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Rayleigh adjustment of narrow barriers in protoplanetary discs

Sharp density features in protoplanetary discs, for instance at the edge of a magnetically dead zone, have recently been proposed as effective barriers to slow down or even stop the problematically fast migration of planetary cores into their central star. Density features on a radial scale approaching the disc vertical scaleheight might not exist, however, since they could be Rayleigh (or more ge

Henry Diab om försoningsavtalet mellan Hamas och Fatah

Nu förra veckan den 5e Maj så skrev de Palestinska organizationerna Hamas och Fatah under ett försoningsavtal som kan ha stora konsekvenserna för den framtida fredsprocessen mellan Israel och Palestina. UPFs reporter Samuel Teeland har talat med Henry Diab,för att höra om hur avtalet förhandlats fram och vilka möjliga effekter det kan ha.

Strategic Alliances within the security realm

Overall the survey showed a very strong faith in alliances with a strategic perspective. There was an equal strong belief in soft variables around alliance success, such as leadership, trust and cultural issues. But as it turns out what really matters are arduous factors such as operations, middle management and formalized routines, processes and responsibilities. All evidence also points to the f

Analysis of intercooler in pem fuel cell systems

Heat exchangers are used in proton exchange membrane fuel cell systems (PEMFCs) for stack cooling, intercooling, water condensation and fuel reforming. Especially, the heat exchanger for the intercooling before the humidifier is investigated in this paper. It is found that, at high pressure or high mass flow rate, the need to cool the air (oxidant) is large. The heat exchanger uses coolant water f

Statistical evaluation of outdoor-to-indoor office MIMO measurements at 5.2 GHz

In this paper, we present a statistical evaluation of an outdoor-to-indoor multiple-input multiple-output (MIMO) measurement campaign performed at 5.2 GHz. 159 measurement locations in an office building are analyzed. Our analysis pays special attention to two key assumptions that are widely used in stochastic channel models. An assumption that is used in practically every channel model is that th

On the role of migration for the distribution of arctic birds - a circumpolar perspective

Popular Abstract in Swedish Om flyttningens betydelse för utbredningsmönster för arktiska fåglar Sara Henningsson Fågelflyttning är en anmärkningsvärt framgångsrik strategi som möjliggör att en större mängd individer kan försörjas genom rörelser mellan olika regioner. Inom dessa olika områden, som ofta ligger mycket långt ifrån varandra, kan fåglarna utnyttja stora säsongsmässigt tillgängliga resFlexibility as well as constraints to the evolution of migration routes has the possibility of affecting large-scale patterns of geographical ranges of animals both by facilitating, but sometimes restricting, accessibility to and colonization of new regions. This dissertation concerns the broad-scale effects migration has on the distributional patterns of birds in the Arctic. I studied the circum

Seasonal variations of atmospheric trace gases in the high Arctic at 79 degrees N

Since March 1992 the total column abundances of several tropospheric and stratospheric trace gases have been monitored year-round from the Network for Detection of Stratospheric Change station in Ny Alesund, Spitsbergen (78.9 degrees N, 11,9 degrees E). A groundbased Fourier transform infrared (FTIR) spectrometer performed these measurements using the Sun as a light source during the summer, and t

Photochemical reactions in biological light perception and regulation

Many photochemical reactions involved in the sensing of and regulation by light and ultraviolet radiation by organisms consist of cis-trans (and trans-cis) isomerisations. This chapter starts with a description of these, and then goes on to the blue-light receptors crypto-chrome and phototropin, which use other chemical mechanisms, and concludes with a discus-sion of ultraviolet-B receptors.

On braided block codes

Two families of braided block codes are analyzed, tightly braided block codes and sparsely braided block codes. Bounds on the free distance of tightly braided block codes are derived. Asymptotic iterative decoding performance of sparsely braided block codes is studied