4,039 research outputs found
Physical mechanisms of interface-mediated intervalley coupling in Si
The conduction band degeneracy in Si is detrimental to quantum computing
based on spin qubits, for which a nondegenerate ground orbital state is
desirable. This degeneracy is lifted at an interface with an insulator as the
spatially abrupt change in the conduction band minimum leads to intervalley
scattering. We present a theoretical study of the interface-induced valley
splitting in Si that provides simple criteria for optimal fabrication
parameters to maximize this splitting. Our work emphasizes the relevance of
different interface-related properties to the valley splitting.Comment: 4 pages, revised versio
Comportamento do algodoeiro BRS Araçá originado de sementes tratadas com cloreto de Mepiquat.
Carcinoma da Tiróide em Crianças e Jovens Adultos: Revisão Retrospectiva de 19 Casos
Introduction: Thyroid carcinoma is rare in children and young adults. Most of management guidelines are based in data from adult population. Several controversies remain regarding the aggressiveness of clinical presentation and therapeutic approach. Objective: To evaluate all differentiated thyroid carcinoma patients with less than 20 years-old at presentation reflecting the experience of our unit in relation to diagnosis, treatment and follow-up of this clinical entity. Material and Methods: This is a retrospective review of clinical records of all children and young adults followed at Oncology Consultation of Department of Endocrinology of Centro Hospitalar e Universitário de Coimbra between 1996 and 2012. Results: Nineteen patients with mean age of 16 years old were followed, 13 girls and 6 boys. None of the patients had previous neck irradiation. A palpable cervical mass was the presenting complaint in 84.6%. FNA was performed in 15 patients and was diagnostic or suspicious of malignancy in 71.4%. Total thyroidectomy was performed in 18 cases (94.7%). Papillary carcinoma was identified in all. Vascular invasion and multicentry occurred in 21.1%. Mean tumor size was 2.5cm. Cervical lymph node involvement was diagnosed in 31.6% and distant metastases in 5.2%. The majority of patients (18 in 19) were classified as stage I disease. All patients received thyroxine suppressive therapy and postoperative radioiodine ablation was given to 84.2% (mean dose 85.7mCi). During mean follow-up of almost 6 years, 16 patients remain disease free. Conclusion: In our series, cervical lymph node and distant metastases rates were similar to that found in adult population. Overall prognosis was very good
Análise da acurácia das simulações do modelo BRAMS na Amazônia Ocidental.
O objetivo deste estudo é avaliar o modelo de previsão numérica do tempo BRAMS (Brazilian Regional Atmospheric Modelling System), a partir da comparação entre os valores preditos e os observados (dados do NCEP (National Center Environmental Prediction). Foram realizadas comparações entre os valores preditos e os observados através da raiz do erro quadrático médio (RMSE) para os prognósticos de precipitação de 24, 48, 72 e 96 hs, no período de novembro de 2008 a março de 2009. Os resultados mostraram que o modelo BRAMS teve uma performance melhor quando assimilado com dados do modelo global do NCEP
Detecting anomalous energy consumption in android applications
The use of powerful mobile devices, like smartphones, tablets and laptops, are changing the way programmers develop software. While in the past the primary goal to optimize software was the run time optimization, nowadays there is a growing awareness of the need to reduce energy consumption. This paper presents a technique and a tool to detect anomalous energy
consumption in Android applications, and to relate it directly with the source code of the application. We propose a dynamically calibrated model for energy consumption for the Android ecosystem, and that supports different devices. The model is then used as an API to monitor the application execution: first, we instrument the application source code so that we can relate energy consumption to the application source code; second, we use a statistical approach, based on fault-localization techniques, to localize abnormal energy consumption in the source code
Twin twin transfusion and fetomaternal transfusion
Introdução: Os autores descrevem um caso de transfusão feto materna (TFM) significativa com repercussão fetal, após ablação de anastomoses vasculares placentares, por síndrome de transfusão feto fetal (STFF).
Caso Clínico:31 anos, saudável, primigesta, gravidez espontânea gemelar, monocoriónica biamniótica.
A ecografia do 1º trimestre, efetuada às 12 semanas, mostrava concordância dos valores do comprimento crânio caudal (CCC), mas discordância dos valores da medida da translucência da nuca (TN). O rastreio combinado do 1º trimestre foi negativo.
Às 16 semanas foi diagnosticado um STFF – estadio II/III de Quintero. A amniocentese revelou um cariótipo normal 46, XY no feto dador e um cariótipo anormal 47, XYY no feto receptor.
