Stereocomplexed Poly(Limonene Carbonate): A Unique Example of the Cocrystallization of Amorphous Enantiomeric Polymers

We report the cocrystallization of the regio‐ and stereoregular chiral copolymer poly(limonene carbonate). To the best of our knowledge, this marks the first example of an amorphous, enantiomerically pure polymer that becomes crystalline upon stereocomplexation with its complementary enantiomer. By analyzing X‐ray powder diffraction data, we propose a packing model in which sheets of enantiopure chains interdigitate with layers of the opposite enantiomer, forming a “steric zipper”.     

A Two Step Synthesis of the Nucleoside Q Precursor 2-Amino-5-cyanopyrrolo[2,3-d]pyrimidin 4-one (PreQo)

PreQ_o (1) is prepared in a 70 % yield by the condensation of chloro(formyl)acetonitrile (2) with 2,6-diaminopyrimidin-4-one (3), and subsequently converted to its amide derivative 5. Isolation of the intermediate 4 in the condensation reaction was also observed giving further insight into the proposed mechanism.     

A Convenient Preparation of 3-Aza-2-phenyl Bicyclo[3.2.2]nonane and Related 2-Substituted Cyclic Amines

2-Phenylazacycloalkanes are readily prepared by reaction of the corresponding unsubstituted N-chloroamines in diethyl ether with 2.5 equivalents of phenyl lithium.     

Polypyrrole stretchable actuators

Here, we report a simple way to prepare stretchable polypyrrole (PPy)‐based actuator materials that can be operated over a wide dynamic strain range and generate useable actuation displacements and pressures. The stretchable actuators were prepared as a laminated composite of PPy and a gold‐coated roughened rubber sheet. By manipulating the corrugated surface of the rubber substrate, the stretchability of PPy was greatly improved. Gold‐coated rubbers could be stretched to 30% without significant change in electrical resistance. The corrugated PPy/gold/rubber laminates successfully showed ～1% of actuation strain even when prestretched to 24%. The actuation strains were smaller than for similar free‐standing PPy films and a detailed analysis of the effects of corrugation and of the rubber substrate are presented to predict actuation strain under various prestretch strains. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

The workings of science

Energy flows and energy efficiencies in the operation of a modern automobile are expressed in terms of simple algebraic approximations. One purpose is to make a car's energy use and the potential for reducing it accessible to non-specialists with technical backgrounds. The overall energy use depends on two factors, vehicle load and powertrain efficiency. The former depends on speed and acceleration and key vehicle characteristics such as mass. The latter depends on heat-engine thermodynamic efficiency, and engine and transmission frictions. The analysis applies to todays automobiles. Numerical values of important parameters are given so that the reader can make his or her own estimates. Various technologies to reduce the energy consumption of automobiles are discussed.     

Action-FRET of a Gaseous Protein

Mass spectrometry is an extremely powerful technique for analysis of biological molecules, in particular proteins. One aspect that has been contentious is how much native solution-phase structure is preserved upon transposition to the gas phase by soft ionization methods such as electrospray ionization. To address this question—and thus further develop mass spectrometry as a tool for structural biology—structure-sensitive techniques must be developed to probe the gas-phase conformations of proteins. Here, we report Förster resonance energy transfer (FRET) measurements on a ubiquitin mutant using specific photofragmentation as a reporter of the FRET efficiency. The FRET data is interpreted in the context of circular dichroism, molecular dynamics simulation, and ion mobility data. Both the dependence of the FRET efficiency on the charge state—where a systematic decrease is observed—and on methanol concentration are considered. In the latter case, a decrease in FRET efficiency with methanol concentration is taken as evidence that the conformational ensemble of gaseous protein cations retains a memory of the solution phase conformational ensemble upon electrospray ionization.

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Stationary Increments Harmonizable Stable Fields: Upper Estimates on Path Behaviour

Studying sample path behaviour of stochastic fields/processes is a classical research topic in probability theory and related areas such as fractal geometry. To this end, many methods have been developed for a long time in Gaussian frames. They often rely on some underlying “nice” Hilbertian structure and can also require finiteness of moments of high order. Therefore, they can hardly be transposed to frames of heavy-tailed stable probability distributions. However, in the case of some linear non-anticipative moving average stable fields/processes, such as the linear fractional stable sheet and the linear multi-fractional stable motion, rather new wavelet strategies have already proved to be successful in order to obtain sharp moduli of continuity and other results on sample path behaviour. The main goal of our article is to show that, despite the difficulties inherent in the frequency domain, such kind of a wavelet methodology can be generalized and improved, so that it also becomes fruitful in a general harmonizable stable setting with stationary increments. Let us point out that there are large differences between this harmonizable setting and the moving average stable one. The real-valued harmonizable stable stochastic field X on which we focus is defined on \(\mathbb {R}^d\) through an arbitrary spectral density belonging to a general and wide class of functions. First, we introduce a wavelet-type random series representation of X and express it as the finite sum \(X=\sum _\eta X^\eta \), where the fields \(X^\eta \) are called the \(\eta \)-frequency parts, since they extend the usual low-frequency and high-frequency parts. Moreover, we show the continuity of the sample paths of the \(X^\eta \)’s and X; also, we discuss the existence and continuity of their partial derivatives of an arbitrary order. Thereafter, we obtain several almost sure upper estimates related to: (a) the anisotropic behaviour of generalized directional increments of the \(X^\eta \)’s and X, on an arbitrary fixed compact cube of \(\mathbb {R}^d\); (b) the behaviour at infinity of the \(X^\eta \)’s, of X, and of their partial derivatives, when they exist. We mention that all the results on sample paths obtained in the article are valid on the same event of probability 1; furthermore, this event is “universal”, in the sense that it does not depend, in any way, on the spectral density associated with X.