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wave reflection

Kan Wang, Gengping Wan, Guilong Wang, Zhengyi He, Shaohua Shi, Lihong Wu, Guizhen Wang
The demand for microwave absorbing materials with strong absorption capability and wide absorption band is increasing due to serious electromagnetic interference issues and defense stealth technology needs. Here the carbon-coated Fe3O4 (Fe3O4@C) yolk-shell composites were successfully synthesized in a large scale for the application of microwave absorption through an in-situ reduction process from carbon-coated γ-Fe2O3 precursor. The results show that the Fe3O4 nanoparticles are uniformly coated with a thin carbon layer about 10nm in thickness and a clear void about 1 nm in width between Fe3O4 core and carbon shell are formed due to the volume shrinkage during the reduction treatment...
October 6, 2017: Journal of Colloid and Interface Science
Thomas G Mayerhöfer, Jürgen Popp
We investigate electric field standing wave effects in the system semiinfinite incidence medium with high index of refraction/layer/vacuum, the latter being the semiinfinite exit medium. If the layer has a lower index of refraction than the incidence medium, then very strong resonances occur between the two critical angles of the system defined by the systems incidence medium/layer and incidence medium/vacuum, as the layer is then a cavity. In particular close to the lower critical angles, the evanescent fields extend strongly into the exit medium...
October 4, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Li Ling, Heather Tugaoen, Jonathon Brame, Shahnawaz Sinha, Chuanhao Li, Jared J Schoepf, Kiril Hristovski, Jae-Hong Kim, Chii Shang, Paul Westerhoff
A photocatalyst-coated optical fiber was coupled with a 318-nm ultraviolet-A light emitting diode, which activated the photocatalysts by interfacial photon-electron excitation while minimizing photonic energy losses due to conventional photocatalytic barriers. The light delivery mechanism was explored via modeling of evanescent wave energy produced upon total internal reflection and photon refraction into the TiO2 surface coating. This is the first work to explore aqueous phase LED-irradiated optical fibers for treating organic pollutants and the first to propose a dual-mechanistic approach to light delivery and photocatalytic performance...
October 13, 2017: Environmental Science & Technology
Alexander K Popov, Sergey A Myslivets
We propose metamaterial (MM) that supports a mixture of three or more normal and backward electromagnetic modes with equal co-directed phase velocities and mutually contra-directed energy fluxes. This enables extraordinary three-wave mixing, greatly enhanced optical parametric amplification, and frequency-changing generation of entangled photons in the reflection direction. Proof-of-principle numerical simulation of such processes is presented based on the particular example of the wave-guided terahertz waves contra-propagating in the MM made of carbon nanotubes...
October 15, 2017: Optics Letters
Xu A Zhang, Yi-An Chen, Abhijeet Bagal, Chih-Hao Chang
Low-index materials are key components in integrated photonics and can enhance index contrast and improve performance. Such materials can be constructed from porous materials, which generally lack mechanical strength and are difficult to integrate. Here we demonstrate enhanced total internal reflection (TIR) induced by integrating robust nanolattice materials with periodic architectures between high-index media. The transmission measurement from the multilayer stack illustrates a cutoff at about a 60° incidence angle, indicating an enhanced light trapping effect through TIR...
October 15, 2017: Optics Letters
Yasunobu Hayabuchi, Akemi Ono, Yukako Homma, Shoji Kagami
Right ventricular (RV) dysfunction is generally evaluated using analyses of tricuspid annular motion. However, it represents only one aspect of RV performance. Whether measuring pulmonary annular motion velocity could serve as a novel way to evaluate global RV and/or RV outflow tract (RVOT) performance in pediatric congenital heart disease (CHD) patients with surgically repaired RVOT was evaluated. In this prospective study, tissue Doppler-derived pulmonary annular motion velocity was measured in children (aged 2-5 years) with RVOT reconstruction (RVOTR group, n = 48) and age-matched healthy children (Control, n = 60)...
October 12, 2017: Heart and Vessels
Gerhard Schumacher, Jens J Kaden, Frederik Trinkmann
The human arterial vascular tree can be described by multi-compartment models using electrical components. Being first introduced in the 1960s by Noordergraaf and Westerhof these hardware-based approaches required several simplifications. We were able to remove the restrictions using modern software simulation tools and improve overall model quality considerably. While the original Westerhof model consisted of 121 Windkessel elements, the refined model has 711 elements and gives realistic pulse waveforms of the aorta, brachial and radial arteries with realistic blood pressures...
