Faculty Scholarship
Showing 701 - 733 of 733 Items
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. © 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.
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. © 2013 The Author(s) Published by the Royal 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.
The tyrosine kinase Abl and its substrate enabled collaborate with the receptor phosphatase Dlar to control motor axon guidance
Date: 1999-01-01
Creator: Zachary Wills, Jack Bateman, Christopher A. Korey, Allen Comer, David, Van Vactor
Access: Open access
- Genetic analysis of growth cone guidance choice points in Drosophila identified neuronal receptor protein tyrosine phosphatases (RPTPs) as key determinants of axon pathfinding behavior. We now demonstrate that the Drosophila Abl tyrosine kinase functions in the intersegmental nerve b (ISNb) motor choice point pathway as an antagonist of the RPTP Dlar. The function of Abl in this pathway is dependent on an intact catalytic domain. We also show that the Abl phosphoprotein substrate Enabled (Ena) is required for choice point navigation. Both Abl and Ena proteins associate with the Dlar cytoplasmic domain and serve as substrates for Dlar in vitro, suggesting that they play a direct role in the Dlar pathway. These data suggest that Dlar, Abl, and Ena define a phosphorylation state-dependent switch that controls growth cone behavior by transmitting signals at the cell surface to the actin cytoskeleton.
Responses of stomatal features and photosynthesis to porewater N enrichment and elevated atmospheric CO2 in Phragmites australis, the common reed
Date: 2021-04-01
Creator: Julian R. Garrison, Joshua S. Caplan, Vladimir Douhovnikoff, Thomas J. Mozdzer, Barry A. Logan
Access: Open access
- PREMISE: Biological invasions increasingly threaten native biodiversity and ecosystem services. One notable example is the common reed, Phragmites australis, which aggressively invades North American salt marshes. Elevated atmospheric CO2 and nitrogen pollution enhance its growth and facilitate invasion because P. australis responds more strongly to these enrichments than do native species. We investigated how modifications to stomatal features contribute to strong photosynthetic responses to CO2 and nitrogen enrichment in P. australis by evaluating stomatal shifts under experimental conditions and relating them to maximal stomatal conductance (gwmax) and photosynthetic rates. METHODS: Plants were grown in situ in open-top chambers under ambient and elevated atmospheric CO2 (eCO2) and porewater nitrogen (Nenr) in a Chesapeake Bay tidal marsh. We measured light-saturated carbon assimilation rates (Asat) and stomatal characteristics, from which we calculated gwmax and determined whether CO2 and Nenr altered the relationship between gwmax and Asat. RESULTS: eCO2 and Nenr enhanced both gwmax and Asat, but to differing degrees; gwmax was more strongly influenced by Nenr through increases in stomatal density while Asat was more strongly stimulated by eCO2. There was a positive relationship between gwmax and Asat that was not modified by eCO2 or Nenr, individually or in combination. CONCLUSIONS: Changes in stomatal features co-occur with previously described responses of P. australis to eCO2 and Nenr. Complementary responses of stomatal length and density to these global change factors may facilitate greater stomatal conductance and carbon gain, contributing to the invasiveness of the introduced lineage.
Circadian signaling in Homarus americanus: Region-specific de novo assembled transcriptomes show that both the brain and eyestalk ganglia possess the molecular components of a putative clock system
Date: 2018-07-01
Creator: Andrew E. Christie, Andy Yu, Micah G. Pascual, Vittoria Roncalli, Matthew C., Cieslak, Amanda N. Warner, Tess J. Lameyer, Meredith E. Stanhope, Patsy S. Dickinson, J. Joe Hull
Access: Open access
- Essentially all organisms exhibit recurring patterns of physiology/behavior that oscillate with a period of ~24-h and are synchronized to the solar day. Crustaceans are no exception, with robust circadian rhythms having been documented in many members of this arthropod subphylum. However, little is known about the molecular underpinnings of their circadian rhythmicity. Moreover, the location of the crustacean central clock has not been firmly established, although both the brain and eyestalk ganglia have been hypothesized as loci. The American lobster, Homarus americanus, is known to exhibit multiple circadian rhythms, and immunodetection data suggest that its central clock is located within the eyestalk ganglia rather than in the brain. Here, brain- and eyestalk ganglia-specific transcriptomes were generated and used to assess the presence/absence of transcripts encoding the commonly recognized protein components of arthropod circadian signaling systems in these two regions of the lobster central nervous system. Transcripts encoding putative homologs of the core clock proteins clock, cryptochrome 2, cycle, period and timeless were found in both the brain and eyestalk ganglia assemblies, as were transcripts encoding similar complements of putative clock-associated, clock input pathway and clock output pathway proteins. The presence and identity of transcripts encoding core clock proteins in both regions were confirmed using PCR. These findings suggest that both the brain and eyestalk ganglia possess all of the molecular components needed for the establishment of a circadian signaling system. Whether the brain and eyestalk clocks are independent of one another or represent a single timekeeping system remains to be determined. Interestingly, while most of the proteins deduced from the identified transcripts are shared by both the brain and eyestalk ganglia, assembly-specific isoforms were also identified, e.g., several period variants, suggesting the possibility of region-specific variation in clock function, especially if the brain and eyestalk clocks represent independent oscillators.
