Information structuring—a new way of perceiving the content of learning

Dominating information by formation seems to be the only realistic solution to overcome the crisis generated by the higher and higher accumulation of information in each domain. The paper is proposing a model of building structured knowledge able to generate in the child's mind strategies for efficient processing of information.     

Thermogravimetric analysis of layered double hydroxides with chloramphenicol and salicylate in the interlayer space

The thermal behavior of the new inorganic-organic nanohybrid materials obtained by intercalation of chloramphenicol and salicylate into layered double hydroxides (LDHs) by direct synthesis method, anion exchange reaction and the reconstruction method was evaluated by dynamic thermogravimetric analysis in air, at heating rates of 5°C min⁻¹. The XRD patterns of the samples are characteristic for those of well crystallized solids with layered double hydroxide structures. The FTIR spectroscopy results show the presence of the organic compound within the network structure of the synthesized LDHs. The kinetic parameters (reaction order (n) apparent activation energy (E _a) and pre-exponential factor (lnA) were calculated by the Coats-Redfern method. The compensation effects were determined.     

Numerical modelling and simulation of Laviron treatment for poly-phenothiazine derivative-modified glassy carbon electrodes

Electropolymerization of a new phenothiazine derivative (bis-phenothiazin-3-yl methane, BPhM) on glassy carbon electrodes leads to electroactive and conducting layers of poly-BPhM. Based on the Laviron method, the kinetic parameters (the heterogeneous electron transfer rate constants k _s and transfer coefficients α) were calculated out of the experimental and theoretical data. The theoretical data have been obtained by using the analogical modelling and numerical simulating method. The modified electrodes present high values of k _s(~50s⁻¹) in phosphate buffer solutions of different pH values. A good correlation of mathematical and numerical simulated kinetic parameters has been obtained, with the experimental values and the norm of residuals being very close to zero.     

Simultaneous determination of methylxanthines in different types of tea by a newly developed and validated TLC method

The aim of this paper is to develop a new simple, fast and economical method for simultaneous quantitative determination of methylxanthine compounds based on TLC combined with image analysis. To obtain certain results, both extraction and chromatographic separation were optimized. The optimum extraction conditions were maceration in ethanol-water 8:2, v/v. The chromatographic separations were done on the silica gel F(254) TLC plates developed with chloroform-dichloromethane-isopropanol, 4:2:1 v/v/v. Detection was performed under UV lamp at 254?nm and the evaluation of the chromatographic plate was based on digital processing of chromatographic images. The developed TLC method was validated for parameters such as specificity, linearity and range, LOD and LOQ, precision, robustness and accuracy. This method was then applied for determination of caffeine, theobromine and theophylline in different types of tea, commercially available. Moreover, the content of methylxanthines detected and determined in commercial tea samples can be used as chemical marker in quality control.     

Silver coordination polymers with remarkably high packing coefficients

Silver meso- and rac-tartrate and silver squarate have been synthesized, and the crystal structure of a new polymorph of the latter is reported. Three reaction products of these silver salts with pyrazine have been obtained and structurally characterized: From silver squarate, a chain polymer with linear coordination of Ag(I) by two pyrazine ligands is formed, whereas the silver tartrates yield solids in which the inner coordination sites around the metal are only partially occupied by N donors; in contrast to expectation, oxygen coordination prevails. All the four new Ag(I) coordination compounds reported show high packing coefficients in the range between 0.789 and 0.885. In order to put these results into a meaningful context, packing coefficients for the crystal structures of almost 30,000 compounds retrieved from the Cambridge Structural Database have been determined. Tartrates pack significantly closer than pyrazine complexes or metal-containing compounds in general. The exceptionally high packing coefficient of the new polymorph of silver squarate is due to stacking of anions and concomitant Ag···Ag contacts, both along the shortest lattice parameter which amounts to only 3.3990(9) ?.     

