, the presence …

Go to article

How Does The Relocation Of Internal Water Affect Resonance Raman Spectra Of Rhodopsin? An Insight From Casscf/Amber Calculations, Tadeusz Andruniow, Massimo Olivucci Nov 2009

How Does The Relocation Of Internal Water Affect Resonance Raman Spectra Of Rhodopsin? An Insight From Casscf/Amber Calculations, Tadeusz Andruniow, Massimo Olivucci

Chemistry Faculty Publications

The effect of relocation of the W2 crystallographic water in bovine rhodopsin has been investigated by comparing and analyzing simulated resonance Raman spectra of I HZX-and 1U19-based quantum mechanics/molecular mechanics (CASSCF/MM) models. The main target is to explore the sensitivity of the simulated resonance Raman spectra to protein cavity change. In particular, we focus on a quantitative investigation of the changes in the vibrational activity of rhodopsin induced by modifications in the protein cavity structure and in the water position. Comparison of the simulated FIR spectra of the Rh-1U19 and Rh-1HZX models with the measured spectrum of rhodopsin reveals that …

Go to article

Size-Biased Branching Population Measures And The Multi-Type X Log X Condition, Peter Olofsson Nov 2009

Size-Biased Branching Population Measures And The Multi-Type X Log X Condition, Peter Olofsson

Mathematics Faculty Research

We investigate the x log x condition for a general (Crump–Mode–Jagers) multi-type branching process with arbitrary type space by constructing a size-biased population measure that relates to the ordinary population measure via the intrinsic martingale Wt. Sufficiency of the x log x condition for a non-degenerate limit of Wt is proved and conditions for necessity are investigated.

Go to article

Validity Of The Spin-Susceptibility “Glue” Approximation For Pairing In The Two-Dimensional Hubbard Model, Ehsan Khatami, A. Macridin, M. Jarrell Nov 2009

Validity Of The Spin-Susceptibility “Glue” Approximation For Pairing In The Two-Dimensional Hubbard Model, Ehsan Khatami, A. Macridin, M. Jarrell

Faculty Publications

We examine the validity of the weak-coupling spin-susceptibility “glue” approximation (SSGA) in a two-dimensional Hubbard model for cuprates. For comparison, we employ the well-established dynamical cluster approximation (DCA) with a quantum Monte Carlo algorithm as a cluster solver. We compare the leading eigenvalues and corresponding eigenfunctions of the DCA and SSGA pairing matrices. For realistic model parameters, we find that the SSGA fails to capture the leading pairing symmetries seen in the DCA. Furthermore, when the SSGA is improved through the addition of a term with d-wave symmetry, the strength of this additional term is found to be larger than …

Go to article

Interior-Point Algorithms For A Class Of Convex Optimization Problems, Goran Lesaja, Verlynda Slaughter Nov 2009

Interior-Point Algorithms For A Class Of Convex Optimization Problems, Goran Lesaja, Verlynda Slaughter

Department of Mathematical Sciences Faculty Publications

In this paper we consider interior-point methods (IPM) for the nonlinear, convex optimization problem where the objective function is a weighted sum of reciprocals of variables subject to linear constraints (SOR). This problem appears often in various applications such as statistical stratified sampling and entropy problems, to mention just few examples. The SOR is solved using two IPMs. First, a homogeneous IPM is used to solve the Karush-Kuhn-Tucker conditions of the problem which is a standard approach. Second, a homogeneous conic quadratic IPM is used to solve the SOR as a reformulated conic quadratic problem. As far as we are …

Go to article

The Nitsche Conjecture, Tadeusz Iwaniec, Leonid V. Kovalev, Jani Onninen Nov 2009

