Electron density of a benzoylated tetrafructopyranose

The electron density distribution (EDD) of a tetrasaccharide composed of four benzoylated fructopyranosyl units was obtained by refinement with scattering factors from the invariom library. X-ray diffraction data was downloaded from the Cambridge Structural Database (CSD). Bond topological and atomic properties were obtained by application of Bader’s QTAIM formalism. From a large number of 105 C–C bonds in the molecule average bond orders for 33 single and 72 aromatic bonds were calculated yielding values of 1.33 and 1.61. Molecular Hirshfeld and electrostatic potential (ESP) surfaces show that only weak non-covalent interactions exist. The phenyl rings of the benzoyl fragments in the outer regions of the molecule generate a positive ESP shell with repulsive properties between adjacent molecules. Weak surface interactions result in a rather unusual low density around 1.3 g cm−3, which is understandable when compared to other carbohydrates where strong O–H⋯O hydrogen bonds allow a 20% more dense packing with densities >1.5 g cm−3 as determined by single crystal X-ray diffraction.

Effect of Vehicle–Bridge Coupled Vibration on the Performance of Magnesium Phosphate Cement Repair Materials

This study evaluates the effect of vehicle–bridge coupled vibration on the mechanical properties of fiber-reinforced magnesium phosphate cement (FR-MPC) composites and the bonding properties of repaired systems. By means of compressive and flexural bond strengths, fiber pullout, mercury intrusion porosimeter (MIP) and backscattered electron imaging (BSE) analysis, an enhanced insight was gained into the evolution of FR-MPC performance before and after vibration. Experimental results showed that the compressive strength and flexural strength of FR-MPC was increased when it was subjected to vibration. However, the effects of vibration on the flexural strength of plain magnesium phosphate cement (MPC) mortars was insignificant. The increased flexural strength of FR-MPC after vibration could be due to the high average bond strength and pull-out energy between the micro-steel fiber and the MPC matrix. Moreover, BSE analysis revealed that the interface structure between FR-MPC and an ordinary Portland cement (OPC) substrate was more compacted after vibration, which could possibly be responsible for the better bonding properties of FR-MPC. These findings are beneficial for construction project applications of FR-MPC in bridge repairing and widening.

Local bond strength prediction of deformed reinforcing bars in concrete considering heterogeneity at interface regions

An analytical model is proposed to predict local bond strength (τf) by incorporating heterogeneity at interface regions for deformed reinforcing bars centrally anchored in concrete. The rib width on the bar surface is introduced as an interfacial characteristic parameter G in the proposed model; this accounts for the heterogeneity. Both τf and the local interfacial fracture energy (GIIf) of each specimen were found to be linked to G and can be determined analytically from the maximum pull-out loads (Fmax) from tests. It was found that the predicted τf was larger than the maximum average bond stress (τavg-max); the discrepancy between the two values reduced with an increase in L/G. Moreover, with an increase in L/G, the predicted τf showed a certain decrease, with the reduction decreasing with stronger interfacial homogeneity. The predicted GIIf was found to be significantly increased because of the weaker boundary effect. The validity of the proposed model was verified using comparisons of predicted Fmax (using the determined values of τf and GIIf) and the experimental Fmax, with the only failure mode being bar pull-out. Moreover, the model can be applied to steel or fibre-reinforced polymer bars and the concrete refers to all types of cementitious materials.

Effects of Adding Active Elements to Aluminum-Based Filler Alloys on the Bonding of 6061 Aluminum Alloy and Alumina

In this study, AA6061/AA6061 and AA6061/alumina were directly brazed with Al10.8Si10Cu, Al10Si10Cu4Ti and Al10Si10Cu4Ti0.1RE filler alloys at 530 °C for 10 min without the use of flux. The addition of titanium and rare-earth elements into Al10.8Si10Cu alloy effectively improved the bonding shear strengths of AA6061/AA6061 and AA6061/alumina joints. The highest joint shear strengths were 61.1 and 19.2 MPa, respectively. The Al10.8Si10Cu filler alloy without titanium and rare-earth elements could not wet on the alumina and caused failure of the AA6061/alumina joint. The shear strengths of the AA6061/AA6061 and AA6061/alumina joints both strongly depended on the active element addition. Due to the high chemical activity of the rare-earth elements, they formed AlLa between the Al10Si10Cu4Ti0.1RE filler alloy and alumina. The addition of rare-earth elements into Al10Si10Cu4Ti filler alloy resulted in significant enhancement of the average bond strength of AA6061/alumina joints, from 8.0 to 14.8 MPa.

