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2008

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Articles 541 - 570 of 5871

Full-Text Articles in Physical Sciences and Mathematics

Size-Biased Generalized Negative Binomial Distribution, Khurshid Ahmad Mir Nov 2008

Size-Biased Generalized Negative Binomial Distribution, Khurshid Ahmad Mir

Journal of Modern Applied Statistical Methods

A size biased generalized negative binomial distribution (SBGNBD) is defined and a recurrence relationship for the moments of SBGNBD is established. The Bayes’ estimator for a parametric function of one parameter when two other parameters of a known size-biased generalized negative binomial distribution is derived. Prior information on one parameter is given by a beta distribution and the parameters in the prior distribution are assigned by computer using Monte Carlo and R-software.

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Non-Parametric Quantile Selection For Extreme Distributions, Wan Zawiah Wan Zin, Abdul Aziz Jemain Nov 2008

Non-Parametric Quantile Selection For Extreme Distributions, Wan Zawiah Wan Zin, Abdul Aziz Jemain

Journal of Modern Applied Statistical Methods

The objective is to select the best non-parametric quantile estimation method for extreme distributions. This serves as a starting point for further research in quantile application such as in parameter estimation using LQ-moments method. Thirteen methods of non-parametric quantile estimation were applied on six types of extreme distributions and their efficiencies compared. Monte Carlo methods were used to generate the results, which showed that the method of Weighted Kernel estimator of Type 1 was more efficient than the other methods in many cases.

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Analyzing Incomplete Categorical Data: Revisiting Maximum Likelihood Estimation (Mle) Procedure, Hoo Ling Ping, M. Ataharul Islam Nov 2008

Analyzing Incomplete Categorical Data: Revisiting Maximum Likelihood Estimation (Mle) Procedure, Hoo Ling Ping, M. Ataharul Islam

Journal of Modern Applied Statistical Methods

Incomplete data poses formidable difficulties in the application of statistical techniques and requires special procedures to handle. The most common ways to solve this problem are by ignoring, truncating, censoring or collapsing those data, but these may lead to inappropriate conclusions because those data might contain important information. Most of the research for estimating cell probabilities involving incomplete categorical data is based on the EM algorithm. A likelihood approach is employed for estimating cell probabilities for missing values and makes comparisons between maximum likelihood estimation (MLE) and the EM algorithm. The MLE can provide almost the same estimates as that …

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Adaptive Estimation Of Heteroscedastic Linear Regression Model Using Probability Weighted Moments, Faqir Muhammad, Muhammad Aslam, G.R. Pasha Nov 2008

Adaptive Estimation Of Heteroscedastic Linear Regression Model Using Probability Weighted Moments, Faqir Muhammad, Muhammad Aslam, G.R. Pasha

Journal of Modern Applied Statistical Methods

An adaptive estimator is presented by using probability weighted moments as weights rather than conventional estimates of variances for unknown heteroscedastic errors while estimating a heteroscedastic linear regression model. Empirical studies of the data generated by simulations for normal, uniform, and logistically distributed error terms support our proposed estimator to be quite efficient, especially for small samples.

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Construction Of Insurance Scoring System Using Regression Models, Noriszura Ismail, Abdul Aziz Jemain Nov 2008

Construction Of Insurance Scoring System Using Regression Models, Noriszura Ismail, Abdul Aziz Jemain

Journal of Modern Applied Statistical Methods

This study suggests the regression models of Lognormal, Normal and Gamma for constructing insurance scoring system. The main advantage of a scoring system is that it can be used by insurers to differentiate between high and low risks insureds, thus allowing the profitability of insureds to be predicted.

