Theoretical Investigation Research Articles

Impact of helical elongation of symmetric oxa[n]helicenes on their structural, photophysical, and chiroptical characteristics.

The adjustment of the main helical scaffold in helicenes is a fundamental strategy for modulating their optical features, thereby enhancing their potential for diverse applications. This work explores the influence of helical elongation (n = 5-9) on the structural, photophysical, and chiroptical features of symmetric oxa[n]helicenes. Crystal structure analyses revealed structural variations with helical extension, impacting torsion angles, helical pitch, and packing arrangements. Through theoretical investigations using density functional theory (DFT) calculations, the impact of helical extension on aromaticity, planarity distortion, and heightened chiral stability were discussed. Photophysical features were studied through spectrophotometric analysis, with insights gained through time-dependent DFT (TD-DFT) calculations. Following optical resolution via chiral high-performance liquid chromatography (HPLC), the chiroptical properties of both enantiomers of oxa[7]helicene and oxa[9]helicene were investigated. A slight variation in the main helical scaffold of oxa[n]helicenes from [7] to [9] induced an approximately three-fold increase in dissymmetry factors with the biggest values of|glum| of oxa[9]helicene (2.2 × 10-3) compared to|glum|of oxa[7]helicene (0.8 × 10-3), findings discussed and supported by TD-DFT calculations.

Comment on ‘Sexual relationships in group analysis: Theoretical investigations and clinical applications’ by Anastassios Koukis

With respect to the article by Koukis (2024) the author questions important points concerning self-exclusion, working through, external group events, boundary incidents and bodily experience. He concludes that it is necessary to restore boundaries and facilitate the therapeutic space.

Experimental and Theoretical Investigation on the SR method grown Semi-Organic Piperazinium Tetrachlorozincate Monohydrate (PTZM) Single Crystal for Optoelectronic Applications

Efficient semi organic nonlinear optical (NLO) Piperazinium Tetrachlorozincate monohydrate (PTZM) [C4H12N2][ZnCL4].H2O single crystals have been grown by slow evaporation solution technique (SEST) and Sankaranarayanan-Ramasamy (SR) method using water as solvent. Single crystal X-ray diffraction (SXRD) analysis reveals the unit cell parameters of the grown crystal. The morphology of the grown crystal was identified by the single crystal XRD analysis. The electrical properties, dielectric constant, dielectric loss and piezoelectric (d33) coefficient were determined. The etch pit density of PTZM crystal has been calculated by using the chemical etching analysis. The laser damage threshold (LDT) analysis was investigated by Nd: YAG laser and the wavelength of laser is 1064nm. The mechanical stability of the grown PTZM crystal was studied using Vickers microhardness measurement. Utilizing quantum chemical calculations, the PTZM compound is analyzed for vibrational properties, HOMO and LUMO characteristics, NBO interactions, and the determination of first-order hyperpolarizability. The nonlinear susceptibility and first-order hyperpolarizability results provide compelling evidence and affirm the PTZM molecule’s potential as a strong candidate for nonlinear optical (NLO) applications.

Observational feasibility of 4D Einstein-Gauss-Bonnet cosmology: bouncing and non-bouncing universes

This paper analyzes the possibility of bouncing and non-bouncing universes in the framework of four-dimensional Einstein-Gauss-Bonnet (4D-EGB) gravity,corresponding respectively to negative and positive coupling constants λ of the Gauss-Bonnet term. We also use the Horndeski-type scalar-tensor theory to assess the role of a scalar charge C as a geometrical contribution to the radiation in the Universe.We modify the expansion history of the universe to allow for modifications induced by the 4D-EGB gravity.Using Planck measurements of the cosmic microwave background anisotropies as well as various datasets of baryonic acoustic oscillations, we set the upper bounds λ ≤ 10-16(km/s/Mpc)-2 and λ ≤ 10-30(km/s/Mpc)-2 for the non-bouncing and bouncing scenarios.The upper limit in the latter case is mainly driven by the requirement to conservatively respect the thermal history at energy scales of the standard model of particle physics.We also find that the contribution of the geometrical radiation-like term of the model cannot exceed 10% of the current radiation in the Universe. The possibility of an early inflationary phase produced by a single scalar field is also studied and found to be feasible in both bouncing and non-bouncing scenarios.This study shows the feasibility of a bouncing universe, even with a normal matter sector, in the 4D-EGB gravity. More theoretical investigation is required to further explore possible observational predictions of the model that can distinguish between general relativity and 4D-EGB gravity.

