Vinsonsloth3055

We present low-temperature measurements of the refractive index of cryofilms of tetrachloromethane and 1,1,1,2-tetrafluoroethane at different condensation and measurement temperatures between 16 and 130 K. Using cryovacuum condensation, we have been able to obtain thin films in an amorphous state for both substances despite them being very bad glass formers. Then, we have studied the evolution of the refractive index with an increasing temperature, including by transitions to ordered or partially disordered crystalline states.An efficient method to access (E)-trisubstituted alkenes is reported via cobalt-catalyzed isomerization of 1,1-disubstituted alkenes using a phosphine-amido-oxazoline ligand. The reaction could also convert mono- and 1,2-disubstituted alkenes to (E)-internal alkenes with benzylic selectivity. This protocol is atom-economy and operationally simple and uses readily available starting materials with good functional tolerance. This catalytic system could be scaled up to gram scale smoothly with a catalyst loading of 0.1 mol %.The mechanical properties of oil well cement slurry are usually measured to evaluate the durability, sustainability, and long-lasting behavior of a cement sheath under wellbore conditions. High-pressure and high-temperature (HPHT) conditions affect the mechanical properties of cement slurry such as its strength, elasticity, and curing time. In this study, an organically modified montmorillonite nanoclay (NC) and silica flour (SF) materials are used to enhance the strength of the class G cement. Four different cement slurries with the addition of different concentrations of NC (1% and 2%) and SF (20%) in a class G cement were tested under temperatures ranging between 70 and 100 °C and pressure ranging between 1000 and 3000 psia. The slurries were prepared by maintaining a water to cement ratio of 0.44. All the slurries were cured for 24 h before any test was conducted. Extensive laboratory experiments were carried out to measure the compressive and tensile strength of cement slurries cured at HPHT conditions. Compressive strength was measured using unconfined compressive strength (UCS) tests, scratch tests, and ultrasonic cement analyzer (UCA). Tensile strength was measured using breakdown pressure tests and Brazilian disc test analysis. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and petrophysical analysis were also carried out to evaluate the performance of new cement additives at HPHT conditions. Results showed that the addition of organically modified NC and SF significantly increased the compressive and tensile strength of the class G cement slurry cured at HPHT conditions.One of the essential challenges for energy conversion and storage devices based on protonic ceramics is that the high temperature (1600-1700 °C) and long-time firing (>10 h) are inevitably required for the fabrication, which makes the sustainable and clean manufacturing of protonic ceramic devices impractical. This study provided a new rapid laser reactive sintering (RLRS) method for the preparation of nine protonic ceramics [i.e., BaZr0.8Y0.2O3-δ (BZY20), BZY20 + 1 wt % NiO, BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb), BCZYYb + 1 wt % NiO, 40 wt % BCZYYb + 60 wt % NiO, BaCe0.85Fe0.15O3-δ-BaCe0.15Fe0.85O3-δ (BCF), BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY0.1), BaCe0.6Zr0.3Y0.1O3-δ (BCZY63), and La0.7Sr0.3CrO3-δ (LSC)] with desired crystal structures and microstructures. Following this, the dual-layer half-cells, comprising the porous electrode and dense electrolyte, were prepared by the developed RLRS technique. After applying the BCFZY0.1 cathode, the protonic ceramic fuel cell (PCFC) single cells were prepared and tested initially. The derived conductivity of the RLRS electrolyte films showed comparable proton conductivity with the electrolyte prepared by conventional furnace sintering. The initial cost estimation based on electricity consumption during the sintering process for the fabrication of PCFC single cells showed that RLRS is more competitive than the conventional furnace sintering. This RLRS can be combined with the rapid additive manufacturing of ceramics for the sustainable and clean manufacturing of protonic ceramic energy devices and the processing of other ceramic devices.The effect of atmosphere on the fabrication of boronized Ti6Al4V/hydroxyapatite (HA) composites was investigated by microwave sintering of the mixture of Ti6Al4V alloy, HA, and TiB2 powders at 1050 °C for 30 min in the mixed gases of Ar + N2, Ar + CO, and Ar + H2, respectively. The presence of N2, CO, and H2 in the atmosphere caused formations of TiN, TiC, and TiH2 in the composites, respectively, together with evident microstructural changes that determined the mechanical properties (compressive strength, compressive modulus, and Vickers microhardness) and wettabilities of the composites after sintering. It was found that the composite exhibited the best mechanical performance with compressive strength of 148.59 MPa, compressive modulus of 13.9 GPa, and Vickers microhardness of 300.39 HV by microwave sintering in the mixed gas of Ar + H2, followed by those obtained in the mixed gases of Ar + N2 and Ar + CO. BLU-667 price All of the composites possessed desirable wettabilities, irrespective of the sintering atmosphere, as demonstrated by their very low water contact angles (≤31.9°). link2 The results indicated that it is critical to control the extents of nitration and carbonization for maintaining the performance of the composites, especially the mechanical properties, whereas there is no strict requirement for the same objective using the mixed gas of Ar + H2 in which qualified composites could be obtained for implant applications.A