Search results for "Note"
showing 10 items of 10709 documents
Analysis of spectral line shapes in low-temperature plasma by means of inverse ill-posed problem solution
2017
Promocijas darbs ir veltīts zemtemperatūras plazmas diagnostikas metodes attīstīšanai, augstfrekvences bezelektrodu lampām (ABL). Darbā tika izstrādāta jauna metode spektroskopisko datu apstrādei un reālo spektrāllīniju kontūru noteikšanai, risinot nekorekto apgriezto uzdevumu, kas balstās uz Tihonova regularizācijas algoritmu. Metode tika testēta aprēķinot patiesās profilu formas izmantojot eksperimentāli iegūtas Hg līnijās, emitētas no specialas formas mikro ABL. Tika pierādīts, ka aparatūras funkcijas neņemšana vērā zemtemperatūras plazmas gadījumā var ieviest lielu neprecizitāti, nosakot profilu formu un platumu un, sekojoši, ABL temperatūru. Tika analizēta arī atkarība no bufergāzes ve…
Efficient metallic spintronic emitters of ultrabroadband terahertz radiation
2016
Terahertz electromagnetic radiation is extremely useful for numerous applications such as imaging and spectroscopy. Therefore, it is highly desirable to have an efficient table-top emitter covering the 1-to-30-THz window whilst being driven by a low-cost, low-power femtosecond laser oscillator. So far, all solid-state emitters solely exploit physics related to the electron charge and deliver emission spectra with substantial gaps. Here, we take advantage of the electron spin to realize a conceptually new terahertz source which relies on tailored fundamental spintronic and photonic phenomena in magnetic metal multilayers: ultrafast photo-induced spin currents, the inverse spin-Hall effect an…
Ultrafast amplification and non-linear magneto-elastic coupling of coherent magnon modes in an antiferromagnet
2021
We investigate the role of domain walls in the ultrafast magnon dynamics of an antiferromagnetic NiO single crystal in a pump-probe experiment with variable pump photon energy. Analysing the amplitude of the energy-dependent photo-induced ultrafast spin dynamics, we detect a yet unreported coupling between the material's characteristic THz- and a GHz-magnon modes. We explain this unexpected coupling between two orthogonal eigenstates of the corresponding Hamiltonian by modelling the magneto-elastic interaction between spins in different domains. We find that such interaction, in the non-linear regime, couples the two different magnon modes via the domain walls and it can be optically exploi…
Dynamical amplification of electric polarization through nonlinear phononics in 2D SnTe
2020
Ultrafast optical control of ferroelectricity using intense terahertz fields has attracted significant interest. Here we show that the nonlinear interactions between two optical phonons in SnTe, a two-dimensional in-plane ferroelectric material, enables a dynamical amplification of the electric polarization within subpicoseconds time domain. Our first-principles time-dependent simulations show that the infrared-active out-of-plane phonon mode, pumped to nonlinear regimes, spontaneously generates in-plane motions, leading to rectified oscillations in the in-plane electric polarization. We suggest that this dynamical control of ferroelectric material, by nonlinear phonon excitation, can be ut…
Terahertz electrical writing speed in an antiferromagnetic memory
2018
The speed of writing of state-of-the-art ferromagnetic memories is physically limited by an intrinsic gigahertz threshold. Recently, realization of memory devices based on antiferromagnets, in which spin directions periodically alternate from one atomic lattice site to the next has moved research in an alternative direction. We experimentally demonstrate at room temperature that the speed of reversible electrical writing in a memory device can be scaled up to terahertz using an antiferromagnet. A current-induced spin-torque mechanism is responsible for the switching in our memory devices throughout the 12-order-of-magnitude range of writing speeds from hertz to terahertz. Our work opens the…
Further Furoclerodanes fromTeucrium “maghrebinum”
2001
Two more pairs of C-12 epimeric neoclerodanes were isolated from the aerial parts of Teucrium “maghrebinum” (Teucriumpolium subspecies still unidentified). They are the known teukotschyn 1, the new 12-epi-teukotschyn 2, the new teughrebin 3 and the new 12-epi-teughrebin 4. The structures of the new products were elucidated mainly by spectroscopic methods.
Presentazione
2013
Il programma di ricerca, partendo dalla terracruda, mira a creare dei materiali nanocompositi, una nuova classe di materiali, caratterizzati da una dispersione delle fasi ultra ne, tipicamente dell’ordine di pochi nanometri; in virtù di questa dispersione, i nanocompositi possiedono proprietà uniche, non condivise dai convenzionali compositi o microcompositi. in altri termini, la ricerca mira a potenziare la terracruda con rinforzi nanostrutturati, allo scopo di migliorare le prestazioni chimico-fisiche e meccaniche del prodotto finale. La proposta di ricerca investe aspetti che riguardano la tradizione culturale e materiale e l’in- novazione come criterio per rinnovare la prassi costruttiv…
Terracruda e Nanotecnologie. Tradizione, Innovazione, Sostenibilità
2013
Il Volume dal titolo Terracruda e Nanotecnologie. Tradizione, Innovazione, Sostenibilità, riporta i risultati della Ricerca PRIN 2008 sull'utilizzo di nanoparticelle nei mattoni in terra cruda.
Prove di resistenza a compressione e a flessione dei campioni in terracruda
2013
The article presents the results of tests of compressive strength and flexural strength under concentrated load of samples in unfired clay with and without the addition of nanodisks of clay studied for the PRIN 2008 entitled Nanotechnology for bricks earthen: tradition, innovation and sustainability.
Ship-in-a-Bottle Synthesis of a Large Guest Occupying Two Y Zeolite Neighbour Supercages: Characterisation and Photocatalytic Activity of the Encapsu…
2003
In a series of papers we reported the ship-in-a-bottle synthesis, photochemical properties and photocatalytic applications of 2,4,6-triphenylpyrylium cation (TP ) encapsulated inside the cavities of large pore zeolites Y and Beta. 2] The identity of encapsulated TP was then confirmed spectroscopically, particularly by the match of the IR spectra of the encapsulated organic material and that of the tetrafluoroborate solid of TP (TPBF4). In addition, the electrochemical response of zeolite Y encapsulated TP (TP@Y) consisted of a reversible single reduction process taking place at the same redox potential as that measured for TPBF4 solutions. Encapsulation of TP has a dramatic influence on its…