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wave reflection

Ying Rao, Yanghua Wang
The contrast of elastic properties across a subsurface interface imposes a dominant influence on the seismic wavefield, which includes transmitted and reflected waves from the interface. Therefore, for an accurate waveform simulation, it is necessary to have an accurate representation of the subsurface interfaces within the numerical model. Accordingly, body-fitted gridding is used to partition subsurface models so that the grids coincide well with both the irregular surface and fluctuating interfaces of the Earth...
February 15, 2018: Scientific Reports
Donald J Hagler, Istvan Ulbert, Lucia Wittner, Lorand Erőss, Joseph R Madsen, Orrin Devinsky, Werner Doyle, Daniel Fabo, Sydney S Cash, Eric Halgren
Sleep spindles are a cardinal feature in human NREM sleep and may be important for memory consolidation. We studied the intracortical organization of spindles in men and women by recording spontaneous sleep spindles from different cortical layers using linear microelectrode arrays. Two patterns of spindle generation were identified using visual inspection, and confirmed with factor analysis. Spindles (10-16Hz) were largest and most common in upper and middle channels, with limited involvement of deep channels...
February 15, 2018: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Massimo Vergassola, Victoria E Deneke, Stefano Di Talia
Early embryogenesis of most metazoans is characterized by rapid and synchronous cleavage divisions. Chemical waves of Cdk1 activity were previously shown to spread across Drosophila embryos, and the underlying molecular processes were dissected. Here, we present the theory of the physical mechanisms that control Cdk1 waves in Drosophila The in vivo dynamics of Cdk1 are captured by a transiently bistable reaction-diffusion model, where time-dependent reaction terms account for the growing level of cyclins and Cdk1 activation across the cell cycle...
February 15, 2018: Proceedings of the National Academy of Sciences of the United States of America
Jian Wei, Qian Zhang, Lili Zhao, Zhengbo Nie, Lei Hao
The uniform ultra-long SiC nanowires (SiCNWs) were incorporated into the epoxy matrix to characterize the morphology effect on their electromagnetic wave absorption performance. The ultra-long SiCNWs with lengths of hundreds of micrometers were fabricated by chemical vapor deposition technique at 1250 °C, and have diameters of 10-60 nm with uniform morphologies. The microwave absorption performance of SiCNW/epoxy resin composites was investigated in the range of 8-18 GHz. Significant absorbing properties were discovered in the composites at frequencies of 8-12...
February 1, 2018: Journal of Nanoscience and Nanotechnology
Jia-Bin You, Wanli Yang
The thermodynamic quantities which are related to energy-level statistics are used to characterize the real-space topology of the Rice-Mele model. Through studying the energy spectrum of the model under different boundary conditions, we found that the non-normalizable wave function for the infinite domain is reduced to the edge state adhered to the boundary. For the finite domain with symmetric boundary condition, the critical point for the topological phase transition is equal to the inverse of the domain length...
January 2018: Physical Review. E
Qianru Yang, Linling Qin, Guoyang Cao, Cheng Zhang, Xiaofeng Li
We propose a graphene-coated photonic system with the excitation of Bloch surface waves (BSWs) for refractive index sensing. Through manipulation of the BSW resonance in the truncated photonic crystal under a Kretschmann configuration, the absorption in a graphene monolayer is significantly enhanced, assisted by the strong electromagnetic confinement of BSWs. The sharp and low reflectivity dip and the strong wave-environment interaction enable highly sensitive optical sensing. First-order perturbation theory and transfer-matrix calculation indicate that the system sensitivity is strongly related to the ratio of the electric field energy in the detection area, operation wavelength, and incident angle...
February 15, 2018: Optics Letters
Zhijie Ma, Stephen M Hanham, Yandong Gong, Minghui Hong
We present an all-dielectric metasurface that simultaneously supports electric and magnetic dipole resonances for orthogonal polarizations. At resonances, the metasurface reflects the incident light with nearly perfect efficiency and provides a phase difference of π in the two axes, making a low-loss half-wave plate in reflection mode. The polarization handedness of the incident circularly polarized light is preserved after reflection; this is different from either a pure electric mirror or magnetic mirror...
