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Religione e capitale sociale : approfondimenti, con riferimento al caso italiano, su di una relazione complessa e rilevante per il Servizio Sociale
No full textLa ricerca intende contribuire all’approfondimento della relazione tra religione e capitale sociale.
Tale tentativo verrà condotto con riferimento al contesto italiano. Il capitale sociale è una risorsa
preziosa per favorire l’inclusione sociale ed il benessere degli individui. Tuttavia, attualmente lo
stato sociale si trova in una crisi irreversibile: ciò ha costretto i Paesi occidentali avanzati ad
interrogarsi su alternative a supporto degli investimenti statali per favorire l’inclusione sociale dei
propri cittadini. In questo scenario, il capitale sociale è diventato negli ultimi anni un oggetto di
interesse, in un momento di necessario abbandono dell’idea tradizionale di welfare.
Questo argomento è rilevante nel dibattito intorno al servizio sociale poiché è urgente, se si deve
aggiornare il paradigma dello stato sociale, che il servizio sociale possa riflettere sul cambiamento
in atto e raccordare le sue politiche di conseguenza. Il capitale sociale, inteso come dotazione di un
territorio dove è elevata la partecipazione e l’impegno dei cittadini teso al bene comune, in Italia è
scarso rispetto ad altri Paesi occidentali. Gli studiosi si domandano tuttora cosa può alimentare la
sua creazione e la sua riproduzione. Dalla religione potrebbe venire una parte della risposta a questo
interrogativo e, poiché in Italia la tuttora rilevante diffusione della religione cattolica dimostra
anche una non trascurabile vitalità, può essere importante capire se, e in quale grado, la religione è
in relazione con il capitale sociale.
In letteratura scientifica la relazione tra religione e capitale sociale è stata trattata da diversi studi,
sebbene non così diffusamente come ci si potrebbe attendere. Tuttavia, le conclusioni cui sono
giunti gran parte degli studiosi risultano non univoche. Questa ricerca si propone, servendosi degli
strumenti teorici ed operativi della più recente sociologia della religione, di studiare la relazione di
questa con il capitale sociale, adottando la distinzione tra domanda ed offerta religiosa e, con
riferimento al caso della domanda, non trascurando la sua multidimensionalità. Una vasta letteratura
ha mostrato l’utilità di isolare cinque dimensioni che tendono decisamente a non covariare.
Così impostata, l’analisi della relazione tra capitale sociale e religione è stata condotta utilizzando
dati relativi alle province italiane. Il capitale sociale è stato operazionalizzato seguendo la proposta
via via perfezionata da R. Cartocci. Per la domanda religiosa, sono state prese in considerazione due
dimensioni, l’identificazione e la partecipazione mentre, per l’offerta religiosa, sono stati selezionati
una serie di indicatori. Seguendo la letteratura, il metodo statistico adottato è stato quello della
analisi bivariata tra i singoli indicatori di fenomeni religiosi e l’indice di capitale sociale.
I risultati mostrano che tra l’offerta e la domanda religiosa, e le due dimensioni di essa considerate,
esistono relazioni di diversa intensità e differente direzione con il capitale sociale.
I risultati ottenuti, per un verso confortano la nostra scelta di trattare in modo più analitico il
fenomeno religioso anche quando s’intende studiare la relazione con il capitale sociale e, per altro
verso, forniscono indicazioni circa almeno alcune delle componenti religiose che con il capitale
sociale mostrano relazioni di un segno e di quello opposto
L'educazione per tutti e per tutta la vita : il contributo pedagogico di Ettore Gelpi
No full textIl presente lavoro si configura come un’analisi monografica su Ettore Gelpi (1933-2002),
intellettuale che dedica la sua vita alla riflessione attenta e puntuale intorno ai temi della
formazione, dello sviluppo, dell’educazione alla democrazia e alla cittadinanza, dell’emancipazione
da ogni forma di sfruttamento, dello sviluppo sostenibile.
