Point Property Research Articles

Collapse and Protein Folding: Should We Be Surprised that Biothermodynamics Works So Well?

A complete understanding of protein function and dynamics requires the characterization of the multiple thermodynamic states, including the denatured state ensemble (DSE). Whereas residual structure in the DSE (as well as in partially folded states) is pertinent in many biological contexts, here we are interested in how such structure affects protein thermodynamics. We examine issues related to chain collapse in light of new developments, focusing on potential complications arising from differences in the DSE's properties under various conditions. Despite some variability in the degree of collapse and structure in the DSE, stability measurements are remarkably consistent between two standard methods, calorimetry and chemical denaturation, as well as with hydrogen-deuterium exchange. This robustness is due in part to the DSEs obtained with different perturbations being thermodynamically equivalent and hence able to serve as a common reference state. An examination of the properties of the DSE points to it as being a highly expanded ensemble with minimal amounts of stable hydrogen bonded structure. These two features are likely to be critical in the broad and successful application of thermodynamics to protein folding. Our review concludes with a discussion of the impact of these findings on folding mechanisms and pathways.

Wiener-Lebesgue Point Property for Sobolev Functions on Metric Spaces

Wiener-Lebesgue Point Property for Sobolev Functions on Metric Spaces

Computer simulation of the truck cabin tests to find ways to meet the requirements of the UNECE Regulation 29

BACKGROUND: Ensuring the required level of passive safety of trucks is a relevant task. To solve this problem, it is necessary to use computer simulation methods. AIM: Search for the ways to ensure the passive safety of trucks by choosing the appropriate cabin design. MATERIALS AND METHODS: During the study, the method of virtual simulation of the truck cabin tests was used in accordance with the requirements of the UNECE Regulation 29. RESULTS: A simulation model of a truck cabin has been developed, which makes it possible to conduct the computer simulation of the tests according to the UNECE Regulation 29. The main requirement of the UNECE Regulation 29 is retaining sufficient space in the cabin to accommodate the driver’s dummy inside it after its testing. As a part of the study, the properties of the material (steel) used for manufacturing of prototype cabins of the truck under development were determined, and the tested specimens were obtained by dissecting the prototype of the cabin, so the obtained results take into account the technological history of the material. The obtained data on the properties of the materials were used in the development of the simulation model of the cabin. The developed and used simulation model takes into account all the design features of the cabin under study, including the location and properties of welding points. Various options of cabin design changes and their impact on the ability to meet the requirements of the UNECE Regulations 29 are investigated. It has been found that it is not possible to fully comply with the requirements of the UNECE Regulation 29 only by increasing (within reasonable limits) the thickness of individual elements of the cabin frame and/or using high-strength steel for their manufacturing. Based on the analysis of the deformation of the prototype cabin frame during the Test C according to the UNECE Regulation 29 Revision 2, proposals for changes to the cabin design to meet the requirement of the UNECE Regulation 29 are formulated. CONCLUSION: The results of the study indicate the prospects of the proposed changes to the cabin design.

Solid Forms of Bio-Based Monomer Salts for Polyamide 512 and Their Effect on Polymer Properties.

Polyamides' properties are greatly influenced by the polymerization process and the type of feedstock used. The solid forms of nylon salts play a significant role in determining the final characteristics of the material. This study focuses on the long-chain bio-nylon 512. Firstly, we systematically investigated the possible solid forms of the nylon 512 salt, including crystal forms and morphologies, by massive experimental screening, single-crystal X-ray diffraction, Hirshfeld surface analysis, and TG-DSC measurements. The regulation and control of the various solid forms were achieved through solid-state transformations (SSTs) and solution-mediated phase transformations (SMPTs). Our findings shows that the nylon 512 salt exists in two crystal forms (anhydrate and dihydrate) and four morphologies (needle-like, plate-like, rod-like, and massive block crystal). Many factors will influence the formation of these solid forms, such as water activity, temperature, solvent, and ultrasonic physical fields. We can choose the right factors to regulate this as needed. On this basis, we studied the effects of different solid forms (crystal forms and morphologies) on the properties of the resulting polyamides prepared using direct solid-state polymerization (DSSP). The solid form of the salt had many effects on the polymer, including its structure, melting point, and mechanical properties. The polyamide obtained through DSSP of the anhydrate salt exhibited a higher melting point (204.22 °C) and greater elastic modulus (3.366 GPa) compared to that of the dihydrate salt, especially for the anhydrate salt of plate-like crystals.

