Track Evolution Research Articles

Timing of Alzheimer's disease biomarker progressions: A two-decade observational study from the Alzheimer's Disease Neuroimaging Initiative (ADNI).

Alzheimer's Disease Neuroimaging Initiative (ADNI) has been pivotal in identifying and refining Alzheimer's disease (AD) biomarkers for clinical trials. This study leverages longitudinal data from participants who have progressed to amyloid-positivity during their study participation to track evolution of biomarkers and cognitive function. We modeled AD biomarker (positron emission tomography [PET], structural, cerebrospinal fluid [CSF], cognition) trajectories before and after observed amyloid-positivity onset time to detect time at which each biomarker had detectable trajectory changes. Analysis of a sub-cohort of the 20-year ADNI study (N=90) recapitulated Alzheimer's progression beginning with amyloid alterations -4.8 to -5.3 years relative to amyloid-positivity, succeeded by neurodegeneration (t=-4.0 to -4.1 years), and CSF tau (t=-0.4 to -0.5 years). Cognitive decline was observed to significantly correspond with emergence of amyloid-positivity (t=0.2 to 2.4 years). Our results corroborate temporal progression curves of AD biomarkers, providing insights on earliest detectable changes in objective and subjective cognitive function assessments.

Numerical Investigation of Track and Intensity Evolution of Typhoon Doksuri (2023)

This study utilized the WRF model to investigate the track evolution and rapid intensification (RI) of Typhoon Doksuri (2023) as it moved across the Luzon Strait and through the South China Sea (SCS). The simulation results indicate that Doksuri has a smaller track sensitivity to the use of different physics schemes, while having a greater intensity sensitivity. Sensitivity numerical experiments with different physics schemes can well capture its northwestward movement in the first two days, but they predict less westward track deflection as the typhoon moves across the Luzon Strait and through the SCS. Moreover, all the experiments successfully simulated Doksuri’s RI, albeit with quite different rates and a time lag of 12 h. Among different combinations of physics schemes, there exists an optimal set of cumulus parameterization and cloud microphysics schemes for track and intensity predictions. Doksuri’s track changes as the typhoon moved across the Luzon Strait and through the SCS were influenced by the topographic effects of the terrain of the Philippines and Taiwan, to different extents. The track changes of Doksuri are explained by the wavenumber-one potential vorticity (PV) tendency budget from different physical processes, highlighting that the horizontal PV advection dominates the PV tendency throughout most of the simulation time due to the offset of vertical PV advection and differential diabatic heating. In addition, this study applies the extended Sawyer–Eliassen (SE) equation to compare the transverse circulations of the typhoon induced by various forcing sources. The SE solution indicates that radial inflow was largely driven in the lower-tropospheric vortex by strong diabatic heating, while being significantly enhanced in the lower boundary layer due to turbulent friction. All other physical forcing terms were relatively insignificant for the induced transverse circulation. The coordinated radial inflow at low levels may have led to the eyewall development in unbalanced dynamics. Intense diabatic heating thus was vital to the severe RI of Doksuri under a weak vertical wind shear.

Observational fine-scale evolutionary characteristics of concentric eyewall Typhoon Doksuri (2023)

The variations in the track and intensity of a tropical cyclone (TC) are closely correlated with the fine-scale evolution of its structure. The fine-scale track, intensity, and structural evolution of Typhoon Doksuri (2023) can be comprehensively analyzed by combining multi-source observations. The results herein show that Doksuri (2023) experienced secondary eyewall formation (SEF), concentric eyewall maintenance (CEM), and eyewall replacement cycle (ERC) processes when entering the South China Sea and prior to landfall. These processes can be further delineated into three subsequent stages. In the first stage, the SEF phase, the secondary (outer) eyewall formed, exhibiting features that were non-concentric with the inner eyewall. Concurrently, the track of Doksuri (2023) displayed notable oscillations in both its forward translational direction and speed, accompanied by the emergence of two radial maxima centers of wind speed. Subsequently, during the second stage, the CEM phase, the geometric centers of the inner and outer eyewalls of Doksuri (2023) coincided, initiating a rapid intensification process characterized by an accelerated forward translational speed. Both the inner and outer eyewalls further contracted during this phase. In the third stage, the ERC phase, the asymmetry of the inner eyewall increased, and the outer eyewall gradually contracted while the inner eyewall dissipated until the replacement was completed prior to landfall. Accordingly, Doksuri (2023) experienced rapid weakening. These findings have the potential to enhance our understanding of the physical mechanisms governing the intricate structures of TCs at fine scales, bolstering the forecast accuracy of TC tracks and intensities.

