809 research outputs found
Variability of stellar granulation and convective blueshift with spectral type and magnetic activity. I. K and G main sequence stars
In solar-type stars, the attenuation of convective blueshift by stellar
magnetic activity dominates the RV variations over the low amplitude signal
induced by low mass planets. Models of stars that differ from the Sun will
require a good knowledge of the attenuation of the convective blueshift to
estimate its impact on the variations. It is therefore crucial to precisely
determine not only the amplitude of the convective blueshift for different
types of stars, but also the dependence of this convective blueshift on
magnetic activity, as these are key factors in our model producing the RV. We
studied a sample of main sequence stars with spectral types from G0 to K2 and
focused on their temporally averaged properties: the activity level and a
criterion allowing to characterise the amplitude of the convective blueshift.
We find the differential velocity shifts of spectral lines due to convection to
depend on the spectral type, the wavelength (this dependence is correlated with
the Teff and activity level), and on the activity level. This allows us to
quantify the dependence of granulation properties on magnetic activity for
stars other than the Sun. The attenuation factor of the convective blueshift
appears to be constant over the considered range of spectral types. We derive a
convective blueshift which decreases towards lower temperatures, with a trend
in close agreement with models for Teff lower than 5800 K, but with a
significantly larger global amplitude. We finally compare the observed RV
variation amplitudes with those that could be derived from our convective
blueshift using a simple law and find a general agreement on the amplitude. Our
results are consistent with previous results and provide, for the first time,
an estimation of the convective blueshift as a function of Teff, magnetic
activity, and wavelength, over a large sample of G and K main sequence stars
The glass ceiling in football in Europe. Levels of representation of ‘visible’ ethnic minorities and women in leadership positions, and the experiences of elite level ‘visible’ ethnic minority coaches
The glass ceiling in football in Europe. Levels of representation of ‘visible’ ethnic minorities and women in leadership positions, and the experiences of elite level ‘visible’ ethnic minority coaches
Measuring Impression Management in Male Leaders of Color
Companies’ survival depends on their ability to attract and maintain diverse leaders. This research examines the tactics used by male leaders of color to secure management positions. The Jones and Pittman’s Impression Management Taxonomy (1982) was used to explore the impression management phenomenon and the constructs of self-promotion, ingratiation, exemplification, intimidation, and supplication as they relate to gender and ethnicity. The statistical analysis was conducted on 240 valid responses where an exploratory factor analysis and a MANOVA provided insight on the variables’ relationships. The findings convey Black/African–American and Latinos scored similarly in their use of supplication versus White male leaders, which indicates that male leaders of color are more likely to be modest in their approach. Additionally, to some extent, all ethnicities with the exception of Asians tended to use the intimidation tactic in the workplace. While diversity is a growing trend in the workplace, this study confirms that it is imperative to have healthy conversations about ethnicity and gender in professional settings
Long range magnetic ordering in a spin-chain compound, CaCuMnO, with multiple bond distances
The results of ac and dc magnetization and heat capacity measurements as a
function of temperature (T = 1.8 to 300 K) are reported for a
quasi-one-dimensional compound, CaCuMnO, crystallizing in a
triclinically distorted KCdCl-type structure. The results reveal that
this compound undergoes antiferromagnetic ordering close to 5.5 K. In addition,
there is another magnetic transition below 3.6 K. Existence of two long-range
magnetic transitions is uncommon among quasi-one-dimensional systems. It is
interesting to note that both the magnetic transitions are of long-range type,
instead of spin-glass type, in spite of the fact that the Cu-O and Mn-O bond
distances are multiplied due to this crystallographic distortion. In view of
this, this compound could serve as a nice example for studying
"order-in-disorder" phenomena.Comment: Physical Review (in press
Effet magnéto-optique et optique des couches minces à base de ferrite de cobalt
Cette étude a pour but la mesure des effets magnéto-optiques (rotation Faraday) en fonction du champ magnétique appliqué et en fonction de la longueur d’onde, ainsi que la mesure de la transmittance (effet optique) des couches minces à base de ferrite de cobalt. Les résultats montrent une forte rotation Faraday spécifique avec des cycles d'hystérésis et des spectres de transmittance d'une bonne transparence dans la gamme Télécom (≈1550 nm).Mots-clés: ferrite de cobalt, sol-gel, couches minces, rotation Faraday, transmittance. Magneto-optical effect and optical thin films cobalt ferriteThis study was designed to measure the magneto-optical effect (Faraday rotation) according to the applied magnetic field and a function of the wavelength and the transmittance measurement (optical effect) thin film based on cobalt ferrite. The results show a high specific Faraday rotation with hysteresis cycles and transmittance spectra of a good transparency in the range Telecom (≈1550 nm).Keywords: cobalt ferrite, sol-gel thin films, Faraday rotation, transmittance