Ring‐opening copolymerization of ε‐caprolactone and δ‐valerolactone to cyclic polyesters by a bimolecular system

AbstractBio‐based plastics have received much attraction because they are an alternative to petroleum‐based plastics in recent years. Among them, aliphatic polyesters have garnered the most attention due to their excellent properties. Polyester is primarily synthesized through ring opening polymerization of monomer, and the catalysts used are mostly synthesized through “click” reaction in the laboratory, which exhibits inferior activity and little commercial value. Herein, a facile approach was developed for the synthesis of high molecular‐weight cyclic aliphatic polyesters, specifically poly(valerolactone‐co‐caprolactone) with varying compositions. This involved the ring‐opening copolymerization of ε‐caprolactone (ε‐CL) and δ‐valerolactone (δ‐VL) in the absence of an initiator with commercial hydrogen bond donor triclorocarban and an organic base. The structure and properties of the prepared cyclic polyester were investigated using GPC, 13C NMR, 1H NMR, MALDI‐TOF mass spectrometry, TOF‐SIMS mass spectrometry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X‐ray diffraction (XRD) techniques. The results show that the molecular weight of cyclic polyester can rapidly exceed 40 kDa, with a PDI of approximately 1.10. In comparison to linear polyester, it has a higher melting point and superior thermodynamic properties, thus presenting greater application potential. Finally, based on nuclear magnetic resonance titration, the potential catalytic processes and mechanisms of bimolecular systems on monomers in different environments were discussed. This study not only offers new insights into the structure and properties of cyclic polyesters, but also presents novel bimolecular catalytic systems using commercial urea hydrogen bond donors for the synthesis of cyclic polymer polyesters.

Analisis Kestabilan Model Penyebaran Penyakit Antraks pada Populasi Ternak dengan Transmisi Tak Langsung dan Penggunaan Desinfektan

Anthrax is an infectious disease caused by the bacterium Bacillus anthracis. This disease causes a fairly high mortality rate in livestock populations that can threaten food security in a region. Therefore, it is necessary to prevent and control its spread. This study aims to examine the model of the spread of anthrax disease in a livestock population by considering indirect transmission and the use of disinfectants. The constructed model is expressed as a system of ordinary differential equations. Dynamical analysis is carried out to identify the stability properties of the disease-free equilibrium point. The results of the dynamical analysis show that the disease-free equilibrium point is conditionally stable, namely when the basic reproduction number is less than one. In addition, the results of numerical experiments show that the use of disinfectants has a significant effect on the dynamics of the spread of anthrax disease, namely the higher the rate of bacterial death due to disinfectants, the fewer cases of anthrax. This study shows that the use of disinfectants can be an effective strategy to control the spread of anthrax disease in livestock populations.

Uncertainty quantification analysis of bifurcations of the Allen–Cahn equation with random coefficients

In this work we consider the Allen–Cahn equation, a prototypical model problem in nonlinear dynamics that exhibits bifurcations corresponding to variations of a deterministic bifurcation parameter. Going beyond the state-of-the-art, we introduce a random coefficient in the linear reaction part of the equation, thereby accounting for random, spatially-heterogeneous effects. Importantly, we assume a spatially constant, deterministic mean value of the random coefficient. We show that this mean value is in fact a bifurcation parameter in the Allen–Cahn equation with random coefficients. Moreover, we show that the bifurcation points and bifurcation curves become random objects. We consider two distinct modeling situations: (i) for a spatially-homogeneous coefficient we derive analytical expressions for the distribution of the bifurcation points and show that the bifurcation curves are random shifts of a fixed reference curve; (ii) for a spatially-heterogeneous coefficient we employ a generalized polynomial chaos expansion to approximate the statistical properties of the random bifurcation points and bifurcation curves. We present numerical examples in 1D physical space, where we combine the popular software package Continuation Core and Toolboxes (COCO) for numerical continuation and the Sparse Grids Matlab Kit for the polynomial chaos expansion. Our exposition addresses both dynamical systems and uncertainty quantification, highlighting how analytical and numerical tools from both areas can be combined efficiently for the challenging uncertainty quantification analysis of bifurcations in random differential equations.

