scholarly journals Broad spectrum pesticide application alters natural enemy communities and may facilitate secondary pest outbreaks

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e4179 ◽  
Author(s):  
Matthew P. Hill ◽  
Sarina Macfadyen ◽  
Michael A. Nash
Keyword(s):  
Natural Enemy ◽  
Control Method ◽  
The Other ◽  
Community Diversity ◽  
Pest Species ◽  
Pesticide Application ◽  
Response Curves ◽  
Large Variability ◽  
Invertebrate Communities ◽  
Pest Outbreaks

BackgroundPesticide application is the dominant control method for arthropod pests in broad-acre arable systems. In Australia, organophosphate pesticides are often applied either prophylactically, or reactively, including at higher concentrations, to control crop establishment pests such as false wireworms and earth mite species. Organophosphates are reported to be disruptive to beneficial species, such as natural enemies, but this has not been widely assessed in Australian systems. Neither has the risk that secondary outbreaks may occur if the natural enemy community composition or function is altered.MethodsWe examine the abundance of ground-dwelling invertebrate communities in an arable field over successive seasons under rotation; barley, two years of wheat, then canola. Two organophosphates (chlorpyrifos and methidathion) were initially applied at recommended rates. After no discernible impact on target pest species, the rate for chlorpyrifos was doubled to elicit a definitive response to a level used at establishment when seedling damage is observed. Invertebrates were sampled using pitfalls and refuge traps throughout the experiments. We applied measures of community diversity, principal response curves and multiple generalised linear modelling techniques to understand the changes in pest and natural enemy communities.ResultsThere was large variability due to seasonality and crop type. Nevertheless, both pest (e.g., mites and aphids) and natural enemy (e.g., predatory beetles) invertebrate communities were significantly affected by application of organophosphates. When the rate of chlorpyrifos was increased there was a reduction in the number of beetles that predate on slug populations. Slugs displayed opposite trends to many of the other target pests, and actually increased in numbers under the higher rates of chlorpyrifos in comparison to the other treatments. Slug numbers in the final rotation of canola resulted in significant yield loss regardless of pesticide application.DiscussionOrganophosphates are a cost-effective tool to control emergent pests in broad-acre arable systems in Australia. We found risks associated with prophylactic application in fields under rotation between different crop types and significant changes to the community of pests and natural enemy. Disrupting key predators reduced effective suppression of other pests, such as slugs, and may lead to secondary outbreaks when rotating with susceptible crops such as canola. Such non-target impacts are rarely documented when studies focus on single-species, rather than community assessments. This study represents a single demonstration of how pesticide application can lead to secondary outbreaks and reinforces the need for studies that include a longer temporal component to understand this process further.

ALDOSTERONE STIMULATION IN VITRO

1965 ◽  
Vol 50 (2) ◽  
pp. 301-309 ◽  
Author(s):  
Jürg Müller
Keyword(s):  
Ammonium Chloride ◽  
Human Urine ◽  
Incubation Medium ◽  
The Other ◽  
Ammonium Ions ◽  
Response Curves ◽  
Urine Extract ◽  
Similar Dose ◽  
Aldosterone Production

ABSTRACT An extract of human urine, which was previously shown to stimulate aldosterone production by rat adrenal sections, was further purified. Evidence was obtained that its aldosterone-stimulating effect was due to the presence of ammonium ions. Addition of ammonium chloride and of urine extract to the incubation medium caused identical increases in aldosterone production in vitro. In addition to ammonium ions, rubidium and caesium ions also stimulated aldosterone production up to 250% that of control values without a significant effect on corticosterone production. Similar dose-response curves were obtained when increasing concentrations of potassium, ammonium, rubidium and caesium ions were tested. Aldosterone production was maximal at concentrations of 7 mval/1 and was significantly lower at higher concentrations. When ammonium chloride and ACTH were simultaneously added to the incubation medium, the production of aldosterone and of corticosterone was lower than with ACTH alone. On the other hand, the stimulating activity on aldosterone and corticosterone production by »TPN« (NADP) and glucose-6-phosphate was enhanced by the simultaneous addition of ammonium chloride.

Are membrane properties essential for the circadian rhythm of Gonyaulax?