Identification of SYWKQCAFNAVSCFamide: A broadly conserved crustacean C-type allatostatin-like peptide with both neuromodulatory and cardioactive properties
Date: 2009-04-15
Creator: Patsy S. Dickinson, Teerawat Wiwatpanit, Emily R. Gabranski, Rachel J. Ackerman, Jake S., Stevens, Christopher R. Cashman, Elizabeth A. Stemmler, Andrew E. Christie
Access: Open access
- The allatostatins comprise three structurally distinct peptide families that regulate juvenile hormone production by the insect corpora allata. A-type family members contain the C-terminal motif -YXFGLamide and have been found in species from numerous arthropod taxa. Members of the B-type family exhibit a -WX6Wamide C-terminus and, like the A-type peptides, appear to be broadly conserved within the Arthropoda. By contrast, members of the C-type family, typified by the unblocked C-terminus -PISCF, a pyroglutamine blocked N-terminus, and a disulfide bridge between two internal Cys residues, have only been found in holometabolous insects, i.e. lepidopterans and dipterans. Here, using transcriptomics, we have identified SYWKQCAFNAVSCFamide (disulfide bridging predicted between the two Cys residues), a known honeybee and water flea C-typelike peptide, from the American lobster Homarus americanus (infraorder Astacidea). Using matrix assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS), a mass corresponding to that of SYWKQCAFNAVSCFamide was detected in the H. americanus brain, supporting the existence of this peptide and its theorized structure. Furthermore, SYWKQCAFNAVSCFamide was detected by MALDI-FTMS in neural tissues from five additional astacideans as well as 19 members of four other decapod infraorders (i.e. Achelata, Anomura, Brachyura and Thalassinidea), suggesting that it is a broadly conserved decapod peptide. In H. americanus, SYWKQCAFNAVSCFamide is capable of modulating the output of both the pyloric circuit of the stomatogastric nervous system and the heart. This is the first demonstration of bioactivity for this peptide in any species.
De novo assembly of a transcriptome for the cricket Gryllus bimaculatus prothoracic ganglion: An invertebrate model for investigating adult central nervous system compensatory plasticity
Date: 2018-07-01
Creator: Harrison P. Fisher, Micah G. Pascual, Sylvia I. Jimenez, David A. Michaelson, Colby T., Joncas, Eleanor D. Quenzer, Andrew E. Christie, Hadley W. Horch
Access: Open access
- The auditory system of the cricket, Gryllus bimaculatus, demonstrates an unusual amount of anatomical plasticity in response to injury, even in adults. Unilateral removal of the ear causes deafferented auditory neurons in the prothoracic ganglion to sprout dendrites across the midline, a boundary they typically respect, and become synaptically connected to the auditory afferents of the contralateral ear. The molecular basis of this sprouting and novel synaptogenesis in the adult is not understood. We hypothesize that well-conserved developmental guidance cues may recapitulate their guidance functions in the adult in order to facilitate this compensatory growth. As a first step in testing this hypothesis, we have generated a de novo assembly of a prothoracic ganglion transcriptome derived from control and deafferented adult individuals. We have mined this transcriptome for orthologues of guidance molecules from four well-conserved signaling families: Slit, Netrin, Ephrin, and Semaphorin. Here we report that transcripts encoding putative orthologues of most of the candidate developmental ligands and receptors from these signaling families were present in the assembly, indicating expression in the adult G. bimaculatus prothoracic ganglion.
