Stability Of Configurations Research Articles

Influence of crystalline structure on creep resistance capability in semi-crystalline Polymers: A coarse-grained molecular dynamics study

In this study, we investigated the intrinsic correlation between the crystal configuration and persistent mechanical stability of semi-crystalline polymers. The creep resistances of microstructures with different grain sizes and the same crystallinity were evaluated using coarse-grained molecular dynamics simulations. It was demonstrated that under tensile loading at constant pressure, microstructures with larger grains have more pronounced resistance to molecular rearrangement and significantly delay creep deformation. The improved creep resistance can be attributed to two factors. First, larger crystal sizes result in an increased moment of inertia, reducing the angular velocity required for the rotational rearrangement of the crystalline phase. Second, the elongated crystalline stems enhance the resistance to intermolecular slippage, elevating the strain energy necessary to disrupt the crystalline structure. These findings reveal the molecular basis of creep resistance at the nanoscale and highlight the pivotal role of crystal morphology in enhancing the long-term mechanical integrity of polymers.

Ab Initio Prediction of Two-Dimensional GeSiBi2 Monolayer as Potential Anode Materials for Sodium-Ion Batteries.

The conceptualization and deployment of electrode materials for rechargeable sodium-ion batteries are key concerns for next-generation energy storage systems. In this contribution, the configuration stability of single-layer GeSiBi2 is systematically discussed based on first-principles calculations, and its potential as an anode material is further investigated. It is demonstrated that the phonon spectrum confirms the dynamic stability and the adsorption energy identifies a strong interaction between Na atoms and the substrate material. The electronic bands indicative of inherent metallicity contribute to the enhancement of electronic conductivity after Na adsorption. The multilayer adsorption of Na provides a theoretical capacity of 361.7 mAh/g, which is comparable to that of other representative two-dimensional anode materials. Moreover, the low diffusion barriers of 0.19 and 0.15 eV further guarantee the fast diffusion kinetics. These contributions signal that GeSiBi2 can be a compatible candidate for sodium-ion batteries anodes.

Catalytic Enantioselective Synthesis of Axially Chiral Diaryl Ethers Via Asymmetric Povarov Reaction Enabled Desymmetrization.

Axially chiral diaryl ethers represent a distinct class of atropisomers, characterized by a unique dual C─O axes system, which have been found in a variety of natural products, pharmaceuticals, and ligands. However, the catalytic enantioselective synthesis of these atropoisomers poses significant challenges, due to the difficulty in controlling both chiral C─O axes, and their more flexible conformations. Herein, an efficient protocol for catalytic enantioselective synthesis of axially chiral diaryl ethers is presented using organocatalyzed asymmetric Povarov reaction-enabled desymmetrization, followed by aromatizations. This method yields a wide range of novel quinoline-based diaryl ether atropoisomers in good yields and high enantioselectivities. Notably, various aromatization protocols are developed, resulting in a diverse set of polysubstituted quinoline-containing diaryl ether atropisomers. Thermal racemization studies suggested excellent configurational stabilities for these novel diaryl ether atropisomers (with racemization barriers up to 38.1kcalmol-1). Moreover, this research demonstrates for the first time that diaryl ether atropisomers lacking the bulky t-Bu group can still maintain a stable configuration, challenging the prior knowledge in the field. The fruitful derivatizations of the functional group-rich chiral products further underscore the value of this method.

Complex evolutionary trajectories in vivo of two novel KPC variants conferring ceftazidime-avibactam resistance

