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2010

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Articles 3391 - 3420 of 8620

Full-Text Articles in Physical Sciences and Mathematics

The Performance Of Multiple Imputation For Likert-Type Items With Missing Data, Walter Leite, S. Natasha Beretvas May 2010

The Performance Of Multiple Imputation For Likert-Type Items With Missing Data, Walter Leite, S. Natasha Beretvas

Journal of Modern Applied Statistical Methods

The performance of multiple imputation (MI) for missing data in Likert-type items assuming multivariate normality was assessed using simulation methods. MI was robust to violations of continuity and normality. With 30% of missing data, MAR conditions resulted in negatively biased correlations. With 50% missingness, all results were negatively biased.

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On Exact 100(1-Α)% Confidence Interval Of Autocorrelation Coefficient In Multivariate Data When The Errors Are Autocorrelated, Madhusudan Bhandary May 2010

On Exact 100(1-Α)% Confidence Interval Of Autocorrelation Coefficient In Multivariate Data When The Errors Are Autocorrelated, Madhusudan Bhandary

Journal of Modern Applied Statistical Methods

An exact 100(1−α)% confidence interval for the autocorrelation coefficient ρ is derived based on a single multinormal sample. The confidence interval is the interval between the two roots of a quadratic equation in ρ . A real life example is also presented.

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Impact Of Measurement Model Modification On Structural Parameter Integrity When Measurement Model Is Misspecified, Weihua Fan May 2010

Impact Of Measurement Model Modification On Structural Parameter Integrity When Measurement Model Is Misspecified, Weihua Fan

Journal of Modern Applied Statistical Methods

In the process of model modification, parameters of residual covariances are often treated as free parameters to improve model fit. However, the effect of such measurement model modifications on the important structural parameter estimates under various measurement model misspecifications has not been systematically studied. Monte Carlo simulation was conducted to compare structural estimates before and after measurement model modifications of adding residual covariances under varying sample sizes and model misspecifications. Results showed that researchers should pay attention when such measurement model modifications are made to initially misspecified model with missing path(s).

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On A Comparison Between Two Measures Of Spatial Association, Faisal G. Khamis, Abdul Aziz Jemain, Kamarulzaman Ibrahim May 2010

On A Comparison Between Two Measures Of Spatial Association, Faisal G. Khamis, Abdul Aziz Jemain, Kamarulzaman Ibrahim

Journal of Modern Applied Statistical Methods

Two measures of spatial association between two variables were used by many researchers. These are the Wartenberg (1985) and Lee (2001) measures. Based on simulation for lattice data, the sensitivity of both measures was studied and compared with different choices of spatial structures, spatial weights and sample sizes using bias and mean square error. Different scenarios are used in terms of assumed numbers and sample sizes. Moran’s I is used to examine the spatial autocorrelation of such a variable with itself. Both the Wartenberg and Lee measures are found to be sensitive, however, Wartenberg’s measure is found to be somewhat …

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Median-Unbiased Optimal Smoothing And Trend Extraction, Dimitrios D. Thomakos May 2010

Median-Unbiased Optimal Smoothing And Trend Extraction, Dimitrios D. Thomakos

Journal of Modern Applied Statistical Methods

The problem of smoothing a time series for extracting its low frequency characteristics, collectively called its trend, is considered. A competitive approach is proposed and compared with existing methods in choosing the optimal degree of smoothing based on the distribution of the residuals from the smooth trend.

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An Evaluation Of Multiple Imputation For Meta-Analytic Structural Equation Modeling, Carolyn F. Furlow, S. Natasha Beretvas May 2010

An Evaluation Of Multiple Imputation For Meta-Analytic Structural Equation Modeling, Carolyn F. Furlow, S. Natasha Beretvas

Journal of Modern Applied Statistical Methods

A simulation study was used to evaluate multiple imputation (MI) to handle MCAR correlations in the first step of meta-analytic structural equation modeling: the synthesis of the correlation matrix and the test of homogeneity. No substantial parameter bias resulted from using MI. Although some SE bias was found for meta-analyses involving smaller numbers of studies, the homogeneity test was never rejected when using MI.

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Can Specification Searches Be Useful For Hypothesis Generation?, Samuel B. Green, Marilyn S. Thompson May 2010

Can Specification Searches Be Useful For Hypothesis Generation?, Samuel B. Green, Marilyn S. Thompson

Journal of Modern Applied Statistical Methods

Previous studies suggest that results from specification searches, as typically employed in structural equation modeling, should not be used to reach strong research conclusions due to their poor reliability. Analyses of computer generated data indicate that search results can be sufficiently reliable for exploratory purposes with properly designed and analyzed studies.

