Mobility and distribution of cadmium, nickel and zinc in contaminated soil profiles from Bangladesh

We investigated the mobility and distribution of cadmium (Cd), nickel (Ni) and zinc (Zn) in four contaminated soil profiles from Bangladesh. The sources of contamination of these profiles were tannery wastes, city sewage and the wastes of pharmaceutical and paper mill factories at different locations in Bangladesh. The samples were collected from the A-, B- and C-horizons of each profile: two sub-samples from the A-horizon at depths of 0–5 cm (A1) and >5 cm (A2), and one sample each from the B- and C-horizons. Soil samples were analysed for total metal content by dissolution in aqua regia followed by sequential extraction of the fractions based on their varying solubility. There were six operationally defined groups of extraction sequences: water soluble (F1), exchangeable (F2), carbonate (F3), oxide (F4), organic (F5) and residual (F6). The total concentration of Cd, Ni and Zn in the A-horizon (0–5 cm) ranged from 0.10 to 0.62, from 31 to 54 and from 85 to 838 mg kg⁻¹, respectively. In the B- and C-horizons, the concentrations of these metals decreased many fold, particularly in the city sewage profile where the decrease for Cd and Zn was approximately fourfold. The distribution of metals among the chemical fractions depended on their total concentrations. In the A1-horizon, Cd had the highest mobility factor [MF = (F1+F2+F3)/(F1+F2+F3+F4+F5+F6) × 100] at 41–43% and Ni had the lowest at 3–13%, while Zn, showed intermediate values at 8–25%. The MF decreased with depth in all soil profiles. Among the fractions, the residual fraction contained the lowest levels of Cd but the highest levels of Ni and Zn. This state affected their relative mobility and distribution in soil profiles. Of the soil profiles, the mobility of all metals was higher in the city sewage soil than in any of the other three soils investigated, suggesting that the former may create a health risk by contaminating agricultural products and ground water as it also contained higher amounts of Cd and Zn.     

Photoinduced magnetization of glass-ceramic alloys in the Cu-As-Cr-Se system

The problem regarding the preparation of semiconductor materials with photoinduced ferromagnetism has been analyzed. One of the possible solutions to this problem has been proposed. For this purpose, finely dispersed crystals of the CuCr₂Se₄ ferromagnetic spinel in the chalcogenide semiconductor glass matrix have been synthesized and the physicochemical properties of the prepared nanocomposite materials have been investigated. The effect of the photoinduced increase in the magnetization stabilized by a magnetic field has been revealed.     

Investigation of the coupling coefficients of stripline resonators in combline filters on a suspended substrate

Expressions for the frequency-dependent coupling coefficients of codirectional resonators used in a miniature design of a stripline filter on a suspended substrate are derived. The obtained expressions fully reflect the specific features of the frequency response of the analyzed structure. It is shown that the numerical analysis of a 1D model of this device performed in the quasi-static approximation provides sufficiently good agreement with experimental results. The influence of the design parameters of the analyzed structure on the frequency-selective properties of band-pass filters designed on the basis of this structure is theoretically investigated, and the capabilities for a substantial improvement of the selectivity of such devices are demonstrated.     

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Electronic and vibrational excitations in layered highT c superconductors

In the series of the layered highT _c superconductors (A)_1,2 B₂Ca _n−1Cu _n O_2n+3,4 (A=Tl or Bi;B=Ba or Sr), withn=number of consecutive Cu-O layers, the electron energy states of some of the Tl-based systems have been investigated. The electron and phonon dispersion curves have been obtained. The electronic states near the Fermi level are dominated by the hybridized Cu(d) and the O(p) orbitals. The dispersion curves are highly two-dimensional with very small dispersion alongc-axis. The number of bands is enhanced with increase in the number of the consecutive Cu-O planes (n). The present results agree with those obtained earlier for other superconducting phases. The phonons are overall dominated by the vibrations of the light mass oxygen atom modes both lying in or outside the Cu-O planes. The low-frequency phonons involve the motions of the heavier Tl, Ba atoms etc.     

Synthesis and film properties of epoxy esters modified with amino resins from glycolysis products of postconsumer PET bottles

Glycolysis of waste polyethylene terephthalate (PET) flakes obtained from grinding postconsumer bottles was carried out at 225–250°C and molar ratios of PET/ethylene glycol were taken as 1/1, 1/1.5, 1/5, and 1/10. Reaction product was extracted by hot water for three times and water‐soluble crystallizable fraction and water‐insoluble fraction were obtained. These fractions were characterized by acid and hydroxyl value determinations, differential scanning calorimeter analysis, and ¹H‐NMR analysis. Glycolysis product was used for synthesis of PET‐based epoxy resin. This epoxy resin was used to prepare epoxy ester resins having 40% and 50% oil content. Epoxy ester resin having 40% oil content was modified with urea‐formaldehyde and melamine‐formaldehyde resins for synthesis of epoxy ester–amino resin. Physical and chemical film properties of epoxy ester and modified epoxy ester resins were investigated. All the epoxy ester and modified epoxy ester films were having excellent adhesion, water, and salt water resistance properties. Modification of PET‐based epoxy ester resins with amino resin has significantly improved hardness, impact resistance, and alkaline and acid resistance of resin films. As a result, PET oligomers obtained from glycolysis of postconsumer PET bottles are suitable for manufacturing of amino‐resin‐modified epoxy ester resins that have improved physical and chemical surface coating properties. POLYM. ENG. SCI., 55:2519–2525, 2015. © 2015 Society of Plastics Engineers     

Preparation and characterization of hydroxyapatite from eggshell

Hydroxyapatite (HAp) was successfully produced by using recycled eggshell. The observed phases of the synthesised materials were dependent on the mechanochemical activation method (ball milling and attrition milling). The structures of the HAp were characterized by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. Attrition milling proved to be more efficient than ball milling, as resulted nanosize, homogenous HAp even after milling.     

Vitamin C and plasma triglycerides in experimental animals and in humans

A chronic latent vitamin C deficiency in guinea pigs enhances triglyceride concentration in blood plasma but does not markedly alter the composition of fatty acids in serum and hepatal triglycerides. An addition of 0·5% ascorbic acid to the diet of golden hamsters tends to normalise alimentary hypertriglyceridemia provoked by a high-glucose fat-free diet not containing vitamin C. A daily administration of 2 × 500 mg of an effervescent ascorbic acid for three months to subjects aged between 50 and 75 who were in a state of a seasonal vitamin C deficiency resulted in a significant depression of triglyceridemia. The hypotriglyceridemic effect of ascorbic acid depended on the starting plasma concentration of triglycerides: the higher the initial triglyceridemia, the more striking the hypotriglyceridemic effect. An administration of 2 × 500 mg of effervescent ascorbic acid every 24 h to a selected group of subjects with an initial triglyceridemia above 200 mg % for the duration of one year brought about a very significant decline of triglyceridemia, and this still persisted six weeks following cessation of ascorbic acid administration. An intervention of vitamin C at the level of triglyceride splitting enzymes is presumed.     

Dual material gate junctionless tunnel field effect transistor

This paper proposes a junctionless tunnel field effect transistor (JLTFET) with dual material gate (DMG) structure and the performance was studied on the basis of energy band profile modulation. The two-dimensional simulation was carried out to show the effect of conduction band minima on the abruptness of transition between the ON and OFF states, which results in low subthreshold slope (SS). Appropriate selection of work function for source and drain side gate metal of a double metal gate JLTFET can also significantly reduce the subthreshold slope (SS), OFF state leakage and hence gives improved I _ON/I _OFF.