68,220 research outputs found
Mining e-mail content for author identification forensics
No full textWe describe an investigation into e-mail content mining for author identification, or authorship attribution, for the purpose of forensic investigation. We focus our discussion on the ability to discriminate between authors for the case of both aggregated e-mail topics as well as across different email topics. An extended set of e-mail document features including structural characteristics and linguistic patterns were derived and, together with a Support Vector Machine learning algorithm, were used for mining the e-mail content. Experiments using a number of e-mail documents generated by different authors on a set of topics gave promising results for both aggregated and multi-topic author categorisation
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Enantioselective Palladium-Catalyzed Total Synthesis of Vitamin E by Employing a Domino Wacker–Heck Reaction
No full textAn enantioselective total synthesis of vitamin E in which a novel palladium-catalyzed domino reaction was employed as the key step is described. This reaction allows the formation of the chiral chroman framework and the concurrent introduction of part of the side chain of vitamin E. The sequence comprises an enantioselective Wacker cyclization and a subsequent Heck reaction. Accordingly, reaction of alkenylphenol 12 with methyl vinyl ketone (13) in the presence of catalytic amounts of Pd(OTFA)(2) (TFA = trifluoroacetate), the enantiopure ligand (S,S)-Bn-BOXAX (8b; Bn = benzyl, BOXAX = 2,2'-bis(oxazolyl)-1,1'-bi- naphthyl, and p-benzoquinone (9) as an oxidant gives access to chiral chroman 10 with an enantioselectivity of 97% ee in 84% yield. Chroman 10 is then converted into 24 by an aldol condensation reaction with (3R)-3,7-dimethyloctanal (11). Subsequent 1,2-addition of methyllithium, elimination of water, and hydrogenation yields vitamin E
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
No full textThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
Estudio numérico y asintótico de modelos discretos en física de semiconductores
No full textEsta tesis presenta el estudio y el desarrollo de modelos de transporte de carga eléctrica en superredes semiconductoras. Las superredes semiconductoras son sistemas fuertemente no lineales cuasi-unidimensionales, formados por una sucesión de barreras y pozos de potencial, y cuya riqueza radica en la gran variedad de patrones y comportamientos distintos que se encuentran variando los parámetros físicos involucrados. Después una breve introducción en la que se presentan las características principales del transporte electrónico en estos sistemas, el contenido de la tesis se centra en el caso particular de las superredes débilmente acopladas. El comportamiento de dispositivos basados en estas superredes lo describe un modelo, propuesto por Luis L. Bonilla en 1994, en el que el mecanismo de túnel resonante secuencial es el principal responsable del transporte de carga. El modelo consiste en un sistema de ecuaciones diferenciales no lineales acopladas, cuyo número viene determinado por el número de periodos de la superred, y que representan la continuidad de carga y la ecuación de Poisson en cada pozo de la superred. En este modelo, toda la información cuántica está recogida en la función de densidad de corriente túnel a través de la barrera que separa dos pozos cuánticos. Tras la descripción del modelo, la memoria presenta los resultados principales del estudio realizado. Estudiamos entonces los estados estacionarios del sistema, construimos numéricamente la curva estacionaria I-V, y elaboramos un análisis de estabilidad lineal de las ramas estacionarias. Este análisis presenta la posible existencia de bifurcaciones de Hopf, que son a su vez estudiamos mediante un desarrollo en escalas múltiples que nos lleva a una ecuación de amplitud. Por otra parte, la memoria presenta una amplia descripción de los métodos numéricos utilizados mediante los cuales hemos podido caracterizar numéricamente la respuesta del sistema a diferentes manipulaciones del voltaje aplicado (sweeping). El resultado principal es la descripción detallada de diversos nuevos escenarios de recolocación de los dominios del campo eléctrico y de la respuesta de la densidad de corriente, que añaden nuevas fenomenologías a las ya conocidas en la literatura. Después, analizamos el modelo a corriente constante. En estas circunstancias, la naturaleza discreta del sistema se pone claramente de manifiesto: aparece el característico fenómeno de anclaje de los frentes de onda cuando el parámetro de control (la corriente) está en un determinado intervalo, fenómeno típico de los sistemas discretos, no compartido con los sistemas continuos. El fenómeno de anclaje y movimiento de los frentes de onda es una bifurcación global de las ecuaciones del modelo en unas ciertas corrientes críticas. Lo podemos estudiar introduciendo el concepto de pozo activo, mediante el cual conseguimos describir la dinámica de los frentes de onda cerca de las corrientes criticas con unas ecuaciones reducidas. En el límite continuo de una superred muy larga en que el campo eléctrico varía poco de un pozo al siguiente, las ecuaciones del modelo se pueden aproximar por una ecuación hiperbólica de primer orden y los frentes de onda del modelo discreto son ondas de choque de la misma. Hemos encontrado la velocidad de estos choques partiendo de las ecuaciones discretas. Finalmente, resumimos los contenidos esenciales de la tesis y presentamos las conclusiones generales, así como una descripción de los que a nuestro entender son los principales problemas abierto
