Drag and inertia coefficients for horizontally submerged rectangular cylinders in waves and currents

The results of an experimental investigation carried out to measure combined wave and current loads on horizontally submerged square and rectangular cylinders are reported in this paper. The wave and current induced forces on a section of the cylinders with breadth-depth (aspect) ratios equal to 1, 0.5, and 0.75 are measured in a wave tank. The maximum value of Keulegan-Carpenter (KC) number obtained in waves alone is about 5 and Reynolds (Re) number ranged from 6.3976103 to 1.186105. The drag (CD) and inertia (CM) coefficients for each cylinder are evaluated using measured sectional wave forces and particle kinematics calculated from linear wave theory. The values of CD and CM obtained for waves alone have already been reported (Venugopal, V., Varyani, K. S., and Barltrop, N. D. P. Wave force coefficients for horizontally submerged rectangular cylinders. Ocean Engineering, 2006, 33, 11-12, 1669-1704) and the coefficients derived in combined waves and currents are presented here. The results indicate that both drag and inertia coefficients are strongly affected by the presenceof the current and show different trends for different cylinders. The values of the vertical component inertia coefficients (CMY) in waves and currents are generally smaller than the inertia coefficients obtained in waves alone, irrespective of the current's magnitude and direction. The results also illustrate the effect of a cylinder's aspect ratio on force coefficients. This study will be useful in the design of offshore structures whose columns and caissons are rectangular sections

A blind HI survey of the M81 group

Results are presented of the first blind HI survey of the M81 group of galaxies. The data were taken as part of the HI Jodrell All Sky Survey (HIJASS). The survey reveals several new aspects to the complex morphology of the HI distribution in the group. All four of the known dwarf irregular (dIrr) galaxies close to M81 can be unambiguously seen in the HIJASS data. Each forms part of the complex tidal structure in the area. We suggest that at least three of these galaxies may have formed recently from the tidal debris in which they are embedded. The structure connecting M81 to NGC2976 is revealed as a single tidal bridge of mass approx. 2.1 x 10^8 Msol and projected spatial extent approx. 80 kpc. Two `spurs' of HI projecting from the M81 complex to lower declinations are traced over a considerably larger spatial and velocity extent than by previous surveys. The dwarf elliptical (dE) galaxies BK5N and Kar 64 lie at the spatial extremity of one of these features and appear to be associated with it. We suggest that these may be the remnants of dIrrs which has been stripped of gas and transmuted into dEs by close gravitational encounters with NGC3077. The nucleated dE galaxy Kar 61 is unambiguously detected in HI for the first time and has an HI mass of approx.10^8 Msol, further confirming it as a dE/dIrr transitional object. HIJASS has revealed one new possible group member, HIJASS J1021+6842. This object contains approx. 2 x 10^7 Msol of HI and lies approx.105arcmin from IC2574. It has no optical counterpart on the Digital Sky Survey.Comment: To be published in Astrophysical Journal Letters 9 pages, including 3 figure

Rapid change in freshwater content of the Arctic Ocean

Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 36 (2009): L10602, doi:10.1029/2009GL037525.The dramatic reduction in minimum Arctic sea ice extent in recent years has been accompanied by surprising changes in the thermohaline structure of the Arctic Ocean, with potentially important impact on convection in the North Atlantic and the meridional overturning circulation of the world ocean. Extensive aerial hydrographic surveys carried out in March–April, 2008, indicate major shifts in the amount and distribution of fresh-water content (FWC) when compared with winter climatological values, including substantial freshening on the Pacific side of the Lomonosov Ridge. Measurements in the Canada and Makarov Basins suggest that total FWC there has increased by as much as 8,500 cubic kilometers in the area surveyed, effecting significant changes in the sea-surface dynamic topography, with an increase of about 75% in steric level difference from the Canada to Eurasian Basins, and a major shift in both surface geostrophic currents and freshwater transport in the Beaufort Gyre.Support for this work was provided by the National Science Foundation Office of Polar Programs under grants 0352687, 0634097 (MGM); 0633979, 0806115 (AP); 0633885, 0352754, 0634226 (MAS, JHM); and 06341222 (MBA)

Effects of urban density on carbon dioxide exchanges: observations of dense urban, suburban and woodland areas of southern England

Anthropogenic and biogenic controls on the surface–atmosphere exchange of CO2 are explored for three different environments. Similarities are seen between suburban and woodland sites during summer, when photosynthesis and respiration determine the diurnal pattern of the CO2 flux. In winter, emissions from human activities dominate urban and suburban fluxes; building emissions increase during cold weather, while traffic is a major component of CO2 emissions all year round. Observed CO2 fluxes reflect diurnal traffic patterns (busy throughout the day (urban); rush-hour peaks (suburban)) and vary between working days and non-working days, except at the woodland site. Suburban vegetation offsets some anthropogenic emissions, but 24-h CO2 fluxes are usually positive even during summer. Observations are compared to estimated emissions from simple models and inventories. Annual CO2 exchanges are significantly different between sites, demonstrating the impacts of increasing urban density (and decreasing vegetation fraction) on the CO2 flux to the atmosphere

Nonlocal mechanism for cluster synchronization in neural circuits

The interplay between the topology of cortical circuits and synchronized activity modes in distinct cortical areas is a key enigma in neuroscience. We present a new nonlocal mechanism governing the periodic activity mode: the greatest common divisor (GCD) of network loops. For a stimulus to one node, the network splits into GCD-clusters in which cluster neurons are in zero-lag synchronization. For complex external stimuli, the number of clusters can be any common divisor. The synchronized mode and the transients to synchronization pinpoint the type of external stimuli. The findings, supported by an information mixing argument and simulations of Hodgkin Huxley population dynamic networks with unidirectional connectivity and synaptic noise, call for reexamining sources of correlated activity in cortex and shorter information processing time scales.Comment: 8 pges, 6 figure

Photoactivatable prodrugs of antimelanoma agent Vemurafenib

In this study, we report on novel photoactivatable caged prodrugs of vemurafenib. This kinase inhibitor was the first approved drug for the personalized treatment of BRAF-mutated melanoma and showed impressive results in clinical studies. However, the occurrence of severe side effects and drug resistance illustrates the urgent need for innovative therapeutic approaches. To conquer these limitations, we implemented photoremovable protecting groups into vemurafenib. In general, this caging concept provides spatial and temporal control over the activation of molecules triggered by ultraviolet light. Thus, higher inhibitor concentrations in tumor tissues might be reached with less systemic effects. Our study describes the first development of caged vemurafenib prodrugs useful as pharmacological tools. We investigated their photochemical characteristics and photoactivation. <i>In vitro</i> evaluation proved the intended loss-of-function and the light-dependent recovery of efficacy in kinase and cellular assays. The reported vemurafenib photo prodrugs represent a powerful biological tool for novel pharmacological approaches in cancer research