Novel multicomponent reaction for the combinatorial synthesis of 2-imidazolines

[reaction: see text] The three-component condensation between an amine, an aldehyde, and an alpha-acidic isocyanide efficiently provides substituted 2-imidazolines in a one-pot reaction under mild conditions.     

Stepwise deletion: a technique for missing-data handling in multivariate analysis

Multivariate data sets often contain gaps in the data matrix. Especially with medical data, missing values are not always avoidable. Most techniques of data analysis do not allow for data gaps; a brief overview is given of the methods currently used to cope with this problem. There are two major groups of missing-data handling techniques: preprocessing techniques used before the data anaysis, and techniques integrated into the data analysis. Preprocessing tecniques can involve deletion of incomplete objects or variables, which loses existing values, or replacement of missing data by estimates, which introduces pseudo-information and bias. Integrated methods are not usually satisfactory. To avoid most of these disadvantages, a new preprocessing technique is proposed for deleting missing data. The algorithm comprises a stepwise deletion of both variables and objects, which retains as much of the data as possible. It is demonstrated on several artificially constructed problem data sets and on some real clinical data collections. It is shown to retain considerably more of the original data sets than other deleting procedures.     

Fabrication process parameters significantly affect the perovskite oxygen carriers materials (OCM) performance in chemical looping with oxygen uncoupling (CLOU)

Journal of Thermal Analysis and Calorimetry - The CLOU performance of the CaTixMn0.9?xMg0.1O3 (CMTM) perovskite-type system was investigated, comparing materials produced at laboratory scale...     

Determination of an acceptable level of spectral data compression by Discrete Wavelet Transforms

Today, due to the ever increasing amount of data generated by analytical instruments, good compression methods are desired to keep computation time acceptable. The lower the volume and noise content of data, the easier it becomes to investigate and interpret the modeling results. Discrete Wavelet Transform (DWT) is an effective data compression and noise suppression tool. Compression can be performed at different levels, in each, the size of signal part of the data reduces to half the size. This work includes an approach for determining an acceptable level of compression of data where the aim is to achieve minimal loss of information and no significant change in the structure of data, which could mean, e.g. no loss in predictive ability or the effective rank of the data-set. The method is based on estimation of the Singular Values (SVs) from a data matrix and the Singular Values at each level of compression followed by the application of Median Absolute Deviation (MAD) of the correlation between original SVs and compression SVs as a simple statistical test for the determination of the optimum level of compression. We illustrate the method using FT-Raman data from aqueous solutions of three sugars (glucose, trehalose and sucrose) and NMR data from mixtures of three alcohols. A sudden change in prediction error sum of square plots from Partial Least Squares (PLS) modeling confirms the results from MAD statistics.     

Nanowires Formed by the Co‐Assembly of a Negatively Charged Low‐Molecular Weight Gelator and a Zwitterionic Polythiophene

Conjugated organic nanowires have been prepared by co‐assembling a carboxylate containing low‐molecular weight gelator (LMWG) and an amino acid substituted polythiophene derivative (PTT). Upon introducing the zwitterionic polyelectrolyte PTT to a basic molecular solution of the organogelator, the negative charges on the LMWG are compensated by the positive charges of the PTT. As a result, nanowires form through co‐assembly. These nanowires are visualized by both transmission electron microscopy (TEM) and atomic force microscopy (AFM). Depending on the concentration and ratio of the components these nanowires can be micrometers long. These measurements further suggest that the aggregates adopt a helical conformation. The morphology of these nanowires are studied with fluorescent confocal laser scanning microscopy (CLSM). The interactions between LMWG and PTT are characterized by steady‐state and time‐resolved fluorescence spectroscopy studies. The steady‐state spectra indicate that the backbone of the PTT adopts a more planar and more aggregated conformation when interacting with LMWG. The time‐ resolved fluorescence decay studies confirm this interpretation.     

Linking Phospholipase Mobility to Activity by Single‐Molecule Wide‐Field Microscopy

Many of the biological processes taking place in cells are mediated by enzymatic reactions occurring in the cell membrane. Understanding interfacial enzymatic catalysis is therefore crucial to the understanding of cellular function. Unfortunately, a full picture of the overall mechanism of interfacial enzymatic catalysis, and particularly the important diffusion processes therein, remains unresolved. Herein we demonstrate that single‐molecule wide‐field fluorescence microscopy can yield important new information on these processes. We image phospholipase enzymes acting upon bilayers of their natural phospholipid substrate, tracking the diffusion of thousands of individual enzymes while simultaneously visualising local structural changes to the substrate layer. We study several enzyme types with different affinities and catalytic activities towards the substrate. Analysis of the trajectories of each enzyme type allows us successfully to correlate the mobility of phospholipase with its catalytic activity at the substrate. The methods introduced herein represent a promising new approach to the study of interfacial/heterogeneous catalysis systems.