Review: Towards the agroecological management of ruminants, pigs and poultry through the development of sustainable breeding programmes. II. Breeding strategies
Agroecology uses ecological processes and local resources rather than chemical inputs to develop productive and resilient livestock and crop production systems. In this context, breeding innovations are necessary to obtain animals that are both productive and adapted to a broad range of local contexts and diversity of systems. Breeding strategies to promote agroecological systems are similar for different animal species. However, current practices differ regarding the breeding of ruminants, pigs and poultry. Ruminant breeding is still an open system where farmers continue to choose their own breeds and strategies. Conversely, pig and poultry breeding is more or less the exclusive domain of international breeding companies which supply farmers with hybrid animals. Innovations in breeding strategies must therefore be adapted to the different species. In developed countries, reorienting current breeding programmes seems to be more effective than developing programmes dedicated to agroecological systems that will struggle to be really effective because of the small size of the populations currently concerned by such systems. Particular attention needs to be paid to determining the respective usefulness of cross-breeding v. straight breeding strategies of well-adapted local breeds. While cross-breeding may offer some immediate benefits in terms of improving certain traits that enable the animals to adapt well to local environmental conditions, it may be difficult to sustain these benefits in the longer term and could also induce an important loss of genetic diversity if the initial pure-bred populations are no longer produced. As well as supporting the value of within-breed diversity, we must preserve between-breed diversity in order to maintain numerous options for adaptation to a variety of production environments and contexts. This may involve specific public policies to maintain and characterize local breeds (in terms of both phenotypes and genotypes), which could be used more effectively if they benefited from the scientific and technical resources currently available for more common breeds. Last but not least, public policies need to enable improved information concerning the genetic resources and breeding tools available for the agroecological management of livestock production systems, and facilitate its assimilation by farmers and farm technicians
Magnetic frustration in a stoichiometric spin-chain compound, CaCoIrO
The temperature dependent ac and dc magnetization and heat capacity data of
CaCoIrO, a spin-chain compound crystallizing in a KCdCl-derived
rhombohedral structure, show the features due to magnetic ordering of a
frustrated-type below about 30 K, however without exhibiting the signatures of
the so-called "partially disordered antiferromagnetic structure" encountered in
the isostructural compounds, CaCoO and CaCoRhO. This class
of compounds thus provides a variety for probing the consequences of magnetic
frustration due to topological reasons in stoichiometric spin-chain materials,
presumably arising from subtle differences in the interchain and intrachain
magnetic coupling strengths. This compound presents additional interesting
situations in the sense that, ac susceptibility exhibits a large frequency
dependence in the vicinity of 30 K uncharacteristic of conventional
spin-glasses, with this frustrated magnetic state being robust to the
application of external magnetic fields.Comment: Physical Review (Rapid Communications), in pres
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Downregulating Notch counteracts KrasG12D-induced ERK activation and oxidative phosphorylation in myeloproliferative neoplasm.
The Notch signaling pathway contributes to the pathogenesis of a wide spectrum of human cancers, including hematopoietic malignancies. Its functions are highly dependent on the specific cellular context. Gain-of-function NOTCH1 mutations are prevalent in human T-cell leukemia, while loss of Notch signaling is reported in myeloid leukemias. Here, we report a novel oncogenic function of Notch signaling in oncogenic Kras-induced myeloproliferative neoplasm (MPN). We find that downregulation of Notch signaling in hematopoietic cells via DNMAML expression or Pofut1 deletion significantly blocks MPN development in KrasG12D mice in a cell-autonomous manner. Further mechanistic studies indicate that inhibition of Notch signaling upregulates Dusp1, a dual phosphatase that inactivates p-ERK, and downregulates cytokine-evoked ERK activation in KrasG12D cells. Moreover, mitochondrial metabolism is greatly enhanced in KrasG12D cells but significantly reprogrammed by DNMAML close to that in control cells. Consequently, cell proliferation and expanded myeloid compartment in KrasG12D mice are significantly reduced. Consistent with these findings, combined inhibition of the MEK/ERK pathway and mitochondrial oxidative phosphorylation effectively inhibited the growth of human and mouse leukemia cells in vitro. Our study provides a strong rational to target both ERK signaling and aberrant metabolism in oncogenic Ras-driven myeloid leukemia
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