Aspect ratio dependence of heat transfer and large-scale flow in turbulent convection

The heat transport and corresponding changes in the large-scale circulation (LSC) in turbulent Rayleigh-B\'{e}nard convection are studied by means of three-dimensional direct numerical simulations as a function of the aspect ratio $\Gamma$ of a closed cylindrical cell and the Rayleigh number $Ra$. For small and moderate aspect ratios, the global heat transfer law $Nu=A\times Ra^{\beta}$ shows a power law dependence of both fit coefficients $A$ and $\beta$ on the aspect ratio. A minimum Nusselt number coincides with the point where the LSC undergoes a transition from a single-roll to a double-roll pattern. With increasing aspect ratio, we detect complex multi-roll LSC configurations. The aspect ratio dependence of the turbulent heat transfer for small and moderate $\Gamma$ is in line with a varying amount of energy contained in the LSC, as quantified by the Proper Orthogonal Decomposition analysis. For $\Gamma\gtrsim 8$ the heat transfer becomes independent of the aspect ratio.Comment: 17 pages, 11 Postscript figures (in parts downscaled), accepted for J. Fluid Mec

X-ray observations of the Compton-thick Seyfert 2 galaxy, NGC 5643

We present results from a ~55 ks long XMM-Newton observation of the obscured AGN, NGC 5643, performed in July 2009. A previous, shorter (about 10 ks) XMM-Newton observation in February 2003 had left two major issues open, the nature of the hard X-ray emission (Compton-thin vs Compton-thick) and of the soft X-ray excess (photoionized vs collisionally ionized matter). The new observation shows that the source is Compton-thick and that the dominant contribution to the soft X-ray emission is by photoionized matter (even if it is still unclear whether collisionally ionized matter may contribute as well). We also studied three bright X-ray sources that are in the field of NGC 5643. The ULX NGC 5643 X-1 was confirmed to be very luminous, even if more than a factor 2 fainter than in 2003. We then provided the first high quality spectrum of the cluster of galaxies Abell 3602. The last source, CXOJ143244.5-442020, is likely an unobscured AGN, possibly belonging to Abell 3602.Comment: 6 pages. Accepted for publication in A&

Amphibians and squamate reptiles from the latest early Pleistocene of Cueva Victoria (Murcia, southeastern Spain, SW Mediterranean): Paleobiogeographic and paleoclimatic implications

The karstic filling of Cueva Victoria in southeastern Spain, dated from the latest early Pleistocene (ca. 1.1 Ma), is famous for providing primate fossil remains (Theropithecus) of typical African origin, in the general controversy on the antiquity of the first hominid settlements in Western Europe and their possible entrance into Europe through the Strait of Gibraltar. Cueva Victoria has also furnished the following fauna of anurans and squamate reptiles: cf. Pelodytes sp. (Pelodytidae), Bufo cf. B. bufo (Bufonidae), Blanus cinereus (Blanidae), Tarentola sp. (Geckonidae), Chalcides cf. Ch. bedriagai (Scincidae), Timon cf. T. lepidus and indeterminate small lacertids (Lacertidae), Natrix maura, Coronella girondica, Rhinechis scalaris and Malpolon cf. M. monspessulanus (Colubridae). This faunal association seems to suggest a mean annual temperature slightly fresher than nowadays (approximately 1°C less than at present in the area), with cooler winters but warmer summers and above all higher mean annual precipitations (+ 400 mm). The landscape may correspond to an open forest environment of a Mediterranean type, with some still water points

Respiratory Rate Derived from Pulse Photoplethysmographic Signal by Pulse Decomposition Analysis

