Coarse Grain Research Articles

Serum Lipidomic Signatures Mediate the Association Between Coarse Grain Preference and Central Obesity in Adults With Normal Weight and High Wheat Intake.

Little is known about the association between grain preference andabdominal fat accumulation, and mediating roles of circulating lipidomicsignatures. We quantified 1245 circulating lipids in 150 normal-weight centralobesity (NWCO) cases and 150 controls using targeted lipidomics. Grainpreference was determined by the highest intake frequency of grains (whiterice, wheat, or coarse grain). In our participants with high wheat intakefrequency, preferring coarse grain over rice was associated with a 60% lowerrisk of NWCO. Of the 585 lipids showing opposing associations with white riceand coarse grains, 46 were significantly linked to either (p<0.05), predominantly alkylacyl phospholipids (PE-Os; n<9) and alkenylacylphospholipids (PE-Ps; nx=7). Network analysis identified a module primarilycomposed of PE-Os and PE-Ps, which was positively associated with coarse grain (p=0.014). Another module, mainly consisting of triacylglycerols (TGs), was associatedwith white rice (p=0.003) and mediated the association between white rice(mediation proportion: 20.30%; p=0.027) or coarse grain preference (11.43%; p=0.040) and NWCO. Specific lipids, such as TG(8:0_16:0_16:0) and TG(8:0_14:0_18:0), exhibited notable mediation effects. In normal-weight individuals with highwheat intake frequency, preferring coarse grain was inversely associated with NWCO, mediated by specific lipidomic signatures.

Study on the mechanical properties of gradient grains based on molecular dynamics

ABSTRACT This study used molecular dynamics simulations to investigate the plastic deformation mechanisms of gradient nano-grained (GNG) copper. The results show that GNG structures have higher yield stress compared to uniform nanocrystalline structures, with the g = 0.30 model exhibiting a significant increase in flow stress. GNG structures can effectively distribute atomic stress, transferring it from coarse grains to fine grains and reducing local stress concentration. Coarse grains undergo severe shear deformation, while grain boundary (GB) activities transition from migration in coarse grains to rotation in fine grains. GNG structures enhance the ability to coordinate deformation through GB motion, suppress dislocation formation, and facilitate interactions between dislocations and GBs, thereby improving strength and toughness.

Modeling Viral Capsid Assembly: A Review of Computational Strategies and Applications

Viral capsid assembly is a complex and critical process, essential for understanding viral behavior, evolution, and the development of antiviral treatments, vaccines, and nanotechnology. Significant progress in studying viral capsid assembly has been achieved through various computational approaches, including molecular dynamics (MD) simulations, stochastic dynamics simulations, coarse-grained (CG) models, electrostatic analyses, lattice models, hybrid techniques, machine learning methods, and kinetic models. Each of these techniques offers unique advantages, and by integrating these diverse computational strategies, researchers can more accurately model the dynamic behaviors and structural features of viral capsids, deepening our understanding of the assembly process. This review provides a comprehensive overview of studies on viral capsid assembly, emphasizing their critical role in advancing our knowledge. It examines the contributions, strengths, and limitations of different computational methods, presents key computational works in the field, and analyzes milestone studies that have shaped current research.

Effect of Cu Additive on the Microstructure and Magnetic Properties of Fe-6.5wt%Si High Silicon Steel by Induction Melting Method

Fe-6.5wt%Si high silicon steel alloy was prepared using the vacuum induction melting method. Ordered phase formation in Fe-6.5wt%Si alloy was inhibited by adding trace Cu and induction cycle heating purification treatment. The microstructure and magnetic properties of high silicon steel were investigated. The results show that with the increase of Cu content, the alloy microstructure first changed from coarse grain to fine isoaxial crystal, followed by strip dendrite, with ordered cracking. The saturated polarization strength of the alloy decreased from 25.1 emu of the sample without adding Cu and heating once to 21.5 emu for seven cycles, the residual magnetic polarization increased from 0.0255 emu to 0.048 emu, the slope of the magnetization curve slowed down, and the coercive force increased from 2.4 Oe to 4.0 Oe. With the increase of cyclic heating times, the microstructure of the alloy without added Cu refined and transitioned from columnar to equiaxial crystals, from isoaxial dendrite to strip with the addition of 0.03 wt%Cu, and from strip to isoaxial structure with the addition of 0.05 wt%Cu. With the increase of cycle heating times, the saturation magnetization strength of the alloy without Cu and with 0.03 wt%Cu alloy increased, while the recalcitrant force reduced. Conversely, the saturation polarization strength decreased for the alloy with 0.05 wt% Cu, and the coercive force was also reduced.

