Thallium fractionation in polluted environmental samples using a modified BCR three-step sequential extraction procedure and its determination by electrothermal atomic absorption spectrometry

Determination of thallium in polluted environmental samples and their extracts obtained by a modified BCR three-step sequential extraction procedure was used to study thallium distribution and mobility in the monitored polluted area affected by acidification (Šobov, Central Slovakia). The results of fractionation applied to 5 soil certified reference materials and 14 environmental samples show that the vast majority of thallium occurred in the residual fraction. This means that highly toxic thallium is strongly entrapped in the parent rock materials remains immobile and its environmental toxicity is therefore reduced. The limit of detection for thallium in the studied fractions was lower than 0.050 mg kg⁻¹, the precision (RSD) of the ultratrace determination of thallium in the studied fractions was better than 17 % and the accuracy of the used method was verified by analyzing certified reference materials. Presented at the XVIIIth Slovak Spectroscopic Conference, Spišská Nová Ves, 15–18 October 2006.     

The nonexistence of expansive commutative group actions on Peano continua having free dendrites

A dendrite D in a metric space X is said to be free if there exists a connected open set U in X such that . In this paper, we prove that there is no expansive commutative group action on any Peano continuum having a free dendrite. In particular, no 1-dimensional compact ANR admits an expansive commutative group action.     

Proteomic analysis reveals metabolic changes during yeast to hypha transition in Yarrowia lipolytica

Fungal dimorphism is important for survival in different environments and has been related to virulence. The ascomycete Yarrowia lipolytica can grow as yeast, pseudomycelial or mycelial forms. We have used a Y. lipolytica parental strain and a Deltahoy1 mutant, which is unable to form hypha, to set up a model for dimorphism and to characterize in more depth the yeast to hypha transition by proteomic techniques. A two-dimensional gel electrophoresis (2-DE) based differential expression analysis of Y. lipolytica yeast and hyphal cells was performed, and 45 differentially expressed proteins were detected; nine with decreased expression in hyphal cells were identified. They corresponded to the S. cerevisiae homologues of Imd4p, Pdx3p, Cdc19, Sse1p, Sol3p, Sod2p, Xpt1p, Mdh1p and to the unknown protein YALIOB00924g. Remarkably, most of these proteins are involved in metabolic pathways, with four showing oxidoreductase activity. Furthermore, taking into account that this is the first report of 2-DE analysis of Y. lipolytica protein extracts, 35 more proteins from the 2D map of soluble yeast proteins, which were involved in metabolism, cell rescue, energy and protein synthesis, were identified.     

Microwave‐assisted synthesis of 2‐(2‐pyridyl)azoles. Study of their corrosion inhibiting properties

An efficient and fast procedure for the synthesis of 2‐(2‐pyridyl)azoles is described using ionic liquids as catalysts under microwave irradiation. The X‐ray crystallographic analyses for three of the four synthesized compounds are presented. Potentiodynamic polarization studies were carried out to analyze the electrochemical behavior of the compounds in corrosive acidic media. Of the four derivatives, one compound was detected to be an effective corrosion inhibitor prototype for oil refinery environments.     

Development of special optical fibers for evanescent-wave chemical sensing

The paper summarizes results achieved in the Institute of Radio Engineering and Electronics in the field of investigation and fabrication of novel fiber-optic structures for evanescent-wave chemical sensing. Several approaches for increasing the evanescent-wave sensitivity of multimode silica optical fibers to gaseous and liquid chemicals are shown. These approaches make use of the decrease of the core diameter in sectorial and capillary sectorial fibers, modification of trajectories of optical rays in the cores of inverted-graded-index fibers, tailoring of the refractive index of porous layers applied on silica cores, an output mode filter preventing the detection of rays propagating at low axial angles or fibers bent in single or multiple turns. Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17, 1998. This work was supported by the Grant Agency of the Czech Republic (projects No. 102/96/0939 and No. 102/98/1358) and by joint project No. 4104 of AS CR and CNRS, France.     

