Numerous Observations Research Articles

Hydrogen‐Driven Phase Differentiation in BN Nucleation on Diamond

AbstractBoron nitride has attracted scientific interest in recent years due to its potential use in electronics, both as hexagonal (hBN) and cubic (cBN) phases. While both are successfully realized through chemical vapor deposition, the heteroepitaxial growth of cBN on another iconic semiconductor, diamond is plagued with mixed‐phase formation. Employing first‐principles computations and a nanoreactor approach, the BN phase preferences are explored on diamond (001) controlled—as it is discovered—by the hydrogen gas concentration. In a limited‐hydrogen environment, the initial BN‐island expands along the diamond surface, forming a 3D metastable cubic phase that grows in the direction normal to the basal plane through kinetically‐limited nucleation, thus overcoming the thermodynamic preference toward the hBN phase. Comparatively, the amorphous phase is favored in the absence of hydrogen, while the hexagonal phase dominates at its high levels, elucidating numerous experimental observations. A obtained kinetic phase diagram connects the phase with hydrogen chemical potential to facilitate targeted phase selection. The results suggest that gas‐mediated nucleation kinetics provide feasible control for the precise synthesis. It also offers valuable guidance for the controllable synthesis of desired BN phases and advances research toward potential BN electronics.

Comparative Analysis of Heat Exchanger Models for Phase Change Material Melting Process: Experimental and Numerical Investigation

ABSTRACTThermal energy storage systems using PCM offer promising solutions for efficient thermal applications. This study aims to provide valuable insights into the PCM melting process and compare the thermal performance of different heat exchanger models. The experimental rig is carefully designed to simulate a shell and tube heat exchanger with five longitudinal copper fins at specific conditions. Three distinct models of the heat exchanger, labeled Models A, B, and C, were examined for their heat transfer efficiency during the melting process. Numerical simulations were conducted for the three models and compared with experimental results. Model A represented the benchmark model. It had uniform fin length, location, and angle. Model B was the modified design aimed at enhancing melting progress. These modifications included a longer lower fin, a shorter side fin compared to the reference, and a lower fin angle to optimize heat transfer performance. Model C incorporates further design modifications, with a longer lower fin, a shorter top fin, and different lower fin location. Numerical simulations and experimental observations revealed significant differences in heat transfer performance among the three models. The average heat transfer rates, measured up to the critical decline point, are crucial parameters for practical applications. A comparison among the three models showed that Model B surpassed the average heat transfer rate up to the critical point of Models A and C by 10% and 4%, respectively, demonstrating its superior practical applicability.

Inverse Problem for the Moisture Transfer Equation: Development of a Method for Finding the Unknown Parameter and Proof of the Convergence of the Iterative Process

This study develops a mathematical model for soil moisture diffusion, addressing the inverse problem of determining both the diffusion coefficient and the variation coefficient in a nonlinear moisture transfer equation. The model incorporates specific boundary and initial conditions and utilizes experimentally measured moisture values at a boundary point as input data. An iterative method, based on an explicit gradient scheme, is introduced to estimate the soil parameters. The initial boundary value problem is discretized, leading to a difference analog and the formulation of a conjugate difference problem. Iterative formulas for calculating the unknown parameters are derived, with a priori estimates ensuring the convergence of the iterative process. Additionally, the research establishes the convergence of the numerical model itself, providing a rigorous foundation for the proposed approach. The study also emphasizes symmetry in moisture calculations, ensuring consistency regardless of the calculation direction (from right to left or left to right) and confirming that moisture distribution remains symmetric within specified intervals. This preservation of symmetry enhances the model’s robustness and accuracy in parameter estimation. The numerical simulations were successfully conducted over a 7-day period, demonstrating the model’s reliability. The discrepancy between the numerical predictions and experimental observations remained within the margin of measurement error, confirming the model’s accuracy.

