Search

Green synthesis of nanomaterials is a current topic of extensive research and a number of green approaches as microorganisms and plant extracts have been explored as an alternative method for their synthesis. In this current work, an attempt has been made to observe the properties of silver oxide nanoparticles (Ag2O NPs), chemically prepared from silver ammonia complex by the traditional sol-gel method using citric acid, as well as from a green approach using aqueous leaf extract of Salix Integra. The synthesized Ag2O NPs were characterized by Powder X-ray Diffraction technique (PXRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM), UV-Visible spectroscopy, Transmission electron microscope (TEM) and Fourier-Transform Infrared Spectroscopy (FT-IR). PXRD analysis showed that, the average particle size of the Ag2O NPs is 17.5 nm and 27.5 nm respectively from the chemical and the green approach. Green approach based Ag2O NPs and Salix Integra leaf extract are tested against gram-negative (E. coli) and gram-positive (S. aureus). In addition the Ag2O Nps were found to be effective against different microbial strains like M. tuberculosis H37Rv, M. Chelonae, M. Abscessus, and M. Fortuitum. Highlights: Synthesis of Ag2O NP's using green and chemical methods from Silver Ammonia Complex. Characterization and comparative studies of the properties of the prepared Ag2O NP's. Studies for the bioapplication of Ag2O NP's for antimicrobial studies. [ABSTRACT FROM AUTHOR]

Introduction: Chronic kidney disease patients on hemodialysis (CKD-5D) are among the worst hit by the coronavirus disease 2019 (COVID-19) pandemic. Need to travel for dialysis, comorbidities, and immunosuppressive state put them at risk of severe disease and poor outcomes. We report our experience of COVID-19 in a cohort of CKD-5D from a public sector tertiary-care center from western India. Material and Methods: We retrospectively analyzed the records of 58 CKD-5D patients with confirmed COVID-19 admitted to our COVID-19 hospital. Suspected COVID-19, acute kidney injury (AKI), or AKI on CKD were excluded. We studied the clinical, demographic, radiological, and laboratory profiles; treatment; and outcomes of the patients. We assessed the potential clinical and laboratory parameters to predict mortality. Results: The mean age of the patients was 48.7 ± 16.9 years, with 55% males. Comorbidities included hypertension (65%), diabetes (19%), and cardiovascular disease (15.5%). The presenting features included fever (69%), respiratory distress (50%), upper respiratory symptoms (36%), and diarrhea (13%). Five (8.6%) were asymptomatic. Bilateral infiltrates on chest imaging were the commonest radiological pattern. The patients were managed with oxygenation, hydroxychloroquine, steroids, anticoagulation, remdesivir, and favipiravir. Twenty-two (37.9%) patients died, predominantly due to respiratory failure. Disease severity and C-reactive protein (CRP) above 175 mg/L at admission were the only parameters predictive of mortality. Conclusion: CKD-5D patients with COVID-19 were less likely to present with the classical syndrome of fever and respiratory distress compared with reports from the general population and had higher mortality. Only disease severity and high CRP (>175 mg/L) were predictive of mortality in our cohort. [ABSTRACT FROM AUTHOR]

Development and application of coarse-graining methods to condensed phases of macromolecules is an active area of research. Multiscale modeling of polymeric systems using coarse-graining methods presents unique challenges. Here we apply a coarse-graining method that self-consistently maps structural correlations from detailed molecular dynamics (MD) simulations of alkane oligomers onto coarse-grained potentials using a combination of MD and inverse Monte Carlo methods. Once derived, the coarse-grained potentials allow computationally efficient sampling of ensemble of conformations of significantly longer polyethylene chains. Conformational properties derived from coarse-grained simulations are in excellent agreement with experiments. The level of coarse graining provides a control over the balance of computational efficiency and retention of chemical identity of the underlying polymeric system. Challenges to extension and application of this and similar structure-based coarse-graining methods to model dynamics and phase behavior in polymeric systems are briefly discussed. [ABSTRACT FROM AUTHOR]

