Fast recovery, high sensitivity NMR probe and preamplifier for low frequencies

1979 ◽  
Vol 50 (2) ◽  
pp. 193-200 ◽  
Author(s):  
D. I. Hoult
Keyword(s):  
High Sensitivity ◽  
Fast Recovery ◽  
Low Frequencies

scholarly journals Frequency Response Stabilization and Comparative Studies of MET Hydrophone at Marine Seismic Exploration Systems

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1944 ◽  
Author(s):  
Egor Egorov ◽  
Anna Shabalina ◽  
Dmitry Zaitsev ◽  
Sergey Kurkov ◽  
Nikolay Gueorguiev
Keyword(s):  
Frequency Response ◽  
Field Tests ◽  
High Sensitivity ◽  
Seismic Exploration ◽  
Joint Stock Company ◽  
Experimental Sample ◽  
Frequency Range ◽  
Stock Company ◽  
Low Frequencies ◽  
Marine Seismic

Low frequency hydrophone with a frequency range of 1−300 Hz for marine seismic exploration systems has been developed. The operation principle of the hydrophone bases on the molecular electronic transfer that allows high sensitivity and low level self-noise at low frequencies (<10 Hz) to be achieved. The paper presents a stabilization method of the frequency response within the frequency range at a depth up to 30 m. Laboratory and marine tests confirmed the stated characteristics as well as the possibility of using this sensor in bottom marine seismic systems. An experimental sample of the hydrophone successfully passed a comparative marine test at Gelendzhik Bay (Black Sea) with the technical support of Joint-Stock Company (JSC) “Yuzhmorgeologiya”. One of the main results is the possibility of obtaining high-quality information in the field of low frequencies, which was demonstrated in the course of field tests.

Signal coding in cockroach photoreceptors is tuned to dim environments

2012 ◽  
Vol 108 (10) ◽  
pp. 2641-2652 ◽  
Author(s):  
K. Heimonen ◽  
E.-V. Immonen ◽  
R. V. Frolov ◽  
I. Salmela ◽  
M. Juusola ◽  
...  
Keyword(s):  
Information Transfer ◽  
Periplaneta Americana ◽  
Single Photon ◽  
Signal To Noise Ratio ◽  
Temporal Integration ◽  
High Sensitivity ◽  
Single Photons ◽  
Low Frequencies ◽  
Whole Cell Patch Clamp ◽  
High Level

In dim light, scarcity of photons typically leads to poor vision. Nonetheless, many animals show visually guided behavior with dim environments. We investigated the signaling properties of photoreceptors of the dark active cockroach ( Periplaneta americana) using intracellular and whole-cell patch-clamp recordings to determine whether they show selective functional adaptations to dark. Expectedly, dark-adapted photoreceptors generated large and slow responses to single photons. However, when light adapted, responses of both phototransduction and the nontransductive membrane to white noise (WN)-modulated stimuli remained slow with corner frequencies ∼20 Hz. This promotes temporal integration of light inputs and maintains high sensitivity of vision. Adaptive changes in dynamics were limited to dim conditions. Characteristically, both step and frequency responses stayed effectively unchanged for intensities >1,000 photons/s/photoreceptor. A signal-to-noise ratio (SNR) of the light responses was transiently higher at frequencies <5 Hz for ∼5 s after light onset but deteriorated to a lower value upon longer stimulation. Naturalistic light stimuli, as opposed to WN, evoked markedly larger responses with higher SNRs at low frequencies. This allowed realistic estimates of information transfer rates, which saturated at ∼100 bits/s at low-light intensities. We found, therefore, selective adaptations beneficial for vision in dim environments in cockroach photoreceptors: large amplitude of single-photon responses, constant high level of temporal integration of light inputs, saturation of response properties at low intensities, and only transiently efficient encoding of light contrasts. The results also suggest that the sources of the large functional variability among different photoreceptors reside mostly in phototransduction processes and not in the properties of the nontransductive membrane.

scholarly journals Rotated Spectral Principal Component Analysis (rsPCA) for Identifying Dynamical Modes of Variability in Climate Systems

