On Entropic Reduction of Fluctuations

We point out that there is no general relation between ground state degeneracy and finite-temperature fluctuations for tilted interfaces.     

Strongly Correlated Alignment of Fluorinated 5,11‐Bis(triethylgermylethynyl)anthradithiophene Crystallites in Solution‐Processed Field‐Effect Transistors

The crystallinity of an organic semiconductor film determines the efficiency of charge transport in electronic devices. This report presents a micro‐to‐nanoscale investigation on the crystal growth of fluorinated 5,11‐bis(triethylgermylethynyl)anthradithiophene (diF‐TEG‐ADT) and its implication for the electrical behavior of organic field‐effect transistors (OFETs). diF‐TEG‐ADT exhibits remarkable self‐assembly through spin‐cast preparation, with highly aligned edge‐on stacking creating a fast hole‐conducting channel for OFETs.     

Robust calibrations on reduced sample sets for API content prediction in tablets: Definition of a cost-effective NIR model development strategy

Owing to spectral variations from other sources than the component of interest, large investments in the NIR model development may be required to obtain satisfactory and robust prediction performance. To make the NIR model development for routine active pharmaceutical ingredient (API) prediction in tablets more cost-effective, alternative modelling strategies were proposed. They used a massive amount of prior spectral information on intra- and inter-batch variation and the pure component spectra to define a clutter, i.e., the detrimental spectral information. This was subsequently used for artificial data augmentation and/or orthogonal projections. The model performance improved statistically significantly, with a 34–40% reduction in RMSEP while needing fewer model latent variables, by applying the following procedure before PLS regression: (1) augmentation of the calibration spectra with the spectral shapes from the clutter, and (2) net analyte pre-processing (NAP). The improved prediction performance was not compromised when reducing the variability in the calibration set, making exhaustive calibration unnecessary. Strong water content variations in the tablets caused frequency shifts of the API absorption signals that could not be included in the clutter. Updating the model for this kind of variation demonstrated that the completeness of the clutter is critical for the performance of these models and that the model will only be more robust for spectral variation that is not co-linear with the one from the property of interest.     

Selective Introduction of Sulfhydryl Groups into Recombinant Proteins for Study of Protein–Protein Interactions

In the present work, we proposed to create special sorbents for the study of protein–protein interactions, based on the fixation of cysteine-inserted beta-casein mutants with thiol-Sepharose resin. As a model system, we used bovine beta-casein, which belongs to the family of intrinsically unstructured proteins. Insertion of distal cysteines into the unfolded protein was not found to significantly change beta-casein properties. An amphiphilic beta-casein molecule has one hydrophilic domain and one hydrophobic domain placed on the N- and C-terminus, thus enabling one to exploit its capacity to engage in different types of intermolecular interactions. Two different casein-Sepharose sorbents incorporating either C-4 or C-208 beta-casein mutants bound to thiol-Sepharose were produced, exposing the hydrophobic domain in the case of the C-4 and the hydrophilic domain in the case of the C-208 mutant, respectively. The results obtained using the proposed sorbents with native beta-casein, another partially unfolded protein prion, and an oligomeric globular glyceraldehyde-3-phosphate dehydrogenase were found to be consistent with the data obtained by ELISA on free protein–protein complexes. Thus, Sepharose modified with various proteins is suitable for isolation of proteins interacting with the chromatographic phase bound partners from multicomponent systems such as milk. The obtained results allow the proposing of a fast and convenient method to be used for isolation of proteins, determination of protein-interacting partners, and the study of multi-protein complexes.

     

Diastereoselective Hydrogen‐Transfer Reactions: An Experimental and DFT Study

Radical reductions of halogenated precursors bearing a heterocycle exo (α) to the carbon‐centered radical proceed with enhanced anti‐selectivity, a phenomenon that we termed “exocyclic effect”. New experimental data and DFT calculations at the BHandHLYP/TZVP level demonstrate that the origin of the exocyclic effect is linked to the strain energy required for a radical intermediate to reach its reactive conformation at the transition state (ΔE^≠_strain). Furthermore, radical reductions of constrained THP systems indicate that high 2,3‐anti inductions are reached only when the radical chain occupies an equatorial orientation. Hydride deliveries to different acyclic substrates and calculations also suggest that the higher anti‐selectivities obtained with borinate intermediates are not related to the formation of a complex mimicking an exocycle. From a broader standpoint, this study reveals important conformational factors for reactions taking place at a center vicinal to a heterocycle or an α‐alkoxy group.     

Mukaiyama aldolisation reactions of α,β-epoxyaldehydes in aqueous media

The Mukaiyama aldolisation reaction in aqueous media of cis and trans α,β-epoxyaldehydes with tert-butyldimethylsilyl ketene acetal in the presence of Lewis's acids was studied. Sc(OTf)₃ gave the best results in terms of selectivity. The same reaction of cis and trans α,β-epoxyaldehydes with the enoxysilane of ethyl pyruvate resulted in epoxy substituted ulosonic derivatives issued from a double sequential condensation of the pyruvate on the epoxy derivatives.     

