scholarly journals Oscillatory Potentials in Achromatopsia as a Tool for Understanding Cone Retinal Functions

2021 ◽  
Vol 22 (23) ◽  
pp. 12717
Author(s):  
Giulia Righetti ◽  
Melanie Kempf ◽  
Christoph Braun ◽  
Ronja Jung ◽  
Susanne Kohl ◽  
...  
Keyword(s):  
Autosomal Recessive ◽  
Autosomal Recessive Disease ◽  
Oscillatory Potentials ◽  
Full Field ◽  
Time Frequency ◽  
Frequency Representation ◽  
Continuous Complex ◽  
Frequency Window ◽  
Retinal Functions

Achromatopsia (ACHM) is an inherited autosomal recessive disease lacking cone photoreceptors functions. In this study, we characterize the time-frequency representation of the full-field electroretinogram (ffERG) component oscillatory potentials (OPs), to investigate the connections between photoreceptors and the inner retinal network using ACHM as a model. Time-frequency characterization of OPs was extracted from 52 controls and 41 achromat individuals. The stimulation via ffERG was delivered under dark-adaptation (DA, 3.0 and 10.0 cd·s·m−2) to assess mixed rod-cone responses. The ffERG signal was subsequently analyzed using a continuous complex Morlet transform. Time-frequency maps of both DA conditions show the characterization of OPs, disclosing in both groups two distinct time-frequency windows (~70–100 Hz and >100 Hz) within 50 ms. Our main result indicates a significant cluster (p < 0.05) in both conditions of reduced relative power (dB) in ACHM people compared to controls, mainly at the time-frequency window >100 Hz. These results suggest that the strongly reduced but not absent activity of OPs above 100 Hz is mostly driven by cones and only in small part by rods. Thus, the lack of cone modulation of OPs gives important insights into interactions between photoreceptors and the inner retinal network and can be used as a biomarker for monitoring cone connection to the inner retina.

Two-Stage Adaptive Line Enhancer and Sliced Wigner Trispectrum for the Characterization of Faults from Gear Box Vibration Data

1999 ◽  
Vol 121 (4) ◽  
pp. 488-494 ◽  
Author(s):  
S. K. Lee ◽  
P. R. White
Keyword(s):  
Background Noise ◽  
Two Stage ◽  
Vibration Signals ◽  
Time Frequency ◽  
Vibration Data ◽  
Frequency Representation ◽  
Frequency Domains ◽  
Adaptive Line Enhancer ◽  
Gear Fault

Impulsive sound and vibration signals in gears are often associated with faults which result from impacting and as such these impulsive signals can be used as indicators of faults. However it is often difficult to make objective measurements of impulsive signals because of background noise signals. In order to ease the measurement of impulsive sounds embedded in background noise, it is proposed that the impulsive signals are enhanced, via a two stage ALE (Adaptive Line Enhancer), and that these enhanced signals are then analyzed in the time and frequency domains using a Wigner higher order time-frequency representation. The effectiveness of this technique is demonstrated by application to gear fault data.

Signal analysis and weighted polynomial approximation

2006 ◽  
Vol 43 (2) ◽  
pp. 159-169
Author(s):  
Nguyen Xuan Ky
Keyword(s):  
Signal Analysis ◽  
Hermite Polynomials ◽  
Type Theorem ◽  
Hermite Functions ◽  
Bernstein Type ◽  
Time Frequency ◽  
Window Functions ◽  
Bernstein Type Theorem ◽  
Frequency Window

We present applications of Hermite polynomials in signal analysis. Among other result, we give a characterization of the so-called time-frequency window functions in terms of the Hermite--Fourier coefficients, a Bernstein-type theorem for the best approximations of window functions by Hermite-functions, time-frequency approximations. Some analogues for Hankel-transforms will also be considered.

scholarly journals Time-frequency Analysis of Multicomponent LFM signal based on Hough and Chirplet Transform

