Properties of the Liquid Crystals Formed by the N-Oxides of Certain 4-(4′-pyridyl)phenyl 4″-n-Alkoxybenzoates: Comparison of the N-Oxide and Cyano-groups as Mesogenic Terminal Substituents

The liquid liquid crystal transition temperatures of the N-oxides of certain 4-(4′-pytidyl)phenyl 4″ -n-alkoxybenzoates are reported. The effects on smectic and nematice thermal stability of the N-oxide function and the cyano-group in terminal positions in mesogens are compared and discussed.     

Weighted Bounds for Variational Walsh–Fourier Series

For 1<p<?? and a weight w??A _p and a function in L ^p ([0,1],w) we show that variational sums with sufficiently large exponents of its Walsh?CFourier series are bounded in L ^p (w). This strengthens a result of Hunt?CYoung and is a weighted extension of a variation norm Carleson theorem of Oberlin?CSeeger?CTao?CThiele?CWright. The proof uses phase plane analysis and a weighted extension of a variational inequality of Lépingle.     

Understanding and tuning the catalytic bias of hydrogenase

When enzymes are optimized for biotechnological purposes, the goal often is to increase stability or catalytic efficiency. However, many enzymes reversibly convert their substrate and product, and if one is interested in catalysis in only one direction, it may be necessary to prevent the reverse reaction. In other cases, reversibility may be advantageous because only an enzyme that can operate in both directions can turnover at a high rate even under conditions of low thermodynamic driving force. Therefore, understanding the basic mechanisms of reversibility in complex enzymes should help the rational engineering of these proteins. Here, we focus on NiFe hydrogenase, an enzyme that catalyzes H(2) oxidation and production, and we elucidate the mechanism that governs the catalytic bias (the ratio of maximal rates in the two directions). Unexpectedly, we found that this bias is not mainly determined by redox properties of the active site, but rather by steps which occur on sites of the proteins that are remote from the active site. We evidence a novel strategy for tuning the catalytic bias of an oxidoreductase, which consists in modulating the rate of a step that is limiting only in one direction of the reaction, without modifying the properties of the active site.     

A 1D model for polymer melting during modulated temperature differential scanning calorimetry

^** Email: a.a.lacey{at}ma.hw.ac.uk^*** Email: cnikolo{at}aegean.gr A 1D model for the melting of polymers, assuming the polymercrystals take the form of lamellæ or thin sheets of material,is discussed. The model is derived on the assumption that themelting point of a lamella depends upon its thickness, thata lamella melts the instant this temperature is exceeded andthat lamellæ with higher melting points grow by accumulatingsurplus of melt. The model is analysed for a temperature controlthat is the sum of a linear and a sinusoidal function of timeas in modulated temperature differential scanning calorimetry,which is a technique for measuring thermal properties of materials.This work is an extension of a previous paper, by the same authors,considering a homogeneous model, based on the same assumptions.Some predictions regarding the output of such calorimetry aremade.