Analysis of Possible Quantum Metastable States in Ballistic Graphene-based Josephson Junctions

Graphene is a relatively new material (2004) made of atomic layers of carbon arranged in a honeycomb lattice. Josephson junction devices are made from graphene by depositing two parallel superconducting leads on a graphene flake. These devices have hysteretic current-voltage characteristics with a supercurrent branch and Shapiro steps appear when irradiated with microwaves. These properties motivate us to investigate the presence of quantum metastable states similar to those found in conventional current-biased Josephson junctions. We present work investigating the nature of these metastable states for ballistic graphene Josephson junctions. We model the effective Washboard potential for these devices and estimate parameters, such as energy level spacing and critical currents, to deduce the design needed to observe metastable states. We propose devices consisting of a parallel on-chip capacitor and suspended graphene. The capacitor is needed to lower the energy level spacing down to the experimentally accessible range of 1-20 GHz. The suspended graphene helps reduce the noise that may otherwise come from two-level states in the insulating oxide layer. Moreover, back-gate voltage control of its critical current introduces another knob for quantum control. We will also report on current experimental progress in the area of fabrication of this proposed device.Comment: 4 pages, 5 figures, Accepted for publication in IEEE Transactions on Applied Superconductivity from ASC 2010. Additional figures, additional calculation

The q-gradient method for global optimization

The q-gradient is an extension of the classical gradient vector based on the concept of Jackson's derivative. Here we introduce a preliminary version of the q-gradient method for unconstrained global optimization. The main idea behind our approach is the use of the negative of the q-gradient of the objective function as the search direction. In this sense, the method here proposed is a generalization of the well-known steepest descent method. The use of Jackson's derivative has shown to be an effective mechanism for escaping from local minima. The q-gradient method is complemented with strategies to generate the parameter q and to compute the step length in a way that the search process gradually shifts from global in the beginning to almost local search in the end. For testing this new approach, we considered six commonly used test functions and compared our results with three Genetic Algorithms (GAs) considered effective in optimizing multidimensional unimodal and multimodal functions. For the multimodal test functions, the q-gradient method outperformed the GAs, reaching the minimum with a better accuracy and with less function evaluations.Comment: 12 pages, 1 figur

'The place I long to be': processos de resiliência em migrantes

Migration has been addressed in studies with a marked focus on its obstacles and difficulties, particularly in the contact with the host country. Recognizing that migrating is a complex process that involves several hardships, it is imperative to understand how migrants overcome adversity and to become aware of the resources mobilised to be cultural adjusted. Based on the theoretical perspective of resilience, this study aims to understand the contexts of adversity, resources and adjustment of Cape Verde migrants in Portugal, who have migrated to continue their studies in higher education. The collected 10 biographical narratives revealed the meanings of their life journeys, both in their country of origin and in the host country. The analysis of the narratives allowed the understanding of the diversity of resilience processes among the participants. The adversities were related to two main dimensions: cultural differences and interpersonal relationships with the Portuguese. In terms of resources, participants stressed the importance of the Cape Verdean diaspora upon arrival to the new country. Along the length of stay for some migrants, this remained the main resource; however, others were developing belongings and significant attachments in a broader context. In terms of cultural adjustment, many configurations have emerged, standing for the fluid nature of the resilience process, which can occur in different ways.info:eu-repo/semantics/publishedVersio

Full Recovery From Cocaine-Induced Toxic Leukoencephalopathy: Emphasizing the Role of Neuroinflammation and Brain Edema

Toxic leukoencephalopathy (TL) is characterized by white matter disease on magnetic resonance imaging (MRI) and evidence of exposure to a neurotoxic agent. We describe a case of cocaine-induced TL in which extensive white matter disease did not preclude full recovery. A 57-year-old man with substance abuse disorder presented with a 5-day history of strange behavior. On admission, he was alert but had difficulty concentrating, psychomotor retardation, and diffuse hyperreflexia. Brain MRI revealed confluent subcortical white matter hyperintensities with restricted diffusion in some but not in other areas. Electroencephalography (EEG) showed mild diffuse slowing. Blood tests were normal except for mild hyperammonemia. Urine screen was positive for cocaine and benzodiazepine but quantitative analysis was significant only for cocaine. Prednisone 60-mg qd was initiated on day 4, tapered over a 5-day period, and discontinued on day 9. He was discharged after 3 weeks. Cognitive function returned to normal 2 weeks after discharge. Five months later, neurologic exam and EEG were normal and MRI showed near-100% resolution of white matter lesions. TL has been attributed to white matter ischemia/hypoxia resulting in demyelination/axonal injury. The clinical, EEG, and MRI findings and time course of recovery of our patient suggest that cocaine-induced inflammation/edema resulted in TL but not in ischemic/hypoxic injury. While inflammation/edema may have regressed when cocaine was discontinued, we cannot exclude a role for prednisone in protecting the patient from the ischemic/hypoxic sequelae of inflammation/edema. MRI is indispensable for diagnosing TL but EEG may provide additional useful diagnostic and prognostic information

