Properties of nanocomposites based on crosslinked elastomeric polyurethane and ultrasmall additives of single-wall carbon nanotubes

It is shown for the first time that the addition of ultrasmall amounts of single-wall carbon nanotubes leads to a significant increase in the main mechanical characteristics of the crosslinked poly(urethane urea) elastomer. The elastic modulus and the tensile strength pass through maxima as the nanotube concentration is increased from 0 to 0.018 wt %; at a nanotube concentration of 0.002 wt %, the maximum values of the modulus and strength are higher by factors of 2.5 and 1.5, respectively, than the corresponding values for the unfilled polymer. The thermomechanical, spectral, and structural characteristics of nanomodified elastomers are investigated, and possible causes of change in their mechanical parameters are discussed.     

Synthesis and fungicidal activity of the quaternary ammonium salts of the 1,3,7-substituted dibenzothiophene-5,5-diones

A series of novel double quaternary ammonium salts based on 5,5-dioxo-5H-dibenzo[b,d]thiophene has been prepared via quaternization of the corresponding 3,7-bis(chloromethyl)dibenzothiophene-5,5-diones with various N,N-dimethylalkylamines. Pronounced fungicidal activity of the C¹-substituted quaternary ammonium salts has been observed.     

Theoretic study of the electronic spectra of neutral and cationic PaO and PaO2

The electronic spectra of neutral PaO and PaO₂ and their mono- (PaO⁺, PaO₂ ⁺) and dications (PaO²⁺, PaO₂ ²⁺) were studied by performing multiconfigurational quantum chemical calculations at the CASSCF/CASPT2 level of theory taking into account spin–orbit coupling. Including the protactinium 7s, 6d, and 5f orbitals as well as selected orbitals of oxygen in the active space, the vertical excitation energies at the ground-state geometries have been computed up to ca. 36,000 cm^?1. The gas-phase electronic spectra at 298 and 3,000 K were evaluated on the basis of the computed oscillator strengths.     

Novel Synthesis of Haloaromatic Tertiary Alcohols Using (η6-Fluoroarene)tricarbonylchromium(0) Complexes

Regioselective synthesis of haloaromatic tertiary alcohols can be achieved by ortho deprotonation/electrophilic reactions of (η⁶- fluoroarene)Cr(CO)₃ complexes with halobenzophenones and metal removal. The coexistence of different halogens in the aromatic rings of these molecules make them unique within the group of tertiary alcohols.     

Measurement of k 0 values for caesium and iridium

The OPAL research reactor in Australia has been used to determine k ₀ values for ^134mCs, ¹³⁴Cs, ¹⁹²Ir and ¹⁹⁴Ir. Values for ²⁴Na have also been measured for quality control. The neutron flux at the irradiation positions was very highly thermalised (f > 2,000), resulting in almost negligible activation by epithermal neutrons. As a consequence, the contribution to the total uncertainty of the k ₀ values from epithermal-related factors such as Q ₀ and $ \bar{E}_{\text{r}} $ was very small. The measured caesium k ₀ values have been compared with the library values as well as with recent measurements by St Pierre et al. and Farina Arboccò et al. While there are k ₀ values for ¹⁹⁴Ir in the library, no ¹⁹²Ir values have been measured previously. Despite ¹⁹²Ir having a higher sensitivity than ¹⁹⁴Ir, k ₀ values were not measured during the establishment of the k ₀-method because the nuclear data available at the time indicated that the activation cross-section of ¹⁹¹Ir deviated significantly from 1/v behaviour (g(T _n ) ≠ 1), which would result in unacceptable errors if k ₀ analysis were to be carried out using the Høgdahl convention. However later nuclear data compilations showed that ¹⁹¹Ir has better 1/v behaviour than previously reported, making it suitable for k ₀ analysis using the Høgdahl convention. For completeness, k ₀ values have been determined using both the Høgdahl and modified-Westcott conventions and these have been compared with library (¹⁹⁴Ir) and calculated values.     

The Mechanism of Biochemical NO-Sensing: Insights from Computational Chemistry

The binding of small gas molecules such as NO and CO plays a major role in the signaling routes of the human body. The sole NO-receptor in humans is soluble guanylyl cyclase (sGC) – a histidine-ligated heme protein, which, upon NO binding, activates a downstream signaling cascade. Impairment of NO-signaling is linked, among others, to cardiovascular and inflammatory diseases. In the present work, we use a combination of theoretical tools such as MD simulations, high-level quantum chemical calculations and hybrid QM/MM methods to address various aspects of NO binding and to elucidate the most likely reaction paths and the potential intermediates of the reaction. As a model system, the H-NOX protein from Shewanella oneidensis (So H-NOX) homologous to the NO-binding domain of sGC is used. The signaling route is predicted to involve NO binding to form a six-coordinate intermediate heme-NO complex, followed by relatively facile His decoordination yielding a five-coordinate adduct with NO on the distal side with possible isomerization to the proximal side through binding of a second NO and release of the first one. MD simulations show that the His sidechain can quite easily rotate outward into solvent, with this motion being accompanied in our simulations by shifts in helix positions that are consistent with this decoordination leading to significant conformational change in the protein.     

