Density Gradient Research Articles

Peripheral Blood Mononuclear Cell Transcriptome of Dairy Cows Naturally Infected with Bovine Leukemia Virus.

The current literature has identified many abnormalities in the immune expression of cows infected with the bovine leukemia virus (BLV). These studies have focused on individual cell, gene, or protein expression, failing to provide a comprehensive understanding of the changes in immune expression in animals with BLV. To identify the overall alterations in immune expression during BLV infection, the transcriptomes of the peripheral blood mononuclear cells (PBMCs) of cows seropositive or seronegative for BLV antibodies were sequenced. Whole blood samples were collected from 20 dairy cows and screened for BLV antibodies and PCR was used to quantify the proviral load of the samples. PBMCs were separated from whole blood using density gradient centrifugation from which RNA was isolated and sequenced. Three seropositive samples (BLV+; n = 3), including one of each PVL category, low (n = 1), moderate (n = 1), and high (n = 1), and three seronegative samples (BLV-; n = 3) were sequenced for differential gene expression analysis. The results showed major differences in the transcriptome profiles of the BLV+ and BLV- PBMCs and revealed a wide variety of immunological pathways affected by BLV infection. Our results suggest that disease state and PBMC gene expression vary depending on BLV proviral load levels and that BLV causes the suppression of normal immune responses and influences B and T cell gene expression, resulting in immune dysfunction.

Mechanical and shape-memory properties of TPMS with hybrid configurations and materials

ABSTRACT Triply periodic minimal surface (TPMS) structures with excellent properties of stable energy absorption, light weight, and high specific strength could potentially spark immense interest for novel and programmable functions by combining smart materials, e.g. shape memory polymers (SMPs). This work proposes TPMS lattices with hybrid configurations and materials that are composed of viscoelastic and shape-memory materials with the aim to bring temperature-dependent mechanical properties and additional dissipation mechanisms. Different configurations and diverse materials of polylactic acid (PLA), fiber-reinforced PLA, and polydimethylsiloxane (PDMS) are induced, generating five types of TPMS lattices, including (Schoen’s I-WP) IWP uniform lattice, IWP lattice with density gradient, hybrid configurations, hybrid materials, and filled PDMS, which are fabricated by 3D printing. The fracture morphologies and the distribution of carbon fibers are demonstrated via scanning electron microscopy with a focus on the influence of carbon fiber on shape-memory and mechanical properties. Shape recovery tests are conducted, which proves good shape memory properties and reusable capability of TPMS lattice. The combined methods of experiments and numerical simulation are adopted to evaluate mechanical properties, which presents multi-stage energy absorption ability and tunable vibration isolation performances associated with temperature and hybridization designs. This work can promote extensive research and provide substantial opportunities for TPMS lattices in the development of functional applications.

Experimental and theoretical studies of alkyl 2-(2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1]nonan-9-ylidene)hydrazine carboxylates: Synthesis, spectroscopic, crystal structure, Hirshfeld surface, and antimicrobial studies

The nine alkyl 2-(2,4,6,8-Tetraaryl-3,7-diazabicyclo[3.3.1]nonan-9-ylidene)hydrazine carboxylates having bicyclic bispidine core were synthesized and characterized using FT-IR, NMR, and mass spectra. Further confirmation of the structure and positioning of the groups was obtained using single crystal XRD investigation. The analysis revealed that one piperidine ring adopts a chair and another a boat form. The aryl groups in the chair conformation are positioned equatorially, whereas those in the boat conformation are orientated axially. The carbazate group (C=N-NH-COOR) aligned the center of the two piperidine rings, with a small deviation towards the boat conformation piperidine ring. The dihedral angle between the chair and boat conformations of the piperidine ring (2f) is 48.51 Å and 45.12 Å, respectively. Hirshfeld and 2D fingerprint analysis show considerable H···H bonding interactions in the crystal. The intermolecular interaction and mechanical stability of crystals were investigated using interaction energy and crystal void analysis. Reduced density gradient and localized orbital locator analyses were used to investigate intramolecular interactions and electron delocalization. The molecule's higher and lower electron densities were investigated utilizing frontier molecular orbital analysis and Molecular Electrostatic Potential. The antimicrobial activity of the compounds was investigated using four bacterial and two fungus strains.