A novel technique to derive respiratory rate from pulse photoplethysmographic (PPG) signals is presented. It exploits some morphological features of the PPG pulse that are known to be modulated by respiration: amplitude, slope transit time, and width of the main wave, and time to the first reflected wave. A pulse decomposition analysis technique is proposed to measure these features. This technique allows to decompose the PPG pulse into its main wave and its subsequent reflected waves, improving the robustness against noise and morphological changes that usually occur in long-term recordings. Proposed methods were evaluated with a data base containing PPG and plethysmography-based respiratory signals simultaneously recorded during a paced-breathing experiment. Results suggest that normal ranges of spontaneous respiratory rate (0.1-0.5 Hz) can be accurately estimated (median and interquartile range of relative error less than 5%) from PPG signals by using the studied features

Multi-taxa neo-taphonomic analysis of bone remains from barn owl pellets and cross-validation of observations: a case study from Dominica (Lesser Antilles)

Paleo- and neo-taphonomic analyses of bone assemblages rarely consider all the occurring taxa in a single study and works concerning birds of prey as accumulators of microvertebrate bone remains mostly focus on small mammals such as rodents and soricomorphs. However, raptors often hunt and consume a large range of taxa, including vertebrates such as small mammals, fishes, amphibians, squamates and birds. Bone remains of all these taxonomic groups are numerous in many paleontological and archaeological records, especially in cave deposits. To better characterize the predators at the origin of fossil and sub-fossil microvertebrate accumulations and the taphonomic history of the deposit, it is thus mandatory to conduct global and multi-taxa taphonomic approaches. The aim of this study is to provide an example of such a global approach through the investigation of a modern bone assemblage from a sample of pellets produced by the Lesser Antillean Barn Owl (Tyto insularis) in the island of Dominica. We propose a new methodology that allows us to compare different taxa (rodents, bats, squamates and birds) and to experiment with a cross-validation process using two observers for each taxonomic group to test the reliability of the taphonomic observations.1. Introduction 2. Materials and Methods 2.1. Owl Pellets Sampling 2.2. Prey Identification 2.3. Taphonomic Analysis 2.3.1. Anatomical Representation 2.3.2. Fragmentation 2.3.3. Surface Modifications 2.3.4. Size/Weight Classes of Preys 2.4. Cross-Validation of Observations 3. Results 3.1. Faunal Spectrum 3.2. Anatomical Representation 3.3. Fragmentation 3.4. Modifications of Bone Surface 4. Discussion 4.1. Diet of Tyto Insularis in Dominica 4.2. Taphonomic Impact of Tyto Insularis on Small Vertebrate Bone Assemblage 4.2.1. Remarks on the Size/Weight Classes of Preys 4.2.2. Anatomical Representation 4.2.3. Fragmentation 4.2.4. Digestion 4.3. Degree of Inter-Observer Differences and Potential Outcomes 4.4. Towards an “Inter-Taxa Calibration” 5. Conclusion

Photoplethysmogram Signal Morphology-Based Stress Assessment

Stress is a healthy natural response to a perceived or actual threat. However, when stress is persistent, it may decrease work productivity, increase the risk of diseases, and affect the quality of life. Stress is reflected in physiological variables, such as heart rate, blood pressure, and pulse wave velocity among others. A photoplethys-mogram (PPG) contains information related to pulse rate and blood pressure. This study analyses parameters derived from PPG signal morphology for mental stress assessment.A low-complexity algorithm is designed using bandpass filtered higher-order derivatives of the PPG signal for estimation of six morphological parameters: the forward pulse wave amplitude A1, the systole and diastole durations T1 and Td, the time delays of reflected waves T12 and T13 from the renal and iliac sites in the central arteries, and the pulse duration Tp. The parameters were investigated on a set of 18 healthy subjects by using a modified Trier Social Stress Test.The results show that the most sensitive PPG morphology parameters to mental stress are the amplitude of forward wave A1, the duration of diastole Td, the time delay of the reflected wave T13, and the pulse-to-pulse interval Tp

Heavy absorption and soft X-ray emission lines in the XMM-Newton spectrum of the Type 2 radio-loud quasar 3C 234

