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phase coherence

Kaveh Gharavi, Gregory W Holloway, Ray R LaPierre, Jonathan Baugh
The superconducting proximity effect is probed experimentally in Josephson junctions fabricated with InAs nanowires contacted by Nb leads. Contact transparencies [Formula: see text] are observed. The electronic phase coherence length at low temperatures exceeds the channel length. However, the elastic scattering length is a few times shorter than the channel length. Electrical measurements reveal two regimes of quantum transport: (i) the Josephson regime, characterised by a dissipationless current up to ∼100 nA, and (ii) the quantum dot (QD) regime, characterised by the formation of Andreev bound states (ABS) associated with spontaneous QDs inside the nanowire channel...
January 20, 2017: Nanotechnology
Jingjiang Xu, Shaozhen Song, Wei Wei, Ruikang K Wang
Wide-field vascular visualization in bulk tissue that is of uneven surface is challenging due to the relatively short ranging distance and significant sensitivity fall-off for most current optical coherence tomography angiography (OCTA) systems. We report a long ranging and ultra-wide-field OCTA (UW-OCTA) system based on an akinetic swept laser. The narrow instantaneous linewidth of the swept source with its high phase stability, combined with high-speed detection in the system enable us to achieve long ranging (up to 46 mm) and almost negligible system sensitivity fall-off...
January 1, 2017: Biomedical Optics Express
Li Huang, Yanfang Zhang, Yu-Yang Zhang, Wenyan Xu, Yande Que, En Li, Jinbo Pan, Yeliang Wang, Yunqi Liu, Shixuan Du, Sokrates T Pantelides, Hong-Jun Gao
Silicon-based two-dimensional (2D) materials are uniquely suited for integration in Si-based electronics. Silicene, an analog of graphene, was recently fabricated on several substrates and was used to make a field-effect transistor. Here, we report that, when Ru(0001) is used as a substrate, a range of distinct monolayer silicon structures forms, evolving towards silicene with increasing Si coverage. Low Si coverage produces a herringbone structure, a hitherto undiscovered 2D phase of silicon. With increasing Si coverage, herringbone elbows evolve into silicene-like honeycomb stripes under tension, resulting in a herringbone-honeycomb 2D superlattice...
January 18, 2017: Nano Letters
Bason Clancy, Joshua Salafsky
Second Harmonic Generation (SHG) has emerged as a highly sensitive probe of protein conformation. SHG can also be used to determine the tilt angle of an SHG-active moiety bound to a surface-adsorbed protein through polarization-dependent measurements. However, due to the coherent nature of SHG, interference occurs between the SHG produced by the SHG-active moieties and background sources at a solid-liquid interface, obscuring the signal of interest. In order to separate the protein-specific signal from the background signal, the phase difference between these two different sources of SHG must be determined...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
Tomoya Horide, Fumitake Kametani, Satoru Yoshioka, Takanori Kitamura, Kaname Matsumoto
Intriguing properties of self-organized nanocomposites of perovskite oxides are usually derived from the complex interface of constituent material phases. A sophisticated control of such a system is required for a broad range of energy and device applications, which demand a comprehensive understanding of the interface at the atomic scale. Here, we visualized and theoretically modeled the highly elastically strained nanorod, the interface region with misfit dislocations and heterointerface distortion, and the matrix with strain-induced oxygen vacancies in the self-organized YBa2Cu3O7-δ nanocomposite films with Ba perovskite nanorods...
January 17, 2017: ACS Nano
D Choudhuri, R Banerjee, S G Srinivasan
The extraordinary creep-resistance of Mg-Nd-based alloys can be correlated to the formation of nanoscale-platelets of β1-Mg3Nd precipitates, that grow along 〈110〉Mg in bulk hcp-Mg and on dislocation lines. The growth kinetics of β1 is sluggish even at high temperatures, and presumably occurs via vacancy migration. However, the rationale for the high-temperature stability of precipitate-matrix interfaces and observed growth direction is unknown, and may likely be related to the interfacial structure and excess energy...
January 17, 2017: Scientific Reports
A Ulvestad, M J Welland, W Cha, Y Liu, J W Kim, R Harder, E Maxey, J N Clark, M J Highland, H You, P Zapol, S O Hruszkewycz, G B Stephenson
Crystallographic imperfections significantly alter material properties and their response to external stimuli, including solute-induced phase transformations. Despite recent progress in imaging defects using electron and X-ray techniques, in situ three-dimensional imaging of defect dynamics remains challenging. Here, we use Bragg coherent diffractive imaging to image defects during the hydriding phase transformation of palladium nanocrystals. During constant-pressure experiments we observe that the phase transformation begins after dislocation nucleation close to the phase boundary in particles larger than 300 nm...
