On Classical Motion

The impetus theory of motion states that to be in motion is to have a non-zero velocity. The at-at theory of motion states that to be in motion is to be at different places at different times, which in classical physics is naturally understood as the reduction of velocities to position developments. I first defend the at-at theory against the criticism raised by Arntzenius that it renders determinism impossible. I then develop a novel impetus theory of motion that reduces positions to velocity developments. As this impetus theory of motion is by construction a mirror image of the at-at theory of motion, I claim that the two theories of motion are in fact epistemically on par—despite the unfamiliar metaphysical picture of the world furnished by the impetus version

Did the Universe Have a Chance?

In a world awash in statistical patterns, should we conclude that the universe’s evolution or genesis is somehow subject to chance? I draw attention to alternatives that must be acknowledged if we are to have an adequate assessment of what chance the universe might have had

Investigation of nickel hydrogen battery technology for the RADARSAT spacecraft

The low Earth orbit (LEO) operations of the RADARSAT spacecraft require high performance batteries to provide energy to the payload and platform during eclipse period. Nickel Hydrogen cells are currently competing with the more traditional Nickel Cadmium cells for high performance spacecraft applications at geostationary Earth orbit (GEO) and Leo. Nickel Hydrogen cells appear better suited for high power applications where high currents and high Depths of Discharge are required. Although a number of GEO missions have flown with Nickel Hydrogen batteries, it is not readily apparent that the LEO version of the Nickel Hydrogen cell is able to withstand the extended cycle lifetime (5 years) of the RADARSAT mission. The problems associated with Nickel Hydrogen cells are discussed in the contex of RADARSAT mission and a test program designed to characterize cell performance is presented

Spin-spin Correlation in Some Excited States of Transverse Ising Model

We consider the transverse Ising model in one dimension with nearest-neighbour interaction and calculate exactly the longitudinal spin-spin correlation for a class of excited states. These states are known to play an important role in the perturbative treatment of one-dimensional transverse Ising model with frustrated second-neighbour interaction. To calculate the correlation, we follow the earlier procedure of Wu, use Szego's theorem and also use Fisher-Hartwig conjecture. The result is that the correlation decays algebraically with distance ($n$) as $1/\surd n$ and is oscillatory or non-oscillatory depending on the magnitude of the transverse field.Comment: 5 pages, 1 figur

Rectifying Horizontal Inequalities: Lessons from African Conflict

In Africa, the decade of the nineteen nineties was characterised by civil war and interstate conflict, but as the decade came to a close and a new millennium emerged many of the protracted conflicts in Africa had officially come to an end. The official resolution of conflict in Sierra Leone, the Democratic Republic of the Congo, Sudan, Liberia and Côte d'Ivoire has helped stem the rampant instability that has plagued the continent for most of its postcolonial history. With the newly established peace agreements comes an even more critical and difficult challenge of creating peaceful societies in these war-ravaged nations. In order to rebuild a nation, one must examine and acknowledge the root causes of the conflict. One of the most prevalent and underrepresented root causes of conflict in Africa and worldwide is that of horizontal inequalities. In that light, the goal of this paper is to provide practical solutions for the long-term resolution of conflict by addressing one of its root causes, that of horizontal inequalities. Reference will be made to solutions proven successful in past cases where conflict emerged as a result of group inequalities, namely Rwanda and Mali. The paper will take the following form: Section one will look at the current literature on conflict and demonstrate the link between horizontal inequalities and conflict. Section two will focus on the two case studies providing background to the conflict, and the action taken after violent conflict ceased. Section three will be dedicated to the lessons learned from the Malian and the Rwandan experience, including policy recommendations that should be instituted for any nation where horizontal inequalities are a major catalyst of conflict.African Journal on Conflict Resolution Vol. 8 (1) 2008: pp. 105-13

