Contact bactericides and fungicides on the basis of amino‐functionalized poly(norbornene)s

This study is aimed at investigating the microbiocidal potential of amino‐functionalized poly(norbornenes) in the solid state. A series of norbornene‐type monomers that carry secondary or tertiary amine functions as well as hexyl and dodecyl groups were prepared. Ring‐opening metathesis polymerization was used to prepare homopolymers of the amine bearing monomers and random copolymers of amine‐ and alkyl‐substituted monomers of high average molar mass. The resulting polymers were characterized by nuclear magnetic resonance, thermogravimetry, differential scanning calorimetry, infrared spectroscopy, and contact angle measurements, and their contact biocidal potential was evaluated according to the Japanese Industry standard Z2801. Tested microorganisms comprised Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Candida albicans, and Aspergillus niger. Microbiocidal activity of selected polymer films against E. coli, S. aureus, and A. niger was found, whereas against C. albicans and P. aeruginosa microbiostatic behavior was observed. Moreover, the most potent copolymer revealed no cytotoxicity rendering a biocidal polymer with potential applications in mammalian‐, and in particular, human‐related fields. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Amorphous carbon nitride a-CNx microelectrode: Fabrication and characterization

Fabrication and characterization of amorphous carbon nitride a-CN_x microelectrodes are reported. These electrodes were prepared by DC-sputtering of a thin carbon layer on sharpened glass tip. The kinetic parameters (k⁰ and α) and the diffusion coefficient of the ferri-ferrocyanide redox probe were determined by steady-state voltammetry (CV) and by electrochemical impedance spectroscopy (EIS), and were used for characterizing both the electrochemical sensitivity of microelectrodes and their dimensions. The cathodic activation procedure of the electrode resulted in an increase of the electron rate constant. This procedure provides a new way for the fabrication of carbon microelectrodes for local electrochemical measurements.     

Bayesian Multivariate Distributional Regression With Skewed Responses and Skewed Random Effects

The normal and the t distribution are classical tools for building random effects regression models where both can be used for the specification of either the conditional response distribution or the random effects distribution. However, the underlying assumption of symmetry can be questionable in many applications. We, therefore, propose regression models where the skew-normal and skew-t distribution are considered for both the response and the random effects specification and embed these models in the framework of distributional regression such that regression predictors can be specified for all distributional parameters. The distributional regression framework also allows us to consider multivariate versions of the skew-normal and the skew-t distribution. For Bayesian inference, we adapt iteratively weighted least-square proposals within Markov chain Monte Carlo simulations such that they can also facilitate the inclusion of nonnormal random effects specifications. Model choice is based on the Watanabe–Akaike information criterion, in particular, to differentiate between skew and nonskew distributional specifications in a number of simulation studies. Finally, to illustrate their practical applicability, the developed models are applied to a study on cholesterol levels originating from the Framingham Heart Study and a dataset from the Demographic and Health Surveys on undernutrition among children in Nigeria. Supplementary material for this article is available online.     

Synthesis of Functionalized Bicyclo[3.1.0]hexanes from Aucubin: An Access to Fused Aminocyclopentitols

Treatment of iodolactone 8a , having a cyclopentano[c]pyran skeleton and deriving from aucubin ( 1 ) (Scheme 1), with sodium trimethylsilanolate permitted a straightforward rearrangement to bicyclo[3.1.0]hexenes 10a and 10b (Schemes 3 and 4). Introduction of an N‐atom via a modified Curtius reaction provided an easy entry to fused aminocyclopentitols (Schemes 4 and 5). Target 4 is a conformationally restricted cyclopropane‐fused analogue of the glycosidase inhibitors mannostatins A ( 2 ) and B ( 3 ).     

Plasma-Assisted Pretreatment of Wheat Straw

O₃ generated in a plasma at atmospheric pressure and room temperature, fed with dried air (or oxygen-enriched dried air), has been used for the degradation of lignin in wheat straw to optimize the enzymatic hydrolysis and to get more fermentable sugars. A fixed bed reactor was used combined with a CO₂ detector and an online technique for O₃ measurement in the fed and exhaust gas allowing continuous measurement of the consumption of O₃. This rendered it possible for us to determine the progress of the pretreatment in real time (online analysis). The process time can be adjusted to produce wheat straw with desired lignin content because of the online analysis. The O₃ consumption of wheat straw and its polymeric components, i.e., cellulose, hemicellulose, and lignin, as well as a mixture of these, dry as well as with 50% water, were studied. Furthermore, the process parameters dry matter content and milled particle size (the extent to which the wheat straw was milled) were investigated and optimized. The developed methodology offered the advantage of a simple and relatively fast (0.5–2 h) pretreatment allowing a dry matter concentration of 45–60%. FTIR measurements did not suggest any structural effects on cellulose and hemicellulose by the O₃ treatment. The cost and the energy consumption for lignin degradation of 100 g of wheat straw were calculated.     