2018 ◽  
Vol 173 ◽  
pp. 03054
Author(s):  
Xueqin Zhang ◽  
Ruolun Liu
Keyword(s):  
Fourier Transform ◽  
Line Detection ◽  
Short Time Fourier Transform ◽  
Time Frequency ◽  
Frequency Representation ◽  
Chirplet Transform ◽  
Frequency Map ◽  
Linear Frequency Modulated Signal ◽  
Short Time

The Chirplet Transform (CT) is effective in the characterization of IF for mono-component linear-frequency-modulated signal. However, During the initialization process, using the peak of the time-frequency map of the short-time Fourier transform to fit the line is greatly affected by noise. For the multi-component signals, it is more difficult to distinguish and fit different IF lines. Since the Hough is good at a common algorithm for the line detection, the ridge edge fitting is replaced by the Hough transform in this paper. The experiment results show significant improvement in the obtained time-frequency representation.

Characterization of the cerebral activity by time–frequency representation of evoked EEG potentials

2011 ◽  
Vol 32 (8) ◽  
pp. 1327-1346 ◽  
Author(s):  
Francesc Clariá ◽  
Montserrat Vallverdú ◽  
Jordi Riba ◽  
Sergio Romero ◽  
Manuel J Barbanoj ◽  
...  
Keyword(s):  
Time Frequency ◽  
Cerebral Activity ◽  
Frequency Representation

scholarly journals Analysis of extra- and intragenic marker haplotypes as part of molecular diagnosis of cystic fibrosis in patients from Serbia

2008 ◽  
Vol 60 (1) ◽  
pp. 5-10 ◽  
Author(s):  
Danijela Radivojevic ◽  
Tanja Lalic ◽  
Marina Djurisic ◽  
Marija Guc-Scekic ◽  
P. Minic ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Autosomal Recessive ◽  
Haplotype Analysis ◽  
Autosomal Recessive Disease ◽  
Strong Linkage Disequilibrium ◽  
Tetranucleotide Repeat ◽  
Haplotype Association ◽  
Cftr Mutations ◽  
Haplotype 1

Cystic fibrosis (CF) is the most common fatal autosomal recessive disease in Caucasians. Since characterization of F508del, the predominant mutation in different countries, more than 1500 mutations have been discovered in the CFTR gene, including a large number of polymorphisms. After molecular screening of 222 CF patients from Serbia, we detected 21 different CFTR mutations, F508del being the most frequent (69.59% of CF alleles). A total of 21 mutations cover almost 80% of CF alleles in this group. Since the molecular basis of CF is highly heterogeneous in our population, studying the haplotype association with normal and CF chromosomes could be very helpful in all cases where one or both mutations remain unidentified. Haplotype analysis was done using six diallelic sites and one tetranucleotide repeat (XV2C-KM19-MP6D9-J44-IVS6a(GATT)-M470V-T854T) on 99 F508del, 90 non-F508del, and 105 normal chromosomes. Strong linkage disequilibrium was observed for CFTR mutations and one haplotype (1-2-2-1-6(2)-1-1), while normal chromosomes were mostly associated with another (1-1-2-1-6(2)-1-2). The obtained results show that in most cases it would be possible with this group of polymorphisms to separate normal chromosomes from chromosomes which carry the CFTR mutation. As far as prenatal diagnosis of cystic fibrosis is concerned, haplotype analysis can be used as a helpful method of indirect diagnosis in families at risk with one or both CF alleles uncharacterized.

scholarly journals Strain Sensitivity Enhancement of Broadband Ultrasonic Signals in Plates Using Spectral Phase Filtering

2021 ◽  
Vol 11 (6) ◽  
pp. 2582
Author(s):  
Lucas M. Martinho ◽  
Alan C. Kubrusly ◽  
Nicolás Pérez ◽  
Jean Pierre von der Weid
Keyword(s):  
Fourier Transform ◽  
Guided Waves ◽  
Strain Level ◽  
Energy Concentration ◽  
Short Time Fourier Transform ◽  
Time Frequency ◽  
Frequency Representation ◽  
The Fourier Transform ◽  
Short Time ◽  
Sensitivity Gain