The Miniaturized Isolation of Neutrophil Granules (MING) method allowed a deep proteome mapping of human neutrophil granules.

Neutrophils are the innate immune system's first line of defense, and their storage organelles are essential to their function. The storage organelles are divided into three different granule types named azurophilic, specific, and gelatinase granules, besides a fourth component called secretory vesicles. The isolation of neutrophil's granules is challenging, and the existing procedures rely on large sample volumes, about 400 mL of peripheral blood, precluding the use of multiple biological and technical replicates. Therefore, the aim of this study was to develop a miniaturized isolation of neutrophil granules (MING) method, using biochemical assays, mass spectrometry-based proteomics and a machine learning approach to investigate the protein content of these organelles. Neutrophils were isolated from 40 mL of blood collected from three apparently healthy volunteers and disrupted using nitrogen cavitation; the organelles were fractionated with a discontinuous 3-layer Percoll density gradient. The isolation was proven successful and allowed for a reasonable separation of neutrophil's storage organelles using a gradient approximately 37 times smaller than the methods described in the literature. Moreover, mass spectrometry-based proteomics identified 368 proteins in at least 3 of the 5 analyzed samples, and using a machine learning strategy aligned with markers from the literature, the localization of 50 proteins was predicted with confidence. When using markers determined within our dataset by a clusterization tool, the localization of 348 proteins was confidently determined. Importantly, this study was the first to investigate the proteome of neutrophil granules using technical and biological replicates, creating a reliable database for further studies.

Population pharmacokinetics of tacrolimus whole blood and peripheral blood mononuclear cell concentrations in stable kidney-transplanted patients.

Therapeutic drug monitoring of tacrolimus based on whole blood drug concentrations is routinely performed. The concentration of tacrolimus in peripheral blood mononuclear cells (PMBCs) is likely to better reflect drug exposure at the treatment target site. We aimed to describe the relationship between tacrolimus whole blood and PBMC concentrations, and the influence of patient characteristics on this relationship by developing a population pharmacokinetic model. We prospectively enrolled 63 stable adult kidney-transplanted patients and collected dense (12-h, n = 18) or sparse (4-h, n = 45) pharmacokinetic profiles of tacrolimus. PBMCs were isolated from whole blood (Ficoll density gradient centrifugation), and drug concentrations in whole blood and PBMCs were analysed using liquid chromatography-mass spectrometry. Patient genotype (CYP3A4/5, ABCB1, NR1I2) was assessed with PCR. Population pharmacokinetic modelling and statistical evaluation was performed using NONMEM. Tacrolimus whole blood concentrations were well described using a two-compartment pharmacokinetic model with a lag-time and first-order absorption and elimination. Tacrolimus PBMC concentrations were best estimated from whole blood concentrations with the use of a scaling factor, the ratio of whole blood to PBMC concentrations (RC:PBMC), which was the extent of tacrolimus distribution into PBMC. CYP3A5*1 non-expressors and NR1I2-25 385T allele expressors demonstrated higher RC:PBMC ratios of 42.4% and 60.7%, respectively. Tacrolimus PBMC concentration could not be accurately predicted from whole blood concentrations and covariates because of significant residual unexplained variability in the distribution of tacrolimus into PBMCs and may need to be measured directly if required for future studies.

Effects of Stocking Density on the Survival, Growth, and Stress Levels of the Juvenile Lined Seahorse (Hippocampus erectus) in Recirculating Aquaculture Systems.

