Статті в журналах з теми "Low Density Spreading"
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1
Chen, Shuang, Kewu Peng, Yushu Zhang, and Jian Song. "Performance evaluation of low-density spreading multiple access." IET Communications 13, no. 1 (January 4, 2019): 108–15. http://dx.doi.org/10.1049/iet-com.2018.5310.
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2
Le, Mai T. P., Guido Carlo Ferrante, Tony Q. S. Quek, and Maria-Gabriella Di Benedetto. "Fundamental Limits of Low-Density Spreading NOMA With Fading." IEEE Transactions on Wireless Communications 17, no. 7 (July 2018): 4648–59. http://dx.doi.org/10.1109/twc.2018.2828853.
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Al-Imari, Mohammed, Muhammad Ali Imran, and Pei Xiao. "Radio Resource Allocation for Multicarrier Low-Density-Spreading Multiple Access." IEEE Transactions on Vehicular Technology 66, no. 3 (March 2017): 2382–93. http://dx.doi.org/10.1109/tvt.2016.2579168.
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4
Millar, Goldwyn, Michel Kulhandjian, Ayse Alaca, Saban Alaca, Claude D'Amours, and Halim Yanikomeroglu. "Low-Density Spreading Design Based on an Algebraic Scheme for NOMA Systems." IEEE Wireless Communications Letters 11, no. 4 (April 2022): 698–702. http://dx.doi.org/10.1109/lwc.2022.3140223.
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Jiroušková, Markéta, Jyoti K. Jaiswal та Barry S. Coller. "Ligand density dramatically affects integrin αIIbβ3-mediated platelet signaling and spreading". Blood 109, № 12 (15 червня 2007): 5260–69. http://dx.doi.org/10.1182/blood-2006-10-054015.
Повний текст джерелаАнотація:
Abstract The impact of ligand density on integrin-mediated cell adhesion and outside-in signaling is not well understood. Using total internal reflection fluorescent microscopy, conformation-specific antibodies, and Ca2+ flux measurements, we found that the surface density of fibrinogen affects αIIbβ3-mediated platelet signaling, adhesion, and spreading. Adhesion to fibrinogen immobilized at low density leads to rapid increases in cytosolic Ca2+ and sequential formation of filopodia and lamellipodia. In contrast, adhesion to high-density fibrinogen results in transient or no increases in Ca2+ and simultaneous formation of filopodia and lamellipodia. αIIbβ3 receptors at the basal surface of platelets engage fibrinogen in a ringlike pattern at the cell edges under both conditions. This engagement is, however, more dynamic and easily reversed on high-density fibrinogen. Src and Rac activity and actin polymerization are important for adhesion to low-density fibrinogen, whereas PKC/PI3 kinases contribute to platelet spreading on high-density fibrinogen. We conclude that 2 fundamentally different signaling mechanisms can be initiated by a single integrin receptor interacting with the same ligand when it is immobilized at different densities.
6
Li, Y. L. "Interfacial Wetting Behavior under Low-Density Ultrasonic Field and Solvent - Assisted Wet Condition." Advanced Materials Research 1015 (August 2014): 458–62. http://dx.doi.org/10.4028/www.scientific.net/amr.1015.458.
Повний текст джерелаАнотація:
In this paper, the author had adopted the low-density ultrasonic field coupling method, coupled the ultrasonic directional beam to metallic melt, and then coupled energy to C/Al interface by sound propagation, eventually accomplish C/Al interfacial wettability and interfacial reaction by using ultrasonic field coupling method, and synthesize Al-Ti-C master alloys by using the same method. Some experiments showed that in the low-density ultrasonic field and under flux auxiliary wetting, there is no explicit incubation period in the prophase of wetting, in the medium term of wetting, the wetting angle between aluminum melt and carbon will reduce with time extension, however, the wetting spreading radius will increase with the extended holding time, and reach wetting balance state in 20 minutes. In the condition of 1023K, the equilibrium wetting angle is less than 22°,and wetting spreading radius is close to 20mm.
7
Gao, A. G., F. P. Lindberg, J. M. Dimitry, E. J. Brown, and W. A. Frazier. "Thrombospondin modulates alpha v beta 3 function through integrin-associated protein." Journal of Cell Biology 135, no. 2 (October 15, 1996): 533–44. http://dx.doi.org/10.1083/jcb.135.2.533.
Повний текст джерелаАнотація:
Integrin-associated protein (IAP) is a receptor for the carboxyl-terminal "cell-binding domain" (CBD) of thrombospondin 1 (TS1). IAP associates with alpha v beta 3 integrin and mAbs against IAP inhibit certain integrin functions. Here we examine the effects of the TS1 CBD and 4N1K (KRFYVVMWKK), a cell-binding peptide derived from it, on the adhesion and spreading on vitronectin (VN) of C32 human melanoma cells which express IAP, alpha v beta 3, and alpha v beta 5. Cells adhere to VN at low surface densities via alpha v beta 5 and spread very slowly while adhesion to higher density VN involves both alpha v beta 5 and alpha v beta 3 and results in rapid spreading. Spreading of the cells, but not adhesion, on sparse VN coatings is markedly enhanced by the presence of soluble TS1, the recombinant CBD and 4N1K, but not the "mutant" peptide 4NGG, KRFYGGMWKK, which fails to bind IAP. This enhanced spreading is completely blocked by mAb LM609 against alpha v beta 3 and the anti-IAP mAb B6H12. Correlated with this enhanced spreading is increased tyrosine phosphorylation of focal adhesion kinase (FAK), paxillin, and a protein of ca. 90 kD. The enhanced spreading induced by TS1 and 4N1K and the constitutive spreading on higher density VN are both blocked by calphostin C (100 nM), wortmannin (10 nM), and tyrosine kinase inhibitors. In contrast, pertussis toxin specifically blocks only the TS1 stimulated spreading on low density VN, indicating that IAP exerts its effects on signal transduction via a heterotrimeric Gi protein acting upstream of a common cell spreading pathway which includes PI-3 kinase, PKC, and tyrosine kinases.
8
Kulhandjian, Michel, Hovannes Kulhandjian, Claude D'amours, and Lajos Hanzo. "Low-Density Spreading Codes for NOMA Systems and a Gaussian Separability-Based Design." IEEE Access 9 (2021): 33963–93. http://dx.doi.org/10.1109/access.2021.3060879.
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Yoshikuni, Masato, Shinji Ide, Nobuyuki Iwata, and Hiroshi Yamamoto. "Field Emission from Low Density Carbon Nanofiber Emitters Prepared by Spray Spreading Method." Molecular Crystals and Liquid Crystals 472, no. 1 (August 20, 2007): 87/[477]—94/[484]. http://dx.doi.org/10.1080/15421400701545155.
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Foster, Natalie D., Andrew J. Miller, Troy A. Hutchins-Delgado, Christopher M. Smyth, Michael C. Wanke, Tzu-Ming Lu, and Dwight R. Luhman. "Thermal activation of low-density Ga implanted in Ge." Applied Physics Letters 120, no. 20 (May 16, 2022): 201902. http://dx.doi.org/10.1063/5.0094900.
Повний текст джерелаАнотація:
The nuclear spins of low-density implanted Ga atoms in Ge are interesting candidates for solid state-based qubits. To date, activation studies of implanted Ga in Ge have focused on high densities. Here, we extend activation studies into the low-density regime. We use spreading resistance profiling and secondary ion mass spectrometry to derive electrical activation of Ga ions implanted into Ge as a function of the rapid thermal anneal temperature and implant density. We show that for our implant conditions, the activation is best for anneal temperatures between 400 and 650 °C with a maximum activation of 69% at the highest fluence. Below 400 °C, remaining implant damage results in defects that act as superfluous carriers, and above 650 °C, surface roughening and loss of Ga ions are observed. The activation increased monotonically from 10% to 69% as the implant fluence increased from [Formula: see text] to [Formula: see text] cm−2. The results provide thermal anneal conditions to be used for initial studies of using low-density Ga atoms in Ge as nuclear spin qubits.
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Aksoy, Yunus Tansu, Pinar Eneren, Erin Koos, and Maria Rosaria Vetrano. "Spreading of a droplet impacting on a smooth flat surface: How liquid viscosity influences the maximum spreading time and spreading ratio." Physics of Fluids 34, no. 4 (April 2022): 042106. http://dx.doi.org/10.1063/5.0086050.
