Miracle-dz/UniFAR-FTUs huggingface dataset:
A computational study of interfaces in WC–Co cemented carbides

Interfaces in WC–Co cemented carbides have been investigated using the density functional theory (DFT). Six different model WC/WC grain boundaries are considered, together with the corresponding WC surfaces and WC/Co phase boundaries. The contribution to the grain boundary energies arising from misfit is estimated using an analytical bond order potential (ABOP) and the effect of magnetism is investigated using spinpolarized and non-spinpolarized calculations. A systematic study of adsorption of Co to WC surfaces, Co segregation to WC/WC grain boundaries and Co substitution at WC/Co phase boundaries has been carried out. Adsorption of Co to most WC surfaces is predicted, and result in a monolayer coverage of Co and sometimes a mixed Co/W or Co/W monolayer. The WC surfaces will become prewetted with Co as soon as the atoms become mobile at finite temperatures. Co substitutional segregation is predicted to all model WC/WC grain boundaries in 0.5 monolayer proportion. The segregation of Co to grain boundaries stabilizes the continuous skeleton network of hard WC grains in cemented carbides. Using the obtained interfacial energies, the wetting and the driving force for cobalt grain boundary infiltration are discussed. A dependence on the wetting efficiency on the carbon chemical potential is predicted, which could be an explanation for the better wetting observed experimentally under W-rich conditions.
Antiferromagnetism and segregation in cuboctahedral FePt nanoparticles

Total energies and magnetic properties of unsupported cuboctahedral near-stoichiometric FePt nanoparticles with up to 561 atoms are compared by means of large scale ab initio calculations within the framework of density functional theory. The results show that for L10 ordered alloys, the two (0 0 1) surfaces perpendicular to the shortened c-axis are preferably covered by Pt atoms. Also, layer-wise antiferromagnetic (AF) configurations are found with practically degenerate energies for perfectly ordered structures. The latent AF tendencies are suppressed by compositional disorder in the core layers.
A Study of the Performance of the Photogalvanic Cells for Solar Energy Conversion and Storage: Methyl Orange–D-Xylose–NaLS System

Abstract The most promising photochemical approach to achieve a better performance of a photogalvanic cell was studied in a photogalvanic system containing Methyl Orange as the photosensitizer, D-Xylose as the reductant, and Sodium Lauryl Sulphate (NaLS) as the surfactant for increasing the solar energy conversion efficiency and storage capacity. The observed values of the photogeneration of photopotential and photocurrent were 890.0 mV and 480.0 μA, respectively. The maximum power of the cell was 427.20 μW, whereas the observed power at the power point was 168.95 μW. The conversion efficiency was 1.6245% and the fill factor 0.3214 was experimentally determined at the power point of the photogalvanic cell. The rate of initial generation of the photocurrent was 69.44 μA min−1, whereas the photogalvanic cell so developed can work for 160.0 min in the dark if it is irradiated for 165 min only.
Total Synthesis of Leucascandrolide A

page v Abstract Leucascandrolide A (I), a polyoxygenated marine macrolide of a new genus (Scheme I), was isolated in 1996 by Pietra and co-workers from the calcareous sponge Leucascandra caveolata. Despite intensive efforts, subsequent expeditions failed to provide additional quantities of I. The biological profile of I is characterized by strong cytotoxic activity against human cancer cell lines as well as powerful inhibition of Candida albicans. This thesis describes the total synthesis of leucascandrolide A. The synthesis planning, outlined in Scheme I, relies on the use of asymmetric synthetic methods recently developed in our laboratories and was chosen for reasons of flexibility and convergency.Leucascandrolide A (I), a polyoxygenated marine macrolide of a new genus (Scheme I), was isolated in 1996 by Pietra and co-workers from the calcareous sponge Leucascandra caveolata. Despite intensive efforts, subsequent expeditions failed to provide additional quantities of I. The biological profile of I is characterized by strong cytotoxic activity against human cancer cell lines as well as powerful inhibition of Candida albicans. This thesis describes the total synthesis of leucascandrolide A. The synthesis planning, outlined in Scheme I, relies on the use of asymmetric synthetic methods recently developed in our laboratories and was chosen for reasons of flexibility and convergency. Me O O O O OMe O Me Me O N O N O MeO H Me Me SO2Ar O Me O OR2 CO2R Me H O OR1 O O Me Me I II III O N O N O MeO H MeO
A generalized level-set/in-cell-reconstruction approach for accelerating turbulent premixed flames

