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

Physical Sciences and Mathematics Commons™

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

Brigham Young University

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 1981 - 2010 of 2906

Full-Text Articles in Physical Sciences and Mathematics

Synthesis Of Resveratrol And Its Analogs, Phase-Transfer Catalyzed Asymmetric Glycolate Aldol Reaction, And Total Synthesis Of 8,9-Methylamido-Geldanamycin, Jing Liu Jul 2007

Synthesis Of Resveratrol And Its Analogs, Phase-Transfer Catalyzed Asymmetric Glycolate Aldol Reaction, And Total Synthesis Of 8,9-Methylamido-Geldanamycin, Jing Liu

Theses and Dissertations

The phytoalexin resveratrol and its acetyl analogs have been made using a decarbonylative Heck reaction. The acid chloride derived from 3,5-dihydroxybenzoic acid was coupled with suitable protected 4-hydroxystyrene in the presence of palladium acetate and N,N-bis-(2,6-diisopropylphenyl)-4,5-dihydro imidazolium chloride to give the substituted stilbene in good yield as the key step. Human HL-60 cell assays showed the 4'-acetyl resveratrol variant improved activity (ED50 17 μM) relative to resveratrol (24 μM). Cinchona phase-transfer catalysts (PTC) were developed for glycolate aldol reactions to give differentially protected 1,2-diol products. Silyl enol ether of diphenylmethoxy-2,5-dimethoxyacetophenone reacted to generate benzhydryl-protected products. O-Allyl trifluorobenzyl cinchonium hydrodifluoride (20 …

Go to article

Statistical Considerations In Designing For Biomarker Detection, Trenton C. Pulsipher Jul 2007

Statistical Considerations In Designing For Biomarker Detection, Trenton C. Pulsipher

Theses and Dissertations

The purpose of this project is to develop a statistical method for use in rapid detection of biological agents using portable gas chromatography mass spectrometry (GC/MS) devices. Of particular interest is 2,6-pyridinedicarboxylic acid (dipicolinic acid, or DPA), a molecule that is present at high concentrations in spores of Clostridium and Bacillus, the latter of which includes the threat organism Bacillus anthracis, or anthrax. Dipicolinic acid may be useful as a first-step discriminator of the biological warfare agent B. anthracis. The results of experiments with B. anthracis Sterne strain and Bacillus thuringiensis spores lead to a conceptual model for the chemical …

Go to article

Infinite Product Group, Keith G. Penrod Jul 2007

Infinite Product Group, Keith G. Penrod

Theses and Dissertations

The theory of infinite multiplication has been studied in the case of the Hawaiian earring group, and has been seen to simplify the description of that group. In this paper we try to extend the theory of infinite multiplication to other groups and give a few examples of how this can be done. In particular, we discuss the theory as applied to symmetric groups and braid groups. We also give an equivalent definition to K. Eda's infinitary product as the fundamental group of a modified wedge product.

Go to article

Development Of A Mevva Based Beryllium-7 Plasma Source, David K. Olson Jul 2007

Development Of A Mevva Based Beryllium-7 Plasma Source, David K. Olson

Theses and Dissertations

We have designed a new type of plasma gun ion source for a Malmberg-Penning trap based on Metal Vapor Vacuum Arc (MeVVA) ion source designs. Our primary intent with this MeVVA-type source is to create a confinable beryllium-7 (7-Be) plasma. 7-Be is a peculiar isotope due to its varying radioactive decay half-life in different electro-chemical configurations. It is also found in an unexpected abundance at high altitudes of the Earth's atmosphere. It is possible ioniziation affects the radioactivity of the isotope, partly explaining this discrepancy with atmospheric models. The short half-life of 7-Be requires us to replace the sample inside …

Go to article

Or Best Offer: A Privacy Policy Negotiation Protocol, Daniel David Walker Jul 2007

Or Best Offer: A Privacy Policy Negotiation Protocol, Daniel David Walker

Theses and Dissertations

Users today are concerned about how their information is collected, stored and used by Internet sites. Privacy policy languages, such as the Platform for Privacy Preferences (P3P), allow websites to publish their privacy practices and policies in machine readable form. Currently, software agents designed to protect users' privacy follow a "take it or leave it" approach when evaluating these privacy policies. This approach is inflexible and gives the server ultimate control over the privacy of web transactions. Privacy policy negotiation is one approach to leveling the playing field by allowing a client to negotiate with a server to determine how …

Go to article

Pipe Diagrams For Thompson's Group F, Aaron L. Peterson Jul 2007

Pipe Diagrams For Thompson's Group F, Aaron L. Peterson

Theses and Dissertations

We review the definition and standard description of Thompson's Group F. We define the set of pipe diagrams and show that this set forms a group isomorphic to F. We use pipe diagrams to prove two theorems about giving a minimal representation for an arbitrary element of F.

