Observation of vortex-antivortex pairing in decaying 2D turbulence of a superfluid gas

In a two-dimensional (2D) classical fluid, a large-scale flow structure emerges out of turbulence, which is known as the inverse energy cascade where energy flows from small to large length scales. An interesting question is whether this phenomenon can occur in a superfluid, which is inviscid and irrotational by nature. Atomic Bose-Einstein condensates (BECs) of highly oblate geometry provide an experimental venue for studying 2D superfluid turbulence, but their full investigation has been hindered due to a lack of the circulation sign information of individual quantum vortices in a turbulent sample. Here, we demonstrate a vortex sign detection method by using Bragg scattering, and we investigate decaying turbulence in a highly oblate BEC at low temperatures, with our lowest being $\sim 0.5 T_c$, where $T_c$ is the superfluid critical temperature. We observe that weak spatial pairing between vortices and antivortices develops in the turbulent BEC, which corresponds to the vortex-dipole gas regime predicted for high dissipation. Our results provide a direct quantitative marker for the survey of various 2D turbulence regimes in the BEC system.Comment: 8 pages, 8 figure

Critical Vortex Shedding in a Strongly Interacting Fermionic Superfluid

We study the critical vortex shedding in a strongly interacting fermionic superfluid of Li6 across the BEC-BCS crossover. By moving an optical obstacle in the sample and directly imaging the vortices after the time of flight, the critical velocity uvor for vortex shedding is measured as a function of the obstacle travel distance L. The observed uvor increases with decreasing L, where the rate of increase is the highest in the unitary regime. In the deep Bose-Einstein condensation regime, an empirical dissipation model well captures the dependence of uvor on L, characterized by a constant value of ��=-[d(1/uvor)/d(1/L)]. However, as the system is tuned across the resonance, a step increase of �� develops about a characteristic distance Lc as L is increased, where Lc is comparable to the obstacle size. This bimodal behavior is strengthened as the system is tuned towards the BCS regime. We attribute this evolution of uvor to the emergence of the underlying fermionic degree of freedom in the vortex-shedding dynamics of a Fermi condensate. ? 2018 American Physical Societ

Assessing music-related memory in people with dementia: a scoping review

OBJECTIVES: There are various type of music-related memory and different aspects of impairment caused by dementia. The purpose of this scoping review was to identify methods and map key concepts in assessing music-related memory in people with dementia. METHOD: The review was conducted using the five steps in the framework proposed by Arksey and O\u27Malley. Databases and other sources were searched to identify relevant studies, and data selection and abstraction were performed. RESULTS: A total of 35 studies that met the selection criteria were finally selected and analysed. We confirmed that the assessment of music-related memory can be systematically classified as assessing short-term or long-term memory, explicit or implicit memory, depending on the type of memory. Regarding the key concept of assessing music-related memory, we mapped a conceptual framework for the interrelationships between music and memory from a person-centered perspective. CONCLUSION: Comprehensive information on music-related memory obtained through the assessment will be helpful for a holistic understanding of the person with dementia. In addition, it will provide meaningful information for specific planning and application of musical experiences that can be effectively used in music therapy. Further research is needed to establish the reliability and validity of the assessment

Effects of Music-Based Interventions on Motor and Non-Motor Symptoms in Patients with Parkinson’s Disease: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis examined previous studies on music-based interventions for individuals with Parkinson’s disease (PD). The effectiveness of the interventions on various motor and non-motor outcomes was evaluated. This review was conducted by searching PubMed, CINAHL, PsycINFO, and Cochrane Library CENTRAL prior to June 2022 for randomized controlled trial (RCT) and controlled clinical trial (CCT) studies published in English. Data were expressed as weighted/standardized mean difference (MD/SMD) with 95% confidence intervals (CI). I2 index was used for heterogeneity. The initial search identified 745 studies, and 13 studies involving 417 participants with PD which met the inclusion criteria included in this review. The results of the meta-analysis revealed that music-based interventions can significantly improve walking velocity (MD = 0.12, 95% CI = 0.07~0.16, p p = 0.002), and mobility (MD = −1.05, 95% CI = −1.53~−0.57, p p = 0.39), cognitive flexibility (MD = 20.91, 95% CI = −10.62~52.44, p = 0.19), inhibition (SMD = 0.07, 95% CI = −0.40~0.55, p = 0.76), and quality of life (SMD = −0.68, 95% CI= −1.68~0.32, p = 0.18). The findings suggest that music-based interventions are effective for the improvement of some motor symptoms, but evidence for non-motor symptoms is limited. Further high-quality studies with a larger sample size are required to obtain the robust effects of music-based interventions on various outcomes among patients with PD

