Properties Of Pairs Research Articles

Dispersion Energy-Stabilized Boron and Phosphorus Lewis Pairs.

An isostructural series of boron/phosphorus Lewis pairs was systematically investigated. The association constants of the Lewis pairs were determined at variable temperatures, enabling the extraction of thermodynamic parameters. The stabilization of the Lewis adduct increased with increasing size of the dispersion energy donor groups, although the donor and acceptor properties of the Lewis pairs remained largely unchanged. This data was utilized to challenge state-of-the-art quantum chemical methods, which finally led to an enhanced workflow for the determination of thermochemical properties of weakly bound Lewis pairs within an accuracy of 0.6 to 1.0 kcal mol-1 for computed association free energies.

Dispersion Energy‐Stabilized Boron and Phosphorus Lewis Pairs

AbstractAn isostructural series of boron/phosphorus Lewis pairs was systematically investigated. The association constants of the Lewis pairs were determined at variable temperatures, enabling the extraction of thermodynamic parameters. The stabilization of the Lewis adduct increased with increasing size of the dispersion energy donor groups, although the donor and acceptor properties of the Lewis pairs remained largely unchanged. This data was utilized to challenge state‐of‐the‐art quantum chemical methods, which finally led to an enhanced workflow for the determination of thermochemical properties of weakly bound Lewis pairs within an accuracy of 0.6 to 1.0 kcal mol−1 for computed association free energies.

The impact of additives applied to the lubricant on the burnishing process and tribological properties

The aim of this study was to determine the impact of additions of tungsten carbide and silicon carbide microparticles to the lubricant used in the burnishing process on the tribological properties of friction pairs. The cylinders made of AISI 1045 steel constituted a workpiece. Burnishing was made with a lubricant the SN150 base oil with addition of tungsten carbide and silicon carbide microparticles. The tested materials were burnished with forces of 1000 N and 1500 N. Before and after the burnishing process, the surface roughness and hardness of the tested materials were measured. The study also presents the results of tribological properties of friction pairs with the tested structural materials. It was found that the addition of tungsten carbide microparticles to the base oil in the burnishing process can result in improved surface quality and reduced surface roughness. The results also confirmed the effect of addition of tungsten carbide and silicon carbide to the lubricant used in the burnishing process on tribological properties.

Hanging on and digging deep: comparative forelimb myology of the koala (Phascolarctos cinereus) and common wombat (Vombatus ursinus)

Abstract Establishing relationships between soft tissues and bones in living species can inform our understanding of functional adaptations in their extinct kin in the absence of direct data on habitual behaviours. The koala and the wombats are the only surviving species of the vombatiform suborder, and represent the extant phylogenetic bracket for dozens of fossil marsupial species across nine families. Here we present the first quantitative architectural data on the forelimb myology of the koala and common wombat, alongside redescriptions based on physical and digital dissections. Despite obvious contrasts in how their forelimbs are used in arboreal (koala) and fossorial (wombat) functional contexts, overall they showed only minor differences in qualitative and quantitative measures of myology. When the architectural properties of antagonistic pairs of muscle groups crossing each joint were compared, the greatest contrasts were seen in muscles crossing the elbow, where the wombat exhibited greater relative emphasis on forceful elbow extension than the koala, indicative of adaptations for digging. Our findings reinforce the importance of the elbow as a useful system to explore when seeking discrimination between habitual patterns of forelimb use in extinct vombatiform species.

Theory of the low- and high-field superconducting phases of UTe2

Recent nuclear magnetic resonance and calorimetric experiments have observed that ${\mathrm{UTe}}_{2}$ exhibits a transition between two distinct superconducting phases as a function of magnetic field strength for a field applied along the crystalline $b$ axis. To determine the nature of these phases, we employ a microscopic two-band minimal Hamiltonian with the essential crystal symmetries and structural details. We also adopt anisotropic ferromagnetic exchange terms. We study the resulting pairing symmetries and properties of these low- and high-field phases in mean-field theory.