Deciphering Mean Flow–Eddy Interaction in Pacific–North American Teleconnection Linked to Storm Tracks at Subseasonal Time Scales

Abstract The features of large-scale atmospheric circulations, storm tracks, and the mean flow–eddy interaction during winter Pacific–North American (PNA) events are investigated using National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis data at subseasonal time scales from 1979 to 2022. The day-to-day variations of storm-track activity and streamfunction reveal that storm-track activity varies along the evolution of mean flow. To better understand storm-track variability with the mean flow–eddy interaction, further exploration is made by analyzing local energy energetics. The changes in horizontal and vertical baroclinic energy conversions from background flow correspond to the storm-track anomalies over the North Pacific, indicating that the anomalies in storm tracks are due to the anomalous mean flow associated with PNA patterns impacting energy conversion through mean flow–eddy interaction. Eddy feedback driven by vorticity and heat fluxes is analyzed. This provides a concrete illustration of how eddy feedback serves as a positive factor for the upper-tropospheric circulation anomalies associated with the PNA pattern. Significance Statement The background flow plays a crucial role in governing storm-track dynamics. Our emphasis is on the Pacific storm tracks (PST) and their relation to Pacific–North American (PNA) patterns at subseasonal time scales. We unveil the relationship between anomalies of PST and PNA patterns using local energetics and eddy feedback on a day-by-day basis. It is noteworthy that the evolution of anomalous storm tracks during PNA events is the manifestation of mean flow–eddy interaction. Additionally, we provide detailed confirmation of the impact of anomalous storm tracks on large-scale anomalies associated with the PNA pattern.

Does selection favour the maintenance of porous species boundaries?

The endpoint of speciation has been viewed as complete isolation and the absence of gene flow between species. If the influx of genes from another species is maladaptive because species have different adaptations and genetic backgrounds, selection should favour the closing of species boundaries and zero gene flow, a process known as reinforcement. Recently, numerous cases of gene flow between species have been identified, many of which involved adaptive introgression of beneficial alleles. These cases could reflect transient states on the way to closed species boundaries or the result of declining strength or efficacy of selection for reinforcement as the level of gene flow approaches zero. An alternative hypothesis, however, is that selection favours porous species boundaries that allow beneficial alleles to cross, especially in changing environments. This perspective evaluates the conditions that would be needed for selection to favour porous species boundaries and the evidence for them. A contrast is made between hybridization in sexual eukaryotes and gene transfer via homologous recombination in bacteria. Current evidence is inconclusive on whether non-zero gene flow is favoured by selection. Studies are needed that quantify selection gradients on rates of gene flow and test for evolution towards intermediate values, especially experiments that manipulate conditions and track evolution for multiple generations. Estimation of gene flow networks for more clades and regional assemblages using emerging genome data will also allow the evolutionary determinants of interspecific gene flow to be better understood.

Refining granite generation by interrogation of zircon and monazite U-Th-Pb and Hf/Nd-O isotopes

