Elimination of bremsstrahlung in activation analysis by the deflection of β-particles in a magnetic field

The structureless background at X-ray and low energy -ray region, resulting from bremsstrahlung due to the stopping of -radiations, causes serious problems in nuclear spectroscopy. In this study, in order to reduce the background and therefore to increase the sensitivity of the nuclear analytical technique and the number of elements observable, a methodology is developed to deflect the -particles by a magnetic field. The experimental setup consists of a permanent magnet /1 kG/, Ge/Li/ solid-state detector, and multichannel analyzer.     

Cyclodextrin Solubilization of the Antibacterial Agents Triclosan and Triclocarban: Effect of Ionization and Polymers

The natural β-cyclodextrin (βCD) and its complexes have limited solubility in aqueous solutions. This low aqueous solubility, as well as low aqueous solubility of the guest molecule (i.e. triclosan or triclocarban (TCC)), can result in low complexation efficiency (CE). The purpose of this study was to enhance the apparent intrinsic solubility (S ₀) of the guest molecule and its βCD complexes through ionization and addition of auxiliary compounds such as polymers, amino acids and metal ions. Both triclosan (pK _a 7.9) and TCC (pK _a 12.7) are weak acids. Addition of ethanol to the complexation medium enhanced S ₀ of both triclosan and TCC but at the same time ethanol lowered the stability constant (K _c ) of their βCD complexes resulting in overall lowering of CE. Addition of small amount of water-soluble polymers enhanced the βCD solubilization of both guests, and addition lysine enhanced the solubilization of TCC. Ionization of triclosan resulted in significant enhancement of CE and enhanced triclosan release from tablets containing triclosan/βCD complex. The effect of ionization was not as pronounced in the case of TCC.This revised version was published online in July 2005 with a corrected issue number.     

Removal of strontium ions by a crosslinked copolymer containing methacrylic acid functional groups</p> </p>

Summary A tail-made polymer matrix is proposed to remove strontium ions from aqueous solutions. The removal behavior of strontium ions on a crosslinked copolymer containing methacrylic acid as functional groups was investigated as a function of sorptive concentration, time, temperature and pH. It was observed that an increase of these parameters enhanced the removal of Sr(II) ions from aqueous solution. It is found that a maximum adsorption of Sr(II) ions can be obtained on the crosslinked copolymer after 30 minutes and at pH 8. The increase of Sr(II) ion concentration in the solution resulted in an increase in the amount of Sr(II) ions adsorbed on the crosslinked copolymer containing methacrylic acid as functional groups. However, after a maximum of Sr(II) concentration in the solution, the percentage of adsorbed Sr(II) ions decreased. The adsorption data are well represented by the Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The adsorption capacity of the copolymer and the free energy change were calculated by using the D-R isotherm. For the adsorption of Sr(II) ions on the crosslinked copolymer the thermodynamic parameters (DH°,DS° andDG°) were calculated.</p> </p>     

Determination of trace elements in Na-bentonitic clay by INAA in Turkey

Instrumental neutron activation analysis was applied to the determination of trace elements in a Na-bentonitic clay. The irradiation was done in the Triga Mark II type reactor of ITU Nuclear Energy Institute. The sample was irradiated in two steps for short- and long- lived isotopes. After irradiation, spectra were taken using a germanium detector, multichannel analyzer Canberra System 100 and a fitting program called Sampo 90. The spectra of short-lived isotopes were analyzed to determine Al, Mg, Na, K, Ca, Ti elements and Mn, V trace elements. The spectra of long-lived isotopes were analyzed to determine Sc, Br, Sb, Cs, La, Ce, Sm, Yb, Hf, Pa, Np trace elements.     

