keyword
MENU ▼
Read by QxMD icon Read
search

Chopper

keyword
https://www.readbyqxmd.com/read/29136366/use-of-an-efficient-measurement-uncertainty-approach-to-compare-room-temperature-and-cryogenic-sample-processing-in-the-analysis-of-chemical-contaminants-in-foods
#1
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 at 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 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 14, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/29107413/modelling-firing-regularity-in-the-ventral-cochlear-nucleus-mechanisms-and-effects-of-stimulus-level-and-synaptopathy
#2
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
https://www.readbyqxmd.com/read/29092522/design-and-operating-characteristic-of-a-vacuum-furnace-for-time-of-flight-inelastic-neutron-scattering-measurements
#3
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
https://www.readbyqxmd.com/read/29092492/note-demodulation-of-spectral-signal-modulated-by-optical-chopper-with-unstable-modulation-frequency
#4
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
https://www.readbyqxmd.com/read/29047553/laser-characteristics-of-nd-3-doped-calcium-barium-niobate-ferroelectric-crystal-at-1-06-and-1-34%C3%A2-%C3%A2-%C3%AE-m
#5
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
https://www.readbyqxmd.com/read/29041086/ultrabroadband-2d-electronic-spectroscopy-with-high-speed-shot-to-shot-detection
#6
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
https://www.readbyqxmd.com/read/28976761/intrabeam-scattering-for-ultracold-collisions
#7
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
https://www.readbyqxmd.com/read/28861566/microfluidic-generation-of-aqueous-two-phase-system-atps-droplets-by-oil-droplet-choppers
#8
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
https://www.readbyqxmd.com/read/28729941/hippocampal-slice-preparation-in-rats-acutely-suppresses-immunoreactivity-of-microtubule-associated-protein-map2-%C3%A2-and-glycogen-levels-without-affecting-numbers-of-glia%C3%A2-or-levels-of-the-glutamate-transporter-vglut1
#9
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
https://www.readbyqxmd.com/read/28729891/vibrational-excitation-of-h2-scattering-from-cu-111-effects-of-surface-temperature-and-of-allowing-energy-exchange-with-the-surface
#10
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
https://www.readbyqxmd.com/read/28707985/nondispersive-infrared-gas-analyzer-for-vapor-density-measurements-of-a-carbonyl-containing-organometallic-cobalt-precursor
#11
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
https://www.readbyqxmd.com/read/28467848/automated-microfluidic-droplet-based-sample-chopper-for-detection-of-small-fluorescence-differences-using-lock-in-analysis
#12
Jean T Negou, L Adriana Avila, Xiangpeng Li, Tesfagebriel M Hagos, Christopher J Easley
Fluorescence is widely used for small-volume analysis and is a primary tool for on-chip detection in microfluidic devices, yet additional expertise, more elaborate optics, and phase-locked detectors are needed for ultrasensitive measurements. Recently, we designed a microfluidic analog to an optical beam chopper (μChopper) that alternated formation of picoliter volume sample and reference droplets. Without complex optics, the device negated large signal drifts (1/f noise), allowing absorbance detection in a mere 27 μm optical path...
June 6, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28463291/high-brightness-low-coherence-digital-holographic-microscopy-for-3d-visualization-of-an-in-vitro-sandwiched-biological-sample
#13
D G Abdelsalam, Takeshi Yasui
We achieve practically a bright-field digital holographic microscopy (DHM) configuration free from coherent noise for three-dimensional (3D) visualization of an in-vitro sandwiched sarcomere sample. Visualization of such sandwiched samples by conventional atomic force microscope (AFM) is impossible, while visualization using DHM with long coherent lengths is challenging. The proposed configuration is comprised of an ultrashort pulse laser source and a Mach-Zehnder interferometer in transmission. Periodically poled lithium niobate (PPLN) crystal was used to convert the fundamental beam by second harmonic generation (SHG) to the generated beam fit to the CCD camera used...
May 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/28452746/development-of-optical-choppers-for-time-resolved-measurements-at-soft-x-ray-synchrotron-radiation-beamlines
#14
Hitoshi Osawa, Takuo Ohkochi, Masami Fujisawa, Shigeru Kimura, Toyohiko Kinoshita
Two types of optical choppers for time-resolved measurements at synchrotron radiation soft X-ray beamlines have been developed. One type uses an air-spindle-type rotation mechanism with a two-stage differential pumping system to maintain the ultra-high vacuum of the X-ray beamline, and the other uses a magnetic bearing. Both can be installed at the soft X-ray beamlines at SPring-8, greatly improving the accessibility of pump-and-probe spectroscopy. The combination of X-ray chopper and pump-and-probe photoemission electron microscope at SPring-8 provides drastic improvements in signal-to-noise ratio and resolution compared with techniques using high-voltage gating of channel plate detectors...