Seahorses are increasingly regarded as a promising farming object suitable for recirculating aquaculture systems (RASs) due to their high economic value. However, reports on the large-scale farming of seahorses in RASs are rare, and some key parameters, such as stocking densities, are still unclear. In the present study, we employed the lined seahorse (Hippocampus erectus), for which large-scale farming has been achieved, to determine the suitable stocking density for three different-sized juveniles in RASs. The three different-sized juveniles had body heights of 4.0, 7.0, and 9.0 cm, and their test density gradients were 1.0, 0.8, 0.6, and 0.4 inds/L; 0.6, 0.5, 0.4, and 0.3 inds/L; and 0.4, 0.3, 0.2, and 0.1 inds/L, respectively. The juveniles were cultivated for one month, and then their survival, growth, and plasma cortisol and brain serotonin contents (two stress-related indicators) were analyzed. The results show that, regardless of the size of the juveniles, a high density can inhibit growth and trigger stress responses. In addition, for small- (4.0 cm) and medium-sized (7.0 cm) juveniles, a high density can also exacerbate size heterogeneity and cause death. Taking into account the welfare and yield of farmed seahorses, the present study suggests that the suitable stocking densities for 4.0, 7.0, and 9.0 cm juveniles in RASs are 0.6, 0.4, and 0.2 inds/L, respectively.

A novel measurement for evaluating the capture efficiency of local ventilation system using background oriented schlieren

In-situ measurement of the capture efficiency of local ventilation systems (CELV) is a challenge in field of indoor air quality control. This study introduced a novel method for assessing the capture efficiency using background oriented schlieren (BOS). A 1:4 model experimental platform was constructed to investigate the feasibility. The CELV was compared using both the BOS and the tracer gas method, and the optimization of BOS device parameters for better CELV results was investigated. The results showed that the CCD camera-BOS could detect thermal airflows with a temperature difference over 40 K. The best post-processing algorithm for CELV by BOS, which was combined density gradient variation-rate and gray-scale method (CE-DGR&GS), was closely matched the results of the tracer gas method (CE-SF6), with a correlation of 0.97. When the capture efficiency exceeded 90%, the deviation between the two methods was less than 10%. However, when the ventilation system captured poorly, the CELV by CE-DGR&GS was over-estimated. Higher NR of BOS image causes large deviation of the calculated capture efficiency, and CELV by BOS under the same flow can differ by as much as 40 % by various cameras. A high-pixel CCD camera with a long focal length lens (f ≥ 35 mm, ISO≤100, f# = 16) was recommended. The interrogation window size for cross-correlation algorithms could be 33%–66% of the collected image pixel resolution. To achieve sufficient optical sensitivity, the distance ratio Zd/Zb was suggested to be 1:2. This study provides a cost-effective and entrie flow-field measurement for assessing local ventilation capture efficiency.

Impact of ionization and transport on pedestal density structure in DIII-D and Alcator C-Mod

Abstract This paper investigates the role of ionization on the pedestal structure using both measurements and modeling for H-mode plasmas on DIII-D and Alcator C-Mod to enhance our ability to predict pedestal behavior in future pilot plants. The impact of the neutral penetration depth on the pedestal density is investigated using dimensionally matching hydrogen and deuterium DIII-D H-mode discharges at low and high electron density. The DIII-D Lyman-α diagnostic measurements show that hydrogen neutrals penetrate deeper inside the plasma on both the high field and low field side, while the pedestal electron density structure is similar for both isotopes. However, as the opaqueness increases we observe that the pedestal density gradient becomes stiff, similar to prior observations on DIII-D and C-Mod (Mordijck 2020 Nuclear Fusion 60 082006). In addition, these results also confirm prior measured and modeled poloidal asymmetries in neutral densities, indicating that to make transport predictions, 2D neutral modeling is necessary. The first direct validation of SOLPS-ITER for the measured brightness, emissivity and neutral densities for three different confinement regimes on C-Mod is introduced. The SOLPS-ITER model shows good agreement, within the constrains of the model for all regimes. In addition, a comparison of SOLPS-ITER modeling for DIII-D and C-Mod shows that as opaqueness increases, the role of divertor fueling and thus poloidal asymmetries in the neutral density profiles decreases. Based on these experimental and modeling results we estimate the size of a potential particle pinch using typical values for the diffusion coefficient for both DIII-D and C-Mod H-mode discharges.

