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Héctor Sánchez-Esquivel, Karen Y Raygoza-Sanchez, Raúl Rangel-Rojo, Boris Kalinic, Niccolò Michieli, Tiziana Cesca, Giovanni Mattei
In this work we present the study of the ultra-fast dynamics of the nonlinear optical response of a honeycomb array of silver triangular nanoprisms, performed using a femtosecond pulsed laser tuned with the dipolar surface plasmon resonance of the nanoarray. Nonlinear absorption and refraction, and their time-dependence, were explored using the z-scan and time-resolved excite-probe techniques. Nonlinear absorption is shown to change sign with the input irradiance and the behavior was explained on the basis of a three-level model...
March 1, 2018: Nanoscale
Shaoxiu Song, Gang Li, Xingwei Hou, Shengzhao Zhang, Yue Yu, Ling Lin
Diffuse reflectance spectroscopy (DRS) is significantly affected from the interference of the ambient light and dark current of the instrument. Optical choppers, together with lock-in/synchronous amplification, can overcome these interferences. However, in spectral measurement, the sampling rate of the spectrometer is different from the Δ-pulse sampling, which is not high enough because of the integration time. In addition, the energy distribution is not perfectly concentrated as expected in modulate chopper technology...
February 10, 2018: Applied Optics
J K Clark, K P Coffey, W K Coblentz, B C Shanks, J D Caldwell, R E Muck, D Philipp, M A Borchardt, R T Rhein, W E Jokela, E A Backes, M G Bertram, W B Smith
Dairy slurry is used commonly as an animal-sourced fertilizer in agronomic production. However, residual effects of slurry application on intake and digestibility of alfalfa (Medicago sativa L.) silage from subsequent harvests are not well known. The objective of this study was to determine if moisture concentration of alfalfa silage and timing of dairy slurry application relative to subsequent harvest affected intake and digestibility by sheep. Katahdin crossbred ewes (n = 18; 48 ± 5.3 kg) in mid-gestation were stratified by BW and allocated randomly in each of 2 periods to 1 of 6 treatments arranged in a 2 × 3 factorial arrangement...
February 1, 2018: Journal of Animal Science
Sergey L Veber, Sergey V Tumanov, Elena Yu Fursova, Oleg A Shevchenko, Yaroslav V Getmanov, Mikhail A Scheglov, Vitaly V Kubarev, Daria A Shevchenko, Iaroslav I Gorbachev, Tatiana V Salikova, Gennady N Kulipanov, Victor I Ovcharenko, Matvey V Fedin
Electron Paramagnetic Resonance (EPR) station at the Novosibirsk Free Electron Laser (NovoFEL) user facility is described. It is based on X-band (∼9 GHz) EPR spectrometer and operates in both Continuous Wave (CW) and Time-Resolved (TR) modes, each allowing detection of either direct or indirect influence of high-power NovoFEL light (THz and mid-IR) on the spin system under study. The optics components including two parabolic mirrors, shutters, optical chopper and multimodal waveguide allow the light of NovoFEL to be directly fed into the EPR resonator...
January 12, 2018: Journal of Magnetic Resonance
Andrew J Myrick, Thomas C Baker
Gas-chromatography-electroantennographic detection (GC-EAD) is a technique used in the identification of volatile organic compounds (VOCs), such as pheromones and plant host odors, which are physiologically relevant to insects. Although pheromones often elicit large EAD responses, other behaviorally relevant odors may elicit responses that are difficult to discern from noise. Lock-in amplification has long been used to reduce noise in a wide range of applications. Its utility when incorporated with GC-EAD was demonstrated previosuly by chopping (or pulsing) effluent-laden air that flowed over an insect antenna...
January 6, 2018: Journal of Chemical Ecology
Yang Zhao, Jiaxin Li, Ke Yang, Siquan Zhu
PURPOSE: To describe a manual prechop technique for splitting the nucleus of the lens using a recently developed reverse chopper. METHODS: During the process, the reverse chopper and the Nagahara chopper are placed diagonally in the peripheral area of the nucleus of the lens after capsulorhexis. The reverse chopper and the Nagahara chopper then are pushed horizontally toward each other so they meet at the center of the lens to split the nucleus of lens into 2 parts...
