Direct and β-delayed multi-proton emission from atomic nuclei with a time projection chamber: the cases of 43Cr, 45Fe, and 51Ni

The two-proton radioactivity of ⁴⁵Fe was studied experimentally with a time projection chamber. The aim of the experiment was the reconstruction of the proton tracks in three dimensions. Energy and angular correlations have been determined and the data are compared with theoretical models, in particular with a three-body model. Moreover, the decay of ⁴³Cr was studied and ??-delayed one-, two- and three-proton emission could be established. The correlations observed for ??-delayed two-proton emission favour a sequential emission. Finally, ??-delayed two-proton emission was observed for the first time for ⁵¹Ni.     

On the relative roles of higher-order nonlinearity and ionization in ultrafast light-matter interactions

Far off-resonant ultrafast and nonlinear light-matter interactions are studied using a one-dimensional atomic model. Results from a pump-probe diagnostic reveal that any higher-order nonlinear refraction is masked by ionization-induced defocusing before it becomes significant. On the other hand, we show that signatures of a higher-order nonlinearity may still be manifest via low-order harmonics of the pump center frequency. Implications for filamentation of femtosecond pulses are pointed out.     

Porous three-dimensional nanorod arrays through selective chemical etching of nanocomposites

Three-dimensional Cu-Si and Cu-SiO(2) nanorod arrays containing ~68 at% Cu have been fabricated by a glancing angle co-deposition technique. By selectively etching Cu in 0.05 M KCN methanol solution, porous nanorods with different shapes form, which are promising for applications in sensors, catalysts, and as medical capsules that are able to be loaded with functional materials.     

Nonclassical oxygen atom transfer reactions of oxomolybdenum(VI) bis(catecholate)

Mechanistic studies indicate that the oxomolybdenum(vi) bis(3,5-di-tert-butylcatecholate) fragment deoxygenates pyridine-N-oxides in a reaction where the oxygen is delivered to molybdenum but the electrons for substrate reduction are drawn from the bound catecholate ligands, forming 3,5-di-tert-butyl-1,2-benzoquinone.     

Probing the functional limits of the norepinephrine transporter with self-reporting, fluorescent stilbazolium dimers

A series of stilbazolium dimers were synthesized and investigated as sterically demanding ligands targeting the norepinephrine transporter (NET). The environmentally sensitive fluorescence of the dyes enables their use as self-reporting ligands; binding to and displacement from NET can be monitored by fluorescence microscopy.     

Cu(II)-promoted methanolysis of N,N-dipicolylacetamide. multistep activation by decoupling of > ̈̈N-C═O resonance via Cu(II)-N binding, delivery of the Cu(II):((-)OCH3) nucleophile, and metal ion assistance of the departure of the leaving group

The methanolysis of the Cu(II) complex of N-acetyl-N,N-bis(2-picolyl)amine (2) was investigated by a kinetic study as a function of pH in methanol at 25 °C and computationally by DFT calculations. The active species is the basic form of the complex (3(-)), or (1:Cu(II))((-)OCH(3))(HOCH(3))), and the rate constant for its solvolysis is k(max) = 1.5 × 10(-4) s(-1). The mechanism involves Cu(II) binding to the amide N lone pair, decoupling it from >N-C═O resonance, concomitant with Cu(II):((-)OCH(3)) delivery to the adjacent >N-C═O unit, followed by Cu(II)-assisted departure of the N,N-bis(2-picolyl)amide from a tetrahedral intermediate.     

Singer's Formant in Sopranos: Fact or Fiction?

Although it is generally agreed that the singer's formant (F_S) is a prerequisite for successful stage performance, the results of this research do not support its presence in the soprano voices of trained female singers. Results are based on a recent investigation testing 10 advanced/professional sopranos in two groups singing sustained vowels at three frequencies: high (932 Hz), mid (622 Hz), and low (261 Hz). Spectrographic analysis shows that the nature of harmonic energy varies in relation to pitch. A resonance band somewhat resembling the tenor F_S was usually evident in vowels sung at low and mid pitch. However, unlike the F_S of typically less than 1 kHz bandwidth associated with tenors, sopranos singing similar pitches produced corresponding bandwidths which were significantly broader, usually at least 2-kHz wide. Vowels sung by sopranos at high-pitch levels exhibited strong fundamental frequency production with strong reinforcement of adjacent harmonics extending to 5 kHz and beyond. This type of production in essence nullifies the necessity for a typical F_S. Absence of the F_S in strong soprano voices might also imply the adaptation of a sufficiently different overall vocal tract configuration, so that techniques geared to developing maximal projection should not be the same as those developed to maximize the F_S in other voices.     

On the C-16 configuration of sitsirikine

The indole alkaloid sitsirikine has been synthesised by a biomimetic conversion of strictosidine and its C-16 configuration established as R by cyclisation to a 16,17-dihydroheteroyohimbine.     

Facile synthesis of unsymmetrical benzotetrathiafulvalenes via cleavage of the corresponding hexathioorthooxalates

Unsymmetrical hexathioorthooxalates of types ($\text{1}$) and ($\text{2}$) undergo elimination of dialkyl disulfide on heating in an organic solvent; the reaction, which is catalyzed by acid, proceeds without fission of the central C:C bond and provides the first general, high yield synthesis of unsymmetrical benzotetrathiafulvalenes of types ($\text{3}$) and ($\text{4}$).