Magnetic and thermoelectric properties of quasi-one-dimensional BaVSe3

Quasi-one-dimensional (Q1D) materials possess extraordinary magnetic and transport characteristics, which render them of critical importance. In this study, we present the synthesis of phase pure Q1D BaVSe3 via a novel heat treatment process and analyze its low-temperature thermoelectric, magnetotransport, and magnetic properties. A comparison is made between this phase pure system and the BaVSe3 infused with the secondary BaSe3 phase that we previously reported todetermine the potential effect of impurities on the magnetic and thermoelectric properties. Our previous study covered the experimental and theoretical investigation on the exotic magnetic properties of BaVSe3 with BaSe3. In phase pure BaVSe3, at TC ∼ 41.2 K, a paramagnetic to ferromagnetic transition with a magnetic moment of 1.74 μB from V4+ was observed,consistent with calculated values. At very low temperatures (<117 K), the material behaved like glass, showed Griffiths-like behaviorand spin valve-like butterfly magnetoresistance (BMR). Experiments indicate that these exotic magnetic properties are caused by the interaction between the A1g and t2g levels of the V 3d orbital and their spin orientation. Magnetic frustration in these materials is caused by V-V inter and intra chain interactions in the 1D spin chains of V. Q1D BaVSe3 (BVS) demonstrated n-type thermoelectricity with a thermoelectric figure of merit of ∼ 0.008, 4 × greater than BaVSe3:BaSe3 (BVS: BS) at room temperature. The thermal transport is determined to be primarily phonon-dependent. The magnetic property studies disclosed that this FM transition metal chalcogenide can contribute to low-temperature spintronics.

Theoretical and experimental investigation of ultrasonic cutting kinematics and its effect on chip formation and surface generation in high-frequency ultrasonic vibration-assisted diamond cutting

Ultrasonic vibration-assisted cutting (UVAC) is regarded as a feasible technology to machine difficult-to-cut materials. High-frequency ultrasonic vibration-assisted cutting (HFUVAC), with a working frequency of more than low and medium frequency (20-60kHz), has been reported to improve material machinability and prolong tool life. This paper presents a comprehensive investigation of the ultrasonic cutting kinematics and the generated chip/surface formation process in HFUVAC of a 316l stainless steel workpiece. First, the ultrasonic cutting kinematics was analyzed and verified by comparing the experimental and theoretical surface texture under different nominal cutting speeds. Based on the ultrasonic cutting kinematics and the simulated strain/stress distributions, the chip and surface formation between conventional cutting (CC) and HFUVAC was analyzed. More importantly, the incremental cutting mode was defined when the cutting stroke, namely the effective cutting length in one vibration cycle was less than 800 nm. The results show that in the incremental cutting mode, defect-free surface was achieved due to suppressed large deformation and friction action. Finally, HFUVAC of the sinusoidal microstructure was performed under the incremental cutting mode, achieving optical requirements with nanometer-scale surface roughness and submicrometric form accuracy, which validates the technical feasibility in HFUVAC of micro-structured surfaces.

