Aqueous Diels–Alder reactions for thermochemical storage and heat transfer fluids identified using density functional theory

Thermal storage and transfer fluids have important applications in industrial, transportation, and domestic settings. Current thermal fluids have relatively low specific heats, often significantly below that of water. However, by introducing a thermochemical reaction to a base fluid, it is possible to enhance the fluid's thermal properties. In this work, density functional theory (DFT) is used to screen Diels–Alder reactions for use in aqueous thermal fluids. From an initial set of 52 reactions, four are identified with moderate aqueous solubility and predicted turning temperature near the liquid region of water. These reactions are selectively modified through 60 total functional group substitutions to produce novel reactions with improved solubility and thermal properties. Among the reactions generated by functional group substitution, seven have promising predicted thermal properties, significantly improving specific heat (by as much as 30.5%) and energy storage density (by as much as 4.9%) compared to pure water.     

Thermal conductance of nanofluids: is the controversy over?

Over the last decade nanofluids (colloidal suspensions of solid nanoparticles) sparked excitement as well as controversy. In particular, a number of researches reported dramatic increases of thermal conductivity with small nanoparticle loading, while others showed moderate increases consistent with the effective medium theories on well-dispersed conductive spheres. Accordingly, the mechanism of thermal conductivity enhancement is a hotly debated topic. We present a critical analysis of the experimental data in terms of the potential mechanisms and show that, by accounting for linear particle aggregation, the well established effective medium theories for composite materials are capable of explaining the vast majority of the reported data without resorting to novel mechanisms such as Brownian motion induced nanoconvection, liquid layering at the interface, or near-field radiation. However, particle aggregation required to significantly enhance thermal conductivity, also increases fluid viscosity rendering the benefit of nanofluids to flow based cooling applications questionable.     

The etching and structural response of Makrofol-N and Makrofol-KG polycarbonate to γ-irradiation

In order to estimate the damage densities produced by γ-rays to Makrofol-N and Makrofol-KG, some structural, optical and etching studies have been performed. It is found that both polymers are insensitive to low γ-doses (up to 10³ krad) but are influenced at higher doses. The changes in etching parameters have been noticed along with the changes in the FTIR and UV–VIS spectra. The results have been discussed on the basis of some basic mechanisms of radiation interactions with organic materials.     

The influence of solar radiations to the physical and structural properties of CR-39

Long chain polymers owe many of their properties to the structural arrangements of their molecules and are extensively used for many industrial and applied sciences. One of such application is their perspective use in the field of solid-state nuclear track detectors. However they are profoundly influenced by low LET radiations exposure and new structural arrangements may emerge. CR-39 is one of the most popular polymeric track detectors, however its aliphatic nature restricts its applications. Thus in the present investigations the damage densities produced by solar radiations to the polymer have been estimated by analyzing the structural, physical and etching properties of the polymer. The polymer is found to be highly sensitive towards solar radiations and great changes in physical and structural properties of polymer have been observed. The sensitivity of the polymer has been found to decrease by 83.40% during eight months.      

Uranium analysis in some food samples collected from Bathinda area of Punjab, India

To strengthen the radiation protection infrastructure in Bathinda, the uranium concentration in daily diet of the residents has been measured and its associated radiation risks were estimated for the adult population. Food samples were collected from major cancer prone areas of the district, from which daily diets were prepared. These diet samples were analyzed using fission track technique. The measured values of the uranium content were found to vary from 0.38 mBq/g in mustard seeds to 4.60 mBq/g in wheat. In case of milk the uranium content is found to vary from 28.57–213.36 mBq/ℓ with mean concentration of 61.35 mBq/ℓ. This leads to a daily dietary intake of 0.90 Bq/day. The measured value of 0.90 Bq d⁻¹, contributes to 1.12 mSv to the cumulative effective dose to the population. This dose is much large than the International Commission for Radiological Protection (ICRP) annual effective dose limit of 1 mSv for the general public [1]. Therefore, it would pose significant health hazard.      

Cinchonine-driven multi-component domino Knoevenagel–Michael strategy: metal-free synthesis of quinoline-based 4H-pyran and tetrahydro-4H-chromene derivatives

Research on Chemical Intermediates - Cinchonine-catalyzed simple, expeditious, and efficient protocol for the synthesis of quinoline-based 4H-pyran and tetrahydro-4H-chromenes has been demonstrated...     

The effect of infrared radiation on etching characteristics of CR-39 plastic track recorder

The effect of infrared radiation on the etching characteristics of CR-39 plastic track recorder has been studied. CR-39, which is commonly employed in cosmic rays studies is found to be affected by IR radiations. The changes in the bulk etch rate, in the track etch rate and in etching efficiency due to infrared radiation exposure of CR-39 are discussed on the basis of scission and cross linking during infrared exposure.     

Electrical and Optical Properties of O6+ Ion Beam–Irradiated Polymers

Variations in dielectric, optical, and structural properties of Lexan and Kapton-H irradiated to 80 MeV O⁶⁺ ion beam were analyzed at different fluences ranging from 10¹¹ to 10¹³ ions/cm² with a scanned beam current of 1 pnA. The structural modifications were characterized with the help of FT-IR and UV-vis spectroscopies. The electrical properties were investigated through capacitance and dielectric loss variations in ion-irradiated and pristine polymers at different frequencies. UV-vis absorption analysis indicates a decrease in the band gap energy in the two polymers. However, the decrease is much more prominent in Lexan (30%) than in Kapton-H (2.5%). The dielectric constant does not show appreciable variations after ion irradiation; however, a small increase has been noticed. An overall increase in the intensities of some typical bonds and stretching was observed in the FT-IR spectra of the pristine and ion-irradiated polymers.     

Modeling Floodplain Filtration for the Improvement of River Water Quality

A mathematical model was developed to describe a treatment method of floodplain filtration for the improvement of river water quality. The process consists of spraying poor quality river water onto the river floodplains and thus allowing soil filtration to treat water before it gets back again into the main river stream. This technique can be readily employed in Korea because it exploits the characteristics of the climate and rivers in the country, as described in an experimental study of Chung et al. The model was analyzed by numerical methods and validated by comparing the simulated values with experimental data. A scenario analysis of the model was also performed in order to have a better understanding of the floodplain filtration process. Our results show that the model was able to predict the reduction in organic matter and NO₃^– in river water through the floodplain filtration. Furthermore, it was found that only a few decimeters of top soil profile were enough to degrade most of the organic matter under wider operational conditions than those reported in the literature. Also, it was found that significant infiltration of atmospheric oxygen took place near the soil surface. The N₂O emission and the NO₃^– leaching increased with the increase in the influent NO₃^– concentration. However, the N₂O emission due to floodplain filtration was not expected to exceed 0.1 mL/m²-day.     

Thermal conductivity of nanoscale colloidal solutions (nanofluids)

Researchers have been perplexed for the past five years with the unusually high thermal conductivity (k) of nanoparticle-laden colloidal solutions (nanofluids). Although various mechanisms and models have been proposed in the literature to explain the high k of these nanofluids, no concrete conclusions have been reached. Through an order-of-magnitude analysis of various possible mechanisms, we show that convection caused by the Brownian movement of these nanoparticles is primarily responsible for the enhancement in k of these colloidal nanofluids.