We report results on a 40 ks XMM-Newton observation of the Type 2 quasar 3C 234. Optical spectropolarimetric data have demonstrated the presence of a hidden broad-line region in this powerful (M_V <~ -24.2 after reddening and starlight correction) narrow-line FRII radio galaxy. Our analysis is aimed at investigating the X-ray spectral properties of this peculiar source which have remained poorly known so far. We analyze the 0.5--10 keV spectroscopic data collected by the EPIC cameras in 2006. The X-ray spectrum of this radio-loud quasar is typical of a local Compton-thin Seyfert 2 galaxy. It exhibits strong absorption (Nh~3.5 x 10^{23} cm^{-2}) and a narrow, neutral Fe Kalpha emission line with an equivalent width of ~140+/-40 eV. Our observation also reveals that the soft portion of the spectrum is characterized by strong emission lines with a very low level of scattered primary continuum. A possible explanation of these features in terms of thermal emission from a two-temperature collisionally ionized plasma emission seems to be unlikely due to the high luminosity estimated for this component (L(0.5-2) ~ 6 x 10^{42} erg/s). It is likely that most of the soft X-ray emission originates from a photoionized plasma as commonly observed in obscured, radio-quiet Seyfert-like AGNs. This X-ray observation has definitively confirmed the presence of a hidden quasar in 3C 234. The line-rich spectrum and the steepness of the hard X-ray continuum (Gamma ~ 1.7) found in this source weaken the hypothesis that the bulk ofthe X-ray emission in radio-loud AGNs with high excitation optical lines arises from jet non-thermal emission.Comment: Accepted by Astronomy and Astrophysic

Suzaku observation of the Phoenix Galaxy

In recent years, several Seyfert 2 galaxies have been discovered that change state when observed in X-rays a few years apart, switching from Compton-thin to reflection-dominated or viceversa. We observed a member of this class of "Changing-look" sources, the Phoenix Galaxy, with Suzaku, with the aim of better understanding the nature of the variations. The Suzaku spectrum was analyzed, and the results compared with previous ASCA and XMM-Newton observations. The source was caught in a Compton-thin state, as in XMM-Newton, but differently from ASCA. Comparing the Suzaku and XMM-Newton observations, a variation in the column density of the absorber on a time scale of years is discovered. A similar change, but on much shorter time scales (i.e. ks) may also explain the count-rate variations during the Suzaku observations. A soft excess is also present, likely due to continuum and line emission from photoionized circumnuclear matter.Comment: Accepted for publication in Astronomy & Astrophysic

The XMM-Newton view of IRAS 09104+4109: evidence for a changing-look Type 2 quasar?

We analyzed the spectroscopic data from the PN and the MOS cameras in the 0.4-10 keV band. We also used an archival BeppoSAX 1-50 keV observation of IRAS 09104+4109 to investigate possible variations of the quasar emission. The X-ray emission in the EPIC band is dominated by the intra-cluster medium thermal emission. We found that the quasar contributes ~35% of the total flux in the 2-10 keV band. Both a transmission- (through a Compton-thin absorber with a Compton optical depth of \tau_C~0.3, i.e. Nh~5 x 10^{23} cm^-2) and a reflection-dominated (\tau_C>1) model provide an excellent fit to the quasar continuum emission. However, the value measured for the EW of Fe Kalpha emission line is only marginally consistent with the presence of a Compton-thick absorber in a reflection-dominated scenario, which had been suggested by a previous, marginal (i.e. 2.5\sigma) detection with the hard X-ray (15-50 keV), non-imaging BeppoSAX/PDS instrument. Moreover, the value of luminosity in the 2-10 keV band measured by the transmission-dominated model is fully consistent with that expected on the basis of the bolometric luminosity of IRAS 09104+4109. From the analysis of the XMM-Newton data we therefore suggest the possibility that the absorber along the line of sight to the nucleus of IRAS 09104+4109 is Compton-thin. Alternatively, the absorber column density could have changed from Compton-thick to -thin in the five years elapsed between the observations. If this is the case, then IRAS 09104+4109 is the first 'changing-look' quasar ever detected.Comment: Accepted by Astronomy and Astrophysic