Label-free electrical quantification of the dielectrophoretic response of DNA

A purely electrical sensing scheme is presented that determines the concentration of macromolecules in solution by measuring the capacitance between planar microelectrodes. Concentrations of DNA in the ng/mL range have been used in samples of 1 microL volume. The method has been applied to the characterisation of the dielectrophoretic response of DNA without the need for any chemical modifications. The influence of electrical parameters like duty cycle, voltage and frequency has been investigated. The results are in good agreement with data from dielectrophoretic studies on fluorescently labelled DNA. Extension of the method down to the single molecule level appears feasible.Comment: 12 pages, 7 figure

Projetos de Aprendizagem Mediados por Ambientes Virtuais no Ensino de EngenhariaEl trica

As experiências relacionadas à metodologia de projetos de aprendizagem têm sua origem nas formulações de John Dewey no início do século XX. A concepção de projeto de aprendizagem defendida nesta pesquisa alia às formulações de Dewey as propostas da professora Lea Fagundes. Esta metodologia tem o aluno como responsável pela sua aprendizagem e reflete os conceitos construtivistas de Piaget. A integração e a construção de conhecimento via projetos é facilitada com o uso dos ambientes virtuais para apoio à aprendizagem que são softwares que permitem interações síncronas ou assíncronas além de possibilitar o registro de todo o caminho percorrido pelo estudante e de todas as atividades de uma disciplina. A partir de dados coletados, no período de 2003 a 2007, em atividades escolares de disciplinas do terceiro período letivo do curso de Engenharia Elétrica da Universidade Federal do Espírito Santo pretende-se analisar (a) em que medida os ambientes virtuais de aprendizagem e a apropriação das tecnologias de informação e comunicação acrescentam na formação do estudante de engenharia, em relação às práticas pedagógicas presenciais e (b) em que medida os projetos de aprendizagem contribuem para o enfrentamento dos problemas que temos, hoje, no ensino de engenharia elétric

Barbarians at the British Museum: Anglo-Saxon Art, Race and Religion

A critical historiographical overview of art historical approaches to early medieval material culture, with a focus on the British Museum collections and their connections to religion

Mono-institutional retrospective cohort analysis of the insurance status dependent access to ENT-professionals and survival in head and neck squamous cell carcinoma

Background!#!To access the influence of insurance status on time of diagnosis, quality of treatment and survival in head and neck squamous cell carcinoma (HNSCC).!##!Methods!#!This mono-institutional retrospective cohort analysis included all HNSCC patients (n = 1,054) treated between 2001 and 2011, and subdivided the cohort according to the insurance status. Differences between the groups were analyzed using the Chi square and the unpaired student's t-test. Survival rates were calculated by Kaplan-Meier and Cox regression for forward selection.!##!Results!#!Nine hundred twenty-five patients showed general, 129 private insurance. The 2 groups were equal regarding age, gender, tumor localization, therapy, and N/M/G/R-status. The T-status differed significantly between the groups showing more advanced tumors in patients with general insurance (p = 0.002). While recurrence-free survival was comparable in both groups, overall survival was significantly better in private patients (p = 0.009). The time frame between first symptom and diagnosis was equal in both groups.!##!Conclusions!#!The time frame between subjective percipience of first symptom and final therapy did not differ between the groups. In our cohort, access to otorhinolaryngological specialists is favorable in both, patients with general and private insurance. Recurrence-free survival was comparable in both groups, indicating successful HNSCC treatment both groups. However, overall survival was significantly better in patients with private insurance suggesting other socioeconomic factors influencing survival

Dielectrophoresis of DNA: Quantification by impedance measurements

Dielectrophoretic properties of DNA have been determined by measuring capacitance changes between planar microelectrodes. DNA sizes ranged from 100 bp to 48 kbp, DNA concentrations from below 0.1 to 70 μg∕ml. Dielectrophoretic spectra exhibited maximum response around 3 kHz and 3 MHz. The strongest response was found for very long DNA (above 10 kbp) and for short 100 bp fragments, which corresponds to the persistence length of DNA. The method allows for an uncomplicated, automatic acquisition of the dielectrophoretic properties of submicroscopical objects without the need for labeling protocols or optical accessibility