The application of multivariate techniques to data from spanish glass-making objects from the Roman Era

Three multivariate techniques (principal components analysis, correspondence factor analysis and spectral map analsis) are applied to x-ray fluorescence data from glass-making objects from the 5th century AD found in Tarragona (Tarraco in the Roman Empire). The information obtained by displaying th eobjects and variables in each reduced factor space is compared. The presence of redundant information is shown. The visualization of groups of objects and of the relationship between objects and variables allows the formulation of hypotheses concerning the origin of the samples and the presence of local glassworks.     

Polybenzoxazines from renewable diphenolic acid

The novel benzoxazine monomers, DPA‐Bz and MDP‐Bz from renewable diphenolic acid (DPA), which mimics the structure of bisphenol A (BPA), were synthesized by traditional approaches. The structure and purity of the monomers was confirmed by FTIR, ¹H NMR, and ¹³C NMR spectra. The thermally activated polymerization of the MDP‐Bz and DPA‐Bz afforded thermosetting polybenzoxazines with higher T_g's, 270 °C and 208 °C respectively, and higher crosslinking density compared to BPA‐Bz, due to the transesterification or esterification reactions occurred during curing process. These reactions are in accordance with the number of independent reactions determined analyzing by SVD the chemical rank of the IR spectra data matrices recorded along the homopolymerization reactions monitored at 200 °C. Spectral and concentration profiles of the active chemical species involved in these processes were obtained by MCR‐ALS. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Two new eudesmane derivatives from Verbesina virginica

<正>Two new eudesmane derivatives were isolated from the leaves and flowers of Verbesina virginica,along with the known 6-O-β-E -p-coumaroyl-4α-hydroxyeudesmane(1).Their structures were determined as 6-O-β-Z-p-coumaroyl-4α-hydroxyeudesmane(2) and 6-O-α-E-p-coumaroyl-1β-4α-dihydroxyeudesmane(3) by spectroscopic methods.     

Multivariate resolution of rank-deficient near-infrared spectroscopy data from the reaction of curing epoxy resins using the rank augmentation strategy and multivariate curve resolution alternating least squares approach

A model of the curing reaction between phenyl glycidyl ether (PGE) and aniline as the curing agent was studied isothermally at 95 °C and monitored in situ by near-infrared spectroscopy (NIR). The spectra were recorded every 5 min. The ubiquitous problem of rank deficiency in reaction network systems was solved by assembling an augmented column-wise matrix containing five process runs from different initial conditions. The data were analyzed using a two-way multivariate curve resolution alternating least squares method (MCR-ALS). Initial estimates of spectra required by MCR-ALS were given by a SIMPLe-to-use Interactive Self-modeling Mixture Analysis (SIMPLISMA) approach. The reactants, product and intermediate spectra were successfully resolved and the concentration profiles properly represented the system studied. The performance of the model was evaluated by two parameters: ALS lack of fit (lof=0.88%) and explained variance (R²=99.99%). To validate the MCR-ALS results, the similarity coefficients (r) between the recovered spectra and the pure species spectra were calculated. These were: PGE (r=0.998), aniline (r=0.994) and tertiary amine (r=0.999).     

Effect of Pr-Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO₃ perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La_1−2x Pr _x Ca _x )MnO₃ (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T _c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.     

PRESSURE-VELOCITY EQUILIBRIUM HYDRODYNAMIC MODELS

This article describes mathematical models for phase separated mixtures of materials that are in pressure and velocity equilibrium but not necessarily temperature equilibrium. General conditions for constitutive models for such mixtures that exhibit a single mixture sound speed are discussed and specific examples are described.     

Validation of the concentration profiles obtained from the near infrared/multivariate curve resolution monitoring of reactions of epoxy resins using high performance liquid chromatography as a reference method

This paper reports the validation of the results obtained by combining near infrared spectroscopy and multivariate curve resolution-alternating least squares (MCR-ALS) and using high performance liquid chromatography as a reference method, for the model reaction of phenylglycidylether (PGE) and aniline. The results are obtained as concentration profiles over the reaction time. The trueness of the proposed method has been evaluated in terms of lack of bias. The joint test for the intercept and the slope showed that there were no significant differences between the profiles calculated spectroscopically and the ones obtained experimentally by means of the chromatographic reference method at an overall level of confidence of 5%. The uncertainty of the results was estimated by using information derived from the process of assessment of trueness. Such operational aspects as the cost and availability of instrumentation and the length and cost of the analysis were evaluated. The method proposed is a good way of monitoring the reactions of epoxy resins, and it adequately shows how the species concentration varies over time.     

Synthesis and study of the thermal crosslinking of bis(m‐aminophenyl) methylphosphine oxide based benzoxazine

Bis(m‐aminophenyl)methylphosphine oxide based benzoxazine (Bz‐BAMPO) was obtained using a three‐step synthetic method from the aromatic diamine and 2‐hydroxybenzaldehyde as starting materials. The structure and purity of the monomer was confirmed by elemental analysis, FTIR, ¹H NMR, ¹³C NMR and ³¹P NMR spectra. The curing kinetics of Bz‐BAMPO was investigated by nonisothermal differential scanning calorimetry (DSC) at different heating rates and by FTIR spectroscopy. The isoconversional method was used to evaluate the dependence of the effective activation energy on the extent of conversion. The evolving factor analysis (EFA) method was applied to the spectroscopic FTIR data obtained in monitoring benzoxazine homopolymerizations. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7162–7172, 2008