EXPERIMENTS ON THE SETTLING OF CARBONATE SAND-MUD SUSPENSIONS

This experimental study addresses the settling behaviour of natural carbonate sediment suspensions. Natural carbonate suspensions differ hydrodynamically from siliciclastic suspensions due to a broader range of grain sizes, shapes, and solid densities of skeletal grains. These variations also underlie hydrodynamic differences between carbonate and siliciclastic turbidity currents. The experiments used coarse, non-cohesive skeletal tropical carbonate sand obtained from the back-reef of Moorea (French Polynesia) and cohesive tropical carbonate mud retrieved from the slopes of Little Bahama Bank. Twenty-one settling experiments were conducted at volumetric sediment concentrations of 9%, 20% and 30%. The suspensions consisted of carbonate sand mixed with cohesive carbonate mud in sand/mud ratios ranging from 96%/04% to 76%/24%. Textural trends in grain size and composition of the experiment deposits were evaluated by laser diffraction analysis and microscopic observations. Three facies were identified, fro m base to top: (1) interval A: weakly graded to ungraded rud/grainstone to float/packstone, occasionally with a fining-upward base at low bulk concentrations and mud proportions; (2) interval B: normally graded grain- to packstone; and (3) interval C: normally graded wacke- to mudstone. Interval B, the least muddy (cleanest sand) with the best sorting, has a normalized thickness consistent across experiments and unaffected by sediment concentration or mud proportion. In contrast, interval C thickens at the expense of interval A as mud proportion increased at each sediment concentration, although this trend lessens for deposits of higher-concentration suspensions where interval A is the dominant facies. In deposits of low-concentration suspensions, the fining-upward base of interval A decreased in normalized thickness with increasing sediment concentration and mud proportion. The experiments demonstrate that grain-size segregation becomes less efficient with increasing sediment concentration and/or cohesiv e mud proportion. Thus, adding cohesive carbonate mud lowers the critical sediment concentration at which grain-size segregation is suppressed, resulting in thicker ungraded interval A deposits. Compared to previous siliciclastic suspension settling experiments, grain-size segregation is suppressed at lower sediment concentrations in carbonate suspensions, although the present experiments used much coarser grain sizes. This work contributes to understanding carbonate suspension-flow deposits such as calciturbidites and calcidebrites, by hinting to (i) vertical and longitudinal (proximal to distal) grain-size sorting processes, and (ii) grain-shape sorting patterns within individual deposits. Both aspects tie to the hydrodynamic behaviour of individual, irregular-shaped grains in sediment suspensions with varying grain composition, as well as rheological changes due to interaction with variable quantities of cohesive carbonate mud.

Provenance of fine-grained Quaternary sediments in the Tengger Sandy Desert recorded by Sr-Nd isotopes and its linkage with Quaternary aeolian silts on the Chinese Loess Plateau

Aeolian dust, a product of aridification, can directly affect the climate system by reflecting and absorbing solar radiation, or indirectly by altering cloud properties. It also plays a role in regulating carbon uptake in marine ecosystems through the iron fertilization effect. The Gobi Deserts in southern Mongolia have traditionally been considered major sources of sandstorms and dust emissions in Asia's interior. However, a recent sediment tracing study using U-Pb age spectra of coarse detrital zircon grains challenges the role of these sandy deserts as sources of aeolian dust for the downwind Chinese Loess Plateau (CLP). This study aimed to identify the provenance area of Quaternary fine-grained sediments in the proximal sandy Desert Tengger and to explore their potential link with aeolian dust in the downwind CLP during the Quaternary. (1) 87Sr/86Sr values ranging from 0.715124 to 0.728164 and 143Nd/144Nd values from 0.511987 to 0.512192 were measured in the acetic acid-insoluble <75 μm fraction of 30 Quaternary sediment samples from the core BJ14, drilled in the Tengger Sandy Desert hinterland. (2) These 143Nd/144Nd values resemble those of riverine sediments eroded from rocks in the Northern Qinghai-Tibet Plateau (NTP) but differ from those eroded from the Gobi Altai Mountains (GAMs). This indicates that the NTP is the primary source of the <75 μm component of the Tengger Sandy Desert sediments during the Quaternary. Alongside previous studies on U-Pb age spectra of detrital zircons, our results suggest that after 0.8 Ma, the contribution of fine-grained detritus from the NTP decreased, although it continued to dominate the provenance of fine-grained sediments. However, the contribution of coarse detritus from the NTP increased significantly, becoming predominant in coarse grains, especially after 0.36 Ma. These changes record enhanced physical weathering and wind transporting capacity driven by temperature differences in the context of global aridification following the Kunlun-Huanghe Movement and the Mid-Pleistocene Transition. (3) After 0.9 Ma, a deviation on 143Nd/144Nd values of the <75 μm Quaternary sediments within the hinterland of Tengger from that of the 28–45 μm fraction in the loess/paleosol sequence in Lingtai in the central CLP suggests that the source-sink linkage between the hinterland Tengger and Chinese Loess Plateau was weak after 0.9 Ma. But high shoreline areas of the paleolake Tengger might be a persistent source area emitting fine-grained detritus to the CLP throughout the Quaternary period. This study indicates further research is needed to enhance our understanding of dust fluxes in northern China.

