Principles Study Research Articles

A Proof of Principle Study Conducted by Community-Dwelling Seniors Using a Novel Passive Gait Assist System

It is vital for rehabilitating patients to perform as many task-related exercises as possible. These patients often need either force or trajectory assistance in order to perform gait. While this can be provided in the form of traditional gait rehabilitation or currently emerging robot-assisted gait training, there is a need for an affordable means to assist gait training. In this study, we present a passive gait assistance device that is composed of a spring-bar system attached to an elastic cord and a specialized shoe. The shoe has two straps attached such that both plantar and dorsiflexion torque can be applied to the user depending on the angle of the pulling force. The merit of the devices is that it is an affordable means to provide the user with gait assistance while allowing some freedom of one’s foot movement. We show that, with 20 community-dwelling seniors, our system successfully produces plantar flexion and dorsiflexion torque according to the gait cycle. Furthermore, electromyography analysis suggests that plantar flexor demand during the late stance phase and dorsiflexor demand during the swing phase are significantly reduced.

First principles study of the different configurations of W and Mo in the γ/γ' phase

Effect of substituting atoms on the formation energy, charge density and density of states are calculated from first principles, and the effect of doping Wolfram and Molybdenum on the structural stability of γ' phase is studied. Wolfram and Molybdenum preferentially replace Aluminum atoms in γ ´ -Ni3 (Al3/8Ti5/8) cells, and the substitution formation energies are − 5.54 eV and − 4.64 eV, respectively, which reduce the energy of the system. Compared with Molybdenum - Aluminum, the outer valence electrons of Wolfram - Aluminum are obviously delocalized, the bonding is strong-er, and the binding energy of Wolfram - Aluminum atom is higher. The diffusion behavior of Wolfram and Molybdenum at the γ/γ' interface was studied by comparing the vacancy formation energy and diffusion barrier before and after diffusion using CI-NEB module in VASP. The results show that after doping Wolfram, the vacancy formation energy of Nickel at the γ/γ' interface is 0.13 eV higher than that of Molybdenum, the diffusion barrier of γ/γ' interface is 15.6% higher than that of Molybdenum, and the reverse diffusion barrier of γ/γ' interface is 19.6% higher than that of Molybdenum.

Exploring the use of NIR and Raman spectroscopy for the prediction of quality traits in PDO cheeses.

The aims of this proof of principle study were to compare two different chemometric approaches using a Bayesian method, Partial Least Square (PLS) and PLS-discriminant analysis (DA), for the prediction of the chemical composition and texture properties of the Grana Padano (GP) and Parmigiano Reggiano (PR) PDO cheeses by using NIR and Raman spectra and quantify their ability to distinguish between the two PDO and among their ripening periods. For each dairy chain consortium, 9 cheese samples from 3 dairy industries were collected for a total of 18 cheese samples. Three seasoning times were chosen for each dairy industry: 12, 20, and 36 months for GP and 12, 24, and 36 months for PR. A portable NIR instrument (spectral range: 950-1,650 nm) was used on 3 selected spots on the paste of each cheese sample, for a total of 54 spectra collected. An Alpha300 R confocal Raman microscope was used to collect 10 individual spectra for each cheese sample in each spot for a total of 540 Raman spectra collected. After the detection of eventual outliers, the spectra were also concatenated together (NIR + Raman). All the cheese samples were assessed in terms of chemical composition and texture properties following the official reference methods. A Bayesian approach and PLS-DA were applied to the NIR, Raman, and fused spectra to predict the PDO type and seasoning time. The PLS-DA reached the best performances, with 100% correctly identified PDO type using Raman only. The fusion of the data improved the results in 60% of the cases with the Bayesian and of 40% with the PLS-DA approach. A Bayesian approach and a PLS procedure were applied to the NIR, Raman, and fused spectra to predict the chemical composition of the cheese samples and their texture properties. In this case, the best performance in validation was reached with the Bayesian method on Raman spectra for fat (R2VAL = 0.74). The fusion of the data was not always helpful in improving the prediction accuracy. Given the limitations associated with our sample set, future studies will expand the sample size and incorporate diverse PDO cheeses.

