Electroweak phase transition and some related phenomena – a brief review

Pramana - In this review we have outlined a very brief history of the Higgs boson search and the development of the strategies for searching for the Higgs boson in its diphoton decay channel. We...     

14C in uranium and thorium minerals: a signature of cluster radioactivity?

Various uranium and thorium minerals have been analysed with accelerator mass spectrometry to determine their ¹⁴C content. It is found that, whenever the contribution from secondary reactions such as the ¹¹B(α,p)¹⁴C is sufficiently low, the ¹⁴C concentration is consistent with that expected from ¹⁴C (spontaneous) cluster radioactivity from radium isotopes of the uranium and thorium natural series. Received: 15 February 1999     

Hearing protection and warning sounds in industry—a review

Member States of the European Economic Community are required to introduce Regulations which, in part, make the wearing of hearing protection mandatory under certain noise exposure conditions. Provisions are also to be introduced which can take into account possible difficulties that the wearer may have in the perception of warning sounds. This paper reviews the evidence that is relevant to any expert appraisal which formed part of a scheme of exemptions from the otherwise mandatory requirement.The evidence indicates that, when worn by people with normal hearing, the protectors will not in general impair the perception of appropriately selected alarm sounds. However, specific conditions are identified where the hearing protectors may reduce the effectiveness of some warning sounds, in particular for those machinery sounds which are associated with potential danger and for those people with an existing noise-induced hearing loss. It is recommended that the design of warning systems and the development of work practices should take account of possible failures in the perception of auditory warnings.     

Molecular ordering in a bipolar nematogenic cyanobiphenyl – a computer simulation approach

The molecular ordering of 4-(6-hydroxypropyloxy)-4′-cyanobiphenyl (H3CBP), a bipolar nematogen, has been carried out at room temperature (300 K) with respect to translatory and orientational motions. The complete neglect differential overlap (CNDO/2) method has been employed to compute the net atomic charge and atomic dipole moment at each atomic center. The modified Rayleigh–Schrodinger perturbation theory with multicentered-multipole expansion method has been employed to evaluate long-range intermolecular interactions, while a 6-exp potential function has been assumed for short-range interactions. The interaction energy values obtained through these computations were used to calculate the probability of each configuration at room temperature using the Maxwell–Boltzmann formula. On the basis of stacking, in-plane, and terminal interactions energy calculations, all possible geometrical arrangements of the molecular pair have been considered. Further, an attempt has been made to develop a model for liquid crystallinity based on probability of dimer complexes.     

Health Impacts in a Changing Climate – An Overview

In the past decades the topic of climate change has been subjected to intense scientific scrutiny, and since the mid-1990’s it has become an increasingly political issue. Because of increased temperatures and more frequent and intense extreme weather events, the number of direct injuries and deaths will increase, along with infectious diseases, whether food, water or vector-borne; respiratory and cardiovascular diseases are expected to rise due to worsened air pollution and extreme heat. In a context of on-going environmental degradation, local food-producing systems, both marine and terrestrial, will be affected and the risk of malnutrition, especially in children, will increase. These impacts on health and livelihood are expected to be significant factors in the spread of regional social crises, potentially leading to forced migration, conflicts and increased poverty.     

Fabrication,performance and applications of integrated nanodielectric properties of materials – a review

Abstract

The design and development of modern technological composites for the electrical and electronic applications are highly crucial. The minitualization, performance and durability of nanocomposites are achieved by integrating the nanodielectric properties of materials. In this review article, the entire upcoming trends in the domain of nanodielectric illustrated with important applications co-related to the various fabrication techniques of integrated nanodielectric composites are provided. The factors affecting the nanodielectric due to operating electric field and material interface which exhibit the high dielectric constant, low loss and moderate breakdown voltage. The complete sketch from concept, fabrication, factors co-related and applications of nanodielectric properties with the future scope are taken into consideration for further developments.     

Sonoproduction of nanobiomaterials – A critical review

Ultrasound (US) demonstrates remarkable potential in synthesising nanomaterials, particularly nanobiomaterials targeted towards biomedical applications. This review briefly introduces existing top-down and bottom-up approaches for nanomaterials synthesis and their corresponding synthesis mechanisms, followed by the expounding of US-driven nanomaterials synthesis. Subsequently, the pros and cons of sono-nanotechnology and its advances in the synthesis of nanobiomaterials are drawn based on recent works. US-synthesised nanobiomaterials have improved properties and performance over conventional synthesis methods and most essentially eliminate the need for harsh and expensive chemicals. The sonoproduction of different classes and types of nanobiomaterials such as metal and superparamagnetic nanoparticles (NPs), lipid- and carbohydrate-based NPs, protein microspheres, microgels and other nanocomposites are broadly categorised based on the physical and/or chemical effects induced by US. This review ends on a good note and recognises US-driven synthesis as a pragmatic solution to satisfy the growing demand for nanobiomaterials, nonetheless some technical challenges are highlighted.     

