7,216 research outputs found
The Subcolonization and Buildup of \u3ci\u3eTetrastichus Julis,\u3c/i\u3e (Hymenoptera: Eulophidae) a Larval Parasitoid of the Cereal Leaf Beetle, (Coleoptera: Chrysomelidae) in the Lower Peninsula of Michigan
Following initial establishment of the parasitoid, Tetrastichus julis (Walker), at a carefully managed field nursery, releases of parasitized Oulema melanopus larvae were made by Michigan county agents at preselected sites throughout the lower peninsula during 1970-74. A follow-up recovery program during 1971-75 revealed continued dispersion and population increase for T. julis. An independent census verified the increasing rates of parasitism
Creep of plasma sprayed zirconia
Specimens of plasma-sprayed zirconia thermal barrier coatings with three different porosities and different initial particle sizes were deformed in compression at initial loads of 1000, 2000, and 3500 psi and temperatures of 1100 C, 1250 C, and 1400 C. The coatings were stabilized with lime, magnesia, and two different concentrations of yttria. Creep began as soon as the load was applied and continued at a constantly decreasing rate until the load was removed. Temperature and stabilization had a pronounced effect on creep rate. The creep rate for 20% Y2O3-80% ZrO2 was 1/3 to 1/2 that of 8% Y2O3-92% ZrO2. Both magnesia and calcia stabilized ZrO2 crept at a rate 5 to 10 times that of the 20% Y2O3 material. A near proportionality between creep rate and applied stress was observed. The rate controlling process appeared to be thermally activated, with an activation energy of approximately 100 cal/gm mole K. Creep deformation was due to cracking and particle sliding
Dilaton constraints and LHC prospects
The Standard Model Higgs searches using the first 1-2 fb-1 of LHC data can be
used to put interesting constraints on new scalar particles other than the
Higgs. We investigate one such scenario in which electroweak symmetry is broken
via strongly coupled conformal dynamics. This scenario contains a neutral
scalar dilaton---the Goldstone boson associated with spontaneously broken scale
invariance---with a mass below the conformal symmetry breaking scale and
couplings to Standard Model particles similar (but not identical) to those of
the Standard Model Higgs boson. We translate the LEP and LHC Higgs limits to
constrain the dilaton mass and conformal breaking scale. The conformal breaking
scale f is constrained to be above 1 TeV for dilaton masses between 145 and 600
GeV, though it can be as low as 400 GeV for dilaton masses below 110 GeV. We
also show that (i) a dilaton chi with mass below 110 GeV and consistent with
the LEP constraints can appear in gg --> chi --> gamma gamma with a rate up to
~10 times the corresponding Standard Model Higgs rate, and (ii) a dilaton with
mass of several hundred GeV is much narrower than the corresponding Standard
Model Higgs, leading to improved search sensitivity in chi --> ZZ --> 4l.Comment: 15 pages, 12 figures, References added, Figure 10 modified, Figure 11
adde
Can the 126 GeV boson be a pseudoscalar?
We test the possibility that the newly-discovered 126 GeV boson is a
pseudoscalar by examining the correlations among the loop-induced pseudoscalar
decay branching fractions to , , , and
final states in a model-independent way. These four decays are controlled by
only two effective operators, so that the rates in and are
predicted now that the rates in and
have been measured. We find that the pseudoscalar possibility is disfavored but
not conclusively excluded. Experimental exclusion of the decay to
well below or conclusive observation of the
decay near the Standard Model rate would eliminate the pseudoscalar
possibility. The exclusion should be possible using existing data.