Lungi dal voler essere una commemorazione e senza alcuna pretesa di esaustività, la presente tesi
di dottorato cerca di studiare la figura e l’eredità culturale di Ettore Gelpi analizzando la sua
fiorente produzione scientifica e proponendo suggerimenti di riflessione per continuare a ragionare
sulle sue idee e le sue ricerche, cercando di metterne in rilievo gli aspetti storicamente rilevanti e
quelli particolarmente attuali come, ad esempio, la formazione di tutti, in ogni luogo e per tutta la
vita, la cultura e la creatività come strumenti di democrazia e di libertà, il costante ruolo della storia
dell’educazione e dell’educazione comparata nell’interpretare i nuovi fenomeni educativi, le
dolorose conseguenze di un’ingiusta divisione del lavoro e del potere a livello internazionale,
l’educazione alla democrazia e alla cittadinanza, la lotta per l’emancipazione da ogni forma di
sfruttamento, lo sviluppo sostenibile e il senso di appartenenza a una patria comune.
Le fasi di studio sulla figura di Ettore Gelpi che portano alla stesura del presente elaborato sono
state principalmente due. La prima fase è quella relativa alla ricerca e allo studio dei testi scritti da
Ettore Gelpi e delle pubblicazioni relative alla sua persona e al suo pensiero, tenendo in
considerazione materiali bibliografici, articoli su riviste, articoli su giornali, fonti di archivio e fonti
inedite. La fase di ricerca successiva riguarda la raccolta di testimonianze attraverso interviste a
testimoni privilegiati che hanno lavorato con Ettore Gelpi e che hanno dato contributi specifici su
determinate fasi della vita o su specifici aspetti del pensiero.
Il lavoro si articola in sei capitoli: i primi due fanno riferimento principalmente alla biografia di
Ettore Gelpi mentre gli altri quattro illustrano il suo pensiero e le sue intuizioni.
Il primo capitolo racchiude un’approfondita biografia dell’autore, corredata da riferimenti al
periodo storico e alle opere principali da lui redatte, seguendo le fasi principali della sua vita:
periodo di formazione e di impegno nell’animazione sociale (dalla nascita al 1971 circa), venti anni
di lavoro presso l’UNESCO (1972-1993 circa), periodo di intensa attività internazionale (dal 1994
circa fino alla morte).
Nel secondo capitolo si analizzano alcune delle attività più importanti di Ettore Gelpi come
educatore e animatore sociale, basandosi soprattutto sulle testimonianze dei testimoni privilegiati: il
lavoro presso la società Umanitaria di Milano e presso i CEMEA (Centri di Esercitazione ai Metodi
dell’Educazione Attiva), la collaborazione con il Formez di Napoli a favore dello sviluppo del
Mezzogiorno, l’impegno sindacale e a favore degli immigrati con l’ECAP-CGIL di Zurigo.
Il terzo capitolo affronta il tema dell’educazione come componente inalienabile della vita di ogni
individuo, a qualsiasi età e in qualsiasi luogo del mondo. L’esperienza ventennale di Ettore Gelpi
come responsabile dell’Educazione Permanente all’UNESCO di Parigi, la sua formazione collegata
alle esperienze dal basso, il suo ruolo di formatore e consulente in ogni parte del mondo fanno di lui
una voce autorevole in campo educativo e gli consentono di fare riflessioni di ampio respiro sulla
funzione della formazione e dell’educazione permanente, soprattutto in riferimento alla relazione tra
educazione, politica e territorio.
Il quarto capitolo analizza il rapporto tra educazione e divisione internazionale del lavoro. Ettore
Gelpi sostiene e dimostra costantemente che, in tutti i sistemi sociali e politici, l’educazione è
inestricabilmente legata alle strutture e ai processi di produzione: lavoro e formazione non possono
essere separati. Accanto alla critica dei rapporti di forza indotti dalla divisione internazionale del
lavoro, egli propone delle opportunità che possono concretamente realizzarsi, purché si sviluppi una
nuova coscienza educativa capace di portare ogni uomo e ogni donna al pieno sviluppo e alla piena
realizzazione: formazione, creatività e cultura sono tre risorse fondamentali per la piena
realizzazione di ogni individuo.
