scholarly journals Informed dispersal of the dandelion

2019 ◽  
Author(s):  
Madeleine Seale ◽  
Oleksandr Zhdanov ◽  
Cathal Cummins ◽  
Erika Kroll ◽  
Mike Blatt ◽  
...  
Keyword(s):  
Meteorological Data ◽  
Dispersal Distance ◽  
Functional Change ◽  
Short Term ◽  
Plant Dispersal ◽  
Informed Dispersal ◽  
Flight Capacity ◽  
The Common ◽  
Dispersal Distances ◽  
Common Dandelion

Animal migration is highly sensitised to environmental and biological cues, yet plant dispersal is considered largely passive. The common dandelion, Taraxacum officinale, is a classic example of a wind-dispersed plant and has an intricate haired pappus facilitating flight. This pappus facilitates enables the formation of a separated vortex ring (SVR) during flight (1); however, the pappus structure is not static but reversibly changes shape by closing in response to moisture. Here we characterise the biomechanical function of the pappus morphing regarding SVR dynamics and flight capacity. When the pappus closes, the falling velocity is greatly increased and the velocity deficit within the vortex decreased. To understand the implications of this structural-functional change, we used historic meteorological data to simulate dispersal distance. Dispersal distances were reduced with the pappus closed, and so was detachment. We propose that moisture-dependent pappus-morphing serves to retain seeds in favourable moist niches, providing a form of informed dispersal (2) that has not been characterised in plants on such a short-term, responsive time scale (3).

Dispersal patterns of juvenile Townsend's ground squirrels in southwestern Idaho

1998 ◽  
Vol 76 (11) ◽  
pp. 2084-2089 ◽  
Author(s):  
Gail S Olson ◽  
Beatrice Van Horne
Keyword(s):  
Survival Rates ◽  
Habitat Type ◽  
Dispersal Distance ◽  
Ground Squirrels ◽  
Short Term ◽  
Dispersal Patterns ◽  
Conservation Area ◽  
Spermophilus Townsendii ◽  
Dispersal Distances ◽  
Two Parameter

Understanding the effects of habitat reduction or fragmentation on animals requires some knowledge of their dispersal patterns. We used radiotelemetry to examine dispersal characteristics of 59 (37 male and 22 female) juvenile Townsend's ground squirrels (Spermophilus townsendii) on the Snake River Birds of Prey National Conservation Area in southwestern Idaho from April to June in 1993 and 1994. We tested for differences between years, sexes, and habitats in the rates and distances of dispersal. We compared the fates of dispersers and nondispersers and tested whether the direction of dispersal differed from random and whether the distribution of dispersal distances could be fitted to a two-parameter exponential function. Of the 38 animals for which dispersal status could be determined, 16 dispersed. The proportion of dispersers was greater for males than for females, but these rates did not differ by year or habitat type. We found no differences between habitats in dispersal distance. Survival rates through immergence into estivation did not differ between dispersers and nondispersers, suggesting that dispersal is not risky over the short term. Direction of dispersal did not differ from random, and the distribution of dispersal distances was adequately fitted to a truncated exponential distribution with a truncation distance of 118 m. Dispersers tended to end up in the habitat type that they started in, suggesting the possibility of habitat imprinting.

scholarly journals Interacting effects of forest fragmentation and howler monkey foraging on germination and disperal of fig seeds

Oryx ◽  
2002 ◽  
Vol 36 (3) ◽  
pp. 266-271 ◽  
Author(s):  
Juan Carlos Serio-Silva ◽  
Victor Rico-Gray
Keyword(s):  
Dispersal Distance ◽  
Alouatta Palliata ◽  
Howler Monkey ◽  
Forest Fragment ◽  
Howler Monkeys ◽  
Conservation Policies ◽  
Dispersal Distances ◽  
Alouatta Palliata Mexicana ◽  
Fragmented Forests ◽  
Individual Trees