Injecting gryllus bimaculatus eggs
Date: 2019-08-01
Creator: Samantha K. Barry, Taro Nakamura, Yuji Matsuoka, Christoph Straub, Hadley W., Horch, Cassandra G. Extavour
Access: Open access
- Altering gene function in a developing organism is central to different kinds of experiments. While tremendously powerful genetic tools have been developed in traditional model systems, it is difficult to manipulate genes or messenger RNA (mRNA) in most other organisms. At the same time, evolutionary and comparative approaches rely on an exploration of gene function in many different species, necessitating the development and adaptation of techniques for manipulating expression outside currently genetically tractable species. This protocol describes a method for injecting reagents into cricket eggs to assay the effects of a given manipulation on embryonic or larval development. Instructions for how to collect and inject eggs with beveled needles are described. This relatively straightforward technique is flexible and potentially adaptable to other insects. One can gather and inject dozens of eggs in a single experiment, and survival rates for buffer-only injections improve with practice and can be as high as 80%. This technique will support several types of experimental approaches including injection of pharmacological agents, in vitro capped mRNA to express genes of interest, double-stranded RNA (dsRNA) to achieve RNA interference, use of clustered regularly interspaced short palindromic repeats (CRISPR) in concert with CRISPR-associated protein 9 (Cas9) reagents for genomic modification, and transposable elements to generate transient or stable transgenic lines.
RPCH modulation of a multi-oscillator network: Effects on the pyloric network of the spiny lobster
Date: 2001-01-01
Creator: Patsy S. Dickinson, Jane Hauptman, John Hetling, Anand Mahadevan
Access: Open access
- The neuropeptide red pigment concentrating hormone (RPCH), which we have previously shown to activate the cardiac sac motor pattern and lead to a conjoint gastric mill-cardiac sac pattern in the spiny lobster Panulirus, also activates and modulates the pyloric pattern. Like the activity of gastric mill neurons in RPCH, the pattern of activity in the pyloric neurons is considerably more complex than that seen in control saline. This reflects the influence of the cardiac sac motor pattern, and particularly the upstream inferior ventricular (IV) neurons, on many of the pyloric neurons. RPCH intensifies this interaction by increasing the strength of the synaptic connections between the IV neurons and their targets in the stomatogastric ganglion. At the same time, RPCH enhances postinhibitory rebound in the lateral pyloric (LP) neuron. Taken together, these factors largely explain the complex pyloric pattern recorded in RPCH in Panulirus.
In situ HCR in non-traditional arthropods
Date: 2024-01-25
Creator: Heather Bruce, Hadley Wilson Horch
Access: Open access
- Visualizing the expression of genes is a fundamental tool in molecular biology. Traditional colorimetric in situ hybridization using long RNA probes has been a staple for visualizing gene expression but has many drawbacks. In situ HCR v3.0, developed by Choi et. al. 2018, offers improvements over traditional in situs in nearly every aspect: probes can simply be ordered rather than painstakingly cloned and transcribed, which also makes them cost-effective; an HCR takes just three days to complete rather than five or more days; HCR is robust and works well for first-time users; and HCR probes can be multiplexed, allowing four to eight genes to be visualized in a single sample. HCR has been used successfully in many arthropods, including insects (Drosophila, Tribolium), crustaceans (Parhyale, Daphnia, Artemia), and chelicerates (Limulus horseshoe crab, Acanthoscurria tarantula). In this demo, you will learn how to design and order HCR probes as well as best practices for experimental design.
Distinct or shared actions of peptide family isoforms: I. Peptidespecific actions of pyrokinins in the lobster cardiac neuromuscular system
Date: 2015-09-01
Creator: Patsy S. Dickinson, Anirudh Sreekrishnan, Molly A. Kwiatkowski, Andrew E. Christie
Access: Open access
- Although the crustacean heart is modulated by a large number of peptides and amines, few of these molecules have been localized to the cardiac ganglion itself; most appear to reach the cardiac ganglion only by hormonal routes. Immunohistochemistry in the American lobster Homarus americanus indicates that pyrokinins are present not only in neuroendocrine organs ( pericardial organ and sinus gland), but also in the cardiac ganglion itself, where pyrokinin-positive terminals were found in the pacemaker cell region, as well as surrounding the motor neurons. Surprisingly, the single pyrokinin peptide identified from H. americanus, FSPRLamide, which consists solely of the conserved FXPRLamide residues that characterize pyrokinins, did not alter the activity of the cardiac neuromuscular system. However, a pyrokinin from the shrimp Litopenaeus vannamei [ADFAFNPRLamide, also known as Penaeus vannamei pyrokinin 2 (PevPK2)] increased both the frequency and amplitude of heart contractions when perfused through the isolated whole heart. None of the other crustacean pyrokinins tested (another from L. vannamei and two from the crab Cancer borealis) had any effect on the lobster heart. Similarly, altering the PevPK2 sequence either by truncation or by the substitution of single amino acids resulted in much lower or no activity in all cases; only the conservative substitution of serine for alanine at position 1 resulted in any activity on the heart. Thus, in contrast to other systems (cockroach and crab) in which all tested pyrokinins elicit similar bioactivities, activation of the pyrokinin receptor in the lobster heart appears to be highly isoform specific.