Ultrasound and its coupled oak blocks treatment based on absorbed energy density for comprehensive insight and scale-up consideration of phenolic and astringency profiles in red wines

Ultrasound and ultrasound-coupled oak blocks techniques on the phenolic and astringency profiles of Petit Verdot wines were discussed in this study. The relationship between techniques at varying absorbed energy density (AED) gradients and astringency was revealed, elucidating potential molecular mechanisms regarding compound interactions. Ultrasound was found to promote phenolics degradation and condensed tannins maturation, while oak blocks improved ellagitannins release into wines, facilitating polycondensation reactions to form larger complexes. Phenolics binding to salivary proteins decreased at low AED values (0–33.07 J/mL), enhanced at high AED values (66.14–165.34 J/mL), and reduced salivary proteins' precipitation ability. Treated samples significantly altered astringency's global terminology and sensory attributes across oral regions, with oak blocks enriching the astringency hierarchy. Multivariate analysis identified an optimal ultrasound AED of 0 to 33.07 J/mL, and an effective PLS-DA model was developed for industrial scale-up considerations, aiming to cost-effectively enhance the organoleptic quality of wines.

Free-swimming bacteria transcriptionally respond to shear flow

Surface-attached cells can sense and respond to shear flow, but planktonic (free-swimming) cells are typically assumed to be oblivious to any flow that carries them. Here, we find that planktonic bacteria can transcriptionally respond to flow, inducing expression changes that are beneficial in flow. Specifically, we use microfluidic experiments and quantitative modeling to show that in the presence of flow, planktonic Pseudomonas aeruginosa induce shear rate-dependent genes that promote growth in low-oxygen environments. Untangling this mechanism revealed that in flow, motile P. aeruginosa spatially redistribute, leading to cell density changes that activate quorum sensing, which in turn enhances the oxygen uptake rate. In diffusion-limited environments, including those commonly encountered by bacteria, flow-induced cell density gradients also independently generate oxygen gradients that alter gene expression. Mutants deficient in this flow-responsive mechanism exhibit decreased fitness in flow, suggesting that this dynamic coupling of biological and mechanical processes can be physiologically significant.

Study of surface layer characteristics in the presence of suspended snow particles using observational data and Large-Eddy Simulation

The snowdrift is a two-phase flow consisting of air and suspended particles. In the presence of snow particles in the air, additional stability appears in the surface layer due to the density gradient. The density gradient reduces turbulence and affects the properties of the surface layer. Therefore, to describe the properties of the flow with included snow particles, additional clarifications are required. A description of the surface layer parameterization with the presence of suspended snow particles is presented in this paper. The formulation of the effect of snow particles consists in reformulation of the Obukhov turbulent length scale. The novel surface layer parameterization allows to take into account the effect of snow particles on turbulent flow and may improve the estimates of friction velocity and boundary-layer height.The parameterization was successfully tested on the observational data. Description of snow particles influence was included in the Large-Eddy Simulation (LES) model. The numerical experiments confirmed an increase in the stability of the surface layer. Mechanism of suspended particles influence on the surface layer is analogous to a thermal stabilization of the turbulent flow, in which negative buoyancy acts to reduce the turbulent kinetic energy.

