Search results for "Spectral analysi"
showing 10 items of 113 documents
Input for baroreflex analysis: which blood pressure signal should be used?
2022
The baroreflex (BR) is an important physiological regulatory mechanism which reacts to blood pressure perturbations with reflex changes of target variables such as the heart period (electrocardiogram derived RR interval) or the peripheral vascular resistance (PVR). Evaluation of cardiac chronotropic (RR as a target variable) and vascular resistance (target PVR) BR arms was in previous studies mainly based on the use of the spontaneous variability of the systolic or diastolic blood pressure (SBP, DBP), respectively, as the input signals. The use of other blood pressure measures such as the mean blood pressure (MBP) as an input signal for BR analysis is still under investigation. Making the a…
Quantifying High-Order Interactions in Cardiovascular and Cerebrovascular Networks
2022
We present a method to analyze the dynamics of physiological networks beyond the framework of pairwise interactions. Our method defines the so-called O-information rate (OIR) as a measure of the higher-order interaction among several physiological variables. The OIR measure is computed from the vector autoregressive representation of multiple time series, and is applied to the network formed by heart period, systolic and diastolic arterial pressure, respiration and cerebral blood flow variability series measured in healthy subjects at rest and after head-up tilt. Our results document that cardiovascular, cerebrovascular and respiratory interactions are highly redundant, and that redundancy …
Cloaking by anomalous localized resonance via spectral analysis of a Neumann-Poincaré operator
2014
The classical notion of Neumann-Poincar´e (NP) operator appears naturally when we attempt to solve Dirichlet or Neumann boundary value problems using layer potentials. In this talk, we will review some properties of NP-operators and show that they can be used to give a mathematical analysis of cloaking by anomalous localized resonance (CALR). More precisely, we shall discuss the following problem. If a body of dielectric material is coated by a plasmonic structure of negative dielectric constant with nonzero loss parameter, then CALR may occur as the loss parameter tends to zero. Anomalous localized resonance is the phenomenon of field blow-up in a localized region and it may (and may not) …
Iterative Reconstruction of Signals on Graph
2020
We propose an iterative algorithm to interpolate graph signals from only a partial set of samples. Our method is derived from the well known Papoulis-Gerchberg algorithm by considering the optimal value of a constant involved in the iteration step. Compared with existing graph signal reconstruction algorithms, the proposed method achieves similar or better performance both in terms of convergence rate and computational efficiency.
Spectral estimators for Doppler analysis of intracoronary ultrasound catheters
2002
With the zero-cross-detection method (ZCD) it has been shown that it is not possible to achieve a reproducible quantitative, and robust evaluation of an inter-coronary audio signal. The authors define spectral estimators to analyze the Doppler-audio signal. Measurements in a blood flow model have shown that the ZCD method underestimates the expected velocity at all speeds. Spectral analysis allows the determination of the actual and peak velocity more robustly and precisely. >
Energy balance in single exposure multispectral sensors
2013
International audience; Recent simulations of multispectral sensors are based on a simple Gaussian model, which includes filters transmittance and substrate absorption. In this paper we want to make the distinction between these two layers. We discuss the balance of energy by channel in multispectral solid state sensors and propose an updated simple Gaussian model to simulate multispectral sensors. Results are based on simulation of typical sensor configurations.
Site effects assessment through historical and instrumental data integration
2006
ABSTRACT This work illustrates the historical data contribution to the analysis of the microtremor survey results carried out in May 2003 in the city of Palermo by the Istituto Nazionale di Geofisica e Vulcanologia and the Dipartimento di Geologia e Geodesia – University of Palermo. The microtremor survey has been carried out within the project SESAME (Site EffectS assessment using AMbient Excitations) funded by the European Commission, devoted to test the effectiveness of the seismic noise, and in particular of Nakamura technique, in the site effects assessment. The Nakamura technique singles out zones characterized by a near-surface geology suitable to produce site effects, by exploiting …
Sistema di misura per l’analisi spettrale di segnali non stazionari: implementazione in VHDL per lo sviluppo di un prototipo su FPGA
2010
SPECTRAL ANALYSIS WITH TAPERED DATA
1983
. A new method based on an upper bound for spectral windows is presented for investigating the cumulants of time series statistics. Using this method two classical results are proved for tapered data. In particular, the asymptotic normality for a class of spectral estimates including estimates for the spectral function and the covariance function is proved under integrability conditions on the spectra using the method of cumulants.
Neo-clerodane diterpenoids from Scutellaria lateriflora
1998
Abstract Three new diterpenoids, scutelaterins A-C, have been isolated from Scutellaria lateriflora and their structures established as (11S,13S,16S)-2β,6α,19-triacetoxy-4α,18;11,16;15,16-triepoxy-neo-clerod-14-ene (scutelaterin A), (11S,13S,16S)-6α,19-diacetoxy-2β-(2′-methyl)butyryloxy-4α,18;11,16;15,16-triepoxy-neo-clerod-14-ene (scutelaterin B) and (11S,13S,15R and S)-6α,19-diacetoxy-2β-(2′-methyl)butyryloxy-4α,18;11,16;15,16-triepoxy-neo-clerodan-15-ol (scutelaterin C) by chemical and spectroscopic means. In addition, the already known neo-clerodanes ajugapitin and scutecyprol A were also found in the same source.