One-Two Quench: A Double Minor Merger Scenario

Using the N-body+Smoothed particle hydrodynamics code, ChaNGa, we identify two merger-driven processes—disk disruption and supermassive black hole (SMBH) feedback—which work together to quench L* galaxies for over 7 Gyr. Specifically, we examine the cessation of star formation in a simulated Milky Way (MW) analog, driven by an interaction with two minor satellites. Both interactions occur within ~100 Myr of each other, and the satellites both have masses 5–20 times smaller than that of their MW-like host galaxy. Using the genetic modification process of Roth et al., we generate a set of four zoom-in, MW-mass galaxies all of which exhibit unique star formation histories due to small changes to their assembly histories. In two of these four cases, the galaxy is quenched by z = 1. Because these are controlled modifications, we are able to isolate the effects of two closely spaced minor merger events, the relative timing of which determines whether the MW-mass main galaxy quenches. This one–two punch works to: (1) fuel the SMBH at its peak accretion rate and (2) disrupt the cold, gaseous disk of the host galaxy. The end result is that feedback from the SMBH thoroughly and abruptly ends the star formation of the galaxy by z ≈ 1. We search for and find a similar quenching event in Romulus25, a hydrodynamical (25 Mpc)3 volume simulation, demonstrating that the mechanism is common enough to occur even in a small sample of MW-mass quenched galaxies at z = 0

The Accretion History of AGNs. I. Supermassive Black Hole Population Synthesis Model

As matter accretes onto the central supermassive black holes in active galactic nuclei (AGNs), X-rays are emitted. We present a population synthesis model that accounts for the summed X-ray emission from growing black holes; modulo the efficiency of converting mass to X-rays, this is effectively a record of the accreted mass. We need this population synthesis model to reproduce observed constraints from X-ray surveys: the X-ray number counts, the observed fraction of Compton-thick AGNs [log (BH /cm-2 )>24], and the spectrum of the cosmic X-ray background (CXB), after accounting for selection biases. Over the past decade, X-ray surveys by XMM-Newton, Chandra, NuSTAR, and Swift-BAT have provided greatly improved observational constraints. We find that no existing X-ray luminosity function (XLF) consistently reproduces all these observations. We take the uncertainty in AGN spectra into account and use a neural network to compute an XLF that fits all observed constraints, including observed Compton-thick number counts and fractions. This new population synthesis model suggests that, intrinsically, 50% +- 9% (56% +- 7%) of all AGNs within z ≃ 0.1 (1.0) are Compton-thick

Cool and gusty, with a chance of rain: Dynamics of multiphase CGM around massive galaxies in the Romulus simulations

Using high-resolution Romulus simulations, we explore the origin and evolution of the circumgalactic medium (CGM) in the zone 0.1 $\leq \mathrm{R}/\mathrm{R}_\mathrm{500} \leq$ 1 around massive central galaxies in group-scale halos. We find that the CGM is both multiphase and highly dynamic. Investigating the dynamics, we identify seven patterns of evolution. We show that these are robust and detected consistently across various conditions. There are two pathways by which the gas cools: (1) filamentary cooling inflows and (2) condensations forming from rapidly cooling density perturbations. In our cosmological simulations, the perturbations are mainly seeded by orbiting substructures. We find that condensations can form even when the median $t_\mathrm{cool} / t_\mathrm{ff}$ of the X-ray emitting gas is above the canonical threshold of 10 or 20. Strong amplitude perturbations can provoke runaway cooling regardless of the state of the background gas. We also find perturbations whose local $t_\mathrm{cool} / t_\mathrm{ff}$ ratios drop below the threshold but which do not condense. Rather, the ratios fall to some minimum value and then bounce. These are weak perturbations that are temporarily swept up in satellite wakes and carried to larger radii. Their $t_\mathrm{cool} / t_\mathrm{ff}$ ratios decrease because the denominator ($t_\mathrm{ff}$) is increasing, not because the numerator ($t_\mathrm{cool}$) is decreasing. For structures forming hierarchically, our study highlights the challenge of using a simple threshold argument to infer the CGM's evolution. It also highlights that the median hot gas properties are suboptimal determinants of the CGM's state and dynamics. Realistic CGM models must factor in the effects and after-effects of mergers and orbiting satellites, along with the CGM's heating and cooling cycles.Comment: 25 pages, 12 figure

Laser-Spectroscopic Investigation of OH-Radical Concentrations in the Exhaust Plane of Jet Engines

Hydroxyl radical (OH) emissions are relevant for oxidation reactions in the post flame chemistry of exhaust gases emitted from jet engines. No direct measurements of OH concentrations are available to date due to the low abundance and the short lifetime of this radical species. The first application of a combined technique based on Raman scattering and laser_induced fluorescence (LIF) spectrometry is presented here for measurements in the exhaust gases of a commercial jet engine operated in a test rig. From the measurements, upper limits for OH concentrations in the exit plane were determined in the range of 90 ppbv for take off and 80 ppbv for ap_idle. The values are significantly below the predictions of model calculations based on HONO and HNO3 in_flight concentration measurements presented recently. Possibilities for further increase of the detection sensitivity for OH are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86750/1/Sick34.pd

