scholarly journals Signal-to-noise ratio, T2 , and T2* for hyperpolarized helium-3 MRI of the human lung at three magnetic field strengths

2016 ◽  
Vol 78 (4) ◽  
pp. 1458-1463 ◽  
Author(s):  
Peter Komlosi ◽  
Talissa A. Altes ◽  
Kun Qing ◽  
Karen E. Mooney ◽  
G. Wilson Miller ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Human Lung ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Hyperpolarized Helium ◽  
Helium 3 ◽  
Noise Ratio ◽  
Field Strengths

scholarly journals Design and Research of Inductive Oil Pollutant Detection Sensor Based on High Gradient Magnetic Field Structure

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 638
Author(s):  
Wei Li ◽  
Chenzhao Bai ◽  
Chengjie Wang ◽  
Hongpeng Zhang ◽  
Lebile Ilerioluwa ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Signal To Noise Ratio ◽  
Detection Accuracy ◽  
Iron Particles ◽  
Signal To Noise ◽  
Gradient Magnetic Field ◽  
High Gradient ◽  
Copper Particles ◽  
Pollutant Detection ◽  
Noise Ratio

An inductive oil pollutant detection sensor based on a high-gradient magnetic field structure is designed in this paper, which is mainly used for online detection and fault analysis of pollutants in hydraulic and lubricating oil systems. The innovation of the sensor is based on the inductance detection method. Permalloy is embedded in the sensing region of the sensor, so that the detection area generates a high gradient magnetic field to enhance the detection accuracy of the sensor. Compared with traditional inductive sensors, the sensor has a significant improvement in detection accuracy, and the addition of permalloy greatly improves the stability of the sensor’s detection unit structure. The article theoretically analyzes the working principle of the sensor, optimizes the design parameters and structure of the sensor through simulation, determines the best permalloy parameters, and establishes an experimental system for verification. Experimental results show that when a piece of permalloy is added to the sensing unit, the signal-to-noise ratio (SNR) of iron particles is increased by more than 20%, and the signal-to-noise ratio of copper particles is increased by more than 70%. When two pieces of permalloy are added, the signal-to-noise ratio for iron particles is increased by more than 70%, and the SNR for copper particles is increased several times. This method raises the lower limit of detection for ferromagnetic metal particles to 20 μm, and the lower limit for detection of non-ferromagnetic metal particles to 80 μm, which is the higher detection accuracy of the planar coil sensors. This paper provides a new and faster online method for pollutant detection in oil, which is of great significance for diagnosing and monitoring the health of oil in mechanical systems.

A triple-drain MOSFET magnetic-field sensor

1985 ◽  
Vol 63 (6) ◽  
pp. 695-698 ◽  
Author(s):  
A. Nathan ◽  
A. M. J. Huiser ◽  
H. P. Baltes ◽  
H. G. Schmidt-Weinmar
Keyword(s):  
Magnetic Field ◽  
Surface Charge ◽  
Signal To Noise Ratio ◽  
Magnetic Field Sensor ◽  
Two Dimensional ◽  
Signal To Noise ◽  
Linear Region ◽  
Field Sensor ◽  
Device Geometry ◽  
Noise Ratio

The two-dimensional distributions of the potential, current, and surface charge for a magnetic-field-sensitive N-channel MOSFET have been computed numerically. The MOSFET is operated in the linear region and is based on a triple-drain configuration. The sensitivity as well as the signal-to-noise ratio is studied for a variety of channel geometries, and an optimal device geometry is presented.

Two recent developments in XMCD

1998 ◽  
Vol 5 (3) ◽  
pp. 992-994 ◽  
Author(s):  
F. Baudelet ◽  
J. M. Dubuisson ◽  
C. Hébert ◽  
C. Créoff ◽  
L. Pointal ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Pressures ◽  
Magnetic Circular Dichroism ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Second Development ◽  
Superconducting Device ◽  
Fast Switching ◽  
Technical Developments ◽  
Noise Ratio

This paper reports on two new technical developments concerning sample environments for X-ray magnetic circular dichroism (XMCD). The first measurements under high pressures of up to 30 GPa are described. The difficulties of combining the techniques of high pressure and XMCD are commented on. The second development involves the use of a fast-switching magnetic field. A new superconducting device is used to perform XMCD measurements on paramagnetic compounds in magnetic fields of up to 6 T. The small amplitude of the XMCD signal imposes, for a given signal-to-noise ratio, a noise less than a few 10−5. The signal-to-noise ratio is improved by the use of a series of acquisitions, switching the magnetic field between each acquisition. A very fast switching mechanism has been built based on mechanical rotation of a superconducting coil, with the sample kept in place inside the coil. The XMCD signals at the L II,III-edges of paramagnetic rare-earth compounds have been measured at 4.5 K in fields of up to 6 T with a switching time of 11 s.

scholarly journals Inference of the chromospheric magnetic field configuration of solar plage using the Ca II 8542 Å line

2020 ◽  
Vol 644 ◽  
pp. A43 ◽  
Author(s):  
A. G. M. Pietrow ◽  
D. Kiselman ◽  
J. de la Cruz Rodríguez ◽  
C. J. Díaz Baso ◽  
A. Pastor Yabar ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Numerical Models ◽  
Signal To Noise Ratio ◽  
Field Configuration ◽  
Magnetic Field Configuration ◽  
Signal To Noise ◽  
Plage Region ◽  
Noise Ratio ◽  
The Magnetic Field

