1,710 research outputs found
A technique for improving the germinability of grape seeds for breeding purposes
A method, using bunches from pre-rooted cuttings which are defoliated very early during bud burst, allows the cultivation of fruiting plants in the glasshouse. The germinability of the seeds obtained in this way is improved, which permits, in particular, progenies of an early mutant of the cultivar "Cot", the seeds of which obtained in the field do practically never germinate.Une technique pour améliorer la germinabilité des graines de vigne pour les besoinsde l'améliorationUne technique, consistant à obtenir des grappes sur des boutures préenracinées puis soumises à un effeuillage trÚs précoce au débourrement, permet de cultiver des plantes fructifÚres en serre. Les graines ainsi obtenues ont une proportion de germination meilleure, ce qui a permis en particulier d'obtenir des descendants d'un mutant précoce du Cot dont les graines obtenues au champ ne germent pratiquement jamais.
Rank-(n â 1) convexity and quasiconvexity for divergence free fields
The CAST experiment at CERN (European Organization of Nuclear Research)
searches for axions from the sun. The axion is a pseudoscalar particle that was
motivated by theory thirty years ago, with the intention to solve the strong CP
problem. Together with the neutralino, the axion is one of the most promising
dark matter candidates. The CAST experiment has been taking data during the
last two years, setting an upper limit on the coupling of axions to photons
more restrictive than from any other solar axion search in the mass range below
0.1 eV. In 2005 CAST will enter a new experimental phase extending the
sensitivity of the experiment to higher axion masses. The CAST experiment
strongly profits from technology developed for high energy physics and for
X-ray astronomy: A superconducting prototype LHC magnet is used to convert
potential axions to detectable X-rays in the 1-10 keV range via the inverse
Primakoff effect. The most sensitive detector system of CAST is a spin-off from
space technology, a Wolter I type X-ray optics in combination with a prototype
pn-CCD developed for ESA's XMM-Newton mission. As in other rare event searches,
background suppression and a thorough shielding concept is essential to improve
the sensitivity of the experiment to the best possible. In this context CAST
offers the opportunity to study the background of pn-CCDs and its long term
behavior in a terrestrial environment with possible implications for future
space applications. We will present a systematic study of the detector
background of the pn-CCD of CAST based on the data acquired since 2002
including preliminary results of our background simulations.Comment: 11 pages, 8 figures, to appear in Proc. SPIE 5898, UV, X-Ray, and
Gamma-Ray Space Instrumentation for Astronomy XI
Fertility preservation in boys : recent developments and new insights
BACKGROUND: Infertility is an important side effect of treatments used for cancer and other non-malignant conditions in males. This may be due to the loss of spermatogonial stem cells (SSCs) and/or altered functionality of testicular somatic cells (e.g. Sertoli cells, Leydig cells). Whereas sperm cryopreservation is the first-line procedure to preserve fertility in post-pubertal males, this option does not exist for prepubertal boys. For patients unable to produce sperm and at high risk of losing their fertility, testicular tissue freezing is now proposed as an alternative experimental option to safeguard their fertility. OBJECTIVE AND RATIONALE: With this review, we aim to provide an update on clinical practices and experimental methods, as well as to describe patient management inclusion strategies used to preserve and restore the fertility of prepubertal boys at high risk of fertility loss. SEARCH METHODS: Based on the expertise of the participating centres and a literature search of the progress in clinical practices, patient management strategies and experimental methods used to preserve and restore the fertility of prepubertal boys at high risk of fertility loss were identified. In addition, a survey was conducted amongst European and North American centres/networks that have published papers on their testicular tissue banking activity. OUTCOMES: Since the first publication on murine SSC transplantation in 1994, remarkable progress has been made towards clinical application: cryopreservation protocols for testicular tissue have been developed in animal models and are now offered to patients in clinics as a still experimental procedure. Transplantation methods have been adapted for human testis, and the efficiency and safety of the technique are being evaluated in mouse and primate models. However, important practical, medical and ethical issues must be resolved before fertility restoration can be applied in the clinic. Since the previous survey conducted in 2012, the implementation of testicular tissue cryopreservation as a means to preserve the fertility of prepubertal boys has increased. Data have been collected from 24 co-ordinating centres worldwide, which are actively offering testis tissue cryobanking to safeguard the future fertility of boys. More than 1033 young patients (age range 3 months to 18 years) have already undergone testicular tissue retrieval and storage for fertility preservation. LIMITATIONS, REASONS FOR CAUTION: The review does not include the data of all reproductive centres worldwide. Other centres might be offering testicular tissue cryopreservation. Therefore, the numbers might be not representative for the entire field in reproductive medicine and biology worldwide. The key ethical issue regarding fertility preservation in prepubertal boys remains the experimental nature of the intervention. WIDER IMPLICATIONS: The revised procedures can be implemented by the multi-disciplinary teams offering and/or developing treatment strategies to preserve the fertility of prepubertal boys who have a high risk of fertility loss.Peer reviewe
The field high-amplitude SX Phe variable BL Cam: results from a multisite photometric campaign. II. Evidence of a binary - possibly triple - system
Short-period high-amplitude pulsating stars of Population I ( Sct
stars) and II (SX Phe variables) exist in the lower part of the classical
(Cepheid) instability strip. Most of them have very simple pulsational
behaviours, only one or two radial modes being excited. Nevertheless, BL Cam is
a unique object among them, being an extreme metal-deficient field
high-amplitude SX Phe variable with a large number of frequencies. Based on a
frequency analysis, a pulsational interpretation was previously given. aims
heading (mandatory) We attempt to interpret the long-term behaviour of the
residuals that were not taken into account in the previous Observed-Calculated
(O-C) short-term analyses. methods heading (mandatory) An investigation of the
O-C times has been carried out, using a data set based on the previous
published times of light maxima, largely enriched by those obtained during an
intensive multisite photometric campaign of BL Cam lasting several months.
results heading (mandatory) In addition to a positive (161 3) x 10
yr secular relative increase in the main pulsation period of BL Cam, we
detected in the O-C data short- (144.2 d) and long-term ( 3400 d)
variations, both incompatible with a scenario of stellar evolution. conclusions
heading (mandatory) Interpreted as a light travel-time effect, the short-term
O-C variation is indicative of a massive stellar component (0.46 to 1
M_{\sun}) with a short period orbit (144.2 d), within a distance of 0.7 AU
from the primary. More observations are needed to confirm the long-term O-C
variations: if they were also to be caused by a light travel-time effect, they
could be interpreted in terms of a third component, in this case probably a
brown dwarf star ( 0.03 \ M_{\sun}), orbiting in 3400 d at a
distance of 4.5 AU from the primary.Comment: 7 pages, 5 figures, accepted for publication in A&
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Measurement of the lifetime
Using a data set corresponding to an integrated luminosity of ,
collected by the LHCb experiment in collisions at centre-of-mass energies
of 7 and 8 TeV, the effective lifetime in the
decay mode, , is measured to be ps. Assuming
conservation, corresponds to the lifetime of the light
mass eigenstate. This is the first measurement of the effective
lifetime in this decay mode.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-017.htm
Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at âs=7 TeV
Bose-Einstein correlations of same-sign charged pions, produced in protonproton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected
by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the
form of an enhancement of pairs of like-sign charged pions with small four-momentum
difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source
is investigated, determining both the correlation radius and the chaoticity parameter. The
measured correlation radius is found to increase as a function of increasing charged-particle
multiplicity, while the chaoticity parameter is seen to decreas
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