A note on quantization in rotating co-ordinates

The quantization of scalar fields in a uniformly rotating frame is reconsidered. It is pointed out that the coordinates usually used do not represent a frame describing uniform circular motion and the metric in the correct coordinates has a singularity. The result obtained earlier with the wrong coordinates, that there is no radiation, nevertheless holds.

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Zusammenfassung Die Quantisierung skalarer Felder in einem gleichförmig rotierenden Koordinatensystem wird erneut betrachtet. Dabei wird hervorgehoben, daß die gewöhnlich verwendeten Koordinaten die gleichförmige Kreisbewegung nicht beschreiben und daß die Metrik in den richtigen Koordinaten eine Singularität aufweist. Trotzdem bleibt das früher mit den falschen Koordinaten abgeleitete Resultat erhalten, daß nämlich ein strahlungsfreier Zustand existiert.

     

Excess molar volume and isentropic compressibility of monoethanolamine in aqueous system at temperatures from 298.15 to 318.15 K

Densities and sound velocities for aqueous monoethanolamine (MEA) system are reported over the entire composition range at different temperatures (298.15, 303.15, 313.15 and 318.15 K). These experimental data have been further used in calculating the excess molar volume, partial molar volumes, isobaric thermal expansion coefficients and the deviation in isentropic compressibility. The excess molar volumes data were fitted to the Redlich–Kister polynomial equation to obtain their coefficients and standard deviations. The partial molar volume at infinite dilution of both water in MEA and MEA in water and have been determined using two different methods. Knowledge of the above properties of these mixtures is a basis for understanding some of the molecular interactions in these systems. From the analysis of the results, the type of interactions between the MEA and water is discussed in terms of the number and size of the alkyl groups attached to the nitrogen atom of MEA.     

Ultrasound-mediated efficient synthesis of dihydrothiopyrano[2,3-<Emphasis Type="Italic">b</Emphasis>]indole-3-carbonitrile derivatives

An efficient one-pot synthesis of fused dihydrothiopyrano[2,3-b]indole-3-carbonitriles has been developed through ultrasound mediated reaction by simply combining malononitrile and various aldehydes with two indoline-2(3H)-thiones. The method has the advantages of high yields, short reaction time, good functional group tolerance and green reaction conditions.     

Potentiometric study of complexation of phenylaza-15-crown-5, 4-nitrobenzo-15-crown-5 and dibenzopyridino-18-crown-6 and other derivative of 18-crowns-6 with Na+ ion in methanol

The complexation reaction of phenylaza-15-crown-5, and 4-nitrobenzo-15-crown-5, benzo-15-crown-5 and dibenzopyrdino-18-crwon-6, dibenzo-18-crown-6,dicyclohexyl-18-crown-6(cis and trans), and 18-crown-6 with Na⁺ ion in methanol have been studied by potentiometric method. The Na⁺ ion-selective electrode has been used both as indicator and reference electrode. The stoichiometry and stability constants of complexes of these crown ethers with sodium ion were evaluated by MINIQUAD program. The major trend of stability of resulting complexes of these macrocycle with Na⁺ ion varied in the order DCY18C6 > DB18C6 > 18C6 > DBPY18C6 > phenylaza-15C5 > benzo-15C5 > 4-nitrobenzo-15C5. The obtained results in particular stability constant of complexes of DBPY18C6, phenylaza-15C5 and 4-nitrobenzo-15C5 with sodium ion in comparison with other crowns ether are novel, and interesting.     

Effect of potassium permanganate on morphological,structural and electro-optical properties of graphene oxide thin films

This work investigated the effect of Potassium Permanganate (KMnO₄) on graphene oxide (GO) properties, especially on electrical properties. The GO thin films were deposited on a glass substrate using drop casting technique and were analysed by using various type of spectroscopy (e.g. Scanning Electron Microscopy (SEM), Ultra- Violet Visible (UV–VIS), Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), optical band gap, Raman Spectroscopy). Furthermore, the electrical experiments were carried out by using current–voltage (I-V) characteristic. The GO thin film with 4.5 g of KMnO₄ resulted in higher conductivity which is 3.11 × 10^?4 S/cm while GO with 2.5 g and 3.5 g of KMnO₄ achieve 2.47 × 10^?9 S/cm and 1.07 × 10^?7 S/cm, respectively. This further affects the morphological (SEM), optical (band gap, UV–Vis, FTIR, and Raman), and crystalline structural (XRD) properties of the GO thin films. The morphological, elemental, optical, and structural data confirmed that the properties of GO is affected by different amount of KMnO₄ oxidizing agent, which revealed that GO can potentially be implemented for electrical and electronic devices.     

