Study of desorption activation energy on Rh-CO systems

The adsorption of CO on an Rh foil and small Rh particles supported by Al₂O₃ polycrystalline surfaces was studied using the temperature programmed desorption (TPD). The supported Rh particles were prepared by evaporation, using the principles of electron bombardment. The activation energy of desorption was calculated. The results show the dependence on the CO exposure of the sample as well as the size effect. The desorption and the recombination peaks were measured. The dissociation of CO and the influence of C atoms on the surface are discussed.     

Coulomb excitation of levels in 143Nd and 145Nd

The low-lying states of ¹⁴³Nd and ¹⁵⁴Nd have been studied by means of Coulomb excitation with ¹⁶O and α-particles. Angular distribution measurements were carried out for some transitions in ¹⁴⁵Nd with 11.2 MeV α-particles. Level energy decay schemes and B(E2)↑ values were measured for two states in ¹⁴³Nd and for six states in ¹⁴⁵Nd. Some spin assignments have been established for the ¹⁴⁵Nd nucleus. ¹⁴³Nd and ¹⁴⁵Nd have been theoretically described by coupling one and three particles, respectively, to quadrupole vibrations, and rather good agreement with experiment was achieved.     

Vector bundles over Grassmannians and the skew-symmetric curvature operator

A pseudo-Riemannian manifold is said to be spacelike Jordan IP if the Jordan normal form of the skew-symmetric curvature operator depends upon the point of the manifold, but not upon the particular spacelike 2-plane in the tangent bundle at that point. We use methods of algebraic topology to classify connected spacelike Jordan IP pseudo-Riemannian manifolds of signature (p,q), where q?11, and where the set {q,…,q+p} does not contain a power of 2.     

A Gluing Construction Regarding Point Particles in General Relativity

We develop a gluing construction which adds scaled and truncated asymptotically Euclidean solutions of the Einstein constraint equations to compact solutions with potentially non-trivial cosmological constants. The result is a one-parameter family of initial data which has ordinary and scaled “point-particle” limits analogous to those of Gralla and Wald (Class Quantum Grav 25:205009, 2008). In particular, we produce examples of initial data which generalize Schwarzschild–de Sitter initial data and gluing theorems of IMP-type (Isenberg et al. in Comm Math Phys 231:529–568).     

Elemental analysis of particulate matter in a metal workshop and of biological samples from exposed workers

During metal welding and cutting, large amounts of particulate matter (PM) are produced that might represent a significant health risk for the exposed workers. In the present pilot study, we performed an elemental analysis of fine PM collected in a metal workshop. Also, elemental analysis of the hair and nail samples collected from workers exposed to the workshop dust and control group was done. Concentrations of 15 elements in PM were measured with X‐Ray Fluorescence (XRF) and Particle Induced X‐ray Emission (PIXE), whereas inductively coupled plasma mass spectrometry (ICP‐MS) was used to determine 12 elements in hair and nail samples. Mean 8‐hr concentrations of PM_2.5, Fe, and Mn in the vicinity of welders were up to 1803, 860, and 30 μg/m³, respectively, whereas in the nearby city, daily PM_2.5 concentrations are on average 11 μg/m³. We found that several elements, especially Fe and Mn, had substantially higher concentrations in hair and nail samples of exposed workers than in the control group, which indicates the accumulation of metals in workers' tissues, although limit values were not exceeded.     

Simultaneous Determination of 11 Elements in Fly Ash by Inductively Coupled Plasma Orthogonal Acceleration Time-of-Flight Mass Spectrometry After Closed-Vessel Microwave-Assisted Extraction with Ammonium Fluoride

A method for simultaneous multi-element analysis of fly ash samples by inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometry (oaTOF-ICP-MS) after closed-vessel microwave extraction with ammonium fluoride was introduced here. Corrosive and/or toxic acids like HF, HCl or HClO₄, as well as HNO₃, which are commonly used during sample preparation of the fly ash samples, are avoided in this method. The spectral effects due to the formation of different Cl, Na, K, Ca, Mg-containing polyatomic species interfering with the determination of a number of elements like As, Se or Ni during the oaTOF-ICP-MS analysis are negligible. Under the optimum experimental extraction conditions evaluated using a fractional factorial design (10 mg of the sample extracted with 5 mL of 140 g/L NH₄F for 10 min at 200°C), analysis of the resulting supernatant with Rh as an internal standard enabled precise and accurate simultaneous determination of 11 elements (Li, Be, Ni, As, Se, Rb, Sb, Cs, W, Tl and U) at trace and ultratrace levels. The accuracy was assessed by analysing two certified reference materials, namely Fine Fly Ash CTA-FFA-1 and Constituent Elements in Coal Fly Ash Standard Reference Material® 1633b. The precision of the reported method was better than 10%.     

