Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 9 de 9
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Phys Rev Lett ; 131(13): 136102, 2023 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-37831989

RESUMO

Transverse spin of surface waves is a universal phenomenon which has recently attracted significant attention in optics and acoustics. It appears in gravity water waves, surface plasmon polaritons, surface acoustic waves, and exhibits remarkable intrinsic spin-momentum locking, which has found useful applications for efficient spin-direction couplers. Here we demonstrate, both theoretically and experimentally, that the transverse spin of surface elastic (Rayleigh) waves has an anomalous sign near the surface, opposite to that in the case of electromagnetic, sound, or water surface waves. This anomalous sign appears due to the hybrid (neither transverse nor longitudinal) nature of elastic surface waves. Furthermore, we show that this sign anomaly can be employed for the selective spin-controlled excitation of symmetric and antisymmetric Lamb modes propagating in opposite directions in an elastic plate. Our results pave the way for spin-controlled manipulation of elastic waves and can be important for a variety of areas, from phononic spin-based devices to seismic waves.

2.
Phys Rev Lett ; 129(27): 275501, 2022 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-36638293

RESUMO

Distinct from the phononic valley pseudospin, the real physical spin of elastic waves adds a novel tool kit capable of envisaging the valley-spin physics of topological valley phononic crystals from a local viewpoint. Here, we report the observation of local elastic valley spin as well as the hidden elastic spin-valley locking mechanism overlooked before. We demonstrate that the selective one-way routing of valley phonon states along the topological interface can be reversed by imposing the elastic spin metasource at different interface locations with opposite valley-spin correspondence. We unveil the physical mechanism of selective directionality as the elastic spin controlled chiral coupling of valley phonon states, through both analytical theory and experimental measurement of the opposite local elastic spin density at different interface locations for different transport directions. The elastic spin of valley topological edge phonons can be extended to other topological states and offers new tool to explore topological metamaterials.

3.
Opt Lett ; 40(24): 5814-7, 2015 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-26670519

RESUMO

We propose a perpendicular elliptical silicon nanohole (PE-SiNH) array for light absorption in thin film silicon solar cells. Our analysis shows that this architecture is capable of increasing the absorption of a thin film silicon solar cell by 11.3% in comparison to that of the optimal circular SiNH array. The process of breaking the mirror symmetries is responsible for the increase of the coupled modes. The PE-SiNH structures show additional near-zero spatial Fourier components compared with the circular SiNH structure, which helps to couple more incident light into slow Bloch modes. The mode interaction between adjacent elliptical nanoholes is in favor of the coupling of the incident light into channeling modes and, therefore, enhances light absorption in the short wavelength region.

4.
Medicine (Baltimore) ; 103(9): e37254, 2024 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-38428885

RESUMO

Dietary patterns have a significant impact on the occurrence of urolithiasis. This study aimed to investigate the causal relationships between the consumption of glucosamine, fresh fruits, and tea, and the predisposition to urinary stones using a Mendelian randomization (MR) approach. Genetic proxies for these dietary factors were obtained from the UK Biobank, while the summary data for urolithiasis genome-wide association analyses were sourced from the FinnGen consortium. Five MR methodologies, namely inverse variance weighted (IVW), MR-Egger regression, weighted median, weighted mode, and simple mode, were employed in the analysis. To validate the findings, sensitivity evaluations such as the MR-PRESSO disruption test and Cochran Q test for heterogeneity were performed. The IVW method showed that glucosamine consumption had a strong inverse association with urolithiasis risk (Odds Ratio [OR] = 0.006, 95% Confidence Interval [CI] 0.0001-0.287, P = .009), surpassing the associations of fresh fruits (OR = 0.464, 95% CI 0.219-0.983, P = .045) and tea (OR = 0.550, 95% CI 0.345-0.878, P = .012). These findings were consistent when verified using alternative MR techniques, and the sensitivity analyses further supported their credibility. The results of this MR analysis demonstrate that regular consumption of glucosamine, fresh fruits, and tea is inversely correlated with the risk of developing urolithiasis.


Assuntos
Frutas , Urolitíase , Humanos , Estudo de Associação Genômica Ampla , Análise da Randomização Mendeliana , Urolitíase/epidemiologia , Urolitíase/genética , Glucosamina , Chá/efeitos adversos
5.
Heliyon ; 10(4): e25704, 2024 Feb 29.
Artigo em Inglês | MEDLINE | ID: mdl-38404890