The focused signal obtained by the time-reversal or the cross-correlation techniques of ultrasonic guided waves in plates changes when the medium is subject to strain, which can be used to monitor the medium strain level. In this paper, the sensitivity to strain of cross-correlated signals is enhanced by a post-processing filtering procedure aiming to preserve only strain-sensitive spectrum components. Two different strategies were adopted, based on the phase of either the Fourier transform or the short-time Fourier transform. Both use prior knowledge of the system impulse response at some strain level. The technique was evaluated in an aluminum plate, effectively providing up to twice higher sensitivity to strain. The sensitivity increase depends on a phase threshold parameter used in the filtering process. Its performance was assessed based on the sensitivity gain, the loss of energy concentration capability, and the value of the foreknown strain. Signals synthesized with the time–frequency representation, through the short-time Fourier transform, provided a better tradeoff between sensitivity gain and loss of energy concentration.

scholarly journals Method for designing multi-input system identification signals using a compact time-frequency representation

2021 ◽  
Author(s):  
Mathias Stefan Roeser ◽  
Nicolas Fezans
Keyword(s):  
System Identification ◽  
Design Method ◽  
Flight Test ◽  
Compact Representation ◽  
Time Frequency ◽  
Stability And Control ◽  
Frequency Representation ◽  
Aerodynamic Parameters ◽  
Definition Of ◽  
And Control

AbstractA flight test campaign for system identification is a costly and time-consuming task. Models derived from wind tunnel experiments and CFD calculations must be validated and/or updated with flight data to match the real aircraft stability and control characteristics. Classical maneuvers for system identification are mostly one-surface-at-a-time inputs and need to be performed several times at each flight condition. Various methods for defining very rich multi-axis maneuvers, for instance based on multisine/sum of sines signals, already exist. A new design method based on the wavelet transform allowing the definition of multi-axis inputs in the time-frequency domain has been developed. The compact representation chosen allows the user to define fairly complex maneuvers with very few parameters. This method is demonstrated using simulated flight test data from a high-quality Airbus A320 dynamic model. System identification is then performed with this data, and the results show that aerodynamic parameters can still be accurately estimated from these fairly simple multi-axis maneuvers.

scholarly journals Characterization of Liposomes Using Quantitative Phase Microscopy (QPM)

Pharmaceutics ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 590
Author(s):  
Jennifer Cauzzo ◽  
Nikhil Jayakumar ◽  
Balpreet Singh Ahluwalia ◽  
Azeem Ahmad ◽  
Nataša Škalko-Basnet
Keyword(s):  
Rapid Development ◽  
Fluorescent Labeling ◽  
Label Free ◽  
Batch Mode ◽  
Full Field ◽  
Quantitative Phase ◽  
Phase Microscopy ◽  
Quantitative Phase Microscopy ◽  
Tracking Ability

The rapid development of nanomedicine and drug delivery systems calls for new and effective characterization techniques that can accurately characterize both the properties and the behavior of nanosystems. Standard methods such as dynamic light scattering (DLS) and fluorescent-based assays present challenges in terms of system’s instability, machine sensitivity, and loss of tracking ability, among others. In this study, we explore some of the downsides of batch-mode analyses and fluorescent labeling, while introducing quantitative phase microscopy (QPM) as a label-free complimentary characterization technique. Liposomes were used as a model nanocarrier for their therapeutic relevance and structural versatility. A successful immobilization of liposomes in a non-dried setup allowed for static imaging conditions in an off-axis phase microscope. Image reconstruction was then performed with a phase-shifting algorithm providing high spatial resolution. Our results show the potential of QPM to localize subdiffraction-limited liposomes, estimate their size, and track their integrity over time. Moreover, QPM full-field-of-view images enable the estimation of a single-particle-based size distribution, providing an alternative to the batch mode approach. QPM thus overcomes some of the drawbacks of the conventional methods, serving as a relevant complimentary technique in the characterization of nanosystems.

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