X-ray diffraction experiments show that solid 4He grown in aerogel is highly polycrystalline, with an hcp crystal structure (as in bulk) and a crystallite size of approximately 100 nm. In contrast to the expectation that the highly disordered solid will have a large supersolid fraction, torsional oscillator measurements show a behavior that is strikingly similar to high purity crystals grown from the superfluid phase. The low temperature supersolid fraction is only approximately 3 x 10(-4), and the onset temperature is approximately 100 mK.
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http://dx.doi.org/10.1103/PhysRevLett.101.165303 | DOI Listing |
Micromachines (Basel)
January 2025
Key Laboratory of Instrumentation Science and Dynamic Measurement Ministry of Education, North University of China, Taiyuan 030051, China.
A Hz level narrow linewidth all-optical microwave oscillator based on the torsional radial acoustic modes (TR) of a single-mode fiber (SMF) is proposed and validated. The all-optical microwave oscillator consists of a 20 km SMF main ring cavity and a 5 km SMF sub ring cavity. The main ring cavity provides forward stimulated Brillouin scattering gain and utilizes a nonlinear polarization rotation effect to achieve TR mode locking.
View Article and Find Full Text PDFJTCVS Open
December 2024
Department of Cardiovascular Surgery, Seirei Mikatahara General Hospital, Hamamatsu, Japan.
Objective: A novel approach to 3-dimensional morphometry of the thoracic aorta was developed by applying centerline analysis based on least-squares plane fitting, and a preliminary study was conducted using computed tomography imaging data.
Methods: We retrospectively compared 3 groups of patients (16 controls without aortic disease, and 16 cases each with acute type B aortic dissection and congenital bicuspid aortic valve). In addition to the standard assessment indices for curvature κ and torsion τ, we conducted coordinate transformation based on the least-squares plane, divided the centerline into 3 representative features (transverse, anterior-posterior, and longitudinal displacements), and analyzed the overall and local displacement in each direction.
J Phys Chem Lett
January 2025
Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa Wako, Saitama 351-0198, Japan.
[Pt(NCN)MeCN] (NCN = 1,3-di(2-pyridyl)benzene, MeCN = acetonitrile) forms oligomers in the ground state due to metallophilic interactions, and a Pt-Pt bond is formed with photoexcitation. Ultrafast excited-state dynamics of the [Pt(NCN)MeCN] dimer in acetonitrile is investigated by femtosecond time-resolved absorption (TA) and picosecond emission spectroscopy. The femtosecond TA signals exhibit 60 cm oscillations arising from the Pt-Pt stretching motion in the S dimer.
View Article and Find Full Text PDFJ Phys Chem Lett
January 2025
Univ Paris Est Creteil and Université Paris Cité, CNRS, LISA, F-94010 Créteil, France.
Large amplitude motions (LAMs), most notably represented by proton tunneling, mark a significant departure from small amplitude vibrations where protons merely oscillate around their equilibrium positions. These substantial displacements require tunneling through potential energy barriers, leading to splittings in, e.g.
View Article and Find Full Text PDFChaos
December 2024
Departamento de Física, Universidade Federal de São Paulo (UNIFESP), Instituto de Ciências Ambientais, Químicas e Farmacêuticas, Câmpus de Diadema, R. São Nicolau 210, 09913-030 Diadema, SP, Brazil.
We report the peculiar organization of oscillations in the forced Brusselator system, found in the parameter space as a nested structure of regular and chaotic phases. To this end, we apply the winding number concept, conceived for nonlinear driven oscillators, to expose all oscillatory phases in the nested structure. First, we use the period and torsion of orbits to describe every periodic oscillation in the parameter spaces, describing the nested structure in high-resolution phase diagrams.
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