A common situation in galactic and intergalactic gas involves cold dense gas in motion relative to hot diffuse gas. Kelvin-Helmholtz instability creates a turbulent mixing layer and populates the ...intermediate-temperature phase, which often cools rapidly. The energy lost to cooling is balanced by the advection of hot high enthalpy gas into the mixing layer, resulting in growth and acceleration of the cold phase. This process may play a major role in determining the interstellar medium and circumgalactic medium phase structure, and accelerating cold gas in galactic winds and cosmic filaments. Cooling in these mixing layers occurs in a thin corrugated sheet, which we argue has an area with fractal dimension D = 5/2 and a thickness that adjusts to match the hot phase mixing time to the cooling time. These cooling sheet properties form the basis of a new model for how the cooling rate and hot gas inflow velocity depend on the size L, cooling time of the mixed phase , relative velocity , and density contrast of the system. Entrainment is expected to be enhanced in environments with short , large , and large . Using a large suite of three-dimensional hydrodynamic simulations, we demonstrate that this fractal cooling layer model accurately captures the energetics and evolution of turbulent interfaces and can therefore be used as a foundation for understanding multiphase mixing with strong radiative cooling.
Extracellular vesicles (EVs) derived from human mesenchymal stromal cells (hMSC-EVs) have been studied in over 200 preclinical applications and dozens of human clinical trials, underscoring the need ...for scalable production processes compatible with GMP environments. Most existing 2D and 3D Bioreactor hMSC-EV production processes require a cell expansion stage utilizing undefined components, followed by a wash and medium exchange to remove expansion medium impurities prior to an EV collection phase in a defined medium. Simplifying this 3D process to include cell expansion and EV collection in one medium requires chemically defined growth conditions, a fed-batch medium design, and an efficient process to maximize cell and EV yield, and final product quality. We have developed a chemically defined, scalable fed-batch bioreactor production medium to enable the streamlined and highly efficient production of hMSC-EVs. This study evaluates hMSC-EV production and EV quality across multiple donors and tissues in microcarrier spinner flask cultures using a traditional cell expansion, wash, collect process vs the single-step production process, including scale-up to a 3L stirred tank bioreactor.
MSC-EVs were produced from hMSCs (hBM and hUC RoosterVial, 1M) in either RoosterNourish-MSC-XF/RoosterReplenish/RoosterCollect-EV or the new highly productive, chemically defined (HiDef-EV) fed-batch system and collected EVs at set times. HiDef-EV cultures led to increased EV production on days 5, 7, 10 and 12 of culture, while maintaining healthy viable cell profiles. The fed-batch process for hMSC-EV production increased the EV collection window from healthy hMSCs resulting in 2-4x increase in hMSC-EV yield over traditional EV production processes. Elimination of the medium exchange and wash steps resulted in utilization of fewer raw materials, retention rather than disposal of EVs produced during cell growth, and significant reductions in total media used and total cost per billion EVs. Additionally, EV Quality Attributes including size, tetraspanin expression, CD-73 activity, RNA, and lipid content are preserved in the HiDef-EV system. Scale up in 3L Eppendorf bioreactor showed comparable cell growth, EV yields and EV quality between traditional and HiDef-EV process. This highly productive chemically defined EV medium is a simplified, time and cost saving solution for the large-scale production of higher purity hMSC-EVs necessary for extensive clinical investigations.
We continue our empirical study of the emission line flux originating in the cool (T ∼ 104 K) gas that populates the halos of galaxies and their environments. Specifically, we present results ...obtained for a sample of nearly half a million individual galaxies, groups, and clusters of galaxies, intersected by more than two million SDSS lines of sight at projected separations of up to a quarter of the virial radius. Adopting simple power-law relationships between the circumgalactic (CGM) cool gas fraction and either the halo or stellar mass, we present expressions for the CGM cool gas fraction as a function of either halo or stellar mass, × or × . Where we can compare, our results are consistent with previous constraints from absorption line studies, our own previous emission line work, and simulations. The cool gas can be the dominant baryonic CGM component, comprising a fraction as high as >90% of halo gaseous baryons, in low-mass halos, Mh ∼ 1010.5 M , and a minor fraction, <5%, in groups and clusters, Mh > 1014 M .
