DFT computations,vibrational spectra,monomer, dimer,NBO and NMR analyses of antifungal agent: 3,5-Dibromosalicylic acid

The experimental and theoretical study on the structures and vibrations of 3,5-dibromosalicylic acid (DBSA) are presented. The FT-IR and FT-Raman of the title compound have been recorded. The molecular structures, vibrational wavenumbers, infrared intensities, Raman activities were calculated. The energies of DBSA are obtained for all the eight conformers from density functional theory with 6-311++G(d,p) basis set calculations. From the computational results, C1 or C5 forms are identified as the most stable conformers of DBSA. The spectroscopic and theoretical results are compared with the corresponding properties for DBSA monomer and dimer of C1 (or C5) conformer. Intermolecular hydrogen bonds are discussed in dimer structure of the molecule. NBO analysis is useful to understand the intramolecular hyperconjugative interaction between lone pair O9 and C7O8. The calculated HOMO–LUMO energies reveal charge transfer occurs within the molecule. The polarizability, first hyperpolarizability, anisotropy polarizability invariant has been computed using quantum chemical calculations. The isotopic chemical shift computed by ¹H and ¹³C nuclear magnetic resonance (NMR) chemical shifts of the DBSA molecule, calculated using the gauge invariant atomic orbital (GIAO) method, also shows good agreement with experimental observations.     

Green Synthesis and Characterization of Cobalt Oxide Nanoparticles Using Psidium guajava Leaves Extracts and Their Photocatalytic and Biological Activities

The advanced technology for synthesizing nanoparticles utilizes natural resources in an environmentally friendly manner. Additionally, green synthesis is preferred to chemical and physical synthesis because it takes less time and effort. The green synthesis of cobalt oxide nanoparticles has recently risen due to its physico-chemical properties. In this study, many functional groups present in Psidium guajava leaf extracts are used to stabilize the synthesis of cobalt oxide nanoparticles. The biosynthesized cobalt oxide nanoparticles were investigated using UV-visible spectroscopic analysis. Additionally, Fourier-transform infrared spectroscopy revealed the presence of carboxylic acids, hydroxyl groups, aromatic amines, alcohols and phenolic groups. The X-ray diffraction analysis showed various peaks ranging from 32.35 to 67.35°, and the highest intensity showed at 36.69°. The particle size ranged from 26 to 40 nm and confirmed the average particle size is 30.9 nm. The green synthesized P. guajava cobalt oxide nanoparticles contain cobalt as the major abundant element, with 42.26 wt% and 18.75 at% confirmed by the EDAX techniques. SEM images of green synthesized P. guajava cobalt oxide nanoparticles showed agglomerated and non-uniform spherical particles. The anti-bacterial activity of green synthesized P. guajava cobalt oxide nanoparticles was evaluated against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli with a 7 to 18 mm inhibitory zone. The photocatalytic activity was evaluated using green synthesized P. guajava cobalt oxide nanoparticles and observed 79% of dye degradation. The MTT assay of P. guajava cobalt oxide nanoparticles showed an excellent cytotoxic effect against MCF 7 and HCT 116 cells compared to normal cells. The percentage of cell viability of P. guajava cobalt oxide nanoparticles was observed as 90, 83, 77, 68, 61, 58 and 52% for MCF-7 cells and 82, 70, 63, 51, 43, 40, and 37% for HCT 116 cells at the concentration of 1.53, 3.06, 6.12, 12.24, 24.48, 50, and 100 μg/mL compared to control cells. These results confirmed that green synthesized P. guajava cobalt oxide nanoparticles have a potential photocatalytic and anti-bacterial activity and also reduced cell viability against MCF-7 breast cancer and HCT 116 colorectal cancer cells.     

Synthesis,In Silico Studies,and Larvicidal Activity of Novel Hydrazinyl 1,3-Thiazine Derivatives

Russian Journal of Organic Chemistry - Looking at the importance of thiazine derivatives as biologically active compounds, herein we describe the synthesis of 4,6-diaryl-2-hydrazinyl-1,3-thiazines...     

