Electronic structure calculations and molecular dynamics simulations of hydrogen adsorption on Beryllium doped complexes

Interaction of molecular hydrogen with Be and Be₂ decorated acetylene is studied using first principles calculations and molecular dynamics simulations. C₂H₂Be and C₂H₂Be₂ complex can interact with maximum of two and four H₂ molecules respectively thereby showing respective H₂ uptake capacity of 10.3 and 15.5 wt % and is well above the target set by U.S. department of energy. Temperature dependent Gibbs free energy corrected adsorption energy shows that H₂ adsorption on C₂H₂Be is energetically favorable below 250 and 200 K and 1 atm. pressure at MP2/6-311++G** and CCSD(T)/6-311++G** level whereas it is energetically favorable on C₂H₂Be₂ at entire temperature and pressure range considered here from 50 K to 400 K and 50 atm to 400 atm. The desorption temperature obtained for C₂H₂Be(2H₂) and C₂H₂Be₂(4H₂) complexes at MP2/6-311++G** level using van't Hoff equation is 281 and 638 K respectively. Molecular dynamics simulations performed at different temperature show that all the adsorbed H₂ molecules remain adsorbed during the simulations on a complex at temperature T only if Gibbs free energy corrected H₂ adsorption energy at that temperature T is positive. H₂ adsorption on Be decorated ethylene is also studied and the results are compared with Be decorated acetylene.     

Respiratory Health of School Children in Relation to Their Body Mass Index (BMI) During Crop Residue Burning Events in North Western India

Particulate matter levels and physiological parameters of 150 school going children were monitored continually for 3 years (2013–2016) at three agriculturally active sites. Percent changes in physiological parameters like forced vital capacity, peak expiratory flow, etc. were estimated using mixed effect model with adjustment of covariates such as BMI. Results show that the increase in fine PM levels were much more in rice seasons than in wheat seasons. During the burning episodes, severe adverse effects on physiological parameters of the selected subjects were observed due to enhanced PM_2.5 levels. Significant changes were observed in FVC (? 5.27 to ? 7.53%) and PEF (? 4.89 to ? 7.12%) in comparison to FEV₁ and FEF_25–75%. Respiratory health in terms of FVC and PEF corresponded very well with the body mass indices of the human subjects for different PM levels in the ambient air. The subjects having lower BMI level were affected more than those with normal and high BMI on exposure to same level of fine particulate matter. It has been concluded that the trends of fall in respiratory parameters were alarming especially for the subjects with lower and higher BMI during crop residue burning episodes.     

Epidemiological Study on Respiratory Health of School Children of Rural Sites of Malwa Region (India) During Post-harvest Stubble Burning Events

A study on effects of particulate matter fractions (PM₁₀, PM_2.5 and PM₁) on health of school children was done from September 2014 to December 2015 covering one wheat and two rice crop seasons. The study was undertaken at 3 rural sites in the districts of Patiala, Fatehgarh Sahib and Sangrur (Malwa region of Punjab). The monthly average values of PM₁₀, PM_2.5 and PM₁ were about 3–4 times higher than the National Ambient Air Quality Standards (NAAQS) given by Central Pollution Control Board during the crop residue burning periods. The MODIS data images of crop residue burning events confirmed the active fire operations over the region. The lung function parameters (Forced Vital Capacity, Forced Expiratory Volume in one second) of children (10–16 years) decreased with increase in particulate matter concentration while no significant effect was observed on Oxygen saturation level of children. The decrease in Forced Vital Capacity was slightly more in male subjects as compared to the female population. The sharp decrease in Pulmonary Function Test parameters during the crop residue burning period indicated the severity of the episodic burning events on the health of the children.     

Sm doping effect on structural,morphological, luminescence and antibacterial activity of CdO nanoparticles

Undoped cadmium oxide along with samarium doped CdO are synthesized by simple soft precipitation method. Resulting precursor was calcined at 400 °C for 2 h. As a result of heating, a pure material was produced. The obtained compound possesses a cubic crystalline structure at nanoscale. Also, FESEM image showed that the resulting material is composed of nanoparticles and its size decreases with increase of Sm doping relative with the particle size calculated from XRD. The photoluminescence shows the emission of violet and blue colour peaks and the peak at 468 nm which is responsible for a better antibacterial activity. The synthesized nanopowders are subjected to two different gram positive (Staphylococcus aureus and Enterococcus faecalis) and two different gram negative (Escherichia coli and Klebsiella pneumoniae) bacterial strains respectively. It is noted that there are high activity of the Sm doped CdO towards gram negative bacteria.     

Energy‐Autonomous,Flexible, and Transparent Tactile Skin

Tactile or electronic skin is needed to provide critical haptic perception to robots and amputees, as well as in wearable electronics for health monitoring and wellness applications. Energy autonomy of skin is a critical feature that would enable better portability and longer operation times. This study shows a novel structure, consisting of a transparent tactile sensitive layer based on single‐layer graphene, and a photovoltaic cell underneath as a building block for energy‐autonomous, flexible, and tactile skin. Transparency of the touch sensitive layer is considered a key feature to allow the photovoltaic cell to effectively harvest light. Moreover, ultralow power consumed by the sensitive layer (20 nW cm^?2) further reduces the photovoltaic area required to drive the tactile skin. In addition to its energy autonomy, the fabricated skin is sensitive to touch, mainly because a transparent polymeric protective layer, spin‐coated on the sensor's active area, makes the coplanar capacitor sensitive to touch, detecting minimum pressures of 0.11 kPa with a uniform sensitivity of 4.3 Pa^?1 along a broad pressure range. Finally, the tactile skin patches are integrated on a prosthetic hand, and the responses of the sensors for static and dynamic stimuli are evaluated by performing tasks, ranging from simple touching to grabbing of soft objects.     