At-scale Model Output Statistics in mountain environments (AtsMOS v1.0)

Abstract. This paper introduces the AtsMOS (At-scale Model Output Statistics) workflow, designed to enhance mountain meteorology predictions through the downscaling of coarse numerical weather predictions using local observational data. AtsMOS provides a modular, open-source toolkit for local and large-scale forecasting of various meteorological variables through modified model output statistics – and may be applied to data from a single station or an entire network. We demonstrate its effectiveness through an example application at the summit of Mt. Everest, where it improves the prediction of both meteorological variables (e.g. wind speed, temperature) and derivative variables (e.g. facial frostbite time) critical for mountaineering safety. As a bridge between numerical weather prediction models and ground observations, AtsMOS contributes to hazard mitigation, water resource management, and other weather-dependent issues in mountainous regions and beyond.

Development of Hashimoto's disease in patients with vitiligo

The aim of this paper is to review the available scientific literature on the relationship between vitiligo and the development of Hashimoto's disease, with particular emphasis on possible pathogenetic mechanisms and clinical implications of this correlation. The relationship between vitiligo and thyroid diseases, especially Hashimoto's disease, has intrigued researchers for years. Numerous clinical observations suggested that patients with vitiligo more often struggle with thyroid problems, but only extensive epidemiological studies allowed for a precise estimate of the scale of this phenomenon.

Resonant Solitary States in Complex Networks

Abstract Partially synchronized solitary states occur frequently when a synchronized system of networked oscillators with inertia is perturbed locally. Several asymptotic states of different frequencies can coexist at the same node.
Here, we reveal the mechanism behind this multistability: additional solitary frequencies arise from the coupling between network modes and the solitary oscillator's frequency, leading to significant energy transfer. This can cause the solitary node's frequency to resonate with a Laplacian eigenvalue. We analyze which network structures enable this resonance and explain longstanding numerical observations.
Another solitary state that is known in the literature is characterized by the effective decoupling of the synchronized network and the solitary node at the natural frequency. Our framework unifies the description of solitary states near and far from resonance, allowing to predict the behavior of complex networks from their topology.

Optimization of Advanced Support Parameters of Surrounding Rock in Tunnels Constructed by ADECO-RS

So as to efficiently address the distortion of surrounding rock in tunnels constructed utilizing ADECO-RS, it is crucial to define suitable parameters for advanced support systems. This study took the 8 # tunnel in the F3 portion of the E60 Expressway in Georgia as an engineering case. Initially, the original support scheme underwent systematic monitoring and analysis in the field. Subsequently, the FLAC3D 6.0 software was employed to examine the influence of the advanced pipe roof and tunnel face fiberglass bolts on the steady state of the surrounding rock. Optimization of the support parameters was also proposed. Further, the sensitivity of different parameters to the distortion of the rock surrounding the tunnel was analyzed and ranked via an orthogonal experiment. Ultimately, the effectiveness of the optimization scheme was evaluated by numerical methods and field observations. The findings of the research indicate the following: (1) The monitoring results of the original support parameters show that the irrational design of the support parameters can bring about deformation non-convergence in the tunnel’s surrounding rock. Support parameters must be optimized. (2) The spacing of the pipe roof is positively correlated with the distortion of the surrounding rock. In contrast, the length and the grouting strength are negatively correlated with the distortion of the surrounding rock. The reinforcement density, length, and lap length of glass fiber bolts exhibit an inverse relationship with the distortion of the surrounding rock. (3) The efficacy of pipe shed grouting in mitigating subsidence and deformation of the vault is superior, followed by the spacing of the supports. In contrast, the length of the supports demonstrates comparatively lesser effectiveness. Under optimal parameters, the vault subsidence was reduced by 23.2%, 10.2%, and 2.0%, respectively. The most significant factor controlling the extrusion deformation of the tunnel face is bolt lap length, followed by reinforcement density and then reinforcement length. Extrusion displacement was reduced by 52.5%, 40.3%, and 9.3%, respectively, under the optimal parameters. (4) In comparison to the primordial support system, the optimized support scheme reduces the subsidence of the vault by about one time and the convergence deformation around the cave by about two times. The research findings offer guidance for analogous engineering support design and parameter optimization.