First principle studies on half-metallicity and pressure-induced half-metallic band gap in 3-d transition metal-based quaternary Heusler ScVCoZ (Z = Si, Ge, Sn, P, As, and Sb) alloys

In the present work, we predict a series of 3-d transition metals-based quaternary Heusler alloys (QHA) ScVCoZ (Z = Si, Ge, Sn, P, As, and Sb) (SVCZ), by employing density functional theory (DFT) calculations. We carried out extensive band structure (BS) and density of states (DOS) analysis to explain the half-metallic and magnetic behavior of the alloys. We found that SVCZ alloys stabilize in the F 4̅ 3m space group and exhibit a ferromagnetic (FM) ground state (GS). Among the QHAs, SVCZ (Z = Si, Ge, and Sb) exhibit intriguing half-metallic properties featuring 100% spin polarization at the Fermi level (EF). Additionally, the effect of pressure indicates a band gap opening in one of the spin channels for SCVZ (Z = P, and As), and the half-metallic characteristics are retained up to a compressive pressure, respectively of 65, and 79 GPa for SCVP and SCVAs. Elastic properties calculations suggest SVCZ alloys satisfy Born stability criteria and are mechanically stable. Among the predicted QHAs, SVCZ (Z = Si, Ge, and Sn) shows brittle nature, whereas SVCZ (Z = P, As, and Sb) are ductile.

Inkjet-printed quantum dots on paper as concept towards high-density long-term data storage

Handling and storing the immense amounts of data native to the information age is a major challenge in terms of technological sustainability and energy demand. To date, tape storage remains the most widespread method for data archiving, while DNA data storage appears to offer the best data density and long-term stability in the future. However, DNA data storage is still in its infancy primarily due to economic and accessibility challenges. This emphasizes the need for more practical and readily available alternatives. We present a method for data storage utilizing inkjet printable quantum dots on paper with photoluminescence (PL) readout. Our proof of principle study showcases the ability to print and stack multiple bits of data on a single spot by exploiting the unique PL properties of quantum dots. This approach utilizes easily accessible resources, including a consumer-grade printer and paper as the substrate. Additionally, we perform initial stability tests, investigate scalability by controlling emission intensity, and evaluate the potential data density achievable by our approach.

Influence of different terminations on the surface properties of MB2: first principles study

Metal diborides MB2 (M = Zr, V, Ta, Nb) are widely used in many optoelectronic devices. Investigation into their surface stability and morphology is the first and essential step in exploring their properties. In the present work, the periodic density functional theory method was performed to study the surface properties and optical properties of MB2 (M = Zr, V, Ta, Nb). The effects of different surface terminations are discussed, which indicates metal terminations have low work functions. The calculation of optical properties indicates that the four borides are suitable for spectral selective materials and optical storage materials. These findings provide valuable theoretical data for the design and application of MB2 in optoelectronic materials.

Doping effects in the alanine-black phosphorene interactions: First principles studies

This work deals with the doping effects in the structural and electronic properties of the black phosphorene layer-alanine interactions. At first the alanine is allowed to interact with the pristine phosphorene, the results indicate that only weak interactions are manifested. Phosphorene layer is transformed into a more reactive material by adding impurity atoms (aluminum, gallium and boron) in such a way that chemisorption is obtained. In this way the most reactive is that system doped with aluminum. Electronic band structure and total density of states are modified since the energy band gap decreases as the alanine is adsorbed and increases when the impurity is incorporated in the structure. At last, the charge density plots exhibit the covalent bonds manifestations between the molecule and the surface impurity.

Adsorption and Recombination of H+ and H3O+ on Graphene-Supported Pt1, Pt13, and Pt14 Nanoclusters: A First Principles Study

Platinum electrocatalysts on graphene-like supports have recently attracted research interest as components of electrochemical devices based on hydrogen oxidation reactions in acid media due to their improved electrochemical properties, high stability, and conductivity. Within the current work, hydrogen adsorption and the recombination effects of a proton and hydroxonium on a graphene-based electrocatalyst were investigated using density functional theory. The interaction between ions and the platinum surface was simulated for various configurations, including different initial ion distances and angles relative to the surface of the graphene sheet as well as different adsorptions on various Pt atoms (vertices or faces for Pt13 and Pt14 nanoclusters). Then, the geometry optimization was performed. Changes in the density of states during the reactions were studied to analyze the occurrences and alterations of the interactions. A comparative analysis of the obtained adsorption energies of H+ and H3O+ with experimental data was conducted. The energy was calculated to be less in absolute value, and intermediates were more stable in adsorption models with the H–Pt–Gr angle of 90° than in models with the angle of 180°. Strong chemical bonding for models with H–Pt distances less than 2 Å was observed from the DOS.

