Parallel co-ordinate geometry and principal component analysis for the interpretation of large multi-response experimental designs

In the evaluation of large or complex data sets the use of visualization methods can be of great benefit. In this paper, the use of parallel co-ordinate geometry (PCG) plots, principal component analysis (PCA) and N-way PCA as visualization procedures for large multi-response experimental designs was compared with the more traditional approach of calculating factor effects by multiple linear regression. PCG plots are a recent addition to the visualization tools and offer a possibility to visualize multi-dimensional data in two dimensions while no calculations are required. It was found that PCA and PCG each have their own benefits and disadvantages. Both methods can be used to some extent to select optimal conditions. Moreover, it was possible to use the PCA score plot as a Pareto optimality plot that allowed to select the experiments considered to be Pareto optimal. Therefore, the examined visualization methods can be useful and complementary aids in the interpretation of large multi-response experimental design data and they add a multivariate dimension to the more classical univariate analysis of such data.     

(E,E)‐2,5‐Di­methoxy‐1,4‐bis­[2‐(3,4,5‐tri­methoxy­phenyl)­ethenyl]­benzene

In the title compound, C₃₀H₃₄O₈, molecular symmetry is coincident with crystallographic inversion symmetry. A three‐dimensional network is generated containing both C—H·π and C—H·n(O) interactions. A comparison of the geometry of this mol­ecule and the structure of a number of 2,4,6‐tri­methoxy‐substituted analogues is provided.     

Wasseruntersuchung

Ohne Zusammenfassung     

Pressure‐assisted CEC versus CEC using methacrylate‐based monolithic columns: Influence of the polymerization‐mixture composition

Pressure‐assisted CEC (pCEC) can either be performed on a CE instrument by adding pressure at the column inlet, or by applying voltage on a capillary liquid chromatography system. This study investigates the pressure's added value in pCEC using an LC instrument as well as the influence of the polymerization‐mixture composition on monolithic columns in such experimental circumstances. Two factors of the polymerization mixture, which is used to prepare the monolithic capillary columns, were varied according to an experimental design approach: the pore‐forming solvent/total monomer ratio and the pore‐forming solvents composition. Initially, the effect of the resulting stationary phase on the elution behavior of mainly pharmaceutical compounds was studied. Four responses were used to evaluate the effects on the chromatography: retention time, retention factor, peak asymmetry and number of theoretical plates. After processing the results, the stationary phase composition with the best chromatographic behavior was determined and tested. The advantageous properties of this stationary phase compared with the design center‐point column were demonstrated. Secondly, the results of these pCEC experiments were compared with those generated in an identical experimental setup previously performed using CEC. Chromatographic conditions were chosen so that the center‐point column showed similar retention in CEC and pCEC. The expected advantage (faster analysis) and drawback (decreased efficiency) of pCEC in the analysis of pharmaceuticals was evaluated. Analysis time and efficiency were both found to depend greatly on the porosity of the column. The conclusion of this comparison is that pCEC did not have a significant added value to CEC. However, this was mainly due to the instrument's limitation of the pressure‐driven flow over the column. A clear benefit of the pCEC setup was apparatus‐related, i.e. the presence of a loop injection system on the pCEC instrument, which avoids the injection problems that were occasionally observed in CEC.     

Selectivity in the Ligand Functionalization of Photocatalytic Metal Oxide Nanoparticles for Phase Transfer and Self-Assembly Applications

The functionalization of photocatalytic metal oxide nanoparticles of TiO₂, ZnO, WO₃ and CuO with amine-terminated (oleylamine) and thiol-terminated (dodecane-1-thiol) alkyl-chain ligands was studied under ambient conditions. A high selectivity was observed in the binding specificity of a ligand towards nanoparticles of these different oxides. It was observed that oleylamine binds stably to only TiO₂ and WO₃, whereas dodecane-1-thiol binds stably only to ZnO and CuO. Similarly, polar-to-nonpolar solvent phase transfer of TiO₂ and WO₃ nanoparticles could be achieved by using oleylamine, but not dodecane-1-thiol, whereas the opposite holds for ZnO and CuO. The surface chemistry of ligand-functionalized nanoparticles was probed by attenuated total reflectance (ATR)-FTIR spectroscopy, which enabled the occupation of the ligands at the active sites to be elucidated. The photostability of the ligands on the nanoparticle surface was determined by the photocatalytic self-cleaning properties of the material. Although TiO₂ and WO₃ degrade the ligands within 24 h under both UV and visible light, ligands on ZnO and CuO remain unaffected. The gathered insights are also highly relevant from an application point of view. As an example, because the ligand-functionalized nanoparticles are hydrophobic in nature, they can be self-assembled at the air-water interface to give nanoparticle films with demonstrated photocatalytic as well as anti-fogging properties.     