nonplanar extended π-system can be found not only in compounds formed by multiple ortho-fused benzenes, such as helicenes and corannulenes, but also in compounds formed by bonding of atoms on the large π-extended rings. (1,3,5-Triazine)2n (n ≥ 3) are the latter type of compounds that are characterized by monomer units composed entirely of a 1,3,5-triazine core (general formula C3N3). The first seven polymers (C3N3)2n (n = 3-9) with a drum shape were investigated computationally. Analyses of natural bonding orbitals and atoms in molecules were applied to investigate the bonding properties. In contrast to the planar structure of the 1,3,5-triazine core, the monomer units in (C3N3)2n (n = 3-9) are transformed from their planar π-system to a warped one. Similar to properties of the nonplanar π-system in [n]helicenes and corannulenes, the nonplanar heterocyclic aromatic configuration of the polymerization units is the determinant of the physical and chemical properties of these polymers. The discovery of nonplanar heterocyclic aromatic structures opens up a broad prospect for the study of azacyclic compounds. The results will be the supplement to the study of heterocyclic helicenes and corannulenes.HIV-1 protease is indispensable for virus propagation and an important therapeutic target for antiviral inhibitors to treat AIDS. As such inhibitors are transition-state mimics, a detailed understanding of the enzyme mechanism is crucial for the development of better anti-HIV drugs. Here, we used room-temperature joint X-ray/neutron crystallography to directly visualize hydrogen atoms and map hydrogen bonding interactions in a protease complex with peptidomimetic inhibitor KVS-1 containing a reactive nonhydrolyzable ketomethylene isostere, which, upon reacting with the catalytic water molecule, is converted into a tetrahedral intermediate state, KVS-1TI. We unambiguously determined that the resulting tetrahedral intermediate is an oxyanion, rather than the gem-diol, and both catalytic aspartic acid residues are protonated. The oxyanion tetrahedral intermediate appears to be unstable, even though the negative charge on the oxyanion is delocalized through a strong n → π* hyperconjugative interaction into the nearby peptidic carbonyl group of the inhibitor. To better understand the influence of the ketomethylene isostere as a protease inhibitor, we have also examined the protease structure and binding affinity with keto-darunavir (keto-DRV), which similar to KVS-1 includes the ketomethylene isostere. We show that keto-DRV is a significantly less potent protease inhibitor than DRV. These findings shed light on the reaction mechanism of peptide hydrolysis catalyzed by HIV-1 protease and provide valuable insights into further improvements in the design of protease inhibitors.Three-dimensional highly ordered multilayer titanium dioxide (TiO2) inverse opal (TIO) structures with two pore sizes were fabricated over a large surface using a self-convective method. The fabricated TIO multilayers were functionalized with gold nanoparticles (AuNPs) by immersing the samples in solution with gold nanoparticles. The photocatalytic activity of TiO2 was enhanced by 85% via plasmonic activation of AuNPs that increased the lifetime of photogenerated holes and electrons. The improved photocatalytic activity was characterized with both UVA and visible light irradiation using an in-house built gas-phase photoreactor.Scales of electronegativity values are used by chemists to describe numerous chemical features such as chemical mechanisms, bond polarity, band gap, atomic hardness, etc. While the many scales provide similar trends, all differ in their predictive quality. Confirmation of the quality of a new scale often uses a previous scale for comparison but does not use independent means to demonstrate the merits of the scale. Utilizing a table of binary compounds of known ionic, covalent, and metallic bonding characters, a means to evaluate electronegativity scales is developed here. link3 By plotting the electronegativity values of the two bonded atoms in binary compounds of a known bonding character, a tripartite separation results that generally divides the three bond types. Using the results of graphs of this sort, the success of bonding separations of 14 different scales of electronegativity has been evaluated on the basis of three quantitative parameters that can provide a measure of the quality of the scales. Three scales, those of Allen, Martynov and Batsanov, and Nagle, have been shown to be superior in their ability to predict the expected separation of bond types. Since this scheme successfully demonstrates the ability to evaluate the quality of electronegativity scales, it can be applied to other scales to establish their effectiveness in predicting bond types in binary compounds and thus the quality of the scales. This scheme is applied to a recently published electronegativity scale to evaluate the ability to determine its quality.CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (NCs) are promising materials due to their excellent optoelectronic properties. This work shows a successful anion exchange reaction in CsPbBr3 nanowire (NW) systems with HCl gas resulting in a blue-green light-emitting CsPbBr3@CsPbBr3-x Cl x core-shell heterojunction. By adjusting the reaction time and the reaction temperature, the structure and light emission of the NWs can be adjusted. The core-shell heterojunction NCs are stably luminescent in 24 h. The rational mechanism of anion exchange in perovskite NCs is also investigated. The work highlights the feasibility of NWs heterogeneously prepared under the HC1 gas atmosphere, which provides a new strategy for studying the two- and multicolor luminescent perovskite NCs.