Journal articles: 'Clumping'

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Dove, Alan W. "Clumping lysosomes." Journal of Cell Biology 154, no. 1 (July 9, 2001): 11. http://dx.doi.org/10.1083/jcb.1541iti6.

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Maroso, Mattia. "Unraveling protein clumping." Science 369, no. 6508 (September 3, 2020): 1203.17–1205. http://dx.doi.org/10.1126/science.369.6508.1203-q.

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Biernaskie, Jay M., and Stuart A. West. "Cooperation, clumping and the evolution of multicellularity." Proceedings of the Royal Society B: Biological Sciences 282, no. 1813 (August 22, 2015): 20151075. http://dx.doi.org/10.1098/rspb.2015.1075.

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The evolution of multicellular organisms represents one of the major evolutionary transitions in the history of life. A potential advantage of forming multicellular clumps is that it provides an efficiency benefit to pre-existing cooperation, such as the production of extracellular ‘public goods’. However, this is complicated by the fact that cooperation could jointly evolve with clumping, and clumping could have multiple consequences for the evolution of cooperation. We model the evolution of clumping and a cooperative public good, showing that (i) when considered separately, both clumping and public goods production gradually increase with increasing genetic relatedness; (ii) in contrast, when the traits evolve jointly, a small increase in relatedness can lead to a major shift in evolutionary outcome—from a non-clumping state with low public goods production to a cooperative clumping state with high values of both traits; (iii) high relatedness makes it easier to get to the cooperative clumping state and (iv) clumping can be inhibited when it increases the number of cells that the benefits of cooperation must be shared with, but promoted when it increases relatedness between those cells. Overall, our results suggest that public goods sharing can facilitate the formation of well-integrated cooperative clumps as a first step in the evolution of multicellularity.

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Rubio-Díez, M. M., F. Najarro, J. O. Sundqvist, A. Traficante, J. Puls, L. Calzoletti, A. Herrero, D. Figer, and J. Martin-Pintado. "Herschel/PACS: Constraining clumping in the intermediate wind region of OB stars." Proceedings of the International Astronomical Union 9, S307 (June 2014): 137–39. http://dx.doi.org/10.1017/s1743921314006565.

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AbstractAt present, it is well established that previously accepted mass-loss rates (Ṁ) of luminous OB stars may be overestimated when clumping is neglected. Our Herschel/PACS Far-Infrared (Far-IR) observations of a set of OB stars allow us to improve our knowledge of clumping stratification, constraining clumping properties in intermediate wind regions. In this work, better sampled clumping structure estimates are provided for ι Ori, ε Ori and ξ Per as well as an initial estimate of the clumping properties of the wind from τ Sco. These observations will allow us to obtain reliable mass-loss rates and improve our understanding of the wind physics.

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Bianco, Michele, Ilian T. Iliev, Kyungjin Ahn, Sambit K. Giri, Yi Mao, Hyunbae Park, and Paul R. Shapiro. "The impact of inhomogeneous subgrid clumping on cosmic reionization – II. Modelling stochasticity." Monthly Notices of the Royal Astronomical Society 504, no. 2 (March 24, 2021): 2443–60. http://dx.doi.org/10.1093/mnras/stab787.

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ABSTRACT Small-scale density fluctuations can significantly affect reionization, but are typically modelled quite crudely. Unresolved fluctuations in numerical simulations and analytical calculations are included using a gas clumping factor, typically assumed to be independent of the local environment. In Paper I, we presented an improved, local density-dependent model for the sub-grid gas clumping. Here, we extend this using an empirical stochastic model based on the results from high-resolution numerical simulations which fully resolve all relevant fluctuations. Our model reproduces well both the mean density-clumping relation and its scatter. We applied our stochastic model, along with the mean clumping one and the Paper I deterministic model, to create large-volume realizations of the clumping field, and used these in radiative transfer simulations of cosmic reionization. Our results show that the simplistic mean clumping model delays reionization compared to local density-dependent models, despite producing fewer recombinations overall. This is due to the very different spatial distribution of clumping, resulting in much higher photoionization rates in the latter cases. The mean clumping model produces smaller H ii regions throughout most of reionization, but those percolate faster at late times. It also causes a significant delay in the 21-cm fluctuations peak and yields lower non-Gaussianity and many fewer bright pixels in the PDF distribution. The stochastic density-dependent model shows relatively minor differences from the deterministic one, mostly concentrated around overlap, where it significantly suppresses the 21-cm fluctuations, and at the bright tail of the 21-cm PDFs, where it produces noticeably more bright pixels.

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Mao, Yi, Jun Koda, Paul R. Shapiro, Ilian T. Iliev, Garrelt Mellema, Hyunbae Park, Kyungjin Ahn, and Michele Bianco. "The impact of inhomogeneous subgrid clumping on cosmic reionization." Monthly Notices of the Royal Astronomical Society 491, no. 2 (October 24, 2019): 1600–1621. http://dx.doi.org/10.1093/mnras/stz2986.