Investigation of hydrogen bonding in small nucleobases using DFT, AIM, NCI and NBO technique

In this work hydrogen bonded base pairing properties of two adenine analogue nucleobases and thymine were investigated. wB97XD/6-311++G(2d,2p) level of theory was employed to optimize the monomers and the base pairs in different orientations. Atoms In Molecule, AIM analysis was carried out to analyse the individual hydrogen bonds in the studied complexes. NH…N and OH…N were found to be major contributors to the overall interaction energy than O…HC and N…HC bonds. Non Covalent Interaction, NCI and Reduced Density Gradient, RDG plots revealed that interactions are mainly weak and intermediate in nature. Finally Natural Bond Orbital, NBO calculations were performed to calculate the second order perturbation energy E(2) which helped to understand the interaction between electron donor and acceptors in the individual complexes.

The influence of important factors on the distribution of heat flows in elements of drum brakes of vehicles

The movement of motor vehicles at high speeds is impossible without a braking system capable of ensuring high braking efficiency. It has been established that the most unstable link of the braking system is the brake mechanism, since from the energy point of view, braking with friction brakes is the process of converting part of the mechanical energy of the motor vehicle into heat. Braking is a long process during which many counterbody parameters change, in particular, thermophysical parameters due to temperature changes, friction coefficient, etc. If, under these circumstances, the surface and volume temperatures exceed the permissible values, then the frictional properties of the friction pairs and the conditions of the interaction of the parts change, which leads to a change in the characteristics of the brake mechanisms and the brake system as a whole. The standards of most countries and international prescriptions regulate braking performance meters not only for one-time emergency braking with cold brakes but also for emergency braking performed after the conversion of a given amount of energy into heat during a given time. It was found that the preservation of the necessary braking efficiency after the conversion of a given amount of energy into heat will be ensured only if the braking system has sufficient energy capacity. The object of the research is the distribution of heat flows in the elements of the brake mechanism, which determine the critical temperature of the friction surfaces. It was established that F. Charron's formula cannot correctly estimate such a distribution due to taking into account only the thermophysical properties of materials of friction pairs. It is shown that the influence of the design parameters of the brake and its modes of operation on the distribution of heat flows in the drum brake of a motor vehicle can also be estimated on grid thermal models with the involvement of the "Fourier-2xyz" software complex.

Understanding the Correlation Between Structure and Entangled Photon Pair Properties with Metal–Organic Frameworks

Spontaneous parametric down conversion (SPDC) is a quantum second-order nonlinear optical process where the photons generated are frequently used in quantum information processing. Materials with large second-order nonlinearities (χ(2)) can be used as entangled photon sources with a high brightness. The source brightness scales as the square of the effective nonlinearity (deff), which is an intrinsic property of the material. Understanding material factors that can significantly alter this intrinsic property is useful in developing new materials that are SPDC efficient. In our work we focus on understanding factors affecting the entangled photon pair properties, such as the arrangements of ligands within the Zn(3-ptz)2 metal–organic framework (MOF) crystal and temperature. We find that the arrangement and alignment of the pyridine rings in the crystal structure significantly affect the deff and birefringence (Δn). Smaller pyridine ring alignments relative to the optic c-axis increase the Δn, which in turn leads to larger photon pair correlation times (τc) in coincidence measurements. Our work has significant implications in understanding the effect of ligand arrangement on deff and τc for any MOF crystal structure, providing a tool to rationalize the optimization of MOF crystals for the development of efficient nonlinear optical devices.

