Study of Polymer-Cement Composite Containing Portland Cement and Aqueous Poly (methyl methacrylate) Latex Polymer by Fourier-Transform Infrared (FT-IR) Spectroscopy

The polymer-cement composite is an immiscible band having modified morphology. Polymer phase improves the toughness of brittle cement and has a reinforcing effect, and interactions between cement components and polymers provide stability. In this study, polymer latex [poly(methyl methacrylate), PMMA] – cement paste was prepared with different weight proportions of polymer content. The main scientific objective of this report has been the analysis and the prediction of high strength with the aim of understanding the interactions of PMMA polymer with Portland cement after hydration reaction of cement pastes and curing the specimens for 28 days. The samples were studied by Fourier transform infrared (FT-IR) spectroscopy. The results are critically examined. It is shown that bands support the interaction of PMMA with cement in the composite.     

Effect of Molecular Crowding on the Temperature–Pressure Stability Diagram of Ribonuclease A

FT‐IR spectroscopic and thermodynamic measurements were designed to explore the effect of a macromolecular crowder, dextran, on the temperature and pressure‐dependent phase diagram of the protein Ribonuclease A (RNase A), and we compare the experimental data with approximate theoretical predictions based on configuration entropy. Exploring the crowding effect on the pressure‐induced unfolding of proteins provides insight in protein stability and folding under cell‐like dense conditions, since pressure is a fundamental thermodynamic variable linked to molecular volume. Moreover, these studies are of relevance for understanding protein stability in deep‐sea organisms, which have to cope with pressures in the kbar range. We found that not only temperature‐induced equilibrium unfolding of RNase A, but also unfolding induced by pressure is markedly prohibited in the crowded dextran solutions, suggesting that crowded environments such as those found intracellularly, will also oppress high‐pressure protein unfolding. The FT‐IR spectroscopic measurements revealed a marked increase in unfolding pressure of 2 kbar in the presence of 30 wt % dextran. Whereas the structural changes upon thermal unfolding of the protein are not significantly influenced in the presence of the crowding agent, through stabilization by dextran the pressure‐unfolded state of the protein retains more ordered secondary structure elements, which seems to be a manifestation of the entropic destabilization of the unfolded state by crowding.     

Influence of the Metal Ion on the Two‐Photon Absorption Properties of Lanthanide Complexes Including Near‐IR Emitters

The synthesis of tris(2‐thenoyltrifluoroacetonate)lanthanide(III) complexes featuring a diethylaminostyryl‐2,2′‐bipyridine coligand was achieved for lanthanum; the near‐infrared (NIR) emitters neodymium, erbium, and ytterbium; and the transition‐metal yttrium. The photophysical properties were thoroughly studied, and it was demonstrated that the conjugated bipyridine ligand acts as a good antenna for the sensitization of the NIR emitters. The two‐photon absorption (TPA) properties of all five complexes were investigated by using both two‐photon excited fluorescence and the Z‐scan method. We demonstrate that the nature of the rare earth ion has almost no influence on the TPA properties centered on the conjugated bipyridyl ligand. Finally, we show that Yb^III is sensitized by a two‐photon antenna effect, and that Nd^III is mostly sensitized by a one‐photon process involving direct excitation of forbidden f–f transitions.     

Real-Time Monitoring of the Mechanical Properties of a Soy Protein and Rubber Polymer during its Production Using Transient Infrared Spectroscopy

Soy protein–based polymers offer promising performance properties, but their characteristics are sensitively dependent on production conditions, so on-line monitoring could help provide the needed control during production. Mid-infrared spectroscopy combined with partial least squares offer the needed analysis, but the opacity of many materials in the mid-infrared range limits its conventional application. Transient infrared spectroscopy is a method of acquiring mid-infrared spectra from moving streams in real time that avoids the opacity problem. We apply transient infrared spectroscopy to a polymer of soy protein and polyisoprene-graft-maleic anhydride–modified natural rubber during its compounding extrusion to measure tensile strength and Young's modulus.     

Stacking‐Induced Diamagnetic/Paramagnetic Conversion of Imidazo[1,2‐a]pyridin‐2(3 H)‐one Derivatives: Near‐Infrared Absorption and Magnetic Properties in the Solid State

Herein, we present three imidazo[1,2‐a]pyridin‐2(3 H)‐one derivatives that are diamagnetic in solution, but paramagnetic in the solid state, possibly owing to a stacking‐induced formation of phenoxide‐type radicals. Notably, a larger bathochromic shift of the absorption (even up to the near‐ infrared region) of these three compounds was observed in the solid state than in solution, which was attributable to the ordered columnar stacking arrangements or their single‐electron character as radicals in the solid state. Interestingly, compared to that in solution, (E)‐3‐(pyridin‐4′‐ylmethylene)imidazo[1,2‐a]pyridine 2(3 H)‐one displayed a largely red‐shifted emission (centered at 660 nm, with tailing above 800 nm) in the solid state. A larger bathochromic shift (260 nm) of the emission is an indication of better order and tight stacking in the solid state, which is brought about by the rigid and polar acceptor. These three compounds also reveal different magnetic susceptibilities at 300 K, thus implying that they possess various columnar stacking structures. Most interestingly, these three radicals exhibit unusual ferromagnetic‐to‐antiferromagnetic phase transitions, which can be attributed to anisotropic contraction and non‐uniform slippage of the columnar stacking chains.     