December 29, 2017: Journal of Investigative Surgery: the Official Journal of the Academy of Surgical Research
Rajendra Prasad, Anurag Badhani, Geetika Badhani Dogra
We describe an efficient technique, "Terminal Chop," for full thickness nuclear segmentation in mature hard cataracts. Terminal chop utilizes the principle of secondary rock breakage system with stress concentration to break these hard nuclei. In this technique consonant to drag picks, a specially designed chopper "Terminator" is used to initiate a unique dispersive mechanical force to create a full thickness nuclear crack (crack formation) at the weakest soft and thin equator, which automatically traverses through the center and to the equator on the other side...
December 2017: Indian Journal of Ophthalmology
Huijie Wang, Jing Wang, Xiangyun Ma, Wenliang Chen, Da Chen, Qifeng Li
The non-dispersive infrared (NDIR) instruments are widely applied to multicomponent gas detection in many fields. In this paper, a NDIR instrument using the galvanometer modulation is proposed, which has a common optical path for multicomponent gas detection. Compared with the conventional NDIR instrument using the chopper modulation, the proposed instrument with a simpler configuration has better detection efficiency and stability. The proposed instrument has been successfully used to measure the main gas components of vehicle emissions...
November 2017: Review of Scientific Instruments
Qianli Chen, Ahmed Elbanna
Metamaterials with acoustic and elastic band gaps are of great interest to scientists and engineers. Here, we introduce a novel mechanism for emergence of multiple band gaps with extreme attenuation by coupling continuous one-dimensional elastic structures. We show that it is possible to develop extreme attenuation at several frequencies from coupling two homogenous bars of different elastodynamic properties even though each bar individually possesses no such gaps. Moreover, if each bar is a composite on its own, multiple resonant band gaps appear in the compound system which do not exist in either bar...
November 24, 2017: Scientific Reports
Lijun Han, Steven J Lehotay, Yelena Sapozhnikova
In this study, analytical results were compared when using different approaches to bulk food sample comminution, consisting of a vertical chopper (Blixer) at room temperature and dry ice cryogenic conditions, followed by further subsample processing (20 g) using liquid nitrogen cryogenic conditions (cryomill). Analysis of the 43 targeted spiked and incurred contaminants in a food mixture consisting of equal parts orange, apple, kale, salmon, and croaker involved quick, easy, cheap, effective, rugged, and safe (QuEChERS) with automated mini-column solid-phase extraction (known as ITSP) cleanup, followed by low-pressure gas chromatography-tandem mass spectrometry (LPGC-MS/MS)...
November 28, 2017: Journal of Agricultural and Food Chemistry
Dan F M Goodman, Ian M Winter, Agnès C Léger, Alain de Cheveigné, Christian Lorenzi
The auditory system processes temporal information at multiple scales, and disruptions to this temporal processing may lead to deficits in auditory tasks such as detecting and discriminating sounds in a noisy environment. Here, a modelling approach is used to study the temporal regularity of firing by chopper cells in the ventral cochlear nucleus, in both the normal and impaired auditory system. Chopper cells, which have a strikingly regular firing response, divide into two classes, sustained and transient, based on the time course of this regularity...
September 20, 2017: Hearing Research
J L Niedziela, R Mills, M J Loguillo, H D Skorpenske, D Armitage, H L Smith, J Y Y Lin, M S Lucas, M B Stone, D L Abernathy
We present the design and operating characteristics of a vacuum furnace used for inelastic neutron scattering experiments on a time-of-flight chopper spectrometer. The device is an actively water cooled radiant heating furnace capable of performing experiments up to 1873 K. Inelastic neutron scattering studies performed with this furnace include studies of phonon dynamics and metallic liquids. We describe the design, control, characterization, and limitations of the equipment. Further, we provide comparisons of the neutron performance of our device with commercially available options...
October 2017: Review of Scientific Instruments
Shengzhao Zhang, Gang Li, Jiexi Wang, Donggen Wang, Ying Han, Hui Cao, Ling Lin, Chunhong Diao
When an optical chopper is used to modulate the light source, the rotating speed of the wheel may vary with time and subsequently cause jitter of the modulation frequency. The amplitude calculated from the modulated signal would be distorted when the frequency fluctuations occur. To precisely calculate the amplitude of the modulated light flux, we proposed a method to estimate the range of the frequency fluctuation in the measurement of the spectrum and then extract the amplitude based on the sum of power of the signal in the selected frequency range...
