Abnormal Rolls and Regular Arrays of Disclinations in Homeotropic Electroconvection

We present the first quantitative verification of an amplitude description for systems with (nearly) spontaneously broken isotropy, in particular for the recently discovered abnormal-roll states. We also obtain a conclusive picture of the 3d director configuration in a spatial period doubling phenomenon involving disclination loops (CRAZY rolls). The first observation of two Lifshitz frequencies in electroconvection is reported.Comment: 4 pages; 4 figure

The Money To Get Started - What Do Farm Boys Expect?

It takes a lot of capital to acquire and to operate an Iowa farm. The study of occupational plans and preferences of Iowa farm boys helps to indicate just how much influence capital needs have on their plans

Occupational plans of Iowa farm boys

This bulletin reports the findings of an exploratory study of the long-range occupational plans of Iowa farm boys in their senior year of high school. The primary objectives of the study were: (1) to relate the theory of choice to occupational planning, (2) to describe the occupational plans of the boys, (3) to determine the characteristics which differentiate boys who plan to farm from boys who plan nonfarm careers and (4) to appraise the relative importance of factors influencing farm-nonfarm occupational plans. Application of the theory of choice to occupational planning resulted in three general hypotheses to explain why some farm boys plan to farm while others plan nonfarm occupations. These hypotheses involved individual differences in (1) occupational satisfaction functions (preference systems), (2) available resources and (3) the results expected from using given resources in farm and nonfarm employments. Various operational hypotheses derived from the general hypotheses were evaluated on the basis of evidence obtained from a state-wide sample of senior farm boys attending Iowa high schools in rural areas and cities under 25,000 population in the spring of 1959

What Careers for Farm Boys?

This is the first of a series of articles reporting the results of a study of the career preferences and plans and choices of farm boys. This article tells of career plans the boys made and of their immediate after high school plans

A dinucleotide deletion in the ankyrin promoter alters gene expression, transcription initiation and TFIID complex formation in hereditary spherocytosis

Ankyrin defects are the most common cause of hereditary spherocytosis (HS). In some HS patients, mutations in the ankyrin promoter have been hypothesized to lead to decreased ankyrin mRNA synthesis. The ankyrin erythroid promoter is a member of the most common class of mammalian promoters which lack conserved TATA, initiator or other promoter cis elements and have high G+C content, functional Sp1 binding sites and multiple transcription initiation sites. We identified a novel ankyrin gene promoter mutation, a TG deletion adjacent to a transcription initiation site, in a patient with ankyrin-linked HS and analyzed its effects on ankyrin expression. In vitro, the mutant promoter directed decreased levels of gene expression, altered transcription initiation site utilization and exhibited defective binding of TATA-binding protein (TBP) and TFIID complex formation. In a transgenic mouse model, the mutant ankyrin promoter led to abnormalities in gene expression, including decreased expression of a reporter gene and altered transcription initiation site utilization. These data indicate that the mutation alters ankyrin gene transcription and contributes to the HS phenotype by decreasing ankyrin gene synthesis via disruption of TFIID complex interactions with the ankyrin core promoter. These studies support the model that in promoters that lack conserved cis elements, the TFIID complex directs preinitiation complex formation at specific sites in core promoter DNA and provide the first evidence that disruption of TBP binding and TFIID complex formation in this type of promoter leads to alterations in start site utilization, decreased gene expression and a disease phenotype in viv

Uma arquitetura XML para computação voluntária P2P

Diversas arquiteturas propostas para computação colaborativa, ou computação voluntária, apresentam as seguintes características: (i) controle centralizado; (ii) setup complexo para não-especialistas. Este artigo introduz a IeC (Infraestrutura Colaborativa): uma arquitetura para computação colaborativa peer-to-peer — P2P — implementada sobre XML, que é de fácil implantação por usuários não-especialistas e de simples utilização por desenvolvedores de aplicações para ambientes colaborativos. O uso de um mecanismo simples de escalonamento distribuído para o balanceamento de carga nos nós computacionais participantes é avaliado em termos da escalabilidade da arquitetura proposta e da qualidade do balanceamento. Tal foi obtido através de simulações usando-se como benchmark um lote de problemas do tipo RCPS — Resource Constrained Project Scheduling

Uma abordagem Branch and Bound para RCPSP em um ambiente de computação colaborativa

Um projeto pode ser representado por uma rede de atividades formando um grafo de precedência, direcionado e acíclico. Quando a quantidade de recursos existentes é limitada, o problema de determinação do menor tempo de realização do projeto é conhecido como RCPSP (Resource Constrained Project Scheduling). A solução ótima para o problema RCPS é reconhecidamente NP-hard. Este artigo mostra um algoritmo distribuído para a solução ótima do problema RCPS usando uma abordagem branch and bound. Este algoritmo foi implementado e avaliado num ambiente de computação colaborativa, do tipo peer to peer, com escalonamento adaptativo distribuído para balanceamento de carga nos nós computacionais. Os resultados sugerem a escalabilidade do algoritmo apenas com a adição de nós computacionais

Modulated structures in electroconvection in nematic liquid crystals

Motivated by experiments in electroconvection in nematic liquid crystals with homeotropic alignment we study the coupled amplitude equations describing the formation of a stationary roll pattern in the presence of a weakly-damped mode that breaks isotropy. The equations can be generalized to describe the planarly aligned case if the orienting effect of the boundaries is small, which can be achieved by a destabilizing magnetic field. The slow mode represents the in-plane director at the center of the cell. The simplest uniform states are normal rolls which may undergo a pitchfork bifurcation to abnormal rolls with a misaligned in-plane director.We present a new class of defect-free solutions with spatial modulations perpendicular to the rolls. In a parameter range where the zig-zag instability is not relevant these solutions are stable attractors, as observed in experiments. We also present two-dimensionally modulated states with and without defects which result from the destabilization of the one-dimensionally modulated structures. Finally, for no (or very small) damping, and away from the rotationally symmetric case, we find static chevrons made up of a periodic arrangement of defect chains (or bands of defects) separating homogeneous regions of oblique rolls with very small amplitude. These states may provide a model for a class of poorly understood stationary structures observed in various highly-conducting materials ("prechevrons" or "broad domains").Comment: 13 pages, 13 figure