scholarly journals Connectome preprocessing by Consensus Clustering increases separability in group neuroimaging studies

2018 ◽  
Author(s):  
Javier Rasero ◽  
Jesus M Cortes ◽  
Daniele Marinazzo ◽  
Sebastiano Stramaglia
Keyword(s):  
Signal To Noise Ratio ◽  
Brain Connectivity ◽  
Point Of View ◽  
Group Comparison ◽  
Consensus Clustering ◽  
Signal To Noise ◽  
New Information ◽  
Processing Step ◽  
Clinical Point ◽  
Neuroimaging Data

AbstractOne of the biggest challenges in preprocessing pipelines for neuroimaging data is to increase the signal-to-noise ratio of the data which will be used for subsequent analyses. In the same line, we suggest in the present work that the application of consensus clustering for brain connectivity matrices to find subgroups of subjects can be a valid additional”connectome processing” step helpful to reduce intra-group variability and therefore increase the separability of distinct classes. In addition, by partitioning the data before any group comparison, we demonstrate that unique regions within each cluster arise and bring new information that could be relevant from a clinical point of view.

scholarly journals Connectome sorting by consensus clustering increases separability in group neuroimaging studies

2019 ◽  
Vol 3 (2) ◽  
pp. 325-343 ◽  
Author(s):  
Javier Rasero ◽  
Ibai Diez ◽  
Jesus M. Cortes ◽  
Daniele Marinazzo ◽  
Sebastiano Stramaglia
Keyword(s):  
Signal To Noise Ratio ◽  
Brain Connectivity ◽  
Point Of View ◽  
Healthy Population ◽  
Group Comparison ◽  
Consensus Clustering ◽  
Signal To Noise ◽  
New Information ◽  
Clinical Point ◽  
Clustering Approach

A fundamental challenge in preprocessing pipelines for neuroimaging datasets is to increase the signal-to-noise ratio for subsequent analyses. In the same line, we suggest here that the application of the consensus clustering approach to brain connectivity matrices can be a valid additional step for connectome processing to find subgroups of subjects with reduced intragroup variability and therefore increasing the separability of the distinct subgroups when connectomes are used as a biomarker. Moreover, by partitioning the data with consensus clustering before any group comparison (for instance, between a healthy population vs. a pathological one), we demonstrate that unique regions within each cluster arise and bring new information that could be relevant from a clinical point of view.

STOCHASTIC RESONANCE IN CHUA’S CIRCUIT DRIVEN BY AMPLITUDE OR FREQUENCY MODULATED SIGNALS

1994 ◽  
Vol 04 (02) ◽  
pp. 441-446 ◽  
Author(s):  
V.S. ANISHCHENKO ◽  
M.A. SAFONOVA ◽  
L.O. CHUA
Keyword(s):  
Numerical Simulation ◽  
Stochastic Resonance ◽  
Signal To Noise Ratio ◽  
Point Of View ◽  
Chua’S Circuit ◽  
Signal Distortion ◽  
Signal To Noise ◽  
Chua's Circuit ◽  
Noise Ratio ◽  
Modulated Signals

Using numerical simulation, we establish the possibility of realizing the stochastic resonance (SR) phenomenon in Chua’s circuit when it is excited by either an amplitude-modulated or a frequency-modulated signal. It is shown that the application of a frequency-modulated signal to a Chua’s circuit operating in a regime of dynamical intermittency is preferable over an amplitude-modulated signal from the point of view of minimizing the signal distortion and maximizing the signal-to-noise ratio (SNR).

scholarly journals NOISE STABILITY OF SIGNAL RECEPTION ALGORITHMS WITH MULTIPULSE PULSE-POSITION MODULATION

2018 ◽  
Vol 42 (1) ◽  
pp. 167-174 ◽  
Author(s):  
V. I. Parfenov ◽  
D. Y. Golovanov
Keyword(s):  
Communication Systems ◽  
Pulse Sequence ◽  
Signal To Noise Ratio ◽  
Point Of View ◽  
Estimation Accuracy ◽  
Pulse Position Modulation ◽  
Signal To Noise ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Noise Ratio

