586 research outputs found
Complex urban environments provide Apis mellifera with a richer plant forage than suburban and more rural landscapes
Growth in the global development of cities, and increasing public interest in beekeeping, has led to increase in the numbers of urban apiaries. Towns and cities can provide an excellent diet for managed bees, with a diverse range of nectar and pollen available throughout a long flowering season, and are often more ecologically diverse
than the surrounding rural environments. Accessible urban honeybee hives are a valuable research resource to gain insights into the diet and ecology of wild pollinators
in urban settings. We used DNA metabarcoding of the rbcL and ITS2 gene regions to characterize the pollen community in Apis mellifera honey, inferring the floral diet,
from 14 hives across an urban gradient around Greater Manchester, UK. We found that the proportion of urban land around a hive is significantly associated with an
increase in the diversity of plants foraged and that invasive and non-native plants appear to play a critical role in the sustenance of urban bees, alongside native plant
species. The proportion of improved grassland, typical of suburban lawns and livestock farms, is significantly associated with decreases in the diversity of plant pollen
found in honey samples. These findings are relevant to urban landscape developers motivated to encourage biodiversity and bee persistence, in line with global bio-food security agendas
Constrained by managerialism : caring as participation in the voluntary social services
The data in this study show that care is a connective process, underlying and motivating participation and as a force that compels involvement in the lives of others, care is at least a micro-participative process. Care or affinity not only persisted in the face of opposition, but it was also used by workers as a counter discourse and set of practices with which to resist the erosion of worker participation and open up less autonomized practices and ways of connecting with fellow staff, clients and the communities they served. The data suggest that while managerialism and taylorised practice models may remove or reduce opportunities for worker participation, care is a theme or storyline that gave workers other ways to understand their work and why they did it, as well as ways they were prepared to resist managerial priorities and directives, including the erosion of various kinds of direct and indirect participation. The degree of resistance possible, even in the highly technocratic worksite in Australia, shows that cracks and fissures exist within managerialism
Cellular and ultrastructural characterization of the grey-morph phenotype in southern right whales (Eubalaena australis)
Southern right whales (SRWs, Eubalena australis) are polymorphic for an X-linked pigmentation pattern known as grey morphism. Most SRWs have completely black skin with white patches on their bellies and occasionally on their backs; these patches remain white as the whale ages. Grey morphs (previously referred to as partial albinos) appear mostly white at birth, with a splattering of rounded black marks; but as the whales age, the white skin gradually changes to a brownish grey color. The cellular and developmental bases of grey morphism are not understood. Here we describe cellular and ultrastructural features of grey-morph skin in relation to that of normal, wild-type skin. Melanocytes were identified histologically and counted, and melanosomes were measured using transmission electron microscopy. Grey-morph skin had fewer melanocytes when compared to wild-type skin, suggesting reduced melanocyte survival, migration, or proliferation in these whales. Grey-morph melanocytes had smaller melanosomes relative to wild-type skin, normal transport of melanosomes to surrounding keratinocytes, and normal localization of melanin granules above the keratinocyte nuclei. These findings indicate that SRW grey-morph pigmentation patterns are caused by reduced numbers of melanocytes in the skin, as well as by reduced amounts of melanin production and/or reduced sizes of mature melanosomes. Grey morphism is distinct from piebaldism and albinism found in other species, which are genetic pigmentation conditions resulting from the local absence of melanocytes, or the inability to synthesize melanin, respectively
Virtual Compton Scattering and the Generalized Polarizabilities of the Proton at Q^2=0.92 and 1.76 GeV^2
Virtual Compton Scattering (VCS) on the proton has been studied at Jefferson
Lab using the exclusive photon electroproduction reaction (e p --> e p gamma).
This paper gives a detailed account of the analysis which has led to the
determination of the structure functions P_LL-P_TT/epsilon and P_LT, and the
electric and magnetic generalized polarizabilities (GPs) alpha_E(Q^2) and
beta_M(Q^2) at values of the four-momentum transfer squared Q^2= 0.92 and 1.76
GeV^2. These data, together with the results of VCS experiments at lower
momenta, help building a coherent picture of the electric and magnetic GPs of
the proton over the full measured Q^2-range, and point to their non-trivial
behavior.Comment: version 2: modified according to PRC Editor's and Referee's
recommendations. Archival paper for the E93-050 experiment at JLab Hall A. 28
pages, 23 figures, 5 cross-section tables. To be submitted to Phys.Rev.
