Formation of fast exotic atoms by radiative Coulomb capture

Interesting surprises in some exotic atom kinetics have been reported recently. These involve muonic atom transfer cross sections, nuclear pion capture and theq 1s effect in CF. These can be explained if the exotic atom population contains a contributing fast component. Such fast atoms can be formed by radiative continuum to bound transitions of fast (keV) muons or pions. Cross sections for formation of such fast pionic and muonic atoms and their velocity distributions are reported. The possibility of these processes competing with the thermalisation channels and contributing effectively to the exotic atom population is discussed.     

Thermodynamic Studies on Amino Acid Solvation in Aqueous Urea

The present paper discusses the behaviour of transfer free energy of some amino acids from water to 4M, 6M and 8M aqueous urea. Dissection of transfer free energy into cavity term, interaction term and electrical term reveals that cavity forming free energy of transfer ΔG⁰_t (cav) plays an important role in dictating actual interaction of amino acids in aqueous urea. Cavity forming free energy of transfer has been estimated by using Scaled Particle Theory (SPT).     

Structure d'alcaloïdes indoliques doubles d'un type nouveau

The Structure of bis-indoline alkaloids of a novel type The structure of folicangine 4 , a bis-indoline alkaloid from the leaves of Voacanga africana, is obtained by correlation with voafolidine 3a and isovoafolidine 3b . It requires an ether bridge between the two parts of the molecule, as in subsessiline (amataine 5a ). Subsessiline-lactone, from the leaves of Voacanga thouarsii has structure 5b proved by correlation with 5a . The CD. curves of double-indole alkaloids of vobtusine type are given (Table 3).     

Radiation detection by using superheated droplets

The superheated emulsion, a radiation detector consisting of superheated droplets dispersed in a gel or a solid matrix, has been in use for some time now. It was initially designed to detect neutrons but also has been modified to detect energetic photons and heavy ions. It has been primarily used as a neutron dosimeter, but has also been used to obtain the energy spectrum for neutrons from Am–Be. The general features of the superheated emulsion detector along with newer analytic methods to obtain more precise results using it as an active device will be presented.     

Spectrophotometric determination of beryllium with chromotropic acid azo dyes of the pyridine series

Summary Beryllium forms coloured complexes with azo dyes of the pyridine series e. g. 2-(pyridyl-2-azo)-chromotropic acid (A), 2-(pyridyl-3-azo)-chromotropic acid (B) and 2-(2-carboxy pyridyl-3-azo)-chromotropic acid (C). The latter two reagents react with aluminium also, but beryllium can be estimated in the presence of large excess of aluminium only with A.At pH 6.5, the colour systems formed show maximum absorptions at 580 nm with A and at 590 nm with B and C and obey Beer's law with optimum ranges of beryllium from 0.5 to 2.0 ppm with A, from 0.2 to 0.8 ppm with B and 0.3 to 2.0 ppm with C. The metal forms a 1:3 complex with A, a 12 complex with B and a 32 complex with C, with instability constants of the order of 10^–13, 10^–9 and 10^–17, respectively.

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Zusammenfassung Im Hinblick auf die spektrophotometrische Berylliumbestimmung wurden drei verschiedene Farbkomplexe untersucht, die Be mit Azofarbstoffen der Pyridinreihe bildet, nämlich mit 2-(Pyridyl-2-azo)-chromotropsäure (A), 2-(Pyridyl-3-azo)-chromotropsäure (B) und 2-(2-Carboxy-pyridyl-3-azo)-chromotropsäure (C). B und C reagieren auch mit Aluminium, jedoch kann Beryllium neben großen Mengen Al mit Reagens A bestimmt werden. Bei pH 6,5 liegen die Absorptionsmaxima bei 580 nm (A) bzw. 590 nm (B, C). Das Beersche Gesetz wird von 0,5 bis 2,0 ppm (A) bzw. 0,2–0,8 ppm (B) bzw. 0,3–2,0 ppm (C) befolgt. Die Zusammensetzung des Komplexes (Be: Reagens) beträgt 13, 12 bzw. 32; die Instabilitätskonstanten sind in der Größenordnung 10^–13, 10^–9 bzw. 10^–17 (für A, B, C).

     

Effect of hydrogen bonding on the titration curves of some phenolic copolymers

Summary p-aminobenzoic acid, p-hydroxy benzoic acid and formaldehyde were condensed in the presence of acid catalyst. The linear product (copolymer) thus obtained was then separated into five fractions by fractional precipitation method. These fractions were titrated in nonaqueous solvents by potentiometric and conductometric methods with sodium methoxide as titrant base. The titration curves showed several interesting features which could be correlated with intramolecular hydrogen bonding and DP of the various fractions.With 5 figures and 1 table     

Central limit theorem for first-passage percolation time across thin cylinders

We prove that first-passage percolation times across thin cylinders of the form [0, n] × [?h _n , h _n ] ^d-1 obey Gaussian central limit theorems as long as h _n grows slower than n ^1/(d+1). It is an open question as to what is the fastest that h _n can grow so that a Gaussian CLT still holds. Under the natural but unproven assumption about existence of fluctuation and transversal exponents, and strict convexity of the limiting shape in the direction of (1, 0, . . . , 0), we prove that in dimensions 2 and 3 the CLT holds all the way up to the height of the unrestricted geodesic. We also provide some numerical evidence in support of the conjecture in dimension 2.     

Photophysical Properties of 7‐(diethylamino)Coumarin‐3‐carboxylic Acid in the Nanocage of Cyclodextrins and in Different Solvents and Solvent Mixtures

The photophysical properties of 7‐(diethylamino) coumarin‐3‐carboxylic acid (7‐DCCA) were studied in cyclodextrins (α, β, γ,‐CDs), different neat solvents and solvent mixtures by using steady state absorption, emission and time‐resolved fluorescence spectroscopy. We have observed that with gradual increase in concentration of β‐CD the fluorescence quantum yield and lifetime decreased in a regular pattern whereas with gradual increase in concentration of γ‐CD the fluorescence quantum yield and lifetime gradually increased. With addition of urea, the fluorescence quantum yield and lifetime of 7‐DCCA in CDs increased. Binding constant calculation shows that 7‐DDCA forms 1:1 complex with β‐CD and with γ‐CD it forms 1:1 and 1:2 (guest:host) inclusion complex. We proposed that the dye molecule formed capping complex with β‐CD by means of hydrogen bonding and after addition of urea the hydrogen bonding network broke down and part of dye molecule entered inside the cavity of β‐CD. The photophysics of 7‐DCCA was studied in dioxane‐water mixture and ethylene glycol‐acetonitrile mixture to know the effect of polarity and viscosity of the media. The photophysics of 7‐DCCA was also studied in different neat solvents. It was found that the photophysics of 7‐DCCA depended on the structural feature of the solvents and solvent mixtures.