Screening and specification of colour changes of nitritometric indicators

The specification of colour changes of nitritometric indicators, viz., cresyl fast violet acetate, amethyst violet, safranine O, neutral red, methylene violet, neutral violet, phenosafranine, brilliant cresyl blue and lissamine blue BF, in the titration of sulphanilamide has been carried out with the help of tristimulus colorimetry. Apart from the determination of true colour co-ordinates and complementary colour co-ordinates, the quantitative parameters specific colour discrimination (SCD), total colour difference (E*) values of CIE La^*b^*, CIE Lu^*v^* and LAB HNU colour spaces together with the standard deviation of colour matching (S) were also evaluated for all the indicators at different concentrations ratios of nitrite and sulphanilamide, for a quantitative measure of quality of colour change. The quality of colour change of many of the studied indicators is further improved by screening with appropriate inert colorants to obtain a colour transition between complementary colours through colourlessness at the equivalence point.     

Optical bistability induced by mirror absorption: measurement of absorption coefficients at the sub-ppm level

We have observed optical bistability caused by absorption-induced thermal expansion of mirrors forming a Fabry-Perot interferometer. From the resulting anomalous transmission line shapes, absorption coefficients of the mirror coatings as low as 0.2parts in 10(6) (ppm) have been successfully measured.     

A multi-orbital iterated perturbation theory for model Hamiltonians and real material-specific calculations of correlated systems

The dynamical mean field theory (DMFT) has emerged as one of the most importantframeworks for theoretical investigations of strongly correlated lattice models and realmaterial systems. Within DMFT, a lattice model can be mapped onto the problem of amagnetic impurity embedded in a self-consistently determined bath. The solution of thisimpurity problem is the most challenging step in this framework. The available numericallyexact methods such as quantum Monte Carlo, numerical renormalization group or exactdiagonalization are naturally unbiased and accurate, but are computationally expensive.Thus, approximate methods, based e.g. on diagrammatic perturbation theory have gainedsubstantial importance. Although such methods are not always reliable in various parameterregimes such as in the proximity of phase transitions or for strong coupling, theadvantages they offer, in terms of being computationally inexpensive, with real frequencyoutput at zero and finite temperatures, compensate for their deficiencies and offer aquick, qualitative analysis of the system behavior. In this work, we have developed such amethod, that can be classified as a multi-orbital iterated perturbation theory (MO-IPT) tostudy N-folddegenerate and non degenerate Anderson impurity models. As applications of the solver, wehave embedded the MO-IPT within DMFT and explored lattice models like the single orbitalHubbard model, covalent band insulator and the multi-orbital Hubbard model fordensity-density type interactions in different parameter regimes. The Hund’s couplingeffects in case of multiple orbitals is also studied. The limitations and quality ofresults are gauged through extensive comparison with data from the numerically exactcontinuous time quantum Monte Carlo method (CTQMC). In the case of the single orbitalHubbard model, covalent band insulators and non degenerate multi-orbital Hubbard models,we obtained an excellent agreement between the Matsubara self-energies of MO-IPT andCTQMC. But for the degenerate multi-orbital Hubbard model, we observe that the agreementwith CTQMC results gets better as we move away from particle-hole symmetry. We have alsointegrated MO-IPT+DMFT with density functional theory based electronic structure methodsto study real material systems. As a test case, we have studied the classic, stronglycorrelated electronic material, SrVO₃. A comparison of density of states and photo emissionspectrum (PES) with results obtained from different impurity solvers and experimentsyields good agreement.     

Enhanced dielectric and magnetic properties of Cr / Co and Mn co-doped single phase multiferroic bismuth ferrite nanoparticles

Multiferroic nanoparticles of single-phase bismuth ferrite (BiFeO₃ or BFO) by choosing transition metal ions of chromium (Cr)/cobalt (Co) in A-sites and manganese (Mn) in B-sites were synthesized by using sol-gel autocombustion method. X-ray diffraction (XRD) data reveal the existence of rhombohedrally distorted perovskite structure for all the samples. High resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX) studies were carried out to estimate the particle size, morphology along with the chemical purity of the samples. Dielectric studies as a function of frequency and temperature resemble typical space charge polarization with almost negligible dielectric losses in the doped samples. Magnetic measurements using vibrating sample magnetometer reveals the considerable enhancement in the magnetic order in Co/Cr and Mn co-doped samples. The obtained structural, microstructural, dielectric and magnetic results were well recommended that the influence of co-doping in BFO will certainly modify its spin cycloid structure and hence enhanced properties in these doped samples. Thus, these co-doped samples were suggested to be well suitable for the multifunctional based devices such as spintronic, multifunctional memories, and for sensors.     