Microstructure formation mechanisms and property regulation methods during ceramic additive manufacturing

Anisotropic surface lamellar defects, dimensional shrinkage, and bending strength are important scientific issues that constrain vat photopolymerization additive manufacturing of biological, electronic, and core ceramics with high precision and complex structures. Through the single-factor experiment of photoinitiator concentration, average particle size, volume fraction, and refractive index constant in ceramic-resin slurry, this work studies the photopolymerization characteristics and profile curves, surface lamellar defects, and crosslinking density, verifies the reliability of the photopolymerization profile equations affected by the slurry composition, and acquires the anisotropic property formation mechanisms and control methods. The single-point scanning photopolymerization profile shape is parabolic, resulting in x-, y-, and z-direction lamellar defects before and after sintering (1550 °C), with no obvious weakening. After the quantitative description of the lamellar defects, the average surface roughnesses before and after sintering of the green body are 6.82 and 4.92 μm, respectively. Additionally, the laser energy attenuation along the penetration direction induces a gradient distribution of crosslinking density in the photopolymerization profile region. The crosslinking density gradient distribution of the decay from the slurry surface toward the depth direction is influenced by the slurry component concentration, leading to a gradient of cured powder concentration, which induces anisotropic behaviors. Through the crosslinking density controlling, the average bending strength in x(y) and z directions is increased by 63.19 % (46 %), the difference in anisotropic strength is reduced by 22.55 %, and the dimensional shrinkage difference of x and z directions is reduced by 48.32 %. This provides a theoretical and experimental research basis for ceramic vat photopolymerization with high dimensional accuracy, excellent performance, and morphology control.

Spectroscopic and Computational Investigations of Azo‐Hydrazone Tautomeric Forms of Diethylamino Phenol‐Based Mono‐azo Molecules and Their In Vitro Biological Evaluations

AbstractThe present work illustrates the synthesis of some new mono‐azo dyes, which include different amines such as 2‐amino thiazole, 2‐amino‐5‐methyl‐1,3,4‐thiadiazole, and 2‐amino‐5‐methyl thiazole with 3‐diethylamino phenol as a common coupling component. The prepared azo moieties were structurally confirmed by spectroscopic techniques like NMR (1H and 13C), FT‐IR, UV –absorption, and emission properties, and HR‐MS spectrometry. Significant variations in the absorption and emission wavelengths of the azo dyes were shown by the solvatochromic behavior, which also provided an important insight into the formation of azo and hydrazone tautomeric forms. The density functional theory of the dyes was carried out to know the HOMO‐LUMO energy gaps, molecular electrostatic potential, and reduced density gradient. Further, they were screened for their in vitro antibacterial and antioxidant activities, and the results showed that the compounds exhibited excellent potentialities against various strains.

Numerical Study of Shock Wave Interaction with V-Shaped Heavy/Light Interface

This paper investigates numerically the shock wave interaction with a V-shaped heavy/light interface. For numerical simulations, we choose six distinct vertex angles (θ=40∘,60∘,90∘,120∘,150∘, and 170∘), five distinct shock wave strengths (Ms=1.12,1.22,1.30,1.60, and 2.0), and three different Atwood numbers (At=−0.32,−0.77, and −0.87). A two-dimensional space of compressible two-component Euler equations are solved using a third-order modal discontinuous Galerkin approach for the simulations. The present findings demonstrate that the vertex angle has a crucial influence on the shock wave interaction with the V-shaped heavy/light interface. The vertex angle significantly affects the flow field, interface deformation, wave patterns, spike generation, and vorticity production. As the vertex angle decreases, the vorticity production becomes more dominant. A thorough analysis of the vertex angle effect identifies the factors that propel the creation of vorticity during the interaction phase. Notably, smaller vertex angles lead to stronger vorticity generation due to a steeper density gradient, while larger angles result in weaker, more dispersed vorticity and a less complex interaction. Moreover, kinetic energy and enstrophy both dramatically rise with decreasing vortex angles. A detailed analysis is also carried out to analyze the vertex angle effects on the temporal variations of interface features. Finally, the impacts of different Mach and Atwood numbers on the V-shaped interface are briefly presented.