2021 ◽  
Vol 34 (2) ◽  
pp. 715-736
Author(s):  
Clément Guilloteau ◽  
Antonios Mamalakis ◽  
Lawrence Vulis ◽  
Phong V. V. Le ◽  
Tryphon T. Georgiou ◽  
...  
Keyword(s):  
Southern Oscillation ◽  
Synthetic Data ◽  
Principal Component ◽  
High Sensitivity ◽  
Frequency Resolution ◽  
Robust Estimator ◽  
Low Frequencies ◽  
High Frequencies ◽  
Modes Of Variability ◽  
Spectral Principal Component Analysis

AbstractSpectral PCA (sPCA), in contrast to classical PCA, offers the advantage of identifying organized spatiotemporal patterns within specific frequency bands and extracting dynamical modes. However, the unavoidable trade-off between frequency resolution and robustness of the PCs leads to high sensitivity to noise and overfitting, which limits the interpretation of the sPCA results. We propose herein a simple nonparametric implementation of sPCA using the continuous analytic Morlet wavelet as a robust estimator of the cross-spectral matrices with good frequency resolution. To improve the interpretability of the results, especially when several modes of similar amplitude exist within the same frequency band, we propose a rotation of the complex-valued eigenvectors to optimize their spatial regularity (smoothness). The developed method, called rotated spectral PCA (rsPCA), is tested on synthetic data simulating propagating waves and shows impressive performance even with high levels of noise in the data. Applied to global historical geopotential height (GPH) and sea surface temperature (SST) daily time series, the method accurately captures patterns of atmospheric Rossby waves at high frequencies (3–60-day periods) in both GPH and SST and El Niño–Southern Oscillation (ENSO) at low frequencies (2–7-yr periodicity) in SST. At high frequencies the rsPCA successfully unmixes the identified waves, revealing spatially coherent patterns with robust propagation dynamics.

scholarly journals Bioinspired Low-Frequency Material Characterisation

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
C. Hopper ◽  
S. Assous ◽  
P. B. Wilkinson ◽  
D. A. Gunn ◽  
P. D. Jackson ◽  
...  
Keyword(s):  
Sound Velocity ◽  
Medical Physics ◽  
Low Frequency ◽  
High Sensitivity ◽  
Prediction Errors ◽  
Low Frequencies ◽  
Longitudinal Sound Velocity ◽  
Velocity Prediction ◽  
Thickness Measurements

New-coded signals, transmitted by high-sensitivity broadband transducers in the 40–200 kHz range, allow subwavelength material discrimination and thickness determination of polypropylene, polyvinylchloride, and brass samples. Frequency domain spectra enable simultaneous measurement of material properties including longitudinal sound velocity and the attenuation constant as well as thickness measurements. Laboratory test measurements agree well with model results, with sound velocity prediction errors of less than 1%, and thickness discrimination of at least wavelength/15. The resolution of these measurements has only been matched in the past through methods that utilise higher frequencies. The ability to obtain the same resolution using low frequencies has many advantages, particularly when dealing with highly attenuating materials. This approach differs significantly from past biomimetic approaches where actual or simulated animal signals have been used and consequently has the potential for application in a range of fields where both improved penetration and high resolution are required, such as nondestructive testing and evaluation, geophysics, and medical physics.

Effects of Frequency on the Directional Auditory Sensitivity of Northern Saw-Whet Owls (Aegolius acadicus)

2021 ◽  
pp. 1-11
Author(s):  
Eileanor P. LaRocco ◽  
Glenn A. Proudfoot ◽  
Megan D. Gall
Keyword(s):  
Auditory Evoked Potentials ◽  
Transfer Functions ◽  
Low Frequency ◽  
High Sensitivity ◽  
Directional Hearing ◽  
Directional Sensitivity ◽  
Low Frequencies ◽  
Aegolius Acadicus ◽  
Spatial Locations ◽  
Prey Items

