Revealing large-scale homogeneity and trace impurity sensitivity of GaAs nanoscale membranes

III-V nanostructures have the potential to revolutionize optoelectronics and energy harvesting. For this to become a reality, critical issues such as reproducibility and sensitivity to defects should be resolved. By discussing the optical properties of MBE grown GaAs nanomembranes we highlight several features that bring them closer to large scale applications. Uncapped membranes exhibit a very high optical quality, expressed by extremely narrow neutral exciton emission, allowing the resolution of the more complex excitonic structure for the first time. Capping of the membranes with an AlGaAs shell results in a strong increase of emission intensity but also to a shift and broadening of the exciton peak. This is attributed to the existence of impurities in the shell, beyond MBE-grade quality, showing the high sensitivity of these structures to the presence of impurities. Finally, emission properties are identical at the sub-micron and sub-millimeter scale, demonstrating the potential of these structures for large scale applications.Comment: just accepted in Nano Letters, http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.7b0025

Plasmonic Waveguide-Integrated Nanowire Laser

Next-generation optoelectronic devices and photonic circuitry will have to incorporate on-chip compatible nanolaser sources. Semiconductor nanowire lasers have emerged as strong candidates for integrated systems with applications ranging from ultrasensitive sensing to data communication technologies. Despite significant advances in their fundamental aspects, the integration within scalable photonic circuitry remains challenging. Here we report on the realization of hybrid photonic devices consisting of nanowire lasers integrated with wafer-scale lithographically designed V-groove plasmonic waveguides. We present experimental evidence of the lasing emission and coupling into the propagating modes of the V-grooves, enabling on-chip routing of coherent and sub diffraction confined light with room temperature operation. Theoretical considerations suggest that the observed lasing is enabled by a waveguide hybrid photonic-plasmonic mode. This work represents a major advance toward the realization of application-oriented photonic circuits with integrated nanolaser sources

Engineering the Size Distributions of Ordered GaAs Nanowires on Silicon

Reproducible integration of III-V semiconductors on silicon can open new path toward CMOS compatible optoelectronics and novel design schemes in next generation solar cells. Ordered arrays of nanowires could accomplish this task, provided they are obtained in high yield and uniformity. In this work, we provide understanding on the physical factors affecting size uniformity in ordered GaAs arrays grown on silicon. We show that the length and diameter distributions in the initial stage of growth are not much influenced. by the Poissonian fluctuation-induced broadening, but rather are determined by the long incubation stage. We also show that the size distributions are consistent with the double exponential shapes typical for macroscopic nucleation with a large critical length after Which the nanowires grow irreversibly. The size uniformity is dramatically improved by increasing the As-4 flux, suggesting, a new path for obtaining highly uniform arrays of GaAs nanowires on silicon

Bottom-up engineering of InAs at the nanoscale: From V-shaped nanomembranes to nanowires

The ability to rationally tune the morphology of nanostructures is a fundamental milestone in nanoscale engineering. In particular, the possibility to switch between different shapes within the same material system represents a further step in the development of complex nanoscale devices and it increases the potential of nanostructures in practical applications. We recently reported a new form of InAs nanostructures growing epitaxially on Si substrates as vertical V-shaped membranes. Here we demonstrate the possibility of modifying the shape of these nanomembranes and turning them into nanowires by modulating the surface roughness of the substrate by varying the surface treatment. We show that the growth of nanomembranes is favored on smooth surfaces. Conversely rough surfaces enhance the growth of nanowires. We also shove that the V/III ratio plays a key role in determining the absolute yield, i.e. how many nanostructures form during growth. These results envisage a new degree of freedom in the engineering of bottom up nanostructures and contribute to the achievement of nanostructure networks. (C) 2015 Elsevier B.V. All rights reserved

Prevalence and correlates of inadequate glycaemic control: results from a nationwide survey in 6,671 adults with diabetes in Brazil