Go to article

A Modified Cluster-Weighted Approach To Nonlinear Time Series, Mark Ballatore Lyman Jul 2007

A Modified Cluster-Weighted Approach To Nonlinear Time Series, Mark Ballatore Lyman

Theses and Dissertations

In many applications involving data collected over time, it is important to get timely estimates and adjustments of the parameters associated with a dynamic model. When the dynamics of the model must be updated, time and computational simplicity are important issues. When the dynamic system is not linear the problem of adaptation and response to feedback are exacerbated. A linear approximation of the process at various levels or “states” may approximate the non-linear system. In this case the approximation is linear within a state and transitions from state to state over time. The transition probabilities are parametrized as a Markov …

Go to article

The Smallest Base And Precious Metal Deposits In The World: Vapor Transport And Deposition Of Co-Cu-Sn-Ag Alloys In Vesicles, Elizabeth Adele Outdoor Hunter Jul 2007

The Smallest Base And Precious Metal Deposits In The World: Vapor Transport And Deposition Of Co-Cu-Sn-Ag Alloys In Vesicles, Elizabeth Adele Outdoor Hunter

Theses and Dissertations

Metallic bronze-Co-Ag alloys ranging from1-90 µm have been discovered in bomb and lava vesicles from the mafic volcanoes of Kilauea in Hawaii and Vesuvius, Stromboli and Etna in Italy. It is inferred that the metals for these alloys were transported (in part) as chloride complexes, and that the metal ratios in the alloys may be a function of S/Cl. Alloy compositions in each system are extremely heterogeneous with Co concentrations from 1% to 94%, Cu from 2% to 89%, Sn from 1% to 22% and Ag from 0.5% to 42%. Maximum abundances (in wt%) of other trace or minor elements …

Go to article

A Comparative Simulation Study Of Robust Estimators Of Standard Errors, Natalie Johnson Jul 2007

A Comparative Simulation Study Of Robust Estimators Of Standard Errors, Natalie Johnson

Theses and Dissertations

The estimation of standard errors is essential to statistical inference. Statistical variability is inherent within data, but is usually of secondary interest; still, some options exist to deal with this variability. One approach is to carefully model the covariance structure. Another approach is robust estimation. In this approach, the covariance structure is estimated from the data. White (1980) introduced a biased, but consistent, robust estimator. Long et al. (2000) added an adjustment factor to White's estimator to remove the bias of the original estimator. Through the use of simulations, this project compares restricted maximum likelihood (REML) with four robust estimation …

Go to article

Synthesis And Antiviral Evaluation Of Some 3'-Carboxymethyl-3'-Deoxyadenosine Derivatives, Houguang Shi Jul 2007

Synthesis And Antiviral Evaluation Of Some 3'-Carboxymethyl-3'-Deoxyadenosine Derivatives, Houguang Shi

Theses and Dissertations

3'-Carboxymethyl-3'-deoxyadenosine derivatives were prepared from 2'-O-TBDMS-3'-deoxy-3'-[(ethoxycarbonyl)methyl]adenosine (1) via simple and efficient procedures. Conversion of 1 to 5'-azido-2'-O-TBDMS-3', 5'-dideoxy -3'-[(ethoxycarbonyl) methyl] adenosine (4) was accomplished via a novel one-pot method employing 5'-activation (TosCl) followed by efficient nucleophilic displacement with tetramethylguanidinium azide. Compound 4 was converted to a 5'-[(N-methylcarbamoyl)amino] derivative (5) via one-pot reduction/acylation employing H2/Pd-C followed by treatment with p-nitrophenyl N-methylcarbamate. The latter step of this two-step process required an efficient source of p-nitrophenyl N-methylcarbamate, thus a highly efficient new method for preparing p-nitrophenyl N-alkylcarbamate was developed. N6-phenylcarbamoyl groups were introduced by treatment with phenylisocyanate, and an efficient new method for …