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ABSTRACT Cosmic reionization was driven by the imbalance between early sources and sinks of ionizing radiation, both of which were dominated by small-scale structure and are thus usually treated in cosmological reionization simulations by subgrid modelling. The recombination rate of intergalactic hydrogen is customarily boosted by a subgrid clumping factor, 〈n2〉/〈n〉2, which corrects for unresolved fluctuations in gas density n on scales below the grid-spacing of coarse-grained simulations. We investigate in detail the impact of this inhomogeneous subgrid clumping on reionization and its observables, as follows: (1) Previous attempts generally underestimated the clumping factor because of insufficient mass resolution. We perform a high-resolution N-body simulation that resolves haloes down to the pre-reionization Jeans mass to derive the time-dependent, spatially varying local clumping factor and a fitting formula for its correlation with local overdensity. (2) We then perform a large-scale N-body and radiative transfer simulation that accounts for this inhomogeneous subgrid clumping by applying this clumping factor-overdensity correlation. Boosting recombination significantly slows the expansion of ionized regions, which delays completion of reionization and suppresses 21 cm power spectra on large scales in the later stages of reionization. (3) We also consider a simplified prescription in which the globally averaged, time-evolving clumping factor from the same high-resolution N-body simulation is applied uniformly to all cells in the reionization simulation, instead. Observables computed with this model agree fairly well with those from the inhomogeneous clumping model, e.g. predicting 21 cm power spectra to within 20 per cent error, suggesting it may be a useful approximation.

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Haim, M., A. Trost, C. J. Maier, G. Achatz, S. Feichtner, H. Hintner, J. W. Bauer, and K. önder. "Cytokeratin 8 interacts with clumping factor B: a new possible virulence factor target." Microbiology 156, no. 12 (December 1, 2010): 3710–21. http://dx.doi.org/10.1099/mic.0.034413-0.

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Staphylococcus aureus is a human pathogen of growing clinical significance, owing to its increasing levels of resistance to most antibiotics. Infections range from mild wound infections to severe infections such as endocarditis, osteomyelitis and septic shock. Adherence of S. aureus to human host cells is an important step, leading to colonization and infection. Adherence is mediated by a multiplicity of proteins expressed on the bacterial surface, including clumping factor B. In this study, we aimed to identify new targets of clumping factor B in human keratinocytes by undertaking a genome-wide yeast two-hybrid screen of a human keratinocyte cDNA library. We show that clumping factor B is capable of binding cytokeratin 8 (CK8), a type II cytokeratin. Using a domain-mapping strategy we identified amino acids 437–464 as necessary for this interaction. Recombinantly expressed fragments of both proteins were used in pull-down experiments and confirmed the yeast two-hybrid studies. Analysis with S. aureus strain Newman deficient in clumping factor B showed the clumping factor B-dependence of the interaction with CK8. We postulate that the clumping factor B–CK8 interaction is a novel factor in S. aureus infections.

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Bible, Amber N., Gurusahai K. Khalsa-Moyers, Tanmoy Mukherjee, Calvin S. Green, Priyanka Mishra, Alicia Purcell, Anastasia Aksenova, Gregory B. Hurst, and Gladys Alexandre. "Metabolic Adaptations of Azospirillum brasilense to Oxygen Stress by Cell-to-Cell Clumping and Flocculation." Applied and Environmental Microbiology 81, no. 24 (September 25, 2015): 8346–57. http://dx.doi.org/10.1128/aem.02782-15.

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ABSTRACTThe ability of bacteria to monitor their metabolism and adjust their behavior accordingly is critical to maintain competitiveness in the environment. The motile microaerophilic bacteriumAzospirillum brasilensenavigates oxygen gradients by aerotaxis in order to locate low oxygen concentrations that can support metabolism. When cells are exposed to elevated levels of oxygen in their surroundings, motileA. brasilensecells implement an alternative response to aerotaxis and form transient clumps by cell-to-cell interactions. Clumping was suggested to represent a behavior protecting motile cells from transiently elevated levels of aeration. Using the proteomics of wild-type and mutant strains affected in the extent of their clumping abilities, we show that cell-to-cell clumping represents a metabolic scavenging strategy that likely prepares the cells for further metabolic stresses. Analysis of mutants affected in carbon or nitrogen metabolism confirmed this assumption. The metabolic changes experienced as clumping progresses prime cells for flocculation, a morphological and metabolic shift of cells triggered under elevated-aeration conditions and nitrogen limitation. The analysis of various mutants during clumping and flocculation characterized an ordered set of changes in cell envelope properties accompanying the metabolic changes. These data also identify clumping and early flocculation to be behaviors compatible with the expression of nitrogen fixation genes, despite the elevated-aeration conditions. Cell-to-cell clumping may thus license diazotrophy to microaerophilicA. brasilensecells under elevated oxygen conditions and prime them for long-term survival via flocculation if metabolic stress persists.

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Wichelhaus, Thomas A., Sylvia Kern, Volker Schäfer, and Volker Brade. "Rapid Detection of Epidemic Strains of Methicillin-Resistant Staphylococcus aureus." Journal of Clinical Microbiology 37, no. 3 (1999): 690–93. http://dx.doi.org/10.1128/jcm.37.3.690-693.1999.

