Size distribution of galaxies in SDSS DR7: weak dependence on halo environment

Using a sample of galaxies selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and a catalog of bulge-disk decompositions, we study how the size distribution of galaxies depends on the intrinsic properties of galaxies, such as concentration, morphology, specific star formation rate (sSFR), and bulge fraction, and on the large-scale environments in the context of central/satellite decomposition, halo environment, the cosmic web: \cluster, \filament, \sheet ~and \void, as well as galaxy number density. We find that there is a strong dependence of the luminosity- or mass-size relation on the galaxy concentration, morphology, sSFR, and bulge fraction. Compared with late-type (spiral) galaxies, there is a clear trend of smaller sizes and steeper slope for early-type (elliptical) galaxies. Similarly, galaxies with high bulge fraction have smaller sizes and steeper slope than those with low bulge fraction. Fitting formula of the average luminosity- and mass-size relations are provided for galaxies of these different intrinsic properties. Examining galaxies in terms of their large scale environments, we find that the mass-size relation has some weak dependence on the halo mass and central/satellite segregation for galaxies within mass range $9.0\le \log M_{\ast} \le 10.5$, where satellites or galaxies in more massive halos have slightly smaller sizes than their counterparts. While the cosmic web and local number density dependence of the mass-size relation is almost negligible.Comment: 12 pages, 11 figure

Nonlinearities in modified gravity cosmology. II. Impacts of modified gravity on the halo properties

The statistics of dark matter halos is an essential component of understanding the nonlinear evolution in modified gravity cosmology. Based on a series of modified gravity N-body simulations, we investigate the halo mass function, concentration and bias. We model the impact of modified gravity by a single parameter \zeta, which determines the enhancement of particle acceleration with respect to GR, given the identical mass distribution (\zeta=1 in GR). We select snapshot redshifts such that the linear matter power spectra of different gravity models are identical, in order to isolate the impact of gravity beyond modifying the linear growth rate. At the baseline redshift corresponding to z_S=1.2 in the standard \Lambda CDM, for a 10% deviation from GR(|\zeta-1|=0.1), the measured halo mass function can differ by about 5-10%, the halo concentration by about 10-20%, while the halo bias differs significantly less. These results demonstrate that the halo mass function and/or the halo concentration are sensitive to the nature of gravity and may be used to make interesting constraints along this line.Comment: 8 pages, 7 figures, accepted for publication in Physical Review

How Does Anxiety Affect Cognitive Control? Proactive and Reactive Control Under State Anxiety

Cognitive control is a construct that prioritizes how we process stimuli and information and execute behaviors to flexibly and efficiently adapt to internal goals and external environmental changes. A recent theory, the Dual Mechanism of Control (DMC), distinguishes this phenomenon by two distinct cognitive control operations: proactive control and reactive control (Braver, 2012). Anxiety increases the allocation of attentional and working memory resources to threat-related stimuli, which impairs cognitive performance (Sarason, 1988), but additional work is needed to assess how anxiety impacts these two distinct forms of cognitive control. In this study, I examined how state anxiety affected proactive control, using the AX-continuous performance task (AX-CPT), and reactive control, using the classic Stroop task. The results showed that state anxiety inhibited proactive control in AX-CPT test, but increased reactive control in the Stroop task. Ultimately, by completing this study, we will better understand how anxiety impacts the proactive and reactive control