Chiral superconductivity in UTe2 probed by anisotropic low-energy excitations

Chiral spin-triplet superconductivity is a topologically nontrivial pairing state with broken time-reversal symmetry, which can host Majorana quasiparticles. The heavy-fermion superconductor UTe2 exhibits peculiar properties of spin-triplet pairing, and the possible chiral state has been actively discussed. However, the symmetry and nodal structure of its order parameter in the bulk, which determine the Majorana surface states, remains controversial. Here we focus on the number and positions of superconducting gap nodes in the ground state of UTe2. Our magnetic penetration depth measurements for three field orientations in three crystals all show the power-law temperature dependence with exponents close to 2, which excludes single-component spin-triplet states. The anisotropy of low-energy quasiparticle excitations indicates multiple point nodes near the ky- and kz-axes in momentum space. These results can be consistently explained by a chiral B3u + iAu non-unitary state, providing fundamentals of the topological properties in UTe2.

Improvement and Assessment of Gaofen-3 Spotlight Mode 3-D Localization Accuracy

The spotlight image acquired by the Gaofen-3 satellite has a resolution of 1 m, which has great potential for 3-D localization. However, there have been no public reports on the 3-D localization accuracy evaluation of Gaofen-3 spotlight synthetic aperture radar (SAR) images. Here, three study areas were selected from this perspective, and the SAR spotlight stereo images of the study area were acquired using Gaofen-3. In the case of no ground control points (GCPs), based on the Rational Polynomial Coefficient (RPC) model, these images were used for initial 3-D localization; the plane accuracy was better than 10 m in general, and the elevation accuracy was worse than 37 m in general. Subsequently, the RPC model was optimized using geometric calibration technology, and the 3-D localization accuracy was assessed again. The elevation accuracy was significantly improved, which was generally better than 5 m. The plan accuracy was also improved, and it was generally better than 6 m. It can be seen that Gaofen-3 spotlight stereo images are of good quality, and high plane accuracy can be obtained even without GCPs. Geometric calibration technology improves the 3-D localization accuracy, and the elevation accuracy optimization effect is remarkable. Moreover, the optimization effect of plane accuracy is affected by the properties of stereo-image pairs. The optimization effect of plane accuracy is obvious for asymmetric stereo-image pairs, and the optimization effect of plane accuracy is general for symmetric stereo-image pairs.

Electron–lattice pair properties in chains with cubic interaction

In this paper, we investigate the one-electron propagation in a nonlinear chain with electron–lattice interaction. The model contains standard cubic nonlinear terms, and we introduce the coupling between the electron and the lattice through the hopping distribution. We solve the coupled equation set to electron and lattice and calculate the electronic position as a function of time. We provide a detailed investigation of the electron and lattice dynamics for a wide range of electron–lattice coupling intensities. Our results demonstrate that depending on the initial condition we consider and the intensity of the electron–lattice interaction, we can obtain (or not) an electron–phonon pair formation. Our results reveal that, depending on the initial velocity of the lattice and the degree of electron–lattice term, we can observe a repulsion between electron and lattice deformations.

Genotoxic effects of the major alkylation damage N7-methylguanine and methyl formamidopyrimidine.

Various alkylating agents are known to preferentially modify guanine in DNA, resulting in the formation of N7-alkylguanine (N7-alkylG) and the imidazole ring opened alkyl-formamidopyrimidine (alkyl-FapyG) lesions. Evaluating the mutagenic effects of N7-alkylG has been challenging due to the instability of the positively charged N7-alkylG. To address this issue, we developed a 2'-fluorine-mediated transition-state destabilization approach, which stabilizes N7-alkylG and prevents spontaneous depurination. We also developed a postsynthetic conversion of 2'-F-N7-alkylG DNA into 2'-F-alkyl-FapyG DNA. Using these methods, we incorporated site-specific N7-methylG and methyl-FapyG into pSP189 plasmid and determined their mutagenic properties in bacterial cells using the supF-based colony screening assay. The mutation frequency of N7-methylG was found to be less than 0.5%. Our crystal structure analysis revealed that N7-methylation did not significantly alter base pairing properties, as evidenced by a correct base pairing between 2'-F-N7-methylG and dCTP in Dpo4 polymerase catalytic site. In contrast, the mutation frequency of methyl-FapyG was 6.3%, highlighting the mutagenic nature of this secondary lesion. Interestingly, all mutations arising from methyl-FapyG in the 5'-GGT(methyl-FapyG)G-3' context were single nucleotide deletions at the 5'-G of the lesion. Overall, our results demonstrate that 2'-fluorination technology is a useful tool for studying the chemically labile N7-alkylG and alkyl-FapyG lesions.

