Strong Single- and Two-Photon Luminescence Enhancement by Nonradiative Energy Transfer across Layered Heterostructure

The strong light-matter interaction in monolayer transition metal dichalcogenides (TMDs) is promising for nanoscale optoelectronics with their direct band gap nature and the ultra-fast radiative decay of the strongly bound excitons these materials host. However, the impeded amount of light absorption imposed by the ultra-thin nature of the monolayers impairs their viability in photonic applications. Using a layered heterostructure of a monolayer TMD stacked on top of strongly absorbing, non-luminescent, multi-layer SnSe2, we show that both single-photon and two-photon luminescence from the TMD monolayer can be enhanced by a factor of 14 and 7.5, respectively. This is enabled through inter-layer dipole-dipole coupling induced non-radiative Forster resonance energy transfer (FRET) from SnSe2 underneath which acts as a scavenger of the light unabsorbed by the monolayer TMD. The design strategy exploits the near-resonance between the direct energy gap of SnSe2 and the excitonic gap of monolayer TMD, the smallest possible separation between donor and acceptor facilitated by van der Waals heterojunction, and the in-plane orientation of dipoles in these layered materials. The FRET driven uniform single- and twophoton luminescence enhancement over the entire junction area is advantageous over the local enhancement in quantum dot or plasmonic structure integrated 2D layers, and is promising for improving quantum efficiency in imaging, optoelectronic, and photonic applications

The Optimal Forest Rotation: Some Economic Dimensions

Forest lands provide numerous things adding to the social, cultural, and economic aspects of life for many people including fuel, water, forage, stabilization of shifting sands, protection of catchment areas, soil erosion and flood control, watershed, habitat for wildlife, and sites for outdoor recreation. Because of their large area and wide geographic dispersion, they are also important in maintaining the natural environment. They are the source of timber, an important industry in many parts of the world. Products made from trees affect everyone, including those who may never have the opportunity to enjoy the natural beauty of a forest or to participate in forest-based recreation

Harmonic to anharmonic tuning of moir\'e potential leading to unconventional Stark effect and giant dipolar repulsion in WS2_2/WSe2_2 heterobilayer

Excitonic states trapped in harmonic moir\'e wells of twisted heterobilayers is an intriguing testbed. However, the moir\'e potential is primarily governed by the twist angle, and its dynamic tuning remains a challenge. Here we demonstrate anharmonic tuning of moir\'e potential in a WS$_2$/WSe$_2$ heterobilayer through gate voltage and optical power. A gate voltage can result in a local in-plane perturbing field with odd parity around the high-symmetry points. This allows us to simultaneously observe the first (linear) and second (parabolic) order Stark shift for the ground state and first excited state, respectively, of the moir\'e trapped exciton - an effect opposite to conventional quantum-confined Stark shift. Depending on the degree of confinement, these excitons exhibit up to twenty-fold gate-tunability in the lifetime ($100$ to $5$ ns). Also, exciton localization dependent dipolar repulsion leads to an optical power-induced blueshift of $\sim$1 meV/$\mu$W - a five-fold enhancement over previous reports.Comment: Accepted in Nature Communication

Availability and Use of Emergency Obstetric Care Services in Four Districts of West Bengal, India

Process indicators have been recommended for monitoring the availability and use of emergency obstetric care (EmOC) services. A health facility-based study was carried out in 2002 in four districts of West Bengal, India, to analyze these process indicators. Relevant records and registers for 2001 of all studied facilities in the districts were reviewed to collect data using a pre-designed schedule. The numbers of basic and comprehensive EmOC facilities were inadequate in all the four districts compared to the minimum acceptable level. Overall, 26.2% of estimated annual births took place in the EmOC facilities (ranged from 16.2% to 45.8% in 4 districts) against the required minimum of 15%. The rate of caesarean section calculated for all expected births in the population varied from 3.5% to 4.4% in the four districts with an overall rate of 4%, which is less than the minimum target of 5%. Only 29.9% of the estimated number of complications (which is 15% of all births) was managed in the EmOC facilities. The combined case-fatality rate in the basic/comprehensive EmOC facilities was 1.7%. Major obstetric complications contributed to 85.7% of maternal deaths, and pre-eclampsia/eclampsia was the most common cause. It can be concluded that all the process indicators, except proportion of deliveries in the EmOC facilities, were below the acceptable level. Certain priority measures, such as making facilities fully functional, effective referral and monitoring system, skill-based training, etc., are to be emphasized to improve the situation