Повний текст джерелаАнотація:
Existing energy balance models, which estimate maximum droplet spreading, insufficiently capture the droplet spreading from low to high Weber and Reynolds numbers and contact angles. This is mainly due to the simplified definition of the viscous dissipation term and incomplete modeling of the maximum spreading time. In this particular research, droplet impact onto a smooth sapphire surface is studied for seven glycerol concentrations between 0% and 100%, and 294 data points are acquired using high-speed photography. Fluid properties, such as density, surface tension, and viscosity, are also measured. For the first time according to the authors' knowledge, we incorporate the fluid viscosity in the modeling of the maximum spreading time based on the recorded data. We also estimate the characteristic velocity of the viscous dissipation term in the energy balance equation. These viscosity-based characteristic scales help to formulate a more comprehensive maximum droplet spreading model. Thanks to this improvement, our model successfully fits the data available in the literature for various fluids and surfaces compared to the existing models.
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Yokoyama, Ryo, Masahiro Kondo, Shunichi Suzuki, Masaru Harada, and Koji Okamoto. "Investigation of the Outflow and Spreading-Solidification Behaviour of Stratified Molten Metal." Journal of Nuclear Engineering 2, no. 2 (May 10, 2021): 168–89. http://dx.doi.org/10.3390/jne2020017.
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The spreading-solidification behaviour of the stratified molten metals was investigated. This is important in understanding the practical fuel debris distribution spread and solidified in the primary containment vessel (PCV) of Fukushima Daiichi Nuclear Power Plants (1F NPPs). In this study, the effect of outflow diameter on the material distribution before discharging was studied both experimentally and numerically. The two simulant metals were chosen so that the density ratio could be similar to the practical fuel and structure elements of the plant. They were arranged in a vessel and discharged on a receiving plate. The spreading experiments were performed using various outlet diameters with a density and reverse density stratification arrangement. After the experiment, X-ray analysis was performed to evaluate the material distribution in the solidified material. Moreover, a numerical analysis was performed to reveal the mechanisms that affect the material distribution after solidification. As a result, the low-density metal accumulated at the centre region regardless of the outlet diameters in the density stratification. In contrast, the outlet diameters affected the material distribution in the reverse density stratification because they affected the material outflow order. These findings may help increase our understanding of the fuel debris distribution in 1F NPPs.
13
Sullivan, Lauren L., Bingtuan Li, Tom E. X. Miller, Michael G. Neubert, and Allison K. Shaw. "Density dependence in demography and dispersal generates fluctuating invasion speeds." Proceedings of the National Academy of Sciences 114, no. 19 (April 25, 2017): 5053–58. http://dx.doi.org/10.1073/pnas.1618744114.
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Density dependence plays an important role in population regulation and is known to generate temporal fluctuations in population density. However, the ways in which density dependence affects spatial population processes, such as species invasions, are less understood. Although classical ecological theory suggests that invasions should advance at a constant speed, empirical work is illuminating the highly variable nature of biological invasions, which often exhibit nonconstant spreading speeds, even in simple, controlled settings. Here, we explore endogenous density dependence as a mechanism for inducing variability in biological invasions with a set of population models that incorporate density dependence in demographic and dispersal parameters. We show that density dependence in demography at low population densities—i.e., an Allee effect—combined with spatiotemporal variability in population density behind the invasion front can produce fluctuations in spreading speed. The density fluctuations behind the front can arise from either overcompensatory population growth or density-dependent dispersal, both of which are common in nature. Our results show that simple rules can generate complex spread dynamics and highlight a source of variability in biological invasions that may aid in ecological forecasting.
14
Papanicolaou, Panos N., and George C. Stamoulis. "Vertical Round Buoyant Jets and Fountains in a Linearly, Density-Stratified Fluid." Fluids 5, no. 4 (December 4, 2020): 232. http://dx.doi.org/10.3390/fluids5040232.
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Turbulent round buoyant jets and fountains issuing vertically into a linearly density-stratified calm ambient have been investigated in a series of laboratory experiments. The terminal (steady-state) height of rise and the mean elevation of subsequent horizontal spreading have been measured in positively buoyant jets (at source level), including pure momentum jets and plumes, as well in momentum-driven negatively buoyant jets (fountains). The results from experiments confirmed the asymptotic analysis that was based on dimensional arguments. The normalized terminal height and spreading elevation with respect to the elevation of injection of momentum-driven (positively) buoyant jets and fountains attained the same asymptotic values. The numerical results from the solution of entrainment equations, using an improved entrainment coefficient function, confirmed the results related to buoyancy dominant flows (plumes), while their predictions in momentum-driven flows were quite low if compared to measurements.
15
Dauphas, Stéphanie, Valérie Beaumal, Alain Riaublanc, and Marc Anton. "Hen Egg Yolk Low-Density Lipoproteins Film Spreading at the Air−Water and Oil−Water Interfaces." Journal of Agricultural and Food Chemistry 54, no. 10 (May 2006): 3733–37. http://dx.doi.org/10.1021/jf053174e.
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Lampitella, Valerio, Marco Trofa, Antonello Astarita, and Gaetano D’Avino. "Discrete Element Method Analysis of the Spreading Mechanism and Its Influence on Powder Bed Characteristics in Additive Manufacturing." Micromachines 12, no. 4 (April 2, 2021): 392. http://dx.doi.org/10.3390/mi12040392.
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Laser powder bed fusion additive manufacturing is among the most used industrial processes, allowing for the production of customizable and geometrically complex parts at relatively low cost. Although different aspects of the powder spreading process have been investigated, questions remain on the process repeatability on the actual beam–powder bed interaction. Given the influence of the formed bed on the quality of the final part, understanding the spreading mechanism is crucial for process optimization. In this work, a Discrete Element Method (DEM) model of the spreading process is adopted to investigate the spreading process and underline the physical phenomena occurring. With parameters validated through ad hoc experiments, two spreading velocities, accounting for two different flow regimes, are simulated. The powder distribution in both the accumulation and deposition zone is investigated. Attention is placed on how density, effective layer thickness, and particle size distribution vary throughout the powder bed. The physical mechanism leading to the observed characteristics is discussed, effectively defining the window for the process parameters.
17
Maanvizhi, M., C. Prakash, and V. Rameshbabu. "Effect of Stitch Density and Stitch Type on the Moisture Management Properties of Seams for High Active Sportswear Application." Fibres and Textiles in Eastern Europe 28, no. 6(144) (December 31, 2020): 72–78. http://dx.doi.org/10.5604/01.3001.0014.3263.
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The impact of stitch density and seam class on the moisture management properties of seams was investigated in this study. A lapped seam (Class 2) using a Flat Lock Stitch class ASTM 607 and a super imposed seam (Class 1) using an Overlock Stitch Class ASTM 514 were constructed with four different stitch densities – SPI 10, SPI 14, SPI 18 and SPI 22, and the moisture management properties of seamed fabric in terms of the spreading speed, area of spreading, absorption time, wetting time, one-way transport index and overall moisture management capability (OMMC) on the seam line were investigated. It was observed from the results that the seams made with low stitch density show better moisture management capability, and the lapped seam exhibits better moisture management capability when compared to the superimposed seam.
18
Weirauch, Douglas A. "Predicting the spreading kinetics of high-temperature liquids on solid surfaces." Journal of Materials Research 13, no. 12 (December 1998): 3504–11. http://dx.doi.org/10.1557/jmr.1998.0478.
Повний текст джерелаАнотація:
The rate of movement of liquid drops toward their equilibrium position on smooth, horizontal solid surfaces (spreading kinetics) is considered in this study. A model for nonreactive liquid spreading which was developed for low-temperature liquids is applied to results for a set of high-temperature liquids and room-temperature liquids. These data were generated in a single laboratory following a consistent experimental methodology. The liquid-solid pairs were chosen to result in weak or no interfacial chemical reaction. Furnace atmospheres were chosen to provide data for liquid metals with submonolayer, thin or thick oxide films. Analysis of the high-temperature spreading kinetics for liquids covering a broad range of viscosity, surface tension, and density shows that they can be predicted with a constant shift factor applied to the deGennes expression for nonreactive spreading. The consequences of gravitational and inertial forces, substrate roughness, weak interfacial reactions, and liquid-metal oxide films are discussed.
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Liu, Shuai, and Hanjie Guo. "Balling Behavior of Selective Laser Melting (SLM) Magnesium Alloy." Materials 13, no. 16 (August 17, 2020): 3632. http://dx.doi.org/10.3390/ma13163632.
