663 research outputs found
Білий куб: формування галерейного простору
У статті розглянуто концепцію «білого куба», специфічного галерейного та музейного простору для демонстрації і споглядання мистецтва. Проаналізовано, як тривалі експерименти з формою демонстрації робіт у музейних приміщеннях були зумовлені потребою створити особливий простір, де кожний експонат був би максимально ізольованим і самодостатнім. Так виник «білий куб», який фактично був легітимізований Альфредом Барром, першим директором музею сучасного мистецтва в Нью-Йорку. Починаючи з Брайана О’Догерті, дослідники вказують, що галерейний простір, яке нібито є максимально нейтральним, насправді є глибоко ідеологізованим. Уваго було приділено і рефлексії художників щодо функції, діяльності та організації простору галереї
Piezoelectric-Layered Structures Based on Synthetic Diamond
Results of theoretical, modeling, and experimental investigation of microwave acoustic properties of piezoelectric layered structure “Me1/AlN/Me2/(100) diamond” have been presented within a wide frequency band 0.5–10 GHz. The highest among known material quality parameter Q × f ~ 1014 Hz for the IIa type synthetic diamond at operational frequency ~10 GHz has been found. Conditions of UHF excitation and propagation of the bulk, surface, and Lamb plate acoustic waves have been established and studied experimentally. Frequency dependencies of the impedance and quality factor have been studied to obtain a number of piezoelectric layered structure parameters as electromechanical coupling coefficient, equivalent circuit parameters, etc. Results of 2D finite element modeling of a given piezoelectric layered structure have been compared with the experimental ones obtained for the real high-overtone bulk acoustic resonator. An origin of high-overtone bulk acoustic resonator’s spurious resonant peaks has been studied. Results on UHF acoustic attenuation of IIa-type synthetic single crystalline diamond have been presented and discussed in terms of Akhiezer and Landau–Rumer mechanisms of phonon–phonon interaction. Identification and classification of Lamb waves belonging to several branches as well as dispersive curves of phase velocities have been executed. Necessity of introducing a more correct Lamb-mode classification has been recognized
Application of Thin Piezoelectric Films in Diamond-Based Acoustoelectronic Devices
The theory of external loading influence on acoustic parameters of piezoelectric five-layered structure as “Al/(001) AlN/Mo/(001) diamond/Me” has been developed. Oscillations in diamond-based high-overtone bulk acoustic resonators (HBARs) have been investigated in terms of 3D FEM simulation. Peculiarities of technology of aluminum-scandium nitride (ASN) films have been discussed. Composition Al0.8Sc0.2N was obtained to create the diamond-based HBAR and SAW resonator. Application of ASN films has resulted in a drastic increasing an electromechanical coupling up to 2.5 times in comparison with aluminum nitride. Development of ASN technology in a way of producing a number of compositions with the better piezoelectric properties has a clear prospective. SAW resonator based on “Al IDT/(001) AlN/(001) diamond” structure has been investigated in the band 400–1500 MHz. The highest-quality factor Q ≈ 1050 was observed for the Sezawa mode at 1412 MHz. Method of measuring HBAR’s parameters within 4–400 K at 0.5–5 GHz has been developed. Results on temperature dependence of diamond’s Q-factor at relatively low frequencies were quite different in comparison with the ones at the frequencies up to 5 GHz. Difference could be explained in terms of changing mechanism of acoustic attenuation from Akhiezer’s type to the Landau-Rumer’s one at higher frequencies in diamond
Anisotropy of DC Electric Field Influence on Acoustic Wave Propagation in Piezoelectric Plate
Anisotropy of dc electric field influence on the different types of acoustic waves in the piezoelectric
plate has been investigated by means of computer simulation. Detail calculations have made for bismuth
germanium oxide crystalsРассмотрена анизотропия влияния однородного электрического поля E на характеристики и
условия распространения волн различных типов в пьезоэлектрической пластине германосилле-
нита
Laser generation of CeAlO3 nanocrystals with perovskite structure
For the first time to the best of our knowledge, CeAlO3 nanocrystals with perovskite structure are synthesized by pulsed laser ablation technique. The morphological and optical properties of the obtained CeAlO3 nanocrystals are investigated. This work opens new prospects for the application of laser ablation methods for the generation of perovskite nanocrystals and development of novel nanocomposite structures, which can be applied for the fabrication of perovskite solar cells, scintillation detectors, catalysts, etc
Femtosecond X-ray emission study of the spin cross-over dynamics in haem proteins
In haemoglobin (consisting of four globular myoglobin-like subunits), the
change from the low-spin (LS) hexacoordinated haem to the high spin (HS)
pentacoordinated domed form upon ligand detachment and the reverse process upon
ligand binding, represent the transition states that ultimately drive the
respiratory function. Visible-ultraviolet light has long been used to mimic the
ligand release from the haem by photodissociation, while its recombination was
monitored using time-resolved infrared to ultraviolet spectroscopic tools.
