Mössbauer studies on impactites from Lonar impact crater

The partly filled skutterudites A _x Fe₄Sb₁₂ (A = La, Pr, Nd, Eu, Yb, and the monovalent homologue Tl) were investigated at 4.2 K by ⁵⁷Fe Mössbauer spectroscopy in external fields up to 13.5 T. Two Fe sites were identified. The observed relative spectral areas are not for all compounds in agreement with filling factors for the A-atoms determined from X-ray experiments. The change in sign and the small value of the induced hyperfine fields for magnetically ordered compounds are strong hints for itinerant ferromagnetism with small ordered moments.     

A new eco-friendly strategy for the synthesis of novel antimicrobial spiro-oxindole derivatives via supramolecular catalysis

Novel spiro-oxindole derivatives were synthesised by one-pot multicomponent reaction using isatins, urea and 1,3-dicarbonyls. β-Cyclodextrin, an oligosaccharide, catalysed the reaction and can be reused for further reaction after recovery. This developed synthetic route is environmentally benign in which water is used as solvent to produce excellent yields of products. The synthesised compounds were evaluated for their antimicrobial activities against two bacteria and two fungi. All the synthesised spiro-oxindoles exhibit significant antimicrobial activity.     

Scanning tunneling microscopy and spectroscopy study of charge inhomogeneities in bilayer graphene

We report a room-temperature scanning tunneling microscopy and spectroscopy study of bilayer graphene prepared by mechanical exfoliation on a SiO₂/Si surface and electrically contacted with gold pads using a mechanical mask. The bulk conductivity shows contributions from regions of varying electron density, indicating significant charge inhomogeneity. Large-scale topographic images show ripple-like structures with a roughness of ∼1 nm, while the small-scale atomic resolution images show graphite-like triangular lattices. The local () tunnel spectra have an asymmetric V-shape with the minima location showing significant spatial variation, indicating inhomogeneity in electron density of order 10¹¹ cm⁻². The minimum in spectrum at a fixed location also shifts linearly with the gate voltage with a slope consistent with the field-induced carrier density.     

Simulation and experimental studies of a vibro-impact capsule system driven by an external magnetic field

This paper studies the electromagnetic field used for driving a vibro-impact capsule prototype for small bowel endoscopy. Mathematical models of the electromagnetic field and the capsule system are introduced, and analytical solution of the magnetic force applied on the capsule is derived and verified by experiment. The impact force between the inner mass of the capsule and the capsule body is also compared via numerical simulation and experimental testing. By comparing the capsule’s progressions under different control parameters (e.g. the excitation frequency and duty cycle), the merits of using the vibro-impact propulsion are revealed. Based on the experimental results, the optimised speed of the prototype can achieve up to 3.85 mm/s. It is therefore that the potential feasibility of using the external electromagnetic field for propelling the vibro-impact capsule system is validated.

     

Simultaneous Trace Level Determination of Potentially Genotoxic Hydrazine,Methylhydrazine and Alkylamines in Pharmaceutical Substances by CE Using Indirect Photometric Detection

A simple, fast, and sensitive capillary electrophoretic method was developed for determining two genotoxic impurities hydrazine and methylhydrazine and eight alkyl amines at trace levels in pharmaceutical substances using indirect photometric detection. The method development involved a systematic screening of various cationic visualizing reagents and optimization of separation conditions to obtain the best resolution and sensitivities. The optimized method was validated for specificity, precision, linearity, and accuracy. Linear calibration curves (R > 0.99) were obtained for all analytes in the range LOQ–200 % of nominal concentrations. The developed CE method was effectively implemented for estimating hydrazine and alkylamines in several active pharmaceutical ingredients (APIs).