Exploring the Synthesis and Application of a Pyrazole Derivative in Corrosion Protection: Theoretical Modeling and Experimental Investigations

This research investigates the inhibitory performance of BM-02, a synthesized pyrazole derivative (R)-5-(4-methoxyphenyl)-1,3-diphenyl-4,5-dihydro-1H-pyrazole, against the corrosion of mild steel in a 1 M hydrochloric acid solution. A comprehensive array of experimental techniques, including weight loss analysis, potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy, were employed to assess the inhibitory effectiveness. BM-02 is identified as a mixed inhibitor, showcasing a remarkable efficiency of 91.5% at a concentration of 10−3 mol/l. The adsorption behavior of the BM-02 molecule was investigated, revealing a physical adsorption model in accordance with the Langmuir isotherm. Furthermore, ATR-IR, 1H NMR, and 13C NMR spectra were acquired, complemented by density functional theory (DFT) calculations and molecular dynamics (MD) simulations to gain deeper insights into the molecular interactions and corrosion inhibition mechanism.

Theoretical and run-test investigation on a 50 MW beam-down concentrating solar power plant in China

The beam-down concentrating solar power plant has the advantages of high concentrating ratio, low installation and maintenance requirements, and low pump consumption. To conduct further theoretical and run-test evaluations of the optical and thermal performance of the beam-down concentrating solar power system, the Yumen Xinneng 50 MW beam-down power plant is analyzed in this research. The variation of the heliostat field efficiency, hyperboloid mirror flux density, receiver flux density, and annual power generation under various operating parameters is discussed. The run-test results from June 12th indicated an average outlet temperature of molten salt reached 559°C between 13:07 and 13:56 under an average direct normal irradiation of 739.7 W/m2. The corresponding inlet temperature increased from 302.3°C to 307.6°C due to the rewarming effect caused by the increase in hot molten salt. Regarding the simulation results, the recommended design parameters for the vertex ratio of the hyperboloid mirror are between 0.775 and 0.8 to mitigate the contradiction between initial investment and optical efficiency. The maximum values of cosine efficiency, shading and blocking efficiency, shading efficiency of the hyperboloid mirror, and attenuation efficiency for the heliostat field are 85.56%, 99.96%, 99.35%, and 97.46% on June 1st for the maximum solar elevation angle of 70.72°. Consequently, the maximum values of the average hyperboloid mirror flux density and receiver flux density are 11.2 kW/m2 and 399.1 kW/m2 on June 1st. The maximum power generation for a 7-day period is 4674.22 MWe in June with a duration time of 100 hours. This paper can further expand research on the comprehensive performance of beam-down power plants.

Perception towards reducing natural gas consumption and imports in Europe: A theoretical and empirical investigation

Perception towards reducing natural gas consumption and imports in Europe: A theoretical and empirical investigation

Influence of sustainability in the positioning of the university brand: Study in universities in Medellín-Colombia

The implementation of university sustainability affects brand perceptions by conferring attributes related to commitment and reputation, especially by students. The proper management of sustainability is related to an improvement in the university brand perceived by its stakeholders, including students. For this reason, this research aims to analyse whether university sustainability positively affects brand positioning among university students. For this purpose, a theoretical and quantitative mixed-method investigation is proposed that allows the establishment of a structural model in which the relationships between the dimensions of university sustainability with the dimensions of brand positioning are evident. The empirical analysis found that some dimensions of university sustainability, such as the institutional framework, campus operations and some dimensions of the substantive functions, positively affect brand positioning in university students and generate commitment to the university from both the prestige and reputation of the brand.

Competing CO and HCOOH Pathways in CO2 Electroreduction

Human activities have significantly contributed to the increase in global carbon emissions, leading to adverse environmental effects such as global warming. Electrochemical reduction of carbon dioxide (CO2RR) presents a promising approach to mitigate carbon emissions. This process not only stores the low energy density renewable energies into high energy density chemical bonds, but also produces a variety of valuable products, including one‐carbon products like HCOOH and CO, as well as multi‐carbon products like CH3CH2OH and C2H4. Among them, HCOOH and CO can be produced with over 90% selectivity on various catalysts, indicating their potential for large‐scale applications. However, the precise reaction pathways toward CO and HCOOH remain unclear, and the competition between these pathways often leads to low product selectivity. This review provides an overview of current research on the selective reduction of CO2 to CO and/or HCOOH, encompassing theoretical simulations, catalyst design, and investigations into reaction mechanisms. Additionally, this review highlights the challenges and prospects for the further development and understanding of selective catalysts for CO and HCOOH production, aiming to provide valuable insights for future studies in this intriguing and significant research field.

