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Zhihua Xie, Yannick Lefier, Miguel Angel Suarez, Mathieu Mivelle, Roland Salut, Jean-Marc Merolla, Thierry Grosjean
Colloidal quantum dots (CQDs) have drawn strong interest in the past for their high prospects in scientific, medical, and industrial applications. However, the full characterization of these quantum emitters is currently restricted to the visible wavelengths, and it remains a key challenge to optically probe single CQDs operating in the infrared spectral domain, which is targeted by a growing number of applications. Here, we report the first experimental detection and imaging at room temperature of single infrared CQDs operating at telecommunication wavelengths...
March 24, 2017: Nano Letters
Carlos L Pérez Díaz, Jonathan Muñoz, Tarendra Lakhankar, Reza Khanbilvardi, Peter Romanov
The quantity of liquid water in the snowpack defines its wetness. The temporal evolution of snow wetness's plays a significant role in wet-snow avalanche prediction, meltwater release, and water availability estimations and assessments within a river basin. However, it remains a difficult task and a demanding issue to measure the snowpack's liquid water content (LWC) and its temporal evolution with conventional in situ techniques. We propose an approach based on the use of time-domain reflectometry (TDR) and CS650 soil water content reflectometers to measure the snowpack's LWC and temperature profiles...
March 21, 2017: Sensors
John J Mulvihill, Benjamin Capps, Yann Joly, Tamra Lysaght, Hub A E Zwart, Ruth Chadwick
Background: The avalanche of commentaries on CRISPR-Cas9 technology, a bacterial immune system modified to recognize any short DNA sequence, cut it out, and insert a new one, has rekindled hopes for gene therapy and other applications and raised criticisms of engineering genes in future generations. Sources of data: This discussion draws on articles that emphasize ethics, identified partly through PubMed and Google, 2014-2016. Areas of agreement: CRISPR-Cas9 has taken the pace and prospects for genetic discovery and applications to a high level, stoking anticipation for somatic gene engineering to help patients...
February 23, 2017: British Medical Bulletin
Miho Itoh, Timothée Leleu
Recent experiments have shown that stereotypical spatiotemporal patterns occur during brief packets of spiking activity in the cortex, and it has been suggested that top-down inputs can modulate these patterns according to the context. We propose a simple model that may explain important features of these experimental observations and is analytically tractable. The key mechanism underlying this model is that context-dependent top-down inputs can modulate the effective connection strengths between neurons because of short-term synaptic depression...
March 23, 2017: Neural Computation
Fabrizio Pittorino, Miguel Ibáñez-Berganza, Matteo di Volo, Alessandro Vezzani, Raffaella Burioni
A collective chaotic phase with power law scaling of activity events is observed in a disordered mean field network of purely excitatory leaky integrate-and-fire neurons with short-term synaptic plasticity. The dynamical phase diagram exhibits two transitions from quasisynchronous and asynchronous regimes to the nontrivial, collective, bursty regime with avalanches. In the homogeneous case without disorder, the system synchronizes and the bursty behavior is reflected into a period doubling transition to chaos for a two dimensional discrete map...
March 3, 2017: Physical Review Letters
Xavier D A Baumans, Vyacheslav S Zharinov, Eline Raymenants, Sylvain Blanco Alvarez, Jeroen E Scheerder, Jérémy Brisbois, Davide Massarotti, Roberta Caruso, Francesco Tafuri, Ewald Janssens, Victor V Moshchalkov, Joris Van de Vondel, Alejandro V Silhanek
The main dissipation mechanism in superconducting nanowires arises from phase slips. Thus far, most of the studies focus on long nanowires where coexisting events appear randomly along the nanowire. In the present work we investigate highly confined phase slips at the contact point of two superconducting leads. Profiting from the high current crowding at this spot, we are able to shrink in-situ the nanoconstriction. This procedure allows us to investigate, in the very same sample, thermally activated phase slips and the probability density function of the switching current Isw needed to trigger an avalanche of events...