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Fifty methicillin-resistant Staphylococcus aureus(MRSA) initial isolates obtained from patients hospitalized in the orthopedic clinic of the Frankfurt University Hospital and 150 methicillin-sensitive Staphylococcus aureus (MSSA) isolates were investigated in this study to determine whether the Slidex Staph-Kit is capable of differentiating between MRSA and MSSA owing to its unique performance characteristics. The Slidex Staph-Kit is a combined latex hemagglutination test designed to detect clumping factor, protein A, and a specific surface immunogen for S. aureus. Clumping factor-positive strains cause erythrocytes sensitized with fibrinogen to hemagglutinate, thereby resulting in visible red clumps. S. aureus strains deficient in clumping factor agglutinate latex particles sensitized with specific antibodies against surface proteins of S. aureus, thereby resulting in visible white clumps. Our results demonstrate that white clumping has a 99% specificity as well as a 98% positive predictive value for MRSA. Clumping factor-negative MRSA, which have been reported to occur in several countries, are epidemic in the Frankfurt area and account for 80% of all MRSA initial isolates in the orthopedic clinic of the Frankfurt University Hospital. Genotyping of all MRSA isolates by macrorestriction analysis of chromosomal DNA revealed that 83% of clumping factor-negative MRSA are closely related to the “southern-German” epidemic strain. This is the first study demonstrating the Slidex Staph-Kit’s capability for identifying epidemic clumping factor-negative S. aureus strains as methicillin resistant even prior to antimicrobial susceptibility testing.

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Dessart, L., D. J. Hillier, and K. D. Wilk. "Impact of clumping on core-collapse supernova radiation." Astronomy & Astrophysics 619 (October 30, 2018): A30. http://dx.doi.org/10.1051/0004-6361/201833278.

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There is both observational and theoretical evidence that the ejecta of core-collapse supernovae (SNe) are structured. Rather than being smooth and homogeneous, the material is made of over-dense and under-dense regions of distinct composition. Here, we have explored the effect of clumping on the SN radiation during the photospheric phase using 1D non-local thermodynamic equilibrium radiative transfer and an ejecta model arising from a blue-supergiant explosion (yielding a Type II-peculiar SN). Neglecting chemical segregation, we adopted a velocity-dependent volume-filling factor approach that assumes that the clumps are small but does not change the column density along any sightline. We find that clumping boosts the recombination rate in the photospheric layers, leading to a faster recession of the photosphere, an increase in bolometric luminosity, and a reddening of the SN colors through enhanced blanketing. The SN bolometric light curve peaks earlier and transitions faster to the nebular phase. On the rise to maximum, the strongest luminosity contrast between our clumped and smooth models is obtained at the epoch when the photosphere has receded to ejecta layers where the clumping factor is only 0.5 – this clumping factor may be larger in nature. Clumping is seen to have a similar influence in a Type II-Plateau SN model. As we neglected both porosity and chemical segregation, our models underestimate the true impact of clumping. These results warrant further study of the influence of clumping on the observables of other SN types during the photospheric phase.

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Schaerer, D. "Multi-line transfer and line blanketing in a clumpy Wolf-Rayet wind." Symposium - International Astronomical Union 163 (1995): 168–69. http://dx.doi.org/10.1017/s0074180900201897.

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We present a Wolf-Rayet wind model including clumping, which is assumed to be due to full-scale supersonic compressible turbulence as suggested by Moffat & Robert (1994). It is shown that clumping leads to a larger transfer of radiative to mechanical luminosity, which corresponds to a momentum ratio of (Ṁv∞)/(L/c) = 12 for a typical WN5 star. We also show how clumping reduces the effects of line blanketing in spectral analyses.

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López-Mimbela, J. Alfredo, and Anton Wakolbinger. "Clumping in multitype-branching trees." Advances in Applied Probability 28, no. 04 (December 1996): 1034–50. http://dx.doi.org/10.1017/s0001867800027543.

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We investigate the ‘clumping versus local finiteness' behavior in the infinite backward tree for a class of branching particle systems in ℝd with symmetric stable migration and critical ‘genuine multitype' branching. Under mild assumptions on the branching we establish, by analysing certain ergodic properties of the individual ancestral process, a critical dimension d c such that the (measure-valued) tree-top is almost surely locally finite if and only if d > d c. This result is used to obtain L 1-norm asymptotics of a corresponding class of systems of non-linear partial differential equations.

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Wozniak, Carl, Scott Drum, Benjamin Hugus, Erica Wozniak, and Phillip Watts. "“Clumping” in Cross Country Skiing." Medicine & Science in Sports & Exercise 47 (May 2015): 29. http://dx.doi.org/10.1249/01.mss.0000476473.34162.75.

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López-Mimbela, J. Alfredo, and Anton Wakolbinger. "Clumping in multitype-branching trees." Advances in Applied Probability 28, no. 4 (December 1996): 1034–50. http://dx.doi.org/10.2307/1428163.

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We investigate the ‘clumping versus local finiteness' behavior in the infinite backward tree for a class of branching particle systems in ℝd with symmetric stable migration and critical ‘genuine multitype' branching. Under mild assumptions on the branching we establish, by analysing certain ergodic properties of the individual ancestral process, a critical dimension dc such that the (measure-valued) tree-top is almost surely locally finite if and only if d > dc. This result is used to obtain L1-norm asymptotics of a corresponding class of systems of non-linear partial differential equations.

