212 research outputs found
La misura del colore per il monitoraggio di interventi di pulitura e consolidamento su dipinti: un caso studio
No full textAdvanced real-time recordings of neuronal activity with tailored patch pipettes, diamond multi-electrode arrays and electrochromic voltage-sensitive dyes
No full textTo understand the working principles of the nervous system is key to figure out its electrical activity and how this activity spreads along the neuronal network. It is therefore crucial to develop advanced techniques aimed to record in real time the electrical activity, from compartments of single neurons to populations of neurons, to understand how higher functions emerge from coordinated activity. To record from single neurons, a technique will be presented to fabricate patch pipettes able to seal on any membrane with a single glass type and whose shanks can be widened as desired. This dramatically reduces access resistance during whole-cell recording allowing fast intracellular and, if required, extracellular perfusion. To simultaneously record from many neurons, biocompatible probes will be described employing multi-electrodes made with novel technologies, based on diamond substrates. These probes also allow to synchronously record exocytosis and neuronal excitability and to stimulate neurons. Finally, to achieve even higher spatial resolution, it will be shown how voltage imaging, employing fast voltage-sensitive dyes and two-photon microscopy, is able to sample voltage oscillations in the brain spatially resolved and voltage changes in dendrites of single neurons at millisecond and micrometre resolution in awake animals
Modification of the structure of diamond with MeV ion implantation
No full textWe present experimental results and numerical simulations to investigate the modification of structural-mechanical properties of ion-implanted single-crystal diamond. A phenomenological model is used to derive an analytical expression for the variation of mass density and elastic properties as a function of damage density in the crystal. These relations are applied together with SRIM Monte Carlo simulations to set up finite element simulations for the determination of internal strains and surface deformation of MeV-ion-implanted diamond samples. The results are validated through comparison with high resolution X-ray diffraction and white-light interferometric profilometry experiments. The former are carried out on 180 key B implanted diamond samples, to determine the induced structural variation, in terms of lattice spacing and disorder, whilst the latter are performed on 1.8 MeV He implanted diamond samples to measure surface swelling. The effect of thermal processing on the evolution of the structural-mechanical properties of damaged diamond is also evaluated by performing the same profilometric measurements after annealing at 1000 degrees C. and modeling the obtained trends with a suitably modified analytical model. The results allow the development of a coherent model describing the effects of MeV-ion-induced damage on the structural-mechanical properties of single-crystal diamond. In particular, we suggest a more reliable method to determine the so-called diamond "graphitization threshold" for the considered implantation type
Isolation of phosphorylated and dephosphorylated forms of the CP43 internal antenna of photosystem II in Hordeum vulgare L
No full textDirect fabrication and IV characterization of sub-surface conductive channels in diamond with MeV ion implantation
No full textAbstract. In the present work we report about the investigation of the conduction mechanism of sp2 carbon
micro-channels in single crystal diamond. The structures are fabricated with a technique which employs
a MeV focused ion-beam to damage diamond in conjunction with variable thickness masks. This process
changes significantly the structural properties of the target material, because the ion nuclear energy loss
induces carbon conversion from sp3 to sp2 state mainly at the end of range of the ions (few micrometers).