Effect of preparation methods of graphene oxide on permeability of free-standing membranes against polar and nonpolar species

ABSTRACT

In this study, graphene oxide (GO) was synthesized using Hummers, modified Hummers and improved Hummers methods, and then freestanding membranes were prepared based on these materials. Effects of different GO preparation methods on C/O ratio and interlayer spacing of freestanding membranes were studied. Structure of these membranes was studied by X-ray diffraction, contact angle, XRF, FT-IR, and FESEM methods. Also, permeability of ammonia, dichloromethane, and water vapor was investigated through these membranes. Results showed that, the sample prepared by the Hummers method had lower C/O ratio, smoother surface and lower permeability for polar species, such as water and ammonia vapors, than nonpolar materials. Membranes prepared using Improved Hummers method showed the least permeability against nonpolar vapors such as dichloromethane.     

One-pot synthesis of α-aminonitriles using a highly efficient and recyclable silica-based scandium (III) interphase catalyst

Both aryl and alkyl imines, which formed in situ from aldehydes and amines undergo smooth nucleophilic addition with trimethylsilyl cyanide in the presence of a catalytic amount of a silica-based scandium (III) interphase catalyst under mild reaction condition to furnish the corresponding α-aminonitriles in good to excellent yields. The catalyst shows high thermal stability (up to 300 °C) and it could also be recovered and reused for at least 6 reaction cycles without considerable lose of its reactivity.     

Preparation,characterization and biodistribution of the <Superscript>99m</Superscript>Tc-salicylidenediamine-N-dione complex

A tetradentate set of N₂O₂ salicylaldehyde-amine-N-dione Schiff base was prepared by condensation with salicylaldehyde, ethylenediamine, 2,4-dione and reduction with NaBH₄. The ligand system was characterized by ¹H-NMR and FT-IR spectroscopy and HPLC. Radiolabeling studies of the ^99mTc-complex were performed using stannous ions as the reducing agent. The purity of the complex was determined by ascending solvent system on paper chromatography and instant thin-layer chromatography (ITLC). The yield of the complex was >90%. Biodistribution of the ^99mTc-complex of the precursor was studied in rabbits. A significant uptake and retention of injected activity was observed in the liver and cleared through the bladder. A faint activity was also observed in kidneys. These results indicate that the proposed system may be suitable for development of a liver/spleen imaging agent for future clinical applications.     

Kinetics and Mechanism of Permanganate Oxidations of Isosorbide in Different Acidic Media

The oxidation kinetics of isosorbide (S) by potassium permanganate in both perchloric and sulfuric acid solutions was investigated spectrophotometrically at a constant ionic strength of 2.0 mol·dm^?3 and at 25 °C. In both acids, the oxidation reactions showed a first-order dependence on \([{\text{MnO}}_{4}^{ - }]\), apparent a less than unit-order dependence with respect to [S] and a fractional-second-order dependence with respect to [H⁺]. Variation of either the ionic strength or dielectric constant of the reactions media did not significantly affect the oxidation rates. In both acids, the final oxidation product of isosorbide was identified by both spectroscopic and chemical tools as the corresponding monoketone derivative, namely (1S,4S,5R)-4-hydroxy-2,6-dioxabicyclo[3.3.0] octan-8-one. Under comparable experimental conditions, the oxidation rate of isosorbide in perchloric acid was lower than that in sulfuric acid. The oxidation mechanism describing the kinetic results was proposed and the rate law expression was derived. The activation parameters of the second-order rate constants were computed and are discussed.