TAIL DISTRIBUTION FOR LARGE CLUSTERS IN IRREVERSIBLE AGGREGATION

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

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Triple Fixation For Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100100196 ◽

1968 ◽

Vol 26 ◽

pp. 90-91 ◽

Cited By ~ 1

Author(s):

M. A. Hayat

Keyword(s):

Electron Microscopy ◽

Endoplasmic Reticulum ◽

Electron Beam ◽

Plasma Membrane ◽

Myelin Sheath ◽

Good Deal ◽

Granular Structure ◽

Oxidizing Agent ◽

Fixation Technique ◽

Large Clusters

Potassium permanganate has been successfully employed to study membranous structures such as endoplasmic reticulum, Golgi, plastids, plasma membrane and myelin sheath. Since KMnO4 is a strong oxidizing agent, deposition of manganese or its oxides account for some of the observed contrast in the lipoprotein membranes, but a good deal of it is due to the removal of background proteins either by dehydration agents or by volatalization under the electron beam. Tissues fixed with KMnO4 exhibit somewhat granular structure because of the deposition of large clusters of stain molecules. The gross arrangement of membranes can also be modified. Since the aim of a good fixation technique is to preserve satisfactorily the cell as a whole and not the best preservation of only a small part of it, a combination of a mixture of glutaraldehyde and acrolein to obtain general preservation and KMnO4 to enhance contrast was employed to fix plant embryos, green algae and fungi.

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A Monoclonal Antibody to the Human Platelet Glycoprotein II b/III a Complex Induces Platelet Activation

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647637 ◽

1988 ◽

Vol 60 (01) ◽

pp. 068-074 ◽

Cited By ~ 33

Author(s):

Piet W Modderman ◽

Han G Huisman ◽

Jan A van Mourik ◽

Albert E G Kr von dem Borne

Keyword(s):

Human Platelet ◽

Adenosine Diphosphate ◽

Dense Granule ◽

Platelet Glycoprotein ◽

Activated Platelets ◽

Complex Functions ◽

Slow Aggregation ◽

Irreversible Aggregation ◽

Platelet Release ◽

Aggregation Of Platelets

SummaryThe platelet glycoprotein (GP) IIb/IIIa complex functions as the receptor for fibrinogen on activated platelets. The effects of two anti-GPIIb/IIIa monoclonal antibodies on platelet function were studied. These antibodies, 6C9 and C17, recognized different epitopes, which were exclusively present on the undissociated GPIIb/IIIa complex. Whereas C17 inhibited the binding of fibrinogen to platelets and platelet aggregation induced by adenosine diphosphate (ADP) or collagen, 6C9 caused irreversible aggregation of platelets, both in the presence and absence of extracellular fibrinogen. When incubated with unstirred (nonaggregating) platelets, 6C9 induced release of alpha and dense granule-constituents as well as binding of 125I-fibrinogen to platelets. The latter was evidently mediated in part by platelet-derived ADP, since it was inhibited to a large extent by apyrase, the ADP-hydrolyzing enzyme. F(ab’)2 fragments of 6C9 did not induce platelet-release reactions but caused (slow) aggregation of platelets in the presence of extracellular fibrinogen.These results indicate that binding of an antibody to a specific site on the platelet GPIIb/IIIa complex may cause fibrinogen-mediated aggregation. The Fc part of the platelet-bound antibody appears to be involved in the induction of platelet release.

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Transmembrane Calcium Influx Associated with von Willebrand Factor Binding to GP Ib in the Initiation of Shear-Induced Platelet Aggregation

Thrombosis and Haemostasis ◽

10.1055/s-0038-1651640 ◽

1993 ◽

Vol 69 (05) ◽

pp. 496-502 ◽

Cited By ~ 123

Author(s):

Yasuo Ikeda ◽

Makoto Handa ◽

Tetsuji Kamata ◽

Koichi Kawano ◽

Yohko Kawai ◽

...

Keyword(s):

Shear Force ◽

Calcium Influx ◽

Fold Increase ◽

Intracellular Camp ◽

Recombinant Fragment ◽

Transmembrane Flux ◽

Irreversible Aggregation ◽

Von Willebrand ◽

Willebrand Factor ◽

Camp Levels

SummaryWe found that the binding of multimeric vWF to GP Ib under a shear force of 108 dynes/cm2 resulted in the transmembrane flux of Ca2+ ions with a two-to three-fold increase in their intracellular concentration ([Ca2+]i). The blockage of this event, obtained by inhibiting the vWF-GP Ib interaction, suppressed aggregation. In contrast, the blockage of vWF binding to GP IIb-IIIa, as well as the prevention of activation caused by increased intracellular cAMP levels, inhibited aggregation but had no significant effect on [Ca2+]i increase. A monomeric recombinant fragment of vWF containing the GP Ib-binding domain of the molecule (residues 445-733) prevented all effects mediated by multimeric vWF but, by itself, failed to support the increase in [Ca2+]i and aggregation. These results suggest that the binding of multimeric vWF to GP Ib initiates platelets aggregation induced by high shear stress by mediating a transmembrane flux of Ca2+ ions, perhaps through a receptor-dependent calcium channel. The increase in [Ca2+]i may act as an intracellular message and cause the activation of GP IIb-IIIa; the latter receptor then binds vWF and mediates irreversible aggregation.