1984 ◽  
Vol 247 (2) ◽  
pp. R250-R256
Author(s):  
H. G. Scholubbers ◽  
W. Taylor ◽  
L. Rensing
Keyword(s):  
Circadian Rhythm ◽  
Phase Shift ◽  
Fluorescence Polarization ◽  
The Other ◽  
Membrane Properties ◽  
Response Curves ◽  
Whole Cells ◽  
Different Temperatures ◽  
Free Running ◽  
Free Running Period

Membrane properties of whole cells of Gonyaulax polyedra were measured by fluorescence polarization. Circadian changes of fluorescence polarization exist in exponentially growing cultures. They show an amplitude larger than that of stationary cultures, indicating that a part of the change is due to or amplified by an ongoing cell cycle. Measurements of parameters of the circadian glow rhythm were analyzed for possible correlation with the membrane data. Considerable differences (Q10 = 2.5-3.0) in fluorescence polarization were found in cultures kept at different temperatures ranging from 15 to 27.5 degrees C. The free-running period length at different temperatures, on the other hand, differed only slightly (Q10 = 0.9-1.1). Stationary cultures showed higher fluorescence polarization compared with growing cultures, whereas the free-running period lengths did not differ in cultures of various densities and growth rates. Temperature steps of different sign changed the fluorescence polarization slightly in different directions. The phase shift of 4-h pulses (-5, -9, +7 degrees C) resulted in maximal phase advances of 4, 6, and 2 h, respectively. The phasing of the phase-response curves was identical in all these experiments, a finding not to be expected if the pulses act via the measured membrane properties. Pulses of drugs that change the fluorescence polarization (e.g., chlorpromazine and lidocaine) did not or only slightly phase-shift the circadian rhythm.

The Parallel Mechanism and Variable Acceleration Control Method

2013 ◽  
Vol 579-580 ◽  
pp. 659-664
Author(s):  
Xiang Bo Ouyang ◽  
Ke Tian Li ◽  
Hong Jian Xia ◽  
Su Juan Wang ◽  
Huan Wei Zhou ◽  
...  
Keyword(s):  
Parallel Mechanism ◽  
Control Method ◽  
The Other ◽  
Connecting Rod ◽  
Motion Platform ◽  
The Third ◽  
Symmetric Structure ◽  
Slide Block ◽  
Operation Process ◽  
Moving Platform

t presents the parallel mechanism and variable acceleration control method, which is composed of slider, connecting rod, moving platform and linear guide etc. The motion platform is supported by three connecting rods through hinging, the other end of the connecting rods are respectively hinged with two sliders. Among them two pairs of connecting rod, two sliders and the moving platform formed a symmetric structure that is the so called Parallel Mechanism. The third connecting rod is parallel to one of two connecting rods, so that the two parallel connecting rods, slide block and the moving platform formed a parallelogram structure, it makes that the moving platform is always parallel to liner guiderail in the process of movement. By controlling the two sliders moving in the way of variable acceleration, it can make the trajectory curve, speed curve and acceleration curve of the moving platform are continuous, smooth, so impact and vibration of the moving platform is limited in the operation process.

scholarly journals Overshooting calibration and age determination from evolved binary systems

2018 ◽  
Vol 615 ◽  
pp. A62 ◽  
Author(s):  
G. Valle ◽  
M. Dell’Omodarme ◽  
P. G. Prada Moroni ◽  
S. Degl’Innocenti
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Relative Error ◽  
Binary Systems ◽  
The Other ◽  
Helium Burning ◽  
Primary Star ◽  
Large Variability ◽  
Convective Core ◽  
The Masses