We studied changes in germination rates and dispersal distance of seeds of Ficus perforata and F. lundelli dispersed by howler monkeys (Alouatta palliata mexicana), in a small (40 ha) ‘disturbed’ and a larger (>600 ha) ‘preserved’ tropical rainforest in southern Veracruz, Mexico. The interaction between A. p. mexicana and Ficus (Urostigma) spp. is beneficial for the interacting species and has important implications for their conservation. Howler monkeys gain from the ingestion of an important food source, germination rates of Ficus seeds are improved by passage through the monkeys' digestive tract, and the seeds are more likely to be deposited in a site suitable for germination and development. Seed dispersal distances are relatively larger in the preserved site, with both the size of the forest area and the spatial pattern of Ficus affecting the dispersal process. In a large forest fragment with ‘regularly’ distributed Ficus individuals the howler monkeys move away from the seed source, increasing the probability that the seeds are desposited on a tree other than Ficus, which is important for the germination and future development of a hemiepiphytic species. In a small forest fragment with trees distributed in clumps howlers repeatedly use the same individual trees, and faeces containing seeds may be dropped on unsuitable trees more often. These are key issues when addressing conservation policies for fragmented forests.

scholarly journals Dispersal Kernel Determines Symmetry of Spread and Geographical Range for an Insect

2009 ◽  
Vol 2009 ◽  
pp. 1-4 ◽  
Author(s):  
Jeffrey D. Holland
Keyword(s):  
Sugar Maple ◽  
Spatial Dynamics ◽  
Geographic Range ◽  
Dispersal Distance ◽  
Dispersal Kernel ◽  
Geographical Range ◽  
Spatial Distributions ◽  
Longhorned Beetle ◽  
Ecological Patterns ◽  
Dispersal Distances

The distance from a source patch that dispersing insects reach depends on the number of dispersers, or random draws from a probability density function called a dispersal kernel, and the shape of that kernel. This can cause asymmetrical dispersal between habitat patches that produce different numbers of dispersers. Spatial distributions based on these dynamics can explain several ecological patterns including megapopulations and geographic range boundaries. I hypothesized that a locally extirpated longhorned beetle, the sugar maple borer, has a new geographical range shaped primarily by probabilistic dispersal distances. I used data on occurrence from Ontario, Canada to construct a model of geographical range in Indiana, USA based on maximum dispersal distance scaled by habitat area. This model predicted the new range boundary within 500 m very accurately. This beetle may be an ideal organism for exploring spatial dynamics driven by dispersal.

scholarly journals Are complications of endoscopic sphincterotomy age related?

Gut ◽  
1997 ◽  
Vol 41 (4) ◽  
pp. 545-548 ◽  
Author(s):  
G T Deans ◽  
P Sedman ◽  
D F Martin ◽  
C M S Royston ◽  
C K Leow ◽  
...  
Keyword(s):  
Laparoscopic Cholecystectomy ◽  
Endoscopic Sphincterotomy ◽  
Short Term ◽  
Endoscopic Retrograde ◽  
Younger Patients ◽  
Age Related ◽  
Increased Risk ◽  
Ascending Cholangitis ◽  
Retroperitoneal Perforation ◽  
The Common

Background—Endoscopic retrograde cholangiopancreatography sphincterotomy is increasingly performed in younger patients undergoing laparoscopic cholecystectomy. However, the safety of endo- scopic sphincterotomy in this age group, relative to that in older patients, is unknown.Aim—To determine whether the development of short term complications following endoscopic sphincterotomy is age related.Patients and methods—A prospective multicentre audit of 958 patients (mean age 73, range 14–97, years) undergoing a total of 1000 endoscopic sphincterotomies.Results—Two deaths occurred, both from postsphincterotomy acute pancreatitis. Postprocedural complications developed in 24 patients: pancreatitis in 10, ascending cholangitis in seven, bleeding in four, and retroperitoneal perforation in three. There were six complications (five cases of pancreatitis and one bleed; 2.2%) and no deaths in the 281 (29.3%) patients aged under 65 years. In comparison, 18 (2.6%) of the 677 patients aged over 65 years developed a complication (cholangitis in seven, pancreatitis in five, bleeding in three, and perforation in three). Patients under 35, 45, 55, and 65 years were not at significantly increased risk of complication than those over these ages (relative risk for those under compared with those over 65 years 0.83, 95% confidence intervals 0.41–1.67, p=0.74).Conclusion—Short term complications following endoscopic sphincterotomy are not related to age. Younger patients undergoing laparoscopic cholecystectomy need not be denied endoscopic sphincterotomy for fear that the risks are greater than if they undergo surgical exploration of the common bile duct.

