Brane-world creation and black holes

An inflating brane world can be created from ``nothing'' together with its anti-de Sitter (AdS) bulk. The resulting space-time has compact spatial sections bounded by the brane. During inflation, the continuum of KK modes is separated from the massless zero mode by the gap m=(3/2)H, where H is the Hubble rate. We consider the analogue of the Nariai solution and argue that it describes the pair production of ``black cigars'' attached to the inflating brane. In the case when the size of the instantons is much larger than the AdS radius, the 5-dimensional action agrees with the 4-dimensional one. Hence, the 5D and 4D gravitational entropies are the same in this limit. We also consider thermal instantons with an AdS black hole in the bulk. These may be interpreted as describing the creation of a hot universe from nothing or the production of AdS black holes in the vicinity of a pre-existing inflating brane world. The Lorentzian evolution of the brane world after creation is briefly discussed. An additional ``integration constant'' in the Friedmann equation-accompanying a term which dilutes like radiation-describes the tidal force in the fifth direction and arises from the mass of a spherical object inside the bulk. In general, this could be a 5-dimensional black hole or a ``parallel'' brane world of negative tension concentrical with our brane-world. In the case of thermal solutions, and in the spirit of the AdS/CFT correspondence, one may attribute the additional term to thermal radiation in the boundary theory. Then, for temperatures well below the AdS scale, the entropy of this radiation agrees with the entropy of the black hole in the AdS bulk.

Gravity in the Randall-Sundrum brane world

We discuss the weak gravitational field created by isolated matter sources in the Randall-Sundrum brane world. For the case of a single wall of positive tension, the field stays localized near the wall if the source is stationary. We calculate the leading Kaluza-Klein corrections to the linearized gravitational field of a nonrelativistic spherical object, which is different from the Schwarzschild solution at large distances. In the case of two branes of opposite tension, linearized Brans-Dicke (BD) gravity is recovered on either wall, with different BD parameters. On the wall with positive tension the BD parameter is larger than 3000 provided that the separation between walls is larger than 4 times the AdS radius. The gravitational field due to shadow matter is also considered.

Topology of the world trade web

Economy, and consequently trade, is a fundamental part of human social organization which, until now, has not been studied within the network modeling framework. Here we present the first, to the best of our knowledge, empirical characterization of the world trade web, that is, the network built upon the trade relationships between different countries in the world. This network displays the typical properties of complex networks, namely, scale-free degree distribution, the small-world property, a high clustering coefficient, and, in addition, degree-degree correlation between different vertices. All these properties make the world trade web a complex network, which is far from being well described through a classical random network description.

The First World War and coal trade geography in Latin America and the Caribbean (1890-1930)

This paper aims to illustrate the dynamics of coal trade between Latin America and its main trade partners, i.e. the USA, Great Britain and Germany, before and after the enormous disruption caused by the First World War. The coal trade was used as an indicator of modernization for Latin American countries, given that oil was at that time of secondary importance. Energy imports have determined the possibilities of each Latin American country in its process of development. Here we address this question and place special emphasis on supply channels, concluding that the trade link with main suppliers was of key significance. Although this was very clear by the end of the period, the process had started well before the First World War, at least for the majority of LA&C countries. These points are developed through a gravity model applied to the bilateral coal trade. The importance of the market supplier share is addressed through cluster methodologies.

[The World's Columbian Exposition. Portfolio of views issued by the Department of photography, C.D. Arnold, chief. Chicago and St. Louis, National Chemigraph Company, 1893, 36 phot., don du marquis Davidsard en 1930]

Donateur : Davidsard (18..-18.. ; marquis)

Alterations of Neuromuscular Function after the World's Most Challenging Mountain Ultra-Marathon

We investigated the physiological consequences of the most challenging mountain ultra-marathon (MUM) in the world: a 330-km trail run with 24000 m of positive and negative elevation change. Neuromuscular fatigue (NMF) was assessed before (Pre-), during (Mid-) and after (Post-) the MUM in experienced ultra-marathon runners (n = 15; finish time = 122.43 hours +/-17.21 hours) and in Pre- and Post- in a control group with a similar level of sleep deprivation (n = 8). Blood markers of muscle inflammation and damage were analyzed at Pre- and Post-. Mean +/- SD maximal voluntary contraction force declined significantly at Mid- (-13+/-17% and -10+/-16%, P<0.05 for knee extensor, KE, and plantar flexor muscles, PF, respectively), and further decreased at Post- (-24+/-13% and -26+/-19%, P<0.01) with alteration of the central activation ratio (-24+/-24% and -28+/-34% between Pre- and Post-, P<0.05) in runners whereas these parameters did not change in the control group. Peripheral NMF markers such as 100 Hz doublet (KE: -18+/-18% and PF: -20+/-15%, P<0.01) and peak twitch (KE: -33+/-12%, P<0.001 and PF: -19+/-14%, P<0.01) were also altered in runners but not in controls. Post-MUM blood concentrations of creatine kinase (3719+/-3045 Ul.1), lactate dehydrogenase (1145+/-511 UI.L-1), C-Reactive Protein (13.1+/-7.5 mg.L-1) and myoglobin (449.3+/-338.2 microg.L-1) were higher (P<0.001) than at Pre- in runners but not in controls. Our findings revealed less neuromuscular fatigue, muscle damage and inflammation than in shorter MUMs. In conclusion, paradoxically, such extreme exercise seems to induce a relative muscle preservation process due likely to a protective anticipatory pacing strategy during the first half of MUM and sleep deprivation in the second half.

Going the distance: human population genetics in a clinal world.

Global human genetic variation is greatly influenced by geography, with genetic differentiation between populations increasing with geographic distance and within-population diversity decreasing with distance from Africa. In fact, these 'clines' can explain most of the variation in human populations. Despite this, population genetics inferences often rely on models that do not take geography into account, which could result in misleading conclusions when working at global geographic scales. Geographically explicit approaches have great potential for the study of human population genetics. Here, we discuss the most promising avenues of research in the context of human settlement history and the detection of genomic elements under natural selection. We also review recent technical advances and address the challenges of integrating geography and genetics.

Building World-Class Schools for Iowa: A Legislative Brief, January 14, 2013

The Iowa Department of Education has joined the Office of the Governor to prepare a set of legislative proposals that will bring Iowa closer to its goal of providing a world-class education to all children, no mater where they live. This legislative brief serves as an overview of the legislation, which I encourage you to read and discuss in greater detail. the goals behind these policies are straightforward: Comprehensive and systematically raise and support the teaching profession while expanding efforts to customize instruction to every student's passion and talents. Iowa's children deserve the best education can provide so they leave our schools with the knowledge and skills necessary for successful and rewarding lives. Iowa has many good schools with hard-working, talented educators who deserves our respect and appreciation. While we honor the past work of generations of Iowans who built a strong foundation, it is our responsibility - and our turn - to make a focused, dedicated effort to improve Iowa's schools. We stand at a pivotal moment in Iowa storied education history, in which we have the opportunity and will as community to make the transition from being "good" to being "great".