Charge generation, charge transport, and residual charge in the electrospinning of polymers: A review of issues and complications

Electrospinning has become a widely implemented technique for the generation of nonwoven mats that are useful in tissue engineering and filter applications. The overriding factor that has contributed to the popularity of this method is the ease with which fibers with submicron diameters can be produced. Fibers on that size scale are comparable to protein filaments that are observed in the extracellular matrix. The apparatus and procedures for conducting electrospinning experiments are ostensibly simple. While it is rarely reported in the literature on this topic, any experience with this method of fiber spinning reveals substantial ambiguities in how the process can be controlled to generate reproducible results. The simplicity of the procedure belies the complexity of the physical processes that determine the electrospinning process dynamics. In this article, three process domains and the physical domain of charge interaction are identified as important in electrospinning: (a) creation of charge carriers, (b) charge transport, (c) residual charge. The initial event that enables electrospinning is the generation of region of excess charge in the fluid that is to be electrospun. The electrostatic forces that develop on this region of charged fluid in the presence of a high potential result in the ejection of a fluid jet that solidifies into the resulting fiber. The transport of charge from the charge solution to the grounded collection device produces some of the current which is observed. That transport can occur by the fluid jet and through the atmosphere surrounding the electrospinning apparatus. Charges that are created in the fluid that are not dissipated remain in the solidified fiber as residual charges. The physics of each of these domains in the electrospinning process is summarized in terms of the current understanding, and possible sources of ambiguity in the implementation of this technique are indicated. Directions for future research to further articulate the behavior of the electrospinning process are suggested. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3682464]

An integrated approach of software development and test processes to distributed teams

The Distributed Software Development (DSD) is a development strategy that meets the globalization needs concerned with the increase productivity and cost reduction. However, the temporal distance, geographical dispersion and the socio-cultural differences, increased some challenges and, especially, added new requirements related with the communication, coordination and control of projects. Among these new demands there is the necessity of a software process that provides adequate support to the distributed software development. This paper presents an integrated approach of software development and test that considers distributed teams peculiarities. The approach purpose is to offer support to DSD, providing a better project visibility, improving the communication between the development and test teams, minimizing the ambiguity and difficulty to understand the artifacts and activities. This integrated approach was conceived based on four pillars: (i) to identify the DSD peculiarities concerned with development and test processes, (ii) to define the necessary elements to compose the integrated approach of development and test to support the distributed teams, (iii) to describe and specify the workflows, artifacts, and roles of the approach, and (iv) to represent appropriately the approach to enable the effective communication and understanding of it.

Inactivating Mutations of the Human Luteinizing Hormone Receptor in Both Sexes

The human luteinizing hormone/chorionic gonadotropin receptor (LHCGR) plays a fundamental role in male and female reproductive physiology. Over the past 15 years, several homozygous or compound heterozygous loss-of-function mutations in the LHCGR gene have been described in males and females. In genetic males, mutations in LHCGR were associated with distinct degrees of impairment in pre- and postnatal testosterone secretion resulting in a phenotypic spectrum. Patients with the severe form of LH resistance have predominantly female external genitalia and absence of secondary sex differentiation at puberty. Patients with milder forms have predominantly male external genitalia with micropenis and/or hypospadias or only infertility without ambiguity. The undermasculization is associated with low basal, as well as human CG-stimulated, testosterone levels and elevated LH levels after pubertal age, without abnormal step-up in testosterone biosynthesis precursors. The testes have only slightly reduced size but mature Leydig cells are absent or scarce (Leydig cell hypoplasia). Genetic females with inactivating LHCGR mutations have female external genitalia, spontaneous breast and pubic hair development at puberty, and normal or late menarche followed by oligoamenorrhea and infertility. Estradiol and progesterone levels are normal for the early to midfollicular phase, but do not reach ovulatory or luteal phase levels. Serum LH levels are high whereas follicle-stimulating hormone levels are normal or only slightly increased. Pelvic ultrasound has demonstrated a small or normal uterus and normal or enlarged ovaries with cysts. The inactivating mutations of the LHCGR have provided important insights into distinct physiological roles of LH in reproduction of both sexes.

Using complex networks to quantify consistency in the use of words

In this paper we have quantified the consistency of word usage in written texts represented by complex networks, where words were taken as nodes, by measuring the degree of preservation of the node neighborhood. Words were considered highly consistent if the authors used them with the same neighborhood. When ranked according to the consistency of use, the words obeyed a log-normal distribution, in contrast to Zipf's law that applies to the frequency of use. Consistency correlated positively with the familiarity and frequency of use, and negatively with ambiguity and age of acquisition. An inspection of some highly consistent words confirmed that they are used in very limited semantic contexts. A comparison of consistency indices for eight authors indicated that these indices may be employed for author recognition. Indeed, as expected, authors of novels could be distinguished from those who wrote scientific texts. Our analysis demonstrated the suitability of the consistency indices, which can now be applied in other tasks, such as emotion recognition.

