Effects of very high turbulence on convective heat transfer

The effects of high-intensity, large-scale turbulence on turbulent boundary-layer heat transfer are studied. Flow fields were produced with turbulence intensities up to 40% and length scales up to several times the boundary layer thickness. In addition, three different types of turbulence will be compared to see whether they have the same effect on the boundary layer. The three are: the far field of a free jet, flow downstream of a grid, and flow downstream of a simulated gas turbine combustor. Each turbulence field will be characterized by several measures: intensity (by component), scale, and spectrum. Heat transfer will be measured on a 2.5 m long, 0.5 m wide flat plate using the energy-balance technique. The same plate will be used in each of the four flow fields; a low-turbulence tunnel for baseline data, and the three flow situations mentioned

Stellar and Molecular Gas Kinematics of NGC1097: Inflow Driven by a Nuclear Spiral

We present spatially resolved distributions and kinematics of the stars and molecular gas in the central 320pc of NGC1097. The stellar continuum confirms the previously reported 3-arm spiral pattern extending into the central 100pc. The stellar kinematics and the gas distribution imply this is a shadowing effect due to extinction by gas and dust in the molecular spiral arms. The molecular gas kinematics show a strong residual (i.e. non-circular) velocity, which is manifested as a 2-arm kinematic spiral. Linear models indicate that this is the line-of-sight velocity pattern expected for a density wave in gas that generates a 3-arm spiral morphology. We estimate the inflow rate along the arms. Using hydrodynamical models of nuclear spirals, we show that when deriving the accretion rate into the central region, outflow in the disk plane between the arms has to be taken into account. For NGC1097, despite the inflow rate along the arms being ~1.2Msun/yr, the net gas accretion rate to the central few tens of parsecs is much smaller. The numerical models indicate that the inflow rate could be as little as ~0.06Msun/yr. This is sufficient to generate recurring starbursts, similar in scale to that observed, every 20-150Myr. The nuclear spiral represents a mechanism that can feed gas into the central parsecs of the galaxy, with the gas flow sustainable for timescales of a Gigayear.Comment: accepted by Ap

A search for transit timing variation

Photometric follow-ups of transiting exoplanets (TEPs) may lead to discoveries of additional, less massive bodies in extrasolar systems. This is possible by detecting and then analysing variations in transit timing of transiting exoplanets. In 2009 we launched an international observing campaign, the aim of which is to detect and characterise signals of transit timing variation (TTV) in selected TEPs. The programme is realised by collecting data from 0.6--2.2-m telescopes spread worldwide at different longitudes. We present our observing strategy and summarise first results for WASP-3b with evidence for a 15 Earth-mass perturber in an outer 2:1 orbital resonance.Comment: Poster contribution to Detection and Dynamics of Transiting Exoplanets (Haute Provence Observatory Colloquium, 23-27 August 2010

Diversity among posterior thalamoperforating branches originated from P1 segment: systematic review

Background: The P1 segment of the posterior cerebral artery (PCA) begins at the termination of the basilar artery and ends at the origin of posterior commu­nicating artery, within the interpeduncular cistern. Perforating branches arising from this segment are called posterior thalamoperforating arteries (TPAs) and the main and biggest artery among those is called TPA. Perforating branches are a crucial component of cerebrovascular system supplying the posterior part of the thalamus, subthalamus, hypothalamus, substantia nigra, perforated substance, posterior part of internal capsule and the nucleus of III and IV cranial nerve. It is very important for neurosurgeon to know the anatomy of perforating branches because of their susceptibility to injury. The aim of this study is to determine the morphometry of posterior TPAs and allow a better understanding of their bran­ching patterns and relation to basilar artery. Materials and methods: An extensive search was undertaken in order to identify published literature related to the posterior cerebral circulation system and the anatomy of posterior TPAs using key words. Medline, Embase, Ovid and Google Scholar databases were searched for publications dated from 1970 until July 2016. We collected and analysed all the data describing the mean number of branches per P1 segment, range of branches, number of analysed PCA, largest diameter of TPA, mean diameter of TPA and average distance from the basilar artery bifurcation. Results: Thirteen cadaver studies were analysed and the data was extracted. We focused on the mean number of branches arising from P1 segment, perforators range, mean diameter of perforating branches, largest diameter of perforating branches. Conclusions: Mean number of branches per hemisphere was 2.91 (min. 1.51, max. 4.1). In more than half of analysed studies, authors did not find any pre­sence of posterior TPAs. Mean diameter of those perforators was 0.51 mm (min. 0.125 mm, max. 0.8 mm). Average distance from basilar artery bifurcation was 2.29 mm (min. 1.93 mm, max. 2.75 mm). There were many branching patterns presented by different authors

Food System Transformation: Integrating a Political-Economy and Social-Ecological Approach to Regime Shifts.

Sustainably achieving the goal of global food security is one of the greatest challenges of the 21st century. The current food system is failing to meet the needs of people, and at the same time, is having far-reaching impacts on the environment and undermining human well-being in other important ways. It is increasingly apparent that a deep transformation in the way we produce and consume food is needed in order to ensure a more just and sustainable future. This paper uses the concept of regime shifts to understand key drivers and innovations underlying past disruptions in the food system and to explore how they may help us think about desirable future changes and how we might leverage them. We combine two perspectives on regime shifts-one derived from natural sciences and the other from social sciences-to propose an interpretation of food regimes that draws on innovation theory. We use this conceptualization to discuss three examples of innovations that we argue helped enable critical regime shifts in the global food system in the past: the Haber-Bosch process of nitrogen fixation, the rise of the supermarket, and the call for more transparency in the food system to reconnect consumers with their food. This paper concludes with an exploration of why this combination of conceptual understandings is important across the Global North/ Global South divide, and proposes a new sustainability regime where transformative change is spearheaded by a variety of social-ecological innovations

Exploring geo-genealogy using internet surname search histories

We present an interactive flow map to visualize aspects of the ways in which surnames have dispersed and migrated around the globe. This work utilizes Internet search queries from the Worldnames Project and uses the density of search locations to determine the node and leaf structures of a flow map. The mapping technique utilized in this work is a variant of geometric minimal Steiner arborescences called the spiral tree. Our implementation is developed in JavaScript to allow for interactive online exploration. Nodes and flow lines can be interactively modified to allow for esthetic changes of color and layout. The results can provide interesting insight into the geography of amateur genealogy