The modulation transfer function. A simplified procedure forcomputer-aided quality evaluation in mammography

Regardless of the indisputable benefits of the modulation transfer function (MTF) method to radiographic image quality evaluation, most radiologists simply do not have the means for utilizing it due to the experimental difficulties in its application to mammography practice. One of the most significant difficulties for radiological departments is having the necessary equipment to digitize slit radiographic images-a microdensitometer, for example-to be used in quality assurance programs. Therefore, the authors propose the application of the transfer function method for quality evaluation of mammography equipment using a different procedure. This procedure is based on the calculation of the MTF from a simulated line spread function derived from the focal-spot projection. Since this technique does not need digitized images and can be performed on a PC, it will allow the use of the transfer function method in quality control programs without the constraints associated with the complexity of classical experimental procedures     

Surface Functionalization with Phosphazenes: Part 6. Modification of Polyethylene-Co-Polyvinylalcohol Copolymer Surface Plates with Fluorinated Alcohols and Azobenzene Derivatives Using Chlorinated Phosphazenes as Coupling Agents

In this paper we describe a two-step surface modification process of poly(ethylene-co-vinyl alcohol) by exploiting hexachlorocyclophosphazene and poly(dichlorophosphazene) as coupling agents. Part of the P–Cl groups of the chlorophosphazenes is first reacted with the surface hydroxylic groups of the substrate to form covalent P–O–C bonds, the remaining being utilized for successive substitution reactions with different nucleophiles (i.e. 2,2,2-trifluoroethanol, heptadecafluorononanol and 4-hydroxyazobenzene). Modified surface properties, such as hydrophobicity improvement with fluorinated alcohols and photochromic features with the azobenzene derivative, were verified by contact angle measurements and UV–Vis spectroscopy, respectively, while changes in surface composition were demonstrated through XPS spectroscopy.     

Surface functionalization with phosphazenes. V. Surface modification of plasma-treated polyamide 6 with fluorinated alcohols and azobenzene derivatives through chlorinated phosphazene intermediates

In this article, we describe the synthesis and characterization of surface-modified polyamide-6, using polydichlorophosphazene and hexachlorocyclophosphazene as coupling agents. The solid surface of this polymer was modified first by the introduction of polar functions (CO, OH, OR, COOH, COOR, etc.) with a cold plasma technique, then by the treatment of the alcoholic groups on the surface with (NPCl₂)_n and (NPCl₂)₃ to graft these substrates through the formation of strong covalent P O C bonds, and eventually by the substitution of the residual chlorines on the polyamide-6 surface with different types of fluorinated alcohols (2,2,2-trifluoroethanol and heptadecafluorononanol) and with 4-hydroxyazobenzene. Contact-angle measurements, together with X-ray photoelectron spectroscopy and ultraviolet–visible spectroscopy techniques, support the occurrence of these surface-functionalization reactions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

ORGANIC GEOCHEMISTRY OF THE GÖYNÜK AND SEYITOMER OIL SHALES OF TURKEY

The Göynük and Seyitomer oil shales overlie coal seams. An investigation of their geochemistry by solid-state and high-resolution nuclear magnetic resonance, infra-red spectroscopy and gas chromatography/mass spectrometry of the extracted bitumen suggests a classification as immature Type I kerogens. However, the n-alkane distribution is consistent with a substantial input from terrestrial plants.     

Synthesis and ion binding properties of polyesters and polyamides with diazacrown-ethers

The synthesis of polymers containing a [22] diaza-crown-ether in the backbone is described. These compounds are obtained by polycondensation of N, N′-diethylene amine and N, N′-diethylene alcohol derivatives of the cyclic diamine [23] with various acid dichlorides, leading to polyesters and polyamides. The cation binding properties of these polymers are studied by water-chloroform extraction using picrate salts, and compared with the properties of the analogous monomeric molecules. The binding properties are strongly dependent on the polymeric structure and comparison with the analogue molecules clearly demonstrates that the observed decrease in complex stability is due mainly to the presence near the rings of ester or amide groups. An intramolecular structure is proposed, based on interactions between the nitrogen bridges and the ester or amide groups which lead to the formation of a five-membered ring.     

