Simulated mixed absorbers and effective atomic numbers for γ attenuation

The total γ-ray interaction cross-sections on mixed absorbers were determined at 662 keV with a view to study the effective atomic numbers for γ-ray absorption under narrow beam good geometry set-up. The measurements were taken for the combination of metallic absorbers like aluminium, copper, lead and mercury and also for the simulated absorbers by rotating the targets. ORTEC HPGe and NaI(Tl) detectors were used for detection of γ-rays. The experimental results compare favourably with theoretical values derived from XCOM package and suggest the usefulness of the concept of effective atomic numbers and the utility of the rotating absorbers technique.     

Polarization and spatial-mode behavior of short-wavelength VCSELs

We have investigated the packaging introduced feedback and resulting variations in the characteristics of Vertical-cavity surface-emitting lasers (VCSELs). An integrated test and characterization method was developed for both the packaged and bare dies as well as on-wafers chips. Using an ‘integrated test bench (ITB)’ for characterization, packaged and ‘un-packaged’ VCSELs from multiple sources were studied. ITB was used to monitor and measure simultaneously several beam-parameters under various bias conditions including both dc and high-speed pulsed pumping at room-temperature, or at higher-/lower-temperatures that are thermo-electrically controlled. Typical beam parameters included state of polarization (SOP), transverse (spatial) modes, wavelength spectra, and output power. A common observation was that majority of devices are affected by the presence of optical windows capping the package. A shift in longitudinal mode was noticeable in packaged versus ‘un-packaged’ (window-removed) devices. But, SOP and transverse modes in various devices are affected severely and in an unpredictable fashion.     

Spin quenching of Mn in complexes and CO binding with Mn deposited on MgO and CaO supports: DFT calculations

An attempt has been made to analyze the spin quenching properties of Mn, as a representative of transition metals, in Mn·MgO, Mn·CaO, OC·Mn·MgO, and OC·Mn·CaO complexes formed at the regular (001) surfaces of MgO and CaO, as well as the adsorption of CO on Mn deposited on MgO and CaO by means of hybrid density functional theory calculations and embedded cluster model. Clusters of moderate sizes were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. A test has been made to examine the effect of artificial flow of charge. While the spin states of Mn in Mn·MgO and Mn·CaO complexes are preserved, the combined effects of adsorbate and substrate in OC·Mn·MgO and OC·Mn·CaO complexes are strong enough to favor the low spin states and to quench the spin. The deposited Mn atoms enhance the adsorption of CO on MgO and CaO surfaces. The significant weakening of bond strength between OC and Mn in complexes supports the concept of bond order conservation. The relation between the strength of CO adsorption and the basicity of the support is verified. The natural bond orbital analysis reveals that the electronic structure of the adsorbed metal represents a qualitative change with respect to that of the free metal. The effects of spin contamination on the geometry, Mulliken charges, and adsorption energy are examined. The binding of CO precursor is dominated by the E(i)^Mn···CO pairwise additive components in MgO and CaO complexs, and the role of the support is not restricted to supporting the metal. The adsorbed CO molecules exhibit no remarkable deviation from linearity. Finally, relations are established between the process of spin quenching and the energy gaps between frontier orbitals. The results show that the spin state of adsorbed metal atoms on oxide supports and the role of precursor molecules on the magnetic and binding properties of complexes need to be explicitly taken into account. © 2012 Wiley Periodicals, Inc.     

Study of (1−x)ZnAl2O4–xSiO2 spinel structures as microwave dielectric materials

Sol–gel method was used to synthesize zinc aluminate (ZnAl₂O₄) dispersed into silica matrix with different compositions of x. Morphological structure of (1?x)ZnAl₂O₄–xSiO₂ samples were investigated by field emission scanning electron microscope (FESEM) and X-ray diffractometer (XRD). The FESEM images showed spherical structures and agglomerated particles occurred inside the samples. XRD analysis indicated the cubic phase formation of the samples. The crystallite size, D was calculated and it was found that the crystallite size are slightly increased from 8 to 17 nm. FTIR spectra analysis shows that the water presence in the samples and also the presence of nitrate group. The dielectric properties have been measured, ε _r value was found to be around 13.0. The S₁₁ parameter analysis shows the samples was resonated at 2.40 GHz and gives different values of bandwidth for microstrip patch antenna application.     

Design and Synthesis of Novel Triazolyl Benzoxazine Derivatives and Evaluation of Their Antiproliferative and Antibacterial Activity

A series of novel triazolyl benzoxazine derivatives have been synthesized via Cu(I)‐catalyzed ‘Click’ cycloaddition. All of the compounds were fully characterized from their spectral data, and their antiproliferative activity was evaluated against three selected human cancer cell lines: cervical cancer cells (HeLa), colorectal adenocarcinoma (HT‐29), and ovarian adenocarcinoma (SKOV‐3). A few representative compounds have also been evaluated for their antibacterial potential against two bacterial strains Pseudomonas aeruginosa and Bacillus subtilis.     