Generation controllable optical chain using an optical pen.

An aperiodic snake-like optical chain has been proposed and generated by using an optical pen technique, whose numbers and positions of focal points are controllable. Moreover, by introducing a fan phase together with a twisted phase into the optical pen technique, a self-rotation optical chain can be obtained; meanwhile, it transforms the bright optical chain into a twisted optical chain with a rotating hollow region in a three-dimensional (3D) space. The properties of the rotatable focal points and the variable diameters of cross-sectional intensities during the propagation of the optical chain are demonstrated in the experimental results. Consequently, this research framework can be applied in the techniques such as deep multiplexing and rotation angle multiplexing while also enabling the realization of multiple capture sites and more intricate manipulations.

Ideal quadratic nodal point in half-Heusler semimetal LaPtBi

The research focus on topological states in electronic systems has recently expanded from traditional linear dispersions to encompass higher-order dispersions. These higher-order dispersions exhibit unique physical properties, including high topological charge, exotic magnetoresponse, and novel transport behaviors. In this study, we employ first-principles calculations to propose the half-Heusler material LaPtBi as an ideal quadratic nodal point semimetal. Our comprehensive analysis of the band structure reveals an ideal nodal point located precisely at the Fermi level, exhibiting quadratic dispersion in all directions. This finding is supported by symmetry analysis and effective model arguments. Moreover, when the spin-orbit coupling effect is considered, the nodal point transitions from triple to quadruple degeneracy, while maintaining its quadratic dispersion. The material also features multiple prominent arc surface states originating from the nodal point, which are distinctly separated from the bulk bands. This separation facilitates experimental verification. Overall, LaPtBi, with its quadratic nodal point and advantageous properties, serves as an ideal platform for further research. The study of this material is expected to enhance our understanding of higher-order topological states in electronic systems, potentially driving future advancements in the field.

Using palm oil residue for food nutrition and quality: from palm fatty acid distillate to vitamin E toward sustainability.

Increasing global palm oil production yields a valuable palm fatty acid distillate (PFAD) - a rich vitamin E (Vit-E) source and multifunctional ingredient in the food agro-industry - that can be utilized to achieve sustainability. This article reviews trends in the use and role of PFAD and its Vit-E in the food sector and proposes an integrated agro-industrial concept toward sustainability. Vit-E can be separated from PFAD with diverse and impactful pharmaceutical activities, including antioxidant, anti-inflammatory, anticancer and anti-ultraviolet effects. Based on in vivo experimental tests, PFAD and Vit-E supplementation can enhance the productivity and quality of livestock-based food products. PFAD is a plasticizer and antistatic packaging material in food packaging systems, and its derivatives can be used as food additives. Meanwhile, the Vit-E molecule in packaging can extend food shelf life by maintaining color stability, reducing lipid oxidation and rancidity, adding antimicrobial properties, and influencing changes in packaging properties such as water vapor, tensile strength, melting point and other physical properties. Toward sustainability, an integrated agro-industrial design has been proposed to implement clean production, increase the added value of palm oil industry residues, minimize environmental risks and increase profits to achieve long-term social welfare. In conclusion, PFAD residues and their Vit-E content have shown broad benefits in the food sector and prospects toward sustainability. © 2024 Society of Chemical Industry.

Effect of ionizing radiation on the microstructure and physical properties of endodontic gutta-percha points.

