Search results for "Radiation"

Die thermische Polymerisation von Methylmethacrylat, 1. Polymerisation in Substanz

1978

Special purification of the monomer and careful preparation of the reaction setup allowed a thorough study of the spontaneous thermal polymerization of methyl methacrylate over a wide range of temperatures (0–140°C). The rates of polymerization are notably lower than the few data previously reported in literature, and the degrees of polymerization slightly higher. The thermal initiation reaction is superimposed by radical production due to the natural ionising radiation (cosmic radiation etc.). This additional initiation becomes significant at temperatures below 60°C. New and more reliable monomer chain transfer constants are given.

Light Induced Modifications of Langmuir-Blodgett-Multilayer Assemblies Containing Amphotropic Azocopolymer

1994

Abstract Photochromic LB-multilayers of amphotropic copolymers having rod-like azobenzene moieties as side groups which exhibit thermotropic liquid crystalline behaviour in the bulk have been characterized by UV-VIS spectroscopy as well as by angular dependent and energy dispersive SAXS. Upon irradiation with UV-light the initial optical in-plane anisotropy and the vertical layered structure of LB-films can be destroyed. A new layered structure can be rebuilt on irradiation with visible light or by annealing. Using linearly polarized light for the irradiation an optical anisotropy (POA) has been induced or reversibly modified by a photoselection process.

Improved column-based radiochemical processing of the generator produced 68Ga.

2011

An improved chemical strategy for processing of the generator produced (68)Ga was developed based on processing of the original (68)Ge/(68)Ga generator eluate on a micro-column. Direct pre-concentration and purification of the eluted (68)Ga is performed on a cation-exchange resin in hydrochloric acid/acetone media. A supplementary step based on a second micro-column filled with a second resin allows direct re-adsorption of (68)Ga eluted from the cation exchanger. (68)Ga is finally striped from the second resin with a small volume of pure water. For this purpose a strong anion exchanger and a novel extraction chromatographic resin based on tetraalkyldiglycolamides are characterized. The stra…

Synthesis and labeling of a squaric acid containing PSMA-inhibitor coupled to AAZTA5 for versatile labeling with 44Sc, 64Cu, 68Ga and 177Lu

2020

Potentiometric studies on azido complexes of the aquodimethyltin(IV) cation in aqueous solution

1974

Summary Mono and polynuclear azide complexes of the aquodimethyltin(IV) cation have been studied in solution at [ClO 4 − ]=3.00 M , by e.m.f. measurements of [H + ], using the competitive reaction method. Throughout the entire range of data, 2.5≤−log[N 3 − ] free ≤4.9, the results are interpreted by assuming that the complexes {[(CH 3 ) 2 Sn] 3 [N 3 ] 3 } 3+ and [(CH 3 ) 2 Sn(N 3 ) 4 ] 2− predominate; the cumulative equilibrium constants for their formation are log β 33 =12.98±0.03 and log β 14 =2.45±0.02.

Optical absorption of zinc selenide doped with cobalt (Zn1−xCoxSe) under hydrostatic pressure

2000

Abstract The optical absorption of the diluted magnetic semiconductor Zn1−xCOxSe (x = 0.02) has been measured at room temperature under hydrostatic pressure up to 14GPa in a membrane diamond-anvil cell. We found two absorption features: (i) an absorption structure in the energy range 1.6−1.8eV, with a negligible pressure shift (i.e., 0.45 ± 0.05 meV/GPa) which we have identified as the Co2+(3d7) internal transition 4A2(F)→+4T1(P) and (ii) an onset in the energy range 2−2.7eV which redshifts with pressure (−8.1±0.6meV/GPa). We have attributed such absorption edge to charge transfer between the ZnSe valence band and the Co2+(3d7) levels.

Transferability of ASTM/NIST alanine–polyethylene recipe at ISS

2000

Abstract Alanine–polyethylene solid state dosimeters were prepared at Istituto Superiore di Sanita (ISS) following the recipe proposed by National Institute of Standards and Technology (NIST) with the goal of testing its transferability. Dosimeters were prepared using 95% alanine and 5% polyethylene, by weight. They are rugged and of increased sensitivity, repeatability and reproducibility as respect to the ISS alanine-paraffin pellets. Reproducibility of about 1% was obtained at 10 Gy and at 3 Gy if one single pellet or a stack of five dosimeters were used, respectively.

ChemInform Abstract: Green Conditions for the Suzuki Reaction Using Microwave Irradiation and a New HNT-Supported Ionic Liquid-Like Phase (HNT-SILLP)…

2014

Aryl iodides are coupled with conversions comparable to aryl bromides whereas conversions of aryl chlorides are significantly lower.

Synthesis and Electronic Spectra of Substitutedp-Distyrylbenzenes for the Use in Light-Emitting Diodes

2000

The influence of substitution on the absorption and Luminescence spectra of oligo(phenylenevinylene)s has been studied using distyrylbenzene (DSB) as a model compound. The degree, character, and pattern of substitution was varied systematically, altering the electronic properties of the DSB, the wavelength of the emitted light could be tuned over a range of 100 nm. The syntheses of 6b—h were performed by twofold Wittig Horner-olefinations of bisphoshonates 1a, b with substituted benzaldehydes 2a—i, 6ivia Heck-reaction of the dibromosulfonylbenzene 3, 6k by Siegrist-reaction of 4 with N-phenylbenzaldimine and the Knoevenagel-reaction of benzyl cyanide with 5 led to 6l.

Evaluation of remote sensing of vegetation fluorescence by the analysis of diurnal cycles

2008

Chlorophyll fluorescence (ChF) emission is a direct indicator of the photosynthetic activity of vegetation, which is a key parameter of the carbon cycle. This paper analyses chlorophyll fluorescence evolution at leaf level during a complete diurnal cycle in simulated and natural conditions, for two species under different stress conditions. Absolute spectral radiance of the ChF emission is obtained allowing a quantitative derivation of the fluorescence yield of the ChF, which correlates well with established fluorescence instruments. The studied cases show that the ChF emission is mainly driven by the photosynthetic active radiation during the whole cycle, but the fluorescence yield is seve…