Furthermore, placing a mask with increasing thickness on the sample it is possible to modulate the channels
depth at their endpoints, allowing their electrical connection with the surface. A single-crystal HPHT
diamond sample was implanted with 1.8 MeV He+ ions at room temperature, the implantation fluence
was set in the range 2.1
× 10
16
−6.3 × 10
17
ions cm−2 , determining the formation of micro-channels with
a graded level of damage extending down to a depth of about 3 μm. After deposition of metallic contacts
at the channels’ endpoints, the electrical characterization was performed measuring the I -V curves at
variable temperatures in the 80
−690 K range. The Variable Range Hopping model was used to fit the
experimental data in the ohmic regime, allowing the estimation of characteristic parameters such as the
density of localized states at the Fermi level. A value of 5.5
× 10
17
states cm−3 eV−1 was obtained, in
satisfactory agreement with values previously reported in literature. The power-law dependence between
current and voltage is consistent with the space charge limited mechanism at moderate electric field
Bessel beam fabrication of graphitic micro electrodes in diamond using laser bursts
No full textWe present the fabrication of conductive graphitic microelectrodes in diamond by using pulsed Bessel beams in the burst mode laser writing regime. The graphitic wires are created in the bulk of a 500 μm thick monocrystalline HPHT diamond (with (100) orientation) perpendicular to the sample surface, without beam scanning or sample translation. In particular, the role of different burst features in the resistivity of such electrodes is investigated for two very different sub-pulse durations namely 200 fs and 10 ps, together with the role of thermal annealing. Micro-Raman spectroscopy is implemented to investigate the laser-induced crystalline modification, and the results obtained by using two different laser repetition rates, namely 20 Hz and 200 kHz, are compared. A comparison of the micro-Raman spectra and of the resistivity of the electrodes fabricated respectively with 10 ps single pulses and with bursts (of sub-pulses) of similar total duration has also been made, and we show that the burst mode writing regime allows to fabricate more conductive micro electrodes, thanks to the heat accumulation process leading to stronger graphitization. Moreover, the microfabrication of diamond by means of the longest available bursts (~ 46.7 ps duration) featured by 32 sub-pulses of 200 fs duration, with intra-burst time delay of 1.5 ps (sub-THz bursts), leads to graphitic wires with the lowest resistivity values obtained in this work, especially at low repetition rate such as 20 Hz. Indeed, micro electrodes with resistivity on the order of 0.01 Ω cm can be fabricated by Bessel beams in the burst mode regime even when the bursts are constituted by femtosecond laser sub-pulses, in contrast with the results of the standard writing regime with single fs pulses typically leading to less conductive micro electrodes
Creation of pure non-crystalline diamond nanostructures: Via room-temperature ion irradiation and subsequent thermal annealing
No full textCarbon exhibits a remarkable range of structural forms, due to the availability of sp3, sp2 and sp1 chemical bonds. Contrarily to other group IV elements such as silicon and germanium, the formation of an amorphous phase based exclusively on sp3 bonds is extremely challenging due to the strongly favored formation of graphitic-like structures at room temperature and pressure. As such, the formation of a fully sp3-bonded carbon phase requires an extremely careful (and largely unexplored) definition of the pressure and temperature across the phase diagram. Here, we report on the possibility of creating full-sp3 amorphous nanostructures within the bulk crystal of diamond with room-temperature ion-beam irradiation, followed by an annealing process that does not involve the application of any external mechanical pressure. As confirmed by numerical simulations, the (previously unreported) radiation-damage-induced formation of an amorphous sp2-free phase in diamond is determined by the buildup of extremely high internal stresses from the surrounding lattice, which (in the case of nanometer-scale regions) fully prevent the graphitization process. Besides the relevance of understanding the formation of exotic carbon phases, the use of focused/collimated ion beams discloses appealing perspectives for the direct fabrication of such nanostructures in complex three-dimensional geometries
Piccolo - Its Historical Development, Construction, and Use in Solo, Chamber and Orchestral Music
No full textThe bachelor's thesis "Picollo. Its Historical Development, Construction and Use in Solo, Chamber and Orchestral Music." is concerned with a picollo, an instrument related to the flute. The first chapter introduces the history of both the flute and the picollo to the reader. It also includes the description of constructional changes of the instruments and their functions from the beginnings until the present day.
In the second chapter, the author focused only on the picollo, its construction and the materials it may be made of (metal, wood). The author also mentioned the significant international producers of picollos and attention was also paid to the maintenance of the instrument. The last chapter examines the possibilities of picollo's use as a solo instrument or as a member of a chamber, symphonic or operatic orchestra
Penetration of prulifloxacin into gynaecological tissues after single and repeated oral administrations
No full textThis study aimed to evaluate the penetration into gynaecological tissues of ulifloxacin, the active metabolite of prulifloxacin, a once-daily fluoroquinolone administered once or in repeated doses
Formation of buried conductive micro-channels in single crystal diamond with MeV C and He implantation
No full textAs demonstrated in previous works, implantation with a MeV ion microbeam through masks with graded
thickness allows the formation of conductive micro-channels in diamond which are embedded in the
insulating matrix at controllable depths [P. Olivero et al., Diamond Relat. Mater. 18 (5–8), 870–876 (2009)].
In the present work we report about the systematic electrical characterization of such micro-channels as a
function of several implantation conditions, namely: ion species and energy, implantation fluence. The
current–voltage (IV) characteristics of the buried channels were measured at room temperature with a two
point probe station. Significant parameters such as the sheet resistance and the characteristic exponent (α)
of the IV power-law trend were expressed as a function of damage density, with satisfactory compatibility
between the results obtained in different implantation conditions
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