scholarly journals Adaptations and responses of the common dandelion to low atmospheric pressure in high altitude environments

2021 ◽  
Author(s):  
Carla C. M. Arce ◽  
Zoe Bont ◽  
Ricardo A. R. Machado ◽  
Paulo F. Cristaldo ◽  
Matthias Erb
Keyword(s):  
High Altitude ◽  
Atmospheric Pressure ◽  
The Common ◽  
Low Atmospheric Pressure ◽  
Common Dandelion

scholarly journals Symbol Grounding Association in Multimodal Sequences with Missing Elements

2018 ◽  
Vol 61 ◽  
pp. 787-806
Author(s):  
Federico Raue ◽  
Andreas Dengel ◽  
Thomas M. Breuel ◽  
Marcus Liwicki
Keyword(s):  
Dynamic Time Warping ◽  
Learning Rule ◽  
Abstract Concepts ◽  
Time Warping ◽  
Short Term ◽  
Recent Approach ◽  
Extra Step ◽  
The Common ◽  
Dynamic Time ◽  
General Scope

In this paper, we extend a symbolic association framework for being able to handle missing elements in multimodal sequences. The general scope of the work is the symbolic associations of object-word mappings as it happens in language development in infants. In other words, two different representations of the same abstract concepts can associate in both directions. This scenario has been long interested in Artificial Intelligence, Psychology, and Neuroscience. In this work, we extend a recent approach for multimodal sequences (visual and audio) to also cope with missing elements in one or both modalities. Our method uses two parallel Long Short-Term Memories (LSTMs) with a learning rule based on EM-algorithm. It aligns both LSTM outputs via Dynamic Time Warping (DTW). We propose to include an extra step for the combination with the max operation for exploiting the common elements between both sequences. The motivation behind is that the combination acts as a condition selector for choosing the best representation from both LSTMs. We evaluated the proposed extension in the following scenarios: missing elements in one modality (visual or audio) and missing elements in both modalities (visual and sound). The performance of our extension reaches better results than the original model and similar results to individual LSTM trained in each modality.

scholarly journals PREDICTING DAILY PM2.5 USING WEIGHTED LONG SHORT-TERM MEMORY NEURAL NETWORK MODEL

2020 ◽  
Vol XLIII-B3-2020 ◽  
pp. 1451-1455
Author(s):  
H. Fan ◽  
M. Yang ◽  
F. Xiao ◽  
K. Zhao
Keyword(s):  
Neural Network ◽  
Air Pollution ◽  
Short Term Memory ◽  
Meteorological Data ◽  
Series Data ◽  
Wind Condition ◽  
Short Term ◽  
Term Memory ◽  
Long Short Term Memory ◽  
Pm2.5 Concentration

Abstract. Over the past few decades, air pollution has caused serious damage on public health, thus making accurate predictions of PM2.5 crucial. Due to the transportation of air pollutants among areas, the PM2.5 concentration is strongly spatiotemporal correlated. However, the distribution of air pollution monitoring sites is not even, making the spatiotemporal correlation between the central site and surrounding sites varies with different density of sites, and this was neglected by most existing methods. To tackle this problem, this study proposed a weighted long short-term memory neural network extended model (WLSTME), which addressed the issue that how to consider the effect of the density of sites and wind condition on the spatiotemporal correlation of air pollution concentration. First, several the nearest surrounding sites were chosen as the neighbour sites to the central station, and their distance as well as their air pollution concentration and wind condition were input to multi-layer perception (MLP) to generate weighted historical PM2.5 time series data. Second, historical PM2.5 concentration of the central site and weighted PM2.5 series data of neighbour sites were input into LSTM to address spatiotemporal dependency simultaneously and extract spatiotemporal features. Finally, another MLP was utilized to integrate spatiotemporal features extracted above with the meteorological data of central site to generate the forecasts future PM_2.5 concentration of the central site. Daily PM_2.5 concentration and meteorological data on Beijing–Tianjin–Hebei from 2015 to 2017 were collected to train models and evaluate the performance. Experimental results with 3 other methods showed that the proposed WLSTME model has the lowest RMSE (40.67) and MAE (26.10) and the highest p (0.59). This finding confirms that WLSTME can significantly improve the PM2.5 prediction accuracy.

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