October 12, 2017: Journal of Applied Physiology
Loïc Berthod, Olga Shavdina, Isabelle Verrier, Thomas Kämpfe, Olivier Dellea, Francis Vocanson, Maxime Bichotte, Damien Jamon, Yves Jourlin
This paper presents substantial improvements of the colloidal photolithography technique (also called microsphere lithography) with the goal of better controlling the geometry of the fabricated nano-scale structures-in this case, hexagonally arranged nanopillars-printed in a layer of directly photopatternable sol-gel TiO₂. Firstly, to increase the achievable structure height the photosensitive layer underneath the microspheres is deposited on a reflective layer instead of the usual transparent substrate. Secondly, an increased width of the pillars is achieved by tilting the incident wave and using multiple exposures or substrate rotation, additionally allowing to better control the shape of the pillar's cross section...
October 12, 2017: Nanomaterials
Michel E Safar
In patients with uncomplicated essential hypertension, cardiac output remains within normal ranges and intravascular volume is normal or low, assuming the presence of a sufficient Windkessel effect and usual resistance and compliance calculations. However, mean circulatory pressure is elevated in these patients. In addition, vascular resistance is augmented, and most importantly, the viscoelasticity of the cardiovascular system is substantially impaired. Such considerations are essential to understanding the mechanisms behind carotid-femoral arterial stiffness, a major risk factor in individuals with hypertension...
October 12, 2017: Nature Reviews. Cardiology
Julia Ramírez, Michele Orini, Ana Mincholé, Violeta Monasterio, Iwona Cygankiewicz, Antonio Bayés de Luna, Juan Pablo Martínez, Pablo Laguna, Esther Pueyo
BACKGROUND: Sudden cardiac death (SCD) and pump failure death (PFD) are common endpoints in chronic heart failure (CHF) patients, but prevention strategies are different. Currently used tools to specifically predict these endpoints are limited. We developed risk models to specifically assess SCD and PFD risk in CHF by combining ECG markers and clinical variables. METHODS: The relation of clinical and ECG markers with SCD and PFD risk was assessed in 597 patients enrolled in the MUSIC (MUerte Súbita en Insuficiencia Cardiaca) study...
2017: PloS One
Lennart van de Velde, Daan W Eeftinck Schattenkerk, Pascale A H T Venema, Hendrik J Best, Bas van den Bogaard, Wim J Stok, Berend E Westerhof, Bert Jan H van den Born
OBJECTIVE: Augmentation index (AIx) is often used to quantify the contribution of wave reflection to central pulse pressure. Recent studies have challenged this view by showing how contractility-induced changes in the forward pressure wave can markedly impact AIx. We hypothesized that changes in preload will also affect AIx through changes in the forward wave and studied this in two experiments. METHODS: Noninvasively obtained aortic pressure was used to study central haemodynamics and wave morphology...
October 7, 2017: Journal of Hypertension
Cecilia Nakeva von Mentzer, Martina Sundström, Karin Enqvist, Mathias Hällgren
To meet the need for a linguistic speech perception test in Swedish, the 'Listen-Say test' was developed. Minimal word pairs were used as speech material to assess seven phonetic contrasts in two auditory backgrounds. In the present study, children's speech discrimination skills in quiet and in four-talker (4T) speech background were examined. Associations with lexical-access skills and academic achievement were explored. The study included 27 school children 7-9 years of age. Overall, the children discriminated phonetic contrasts well in both conditions (quiet: Mdn 95%; 4T speech; Mdn 91% correct)...
October 10, 2017: Logopedics, Phoniatrics, Vocology
Woo Jin Byun, Hyung Do Choi, Yong Heui Cho
Orbital angular momentum (OAM) mode combining and canceling in the near-field was investigated using a Cassegrain dual-reflectarray antenna composed of multiple microstrip patches on the main and sub-reflectarrays. Microstrip patches on dielectric substrates were designed to radiate the particular OAM modes for arithmetic mode combining, where two OAM wave-generating reflectarrays are very closely placed in the near-field. We conducted near-field antenna measurements at 18 [GHz] by manually replacing the sub-reflectarray substrates with different OAM mode numbers of 0, ±1, when the OAM mode number of the main reflectarray was fixed to +1...
