Coulomb blockade and quantum tunnelling in the low-conductivity phase of granular metals

We study the effects of Coulomb interaction and inter-grain quantum tunnelling in an array of metallic grains using the phase-functional approach for temperatures $T$ well below the charging energy $E_{c}$ of individual grains yet large compared to the level spacing in the grains. When the inter-grain tunnelling conductance $g\gg1$, the conductivity $\sigma$ in $d$ dimensions decreases logarithmically with temperature ($\sigma/\sigma_{0}\sim1-\frac{1}{2\pi gd}\ln(gE_{c}/T)$), while for $g\to0$, the conductivity shows simple activated behaviour ($\sigma \sim \exp(-E_c/T)$). We show, for bare tunnelling conductance $g \gtrsim 1$, that the parameter $\gamma \equiv g(1-2/(g\pi)\ln(gE_{c}/T))$ determines the competition between charging and tunnelling effects. At low enough temperatures in the regime $1\gtrsim \gamma \gg 1/\sqrt{\beta E_{c}}$, a charge is shared among a finite number $N=\sqrt{(E_{c}/T)/\ln(\pi/2\gamma z)}$ of grains, and we find a soft activation behaviour of the conductivity, $\sigma\sim z^{-1}\exp(-2\sqrt{(E_{c}/T)\ln(\pi/2\gamma z)})$, where $z$ is the effective coordination number of a grain.Comment: 11 pages REVTeX, 3 Figures. Appendix added, replaced with published versio

ESTIMATION OF TOTAL PHENOLIC AND FLAVONOID CONTENT OF POLYHERBAL FORMULATION DASHANG LEPA

Background: Indian system of medicine mainly based on polyherbal compound to treat various types of diseases. Dashang lepa is one of the prestigious formulation of ten indigenous drugs which are having predominantly anti-inflammatory properties and clinically used in inflammatory swelling like boil, furunculosis, cellulitis, erysipelas etc. As several reports are on various individual phytochemical, phenolic and flavonoid content but none is having study of polyherbal compound Dashang lepa. Objectives: Total phenolic and total flavonoid content were studied of alcoholic extract of Dashang lepa. Method: Methanolic extraction was done by hot percolation method through soxhlet apparatus. Phenolic content was estimated using Follin ciocalteau reagent, flavonoid using aluminum chloride (2%) reagent as quercetin equivalent. Results: Estimation of total phenolic and total flavonoid content showed that Dashang lepa extract was having phenolic content (15.8±1.14) ug Gallic acid equivalents (GAE) and flavonoid content (22.4±2.54) in ug of quercetin equivalents (QE)

Optical conductivity of a granular metal at not very low temperatures

We study the finite-temperature optical conductivity, sigma(omega,T), of a granular metal using a simple model consisting of a array of spherical metallic grains. It is necessary to include quantum tunneling and Coulomb blockade effects to obtain the correct temperature dependence of sigma(omega, T), and to consider polarization oscillations to obtain the correct frequency dependence. We have therefore generalized the Ambegaokar-Eckern-Schoen (AES) model for granular metals to obtain an effective field theory incorporating the polarization fluctuations of the individual metallic grains. In contrast to the DC conductivity, which is determined by inter-grain charge transfer and obeys an Arrhenius law at low temperature, the AC conductivity is dominated by a resonance peak for intra-grain polarization oscillations, which has a power-law tail at low frequencies. More importantly, although the resonance frequency agrees with the classical prediction, the resonance width depends on intergrain quantum tunneling and Coulomb blockade parameters, in addition to the classical Drude relaxation within the grain. This additional damping is due to inelastic cotunneling of polarization fluctuations to neighbouring grains and it qualitatively differs from the DC conductivity in its temperature dependence quite unlike the expectation from Drude theory.Comment: Added figures, published version, 16 pages, REVTe

Identification of therapeutic targets for controlling COVID-19 pandemic by traditional system of Ayurvedic medicines: A systematic review

11-24COVID-19 is a severe respiratory disorder caused by the SARS COV-2 virus that involves limited innate immunity. Numerous publications have suggested that plants/minerals used in the traditional system of Ayurveda, has revealed much about the biology of COVID-19. One theory is that combination of anti viral, anti inflammatory, agents activating immune cells, herbs and metals may be helpful for severe acute respiratory syndrome coronavirus infection. Anti-viral drugs used for COVID-19 are those which block RNA synthesis and virus invasion, and bind to receptor proteins on the surface of cells, cell cycle protein, and physiological and pathological processes inhibitor. Anti-inflammatory drugs used for COVID-19 are those which controls transcription of DNA, cytokine production, break down the basement membrane, regulate outer mitochondrial membrane permeability, controlling the host cell life, stimulates activated B-cell and T-cell proliferation, virus dissemination, a slowdown of cell metabolism or secretion of cytokines. Drugs which is having role in the innate immunity, inhibits ROS, enhances cell lifespan, activates macrophages, physiological effects on cells activates the Lung resident immune cells. The focus of this review is to elucidate the Ayurvedic pharmacological properties with their therapeutic targets