Martignac: Computational Workflows for Reproducible, Traceable, and Composable Coarse-Grained Martini Simulations.

Despite their wide use and far-reaching implications, molecular dynamics (MD) simulations suffer from a lack of both traceability and reproducibility. We introduce Martignac: computational workflows for the coarse-grained (CG) Martini force field. Martignac describes Martini CG MD simulations as an acyclic directed graph, providing the entire history of a simulation─from system preparation to property calculations. Martignac connects to NOMAD, such that all simulation data generated are automatically normalized and stored according to the FAIR principles. We present several prototypical Martini workflows, including system generation of simple liquids and bilayers, as well as free-energy calculations for solute solvation in homogeneous liquids and drug permeation in lipid bilayers. By connecting to the NOMAD database to automatically pull existing simulations and push any new simulation generated, Martignac contributes to improving the sustainability and reproducibility of molecular simulations.

A quasi-in-situ EBSD study on the effect of abnormal grain growth on mechanical properties of the friction-stir welds of 2219 aluminum alloy

Abnormal grain growth appears in the friction stir welds of 2219 aluminum alloy during solution treatment. In this study, the effect of abnormal grain growth on the mechanical properties of the friction-stir welds of 2219 aluminum alloy was investigated, combined with the quasi-in-situ EBSD experiment. The results show that the solution-treated welds with coarse grains have lower tensile strength and elongation than the base metal, but the fracture mode remains the same. According to the bulging testing results, the limiting dome height and ultimate bulging rate of the solution-treated tailor-welded blanks are 85% and 77% of the base metal, respectively. After T6 treatment, the mechanical properties of the weld with coarse grains, especially the elongation after fracture, further decrease compared to the base metal. The stress concentration caused by abnormal grains is the main reason for the decreased mechanical properties of the solution-treated weld. There are copper-poor zones along the grain boundaries because of the rapid precipitation at grain boundaries during T6 treatment. Therefore, abnormal grain growth makes intergranular cracks easier to initiate and propagate, which results in the decrease of elongation of the T6-treated weld.

Spall response and microstructure evolution of additively manufactured AlSi10Mg alloy with different states

The spall response and microstructure evolution of additively manufactured AlSi10Mg alloy with different states were investigated systematically through plate impact experiments, microstructure and texture characterization and quasi-static tensile tests. The results show that the microstructure, texture and spall response are related to the impact velocity and material state. Before deformation and fracture failure occur, the as-built and annealed specimens possess the same <001> texture along the building direction; the former consists of numerous networks, columnar grains and fine equiaxed grains, and the latter is comprised of coarser grain structure and coarse particles. For both the as-built and annealed specimens, as the impact velocity increases, the Hugoniot elastic limit (HEL) stress and spall strength are slightly affected by the impact velocity; however, the peak shock stress tends to increase. Under the same impact velocity conditions, compared with the as-built specimen, the annealed specimen corresponds to a similar peak shock stress but a lower Hugoniot elastic limit stress and spall strength. Independent of the material state, as the impact velocity increases, the damage gradually increases, namely, from incipient spall to complete spall; the grain structure, including size and shape changes; and the texture remains almost unchanged. Under the same impact velocity conditions, compared with the as-built specimen, the annealed specimen has a coarser grain structure and a similar texture. Voids tend to nucleate at grain boundaries (at the bottom of the melt pool) and large particles. Compared with the as-built specimen, the annealed specimen has greater strain rate sensitivity. The effect of the material state on the tensile strength is dependent on the strain rate, and the annealing treatment may significantly decrease the tensile strength under low strain rate conditions; and weakly decrease it under high strain rate conditions. Finally, the spall strength dependence on the material state and the effect of the strain rate on the spall behavior were discussed.