RESUMO

Background: Recent studies increasingly suggest notable changes in both the quantity and types of gut microbiota among individuals suffering from urinary tract stones. However, the causal relationship between GMB and urinary tract stone formation remains elusive, which we aim to further investigate in this research through Mendelian Randomization (MR) analysis. Materials and methods: Single nucleotide polymorphisms (SNPs) associated with the human GMB were selected from MiBioGen International Consortium GWAS dataset. Data on urinary tract stone-related traits and associated SNPs were sourced from the IEU Open GWAS database. To investigate the causal relationships between gut microbiota and urinary tract stones, Mendelian Randomization (MR) was applied using genetic variants as instrumental variables, utilizing a bidirectional two-sample MR framework. This analysis incorporated various statistical techniques such as inverse variance weighting, weighted median analysis, MR-Egger, and the maximum likelihood method. To ensure the reliability of the findings, a range of sensitivity tests were conducted, including Cochran's Q test, the MR-Egger intercept, leave-one-out cross-validation, and examination of funnel plots. Results: The results revealed the causal relationship between the increase in the abundance of 10 microbial taxa, including Genus-Barnesiella (IVW OR = 0.73, 95%CI 0.73-0.89, P = 2.29 × 10-3) and Genus-Flavonifractor (IVW OR = 0.69, 95%CI 0.53-0.91, P = 8.57 × 10-3), and the decreased risk of urinary tract stone formation. Conversely, the development of urinary tract stones was observed to potentially instigate alterations in the abundance of 13 microbial taxa, among which Genus-Ruminococcus torques group was notably affected (IVW OR = 1.07, 95%CI 0.64-0.98, P = 1.86 × 10-3). In this context, Genus-Clostridium sensustricto1 exhibited a bidirectional causal relationship with urinary tract stones, while the remaining significant microbial taxa demonstrated unidirectional causal effects in the two-sample MR analysis. Sensitivity analyses did not identify significant estimates of heterogeneity or pleiotropy. Conclusion: To summarize, the results of this study suggest a likely causative link between gut microbiota and the incidence of urinary tract stones. This insight opens up potential pathways for discovering biomarkers and therapeutic targets in the management and prevention of urolithiasis. However, further in-depth research is warranted to investigate these associations.

6.
Ultrasonics ; 138: 107229, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38113587

RESUMO

The second harmonic Lamb waves have high sensitivity to microstructural defects in materials and are therefore promising for incipient damage detection and monitoring of thin-walled structures. Existing studies have shown that the second harmonic Lamb waves can be cumulative with increasing propagation distance under the internal resonance conditions, which is conducive to nonlinear wave measurements in view of structural health monitoring. However, when propagating in a lossy structure with damping, the cumulative properties of the second harmonic Lamb waves are affected by energy dissipation and thus need to be re-examined. In this paper, a method for predicting the cumulative characteristics of second harmonic Lamb waves in damped plates is proposed. Instead of using material damping parameters which are difficult to obtain in practice, the proposed method relies on the attenuation patterns of Lamb waves at fundamental and double frequencies while taking into account the influence of the wave beam divergence. The proposed methodology is validated by finite element simulations and experiments. The results show that the cumulative second harmonic Lamb waves in the damped plate tend to increase and then decrease, and a "sweet" zone of relatively large amplitude can be predicted using the proposed method. The elucidation of the cumulative characteristics of the second harmonic Lamb waves provides guidance for effective system design for structural damage detection and monitoring applications.

7.
Nat Commun ; 12(1): 6954, 2021 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-34845209

RESUMO

Directional routing of one-way classical wave has raised tremendous interests about spin-related phenomena. This sparks specifically the elastic wave study of pseudo-spin in meta-structures to perform robust manipulations. Unlike pseudo-spin in mathematics, the intrinsic spin angular momentum of elastic wave is predicted quite recently which exhibits selective excitation of unidirectional propagation even in conventional solids. However, due to the challenge of building up chiral elastic sources, the experimental observation of intrinsic spin of elastic wave is still missing. Here, we successfully measure the elastic spin in Rayleigh and Lamb modes by adopting elaborately designed chiral meta-sources that excite locally rotating displacement polarization. We observe the unidirectional routing of chiral elastic waves, characterize the different elastic spins along different directions, and demonstrate the spin-momentum locking in broad frequency ranges. We also find the selective one-way Lamb wave carries opposite elastic spin on two plate surfaces in additional to the source chirality.

8.
Ultrasonics ; 103: 106085, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32062179

RESUMO

In this work, the finite element method (FEM) is used to investigate the propagation of laser-generated Rayleigh wave along the material surface at the quarter-arc transition surface under the thermoelastic regime, and to establish the relationship between the circular-arc radius and the time domain characteristics of reflected and transmitted Rayleigh waves. The simulation shows that the amplitude of the reflected Rayleigh wave decreases whereas the amplitude of the transmitted Rayleigh wave increases as the radius increases, which is significantly different from the well-studied interaction of Rayleigh waves with the perpendicular transition surface. By introducing the circular-arc defects which are easily formed in some engineering components during the material surface quenching, we find that the depth gauging of the surface circular-arc defects is more accurate in comparison to the surface rectangular defects based on the arrival time of the transmitted Rayleigh wave. This is further verified by the corresponding experimental results. These foundings are of practical values for detecting the depth of the arc defect quantitatively by the laser ultrasonic technique.

9.
Sci Rep ; 6: 24437, 2016 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-27075601

RESUMO

In this work, we present a method for the design of gradient index devices for elastic waves in plates. The method allows the design of devices to control the three fundamental modes, despite the fact that their dispersion relation is managed by different elastic constants. It is shown that by means of complex graded phononic crystals and thickness variations it is possible to independently design the three refractive indexes of these waves, allowing therefore their simultaneous control. The effective medium theory required for this purpose is presented, and the method is applied to the design of the Luneburg and Maxwell lenses as well as to the design of a flat gradient index lens. Finally, numerical simulations are used to demonstrate the performance of the method in a broadband frequency region.

SELEÇÃO DE REFERÊNCIAS
Detalhe da pesquisa