More and more ceftazidime-avibactam-resistant KPC-producing Klebsiella pneumoniae have been reported with its widespread use, and the detection rate of KPC variants has increased dramatically. However, the evolutionary mechanism and fitness effects during KPC mutation remained unknown. Here, we report the complex in vivo evolutionary trajectories of two novel KPC variants, KPC-155 (L169P/GT242A) and KPC-185 (D179Y/GT242A), from K. pneumoniae in the same patient. The novel variants were shown to confer ceftazidime-avibactam resistance but restore carbapenem susceptibility based on the results of plasmid transformation assays, cloning experiments, and enzyme kinetic measurements. In vitro, competition experiments highlighted the adaptive advantage conferred by strains carrying these KPC variants, which could lead to the rapid spread of these ceftazidime-avibactam-resistant strains. The growth curve indicated that blaKPC-185 had better growth conditions at lower avibactam concentration compared to blaKPC-155, which was consistent with ceftazidime-avibactam use in vivo. In addition, replicative transposition of the IS26-flanked translocatable unit (IS26-ISKpn6-blaKPC-ISKpn27-IS26) also contributes to the blaKPC amplification and formation of two copies (blaKPC-2 and blaKPC-185), conferring both carbapenem and ceftazidime-avibactam resistance. However, strains with double copies showed reduced competitive advantage and configuration stability. The comparative plasmid analysis of IS26 group (IS26-blaKPC-IS26) and Tn1721 group (Tn1721-blaKPC-IS26) revealed that IS26-insertion could influence the distribution of resistance genes and ability of self-conjugation. The dynamic changes in blaKPC configuration highlight the need for consistent monitoring including antimicrobial susceptibility testing and determination of blaKPC subtypes – during clinical treatment, especially when ceftazidime-avibactam is administered.

Theoretical investigation on gas sensing characteristics of 3d transition metal atom doped C9N7 for toxic gases (CO, NO, NO2, and SO2)

This study investigates the sensing performance of a series of 3d transition metal doped C9N7 sensor structures for four toxic gases (CO, NO, NO2, and SO2). A series of sensor configurations with single and double 3d transition metal atoms doped with C9N7 (TM-C9N7 and TM2-C9N7) are constructed. The stability of the sensor configuration is evaluated by calculating the formation energy and dissolution potential. The stability analysis results indicate that except Sc-C9N7, Mn2-C9N7, and Cr2-C9N7, all sensor configurations have good structural stability. For screened sensor structures with good structural stability, the adsorption energy values of four toxic gases and three common gases (N2, O2, and CO2) are compared to evaluate their selectivity towards toxic gases. Moreover, the recovery times are also calculated to further evaluate the sensing performance. Through comprehensive evaluation, four sensor structures (Fe-C9N7, Cu-C9N7, Zn-C9N7, and Zn2-C9N7) with high selectivity and relatively short recovery time for toxic gases are determined. Among them, Fe-C9N7 is suitable for sensors of toxic gases NO2, and SO2, while Cu-C9N7, Zn-C9N7, and Zn2-C9N7 have good sensing performance for all four toxic gases.

Competitive adsorption behavior of As(V) and Sb(V) on Hematite: Facet and pH dependent coordination affinity and role of outer-sphere complexes

The environmental mobility and fate of arsenic (As) and antimony (Sb) are influenced by ubiquitous iron minerals, but little is known about whether their co-adsorption behavior is affected by the exposed facets. Herein, we used cubic and rod-shaped hematite nanocrystals (HNC and HNR) to investigate the effect of exposed facets on competitive adsorption behaviors. TEM analysis indicated that the primary exposed facets of HNC and HNR were {110} and {012}, separately. Calculations supported the predictions of our model, revealing that the competition in acidic and alkaline environments was mainly influenced by the affinity and bond stability of facet-related adsorption configurations. However, the competition in neutral conditions was jointly influenced by facet-related coordination and adsorption behavior, due to the dependence of Sb(V) on protonation sites. On HNR (pH = 3), the adsorption of Sb(V) (50.6 %) was approximately twice that of As(V) (27.8 %) for its significant advantage in bidentate coordination on the {110} facet, whereas on HNC, As(V) (65.9 %) and Sb(V) (69.3 %) exhibited similar competitiveness. Notably, As(V) and Sb(V) tend to be adsorbed through outer-sphere coordination under alkaline conditions. On the {012} facet, As(V) and Sb(V) exhibited similar competitiveness for outer-sphere sites, whereas on the {110} facet, As(V) outer-sphere coordination showed stronger affinity, giving it an edge in competing on HNR. Overall, this study elucidated the critical role of varying exposed facets in the competitive adsorption process and proposed novel strategies for the selective removal of coexisting As(V) and Sb(V) through tailored fixed-facet iron oxides.

