Electrical properties of Al/p–Ge and Al/Methyl Green/p–Ge diodes

Methyl green (MG) film has been grown for the first time on p–Ge semiconductor using a simple and low-cost drop coating method. The current–voltage (I–V) characteristics of Al/p–Ge and Al/MG/p–Ge diodes have been investigated in the temperature range of 20–300 K. A potential barrier height as high as 0.82 eV has been achieved for Al/MG/p–Ge diode, which has high rectification rate, at room temperature. It is seen that the barrier height of the Al/MG/p–Ge diode at the room temperature is larger than that of Al/p–Ge diode and ideality factor value of 1.14 calculated for Al/MG/p–Ge diode is lower than Al/p–Ge diode. The temperature coefficient of barrier height of the Al/MG/p–Ge diode has been calculated as 2.6 meV/K. The evaluation of current–voltage characteristics shows that the barrier height of the diode increases with the increasing temperature.     

Antioxidant Properties and Phenolic Composition of Sideritis Species

The antioxidant properties and phenolic composition of 27 Sideritis species were studied. Plant samples were extracted with petroleum ether using a Soxhlet apparatus. The defatted plant materials were extracted with 70% methanol. Antioxidant activities of the extracts were measured using Fe⁺² induced linoleic acid peroxidation, as indicated by thiobarbituric acid reactive substance (TBARS) production. Free radical scavenging activities were determined based on 1,1-diphenyl-2-picrylhydrazyl radical (DPPH). Results were compared with standard BHT. Total phenol concentration of the extracts was estimated with Folin-Ciocalteu reagent using gallic acid as standard, and phenolic components were quantified by HPLC-DAD.     

Rates of Ideal Convergence for Approximation Operators

In this paper, we study a general Korovkin-type approximation theory by using the notion of ideal convergence which includes many convergence methods, such as, the usual convergence, statistical convergence, A-statistical convergence, etc. We mainly compute the rate of ideal convergence of sequences of positive linear operators.     

Rates of -statistical convergence of positive linear operators

In this paper we study the rates of A-statistical convergence of sequences of positive linear operators mapping the weighted space C_ρ1 into the weighted space B_ρ2.     

Magnetic instabilities in Fe3C cementite particles observed with Fe K-edge x-ray circular dichroism under pressure

The ferromagnetic interstitial iron compound Fe(3)C (cementite) is expected to have Invar properties, whereby a high-moment to low-moment transition should occur when the atomic volume is reduced below a critical value. We, therefore, examine the pressure dependence of the Fe K-edge x-ray magnetic circular dichroism in Fe(3)C at ambient temperature and pressures up to 20 GPa. We find clear evidence for a high-moment to low-moment transition around 10 GPa.     

The influence of substitution of Co for Mn on magnetism of the HoMn6−xCoxSn6 compounds (0⩽x⩽0.25)

We have studied the effects of Co substitution for Mn on the structure and magnetic properties of the HoMn_6−xCo_xSn₆ compounds (0?x?0.25) with HfFe₆Ge₆-type structure (space group P6/mmm) by X-ray powder diffraction and magnetization measurements. A monotonic decrease of the lattice parameters a and c is observed with increasing Co content. While the compounds with x=0 and 0.05 exhibit ferrimagnetism in the whole temperature range, the compounds with 0.1?x?0.15 show ferrimagnetism, helimagnetism and re-entrant ferrimagnetism with decreasing temperature. For the compounds with x=0 and 0.05, the spin reorientation temperature is observed. A metamagnetic transition from helimagnetic magnetic ordering to ferrimagnetism is observed for the compounds with x=0.1 and 0.2. The results are summarized in the HoMn_6−xCo_xSn₆ magnetic phase diagram.     

A note on locally Lipschitzian functions

An oversight in a paper of Correa and Lemaréchal (this journal, 1993) is noted; a counterexample is given.     

The natural phenolic compounds and their antioxidant and anticholinesterase potential of herb Leiotulus dasyanthus (K. Koch) Pimenov & Ostr.

Abstract

The presented work reports anticholinesterase and antioxidant activities of extracts, fractions from aerial parts, fruits, flowers, roots and isolated compounds of roots from Leiotulus dasyanthus (bergapten, pimpinellin, umbelliferone, quercetin, rutin and kaempferol). Phenolic contents, antioxidant activities of samples were carried out by Folin-Ciocalteu, DPPH, TBA methods. Anticholinesterase activity was evaluated by Ellman’s method. The highest and lowest total phenolic content were detected in root MeOH extract (88.6?mg GAE g^?1 DW) and aerial part (51.83?mg GAE g^?1 DW), respectively. The highest antioxidant activity among isolated secondary metabolites got coumarins umbelliferone, bergapten and pimpinellin. Pimpinellin (66.55%) and umbelliferone (61.09%) demonstrated strong inhibition towards acetylcholinesterase and butyrylcholinesterase, respectively. Dichloromethane fraction of root demonstrated significant inhibition against AChE (49.66%) and BuChE (92.21%) at 20 µg/mL. Dichloromethane fractions of roots had a notableness antioxidant and anticholinesterase activities. The further studies on roots will be important for development use of this plant for pharmaceutical and food research needs.