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Measuring Openness, Gaetano Ferrieri May 2010

Measuring Openness, Gaetano Ferrieri

Journal of Modern Applied Statistical Methods

A method for measuring international openness is elaborated. This synthetic indicator measures the capacity of countries for a given phenomenon adjusted for their weight in the same phenomenon. The method implemented and applied to international trade and illustrated here as a case study in merchandise exports, has a wide range of applications in the socio-economic field.

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Another Look At Resampling: Replenishing Small Samples With Virtual Data Through S-Smart, Haiyan Bai, Wei Pan, Leigh Lihshing Wang, Phillip Neal Ritchey May 2010

Another Look At Resampling: Replenishing Small Samples With Virtual Data Through S-Smart, Haiyan Bai, Wei Pan, Leigh Lihshing Wang, Phillip Neal Ritchey

Journal of Modern Applied Statistical Methods

A new resampling method is introduced to generate virtual data through a smoothing technique for replenishing small samples. The replenished analyzable sample retains the statistical properties of the original small sample, has small standard errors and possesses adequate statistical power.

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Shrinkage Estimation In The Inverse Rayleigh Distribution, Gyan Prakash May 2010

Shrinkage Estimation In The Inverse Rayleigh Distribution, Gyan Prakash

Journal of Modern Applied Statistical Methods

The properties of the shrinkage test–estimators of the parameter were studied for an inverse Rayleigh model under the asymmetric loss function. Both the single and double–stage shrinkage test–estimators are considered.

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Nonlinear Parameterization In Bi-Criteria Sample Balancing, Stan Lipovetsky May 2010

Nonlinear Parameterization In Bi-Criteria Sample Balancing, Stan Lipovetsky

Journal of Modern Applied Statistical Methods

Sample balancing is widely used in applied research to adjust a sample data to achieve better correspondence to Census statistics. The classic Deming-Stephan iterative proportional approach finds the weights of observations by fitting the cross-tables of sample counts to known margins. This work considers a bi-criteria objective for finding weights with maximum possible effective base size. This approach is presented as a ridge regression with the exponential nonlinear parameterization that produces nonnegative weights for sample balancing.

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Combining Independent Tests Of Conditional Shifted Exponential Distribution, Abedel-Qader S. Al-Masri May 2010

Combining Independent Tests Of Conditional Shifted Exponential Distribution, Abedel-Qader S. Al-Masri

Journal of Modern Applied Statistical Methods

The problem of combining n independent tests as n→∞ for testing that variables are uniformly distributed over the interval (0, 1) compared to their having a conditional shifted exponential distribution with probability density function f (xθ ) = e−(x−γθ) , x ≥γθ , θ ∈[a,∞), a ≥ 0 was studied. This was examined for the case where θ1, θ2, … are distributed according to the distribution function (DF) F and when the DF is Gamma (1, 2). Six omnibus methods were compared via the Bahadur efficiency. It is shown that, as γ → 0 and …

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Estimations On The Generalized Exponential Distribution Using Grouped Data, Hassan Pazira, Parviz Nasiri May 2010

Estimations On The Generalized Exponential Distribution Using Grouped Data, Hassan Pazira, Parviz Nasiri

Journal of Modern Applied Statistical Methods

Classical and Bayesian estimators are obtained for the shape parameter of the Generalized-Exponential distribution under grouped data. In Bayesian estimation, three types of loss functions are considered: the Squared Error loss function which is classified as a symmetric function, the LINEX and Precautionary loss functions which are asymmetric. These estimators are compared with the corresponding estimators derived from un-grouped data empirically using Monte-Carlo simulation.

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A Comparative Study For Bandwidth Selection In Kernel Density Estimation, Omar M. Eidous, Mohammad Abd Alrahem Shafeq Marie, Mohammed H. Baker Al-Haj Ebrahem May 2010

A Comparative Study For Bandwidth Selection In Kernel Density Estimation, Omar M. Eidous, Mohammad Abd Alrahem Shafeq Marie, Mohammed H. Baker Al-Haj Ebrahem

Journal of Modern Applied Statistical Methods

Nonparametric kernel density estimation method does not make any assumptions regarding the functional form of curves of interest; hence it allows flexible modeling of data. A crucial problem in kernel density estimation method is how to determine the bandwidth (smoothing) parameter. This article examines the most important bandwidth selection methods, in particular, least squares cross-validation, biased crossvalidation, direct plug-in, solve-the-equation rules and contrast methods. Methods are described and expressions are presented. The main practical contribution is a comparative simulation study that aims to isolate the most promising methods. The performance of each method is evaluated on the basis of the …