Patients undergoing radiotherapy for head or neck cancer often require root canal treatments, which can be compromised by the effects of radiation. This investigation aimed to determine whether ionizing radiation (IR), in doses similar to those used in conventional therapy, affects the surface and physicomechanical properties of various brands of endodontic gutta-percha points (EGPs). One hundred and twenty-three EGPs from three brands (Meta-Biomed, Dentsply, and Hygenic) were divided into groups and either exposed or not exposed to IR at a total dose of 50 Gy, divided into 25 fractions. Tensile strength and microhardness tests were performed on all EGPs. Scanning electron microscopy was utilized to identify possible microstructural surface changes due to IR exposure. The proportion of organic to inorganic components in each brand was also determined. Exposure to IR resulted in significant changes only in the EGPs from the Meta-Biomed brand, including a notable decrease in tensile strength and an increase in microhardness. Furthermore, the surface microstructure of these EGPs displayed dark lines and striations over a large area, with some lines deeply embedded in the center and cavities of variable depths and extensions observed, leading to irregular and non-smooth surfaces. This brand had the highest proportion of organic components. The physicomechanical properties and surface microstructure of Meta-Biomed brand EGPs were significantly affected by IR at doses used in conventional therapy for head or neck cancer, while the other brands were less affected or unaffected.

A machine-learning interatomic potential to study dry/wet oxidation process of silicon

We developed an accurate and efficient machine learning potential with DFT accuracy and applied it to the silicon dry/wet oxidation process to investigate the underlying physics of thermal oxidation of silicon (001) surfaces. The accuracy of the potential was verified by comparing the melting point and structural properties of silicon, the structural properties of a-SiO2, and the adsorption properties on the silicon surface with experiment and DFT data. In subsequent thermal oxidation simulations, we successfully reproduced the accelerated growth phenomenon of the wet oxidation in the experiment, discussed the oxide growth process in detail, and elucidated that the accelerated growth is due to hydrogen in the system that both enhances the adsorption of oxygen on the silicon surface and promotes the migration of oxygen atoms. Finally, we annealed the oxidized structure, counted the defect information in the structure before and after annealing, and analyzed the defect evolution behavior during the annealing process.

Kondo breakdown in multi-orbital Anderson lattices induced by destructive hybridization interference

In this paper we consider a multi-band extension to the periodic Anderson model. We use a single site DMFT(NRG) in order to study the impact of the conduction band mediated effective hopping of the correlated electrons between the correlated orbitals onto the heavy Fermi-liquid formation. Whereas the hybridization of a single impurity model with two distinct conduction bands always adds up constructively, T_{K}\propto \exp(-\mathrm{const}\, U/(\Gamma_1+\Gamma_2))TK∝exp(−constU/(Γ1+Γ2)), we show that this does not have to be the case in lattice models, where, in remarkable contrast, also an low-energy Fermi-liquid scale T_0\propto \exp(-\mathrm{const}\, U/(\Gamma_1-\Gamma_2))T0∝exp(−constU/(Γ1−Γ2)) can emerge due to quantum interference effects in multi-band models, where UU denotes the local Coulomb matrix element of the correlated orbitals and \Gamma_iΓi the local hybridization strength of band ii. At high symmetry points, heavy Fermi-liquid formation is suppressed which is associated with a breakdown of the Kondo effect. This results in an asymptotically scale-invariant (i.e., power-law) spectrum of the correlated orbitals \propto|\omega|^{1/3}∝|ω|1/3, indicating non-Fermi liquid properties of the quantum critical point, and a small Fermi surface including only the light quasi-particles. This orbital selective Mott phase demonstrates the possibility of metallic local criticality within the general framework of ordinary single site DMFT.

Global dynamics and numerical simulation of a modified epidemiological model for viral marketing on social networks

