Use of capillary gas chromatography/sensory analysis as an additional tool for sampling technique comparison in peach aroma analysis

Capillary GC/sensory analysis was used to judge if dynamic headspace on sliced pulp and on intact fruit, and solvent extraction could collect the “character impact” and the “contributory” aroma compounds in peaches. Capillary GC/sensory data showed that the headspace techniques selectively recovered the “contributory” volatile compounds, which are strictly related to the characteristic odor of the various peach cultivars, whereas solvent extraction better quantified the “character impact” compounds (lactones).     

Effect of overlapping cellulose nanofibrils and nanoclay layers on mechanical and barrier properties of spray-coated papers

Cellulose - This work evaluates the effect of spray-coating papers using cellulose nanofibrils (CNFs) and nanoclay (NC) on the mechanical and barrier properties for application such as reinforced...     

Experimental two-phase pressure gradients during evaporation of pure and mixed refrigerants in a smooth horizontal tube. Comparison with correlations

The paper reports the results of an experimental study on pressure drop during horizontal flow boiling of refrigerants R22, R507, R404A, R134a, R407C and R410A. The test section is a smooth, horizontal, stainless steel tube (6 mm I.D., 6 m length) uniformly heated by Joule effect. The experimental tests are carried out at an almost constant evaporating pressure of 7.0 bar varying the mass flow rate in the range 280–1,080 kg/m² s. The experimental comparison clearly shown that the pressure drop of R22 is significantly higher as compared to all the other fluids. The results are compared against well-known pressure drop prediction methods. The available correlations can be used for both pure fluids and mixtures with no corrective factors, provided the mixture properties are evaluated at local compositions. The Chawla friction correlation is the best-fitting of our experimental data in combination with the heterogeneous momentum pressure drop model on the basis of the Rouhani-Axelsson void fraction correlation.     

Search for narrow resonances in e+e− annihilation into hadrons at adone

A search for narrow resonances in the reaction e⁺e^? → hadrons in the mass regions 1915–2345 MeV and 2970–3090 MeV has been perforned at ADONE, the Frascati storage ring. With 90% confidence level our data exclude the production of narrow resonances with integrated cross section larger than 20% of the integrated cross section for production of the J/Ψ (3100 MeV).     

Momentum analysis of kaon and pion pairs produced from time-like photons at 1.6 GeV energy

We present results for the total cross section of e⁺e^? annihilation into two hadrons at 1.6 GeV: σ_ππ = σ_KK = (1.8 ± 1.1) × 10^-33 cm².From these values we obtain the time-like electromagnetic form factors these mesons: |F_π|² = 0.24 ± 0.14 and |F_K|² = 0.46 ± 0.26.     

Application of factorial design to study of heavy metals biosorption by waste biomass from beverage distillery

A full factorial design leading to 20 sets of sorption runs was conducted to study the influence of four variables (bleaching earth and biomass concentrations, pH, and sorption time) on the iron, nickel, and chromium removal from stainless steel effluent using waste biomass from a beverage industry. Similar factor effects and interactions were found for each metalinvolved in this biosorption study, and the main factors were pH (positive effect) and biomass concentration (negative effect). Response surface methodology was adopted and an empirical linear polynomial model constructed on the basis of the specific uptake (mg of metal/g of biomass as dry weight) for each metal species. Under optimized process conditions (pH 4.0, biomass concentration of 2.0 g/L, absence of Celite), uptake values of 155 mg of Fe/g, 38 mg of Cr/g, and 0.4 mg of Ni/g were achieved after 3 h. This corresponded to a reduction in heavy metals concentration of approx 94% for Cr, 57% for Fe, and 25% for Ni.     

Osmotic and aging effects in caviar oocytes throughout water and lipid changes assessed by 1H NMR T1 and T2 relaxation and MRI

By combining NMR relaxation spectroscopy and magnetic resonance imaging techniques, unsalted (us) and salted (s) caviar (Acipenser transmontanus) oocytes were characterized over a storage period of up to 90 days. The aging and the salting effects on the two major cell constituents, water and lipids, were separately assessed. T1 and T2 decays were interpreted by assuming a two-site exchange model. At Day 0, two water compartments that were not in fast exchange were identified by the T1 relaxation measurements on the us oocytes. In the s samples, T1 decay was monoexponential. During the time of storage, an increment of the free water amount was found for the us oocytes, ascribed to an increased metabolism. T1 and T2 of the s oocytes shortened as a consequence of the osmotic stress produced by salting. Selective images showed the presence of water endowed with different regional mobility that severely changed during the storage. Lipid T1 relaxation decays collected on us and s samples were found to be biexponential, and the T1 values lengthened during storage. In us and s oocytes, the increased lipid mobility with the storage was ascribed to lipolysis. Selective images of us samples showed lipids that were confined to the cytoplasm for up to 60 days of storage.     