Er-doped twin-core fibre coupler as a saturable-absorber-based narrow-band filter for fibre lasers

We have proposed and demonstrated experimentally that an Er-doped twin-core fibre (ErTCF) can be employed as a tracking narrow-band filter in fibre ring lasers for line narrowing and enhancement of the spectral stability. The device mimics a saturable absorber with inhomogeneous broadening. The slow erbium ion saturation dynamics in the ErTCF prevents wavelength hopping whilst it enables the filter to track the operation wavelength on its tuning. We have improved the device operation by utilizing the inherent filtering effect of a twin-core fibre coupler. Presented at the 1st Czech-Chinesse Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17, 1998 This research has been in part supported by the Commission of the European Union in the frame of Copernicus programme, Project # 7882 and by the Ministry of Education of the Czech Republic under Contract OC 241.10/1998.     

Utilization of saffron (<Emphasis Type="Italic">Crocus sativus L.</Emphasis>) as sensitizer in dye-sensitized solar cells (DSSCs)

Photoelectrodes of dye-sensitized solar cells (DSSCs) have been prepared using nanosized titanium dioxide that have soaked in a solution of different saffron (Crocus sativus L.) spice content in ethanol. The optimized polyacrylonitrile (PAN)-based gel polymer electrolyte with 40.93 wt.% ethylene carbonate, 37.97 wt.% propylene carbonate, 4.37 wt.% tetrapropylammonium iodide, 9.86 wt.% PAN, 1.24 wt.% 1-butyl-3-methylimidazolium iodide, 4.35 wt.% lithium iodide and 1.28 wt.% iodine has been used as the electrolyte for DSSC. The electrolyte has conductivity of 2.91 mS cm^?1 at room temperature (298 K). DSSCs were also sensitized with saffron solution that has been added with 30 wt.% chenodeoxycholic acid (CDCA) co-adsorbent and designated as DSSC P4. The solar cell converts light-to-electricity at an efficiency of 0.31%. This is 29% enhancement in efficiency for the DSSC without addition of CDCA in the saffron-ethanol solution. The DSSC exhibits current density at short-circuit (J _sc ) of 1.26 mA cm^?2, voltage at open circuit (V _oc ) of 0.48 V and 51% fill factor. DSSC P4 also exhibits the highest incident photon-to-current density of more than 40% at 340 nm wavelength.     

Enhancing the Decolorization of Methylene Blue Using a Low-Cost Super-Absorbent Aided by Response Surface Methodology

The presence of organic dyes from industrial wastewater can cause pollution and exacerbate environmental problems; therefore, in the present work, activated carbon was synthesized from locally available oil palm trunk (OPT) biomass as a low-cost adsorbent to remove synthetic dye from aqueous media. The physical properties of the synthesized oil palm trunk activated carbon (OPTAC) were analyzed by SEM, FTIR-ATR, and XRD. The concurrent effects of the process variables (adsorbent dosage (g), methylene blue (MB) concentration (mg/L), and contact time (h)) on the MB removal percentage from aqueous solution were studied using a three-factor three-level Box–Behnken design (BBD) of response surface methodology (RSM), followed by the optimization of MB adsorption using OPTAC as the adsorbent. Based on the results of the analysis of variance (ANOVA) for the three parameters considered, adsorbent dosage (X₁) is the most crucial parameter, with an F-value of 1857.43, followed by MB concentration (X₂) and contact time (X₃) with the F-values of 95.60 and 29.48, respectively. Furthermore, the highest MB removal efficiency of 97.9% was achieved at the optimum X₁, X₂, and X₃ of 1.5 g, 200 mg/L, and 2 h, respectively.     

A FeCl3-promoted highly atropodiastereoselective cascade reaction: synthetic utility of radical cations in indolostilbene construction

The FeCl₃-promoted oxidative cyclization/coupling of acetamidostilbenes possessing 3-methoxy, 4-methoxy and 3,5-methoxy substitutions (21), (22) and (23) is described. Only 3,5-substitution gave rise to novel indolostilbenes, each possessing two stereogenic axes (axially chiral but racemic dimers (39) and (40)). The 4-methoxy substituted acetamidostilbenes, by contrast, yielded the bisindoline dimer (36).