IDIOPATHIC NORMAL PRESSURE HYDROCEPHALUS (HAKIM-ADAMS SYNDROME): CLINICAL SYMPTOMS, DIAGNOSIS AND TREATMENT

Idiopathic normal pressure hydrocephalus is a chronic steadily progressing disease. Nowadays a vital and acute socially significant problem still has not been solved. The etiology and pathogenesis of this disease remain so far poorly understood. Variable clinical manifestations, as well as difficulties in differential diagnosis with other neurodegenerative diseases - lead to unde r- diagnosing of the illness that causes a significant decrease in patient’s quality of life and even results in disability. The n umber of patients with idiopathic normal pressure hydrocephalus has been steadily increasing. That is why, the coverage and a full study of this problem is of great interest for a broad circle of medical professionals

Vertical Engineering for Large Brillouin Gain in Unreleased Silicon-Based Waveguides

[EN] Strong acousto-optic interaction in high-index waveguides and cavities generally requires the releasing of the high-index core to avoid mechanical leakage into the underlying low-index substrate. This complicates fabrication, limits thermalization, reduces the mechanical robustness, and hinders large-area optomechanical devices on a single chip. Here, we overcome this limitation by employing vertical photonic-phononic engineering to drastically reduce mechanical leakage into the cladding by adding a pedestal with specific properties between the core and the cladding. We apply this concept to a silicon-based platform, due to the remarkable properties of silicon to enhance optomechanical interactions and the technological relevance of silicon devices in multiple applications. Specifically, the insertion of a thick silicon nitride layer between the silicon guiding core and the silica substrate contributes to reducing gigahertz-frequency phonon leakage while enabling large values of the Brillouin gain in an unreleased platform. We numerically obtain values of the Brillouin gain around 300 ( W m ) ¿ 1 for different configurations, which could be further increased by operation at cryogenic temperatures. These values should enable Brillouin-related phenomena in centimeter-scale waveguides or in more compact ring resonators. Our findings could pave the way toward large-area unreleased-cavity and waveguide optomechanics on silicon and other high-index photonic technologies.This work was supported by the European Commission (PHENOMEN Grant No. H2020-EU-713450), the Universitat Politecnica de Valencia (Grant No. PAID-01-169), the Ministerio de Ciencia, Innovacion y Universidades (Grants No. PGC2018-094490-B and No. PRX18/00126), and the Generalitat Valenciana (Grant No. PROMETEO/2019/123)Mercadé-Morales, L.; Korovin, AV.; Pennec, Y.; Ahopelto, J.; Djafari-Rouhani, B.; Martínez Abietar, AJ. (2021). Vertical Engineering for Large Brillouin Gain in Unreleased Silicon-Based Waveguides. Physical Review Applied. 15(3):1-9. https://doi.org/10.1103/PhysRevApplied.15.0340211915

Unidirectional Coherent Phonon Emission in an Optomechanic Nanobeam Containing Coupled Cavities

Nonreciprocal phonon emission is predicted theoretically from the coherent excitation of two coupled optomechanical cavities arranged along a phoxonic crystal nanobeam. The latter consists of a periodic array of holes and stubs and exhibits simultaneous photonic and phononic bandgaps. It is shown that nonreciprocal phonon emission arises from a combined effect of the spatial symmetry of the cavities and their underlying coupled phononic modes and the temporal phase shift between the excitation sources. This demonstration paves the way for the development of advanced integrated phonon networks and circuits, in which mechanical waves connect different elements in phononic and optomechanical structures

Continuous actions of pseudocompact groups and axioms of topological group

summary:In this paper, we show that it is possible to extend the Ellis theorem, establishing the relations between axioms of a topological group on a new class $\mathcal N$ of spaces containing all countably compact spaces in the case of Abelian group structure. We extend statements of the Ellis theorem concerning separate and joint continuity of group inverse on the class of spaces $\mathcal N$ that gives some new examples and statements for the $C_p$-theory and theory of topologically homogeneous spaces

Unidirectional Coherent Phonon Emission in an Optomechanic Nanobeam Containing Coupled Cavities

Nonreciprocal phonon emission is predicted theoretically from the coherent excitation of two coupled optomechanical cavities arranged along a phoxonic crystal nanobeam. The latter consists of a periodic array of holes and stubs and exhibits simultaneous photonic and phononic bandgaps. It is shown that nonreciprocal phonon emission arises from a combined effect of the spatial symmetry of the cavities and their underlying coupled phononic modes and the temporal phase shift between the excitation sources. This demonstration paves the way for the development of advanced integrated phonon networks and circuits, in which mechanical waves connect different elements in phononic and optomechanical structures