Consideration concerning interlaboratory test for cement in the last 20 years

Since 1988, over 40 laboratories representing research institutes, cement plants, pre-cast units, hydro plant construction companies, industrial construction companies, building companies, etc. from nine countries—Romania, Republic of Moldova, Croatia, Serbia, Macedonia, Bulgaria, Hungary, Ukraine and Lebanon—take part every year in an interlaboratory test organized by our laboratory. The subject of the interlaboratory test for cement was 37 laboratory tests: 12 chemical determinations, 7 physical tests and 9 mechanical tests carried out with 2 types of sand, from CEPROCIM and from each participant laboratory. The paper presents the evolution of two statistical parameters (standard deviation of reproducibility and/or coefficient of variation) for a period of 20 years and for 11 laboratory tests. The results strongly prove that interlaboratory test is one of the most efficient tools to establish a common language for all the participant laboratories performing cement testing procedures.     

Electrical conduction mechanism and gas sensing properties of Pd-doped TiO2 films

Undoped and Pd-doped titanium oxide thin films (0.5 wt.%) were prepared by the sol-gel technique (dip-coating) on glass and silicon substrates. The as-deposited thin films were compacted by subjecting them to different annealing temperatures (300 °C, 500 °C). The dependences of the electrical conductivity vs. inverse temperature were investigated in air and in vacuum. A study of the effects of Pd-doping, annealing temperature and ambient conditions on their electrical properties was performed. The sensing behavior of titanium oxide thin films exposed to some reducing gases (methane, acetone, ethanol, formaldehyde and liquefied petroleum gas) was carried out, by means of electrical conductivity measurements. All the studied films are most sensitive to formaldehyde, with a special remark for the Pd-doped ones deposited on silicon substrates.     

GRAFTED STYRENE-DIVINYLBENZENE COPOLYMERS CONTAINING BENZALDEHYDES AND THEIR WITTIG REACTIONS WITH VARIOUS PHOSPHONIUM SALTS

A chloromethylated styrene-divinylbenzene copolymer support system functionalized with 4-benzaldehyde and 2-benzaldehyde was prepared.The degree of functionalization with aldehyde groups is well suited for the subsequent use of the products as Wittig reagents.The polymer bound aldehyde was reacted with Wittig reagents to give olefin groups grafted on styrene-divinylbenzene copolymers.The reactions were carried out in phase transfer catalysis conditions.A simple procedure for the calculation of the degree of functionalization and the statistical modeling of the structural repetitive unit of the copolymer are reported.     

Permeation of gases through metallized polymer membranes

The permeation of He, H₂, CO₂, Ar, N₂ and Kr at 50°C through polyethyleneterephthalate, PET, membranes metallized with Pd, Ni and Cu was studied. It was found that metallizing a PET membrane changed its permeability for the gases studied, and that the permeability for H₂ varied slightly with differing H₂ pressure. In the range of 0-50°C the temperature dependence of the permeability for He and H₂ was determined. The results obtained were interpreted by assuming that the permeation of all gases, including H₂, through the metal layers of the membranes takes place by diffusion through fine defects which exist in their structure and, moreover, that H₂ also permeates through the Pd and Ni layers themselves. An important point is that by this method an increase of up to an order of magnitude of the membrane selectivity for H₂ was obtained     

Design and synthesis of water-soluble bioconjugatable trans-AB-porphyrins

Three free base porphyrins have been prepared that bear a polar and facially encumbering 2,4,6-tris-(carboxymethoxy)phenyl motif at one meso (5-) position. The only other substituent (15-position) comprises phenyl, formyl, or p-aminophenyl. The porphyrins exhibit solubility in water (or aqueous buffer solutions) at pH ≥7 and concentrations >1 mM at room temperature. The concise syntheses, water solubility, and bioconjugatable handle make these porphyrin constructs suitable for biological applications.     

Univalence criterion and convexity for an integral operator

For analytic functions f and g in the open unit disk U, a new integral operator I₁(f,g)(z) is introduced. The main object of this paper is to obtain a univalence condition and the order of convexity for the integral operator I₁(f,g)(z).     

Nondestructive imaging of a type I optical fiber Bragg grating

Nondestructive images of refractive-index variation within a type I fiber Bragg grating have been recorded by the differential interference contrast imaging technique. The images reveal detailed structure within the fiber core that is consistent with the formation of Talbot planes in the diffraction pattern behind the phase mask that had been used to fabricate the grating.     

Thermal behaviour and characterisation of new biologically active Cu(II) complexes with benzimidazole as main ligand

Four coordination compounds of copper(II) were synthesised and characterised in solid state by elemental analysis, infrared, electronic and EPR spectroscopy, as well as by thermal analysis (TG/DTA). The complexes were formulated on the basis of experimental data as: [Cu(BzIm)₂(H₂O)]·H₂O (1), [Cu₂(Acr)₄(HBzIm)₂] (2), [Cu(Acr)₂(HBzIm)₂] (3) and [Cu(Acr)₂(HBzIm)₂(H₂O)]·H₂O (4). IR data are in accordance with the unidentate nature of benzimidazole, in complexes (2), (3) and (4), and bridge bidentate nature of benzimidazole, in complex (1), while acrylato acts as uni- or bridge/chelate ligand. The electronic spectra display the characteristic pattern of square planar, square pyramidal, or octahedral stereochemistry, also confirmed by EPR spectra. Thermal decomposition evidenced several well-defined steps as dehydration of complexes (1) and (4), benzimidazole molecule releases for all complexes and acrylate decomposition in carbonate for complexes (3) and (4). In all four cases, the final residue after thermal treatment in air flow is copper(II) oxide, formed during the decomposition steps for complexes (3) and (4), and, respectively, after the oxidation of the metallic copper for complexes (1) and (2). Antimicrobial activities of the complexes have been determined by in vitro assays, against various Gram-negative and Gram-positive bacterial and fungal strains. Copper(II) complexes were also evaluated for their cytotoxicity on eukaryotic cells.     

Antioxidant activity evaluation by physiologically relevant assays based on haemoglobin peroxidase activity and cytochrome c-induced oxidation of liposomes

Two new protocols for exploring antioxidant-related chemical composition and reactivity are described: one based on a chronometric variation of a haemoglobin ascorbate peroxidase assay and one based on cytochrome c-induced oxidation of lecithin liposomes. Detailed accounts are given on their design, application, critical correlations with established methods and mechanisms. These assays are proposed to be physiologically relevant and bring new information regarding a real sample, both qualitative and quantitative. The well-known assays used for evaluation of antioxidant (re)activity are revisited and compared with these new methods. Extracts of the Hedera helix L. are examined as test case, with focus on seasonal variation and on leaf, fruit and flower with respect to chromatographic, spectroscopic and reactivity properties. According to the set of assays performed, winter are the most antioxidant, followed by summer leaves, and then by flowers and fruits.