We are launching FindBounce, a Mathematica package for the evaluation of the Euclidean bounce action that enters the decay rate of metastable states in quantum and thermal field theories. It is based ...on the idea of polygonal bounces, which is a semi-analytical approach to solving the bounce equation by discretizing the potential into piecewise linear segments. This allows for a fast and robust evaluation of arbitrary potentials with specified precision and any number of scalar fields. Time cost grows linearly with the number of fields and/or the number of segments. Computation with 20 fields takes ∼2 s with 0.5% accuracy of the action. The FindBounce function is simple to use with the native Mathematica look and feel, it is easy to install, and comes with detailed documentation and physical examples, such as the calculation of the nucleation temperature. We also provide timing benchmarks with comparisons to existing tools, where applicable.
Program title:FindBounce
CPC Library link to program files:http://dx.doi.org/10.17632/tysw84skx3.1
Developer’s repository link:https://github.com/vguada/FindBounce
Licensing provisions: GNU General Public License 3
Programming language:Mathematica
Nature of problem: Evaluation of the Euclidean bounce action that controls the decay rate of metastable local minima in thermal and quantum field theories.
Solution method: Semi-analytical solution of a system of coupled differential equations, based on the polygonal bounce idea (Guada et al., 2019).
Restrictions:Mathematica version 10 or above, works in D=3,4.
Electrochemotherapy and irreversible electroporation are gaining importance in clinical practice for the treatment of solid tumors. For successful treatment, it is extremely important that the ...coverage and exposure time of the treated tumor to the electric field are within the specified range. In order to ensure successful coverage of the entire target volume with sufficiently strong electric fields, numerical treatment planning has been proposed and its use has also been demonstrated in practice. Most of numerical models in treatment planning are based on charge conservation equation and are not able to provide time course of electric current, electrical conductivity, or electric field distribution changes established in the tissue during pulse delivery. Recently, a model based on inverse analysis of experimental data that delivers time course of tissue electroporation has been introduced. The aim of this study was to apply the previously reported time-dependent numerical model to a complex in vivo example of electroporation with different tissue types and with a long-term follow-up. The model, consisting of a tumor placed in the liver with 2 needle electrodes inserted in the center of the tumor and 4 around the tumor, was validated by comparison of measured and calculated time course of applied electric current. Results of simulations clearly indicated that proposed numerical model can successfully capture transient effects, such as evolution of electric current during each pulse, and effects of pulse frequency due to electroporation effects in the tissue. Additionally, the model can provide evolution of electric field amplitude and electrical conductivity in the tumor with consecutive pulse sequences.
In order to obtain the maximum amount of energy from tidal stream extraction devices, deployment in large arrays should be studied. The area of seabed with favorable conditions is fairly limited; ...therefore layout spacing has to be optimized. In this paper a feasibility study for a novel experimental facility, suitable for the testing of an array of tidal devices, is presented. To avoid space and scale limitations of towing tanks, testing is proposed to be performed in large lakes or calm seas using a self-propelled vessel, which will carry an array of devices with variable spacing, creating relevant speed differences and measuring their performance and loading. Using hydrodynamic scaling laws, an appropriate size for test turbines and the range of vessel speed was determined to fulfill experimental requirements. Computational fluid dynamic simulations, using the actuator disc method, have suggested a suitable turbine array configuration to resemble real application conditions. A simplified model of the vessel was analyzed using the finite elements method to determine the main scantlings. The hull resistance calculated by empirical formulae was found to be negligible compared to the resistance of the tested turbine. It was confirmed that turbine size and speed determined by scaling laws are also reasonable from a propulsion point of view.
We are launching FindBounce, a Mathematica package for the evaluation of the Euclidean bounce action that enters the decay rate of metastable states in quantum and thermal field theories. It is based ...on the idea of polygonal bounces, which is a semi-analytical approach to solving the bounce equation by discretizing the potential into piecewise linear segments. This allows for a fast and robust evaluation of arbitrary potentials with specified precision and any number of scalar fields. Time cost grows linearly with the number of fields and/or the number of segments. Computation with 20 fields takes \(\sim 2\) seconds with \(0.5\%\) accuracy of the action. The FindBounce function is simple to use with the native Mathematica look and feel, it is easy to install, and comes with detailed documentation and physical examples, such as the calculation of the nucleation temperature. We also provide timing benchmarks with comparisons to existing tools, where applicable.