CHARACTERIZATION OF ORGANIC ANION TRANSPORTING POLYPEPTIDE 1A1 (OATP1A1) IN THE BILE ACID HOMEOSTASIS OF MICE

Organic anion transporting polypeptides (human: OATPs; all other species: Oatps; gene symbol: SLCO/Slco) are sodium-independent transport systems that mediate the transmembrane transport of a wide range of amphipathic endogenous and exogenous organic compounds. In mice, Oatp1a1, 1a4, and 1b2 are thought to account for the bulk of Na-independent bile acid (BA) uptake into liver during normal physiological conditions. The overall goal of this dissertation has focused on characterization of the in vivo role of mouse Oatp1a1 in BA homeostasis by using Oatp1a1-null mice. To achieve this overall goal, three specific aims were examined in the present dissertation. In the first specific aim, a simple and sensitive UPLC-MS/MS method was established and validated for the simultaneous analysis of various BAs, and applied to investigate liver BA content in C57BL/6 mice fed 1% cholic acid (CA), 0.3% deoxycholic acid (DCA), 0.3% chenodeoxycholic acid (CDCA), 0.3% lithocholic acid (LCA), 3% ursodeoxycholic acid (UDCA), or 2% cholestyramine (resin). The purpose of this study was to understand the BA metabolic pathways in mice by using this newly developed BA-quantification method, and thus to provide tools and knowledge for the future study in Oatp1a1-null mice. Gender differences in liver BA composition were observed after feeding CA, DCA, CDCA, and LCA, but were not prominent after feeding UDCA. Sulfation of CA and CDCA was found at the 7-OH position, and increased by feeding CA or CDCA more in male than female mice. In contrast, sulfation of LCA and taurolithocholic acid (TLCA) was female predominant, and increased by feeding UDCA and LCA. The metabolic pathways of each BA in vivo are proposed, and can be used to interpret BA-mediated gene regulation and hepatotoxicity. In the second specific aim, the hypothesis that Oatp1a1 is important in transporting unconjugated BAs was evaluated. The purpose of this study was to determine whether knockout of Oatp1a1 will alter BA metabolism in mice. To address this aim, the concentrations of individual BAs in serum, liver, and bile were compared between WT and Oatp1a1-null mice. The gender-divergent expression of Oatp1a1 was considered in the efforts to identify the endogenous BA substrates for Oatp1a1. In addition, DCA feeding and pharmacokinetic studies were conducted in WT and Oatp1a1-null mice to investigate the role of Oatp1a1 in the disposition of DCA. Data from this study show a critical role of Oatp1a1 in DCA metabolism of mice. Oatp1a1 in mouse liver does not appear to transport DCA, because knockout of Oatp1a1 does not prevent hepatic uptake and hepatotoxicity of DCA. Instead, knockout of Oatp1a1 increases the intestinal permeability and thus increases intestinal absorption of DCA. In addition, Knockout of Oatp1a1 markedly alters the composition and amount of intestinal bacteria. The alterations of intestinal bacteria in Oatp1a1-null mice result in marked changes of BA composition in the intestinal contents and feces, but have no effect on the total fecal BA excretion, due to the same billiary input of BAs in WT and Oatp1a1-null mice. In the third specific aim, the hypothesis that knockout of Oatp1a1 decreases liver toxicity in mice during extrahepatic cholestasis was evaluated. The purpose of this study was to determine the in vivo role of Oatp1a1 in mice after bile duct ligation (BDL) by using Oatp1a1-null mice. Knockout of Oatp1a1 increased liver toxicity in mice after BDL, which may be due to the increase of secondary BAs in livers of mice. Knockout of Oatp1a1 resulted in an impaired cytoprotective response in mice during BDL-induced cholestasis. In addition, antibiotic treatment potentiated liver toxicity in Oatp1a1-null mice after BDL by increasing the intestinal absorption of BAs. Thus, Oatp1a1 plays a unique and essential protective role in the adaptive response to obstructive cholestasis liver injury. Altogether, this dissertation demonstrates that: (1) A simple and sensitive UPLC-MS/MS method was established for the simultaneous analysis of various BAs and was applied to investigate the BA metabolism in mice fed CA, CDCA, DCA, LCA, UDCA, or resin; (2) Oatp1a1 does not mediate the hepatic uptake of DCA, but plays a critical role in the intestinal metabolism of DCA; (3) Knockout of Oatp1a1 increases intestinal bacteria and thus alters the urinary metabolomics in mice; and (4) Knockout of Oatp1a1 increases liver toxicity in mice after BDL, which may be due to the increase of secondary BAs in both serum and livers of mice

Is Contextual Cue Learning Flexible? an Eye-movement Study of the Contextual Cueing Task

Visual searching can be facilitated without awareness when the target is repeatedly presented in an invariant context in tasks such as contextual cueing (Chun & Jiang 1998). A behavioral cost (increased reaction time) was observed when the target was moved to a new location but no such cost was observed when the target returned to the initial location. The lack of cost for return suggests two possible explanations: One is that the learning can update the initial learning to acquire both target locations, which suggests the implicit learning is flexible. The other is that the contextual cue leaning cannot update the initial learning but perseverates for the initial target location, which would not provide evidence the learning is flexible. To clarify the mechanism by which returns impose no behavioral cost, thirty-two participants were recruited for a contextual cueing task with both eye-movement and reaction time as dependent variables. All participants were required to identify the orientation of target in each array. After nine blocks (phase A1), the target in repeated array swapped with a distractor in the diagonal quadrant for another nine blocks (phase B), then the target returned to its initial location (phase A2). A behavioral cost of reaction time was observed after the initial swap in phase B. No significant contextual cueing effect was observed until the last epoch of phase B. However, no evidence of a behavioral cost was observed after the return in phase A2. Further analysis showed the behavioral cost in Phase B was found to be due in part to proactive interference from learning in Phase A1. The mechanism for immediate recovery after return in phase A2 was likewise perseveration of learning from Phase A1, which in most instances was sustained throughout all Phase B. The present study shows no evidence that participants could learn two targets locations which were subsequently presented in the same context in the contextual cueing task within the limited time available to them. Therefore, no evidence was found to support the flexibility of implicit learning in this task