May 1, 2017: Journal of Synchrotron Radiation
https://www.readbyqxmd.com/read/28430320/remnant-extraction-by-using-an-intraocular-lens-injector-with-essential-flow
#15
Momoko Yamakawa, Mami Kusaka, Shogo Yamada, Masayuki Akimoto
PURPOSE: To describe a new technique for remnant removal in cases of posterior capsular rupture during cataract surgery and Soemmering ring extraction during intraocular lens (IOL) removal. METHODS: An IOL injector, inserted into the anterior chamber, provides a new exit for residual lens fragments. Passive fluid flow, supplied by an anterior chamber maintainer or some ocular viscoelastic device (OVD) injection, delivers the residual fragments into a lumen of the injector in assistance with a second device such as a phaco-chopper and vitreous cutter...
June 26, 2017: European Journal of Ophthalmology
https://www.readbyqxmd.com/read/28401413/concentration-dependent-approach-for-accurate-determination-of-two-photon-absorption-cross-section-of-fluorescent-dye-molecule
#16
Sandeep Kumar Maurya, Chayan Dutta, Debabrata Goswami
We have investigated the concentration dependent of two-photon induced fluorescence (TPIF) in methanolic solution of Rhodamine 6G and Rhodamine B dye using 120 fs laser pulses at 780 nm, 76 MHz repetition rate. TPIF study of these dyes was compared with their respective one photon fluorescence intensity. We have shown the effect of chopper on TPIF intensity from Rhodamine dyes, which have shown direct influence on the determined TPA Cross section of these dyes.
July 2017: Journal of Fluorescence
https://www.readbyqxmd.com/read/28380905/broadband-2d-electronic-spectrometer-using-white-light-and-pulse-shaping-noise-and-signal-evaluation-at-1-and-100-khz
#17
Nicholas M Kearns, Randy D Mehlenbacher, Andrew C Jones, Martin T Zanni
We have developed a broad bandwidth two-dimensional electronic spectrometer that operates shot-to-shot at repetition rates up to 100 kHz using an acousto-optic pulse shaper. It is called a two-dimensional white-light (2D-WL) spectrometer because the input is white-light supercontinuum. Methods for 100 kHz data collection are studied to understand how laser noise is incorporated into 2D spectra during measurement. At 100 kHz, shot-to-shot scanning of the delays and phases of the pulses in the pulse sequence produces a 2D spectrum 13-times faster and with the same signal-to-noise as using mechanical stages and a chopper...
April 3, 2017: Optics Express
https://www.readbyqxmd.com/read/28372395/note-one-order-of-magnitude-better-signal-to-noise-ratio-for-neutron-backscattering
#18
Markus Appel, Bernhard Frick
We report on a new achievement which allows increasing the signal-to-noise ratio of reactor backscattering spectrometers by more than one order of magnitude by sacrificing at most 50% of the count rate. This method was recently tested on the backscattering instrument IN16B at ILL, where signal-to-noise ratios of more than 10 000 for standard samples and up to 40 000 for strong scatterers were measured with only 37% reduction in intensity. The described method is applicable at any reactor backscattering spectrometer equipped with a so-called background chopper which can optionally function as a pulse suppression chopper and presents a major advancement for high energy resolution spectroscopy with neutrons...
March 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/28287313/the-early-days-of-commercial-ft-ir-spectrometry-a-personal-perspective
#19
Peter R Griffiths
The development of Fourier transform infrared (FT-IR) spectrometers in the mid-1960s followed along three lines. Interferometers for far-infrared FT spectrometry typically had a slow scan speed and the beam of radiation was modulated by a rotating chopper. Several instruments based on this system were developed commercially. Very high-resolution near-infrared FT spectrometers were based on cats-eye retroreflectors mounted in a step-scan interferometer; the beam of radiation was usually modulated by dithering one of the cats-eyes (phase modulation)...
March 2017: Applied Spectroscopy
https://www.readbyqxmd.com/read/28238065/cuprizone-containing-pellets-are-less-potent-to-induce-consistent-demyelination-in-the-corpus-callosum-of-c57bl-6-mice
#20
Tanja Hochstrasser, Gianna Lisa Exner, Stella Nyamoya, Christoph Schmitz, Markus Kipp
The chopper chelator cuprizone serves as a valuable chemical tool to induce consistent and reproducible demyelination in the central nervous system. However, the daily preparation of fresh cuprizone powder mixed in finely ground rodent chow might well be a particular health problem. Alternative methods, such as the fabrication of cuprizone-containing pellets, are available. The effectiveness of this method is, however, not known. In the present study, we compared whether intoxication of C57BL/6 mice with 0...
April 2017: Journal of Molecular Neuroscience: MN
keyword
keyword
39244
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"