Intramolecular transfer reactions induced by electron-impact. Transsulfonations and transmethylations in polymethylene glycol dimethanesulfonates

The dimethanesulfonate esters of polymethylene glycols undergo three types of double-group transfer reactions as a result of electron-impact mass spectrometry: 1. Transfer of a hydrogen and one methanesulfonate group to the second methanesulfonate with cleavage to yield a protonated methanesulfonic acid anhydride. 2. Transfer of two hydrogens to a methanesulfonate group with cleavage to yield a protonated methanesulfonic acid. 3. Transfer of a hydrogen and a methyl group to the second methanesulfonate with cleavage to yield a protonated methyl methanesulfonate. Bicyclic transition states are proposed for these reactions.     

Simultaneous attainment of high electron and ion temperatures in discharges with internal transport barriers in ASDEX upgrade

Internal transport barriers have been demonstrated to exist also under conditions with T(e) approximately T(i) approximately 10 keV and predominant electron heating of the tokamak core region. Central electron cyclotron heating was added to neutral beam injection-heated ASDEX Upgrade discharges with a preexisting internal transport barrier, established through programmed current ramping leading to shear reversal. Compared to a reference internal transport barrier discharge without electron cyclotron resonance heating, the electron heat conductivity in the barrier region was found not to increase, in spite of a fivefold increase in electron heat flux, and also angular momentum and ion energy transport did not deteriorate.     

Chirality and helix stability of polyglutamic acid enantiomers

In this work the chirality and the relative thermal stability of ordered micellar aggregates of poly-L- and poly-D-glutamic acids with the cationic surfactant C14TAB is examined. The complexed mesophases poly-L-Glu/C14TAB and poly-d-Glu/C14TAB were characterized by circular dichroism (CD) in the temperature range 10-70 degrees C for their chirality and thermal stability as well as by X-ray diffraction (XRD) for the micellar ordered structure. Low angle XRD analysis showed that both micellar aggregates poly-L-Glu/C14TAB and poly-D-Glu/C14TAB are hexagonally packed in a MCM-41 fashion with an intermicellar distance identical and equal to 3.55+/-0.10 nm. The CD spectra indicated that both complexes poly-L-Glu/C14TAB and poly-D-Glu/C14TAB possess a mainly alpha-helix structure and are exact mirror images to each other. The same mirror images and a mainly alpha-helix configuration were also observed by CD for the free poly-l- and poly-d-glutamic acids at room temperature. As the temperature increases from 10 up to 70 degrees C the alpha-helix of the poly-l-glutamic acid is gradually transformed to a mixture containing increased amounts of the 3(10)-helix while the alpha-helix structure of the poly-d-glutamic acid is constantly degenerated. In contrast the alpha-helices of the corresponding complexes poly-L-Glu/C14TAB and poly-d-Glu/C14TAB are degenerated upon heating without appreciable increase of the 3(10)-helices as an intermediate configuration. This difference in helix conservation is attributed to increase protection of the l-enantiomers, compared to d-enantiomers, which might be related to the survival of l-aminoacids in the living world.     

Perspectives from above and beyond the proton drip-line

This paper will review the dramatic increase in our knowledge of one and two proton unbound nuclei [1] such as recoil decay tagging [2] are revealing unique insights into the structure of nuclei beyond the proton drip-line. These studies of excited states provide complementary information to proton radioactivity studies, particularly regarding the role of deformation [3]. Radioactive beams are being used to study two-proton unbound resonances and to study explosive nuclear astrophysical reactions in the region of the proton drip-line.     

Synthesis of highly loaded Cu/Ce mesoporous silica. Active catalyst for the simultaneous reduction of SO2 and NO with CO

We report the synthesis of a thermally stable, highly loaded (15 wt.%) Cu/Ce bimetallic mesoporous silica with high surface area and metal dispersion, which was the first template assisted mesoporous network successfully tested for the simultaneous reduction of SO2 and NO with CO, achieving complete conversion of the reactants to elemental sulfur and N2 at high space velocity 32,000 h(-1).     

On the correlation between the mean electronegativities of phosphates and their asymmetric P?O?P stretching frequencies

The frequency of P–O–P asymmetric stretching vibration in tri- and tetra-metaphosphate salts is correlated with the mean electronegativity of the structure. A qualitative explanation for this phenomenon is discussed.

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P–O–P - . .

     

The activity patterns of the rare earth oxides in heterogeneous catalysis

The catalytic activity of rare earth oxides for simple catalytic reactions show patterns which broadly resemble each other and also reactions in which the number of 4f-electrons changes. If simple concepts of electron transfer are augmented, it emerges that any rate controlling step which involves the adsorption of a species by electron transfer to it, leads to an activity pattern with maxima for f⁰ and f⁷ and f¹⁴ structures.

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, , 4f-. , , , , f¹ f⁸ f⁰, f⁷ f¹⁴ .