Hydrogen adsorption and desorption on the Pt and Pd subnano clusters – a review

In this review, we present our recent first principles studies on the sequential H₂ dissociative chemisorption and H desorption on the Pt_n and Pd_n clusters (n=2-9, 13). Upon full saturation by H atoms, the calculated H₂ dissociative chemisorption energy and H desorption energy on Pt₁₃ and Pd₁₃ clusters are similar to the corresponding values on smaller close-packed clusters. Indeed, the catalytic performances of these subnano clusters do not vary significantly with the particle sizes or shapes. Instead, they are dependent on the surface metal atoms which can be accessed by H atoms. In addition to the coverage dependency of the H₂dissociative chemisorption and H sequential desorption energies, the phase transition of both Pt₁₃ and Pd₁₃from the icosahedral to fcc-like structures at certain H coverage was also investigated.     

Fully printed organic solar cells – a review of techniques,challenges and their solutions

The emergence of solar cells on flexible and bendable substrates has made the printing process a ubiquitous tool for the fabrication of these devices. The various printing techniques available now such as inkjet, screen and flexography offer cost- effectiveness, user-friendliness and suitability for mass production. While downscaling the fill factor and efficiency of organic solar cells. A multilayered structure, the combination of different printing techniques avails the variety of thickness and resolution required for each layer in the production of an organic solar cell. In this review article, we discuss the suitability of the inkjet and screen printing processes to produce organic solar cells. We also discuss various challenges involved in the fabrication of organic solar cells using these two techniques and the possible solutions for the same. We also provide an analogy that both processes share. Further, we consider future possibilities of combining these printing technologies to produce organic solar cells to improve device performance.     

Radon levels in underground workplaces – results of a nationwide survey in Italy

In Italy an extensive survey has been carried out with the aim to evaluate annual average radon concentration in underground workplaces.The survey covered 933 underground rooms located in 311 bank workplaces spread throughout in all Italian regions; at this scope the sampling was stratified random in order to be representative on national scale. The annual radon concentration was estimated by using passive radon dosemeters (NRPB/SSI type holder and CR-39 as detector): the devices were exposed for a period of about 3 months and 4 cycles were performed to cover a solar year. The radon levels in underground workplaces ranged from 27 to 4851 Bq/m³ with an overall mean value of 153 Bq/m³. As expected, radon distribution is not uniform throughout Italy: in several regions high radon annual averages have been found, confirming previous surveys.The analysis of data shows a high variability among regions and intra-region but low spread among rooms belonging to the same workplace.About 5% of underground workplaces displayed radon concentration exceeding 400 Bq/m³, and the 4.4% exceeds 500 Bq/m³, the national action level for the exposure to natural radioactivity in workplaces.     

Dissolved gas and ultrasonic cavitation – A review

The physics and chemistry of nonlinearly oscillating acoustic cavitation bubbles are strongly influenced by the dissolved gas in the surrounding liquid. Changing the gas alters among others the luminescence spectrum, and the radical production of the collapsing bubbles. An overview of experiments with various gas types and concentration described in literature is given and is compared to mechanisms that lead to the observed changes in luminescence spectra and radical production. The dissolved gas type changes the bubble adiabatic ratio, thermal conductivity, and the liquid surface tension, and consequently the hot spot temperature. The gas can also participate in chemical reactions, which can enhance radical production or luminescence of a cavitation bubble. With this knowledge, the gas content in cavitation can be tailored to obtain the desired output.     

Lattice Bhatnagar—Gross—Krook Simulations of Turbulent Natural Convection in a Cavity

A thermal lattice Bhatnagar-Gross-Krook (LBGK) model with a robust boundary scheme is developed for Boussinesq incompressible fluids.In the model the velocity and temperature fields are solved by two independent LBGK equations which are combined into a coupled equation for the whole system.The two-dimensional natural convection flow of air in a differentially heated cavity of an aspect ratio of four is simulated for the Rayleigh number up to 10^10.The numerical results are found to be in good agreement with those of previous studies.     

