Determination of carbidic carbon in steels

An attempt has been made to develop a simple analytical technique that can readily be used in an industrial laboratory to isolate and quantify the precipitated carbides in steel samples. Attempt has also been made to correlate this value with the thermodynamically predicted values. There is good agreement between the predicted and experimental results. More work is in progress to develop this technique for the preparation of Certifed Reference Materials with dissolved and precipitated carbon in steels.     

An X-band time domain electron paramagnetic resonance spectrometer

A computer-controlled X-band time domain electron paramagnetic resonance (EPR) spectrometer, with a time resolution of the order of 0.5μsec, has been constructed with many of the crucial microwave components designed and fabricated by the Microwave Engineering Group of TIFR. The spectrometer operates either in a microwave power pulsed mode for determination of spin-lattice relaxation times by the saturation recovery technique or in the kinetic mode for determination of the time dependence of EPR signal after laser excitation. It has an automatic frequency control, an automatic phase control and, most importantly, a field-frequency lock which ensures good stability of the EPR line positions enabling signal averaging for extended periods. The constructional details of the spectrometer and its performance in both the modes are described here by reporting results on certain typical systems.     

Initially and eventually dominating nonoscillatory solutions in integro-differential difference equations

For the system T′(t) + p(t) T(t) + q(t) T(t ? τ) = ∝₀^tK(t ? μ) T(μ) dμ for t ? 0, T(t) = g(t) for t ∈ [?τ, 0], conditions have been obtained which ensure that a solution of this system is dominated by a nonoscillatory solution in the interval ¦τ, ∞).     

Spin resonances in amorphous Y-Fe alloys

We present spin resonance measurements on amorphous Y_1?xFe_x alloys using both bulk (a-YFe₂) and thin film (x = 0.70, 0.77, 0.83) samples. At 300 K, in every sample, we have found one strong line (S₁) whose frequency and angular dependances imply that it is a uniform mode ferromagnetic resonance in a very thin (≈20–40 nm) surface layer. Previous static measurements indicate that these alloys have no long range order at 300 K. The effective magnetization of the surface layer is a non-monotonic function of the Fe content. Rutherford back scattering experiments on bulk samples are used to demonstrate that there is no significant variation in composition, with depth. We show that S₁ cannot be attributed to segregation, surface contamination or crystallinity. We propose that the surface layer is another amorphous phase of the alloy. A second resonance (S₃) has been ascribed to some of the superparamagnetic spin clusters known to be present in these systems. As reported earlier, we observe other resonances whose origin is not fully understood.     

Stereospecific synthesis and antibiotic activity of some cephalosporin analogs

The strategy used for the stereospecific synthesis of benzofused octams as cepham analogs was the conversion of a 3,4-dihydrothioisocarbostyril to a thioimidate, cycloaddition reaction to form a fused β-lactam and subsequent removal of the alkylthio group by Raney nickel hydrogenolysis. Using azidoacetyl chloride for forming the β-lactam and following known procedures, an amido side chain was generated. Two of the carba analogs of cephalosporin so produced showed low levels of antibacterial activity against a number of gram positive and gram negative organisms.     

AB-initio effective potentials derived from many-body green's function theory: Application to Li

The many-body Green's function technique, developed by Schneider, Taylor and Yaris for electron scattering problems, is applied to the calculation of ab-initio effective potentials (pseudo-potentials) in atoms and molecules. Computational results on the ionization potentials, excitation energies and bound-bound oscillator strengths in lithium show quantitative agreement with experiment and contain all the heuristically expected physical effects.     

Solid-State Isolation of Cyclic Alkyl(Amino) Carbene (cAAC)-Supported Structurally Diverse Alkali Metal-Phosphinidenides

Cyclic alkyl(amino) carbene (cAAC)-supported, structurally diverse alkali metal-phosphinidenides 2 – 5 of general formula ((cAAC)P-M)_n(THF)_x [ 2 : M=K, n=2, x=4; 3 : M=K, n=6, x=2; 4 : M=K, n=4, x=4; 5 : M=Na, n=3, x=1] have been synthesized by the reduction of cAAC-stabilized chloro-phosphinidene cAAC=P-Cl ( 1 ) utilizing metallic K or KC₈ and Na-naphthalenide as reducing agents. Complexes 2 – 5 have been structurally characterized in solid state by NMR studies and single crystal X-ray diffraction. The proposed mechanism for the electron transfer process has been well-supported by cyclic voltammetry (CV) studies and Density Functional Theory (DFT) calculations. The solid state oligomerization process has been observed to be largely dependent on the ionic radii of alkali metal ions, steric bulk of cAAC ligands and solvation/de-solvation/recombination of the dimeric unit [(cAAC)P-M(THF)_x]₂.     

Most recent strategies targeting estrogen receptor alpha for the treatment of breast cancer

Molecular Diversity - Breast cancer is the most prominent, frequently diagnosed and leading cause of death among women. Estrogen is an agonist of estrogen receptor alpha (ER-α), expressed in...     

Impedance matching in RF excited fast axial flow CO2 laser: The role of the capacitance due to laser head

Impedance matching in an indigenously developed 2 kW RF-excited fast axial flow (RF-FAF) CO₂ laser was seen to be significantly influenced by the capacitance formed between the laser head and the electrodes. We find in the published literature that this capacitance is generally assumed to be negligible while designing the matching network in the RF-FAF CO₂ lasers. It is shown that this capacitance could have a significant value and consequently would modify the design of the matching network remarkably for a specific laser design studied in the present case. The widely used discharge load model for capacitively coupled RF (CCRF) discharge excited CO₂ laser plasma is extended to include this capacitance. The method of measurement of this capacitance using a bridge and the ANSYS software based simulation of its formation due to the laser head structure are discussed.     

Nanocomposite of bimetallic nanodendrite and reduced graphene oxide as a novel platform for molecular imprinting technology

In this present work, for the first time, we are reporting a green synthesis approach for the preparation of vinyl modified reduced graphene oxide-based magnetic and bimetallic (Fe/Ag) nanodendrite (RGO@BMNDs). Herein, the RGO@BMNDs acts as a platform for the synthesis of the pyrazinamide (PZA)-imprinted polymer matrix and used for designing of the electrochemical sensor. We have demonstrated how the change in morphology could affect the electrochemical and magnetic property of nanomaterials and for this the reduced graphene oxide-based bimetallic nanoparticle (Fe/Ag) was also prepared It was found that the combination of graphene and bimetallic nanodendrites shows improvement as well as enhancement in the electrocatalytic activity and adsorption capacity, in comparison to their respective nanoparticles. The application of imprinted-RGO@BMNDs sensor was explored for trace level detection of PZA (Limit of detection = 6.65 pg L⁻¹, S/N = 3), which is a drug used for the cure of Tuberculosis. This is lowest detection limit reported so far for the detection of PZA. The sensor is highly selective, cost-effective, simple and free from any interfering effect. The real time application of the sensor was explored by successful detection of PZA in pharmaceutical and human blood serum, plasma and urine samples.