6,491 results match your criteria density fluctuations

Adipsin promotes bone marrow adiposity by priming mesenchymal stem cells.

Elife 2021 Jun 22;10. Epub 2021 Jun 22.

Naomi Berrie Diabetes Cente, Columbia University, New York, United States.

Background: Marrow adipose tissue (MAT) has been shown to be vital for regulating metabolism and maintaining skeletal homeostasis in the bone marrow (BM) niche. As a reflection of BM remodeling, MAT is highly responsive to nutrient fluctuations, hormonal changes, and metabolic disturbances such as obesity and diabetes mellitus. Expansion of MAT has also been strongly associated with bone loss in mice and humans. Read More

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Resonance in Physiologically Structured Population Models.

Bull Math Biol 2021 Jun 21;83(8):86. Epub 2021 Jun 21.

Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands.

Ecologists have long sought to understand how the dynamics of natural populations are affected by the environmental variation those populations experience. A transfer function is a useful tool for this purpose, as it uses linearization theory to show how the frequency spectrum of the fluctuations in a population's abundance relates to the frequency spectrum of environmental variation. Here, we show how to derive and to compute the transfer function for a continuous-time model of a population that is structured by a continuous individual-level state variable such as size. Read More

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Seasonal fluctuations in symbiotic bacteria and their role in environmental adaptation of the scleractinian coral Acropora pruinosa in high-latitude coral reef area of the South China Sea.

Sci Total Environ 2021 Jun 11;792:148438. Epub 2021 Jun 11.

Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Coral Reef Research Center of China, School of Marine Sciences, Guangxi University, Nanning, China.

Coral-associated bacterial communities are paramount for coral ecosystems and holobiont health. However, the role of symbiotic bacteria in the adaptation of high-latitude corals to seasonal fluctuations remains underexplored. Therefore, we used 16S rRNA-based high-throughput sequencing to analyze the symbiotic bacterial diversity, composition, and core bacterial community in high-latitude coral and explored the seasonal fluctuation characteristics of symbiotic bacterial communities. Read More

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Global Theory of Microtearing Modes in the Tokamak Pedestal.

Phys Rev Lett 2021 Jun;126(22):225001

Institute for Fusion Studies, University of Texas, Austin, Texas 78712, USA.

The pedestal of H-mode tokamaks displays strong magnetic fluctuations correlated with the evolution of the electron temperature. The microtearing mode (MTM), a temperature-gradient-driven instability that alters magnetic topology, is compatible with these observations. Here we extend the conventional theory of the MTM to include the global variation of the temperature and density profiles. Read More

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An Evolutionary and Ecological Community Model for Distribution of Phenotypes and Abundances among Competing Species.

Am Nat 2021 Jul 24;198(1):13-32. Epub 2021 May 24.

AbstractHere, we propose a theory for the structure of communities of competing species. We include ecologically realistic assumptions, such as density dependence and stochastic fluctuations in the environment, and analyze how evolution caused by - and -selection will affect the packing of species in the phenotypic space as well as the species abundance distribution. Species-specific traits have the same matrix of additive genetic variances and covariances, and evolution of mean traits is affected by fluctuations in population size of all species. Read More

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Turbulence scale effects and resolution requirements in aero-optics.

Appl Opt 2021 May;60(15):4426-4433

While optical aberrations caused by atmospheric turbulence have been extensively investigated and well characterized, recent research has identified structural differences in optical phase distortions caused by aircraft-induced, compressible turbulence. These so-called aero-optical distortions can be a critical obstacle in the development of airborne optical systems and reduce the fidelity and on-target intensity of optical beams. Using a model index-of-refraction spectrum that accounts for changes in density due to both temperature and pressure fluctuations in aero-optically active flow fields, expressions for the two-dimensional phase distortion over an aperture are developed. Read More

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Dynamics of Ionic Liquid through Intrinsic Vibrational Probes Using the Dispersion-Corrected DFT Functionals.

J Phys Chem B 2021 Jun 18. Epub 2021 Jun 18.

Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India.

First principles molecular dynamics simulations have been utilized to study the spectral properties of the protic ionic liquid, methylammonium formate (MAF). All simulations were performed using density functional theory (DFT) and various van der Waals-corrected exchange-correlation functionals. We calculated the vibrational stretch frequency distributions, determined the time-frequency correlations of the intrinsic vibrational probes, the N-H and C-O modes in MAF, and the frequency-structure correlations. Read More

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Mechanoelectric Response of Single-Crystal Rubrene from Ab Initio Molecular Dynamics.

J Phys Chem Lett 2021 Jun 17:5857-5863. Epub 2021 Jun 17.

Department of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom.