Diabetes is a significant public health burden on the basis of its increased incidence, morbidity, and mortality. This study aimed to estimate the prevalence of inadequate glycaemic control and its correlates in a large multicentre survey of Brazilian patients with diabetes. A cross-sectional study was conducted in a consecutive sample of patients aged 18 years or older with either type 1 or type 2 diabetes, attending health centres located in ten large cities in Brazil (response rate = 84%). Information about diabetes, current medications, complications, diet, and satisfaction with treatment were obtained by trained interviewers, using a standardized questionnaire. Glycated haemoglobin (HbA1c) was measured by high-performance liquid chromatography in a central laboratory. Patients with HbA1c ≥ 7 were considered to have inadequate glycaemic control. Overall 6,701 patients were surveyed, 979 (15%) with type 1 and 5,692 (85%) with type 2 diabetes. The prevalence of inadequate glycaemic control was 76%. Poor glycaemic control was more common in patients with type 1 diabetes (90%) than in those with type 2 (73%), P < 0.001. Characteristics significantly associated with improved glycaemic control included: fewer years of diabetes duration, multi professional care, participation in a diabetes health education program, and satisfaction with current diabetes treatment. Despite increased awareness of the benefits of tight glycaemic control, we found that few diabetic patients in Brazil met recommended glycaemic control targets. This may contribute to increased rates of diabetic complications, which may impact health care costs. Our data support the public health message of implementation of early, aggressive management of diabetes

A SARS-CoV-2 protein interaction map reveals targets for drug repurposing

The novel coronavirus SARS-CoV-2, the causative agent of COVID-19 respiratory disease, has infected over 2.3 million people, killed over 160,000, and caused worldwide social and economic disruption1,2. There are currently no antiviral drugs with proven clinical efficacy, nor are there vaccines for its prevention, and these efforts are hampered by limited knowledge of the molecular details of SARS-CoV-2 infection. To address this, we cloned, tagged and expressed 26 of the 29 SARS-CoV-2 proteins in human cells and identified the human proteins physically associated with each using affinity-purification mass spectrometry (AP-MS), identifying 332 high-confidence SARS-CoV-2-human protein-protein interactions (PPIs). Among these, we identify 66 druggable human proteins or host factors targeted by 69 compounds (29 FDA-approved drugs, 12 drugs in clinical trials, and 28 preclinical compounds). Screening a subset of these in multiple viral assays identified two sets of pharmacological agents that displayed antiviral activity: inhibitors of mRNA translation and predicted regulators of the Sigma1 and Sigma2 receptors. Further studies of these host factor targeting agents, including their combination with drugs that directly target viral enzymes, could lead to a therapeutic regimen to treat COVID-19

Outcome of axonal and demyelinating forms of Guillain-Barre syndrome in children

WOS: 000184143600008PubMed ID: 12849884Previous reports have suggested that outcome is worse in the axonal compared with the demyelinating form of Guillain-Barre syndrome (GBS). We performed a retrospective study of 23 children with electrophysiologically confirmed cases of predominant subtypes of GBS to investigate this issue. The patients were classified based on the electrodiagnostic features: Ten (44%) had acute inflammatory demyelinating polyradiculoneuropathy, eight (35%) had acute motor axonal neuropathy, and five (21%) had acute motor-sensory axonal neuropathy. All patients received a standard intravenous immunoglobulin therapy (0.4 g /kg /day for 5 consecutive days). In the acute phase of the disease, patients with the axonal forms of GBS were more disabled than were those with the demyelinating GBS, as measured by GBS scores. Mechanical ventilation was required in five (38%) patients in the axonal group compared with one (10%) patient in the demyelinating group. There was no significant difference at 6 months in GBS scores between demyelinating and axonal forms of GBS. All 20 survivors recovered completely by 12 months. After standard intravenous immunoglobulin therapy, children with axonal forms of GBS recover more slowly than those with the demyelinating form, but outcome at 12 months appears to be equally favorable in two groups. (C) 2003 by Elsevier Inc. All rights reserved

Landau-Kleffner syndrome beginning with stuttering: Case report

WOS: 000180382800015PubMed ID: 12546439Landau-Kleffner syndrome is marked by an acquired aphasia in children who have had normal language and motor development. A 3.5-year-old girl was referred to our clinic with stuttering. She was diagnosed as having benign myoclonic epilepsy of infancy at 3.5 months of age and treated with valproic acid. Her electroencephalogram (EEG) returned to normal at the end of the first year. The therapy was stopped after a 2-year seizure-free period. She started to stutter prominently 3 months after the discontinuation of antiepilepsy drugs. She had no verbal agnosia. Her EEG revealed multiple spike and wave discharges. She was diagnosed as having Landau-Kleffner syndrome. Her previous epilepsy history had contributed to her having obtained an EEG in the early period. We suggest that if a child with normal language function starts to stutter, Landau-Kleffner syndrome must be considered in the differential diagnosis