Concentrations of radon and its daughter products in and around Bangalore city

Indoor radon and its progeny levels were measured during 2005-06 in Bangalore rural district and in Bangalore City by using Solid State Nuclear Track Detector (SSNTD)-based twin cup dosemeters, and the activity of radium present in soils and rocks was measured by using HPGe detector. Fifty dwellings of different types were chosen for the measurement. The dosimeters containing the detector (LR-115 Type II Film) used in each house were fixed 2 m above the floor. After an exposure time of 90 days, films were etched to reveal tracks. From the track density, the concentrations of radon were evaluated. The value of radon concentration in the indoor air near granite quarries varies from 55 to 300 Bq.m(-3) with a median of 155 Bq.m(-3) and its progeny varies from 0.24 to 19.6 mWL with a median of 8.4 mWL. In Bangalore City, the concentration of radon varies from 18.4 to 110 Bq.m(-3) with a median of 45 Bq.m(-3) and its progeny varies from 1.62 to 11.24 mWL with a median of 4.15 mWL. Higher concentrations of radon and its progeny were observed in granite quarries compared with Bangalore City. The main reason for the higher indoor radon and its progeny concentration is due to the mining activity and the types of the bedrock. The concentration of radon mainly depends on the activity of radium present in soils and rocks and the types of building materials used. The activity of radium varies in granitic regions of Bangalore rural district from 42.0 to 163.6 Bq.kg(-1) with a median of 112.8 Bq.kg(-1). The concentrations of indoor radon and its daughter products and equivalent effective dose are discussed.     

Silver nanoparticles anchored TiO2 nanotubes prepared using saponin extract as heterogeneous and recyclable catalysts for reduction of dyes

In the present study, we made an effort to synthesize silver nanoparticles anchored onto TiO₂ nanotubes using saponin extracted from Simarouba glauca oil seed meal. Obtained silver anchored TiO₂ nanotubes (Ag-TiO₂) were characterized using spectroscopic, microscopic and X‐ray diffraction techniques and used as catalysts for reduction of nitrophenol (NP), Methylene blue (MB), Methyl orange (MO) and Congo red (CR). The reduction reactions were carried out in aqueous medium in presence of NaBH₄ at room temperature. Progress of the catalytic reaction was observed by decolorization of the dye solution and monitored by recording UV–Vis spectra. It was observed that Ag-TiO₂ nanotubes emerged as an effective catalyst in reducing the dyes in the time range of 2–7 min with pseudo first-order kinetics and also effective in the simultaneous reduction of all dyes in 12 min. In addition, the catalyst showed a good recovery yield with unaffected catalytic efficiency up to ten cycles.     

Estimation of U, <Superscript>226</Superscript>Ra,and <Superscript>210</Superscript>Po Concentrations in Cauvery River Basin,South Interior Karnataka Region,India

The radioactivity concentration of ²¹⁰Po, ²²⁶Ra, and U in Cauvery river basin was analyzed using radiochemical analysis, emanometry, and LED fluorimetry, respectively. Due to transfer with water in cracks and pores, leaching, and heavy usage of phosphate fertilizers, ²¹⁰Po, ²²⁶Ra, and U radionuclides get into the environmental samples studied. The ²¹⁰Po concentration ranges from 0.7 ± 0.11 to 5.0 ± 0.7 and from 0.83 ± 0.12 to 5.2 ± 0.8 mBq L^–1; the ²²⁶Ra concentration, from 11.7 ± 1.8 to 62 ± 9 and from 10.5 ± 1.6 to 68 ± 10 mBq L^–1; and the U concentration, from 0.08 ± 0.01 to 4.4 ± 0.7 and from 2.0 ± 0.3 to 7.4 ± 1.1 ppb in river and borewell water samples, respectively.     

Gravity measurements and terrain corrections using a digital terrain model in the NW Himalaya

Areas recently gravity surveyed in the NW Himalaya are characterized by high-elevation and high-amplitude topographic undulations. A new method of applying combined Bouguer and terrain corrections using a digital terrain model is highly accurate and offers advantages over conventional techniques by saving efforts and being more flexible. Partitioning parameters for station-dependent inner-zone compartments and station-independent outer zones can be optimally selected for the desired accuracy requirements. A digital terrain database is used to obtain the outer-zone corrections. In the situation of the NW Himalaya surveys, a 1.2 km inner zone is divided into 112 compartments for each station and a digital terrain database containing nearly 16 000 data points for 30″×30″ compartments was applied using the computer program EFFECT.FOR, to compute combined Bouguer and terrain corrections for a 20 km range. The terrain corrections between 20 and 170 km were computed using National Geophysical Data Centre (NGDC) 5′×5′ gridded global elevation database. The magnitude of the terrain correction varies between 3 and 50 mGal. The effects of the 20 km range terrain correction are more pronounced on short-medium wavelength anomalies. The Swarghat gravity high is further enhanced while several high-frequency pseudo-anomalies disappear after applying the terrain corrections. The refined Bouguer anomaly varies from −160 mGal at the southern end of the section, to −310 mGal at the northern end, suggesting a Moho depth variation from 45 to nearly 60 km. The steepness of the northward negative gravity gradient, typical for the Himalaya, is considerably reduced after applying a terrain correction for the 170 km range.     

