NW-oriented features on both sides of the Atlantic Ocean: evidence for a Paleozoic collision that formed the Labrador-Biscay wrench fault zone?

Northwest-oriented features have been recognized for many years as fundamental components of the geology of the northwestern European continental shelves. Similarly oriented lineations and faults have been mapped throughout southwestern Britain, western France and across the English Channel. On land in Europe, similar trends are identified as far east as the Urals. Features of similar orientation, extending over a broad area on the North American continental shelf, have recently been identified from geophysical trends. On land in eastern Canada NW-SE faults have been mapped geologically and detected using geophysical and remote sensing data. A Mercator projection map on which the Atlantic Ocean has been restored to its pre-Mesozoic configuration, i.e. before the initiation of the most recent opening of the North Atlantic Ocean, shows that the features are similarly oriented. Although some of the trends showing this direction may be younger, the geological data from both sides of the Atlantic Ocean suggest that the event that led to the formation of these NW-SE features post-dated the Variscan orogeny and may have been associated with the collision between Gondwana and Laurasia. The geometric patterns of the features interpreted as associated with the collision are consistent with patterns produced by a simple physical sandbox model of indentation with a rigid confinement to the west and a small lateral confinement to the east. This configuration is similar to that expected of Gondwana and Laurasia during the late Paleozoic. Faults considered younger than this collision may represent tectonic rejuvenations associated with the initiation of the opening of the North Atlantic Ocean. RÉSUMÉ L'orientation obscrvée du nord-est vers le sud-est des formations rocheuses est reconnue depuis de nombreuses années comme une caractéristique géologique fondamentale des plateaux continentaux du nord-ouest de l'Europe. Des structures linéaires et des failles d'orientation similaires ont été répertoriées dans tout le sud-ouest de l'Angleterre, dans I'ouest de la France et à travers la Manche. Sur le continent européen, des tendances analogues ont pu fitre observées aussi loin à l'est que dans la chaine de l''Oural. Ces caractérstiques orientées qui recouvrent une vaste région du plateau continental de l'Amerique du Nord ont récemment été observées à partir de tendances géophysiques. Dans l'Est canadien, des failles orientées NO-SE ont été portées sur des cartes géologiques et déectées a l'aid.e de données géophysiques et de télélédétection. Ces caractéristiques observées ont été portées sur une carte a projection de Mercator oò figure l'océan Atlantique dans sa configuration d'origine pendant l'ère pré-mésozoTque, soit avant que ne s'amorce rouverture la plus récente de l'Atlantique Nord. Ces caractéristiques nsproduisent la même orientation lorsqu'elles sont portées ainsi sur la carte. Bien que certaines des tendances qui signalent cette orientation semblent d'apparition plus récente, les données géologiques des deux côtés de l'Atlantique portent à croire que le phénomène qui a mené la création de ces linéations NO-SE est survenu après l'orogenése de varisque et peut fltre relié à l'hypercollision survenue entre la Gondwanie et la Laurasie. Les formes géomètriques de ces linéations interprétées en relation avec la collision sont du même type que eel les produites dans un modèle d'échancrure géologique dans un simple carré de sable, celles-ci présentant un confinement rigide è l'ouest et un petit confinement latéral è Test. Il s'agit d'une configuration semblable à celle qui serait caractéristique de la Gondwanie et de la Laurasie. Les failles jugés plus récentes et issues de cette collision pourraient être attribuables à une régénération tectonique qui a accompagné le début de rouverture de l'Atlantique Nord. Traduit par la rédactio

The Structure of Real Interest Rates in Chile.

This paper describes the structure of real interest rates (the real yield curve) in Chile and shows its evolution through time. It provides a practical tool for the systematic study of the determinants of Chilean yield curves. Empirical estimations are based on transaction and auction data for Central Bank bonds and pension recognition bonds issued by the government, applying the Nelson and Siegel method. Estimation results are used to measure the liquidity premium in the market maker’s bond yield, simulate the evolution of the very short and long-term rates, and analyze issues of Central Bank zero-coupon bonds and the response of domestic interest rates to local and international economic events.