A cellular automata model for recrystallization annealing of aged GH4169 superalloy and its application

For the forging of GH4169, there are often serious mixed and coarse grains that need to be uniformly refined through a multi-stage annealing process. However, it will need to take a lot of time and cost to explore suitable multi-stage annealing process parameters if we only employ the experimental method. The cellular automata (CA) simulation can reveal the evolution of microstructure during forming and annealing, which can obviously reduce the number of experiments. Therefore, in the study, a CA model to simulate the evolution of grain microstructure, dislocation density and δ phase is established. The results demonstrate that the established CA model can effectively predict the microstructural evolution of GH4169. The correlation coefficient exceeds 0.94. Furthermore, using the CA simulation, an optimized multi-stage annealing parameter of “1000 ℃×3min+1000 ℃-5 min-950 ℃+950 ℃×50min” has been identified, which is also verified by experiments. These findings further verify the accuracy and reliability of the model in simulating microstructural evolution during the annealing process of GH4169 forgings. Eventually, based on the CA simulation, the formation mechanism for the uneven grain growth in the annealed microstructure is revealed. At original deformed grain boundaries, dynamic recrystallization (DRX) grains grow slowly, whereas static recrystallization (SRX) grains at DRX boundaries or δ phase boundaries within original deformed grains grow rapidly.

Comparative Study Between Friction Stir Welding and Tungsten Inert Gas Welding Processes

This study compares the properties of the aluminium alloy welded joints prepared by friction stir welding (FSW) to that of tungsten inert gas (TIG). It concentrated on the microstructure, hardness, corrosion resistance, and wear resistance. It has been found that the joints prepared by FSW have fine microstructure while coarse grains microstructure was obtained for joints produced by TIG welding. Also, the lowest Rockwell hardness measured at the centre of the welding line is 52 for joints prepared by FSW and 46 for ones produced by TIG welding. For corrosion resistance the reslt of tests indicated that the welded joints of the TIG process had higher corrosion resistance, the mass loss after 72 hours is 0.2519 grams from TIG joints and it is about double in the case of FSW joints (0.5263 grams). However, TIG joints have lower wear resistance compared to joints produced by the FSW process. It seems that the grain size of the welded joints, in these two considered welding processes, has a great effect on the investigated properties.

Grain size dependent deformation microstructure evolution and work-hardening in CoCrNi medium entropy alloy

This study clarified the grain size dependence of the deformation microstructure evolution and work-hardening behavior in CoCrNi medium entropy alloy. We fabricated fully recrystallized specimens with coarse-grained (CG) and ultrafine-grained (UFG) specimens by severe plastic deformation and subsequent annealing processes. Tensile deformation was applied to the specimens at room temperature. The UFG specimen exhibited both high strength and high ductility compared to conventional UFG metals due to the high work-hardening ability. In the CG specimen, three distinct types of deformation microstructures consisting of dislocations and deformation twins developed depending on grain orientations, similar to the single-crystalline specimens. In the UFG specimen, widely extended stacking faults and randomly-tangled dislocations were found to coexist in most grains. Deformation twins were found to nucleate without evidence of dislocation reactions regardless of grain orientations, implying abnormal nucleation mechanisms of deformation twins in the UFG specimen. Dislocation densities quantified by in-situ synchrotron XRD measurements during tensile deformation were higher in the UFG specimen than those in the CG specimen and conventional UFG metals. Our analysis showed that the work-hardening behavior of the specimens was primarily controlled by increases in dislocation density as well as the introduction of planar defects during deformation. Through comparisons with the CG specimen and conventional UFG metals, we concluded that the excellent work-hardening ability of the UFG specimen was mainly due to the evolution of unique deformation microstructures and rapid increase in dislocation density, which could be due to inhibited dynamic recovery in the MEA.