In-situ geochemical and isotopic analyses of zircon and monazite can provide compelling and detailed insights into the source and evolution of their hosting granite. Here we investigated the U-Th-Pb and Hf/Nd-O isotopic signatures of zircon and monazite in two petrological zones (i.e., fine- to medium-grained zone and medium-grained zone) of the Laojunshan granite pluton in the Qinling Orogen, central China, to better constrain their source nature and evolution processes. Co-existing magmatic zircon and monazite in both zones gave identical crystallization ages of ca. 113 Ma. In the fine- to medium-grained zone, both magmatic and xenocrystic zircons were identified, which respectively have εHf(t) values of −6.5 to −5.0 and − 17.4 to +5.1, and δ18OVSMOW values of +5.25‰ to +5.78‰ and + 5.17‰ to +9.15‰. The age distribution pattern and HfO isotopic characteristics of the xenocrystic zircons are similar to those of detrital zircons from the wall rock, i.e., meta-sedimentary rocks in the Kuanping unit. Monazite grains in this zone have relatively low SiO2, ThO2 but high CaO contents, dominated by cheralite-type substitution. These monazites have εNd(t) values of −5.8 to −4.6 and δ18O values of +3.79‰ to +5.66‰, except one grain (εNd(t) = −10.4 to −9.6, δ18O = +9.22‰ to +9.81‰), which is likely a xenocrystic crystal assimilated from wall rocks. The identical UPb age but contrasting NdO isotopic compositions between the xenocrystic monazite and the magmatic monazite grains indicate that the former might have experienced solid-state recrystallization process and completely lost radiogenic Pb. Both zircon and monazite geochemical and isotopic signatures consistently indicate that crustal assimilation occurred in the fine- to medium-grained granite zone. In contrast, in the medium-grained zone, only magmatic zircons and monazites were identified. The magmatic zircons have εHf(t) values of −3.2 to +2.7, and δ18O values of +4.65‰ to +6.36‰. The magmatic monazites are characterized by huttonite-type substitution with high SiO2, ThO2 but low CaO contents. Their εNd(t) values vary from −5.7 to +1.6 (mostly < −4.4) and δ18O values from +4.65‰ to +6.36‰. Given that the isotopic features of zircons and monazites in this zone are consistent with their whole-rock isotope features and no inherited/xenocrystic grains were observed, the zircons and monazites should record the source isotope compositions. The presence of highly radiogenic Nd isotopes in monazite coupled with its normal mantle-like O isotopes suggest minor involvement of juvenile mantle-derived components in the magma source. Accordingly, we advocate combined study of zircon and monazite, which can better track granite source nature and evolution processes than individual mineral.

Characterizing Metabolic Heterogeneity of Hepatocellular Carcinoma with Hyperpolarized 13C Pyruvate MRI and Mass Spectrometry.

Purpose To characterize the metabolomic profiles of two hepatocellular carcinoma (HCC) rat models, track evolution of these profiles to a stimulated tumor state, and assess their effect on lactate flux with hyperpolarized (HP) carbon 13 (13C) MRI. Materials and Methods Forty-three female adult Fischer rats were implanted with N1S1 or McA-RH7777 HCC tumors. In vivo lactate-to-pyruvate ratio (LPR) was measured with HP 13C MRI at 9.4 T. Ex vivo mass spectrometry was used to measure intratumoral metabolites, and Ki67 labeling was used to quantify proliferation. Tumors were first compared with three normal liver controls. The tumors were then compared with stimulated variants via off-target hepatic thermal ablation treatment. All comparisons were made using the Mann-Whitney test. Results HP 13C pyruvate MRI showed greater LPR in N1S1 tumors compared with normal liver (mean [SD], 0.564 ± 0.194 vs 0.311 ± 0.057; P < .001 [n = 9]), but not for McA-RH7777 (P = .44 [n = 8]). Mass spectrometry confirmed that the glycolysis pathway was increased in N1S1 tumors and decreased in McA-RH7777 tumors. The pentose phosphate pathway was also decreased only in McA-RH7777 tumors. Increased proliferation in stimulated N1S1 tumors corresponded to a net increase in LPR (six stimulated vs six nonstimulated, 0.269 ± 0.148 vs 0.027 ± 0.08; P = .009), but not in McA-RH7777 (eight stimulated vs six nonstimulated, P = .13), despite increased proliferation and metastases. Mass spectrometry demonstrated relatively increased lactate production with stimulation in N1S1 tumors only. Conclusion Two HCC subtypes showed divergent glycolytic dependency at baseline and during transformation to a high proliferation state. This metabolic heterogeneity in HCC should be considered with use of HP 13C MRI for diagnosis and tracking. Keywords: Molecular Imaging-Probe Development, Liver, Abdomen/GI, Oncology, Hepatocellular Carcinoma © RSNA, 2024 See also commentary by Ohliger in this issue.