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Skeith, Leslie, and Adrienne Lee. "Abnormal chromatin clumping in myeloblasts." Blood 127, no. 21 (May 26, 2016): 2645. http://dx.doi.org/10.1182/blood-2016-02-698506.

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Eckert, D., M. Roncarelli, S. Ettori, S. Molendi, F. Vazza, F. Gastaldello, and M. Rossetti. "Gas clumping in galaxy clusters." Monthly Notices of the Royal Astronomical Society 447, no. 3 (January 7, 2015): 2198–208. http://dx.doi.org/10.1093/mnras/stu2590.

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Wilk, Kevin D., D. John Hillier, and Luc Dessart. "Understanding nebular spectra of Type Ia supernovae." Monthly Notices of the Royal Astronomical Society 494, no. 2 (March 9, 2020): 2221–35. http://dx.doi.org/10.1093/mnras/staa640.

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ABSTRACT In this study, we present one-dimensional, non-local-thermodynamic-equilibrium, radiative transfer simulations (using cmfgen) in which we introduce micro-clumping at nebular times into two Type Ia supernova ejecta models. We use one sub-Chandrasekhar (sub-MCh) ejecta model with 1.04 M⊙ and one Chandrasekhar (MCh) ejecta model with 1.40 M⊙. We introduce clumping factors f = 0.33, 0.25, and 0.10, which are constant throughout the ejecta, and compare results to the unclumped f = 1.0 case. We find that clumping is a natural mechanism to reduce the ionization of the ejecta, reducing emission from [Fe iii], [Ar iii], and [S iii] by a factor of a few. For decreasing values of the clumping factor f, the [Ca ii] λλ7291,7324 doublet became a dominant cooling line for our MCh model but remained weak in our sub-MCh model. Strong [Ca ii] λλ7291,7324 indicates non-thermal heating in that region and may constrain explosion modelling. Due to the low abundance of stable nickel, our sub-MCh model never showed the [Ni ii] 1.939-μm diagnostic feature for all clumping values.

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Moreno, Eduardo, Angela McGaughran, Christian Rödelsperger, Manuel Zimmer, and Ralf J. Sommer. "Oxygen-induced social behaviours in Pristionchus pacificus have a distinct evolutionary history and genetic regulation from Caenorhabditis elegans." Proceedings of the Royal Society B: Biological Sciences 283, no. 1825 (February 24, 2016): 20152263. http://dx.doi.org/10.1098/rspb.2015.2263.

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Wild isolates of the nematode Caenorhabditis elegans perform social behaviours, namely clumping and bordering, to avoid hyperoxia under laboratory conditions. In contrast, the laboratory reference strain N2 has acquired a solitary behaviour in the laboratory, related to a gain-of-function variant in the neuropeptide Y-like receptor NPR-1. Here, we study the evolution and natural variation of clumping and bordering behaviours in Pristionchus pacificus nematodes in a natural context, using strains collected from 22 to 2400 metres above sea level on La Réunion Island. Through the analysis of 106 wild isolates, we show that the majority of strains display a solitary behaviour similar to C. elegans N2, whereas social behaviours are predominantly seen in strains that inhabit high-altitude locations. We show experimentally that P. pacificus social strains perform clumping and bordering to avoid hyperoxic conditions in the laboratory, suggesting that social strains may have adapted to or evolved a preference for the lower relative oxygen levels available at high altitude in nature. In contrast to C. elegans , clumping and bordering in P. pacificus do not correlate with locomotive behaviours in response to changes in oxygen conditions. Furthermore, QTL analysis indicates clumping and bordering to represent complex quantitative traits. Thus, clumping and bordering behaviours represent an example of phenotypic convergence with a different evolutionary history and distinct genetic control in both nematode species.

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Dominiecki, Mary E., and Jerrold Weiss. "Antibacterial Action of Extracellular Mammalian Group IIA Phospholipase A2 against Grossly ClumpedStaphylococcus aureus." Infection and Immunity 67, no. 5 (May 1, 1999): 2299–305. http://dx.doi.org/10.1128/iai.67.5.2299-2305.1999.

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ABSTRACT Fibrinogen-dependent interactions of Staphylococcus aureus are believed to contribute to bacterial virulence by promoting bacterial attachment to fibrinogen-coated surfaces and inducing the formation of bacterial clumps that are likely resistant to phagocytosis. Although S. aureus produces several fibrinogen-binding proteins, the cell wall-associated protein clumping factor (encoded by clfA) appears to be most important in bacterial interactions with immobilized or soluble purified fibrinogen. We have compared bacterial clumping in several strains of S. aureus, including isogenic ClfA+ and ClfA− Newman strains, in the presence of purified rabbit fibrinogen, human plasma, and inflammatory fluid and examined the effect of clumping on bacterial sensitivity to mammalian group IIA phospholipase A2 (PLA2). This enzyme is the major extracellular bactericidal agent in inflammatory fluid active against S. aureus. Both ClfA-dependent and ClfA-independent bacterial clumping was observed, depending on the source and fibrinogen content of the biological fluid. In each case, clumping only partially reduced the antibacterial activity of PLA2, suggesting that this extracellular enzyme can substantially penetrate dense bacterial clumps. Bacterial clumps could be dispersed by added proteases, restoring full antibacterial activity to PLA2. Thus, the extracellular mobilization of group IIA PLA2 during inflammation may provide a mechanism by which the host can control the proliferation and survival of S. aureus even after bacterial clumping.

