Scale Separation Research Articles

Phase separation in the presence of fractal aggregates.

Liquid-liquid phase separation in diverse manufacturing and biological contexts often occurs in the presence of aggregated particles or complex-shaped structures that do not actively participate in the phase separation process, but these "background" structures can serve to direct the macroscale phase separation morphology by their local symmetry-breaking presence. We perform Cahn-Hilliard phase-field simulations in two dimensions to investigate the morphological evolution, wetting, and domain growth phenomena during the phase separation of a binary mixture in contact with model fractal aggregates. Our simulations reveal that phase separation initially accelerates around the fractal due to the driving force of wetting, leading to the formation of the target composition patterns about the fractals, as previously observed for circular particles. After the formation of a wetting layer on the fractal, however, we observe a dramatic slowing-down in the kinetics of phase separation, and the characteristic domain size eventually "pins" to a finite value or approaches an asymptotic scaling regime as an ordinary phase if the phase separation loses memory of the aggregates when the scale of phase separation becomes much larger than the aggregate. Furthermore, we perform simulations to examine the effects of compositional interference between fractals with a view to elucidating interesting novel morphological features in the phase-separating mixture. Our findings should be helpful in understanding the qualitative aspects of the phase separation processes in mixtures containing particle aggregates relevant for coating, catalyst, adhesive, and electronic applications as well as in diverse biological contexts, where phase separation occurs in the presence of irregular heterogeneities.

S-HGMS coupling with alkali precipitation for the scale inhibition in recirculating cooling water with high hardness: Performance, mechanism and field application

Recirculating cooling water (RCW) contains various scale-forming ions, such as Ca2+ and Mg2+, which tend to form the hard scale in the heat transfer process. In this study, a novel method via superconducting high-gradient magnetic separation (S-HGMS) coupling with alkali precipitation for scale inhibition in RCW was proposed, which could achieve efficient removal of total hardness (91.64 %). The scale inhibition mechanism of the S-HGMS coupling is attributed to the increase of ionic hydration shell thickness and the formation of hydrogen bonds, enhancing the solubility of scale-forming ions and diminishing their nucleation rate. Furthermore, this coupling induces a crystalline transformation from recalcitrant calcite to looser aragonite, contributing to the separation of scale from the pipe wall. Significantly, the proposed method was implemented in the field application by establishing a pilot-scale system with a capacity of 800–1000 L/h, which realized a stable reduction in the total hardness of the RCW from 1270 mg/L to below 127 mg/L at a magnetic flow ratio of 0.05 T·s/m. Moreover, the heat exchanger surface scaling was effectively controlled after 71 days of continuous treatment. This study helps promote the industrial application of S-HGMS technology for scale inhibition in high-hardness water.

Jets with a Twist: The Emergence of FR0 Jets in a 3D GRMHD Simulation of Zero-angular-momentum Black Hole Accretion

Spinning supermassive black holes (BHs) in active galactic nuclei magnetically launch relativistic collimated outflows, or jets. Without angular momentum supply, such jets are thought to perish within 3 orders of magnitude in distance from the BH, well before reaching kiloparsec scales. We study the survival of such jets at the largest scale separation to date, via 3D general relativistic magnetohydrodynamic simulations of rapidly spinning BHs immersed into uniform zero-angular-momentum gas threaded by a weak vertical magnetic field. We place the gas outside the BH sphere of influence, or the Bondi radius, chosen to be much larger than the BH gravitational radius, R B = 103 R g. The BH develops dynamically important large-scale magnetic fields, forms a magnetically arrested disk (MAD), and launches relativistic jets that propagate well outside R B and suppress BH accretion to 1.5% of the Bondi rate, ṀB . Thus, low-angular-momentum accretion in the MAD state can form large-scale jets in Fanaroff–Riley (FR) type I and II galaxies. Subsequently, the disk shrinks and exits the MAD state: barely a disk (BAD), it rapidly precesses, whips the jets around, globally destroys them, and lets 5%–10% of ṀB reach the BH. Thereafter, the disk starts rocking back and forth by angles 90°–180°: the rocking accretion disk (RAD) launches weak intermittent jets that spread their energy over a large area and suppress BH accretion to ≲2% ṀB . Because the BAD and RAD states tangle up the jets and destroy them well inside R B, they are promising candidates for the more abundant, but less luminous, class of FR0 galaxies.