Black Carbon in Climate Studies: A Bibliometric Analysis of Research Trends and Topics

Black carbon is a short-lived climate warming agent and serves as a crucial factor influencing the climate. Numerous models, observations, and laboratory studies have been conducted to quantify black carbon’s direct or indirect impacts on the climate. Here, we applied bibliometric analysis to identify research trends and key topics on black carbon in the climate field. Based on the Web of Science (WOS) Core Collection database, a total of 4903 documents spanning the period from 2000 to 2023 were retrieved and screened, focusing on the topic of black carbon in the climate field, resulting in the Black-Carbon Climate Local (BCL) dataset. Our study examines the influence and trends of major countries, institutions, and authors in this field. The results show that China and the United States hold leading positions in terms of the number of publications. Based on keyword networks, the BCL dataset is segmented into six distinct research directions, and representative keywords of each direction include biomass burning, radiative forcing, air pollution, aerosol optical depth, optical properties, and biochar. This study helps to identify the current research status and trends of black carbon in the climate, highlighting main research directions and emerging topics.

Three-Dimensional Numerical Simulation of High-Speed Shear Crushing of High-Density Fluid

Plasma atomization is a technology that can produce high sphericity, small particle diameters, and high-purity copper powder, which is of great significance for the development of metal additive manufacturing. At present, although plasma atomization can realize the industrial preparation of spherical copper powder, there are still some problems, such as unclear understanding of the atomization process and a lack of theoretical support for powder quality control. This leads to the inability to predict the average particle diameter of powder in advance based on the actual atomization conditions and to optimize the process parameters, which seriously affects the further development of the plasma atomization process. We mainly studied the non-stationary simulation of a DC argon plasma torch. The purpose of this paper was to study the specific influence law of the average particle diameter of the powder in the process of plasma atomization by means of numerical simulation and experimental observation. The aim was to establish the mapping relationship between the atomization condition and the average particle diameter of the powder and realize the controllable preparation of the plasma atomized powder. At the same time, we used industrial-grade plasma atomization equipment to carry out pulverizing experiments to verify the plasma atomization theory and the powder average particle diameter control scheme proposed in this paper, thus proving the reliability of this study.

Fine Structure of Flat Bands in a Chiral Model of Magic Angles

AbstractWe analyse symmetries of Bloch eigenfunctions at magic angles for the Tarnopolsky–Kruchkov–Vishwanath chiral model of the twisted bilayer graphene (TBG) following the framework introduced by Becker–Embree–Wittsten–Zworski. We show that vanishing of the first Bloch eigenvalue away from the Dirac points implies its vanishing at all momenta, that is, the existence of a flat band. We also show how the multiplicity of the flat band is related to the nodal set of the Bloch eigenfunctions. We conclude with two numerical observations about the structure of flat bands.

Laplacian edge detection method based on a new approximation of the second-order fractional derivative in the Caputo-Fabrizio sense

Edge detection is an important issue in image processing and computer vision problems. It includes all mathematical methods that aim to identify the discontinuous points in the image. This process leads to construct curves that indicate the boundaries of an object and therefore extract feature information. In recent years, this task has received great attention from researchers and scientists, as we find in the literature many methods with their different algorithms. Up to now, there are two methods, the gradient and Laplacian methods. The first depends on the first derivative, where pixels with a high gradient are considered edges, whereas the second depends on the second derivative, such as the pixel whose second derivative is zero, it is marked as an edge point. Although these methods have achieved remarkable success, they are sensitive to noise and sometimes produce false edges. For this reason, in this paper, we propose an efficient edge detection method based on the fractional Laplacian operator in the Caputo-Fabrizio sense. In this method we develop a new approximation formula to the second-order with the Caputo-Fabrizio fractional derivative. Then, we construct a new fractional mask to compute the Laplacian convolution. To check the effectiveness of our proposed method, we have provided some test images that are affected by a Gaussian noise. The numerical results and visual observation show that our proposed edge detection method gives better performance compared to the classical Laplacian method in terms of the peak signal to noise ratio (psnr) and fine details extraction.