Nel quinto capitolo si affronta il tema della “complessità umana” come fattore costitutivo della
vita dell’uomo: diversità sessuale, pluralismo linguistico e religioso, handicap, diversità culturali e
somatiche fanno parte della vita dell’individuo ma, troppo spesso, discriminano alcuni a favore di
altri. L’alternativa a questo stato di cose è affrontare la complessità umana cercando di far dialogare
i diversi punti di vista, accogliendo gli insegnamenti della storia e i contributi delle diverse
discipline e dei diversi approcci culturali: solo in questo modo si può affrontare adeguatamente la
complessità e lavorare attivamente per il domani dell’intera umanità, non solo di una sua parte.
Il sesto capitolo è dedicato a quella che Ettore Gelpi definisce la “coscienza terrestre” per indicare
che la prima patria di ogni individuo è la Terra. L’uomo deve imparare a vivere sul pianeta, a
rispettarlo, a condividere con gli altri esseri umani, a non essere più di una sola cultura ma, prima di
tutto, “terrestre”
Studies of nanostructured materials for dye sensitized solar cells (dssc) electrodes
No full textExploitation of solar irradiation, in particular by development of photovoltaic technologies, is a widely recognized target for renewable energy production. Present R&D trends span from highly efficient expensive devices for aerospatial industry to less efficient cheap devices for building integration. In last contest, where the coverage of buildings or greenhouses requires versatile shapes and colours and low production costs, the so-called Dye Sensitized Solar Cells (DSSC) have attracted a particular interest, starting from the publication of the seminal paper of Gratzel and O’Reagan in 1991. A DSSC is a photoelectrochemical system, as the ones studied since 1960s, based on a dye sensitized semiconductor, where a nanostructured high specific surface area porous titania electrode was introduced as a turning point to reach energy conversion up to 11%. The development of the photoanode functionality, depending on both the porous semiconductor and the dye, is one of the keys to improve the efficiency of DSSC. The research is directed on one side to the synthesis of highly absorbing dyes over a wide spectral range; on the other side to the development of novel semiconductor nanostructures providing better optical and electronic transport properties. Electrodes with the high specific surface necessary for efficient dye anchorage are usually produced by sinterization of titania nanobeads. However, several different shapes and morphologies are under investigations, in order to overcome the poor electron conduction characteristics of this kind of anodes. In particular, well-ordered vertically aligned titania nanotubes have been proposed, thanks to the long electron diffusion length predicted for this geometry. In parallel, research is in progress with the aim of producing sustainable devices based on widely available and cheap materials, focussing on the cathode. The last is a conductive surface functionalized with Pt nanoclusters, enabling both electron conduction and catalysis of the reduction reaction occurring in the iodine-based electrolyte that provides electrochemical carrier transport in the device. Since carbon is known to be a catalyst for the iodine reduction, several efforts are devoted to exploit carbon based catalysts for Pt substitution at the DSSC cathode.
This thesis deals with the study of DSSC photoanodes based on different nanostructured titania morphologies, and novel carbon-based cathode nanomaterials.
To this purpose, the procedure to fabricate small lab-scale devices based on both commercial and novel materials was set-up, and the devices were routinely characterized by current-voltage measurements under AM1.5 standard illumination. Moreover, a great effort was devoted to the standardization of the protocols to prepare photoanodes and cathodes, and to assemble the complete device, in order to allow meaningful comparison of performances.
As novel material for the cathode, carbon nanostructures were made on purpose by CVD on different substrates, characterized, and then tested in complete devices. The efficiency of the cells with carbon-based cathodes is still low compared to those obtained with standard materials, and work is in progress in order to synthesize carbon nanostructures with improved catalytic performance.