Microwave-assisted extraction of phenolic antioxidants from potato peels

A response surface method was used to optimize the microwave-assisted extraction parameters such as extraction time (t) (min), solvent (methanol) concentration (S) (v/v) and microwave power level (MP) for extraction of antioxidants from potato peels. Max. total phenolics content of 3.94 mg g?1 dry weight (dw) was obtained at S of 67.33%, t of 15 min and a MP of 14.67%. For ascorbic acid (1.44 mg g?1 dw), caffeic acid (1.33 mg g?1 dw), ferulic acid (0.50 mg g?1 dw) max contents were obtained at S of 100%, t of 15 min, and MP of 10%, while the max chlorogenic acid content (1.35 mg g?1 dw) was obtained at S of 100%, t of 5 min, and MP of 10%. The radical scavenging activity of the extract was evaluated by using the DPPH assay and optimum antioxidant activity was obtained at S of 100%, t of 5 min, and MP of 10%.     

Inelastic interaction of nearly equal solitons for the quartic gKdV equation

This paper describes the interaction of two solitons with nearly equal speeds for the quartic (gKdV) equation

$\partial_tu+\partial_x(\partial_x^2u+u^4)=0,\quad t,x\in \mathbb{R}.$

(0.1)

We call soliton a solution of (0.1) of the form u(t,x)=Q _c (x?ct?y ₀), where c>0, y ₀∈? and \(Q_{c}''+Q_{c}^{4}=cQ_{c}\). Since (0.1) is not an integrable model, the general question of the collision of two given solitons \(Q_{c_{1}}(x-c_{1}t)\), \(Q_{c_{2}}(x-c_{2}t)\) with c ₁≠c ₂ is an open problem.

We focus on the special case where the two solitons have nearly equal speeds: let U(t) be the solution of (0.1) satisfying

$\lim_{t\to-\infty}\|{U}(t)-Q_{c_1^-}(.-c_1^-t)-Q_{c_2^-}(.-c_2^-t)\|_{H^1}=0,$

for \(\mu_{0}=(c_{2}^{-}-c_{1}^{-})/(c_{1}^{-}+c_{2}^{-})>0\) small. By constructing an approximate solution of (0.1), we prove that, for all time t∈?,

$\begin{array}{l}\displaystyle{U}(t)={Q}_{c_1(t)}(x-y_1(t))+{Q}_{c_2(t)}(x-y_2(t))+{w}(t)\\[6pt]\displaystyle\quad\mbox{where }\|w(t)\|_{H^1}\leq|\ln\mu_0|\mu_0^2,\end{array}$

with y ₁(t)?y ₂(t)>2|ln?μ ₀|+C, for some C∈?. These estimates mean that the two solitons are preserved by the interaction and that for all time they are separated by a large distance, as in the case of the integrable KdV equation in this regime.

However, unlike in the integrable case, we prove that the collision is not perfectly elastic, in the following sense, for some C>0,

$\lim_{t\to+\infty}c_1(t)>c_2^-\biggl(1+\frac{\mu_0^5}{C}\biggr),\quad \lim_{t\to+\infty}c_2(t)

and \({w}(t)\not\to0\) in H ¹ as t→+∞.

     

Enantioselective capillary electrochromatography: recent developments and new trends

Since its development in the early 1970s, CEC has been studied quite extensively, but unfortunately its use is still mostly located at an academic level. Reasons for this are the limited availability of commercially available stationary phases (SPs) and columns, along with some practical limitations, such as column fragility, lack of column robustness and reproducibility. Nevertheless, CEC maintains a place among the separation techniques, probably because of its unique feature to combine two separation principles. Also in the field of chiral separations, CEC is often used as a separation technique and already showed its potential for this kind of analyses. This overview will focus on the recent applications, i.e. between 2006 and 2010, in enantioselective analysis by means of CEC. For the selected applications, the used SPs (chiral selectors) and their potential for future method development or screening purposes will be evaluated and critically discussed.     

Simulation of Premixed Turbulent Combustion in a Gas Engine using the Immersed Boundary Method and a Level Set Flame Model

An efficient simulation approach for turbulent flame brush propagation is a level set formulation closed by the turbulent flame speed. A formulation of the level set equation with the corresponding treatment of the turbulent mass burning rate that is compatible with standard Finite Volume discretization schemes available in computational fluid dynamics codes is employed. In order to simplify and to speed up the meshing process in complicated geometries (here in gas engines) the immersed boundary method in a continuous formulation, where the forces replacing the boundaries are introduced in the momentum conservation equations before discretization, is employed. In our contribution, aspects of the numerical implementation of the level set flame model combined with the immersed boundary formulation in OpenFOAM are presented. First representative simulation results of a homogeneous methane/air mixture combustion in a simplified engine geometry are shown. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)