Use of sigma-delta modulation to control EMI from switch-mode powersupplies

Conducted electromagnetic interference (EMI) is a major cause of concern in switch-mode power supplies (SMPSs) which commonly use standard pulsewidth modulation (PWM). In this paper, sigma-delta (ΣΔ) modulation is proposed as an alternative switching technique to reduce conducted EMI from an SMPS. The result of using ΣΔ modulation is a spread in the spectrum of the conducted emissions so that large concentrations of power at discrete frequencies are avoided. Experimental time-domain waveforms and spectra of the switching function of first-order and second-order ΣΔ modulators are presented to prove the viability of the scheme for EMI mitigation. These modulators are then applied to a DC-DC converter in an off-the-shelf computer power supply and experimental results show a reduction of roughly 5-10 dB·μV in EMI emissions over standard PWM modulators     

Enhancement of biological hydrogen production using green alga Chlorococcum minutum

It is estimated that the fossil fuel reserves are going to deplete continuously due to extensive usage. In order to cope with this crisis, it is necessary to increase the efforts towards production of biofuels such as biological hydrogen (H₂). It is well-known fact that the biological hydrogen is a clean and ideal energy and liberates high amount of energy per unit mass. Several groups are working for the large scale production of H₂ chemically and also using photosynthetic organisms, but output is not satisfactory. The best way to achieve enhancement of H₂ is through altering the photosynthetic process by applying various stress conditions or by natural selection. In the process of selection, Chlorococcum minutum was found with improved H₂ output when compared to model green alga Chlamydomonas reinhardtii in a massively parallel and competitive high-throughput screen of different green algae. Both the species belongs to class chlorophyceae of green algae and live in fresh water conditions. In extent various light, pH and temperature conditions were applied and achieved the enhancement of H₂ production in this species under in vitro settings. Augmented hydrogenase activity was found in Chlorococcum minutum when compared to model alga and this may be one of the reason behind improved H₂ output. Hence this species may be considered as one of the best species with respect to H₂ production and also this work may be useful for future renewable energy research.     

Multi-rate Polyphase DSP and LMS Calibration Schemes for Oversampled ADCs

A scaling-friendly approach for the low-power calibration of oversampled analog-to-digital (A/D) systems is presented. A 22-dB amplifier relaxes the design constraints of the analog front-end (AFE). The integrator non-idealities in the AFE of the sigma-delta (ΣΔ) ADC are calibrated using a multi-rate polyphase least-mean squares (LMS) algorithm. The proposed half- (f _s/2) and quarter-rate (f _s/4) LMS calibration schemes reduce computational complexity and achieve more than 2.5× savings in digital power consumption for low-OSR (over-sampling ratio) ΔΣ ADCs, which require higher adaptive filter orders and sampling frequencies. The proposed scheme can have further applications in serial-link I/O and sub-band echo cancellation architectures.     

Variations of radon and thoron concentrations in different types of dwellings in Mysore city, India

²²²Rn and ²²⁰Rn, the immediate decay products of radium isotopes,are causative agents of lung cancer. ²²²Rn and ²²⁰Rn concentrationsin houses with different floorings, roofs and walls and in differentrooms of houses have been measured in Mysore city, Karnatakastate, India, using solid-state nuclear track detectors. Theradon and thoron concentrations in dwellings with granite flooringsare found to be higher compared with other types. A correlationbetween the indoor radon concentration and dose in air fromterrestrial gamma radiation is observed.     

Analysis of the Bridged T-Coil Circuit Using the Extra-Element Theorem

The bridged T-coil (BTC) circuit is often employed to extend the bandwidth of a wideband amplifier beyond the transition frequency f_T of the driver device. Although the optimal design solution is well known, extreme algebraic complexity has caused its derivation to remain arcane. This brief presents an analysis of the BTC circuit using the extra element theorem which breaks the overall problem down into a series of simple network analyses and produces the final result as the product of the transfer function without the "extra element" and a multiplicative correction factor. The design is completed by using pole-zero cancellation to reduce the order of the transfer functions