Mixture Design Optimization of an Analytical Procedure for Iron Extraction and Determination From Cassava Leaves by Slurry Sampling Flame Atomic Absorption Spectrometry

ABSTRACT

This paper applies statistical simplex-centroid design to mixture modeling for optimization of the liquid phase composition of cassava slurry leaves in the development of an analytical procedure for iron determination using flame atomic absorption spectrometry (FAAS). This procedure is based on a slurry formation from powdered cassava leaves and a liquid mixture composed of HNO₃, HCl, and H₂O₂ after an ultrasonication process. A quadratic model fitted to the analytical response shows the existence of an experimental region, characterized by low proportions of H₂O₂, for which higher responses are obtained. The proposed procedure allows the determination of iron in the cassava leaves with a detection limit of 1.1 µg g^?1. The precision expressed as relative standard deviation (%RSD, n = 10) was 1.5% for iron concentrations of 25 µg g^?1. The developed procedure was validated by the comparison of results obtained from the application of the digestion procedure and the analysis of certified reference materials: Apple leaves (NIST 1515). Results found were in agreement with the certified values. The proposed method was applied for the determination of iron in four samples of cassava leaves acquired in markets of Feira de Santana City, Brazil. The concentration of iron found in the cassava leaves varied from 250.8 ± 0.7 to 283.4 ± 0.7 µg g^?1.     

Metal–insulator transition in a quantum well under the influence of magnetic field

Ionization energies of a shallow donor in a quantum well of the Cd_1-xinMn_xinTe/Cd_1-xoutMn_xoutTe superlattice system are obtained. A variational procedure within the effective mass approximation is employed in the presence of magnetic field. Within the one-electron approximation the occurrence of Mott transition is seen when the binding energy of a donor vanishes is observed. The effects of Anderson localization and exchange and correlation in the Hubbard model are included in our model. It is found that the ionization energy (i) decreases as well width increases for a given magnetic field, (ii) decreases when well width increases, (iii) the critical concentration at which the metal–insulator transition occurs is enhanced in the external magnetic field and (iv) spin polaronic shifts not only with the increase in a magnetic field but also with the well width increases. All the calculations have been carried out with finite barriers and the results are compared with available data in the literature.     

Design and evaluation of a Blu-ray pickup head system for determining the tilt angle and displacement of the test plane

We present an optical system design for determining the tilt angle and displacement of the test plane. The proposed optical system consists of a Blu-ray pickup head and a pigtailed laser diode with a uniform Gaussian beam. The optical system is evaluated by two optical design software packages, Code V and LightTools. A quadrant detector is used to detect the relative relationship of the V_A, V_B, V_C and V_D output signals, which can be used to measure the tilt angle and displacement on the test plane. Both the tilt angle and displacement on the test plane can be determined from the change in the beam shape on the quadrant detector. The proposed system can generate a circular uniform beam shape to reduce the misjudgment and to enhance the measurement accuracy. Various simulation cases are presented in detail to show the feasibility of the proposed system.     

Optical performance of a versatile illumination system for high divergence LED sources

An efficient flat-top illuminating optical system optimized for an extended light source is presented. The source is a high-brightness high divergence light emitting diode (LED), sized 1 mm × 1 mm, producing monochromatic emission (525 ± 5 nm) with viewing angle of 130°. The design is based on a rotationally symmetrical catadioptric system, developed on a geometrical optics basis, and modelled with ZEMAX^® software. The device consists of two optical systems: (i) a collimating system which, in turn, is formed by an aspheric lenses system (low numerical apertures, NA < 0.26) and two-mirror system (0.26 < NA < 0.86), and (ii) an external mirror (NA > 0.86) designed and optimized for each purpose. By itself, the collimating system works with a residual divergence of θ_C = 1.46°. The external mirror can be adequately designed to produce some given conditions. For instance, a flat-top profile is obtained in the selected focusing plane, with a maximum transversal intensity variation of 2.5% over 18 mm. In addition, when the focusing mirror is allowed to move along the optical axis in a ±1 mm range, other interesting profiles can be reached for a given working distance, therefore increasing the versatility of the system.     