Computational investigation of nanoemulsion-released tocopherol for treating cardiovascular diseases: Insights from molecular dynamic simulation and deep learning prediction

This research investigated the potential of tocopherol released from nanoemulsion as a therapeutic agent for cardiovascular diseases (CVD) through comprehensive in-silico site-specific molecular docking analysis and AI- driven Molecular Dynamic Simulation, between tocopherol and seven CVD-related proteins (Angiotensin Converting Enzyme (ACE) (1O8a), Human Angiotensin Receptor (4YAY), P38 Mitogen-Activated Protein Kinase (MAPK) (4DLI), HMG-CoA Reductase (1HW9), β-1-Adrenergic Receptor (2YCW), Human C-reactive Protein (1BO9), and Cyclooxygenase-2 (1CX2)). Our findings revealed significant interactions. α-Tocopherol exhibited strong binding affinities, particularly with the 2YCW protein, evidenced by a Vina score of -11.9 ± 0.86 kcal/mol and an inhibition constant of 1.4 ± 0.12 µM. Extensive hydrophobic interactions and significant hydrogen bonds were identified as critical for the stability of these complexes. Furthermore, Molecular Dynamics (MD) simulations, RMSD, Rg, RMSF, and Free Energy Landscape (FEL) profiles, and a deep convolutional neural network (CNN) used for predicting interaction sites from protein sequences, illustrated that the protein-ligand complexes attained dynamic configuration stability with RMSD values converging around 0.3 nm, underscoring the robustness of tocopherol-protein interactions. The pathway analysis highlights the possibility of tocopherol's involvement in interacting with several key biological pathways, Dilated Cardiomyopathy, Arrhythmogenic Right Ventricular Cardiomyopathy, Hypertrophic Cardiomyopathy, and Apoptosis.This study revealed significant insights into the interactions of Nanoemulsion-released tocopherol with key proteins involved in the development of cardiovascular diseases, aimed at improving cardiovascular health. However, the findings of the study require meticulous experimental study and clinical trials to provide accurate results and validate tocopherol's therapeutic efficacy.

Ab initio study of the adsorption of O, O2, H2O and H2O2 on UO2 surfaces using DFT+U and non-collinear magnetism

In order to model correctly the corrosion of spent nuclear fuel under disposal conditions, it is important to understand its behavior in the presence of oxidants. To advance in this direction, we consider the oxidation of UO2. We investigate computationally the adsorption of various species on its three most stable surfaces: (111), (110), and (100), with emphasis on incorporating a full non-collinear PBE+U approach. Various species, namely O, O2, H2O and H2O2 are considered due to their relevance for the oxidation of UO2. The dissociation energy and an estimate for the dissociation barrier for O2 were obtained, using the preferred adsorption configurations of O and O2. The adsorption configurations for H2O in our study compare well with previous studies that used collinear approximations, both in terms of relative stability of configurations and bond lengths. Differences in adsorption energies were found, which may be important for reaction kinetics. Dissociative reactions in which the water molecule splits in hydrogen and hydroxyl occur only on one of the three surfaces. The hydrogen further reacts with a surface oxygen to also form a hydroxyl group. Not surprisingly, we find that H2O2 binds more strongly to the three surfaces than water (lower formation energy), and similar to H2O adsorption, dissociative reactions may occur. The dissociated hydrogen reacts with a surface oxygen to form a hydroxyl group and the hydroperoxyl molecule binds with a surface uranium. Our study, which includes a detailed study of electron transfer, magnetic structure and the preferred adsorption configurations, gives insight into the uranium oxidation states and the influence of surface geometry on adsorption. The findings contribute to a more comprehensive understanding of the early stages of UO2 oxidation.

