Normalizing the Taylor expansion of non-deterministic {\lambda}-terms, via parallel reduction of resource vectors

It has been known since Ehrhard and Regnier's seminal work on the Taylor expansion of $\lambda$-terms that this operation commutes with normalization: the expansion of a $\lambda$-term is always normalizable and its normal form is the expansion of the B\"ohm tree of the term. We generalize this result to the non-uniform setting of the algebraic $\lambda$-calculus, i.e. $\lambda$-calculus extended with linear combinations of terms. This requires us to tackle two difficulties: foremost is the fact that Ehrhard and Regnier's techniques rely heavily on the uniform, deterministic nature of the ordinary $\lambda$-calculus, and thus cannot be adapted; second is the absence of any satisfactory generic extension of the notion of B\"ohm tree in presence of quantitative non-determinism, which is reflected by the fact that the Taylor expansion of an algebraic $\lambda$-term is not always normalizable. Our solution is to provide a fine grained study of the dynamics of $\beta$-reduction under Taylor expansion, by introducing a notion of reduction on resource vectors, i.e. infinite linear combinations of resource $\lambda$-terms. The latter form the multilinear fragment of the differential $\lambda$-calculus, and resource vectors are the target of the Taylor expansion of $\lambda$-terms. We show the reduction of resource vectors contains the image of any $\beta$-reduction step, from which we deduce that Taylor expansion and normalization commute on the nose. We moreover identify a class of algebraic $\lambda$-terms, encompassing both normalizable algebraic $\lambda$-terms and arbitrary ordinary $\lambda$-terms: the expansion of these is always normalizable, which guides the definition of a generalization of B\"ohm trees to this setting

The nuclear envelope can control gene expression and cell cycle progression via miRNA regulation

This article is available open access through the publisher’s website. Copyright @ 2010 Landes Bioscience.The nuclear envelope can regulate gene expression through its interaction with chromatin and by the sequestration of specific transcription factors. In this study, we show that such regulation can be achieved via microRNA regulation. We identify a set of miRNAs that are dysregulated in the absence of a fully functional nuclear lamina. We then focus on miRNA-31 and experimentally confirm its targets. The target set identified is significantly enriched in genes involved in controlling progress through the cell cycle such as Cdkn2a. Normalizing miRNA-31 levels, either using a specific inhibitor or by restoration of the nuclear lamina, also normalizes cell cycle distribution and cell proliferation rates. We show that the 3’UTR of p16Ink4a/p19Arf has a functional miRNA-31 binding site which contributes to the observed regulation of cell cycle progression. Our findings are the first demonstration that the nuclear envelope can control gene expression by regulating specific miRNA levels, and that miRNA-31 is involved in the regulation of cell proliferation and progress through the cell cycle at least in part by regulating the levels of p16Ink4a/p19Arf.The EPA Trust and the MRC

Adapting tam and ECT: continuance intention of e-shopping in Saudi Arabia

The objective of this study is to clarify the theoretical problem and identify factors that could explain the level of continuance intention of e-shopping in context of Saudi Arabia. The study proposes a revised technology acceptance model that integrates expectation confirmation theory to measure age differences with regard to continuance online shopping intentions. Structural equation model confirms model fit. The research findings confirm that Perceived usefulness, enjoyment, and subjective norms are determinants of online shopping continuance. The structural weights are mostly equivalent between the young and old groups, but the regression path from subjective norms to perceived usefulness is not invariant, with that relationship being stronger for the younger respondents. This research moves beyond online shopping intentions and includes factors affecting online shopping continuance. The model explains 65% of the intention to continue shopping online. The research findings suggest that online strategies cannot ignore either the direct and indirect effects on continuance intentions

UNCERTAINTY AND THE MANAGEMENT OF SALINITY WITH IRRIGATION WATER

The impact of uncertain salt balances in irrigate fields is assessed with a hydroeconomic model that incorporates the effects of salinity. Uncertainty in two parameters that jointly determine root zone salinity is investigated and the conclusions prove to depend upon the way in which these parameters enter the mass-balance equation for soil salinity. It is shown that water has a risk reducing marginal effect on output when growers are risk averse and, under certain conditions, when they are risk neutral. The effects of prices, water quality, and crop salt sensitivity on the conclusions are analyzed and an empirical example is employed to illustrate the magnitude of the impacts.Crop Production/Industries,

Dynamics of the formation of a hydrogel by a pathogenic amyloid peptide: islet amyloid polypeptide

Many chronic degenerative diseases result from aggregation of misfolded polypeptides to form amyloids. Many amyloidogenic polypeptides are surfactants and their assembly can be catalysed by hydrophobic-hydrophilic interfaces (an air-water interface in-vitro or membranes in-vivo). We recently demonstrated the specificity of surface-induced amyloidogenesis but the mechanisms of amyloidogenesis and more specifically of adsorption at hydrophobic-hydrophilic interfaces remain poorly understood. Thus, it is critical to determine how amyloidogenic polypeptides behave at interfaces. Here we used surface tensiometry, rheology and electron microscopy to demonstrate the complex dynamics of gelation by full-length human islet amyloid polypeptide (involved in type II diabetes) both in the bulk solution and at hydrophobic-hydrophilic interfaces (air-water interface and phospholipids). We show that the hydrogel consists of a 3D supramolecular network of fibrils. We also assessed the role of solvation and dissected the evolution over time of the assembly processes. Amyloid gelation could have important pathological consequences for membrane integrity and cellular functions

On linear combinations of lambda-terms

International audienceWe define an extension of lambda-calculus with linear combinations, endowing the set of terms with a structure of R-module, where R is a fixed set of scalars. Terms are moreover subject to identities similar to usual pointwise definition of linear combinations of functions with values in a vector space. We then extend beta-reduction on those algebraic lambda-terms as follows: at + u reduces to at + u as soon as term t reduces to t and a is a non-zero scalar. We prove that reduction is confluent. Under the assumption that the set R of scalars is positive (i.e. a sum of scalars is zero iff all of them are zero), we show that this algebraic lambda-calculus is a conservative extension of ordinary lambda-calculus. On the other hand, we show that if R admits negative elements, then every term reduces to every other term. We investigate the causes of that collapse, and discuss some possible fixes

Going for Wood

I. I would never have chosen a window seat, but there I was, staring at great banks of clouds while the plane, rocked by invisible currents, sailed upward

Current measuring in shallow waters by towed electrodes

The e.m.f. produced in the sea by water movement has been measured over two tidal periods in shallow water. Simultaneous measurements of the drift of the ship towing the electrodes provide a means of calibrating the apparatus. The results are compared with existing tidal stream data