Achieving an excellent combination of strength and ductility in metastable β titanium alloys via coupling isothermal ω phase and TRIP/TWIP effects

TRIP/TWIP metastable β titanium alloys demonstrate high strain hardening rates and excellent tensile ductility. However, the precipitation of nanometer-sized ω phase through microstructural control significantly improves strength but often results in a significant decrease in ductility. This research proposes a novel strategy by precipitating isothermal ω phase (ωiso) and integrating mechanical twinning/martensitic transformation to address these challenges. The single-phase β coarse-grained (CG) specimens of metastable Ti25Nb (at.%) alloy were subjected to solution treatment in the β phase region, followed by aging at 300 °C for 60 min to obtain CG60. The ωiso-reinforced CG60 specimen exhibited a 12 % uniform elongation (1 % higher than CG specimen) and a yield strength of 857 MPa (approximately 67 % higher than CG specimens). In the CG60 specimen, deformation mechanisms were mainly attributed to the TRIP, TWIP and dislocation slip, with TWIP being predominant. As aging time increased, ω phase (localized barriers) and improved β matrix stability progressively suppressed TRIP and TWIP effects, with TWIP being completely inhibited first. Transmission electron microscopy and computational findings suggest that a denser distribution of ωiso contributes more significantly to the strengthening of the alloy.

Understanding the influence of configurations and intermolecular interaction on thermomechanical and dynamics properties of polymer–clay nanocomposites via molecular dynamics simulations

AbstractPolymer‐clay nanocomposites (PCNs) have emerged as highly versatile structural materials that possess exceptional thermomechanical and dynamic properties, all the while retaining their inherent attributes of being lightweight and optically clear. The fabrication of nanocomposites involves the incorporation of carefully calibrated quantities of clay nanofillers into polymer matrixes. Current research expands upon existing coarse‐grained (CG) models of nanoclay and poly (methyl methacrylate) (PMMA) and utilize molecular dynamics simulations to methodically explore the thermomechanical characteristics of PCNs. Specifically, the effects of exfoliated and stacked configurations of nanoclays, as well as variations in intermolecular interactions between the nanoclay and polymer constituents were tested. Tensile and shear simulations, as well as interfacial behaviors, are conducted. The intermolecular interaction could have significant influences on Shear Modulus and Young's Modulus, and those influences have their characteristics due to different configurations and different force directions, such as in most cases, exfoliated structures exhibit higher mechanical modulus compared with stacked configurations at varying interaction strengths. Additionally, in the in‐plane direction, they demonstrate stronger resistance effects compared with the out‐of‐plane direction. The interaction between PMMA and nanoclay slows down the global dynamics of PMMA, with a stronger effect observed for higher interaction strength. The impact of nanoclay on the segmental dynamics of PMMA decreases as we move away from the nanoclay layers toward the pure PMMA matrix. These findings provide molecular insights into the arrangement of components in PCNs during deformation and highlight the significance of nanoclay and the interface in determining their mechanical and dynamic properties.Highlights Variation patterns of mechanical modulus with interactions and configurations. The property difference in mechanical modulus due to configurations. Positive correlation between polymer Tg and intermolecular interaction. Global and local confinement effects on molecular stiffness during tension. Dynamical heterogeneity behavior on different interactions and temperatures.

An Efficient SPH Framework for Modeling Binary Granular Mixtures and Implications for Granular Flows

ABSTRACTA two‐way coupling numerical framework based on smoothed particle hydrodynamics (SPH) is developed in this study to model binary granular mixtures consisting of coarse and fine grains. The framework employs updated Lagrangian SPH to simulate fine grains, with particle configurations updated at each time step, and total Lagrangian SPH to efficiently model coarse grains without updated particle configurations. A Riemann solver is utilized to introduce numerical dissipation in fine grains and facilitate their coupling with coarse grains. To enhance computational efficiency, a multiple time‐stepping scheme is initially applied to manage the time integration coupling between coarse and fine grains. Several numerical experiments, including granular column collapse, low‐speed impact craters, and granular flow impacting blocks, are conducted to validate the stability and accuracy of the proposed algorithm. Subsequently, two more complex scenarios involving a soil–rock mixture slope considering irregular coarse particle shapes, and bouldery debris flows on natural terrain, are simulated to showcase the potential engineering applications. Finally, a detailed analysis is performed to evaluate the computational efficiency advantages of the present approach. The findings of this study are consistent with previous experimental and numerical results, and the implementation of a multiple time‐stepping scheme can improve computational efficiency by up to 600%, thereby providing significant advantages for large‐scale engineering simulations.

