The present study explores the burning of microscale porous silicon channels with sodium perchlorate. These on-chip porous silicon energetics were embedded in crystalline silicon, and therefore surrounded on three sides by an efficient thermal conductor. For slow burning systems, this presents complications as heat loss to the crystalline silicon substrate can result in inconsistent burning or flame extinction. We investigated <100 μm wide porous silicon strips, sparsely filled with sodium perchlorate (NaClO4), to probe the limits of on-chip combustion. Four different etch times were attempted to decrease the dimensions of the porous silicon strips. The smallest size achieved was 12 x 64 µm, and despite the small dimensions, demonstrated the same flame speed as the larger porous silicon strips of 6-7 m/s. We predict that unreacted porous silicon acts as a thermal insulator to aid combustion for slow burning porous silicon channels, and SEM images provide evidence to support this. We also investigated the small scale combustion of a rapidly burning sample (∼1200 m/s). Despite the rapid flame speed, the propagation followed a designed, winding flame path. The use of these small scale porous silicon samples could significantly reduce the energetic material footprint for future microscale applications.

We present the first quantitative assessment of combustion dynamics of on-chip porous silicon (PS) energetic material using sulfur and nitrate-based oxidizers with potential for improved moisture stability and/or minimized environmental impact compared to sodium perchlorate (NaClO4). Material properties of the PS films were characterized using gas adsorption porosimetry, and profilometry to calculate specific surface area, porosity and etch depth. The PS/sulfur energetic composite was formed using three pore loading techniques, where the combustion speeds ranged from 2.9 – 290 m/s. The nitrate-based oxidizers were solution-deposited using different compatible solvents, and depending on the metal-nitrate yielded combustion speeds of 3.1 – 21 m/s. Additionally, the combustion enthalpies from bomb calorimetry experiments are reported for the alternative PS/oxidizer systems in both nitrogen and oxygen environments.

The electrical heating of Ni/Al laminate foils allows interrogation of phenomena at heating rates as high as 10^12 K/s. In the 2011 Fall MRS meeting, we reported on emission spectra from rapidly heated Ni/Al laminates resolved temporally over 350 ns, which provided qualitative evidence of rapid and exothermic vapor phase mixing of Ni and Al in these experiments which we term electrical explosions. These results were significant, because thermal diffusion processes normally limit Ni/Al reactions to much slower energy release rates, potentially limiting their applications. Here we present further evidence of exothermic Ni/Al mixing, quantified by experimental velocity measurements of encapsulation material and interpreted by numerical calculations of energy partitioning into different processes. These calculations agreed well with experiments from different Al, Cu, and Ni samples, sputter-deposited and lithographically patterned into bow-tie bridge structures. Velocity measurements of up to 5 km/s for 11.5 μm thick parylene encapsulation layers were accurately predicted using a single, empirical fitting parameter which depended on the electrical circuit used. The calculations also agreed with encapsulation layers accelerated by electrically exploded Ni/Al laminates as long as an additional 1.2 kJ/g of energy was included in the model. This value is precisely the enthalpy of mixing between Ni and Al, and therefore quantifies the transduction of energy into encapsulation layer kinetic energy.

State power is widely thought to be coercive. The view that governments must wield force or that their power is necessarily coercive is widespread in contemporary political thought. John Rawls is representative in claiming that (political power is always coercive power backed up by the government(s use of sanctions, for government alone has the authority to use force in upholding its laws.( This belief in the centrality of coercion and force plays an important but not well appreciated role in contemporary political thought. I wish to challenge this belief and the considerations that motivate it. States are not necessarily coercive or coercive (by definition.( Their claimed authority is prior to the force they wield. Legitimate states should need to resort to coercion and force much less than other states, and that fact seems unappreciated in contemporary political thought.

Maurice Lagueux's new book, winner of the Governor General's Award, is a collection of essays on different topics in Marxist philosophy and social thought. Often very critical of the ideas and theses he examines, the unifying theme of the collection is indicated by the subtitle, “une saison dans l'histoire de la pensée critique”. Lagueux's efforts are largely devoted to evaluating the ideas that captured the imagination of much of the left, especially in Quebec, during the sixties, “une saison où la gauche avait le vent dans les voiles”.

We are a species addicted to conversation. In a remarkable book, Allan Gibbard argues that conversation is “far more than a carrier of information. In talk we work out not only what to believe about things and events and people, but how to live. We work out how to feel about things in our lives, and in the lives of others” (pp. 3–4). In discussion we arrive at the norms that govern our lives. We determine thus what is to count as morally right or permissible, or as rational, or simply what it makes sense to do or feel. The importance of conversation to our normative life is increasingly evident as Gibbard's tale unfolds.

Why be moral? The question is very old. It takes many forms and is subject to many interpretations. On one interpretation, the question does not make sense (failed presupposition); to ask it is evidence of misunderstanding. This view is not as popular as it once was. The more fashionable answer today is that we have reasons to be moral. These reasons may themselves be moral, or they may be non-moral. In the first case, we may not have the answer we wanted to our question. If we think of reasons as considerations favouring a course of action, decisively in the absence of other reasons, then the fact that there are moral reasons to act morally merely tells us that there are moral considerations in favour of acts required or recommended by morality. It leaves open the question of whether we act against or contrary to reason simpliciter when we fail to act as we morally should. By contrast, if there are non-moral reasons to act morally, then to refrain from doing what is morally required of us is a failure of reason; it is to act contrary to the considerations relevant to the choices one faces.

Suppose that we have negative, natural rights to our lives, liberty, and possessions and that these rights are absolute or indefeasible. Then at best only minimal states will be legitimate, where such are states that restrict their activities to the enforcement of the basic rights of individuals and the like. (Indeed, it is possible that no actual states, minimal or not, will be legitimate.) Such appears to be the consequence of absolute natural rights. When made aware of these implications of absolute natural rights, many philosophers deny their existence. In the absence of a convincing defense of absolute natural rights, the defense of the minimal state thereby loses force.