1,579 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
Chasing Funding “To Eat Our Own Tail”: The Invisible Emotional Work of Making Social Change
This article presents findings from a multi-site study conducted in Montréal, QC, and Toronto, ON, Canada, on “social innovation” networks, focusing on the forms of emotional and relational work that many participants described. The article explores how these tasks related to how workers in the two nonprofit “backbone” organizations described their contributions to the impacts they hoped to make. The intersections of these forms of work and particular identities are framed within a feminist lens—when and how are these forms of relational work recognized or made invisible? This work is contextualized within neoliberal reforms, the restructuring of the state, and external funding requirements and how these determine what forms of work are deemed “impactful” in making significant social change around broad issues of homelessness and social exclusion.Cet article présente les résultats d’une étude multi-sites sur les réseaux « d’innovation sociale » menée à Montréal, QC et Toronto, ON, Canada, et met l’accent sur des formes de travail émotionnel et relationnel décrites par de nombreux participants. Les auteurs explorent la relation entre ces tâches et la manière dont les travailleurs de deux organismes à but non lucratif centraux décrivent leurs contributions aux impacts qu’ils espéraient avoir. Les intersections de ces travaux et des identités particulières s’inscrivent dans une perspective féministe—quand et comment les formes de travail relationnelles sont-elles reconnues ou rendues invisible? Cet article s’inscrit dans le cadre des réformes néolibérales, de la restructuration de l’État et des besoins des bailleurs de fonds externes, et comment ceux-ci déterminent quelles formes de travail sont considérées comme ayant un impact « décisif » sur le changement social important autour des grandes questions de l’itinérance et d’exclusion sociale
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
Electrical properties of breast cancer cells from impedance measurement of cell suspensions
Impedance spectroscopy of biological cells has been used to monitor cell status, e.g. cell proliferation, viability, etc. It is also a fundamental method for the study of the electrical properties of cells which has been utilised for cell identification in investigations of cell behaviour in the presence of an applied electric field, e.g. electroporation. There are two standard methods for impedance measurement on cells. The use of microelectrodes for single cell impedance measurement is one method to realise the measurement, but the variations between individual cells introduce significant measurement errors. Another method to measure electrical properties is by the measurement of cell suspensions, i.e. a group of cells within a culture medium or buffer. This paper presents an investigation of the impedance of normal and cancerous breast cells in suspension using the Maxwell-Wagner mixture theory to analyse the results and extract the electrical parameters of a single cell. The results show that normal and different stages of cancer breast cells can be distinguished by the conductivity presented by each cell. © 2010 IOP Publishing Ltd
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
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
Relações de causa e efeito entre condições ambientais, urediniósporos e severidade de ferrugem-asiática da soja.
O objetivo deste trabalho foi estabelecer relações entre condições ambientais, o número de urediniósporos de Phakopsora pachyrhizi e a severidade da ferrugem-asiática-da-soja. Para quantificar urediniósporos de P. pachyrhizi, coletores foram instalados em campos de soja, em Itambé e Mandaguari, PR. Avaliações de severidade foram realizadas e dados climáticos foram coletados nos dois locais. As variáveis elaboradas foram: número de dias com umidade favorável (>60%), número de dias com temperatura favorável (18 a 32º C), preciptação acumulada e urediniósporos coletados. Uma variável baseada no controle químico também foi elaborada. Correlações entre as variáveis foram estimadas. A análise de trilha foi empregada para desdobrar as correlações. Cerca de 76% da variação das relações de causa e efeito entre as variáveis foi explicada pela análise de trilha. O número de dias para efetuar o controle químico teve efeito direto sob a severidade. O número de dias com temperatura favorável e as precipitações tiveram efeito indireto na severidade, atuando via manutenção de condições favoráveis de umidade
Comparative analyze of the kefir fermentation process and microbiota, using milk and cheese whey as substrates
Kefir, a mixed culture that ferments lactose, is known for the production of a refreshing
fermented beverage popular in EasternEuropean countries by inoculating milk with kefir grains.
Kefir grains are gelatinous white or creamcoloured, water insoluble, irregular granules with
diameter ranging 0,33,5 cm. They are composed mostly of proteins and polysaccharides in
which the complex microbiota is enclosed. The beverage consists of a microbial diversity that
includes lactic acid bacteria, yeasts and their metabolites. The aim of this work was to compare
the fermentation and the microbiota of kefir , using milk and cheese whey as substrates. The
grains were added in the proportion of 5% in 250ml of each substrate. Assays were performed at
25 °C for 48h. The concentrations of lactose, ethanol, lactic acid and acetic acid were quantified
by HPLC. To determinate the composition of microbiota in Kefir of fermentation, PCRDGGE
analysis was used.The fermentation of milk and cheese whey by kefir grains are observed in this
study. It can be observed that the lactose concentration at the end of the milk fermentation was
lower in comparison with that obtained at 48 h for cheese whey fermentation. Despite the higher
lactose consumption during the fermentation of milk by kefir grains, the concentrations of
ethanol, acetic acid and lactic acid did not show significant differences with those obtained during
the cheese whey fermentation. No changes in the DGGE profiles in all fermentations were
observed to fungal and bacterial communities. It was thus concluded that lactose from cheese
whey is converted to products with higher yields than lactose from milk, in addition to showing
the same group of microorganisms for both fermentation process
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