Effects of Substrate Texture and Moisture Conditions on Ultra-High Performance Concrete and Silica Fume Concrete Overlay Bond Strengths

Direct tension tests were conducted to investigate the effects of substrate moisture conditions and texture on ultra-high performance concrete (UHPC) overlay bond strengths. Improper substrate surface preparation can result in inadequate bond strengths and, in severe cases, lack of bond. To demonstrate the importance of surface preparation, pull-off tests were performed on overlaid slabs that had two extreme substrate surface moisture conditions (saturated and dried) prior to overlay application. Saturated slabs had a tined, tined-light sand blasted, or tined-medium sand blasted substrate surface texture. Dried slabs had either a tined or an exposed aggregate surface texture. Saturated specimens with tined, tined-light sand blasted, and tined-medium sand blasted surface textures achieved average bond strengths of 0.924, 1.45, and 1.95 MPa, respectively. Dried substrate surfaced specimens had zero bond strength. Surface moisture conditions that ranged from saturated to dry were also investigated by allowing the substrate surfaces to dry for 15, 30, 45, and 60 minutes prior to application of an UHPC overlay. Tined-light sand blasted specimens with surfaces that dried for 15, 30, 45, and 60 minutes achieved average bond strengths of 2.86, 2.01, 1.59, and 0.165 MPa, respectively. Results showed tined-light sand blasted specimens with proper saturating achieved adequate bond strengths, and properly saturated, tined-medium sand blasted specimens produced excellent bond strengths. Results also exposed the drastic consequences of not maintaining a saturated substrate surface prior to overlay application and delaying overlay application up to 60 minutes can drastically reduce bond strength.

Fe-doped effects on phase transition and electronic structure of CeO2 under compressed conditions from ab initio calculations

Ab initio study of high-pressure phase transition and electronic structure of Fe-doped CeO2 with Fe concentrations of 3.125, 6.25, and 12.5 at% has been reported. At a constant-pressure consideration, the lattice constants and the volume of the supercell were decreased with an increasing concentration of Fe. The average bond length of Fe–O is lower than that of Ce–O. As a result, Fe doping induces the reduced volume of the cell, which is in good agreement with previous experiments. At high pressure (~ 30 GPa), it was found that the transition pressure from the fluorite to the cotunnite orthorhombic phase decreases at a higher concentration of Fe, indicating that the formation energy of the compound is induced by Fe-doping. Furthermore, compression leads to interesting electronic properties too. Under higher pressures, the bandgap increases in the cubic structure under compression and then suddenly plummets after the transition to the orthorhombic phase. The 3d states of Fe mainly induced the impurity states in the bandgap. In both the undoped and Fe-doped systems, the bandgap increased in the cubic phase at high pressure, while the gap and p-d hybridization decrease in the orthorhombic phase.

Conformational Analysis of [60]PCBM from DFT Simulations of Electronic Energies, Bond Strain and the 13C NMR Spectrum: Input Geometry Determination and Ester Bond Rotation Dynamics

With the aim of determining the best input geometry for DFT calculations of [60]PCBM, the geometry of 24 chemically possible [60]PCBM conformers were optimised and their electronic energies and average bond strains were determined. A DFT analysis of the relevant dihedral angles provided insights into the dynamical behaviour of the ester group through sterically restricted bond rotations. In addition, the 13C NMR spectra of the six better performing conformers were simulated and compared with an experiment. There is a close correlation between average bond strain, total electronic energy and mean absolute error of the simulated 13C NMR spectra of the ester carbons. The best overall candidate conformer for the input geometry had the C61-C4, C4-C3 and C3-C2 single bonds of the alkyl chain in syn, anti and anti arrangements, respectively, and had the C2-C1 and C1-O single bonds of the ester in syn and anti arrangements, respectively. This contrasts strikingly with most representations of PCBM in the literature, which depict all relevant bonds in anti arrangements.

