Über Differentialoperatoren undD-Moduln in positiver Charakteristik

This paper is about differential operators andD-modules on a smooth variety over a field of positive characteristic. Beside some generalities the main results are theD-affinity of the projective space, theD-quasi-affinity of the ordinary flag manifolds (G/B) and theD-affinity of the ordinary flag manifold of Sl₃. In contrast to characteristic 0 generally there exists some non-vanishing higher cohomology group of the associated graded algebra gr(D) on an ordinary flag manifold.     

Electrons from target and projectile ionization in simple collision systems

Summary Absolute double differential cross-sections for target ionization and projectile electron loss were determined in collisions of H⁺, H₂ ⁺,³He⁺ and³He⁺⁺ ions (0.4 to 2.0 Me V/u) with He and Ar gas targets at electron emission angles from 0° up to 60°. The experimental results are qualitatively well described by plane-wave Born approximations including screening of the projectile in target ionization and of the target atom in the case of electron loss.

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Riassunto Sono state determinate le sezioni d’urto doppie differenziali assolute per la ionizzazione del bersaglio e la perdita dell’elettrone proiettile in collisioni di ioni H⁺, H ₂ ⁺ ,³He⁺ e³He⁺⁺ (da 0.4 a 2.0 Me V/u) con bersagli di gas He e Ar ad angoli di emissione degli elettroni da 0° a 60°. I risultati sperimentali sono qualitativamente ben descritti dalle approssimazioni di Born per onde piane che comprendono la schermatura del proiettile nella ionizzazione del bersaglio e dell’atomo bersaglio nel caso di perdita dell’elettrone.

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Резюме Определяются абсолютные дважды дифференшиальные поперечные сечения для ионизации мишени и потери электровов налетающими частишами при соударениях ионов H⁺, H ₂ ⁺ ,³He⁺ и³He⁺⁺ (от 0.4 до 2.0 Me V/u) в случае газовых Не и Ar мишеней при углах эмиссии электронов от 0° до 60°. Экспериментальные результаты качественно хорощо описываются с помощью плоско-волнового борновского приближения, включая экранирование налетающей частицы при ионизации мишени в случае потери электрона.

     

Competitive Intramolecular Aryl‐ and Alkyl‐C?H Bond Activation and Ligand Evaporation from Gaseous Bisimino Complexes [Pt(L)(CH3)((CH3)2S)]+ (L=C6H5NC(CH3)?C(CH3)NC6H5)

Mechanistic details for the formation of methane from the title compound as well as the combined elimination of (CH₃)₂S/CH₄ are derived from various mass‐spectrometric experiments including deuterium‐labeling studies and DFT calculations. For the first process, i.e., methane formation, we have identified three competing pathways in which the intact, Pt‐bonded methyl group combines with a H‐atom that originates from a phenyl substituent (ca. 7%), the dimethyl sulfide ligand (ca. 41%), and a methyl group of the diazabutadiene backbone (ca. 52%). In contrast, in the combined (CH₃)₂S/CH₄ elimination, the methane is specifically formed from the Pt‐bound CH₃ group and a H‐atom provided by one of the phenyl groups (‘cyclometalation’).     

Targeted analysis of protein citrullination using chemical modification and tandem mass spectrometry

Protein citrullination originates from enzymatic deimination of polypeptide‐bound arginine and is involved in various biological processes during health and disease. However, tools required for a detailed and targeted proteomic analysis of citrullinated proteins in situ, including their citrullination sites, are limited. A widely used technique for detection of citrullinated proteins relies on antibody staining after specific derivatization of citrulline residues by 2,3‐butanedione and antipyrine. We have recently reported on the details of this reaction. Here, we show that this chemical modification can be utilized to specifically detect and identify citrullinated peptides and their citrullination sites by liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. Using model compounds, we demonstrate that in collision‐induced dissociation (CID) a specific, modification‐derived fragment ion appears as the dominating signal at m/z 201.1 in the MS/MS spectra. When applying electron transfer dissociation (ETD), however, the chemical modification of citrulline remained intact and extensive sequence coverage allowed identification of peptides and their citrullination sites. Therefore, LC/MS/MS analysis with alternating CID and ETD has been performed, using CID for specific, signature ion‐based detection of derivatized citrullinated peptides and ETD for sequence determination. The usefulness of this targeted analysis was demonstrated by identifying citrullination sites in myelin basic protein deiminated in vitro. Combining antibody‐based enrichment of chemically modified citrulline‐containing peptides with specific mass spectrometric detection will increase the potential of such a targeted analysis of protein citrullination in the future. Copyright © 2009 John Wiley & Sons, Ltd.     

Interior of nonuniform black strings

We consider nonuniform black strings inside their event horizon. We present numerical evidence, that the singularity touches the horizon as the horizon topology changing transition is reached.     

Selenium(IV) fluoride and oxofluoride anions

The [((C₆H₅)₃P)₂N]⁺, [(C₆H₅)₄P]⁺ and [N(CH₃)₄]⁺ salts of SeF₅⁻, SeF₆²⁻ and SeOF₃⁻ and CsSeO₂F were prepared and characterized. Crystal structures were obtained for [((C₆H₅)₃P)₂N][SeF₅] and [((C₆H₅)₃P)₂N][SeOF₃] CH₂Cl₂. In contrast to oxygen-bridged dimeric TeOF₃⁻, the SeOF₃⁻ anion in [((C₆H₅)₃P)₂N][SeOF₃] CH₂Cl₂ is monomeric and represents the first experimentally well determined molecular structure of a monomeric trifluoro-chalcogenite anion. Similarly, [((C₆H₅)₃P)₂N][SeF₅] represents the first example of a structure containing a well-isolated undistorted SeF₅⁻ anion. The NMR and the vibrational spectra and their assignments were re-examined and corrected by comparison with high-level theoretical calculations. Whereas the previously published normal coordinate analysis of SeF₅⁻ is correct, that for SeOF₃⁻ needs major revision.