Arpita Adhikari

Bio: Arpita Adhikari is an academic researcher from University of Calcutta. The author has contributed to research in topics: Disdrometer & Precipitation. The author has an hindex of 12, co-authored 41 publications receiving 410 citations. Previous affiliations of Arpita Adhikari include Budge Budge Institute of Technology & Islamic Azad University.

Characteristics of Raindrop Size Distribution Over a Tropical Location, Kolkata

Abstract: Raindrop size distribution (DSD) characteristics of monsoon and pre-monsoon seasons over Kolkata are analyzed by using three years raindrop size data from Joss–Waldvogel disdrometer located at Kolkata. The probability of occurrence DSD for different rain rate cluster has been observed for monsoon and pre-monsoon season. The mean raindrop concentration at a particular drop diameter and rain rate has been observed for both the seasons. The variations of number concentration with drop diameter and time have also been shown for monsoon and pre-monsoon season. The diurnal variations of DSD have also been investigated.

Toxicity of Carbon Nanomaterials

Abstract: The outstanding multidisciplinary applicability of nanomaterials has paved the path for the rapid advancement of nanoscience during the last few decades. Such technological progress subsequently results in an inevitable environmental exposure of nanomaterials. Presently, nanomaterials are employed in an extensive range of commercial products. Safe and sustainable incorporation of nanomaterials in industrial products requires a profound and comprehensive understanding of their potential toxicity. Among different nanomaterials, carbon nanomaterials marked its notable superiority toward the development of state-of-the-art nanotechnology due to the significant contribution of each of the carbon allotropes with varied dimensionality. The zero-dimensional fullerene, one-dimensional carbon nanotube, and two-dimensional graphene possess an exclusive combination of distinctive properties that are utilized in most of the nanotechnology-based products nowadays. However, potential risk factors are associated with the production and the use of carbon nanomaterials. Consequently, the number of studies regarding the assessment of the toxicity of these nanomaterials has increased rapidly in the past decade. This chapter will summarize the recent scientific efforts on the toxicity evaluation of different carbon nanomaterials.

Lac-extract doped Polyaniline Nano-Ribbons as Fluorescence Sensor and Molecular Switch for Detection of Aqueous AsO43- and Fe3+ contaminants

Abstract: • Synthesis of polyaniline nanoribbons doped with a natural dye extracted from lac insect (LAC-PANI). • Demonstration of its highly specific fluorescence sensing properties against aqueous AsO 4 3− and Fe 3+ ions. • Sharp increase and quenching of fluorescence intensity upon exposure to Fe 3+ and AsO 4 3− , respectively. • Demonstration as a NOT-AND compound molecular logic gate for simultaneous detection of Fe 3+ and AsO 4 3− . Detection of contaminants dissolved in water is an essential step for water quality monitoring and can guide us from consuming unhealthy water. Herein, we demonstrate the development of a novel low-cost polymer by doping polyaniline nanoribbons with lac-extract ( LAC-PANI ) and report its excellent fluorescence sensing properties against aqueous AsO 4 3− and Fe 3+ ions, both of which AsO 4 3− and Fe 3+ can pose health hazard for humans with the former being extremely toxic. When excited with radiation of 320 nm, the sensor showed contrasting fluorescence response against AsO 4 3− and Fe 3+ ions as the luminescence intensity showed sharp quenching upon exposure to Fe 3+ but against AsO 4 3− it showed a sharp rise in intensity. When other cations and oxoanions were concurrently tested with Fe 3+ and AsO 4 3− respectively, the sensor showed high specificity only to these two ions. Furthermore, a reversible and distinct fluorescence turn on–off-on switching response was observed upon sequential addition of AsO 4 3− , Fe 3+ and AsO 4 3− ions which points to the utility of the sensor as a NOT-AND compound molecular logic gate for simultaneous detection of two electronically divergent analyte classes. Thus, the LAC-PANI sensor developed in this work shows enormous potential for next generation fluorescence sensor useful for water quality monitoring.

