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Sunggu Yang, Mariton D Santos, Cha-Min Tang, Jae Geun Kim, Sungchil Yang
Synaptic plasticity is a fundamental component of information processing in the brain. Presynaptic facilitation in response to repetitive stimuli, often referred to as paired-pulse facilitation (PPF), is a dominant form of short-term synaptic plasticity. Recently, an additional cellular mechanism for short-term facilitation, short-term postsynaptic plasticity (STPP), has been proposed. While a dendritic mechanism was described in hippocampus, its expression has not yet been demonstrated at the levels of the spine...
2016: Frontiers in Cellular Neuroscience
Azadeh Akhtari-Zavareh, Marc De Graef, Karen L Kavanagh
A new analytical model is developed for the magnetic phase shift of uniformly magnetized nanowires with ideal cylindrical geometry. The model is applied to experimental data from off-axis electron holography measurements of the phase shift of CoFeB nanowires, and the saturation induction of a selected wire, as well as its radius, aspect ratio, position and orientation, is determined by fitting the model parameters. The saturation induction value of 1.7T of the CoFeB nanowire is found to be similar, to be within the measurement error, to values reported in the literature...
October 4, 2016: Ultramicroscopy
Yangbo Xie, Chen Shen, Wenqi Wang, Junfei Li, Dingjie Suo, Bogdan-Ioan Popa, Yun Jing, Steven A Cummer
Acoustic holographic rendering in complete analogy with optical holography are useful for various applications, ranging from multi-focal lensing, multiplexed sensing and synthesizing three-dimensional complex sound fields. Conventional approaches rely on a large number of active transducers and phase shifting circuits. In this paper we show that by using passive metamaterials as subwavelength pixels, holographic rendering can be achieved without cumbersome circuitry and with only a single transducer, thus significantly reducing system complexity...
October 14, 2016: Scientific Reports
Akihiro Suzuki, Kei Shimomura, Makoto Hirose, Nicolas Burdet, Yukio Takahashi
The phase shift of light or electrons in objects is now necessary for probing weak-phase objects such as unstained biological specimens. Optical microscopy (OM) and transmission electron microscopy (TEM) have been used to observe weak-phase objects. However, conventional OM has low spatial resolution and TEM is limited to thin specimens. Here, we report on the development of dark-field X-ray ptychography, which combines X-ray ptychography and X-ray in-line holography, to observe weak-phase objects with a phase resolution better than 0...
October 13, 2016: Scientific Reports
Kazuo Yamamoto, Yasutoshi Iriyama, Tsukasa Hirayama
All-solid-state Li-ion batteries having incombustible solid electrolytes are promising energy storage devices because they have significant advantages in terms of safety, lifetime and energy density. Electrochemical reactions, namely, Li-ion insertion/extraction reactions, commonly occur around the nanometer-scale interfaces between the electrodes and solid electrolytes. Thus, transmission electron microscopy (TEM) is an appropriate technique to directly observe such reactions, providing important information for understanding the fundamental solid-state electrochemistry and improving battery performance...
October 12, 2016: Microscopy
Anouar Rahmouni, Yahya Bougdid, Sara Moujdi, Dmitry V Nesterenko, Zouheir Sekkat
Holographic storage is one of the most important applications in the field of optics, especially for recording and retrieving data, and information storage by interference patterns in photosensitive materials are no exception in this regard. In this work, we give evidence that holograms recorded by interference of two-coherent laser beams in azo dye doped polymer films can be controlled by a third incoherent assisting laser beam. We show that light diffraction can be increased or decreased by an assisting beam depending on the respective orientation of the polarizations of the recording and the assisting beams...
