Search results for "Maxim"

The arid–humid transition in the Sahara and the Sahel during the last deglaciation

1990

At the time of the Last Glacial Maximum, the Sahara and Sahel regions of North Africa were extremely dry. New records of rainfall show that during the subsequent deglaciation, the transition from arid to humid conditions in these regions occurred synchronously in two main steps. Comparison with other records of palaeoclimate in Europe and the North Atlantic Ocean shows that certain common factors controlled changes in ocean and atmosphere dynamics during the deglaciation.

2013

To estimate the body temperature (BT) of seven dinosaurs Gillooly, Alleen, and Charnov (2006) used an equation that predicts BT from the body mass and maximum growth rate (MGR) with the latter preserved in ontogenetic growth trajectories (BT-equation). The results of these authors evidence inertial homeothermy in Dinosauria and suggest that, due to overheating, the maximum body size in Dinosauria was ultimately limited by BT. In this paper, I revisit this hypothesis of Gillooly, Alleen, and Charnov (2006). I first studied whether BTs derived from the BT-equation of today’s crocodiles, birds and mammals are consistent with core temperatures of animals. Second, I applied the BT-equation to a …

Dépendance de la fatigue à la longueur musculaire : approche mécanique et neurophysiologique

2006

The objective of this work is to evaluate the fatigue dependency on the knee extensor muscles length. Exercises varying the type of contraction (isometric and eccentric) and intensity of contraction (maximal and sub-maximal) are performed in order to disrupt the neuromuscular system by different factors of fatigue: central and peripheral. These exercises are performed at two muscular lengths (S and L, corresponding respectively to 40 and 100° of knee flexion). Neuromuscular parameters (maximal torque, muscular twitch, voluntary activation level, electromyographic activity, etc.) are analyzed in pre- and post-fatigue conditions in the type of contraction required by the fatiguing exercise. I…

Time of emergence of Mediterranean summer maximum temperature.

2016

The time at which the signalof climate change emerges from the noise of natural climate variability is called “time of emergence”. This timeis analyzed here based on summertime mean maximum temperature in the Mediterranean basin for RCP8.5 andRCP4.5 scenarios. This time would be around 2040-50 (2060-70) in the eastern (western) basin. Differencesbetween the optimistic and pessimistic scenarios give a mean shift of around 15 years with the time ofemergence occurring earlier for RCP8.5 scenario.

“SEE, HEAR, REMAIN SILENT AND… BORED” IN THE FIELDWORK OF A PRISON: AN AUTOETHNOGRAFIC STORY

2017

Como modalidad de investigación narrativa, la autoetnografía enfatiza la parte más personal del proceso de investigación. En este artículo, el relato autoetnográfico se utiliza para reflexionar sobre el trabajo de campo de un estudio etnográfico previo desarrollado en el polideportivo de una prisión de máxima seguridad española. Los datos recogidos en aquella ocasión han sido reexaminados ahora para explicitar críticamente los pasos dados. De este modo, se ponen de manifiesto tanto los dilemas éticos enfrentados, las complejas relaciones sociales que el proceso de investigación encerró, así como la falibilidad de las decisiones tomadas. 

Dual-polarization-pump CW laser operation in Nd3+:LiNbO3 channel waveguides fabricated by reverse proton exchange

2008

Abstract In this work, continuous-wave laser action at 1084.5 nm at room temperature in LiNbO 3 :Nd 3+ channel waveguides, fabricated by reverse proton exchange (RPE), is reported. The sample was pumped at λ  = 808 nm in either σ or π-polarized configurations, TE- and TM-pumping schemes, being the laser emission π-polarized at all power levels. The laser characteristics, as function of the pumping scheme (TE or TM), have been obtained. In both cases, the laser emission was stable, without any reduction in the output power even under continuous pump operation at maximum power at room temperature, indicating high resistance to photorefractive damage.

Hidden Mediterranean diversity: Assessing species taxa by molecular phylogeny within the opilionid family Trogulidae (Arachnida, Opiliones)

2009

This is the first comprehensive study to evaluate the relationships between the western palearctic harvestman families Dicranolasmatidae, Trogulidae and Nemastomatidae with focus on the phylogeny and systematics of Trogulidae, using combined sequence data of the nuclear 28S rRNA and the mitochondrial cytochrome b gene. Bayesian analysis and Maximum parsimony do not reliably resolve Dicranolasma as distinct family but place it on a similar phylogenetic level as several lineages of Trogulidae. Nemastomatidae and Trogulidae turned out to be monophyletic, as did genera Anelasmocephalus and Trogulus within the Trogulidae. The genera Calathocratus, Platybessobius and Trogulocratus each appeared p…

Aminolysis of monoacetyl derivatives of 2,2′ -dihydroxydiphenylmethanes

1974

A neighboring group effect was found for the aminolysis of the second acetyl group in acetates of 2,2′-dihydroxydiphenylmethane derivatives containing a nitrophenol and a methylphenol unit. Kinetic measurements with an excess of n-butylamine in dioxane were done with 2-(2-hydroxy-3, 5-dinitrobenzyl)-4-methylphenyl acetate (1), 2-(2-hydroxy-5-nitro-benzyl)-4-methylphenyl acetate (2), and 2-(2-hydroxy-3-nitro-5-methylbenzyl)-4-methyl-phenyl acetate (3). The maximum rate was found for compound 2. When the concentration of n-butylamine was varied over a large range, the results obtained for compound 2 could be explained best, by assuming that the acetyl group in the methylphenol unit is aminoli…

A nonlocal problem arising from heat radiation on non-convex surfaces

1997

We consider both stationary and time-dependent heat equations for a non-convex body or a collection of disjoint conducting bodies with Stefan-Boltzmann radiation conditions on the surface. The main novelty of the resulting problem is the non-locality of the boundary condition due to self-illuminating radiation on the surface. Moreover, the problem is nonlinear and in the general case also non-coercive. We show that the non-local boundary value problem admits a maximum principle. Hence, we can prove the existence of a weak solution assuming the existence of upper and lower solutions. This result is then applied to prove existence under some hypotheses that guarantee the existence of sub- and…

FINITE ELEMENT APPROXIMATION OF NONLOCAL HEAT RADIATION PROBLEMS

1998

This paper focuses on finite element error analysis for problems involving both conductive and radiative heat transfers. The radiative heat exchange is modeled with a nonlinear and nonlocal term that also makes the problem non-monotone. The continuous problem has a maximum principle which suggests the use of inverse monotone discretizations. We also estimate the error due to the approximation of the boundary by showing continuous dependence on the geometric data for the continuous problem. The final result of this paper is a rigorous justification and error analysis for methods that use the so-called view factors for numerical modeling of the heat radiation.