1,378 research outputs found
The Nonexistence of Instrumental Variables
The method of instrumental variables (IV) and the generalized method of moments (GMM) has become a central technique in health economics as a method to help to disentangle the complex question of causality. However the application of these techniques require data on a sufficient number of instrumental variables which are both independent and relevant. We argue that in general such instruments cannot exist. This is a reason for the widespread finding of weak instruments.
A National Strategy for Ventilator and ICU Resource Allocation During the Coronavirus Disease 2019 Pandemic
GREEN SYNTHESIS OF NANOSTRUCTURED ZINC PARTICLES USING AQUEOUS LEAF EXTRACT OF SCHREBERA SWIETENIOIDES ROXB. AND THEIR CATALYTIC APPLICATION IN DEGRADATION OF METHYL ORANGE, CRYSTAL VIOLET DYES AND CHROMIUM METAL
Objective: The present work was aimed to synthesized the zinc nanoparticles (ZnO NPs) using aqueous leaf extract of Schrebera swietenioides Roxb., and further, the green-synthesized ZnO NPs were studied for its efficacy in the degradation of hazardous dyes like methyl orange, crystal violet and hazardous metal such as chromium.
Methods: The ZnO NPs were synthesized using aqueous leaf extract of S. swietenioides Roxb., as a green reducing agent and 0.1 M Zinc acetate as metal source and the NPs synthesis was completed within a short period of 6 h. The ZnO NPs synthesized were characterized using SEM, TEM, EDS, XRD, FT-IR and UV-visible spectrophotometer. Further, the synthesized NPs were applied for reduction of pollutant days such as methyl orange, crystal violet and pollutant metal chromium.
Results: The synthesis of NPs was monitored by observing the color change in the reaction mixture and UV visible spectral analysis. The UV spectral analysis shows a characteristic absorption wavelength at 379 nm. The synthesized NPs were hexagonal wurtzite form crystals having a spherical shape with rough surfaces with an average size of 68 nm and having 73.7 % of zinc content. At a NPs dose of 1.0 g/l the photocatalytic reduction was observed as 85.33±0.02 %, 86.82±0.095 % and 86.73±0.104 % for crystal violet dye, methyl orange dye and chromium metal, respectively. The NPs shows a high % photocatalytic reduction of chromium metal, crystal violet dye and methyl orange dye with less contact time confirms that the synthesized ZnO NPs were effectively catalyzed the degradation of methyl orange, crystal violet dyes and chromium metal. The NPs were observed to be recyclable and can shows high reduction activity after the completion of three cycles of degradation.
Conclusion: Hence it can be concluded that synthesized greener nanocatalyst was efficient for pollutant treatment and demonstrated the power of green biosynthesis for metallic nanoparticles
U.S. demand for imported and domestically-produced foods: an investigation of intertemporal and cross substitution
Pressure-induced amorphization and polyamorphism in one-dimensional single crystal TiO2 nanomaterials
The structural phase transitions of single crystal TiO2-B nanoribbons were
investigated in-situ at high-pressure using the synchrotron X-ray diffraction
and the Raman scattering. Our results have shown a pressure-induced
amorphization (PIA) occurred in TiO2-B nanoribbons upon compression, resulting
in a high density amorphous (HDA) form related to the baddeleyite structure.
Upon decompression, the HDA form transforms to a low density amorphous (LDA)
form while the samples still maintain their pristine nanoribbon shape. HRTEM
imaging reveals that the LDA phase has an {\alpha}-PbO2 structure with short
range order. We propose a homogeneous nucleation mechanism to explain the
pressure-induced amorphous phase transitions in the TiO2-B nanoribbons. Our
study demonstrates for the first time that PIA and polyamorphism occurred in
the one-dimensional (1D) TiO2 nanomaterials and provides a new method for
preparing 1D amorphous nanomaterials from crystalline nanomaterials.Comment: 4 figure
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