Analytical method for band structure calculation of photonic bandgap fibers with depressed index cladding rods

An approximate analytical approach for revealing bandgap information for photonic band gap fibers with depressed index cladding rods is presented. The method considers isolated rods in cladding, with three layers structure: higher index in the core, lower-index depressed layer and silica cladding. Good consistency is found between the results of the approximate analytical method and those from accurate numerical simulations.     

Numerical simulation and PIV study of compressible vortex ring evolution

Formation and evolution of a compressible vortex ring generated at the open end of a short driver section shock tube has been simulated numerically for pressure ratios (PR) of 3 and 7 in the present study. Numerical study of compressible vortex rings is essential to understand the complicated flow structure and acoustic characteristics of many high Mach number impulsive jets where simultaneously velocity, density and pressure fields are needed. The flow development, incident shock formation, shock diffraction, vortex ring formation and its evolution are simulated using the AUSM+ scheme. The main focus of the present study is to evaluate the time resolved vorticity field of the vortex ring and the shock/expansion waves in the starting jet for short driver section shock tubes—a scenario where little data are available in existing literature. An embedded shock and a vortex induced shock are observed for PR =  7. However the vortex ring remains shock free, compact and unaffected by the trailing jet for PR =  3. Numerical shadowgraph shows the evolution of embedded shock and shock/expansion waves along with their interactions. The velocity and vorticity fields obtained from simulation are validated with the particle image velocimetry results and these data match closely. The translational velocity of the vortex ring, velocity across the vortex and the centre line velocity of the jet obtained from simulation also agree well with the experimental results.     

Über chemische Reaktionen zwischen Kolloiden. 2. Quecksilber und Schwefel

Zusammenfassung Es wurde festgestellt, da? beim Mischen von Quecksilbersol und Schwefelsol kolloides Sulfid entsteht. Und zwar konnte dies dadurch nachgewiesen werden, da? überschüssiger Schwefel aus dem Gemisch der ausgeflockten Kolloide durch Ausziehen mit Natriumsulfitl?sung entfernt wurde, worauf der Rückstand als Merkurisulfid identifiziert werden konnte. In analoger Weise wie früher bei Kupfer- und Schwefelsol konnte gezeigt werden, da? auch hier die kolloiden Stoffe die Reaktionstr?ger sind. Die Umsetzung zwischen kolloidem Quecksilber und Schwefel verlief wesentlich weniger schnell als zwischen Kupfer und Schwefel. So konnte noch eine gewisse Zeit nach dem Zusammengeben der Sole trotz Anwendung eines überschusses an kolloidem Schwefel nicht gebundenes Quecksilber bzw. umgekehrt bei überschüssigem Quecksilber freier Schwefel nachgewiesen werden.     

Electrochemical Oxidation of Metolazone at a Glassy Carbon Electrode

Metolazone is a diuretic agent used in patients with edematous states and/or hypertension. The electrochemical behavior of metolazone on a glassy carbon electrode was investigated using cyclic, differential pulse, and square‐wave voltammetry at different pHs. The pH dependent oxidation of metolazone occurs in two consecutive steps in a diffusion‐controlled mechanism and involves the formation of a main oxidation product. The first oxidation process is reversible, and involves two electrons and two protons corresponding to the oxidation of nitrogen in the sulfonamide moiety. The second oxidation process is irreversible, also occurs in the sulfonamide moiety, involves a one electron‐transfer, and is followed by deprotonation to produce a cation radical, which reacts with water and yields a hydroxylated product. The diffusion coefficient of metolazone was calculated to be 3.43×10^?6 cm² s^?1 in pH 7.0 0.1 M phosphate buffer.     