Protein–Inorganic Array Construction: Design and Synthesis of the Building Blocks

Herein we describe the design and synthesis of the first series of di‐functional ligands for the directed construction of inorganic‐protein frameworks. The synthesized ligands are composed of a metal‐ion binding moiety (terpyridine‐based) conjugated to an epoxysuccinyl peptide, known to covalently bind active cysteine proteases through the active‐site cysteine. We explore and optimize two different conjugation chemistries between the di‐functionalized metal‐ion ligand and the epoxysuccinyl‐containing peptide moiety: peptide‐bond formation (with limited success) and Cu^I‐catalysed click chemistry (with good results). Further, the complexation of the synthesized ligands with Fe^II and Ni^II ions is investigated: the di‐functional ligands are confirmed to behave similarly to the parent terpyridine. As designed, the peptidic moiety does not interfere with the complexation reaction, in spite of the presence of two triazole rings that result from the click reaction. ES‐MS together with NMR and UV/Vis studies establish the structure, the stoichiometry of the complexation reactions, as well as the conditions under which chemically sensitive peptide‐containing polypyridine ligands can undergo the self‐assembly process. These results establish the versatility of our approach and open the way to the synthesis of di‐functional ligands containing more elaborated polypyridine ligands as well as affinity labels for different enzyme families. As such, this paper is the first step towards the construction of robust supramolecular species that cover a size‐regime and organization level previously unexplored.     

Thermal desorption/gas chromatography/mass spectrometry approach for characterization of the volatile fraction from amber specimens: A possibility of tracking geological origins

Research on the chemical composition of fossil resins has evolved during the last decades as a multidisciplinary field and is strongly oriented toward the correlation with their geological and botanical origin. Various extraction procedures and chromatographic techniques have been used together for identifying the volatile compounds contained in the fossil resin matrix. Hyphenation between thermal desorption (TD), gas chromatography (GC) and mass spectrometry detection (MS) has been chosen to investigate the volatile compounds fraction from ambers with a focus on Romanite (Romanian amber) and Baltic amber species. A data analysis procedure was developed for the main purpose of fingerprinting ambers based on the MS identity of the peaks generated by the volatile fraction, together with their relative percentual area within the chromatogram. Chromatographic data analysis was based entirely on Automated Mass Spectral Deconvolution & Identification System (AMDIS) software to produce deconvoluted mass spectra which were used to build-up a mixed mass spectra and relative retention scale library. Multivariate data analysis was further applied on AMDIS results with successful discrimination between Romanite and Baltic ambers. A special trial was conducted to generate pyrolysis “like” macromolecular structure breakdown to volatile compounds by gamma irradiation with a high absorbed dose of 500 kGy. Contrary to our expectations the volatile fraction fingerprints were not modified after irradiation experiments. A complementary non-destructive new approach by ESR spectroscopy was also proposed for discriminating between Romanite and Baltic ambers.     

Active colloidal suspensions exhibit polar order under gravity

Recently, the steady sedimentation profile of a dilute suspension of chemically powered colloids was studied experimentally [J. Palacci et al., Phys. Rev. Lett. 105, 088304 (2010)]. It was found that the sedimentation length increases quadratically with the swimming speed of the active Brownian particles. Here we investigate theoretically the sedimentation of self-propelled particles undergoing translational and rotational diffusion. We find that the measured increase of the sedimentation length is coupled to a partial alignment of the suspension with the mean swimming direction oriented against the gravitational field. We suggest realistic parameter values to observe this polar order. Furthermore, we find that the dynamics of the active suspension can be derived from a generalized free energy functional.     

Annealing study of two-dimensional patterned Ge nanostructures via nanosphere lithography

Experimental studies on patterning hexagonal Ge nanostructures have been conducted on Si substrates through deposition of Ge with colloidal particles as a mask. The deposited Ge thin film possesses, according to the X-ray diffraction measurements, in plane texture, being epitaxial and aligned with the (111) Si substrate. The size distribution of the patterned Ge nanostructures is narrow, as indicated by the atomic force microscopy and scanning electron microscopy measurements. We have obtained Ge nanostructures with lateral dimension of 490 nm (height 12 nm), 200 nm (height 6 nm) and 82 nm (height 6 nm) by using different sizes of polystyrene spheres. We have performed in depth studies of the Ge nanostructures’ behavior due to thermal and rapid thermal post-annealing processes. FT micro-Raman spectroscopy shows that there is no Si intermixing during the annealing process. In order to quantify the changes in the height and lateral dimension, we have performed atomic force microscopy and white light interferometry analysis. The changes in shape and the decrease in the area of a cross-section of Ge nanostructure will be discussed in respect to similar results shown in the literature for Ge thin films during the annealing process.