Study of spectral structure signal by finite difference method

A method for estimating the spectral parameters of a polyharmonic process by the method of central finite differences of even order is considered for the case when the series of numerical observations is quite large and the number of harmonic components in the process under study is a priori unknown.

Spontaneous imbibition in thin anisotropic fibrous media: Experiments and numerical modeling

In this study, we investigate the temporal and spatial evolution of wetting saturation during spontaneous imbibition in anisotropic fibrous porous media using both experimental and numerical methods. We present a novel experimental approach to systematically study spontaneous imbibition in these media, allowing for a comprehensive assessment of how microstructure influences wicking performance. The experimental method, which exhibits high reproducibility, was used to validate the numerical model. The numerical model was parameterized using only the porosity and filament diameter of the porous media in conjunction with the material properties of the imbibing fluid. The essential capillary saturation curve for the numerical model was derived using the pore morphology method. The numerical results effectively replicated the experimental results. Our experimental and numerical observations revealed a diffusive wetting front within the porous media, which progressively expanded and decelerated during the imbibition process. The results highlight the significant influence of filament size on the wetting saturation dynamics and the height of the wetting front during spontaneous imbibition.

Diagnostic Alignment to Optimize Inter-rater Reliability Among Lung Transplant Pathologists

BackgroundPoor agreement among lung transplant pathologists has been reported in the assessment of rejection. In addition to acute rejection (AR) and lymphocytic bronchiolitis (LB), acute lung injury (ALI) and organizing pneumonia (OP) were recently identified as histopathologic risk factors for chronic lung allograft dysfunction (CLAD). Therefore, maximizing inter-rater reliability (IRR) for identifying these histopathologic risk factors is important to guide individual patient care and to support incorporating them in inclusion criteria for clinical trials in lung transplantation. MethodsNine pathologists across eight North American lung transplant centers were surveyed for practices in the assessment of lung transplant transbronchial biopsies. We conducted seven diagnostic alignment sessions with pathologists discussing histomorphologic features of CLAD high-risk histopathology. Then, each pathologist blindly scored 75 digitized slides. Fleiss’ kappa, accounting for agreement across numerous observers, was used to determine IRR across all raters for presence of any high-risk finding and each individual entity. ResultsIRR (95% confidence intervals) and % agreement for any high-risk finding (AR, LB, ALI and/or OP) and each individual finding is as follows: Any Finding, k = 0.578 (0.487, 0.668), 78.9%; AR, k = 0.582 (0.481, 0.651), 79.1%; LB, k = 0.683 (0.585, 0.764), 83.5%; ALI, k = 0.418 (0.312, 0.494), 70.9%; OP, k = 0.621 (0.560, 0.714), 81.0%. ConclusionsAfter pre-study diagnostic alignment sessions, a multi-center group of lung transplant pathologists seeking to identify histopathology high-risk for CLAD achieved good IRR.

Data-driven through-process modelling of aluminum extrusion: Predicting mechanical properties

This paper reports on a case study on zero-defect manufacturing, using a data driven approach for predicting final product properties from material and manufacturing process information. The case is a company that produces aluminum automotive parts, having an integrated value chain from casting, extrusion, forming and component assembly. This value chain is unique in terms of the intervened and interdependent system of material, process and product properties, where the traditional scientific approach has been to apply physics-based, through-process models to explain the complex thermo-mechanical evolution. Here, an alternative and complementary data-driven model is trained and tested on process data for a 6xxx-alloy product range using machine learning, which then is compared to a physics-based as well as a simple hybrid model. The presented results indicate that a machine learning approach is advantageous when numerous relevant observations are available, inherently adapting to the specific company-level conditions. The main strengths of a physics-based model, on the other hand, is general applicability and self-sufficiency with no need of prior observations.