Natural radioactivity in soil samples of Kocaeli basin, Turkey

The city of Kocaeli is in the western part of Anatolia in Turkey and has a population of approximately 1.000.000. There is no information about radioactivity in the Kocaeli soils samples so far. For this reason, the concentrations of the natural radionuclides in soil samples from 27 different sampling stations in Kocaeli Basin and its surroundings have been determined. The results have been compared with other radioactivity measurements in different country"s soils. The typical concentrations of ¹³⁷Cs, ²³⁸U, ⁴⁰K, ²²⁶Ra, ²³²Th found in surface soil samples ranged from 2±0.6 to 25±6 Bq/kg, from 11±4 to 49±10 Bq/kg, from 161±30 to 964±127 Bq/kg, from 10±4 to 58±11 Bq/kg, and from 11±3 to 65±13 Bq/kg, respectively.     

Leaching of uranium with the H2O2-Na2SO4-H2SO4 (HSS) system and the efficiency of Acigol Lake water

The applicability of a new leaching method, the HSS (H₂O₂-Na₂SO₄-H₂SO₄) system, in the extraction of uranium from Saricaolu-Bergama Region low grade ore, and the efficiency of Acigol Lake (Denizli)-Turkey water as a natural source of Na₂SO₄ has been investigated. The effect of H₂SO₄ concentration, temperature, leaching time, H₂O₂ and Na₂SO₄ concentrations and the amount of Acigol Lake water on the extraction of uranium was examined. HSS was found suitable for the extraction of uranium from Saricaolu-Bergama Region samples and it was observed that the acid consumption could be decreased by adding Na₂SO₄.     

NMR spectroscopy of organophosphorus compounds II: Stereochemistry of [1-(2H-azirin-2-yl)alkyl]phosphonates

Summary The conformation and relative configuration of [1-(2H-azirin-2-yl)alkyl]phosphonates (2) has been established by thorough investigation of some characteristic representatives of the series by¹H,¹³C,¹⁵N, and³¹P NMR spectroscopy. It is shown that the chemical shift of the proton located to the phosphonate group can be used as a criterion for the discrimination and stereochemical assignment of diastereoisomers. NMR spectroscopic features of the compounds are discussed in terms of structural relationships.Dedicated to Univ.-Prof. Dr.K. Schlögl with the best wishes to his 70^th birthday     

On input/output stabilization of singular integrodifferential systems

In this paper we consider a class of systems described by singular integrodifferential equations. This type of systems appear, for example, in the modeling of certain aeroelastic control problems. We study these systems in frequency domain framework and show the existence of finite-dimensional stabilizing controllers. An algorithmic procedure is outlined for the construction of such controllers. In order to illustrate the numerical aspects of this algorithm, we present an example involving the classical Theodorsen model of an airfoil, which fits in the class of systems considered here.This work was supported in part by the National Science Foundation under Grants DMS-8907019 and MSS-9203418.     

On the interpretation of random forces derived by projection operators

We study the derivation of a Langevin equation from a microscopic basis in order to elucidate the nature of the random force. We arrive at the conclusion that the consistent interpretation of the microscopic Langevin equation in terms of a stochastic differential equation (SDE) is according to I o rules. In addition, the random force is in general not Gaussian, and it is hence not completely characterized by its second moments.     

Optimization Strategy for Isocratic Separation of α-Aspartame and Its Breakdown Products by Reversed Phase Liquid Chromatography

α-Aspartame (L-α-aspartyl-L-phenylalanine methyl ester) is increasingly being used in wide variety of commonly consumed food products. This structure contains ester and peptide bonds. The ester linkage may hydrolyze to produce L-α-aspartyl-L-phenylalanine or cyclohydrolyze to produce the corresponding diketopiperazine ring. This ring can open to form L-α-aspartyl-L-phenylalanine and ultimately this compound can hydrolyze to L-phenylalanine and L-aspartic acid. The pH, buffer type, concentration, the presence of water and temperature are other important factors affecting its stability. Because α-aspartame can lose its sweetness under these conditions determination of aspartame and its breakdown products is extremely important for diet foods quality. The optimum mobile phase for the chromatographic separation was found to be acetonitrile-water (20:80, ν/ν) with 5.10^?3 M hexanesulfonic acid and a pH of 2.6.