Plasma surface modification of chitosan membranes: characterization and preliminary cell response studies

Surface modification of biomaterials is a way to tailor cell responses whilst retaining the bulk properties. In this work, chitosan membranes were prepared by solvent casting and treated with nitrogen or argon plasma at 20 W for 10-40 min. AFM indicated an increase in the surface roughness as a result of the ongoing etching process. XPS and contact angle measurements showed different surface elemental compositions and higher surface free energy. The MTS test and direct contact assays with an L929 fibroblast cell line indicated that the plasma treatment improved the cell adhesion and proliferation. Overall, the results demonstrated that such plasma treatments could significantly improve the biocompatibility of chitosan membranes and thus improve their potential in wound dressings and tissue engineering applications.     

Possibilities of column coupling electrophoresis provided with a fiber-based diode array detection in enantioselective analysis of drugs in pharmaceutical and clinical samples

The present work illustrated possibilities of column coupling electrophoresis combined with ionizable chiral selector and diode array detection (DAD) for the enantioselective analysis of trace drugs (pheniramine and its analogs) in pharmaceutical and clinical samples. Isotachophoresis (ITP), on-line coupled with capillary zone electrophoresis (CZE), served as an ideal injection technique (high sample load capacity, narrow and sharp drugs zones) of on-line pretreated samples (preseparation, purification and preconcentration of drugs) for the CZE stage. Enhanced (enantio)separation selectivity of CZE with ionizable chiral selector (carboxyethyl-beta-cyclodextrin recognized between drugs enantiomers on one hand as well as between drugs and sample matrix constituents on the other hand) enabled to obtain pure zones of the drugs enantiomers, suitable for their detection and quantitation. DAD in comparison with single wavelength UV detection enhanced value of analytical information verifying purity of drugs enantiomers zones (indicating interferents with different spectra to those of drugs). Obtained results indicated pure zones of interest confirming effective ITP-CZE (enantio)separation process. Distinguishing the trace analytes signals superposed on the baseline noise was provided with sufficient reliability (for this purpose the background correction and smoothing procedure had to be applied to the raw DAD spectra). The proposed ITP-CZE-DAD methods were characterized by favorable performance parameters (sensitivity, linearity, precision, recovery, accuracy, robustness, selectivity) and successfully applied for (i) enantiomeric purity testing of dexbrompheniramine in commercial pharmaceutical tablets and (ii) enantioselective metabolic study of pheniramine in human urine.     

Interference-free determination of thallium in aqua regia leaches from rocks, soils and sediments by D(2)-ETAAS method using mixed palladium-citric acid-lithium chemical modifier

The mixture of palladium (chloride) with citric acid and lithium is proposed as a new chemical modifier for the elimination of interference occurred during the determination of Tl in aqua regia extracts from rocks, soils and sediments by electrothermal atomic absorption spectrometry using instrumentation with deuterium-lamp background correction (D₂-ETAAS). Palladium was preferred to rhodium and platinum as to analyte stabilization, citric acid served as an effective reducing agent facilitating formation of Pd-Tl stable covalent bonds playing an important role in the analyte stabilization. Citric acid in addition helps to remove most of interfering chloride at low temperature. The further addition of Li increased significantly the robustness of chemical modifier against strongly interfering ZnCl₂ matrix by binding free chlorine into a more stable LiCl molecule. In the presence of the proposed chemical modifier the temperature for the final step of pyrolysis was adjustable up to 1000 °C, without any noticeable loss of volatile Tl species and the interference of the rest chloride matrix was significantly reduced. The application of the modifier to direct determination of Tl in aqua regia extracts from rocks, soils and sediments has ensured the characteristic mass and LOD value for the original sample 13 pg and 0.043 μg g⁻¹, respectively (10-μL aliquots of sample) and has enabled the use of matrix-free standard solutions for attaining accurate analysis. The accuracy was verified by the analysis of certified reference samples and by the comparison of results with those found by an inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometer (ICP-oa-TOFMS) method.