DeepNeo: a webserver for predicting immunogenic neoantigens.

Non-self epitopes, whether originated from foreign substances or somatic mutations, trigger immune responses when presented by major histocompatibility complex (MHC) molecules and recognized by T cells. Identification of immunogenically active neoepitopes has significant implications in cancer and virus medicine. However, current methods are mostly limited to predicting physical binding of mutant peptides and MHCs. We previously developed a deep-learning based model, DeepNeo, to identify immunogenic neoepitopes by capturing the structural properties of peptide-MHC pairs with T cell reactivity. Here, we upgraded our DeepNeo model with up-to-date training data. The upgraded model (DeepNeo-v2) was improved in evaluation metrics and showed prediction score distribution that better fits known neoantigen behavior. The immunogenic neoantigen prediction can be conducted at https://deepneo.net.

Research on the friction and wear mechanism of a polymer interface at low temperature based on molecular dynamics simulation

Two polymers and five metal pairs were tested at six low temperature points and three constant load speeds. The tribological properties were determined by joint iterative coupling of the temperature, load and friction velocity value. Molecular dynamics simulation was used to study the micro-tribological properties of friction pairs at the atomic scale. The macro-tribological performance test results were similar to the results of the molecular dynamics simulation and exhibited the same trend. Two profound hypothermia points were predicted. The evolution of the tribological mechanism and properties of the polymer interface under different working conditions at low temperature were revealed on the macroscopic and atomic scales.

Using Peptide Nucleic Acid Hybridization Probes for Qualitative and Quantitative Analysis of Nucleic Acid Therapeutics by Capillary Electrophoresis.

The space of advanced therapeutic modalities is currently evolving in rapid pace necessitating continuous improvement of analytical quality control methods. In order to evaluate the identity of nucleic acid species in gene therapy products, we propose a capillary electrophoresis-based gel free hybridization assay in which fluorescently labeled peptide nucleic acids (PNAs) are applied as affinity probes. PNAs are engineered organic polymers that share the base pairing properties with DNA and RNA but have an uncharged peptide backbone. In the present study, we conduct various proof-of-concept studies to identify the potential of PNA probes for advanced analytical characterization of novel therapeutic modalities like oligonucleotides, plasmids, mRNA, and DNA released by recombinant adeno-associated virus. For single-stranded nucleic acids up to 1000 nucleotides, the method is an excellent choice that proved to be highly specific by detecting DNA traces in complex samples, while having a limit of quantification in the picomolar range when multiple probes are used. For double-stranded samples, only fragments that are similar in size to the probe could be quantified. This limitation can be circumvented when target DNA is digested and multiple probes are used opening an alternative to quantitative PCR.

Experimental research on the mechanism of the delamination extension of the carbon strip with heavy electrical current at the speed of 360 km/h

Delamination wear leads to a surge in the wear loss of the carbon strip. It also has a significant influence on the physicochemical properties of the contact pairs in the pantograph-catenary system (over 250 km/h). In this paper, the pure carbon/copper-alloy friction pair was chosen as the research object to study the wear evolution mechanisms and the law of delamination wear extension of the carbon strip, using a ring-on -block wear tester with a design speed of 400 km/h. And the arc discharge energy was calculated to investigate the quantitative relationship between the delamination wear and the arc discharge in the process of the test. The experimental results show that the frictional coefficient increases gradually with the experiment. The frictional coefficient with electric current is much bigger than that without electric current under the same test conditions. Under the intense arcing (when the average single arc discharge energy e > 76J), the delamination wear initially appears on one edge of the strip and gradually extends to the middle of the strip when sliding time t exceeds a certain value, which results in the increase of the wear of the strip and the further enhancement of the arc discharge. The result also indicates that delamination wear and its extension are occurred by the cumulative effect of the heat caused by the long-time strong arc discharge.

