Indole diterpenoid natural products as the inspiration for new synthetic methods and strategies.

Indole terpenoids comprise a large class of natural products with diverse structural topologies and a broad range of biological activities. Accordingly, indole terpenoids have and continue to serve as attractive targets for chemical synthesis. Many synthetic efforts over the past few years have focused on a subclass of this family, the indole diterpenoids. This minireview showcases the role indole diterpenoids have played in inspiring the recent development of clever synthetic strategies, and new chemical reactions

Oxidation resistance of graphene-coated Cu and Cu/Ni alloy

The ability to protect refined metals from reactive environments is vital to many industrial and academic applications. Current solutions, however, typically introduce several negative effects, including increased thickness and changes in the metal physical properties. In this paper, we demonstrate for the first time the ability of graphene films grown by chemical vapor deposition to protect the surface of the metallic growth substrates of Cu and Cu/Ni alloy from air oxidation. SEM, Raman spectroscopy, and XPS studies show that the metal surface is well protected from oxidation even after heating at 200 \degree C in air for up to 4 hours. Our work further shows that graphene provides effective resistance against hydrogen peroxide. This protection method offers significant advantages and can be used on any metal that catalyzes graphene growth

Comparing apples and oranges: assessment of the relative video quality in the presence of different types of distortions

<p>Abstract</p> <p>Video quality assessment is essential for the performance analysis of visual communication applications. Objective metrics can be used for estimating the relative quality differences, but they typically give reliable results only if the compared videos contain similar types of quality distortion. However, video compression typically produces different kinds of visual artifacts than transmission errors. In this article, we focus on a novel subjective quality assessment method that is suitable for comparing different types of quality distortions. The proposed method has been used to evaluate how well different objective quality metrics estimate the relative subjective quality levels for content with different types of quality distortions. Our conclusion is that none of the studied objective metrics works reliably for assessing the co-impact of compression artifacts and transmission errors on the subjective quality. Nevertheless, we have observed that the objective metrics' tendency to either over- or underestimate the perceived impact of transmission errors has a high correlation with the spatial and temporal activity levels of the content. Therefore, our results can be useful for improving the performance of objective metrics in the presence of both source and channel distortions.</p

Communicating product user reviews and ratings in interfaces for e-commerce: a multimodal approach

This paper describes a comparative empirical evaluation study that uses multimodal presentations to communicate review messages in an e-commerce platform. Previous studies demonstrate the effective use of multimodality in different problem domains (e.g. e-learning). In this paper, multimodality and expressive avatars are used to communicate information related to product reviews messages. The data of the reviews was opportunistically collected from Facebook and Twitter. Two independent groups of users were used to evaluate two different presentations of reviews and ratings using as a basis an experimental e- commerce platform. The control group used a text-based with emojis presentation and the experimental group used a multimodal approach based on expressive avatars. Three parameters of usability were measured. These were efficiency, effectiveness, user satisfaction, and user preference. The result showed that the two approaches performed similarly. These findings provide a basis for further experiments in which text, emojis and expressive avatars can be combine to communicate a larger volume of reviews and ratings

Elucidating the molecular programming of a nonlinear non-ribosomal peptide synthetase responsible for fungal siderophore biosynthesis

Siderophores belonging to the ferrichrome family are essential for the viability of fungal species and play a key role for virulence of numerous pathogenic fungi. Despite their biological significance, our understanding of how these iron-chelating cyclic hexapeptides are assembled by non-ribosomal peptide synthetase (NRPS) enzymes remains poorly understood, primarily due to the nonlinearity exhibited by the domain architecture. Herein, we report the biochemical characterization of the SidC NRPS, responsible for construction of the intracellular siderophore ferricrocin. In vitro reconstitution of purified SidC reveals its ability to produce ferricrocin and its structural variant, ferrichrome. Application of intact protein mass spectrometry uncovers several non-canonical events during peptidyl siderophore biosynthesis, including inter-modular loading of amino acid substrates and an adenylation domain capable of poly-amide bond formation. This work expands the scope of NRPS programming, allows biosynthetic assignment of ferrichrome NRPSs, and sets the stage for reprogramming towards novel hydroxamate scaffolds

