1,721,028 research outputs found
Analisi ricognitiva delle trasformazioni urbane e territoriali della Sardegna. Individuazione dei fenomeni capaci di innescare processi di sviluppo
No full textA novel approach to determine the start-up conditions in microwave negative impedance oscillator design
No full textIn the design of sinusoidal oscillators, it is possible to exploit linear CAD techniques to determine the start-up conditions. In microwave negative impedance oscillators, the start-up can be tested through the application of the Nyquist criteria at the open loop gain, that in this context can be represented by the product of both reflection coefficients in a section. This work presents a novel approach to determine the whole set of values of the reflection coefficients product for which the oscillation start-up and build-up, for a given frequency, are guaranteed under the small signal hypothesis. Therefore the well known start-up condition normally expressed in terms of impedances, has been translated in terms of reflection coefficients product. In this way for a specific reflection coefficient of resonant passive network, it is possible to draw the set of reflection coefficients values of active device, for which the presence of negative real part poles is achieved. Moreover it is going to be established a sufficient condition to determine the start-up for a given frequency. This condition define an area on the Smith chart (the Eye) which bind the choice of resonant circuit reflection coefficient. Finally we succeeded to define a criterion to choose the characteristic impedance value which guarantee the effectiveness of the common oscillation tests, used in CAD systems
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
Theoretical investigation of FeTe magnetic ordering under hydrostatic pressure
No full textWe investigate the pressure phase diagram of FeTe, predicting structural and magnetic properties in the normal state at zero temperature within density functional theory. We carefully examined several possible different crystal structures over a pressure range up to ≈30 GPa: simple tetragonal (PbO type), simple monoclinic, orthorhombic (MnP type), hexagonal (NiAs and wurzite type), and cubic (CsCl and NaCl type). We predict pressure to drive the system through different magnetic ordering (notably also some ferromagnetic phases), eventually suppressing magnetism at around 17 GPa. We speculate the ferromagnetic order to be the reason for the absence of a superconducting phase in FeTe at variance with the case of FeSe. © 2013 American Physical Society
La costruzione dell'identità territoriale: un metodo per la definizione di elementi dell'organizzazione dello spazio sui quali impostare politiche di gestione dei centri urbani
No full textIl metodo si basa sulla definizione di alcuni descrittori come luoghi urbani in grado di
addensare in sé significati che possono orientare e promuovere comportamenti in relazione
agli stessi. Il progetto si sviluppa attorno all'obiettivo principale di coinvolgimento di
comunità d'ambito, secondo un percorso di formazione legato alla rappresentazione di
conoscenze sul territorio. In tale direzione, il progetto si costituisce come strumento in grado
di prefigurare e di favorire politiche territoriali calibrate sul sistema delle risorse, dei valori e
dei significati attribuiti dalle società locali nella costruzione dei propri spazi insediativi e delle
relazioni con il territorio. Il contesto di riferimento è rappresentato da alcuni centri localizzati
in aree di notevole rilevanza storico-ambientale, che esprimono istanze positive di
"costruzione di territorio" nelle sue componenti costitutive di urbanità, intesa come forme di
socialità e di solidarietà urbana, di natura e di storia. In particolare, il dispositivo elaborato nel
corso del lavoro permette di collocare le azioni progettuali in un ambito operativo, finalizzato
all'individuazione di alcuni criteri guida utili per la costruzione di un progetto comunicativo
che coinvolge le comunità d'ambito nel progetto del proprio territorio
Respiratory state and phosphatidylserine import in brain mitochondria in vitro
No full textThe mechanism of phosphatidylserine (PS)
movement from donor membranes into rat brain mitochondria
was investigated. Mitochondria were incubated
with liposomes and subjected to density gradient centrifugation.
The energized state was monitored by flow
cytometry measuring the fluorescence of membranepotential-
sensitive rhodamine-123 dye. Mitochondria
density decreased upon increase of the respiratory rate,
as a consequence of their association with liposomes.
After interaction of mitochondria with 14C-PS containing
liposomes, 14C-PS became a substrate of PS decarboxylase,
as monitored by the formation of 14C-phosphatidylethanolamine
(PE), indicating translocation of 14CPS
to the inner membrane. The kinetics of 14C-PE formation
showed a high rate upon addition of ADP, malate
and pyruvate (state 3) compared to control (state 1). In
state 3, 14C-PE formation decreased in the presence of
NaN3. Mitochondria-associated membranes (MAM) are
the major site of PS synthesis. However, their role in the
translocation of PS to mitochondria has not been completely
elucidated. A crude mitochondrial fraction (P2)
containing MAM, synaptosomes and myelin was prelabeled
with 14C-PS and incubated in different respiratory
states. At a high respiratory rate, low-density labeled
mitochondria, whose band overlaps that of synaptosomes,
were obtained by centrifugation. A parallel decrease
of both radioactivity and protein in MAM fraction
was observed, indicating that the association of MAM
and mitochondria had occurred. Synthesis and translocation
of 14C-PS in P2 membranes were also studied by
incubating P2 with 14C-serine. In the resting state 14CPS
accumulated in MAM, indicating that the transfer to
mitochondria was a limiting step. In state 3 both the
transfer rate of 14C-PS and its conversion to 14C-PE increased.
Respiratory mitochondrial activity modulated
the association of MAM and mitochondria, triggering a
mechanism that allowed the transport of PS across the
outer mitochondrial membrane
Electronic, dynamical and superconducting properties of MgB2: doping, surface and pressure effects
No full textWe report a detailed first-principles local-density-functional investigation of the structural, electronic, dynamical and superconducting properties of MgB2 focusing on different aspects related to this material. In particular, we examine Al doping, as well as reduced dimensionality and pressure effects on the electronic and superconducting properties of this compound. Our ab initio calculations for the case of 50% Al doping are able to correctly reproduce the measured frequencies of the E-2g phonon and explain the disappearance of superconductivity in terms of filling effects on both carrier concentration and electron-phonon coupling. The surface study shows that an enhanced density of states at the Fermi level is found in the B-terminated case. However, we find the Mg-terminated surface to be the most stable structure in the whole range admitted by the chemical potentials, in agreement with very recent experimental results. Finally, the study of the E-2g phonon frequency under pressure is able to explain the critical temperature lowering under applied pressure
- …