Neuropeptidergic signaling in the American Lobster Homarus Americanus: New insights from high-throughput nucleotide sequencing
Date: 2015-12-01
Creator: Andrew E. Christie, Megan Chi, Tess J. Lameyer, Micah G. Pascual, Devlin N., Shea, Meredith E. Stanhope, David J. Schulz, Patsy S. Dickinson
Access: Open access
- Peptides are the largest and most diverse class of molecules used for neurochemical communication, playing key roles in the control of essentially all aspects of physiology and behavior. The American lobster, Homarus americanus, is a crustacean of commercial and biomedical importance; lobster growth and reproduction are under neuropeptidergic control, and portions of the lobster nervous system serve as models for understanding the general principles underlying rhythmic motor behavior (including peptidergic neuromodulation). While a number of neuropeptides have been identified from H. americanus, and the effects of some have been investigated at the cellular/systems levels, little is currently known about the molecular components of neuropeptidergic signaling in the lobster. Here, a H. americanus neural transcriptome was generated and mined for sequences encoding putative peptide precursors and receptors; 35 precursor- and 41 receptor-encoding transcripts were identified. We predicted 194 distinct neuropeptides from the deduced precursor proteins, including members of the adipokinetic hormone-corazonin-like peptide, allatostatin A, allatostatin C, bursicon, CCHamide, corazonin, crustacean cardioactive peptide, crustacean hyperglycemic hormone (CHH), CHH precursor-related peptide, diuretic hormone 31, diuretic hormone 44, eclosion hormone, FLRFamide, GSEFLamide, insulin-like peptide, intocin, leucokinin, myosuppressin, neuroparsin, neuropeptide F, orcokinin, pigment dispersing hormone, proctolin, pyrokinin, SIFamide, sulfakinin and tachykinin-related peptide families. While some of the predicted peptides are known H. americanus isoforms, most are novel identifications, more than doubling the extant lobster neuropeptidome. The deduced receptor proteins are the first descriptions of H. americanus neuropeptide receptors, and include ones for most of the peptide groups mentioned earlier, as well as those for ecdysistriggering hormone, red pigment concentrating hormone and short neuropeptide F. Multiple receptors were identified for most peptide families. These data represent the most complete description of the molecular underpinnings of peptidergic signaling in H. americanus, and will serve as a foundation for future gene-based studies of neuropeptidergic control in the lobster.
AMGSEFLamide, a member of a broadly conserved peptide family, modulates multiple neural networks in Homarus americanus
Date: 2019-01-01
Creator: Patsy S. Dickinson, Evyn S. Dickinson, Emily R. Oleisky, Cindy D. Rivera, Meredith E., Stanhope, Elizabeth A. Stemmler, J. Joe Hull, Andrew E. Christie
Access: Open access
- Recent genomic/transcriptomic studies have identified a novel peptide family whose members share the carboxyl terminal sequence –GSEFLamide. However, the presence/identity of the predicted isoforms of this peptide group have yet to be confirmed biochemically, and no physiological function has yet been ascribed to any member of this peptide family. To determine the extent to which GSEFLamides are conserved within the Arthropoda, we searched publicly accessible databases for genomic/transcriptomic evidence of their presence. GSEFLamides appear to be highly conserved within the Arthropoda, with the possible exception of the Insecta, in which sequence evidence was limited to the more basal orders. One crustacean in which GSEFLamides have been predicted using transcriptomics is the lobster, Homarus americanus. Expression of the previously published transcriptome-derived sequences was confirmed by reverse transcription (RT)-PCR of brain and eyestalk ganglia cDNAs; mass spectral analyses confirmed the presence of all six of the predicted GSEFLamide isoforms – IGSEFLamide, MGSEFLamide, AMGSEFLamide, VMGSEFLamide, ALGSEFLamide and AVGSEFLamide – in H. americanus brain extracts. AMGSEFLamide, of which there are multiple copies in the cloned transcripts, was the most abundant isoform detected in the brain. Because the GSEFLamides are present in the lobster nervous system, we hypothesized that they might function as neuromodulators, as is common for neuropeptides. We thus asked whether AMGSEFLamide modulates the rhythmic outputs of the cardiac ganglion and the stomatogastric ganglion. Physiological recordings showed that AMGSEFLamide potently modulates the motor patterns produced by both ganglia, suggesting that the GSEFLamides may serve as important and conserved modulators of rhythmic motor activity in arthropods.
