3,706 research outputs found
The reaction of [bispyridinotetrakis(t-butyl)phthalocyaninato]iron(II) with dioxygen to give mu-oxo-bis[tetrakis(t-butyl)phthalocyaninato]iron(III)
No full textThe reaction of [bispyridinotetrakis(t-butl)phthalocyaninato]iron(II), (py)(2)FePc'. with dioxygen in CH2Cl2, gives almost quantitatively the oxo-bridged mu-oxo-bis[tetrakis(t-butyl)phthalocyaninato]iron(III) as the final, stable product. The reaction order with respect to the starting complex changes within a run. For t = 0. the rate is proportional to the ratio a(1) root y(0)/(a(2) + root y(0)) (Equation 1) where),, is the initial absorbance of the solution and a, and a, are linear functions of [O-2]. For t > 0, the instantaneous rate is instead described by the equation Rate = b [O-2] [A]/([A](0) - [A]) (Equation 2). where A is (py)(2)FePc' and the coefficient b is again proportional to [O-2]. A mechanism is proposed implying the presence of trace amounts of (py)(S)FePc' (S = axially bound CH2Cl2) in equilibrium with (py)(2)FePc'. Both species are able to generate the transient pentacoordinate (py)FePc' that may react with py and S, giving back the hexacoordinate precursors, or with dioxygen. giving ultimately the mu-oxo complex. At t = 0. the species (py)(S)FePc'. expected to be much more labile than (py),FePc'. is at its maximum concentration and is assumed to give the prevaling contribution to the instantaneous C rate. As the reaction proceeds, and free pyridine accumulates in the solution. the concentration of (py)(S)FePc' decreases rapidly and the transient (py) FePc' is produced essentially by the bispyridino complex. This fact and the still growing concentration of free pyridine account for the Equation 2. Finally, when the py concentration is buffered by addition of small amounts of base. the reaction attains a simple first order law. Present data further support the iron(III) formulation of the final mu-OXO product and are inconsistent with the iron(II) hypothesis put forward by some authors. Copyright (c) 2006 Society of Porphyrins & Phthalocyanines
The reaction of mu-oxo-bis(phthalocyaninato)iron(III) with hydrogen sulphide in the presence of pyridine. Evidence for axial coordination of dichloromethane
No full textThe oxo-bridged complex (py)FePc-O-FePc(py) (py = pyridine, Pc = phthalocyaninato dianion) reacts in dichloromethane with hydrogen sulphide giving elementary sulphur and the reduced (py)(2)(FePc) complex in the stoichiometric ratio 1:1. Under excess py and H,S, the reaction is first-order and the rate constant at a given py concentration is an increasing function of the reducing agent concentration, with asymptotic tendency to a limiting value. This latter depends on the pyridine concentration being higher the lower is the base concentration. When the reaction is carried out in pure pyridine, the rate constant is, instead, a strictly linear function of [H2S], with zero intercept. A reaction mechanism is proposed where the dichloromethane is directly involved in the axial coordination about the iron centers and H2S competes efficiently with both pyridine and solvent. Copyright (c) 2005 Society of Porphyrins & Phthalocyanines
Giappone. La corte suprema: il Juki Net non viola il diritto alla privacy dei cittadini
No full textLa cronaca analizza la sentenza della corte suprema secondo cui il Juki Net non viola il diritto alla privacy dei cittadin
Direct replacement of antibodies with molecularly imprinted polymer (MIP) nanoparticles in ELISA - development of a novel assay for vancomycin
No full textA simple and straightforward technique for coating microplate wells with molecularly imprinted polymer nanoparticles (nanoMIPs) to develop ELISA type assays is presented here for the first time. NanoMIPs were synthesized by a solid phase approach with immobilized vancomycin (template) and characterized using Biacore 3000, dynamic light scattering and electron microscopy. Immobilization, blocking and washing conditions were optimized in microplate format. The detection of vancomycin was achieved in competitive binding experiments with a HRP-vancomycin conjugate. The assay was capable of measuring vancomycin in buffer and in blood plasma within the range 0.001-70 nM with a detection limit of 0.0025 nM (2.5 pM). The sensitivity of the assay was three orders of magnitude better than a previously described ELISA based on antibodies. In these experiments nanoMIPs have shown high affinity and minimal interference from blood plasma components. Immobilized nanoMIPs were stored for 1 month at room temperature without any detrimental effects to their binding properties. The high affinity of nanoMIPs and the lack of a requirement for cold chain logistics make them an attractive alternative to traditional antibodies used in ELIS
Proprietà redox dei complessi a ponte di ossigeno mu-osso-bis(ftalocianinatoferro(III)) e mu-osso-bis(tetrakis(t-butil)ftalocianinatoferro(III))
No full textThe chameleon-like coordinating ability of 2,3-di(pyridyl)pyrazine-type ligands