The interface effect on the lithiation of silicon/graphene composites: The first principles study

AbstractTo reveal the interaction mechanism between lithium (Li) and silicon/graphene (Si/Gra) interface at the atomic scale, it was calculated that the energy band structure, density of states, charge transfer, radial distribution function and Li diffusion coefficient based on the first principles. The results indicated that the volume expansion of Si was effectively limited by the Si/Gra interface during Li insertion. There appeared the interface effect of Si/Gra on the combination of Li and Si atoms, according to the longer Li‐C (2.9 Å) and the larger electron cloud near the Li atom at the Si/Gra interface. The better diffusion channel for Li atoms was constructed at the Si/Gra interface, due to the lower diffusion energy barrier (0.42–0.44 eV) and higher diffusion coefficient (DLi = 0.784 × 10−4 cm2/s) for Li+ diffusion.

First principles study of the electronic structure, mechanical and optical properties of cubic perovskite NaCaCl3 under pressure

Based on the first-principles methods, the electronic, mechanical and optical properties of NaCaCl3 crystal were investigated under various pressures for the first time. At 0 GPa, the lattice constant and bulk modulus were calculated to be 5.278 Å and 27.011 GPa, respectively. Analysis of Poisson's ratio and Pugh's ratio indicated that NaCaCl3 exhibits ductile characteristics, which increases with the increasing pressure. Based on the crystal mechanical stability condition, the phase transition pressure of NaCaCl3 was calculated to be 5.12 GPa. The electronic property demonstrated that NaCaCl3 exhibits an indirect and wide band gap insulator (3.84 eV) at 0 GPa, and the band gap increases with the increasing pressure. The results of optical properties show that all spectrums of NaCaCl3 exhibit a blue shift when the pressure increases. The excellent ultraviolet absorption suggests that NaCaCl3 has a potential application in vacuum ultraviolet devices. And it is also suitable as transparent coating and window materials in the infrared and visible regions due to small reflectivity and absorption.

Gallium phosphide nanoribbon-based carbon monoxide sensors: insights from first principles study

The priority of research efforts over the past two decades has been focused on the effective detection of harmful gases and the development of small, efficient, and reliable nanodimensional sensors. The adsorption of carbon monoxide (CO) gas molecules on zigzag gallium phosphide nanoribbons (zGaPNRs) has been studied using first-principle calculations within the context of Density Functional Theory (DFT). Here, we have evaluated the potential of single-atom thick zGaPNRs in different configurations of nanoribbons for the detection of CO. Many possible configurations of studying the CO molecule adsorption on zGaPNRs have been explored. It is established that the interaction of CO molecules has an impact on the electrical and transport properties of zGaPNRs. The H-GaP-H is the most stable structure with the binding energy ([Formula: see text]) of −5.70[Formula: see text]eV. The stability is compromised with CO adsorption with CO-GaP-CO being the least stable structure. Pristine structure is semiconducting with the energy band gap ([Formula: see text]) of −3.95[Formula: see text]eV. The computed sensitivity (S) values are found to be highest for Co-GaPNRs with the S value of [Formula: see text] and the least sensitive structure is H-GaP-CO with the computed S as [Formula: see text]. Additionally, it is noted that CO molecules always establish a stable chemical bond with the nanoribbon edges through the C-side. The unique behavior is revealed by the transport characteristics, which demonstrates that when CO adsorption occurs near the Ga edge, the current magnitude is noticeably greater. Our research demonstrates the potential of specific CO adsorption and detection for the development of nanosensors.

Adsorption behaviors of organic molecules on Nb/Zr–modified bismuthene: A first–principles study

In this work, the geometric and electronic properties of the adsorption of volatile organic molecules (VOCs) such as CH2O, C2H4O, C2H6O on bismuthene monolayer with transition metal (TM = Nb, Zr) atoms adsorbed are investigated by using first–principles methods, aiming to explore the potential applications of TM–modified bismuthene monolayer in the field of organic molecular gas sensors. In contrast to the adsorption of organic molecules on Zr–bismuthene, Nb–bismuthene appears the chemisorption with multiple organic molecules, and it can be found that Nb–bismuthene could stably adsorb target molecules and exhibit outstanding charge transfer. The longer desorption time of organic molecules on Nb–bismuthene and the higher organic molecular adsorption capacity of the substrate at most temperatures, which suggests that Nb–bismuthene is suitable as a disposable sorbent for organic molecules, providing a viable direction for the application of Nb–bismuthene monolayer as a sensitive material for the removal of organic molecules.

