Free radical scavenging activity and phenolic content in achenes and thalamus from Fragaria chiloensis ssp. chiloensis, F. vesca and F. x ananassa cv. Chandler

The total phenolic, flavonoid and anthocyanin content of achenes (true fruit) and thalamus (receptacle) from the native South American Fragaria chiloensis ssp. chiloensis (f. patagonica and f. chiloensis), Fragaria vesca and Fragaria x ananassa cv. Chandler was determined by spectrophotometric means. Highest phenolic content was found in F. vesca while lowest content was measured for white strawberry (F. chiloensis ssp. chiloensis, f. chiloensis). The total anthocyanin and total flavonoid contents in the samples investigated was lower for the white strawberry and higher in F. x ananassa cv. Chandler. Total flavonoid content showed a better correlation than total anthocyanins with the free radical scavenging effect of the extracts measured by means of the DPPH discoloration assay. In the superoxide anion assay all the acetone extracts of strawberries showed similar activity. The data presented in this study demonstrate that the amount of phenolic compounds differ significantly between species and subspecies and determine the free radical scavenging activity of fruits. On a w/w basis, higher total phenolics including flavonoids was found in achenes. The highest total anthocyanin content was found in the achenes of F. chiloensis and F. vesca, while F. ananassa presented higher antocyanin content in thalamus. The main anthocyanin in thalamus of F. ananassa (95%) were pelargonidin derivatives which were also present in F. chiloensis ssp. chiloensis f. patagonica (62.6%) but were not detected in F. vesca and F. chiloensis ssp. chiloensis f. chiloensis. In F. vesca and F. chiloensis ssp. chiloensis f. chiloensis only cyanidin derivatives were found both in thalamus and achenes.     

Carburization and decarburization kinetics of iron in CH4 — H2 mixtures between 1000 – 1100 °C

In this study the rate constants of the methane decomposition reaction on iron surfaces were determined in the 1000–1100°C temperature range, by grav? metric methods. Earlier works showed that the reaction velocity was given by The results indicate that the constant values vary from 2.72 × 10^?6 to $\text{16.74 × 10}{}^{\mathrm{?6}}\text{mol C/cm}{}^2\text{/sec/atm}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ for k and 2.61 × 10^?8 to $\text{8.62 × 10}{}^{\mathrm{?8}}\text{mol C/cm}{}^2\text{/sec/atm}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ for k′ between 1000 and 1100°C.     

Modeling of a bacterial and fungal biofilter applied to toluene abatement: Kinetic parameters estimation and model validation

Biofiltration has been established as a promising alternative to conventional air pollution control technologies. However, gas biofilters modeling has been less developed than experimental research due to the complexity of describing the fundamental processes and the lack of globally accepted physical, chemical and biological parameters. In addition, biofiltration modeling based on degradation activity of fungi has been rarely considered. For this reason, in this work, a dynamic model describing toluene abatement by a bacterial and fungal biofilter is developed, calibrated and validated. The mathematical model is based on detailed mass balances which include the main processes involved in the system: convection, absorption, diffusion and biodegradation. The model was calibrated and validated using experimental data obtained from two equal lab-scale biofilters packed with coconut fiber and pine leaves, respectively. Both reactors were operated under similar conditions during 100 days at an empty bed residence time of 60 s and an average inlet load of 77 g toluene m⁻³ h⁻¹. Biofilters were initially inoculated with a bacterial consortium, even though reactors were mostly colonized by fungi after 60 days of operation according to microscopic observation and reactors pH. Removal efficiency increased notably from 20% for the bacterial period to 80% for the fully developed fungal biofilters. Since kinetic parameters are strongly dependent on the biological population, semi-saturation constants for toluene and maximum growth rates were determined for bacterial and fungal operation periods. Kinetic parameters were fitted by means of an optimization routine using either outlet concentrations or removal efficiency data from the coconut fiber biofilter. A novel procedure in gas biofilters modeling was considered for checking the model calibration, by the assessment of the parameters confidence interval based on the Fisher Information Matrix (FIM). Kinetic parameters estimated in the coconut fiber reactor were validated in the pine leaves biofilter for bacterial and fungal operation. Adequate model fitting to the experimental outlet gas concentration for both bacterial and fungal operation periods was verified by using a standard statistical test.     

Ignition and Burning of Fibreboard Exposed to Transient Irradiation

Fire Technology - Natural materials like wood are increasingly used in the construction industry, making the understanding of their ignition and burning behaviour in fires crucial. The state of the...     

Synthesis and Characterization of Nanostructured Cerium Dioxide Thin Films Deposited by Ultrasonic Spray Pyrolysis

Nanostructured thin films of cerium dioxide have been prepared on single-crystalline silicon substrates by ultrasonic spray pyrolysis using cerium acetylacetonate as a metal–organic precursor dissolved in anhydrous methanol and acetic acid as an additive. The morphology, structure, optical index, and electrical properties were studied by X-ray diffraction, scanning electron microscopy, atomic force microscopy, ellipsometry, and impedance spectroscopy. The use of additives is very important to obtain crack-free films. The substrate temperature and flow rate was optimized for obtaining smooth ( R _a<0.4 nm), dense ( n >2), and homogeneous nanocrystalline films with grain sizes as small as 10 nm. The influence of thermal annealing on the structural properties of films was studied. The low activation energy calculated for total conductivity (0.133 eV) is attributed to the nanometric size of the grains.     

Optimized reduction of spur tones in fractional frequency synthesizers

In this article the contribution of the digital \Upsigma\Updelta\Upsigma\Updelta modulator in fractional frequency synthesizers is explored. Due to the circuit’s non linear behavior, the spur tones generated by the digital \Upsigma\Updelta\Upsigma\Updelta modulation degrade the synthesizer’s phase noise even in regions where the charge pump noise is dominant. A new method to dither digital MASH \Upsigma\Updelta\Upsigma\Updelta modulators for fractional frequency synthesizers is proposed. The method barely increases the circuit complexity and has the same performance as more cumbersome architectures. Also, a new design consideration to linearize the voltage control oscillator is proposed. Experimental results are obtained in an on-chip fractional synthesizer manufactured in CMOS technology.     

Manganese Preconcentration and Speciation in Bioaccessible Fraction of Enteral Nutrition Formulas by Cloud Point Extraction (CPE) and Atomic Absorption Spectroscopy

The present study develops a new method for manganese (Mn) preconcentration and speciation in bioaccessible fraction (soluble and dialyzable fraction) of enteral nutrition formulas by cloud point extraction (CPE) and atomic absorption spectroscopy (AAS). For this purpose, a non-ionic surfactant (Triton X-100) and three chelating reagents [8-hydroxyquinoline (8-HQ); 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP); and ammonium pyrrolidine dithiocarbamate (APDC)] were used with different operating conditions. The results showed that an efficient extraction of ionic Mn could be achieved with the following conditions: pH?=?10; chelating reagent concentrations of [8-HQ]?=?0.36 M, [PMBP]?=?0.09 M, and [APDC]?=?0.09 M; surfactant Triton X-100 at 25% (w/v), and equilibration temperature-time of 85 °C and 30 min. Limits of detection and quantitation are 0.015 and 0.050 mg L^?1 respectively. Furthermore, when analyzing the bioaccessible fraction of the enteral nutrition formulas, the proposed approach can be used to distinguish between ionic (free) Mn and Mn that has been previously bound to existing substances obtained from enzymatic digestion. These Mn speciation findings can be used to validate results obtained from the bioaccessibility assays.