Showing 941 - 950 of 2039 Items
Date: 2019-12-01
Creator: David A. Watts
Vladimir Douhovnikoff
Eric Post
Access: Open access
- The recent expansion of arctic deciduous shrubs has been well documented across a range of habitats, but the phenomenon is not universal. Their spread is often associated with increases in temperature and other abiotic factors, while variation in habitat moisture and herbivory can mediate the location and rate of this rise in abundance. Much less is known about the mode of increase of arctic shrubs. For one such shrub, Salix glauca, we used microsatellite markers to assess the prevalence of clonal growth (i.e. vegetative spread) and sexual reproduction (i.e. recruitment from seed) at sites with maritime and continental climates and differing in the density of large herbivores. We sampled individuals in plots reflecting the spatial scale of expansion in locations where S. glauca recently increased in abundance. The 400 samples collected across the four sites comprised 310 genotypes. Though evidence of sexual recruitment was common across all sites, coastal sites contained both more and larger clonal genotypes. While we expected soil conditions would be influential, the factors that best predicted the likelihood of clonality, genet size and vascular plant cover, suggest the light environment is of primary importance. Furthermore, in spite of the large distances between sites, there was no suggestion of genetic differentiation into distinct populations. These results indicate that differences in climate and herbivory can influence not only where and how extensively deciduous shrubs spread, but how they are likely to do so. We suggest future research integrating how mode of increase is associated with the rate of spread will advance projections of change in arctic ecosystems.
Date: 2008-12-01
Creator: Laura A. Henry
Vladimir Douhovnikoff
Access: Open access
- This review examines the literature available on the state of the environment and environmental protection in the Russian Federation. As the largest country on Earth, rich in natural resources and biodiversity, Russia's problems and policies have global consequences. Environmental quality and management are influenced by the legacy of Soviet economic planning and authoritarian governance, as well as by Russia's post-Soviet economic recession and current strategies of economic development. Russia achieved a reduction in some pollutants owing to the collapse of industrial production in the 1990s, but many environmental indicators suggest growing degradation. Russia has signed on to a number of international environmental agreements, but its record on implementation is mixed, and it discourages environmental activism. Scholarship on the Russian environment is a limited, but growing, field, constrained by challenges of data availability, yet it offers great potential for testing scientific and social scientific hypotheses. ©2008 by Annual Reviews.
Date: 1994-01-01
Creator: D. Gibaut
K. Kinoshita
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
Access: Open access
- The branching fractions for the five-charged-particle decays of the τ lepton have been measured in e+e- annihilations using the CLEO II detector at the Cornell Electron Storage Ring. Assuming all charged particles to be pions, the results are B(3π-2π+0 neutrals ντ)=(0.097±0. 005±0.011)%, B(3π-2π+ντ)=(0.077±0.005 ±0.009)%, B(3π-2π+π0ντ)=(0.019±0.004±0.004) %, and B(3π-2π+2π0ντ)<0.011% at the 90% C.L. B(3π-2π-π0ντ) is measured for the first time by exclusive π0 reconstruction. The results are compared with the predictions from the partially conserved-axial-current and conserved-vector-current hypotheses assuming isospin invariance. © 1994 The American Physical Society.
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.
Date: 1994-01-01
Creator: M. Artuso
D. He
M. Goldberg
N. Horwitz
R., Kennett
G. C. Moneti
F. Muheim
Y. Mukhin
S. Playfer
Y. Rozen
S. Stone
M. Thulasidas
G. Vasseur
G. Zhu
J. Bartelt
S. E. Csorna
Z. Egyed
V. Jain
P. Sheldon
D. S. Akerib
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
Access: Open access
- A measurement of the cross section for γγ→pp̄ is performed at two-photon center-of-mass energies between 2.00 and 3.25 GeV. These results are obtained using e+e-→e+e-pp̄ events selected from 1.31 fb-1 of data taken with the CLEO II detector. The measured cross section is in reasonable agreement with previous measurements and is in excellent agreement with recent calculations based on a diquark model. However, leading order QCD calculations performed using the Brodsky-Lepage formalism are well below the measured cross section. © 1994 The American Physical Society.
Date: 2005-01-01
Creator: Richard S. Dodd
Daniel Hüberli
Vlad Douhovnikoff
Tamar Y. Harnik
Zara, Afzal-Rafii
Matteo Garbelotto
Access: Open access
- California coastal woodlands are suffering severe disease and mortality as a result of infection from Phytophthora ramorum. Quercus agrifolia is one of the major woodland species at risk. This study investigated within- and among-population variation in host susceptibility to inoculation with P. ramorum and compared this with population genetic structure using molecular markers. Susceptibility was assessed using a branch-cutting inoculation test. Trees were selected from seven natural populations in California. Amplified fragment length polymorphism molecular markers were analysed for all trees used in the trials. Lesion sizes varied quantitatively among individuals within populations, with up to an eightfold difference. There was little support for population differences in susceptibility. Molecular structure also showed a strong within-population, and weaker among-population, pattern of variation. Our data suggest that susceptibility of Q. agrifolia to P. ramorum is variable and is under the control of several gene loci. This variation exists within populations, so that less susceptible local genotypes may provide the gene pool for regeneration of woodlands where mortality is high. © New Phytologist (2004).