Decay of a Bose-Einstein condensate in a dissipative lattice – the mean-field approximation and beyond

The dynamical evolution of a Bose-Einstein condensate in an open optical lattice is studied. Based on the Bose-Hubbard model we rederive the mean-field limit for the case of an environmental coupling including dissipation and phase-noise. Moreover, we include the next order correlation functions to investigate the dynamical behavior beyond mean field. We observe that particle loss can lead to surprising dynamics, as it can suppress decay and at the same time restore the coherence of the condensate. These behavior can be used to engineer the evolution, e.g. in the form of a stochastic resonance-like response, to inhibit tunneling or to create stable nonlinear structures of the condensate.     

Modeling cavitation in a rapidly changing pressure field – Application to a small ultrasonic horn

Ultrasonic horn transducers are frequently used in applications of acoustic cavitation in liquids. It has been observed that if the horn tip is sufficiently small and driven at high amplitude, cavitation is very strong, and the tip can be covered entirely by the gas/vapor phase for longer time intervals. A peculiar dynamics of the attached cavity can emerge with expansion and collapse at a self-generated frequency in the subharmonic range, i.e. below the acoustic driving frequency. The term “acoustic supercavitation” was proposed for this type of cavitation Žnidarčič et al. (2014) [1].We tested several established hydrodynamic cavitation models on this problem, but none of them was able to correctly predict the flow features. As a specific characteristic of such acoustic cavitation problems lies in the rapidly changing driving pressures, we present an improved approach to cavitation modeling, which does not neglect the second derivatives in the Rayleigh–Plesset equation. Comparison with measurements of acoustic supercavitation at an ultrasonic horn of 20 kHz frequency revealed a good agreement in terms of cavity dynamics, cavity volume and emitted pressure pulsations.The newly developed cavitation model is particularly suited for simulation of cavitating flow in highly fluctuating driving pressure fields.     

Prospects of ultrasonically extracted food bioactives in the field of non-invasive biomedical applications – A review

Foods incorporated with bioactive compounds, called nutraceuticals, can fight or prevent or alleviate diseases. The contribution of nutraceuticals or phytochemicals to non-invasive biomedical applications is increasing. Although there are many traditional methods for extracting bioactive compounds or secondary metabolites, these processes come with many disadvantages like lower yield, longer process time, high energy consumption, more usage of solvent, yielding low active principles with low efficacy against diseases, poor quality, poor mass transfer, higher extraction temperature, etc. However, nullifying all these disadvantages of a non-thermal technology, ultrasound has played a significant role in delivering them with higher yield and improved bio-efficacy. The physical and chemical effects of acoustic cavitation are the crux of the output. This review paper primarily discusses the ultrasound-assisted extraction (USAE) of bioactives in providing non-invasive prevention and cure to diseases and bodily dysfunctions in human and animal models. The outputs of non-invasive bioactive components in terms of yield and the clinical efficacy in either in vitro or in vitro conditions are discussed in detail. The non-invasive biomedical applications of USAE bioactives providing anticancer, antioxidant, cardiovascular health, antidiabetic, and antimicrobial benefits are analyzed in-depth and appraised. This review additionally highlights the improved performance of USAE compounds against conventionally extracted compounds. In addition, an exhaustive analysis is performed on the role and application of the food bioactives in vivo and in vitro systems, mainly for promoting these efficient USAE bioactives in non-invasive biomedical applications. Also, the review explores the recovery of bioactives from the less explored food sources like cactus pear fruit, ash gourd, sweet granadilla, basil, kokum, baobab, and the food processing industrial wastes like peel, pomace, propolis, wine residues, bran, etc., which is rare in literature.     

Sonochemical degradation of poly- and perfluoroalkyl substances – A review

Poly- and perfluoroalkyl substances (PFAS) have received considerable attention from environmental scientists and engineers because of their stability and widespread. Sonochemical process has been widely used in the environmental field to remove pollutants due to its advantages in terms of operational simplicity, no secondary pollutant formation and safety. Currently, many studies have reported sonochemical degradation of various PFAS in laboratory settings and showed excellent removal potential. This article reviewed the effects of different power densities, ultrasonic frequencies, temperatures, atmosphere conditions, additives, and initial concentration and chemical properties of PFAS on the sonochemical degradation of PFAS. Sonochemical methods combined with conventional techniques for PFAS removal were elaborated as well. Additionally, this article discussed the challenges and prospects of using sonochemical approaches for PFAS remediation.