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Search Results: 1 - 10 of 308058 matches for " Eric J. Warrant "
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Nocturnal Homing: Learning Walks in a Wandering Spider?
Thomas N?rgaard,Yakir L. Gagnon,Eric J. Warrant
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0049263
Abstract: Homing by the nocturnal Namib Desert spider Leucorchestris arenicola (Araneae: Sparassidae) is comparable to homing in diurnal bees, wasps and ants in terms of path length and layout. The spiders' homing is based on vision but their basic navigational strategy is unclear. Diurnal homing insects use memorised views of their home in snapshot matching strategies. The insects learn the visual scenery identifying their nest location during learning flights (e.g. bees and wasps) or walks (ants). These learning flights and walks are stereotyped movement patterns clearly different from other movement behaviours. If the visual homing of L. arenicola is also based on an image matching strategy they are likely to exhibit learning walks similar to diurnal insects. To explore this possibility we recorded departures of spiders from a new burrow in an unfamiliar area with infrared cameras and analysed their paths using computer tracking techniques. We found that L. arenicola performs distinct stereotyped movement patterns during the first part of their departures in an unfamiliar area and that they seem to learn the appearance of their home during these movement patterns. We conclude that the spiders perform learning walks and this strongly suggests that L. arenicola uses a visual memory of the burrow location when homing.
The Dung Beetle Dance: An Orientation Behaviour?
Emily Baird,Marcus J. Byrne,Jochen Smolka,Eric J. Warrant,Marie Dacke
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030211
Abstract: An interesting feature of dung beetle behaviour is that once they have formed a piece of dung into a ball, they roll it along a straight path away from the dung pile. This straight-line orientation ensures that the beetles depart along the most direct route, guaranteeing that they will not return to the intense competition (from other beetles) that occurs near the dung pile. Before rolling a new ball away from the dung pile, dung beetles perform a characteristic “dance,” in which they climb on top of the ball and rotate about their vertical axis. This dance behaviour can also be observed during the beetles' straight-line departure from the dung pile. The aim of the present study is to investigate the purpose of the dung beetle dance. To do this, we explored the circumstances that elicit dance behaviour in the diurnal ball-rolling dung beetle, Scarabaeus (Kheper) nigroaeneus. Our results reveal that dances are elicited when the beetles lose control of their ball or lose contact with it altogether. We also find that dances can be elicited by both active and passive deviations of course and by changes in visual cues alone. In light of these results, we hypothesise that the dung beetle dance is a visually mediated mechanism that facilitates straight-line orientation in ball-rolling dung beetles by allowing them to 1) establish a roll bearing and 2) return to this chosen bearing after experiencing a disturbance to the roll path.
Hornets Can Fly at Night without Obvious Adaptations of Eyes and Ocelli
Almut Kelber, Fredrik Jonsson, Rita Wallén, Eric Warrant, Torill Kornfeldt, Emily Baird
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0021892
Abstract: Hornets, the largest social wasps, have a reputation of being facultatively nocturnal. Here we confirm flight activity of hornet workers in dim twilight. We studied the eyes and ocelli of European hornets (Vespa crabro) and common wasps (Vespula vulgaris) with the goal to find the optical and anatomical adaptations that enable them to fly in dim light. Adaptations described for obligately nocturnal hymenoptera such as the bees Xylocopa tranquebarica and Megalopta genalis and the wasp Apoica pallens include large ocelli and compound eyes with wide rhabdoms and large facet lenses. Interestingly, we did not find any such adaptations in hornet eyes or ocelli. On the contrary, their eyes are even less sensitive than those of the obligately diurnal common wasps. Therefore we conclude that hornets, like several facultatively nocturnal bee species such as Apis mellifera adansonii, A. dorsata and X. tenuiscapa are capable of seeing in dim light simply due to the large body and thus eye size. We propose that neural pooling strategies and behavioural adaptations precede anatomical adaptations in the eyes and ocelli when insects with apposition compound eyes turn to dim light activity.

生物物理学报 , 1991,
Abstract: Retinula cell responses were recored continuously from the compound eye of Buch cricket with the intracellular electrode recording method at different adaption states (light-and dark-adapted states) during a 24-h period(day and night times). The angular, spectral, polarization and absolute sensitivities well as the time course of the adaptation changes of the retinula cell in the side region of th compound eyes of the Bush cricket were investigated on which no report has been seen.