October 11, 2016: Journal of Physical Chemistry. B
Alborz Feizi, Yibo Zhang, Alon Greenbaum, Alex Guziak, Michelle Luong, Raymond Yan Lok Chan, Brandon Berg, Haydar Ozkan, Wei Luo, Michael Wu, Yichen Wu, Aydogan Ozcan
Monitoring yeast cell viability and concentration is important in brewing, baking and biofuel production. However, existing methods of measuring viability and concentration are relatively bulky, tedious and expensive. Here we demonstrate a compact and cost-effective automatic yeast analysis platform (AYAP), which can rapidly measure cell concentration and viability. AYAP is based on digital in-line holography and on-chip microscopy and rapidly images a large field-of-view of 22.5 mm(2). This lens-free microscope weighs 70 g and utilizes a partially-coherent illumination source and an opto-electronic image sensor chip...
September 30, 2016: Lab on a Chip
P W M Tsang, T-C Poon, J-P Liu, T Kim, Y S Kim
In this paper we report a low complexity compression method that is suitable for compact optical scanning holography (OSH) systems with different optical settings. Our proposed method can be divided into 2 major parts. First, an automatic decision maker is applied to select the rows of holographic pixels to be scanned. This process enhances the speed of acquiring a hologram, and also lowers the data rate. Second, each row of down-sampled pixels is converted into a one-bit representation with delta modulation (DM)...
October 6, 2016: Scientific Reports
Maria Antonietta Ferrara, Edoardo De Tommasi, Giuseppe Coppola, Luca De Stefano, Ilaria Rea, Principia Dardano
The frustule of diatoms, unicellular microalgae, shows very interesting photonic features, generally related to its complicated and quasi-periodic micro- and nano-structure. In order to simulate light propagation inside and through this natural structure, it is important to develop three-dimensional (3D) models for synthetic replica with high spatial resolution. In this paper, we present a new method that generates images of microscopic diatoms with high definition, by merging scanning electron microscopy and digital holography microscopy or atomic force microscopy data...
2016: International Journal of Molecular Sciences
Luis Alfredo Rodríguez, Cristina Bran, David Reyes, Eider Berganza, Manuel Vázquez, Christophe Gatel, Etienne Snoeck, Agustina Asenjo
The comprehension of the magnetic configuration in FeCoCu nanowires with a diameter-modulated cylindrical geometry will allow controlling the domain wall motion in this low-dimensional system under the application of magnetic fields and/or the injection of current pulses. Here we perform a quantitative magnetic characterization of isolated diameter-modulated FeCoCu nanowires by combining nanoscale magnetic characterization techniques such as electron holography, magnetic force microscopy, and micromagnetic simulations...
October 6, 2016: ACS Nano
Nicholas Hoai Nam Nguyen
PURPOSE: To evaluate the performance of a holographic logMAR chart for the subjective spherical refraction of the human eye. METHODS: Bland-Altman analysis was used to assess the level of agreement between subjective spherical refraction using the holographic logMAR chart and conventional autorefraction and subjective spherical refraction. RESULTS: The 95% limits of agreement (LoA) were calculated between holographic refraction and the two standard methods (subjective and autorefraction)...
October 2016: Optometry and Vision Science: Official Publication of the American Academy of Optometry
Dilband Muhammad, Cuong M Nguyen, Jihoon Lee, Hyuk-Sang Kwon
We present a spatially incoherent dual path Fourier holographic system. Conceptually it is similar to Fourier incoherent single channel holography (FISCH). Although our incoherent off-axis Fourier holographic (IOFH) system does not have the robustness of a single channel system, it has three advantages over FISCH, with two being quite obvious from setup. First, no SLM is required, thus making the system simple and cost-effective. Second, it is capable of high light throughput because in FISCH, the use of SLM reduces light intensity in half by splitting one beam into two; furthermore, an analyzer is required to create interference which also reduces light intensity...
September 19, 2016: Optics Express
I S Wahyutama, G K Tadesse, A Tünnermann, J Limpert, J Rothhardt
Lensless coherent diffractive imaging usually requires iterative phase-retrieval for recovering the missing phase information. Holographic techniques, such as Fourier-transform holography (FTH) or holography with extended references (HERALDO), directly provide this phase information and thus allow for a direct non-iterative reconstruction of the sample. In this paper, we analyze the effect of detector noise on the reconstruction for FTH and HERALDO with linear and rectangular references. We find that HERALDO is more sensitive to this type of noise than FTH, especially if rectangular references are employed...