The aim of this work is to conduct a rigorous mathematical analysis for global dynamics and numerical simulation of a recognized viral marketing (VM) model, which is described by a system of ordinary differential equations (ODEs). We first establish positivity and boundedness of solutions and then investigate local and global asymptotic stability properties of possible equilibrium points. As an important consequence, complex dynamics of the VM model is determined fully.Secondly, we develop the Mickens’ methodology to design a nonstandard finite difference (NSFD) scheme, which is useful in numerical simulation of the VM model. The main advantage of the constructed NSFD scheme is that it has the ability to preserve important mathematical features of the continuous-time model for all finite values of the step size. These features include the positivity and boundedness of solutions, positively invariant sets, equilibrium points and their asymptotic stability properties. Consequently, the NSFD scheme is not only effective to simulate dynamics of the VM model, but also easy to be implemented.Thirdly, to emphasize implications of the constructed mathematical analysis, an extended version combining the integer-order ODE model under consideration with the Caputo fractional derivative is considered and analyzed. From the mathematical analysis performed for the integer-order VM model, global dynamics of the fractional-order VM model is also investigated rigorously.Finally, the theoretical insights are supported by a set of illustrative numerical experiments.The findings of this research not only improve some existing results in the literature, but may also provide several useful real-life applications.

Enhancement of Rheological Properties of Nano-Fe2O3-Modified Drilling Fluids

Summary In this study, we explore the potential of using nanoparticles (NPs) to enhance the properties of water-based drilling fluids (WBDFs). Specifically, we investigate the effects of nano-Fe2O3 on the rheological behavior of drilling fluid muds under high-temperature and high-pressure (HTHP) conditions to determine the optimal concentration of Fe2O3 NPs to maintain consistent rheology and improve drilling fluid systems. Results show that as temperature increases, the rheological properties of water-based muds (WBMs) decrease, leading to compromised structural integrity. To address this issue, nano-Fe2O3 is introduced into the system. We prepared and evaluated six WBM formulations with varying weight percentages of Fe2O3 NPs, and found that an optimal NP concentration of 2.5 g wt% resulted in a 13.8% reduction in American Petroleum Institute (API) filtrate volume and a 40% reduction in filter-cake thickness. Under conditions of 300°F temperature and 10,000 psi pressure, consistent reductions were observed in the rheological properties of plastic viscosity (PV), yield point (YP), and gel strength with the addition of Fe2O3 NPs. The YP-PV span was measured at 2.7, and the yield strength was determined to be 11 lb/100 ft2. Regarding fluid loss, Drilling Mudcake A containing 0.5 wt% NPs experienced a loss of 6 mL of fluid after 30 minutes, whereas Mudcake E containing 3 wt% NPs exhibited a fluid loss of 5.1 mL in the API filter press test. According to the Bingham plastic model, Muds E and F, containing 2.5 wt% and 3 wt% NPs, respectively, displayed the maximum shear stress vs. shear rate. This highlights the efficacy of nano-Fe2O3 in adjusting the properties of drilling fluids, presenting opportunities for enhanced performance and efficiency in drilling operations.

Laboratory aging method for simulating the extracted aged asphalt from reclaimed asphalt pavement

This study compared the performance of extracted asphalt and laboratory aged asphalt. The five-year service asphalt mixtures were used for extraction in this study. The laboratory aged asphalt experienced the Rolling thin film oven (RTFO) aging the Pressure aging vessel (PAV) aging with variable duration (5, 10, 15, 20, and 25 hours). By comparing the softening point, viscosity, and rheological properties of both, an aging simulation protocol was established. For laboratory aged asphalt binder, the softening point increases by 3.56 %, 5.68 %, 7.43 %, 8.16 %, and 8.74 % at PAV aging times of 5 h, 10 h, 15 h, 20 h, and 25 h, respectively. The rutting index and viscosity of the aged asphalt gradually increases with the PAV duration. There is a substantial increase in creep recovery rate and a significant decrease in non-recoverable creep compliance for aged asphalt. The rheological aging index demonstrates a linear increasing trend. The sulfoxide (SO) and aromatic (CO) aging indexes of the laboratory-simulated aged asphalt progressively rise with prolonged PAV aging time. The SO and CO aging indexes of the extracted asphalt consistent with RTFO aged asphalt experienced PAV aging 20 and 25 hours. The extracted asphalt can be simulated in the laboratory under standard RTFO conditions and a 22.26 hours PAV duration at a pressure of 2.1 MPa ± 0.1 MPa. This study introduces a methodology for simulating asphalt aging in an authentic service environment by adjusting the laboratory aging test conditions.

