Mass Distribution in Galaxy Clusters: the Role of AGN Feedback

We use 1 kpc resolution cosmological AMR simulations of a Virgo-like galaxy cluster to investigate the effect of feedback from supermassive black holes (SMBH) on the mass distribution of dark matter, gas and stars. We compared three different models: (i) a standard galaxy formation model featuring gas cooling, star formation and supernovae feedback, (ii) a "quenching" model for which star formation is artificially suppressed in massive halos and finally (iii) the recently proposed AGN feedback model of Booth & Schaye (2009). Without AGN feedback (even in the quenching case), our simulated cluster suffers from a strong overcooling problem, with a stellar mass fraction significantly above observed values in M87. The baryon distribution is highly concentrated, resulting in a strong adiabatic contraction (AC) of dark matter. With AGN feedback, on the contrary, the stellar mass in the bright central galaxy (BCG) lies below observational estimates and the overcooling problem disappears. The stellar mass of the BCG is seen to increase with increasing mass resolution, suggesting that our stellar masses converges to the correct value from below. The gas and total mass distributions are in striking agreement with observations. We also find a slight deficit (~10%) of baryons at the virial radius, due to the effect of AGN-driven shock waves pushing gas to Mpc scales and beyond. This baryon deficit results in a slight adiabatic expansion of the dark matter distribution, that can be explained quantitatively by AC theory.Comment: 17 pages, 12 figures, submitted to MNRAS, new version after referee report

Contemporary Photographic Practices on the British Fairground

The fairground is a somewhat magical and uncharted realm of illusion, deception, thrill and adventure. It offers a glimpse of the improbable and impossible, and a taste or touch of the unattainable. This article looks at the crossover of photography and the British fairground following the gradual take-up of photography in the post-war period. It briefly covers early traditions concomitant with the specialised practice of photography, then it identifies photographic practices on the fairground through distinct communities of engagement including professional and amateur photographers attracted to the spectacle of the fair, ethnographic explorers, dedicated enthusiasts, showpeople and the general public of “punters”. In each case photographs from these communities are presented as well as a selection of photographs depicting these communities of photographers in action. The article concludes with the current situation of camera phone technology, social media and digitally manipulated photographic art as a new aesthetic of the fairground

Regulation of β(1)- and β(3)-adrenergic agonist-stimulated lipolytic response in hyperthyroid and hypothyroid rat white adipocytes

1. This study examined the effects of thyroid status on the lipolytic responses of rat white adipocytes to β-adrenoceptor (β-AR) stimulation. The β(1)- and β(3)-AR mRNAs and proteins were measured by Northern and saturation analyses, respectively. Glycerol production and adenyl cyclase (AC) activity induced by various non-selective and selective β(1)/β(3)-AR agonists and drugs which act distal to the receptor in the signalling cascade were measured in cells from untreated, tri-iodothyronine (T(3))-treated and thyroidectomized rats. 2. The β(3)-AR density was enhanced (72%) by T(3)-treatment and reduced (50%) by introduction of a hypothyroid state while β(1)-AR number remained unaffected. The β(1)- and β(3)-AR density was correlated with the specific mRNA level in all thyroid status. 3. The lipolytic responses to isoprenaline, noradrenaline (β(1)/β(3)/β(3)-AR agonists) and BRL 37344 (β(3)-AR agonist) were potentiated by 48, 58 and 48%, respectively in hyperthyroidism and reduced by about 80% in hypothyroidism. 4. T(3)-treatment increased the maximal lipolytic response to the partial β(3)-AR (CGP 12177) and β(1)-AR (xamoterol) agonists by 234 and 260%, respectively, increasing their efficacy (intrinsic activity: 0.95 versus 0.43 and 1.02 versus 0.42). The maximal AC response to these agonists was increased by 84 and 58%, respectively, without changing their efficacy. 5. In the hypothyroid state, the maximal lipolytic and AC responses were decreased with CGP (0.17±0.03 versus 0.41±0.08 μmol glycerol/10(6) adipocytes; 0.048±0.005 versus 0.114±0.006 pmol cyclic AMP min(−1) mg(−1)) but not changed with xamoterol. 6. The changes in lipolytic responses to postreceptor-acting agents (forskolin, enprofylline and dibutenyl cyclic AMP, (Bu)(2)cAMP) suggest the modifications on receptor coupling and phosphodiesterase levels in both thyroid states. 7. Thyroid status affects lipolysis by modifying β(3)-AR density and postreceptor events without changes in the β(1)-AR functionality

Dark webs: goth subcultures in cyberspace

While Goths tend to be neglected in more mainstream media, they are thriving as part of online communities as part of the phenomenon of net.Goths. This paper considers some of the recent manifestations of such subcultural activities online, especially in relation to the practice of demarcating the boundaries of participation through displays of cultural capital (such as music and fashion), and aspects of communication that have emerged on the Internet such as ?trolling?. The overarching concern of this paper is to explore some of the ways in which defining a subculture virtually may reinforce activities of the group in other environments