Nucleation and Post-Nucleation Growth in Diffusion-Controlled and Hydrodynamic Theory of Solidification

Two-step nucleation and subsequent growth processes were investigated in the framework of the single mode phase-field crystal model combined with diffusive dynamics (corresponding to colloid suspensions) and hydrodynamical density relaxation (simple liquids). It is found that independently of dynamics, nucleation starts with the formation of solid precursor clusters that consist of domains with noncrystalline ordering (ringlike projections are seen from certain angles), and regions that have amorphous structure. Using the average bond order parameter q¯6, we distinguished amorphous, medium range crystallike order (MRCO), and crystalline local orders. We show that crystallization to the stable body-centered cubic phase is preceded by the formation of a mixture of amorphous and MRCO structures. We have determined the time dependence of the phase composition of the forming solid state. We also investigated the time/size dependence of the growth rate for solidification. The bond order analysis indicates similar structural transitions during solidification in the case of diffusive and hydrodynamic density relaxation.

Geochronology of Himalayan shear zones: unravelling the timing of thrusting from structurally complex fault rocks

Dating structurally complex fault rocks often results in internally inconsistent ages, as several mineral generations are intergrown at scales << 10 µm and almost always altered to various degrees. Firstly, electron probe microanalysis is necessary to assess both inventory and spatial distribution of minerals and their retrogression/alteration phases. We then used 40Ar/39Ar stepheating combining two independent indicators that allow the discrimination of coexisting mica generations from each other: (i) mica stoichiometry, which is proxied by 39Ar concentration in combination with 37Ar/39Ar and 38Ar/39Ar (Ca/K and Cl/K) ratios; (ii) furnace temperature, at which the degassing peak accompanying dehydration and structural collapse is observed. As dehydration rates depend on average bond strength in the crystal structure, it is predicted and observed that the temperature of the differential Ar release peak is variable among different minerals. We observe that the Ca/Cl/K signatures of pure micas coincide with the Ar release peak. The Main Central Thrust zone in the Garhwal Himalaya records a protracted history. Foliation of Vaikrita Thrust formed at 15-8 Ma, followed by static decompression at 7 Ma; foliation of structurally lower Munsiari Thrust formed around 5 Ma. Our elaborate and time-consuming petrochronological procedure should become routine whenever analysing polydeformed metamorphic rocks.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5357212Thematic collection: This article is part of the Isotopic Dating collection available at: https://www.lyellcollection.org/cc/isotopic-dating-of-deformation

Geochronology of Himalayan shear zones: unravelling the timing of thrusting from structurally complex fault rocks

&lt;p&gt;Dating structurally complex fault rocks often results in internally inconsistent ages, as several mineral generations are intergrown at scales &lt;&lt; 10 &amp;#181;m and almost always altered to various degrees. We describe here &lt;sup&gt;39&lt;/sup&gt;Ar-&lt;sup&gt;40&lt;/sup&gt;Ar stepheating using the combination of two independent indicators that allow the discrimination of coexisting mica generations from each other and from the ubiquitous retrogression/alteration phases. A necessary first step is electron probe microanalysis to assess both inventory and spatial distribution of the mineral phases that need to be distinguished a posteriori by &lt;sup&gt;39&lt;/sup&gt;Ar-&lt;sup&gt;40&lt;/sup&gt;Ar systematics. One indicator is based on mica stoichiometry, which can be proxied by the &lt;sup&gt;39&lt;/sup&gt;Ar concentration in combination with the &lt;sup&gt;37&lt;/sup&gt;Ar/&lt;sup&gt;39&lt;/sup&gt;Ar and &lt;sup&gt;38&lt;/sup&gt;Ar/&lt;sup&gt;39&lt;/sup&gt;Ar (i.e. Ca/K and Cl/K) ratios. The other indicator is the furnace temperature, at which a degassing peak accompanying dehydration and structural collapse is observed. As dehydration rates depend on the average bond strength in the crystal structure, it is predicted (and indeed observed) that the temperature of the differential Ar release peak is variable among different minerals. As the Ca/Cl/K signatures of pure micas coincide with the Ar release peak, their combination identifies the isochemical steps that correspond to the degassing of pristine micas. Only these should be used to date the activity of shear zones.&lt;/p&gt;&lt;p&gt;This procedure should become routine in analysing polydeformed metamorphic rocks.&lt;/p&gt;