Carcinogenicity and non-carcinogenicity health risks due to PM2.5 bound trace metals at a sub urban site in Northwest Indo-Gangetic Plain.

This study investigates the PM2.5 bound metals using yearlong measurements at a regionally representative suburban site in the Northwest Indo-Gangetic Plain (NWIGP). The order of the measured annual average concentrations of PM2.5 bound metals is Fe > Zn > Ba > Sn > Pb > Cd > Ni > Mn > Cr > Li. Lithium bound to airborne PM2.5 has been reported for the first time in NWIGP. Ni (72.4 ng m-3) and Cd (36.9 ng m-3) have exceeded the acceptable limits set by NAAQS, India. Estimated the hazard quotient (HQ > 1) of Mn and hazard index (HI > 1) of measured metals exceeded the threshold limits indicating the potential non-carcinogenic health risk due to inhalation exposure of PM2.5 bound trace metals. Further, excessive lifetime cancer risk due to inhalation exposure to Cd, Ni and Cr was estimated and found to exceed the threshold limit set by the USEPA for adults and children.

Mechanoluminescence of SrAl2 O4 :Eu,Dy nanophosphors induced by low impact velocity.

The present paper reports the impulsive excitation of mechanoluminescence (ML) in Sr0.97 Al2 O4 :Eu0.01 ,Dy0.02 nanophosphors prepared using a combustion technique. The phosphors are characterized using X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL). The XRD results show that the samples exhibit a monoclinic α-phase in the crystal structure. The space group of SrAl2 O4 :Eu,Dy nanophosphors is monoclinic P21 . The PL and ML spectra of SrAl2 O4 :Eu,Dy nanophosphors are excited using light with a wavelength of 365 nm and emission is found at 516 nm. The prepared nanophosphors exhibits an intense ML that can be seen in daylight with the naked eye. When a sample powder is deformed impulsively by the impact of a moving piston, the ML intensity initially increases linearly with time, attains a peak value, Im , at time tm , and then decreases with time. The peak ML intensity, Im , and total ML intensity, IT , increase linearly with applied pressure and impact velocity. The ML intensity decreases with successive impacts of load onto the phosphors, and the diminished ML intensity can be approximately recovered by UV irradiation. The activation energy using thermoluminescence is found to be 0.57 eV for SrAl2 O4 :Eu,Dy nanophosphors. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis, characterization and thermoluminescence studies of (ZnS)1-x (MnTe)x nanophosphors.

The present paper reports the thermoluminescence (TL) of (ZnS)1-x (MnTe)x nanophosphors that were prepared by a wet chemical synthesis method. The structure investigated by X-ray diffraction patterns confirms the formation of a sphalerite phase whose space group was found to be F 4¯3m. From XRD, TEM and SEM analyses the average sizes of the particles were found to be 12 nm, 11 nm and 15 nm, respectively. Initially the TL intensity increased with increasing values of x because the number of luminescence centres increased; however, for higher values of x the TL intensity decreased because of the concentration quenching. Thus the TL, mechanoluminescence and photoluminescence intensities are optimum for a particular value of x, that is for x = 0.05. Thermoluminescence of the (ZnS)1-x (MnTe)x nanophosphor has not been reported previously. There were two peaks seen in the thermoluminescence glow curves in which the first peak lay at 105-100 °C and the second peak lay at 183.5-178.5 °C. The activation energies for the first and second peaks were found to be 0.45 eV and 0.75 eV, respectively.

Synthesis, characterization and thermoluminescence studies of Mn-doped ZnS nanoparticles.

ZnS:Mn nanoparticles were prepared by a chemical precipitation method and characterized by X-ray diffraction (XRD), field emission gun scanning electron microscope (FEGSEM), and high resolution transmission electron microscopy (HRTEM). Capping agent (mercaptoethanol) concentrations used were 0 M, 0.005 M, 0.01 M, 0.015 M, 0.025 M, 0.040 M, and 0.060 M, and resulted in nanoparticles sizes of 2.98 nm, 2.9 nm, 2.8 nm, 2.7 nm, 2.61 nm, 2.2 nm and 2.1 nm, respectively. The thermoluminescence (TL) glow curve was recorded by heating the sample exposed to UV-radiation, at a fixed heating rate 1°C sec(-1). The TL intensity initially increased with temperature, attained a peak value Im for a particular temperature, and then decreased with further increase in temperature. The peak TL intensity increased with decreasing nanoparticle size, whereas the temperature corresponding to the peak TL intensity decreased slightly with reducing nanocrystal size. As a consequence of increase in surface-to-volume ratio and increased carrier recombination rates, the TL intensity increased with decreasing nanoparticle size. It was found that, whereas activation energy slightly decreased with decreasing nanoparticle size, the frequency factor decreased significantly with reduction in nanoparticle size.