The Nitsche Conjecture, Tadeusz Iwaniec, Leonid V. Kovalev, Jani Onninen

Mathematics - All Scholarship

The conjecture in question concerns the existence of a harmonic homeomorphism between circular annuli A(r,R) and A(r*,R*), and is motivated in part by the existence problem for doubly-connected minimal surfaces with prescribed boundary. In 1962 J.C.C. Nitsche observed that the image annulus cannot be too thin, but it can be arbitrarily thick (even a punctured disk). Then he conjectured that for such a mapping to exist we must have the following inequality, now known as the Nitsche bound: R*/r* is greater than or equal to (R/r+r/R)/2. In this paper we give an affirmative answer to his conjecture. As a corollary, …

Go to article

Improving Replica Exchange Using Driven Scaling, Steven W. Rick Nov 2009

Improving Replica Exchange Using Driven Scaling, Steven W. Rick

Chemistry Faculty Publications

Replica exchange is a powerful simulation method in which simulations are run at a series of temperatures, with the highest temperature chosen so phase space can be sampled efficiently. In order for swaps to be accepted, the energy distributions of adjacent replicas must have some overlap. This can create the need for many replicas for large systems. In this paper, we present a new method in which the potential energy is scaled by a parameter, which has an explicit time dependence. Scaling the potential energy broadens the distribution of energy and reduces the number of replicas necessary to span a …

Go to article

An Anytime Algorithm For Computing Inconsistency Measurement, Yue Ma, Guilin Qi, Guohui Xiao, Pascal Hitzler, Zuoquan Lin Nov 2009

An Anytime Algorithm For Computing Inconsistency Measurement, Yue Ma, Guilin Qi, Guohui Xiao, Pascal Hitzler, Zuoquan Lin

Computer Science and Engineering Faculty Publications

Measuring inconsistency degrees of inconsistent knowledge bases is an important problem as it provides context information for facilitating inconsistency handling. Many methods have been proposed to solve this problem and a main class of them is based on some kind of paraconsistent semantics. In this paper, we consider the computational aspects of inconsistency degrees of propositional knowledge bases under 4-valued semantics. We first analyze its computational complexity. As it turns out that computing the exact inconsistency degree is intractable, we then propose an anytime algorithm that provides tractable approximation of the inconsistency degree from above and below. We show that …

Go to article

The Regular Excluded Minors For Signed-Graphic Matroids, Hongxun Qin, Dan Slilaty, Xiangqian Zhou Nov 2009

The Regular Excluded Minors For Signed-Graphic Matroids, Hongxun Qin, Dan Slilaty, Xiangqian Zhou

Mathematics and Statistics Faculty Publications

We show that the complete list of regular excluded minors for the class of signed-graphic matroids is M*(G1),...,M*(G29),R15,R16. Here G1,...,G29 are the vertically 2-connected excluded minors for the class of projective-planar graphs and R15 and R16 are two regular matroids that we will define in the article.

Go to article

John Muir: A Rugged, Religious, Sensitive Mountain Man, Bradley B. Ward Nov 2009

John Muir: A Rugged, Religious, Sensitive Mountain Man, Bradley B. Ward

MALS Final Projects, 1995-2019

John Muir is known for having helped found the Sierra Club, and for having been its first president. Muir Woods, a grove of old-growth redwoods and popular tourist destination north of San Francisco, is named for him. California's state quarter features Muir and world-renowned Yosemite National Park, which he assisted in founding. He also fought to prevent the Tuolumne River from being dammed to create the Hetch Hetchy reservoir. Thus, Muir clearly possessed conservationist attitudes and ardently practiced them.

Go to article

Instability In Leapfrog And Forward–Backward Schemes, Wen-Yih Sun Nov 2009

Instability In Leapfrog And Forward–Backward Schemes, Wen-Yih Sun

Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications

No abstract provided.