An extended numerical technique for the simulation of accelerating turbulent premixed flames in large scale geometries is presented. It is based on a hybrid capturing tracking technique. It resembles a tracking scheme in that the front geometry is explicitly computed using a level-set method. The basic flow properties are provided by solving the compressible flow equations. The flame-flow-coupling is achieved by an in-cell-reconstruction technique. In cells cut by the flame, the discontinuous solution is reconstructed from given cell averages by invoking explicitly some Rankine–Hugoniot type jump conditions. Then the reconstructed states and again the front geometry are used to define accurate effective numerical fluxes across grid cell interfaces intersected by the front during the time step considered. Hence, the scheme also resembles a capturing scheme in that only cell averages of conserved quantities are computed. To be able to model inherently unsteady effects, like quenching, reignition, etc, during flame acceleration, we modified the standard Rankine–Hugoniot jump conditions. A source term appearing in the modified jump conditions is computed by evaluating a suitable functional on the basis of a one-dimensional flame structure module, that is attached in the normal direction to the flame front. This module additionally yields quantities such as the net mass burning rate, necessary for the propagation of the level set, and the specific heat release important for the energy release due to the consumption of fuel. Generally, the flame structure calculation takes into account internal physical effects which are not active in the outer flow but essential for the front motion and its feedback on the surrounding fluid. If a suitable set of different (turbulent) combustion models to compute the flame structure is provided, the new numerical technique allows us to consistently represent laminar deflagrations, fast turbulent deflagrations as well as detonation waves. Supplemented with suitable criteria that capture the essence of a deflagration-to-detonation-transition (DDT), the complete evolution of such an event can be implemented in principle.
Tris(triisopropylsilyl)silane and the Generation of Bis(triisopropylsilyl)silylene

Tris(triisopropylsilyl)silane (iPr3Si)3SiH has been synthesized and studied by X-ray and neutron diffraction. It possesses an unusual structure in which the four silicon atoms are nearly coplanar, ∠Si−Si−Si = 118.41(5)°. The Si−H distance is found to have a normal value of 1.506(2) A. Thermal and room-temperature photochemical decomposition of (iPr3Si)3SiH leads to the elimination of iPr3SiH and the generation of bis(triisopropylsilyl)silylene, [(iPr3Si)2Si:]. Reactions of (iPr3Si)2Si: include precedented insertions into H−Si bonds and addition to the π-bonds of olefins, alkynes, and dienes. Despite theoretical predictions of a triplet ground state for [(iPr3Si)2Si:], stereospecific addition to cis- and trans-2-butene was observed.
Cycloalkylmethyl radicals. Part 4. Electron spin resonance study of conformational equilibria in cyclohexenylmethyl and 4-alkylcyclohexenylmethyl radicals

For cyclohex-2-enylmethyl and 4-alkylcyclohex-2-enylmethyl radicals the quasi-axial and the quasi-equatorial conformers can both be observed by e.s. r. spectroscopy. Similarly, the axial and equatorial conformers of cyclohex-3-enylmethyl radical can be distinguished by e.s. r. spectroscopy. The conformational free-energy difference of the CH2˙ group in the 2-position, –ΔG°300, was found to be 0.17 ± 0.03 kcal mol–1 and in the 3-position –ΔG°300= 0.0 ± 0.1 kcal mol–1. The Arrhenius parameters for inversion of the half-chair conformation of cyclohex-2-enylmethyl radical were determined by line-shape analysis of the exchange-broadened spectra and found to be: log(kf/s–1)= 12.3 –(5.7 kcal mol–1)/2.3RT and log (kb/s–1)= 12.0 –(5.5 kcal mol–1)/2.3RT. The barrier to rotation about the Ċα–Cβ bond in a cyclohexenylmethyl radical is much less than the barrier in a cyclohexylmethyl radical because the former radical has only one syn-axial hydrogen on C(5) to impede the rotation whereas the latter radical has two syn-axial hydrogens on C(3) and C(5).
On the constancy of sediment-water partition coefficients of hydrophobic organic pollutants