Impact of prevailing atmospheric conditions on diurnal variability of the pre-monsoon rainfall over a tropical location, Kolkata

Abstract: • Pre-monsoon rainfall over Kolkata is categorized on the basis of time of occurrence. • Rain events are categorized as expected (14:30 IST-18:30 IST) and delayed (after 18:30 IST). • Small value of the IWV to LWP ratio results in significant precipitation for the delayed events. • Ground level temperature of the delayed events exhibits 1K higher values than the expected ones. • Variation of CAPE shows discernible increasing trend prior to two types of rain events. The annual rainfall amount over Gangetic West Bengal is predominantly determined by monsoon (June to September) and pre-monsoon (March to May) rain events. Consequently, such seasonal precipitation is directly linked to the socio-economic advancement of the area. In this paper, some characteristics of pre-monsoon rainfall over a tropical urban location, Kolkata have been explored utilizing ground-based observations. Pre-monsoon rainfall over Kolkata is characterized by convective rain events and thunderstorms, mostly occurring from afternoon to night (15:30 IST − 21:30 IST) span. Emphasis has been given to the set-in time of pre-monsoon rain events, based upon which they are classified as expected (14:30 IST − 18:30 IST) and delayed (after 18:30 IST). Efforts have been made to assess the sustaining atmospheric conditions (in terms of temperature, water vapour, liquid water content and instability parameter) associated with such rain events prevailing over two non-overlapping time spans of pre-monsoon season. The mean diurnal variations of integrated water vapour (IWV), liquid water path (LWP), and instability parameter, namely, convective available potential energy (CAPE) during the expected and delayed rain event dates show distinct intensity in the increasing trends prior to the respective rainfall peaks. It has been observed that for the delayed events, the temperature difference between ground and 2000 m altitude begins to fall at a later part of the evening in comparison with the expected ones. Overall the investigated parameters exhibited distinguishable nature of variations for the two classes of rain events over the study location.

Light Scattering by a Spheroidal Particle

Abstract: The solution of electromagnetic scattering by a homogeneous prolate (or oblate) spheroidal particle with an arbitrary size and refractive index is obtained for any angle of incidence by solving Maxwell's equations under given boundary conditions. The method used is that of separating the vector wave equations in the spheroidal coordinates and expanding them in terms of the spheroidal wavefunctions. The unknown coefficients for the expansion are determined by a system of equations derived from the boundary conditions regarding the continuity of tangential components of the electric and magnetic vectors across the surface of the spheroid. The solutions both in the prolate and oblate spheroidal coordinate systems result in a same form, and the equations for the oblate spheroidal system can be obtained from those for the prolate one by replacing the prolate spheroidal wavefunctions with the oblate ones and vice versa. For an oblique incidence, the polarized incident wave is resolved into two components, the TM mode for which the magnetic vector vibrates perpendicularly to the incident plane and the TE mode for which the electric vector vibrates perpendicularly to this plane. For the incidence along the rotation axis the resultant equations are given in the form similar to the one for a sphere given by the Mie theory. The physical parameters involved are the following five quantities: the size parameter defined by the product of the semifocal distance of the spheroid and the propagation constant of the incident wave, the eccentricity, the refractive index of the spheroid relative to the surrounding medium, the incident angle between the direction of the incident wave and the rotation axis, and the angles that specify the direction of the scattered wave.

Graphene and its sensor-based applications: A review

Abstract: This paper presents an overview of the work done on graphene in recent years. It explains the preparation techniques, the properties of graphene related to its physio-chemical structure and some key applications. Graphene, due to its outstanding electrical, mechanical and thermal properties, has been one of the most popular choices to develop the electrodes of a sensor. It has been used in different forms including nanoparticle and oxide forms. Along with the preparation and properties of graphene, the categorization of the applications has been done based on the type of sensors. Comparisons between different research studies for each type have been made to highlight their performances. The challenges faced by the current graphene-based sensors along with some of the probable solutions and their future opportunities are also briefly explained in this paper.

Effect of Morphology and Size of Halloysite Nanotubes on Functional Pectin Bionanocomposites for Food Packaging Applications.

Abstract: Pectin bionanocomposite films filled with various concentrations of two different types of halloysite nanotubes were prepared and characterized in this study as potential films for food packaging applications. The two types of halloysite nanotubes were long and thin (patch) (200–30 000 nm length) and short and stubby (Matauri Bay) (50–3000 nm length) with different morphological, physical, and dispersibility properties. Both matrix (pectin) and reinforcer (halloysite nanotubes) used in this study are considered as biocompatible, natural, and low-cost materials. Various characterization tests including Fourier transform infrared spectroscopy, field emission scanning electron microscopy, release kinetics, contact angle, and dynamic mechanical analysis were performed to evaluate the performance of the pectin films. Exceptional thermal, tensile, and contact angle properties have been achieved for films reinforced by patch halloysite nanotubes due to the patchy and lengthy nature of these tubes, which form a b...