Monteverde: Ecology and Conservation of a Tropical Cloud Forest - Chapter Updates (English)
Date: 2014-01-01
Creator: Nalini M Nadkarni, Nathaniel T Wheelwright
Access: Open access
- The Monteverde Cloud Forest Reserve has captured the worldwide attention of biologists, conservationists, and ecologists and has been the setting for extensive investigation over the past 40 years. Roughly 40,000 ecotourists visit the Cloud Forest each year, and it is often considered the archetypal high-altitude rain forest. “Monteverde: Ecology and Conservation of a Tropical Cloud Forest”, edited by Nalini Nadkarni and Nathaniel T. Wheelwright (Oxford University Press, 2000 and Bowdoin’s Scholar’s Bookshelf. Book 1 ), features synthetic chapters and specific accounts written by more than 100 biologist and local residents, presenting in a single volume everything known in 2000 about the biological diversity of Monteverde, Costa Rica, and how to protect it. The new short chapters written in 2014 by original contributors, and presented here update and expand that knowledge through 2014.
Invariants for tendex and vortex fields
Date: 2012-11-08
Creator: Kenneth A. Dennison, Thomas W. Baumgarte
Access: Open access
- Tendex and vortex fields, defined by the eigenvectors and eigenvalues of the electric and magnetic parts of the Weyl curvature tensor, form the basis of a recently developed approach to visualizing spacetime curvature. In analogy to electric and magnetic fields, these fields are coordinate-dependent. However, in a further analogy, we can form invariants from the tendex and vortex fields that are invariant under coordinate transformations, just as certain combinations of the electric and magnetic fields are invariant under coordinate transformations. We derive these invariants, and provide a simple, analytical demonstration for nonspherically symmetric slices of a Schwarzschild spacetime. © 2012 American Physical Society.
Recent decreases in fossil-fuel emissions of ethane and methane derived from firn air
Date: 2011-08-11
Creator: Murat Aydin, Kristal R. Verhulst, Eric S. Saltzman, Mark O. Battle, Stephen A., Montzka, Donald R. Blake, Qi Tang, Michael J. Prather
Access: Open access
- Methane and ethane are the most abundant hydrocarbons in the atmosphere and they affect both atmospheric chemistry and climate. Both gases are emitted from fossil fuels and biomass burning, whereas methane (CH 4) alone has large sources from wetlands, agriculture, landfills and waste water. Here we use measurements in firn (perennial snowpack) air from Greenland and Antarctica to reconstruct the atmospheric variability of ethane (C 2H 6) during the twentieth century. Ethane levels rose from early in the century until the 1980s, when the trend reversed, with a period of decline over the next 20 years. We find that this variability was primarily driven by changes in ethane emissions from fossil fuels; these emissions peaked in the 1960s and 1970s at 14-16 teragrams per year (1 Tg = 10 12 g) and dropped to 8-10 Tg yr -1 by the turn of the century. The reduction in fossil-fuel sources is probably related to changes in light hydrocarbon emissions associated with petroleum production and use. The ethane-based fossil-fuel emission history is strikingly different from bottom-up estimates of methane emissions from fossil-fuel use, and implies that the fossil-fuel source of methane started to decline in the 1980s and probably caused the late twentieth century slow-down in the growth rate of atmospheric methane. © 2011 Macmillan Publishers Limited. All rights reserved.