Complementing the United States Household Food Security Survey Module with Items Reflecting Social Unacceptability

BackgroundSocial unacceptability of food access is part of the lived experience of food insecurity but is not assessed as part of the United States Household Food Security Survey Module (HFSSM). ObjectivesThe objectives were as follows: 1) to determine the psychometric properties of 2 additional items on social unacceptability in relation to the HFSSM items and 2) to test whether these 2 items provided added predictive accuracy to that of the HFSSM items for mental health outcomes. MethodsCross-sectional data used were from the Intersection of Material-Need Insecurities and HIV and Cardiovascular Health substudy of the Multicenter AIDS Cohort Study/Women’s Interagency HIV Study Combined Cohort Study. Data on the 10-item HFSSM and 2 new items reflecting social unacceptability were collected between Fall 2020 and Fall 2021 from 1342 participants from 10 United States cities. The 2 social unacceptability items were examined psychometrically in relation to the HFSSM-10 items using models from item response theory. Linear and logistic regression was used to examine prediction of mental health measured by the 20-item Center for Epidemiologic Studies Depression scale and the 10-item Perceived Stress Scale. ResultsThe social unacceptability items were affirmed throughout the range of severity of food insecurity but with increasing frequency at higher severity of food insecurity. From item response theory models, the subconstructs reflected in the HFSSM-10 and the subconstruct of social unacceptability were distinct, not falling into one dimension. Regression models confirmed that social unacceptability was distinct from the subconstructs reflected in the HFSSM-10. The social unacceptability items as a separate scale explained more (∼1%) variation in mental health than when combined with the HFSSM-10 items in a single scale, and the social unacceptability subconstruct explained more (∼1%) variation in mental health not explained by the HFSSM-10. ConclusionsTwo social unacceptability items used as a separate scale along with the HFSSM-10 predicted mental health more accurately than did the HFSSM-10 alone.

On a novel skewed generalized t distribution: Properties, estimations, and its applications

With the progress of information technology, large amounts of asymmetric, leptokurtic, and heavy-tailed data are arising in various fields, such as finance, engineering, genetics, and medicine. It is very challenging to model those kinds of data, especially for extremely skewed data, accompanied by very high kurtosis or heavy tails. In this article, we propose a class of novel skewed generalized t distribution (SkeGTD) as a scale mixture of skewed generalized normal. The proposed SkeGTD has excellent adaptiveness to various data, because of its capability of allowing for a large range of skewness and kurtosis and its compatibility of the separated location, scale, skewness, and shape parameters. We investigate some important properties of this family of distributions. The maximum likelihood estimation, L-moments estimation, and two-step estimation for the SkeGTD are explored. To illustrate the usefulness of the proposed methodology, we present simulation studies and analyze two real datasets.

A note on O6 intersections in AdS flux vacua

The DGKT-CFI construction of AdS flux vacua in type IIA string theory has interesting features such as classical moduli stabilization and a parametric scale separation between the Hubble scale and the Kaluza-Klein scale. A possible worry regarding the consistency of these vacua is that pathologies could arise due to intersections of the O6-planes, which are not well understood in the 10D solution. In this note, we show in explicit examples that such intersections are absent if one compactifies on smooth Calabi-Yau manifolds instead of toroidal orbifolds. In particular, we show that the blow-up of the T6/ℤ3 orbifold yields a single O6-plane which wraps a smooth submanifold without any (self-)intersections. On the other hand, blowing up the T6/ℤ32\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mathbb{Z}}_3^2 $$\\end{document} orbifold seems to yield an O6-plane which self-intersects. However, we show that this is due to an inconsistent orientifold involution in the original DGKT model. Imposing a consistent involution again yields a single smooth O6-plane without self-intersections on the blown-up manifold.