Persistence of plug-in rule in classification of high dimensional multivariate binary data

In this paper, we consider the classification problem when the predictors are multivariate binary random variables. Variables are modeled as independent, but not necessarily identical, Bernoulli. A triangular array for parameters, (P11(n),...,P1d(n), P21(n),....,P2d(n)), is assumed to allow parameters to change and the number of the variables, d, to increase for adopting more flexible models as the sample size, n, increases. Our results are obtained under moderate assumptions on the triangular array of the probability vectors. We use maximum likelihood estimators for the parameters and plug them into the Bayes classifier. This is a plug-in classifier, a sort of objective Bayes rule. It is shown in Wilbur et al. [2002. Variable selection in high-dimensional multivariate binary data with application to the analysis of microbial DNA fingerprints. Biometrics 58, 378-386] via simulations that the plug-in rule classifies quite well even when the assumption of independence is violated. The main interest in this paper is in the complex case of d/nv&#8594;c for some v&gt;0 and c&gt;0 for which very little is known. Using linearity of the plug-in rule, we show its persistence, a generalization of the notion of consistency, when the variance of the plug-in rule or a quantity measuring signal to noise ratio is divergent; otherwise we show there exists an example of non-persistence of the plug-in rule. In case of non-persistence, we introduce the notion of sparsity and overcome non-persistence by selecting a subset of the variables. This shows why a variable selection procedure may be effective especially for contemporary practical problems with high dimensional data [Wilbur et al., 2002. Variable selection in high-dimensional multivariate binary data with application to the analysis of microbial DNA fingerprints

Mechanism of phase transition, from vapor to solid: Transient liquid phase is between the two

The mechanism of phase transition, from vapor to solid, is studied by producing non-stoichiometric ZnO and CdS nanoclusters (NCs) by low-energy cluster beam deposition technique, and examining their morphological and compositional evolution over a long span of time. It is concluded that the transition of vapor to solid goes through a transient liquid phase: coagulation of a large number of atomic clusters first forms liquid NCs which then solidify. The nature of the material and the experimental conditions determine crystallinity and shape of the NCs during the solidification process

Nickel-Catalyzed Amination of Aryl Chlorides and Sulfamates in 2-Methyl-THF.

The nickel-catalyzed amination of aryl O-sulfamates and chlorides using the green solvent 2-methyl-THF is reported. This methodology employs the commercially available and air-stable precatalyst NiCl2(DME), is broad in scope, and provides access to aryl amines in synthetically useful yields. The utility of this methodology is underscored by examples of gram-scale couplings conducted with catalyst loadings as low as 1 mol % nickel. Moreover, the nickel-catalyzed amination described is tolerant of heterocycles and should prove useful in the synthesis of pharmaceutical candidates and other heteroatom-containing compounds

Nickel-Catalyzed Suzuki–Miyaura Coupling of Aliphatic Amides

We report the Ni-catalyzed Suzuki–Miyaura coupling of aliphatic amide derivatives. Prior studies have shown that aliphatic amide derivatives can undergo Ni-catalyzed carbon–heteroatom bond formation but that Ni-mediated C–C bond formation using aliphatic amide derivatives has remained difficult. The coupling disclosed herein is tolerant of considerable variation with respect to both the amide-based substrate and the boronate coupling partner and proceeds in the presence of heterocycles and epimerizable stereocenters. Moreover, a gram-scale Suzuki–Miyaura coupling/Fischer indolization sequence demonstrates the ease with which unique polyheterocyclic scaffolds can be constructed, particularly by taking advantage of the enolizable ketone functionality present in the cross-coupled product. The methodology provides an efficient means to form C–C bonds from aliphatic amide derivatives using nonprecious-metal catalysis and offers a general platform for the heteroarylation of aliphatic acyl electrophiles