Liquid chromatographic determination of maleic hydrazide in technical and formulated products: collaborative study

Fourteen collaborating laboratories assayed maleic hydrazide (MH), 6-hydroxypyridazin-3(2H)-one, in technical and formulated products by reversed-phase liquid chromatography (LC) with sulfanilic acid as an internal standard. The active MH in the samples (6 lots) ranged from 16% (expressed as the potassium salt) to 98% (MH in the technical). A small amount of 1 M KOH was added to the technical MH and analytical standards to create the potassium salt of the analyte which is soluble in water. Test samples and standards were extracted with water containing the internal standard before analysis by LC on a C8 column with an ion-pairing eluting solution and UV detection at 254 nm. The concentration of MH was calculated by comparing the peak area response ratios of the analyte and the internal standard with those in the analytical standard solution. Eleven laboratories weighed each test sample twice with single analysis. Three laboratories weighed each sample once and made duplicate injections on the LC system. The data were analyzed using the 11 laboratories' results. A second data analysis was done including all laboratory results using a Youden pair approach, selecting one of 2 duplicate assay values randomly for each laboratory and sample. In the first data analysis, the repeatability standard deviation ranged from 0.07 to 1.39%; reproducibility standard deviation ranged from 0.22 to 1.39%. In the second data analysis (using all laboratory data), repeatability standard deviation ranged from 0.09 to 0.86%; reproducibility standard deviation ranged from 0.22 to 1.31%.     

Tetrahelix conformations and transformation pathways in Pt1Pd12 clusters

The threshold method is used to explore the potential energy surface of the Pt(1)Pd(12) bimetallic cluster, defined by the Gupta semiempirical potential. A set of helical structures, which follow a Bernal tetrahelix pattern, correspond to local minima for the Pt(1)Pd(12) cluster, characterizing the region of the energy landscape where these structures are present. Both right-handed and left-handed chiral forms were discovered in our searches. Energetic and structural details of each of the tetrahelices are reported as well as the corresponding transition probabilities between these structures and with respect to the icosahedron-shaped global minimum structure via a disconnectivity graph analysis.     

Low-energy electron scattering with the purine bases of DNA/RNA using the R-matrix method

R-matrix calculations on electron collisions with the purine bases found in DNA and RNA (i.e., adenine and guanine) are presented. Resonant anion states of these systems are identified by employing different approximation levels of ab initio theoretical methods, such as the static exchange, the static exchange plus polarization, and the close-coupling methods. The results are compared with other available calculations and experiments. All of these ab initio approximations, which we refer to as a scattering "model," give four shape resonances of (2)A' (π) symmetry within the energy range of 10 eV for both molecules. For adenine, the most sophisticated method, the close-coupling model, gives two very narrow (2)A' (σ) symmetry Feshbach-type resonances at energies above 5 eV. Quantitative results for the total elastic and electronic excitation cross sections are also presented.     

Hydrolysis of the Peptide Bond in N-Acetylated L-Methionylglycine Catalyzed by Various Palladium(II) Complexes: Dependence of the Hydrolytic Reactions on the Nature of the Chelate Ligand in cis-[Pd( L)(H 2O) 2] 21 Complexes

Hydrolytic reactions between various palladium(II) complexes of the type cis-[Pd(L)(H₂O)₂]²⁺ in which L is ethylenediamine (en), 1,2-propylenediamine (1,2-pn), isobutylenediamine (ibn), 1,2-diaminocyclohexane (1,2-dach), N-methylethylenediamine (Meen), N,N,N,N-tetramethylethylenediamine (Me₄en), S-methyl L-cysteine (MeS-L-HCys), L-methionine (L-HMet), and 2,5-dithiahexane (dth) and dipeptide N-acetylated L-methionylglycine (MeCOMet-Gly) were studied by ¹H NMR spectroscopy. The reactions were carried out in the pH range 2.0–2.5 and at 50°C. In all these reactions, palladium(II) complex bound to a methionine residue effects the regioselective cleavage of the amide bond involving the carboxylic group of methionine. We found that the rate of hydrolysis and mechanism of this reaction are strongly dependent from the nature of the chelate ligand L in palladium(II) complexes of the type cis-[Pd(L)(H₂O)₂]²⁺.