Go to article

Extreme Ultraviolet Polarimetry With Laser-Generated High-Order Harmonics, Nicole Brimhall Jul 2007

Extreme Ultraviolet Polarimetry With Laser-Generated High-Order Harmonics, Nicole Brimhall

Theses and Dissertations

We developed an extreme ultraviolet (EUV) polarimeter, which employs laser-generated high-order harmonics as the light source. This relatively high-flux directional EUV source has available wavelengths between 8 nm and 62 nm and easily rotatable linear polarization. The polarimeter will aid researchers at BYU in characterizing EUV thin films and improving their understanding of materials for use in EUV optics. This first-time workhorse application of laser high harmonics enables polarization-sensitive reflection measurements not previously available in the EUV. We have constructed a versatile positioning system that places harmonics on the microchannel plate detector with an accuracy of 0.3 mm, which allows …

Go to article

Reservoir Characterization And Outcrop Analogs To The Navajo Sandstone In The Central Utah Thrust Belt Exploration Play, Ashley Dalrymple Jul 2007

Reservoir Characterization And Outcrop Analogs To The Navajo Sandstone In The Central Utah Thrust Belt Exploration Play, Ashley Dalrymple

Theses and Dissertations

Reservoir heterogeneity plays an important role in oil field economics and completion strategies. We herein characterize the reservoir heterogeneity of the Early Jurassic Navajo Sandstone in the Justensen Flat/Devils Canyon area of the San Rafael Swell, Utah. These outcrops are located approximately 60 kilometers (45 mi) east of the recently discovered Covenant oil field which is located in the central Utah thrust belt exploration play. The reservoir for the Covenant field is the Navajo Sandstone. This study can serve as an outcrop analogue for this developing play and other eolian reservoirs worldwide. There are eight facies within the Navajo Sandstone …

Go to article

Sensitivity To Distributional Assumptions In Estimation Of The Odp Thresholding Function, Wendy Jill Bunn Jul 2007

Sensitivity To Distributional Assumptions In Estimation Of The Odp Thresholding Function, Wendy Jill Bunn

Theses and Dissertations

Recent technological advances in fields like medicine and genomics have produced high-dimensional data sets and a challenge to correctly interpret experimental results. The Optimal Discovery Procedure (ODP) (Storey 2005) builds on the framework of Neyman-Pearson hypothesis testing to optimally test thousands of hypotheses simultaneously. The method relies on the assumption of normally distributed data; however, many applications of this method will violate this assumption. This thesis investigates the sensitivity of this method to detection of significant but nonnormal data. Overall, estimation of the ODP with the method described in this thesis is satisfactory, except when the nonnormal alternative distribution has …

Go to article

Extensible Pre-Authentication In Kerberos, Phillip L. Hellewell Jul 2007

Extensible Pre-Authentication In Kerberos, Phillip L. Hellewell

Theses and Dissertations

Organizations need to provide services to a wide range of people, including strangers outside their local security domain. As the number of users grows larger, it becomes increasingly tedious to maintain and provision user accounts. It remains an open problem to create a system for provisioning outsiders that is secure, flexible, efficient, scalable, and easy to manage. Kerberos is a secure, industry-standard protocol. Currently, Kerberos operates as a closed system; all users must be specified upfront and managed on an individual basis. This paper presents EPAK (Extensible Pre-Authentication in Kerberos), a framework that enables Kerberos to operate as an open …

Go to article

Obstacle Avoidance And Path Traversal Using Interactive Machine Learning, Jonathan M. Turner Jul 2007

Obstacle Avoidance And Path Traversal Using Interactive Machine Learning, Jonathan M. Turner

Theses and Dissertations

Recently there has been a growing interest in using robots in activities that are dangerous or cost prohibitive for humans to do. Such activities include military uses and space exploration. While robotic hardware is often capable of being used in these types of situations, the ability of human operators to control robots in an effective manner is often limited. This deficiency is often related to the control interface of the robot and the level of autonomy that control system affords the human operator. This thesis describes a robot control system, called the safe/unsafe system, which gives a human operator the …