Investigating the effect of BT direction on W source-to-core pathways during the SAS-VW campaign on DIII-D

Experiments using the V-shaped closed slot tungsten (W) coated SAS-VW divertor in DIII-D studied the effects of the BT direction on core contamination of eroded tungsten from a closed slot divertor configuration. Core W content is inferred using soft-X ray tomography (SXR) and vacuum ultraviolet spectroscopy (SPRED), while W divertor erosion is inferred from visible spectroscopy of W emission (400.9 nm) measured by in-slot filterscopes (filtered photo-multipliers). Post-mortem analysis from the campaign discovered tile misalignment leading to suspected pronounced leading-edge erosion in the unfavorable BT direction (ion B→×∇B→ drift away from divertor) likely not captured by diagnostics. However, empirical findings show up to ∼ 2-3x larger core contamination in the favorable BT direction even considering no additional W erosion from leading edges. A “source-to-core efficiency factor” is derived to estimate the effects of leading-edge erosion and compare W contamination for two pairs of H-mode discharges in opposite BT directions. While having differing absolute parameters, similar core impurity density gradients suggest comparable core impurity transport. These results show that favorable BT may have stronger source-to-core pathways for W impurities sourced from the outer divertor region. Possible explanations could include the effects of E→×B→ drifts on W transport in the scrape-off-layer (SOL) as well as previously determined fast SOL inner target directed flows in favorable BT.

DFT investigation of the adsorption and sensing ability of pure, Al and Ca-doped B12N12 nanocages toward thalidomide drug

In recent years, nanomaterials (NM) have been proven to be efficiency and applicable in several fields of our daily life, including in drug delivery systems. Herein, density functional theory (DFT) molecular modelling is used to probe the ability of pure, Al and Ca doped B12N12 fullerene-like nanocage for the detection and the sensing of thalidomide (TLD) drug. Thus, wB97XD/6-311G(d,p) level has been employed to study the structure-property relationship between the aforementioned NM and TLD. It turns from the analysis of thermodynamic parameters that all NMs investigated can spontaneously fix TLD at their external surface to form stable adsorbent-adsorbate molecular systems in standard conditions. The values of the Gibbs free adsorption energy for the most stable B12N12-TLD state is for instance found to be −8.97 and −6.98 kcal/mol in gas and aqueous phases respectively. QTAIM analyses, complemented by analyses of non covalent interactions through the reduced gradient density (RDG) revealed that the systems are further stabilized by a dative B-O bond as well as a strong N-H…N hydrogen bond between the adsorbent and the adsorbate. The HOMO-LUMO energy difference of CaB12N12 is found to reduced by about 36.42 % upon the adsorption of TLD, proving the interesting sensitivity of this NM toward the drug investigated. Finally, pure B12N12 and CaB12N12 are appropriate for the sensing of TLD in both gas phase and aqueous medium, the former NM even prensenting a release time of about 3.36 x 10−6 s in gas phase from the theoretical point of view.

Determination of a diffusion coefficient function for long rooms using a least square optimization approach

Over the last decades, considerable attention has been devoted to improving the diffusion equation model within the field of room acoustics. It has been found that this model is subject to certain limitations, with one constraint regarding the diffusion coefficient. The diffusion coefficient, a parameter integrated into the model, is a value that scales the sound intensity to the gradient of the sound energy density. Currently, this value is often treated as a constant, but research has shown that it is spatially dependent. This paper explores a method to optimise the diffusion coefficient for long rooms such as corridors and tunnels by comparing the results of the diffusion equation model with those computed with the radiosity model and using the least-square optimization method, minimising the difference between the results of both methods. The parameters of a diffusion coefficient function are optimised, targeting a function that can be applied to a range of elongated spaces.

Synthesis and Performance Evaluation of Zwitterionic C-N Bonded Triazole-Tetrazole-Based Primary Explosives.