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Macroscopic surface morphology and balling mechanism of AZ61 magnesium alloy prepared by Selective laser melting (SLM) have been investigated. This article studied and analyzed the surface morphology and balling phenomenon of Mg in the laser processing from the aspects of Mg inherent metal properties and laser processing. In terms of laser processing, the results show that, in the direction of increasing scanning speed, the energy density decreases, and the phenomenon of balling and porosity on the surface of the magnesium alloy is serious. When the energy density is 133.9–187.5 J/mm3, balling particles are significantly reduced. It can be seen from the low-magnification SEM image that, even at a scanning speed of 250 mm/s (Ev is 187.5 J/mm3), there are still a few small-sized balling particles on the surface. Therefore, in terms of inherent metal properties, the wettability, capillary instability, thermodynamic, and kinetic analysis of the balling behavior of Mg and other metal (Al, Fe, Cu, Ni, Ti) droplets in the SLM process has been carried out, and the dynamic model of magnesium droplet spreading/solidification was established basic on the result of experiment and metal inherent properties. The results show that SLMed magnesium alloy is a competitive process of melt diffusion and solidification. The final result depends on the intrinsic properties of the magnesium alloy and the applied laser processing parameters. The spreading process of Mg melt is very fast. Although the solidification time of Mg melts changes slowly with the increase of metal droplet temperature, the spreading speed is still very fast due to the low melt density, so the balling phenomenon of SLMed Mg can be controlled to a certain extent. Theoretically calculated, the solidification time of Mg melt droplet is longer than the wetting time at 1173 K (900 °C), so the spreading process is dominant, which can minimize the balling and realize the densification of SLMed Mg. The dynamic spreading of molten pool, the analysis of wetting and solidification process, and the establishment of SLM balling model can provide reference for the design of the SLM forming parameters of Mg and other different metals.
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Watt, F. M. "Effect of seeding density on stability of the differentiated phenotype of pig articular chondrocytes in culture." Journal of Cell Science 89, no. 3 (March 1, 1988): 373–78. http://dx.doi.org/10.1242/jcs.89.3.373.
Повний текст джерелаАнотація:
Articular chondrocytes are known to be phenotypically unstable in culture. One condition that has been reported to suppress dedifferentiation is cultivation at high density on tissue-culture plastic. The aim of the experiments described here was to study the effect of seeding density on chondrocyte proliferation and 35SO4 incorporation, and on the types of collagen and proteoglycan synthesized. I found that cells seeded at low or high density reached the same final density at confluence, and that 35SO4 incorporation, while initially higher (per cell) in high-density cultures, fell under both conditions, reaching the same low level after 3 weeks. The proportion of cells expressing keratan sulphate fell in low- but not high-density cultures and the decline was not prevented by inhibition of cell division. In all the cultures cells expressing keratan sulphate tended to have a rounded morphology. After 21 days in culture, chondrocytes grown at high density expressed predominantly large proteoglycans that aggregated with hyaluronic acid, whereas in low-density cultures a smaller, non-aggregating form was also present. By 21 days in culture cells at both high and low density were expressing type I collagen, although the high-density cells also had an extensive extracellular matrix of type II collagen. These observations support the conclusion that high seeding density stabilizes the chondrocyte phenotype to a greater extent than low seeding density. They also suggest that enhanced dedifferentiation at low density may be due to cell spreading, rather than to selective proliferation of a phenotypically unstable subpopulation of cells.
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Ren, Jinlian, Weigang Lu, and Tao Jiang. "Numerical Simulation of the Generalized Newtonian Free Surface Flows by a Density Reinitialization SPH Method." Mathematical Problems in Engineering 2015 (2015): 1–17. http://dx.doi.org/10.1155/2015/915973.
Повний текст джерелаАнотація:
A periodic density reinitialization smoothed particle hydrodynamics (PDRI-SPH) method is proposed to treat the generalized Newtonian free surface flows, which is based on the concept of Taylor series expansion. Meanwhile, an artificial stress term is also presented and tested, for the purpose of eliminating the unphysical phenomenon of particle clustering in fluid stretching. The free surface phenomena of a Cross model droplet impacting and spreading on an inclined rigid plate at low impacting angles are investigated numerically using the proposed PDRI-SPH method. In particular, the effect of the surface inclination and the different regimes of droplet impact, spreading and depositing on an inclined surface, are illustrated; the influence of surface inclination on the tensile instability is also concerned. The numerical results show that the accuracy and the stability of the conventional SPH are all improved by the periodic density reinitialization scheme. All numerical results agree well with the available reference data.
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Jirouskova, Marketa, Jyoti K. Jaiswal та Barry S. Coller. "Outside-In Signaling by Integrin αIIbβ3 Is Dramatically Affected by the Density of Adsorbed Fibrinogen and Results in Differences in Calcium Mobilization, Integrin Engagement, and Platelet Morphology." Blood 108, № 11 (16 листопада 2006): 1506. http://dx.doi.org/10.1182/blood.v108.11.1506.1506.
Повний текст джерелаАнотація:
Abstract αIIbβ3-mediated outside-in signaling following platelet adhesion to fibrinogen affects platelet adhesion, degranulation, and spreading, but the precise mechanisms involved remain incompletely understood. In this study, we demonstrate that the character of αIIbβ3 signaling is dependent on the surface density of the adsorbed ligand. Time-lapse total internal reflection fluorescence microscopy (TIR-FM) allowed us to visualize the interactions between fibrinogen and the αIIbβ3 integrins on the basal membrane of adhering platelets using a fluorescently-labeled antibody specific for β3. We observed significant morphological and biochemical differences in the initial interaction between αIIbβ3 and fibrinogen depending on the fibrinogen surface density. These included differences in the kinetics of filopodia and lamellipodia formation. Although filopodia started to form at the same time after initial platelet contact with both low-density (adsorbed from 3 μg/ml) fibrinogen (~ 40–50 s), new filopodia formed for a significantly shorter period of time on low- than on high-density fibrinogen [120 s (n = 79) vs. 235 s (n = 62); medians; p< 0.001]. Lamellipodia started to form in platelets adhering to low-density fibrinogen significantly later than in platelets on high-density fibrinogen (140 s vs. 110 s; p = 0.04). Moreover, once lamellipodia started to appear, formation of new filopodia ceased in platelets adhering to low-density fibrinogen. In contrast, in platelets on high-density fibrinogen new filopodia continued to form even in the presence of lamellipodia for another 155 s. We also observed that a higher percentage of platelets adherent to high-density fibrinogen (52 ± 6 %) failed to develop a cytoplasmic Ca2+ signal compared to platelets adherent to low-density fibrinogen (13 ± 11 %; n = 3; p<0.001). In addition, only 8 ± 6 % of platelets on high-density fibrinogen developed sustained Ca2+ oscillations compared to 39 ± 14 % of platelets on low-density fibrinogen (n = 3; p = 0.01). TIR-FM analysis of platelets stained with a monoclonal antibody specific for a ligand-induced binding site in the PSI domain of β3 (AP5), showed that on low-density fibrinogen only receptors in a very thin and stationary ring at the edge of fully spread platelets were stained, whereas on high-density fibrinogen AP5 stained a thicker, more diffuse, and more mobile ring. These observations suggested that αIIbβ3 interactions with high-density fibrinogen are more transient than those with low-density fibrinogen. To test this directly, platelets adherent to fibrinogen for 1 h were treated with αIIbβ3 antagonists or EDTA and the loss of adhesion was then measured. Treatement with c7E3, tirofiban, or EDTA resulted in loss of 66 ± 13%, 57 ± 21%, and 63 ± 25%, respectively, of platelets on high density fibrinogen. In contrast, the same treatments resulted in loss of only 25 ± 3%, 34 ± 14%, and 31 ± 21% of platelets on low-density fibrinogen (n = 3; p ≤ 0.01 for each treatment). Thus, we provide evidence that the density of a single immobilized ligand can profoundly affect the morphological and biochemical nature of events leading to platelet adhesion, spreading, and outside-in signaling. These observations have potential significance for hemostasis, thrombosis, and the development of biocompatible materials.
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Lister, John R., and Ross C. Kerr. "The propagation of two-dimensional and axisymmetric viscous gravity currents at a fluid interface." Journal of Fluid Mechanics 203 (June 1989): 215–49. http://dx.doi.org/10.1017/s0022112089001448.