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Applying Multiple Imputation With Geostatistical Models To Account For Item Nonresponse In Environmental Data, Breda Munoz, Virginia M. Lesser, Ruben A. Smith May 2010

Applying Multiple Imputation With Geostatistical Models To Account For Item Nonresponse In Environmental Data, Breda Munoz, Virginia M. Lesser, Ruben A. Smith

Journal of Modern Applied Statistical Methods

Methods proposed to solve the missing data problem in estimation procedures should consider the type of missing data, the missing data mechanism, the sampling design and the availability of auxiliary variables correlated with the process of interest. This article explores the use of geostatistical models with multiple imputation to deal with missing data in environmental surveys. The method is applied to the analysis of data generated from a probability survey to estimate Coho salmon abundance in streams located in western Oregon watersheds.

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On The Appropriate Transformation Technique And Model Selection In Forecasting Economic Time Series: An Application To Botswana Gdp Data, D. K. Shangodoyin, K. Setlhare, K. K. Moseki, K. Sediakgotla May 2010

On The Appropriate Transformation Technique And Model Selection In Forecasting Economic Time Series: An Application To Botswana Gdp Data, D. K. Shangodoyin, K. Setlhare, K. K. Moseki, K. Sediakgotla

Journal of Modern Applied Statistical Methods

Selected data transformation techniques in time series modeling are evaluated using real-life data on Botswana Gross Domestic Product (GDP). The transformation techniques considered were modified, although reasonable estimates of the original with no significant difference at α = 0.05 level were obtained: minimizing square of first difference (MFD) and minimizing square of second difference (MSD) provided the best transformation for GDP, whereas the Goldstein and Khan (GKM) method had a deficiency of losing data points. The Box-Jenkins procedure was adapted to fit suitable ARIMA (p, d, q) models to both the original and transformed series, with AIC and SIC as …

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An Equivalence Test Based On N And P, Markus Neuhäeuser May 2010

An Equivalence Test Based On N And P, Markus Neuhäeuser

Journal of Modern Applied Statistical Methods

An equivalence test is proposed which is based on the P-value of a test for a difference and the sample size. This test may be especially appropriate for an exploratory re-analysis if only a non-significant test for a difference was reported. Thus, neither a confidence interval is available, nor is there access to the raw data. The test is illustrated using two examples; for both applications the smallest equivalence range for which equivalence could be demonstrated is calculated.

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Jmasm30 Pi-Lca: A Sas Program Computing The Two-Point Mixture Index Of Fit For Two-Class Lca Models With Dichotomous Variables (Sas), Dongquan Zhang, C. Mitchell Dayton May 2010

Jmasm30 Pi-Lca: A Sas Program Computing The Two-Point Mixture Index Of Fit For Two-Class Lca Models With Dichotomous Variables (Sas), Dongquan Zhang, C. Mitchell Dayton

Journal of Modern Applied Statistical Methods

The two-point mixture index of fit enjoys some desirable features in model fit assessment and model selection, however, a need exists for efficient computational strategies. Applying an NLP algorithm, a program using the SAS matrix language is presented to estimate the two-point index of fit for two-class LCA models with dichotomous response variables. The program offers a tool to compute π ∗ for twoclass models and it also provides an alternative program for conducting latent class analysis with SAS. This study builds a foundation for further research on computational approaches for M-class models.

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Multiwavelength Observations Of 1rxh J173523.7-354013: Revealing An Unusual Bursting Neutron Star, N. Degenaar, P. G. Jonker, M. A. P. Torres, R. Kaur, N. Rea, G. L. Israel, A. Patruno, G. Trap, E. M. Cackett, P. D'Avanzo, G. Lo Curto, G. Novara, H. Krimm, S. T. Holland, A. De Luca, P. Esposito, R. Wijnands May 2010

Multiwavelength Observations Of 1rxh J173523.7-354013: Revealing An Unusual Bursting Neutron Star, N. Degenaar, P. G. Jonker, M. A. P. Torres, R. Kaur, N. Rea, G. L. Israel, A. Patruno, G. Trap, E. M. Cackett, P. D'Avanzo, G. Lo Curto, G. Novara, H. Krimm, S. T. Holland, A. De Luca, P. Esposito, R. Wijnands

