1,087 research outputs found
FliPer: Checking the reliability of global seismic parameters from automatic pipelines
Our understanding of stars through asteroseismic data analysis is limited by
our ability to take advantage of the huge amount of observed stars provided by
space missions such as CoRoT, Kepler, K2, and soon TESS and PLATO. Global
seismic pipelines provide global stellar parameters such as mass and radius
using the mean seismic parameters, as well as the effective temperature. These
pipelines are commonly used automatically on thousands of stars observed by K2
for 3 months (and soon TESS for at least around 1 month). However, pipelines
are not immune from misidentifying noise peaks and stellar oscillations.
Therefore, new validation techniques are required to assess the quality of
these results. We present a new metric called FliPer (Flicker in Power), which
takes into account the average variability at all measured time scales. The
proper calibration of FliPer enables us to obtain good estimations of global
stellar parameters such as surface gravity that are robust against the
influence of noise peaks and hence are an excellent way to find faults in
asteroseismic pipelines.Comment: 4 pages, 3 figures, Proceedings for SF2A 2017 (Paris
Experimental investigation on crack propagation paths in spur gears
Spur gears subjected to bending fatigue may nucleate cracks at the tooth root fillet.
In thin rim gears these cracks may propagate in a safe way (through the tooth) or in catastrophic
way (through the rim). Crack propagation direction is mainly influenced by both wheel geometry
parameters and crack initiation point, as already pointed out by theoretical and numerical results
available in literature. Aim of this work is to set up an experimental activity in order to verify
the onset of the bending crack and its propagation path in spur gears with different geometries.
In particular, a special device connected to a standard fatigue machine was realized to perform
bending tests for both standard and thin rim gears. During bending tests, an IR thermocamera
was utilized to monitor the surface thermal profile in the tooth root fillet zone
ACTIVE THERMOGRAPHY TECHNIQUE FOR FATIGUE DAMAGE CHARACTERIZATION IN GEARS
Active Thermography (AT) is a Non Destructive Technique (NDT) that may be an efficient
alternative to evaluate possible microstructural alterations inside materials due to damaging
conditions. In this paper, a fatigue damage identification on two different gears (standard and
thin-rim) was conducted by using an AT approach with a Lock-In technique. Both gears were
previously tested under bending fatigue conditions, by loading the teeth at the so called Single
Contact Point by a dedicated equipment. Damaged and undamaged zones were identified, phase
maps and thermal diffusivities were estimated. In this way, a possible fatigue damage
characterisation was pointed out by using the thermal diffusivity variation as damage parameter
Learning from the children : exploring preschool children's encounters with ICT at home
This paper is an account of our attempts to understand preschool children's experiences with information and communication technologies (ICT) at home. Using case study data, we focus on what we can learn from talking directly to the children that might otherwise have been overlooked and on describing and evaluating the methods we adopted to ensure that we maximised the children's contributions to the research. By paying attention to the children's perspectives we have learned that they are discriminating users of ICT who evaluate their own performances, know what gives them pleasure and who differentiate between operational competence and the substantive activities made possible by ICT
Magma dynamics during the 2007 Stromboli eruption (Aeolian Islands. Italy): mineralogical, geochemical and isotopic data
After the 6 month-long effusive event of 2002-2003, a new lava effusion occurred at Stromboli between 27
February and 2 April 2007. Despite the different durations, approximately the same volume of magma was
emitted in both eruptions, in the order of 107
m3
. A paroxysmal eruption occurred at the summit craters in
both the 2002â2003 and 2007 episodes, during which a signiïŹcant amount of low porphyritic (LP), volatile-
rich magma was erupted. In both cases, the paroxysm did not interrupt the lava emission. Here, we present
compositional data, including texture, mineralogy, chemistry and Sr and Nd isotope ratios of bulk-rock,
groundmass and separated minerals of lavas erupted in 2007, together with chemistry and Sr and Nd isotope
composition of the pumices emitted during the 15 March paroxysm. As a whole, the lavas have the same
texture and chemistry that characterize the highly porphyritic (HP) products usually erupted at Stromboli
during normal Strombolian activity and effusive events. Compared to the previous HP products, the 2007
lavas show minor but systematic mineralogical and isotopic variations which are consistent with a modest
increase of the magma supply rate of the volcano. Compositional variations during the entire duration of the
event are very modest. Glass chemistry changes in lavas erupted in the second half of March can be explained
by theminormixing between the volatile-rich LPmagma rising through the shallowmagmatic systemduring the
15 March paroxysm and the degassed residing HP magma. A ïŹrst conclusion of this study is that there is no
compositional evidence supporting major changes in the magma dynamics of the volcano accompanying the
effusive activity, as also suggested for the 2002â2003 event. The activity of Stromboli is controlled by a steady
state feeding system in which reïŹlling, mixing, degassing and crystallization at shallow level continuously
operate,withmodest oscillations in themagma supply rate. Switching between normal Strombolian and effusive
activity is related to periods of relatively more vigorous reïŹlling of the shallow system, leading to progressive
pressure increase in the upper conduits associated with only minor compositional variations in the erupted
products
Magnetic variability in the young solar analog KIC 10644253: Observations from the Kepler satellite and the HERMES spectrograph
The continuous photometric observations collected by the Kepler satellite
over 4 years provide a whelm of data with an unequalled quantity and quality
for the study of stellar evolution of more than 200000 stars. Moreover, the
length of the dataset provide a unique source of information to detect magnetic
activity and associated temporal variability in the acoustic oscillations. In
this regards, the Kepler mission was awaited with great expectation. The search
for the signature of magnetic activity variability in solar-like pulsations
still remained unfruitful more than 2 years after the end of the nominal
mission. Here, however, we report the discovery of temporal variability in the
low-degree acoustic frequencies of the young (1 Gyr-old) solar analog KIC
10644253 with a modulation of about 1.5 years with significant temporal
variations along the duration of the Kepler observations. The variations are in
agreement with the derived photometric activity. The frequency shifts extracted
for KIC 10644253 are shown to result from the same physical mechanisms involved
in the inner sub-surface layers as in the Sun. In parallel, a detailed
spectroscopic analysis of KIC 10644253 is performed based on complementary
ground-based, high-resolution observations collected by the HERMES instrument
mounted on the MERCATOR telescope. Its lithium abundance and chromospheric
activity S-index confirm that KIC 10644253 is a young and more active star than
the Sun.Comment: Accepted for publication in A&A, 12 pages, 8 figure
Acoustic oscillations and dynamo action in the G8 sub-giant EK Eri
We present further evidence of the presence of acoustic oscillations on the
slowly-rotating, over-active G8 sub-giant EK Eri. This star was observed with
the 1-m Hertzsprung SONG telescope, at the Observatorio del Teide for two
different runs of 8 and 13 nights, respectively, and separated by about a year.
