Dolomitization Processes in Hydrocarbon Reservoirs: Insight from Geothermometry Using Clumped Isotopes

Clumped isotopes geothermometry was applied to two dolomitic hydrocarbon reservoirs. Results indicate that late burial dolomitization occurred at ~110°C in the Albian Pinda dolostone (offshore Angola) and ~90°C in the Mano-Meillon dolostone (Aquitaine Basin, France), and did not continue on during subsequent burial/thermal evolution to present-day conditions (150-160°C). This study illustrates the great potential of the clumped isotopes approach to help unravel dolomitization processes in hydrocarbon reservoirs

CHA visit to the War Museum

During CHA council meetings last November of 2006 CHA council members were given a first-rate tour of the recently completed Canadian War Museum, located on the LeBreton Flats, a plain of wetland and former industrial land adjascent to networks of mill races and hydro dams on the right bank of the Ottawa River. The tour was given by CWM World War. One curator and historian Tim Cook. The tour allowed visitors to take in the remarkable breadth, chronological and thematic, of the CWM permanent exhibition, from the pre-contact(native) ways of fighting to the Seven Years War and all the way up to and well into the 20th century marked by two World Wars, the Korean War etc. Dr. Cook shared with visitors the challenges of preparing a display — what works, what does not work

Solving kk-SUM using few linear queries

The $k$-SUM problem is given $n$ input real numbers to determine whether any $k$ of them sum to zero. The problem is of tremendous importance in the emerging field of complexity theory within $P$, and it is in particular open whether it admits an algorithm of complexity $O(n^c)$ with $c<\lceil \frac{k}{2} \rceil$. Inspired by an algorithm due to Meiser (1993), we show that there exist linear decision trees and algebraic computation trees of depth $O(n^3\log^3 n)$ solving $k$-SUM. Furthermore, we show that there exists a randomized algorithm that runs in $\tilde{O}(n^{\lceil \frac{k}{2} \rceil+8})$ time, and performs $O(n^3\log^3 n)$ linear queries on the input. Thus, we show that it is possible to have an algorithm with a runtime almost identical (up to the $+8$) to the best known algorithm but for the first time also with the number of queries on the input a polynomial that is independent of $k$. The $O(n^3\log^3 n)$ bound on the number of linear queries is also a tighter bound than any known algorithm solving $k$-SUM, even allowing unlimited total time outside of the queries. By simultaneously achieving few queries to the input without significantly sacrificing runtime vis-\`{a}-vis known algorithms, we deepen the understanding of this canonical problem which is a cornerstone of complexity-within-$P$. We also consider a range of tradeoffs between the number of terms involved in the queries and the depth of the decision tree. In particular, we prove that there exist $o(n)$-linear decision trees of depth $o(n^4)$

Exploring, Engaging, Understanding in Museums

Patterns of accessibility through the space of the exhibition, connections or separations among spaces or exhibition elements, sequencing and grouping of elements, form our perceptions and shape our understanding. Through a review of several previous studies and the presentation of new work, this paper suggests that these patterns of movement form the basis of visitor understanding and that these effects can be deliberately controlled and elaborated through a closer examination of the influence of the visual and perceptual properties of an exhibition. Furthermore, it is argued that there is also a spatial discourse based on patterns of access and visibility that flows in its own right, although not entirely separate from the curatorial narrative

Alterglobalization, Global Social Movements, and the Possibility of Political Transformation Through Sport

Alterglobalization is the name for a large spectrum of global social movements that present themselves as supporting new forms of globalization, urging that values of democracy, justice, environmental protection, and human rights be put ahead of purely economic concerns. This article develops a framework for the study of the influence of alterglobalization on sport by: outlining a periodization of social move¬ments and sport; proposing a typology of responses to the politics of globalization; and proposing a typology of recent social movements associated with sport. The arti¬cle does not report on an empirical research project, but provides a stock take of what has happened since the 1990s regarding the politics of globalization and the politics of sport, with specific reference to global social movements. The questions raised in this article include: What form do the movements challenging the world sports order today take? Does an alterglobalization movement exist in sport? What alternative models of sport do they propose

Practical improvements to class group and regulator computation of real quadratic fields

We present improvements to the index-calculus algorithm for the computation of the ideal class group and regulator of a real quadratic field. Our improvements consist of applying the double large prime strategy, an improved structured Gaussian elimination strategy, and the use of Bernstein's batch smoothness algorithm. We achieve a significant speed-up and are able to compute the ideal class group structure and the regulator corresponding to a number field with a 110-decimal digit discriminant

The secular evolution of discrete quasi-Keplerian systems. I. Kinetic theory of stellar clusters near black holes

We derive the kinetic equation that describes the secular evolution of a large set of particles orbiting a dominant massive object, such as stars bound to a supermassive black hole or a proto-planetary debris disc encircling a star. Because the particles move in a quasi-Keplerian potential, their orbits can be approximated by ellipses whose orientations remain fixed over many dynamical times. The kinetic equation is obtained by simply averaging the BBGKY equations over the fast angle that describes motion along these ellipses. This so-called Balescu-Lenard equation describes self-consistently the long-term evolution of the distribution of quasi-Keplerian orbits around the central object: it models the diffusion and drift of their actions, induced through their mutual resonant interaction. Hence, it is the master equation that describes the secular effects of resonant relaxation. We show how it captures the phenonema of mass segregation and of the relativistic Schwarzschild barrier recently discovered in $N$-body simulations.Comment: 24 pages, 3 figure