Go to article

Estimating The Parameters Of Rayleigh Cumulative Exposure Model In Simple Step-Stress Testing. Natasha Beretvas Is An, Mohammed Al-Haj Ebrahem, Abedel-Qader Al-Masri Nov 2009

Estimating The Parameters Of Rayleigh Cumulative Exposure Model In Simple Step-Stress Testing. Natasha Beretvas Is An, Mohammed Al-Haj Ebrahem, Abedel-Qader Al-Masri

Journal of Modern Applied Statistical Methods

Assumes the life distribution of a test unit for any stress follows a Rayleigh distribution with scale parameterθ , and that Ln(θ ) is a linear function of the stress level. Maximum likelihood estimators of the parameters under a cumulative exposure model are obtained. The approximate variance estimates obtained from the asymptotic normal distribution of the maximum likelihood estimators are used to construct confidence intervals for the model parameters. A simulation study was conducted to study the performance of the estimators. Simulation results showed that in terms of bias, mean squared error, attainment of the nominal confidence level, symmetry …

Go to article

Estimation Of The Standardized Mean Difference For Repeated Measures Designs, Lindsey J. Wolff Smith, S. Natasha Beretvas Nov 2009

Estimation Of The Standardized Mean Difference For Repeated Measures Designs, Lindsey J. Wolff Smith, S. Natasha Beretvas

Journal of Modern Applied Statistical Methods

This simulation study modified the repeated measures mean difference effect size, d=RM , for scenarios with unequal pre- and post-test score variances. Relative parameter and SE bias were calculated for dRM ≠ versus dRM = . Results consistently favored d≠RM over d=RM with worse positive parameter and negative SE bias identified for d=RM for increasingly heterogeneous variance conditions.

Go to article

Refuge Update – November/December 2009, Volume 6, Number 6 Nov 2009

Refuge Update – November/December 2009, Volume 6, Number 6

RefugeUpdate (USFWS-NWRS)

Table of Contents:

Tufted Puffin Released A rehabilitated puffin gingerly tests freedom at Oregon Islands National Wildlife Refuge.

FOCUS: Stories of Hope From cemeteries to woodpeckers, to newspaper columns and support at the ballot box, refuges represent stories of hope as they pursue their mission.

Bats in the Barn Scientists and volunteers wrap a barn in plastic and count the bats inside.

Sense of Wonder Award Jim Burkhart shares the joy and mysteries of the natural world with visitors to Okefenokee National Wildlife Refuge, GA.

Go to article

Smartstore: A New Metadata Organization Paradigm With Semantic-Awareness For Next-Generation File Systems, Yu Hua, Hong Jiang, Yifeng Zhu, Dan Feng, Lei Tian Nov 2009

Smartstore: A New Metadata Organization Paradigm With Semantic-Awareness For Next-Generation File Systems, Yu Hua, Hong Jiang, Yifeng Zhu, Dan Feng, Lei Tian

CSE Conference and Workshop Papers

Existing storage systems using hierarchical directory tree do not meet scalability and functionality requirements for exponentially growing datasets and increasingly complex queries in Exabyte-level systems with billions of files. This paper proposes semantic-aware organization, called SmartStore, which exploits metadata semantics of files to judiciously aggregate correlated files into semantic-aware groups by using information retrieval tools. Decentralized design improves system scalability and reduces query latency for complex queries (range and top-k queries), which is conducive to constructing semantic-aware caching, and conventional filename-based query. SmartStore limits search scope of complex query to a single or a minimal number of semantically related groups …

Go to article

Why It Managers Don't Go For Cyber-Insurance Products, Tridib Bandyopadhyay, Vijay S. Mookerjee, Ram C. Rao Nov 2009

Why It Managers Don't Go For Cyber-Insurance Products, Tridib Bandyopadhyay, Vijay S. Mookerjee, Ram C. Rao

Faculty Articles

Despite positive expectations, cyber-insurance products have failed to take center stage in the management of IT security risk. Market inexperience, leading to conservatism in pricing cyber-insurance instruments, is often cited as the primary reason for the limited growth of the cyber-insurance market. In contrast, here we provide a demand-side explanation for why cyber-insurance products have not lived up to their initial expectations. We highlight the presence of information asymmetry between customers and providers, showing how it leads to overpricing cyber-insurance contracts and helps explain why cyber insurance might have failed to deliver its promise as a cornerstone of IT security-management …

Go to article

First Prev Next Last