Повний текст джерелаАнотація:
Viscous gravity currents resulting from the introduction of fluid between an upper layer of fluid of lesser density and a lower layer of greater density are analysed. The nonlinear equations governing the spread and shape of the intrusion are formulated for the cases of intrusion at low Reynolds number between deep ambient layers and of flow over a shallow layer of viscous fluid with a rigid lower boundary. Similarity solutions of these equations are obtained in both two-dimensional and axisymmetric geometries, under the assumption that the volume of intruding fluid increases with time like tα. The theoretical predictions are shown to be in reasonable agreement with experimental observations of the spreading of glucose syrups and of viscous hydrocarbons between fluid layers of differing densities. Scaling arguments are used to derive many new results for the rates of spread of intrusions in a wide variety of further situations. A compendium of spreading relations, including some previously isolated results, is derived within a coherent framework and tabulated.
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Xiao, Yang, and Kaiyao Wang. "Secure Communication for Cognitive Networks Based on MIMO and Spreading LDPC Codes." WSEAS TRANSACTIONS ON SIGNAL PROCESSING 17 (December 31, 2021): 114–22. http://dx.doi.org/10.37394/232014.2021.17.16.
Повний текст джерелаАнотація:
The existing cognitive radio (CR) systems lack the ability to deal with the attack of a pretended primary user (PPU), which can palsy cognitive network. To solve the problem, in this paper, a secure cognitive radio (CR) system is proposed. The proposed systems combines MIMO and spread spectrum techniques as well as low density parity check (LDPC) codes to cancel the electronic interference of PPU. The simulation results in Rayleigh flat-fading channel show that, comparing with MIMO cognitive system without the proposed method, the proposed approach can effectively cancel electronic interference from enemy and channel noises interference, and obtain about 9dB gain.
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Jiang, Xin Sheng, Guo Jun Sun, Biao He, Yi Hong Ou, Dong Wang, and Jian Zhong Zhou. "Research on the Initial Features and Spreading Rules of Large Scale Oil Fire." Advanced Materials Research 960-961 (June 2014): 358–65. http://dx.doi.org/10.4028/www.scientific.net/amr.960-961.358.
Повний текст джерелаАнотація:
The initial features of large scale oil fires were studied through combustion experiments in oil basins. Four basins were prepared, the diameters of two of them were 2.5m, and another two were 2m. Oil in the basins was ignited simultaneously, and the experiments were conducted twice. The thermal radiation, temperature distribution and components of pollutants were detected and analyzed. Then, some initial features and instructive rules of large scale oil fire disasters were concluded. Known from the experiments, the temperature is high in center areas and low around, in the vertical direction the temperature is high both in upper part and bottom and low in the middle. In addition, the density values of gas pollutants sampled during the experiments can reach to several hundred times of the standard values.
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Mart, Y. "The structural evolution of oceanic core complexes: A concept based on analog modeling." Geodynamics & Tectonophysics 11, no. 1 (March 19, 2020): 1–15. http://dx.doi.org/10.5800/gt-2020-11-1-0458.
Повний текст джерелаАнотація:
Oceanic core complexes are lithological assemblages of predominantly peridotites and serpentinites, located along intersections of some slow-spreading oceanic accreting rifts and fracture zones, embedded in the predominantly basaltic oceanic lithosphere, and fresh and old basalts are juxtaposed across the fracture zone. Centrifuge-based experimental models indicated that subduction would initiate at sites where two lithospheric slabs are juxtaposed, provided that the density difference between them is at least 200 kg/m3 and the friction along their contact plane is low. It was discerned that the modeled underthrust denser lithosphere would reach the modeled asthenosphere and represent tectonic subduction. In many such occurrences, extension in the over-riding slab would develop normal faults that could be penetrated by the lighter fraction of the subducted slab, generating volcanism and diapirism. These experiments suggest further that since the density contrasts and the low friction constraints could be satisfied at the intersections of fracture zones and slow-spreading oceanic ridges, subduction could occur there too and not only along ocean-continent boundaries. Furthermore, since the thermal gradient in ridge-fracture zone intersections is very steep and volatiles in the underthrust slab abound in the subducted slab, a portion of the underthrust basalts would undergo serpentinization and another segment could become peridotitic. It is suggested further that the light serpentinite would ascend through the normal faults in the over-riding slab and reach the seafloor diapirically, carrying along large sections of peridotite, to produce the serpentinite-peridotite petrology that typifies oceanic core complex at junctions of fracture zones and slow spreading ridges.
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Moskowitz, Keith, Bohdan Kudryk, and Barry Coller. "Fibrinogen Coating Density Affects the Conformation of Immobilized Fibrinogen: Implications for Platelet Adhesion and Spreading." Thrombosis and Haemostasis 79, no. 04 (1998): 824–31. http://dx.doi.org/10.1055/s-0037-1615072.
Повний текст джерелаАнотація:
SummaryAdhesion of platelets to immobilized fibrinogen appears to play an important role in a variety of physiologic and pathologic phenomena. We previously observed that the fibrinogen concentration used to coat polystyrene wells affected the morphology and distribution of GP IIb/ IIIa receptors on the surface of platelets adherent to the fibrinogen. One possible explanation for these differences is that fibrinogen immobilized at high density adopts a different conformation than fibrinogen immobilized at low density. To address this possibility, we studied the binding of a panel of anti-fibrinogen monoclonal antibodies (mAbs) to fibrinogen immobilized at different coating densities. Three different patterns of binding were observed: 1) a linear increase in binding to wells coated with 1-10 μg/ml fibrinogen, followed by a lesser increase or plateau at higher fibrinogen concentrations (mAbs Fd4-4E1, Fd4-7B3, 1D4, 4-2); 2) minimal reactivity at all fibrinogen concentrations (mAbs GC4-1A12, 2C34); 3) a biphasic response, with a linear increase up to 10 μg/ml fibrinogen and then a significant decline in binding at higher fibrinogen concentrations (mAbs 311, 31A9, FPA 19/7, 9C3, 1C5-A5/2, 44-3). The patterns of mAb binding to fibrinogen immobilized from plasma were similar. Most mAbs that demonstrated a biphasic response bound poorly or not at all to soluble fibrinogen, while mAbs that demonstrated a linear/plateau response were able to bind soluble fibrinogen. At equal surface densities, mAbs that bound biphasically, particularly mAb 1C5-A5/2, were more reactive to urea-denatured than native fibrinogen. mAbs 1C5-A5/2 and 44-3 are specific for γ 1-78 and 95-265, respectively, suggesting that the fibrinogen γ-chain may be sensitive to changes in conformation induced by immobilization. In summary, these data suggest that fibrinogen immobilized at 1-10 μg/ml adopts a conformation unlike soluble fibrinogen, while fibrinogen immobilized at >30 μg/ml adopts a more solution-like conformation. These differences in fibrinogen conformation may partially account for the ability of platelets to bind to immobilized fibrinogen without the addition of agonist, as well as the differences in spreading and GPIIb/IIIa distribution on platelets adherent to high- versus low-density immobilized fibrinogen.
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Kachelmyer, C. R., A. S. Rogachev, and A. Varma. "Mechanistic and processing studies in combustion synthesis of niobium aluminides." Journal of Materials Research 10, no. 9 (September 1995): 2260–70. http://dx.doi.org/10.1557/jmr.1995.2260.
Повний текст джерелаАнотація:
Combustion synthesis of NbAl3 and Nb2Al was studied using the volume combustion mode. The effects of heating rate and green density were examined for NbAl3 synthesis. The effect of green density was also investigated for Nb2Al. Greater reaction completion was achieved at higher heating rates and green densities. In both NbAl3 and Nb2Al samples, the reaction was initiated above the melting point of Al. Quenching (Nb+3Al) samples pressed at relatively high and low densities below the ignition temperature, and results of a particle-foil experiment, identified the spreading characteristic of molten Al over Nb, providing mechanistic details about niobium aluminide product formation.
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Estri, Mutia Nur, and Supriyanto Supriyanto. "EVALUASI POLA SPASIAL TUBERKULOSIS DI BANYUMAS MENGGUNAKAN FUZZY SET BERBASIS SISTEM INFORMASI GEOGRAFIS." Jurnal Ilmiah Matematika dan Pendidikan Matematika 1, no. 1 (April 24, 2009): 7. http://dx.doi.org/10.20884/1.jmp.2009.1.1.2974.
