Showing 701 - 710 of 733 Items
Sensory-based niche partitioning in a multiple predator-multiple prey community
Date: 2015-05-20
Creator: Jay J. Falk, Hannah M. Ter Hofstede, Patricia L. Jones, Marjorie M. Dixon, Paul A., Faure, Elisabeth K.V. Kalko, Rachel A. Page
Access: Open access
- Many predators and parasites eavesdrop on the communication signals of their prey. Eavesdropping is typically studied as dyadic predator-prey species interactions; yet in nature, most predators target multiple prey species and most prey must evade multiple predator species. The impact of predator communities on prey signal evolution is not well understood. Predators could converge in their preferences for conspicuous signal properties, generating competition among predators and natural selection on particular prey signal features. Alternatively, predator species could vary in their preferences for prey signal properties, resulting in sensory-based niche partitioning of prey resources. In the Neotropics, many substrate-gleaning bats use the mate-attraction songs of male katydids to locate them as prey. We studied mechanisms of niche partitioning in four substrate- gleaning bat species and found they are similar in morphology, echolocation signal design and prey-handling ability, but each species preferred different acoustic features of male song in 12 sympatric katydid species. This divergence in predator preference probably contributes to the coexistence of many substrate-gleaning bat species in the Neotropics, and the substantial diversity in the mate-attraction signals of katydids. Our results provide insight into how multiple eavesdropping predator species might influence prey signal evolution through sensory-based niche partitioning.
TAKs, thylakoid membrane protein kinases associated with energy transduction
Date: 1999-04-02
Creator: Shaun Snyders, Bruce D. Kohorn
Access: Open access
- The phosphorylation of proteins within the eukaryotic photosynthetic membrane is thought to regulate a number of photosynthetic processes in land plants and algae. Both light quality and intensity influence protein kinase activity via the levels of reductants produced by the thylakoid electron transport chain. We have isolated a family of proteins called TAKs, Arabidopsis thylakoid membrane threonine kinases that phosphorylate the light harvesting complex proteins. TAK activity is enhanced by reductant and is associated with the photosynthetic reaction center II and the cytochrome b6f complex. TAKs are encoded by a gene family that has striking similarity to transforming growth factor Ī² receptors of metazoans. Thus thylakoid protein phosphorylation may be regulated by a cascade of reductant-controlled membrane-bound protein kinases.
Fermions destabilize electroweak strings
Date: 1995-01-01
Creator: Stephen G. Naculich
Access: Open access
- Z strings in the Weinberg-Salam model including fermions are unstable for all values of the parameters. The cause of this instability is the fermion vacuum energy in the Z-string background. Z strings with nonzero fermion densities, however, may still be stable. Ā© 1995 The American Physical Society.
The 10kb Drosophila virus 28S rDNA intervening sequence is flanked by a disect repeat of 14 base pairs of coding sequence
Date: 1980-08-25
Creator: Peter M.M. Rae, Bruce D. Kohorn, Robert P. Wade
Access: Open access
- Most repeat units of rDNA in Drosophila virilis are interrupted in the 28S rRNA coding region by an intervening sequence about 10 kb in length; uninterrupted repeats have a length of about 11 kb. We have sequenced the coding/intervening sequence junctions and flanking regions in two independent clones of interrupted rDNA, and the corresponding 28S rRNA coding region in a clone of uninterrupted rDNA. The intervening sequence is terminated at both ends by a direct repeat of a fourteen nucleotide sequence that is present once in the corresponding region of an intact gene. This is a phenomenon associated with transposable elements in other eukaryotes and in prokaryotes, and the Drosophila rDNA intervening sequence is discussed in this context. We have compared more than 200 nucleotides of the D. virilis 28S rRNA gene with sequences of homologous regions of rDNA in Tetrahymena pigmentosa (Wild and Sommer, 1980) and Xenopus laevis (Gourse and Gerbi, 1980): There is 93% sequence homology among the diverse species, so that the rDNA region in question (about two-thirds of the way into the 28S rRNA coding sequence) has been very highly conserved in eukaryote evolution. The intervening sequence in T. pigmentosa is at a site 79 nucleotides upstream from the insertion site of the Drosophila intervening sequence. Ā© 1980 IRL Press Limited.
Disruption of Thylakoid-associated Kinase 1 Leads to Alteration of Light Harvesting in Arabidopsis
Date: 2001-08-24
Creator: Shaun Snyders, Bruce D. Kohorn
Access: Open access
- To survive fluctuations in quality and intensity of light, plants and algae are able to preferentially direct the absorption of light energy to either one of the two photosystems PSI or PSII. This rapid process is referred to as a state transition and has been correlated with the phosphorylation and migration of the light-harvesting complex protein (LHCP) between PSII and PSI. We show here that thylakoid protein kinases (TAKs) are required for state transitions in Arabidopsis. Antisense TAK1 expression leads to a loss of LHCP phosphorylation and a reduction in state transitions. Preferential activation of PSII causes LHCP to accumulate with PSI, and TAK1 mutants disrupt this process. Finally, TAKs also influence the phosphorylation of multiple thylakoid proteins.
One-instanton predictions for non-hyperelliptic curves derived from M-theory
Date: 1998-12-21
Creator: Isabel P. Ennes, Stephen G. Naculich, Henric Rhedin, Howard J. Schnitzer
Access: Open access
- One-instanton predictions are obtained from certain non-hyperelliptic Seiberg-Witten curves derived from M-theory for N = 2 supersymmetric gauge theories. We consider SU(N1) Ć SU(N2) gauge theory with a hypermultiplet in the bifundamental representation together with hypermultiplets in the defining representations of SU(N1) and SU(N2). We also consider SU(N) gauge theory with a hypermultiplet in the symmetric or antisymmetric representation, together with hypermultiplets in the defining representation. The systematic perturbation expansion about a hyperelliptic curve together with the judicious use of an involution map for the curve of the product groups provide the principal tools of the calculations. Ā© 1999 Elsevier Science B.V.
