clustering behavior
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Encyclopedia ◽  
2021 ◽  
Vol 1 (4) ◽  
pp. 1010-1025
Author(s):  
Panayiotis Dimitriadis ◽  
Theano Iliopoulou ◽  
G.-Fivos Sargentis ◽  
Demetris Koutsoyiannis

The stochastic analysis in the scale domain (instead of the traditional lag or frequency domains) is introduced as a robust means to identify, model and simulate the Hurst–Kolmogorov (HK) dynamics, ranging from small (fractal) to large scales exhibiting the clustering behavior (else known as the Hurst phenomenon or long-range dependence). The HK clustering is an attribute of a multidimensional (1D, 2D, etc.) spatio-temporal stationary stochastic process with an arbitrary marginal distribution function, and a fractal behavior on small spatio-temporal scales of the dependence structure and a power-type on large scales, yielding a high probability of low- or high-magnitude events to group together in space and time. This behavior is preferably analyzed through the second-order statistics, and in the scale domain, by the stochastic metric of the climacogram, i.e., the variance of the averaged spatio-temporal process vs. spatio-temporal scale.


2021 ◽  
Author(s):  
Ishita Dasgupta ◽  
Thomas L. Griffiths

A central component of human intelligence is the ability to make abstractions, to gloss over some details in favor of drawing out higher-order structure. Clustering stimuli together is a classic example of this. However, the crucial question remains of how one should make these abstractions -- what details to retain and what to throw away? How many clusters to form? We provide an analysis of how a rational agent with limited cognitive resources should approach this problem, considering not only how well a clustering fits the data but also by how 'complex' it is, i.e. how cognitively expensive it is to represent. We show that the solution to this problem provides a way to reinterpret a wide range of psychological models that are based on principles from non-parametric Bayesian statistics. In particular, we show that the Chinese Restaurant Process prior, ubiquitous in models of human and animal clustering behavior, can be interpreted as minimizing an intuitive formulation of representational complexity.


Biomolecules ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 377
Author(s):  
Que N. Van ◽  
Priyanka Prakash ◽  
Rebika Shrestha ◽  
Trent E. Balius ◽  
Thomas J. Turbyville ◽  
...  

RAS proteins are mutated in approximately 20% of all cancers and are generally associated with poor clinical outcomes. RAS proteins are localized to the plasma membrane and function as molecular switches, turned on by partners that receive extracellular mitogenic signals. In the on-state, they activate intracellular signal transduction cascades. Membrane-bound RAS molecules segregate into multimers, known as nanoclusters. These nanoclusters, held together through weak protein–protein and protein–lipid associations, are highly dynamic and respond to cellular input signals and fluctuations in the local lipid environment. Disruption of RAS nanoclusters results in downregulation of RAS-mediated mitogenic signaling. In this review, we discuss the propensity of RAS proteins to display clustering behavior and the interfaces that are associated with these assemblies. Strategies to therapeutically disrupt nanocluster formation or the stabilization of signaling incompetent RAS complexes are discussed.


2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Abdullah Saleh Al-Ghamdi

This study provided detailed information on the attributes of wild olive species in the Al- Baha region, Saudi Arabia. The study area lay along the Sarah mountain, encompassing the districts of Al-Qura, Al-Mandaq, Al- Baha and the southern part of Baljurashi. This indicates the preference of wild olive for high foggy mountain conditions, which was pre-determined by the study to be a medium-high vegetation density zone. Information extracted from high resolution satellite imagery Pleaides revealed that there are 717,894 wild olive trees (360 trees per km2) in the study area, covering 1,991 km2 .The districts of Al-Mandaq and Al-Baha have higher wild olive density with younger and highly clustered trees, whereas Al-Qura and Baljurashi districts have lower wild olive density, with medium clustered older trees. The districts of Al-Aqiq, Qelwa and Mekhwa have the least density of wild olive with younger trees and light clustering. Clustering behavior was enumerated directly at the sampling plots and the results depicted that the majority of wild olives occur in clusters with mostly 5-10 trees per cluster. The olive tree is found naturally in Al-Baha and can reportedly maintain its populations in natural old growth forests for several hundred years. This study identified the age of wild olive trees in the study area. The results indicated that there were more (68%) of young age class (<50 years old) of wild olive trees, whereas Baljurashi showed the highest percentage of old age class (>150 years). The majority (88.6%) of the wild olive trees were healthy, while more unhealthy trees were observed in Al-Mandaq and Al-Baha districts. As observed during the groundwork, unhealthy trees particularly due to dieback, were more discerned with juniper affecting vegetation in Al-Mandaq and South Baha, with 45% and 18% respectively. Similarly, this study recorded trace of unhealthy vegetation, with 11.4% of the wild olive trees in an unhealthy condition. This information would be essential in ‘Identifying the Landscape Preference of Wild Olive in Al-Baha Region Saudi Arabia’.  


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