Der disperse Bau der festen Systeme und seine thermodynamische Begründung,XIV

Zusammenfassung Es wurden in dieser Arbeit meine Vorstellungen über das Wesen des Verlaufs der Reaktionen im festen Zustande experimentell best?tigt. Diese Best?tigung stellt neue Beweise der Grundlage meiner Theorie über den Bau der Realkristallsysteme dar. Deutsch bearbeitet von K. Hoffmann (Leipzig).     

Die Grenzen der Kossel'schen Theorie des Kristallwachstums

Zusammenfassung Kurze erneute Hinweise auf die Widersprüche zwischen der Kossel'schen Idealtheorie des Kristallwachstums und der Realtheorie des Verfassers.     

Infrared-spectroscopic detection and distinction of indium cations of different oxidation states in zeolites

In⁺ cations introduced by reductive solid-state ion exchange into zeolites (Y, ZSM-5, mordenite) and cationic InO⁺ species created by oxidation of the incorporated univalent cations were found to be detectable and distinguishable by IR spectroscopy using pyridine as probe molecule. Relatively weak interactions of In⁺ lattice cations with pyridine give rise, after degassing at temperatures not higher than 370 K, to typical bands at 1446 and 1599 cm⁻¹. After oxidation to InO⁺, these bands are shifted to 1452 and 1610 cm⁻¹, being significantly more resistant towards degassing. Because of restrictions in the accessibility of InO⁺ to pyridine, the respective bands are absent in the spectra of mordenite.     

Structure and properties of non-classical polymers II. Band structure and spin densities

Theoretical investigation of the band structure of three types of nonclassical polymers, namely alternant (one- and two-dimensional), nonalternant and heteroatomic, are carried out. Although polyradicals, these polymers have a considerable delocalization energy which may determine their relative stability.The spin-density distribution of the alternant type of non-classical polymers corresponds to a ferrimagnetic ground state at 0 K.The non-classical polymers represent a new class of organic systems as their band structure and magnetic properties essentially differ from those of common polymers.     

Functional oropharyngeal sensory disruption interferes with the cortical control of swallowing

Background  

Sensory input is crucial to the initiation and modulation of swallowing. From a clinical point of view, oropharyngeal sensory deficits have been shown to be an important cause of dysphagia and aspiration in stroke patients. In the present study we therefore investigated effects of functional oropharyngeal disruption on the cortical control of swallowing. We employed whole-head MEG to study cortical activity during self-paced volitional swallowing with and without topical oropharyngeal anesthesia in ten healthy subjects. A simple swallowing screening-test confirmed that anesthesia caused swallowing difficulties with decreased swallowing speed and reduced volume per swallow in all subjects investigated. Data were analyzed by means of synthetic aperture magnetometry (SAM) and the group analysis of the individual SAM data was performed using a permutation test.     

Derivatives of 3-thienylphosphonic acid and 1,2-oxaphosphol-3-ene

Alkylsulfenyl chlorides react with 5-methyl-1,3,4-hexatrienyl-3-phosphonic esters giving derivatives of 3-thienylphosphonic acid and 1,2-oxaphosphol-3-ene.     

An RP-LC-UV-TWIMS-HRMS and Chemometric Approach to Differentiate between Momordica balsamina Chemotypes from Three Different Geographical Locations in Limpopo Province of South Africa

Momordica balsamina leaf extracts originating from three different geographical locations were analyzed using reversed-phase liquid chromatography (RP-LC) coupled to travelling wave ion mobility (TWIMS) and high-resolution mass spectrometry (HRMS) in conjunction with chemometric analysis to differentiate between potential chemotypes. Furthermore, the cytotoxicity of the three individual chemotypes was evaluated using HT-29 colon cancer cells. A total of 11 molecular species including three flavonol glycosides, five cucurbitane-type triterpenoid aglycones and three glycosidic cucurbitane-type triterpenoids were identified. The cucurbitane-type triterpenoid aglycones were detected in the positive ionization mode following dehydration [M + H − H₂O]⁺ of the parent compound, whereas the cucurbitane-type triterpenoid glycosides were primarily identified following adduct formation with ammonia [M + NH₄]⁺. The principle component analysis (PCA) loadings plot and a variable influence on projection (VIP) analysis revealed that the isomeric pair balsaminol E and/or karavilagen E was the key molecular species contributing to the distinction between geographical samples. Ultimately, based on statistical analysis, it is hypothesized that balsaminol E and/or karavilagen E are likely responsible for the cytotoxic effects in HT-29 cells.     

Effect of tetraalkylammonium salts on the tacticity of poly(methyl methacrylate), 2.. Initiation by potassium tert-butoxide

The anionic polymerization of methyl methacrylate was carried out in the presence of potassium tert-butoxide (t-BuOK)/quaternary ammonium salts (QAS) in toluene and tetrahydrofuran at −60°C. It was found that in toluene some QAS additives substantially increase the syndiotacticity of poly(methyl methacrylate). Two types of QAS were distinguished, quite different in their action. The addition of QAS with one or two longchain alkyl groups (>C₁₂), does not change significantly the mode of the monomer addition, whereas the polymerization in the presence of tetraalkylammonium salts with four equal substituents and dimethyldidodecylammonium bromide yields predominantly a syndiotactic polymer with high conversion and comparatively low polydispersity (M̄_w/M̄_w = 1.3−1.5). In some cases QAS additives are more effective modifiers than cryptand [2.2.2].     

Effect of tetraalkylammonium salts on the tacticity of poly(methyl methacrylate), 1. Initiation by ethyl α-lithioisobutyrate

The anionic polymerization of methyl methacrylate (MMA) was carried out in the presence of ethyl α-lithioisobutyrate (α-LiEtIB)/quaternary ammonium salts (QAS) in toluene and tetrahydrofuran/toluene (vol. ratio 75/25) at −60°C. It was found that the tacticity of PMMA strongly depends on size and shape of QAS. A highly isotactic polymerization in toluene was observed, when using the system α-LiEtIB/trimethylhexadecylammonium bromide. The initiator system α-LiEtIB/tetrahexylammonium chloride produces polymers with a high (>50%) syndiotactic content and relatively low polydispersity. The influence of QAS on the mode of polymerization is due to specific salt effect resulting from the cation exchange reaction, from the participation of the bulky substituent in the primary solvation shell, and ionic aggregation between the growing anion, Q⁺ and LiX.