33,852 research outputs found
A New \u3ci\u3eFlexamia\u3c/i\u3e (Homoptera: Cicadellidae: Deltocephalinae) From Southern Michigan
A new species, Flexamia huroni, is described from a prairie fen in south- eastern Michigan. This leafhopper is closely related to the western F. serrata B & T, a specialist on mat muhly (Muhlenbergia richardsonis). Like its sister species, F. huroni was found only in close association with mat muhly, a grass listed as a threatened species in Michigan and Wisconsin. The regional rarity of mat muhly, its association with a globally imperiled plant commnity (prairie fen) and the absence of F. huroni from several fens known to contain this grass, make this new Flexamia a strong candidate for listing as endangered in Michigan
Isobar-free neon isotope measurements of flux-fused potential reference minerals on a Helix-MC-Plus^(10K) mass spectrometer
This work presents new analytical techniques for extraction and analysis of neon from a suite of different mineral phases, including quartz, pyroxene, hematite, apatite, zircon, topaz, and fluorite. Neon was quantitatively extracted at 1100 °C from all of these minerals using an in-vacuum lithium borate-flux fusion technique. Evolved neon was purified using a cryogenic method capable of separating Ne from He present in abundances ~8 orders of magnitude higher, typical of samples carrying nucleogenic/radiogenic noble gases. The purified neon was measured on a Helix-MC-Plus^(10K) mass spectrometer that permits isobar-free measurement of all three neon isotopes. When operated at its highest mass resolving power (MRP) of ~10,300, the shoulder representing solely ²²Ne on the low mass-side of the ²²Ne-CO₂⁺² doublet is wide enough to permit measurement of isobar free ²²Ne. Operating in this mode comes with the penalty of a 50% reduction in neon sensitivity. Coupled with a mathematical isobar-stripping method, this approach excludes 99.5% of the CO₂⁺² while still collecting >99% of the ²²Ne beam. Routine edge-centering on the dynamic CO₂⁺² peak prior to introduction of a sample permits rapid and robust relocation of the desired measure point in the mass spectrum.
Cosmogenic ²¹Ne and ²²Ne concentrations obtained using these methods on the Cronus-A quartz and Cronus-P pyroxene international reference materials are in excellent agreement with previous work or expectations. Similarly, the concentration of nucleogenic ²¹Ne and ²²Ne in Durango apatite and the CIT hematite standard agree well with previous work. Durango apatite has notable heterogeneity in neon concentrations, consistent with previous observations of heterogeneous He, U and Th concentrations in this apatite. Nucleogenic neon concentrations are also presented for previously unstudied minerals including a Sri Lanka zircon (SLC), a topaz from the Imperial Topaz mine in Brazil (ITP1), and a fluorite (W-90) from New Hampshire. Taken together this set of potential reference minerals and the associated dataset provide a starting point for intercalibration among multiple mineral phases carrying ²¹Ne and ²²Ne of cosmogenic or nucleogenic origin
Field-guided proton acceleration at reconnecting X-points in flares
An explicitly energy-conserving full orbit code CUEBIT, developed originally
to describe energetic particle effects in laboratory fusion experiments, has
been applied to the problem of proton acceleration in solar flares. The model
fields are obtained from solutions of the linearised MHD equations for
reconnecting modes at an X-type neutral point, with the additional ingredient
of a longitudinal magnetic field component. To accelerate protons to the
highest observed energies on flare timescales, it is necessary to invoke
anomalous resistivity in the MHD solution. It is shown that the addition of a
longitudinal field component greatly increases the efficiency of ion
acceleration, essentially because it greatly reduces the magnitude of drift
motions away from the vicinity of the X-point, where the accelerating component
of the electric field is largest. Using plasma parameters consistent with flare
observations, we obtain proton distributions extending up to gamma-ray-emitting
energies (>1MeV). In some cases the energy distributions exhibit a bump-on-tail
in the MeV range. In general, the shape of the distribution is sensitive to the
model parameters.Comment: 14 pages, 4 figures, accepted for publication in Solar Physic
Taxa of Idiocerus Lewis new to Canada (Rhynchota: Homoptera: Cicadellidae)
Six new species and one new subspecies of <i>Idiocerus</i> are described: <i>I. cabottii</i> from N.S., <i>I. canae</i> from Alberta, <i>I. glacialis</i> and <i>I. indistinctus</i> from B.C., and <i>I. albolinea</i>, <i>I. musteus arsiniatus</i> and <i>I. setaceus</i>, widespread east of the Cordilleran region. The identities of <i>I. duzeei</i> Provancher (N.S.-Ont.) and <i>I. interruptus</i> Gillette & Baker (N.S.-Colo.) are discussed, and these species are removed from synonymy
Determination of the Baryon Density from Large Scale Galaxy Redshift Surveys
We estimate the degree to which the baryon density, , can be
determined from the galaxy power spectrum measured from large scale galaxy
redshift surveys, and in particular, the Sloan Digital Sky Survey. A high
baryon density will cause wiggles to appear in the power spectrum, which should
be observable at the current epoch. We assume linear theory on scales and do not include the effects of redshift distortions, evolution,
or biasing. With an optimum estimate of to ,
the uncertainties in are roughly 0.07 and 0.016 in flat
and open () cosmological models, respectively. This result
suggests that it should be possible to test for consistency with big bang
nucleosynthesis estimates of if we live in an open universe.Comment: 23 Pages, 10 Postscript figure
Nuclear Model of Binding alpha-particles
The model of binding alpha-particles in nuclei is suggested. It is shown good
(with the accuracy of 1-2%) description of the experimental binding energies in
light and medium nuclear systems. Our preliminary calculations show enhancement
of the binding energy for super heavy nuclei with Z~120.Comment: 4 pages, 2 figures, Will be puplished in World Scientific as Procs.
Int. Symposium on Exotic Nuclei, "EXON - 2004", July 5 - 12, 2004, Peterhof,
Russi
Computer model calibration with large non-stationary spatial outputs: application to the calibration of a climate model
Bayesian calibration of computer models tunes unknown input parameters by
comparing outputs with observations. For model outputs that are distributed
over space, this becomes computationally expensive because of the output size.
To overcome this challenge, we employ a basis representation of the model
outputs and observations: we match these decompositions to carry out the
calibration efficiently. In the second step, we incorporate the non-stationary
behaviour, in terms of spatial variations of both variance and correlations, in
the calibration. We insert two integrated nested Laplace
approximation-stochastic partial differential equation parameters into the
calibration. A synthetic example and a climate model illustration highlight the
benefits of our approach
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