Diborane as a reducing agent: Part VIII–Reduction of trifluoroacetylindoles to trifluoroethyl- and hydroxytrifluoroethylindoles and novel dimeric 2-trifluoro-l[1'-(3'-alkylindolino)]ethylboranes

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Prediction of traffic movement for autonomous vehicles

Living in the twenty-first century, there has been a massive growth in the number of autonomous vehicles present on the streets. Technology which once seemed impossible is being used in increasing number of vehicles day-by-day. With the technical advancement also comes challenges, it is not at all easy to develop and safely deploy these self-driving vehicles. So, in this chapter, a particular problem is being tackled, which is to predict future coordinates of all agents like cars, pedestrians, cyclists, etc., around AV. The main motive of this particular chapter is to measure the result efficiency of different deep learning models by evaluating the root mean square error (MSE) score. The models take as input the present state of the surroundings and based on that predicts the movement of the agents

FORMULATION DEVELOPMENT STUDIES OF BILAYER TABLET GLIPIZIDE: A NOVEL AND EVOLUTIONARY APPROACH IN THE TREATMENT OF DIABETES.

AbstractObjective:The aim of present study is to formulate glipizide sustained release (SR) and immediate release (IR) bilayer matrix tablet by different concentration of Hydroxypropyl methylcellulose (HPMC) and Ethyl Cellulose (EC) to control the release pattern.Method:The sustained release layer of glipizide was prepared by using different grades of HPMC like, HPMC K-100, HPMC K-50 and Ethyl Cellulose along with other excipients by wet granulation technique. The immediate release layer of glipizide was prepared by Lactose and Sodium starch glycolate by wet granulation Method.Result:The powders were evaluated for their flow properties and the finished tablets were evaluated for their physical parameters. The both immediate release and sustained release layers of glipizide were characterized by FT-IR and in vitro dissolution studies. The drug release study of glipizide was evaluated using USP-II paddle type dissolution apparatus. The release rate of glipizide in immediate release layer was studied for 1h in pH 7.4 phosphate buffer media and that of glipizide in sustained release layer was studied for 10 h in pH 7.4 phosphate buffer media.Conclusion:From the six batches F3 batch showed good release behaviour 91.92percent of drug is released over 10 hours and r2 value is 0.977 in zero-order kinetics. Glipizide is a poorly water soluble (BCS class 2) antidiabetic drug. Due to the poor water solubility of this drug, its bioavailability is dissolution rate-limited. Total four trial batches of each drug have been manufactured   to optimize and develop a robust and stable formulation, the stability studies of the products also comply with ICH guidelineKeywords: Bilayer tablets, Glipizide, HPMC, Sustained release, Wet granulation

Nonlinear Optics in Dielectric Guided-Mode Resonant Structures and Resonant Metasurfaces

Nonlinear optics is an important area of photonics research for realizing active optical functionalities such as light emission, frequency conversion, and ultrafast optical switching for applications in optical communication, material processing, precision measurements, spectroscopic sensing and label-free biological imaging. An emerging topic in nonlinear optics research is to realize high efficiency optical functionalities in ultra-small, sub-wavelength length scale structures by leveraging interesting optical resonances in surface relief metasurfaces. Such artificial surfaces can be engineered to support high quality factor resonances for enhanced nonlinear optical interaction by leveraging interesting physical mechanisms. The aim of this review article is to give an overview of the emerging field of nonlinear optics in dielectric based sub-wavelength periodic structures to realize efficient harmonic generators, wavelength mixers, optical switches etc. Dielectric metasurfaces support the realization of high quality-factor resonances with electric field concentrated either inside or in the vicinity of the dielectric media, while at the same time operate at high optical intensities without damage. The periodic dielectric structures considered here are broadly classified into guided-mode resonant structures and resonant metasurfaces. The basic physical mechanisms behind guided-mode resonances, electromagnetically-induced transparency like resonances and bound-states in continuum resonances in periodic photonic structures are discussed. Various nonlinear optical processes studied in such structures with example implementations are also reviewed. Finally, some future directions of interest in terms of realizing large-area metasurfaces, techniques for enhancing the efficiency of the nonlinear processes, heterogenous integration, and extension to non-conventional wavelength ranges in the ultra-violet and infrared region are discussed