Streamer Wave Events Observed in Solar Cycle 23

In this paper we conduct a data survey searching for well-defined streamer wave events observed by the Large Angle and Spectrometric Coronagraph (LASCO) on-board the Solar and Heliospheric Observatory (SOHO) throughout Solar Cycle 23. As a result, 8 candidate events are found and presented here. We compare different events and find that in most of them the driving CMEs ejecta are characterized by a high speed and a wide angular span, and the CME-streamer interactions occur generally along the flank of the streamer structure at an altitude no higher than the bottom of the field of view of LASCO C2. In addition, all front-side CMEs have accompanying flares. These common observational features shed light on the excitation conditions of streamer wave events. We also conduct a further analysis on one specific streamer wave event on 5 June 2003. The heliocentric distances of 4 wave troughs/crests at various exposure times are determined; they are then used to deduce the wave properties like period, wavelength, and phase speeds. It is found that both the period and wavelength increase gradually with the wave propagation along the streamer plasma sheet, and the phase speed of the preceding wave is generally faster than that of the trailing ones. The associated coronal seismological study yields the radial profiles of the Alfv\'en speed and magnetic field strength in the region surrounding the streamer plasma sheet. Both quantities show a general declining trend with time. This is interpreted as an observational manifestation of the recovering process of the CME-disturbed corona. It is also found that the Alfv\'enic critical point is at about 10 R$_\odot$ where the flow speed, which equals the Alfv\'en speed, is $\sim$ 200 km s$^{-1}$

Enhanced Room Temperature Coefficient of Resistance and Magneto-resistance of Ag-added La0.7Ca0.3-xBaxMnO3 Composites

In this paper we report an enhanced temperature coefficient of resistance (TCR) close to room temperature in La0.7Ca0.3-xBaxMnO3 + Agy (x = 0.10, 0.15 and y = 0.0 to 0.40) (LCBMO+Ag) composite manganites. The observed enhancement of TCR is attributed to the grain growth and opening of new conducting channels in the composites. Ag addition has also been found to enhance intra-granular magneto-resistance. Inter-granular MR, however, is seen to decrease with Ag addition. The enhanced TCR and MR at / near room temperature open up the possibility of the use of such materials as infrared bolometric and magnetic field sensors respectively.Comment: 22 pages of Text + Figs:comments/suggestions([email protected]

Deflection of coronal rays by remote CMEs: shock wave or magnetic pressure?

We analyze five events of the interaction of coronal mass ejections (CMEs) with the remote coronal rays located up to 90^\circ away from the CME as observed by the SOHO/LASCO C2 coronagraph. Using sequences of SOHO/LASCO C2 images, we estimate the kink propagation in the coronal rays during their interaction with the corresponding CMEs ranging from 180 to 920 km/s within the interval of radial distances form 3 R. to 6 R. . We conclude that all studied events do not correspond to the expected pattern of shock wave propagation in the corona. Coronal ray deflection can be interpreted as the influence of the magnetic field of a moving flux rope related to a CME. The motion of a large-scale flux rope away from the Sun creates changes in the structure of surrounding field lines, which are similar to the kink propagation along coronal rays. The retardation of the potential should be taken into account since the flux rope moves at high speed comparable with the Alfven speed.Comment: Accepted for Publication in Solar Physic

Zone center phonons of the orthorhombic RMnO3 (R = Pr, Eu, Tb, Dy, Ho) perovskites

A short range force constant model (SRFCM) has been applied for the first time to investigate the phonons in RMnO3 (R = Pr, Eu, Tb, Dy, Ho) perovskites in their orthorhombic phase. The calculations with 17 stretching and bending force constants provide good agreement for the observed Raman frequencies. The infrared frequencies have been assigned for the first time. PACS Codes: 36.20.Ng, 33.20.Fb, 34.20.CfComment: 8 pages, 1 figur

Perceived Physical and Mental Health and Healthy Eating Habits During the COVID-19 Pandemic in Korea

Background: The coronavirus disease 2019 (COVID-19) pandemic has disrupted the lives of people around the world since 2020. This study aims to reveal perceived impact of the coronavirus pandemic on physical and mental health and eating behaviors among people with disabilities and without disabilities in South Korea, as compared to other countries.Methods: A secondary analysis of a prospective cross-sectional study which was conducted with a web-based global survey.Results: Among the 3,550 responses from 65 countries, 2,621 responses with nation information were set as full data, 189 for South Korea and 2,432 for other countries. In Korea, there was no significant difference in healthy lifestyle behaviors between people with and without disabilities before the COVID-19 pandemic. Perceived physical and mental health and changes in eating habits during the COVID-19 pandemic showed no significant difference between people with and without disabilities in Korea. There were significant differences in physical health and dietary habits, but no differences in its effect on mental health between people living in Korea and other countries in both people with and without disabilities groups. In other words, more than 60% of people in all groups (disability vs. non-disability, Korea vs. non-Korea) reported worse mental health than before the COVID-19 pandemic.Conclusion: In Korea and other countries, mental health showed a tendency to deteriorate regardless of the presence or absence of disability during the COVID-19 pandemic. In terms of healthy eating habits, Koreans were relatively less affected than people from other countrie