Measurement of the inclusive B* cross section above the (4S)
Date: 1991-01-01
Creator: D. S. Akerib, B. Barish, D. F. Cowen, G. Eigen, R., Stroynowski, J. Urheim, A. J. Weinstein, R. Morrison, D. Schmidt, M. Procario, D. R. Johnson, K. Lingel, P. Rankin, J. G. Smith, J. Alexander, C. Bebek, K. Berkelman, D. Besson, T. E. Browder, D. G. Cassel, E. Cheu, D. M. Coffman, P. S. Drell, R. Ehrlich, R. S. Galik, M. Garcia-Sciveres, B. Geiser, B. Gittelman, S. W. Gray, D. L. Hartill, B. K. Heltsley
Access: Open access
- Using the CLEO II detector at the Cornell Electron Storage Ring, we have determined the inclusive B* cross section above the (4S) resonance in the energy range from 10.61 to 10.70 GeV. We also report a new measurement of the energy of the B*B transition photon of 46.20.30.8 MeV. © 1991 The American Physical Society.
Collapse of a magnetized star to a black hole
Date: 2003-01-01
Creator: T.W. Baumgarte, S.L. Shapiro
Access: Open access
Comparison between the fCCZ4 and BSSN formulations of Einstein equations in spherical polar coordinates
Date: 2015-01-01
Creator: N. Sanchis-Gual, P.J. Montero, J.A. Font, E. Müller, T.W., Baumgarte
Access: Open access
Measurement of the τ-lepton mass
Date: 1993-01-01
Creator: R. Balest, M. Daoudi, W. T. Ford, D. R. Johnson, K., Lingel, M. Lohner, P. Rankin, J. G. Smith, J. P. Alexander, C. Bebek, K. Berkelman, D. Besson, T. E. Browder, D. G. Cassel, H. A. Cho, D. M. Coffman, P. S. Drell, R. Ehrlich, R. S. Galik, M. Garcia-Sciveres, B. Geiser, B. Gittelman, S. W. Gray, D. L. Hartill, B. K. Heltsley, K. Honscheid, C. D. Jones, J. Kandaswamy, N. Katayama, P. C. Kim, D. L. Kreinick
Access: Open access
- Using data from the CLEO II detector at CESR, we measure the τ-lepton mass by exploiting the unique kinematics of events in which both τ's decay hadronically. The result is mτ=1777.8±0.7±1.7 MeV/c2. By comparing our result with other measurements near τ-pair threshold, we extract an upper limit on the τ-neutrino mass of 75 MeV/c2 at 95% confidence level. © 1993 The American Physical Society.
Measurement of baryon production in B-meson decay
Date: 1992-01-01
Creator: G. Crawford, R. Fulton, T. Jensen, D. R. Johnson, H., Kagan, R. Kass, R. Malchow, F. Morrow, J. Whitmore, P. Wilson, D. Bortoletto, D. Brown, J. Dominick, R. L. McIlwain, D. H. Miller, M. Modesitt, C. R. Ng, S. F. Schaffner, E. I. Shibata, I. P.J. Shipsey, M. Battle, H. Kroha, K. Sparks, E. H. Thorndike, C. H. Wang, M. S. Alam, I. J. Kim, W. C. Li, X. C. Lou, B. Nemati, V. Romero
Access: Open access
- Using the CLEO detector at the Cornell Electron Storage Ring, we observe B-meson decays to c+ and report on improved measurements of inclusive branching fractions and momentum spectra of other baryons. For the inclusive decay Bc+X with c+pK-+, we find that the product branching fraction B(Bc+X)B(c+pK-+)=(0.273±0.051±0.039)%. Our measured inclusive branching fractions to noncharmed baryons are B(BpX)=(8.0±0.5±0.3)%, B(BX)=(3.8±0.4±0.6)%, and B(B-X)=(0.27±0.05±0.04)%. From these rates and studies of baryon-lepton and baryon-antibaryon correlations in B decays, we have estimated the branching fraction B(Bc+X) to be (6.40.8±0.8)%. Combining these results, we calculate B(c+pK-) to be (4.3±1.0±0.8)%. © 1992 The American Physical Society.
Applications of subleading-color amplitudes in N = 4 SYM theory
Date: 2011-12-01
Creator: Stephen G. Naculich, Horatiu Nastase, Howard J. Schnitzer
Access: Open access
- A number of features and applications of subleading-color amplitudes of N = 4 SYM theory are reviewed. Particular attention is given to the IR divergences of the subleading-color amplitudes, the relationships of N = 4 SYM theory to N = 8 supergravity, and to geometric interpretations of one-loop subleading-color and N k MHV amplitudes of N = 4 SYM theory. Copyright © 2011 Stephen G. Naculich et al.