Temperature driven pseudocapactive performance of WO3/MXene nanocomposite for asymmetric aqueous supercapacitors

The WO3 nanostructured materials are widely used as a pseudocapacitive charge storage electrodes. However it is restricted by poor cyclic stability. To overcome it, hybrid nanocomposites materialization of WO3 with fascinating 2D MXene is an excellent strategy. Though both materials consumes acid based electrolytes and possesses layered structures, WO3 protects MXene from self-restacking and/or aggregation of their adjacent layers owing to its strong van-der Waals interaction. Moreover layered structure of MXene offers synergistic action of various metal elements, fast diffusion of ions, increase the voltage window and cycle life. Herein we report hybrid nanocomposite of orthorhombic WO3 nanoplates with 2D MXene nanoflakes prepared by a single-step hydrothermal method. The electrochemical investigations exhibits the specific capacitances of 21 F g−1 (MXene), 112 F g−1 (WO3), and 290 F g−1 (WO3/MXene-20) at 0.5 A g−1 in 1 M H2SO4 aqueous electrolyte. Furthermore temperature dependent investigation of a hybrid nanocomposite (WO3/MXene-20) demonstrates consistent enhancement in the specific capacitance with the increasing temperature and a maximum capacitance of 376 F g−1 at 0.5 A g−1 is achieved at 50 °C. Eventually an asymmetric aqueous supercapacitor (AASC) fabricated using hybrid nanocomposite (WO3/MXene-20) demonstrates an outstanding cyclic stability up to 20,000 cycles at 5 A g−1 upholding 72 % capacitance retention and 73 % coulombic efficiency. The exceptional cyclic stability of the AASC configuration emphasizes the prospective of WO3/MXene hybrid nanocomposites for durable energy storage applications.

Protective efficacy of nafronyl in diabetic retinopathy through targeted inhibition of key enzymes.

Diabetic retinopathy is governed by abnormal apoptosis, increased capillary pressure, and other linked pathology that needs an efficient treatment by multitargeted approaches. Thus, the current study aimed to explore the potential of inhibition of targeted enzymes (DPP4, ACE-2, and aldose reductase) and free radical scavenging capabilities of selected compounds (nafronyl or naftidrofuryl) through in silico and in vivo investigations. Significant binding energies were observed in complexes of aldolase reductase, angiotensin type 1 receptor, and DPP4 against the nafronyl and sitagliptin more than -7.5kcal/mol. Further validation of free energy was confirmed by calculations of molecular mechanics Poisson-Boltzmann surface area (MMPBSA), and configurational stabilities examined by PCA (principal component analysis). Additionally, drug-likeness was examined by the Swiss ADME web tool, which showed significant findings. Consequently, in vivo experimentations showed significant inflammation and alterations in retinal layers of inner plexiform (inner limiting membrane, nerve fibers, and ganglionic cells), inner nuclear layer (bipolar cells and horizontal cells), and photoreceptors cells. Whereas the treatments (nafronyl and sitagliptin) caused significant improvements in the histoarchitecture of the retina. Additionally, the HOMA indices (IR-insulin resistance, sensitivity, and β cells functioning) and levels of free radicals were significantly altered in the diabetic control group in comparison to intact control. Nafronyl administration showed significant ameliorations in HOMA indices as well as antioxidant levels. Based on the results, it can be concluded that nafronyl efficiently interacts with target enzymes, which may result in potent inhibition and ameliorations in retinal histology as well as glucose homeostasis and antioxidants.

The synergistic anti‐corrosion performance and mechanism of meso‐tetra(4‐carboxyphenyl)porphine on steel bars in alkaline environments

