Dynamic regulation of the tryptophan operon: A modeling study and comparison with experimental data

A mathematical model for regulation of the tryptophan operon is presented. This model takes into account repression, feedback enzyme inhibition, and transcriptional attenuation. Special attention is given to model parameter estimation based on experimental data. The model's system of delay differential equations is numerically solved, and the results are compared with experimental data on the temporal evolution of enzyme activity in cultures of Escherichia coli after a nutritional shift (minimal + tryptophan medium to minimal medium). Good agreement is obtained between the numeric simulations and the experimental results for wild-type E. coli, as well as for two different mutant strains.

Management science, economics and finance: A connection

This paper provides a brief review of the connecting literature in management science, economics and finance, and discusses some research that is related to the three disciplines. Academics could develop theoretical models and subsequent econometric models to estimate the parameters in the associated models, and analyze some interesting issues in the three disciplines.

Astros no rock: uma perspectiva sociocultural no uso da canção na educação em ciências

A incorporação de elementos da cultura primeira do estudante no processo de ensino-aprendizagem foi defendida pelo pedagogo francês Georges Snyders (1988) em sua obra \"A Alegria na Escola\". Esta pesquisa contribuiu com essa interface, identificando, no discurso de canções do rock n\' roll, elementos textuais que possibilitem reflexões no âmbito conceitual, epistemológico e sociopolítico sobre a exploração do espaço. O objeto de estudo neste trabalho são canções do período entre as décadas de 1960 e 1970 que possuem representações sobre a astronomia e as missões espaciais. O uso do rock justificou-se pelo fato de temas sobre exploração espacial aparecerem no trabalho de diversos artistas desse gênero musical, permitindo reflexões em nível conceitual, epistemológico e sociopolítico sobre a ciência, a tecnologia e suas relações com a sociedade e o ambiente. Além disso, identificamos que tanto o rock quanto as missões espaciais foram fenômenos culturais que dependeram em sua gênese dos avanços da tecnologia e da ciência e tiveram sua repercussão na sociedade através de processos midiáticos. Essas canções foram selecionadas entre os diversos gêneros de rock, e analisadas a partir de referenciais semiodiscursivos. As atividades foram aplicadas em situações formais de ensino - ensino médio e ensino superior -, em formação continuada de professores e projetos de ensino não formal na escola. No processo de ensinoaprendizagem, foram desenvolvidas atividades que envolviam leitura-comentada da canção, identificando na letra, melodia e harmonia, aspectos que evidenciavam um discurso crítico sobre a ciência e sua relação com a sociedade e o ambiente. Essas atividades envolveram três instâncias: Elaboração, Aplicação e Análise. Como referencial norteador dessas etapas, nos valemos das teorias socioculturais de Vigotski (2001), Snyders (1988) e Freire (2013).

Study and evaluation of several cache replacement policies on a commercial MIPS Processor

Actualmente, el rendimiento de los computadores es un tema candente. Existen importantes limitaciones físicas y tecnológicas en los semiconductores de hoy en día, por lo que se realiza un gran esfuerzo desde las universidades y la industria para garantizar la continuidad de la ley de Moore. Este proyecto está centrado en el estudio de la cache y la jerarquía de memoria, uno de los grandes temas en la materia. Para ello, hemos escogido MIPSfpga, una plataforma hardware abierta de Imagination Technologies, lo que nos ha permitido implementar y testear diferentes políticas de reemplazamiento como prueba de concepto, demostrando, además, las bondades de la plataforma.

Kinetic study and thermal decomposition behavior of viscoelastic memory foam

A systematic investigation of the thermal decomposition of viscoelastic memory foam (VMF) was performed using thermogravimetric analysis (TGA) to obtain the kinetic parameters, and thermogravimetric analysis coupled to Fourier Transformed Infrared Spectrometry (TGA-FTIR) and thermogravimetric analysis coupled to Mass Spectrometry (TGA-MS) to obtain detailed information of evolved products on pyrolysis and oxidative degradations. Two consecutive nth-order reactions were employed to correlate the experimental data from dynamic and isothermal runs performed at three different heating rates (5, 10 and 20 K/min) under an inert atmosphere. On the other hand, for the kinetic study of the oxidative decomposition, the data from combustion (synthetic air) and poor oxygen combustion (N2:O2 = 9:1) runs, at three heating rates and under dynamic and isothermal conditions, were correlated simultaneously. A kinetic model consisting of three consecutive reactions presented a really good correlation in all runs. TGA-FTIR analysis showed that the main gases released during the pyrolysis of VMF were determined as ether and aliphatic hydrocarbons, whereas in combustion apart from the previous gases, aldehydes, amines and CO2 have also been detected as the main gases. These results were confirmed by the TGA-MS.

Quarterly Journal of Science, Literature and the Arts.

1829 (July - Dec.)

Rules and orders relating to a Professor of the Mathematicks, of Natural and Experimental Philosophy, in Harvard College, 18 January 1726

This folder contains a single document describing the "rules and orders" of the Hollis Professor of Mathematics and Natural Philosophy. The document begins by defining the subjects to be taught by the Hollis Professor including natural and experimental philosophy, elements of geometry, and the principles of astronomy and geography. It then outlines the number of public and private lectures to be given to students, how much extra time the professor should spend with students reviewing any difficulties they may encounter understanding class subject matter discussed, and stipulates that the professor's duties shall be restricted solely to his teaching activities and not involve him in any religious activities at the College or oblige him to teach any additional studies other than those specified for the Hollis Professor of Mathematics and Natural Philosophy. Furthermore, the rules establish the professor's salary at £80 per year and allow the professor to receive from students, except those students studying theology under the Hollis Professor of Divinity, an additional fee as determined by the Corporation and Board of Overseers, to supplement his income. Moreover, the rules assert that all professorship candidates selected by the Harvard Corporation must be approved by Thomas Hollis during his lifetime or by his executor after his death. Finally, the rules state that the Hollis professor take an oath to the civil government and declare himself a member of the Protestant reformed religion. This document is signed by Thomas Hollis and four witnesses, John Hollis, Joshua Hollis, Richard Solly, and John Williams.

John Winthrop's proposal respecting electrical globes and jars, ca. 1758

In this proposal, John Winthrop explains the need to replace damaged "electric globes" used in the College's collection of scientific apparatus. He states that Benjamin Franklin, at the time residing in London, was willing to seek replacement globes for the College's collection. Winthrop then proceeds to assert that the College should acquire "square bottles, of a moderate size, fitted in a wooden box, like what they call case bottles for spirits" instead of the large jars included in the scientific apparatus, because those jars cracked frequently.