Повний текст джерелаАнотація:
Tuberculosis prevention in Banyumas which still become problem is the owness of case finding of positive Tuberculosis victims. It is caused by lack of supporting aspect from community. For 2007 there are 4229 cases and 367 of them are active patients who take medical treatment. This research aim to for: a). to making a map of thematic which good for knowing pattern spreading of disease of TB in Banyumas, b). knowing factors having an effect on to spreading of disease of TB in Banyumas, and c). knowing subdividing pattern (regional clustering) pursuant to spreading of disease of TB in Banyumas. This research uses method of fuzzy set with approach of Geographical Information System.Results which are obtained from this research are: a) Tuberculosis event is significantly related to poverty. It is caused by low education level and occupation of Tuberculosis victim. b) Tuberculosis spreading is not related directly to population density, age, disease status of Tuberculosis victims and distance from medical facility. Spatial distribution pattern of Tuberculosis does not follow a certain pattern and c) Tuberculosis clustering tend to cluster at poor area in the city and spread follows the river flow.
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Morrison, R. F., and E. R. Seidel. "Cell spreading and the regulation of ornithine decarboxylase." Journal of Cell Science 108, no. 12 (December 1, 1995): 3787–94. http://dx.doi.org/10.1242/jcs.108.12.3787.
Повний текст джерелаАнотація:
The aim of this study was to investigate the effect of cell spreading on the induction of ornithine decarboxylase and the rate of putrescine uptake in anchorage-dependent and anchorage-independent cells. Plating non-transformed IEC-6 epithelial cells at high versus low cell density restricted cell spreading from 900 microns 2 to approximately 140 microns 2, blunted the transient induction of ornithine decarboxylase activity from 202 to 32 pmol 14CO2/mg protein per hour and reduced the rate of [14C] putrescine uptake from 46 to 23 pmol/10(5) cells per hour. The mean spreading area of the cell population was controlled by coating tissue culture dishes with the nonadhesive polymer, polyHEMA. Ornithine decarboxylase activity and putrescine uptake correlated with cell spreading with minimal spreading (263 microns 2) corresponding to an 83% decrease in ornithine decarboxylase activity and 51% decrease in the rate of putrescine uptake. Adding the RGD peptide, Gly-Arg-Gly-Glu-Ser-Pro to the medium of sparsely plated cells resulted in rapid reductions in cell spreading concomitant with dose-dependent decreases in ornithine decarboxylase activity and putrescine uptake. Finally, minimizing cell spreading by depriving cells of substratum contact completely abolished serum-induced increases in ornithine decarboxylase and reduced the rate of putrescine uptake by 47%. In contrast to IEC-6 cells, ornithine decarboxylase of neoplastic HTC-116 cells was constitutively expressed with basal and stimulated activity (193 and 982 pmol 14CO2/mg protein per hour, respectively) completely independent of cell adhesion. Putrescine uptake, however, was abolished in the absence of cell adhesion. These data suggest that the induction of ornithine decarboxylase activity and the rate of putrescine uptake correlate with spreading of anchorage-dependent IEC-6 cells and that ornithine decarboxylase activity but not putrescine uptake, appears to be independent of spreading of neoplastic HTC-116 cells.
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Koch, Dorothy M., and Donald L. Koch. "Numerical and theoretical solutions for a drop spreading below a free fluid surface." Journal of Fluid Mechanics 287 (March 25, 1995): 251–78. http://dx.doi.org/10.1017/s0022112095000942.
Повний текст джерелаАнотація:
Numerical solutions are derived for a viscous, buoyant drop spreading below a free fluid surface. The drop has zero interfacial tension, and we consider viscosity contrasts 0.1 < λ < 10 with the surrounding fluid half-space. The density contrast between the drop and outer fluid is assumed to be small compared with the density contrast at the fluid surface. The numerical solutions for the approach and initial spread of the drop below the fluid surface are obtained using the boundary integral method. To facilitate an investigation over a larger range of viscosity contrasts and for longer time periods, we solve for the motion of gravity currents at the fluid surface. For this geometry we also solve the boundary integral equations for the cases λ = 0 and 1/λ = 0.For extensive drop spreading, the motion is described by asymptotic solutions. Three asymptotic solutions are derived, which apply for different values of the viscosity contrast relative to the aspect ratio ((radial extent R)/(drop thickness a)). For very low-viscosity drops (λ [Lt ] a/R[ln(R/a)]-1), the greatest resistance to spreading occurs at the drop rim, and the asymptotic solution is found using slender body theory. Drops with intermediate viscosity contrast (a/R [Lt ] λ [Lt ] R/a) are slowed primarily by shear stresses at the lower drop surface, and a lubrication solution (Lister & Kerr 1989) applies. The greatest resistance to the spread of very viscous drops (λ [Gt ] R/a) comes from the radial stresses within the drop, and the asymptotic solution is independent of the outer fluid. All drops having 0 [Lt ] λ [Lt ] ∞ will eventually spread according to lubrication theory, when their aspect ratio becomes sufficiently large relative to viscosity contrast.Theoretical results are compared with numerical and experimental results for drops and gravity currents spreading at a fluid surface. The solutions can be applied to aspects of planetary mantle flow where temperature variations cause significant viscosity contrasts. The low-viscosity solution has been applied to study the encounter of a hot, low-viscosity upwelling plume with a planet surface (Koch 1994). Here we apply the high-viscosity asymptotic solution to study how cold downwelling slabs spread at a depth of neutral buoyancy in the Earth's mantle.
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Ramli, Aizat Faiz, Muhammad Ikram Shabry, Mohd Azlan Abu, and Hafiz Basarudin. "A Study on the Impact of Nodes Density on the Energy Consumption of LoRa." International Journal of Interactive Mobile Technologies (iJIM) 15, no. 14 (July 28, 2021): 157. http://dx.doi.org/10.3991/ijim.v15i14.19825.
Повний текст джерелаАнотація:
LoRaWAN is one of the leading Low power wide area network (LPWAN) LPWAN technologies that compete for the formation of big scale Internet of Things (IoT). It uses LoRa protocol to achieve long range, low bit rate and low power communication. Large scale LoRaWAN based IoT deployments can consist of battery powered sensor nodes. Therefore, the energy consumption and efficiency of these nodes are crucial factors that can influence the lifetime of the network. However, there is no coherent experimental based research which identifies the factors that influence the LoRa energy efficiency at various nodes density. In this paper, results on measuring the packet delivery ratio, packet loss, data rate and energy consumption ratio ECR to gauge the energy efficiency of LoRa devices at various nodes density are presented. It is shown that the ECR of LoRa is inversely proportional to the nodes density and that the ECR of the network is smaller at higher traffic indicating better network energy efficiency. It is also demonstrated that at high node density, spreading factor SF of 7 and 9 can improve the energy efficiency of the network by 5 and 3 times, respectively, compare to SF 11.
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Stocker, Thomas, Joachim Pircher, Artid Skenderi, Andreas Ehrlich, Clemens Eberle, Remco Megens, Tobias Petzold, et al. "The Actin Regulator Coronin-1A Modulates Platelet Shape Change and Consolidates Arterial Thrombosis." Thrombosis and Haemostasis 118, no. 12 (November 19, 2018): 2098–111. http://dx.doi.org/10.1055/s-0038-1675604.
Повний текст джерелаАнотація:
AbstractCoronin-1A (Coro1A) belongs to a family of highly conserved actin-binding proteins that regulate cytoskeletal re-arrangement. In mammalians, Coro1A expression is most abundant in the haematopoietic lineage, where it regulates various cellular processes. The role of Coro1A in platelets has been previously unknown. Here, we identified Coro1A in human and mouse platelets. Genetic absence of Coro1A in mouse platelets inhibited agonist-induced actin polymerization and altered cofilin phosphoregulation, leading to a reduction in spreading and low-dose collagen induced aggregation. Furthermore, Coro1A-deficient mice displayed a defect in ferric chloride-induced arterial thrombosis with prolonged thrombus formation and reduced thrombus size. Immunofluorescence analysis revealed a less compact thrombus structure with reduced density of platelets and fibrinogen. In summary, Coro1A has a role in platelet biology with impact on spreading, aggregation and thrombosis.
