Trophic dynamics of two sympatric species of riparian spider (Araneae: Tetragnathidae)

1995 ◽  
Vol 73 (8) ◽  
pp. 1545-1553 ◽  
Author(s):  
D. Dudley Williams ◽  
Laura G. Ambrose ◽  
Laura N. Browning
Keyword(s):  
Water Surface ◽  
Prey Capture ◽  
Sympatric Species ◽  
Three Dimensions ◽  
Trophic Dynamics ◽  
The West ◽  
Insect Emergence ◽  
Large Numbers ◽  
The Mean ◽  
Minimum Estimate

Four species of Tetragnatha were found along the banks of Duffin Creek, Ontario: T. versicolor Walckenaer, T. elongata Walckenaer, T. laboriosa Hentz, and T. straminea Emerton. However, only the first two species were common; together they represented 91% of all species of spiders observed. Highest densities of T. elongata occurred in July, a time when numbers of T. versicolor were at their lowest. Growth rates differed between the two species. Both species were more common (2–3 times) on the east bank of the river than on the west. The locations (in three dimensions) of individual spiders along the banks were similar for both species, although T. elongata frequented shrubs overhanging the river more than T. versicolor, which was found farther away from the water's edge. The mean number of prey caught by T elongata was significantly higher than that caught by T. versicolor. Webs caught most prey when located 2–4 m from the water's edge, both in annual vegetation (grass level to a height of about 0.5 m) and in tall shrubs (1.5–2 m). Large numbers of prey were caught also in webs spun in shrubs and tree branches that hung over the water surface at a height of 1–2 m. The number of prey caught was not related to web diameter. Maximum prey capture by T. elongata coincided with the time of maximum total insect emergence in the river. Although the insect taxa found in the webs reflected those that were emerging in greatest numbers, typically chironomids and mayflies, other commonly emerging taxa (e.g., caddisflies and stoneflies) were conspicuously absent. The minimum estimate of the proportion of total insect emergence from this river that is captured by these two spider species is 0.2%.

scholarly journals Elements of a stochastic 3D prediction engine in larval zebrafish prey capture

2019 ◽  
Author(s):  
Andrew D Bolton ◽  
Martin Haesemeyer ◽  
Josua Jordi ◽  
Ulrich Schaechtle ◽  
Feras Saad ◽  
...  
Keyword(s):  
Computational Models ◽  
Prey Capture ◽  
Recursive Algorithm ◽  
Three Dimensional ◽  
Physical World ◽  
Three Dimensions ◽  
Hunting Behavior ◽  
Larval Zebrafish ◽  
Behavioral Rules ◽  
The Mean

ABSTRACTMany predatory animals rely on accurate sensory perception, predictive models, and precise pursuits to catch moving prey. Larval zebrafish intercept paramecia during their hunting behavior, but the precise trajectories of their prey have never been recorded in relation to fish movements in three dimensions.As a means of uncovering what a simple organism understands about its physical world, we have constructed a 3D-imaging setup to simultaneously record the behavior of larval zebrafish, as well as their moving prey, during hunting. We show that zebrafish robustly transform their 3D displacement and rotation according to the position of their prey while modulating both of these variables depending on prey velocity. This is true for both azimuth and altitude, but particulars of the hunting algorithm in the two planes are slightly different to accommodate an asymmetric strike zone. We show that the combination of position and velocity perception provides the fish with a preferred future positional estimate, indicating an ability to project trajectories forward in time. Using computational models, we show that this projection ability is critical for prey capture efficiency and success. Further, we demonstrate that fish use a graded stochasticity algorithm where the variance around the mean result of each swim scales with distance from the target. Notably, this strategy provides the animal with a considerable improvement over equivalent noise-free strategies.In sum, our quantitative and probabilistic modeling shows that zebrafish are equipped with a stochastic recursive algorithm that embodies an implicit predictive model of the world. This algorithm, built by a simple set of behavioral rules, allows the fish to optimize their hunting strategy in a naturalistic three-dimensional environment.

scholarly journals Relaxation Times in Strictly Disk Systems

1971 ◽  
Vol 10 ◽  
pp. 15-19
Author(s):  
George B. Rybicki
Keyword(s):  
Numerical Experiments ◽  
Relaxation Times ◽  
Galactic Structure ◽  
Large Numbers ◽  
Order Of Magnitude ◽  
Vlasov Limit ◽  
The Mean ◽  
Gravitating Systems

AbstractIt is shown that the time of relaxation by particle encounters of self-gravitating systems in the plane interacting by 1/r2 forces is of the same order of magnitude as the mean orbit time. Therefore such a system does not have a Vlasov limit for large numbers of particles, unless appeal is made to some non-zero thickness of the disk. The relevance of this result to numerical experiments on galactic structure is discussed.