Practical Applications of Cosmology to Human Society  [PDF]
Eric J. Chaisson
Natural Science (NS) , 2014, DOI: 10.4236/ns.2014.610077
Abstract: Complex systems throughout Nature display structures and functions that are built and maintained, at least in part, by optimal energies flowing through them—not specific, ideal values, rather ranges in energy rate density below which systems are starved and above which systems are destroyed. Cosmic evolution, as a physical cosmology that notably includes life, is rich in empirical findings about many varied systems that can potentially help assess global problems facing us here on Earth. Despite its grand and ambitious objective to unify theoretical understanding of all known complex systems from big bang to humankind, cosmic evolution does have useful, practical applications from which humanity could benefit. Cosmic evolution’s emphasis on quantitative data analyses might well inform our attitudes toward several serious issues now challenging 21st-century society, including global warming, smart machines, world economics, and cancer research. This paper comprises one physicist’s conjectures about each of these applied topics, suggesting how energy-flow modeling can guide our search for viable solutions to real-world predicaments confronting civilization today.


生物物理学报 , 1990,
Abstract: In Locust and Bush cricket, regular changes of the angular sensitivity of the retinula cells of the ommatidia in the side region of the compound eye have been investigated by intercellular recording method under dark and light adapted states during the day and night times. The results show that the regular changes of the angular sensitivity of the retinula cells not only depend on adapted states, but also on the changes of the day and night times.Corresponding changes of the diameter of the aoss - sectional area of the distal rhabdom in the ommatidia have been confirmed and measured by means of a microscope method. We propose a new mechanism of pupil control in the insect compound eye.
H2 Gas Charging of Zero-Valent Iron and TCE Degradation  [PDF]
Chen Zhao, Eric J. Reardon
Journal of Environmental Protection (JEP) , 2012, DOI: 10.4236/jep.2012.33034
Abstract: Granular zero-valent iron (ZVI) has been widely used to construct permeable reactive barriers (PRB) for the in situ remediation of groundwater contaminated with halogenated hydrocarbons. In the anaerobic condition of most groundwater flow systems, iron undergoes corrosion by water and results in hydrogen gas generation. Several studies have shown that some of the hydrogen gas generated at the iron/water interface can diffuse into the iron lattice. Hydrogen gas also can be an electron donor for dechlorination of chlorinated compounds. In this study, the possibility of hydrogen gas bound in the lattice of ZVI playing a role in dehalogenation and improving the degradation efficiency of ZVI was evaluated. Two different granular irons were tested: one obtained from Quebec Metal Powders Ltd (QMP) and the other from Connelly-GPM. Ltd. For each type of iron, two samples were mixed with water and sealed in testing cells. Since the rate of hydrogen entry varies directly with the square root of the hydrogen pressure, one sample was maintained for several weeks under near-vacuum conditions to minimize the amount of hydrogen entering the iron lattice. The other sample was maintained for the same period at a hydrogen pressure of over 400 kPa to maximize the amount of hydrogen entering the iron lattice. The degradation abilities of the reacted ironsand the original iron materials were tested by running several sets of batch tests. The results of this study show little to no improvement of inorganic TCE degradation reactions due to the presence of lattice-stored hydrogen in iron material. This is probably due to the high energiesrequired to release hydrogen trapped in the iron lattice. However, there are certain chemical compounds that can promote hydrogen release from the iron lattice, and there may be bacteria that can utilize lattice-bound hydrogen to carry out dechlorination reactions.