Investigating Hessian-based inversion velocity analysis

Inversion velocity analysis (IVA) is an image-domain method built upon the spatial scale separation of the model. Accordingly, the IVA method is performed with an iterative process composed of two minimization steps consisting of migration (inner loop) and tomography (outer loop), respectively, with each step accounting for its Hessian or not. The migration part provides the common-image gathers (CIGs) with extension in the horizontal subsurface offset. Then, the differential semblance optimization (DSO) misfit measures the focusing of the events in the CIGs, which indicates the quality of the velocity model. Commonly, the velocity updates are obtained from the DSO gradient. IVA is a modified version in which the approximate inverse replaces the adjoint of the inner loop process; in that case, the migration Hessian is approximately diagonal in the high-frequency regime. In this work, we report on implementation of the tomographic Hessian (i.e., the second derivative of the DSO misfit with respect to the background model) for the estimation of the background velocity model. We apply the second-order adjoint-state method to obtain the application of the tomographic Hessian on a vector. Then, we use the truncated-Newton (TN) method to obtain the update directions by computing approximately the application of the inverse of the tomographic Hessian on the descent direction. We also make a theoretical comparison between tomography in the IVA and full-waveform inversion contexts. Two numerical examples are used to compare, in terms of geophysical results and computational costs, the TN method with different gradient-based optimization methods applied to the IVA. A small model allows us to evaluate the eigenvalues of the tomographic Hessian, which explains the large damping needed in the TN case.

Shedding light on dark bubble cosmology

Dark bubble cosmology is an alternative paradigm to compactification, which can circumvent issues of moduli stabilization and scale separation. In this paper we investigate how electromagnetic fields can be incorporated in this framework. Worldvolume fields backreact on the ambient universe in which the bubble expands, which in turn affects the energy-momentum distribution and the effective gravity induced on the brane. We compute these effects, showing that the resulting four-dimensional cosmology consistently includes electromagnetic waves.

Evolution of cooperation in deme-structured populations on graphs.

Understanding how cooperation can evolve in populations despite its cost to individual cooperators is an important challenge. Models of spatially structured populations with one individual per node of a graph have shown that cooperation, modeled via the prisoner's dilemma, can be favored by natural selection. These results depend on microscopic update rules, which determine how birth, death, and migration on the graph are coupled. Recently, we developed coarse-grained models of spatially structured populations on graphs, where each node comprises a well-mixed deme, and where migration is independent from division and death, thus bypassing the need for update rules. Here, we study the evolution of cooperation in these models in the rare-migration regime, within the prisoner's dilemma. We find that cooperation is not favored by natural selection in these coarse-grained models on graphs where overall deme fitness does not directly impact migration from a deme. This is due to a separation of scales, whereby cooperation occurs at a local level within demes, while spatial structure matters between demes.

Efficient computational homogenisation of 2D beams of heterogeneous elasticity using the patch scheme

Modern ‘smart’ materials have complex heterogeneous microscale structure, often with unknown macroscale closure but one we need to realise for large scale engineering and science. The multiscale Equation-Free Patch Scheme empowers us to non-intrusively, efficiently, and accurately predict large scale, system level, solutions through computations on only small sparse patches of the given detailed microscale system. Here the microscale system is that of a 2D beam of heterogeneous elasticity, with either fixed–fixed, fixed–free, or periodic boundary conditions. We demonstrate that the described multiscale Patch Scheme simply, efficiently, and stably predicts the beam’s macroscale, with a controllable accuracy, at finite scale separation. Dynamical systems theory supports the scheme. This article points the way for others to use this innovative systematic non-intrusive approach, via a developing toolbox of functions, to model and compute accurately macroscale system-levels of general complex physical and engineering systems.