Theoretical and Experimental Investigation on the Effect of Beam Misalignment on a Second Harmonic 0.8 THz Gyrotron

Theoretical and Experimental Investigation on the Effect of Beam Misalignment on a Second Harmonic 0.8 THz Gyrotron

Experimental and theoretical investigation of failure mechanism in Al2O3/SiC composite under plane shock waves

The investigation of fracture and fragmentation is essential for evaluating the protection performance and structural design of ceramic armour. This paper focused on the dynamic failure and fracture mechanisms of the fine-grained Al2O3/SiC composite subjected to plane shock waves. The macroscopic shock response characteristic was determined through a series of plane impact tests, which included the Hugoniot curves of the composite. The results indicated that the fracture mechanism is significantly influenced by specific stress characteristics. The transgranular fracture in large grains and intergranular fracture in small grains exhibit obvious local plastic deformation characteristics. Moreover, the presence of second-phase SiC particles markedly influences both crack propagation and the microfracture mode of the composite. Lastly, a statistical analysis of the ceramic fragments was conducted after the soft recovery of specimens in impact experiments, and analytical models were developed and modified to predict the distribution of fragments under plane shock loading.

Theoretical investigations of structural, electronic, magnetic, and optical properties of group V (X = V, Nb, Ta) added CeO2-X materials for optoelectronic applications.

Depletion of natural resources, responsible for energy production, is a serious concern for researchers to develop alternate energy resources or materials. Scientists have proposed various energy materials which are based on semiconductors and their underlying physics. Cerium oxide (CeO2) is a versatile energy material which receives much attention owing to excellent photocatalytic, photonic, thermal stability, and optoelectronic applications. Even though CeO2 exhibited remarkable physical properties, but yet, they can be enhanced upon suitable doping. Focus on current research is to dope group V elements into CeO2 in order to enhance its electronic and optical response. The density of states (DOS) and band gaps of proposed materials are calculated, and significant improvement is noted after applying TB-mbj method. Optical absorption spectra of V/Nb/Ta-doped CeO2 show blueshift and decrease in reflectivity along with the presence of magnetism illustrate potential uses of these materials in future UV optoelectronics, spintronics, sensing, and energy harvesting devices. This research is based on computational work carried using Wien2k code where PBE-GGA approximation is used to approximate exchange and correlation potentials. Supercells of vanadium/niobium/tantalum-doped CeO2 are constructed, and spin-polarized density of states (DOS) along with optical constant are calculated. TB-mbj method is used to bring improvements in DOS and band gaps of proposed materials. Iterations are conducted using convergence criterion, and non-relativistic calculations are performed.

Zinc(II) coordination compound with N′-(pyridin-2-ylmethylene)nicotinohydrazide: Synthesis, crystal structure, computational and cytotoxicity studies

