The Tale of two Crises in the Time of Covid-19

We document the challenges faced by a sub-district called Phulbari in Bangladesh during Covid-19 lockdown. We do so using a series of 24 interviews with a wide range of individuals conducted during May 2020. What emerges is a picture of an under-resourced local administra- tion trying their best to cope with the situation. The local administration’s efforts have been complemented by efforts of the civil society. While social distancing policies have potentially helped prevent a Covid-19 outbreak, it has created an economic crisis in its wake. We suggest some specific policy proposals that can help alleviate the economic crisis without risking an outbreak

Plasmon induced transparency in graphene based terahertz metamaterials

Plasmon induced transparency (PIT) effect in a terahertz graphene metamaterial is numerically and theoretically analyzed. The proposed metamaterial comprises of a pair of graphene split ring resonators placed alternately on both sides of a graphene strip of nanometer scale. The PIT effect in the graphene metamaterial is studied for different vertical and horizontal configurations. Our results reveal that there is no PIT effect in the graphene metamaterial when the centers of both the split ring resonators and the graphene strip are collinear to each other. This is a noteworthy feature, as the PIT effect does not vanish for similar configuration in a metal-based metamaterial structure. We have further shown that the PIT effect can be tuned by varying the Fermi energy of graphene layer. A theoretical model using the three level plasmonic system is established in order to validate the numerical results. Our studies could be significant in designing graphene based frequency agile ultra-thin devices for terahertz applications

Time-resolved measurement of single pulse femtosecond laser-induced periodic surface structure formation

Time-resolved diffraction microscopy technique has been used to observe the formation of laser-induced periodic surface structures (LIPSS) from the interaction of a single femtosecond laser pulse (pump) with a nano-scale groove mechanically formed on a single-crystal Cu substrate. The interaction dynamics (0-1200 ps) was captured by diffracting a time-delayed, frequency-doubled pulse from nascent LIPSS formation induced by the pump with an infinity-conjugate microscopy setup. The LIPSS ripples are observed to form sequentially outward from the groove edge, with the first one forming after 50 ps. A 1-D analytical model of electron heating and surface plasmon polariton (SPP) excitation induced by the interaction of incoming laser pulse with the groove edge qualitatively explains the time-evloution of LIPSS formation.Comment: 4 pages, 5 figure

Mathematical Modeling And Experimental Studies On Biochemical Conversion Of Cr(Vi) Of Tannery Effluent To Cr(Iii) In A Chemostat

Biodegradation of hexavalent chromium present in tannery waste has been studied using Pseudomonas sp. (JUBTCr1) and Bacillus sp. (JUBTCr3) isolated from their native source. A 5L double-jacketed chemostat with 4L working volume has been used as contacting device for the kinetic investigation of the biodegradation process. Varying the feed volumetric rate from 118-133 ml/h for different inlet hexavalent chromium concentrations (30 to 90 mg/dm3), an attempt has been made to study the reaction engineering behavior of the system. It is observed that Haldane type substrate inhibited model can satisfactorily be used to predict the extent of bioconversion for different dilution rate. Using the kinetic parameters of proposed Haldane equation, a CSTR model was developed. Model prediction agreed well with experimental data

Flow properties of driven-diffusive lattice gases: theory and computer simulation

We develop n-cluster mean-field theories (0 < n < 5) for calculating the flow properties of the non-equilibrium steady-states of the Katz-Lebowitz-Spohn model of the driven diffusive lattice gas, with attractive and repulsive inter-particle interactions, in both one and two dimensions for arbitrary particle densities, temperature as well as the driving field. We compare our theoretical results with the corresponding numerical data we have obtained from the computer simulations to demonstrate the level of accuracy of our theoretical predictions. We also compare our results with those for some other prototype models, notably particle-hopping models of vehicular traffic, to demonstrate the novel qualitative features we have observed in the Katz-Lebowitz-Spohn model, emphasizing, in particular, the consequences of repulsive inter-particle interactions.Comment: 12 RevTex page

Collective traffic-like movement of ants on a trail: dynamical phases and phase transitions

The traffic-like collective movement of ants on a trail can be described by a stochastic cellular automaton model. We have earlier investigated its unusual flow-density relation by using various mean field approximations and computer simulations. In this paper, we study the model following an alternative approach based on the analogy with the zero range process, which is one of the few known exactly solvable stochastic dynamical models. We show that our theory can quantitatively account for the unusual non-monotonic dependence of the average speed of the ants on their density for finite lattices with periodic boundary conditions. Moreover, we argue that the model exhibits a continuous phase transition at the critial density only in a limiting case. Furthermore, we investigate the phase diagram of the model by replacing the periodic boundary conditions by open boundary conditions.Comment: 8 pages, 6 figure