Monthly Archives: September 2023

Exploring the structural, mechanical and thermodynamic properties of Ti‐V solid solutions

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Exploring the structural, mechanical and thermodynamic properties of Ti-V solid solutions

This work investigates the structural stability, mechanical and thermodynamic properties of two Ti-V solid solutions. It is found that the Ti-V compound prefers to form the V(Ti)ss solid solution, which remains the cubic structure. Based on the Born stability criteria, the V(Ti)ss solid solution is a mechanical stability. In particular, the V(Ti)ss solid solution shows higher volume deformation resistance and better ductility compared to the pure Ti.


Abstract

Although Ti-V based high-temperature alloys are used in aerospace engine, rocket engine and hot sections, the structure and mechanical properties of Ti-V alloys remains controversy. To explore the correlation between structural and mechanical properties, we apply employed the DFT method to study the phases stability, mechanical and thermodynamic properties of Ti-V solid solution. Two Ti-V solid solutions: Ti(V)ss solid solution and V(Ti)ss solid solution are discussed. Two Ti-V solid solutions are thermodynamic stability. In particular, the Ti-V solid solution prefers to form V(Ti)ss solid solution, in while the V(Ti)ss solid solution remains cubic structure. Furthermore, the Ti(V)ss solid solution is a mechanical instability. However, the V(Ti)ss solid solution is a mechanical stability. Here, the bulk modulus, shear modulus and Young's modulus of V(Ti)ss solid solution are 136.9, 23.5 and 66.7 GPa. In particular, the bulk modulus of V(Ti)ss solid solution is higher than the bulk modulus of the pure Ti. In addition, the V(Ti)ss solid solution shows better ductility compared to the pure Ti and V. Naturally, the stability and mechanical properties of V(Ti) solid solution is related to the Ti-V metallic bond because of the localized hybridization between the Ti(3d) and V(3d).

Revealing the impact of polystyrene‐functionalization of Au octahedral nanocrystals of different sizes on formation and structure of mesocrystals

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The self-assembly of anisotropic nanocrystals (stabilized by organic capping molecules) with pre-selected composition, size, and shape allows for the creation of nanostructured materials with unique structures and features. For such a material, the shape and packing of the individual nanoparticles play an important role. This work presents a synthesis procedure for ω-thiol-terminated polystyrene (PS-SH) functionalized gold nanooctahedra of variable size (edge length 37, 46, 58, and 72 nm). The impact of polymer chain length (Mw: 11k, 22k, 43k, and 66k g∙mol-1) on the growth of colloidal crystals (e.g. mesocrystals) and their resulting crystal structure is investigated. Small-angle X-ray scattering (SAXS) and scanning transmission electron microscopy (STEM) methods provide a detailed structural examination of the self-assembled faceted mesocrystals based on octahedral gold nanoparticles of different size and surface functionalization. Three-dimensional angular X-ray cross-correlation analysis (AXCCA) enables high-precision determination of the superlattice structure and relative orientation of nanoparticles in mesocrystals. This approach allows us to perform non-destructive characterization of mesocrystalline materials and reveals their structure with resolution down to the nanometer scale.

Antibacterial and Toxic Activity of Geopropolis extracts from Melipona subnitida (Ducke, 1910) (Hymenoptera: Apidae) and Scaptotrigona depilis (Moure, 1942) (Hymenoptera: Apidae).

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Bacteria are associated with many infections that affect humans and present antibiotic resistance mechanisms, causing problems in health organisations and increased mortality rates. Therefore, it is necessary to find new antibacterial agents that can act in the treatment of these microorganisms. Geopropolis is a natural product made by stingless bees, formed by a mixture of plant resins, salivary secretions, wax and soil particles, presenting a diverse chemical composition. Thus, this study aimed to evaluate antibacterial activity, antibiotic modulation and the toxicity of geopropolis extract from the stingless bees, Melipona subnitida (Ducke, 1910) and Scaptotrigona depilis (Moure, 1942) against standard and multi-resistant Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa bacteria. Geopropolis samples were collected in a meliponary located in Camaragibe, Pernambuco, Brazil. To determine the Minimum Inhibitory Concentration (MIC) and antibiotic modulation we performed broth microdilution tests. Mortality tests were used to verify extract toxicity in the model Drosophila melanogaster. The microbiological tests showed that the M. subnitida extracts had better inhibitory effects compared to S. depilis, presenting direct antibacterial activity against standard and multi-resistant strains. The extracts potentialized antibiotic effects, suggesting possible synergy and did not present toxicity in the model used.

