Heterogeneous substitution systems revisited

Matthes and Uustalu (TCS 327(1-2):155-174, 2004) presented a categorical description of substitution systems capable of capturing syntax involving binding which is independent of whether the syntax is made up from least or greatest fixed points. We extend this work in two directions: we continue the analysis by creating more categorical structure, in particular by organizing substitution systems into a category and studying its properties, and we develop the proofs of the results of the cited paper and our new ones in UniMath, a recent library of univalent mathematics formalized in the Coq theorem prover.Comment: 24 page

The Substitution Principle Revisited

In their Anachronic Renaissance, Alexander Nagel and Christopher Wood identify two principles upon which, in fifteenth-century Europe, a work of art might establish its validity or authority: substitution and performance. It has become established wisdom that the dual schema of substitution and performance follows Hans Belting's dualism of the medieval cult of the image and the modern aesthetic system of art. This, I submit, is not just a mistake, but also prevents from evaluating one of the book's most ambitious contributions to art-historical theory on its own merits. An analysis of the structure of the claims made by Nagel and Wood brings to light that the two concepts—substitution and performance—do not play the same role as the conceptual pair of Bild and Kunst in Belting's influential work

The stability of parallel-propagating circularly polarized Alfvén waves revisited

The parametric instability of parallel-propagating circularly polarized Alfven waves (pump waves) is revisited. The stability of these waves is determined by the linearized system of magnetohydrodynamic equations with periodic coefficients. The variable substitution that reduces this system of equations to a system with constant coefficients is suggested. The system with constant coefficients is used to derive the dispersion equation that was previously derived by many authors with the use of different approaches. The dependences of general stability properties on the dimensionless amplitude of the pump wave a and the ratio of the sound and Alfven speed b are studied analytically. It is shown that, for any a and b, there are such quantities k(1) and k(2) that a perturbation with the dimensionless wavenumber k is unstable if k(1)(2) 1, k(1) is a monotonically increasing function of a. For any b, k(1) tends to a limiting value approximately equal to 1.18 as a -> infinity

Service Substitution Revisited

International audienceThe current state of the art concerning the problem of service substitution raises the following issue: the complexity of the substitution process scales up with the number of available services that may serve as candidate substitutes for a target service. To deal with this issue, we propose a framework that is based on two substitution relations and corresponding theorems. The proposed relations and theorems allow organizing available services into groups. Then, the complexity of retrieving candidate substitute services for the target service and generating corresponding adapters scales up with the number of available groups, instead of scaling up with the number of available services

Despite its role in assembly, methionine 35 is not necessary for amyloid β-protein toxicity

Author Manuscript 2011 June 1.An important component of the pathologic process underlying Alzheimer’s disease is oxidative stress. Met[superscript 35] in amyloid β-protein (Aβ) is prone to participating in redox reactions promoting oxidative stress, and therefore is believed to contribute significantly Aβ-induced toxicity. Thus, substitution of Met[superscript 35] by residues that do not participate in redox chemistry would be expected to decrease Aβ toxicity. Indeed, substitution of Met[superscript 35] by norleucine (Nle) was reported to reduce Aβ toxicity. Surprisingly, however, substitution of Met[superscript 35] by Val was reported to increase toxicity. Aβ toxicity is known to be strongly related to its self-assembly. However, neither substitution is predicted to affect Aβ assembly substantially. Thus, the effect of these substitutions on toxicity is difficult to explain. We revisited this issue and compared Aβ40 and Aβ42 with analogs containing Met[superscript 35]→Nle or Met[superscript 35]→Val substitutions using multiple biophysical and toxicity assays. We found that substitution of Met[superscript 35] by Nle or Val had moderate effects on Aβ assembly. Surprisingly, despite these effects, neither substitution changed Aβ neurotoxicity significantly in three different assays. These results suggest that the presence of Met[superscript 35] in Aβ is not important for Aβ toxicity, challenging to the prevailing paradigm, which suggests that redox reactions involving Met35 contribute substantially to Aβ-induced toxicity.Alzheimer's Association (Grant IIRG- 07-5833)National Institutes of Health (U.S.) (Grant AG027818

Hierarchic Superposition Revisited

Many applications of automated deduction require reasoning in first-order logic modulo background theories, in particular some form of integer arithmetic. A major unsolved research challenge is to design theorem provers that are "reasonably complete" even in the presence of free function symbols ranging into a background theory sort. The hierarchic superposition calculus of Bachmair, Ganzinger, and Waldmann already supports such symbols, but, as we demonstrate, not optimally. This paper aims to rectify the situation by introducing a novel form of clause abstraction, a core component in the hierarchic superposition calculus for transforming clauses into a form needed for internal operation. We argue for the benefits of the resulting calculus and provide two new completeness results: one for the fragment where all background-sorted terms are ground and another one for a special case of linear (integer or rational) arithmetic as a background theory

Turkish money demand, revisited: some implications for inflation and currency substitution under structural breaks

In this paper, a money demand model constructed on currency in circulation is used to determine the appropriate alternative cost to hold monetary balances in the Turkish economy. Our estimation results, using contemporaneous multivariate co-integration methodology, indicate that the most significant alternative cost to demand for money is the depreciation rate of the nominal exchange rate. This brings out the importance of having a currency substitution phenomenon settled in the economy when economic agents make their decisions as to their monetary transactions. Moreover, we find that domestic inflationary framework has been subject to a weakly exogenous characteristic and conclude that the main factors leading to domestic inflation are determined out of the money demand variable space.Money Demand ; Inflation ; Currency Substitution ; Turkish Economy ;

(HO)RPO Revisited

The notion of computability closure has been introduced for proving the termination of the combination of higher-order rewriting and beta-reduction. It is also used for strengthening the higher-order recursive path ordering. In the present paper, we study in more details the relations between the computability closure and the (higher-order) recursive path ordering. We show that the first-order recursive path ordering is equal to an ordering naturally defined from the computability closure. In the higher-order case, we get an ordering containing the higher-order recursive path ordering whose well-foundedness relies on the correctness of the computability closure. This provides a simple way to extend the higher-order recursive path ordering to richer type systems