February 15, 2018: Optics Letters
Michael Everett Rule, Carlos E Vargas-Irwin, John P Donoghue, Wilson Truccolo
Previous studies on the origin and properties of spatial patterns in motor cortex beta local field potential (β-LFP) oscillations have focused on planar traveling waves. However, it is unclear (a) whether β-LFP waves are limited to plane waves, or even (b) whether they are propagating waves of excito-excitatory activity, i.e. primarily traveling waves in excitable media; they could reflect, instead, reorganization in the relative phases of transient oscillations at different spatial sites. We addressed these two problems in β-LFPs recorded via microelectrode arrays implanted in three adjacent motor-cortex areas of non-human primates during steady-state movement preparation...
February 14, 2018: Journal of Neurophysiology
Jerzy Wójtowicz, Aleksandra Łempicka, Włodzimierz Łuczyński, Wojciech Szczepański, Aleksandra Zomerfeld, Kornel Semeran, Artur Bossowski
BACKGROUND: A non-invasive estimation of central aortic pressure and echocardiographic parameters, and appropriate interpretation thereof make it possible to determine the status of the vascular wall and myocardium. These parameters are early markers of unfavorable remodeling of the cardiovascular system. OBJECTIVES: The aim of this study was to analyze the central aortic pressure and echocardiographic parameters of overweight/obese children (with or without concomitant arterial hypertension)...
December 2017: Advances in Clinical and Experimental Medicine: Official Organ Wroclaw Medical University
Tuomas V Kenttä, Moritz F Sinner, Bruce D Nearing, Rebecca Freudling, Kimmo Porthan, Jani T Tikkanen, Martina Müller-Nurasyid, Katharina Schramm, Matti Viitasalo, Antti Jula, Markku S Nieminen, Annette Peters, Veikko Salomaa, Lasse Oikarinen, Richard L Verrier, Stefan Kääb, M Juhani Junttila, Heikki V Huikuri
BACKGROUND: We developed a novel electrocardiographic marker, T-wave area dispersion (TW-Ad), which measures repolarization heterogeneity by assessing interlead T-wave areas during a single cardiac cycle and tested whether it can identify patients at risk for sudden cardiac death (SCD) in the general population. METHODS AND RESULTS: TW-Ad was measured from standard digital 12-lead ECG in 5618 adults (46% men; age, 50.9±12.5 years) participating in the Health 2000 Study-an epidemiological survey representative of the Finnish adult population...
February 2018: Circulation. Arrhythmia and Electrophysiology
Paula Byrne, John Cullinan, Catríona Murphy, Susan M Smith
OBJECTIVE: To describe the prevalence of statin utilisation by people aged over 50 years in Ireland and the factors associated with the likelihood of using a statin, focusing particularly on those using statins for primary prevention of cardiovascular disease (CVD). METHODS: This is a cross-sectional analysis of cardiovascular risk and sociodemographic factors associated with statin utilisation from wave 1 of The Irish Longitudinal Study on Ageing. A hierarchy of indications for statin utilisation, consisting of eight mutually exclusive levels of CVD-related diagnoses, was created...
February 8, 2018: BMJ Open
Yoshie Nogami, Yoshihiro Seo, Masayoshi Yamamoto, Tomoko Ishizu, Kazutaka Aonuma
Wave intensity (WI) is a novel noninvasive index of circulatory dynamics that reflects ventriculo-arterial coupling. It is calculated as the product of the first derivative of blood pressure and that of flow velocity measured by carotid echocardiography. This study aimed to clarify the clinical implications of WI and its relation with carbon dioxide production (VE/VCO 2 slope). Twenty-one healthy volunteers (control group) and 21 patients with hypertension (HT group) underwent cardiopulmonary exercise testing (CPX) and exercise stress echocardiography...
February 12, 2018: Heart and Vessels
S Frecentese, L P Argani, A B Movchan, N V Movchan, G Carta, M L Wall
This paper focuses on the modelling of fluid-structure interaction and wave propagation problems in a stented artery. Reflection of waves in blood vessels is well documented in the literature, but it has always been linked to a strong variation in geometry, such as the branching of vessels. The aim of this work is to detect the possibility of wave reflection in a stented artery due to the repetitive pattern of the stents. The investigation of wave propagation and possible blockages under time-harmonic conditions is complemented with numerical simulations in the transient regime...
January 2018: Proceedings. Mathematical, Physical, and Engineering Sciences
Fernando Suarez Sipmann, Arnoldo Santos, Gerardo Tusman
Acute respiratory distress syndrome (ARDS) is the most severe form of acute respiratory failure characterized by diffuse alveolar and endothelial damage. The severe pathophysiological changes in lung parenchyma and pulmonary circulation together with the effects of positive pressure ventilation profoundly affect heart lung interactions in ARDS. The term pulmonary vascular dysfunction (PVD) refers to the specific involvement of the vascular compartment in ARDS and is expressed clinically by an increase in pulmonary arterial (PA) pressure and pulmonary vascular resistance both affecting right ventricular (RV) afterload...