Synthesis of naphthalene and indene precursors to naphthoic and indenoic acids

As part of ongoing research to investigate structural requirements for lactate dehydrogenase inhibition by highly substituted naphthoic and indenoic acids, certain naphthalene and indene precursors to those types of compounds are required. Described here are efficient preparations of 1-naphthoic acid precursors 6-benzyl-2,3-dimethoxy-1-propylnaphthalenes, including compounds with substituted benzyl groups and 7-benzyl-2,3-dimethoxy-1-propylnaphthalene. Also described are the syntheses of indenoic acid precursors 2-benzyl-5,6-dimethoxy-7-propyl-1H-indenes, including compounds with substituted benzyl groups. These compounds were made from the key intermediates 6,7-dimethoxy-5-propyl-1-tetralone, 6,7-dimethoxy-8-propyl-1-tetralone, and 5,6-dimethoxy-4-propyl-1-indanone.     

An alternating direction scheme on a nonuniform mesh for reaction-diffusion parabolic problems

In this paper we develop a numerical method for two-dimensionaltime-dependent reaction-diffusion problems. This method, whichcan immediately be generalized to higher dimensions, is shownto be uniformly convergent with respect to the diffusion problems.This method, which can immediately be generalized to higherdimensions, is shown to be uniformly convergent with respectto the diffusion parameter.     

Lead in micro-samples of whole blood by Rhenium-cup in-torch vaporization-inductively coupled plasma-atomic emission spectrometry (ITV-ICP-AES)

A method is described for screening of lead in diluted micro-samples of whole blood by a Re-cup, in-torch vaporization (ITV) sample introduction system for inductively coupled plasma-atomic emission spectrometry (ICP-AES). The method required minimum sample preparation. For example, blood was diluted with water and Triton X-100 in 0.5% HNO₃ and, 5 μL were deposited on the Re-cup of the ITV sample introduction system. Samples were dried and charred in-situ prior to vaporization. Levels 1, 2, 3 and 4 (Pb concentration: 4.04, 10.3, 20.59 and 39.36 μg/dL) of NIST Standard Reference Material 955b ‘lead in bovine blood’ were used to test accuracy and precision. Accuracy was acceptable and precision was below 10% for levels 2–4 and 15% for level 1.     

Modulation of Relaxivity,Suspension Stability,and Biodistribution of Dendronized Iron Oxide Nanoparticles as a Function of the Organic Shell Design

Nanoparticles (NPs) with a mean diameter of 10 nm are functionalized with three dendrons: D1 a PEGylated PAMAM dendron of generation 0.5, D2 a hydrophilic oligoethyleneglycol‐derivatized dendron (D2) displaying a phosphonic acid at the focal point, and D2–2P the same dendron than D2 but with two phosphonic acid anchoring agents. Their grafting is confirmed by IR spectroscopy and elemental analysis. All dendronized NPs are stable over a long period of time in suspensions in water and in different physiological media and display a mean hydrodynamic diameter smaller than 50 nm whatever the molecule architecture. NMRD profiles and relaxivity measurements highlight the influence of the molecule architecture on the water diffusion close to the magnetic core thus influencing the relaxation properties at low magnetic field. The high hydrophilic architecture of the dendron D2 by contrast to dendron D1 allows maintaining the colloidal stability in different conditions while ensuring a very good accessibility of water molecule close to the magnetic core. Coupling of a fluorescent dye on dendrons have allowed investigating the biodistribution of dendronized NPs, which are found to be quickly eliminated through urinary and hepatobiliary pathways within 4 h. Furthermore, no enhanced permeation and retention effect in tumors can be observed.