Optimierung eines Infektionsmodells für Dengue-M/E pseudotypisierte HIV-1-Partikel
No full textIm ersten Teil dieser Arbeit wurden Dengue-M/E pseudotypisierte HIV-1-Partikel mit den Hüllproteinen aller DENV Serotypen hergestellt. Dies erfolgte mit Hilfe von jeweils zwei Plasmiden. Ein Plasmid codiert für das Virusgenom (pNLlucAM), das andere Plasmid codiert für die M/E-Hüllproteine des entsprechenden DENV. Um die Menge der infektiösen Titer von M/E-Pseudotypen zu steigern, wurde die Luciferase-Aktivität der co-transfizierten HEK293T-Zellen gemessen. Zusätzlich wurden die partikelhaltigen Zellkultur-überstände auf Infektiosität der Pseudotypen getestet. Ergebnis war ein umgekehrter Zusammenhang. Bei Steigerung der Menge an Plasmid-DNA bei der Transfektion ging die Luciferase-Aktivität in den transfizierten HEK291T-Zellen zurück, während die Infektiosität der Partikel anstieg. Der Schwellenwert für die DNA-Menge war bei 45 μg Plasmid-DNA im molaren Verhältnis 1:14 von Virusvektor zu M/E-Expressionsvektor. Die 45 μg Plasmid-DNA bezog sich auf 5·106 Zellen in einem 6-well, was einer Fläche von etwa 9 cm2 entsprach. Bei einer transfizieren Plasmid-Menge über 45 μg wurden abnehmende Pseudotypen-Titer gemessen. Bei geringeren Plasmid-Mengen sank die Infektiosität um den Faktor 100. Demnach wurde die transfizierte DNA-Menge gegenüber dem Incella Transfektionsprotokoll und vorherigen Arbeiten um das 17,5-fache gesteigert. In den Kontrollexperimenten mit HIV-1 pseudotypisierten HIV-1-Partikeln hingegen wurden die höchsten Infektiositäten der partikelhaltigen Überstände bei geringen Plasmid-Mengen gemessen, wodurch sich die Resultate konkret auf Dengue-M/E pseudotypisierten HIV-1 Partikel beziehen.
Im zweiten Teil der Arbeit wurde der Einfluss der Partikelfiltration, des FCS und der Zelldichte auf die Infektion untersucht, um das Infektionsmodell zu verbessern. Die größte Bedeutung für die Infektionen zeigten die Zelldichten der DENV permissiven VeroB4-Zelllinie. Bei zu hohen Zelldichten trat eine Zellkontakthemmung auf, welche die Infektion einschränkte und selektiv auch inhibierte. Ergebnis war eine optimale Zelldichte von etwa 70% zum Zeitpunkt der Infektion, um gleichmäßig Infektionsraten zu erzielen.
Im dritten Teil der Arbeit wurden die Transfektions-Ausbeuten durch TCID50-Bestimmungen quantifiziert. Die infektiöse Dosis DENV-2 pseudotypisierter HIV-1-Partikel entsprach einer Verdünnung von 1:100. Demnach können mit einer Transfektion in 6-well-Platten etwa 3000 Infektionsexperimente (im 96-well-Format) durchgeführt werden. Die Ergebnisse zeigten eine Steigerung der Infektiosität der partikelhaltigen Zellkulturüberstände um das 150-fache im Gegensatz zu vorherigen Arbeiten. Daher konnten durch die gesteigerten transfizierten Plasmid-Mengen deutlich mehr Dengue-M/E pseudotypisierte HIV-1-Partikel gebildet werden.In the first part of this study dengue-M/E pseudotyped HIV-1 particles with the envelope proteins of all four DENV serotypes were produced. The particles were made using two plasmids. One plasmid encodes the viral HIV-1 (env- Luc+) genome (pNLlucAM) while the other plasmid encodes for example the DENV-1-M/E envelope proteins, respectively. To increase the amount of the infectious titers of M/E pseudotypes the luciferase activity of the co-transfected HEK293T cells were measured. Additionally, the infectiosity of the cell culture supernatant containing the particles was tested by VeroB4 infection. The outcome was a reversed correlation. With the increase of transfected plasmid DNA the luciferase activity in the transfected HEK293T cells decreased, whereas the infectiosity of the pseudotyped particles increased. The threshold of the DNA amount was 45 μg plasmid DNA with a molar ratio of 1:14 of viral vector to M/E expression vector. The 45 μg plasmid DNA referred to 5·106 cells in the 6-well-cell culture plate which is equivalent to a surface of approximately 9 cm2. At a transfected amount of plasmid above 45 μg decreasing infectiosities were detected. At a lower amount of plasmid the infectiosity decreased by a factor of 100. Thus, the transfected amount of DNA was 17,5-fold higher compared to the Incella transfection protocol and previous studies. During the control experiments with HIV-1 pseudotyped HIV-1 particles however the slightest amounts of plasmid DNA resulted in the highest infeciosities of the cell culture supernatant containing the particles. Therefore these results are highly specific for the generation of dengue-M/E pseudotyped HIV-particles.
