Analysis of human vergence dynamics

Disparity vergence is commonly viewed as being controlled by at least two mechanisms, an open-loop vergence-specific burst mechanism analogous to the ballistic drive of saccades, and a closed-loop feedback mechanism controlled by the disparity error. We show that human vergence dynamics for disparity jumps of a large textured field have a typical time course consistent with predominant control by the open-loop vergence-specific burst mechanism, although various subgroups of the population show radically different vergence behaviors. Some individuals show markedly slow divergence responses, others slow convergence responses, others slow responses in both vergence directions, implying that the two vergence directions have separate control mechanisms. The faster time courses usually had time-symmetric velocity waveforms implying open-loop burst control, while the slow response usually had time-asymmetric velocity waveforms implying closed-loop feedback control. A further type of behavior in a distinct subpopulation is a compound anomalous divergence response consisting of an initial convergence movement followed by a large corrective divergence movement with time courses implying closed-loop feedback control. The closed-loop response for slow responses to disparity steps exhibited pronounced oscillations in the velocity trace, implying the involvement of a sampled-data system with a rate of about 3 samples/s. This analysis of the variety of human vergence responses thus contributes substantially to the understanding of the oculomotor control mechanisms underlying the generation of vergence movements

Applicable anode based on Co3O4–SrCO3 heterostructure nanorods-incorporated CNFs with low-onset potential for DUFCs

Besides the high-current density, lower onset potential of urea electrooxidation is key parameter which influences the direct urea fuel cell performance. In the present article, low-onset potential has been reported for nickel-free (NF) electrocatalyst in urea electrooxidation. The nickel-free electrocatalyst: Co3O4–SrCO3 heterostructure nanorods-incorporated carbon nanofibers (CNFs) were synthesized by electrospinning technique, followed by calcination of electrospun mat composed of strontium acetate, cobalt acetate, and poly(vinyl alcohol) sol–gel in inert environment at 750 °C. Physiochemical characterizations confirmed the formation of Co3O4–SrCO3 heterostructure nanorods-incorporated CNFs. The electrochemical activity of resultant nickel-free electrocatalyst toward the electrooxidation of urea in alkaline medium is evaluated using cyclic voltammetry measurements (CV). Co3O4–SrCO3 heterostructure nanorods-incorporated CNFs reveals high-current density of 21.33 mA/cm2 at low-fuel concentration. Notably, the low-onset potential has been observed, showing a good application prospect in direct urea fuel cells.This Publication was made possible by NPRP grant # [8-1344-1-246] from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of authors

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Preparation and characterization of wollastonite/titanium oxide nanofiber bioceramic composite as a future implant material

In this study, novel composites consisting of electrospun titanium dioxide (TiO2) nanofibers incorporated into high-purity wollastonite glass ceramics were prepared as materials for use in hard tissue engineering applications. These materials were characterized and investigated by means of physical, mechanical and in vitro studies. The proposed composite showed greater densification and better mechanical characteristics compared to pure wollastonite. The influence of densification temperature and TiO2 content was investigated. Typically, TiO2/wollastonite composites having 0, 10, 20 and 30wt% metal oxide nanofibers were sintered at 900, 1100 and 1250°C. The results indicated that increasing TiO2 nanofibers content leads to increase the bulk density, compressive strength and microhardness with negligible, high and moderate influence for the densification temperature, respectively. While porosity and water adsorption capacity decreased with increasing the metal oxide nanofibers with a considerable impact for the sintering temperature in both properties. Moreover, bone-like apatite formed on the surface of wollastonite and wollastonite/TiO2 nanofibers soaked in simulated body fluid (SBF). All these results show that the inclusion of TiO2 nanofibers improved the characteristics of wollastonite while preserving its in vitro bioactivity; hence, the proposed composite may be used as a bone substitute in high load bearing sites.National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MOE) (No. 2014R1A1A2058967)

Stable and effective super-hydrophilic polysulfone nanofiber mats for oil/water separation

