36,856 research outputs found
Effects of burying and removing dead leaves from the ground on the development of scab epidemics in an apple organic orchard.
Ascospores produced on scabbed leaves in the leaf litter constitute the primary
inoculum causing scab infections in apple orchards during the year. The trial, carried
out in a commercial organic orchard, permitted to evaluate the effects of the
removal of dead leaves located on the inter-row supplemented by the ploughing in of
the leaves left on the row, on the development of scab epidemics. From the first
recorded contamination to harvest time, lesions on leaves and fruits were counted to
determine reduction in disease incidence and severity, compared with the untreated
plots. Disease severity as a function of the distance from the untreated plot was also
observed, to evaluate the spore dispersal gradient within the orchard. The results
show that the ploughing in and the removal of the litter reduced disease incidence by
62% on leaves, and by almost 82% on fruits to harvest. Moreover, measurements of
the dispersal gradient show that the spores do not disperse, or little, beyond 20m of
the untreated zone
Approximate entropy and auto mutual information analysis of the electroencephalogram in Alzheimer's disease patients
Black Hole Formation and Classicalization in Ultra-Planckian 2 -> N Scattering
We establish a connection between the ultra-Planckian scattering amplitudes
in field and string theory and unitarization by black hole formation in these
scattering processes. Using as a guideline an explicit microscopic theory in
which the black hole represents a bound-state of many soft gravitons at the
quantum critical point, we were able to identify and compute a set of
perturbative amplitudes relevant for black hole formation. These are the
tree-level N-graviton scattering S-matrix elements in a kinematical regime
(called classicalization limit) where the two incoming ultra-Planckian
gravitons produce a large number N of soft gravitons. We compute these
amplitudes by using the Kawai-Lewellen-Tye relations, as well as scattering
equations and string theory techniques. We discover that this limit reveals the
key features of the microscopic corpuscular black hole N-portrait. In
particular, the perturbative suppression factor of a N-graviton final state,
derived from the amplitude, matches the non-perturbative black hole entropy
when N reaches the quantum criticality value, whereas final states with
different value of N are either suppressed or excluded by non-perturbative
corpuscular physics. Thus we identify the microscopic reason behind the black
hole dominance over other final states including non-black hole classical
object. In the parameterization of the classicalization limit the scattering
equations can be solved exactly allowing us to obtain closed expressions for
the high-energy limit of the open and closed superstring tree-level scattering
amplitudes for a generic number N of external legs. We demonstrate matching and
complementarity between the string theory and field theory in different large-s
and large-N regimes.Comment: 55 pages, 7 figures, LaTeX; v2: typos removed; final version to
appear in Nucl. Phys.
Multilevel correlates of household anthropometric typologies in Colombian mothers and their infants
Background. The aim of this study was to establish the association of maternal, family, and contextual correlates of anthropometric typologies at the household level in Colombia using 2005 Demographic Health Survey (DHS/ENDS) data.Methods. Household-level information from mothers 18-49 years old and their children less than 5 years old was included. Stunting and overweight were assessed for each child. Mothers were classified according to their body mass index. Four anthropometric typologies at the household level were constructed: normal, underweight, overweight, and dual burden. Four three-level [households (n = 8598) nested within municipalities (n = 226), nested within states (n = 32)] hierarchical polytomous logistic models were developed. Household log-odds of belonging to one of the four anthropometric categories, holding 'normal' as the reference group, were obtained.Results. This study found that anthropometric typologies were associated with maternal and family characteristics of maternal age, parity, maternal education, and wealth index. Higher municipal living conditions index was associated with a lower likelihood of underweight typology and a higher likelihood of overweight typology. Higher population density was associated with a lower likelihood of overweight typology.Conclusion. Distal and proximal determinants of the various anthropometric typologies at the household level should be taken into account when framing policies and designing interventions to reduce malnutrition in Colombia. Copyright © The Author(s) 2018
Child education and work choices in the presence of a conditional cash transfer programme in rural Colombia
This research is part of a large evaluation effort, undertaken by a consortium formed by IFS, Econometria and SEI, which has considered the effects of Familias en Accion on a variety of outcomes one year after its implementation. In early reports, we focussed on the effects of the programme on school enrolment. In this paper, we both expand those results, by carefully analysing anticipation effects along with other issues, and complement them with an analysis of child labour - both paid and unpaid (including domestic) work. The child labour analysis is made possible due to a rich time use module of the surveys that has not previously been analysed. We find that the programme increased the school participation rates of 14 to 17 year old children quite substantially, by between 5 and 7 percentage points, and had lower, but non-negligible effects on the enrolment of younger children of between 1.4 and 2.4 percentage points. In terms of work, the effects are generally largest for younger children whose participation in domestic work decreased by around 10 to 12 percentage points after the programme but whose participation in income-generating work remained largely unaffected by the programme. We also find evidence of school and work time not being fully substitutable, suggesting that some, but not all, of the increased time at school may be drawn from children's leisure time
Light forces in ultracold photoassociation
We study the time-resolved photoassociation of ultracold sodium in an optical
dipole trap. The photoassociation laser excites pairs of atoms to molecular
states of large total angular momentum at high intensities (above 20
kW/cm). Such transitions are generally suppressed at ultracold
temperatures by the centrifugal barriers for high partial waves. Time-resolved
ionization measurements reveal that the atoms are accelerated by the dipole
potential of the photoassociation beam. We change the collision energy by
varying the potential depth, and observe a strong variation of the
photoassociation rate. These results demonstrate the important role of light
forces in cw photoassociation at high intensities.Comment: 7 pages, 3 figure
Lifetime Measurement of the 8s Level in Francium
We measure the lifetime of the 8s level on a magneto-optically trapped sample
of ^{210}Fr atoms with time-correlated single-photon counting. The 7P_{1/2}
state serves as the resonant intermediate level for two-photon excitation of
the 8s level completed with a 1300 nm laser. Analysis of the fluorescence decay
through the the 7P_{3/2} level gives 53.30 +- 0.44 ns for the 8s level
lifetime.Comment: 4 pages, 4 figure
Space VLBI Observations of 3C371
We present the first space VLBI observations of 3C~371, carried out at a
frequency of 4.8 GHz. The combination of the high resolution provided by the
orbiting antenna Highly Advanced Laboratory for Communications and Astronomy
(HALCA) and the high sensitivity of the VLBA allows imaging of the jet of
3C~371 with an angular resolution of approximately 0.26 mas, which for this
relatively nearby source corresponds to 0.4 h pc. Comparison
between two epochs separated by 66 days reveals no apparent motions in the
inner 7 mas jet structure above an upper limit of c. This
value, the absence of detectable counterjet emission from the presumably
symmetric jet, plus the presence of extended double-lobe structure, are
consistent with the knots in the jet being stationary features such as standing
shocks. The jet intensity declines with the angular distance from the core as
. This is more gradual than that derived for 3C~120,
, for which there is evidence for strong intereactions between
the jet and ambient medium. This suggests that in 3C~371 there is a greater
level of {\it in situ} acceleration of electrons and amplification of magnetic
field. We interpret sharp bends in the jet at sites of off-center knots as
further evidence for the interaction between the jet and external medium, which
may also be responsible for the generation of standing recollimation shocks.
These recollimation shocks may be responsible for the presumably stationary
components. The radio properties of 3C~371 are intermediate between those of
other radio galaxies with bright cores and those of BL Lacertae objects.Comment: 5 pages, 4 figures. Accepted for publication in Ap
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