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The physical environment of the aerosphere is both complex anddynamic, and poses many challenges to the locomotor systemsof the three extant evolutionary lineages of flying animals.Many features of the aerosphere, operating over spatial andtemporal scales of many orders of magnitude, have the potentialto be important influences on animal flight, and much as marineecologists have studied the relationship between physical oceanographyand swimming locomotion, a subfield of aeroecology can focusattention on the ways the biology of flight is influenced bythese characteristics. Airflows are altered and modulated bymotion over and around natural and human-engineered structures,and both vortical flow structures and turbulence are introducedto the aerial environment by technologies such as aircraft andwind farms. Diverse aspects of the biology of flight may bebetter understood with reference to an aeroecological approach,particularly the mechanics and energetics of flight, the sensingof aerial flows, and the motor control of flight. Moreover,not only does the abiotic world influence the aerospheric conditionsin which animals fly, but flying animals also, in turn, changethe flow environment in their immediate vicinity, which caninclude the air through which other animals fly, particularlywhen animals fly in groups. Flight biologists can offer considerableinsight into the ecology of the aerial world, and an aeroecologicalapproach holds great promise for stimulating and enriching thestudy of the biology of flight. 相似文献
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Kalko EK Estrada Villegas S Schmidt M Wegmann M Meyer CF 《Integrative and comparative biology》2008,48(1):60-73
Bats feature prominently among organisms that occupy the aerosphereas they extensively use this environment for foraging, but alsofor dispersal, migration, and behavioral interactions. Differentialuse of the aerosphere is an important factor structuring batassemblages, with species exhibiting distinct morphological,physiological, and sensory adaptations to different habitattypes. This necessitates comprehensive sampling methodologiessuch as combined ground-level and canopy-level mist nettingas well as acoustic monitoring to assess the presence, diversity,and activity of different functional groups of species adequately.Recent technological advances in acoustic detection and in methodsof analysis, coupled with the expansion of libraries of echolocationcalls for species identification, now allow for the reliablequantification of species numbers and activity of the scarcelyknown group of aerial insectivorous bats, particularly in species-richtropical assemblages. We provide a brief, exemplary overviewof recent studies on bats conducted in Panamá to demonstratethe necessity of comprehensive sampling methods and applicationof new technologies in order to adequately depict assemblagecomposition and responses of bats to structural changes in habitatsinduced by fragmentation. In addition to acoustic methods, miniaturizationof radio transmitters has provided new insights into the patternsof spatial use of the aerosphere by bats and has identifiedspecies-specific differences in mobility as one of the importanttraits that determines bats reactions to anthropogenicalterations of the landscape. Following the goals of the symposiumon aeroecology, we propose new avenues of research for probingthe aerosphere. We discuss how integration of a diverse arrayof remote sensing tools with data on species distribution andspecies traits, such as mobility and edge-sensitivity, mightprovide novel opportunities for the development, and applicationof conservation-oriented monitoring systems. 相似文献
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Organisms in the aerosphere have been detected by radar sinceits development in the 1940s. The national network of Dopplerweather radars (WSR-88D) in the United States can readily detectbirds, bats, and insects aloft. Level-II data from the radarcontain information on the reflectivity and radial velocityof targets and on width of the spectrum (SD of radial velocitiesin a radar pulse volume). Information on reflectivity can beused to quantify density of organisms aloft and radial velocitycan be used to discriminate different types of targets basedon their air speeds. Spectral width can also provide some usefulinformation when organisms with very different air speeds arealoft. Recent work with dual-polarization radar suggests thatit may be useful for discriminating birds from insects in theaerosphere, but more development and biological validation arerequired. 相似文献
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Dynamic texture spreading is a filling-in phenomenon where a colored pattern perceptually spreads onto an area confined by virtual contours in a multi-aperture motion display. The spreading effect is qualitatively similar to static texture spreading but widely surpasses it in strength, making it particularly suited for quantitative studies of visual interpolation processes. We first carried out two experiments to establish with objective tasks that texture spreading is a genuine representation of surface qualities and thus goes beyond mere contour interpolation. Two subsequent experiments serve to relate the phenomenon to ongoing discussions about potentially responsible mechanisms for spatiotemporal integration. With a phenomenological method, we examined to what extent simple sensory persistence might be causally involved in the effect under consideration. Most of our findings are consistent with the idea of sensory persistence, and indicate that information fragments are integrated over a time window of about 100 to 180 ms to form a complete surface representation. 相似文献