March 16, 2017: Scientific Reports
M Stefanski, M Lukaszewicz, D Hreniak, W Strek
The laser induced white emission (LIWE) was observed from Eu(3+):Sr2CeO4 nanocrystals. The samples were obtained in form of powders by the modified sol-gel route. The structure and morphology of the phosphors were investigated by powder X-ray diffraction and transmission electron microscope techniques. The intense LIWE occurred under reduced pressure and focused beam of near infrared laser excitation. The power and pressure dependencies exhibit evident threshold character typical for the avalanche effect. The photoconductivity of the Eu(3+):Sr2CeO4 nanocrystals measured as a function of different powers of excitation source was analyzed...
March 14, 2017: Journal of Chemical Physics
Alexander J Klimas, Vadim M Uritsky
Scaling properties of a two-dimensional (2d) plasma physical current-sheet simulation model involving a full set of magnetohydrodynamic (MHD) equations with current-dependent resistivity are investigated. The current sheet supports a spatial magnetic field reversal that is forced through loading of magnetic flux containing plasma at boundaries of the simulation domain. A balance is reached between loading and annihilation of the magnetic flux through reconnection at the current sheet; the transport of magnetic flux from boundaries to current sheet is realized in the form of spatiotemporal avalanches exhibiting power-law statistics of lifetimes and sizes...
February 2017: Physical Review. E
S Franz, S Spigler
Disordered systems are characterized by the existence of many sample-dependent local-energy minima that cause a step-wise response when the system is perturbed. In this article we use an approach based on elementary probabilistic methods to compute the complete probability distribution of the jumps (static avalanches) in the response of mean-field systems described by replica symmetry breaking; we find a precise condition for having a power-law behavior in the distribution of avalanches caused by small perturbations, and we show that our predictions are in remarkable agreement both with previous results and with what is found in simulations of three-dimensional systems of soft spheres, either at jamming or at slightly higher densities...
February 2017: Physical Review. E
Xiuliang Chen, Chengjie Ding, Haifeng Pan, Kun Huang, Julien Laurat, Guang Wu, E Wu
We report on a high-speed temporal and spatial multiplexed single-photon counter with photon-number-resolving capability up to four photons. The infrared detector combines a fiber loop to split, delay and recombine optical pulses and a 200 MHz dual-channel single-photon detector based on InGaAs/InP avalanche photodiode. To fully characterize the photon-number-resolving capability, we perform quantum detector tomography and then reconstruct its positive-operator-valued measure and the associated Wigner functions...
March 15, 2017: Scientific Reports
Yonatan Israel, Ron Tenne, Dan Oron, Yaron Silberberg
Despite advances in low-light-level detection, single-photon methods such as photon correlation have rarely been used in the context of imaging. The few demonstrations, for example of subdiffraction-limited imaging utilizing quantum statistics of photons, have remained in the realm of proof-of-principle demonstrations. This is primarily due to a combination of low values of fill factors, quantum efficiencies, frame rates and signal-to-noise characteristic of most available single-photon sensitive imaging detectors...
March 13, 2017: Nature Communications
Ivan Michel Antolovic, Samuel Burri, Claudio Bruschini, Ron A Hoebe, Edoardo Charbon
sCMOS imagers are currently utilized (replacing EMCCD imagers) to increase the acquisition speed in super resolution localization microscopy. Single-photon avalanche diode (SPAD) imagers feature frame rates per bit depth comparable to or higher than sCMOS imagers, while generating microsecond 1-bit-frames without readout noise, thus paving the way to in-depth time-resolved image analysis. High timing resolution can also be exploited to explore fluorescent dye blinking and other photophysical properties, which can be used for dye optimization...
March 13, 2017: Scientific Reports
Ryan Warburton, Constantin Aniculaesei, Matteo Clerici, Yoann Altmann, Genevieve Gariepy, Richard McCracken, Derryck Reid, Steve McLaughlin, Marco Petrovich, John Hayes, Robert Henderson, Daniele Faccio, Jonathan Leach
Recording processes and events that occur on sub-nanosecond timescales poses a difficult challenge. Conventional ultrafast imaging techniques often rely on long data collection times, which can be due to limited device sensitivity and/or the requirement of scanning the detection system to form an image. In this work, we use a single-photon avalanche detector array camera with pico-second timing accuracy to detect photons scattered by the cladding in optical fibers. We use this method to film supercontinuum generation and track a GHz pulse train in optical fibers...