Unraveling GPCRs Allosteric Modulation. Cannabinoid 1 Receptor as a Case Study.

G-protein-coupled receptors (GPCRs) constitute one of the most prominent families of integral membrane receptor proteins that mediate most transmembrane signaling processes. Malfunction of these signal transduction processes is one of the underlying causes of many human pathologies (Parkinson's, Huntington's, heart diseases, etc), provoking that GPCRs are the largest family of druggable proteins. However, these receptors have been targeted traditionally by orthosteric ligands, which usually causes side effects due to the simultaneous targeting of homologous receptor subtypes. Allosteric modulation offers a promising alternative approach to circumvent this problematic and, thus, comprehending its details is a most important task. Here we use the Cannabinoid type-1 receptor (CB1R) in trying to shed light on this issue, focusing on positive allosteric modulation. This is done by using the protein-dipole Langevin-dipole (PDLD) within the linear response approximation (LRA) framework (PDLD/S-2000) along with our coarse-grained (CG) model of membrane proteins to evaluate the dissociation constants (KBs) and cooperativity factors (αs) for a diverse series of CB1R positive allosteric modulators belonging to the 2-phenylindole structural class, considering CP55940 as an agonist. The agreement with the experimental data evinces that significantly populated allosteric modulator:CB1R and allosteric modulator:CP55940:CB1R complexes have been identified and characterized successfully. Analyzing them, it has been determined that CB1R positive allosteric modulation lies in an outwards displacement of transmembrane α helix (TM) 4 extracellular end and in the regulation of the range of motion of a compound TM7 movement for binary and ternary complexes, respectively. In this respect, we achieved a better comprehension of the molecular architecture of CB1R positive allosteric site, identifying Lys1923.28 and Gly1943.30 as key residues regarding electrostatic interactions inside this cavity, and to rationalize (at both structural and molecular level) the exhibited stereoselectivity in relation to positive allosteric modulation activity by considered CB1R allosteric modulators. Additionally, putative/postulated allosteric binding sites have been screened successfully, identifying the real CB1R positive allosteric site, and most structure-activity relationship (SAR) studies of CB1R 2-phenylindole allosteric modulators have been rationalized. All these findings point out towards the predictive value of the methodology used in the current work, which can be applied to other biophysical systems of interest. The results presented in this study contribute significantly to understand GPCRs allosteric modulation and, hopefully, will encourage a more thorough exploration of the topic.

Study on the influence of primary peak temperature on the microstructure and impact properties of heat affected zone of a 1000 MPa grade hydropower steel

ABSTRACT The microstructure of various zones in the heat-affected zone (HAZ) of 1000 MPa grade ultra-high-strength steel were investigated by welding thermal simulation. The results showed that the grain sizes were smallest at 950°C, when it was at the fine grain section in HAZ. The continuous reduction in grain size was due to the recovery and recrystallization. Samples subjected to thermal cycles at lower than 950°C exhibited high impact absorption energy of more than 100 J, with distinct fibrous zones and shear lips on the fracture surfaces, indicative of high impact toughness. However, the impact toughness of samples from the CGHAZ, which underwent thermal cycles at higher than 1100°C, decreased significantly to about 10 J, with the fracture surfaces showing macroscopic brittle fracture features and covered entirely by cleavage planes. Microstructural analysis revealed that coarse grains and brittle martensite were the primary causes of embrittlement in the CGHAZ.

Effects of All-Atom and Coarse-Grained Molecular Mechanics Force Fields on Amyloid Peptide Assembly: The Case of a Tau K18 Monomer.

