504 research outputs found
Host speciWcity of diVerent populations of the leaf beetle Diorhabda elongata (Coleoptera: Chrysomelidae), a biological control agent of saltcedar (Tamarix spp.)
Abstract The leaf beetle, Diorhabda elongata (Brullé) sensu lato, was released in 2001 for the classical biological control of exotic saltcedars, a complex of invasive Tamarix species and hybrids. It did not establish at sites south of 37°N latitude where summer daylengths are below the critical photoperiod of the northern-adapted populations of the beetle that were released. Therefore, we assessed the host speciWcity of four D. elongata populations collected from more southern latitudes in the Old World (Tunisia, Crete, Uzbekistan, and Turpan, China). All populations were similar to each other and the previously released populations of D. elongata in their host speciWcity. Larval/pupal survival for all populations was 34-100% on Tamarix test plants, 0-76% on native Frankenia plants (both in the order Tamaricales), and 0% on the remaining 28 species of plants on which all the larvae died as 1st instars. D. elongata laid high numbers of eggs on saltcedar, generally fewer eggs on athel (a moderately valued evergreen species of Tamarix) except for Uzbekistan beetles, and few to no eggs on three species of Frankenia. Few to no adults were found on Frankenia plants which also were poor maintenance hosts. The release of any of the four D. elongata populations in the southern US and northern Mexico should pose no risk to plants outside the order Tamaricales and a low risk to native, non-target Frankenia plants. Athel may be less damaged than saltcedar. Published by Elsevier Inc
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No impact of hygienic behavior and viral coinfection on the development of European foulbrood in honey bee (Apis mellifera) colonies during blueberry pollination in Michigan
European foulbrood (EFB) is a severe disease of honey bee (Apis mellifera) larvae caused by the bacterium Linnaeus [Hymenoptera: Apidae]) Melissococcus plutonius (ex White) Bailey and Collins (Lactobacillales: Enterococcaceae). Many beekeepers in North America report severe EFB following blueberry pollination, but it is not clear what factors during pollination are related to clinical disease. Additionally, the impact that other factors such as viral load and hygienic behavior have on EFB has not been studied. In Spring of 2020 we enrolled 60 commercial honey bee colonies in a prospective cohort study. Colonies were inspected 3 times over the season with hive metrics and samples taken for viral testing. Each colony was tested for hygienic behavior twice and the score was averaged. Viral loads were determined by qPCR for deformed wing virus (DWV) A and B. We found no statistical difference in the EFB prevalence or severity between the 2 yards at any timepoint; 50% (n = 16) of the colonies in the holding yard and 63% (n = 17) in blueberry developed moderate to severe EFB over the study period. When colonies from both yards were pooled, we found no relationship between viral load or hygienic behavior and development of EFB. These results suggest that other factors may be responsible for driving EFB virulence and hygienic behavior is not likely helpful in managing this disease
A Comparison of Polarization Observables in Electron Scattering from the Proton and Deuteron
Recoil proton polarization observables were measured for both the p(,e) and d(,en reactions at two values of Q using a newly commissioned proton
Focal Plane Polarimeter at the M.I.T.-Bates Linear Accelerator Center. The
hydrogen and deuterium spin-dependent observables and
, the induced polarization and the form factor ratio
were measured under identical kinematics. The deuterium and
hydrogen results are in good agreement with each other and with the plane-wave
impulse approximation (PWIA).Comment: 9 pages, 1 figure; accepted by Phys. Rev. Let
Radiative Correction to the Transferred Polarization in Elastic Electron-Proton Scattering
Model independent radiative correction to the recoil proton polarization for
the elastic electron-proton scattering is calculated within method of electron
structure functions. The explicit expressions for the recoil proton
polarization are represented as a contraction of the electron structure and the
hard part of the polarization dependent contribution into cross-section. The
calculation of the hard part with first order radiative correction is
performed. The obtained representation includes the leading radiative
corrections in all orders of perturbation theory and the main part of the
second order next-to-leading ones. Numerical calculations illustrate our
analytical results.Comment: 14 pages, 4 figure
Polarization transfer in the HeH reaction
Polarization transfer in the 4He(e,e'p)3H reaction at a Q^2 of 0.4 (GeV/c)^2
was measured at the Mainz Microtron MAMI. The ratio of the transverse to the
longitudinal polarization components of the ejected protons was compared with
the same ratio for elastic ep scattering. The results are consistent with a
recent fully relativistic calculation which includes a predicted medium
modification of the proton form factor based on a quark-meson coupling model.Comment: 5 pages, Latex, 2 postscript figures, submitted to Physics Letters