Às 17 semanas foi efetuada ablação laser das anastomoses vasculares placentares, tendo ocorrido a morte do feto dador às 18 semanas.
Às 22 semanas foi diagnosticada anemia fetal, por TFM, confirmada por citometria de fluxo.
Às 26 semanas foi constatada dilatação de ansa intestinal - suspeita de atrésia intestinal.
Parto por cesariana às 37 semanas. RN: sexo masculino, 2660g, Índice de Apgar 5/8/10. Confirmada atrésia ileal tipo II e efetuada enterectomia segmentar. Evolução clínica favorável.
Conclusão: Trata-se de um caso de transfusão feto-fetal seguido de transfusão feto-materna, com atrésia intestinal em provável relação com anemia fetal, em feto com cromossomopati
Peripheral Attentional Targets under Covert Attention Lead to Paradoxically Enhanced Alpha Desynchronization in Neurofibromatosis Type 1
The limited capacity of the human brain to process the full extent of visual information reaching the visual cortex requires the recruitment of mechanisms of information selection through attention. Neurofibromatosis type-1 (NF1) is a neurodevelopmental disease often exhibiting attentional deficits and learning disabilities, and is considered to model similar impairments common in other neurodevelopmental disorders such as autism. In a previous study, we found that patients with NF1 are more prone to miss targets under overt attention conditions. This finding was interpreted as a result of increased occipito-parietal alpha oscillations. In the present study, we used electroencephalography (EEG) to study alpha power modulations and the performance of patients with NF1 in a covert attention task. Covert attention was required in order to perceive changes (target offset) of a peripherally presented stimulus. Interestingly, alpha oscillations were found to undergo greater desynchronization under this task in the NF1 group compared with control subjects. A similar pattern of desynchronization was found for beta frequencies while no changes in gamma oscillations could be identified. These results are consistent with the notion that different attentional states and task demands generate different patterns of abnormal modulation of alpha oscillatory processes in NF1. Under covert attention conditions and while target offset was reported with relatively high accuracy (over 90% correct responses), excessive desynchronization was found. These findings suggest an abnormal modulation of oscillatory activity and attentional processes in NF1. Given the known role of alpha in modulating attention, we suggest that alpha patterns can show both abnormal increases and decreases that are task and performance dependent, in a way that enhanced alpha desynchronization may reflect a compensatory mechanism to keep performance at normal levels. These results suggest that dysregulation of alpha oscillations may occur in NF1 both in terms of excessive or diminished activation patterns
Transthyretin is not necessary for thyroid hormone metabolism in conditions of increased hormone demand
Thyroid hormones circulate in blood mainly bound to plasma proteins. Transthyretin is the major thyroxine plasma carrier in mice. Studies in transthyretin-null mice revealed that the absence of transthyretin results in euthyroid hypothyroxinemia and normal thyroid hormone tissue distribution, with the exception of the choroid plexus in the brain. Therefore, transthyretin does not influence normal thyroid hormone homeostasis under standard laboratory conditions. To investigate if transthyretin has a buffer/storage role we challenged transthyretin-null and wild-type mice with conditions of increased hormone demand: (i) exposure to cold, which elicits thermogenesis, a process that requires thyroid hormones; and (ii) thyroidectomy, which abolishes thyroid hormone synthesis and secretion and induces severe hypothyroidism. Transthyretin-null mice responded as the wild-type both to changes induced by stressful events, namely in body weight, food intake and thyroid hormone tissue content, and in the mRNA levels of genes whose expression is altered in such conditions. These results clearly exclude a role for transthyretin in thyroid hormone homeostasis even under conditions of increased hormone demand.POCTI/NSE/37315/2001, from Fundação para a Ciência e Tecnologia
(Portugal) and FEDER; J C S is a recipient of a PhD
fellowship from Fundação para a Ciência e Tecnologia
(Portugal
Timing resistive plate chambers for thermal neutron detection with 3D position sensitivity
An optimized design of a neutron detector based on timing RPCs (Resistive
Plate Chambers) with boron-10 neutron converters is presented. The detector is
composed of a stack of ten double gap RPCs with aluminium cathode plates coated
on both sides with . This design enables simultaneous
determination with high accuracy of both the neutron time-of-flight (down to ns
resolution) and the interaction position in 3D (down to 0.25 mm resolution
across and ~1 mm along the beam). It is shown that the detection efficiency can
approach 60% for neutrons with = 4.7 \.A. A new geometry with less
material budget is introduced for the signal pick-up strip arrays. The results
of simulation-based optimization of the design are reported considering the
trade-off between the detection efficiency, the count rate capability and the
amount of elastic scattering on the detector components
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