Evaluation of Cu, Mn, and Se in Vegetables Using Ultrasonic Extraction and GFAAS Quantification

This paper proposes a method for the determination of copper, manganese, and selenium in vegetables of conventional and organic farming in the state of S?o Paulo/Brazil using ultrasonic extraction of analytes and subsequent quantification by graphite furnace atomic absorption spectrometry (GFAAS). Using 0.10 mol L⁻¹ of hydrochloric acid as the extracting solution, the following optimal extraction conditions were established: sample mass of 100 mg, sample grain size of <60 μm, sonication time of five cycles of 40 s, and sonication power of 136 W. The analytes were determined by GFAAS, applying drying temperatures of 90 °C to 250 °C, pyrolysis temperature of 1,300 °C, atomization temperature of 2,300 °C, and cleaning temperature of 2,800 °C. Palladium nitrate was co-injected with the samples as a chemical modifier and tungsten as a permanent modifier. The accuracy and precision of the proposed extraction method were evaluated based on a certified standard, RM 8433 Corn Bran (NIST RM 8433). The results obtained by the ultrasonic extraction method were equivalent to those obtained by the method of acid mineralization of samples in a microwave oven. However, the proposed methodology reduces the analytical time considerably, favoring the analytical speed. Moreover, the quantity of residues generated and discharged into the environment is also considerably lower.     

Regional sub-hourly extreme rainfall estimates in Sicily under a scale invariance framework

Design of urban drainage systems or flood risk assessment in small catchments often requires knowledge of very short-duration rainfall events (less than 1 h). Unfortunately, data for these events are often unavailable or too scarce for a reliable statistical inference. However, regularities in the temporal pattern exhibited by storm records, known as scaling properties of rainfall, could help in characterizing extreme storms at partially gauged sites better than the application of traditional statistical techniques. In this work, a scaling approach for estimating the distribution of sub-hourly extreme rainfall in Sicily (Italy) is presented based on data from high-resolution rain gauges with a short functioning period and from low-resolution rain gauges with longer samples. First, simple scaling assumption was tested for annual maxima rainfall (AMR) data from 10 min to 24 h duration, revealing that the simple scaling regime holds from 20 to 60 min for most of the stations. Then, scaling homogeneous regions were classified based on the values of the scaling exponent. In each region, this parameter was regionalized through power-law relationships with the median of 1 h AMR data. After that, regional Depth Duration Frequency (DDF) curves were developed by combining the scale-invariant framework with the generalized extreme value (GEV) probability distribution and used to estimate T-year sub-hourly extreme rainfalls at sites where only rainfall data for longer durations (≥ 1 h) were available. The regional GEV simple scaling model was validated against sub-hourly historical observations at ten rain gauges, generally yielding, in relation to the scaling exponent value, to similar or better sub-hourly estimates than empirical approach.

     

Dairy maturation of milk used in the manufacture of Parmigiano-Reggiano cheese: effects on physico-chemical characteristics, rennet-coagulation aptitude and rheological properties

The aim of this research was to study the effects of dairy maturation on the physico-chemical characteristics and technological properties of milk used for Parmigiano-Reggiano cheese manufacture. Three different operating conditions (CF1, CF2 and CF3) were considered. Full cream milk from the evening milking was stored on the farm and delivered to the cheese factory in churns (CF1) or in thermoregulated tanks at a temperature not lower than 18 degrees C (CF2 and CF3). The natural creaming (10-12 h overnight) was performed in a traditional large flat vat containing 10-12 hl (CF1 and CF2) or in thermoregulated large flat vats containing 60 hl at about 15 degrees C (CF3). Twenty-four, 24 and 22 maturation trials were performed in CF1, CF2, and CF3, respectively, during 2 consecutive years. A significant increase (P相似文献   

A som study of DC-PBH laser catastrophic failures

OBIC and PL imaging modes of a SOM have been successfully applied to the failure analysis of catastrophically degraded DC-PBH lasers. High lateral resolution, variable in-depth penetration and selective excitation are the most interesting features. A degradation mechanism has been found due to the development of leakage paths in the confining junctions.     

An empirical equation of state for gases

A simple pressure-explicit empirical equation of state for gases is presented which contains five constants in addition to the gas constant. It has been applied to carbon dioxide, hydrogen and nitrogen. The equation gives good accuracy (with maximum errors slightly higher than 1%) for densities up to critical and for temperatures from slightly above critical up to very high values. Below critical temperature it can still be applied with reasonable accuracy to the vapor. Thermodynamic functions (internal energy, enthalpy and entropy) derived from this equation show simple form and satisfactory accuracy over a wide range of temperature and density.     

A criterion for the assessment of the reliability of ASHRAE conduction transfer function coefficients

This paper presents a new mathematical approach, which, when applied to conduction transfer functions (CTFs) of a multi-layered wall, is able to predict the reliability of building simulations. This new procedure can be used to identify the best set of CTF coefficients, which are a critical point at the core of the ASHRAE calculation methodology founded on the transfer function method. To evaluate the performance of different CTF coefficient sets, the authors performed a large number of thermal simulations on the multi-layered walls included in the ASHRAE Handbook, volume fundamentals, and on other walls typical of Mediterranean building heritage. Those data were employed to test an algorithm able to assess the reliability of the simulations. The numerical results show that it is possible to select the optimal number of coefficients on the basis of the size of the poles of a CTF. The proposed criterion, which employs a pole threshold value, is highly accurate, fast and easy to integrate in the most diffuse building simulation tools.