We determined a significant excess of power around Hz in the first observing run and we were able to determine the large
separation Hz. No significant excess of power
was instead detected in a subsequent SONG observing season, as also supported
by our analysis of the simultaneous TESS photometric observations. We propose a
new amplitude-luminosity relation in order to account for the missing power in
the power spectrum. Based on the evolutionary stage of this object we argue
that standard dynamo cannot be excluded as a possible origin
for the observed magnetic field.Comment: 8 pages, 8 figures, accepted for publication in A&
Reply to comment by D. Carbone and D. PatanĂš on âMulti-disciplinary investigation on a lava fountain preceding a flank eruption: the 10 May 2008 Etna caseâ
Bonaccorso et al. [2011a] investigated the source and magma dynamics of the 10 May 2008 lava fountain at the South-East Crater (SEC) of Mount Etna through a multidisciplinary approach that integrated a wide data set ranging from bulk rock compositions of the erupted products to seismic tremor and long-period events, tilt and gravity signals. Using a large dataset, the study provided a robust framework in which the mechanism of the 10 May 2008 lava fountain is explained as a violent release of bubble-rich magma layer previously trapped at the top of a shallow reservoir located between â0.5 and 1.5 km above sea level (asl). This result is in agreement with recent relevant literature [Allard et al., 2005; Vergniolle and Ripepe, 2008; Aiuppa et al., 2010; Andronico and Corsaro, 2011; Bonaccorso et al., 2011b; Calvari et al., 2011; Vergniolle and Gaudemer, 2012].
In the introduction of their comment Carbone and PatanĂš [submitted] affirm that in their opinion the interpretation that âthe lava fountain was generated by the fragmentation of a foam layer trapped at the top of shallow reservoirâ is not soundly based. This commentâs conclusion is puzzling because one of the commentâs authors (D. PatanĂš) is also a co-author on the paper by Aiuppa et al. [2010] where the same conclusion, now criticized, was well supported (see figure 5 and conclusions of that paper). In particular, in the conclusions Aiuppa et al. [2010] reported that âThe paroxysmal SEC episodes mark the violent release of a bubble-rich magma layer, with bubbles having relatively shallow reservoir ...", that is, the same conclusion now criticized in the comment. After this, the comment raises issues concerning the analysis and interpretation of gravity and tilt data in the multidisciplinary approach presented by Bonaccorso et al. [2011a]. The comment by Carbone and PatanĂš is divided into 4 paragraphs, labelled â1. Introductionâ, â2. Gravity changesâ, â3. Tilt changesâ and â4. Concluding remarksâ with only paragraphs 2 and 3 containing specific comments. In this reply, we address these two paragraphs, and we shall show how the assumptions underlying the comment are merely speculative and why the results presented by Bonaccorso et al.[2011a] remain valid
F4-Neuroprostane Effects on Human Sperm
Swim-up selected human sperm were incubated with 7 ng F4-neuroprostanes (F4-NeuroPs) for 2 and 4 h. Sperm motility and membrane mitochondrial potential (MMP) were evaluated. The percentage of reacted acrosome was assessed by pisum sativum agglutinin (PSA). Chromatin integrity was detected using the acridine orange (AO) assay and localization of the ryanodine receptor was performed by immunofluorescence analysis. Sperm progressive motility (p = 0.02) and the percentage of sperm showing a strong MMP signal (p = 0.012) significantly increased after 2 h F4-NeuroP incubation compared to control samples. The AO assay did not show differences in the percentage of sperm with dsDNA between treated or control samples. Meanwhile, a significantly higher number of sperm with reacted acrosomes was highlighted by PSA localization after 4 h F4-NeuroP incubation. Finally, using an anti-ryanodine antibody, the immunofluorescence signal was differentially distributed at 2 and 4 h: a strong signal was evident in the midpiece and postacrosomal sheath (70% of sperm) at 2 h, whereas a dotted one appeared at 4 h (53% of sperm). A defined concentration of F4-NeuroPs in seminal fluid may induce sperm capacitation via channel ions present in sperm cells, representing an aid during in vitro sperm preparation that may increase the positive outcome of assisted fertilization
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