March 7, 2017: Scientific Reports
Dmitry V Denisov, Kinga A Lőrincz, Wendelin J Wright, Todd C Hufnagel, Aya Nawano, Xiaojun Gu, Jonathan T Uhl, Karin A Dahmen, Peter Schall
Slowly strained solids deform via intermittent slips that exhibit a material-independent critical size distribution. Here, by comparing two disparate systems - granular materials and bulk metallic glasses - we show evidence that not only the statistics of slips but also their dynamics are remarkably similar, i.e. independent of the microscopic details of the material. By resolving and comparing the full time evolution of avalanches in bulk metallic glasses and granular materials, we uncover a regime of universal deformation dynamics...
March 6, 2017: Scientific Reports
Christopher Van Tilburg, Colin K Grissom, Ken Zafren, Scott McIntosh, Martin I Radwin, Peter Paal, Pascal Haegeli, William Will R Smith, Albert R Wheeler, David Weber, Bruce Tremper, Hermann Brugger
To provide guidance to clinicians and avalanche professionals about best practices, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for the prevention, rescue, and medical management of avalanche and nonavalanche snow burial victims. Recommendations are graded on the basis of quality of supporting evidence according to the classification scheme of the American College of Chest Physicians.
March 2017: Wilderness & Environmental Medicine
Guy Koplovitz, Darinka Primc, Oren Ben Dor, Shira Yochelis, Dvir Rotem, Danny Porath, Yossi Paltiel
There is an increasing demand for realizing a simple Si based universal memory device working at ambient temperatures. In principle, nonvolatile magnetic memory can operate at low power consumption and high frequencies. However, in order to compete with existing memory technology, size reduction and simplification of the used material systems are essential. In this work, the chiral-induced spin selectivity effect is used along with 30-50 nm ferromagnetic nanoplatelets in order to realize a simple magnetic memory device...
March 3, 2017: Advanced Materials
Ivan Veronese, Norberto Chiodini, Simone Cialdi, Eduardo D'Ippolito, Mauro Fasoli, Salvatore Gallo, Stefano La Torre, Eleonora Mones, Anna Vedda, Gianfranco Loi
Over the years, many efforts have been done to develop radiation detectors to afford the complex issues of small field dosimetry and to fulfil the needs of increasing accuracy, precision and in-vivo dose monitoring required by the new advanced treatment modalities. In this context, a growing interest has surged in the development of sensors based on scintillating optical fibres. In this paper, the near-infrared radioluminescence and dosimetric properties of Yb-doped silica optical fibres, coupled with a laboratory prototype based on an avalanche photo-diode, were studied by irradiating the fibres with photons and electron beams generated by a Varian Trilogy accelerator...
March 2, 2017: Physics in Medicine and Biology
G Acconcia, I Labanca, I Rech, A Gulinatti, M Ghioni
The minimization of Single Photon Avalanche Diodes (SPADs) dead time is a key factor to speed up photon counting and timing measurements. We present a fully integrated Active Quenching Circuit (AQC) able to provide a count rate as high as 100 MHz with custom technology SPAD detectors. The AQC can also operate the new red enhanced SPAD and provide the timing information with a timing jitter Full Width at Half Maximum (FWHM) as low as 160 ps.
February 2017: Review of Scientific Instruments
Premkumar Leishangthem, Anshul D S Parmar, Srikanth Sastry
Amorphous solids are ubiquitous among natural and man-made materials. Often used as structural materials for their attractive mechanical properties, their utility depends critically on their response to applied stresses. Processes underlying such mechanical response, and in particular the yielding behaviour of amorphous solids, are not satisfactorily understood. Although studied extensively, observed yielding behaviour can be gradual and depend significantly on conditions of study, making it difficult to convincingly validate existing theoretical descriptions of a sharp yielding transition...
March 1, 2017: Nature Communications
Jong-Bum You, Hyeokbin Kwon, Jonghoon Kim, Hyo-Hoon Park, Kyoungsik Yu
We demonstrate silicon ridge waveguide photo-detectors capable of sub-bandgap light absorption and avalanche multiplication. The proposed waveguide photo-detectors contain highly doped PN junction, where a strong electric field can generate the photon-assisted tunneling current for sub-bandgap light incidence and amplify the generated photo-current by the avalanche multiplication effect. The voltage-dependent sub-bandgap absorption coefficient and multiplication gain are experimentally evaluated for various doping configurations to find optimal photo-response with low dark currents...
February 20, 2017: Optics Express
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