Competitive adsorption of anionic dyes onto DMOA modified MCM-41

Research on Chemical Intermediates - The single and binary adsorption of two anionic dyes Acid Yellow 17 (AY17) and Naphtol Green B (NGB) onto N–N–Dimethyl-n-octylamine (DMOA) modified...     

238U and 222Rn activity concentrations and total radioactivity levels in lake waters

The concentrations and distributions of natural radioactivity, uranium and radon in lake waters from around Van, Turkey were investigated with an aim of evaluating the environmental radioactivity. Fourteen lake waters were collected from different six lakes around Van (Turkey) to determine ²³⁸U, ²²²Rn and total alpha and total beta distributions in 2009. The total α and total β activities were counted by using α/β counter of the multi-detector low background system (PIC-MPC-9604) and the ²³⁸U concentrations were determined by inductively coupled plasma-mass spectrometry (Thermo Scientific Element 2) and radon concentrations were measured with the solid state nuclear track detector technique. The activity concentrations ranging from ND to 0.039 Bq L^?1 and from 0.026 to 3.728 Bq L^?1 for total alpha and beta, respectively, and uranium concentrations ranging from 0.083 to 3.078 μg L^?1, and radon concentrations varying between 47.80 and 354.86 Bq m^?3 were observed in the lake waters.     

Optical and EPR spectroscopy of manganese ions in Sr3Ga2Ge4O14 crystals

Results of investigations of the spectroscopic properties of manganese-activated single crystals of Sr₃Ga₂Ge₄O₁₄ by the methods of optical and EPR spectroscopy are reported. It is shown that magnagese activator ions form substitutional centers Mn³⁺ and Mn²⁺ in 1a-octahedral positions of the Sr₃Ga₂Ge₄O₁₄ lattice. Changes in the opticla properties of Sr₃Ga₂Ge₄O₁₄: Mn after vacuum thermal annealing are attributed to charge transfer of some of the manganese ions (Mn³⁺→Mn²⁺). The relationship between the spectroscopical properties of Mn²⁺ ions and the crystallochemical structure of the system are discussed. I. Franko L’vov State University, 50, Dragomanov St., L’vov, 290005, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 779–783, November–December, 1997.     

Advance selling to strategic consumers

Advance selling of goods and services is a form of separating purchase from consumption. It is often employed when consumers are uncertain about their consumption utilities until a short time period before consumption. A book to be released, a concert to attend, or a cruise to take are some examples. Invariably, in consumers’ mind inventory availability (of copies, seats, or rooms) is a concern. In this paper we study a retailer’s inventory and pricing decisions in an advance selling scenario that involves consumers who are strategic. Some consumers not only consider advance and spot prices, but also the uncertainty in future availability of the product (during the spot period) and in their consumption utility from it. We characterize the optimal inventory management and pricing policies, and discuss several interesting aspects of the solution. For example, it can be optimal for the retailer to limit advance sales even if there is more demand for it, and it can be optimal for the retailer to limit its inventory even though there is more capacity to keep it, but not both.     

The NaCl–AlCl<Subscript>3</Subscript>–HCl–H<Subscript>2</Subscript>O system at 25°С

Solubility was studied in the system NaCl–AlCl₃–HCl–H₂O at 25°C in the section 28 wt % HCl. The system is of the eutonic type and has an extensive sodium chloride crystallization region. The composition of the eutonic solution is the following, wt %: NaCl, 0.47; AlCl₃ ? 6H₂O, 8.88; HCl, 25.38; and H₂O, 65.27. The lines of saturated solutions were approximated by polynomial equations.     

K3,3-free intersection graphs of finite groups

The intersection graph of a group G is an undirected graph without loops and multiple edges defined as follows: the vertex set is the set of all proper non-trivial subgroups of G, and there is an edge between two distinct vertices H and K if and only if H∩K≠1 where 1 denotes the trivial subgroup of G. In this paper we classify all finite groups whose intersection graphs are K_3,3-free.     

The concentration of <Superscript>238</Superscript>U and the levels of gross radioactivity in surface waters of the Van Lake (Turkey)

Gross α and gross β activities and ²³⁸U concentrations were determined in 18 surface water samples collected from Van Lake. The instrumentations used to count the gross α and gross β activities and to determine the ²³⁸U concentrations were α/β counter of the multi-detector low background system (PIC-MPC-9604) and Inductively Coupled Plasma-Mass Spectrometry (Thermo Scientific Element 2), respectively. Concentrations ranging from 0.001 to 0.021 Bq L⁻¹ and from 0.111 to 2.794 Bq L⁻¹ were observed for the gross α and β activities in surface waters, respectively. For all samples the gross β activities were higher than the corresponding gross α activities. The results indicated that the gross α radioactive contamination in water samples was lower than recommended values for the guideline of drinking waters and most of the gross β activities in water samples were higher than those in the same procedure. The ²³⁸U concentrations ranged from 74.49 to 113.2 μg L⁻¹ in surface waters. The obtained results have showed that ²³⁸U concentrations are higher than guideline values for uranium.     

Amination with Pd-NHC complexes: rate and computational studies on the effects of the oxidative addition partner

Pd-PEPPSI-IPent, a recently-developed N-heterocyclic carbene (NHC) complex, has been evaluated in amination reactions with secondary amines and it has shown superb reactivity under the most mildly basic reaction conditions. Rate and computational studies were conducted to provide insight into the mechanism of the transformation. The IPent catalyst coordinates to the amine much more strongly than the IPr variant, thus favouring deprotonation with comparatively weak bases. Indeed the reaction is first order in base and only slightly more than zeroth order in amine.     

Frequency- and voltage-dependent dielectric properties and electrical conductivity of Au/PVA (Bi-doped)/n-Si Schottky barrier diodes at room temperature

In this study, frequency and voltage dependence of dielectric constant (ε′), dielectric loss (ε″), loss tangent (tanδ), the real and imaginary parts of electric modulus (M′ and M″) and ac electrical conductivity (σ _ac) of an Au/PVA (Bi-doped)/n-Si Schottky barrier diode have been investigated in detail by using experimental C–V and G–V measurements in the wide frequency range of 5 kHz–10 MHz and the voltage range of ±2 V at room temperature. Experimental results indicate that the values of ε′,ε″, tanδ and σ _ac are strongly frequency and voltage dependent. It has found that the values of ε′,ε″ and tanδ decrease while the values of σ _ac, M′ and M″ increase. It is clear that the values of M″ show a distinctive peak with a U-shape and its position shifts towards the positive-bias region with increasing frequency. Such behavior of the peak can be attributed to the particular distribution of interface states located at the Si/PVA interface and interfacial polarization. It can be concluded that the interfacial polarization and the charge at the interface can easily follow the ac signal at low frequencies.