On embedding of the Bratteli diagram into a surface

We study C*-algebras O_{\lambda} which arise in dynamics of the interval exchange transformations and measured foliations on compact surfaces. Using Koebe-Morse coding of geodesic lines, we establish a bijection between Bratteli diagrams of such algebras and measured foliations. This approach allows us to apply K-theory of operator algebras to prove strict ergodicity criterion and Keane's conjecture for the interval exchange transformations.Comment: final versio

Predicted efficiency of Si wire array solar cells

Solar cells based on arrays of CVD-grown Si nano- or micro-wires have attracted interest as potentially low-cost alternatives to conventional wafer-based Si photovoltaics [1-6], and single-wire solar cells have been reported with efficiencies of up to 3.4% [7]. We recently presented device physics simulations which predicted efficiencies exceeding 17%, based on experimentally observed diffusion lengths within our wires [8]. However, this model did not take into account the optical properties of a wire array device - in particular the inherently low packing fraction of wires within CVD-grown wire arrays, which might limit their ability to fully absorb incident sunlight. For this reason, we have combined a device physics model of Si wire solar cells with FDTD simulations of light absorption within wire arrays to investigate the potential photovoltaic efficiency of this cell geometry. We have found that even a sparsely packed array (14%) is expected to absorb moderate (66%) amounts of above-bandgap solar energy, yielding a simulated photovoltaic efficiency of 14.5%. Because the wire array comprises such a small volume of Si, the observed absorption represents an effective optical concentration, which enables greater operating voltages than previously predicted for Si wire array solar cells

Mind and body, form and content: how not to do petitio principii analysis

Few theoretical insights have emerged from the extensive literature discussions of petitio principii argument. In particular, the pattern of petitio analysis has largely been one of movement between the two sides of a dichotomy, that of form and content. In this paper, I trace the basis of this dichotomy to a dualist conception of mind and world. I argue for the rejection of the form/content dichotomy on the ground that its dualist presuppositions generate a reductionist analysis of certain concepts which are central to the analysis of petitio argument. I contend, for example, that no syntactic relation can assimilate within its analysis the essentially holistic nature of a notion like justification. In this regard, I expound a form of dialectical criticism which has been frequently employed in the philosophical arguments of Hilary Putnam. Here the focus of analysis is upon the way in which the proponent of a position proceeds to explain or argue for his/her own particular theses. My conclusion points to the use of such dialectic within future analyses of petitio principii

Recovery from Hepatorenal Syndrome after Orthotopic Liver Transplantation

Three patients with progressive renal failure and advanced hepatic insufficiency due to cirrhosis of the liver underwent orthotopic liver transplantation. All three patients had immediate improvement in hepatic function and within two weeks after liver replacement regained nearly normal kidney function. However, the renal recovery was delayed in each case, and its course was not uniform. Plasma renin activity was high, and renin substrate was low before transplantation in one case in which these measurements were obtained; both returned to normal soon after liver replacement. (N Engl J Med 289:1155–1159, 1973). © 1973, Massachusetts Medical Society. All rights reserved

The AF structure of non commutative toroidal Z/4Z orbifolds

For any irrational theta and rational number p/q such that q|qtheta-p|<1, a projection e of trace q|qtheta-p| is constructed in the the irrational rotation algebra A_theta that is invariant under the Fourier transform. (The latter is the order four automorphism U mapped to V, V mapped to U^{-1}, where U, V are the canonical unitaries generating A_theta.) Further, the projection e is approximately central, the cut down algebra eA_theta e contains a Fourier invariant q x q matrix algebra whose unit is e, and the cut downs eUe, eVe are approximately inside the matrix algebra. (In particular, there are Fourier invariant projections of trace k|qtheta-p| for k=1,...,q.) It is also shown that for all theta the crossed product A_theta rtimes Z_4 satisfies the Universal Coefficient Theorem. (Z_4 := Z/4Z.) As a consequence, using the Classification Theorem of G. Elliott and G. Gong for AH-algebras, a theorem of M. Rieffel, and by recent results of H. Lin, we show that A_theta rtimes Z_4 is an AF-algebra for all irrational theta in a dense G_delta.Comment: 35 page

Realism and the wave-function

Realism -- the idea that the concepts in physical theories refer to 'things' existing in the real world -- is introduced as a tool to analyze the status of the wave-function. Although the physical entities are recognized by the existence of invariant quantities, examples from classical and quantum physics suggest that not all the theoretical terms refer to the entities: some terms refer to properties of the entities, and some terms have only an epistemic function. In particular, it is argued that the wave-function may be written in terms of classical non-referring and epistemic terms. The implications for realist interpretations of quantum mechanics and on the teaching of quantum physics are examined.Comment: No figure

How Events Come Into Being: EEQT, Particle Tracks, Quantum Chaos, and Tunneling Time

In sections 1 and 2 we review Event Enhanced Quantum Theory (EEQT). In section 3 we discuss applications of EEQT to tunneling time, and compare its quantitative predictions with other approaches, in particular with B\"uttiker-Larmor and Bohm trajectory approach. In section 4 we discuss quantum chaos and quantum fractals resulting from simultaneous continuous monitoring of several non-commuting observables. In particular we show self-similar, non-linear, iterated function system-type, patterns arising from quantum jumps and from the associated Markov operator. Concluding remarks pointing to possible future development of EEQT are given in section 5.Comment: latex, 27 pages, 7 postscript figures. Paper submitted to Proc. Conference "Mysteries, Puzzles And Paradoxes In Quantum Mechanics, Workshop on Entanglement And Decoherence, Palazzo Feltrinelli, Gargnano, Garda Lake, Italy, 20-25 September, 199

Theories of Reference: What Was the Question?

The new theory of reference has won popularity. However, a number of noted philosophers have also attempted to reply to the critical arguments of Kripke and others, and aimed to vindicate the description theory of reference. Such responses are often based on ingenious novel kinds of descriptions, such as rigidified descriptions, causal descriptions, and metalinguistic descriptions. This prolonged debate raises the doubt whether different parties really have any shared understanding of what the central question of the philosophical theory of reference is: what is the main question to which descriptivism and the causal-historical theory have presented competing answers. One aim of the paper is to clarify this issue. The most influential objections to the new theory of reference are critically reviewed. Special attention is also paid to certain important later advances in the new theory of reference, due to Devitt and others

O realismo interno confrontado com "seus inimigos"

Analisamos brevemente a perspectiva realista interna, proposta por Putnam, contrastando-a com as suas principais rivais: a realista metafísica e a relativista radical. Tomamos como ponto de partida o debate contemporâneo em que o realismo interno se encontra envolvido, em especial, o desafio que o relativismo extremo impõe à epistemologia contemporânea. Parece pacífico entre os filósofos que tal desafio não será superado pelo projeto clássico de buscas por certezas absolutas. A história da ciência já nos deu muitas evidências de que as teorias não são redes que captam a realidade em si. Mas, por si só, isso não implica que a nossa visão de conhecimento seja determinada simplesmente por aspectos temporais e espaciais, pelo sujeito falível e pelo contexto em que se encontra. Nesse cenário, são empreendimentos difíceis, mas merecedores de atenção, as tentativas, de filósofos como Putnam, de construir teorias que não desconsiderem a história nem abracem, ao mesmo tempo, o relativismo radical