In the second part of this study the impact of particle filtration, FCS concentration and the cell density on VeroB4 infections were determined to improve the pseudotype infection model. The disseminated cells showed the major significance. At excessive cell densities a cell contact inhibition occurred which restricted and selectively inhibited the infections. The result was an ideal cell density of approximately 70% at the time of the infection to detect consistent infection rates.
In the third part of this study the yields of the transfections were quantified by a TCID50 assay. The infectious dose of DENV-2 pseudotyped HIV-1 particles equated to a dilution of 1:100. Thus, about 3000 infection experiments (in 96-well) can be performed with supernatants transfected in 6-well-cell cultures. The results showed a general 150-fold increase of the infectiosity of the cell culture supernatant containing the particles compared to previous studies. Therefore significantly more dengue-M/E pseudotyped HIV-1 particles were generated by the optimized protocol for pseudotype generation, presented in this study
The long-wavelength view of GG Tau A: rocks in the ring world
No full textWe present the first detection of GG Tau A at centimetre wavelengths, made with the Arcminute Microkelvin Imager Large Array at a frequency of 16 GHz (λ = 1.8 cm). The source is detected at >6 σrms with an integrated flux density of S16GHz = 249 ± 45 µJy. We use these new centimetre-wave data, in conjunction with additional measurements compiled from the literature, to investigate the long-wavelength tail of the dust emission from this unusual protoplanetary system. We use an MCMC-based method to determine maximum likelihood parameters for a simple parametric spectral model and consider the opacity and mass of the dust contributing to the microwave emission. We derive a dust mass of Md ~ 0.1 Msun, constrain the dimensions of the emitting region and find that the opacity index at λ > 7 mm is less than unity, implying a contribution to the dust population from grains exceeding ~4 cm in size. We suggest that this indicates coagulation within the GG Tau A system has proceeded to the point where dust grains have grown to the size of small rocks with dimensions of a few centimetres. Considering the relatively young age of the GG Tau association in combination with the low derived disc mass, we suggest that this system may provide a useful test case for rapid core accretion planet formation models
Simulation of thermal plant optimization and hydraulic aspects of thermal distribution loops for large campuses
No full textFollowing an introduction, the author describes Texas A&M University and its utilities system. After that, the author presents how to construct simulation models for chilled water and heating hot water distribution systems. The simulation model was used in a $2.3 million Ross Street chilled water pipe replacement project at Texas A&M University. A second project conducted at the University of Texas at San Antonio was used as an example to demonstrate how to identify and design an optimal distribution system by using a simulation model. The author found that the minor losses of these closed loop thermal distribution systems are significantly higher than potable water distribution systems. In the second part of the report, the author presents the latest development of software called the Plant Optimization Program, which can simulate cogeneration plant operation, estimate its operation cost and provide optimized operation suggestions. The author also developed detailed simulation models for a gas turbine and heat recovery steam generator and identified significant potential savings. Finally, the author also used a steam turbine as an example to present a multi-regression method on constructing simulation models by using basic statistics and optimization algorithms. This report presents a survey of the author??s working experience at the Energy Systems Laboratory (ESL) at Texas A&M University during the period of January 2002 through March 2004. The purpose of the above work was to allow the author to become familiar with the practice of engineering. The result is that the author knows how to complete a project from start to finish and understands how both technical and nontechnical aspects of a project need to be considered in order to ensure a quality deliverable and bring a project to successful completion. This report concludes that the objectives of the internship were successfully accomplished and that the requirements for the degree of Degree of Engineering have been satisfied
Suplemento 39. Diversidad y reconocimiento, aproximaciones al multiculturalismo e interculturalidad en América Latina: Boletín Interno de los investigadores del área de Antropología. 88 (2006) noviembre. Diario de Campo
No full text- Presentación: Multiculturalismo e interculturalidad en América Latina por Alicia M. Barabas. - Notas sobre Multiculturalismo e Interculturalidad por Alicia M. Barabas. - Interculturalidad. Una revisión desde y con los pueblos indígenas (Argentina) por Liliana Tamagno. - Descubriendo la multiculturalidad. El caso chileno por Luis Campos Muñoz. - Indios, negros y ciudadanos. Luchas multiculturales por el reconocimiento (Brasil) por Gabriel O. Álvarez. - Bolivia. Plurinacional e Intercultural por Xavier Albó. - Multiculturalidad e indianismo en el Perú por Juan M. Ossio. - Antropología abierta, antropología ambigua. Tendencias actuales de la antropología ecuatoriana por Segundo E. Moreno Yánez. - Interculturalidad y diversidad cultural en el marco de la revolución bolivariana en Venezuela por Nelly Arvelo Jiménez. - El pluralismo cultural en México por Cristina Oehmichen
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