First principle studies on structural, elastic, electronic, optical, and thermoelectric properties of new perovskite TlTaO3: For renewable energy applications.

The structural, optoelectronics, and transport properties of TlTaO3 compounds were determined utilizing the full potential augmented plane wave approach using first-principle method. We have considered the generalized gradient approximation for structural optimization and modified Becke-Johnson for electronic properties. The electronic properties reveal that the studied TlTaO3 possesses direct bandgap of magnitude 1.52 eV. Between 0 and 12 eV, optical spectra calculations are made, taking into account the real and imaginary parts of the dielectric function, refractive index, and loss function. The transport properties are estimated considering Boltzmann transport theory. The Seebeck coefficient, electrical conductivity, thermal conductivity, and power factor are all assessed using the Boltzmann transport theory. The optimized thermoelectric response of the examined TlTaO3 is produced by the improved carrier mobility, which also improves the thermoelectric efficiency of the TlTaO3. The obtained results will act as a theoretical road map for upcoming experimental and commercial TlTaO3 applications.

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ContextThe study investigates the impact of Hubbard U correction and spin-orbit coupling (SOC) on the structural, mechanical, electronic, and optical properties of Ti2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document} and SrTiO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document} compounds. The research is motivated by the potential applications of these materials in photovoltaics, with a focus on understanding their properties for such use. The ductility, ionicity, and mechanical stability of both compounds at zero pressure are assessed, indicating their potential as resilient materials. Also, the compounds display high refractive indices and absorption coefficients, indicating their suitability for solar harvesting applications. The predicted bandgaps align primarily with the UV–Vis areas of the electromagnetic spectrum, highlighting their potential in this domain.MethodsComputational techniques employed in this study are density functional theory (DFT) with and without spin-orbit coupling, as well as DFT+U methods, implemented using the Quantum ESPRESSO (QE) package. The study adopts the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional, while employing a plane-wave basis set with an energy cutoff of 50 Ry for wavefunctions and 500 Ry for charge density.

Electronic and optical properties of Cr / Cl co-doped in single-layer MoS2: A first principles study

This study aims to investigate the co-doping effect of Cr and Cl in monolayer molybdenum disulfide (MoS2) crystals. Density functional theory (DFT) was used to study the electronic structure and optical properties of the doped material, employing the PBE-GGA calculation method for the exchange-correlation energy. Key factors such as density of states, band structure, dielectric function, photoconductivity, refractive index, and absorptivity were analyzed. The findings indicate that co-doping of Cr and Cl reduces the band gap and introduces impurity energy levels within the band gap, thereby improving the photocatalytic performance.

Principle study on the bidirectional detonation driving technique for dual-state synchronous-running shock tunnels

爆轰驱动激波风洞是用来产生高超声速高焓试验气流的地面试验装置，通常分为正向爆轰驱动激波风洞和反向爆轰驱动激波风洞两种。本文针对单独正向或反向驱动模式的不足，提出一种新型的爆轰双向驱动模式，同时利用爆轰波的高能波阵面和泰勒稀疏波尾部平稳端，在一次试验中同时实现中焓与高焓两种高超声速试验气流。本文利用高温热化学反应流动数值计算技术，模拟并分析了爆轰双向驱动激波风洞中的关键波动力学过程，数值计算结果表明，爆轰双向驱动技术是可行的，而且正向驱动端和反向驱动端的状态调整具有相对独立性，可以覆盖中高焓大范围跨流域试验能力。

Polygenic liability for antipsychotic dosage and polypharmacy - a real-world registry and biobank study.

