2,336 research outputs found
Bulges and disks in the local Universe. Linking the galaxy structure to star formation activity
We use a sample built on the SDSS DR7 catalogue and the bulge-disc
decomposition of Simard et al. (2011) to study how the bulge and disc
components contribute to the parent galaxy's star formation activity, by
determining its position in the star formation rate (SFR) - stellar mass
(M) plane at 0.020.1. We use the bulge and disc colours as proxy
for their SFRs. We study the mean galaxy bulge-total mass ratio (B/T) as a
function of the residual from the MS () and find that the
B/T- relation exhibits a parabola-like shape with the peak of the
MS corresponding to the lowest B/Ts at any stellar mass. The lower and upper
envelop of the MS are populated by galaxies with similar B/T, velocity
dispersion and concentration () values. Bulges above the MS are
characterised by blue colours or, when red, by a high level of dust
obscuration, thus indicating that in both cases they are actively star forming.
When on the MS or below it, bulges are mostly red and dead. At stellar masses
above M, bulges on the MS or in the green valley tend to
be significantly redder than their counterparts in the quiescence region,
despite similar levels of dust obscuration. The disc color anti-correlates at
any mass with the distance from the MS, getting redder when approaching the MS
lower envelope and the quiescence region. We conclude that the position of a
galaxy in the LogSFR-LogM plane depends on the star formation
activity of its components: above the MS both bulge and disk are actively star
forming. The nuclear activity is the first to be suppressed, moving the
galaxies on the MS. Once the disk stops forming stars as well, the galaxy moves
below the MS and eventually to the quiescence region. This is confirmed by a
large fraction () of passive galaxies with a secure two component
morphology.Comment: Version modified after referee comment
Exotic Matter research in Space
The direct detection of annihilation products in cosmic rays offer an
alternative way to search for dark matter particles candidates. Here we will
see in particular that the study of the spectrum of antiproton and positrons
offer good possibilities to perform this search and we will review our
experimental effort in this direction.Comment: 10 pages, 2 figures, Invited talk at the Ninth Marcel Grossmann
Meeting, Rome, July 2 - 8, 200
Antimatter research in Space
Two of the most compelling issues facing astrophysics and cosmology today are
to understand the nature of the dark matter that pervades the universe and to
understand the apparent absence of cosmological antimatter. For both issues,
sensitive measurements of cosmic-ray antiprotons and positrons, in a wide
energy range, are crucial. Many different mechanisms can contribute to
antiprotons and positrons production, ranging from conventional reactions up to
exotic processes like neutralino annihilation. The open problems are so
fundamental (i.e.: is the universe symmetric in matter and antimatter ?) that
experiments in this field will probably be of the greatest interest in the next
years. Here we will summarize the present situation, showing the different
hypothesis and models and the experimental measurements needed to lead to a
more established scenario.Comment: 10 pages, 7 figures, Invited talk at the 18th European Cosmic Ray
Symposium, Moscow, July 2002, submitted to Journal of Physics
Ultrasound Guidance in Paravertebral Injections of Oxygen-Ozone: Treatment of Low Back Pain
Background: Paravertebral injection of ozone is an established clinical practice for the treatment of Low Back Pain (LBP). The role of Ultrasound Guidance (USG) in mini invasive procedures has become important in many clinical practice thanks to the greater precision this technique can add. As matter of fact, a large volume of ozone in a single administration may have some adverse or side effects. In this study we wanted to verify if the use of USG in Oxygen/ Ozone (O2/O3) infiltrations could allow the administration of a smaller volume of gas mixture, increasing the safety and the comfort of the procedure itself, obtaining however similar or better results in pain decrease.
Methods: We compared two groups of 25 patients affected by LBP, undergoing 10 infiltrations of O2/O3, by using USG (group U) or only anatomical landmarks (group AL). Pain intensity, by calculating Visual Analogical Scale (VAS) difference before and after the treatment, and the discomfort were evaluated in both groups.
Results: The mean of the VAS before the treatment was 6.44 in group U and 6.48 in group AL. The mean of the VAS after the treatment was 2.22 in group U and 3.04 in group AL. The mean of discomfort rate was 2.84 in group U and 5.44 in group AL. The number of patients with unbearable discomfort was 0 in group U and 7 in group AL.
Conclusions: As many other treatment, also paravertebral injections of O2/O3 benefits of the advantages of the US device which makes this treatment safer and more accurate
Light-harvesting antennae based on copper indium sulfide (CIS) quantum dots
Copper indium sulfide quantum dots (CIS QDs) and their core-shell analogues (CIS@ZnS QDs) were functionalized with pyrene chromophores via a dihydrolipoamide bifunctional binding moiety: UV excitation of the pyrene chromophores resulted in sensitized emission of the CIS core because of an efficient energy transfer process; the core-shell hybrid system exhibits a 50% increased brightness when excited at 345 nm
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