Stability analysis of wheat lines with increased level of arabinoxylan

Plant breeders have long sought to develop lines that combine outstanding performance with high and stable quality in different environments. The high-arabinoxylan (AX) Chinese variety Yumai-34 was crossed with three Central European wheat varieties (Lupus, Mv-Mambo, Ukrainka) and 31 selected high-AX lines were compared for physical (hectolitre weight, thousand grain weight, flour yield), compositional (protein content, gluten content, pentosan) and processing quality traits (gluten index, Zeleny sedimentation, Farinograph parameters) in a three-year experiment (2013–2015) in the F7-F9 generations. The stability and heritability of different traits, including the relative effects of the genotype (G) and environment (E), were determined focusing on grain composition. The contents of total and water-soluble pentosans were significantly affected by G, E and G×E interactions, but the heritability of total (TOT)pentosan was significantly lower (0.341) than that of water-extractable (WE)-pentosan (0.825). The main component of the pentosans, the amount and composition (arabinose: xylose ratio) of the arabinoxylan (AX), was primarily determined by the environment and, accordingly, the broader heritability of these parameters were 0.516 and 0.772. However, genotype significantly affected the amount of water-soluble arabinoxylan and its composition and thus the heritability of these traits was also significant (0.840 and 0.721). The genotypes exhibiting higher stability of content of TOT-pentosan also showed more stable contents of WE-pentosan. There was a positive correlation between the stability of contents of WE-pentosan and WE-AX, while the stability of the WE-AX content and AX composition were also strongly correlated. Water absorption was strongly genetically determined with a heritability of 0.829 with the genotype determining 38.67% of the total variance. Many lines were grouped in the GGE biplot, indicating that they did not significantly differ stability

Stability analysis of wheat populations and mixtures based on the physical, compositional and processing properties of the seeds

Six cropping populations, three variety mixtures and one diversity population were developed from winter wheat varieties and studied for physical, compositional and end-use quality traits for three years (2011–2013) under different European climatic and management conditions in order to study the stability of these traits resulted by the genetic diversity. The beneficial compositional and nutritional properties of the populations were assessed, while variation and stability of the traits were analysed statistically. No significant differences were found among the populations in low-input and organic management farming systems in the physical, compositional and processing properties, but there was a difference in the stability of these traits. Most of the populations showed higher stability than the control wheat variety, and populations developed earlier had higher stability than those developed later. Furthermore, some populations were found to be especially unstable for some traits at certain sites (mostly at Austrian, Swiss and UK organic sites). Protein content of the populations was high (13.0–14.7%) without significant difference among them, but there was significant variation in their gluten content (28–36%) and arabinoxylan content (14.6–20.3 mg/g). The most outstanding population for both protein and arabinoxylan content was a Hungarian cropping population named ELIT-CCP. It was concluded that the diversity found in the mixtures and CCPs have stabilizing effect on the quality parameters, but a higher stability was observed under low-input than under organic conditions. These results could be beneficial not only for breeders but also for the consumers in the long run

Prognostic significance of CD44s expression in resected non-small cell lung cancer

<p>Abstract</p> <p>Background</p> <p>CD44s is a cell adhesion molecule known to mediate cellular adhesion to the extracellular matrix, a prerequisite for tumor cell migration. CD44s plays an important role in invasion and metastasis of various cancers. In the present study, we sought to determine whether CD44s is involved in clinical outcomes of patients with resected non-small cell lung cancer (NSCLC).</p> <p>Methods</p> <p>Using immunohistochemical staining, we investigated CD44s protein expression using tissue array specimens from 159 patients with resected NSCLC (adenocarcinoma (AC; <it>n </it>= 82) and squamous cell carcinoma (SCC; <it>n </it>= 77). Additionally, the immunoreactivity of cyclooxygenase (COX)-2 was also studied. The clinicopathological implications of these molecules were analyzed statistically.</p> <p>Results</p> <p>High CD44s expression was detected more frequently in NSCLC patients with SCC (66/72; 91.7%) than in those with AC histology (<it>P <</it>0.001). Additionally, high CD44s expression was significant correlated with more advanced regional lymph node metastasis (<it>P </it>= 0.021). In multivariate analysis of survival in NSCLC patients with AC histology, significant predictors were lymph node metastasis status (<it>P </it>< 0.001), high-grade tumor differentiation (<it>P = </it>0.046), and high CD44s expression (<it>P = </it>0.014). For NSCLC patients with SCC histology, the significant predictor was a more advanced tumor stage (<it>P = </it>0.015). No significant association was found between CD44s and clinical outcome (<it>P </it>= 0.311).</p> <p>Conclusions</p> <p>High CD44s expression was a negative prognostic marker with significance in patients with resected NSCLC, particularly those with AC histology, and was independent of tumor stage.</p