Surface energy and surface area measurements by 19F MAS NMR of adsorbed trifluoroacetic acid

Trifluoroacetic acid, when adsorbed on the surface of inorganic materials, is a useful (19)F NMR probe molecule for studying surface properties including surface energy and surface area.     

Novel type of isoprenoid membrane anchors: an investigation of binding properties with dipalmitoylphosphatidylcholine vesicles

In this work, we present a new type of amphiphilic membrane‐anchoring agents that can be easily obtained by the Diels‐Alder reaction between terpene myrcene and N‐substituted maleimides. The interaction between the compounds and small unilamellar dipalmitoylphosphatidylcholine vesicles was investigated using infrared spectroscopy, microgravimetry, and turbidimetry. The ability of the compounds to embed in the phospholipid membrane was shown to be strongly dependent on the charge of their polar group. The insertion of the compounds studied into the lipid bilayer did not lead to disruption of the dipalmitoylphosphatidylcholine vesicles up to the highest tested drug to lipid molar ratio of 0.5 to 0.6. Low lipid solubilization ability of the compounds as well as their rigid nonplanar structure makes them an interesting alternative to the common membrane‐anchoring structural motifs.     

Resonance of a turbulent flame in a high-frequency acoustic wave

Resonance of a weakly turbulent flame in a high-frequency acoustic wave is obtained. Because of the resonance, an acoustic wave may increase noticeably the amplitude of flame wrinkles, and the respective increase in propagation velocity of the turbulent flame front becomes larger by a factor of 10-20. The effect of resonance is especially important for turbulent flames with realistic thermal expansion propagating in a closed burning chamber, which may account for considerable scattering of experimental results on turbulent flame velocity.     

Rate constants for the beta-elimination of tosyl radical from a variety of substituted carbon-centered radicals

The rate constants for the beta-elimination of tosyl radical (Ts*) from a series of carbon-centered radicals have been determined by using the radical clock methodology. Depending on the substituents R in Ts-CH(2)-CH*R radicals, the rate constants at 293 K vary by more than 2 orders of magnitude in the range of 10(3)-10(6) s(-1). The lowest values were found for the 2-naphthyl and carbamoyl substituents, whereas the benzyl substituent is located at the other extremity. The effect of the substituent upon the stabilization of the starting radical exerts a predominant influence in this reaction in decreasing the rate of fragmentation.     

The electrochemical behaviour of [Co(sep)]3+ bound with p-sulfonatothiacalix[4]arene and tetracarboxy-p-sulfonatocalix[4]arene in correlation with inclusive and non-inclusive binding modes

The comparative study of the ion-pairing of Co(III) sepulchrate ([Co(sep)]³⁺) with p-sulfonatothiacalix[4]arene and p-sulfonatocalix[4]arene tetracarbonic acid by ¹H NMR and pH-metric data in solution and X-ray data in solid state elucidates pH dependent effect of carboxylate groups on the stoichiometry and the mode of the ion pairing. The electrochemical data of [Co(sep)]³⁺ bound with both calix[4]arenes have been analyzed in the correlation with stoichiometry and the mode of their binding. The pH-dependent effect of tetracarboxy-p-sulfonatocalix[4]arene on the electrochemical behavior of [Co(sep)]³⁺ has been found to correlate with the participation of carboxylate groups in the host?Cguest binding.     

C-H amination/cyclocarbonylation of allene carbamates: a versatile platform for the synthesis of α,β-unsaturated γ-lactams

Despite their utility as building blocks for the construction of a variety of nitrogen-containing heterocyclic scaffolds, the preparation of allenic amines 2 via the direct C-H amination of allenes of the general structure 1 has not been well-explored. In this report, we describe our preliminary studies on the factors that control the chemoselectivity of Rh-catalyzed aminations of allenes to give either bicyclic methylene aziridines or the desired allenic amines 2. Additionally, the conversion of selected allenic amines to α,β-unsaturated γ-lactam scaffolds via a facile Ru₃(CO)₁₂ catalyzed cyclocarbonylation is described.     

Structural Changes and Electrodynamic Effects in Polymers under Fast Uniaxial Compression

Rheological explosion in polymers under uniaxial compression in an open volume occurs at the end of continuous rapid plastic deformation after several stages of creep. Two types of polymers were chosen for this study: brittle glassy amorphous polystyrene and thermoplastic semi-crystalline polypropylene. Electric pulses were detected during explosion, and their spectra were analyzed with two models.X-ray diffraction methods were used to investigate changes in the structure and morphology of polymers during deformation and rheological explosion. The pores appear in polymer in this process, and their shape and size distribution were derived from X-ray experiments. The main reason for the formation of pores in polymer samples in rheological explosion experiments is the intense microshifts in the polymer volume under the action of high applied pressure.