AbstractCorrosion protection of steel bars in alkaline concrete environments poses a common challenge in marine engineering. One approach to mitigate steel bar corrosion is the addition of corrosion inhibitors to the concrete. In alkaline environments, the passivation of rebars occurs through anodic passivation coupled with the cathodic oxygen reduction reaction (ORR). The catalysis of ORR can expedite anode passivation. To investigate the corrosion inhibition of steel bars in alkaline environments, meso‐tetra(4‐carboxyphenyl)porphine (TCPP), known for its ORR catalytic properties, is selected. TCPP forms adsorption films on the surface of steel bars, facilitating the formation of passivation films. TCPP primarily adsorbs onto active sites on the surface of the passivation film, where lattice iron ions have leached. The adsorbed TCPP accelerates the formation of the passivation film through ORR catalysis, inhibiting the development of passivation film defects and enhancing the integrity and protection of the passivation film. The most significant effect is observed when the concentration of TCPP is 0.5 mmol/L. The physical adsorption of TCPP is primarily determined by the negative charge centers, namely the carboxyl group O and the pyrrole N. However, due to steric hindrance caused by the unrestricted rotation of the carboxyl benzene, the pyrrole N does not play a dominant role in chemical adsorption. Instead, the active site for chemical adsorption is the carboxyl group O. The adsorption process significantly reduces the diffusion coefficient of TCPP molecules, providing a robust and stable adsorption binding. Phthalocyanine molecules without carboxyl benzene groups adopt a planar structure, allowing them to form stable adsorption configurations on the iron surface through flat adsorption. This observation provides guidance for the design of novel metal phthalocyanine molecules. Specifically, the development of metal phthalocyanine molecules with modifying groups that are coplanar with the phthalocyanine ring and possess restricted rotation can achieve flat adsorption, improve coverage rate, and enhance adsorption configuration stability.

Interfacial Interaction between Functionalization of Polysulfone Membrane Materials and Protein Adsorption.

This study that modified polysulfone membranes with different end-group chemical functionalities were prepared using chemical synthesis methods and experimentally characterized. The molecular dynamics (MD) method were used to discuss the adsorption mechanism of proteins on functionalized modified polysulfone membrane materials from a molecular perspective, revealing the interactions between different functionalized membrane surfaces and protein adsorption. Theoretical analysis combined with basic experiments and MD simulations were used to explore the orientation and spatial conformational changes of protein adsorption at the molecular level. The results show that BSA exhibits different variability and adsorption characteristics on membranes with different functional group modifications. On hydrophobic membrane surfaces, BSA shows the least stable configuration stability, making it prone to nonspecific structural changes. In addition, surface charge effects lead to electrostatic repulsion for BSA and reduce the protein adsorption sites. These MD simulation results are consistent with experimental findings, providing new design ideas and support for modifying blood-compatible membrane materials.

Stellar model with non-zero strange quark mass (ms≠0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_s\ e 0$$\\end{document}) and Mak–Harko density profile admitting observational results

This article describes the configuration of strange quark stars composed of three flavour quarks in hydrostatic equilibrium considering the energy density profile of Mak and Harko and non-zero strange quark mass (ms≠0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_s\ e {0}$$\\end{document}). A suitable stellar model is proposed assuming equation of state of interior matter as modified MIT equation of state in bag model p=13(ρ-4Bg)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p=\\frac{1}{3}(\\rho -4B_g)$$\\end{document}, where Bg\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_g$$\\end{document} is known as bag constant, to predict the viability of strange stars. The interior of such compact stars is mainly composed of quarks and electrons to establish charge neutrality condition. We have checked the various stability windows depending on the energy per baryon for different values of bag constant Bg\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_g$$\\end{document} and mass of strange quark ms\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_s$$\\end{document}. We have studied the effect of non-zero mass of the strange quark (ms\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_s$$\\end{document}) on the physical properties of the strange star in the context of the modified MIT bag equation of state. We note that the maximum stellar mass decreases with increasing ms\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_s$$\\end{document}. The model is suitable for predicting the radius, central density and other properties of compact stars having mass ≤2.01M⊙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\le 2.01M_{\\odot }$$\\end{document}, such as 4U1820-30\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$4U~1820-30$$\\end{document}, PSRJ1614-2230\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$PSR~J1614-2230$$\\end{document} etc, which are supposed to be strange stars. The radius of few recently observed compact stars are predicted in our model and they are found to be compatible with the value as predicted from observation. The model is found to be suitable in view of all the necessary criterion along with fulfilment of stability of the stellar configuration as well as stable in view of small radial perturbations.