September 19, 2016: Optics Express
Kristan Jensen
We revisit two-dimensional holography with the Sachdev-Ye-Kitaev models in mind. Our main result is to rewrite a generic theory of gravity near a two-dimensional anti-de Sitter spacetime throat as a novel hydrodynamics coupled to the correlation functions of a conformal quantum mechanics. This gives a prescription for the computation of n-point functions in the dual quantum mechanics. We thereby find that the dual is maximally chaotic.
September 9, 2016: Physical Review Letters
Elsa S R Fonseca, Paulo T Fiadeiro, Manuela Pereira, António Pinheiro
Numerical reconstruction of digital holograms relies on a precise knowledge of the original object position. However, there are a number of relevant applications where this parameter is not known in advance and an efficient autofocusing method is required. This paper addresses the problem of finding optimal focusing methods for use in reconstruction of digital holograms of macroscopic amplitude and phase objects, using digital in-line phase-shifting holography in transmission mode. Fifteen autofocus measures, including spatial-, spectral-, and sparsity-based methods, were evaluated for both synthetic and experimental holograms...
September 20, 2016: Applied Optics
Staffan Tjörnhammar, Finn Klemming Eklöf, Zhangwei Yu, Davood Khodadad, Emil Hällstig, Mikael Sjödahl, Fredrik Laurell
In this paper, we present a tailored multiwavelength Yb-fiber laser source in the 1.03 μm spectral region for spatially multiplexed digital holographic acquisitions. The wavelengths with bandwidths below 0.1 nm were spectrally separated by approximately 1 nm by employing fiber Bragg gratings for spectral control. As a proof of concept, the shape of a cylindrically shaped object with a diameter of 48 mm was measured. The holographic acquisition was performed in single-shot dual-wavelength mode with a synthetic wavelength of 1...
September 20, 2016: Applied Optics
Johan Öhman, Mikael Sjödahl
Poor axial resolution in holographic particle imaging applications makes particle positioning in 3D space more complex since the positions are not directly obtained. In this paper we estimate the axial position of micrometer particles by finding the location where the wavefront curvature from the scattered light becomes zero. By recording scattered light at 90° using off-axis holography, the complex amplitude of the light is obtained. By reconstruction of the imaged scene, a complex valued volume is produced...
September 20, 2016: Applied Optics
Nahid Talebi
Interference patterns are not only a defining characteristic of waves, but also have several applications; characterization of coherent processes and holography. Spatial holography with electron waves, has paved the way towards space-resolved characterization of magnetic domains and electrostatic potentials with angstrom spatial resolution. Another impetus in electron microscopy has been introduced by ultrafast electron microscopy which uses pulses of sub-picosecond durations for probing a laser induced excitation of the sample...
2016: Scientific Reports
Vadim Migunov, Christian Dwyer, Chris B Boothroyd, Giulio Pozzi, Rafal E Dunin-Borkowski
The technique of double exposure electron holography, which is based on the superposition of two off-axis electron holograms, was originally introduced before the availability of digital image processing to allow differences between electron-optical phases encoded in two electron holograms to be visualised directly without the need for holographic reconstruction. Here, we review the original method and show how it can now be extended to permit quantitative studies of phase shifts that oscillate in time. We begin with a description of the theory of off-axis electron hologram formation for a time-dependent electron wave that results from the excitation of a specimen using an external stimulus with a square, sinusoidal, triangular or other temporal dependence...
August 18, 2016: Ultramicroscopy
Qiu Wang, Xueqian Zhang, Yuehong Xu, Jianqiang Gu, Yanfeng Li, Zhen Tian, Ranjan Singh, Shuang Zhang, Jiaguang Han, Weili Zhang
As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude...
2016: Scientific Reports
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