Nuclear power technologies development: Historical track and future evolution

Understanding the evolution mechanism of nuclear power technology development is crucial for predicting its future path and devising a sound strategic plan. While classical economic theory provides the relationships between of technological progress and economic growth on specific assumptions, it is necessary to explore the evolutionary mechanism of technology development without prior assumptions. Furthermore, given the various forms of technological development, including basic research, patent technology, and product trade, the intricate relationship between them and economic growth necessitates further elucidation. This study aims to shed light on the evolutionary process of nuclear power technology development by constructing complex systems of “Science-Technology-Product-Economic growth,” applying Bayesian dynamic system modeling methods to establish the evolutionary equation of the complex systems and revealing the historical track and future evolution of nuclear power technology development. This study offers a fresh perspective to unravel the evolution of nuclear power technology development, facilitates a nuanced characterization of energy technology progress, and assists in developing an optimized learning curve for energy technology.

Rail Wear Evolution on Small-Radius Curves under Mixed Traffic Conditions, In-Field Investigations

This paper’s aim is to assess the rail wear evolution of railway tracks under mixed traffic conditions for sharp curves. Field investigations were conducted over a period of five years, at 800 points on a rail track, for two curves that underwent maintenance interventions: sleeper and rail replacements during measurements. Lateral and vertical wear measurements were monitored with mechanical instruments, and Prokon and Sap simulations were performed in order to determine the bearing capacity of the rail at different stages of wear. The results obtained after five years of investigation show wear speed propagation on the outer rail of small-radius curves as well as the bending moments and admissible stress variation. At more than 18% of the studied points, lateral wear exceeded the maximum admissible limit, showing a faster propagation speed on the outer rail compared to the vertical wear rate.

Diabatic effects on the evolution of storm tracks

Abstract. Despite the crucial role of moist diabatic processes in mid-latitude storm tracks and related model biases, we still lack a more complete theoretical understanding of how diabatic processes affect the evolution of storm tracks. To alleviate this shortcoming, we investigate the role of diabatic processes in the evolution of the northern hemispheric storm tracks using a framework based on the tendency of the slope of isentropic surfaces as a measure of baroclinic development. We identify opposing behaviours in the near-surface and free troposphere for the relationship between the flattening of the slope of isentropic surfaces and its restoration by diabatic processes. Near the surface (900–825 hPa), cold air advection associated with cold air outbreaks initially acts to flatten isentropic surfaces, with air–sea interactions ensuing to restore surface baroclinicity. In the free troposphere (750–350 hPa), on the other hand, the diabatic generation of the slope of isentropic surfaces precedes its depletion due to tilting by eddies, suggesting the primary importance of moist diabatic processes in triggering subsequent baroclinic development. The same phasing between diabatic and tilting tendencies of the slope is observed both in upstream and downstream sectors of the North Atlantic and North Pacific storm tracks. This suggests that the reversed behaviour between near-surface and free troposphere is a general feature of mid-latitude storm tracks. In addition, we find a correspondence between the diabatic generation of the slope of isentropic surfaces and enhanced precipitation as well as moisture availability, further underlining the crucial role of moisture and moist processes in the self-maintenance of storm tracks.

Failure time prediction for vehicle dynamics under performance degradation of dampers and track evolution

During long-term service, railway vehicles will experience damper performance degradation and track evolution, both have significant effects on the vehicle dynamics performance. This study aims to develop a mathematical model for assessing the failure time of the vehicle system dynamics when considering two random factors. As for the methodology, Wiener processes are used to propose a damper degradation model. Moreover, a continuous-time Markov chain is adopted to describe the state transaction of the track irregularities. In addition, the Monte Carlo method is employed to sample the dynamic responses of the vehicle using stochastic parameters. Finally, the Bayesian theory is utilized to establish the reliability model of the Weibull mixtures under the Dirichlet process prior. The results are obtained through a numerical example: the dampers’ individual differences directly affect effect on the rate of degradation of the vehicle dynamics performance. Furthermore, different indexes positively correlate with each other, mixture models are composed of a small number of components, and Weibull mixtures closely approximate the distribution of the failure time. Compared to other dampers, the anti-yaw dampers have a more significant impact on the vehicle system dynamics. Other results show that each type of damper can adopt a uniform replacement period whereas anti-yaw dampers should be more effectively monitored.