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Tu, Chenming, Qing Liang, Chunhui Tao, Zhikui Guo, Zhengwang Hu, and Chao Chen. "Gravity Data Reveal New Evidence of an Axial Magma Chamber Beneath Segment 27 in the Southwest Indian Ridge." Minerals 12, no. 10 (September 27, 2022): 1221. http://dx.doi.org/10.3390/min12101221.
Повний текст джерелаАнотація:
Hydrothermal systems are integral to mid-ocean ridge activity; they form massive seafloor sulfide (SMS) deposits rich in various metallic elements, which are potential mineral resources. Since 2007, many hydrothermal fields have been discovered along the ultraslow-spreading Southwest Indian Ridge (SWIR). The Duanqiao hydrothermal field is located at segment 27’s axis between the Indomed and Gallieni transform faults; tomography models reveal an obvious low-velocity anomaly beneath it, indicating a possible axial magma chamber (AMC). However, confirmation of an AMC’s existence requires further study and evidence. In this study, we first calculated the gravity effect to identify the heterogeneous distribution of crustal density beneath segment 27 and the surrounding area. Next, we used the gravity-inversion method to obtain the crustal density structure beneath the study area. The results indicate that a thickened crust and low-density crustal materials exist beneath segment 27. The low-density anomaly in the lower crust beneath the Duanqiao hydrothermal field suggests the existence of an AMC covered with a cold and dense upper crust. The density results identify several faults, which provide potential channels for magma migration. In addition, the melt migrates westward and redistributes laterally toward the segment’s western end. However, when migrating toward the segment’s eastern end, the melt is affected by a rapid cooling mechanism. Therefore, the segment’s ends present different density features and morphologies of nontransform discontinuities (NTDs).
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Chametla, R. O., and O. Chrenko. "Spreading pressure bumps in gas-dust discs can stall planet migration via planet-vortex interactions." Monthly Notices of the Royal Astronomical Society 512, no. 2 (March 8, 2022): 2189–201. http://dx.doi.org/10.1093/mnras/stac611.
Повний текст джерелаАнотація:
ABSTRACT We investigate the gravitational interaction between low- to intermediate-mass planets ($M_p \in [0.06-210]\, \mathrm{ M}_{\oplus }$) and two previously formed pressure bumps in a gas-dust protoplanetary disc. We explore how the disc structure changes due to planet-induced perturbations and also how the appearance of vortices affects planet migration. We use multifluid 2D hydrodynamical simulations and the dust is treated in the pressureless-fluid approximation, assuming a single grain size of $5\, \mu {\mathrm{m}}$. The initial surface density profiles containing two bumps are motivated by recent observations of the protoplanetary disc HD163296. When planets are allowed to migrate, either a single planet from the outer pressure maximum or two planets from each pressure maximum, the initial pressure bumps quickly spread and merge into a single bump which is radially wide and has a very low amplitude. The redistribution of the disc material is accompanied by the Rossby Wave Instability and an appearance of mini-vortices that merge in a short period of time to form a large vortex. The large vortex induces perturbations with a spiral wave pattern that propagate away from the vortex as density waves. We found that these vortex-induced spiral waves strongly interact with the spiral waves generated by the planet and we called this mechanism the ‘Faraway Interaction’. It facilitates much slower and/or stagnant migration of the planets and it excites their orbital eccentricities in some cases. Our study provides a new explanation for how rocky planets can come to have a slow migration in protoplanetary discs where vortex formation occurs.
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Wraith, Katie S., Simbarashe Magwenzi, Ahmed Aburima, Yichuan Wen, David Leake, and Khalid M. Naseem. "Oxidised low-density lipoproteins induce platelet adhesion, activation and spreading through novel CD36-tyrosine kinase/Rho kinase dependent signalling pathways." Atherosclerosis 232, no. 2 (February 2014): e7. http://dx.doi.org/10.1016/j.atherosclerosis.2013.11.018.
Повний текст джерела
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Xia, Yan, Ted Hsuan Yun Chen, and Mikko Kivelä. "Limits of Multilayer Diffusion Network Inference in Social Media Research." Proceedings of the International AAAI Conference on Web and Social Media 16 (May 31, 2022): 1145–56. http://dx.doi.org/10.1609/icwsm.v16i1.19365.
Повний текст джерелаАнотація:
Information on social media spreads through an underlying diffusion network that connects people of common interests and opinions. This diffusion network often comprises multiple layers, each capturing the spreading dynamics of a certain type of information characterized by, for example, topic, language, or attitude. Researchers have previously proposed methods to infer these underlying multilayer diffusion networks from observed spreading patterns, but little is known about how well these methods perform across the range of realistic spreading data. In this paper, we conduct an extensive series of synthetic data experiments to systematically analyze the performance of the multilayer diffusion network inference framework, under varied network structure (e.g. density, number of layers) and information diffusion settings (e.g. cascade size, layer mixing) that are designed to mimic real-world spreading on social media. Our results show extreme performance variation of the inference framework: notably, it achieves much higher accuracy when inferring a denser diffusion network, while it fails to decompose the diffusion network correctly when most cascades in the data reach a limited audience. In demonstrating the conditions under which the inference accuracy is extremely low, our paper highlights the need to carefully evaluate the applicability of the inference before running it on real data. Practically, our results serve as a reference for this evaluation, and our publicly available implementation, which outperforms previous implementations in accuracy, supports further testing under personalized settings.
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Noll, Stefan, Martin Rambach, Michael Grieb, Dick Scholten, Anton J. Bauer, and Lothar Frey. "Influence of Annealing, Oxidation and Doping on Conduction-Band near Interface Traps in 4H-SiC Characterized by Low Temperature Conductance Measurements." Materials Science Forum 821-823 (June 2015): 476–79. http://dx.doi.org/10.4028/www.scientific.net/msf.821-823.476.
Повний текст джерелаАнотація:
Current power MOSFET devices on Silicon Carbide show a limited inversion channel mobility, which can be a result of the expected very high density of interface states near the conduction band . In the current work, the effect of the post implantation annealing temperature, the thermal oxidation and the nitrogen doping of the n-epi layer on the density of these interface traps is investigated using capacity-conductance measurements. Instead of the usage of very high frequencies as used in , in this investigation the measurements were performed in liquid nitrogen to decrease the recharging times of the interface traps.Due to the different processing the samples showed a wide spreading of the inversion channel mobility. The conductance measurements show a characteristic peak caused by the conduction band near interface traps especially for the low temperature measurements. But these traps could not be correlated to the mobility. Instead, a correlation to the nitrogen doping of the epi layer could be observed.
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Govender, Preyin, Deborah Clare Blaine, and Natasha Sacks. "INFLUENCE OF POWDER CHARACTERISTICS ON THE SPREADABILITY OF PRE-ALLOYED TUNGSTEN- CARBIDE COBALT." South African Journal of Industrial Engineering 32, no. 3 (2021): 284–89. http://dx.doi.org/10.7166/32-3-2664.
Повний текст джерелаАнотація:
With rising interest in additive manufacturing (AM) techniques, there is an increased focus on research that evaluates critical parameters that guide the selection of powders that are suitable for AM. One such parameter is a powder’s spreadability, described by metrics such as powder bed density and percentage coverage. This study focused on three spray-dried WC-Co powders (two 12 wt% and one 17 wt% Co) and evaluated the influence of typical powder characteristics, such as particle size and shape, apparent density, and flow rate, on their spreadability. It was found that particle size distribution influenced the powder spreadability. Larger particles hindered the even spreading of powder over the base plate, resulting in low powder bed density and percentage coverage. This also correlated with the powders’ apparent densities. The flow rate and angle of repose gave an indication of how cohesive the powders are. The more cohesive a powder, the poorer the spreadability, resulting in a lower powder bed density and percentage coverage.
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Wang, Pu, and Marta C. González. "Understanding spatial connectivity of individuals with non-uniform population density." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1901 (August 28, 2009): 3321–29. http://dx.doi.org/10.1098/rsta.2009.0089.
Повний текст джерелаАнотація:
We construct a two-dimensional geometric graph connecting individuals placed in space within a given contact distance. The individuals are distributed using a measured country’s density of population. We observe that while large clusters (group of individuals connected) emerge within some regions, they are trapped in detached urban areas owing to the low population density of the regions bordering them. To understand the emergence of a giant cluster that connects the entire population, we compare the empirical geometric graph with the one generated by placing the same number of individuals randomly in space. We find that, for small contact distances, the empirical distribution of population dominates the growth of connected components, but no critical percolation transition is observed in contrast to the graph generated by a random distribution of population. Our results show that contact distances from real-world situations as for WIFI and Bluetooth connections drop in a zone where a fully connected cluster is not observed, hinting that human mobility must play a crucial role in contact-based diseases and wireless viruses’ large-scale spreading.
