Satellite hyperfine fields in low concentration NiMn alloys

Concentration- and temperature dependent measurements were made on NiMn-alloys with the perturbed angular correlation technique (PAC). At room-temperature, samples of 1.3; 2.4; 3.6; 5.6; 6.9 and 8.3 at%Mn were examined. Field values on both sides of the Ni-value were observed with a pronounced concentration dependence above 3 at%Mn. The 3.6 at%Mn-sample was examined as function of temperature between 284 K and 573 K. Each of the fields has the same temperature-behaviour, resulting in the same Curie-temperature, which is however smaller than the Curie-temperature for pure Ni.     

The time-local view of nonequilibrium statistical mechanics. II. Generalized Langevin equations

On a semiphenomenological level, generalized Langevin equations are usually obtained by adding a random force (RF) term to macroscopic deterministic equations assumed to be known. Here this procedure is made rigorous by conveniently redefining the RF, which is shown to be colored noise weakly correlated with the observables at earlier times due to the finite lifetime of microscopic events. Corresponding fluctuation-dissipation theorems are derived. Explicit expressions for the spectral density of the fluctuations are obtained in a particularly simple form, with the deviation of the line shape from the Lorentzian being related most explicitly to the spectral density of the RF. Well-known low-frequency expressions and the Einstein relation of (generalized) Brownian motion theory are modified so as to include lifetime effects. New sum rules are obtained relating dissipative quantities to contour integrals (in the complex frequency domain) over spectral densities or corresponding response functions. The Heisenberg dynamics of a complete set of macroobservables is shown to be equivalent to a generalized Orstein-Uhlenbeck stochastic process which is a non-Markovian process due to the lifetime effects.     

The influence of phosphorus on the structure and hydrodesulfurization activity of sulfided Fe and Fe-Mo catalysts supported on carbon and alumina

Phosphorus-containing Fe and Fe?Mo sulfide catalysts supported on γ-Al₂O₃ and activated carbon were evaluated for their thiophene HDS activities at atmospheric pressure. The thiophene HDS activity of the carbon-supported catalysts decreased considerably in the presence of phosphorus, while the activity of the alumina-supported catalysts was not affected. It was shown by Mössbauer spectroscopy that in both the oxidic carbon- and alumina-supported catalyst precursors the presence of phosphorus resulted in an improved dispersion of the Fe phase. In the sulfided carbon-supported Fe and Fe?Mo catalysts, the presence of phosphorus resulted in the formation of an “Fe(II)-phosphate” phase, which was held responsible for the decrease in HDS activity. With regard to the sulfided alumina-supported catalysts, it was found that phosphorus did not influence the structure of the metal sulfide species.     

Local symmetry in some quasicrystalline AlTFe alloys

Mössbauer spectra of AlTFe-alloys with T=Cr or Mn, show a quadrupole splitting QS≈0.4 mm/s. This shows that the iron atom is not in an icosahedral site. In order to investigate the local symmetry further, we applied an external magnetic field H_ext≈5T, so that the asymmetry parameter ν can be obtained. Using a one site approximation the results are: ν=0.7 for decagonal Al₇(Mn_0.7Fe_0.3)₂ and ν=0.8 for icosahedral Al₆Cr_0.7Fe_0.3. This means that the iron atoms are in sites with a symmetry lower than axially symmetric. Most of the vertices in a Penrose lattice show such a symmetry.     

Isospin selection rules for real photons observed in the6Li(γ,d) reaction

The high spin structure of the nucleus¹²⁹Ba has been investigated using a¹⁸O induced reaction. The known bands could be followed up to a maximum spin (55/2) ?. Some 56 states and 78 transitions could be placed in the level scheme. Band crossings were established in both positive and negative parity structures. They display features of strong polarization effects due to the alignment of h_11/2 protons.     

Simultaneous Spectrophotometric Determination of Imipramine Hydrochloride with Chlordiazepoxide and Nortriptyline Hydrochloride with Fluphenazine Hydrochloride

Spectrophotometry was used with multivariate calibration to simultaneously determine compounds in mixtures. Two antidepressant mixtures were investigated: imipramine hydrochloride and chlordiazepoxide and nortriptyline hydrochloride and fluphenazine hydrochloride. Considerable spectral overlap and large differences in component concentrations were challenges. Since this type of analysis is often performed using complex algorithms, a simple strategy was used here for the simultaneous determination of both mixture components by classical least squares, principal component regression, and partial least squares. Experimental design was used to select the optimum parameters including the wavelength range, sampling interval, software, and derivative order. Accuracy was enhanced by proper wavelength selection. In addition, derivatives of the raw spectra improved the selectivity. The standard deviation, deviation of mean recovery from 100%, and prediction ability of the models were used as the responses. In respect to these terms, first-order derivatization of the spectra and a sampling interval of 1?nm provided the best results. In particular, the low concentration compounds in the mixtures (chlordiazepoxide and fluphenazine) were determined more accurately with precision lower than 3%. The strategy was used for the quality control of pharmaceuticals containing the mixtures without chemical pretreatment.     

Highly sensitive fluorescent sensor targeting CuCl2 based on thiophene attached anthracene compound (TA)

A novel thiophene attached anthracene (TA) based fluorescent compound was designed and synthesized. The TA showed a high quantum yield (Qy = 0.34) in regard to fluorescence. We applied this TA compound to detect specific metal compound and found that it could identify CuCl₂ from other metals through dramatic fluorescence change at λ_max = 460 nm. It showed strong quenching fluorescence property with CuCl₂ while with other metal compounds it exhibited strong blue fluorescence emission. UV/Vis absorption spectroscopy clearly demonstrated that the quenching property of TA at λ_max = 460 nm was due to overlapping of the fluorescence peak of TA at λ_max = 460 nm and the absorption band of CuCl₂ (from 190 nm to 525 nm). Binding constant (K′), which was 0.0895 mM^?2, indicated a complexation ratio between TA and CuCl₂ as 1:2 and this interaction induced quenching property.     

Isolation of lanthanides from spent nuclear fuel by means of high performance ion chromatography (HPIC) prior to mass spectrometric analysis

Pure and complete fractions of neodymium, samarium, europium, gadolinium and dysprosium were isolated by means of high performance ion chromatography, using a cation exchange column and gradient elution with alpha-hydroxyisobutyric acid solutions (α-HIBA). Intermediate precision and robustness of the isolation method was investigated, identifying eluent pH as the most important parameter. Investigation of the elution behaviour of the most important fission and activation products and actinides indicated that preventing the accumulation of cesium on the cation exchange column required further isocratic elution with a higher concentrated α-HIBA solution after elution of the lanthanides. A sample matrix free of carbon was achieved by means of acid digestion, followed by UV photo-oxidation, resulting in samples suitable for mass spectrometric analysis.