6,968 research outputs found
The relationships between organic farming and agroecology.
While acknowledging an extension of agroecology in the organic sector and a growing influence of agroecology in the academic world, we explore their relationships. These relationships cannot be reduced to an opposition between a scientific field and a practical domain. A Brazilian case study based on the analysis of researchers and social actors trajectories exemplifies the diversity of existing relations, whether inclusive or exclusive. With a literature review, this allows characterising the specific attributes of both organic agriculture and agroecology. We discuss them in the light of current challenges for organic farming research and development
Comment on "Two Phase Transitions in the Fully frustrated XY Model"
The conclusions of a recent paper by Olsson (Phys. Rev. Lett. 75, 2758
(1995), cond-mat/9506082) about the fully frustrated XY model in two dimensions
are questioned. In particular, the evidence presented for having two separate
chiral and U(1) phase transitions are critically considered.Comment: One page one table, to Appear in Physical Review Letter
Genetic heterogeneity of residual variance in broiler chickens
Aims were to estimate the extent of genetic
heterogeneity in environmental variance. Data comprised 99 535 records of
35-day body weights from broiler chickens reared in a controlled
environment. Residual variance within dam families was estimated using
ASREML, after fitting fixed effects such as genetic groups and hatches, for
each of 377 genetically contemporary sires with a large number of progeny
(100 males or females each). Residual variance was computed separately
for male and female offspring, and after correction for sampling, strong
evidence for heterogeneity was found, the standard deviation between sires
in within variance amounting to 15–18% of its mean. Reanalysis using
log-transformed data gave similar results, and elimination of 2–3% of
outlier data reduced the heterogeneity but it was still over 10%. The
correlation between estimates for males and females was low, however. The
correlation between sire effects on progeny mean and residual variance for
body weight was small and negative (-0.1). Using a data set bigger than any
yet presented and on a trait measurable in both sexes, this study has shown
evidence for heterogeneity in the residual variance, which could not be
explained by segregation of major genes unless very few determined the
trait
Extradigital glomus tumour causing thigh pain: a case report
Glomus tumours are rare and benign, arising from a neuromyoarterial glomus body,
most commonly in the hand. We report a patient with such a tumour in an atypical
site, the right vastus lateralis. Pain was aggravated by muscle contraction, and
ultrasonography and MRI were required to locate the lesion accurately. Surgical
excision gave immediate pain relief
Improving the economic value of photographic screening for optical coherence tomography-detectable macular oedema : a prospective, multicentre, UK study
Peer reviewedPublisher PD
Stellar luminosity functions of rich star clusters in the Large Magellanic Cloud
We show the results of deep V and I HST photometry of 6 rich star clusters in
the Large Magellanic Cloud with different ages and metallicities. The number of
stars with measured magnitudes in each cluster varies from about 3000 to 10000.
We build stellar density and surface brightness profiles for the clusters and
extract half-light radii and other structural parameters for each. We also
obtain luminosity functions, Phi (Mv), down to Mv ~ 6 (m/msun > 0.6), and
investigate their dependence with distance from the cluster centre well beyond
their half-light radius. In all clusters we find a systematic increase in the
luminosity function slope with radial distance from the centre. Among the
clusters displaying significant mass segregation are the two youngest in the
sample: NGC 1805 and NGC 1818. For these two clusters we obtain present-day
mass functions. The NGC 1818 mass function is in excellent agreement with that
derived by other authors, also using HST data. They young cluster mass function
slopes differ, that of NCG 1805 being systematically steeper than NGC 1818.
Since these are very young stellar systems (age < 40 Myrs), these variations
may reflect the initial conditions rather than evolution due to internal
dynamics.Comment: 10 pages, 24 figure
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