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da Cunha Lima, A. T., I. C. da Cunha Lima, and M. P. de Almeida. "Analysis of turbulence power spectra and velocity correlations in a pipeline with obstructions." International Journal of Modern Physics C 28, no. 02 (February 2017): 1750019. http://dx.doi.org/10.1142/s012918311750019x.
Повний текст джерелаАнотація:
We calculate the power spectral density and velocity correlations for a turbulent flow of a fluid inside a duct. Turbulence is induced by obstructions placed near the entrance of the flow. The power spectral density is obtained for several points at cross-sections along the duct axis, and an analysis is made on the way the spectra changes according to the distance to the obstruction. We show that the differences on the power spectral density are important in the lower frequency range, while in the higher frequency range, the spectra are very similar to each other. Our results suggest the use of the changes on the low frequency power spectral density to identify the occurrence of obstructions in pipelines. Our results show some frequency regions where the power spectral density behaves according to the Kolmogorov hypothesis. At the same time, the calculation of the power spectral densities at increasing distances from the obstructions indicates an energy cascade where the spectra evolves in frequency space by spreading the frequency amplitude.
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Kinoshita, Y., C. Kinoshita, J. G. Heuer, and M. Bothwell. "Basic fibroblast growth factor promotes adhesive interactions of neuroepithelial cells from chick neural tube with extracellular matrix proteins in culture." Development 119, no. 3 (November 1, 1993): 943–56. http://dx.doi.org/10.1242/dev.119.3.943.
Повний текст джерелаАнотація:
Fibroblast growth factors have been increasingly assigned mitogenic and trophic roles in embryonic and postnatal development of the nervous system. Little is known, however, of their functional roles in early embryonic neural development at the neural tube stage. We have examined the effect of basic fibroblast growth factor (bFGF) on the adhesive behavior in culture of dissociated brachio-thoracic neural tube cells from 26- to 30-somite stage chick embryos. Cells plated on collagen-coated substratum at a low density attach to the substratum but show poor cell spreading. Addition of bFGF markedly promotes cell spreading, yielding an epithelial morphology. This effect becomes discernible 6–8 hours after cell plating with bFGF and is completed by 24 hours, with half-maximal and maximal effects attained at around 0.4 and 10 ng/ml, respectively. The number of cells remain largely constant up to 24 hours, and then cell survival and/or mitogenic effects of bFGF become apparent. The cell spreading effect is abolished by cycloheximide treatment, inhibited by the anti-beta 1-integrin antibody CSAT, and accompanied by about twofold increases in the expression of beta 1-integrin and vinculin, components of focal adhesion complexes. Cells cultured with bFGF for 24 hours exhibit enhanced cell attachment and cell spreading with little time lag following cell plating. In earlier embryonic stages, developmentally less mature cells depend much more on bFGF for their cell spreading and survival, while in later stages the cell spreading response to bFGF becomes undetectable as neural tube develops to spinal cord. The cell spreading effect of bFGF is realized on specific extracellular matrix proteins including laminin, fibronectin and collagen, but not on vitronectin, arg-gly-asp peptide (PepTite-2000), poly-L-ornithine or others. These results suggest that, in an early stage of neural tube development, bFGF is involved in the developmental regulation of adhesive interactions between neuroepithelial cells and the extracellular matrix, thereby controlling their proliferation, migration and differentiation.
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Miller, Yury I., Dorothy S. Worrall, Colin D. Funk, James R. Feramisco, and Joseph L. Witztum. "Actin Polymerization in Macrophages in Response to Oxidized LDL and Apoptotic Cells: Role of 12/15-Lipoxygenase and Phosphoinositide 3-Kinase." Molecular Biology of the Cell 14, no. 10 (October 2003): 4196–206. http://dx.doi.org/10.1091/mbc.e03-02-0063.
Повний текст джерелаАнотація:
Formation of filamentous F-actin drives many cellular processes, including phagocytosis and cell spreading. We have recently reported that mouse macrophage 12/15-lipoxygenase (12/15-LO) activity promotes F-actin formation in filopodia during phagocytosis of apoptotic cells. Oxidized low-density lipoprotein (OxLDL) also stimulates robust F-actin formation and spreading of macrophages. However, unlike apoptotic cells, OxLDL did not cause specific translocation of 12/15-LO to the cell membrane, neither in macrophages nor in GFP-15LO–transfected COS-7 cells. Moreover, inhibition of 12/15-LO activity in macrophages by a specific inhibitor or by 12/15-LO gene disruption did not affect OxLDL-induced actin polymerization. Among LDL modifications modeling OxLDL, LDL modified by incubation with 15LO-overexpressing fibroblasts was as active in eliciting F-actin response as was OxLDL. This LDL modification is well known to produce minimally modified LDL (mmLDL), which is bioactive and carries lipid oxidation products similar to those produced by 12/15-LO catalysis. MmLDL activated phosphoinositide 3-kinase (PI3K), and PI3K inhibitors abolished mmLDL-induced macrophage spreading. We hypothesize that OxLDL and mmLDL may contribute oxidized lipids to the macrophage cell membrane and thereby mimic intracellular 12/15-LO activity, which leads to uncontrolled actin polymerization and dramatic cytoskeletal changes in macrophages.
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Parizek, Martin, Nikola Slepickova Kasalkova, Lucie Bacakova, Zdenek Svindrych, Petr Slepicka, Marketa Bacakova, Vera Lisa, and Vaclav Svorcik. "Adhesion, Growth, and Maturation of Vascular Smooth Muscle Cells on Low-Density Polyethylene Grafted with Bioactive Substances." BioMed Research International 2013 (2013): 1–18. http://dx.doi.org/10.1155/2013/371430.
Повний текст джерелаАнотація:
The attractiveness of synthetic polymers for cell colonization can be affected by physical, chemical, and biological modification of the polymer surface. In this study, low-density polyethylene (LDPE) was treated by an Ar+plasma discharge and then grafted with biologically active substances, namely, glycine (Gly), polyethylene glycol (PEG), bovine serum albumin (BSA), colloidal carbon particles (C), or BSA+C. All modifications increased the oxygen content, the wettability, and the surface free energy of the materials compared to the pristine LDPE, but these changes were most pronounced in LDPE with Gly or PEG, where all the three values were higher than in the only plasma-treated samples. When seeded with vascular smooth muscle cells (VSMCs), the Gly- or PEG-grafted samples increased mainly the spreading and concentration of focal adhesion proteins talin and vinculin in these cells. LDPE grafted with BSA or BSA+C showed a similar oxygen content and similar wettability, as the samples only treated with plasma, but the nano- and submicron-scale irregularities on their surface were more pronounced and of a different shape. These samples promoted predominantly the growth, the formation of a confluent layer, and phenotypic maturation of VSMC, demonstrated by higher concentrations of contractile proteins alpha-actin and SM1 and SM2 myosins. Thus, the behavior of VSMC on LDPE can be regulated by the type of bioactive substances that are grafted.
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Link, Arthur F., Trey Turnblacer, Cierra K. Snyder, Sarah E. Daugherty, and Ryan M. Utz. "Low Recruitment of Native Trees in a Deciduous Forest Associated with Japanese Barberry (Berberis thunbergii) Invasion." Invasive Plant Science and Management 11, no. 1 (February 6, 2018): 20–26. http://dx.doi.org/10.1017/inp.2018.1.
Повний текст джерелаАнотація:
AbstractInvasive plants may dramatically impact forest ecosystems by establishing dense populations and suppressing the recruitment of native tree species. One invasive shrub currently spreading throughout eastern deciduous forests of North America, Japanese barberry (Berberis thunbergii DC), may be limiting tree recruitment in stands where it invades. Once established, B. thunbergii becomes densely populated within forest understories and suppresses native plants by competing for limited resources, altering soil conditions, and changing the understory microclimate. To quantify native seedling inhibition caused by B. thunbergii invasion, we conducted an observational study on seedling abundance within forest plots that were either invaded or not invaded by B. thunbergii and used survey data to generate Bayesian models of native seedling densities along gradients of increasing B. thunbergii stem counts and aboveground plant dry mass. Model outputs predicted that B. thunbergii–invaded plots had 82% lower seedling densities compared with uninvaded plots. Native tree seedling densities were very low even in areas with moderate B. thunbergii density, suggesting that reduced tree seedling densities are observed even at low densities of invasion. Our findings indicate that forests invaded with B. thunbergii harbor substantially lower densities of native tree seedlings, with potentially significant long-term consequences for forest ecological integrity, biodiversity, and ecosystem services.
