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"Rajeev, P. P."
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Financial Access of the Urban Poor in India : a Story of Exclusion
\"This book focuses on the issue of financial exclusion with particular reference to the urban informal sector in India. Continuing the work of its predecessor, the current Government of India is also placing considerable importance on driving policy initiatives for financial inclusion. However, financial exclusion in urban areas, especially of the lower strata of the society has not received the attention it deserves from researchers and policymakers, even though urban poverty and deprivations are of considerable importance in the present Indian context. The challenges of financial inclusion and accessibility in the urban areas differ substantially from those found in the rural regions given the fact that the possibility of physical access to financial services is much higher in urban areas. In order to provide a macro perspective, the book begins with an analysis of the unit record data on nature and extent of financial inclusion and access to credit in urban India, based on Debt and Investment survey data (59th and 70th rounds) provided by the National Sample Survey Office (NSSO). In subsequent steps, the book discusses findings from a primary survey carried out in the state of Karnataka of self-employed persons engaged in informal services sector. This exercise has helped to comprehend the ways in which they currently meet their financial needs for different income generating purposes, the terms and conditions under which they do so, and the challenges that remained for possible interventions. Experiences of other developing nations in their attempts to ensure financial inclusion and the lesson learnt thereby are the other highlights of the book.\"--Publisher's website.
Book
2020 roadmap on plasma accelerators
Plasma-based accelerators use the strong electromagnetic fields that can be supported by plasmas to accelerate charged particles to high energies. Accelerating field structures in plasma can be generated by powerful laser pulses or charged particle beams. This research field has recently transitioned from involving a few small-scale efforts to the development of national and international networks of scientists supported by substantial investment in large-scale research infrastructure. In this New Journal of Physics 2020 Plasma Accelerator Roadmap, perspectives from experts in this field provide a summary overview of the field and insights into the research needs and developments for an international audience of scientists, including graduate students and researchers entering the field.
Journal Article
Automation and control of laser wakefield accelerators using Bayesian optimization
Laser wakefield accelerators promise to revolutionize many areas of accelerator science. However, one of the greatest challenges to their widespread adoption is the difficulty in control and optimization of the accelerator outputs due to coupling between input parameters and the dynamic evolution of the accelerating structure. Here, we use machine learning techniques to automate a 100 MeV-scale accelerator, which optimized its outputs by simultaneously varying up to six parameters including the spectral and spatial phase of the laser and the plasma density and length. Most notably, the model built by the algorithm enabled optimization of the laser evolution that might otherwise have been missed in single-variable scans. Subtle tuning of the laser pulse shape caused an 80% increase in electron beam charge, despite the pulse length changing by just 1%.
Laser wakefield accelerators are compact sources of ultra-relativistic electrons which are highly sensitive to many control parameters. Here the authors present an automated machine learning based method for the efficient multi-dimensional optimization of these plasma-based particle accelerators.
Journal Article
Narrow bandwidth, low-emittance positron beams from a laser-wakefield accelerator
The rapid progress that plasma wakefield accelerators are experiencing is now posing the question as to whether they could be included in the design of the next generation of high-energy electron-positron colliders. However, the typical structure of the accelerating wakefields presents challenging complications for positron acceleration. Despite seminal proof-of-principle experiments and theoretical proposals, experimental research in plasma-based acceleration of positrons is currently limited by the scarcity of positron beams suitable to seed a plasma accelerator. Here, we report on the first experimental demonstration of a laser-driven source of ultra-relativistic positrons with sufficient spectral and spatial quality to be injected in a plasma accelerator. Our results indicate, in agreement with numerical simulations, selection and transport of positron beamlets containing
N
e
+
≥
10
5
positrons in a 5% bandwidth around 600 MeV, with femtosecond-scale duration and micron-scale normalised emittance. Particle-in-cell simulations show that positron beams of this kind can be guided and accelerated in a laser-driven plasma accelerator, with favourable scalings to further increase overall charge and energy using PW-scale lasers. The results presented here demonstrate the possibility of performing experimental studies of positron acceleration in a laser-driven wakefield accelerator.
Journal Article
Agroecological Responses of Heavy Metal Pollution with Special Emphasis on Soil Health and Plant Performances
Following the modern-day urbanization and industrialization, heavy metal contamination has become a prime concern for today’s society. Starting from the agricultural soil in our food basket these heavy metals and metalloids, like - Cr, Mn, Co, Ni, Cu, Zn, Cd, Sn, Hg,Pb and others, showing significant toxic impacts. The intensification of agricultural land-use and changes in farming practices along with technological advancement has led to heavy metal pollution in soil. Metals/ metalloids concentrations in the soil are increasing at alarming rate due to modern day agricultural practices as these could not be degraded and affect plant growth, food safety and soil microflora. The biological and geological reorganization of heavy metal depends chiefly on green plants and their metabolism. Metal toxicity has direct effects and importance to flora that forms the integral component of ecosystem. Altered biochemical, physiological and metabolic processes are found in plants growing in regions of high metal pollution. However, metals like Cu, Mn, Co, Zn and Cr are required in trace amounts by plants for their metabolic activities. The present review aims to catalogue major published works related to heavy metal contamination in modern day agriculture, and draw a possible road map towards future research in this domain.