In this work, we report on the synthesis of a novel zinc(II) coordination compound [ZnL2] (1), which was readily obtained from the reaction of Zn(OAc)·2H2O and N′-(pyridin-2-ylmethylene)nicotinohydrazide (HL) in methanol. Recrystallization of 1 from dimethylformamide under ambient conditions allowed to produce yellow block-like crystals of 1·H2O. Complex 1·H2O was characterized by FT-IR and 1H NMR spectroscopy, while its optical properties were studied by UV–vis and spectrofluorimetry in methanol. The crystal structure of the title complex was revealed by single crystal X-ray diffraction and further explored in detail by the Hirshfeld surface analysis. Theoretical investigations based on the DFT calculations have also been applied to show the electronic properties of complex 1. The antitumor activities of the parent ligand HL and complex 1 were studied using Dalton's lymphoma malignant cancer model. Both compounds were found to induce concentration-dependent cytotoxicity and apoptotic cell death, leading to a decrease in cell viability, body weight, and tumor volume in mice with the superior activity of complex 1 over HL. Mice treated with complex 1 demonstrated an increase in life span with a survival period of 23 days. Finally, using a molecular docking approach, we have probed complex 1 to inhibit the recombinant mouse tumor-necrosis factor alpha (mTNF).

A Theoretical Calculation of Electrical Energy Production from the Incineration of Baghdad Municipal Solid Wastes

A theoretical investigation study was carried out to determine the requirements of establishing a steam power plant by incinerating municipal solid wastes generated from the city of Baghdad. Survey data the generated quantities of municipal solid wastes from both Al-Karth and Al-Rusafa sectors of the city were utilized to predict the theoretical possible energy production that can be obtained from the incineration of this waste under controlled parameters. Results reviled that the high heating value of Baghdad’s municipal solid wastes is of about (12.789 MJ/kg) and the possible electrical energy production in the steam power plants in Al-Karth and Al-Rusafa are (119.287 MW, 203.917 MW) respectively using a steam turbine of efficiency (25%). Resulted emissions of CO2 gases are estimated to be 4209.995 ton/day. So the emission of CO2 is the main problem of this method because of its effect on global warming but it is less effect on environment from Methane, Sulphur Oxides and Nitrogen Oxides. The quantity of plastic wastes in Municipal Solid Wastes is important in increasing their average high heating value. 

DFT studies on electronic and structure properties of PbSe1-xSx alloys for thermoelectric materials using VCA and RS.

In this work, Density Functional Theory (DFT) was employed to investigate the crystal structure and electronic properties of lead selenide (PbSe) and lead sulfide (PbS) semiconductors and their pseudo binary alloys PbSe1-xSx. The virtual crystal approximation (VCA) and randomly substituted solid models were employed to study these materials. In addition, the thermoelectric properties as function of the alloy composition were studied. Lattice parameters obtained using the generalized gradient approximation (GGA) were compared with theoretical and experimental results. The electronic bands were calculated for different sulfur compositions (0≤x≤1, Δx=0.1) using the Generalized Gradient Approximation of TB09LDA (MGGA). It was observed that the transition from the valence band to the conduction band takes place at the L point, which agrees with previous theoretical investigations. Slight deviations from Vegard's law were observed in the lattice parameters and bandgap of the alloys, especially for the sulfur-rich alloys. Effective band diagrams obtained from the unfolding of supercell band diagrams, reported for the first time for this system, show that the impacts of alloy disorder are low in the vicinity of the L point. The influence of the alloy composition on the transport properties was studied within the framework of Boltzmann’s semiclassical theory. The electrical conductivity shows a thermally activated increase which influences the total thermal conductivity above T>600-700 K, and the figure of merit ZT. Seebeck coefficient dependence with the chemical potential suggests an ambipolar behavior of the alloys, which present both n and p character. The alloys have the ZT maxima above 900 K influenced by the PbSe1-xSx alloy composition. Remarkably, the alloy with x=0.5 present a maximum ZT value comparable to that of PbSe, which indicates that is promising to substituting selenium by sulfur atoms to tailor the thermoelectrical properties. This work shows the suitability of the VCA approximation and the band unfolding method, to describe the composition-dependent properties of the PbSe1-xSx pseudo binary alloys.