Social representations and the politics of participation
Recent work has called for the integration of different perspectives into the field of political psychology (Haste, 2012). This chapter suggests that one possible direction that such efforts can take is studying the role that social representations theory (SRT) can play in understanding political participation and social change. Social representations are systems of common-sense knowledge and social practice; they provide the lens through which to view and create social and political realities, mediate people's relations with these sociopolitical worlds and defend cultural and political identities. Social representations are therefore key for conceptualising participation as the activity that locates individuals and social groups in their sociopolitical world. Political participation is generally seen as conditional to membership of sociopolitical groups and therefore is often linked to citizenship. To be a citizen of a society or a member of any social group one has to participate as such. Often political participation is defined as the ability to communicate one's views to the political elite or to the political establishment (Uhlaner, 2001), or simply explicit involvement in politics and electoral processes (Milbrath, 1965). However, following scholars on ideology (Eagleton, 1991; Thompson, 1990) and social knowledge (Jovchelovitch, 2007), we extend our understanding of political participation to all social relations and also develop a more agentic model where individuals and groups construct, develop and resist their own views, ideas and beliefs. We thus adopt a broader approach to participation in comparison to other political-psychological approaches, such as personality approaches (e.g. Mondak and Halperin, 2008) and cognitive approaches or, more recently, neuropsychological approaches (Hatemi and McDermott, 2012). We move away from a focus on the individual's political behaviour and its antecedents and outline an approach that focuses on the interaction between psychological and political phenomena (Deutsch and Kinnvall, 2002) through examining the politics of social knowledge
Spectral functions of isoscalar scalar and isovector electromagnetic form factors of the nucleon at two-loop order
We calculate the imaginary parts of the isoscalar scalar and isovector
electromagnetic form factors of the nucleon up to two-loop order in chiral
perturbation theory. Particular attention is paid on the correct behavior of Im
and Im at the two-pion threshold
in connection with the non-relativistic 1/M-expansion. We recover the
well-known strong enhancement near threshold originating from the nearby
anomalous singularity at . In the
case of the scalar spectral function Im one finds a significant
improvement in comparison to the lowest order one-loop result. Higher order
-rescattering effects are however still necessary to close a remaining
20%-gap to the empirical scalar spectral function. The isovector electric and
magnetic spectral functions Im get additionally enhanced near
threshold by the two-pion-loop contributions. After supplementing their
two-loop results by a phenomenological -meson exchange term one can
reproduce the empirical isovector electric and magnetic spectral functions
fairly well.Comment: 10 pages, 6 figures, submitted to Physical Review
Measurement of the Induced Proton Polarization P_n in the 12C(e,e'\vec{p}) Reaction
The first measurements of the induced proton polarization, P_n, for the 12C
(e,e'\vec{p}) reaction are reported. The experiment was performed at quasifree
kinematics for energy and momentum transfer (\omega,q) \approx (294 MeV, 756
MeV/c) and sampled a recoil momentum range of 0-250 MeV/c. The induced
polarization arises from final-state interactions and for these kinematics is
dominated by the real part of the spin-orbit optical potential. The
distorted-wave impulse approximation provides good agreement with data for the
1p_{3/2} shell. The data for the continuum suggest that both the 1s_{1/2} shell
and underlying l > 1 configurations contribute.Comment: 5 pages LaTeX, 2 postscript figures, accepted by Physical Reveiw
Letter
The ratio of proton's electric to magnetic form factors measured by polarization transfer
The ratio of the proton's elastic electromagnetic form factors was obtained
by measuring the transverse and longitudinal polarizations of recoiling protons
from the elastic scattering of polarized electrons with unpolarized protons.
The ratio of the electric to magnetic form factor is proportional to the ratio
of the transverse to longitudinal recoil polarizations. The ratio was measured
over a range of four-momentum transfer squared between 0.5 and 3.5 GeV-squared.
Simultaneous measurement of transverse and longitudinal polarizations in a
polarimeter provides good control of the systematic uncertainty. The results
for the ratio of the proton's electric to magnetic form factors show a
systematic decrease with increasing four momentum squared, indicating for the
first time a marked difference in the spatial distribution of charge and
magnetization currents in the proton.Comment: 5 pages, 2 figures, version of paper after corrections due to
referees comments and shortened by removing one figure for Physical Review
Letter
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