A glutathione biosensor based on a glassy carbon electrode modified with CdO nanoparticle-decorated carbon nanotubes in a nafion matrix

A nanocomposite consisting of cadmium oxide decorated with carbon nanotubes (CdO.CNT NC) was prepared by a wet-chemical technique, and its optical, morphological, and structural properties were characterized by FTIR, UV/Vis, FESEM coupled to XEDS, XPS, and XRD methods. A flat glassy carbon electrode was modified with the nanocomposite to obtain a sensor for L-glutathione (GSH) which displays improved sensitivity, a large dynamic range and good long-term stability. The calibration plot (best acquired at a voltage of 0.5 V) is linear (r ² = 0.99) in the 0.1 nM to 0.01 M GSH concentration range. The detection limit is as low as 30.0 pM, and the sensitivity is ~9.49 μA?μM^?1?cm^?2. To the best of our knowledge, this is the first report on the determination of GSH using such a modified glassy carbon electrode (GCE) in combination with I-V method. The GCE was applied to the selective determination of GSH in spiked rabbit serum samples and gave acceptable results.

Open image in new window

Graphical abstract A selective glutathione biosensor based on wet-chemically prepared CdO.CNT/Nafion/GCE was fabricated by reliable I-V method and shows good analytical parameters such as high sensitivity, low detection limit, long-term stability, and large dynamic range.

     

A glassy carbon electrode modified with carbon nano-fragments and bismuth oxide for electrochemical analysis of trace catechol in the presence of high concentrations of hydroquinone

Microchimica Acta - A glassy carbon electrode was modified with carbon nanofragments and bismuth oxide, and the resulting electrode (CNF-Bi/GCE) was applied to the voltammetric determination of...     

Synthesis,Characterization, and in vitro Cytotoxicity of Gold(I) Complexes of 2‐(Diphenylphosphanyl)ethylamine and Dithiocarbamates

Gold(I) complexes of 2‐(diphenylphosphanyl)ethylamine or (2‐aminoethyl)diphenylphosphine (AEP), and dithiocaarbamates (R₂NCS₂) were prepared by the reaction of these ligands with (CH₃)₂S‐AuCl in dichloromethane. The synthesized complexes [Au(AEP)Cl] ( 1 ), [Au(AEP)₂]Cl ( 2 ), and [Au₂(R₂NCS₂)₂]_n (R₂ = dimethyl ( 3 ), diethyl ( 4 ), and dibenzyl ( 5 )) were characterized by elemental analysis, IR, ¹H, ¹³C and ³¹P NMR spectroscopy. The complexes were evaluated for anticancer activity against three cancer cells, A549 (human lung carcinoma), HCT15 (human colon cancer), and MCF7 (human breast cancer) cell lines. Three of the five tested complexes showed significant in vitro cytotoxicity and for A549, the inhibition effect of three compounds is greater than cisplatin.     

Molecular structure investigation and biological evaluation of Michael adducts derived from dimedone

Trimolecular salt Michael adducts 2a–c were synthesized in excellent yields up to 92 % via one-pot multicomponent reactions in an aqueous medium. The chemical structures of compounds 2a–c were characterized by X-ray single-crystal diffraction techniques. Calculations of the density functional theory for the synthesized compound were performed. The stability of the products was deduced by TGA analysis. Compounds 2a–c were screened in vitro for different bio-assays such as thymidine phosphorylase inhibition assay, urease inhibition assay, β-glucuronidase inhibition assays and cytotoxicity against PC-3 and HeLa cell lines.     

How does hybrid bridging core modification enhance the nonlinear optical properties in donor‐π‐acceptor configuration? A case study of dinitrophenol derivatives

This study spotlights the fundamental insights about the structure and static first hyperpolarizability (β) of a series of 2,4‐dinitrophenol derivatives (1–5), which are designed by novel bridging core modifications. The central bridging core modifications show noteworthy effects to modulate the optical and nonlinear optical properties in these derivatives. The derivative systems show significantly large amplitudes of first hyperpolarizability as compared to parent system 1 , which are 4, 46, 66, and 90% larger for systems 2, 3, 4 , and 5 , respectively, at Moller–Plesset (MP2)/6‐31G* level of theory. The static first hyperpolarizability and frequency dependent coupled‐perturbed Kohn–Sham first hyperpolarizability are calculated by means of MP2 and density functional theory methods and compared with respective experimental values wherever possible. Using two‐level model with full‐set of parameters dependence of transition energy (ΔΕ), transition dipole moment (μ⁰) as well as change in dipole moment from ground to excited state (Δμ), the origin of increase in β amplitudes is traced from the change in dipole moment from ground to excited state. The causes of change in dipole moments are further discovered through sum of Mulliken atomic charges and intermolecular charge transfer spotted in frontier molecular orbitals analysis. Additionally, analysis of conformational isomers and UV‐Visible spectra has been also performed for all designed derivatives. Thus, our present investigation provides novel and explanatory insights on the chemical nature and origin of intrinsic nonlinear optical (NLO) properties of 2,4‐dinitrophenol derivatives. © 2014 Wiley Periodicals, Inc.