Laser Optogalvanic Spectroscopy: Experimental Details and Potential Applications in R and D

Laser Optogalvanic Spectroscopy (LOGS) is an extremely sensitive detection technique based on the 'Optogalvanic Effect'. The impedance change of gaseous discharge following the absorption of resonant laser light by the discharge species has proved to be a powerful spectroscopic tool to investigate all kinds of matter in vapour phase in discharge plasmas and flames. LOGS does not require any optical detector and the signal-to-noise ratios are often greater than 10/sup 3/. The advent of tunable lasers has pushed LOGS as a unique detection technique, efficient over a wide frequency spectrum from UV through visible to IR. As a simple and most sensitive detection technique, LOGS can have diverse practical applications in science and technology. The experimental details with different discharge excitations and the potential applications of LOGS are briefly described. Some prominent practical applications like wavelength calibration, laser linewidth determination, trace element detection, isotope analysis, material characterisation, laser frequency and power stabilisation, Rydberg atom spectroscopy and combustion and plasma diagnostics are briefly discussed

Phase-shift Cavity Ring-down Technique for Detection of NO2 in PPM Concentration

A phase-shift cavity ring-down spectroscopy (PS-CRDS) experimental set-up has been established using a broadband diode laser for the measurement of phase shift due to absorption of NO2 in a sealed off cavity ring-down cell. The PS-CRDS technique is verified by optimising various parameters of CRDS cavity and excitation laser. The PS-CRDS signals were measured on the first harmonics using a lock-in-amplifier. The square modulated laser pulses were used in the experiment to obtain the decay time. Measurements of the signal strengths at different CRDS cavity lengths wre also carried out to verify the detection sensitivity for ppm level concentration measurement of trace gases.Defence Science Journal, Vol. 64, No. 5, September 2014, pp.426-430, DOI:http://dx.doi.org/10.14429/dsj.64.503

Phase-shift Cavity Ring Down Spectroscopy Set-up for NO2 Sensing : Design and Fabrication

An indigenously designed cavity ring down spectroscopy cell of 80 cm length of mild steel material was fabricated by attaching two 1″ diameter high reflecting concave mirrors with reflectivity 99.997 % at 405 nm and radius of curvature was 1 m in specially designed mirror holding assemblies to the cell at two ends. Fine alignment of the resonator is facilitated with three tip-tilt adjusting screws to the mirror-mounting plate assembly. The PS-CRDS experimental set-up is evaluated by measuring the phase shift values corresponding to the absorption of NO2 gas filled at low pressures in the cell. The limit of detection of pure NO2 using the set-up under given conditions of Ar @ 50 mbar is estimated to be 1.50 × 1011 cm-3 and @ 60 mbar as 2 × 1011 cm-3.Defence Science Journal, Vol. 65, No. 1, January 2015, pp.25-30, DOI:http://dx.doi.org/10.14429/dsj.65.779

Evaluation of 976 nm Multimode Single Emitter Laser Diodes for Efficient Pumping of 100 W+ Yb-doped Fiber Laser

Experimental evaluation of spectral and power-current (P-I) characteristics of fiber coupled single emitter multimode laser diodes used for development of efficient pumping assembly is reported. Fiber coupled laser diodes emitting around 976 nm are best suited for pumping Yb-doped fiber lasers because of excellent coupling efficiency and reduced thermal load. We have experimentally investigated emission spectrum of fiber coupled multimode laser diodes at different temperatures and drive currents. It is found that peak emission wavelength shifts towards the longer wavelength with increase in temperature and drive current. P-I characteristics of fiber coupled laser diodes have been obtained and presented for drive current from 0.4 A to 11.5 A. Based on experiment, we have constructed spectrally matched laser diode assembly for efficient pumping of 100 W fiber laser. It requires very precise control of temperature and drive current to maintain the emission spectrum. Total 162 W power is pumped in to the Yb-doped fiber laser cavity through multi-mode pump combiners and we have obtained 110 W fiber laser output power @1070 nm. The achieved optical-to-optical efficiency is 68 per cent

Prevalence of elongation and calcification patterns of elongated styloid process in south india

Objective: Very few studies have been reported in the literature classifying the elongation and calcification patterns of styloid process. The present study was done to investigate the prevalence of elongation and calcification patterns of styloid process in patients attending a dental institution in south India. Study design: 600 digital panoramic radiographs of patients with dental problems were obtained from the outpatient department of the Dental institution. The apparent length of the styloid process was measured by a single experienced oral radiologist, with the help of the measuring tools on the accompanying software. The type of elongation and calcification patterns of each elongated styloid process was classified as per Langlai's classification with few modifications. Finally the data was subjected to statistical analysis. Results: Out of 520 measurable styloid processes (260 panoramic radiographs), 154 styloid processes had length greater than 3cm. The mean average length of elongated styloid process was 3.67±0.62 cm. No significant association was obtained between age and length of styloid process. In present study, the type of elongation pattern has no effect on the calcification pattern. Our results suggested that Type I elongated styloid processes were most likely to be completely calcified (type D), but statistically not significant. Conclusion: Type I pattern of elongation was found to be more prevalent in elder age group and was completely calcified in most of the cases. Interestingly, only three patients (out of 260) showed symptomatic elongation of styloid process. A relatively high prevalence of type IV elongation pattern (9 /154) was obtained in the present study, when compared to type III styloid process. Further large scale imaging studies are required to evaluate the presence of type IV elongation pattern in various population groups