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Wetchayont, Parichat, and Katawut Waiyasusri. "Using Moran’s I For Detection And Monitoring Of The Covid-19 Spreading Stage In Thailand During The Third Wave Of The Pandemic." GEOGRAPHY, ENVIRONMENT, SUSTAINABILITY 14, no. 4 (December 29, 2021): 155–67. http://dx.doi.org/10.24057/2071-9388-2021-090.
Повний текст джерелаАнотація:
Spatial distribution and spreading patterns of COVID-19 in Thailand were investigated in this study for the 1 April – 23 July 2021 period by analyzing COVID-19 incidence’s spatial autocorrelation and clustering patterns in connection to population density, adult population, mean income, hospital beds, doctors and nurses. Clustering analysis indicated that Bangkok is a significant hotspot for incidence rates, whereas other cities across the region have been less affected. Bivariate Moran’s I showed a low relationship between COVID-19 incidences and the number of adults (Moran’s I = 0.1023- 0.1985), whereas a strong positive relationship was found between COVID-19 incidences and population density (Moran’s I = 0.2776-0.6022). Moreover, the difference Moran’s I value in each parameter demonstrated the transmission level of infectious COVID-19, particularly in the Early (first phase) and Spreading stages (second and third phases). Spatial association in the early stage of the COVID-19 outbreak in Thailand was measured in this study, which is described as a spatio-temporal pattern. The results showed that all of the models indicate a significant positive spatial association of COVID-19 infections from around 10 April 2021. To avoid an exponential spread over Thailand, it was important to detect the spatial spread in the early stages. Finally, these findings could be used to create monitoring tools and policy prevention planning in future.
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Trapman, L., G. Rosotti, A. D. Bosman, M. R. Hogerheijde, and E. F. van Dishoeck. "Observed sizes of planet-forming disks trace viscous spreading." Astronomy & Astrophysics 640 (July 28, 2020): A5. http://dx.doi.org/10.1051/0004-6361/202037673.
Повний текст джерелаАнотація:
Context. The evolution of protoplanetary disks is dominated by the conservation of angular momentum, where the accretion of material onto the central star is fed by the viscous expansion of the outer disk or by disk winds extracting angular momentum without changing the disk size. Studying the time evolution of disk sizes therefore allows us to distinguish between viscous stresses or disk winds as the main mechanism of disk evolution. Observationally, estimates of the size of the gaseous disk are based on the extent of CO submillimeter rotational emission, which is also affected by the changing physical and chemical conditions in the disk during the evolution. Aims. We study how the gas outer radius measured from the extent of the CO emission changes with time in a viscously expanding disk. We also investigate to what degree this observable gas outer radius is a suitable tracer of viscous spreading and whether current observations are consistent with viscous evolution. Methods. For a set of observationally informed initial conditions we calculated the viscously evolved density structure at several disk ages and used the thermochemical code DALI to compute synthetic emission maps, from which we measured gas outer radii in a similar fashion as observations. Results. The gas outer radii (RCO, 90%) measured from our models match the expectations of a viscously spreading disk: RCO, 90% increases with time and, for a given time, RCO, 90% is larger for a disk with a higher viscosity αvisc. However, in the extreme case in which the disk mass is low (Mdisk ≤ 10−4 M⊙) and αvisc is high (≥10−2), RCO, 90% instead decreases with time as a result of CO photodissociation in the outer disk. For most disk ages, RCO, 90% is up to ~12× larger than the characteristic size Rc of the disk, and RCO, 90%/Rc is largest for the most massive disk. As a result of this difference, a simple conversion of RCO, 90% to αvisc overestimates the true αvisc of the disk by up to an order of magnitude. Based on our models, we find that most observed gas outer radii in Lupus can be explained using viscously evolving disks that start out small (Rc(t = 0) ≃ 10 AU) and have a low viscosity (αvisc = 10−4−10−3). Conclusions. Current observations are consistent with viscous evolution, but expanding the sample of observed gas disk sizes to star-forming regions, both younger and older, would better constrain the importance of viscous spreading during disk evolution.
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Dobreva, Iveta, Gérard Waeber, Richard W. James, and Christian Widmann. "Interleukin-8 Secretion by Fibroblasts Induced by Low Density Lipoproteins Is p38 MAPK-dependent and Leads to Cell Spreading and Wound Closure." Journal of Biological Chemistry 281, no. 1 (October 26, 2005): 199–205. http://dx.doi.org/10.1074/jbc.m508857200.
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Paine, R., D. Gaposchkin, C. Kelly, and S. E. Wilcoxen. "Regulation of cytokeratin expression in rat lung alveolar epithelial cells in vitro." American Journal of Physiology-Lung Cellular and Molecular Physiology 269, no. 4 (October 1, 1995): L536—L544. http://dx.doi.org/10.1152/ajplung.1995.269.4.l536.
Повний текст джерелаАнотація:
Type II pneumocytes are the stem cells for the alveolar epithelium, proliferating and differentiating into type I cells during lung growth or after injury. The pattern of cytokeratin expression by type II cells in vitro has been linked to the state of differentiation of these cells. In particular, cytokeratin 19 expression has been associated with the type II cell phenotype. We now examine the roles of cell shape and cell-cell interactions in the regulation of cytokeratin expression by rat type II cells in vitro. Type II cell spreading and intercellular contacts were modulated by seeding cultures at high or low density (3.5 or 0.5 x 10(5) cells/cm2). When cultured at high density, cells demonstrated increased cytokeratin 19 protein synthesis and diminished cytokeratin 18 protein synthesis compared with highly spread cells at low density. This effect was a reflection of changes in the abundance of mRNAs for the individual cytokeratins. Alveolar epithelial cells at high density also formed extensive desmosomes between the cells. Desmosome formation was significantly decreased when cells were seeded at low density or in reduced (0.05 mM) calcium medium. Cytokeratin 19 mRNA and protein expression were also significantly decreased when desmosome formation was inhibited in reduced calcium medium, while calcium content of the medium had little effect on cytokeratin 18. These studies suggest that type II cell expression of cytokeratin 19, a differentiation-related cytokeratin, is regulated by factors influencing cell shape and intercellular contacts between epithelial cells. They further suggest that cell-cell interactions between epithelial cells may play a role in the modulation of epithelial cell phenotype.
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Li, Nami, X. Q. Xu, Y. F. Wang, X. Lin, N. Yan, and G. S. Xu. "Impact of pedestal density gradient and collisionality on ELM dynamics." Physics of Plasmas 29, no. 12 (December 2022): 122302. http://dx.doi.org/10.1063/5.0111669.
Повний текст джерелаАнотація:
BOUT++ turbulence simulations are conducted to capture the underlying physics of small ELM characteristics achieved by increasing separatrix density via controlling strike points from vertical to horizontal divertor plates for three EAST discharges. BOUT++ linear simulations show that the most unstable modes change from high-n ideal ballooning modes to intermediate-n peeling–ballooning modes and eventually to peeling–ballooning stable plasmas in the pedestal. Nonlinear simulations show that the fluctuation is saturated at a high level for the lowest separatrix density. The ELM size decreases with increasing separatrix density, until the fraction of this energy lost during the ELM crash becomes less than 1% of the pedestal stored energy, leading to small ELMs. Simulations indicate that small ELMs can be triggered either by the marginally peeling–ballooning instability near the peak pressure gradient position inside the pedestal or by a local instability in the pedestal foot with a larger separatrix density gradient. The pedestal collisionality scan for type-I ELMs with steep pedestal density gradient shows that both linear growth rate and ELM size decrease with increasing collisionality. On the contrary, the pedestal collisionality and pedestal density width scan with a weak pedestal density gradient indicate small ELMs can either be triggered by a high-n ballooning mode or by a low-n peeling mode in a low collisionality region 0.04–0.1. The simulations indicate the weaker the linear unstable modes near marginal stability with small linear growth rate, the lower nonlinearly saturated fluctuation intensity and the smaller turbulence spreading from the linear unstable zone to stable zone in the nonlinear saturation phase, leading to small ELMs.