Adduct‐Type Compounds for Nonlinear Optical Crystals

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The performance prerequisites for nonlinear optical (NLO) crystals encompass a substantial second-harmonic generation (SHG), a considerable laser induced damage threshold, and a moderate degree of birefringence. Nevertheless, the presence of particular anions may result in deficiencies within certain properties. The utilization of mixed anionic groups has emerged as an effective strategy to achieve a balance among numerous performance parameters of NLO crystals, particularly in terms of SHG responses and bandgaps. Compared with other heteroanionic compounds, adduct-type compounds feature more concise structures with specific properties. Herein, we aim to provide an overview of the recent advancements in adduct-type NLO crystals, focusing on their structures and properties. Furthermore, we analyze the coordination chemistry and disadvantages involved in adducts, and discuss the current synthesis methods as well as future directions for further exploration.

Quantifying the Ground‐State Hydrogen‐Bond Formation of a Super‐Photoacid by Inspecting Its Excited‐State Dynamics

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The identification and quantification of hydrogen (H)-bonded complexes form the cornerstone of reaction-mechanism analysis in ultrafast proton transfers. Traditionally, the Benesi-Hildebrand method has been employed to obtain the formation constants of H-bonded complexes, given that H-bonding additives induce an alteration in spectral features exclusively through H-bond formation. However, if the additive introduction impacts the bulk polarity of the solution, inducing a spectral shift, the spectroscopic method's accuracy in analyzing the H-bond formation becomes compromised. In this study, we scrutinize H-bond formation under the influence of an H-bond accepting solute in an aprotic solvent. This is achieved by quantifying the fractions of two concurrent pathways involved in the excited-state proton transfer (ESPT) of a super-photoacid: the ultrafast ESPT of an H-bonded complex vs. the diffusion-controlled ESPT of the free acid. Our method offers improved accuracy compared to conventional steady-state spectroscopic techniques, by directly quantifying the H-bonded complexes using the time-resolved spectroscopic method, thereby circumventing the aforementioned limitation.

Biotechnology in India: An Analysis of ‘Biotechnology Industry Research Assistance Council’ (BIRAC)‐Supported Projects

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Biotechnology in India: An Analysis of ‘Biotechnology Industry Research Assistance Council’ (BIRAC)-Supported Projects

A detailed analysis of over 2000 biotechnology projects in India reveals the diversity of an emerging industry that spans not only human healthcare (medical devices, therapeutics, vaccines, regenerative medicine, …), but also (bio)agriculture (plant breeding and cloning, animal biotechnology, crop disease and pest control, …) and industrial biotechnology (fine chemicals, environmental, clean energy, …).


Abstract

A comprehensive analysis of 2165 projects funded by India's Department of Biotechnology since 2005 through private-public partnerships, and as of 2012 through the ‘Biotechnology Industry Research Assistance Council (BIRAC)’ until BIRAC's tenth anniversary at the end of March 2022 reveals details of the science and technology underpinning past and current biotechnology research and development projects in the country. They are led by human healthcare projects (74.9 % overall), of which medical technology (58.7 %) and therapeutics (24.5 %) are the main drivers, ahead of vaccines (4.3 %), regenerative medicine (3.9 %), public health (3.5 %) and others (5.1 %). Agricultural projects (15.2 % overall) have mainly been driven by plant breeding and cloning (24.6 %), animal biotechnology (20.4 %), agri-informatics (13.4 %), aquaculture (6.1 %), and (bio)fertilizers (4.3 %). The key components of industrial biotechnology (9.9 % overall) have been fine chemicals (44.7 %), environmental projects (23.3 %), clean energy (18.1 %) and industrial enzymes (12.1 %). Analysis of the projects funded pre- versus post-2017, compared to the distribution of equity funding as of early 2022 identifies trends in terms of growth areas and locations of industrial biotechnology projects and activities in India.

Donor‐acceptor tin(IV) complexes with α‐diimine and catecholate ligands

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A series of new octahedral bis-3,6-di-tert-butylcatecholates based on tin(IV) containing metal-coordinated N-donor ligands (substituted iminopyridines and diazabutadienes) has been synthesized and structurally characterized. The compounds, both solid and in solution, are intensely colored. They absorb in the visible region of the spectrum. Charge transfer between the catecholate donor and the diimine acceptor is responsible for the absorption. This observation is in good agreement with the DFT calculations and with the electrochemical studies carried out by CV.