A robust understanding of the mechanoelectric response of organic semiconductors is crucial for the development of materials for flexible electronics. In particular, the prospect of using external mechanical strain to induce a controlled modulation in the charge mobility of the material is appealing. Here we develop an accurate computational protocol for the prediction of the mechanical strain dependence of charge mobility. Read More

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Varying Manpower Alters Dental Health in a Developing Health Care System.

Int Dent J 2021 Jun 13. Epub 2021 Jun 13.

Dental Research Center, Research Institute of Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

Objectives: This study assessed relationships between oral health care workforce and dental health in 12-year-olds in a developing health care system in Iran from 1992 to 2014 and compared these findings with the most recent corresponding findings in selected countries.

Methods: Data regarding oral health care workers from 1962 to 2014 were extracted from the comprehensive human resource data bank of the Shahid Beheshti Research Institute of Dental Sciences. Data regarding decayed, missing, and filled permanent teeth (DMFT) of 12-year-olds, extracted from official statistics, described dental health. Read More

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Extremal statistics for stochastic resetting systems.

Phys Rev E 2021 May;103(5-1):052119

School of Chemistry, Center for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv 6997801, Israel.

While averages and typical fluctuations often play a major role in understanding the behavior of a nonequilibrium system, this nonetheless is not always true. Rare events and large fluctuations are also pivotal when a thorough analysis of the system is being done. In this context, the statistics of extreme fluctuations in contrast to the average plays an important role, as has been discussed in fields ranging from statistical and mathematical physics to climate, finance, and ecology. Read More

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Interfacial segregation of interacting vacancies and their role on the wetting critical properties of the Blume-Emery-Griffiths model.

Phys Rev E 2021 May;103(5-1):052803

Instituto de Física de Líquidos y Sistemas Biológicos, UNLP-CONICET, La Plata 1900, Argentina.

We study the wetting critical behavior of the three-state (s=±1,0) Blume-Emery-Griffiths model using numerical simulations. This model provides a suitable scenario for the study of the role of vacancies on the wetting behavior of a thin magnetic film. To this aim we study a system confined between parallel walls with competitive short-range surface magnetic fields (h_{L}=-|h_{1}|). Read More

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Lévy on-off intermittency.

Phys Rev E 2021 May;103(5-1):052115

Laboratoire de Physique de l'Ecole normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, F-75005 Paris, France.

We present an alternative form of intermittency, Lévy on-off intermittency, which arises from multiplicative α-stable white noise close to an instability threshold. We study this problem in the linear and nonlinear regimes, both theoretically and numerically, for the case of a pitchfork bifurcation with fluctuating growth rate. We compute the stationary distribution analytically and numerically from the associated fractional Fokker-Planck equation in the Stratonovich interpretation. Read More

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Quantitative phase field simulations of polycrystalline solidification using a vector order parameter.

Phys Rev E 2021 May;103(5-1):053310

Department of Physics and Centre for the Physics of Materials, McGill University, Montreal, Quebec H3A 2T8, Canada.

A vector order parameter phase field model derived from a grand potential functional is presented as an alternative approach for modeling polycrystalline solidification of alloys. In this approach, the grand potential density is designed to contain a discrete set of finite wells, a feature that naturally allows for the growth and controlled interaction of multiple grains using a single vector field. We verify that dendritic solidification in binary alloys follows the well-established quantitative behavior in the thin interface limit. Read More

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Growth mechanism of interfacial fluid-mixing width induced by successive nonlinear wave interactions.

Phys Rev E 2021 May;103(5-1):053109

Institute of Applied Physics and Computational Mathematics, Beijing 100094, China.

Interfacial fluid mixing induced by successive waves, such as shock, rarefaction, and compression waves, plays a fundamental role in engineering applications, e.g., inertial confinement fusion, and in natural phenomena, e. Read More

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How attractive and repulsive interactions affect structure ordering and dynamics of glass-forming liquids.

Phys Rev E 2021 May;103(5-1):052105

Department of Physics, Banaras Hindu University, Varanasi-221 005, India.

The theory developed in our previous papers [Phys. Rev. E 99, 030101(R) (2019)10. Read More

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Impacts of global warming on marine microbial communities.

Sci Total Environ 2021 May 21;791:147905. Epub 2021 May 21.

Sathyabama Institute of Science and Technology, Chennai 600119, Tamil Nadu, India; School of Medicine, Loma Linda University, CA, USA; Musculoskeletal Disease Research Laboratory, US Department of Veteran Affairs, Loma Linda, CA, USA. Electronic address:

Global warming in ocean ecosystems alters temperature, acidification, oxygen content, circulation, stratification, and nutrient inputs. Microorganisms play a dominant role in global biogeochemical cycles crucial for a planet's sustainability. Since microbial communities are highly dependent on the temperature factor, fluctuations in the same will lead to adverse effects on the microbial community organization. Read More

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Phase equilibrium and dielectric relaxation in mixture of 5CB with dilute dimethyl phthalate: effect of coupling between orientation and composition fluctuations on molecular dynamics in isotropic one-phase state.