Mitigation of Shock-Induced Separation Using Square-Shaped Micro-Serrations—A Preliminary Study

Suppressing shock-induced flow separation has been a long-standing problem in the design of supersonic vehicles. To reduce the structural and design complexity of control devices, a passive control technique based on micro-serrations is proposed and its controlling effects are preliminarily investigated under test conditions in which the Mach number is 2.5 and the ramp creating an incident shock is 15 deg. Meanwhile, a vorticity-based criterion for assessing separation scales is developed to resolve the inapplicability of the zero skin friction criterion caused by wall unevenness. The simulations demonstrate that the height of the first stair significantly influences the separation length. Generally, the separation length is shorter at higher stairs, but when the height is greater than half of the thickness of the incoming boundary layer, the corresponding separation point moves upstream. A stair with a height of only 0.4 times the thickness of the boundary layer reduces the separation length by 2.69%. Further parametric analysis reveals that while the remaining serrations have limited effects on the flow separation, an optimization of their shape (depth and width) can create more favorable spanwise vortices and offer a modest improvement of the overall controlling performance. Compared to the plate case, a 9.13% reduction in the separation length can be achieved using a slightly serrated design in which the leading stair is 0.1 high and the subsequent serrations are 0.2 deep and 0.05 wide (nondimensionalized, with the thickness of the incoming boundary layer). Meanwhile, the micro-serration structure even brings less drag. Considering the minor modification to the structure, the proposed method has the potential for use in conjunction with other techniques to exert enhanced control on separations.

Inflammatory Knee Synovitis: Evaluation of an Accelerated FLAIR Sequence Compared With Standard Contrast-Enhanced Imaging.

The aim of this study was to assess the diagnostic value and accuracy of a deep learning (DL)-accelerated fluid attenuated inversion recovery (FLAIR) sequence with fat saturation (FS) in patients with inflammatory synovitis of the knee. Patients with suspected knee synovitis were retrospectively included between January and September 2023. All patients underwent a 3 T knee magnetic resonance imaging including a DL-accelerated noncontrast FLAIR FS sequence (acquisition time: 1 minute 38 seconds) and a contrast-enhanced (CE) T1-weighted FS sequence (acquisition time: 4 minutes 50 seconds), which served as reference standard. All knees were scored by 2 radiologists using the semiquantitative modified knee synovitis score, effusion synovitis score, and Hoffa inflammation score. Diagnostic confidence, image quality, and image artifacts were rated on separate Likert scales. Wilcoxon signed rank test was used to compare the semiquantitative scores. Interreader and intrareader reproducibility were calculated using Cohen κ. Fifty-five patients (mean age, 52 ± 17 years; 28 females) were included in the study. Twenty-seven patients (49%) had mild to moderate synovitis (synovitis score 6-13), and 17 patients (31%) had severe synovitis (synovitis score >14). No signs of synovitis were detected in 11 patients (20%) (synovitis score <5). Semiquantitative assessment of the whole knee synovitis score showed no significant difference between the DL-accelerated FLAIR sequence and the CE T1-weighted sequence (mean FLAIR score: 10.69 ± 8.83, T1 turbo spin-echo FS: 10.74 ± 10.32; P = 0.521). Both interreader and intrareader reproducibility were excellent (range Cohen κ [0.82-0.96]). Assessment of inflammatory knee synovitis using a DL-accelerated noncontrast FLAIR FS sequence was feasible and equivalent to CE T1-weighted FS imaging.

Multiscale simulation scheme by using a finite-difference derivative framework for lubrication surface

To exactly describe lubrication problems modelling micro-scale influence in rough lubricated contact is unavoidable. In this study a novel computational scheme for lubricated problem is presented based on two-scale homogenization method, which facilitates solving the two-scale problem. Homogenization model of mass fluxes is implemented at the micro-scale domain, and represents the influence of surface topography. A linearization method is developed to derive finite derivatives of mass fluxes at the micro-scale domain defined by scale separation. The key strength of the proposed procedure is the finite difference derivative coupling which represents the lubricated problem inclusive of the effect of surface topography. The effectiveness of the proposed multiscale scheme is validated by comparing with the deterministic method. The numerical results show that increasing topography amplitude can improve the performance of journal bearing in terms of load carrying capacity and friction coefficient.