If precautions are taken to eliminate or account for nonsettling (or nonfilterable) microparticles or organic macromolecules that remain in the aqueous phase during laboratory sorption tests, the observed partition coefficients (Kp or Koc) for a group of model hydrophobic organic compounds (PCBs) are found to remain constant over a wide range of solid-to-solution ratios. Further, the partition coefficients for either sorptive uptake or desorptive release are indistinguishable and confirm the reversible nature of hydrophobic sorption. It is proposed that descriptions of the 'speciation' of hydrophobic compounds in natural waters should include not only dissolved and sorbed-to-sediment fractions but also a component sorbed to nonsettling microparticles or organic macromolecules.
Soil moisture change caused by experimental extreme summer drought is similar to natural inter-annual variation in a loamy sand in Central Europe

Intensification of weather extremes is currently emerging as one of the most important facets of climate change. Research frontiers are in analyzing (1) the consequences for the hydrological cycle and (2) the effects of multifactor scenarios on ecosystems. However, in all theoretical and experimental scenarios, challenges arise as to how precipitation regimes translate into variation in soil moisture. Here, we explore soil-moisture response to experimental changes in the precipitation regime in Central Europe over a period of 5 y, particularly focusing on the effects of recurrent extreme weather events. Intraannual difference in weekly precipitation sums imposed by extreme-drought or heavy-rainfall manipulations clearly exceeded interannual variation in the ambient precipitation pattern during the growing season between 2005 and 2009. However, soil-moisture variability in the experimental plots did not clearly reflect any altered patterns in response to the manipulated precipitation regime. Natural variation in soil moisture between years was similar to within-season differences between manipulations. Strong differences in soil-moisture dynamics during the growing season can, however, be generated by changing the temporal distribution of rainfall events while keeping the magnitude of the precipitation sum constant. Our findings confirm a common methodological dilemma in precipitation-change experiments searching for a logical way to determine how precipitation change affects communities and ecosystems on relatively short time scales: Alteration of weather regimes according to extreme-value statistics and future scenarios vs. systematic alteration of soil moisture. For Central Europe, our data suggest that other factors rather than the magnitude of rainfall exclusion or addition would appear to be decisive for ecosystem response to more extreme precipitation regimes. Response of soil moisture to frequency, return interval, and timing of events is a promising approach for further exploration. In addition, buffer capacity of the ecosystem under study has to be taken into account.
Melting temperature of colloidal crystals of polystyrene spheres

The melting temperature (Tm) of colloidal crystals of polystyrene spheres has been measured by the reflection spectroscopy as a function of sphere concentration. Seven kinds of spheres their diameters ranging from 85 to 212 nm, and their monodispersity indices (standard deviation of spheres divided by the mean diameter) between 0.014 and 0.26, are used after further purification and deionization processes. A phase diagram, including liquid‐like and crystal‐like (body‐centered‐cubic and face‐centered‐cubic lattices) structures, is obtained as a function of Tm against sphere concentration. The data of Tm are analyzed successfully with the theory of Williams, Crandall, and Wojtowicz, and the heat and entropy of melting are estimated. Tm values are consistent with the theory of Robbins and co‐workers which treats the repulsive Yukawa potential between colloidal spheres.
Nitrogen‐Doped Single‐Walled Carbon Nanotubes Grown on Substrates: Evidence for Framework Doping and Their Enhanced Properties

Nitrogen‐doped single‐walled carbon nanotubes (SWCNTs) are synthesized directly on silicon and quartz substrates through a normal chemical vapor deposition (CVD) method. Thermogravimetry mass spectrometry measurements and Raman spectroscopy give firm evidence for framework nitrogen doping. X‐ray‐photoelectron‐spectroscopy analysis further obtains the bonding style of the nitrogen atoms in the carbon framework. The nitrogen doping significantly changes the properties of the SWCNTs. All of the tubes behave like metallic tubes in field‐effect transistors. The doped nitrogen atoms introduce a stronger affinity for the SWCNTs to metal nanoparticles. Compared with pristine SWCNTs, the nitrogen‐doped tubes show enhanced sensitivity and selectivity for electrochemical detection of some electrophilic species including O2, H2O2, and Fe3+. They also present improved electrocatalytic activity for oxygen reduction. These unique properties of the nitrogen‐doped SWCNTs endow them with important potential applications in various fields.
Ab initio prediction of the rovibrational levels of the He–CO+ ionic complex