Tailoring the in-situ formation of intermetallic phases in the self-lubricating Al–WS2 composite for enhanced tribological performance with wear track evolution analysis

Self-lubricating aluminium matrix composites with enhanced tribological properties are sought for weight critical applications. In previous studies, the Al composites incorporating the solid lubricant WS2 have been shown to reduce both the coefficient of friction and wear rate, positioning them as promising candidates in various tribological applications (e.g. automotive industry). However, the impact of interfacial reactions between Al and WS2 during composite production on tribological performance has still not yet been explored. This study highlights the hardening effect of the reaction products. Despite some literature assuming a negative impact of these reactions as they consume WS2 in the composites, this study presents evidence that this cannot be generalised for the overall outcome. Interestingly, a controlled amount is shown to be beneficial for tribological properties. In this work, the tribological influence of the Al–W intermetallic structure forming during spark plasma sintering of the Al–WS2 composites was investigated. The microstructure was tailored by adjusting the manufacturing temperature between 500 and 600 °C. The Al–WS2 fabricated at 580 °C exhibited the lowest coefficient of friction and specific wear rate (reduced by 20 % and 97 %, respectively, compared to the one fabricated at 500 °C. Furthermore, the worn surface morphology in different stages during friction was evaluated by a novel wear track evolution analysis. This study confirmed that offering a balance between the fraction of solid lubricants and in-situ formed hard intermetallic structure is crucial to the effective formation a protective layer on the worn surface.

Rail wear rate on the Belgian railway network – a big-data analysis

ABSTRACT This paper presents a big data-based analysis of the rail wear of the whole Belgian railway network measured in 2012 and 2019. Wear rates are reported, discussed, and quantitatively formulated as functions of critical factors in terms of curve radius, annual tonnage (rail age), high rail in curves, an average from both rails in straight tracks at rail top (vertical wear) and gauge corner (45° wear) and for steel grade R200 and R260. The influence of preventive grinding is also analysed. The wear rates are derived in an aggregated manner for the whole network. The wear rates do not show significant change with changes in rolling stock over the years, implying that the wear rates could also hold for other networks. It is found that R200 shows, on average, a 34% higher wear rate than R260. Also, the wear rate per tonnage is lower for high-loaded tracks. Thus, time is a relevant factor in explaining the wear evolution of low-loaded tracks; for instance, the effect of corrosion may have an important role. The paper provides statistically significant information that can be used for wear modelling, understanding and treating rolling contact fatigue based on the wear rate and developing tailored rail maintenance strategies.

Intertrack interaction at ultra-high dose rates and its role in the FLASH effect

Background: The mechanism responsible for the FLASH effect remains undetermined yet critical to the clinical translation of FLASH radiotherapy. The potential role of intertrack interactions in the FLASH effect, arising from the high spatio-temporal concentrations of particle tracks at UHDRs, has been widely discussed but its influence is unknown.Methods: We construct an analytical model of the distribution, diffusive evolution, and chemical interaction of particle tracks in an irradiated target. We fit parameters of the model to Monte Carlo (MC) simulations of electron tracks, and include the effects of scavenging capacities of different target media. We compare the model’s predictions to MC simulations of many interacting electron tracks, and use the comparison to predict the prevalence of intertrack interactions in the parameter space where the FLASH effect is observed in vivo, and where differential reactive species (RS) yields have been observed in aqua.Results: MC simulations of interacting electron tracks demonstrate negligible changes in RS yields at 12 Gy both in oxygenated water and in cellular scavenging conditions, but significant changes at 58 Gy in oxygenated water. The model fits well to the simulation data, and predicts that pulse doses &gt;90Gy delivered in 0.5 μs would be necessary for intertrack interactions to affect RS yields in cellular scavenging conditions, and &gt;13Gy in 0.5 μs for water at 4% O2. The model defines optimal beam parameters (e.g., dose, pulse width, LET) to maximize intertrack interactions, and indicates that decreasing the pulse width of electron pulses further below ≈0.5 μs has no effect on intertrack interactions.Conclusion: The results of the MC simulations indicate that intertrack interactions do not play a role in the parameters space where the FLASH effect is observed. However, potentially critical limitations in the simulations performed provide the possibility that intertrack interactions occur much more readily than predicted. More accurate simulations, as well as experimental characterization of RS yields across the pulse parameter space, are necessary to more confidently confirm or deny the role of intertrack interactions in the FLASH effect.

GUMI-BEAR, a modular, unsupervised population barcoding method to track variants and evolution at high resolution.