Near infrared spectroscopy and multivariate analysis to evaluate wheat flour doughs leavening and bread properties

A mixture design of experiment approach was followed to explore formulation effects on the technological properties of wheat flours optimized for industrial bread-making purposes. Ten different flour mixtures were investigated by means of near infrared spectroscopy (NIRS) to obtain information on flour performance in a critical phase such as dough leavening. For each mixture, a laboratory-scale bread making experiment was carried out according to a standardized recipe and the leavening phase of each dough sample was monitored by means of NIRS at different times. Parallel factor analysis (PARAFAC) was used to highlight the existence of differences among the mixtures on the basis of NIR spectrum variability with respect to the leavening time. Additionally, the relationship among the 3-way NIR dataset and some parameters measured on the baked bread loaves (dimensions, volume, weight) was investigated by means of the n-way extension of partial least squares regression (nPLS), in order to evaluate product properties from its leavening step and mixture formulation. The results give better insight on the relationships among wheat flour formulation and its performance in the leavening phase and as far as some properties of the final product are concerned, thus offering a way to monitor the leavening phase and give information on its influence on the final product properties.     

Muscle oxygenation measurement in humans by noninvasive optical spectroscopy and Locally Weighted Regression

We have developed a method to make real-time, continuous, noninvasive measurements of muscle oxygenation (Mox) from the surface of the skin. A key development was measurement in both the visible and near infrared (NIR) regions. Measurement of both oxygenated and deoxygenated myoglobin and hemoglobin resulted in a more accurate measurement of Mox than could be achieved with measurement of only the deoxygenated components, as in traditional near-infrared spectroscopy (NIRS). Using the second derivative with respect to wavelength reduced the effects of scattering on the spectra and also made oxygenated and deoxygenated forms more distinguishable from each other. Selecting spectral bands where oxygenated and deoxygenated forms absorb filtered out noise and spectral features unrelated to Mox. NIR and visible bands were scaled relative to each other in order to correct for errors introduced by normalization. Multivariate Curve Resolution (MCR) was used to estimate Mox from spectra within each data set collected from healthy subjects. A Locally Weighted Regression (LWR) model was built from calibration set spectra and associated Mox values from 20 subjects using 2562 spectra. LWR and Partial Least Squares (PLS) allow accurate measurement of Mox despite variations in skin pigment or fat layer thickness in different subjects. The method estimated Mox in five healthy subjects with an RMSE of 5.4%.     

Theoretical analysis of correlation between ionization threshold fluence in IR‐MALDI and IR absorption spectrum of matrix molecules

To investigate the correlation between the wavelength dependence of ionization threshold fluence of target molecule in matrix‐assisted laser desorption/ionization by infrared (IR) laser and the IR absorption spectrum of matrix molecule, we have analyzed the IR absorption spectra of four matrix molecules using density functional theory and correlated ab initio molecular orbital method. The calculated IR absorption spectra of the isolated molecules showed more qualitative correlation with the wavelength dependence of ionization threshold fluence than those of the solid state structures. We can consider that a portion of matrix molecules lost the ordered crystal structure and that the transition to the diluted or isolated state occurred at the early process of IR laser irradiation. © 2012 Wiley Periodicals, Inc.     

Efficient Microscale Preparation of Isotopically Enriched 1‐[79Br]Bromo‐2‐Fluoroethylene, [79Br]BrHC˭CHF

Abstract

An efficient preparation of 1‐[⁷⁹Br]bromo‐2‐fluoroethylene, [⁷⁹Br]BrHC?CHF, was carried out by a three‐step procedure: (a) natural 1‐bromo‐2‐fluoroethylene, BrHC?CHF, was iodinated to 1‐fluoro‐2‐iodoethylene, FHC?CHI; (b) 1‐fluoro‐2‐iodoethylene was ⁷⁹Br₂‐brominated to 1,2‐di[⁷⁹Br]bromo‐1‐fluoro‐2‐iodoethane, [⁷⁹Br]BrFCHCH[⁷⁹Br]BrI; and (c) 1,2‐di[⁷⁹Br]bromo‐1‐fluoro‐2‐iodoethane was dehalogenated to 1‐[⁷⁹Br]bromo‐2‐fluoroethylene, [⁷⁹Br]BrHC?CHF. The yield of isolated product, on a 2‐mmol scale, was 62% with respect to ⁷⁹Br₂.     

Structure and spectroscopic aspects of water‐halide ion clusters: A study based on a conjunction of stochastic and quantum chemical methods

In this article, we propose a stochastic search based method, namely genetic algorithm in conjunction with density functional theory to evaluate structures of water‐halide microclusters, with the halide ion being Cl^?, Br^?, and I^?. Once the structures are established, we evaluate the infrared spectroscopic modes, vertical detachment energies and natural population analysis based charges. We compare our results with available experimental and theoretical results. © 2012 Wiley Periodicals, Inc.