The collision branching process

We consider a branching model, which we call the collision branching process (CBP), that accounts for the effect of collisions, or interactions, between particles or individuals. We establish that there is a unique CBP, and derive necessary and sufficient conditions for it to be nonexplosive. We review results on extinction probabilities, and obtain explicit expressions for the probability of explosion and the expected hitting times. The upwardly skip-free case is studied in some detail.

Book review of Mark McGillivray and Gary Smith's (eds.) "Australia and Asia", Melbourne: Oxford University Press, 1997. vii + 248 pp

The political capital invested in Australia's engagement with Asia over the past decade has sparked a lively discussion in the Australian academic community. The back cover of the book under review suggests that there are 'few bigger contemporary issues facing Australia than its relationship with Asia'. If the volume of scholarly material being produced on this issue is any indication, they are right. Like a number of similar works covering the shift in Australian foreign, defence, and trade policies towards Asia over the last decade, this book acknowledges a particular debt of gratitude to the Keating government for establishing regional engagement at the forefront of our national consciousness. Unlike some others however, this book seeks to place Australia's more recent 'discovery' of Asia into a broader historical framework.

John Waldridge, The Leaven of the Ancients: Suhrawardi and the Heritage of the Greeks, SUNY Series in Islam (Albany: State University of New York Press, 1999). Pp. 323

In the Leaven of the Ancients, John Walbridge studies the appropriation of non–Peripatetic philosophical ideas by an anti–Aristotelian Islamic philosopher, Shihab al-Din al-Suhrawardi (d. 1191). He proposes a comprehensive explanation of the origin of Suhrawardi's philosophical system, a revival of the “wisdom of the Ancients” and its philosophical affiliations “grounded” in Greek philosophy (p. xiii). Walbridge attempts to uncover the reasons for Suhrawardi's rejection of the prevailing neo–Aristotelian synthesis in Islamic philosophy, Suhrawardi's knowledge and understanding of non–Aristotelian Greek philosophy, the ancient philosophers Suhrawardi was attempting to follow, the relationship between Suhrawardi's specific philosophical teachings (logic, ontology, physics, and metaphysics), and his understanding of non–Aristotelian ancient philosophy and the relationship between Suhrawardi's system and the major Greek philosophers, schools, and traditions—in particular the Presocratics, Plato, and the Stoics (p. 8). Copyright © 2003 Cambridge University Press

The influence of collision energy and strain accumulation on the kinetics of mechanical alloying

The kinetics of mechanical alloying have been investigated by examining the effect that ball mass has on the rate at which titanium carbide forms from the elements. By varying the ball density while keeping the ball diameter and the charge ratio constant, the collision energy was independently controlled. Grinding media with a density from 3.8 g cm(-3) (agate) to 16.4 g cm(-3) (tungsten carbide) were used. The reaction rate increases exponentially with ball mass until a critical level is reached, which is determined by the induced temperature rise. Above this level, collisions of higher energy have no advantage. It is also shown that the reaction rate increases exponentially with the rate at which strain accumulates in the reactants. It is suggested that the strain accumulation rate in mechanically induced reactions is analogous to temperature in thermally induced chemical reactions.

Synchronous collision malignant melanoma and adenocarcinoma of the rectum

Collision tumors consist of two independent but coexisting tumors. This uncommon situation might be easily mistaken for a composite tumor where one histogenetic event originates from two apparently distinct neoplasms. Colorectal collisions are particularly unusual; here, we report the exceedingly rare case of a 61-year-old man with malignant melanoma and adenocarcinoma colliding in the rectum. Collision tumors have an idiopathic pathophysiology and in fact ""accidental meeting"" is accepted by many authors. This article discusses the concepts about cancer development, which are overlooked by this hypothesis, another theory to explain that this rare occurrence involves microenvironment changes.

Kinematics of oblique collision and ramping inferred from microstructures and strain in middle crustal rocks, central Southern Alps, New Zealand

The hanging wall of the Alpine Fault near Franz Josef Glacier has been exhumed during the past similar to2-3 m.y. providing a sample of the ductilely deformed middle crust of a modem obliquely convergent orogen. Presently exposed rocks of the Pacific Plate are inferred to have undergone several phases of ductile deformation as they moved westward above a mid-crustal detachment. Initially they were transpressed across the outboard part of the orogen, resulting in oblate fabrics with a down-dip stretch. Later, they encountered the Alpine Fault, experiencing an oblique-slip backshearing on vertical planes. This escalator-like deformation tilted and thinned the incoming crust onto that crustal-scale oblique ramp. This style of hanging wall deformation may affect only the most rapidly uplifting, central part of the Southern Alps because of the low flexural rigidity of the crust in that region and its displacement over a relatively sharp ramp-angle at depth. A 3D transpressive flow affected mylonites locally near the fault, but their shear direction remained parallel to plate motion, ruling out ductile 'extrusion' as an important process in this orogen. Outside the mylonite zone, late Cenozoic shortening is inferred to be modest (30-40%), as measured from deformation of younger biotite grains. Oblique collision is dominated by translation on the Alpine Fault, and rocks migrate rapidly through the deforming zone, preventing the accumulation of large finite strains. Transpression may play a minor role in oblique collision. (C) 2001 Elsevier Science Ltd. All rights reserved.