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Sustained Attention In Children With Two Etiologies Of Early Hydrocephalus, Maegan D. Swartwout, Paul T. Cirino, Amy W. Hampson, Jack M. Fletcher, Michael E. Brandt, Maureen Dennis Nov 2008

Sustained Attention In Children With Two Etiologies Of Early Hydrocephalus, Maegan D. Swartwout, Paul T. Cirino, Amy W. Hampson, Jack M. Fletcher, Michael E. Brandt, Maureen Dennis

Faculty, Staff and Student Publications

Several studies have shown that children with spina bifida meningomyelocele (SBM) and hydrocephalus have attention problems on parent ratings and difficulties in stimulus orienting associated with a posterior brain attention system. Less is known about response control and inhibition associated with an anterior brain attention system. Using the Gordon Vigilance Task (Gordon, 1983), we studied error rate, reaction time, and performance over time for sustained attention, a key anterior attention function, in 101 children with SBM, 17 with aqueductal stenosis (AS; another condition involving congenital hydrocephalus), and 40 typically developing controls (NC). In SBM, we investigated the relation between cognitive …

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Morphology Of The Dayside Ionosphere Of Venus: Implications For Ion Outflows, Jane L. Fox Nov 2008

Morphology Of The Dayside Ionosphere Of Venus: Implications For Ion Outflows, Jane L. Fox

Physics Faculty Publications

The nightside ionosphere of Venus is formed mostly by day-to-night transport of ions below the ionopause, with a small contribution from precipitation of energetic electrons from the wake. This nightward flux of ions should result in dayside ionospheres that are characterized by smaller electron density scale heights at high altitudes than those that are characteristic of diffusive equilibrium. In order to determine both the maximum possible values of the upward fluxes and the upward fluxes implied by comparison of our computed ion and electron density profiles to measurements, we have constructed more than 60 models of the high solar activity …

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Nonlinear Magneto-Optic Polarization Rotation With Intense Laser Fields, Paul S. Hsu, Anil K. Patnaik, George R. Welch Nov 2008

Nonlinear Magneto-Optic Polarization Rotation With Intense Laser Fields, Paul S. Hsu, Anil K. Patnaik, George R. Welch

Physics Faculty Publications

We have studied the nonlinear Faraday effect with intense linear polarized light in an optically thick atomic rubidium vapor. We demonstrate that the polarization rotation rate (rotation angle per unit magnetic field, in the limit of low field) has a maximum value as the intensity and density are increased. We also show that the optimal sensitivity of an optical magnetometer based on this system reaches a saturation value as the intensity and density are increased.

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Genetic Markers Of Igg Influence The Outcome Of Infection With Hepatitis C Virus, Janardan P. Pandey, Aryan M. Namboodiri, Yuqun Luo, Yuping Wu, Robert C. Elston, David L. Thomas, Hugo R. Rosen, James J. Goedert Nov 2008

Genetic Markers Of Igg Influence The Outcome Of Infection With Hepatitis C Virus, Janardan P. Pandey, Aryan M. Namboodiri, Yuqun Luo, Yuping Wu, Robert C. Elston, David L. Thomas, Hugo R. Rosen, James J. Goedert

Mathematics and Statistics Faculty Publications

We examined the role that immunoglobulin GM and KM allotypes—genetic markers of γ and κ chains, respectively—play in the outcome of hepatitis C virus (HCV) infection in white Americans. A total of 119 persons who had cleared HCV and 111 with persistent HCV infection were genotyped for the presence of several GM and KM determinants. Persistent HCV infection was more than three times as likely (odds ratio, 3.50; P = .01) in subjects who were carriers of the GM3 allele than in those who were noncarriers. These results show that particular GM alleles may be important determinants of the outcome …

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Trapping And Characterization Of A Reaction Intermediate In Carbapenem Hydrolysis By B. Cereus Metallo-Β-Lactamase, Mariana F. Tioni, Leticia L. Llarrull, Andrés A. Poeylaut-Palena, Marcelo A. Martí, Miguel Saggu, Gopal R. Periyannan, Ernesto G. Mata, Brian Bennett, Daniel H. Murgida, Alejandro J. Vila Nov 2008

