Advances in guava propagation.

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Structural, mechanical, and optoelectronic properties of CH3NH3PbI3 as a photoactive layer in perovskite solar cell

DATA AVAILABILITY STATEMENT : Data associated with this article, such as crystal structure information, averaged values of the real and imaginary parts of the complex dielectric function, and absorptivity data used to theoretically predict the upper limit of solar efficiency, is openly available at a github pseudo-cubic repository (https://github.com/elkana35/MAPbI3_pseudo-cubic.git (accessed on 3 May 2023)).Please read abstract in the article.University of Stellenbosch National Institute for Theoretical and Computational Science and the APC was funded by University of Venda.https://www.mdpi.com/journal/photonicshj2024PhysicsSDG-09: Industry, innovation and infrastructur

A density functional theory insight into structural, mechanical, and optical properties of Rb 2LiTlF 6 double perovskite

DATA AVAILABILITY STATEMENT : The data that support the findings of this study are openly available in Github at https://github.com/elkana35/elkana.rugut, reference number 0.Please read abstract in article.University of Stellenbosch National Institute for Theoretical and Computational Science.https://onlinelibrary.wiley.com/journal/15272648PhysicsSDG-09: Industry, innovation and infrastructur

Africa’s response to the COVID-19 pandemic : A review of the nature of the virus, impacts and implications for preparedness

Background: COVID-19 continues to wreak havoc in different countries across the world, claiming thousands of lives, increasing morbidity and disrupting lifestyles. The global scientific community is in urgent need of relevant evidence, to understand the challenges and knowledge gaps, as well as the opportunities to contain the spread of the virus. Considering the unique socio-economic, demographic, political, ecological and climatic contexts in Africa, the responses which may prove to be successful in other regions may not be appropriate on the continent. This paper aims to provide insight for scientists, policy makers and international agencies to contain the virus and to mitigate its impact at all levels. Methods: The Affiliates of the African Academy of Sciences (AAS), came together to synthesize the current evidence, identify the challenges and opportunities to enhance the understanding of the disease. We assess the potential impact of this pandemic and the unique challenges of the disease on African nations. We examine the state of Africa’s preparedness and make recommendations for steps needed to win the war against this pandemic and combat potential resurgence. Results: We identified gaps and opportunities among cross-cutting issueswhich must be addressed or harnessed in this pandemic. Factors such as the nature of the virus and the opportunities for drug targeting, point of care diagnostics, health surveillance systems, food security, mental health, xenophobia and gender-based violence, shelter for the homeless, water and sanitation, telecommunications challenges, domestic regional coordination and financing. Conclusion: Based on our synthesis of the current evidence, while there are plans for preparedness in several African countries, there are significant limitations. A multi-sectoral efforts from the science, education, medical, technology, communication, business, and industry sectors, as well as local communities, must work collaboratively to assist countries in order to win this fight

Predicting the Electrochemical Properties of MnO2Nanomaterials Used in Rechargeable Li Batteries: Simulating Nanostructure at the Atomistic Level

Nanoporous ?-MnO2 can act as a host lattice for the insertion and deinsertion of Li with application in rechargeable lithium batteries. We predict that, to maximize its electrochemical properties, the ?-MnO2 host should be symmetrically porous and heavily twinned. In addition, we predict that there exists a “critical (wall) thickness” for MnO2 nanomaterials above which the strain associated with Li insertion is accommodated via a plastic, rather than elastic, deformation of the host lattice leading to property fading upon cycling. We predict that this critical thickness lies between 10 and 100 nm for ?-MnO2 and is greater than 100 nm for ?-MnO2: the latter accommodates 2 × 2 tunnels compared with the smaller 1 × 1 tunnels found in ?-MnO2. This prediction may help explain why certain (nano)forms of MnO2 are electrochemically active, while others are not. Our predictions are based upon atomistic models of ?-MnO2 nanomaterials. In particular, a systematic strategy, analogous to methods widely and routinely used to model crystal structure, was used to generate the nanostructures. Specifically, the (space) symmetry associated with the nanostructure coupled with basis nanoparticles was used to prescribe full atomistic models of nanoparticles (0D), nanorods (1D), nanosheets (2D), and nanoporous (3D) architectures. For the latter, under MD simulation, the amorphous nanoparticles agglomerate together with their periodic neighbors to formulate the walls of the nanomaterial; the particular polymorphic structure was evolved using simulated amorphization and crystallization. We show that our atomistic models are in accord with experiment. Our models reveal that the periodic framework architecture, together with microtwinning, enables insertion of Li anywhere on the (internal) surface and facilitates Li transport in all three spatial directions within the host lattice. Accordingly, the symmetrically porous MnO2 can expand and contract linearly and crucially elastically under charge/discharge. We also suggest tentatively that our predictions for MnO2 are more general in that similar arguments may apply to other nanomaterials, which might expand and contract elastically upon charging/discharging

Structural, Electronic, Mechanical, and Thermodynamic Properties of Na Deintercalation from Olivine NaMnPO4: First-Principles Study

The impact of Na atom deintercalation on olivine NaMnPO4 was investigated in a first-principle study for prospective use as cathode materials in Na-ion batteries. Within the generalized gradient approximation functional with Hubbard (U) correction, we used the plane-wave pseudopotential approach. The calculated equilibrium lattice constants are within 5% of the experimental data. The difference in equilibrium cell volumes for all deintercalated phases was only 6%, showing that NaMPO4 is structurally more stable. The predicted voltage window was found to be between 3.997 and 3.848 V. The Na1MnPO4 and MnPO4 structures are likely to be semiconductors, but the Na0.75MnPO4, Na0.5MnPO4, and Na0.25MnPO4 structures are likely to be metallic. Furthermore, all independent elastic constants for NaxMPO4 structures were shown to meet the mechanical stability requirement of the orthorhombic lattice system

Electronic, Structural, and Optical Properties of Mono-Doped and Co-Doped (210) TiO2 Brookite Surfaces for Application in Dye-Sensitized Solar Cells—A First Principles Study

Titanium dioxide (TiO2) polymorphs have recently gained a lot of attention in dye-sensitized solar cells (DSSCs). The brookite polymorph, among other TiO2 polymorphs, is now becoming the focus of research in DSSC applications, despite the difficulties in obtaining it as a pure phase experimentally. The current theoretical study used different nonmetals (C, S and N) and (C-S, C-N and S-N) as dopants and co-dopants, respectively, to investigate the effects of mono-doping and co-doping on the electronic, structural, and optical structure properties of (210) TiO2 brookite surfaces, which is the most exposed surface of brookite. The results show that due to the narrowing of the band gap and the presence of impurity levels in the band gap, all mono-doped and co-doped TiO2 brookite (210) surfaces exhibit some redshift. In particular, the C-doped, and C-N co-doped TiO2 brookite (210) surfaces exhibit better absorption in the visible region of the electromagnetic spectrum in comparison to the pure, S-doped, N-doped, C-S co-doped and N-S co-doped TiO2 brookite (210) surfaces