Comparative study on ultrasonic assisted adsorption of dyes from single system onto Fe3O4 magnetite nanoparticles loaded on activated carbon: Experimental design methodology

The present study the ultrasound assisted adsorption of dyes in single system onto Fe₃O₄ magnetite nanoparticles loaded on activated carbon (Fe₃O₄-MNPs-AC) was described following characterization and identification of this adsorbent by conventional techniques likes field emission scanning electron microscopy, transmission electron microscopy, particle-size distribution, X-ray diffraction and Fourier transform infrared spectroscopy. A central composite design in conjunction with a response surface methodology according to f-test and t-test for recognition and judgment about significant term led to construction of quadratic model which represent relation among responses and effective terms. This model has unique ability to predict adsorption data behavior over a large space around central and optimum point. Accordingly Optimum conditions for well and quantitative removal of present dyes was obtained best operation and conditions: initial SY, MB and EB dyes concentration of 15, 15 and 25 mg L⁻¹, 4.0, 6.0 and 5.0 of pH, 360, 360 and 240 s sonication time and 0.04, 0.03 and 0.032 g of Fe₃O₄-MNPs-AC. Replication of similar experiment (N = 5) guide that average removal percentage of SY, MB and EB were found to be 96.63 ± 2.86%, 98.12 ± 1.67% and 99.65 ± 1.21% respectively. Good agreement and closeness of Predicted and experimental result and high adsorption capacity of dyes in short time strongly confirm high suitability of present method for waste water treatment, while easy separation of present nanoparticle and its good regeneration all support good applicability of Fe₃O₄-MNPs-AC for waste water treatment. The kinetic study can be represented by combination of pseudo second-order and intraparticle diffusion. The obtained maximum adsorption capacities correspond to Langmuir as best model for representation of experimental data correspond to dyes adsorption onto Fe₃O₄-MNPs-AC were 76.37, 78.76 and 102.00 mg g⁻¹ for SY, MB and EB, respectively. In addition, the performance comparison of ultrasound-assisted, magnetic stirrer assisted and vortex assisted adsorption methods demonstrates that ultrasound is an effective and good choice for facilitation of adsorption process via. Compromise of simple and facile diffusion.     

Procedure for retrieval of atmospheric aerosol backscatter coefficient profiles from results of multi-wavelength lidar sounding

A measurement procedure is proposed to retrieve the profiles of atmospheric aerosol backscatter coefficients (β_a) from the results of multi-wavelength sounding of the atmosphere by a laser location system based on a Nd: YAG-laser. The procedure uses a regression dependence between spectral values of β_a (background aerosol model) and involves the determination of coefficients which characterize the relative spectral behavior of aerosol extinction. The stability of the procedure to spatial variations of the above coefficients, a deviation of β_a from the dependence used, and calibration and measurement errors is examined. This procedure is compared with the widely used Fernald method by means of a numeric experiment. This procedure is demonstrated to be effective for retrieving vertical profiles of β _a in the troposphere, especially in the short-wavelength region. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 347–353, May–June, 2008.     

A BSSE-corrected CASSCF/NEVPT2 procedure. An application to weakly bonded OH.. π heterodimer complexes

In this work, a stable NEVPT2-based computational procedure was developed, capable of studying weakly bonded OH..π heterodimer complexes. The procedure was applied to the evaluation of the weak OH..π intermolecular interaction energy of the ethene–water C₂H₄–H₂O complex, as a model case. The counterpoise method of Boys and Bernardi was used with the strongly contracted (SC) and partially contracted (PC) variants of the NEVPT2 method and the energetic results were benchmarked against CCSD(T) calculations. In particular, for the first time a computational methodology is proposed for the appropriate specification of the active space in order to study weakly bonded OH..π heterodimer complexes, using the super-molecular approach. The treatment of weakly bonded OH..π and van der Waals complexes using CASSCF wavefunctions with second-order perturbation theory seems to render trustable and accurate results. Also, the present methodology suggests an efficient way for the specification of the ‘ghost’ basis functions in the multiconfigurational heterodimer case. The Basis Set Superposition Error (BSSE) was eliminated in both CASSCF(2,2) and CASSCF(10,7) selected case studies of the C₂H₄–H₂O dimer. The behavior of BSSE lowering as the basis set increases was verified. The computational procedure which was developed in this paper can be easily adapted to the multiconfigurational NEVPT2 treatment of a large variety of weakly bonded heterodimers. Finally, the procedure was successfully tested in the benzene-water heterodimer.     

Rotational analysis of weak (4, 6) hot band in the comet-tail (AΠi-XΣ) system of the CO

The ro-vibrational spectrum of the weak (4, 6) hot band in the comet-tail (A²Π_i-X²Σ⁺) system of CO⁺ is observed by employing optical heterodyne and magnetic rotation enhanced velocity modulation spectroscopy. One hundred and twenty-four spectral lines are assigned to this band; thus, precise molecular constants of the levels involved are obtained from a weighted nonlinear least-squares fitting procedure combining with our previous spectrum of the (3, 6) band.     