January 16, 2017: Nature Materials
H Chu, L Zhao, A de la Torre, T Hogan, S D Wilson, D Hsieh
Layered perovskite iridates realize a rare class of Mott insulators that are predicted to be strongly spin-orbit coupled analogues of the parent state of cuprate high-temperature superconductors. Recent discoveries of pseudogap, magnetic multipolar ordered and possible d-wave superconducting phases in doped Sr2IrO4 have reinforced this analogy among the single layer variants. However, unlike the bilayer cuprates, no electronic instabilities have been reported in the doped bilayer iridate Sr3Ir2O7. Here we show that Sr3Ir2O7 realizes a weak Mott state with no cuprate analogue by using ultrafast time-resolved optical reflectivity to uncover an intimate connection between its insulating gap and antiferromagnetism...
January 16, 2017: Nature Materials
Miriam Ben-Hamo, Tracy A Larson, Leanne S Duge, Carl Sikkema, Charles W Wilkinson, Horacio O de la Iglesia, Mónica M C González
In mammals, a master circadian clock within the suprachiasmatic nucleus (SCN) of the hypothalamus maintains the phase coherence among a wide array of behavioral and physiological circadian rhythms. Affective disorders are typically associated with disruption of this fine-tuned "internal synchronization," but whether this internal misalignment is part of the physiopathology of mood disorders is not clear. To date, depressive-like behavior in animal models has been induced by methods that fail to specifically target the SCN regulation of internal synchronization as the mode to generate depression...
November 2016: ENeuro
Sandeep Mavadia, Virginia Frey, Jarrah Sastrawan, Stephen Dona, Michael J Biercuk
The wide-ranging adoption of quantum technologies requires practical, high-performance advances in our ability to maintain quantum coherence while facing the challenge of state collapse under measurement. Here we use techniques from control theory and machine learning to predict the future evolution of a qubit's state; we deploy this information to suppress stochastic, semiclassical decoherence, even when access to measurements is limited. First, we implement a time-division multiplexed approach, interleaving measurement periods with periods of unsupervised but stabilised operation during which qubits are available, for example, in quantum information experiments...
January 16, 2017: Nature Communications
Jonathan M Austyn
The aim of this review is to provide a coherent framework for understanding dendritic cells (DCs). It has seven sections. The introduction provides an overview of the immune system and essential concepts, particularly for the nonspecialist reader. Next, the "History" section outlines the early evolution of ideas about DCs and highlights some sources of confusion that still exist today. The "Lineages" section then focuses on five different populations of DCs: two subsets of "classical" DCs, plasmacytoid DCs, monocyte-derived DCs, and Langerhans cells...
December 2016: Microbiology Spectrum
Liwei Xu, Bitian Wang, Gongcheng Xu, Wei Wang, Zhian Liu, Zengyong Li
Noninvasive and accurate assessment of driving fatigue in relation to brain activity during long-term driving can contribute to traffic safety and accident prevention. This study evaluated functional connectivity (FC) in relevant brain regions. Synergistic mechanisms in different brain regions were detected by a novel simulator, which combined semi-immersive virtual reality technology and functional near-infrared spectroscopy. Each subject was instructed to complete driving tasks coupled with a mental calculation task...
January 10, 2017: Neuroscience Letters
Aniceto Belmonte
Field conjugation arrays use adaptive combining techniques on multi-aperture receivers to improve the performance of coherent laser communication links by mitigating the consequences of atmospheric turbulence on the down-converted coherent power. However, this motivates the use of complex receivers as optical signals collected by different apertures need to be adaptively processed, co-phased, and scaled before they are combined. Here, we show that multiple apertures, coupled with optical delay lines, combine retarded versions of a signal at a single coherent receiver, which uses digital equalization to obtain diversity gain against atmospheric fading...
January 15, 2017: Optics Letters
Pascal Picart, Silvio Montresor, Oleksandr Sakharuk, Leonid Muravsky
This Letter presents an alternative approach for image refocusing in digital Fresnel holography. In the literature, a large majority of reported focus detection criteria is based on amplitude contrast or phase contrast. We propose a focus detection criterion based on the speckle phase coherence factor. This factor reaches its maximum value at the best focus distance. At any reconstruction distance, estimation of the coherence factor is based on robust noise estimation from anisotropic diffusion. We propose a theoretical relation to estimate the coherence factor from the measured standard deviation...