No full textThis survey is dedicated to the multifaceted modes of binding of metal ions by polyazine N donors like 2,3-di(2-pyridyl)pyrazine (dpp), 5,6-di(2-pyridyl)quinoxaline (dpq) and 9,10-di(2-pyridyl)benzoquinoxaline (dpbq) and related substituted analogs, covered until the end of 2016. These compounds display the potential coordination of the dipyridinopyrazine block consisting of two pyridine and two pyrazine N donor atoms. This report illustrates the structural features of the mono-, di- and multinuclear complexes, whenever crystallographic information was available. In the absence of X-ray work, as is the case for tri-, tetra-, and multinuclear systems, the overall organization of the complex systems is that proposed by the authors. Synthetic procedures, physicochemical properties, especially UV–visible spectroscopic and electrochemical behaviour, are given some attention. © 2017 Elsevier B.V
Analitical deriving of the field capacity through soil bundle model
No full textThe concept of field capacity as soil hydraulic parameter is widely used in many hydrological
applications. Althought its recurring usage, its definition is not univocal. Traditionally, field capacity
has been related to the amount of water that remains in the soil after the excess water has drained
away and the water downward movement experiences a significant decresase. Quantifying the
drainage of excess of water may be vague and several definitions, often subjective, have been
proposed. These definitions are based on fixed thresholds either of time, pressure, or flux to which
the field capacity condition is associated. The fluxbased definition identifies the field capacity as the
soil moisture value corresponding to an arbitrary fixed threshold of free drainage flux. Recently, many
works have investigated the fluxbased definition by varying either the drainage threshold, the
geometry setting and mainly the description of the drainage flux. Most of these methods are based on
the simulation of the flux through a porous medium by using the Darcy’s law or Richard’s equation.
Using the abovementioned fluxbased definition, in this work we propose an alternative analytical
approach for deriving the field capacity based on a bundleoftubes model. The pore space of a
porous medium is conceptualized as a bundle of capillary tubes of given length of different radii,
derived from a known distribution. The drainage from a single capillary tube is given by the analytical
solution of the differential equation describing the water height evolution within the capillary tube. This
equation is based on the Poiseuille’s law and describes the drainage flux with time as a function of
tube radius. The drainage process is then integrated for any portion of soil taking into account the
tube radius distribution which in turns depends on the soil type. This methodology allows to
analytically derive the dynamics of drainage water flux for any soil type and consequently to define
the soil field capacity as the latter reachs a given threshold value. The theoretical model also
accounts for the tortuosity which characterizes the water pathways in real soils, but neglects the
voids mutual interconnections
Investigating the changes in extreme rainfall in Sicily
No full textChanges in extreme rainfall are one of the most relevant sign of current climate alterations. Many studies have demonstrated an increase in rainfall intensity and a reduction of frequency in several areas of the world. This could be probably due to an acceleration of the hydrological cycle caused by temperature increase and could have, as consequence, the increase of flooding hazard.
In the past, Sicily has been screened for several signals of possible climate change. Annual, seasonal and monthly rainfall data in the entire Sicilian region have been analyzed, showing a global reduction of total annual rainfall, which is mainly due to the winter reduction. Moreover, some annual maximum rainfall series of different durations have been analyzed in order to detect the presence of linear and non-linear trends. Results indicated that for short durations, historical series generally exhibit increasing trends while for longer durations the trends are mainly negative.
Starting from these previous assessments, the aim of this study is to investigate and quantify changes in extreme rainfall in Sicily. Here the entire regional database of annual maximum rainfall series relative to different durations has been analyzed in order to identify the presence of significant trends at site.
Moreover, in this study also the daily rainfall series, recorded in the whole Sicily, have been analyzed. This study classifies the daily rainfall in six classes as function of the intensity and then analyzes how the events relative to each class change in time in terms of occurence and intensity
Nuovi complessi di Pd(II) di tipo porfirazinico mono- e pentametallici come fotosensibilizzatori in soluzione di DMF per la produzione di ossigeno di singoletto 1O2
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