Metal enrichment in elliptical galaxies and globular clusters through the study of iron and H-beta spectral indices

Chemical evolution of elliptical galaxies and globular clusters is addressed through a combined study of the iron indices at 5270 and 5335 A, and of the H-Beta line strength. The observational database of 74 standard stars (both dwarfs and giants) referred to in a previous paper (Buzzoni et al. (1992)) complemented with the data of Faber et al. (1985) and Gorgas et al. (1993) allowed us to explore here Fe and H-Beta index dependence on stellar temperature, gravity, and metallicity. The derived fitting functions were then included into Buzzoni's (1989) code for population synthesis in order to derive expected integrated indices for simple stellar populations and compare with observations. Partition of metals in the current chemical mix of galaxies and globulars has been constrained supporting the claim that light alpha elements might be enhanced in the globular cluster metal-poor population. An alternative conclusion resting on the standard framework with (alpha/Fe) = 0 would require a systematically larger age, about 18-20 Gyr. Iron and magnesium in ellipticals are found in average solar but a systematic trend of (Mg/Fe) vs global metallicity does exist with iron more deficient with respect to magnesium at high Z. We conclude that this effect might indicate that Fe abundance per unit mass in the galaxies is constant (suggesting a constant rate per unit mass of SN I events) while light metals supplied by SNe II should have been more effectively enriched with increasing galactic total mass

The Magnesium Mg/2 Index as an Indicator of Metallicity in Elliptical Galaxies

A quantitative calibration of the Mg_2_ index [Faber et al.,AJ,82,941(1977)] is attempted deriving a metallicity scale for elliptical galaxies. The dependence of the index on stellar temperature,gravity and metallicity has been studied through spectroscopic observations of 87 standards applying the derived calibration to models for stellar population synthesis. Buzzoni's [ApJS, 71,817(1989)] computational code has been used to explore the behavior of the index versus age, IMF, and metallicity of simple stellar populations (SSPs) inferring galactic metallicity for the Davies et al. [ApJS, 69, 581(1987)] extensive observational database. It appears that ellipticals are old metal-rich systems, with age about 15 Gyr and (Fe/HI = +0.15. A large spread of nearly one order of magnitude is however derived for metallicity among single galaxies confirming that [Fe/H] is the driving parameter inducing the color spread in the galaxy population. Evolutionary behavior of Mg_2_ is briefly discussed giving its expected variations at early epochs for comparison with high-redshift galaxies

Effect of Collateral Flow on Catheter-Based Assessment of Cardiac Microvascular Obstruction.

Cardiac microvascular obstruction (MVO) associated with acute myocardial infarction (heart attack) is characterized by partial or complete elimination of perfusion in the myocardial microcirculation. A new catheter-based method (CoFI, Controlled Flow Infusion) has recently been developed to diagnose MVO in the catheterization laboratory during acute therapy of the heart attack. A porcine MVO model demonstrates that CoFI can accurately identify the increased hydraulic resistance of the affected microvascular bed. A benchtop microcirculation model was developed and tuned to reproduce in vivo MVO characteristics. The tuned benchtop model was then used to systematically study the effect of different levels of collateral flow. These experiments showed that measurements obtained in the catheter-based method were adversely affected such that collateral flow may be misinterpreted as MVO. Based on further analysis of the measured data, concepts to mitigate the adverse effects were formulated which allow discrimination between collateral flow and MVO

Home-based palliative approach for people with severe multiple sclerosis and their carers: Study protocol for a randomized controlled trial