January 15, 2017: Optics Letters
UnChul Park, In Hwan Cho, Sang Woong Moon, Hyeong Gon Yu
PURPOSE: To evaluate long-term changes of subfoveal choroidal thickness (SCT) in Behçet's disease (BD) patients with posterior uveitis. METHODS: Changes in SCT measured with enhanced depth imaging optical coherence tomography during quiescent phase were assessed during >24 months in 63 BD patients and control group. RESULTS: Baseline characteristics showed no difference, but the BD group showed poorer visual acuity (p = 0.013) and smaller SCT (p = 0...
January 12, 2017: Ocular Immunology and Inflammation
Christopher Habbel, Holger Hetterich, Marian Willner, Julia Herzen, Kristin Steigerwald, Sigrid Auweter, Ulrich Schüller, Jörg Hausleiter, Steffen Massberg, Maximilian Reiser, Franz Pfeiffer, Tobias Saam, Fabian Bamberg
OBJECTIVES: The aim of this study was to determine the diagnostic accuracy of grating-based phase-contrast computed tomography (gb-PCCT) to classify and quantify coronary vessel characteristics in comparison with optical coherence tomography (OCT) and histopathology in an ex vivo setting. MATERIALS AND METHODS: After excision from 5 heart specimens, 15 human coronary arteries underwent gb-PCCT examination using an experimental imaging setup consisting of a rotating molybdenum anode x-ray tube, a Talbot-Lau grating interferometer, and a single photon counting detector...
January 10, 2017: Investigative Radiology
Jeremy B Clark, Florent Lecocq, Raymond W Simmonds, José Aumentado, John D Teufel
Quantum fluctuations of the electromagnetic vacuum produce measurable physical effects such as Casimir forces and the Lamb shift. They also impose an observable limit-known as the quantum backaction limit-on the lowest temperatures that can be reached using conventional laser cooling techniques. As laser cooling experiments continue to bring massive mechanical systems to unprecedentedly low temperatures, this seemingly fundamental limit is increasingly important in the laboratory. Fortunately, vacuum fluctuations are not immutable and can be 'squeezed', reducing amplitude fluctuations at the expense of phase fluctuations...
January 11, 2017: Nature
A M R V L Monteiro, D J Groenendijk, N Manca, E Mulazimoglu, S Goswami, Ya Blanter, L M K Vandersypen, A D Caviglia
Novel physical phenomena arising at the interface of complex oxide heterostructures offer exciting opportunities for the development of future electronic devices. Using the prototypical LaAlO3/SrTiO3 interface as a model system, we employ a single-step lithographic process to realize gate-tunable Josephson junctions through a combination of lateral confinement and local side gating. The action of the side gates is found to be comparable to that of a local back gate, constituting a robust and efficient way to control the properties of the interface at the nanoscale...
January 19, 2017: Nano Letters
Daniel Velazquez-Villoria, Pablo Marti Rodrigo, Maria L DeNicola, Miguel A Zapata Vitori, Antonio Segura García, Jose García-Arumí
PURPOSE: To report a case of hypertensive choroidopathy with detailed chorioretinal images obtained using swept source optical coherence tomography. METHODS: We report the case of a 36-year-old pregnant woman who presented with extensive bilateral exudative retinal detachments (visual acuity of hands movement bilaterally), high blood pressure, and severe alteration of the laboratory test results resulting in the diagnosis of HELLP syndrome. The baby was delivered by emergency cesarean section and the patient was hospitalized in the intensive care unit...
January 6, 2017: Retinal Cases & Brief Reports
G Lantz, B Mansart, D Grieger, D Boschetto, N Nilforoushan, E Papalazarou, N Moisan, L Perfetti, V L R Jacques, D Le Bolloc'h, C Laulhé, S Ravy, J-P Rueff, T E Glover, M P Hertlein, Z Hussain, S Song, M Chollet, M Fabrizio, M Marsi
The study of photoexcited strongly correlated materials is attracting growing interest since their rich phase diagram often translates into an equally rich out-of-equilibrium behaviour. With femtosecond optical pulses, electronic and lattice degrees of freedom can be transiently decoupled, giving the opportunity of stabilizing new states inaccessible by quasi-adiabatic pathways. Here we show that the prototype Mott-Hubbard material V2O3 presents a transient non-thermal phase developing immediately after ultrafast photoexcitation and lasting few picoseconds...
January 9, 2017: Nature Communications
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