Trapping And Characterization Of A Reaction Intermediate In Carbapenem Hydrolysis By B. Cereus Metallo-Β-Lactamase, Mariana F. Tioni, Leticia L. Llarrull, Andrés A. Poeylaut-Palena, Marcelo A. Martí, Miguel Saggu, Gopal R. Periyannan, Ernesto G. Mata, Brian Bennett, Daniel H. Murgida, Alejandro J. Vila

Physics Faculty Research and Publications

Metallo-β-lactamases hydrolyze most β-lactam antibiotics. The lack of a successful inhibitor for them is related to the previous failure to characterize a reaction intermediate with a clinically useful substrate. Stopped-flow experiments together with rapid freeze−quench EPR and Raman spectroscopies were used to characterize the reaction of Co(II)−BcII with imipenem. These studies show that Co(II)−BcII is able to hydrolyze imipenem in both the mono- and dinuclear forms. In contrast to the situation met for penicillin, the species that accumulates during turnover is an enzyme−intermediate adduct in which the β-lactam bond has already been cleaved. This intermediate is a metal-bound anionic species …

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Laser Channeling Of Bethe-Heitler Pairs, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel Nov 2008

Laser Channeling Of Bethe-Heitler Pairs, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel

Physics Faculty Research & Creative Works

Electron-positron pair creation is analyzed for an arrangement involving three external fields: a high-frequency gamma photon, the Coulomb field of a nucleus, and a strong laser wave. The frequency of the incoming gamma photon is assumed to be larger than the threshold for pair production in the absence of a laser, and the peak electric field of the laser is assumed to be much weaker than Schwinger's critical field. The total number of pairs produced is found to be essentially unchanged by the laser field, while the differential cross section is drastically modified. We show that the laser can channel …

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Toward Evaluating Lighting Design Interface Paradigms For Novice Users, William Brandon Kerr, Fabio Pellacini Nov 2008

Toward Evaluating Lighting Design Interface Paradigms For Novice Users, William Brandon Kerr, Fabio Pellacini

Computer Science Technical Reports

Lighting design is a complex and fundamental task in computer cinematography, involving adjustment of light parameters to define final scene appearance. Many lighting interfaces have been proposed to improve lighting design work flow. These paradigms exist in three paradigm categories: direct light parameter manipulation, indirect light feature manipulation (e.g., shadow dragging), and goal-based optimization of light through painting. To this date, no formal evaluation of the relative effectiveness of these methods has been performed. In this paper, we present a first step toward evaluating the three paradigms in the form of a user study with novice users. We focus our …

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Managing Gambel Oak In Southwestern Ponderosa Pine Forests: The Status Of Our Knowledge, Scott R. Abella Nov 2008

Managing Gambel Oak In Southwestern Ponderosa Pine Forests: The Status Of Our Knowledge, Scott R. Abella

Public Policy and Leadership Faculty Research

Gambel oak (Quercus gambelii) is a key deciduous species in southwestern ponderosa pine (Pinus ponderosa) forests and is important for wildlife habitat, soil processes, and human values. This report (1) summarizes Gambel oak’s biological characteristics and importance in ponderosa pine forests, (2) synthesizes literature on changes in tree densities and fire frequencies since Euro-American settlement in pine-oak forests, (3) suggests management prescriptions for accomplishing various oak management objectives (for example, increasing diameter growth or acorn production), and (4) provides an appendix containing 203 Gambel oak literature citations organized by subject. Nine studies that reconstructed Gambel oak density changes since settlement …

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Inside Unlv, Shane Bevell, Tony Allen, Karen Sharp, Mamie Peers, Cate Weeks Nov 2008

Inside Unlv, Shane Bevell, Tony Allen, Karen Sharp, Mamie Peers, Cate Weeks

Inside UNLV

No abstract provided.