To propose new mechanism-based therapeutics for Alzheimer's disease (AD), it is crucial to study the kinetics and oligomerization/aggregation mechanisms of the hallmark tau proteins, which have various isoforms and are intrinsically disordered. In this study, multiple all-atom (AA) and coarse-grained (CG) force fields (FFs) have been benchmarked on molecular dynamics (MD) simulations of K18 tau (M243-E372), which is a truncated form (130 residues) of full-length tau (441 residues). FF19SB is first excluded because the dynamics are too slow, and the conformations are too stable. All other benchmarked AAFFs (Charmm36m, FF14SB, Gromos54A7, and OPLS-AA) and CGFFs (Martini3 and Sirah2.0) exhibit a trend of shrinking K18 tau into compact structures with the radius of gyration (ROG) around 2.0 nm, which is much smaller than the experimental value of 3.8 nm, within 200 ns of AA-MD or 2000 ns of CG-MD. Gromos54A7, OPLS-AA, and Martini3 shrink much faster than the other FFs. To perform meaningful postanalysis of various properties, we propose a strategy of selecting snapshots with 2.5 < ROG < 4.5 nm, instead of using all sampled snapshots. The calculated chemical shifts of all C, CA, and CB atoms have very good and close root-mean-square error (RMSE) values, while Charmm36m and Sirah2.0 exhibit better chemical shifts of N than other FFs. Comparing the calculated distributions of the distance between the CA atoms of CYS291 and CYS322 with the results of the FRET experiment demonstrates that Charmm36m is a perfect match with the experiment while other FFs exhibit limitations. In summary, Charmm36m is recommended as the best AAFF, and Sirah2.0 is recommended as an excellent CGFF for simulating tau K18.

Microstructure and mechanical properties of CuCrFeNi medium entropy alloys synthesized via mechanical alloying and spark plasma sintering

In this study, two novel Co-free medium entropy alloys (MEAs) with compositions of Cu20Cr10Fe35Ni35 (Cu20) and Cu10Cr20Fe35Ni35 (Cu10) were successfully prepared by a combination of mechanical alloying (MA) and spark plasma sintering (SPS). The Cu20 alloy exhibited a heterogeneous microstructure consisting of coarse and ultrafine grains (UFG) with a face-centered cubic (FCC) structure. In contrast, the Cu10 alloy showed a homogeneous UFG microstructure with an FCC matrix and a small amount of BCC phase. Moreover, both alloys contained a small amount of Cr7C3 particles, introduced by milling media during MA. In comparison with the Cu20 alloy, the Cu10 alloy exhibited better tensile properties, e.g., yield strength of 712 MPa, ultimate tensile strength of 843 MPa, and elongation of 20.1 %, demonstrating an excellent balance between strength and ductility compared to some well-established FCC-structured multi-component MEAs and high entropy alloys (HEAs). The enhanced tensile properties of the Cu10 alloy are attributed to the synergistic effects of grain refinement and Orowan strengthening by the fine Cr7C3 particles. The findings of this work provide valuable insights for designing cost-effective HEAs and MEAs with high strength and desirable ductility for various structural applications.

Experimental Investigation on the Permeability and Fine Particle Migration of Debris-Flow Deposits with Discontinuous Gradation: Implications for the Sustainable Development of Debris-Flow Fans in Jiangjia Ravine, China

The particle size distribution (PSD) is a crucial parameter used to characterize the material composition of debris-flow deposits which determines their hydraulic permeability, affecting the mobility of debris flows and, hence, the sustainable development of debris-flow fans. Three types of graded bedding structures—normal, reverse, and mixed graded bedding structures—are characterized by discontinuous gradation within a specific deposit thickness. A series of permeability tests were conducted to study the effects of bed sediment composition, particularly coarse grain sizes and fine particle contents, on the permeability and migration of fine particles in discontinuous debris-flow deposits. An increase in fine particles within the discontinuously graded bed sediment led to a power-law decrease in the average permeability coefficient. With fine particle contents of 10% and 15% in the bed sediments, the final permeability coefficient consistently exceeded the initial value. However, this trend reversed when the fine particle contents were increased to 20%, 25%, and 30%. Lower fine particle contents indicated enhanced permeability efficiency due to more interconnected voids within the coarse particle skeleton. Conversely, an increase in fine particle content reduced the permeability efficiency, as fine particles tended to aggregate at the lower section of the seepage channel. An increase in coarse particle size decreased the formation of flow channels at the coarse–fine particle interface, causing fine particles to move slowly along adjacent or clustered slow flow channels formed by fine particles, resulting in decreased permeability efficiency. Three formulae are proposed to calculate the permeability coefficients of discontinuously graded bed sediments, which may aid in understanding the initiation mechanism of channel deposits. Based on experimental studies and field investigations, it is proposed that achieving sustainable development of debris-flow fans requires a practical approach that integrates three key components: spatial land-use planning, in situ monitoring of debris flows and the environment, and land-use adjustment and management. This comprehensive and integrated approach is essential for effectively managing and mitigating the risks associated with debris flows, ensuring sustainable development in vulnerable areas.