Background: Preliminary evidence suggests that palliative care may be useful for people with severe multiple sclerosis (MS). The aim of this study is to determine the effectiveness of a home-based palliative approach (HPA) for people with severe MS and their carers. Methods/design: This is a single-blind randomized controlled trial with a nested qualitative study. Seventy-five severe MS-carer dyads are being randomized (at three centers, one in each area of Italy) to HPA or usual care (UC) in a 2:1 ratio. Each center has a specially trained team consisting of four professionals (physician, nurse, psychologist, social worker). The team makes a comprehensive assessment of the needs of the dyads. HPA content is then agreed on, discussed with the patient's caring physician, and delivered over six months. The intervention is not intended to replace existing services. At later visits, the team checks the HPA delivery and reviews/modifies it as necessary. Discussion: The results of our study will show whether the HPA is feasible and beneficial to people with severe MS and their carers living in the three Italian geographic areas. The nested qualitative study will add to the understanding of the strengths and limitations of the intervention

In vitro investigations of red blood cell phase separation in a complex microchannel network

Microvascular networks feature a complex topology with multiple bifurcating vessels. Nonuniform partitioning (phase separation) of red blood cells (RBCs) occurs at diverging bifurcations, leading to a heterogeneous RBC distribution that ultimately affects the oxygen delivery to living tissues. Our understanding of the mechanisms governing RBC heterogeneity is still limited, especially in large networks where the RBC dynamics can be nonintuitive. In this study, our quantitative data for phase separation were obtained in a complex in vitro network with symmetric bifurcations and 176 microchannels. Our experiments showed that the hematocrit is heterogeneously distributed and confirmed the classical result that the branch with a higher blood fraction received an even higher RBC fraction (classical partitioning). An inversion of this classical phase separation (reverse partitioning) was observed in the case of a skewed hematocrit profile in the parent vessels of bifurcations. In agreement with a recent computational study [P. Balogh and P. Bagchi, Phys. Fluids 30,051902 (2018)], a correlation between the RBC reverse partitioning and the skewness of the hematocrit profile due to sequential converging and diverging bifurcations was reported. A flow threshold below which no RBCs enter a branch was identified. These results highlight the importance of considering the RBC flow history and the local RBC distribution to correctly describe the RBC phase separation in complex networks

In vitro analysis of time-dependent red blood cell phase separation in a complex microchannel network

In this study we provided quantitative data on red blood cell (RBC) partitioning in 21 divergent bifurcations embedded in a complex in vitro network. In the majority of bifurcations the branch receiving a higher blood fraction received an even higher RBC fraction (classical partitioning). However, in some bifurcations the low-flow branch received a higher RBC flow fraction (reverse partitioning). Moreover, we found that the phase separation is strongly time dependent and some selected bifurcations oscillated between the two types of partitioning

Local vs. Global Blood Flow Modulation in Artificial Microvascular Networks: Effects on Red Blood Cell Distribution and Partitioning

Our understanding of cerebral blood flow (CBF) regulation during functional activation is still limited. Alongside with the accepted role of smooth muscle cells in controlling the arteriolar diameter, a new hypothesis has been recently formulated suggesting that CBF may be modulated by capillary diameter changes mediated by pericytes. In this study, we developed in vitro microvascular network models featuring a valve enabling the dilation of a specific micro-channel. This allowed us to investigate the non-uniform red blood cell (RBC) partitioning at microvascular bifurcations (phase separation) and the hematocrit distribution at rest and for two scenarios modeling capillary and arteriolar dilation. RBC partitioning showed similar phase separation behavior during baseline and activation. Results indicated that the RBCs at diverging bifurcations generally enter the high-flow branch (classical partitioning). Inverse behavior (reverse partitioning) was observed for skewed hematocrit profiles in the parent vessel of bifurcations, especially for high RBC velocity (i.e., arteriolar activation). Moreover, results revealed that a local capillary dilation, as it may be mediated in vivo by pericytes, led to a localized increase of RBC flow and a heterogeneous hematocrit redistribution within the whole network. In case of a global increase of the blood flow, as it may be achieved by dilating an arteriole, a homogeneous increase of RBC flow was observed in the whole network and the RBCs were concentrated along preferential pathways. In conclusion, overall increase of RBC flow could be obtained by arteriolar and capillary dilation, but only capillary dilation was found to alter the perfusion locally and heterogeneously