Date: 1993-01-01
Creator: M. Battle
J. Ernst
H. Kroha
Y. Kwon
S., Roberts
K. Sparks
E. H. Thorndike
C. H. Wang
J. Dominick
S. Sanghera
V. Shelkov
T. Skwarnicki
R. Stroynowski
I. Volobouev
P. Zadorozhny
M. Artuso
D. He
M. Goldberg
N. Horwitz
R. Kennett
G. C. Moneti
F. Muheim
Y. Mukhin
S. Playfer
Y. Rozen
S. Stone
M. Thulasidas
G. Vasseur
G. Zhu
J. Bartelt
S. E. Csorna
Access: Open access
- We report results from a search for the decays B0→π+π-, B0→K+π-, and B0→K+K-. We find 90% confidence level upper limits on the branching fractions, Bππ<2.9×10-5, BKπ<2.6×10-5, and BKK<0.7×10-5. While there is no statistically significant signal in the individual modes, the sum of Bππ and BKπ exceeds zero with a significance of more than 4 standard deviations, indicating that we have observed charmless hadronic B decays. © 1993 The American Physical Society.
Date: 1993-01-01
Creator: S. Sanghera
T. Skwarnicki
R. Stroynowski
M. Artuso
M., Goldberg
N. Horwitz
R. Kennett
G. C. Moneti
F. Muheim
S. Playfer
Y. Rozen
P. Rubin
S. Stone
M. Thulasidas
W. M. Yao
G. Zhu
A. V. Barnes
J. Bartelt
S. E. Csorna
Z. Egyed
V. Jain
P. Sheldon
D. S. Akerib
B. Barish
M. Chadha
D. F. Cowen
G. Eigen
J. S. Miller
J. Urheim
A. J. Weinstein
D. Acosta
Access: Open access
- We present a measurement of the lepton decay asymmetry Afb in the reaction B̄→D*l-ν̄l using data collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR). The value of Afb confirms that the chirality of the weak interaction is predominantly left-handed in b→c transitions as expected in the standard model, if it is assumed that the lepton current is also left-handed. Using Afb and the previously determined branching ratio, q2 distribution, and D* polarization, we obtain the first measurement of the form-factor ratios that are used to describe this semileptonic decay. © 1993 The American Physical Society.
Date: 2018-12-01
Creator: Andrew E. Christie
Meredith E. Stanhope
Helen I. Gandler
Tess J. Lameyer
Micah G., Pascual
Devlin N. Shea
Andy Yu
Patsy S. Dickinson
J. Joe Hull
Access: Open access
- The American lobster, Homarus americanus, is a model for investigating the neuromodulatory control of physiology and behavior. Prior studies have shown that multiple classes of chemicals serve as locally released/circulating neuromodulators/neurotransmitters in this species. Interestingly, while many neuroactive compounds are known from Homarus, little work has focused on identifying/characterizing the enzymes responsible for their biosynthesis, despite the fact that these enzymes are key components for regulating neuromodulation/neurotransmission. Here, an eyestalk ganglia-specific transcriptome was mined for transcripts encoding enzymes involved in neuropeptide, amine, diffusible gas and small molecule transmitter biosynthesis. Using known Drosophila melanogaster proteins as templates, transcripts encoding putative Homarus homologs of peptide precursor processing (signal peptide peptidase, prohormone processing protease and carboxypeptidase) and immature peptide modifying (glutaminyl cyclase, tyrosylprotein sulfotransferase, protein disulfide isomerase, peptidylglycine-α-hydroxylating monooxygenase and peptidyl-α-hydroxyglycine-α-amidating lyase) enzymes were identified in the eyestalk assembly. Similarly, transcripts encoding full complements of the enzymes responsible for dopamine [tryptophan-phenylalanine hydroxylase (TPH), tyrosine hydroxylase and DOPA decarboxylase (DDC)], octopamine (TPH, tyrosine decarboxylase and tyramine β-hydroxylase), serotonin (TPH or tryptophan hydroxylase and DDC) and histamine (histidine decarboxylase) biosynthesis were identified from the eyestalk ganglia, as were those responsible for the generation of the gases nitric oxide (nitric oxide synthase) and carbon monoxide (heme oxygenase), and the small molecule transmitters acetylcholine (choline acetyltransferase), glutamate (glutaminase) and GABA (glutamic acid decarboxylase). The presence and identity of the transcriptome-derived transcripts were confirmed using RT-PCR. The data presented here provide a foundation for future gene-based studies of neuromodulatory control at the level of neurotransmitter/modulator biosynthesis in Homarus.
Date: 1992-01-01
Creator: D. Bortoletto
D. N. Brown
J. Dominick
R. L. Mcilwain
T., Miao
D. H. Miller
M. Modesitt
S. F. Schaffner
E. I. Shibata
I. P.J. Shipsey
M. Battle
J. Ernst
H. Kroha
S. Roberts
K. Sparks
E. H. Thorndike
C. H. Wang
S. Sanghera
T. Skwarnicki
R. Stroynowski
M. Artuso
M. Goldberg
N. Horwitz
R. Kennett
G. C. Moneti
F. Muheim
S. Playfer
Y. Rozen
P. Rubin
S. Stone
M. Thulasidas
Access: Open access
- Using the decay modes, D*+→D+π0 and D*0→D0π0, we have measured the D*+-D+ and D*0-D0 mass differences to be 140±0.08±0.06 and 142.12±0.05±0.05 MeV, respectively. Combining these measurements with the Particle Data Group average for the D*+-D0 mass difference, we obtain isospin mass splittings for D*+-Dusp*0 and D+-D0 of 3.32±0.08±0.05 and 4.80±0.10 ±0.06 MeV. We discuss the implications of these measurements for models of isospin mass differences and model-dependent estimates of fD. © 1992 The American Physical Society.