680 research outputs found
Dynamics of the magnetic and structural a -> e phase transition in Iron
We have studied the high-pressure iron bcc to hcp phase transition by
simultaneous X-ray Magnetic Circular Dichroism (XMCD) and X-ray Absorption
Spectroscopy (XAS) with an X-ray dispersive spectrometer. The combination of
the two techniques allows us to obtain simultaneously information on both the
structure and the magnetic state of Iron under pressure. The magnetic and
structural transitions simultaneously observed are sharp. Both are of first
order in agreement with theoretical prediction. The pressure domain of the
transition observed (2.4 0.2 GPa) is narrower than that usually cited in
the literature (8 GPa). Our data indicate that the magnetic transition slightly
precedes the structural one, suggesting that the origin of the instability of
the bcc phase in iron with increasing pressure is to be attributed to the
effect of pressure on magnetism as predicted by spin-polarized full potential
total energy calculations
A re-interpretation of the Triangulum-Andromeda stellar clouds: a population of halo stars kicked out of the Galactic disk
The Triangulum-Andromeda stellar clouds (TriAnd1 and TriAnd2) are a pair of
concentric ring- or shell-like over-densities at large ( 30 kpc)
and ( -10 kpc) in the Galactic halo that are thought to have been
formed from the accretion and disruption of a satellite galaxy. This paper
critically re-examines this formation scenario by comparing the number ratio of
RR Lyrae to M giant stars associated with the TriAnd clouds with other
structures in the Galaxy. The current data suggest a stellar population for
these over-densities ( at 95% confidence) quite unlike
any of the known satellites of the Milky Way ( for
the very largest and for the smaller satellites) and more
like the population of stars born in the much deeper potential well inhabited
by the Galactic disk (). N-body simulations of a
Milky-Way-like galaxy perturbed by the impact of a dwarf galaxy demonstrate
that, in the right circumstances, concentric rings propagating outwards from
that Galactic disk can plausibly produce similar over-densities. These results
provide dramatic support for the recent proposal by Xu et al. (2015) that,
rather than stars accreted from other galaxies, the TriAnd clouds could
represent stars kicked-out from our own disk. If so, these would be the first
populations of disk stars to be found in the Galactic halo and a clear
signature of the importance of this second formation mechanism for stellar
halos more generally. Moreover, their existence at the very extremities of the
disk places strong constraints on the nature of the interaction that formed
them.Comment: 27 pages, 8 figures; published in MNRA
Ethanol Vapours to Complement or Replace Sulfur Dioxide Fumigation of Table Grapes
Recent studies have shown that dipping table grapes in ethanol solutions at harvest improved storage of the fruit. We report here the first results obtained by treating "Chasselas" table grapes (Vitis vinifera) with ethanol vapours over the storage period. We tested the effect of ethanol at 0, 4 and 8 g/kg fruit during cold storage for 2, 4 and 6 weeks. We measured berry shatter, stem browning, Botrytis rot incidence and sensory appreciation by tasting panels. Ethanol vapours reduced Botrytis rot incidence and berry shatter, but hastened stem browning. Sensory analyses did not detect any differences between treatments
Changes in Grape Maturity Induced by Spraying Ethanol
Three different ethanol solutions were sprayed onto Cabernet Sauvignon (Vitis vinifera L.) clusters during the ripening period: 2.5, 5 and 10% by volume in water. Controls were sprayed with water alone. Three different times of spraying were also tested: 8, 10 and 13 weeks post-flowering. One of the observed changes was a lower titratable acidity in grape samples at harvest, when the clusters were sprayed with ethanol at 10 weeks, in comparison with controls. The wines made with grapes treated with ethanol after mid-veraison, had higher ODs at 520 nm than did the controls. This may due to a combined effect of red pigment levels and acidity. In addition, following malolactic fermentation, the acidity levels of wines made with ethanoltreated grapes were slightly higher than those made with the control grapes. Spraying ethanol at 13 weeks post-flowering increased the berry weight by 10% at harvest without decreasing the °Brix value. The corresponding wines had similar degrees of alcohol. This observation was made for the first time in 2001
Sleep problems are associated with poor outcomes in remedial teaching programmes: A preliminary study