Molecular dynamics simulations of nanosheets of polymeric carbon nitride and comparison with experimental observations

A computational study of the properties of polymeric carbon nitride using molecular dynamics is presented. The analysis of ideal infinite-extent sheets permits to evaluate the effect of temperature on the network of hydrogen bonds responsible for the linkage of the material. The weakening of this binding mechanism at sufficiently high temperatures, together with the inter-layer interactions characteristic of this type of 2D materials, is shown to determine the conformation properties of polymeric carbon nitride at the nanoscale. The results obtained from the simulation of finite samples in the canonical ensemble at varying temperatures are consistent with those from the characterization of our experimentally synthesized samples. Hydrogen bonding between adjacent polymer ribbons leads this process and is the cause of the typical crumpled structure of this material

Negative thermal expansion of nanoporous anodic aluminum oxide membranes

We have measured the thermal expansion of Ni nanowires (NWs) electrodeposited into self-organized nanoporous amorphous aluminum oxide (AAO) membranes without an Al substrate using X-ray diffraction between 110 K and 350 K. The results indicate an average thermal expansion of the Ni NWs - along the wire axis - of α ¯ NiNW = − 1.6 ± 1.5 × 10 − 6 K − 1. Assuming a bulk-like thermal expansion of the isolated Ni NWs, this result indicates that AAO also has a negative thermal expansion. We estimate the thermal expansion of nanoporous AAO to be α AAO = − 5 ± 1 × 10 − 6 K − 1. We show that data obtained previously on the thermal expansion of metallic NWs grown in the nanoporous AAO may be interpreted as originating from a negative thermal expansion of the matrix.Fil: Forzani, Luisina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Ramos, C. A.. Centro Atómico Bariloche (cab); ArgentinaFil: Vassallo Brigneti, Ettore Ciro. Instituto Tecnológico y de Estudios Superiores de Occid; MéxicoFil: Gennaro, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Koropecki, Roberto Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentin

UNIVERSIDADE/EMPRESA/GOVERNO O TRIPÉ DA INOVAÇÃO: ESTUDO DE CASO NAS FUNDAÇÕES DE APOIO DA UFSC

O objetivo desse artigo é Investigar se as Fundações de Apoio da UFSC apresentam um programa de interação Universidade, Empresa e Governo que proporcione condições para inovação numa sociedade baseada no conhecimento. As referidas Fundações são de direito privado cuja finalidade é dar apoio a projetos de pesquisa, ensino, extensão e de desenvolvimento institucional, científico e tecnológico, de interesse das Instituições Federais de Ensino Superior (IFES), e, também das Instituições de Pesquisa, que obtiveram junto ao Ministério da Educação o credenciamento como Fundação de Apoio. Hoje, a Universidade assume um papel relevante para o desenvolvimento econômico e social, especialmente na formação de empregos, inovação, modos de produção e sustentabilidade, o que é variável em diversas sociedades de acordo com as tradições acadêmicas. A Universidade, Empresa e governo que adota o modelo da Hélice Tríplice, são consideradas inovadoras por buscarem a inovação organizacional e tecnológica, cujo modelo é visto também, como uma estratégia no que tange à sensibilização aos problemas sociais locais e de projetos de extensão social

Dexamethasone as Abortive Treatment for Refractory Seizures or Status Epilepticus in the Inpatient Setting

Refractory seizures or status epilepticus (RS/SE) continues to be a challenge in the inpatient setting. Failure to abort a seizure with antiepileptic drugs (AEDs) may lead to intubation and treatment with general anesthesia exposing patients to complications, extending hospitalization, and increasing the cost of care. Studies have shown a key role of inflammatory mediators in seizure generation and termination. We describe 4 patients with RS/SE that was aborted when dexamethasone was added to conventional AEDs: a 61-year-old female with temporal lobe epilepsy who presented with delirium, nonconvulsive status epilepticus, and oculomyoclonic status; a 56-year-old female with history of traumatic left frontal lobe hemorrhage who developed right face and hand epilepsia partialis continua followed by refractory focal clonic seizures; a 51-year-old male with history of traumatic intracranial hemorrhage who exhibited left-sided epilepsia partialis continua; and a 75-year-old female with history of breast cancer who manifested nonconvulsive status epilepticus and refractory focal clonic seizures. All patients continued experiencing RS/SE despite first- and second-line therapy, and one patient continued to experience RS/SE despite third-line therapy. Failure to abort RS/SE with conventional therapy motivated us to administer intravenous dexamethasone. A 10-mg load was given (except in one patient) followed by 4.0- 5.2 mg q6h. All clinical and electrographic seizures stopped 3-4 days after starting dexamethasone. When dexamethasone was discontinued 1-3 days after seizures stopped, all patients remained seizure-free on 2-3 AEDs. The cessation of RS/SE when dexamethasone was added to conventional antiseizure therapy suggests that inflammatory processes are involved in the pathogenesis of RS/SE