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Gräfener, Götz. "Clumping in stellar winds and interiors." Proceedings of the International Astronomical Union 12, S329 (November 2016): 207–14. http://dx.doi.org/10.1017/s1743921317003246.

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AbstractThe uncertain clumping properties pose a major problem for the quantitative analysis and the modelling of hot star winds. New results suggest that also the outer envelopes of massive stars may be affected by clumping, with important consequences for their observable radii and ionising properties. In this talk I will discuss how clumping is incorporated in stellar interior and wind/atmosphere models, how current theoretical results compare with observations, and what we can learn from a combination of stellar interior models and winds.

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Naess, A. "Extreme Response of Nonlinear Structures With Low Damping Subjected to Stochastic Loading." Journal of Offshore Mechanics and Arctic Engineering 121, no. 4 (November 1, 1999): 255–60. http://dx.doi.org/10.1115/1.2829576.

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The response of structures with low damping to random loading is generally characterized by significant clumping of the large response peaks. This clumping is known to affect the extreme responses of the structure. In the paper, we shall propose an approximate method to account for this effect on first passage times and extreme values of narrow-band random vibrations, both Gaussian and non-Gaussian. The method is based on the concept of joint crossing rates of a stochastic process. This makes it possible to introduce a correlation structure to the sequence of peak values, allowing the introduction of an approximate estimate of the effect of clumping on large excursions of the underlying narrow-band process. The advantage of the proposed method is that explicit, closed-form expressions for the clumping effect on first passage times and extreme values are obtained. The method is illustrated by application to specific examples.

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Walsh, Arthur C. "Change in Charge Adds to Clumping?" Science News 151, no. 11 (March 15, 1997): 155. http://dx.doi.org/10.2307/3980476.

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Chang, Bei-Hung, and Stuart Pocock. "Analyzing data with clumping at zero." Journal of Clinical Epidemiology 53, no. 10 (October 2000): 1036–43. http://dx.doi.org/10.1016/s0895-4356(00)00223-7.

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Kaurov, Alexander A., and Nickolay Y. Gnedin. "RECOMBINATION CLUMPING FACTOR DURING COSMIC REIONIZATION." Astrophysical Journal 787, no. 2 (May 13, 2014): 146. http://dx.doi.org/10.1088/0004-637x/787/2/146.

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Bookstein, A., S. T. Klein, and T. Raita. "Clumping properties of content‐bearing words." Journal of the American Society for Information Science 49, no. 2 (1998): 102–14. http://dx.doi.org/10.1002/(sici)1097-4571(1998)49:2<102::aid-asi2>3.0.co;2-2.

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Bookstein, A., S. T. Klein, and T. Raita. "Clumping properties of content-bearing words." Journal of the American Society for Information Science 49, no. 2 (February 1998): 102–14. http://dx.doi.org/10.1002/(sici)1097-4571(199802)49:2<102::aid-asi2>3.0.co;2-5.

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Espersen, F., I. Clemmensen, and V. Barkholt. "Isolation of Staphylococcus aureus clumping factor." Infection and Immunity 49, no. 3 (1985): 700–708. http://dx.doi.org/10.1128/iai.49.3.700-708.1985.

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Wilson, T. L., and C. M. Walmsley. "Small-scale clumping in molecular clouds." Astronomy and Astrophysics Review 1, no. 2 (1989): 141–76. http://dx.doi.org/10.1007/bf00872714.

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Leung, Michael J., Nichalas Nuttall, Margaret Mazur, Tania L. Taddei, Michael McComish, and John W. Pearman. "Case of Staphylococcus schleiferi Endocarditis and a Simple Scheme To Identify Clumping Factor-Positive Staphylococci." Journal of Clinical Microbiology 37, no. 10 (1999): 3353–56. http://dx.doi.org/10.1128/jcm.37.10.3353-3356.1999.

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Staphylococcus schleiferi is a coagulase-negative staphylococcus infrequently reported as a human pathogen. We report a case of prosthetic valve endocarditis attributed to this organism, contrast it to another Staphylococcus species that gives similar clumping factor results (S. lugdunensis), and propose a simple, effective identification scheme for identification of clumping factor-positive staphylococci.

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Bertolino, Giampiera, Patrizia Noris, Pierangelo Spedini, and Carlo L. Balduini. "Ristocetin-induced Platelet Agglutination Stimulates GPIIb/IIIa-dependent Calcium Influx." Thrombosis and Haemostasis 73, no. 04 (1995): 689–92. http://dx.doi.org/10.1055/s-0038-1653842.

