43 research outputs found
On the photometric variability of blue supergiants in NGC 300 and its impact on the Flux-weighted Gravity-Luminosity Relationship
We present a study of the photometric variability of spectroscopically
confirmed supergiants in NGC 300, comprising 28 epochs extending over a period
of five months. We find 15 clearly photometrically variable blue supergiants in
a sample of nearly 70 such stars, showing maximum light amplitudes ranging from
0.08 to 0.23 magnitudes in the V band, and one variable red supergiant. We show
their light curves, and determine semi-periods for two A2 Ia stars. Assuming
that the observed changes correspond to similar variations in the bolometric
luminosity, we test for the influence of this variability on the Flux-weighted
Gravity--Luminosity Relationship and find a negligible effect, showing that the
calibration of this relationship, which has the potential to measure
extragalactic distances at the Cepheid accuracy level, is not affected by the
stellar photometric variability in any significant way.Comment: 9 pages, 3 figures, 3 tables. Accepted for publication in the
Astrophysical Journa
Martensitic transition and magnetoresistance in a Cu-Al-Mn shape memory alloy. Influence of aging
We have studied the effect of ageing within the miscibility gap on the
electric, magnetic and thermodynamic properties of a non-stoichiometric Heusler
Cu-Al-Mn shape-memory alloy, which undergoes a martensitic transition from a
-based (-phase) towards a close-packed structure (-phase).
Negative magnetoresistance which shows an almost linear dependence on the
square of magnetization with different slopes in the - and -phases,
was observed. This magnetoresistive effect has been associated with the
existence of Mn-rich clusters with the CuAlMn-structure. The effect of an
applied magnetic field on the martensitic transition has also been studied. The
entropy change between the - and -phases shows negligible dependence
on the magnetic field but it decreases significantly with annealing time within
the miscibility gap. Such a decrease is due to the increasing amount of
CuMnAl-rich domains that do not transform martensitically.Comment: 9 pages, 9 figures, accepted for publication in PR
Report from the OECI Oncology Days 2014
The 2014 OECI Oncology Days was held at the ‘Prof. Dr. Ion Chiricuta’ Oncology Institute in Cluj, Romania, from 12 to 13 June. The focus of this year’s gathering was on developments in personalised medicine and other treatment advances which have made the cost of cancer care too high for many regions throughout Europe
Temperature dependence of the second order elastic constants of Cu-Zn-Al shape memory alloy in its martensitic and beta phases
The temperature dependence of the sound velocities for 13 propagation modes has been measured in a single crystal of Cu-Zn-Al monoclinic
1
8
R
martensite, using the pulse-echo method. By numerical procedure the complete set of nine second-order adiabatic elastic constants
(
C
ij
)
of the closest orthorhombic reference phase, their relative thermal variation
(
Γ
ij
)
, and the Debye temperature
(
θ
D
)
have been obtained. The values found in the martensitic phase have been compared to data avalaible for the high-temperature bcc
β
-phase in the same alloy system. The velocity surfaces in the corresponding crystallographic directions of both phases have also been computed at different temperatures. It has been shown that the mechanical stability of the lattice for some particular distortions decreases as the transformation temperature is approached in both the martensitic as well as in the
β
phase
Magnetic field induced entropy change and magnetoelasticity in Ni-Mn-Ga alloys
The magnetocaloric effect that originates from the martensitic transition in the ferromagnetic Ni-Mn-Ga
shape-memory alloy is studied. We show that this effect is controlled by the magnetostructural coupling at both
the martensitic variant and magnetic domain length scales. A large entropy change induced by moderate
magnetic fields is obtained for alloys in which the magnetic moment of the two structural phases is not very
different. We also show that this entropy change is not associated with the entropy difference between the
martensitic and the parent phase arising from the change in the crystallographic structure which has been
found to be independent of the magnetic field within this range of fields