An algorithm for estimating time positions and amplitudes of a periodic pulse sequence from a small number of samples was proposed. The number of these samples was determined only by the number of pulses. The performance of this algorithm was considered on the assumption that the spectrum of the original signal is limited with an ideal low-pass filter or the Nyquist filter, and conditions for the conversion from one filter to the other were determined. The efficiency of the proposed algorithm was investigated through analyzing in which way the dispersion of estimates of time positions and amplitudes depends on the signal-to-noise ratio and on the number of pulses in the sequence. It was shown that, from this point of view, the efficiency of the algorithm decreases with increasing number of sequence pulses. Besides, the efficiency of the proposed algorithm decreases with decreasing signal-to-noise ratio.It was found that, unlike the classical maximum likelihood algorithm, the proposed algorithm does not require a search for the maximum of a multivariable function, meanwhile characteristics of the estimates are practically the same for both these methods. Also, it was shown that the estimation accuracy of the proposed algorithm can be increased by an insignificant increase in the number of signal samples.The results obtained may be used in the practical design of laser communication systems, in which the multipulse pulse-position modulation is used for message transmission. 

scholarly journals Collecting Microplastics in Gardens: Case Study (i) of Soil

2021 ◽  
Vol 9 ◽  
Author(s):  
Zahra Sobhani ◽  
Yunlong Luo ◽  
Christopher T. Gibson ◽  
Youhong Tang ◽  
Ravi Naidu ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Point Of View ◽  
Signal To Noise ◽  
Statistical Point ◽  
Image Mapping ◽  
Noise Ratio ◽  
In The Beginning ◽  
Raman Image ◽  
Selection Of

As an emerging contaminant, microplastic is receiving increasing attention. However, the contamination source is not fully known, and new sources are still being identified. Herewith, we report that microplastics can be found in our gardens, either due to the wrongdoing of leaving plastic bubble wraps to be mixed with mulches or due to the use of plastic landscape fabrics in the mulch bed. In the beginning, they were of large sizes, such as > 5 mm. However, after 7 years in the garden, owing to natural degradation, weathering, or abrasion, microplastics are released. We categorize the plastic fragments into different groups, 5 mm–0.75 mm, 0.75 mm–100 μm, and 100–0.8 μm, using filters such as kitchenware, meaning we can collect microplastics in our gardens by ourselves. We then characterized the plastics using Raman image mapping and a logic-based algorithm to increase the signal-to-noise ratio and the image certainty. This is because the signal-to-noise ratio from a single Raman spectrum, or even from an individual peak, is significantly less than that from a spectrum matrix of Raman mapping (such as 1 vs. 50 × 50) that contains 2,500 spectra, from the statistical point of view. From the 10 g soil we sampled, we could detect the microplastics, including large (5 mm–100 μm) fragments and small (<100 μm) ones, suggesting the degradation fate of plastics in the gardens. Overall, these results warn us that we must be careful when we do gardening, including selection of plastic items for gardens.

Low-Frequency Scanning Capacitance Microscopy

1997 ◽  
Vol 500 ◽  
Author(s):  
Š. Lányi ◽  
M. Hruškovic
Keyword(s):  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Point Of View ◽  
Dielectric Losses ◽  
Frequency Range ◽  
Signal To Noise ◽  
Input Stage ◽  
Frequency Scanning ◽  
Noise Ratio ◽  
Parallel Conductance

ABSTRACTThe operation principle and main properties of a Scanning Capacitance Microscope (SCM) are described. It is called low-frequency, because in its design typical low-frequency techniques are utilised. The main attention is focused on its lateral resolution, signal-to-noise ratio and the possibility to detect dielectric losses.Mapping the electrostatic field of a shielded microscope probe was used to calculate the stray capacitance, flux density, sensitivity and contrast obtained on a flat conducting surface, as well as on a surface covered by a thin dielectric film. The effect of dielectric losses, represented by a parallel conductance, on the detected capacitance and the resulting phase shift has been derived.Using the results of mapping, the requirements on a SCM input stage and the possible solutions are discussed. From the point of view of frequency range and noise the best is an electrometric input stage, with input impedance represented by its capacitance.The achieved signal-to-noise ratio of the low frequency Scanning Capacitance Microscope renders the extension of the working frequency range to lower frequencies. The input stage can be optimised for a frequency range from about 1 kHz to a few MHz, with the possibility to extend it to about 10 MHz at the cost of reduced sensitivity at the lowest frequencies.