Evaluation of Lost Circulation Material Sealing for Geothermal Drilling

Lost circulation is a pervasive problem in geothermal wells that can create prohibitive costs during drilling. The main issue with treatment is that the mechanism of plug formation is poorly understood. Here we applied two experimental approaches to characterize the clogging effectiveness of different materials. Fracture flow tests with different geometries were conducted with various individual materials and mixtures at relevant conditions. A high-temperature flow loop system was also developed to inject single- and mixed-material plugs into a gravel pack with a non-uniform geometry to compare with the fracture tests. The fracture tests revealed that single materials tended to form no plug or an unstable plug, while mixtures of materials were uniformly better at sealing fractures. Gravel pack tests at high temperatures show most of the materials are intact but degraded. The fibrous materials can create partial or unstable plugs in the gravel pack, but mixed-material plugs are far more effective at clogging. Both test types suggest that (1) mixed materials are more effective at blocking fluid flow and (2) fibrous materials seal fracture openings better, while granular materials seal inside fractures or pore throats better. Further research is needed to study the long-term stability of different plug configurations.

Configuration uncertainty propagation of gravitational-wave observatory using a directional state transition tensor

Configuration stability is essential for a space-based Gravitational-Wave (GW) observatory, which can be impacted by orbit insertion uncertainties. Configuration uncertainty propagation is vital for investigating the influences of uncertainties on configuration stability and can be potentially useful in the navigation and control of GW observatories. Current methods suffer from drawbacks related to high computational burden. To this end, a Radial-Tangential-Ddirectional State Transition Tensor (RT-DSTT)-based configuration uncertainty propagation method is proposed. First, two sensitive directions are found by capturing the dominant secular terms. Considering the orbit insertion errors along the two sensitive directions only, a reduced-order RT-DSTT model is developed for orbital uncertainty propagation. Then, the relationship between the uncertainties in the orbital states and the uncertainties in the configuration stability indexes is mapped using high-order derivatives. The result is a semi-analytical solution that can predict the deviations in the configuration stability indexes given orbit insertion errors. The potential application of the proposed RT-DSTT-based method in calculating the feasible domain is presented. The performance of the proposed method is validated on the Laser Interferometer Space Antenna (LISA) project. Simulations show that the proposed method can provide similar results to the STT-based method but requires only half of the computational time.

A spectroscopic investigation of thermal instability for cylindrical equilibria with background flow

Context. Flows are omnipresent and govern the dynamics of plasma. Solar tornadoes are a class of apparently rotating prominences that might be formed by thermal instability. In spectroscopic studies on thermal instability, background flow is commonly neglected. Aims. We here determine the effect of background flow on thermal instability in cylindrical magnetic field configurations. How various parameters affect the distribution of eigenmodes in the magnetohydrodynamic (MHD) spectrum is also explored. We investigate whether discrete thermal modes exist. Methods. In an analytical study, we extended upon the literature by including a generic background flow in a cylindrical coordinate system. The non-adiabatic MHD equations are linearised, Fourier-analysed, and examined to understand how a background flow changes the continua. An approximate expression for discrete thermal modes is derived using a Wentzel-Kramers-Brillouin (WKB) analysis. The analytical results are then verified for a benchmark equilibrium using the eigenvalue code Legolas. The eigenfunctions of discrete thermal modes are visualised in 2D and 3D. Results. The thermal continuum is Doppler-shifted due to the background flow, just like the slow and Alfvén continua. Discrete modes are altered because the governing equations contain flow-related terms. An approximate expression to predict the appearance of discrete thermal modes based on the equilibrium parameters is derived. All analytical expressions match the numerical results. The distribution of the density perturbations of the discrete thermal modes is not a uniform or singular condensation, due to the shape of the eigenfunctions and the dependence of the assumed waveform on the coordinates and wavenumbers. A 3D visualisation of the total velocity field shows that the helical field is heavily influenced by the radial velocity perturbation. Conclusions. We derived analytic expressions for non-adiabatic MHD modes of a cylindrical equilibrium with background flow and verified them using a coronal equilibrium. However, the equations are valid for and can be applied in other astrophysical environments.

Review of the Configuration and Transient Stability of Large-Scale Renewable Energy Generation Through Hybrid DC Transmission

Review of the Configuration and Transient Stability of Large-Scale Renewable Energy Generation Through Hybrid DC Transmission

Nonlinear dynamics and onset of steady precession of a ring on a vertical rod.

