1,721,024 research outputs found
Determination of pharmaceutical thiols by liquid chromatography with electrochemical detection. Use of an electrode with a conductive carbon cement matrix, chemically modified with cobalt phtalocyanine
No full textAn electrode made with a conductive carbon cement (CCC) matrix and modified with cobalt phthalocyanine was utilized for
the detection of some thiols of pharmaceutical interest: captopril, thiopronine, penicillamine. The performance of the electrode and the influence of pH were examined by hydrodynamic voltammograms and compared with those of unmodified CCC and glassy carbon electrodes. Calibration curves were performed in aqueous solutions at acidic pH in the range 5x 10-6 to 1 x 10-4 M. Stability experiments showed that electrode esponse in flowing solutions decreased about 1% for hour. Satisfactory liquid chromatographic (LC) separation by everse phase was obtained for the three compounds. Limits of detection reached with LC were in the range of pmoles. The modified electrode showed quite satisfactory performance: good sensitivity, good stability and detection of low concentration of the examined thiols
Influence of water on the electroanalytical behaviour of (K,Na)HSO4 eutectic melt. Characterization of Hg32+.
No full textErrata corrige, 69 (1979) Author Index, p. 3
An Electroanalytical Investigation on the Electrocatalysed Coupling of Allyl Halides Promoted by the Nickel -Triphenylphosphine System.
No full textThe electrochemical reduction of allyl halides is strongly catalysed when it is carried out by cathodically generating and continuously recycling the nickel(0) complex promoter |Ni(PPh3)4|(PPh3= triphenylphosphine). This species undergoes oxidative addition by allyl halides leading to π-bonded organometallic nickel(I) derivatives, the metal-carbon bond of which is cleaved by means of an electrochemical reduction providing 1,5-hexadiene as the coupling product and renewing the nickel(0) promoter, thus allowing an electrocatalytic cycle to be completed. Voltammetric, coulometric and gas-chromatographic data are presented and analysed. To account for the catalytic action of the nickel(0) complex, a mechanistic scheme is proposed which is consistent with the kinetic data obtained by studying the chemical reaction coupled with charge transfers by means of the voltammetric technique. © 1984 Elsevier Sequoia S.A
Adaptive Hybrid Optical Switching: Performance and Energy efficiency
No full textHybrid optical switching (HOS) has the potential to provide highly efficient operation through combining various switching paradigms and different implementation options within the same network. The flexibility of choosing between circuit,
packet or burst switching and electronic or optical implementation results in an improvement of both energy and data transport efficiency because the most appropriate method and less power consuming elements can be selected and used for transmission of data through the network while temporarily inactive elements
are switched off or put in a low-power mode.
In this paper, we introduce a novel network concept that we refer to as adaptive hybrid optical switching (AHOS) and present and investigate several architectures and realization options for AHOS nodes. The corresponding control plane comprises two layers, of which one implements routing, signalling and link management functions as defined in the GMPLS standard while the other is responsible for managing already established circuits
and scheduling the transmission of packets and bursts.
We present results on both performance and energy consumption for different AHOS node realizations, network configurations and traffic patterns, which prove the potential for a high improvement in energy efficiency with respect to conventional electronic packetswitched networks
An Electroanalytical Investigation on the Olefin Isomerization Reaction Promoted by Electrogenerated Cationic Nickel Hydride.
No full textThe isomerization of allylbenzene has been carried out by the cationic nickel hydrides [NHiL4]+ (L = 1 2dppe; PPh3; P(OEt)3) directly prepared in situ by electrogenerating the corresponding Ni(0) complexes in the presence of hydrogen ions. Such a procedure allows one also to take advantage of the catalytic activity of the poorly stable hydrides obtained when L = PPh3 or P(OEt)3. In these cases, a small but finite steady-state concentration of the promoter can be maintained in the solution by the occurrence of an electrocatalytic process cyclically renewing this species, thus making possible its interaction with olefin molecules in spite of its instability. The results obtained point out that high stability for the cationic nickel hydrides is accompanied by quite a low promoting activity, while hydrides which decay quickly also exhibit high reactivity. The information collected concerning the reaction pathway through which the catalyzed isomerization reactions occur, has then been exploited for devising an electrocatalytic process in which the coupling of allyl bromide and the isomerization of the diolefin product can occur simultaneously. © 1987
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
Hybrid Optical Switching for Energy-Efficiency and QoS Differentiation in Core Networks
No full textIn the future, the Internet may ultimately be
constrained by energy consumption and the capability to
provide quality of service (QoS). As regards the Internet
core, hybrid optical switching (HOS) is promising to provide
service differentiation and reduced energy consumption
in respect to current electronic switching solutions. In
this paper we present a novel hybrid HOS network architecture
that efficiently integrates the optical packet, burst,
and circuit switching on the same network. The proposed
HOS network envisages the use of two parallel switches, a
slow optical switch for the transmission of circuits and long
bursts, and a fast switch for the transmission of packets and
short bursts. The most appropriate switching method is selected
for the traffic generated by different applications
and the less power consuming elements are utilized for
transmission, ensuring flexibility, QoS differentiation,
and low energy consumption. The HOS network is organized
in an overlay model with the HOS control layer
performing routing, signaling, and link management, and
with the HOS forwarding layer managing the reservation
of resources and data scheduling. Performance and energy
efficiency of the analyzed network are assessed by means of
a combined analytical and simulation approach
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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