Dissipation of AGN Jets in a Clumpy Interstellar Medium

Accreting supermassive black holes frequently power jets that interact with the interstellar medium (ISM)/circumgalactic medium, regulating star formation in the galaxy. Highly supersonic jets launched by active galactic nuclei (AGN) power a cocoon that confines them and shocks the ambient medium. We build on the models of narrow conical jets interacting with a smooth ambient medium, including the effect of dense clouds, which are an essential ingredient of a multiphase ISM. The key physical ingredient of this model is that the clouds along the supersonic jet beam strongly decelerate the jet head but the subsonic cocoon easily moves around the clouds without much resistance. We propose scalings for important physical quantities—cocoon pressure, head and cocoon speed, and jet radius. For the first time, we obtain the analytic condition on the ambient medium’s clumpiness for the jet to dissipate within the cocoon and verify it with numerical simulations of conical jets interacting with a uniform ISM with embedded spherical clouds. A jet is defined to be dissipated when the cocoon speed exceeds the speed of the jet head. We compare our models with more sophisticated numerical simulations and direct observations of jet–ISM interaction (e.g., quasar J1316+1753), and we discuss implications for the Fermi/eROSITA bubbles. Our work also motivates effective subgrid models for AGN jet feedback in a clumpy ISM unresolved by the present generation of cosmological galaxy formation simulations.

Inverse opal optical Tamm state for sensing applications

We report the excitation of optical Tamm states (OTS) in inverse opal (IO) - based three-dimensional photonic crystal on a flat metal substrate, validated through both numerical simulations and experimental observations. Large area, uniform Tamm inverse opal (Tamm-IO) structures were fabricated without the use of any corrosive chemicals. Upon infiltration of non-reactive solvents such as methanol and ethanol into the IO, a noticeable shift of the OTS, consistent with our simulations is observed, and the temporal dynamics of the same have been investigated. The experimentally obtained sensitivity is ∼ 110 nm/RIU which is of the same order as the computed value, making the IO OTS to be an attractive sensing tool.

Formation and evolution of a protoplanetary disk: Combining observations, simulations, and cosmochemical constraints

The formation and evolution of protoplanetary disks remains elusive. We have numerous astronomical observations of young stellar objects of different ages with their envelopes and/or disks. Moreover in the last decade there has been tremendous progress in numerical simulations of star and disk formation. New simulations use realistic equations of state for the gas and treat the interaction of matter and the magnetic field with the full set of nonideal magnetohydrodynamic (MHD) equations. However, it is still not fully clear how a disk forms and whether it happens from inside-out or outside-in. Open questions remain regarding where material is accreted onto the disk and comes from, how dust evolves in disks, and the timescales of appearance of disk's structures. These unknowns limit our understanding of how planetesimals and planets form and evolve. We attempted to reconstruct the evolutionary history of the protosolar disk, guided by the large amount of cosmochemical constraints derived from the study of meteorites, while using astronomical observations and numerical simulations as a guide to pinpointing plausible scenarios. Our approach is highly interdisciplinary and we do not present new observations or simulations in this work. Instead, we combine, in an original manner, a large number of published results concerning young stellar objects observations, and numerical simulations, along with the chemical, isotopic and petrological nature of meteorites. We have achieved a plausible and coherent view of the evolution of the protosolar disk that is consistent with cosmochemical constraints and compatible with observations of other protoplanetary disks and sophisticated numerical simulations. The evidence that high-temperature condensates, namely, calcium-aluminum inclusions (CAIs) and amoeboid olivine aggregates (AOAs), formed near the protosun before being transported to the outer disk can be explained in two ways: there could have either been an early phase of vigorous radial spreading of the disk that occurred or fast transport of these condensates from the vicinity of the protosun toward large disk radii via the protostellar outflow. The assumption that the material accreted toward the end of the infall phase was isotopically distinct allows us to explain the observed dichotomy in nucleosynthetic isotopic anomalies of meteorites. It leads us toward intriguing predictions on the possible isotopic composition of refractory elements in comets. At a later time, when the infall of material waned, the disk started to evolve as an accretion disk. Initially, dust drifted inward, shrinking the radius of the dust component to $ 45$ au, probably about to about half of the width of the gas component. Next, structures must have emerged, producing a series of pressure maxima in the disk, which trapped the dust on Myr timescales. This allowed planetesimals to form at radically distinct times without significantly changing any of the isotopic properties. We also conclude that there was no late accretion of material onto the disk via streamers. The disk disappeared at about 5 My, as indicated by paleomagnetic data in meteorites. The evolution of the protosolar disk seems to have been quite typical in terms of size, lifetime, and dust behavior. This suggests that the peculiarities of the Solar System with respect to extrasolar planetary systems probably originate from the chaotic nature of planet formation and not from the properties of the parental disk itself.

