The Internal Bremsstrahlung following the Electron Capture decay of55Fe

The Internal Bremsstrahlung Electron Capture spectrum from⁵⁵Fe was measured with a HPGe detector. The total spectrum was unfolded taking into account the secondary detection effects and agrees with Glauber and Martin calculations. The measured intensity relative to K capture in the range 35 to 231 keV is 3.24(6)·10^?5 while the calculated one is 3.20·10^?5. TheQ value for the electron capture was deduced as 230.7(19) keV.     

Synthesis of novel imidazo[1,2-a][3,1]benzothiazines 4, imidazo[1,2-a]-[1,2,4]benzotriazines 5, and 4H-imidazo[2,3-c]pyrido[2,3-e][1,4]oxazines 6

Starting from the readily available 2-aminobenzhydrols ( 7 ), 3-amino-1,2,4-benzotriazine ( 11 ) and 2-amino-3-pyridinol ( 12 ), novel derivatives of 5-phenyl-5H-imidazo[1,2-a][3,1]benzothiazine-2-carboxylic acid, ethyl ester ( 4 ), imidazo[2,1-c][1,2,4]benzotriazine-2-carboxylic acid, ethyl ester ( 5 ) and 4H-imidazo[2,3-c]pyrido-[2,3-e][1,4]oxazine ( 6 ) were prepared.     

Comparative Action Spectrum for Ultraviolet Light Killing of Mouse Melanocytes from Different Genetic Coat Color Backgrounds

The photobiology of mouse melanocyte lines with different pigment genotypes was studied by measuring colony-forming ability after irradiation. The cell lines were wild-type black (melan-a) and the mutants brown (melan-b) and albino (melan-c). Four lamps emitting various UV wavelengths were used. These were germicidal (UVC, 200–280 Dm), 82.3% output at 254 nm, TL01 (UVB, 280–320 nm), 64.2% at 310–311 nm, FS20, broadband with peak output at 312 nm and Alisun-S (UVA, 320–400 nm), broadband with peak output at 350–354 nm. Appropriate filtration reduced the contaminating UVC to nonlethal levels for the longer waverange lamps. Wild-type melan-a was resistant to UVC and UVA compared to the other two cell lines, but the differences were small. The melan-c cell line was more resistant to UVB and markedly more resistant to FS20 than the pigmented lines. With the exception of FS20 responses, melan-b was more sensitive than melan-a to killing by the various UV lamps. There were more pyrimidine dimers (cyclobutane dimers and 6–4 photoproducts) produced in melan-a than in melan-c cells by UVC, UVB and FS20 lamps. Unlike melan-c, melan-a and melan-b showed a strong free radical signal of melanin character with a detectable contribution of pheomelanin-like centers. The contribution of pheome-lanin was higher in melan-b than in melan-a, while the total melanin content in these two cell lines was comparable. The abundant melanin granules of wild-type melan-a melanocytes were well melanized and ellipsoidal, whereas those of melan-b melanocytes tended to be spherical. In the albino line (melan-c) the melanocytes contained only early-stage melanosomes, all of which were devoid of melanin. The results indicate that pigment does not protect against direct effect DNA damage in the form of pyrimidine dimers nor does it necessarily protect against cell death. High pigment content is not very protective against killing by UVC and UVA, and it may photosensitize in UVB the very wavelength range that is of greatest concern with respect to the rising incidence in skin cancer, especially melanoma. It is clear from these studies that, in pigment cells, monochromatic results cannot predict polychromatic responses and that cell death from solar irradiations is a complex phenomenon that depends on more than DNA damage.     

Possible production of O2(1Δg) and O2(1Σ+g) in the reaction of NO with O3

High-resolution spectra of the NO₂ continuum emission produced from the reaction NO + O₃ → NO₂ + O₂ have been investigated to detect any possible emission from O₂(¹Δ_g) at 1270 nm or O₂(¹Σ⁺_g) at 762 nm. The photolysis of O₃/O₂ mixtures at 253.7 nm, which produces both states of O₂ with known quantum efficiency, has been used as an internal standard. From the results it is concluded that less than 1/300 and 1/200 of the NO + O₃ reactive collissions result in production of O₂(¹Δ_g) or O₂(¹Σ⁺_g), respectively, at room temperature.     

Ascorbinometrische Bromatbestimmung

Zusammenfassung In schwach saurer (0,2–0,5 n)-Lösung sind Bromate in Anwesenheit von seleniger Säure als Katalysator mit Ascorbinsäure bestimmbar. Man fügt zur Lösung HgCl₂, welches die entstehenden Bromide in einer wenig dissoziierten Komplexform bindet und den Endpunkt der Titration durch Kalomelausscheidung kenntlich macht. Setzt man MnSO₄ zur Lösung und beendet die Titration langsam, so vermeidet man eine Übertitration. Die Bestimmung ist bei Zimmertemperatur durchzuführen. Die störende Wirkung fremder Salze wurde untersucht.     

Increase in isotopic selectivity with pressure in the multiphoton infrared decomposition of CF3Br

The C-13 isotopic selectivity in the multiphoton decomposition of CF₃Br has been shown to increase with increasing pressure of substrate for photolysis far to the red of the resonant, low intensity absorption band using relatively low fluence radiation. However, the quantum efficiency would appear to decrease as pressure is increased.     

Retention and Thermodynamic Studies of Piperazine Diastereomers in Reversed-Phase Liquid Chromatography

The effect of organic modifier concentration on retention and selectivity of two piperazine diastereomers in a typical n-octadecyl-bonded silica (ODS) column was investigated at pH 6.4 and pH 3.0 using phosphate-buffered acetonitrile (MeCN/H₂O) and methanol (MeOH/H₂O) mobile phases. The results show the logarithmic retention factors decrease with increasing organic concentration in a less rectilinear fashion in the MeCN/H₂O system than in the MeOH/H₂O system at high organic concentrations at both pHs. At pH 6.4, the MeOH/H₂O system provided significantly higher diastereomer selectivity than the MeCN/H₂O system, which can be ascribed to the hydrogen bonding interaction of methanol (as a hydrogen donor) with the piperazine amine moiety of the solute (as a hydrogen acceptor). At pH 3.0, both mobile phases provided high selectivity, in which both acetonitrile and methanol acted as hydrogen acceptors, while the protonated amine acted as the hydrogen donor. The effect of temperature on retention and selectivity was also studied in the two mobile phase systems at both pHs. It was found that at pH 6.4 the retention and selectivity were enthalpically driven in the MeOH/H₂O system, while entropically driven in the MeCN/H₂O system. However, the retention was entropically driven and the selectivity enthalpically driven in both systems at pH 3.0. Locally preferential solvating and hydrogen bonding effects are proposed to explain the anomalous retention and selectivity behaviors.     

Nanotube brushes: polystyrene grafted covalently on CNx nanotubes by nitroxide-mediated radical polymerization

Polymer brushes consisting of polystyrene (PS) chains bonded covalently to N-doped multiwalled carbon nanotubes (CNx) were synthesized by a "grafting from" route using nitroxide mediated radical polymerization (NMRP).