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SummaryWe found that intracellular Ca2+ concentration i[Ca2+]i) increased during ristocetin-induced agglutination of aequorin loaded platelets resuspended in plasma. Chelation of extracellular Ca2+ had no effect on platelet clumping, but delayed and greatly reduced Ca2+ increase, indicating that it derived for the most part from Ca2+ influx. Nine monoclonal antibodies (MA) against glycoprotein (GP) Ib largely prevented ristocetin-induced platelet clumping and [Ca2+]i increase, while three anti-GPIb MA with no effect on platelet clumping did not interfere with Ca2+ movement. In unstirred samples platelet agglutination was greatly reduced and [Ca2+]i increase was abolished, suggesting that close plate- let-to-platelet contact, in addition to von Willebrand factor (vWF) binding to GPIb, is necessary for Ca2+ transient. Nine MA against GPIIb/IIIa, the gly-arg-gly-asp-ser (GRGDS) peptide and GPIIb/IIIa complex dissociation had no effect on platelet agglutination, but significantly reduced Ca2+ increase. Our results suggest that platelet clumping induced by vWF binding to GPIb is responsible for GPIIb-IIIa dependent Ca2+ influx.

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Vink, J. S. "Clumps in stellar winds." ASTRA Proceedings 1 (July 30, 2014): 39–41. http://dx.doi.org/10.5194/ap-1-39-2014.

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Abstract. We discuss the origin and quantification of wind clumping and mass–loss rates (Ṁ), particularly in close proximity to the Eddington (Γ) limit, relevant for very massive stars (VMS). We present evidence that clumping may not be the result of the line-deshadowing instability (LDI), but that clumps are already present in the stellar photosphere.

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Tan, Geok Chin, Melissa Stalling, Gretchen Dennis, Maria Nunez, and Samir B. Kahwash. "Pseudothrombocytopenia due to Platelet Clumping: A Case Report and Brief Review of the Literature." Case Reports in Hematology 2016 (2016): 1–4. http://dx.doi.org/10.1155/2016/3036476.

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Platelet clumping is a common laboratory phenomenon that complicates or precludes reporting of platelet count. It is often, but not always, a phenomenon commonly caused by the anticoagulant EDTA. Herein, we discuss a case of a 14-year-old girl who was found to have platelet clumping and discuss the work-up she underwent to investigate her pseudothrombocytopenia.

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Peng, Jingjing, Wenjie Fan, Lizhao Wang, Xiru Xu, Jvcai Li, Beitong Zhang, and Dingfang Tian. "Modeling the Directional Clumping Index of Crop and Forest." Remote Sensing 10, no. 10 (October 1, 2018): 1576. http://dx.doi.org/10.3390/rs10101576.

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The Clumping Index (Ω) was introduced to quantify the spatial distribution pattern of vegetation elements. It is crucial to improve the estimation accuracy of vital vegetation parameters, such as Leaf Area Index (LAI) and Gross Primary Production (GPP). Meanwhile, the parameterization of Ω is challenging partly due to the varying observations of canopy gaps from different view angles. Many previous studies have shown the increase of Ω with view zenith angle through samples of gap size distribution from in situ measurements. In contrast, remote sensing retrieval algorithms only assign a constant value for each biome type to roughly correct the clumping effect as a compromise between the accuracy and efficiency. In this paper, analytical models are proposed that estimate the directional clumping index (Ω(θ)) of crop and forest at canopy level. The angular variation trend and magnitude of crop Ω(θ) was analyzed within row structure where vegetation elements are randomly spaced along rows. The forest model predicts Ω(θ) with tree density, distribution pattern, crown shape, trunk size, and leaf area and angle distribution function. The models take into account the main directional characteristics of clumping index using easy-to-measure parameters. Test cases showed that Ω(θ) magnitude variation for black spruce forest was 102.3% of the hemispherical average clumping index ( Ω ˜ ), whereas the Larch forest had 48.7% variation, and row crop variation reached 32.4%. This study provided tools to assess Ω(θ) of discontinuous canopies.

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Luo, Hongliang, Kai Wan, and Hua H. Wang. "High-Frequency Conjugation System Facilitates Biofilm Formation and pAMβ1 Transmission by Lactococcus lactis." Applied and Environmental Microbiology 71, no. 6 (June 2005): 2970–78. http://dx.doi.org/10.1128/aem.71.6.2970-2978.2005.

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ABSTRACT The importance of conjugation as a mechanism to spread biofilm determinants among microbial populations was illustrated with the gram-positive bacterium Lactococcus lactis. Conjugation triggered the enhanced expression of the clumping protein CluA, which is a main biofilm attribute in lactococci. Clumping transconjugants further transmitted the biofilm-forming elements among the lactococcal population at a much higher frequency than the parental nonclumping donor. This cell-clumping-associated high-frequency conjugation system also appeared to serve as an internal enhancer facilitating the dissemination of the broad-host-range drug resistance gene-encoding plasmid pAMβ1 within L. lactis, at frequencies more than 10,000 times higher than those for the nonclumping parental donor strain. The implications of this finding for antibiotic resistance gene dissemination are discussed.

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van Leeuwen, M., J. A. N. van Aardt, T. Kampe, and K. Krause. "A BOX-COUNTING METHOD TO CHARACTERIZE DEGREES OF FOLIAGE CLUMPING USING AIRBORNE AND SIMULATED LIDAR DATA." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-7/W3 (April 30, 2015): 1325–31. http://dx.doi.org/10.5194/isprsarchives-xl-7-w3-1325-2015.