Yolk-shell electron-rich Ru@hollow pyridinic-N-doped carbon nanospheres with tunable shell thickness and ultrahigh surface area for biomass-derived levulinic acid hydrogenation under mild conditions

Aiming to efficiently upgrade renewable biomass-derived levulinic acid (LA) into γ-valerolactone (GVL), we have devised yolk-shell electron-rich Ru@hollow pyridinic-N-doped carbon nanospheres, featuring a tunable shell thickness (20−70nm) and an ultrahigh surface area (4016 m2 g−1). Experimental and theoretical investigations reveal that the strategic formation of the yolk-shell structure and appropriate thinning of the carbon shell facilitate the generation of electron-rich Ru0 and a positive shift of the d-band center towards the Fermi level by increasing surface pyridinic-N species. These modifications suitably intensify Ru0−H interaction, promote reactant adsorption, stimulate electron transfer between active H and the C=O group of LA, and ultimately reduce apparent activation energy. Consequently, a high LA turnover frequency (18733.4h−1 at 30 °C) and GVL selectivity (99.9%), alongside excellent stability up to eight cycles, are achieved, markedly outperforming externally-supported analogues. These findings afford valuable insights into designing yolk-shell nanostructures for biomass upgrading through microenvironment engineering.

Mean-field model for BaFe[formula omitted]Ti[formula omitted]O19 ([formula omitted] = 0 and 0.2) hexaferrite: Structural and magnetic properties

An experimental and theoretical investigation of the magnetic properties of Ti-doped barium hexaferrite (BaM) is conducted. Polycrystalline samples of BaFe12−xTixO19 with x≤ 0.2 were synthesized using the solid-state reaction method. X-ray diffraction (XRD) analyses, along with Rietveld refinement, confirmed the presence of BaFe12O19 as the predominant BaM phase and a minor amount of hematite in all samples. Structural analysis revealed a slight increase in lattice parameters a and c for x=0.2. A result mostly related to the preferential occupation of Ti4+ ions at the 4f2 and 12k sites, coupled with the reduction of Fe3＋ ions to Fe2＋. It was also found that the magnetic response of samples is affected by Ti4+ substitution. Saturation magnetization slightly decreased from ∼ 45 (x = 0) to ∼ 44 emu/g (x = 0.2), the anisotropy constant from ∼4.08× 105 to ∼4.06× 105 erg/g2, while coercivity slightly increased from ∼ 2456 to ∼ 2468 Oe, and the anisotropy field from ∼ 18.2 to ∼ 18.6 kOe. The magnetic features of the samples were analyzed in terms of a proposed model based on the mean-field theory. Results indicated that the substitution of Ti4+ ions resulted in a decrease in the magnetic moment of the 2b sublattice. Such behavior is influenced by its closest neighboring sites 12k and 4f2 sublattices, which are the preferred occupancy sites for the Ti4+ cations.

Theoretical insights into long-range coupling of electron-hole pairs in TCTA–PO-T2T exciplex

This work reports theoretical investigations concerning long-range coupling of electron-hole pairs in spatially separated exciplex (SSE) systems via Density Functional Theory and Time-Dependent Density Functional Theory. Based on TCTA−PO-T2T parent exciplex, where 4,4′,4″-Tris(carbazol-9-yl)triphenylamine (TCTA) serves as donor (D) and 2,4,6-Tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (PO-T2T) as acceptor (A), SSEs are constructed by intentionally tuning the D−A distance. The calculation results demonstrate that all SSEs, even if the D−A distance is over 14 Å, exhibit the clear and strong charge transfer character in terms of DCT, qCT, and t indexes. As the D−A distance increases, the energy gap of SSEs is increased, resulting in the blueshift of emission spectra. Calculation and experiment results show a good consistency, indicating that our model could well describe SSEs. Meanwhile, the reduced energy gap between CT and 3LE and more degenerate states could boost reverse intersystem crossing via vibronic coupling and hyperfine coupling, eventually improving the electroluminescent performance of SSEs. Our study suggests that manipulation of relative energy alignment via controlling D−A distance not only promotes the properties of exciplexes, but also offers guidance for designing thermally activated delayed fluorescence emitters through-space charge transfer.