Context. It has so far proven impossible to reproduce all aspects of the solar plage chromosphere in quasi-realistic numerical models. The magnetic field configuration in the lower atmosphere is one of the few free parameters in such simulations. The literature only offers proxy-based estimates of the field strength, as it is difficult to obtain observational constraints in this region. Sufficiently sensitive spectro-polarimetric measurements require a high signal-to-noise ratio, spectral resolution, and cadence, which are at the limit of current capabilities. Aims. We use critically sampled spectro-polarimetric observations of the Ca II 8542 Å line obtained with the CRISP instrument of the Swedish 1-m Solar Telescope to study the strength and inclination of the chromospheric magnetic field of a plage region. This will provide direct physics-based estimates of these values, which could aid modelers to put constraints on plage models. Methods. We increased the signal-to-noise ratio of the data by applying several methods including deep learning and PCA. We estimated the noise level to be 1 × 10−3 Ic. We then used STiC, a non-local thermodynamic equilibrium inversion code to infer the atmospheric structure and magnetic field pixel by pixel. Results. We are able to infer the magnetic field strength and inclination for a plage region and for fibrils in the surrounding canopy. In the plage we report an absolute field strength of |B| = 440 ± 90 G, with an inclination of 10° ±16° with respect to the local vertical. This value for |B| is roughly double of what was reported previously, while the inclination matches previous studies done in the photosphere. In the fibrillar region we found |B| = 300 ± 50 G, with an inclination of 50° ±13°.

scholarly journals Interelement Decoupling Strategies at UHF MRI

2021 ◽  
Vol 9 ◽  
Author(s):  
Irena Zivkovic
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Signal To Noise Ratio ◽  
Larmor Frequency ◽  
Resonance Imaging ◽  
Signal To Noise ◽  
Ultrahigh Field ◽  
Coil Arrays ◽  
Noise Ratio ◽  
Rf Signal

Moving to the ultrahigh field magnetic resonance imaging (UHF MRI) brought many benefits such as potentially higher signal-to-noise ratio, contrast-to-noise ratio, and improved spectral resolution. The UHF MRI regime also introduced some challenges which could prevent full exploitation of mentioned advantages. A higher static magnetic field means increase in Larmor frequency, which further implies the shorter wavelength in a tissue. The shorter wavelength causes interferences of the RF signal and inhomogeneous excitation, which can be partially resolved by the introduction of the multichannel coil arrays. The biggest problem in UHF multichannel densely populated arrays is the existence of the interelement coupling, which should be minimized as much as possible. This article presents the nonconventional, recently developed decoupling techniques used in UHF MRI.

scholarly journals Optimizing Momentum Resolution with a New Fitting Method for Silicon-Strip Detectors

Instruments ◽  
2018 ◽  
Vol 2 (4) ◽  
pp. 22 ◽  
Author(s):  
Gregorio Landi ◽  
Giovanni Landi
Keyword(s):  
Magnetic Field ◽  
Signal To Noise Ratio ◽  
Linear Increase ◽  
Low Noise ◽  
Signal To Noise ◽  
High Noise ◽  
Strip Detectors ◽  
Fitting Method ◽  
Momentum Resolution ◽  
Noise Ratio

Two new fitting methods are explored for momentum reconstruction. They give a substantial increase of momentum resolution compared to standard fit. The key point is the use of a different (realistic) probability distribution for each hit (heteroscedasticity). In the first fitting method an effective variance is calculated for each hit, the second method uses the search of the maximum likelihood. The tracker model is similar to the PAMELA tracker with its two sided detectors. Here, each side is simulated as a momentum reconstruction device. One of the two is similar to silicon micro-strip detectors of large use in running experiments. The gain obtained in momentum resolution is measured as the virtual magnetic field and the virtual signal-to-noise ratio required by the standard fits to overlap with the best of the new methods. For the low noise side, the virtual magnetic field must be increased 1.5 times to reach the overlap and 1.8 for the other. For the high noise side, the increases must be 1.8 and 2.0. The signal-to-noise ratio has to be increased by 1.6 for the low noise side and 2.2 for the high noise side ( η -algorithms). Each one of our two methods shows a very rapid linear increase of the resolution with the number N of detector layers, the two standard fits have the usual slow growth less than N .

Determination of the Best Emulsion for the Microscopy of Crystals

1981 ◽  
Vol 39 ◽  
pp. 32-33
Author(s):  
David A. Grano ◽  
Kenneth H. Downing
Keyword(s):  
Spatial Frequency ◽  
Information Transfer ◽  
Signal To Noise Ratio ◽  
Experimental Situation ◽  
Photographic Emulsion ◽  
Modulation Transfer ◽  
Signal To Noise ◽  
Frequency Space ◽  
Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

Experiments in Bright-Field Imaging with Hollow-Cone Illumination

1981 ◽  
Vol 39 ◽  
pp. 226-227
Author(s):  
W. Kunath ◽  
K. Weiss ◽  
E. Zeitler
Keyword(s):  
Signal To Noise Ratio ◽  
Carbon Support ◽  
Electronic System ◽  
Optic Axis ◽  
Hollow Cone ◽  
Signal To Noise ◽  
Bright Field ◽  
Noise Ratio ◽  
Single Field ◽  
Field Imaging

Bright-field images taken with axial illumination show spurious high contrast patterns which obscure details smaller than 15 ° Hollow-cone illumination (HCI), however, reduces this disturbing granulation by statistical superposition and thus improves the signal-to-noise ratio. In this presentation we report on experiments aimed at selecting the proper amount of tilt and defocus for improvement of the signal-to-noise ratio by means of direct observation of the electron images on a TV monitor.Hollow-cone illumination is implemented in our microscope (single field condenser objective, Cs = .5 mm) by an electronic system which rotates the tilted beam about the optic axis. At low rates of revolution (one turn per second or so) a circular motion of the usual granulation in the image of a carbon support film can be observed on the TV monitor. The size of the granular structures and the radius of their orbits depend on both the conical tilt and defocus.

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