Physics and Astronomy Faculty Research Publications

On 2008 May 14, the Burst Alert Telescope onboard the Swift mission triggered on a type-I X-ray burst from the previously unclassified ROSAT object 1RXH J173523.7-354013, establishing the source as a neutron star X-ray binary. We report on X-ray, optical and near-infrared observations of this system. The X-ray burst had a duration of ~2 h and belongs to the class of rare, intermediately long type-I X-ray bursts. From the bolometric peak flux of ~3.5 × 10-8ergcm-2s-1, we infer a source distance of D <~ 9.5 kpc. Photometry of the field reveals an optical counterpart that declined from R = 15.9 during the X-ray burst to R = 18.9 thereafter. Analysis of post-burst Swift/X-ray Telescope observations as well as archival XMM-Newton and ROSAT data suggests that the system is persistent at a 0.5-10 keV luminosity of ~2 × 1035 (D/9.5 kpc)2ergs-1. Optical and infrared photometry …

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Web Reviews: Astronomy Star Gazing Tools, Lisa Johnston May 2010

Web Reviews: Astronomy Star Gazing Tools, Lisa Johnston

Sci-Tech News

Spring is here, and when this arrives at your email doorstop, summer will be around the corner! What this means, in the SciTech library, is recreational astronomers appear looking for answers. So next time an astro-newbie is attempting to check out a reference book on Deep-Space NGC Objects (when all they really want to know is what that bright star above the garage is each night), you can smile and say, "Let me show you some great online tools that will help find out which star, or planet, that is." All of these web applets are freely available and easy …

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Sci-Tech Book News Reviews, Susan Fingerman May 2010

Sci-Tech Book News Reviews, Susan Fingerman

Sci-Tech News

This section consists of 100 book reviews selected from Sci-Tech Book News, reprinted with the permission of Book News, Inc.

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Reducing The Impact Of Ethnic Tensions On Economic Growth – Economic Or Political Institutions?, Atin Basu Choudhary, Jim Bang, Michael Reksulak May 2010

Reducing The Impact Of Ethnic Tensions On Economic Growth – Economic Or Political Institutions?, Atin Basu Choudhary, Jim Bang, Michael Reksulak

Atin Basu Choudhary

We use a standard growth regression model and show that ethnic tensions reduce per capita growth rates. We also find evidence that “good” economic and political institutions improve per capita growth rates. More importantly, good economic institutions mitigate the effect of ethnic tensions on per capita growth while good political institutions do not. Consequently, it is foremost capitalist freedom that promotes peace and development.

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The Costs Of Residential Water Scarcity In Cyprus: Impact Of Climate Change And Policy Options, Theodoros Zachariadis May 2010

The Costs Of Residential Water Scarcity In Cyprus: Impact Of Climate Change And Policy Options, Theodoros Zachariadis

Theodoros Zachariadis

This paper presents an assessment of the costs of water scarcity in Cyprus, today and in the next twenty years, accounting also for the effect of projected climate change in the region. We focus on the residential sector, accounting also for tourism and industry. Using a simple demand function we first compute total scarcity costs in Cyprus for the entire period 2010¡V2030 for three scenarios of future water demand. Our central estimate shows that the present value of total costs due to water shortages in this period will amount to 72 million Euros (at 2009 prices), and if future water …

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Assessing Noninferiority In A Three-Arm Trial Using The Bayesian Approach, Pulak Ghosh, Farouk S. Nathoo, Mithat Gonen, Ram C. Tiwari May 2010

Assessing Noninferiority In A Three-Arm Trial Using The Bayesian Approach, Pulak Ghosh, Farouk S. Nathoo, Mithat Gonen, Ram C. Tiwari

Memorial Sloan-Kettering Cancer Center, Dept. of Epidemiology & Biostatistics Working Paper Series

Non-inferiority trials, which aim to demonstrate that a test product is not worse than a competitor by more than a pre-specified small amount, are of great importance to the pharmaceutical community. As a result, methodology for designing and analyzing such trials is required, and developing new methods for such analysis is an important area of statistical research. The three-arm clinical trial is usually recommended for non-inferiority trials by the Food and Drug Administration (FDA). The three-arm trial consists of a placebo, a reference, and an experimental treatment, and simultaneously tests the superiority of the reference over the placebo along with …

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Quikscat Analysis Of Hurricane Force Extratropical Cyclones In The Pacific Ocean, Peter Jzyk May 2010

Quikscat Analysis Of Hurricane Force Extratropical Cyclones In The Pacific Ocean, Peter Jzyk