Many animals use sound as a medium for detecting or locating potential prey items or predation threats. Northern saw-whet owls (<i>Aegolius acadicus</i>) are particularly interesting in this regard, as they primarily rely on sound for hunting in darkness, but are also subject to predation pressure from larger raptors. We hypothesized that these opposing tasks should favor sensitivity to low-frequency sounds arriving from many locations (potential predators) and high-frequency sounds below the animal (ground-dwelling prey items). Furthermore, based on the morphology of the saw-whet owl skull and the head-related transfer functions of related species, we expected that the magnitude of changes in sensitivity across spatial locations would be greater for higher frequencies than low frequencies (i.e., more “directional” at high frequencies). We used auditory-evoked potentials to investigate the frequency-specific directional sensitivity of Northern saw-whet owls to acoustic signals. We found some support for our hypothesis, with smaller-magnitude changes in sensitivity across spatial locations at lower frequencies and larger-magnitude changes at higher frequencies. In general, owls were most sensitive to sounds originating in front of and above their heads, but at 8 kHz there was also an area of high sensitivity below the animals. Our results suggest that the directional hearing of saw-whet owls should allow for both predator and prey detection.

scholarly journals Sensitivity to Rocuronium-Induced Neuromuscular Block and Reversibility with Sugammadex in a Patient with Myotonic Dystrophy

2012 ◽  
Vol 2012 ◽  
pp. 1-4 ◽  
Author(s):  
Akihiro Kashiwai ◽  
Takahiro Suzuki ◽  
Setsuro Ogawa
Keyword(s):  
General Anesthesia ◽  
Myotonic Dystrophy ◽  
Neuromuscular Blockade ◽  
Spontaneous Recovery ◽  
Neuromuscular Block ◽  
High Sensitivity ◽  
Additional Dose ◽  
Fast Recovery ◽  
Train Of Four ◽  
The Times

We report a patient with myotonic dystrophy who showed prolonged rocuronium-induced neuromuscular blockade, although with a fast recovery with sugammadex. During general anesthesia with propofol and remifentanil, the times to spontaneous recovery of the first twitch (T1) of train of four to 10% of control values after an intubating dose of rocuronium 1 mg/kg and an additional dose of 0.2 mg/kg were 112 min and 62 min, respectively. Despite the high sensitivity to rocuronium, sugammadex 2 mg/kg administered at a T1 of 10% safely and effectively antagonized rocuronium-induced neuromuscular block in 90 s.

Electrostatic imaging in radiology: limitations and prospects

1979 ◽  
Vol 292 (1390) ◽  
pp. 273-283 ◽  
Keyword(s):  
Soft Tissues ◽  
High Sensitivity ◽  
Medical Application ◽  
Lower Sensitivity ◽  
Latent Image ◽  
Surface Distribution ◽  
Low Frequencies ◽  
Spatial Frequencies ◽  
Edge Contrast ◽  
Multiple Copies

In this radiographic technique, the latent image takes the form of a surface distribution of electric charge which may be rendered visible in various ways. The charge distribution is formed either on a selenium surface (xeroradiography) or by collecting ions on an insulating foil (ionography). Conventional powder development techniques yield visible images in which high spatial frequencies are enhanced (‘edge contrast’) and low frequencies largely suppressed. This contrast pattern is useful for the radiological study of soft tissues, vascular structure, bones and joints. Xeroradiography is less sensitive than film-screen radiography and this restricts its medical application to sites where gonad exposure is minimal. Ionography with compressed xenon has high sensitivity but is not yet fully developed commercially. It requires a rigid link between the X-ray tube and the recording chamber. The latent image is produced on plastic foil which can then be developed in many different ways to yield either edge contrast or density images. Liquid ionography avoids the need for high pressure and allows multiple copies of the latent image to be made. There are some special applications of ionography in the research laboratory but in industrial work xeroradiography, despite lower sensitivity, is likely to be more convenient for any applications which demand edge contrast pictures.