Is the fracto-mechanoluminescence of ZnS:Mn phosphor dominated by charged dislocation mechanism or piezoelectrification mechanism?

Mathematical approaches made for both the charged dislocation model and piezoelectrically induced electron bombardment model of fracto-mechanoluminescence (FML), the luminescence induced by fracture of solids, in ZnS:Mn phosphor indicate that the piezoelectrically induced electron bombardment model provides a dominating process for the FML of ZnS phosphors. The concentration of 3000 ppm Mn(2+) is optimal for ML intensity of ZnS:Mn phosphor. The decay time of ML gives the relaxation time of the piston used to deform the sample and the time tm of maximum of ML is controlled by both the relaxation time of the piston and decay time of charges on the newly created surfaces of crystals. As the product of the velocity of dislocations and pinning time of dislocations gives the mean free path of a moving dislocation. Both factors play an important role in the ML excitation of impurity doped II-VI semiconductors. The linear increase of total ML intensity IT with the impact velocity indicates that the damage increases linearly with impact velocity of the load. Thus, the ML measurement can be used remotely to monitor the real-time damage in the structures, and therefore, the ML of ZnS:Mn phosphor has also the potential for a structural health monitoring system.

Persistent luminescence of CaMgSi2O6:Eu(2+),Dy(3+) and CaMgSi2O6:Eu(2+),Ce(3+) phosphors prepared using the solid-state reaction method.

CaMgSi2O6:Eu(2+),Dy(3+) and CaMgSi2O6:Eu(2+),Ce(3+) phosphors were synthesized using the solid-state reaction method. X-Ray diffraction (XRD) and photoluminescence (PL) analyses were used to characterize the phosphors. The XRD results revealed that the synthesized CaMgSi2O6:Eu(2+),Dy(3+) and CaMgSi2O6:Eu(2+),Ce(3+) phosphors were crystalline and are assigned to the monoclinic structure with a space group C2/c. The calculated crystal sizes of CaMgSi2O6:Eu(2+),Dy(3+) and CaMgSi2O6:Eu(2+),Ce(3+) phosphors with a main (221) diffraction peak were 44.87 and 53.51 nm, respectively. Energy-dispersive X-ray spectroscopy (EDX) confirmed the proper preparation of the sample. The PL emission spectra of CaMgSi2O6:Eu(2+),Dy(3+) and CaMgSi2O6:Eu(2+),Ce(3+) phosphors have a broad band peak at 444.5 and 466 nm, respectively, which is due to electronic transition from 4f(6) 5d(1) to 4f(7). The afterglow results indicate that the CaMgSi2O6:Eu(2+),Dy(3+) phosphor has better persistence luminescence than the CaMgSi2O6:Eu(2+),Ce(3+) phosphor.

Effect of particle size on activation energy and peak temperature of the thermoluminescence glow curve of undoped ZnS nanoparticles.

This paper reports the effect of particle size on the thermoluminescence (TL) of undoped ZnS nanoparticles. ZnS nanoparticles were prepared using a chemical precipitation method in which mercaptoethanol was used as the capping agent. The nanoparticles were characterized by X-ray diffraction, field emission gun-scanning electron microscopy and high-resolution transmission electron microscopy. When the concentrations of mercaptoethanol used are 0, 0.005, 0.01, 0.015, 0.025, 0.040 and 0.060 M, the sizes of the nanoparticles are 2.86, 2.81, 2.69, 2.40, 2.10, 1.90 and 1.80 nm, respectively. Initially, the TL intensity of UV-irradiated ZnS nanoparticles increases with temperature, attains a peak value Im for a particular temperature Tm, and then decreases with further increases in temperature. The values of both Im and Tm increase with decreasing nanoparticle size. Whereas the activation energy decreases slightly with decreasing nanoparticle size, the frequency factor decreases significantly as the nanoparticle size is reduced. The order of kinetics for the TL glow curve of ZnS nanoparticles is 2. Expressions are derived for the dependence of activation energy (Ea) and Tm on nanoparticle size, and good agreement is found between the experimental and theoretical results.