On a Smooth Dual Gap Function for a Class of Quasi-Variational Inequalities

A well-known technique for the solution of quasi-variational inequalities (QVIs) consists in the reformulation of this problem as a constrained or unconstrained optimization problem by means of so-called gap functions. In contrast to standard variational inequalities, however, these gap functions turn out to be nonsmooth in general. Here, it is shown that one can obtain an unconstrained optimization reformulation of a class of QVIs with affine operator by using a continuously differentiable dual gap function. This extends an idea from Dietrich (J. Math. Anal. Appl. 235:380–393 [24]). Some numerical results illustrate the practical behavior of this dual gap function approach.     

Modular Assembly of Host–Guest Metal–Phenolic Networks Using Macrocyclic Building Blocks

The manipulation of interfacial properties has broad implications for the development of high‐performance coatings. Metal–phenolic networks (MPNs) are an emerging class of responsive, adherent materials. Herein, host–guest chemistry is integrated with MPNs to modulate their surface chemistry and interfacial properties. Macrocyclic cyclodextrins (host) are conjugated to catechol or galloyl groups and subsequently used as components for the assembly of functional MPNs. The assembled cyclodextrin‐based MPNs are highly permeable (even to high molecular weight polymers: 250–500 kDa), yet they specifically and noncovalently interact with various functional guests (including small molecules, polymers, and carbon nanomaterials), allowing for modular and reversible control over interfacial properties. Specifically, by using either hydrophobic or hydrophilic guest molecules, the wettability of the MPNs can be readily tuned between superrepellency (>150°) and superwetting (ca. 0°).     

Using Background Knowledge from Preceding Studies for Building a Random Forest Prediction Model: A Plasmode Simulation Study

There is an increasing interest in machine learning (ML) algorithms for predicting patient outcomes, as these methods are designed to automatically discover complex data patterns. For example, the random forest (RF) algorithm is designed to identify relevant predictor variables out of a large set of candidates. In addition, researchers may also use external information for variable selection to improve model interpretability and variable selection accuracy, thereby prediction quality. However, it is unclear to which extent, if at all, RF and ML methods may benefit from external information. In this paper, we examine the usefulness of external information from prior variable selection studies that used traditional statistical modeling approaches such as the Lasso, or suboptimal methods such as univariate selection. We conducted a plasmode simulation study based on subsampling a data set from a pharmacoepidemiologic study with nearly 200,000 individuals, two binary outcomes and 1152 candidate predictor (mainly sparse binary) variables. When the scope of candidate predictors was reduced based on external knowledge RF models achieved better calibration, that is, better agreement of predictions and observed outcome rates. However, prediction quality measured by cross-entropy, AUROC or the Brier score did not improve. We recommend appraising the methodological quality of studies that serve as an external information source for future prediction model development.     

Triplet-Triplet Energy Transfer: A Simple Strategy for an Efficient Visible Light-Induced Photoclick Reaction

Photoclick reactions combine the advantages offered by light-driven processes and classical click chemistry and have found applications ranging from surface functionalization, polymer conjugation, photo-crosslinking, and protein labeling. Despite these advances, the dependency of most of the photoclick reactions on UV light poses a severe obstacle for their general implementation, as this light can be absorbed by other molecules in the system resulting in their degradation or unwanted reactivity. However, the development of a simple and efficient system to achieve bathochromically shifted photoclick transformations remains challenging. Here, we introduce triplet-triplet energy transfer as a fast and selective way to enable visible light-induced photoclick reactions. Specifically, we show that 9,10-phenanthrenequinones ( PQ s) can efficiently react with electron-rich alkenes ( ERA s) in the presence of a catalytic amount (as little as 5 mol %) of photosensitizers. The photocycloaddition reaction can be achieved under green (530 nm) or orange (590 nm) light irradiation, representing a bathochromic shift of over 100 nm as compared to the classical PQ-ERA s system. Furthermore, by combining appropriate reactants, we establish an orthogonal, blue and green light-induced photoclick reaction system in which the product distribution can be precisely controlled by the choice of the color of light.