When to approach novel prey cues? Social learning strategies in frog-eating bats
Date: 2013-10-23
Creator: Patricia L. Jones, Michael J. Ryan, Victoria Flores, Rachel A. Page
Access: Open access
- Animals can use different sources of information when making decisions. Foraging animals often have access to both self-acquired and socially acquired information about prey. The fringe-lipped bat, Trachops cirrhosus, hunts frogs by approaching the calls that frogs produce to attract mates.We examined howthe reliability of self-acquired prey cues affects social learning of novel prey cues. We trained bats to associate an artificial acoustic cue (mobile phone ringtone) with food rewards. Bats were assigned to treatments in which the trained cue was either an unreliable indicator of reward (rewarded 50% of the presentations) or a reliable indicator (rewarded 100% of the presentations), and they were exposed to a conspecific tutor foraging on a reliable (rewarded 100%) novel cue or to the novel cue with no tutor. Bats whose trained cue was unreliable and who had a tutor were significantly more likely to preferentially approach the novel cue when compared with bats whose trained cue was reliable, and to bats that had no tutor. Reliability of self-acquired prey cues therefore affects social learning of novel prey cues by frog-eating bats. Examining when animals use social information to learn about novel prey is key to understanding the social transmission of foraging innovations. Ā© 2013 The Author(s) Published by the Royal Society.
Measurements and models of the atmospheric Ar/N2 ratio
Date: 2003-08-01
Creator: Mark Battle, Michael Bender, Melissa B. Hendricks, David T. Ho, Robert, Mika, Galen McKinley, Song Miao Fan, Tegan Blaine, Ralph F. Keeling
Access: Open access
- The Ar/N2 ratio of air measured at 6 globally distributed sites shows annual cycles with amplitudes of 12 to 37 parts in 106. Summertime maxima reflect the atmospheric Ar enrichment driven by seasonal warming and degassing of the oceans. Paired models of air-sea heat fluxes and atmospheric tracer transport predict seasonal cycles in the Ar/N2 ratio that agree with observations, within uncertainties.
Measurement of the BĢāD*lĪ½Ģ branching fractions and -Vcb-
Date: 1995-01-01
Creator: B. Barish, M. Chadha, S. Chan, D. F. Cowen, G., Eigen, J. S. Miller, C. O'Grady, J. Urheim, A. J. Weinstein, D. Acosta, M. Athanas, G. Masek, H. P. Paar, J. Gronberg, R. Kutschke, S. Menary, R. J. Morrison, S. Nakanishi, H. N. Nelson, T. K. Nelson, C. Qiao, J. D. Richman, A. Ryd, H. Tajima, D. Sperka, M. S. Witherell, M. Procario, R. Balest, K. Cho, M. Daoudi, W. T. Ford
Access: Open access
- We study the exclusive semileptonic B meson decays B-āD*0l-Ī½Ģ and BĢ0āD*+l-Ī½Ģ using data collected with the CLEO II detector at the Cornell Electron-positron Storage Ring (CESR). We present measurements of the branching fractions scrB(BĢ0āD*+l-Ī½Ģ)= (0.5/f00)[4.49Ā±0.32(stat.)Ā±0.39 (syst.)]% and scrB(B-āD*0l-(Ī½Ģ)= (0.5/f+-)[5.13Ā±0.54 (stat) Ā±0.64 (syst)]%, where f00 and f+- are the neutral and charged B meson production fractions at the Ī„(4S) resonance, respectively. Assuming isospin invariance and taking the ratio of charged to neutral B meson lifetimes measured at higher energy machines, we determine the ratio f+-/f00=1.04Ā±0.13 (stat) Ā±0.12 (syst) Ā±0.10 (lifetime); further assuming f+-+f00=1 we also determine the partial width Ī(BĢāD*lĪ½Ģ)=[29.9Ā±1.9 (stat) Ā±2.7 (syst.) Ā±2.0 (lifetime)] ns-1 (independent of f+-/f00). From this partial width we calculate BĢāD*lĪ½Ģ branching fractions that do not depend on f+-/f00 or the individual B lifetimes, but only on the charged to neutral B lifetime ratio. The product of the CKM matrix element -Vcb- times the normalization of the decay form factor at the point of no recoil of the D* meson, scrF(y=1), is determined from a linear fit to the combined differential decay rate of the exclusive BĢāD*lĪ½Ģ decays: -Vcb-scrF(1)=0.0351Ā±0.0019 (stat) Ā±0.0018 (syst) Ā±0.0008 (lifetime). The value for -Vcb- is extracted using theoretical calculations of the form factor normalization. Ā© 1995 The American Physical Society.
The twin spot generator for differential Drosophila lineage analysis
Date: 2009-07-28
Creator: Ruth Griffin, Anne Sustar, Marianne Bonvin, Richard Binari, Alberto, del Valle Rodriguez, Amber M. Hohl, Jack R. Bateman, Christians Villalta, Elleard Heffern, Didier Grunwald, Chris Bakal, Claude Desplan, Gerold Schubiger, C. Ting Wu, Norbert Perrimon
Access: Open access
- In Drosophila melanogaster, widely used mitotic recombination-based strategies generate mosaic flies with positive readout for only one daughter cell after division. To differentially label both daughter cells, we developed the twin spot generator (TSG) technique, which through mitotic recombination generates green and red twin spots that are detectable after the first cell division as single cells. We propose wide applications of TSG to lineage and genetic mosaic studies.