GLOBAL FLUCTUATIONS FOR LINEAR STATISTICS OF β-JACOBI ENSEMBLES

2012 ◽  
Vol 01 (04) ◽  
pp. 1250013 ◽  
Author(s):  
IOANA DUMITRIU ◽  
ELLIOT PAQUETTE
Keyword(s):  
Gaussian Process ◽  
Covariance Matrix ◽  
Law Of Large Numbers ◽  
Test Functions ◽  
Linear Statistics ◽  
Jacobi Ensemble ◽  
Large Numbers ◽  
The Mean ◽  
Shifted Chebyshev Polynomial ◽  
Global Fluctuations

We study the global fluctuations for linear statistics of the form [Formula: see text] as n → ∞, for C1 functions f, and λ1, …, λn being the eigenvalues of a (general) β-Jacobi ensemble. The fluctuation from the mean [Formula: see text] turns out to be given asymptotically by a Gaussian process. We compute the covariance matrix for the process and show that it is diagonalized by a shifted Chebyshev polynomial basis; in addition, we analyze the deviation from the predicted mean for polynomial test functions, and we obtain a law of large numbers.

Pituitary dimensions and volume measurements in pregnancy and post partum

1998 ◽  
Vol 39 (1) ◽  
pp. 64-69 ◽  
Author(s):  
H. Dinç ◽  
F. Esen ◽  
A. Demirci ◽  
A. Sari ◽  
H. Resit Gümele
Keyword(s):  
Pituitary Gland ◽  
Matched Control ◽  
Post Partum ◽  
Three Dimensions ◽  
Maximum Height ◽  
Third Trimester ◽  
Normal Pituitary Gland ◽  
Volume Measurements ◽  
Length Width ◽  
The Mean

Purpose: Our purpose was to clarify and further characterize the changes in height, length, width, volume, and shape in the normal pituitary gland and in width in the infundibulum during pregnancy and the first 6 months post partum. Material and Methods: Cranial MR imaging was performed in 78 women who were pregnant in the second or third trimester or who were post partum, and in 18 age-matched control subjects who were not pregnant. Volume measurements were performed in 2 ways; volume 1=1/2xheightxlengthxwidth; and volume 2=area (measured by trackball)xslice thickness Results: Gland volume, height, width, length, and convexity, and infundibular width increased during pregnancy. the highest values were seen during the 3 days immediately post partum. When compared with volunteers, volumes 1 and 2 showed the largest increase (120%) among the parameters. Gland height showed the best correlation (r=0.94, p>0.00001) with gestational age. the mean height of the gland was 8.76 mm in the third trimester. None of the pregnant women had a gland height of above 10 mm during pregnancy. Only 2 subjects had gland heights of 10.04 and 10.2 mm during the 0–3 days post partum. After this first post-partum period of 3 days, the gland size, shape, and volume and the infundibular width returned to normal within 6 months Conclusion: the pituitary gland enlarges in three dimensions throughout pregnancy. During pregnancy, the volume of the gland shows the highest percentage of increase compared to its length, height, and width. the maximum height of the gland does not exceed 10 mm during pregnancy but it may exceed 10 mm during the 3 days immediately post partum.

The Role of Intraseasonal Variability in the Nature of Asian Monsoon Precipitation

2007 ◽  
Vol 20 (17) ◽  
pp. 4402-4424 ◽  
Author(s):  
Carlos D. Hoyos ◽  
Peter J. Webster
Keyword(s):  
Indian Ocean ◽  
Time Scales ◽  
Temporal Variability ◽  
Asian Monsoon ◽  
Monsoon Rainfall ◽  
Mountain Range ◽  
Monsoon Precipitation ◽  
The West ◽  
The Mean ◽  
Rainfall Estimates