Critical Global Health: Responding to Poverty, Inequality and Climate Change

A recent article by Sol Benatar calls on the global health community to reassess its approach to twin crises of global poverty and climate change. I build on his article by challenging mainstream narratives that claim satisfactory progress in efforts to reduce poverty and improve health for all, and arguing that any eradication of poverty that is consistent with environmental sustainability will require a more explicit emphasis on the redistribution of power and wealth. I suggest that the global health community has been largely socialised into accepting that progress and future solutions can be attained through more neoliberal development, technological advancement and philanthropic endeavour and that a more critical global health is required. I propose three steps that the global health community should take: first, create more space for the social, political and political sciences within global health; second, be more prepared to act politically and challenge power; and third, do more to bridge the global-local divide in recognition of the fact that progressive change requires mobilisation from the bottom-up in conjunction with top-down policy and legislative change

Exact solution of a 2d random Ising model

The model considered is a d=2 layered random Ising system on a square lattice with nearest neighbours interaction. It is assumed that all the vertical couplings are equal and take the positive value J while the horizontal couplings are quenched random variables which are equal in the same row but can take the two possible values J and J-K in different rows. The exact solution is obtained in the limit case of infinite K for any distribution of the horizontal couplings. The model which corresponds to this limit can be seen as an ordinary Ising system where the spins of some rows, chosen at random, are frozen in an antiferromagnetic order. No phase transition is found if the horizontal couplings are independent random variables while for correlated disorder one finds a low temperature phase with some glassy properties.Comment: 10 pages, Plain TeX, 3 ps figures, submitted to Europhys. Let

Holocene Glacier Fluctuations in the Torngat Mountains, Northern Labrador

Lichen measurements and other relative-age data were collected from deposits of several cirque glaciers in the Torngat Mountains of northern Labrador. Lichen growth stations were established, but no lichen-growth curve has yet been determined for the local area. However, moraines can be correlated between valleys on the basis of the largest diameter thallus of Rhizocarpon geographicum sensu lato combined with other relative-age data. These data suggest several discrete periods of Holocene glacier recession. If the R. geographicum s. I. growth curve established for the northern Cumberland Peninsula of Baffin Island (MILLER, 1975) is valid for similar environments in the Torngat Mountains, then glacier recession occurred 1850, ≥ 2800, > 2800, ≥ 4000, and > > 4000 yr BP. The latest three periods of glacier recession may correlate with periods of glacier recession on the Cumberland Peninsula of Baffin Island.On a effectué des mesures de lichens et recueilli des données sur l'âge relatif des dépôts de plusieurs cirques glaciaires des monts Torngat, au nord du Labrador. On y a déterminé des aires témoins de croissance des lichens, sans avoir pu encore dresser de courbe pour la région. Toutefois, on a pu établir des correspondances entre les moraines de vallées à partir des plus grands diamètres de thalles de Rhizocarpon geographicum sensu lato en combinaison avec d'autres données sur les âges relatifs. Ces données laissent croire qu'il y a eu plusieurs périodes discontinues de récession glaciaire au cours de l'Holocène. Si la courbe de croissance de R. geographicum s. I. déjà dressée pour le nord de la péninsule de Cumberland, île de Baffin, s'applique à des milieux similaires dans les monts Torngat, on peut avancer qu'il y a eu des périodes de récession glaciaire vers 1850, ≥ 2800, > 2800, ≥ 4000 et > > 4000 ans BP. Les trois dernières périodes pourraient correspondre à celles qu'a connues la péninsule de Cumberland, île de Baffin

Boundary correlation function of fixed-to-free bcc operators in square-lattice Ising model

We calculate the boundary correlation function of fixed-to-free boundary condition changing operators in the square-lattice Ising model. The correlation function is expressed in four different ways using $2\times2$ block Toeplitz determinants. We show that these can be transformed into a scalar Toeplitz determinant when the size of the matrix is even. To know the asymptotic behavior of the correlation function at large distance we calculate the asymptotic behavior of this scalar Toeplitz determinant using the Szeg\"o's theorem and the Fisher-Hartwig theorem. At the critical temperature we confirm the power-law behavior of the correlation function predicted by conformal field theory