For the study of photoanodes, a simple model, based on geometrical considerations, was developed in order to calculate the specific surface of both conventional spherical nanoparticles -based electrodes, and new photoanodes based on tubular nanostructures (titania nanotubes, TNT). The knowledge of the specific surface enables to estimate the dye (N719) load on the electrode and then, neglecting light diffusion phenomena as a first approximation, the photoanode optical absorption. From the absorption of the electrode is finally possible to estimate the short circuit current density under standard solar illumination. To take into account the light diffusion in the mesoporous film, an absorption enhancement factor was considered. In order to calculate the maximum achievable short circuit current density, a statistical ray approach was used to simulate the case of limit light trapping. In parallel, the experimental measure of the diffuse and collinear optical trasmittivity and reflectivity of a NP-based electrode enabled quantification of the real enhancement factor of the absorption coefficient as a function of the wavelength.
The experimental values of the short circuit current density, obtained by measuring the characteristics of a complete cell, were discussed and compared to the values predicted by applying the optical model.
Novel photoanodes based on titania TNT grown on transparent electrodes (fluorine doped tin oxide coated glasses, FTO) were prepared and tested in complete cells. A large bibliography shows the possibility to grow by electrochemical process titania TNT with controlled variable morphologies, up to tens of microns of length from titanium foils. Nevertheless, in order to fully exploit the solar irradiation, growth of TNT on FTO is mandatory. For this purpose, different electrochemical conditions were applied to synthesize TNT from Ti films sputtered on FTO. Tubular structures were
easily produced, but the interface Ti-FTO is severely damaged by the anodization process, so that film peeling remains a challenge for most of the conditions. TNT films up to 3.5 m thick were obtained in carefully chosen anodization conditions and tested as photoanodes in real cells, showing, however, conversion efficiency lower than that attainable from standard NP-based devices.
In conclusion, small lab-scale DSSC, based both on conventional and novel materials, have been fabricated and characterized. The performances of devices using cathodes based on carbon nanostructures were measured, pointing out the necessity of improving the catalytic properties, in order to reach the standard Pt nanoparticles characteristics. The optical functionality of photoanodes was assessed. The light scattering properties of practical photoanodes were experimentally quantified and related to illuminated IV characteristics of real cells. Several photoanodes were realized by electrochemical processing of Ti films on FTO, and used to assembly complete devices. Complete characterizations of the cells, jointly with the optical model, pointed out the necessity of overcoming the technological bottlenecks in the anodization process, in order to produce high specific surface morphologies
Electron-vibron interaction e ects on the electronic transport through molecular systems
No full textThe emerging eld of molecular electronics, in which individual molecules play the role of
active devices, is receiving great amount of attention due to its possible technological impact.
Recent advances in nanoscale fabrication and engineering techniques have made possible to
study the transport properties of devices on the molecular scale. At this level, one inherently
probes the quantum mechanical nature of matter which manifests a number of e ects not
well understood yet. One such e ect is the mutual interaction between electrical current and
molecular vibrations. The coupling between mechanical and electronic degrees of freedom in
nanoscale devices is also at the heart of NanoElectroMechanical Systems (NEMS) physics.
Potential applications of these systems include ultrasensitive motion detection, mass sensing,
bio-molecular studies and quantum enabled technologies.
In the rst part of thesis, I focused my investigation on electronic transport properties of
very short molecules connected between metallic leads taking into account electron-vibration
interaction inside the device with a single vibrational mode. Within two models widely
used in the literature, I implemented a computational scheme for the dynamics of the
oscillator mode coupled with an out-of-equilibrium molecular junction providing also a novel
and more physically sounding derivation. I concentrated my attention on the physical
regime where the vibrational motion of the oscillator is 'slow' with respect to all electronic
energy scales and can be considered classical. I exploited the Keldysh formalism within Non
Equilibrium Green's Function theory (NEGF) for the electronic subsystem together with
stochastic dynamics for the vibrational degrees of freedom. As main result, the inclusion
of dynamical e ects of the oscillator motion strongly modi es the physical scenario which
would be obtained by a static description, even if the oscillator dynamics is much slower
than the electron tunneling rate.
