Manish Joshi - Academia.edu (original) (raw)

Papers by Manish Joshi

ABSTRACT Measurement of radium (226Ra) and thorium (232Th) content, and exhalation rate of radon ... more ABSTRACT Measurement of radium (226Ra) and thorium (232Th) content, and exhalation rate of radon (222Rn) and thoron (220Rn) from soil and building materials are important in the context of modeling indoor radon and thoron concentration. In this study, exhalation rates of radon and thoron from commonly used building materials in India were measured using active measurement techniques. Also the activity concentrations of 226Ra, 232Th and potassium (40K) in building materials were measured by HPGe gamma spectrometric technique. The activity concentration of 226Ra, 232Th and 40K varied from 16.4 ± 4.4 to 114.7 ± 3.4, 13.3 ± 1.5 to 153.9 ± 16.6 and below detection limit to 1,007 ± 40 Bq/kg with arithmetic mean 40.3, 61.9 and 822 Bq/kg, respectively, for the examined building material samples. The radon exhalation rates from the building materials varied from 0.5 ± 0.01 to 62.9 ± 12.5 mBq/kg/h for powder samples, 73 ± 5 to 6,000 ± 310 mBq/m2/h for structural building materials while the thoron exhalation rates varied from 0.07 ± 0.27 to 15.03 ± 2.1 mBq/kg/h for samples in powder form. Radium equivalent activity calculated for coarse aggregate and brick powder samples ranged between 73 and 343 Bq/kg

Negative ionisers have been proved to be effective in reducing indoor particulates in general and... more Negative ionisers have been proved to be effective in reducing indoor particulates in general and activity concentrations due to radon and thoron (220Rn) decay products in workplace environments in particular. However, in comparison, there exist few studies on the effect of positive ions for mitigation. In the present work, particle and activity concentration reduction has been compared for three experimental conditions (two for positive ions and one for negative) in an unoccupied room with elevated (220)Rn levels. The negative ioniser configuration provided a better concentration reduction factor of 4.59 with smallest characteristic depletion time. A theoretical estimate of the dose reduction factor is found to be 3.96 and 3.74, respectively, for positive and negative ioniser configuration.

ABSTRACT Negative ion generators (NIGs) have been efficiently used for the reduction of airborne ... more ABSTRACT Negative ion generators (NIGs) have been efficiently used for the reduction of airborne particulates in indoor environments. The mechanisms of particle removal include particle charging by emitted ions and electro-migration from air to wall surfaces. This study explores the dependence of size on particle removal from air in the presence of an ioniser. The test aerosols used were the combustion particulates generated using mosquito repellent coils that are very often used in urban homes in the Asian and African regions. In addition to the main component allethrin, organic fillers are added to these coils to aid smouldering. This could lead to a heavy airborne particulate loading over a very wide size range, all of which may not be beneficial. Room experiments showed that the particle concentration was reduced by a factor of about 15 for sizes of 40 nm and decreased to about 1.5 for 0.3 µm, thus leading to an increase in the median diameters in the presence of the ioniser. Implications to the deposition of these particles in the human respiratory tract system are discussed and there is a significant reduction in the deposition when the ioniser is operated.

ABSTRACT This paper reports the measurements of indoor radon and thoron concentrations in selecte... more ABSTRACT This paper reports the measurements of indoor radon and thoron concentrations in selected Northern Indian dwellings (differing in ventilation rate). These were carried out using single entry pin hole based radon thoron dosimeters. In order to correlate the indoor levels with source term, the radon and thoron exhalation rates from soil samples collected from the same dwellings were also measured. Active measurement techniques with scintillation radon monitor and scintillation thoron monitor were used for exhalation measurements from soil sample. For thoron exhalation rate measurements, a small volume chamber was used. The indoor radon and thoron concentration in different rooms varied from 14 to 97 Bq/m3 and 23 to 189 Bq/m3, respectively. The radon mass exhalation and thoron mass emanation rates of soil samples varied from 28.2 to 91.2 mBq/kg/h and 3.42 to 12.1 mBq/kg/h, respectively. A weak correlation was found between indoor concentration and soil exhalation rates for these dwellings. Indoor radon concentrations from various rooms in the dwellings were lower than the limit (100 Bq/m3) recommended by WHO (2009).