However, these are neither element- nor spin-sensitive. Here we investigate the
transition state in the case of Myoglobin-NO (MbNO) using femtosecond Fe Kalpha
and Kbeta non-resonant X-ray emission spectroscopy (XES) at an X-ray
free-electron laser upon photolysis of the Fe-NO bond. We find that the
photoinduced change from the LS (S = 1/2) MbNO to the HS (S = 2)
deoxy-myoglobin (deoxyMb) haem occurs in ca. 800 fs, and that it proceeds via
an intermediate (S = 1) spin state. The XES observables also show that upon NO
recombination to deoxyMb, the return to the planar MbNO ground state is an
electronic relaxation from HS to LS taking place in ca. 30 ps. Thus, the entire
ligand dissociation-recombination cycle in MbNO is a spin cross-over followed
by a reverse spin cross-over process
Slow Magnetic Relaxation of Dy Adatoms with In-Plane Magnetic Anisotropy on a Two-Dimensional Electron Gas
We report on the magnetic properties of Dy atoms adsorbed on the (001) surface of SrTiO3. X-ray magnetic circular dichroism reveals slow relaxation of the Dy magnetization on a time scale of about 800 s at 2.5 K, unusually associated with an easy-plane magnetic anisotropy. We attribute these properties to Dy atoms occupying hollow adsorption sites on the TiO2-terminated surface. Conversely, Ho atoms adsorbed on the same surface show paramagnetic behavior down to 2.5 K. With the help of atomic multiplet simulations and first-principles calculations, we establish that Dy populates also the top-O and bridge sites on the coexisting SrO-terminated surface. A simple magnetization relaxation model predicts these two sites to have an even longer magnetization lifetime than the hollow site. Moreover, the adsorption of Dy on the insulating SrTiO3 crystal leads, regardless of the surface termination, to the formation of a spin-polarized two-dimensional electron gas of Ti 3dxy character, together with an antiferromagnetic Dy-Ti coupling. Our findings support the feasibility of tuning the magnetic properties of the rare-earth atoms by acting on the substrate electronic gas with electric fields.We acknowldege funding from the National Research Council (CNR) within the CNR/CAS Cooperative Programme project "Advanced characterization methods for the study of rare-earth single-ion magnets on oxide substrates", from the Czech Academy of Sciences (Mobility Plus Project No. CNR-19-03), and from the Swiss National Science Foundation (200020_176932 and 200021_175941). ICN2 was funded by the CERCA Programme/Generalitat de Catalunya and supported by the Spanish Ministry of Economy and Competitiveness, MINECO (grant nos. SEV-2017-0706 and PID2019-107338RB-C65/AEI/10.13039/501100011033). IMDEA Nanociencia acknowledges support from the Severo Ochoa Programme for Centres of Excellence in R&D (MINECO, grant SEV-2016-0686).Peer reviewe
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