1,720,990 research outputs found
Efficiency enhancement of the electrocatalytic reduction of CO2: fac-[Re(v-bpy)(CO)3Cl] electropolymerized onto mesoporous TiO2 electrodes
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Indium tin oxide electrodes modified with tris(2,2'-bipyridine-4,4'-dicarboxylic acid) iron(II) and the catalytic oxidation of tris(4,4'-di-tert-butyl-2,2'-bipyridine) cobalt(II).
No full textIndium tin oxide (ITO) electrodes modified by attachment of tris(2,2'-bipyridine-4,4'-dicarboxylic acid) iron(II) are examined. The mode of attachment is believed to be via the COOH functions in a manner similar to attachment of similar carboxylate-containing compounds to TiO2 surfaces. On the surface the complex resides as a stable electrochemically active monolayer. These modified electrodes can efficiently catalyze the oxidation of certain cobalt complexes, specifically, tris(4,4'-di-tert-butyl-2,2'-bipyridine) cobalt(II). On the unmodified ITO surfaces this cobalt complex is essentially electrochemically inert. The catalytic process approaches diffusional control at very slow scan speeds. Also, the electro-catalysis is sufficiently efficient that the peak oxidation current for Co2+, under certain conditions, exceeds the i(p) for the surface oxidation of the adsorbed Fe2+ by > x 100 and the current for the uncatalyzed oxidation of Co2+ by considerably more than that
Anti-tumor properties of silver
No full textThe use of silver dates to the period when people used it to mint coins or forge jewels. Towards the end of the 1960s, Resenmberg reported a study on the antitumor activity of cisplatin, and after a few years, cisplatin began to be used all over the world against different types of neoplasias mainly involving testes, ovaries, tumors of the district head-neck. Laryngeal carcinoma cell line HEP2 and tongue carcinoma cell lines PE15 and PE46, were cultured. Cell lines were treated with increasing concentration Ag in order to evaluate the optimal concentration levels that did not significantly affect cell viability. Basing on these data, the concentration adopted for the treatment was 0.007%. Gene expression profile was carried out for 10 genes belong to cell cycle pathways. Significantly up-regulated genes showed ≥ 2-fold change in expression while significantly down-regulated genes showed ≤ 0.5 -fold change in expression. Treatment appears to not significantly affect gene expression in the HEP2 cell line. In fact the only significantly down-regulated gene was CCNE1. All other genes have an expression comparable to that of untreated control. In recent years, the complexes containing gold and silver have been thoroughly studied for their electronic and chemical capabilities and their potential as a valid alternative in the development of new technologies. Further studies on the mechanisms of the biological effect discovered can become fundamental for the development of new high efficiency drugs with minimal minimum effects for the treatment of malignant neoplasia in humans and animals
Hematite-based photoelectrochemical interfaces for solar fuel production
No full textThe production of solar fuels, i.e. energy-rich molecules obtained from sunlight-driven processes, represents one of the most pursued strategies to satisfy the increasing global energy demand in a sustainable way. Indeed, solar energy possesses the appealing features of being abundant, inexhaustible and widely geographically distributed, yet intermittent. Thus, a common approach consists in the development of specific devices (e.g. photoelectrochemical cells, PECs) allowing for its storage in the form of chemical energy. In order to produce viable PEC systems, the main focus should be the optimization of the light absorbing component(s), which generally comprise the exploitation of semiconductors (SCs). These materials must be efficient, durable, cheap and energetically suitable to perform the reaction(s) leading to the desired solar fuel(s). Hematite (α-Fe2O3) possesses these features, being composed by earth abundant elements, as well as being capable of harvesting a sizable portion of the solar spectrum. Its valence band maximum, more positive than the redox potential of water oxidation, makes it an interesting candidate for the photoinduced oxygen production via water splitting. In this short review, we will mainly discuss the capitalization on hematite properties for such process, while implementing suitable optimization techniques in its synthesis (namely nanostructuring, doping and surface functionalization). Examples of case studies also from our laboratory will be discussed, in which various hematite-based interfaces are probed using advanced characterization techniques (e.g. electrochemical impedance spectroscopy and transient photocurrent analysis). These studies aimed at gaining insights into the key processes involved in the photocurrent generation, thus contributing to the rational design of future more efficient photoactive interfaces. This is a challenging goal since at present all the reported hematite-based photoanodes display performances that are far below the maximum thermodynamically attainable photocurrent (i.e. 12.6 mA/cm2). Finally, we will report on recent examples of hematite-based PEC systems yielding value-added organic compounds as the photoinduced oxidation products. This latter strategy, even if currently at its infancy, is believed to be a groundbreaking approach towards the production of organics exploiting sunlight energy in a sustainable electrochemical process
Self-assembled multinuclear complexes for cobalt(II/III) mediated sensitized solar cells
No full textIn this work, we designed a tetranuclear self-assembled dye 4 (2Z907-Ag+-(Ru(TMAM))) exploiting a combination of the antenna effect and positively-charged groups designed to repel the oxidized form of cationic cobalt redox mediators, in order to reduce recombination and increase the efficiency of dye sensitized solar cells (DSSCs). Charge transfer and excited dynamics were probed by photoelectrochemical and photophysical measurements. The sensitized cell performance, recorded with a [Co(bpy)3]3+/2+ redox mediator and PEDOT counter electrode, showed an improvement when passing from Z907 to the multinuclear systems. The enhancement of the efficiency compared to Z907 resulted mainly from a superior steric and electrostatic shielding determined by the simultaneous presence of long alkyl chains and quaternary ammonia ion units in the architecture of 4
Efficacy of a new coating of implant-abutment connections in reducing bacterial loading: an in vitro study
No full textBackground. Titanium is the gold standard for dental implants, since it has demonstrated excellent biocompatibility and osseointegration properties. The rate of osseointegration is however affected by the surface morphology and peri-implant infections may affect fixture and the long-term osseointegration outcome. Thus chemical composition of a coating at the implant-abutment junction (IAJ) surface is expected to play a key role in preventing bacterial infection. Purpose. In the present study a new antimicrobial polysiloxane coating functionalized with chlorexidine digluconate (PXT) has been tested in an in vitro model. Materials and methods. Twenty implants were coated in the internal chamber with PXT and twenty were used as controls. Results and conclusions. Ten of the coated implants, preliminarily tested against Gram positive and negative bacteria and fungi, showed a complete inactivation of the microbial species after a 15 min contact. On the remaining ten treated implants a series of microbiological tests and PCR analysis, after contamination of the implant external medium, in which the implant have been immersed, with genetic modified Tannerella forsythia (TF) and Porphyromonas Gingivalis (PG), leads to the conclusion that the coating is capable of inactivating the microbial species penetrating the internal of the implant through the implant abutment junction
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
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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