Abstract B068: Human pancreatic cancer single cell atlas reveals association of CXCL10 positive fibroblasts and basal subtype tumor cells

Abstract Pancreatic ductal adenocarcinoma (PDAC) patients with tumors enriched for the basal-like molecular subtype exhibit severe resistance to standard of care treatments and have significantly worse overall survival, compared to patients with classical subtype enriched tumors. It is therefore important to develop resources that allow identification of novel targets in a statistically rigorous way to overcome therapeutic challenges. Here we compiled a single cell RNA sequencing (scRNAseq) atlas of the human pancreas with 229 individual patient samples, aggregated from raw data obtained from published studies. We mapped cell-type specific scRNAseq gene signatures in newly generated (n=12) and existing (n=13) spatial transcriptomics (ST) data from PDAC samples. Analysis of tumor cells from our scRNAseq atlas revealed nine transcriptionally distinct populations, two of which strongly align with a basal gene signature, correlating with worse overall survival in PDAC bulk RNAseq datasets. Deconvolution showed one of the basal populations identified to be the predominant tumor subtype in non- dissociated ST tissues and in vitro tumor cell and organoid PDAC lines. In bulk RNAseq datasets, we uncovered that myofibroblasts (myFb) expressing CXCL10 consistently correlated with both basal subtypes and were found near basal tumor cells using immunostaining. We also identified that besides immune cells, ductal cells also express CXCR3, the receptor for CXCL10, further suggesting a relationship between these cell types in PDAC tumor microenvironment (TME). Overall, we show that our newly built scRNAseq atlas, containing over 700,000 cells, integrated with ST data is a powerful resource, given that it corroborates numerous PDAC TME observations in the literature, with increased statistical power. Moreover, we uncovered a novel association between CXCL10+ myFb and basal tumor cells, underscoring the presence of unique spatial niches in PDAC that should be explored for the development of targeted therapies for this dismal disease. Citation Format: Ian M Loveless, Samantha B Kempt, Yuesong Wu, Daniel J Salas-Escabillas, Kailee Hartway, Madison George, Yetunde Makinwa, Thais Stockdale, Samuel D Zwernik, Kendyll Gartrelle, Rohit G Reddy, Daniel Long, Allison Wombell, Julie M Clark, Albert M Levin, David Kwon, Ling Huang, Ralph Francescone, Débora B Vendramini-Costa, Ben Stanger, Adam Alessio, Andrew M Waters, Yuehua Cui, Brian Theisen, Howard C Crawford, Nina G Steele. Human pancreatic cancer single cell atlas reveals association of CXCL10 positive fibroblasts and basal subtype tumor cells [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B068.

The (absence of the) presence-absence distinction in motivation science.

A focal stimulus (object, end state, outcome, event, experience, characteristic, possibility, etc.) may represent a presence, an occurrence, or something, or it may represent an absence, a nonoccurrence, or nothing. This presence-absence distinction has received extensive and explicit attention in cognitive psychology (it is the central figure), but it has received minimal and primarily implicit attention in motivation science (it is the ground, not the figure). Herein, we explicitly place the presence-absence distinction in the role of figure in a motivational account of behavior, and we do so in the context of the foundational approach-avoidance motivation distinction. We review pertinent literature in cognitive psychology and motivation science, and we provide a model integrating the approach-avoidance and the presence-absence distinctions, along with numerous examples, illustrations, and observations. We believe that attending to the presence-absence distinction in motivation science holds great promise for theory, research, and application, and we encourage researchers to attend to this distinction moving forward. (PsycInfo Database Record (c) 2024 APA, all rights reserved).