We carry out a comprehensive Bayesian correlation analysis between hot halos and direct masses of supermassive black holes (SMBHs), by retrieving the X-ray plasma properties (temperature, luminosity, ...density, pressure, and masses) over galactic to cluster scales for 85 diverse systems. We find new key scalings, with the tightest relation being − , followed by − . The tighter scatter (down to 0.2 dex) and stronger correlation coefficient of all the X-ray halo scalings compared with the optical counterparts (as the − ) suggest that plasma halos play a more central role than stars in tracing and growing SMBHs (especially those that are ultramassive). Moreover, correlates better with the gas mass than dark matter mass. We show the important role of the environment, morphology, and relic galaxies/coronae, as well as the main departures from virialization/self-similarity via the optical/X-ray fundamental planes. We test the three major channels for SMBH growth: hot/Bondi-like models have inconsistent anticorrelation with X-ray halos and too low feeding; cosmological simulations find SMBH mergers as subdominant over most of cosmic time and too rare to induce a central-limit-theorem effect; the scalings are consistent with chaotic cold accretion, the rain of matter condensing out of the turbulent X-ray halos that sustains a long-term self-regulated feedback loop. The new correlations are major observational constraints for models of SMBH feeding/feedback in galaxies, groups, and clusters (e.g., to test cosmological hydrodynamical simulations), and enable the study of SMBHs not only through X-rays, but also via the Sunyaev-Zel'dovich effect (Compton parameter), lensing (total masses), and cosmology (gas fractions).
Disruptive digital innovation (DDI) often creates hypercompetitive market environment that forces firms to be agile to survive and remain competitive. Whereas most studies have focused on larger ...firms' effort to be agile, few have looked at how small‐ and medium‐sized enterprises (SMEs) respond to DDI. The study attempts to answer the research question of how SMEs achieve agility to respond to DDI. Drawing on a case study of an innovative SME, our study develops a framework on agility based on the processes of mitigating organizational rigidity, developing innovative capabilities, and balancing the tension of organizational ambidexterity. Specifically, our findings show that for SMEs, mitigating organizational rigidity is enabled by the mechanism of achieving boundary openness while developing innovative capability is enabled by the mechanism of achieving organizational adaptability. At the same time, given the inherent challenges of resource constraints, SMEs also need to balance the tension of organizational ambidexterity.
Abstract
In situ observations of interstellar neutral (ISN) helium atoms by the IBEX-Lo instrument on board the Interstellar Boundary Explorer (IBEX) mission are used to determine the velocity and ...temperature of the pristine very local interstellar medium (VLISM). Most ISN helium atoms penetrating the heliosphere, known as the primary population, originate in the pristine VLISM. As the primary atoms travel through the outer heliosheath, they charge exchange with He
+
ions in slowed and compressed plasma, creating the secondary population. With more than 2.4 million ISN helium atoms being sampled by IBEX during ISN seasons 2009–2020, we compare the observations with the predictions of a parameterized model of ISN helium transport in the heliosphere. We account for the filtration of ISN helium atoms at the heliospheric boundaries by charge-exchange and elastic collisions. We examine the sensitivity of the ISN helium fluxes to the interstellar conditions described by the pristine VLISM velocity, temperature, magnetic field, and composition. We show that comprehensive modeling of the filtration processes is critical for interpreting ISN helium observations, as the change in the derived VLISM conditions exceeds the statistical uncertainties when accounting for these effects. The pristine VLISM parameters found by this analysis are the flow speed (26.6 km s
−1
), inflow direction in ecliptic coordinates (255.°7, 5.°04), temperature (7350 K), and
B
−
V
plane inclination to the ecliptic plane (53.°7). The derived pristine VLISM He
+
density is 9.7 × 10
−3
cm
−3
. Additionally, we show a strong correlation between the interstellar plasma density and magnetic field strength deduced from these observations.
Abstract
The two Voyager spacecraft have now been immersed in the very local interstellar medium for several years. Both spacecraft carry a plasma wave instrument capable of detecting plasma waves ...that yield electron density through the determination of the electron plasma frequency. Recent observations by Voyager 1 show increases in density at shocks and pressure fronts that are commensurate with increases in the magnetic field at these structures. Voyager 1 has not observed electron plasma oscillations, thought to be a signature of a nearby shock, since 2019, although Voyager 2 continues to observe these as recently as 2022 November. Voyager 1 also detects a faint thermal emission at the electron plasma frequency that shows the evolution of the plasma density as Voyager moves deeper into the medium. Here, we show the most recent observations from both Voyagers showing the increasing densities in the region upstream of the heliopause. We also investigate the fate of solar transients as they move ever deeper into the interstellar medium.
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