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Supply Curves For Rooftop Solar Pv-Generated Electricity For The United States, Paul Denholm, Robert Margolis Nov 2008

Supply Curves For Rooftop Solar Pv-Generated Electricity For The United States, Paul Denholm, Robert Margolis

Publications (E)

In this report, we examine several possible methods for generating PV supply curves based exclusively on rooftop deployment. We begin by introducing a framework methodology for a basic supply curve based on estimated distribution of population and buildings, rooftop availability and orientation, and geographical variation in resource. We then discuss limitations to this basic methodology and introduce alternative supply curves that consider additional factors – changes in PV efficiency and configuration, rooftop availability, and grid limitations – while emphasizing the data and methodological limitations to each approach. The resulting curves potentially could be used as inputs to other models or …

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Locating Oil Spills Under Sea Ice Using Ground-Penetrating Radar, John H. Bradford, Lee M. Liberty, David F. Dickens Nov 2008

Locating Oil Spills Under Sea Ice Using Ground-Penetrating Radar, John H. Bradford, Lee M. Liberty, David F. Dickens

CGISS Publications and Presentations

The accelerating level of interest in arctic oil and gas exploration was demonstrated in the overwhelming response to recent lease sales in the Alaskan OCS region. As development increases, the potential for accidental oil spills in the arctic marine environment increases. The need for reliable systems to detect oil trapped in a range of ice conditions remains at the forefront of continued efforts to improve response to ocean spills.

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Two-Factor Mutual Authentication Based On Smart Cards And Passwords, Guomin Yang, Duncan S. Wong, Huaxiong Wang, Xiaotie Deng Nov 2008

Two-Factor Mutual Authentication Based On Smart Cards And Passwords, Guomin Yang, Duncan S. Wong, Huaxiong Wang, Xiaotie Deng

Research Collection School Of Computing and Information Systems

One of the most commonly used two-factor user authentication mechanisms nowadays is based on smart-card and password. A scheme of this type is called a smart-card-based password authentication scheme. The core feature of such a scheme is to enforce two-factor authentication in the sense that the client must have the smart-card and know the password in order to gain access to the server. In this paper, we scrutinize the security requirements of this kind of schemes, and propose a new scheme and a generic construction framework for smart-card-based password authentication. We show that a secure password based key exchange protocol …

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Market Liquidity Provision For On-Demand Computing, Zhiling Guo Nov 2008

Market Liquidity Provision For On-Demand Computing, Zhiling Guo

Research Collection School Of Computing and Information Systems

This paper focuses on a market intermediary’s role of liquidity provision to support on-demand computing in a dynamic market trading environment. We outline a framework in which a number of distributed agents sell and buy assets based on their changing utilities over time and a service provider acts as a market maker performing market intervention. We present benchmark models based on socially optimal liquidity provision and a brokerage framework. We then examine the benefits and the dealer’s incentives to provide market liquidity.

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Type I Error Rates Of The Kenward-Roger F-Test For A Split-Plot Design With Missing Values And Non-Normal Data, Miguel A. Padilla, Youngkyoung Min, Guili Zhang Nov 2008

Type I Error Rates Of The Kenward-Roger F-Test For A Split-Plot Design With Missing Values And Non-Normal Data, Miguel A. Padilla, Youngkyoung Min, Guili Zhang

Journal of Modern Applied Statistical Methods

The Type I error of the Kenward-Roger (KR) F-test was assessed through a simulation study for a between- by within-subjects split-plot design with non-normal ignorable missing data. The KR-test for the between- and within-subjects main effect was robust under all simulation variables investigated and when the data were missing completely at random (MCAR). This continued to hold for the between-subjects main effect when data were missing at random (MAR). For the interaction, the KR F-test performed fairly well at controlling Type I under MCAR and the simulation variables investigated. However, under MAR, the KR F-test for the …

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Constructing Confidence Intervals For Spearman’S Rank Correlation With Ordinal Data: A Simulation Study Comparing Analytic And Bootstrap Methods, John Ruscio Nov 2008

Constructing Confidence Intervals For Spearman’S Rank Correlation With Ordinal Data: A Simulation Study Comparing Analytic And Bootstrap Methods, John Ruscio

Journal of Modern Applied Statistical Methods

Research shows good probability coverage using analytic confidence intervals (CIs) for Spearman’s rho with continuous data, but poorer coverage with ordinal data. A simulation study examining the latter case replicated prior results and revealed that coverage of bootstrap CIs was usually as good or better than coverage of analytic CIs.