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Aggregation of Cat Platelets in Vitro

Thrombosis and Haemostasis ◽

10.1055/s-0038-1654191 ◽

1970 ◽

Vol 23 (03) ◽

pp. 601-620 ◽

Cited By ~ 14

Author(s):

Th. B Tschopp

Keyword(s):

Adenosine Monophosphate ◽

Blood Collection ◽

Base Line ◽

Reversible Aggregation ◽

Low Concentrations ◽

Irreversible Aggregation ◽

High Concentrations ◽

Two Phases ◽

Improved Technique

SummaryAggregation of cat platelets in the citrated plasma is examined by means of Born’s absorptiometer. A marked tendency of the platelets of this species to spontaneous aggregation necessitated first of all the development of an improved technique of blood collection.A hypothesis according to which 5-HT is released from the platelets, explains the absence of oscillations on the base line of the absorptiometer, the absence of platelet swelling, when ADP is added, and the effect of stirring on the aggregation curves in cat PRP. The average volume of cat platelets amounts to 10.46 μ3 when directly fixed in the blood, when fixed from PRP to 12.17 μ3, when fixed from stirred PRP to 13.51 μ3.In low concentrations (0.3-2 μM) ADP produce reversible aggregation; in narrowly restricted, individually dissimilar mean concentrations irreversible aggregation in two phases and in high concentrations, irreversible aggregation in one phase. Like ADP serotonin produces 2 phase irreversible aggregation in concentrations of 3-10 μM, but unlike ADP, the aggregation velocity decreases again with high 5-HT concentrations (>100 μM). Adrenaline does not produce aggregation and it is likely that adenosine and adenosine monophosphate inhibit the aggregation by serotonin but not by ADP. Species differences in the aggregation of human, rabbit and cat platelets are discussed.

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The interaction of a manganese-oxidising bacterium as part of a biofilm growing on distribution pipe materials

Water Science & Technology ◽

10.2166/wst.2000.0458 ◽

2000 ◽

Vol 41 (4-5) ◽

pp. 295-300 ◽

Cited By ~ 3

Author(s):

F. Murdoch ◽

P.G. Smith

Keyword(s):

Biofilm Formation ◽

Bacterial Activity ◽

Confocal Laser ◽

Pipe Surface ◽

X Ray ◽

Pseudomonas Spp ◽

Eds Analysis ◽

Large Clusters ◽

Pipe Materials ◽

Confocal Laser Microscope

The deposition of manganese within a biofilm growing on the surface of high-density polyethlene (HDPE) and polyvinychloride (PVC) was studied over a period of four months. The manganese rich water used in the study was inoculated with a manganese oxidising Pseudomonas spp. The level of Mn2+ in the water was monitored and was found to decrease as the biofilm formation increased. This was confirmed by energy dispersive X-ray spectroscopy (EDS) analysis which showed the detection of manganese was dependent on the presence of a biofilm. After two months a 100% removal of Mn2+ was observed in all the flasks inoculated by the Pseudomonas spp. and manganese micro-nodules, the formation of which were reported in Murdoch and Smith (1999), were being formed in large clusters across the surfaces of both the HDPE and PVC. The manganese peak area from the EDS spectrum analysis of the micro-nodules was significantly larger than was measured in the biofilm when these micro-nodules were absent. The scanning confocal laser microscope (SCLM) images of three-week samples showed high bacterial activity around areas where manganese micro-nodules were starting to form on the pipe surface.

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EphA2 super-enhancer promotes tumor progression by recruiting FOSL2 and TCF7L2 to activate the target gene EphA2

Cell Death and Disease ◽

10.1038/s41419-021-03538-6 ◽

2021 ◽

Vol 12 (3) ◽

Author(s):

Shuang Cui ◽

Qiong Wu ◽

Ming Liu ◽

Mu Su ◽

ShiYou Liu ◽

...