Fracto-mechanoluminescence induced by impulsive deformation of II-VI semiconductors.

When II-VI semiconductors are fractured, initially the mechanoluminescence (ML) intensity increases with time, attains a maximum value Im at a time tm, at which the fracture is completed. After tm, the ML intensity decreases with time, Im increase linearly with the impact velocity v0 and IT initially increase linearly with v0 and then it attains a saturation value for a higher value of v0. For photoluminescence, the temperature dependence comes mainly from luminescence efficiency, ηo; however, for the ML excitation, there is an additional factor, rt dependent on temperature. During fracture, charged dislocations moving near the tip of moving cracks produce intense electric field, causes band bending. Consequently, tunneling of electrons from filled electron traps to the conduction band takes place, whereby the radiative electron-hole recombination give rise to the luminescence. In the proposed mechanism, expressions are derived for the rise, the time tm corresponding to the ML intensity versus time curve, the ML intensity Im corresponding to the peak of ML intensity versus time curve, the total fracto-mechanoluminescence (FML) intensity IT, and fast and slow decay of FML intensity of II-VI semiconductors. The FML plays a significant role in understanding the processes involved in biological detection, earthquake lights and mine failure.

Mechanoluminescence of Ba2 MgSi2 O7 doped with Eu(2+) and Dy(3+) phosphor by impulsive deformation.

Di-barium magnesium silicate phosphor doped with Eu(2+) and Dy(3+) was prepared using a solid-state reaction technique under a reducing atmosphere. The sample underwent impulsive deformation by impact from a piston for mechanoluminescence (ML) investigations. The temporal ML characteristics of the phosphor were observed, which expressed a single sharp peak with a long decaying period. To investigate the luminescence centre responsible for the ML peak, the ML spectrum of the phosphor was also observed. The recorded ML spectrum was similar in shape and peak wavelength to the photoluminescence (PL) spectrum, which verifies the existence of a single emission centre due to the transition of Eu(2+) ions, i.e. transitions from any of the sublevels of the 4f(6)5d(1) configuration to the (8)S7/2 level of the 4f(7) configuration. Decay rates for different impact velocities were also calculated using curve-fitting techniques. The time of the ML peak and the rate of decay did not change significantly with respect to increasing impact velocity of the load and peak ML intensity varied linearly. The mechanism of the ML emission was also discussed.

Characterization and luminescence properties of CaMgSi2O6:Eu2+ blue phosphor.

A blue CaMgSi2O6:Eu(2+) phosphor was prepared by the solid-state reaction method and the phosphor characterized in terms of crystal structure, particle size, photoluminescence (PL), thermoluminescence (TL) and mechanoluminescence (ML) properties using X-ray diffraction (XRD), transmission electron microscopy (TEM), PL spectroscopy, TLD reader and ML impact technique. The XRD result shows that phosphor is formed in a single phase and has a monoclinic structure with the space group C2/c. Furthermore, the PL excitation spectra of Eu(2+) -doped CaMgSi2 O6 phosphor showed a strong band peak at 356 nm and the PL emission spectrum has a peak at 450 nm. The depths and frequency factors of trap centers were calculated using the TL glow curve by deconvolution method in which the trap depths were found to be 0.48 and 0.61 eV. The formation of CaMgSi2O6:Eu(2+) phosphor was confirmed by Fourier transform infrared spectroscopy. The ML intensity increased linearly with the impact velocity of the piston used to deform the phosphor. It was shown that the local piezoelectricity-induced electron bombardment model is responsible for the ML emission. Finally, the optical properties of CaMgSi2O6:Eu(2+) phosphors are discussed.

Survey of the literature on mechanoluminescence from 1605 to 2013.