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We investigate the impact of past climates on plant diversification by tracking the "footprint" of climate change on a phylogenetic tree. Diversity within the cosmopolitan carnivorous plant genus Drosera (Droseraceae) is focused within Mediterranean climate regions. We explore whether this diversity is temporally linked to Mediterranean-type climatic shifts of the mid-Miocene and whether climate preferences are conservative over phylogenetic timescales. Phyloclimatic modeling combines environmental niche (bioclimatic) modeling with phylogenetics in order to study evolutionary patterns in relation to climate change. We present the largest and most complete such example to date using Drosera. The bioclimatic models of extant species demonstrate clear phylogenetic patterns; this is particularly evident for the tuberous sundews from southwestern Australia (subgenus Ergaleium). We employ a method for establishing confidence intervals of node ages on a phylogeny using replicates from a Bayesian phylogenetic analysis. This chronogram shows that many clades, including subgenus Ergaleium and section Bryastrum, diversified during the establishment of the Mediterranean-type climate. Ancestral reconstructions of bioclimatic models demonstrate a pattern of preference for this climate type within these groups. Ancestral bioclimatic models are projected into palaeo-climate reconstructions for the time periods indicated by the chronogram. We present two such examples that each generate plausible estimates of ancestral lineage distribution, which are similar to their current distributions. This is the first study to attempt bioclimatic projections on evolutionary time scales. The sundews appear to have diversified in response to local climate development. Some groups are specialized for Mediterranean climates, others show wide-ranging generalism. This demonstrates that Phyloclimatic modeling could be repeated for other plant groups and is fundamental to the understanding of evolutionary responses to climate change. 相似文献
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Saffo MB 《Integrative and comparative biology》2002,42(2):291-294
Research on symbiosis (including antagonistic and mutualistic associations) wrestles, directly or indirectly, with the paradox: why are symbiotic associations so prevalent in the biosphere in the face of ubiquitous immune or antibiotic defenses among organisms? The symposium "Living Together: the Dynamics of Symbiotic Interactions" considered several questions: 1. How do symbiotic species partners come together? Do symbioses share similar patterns of signal recognition and response? 2. What roles do nutrients and metabolites play in symbiotic interactions, and how are metabolic exchanges affected by environmental changes? 3. In what ways do the dynamics of multispecies symbioses differ from two-species associations? 4. How do antagonistic (parasitic, pathogenic) symbioses differ from mutualistic ones? In what ways do changes in the biotic and physical environment affect the evolutionary balance of symbiotic associations? 5. What are the coevolutionary patterns of symbiotic associations? 6. Which research techniques, and strategies of experimental design, might be useful across a broad range of symbiotic associations?Two themes emerged from the symposium. First, all the participants have incorporated multiple techniques and perspectives into their work, approaches which facilitate the understanding of symbiotic dynamics at several levels of biological organization. Secondly, many of the papers addressed genetic and environmental variation in symbiotic interactions. Such approaches are useful tools for analysis of the mechanics of interspecies interactions and for characterization of the most important factors which influence them. They provide us with the tools to evaluate symbioses in a world of complexity, variation and change. 相似文献
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A natural mutant of human lysozyme, D67H, causes hereditary systemic nonneuropathic amyloidosis, which can be fatal. In this disease, insoluble beta-stranded fibrils (amyloids) are found in tissues stemming from the aggregation of partially folded intermediates of the mutant. In this study, we specifically compare the conformation and properties of the structures adopted from the induced unfolding, at elevated temperature, using molecular dynamics. To increase the sampling of the unfolding conformational landscape, three 5 ns trajectories are performed for each of the wild-type and mutant D67H proteins resulting in a total of 30 ns simulation. Our results show that the mutant unfolds slightly faster than the wild-type with both wild-type and mutant proteins losing most of their native secondary structure within the first 2 ns. They both develop random transient beta-strands across the whole polypeptide chain. Clustering analysis of all the conformations shows that a high population of the mutant protein conformations have a distorted beta-domain. This is consistent with experimental results suggesting that this region is pivotal in the formation of conformations prone to act as "seeds" for amyloid fiber formation. 相似文献
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Zhang F Aravanis AM Adamantidis A de Lecea L Deisseroth K 《Nature reviews. Neuroscience》2007,8(8):577-581
Neuropsychiatric disorders, which arise from a combination of genetic, epigenetic and environmental influences, epitomize the challenges faced in understanding the mammalian brain. Elucidation and treatment of these diseases will benefit from understanding how specific brain cell types are interconnected and signal in neural circuits. Newly developed neuroengineering tools based on two microbial opsins, channelrhodopsin-2 (ChR2) and halorhodopsin (NpHR), enable the investigation of neural circuit function with cell-type-specific, temporally accurate and reversible neuromodulation. These tools could lead to the development of precise neuromodulation technologies for animal models of disease and clinical neuropsychiatry. 相似文献