     

Triphenylphosphine-Catalyzed,Novel, One-Pot,Multicomponent Synthesis of Functionalized β-Acetamido Carbonyls

An efficient triphenylphosphine-catalyzed synthesis of β-acetamido carbonyls via multicomponent reaction of aromatic aldehydes, enolizable ketones or β-keto esters, acid chlorides and acetonitrile at room temperature is described. The process is remarkably simple, environmentally benign, and uses Lewis base for the first time in such type of reaction.     

One‐pot,Multicomponent Cascade Reaction for the Synthesis of Various Aralkyl/alkylthio‐3,5‐dimethyl‐1H‐pyrazolyl‐4H‐1,2,4‐triazol‐4‐amine and Their Docking Studies

A facile and simple one‐pot procedure for the synthesis of various aralkyl/alkylthio‐3,5‐dimethyl‐1H‐pyrazolyl‐4H‐1,2,4‐triazol‐4‐amines has been described via a multicomponent reaction of 4‐amino‐5‐hydrazinyl‐4H‐1,2,4‐triazole‐3‐thiol, acetylacetone, and various aryl/alkyl halides in good yields. All the newly synthesized compounds were characterized by using analytical and spectral studies. Our in silico studies confirmed that 4e , 4f , 4g , and 4j have the best inhibition activity among the synthesized compounds with a high selective index against the Tubulin protein and showed best interactions with receptor structure. The present study provides a novel series of compounds with a promising inhibitor to prevent on Tubulin protein.     

Synthesis of 1,2,3-thiadiazoles

Several methods were explored for preparing certain 4,5-disubstituted-1,2,3-thiadiazoles. The reaction of phenoxyacetyl chlorides with diazoacetylamides yielded α-diazo-β-ketoacetamides which were cyclized, with hydrogen sulfide and ammonium hydroxide, to 4-carboxamido-5-phenoxymethyl-1,2,3-thiadiazoles. However, treatment of α-diazo-α-benzoylacetamides with hydrogen sulfide and ammonium hydroxide yielded hydrazones rather than thiadiazoles. The reaction of α-[(ethoxycarbonyl)hydrazono]benzenepropanoic acid ( 25 ) with thionyl chloride yielded 5-phenyl-1,2,3-thiadiazole-4-carbocylic acid (26a) , the corresponding acid chloride 26b , and 5-(phenylmethyl)-2H-1,3,4-oxadiazine-2,6(3H)dione ( 27 ). The yields of 26a, 26b , and 27 were dependent on the reaction conditions employed. Oxadiazine 27 could also be converted to acid chloride 26b with thionyl chloride. Reduction of 1-([5-(4-chlorophenoxy)methyl-1,2,3-thiadiazol-4-yl]-carbonyl)piperidine ( 10b ) with diborane yielded a boron complex which produced 1-([5-((4-chlorophenoxy)methyl)-1,2,3-thiadiazol-4-yl]methyl)piperidine ( 31 ) upon recrystallization from ethanol.     

Energy transfer photophysics from serum albumins to sequestered 3-hydroxy-2-naphthoic acid, an excited state intramolecular proton-transfer probe

The steady-state and time-resolved studies of the sensitized emission of the excited-state proton transfer (ESIPT) probe 3-hydroxy-2-naphthoic acid (3HNA) when bound to bovine serum albumin (BSA) and human serum albumin (HSA) indicate that the nonradiative dipole-dipole F?rster type energy transfer from Trp singlet state of proteins to the ESIPT singlet state of 3HNA is greater in the case of HSA. This is supported by the distance and the orientation of the donor-acceptor pair obtained from the protein-ligand docking studies. The docking studies of the complex of BSA-3HNA also indicate that Trp 134 rather than Trp 213 is involved in the energy transfer process. The local environment of Trp 134 in BSA rather than that of Trp 213 is perturbed because of interaction with 3HNA as revealed by the optical resolution of Trp 134 phosphorescence in the complex at 77 K. Docking studies support the larger rotational correlation time, thetac (approximately 50 ns), observed for Trp residue/residues in the complexes of HSA and BSA compared with that in the free proteins.