Guiding charged particles in vacuum via Lagrange points

We propose a method for guiding charged particles such as electrons and protons, in vacuum, by employing the exotic properties of Lagrange points. This leap is made possible by the dynamics unfolding around these equilibrium points, which stably capture such particles, akin to the way Trojan asteroids are held in Jupiter’s orbit. Unlike traditional methodologies that allow for either focusing or three-dimensional storage of charged particles, the proposed scheme can guide both non-relativistic and relativistic electrons and protons in small cross-sectional areas in an invariant fashion over long distances without any appreciable loss in energy – in a manner analogous to photon transport in optical fibers. Here, particle guiding is achieved by employing twisted electrostatic potentials that in turn induce stable Lagrange points in vacuum. In principle, guidance can be realized within the fundamental mode of the resulting waveguide, thereby presenting a prospect for manipulating these particles in the quantum domain. Our findings may be useful in a wide range of applications in both scientific and technological pursuits. These applications could encompass electron microscopies and lithographies, particle accelerators, quantum and classical communication/sensing systems, as well as methods for shuttling entangled qubits between nodes within a quantum network.

The research of mean equicontinuity, mean sensitivity, and shadowing property

We study the dynamical properties of mean equicontinuity, mean sensitivity, tracking property, and periodic points set in the hyperspace of uniform space. Let (Y,ξ) be uniform space, T:Y→Y be uniformly continuous and (C(Y),Cξ) be hyperspace of (Y,ξ).Then, we can get some conclusions: (a) T is mean equicontinous if and only if the induced map CT is mean equicontinous; (b) if the induced map CT is mean sensitive, then T is mean sensitive; (c) the induced map CT has tracking property implying that T has tracking property; (d) P(T) is dense in Y implying that P(CT) is dense in C(Y). In addition, we also study dynamical property of (G,h)− tracking property in metric G− space, and prove that if the map T has (G,h)− tracking property, then, for any k>1, the map Tk has (G,h)− tracking property.

Matrix extreme points and free extreme points of free spectrahedra

Free spectrahedra are dimension free solution sets to linear matrix inequalities of the form L A ( X ) = I d ⊗ I n + A 1 ⊗ X 1 + A 2 ⊗ X 2 + ⋯ + A g ⊗ X g ⪰ 0 , where the A i and X i are symmetric matrices and the X i have any size n × n . Free spectrahedra are ubiquitous in systems engineering, operator algebras, and the theory of matrix convex sets. Matrix and free extreme points of free spectrahedra are particularly important. We present theoretical, algorithmic, and experimental results illuminating basic properties of extreme points. For example, though many authors have studied matrix and free extreme points, it has until now been unknown if these two types of extreme points are actually different. This paper settles that issue. We also present and analyze several algorithms. Namely, we perfect an algorithm for computing an expansion of an element of a free spectrahedron in terms of free extreme points. We also give algorithms for testing if a point is matrix extreme and for computing matrix extreme points that are not free extreme.

Prediction of Flash Point of Materials Using Bayesian Kernel Machine Regression Based on Gaussian Processes With LASSO‐Like Spike‐and‐Slab Hyperprior

ABSTRACTThe determination of flash points is a critical aspect of chemical safety, essential for assessing explosion hazards and fire risks associated with flammable solutions. With the advent of new chemical blends and the increasing complexity of chemical waste management, the need for accurate and reliable flash point prediction methods has become more pronounced. This study introduces a novel predictive approach using Bayesian kernel machine regression (BKMR) with Gaussian process priors, designed to meet the growing demand for precise flash point estimation in the context of chemical safety. The BKMR model, underpinned by Bayesian statistics, offers a comprehensive framework that not only quantifies prediction uncertainty but also enhances interpretability amidst experimental data variability. Our comparative analysis reveals that BKMR surpasses traditional predictive models, including support vector machines, kernel ridge regression, and Gaussian process regression, in terms of accuracy and reliability across multiple metrics. By elucidating the intricate interactions between molecular features and flash point properties, the BKMR model provides profound insights into the chemical dynamics that influence flash point determinations. This study signifies a methodological leap in flash point prediction, offering a valuable tool for chemical safety analysis and contributing to the development of safer chemical handling and storage practices.