Composites of TiO2 and different amounts of plasmonic noble metal Au (0.25–2 wt%) were synthesized by employing the wet impregnation technique. The results of SEM, TEM, XRD and N2 physisorption ...analyses reveal that the morphologies of the prepared composites are similar to the morphology of bare TiO2 support and are not influenced by the increasing amount of deposited Au nanoparticles. On the other hand, the size of Au ensembles in the TiO2 + Au composites increased from 27.1 to 54.9 nm with the increasing amount of Au. With the increase of the diameter of Au ensembles, the intensity of the surface plasmon resonance (SPR) effect of Au ensembles in the UV–Vis diffuse reflectance spectra of the composites increased. The X-ray photoelectron spectroscopy (XPS) analysis of the valence band maxima (VBM) of the investigated photocatalysts revealed that the height of the Schottky barrier (SBH) at the Au/TiO2 junction in the investigated TiO2 + Au composites decreased from 0.4 to 0.15 eV with the increasing amount of Au (and their size). Therefore, the visible-light-generated “hot electrons” in Au ensembles of TiO2 + 2% Au composite have to overcome a lower energy barrier during the injection into the conduction band (CB) of the TiO2 support than “hot electrons” in the Au ensembles in the TiO2 + 0.25% Au composite. This makes the “hot electrons” in the TiO2 + 2% Au composite less accessible for the recombination with the visible-light generated holes, as the “hot electrons” do not agglomerate at the Schottky barrier (SB). This phenomenon was well expressed in the results of electrochemical impedance spectroscopy (EIS) analysis: under visible-light illumination, the TiO2 + 2% Au composite generated the highest amount of charge carriers among all investigated photocatalysts. The beneficial effect of the low SBH in the TiO2 + 2% Au solid was also expressed in the photoluminescence (PL) emission spectra, where the TiO2 + 2% Au composite showed the lowest charge carrier recombination rate. Further, the TiO2 + 2% Au composite expressed the highest visible-light triggered photocatalytic activity in the hydroxyl radical (OH·) generation and water-dissolved bisphenol A (BPA) oxidation test.
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•The diameter of Au ensembles in TiO2 + Au increases with increasing amount of Au.•Schottky barrier height (SBH) decreases with increasing diameter of Au ensembles.•Low SBH ...facilitates injection of visible-light generated electrons on Au into TiO2.•Surface plasmon resonance (SPR) effect increases with the diameter of Au ensembles.•Low SBH and high SPR effect are essential to obtain high photocatalytic activity.
Composites of TiO2 and different amounts of plasmonic noble metal Au (0.25–2 wt%) were synthesized by employing the wet impregnation technique. The results of SEM, TEM, XRD and N2 physisorption analyses reveal that the morphologies of the prepared composites are similar to the morphology of bare TiO2 support and are not influenced by the increasing amount of deposited Au nanoparticles. On the other hand, the size of Au ensembles in the TiO2 + Au composites increased from 27.1 to 54.9 nm with the increasing amount of Au. With the increase of the diameter of Au ensembles, the intensity of the surface plasmon resonance (SPR) effect of Au ensembles in the UV–Vis diffuse reflectance spectra of the composites increased. The X-ray photoelectron spectroscopy (XPS) analysis of the valence band maxima (VBM) of the investigated photocatalysts revealed that the height of the Schottky barrier (SBH) at the Au/TiO2 junction in the investigated TiO2 + Au composites decreased from 0.4 to 0.15 eV with the increasing amount of Au (and their size). Therefore, the visible-light-generated “hot electrons” in Au ensembles of TiO2 + 2% Au composite have to overcome a lower energy barrier during the injection into the conduction band (CB) of the TiO2 support than “hot electrons” in the Au ensembles in the TiO2 + 0.25% Au composite. This makes the “hot electrons” in the TiO2 + 2% Au composite less accessible for the recombination with the visible-light generated holes, as the “hot electrons” do not agglomerate at the Schottky barrier (SB). This phenomenon was well expressed in the results of electrochemical impedance spectroscopy (EIS) analysis: under visible-light illumination, the TiO2 + 2% Au composite generated the highest amount of charge carriers among all investigated photocatalysts. The beneficial effect of the low SBH in the TiO2 + 2% Au solid was also expressed in the photoluminescence (PL) emission spectra, where the TiO2 + 2% Au composite showed the lowest charge carrier recombination rate. Further, the TiO2 + 2% Au composite expressed the highest visible-light triggered photocatalytic activity in the hydroxyl radical (OH·) generation and water-dissolved bisphenol A (BPA) oxidation test.
