Co-thickness and oxidation states effect on magnetic anisotropy in Co/MgO heterostructure

Interfacial magnetism and magnetic anisotropy constant ($K_i$) in Co/MgO heterostructure have been studied using ab-initio density functional calculations. It is found that interfacial Co spin magnetic moment shows a strong interdependence on Co-O bond lengths and a reasonable spin-polarization of ～80% is established as a function of Co layers. Our results revealed a saturated positive (out-of-plane) $K_i$ of +2.80 mJ/m² at ≥12 Co layers (～1.6 nm Co thickness), which is associated with orbital magnetic moment difference in [100] and [001] direction along with a strong hybridization between $d_{xy}$ and $d_{x^2?y^2}$ orbitals through orbital angular momentum operator $\stackrel{?}{L_z}$. Furthermore, it is shown that the $K_i$ magnitude almost remains constant and weakens in the case of under- and over-oxidations in the interfacial MgO and Co layers, respectively. Interestingly, $K_i$ improved for oxygen migrated interface due to enhanced $d_{xy}$ and $d_{x^2?y^2}$ orbitals coupling. The disordered interfaces stability is checked by analyzing the formation energy. Hence, the present findings disclose that the higher Co thickness in ordered Co/MgO structure supports to out-of-plane [001] (positive) $K_i$, which could be useful for its technological implementation in high-density magnetic data storage devices with high thermal stability.     

Enhanced solubility of galangin based on the complexation with methylated microbial cyclosophoraoses

Methylated cyclosophoraoses (M-Cys) were synthesized by reaction using dimethyl sulfate with native Cys (unbranched cyclic β-1,2-d-glucans) isolated from Rhizobium leguminosarum biovar viciae VF-39. Its structure was proven using nuclear magnetic resonance (¹H NMR) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Based on the enhanced hydrophobicity by methylation of Cys, we investigated the inclusion property with the water-insoluble flavonoid, galangin, through a phase solubility study using ultraviolet–visible spectroscopy. The solubility of galangin was enhanced 5.6-fold according to the added concentrations (1 mM) of M-Cys, compared to the 1.9-fold and 3.4-fold enhancements by β-Cyclodextrin (β-CD) and heptakis (2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD), respectively. M-Cys was also shown to have the highest binding constant (5,534 M^?1) with galangin among the tested host molecules (β-CD, DM-β-CD, Cys, and M-Cys). From this result, we can infer that the complex of galangin with M-Cys is more stable than any of the other host molecules. The continuous variation method showed that the galangin/M-Cys complex was suitable for 1:1 stoichiometry. The formation of the complex was confirmed with ¹H NMR, FT-IR, differential scanning calorimetry, and scanning electron microscopy. Furthermore, the hypothetical molecular model of 1:1 galangin/M-Cys complex was suggested by molecular docking simulations. The cytotoxicity to the human cervical adenocarcinoma cell lines was enhanced by the galangin/M-Cys complex compared with free galangin. The obtained results indicate that M-Cys can be utilized as an effective complexing agent for galangin.     

Optical and Electrical Properties of Polymerizing Plasmas and Their Correlation with DLC Film Properties

Diamond-like carbon (DLC) films were grown from radiofrequency plasmas of acetylene-argon mixtures, at different excitation powers, P. The effects of this parameter on the plasma potential, electron density, electron temperature, and plasma activity were investigated using a Langmuir probe. The mean electron temperature increased from about 0.5 to about 7.0 eV while the mean electron density decreased from about 1.2 × 10⁹ to about 0.2 × 10⁹ cm^–3 as P was increased from 25 to 150 W. Both the plasma potential and the plasma activity were found to increase with increasing P. Through actinometric optical emission spectrometry, the relative concentrations of CH, [CH], and H, [H], in the discharge were mapped as a function of the applied power. A rise in [H] and a fall in [CH] with increasing P were observed and are discussed in relation to the plasma characteristics and the subimplantation model. The optical properties of the films were calculated from ultraviolet-visible spectroscopic data; the surface resistivity was measured by the two-point probe method. The optical gap, E _G, and the surface resistivity, _s, fall with increasing P. E _G and _s are in the ranges of about 2.0–1.3 eV and 10¹⁴–10¹⁶ /, respectively. The plasma power also influences the film self-bias, V _b, via a linear dependence, and the effect of V _b on ion bombardment during growth is addressed together with variation in the relative densities of sp² and sp³ bonds in the films as determined by Raman spectroscopy.     

Screening of urban aerosol particulate composites for selected metal distribution and their dependence on meteorological parameters

Local atmospheric aerosol particulate samples, collected as composites on daily 6-12 hour basis, at Quaid-i-Azam University campus, Islamabad, Pakistan, using high volume sampling technique, were analysed for Pb, Na, K, Fe, Mn, Cd, Cr, Ni, Zn and Co by FAAS method. The monitoring period ran from October, 2001 through March, 2002, with a total of 105 samples collected on cellulose filters, treated in part with the HNO3-based wet digestion method for metal quantification, and for particle size distribution separately. The metal content of the aerosols was examined in relation to dependence on meteorological parameters, such as temperature, relative humidity, wind speed, sun shine and pan evaporation. Statistical correlation analysis was conducted for multiple metal pairs in aerosols, and the data were examined in relation to meteorological parameters and relevant aerosol particle size fractions. The study revealed no viable strong correlation between the meteorological parameters and metal levels; in general, however, a significant positive correlation was found for temperature. A strong positive correlation was observed for PM<25 and PM2.5-10. For coarse particles (PM10-100 and PM>100), however, a negative correlation was observed. The levels of Na, K, Fe and Zn were found in the range of 1-5 microg/m3 while those for the rest of the metals in the sub microg/m3 range. Principal component analysis and cluster analysis were performed on dataset for source identification and appointment. Largest contribution (33%) was shown by the industrial emissions followed by traffic/road dust (16.7%).     

Synthesis, characterization, in vitro cytotoxicity and anti-inflammatory activity of palladium(II) complexes with tertiary phosphines and heterocyclic thiolates: Crystal structure of [PdC28H19N8PS2]

The new four-coordinated mononuclear palladium(II) complexes 1-9 with chelating heterocyclic thiolates and tertiary phosphines with general formula [Pd(L)_nCl(R′R₂P)] (L = Pym2SH (pyrimidine-2-thiolate), Pur6SH (purine-6-thiolate), Py2SH (pyridine-2-thiolate), R₃P = PPh₃, P(o-tolyl)₃, PPh₂Cl), n = 1, 2) have been synthesized by the direct reaction of [PdCl₂(R′R₂P)₂] with polyfunctional heterocyclic thiolates which display a wide variety of coordinations. These compounds were characterized by elemental analysis, FT-IR and multinuclear (¹H, ¹³C and ³¹P) NMR. The X-ray diffraction study of non-ionic compound 5 showed that the thiolate acts as unidentate and that the chelating (-N,S) ligand adopts a slightly distorted square planar geometry around the palladium atom. In vitro the anti-inflammatory inhibition of compounds 1-9 was 10-15% greater than that of the standard drug Declofenac. Compounds 1 and 4 showed mostly a moderate to low cytotoxicity against seven human tumor cell lines whereas compound 3 was somewhat more active.