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Monitoring forest productivity and health is key to sustainable ecosystem management and informed decision making. A key parameter used in monitoring forest resources is the leaf area index (LAI), which is defined as the one-sided leaf area per unit ground area and is used to describe the canopy radiation regime, among other forest biophysical dynamics. Traditional optics-based methods to estimate LAI rely on the measurement of canopy transmission and foliage clumping. Extending optical methods to LiDAR data has been challenging and studies have reported effective LAI assessments, with no further quantification of foliage clumping. This study investigates the use of the box-counting method to assess the fractal dimension of point cloud data for contrasting forest types and along a gradient of foliage dispersal. We demonstrate the box-counting method on simulated ‘range-to-hit’, as well as acquired airborne discrete LiDAR data. Coherent results obtained from the different test cases hint at the potential of the box-counting fractal dimension to characterize foliage clumping and bode well for the use of clumping assessments in support of airborne, wall-to-wall estimates of LAI.

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Oskinova, L. M., A. Feldmeier, and P. Kretschmar. "Clumped stellar winds in supergiant high-mass X-ray binaries." Proceedings of the International Astronomical Union 8, S290 (August 2012): 287–88. http://dx.doi.org/10.1017/s1743921312020042.

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AbstractThe clumping of massive star winds is an established paradigm, which is confirmed by multiple lines of evidence and is supported by stellar wind theory. We use the results from time-dependent hydrodynamical models of the instability in the line-driven wind of a massive supergiant star to derive the time-dependent accretion rate on to a compact object in the Bondi-Hoyle-Lyttleton approximation. The strong density and velocity fluctuations in the wind result in strong variability of the synthetic X-ray light curves. Photoionization of inhomogeneous winds is different from the photoinization of smooth winds. The degree of ionization is affected by the wind clumping. The wind clumping must also be taken into account when comparing the observed and model spectra of the photoionized stellar wind.

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Cui, Li-li, Tuure Kinnunen, Johannes Boltze, Johanna Nystedt, and Jukka Jolkkonen. "Clumping and Viability of Bone Marrow Derived Mesenchymal Stromal Cells under Different Preparation Procedures: A Flow Cytometry-Based In Vitro Study." Stem Cells International 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/1764938.

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Complications of microocclusions have been reported after intra-arterial delivery of mesenchymal stromal cells. Hence, quantification and efficient limitation of cell clumps in suspension before transplantation is important to reduce the risk. We used a flow cytometry-based pulse-width assay to assess the effects of different cell suspension concentrations (0.2–2.0 × 106/mL), storage solutions (complete growth medium, Dulbecco’s phosphate-buffered saline, and normal saline), storage time in suspension (0–9 h), and freeze-thawing procedure on the clumping of rat bone marrow derived mesenchymal stromal cells (BMMSCs) and also evaluated cell viability at the same time. Surprisingly, increasing the cell concentration did not result in more cell clumps in vitro. Freshly harvested (fresh) cells in normal saline had significantly fewer cell clumps and also displayed high viability (>90%). A time-dependent reduction in viability was observed for cells in all three storage solutions, without any significant change in the clumping tendency except for cells in medium. Fresh cells were more viable than their frozen-thawed counterparts, and fresh cells in normal saline had fewer cell clumps. In conclusion, cell clumping and viability could be affected by different cell preparation procedures, and quantification of cell clumping can be conducted using the flow cytometry-based pulse-width assay before intra-arterial cell delivery.

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Dessart, Luc, and Edouard Audit. "Influence of macroclumping on type II supernova light curves." Astronomy & Astrophysics 629 (August 28, 2019): A17. http://dx.doi.org/10.1051/0004-6361/201935794.

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Core-collapse supernova (SN) ejecta are probably structured on both small and large scales, with greater deviations from spherical symmetry nearer the explosion site. Here, we present 2D and 3D gray radiation hydrodynamics simulations of type II SN light curves from red and blue supergiant star explosions to investigate the impact of inhomogeneities in density or composition on SN observables, with a characteristic scale set to a few percent of the local radius. Clumping is found to hasten the release of stored radiation, boosting the early time luminosity and shortening the photospheric phase. Around the photosphere, radiation leaks between the clumps where the photon mean free path is greater. Since radiation is stored uniformly in volume, a greater clumping can increase this leakage by storing more and more mass into smaller and denser clumps containing less and less radiation energy. An inhomogeneous medium in which different regions recombine at different temperatures can also impact the light curve. Clumping can thus be a source of diversity in SN brightness. Clumping may lead to a systematic underestimate of ejecta masses from light curve modeling, although a significant offset seems to require a large density contrast of a few tens between clumps and interclump medium.

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Anderson, Martha C., J. M. Norman, William P. Kustas, Fuqin Li, John H. Prueger, and John R. Mecikalski. "Effects of Vegetation Clumping on Two–Source Model Estimates of Surface Energy Fluxes from an Agricultural Landscape during SMACEX." Journal of Hydrometeorology 6, no. 6 (December 1, 2005): 892–909. http://dx.doi.org/10.1175/jhm465.1.