Aims. The capability of grid-based techniques to estimate the age together with the convective core overshooting efficiency of stars in detached eclipsing binary systems for main sequence stars has previously been investigated. We have extended this investigation to later evolutionary stages and have evaluated the bias and variability on the recovered age and convective core overshooting parameter accounting for both observational and internal uncertainties. Methods. We considered synthetic binary systems, whose age and overshooting efficiency should be recovered by applying the SCEPtER pipeline to the same grid of models used to build the mock stars. We focus our attention on a binary system composed of a 2.50 M⊙ primary star coupled with a 2.38 M⊙ secondary. To explore different evolutionary scenarios, we performed the estimation at three different times: when the primary is at the end of the central helium burning, when it is at the bottom of the RGB, and when it is in the helium core burning phase. The Monte Carlo simulations have been carried out for two typical values of accuracy on the mass determination, that is, 1% and 0.1%. Results. Adopting typical observational uncertainties, we found that the recovered age and overshooting efficiency are biased towards low values in all three scenarios. For an uncertainty on the masses of 1%, the underestimation is particularly relevant for a primary in the central helium burning stage, reaching − 8.5% in age and − 0.04 (− 25% relative error) in the overshooting parameter β. In the other scenarios, an undervaluation of the age by about 4% occurs. A large variability in the fitted values between Monte Carlo simulations was found: for an individual system calibration, the value of the overshooting parameter can vary from β = 0.0 to β = 0.26. When adopting a 0.1% error on the masses, the biases remain nearly unchanged but the global variability is suppressed by a factor of about two. We also explored the effect of a systematic discrepancy between the artificial systems and the model grid by accounting for an offset in the effective temperature of the stars by ± 150 K. For a mass error of 1% the overshooting parameter is largely biased towards the edges of the explored range, while for the lower mass uncertainty it is basically unconstrained from 0.0 to 0.2. We also evaluate the possibility of individually recovering the β value for both binary stars. We found that this is impossible for a primary near to central hydrogen exhaustion owing to huge biases for the primary star of + 0.14 (90% relative error), while in the other cases the fitted β are consistent, but always biased by about − 0.04 (− 25% relative error). Finally, the possibility to distinguish between models computed with mild overshooting from models with no overshooting was evaluated, resulting in a reassuring power of distinction greater than 80%. However, the scenario with a primary in the central helium burning was a notable exception, showing a power of distinction lower than 5%.

scholarly journals Preferred temperature and thermal breadth of birds wintering in peninsular Spain – the limited effect of temperature on species distribution

2016 ◽  
Author(s):  
Luis M. Carrascal ◽  
Sara Villén-Pérez ◽  
David Palomino
Keyword(s):  
Species Abundance ◽  
Bird Species ◽  
Effect Of Temperature ◽  
Response Curves ◽  
Large Variability ◽  
Preferred Temperature ◽  
Mean Temperature ◽  
The Mean ◽  
Thermal Preferences ◽  
Peninsular Spain

Background. Availability of environmental energy, as measured by temperature, is expected to limit the abundance and distribution of endotherms wintering at temperate latitudes. A prediction of this hypothesis is that birds should attain their highest abundances in warmer areas. However, there may be a spatial mismatch between species preferred habitats and species preferred temperatures, so some species might end-up wintering in sub-optimal thermal environments. Methods. We model the influence of minimum winter temperature on the relative abundance of 106 terrestrial bird species wintering in peninsular Spain, at 10x10 Km2 resolution, using 95%-quantile regressions. We analyze general trends across species on the shape of the response curves, the environmental preferred temperature (at which the species abundance is maximized), the mean temperature in the area of distribution and the thermal breadth (area under the abundance-temperature curve). Results. There is a large interspecific variability on the thermal preferences and specialization of species. Despite this large variability, there is a preponderance of positive relationships between species abundance and temperature, and on average species attain their maximum abundances in areas 1.9 ºC warmer than the average temperature available in peninsular Spain. The mean temperature in the area of distribution is lower than the thermal preferences of the species, although both parameters are highly correlated. Discussion. Most species prefer the warmest environments to overwinter, which suggests that temperature imposes important restrictions to birds wintering in the Iberian Peninsula. However, most individuals overwinter in locations colder than the species thermal preferences, probably reflecting a limitation of environments combining habitat and thermal preferences. Beyond these general trends, there is a high inter-specific variation in the versatility of species using the available thermal space .

Neighbor Topology for Dynamic Plane Coverage in Swarm Leading Control

2012 ◽  
Vol 3 (1) ◽  
pp. 59-75
Author(s):  
Keitaro Naruse ◽  
Tatsuya Sato
Keyword(s):  
Small Area ◽  
Control Method ◽  
The Other ◽  
Large Field ◽  
Multiple Robots ◽  
Coverage Problem ◽  
Coverage Area ◽  
Fixed Distance ◽  
Equal Density ◽  
Dynamic Plane

The objective of this paper is to solve the dynamic plane coverage problem by the movement of multiple robots, for example, sprinkling water to a large field by several vehicles or aircrafts, in which all of the points in the field should be covered by the robots in an almost equal density. One of the ways to solve it is the swarm leading control method, in which one of the robots, called a target, moves along a path in the field, and all the other robots move around the target with a fixed distance. In the process, the topology of the robots affects to the efficiency of the dynamic plane coverage problem. If the topology is a tight one, the swarm can be stable but the coverage area can be limited in a small area. On the other hand, if it is a loose one, an opposite thing can be happened. In this paper, the relation between the topology and the efficiency is discussed numerically.

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