We present results from atomically detailed molecular dynamics simulation of an octane–water liquid–liquid interface. We specifically focus on water structure, orientation, coordination numbers, and hydrogen bonding at the interface. In addition, we probe the interface through insertions of different nonpolar solutes at various locations in the system. Several interesting details of the interface emerge from our calculations. We find that the number density profiles of both water and octane vary monotonically through the interface in a sigmoidal fashion over approximately 1 nm 1-99 interfacial width. Interestingly, the overall heavy-atom density profile shows a distinct minimum in the interfacial region that reflects the hydrophobic nature of the hydration at the octane–water interface. Furthermore, calculations of excess chemical potentials of attractive Lennard-Jones and purely repulsive hydrophobic solutes display an interfacial minimum, indicating the relative ease of cavity formation at the interface. The inhomogeneous nature of the interface affects the water structure and hydrogen-bonding properties at the interface. We find that water coordination number as well as the number of hydrogen bonds water molecules make with their neighbors decreases through the interface as we move from bulk water to the octane phase. As a result, we find populations of water with low coordination numbers, including monomeric water species in the interfacial region. Although the number of hydrogen bonds per water is low in the interfacial region, a larger fraction of coordination waters is hydrogen bonded to the central water in the interfacial region. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The triacontanoic acid monolayers at the water-hexane interface were studied to demonstrate that a small change in the headgroup structure, which alters the hydrogen bonding interactions, leads to a large conformational change from disordered to ordered tailgroups. The molecular dynamics simulations demonstrate the presence of hydrogen bonding between the triacontanoic acid headgroups that is likely responsible for the tail ordering.

The theoretical treatment of multicomponent diffusion is complicated by the generally unknown dependence of diffusivities on the local concentration of species. As pointed out by Nauman and Savoca in 2001, the standard treatment uses an n-1 by n-1 matrix of diffusion coefficients for an n-component system and can give anomalous and nonphysical results when there is no dominant component and when the various components have significantly different diffusivities. Although theoretically resolved by postulating diffusivities with suitable concentration dependence, there has been no practical resolution of this problem short of unrealistic, exhaustive experimentation. Nauman and Savoca proposed two models for multicomponent diffusion that produce only physically possible results, but they were unable to suggest which model was better. This article reports on molecular dynamic experiments that were designed to differentiate between the models. Specifically studied were ternary, liquid mixtures of ethane, octane, and hexadecane. It was found that the proportional flux model agrees with the molecular simulations. No cross-diffusion was observed in agreement with this model and in contrast to the alternative, pair-wise flux model The proportional flux model is easy to implement and requires a minimum of data, although detailed, compositional dependent diffusion coefficients can be incorporated into the model when such data are available. [ABSTRACT FROM AUTHOR]

Systems with nanoscopic features contain a high density of interfaces. Thermal transport in such systems can be governed by the resistance to heat transfer, the Kapitza resistance (RK), at the interface. Although soft interfaces, such as those between immiscible liquids or between a biomolecule and solvent, are ubiquitous, few studies of thermal transport at such interfaces have been reported. Here we characterize the interfacial conductance, 1/RK, of soft interfaces as a function of molecular architecture, chemistry, and the strength of cross-interfacial intermolecular interactions through detailed molecular dynamics simulations. The conductance of various interfaces studied here, for example, water-organic liquid, water-surfactant, surfactant-organic liquid, is relatively high (in the range of 65-370 MW/m2 K) compared to that for solid-liquid interfaces ( approximately 10 MW/m2 K). Interestingly, the dependence of interfacial conductance on the chemistry and molecular architecture cannot be explained solely in terms of either bulk property mismatch or the strength of intermolecular attraction between the two phases. The observed trends can be attributed to a combination of strong cross-interface intermolecular interactions and good thermal coupling via soft vibration modes present at liquid-liquid interfaces.