Influenza A virus reassortment is strain dependent.

RNA viruses can exchange genetic material during coinfection, an interaction that creates novel strains with implications for viral evolution and public health. Influenza A viral genetic exchange can occur when genome segments from distinct strains reassort in coinfected cells. Predicting potential genomic reassortment between influenza strains has been a long-standing goal. Experimental coinfection studies have shed light on factors that limit or promote reassortment. However, determining the reassortment potential between diverse Influenza A strains has remained elusive. To address this challenge, we developed a high throughput genotyping approach to quantify reassortment among a diverse panel of human influenza virus strains encompassing two pandemics (swine and avian origin), three specific epidemics, and both circulating human subtypes A/H1N1 and A/H3N2. We found that reassortment frequency (the proportion of reassortants generated) is an emergent property of specific pairs of strains where strain identity is a predictor of reassortment frequency. We detect little evidence that antigenic subtype drives reassortment as intersubtype (H1N1xH3N2) and intrasubtype reassortment frequencies were, on average, similar. Instead, our data suggest that certain strains bias the reassortment frequency up or down, independently of the coinfecting partner. We observe that viral productivity is also an emergent property of coinfections, but uncorrelated to reassortment frequency; thus viral productivity is a separate factor affecting the total number of reassortants produced. Assortment of individual segments among progeny and pairwise segment combinations within progeny generally favored homologous combinations. These outcomes were not related to strain similarity or shared subtype but reassortment frequency was closely correlated to the proportion of both unique genotypes and of progeny with heterologous pairwise segment combinations. We provide experimental evidence that viral genetic exchange is potentially an individual social trait subject to natural selection, which implies the propensity for reassortment is not evenly shared among strains. This study highlights the need for research incorporating diverse strains to discover the traits that shift the reassortment potential to realize the goal of predicting influenza virus evolution resulting from segment exchange.

Numerical study of the formation and stability of a pair of particles of different sizes in inertial microfluidics

The formation of pairs and trains of particles in inertial microfluidics is an important consideration for device design and applications, such as particle focusing and separation. We study the formation and stability of linear and staggered pairs of nearly rigid spherical particles of different sizes in a pressure-driven flow through a straight duct with a rectangular cross section under mild inertia. An in-house lattice-Boltzmann-immersed-boundary-finite-element code is used for three-dimensional simulations. We find that the stability and properties of pairs of heterogeneous particles strongly depend on particle sizes and their size ratio, while the formation of the pairs is also determined by the initial lateral position and the axial order of the particles. Our findings imply that perturbations of particle trajectories caused by other particles, as they are expected to happen even in dilute suspensions, can be important for the formation of stable pairs in inertial microfluidics.

Proximinality of subspaces and the quotient lifting property

The Quotient Lifting Property (QLP) for pairs of spaces and its relation to the proximinality of subspaces are studied. Even though this property is not hereditary, for finite-dimensional subspaces of , we show that for a choice of a basis, all subspaces spanned by any sub-collection from the base, generate subspaces with QLP. Spaces of dimension greater than two with the total quotient lifting property are shown to be Hilbert spaces.

Transverse electronic transport properties of single DNA nucleobase pairs between different electrode materials

Detection of gene mutation through electronic transport properties measurements is an attractive research topic. For this purpose, we computed the current–voltage characteristics of adenine-thymine and guanine-cytosine nucleobase pairs, using a combination method of density-functional theory with non-equilibrium Green’s function. Gene mutation was also simulated by structural change in nucleobase pairs by a double proton transfer mechanism. Four different metal electrodes were tested. Comparing the results, nucleobase pairs between platinum surfaces showed distinct electronic transport properties. Such as reverse rectifying direction and negative differential resistance behaviors. The discrepancy can be explained from series of electronic and structural analyses. All these results made identification of structural changes in individual DNA nucleobase pairs possible.