Spatiotemporal evolution of SARS-CoV-2 Alpha and Delta variants during large nationwide outbreak of COVID-19, Vietnam, 2021

We analyzed 1,303 SARS-CoV-2 whole-genome sequences from Vietnam, and found the Alpha and Delta variants were responsible for a large nationwide outbreak of COVID-19 in 2021. The Delta variant was confined to the AY.57 lineage and caused >1.7 million infections and >32,000 deaths. Viral transmission was strongly affected by nonpharmaceutical interventions

Safety and efficacy of fluoxetine on functional outcome after acute stroke (AFFINITY): a randomised, double-blind, placebo-controlled trial

Background Trials of fluoxetine for recovery after stroke report conflicting results. The Assessment oF FluoxetINe In sTroke recoverY (AFFINITY) trial aimed to show if daily oral fluoxetine for 6 months after stroke improves functional outcome in an ethnically diverse population. Methods AFFINITY was a randomised, parallel-group, double-blind, placebo-controlled trial done in 43 hospital stroke units in Australia (n=29), New Zealand (four), and Vietnam (ten). Eligible patients were adults (aged ≥18 years) with a clinical diagnosis of acute stroke in the previous 2–15 days, brain imaging consistent with ischaemic or haemorrhagic stroke, and a persisting neurological deficit that produced a modified Rankin Scale (mRS) score of 1 or more. Patients were randomly assigned 1:1 via a web-based system using a minimisation algorithm to once daily, oral fluoxetine 20 mg capsules or matching placebo for 6 months. Patients, carers, investigators, and outcome assessors were masked to the treatment allocation. The primary outcome was functional status, measured by the mRS, at 6 months. The primary analysis was an ordinal logistic regression of the mRS at 6 months, adjusted for minimisation variables. Primary and safety analyses were done according to the patient's treatment allocation. The trial is registered with the Australian New Zealand Clinical Trials Registry, ACTRN12611000774921. Findings Between Jan 11, 2013, and June 30, 2019, 1280 patients were recruited in Australia (n=532), New Zealand (n=42), and Vietnam (n=706), of whom 642 were randomly assigned to fluoxetine and 638 were randomly assigned to placebo. Mean duration of trial treatment was 167 days (SD 48·1). At 6 months, mRS data were available in 624 (97%) patients in the fluoxetine group and 632 (99%) in the placebo group. The distribution of mRS categories was similar in the fluoxetine and placebo groups (adjusted common odds ratio 0·94, 95% CI 0·76–1·15; p=0·53). Compared with patients in the placebo group, patients in the fluoxetine group had more falls (20 [3%] vs seven [1%]; p=0·018), bone fractures (19 [3%] vs six [1%]; p=0·014), and epileptic seizures (ten [2%] vs two [<1%]; p=0·038) at 6 months. Interpretation Oral fluoxetine 20 mg daily for 6 months after acute stroke did not improve functional outcome and increased the risk of falls, bone fractures, and epileptic seizures. These results do not support the use of fluoxetine to improve functional outcome after stroke

Trapping of electrons around nanoscale metallic wires embedded in a semiconductor medium

We predict that conduction electrons in a semiconductor film containing a centered square array of metal nanowires normal to its plane are bound in quantum states around the central wires, if a positive bias voltage is applied between the wires at the square vertices and these latter. We obtain and discuss the eigenenergies and eigenfunctions of two models with different dimensions. The results show that the eigenstates can be grouped into different shells. The energy differences between the shells is typically a few tens of meV, which corresponds to frequencies of emitted or absorbed photons in a range of 3 THz to 20 THz approximately. These energy differences strongly depend on the bias voltage. We calculate the linear response of individual electrons on the ground level of our models to large-wavelength electromagnetic waves whose electric field is in the plane of the semiconductor film. The computed oscillator strengths are dominated by the transitions to the states in each shell whose wave function has a single radial node line normal to the wave electric field. We include the effect of the image charge induced on the central metal wires and show that it modifies the oscillator strengths so that their sum deviates from the value given by the Thomas-Reiche-Kuhn rule. We report the linear response, or polarizability, versus photon energy, of the studied models and their absorption spectra. These latter show well-defined peaks as expected from the study of the oscillator strengths. We show that the position of these absorption peaks is strongly dependent on the bias voltage so that the frequency of photon absorption or emission in the systems described here is easily tunable. This makes them good candidates for the development of novel infrared devices

Trapping of Electrons around Nanoscale Metallic Wires Embedded in a Semiconductor Medium

peer reviewedWe predict that conduction electrons in a semiconductor film containing a centered square array of metal nanowires normal to its plane are bound in quantum states around the central wires, if a positive bias voltage is applied between the wires at the square vertices and the latter. We obtain and discuss the eigenenergies and eigenfunctions of two models with different dimensions. The results show that the eigenstates can be grouped into different shells. The energy differences between the shells is typically a few tens of meV, which corresponds to frequencies of emitted or absorbed photons in a range of 3THz to 20THz approximately. These energy differences strongly depend on the bias voltage. We calculate the linear response of individual electrons on the ground level of our models to large-wavelength electromagnetic waves whose electric field is in the plane of the semiconductor film. The computed oscillator strengths are dominated by the transitions to the states in each shell whose wave function has a single radial node line normal to the wave electric field. We include the effect of the image charge induced on the central metal wires and show that it modifies the oscillator strengths so that their sum deviates from the value given by the Thomas-Reiche-Kuhn rule. We report the linear response, or polarizability, versus photon energy, of the studied models and their absorption spectra. The latter show well-defined peaks as expected from the study of the oscillator strengths. We show that the position of these absorption peaks is strongly dependent on the bias voltage so that the frequency of photon absorption or emission in the systems described here is easily tunable. This makes them good candidates for the development of novel infrared devices.J.0124.1