Analysis of organic components of smokeless gunpowders: high-performance liquid chromatogaphy vs. micellar electrokinetic capillary chromatography

The aim of the present study was to verify the analytical performances of high-performance liquid chromatography (HPLC) and micellar electrokinetic capillary chromatography (MEKC) for the separation and qualitative determination of a selected group of organic components of smokeless gunpowders. The HPLC method was based on a gradient reversed-phase elution with a mobile phase composed of 0.17 M H(3)PO(4)/methanol; detection was performed by UV absorption at the wavelengths of 220, 254, and 270 nm. The MEKC experiments were carried out by using uncoated fused-silica capillaries (50 microm inside diameter, 50 cm effective length) and a running buffer composed of 10 mM sodium tetraborate at pH 9.24 added with 25 mM sodium dodecyl sulfate (SDS); the applied voltage was 25 kV; detection was either at a fixed wavelength UV of 214 nm or with a diode-array detector operating in the wavelength range from 190 to 350 nm. Both reversed-phase HPLC and MEKC techniques succeeded in resolving the tested standard mixtures of organic components of smokeless powders. Although the sequence of elution of the different analytes was slightly different between HPLC and MEKC, a statistical analysis based on the Spearman's rank correlation test showed that the two separation patterns were highly correlated. HPLC and MEKC were comparable in terms of elution/migration time precision, whereas MEKC showed higher reproducibility of peak areas. The interfacing of capillary electrophoresis with diode array UV detection provided distinct UV spectra of the individual analytes, thus improving, on the detection side, the analytical selectivity and identification power of capillary electrophoresis.     

Rapid and direct analysis of gamma-hydroxybutyric acid in urine by capillary electrophoresis-electrospray ionization ion-trap mass spectrometry

The present work was aimed at the development of a capillary electrophoretic analysis of gamma-hydroxybutyric acid (GHB) using electrospray ion trap mass spectrometry to achieve the direct and unequivocal detection of this analyte in human urine. Optimized capillary electrophoretic conditions were: injection, 20 s at 0.5 psi (1 psi = 6894.76 Pa); buffer electrolyte, 12.5 mM ammonium formate adjusted to pH 8.35 with diethylamine; fused silicacapillary: 100 cm x 50 microm i.d.; separation voltage, 25 kV (forward polarity) + 0.5 psi; room temperature. Electrospray and mass spectrometric conditions were: drying gas and nebulizing gas (nitrogen) at flow rate 3 l/min, temperature 250 degrees C, nebulizer pressure: 10 psi; sheath liquid solution: methanol-water (90:10) containing 0.1% ammonia delivered at 3 microl/min; spray voltage 3.5 kV. Mass spetrometric detection was carried out in the selected ion monitoring mode of negative molecular ions at 103 m/z for GHB and 115 m/z for maleic acid (I.S.). Under these conditions the baseline separation of GHB and the I.S. was obtained. The selectivity of the analysis allowed for direct injection of unextracted urine, previously diluted 1:4 with water. Linearity was assessed in the GHB concentration range from 80 to 1280 microg/ml in urine. Analytical sensitivity (as limit of detection) resulted about 5 microg/ml in water and 20 microg/ml in original urine. Analytical precision was fairly acceptable with R.S.D. values lower than 5% for migration times and 18% for quantitation in real samples, in both intra day and day-to-day experiments. On these grounds, the developed method can be adopted for rapid identification of acute intoxications from GHB in humans.     

Ab Initio Calculation of Rate Constants for Molecule–Surface Reactions with Chemical Accuracy

The ab initio prediction of reaction rate constants for systems with hundreds of atoms with an accuracy that is comparable to experiment is a challenge for computational quantum chemistry. We present a divide‐and‐conquer strategy that departs from the potential energy surfaces obtained by standard density functional theory with inclusion of dispersion. The energies of the reactant and transition structures are refined by wavefunction‐type calculations for the reaction site. Thermal effects and entropies are calculated from vibrational partition functions, and the anharmonic frequencies are calculated separately for each vibrational mode. This method is applied to a key reaction of an industrially relevant catalytic process, the methylation of small alkenes over zeolites. The calculated reaction rate constants (free energies), pre‐exponential factors (entropies), and enthalpy barriers show that our computational strategy yields results that agree with experiment within chemical accuracy limits (less than one order of magnitude).