1,412 research outputs found
Towards Grower-friendly Apple Crop Thinning by Tree Shading
Light management with shading nets, which reduce sunlight by 74%, might be an
alternative to chemicals commonly used for thinning on apple trees. To study the effect of
shading on crop load and fruit quality, trials were conducted in field experiments with the
cultivars Golden Delicious and Elstar in 2006. Trees were either covered 25 days after full
bloom (DAFB) with a net during three days, or until the peak of fruit fall, observed after
seven days shading. Ideal time length for optimal crop yield was seven days shading for
Elstar and three days shading for Golden Delicious. Alternate bearing could be decreased
as flower initiation counts the following year showed. In both experiments, inner quality of
fruit such as sugar and firmness showed good values at optimal shading duration
compared with chemical + hand thinning. In 2007, a second field trial was conducted with
cultivars Golden Delicious and Topaz to study the time period for shading in further detail.
Shading was done for three days at 19, 26 and 33 DAFB using two net types (three- and
two-meter-net width, covering the trees entirely or only down to 50 cm above ground). For
Golden Delicious, shading after 19 and 26 days reduced fruits per 100 flower cluster to the
same extent as with chemical + hand thinning. There was no difference between the two
net types. For Topaz, shading after 19 days showed the best results. Regarding inner
quality of both cultivars, only sugar content for Golden Delicious could be significantly
improved after 19 and 26 days shading. Further analyses are still under way (e.g. for
acidity).
This study is part of an effort for increasing European consumption with fruit from
sustainable production systems, the ISAFRUIT-EU-project
PPM-Extended (PPMX) - a catalogue of positions and proper motions
Aims: We build a catalogue PPM-Extended (PPMX) on the ICRS system which is
complete down to a well-defined limiting magnitude and contains the best
presently available proper motions to be suited for kinematical studies in the
Galaxy.
Methods: We perform a rigorous weighted least-squares adjustment of
individual observations, spread over more than a century, to determine mean
positions and proper motions. The stellar content of PPMX is taken from GSC 1.2
supplemented by catalogues like ARIHIP, PPM and Tycho-2 at the bright end. All
observations have been weighted according to their individual accuracy. The
catalogue has been screened towards rejecting false entries in the various
source catalogues.
Results: PPM-Extended (PPMX) is a catalogue of 18,088,920 stars containing
astrometric and photometric information. Its limiting magnitude is about 15.2
in the GSC photometric system. PPMX consists of three parts: a) a survey
complete down to R_U = 12.8 in the magnitude system of UCAC2; b) additional
stars of high-precision proper motions, and c) all other stars from GSC 1.2
identified in 2MASS. The typical accuracy of the proper motions is 2mas/y for
66 percent of the survey stars (a) and the high-precision stars (b), and about
10 mas/y for all other stars. PPMX contains photometric information from
ASCC-2.5 and 2MASS.Comment: 9 pages, 8 figures, accepted for publication in Astronomy and
Astrophysic
Optical control of coherent interactions between quantum dot electron spins
Coherent interactions between spins in quantum dots are a key requirement for
quantum gates. We have performed pump-probe experiments in which pulsed lasers
emitting at different photon energies manipulate two distinct subsets of
electron spins within an inhomogeneous InGaAs quantum dot ensemble. The spin
dynamics are monitored through their precession about an external magnetic
field. These measurements demonstrate spin precession phase shifts and
modulations of the magnitude of one subset of oriented spins after optical
orientation of the second subset. The observations are consistent with results
from a model using a Heisenberg-like interaction with microeV-strength.Comment: 5 pages, 4 figure
QCD and electroweak corrections to WZ scattering at the LHC
We present the first computation of the full next-to-leading-order QCD and
electroweak corrections to the WZ scattering process at the LHC. All off-shell,
gauge-boson-decay, and interference effects are taken into account for the
process at the orders and . The electroweak
corrections feature the typical Sudakov behaviour towards high energy and
amount to relative to the electroweak contribution to the integrated
cross section. Moreover, the corrections induce significant shape distortions
in differential distributions. The next-to-leading-order analysis of the quark-
and gluon-induced channels is supplemented by a leading-order study of all
possible contributions to the full 4\ell+2\mbox{jets} production cross
section in a realistic fiducial phase-space volume
Effect of pump-probe detuning on the Faraday rotation and ellipticity signals of mode-locked spins in InGaAs quantum dots
We have studied the Faraday rotation and ellipticity signals in ensembles of
singly-charged (In,Ga)As/GaAs quantum dots by pump-probe spectroscopy. For
degenerate pump and probe we observe that the Faraday rotation signal amplitude
first grows with increasing the time separation between pump and probe before a
decay is observed for large temporal separations. The temporal behavior of the
ellipticity signal, on the other hand, is regular: its amplitude decays with
the separation. By contrast, for detuned pump and probe the Faraday rotation
and ellipticty signals both exhibit similar and conventional behavior. The
experimental results are well described in the frame of a recently developed
microscopic theory [Phys. Rev. B 80, 104436 (2009)]. The comparison between
calculations and experimental data allows us to provide insight into the
spectral dependence of the electron spin precession frequencies and extract the
electron g-factor dependence on energy.Comment: 9 pages, 7 figure
Sterilization of lung matrices by supercritical carbon dioxide
Lung engineering is a potential alternative to transplantation for patients with end-stage pulmonary failure. Two challenges critical to the successful development of an engineered lung developed from a decellularized scaffold include (i) the suppression of resident infectious bioburden in the lung matrix, and (ii) the ability to sterilize decellularized tissues while preserving the essential biological and mechanical features intact. To date, the majority of lungs are sterilized using high concentrations of peracetic acid (PAA) resulting in extracellular matrix (ECM) depletion. These mechanically altered tissues have little to no storage potential. In this study, we report a sterilizing technique using supercritical carbon dioxide (ScCO(2)) that can achieve a sterility assurance level 10(ā6) in decellularized lung matrix. The effects of ScCO(2) treatment on the histological, mechanical, and biochemical properties of the sterile decellularized lung were evaluated and compared with those of freshly decellularized lung matrix and with PAA-treated acellular lung. Exposure of the decellularized tissue to ScCO(2) did not significantly alter tissue architecture, ECM content or organization (glycosaminoglycans, elastin, collagen, and laminin), observations of cell engraftment, or mechanical integrity of the tissue. Furthermore, these attributes of lung matrix did not change after 6 months in sterile buffer following sterilization with ScCO(2), indicating that ScCO(2) produces a matrix that is stable during storage. The current study's results indicate that ScCO(2) can be used to sterilize acellular lung tissue while simultaneously preserving key biological components required for the function of the scaffold for regenerative medicine purposes
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