Demonstration of a thick holographic Stokesmeter

A holographic Stokesmeter has the potential to be useful in high-speed polarization imaging applications. Highly polarization-sensitive gratings are an important component for this device. Using two sets of multiplexed gratings, we measured the Stokes parameters for three different polarization states of an input beam. These measured values compared well to values measured using the quarter-wave plate/linear polarizer method. This establishes the feasibility of such a Stokesmeter in its original configuration. We demonstrate further the basic mechanism behind a compact architecture for this device, requiring only a single substrate and a single imaging system, and describe a spectrally scanned polarimetric imaging system.     

Criteria for ferromagnetic–insulator–ferromagnetic tunneling

The Rowell criteria, commonly used to identify tunneling in magnetic tunnel junctions (MTJ), are scrutinized. While neither the exponential-thickness dependence of the conductivity nor fits of non-linear transport data are found to be reliable tunneling criteria, the temperature-dependent conductivity does remain a solid criterion. Based on experimental studies of the bias and temperature-dependent resistance and magnetoresistance of MTJs, with and without shorted barriers, a new set of criteria is formulated.     

Ultra high performance liquid chromatography tandem mass spectrometry method for the simultaneous determination of multiple bioactive constituents in fruit extracts of Myristica fragrans and its marketed polyherbal formulations using a polarity switching technique

Fruits of Myristica fragrans Houtt. are the source of two valuable spices: nutmeg and mace, traditionally used for its flavoring and medicinal properties and found as an ingredient in many marketed polyherbal formulations and food products. In this study, a sensitive and efficient ultra high performance liquid chromatography electrospray ionization tandem mass spectrometry method was developed and validated for the rapid determination of 16 bioactive constituents in different parts of the fruit of M. fragrans and its marketed polyherbal formulations using a polarity switching technique. Chromatographic separation was achieved on an Aquity UPLC BEH C₁₈ column in 9.4 min. Quantitative analysis was performed using multiple reaction monitoring mode with continuous polarity switching in a single analysis. The developed method was found to be accurate with overall recovery in the range from 95.95 to 102.07% (RSD ≤ 1.91%), precise (RSD ≤ 1.98%), and linear (r² ≥ 0.9992) over the concentration range of 0.1–200 ng/mL. Quantitative analysis indicated that the total content of the 16 bioactive constituents was highest in the mace of M. fragrans. Thus, this rapid and sensitive method could be utilized as a promising reference method for the quality control of M. fragrans and its marketed herbal formulations/food products.     

Thermal Emission Spectrum of the Cobalt Monobromide Molecule

ABSTRACT

The thermal emission spectrum of the CoBr molecule has been photographed for the first time in the spectral region 4200–6000 Å using the high-temperature excitation technique and the 2-meter plane grating spectrograph (PGS-2). The spectrum has been recorded at a reciprocal linear dispersion of 7.3 Å/mm. About 203 red degraded and line-like bands have been recorded, out of which 172 are entirely new. The observed bands have been classified into 31 systems, of which 23 are entirely new. The vibrational analyses have been carried out using band head measurements and the Deslandre table. The ground state of the CoBr molecule is found to be ³Φ with the vibrational constants 318.3, 329.5, and 332.7 cm^?1.     

Ultra-low level optical detection of mercuric ions using biogenic gold nanotriangles

Mercury is a serious environmental pollutant known to have detrimental health effects in all life forms. Here, we report the use of biologically synthesized aqueous gold nanotriangles for sensitive and selective optical detection of femto-molar levels of mercury ions by exploiting the high amalgamation tendency of mercury metal towards gold. Aqueous chloroaurate ions were reduced using lemongrass (Cymbopogon flexuosus) leaf extract at room temperature to form gold nanotriangles. Mercuric (Hg(2+)) ions were reduced in the presence of these triangles to facilitate amalgamation and the optical properties were monitored. We observe a significant change in the longitudinal plasmon absorption band of the nanotriangles even at femto-molar concentrations of mercuric ions. High-resolution transmission electron microscopy confirms changes in particle morphology at such low concentrations. This protocol shows no sensitivity to other environmentally relevant metal ions, including Pb(2+), Zn(2+), Cd(2+), Fe(2+), Ni(2+), Sr(2+), Ca(2+), Mn(2+), and Cu(2+), confirming further that change in the optical properties of gold nanotriangles in the presence of reduced mercuric ions is solely due to the strong amalgamation tendency of mercury metal.     

Experimental set up for in situ transmission electron microscopy observations of chemical processes

Recently, the applications of transmission electron microscopy (TEM) related techniques have extended from ex situ nanoscale characterization of structure and chemistry of products to dynamic measurements of nanostructures during reaction processes. Commercially available modified TEM specimen holders and TEM columns are being routinely employed to follow the structural and chemical changes at elevated temperatures and even under controlled atmosphere. Experiments performed under these rigorous conditions require careful considerations to avoid undesirable effects from the gas impurities or contaminations from TEM grids and/or holders. The reactivity of sample, grid, holder, TEM components, and gaseous environments must be evaluated for each reaction process. This tutorial is aimed to outline some of the important factors that should be considered for experimental set up used for in situ observations to ensure the results are comparable to the ones obtained during ex situ experiments under identical conditions.