Abstract The structure of the mean precipitation of the south Asian monsoon is spatially complex. Embedded in a broad precipitation maximum extending eastward from 70°E to the northwest tropical Pacific Ocean are strong local maxima to the west of the Western Ghats mountain range of India, in Cambodia extending into the eastern China Sea, and over the eastern tropical Indian Ocean and the Bay of Bengal (BoB), where the strongest large-scale global maximum in precipitation is located. In general, the maximum precipitation occurs over the oceans and not over the land regions. Distinct temporal variability also exists with time scales ranging from days to decades. Neither the spatial nor temporal variability of the monsoon can be explained simply as the response to the cross-equatorial pressure gradient force between the continental regions of Asia and the oceans of the Southern Hemisphere, as suggested in classical descriptions of the monsoon. Monthly (1979–2005) and daily (1997–present) rainfall estimates from the Global Precipitation Climatology Project (GPCP), 3-hourly (1998–present) rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM) microwave imager (TMI) estimates of sea surface temperature (SST), reanalysis products, and satellite-determined outgoing longwave radiation (OLR) data were used as the basis of a detailed diagnostic study to explore the physical basis of the spatial and temporal nature of monsoon precipitation. Propagation characteristics of the monsoon intraseasonal oscillations (MISOs) and biweekly signals from the South China Sea, coupled with local and regional effects of orography and land–atmosphere feedbacks are found to modulate and determine the locations of the mean precipitation patterns. Long-term variability is found to be associated with remote climate forcing from phenomena such as El Niño–Southern Oscillation (ENSO), but with an impact that changes interdecadally, producing incoherent responses of regional rainfall. A proportion of the interannual modulation of monsoon rainfall is found to be the direct result of the cumulative effect of rainfall variability on intraseasonal (25–80 day) time scales over the Indian Ocean. MISOs are shown to be the main modulator of weather events and encompass most synoptic activity. Composite analysis shows that the cyclonic system associated with the northward propagation of a MISO event from the equatorial Indian Ocean tends to drive moist air toward the Burma mountain range and, in so doing, enhances rainfall considerably in the northeast corner of the bay, explaining much of the observed summer maximum oriented parallel to the mountains. Similar interplay occurs to the west of the Ghats. While orography does not seem to play a defining role in MISO evolution in any part of the basin, it directly influences the cumulative MISO-associated rainfall, thus defining the observed mean seasonal pattern. This is an important conclusion since it suggests that in order for the climate models to reproduce the observed seasonal monsoon rainfall structure, MISO activity needs to be well simulated and sharp mountain ranges well represented.

scholarly journals Limit Theorems and Fluctuations for Point Vortices of Generalized Euler Equations

2021 ◽  
Vol 182 (3) ◽  
Author(s):  
Carina Geldhauser ◽  
Marco Romito
Keyword(s):  
Euler Equations ◽  
Mean Field ◽  
Point Vortices ◽  
Positive Temperature ◽  
Field Limit ◽  
Mean Field Limit ◽  
Large Numbers ◽  
The Mean ◽  
Formal Solutions ◽  
2D Torus

AbstractWe prove a mean field limit, a law of large numbers and a central limit theorem for a system of point vortices on the 2D torus at equilibrium with positive temperature. The point vortices are formal solutions of a class of equations generalising the Euler equations, and are also known in the literature as generalised inviscid SQG. The mean-field limit is a steady solution of the equations, the CLT limit is a stationary distribution of the equations.

A New Lautoconus Species Radiation from Gambia, West Africa

The Festivus ◽  
2018 ◽  
Vol 50 (3) ◽  
pp. 164-172
Author(s):  
Edward Petuch ◽  
David Berschauer
Keyword(s):  
New Species ◽  
West Africa ◽  
River Mouth ◽  
Sympatric Species ◽  
West African ◽  
The West ◽  
Species Radiation ◽  
West African Coast ◽  
African Coast ◽  
Reef Fauna

Six sympatric species of the cone shell genus Lautoconus Monterosato, 1923 have been discovered on an isolated rock reef near the Gambia River Mouth, Gambia, West Africa. Of these, four were found to be new to science and, together, they represent a previously unknown Gambian endemic species radiation. These include: Lautoconus fernandi new species, L. gambiensis new species, L. rikae new species, and L. wolof new species. The poorly-known Gambian endemic cone, Lautoconus orri (Ninomiya and da Motta, 1982) was also found to be a component of the rock reef fauna, as was the wide-ranging L. guinaicus (Hwass, 1792) (Senegal to Ghana). The Gambian cluster of sibling species represents the farthest-south separate radiation of Lautoconus known from the West African coast.

scholarly journals La Niña–like Mean-State Response to Global Warming and Potential Oceanic Roles

