Polyaniline/montmorillonite nanocomposite thin layers deposited on different substrates

Preparation method of polyaniline/montmorillonite (PANI/MMT) nanocomposite in the form of thin layer deposited on various substrates is optimized in this work to obtain high electrical conductivity. Simple method (i.e. polymerization of anilinium sulfate in the presence of MMT) has been used for the preparation and following four conditions were varied: preparation temperature (T = 10 or 20 °C), preparation time (t = 4 or 6 h), size fraction of MMT (p < 1 or 5 µm), and type of substrate (microscope glass slides, silica glass slides, polyester foils). Therefore, 24 samples were prepared, characterized and their electrical conductivity was compared. Raman spectroscopy and scanning electron microscopy were used for the characterization of the structure of samples. Thickness of layers was measured using atomic force microscopy. Based on the comparison of samples and with respect to the aim of obtaining high electrical conductivity, it was found that the most suitable substrate is polyester foil and preparation conditions are T = 20 °C, t = 6 h, p < 5 µm. To obtain highly conductive layers on glass substrates (although less conductive than layers on foil), preparation time have to be shortened to 4 h.     

Raman study of PANI thin film during long time period in dependence on storage conditions

Conducting polymer polyaniline which is nowadays in forefront of the interest was in our study prepared in a form of thin films from anilinium sulfate by its chemical oxidation using ammonium peroxydisulfate. During the oxidation process, the polyaniline was deposited on glass slides and immersed into reaction mixture. Two sets of polyaniline thin films were prepared with different oxidation times (10, 20, 30, and 40 min). The first set was kept dry in desiccator and the second one was freely exposed to air moisture. Raman spectroscopy, nondestructive technique which is very sensitive to changes in structure of polymers, was used for the characterization of the protonation state of prepared polyaniline thin films. It was found that storage conditions affect the protonation state which in case of samples kept in desiccator is maintained without significant changes for longer time. Raman spectroscopy also revealed the dependence of protonation state on the oxidation time and 10 min proved as not sufficient for the creation of the protonation form of polyaniline.     

The possible production of natural flavours by amino acid degradation

Abstract  

This work describes the degradation of phenylalanine and tryptophane catalysed by their complexes with Fe(II), Co(II), and Cu(II). The influences of the central atom and of the reaction conditions on the degradation of the amino acids were observed. The necessary condition of the degradation is the possibility of a redox reaction on the central atom between M(II) and M(III). Moreover, the coordination sphere of the central cation of the transition metal must not be sterically shielded. The necessary conditions are fulfilled only in the Fe(II) complexes. The degradation is strictly anaerobic because due to the influence of oxygen, an irreversible oxidation of Fe(II) to Fe(III) proceeds. This reaction results in 5-hydroxy-1H-indol instead of the mixture of the degradation products, such as benzaldehyde, phenylacetaldehyde, and phenylacetic acid. The influence of the temperature on the catabolism is very important because the reaction accelerates with temperature increase. The phenylalanine anion acts as a reducing agent, and Fe(II) is spontaneously reduced to Fe(0).     

Synthetic UDP-furanoses as potent inhibitors of mycobacterial galactan biogenesis

UDP-galactofuranose (UDP-Galf) is a substrate for two types of enzymes, UDP-galactopyranose mutase and galactofuranosyltransferases, which are present in many pathogenic organisms but absent from mammals. In particular, these enzymes are involved in the biosynthesis of cell wall galactan, a polymer essential for the survival of the causative agent of tuberculosis, Mycobacterium tuberculosis. We describe here the synthesis of derivatives of UDP-Galf modified at C-5 and C-6 using a chemoenzymatic route. In cell-free assays, these compounds prevented the formation of mycobacterial galactan, via the production of short "dead-end" intermediates resulting from their incorporation into the growing oligosaccharide chain. Modified UDP-furanoses thus constitute novel probes for the study of the two classes of enzymes involved in mycobacterial galactan assembly, and studies with these compounds may ultimately facilitate the future development of new therapeutic agents against tuberculosis.     

Comparison of IFCC and NGSP methods for determination of glycated haemoglobin using advanced regression techniques

The objective of this work was a correct statistical comparison of two assay methods for determination of glycated haemoglobin HbA1c. The immunoturbidimetric determination of HbA1c was performed in two ways: using an automatic analyser Hitachi 912, calibrated according to the IFCC reference system (International Federation of Clinical Chemistry and Laboratory Medicine) and using an analyser Advia 1200 and the NGSP reference system (National Glycohaemoglobin Standardization Program). For statistical comparison of these two analytical methods several advanced regression methods were used, which respect random errors of both compared methods. Specifically, Deming regression with and without weights, orthogonal regression, and Passing-Bablok regression were employed. The results demonstrate that the investigated analytical assay methods do not correspond to each other. The summarized results indicate usefulness of better harmonisation of two existing reference systems.     

Dynamic nuclear polarization at 9T using a novel 250 GHz gyrotron microwave source. 2003

In this communication, we report enhancements of nuclear spin polarization by dynamic nuclear polarization (DNP) in static and spinning solids at a magnetic field strength of 9 T (250 GHz for g = 2 electrons, 380 MHz for ¹H). In these experiments, ¹H enhancements of up to 170 ± 50 have been observed in 1-¹³C-glycine dispersed in a 60:40 glycerol/water matrix at temperatures of 20 K; in addition, we have observed significant enhancements in ¹⁵N spectra of unoriented pf1-bacteriophage. Finally, enhancements of ∼17 have been obtained in two-dimensional ¹³C–¹³C chemical shift correlation spectra of the amino acid U–¹³C, ¹⁵N-proline during magic angle spinning (MAS), demonstrating the stability of the DNP experiment for sustained acquisition and for quantitative experiments incorporating dipolar recoupling. In all cases, we have exploited the thermal mixing DNP mechanism with the nitroxide radical 4-amino-TEMPO as the paramagnetic dopant. These are the highest frequency DNP experiments performed to date and indicate that significant signal enhancements can be realized using the thermal mixing mechanism even at elevated magnetic fields. In large measure, this is due to the high microwave power output of the 250 GHz gyrotron oscillator used in these experiments.     

Large-scale ultrasonic cleaning system: Design of a multi-transducer device for boat cleaning (20kHz)

The present study is part of a global project which consists in the development of an automatic cleaning station for immersed boats (cockle, ninepin, etc.) in a self-service mode, associating an innovative ultrasonic device for cleaning with a specific water treatment. The originality of the process is that cleaning is performed by three transducers operating simultaneously at low frequency and moving along the surface, thanks to programmable logic controllers, and that it includes a suction to collect the dirt removed. Therefore, the time required for boat maintenance is shortened, ensuring high quality cleaning without the need for dry docks and avoiding additional pollution in the harbor areas. One of the key points was the evaluation of washing efficiency, as it is really hard to give a quantitative estimation of the dirt removed. To obtain the first design laws, feasibility tests have been carried out on dirty cockle samples and on real boat hulls with a laboratory ultrasonic device. The influence of a large number of parameters was tested such as transducer-probe distance, displacement speed and transmitted power. The obtained data allowed us to design an optimized cleaning device combining high efficiency and speed.     

Seismic rays as Finsler geodesics

We prove that, in general, for anisotropic nonuniform continua, seismic rays are geodesics in Finsler geometry. In particular, for separable velocity functions, the geometry is Wagnerian. We provide concrete examples with theoretical discussions and introduce the seismic Finsler metric.