Backward electroproduction of pi0 mesons on protons in the region of nucleon resonances at four momentum transfer squared Q**2 = 1.0 GeV**2
Exclusive electroproduction of pi0 mesons on protons in the backward
hemisphere has been studied at Q**2 = 1.0 GeV**2 by detecting protons in the
forward direction in coincidence with scattered electrons from the 4 GeV
electron beam in Jefferson Lab's Hall A. The data span the range of the total
(gamma* p) center-of-mass energy W from the pion production threshold to W =
2.0 GeV. The differential cross sections sigma_T+epsilon*sigma_L, sigma_TL, and
sigma_TT were separated from the azimuthal distribution and are presented
together with the MAID and SAID parametrizations.Comment: 17 pages, 11 figures, information can be found at
http://hallaweb.jlab.org/experiment/E93-050/vcs.html updated content about
SAID analysis updated MAID results following new reference nucl-th/0310041
updated figure
Polarization transfer in the d(epol,e' ppol)n reaction up to Q^2=1.61 (GeV/c)^2
The recoil proton polarization was measured in the d(epol,e' ppol)n reaction
in Hall A of the Thomas Jefferson National Accelerator Facility (JLab). The
electron kinematics were centered on the quasielastic peak (x_{Bj}~1) and
included three values of the squared four-momentum transfer, Q^2=0.43, 1.00 and
1.61 (GeV/c)^2. For Q^2=0.43 and 1.61 (GeV/c)^2, the missing momentum, p_m, was
centered at zero while for Q^2=1.00 (GeV/c)^2 two values of p_m were chosen: 0
and 174 MeV/c. At low p_m, the Q^2 dependence of the longitudinal polarization,
P_z', is not well described by a state-of-the-art calculation. Further, at
higher p_m, a 3.5 sigma discrepancy was observed in the transverse
polarization, P_x'. Understanding the origin of these discrepancies is
important in order to confidently extract the neutron electric form factor from
the analogous d(epol,e' npol)p experiment.Comment: 6 pages, 4 figures; updated text, figures and table
The reaction dynamics of the 16O(e,e'p) cross section at high missing energies
We measured the cross section and response functions (R_L, R_T, and R_LT) for
the 16O(e,e'p) reaction in quasielastic kinematics for missing energies 25 <=
E_miss <= 120 MeV at various missing momenta P_miss <= 340 MeV/c. For 25 <
E_miss < 50 MeV and P_miss \approx 60 MeV/c, the reaction is dominated by
single-nucleon knockout from the 1s1/2-state. At larger P_miss, the
single-particle aspects are increasingly masked by more complicated processes.
For E_miss > 60 MeV and P_miss > 200 MeV/c, the cross section is relatively
constant. Calculations which include contributions from pion exchange currents,
isobar currents and short-range correlations account for the shape and the
transversity but only for half of the magnitude of the measured cross section.Comment: 6 pages, 4 figures, submitted to Phys Rev Lett, formatting error
fixe
Large Momentum Transfer Measurements of the Deuteron Elastic Structure Function A(Q^2) at Jefferson Laboratory
The deuteron elastic structure function A(Q^2) has been extracted in the Q^2
range 0.7 to 6.0 (GeV/c)^2 from cross section measurements of elastic
electron-deuteron scattering in coincidence using the Hall A Facility of
Jefferson Laboratory. The data are compared to theoretical models based on the
impulse approximation with inclusion of meson-exchange currents, and to
predictions of quark dimensional scaling and perturbative quantum
chromodynamicsComment: Submitted to Physical Review Letter
Measurement of Inclusive Spin Structure Functions of the Deuteron
We report the results of a new measurement of spin structure functions of the
deuteron in the region of moderate momentum transfer ( = 0.27 -- 1.3
(GeV/c)) and final hadronic state mass in the nucleon resonance region (
= 1.08 -- 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam
at Jefferson Lab off a dynamically polarized cryogenic solid state target
(ND) and detected the scattered electrons with the CEBAF Large
Acceptance Spectrometer (CLAS). From our data, we extract the longitudinal
double spin asymmetry and the spin structure function . Our
data are generally in reasonable agreement with existing data from SLAC where
they overlap, and they represent a substantial improvement in statistical
precision. We compare our results with expectations for resonance asymmetries
and extrapolated deep inelastic scaling results. Finally, we evaluate the first
moment of the structure function and study its approach to both the
deep inelastic limit at large and to the Gerasimov-Drell-Hearn sum rule
at the real photon limit (). We find that the first moment varies
rapidly in the range of our experiment and crosses zero at between
0.5 and 0.8 (GeV/c), indicating the importance of the resonance at
these momentum transfers.Comment: 13 pages, 8 figures, ReVTeX 4, final version as accepted by Phys.
Rev.
Relativistic effects and two-body currents in using out-of-plane detection
Measurements of the reaction were performed
using an 800-MeV polarized electron beam at the MIT-Bates Linear Accelerator
and with the out-of-plane magnetic spectrometers (OOPS). The
longitudinal-transverse, and , and the
transverse-transverse, , interference responses at a missing momentum
of 210 MeV/c were simultaneously extracted in the dip region at Q=0.15
(GeV/c). On comparison to models of deuteron electrodisintegration, the
data clearly reveal strong effects of relativity and final-state interactions,
and the importance of the two-body meson-exchange currents and isobar
configurations. We demonstrate that these effects can be disentangled and
studied by extracting the interference response functions using the novel
out-of-plane technique.Comment: 4 pages, 4 figures, and submitted to PRL for publicatio
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