∑关系线性理论的应用(Ⅰ)——∑4关系在晶体结构测定中的应用

本文系统论述实现Σ₄关系计算的具体方法及其实际应用价值。对五个不同类型的已知晶体结构计算表明,利用Σ₄关系能够获得大量的、可靠性较高的O,π型结构半不变量相角。文中讨论了它们在测定晶体结构中的可能应用前景。 关键词：     

Elements of Cost-Based Tolerancing

One goal for optical design is to assign tolerances so that the as-built systems satisfy all required specifications and have the lowest fabrication and assembly expense. Tolerances affect not only the image quality, but also the production cost. Thus tolerance assignment is a critical step in the optical design process. In this paper we discuss the essential elements of a cost-based tolerancing method. The paper concludes with an example comparing results from a cost-based tolerancing procedure with results from a conventional approach.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15-17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan.     

Hydrodynamic cavitation degradation of Rhodamine B assisted by Fe3+-doped TiO2: Mechanisms,geometric and operation parameters

In this paper, a novel method, hydrodynamic cavitation (HC) combined with Fe³⁺-doped TiO₂, for the degradation of organic pollutants in aqueous solution is reported. The venturi tubes with different geometric parameters (size, shape and half divergent angle) are designed to obtain a strong HC effect. The structure, morphology and chemical composition of prepared Fe³⁺-doped TiO₂ as catalyst are characterized via using XRD, SEM, TEM, XPS, UV-vis DRS and PL methods. The effects of added TiO₂ (heat-treated at different temperatures for different times) and Fe³⁺-doped TiO₂ (with different mole ratios of Fe and Ti) on the HC catalytic degradation of RhB are discussed. The influences of operation parameters including inlet pressure, initial RhB concentration and operating temperature on the HC catalytic degradation of RhB are studied by Box-Behnken design (BBD) and response surface methodology (RSM). Under 3.0 bar inlet pressure for 10 mg/L initial concentration of RhB solution at 40 °C operating temperature in the presence of Fe³⁺-doped TiO₂ with 0.05:1.00 M ratio of Fe and Ti, the best HC degradation ratio can be obtained (91.11%). Furthermore, a possible mechanism of HC degradation of organic pollutants in the presence of Fe³⁺-doped TiO₂ is proposed. Perhaps, this study may provide a feasible method for a large-scale treatment of dye wastewater.     

Fabrication of diarylide yellow pigments/modified SiO2 core-shell hybrid composite particles for electrophoretic displays

Diarylide yellow pigments/modified SiO₂ core-shell hybrid composite particles were fabricated via a newly developed two-step procedure. The surface of diarylide yellow pigments was coated with SiO₂ by the hydrolysis of Na₂SiO₃. The obtained particles were then modified with in situ generated 3-aminopropylsilanetriol or succinic acid to form composite particles containing amino or carboxyl groups. The FT-IR spectra, TGA and TEM showed that the particles had a core-shell structure, the SEM suggested that the surface morphology of the composite particles was smooth, and the XPS and zeta potential measurement indicated that the composite particles had a high charge load. The obtained composite particles have been applied as electrophoretic particles in the electronic paper, which demonstrated that the newly developed procedure is an effective way to produce various organic/inorganic composite particles used for electrophoretic displays.     

Simultaneous low-level determination of iodine and manganese in biological materials by radiochemical neutron activation analysis

A new RNAA procedure was developed for simultaneous determination of low levels of I and Mn in biological materials. The procedure is based on sample decomposition by alkaline-oxidative fusion in a mixture of Na₂O₂ + NaOH at 900°C followed by extraction of elementary iodine by chloroform. Subsequently, Mn is separated either by precipitation of hydrated MnO₂ or by extraction of the Mn-diethyldithiocarbamate complex in chloroform. The accuracy of the RNAA procedure developed was proven by analysis of several low-level biological reference materials. Detection limits of I and Mn achievable in both institutes and the degree of interference for the Mn determination due to ⁵⁶Fe(n,p)⁵⁶Mn reaction with fast neutrons are discussed.     

A new approach to synthesize LiAsF6 and other lithium based fluorochemicals for rechargeable lithium cells

A new method to synthesize inorganic lithium based fluorinated compounds like LiAsF₆ (Lithium hexafluoro arsenate) has been developed by a low temperature solid state procedure. LiAsF₆ is used extensively in the lithium cells because of its stability to withstand high voltages during cycling. The procedure developed to synthesize lithium based fluorinated compounds is a single step procedure and fluorination is done in-situ. This is an environmentally friendly method and is less expensive than the other known procedures.     

