25,158 research outputs found
Vorton Formation
In this paper we present the first analytic model for vorton formation. We
start by deriving the microscopic string equations of motion in Witten's
superconducting model, and show that in the relevant chiral limit these
coincide with the ones obtained from the supersonic elastic models of Carter
and Peter. We then numerically study a number of solutions of these equations
of motion and thereby suggest criteria for deciding whether a given
superconducting loop configuration can form a vorton. Finally, using a recently
developed model for the evolution of currents in superconducting strings we
conjecture, by comparison with these criteria, that string networks formed at
the GUT phase transition should produce no vortons. On the other hand, a
network formed at the electroweak scale can produce vortons accounting for up
to 6% of the critical density. Some consequences of our results are discussed.Comment: 41 pages; color figures 3-6 not included, but available from authors.
To appear in Phys. Rev.
Improvement in the management of no-till in the central-southern-Brazil.
The soil performs important functions for the maintenance of life. The management practices based on the conservation of soil and water in no till system may improve environmental sustainability
Molecular Evaluation of exons 8 and 22 of the SHANK3 gene in Autism Spectrum Disorders
Autism spectrum disorders are a group of neurodevelopmental disorders with a complex and heterogeneous etiology. Studies have shown that genetic factors play an important role in the aetiology of these diseases. Recently, de novo mutations, frameshifts and deletions have been described in the SHANK3 gene, also known as ProSAP2 gene, which encodes a synaptic scaffolding protein. All the participants of this study had normal karyotypes and underwent screening for Fragile-X syndrome. Subsequently, they were analyzed by direct sequencing of different points of exons 8 and 22 of the SHANK3 gene. None of the study participants presented with changes in these regions. These findings may be due to the fact that mutations, deletions and duplications of the SHANK3 gene are rare
Ovarian Hyperstimulation Syndrome in a Spontaneous Pregnancy
Introdução: O Síndrome de Hiperestimulação do Ovário (SHO) geralmente é descrito como uma complicação iatrogénica dos tratamentos de indução da ovulação. Raramente, pode estar associado a ciclos ovulatórios espontâneos, sendo mais frequente em gravidez múltipla, patologia molar e hipotiroidismo. A apresentação clínica é variável, podendo nos casos mais graves ser fatal.
Caso clínico: Grávida de 13 semanas, nulípara, sem história de tratamentos de infertilidade, referenciada por aumento bilateral do volume ovárico e ascite. Apresentava ligeiro desconforto abdominal, tendo a ecografia revelado ovários aumentados de volume, multiquísticos e ascite ligeira. Os níveis de estradiol estavam aumentados, com hCG e TSH normais. A terapêutica foi expectante, com uma evolução favorável.
Discussão: O SHO espontâneo apesar de ser uma entidade rara, deve ser equacionada como hipótese diagnóstica nas situações de massa pélvica na gravidez. Estão descritos 3 possíveis mecanismos para o SHO espontâneo, baseados na permissividade do receptor ovárico da FSH para a hCG e/ou TSH, podendo ocorrer com níveis normais ou elevados de hCG e/ou TSH.
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