scholarly journals The Degradation of Automotive Radar Sensor Signals Caused by Vehicle Vibrations and Other Nonlinear Movements

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6195
Author(s):  
Florian Hau ◽  
Florian Baumgärtner ◽  
Martin Vossiek
Keyword(s):  
Continuous Wave ◽  
Signal To Noise Ratio ◽  
Linear Acceleration ◽  
Point Of View ◽  
Additional Contribution ◽  
General Description ◽  
Constant False Alarm Rate ◽  
Automotive Radar ◽  
Signal To Noise ◽  
Noise Ratio

As the demands on modern radar systems with respect to accuracy, reliability, and availability increase, a detailed assessment of the influence of nonlinear movements has become necessary. In particular, from the point of view of radar, different types of movements, such as any kind of acceleration, braking situation, or vehicle vibration, are essential parts of any traffic scenario. These unavoidable motions, in which the relative velocity changes within one measurement cycle, are called nonlinear movements. These nonlinearities contribute to intermediate frequencies, which are comparable to the extensively described nonlinearities of a frequency ramp. This additional contribution to the intermediate signal has a direct effect on the signal-to-noise ratio and thus on the accuracy and probability of target detection. This paper presents a study of various types of nonlinear motion and a detailed definition of the resulting parameters based on a variety of vehicle-based measurements. An advanced signal model of frequency-modulated continuous wave (FMCW) radar is introduced and verified in addition to a detailed mathematical description of spectral signal behaviour in sinusoidal motions and linear acceleration. The theoretical and experimental results in idealised point targets are transferred to real complex road users. Furthermore, by applying established automotive signal processing steps in the form of an ordered statistical constant false alarm rate (OS CFAR), the consequences of determining the noise level are also shown. In combination with the already introduced signal behaviour, these results enabled general description of the signal-to-noise ratio of nonlinear movements in complex traffic scenarios.

scholarly journals Fatal bupivacaine overdose through intrathecally positioned epidural catheter

2013 ◽  
Vol 19 (1) ◽  
pp. 10-12
Author(s):  
Lina Davies Forsman ◽  
Mats Öström ◽  
Mikael Svanström ◽  
Anders Eriksson
Keyword(s):  
Epidural Catheter ◽  
Drug Effects ◽  
Point Of View ◽  
Continuous Epidural Infusion ◽  
Segmental Analysis ◽  
Vital Functions ◽  
New Information ◽  
Clinical Point ◽  
The Central Nervous System ◽  
Epidural Catheters

ABSTRACT We describe a fatality due to an intrathecally positioned epidural catheter and an infusion rate of bupivacaine set 10 times higher than planned. The undetected misplacement, despite safety routines, is discussed along with the toxicological findings and new information on the intrathecal distribution of bupivacaine. From a clinical point of view, the human factor, in combination with an indistinct decimal point on the pump, was considered as the reason for the unfortunate overdose. In continuous epidural infusion of local anesthetics, the importance of guidelines and informed staff in managing complications of epidural lumbar infusion as well as careful monitoring of the vital functions is essential. Guidelines are also vital during the procedure of insertion of epidural catheters. When using combined spinal and epidural anaesthesia, we believe that an epidural catheter should be inserted, and its position tested, prior to spinal anesthesia. The case also illustrates the need of innovative investigation techniques to confirm the suspicion of unusual manifestations of inadvertent drug effects. Segmental analysis, together with analyses in a control case, enabled us to elucidate the high and varying tissue concentrations in the central nervous system.