Range of orbital angular momenta available for complete fusion between heavy ions

The same compound nucleus, 158Er, has been formed through three different entrance channels, with projectiles 16O, 40Ar and 84Kr. Excitation functions for reactions (HI, 5n) and (HI, 6n) are well fitted by statistical model calculations, provided that a certain window in orbital angular momentum should be taken in order to produce complete fusion in the case of Ar ions and Kr ions. Curiously enough, low l-waves should be avoided. It implies that, during the interaction leading to complete fusion, the energy dissipation by tangential friction should be rather large

Education at the Margins of the Political

This paper argues that the political can respond to that which exceeds it without reducing it to the same, and that public education is one of the most important places where this can happen. I present a rationale for public education to assist that which exceeds the political: singularity, solitude and difference. What I maintain is that the political must welcome this excess, especially through public education, or else it would not be possible to provide the educational context for that which might be of significance to individuals without having socio-political value

Projectile fragmentation reactions and production of nuclei near the neutron drip-line

The reaction mechanism of projectile fragmentation at intermediate energies has been investigated observing the target dependence of the production cross sections of very neutron-rich nuclei. Measurement of longitudinal momentum distributions of projectile-like fragments within a wide range of fragment mass and its charge was performed using a hundred-MeV/n $^{40}$Ar beam incident on Be and Ta targets. By measurement of fragment momentum distribution, a parabolic mass dependence of momentum peak shift was observed in the results of both targets, and a phenomenon of light-fragment acceleration was found only in the Be-target data. The analysis of production cross sections revealed an obvious enhancement of the target dependence except target size effect when the neutron excess is increased. This result implies the breakdown of factorization (BOF) of production cross sections for very neutron-rich nuclei near the drip line.Comment: 16 pages, 18 figures, submitted to Phys. Rev.

Tracking the phase-transition energy in disassembly of hot nuclei

In efforts to determine phase transitions in the disintegration of highly excited heavy nuclei, a popular practice is to parametrise the yields of isotopes as a function of temperature in the form $Y(z)=z^{-\tau}f(z^{\sigma}(T-T_0))$, where $Y(z)$'s are the measured yields and $\tau, \sigma$ and $T_0$ are fitted to the yields. Here $T_0$ would be interpreted as the phase transition temperature. For finite systems such as those obtained in nuclear collisions, this parametrisation is only approximate and hence allows for extraction of $T_0$ in more than one way. In this work we look in detail at how values of $T_0$ differ, depending on methods of extraction. It should be mentioned that for finite systems, this approximate parametrisation works not only at the critical point, but also for first order phase transitions (at least in some models). Thus the approximate fit is no guarantee that one is seeing a critical phenomenon. A different but more conventional search for the nuclear phase transition would look for a maximum in the specific heat as a function of temperature $T_2$. In this case $T_2$ is interpreted as the phase transition temperature. Ideally $T_0$ and $T_2$ would coincide. We invesigate this possibility, both in theory and from the ISiS data, performing both canonical ($T$) and microcanonical ($e=E^*/A$) calculations. Although more than one value of $T_0$ can be extracted from the approximate parmetrisation, the work here points to the best value from among the choices. Several interesting results, seen in theoretical calculations, are borne out in experiment.Comment: Revtex, 10 pages including 8 figures and 2 table

The liquid to vapor phase transition in excited nuclei

For many years it has been speculated that excited nuclei would undergo a liquid to vapor phase transition. For even longer, it has been known that clusterization in a vapor carries direct information on the liquid- vapor equilibrium according to Fisher's droplet model. Now the thermal component of the 8 GeV/c pion + 197Au multifragmentation data of the ISiS Collaboration is shown to follow the scaling predicted by Fisher's model, thus providing the strongest evidence yet of the liquid to vapor phase transition.Comment: four pages, four figures, first two in color (corrected typo in Ref. [26], corrected error in Fig. 4