In this study, we pioneered the synthesis of nanoflower-shaped TiO2-supported Au photocatalysts and investigated their properties. Au nanoflowers (Au NFs) were prepared by a Na-citrate and ...hydroquinone-based preparation method, followed by wet impregnation of the derived Au NFs on the surface of TiO2 nanorods (TNR). A uniform and homogeneous distribution of Au NFs was observed in the TNR + NF(0.7) sample (lower Na-citrate concentration), while their distribution was heterogeneous in the TNR + NF(1.4) sample (higher Na-citrate concentration). The UV-Vis DR spectra revealed the size- and shape-dependent optical properties of the Au NFs, with the LSPR effect observed in the visible region. The solid-state EPR spectra showed the presence of Ti3+, oxygen vacancies and electron interactions with organic compounds on the catalyst surface. In the case of the TNR + NF(0.7) sample, high photocatalytic activity was observed in the H2-assisted reduction of NO2 to N2 at room temperature under visible-light illumination. In contrast, the TNR + NF(1.4) catalyst as well as the heat-treated samples showed no ability to reduce NO2 under visible light, indicating the presence of deformed Au NFs limiting the LSPR effect. These results emphasized the importance of the choice of synthesis method, as this could strongly influence the photocatalytic activity of the Au NFs.
Abstract
The performance of the Cu/ZnO catalyst system with the AlMg‐oxide phase is studied for CO
2
hydrogenation to methanol. The catalyst is prepared by thermal treatment of the hydrotalcite phase ...containing intimately mixed metal cations in the hydroxide form. CuO in the presence of ZnO and disordered AlMg‐oxide phase gets easily reduced to Cu during the hydrogenation reaction. Its catalytic activity at relatively low Cu metal content (∼14 at.%) remains stable during 100 hours on stream at 260 °C with constant space‐time yield for methanol (∼1.8 g
MeOH
g
cat
−1
h
−1
) and high methanol selectivity (>85 %) The improved performance is attributed to the neutralization of surface acidity, increased number of weak basic sites in the disordered phase, and lower tendency for coke formation.
Two commercially available TiO2 (hexagonal-like and spherical-like particles) were used to investigate the effect of g-C3N4 “melting” on the photocatalytic properties of g-C3N4/TiO2 composites. ...Improvement in the contact between the components was observed when they were thermally treated at 350 °C for an extended period of time (between 2 and 72 h) due to the partial melting and phase fusion of g-C3N4. Consequently, the enhanced contact between the phases allows easier injection of photogenerated electrons from the conduction band of g-C3N4 into TiO2, improving charge carrier separation. The prepared composites were tested for bisphenol A degradation under visible-light illumination, which showed that the components that had been calcined for 24 h performed better due to the improved charge carrier separation. Superoxide anionic radicals and photogenerated holes were identified as active species in the photooxidation experiments conducted under visible-light illumination.
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•All investigated g-C3N4/TiO2 composites exhibit visible-light photocatalytic activity.•A prolonged calcination increases the photocatalytic activity of the composites.•The enhanced catalytic activity is attributed to improved g-C3N4/TiO2 interface area.•The origin of the improved g-C3N4/TiO2 interface area lies in the “melting” of g-C3N4.•The main active species for the photooxidation of bisphenol A are O2−· and holes.
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