Developing advanced metal-free nitrogen-enriched primary explosives is challenging due to the inherent risks associated with their synthesis and handling. However, there is an urgent need to develop novel lead-free, nitrogen-rich primary explosives that offer balanced energetic properties. C-N bonded bicyclic compound 3-azido-1-(1H-tetrazol-5-yl)-1H-1,2,4-triazol-5-amine (4), its salts, and 3,5-diazido-1H-1,2,4-triazole (8) were synthesized from inexpensive starting materials resulting in a fine blend of sensitivity and stability. These compounds exhibit high nitrogen content (79.78 to 83.43%), good thermal stability (129-210 °C), excellent detonation performance (VOD: 8592-9361 ms-1, DP: 27.1-33.8 GPa), and acceptable sensitivity (IS: 2.5-30 J, FS: 72-288 N). The hot needle tests of compounds 4 and 8 exhibit excellent ignition performance. All of the newly synthesized compounds were fully characterized using infrared spectroscopy (IR), high-resolution mass spectroscopy (HRMS), multinuclear magnetic spectroscopy (NMR), elemental analysis (EA), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), and 2, 4, and 8 were confirmed by single-crystal X-ray crystallographic studies. The molecular electrostatic potential (ESP), noncovalent interactions reduced density gradient (NCI-RDG) method, and QTAIM analysis were performed to investigate the intermolecular interactions. Together with promising performance properties, ease of synthesis, and ignitability, they are highly suitable candidates to pave new avenues for future applications.

Crystal Growth, Structural Elucidation, Chemical Reactivity, Topology Exploration (ELF, LOL, AIM, RDG) and NLO Activity of 4-Cumyl Phenol Crystal Using Quantum Chemical Calculation

The main objective of the study is to analyze the structural behavior and NLO activity of 4-cumyl phenol by experimental and theoretical spectroscopic techniques. Its computational result is compared with the cumene compound. The optimized structural parameters of the title compound were computationally obtained at the B3LYP/6-31G (d, p) basis set. The fundamental modes of vibration were examined by experimental FT-IR, and FT-Raman techniques. The distribution of the vibrational bands was carried out with the help of normal coordinate analysis (NCA). The resulting harmonic wavenumbers were scaled by using NCA method. Topological analysis, such as Electron localization function (ELF), natural bond orbital analysis (NBO), reduced density gradient (RDG) and atoms in molecule (AIM) analysis, molecular electrostatic potential (MEP) have been used to evaluate the intermolecular interaction, especially the hydrogen bonds. UV-visible spectrum of the compound was recorded in the region 200–900 nm and the electronic properties and HOMO-LUMO energies were calculated by time dependent density functional theory approach.

Δ-Machine Learning to Elevate DFT-Based Potentials and a Force Field to the CCSD(T) Level Illustrated for Ethanol.

Progress in machine learning has facilitated the development of potentials that offer both the accuracy of first-principles techniques and vast increases in the speed of evaluation. Recently, Δ-machine learning has been used to elevate the quality of a potential energy surface (PES) based on low-level, e.g., density functional theory (DFT) energies and gradients to close to the gold-standard coupled cluster level of accuracy. We have demonstrated the success of this approach for molecules, ranging in size from H3O+ to 15-atom acetyl-acetone and tropolone. These were all done using the B3LYP functional. Here, we investigate the generality of this approach for the PBE, M06, M06-2X, and PBE0 + MBD functionals, using ethanol as the example molecule. Linear regression with permutationally invariant polynomials is used to fit both low-level and correction PESs. These PESs are employed for standard RMSE analysis for training and test data sets, and then general fidelity tests such as energetics of stationary points, normal-mode frequencies, and torsional potentials are examined. We achieve similar improvements in all cases. Interestingly, we obtained significant improvement over DFT gradients where coupled cluster gradients were not used to correct the low-level PES. Finally, we present some results for correcting a recent molecular mechanics force field for ethanol and comment on the possible generality of this approach.