Influence of DC-Joule Heat on Giant Magneto-Impedance of Co-Based Melt Extraction Wires

2009 ◽  
Vol 79-82 ◽  
pp. 1615-1618 ◽  
Author(s):  
Shu Ling Zhang ◽  
Da Wei Xing ◽  
Huan Wang ◽  
Xin Xin ◽  
Jian Fei Sun
Keyword(s):  
High Sensitivity ◽  
Joule Heat ◽  
Heat Current ◽  
Extraction Technology ◽  
Low Frequencies ◽  
Melt Extraction ◽  
Sensor Applications ◽  
Impedance Response ◽  
Amorphous Wires ◽  
Field Sensitivity

Co68.25Fe4.5Si12.25B15 naked amorphous wires of 60μm in diameter are prepared by melt extraction technology and annealed by DC-Joule heat at current from 40mA to 250mA for 10min. Impedance response is measured at low frequencies(≤13MHz) using HP4192 impedance analyzer. We get better GMI effect by heating wires at 60mA and 180mA.The connection between GMI response and transformation of structure under different heat current has been discussed. After proper heat treatment, magneto impedance response is strong even at 0.5MHz with GMI amplitude of 193.1% and field sensitivity of 59.4%/Oe. The maximum △Z/Z reaches 476.9% and the largest field sensitivity is up to 91.8%/Oe. These results indicate proper annealed Co-based melt extraction wires are suitable for high sensitivity sensor applications.

NQR Studies of Atomic Arrangements and Chemical Bonding in Glasses

1990 ◽  
Vol 45 (3-4) ◽  
pp. 268-272 ◽  
Author(s):  
Donghoon Lee ◽  
S. J. Gravina ◽  
P. J. Bray
Keyword(s):  
Chemical Bonding ◽  
Continuous Wave ◽  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
Signal To Noise ◽  
Low Frequencies ◽  
Large N ◽  
Noise Ratio ◽  
Very High

Abstract A very high sensitivity continuous wave NQR spectrometer was developed to detect pure NQR transitions at low frequencies (down to 200 kHz). A signal-to-noise ratio of more than 100 to 1 has been achieved at about 1.36 MHz for crystalline B 2 0 3 . Two large n B responses have been found in vitreous B 2 0 3 (NMR detected only one site) with linewidths of less than 30 kHz. 27 A1 NQR spectra were obtained for OC-A1203 (Corundum), the mineral andalusite (a form of A1203 • Si0 2), and a glass having the composition of anorthite (CaO • A1203 • 2Si0 2).

scholarly journals Cerebral stroke in a teenage girl with paroxysmal nocturnal hemoglobinuria

2017 ◽  
Vol 9 (2) ◽  
Author(s):  
Francesco Gervasi ◽  
Lucia D’Amelio ◽  
Antonino Trizzino ◽  
Fabrizia Ferraro ◽  
Delia Russo ◽  
...  
Keyword(s):  
Paroxysmal Nocturnal Hemoglobinuria ◽  
White Blood Cells ◽  
Macrocytic Anemia ◽  
High Sensitivity ◽  
Blood Analysis ◽  
Cerebral Stroke ◽  
Fast Recovery ◽  
Intravenous Therapy ◽  
Ischemic Lesion ◽  
Cerebral Arterial Thrombosis

We report a case of paroxysmal nocturnal hemoglobinuria (PNH) in a 14 year-old girl presenting a cerebral arterial thrombosis. The initial diagnosis was carential anemia due to menarche following identification of slight macrocytic anemia, leucopenia and mild thrombocytopenia at routine blood analysis. The child was eventually referred to a children’s hospital after the onset of progressive fatigue, anorexia and paleness. Severe anemia (hemoglobin 6 g/dL) with negative Coombs test, mild leucopenia (white blood cells 4.9×109/L) and thrombocytopenia (platelets 97×109/L) and high values of lactate dehydrogenase (2855 U/L) were identified; a packed red cells transfusion was administered. Her condition worsened and she subsequently presented complete right hemiplegia, aphasia and coma; magnetic resonance imaging revealed a massive ischemic lesion. A diagnosis of PNH was eventually made following high sensitivity flow cytometry, which identified a PNH clone (CD66b negative equal to 93.7% of granulocytes). Fast recovery from neurologic and hematological problems occurred in response to anticoagulant therapy and intravenous therapy with eculizumab. We are convinced that PNH should be included in the differential diagnosis of children presenting with cytopenia.

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