October 2017: Review of Scientific Instruments
Jinglong Lan, Xiaoxu Huang, Xiaofeng Guan, Bin Xu, Huiying Xu, Zhiping Cai, Xiaodong Xu, Dongzhen Li, Jun Xu
We report on diode-pumped Nd(3+)-doped calcium barium niobate ferroelectric crystal (Nd:CBN-28) lasers at 1.06 and 1.34 μm. The maximum output power of the 1.06 μm laser reaches 0.69 W in the continuous-wave regime, which is believed to be the highest output power with Nd:CBN-28 crystal to date. Using a chopper to modulate the pump, the highest output power further improves to 0.77 W. Passively Q-switched laser operation at 1.06 μm, using a Cr:YAG saturable absorber, is realized with a maximum average output power of 89 mW, a pulse width of 220 ns, and a pulse energy 10...
May 10, 2017: Applied Optics
Minjung Son, Sandra Mosquera-Vázquez, Gabriela S Schlau-Cohen
Two-dimensional electronic spectroscopy (2DES) is an incisive tool for disentangling excited state energies and dynamics in the condensed phase by directly mapping out the correlation between excitation and emission frequencies as a function of time. Despite its enhanced frequency resolution, the spectral window of detection is limited to the laser bandwidth, which has often hindered the visualization of full electronic energy relaxation pathways spread over the entire visible region. Here, we describe a high-sensitivity, ultrabroadband 2DES apparatus...
August 7, 2017: Optics Express
Chandika Amarasinghe, Arthur G Suits
We demonstrate a method to probe cold and ultracold chemistry in a single molecular beam. The approach exploits beam slippage, the velocity difference of different species in the same beam, to establish the relative velocity. Average collision energies of 2.5 mK are achieved but with a spread of 100% or more. However, by implementing a dual-slit chopper that can separately fix the velocities of the two species at the interaction region, we achieve precise control over the relative velocity and narrow its spread...
October 9, 2017: Journal of Physical Chemistry Letters
Chunmei Zhou, Pingan Zhu, Ye Tian, Xin Tang, Rui Shi, Liqiu Wang
Existing approaches for droplet generation with an ultra-low interfacial tension using aqueous two-phase systems, ATPS, are either constricted by a narrow range of flow conditions using passive methods or subjected to complex chip fabrication with the integration of external components using active actuation. To address these issues, we present a simple approach to produce uniform ATPS droplets facilitated by oil-droplet choppers in microfluidics. Our solution counts on the synchronized formation of high-interfacial-tension oil-in-water and low-interfacial-tension water-in-water droplets, where the ATPS interface is distorted by oil droplets and decays into water-in-water droplets...
September 26, 2017: Lab on a Chip
Liana R Stein, Charles F Zorumski, Yukitoshi Izumi
INTRODUCTION: With its preservation of cytoarchitecture and synaptic circuitry, the hippocampal slice preparation has been a critical tool for studying the electrophysiological effects of pharmacological and genetic manipulations. To analyze the maximum number of slices or readouts per dissection, long incubation times postslice preparation are commonly used. We were interested in how slice integrity is affected by incubation postslice preparation. METHODS: Hippocampal slices were prepared by three different methods: a chopper, a vibratome, and a rotary slicer...
July 2017: Brain and Behavior
Geert-Jan Kroes, J I Juaristi, M Alducin
In scattering of H2 from Cu(111), vibrational excitation has so far defied an accurate theoretical description. To expose the causes of the large discrepancies with experiment, we investigate how the feature due to vibrational excitation (the "gain peak") in the simulated time-of-flight spectrum of (v = 1, j = 3) H2 scattering from Cu(111) depends on the surface temperature (Ts) and the possibility of energy exchange with surface phonons and electron-hole pairs (ehp's). Quasi-classical dynamics calculations are performed on the basis of accurate semiempirical density functionals for the interaction with H2 + Cu(111)...
June 29, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
James E Maslar, William A Kimes, Brent A Sperling, Ravindra K Kanjolia
A nondispersive infrared (NDIR) gas analyzer was demonstrated for measuring the vapor-phase density of the carbonyl-containing organometallic cobalt precurso μ(2)-η(2)-((t)Bu-acetylene) dicobalthexacarbonyl (CCTBA). This sensor was based on direct absorption by CCTBA vapor in the C≡O stretching spectral region and utilized a stable, broadband IR filament source, an optical chopper to modulate the source, a bandpass filter for wavelength isolation, and an InSb detector. The optical system was calibrated by selecting a calibration factor to convert CCTBA absorbance to a partial pressure that, when used to calculate CCTBA flow rate and CCTBA mass removed from the ampoule, resulted in an optically determined mass that was nominally equal to a gravimetrically-determined mass...
January 1, 2017: Applied Spectroscopy
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