In Vitro Model Systems to Investigate Drug Resistance Mechanisms in Pancreatic Cancer Cells  [PDF]
Eric Romney, Vinay J. Nagaraj
Advances in Biological Chemistry (ABC) , 2015, DOI: 10.4236/abc.2015.57026
Abstract: With a 5-year survival rate of less than 6%, the diagnosis of pancreatic cancer is devastating news for any patient. Gemcitabine, the most commonly used chemotherapy drug, only improves survival by approximately 1.5 months. A major obstacle to the treatment of pancreatic cancer with gemcitabine is the development of drug resistance. To better understand the precise mechanisms by which patient tumor cells gain resistance to gemcitabine, a cell culture model system that more accurately reflects the development of drug resistance in vivo is required. In this study, cultured pancreatic adenocarcinoma BxPC-3 cells were subjected to two different treatment regimens. The first method—termed pulse method—involves periodically treating separate cultures of BxPC-3 cells with constant predetermined doses of gemcitabine. The second treatment regimen—termed incremental method—consists of treating BxPC-3 cells with increasing doses of gemcitabine from 10 to 100 nM. While all treated cells showed enhanced resistance to gemcitabine, low-dose pulse treatments were sufficient to produce highly drug-resistant cells as evidenced by higher IC50 measurements. Pulse treatments also resulted in slower growth rates and increased doubling time of the drug-resistant cells. Morphological changes indicate cellular abnormalities linked to likely epithelial-to-mesenchymal transition and drug resistance. Our preliminary results indicate that the pulse method may better simulate resistance observed in patients undergoing chemotherapy and may serve as a superior model to investigate drug-resistance. This model can also help with identification of appropriate markers that determine the presence of drug-resistant cells and help clinicians adjust treatment strategies to improve outcomes for patients suffering from pancreatic cancer.
Applying Downscaled Global Climate Model Data to a Groundwater Model of the Suwannee River Basin, Florida, USA  [PDF]
Eric Swain, J. Hal Davis
American Journal of Climate Change (AJCC) , 2016, DOI: 10.4236/ajcc.2016.54037
Abstract: The application of Global Climate Model (GCM) output to a hydrologic model allows for comparisons between simulated recent and future conditions and provides insight into the dynamics of hydrology as it may be affected by climate change. A previously developed numerical model of the Suwannee River Basin, Florida, USA, was modified and calibrated to represent transient conditions. A simulation of recent conditions was developed for the 372-month period 1970-2000 and was compared with a simulation of future conditions for a similar-length period 2039-2069, which uses downscaled GCM data. The MODFLOW groundwater-simulation code was used in both of these simulations, and two different MODFLOW boundary condition “packages” (River and Streamflow-Routing Packages) were used to represent interactions between surface-water and groundwater features. The hydrologic fluxes between the atmosphere and landscape for the simulation of future conditions were developed from dynamically downscaled precipitation and evapotranspiration (ET) data generated by the Community Climate System Model (CCSM). The downscaled precipitation data were interpolated for the Suwannee River model grid, and the downscaled ET data were used to develop potential ET and were interpolated to the grid. The future period has higher simulated rainfall (10.8 percent) and ET (4.5 percent) than the recent period. The higher future rainfall causes simulated groundwater levels to rise in areas where they are deep and have little ET in either the recent or future case. However, in areas where groundwater levels were originally near the surface, the greater future ET causes groundwater levels to become lower despite the higher projected rainfall. The general implication is that unsaturated zone depth could be more spatially uniform in the future and vegetation that requires a range of conditions (substantially wetter or drier than average) could be detrimentally affected. This vegetation would include wetland species, especially in areas inland from the coast.
Use of SWAT to Model Impact of Climate Change on Sediment Yield and Agricultural Productivity in Western Oregon, USA  [PDF]
G. W. Mueller-Warrant, C. L. Phillips, K. M. Trippe
Open Journal of Modern Hydrology (OJMH) , 2019, DOI: 10.4236/ojmh.2019.92004
Abstract: Climate change predictions for the Pacific Northwest region of the United States of America include increasing temperatures, intensification of winter precipitation, and a shift from mixed snow/rain to rain-dominant events, all of which may increase the risk of soil erosion and threaten agricultural and ecological productivity. Here we used the agricultural/environmental model SWAT with climate predictions from the Coupled Model Intercomparison Project 5 (CMIP5) “high CO2 emissions” scenario (RCP8.5) to study the impact of altered temperature and precipitation patterns on soil erosion and crop productivity in the Willamette River Basin of western Oregon. An ensemble of 10 climate models representing the full range in temperature and precipitation predictions of CIMP5 produced substantial increases in sediment yield, with differences between yearly averages for the final (2090-2099) and first (2010-2019) decades ranging from 3.9 to 15.2 MT·ha-1 among models. Sediment yield in the worst case model (CanESM2) corresponded to loss of 1.5 - 2.7 mm·soil·y-1, equivalent to potentially stripping productive topsoil from the landscape in under two centuries. Most climate models predicted only small increases in precipitation (an average of 5.8% by the end of the 21st century) combined with large increases in temperature (an average of 0.05°C·
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