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At the heart of microbial ecology lies a true scientific dichotomy. On the one hand, we know microbes are responsible for processes on which all other life on Earth is dependent; their removal would mean the cessation of all known life. However, in opposition, the majority of extant microbial species in natural environments have never been cultured or studied in a laboratory as living organisms. Owing to these factors, the question of "who does what?" has been a major barrier to understanding how microbially mediated ecosystem level events occur. Recently, the use of stable isotopes (13C) to trace carbon from specific substrates into microbes that assimilate carbon from that substrate has significantly advanced our understanding of the relationship between environmental processes and microbial phylogeny. 相似文献
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Phase-separation and domain-formation in cholesterol-sphingomyelin mixture: pulse-EPR oxygen probing
Membranes made of Chol/ESM (cholesterol/egg sphingomyelin) mixtures were investigated using saturation-recovery electron paramagnetic resonance spin-labeling methods, in which bimolecular collisions of relaxation agents (oxygen or nickel ethylenediamine diacetic acid) with spin labels are measured. Liquid-disordered (ld) and liquid-ordered (lo) phases, and cholesterol bilayer domains (CBDs) were discriminated and characterized by profiles of the oxygen transport parameter (OTP). In the ld phase, coexisting with the lo phase, the OTP profile is bell-shaped and lies above that in the pure ESM membrane. Changes in the OTP profile across the lo phase are complex. When the lo phase coexists with the ld phase, the OTP profile is similar to that across the pure ESM membrane but with a steeper bell shape. With an increase in cholesterol concentration (up to the cholesterol-solubility threshold), the profile becomes rectangular, with low OTP values from the membrane surface to the depth of C9, and high values in the membrane center. This approximately threefold increase in the OTP occurs at the depth at which the rigid ring structure of cholesterol is immersed. Further addition of cholesterol and the formation of the CBD does not affect the OTP profile across the lo phase. OTP values in the CBD are significantly lower than in the lo phase. 相似文献
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Simulations of an RNA hairpin containing a GNRA tetraloop were conducted to allow the characterization of its secondary structure formation and dynamics. Ten 10 ns trajectories of the folded hairpin 5'-GGGC[GCAA]GCCU-3' were generated using stochastic dynamics and the GB/SA implicit solvent model at 300 K. Overall, we find the stem to be a very stable subunit of this molecule, whereas multiple loop conformations and transitions between them were observed. These trajectories strongly suggest that extension of the C6 base away from the loop occurs cooperatively with an N-type-->S-type sugar pucker conversion in that residue and that similar pucker transitions are necessary to stabilize other looped-out bases. In addition, a short-lived conformer with an extended fourth loop residue (A8) lacking this stabilizing 2'-endo pucker mode was observed. Results of thermal perturbation at 400 K support this model of loop dynamics. Unfolding trajectories were produced using this same methodology at temperatures of 500 to 700 K. The observed unfolding events display three-state behavior kinetically (including native, globular, and unfolded populations) and, based on these observations, we propose a folding mechanism that consists of three distinct events: (i) collapse of the random unfolded structure and sampling of the globular state; (ii) passage into the folded region of configurational space as stem base-pairs form and gain helicity; and (iii) attainment of proper loop geometry and organization of loop pairing and stacking interactions. These results are considered in the context of current experimental knowledge of this and similar nucleic acid hairpins. 相似文献
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Reactive oxygen species (ROS) dictate biological outcomes and are linked with myriad pathologies. However, measuring ROS in vivo remains a major obstacle in the field. Here, Albrecht et al. (2011) demonstrate the efficacy of redox-sensitive GFP in measuring glutathione redox state and H(2)O(2) levels of tissues in Drosophila. 相似文献
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Luana Scheffer Arkady Bitler Eshel Ben-Jacob Rafi Korenstein 《European biophysics journal : EBJ》2001,30(2):83-90
We present a novel approach, based on atomic force microscopy, for exploring the local elastic properties of the membrane-skeleton complex in living cells. Three major elements constitute the basis for the proposed method: (1) pulling the cell membrane by increasing the adhesion of the tip to the cell surface provided via appropriate tip modification; (2) measuring force-distance curves with emphasis on selecting the appropriate withdrawal regions for analysis; (3) fitting of the theoretical model for axisymmetric bending of an annular thick plate to the experimental curve in the withdrawal region, prior to the detachment point of the tip from the cell membrane. This approach, applied to human erythrocytes, suggests a complimentary technique to the commonly used methods. The local use of this methodology for determining the bending modulus of the cell membrane of the human erythrocyte yields a value of (2.07+/-0.32) x 10(-19) J. 相似文献