scholarly journals Photosynthesis dynamics and regulation sensed in the frequency domain

2021 ◽  
Author(s):  
Ladislav Nedbal ◽  
Dušan Lazár
Keyword(s):  
Experimental Data ◽  
Frequency Domain ◽  
Time Domain ◽  
Fluorescence Emission ◽  
Plant Responses ◽  
Wide Range ◽  
Harmonic Modulation ◽  
Photosynthetic Regulation ◽  
Time Domain Response ◽  
Changing Light

AbstractFoundations of photosynthesis research have been established mainly by studying the response of plants to changing light, typically to sudden exposure to a constant light intensity after a dark acclimation or to light flashes. This approach remains valid and powerful, but can be limited by requiring dark acclimation prior to time-domain measurements and often assumes that rate constants determining the photosynthetic response do not change between the dark- and light-acclimation.We present experimental data and a mathematical model demonstrating that these limits can be overcome by measuring plant responses to sinusoidally modulated light of varying frequency. By its nature, such frequency domain characterization is performed in light-acclimated plants with no need for prior dark acclimation. Amplitudes, phase shifts and upper harmonic modulation extracted from the data for a wide range of frequencies can target different kinetic domains and regulatory feedbacks. The occurrence of upper harmonic modulation reflects non-linear phenomena, including photosynthetic regulation. To support these claims, we present a frequency and time domain response in chlorophyll fluorescence emission of the green alga Chlorella sorokiniana in the frequency range 1000 – 0.001 Hz. Based on these experimental data and on numerical as well as analytical mathematical models, we propose that the frequency domain measurements can become a versatile new tool in plant sensing.One sentence summaryIt is proposed to characterize photosynthesis in the frequency domain without the need for dark adaptation and, thus, without assumptions about the dark-to-light transition.

scholarly journals Scattering of an Impact Wave by a Crack in a Composite Plate

1992 ◽  
Vol 59 (3) ◽  
pp. 596-603 ◽  
Author(s):  
S. K. Datta ◽  
T. H. Ju ◽  
A. H. Shah
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Impact Load ◽  
Near Field ◽  
Boundary Integral ◽  
Transition Elements ◽  
Element Discretization ◽  
Crack Tips ◽  
Time Domain Response ◽  
The Time Domain

The surface responses due to impact load on an infinite uniaxial graphite/epoxy plate containing a horizontal crack is investigated both in time and frequency domain by using a hybrid method combining the finite element discretization of the near-field with boundary integral representation of the field outside a contour completely enclosing the crack. This combined method leads to a set of linear unsymmetric complex matrix equations, which are solved to obtain the response in the frequency domain by biconjugate gradient method. The time-domain response is then obtained by using an FFT. In order to capture the time-domain characteristics accurately, high-order finite elements have been used. Also, both the six-node singular elements and eight-node transition elements are used around the crack tips to model the crack-tip singularity. From the numerical results for surface responses it seems possible to clearly identify both the depth and length of this crack.

scholarly journals Innovative Multi-Site Photoplethysmography Analysis for Quantifying Pulse Amplitude and Timing Variability Characteristics in Peripheral Arterial Disease

2018 ◽  
Author(s):  
Michael Bentham ◽  
Gerard Stansby ◽  
John Allen
Keyword(s):  
Peripheral Arterial Disease ◽  
Frequency Domain ◽  
Time Domain ◽  
Domain Analysis ◽  
Arterial Disease ◽  
Timing Variability ◽  
Wide Range ◽  
Healthy Control ◽  
The Time Domain ◽  
Peripheral Arterial

Photoplethysmography (PPG) is a simple-to-perform vascular optics measurement technique that can detect changes in blood volume in the microvascular tissue bed. Beat-to-beat analysis of the PPG waveform enables the study of the variability of pulse features such as amplitude and pulse arrival time (PAT), and when quantified in the time and frequency domains, has considerable potential to shed light on perfusion changes associated with peripheral arterial disease (PAD). In this pilot study innovative multi-site bilateral finger and toe PPG recordings from 43 healthy control subjects and 31 PAD subjects were compared (recordings each at least 5 minutes, collected in a warm temperature-controlled room). Beat-to-beat normalized amplitude and PAT variability was then quantified in the time-domain using SD and IQR measures and in the frequency-domain bilaterally using Magnitude Squared Coherence (MSC). Significantly reduced normalized amplitude variability (healthy control 0.0384 (IQR 0.0217-0.0744) vs PAD 0.0160 (0.0080-0.0338) (p<0.001) and significantly increased PAT variability (healthy control 0.0063 (0.0052-0.0086) vs PAD 0.0093 (0.0078-0.0144) (p<0.001) was demonstrated in PAD using the time-domain analysis. Frequency-domain analysis demonstrated significantly lower MSC values across a range of frequency bands for PAD patients. These changes suggest a loss of right-to-left body side coherence and cardiovascular control in PAD. This study has also demonstrated the feasibility of using these measurement and analysis methods in studies investigating multi-site PPG variability for a wide range of cardiac and vascular patient groups.

scholarly journals Determination of the response of a class of nonlinear time invariant systems

1981 ◽  
Vol 4 (3) ◽  
pp. 615-623
Author(s):  
Sudhangshu B. Karmakar
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Inverse Laplace Transform ◽  
New Approach ◽  
Functional Expansion ◽  
Expansion Time ◽  
Time Domain Response ◽  
The Time Domain ◽  
Time Invariant

This paper illustrates by means of a simple example a new approach for the determination of the time domain response of a class of nonlinear systems. The system under investigation is assumed to be described by a nonlinear differential equation with forcing term. The response of the system is first obtained in terms of the input in the form of a Volterra functional expansion. Each of the components in the expansion is first transformed into a multidimensional frequency domain and then to a single dimensional frequency domain by the technique of association of variables. By taking into consideration the conditions for the rapid convergence of the functional expansion the response of the system in the frequency domain can effectively be obtained by taking only the first few terms of the expansion. Time domain response is then found by inverse Laplace transform.