We report on the unexpected precessional motion that occurs when a small, rigid ring is rotated on a vertical smooth rod. Using high-speed imaging, two distinct regimes of motion are observed experimentally. (i) Oscillatory motion when the ring has a single contact with the rod (transient motion). (ii) Steady state (terminal velocity) when the ring has two instantaneously stationary contacts with the rod. These two regimes and the transition between them are analyzed through qualitative, analytical, and numerical means. One key feature of the steady-state motion is energy dissipation through rolling resistance and air drag. Our model predicts that steady-state motion occurs only when certain geometric conditions (the ratio of the radii of a ring and a rod, and the tilt angle) are fulfilled. As the steady-state regime is often found to be the preferred final state, the dynamic stability of the single contact configuration is investigated through bifurcation, phase-space, and linear stability analyses. Our numerical simulation accounts for the stick-slip transition at the contact point, and is in good agreement with experimental data across all experiments. Our findings have potential applications in various engineering fields, such as studying the vibrational detachment of threaded fasteners and developing gravity-driven centrifuges.

Optimizing Subtalar Arthrodesis: A Human Cadaveric Evaluation of a Novel Partially-Threaded Screw Combination in the Delta Configuration.

Background and Objectives: Despite the established role of subtalar joint arthrodesis (SJA) for treatment of subtalar osteoarthritis, achieving bone union remains challenging, with up to 46% non-union rates. Adequate compression and stable fixation are crucial for successful outcomes, with internal screw fixation being the gold standard for SJA. The delta configuration, featuring highly divergent screws, offers stability, however, it can result in hardware irritation in 20-30% of patients. Solutions to solve this complication include cannulated compression screw (CCS) countersinking or cannulated compression headless screw (CCHS) application. The aim of this biomechanical study was to investigate the stability of a delta configuration for SJA utilizing either a combination of a posterior CCHS and an anterior CCS or a standard two-CCS combination. Materials and Methods: Twelve paired human cadaveric lower legs were assigned pairwise to two groups for SJA using either two CCSs (Group 1) or one posterior CCHS and one anterior CCS (Group 2). All specimens were tested under progressively increasing cyclic loading to failure, with monitoring of the talocalcaneal movements via motion tracking. Results: Initial stiffness did not differ significantly between the groups, p = 0.949. Talocalcaneal movements in terms of varus-valgus deformation and internal-external rotation were significantly bigger in Group 1 versus Group 2, p ≤ 0.026. Number of cycles until reaching 5° varus-valgus deformation was significantly higher in Group 2 versus Group 1, p = 0.029. Conclusions: A delta-configuration SJA utilizing a posterior CCHS and an anterior CCS is biomechanically superior versus a standard configuration with two CCSs. Clinically, the use of a posterior CCHS could prevent protrusion of the hardware in the heel, while an anterior CCS could facilitate less surgical time and thus less complication rates.

Equilibrium configurations of line arrays with respect to the deviatoric mean drift forces

Monochromatic waves incident on an array of structures give rise to nonlinear, time-constant mean drift forces (MDFs). These forces depend on the array's spatial configuration; their magnitude and the direction is, in general, different for every structure in the array. If the spatial configuration of an array is not fixed, as is the case in arrays of individually anchor-moored structures, the time-constant differences in MDF on individual bodies can lead to a change in spatial configuration, which could, in turn, significantly affect both the first-order, time-harmonic response of the array, as well as the downwave component of the MDF. Here, we explore the dependency of these deviatoric forces on array configurations and on the frequency of the incident monochromatic waves. We consider configurations of line arrays (consisting of 2–5 vertical circular cylinders) that are described by 1 or 2 parameters, and we focus on the along-array component of deviatoric forces. Using multiple scattering computational simulations, we identify the array configurations in which the deviatoric drift forces are zero, and we discuss the stability of these equilibrium configurations with respect to class-preserving configuration perturbations. Both stable and unstable equilibria exist, but the relative number of unstable equilibria grows as the number of degrees of freedom of the configuration perturbations increases. Interestingly, the stable configurations experience a generally lower downwave mean drift force on the entire array than the unstable ones. Overall, the variations in the deviatoric and the downwave MDFs between equilibria are significant (on the order of the isolated body MDF).