Structural aspects of α/β transformation in hot deformed CuZn-39Pb3 alloy

Hot compression tests were performed on commercial CuZn39Pb3 alloy deformed at strain rate of 0.0007 s^–1and 0.02 s^–1within temperature range of 923 K–1023 K. Flow stress vs. deformation temperature and strain rate dependence was found to follow the relation: . Both dynamic recovery and dynamic recrystallization have operated in the presence of fine lead particles being responsible for effective flow stress reduction with increasing deformation temperature. Transformation of - to phase above the temperature approx. 1000 K and the following fast cooling of hot deformed samples produced fine, plate-like structure of -grains, within retained -matrix. Moreover, coherent fine Fe-particles were observed within -grains being not detected at any area of -matrix. The last effect was supposed to result from lower solubility of iron in -phase than that for -phase.     

Suppression of “salt and pepper” noise based on Youden designs

This paper presents a new class of algorithms based on Youden designs to detect and restore edges present in an image imbedded by mixture or “salt and pepper” noise. The mixture noise consists of a uncorrelated or correlated noisy background plus uncorrelated impulsive noise. The objective is to restore pixels affected by the impulsive part of the mixture noise. The approach is to consider that these pixels have lost their true value and their estimate is obtained via the normal equation that yields the least sum of square error (LSSE). This procedure is known in the literature as “The Missing Value Approach Problem”. The estimates are introduced into the image data and an ANOVA technique based on Youden design is carried out. We introduce Youden designs which are special Symmetric Balanced Incomplete block (SBIB) designs, the pertinent statistical tests and estimates of the factor effects. We derive the estimate of the missing value for the uncorrelated noise environment as well as for the correlated one. The high level of performance of these algorithms can be evaluated visually via the input/output images and objectively via the input/output signal-to-noise ratio (SNR).     

Poly(3-nonylthiophene-co-methylthiophene)s: New soluble conductive copolymers

New conductive soluble copolymers of 3-nonylthiophene (3NT) and 3-methylthiophene (3MT) were chemically synthetized using FeCl₃ in chloroform solution as a catalyst at room temperature and a N₂ atmosphere. The structural properties of the undoped and iodine doped 3NT-co-3MT have been studied by UV-Vis, FTIR, 1H- and ¹³C-NMR, GPC, DSC, TGA, WAXD, magnetic susceptibility and charge transfer measurements. The results show that copolymers (3NT-co-3MT) have a random arrangement. These copolymers have good thermal stability dependent on the 3NT. 3MT content and low magnetic susceptibility (typical for compounds of this class) which decreases with increasing temperature. The conductivity of the iodine doped copolymer (3NT-co-3MT) (measured in the dark at room temperature) increases distinctly in comparison to the undoped samples (2–8×10^–9 Sm^–1).     

Preparation and properties of new lactose-based surfactants

A new group of nonionic saccharide-based surfactants, N-alkanoyl-N-methyllactitolamines (alkanoyl: decanoyl, lauroyl, myristoyl, palmitoyl, stearoyl), were synthesized and characterized. Surface properties such as critical micelle concentration, standard free energy of adsorption, standard free energy of micellization, surface tension reduction efficiency, effectiveness of surface tension reduction, surface excess concentration, and surface area demand per molecule as well as foaming properties (i.e., foam volume and foam stability), contact angle, antiraicrobial activity, and biodegradability were determined. The selected performance properties were evaluated in relation to commercially available alkyl polyglucosides (Glukopon 600 EC(HH)-a Henkel product), and oligooxyethylenated decyl (C₁₀E₄) and dodecyl (E₁₂E₅) alcohols. The foaming-stabilizing effect and contact angle suggest that the lactose-derived surfactants that were studied share some common properties with alkyl polyglucosides that are different from those with an oligooxyethylene grouping. All tested N-alkanoyl-N-methyllactitolamines were practically nontoxic to bacteria and yeasts. These compounds are readily biodegradable in the Closed Bottle test inoculated with activated sludge. N-Alkanoyl-N-methyllactitolamines with lower chain lengths (C₁₀–C₁₄) biodegraded at a slightly faster rate. Biological properties showed that this class of compounds fulfills all requirements needed for environmental acceptance.     