Cellular lineage tracking provides a means to observe population makeup at the clonal level, allowing exploration of heterogeneity, evolutionary and developmental processes and individual clones' relative fitness. It has thus contributed significantly to understanding microbial evolution, organ differentiation and cancer heterogeneity, among others. Its use, however, is limited because existing methods are highly specific, expensive, labour-intensive, and, critically, do not allow the repetition of experiments. To address these issues, we developed gUMI-BEAR (genomic Unique Molecular Identifier Barcoded Enriched Associated Regions), a modular, cost-effective method for tracking populations at high resolution. We first demonstrate the system's application and resolution by applying it to track tens of thousands of Saccharomyces cerevisiae lineages growing together under varying environmental conditions applied across multiple generations, revealing fitness differences and lineage-specific adaptations. Then, we demonstrate how gUMI-BEAR can be used to perform parallel screening of a huge number of randomly generated variants of the Hsp82 gene. We further show how our method allows isolation of variants, even if their frequency in the population is low, thus enabling unsupervised identification of modifications that lead to a behaviour of interest.

Three-dimensional charge density wave in the dual heavy fermion system UPt2Si2

Heavy fermion liquids offer via their Kondo lattice diverse possibilities for exotic ground states. Using variable-temperature atomic pair distribution function analysis, we study the local atomic structure of the ``dual'' heavy fermion liquid $\mathrm{U}{\mathrm{Pt}}_{2}{\mathrm{Si}}_{2}$, which exhibits antiferromagnetism consistent with localized $5f$-electron states and transport properties characteristic to itinerant $5f$-``$spd$'' hybridized electron systems. We show that $\mathrm{U}{\mathrm{Pt}}_{2}{\mathrm{Si}}_{2}$ exhibits periodic lattice distortions (PLDs) involving both uranium and platinum atoms that are characteristic to three-dimensional charge density waves. The temperature evolution of the PLDs tracks that of the transport and magnetic properties, suggesting the presence of little-known $5f$-electron-lattice interactions. We argue that PLDs in heavy fermion liquids in general, and in particular in $\mathrm{U}{\mathrm{Pt}}_{2}{\mathrm{Si}}_{2}$, appear as new degrees of freedom that entangle competing electronic states and, as such, must be accounted for when their rich physics is considered.

TRAX-CHEMxt: Towards the Homogeneous Chemical Stage of Radiation Damage.

The indirect effect of radiation plays an important role in radio-induced biological damages. Monte Carlo codes have been widely used in recent years to study the chemical evolution of particle tracks. However, due to the large computational efforts required, their applicability is typically limited to simulations in pure water targets and to temporal scales up to the µs. In this work, a new extension of TRAX-CHEM is presented, namely TRAX-CHEMxt, able to predict the chemical yields at longer times, with the capability of exploring the homogeneous biochemical stage. Based on the species coordinates produced around one track, the set of reaction-diffusion equations is solved numerically with a computationally light approach based on concentration distributions. In the overlapping time scale (500 ns-1 µs), a very good agreement to standard TRAX-CHEM is found, with deviations below 6% for different beam qualities and oxygenations. Moreover, an improvement in the computational speed by more than three orders of magnitude is achieved. The results of this work are also compared with those from another Monte Carlo-based algorithm and a fully homogeneous code (Kinetiscope). TRAX-CHEMxt will allow for studying the variation in chemical endpoints at longer timescales with the introduction, as the next step, of biomolecules, for more realistic assessments of biological response under different radiation and environmental conditions.

Tropical cyclones position and intensity in the Southwest Indian Ocean as represented by CFS and ERA5 atmospheric reanalysis datasets