Measurement and/or prediction of indoor radon ( 222 Rn) concentration are important due to the im... more Measurement and/or prediction of indoor radon ( 222 Rn) concentration are important due to the impact of radon on indoor air quality and consequent inhalation hazard. In recent times, computational fluid dynamics (CFD) based modeling has become the cost effective replacement of experimental methods for the prediction and visualization of indoor pollutant distribution. The aim of this study is to implement CFD based modeling for studying indoor radon gas distribution. This study focuses on comparison of experimentally measured and CFD modeling predicted spatial distribution of radon concentration for a model test room. The key inputs for simulation viz. radon exhalation rate and ventilation rate were measured as a part of this study. Validation experiments were performed by measuring radon concentration at different locations of test room using active (continuous radon monitor) and passive (pin-hole dosimeters) techniques. Modeling predictions have been found to be reasonably matching with the measurement results. The validated model can be used to understand and study factors affecting indoor radon distribution for more realistic indoor environment.

Building materials are the second major source of indoor radon after soil. The contribution of bu... more Building materials are the second major source of indoor radon after soil. The contribution of building materials towards indoor radon depends upon the radium content and exhalation rates and can be used as a primary index for radon levels in the dwellings. The radon flux data from the building materials was used for calculation of the indoor radon concentrations and doses by many researchers using one and two dimensional model suggested by various researchers. In addition to radium content, the radon wall flux from a surface strongly depends upon the radon diffusion length (L) and thickness of the wall (2d). In the present work the indoor radon concentrations from the measured radon exhalation rate of building materials calculated using different models available in literature and validation of models was made through measurement. The variation in the predicted radon flux from different models was compared with d/L value for wall and roofs of different dwellings. The results showed that the radon concentrations predicted by models agree with experimental value. The applicability of different model with d/L ratio was discussed. The work aims to select a more appropriate and general model among available models in literature for the prediction of indoor radon.

Journal of minimal access surgery, 2011

Single-incision laparoscopic surgery (SILS) is a rapidly evolving field as a bridge between tradi... more Single-incision laparoscopic surgery (SILS) is a rapidly evolving field as a bridge between traditional laparoscopic surgery and natural orifice transluminal endoscopic surgery. We present a case of SILS splenectomy performed with conventional laparoscopic instruments in a 7-month-old boy with the diagnosis of multiple splenic abscesses. A 3-cm umbilical incision was used for the placement of two (5 mm) trocars and one 10-mm videoscope (30°). Conventional laparoscopic dissector and grasper were the main tools during surgical procedure. Spleen was removed through the umbilical incision. Although procedures like aingle-incision cholecystectomy have been reported, to the best of our knowledge this is the first report of SILS splenectomy using conventional laparoscopic instruments reported from India and is perhaps the first in an infant in the world literature.

Current opinion in pulmonary medicine, 2014

Cannabis sativa (marijuana) is used throughout the world, and its use is increasing. In much of t... more Cannabis sativa (marijuana) is used throughout the world, and its use is increasing. In much of the world, marijuana is illicit. While inhalation of smoke generated by igniting dried components of the plant is the most common way marijuana is used, there is concern over potential adverse lung effects. The purpose of this review is to highlight recent studies that explore the impact upon the respiratory system of inhaling marijuana smoke. Smoking marijuana is associated with chronic bronchitis symptoms and large airway inflammation. Occasional use of marijuana with low cumulative use is not a risk factor for the development of chronic obstructive pulmonary disease. The heavy use of marijuana alone may lead to airflow obstruction. The immuno-histopathologic and epidemiologic evidence in marijuana users suggests biological plausibility of marijuana smoking as a risk for the development of lung cancer; at present, it has been difficult to conclusively link marijuana smoking and cancer development. There is unequivocal evidence that habitual or regular marijuana smoking is not harmless. A caution against regular heavy marijuana usage is prudent. The medicinal use of marijuana is likely not harmful to lungs in low cumulative doses, but the dose limit needs to be defined. Recreational use is not the same as medicinal use and should be discouraged.