Journal Article
A laser–plasma platform for photon–photon physics: the two photon Breit–Wheeler process
We describe a laser–plasma platform for photon–photon collision experiments to measure fundamental quantum electrodynamic processes. As an example we describe using this platform to attempt to observe the linear Breit–Wheeler process. The platform has been developed using the Gemini laser facility at the Rutherford Appleton Laboratory. A laser Wakefield accelerator and a bremsstrahlung convertor are used to generate a collimated beam of photons with energies of hundreds of MeV, that collide with keV x-ray photons generated by a laser heated plasma target. To detect the pairs generated by the photon–photon collisions, a magnetic transport system has been developed which directs the pairs onto scintillation-based and hybrid silicon pixel single particle detectors (SPDs). We present commissioning results from an experimental campaign using this laser–plasma platform for photon–photon physics, demonstrating successful generation of both photon sources, characterisation of the magnetic transport system and calibration of the SPDs, and discuss the feasibility of this platform for the observation of the Breit–Wheeler process. The design of the platform will also serve as the basis for the investigation of strong-field quantum electrodynamic processes such as the nonlinear Breit–Wheeler and the Trident process, or eventually, photon–photon scattering.
Journal Article
Laser-wakefield accelerators for high-resolution X-ray imaging of complex microstructures
Laser-wakefield accelerators (LWFAs) are high acceleration-gradient plasma-based particle accelerators capable of producing ultra-relativistic electron beams. Within the strong focusing fields of the wakefield, accelerated electrons undergo betatron oscillations, emitting a bright pulse of X-rays with a micrometer-scale source size that may be used for imaging applications. Non-destructive X-ray phase contrast imaging and tomography of heterogeneous materials can provide insight into their processing, structure, and performance. To demonstrate the imaging capability of X-rays from an LWFA we have examined an irregular eutectic in the aluminum-silicon (Al-Si) system. The lamellar spacing of the Al-Si eutectic microstructure is on the order of a few micrometers, thus requiring high spatial resolution. We present comparisons between the sharpness and spatial resolution in phase contrast images of this eutectic alloy obtained
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X-ray phase contrast imaging at the Swiss Light Source (SLS) synchrotron and X-ray projection microscopy
via
an LWFA source. An upper bound on the resolving power of 2.7 ± 0.3
μ
m of the LWFA source in this experiment was measured. These results indicate that betatron X-rays from laser wakefield acceleration can provide an alternative to conventional synchrotron sources for high resolution imaging of eutectics and, more broadly, complex microstructures.
Journal Article
Formulation and Development of Transferrin Targeted Solid Lipid Nanoparticles for Breast Cancer Therapy
Breast cancer is conventionally treated by surgery, chemotherapy and radiation therapy followed by post operational hormonal therapy. Tamoxifen citrate is a best option to treat breast cancer because its selective estrogen receptor modulation activity. Owing to its antiestrogenic action on breast as well as uterine cells, Tamoxifen citrate shows uterine toxicity. The dose 20 mg per day of Tamoxifen citrate required to show therapeutic effect causes side effects and toxicity to vital organs such as liver, kidney and uterus. In the present study, transferrin-conjugated solid lipid nanoparticles (SLNs) were successfully prepared to enhance the active targeting of tamoxifen citrate in breast cancer. Developed formulations were evaluated for particle size, surface charge, surface morphology and in vitro dissolution studies. Developed formulations exhibited more cytotoxicity as compared to pure Tamoxifen citrate solution in time as well as concentration dependent manner on human breast cancer MCF-7 cells. Further, cell uptake and flow cytometry studies confirmed the qualitative uptake of developed D-SLN and SMD-SLN by human breast cancer MCF-7 cells. Overall, proposed study highlights that transferrin engineered nanocarriers could enhance the therapeutic response of nanomedicines for breast cancer treatment.
Journal Article
Self-guided propagation of laser pulses reflected at high intensity from plasma mirrors
The reflectivity and optical quality of laser pulses reflected off 125μm Kapton™ tape was investigated for use as a repeatable plasma mirror. Reflectivities of around 70% were measured at ≈2 × 10 21Wm−2 while maintaining the quality of the laser beam. The ability of the reflected pulse to drive a laser wakefield accelerator was investigated. Self-guided propagation of the reflected beam through a gas cell was observed and shown to depend on the plasma density. Particle-in-cell simulations showed that a wakefield would have been generated, driven solely by the energy within the central high intensity feature of the focal spot. The use of plasma mirrors at these elevated intensities would open up the possibilities of extremely compact configurations for laser wakefield accelerator stages.
Journal Article
DNA DSB Repair Dynamics following Irradiation with Laser-Driven Protons at Ultra-High Dose Rates
Protontherapy has emerged as more effective in the treatment of certain tumors than photon based therapies. However, significant capital and operational costs make protontherapy less accessible. This has stimulated interest in alternative proton delivery approaches, and in this context the use of laser-based technologies for the generation of ultra-high dose rate ion beams has been proposed as a prospective route. A better understanding of the radiobiological effects at ultra-high dose-rates is important for any future clinical adoption of this technology. In this study, we irradiated human skin fibroblasts-AG01522B cells with laser-accelerated protons at a dose rate of 10
9
Gy/s, generated using the Gemini laser system at the Rutherford Appleton Laboratory, UK. We studied DNA double strand break (DSB) repair kinetics using the p53 binding protein-1(53BP1) foci formation assay and observed a close similarity in the 53BP1 foci repair kinetics in the cells irradiated with 225 kVp X-rays and ultra- high dose rate protons for the initial time points. At the microdosimetric scale, foci per cell per track values showed a good correlation between the laser and cyclotron-accelerated protons indicating similarity in the DNA DSB induction and repair, independent of the time duration over which the dose was delivered.
Journal Article