scholarly journals Sensitivity Analysis of the Simply Noise-matched Receiving Coil for NMR Experiments

2020 ◽  
Vol 20 (5) ◽  
pp. 236-240
Author(s):  
Peter Andris ◽  
Ivan Frollo
Keyword(s):  
Noise Figure ◽  
Signal To Noise Ratio ◽  
Input Voltage ◽  
Point Of View ◽  
Signal To Noise ◽  
Constant Input ◽  
Optimal Value ◽  
Receiving Coil ◽  
Theoretical Results ◽  
Output Snr

AbstractThe article analyzes the sensitivity of unmatched receiving coil for the NMR scanner. Receiver of the scanner was investigated from the point of view of noise features. Theory of the noise figure has been modified to utilize the receiver for digitization of its own noise and the noise figure calculation. The resulting noise figure has been measured with different source impedances and the optimal value has been acquired. Influence of the noise figure on the resulting signal-to-noise ratio has been calculated for the sensitivity judgement. The output SNR has been investigated for constant input SNR as well as for constant input voltage. Many results are depicted in figures. Also examples of theoretical results are depicted graphically.

scholarly journals Physical noise propagation in color image construction: a geometrical interpretation

2019 ◽  
Vol 2019 (1) ◽  
pp. 375-380
Author(s):  
Axel Clouet ◽  
Jérôme Vaillant ◽  
David Alleysson
Keyword(s):  
Near Infrared ◽  
Color Image ◽  
Signal To Noise Ratio ◽  
Point Of View ◽  
Signal To Noise ◽  
Low Light ◽  
Image Construction ◽  
Color Sensor ◽  
Light Sensor ◽  
Noise Ratio

To avoid false colors, classical color sensors cut infrared wavelengths for which silicon is sensitive (with the use of an infrared cutoff filter called IR-cut). However, in low light situation, noise can alter images. To increase the amount of photons received by the sensor, in other words, the sensor's sensitivity, it has been proposed to remove the IR-cut for low light applications. In this paper, we analyze if this methodology is beneficial from a signal to noise ratio point of view when the wanted result is a color image. For this aim we recall the formalism behind physical raw image acquisition and color reconstruction. A comparative study is carried out between one classical color sensor and one specific color sensor designed for low light conditions. Simulated results have been computed for both sensors under same exposure settings and show that raw signal to noise ratio is better for the low light sensor. However, its reconstructed color image appears more noisy. Our formalism illustrates geometrically the reasons of this degradation in the case of the low light sensor. It is due on one hand to the higher correlation between spectral channels and on the other hand to the near infrared part of the signal in the raw data which is not intrinsically useful for color.

scholarly journals ANALYSIS OF DENOISING INTERPRETATION OF REMOTE SENSING IMAGE BASED ON ICA-WAVELET TRANSFORM

2020 ◽  
Vol XLII-3/W10 ◽  
pp. 411-414
Author(s):  
L. Sun ◽  
X. S. Gan
Keyword(s):  
Remote Sensing ◽  
Image Denoising ◽  
Signal To Noise Ratio ◽  
Control Point ◽  
Remote Sensing Image ◽  
Signal To Noise ◽  
Processing Step ◽  
Feature Information ◽  
Noise Ratio

Abstract. The noise will blur the key information of the remote sensing image, such as edge texture and important feature information, which will result in the loss of key information contained in the remote sensing image, resulting in the degradation of the overall quality of the image, which will bring difficulties to the interpretation work. Therefore, in order to obtain higher precision, signal-to-noise ratio and improve the quality of remote sensing image, denoising the remote sensing image containing noise is a crucial step and processing step for image remote sensing image application.In this paper, the ICA wavelet analysis algorithm is applied to the application of real-time remote sensing image denoising. A series of pre-processing procedures such as control point correction, image fusion and image mosaic are carried out on the Asian sub-level remote sensing image, and the signal-to-noise ratio of the remote sensing image is adopted. (SNR/dB) and mean square error (RMSE) verify the image quality after denoising.

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