Large Scale GPU Based Simulations of Turbulent Bubbly Flow in a Square Duct

In this paper, we present the results of a numerical study of air-water turbulent bubbly flow in a periodic vertical square duct. The study is conducted using a novel numerical technique which leverages Volume of Fluid method for interface capturing and Sharp Surface Force method for accurate representation of the surface tension forces. A three-dimensional geometry construction method is employed during solution of interface equation which gives absolute conservation of mass and sharp interface between gas and liquid phases. The entire algorithm has been implemented on a data parallel mode on multiple graphics processing units (GPU) taking advantage of the large number of available cores. We have studied the dynamics of a swarm of spherical bubbles co-flowing with the upward turbulent flow and compared results with an unladen turbulent flow. The frictional Reynolds number of the unladen $Re_{\tau}$ is 360, which is sufficient to sustain a turbulent flow. We observe the turbulence-driven secondary flows in the mean flow, with complex instantaneous turbulent vortical structures. The interaction of these secondary flows with the upwards rising bubbles is very complex and leads to significant changes in the instantaneous and time-averaged flow field. We present the results of mean void fraction distribution, mean velocities, longitudinal and transverse turbulence intensities along the wall, corner bisector, and wall bisector. A peak in the void fraction distribution near the walls is observed representing the migration of bubbles to a preferred section of the duct. The effects of turbulence-driven secondary flows and instantaneous large eddies on preferential concentration of the bubbles are discussed. The dispersed bubbles are seen to break the long elongated turbulent structures commonly observed in the unladen turbulent flow

Insights Into Chemical Reactions at the Beginning of the Universe: From HeH+ to H3+

At the dawn of the Universe, the ions of the light elements produced in the Big Bang nucleosynthesis recombined with each other. In our present study, we have tried to mimic the conditions in the early Universe to show how the recombination process would have led to the formation of the first ever formed diatomic species of the Universe: HeH+, as well as the subsequent processes that would have led to the formation of the simplest triatomic species: H3+. We have also studied some special cases: higher positive charge with fewer number of hydrogen atoms in a dense atmosphere, and the formation of unusual and interesting linear, dicationic He chains beginning from light elements He and H in a positively charged atmosphere. For all the simulations, the ab initio nanoreactor (AINR) dynamics method has been employed

Insights into the Nature of Self‐Extinguishing External Donors for Ziegler-Natta Catalysis: A Combined Experimental and DFT Study

Developing donors for Ziegler‐Natta (ZN) catalysis to control the polymerization reaction and produce polymers with desirable properties has always been challenging due to the multi‐component nature of the catalytic systems. Here, we have developed a new synthetic protocol for making two external donors, D₁ (2,2,2‐trifluoroethyl myristate) and D₂ (2,2,2‐trifluoroethyl palmitate) that show self‐extinguishing properties, followed by a systematic DFT study to understand this peculiar property of these donors. D₁ and D₂ can undergo parallel reactions with aluminum and titanium species present in the system to produce ketones and aldehydes, which are poisons for ZN catalytic systems, thus explaining their self‐extinguishing nature. The non‐covalent interaction between the long alkyl chain of the donors with the surface plays a vital role in determining the donors′ self‐extinguishing nature. There is a significant thermodynamic preference for the binding of the donor with the longer alkyl chain at the titanium center. The current work, therefore, provides interesting insights into how self‐extinguishing donors function in ZN catalytic systems

The impact of the use of personal-protective-equipment on the minimization of effects of exposure to pesticides among farm-workers in India

IntroductionAlthough excessive use of pesticides and unsafe agricultural practices may contribute to numerous intoxications, the role of PPE (personal-protective-equipment) in the minimization of toxicological effects due to pesticide exposure has not been addressed so far. The present study aimed to assess the impact of the use of PPE on the minimization of effects of exposure to pesticides among farm-workers.MethodsA community-based follow-up study with questionnaire-based survey and field observations was undertaken among farm-workers (n = 180) of Rangareddy district, Telangana, India. Biomarkers of exposure such as cholinesterase activity, inflammatory markers (TNF-α, IL-1β, IL-6, cortisol, and hs-C reactive protein), nutrients (vitamins A, E), liver function (total protein and A/G ratio, AST and ALT levels) were investigated in the laboratory by following the standard protocols.ResultsFarm-workers who had a mean farming exposure of 18 years of and who neither followed safe pesticide handling practices nor used PPE and also showed reluctance to obey good agricultural practices (GAPs). Inhibition of AChE (acetylcholine esterase) with increased inflammation was found among farm-workers as compared to their respective normal values when they have not used PPE. Linear regression statistical analysis revealed a profound effect on inhibition in the AChE activity and various inflammatory markers with the increase in the duration of pesticide exposure. Further, there was no effect of the duration of pesticide exposure on the levels of vitamins A, E, ALT, AST, total protein, and A/G ratio. Further, intervention studies carried out on the use of PPE provided (commercially available and cost-effective) for 90 days showed a significant reduction in the biomarker levels (p < 0.01).ConclusionThis study demonstrated the importance of the use of PPE during pesticide applications and other agricultural tasks to minimize pesticide-associated adverse health effects

A theoretical study of ethylene polymerization catalysis incorporating counterion effects

Bibliography: p. 127-13

Exploring the activation of olefin polymerisation catalysts with density functional theory

Bibliography: p. 87-91

The Discovery of an Aromatic Silicon Aluminium Compound Through A Novel Four-Pronged Computational Approach

Traditional experimental methods for the design of molecules are time-consuming and inefficient, prompting a shift towards computational approaches. Here, we unveil a strategy that transcends traditional paradigms. Rooted in first principles and liberated from experimental constraints, our newly developed four-stage approach allows the discovery of new molecules that display interesting properties. The current work showcases an interesting molecule that has been discovered through this approach: a four membered cyclic compound of silicon and aluminium that displays 2π aromaticity, and capable of the activation of important small molecules

Why are Aromatic Additives Effective in Asymmetric Organocatalysis?

The presence of an aromatic additive has been seen to enhance, often significantly, the yield and enantioselectivityof the desired product in asymmetric organocatalysis.Considering their success across a dizzying range of organocatalysts and organic transformations, it would seem unlikely that a common principleexists by which they function.However, the current investigations with DFT reveal that such a general principle indeed does exist: thearomatic additivesandwiches itself, through hydrogen bonding and π•••π stacking, between theorganocatalyst coordinatedelectrophile and nucleophile. This is seen to occur for a wide range of experimentally reported systems.That such complex formation leads to enhanced stereoselectivity isthen demonstrated for two cases: the cinchona alkaloid complex (BzCPD), catalysing thiocyanation(2-naphthol additive employed), as well as for the L-pipecolicacidcatalyst (2,4-dinitrophenol additive employed), catalysingtheasymmetric nitroaldol reaction.These findings are likely to have a significant impact on the field of asymmetric organocatalysis