Design and Simulation of FBAR for Quality Factor Enhancement

Thin film bulk acoustic resonator (FBAR) higher quality factor (Q) provides steep skirt and low insertion losses in the pass band. In this paper, three different loss sources are identified and FBAR is design and simulated in order to reduce the losses. Firstly, the FBAR’s top electrode is simulated for the areas of 150 × 150, 300 × 300 and 400 × 400 μm² and the quality factor is improved as the area increased to 102, 432.6 and 743.7 respectively. The impedance of the FBAR is reduced as the area of the electrode is increased. Secondly, the anchor width is reduced from 60 to 45 μm and the quality factor is increased from 341 to 432.6 respectively. The losses through the anchor reduce as the anchor reduces. Electrode area and anchor area simulation are showing the notable effect and no other paper is reported for the comparison. Thirdly, the damping factor coefficient (β) is varied as 4.7e^?14, 3.84e^?14 and 2.5e^?14. The quality factor is increased as the damping factor reduces and reported as 283.2, 341.2 and 444.5 respectively. The damping reduction leads the FBAR structure to vibrate more freely at the resonance. The losses through damping are reduced and more energy has stored at the resonance so it increases the quality factor.     

Structural and microwave properties of Ag-doped strontium hexaferrite

A series of silver-doped strontium hexaferrite with the chemical formula SrAg_ZFe_12-zO₁₉ (0.0?≤?z?≤?1.0) were synthesized by the Co-precipitation method. The crystal structure, morphology, and properties of microwave absorption with Ag concentration were studied. The structural analysis by XRD revealed that the samples are crystallized with an M-type hexagonal structure. The values of lattice parameters, the volume of the unit cell, and X-ray density are increasing with the increase of Ag doping. The least values of Rietveld refinements have confirmed a good correlation between experimental and calculated data. Hexagonal plate-like morphology was observed in SEM images and the grain size decreases with Ag doping. Microwave properties have been measured by a vector network analyzer. Real and imaginary parts of electrical permittivity dependence with the frequencies in X-band (8–12 GHz) have been studied. The Reflection loss (RL) was investigated for all samples in X-band frequencies. Maximum RL of ? 21.95 dB at 10.0 GHz was observed for the composition of silver, z?=?0.4. Improved RL when compared with the pure sample indicating enhanced impedance matching and attenuation constant hence the material can show maximum energy loss for the incident microwaves. The results so obtained are explained based on composition and microwave phenomena. The present studies have confirmed the nature of microwave absorption for Ag-doped strontium hexaferrite.

     

Synthesis and modulation of the optical properties of carbon quantum dots using microwave radiation

Abstract

Carbon quantum dots have exhibited highly fluorescent characteristics as nanomaterials. Soluble in water and easily synthesized by multiple simple techniques, there are immense fabrication possibilities by permuting their properties via changing precursors, synthesis route, reaction parameters, etc. As economic and environment-friendly seed material, they are being viewed as an alternative to conventional fluorescent materials in myriad of applications including displays, cancer detection, drug delivery carriers in biomedicine, absorbing material in photovoltaics, etc. In this work, the hydrophilic carbon quantum dots were synthesized from the aqueous solution of citric acid and urea through microwave radiation for varying heat durations. The method is facile, faster and friendly to the environment without any need for high temperature and complicated chemical techniques. It was observed that the bandgap of the fabricated carbon quantum dots and its optical properties namely absorbance, photoluminescence enhanced with an increase in exposure of samples to heat up to an optimum limit, owing to the increase in density of states. However, further exposure to heat for longer duration degraded the absorbance and bandgap while photoluminescence gets saturated. Stokes’ shift revealed that all the synthesized carbon quantum dots possess stable emission. This was reconfirmed from consistent emission peak positions under varying excitation in the samples. The absorbance and PL spectrum exhibited by the synthesized dots makes it a suitable material for boosting the performance of organic solar cell.     

Effect of conventional and microwave heating on the structural and physicochemical properties of silver-doped hydroxyapatite nanopowders

ABSTRACT

This paper discussed the influence of duration and modes of heating on structural and physicochemical properties of silver-doped hydroxyapatite (Ag-HAP) nanopowders (NPs). Conventional electric furnace and microwave (MW) heating modes were employed during the synthesis. MW mode of synthesis was relatively an efficient method as it prepared monolithic HAP NP in just one minute of heating. With the increase in duration of heating in both modes of heating; lattice parameters, crystal size, lattice strain, Ca/P ratio, and degree of crystallinity of HAP phase increased. The morphology of particles was rod-shaped having aspect ratio between 2 and 3. EDX confirmed the presence of Ag and corroborated the formation of apatite. The hydrodynamic diameter of Ag-HAP NPs was significantly bigger than the particle sizes calculated using XRD, FESEM, and TEM. Thus, an overall examination concluded MW as an efficient mode of synthesis, able to produce Ag-HAP NPs in a possible minimum time.