Low volatile monofunctional reactive diluents for radiation curable formulations

In the last decades the importance of UV curable formulations has increased continuously. Their fast curing speed, solvent-free polymerization conditions, and the formation of hard and highly crosslinked photopolymer networks represent major benefits. Commercial UV resins generally consist of multi-functional vinyl oligomers, photoinitiators, additives, and reactive diluents. Mono- and multi-functional reactive diluents serve as thinners to lower the overall resin viscosity and to improve processability. However, many monofunctional reactive diluents like isobornyl (meth)acrylate or benzyl (meth)acrylate exhibit high volatility, often already at room temperature. This causes adverse effects such as unpleasant odor, potential health risks, and changing resin composition during processing. A new group of monomers that show high potential for replacing traditional highly volatile reactive diluents are salicylate (meth)acrylates. In this work, salicylate-based thinners are synthesized, polymerized, and characterized with respect to their viscosity, volatility, thermal stability, photoreactivity, and thermomechanical properties of their homopolymers. Additionally, a first example of their diluting effect in a highly viscous difunctional polyester urethane methacrylate is demonstrated with 30 wt% of a cycloaliphatically and an aromatically substituted salicylate methacrylate. The polymers of the diluted resin exhibit similarly high glass transition temperatures of 110 and 126 °C, which are in the range of the polymers of the undiluted resin.     

Non-bilayer formation in the DPPE-DPPG vesicle system induced by deep rough mutant of Salmonella minnesota R595 lipopolysaccharide

The vesicle system consisting of 80 mol% dipalmitoylphosphatidylethanolamine (DPPE) and 20 mol% dipalmitoylphosphatidylglycerol (DPPG) undergoes to structural changes caused by various concentrations of Salmonella minnesota R595 lipopolysaccharide (LPS). The phenomenon was investigated by methods applying small- and wide-angle X-ray scattering (SAXS and WAXS), calorimetry (DSC) and freeze-fracture. In the low LPS concentration regime (investigated at 0.02 LPS/DPPE–DPPG molar ratio) a phase separation was observed. Two kind of domains are formed which are rich and poor in DPPE and in these domains cubic and lamellar structures are present, respectively. Increasing the LPS concentration up to 0.1 LPS/DPPE–DPPG molar ratio the phase separation is more expressed and the temperature domains of the phase transitions are more different. Increasing the temperature chain melting of the lamellar phase occurs first and destruction of the cubic phase is observed later. At high LPS concentration (equimolar ratio of LPS/DPPE–DPPG), where this amphiphilic molecule cannot be considered any more a guest molecule, the cubic structure dominates the phase behaviour of the LPS molecules.     

Cobalt(II) complexes with disubstituted 3-aminopyrazole derivative: Mononuclear Co(II) complex with in situ prepared formamidine ligand

In the reaction of Co(NO₃)₂ · 6H₂O with 4-acetyl-3-amino-5-methylpyrazole (aamp) two octahedral Co(II) complexes, [Co(aamp)₂(H₂O)₄](NO₃)₂, 1, and [Co(ampf)(MeOH)₂NO₃]NO₃ (ampf = N,N′-bis(4-acetyl-5-methylpyrazole-3-yl)formamidine), 2, were obtained, depending on the reaction conditions. The presence of water in the reaction system leads to incorporation of water molecules into the crystal lattice and 1 was formed. In an anhydrous environment, due to addition of CH(OEt)₃, the fusion of two aamp was induced through their NH₂-groups, incorporating the methine group of CH(OEt)₃. As a result, complex 2, containing an adenino-mimetic NNO pharmacophore ligand, was obtained. The crystal and molecular structure of both compounds was determined. The coordination of aamp in 1 was achieved through N2 of the pyrazole ring. On the contrary, in 2, an unusual coordination mode of pyrazole is found: one of the pyrazole moieties, due to steric hindrance, coordinates through the oxygen atom of the acetyl group instead of N2. The complexes were characterized by elemental analysis and electronic spectra. For 2 a comprehensive IR spectral analysis is given. The metal-ligand interactions in 2 are analyzed by quantum chemical computations. The desolvation mechanism of both compounds is discussed in detail.