January 2018: Annals of Translational Medicine
Vadim M Uritsky, Merrill A Roberts, C Richard DeVore, Judith T Karpen
Extreme-ultraviolet and X-ray jets occur frequently in magnetically open coronal holes on the Sun, especially at high solar latitudes. Some of these jets are observed by white-light coronagraphs as they propagate through the outer corona toward the inner heliosphere, and it has been proposed that they give rise to microstreams and torsional Alfvén waves detected in situ in the solar wind. To predict and understand the signatures of coronal-hole jets, we have performed a detailed statistical analysis of such a jet simulated with an adaptively refined magnetohydrodynamics model...
March 10, 2017: Astrophysical Journal
L Chiva, J I Pagán, I López, A J Tenza-Abril, L Aragonés, I Sánchez
Actions taken to prevent or reduce coastal erosion often do not have the desired effect, leading to major problems instead of solving the original one. This research focuses on why a nourished beach- with borrowed sand and 0.05% of particles <0.063 mm- causes the presence of suspended particles that are observed by beach users as turbidity. This means that the colour of the water was not its characteristic blue, even with calm wave conditions. This research involved a shoreline evolution analysis and a sedimentological study of the sand from 1977 to 2017...
February 8, 2018: Science of the Total Environment
Stjepana Kovac, Erwin-Josef Speckmann, Ali Gorji
Brain direct current (DC) potentials denote sustained shifts and slow deflections of cerebral potentials superimposed with conventional EEG waves and reflect alterations in the excitation level of the cerebral cortex and subcortical structures. Using galvanometers, such sustained displacement of the EEG baseline was recorded in the early days of electroencephalography. To stabilize the EEG baseline and eliminate artefacts, EEG was performed later by voltage amplifiers with high-pass filters that dismiss slow DC potentials...
February 8, 2018: Progress in Neurobiology
Bianca Borchert-Mörlins, Nima Memaran, Martin Sauer, Britta Maecker-Kolhoff, Karl-Walter Sykora, Ricarda Blöte, Elena Bauer, Bernhard M W Schmidt, Anette Melk, Rita Beier
Advances in allogeneic hematopoietic stem cell transplantation (HSCT) in malignant and non-malignant diseases result in more long-term survivors, in whom cardiovascular (CV) disease is one leading non-cancer cause of death. This study aimed to evaluate risk factors and subclinical CV organ damage in survivors after HSCT in pediatric age. We enrolled 64 children in a cross-sectional approach 3.3 ± 3.1 years after HSCT. Anthropometric data, laboratory values, office and 24-h ambulatory blood pressure monitoring (ABPM) were evaluated, showing a high prevalence of obesity, hypertension and dyslipidemia...
February 9, 2018: Bone Marrow Transplantation
Jiajia Li, Leiyu Shi, Hailun Liang, Gan Ding, Lingzhong Xu
BACKGROUND: Despite economic growth and improved health outcomes over the past few decades, China still experiences striking urban-rural health inequalities. Urban and rural residents distinguished by the hukou system may experience profound disparities because of institutional effect. The aim of this study is to estimate trends in urban-rural disparities in self-care, outpatient care, and inpatient care utilization from a perspective of the hukou system. METHODS: Data were extracted from the seven latest waves of the China Health and Nutrition Survey (CHNS)...
February 9, 2018: BMC Health Services Research
Zhihui Zeng, Changxian Wang, Youfang Zhang, Peiyu Wang, Seyed Ismail Seyed Shahabadi, Yongmao Pei, Mingji Chen, Xuehong Lu
Ultralight and highly elastic reduced graphene oxide (RGO)/lignin-derived carbon (LDC) composite aerogels with aligned micron-sized pores and cell walls are prepared using a facile freeze-drying method. The presence of a small fraction of LDC in the cell walls enhances the interfacial polarization effect while almost maintaining the amount of charge carriers and conductivity of the cell walls, greatly boosting wave absorption capability of the cell walls. RGO/LDC aerogels also show a greater number of large cell walls with better integrity than RGO aerogels, further improving the multiple reflection ability of the aligned cell walls...
February 9, 2018: ACS Applied Materials & Interfaces
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