Go to article

Using Box-Scores To Determine A Position's Contribution To Winning Basketball Games, Gilbert W. Fellingham, C. Shane Reese, Garritt L. Page Jul 2007

Using Box-Scores To Determine A Position's Contribution To Winning Basketball Games, Gilbert W. Fellingham, C. Shane Reese, Garritt L. Page

Faculty Publications

While it is generally recognized that the relative importance of different skills is not constant across different positions on a basketball team, quantification of the differences has not been well studied. 1163 box scores from games in the National Basketball Association during the 1996-97 season were used to study the relationship of skill performance by position and game outcome as measured by point differentials. A hierarchical Bayesian model was fit with individual players viewed as a draw from a population of players playing a particular position: point guard, shooting guard, small forward, power forward, center, and bench. Posterior distributions for …

Go to article

A Dynamic Attribute-Based Load Shedding Scheme For Data Stream Management Systems, Amit Ahuja, Yiu-Kai D. Ng Jul 2007

A Dynamic Attribute-Based Load Shedding Scheme For Data Stream Management Systems, Amit Ahuja, Yiu-Kai D. Ng

Faculty Publications

A data stream being transmitted over a network channel with capacity less than the data transmission rate of the data stream causes sequential network problems. In this paper, we present a new approach for shedding less-informative attribute data from a data stream to maintain a data transmission rate less than the network channel capacity. A scheme for shedding attributes and their data, instead of tuples, becomes imperative in data stream load shedding, since shedding a complete tuple would lead to shedding informative attribute data along with less-informative attribute data in the tuple. Our load shedding approach handles intra-stream, as well …

Go to article

Conceptual Xml For Systems Analysis, Reema Al-Kamha Jun 2007

Conceptual Xml For Systems Analysis, Reema Al-Kamha

Theses and Dissertations

Because XML has become a new standard for data representation, there is a need for a simple conceptual model that works well with XML-based development. In this research we present a conceptual model for XML, called C-XML, which meets this new need of systems analysts who store their data using XML. We describe our implementation of an automatic conversion from XML Schema to C-XML that preserves information and constraints. With this conversion, we can view an XML Schema instance graphically at a higher level of abstraction. We also describe our implementation of an automatic conversion from C-XML to XML Schema. …

Go to article

Intelligent Rotoscoping: A Semi-Automated Interactive Boundary Tracking Approach To Video Segmentation, Seth R. Holladay Jun 2007

Intelligent Rotoscoping: A Semi-Automated Interactive Boundary Tracking Approach To Video Segmentation, Seth R. Holladay

Theses and Dissertations

Video segmentation is an application of computer vision aimed at automating the extraction of an object from a series of video frames. However, it is a difficult problem, especially to compute at real-time, interactive rates. Although general application to video is difficult because of the wide range of image scenarios, user interaction can help to reduce the problem space and speed up the computation. This thesis presents a fast object-tracking tool that selects an object from a series of frames based on minimal user input. Our Intelligent Rotoscoping tool aims for increased speed and accuracy over other video segmentation tools, …

Go to article

Finding Termination And Time Improvement In Predicate Abstraction With Under-Approximation And Abstract Matching, Dritan Kudra Jun 2007

Finding Termination And Time Improvement In Predicate Abstraction With Under-Approximation And Abstract Matching, Dritan Kudra

Theses and Dissertations

The focus of current formal verification methods is mitigating the state explosion problem. One of these formal methods is predicate abstraction, which reduces concrete states of a system to bitvectors of true/false valuations of a set of predicates. Predicate abstraction comes in two flavors, over-approximation and under-approximation. A drawback of over-approximation is that it produces too many spurious errors for data-intensive applications. A more recent under-approximation technique which does not produce spurious errors, does abstract matching on concrete states (AMCS). AMCS adds behaviors to an abstract system by augmenting the set of initial predicates, making use of a theorem prover. …

Go to article

Cognitive And Behavioral Model Ensembles For Autonomous Virtual Characters, Jeffrey S. Whiting Jun 2007

Cognitive And Behavioral Model Ensembles For Autonomous Virtual Characters, Jeffrey S. Whiting