Motivated by recent experiments on single-electron-transistor made of a single suspended
carbon nanotubes, I have further investigated the renormalization e ects of the bending
mode oscillation frequency of the nanotube as function of the external charge injection
(due to the applied bias and gate voltages). I also included in the model the e ects of an
external antenna driving the oscillations of the nanotube. Interestingly, simulations of the
stochastic Langevin equation for the vibrational degree of freedom developed in the rst part
of the thesis, including the e ect of the external antenna, reproduce semi-quantitatively the
experimental results. I have also shown that, even in the presence of a magnetic eld applied
perpendicular to the nanotube device, the nanotube dynamics can be fruitful described by
a Langevin equation. In this case, the main result is that the magnetic eld provides an
additional damping mechanism to the resonator mechanical motion.
In the last part of the thesis, I studied electron transport through molecular systems at
high injected carrier densities, where the presence of the electron-electron interactions is not
negligible. I have also considered the e ect of the interaction with an high frequency molecu-
lar mode (center of mass motion of the molecule) inside the device, which cannot be treated
semiclassically anymore. In order to investigate systems with strong electron-phonon and
electron-electron interactions, I have used an approximation-free numerical technique, suita-
ble for non-equilibrium quantum many-body systems: the Density Matrix Renormalization
Group (DMRG). I numerically investigated with DMRG the electronic transport proper-
ties of a nanomechanical shuttling device in the Kondo regime. Nanomechanical shuttling
systems (NMSS) and NEMS in general o er a unique platform for design of an electron transistor in which spin and charge transfer can be controlled mechanically. My study is
motivated by recent contrasting experimental results found in the conductance measured
through C60 junctions in the low temperature and low bias regime, where very small or re-
latively large conductance values are detected. I focused on the e ects of tunneling barrier
modulation on the electronic conductance and on the static and dynamical properties of the
center of mass phononic mode, clarifying the nature of a dip found in the conductance at
particle-hole symmetric point
Electronic properties of strained graphene
No full textGraphene is an atomically thick single layer of carbon atoms arranged according to
a honeycomb lattice. Its quite recent discovery, due to Geim and Novoselov, and the
realization of sufficiently large graphene flakes in the laboratory have stimulated an
enormous outburst of both experimental and theoretical investigation (Science 306, 666
(2004)). Indeed in 2010, Geim and Novoselov were awarded the Nobel Prize in Physics
for groundbreaking experiments regarding the two-dimensional material graphene (Rev.
Mod. Phys. 83, 837 (2011), Rev. Mod. Phys. 83, 851 (2011)).
The electronic band structure of graphene consists of two bands. In pristine graphene,
they touch each other at the Fermi level in a linear, cone-like fashion at the so-called
Dirac points K and K0. These two special points coincide with the corners of the
hexagonal first Brillouin zone (1BZ).
Transport measurements show that graphene has a remarkably high electron mobility
at room temperature. Specifically, the electron mobility for graphene on a silicon dioxide
(SiO2) substrate is 105 cm2 V−1 s−1, whereas for suspended graphene (i.e. without
substrate) it is 106 cm2 V−1 s−1 (Phys. Rev. Lett. 101, 096802 (2008)), which are
values comparable with those obtained in more complex systems, as a modulation-doped
field transistor (MODFET). Besides a high mobility, graphene presents a relatively high
optical transparency, in addition to a remarkable flexibility, robustness and environmen-
tal stability. These properties make graphene an attractive material for applications also
in photonics, optoelectronics and plasmonics (Nature Photonics 4, 611 (2010)).
Graphene is also notable for its remarkable mechanical properties. In particular, recent
ab initio calculations (Phys. Rev. B 76, 064120 (2007)) as well as experiments (Nature
457, 706 (2009)) have demonstrated that graphene single layers can reversibly sustain elastic deformations as large as 20%. In microelectronics, the effect of strain is often
used to modify the electronic and transport properties of materials in order to improve
the performance of the devices. In graphene, the application of strain (e.g. by stretching
or bending) allows to tune its electronic properties.