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An Optimum Allocation With A Family Of Estimators Using Auxiliary Information In Sample Survey, Gajendra K. Vishwakarma, Housila P. Singh Nov 2008

An Optimum Allocation With A Family Of Estimators Using Auxiliary Information In Sample Survey, Gajendra K. Vishwakarma, Housila P. Singh

Journal of Modern Applied Statistical Methods

The problem of obtaining optimum allocation using auxiliary information in stratified random sampling. An optimum allocation with a family of estimators is obtained and its efficiency is compared with that of Neyman allocation based on Srivastava (1971) class of estimators and the optimum allocation suggested by Zaidi et al., (1989). It is shown that the proposed allocation is better in the sense having smaller variance compared to other optimum allocation.

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On Some Properties Of Quasi-Negative-Binomial Distribution And Its Applications, Anwar Hassan, Sheikh Bilal Nov 2008

On Some Properties Of Quasi-Negative-Binomial Distribution And Its Applications, Anwar Hassan, Sheikh Bilal

Journal of Modern Applied Statistical Methods

The quasi-negative-binomial distribution was applied to queuing theory for determining the distribution of total number of customers served before the queue vanishes under certain assumptions. Some structural properties (probability generating function, convolution, mode and recurrence relation) for the moments of quasi-negative-binomial distribution are discussed. The distribution’s characterization and its relation with other distributions were investigated. A computer program was developed using R to obtain ML estimates and the distribution was fitted to some observed sets of data to test its goodness of fit.

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Metric Regularity Of Mappings And Generalized Normals To Set Images, Boris S. Mordukhovich, Nguyen Mau Nam, Bingwu Wang Nov 2008

Metric Regularity Of Mappings And Generalized Normals To Set Images, Boris S. Mordukhovich, Nguyen Mau Nam, Bingwu Wang

Mathematics Research Reports

The primary goal of this paper is to study some notions of normals to nonconvex sets in finite-dimensional and infinite-dimensional spaces and their images under single-valued and set-valued mappings. The main motivation for our study comes from variational analysis and optimization, where the problems under consideration play a crucial role in many important aspects of generalized differential calculus and applications. Our major results provide precise equality formulas (sometimes just efficient upper estimates) allowing us to compute generalized normals in various senses to direct and inverse images of nonconvex sets under single-valued and set-valued mappings between Banach spaces. The main tools …

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Ubi-App: A Ubiquitous Application For Universal Access From Handheld Devices, Shameem Ahmed, Moushumi Sharmin, Sheikh Iqbal Ahamed Nov 2008

Ubi-App: A Ubiquitous Application For Universal Access From Handheld Devices, Shameem Ahmed, Moushumi Sharmin, Sheikh Iqbal Ahamed

Mathematics, Statistics and Computer Science Faculty Research and Publications

Universal access from a handheld device (such as a PDA, cell phone) at any time or anywhere is now a reality. Ubicomp Assistant (UA) (Sharmin et al. in Proceedings of the 21st annual ACM symposium on applied computing (ACM SAC 2006), Dijon, France, pp 1013–1017, 2006) is an integral service of MARKS (Sharmin et al. in Proceedings of the third international conference on information technology: new generations (ITNG 2006), Las Vegas, Nevada, USA, pp 306–313, 2006). It is a middleware developed for handheld devices, and has been designed to accommodate different types of users (e.g., education, healthcare, marketing, or business). …

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2d Regional Correlation Analysis Of Single-Molecule Time Trajectories, Xuefei Wang, H. Peter Lu Nov 2008