Soft Matter 2021 Jun 14. Epub 2021 Jun 14.

Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.

Phase equilibrium and dielectric relaxation were examined for mixtures of liquid-crystalline (LC)-forming 4-cyano-4'-pentylbiphenyl (5CB) with dilute dimethyl phthalate (DMP). The mixtures were in an isotropic one-phase state at high temperatures T but were separated into nematic and isotropic phases at low T < TIN (isotropic-to-nematic transition temperature), and the isotropic phase disappeared and a nematic one-phase state was realized on a further decrease of T below another transition temperature . These TIN and data (phase diagram) were described considerably well by a simple model of free energy contributed from a Flory-Huggins type mixing entropy (no enthalpic contribution) and a Landau-de Gennes type nematic interaction. Read More

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Investigation of the Turbulent Boundary Layer Structure over a Sparsely Spaced Biomimetic Spine-Covered Protrusion Surface.

ACS Omega 2021 Jun 28;6(22):14220-14229. Epub 2021 May 28.

College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu 212003, China.

Multiperspective particle image velocimetry was used to investigate the turbulent boundary layer structure over biomimetic spine-covered protrusion (BSCP) samples inspired by dorsal skin of pufferfish. The comparison of BSCP samples of two sparse "-type" arrangements (aligned and staggered) with roughness height = 5-7 (nearly hydraulically smooth) and smooth case were manufactured in bulk Reynolds number = 37,091, 44,510. The negative value of the roughness function Δ shows a downward shift of the mean velocity profile of BSCP samples, which shows a drag reduction effect. Read More

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Community Trait Responses of Three Dominant Macrophytes to Variations in Flooding During 2011-2019 in a Yangtze River-Connected Floodplain Wetland (Dongting Lake, China).

Front Plant Sci 2021 28;12:604677. Epub 2021 May 28.

Key Laboratory of Agro-ecological Processes in Subtropical Region, The Chinese Academy of Sciences, Changsha, China.

In lacustrine wetlands connected to rivers, the changes in flood regimes caused by hydrological projects lead to changes in the community traits of dominant macrophytes and, consequently, influence the structure and function of wetland vegetation. However, community trait responses of macrophytes to the timing and duration of flood disturbance have been rarely quantified. In 2011-2019, we investigated plant species diversity, density, and biomass in three dominant macrophyte communities ( C. Read More

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Starvation induces shrinkage of the bacterial cytoplasm.

Proc Natl Acad Sci U S A 2021 Jun;118(24)

Department of Biology, Washington University in St. Louis, St. Louis, MO 63130;

Environmental fluctuations are a common challenge for single-celled organisms; enteric bacteria such as experience dramatic changes in nutrient availability, pH, and temperature during their journey into and out of the host. While the effects of altered nutrient availability on gene expression and protein synthesis are well known, their impacts on cytoplasmic dynamics and cell morphology have been largely overlooked. Here, we discover that depletion of utilizable nutrients results in shrinkage of 's inner membrane from the cell wall. Read More

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Adiabatic dynamic causal modelling.

Neuroimage 2021 Jun 8;238:118243. Epub 2021 Jun 8.

The Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, UK.

This technical note introduces adiabatic dynamic causal modelling, a method for inferring slow changes in biophysical parameters that control fluctuations of fast neuronal states. The application domain we have in mind is inferring slow changes in variables (e.g. Read More

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Regulation of microglia population dynamics throughout development, health, and disease.

Glia 2021 Jun 11. Epub 2021 Jun 11.

Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada.

The dynamic expansions and contractions of the microglia population in the central nervous system (CNS) to achieve homeostasis are likely vital for their function. Microglia respond to injury or disease but also help guide neurodevelopment, modulate neural circuitry throughout life, and direct regeneration. Throughout these processes, microglia density changes, as does the volume of area that each microglia surveys. Read More

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Dielectric Constant of Liquid Water Determined with Neural Network Quantum Molecular Dynamics.

Phys Rev Lett 2021 May;126(21):216403

Collaboratory for Advanced Computing and Simulations, Department of Chemical Engineering and Materials Science, Department of Physics & Astronomy, and Department of Computer Science, University of Southern California, Los Angeles, California 90089, USA.

The static dielectric constant ϵ_{0} and its temperature dependence for liquid water is investigated using neural network quantum molecular dynamics (NNQMD). We compute the exact dielectric constant in canonical ensemble from NNQMD trajectories using fluctuations in macroscopic polarization computed from maximally localized Wannier functions (MLWF). Two deep neural networks are constructed. Read More

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Observation of first and second sound in a BKT superfluid.