Preparation of visible light responsive N doped TiO2 via a reduction-nitridation procedure by nonthermal plasma treatment

A visible light responsive N-doped TiO₂ was prepared via a reduction-nitridation procedure by nonthermal plasma treatment. X-ray diffraction, N₂ adsorption, UV-vis spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy were used to characterize the prepared TiO₂ samples. The plasma treatment did not change the phase composition and particle sizes of TiO₂ samples, but extended its absorption edges to the visible light region. The photocatalytic activities were tested in the degradation of an aqueous solution of a reactive dyestuff, methylene blue, under visible light. The photocatalytic activities of TiO₂ prepared by reduction-nitridation procedure were much higher than that of samples prepared by simple nitridation treatment. The enhanced activity was ascribed to the substitutional N-doping and appropriate concentration of oxygen vacancies. TOHN10 prepared by reduction-nitridation procedure exhibited excellent photocatalytic stability. A possible mechanism for the photocatalysis was proposed.     

Photoemission intensity oscillations in the valence bands of C70 film

We have measured and analyzed the photoemission spectra (PES) of a C₇₀ film in the photon energy region from 13.4 eV to 98.4 eV. The photoelectron intensities of two C 2p π-derived features (denoted by A and B) oscillate regularly in the whole energy region with some fine structures below ∼30 eV. To obtain the detailed information of the oscillations, we have developed a sophisticated but practical procedure for intensity calculation. The procedure consists of two core concepts. The first is ascribing the PES features to their corresponding molecular orbitals with the help of density functional calculations. The second is a background subtraction algorithm. With this procedure, we obtained the oscillating behavior for individual features (A and B), which is by and large consistent with the predictions based on the spherical symmetric approximation although C₇₀ has the ellipsoidal shape. Owing to the solid state effect, the oscillating amplitudes of the A/B intensity ratios are smaller than those of gas phase C₇₀, but an orbital shift reported recently was not observed on our sample. The oscillating curve of a deeper feature, which consists of both σ and π states, are also reported.     

Simultaneous low-level determination of iodine and manganese in biological materials by radiochemical neutron activation analysis

A new RNAA procedure was developed for simultaneous determination of low levels of I and Mn in biological materials. The procedure is based on sample decomposition by alkaline-oxidative fusion in a mixture of Na₂O₂ + NaOH at 900°C followed by extraction of elementary iodine by chloroform. Subsequently, Mn is separated either by precipitation of hydrated MnO₂ or by extraction of the Mn-diethyldithiocarbamate complex in chloroform. The accuracy of the RNAA procedure developed was proven by analysis of several low-level biological reference materials. Detection limits of I and Mn achievable in both institutes and the degree of interference for the Mn determination due to ⁵⁶Fe(n,p)⁵⁶Mn reaction with fast neutrons are discussed.     

具有二次像面的三反射光学系统的研究

论述了一种具有二次像面的偏视场三反射光学系统的设计方法,定性地讨论了设计参量β1,Δ,f’1对系统传递函数的影响给出两种结构型式,两个设计结果,并从系统成像质量的好坏、加工的难易程度及结构的可实现性分析了两种结构型式的优缺点.     

Determination of temperature and concentrations of main components in flames by fitting measured Raman spectra

The procedure of deriving flame temperature and major species concentrations by fitting measured Raman spectra in hydrocarbon flames is described. The approach simplifies the calibration procedure to determine temperature and major species concentrations from the measured Raman spectra. The calculations of the Raman spectra are performed using data online positions and cross sections from the current literature. Utilizing all spectral information for deriving temperature and major species concentrations substantially increases accuracy, while interferences can easily be detected and filtered out of the measured spectrum. Temperatures from the separate Raman spectra of N₂, H₂O, O₂, CO₂ and CO are systematically compared with each other over the span of more than 1,700 K. The agreement between them is generally better than 100 K. The developed procedure also allows us to determine the mole fractions of the major species with absolute accuracy of ±10 %.     

Ullah-Dorsey Scaling of Fluctuation Conductivity Near the Superconducting Transition in (LaSe)1.14(NbSe2)

Magnetotransport measurements with the quasi two-dimensional misfit-layer compound (LaSe)_1.14(NbSe₂) with critical temperature T _c = 1.23 K are presented. The temperature dependence of the upper critical magnetic field H _c2 has been determined from an analysis of magnetoresistance data through the scaling procedure obtained theroretically by Ullah and Dorsey for the fluctuation conductivity. We show that in contrast to a direct determination of H _c2(T) with a positive curvature the temperature dependence of H _c2 obtained via the scaling procedure reveals a negative curvature in agreement with the Werthammer-Helfand-Hohenberg theory for conventional type-II superconductors.