Mechanoluminescence (ML) is a type of luminescence induced by any mechanical action on solids. The light emissions induced by elastic deformation, plastic deformation and fracture of solids are called elastico ML (EML), plastico ML (PML) and fracto ML (FML), respectively. Whereas nearly 50% of all organic molecular solids and inorganic salts exhibit FML, only a few solids exhibit EML and PML. The EML and FML of certain solids are so intense that they can be seen during daylight with the naked eye. Mechanolumnescence has a great potential for use in different types of mechano-optical devices such as stress sensors, damage sensors, impact sensors, fracture sensors and safety management monitoring systems. This article reports a survey of the literature from 1605 to 2013. Mechanoluminescence is studied by physicists, chemists, material scientists, geologists, medical scientists, engineers and technologists, among others and researchers will certainly benefit from the literature survey on ML given here. In addition, the field of mechanoluminescence may attract the interest of many new researchers.

Intense photon emission induced by fracture of γ-irradiated Dy-, Tm-, Sm- and Mn-doped CaSO4 single crystals.

When an γ-irradiated Dy-, Tm-, Sm- or Mn-doped CaSO4 crystal is impulsively deformed, two peaks appear in the ML intensity versus time curve, whereby the first ML peak is found in the deformation region and the second in the post-deformation region of the crystals. In this study, intensities Im1 and Im2 corresponding to first and second ML peaks, respectively, increased linearly with an impact velocity v0 of the piston used to deform the crystals, and times tm1 and tm2 corresponding to the first and second ML peaks, respectively, decreased with impact velocity. Total ML intensity initially increased with impact velocity and then reached a saturation value for higher values of impact velocity. ML intensity increased with increasing γ-doses and size of crystals. Results showed that the electric field produced as a result of charging of newly-created surfaces caused tunneling of electrons to the valence band of the hole-trapping centres. The free holes generated moved in the valence band and their subsequent recombination with electron trapping centres released energy, thereby resulting in excitation of luminescent centres.

Effect of Yoga on Immune Parameters, Cognitive Functions, and Quality of Life among HIV-Positive Children/Adolescents: A Pilot Study.

CONTEXT: HIV/AIDS individuals have problems relating to immune system, quality of life (QOL), and cognitive functions (CFs). Yoga is found to be useful in similar conditions. Hardly, any work is reported on yoga for HIV-positive adults/adolescents. Hence, this study is important. AIM: The aim of the study is to determine the effect of yoga on immune parameters, CFs, and QOL of HIV-positive children/adolescents. SETTINGS AND DESIGN: Single-group, pre-post study with 4-month yoga intervention. METHODS: The study had 18 children from an HIV/AIDS rehabilitation center for children/adolescents. CD4, CD8, CD4/CD8 ratio, and viral loads were studied. CF tests included six letter cancellation test, symbol digit modalities test, digit-span forward backward test, and Stroop tests. QOL was assessed using PedsQL-QOL and fatigue questionnaire. Depression was assessed using CDI2-SR. STATISTICAL ANALYSIS USED: t-test and Wilcoxon signed-rank tests, as applicable. RESULTS: The study included 18 children/adolescents. There was improvement in general health of the participants. There was statistically significant increase in CD4 cells counts (p = 0.039) and significant decrease in viral load (p = 0.041). CD4/CD8 ratio moved to normal range. QOL significantly improved. CFs had mixed results with improved psychomotor performance (PP) and reduced executive functions. CONCLUSIONS: There was improvement in general health and immune parameters. While depression increased, QOL improved. CFs showed mixed results with improved PP and reduced executive functions.

Volatile organic compound measurements point to fog-induced biomass burning feedback to air quality in the megacity of Delhi.

We report the first ambient measurements of thirteen VOCs for investigations of emissions and air quality during fog and non-fog wintertime conditions at a tower site (28.57° N, 77.11° E, 220 m amsl) in the megacity of Delhi. Measurements of acetonitrile (biomass burning (BB) tracer), isoprene (biogenic emission tracer in daytime), toluene (a traffic exhaust tracer) and benzene (emitted from BB and traffic), together with soluble and reactive oxygenated VOCs such as methanol, acetone and acetaldehyde were performed during the winters of 2015-16 and 2016-17, using proton transfer reaction mass spectrometry. Remarkably, ambient VOC composition changes during fog were not governed by solubility. Acetaldehyde, toluene, sum of C8-aromatics (e.g. xylenes), sum of C9-aromatics (e.g. trimethyl benzenes) decreased by ≥30% (>95% confidence interval), whereas acetonitrile and benzene showed significant increases by 20% (>70% confidence interval), even after accounting for boundary layer dilution. During fog, the lower temperatures appeared to induce an emissions feedback from enhanced open BB within Delhi for warming, releasing both gaseous and aerosol pollutants with consequences for fog chemistry, sustenance and intensity. The potential feedback is important to consider for improving current emission parametrizations in models used for predicting air quality and fog in such atmospheric environments.