The intermolecular potential for the van der Waals complex of the carbon monoxide cation with helium is studied by means of the partially spin adapted coupled cluster RCCSD(T) method and the aug-cc-pVXZ family of basis sets. In the ground electronic state, correlated with the lowest electronic asymptote X 2Σ+ of the monomer CO+, the complex He(1 S)-CO+(2Σ+) has a nonlinear equilibrium structure with a Jacobi angle of about 46° and a binding energy of about 275 cm−1. For the complex He(1 S)–CO+(A 2Π) we find equilibrium Jacobi angles of 78° and 90° and electronic binding energies of about 160 cm−1 and 303 cm−1 for the A′′ and A′ components, respectively, coalescing into the Π state at linearity. Two-dimensional intermolecular potential energy surfaces are constructed for the ground electronic state and used to compute rotation-vibration states up to J = 10 with the numerically exact discrete variable representation (DVR) technique. The He–CO+ complex is found to have 19 bound even-parity J = 0 states and 16 bound odd-parity J = 1 states and to exhibit strong angular–radial coupling and quasi-linear behaviour.
Mesoporous silica-based nanodevices for biological applications

This review highlights and addresses issues related to research on the development of mesoporous silica nanomaterials (MSNs) based nanodevices for biological applications. Through the review, a variety of synthetic routes and surface functionalization is first introduced with regard to the preparation of MSNs with different chemical and physical features. Then, the effects of their various structural and compositional features on the induced biological activities are described, as recent biological applications of MSNs are summarized, typified by drug/biomolecule delivery, bioimaging, biocatalysis and biosensing. Conclusions are reached and prospects in the field are also envisioned.
Coulometric Titrations in Wine Samples: Studies on the Determination of S(IV) and the Formation of Adducts

In this experiment, the sulfite in white wine samples is quantified by coulometric titration with iodine, using a procedure that minimizes errors due to air oxidation. Some aspects of the distinction of S(IV) forms in such matrices are discussed on the basis of the formation of adducts between sulfite and carbonyl compounds present in the wine. The reactivity of these S(IV)-bound compounds toward the reaction with iodine is addressed and the stability of the adducts as the sample pH is changed is discussed.
Molecular and mesoscopic study of ionic liquids and their use as solvents of active agents released by polymeric vehicles

This work explores the diffusivity of the drug albendazole contained in a polymeric vehicle, Styrene-Divinylbenzene (ST-DVD), when it is subject to different environments. The environments consist of water and three different ionic liquids. First, the solubility parameters of these ionic liquids, [BMIM][PF6], [HMIM][Br] and [BMIM][BF4], and albendazole were evaluated by means of molecular dynamics employing COMPASS force-field and a NPT ensemble at 298 K. Then a mesoscopic simulation using Dissipative Particle Dynamics (DPD) was used. In the presence of ionic liquids the albendazole exhibits a diffusivity in [BMIM][PF6] around ten times that shown in [BMIM][BF4] or [HMIM][Br]. This is connected with the corresponding solvent power. The results obtained from these molecular and mesoscopic simulations are consistent with reported experimental results and are useful to predict and evaluate the solvent power of ionic liquids applied to drugs of pharmaceutical use.
Gibbsite and Goethite Solubility

2-Ketogluconate (kG) is a microbial byproduct that has been isolated from the rhizosphere of several plants and has been found to accumulate around bacteria adhering to rock surfaces. It has long been suspected that kG may play a role in enhancing the bioavailability of soil nutrients. However, quantitative information relevant to its behavior in soils, its reactions with mineral surfaces, and its aqueous complexation of metal cations is unavailable. The objectives of this research were to examine the influence of kG on gibbsite and goethite solubility and to describe these effects by considering the aqueous complexation of Al 3+ and Fe 3+ by kG. Secondary to this was to compare the impact of kG on mineral solubility to that of citrate. The equilibrium solubility of gibbsite and goethite was examined at ambient (20-22°C) or controlled (25°C) temperatures as a function of pH, ionic strength, and kG or citrate concentration. Both ligands were observed to significantly enhance mineral solubility (as determined by the total soluble concentrations of Al and Fe), with kG and citrate having similar impacts on gibbsite solubility, but with kG having a lesser impact than dtrate on goethite solubility. The solubility data were employed to characterize the aqueous complexation chemistry of Al- and Fe(III)-kG and citrate. In the 4 < pH < 8.5 range, the mononuclear species AlkG 2+ (aq), Al(OH) 2 kG 0 (aq), and Al(OH) 3 kG - (aq) describe Al-kG speciation, with the latter two species mechanistically described by the bidentate complexation of AlOH 2+ (aq) and Al(OH) + 2 (aq) [also written as AlOH(H -1 kG) 0 (aq) and Al(OH) 2 (H -1 kG) (aq)]. Iron(III)-kG complexation is described by the FekG 2+ (aq) and Fe(OH) 3 kG 2- 2 (aq) [or FeOH[(H -1 )kG] 2- 2 (aq)l species. For the citrate systems, the chemical models required to describe metal speciation differed from those reported in the literature: Alcit 0 (aq), Al(OH) 2 cit 2- (aq), and Al(OH) 3 cit 3- (aq) for Al-citrate speciation and Fecit°(aq), Fe(OH) 2 cit 2- (aq), and Fe(OH) 3 cit 3- (aq) for Fe(III)-citrate.
Theory of Radiation Chemistry. VII. Structure and Reactions in Low LET Tracks