Journal of Applied Polymer Science, 1998

A modified new aromatic diamine 2,5-bis[(4-aminophenyl)4-benzamide]-3,4-diphenyl thiophene ( VI) ... more A modified new aromatic diamine 2,5-bis[(4-aminophenyl)4-benzamide]-3,4-diphenyl thiophene ( VI) with preformed amide linkages and pendant phenyl substituents was synthesized, characterized by IR, NMR, mass spectroscopy, and a physical constant. Novel poly(amide-amide)s were synthesized from VI and aromatic diacid chlorides in N,N-dimethylacetamide by a solution polycondensation technique. The polymers were obtained in 98-100% yields and showed reduced viscosities in the range of 0.80-2.68 dL/g. They were readily soluble in aprotic polar solvents. These poly(amide-amide)s showed glass transition temperatures of 277-280ЊC as measured by DSC and showed no weight loss below 412ЊC in a nitrogen atmosphere. The polymers showed moisture regain in the range of 9.

American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons, 2003

Mutation Research/environmental Mutagenesis and Related Subjects, 1985

A narrow genetic base for important traits that determine plant type, yield and grain type has be... more A narrow genetic base for important traits that determine plant type, yield and grain type has been the main reason for slow progress in the improvement and development of triticales. Hence, with a view to enlarging the genetic base for different yield attributes, two triticale strains, DTS 141(A) and Beagle were mutagenized with three mutagens. One physical mutagen, γ-rays and two chemical mutagens, EMS and NMU, were used with three does of each. An analysis of induced variation was made in the M2 generation. Significant increases in genetic variance were observed for the four characters, productive tillers, grains per spike, 100-grain weight and grain yield per plant. This increase was the least in 100-grain weight. There was general reduction of mean values in the populations treated with mutagens. However, increase in 100-grain weight in a few treated ‘Beagle’ groups was observed. Increase in variance indicates that there were mutations with both positive and negative effects. Reduction in mean values might be due to the more frequent occurrence of deleterious mutations.

Cheminform, 1992

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Journal of Nanoparticle Research, 2012

Regional studies focusing on the role of atmospheric nanoparticles in climate change have gained ... more Regional studies focusing on the role of atmospheric nanoparticles in climate change have gained impetus in the last decade. Several multiinstitutional studies involving measurement of nanoparticles with several kinds of instruments are on the rise. It is important to harmonize these measurements as the instruments may work on different techniques or principles and are developed by different manufacturers. Scanning mobility particle sizers (SMPS) are often used to measure size distribution of nanoparticles in the airborne phase. Two such commercially available instruments namely, GRIMM and TSI-SMPS have been compared for ambient and laboratory generated conditions. A stand-alone condensation particle counter (CPC) of TSI make was used as a reference for particle concentration measurements. The consistency of the results in terms of mean size and geometric standard deviation was seen to be excellent for both the SMPSs, with GRIMM always showing slightly (approximately 10 %) lower mean size. The integrated number concentration from GRIMM-SMPS was seen to be closer to stand-alone reference CPC compared to TSI-SMPS, for an ambient overnight comparison. However, a concentration-dependent response, i.e. the variations between the two instruments increasing with the concentration, was observed and possible reasons for this have been suggested. A separate experiment was performed for studying the modifying effect of diffusion dryer and sheath air dryer on the measured aerosol size spectra. A significant hygroscopic growth was noted when diffusion dryer was attached to one of the SMPS. The introduction of sheath air dryer in GRIMM-SMPS produced a significant shift towards lower mean size. These results have been compared and discussed with the recent inter-comparison results to strengthen and harmonize the measurement protocols.

Journal of Applied Polymer Science, 1997

High etch resistance to oxygen plasma for silicon-containing polymers, and the high thermal and m... more High etch resistance to oxygen plasma for silicon-containing polymers, and the high thermal and mechanical robustness of the etching product, silicon oxide, make it attractive to design novel siliconcontaining block copolymers for direct patterning of nanostructures on a desired substrate. Here, we report the synthesis of a series of block copolymers from silicon-containing styrenic monomers and styrene (St) or 4-acetoxystyrene (AcOSt) using living free radical polymerization via a R-hydride nitroxide-mediated unimer (R-H unimer). Controlled polymerization with narrow polydispersity (PDI < 1.25) and high yield (up to 80%) were achieved by optimizing polymerization time and temperature, addition of solvents, use of rate accelerants, monomer addition sequence, and solvent polarity. Block copolymer morphologies before and after O 2 plasma were studied using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). When silicon-containing block formed the major phase and silicon concentration was greater than 12 wt %, the morphology and domain size were maintained after O2 plasma.