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Abstract The effects of nonrandom leaf area distributions on surface flux predictions from a two-source thermal remote sensing model are investigated. The modeling framework is applied at local and regional scales over the Soil Moisture–Atmosphere Coupling Experiment (SMACEX) study area in central Iowa, an agricultural landscape that exhibits foliage organization at a variety of levels. Row-scale clumping in area corn- and soybean fields is quantified as a function of view zenith and azimuth angles using ground-based measurements of canopy architecture. The derived clumping indices are used to represent subpixel clumping in Landsat cover estimates at 30-m resolution, which are then aggregated to the 5-km scale of the regional model, reflecting field-to-field variations in vegetation amount. Consideration of vegetation clumping within the thermal model, which affects the relationship between surface temperature and leaf area inputs, significantly improves model estimates of sensible heating at both local and watershed scales in comparison with eddy covariance data collected by aircraft and with a ground-based tower network. These results suggest that this economical approach to representing subpixel leaf area hetereogeneity at multiple scales within the two-source modeling framework works well over the agricultural landscape studied here.

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Fernandez-Ricaud, Luciano, Daniel Dalevi, Anders Blomberg, and Olle Nerman. "Testing of Chromosomal Clumping of Gene Properties." Statistical Applications in Genetics and Molecular Biology 8, no. 1 (January 26, 2009): 1–27. http://dx.doi.org/10.2202/1544-6115.1428.

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Lépine, Sébastien. "Effects of wind clumping on colliding winds." Symposium - International Astronomical Union 163 (1995): 411–15. http://dx.doi.org/10.1017/s0074180900202386.

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Recent studies of variable Wolf-Rayet emission lines reveal a hierarchy of structures, characterized by power laws analogous to what is expected from supersonic compressible turbulence. The collision of inhomogeneous winds can be very different from the case of smooth winds. The difference will mainly depend on two factors: (i) the relative importance of the inhomogeneous compared to the homogeneous component; and (ii) the characteristic filling factor of the inhomogeneous component. Using relations derived from observations of variable line structures (“blobs”), it can be deduced that the flux emitted by the inhomogeneous part of the wind of a WR star is dominated by its smallest structures. This implies that a significant fraction of the underlying emission line profile could be produced by small, undetectable inhomogeneities. It can also be deduced that the volume spanned by the inhomogeneities is dominated by the largest structures. This in turn implies that the filling factor should be low, or that we are dealing with a fractal-like hierarchy. It is suggested that the wind is composed of dense structures separated by large “voids” which may actually be filled by a homogeneous wind component. The interacting zone of two inhomogeneous colliding winds should thus be much more extended in space than for a smooth-wind model, because the dense, inhomogeneous structures are able to penetrate through the large “voids”.

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Holmes, Bob. "Simple algae take clumping leap of evolution." New Scientist 220, no. 2943 (November 2013): 12. http://dx.doi.org/10.1016/s0262-4079(13)62670-6.

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Zhou, Ming, Kaikai Chen, Xiao Li, Lincong Liu, Qunfeng Zeng, Youtang Mo, Long Jin, et al. "Clumping Stability of Vertical Nanofibers on Surfaces." Langmuir 34, no. 38 (August 20, 2018): 11629–36. http://dx.doi.org/10.1021/acs.langmuir.8b02009.

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English, Arthur W., Paul R. Lennard, and T. Richard Nichols. "Clumping and splitting in the neuromuscular system." Behavioral and Brain Sciences 12, no. 4 (December 1989): 652–53. http://dx.doi.org/10.1017/s0140525x00025085.

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Kibble, T. W. B., and Richard Lieu. "Average Magnification Effect of Clumping of Matter." Astrophysical Journal 632, no. 2 (October 20, 2005): 718–26. http://dx.doi.org/10.1086/444343.

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Al-Joudi, FS, and JAK Jamil. "Imprisonment-Associated Sperm Clumping and Male Infertility." Journal of International Medical Research 40, no. 1 (February 2012): 393–97. http://dx.doi.org/10.1177/147323001204000142.

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Moake, Joel L. "Thrombotic Thrombocytopenic Purpura: The Systemic Clumping “Plague”." Annual Review of Medicine 53, no. 1 (February 2002): 75–88. http://dx.doi.org/10.1146/annurev.med.53.082901.103948.

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Li, Huisong, Francois Berenger, Bor-Yuh Evan Chang, and Xavier Rival. "Semantic-directed clumping of disjunctive abstract states." ACM SIGPLAN Notices 52, no. 1 (May 11, 2017): 32–45. http://dx.doi.org/10.1145/3093333.3009881.

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Morandi, Andrea, and Wei Cui. "Measuring the gas clumping in Abell 133." Monthly Notices of the Royal Astronomical Society 437, no. 2 (November 19, 2013): 1909–17. http://dx.doi.org/10.1093/mnras/stt2021.

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Zhou, Ming, Yu Tian, Hongbo Zeng, Noshir Pesika, and Jacob Israelachvili. "Clumping Criteria of Vertical Nanofibers on Surfaces." Advanced Materials Interfaces 2, no. 5 (February 20, 2015): 1400466. http://dx.doi.org/10.1002/admi.201400466.

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Journal articles on the topic 'Clumping'

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