Effects of Music-Based Interventions on Motor and Non-Motor Symptoms in Patients with Parkinson’s Disease: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis examined previous studies on music-based interventions for individuals with Parkinson’s disease (PD). The effectiveness of the interventions on various motor and non-motor outcomes was evaluated. This review was conducted by searching PubMed, CINAHL, PsycINFO, and Cochrane Library CENTRAL prior to June 2022 for randomized controlled trial (RCT) and controlled clinical trial (CCT) studies published in English. Data were expressed as weighted/standardized mean difference (MD/SMD) with 95% confidence intervals (CI). I2 index was used for heterogeneity. The initial search identified 745 studies, and 13 studies involving 417 participants with PD which met the inclusion criteria included in this review. The results of the meta-analysis revealed that music-based interventions can significantly improve walking velocity (MD = 0.12, 95% CI = 0.07~0.16, p &lt; 0.00001), stride length (MD = 0.04, 95% CI = 0.02~0.07, p = 0.002), and mobility (MD = −1.05, 95% CI = −1.53~−0.57, p &lt; 0.0001). However, the results did not support significant effects for music-based interventions on cadence (MD = 3.21, 95% CI = −4.15~10.57, p = 0.39), cognitive flexibility (MD = 20.91, 95% CI = −10.62~52.44, p = 0.19), inhibition (SMD = 0.07, 95% CI = −0.40~0.55, p = 0.76), and quality of life (SMD = −0.68, 95% CI= −1.68~0.32, p = 0.18). The findings suggest that music-based interventions are effective for the improvement of some motor symptoms, but evidence for non-motor symptoms is limited. Further high-quality studies with a larger sample size are required to obtain the robust effects of music-based interventions on various outcomes among patients with PD.</jats:p

Kibble–Zurek universality in a strongly interacting Fermi superfluid

The Kibble-Zurek mechanism describes the spontaneous formation of topological defects in a system crossing a continuous phase transition(1,2). Its central premise is the notion of universality, which states that the characteristic scaling exponent describing the dependence of the defect density on the quench rate is determined by the underlying symmetries of the system. Whether this universality can be extended to strongly interacting systems, such as a unitary Fermi gas, is an open question that has recently drawn attention in the context of holographic theories(3,4). Here, we report the observation of the Kibble-Zurek universality in a strongly interacting Fermi superfluid. As the microscopic nature of superfluidity is tuned from Bose-Einstein condensation of tightly bound molecules to Bardeen-Cooper-Schrieffer superfluidity of long-range fermion pairs, the thermal quench formation of vortices reveals a constant scaling exponent arising from the U(1) gauge symmetry of the system. In rapid quenches, destructive vortex collisions lead to the saturation of vortex densities, the values of which can be universally scaled by the interaction-dependent area of the vortex cores. This work paves the way for precision studies of non-equilibrium dynamics in a highly tunable, strongly correlated many-fermion systems(5,6).11Nsciescopu

Critical vortex shedding in a strongly interacting fermionic superfluid

We study the critical vortex shedding in a strongly interacting fermionic superfluid of Li-6 across the BEC-BCS crossover. By moving an optical obstacle in the sample and directly imaging the vortices after the time of flight, the critical velocity u(vor) for vortex shedding is measured as a function of the obstacle travel distance L. The observed uvor increases with decreasing L, where the rate of increase is the highest in the unitary regime. In the deep Bose-Einstein condensation regime, an empirical dissipation model well captures the dependence of u(vor) on L, characterized by a constant value of n = -[d(1/u(vor))/d(1/L)]. However, as the system is tuned across the resonance, a step increase of. develops about a characteristic distance L-c as L is increased, where L-c is comparable to the obstacle size. This bimodal behavior is strengthened as the system is tuned towards the BCS regime. We attribute this evolution of u(vor) to the emergence of the underlying fermionic degree of freedom in the vortex-shedding dynamics of a Fermi condensate.OAIID:RECH_ACHV_DSTSH_NO:T201817086RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A078615CITE_RATE:8.839FILENAME:065_PRL121_225301_Critical Vortex Shedding.pdfDEPT_NM:물리·천문학부EMAIL:[email protected]_YN:YFILEURL:https://srnd.snu.ac.kr/eXrepEIR/fws/file/5ebf4d07-f53b-4a1d-b94c-a6a64e2099e9/linkN