Scalable general high voltage MOSFET model including quasi-saturation and self-heating effects

In this work, we present for the first time, a highly scalable general high voltage MOSFET model, which can be used for any high voltage MOSFET with extended drift region. This model includes physical effects like the quasi-saturation, impact-ionization and self-heating, and a new general model for drift resistance. The model is validated on the measured characteristics of two widely used high voltage devices in the industry i.e. LDMOS and VDMOS devices, and implemented on commercial circuit simulators like SABER (Synopsys), ELDO (Mentor Graphics), Spectre (Cadence) and UltraSim (Cadence). The accuracy of the model is better than 10% for DC I–V and g–V characteristics and shows good behavior for all capacitances which are unique for these devices showing peaks and shift of peaks with bias variation. The model also exhibits excellent scalability with transistor width, drift length, number of fingers and temperature.     

Structural regeneration of LaCoO3 perovskite-based catalysts during the NO + H2 + O2 reactions

In situ X-ray diffraction (XRD) analysis was used to investigate structural evolutions of LaCoO₃ catalysts and then further modified by palladium (Pd) addition, under various controlled atmospheres, particularly during the reduction of NO by hydrogen in lean conditions. Complementary, XPS measurements provided information about changes in the chemical environments of Pd, Co and nitrogen during sequential temperature-programmed reactions. A preactivation thermal treatment under hydrogen led to the destruction of the perovskite structure while in the course of the NO + H₂ + O₂ reactions, the regeneration of the perovskite structure evidenced by XRD at 873 K started at lower temperature (573 K) at the surface. Palladium has been incorporated in order to evidence its effective role in the surface modifications of LaCoO₃ and its consequence on the catalytic activity.     

VBNC Legionella pneumophila cells are still able to produce virulence proteins

Legionella pneumophila is the agent responsible for legionellosis. Numerous bacteria, including L. pneumophila, can enter into a viable but not culturable (VBNC) state under unfavorable environmental conditions. In this state, cells are unable to form colonies on standard medium but are still alive. Here we show that VBNC L. pneumophila cells, obtained by monochloramine treatment, were still able to synthesize proteins, some of which are involved in virulence. Protein synthesis was measured using ³⁵S-labeling and the proteomes of VBNC and culturable cells then compared. This analysis allowed the identification of nine proteins that were accumulated in the VBNC state. Among them, four were involved in virulence, i.e., the macrophage infectivity potentiator protein, the hypothetical protein lpl2247, the ClpP protease proteolytic subunit and the 27 kDa outer membrane protein. Others, i.e., the enoyl reductase, the electron transfer flavoprotein (alpha and beta subunits), the 50S ribosomal proteins (L1 and L25) are involved in metabolic and energy production pathways. However, resuscitation experiments performed with Acanthamoeba castellanii failed, suggesting that the accumulation of virulence factors by VBNC cells is not sufficient to maintain their virulence.     

Sensitivity of Aeromonas hydrophila carbapenemase to delta3-cephems: comparative study with other metallo-beta-lactamases

Ceftriaxone and ceftriaxone S-oxide behaved as inactivators against the metallo-beta-lactamase of Aeromonas hydrophila AE036 and as substrates for the zinc beta-lactamase produced by Bacillus cereus (569/H/9) and Stenotrophomonas maltophilia ULA 511. Moreover, RO 09-1428, a catechol-cephalosporin, was not recognized by the A. hydrophila enzyme. Panipenem, cephalosporin C, cephalosporin C-gamma-lactone, and loracarbef were substrates for the three studied beta-lactamases.     

An in situ study of the NO + H2 + O2 reaction on Pd/LaCoO3 based catalysts

In situ X-ray diffraction (XRD) and quasi in situ X-ray photoelectron spectroscopy (XPS) measurements were complementary used to investigate structural and surface modifications of a palladium-supported on LaCoO₃ perovskite catalyst under various controlled atmospheres, particularly during the reduction of NO by hydrogen under lean conditions, in the presence of a large excess of oxygen.

An extensive reduction of the perovskite was evidenced during the pre-activation thermal treatment of the palladium-supported catalyst under hydrogen at 773 K leading to the formation of Pd particles in contact with Co⁰ and La₂O₃. In the presence of an excess of oxygen, the catalyst structure changes during the reaction. The reduced solid is progressively transformed into LaCoO₃ in the range of 873–1173 K. However, such a bulk transformation probably occurs at lower temperatures at the surface of the solid according to XPS analyses. At the same time, the binding energy (BE) level of the Pd 3d_5/2 photopeak increases up to 337.5 eV which reveals the stabilisation of oxidic palladium species in a different chemical environment than that corresponding to PdO. Such changes induced different catalytic properties of the catalyst during the reduction of NO by H₂.