Typical superparamagnetism with improved electrical properties of nano modified bismuth ferrite multiferroic composites

Multiferroic composites with the chemical formula, (0.5) BiFeO₃ + (0.5) Ni_0.5Zn_0.5Fe₂O₄, in bulk and nano forms were synthesized by preparing bismuth ferrite (BiFeO₃ or BFO) in bulk (B) and nano (N) forms and nickel zinc ferrite (Ni_0.5Zn_0.5Fe₂O₄or NZFO) in nano form. Single phase BFO was synthesized using conventional solid-state reaction as well as sol-gel autocombustion methods and NZFO powders were prepared by using sol-gel autocombustion method, respectively. X-ray diffraction (XRD) studies reveal the existence of rhombohedrally distorted perovskite structure for BFO and cubic spinel phase for NZFO in single phase as well as composite samples. Microstructural studies and energy dispersive spectroscopy (EDS) data reveal the formation of grains, intergranular porosities and chemical purity of the synthesized samples. Dielectric and AC conductivity measurements confirm the existence of space charge polarization along with the small polaron model in these composites. Ferroelectric and magnetic studies show that there was a considerable enhancement in the ferroelectric and magnetic orders for the nano form of the BFO (N) + NZFO composite. The observed remnant polarization values 2.80388 & 7.75901 μC/cm², saturation magnetization values 37.96072 & 40.47491emu/gm for bulk BFO (B) + NZFO and nano BFO (N) + NZFO composites, respectively. Interestingly, both the samples exhibit superparamagnetic behaviour at room temperature with coercivities close to zero. This typical behaviour is attributed to the corresponding anisotropic contributions originated from the individual constituents. The observed variations in BFO (N) + NZFO sample attributed to the corresponding structural modifications brought about by the variations due to its size effect in the present work.     

Application of the INAA methods for KRISS infant formula CRM analysis: standardization of INAA at KRISS

We have established an instrumental neutron activation analysis (INAA) method, including k₀-based INAA, at the Korea Research Institute of Standards and Science (KRISS) for the certification of reference materials. As part of establishing INAA measurements, KRISS infant formula certified reference material was analysed for multiple elements at three different metrological institutes: KRISS and NIST for the standard comparator method, and JSI for the k₀-INAA method. The mass fraction of most elements was consistent within expanded uncertainty (k?=?2). In addition, the results were used to verify the validity of elemental analysis of Zn using the standard comparator INAA at KRISS, and spreadsheet-based INAA calculations were evaluated.

     

Design,Synthesis, and Anti-Proliferative Activity of Quinoxaline Linked 1,2,4-Oxadiazole Hybrids

Russian Journal of General Chemistry - Herein, synthesis of some new quinoxaline-1,2,4-oxadiazole derivatives is presented, and their in vitro anti-cancer activity against four human cancer cell...     

A Stereoselective Aldol Approach for the Total Syntheses of Two 6‐Alkylated 2H‐Pyran‐2‐ones

A simple and highly efficient stereoselective total synthesis of the 6‐alkylated pyranones (6R)‐6‐[(1E,4R,6R)‐4,6‐dihydroxy‐10‐phenyldec‐1‐en‐1‐yl]‐5,6‐dihydro‐2H‐pyran‐2‐one ( 1 ) and (6S)‐5,6‐dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one ( 2 ) was developed using Crimmins' aldol reaction, SmI₂ reduction, Grubbs‐II‐catalyzed olefin cross‐metathesis, and Still's modified Horner? Wadsworth? Emmons reaction.     

Performance of digital gamma ray spectrometer for loss free counting and its application to NAA using short-lived radionuclides

A digital gamma-ray spectrometer with loss-free counting system was used for real time correction for dead time (DT) due to pulse processing in the electronics. This spectrometer was used for radioactive assay of samples having constant as well as varying DT conditions. The system was tested by measuring activity of short and medium lived nuclides namely ²⁸Al, ⁵²V and ¹²⁸I in the DT ranges of 80–2 %. Using this spectrometer and neutron activation analysis (NAA), concentrations of Al, V, Ti, Ca, Dy and Mn were determined in some samples and reference materials.