Local electroneutrality breakdown for electrolytes within varying-section nanopores

We determine the local charge dynamics of a z-z\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z-z$$\\end{document} electrolyte embedded in a varying-section channel. By means of an expansion based on the length scale separation between the axial and transverse direction of the channel, we derive closed formulas for the local excess charge for both, dielectric and conducting walls, in 2D (planar geometry) as well as in 3D (cylindrical geometry). Our results show that, even at equilibrium, the local charge electroneutrality is broken whenever the section of the channel is not homogeneous for both dielectric and conducting walls as well as for 2D and 3D channels. Interestingly, even within our expansion, the local excess charge in the fluid can be comparable to the net charge on the walls. We critically discuss the onset of such local electroneutrality breakdown in particular with respect to the correction that it induces on the effective free energy profile experienced by tracer ions.Graphical abstract

Kinetic Energy Cascade Induced by the Interaction of Mean Flow, Topography, and Mesoscale Eddies East of Taiwan: A Scale-to-Scale Analysis

Abstract The scale-to-scale kinetic energy (KE) cascade induced by the nonlinear interaction among topography, the Kuroshio, and mesoscale eddies is systematically investigated in the coarse-graining framework based on simulated data from the well-validated Regional Ocean Model System. The KE transfer exhibits inhomogeneous spatial and temporal distributions and varies with length scale. During current–topography interaction, the KE transfers downscale across larger scales and reversely across smaller scales with an inherent separation scale of 150 km northeast of Taiwan, resulting in a significant positive net KE flux for mesoscale motions. The transfer around Suao Ridge is consistently downscaled with significant seasonal variation that is stronger in summer and weaker in winter. South of Suao Ridge, the transfer is one order of magnitude weaker and changes greatly with time. The cyclonic (anticyclonic) eddy weakens (enhances) KE transfer in most study areas. In particular, the cyclonic eddy reverses the transfer direction around Suao Ridge. The anticyclonic eddy triggers a significant bidirectional transfer south of Suao Ridge. Analyses show that the special arc-shaped topographic feature and northwestward Kuroshio intrusion current are responsible for the nature of bidirectional KE transfer northeast of Taiwan. The direction of mean current relative to the topography gradient determines the Rossby number magnitude and the KE transfer direction. The large-scale circulation determines the transfer intensity by changing the horizontal shear and barotropic instabilities. The KE transfer caused by nonlinear dynamics contributes significantly to the total anticyclonic eddy-induced net KE flux changes. In particular, the inverse KE cascade plays a key role in net KE flux changes in mesoscale motions east of Taiwan. Significance Statement In this work, we clarify the scale-to-scale kinetic energy transfer east of Taiwan. Energy transfer varies in different subareas. It is bidirectional northeast of Taiwan, consistently downscale around Suao Ridge, and weak and variable south of Suao Ridge. These transfer characteristics are closely related to the direction of mean flow relative to the topography gradient. Mesoscale eddies can trigger bidirectional transfer and even reverse the transfer direction. The reverse cascade is as important as the forward cascade for the total mesoscale energy change. This study not only shows an example of KE cascade when strong currents pass through continental slope, sea ridge, and open ocean, but also is of great significance for studying the dynamical and ecological environment variation of marginal sea.

The Processes and Relationships in Composers Scale

We introduce a new inventory labeled the Processes and Relationships in Composers Scale (PRCS). This is a novel inventory developed to self-assess creative and social factors inherent in music composition. The PRCS consists of two separate scales of 12 items each, namely the Composing Processes Scale (CPS) and the Social Relationship Scale (SRS). An exploratory factor analysis revealed that the CPS scale has a single factor structure, while the SRS scale relies on three main factors: loneliness, support, and friendship. The total score of the CPS was found to be highly reliable, whereas the SRS obtained a lower score. The PRCS can contribute new insights into how creative and social processes can be self-assessed by music composers with different backgrounds and levels of musical expertise. Our work aims to deepen understanding of the relationship between musical creativity and social life, contributing to existing scholarship that has explored this connection in musical activities specifically.