NUMERICAL SIMULATION ON THE MECHANICAL BEHAVIOR OF OUTER STEREOCILIA IN CORTI

2016 ◽  
Vol 17 (03) ◽  
pp. 1750045
Author(s):  
WENJUAN YAO ◽  
YIQIANG CHEN
Keyword(s):  
Experimental Data ◽  
Frequency Domain ◽  
Time Domain ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Outer Hair Cells ◽  
Tectorial Membrane ◽  
Fe Model ◽  
Velocity Difference ◽  
Sinusoidal Excitation

In this paper, a two-dimensional model of the organ of Corti (OC) which includes basilar membrane (BM), tectorial membrane (TM), inner and outer hair cells and reticular lamina (RL) is established by Comsol. Based on experimental data that sinusoidal excitation was applied on the pectinate zone of the BM, the incentives are added to the corresponding position of the model. Transient analysis is made and the displacement of six different positions is achieved. The results are in good agreement with experimental data, which confirms the validity of the FE model. Based on time-domain and frequency-domain analysis, the relative motion between stereocilia and TM and RL is studied under sinusoidal excitation. The results show that, under time-domain analysis, the whole trend of relative displacement and velocity difference of Inner is similar to that of Outer, while there is little different when comparing with Middle. The relative velocity difference of Middle and Inner lag behind Outer with roughly 0.01[Formula: see text]s. Under frequency-domain analysis, at characteristic frequency, the deviation of each stereocilium is the largest. In the meantime, the frequency that the maximum value of outer stereocilia achieved is different. This new finding may cause the difference of lateral vibration of BM and indicate the frequency sensitivity of BM.

Approximate Structural Response Characterization Using Parametric and Envelope Models for Multimodal Systems

1986 ◽  
Vol 108 (1) ◽  
pp. 39-43
Author(s):  
P. Davies ◽  
J. K. Hammond
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Structural Response ◽  
Parametric Models ◽  
Response Signal ◽  
Response Characteristics ◽  
Multimodal Systems ◽  
Time Domain Response ◽  
The Time Domain

In the study of the response of systems to an excitation there are circumstances when it is desirable to obtain some overall or average characterization of the system and its response rather than a detailed description. In this paper two methods are used to describe the overall features of the system: one appropriate for the frequency domain and one for the time domain. For modally dense systems the main features of the frequency response function are described in terms of low-order parametric models. While these models may be adequate for the frequency domain representation, they may not produce a good approximation to the response of the system in the time domain. The second approach relates the envelope of the input signal to the envelope of the response signal, in order to describe the overall time domain response characteristics.

The Application of Adaptive Canceling in Chaos Identification

2003 ◽  
Author(s):  
Shuyong Liu ◽  
Shijian Zhu ◽  
Zhenming Liu ◽  
Weiian Qian
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Chaotic Signal ◽  
Lms Algorithm ◽  
Measuring System ◽  
Adaptive Technique ◽  
Time Domain Response ◽  
The Time Domain

The time domain response of a system is inevitably contaminated by noise arising from the environment as well as the measuring system itself. So an effective method is needed to reduce the noise components. The characteristic of the chaotic signal and noise in the frequency domain is analyzed. An adaptive canceling system based on the LMS algorithm is applied to process the contaminated signal. The simulation result shows that the adaptive technique can meet the goal.

scholarly journals A Computationally Efficient Algorithm for Feedforward Active Noise Control Systems

Electronics ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 1504 ◽  
Author(s):  
Stefano Gaiotto ◽  
Antonino Laudani ◽  
Gabriele Maria Lozito ◽  
Francesco Riganti Fulginei
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Noise Control ◽  
Active Noise Control ◽  
Parameter Tuning ◽  
Processing Load ◽  
Block Basis ◽  
Active Noise ◽  
Wide Range ◽  
The Time Domain

In this paper, a novel algorithm with high computational efficiency is proposed for the filter adaptation in a feedforward active noise control system. The proposed algorithm Zero Forcing Block Adaptive Filter (ZF-BAF) performs filter adaptation on a block-by-block basis in the frequency domain. Filtering is performed in the time domain on a sample-by-sample basis. Working in the frequency domain permits us to get sub-linear complexity, whereas filtering in the time domain minimizes the latency. Furthermore, computational burden is tunable to meet specific requirements about adaptation speed and processing load. No other parameter tuning according to the working condition is required. Computer simulations, performed in different realistic cases against other high-performing time and frequency-domain algorithms, show that achievable performances are comparable, or even better, with those of the algorithms perfectly tuned for each specific case. Robustness exhibited in the tests suggests that performances are expected to be even better in a wide range of real cases where it is impossible to know a priori how to tune the algorithms.

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