2017 ◽  
Vol 30 (11) ◽  
pp. 4207-4225 ◽  
Author(s):  
Tsubasa Kohyama ◽  
Dennis L. Hartmann ◽  
David S. Battisti
Keyword(s):  
Global Warming ◽  
Southern Oscillation ◽  
Forced Response ◽  
Equatorial Pacific ◽  
La Niña ◽  
The West ◽  
La Nina ◽  
The Mean ◽  
Mean State ◽  
Sst Gradient

Abstract The majority of the models that participated in phase 5 of the Coupled Model Intercomparison Project global warming experiments warm faster in the eastern equatorial Pacific Ocean than in the west. GFDL-ESM2M is an exception among the state-of-the-art global climate models in that the equatorial Pacific sea surface temperature (SST) in the west warms faster than in the east, and the Walker circulation strengthens in response to warming. This study shows that this “La Niña–like” trend simulated by GFDL-ESM2M could be a physically consistent response to warming, and that the forced response could have been detectable since the late twentieth century. Two additional models are examined: GFDL-ESM2G, which differs from GFDL-ESM2M only in the oceanic components, warms without a clear zonal SST gradient; and HadGEM2-CC exhibits a warming pattern that resembles the multimodel mean. A fundamental observed constraint between the amplitude of El Niño–Southern Oscillation (ENSO) and the mean-state zonal SST gradient is reproduced well by GFDL-ESM2M but not by the other two models, which display substantially weaker ENSO nonlinearity than is observed. Under this constraint, the weakening nonlinear ENSO amplitude in GFDL-ESM2M rectifies the mean state to be La Niña–like. GFDL-ESM2M exhibits more realistic equatorial thermal stratification than GFDL-ESM2G, which appears to be the most important difference for the ENSO nonlinearity. On longer time scales, the weaker polar amplification in GFDL-ESM2M may also explain the origin of the colder equatorial upwelling water, which could in turn weaken the ENSO amplitude.

ASYNCHRONOUS UPDATING RESTORES THE LAW OF LARGE NUMBERS IN GLOBALLY COUPLED SYSTEMS

2002 ◽  
Vol 12 (03) ◽  
pp. 663-669 ◽  
Author(s):  
SUDESHNA SINHA
Keyword(s):  
Law Of Large Numbers ◽  
Mean Field ◽  
Coupled Systems ◽  
Large N ◽  
Large Numbers ◽  
Statistical Behavior ◽  
Remarkable Result ◽  
Asynchronous Updating ◽  
The Mean ◽  
The Law

It was observed in earlier studies, that the mean field of globally coupled maps evolving under synchronous updating rules violated the law of large numbers, and this remarkable result generated widespread research interest. In this work we demonstrate that incorporating increasing degrees of asynchronicity in the updating rules rapidly restores the statistical behavior of the mean field. This is clear from the decay of the mean square deviation of the mean field with respect to lattice size N, for varying degrees of asynchronicity, which shows 1/N behavior upto very large N even when the updating is far from fully asynchronous. This is also evidenced through increasing 1/f2 behavior regimes in the power spectrum of the mean field under increasing asynchronicity.

Understanding the Islamic State—A Review Essay

2016 ◽  
Vol 40 (4) ◽  
pp. 127-165 ◽  
Author(s):  
Daniel Byman
Keyword(s):  
Review Essay ◽  
Military Force ◽  
Islamic State ◽  
The West ◽  
High Quality ◽  
Terrorist Threat ◽  
Security Forces ◽  
Large Numbers ◽  
Raison D’État ◽  
Foreign Fighters

This article reviews several recent books on the Islamic State in order to understand its goals, motivations, strategy, and vulnerabilities. It argues that the Islamic State's ideology is powerful but also highly instrumental, offering the group legitimacy and recruiting appeal. Raison d'etat often dominates its decisionmaking. The Islamic State's strength is largely a consequence of the policies and weaknesses of its state adversaries. In addition, the group has many weaknesses of its own, notably its brutality, reliance on foreign fighters, and investment in a state as well as its tendency to seek out new enemies. The threat the Islamic State poses is most severe at the local and regional levels. The danger of terrorism to the West is real but mitigated by the Islamic State's continued prioritization of the Muslim world and the heightened focus of Western security forces on the terrorist threat. A high-quality military force could easily defeat Islamic State fighters, but there is no desire to deploy large numbers of Western ground troops, and local forces have repeatedly shown many weaknesses. In the end, containing the Islamic State and making modest rollback efforts may be the best local outcomes.

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