The low LET track of an electron is composed of a random sequence of more or less isolated entities called spurs, blobs, and short tracks. The distribution function for these track entities has been considered in detail by a Monte Carlo technique. In order to evaluate the effect of the more accurate structure on calculated chemical yields, as contrasted with the simpler spur model, the diffusion equations were solved numerically for the one radical case. The more elaborate track model introduced here has a kind of high LET component embedded in it through the ``short tracks. '' This investigation shows that for electron irradiations all LET effects result from the variation in fraction of energy deposited in short tracks. Effects of overlapping of various track entities during the diffusion and reaction phase are negligible.
3:1 Molecular Complex of Hydroquinone and C60

The preparation of a 3:1 complex of hydroquinone (HQ) and C60, (HQ)3C60, is reported and its X-ray crystal structure described. The HQ host builds up a single H-bonded super-polonium network with super-cubes as building blocks, which accommodate the large C60 guest molecules. The enclathration of C60 is rather tight (high density of the complex) owing, in part, to favorable charge-transfer host-guest interactions (π-donor-acceptor complex). Nonetheless, the C60 molecules arc orientationally disordered, and no individual bond lengths could be measured. In contrast, the HQ host network is essentially ordered and well-defined with normal intramolecular geometry. No appreciable (powder) conductivity could be observed for (HQ)3C60, yet ESR spectra of single crystals showed interesting narrow signals.
Raman scattering study of potassium calcium fluoride KCaF3

Raman spectra of the perovskite crystal KCaF3 were recorded between 40 and 700 K and assigned in the monoclinic room temperature phase. Compared to the 14Ag ⊕ 10Bg Raman modes predicted by group theory calculations, only 9Ag and 7Bg modes were observed. Three soft modes, due to condensation of zone boundary modes of the R–M phonon branch of the cubic phase were observed and shown to display a Landau-type behavior. The observation of a central component and the evolution with temperature of characteristic parameters of hard Raman modes, close to the transition, are reported and discussed in terms of a precursor disordered phase preceding the lower temperature phase. Les spectres Raman du compose cristallise KCaF3, de structure perovskite, ont ete enregistres de 40 a 700 K, et une attribution de ces spectres a ete proposee en symetrie monoclinique, correspondant a la phase a temperature ambiante. La theorie des groupes prevoit l'existence de 14Ag ⊕ 10Bg modes Raman mais seuls 9Ag et 7Bg sont observes. Trois modes mous, associes a la condensation de modes de bord de zone de la branche de phonons R–M, responsable de la transition, ont ete observes et interpretes par un modele de Landau. L'existence d'une composante centrale ainsi que l'evolution en fonction de la temperature de parametres caracteristiques de modes “durs” Raman, a l'approche de la transition, est discutee dans le cadre de l'apparition d'une phase desordonnee, precurseur de la phase ambiante.
Preparation of Microcapsules for Self-Healing Polymers

In this paper, melamin-formaldehyde microcapsules filled with pentaerythritol tetrakis (3-mercaptopropionate) (PETMP) or epoxy were prepared via oil-in-water emulsion polymerization method. Two different routes were chosen from literature, and applied with some changes. The effects of modification of reaction conditions on the resulting capsules were studied. It was found that too low pH value in the emulsion causes burst polymerization of the wall material, without microcapsule formation. When pH was set to 4.5 spherical microcapsules were formed. Optical microscopy was used to evaluate the microcapsules.