AbstractTropical cyclones are the most devastating meteorological systems that affect the Southwestern Indian Ocean (SWIO) bordering nations. The understanding of their track and intensity evolution is essential for the characterization of the systems. The National Centers for Environmental Prediction–Climate Forecast System (CFS) dataset and the ECWMF fifth‐generation reanalysis (ERA5) are evaluated against best‐track data from the International Best‐Track Archive for Climate Stewardship (IBTrACS) from 1980 to 2019 cyclone seasons. The cyclones were tracked within the reanalyses using a tracking algorithm based on relative vorticity and identified using a spatiotemporal matching method. Climatology from IBTrACS showed significant negative (positive) trend in the total number (number of intense) of systems; however, the evaluation of trends has to be cautious because it may be limited due to uncertainties in the first decades of data. Results for reanalyses showed that both performed similarly although some peculiarities were noted. CFS presented a slightly higher probability of detection, related to its special treatment of tropical cyclone‐like vortex, being able to reproduce all systems between 2000 and 2019. For positions, the majority of the systems have average errors around 50–60 km and the errors generally decrease with the intensity of the systems in both reanalyses, with ERA5 being slightly better during the early stages, while CFS outperforms ERA5 for intensity beyond the IBTrACS's moderate tropical storm category. Intensity follows a reverse pattern of position, with reanalyses largely degrading systems' intensity as they intensify. CFS (ERA5) appeared to be slightly better in terms of maximum wind (minimum sea‐level pressure), representing stronger systems although both datasets were unable to reproduce wind intensities beyond the tropical cyclone category. All evaluated parameters showed improvements when the most recent data period (2000–2019) is considered, especially in ERA5, tailored to an improved quality of the observations that are used to generate best‐track data and also to nudge the reanalyses through data assimilation. Based on the reanalyses characteristics revealed here, the choice of the most suitable dataset to address a specific study within the SWIO region may be dependent on the desired parameters and period.

Simultaneous modeling of powder rigid motion and molten pool evolution for powder-based additive manufacturing

The rigid motions of powders widely exist in powder-based laser additive manufacturing, like powder deposition, entrainment and spattering. These phenomena simultaneously happen as the laser melts these powders, and can have significant impacts on the quality of the printed products. However, existing models can hardly efficiently reproduce the co-existence of melting and rigid motion which greatly influences the molten pool and molten track evolution. The bottleneck therein lies in the demand that unresolved Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) has on the CFD grid size, that is, larger than 3 times of the particle diameter. However, this large size ratio (CFD grid cell vs particle diameter) handicaps the description of the particle deformation during melting. Hence in this paper, a kernel approximation-based semi-resolved CFD-DEM numerical model that allows the refinement of CFD grid is employed, and then coupled with the Volume of Fluid (VOF) method to reproduce the metal-gas interface. On this basis, the rigid motions of the powders, like entrainment and spattering, are finally simultaneously realized as molten pool evolves at high efficiency. Powders remained in the unclosed molten pool trail defect are well explained with the proposed model as well. And it can also be applied to model the particle-fluid interactions in Directed Energy Deposition. It is believed that this semi-resolved VOF-DEM Additive Manufacturing model will serve as a good tool for future investigations into the particle behaviors in powder-based additive manufacturing.

Ab initio prediction and characterization of membrane binding of HIV-1 broadly neutralizing antibodies by multi-scale simulations.

Rare but potent broadly neutralizing antibodies (bnAbs) engage the HIV virion membrane and the membrane proximal exposed region (MPER) peptide during neutralization. A preliminary lipid mediated binding step is suggested to increase antigen avidity but it remains unclear how initial membrane association occurs and thus what features are essential to mature bnAbs against a lipid-antigen epitope. In this study, we derived computational methods to investigate biophysical features of MPER bnAbs driving membrane association. We performed microsecond atomistic simulations of Fabs docked in a lipid bilayer. Phospholipid binding in CDR loops is predicted in all 4 replicates of PGZL1, 4E10 and 10E8 where a phospholipid headgroup position closely matches the phosphate position in lipid-soaked x-ray crystallography structures (mean RMSD 0.6, 0.7, 2.7 Å respectively). Interaction profiles also highlight how framework regions FRH3 (PGZL1 and 4E10) or FRL3 (10E8) significantly associate with lipids. We then conducted fixed velocity pulling simulations for 4E10 and mutants with reduced affinity for lipid vesicles in vitro. Max force calculates differences in energy required to dissociate Fabs, establishing a bona fide tool to approximate membrane affinities. We expanded this platform to track evolution of binding affinity with inferred germline, intermediate, and mature PGZL1 variants that show increasing binding strengths. To reduce bias from pre-docked membrane conformations, we generated coarse grained models with a Fab initiated above a bilayer. Spontaneous membrane binding events (>1 µs) are detected in over half of the 18 independent 14 µs bnAb trajectories but only in 2 of 18 replicates for negative control BSA. Altogether we present a computational toolkit to biophysically evaluate residue-specific and surface level features of membrane binding antibodies and differentiate membrane affinities, facilitating future studies of complete MPER or other auto-reactive bnAb maturation pathways.