Academic Performance and Academic Self-Efficacy among Pre-University Students in Malaysia

This research investigated the relationship between academic performance and self-efficacy among pre-university students in Malaysia using cross-sectional survey data. The sample comprised 171 pre-university undergraduates, aged between 18 and 20, studying at a public university in Kuala Lumpur. They were derived from the population to form the sample using stratified random sampling. Two separate scales measuring academic self-efficacy and academic performance (i.e., the CEVEAPEU) were used to collect the survey data. The study used descriptive statistics, independent sample t-test, Pearson correlation, and multiple regression to analyze the data. The results indicate that a majority of the students reported a high level of academic self-efficacy and established a strong positive relationship between self-efficacy and academic performance. No statistically significant gender differences were found in the respondents’ academic self-efficacy, but academic performance was significantly influenced by academic self-efficacy. The findings suggest the potential involvement of additional variables, such as CGPA, in shaping students’ academic performance, highlighting the need for further exploration of these variables in future studies.

Effect of sinusoidal pulsating speed enhancement on the mixing performance of plastics machinery

Abstract Numerous vibration-assisted methods have been adopted to solve problems in polymer processing, but the introduction of vibration fields is typically done on small extruders or injectors in school laboratories and industrial research rooms, which profoundly limits the application of vibration technology. The purpose of this study is to put forward a simple vibration excitation method for all scale extruders or injection molding machines. To recover the mixing performance of that excitation method, a numerical investigation was carried out using the CFD software ANSYS POLYFLOW 19.2, and the analysis and comparison were made between the mixing performance of a simplified screw element with and without a sinusoidal pulsating speed field. The results showed that not all dynamic states with the superimposed excitation field have better mixing performance than the steady state without any pulsating field. Nevertheless, the introduction of a pulsating speed field under certain parameters setting can indeed enhance the stretching rate, reduce the separation scale, increase the mixing efficiency, and lower the screw force. These findings are of great importance and provide valuable references for the development and application of vibration-assisted molding technology in plastics machinery.

Characterization of very-large-scale motions in supersonic and hypersonic turbulent boundary layers

Very-large-scale motions are commonly observed in moderate- and high-Reynolds-number wall turbulence, constituting a considerable portion of the Reynolds stress and skin friction. This study aims to investigate the behaviour of these motions in high-speed and high-Reynolds-number turbulent boundary layers at varying Mach numbers. With the aid of high-precision numerical simulations, numerical experiments and theoretical analysis, it is demonstrated that the very-large-scale motions are weakened in high-Mach-number turbulence at the same friction Reynolds numbers, leading to the reduction in turbulent kinetic energy in the outer region. Conversely, the lower wall temperature enhances the very-large-scale motions but shortens the scale separation between the structures in the near-wall and outer regions.

P290 Evaluation of response to chronic and acute stress in patients with Crohn’s disease

Abstract Background Impaired response to stress in patients with chronic inflammatory disease, such as rheumatoid arthritis, is associated with decreased cortisol secretion. The aim of this study was the evaluation of response to chronic and acute stress in patients with Crohn’s Disease (CD). Methods Data was collected from patients who underwent surgery due to complications of Crohn’s (n=26)(CD group) or due to other indications (n=31) (control group). Patients on corticosteroid treatment during last 3 months and other immunological comorbidities were excluded. Cortisol concentration of the hair (proximal 3cm to the sculp) was measured as an indicative marker of stress taking place the last 3 months (chronic stress). Cortisol concentration in the saliva was measured at day 2 post surgery in a daily fluctuation manner (6 measurements in 24h), as an indicative marker of response to acute stress. The chemiluminescence method was used for cortisol measurements. Cortisol concentrations were correlated with DASS 21 questionnaire (validated Greek version),consisting of 21 questions which correspond to separate measurment scales for stress, anxiety or depression. SPSS was used for statistical analysis. Results Hair samples were measured from 17 CD patients and 20 controls. CD patients had significant lower concentrations of hair cortisol (median = 6.375 pgF/mg, IQR = 4.821 - 9.949) compared to control group (median = 9.643 pgF/mg, IQR = 6.602-14.637) (Mann-Whitney U-test P = 0.034). Saliva samples were measured from 21 CD patients and 27 controls. In regards to the post surgical cortisol fluctuation (acute stress), there was no significant difference between the two groups. No significant difference was observed between cortisol concentrations, and questionnaires results. Conclusion In CD, as in other immunological diseases, hypothalamic-pituitary–adrenal axis appears to be affected, leading in decreased response to chronic stress. This observation may have important implications for the pathophysiology, prognosis and treatment of CD.