Recently, there has been a great interest towards the study and the realization of
graphene-based electronic devices designed by a suitable tailoring of the electronic struc-
ture exploiting not only electric field effect but also applied strain. Both these techniques
allow to tune the electronic properties of graphene in a reversible and clean way, i.e.
without adding any source of disorder. Therefore, an in-depth knowledge of the effects
of the strain on graphene could be exploited to improve graphene-based devices.
In this Thesis, we study theoretically the influence that applied strain can have on
several properties related the electronic structure, such as the optical properties, the
plasmonic properties, and the transport properties.
First of all, we have discussed the strain dependence of the electronic band struc-
ture, and derived the strain and electric field dependence of the optical conductivity
of graphene under uniaxial strain. Within a tight-binding model, including strain-
dependent nearest neighbour hoppings and orbital overlaps, we have interpreted the
evolution of the band dispersion relations with strain modulus and direction in terms of
the proximity to several electronic topological transitions (ETT). These correspond to
the change of topology of the Fermi line as a function of strain. In the case of graphene,
one may distinguish among three distinct ETTs. We also recover the evolution of the
location of the Dirac points, which move away from the corners of the 1BZ as a function
of strain. For sufficiently small strain modulus, however, one may still linearly expand
the band dispersion relations around the new Dirac points, thereby recovering a cone
approximation, but now with elliptical sections at constant energy, as a result of the
strain-induced deformation.
For increasing strain, two inequivalent Dirac points may merge into one, which usually
occurs at either midpoint M` (` = 1, 2, 3) of the 1BZ boundary, depending on the strain
direction. This corresponds to the breaking down of linearity of the band dispersions
along a given direction through the Dirac points, the emergence of low-energy quasipar-
ticles with an anisotropic massive low-energy spectrum, and the opening of a gap in the
energy spectrum. Besides, we confirm that such an event depends not only on the strain
modulus, but characteristically also on the strain direction. In particular, no gap opens
when strain is applied along the armchair direction. We derived the energy dependence of the density of states (DOS), and recovered a linear dependence at low energy within
the cone approximation, albeit modified by a renormalized strain-dependent slope. In
particular, such a slope has been shown to increase with increasing strain modulus, re-
gardless of the strain direction, thus suggesting that applied strain may obtain a steeper
DOS in the linear regime.
We have also calculated the DOS beyond the Dirac cone approximation. The proxim-
ity to ETTs gives rise to (possibly degenerate) Van Hove singularities in the density of
states, appearing as logarithmic peaks in the DOS. Finally, we generalized our previous
results for the optical conductivity to the case of strained graphene. We studied the
frequency dependence of the longitudinal optical conductivity as a function of strain
modulus and direction, as well as of field orientation. Our main results are that (a)
logarithmic peaks appear in the optical conductivity at sufficiently high frequency, and
can be related to the ETTs in the electronic spectrum under strain, and depending on
the strain direction; (b) the relative weight of the peaks in general depends on the strain
direction and field orientation, and contributes to the generally anisotropic pattern of
the optical conductivity as a function of field orientation; (c) the opening of a band gap,
where allowed, is signalled by a vanishing optical conductivity. The optical conductivity
is directly related to measurable quantities, such as the transmittance and reflectance.
Thus, an experimental study of the optical conductivity in the visible range of frequen-
cies as a function of strain modulus and direction, as well as of field orientation, should
enable one to identify the occurrence of the three distinct ETTs predicted for graphene.
In addition, according to our results, the asymmetry induced by uniaxial strain in the op-
tical conductivity causes an observable degree of dichroism. Indeed, the optical response
of uniaxially strained graphene to linearly polarized light depends on the direction of
the polarization. Moreover, the optical response of graphene can give information about
the magnitude and the direction of strain in a graphene sample. Finally, these results
about the effect of uniaxial strain on the electronic structure and optical conductivity
are in agreement with recent ab initio calculations (EPL 92, 67001 (2010)).