A revised 1000 year atmospheric δ13 C-CO2 record from Law Dome and South Pole, Antarctica
Date: 2013-08-16
Creator: M. Rubino, D. M. Etheridge, C. M. Trudinger, C. E. Allison, M. O., Battle, R. L. Langenfelds, L. P. Steele, M. Curran, M. Bender, J. W.C. White, T. M. Jenk, T. Blunier, R. J. Francey
Access: Open access
- We present new measurements of δ13C of CO2 extracted from a high-resolution ice core from Law Dome (East Antarctica), together with firn measurements performed at Law Dome and South Pole, covering the last 150 years. Our analysis is motivated by the need to better understand the role and feedback of the carbon (C) cycle in climate change, by advances in measurement methods, and by apparent anomalies when comparing ice core and firn air δ13C records from Law Dome and South Pole. We demonstrate improved consistency between Law Dome ice, South Pole firn, and the Cape Grim (Tasmania) atmospheric δ13C data, providing evidence that our new record reliably extends direct atmospheric measurements back in time. We also show a revised version of early δ13C measurements covering the last 1000 years, with a mean preindustrial level of -6.50‰. Finally, we use a Kalman Filter Double Deconvolution to infer net natural CO2 fluxes between atmosphere, ocean, and land, which cause small δ13C deviations from the predominant anthropogenically induced δ13C decrease. The main features found from the previous δ13C record are confirmed, including the ocean as the dominant cause for the 1940 A.D. CO2 leveling. Our new record provides a solid basis for future investigation of the causes of decadal to centennial variations of the preindustrial atmospheric CO2 concentration. Those causes are of potential significance for predicting future CO2 levels and when attempting atmospheric verification of recent and future global carbon emission mitigation measures through Coupled Climate Carbon Cycle Models. Key Points New and revised, firn and ice δ13C-CO2 measurements from Antarctica Improve consistency between ice and firn δ13C-CO2 measurements Net natural CO2 fluxes between atmosphere, ocean and land inferred ©2013. American Geophysical Union. All Rights Reserved.
Evaluation of the free energy of two-dimensional Yang-Mills theory
Date: 1996-01-01
Creator: Michael Crescimanno, Stephen G. Naculich, Howard J. Schnitzer
Access: Open access
- The free energy in the weak-coupling phase of two-dimensional Yang-Mills theory on a sphere for [Formula presented] and [Formula presented] is evaluated in the [Formula presented] expansion using the techniques of Gross and Matytsin. Many features of Yang-Mills theory are universal among different gauge groups in the large [Formula presented] limit, but significant differences arise in subleading order in [Formula presented]. © 1996 The American Physical Society.
IR divergences and Regge limits of subleading-color contributions to the four-gluon amplitude in N=4 SYM theory
Date: 2009-11-11
Creator: Stephen G. Naculich, Howard J. Schnitzer
Access: Open access
- We derive a compact all-loop-order expression for the IR-divergent part of the = 4 SYM four-gluon amplitude, which includes both planar and all subleading-color contributions, based on the assumption that the higher-loop soft anomalous dimension matrices are proportional to the one-loop soft anomalous dimension matrix, as has been recently conjectured. We also consider the Regge limit of the four-gluon amplitude, and we present evidence that the leading logarithmic growth of the subleading-color amplitudes is less severe than that of the planar amplitudes. We examine possible 1/N 2 corrections to the gluon Regge trajectory, previously obtained in the planar limit from the BDS ansatz. The double-trace amplitudes have Regge behavior as well, with a nonsense-choosing Regge trajectory and a Regge cut which first emerges at three loops. © SISSA 2009.
All-loop group-theory constraints for color-ordered SU(N) gauge-theory amplitudes
Date: 2012-01-16
Creator: Stephen G. Naculich
Access: Open access
- We derive constraints on the color-ordered amplitudes of the L-loop four-point function in SU(N) gauge theories that arise solely from the structure of the gauge group. These constraints generalize well-known group theory relations, such as U(1) decoupling identities, to all loop orders. © 2011 Elsevier B.V.
Can the electroweak symmetry-breaking sector be hidden?
Date: 1992-10-29
Creator: S. G. Naculich, C. P. Yuan
Access: Open access
- In a recent paper, Chivukula and Golden claimed that the electroweak symmetry-breaking sector could be hidden if there were many inelastic channels in the longitudinal WW scattering process. They presented a model in which the W's couple to pseudo-Goldstone bosons, which may be difficult to detect experimentally. Because of these inelastic channels, thw WW interactions do not become strong in the TeV region. We demonstrate that, despite the reduced WW elastic amplitudes in this model, the total event rate (∼ 5000 extra longitudinal W+W- pairs produced in one standard SSC year) does not decrease with an increasing number of inelastic channels, and is roughly the same as in a model with a broad high-energy resonance and no inelastic channels. © 1992.
