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We demonstrate permanent water trapping in reduced graphene oxide after high relative humidity exposure. For this purpose, we grew graphene oxide films via spin-coating on glass substrates followed by thermal reduction. The electrical resistance of the planar device was then measured. We observed that resistance is significantly increased after water vapor exposure and remains stable even after 250 days in ambient conditions. Various techniques were applied to desorb the water and decrease (recover) the material's resistance, but it was achieved only with low temperature thermal annealing (180 °C) under forming gas (H2/N2 mixture). The permanent effect of water absorption was also detected by x-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

By measuring the proton spin–lattice relaxation times (T1H) in the solid-state for black spruce softwood, the molecular mobilities of carbohydrates and lignin have been evaluated as a function of pH. These studies have shown that the mobility of the polymeric constituents of wood is affected by the ionization of the different functional groups at different pH's. The analyses of the proton-spin–lattice relaxation time data at constant humidity revealed that the maximum T1H for both carbohydrates and lignin occurs at about neutrality, while it was found to be depressed at the two extremes of the pH range. By treating a wood sample with propylene oxide, the esterification of the acid groups was affected, thus deactivating the ionization process and their contribution to T1H. The experimental T1H values for cellulose and lignin after the esterification were significantly decreased at pH 6 confirming that their ionization plays a very significant role in determining chain mobility. [ABSTRACT FROM AUTHOR]

A new method for the chemical determination of Platelet-Activating Factor (PAF) has been developed. The method is based on the derivatization of the PAF molecule into a fluorescent derivative, through a three step procedure and the determination of the obtained derivative with HPLC combined with a fluorescent detector. Initially, PAF is converted to hepta-fluorobutyroyl-derivative which is hydrolyzed with water. The hydrolyzed derivative of PAF reacts with 7-methoxycoumarin-4-acetic acid to yield a fluorescent derivative of PAF, which is subjected to HPLC analysis on a reverse C18 column and measured with a fluorescent detector. The range of linearity and the detection limit of the method has been detected. The method is linear up to 10 ng PAF with a detection limit of 0.3 ng, at a signal to noise ratio above 3. This new method was successfully applied to human blood after its extraction and purification by a published method. Finally, the entire method has also been applied to standard phospholipids. [ABSTRACT FROM AUTHOR]

Over the past few years substantial efforts in our laboratory have been devoted toward the development of novel NMR techniques for the analysis of soluble and solid lignocellulosic substances. These efforts were undertaken in order to expand the frontiers of application of NMR for the detection of functional groups present in such materials. Our methodology involves the selective phosphorus-tagging of a variety of functional groups present in lignin and carbohydrates, followed by solution and solid stateP NMR spectroscopies. This paper attempts to review the status of this technique by discussing its development for the analysis of soluble and solid lignocellulosic samples. SolutionP NMR can be used to examine soluble lignin and carbohydrate samples after phosphitylation with 1,3,2 dioxaphospholanyl chloride. This is a novel and powerful means to determine the three principal forms of phenolic hydroxyls present in lignins i.e. p-hydroxyphenyl, guaiacyl, and syringyl structures. In addition, primary hydroxyls, carboxylic acids, and the two diastereomeric forms of arylglycerol- beta-aryl ether units (β-O-4 structures) present in lignins can also be determined from a singleP NMR experiment. When applied to carbohydrates, the technique gave characteristic signals for the alpha and beta anomers and the epimeric forms of monosaccharides. Completely resolvedP NMR spectra were also obtained when lignin-carbohydrate model compounds were examined. Solid stateP NMR can be used to determine quinone chromophore groups present in solid lignocellulosic samples. The method is based on literature accounts that describe adduct formation between trimethyl phosphite and quinones followed by solid stateP NMR. This reaction when reexamined in our laboratory showed that the presence of carboxylic acids in high yield pulps significantly affected the solid stateP NMR signal intensity. This realization permitted the development of an experimental protocol that allowed solid stateP NMR signals to be received from high yield pulps that contain information only on ortho-quinones and coniferaldehyde chromophores. It was thus found that about 0.7 ortho-quinone groups are present in every 100 C units within the lignin of a black spruce refiner mechanical pulp sample, in agreement with previously applied independent techniques. [ABSTRACT FROM AUTHOR]

Abstract: Continuous monitoring of food properties during drying is of stark relevance for the food processing industry. The main task of this research is to apply laser backscattering technology to simultaneously predict variations in hardness, moisture content and soluble solids content (SSC) of apples during drying. A laser diode with a wavelength of 635nm was used to non-destructively analyze photon migration in the apple tissue. The backscattering area in pixel numbers, representing the illuminated area after laser light injection, and light luminescence measured by grey values were used for estimating changes in internal quality parameters during drying. A decrease in moisture content caused a reduction in photon scattering determined by diminished light propagation in the fruit tissue. Additionally, scattering images showed less photon migration as the SSC increased due to the light absorption of light at 635nm by fruit compounds. To estimate moisture content, calibration models gave the highest coefficients of determination (R 2 =0.8 and 0.89) with standard errors of cross validation (SECV) of 11.6 and 9.8 for backscattering area and light luminescence, respectively. However, predictions obtained for SSC were slightly lower. Laser light measurement at 635nm was found to be adequate for predicting changes in moisture content and SSC of apple during drying over different stages. On the contrary, photon scattering at 635nm is not recommended as estimator of change in hardness during apple drying, based on the results. [Copyright &y& Elsevier]