After an in-depth study of the changes of electronic structure due to uniaxial strain,
we dealt with the strain-induced modifications of the plasmons. By studying the elec-
tronic polarization, we have derived the dispersion relation of the plasmon modes in
graphene. Besides including electron-electron correlation at the random phase approx-
imation (RPA) level, we have considered local field effects (LFE), that are specific to
the peculiar lattice structure under study, and we have also taken into account the z-extension of the electron wave functions. Both terms are sizable in electron-electron
scattering processes with large exchange momentum (q /a).
As a consequence of the two-band character of the electronic band structure of graphene,
we have found in general two plasmonic branches: (1) a low-energy branch, with a square-
root behavior at small wavevectors, and (2) a high-energy branch, weakly dispersing at
small wavevectors. In particular, we have found that the high-energy plasmon mode
disappears neglecting LFE. While in the absence of LFE only scattering processes with
momenta within the 1BZ are considered, LFE allow to include all scattering processes
with arbitrarily low wavelengths, thereby taking into account the discrete nature of the
crystalline lattice. Hence, the Umklapp electron-electron scattering processes have fun-
damental role in order that the system sustains the high-energy plasmon mode. More-
over, we have found an intermediate energy pseudo-plasmon mode, associated with a
logarithmic divergence of the polarization, which can be related to an interband transi-
tion between the Van Hove singularities in the valence and conduction bands of graphene,
and it can be identified with a ! transition. In graphene, to date there are measure-
ments about the low energy plasmon (Nature 487, 77 (2012), Nature Photonics 6, 749
(2012)) and the pseudo-plasmon excitation (Phys. Rev. B 77, 233406 (2008)), whereas
there is no clear experimental evidence about the high energy plasmon. Usually, experi-
mental methodologies to detect plasmon dispersion relation, such as electron energy loss
spectroscopy (EELS), measure the collective excitation at small wavevectors (q ! 0).
The detection of the high energy branch at small wavevector could be difficult, first of
all, because of the reduced spectral weight associated with the high energy branch, but
also because these plasmons could be damped by the promotion of electrons from the
valence band into the higher ( ) energy band.
Due to the robustness of the Dirac cones with respect to the application of uniax-
ial strain, for sufficiently small strain modulus, it is possible to use the massless Dirac
approximation in order to describe the low energy electronic properties. In particular,
exploiting the massless Dirac approximation, we have studied the dependence on applied
uniaxial strain of density-density and current-current linear-response electronic correla-
tion functions of graphene. Starting from these linear correlation functions, it is possible
to obtain analytical results about several measurable quantities of strained graphene,
such as the plasmonic dispersion relation, the optical conductivity, as well as the static
magnetic and electric susceptibilities. After deriving a general correspondence between
strained and unstrained correlation functions, we derived the strain dependence of the low-energy plasmon dispersion relation and of the optical conductivity. Specifically,
we found that the prefactor in the pq-dependence of the plasmon frequency develops
an anisotropic character, with maximum (minimum) occurring when the wavevector is
orthogonal (longitudinal) to the direction of applied strain. We have obtained that uni-
axial strain induces an anisotropy on both the plasmonic dispersion relation and the
electronic dispersion relation. Hence, we presume that the application of uniaxial strain
on graphene could induce a modification of the plasmaronic resonance. We remind that
plasmaron is an excitation which arises from the coupling of charge carriers and plas-
mons. Indeed, by means of a heuristic argument we found that uniaxial strain applied
on graphene should induce a shifting and broadening of the plasmaron resonance en-
ergy, proportionally to the strain modulus. Therefore, by suitably applying uniaxial
strain, one gains further control on the energy of the plasmaronic excitation, besides
the possibility of tuning the relative dielectric constant r. In addition, we have derived
a strain-induced anisotropic enhancement of the deviations from the photonic behavior
of the theoretically predicted transverse collective excitation, which should facilitate its
experimental detection in suitably strained graphene samples.
