1,720,977 research outputs found
Second-Generation Tris(2-pyridylmethyl)amine–Zinc Complexes as Probes for Enantiomeric Excess Determination of Amino Acids
No full textSelf-assembly through imine condensation chemistry in combination with metal coordination is becoming one of the leading strategies for the preparation of stereodynamic probes for the determination of enantiomeric excess. Recently, we reported a novel molecular architecture based on a modified tris(2-pyridylmethyl)amine–zinc(II) complex [TPMA = tris(2-pyridylmethyl)amine] that is able to function as an optical probe for the determination of the enantiomeric excess of amino acids. Herein, we report on how a slight modification of the TPMA ligand enhances both the dichroic response and the stability of the system. The novel probe provides a much higher dichroic signal compared with the previously reported system
Culture of skeletal muscle cells in unprecedented proximity to a gold surface
No full textCulturing of skeletal muscle cells on conductive surfaces is required to develop electronic device-muscle junctions for tissue engineering and medical applications. We characterized from a molecular and morphological point of view myogenic cells cultured on gold and on cysteamine-coated gold, as compared to the standard plastic for cell culture. Our results show that cell proliferation and survival are comparable between cells grown on either of the gold surface or plastic. The majority of the cells cultured on gold surfaces retain the ability to respond to differentiation cues, as shown by nuclear translocation of myogenin. Following terminal differentiation, the myotubes cultured on cysteamine-coated gold resemble myotube cultures obtained on plastic for the size and orientation of the myotube bundles retaining most of myosin expression; on the contrary, the myotube cultures on gold show a clumped morphology, likely due to repulsive cell-substratum interaction resulting in aberrant differentiation. On the basis of the aforementioned evidences, the culture of muscle cells on cysteamine-coated gold represents an advance with respect to previously reported substrata. The cysteamine self-assembled monolayer coating is a simple approach to accomplish cultures of myotubes in unprecedented tight proximity to conductive surfaces. © 2008 Wiley Periodicals, Inc
Photoinduced hydrogen evolution with new tetradentate cobalt(ii) complexes based on the TPMA ligand
Full text linkHydrogen production from water splitting is nowadays recognized as a target, fundamental reaction for the production of clean fuels. Indeed, tremendous efforts have been devoted towards the research of suitable catalysts capable of performing this reaction. With respect to heterogeneous systems, molecular catalysts such as metal complexes are amenable to chemical functionalization in order to fine tune the catalytic properties. In this paper a new class of tris(2-pyridylmethyl)-amine (TPMA) cobalt(ii) complexes (CoL0-4) has been synthesized and employed as hydrogen evolving catalysts under photochemical conditions taking advantage of Ru(bpy)32+(where bpy is 2,2′-bipyridine) as a light-harvesting sensitizer and ascorbic acid as a sacrificial electron donor. Tuning of the photocatalytic activity has been attempted through the introduction of different substituents at the catalyst periphery rather than through a direct chemical modification of the chelating TPMA ligand. The results show that CoL0-4 behave as competent hydrogen evolving catalysts (HECs), although the effects played by the different substituents on the catalysis are relatively modest. Possible reasons supporting the observed behavior as well as possible improvements of the aforementioned tuning approach are discussed
Synthesis, characterization, and electrochemical behavior of LiMnxFe(1-x)PO4composites obtained from phenylphosphonate-based organic-inorganic hybrids
Full text linkThe synthesis of organic-inorganic hybrid compounds based on phenylphosphonate and their use as precursors to form LiMnxFe(1−x)PO4 composites containing carbonaceous substances with sub-micrometric morphology are presented. The experimental procedure includes the preliminary synthesis of Fe2+ and/or Mn2+ phenylphosphonates with the general formula Fe(1−x)Mnx[(C6H5PO3)(H2O)] (with 0 < x < 1), which are then mixed at different molar ratios with lithium carbonate. In this way the carbon, obtained from in situ partial oxidation of the precursor organic part, coats the LiMnxFe(1−x)PO4 particles. After a structural and morphological characterization, the electrochemical behavior of lithium iron manganese phosphates has been compared to the one of pristine LiFePO4 and LiMnPO4, in order to evaluate the doping influence on the material
Phase Transition of TiO2 Nanotubes: An X-ray Study as a Function of Temperature
No full textHere, a study aimed to determine the phase transition temperature of
titanium dioxide nanotubes, both in the presence and in the absence of a Ti layer
underneath, is reported. Titania nanotube arrays with different diameters and wall
thickness were synthesized via anodic growth at different potential values on a titanium
foil. Ex and in situ high-temperature X-ray diffraction measurements were performed,
respectively, on the arrays as such and on the powder obtained by detaching the
nanotubes from the metallic substrate. Our results demonstrate that the presence of Ti
dramatically influences the crystallization process decreasing the temperature formation
of rutile, which tends to appear initially at the Ti/TiO2 interfac
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Triggering Assembly and Disassembly of a Supramolecular Cage
Full text linkA novel supramolecular cage built from the self-assembly of tris(2-pyridylmethyl)amine zinc complexes through imine condensation chemistry is reported. The cage recognition properties over a variety of structurally related guests, together with the kinetic study of the template assembly and disassembly, have been investigated in detail. This knowledge has been used to selectively modulate the rate of both assembly and disassembly processes. In particular, a novel disassembly method induced by strain release of the guest has been developed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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