Nature 2021 Jun 9;594(7862):191-194. Epub 2021 Jun 9.

Cavendish Laboratory, University of Cambridge, Cambridge, UK.

Superfluidity in its various forms has been of interest since the observation of frictionless flow in liquid helium II. In three spatial dimensions it is conceptually associated with the emergence of long-range order at a critical temperature. One of the hallmarks of superfluidity, as predicted by the two-fluid model and observed in both liquid helium and in ultracold atomic gases, is the existence of two kinds of sound excitation-the first and second sound. Read More

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Solvent Vapor Annealing, Defect Analysis, and Optimization of Self-Assembly of Block Copolymers Using Machine Learning Approaches.

ACS Appl Mater Interfaces 2021 Jun 8;13(24):28639-28649. Epub 2021 Jun 8.

Department of Chemistry, University of Alberta, 11227-Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada.

Self-assembly of block copolymers (BCPs) is an alternative patterning technique that promises high resolution and density multiplication with lower costs. The defectivity of the resulting nanopatterns remains too high for many applications in microelectronics and is exacerbated by small variations of processing parameters, such as film thickness, and fluctuations of solvent vapor pressure and temperature, among others. In this work, a solvent vapor annealing (SVA) flow-controlled system is combined with design of experiments (DOE) and machine learning (ML) approaches. Read More

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Manifestations of metastable criticality in the long-range structure of model water glasses.

Nat Commun 2021 Jun 7;12(1):3398. Epub 2021 Jun 7.

Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA.

Much attention has been devoted to water's metastable phase behavior, including polyamorphism (multiple amorphous solid phases), and the hypothesized liquid-liquid transition and associated critical point. However, the possible relationship between these phenomena remains incompletely understood. Using molecular dynamics simulations of the realistic TIP4P/2005 model, we found a striking signature of the liquid-liquid critical point in the structure of water glasses, manifested as a pronounced increase in long-range density fluctuations at pressures proximate to the critical pressure. Read More

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Real-time monitoring of volume flow, mass flow and shredder power consumption in mixed solid waste processing.

A Curtis R Sarc

Waste Manag 2021 Jun 4;131:41-49. Epub 2021 Jun 4.

Department of Environmental and Energy Process Engineering, Chair of Waste Processing Technology and Waste Management, Montanuniversitaet Leoben, Leoben, Austria. Electronic address:

Real-time material flow monitoring is not yet implemented in mixed solid waste processing, but it is important for an efficient quality assured production and the development of the smart waste factory. The present paper shows results of practical investigation of the Real-Time Material Flow Monitoring in a large-scale Solid Recovered Fuel (SRF) production plant and a semi large-scale processing line (Technical line 4.0) using mixed solid waste. Read More

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Behavior of Water Near Multimodal Chromatography Ligands and Its Consequences for Modulating Protein-Ligand Interactions.

J Phys Chem B 2021 Jun 7;125(23):6112-6120. Epub 2021 Jun 7.

Howard P. Isermann Department of Chemical and Biological Engineering and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States.

Multimodal chromatography is a powerful approach for purifying proteins that uses ligands containing multiple modes of interaction. Recent studies have shown that selectivity in multimodal chromatographic separations is a function of the ligand structure and geometry. Here, we performed molecular dynamics simulations to explore how the ligand structure and geometry affect ligand-water interactions and how these differences in solution affect the nature of protein-ligand interactions. Read More

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Comparison of the pH- and thermally-induced fluctuations of a therapeutic antibody Fab fragment by molecular dynamics simulation.

Comput Struct Biotechnol J 2021 4;19:2726-2741. Epub 2021 May 4.

Department of Biochemical Engineering, University College London, Gordon Street, London WC1E 7JE, United Kingdom.

Successful development of protein therapeutics depends critically on achieving stability under a range of conditions. A deeper understanding of the drivers of instability across different stress conditions, will enable the engineering of more robust protein scaffolds. We compared the impacts of low pH and high temperature stresses on the structure of a humanized antibody fragment (Fab) A33, using atomistic molecular dynamics simulations, using a recent 2. Read More

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Functional trait effects on ecosystem stability: assembling the jigsaw puzzle.

Trends Ecol Evol 2021 Jun 1. Epub 2021 Jun 1.

Department of Botany, Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czech Republic; Biology Research Centre, Czech Academy of Sciences, Institute of Entomology, 37005, České Budějovice, Czech Republic.

Under global change, how biological diversity and ecosystem services are maintained in time is a fundamental question. Ecologists have long argued about multiple mechanisms by which local biodiversity might control the temporal stability of ecosystem properties. Accumulating theories and empirical evidence suggest that, together with different population and community parameters, these mechanisms largely operate through differences in functional traits among organisms. Read More

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