Finally, we have studied the effect of a strain-induced one-dimensional profile on sev-
eral ballistic transport properties of graphene. This study may be useful for the realiza-
tion of a new class of ballistic devices designed by a suitable tailoring of the electronic
structure exploiting not only the electric field effect but also applied strain. In particular,
we have studied the cases of a single strain-induced sharp barrier, and of a superstructure
of several, periodically repeated, such sharp barriers. In both cases, we have dealt with
the analysis of the angular dependence of the tunneling transmission, the conductivity,
and the Fano factor. In particular, we have found that a strain-induced superlattice
in graphene can accommodate additional resonant quasiparticle states, besides the ones
usually found across a single barrier. We thus surmise that a strain-induced superlat-
tice in graphene could be used as a filter for well-defined electronic resonant modes.
After considering the cases of a single sharp tunneling barrier, and of a superstructure
of several, periodically repeated, such sharp barriers, we have specifically studied the
more realistic case in which both the modulus of applied uniaxial strain, and possibly
an applied gate potential, depend continuously on position
Focus On Somalia: Radio Mogadishu Archive Digitalization
No full textAfter more than 60 years of analogue storage in an inadequate environment, the Radio Mogadishu audio archive is being digitized in order to save it from deterioration and introduce the unique Somali historical recordings to new audience, thanks to the ministry of information of the Federal Government of Somalia and the support of the AU/UN Information Support Team, French Government and other International partners.Kaddib, in ka badan 60 sano markii lagu hayay kayda Raadiyo Moqdishu meel aan sidaas u habboonayan, waxaa labillaabay in codadka dijital laga dhigo, si looga badbaadiyo baaba', unana noqd jiilka cusub raadraac taariikheed. Mashruucan waxaa dhaqan geliyay wasaaradda Warfaafinta ee Dawladda Federalka ee Soomaaliyeed, iyadoo gacan ka heshay kooxda warfaafinta AU/UN, dawladda Fransiiska iyo kuwa kale.Dopo più di 60 anni di stoccaggio in un ambiente inadeguato, l'archivio audio di Radio Mogadiscio viene infine digitalizzato per preservarlo dal deterioramento e per rendere le registrazioni storiche accessibili a un nuovo pubblico, alle nuove generazioni. Il progetto è a cura del ministero delle informazioni del governo federale di Somalia e si avvale del supporto di AU/UN Information team, governo francese e altri partner internazionali.Link: https://vimeo.com/8076010
a) Meel doora ka jeertay duur waaye; b) Minaa alkuunkaa ku uureeyaa
No full text"Meel doora ka yeertay duur waaye" , "Minaa alkunkaa ku uureeyaa", hees badeed. F. Giannattasio ayaa ka duubay 22/04/85, koox kalluumaysato ah oo ku nool Jasiira, gobolka Banaadir. Waxaa duubistaas ka qayb qaatay Aweys Maxamed Waasuge, oo kala shaqaynaayay Giannattasio xagga baarista muusikada soomaaliyeed, isagoo markaas ka ahaa Masraxa Qaranka Soomaaliyeed soosaare 1984-89._-_"Meel doora ka jeertay duur waaye” (Il luogo in cui canta il gallo è boscaglia), "Minaa alkunkaa ku uureeyaa" (Se il tuo fidanzato ti mette incinta), incipit; canti dei pescatori. Registrazione effettuata da Francesco Giannattasio il 22 aprile 1985 a Jasiira, nella regione Banaadir, con un gruppo di pescatori del villaggio. Partecipa alla registrazione Aweys Maxamed Waasuge, allora regista del Teatro Nazionale Somalo e, dal 1984 al 1989, collaboratore di Giannattasio alla ricerca sulla musica somala._-_"Meel doora ka jeertay duur waaye” (The place where the cock sings is the bush), "Minaa alkunkaa ku uureeyaa" (If your boyfriend gets you pregnant), opening words; fishermen songs. Recorded by Francesco Giannattasio on April, 22th 1985 at Jasiira, in the Banaadir region, with a group of fishermen of the village. In the presence of Aweys Maxamed Waasuge, director of the Somali National Theatre and Giannattasio's collaborator in his research on Somali music from 1984 to 1989
