Synthesis of melamine based polymer complexes and their thermal degradations and magnetic properties

In this study, new polymer Fe(III) and Cr(III) complexes were synthesized. These polymer complexes were characterized by using elemental analysis, FT-IR spectroscopy, MS, thermal analyses and magnetic susceptibility measurement technics. Their thermal degradations were investigated, and co-polymerization was compared to aliphatic polymerization by using 1,2-dibromomethylbenzene and o-phenylenedialdehyde. Finally, metal ratios of the complexes were determined by using atomic absorption spectroscopy. The complexes are distorted octahedral low-spin (S = 1/2) Fe(III) and distorted octahedral (S = 3/2) Cr(III) bridged by COO^? and catechol groups.     

Experimental investigation of the effects of length to diameter ratio and nozzle number on the performance of counter flow Ranque–Hilsch vortex tubes

In this experimental study, performance of counter flow type Ranque-Hilsch vortex tubes (RHVT), with a length to diameter ratio of 10, 15 and 18, were investigated with 2, 4, 6 nozzles. The measure of performance was chosen as the difference between the temperatures of hot output stream and cold output stream. The performances of RHVTs were experimentally tested by making use of velocity and temperature measurements of the input and output streams. It was determined that the difference between the temperatures of these streams, changed between 9 and 56 K. When all the results were assessed, it was concluded that the best performance was obtained when the ratio of vortex tube’s length to the diameter was 15 and the nozzle number was at least four, and the inlet pressure was as high as possible. Desired performance could be obtained by controlling the rate of the hot output stream.     

Determination of Folic Acid by CE in Various Cultivated Variety of Lentils

A simple extraction and determination method for folic acid (FA) in lentil samples was developed employing capillary electrophoresis. The analysis was performed in a 75 μm ID fused silica capillary using a running buffer of 10 mM sodium borate (10%, v/v, methanol, pH 9) at +18 kV and a detection wavelength at 200 nm. Methylparaben was used as the internal standard. FA signal response was linear in the range between 1.2 × 10^?5 and 4.8 × 10^?5 M. Limit of detection (inter-day) was determined at 6.12 × 10^?7 M (3.3 σs^?1). The amount of FA found in green, red and mignon lentils was found to range between 0.408 and 0.742 mg g^?1.     

Reverse self-assembly: (111)-oriented gold crystallization at alkylthiol monolayer templates

It has long been known that thiol-terminated molecules self-assemble as commensurate monolayers on Au(111) surfaces. By spreading floating octadecanethiol monolayers on aqueous solutions of chloroauric acid (HAuCl4) and using x rays to reduce the gold ions as well as to probe the structure, we have observed the nucleation of (111)-oriented Au nanoparticles at thiol surfaces. This process may be similar to the formation of biogenic gold by bacteria. The thiol monolayer acts as a "soft template," changing its structure as Au crystals form so that there is a sqrt[3]×sqrt[3] commensurate relationship.     

Spectrophotometric determination of selenium(IV) with 4-methyl-<Emphasis Type="Italic">o</Emphasis>-phenylenediamine based on piazselenol formation

A method has been developed for the spectrophotometric determination of selenium(IV) using 4-methyl-o-phenylenediamine (MOPDA) as a chromogenic reagent. In hydrochloric acid media at about pH 2, MOPDA forms a piazselenol complex with selenium(IV), which gives an absorption maximum at 332 nm. After transfer of the formed piazselenol complex into organic phase with n-hexane, the absorbance of the piazselenol complex was measured by a UV-Vis spectrophotometer. The effective parameters of the experimental conditions such as pH, formation time of the complex, amount of MOPDA, ionic strength, volume of sample and effects of diverse ions, were investigated. The detection limit of the proposed method was found to be 0.95 μg/L Se(IV) (n = 14, 3σ). The method was successfully applied to tap water, sea water and wastewater samples from washings of flue gases with satisfactory results.     

Cold valleys of superheavy elements with deformed targets and projectiles

The dependence of the cold driving potential on the deformation of the incoming target and projectile is investigated in the case of the synthesis of the superheavy nuclei ²⁵⁶No, ²⁸⁶112, ²⁹²114, ²⁹⁶116, and ³⁰⁶122. The occurrence of valleys in the driving potential as a function on the interfragment distance and the mass asymmetry is studied for different fixed orientations of the colliding nuclei such as the pole-pole, pole-equator, equator-equator, and equator-equator-crossed and compared to the case when the nuclei are assumed to be spherical or when the potential is averaged over the orientation.     

Low temperature plasma production of hydrogenated nanocrystalline silicon thin films

The hydrogenated nanocrystalline silicon (nc-Si:H) thin films were produced by capacitively-coupled plasma enhanced chemical vapor deposition (PECVD) technique at low substrate temperatures (T_s ≈ 40–200 °C). Firstly, for particular growth parameters, the lowest stable T_s was determined to avoid temperature fluctuations during the film deposition. The influence of the T_s on the structural and optical properties of the films was investigated by the Fourier transform infrared (FTIR), UV–visible transmittance/reflectance and X-ray diffraction (XRD) spectroscopies. Also, the films deposited at the center of the PECVD electrode and those around the edge of the PECVD electrode were compared within each deposition cycle. The XRD and UV–visible reflectance analyses reveal the nanocrystalline phase for the films grown at the edge at all T_s and for the center films only at 200 °C. The crystallinity fraction and lateral dark conductivity decrease with lowered T_s. FTIR analyses were used to track the hydrogen content, void fraction and amorphous matrix volume fraction within the films. The optical constants obtained from the UV–visible transmittance spectroscopy were correlated well with the FTIR results. Finally, the optimal T_s was concluded for the application of the produced nc-Si:H in silicon-based thin film devices on plastic substrates.     

Proton NMR relaxation in albumin solutions doped with Mn(II)

The aim of this study is to obtain further information about the source of proton relaxation in the Mn(II)-human serum albumin complex. For this purpose, proton relaxation rates in albumin solutions 1/T ₁ and 1/T ₂ were measured versus increasing amounts of manganese [Mn_t]. The fractions of manganese bound to albumin [Mn_b] and free manganese [Mn_f] were then determined from proton relaxation rate enhancement data. Paramagnetic contributions of bound manganese to the observed relaxation rates (1/T _1p^*)_b and (1/T _2p^*)_b were also determined. Finally, the (1/T _2p^*)_b/(1/T _1p^*)_b ratio was used in a derived equation to estimate an effective correlation time τ. Mean τ value of the complex was found to be in the order of 3 ns, while the hydration number of bound manganese q was estimated to be about 4. The 1/τ was found to be the sum of the inverse values of rotational correlation time 1/τ _r, mean residence time of water in hydration spheres of the complex 1/τ _m, and longitudinal electronic relaxation time of manganese 1/τ _s in the complex. In conclusion, the relaxation mechanism in albumin solutions containing Mn(II) can be interpreted through dipolar and scalar interactions modulated by τ _r, τ _m and τ _s. This analysis enables one to get reasonable figures for the τ _r and q of Mn(II) in albumin solution.