Theses and Dissertations

Cognitive and behavioral models have become popular methods to create autonomous self-animating characters. Creating these models presents the following challenges: (1) Creating a cognitive or behavioral model is a time intensive and complex process that must be done by an expert programmer (2) The models are created to solve a specific problem in a given environment and because of their specific nature cannot be easily reused. Combining existing models together would allow an animator, without the need of a programmer, to create new characters in less time and would be able to leverage each model's strengths to increase the character's …

Go to article

Mapping Middle Paleozoic Erosional And Karstic Patterns With 3-D Seismic Attributes And Well Data In The Arkoma Basin, Oklahoma, Alonzo R. Brinkerhoff Jun 2007

Mapping Middle Paleozoic Erosional And Karstic Patterns With 3-D Seismic Attributes And Well Data In The Arkoma Basin, Oklahoma, Alonzo R. Brinkerhoff

Theses and Dissertations

Newly available industry well data and seismic attribute analysis reveal that late Ordovician-early Devonian Hunton Group strata are more widespread (i.e., not removed by mid-Devonian erosion) in the central and southern portions of the Arkoma Basin in eastern Oklahoma than previously thought. This study demonstrates the value of applying seismic attribute analysis to problems of quantifying and mapping stratigraphic features caused by erosions and/or karstification. Well and seismic isochron data in the Red Oak petroleum field for the Viola-Woodford interval (the units that lie stratigraphically beneath and above, respectively, the Huton Group) show isolated ~40-m thick lenses of Hunton rocks, …

Go to article

Vision-Based Control And Flight Optimization Of A Rotorcraft Uav, David Christian Hubbard Jun 2007

Vision-Based Control And Flight Optimization Of A Rotorcraft Uav, David Christian Hubbard

Theses and Dissertations

A Rotorcraft UAV provides an ideal experimental platform for vision-based navigation. This thesis describes the flight tests of the US Army PALACE pro ject, which implements Moravec's pseudo-normalized correlation tracking algorithm. The tracker uses the movement of the landing site in the camera, a laser range, and the aircraft attitude from an IMU to estimate the relative motion of the UAV. The position estimate functions as a GPS equivalent to enable the rotorcraft to maneuver without the aid of GPS. Flight tests were performed with obstacles and over concrete, asphalt, and grass in daylight conditions with a safe landing area …

Go to article

Active Learning For Part-Of-Speech Tagging: Accelerating Corpus Annotation, George Busby, Marc Carmen, James Carroll, Robbie Haertel, Deryle W. Lonsdale, Peter Mcclanahan, Eric K. Ringger, Kevin Seppi Jun 2007

Active Learning For Part-Of-Speech Tagging: Accelerating Corpus Annotation, George Busby, Marc Carmen, James Carroll, Robbie Haertel, Deryle W. Lonsdale, Peter Mcclanahan, Eric K. Ringger, Kevin Seppi

Faculty Publications

In the construction of a part-of-speech annotated corpus, we are constrained by a fixed budget. A fully annotated corpus is required, but we can afford to label only a subset. We train a Maximum Entropy Markov Model tagger from a labeled subset and automatically tag the remainder. This paper addresses the question of where to focus our manual tagging efforts in order to deliver an annotation of highest quality. In this context, we find that active learning is always helpful. We focus on Query by Uncertainty (QBU) and Query by Committee (QBC) and report on experiments with several baselines and …

Go to article

Temporally Correlated Dirichlet Processes In Pollution Receptor Modeling, Matthew J. Heaton May 2007

Temporally Correlated Dirichlet Processes In Pollution Receptor Modeling, Matthew J. Heaton

Theses and Dissertations

Understanding the effect of human-induced pollution on the environment is an important precursor to promoting public health and environmental stability. One aspect of understanding pollution is understanding pollution sources. Various methods have been used and developed to understand pollution sources and the amount of pollution those sources emit. Multivariate receptor modeling seeks to estimate pollution source profiles and pollution emissions from concentrations of pollutants such as particulate matter (PM) in the air. Previous approaches to multivariate receptor modeling make the following two key assumptions: (1) PM measurements are independent and (2) source profiles are constant through time. Notwithstanding these assumptions, …

Go to article

On Connections Between Univalent Harmonic Functions, Symmetry Groups, And Minimal Surfaces, Stephen M. Taylor May 2007

On Connections Between Univalent Harmonic Functions, Symmetry Groups, And Minimal Surfaces, Stephen M. Taylor