Senior Honors Projects

Since June 1999, NASA’s Quick Scatterometer Spacecraft (QuikSCAT) has been providing forecasters at the Ocean Prediction Center (OPC) with Near-Real-Time (N.R.T.) surface wind speed and direction data over the world’s oceans. QuikSCAT has allowed forecasters to better predict potential hazards such as storm surges and issue warnings when necessary. Over the past decade, QuikSCAT has received a number of upgrades which improved the forecasters’ abilities to predict the weather more accurately and issue warnings, accordingly. Improvements included the availability of the QuikSCAT data within the forecasters’ workstations starting in October 2001, the introduction of higher resolution satellite data in May …

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The Postsecret Phenomenon: A Contemporary Application Of Existential Psychotherapy, Dan Martin May 2010

The Postsecret Phenomenon: A Contemporary Application Of Existential Psychotherapy, Dan Martin

Senior Honors Projects

In November 2004, as a whimsical break from his monotonous job, Frank Warren decided he would start a small art project in his community. This idea, which he entitled “PostSecret,” involved leaving blank post cards in various public locations that simply asked to “Share a Secret” and listed a few guidelines. Frank’s goal was to “create this non-judgmental, safe place where people could feel comfortable sharing parts of their lives that they've never told a soul.” What he expected to be a small result became a weekly blog, five published books, a traveling art gallery, and a lecture series given …

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A South County Almanac: Recollections And Observations Of The Outdoors In Southern Rhode Island, Nevan Richard May 2010

A South County Almanac: Recollections And Observations Of The Outdoors In Southern Rhode Island, Nevan Richard

Senior Honors Projects

Since its publication in 1949, “A Sand County Almanac: With Sketches Here and There” has served as the benchmark for writing about the environment and nature. “Sand County” was written by famed environmentalist Aldo Leopold, who for most of his lifetime worked towards the conservation of wildlife and natural resources. In “Sand County,” Aldo Leopold recounts his experiences and observations in various essays and journal entries from his many years of living in Wisconsin, as well his travels across the North American continent. With its publication after Mr. Leopold’s death, it changed the face of the American conservation movement, later …

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Dna Polymerases: Perfect Enzymes For An Imperfect World, Anthony J. Berdis May 2010

Dna Polymerases: Perfect Enzymes For An Imperfect World, Anthony J. Berdis

Chemistry Faculty Publications

This Special Thematic Issue explores the molecular properties of DNA polymerases as extraordinary biological catalysts. In this short introductory chapter, I briefly highlight some of the most important concepts from the articles contained within this Special Issue. The contents of this Special Issue are arranged into distinct sub-categories corresponding to mechanistic studies of faithful DNA polymerization, studies of "specialized" DNA polymerases that function on damaged DNA, and DNA polymerases that are of therapeutic importance against various diseases. Emphasis is placed on understanding the dynamic cellular roles and biochemical functions of DNA polymerases, and how their structure and mechanism impact their …

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Non-Natural Nucleotides As Probes For The Mechanism And Fidelity Of Dna Polymerases, Irene Lee, Anthony J. Berdis May 2010

Non-Natural Nucleotides As Probes For The Mechanism And Fidelity Of Dna Polymerases, Irene Lee, Anthony J. Berdis

Chemistry Faculty Publications

DNA is a remarkable macromolecule that functions primarily as the carrier of the genetic information of organisms ranging from viruses to bacteria to eukaryotes. The ability of DNA polymerases to efficiently and accurately replicate genetic material represents one of the most fundamental yet complex biological processes found in nature. The central dogma of DNA polymerization is that the efficiency and fidelity of this biological process is dependent upon proper hydrogen-bonding interactions between an incoming nucleotide and its templating partner. However, the foundation of this dogma has been recently challenged by the demonstration that DNA polymerases can effectively and, in some …

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Terminal Deoxynucleotidyl Transferase: The Story Of A Misguided Dna Polymerase, Edward A. Motea, Anthony J. Berdis May 2010

Terminal Deoxynucleotidyl Transferase: The Story Of A Misguided Dna Polymerase, Edward A. Motea, Anthony J. Berdis

Chemistry Faculty Publications

Nearly every DNA polymerase characterized to date exclusively catalyzes the incorporation of mononucleotides into a growing primer using a DNA or RNA template as a guide to direct each incorporation event. There is, however, one unique DNA polymerase designated terminal deoxynucleotidyl transferase that performs DNA synthesis using only single-stranded DNA as the nucleic acid substrate. In this chapter, we review the biological role of this enigmatic DNA polymerase and the biochemical mechanism for its ability to perform DNA synthesis in the absence of a templating strand. We compare and contrast the molecular events for template-independent DNA synthesis catalyzed by terminal …

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