Mass\u2013metallicity relation from cosmological hydrodynamical simulations and X-ray observations of galaxy groups and clusters

Recent X-ray observations of galaxy clusters show that the distribution of intra-cluster medium (ICM) metallicity is remarkably uniform in space and time. In this paper, we analyse a large sample of simulated objects, from poor groups to rich clusters, to study the dependence of the metallicity and related quantities on the mass of the systems. The simulations are performed with an improved version of the smoothed-particle-hydrodynamic GADGET-3 code and consider various astrophysical processes including radiative cooling, metal enrichment and feedback from stars and active galactic nuclei (AGNs). The scaling between the metallicity and the temperature obtained in the simulations agrees well in trend and evolution with the observational results obtained from two data samples characterized by a wide range of masses and a large redshift coverage. We find that the iron abundance in the cluster core (r < 0.1R500) does not correlate with the temperature nor presents a significant evolution. The scale invariance is confirmed when the metallicity is related directly to the total mass. The slope of the best-fitting relations is shallow (\u3b2 \u2dc -0.1) in the innermost regions (r < 0.5R500) and consistent with zero outside. We investigate the impact of the AGN feedback and find that it plays a key role in producing a constant value of the outskirts metallicity from groups to clusters. This finding additionally supports the picture of early enrichment

Complex diffuse emission in the z = 0.52 cluster PLCK G004.5-19.5

We present radio observations of the galaxy cluster PLCK G004.5-19.5 (z = 0.52) using the Giant Metrewave Radio Telescope at 150 MHz, 325 MHz, and 610 MHz. We find an unusual arrangement of diffuse radio emission in the center and periphery of the cluster, as well as several radio galaxies with head-tail emission. A patch of peripheral emission resembles a radio relic, and central emission resembles a radio halo. Reanalysis of archival XMM-Newton X-ray data shows that PLCK G004.5-19.5 is disturbed, which has a known correlation with the existence of radio relics and halos. Given that the number of known radio halos and radio relics at z &gt; 0.5 is very limited, PLCK G004.5-19.5 is an important addition to understanding merger-related particle acceleration at higher redshifts

Multiple-frequency Impedance Measurements in Continuous Flow for the Evaluation of Electrical Lysis of Yeast Cells

AbstractThis paper reports on an electrical lysis device with integrated cell counting and evaluation of the lysis efficiency by multiplefrequency impedance measurements. Conventional techniques use chemical reagents to lyse cells, causing unwanted interference with possible intracellular content analysis downstream. Electrical lysis is quite simple to implement but optical observation of the lysis is difficult in the case of yeast cells, as lysis induces no visual difference. Counting the lysed cells is also essential for analysis downstream to provide an estimate of the analyte concentration per cell. Although cell counting can be performed by impedance measurement at one single frequency, multiple-frequency measurements allow the differentiation between living and dead cells and the evaluation of the lysis efficiency in continuous flow. The presented device could further be used for the evaluation of the lysis of other cell types, such as bacteria or mammalian cells

Multiple-frequency impedance measurements in continuous flow for automated evaluation of yeast cell lysis

This paper reports on an electrical lysis device integrating multiple-frequency impedance measurements for automated evaluation of the lysis efficiency and counting of the lysed cells. Conventional techniques use chemical reagents to dissolve the cell membrane, causing unwanted interference with possible intracellular content analysis downstream. Conversely, electrical lysis does not use reagents but electrical fields to disrupt the membrane, and is easy to integrate with microfabrication techniques. Besides, yeast cell lysis is difficult to evaluate, as it induces no significant visual difference. The presented device uses an innovative approach allowing automated evaluation of the lysis efficiency in continuous flow by multiple-frequency impedance measurements. This technique is able to count and differentiate living and dead cells without optical setup, providing an estimation of the sample viability after lysis. Counting the cells effectively lysed is essential for downstream analysis in order to provide an estimate of the analyte concentration per cell. The lysis is performed using AC electrical fields and so-called “liquid electrodes”, leading to an efficiency of 98%

In situ evaluation of single-cell lysis by cytosol extraction observation through fluorescence decay and dielectrophoretic trapping time

We present a new method for lysis of single cells in continuous flow, where cells are sequentially trapped, lysed and released in an automatic process. Using optimized frequencies, dielectrophoretic trapping allows exposing cells in a reproducible way to high electrical fields for long durations, thereby giving good control on the lysis parameters. In situ evaluation of cytosol extraction on single cells has been studied for Chinese hamster ovary (CHO) cells through out-diffusion of fluorescent molecules for different voltage amplitudes. A diffusion model is proposed to correlate this out-diffusion to the total area of the created pores, which is dependent on the potential drop across the cell membrane and enables evaluation of the total pore area in the membrane. The dielectrophoretic trapping is no longer effective after lysis because of the reduced conductivity inside the cells, leading to cell release. The trapping time is linked to the time required for cytosol extraction and can thus provide additional validation of the effective cytosol extraction for non-fluorescent cells. Furthermore, the application of one single voltage for both trapping and lysis provides a fully automatic process including cell trapping, lysis, and release, allowing operating the device in continuous flow without human intervention

Cell Viability Assessment By Flow Cytometry Using Yeast As Cell Model

This paper reports the new combination of cell sorting and counting capabilities on a single device. Most state-of-the-art devices combining these technologies use optical techniques requiring complicated experimental setups and labeled samples. The use of a label-free, electrical device significantly decreases the system complexity and makes it more appropriate for use in point-of-care diagnostics. Living and dead yeast cells are separated by dielectrophoretic forces and counted using coulter counters. The combination of these two methods allows the determination of the percentage of living and dead cells for viability studies of cell samples. The device could further be used for sorting and counting of blood cells in applications such as diagnosis of insufficient cell concentrations, identification of cell deficiencies or bacterial contamination. The use of dielectrophoresis (DEP) as sorting principle allows to separate cells based on their dielectric properties in the place of size-based separation, enabling sorting of large panels of cells and separation of infected and non-infected cells of the same type

Continuous-flow electrical lysis device with integrated control by dielectrophoretic cell sorting

We present a device capable of electrical cell lysis and evaluation of lysis efficiency in continuous flow using dielectrophoretic cell sorting. We use a combination of AC electrical fields and so-called liquid electrodes to avoid bubble creation at the electrode surface. The electrical field distribution is calculated in different electrode configurations by numerical simulations. Cell sorting shows high lysis efficiency, 99% of yeast cells sorted after lysis featuring dielectric properties similar to dead cells. A study of the potential device throughput is performed