Theses and Dissertations

We survey standard topics in elementary differential geometry and complex analysis to build up the necessary theory for studying applications of univalent harmonic function theory to minimal surfaces. We then proceed to consider convex combination harmonic mappings of the form f=sf_1+(1-s) f_2 and give conditions on when f lifts to a one-parameter family of minimal surfaces via the Weierstrauss-Enneper representation formula. Finally, we demand two minimal surfaces M and M' be locally isometric, formulate a system of partial differential equations modeling this constraint, and calculate their symmetry group. The group elements generate transformations that when applied to a prescribed harmonic …

Go to article

Asymmetric Dihydroxylation And Aziridination Of Allenes And Related Chemistry, Renmao Liu May 2007

Asymmetric Dihydroxylation And Aziridination Of Allenes And Related Chemistry, Renmao Liu

Theses and Dissertations

A novel method for asymmetric synthesis of α-hydroxy ketone with excellent regio- and stereoselectivity has been established by the systematic investigation of asymmetric dihydroxylation of allenes. The efficiency of kinetic resolution of racemic allenes was also investigated by using the AD reaction on both 1,3-disubstituted and trisubstituted allenes. Steric effects, electronic effects and allene substitution are also discussed. Aziridines were formed by copper-catalyzed intramolecular nitrene addition to alkenes. The carbamate group was used as the tether between the alkene and the nitrene. Subsequent nucleophilic attack of the aziridine was accomplished using RSH, R2NH, N3-,or ROH as the nucleophile. This addition …

Go to article

Towards Early State Disease Detection In Microdevices: Fabrication And Testing Of Micro Total Analysis Systems For Bioanalytical Applications, Tao Pan May 2007

Towards Early State Disease Detection In Microdevices: Fabrication And Testing Of Micro Total Analysis Systems For Bioanalytical Applications, Tao Pan

Theses and Dissertations

The past few years have seen a rapid expansion in interest in the characterization of the entire complement of proteins, or proteome. Micro total analysis systems (μTAS) are an emerging promising method, offering rapid, sensitive and low sample consumption separations. I have demonstrated microchip capillary electrophoresis (CE) devices made of CaF2. New methods have been developed for micromachining enclosed capillaries in CaF2. CE analysis of fluorescently labeled amino acids was used to illustrate bioanalytical applications of these microdevices. Initial on-chip infrared spectroscopy results for qualitative analyte identification were achieved in microfluidic CaF2 channels. I have also shown the evaluation of …

Go to article

Origin And Tectonic Evolution Of Gondwana Sequence Units Accreted To The Banda Arc: A Structural Transect Through Central East Timor, Elizabeth Anick Zobell May 2007

Origin And Tectonic Evolution Of Gondwana Sequence Units Accreted To The Banda Arc: A Structural Transect Through Central East Timor, Elizabeth Anick Zobell

Theses and Dissertations

Petrographic and age analysis of sandstones, detailed structural analysis and gravity modeling were conducted to investigate the origin of the Gondwana Sequence in the Timor Region, and to better constrain the tectonic evolution of the active Banda Arc. Our field studies and U/Pb zircon age analysis helped assign most units to either Asian or Australian affinity. Detrital zircon from uplifted Banda forearc units (Asian affinity) have U/Pb ages as young as 80 Ma (Standley and Harris, in press). In contrast, analysis of detrital zircon from Gondwana Sequence sandstones accreted to the Banda Arc from Savu to East Timor are no …

Go to article

Probabilistic Searching Using A Small Unmanned Aerial Vehicle, Steven R. Hansen, Timothy W. Mclain, Michael A. Goodrich May 2007

Probabilistic Searching Using A Small Unmanned Aerial Vehicle, Steven R. Hansen, Timothy W. Mclain, Michael A. Goodrich

Faculty Publications

Ground breaking concepts in optimal search theory were developed during World War II by the U.S. Navy. These concepts use an assumed detection model to calculate a detection probability rate and an optimal search allocation. Although this theory is useful in determining when and where search effort should be applied, it offers little guidance for the planning of search paths. This paper explains how search theory can be applied to path planning for an SUAV with a fixed CCD camera. Three search strategies are developed: greedy search, contour search, and composite search. In addition, the concepts of search efficiency and …

Go to article

First Prev Next Last