In-depth Study of the Pluralistic Agricultural Extension System in India

This In-Depth Study of the Pluralistic Agricultural Extension System in India is a full analysis of the pluralistic extension system in India, how it has changed over many years and the direction it is currently moving. Chapter-1 outlines the Evolution of the Pluralistic Agricultural Extension System in India and the changes that have occurred since about 1871, including the establishment of the Department of Agriculture in 1882. Following independence in 1947, many changes have happened as outlined in this first chapter, including the Community Development Program (CDP), the Intensive Agricultural District Program (IADP), including dissemination of high-yielding varieties during the Green Revolution, the Training and Visit (T&V) approach and then the move to the decentralized, farmer-led and market driven approach influenced by the Agricultural Technology Management Agency (ATMA) model. Chapter-2 gives an Overview of the Public Extension System within the Ministry of Agriculture (MoA), the State Departments of Agriculture and then provides more detailed information about the Krishi Vigyan Kendra (KVK) and the public extension system in India. It starts with an overview of the organizational structure at the national level, including the Department of Agricultural Research and Extension (DARE), then into the Department of Agriculture and Cooperation (DAC) and Directorate of Extension within DAC. Then, it moves into the KVKs, which are a critical linkage at the district level between research, extension and farmers. In short, KVKs focus on the specific agro-ecological conditions within each district and then, after conducting research on these different crops, livestock and other farming systems. Then it moves into the development of the ATMA model through two World Bank projects, which is now expand across all Indian districts. Chapter-3 outlines the Directorates of Extension Education within each State Agricultural Universities (SAUs). India is unique in having Extension units established within each SAU, since this extension approach was first introduced by selected US Land Grant Universities into these SAUs in the late 1950s and early 1960s. This chapter outlines the historical development of the extension within each SAU and then outlines the mandate, organizational structure, human resources and methods used within these SAUs and their relationship with the public extension system. Chapter-4 outlines the Private Sector Advisory Services being provided in India, especially in the provision of good advisory services through private Agri-Business Companies through the sale of inputs to farmers. In India, there are over 280,000 input supply firms, but many do not have sufficient knowledge and experience in providing good advisory services to farmers. At first, the public and private sector did not want to work together but through the ATMA approach, the public and private sector started working together and then, in 2004, the National Institute of Agricultural Extension Management (MANAGE) started training and giving diplomas to the participants from these private sector firms, especially in Andhra Pradesh (see: http://www.manage.gov.in/daesi/daesi.htm). Chapter-5 summarizes the role and activities of the different Commodity Boards currently operating in India, including: Central Silk Board (CSB), Coconut Development Board (CDB), Coffee Board, Coir Board, Rubber Board, Spices Board, Tea Board, Tobacco Board, National Dairy Development Board (NDDB), National Horticulture Board (NHB), Cashew Export Promotion Council (CEPC), National Jute Board (NJB), and the National Federation of Cooperative Sugar Factories (NFCSF) and how each of these boards carry out extension and advisory services to the farmers being served. Chapter-6 outlines the Institutional Mechanism for Capacity Building to strengthen the pluralistic extension system in India. This chapter starts with an overview of the National Institute of Agricultural Extension Management (MANAGE), which is an autonomous organization that has had the most impact on strengthening the extension system in India. Next, it discusses the paradigm shift within the National Institute of Agricultural Marketing (NAIM) in India; and then outlines the role of the Extension Education Institutes (EEIs). Finally, it moves to outline the role and structure of the State Agricultural Management and Extension Training Institutes (SAMETIs), especially in strengthening the ATMA model in India. Chapter-7 is the conclusion chapter that outlines the Strengths and Weaknesses of India’s Pluralistic Extension System. It starts by outlining the Policy Framework and Reforms for strengthening the pluralistic extension system in India. Next, it outlines how to strengthen research-extension linkages as well as capacity building among extension workers. Next, it addresses how to empower farmers, including women farmers. It also outlines the use of Information Technology (IT) and how to strengthen it through different approaches. This chapter also outlines the changing role of government in extension and how the ATMA model can be strengthened following very specific details. The other issue is how to strengthen the SAMETIs, since they still need to be strengthened in providing service to district and block level extension workers. This chapter ends with a brief summary the key role that the public extension system can play in India

The INtegrated CAtchment model of phosphorus dynamics (INCA-P): description and demonstration of new model structure and equations

INCA-P is a dynamic, catchment-scale phosphorus model which has been widely applied during the last decade. Since its original release in 2002, the model structure and equations have been significantly altered during several development phases. Here, we provide the first full model description since 2002 and then test the latest version of the model (v1.4.4) in a small rural catchment in northeast Scotland. The particulate phosphorus simulation was much improved compared to previous model versions, whilst the latest sorption equations allowed us to explore the potential time lags between reductions in terrestrial inputs and improvements in surface water quality, an issue of key policy relevance. The model is particularly suitable for use as a research tool, but should only be used to inform policy and land management in data-rich areas, where parameters and processes can be well-constrained. More long-term data is needed to parameterise dynamic models and test their predictions