Linear Response of Bound Electrons to a Quasi-Static Oscillating Field in GaN Nanowire Structures

There is a growing body of literature that recognizes the importance of nanostructured semiconductor materials. Their potential novel properties arise when the physical dimensions of the structure reach the nanometer scale. In particular, one-dimensional systems made of wide-bandgap semiconducting ordered alloys such as GaN have attracted significant interest due to their remarkable properties for electronics, optics, and photonics. In this work, we studied the problem of charge trapping around individual infinite metallic nanowires, with a two-dimensional numerical approach combining Schrödinger’s and Poisson’s equations. The effect of wire radius and distance between wires were first investigated in detail. We then emphasize the finding that under different applied voltages, the system exhibits a potential to respond to an electromagnetic radiation in a tunable way. This effect is stronger for smaller systems. However, for a given system size, we found out that the energy values as well as the energy steps are larger for both thick and narrow wires due to the quantum confinement of electrons, with a minimum energy observed for a radius of about 10% of the system dimension. We also investigated the linear response of bound electrons around an isolated wire exposed to a quasi-static oscillating electric field. To this purpose, we defined the average charge radius as the integral of the product of the wave function squared by the position operator over the surface of a square cell. Our results show that the wave functions can be grouped into different classes. Inside a class, the average radii have almost the same value for all wave functions and the energy values depend in a quadratic manner on the order of the eigen wave function. Due to the relatively large cell size and to the almost unimpeded motion of the electrons around the metal wires, the nanostructures proposed in work are expected to exhibit a large electrical polarizability. Our results confirm this assertion and our numerical formalism allowed us to determine the linear response, or polarizability, in representative systems. To this perspective, the transition probabilities between different energy levels, as well as the oscillator strengths are important quantities to consider. The systems proposed in this work could be of great practical interest. Indeed, the energy of excitation between two different classes of levels is in the range of 10 meV, or a few tens of meV at most. This corresponds to photon frequencies in the THz range, where emitters and detectors are not numerous. A possible application as radiation detector could use the modification of the in-plane electrical conductivity brought by an electromagnetic wave. Indeed, the overlap between wave functions on neighboring sites depends on the electron state of excitation which is changed by the incident wave. Another possible process is the ionization of the bound states which could induce a capacitive current in the central wire

High-performance Pd-coated Ni nanowire electrocatalysts for alkaline direct ethanol fuel cells

The major hindrance for a successful commercialization of direct ethanol fuel cells (DEFCs) is the sluggish ethanol oxidation reaction (EOR) and the rapid poisoning of anodic catalysts by by-products. In this work, a high-performance PdNi nanowire (PdNi-NWs) catalyst was prepared via a two-step process in polyol medium based on the galvanic replacement reaction. By carefully screening parameters for a uniform deposition of Pd layers on Ni nanowires, the PdNi-NWs electrode exhibits a significant enhancement of both catalytic activity and durability for the EOR in alkaline media, which may be ascribed to the electronic structure modification and bifunctional electrocatalytic mechanism with hydroxyl and ethanol bindings on Ni and Pd, respectively. Moreover, these nanowire structures are efficient electron and mass transfer and enriched with abundant active sites by oxygen-rich compounds of Ni. The highest electrocatalytic performance has achieved with a low Pd:Ni molar ratio of 18:100, which reaches 9.3 times superior mass activity and the EOR onset potential shifts 50 mV negatively compared with Pd nanoparticles (PdNPs). These results highlight the active role of PdNi-NWs catalysts in DEFCs.Peer reviewe

Crack Identification on the Fresh Chilli (Capsicum) Fruit Destemmed System

Destemming fresh chilli fruit (Capsicum) in large productivity is necessary, especially in the Mekong Delta region. Several studies have been done to solve this problem with high applicability, but a certain percentage of the output consisted of cracked fruits, thus reducing the quality of the system. The manual sorting results in high costs and low quality, so it is necessary that automatic grading is performed after destemming. This research focused on developing a method to identify and classify cracked chilli fruits caused by the destemming process. The convolution neural network (CNN) model was built and trained to identify cracks; then, appropriate control signals were sent to the actuator for classification. Image processing operations are supported by the OpenCV library, while the TensorFlow data structure is used as a database and the Keras application programming interface supports the construction and training of neural network models. Experiments were carried out in both the static and working conditions, which, respectively, achieved an accurate identification rate of 97 and 95.3%. In addition, a success rate of 93% was found even when the chilli body is wrinkled due to drying after storage time at 120 hours. Practical results demonstrate that the reliability of the model was useful and acceptable