Problematic behaviour and deficient academic performance have been reported in children with sleep problems, but whether sleep problems are common among children presenting with primary behavioural and performance concerns in remedial programmes is not well studied. We studied this possibility in 80 Australian school children aged 6–15 years and then compared 15 of these children from mainstream schools to 15 demographically matched children in specialist behavioural programmes for problematic behaviour and academic difficulties. Methods: Parents completed the Child Behaviour Checklist and the Sleep Disorders Scale for Children. Questionnaires assessed behaviour, academic performance and symptoms of diverse sleep disorders, expressed as T-scores (mean (SD) = 50 (10)). Teachers rated students' academic performance (A, B, C, D, E). Results: When compared with the 15 controls, the 15 index children had significantly more sleep problems, in addition to parental concerns about school performance. In the total sample ( n = 80), poor sleep including symptoms of daytime sleepiness, parasomnias, behavioural sleep problems and combined sleep problems was associated with poor academic performance and daytime behavioural issues. Conclusions: This preliminary study suggests that children in remedial school programmes may have poor sleep compared with those in mainstream schools. Sleep problems were associated with problematic behaviour and poor academic performance. If sleep disturbances worsen daytime behaviour, then diagnosis and treatment of underlying sleep disorders could offer a novel therapeutic opportunity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72509/1/j.1440-1754.2007.01237.x.pd
Ethylene and other stimuli affect expression of the UDP glucose-flavonoid 3-O-glucosyltransferase in a non-climacteric fruit
The UDP glucose-flavonoid 3-O-glucoslyltransferase (UFGT) is a key enzyme for biosynthesis and stability of anthocyanin pigments of red grapes. Understanding factors affecting expression of this enzyme is thus important for the control of grape colour. A 1640 bp promoter region of the grapevine ufgt gene was cloned and sequenced. Sequence analysis revealed seven putative ethylene-responsive cis-elements and others related to three major signals known to induce anthocyanin accumulation in plant tissues: light, sugar, and abscisic acid. In order to evaluate the ability of ethylene and other signals to drive expression from the ufgt promoter, we ran transient expression experiments using an anthocyanin-rich grape cell culture, with very low green auto-fluorescence. After biolistic bombardment, the cells were treated with various combinations of the four signals on gfp expression (green fluorescent protein). The comparison of fluorescent light intensity in cells subjected to the various treatments showed that ethylene better stimulates expression of the ufgt promoter in the dark than under light. In addition, results showed that there may be a positive interaction between ethylene and abscisic acid. This system, a promoter of interest driving the gfp expression in cells with low auto-fluorescence, may be a good tool for studies about synergistic or antagonist roles of transcription factors. Moreover, treatment of grape berries with a specific inhibitor of ethylene receptors (1-methylcyclopropene) inhibited ufgt mRNA accumulation. This confirms that the ethylene signal is likely a regulator of grape UFGT expression in a non-climacteric fruit.
Structural and optical studies of FeSb2 under high pressure
Nanostructured orthorhombic FeSb2 and an amorphous phase were formed by
mechanical alloying starting from a mixture of high purity elemental Fe and Sb
powders. The effects of high pressures on structural and optical properties
were studied using X-ray diffraction (XRD) and Raman spectroscopy (RS). XRD
patterns showed the presence of the orthorhombic FeSb2 phase up to the maximum
pressure applied (28.2 GPa). The XRD patterns showed also an increase in the
amount of the amorphous phase with increasing pressure up to 23.3 GPa. At 14.3
GPa, together with the former phases, a new phase was observed and indexed to a
tetragonal FeSb2 phase, but its volume fraction is small at least up to 23.3
GPa. For the orthorhombic FeSb2 phase, the pressure dependence of the volume
fitted to a Birch-Murnaghan equation of state gave a bulk modulus = 74.2 +- 3.0
GPa and its pressure derivative = 7.5 +- 0.6. RS measurements were performed
from atmospheric pressure up to 45.2 GPa. For the orthorhombic FeSb2 phase, the
Raman active mode was observed up to the maximum pressure applied, while the
mode disappeared at 16.6 GPa. For pressures higher than 21 GPa, the Raman
active mode of a tetragonal FeSb2 phase was observed, confirming ab initio
calculations reported in the literature.Comment: 31 pages, 11 figures and 2 tables. Already submitted for publicatio
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