Observation of a new charmed strange meson
Date: 1994-01-01
Creator: Y. Kubota, M. Lattery, J. K. Nelson, S. Patton, D., Perticone, R. Poling, V. Savinov, S. Schrenk, R. Wang, M. S. Alam, I. J. Kim, B. Nemati, J. J. O'Neill, H. Severini, C. R. Sun, M. M. Zoeller, G. Crawford, C. M. Daubenmier, R. Fulton, D. Fujino, K. K. Gan, K. Honscheid, H. Kagan, R. Kass, J. Lee, R. Malchow, F. Morrow, Y. Skovpen, M. Sung, C. White, F. Butler
Access: Open access
- Using the CLEO II detector, we have obtained evidence for a new meson decaying to D0K+. Its mass is 2573.2-1.6+1.7±0.8±0.5 MeV/c2 and its width is 16-4+5±3 MeV/c2. Although we do not establish its spin and parity, the new meson is consistent with predictions for an L=1, S=1, JP=2+ charmed strange state. © 1994 The American Physical Society.
Observation of inclusive B decays to the charmed baryons c++ and c0
Date: 1994-01-01
Creator: M. Procario, R. Balest, K. Cho, M. Daoudi, W. T., Ford, D. R. Johnson, K. Lingel, M. Lohner, P. Rankin, J. G. Smith, J. P. Alexander, C. Bebek, K. Berkelman, K. Bloom, T. E. Browder, D. G. Cassel, H. A. Cho, D. M. Coffman, P. S. Drell, R. Ehrlich, R. S. Galik, M. Garcia-Sciveres, B. Geiser, B. Gittelman, S. W. Gray, D. L. Hartill, B. K. Heltsley, C. D. Jones, S. L. Jones, J. Kandaswamy, N. Katayama
Access: Open access
- Using data collected in the region of the γ(4S) resonance with the CLEO II detector operating at the Cornell Electron Storage Ring, we report on evidence for the production of ++ and c0 baryons in B decays, with c→Λc+π. This observation is based on 77±19 c++ and 76±21 c0 candidates from B decays. We find the product branching fractions B(B̄→cX)B(Λc+→pK-π+) for c=c++, c0, and c+ to be (2.1 ± 0.8 ± 0.7) × 10-4, (2.3 ± 0.8 ± 0.7) × 10-4, and less than 4.8 × 10-4 at 90% confidence level, respectively. A study of the c++ and c0 momentum spectra indicates that B decays to two-body final states with c are suppressed. © 1994 The American Physical Society.
Evidence for penguin-diagram decays: First observation of B→K*(892)γ
Date: 1993-01-01
Creator: R. Ammar, S. Ball, P. Baringer, D. Coppage, N., Copty, R. Davis, N. Hancock, M. Kelly, N. Kwak, H. Lam, Y. Kubota, M. Lattery, J. K. Nelson, S. Patton, D. Perticone, R. Poling, V. Savinov, S. Schrenk, R. Wang, M. S. Alam, I. J. Kim, B. Nemati, J. J. O'Neill, H. Severini, C. R. Sun, M. M. Zoeller, G. Crawford, M. Daubenmeir, R. Fulton, D. Fujino, K. K. Gan
Access: Open access
- We have observed the decays B0→K*(892)0γ and B-→K*(892)-γ, which are evidence for the quark-level process b→sγ. The average branching fraction is (4.5±1.5±0.9) ×10-5. This value is consistent with standard model predictions from electromagnetic penguin diagrams. © 1993 The American Physical Society.
Improved matrix-model calculation of the N = 2 prepotential
Date: 2004-04-01
Creator: Marta Gómez-Reino, Howard J. Schnitzer, Stephen G. Naculich
Access: Open access
- We present a matrix-model expression for the sum of instanton contributions to the prepotential of an N = 2 supersymmetric U (N) gauge theory, with matter in various representations. This expression is derived by combining the renormalization-group approach to the gauge theory prepotential with matrix-model methods. This result can be evaluated order-by-order in matrix-model perturbation theory to obtain the instanton corrections to the prepotential. We also show, using this expression, that the one-instanton prepotential assumes a universal form. © SISSA/ISAS 2004.