Aldonamide-type gemini surfactants: Synthesis, structural analysis, and biological properties

A new group of nonionics, so-called sugar surfactants having a gemini structure, N,N′-bisalkyl-N,N′-bis[(3-gluconylamido)propyl]ethylenediamines [bis(C _n GA): C _n =n-C₈H₁₇, n-C₁₂H₂₅], N,N′-bisdodecyl-N,N′-bis[(3-glucoheptonylamido)propyl]ethylenediamine [bis(C₁₂GH)], and N,N′-bisalkyl-N,N′-bis[(3-lactobionylamido)propyl]ethylenediamines [bis(C _n LA): C _n =n-C₈H₁₇, n-C₁₂H₂₅], were prepared in a convenient four-step procedure from easily accessible reagents. Their structure and purity were confirmed by means of elemental analysis, electrospray ionization MS (ESI-MS), and NMR spectra—¹H, ¹³C, ¹H−¹³C COSY, and distortionless enhancement by polarization transfer. All tested surfactants were practically nontoxic to gram-negative bacteria and fungi, but they inhibited the growth of some gram-positive bacteria. From the results of the Closed Bottle test (OECD Guideline 301D) for biodegradability measurements, it was concluded that the tested aldonamide gemini structures are biodegraded by environmental microorganisms to 16–55% of the initial levels by day 28, the extent depending on both the aldonamide type and the alkyl chain length. Consequently, N,N′-bisalkyl-N,N′-bis[(3-aldonylamido)propyl]ethylenediamines are a surfactant class having low ecotoxicity and fulfilling requirements desired from an ecological standpoint.     

The relation between electrochemical and catalytic activities of iron(II) polyphthalocyanine in the reduction of oxygen

The catalytic activity of iron(II) polyphthalocyanine synthesized in the presence of known FeCl₂ excess as against the stoichiometric amount of pyromellitic dianhydride (PDMA) in the decomposition reaction of hydrogen peroxide as well as the electrochemical activity in the reduction of oxygen in acidic medium was investigated. On the grounds of the dependence of electrochemical activity on catalytic activity there were recognized two different mechanisms of hydrogen peroxide decomposition during the reduction of oxygen, according to the electric properties of iron(II) polyphthalocyanines examined.     

Vinylogous Urethane Vitrimers

Vitrimers are a new class of polymeric materials with very attractive properties, since they can be reworked to any shape while being at the same time permanently cross‐linked. As an alternative to the use of transesterification chemistry, we explore catalyst‐free transamination of vinylogous urethanes as an exchange reaction for vitrimers. First, a kinetic study on model compounds reveals the occurrence of transamination of vinylogous urethanes in a good temperature window without side reactions. Next, poly(vinylogous urethane) networks with a storage modulus of ≈2.4 GPa and a glass transition temperature above 80 °C are prepared by bulk polymerization of cyclohexane dimethanol bisacetoacetate, m‐xylylene diamine, and tris(2‐aminoethyl)amine. The vitrimer nature of these networks is examined by solubility, stress‐relaxation, and creep experiments. Relaxation times as short as 85 s at 170 °C are observed without making use of any catalyst. In addition, the networks are recyclable up to four times by consecutive grinding/compression molding cycles without significant mechanical or chemical degradation.     

Computations on Metallofullerenes Derivatized during Extraction: La@C80-C6H3Cl2 and La@C82-C6H3Cl2

Recently, an extraction of la metallofullerenes from soot using 1,2,4-trichlorobenzene has been reported for La@C₈₀ and La@C₈₂. In both cases, the cages were derivatized by the solvent (forming La@C₈₀-C₆H₃Cl₂ and La@C₈₂-C₆H₃Cl₂) and the following X-ray analysis disclosed rather unexpected cages: C₈₀(C _2v ;3) and C₈₂(C _3v ;7). In order to explain the challenging observations, a two-step computational treatment is presented. The first step deals with the high-temperature gas-phase formation of the underivatized endohedrals while the second step models the reaction with the solvent. The Gibbs free energies were evaluated for representative temperatures and the computational scheme was able to confirm high relative populations for the observed derivatized cages.     

Structural and electrical properties of soluble conducting poly(3-pentylthiophene)

A solution of processible poly (3-pentylthiophene) (P3PT) was synthesized by chemical polymerization. The structure of the resulting polymer was investigated by gel permeation chromatography (GPC); infrared;¹H and¹³C nuclear magnetic resonance; Ultraviolet visible spectroscopy (UV-Vis) and wide-angle X-ray scattering (WAXS) techniques. It was found that the microstructure of the chains has a low number of irregular couplings and thus has desirable electrical properties. In the small-angle region of X-ray scattering, a pronounced peak was observed with ad (coherence length) value of 1.51 nm for P3PT and 1.835 nm for poly (3-heptylthiophene (P3Hept). Electron spin resonance measurements showed that P3PT has 10¹⁸ spins g^–1, ag value 2.0039, and a H _pp of about 6 Gauss. The Pauli-like susceptibility after doping P3PT with I₂ is of the same order as for poly paraphenylene (PPP) doped with AsF₅, and corresponds to a density of states at the Fermi level about 0.01 states eV^–1 per carbon atom in the thiophene ring. The current-voltage (I–V) characteristics obtained for different temperatures were always linear. The dark room temperature conductivity was 10^–8 Sm^–1 and distinctly increased after doping. The P3PT studied is a good candidate for potential commercial applications.