Genomic prediction of antipsychotic dose and polypharmacy has been difficult, mainly due to limited access to large cohorts with genetic and drug prescription data. In this proof of principle study, we investigated if genetic liability for schizophrenia is associated with high dose requirements of antipsychotics and antipsychotic polypharmacy, using real-world registry and biobank data from five independent Nordic cohorts of a total of N = 21,572 individuals with psychotic disorders (schizophrenia, bipolar disorder, and other psychosis). Within regression models, a polygenic risk score (PRS) for schizophrenia was studied in relation to standardized antipsychotic dose as well as antipsychotic polypharmacy, defined based on longitudinal prescription registry data as well as health records and self-reported data. Meta-analyses across the five cohorts showed that PRS for schizophrenia was significantly positively associated with prescribed (standardized) antipsychotic dose (beta(SE) = 0.0435(0.009), p = 0.0006) and antipsychotic polypharmacy defined as taking ≥2 antipsychotics (OR = 1.10, CI = 1.05-1.21, p = 0.0073). The direction of effect was similar in all five independent cohorts. These findings indicate that genotypes may aid clinically relevant decisions on individual patients´ antipsychotic treatment. Further, the findings illustrate how real-world data have the potential to generate results needed for future precision medicine approaches in psychiatry.

First principle studies on structural, electronic, elastic, optical, and thermoelectric properties of XGeCl3 (X = Rb/Cs): Promising compounds for green energy application

AbstractThis study employed density functional theory (DFT) embedded in Wien2K code to evaluate the physical features of the XGeCl3 (X = Rb/Cs) cubic halide perovskites. The structural optimization has been performed considering generalized gradient approximation (GGA) and electronic properties have been computed considering modified Becke‐Johnson potential (mBJ). The formation energy and phonon dispersion analysis establish the stability of the investigated compounds. Mechanical stability is further confirmed by the computed diverse elastic coefficients. It has been discovered that the examined substances are naturally ductile. The refractive index, reflectivity, and absorption coefficient, are among the optical parameters that have been estimated and analyzed. Interesting results have been obtained for the transport properties of XGeCl3 (X = Rb/Cs). The XGeCl3 (X = Rb/Cs) exhibits a high Seebeck coefficient (X = Rb/Cs) and the largest figure of merit (about 0.99), indicating significant potential for thermoelectric applications.

Application of GaS nanotubes as efficient catalysts in photocatalytic hydrolysis: a first principles study.

Photocatalytic hydrogen production is a promising and sustainable technology that converts solar energy into hydrogen energy with the assistance of semiconductor photocatalysts. Herein, we investigated the geometric structure and electronic and photocatalytic properties of single-walled GaS nanotubes under the framework of density functional theory with HSE06 as an exchange-correlation function. This paper presents the first study on the geometric structure, electron, and photocatalytic properties of single-walled GaS nanotubes. The results show that the strain energy and formation energy of GaS nanotubes decrease, while the structure is more stable, with increasing radius. Our study shows that after rolling from the slab, the nanotubes undergo a transition from an indirect band gap to a direct band gap and have appropriate band gaps for absorbing visible light. Moreover, it is speculated that the large disparity between the effective mass of electrons and holes can reduce charge carrier recombination. Among them, the nanotube with a diameter larger than (35, 0) showed promising band edge positions for photocatalytic hydrolysis redox potential with pH values between 0 and 7. Based on these properties, we believe that GaS nanotubes will be promising in photocatalytic hydrolysis.

A bicomponent synergistic MoxW1-xS2/aluminum nitride vdW heterojunction for enhanced photocatalytic hydrogen evolution: a first principles study.

The coupling of two-dimensional van der Waals heterojunctions is an effective way to achieve photocatalytic hydrogen production. This paper designs the MoxW1-xS2/AlN (x = 0, 0.25, 0.5, 0.75, 1) van der Waals heterojunction as a possible photocatalytic material. By using first-principles calculations, the effects of different Mo/W ratios on the band gap and photocatalytic hydrogen production performance of heterojunctions were investigated. The results show that the heterojunction is a direct Z-scheme photocatalyst and can achieve overall water splitting. By calculating the absorption spectrum, it is found that the heterojunction has a wider visible light absorption range when the bimetal is added, and there is still a strong absorption peak at 615 nm. With the increase of the Mo atom ratio, the absorption spectrum is red-shifted. The Gibbs free energy of the two-component Mo0.5W0.5S2/AlN heterojunction is only -0.028 eV. Our work provides a new perspective for the modification of 2D transition metal dichalcogenide photocatalytic heterojunctions.