The Impact of Baryons on the Large-Scale Structure of the Universe

Numerical simulations play an important role in current astronomy researches. Previous dark-matter-only simulations have represented the large-scale structure of the Universe. However, nowadays, hydro-dynamical simulations with baryonic models, which can directly present realistic galaxies, may twist these results from dark-matter-only simulations. In this chapter, we mainly focus on these three statistical methods: power spectrum, two-point correlation function and halo mass function, which are normally used to characterize the large-scale structure of the Universe. We review how these baryon processes influence the cosmology structures from very large scale to quasi-linear and non-linear scales by comparing dark-matter-only simulations with their hydro-dynamical counterparts. At last, we make a brief discussion on the impacts coming from different baryon models and simulation codes

A waste heat-driven cooling system based on combined organic Rankine and vapour compression refrigeration cycles

In this paper, a heat driven cooling system that essentially integrated an organic Rankine cycle power plant with a vapour compression cycle refrigerator was investigated, aiming to provide an alternative to absorption refrigeration systems. The organic Rankine cycle (ORC) subsystem recovered energy from the exhaust gases of internal combustion engines to produce mechanical power. Through a transmission unit, the produced mechanical power was directly used to drive the compressor of the vapour compression cycle system to produce a refrigeration effect. Unlike the bulky vapour absorption cooling system, both the ORC power plant and vapour compression refrigerator could be scaled down to a few kilowatts, opening the possibility for developing a small-scale waste heat-driven cooling system that can be widely applied for waste heat recovery from large internal combustion engines of refrigerated ships, lorries, and trains. In this paper, a model was firstly established to simulate the proposed concept, on the basis of which it was optimized to identify the optimum operation condition. The results showed that the proposed concept is very promising for the development of heat-driven cooling systems for recovering waste heat from internal combustion engines’ exhaust gas

Alignments of galaxies within cosmic filaments from SDSS DR7

Using a sample of galaxy groups selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), we examine the alignment between the orientation of galaxies and their surrounding large scale structure in the context of the cosmic web. The latter is quantified using the large-scale tidal field, reconstructed from the data using galaxy groups above a certain mass threshold. We find that the major axes of galaxies in filaments tend to be preferentially aligned with the directions of the filaments, while galaxies in sheets have their major axes preferentially aligned parallel to the plane of the sheets. The strength of this alignment signal is strongest for red, central galaxies, and in good agreement with that of dark matter halos in N-body simulations. This suggests that red, central galaxies are well aligned with their host halos, in quantitative agreement with previous studies based on the spatial distribution of satellite galaxies. There is a luminosity and mass dependence that brighter and more massive galaxies in filaments and sheets have stronger alignment signals. We also find that the orientation of galaxies is aligned with the eigenvector associated with the smallest eigenvalue of the tidal tensor. These observational results indicate that galaxy formation is affected by large-scale environments, and strongly suggests that galaxies are aligned with each other over scales comparable to those of sheets and filaments in the cosmic web.Comment: 11 pages, 10 figures, accepted for publication in Ap

Galaxy-halo size relation from Sloan Digital Sky Survey Data Release 7 and the ELUCID simulation

Based on galaxies in the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and dark matter haloes in the dark matter only, cosmological and constrained ELUCID simulation, we investigate the relation between the observed radii of central galaxies with stellar mass $\gtrsim 10^{8} h^{-2}{\rm M}_\odot$ and the virial radii of their host dark matter haloes with virial mass $\gtrsim 10^{10.5} h^{-1}{\rm M}_\odot$, and the dependence of galaxy-halo size relation on the halo spin and concentration. Galaxies in observation are matched to dark matter (sub-)haloes in the ELUCID simulation using a novel neighborhood subhalo abundance matching method. For galaxy 2D half-light radii $R_{50}$, we find that early- and late-type galaxies have the same power-law index 0.55 with $R_{50} \propto R_{\rm vir}^{0.55}$, although early-type galaxies have smaller 2D half-light radii than late-type galaxies at fixed halo virial radii. When converting the 2D half-light radii $R_{50}$ to 3D half-mass radii $r_{1/2}$, both early- and late-type galaxies display similar galaxy-halo size relations with $\log r_{1/2} = 0.55 \log (R_{\rm vir}/210 h^{-1}{\rm kpc}) + 0.39$. We find that the galaxy-halo size ratio $r_{1/2}/ R_{\rm vir}$ decreases with increasing halo mass. At fixed halo mass, there is no significant dependence of galaxy-halo size ratio on the halo spin or concentration.Comment: 10 pages, 8 figures, accepted for publication in MNRA