Large unexplained suite of chemically reactive compounds present in ambient air due to biomass fires.

Biomass fires impact global atmospheric chemistry. The reactive compounds emitted and formed due to biomass fires drive ozone and organic aerosol formation, affecting both air quality and climate. Direct hydroxyl (OH) Reactivity measurements quantify total gaseous reactive pollutant loadings and comparison with measured compounds yields the fraction of unmeasured compounds. Here, we quantified the magnitude and composition of total OH reactivity in the north-west Indo-Gangetic Plain. More than 120% increase occurred in total OH reactivity (28 s-1 to 64 s-1) and from no missing OH reactivity in the normal summertime air, the missing OH reactivity fraction increased to ~40 % in the post-harvest summertime period influenced by large scale biomass fires highlighting presence of unmeasured compounds. Increased missing OH reactivity between the two summertime periods was associated with increased concentrations of compounds with strong photochemical source such as acetaldehyde, acetone, hydroxyacetone, nitromethane, amides, isocyanic acid and primary emissions of acetonitrile and aromatic compounds. Currently even the most detailed state-of-the art atmospheric chemistry models exclude formamide, acetamide, nitromethane and isocyanic acid and their highly reactive precursor alkylamines (e.g. methylamine, ethylamine, dimethylamine, trimethylamine). For improved understanding of atmospheric chemistry-air quality-climate feedbacks in biomass-fire impacted atmospheric environments, future studies should include these compounds.

Contribution of post-harvest agricultural paddy residue fires in the N.W. Indo-Gangetic Plain to ambient carcinogenic benzenoids, toxic isocyanic acid and carbon monoxide.

In the north west Indo-Gangetic Plain (N.W.IGP), large scale post-harvest paddy residue fires occur every year during the months of October-November. This anthropogenic perturbation causes contamination of the atmospheric environment with adverse impacts on regional air quality posing health risks for the population exposed to high concentrations of carcinogens such as benzene and toxic VOCs such as isocyanic acid. These gases and carbon monoxide are known to be emitted from biomass fires along with acetonitrile. Yet no long-term in-situ measurements quantifying the impact of this activity have been carried out in the N.W. IGP. Using high quality continuous online in-situ measurements of these gases at a strategic downwind site over a three year period from 2012 to 2014, we demonstrate the strong impact of this anthropogenic emission activity on ambient concentrations of these gases. In contrast to the pre-paddy harvest period, excellent correlation of benzenoids, isocyanic acid and CO with acetonitrile (a biomass burning chemical tracer); (r≥0.82) and distinct VOC/acetonitrile emission ratios were observed for the post-paddy harvest period which was also characterized by high ambient concentrations of these species. The average concentrations of acetonitrile (1.62±0.18ppb), benzene (2.51±0.28ppb), toluene (3.72±0.41ppb), C8-aromatics (2.88±0.30ppb), C9-aromatics (1.55±0.19ppb) and CO (552±113ppb) in the post-paddy harvest periods were about 1.5 times higher than the annual average concentrations. For isocyanic acid, a compound with both primary and secondary sources, the concentration in the post-paddy harvest period was 0.97±0.17ppb. The annual average concentrations of benzene, a class A carcinogen, exceeded the annual exposure limit of 1.6ppb at NTP mandated by the National Ambient Air Quality Standard of India (NAAQS). We show that mitigating the post-harvest paddy residue fires can lower the annual average concentration of benzene and ensure compliance with the NAAQS. Calculations of excessive lifetime cancer risk due to benzene amount to 25 and 10 per million inhabitants for children and adults, respectively, exceeding the USEPA threshold of 1 per million inhabitants. Annual exposure to isocyanic acid was close to 1ppb, the concentration considered to be sufficient to enhance risks for cardiovascular diseases and cataracts. This study makes a case for urgent mitigation of post-harvest paddy residue fires as the unknown synergistic effect of multi-pollutant exposure due to emissions from this anthropogenic source may be posing grave health risks to the population of the N.W. IGP.