A Modular Approach for Interlocking Enzymes in Whatman Paper

A potentially universal approach is presented for enzyme attachment to cellulose that significantly enhances enzyme stability while retaining high activity, and involves no chemical functionalization of cellulose. Bovine serum albumin (BSA) was interlocked in cellulose to form a protein‐friendly surface (named BSA‐Paper), while also providing COOH and NH₂ groups for subsequent attachment of enzymes. The desired enzyme is then mixed with additional BSA and interlocked on BSA‐Paper. The second BSA layer dilutes and crosslinks the enzyme for improved stability. Laccase was tested as a model enzyme for interlocking on BSA‐Paper, and was found to retain over 100 % activity and was 240 times more stable at 25 °C (half life=180 d) than laccase. This new approach was also tested with a few other enzymes with encouraging results, thus providing a potentially universal method for stabilization of enzymes on cellulose with retention of high activities.     

Microstructure of polycarbonate seen by positrons as an in-situ probe

Positron Annihilation Lifetime Spectroscopy (PALS) is used to probe the micro-structural changes in the polymer polycarbonate in terms of the changes in free volume hole size and their content as a function of temperature. The measured spectra are best fitted to three lifetime component analysis. The average hole size in the amorphous regions is determined from the measured Ortho Positronium (O-Ps) lifetime ₃ by following the treatment of Nakanishi et al. On the other hand, information about defects in the crystalline regions is revealed by trapped positrons lifetime ₂. In this polymer the average hole radius varies from 2.71 Å to 2.77 Å. The present study indicates that this polymer has a glass transition temperature of 152°C. Further, we have calculated the trapping rates in the ordered and disordered regions of the polymer based on Goldanskii's kinetic equations and an attempt is made for the first time to estimate the activation energy in the amorphous and crystalline regions separately.     

Higher Order KFVS Algorithms Using Compact Upwind Difference Operators

A family of high order accurate compact upwind difference operators have been used, together with the split fluxes of the KFVS (kinetic flux vector splitting) scheme to obtain high order semidiscretizations of the 2D Euler equations of inviscid gas dynamics in general coordinates. A TVD multistage Runge–Kutta time stepping scheme is used to compute steady states for selected transonic/supersonic flow problems which indicate the higher accuracy and low diffusion realizable in such schemes.     

Understanding the Role of Grain Boundaries on Charge-Carrier and Ion Transport in Cs2AgBiBr6 Thin Films

Halide double perovskites have gained significant attention, owing to their composition of low-toxicity elements, stability in air, and recent demonstrations of long charge-carrier lifetimes that can exceed 1 µs. In particular, Cs₂AgBiBr₆ is the subject of many investigations in photovoltaic devices. However, the efficiencies of solar cells based on this double perovskite are still far from the theoretical efficiency limit of the material. Here, the role of grain size on the optoelectronic properties of Cs₂AgBiBr₆ thin films is investigated. It is shown through cathodoluminescence measurements that grain boundaries are the dominant nonradiative recombination sites. It also demonstrates through field-effect transistor and temperature-dependent transient current measurements that grain boundaries act as the main channels for ion transport. Interestingly, a positive correlation between carrier mobility and temperature is found, which resembles the hopping mechanism often seen in organic semiconductors. These findings explain the discrepancy between the long diffusion lengths >1 µm found in Cs₂AgBiBr₆ single crystals versus the limited performance achieved in their thin film counterparts. This work shows that mitigating the impact of grain boundaries will be critical for these double perovskite thin films to reach the performance achievable based on their intrinsic single-crystal properties.     

Securing and Self recovery of Virtual Machines in cloud with an Autonomic Approach using Snapshots

Mobile Networks and Applications - The advent of cloud computing has been so enormous that, cloud has been seen as the most enduring technology of today’s technology scenario. It is known to...