The only loophole in our argument is the possibility that the signal
comes from pseudoscalar decays to a pair of new neutral gauge bosons with mass
near the pole.Comment: 8 pages, 2 figures, v2: references added, Fig. 1 improved,v3: minor
error in numbers on last paragraph of pg5 fixe
Constraints on large scalar multiplets from perturbative unitarity
We determine the constraints on the isospin and hypercharge of a scalar
electroweak multiplet from partial-wave unitarity of tree-level scattering
diagrams. The constraint from SU(2)_L interactions yields T <= 7/2 (i.e., n <=
8) for a complex scalar multiplet and T <= 4 (i.e., n <= 9) for a real scalar
multiplet, where n = 2T+1 is the number of isospin states in the multiplet.Comment: 10 pages, 1 figure. v2: refs added, minor additions to text,
submitted to PR
Hedgehog Pathway Activation Alters Ciliary Signaling in Primary Hypothalamic Cultures
Primary cilia dysfunction has been associated with hyperphagia and obesity in both ciliopathy patients and mouse models of cilia perturbation. Neurons throughout the brain possess these solitary cellular appendages, including in the feeding centers of the hypothalamus. Several cell biology questions associated with primary neuronal cilia signaling are challenging to address in vivo. Here we utilize primary hypothalamic neuronal cultures to study ciliary signaling in relevant cell types. Importantly, these cultures contain neuronal populations critical for appetite and satiety such as pro-opiomelanocortin (POMC) and agouti related peptide (AgRP) expressing neurons and are thus useful for studying signaling involved in feeding behavior. Correspondingly, these cultured neurons also display electrophysiological activity and respond to both local and peripheral signals that act on the hypothalamus to influence feeding behaviors, such as leptin and melanin concentrating hormone (MCH). Interestingly, we found that cilia mediated hedgehog signaling, generally associated with developmental processes, can influence ciliary GPCR signaling (Mchr1) in terminally differentiated neurons. Specifically, pharmacological activation of the hedgehog-signaling pathway using the smoothened agonist, SAG, attenuated the ability of neurons to respond to ligands (MCH) of ciliary GPCRs. Understanding how the hedgehog pathway influences cilia GPCR signaling in terminally differentiated neurons could reveal the molecular mechanisms associated with clinical features of ciliopathies, such as hyperphagia-associated obesity
Charged Higgs phenomenology in the flipped two Higgs doublet model
We study the phenomenology of the charged Higgs boson in the "flipped" two
Higgs doublet model, in which one doublet gives mass to up-type quarks and
charged leptons and the other gives mass to down-type quarks. We present the
charged Higgs branching ratios and summarize the indirect constraints. We
extrapolate existing LEP searches for H+H- and Tevatron searches for t tbar
with t --> H+ b into the flipped model and extract constraints on MH+ and the
parameter tan(beta). We finish by reviewing existing LHC charged Higgs searches
and suggest that the LHC reach in this model could be extended for charged
Higgs masses below the tb threshold by considering t tbar with t --> H+ b and
H+ --> q qbar, as has been used in Tevatron searches.Comment: 23 pages, 7 figures. V2: added refs on H+W- associated productio
New results for a photon-photon collider
We present new results from studies in progress on physics at a two-photon
collider. We report on the sensitivity to top squark parameters of MSSM Higgs
boson production in two-photon collisions; Higgs boson decay to two photons;
radion production in models of warped extra dimensions; chargino pair
production; sensitivity to the trilinear Higgs boson coupling; charged Higgs
boson pair production; and we discuss the backgrounds produced by resolved
photon-photon interactions.Comment: 17 pages, 15 figure
Single-particle dynamics of the Anderson model: a local moment approach
A non-perturbative local moment approach to single-particle dynamics of the
general asymmetric Anderson impurity model is developed. The approach
encompasses all energy scales and interaction strengths. It captures thereby
strong coupling Kondo behaviour, including the resultant universal scaling
behaviour of the single-particle spectrum; as well as the mixed valent and
essentially perturbative empty orbital regimes. The underlying approach is
physically transparent and innately simple, and as such is capable of practical
extension to lattice-based models within the framework of dynamical mean-field
theory.Comment: 26 pages, 9 figure
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