October 9, 2017: Scientific Reports
Costas Tsioufis, Dimitrios Konstantinidis, Elias Nikolakopoulos, Evi Vemou, Theodoros Kalos, Georgios Georgiopoulos, Nikos Vogiatzakis, Aristos Ifantis, Konstantinos Konstantinou, V Gennimata, Dimitris Tousoulis
It is well known that atrial fibrillation (AF) is the most frequent cardiac arrhythmia worldwide and substantially increases the risk for thromboembolic disease. One of the main problems is that it remains undiagnosed (about 20% of all cases of AF). On the other hand, hypertension amplifies the risk for both AF occurrences through hemodynamic and non-hemodynamic mechanisms and cerebrovascular ischemia. Under this prism, prompt diagnosis of undetected AF in hypertensive patients is of pivotal importance. Biomarkers could be used in AF diagnosis as well as in predicting the transition of paroxysmal AF to sustained AF...
October 6, 2017: Current Medicinal Chemistry
Beñat Gurrutxaga-Lerma
The elastodynamic image forces acting on straight screw dislocations in the presence of planar phase boundaries are derived. Two separate dislocations are studied: (i) the injected, non-moving screw dislocation and (ii) the injected (or pre-existing), generally non-uniformly moving screw dislocation. The image forces are derived for both the case of a rigid surface and of a planar interface between two homogeneous, isotropic phases. The case of a rigid interface is shown to be solvable employing Head's image dislocation construction...
September 2017: Proceedings. Mathematical, Physical, and Engineering Sciences
Luan T Nguyen, Ryan T Modrak
Delaminations, cracks and other defects in engineered structures often lie close to the theoretical resolution limit for ultrasonic waves. While ultrasonic waveform tomography has succeeded in detecting such features, recovery is difficult because it requires computationally expensive high-frequency numerical wave simulations and an accurate understanding of large-scale background variations of the engineered structure. Without such knowledge, small defects may be incorrectly imaged or go undetected altogether...
September 21, 2017: Ultrasonics
T McNicholas, K Tobin, S O'Callaghan, R A Kenny
Introduction: atrial fibrillation (AF) and orthostatic hypotension (OH) share common risk factors such as age, hypertension and cardiovascular (CV) disease. The autonomic nervous system (ANS) also plays a role in the pathogenesis of both AF and OH. The aim of this study is to assess whether individuals with AF are more likely to have OH than those without AF. Methods: data from wave 1 of The Irish Longitudinal Study on Ageing were used. Beat-to-beat blood pressure was measured during active stand lasting 110 s...
June 15, 2017: Age and Ageing
Adrian E Bauman, Anne C Grunseit, Vegar Rangul, Berit L Heitmann
BACKGROUND: Most studies of physical activity (PA) epidemiology use behaviour measured at a single time-point. We examined whether 'PA patterns' (consistently low, consistently high or inconsistent PA levels over time) showed different epidemiological relationships for anthropometric and mortality outcomes, compared to single time-point measure of PA. METHODS: Data were the Danish MONICA (MONItoring Trends and Determinants in CArdiovascular Disease) study over three waves 1982-3 (time 1), 1987-8 (time 2) and 1993-4 (time 3)...
October 5, 2017: BMC Public Health
Angela S Koh, Fei Gao, Jin Liu, Kevin Timothy Fridianto, Jianhong Ching, Ru San Tan, Jia-Ing Wong, Serene Jm Chua, Shuang Leng, Liang Zhong, Bryan Mh Keng, Fei Qiong Huang, Jian-Min Yuan, Woon-Puay Koh, Jean-Paul Kovalik
BACKGROUND: Increasing arterial stiffness is an important contributor to declining cardiovascular health in ageing. Changes in whole-body fuel metabolism could be related to alterations in arterial stiffness in ageing adults. METHODS: Targeted high-performance liquid and gas chromatography mass spectrometry were used to measure 84 circulating metabolites in a group of community elderly adults ( n = 141, 58% men; mean age = 70.6 ± 11.2 years) without cardiovascular disease...
October 1, 2017: Diabetes & Vascular Disease Research
Mary N Woessner, Mitch D VanBruggen, Carl F Pieper, Erin K O'Reilly, William E Kraus, Jason D Allen
BACKGROUND: Peripheral artery disease (PAD) is caused by atherosclerotic occlusions in the legs. It affects approximately 8-12 million people in the United States alone, one-third of whom suffer from intermittent claudication (IC), defined as ischemic leg pain that occurs with walking and improves with rest. Patients with IC suffer a markedly impaired quality of life and a high perception of disability. Improving pain-free walking time is a primary goal of rehabilitation in this population...
October 3, 2017: JMIR Research Protocols
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