Keyword(s):

Tumor Progression ◽

Tumor Cells ◽

Target Gene ◽

Super Enhancer ◽

Proliferation And Metastasis ◽

Active Transcription ◽

Hct 116 ◽

Large Clusters

AbstractSuper-enhancers or stretch enhancers (SEs) consist of large clusters of active transcription enhancers which promote the expression of critical genes that define cell identity during development and disease. However, the role of many super-enhancers in tumor cells remains unclear. This study aims to explore the function and mechanism of a new super-enhancer in various tumor cells. A new super-enhancer that exists in a variety of tumors named EphA2-Super-enhancer (EphA2-SE) was found using multiple databases and further identified. CRISPR/Cas9-mediated deletion of EphA2-SE results in the significant downregulation of its target gene EphA2. Mechanistically, we revealed that the core active region of EphA2-SE comprises E1 component enhancer, which recruits TCF7L2 and FOSL2 transcription factors to drive the expression of EphA2, induce cell proliferation and metastasis. Bioinformatics analysis of RNA-seq data and functional experiments in vitro illustrated that EphA2-SE deletion inhibited cell growth and metastasis by blocking PI3K/AKT and Wnt/β-catenin pathway in HeLa, HCT-116 and MCF-7 cells. Overexpression of EphA2 in EphA2-SE−/− clones rescued the effect of EphA2-SE deletion on proliferation and metastasis. Subsequent xenograft animal model revealed that EphA2-SE deletion suppressed tumor proliferation and survival in vivo. Taken together, these findings demonstrate that EphA2-SE plays an oncogenic role and promotes tumor progression in various tumors by recruiting FOSL2 and TCF7L2 to drive the expression of oncogene EphA2.

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On the scaling of fragmentation and energy dissipation in collisions of dust aggregates

Granular Matter ◽

10.1007/s10035-021-01101-w ◽

2021 ◽

Vol 23 (2) ◽

Author(s):

Philipp Umstätter ◽

Herbert M. Urbassek

Keyword(s):

Energy Dissipation ◽

Collision Energy ◽

Velocity Range ◽

Collision Velocity ◽

Granular Mechanics ◽

Extra Factor ◽

Cluster Fragmentation ◽

Silica Clusters ◽

Large Clusters ◽

Small Clusters

Abstract Fragmentation of granular clusters may be studied by experiments and by granular mechanics simulation. When comparing results, it is often assumed that results can be compared when scaled to the same value of $$E/E_{\mathrm{sep}}$$ E / E sep , where E denotes the collision energy and $$E_{\mathrm{sep}}$$ E sep is the energy needed to break every contact in the granular clusters. The ratio $$E/E_{\mathrm{sep}}\propto v^2$$ E / E sep ∝ v 2 depends on the collision velocity v but not on the number of grains per cluster, N. We test this hypothesis using granular-mechanics simulations on silica clusters containing a few thousand grains in the velocity range where fragmentation starts. We find that a good parameter to compare different systems is given by $$E/(N^{\alpha }E_{\mathrm{sep}})$$ E / ( N α E sep ) , where $$\alpha \sim 2/3$$ α ∼ 2 / 3 . The occurrence of the extra factor $$N^{\alpha }$$ N α is caused by energy dissipation during the collision such that large clusters request a higher impact energy for reaching the same level of fragmentation than small clusters. Energy is dissipated during the collision mainly by normal and tangential (sliding) forces between grains. For large values of the viscoelastic friction parameter, we find smaller cluster fragmentation, since fragment velocities are smaller and allow for fragment recombination. Graphic abstract

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A Bimodal Extension of the Exponential Distribution with Applications in Risk Theory

Symmetry ◽

10.3390/sym13040679 ◽

2021 ◽

Vol 13 (4) ◽

pp. 679

Author(s):

Jimmy Reyes ◽

Emilio Gómez-Déniz ◽

Héctor W. Gómez ◽

Enrique Calderín-Ojeda

Keyword(s):

Exponential Distribution ◽

Hazard Rate ◽

Rate Function ◽

Estimation Methods ◽

Inverse Gaussian ◽

New Family ◽

Tail Distribution ◽

Zero Values ◽

The Mean ◽

Positive Support

There are some generalizations of the classical exponential distribution in the statistical literature that have proven to be helpful in numerous scenarios. Some of these distributions are the families of distributions that were proposed by Marshall and Olkin and Gupta. The disadvantage of these models is the impossibility of fitting data of a bimodal nature of incorporating covariates in the model in a simple way. Some empirical datasets with positive support, such as losses in insurance portfolios, show an excess of zero values and bimodality. For these cases, classical distributions, such as exponential, gamma, Weibull, or inverse Gaussian, to name a few, are unable to explain data of this nature. This paper attempts to fill this gap in the literature by introducing a family of distributions that can be unimodal or bimodal and nests the exponential distribution. Some of its more relevant properties, including moments, kurtosis, Fisher’s asymmetric coefficient, and several estimation methods, are illustrated. Different results that are related to finance and insurance, such as hazard rate function, limited expected value, and the integrated tail distribution, among other measures, are derived. Because of the simplicity of the mean of this distribution, a regression model is also derived. Finally, examples that are based on actuarial data are used to compare this new family with the exponential distribution.

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