Arquitetura brutalista e estratégia de transportes no triângulo mineiro: estações ferroviárias da Mogiana e Terminal Rodoviário Presidente Castelo Branco

Em 1989, Brandão descrevia o Triângulo Mineiro como “fruto da ambiguidade de seu estigma de fazer parte de Minas, mas ser articulada economicamente a São Paulo.” A mesorregião do Triângulo Mineiro e Alto Paranaíba, faz fronteira com os estados de Goiás, São Paulo e Mato Grosso do Sul, interligando também com a Central Mineira e com o Oeste de Minas, sendo a característica de “rota de passagem” como principal fator do desenvolvimento de sua economia. O posicionamento estratégico da região, como eixo de ligação da capital paulista ao chamado Brasil Central, pode ser considerado um importante fator no estreitamento dos laços entre a região e São Paulo, somado ao sentimento de não pertencimento do Triângulo ao estado de Minas Gerais, o qual resultou por décadas em manifestações separatistas na região. A arquitetura moderna produzida no Triângulo Mineiro e Alto Paranaíba deu um salto significativo no momento de construção da nova capital federal, em finais da década de 1950, onde o papel de mediação, principalmente da cidade de Uberlândia, no processo de infra-estruturação da nova cidade foi determinante nos avanços construtivos do Triângulo. Esse momento coincidiu com o início do processo de verticalização das principais cidades da região e o aumento de arquitetos residentes nas cidades. Por meio, em especial, dos edifícios para as estações ferroviárias da Cia Mogiana, de Oswaldo Arthur Bratke em Uberaba e Uberlândia (déc. 1960) e do Terminal Rodoviário Presidente Castelo Branco em Uberlândia, dos arquitetos Fernando Graça, Flávio Almada e Ivan Curpertino (1970), este trabalho objetiva conduzir uma discussão acerca da produção de arquitetura moderna no Triângulo Mineiro ligada às estratégias de transportes intermunicipais como própria cultura de desenvolvimento econômico da região. Nos interessa valer do debate entre o uso da estética brutalista, e da própria escolha por uma arquitetura moderna, como artifício no plano de desenvolvimento das empresas de transporte, e dos governos locais. Sobretudo, discutir as interlocuções do Triângulo Mineiro com São Paulo, rebatendo-as na formação do conjunto arquitetonico moderno produzido na região. Este trabalho é fruto da pesquisa de mestrado da autora cujo tema central é a difusão da arquitetura moderna no Triângulo Mineiro e Alto Paranaíba, pelo Iau/Usp, e financiado pela Capes.

Ensino de Arquitetura e Urbanismo com auxilio de ferramentas digitais

Este texto pretende discutir a importância do desenho à mão livre no processo projetivo arquitetônico inserido no contexto da era digital, por meio do uso das mesas digitais, comumente chamadas de tablets. A relevância desta discussão consiste em identificar como os desenhos feitos com tablets mantêm a percepção e o traço individual de cada pessoa. Pretende-se, com isto, não apenas rever e atualizar as disciplinas de desenho nos cursos de arquitetura, suas práticas e seus procedimentos, mas também, discutir o papel da linguagem e representação – analógica ou digital – e sua integração com outras disciplinas. São apresentadas algumas considerações sobre o uso dessa ferramenta nas seguintes disciplinas: História da Arquitetura e Urbanismo, Paisagismo e Projeto, ministradas no Instituto de Arquitetura e Urbanismo da Universidade de São Paulo, Brasil. As tablets são apresentadas como um meio de conexão entre o projeto analógico e digital, capazes de capturar a pressão e a velocidade do traço, aproximando a potencialidade e racionalidade do processo feito no computador com o gesto criativo do desenho à mão livre, resultando em uma sinergia entre essas duas linguagens.

New Improved Version of J 1 ...J 4 Interferometry Method and its Application to Nanometric Vibration Measurements

Piezoelectric ceramics, such as PZT, can generate subnanometric displacements, bu t in order to generate multi- micrometric displacements, they should be either driven by high electric voltages (hundreds of volts ), or operate at a mechanical resonant frequency (in narrow band), or have large dimensions (tens of centimeters). A piezoelectric flextensional actuator (PFA) is a device with small dimensions that can be driven by reduced voltages and can operate in the nano- and micro scales. Interferometric techniques are very adequate for the characterization of these devices, because there is no mechanical contact in the measurement process, and it has high sensitivity, bandwidth and dynamic range. A low cost open-loop homodyne Michelson interferometer is utilized in this work to experimentally detect the nanovi brations of PFAs, based on the spectral analysis of the interfero metric signal. By employing the well known J 1 ...J 4 phase demodulation method, a new and improved version is proposed, which presents the following characteristics: is direct, self-consistent, is immune to fading, and does not present phase ambiguity problems. The proposed method has resolution that is similar to the modified J 1 ...J 4 method (0.18 rad); however, differently from the former, its dynamic range is 20% larger, does not demand Bessel functions algebraic sign correction algorithms and there are no singularities when the static phase shift between the interferometer arms is equal to an integer multiple of  /2 rad. Electronic noise and random phase drifts due to ambient perturbations are taken into account in the analysis of the method. The PFA nanopositioner characterization was based on the analysis of linearity betw een the applied voltage and the resulting displacement, on the displacement frequency response and determination of main resonance frequencies.