2d Regional Correlation Analysis Of Single-Molecule Time Trajectories, Xuefei Wang, H. Peter Lu

Chemistry Faculty Publications

We report a new approach of 2D regional correlation analysis capable of analyzing fluctuation dynamics of complex multiple correlated and anticorrelated fluctuations under a noncorrelated noise background. Using this new method, by changing and scanning the start time and end time along a pair of fluctuation trajectories, we are able to map out any defined segments along the fluctuation trajectories and determine whether they are correlated, anticorrelated, or noncorrelated; after which, a cross-correlation analysis can be applied for each specific segment to obtain a detailed fluctuation dynamics analysis. We specifically discuss an application of this approach to analyze single-molecule fluorescence …

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Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai Nov 2008

Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such as …

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Magnetic Field Measurements Of O Stars With Fors 1 At The Vlt., S. Hubrig, M. Schöller, R. Schnerr, J. González, Richard Ignace, H. Henrichs Nov 2008

Magnetic Field Measurements Of O Stars With Fors 1 At The Vlt., S. Hubrig, M. Schöller, R. Schnerr, J. González, Richard Ignace, H. Henrichs

ETSU Faculty Works

Context.The presence of magnetic fields in O-type stars has been suspected for a long time. The discovery of these fields would explain a wide range of well documented enigmatic phenomena in massive stars, in particular cyclical wind variability, Hα emission variations, chemical peculiarity, narrow X-ray emission lines, and non-thermal radio/X-ray emission. Aims.To investigate the incidence of magnetic fields in O stars, we acquired 38 new spectropolarimetric observations with FORS 1 (FOcal Reducer low dispersion Spectrograph) mounted on the 8-m Kueyen telescope of the VLT. Methods.Spectropolarimetric observations were obtained at different phases for a sample of 13 O …

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Focus On Rna Isolation: Obtaining Rna For Microrna (Mirna) Expression Profiling Analyses Of Neural Tissue, Wang-Xia Wang, Bernard R. Wilfred, Donald A. Baldwin, R. Benjamin Isett, Na Ren, Arnold J. Stromberg, Peter T. Nelson Nov 2008

Focus On Rna Isolation: Obtaining Rna For Microrna (Mirna) Expression Profiling Analyses Of Neural Tissue, Wang-Xia Wang, Bernard R. Wilfred, Donald A. Baldwin, R. Benjamin Isett, Na Ren, Arnold J. Stromberg, Peter T. Nelson

Sanders-Brown Center on Aging Faculty Publications

MicroRNAs (miRNAs) are present in all known plant and animal tissues and appear to be somewhat concentrated in the mammalian nervous system. Many different miRNA expression profiling platforms have been described. However, relatively little research has been published to establish the importance of 'upstream' variables in RNA isolation for neural miRNA expression profiling. We tested whether apparent changes in miRNA expression profiles may be associated with tissue processing, RNA isolation techniques, or different cell types in the sample. RNA isolation was performed on a single brain sample using eight different RNA isolation methods, and results were correlated using a conventional …

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Asymptotic Behavior Of Linearized Viscoelastic Flow Problem, Yinnian He, Yi Li Nov 2008

Asymptotic Behavior Of Linearized Viscoelastic Flow Problem, Yinnian He, Yi Li

Mathematics and Statistics Faculty Publications

In this article, we provide some asymptotic behaviors of linearized viscoelastic flows in a general two-dimensional domain with certain parameters small and the time variable large.

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Co2 Eor And Co2 Sequestration – The Case For Collaboration, University Of North Dakota. Energy And Environmental Research Center Nov 2008

Co2 Eor And Co2 Sequestration – The Case For Collaboration, University Of North Dakota. Energy And Environmental Research Center

EERC Brochures and Fact Sheets

Fact sheet on energy policies and how they pertain to enhanced oil recovery (EOR) and CO2 capture and sequestration (CCS). [This item is an outdated or superseded version and retained for historical purposes only. It may no longer reflect current information, policies, or practices.]

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