Hydrophobicity of polysulfone is the main constraint facing wide application in the most important field; water treatment, although this polymer shows promising characteristics to be used in different separation technologies. In this study, super-hydrophilic polysulfone nanofiber mats are introduced using novel modifications. The introduced nanofibers were synthesized by electrospinning of polysulfone/NaOH/DMF electrospun solution. The prepared electrospun nanofibers have been activated by deposition of a polyamide layer using interfacial polymerization (IP) reaction between m-phenylenediamine and 1,3,5-benzenetricarbonyl chloride. Three different heat treatment methodologies were investigated to enhance the characteristics of the activated nanofiber mats; normal drying at 70 °C, and soaking in boiled water followed by either normal drying at 70 °C or storing in the water. Investigation of the mechanical properties indicated that incorporation of NaOH improves the tensile stress by 40% compared to the pristine polysulfone nanofibers. Interestingly, treatment of the activated nanofiber mats in the boiled water followed by storing in water led to produce super-hydrophilic mats with water contact angle of 3° due to enhancing the IP reaction on the surface of the individual nanofibers. In oil/water separation process, the proposed heat treatment for the modified nanofiber mats resulted in increase the water flux from 8 to 12.21 m3/m2 day with oil rejection of 99.976%.1- National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MOE) (No.2014R1A1A2058967). 2- Deanship of Scientific Research at King Saud University for funding the work through the research group project No. RGP- 1435-001

Ammonium phosphate as promised hydrogen storage material

Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Most of the reported hydrogen storage materials are either expensive or based on synthetically complicated compounds. Ammonium phosphates are cheap and available product; it is being used as fertilizer. These compounds could be utilized as hydrogen storage materials. Stoichiometrically, mono-, di- and tri-ammonium phosphate can lead to evolve 3.875, 7.867 and 11.903 hydrogen equivalent, respectively. Using Pt/C (20 wt %) leads to produce 17.28, 11.35 and 10.15% from the equivalent hydrogen in the mono-, di- and tri-ammonium phosphate, respectively. Analyzing the obtained gases by GC confirms evolution of pure hydrogen. Moreover, ion chromatography detects and ions in the liquid which indicates hydrolysis of the ammonium phosphate. Ni/C and Co/C NPs can be exploited as catalysts; Ni/C containing 20 wt% metal reveals comparable results to Pt/C. Overall, this study opens promising avenue to develop new catalysts to enhance the hydrolysis of ammonium phosphate to produce hydrogen. Comparing to the reported hydrogen storage materials, ammonium phosphates possess comparable hydrogen content 97.28, 118.3 and 115.72 kg/m3 for mono-, di- and tri-ammonium phosphate, respectively which is very close to the MgH2 (115.5 kg/m3) and not so far from ammonia borane (148.2 kg/m3). However, in contrast to these compounds, hydrogen can be released from the introduced storage materials by hydrolysis only using the proper catalyst. Furthermore, the hydrolysis process results in producing different acids; nitrous, nitric and phosphoric acid which should be considered in the reactor construction precautions

Effective and stable FeNi@ N-doped graphene counter electrode for enhanced performance dye sensitized solar cells

N-doped FeNi@graphene is introduced as effective and stable non-precious counter electrode for the dye sensitized solar cells. After preparation of graphene oxide using the chemical route, the obtained product has been refluxed in presence of nickel acetate, ferrous acetate and urea at 150°C for 12h. Then, the solid product was mixed with melamine and sintered under nitrogen atmosphere at 850°C. The invoked characterization techniques affirmed formation of N-doped graphene decorated by FeNi bimetallic nanoparticles. In dye sensitized solar cell, the prepared material revealed good performance as counter electrode as the estimated efficiency was 4.12% with a photocurrent and an open circuit voltage of 8.96mA/cm2 and 0.73V, respectively, Moreover, the cyclic voltammetry measurements indicated very good catalytic activity and distinct stability.National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MOE) (No. 2014R1A1A2058967)