Bayesian two-compartment and classic single-compartment minimal models: comparison on insulin modified IVGTT and effect of experiment reduction

Models describing plasma glucose and insulin concentration of an intravenous glucose tolerance test (IVGTT) allow a noninvasive cost-effective approach to estimate important indexes characterizing the efficiency of glucose-insulin control system, i.e., glucose effectiveness (S(G)) and insulin sensitivity (S(I)). To overcome some limitations of the classic single compartment minimal model (1CMM) of glucose kinetics , a two-compartment Bayesian minimal model (2CBMM) has been recently proposed for the standard IVGTT. This study aims to assess 2CBMM ability to describe the insulin-modified IVGTT (IM-IVGTT) which is the protocol of choice since it allows to study insulinopenic states. Both a full-length IM-IVGTT (240 min) as well as a reduced version (90 min) of it are studied. Results of the maximum a posteriori identification of IM-IVGTT (240 min) in 13 normals agree with those of standard IVGTT, i.e., a 42% decrease (P < 0.002) of S(G) and a 13% increase (P < 0.006) of S(I) with respect to ICMM. When identified from IM-IVGTT (90 min), 2CBMM not only provides S(G) and S(I) estimates 46% lower (P < 0.002) and 41% higher (P < 0.002) than 1CMM ones respectively, but also seems to overcome some limitations of the 240 min-based identification that probably arise because the minimal model is unable to properly account for the hyperglycemic hormonal response taking place in the second half of IM-IVGTT.     

A new dynamic index of insulin sensitivity

Insulin sensitivity is a crucial parameter of glucose metabolism. The standard measures of insulin sensitivity obtained by an euglycaemic hyperinsulinaemic clamp, S/sub I/(clamp), or by the minimal model (MM), S/sub I/, do not account for the dynamics of insulin action, i.e., how fast or slow insulin action reaches its plateau value. This is an important physiological information. In this paper we formally define a new insulin sensitivity index which also incorporates information on the dynamics of insulin action, S/sub I//sup D/, show its properties, and exemplify how it can be measured both with the clamp and the MM method. Then, by resorting to real and synthetic data, we show both in IVGTT MM and clamp studies why this new index S/sub I//sup D/ offers, in comparison with S/sub I/, a more comprehensive picture of the control of insulin on glucose.     

Mapping of change in cerebral glucose utilization using fluorine-18 fluorodeoxyglucose double injection and the constrained weighted-integration method

The authors developed a method for mapping the change in cerebral glucose utilization at two different physiological states using [(18 )F]fluorodeoxyglucose (FDC) double infection and the constrained weighted-integration method. The authors studied young normal subjects without (baseline-baseline group, n=5) and with (baseline-stimulation group, n=5) vibrotactile stimulation of the fingertips of the right hand. Dynamic scans were performed using positron emission tomography (PET) following an initial dose (the first session, 0-30 min) and an additional dose (the second session, 30-60 min). The parametric images of the net clearance of FDG from blood to brain (K*), unidirectional blood-to-brain clearance (K(1)*), and cerebral metabolic rate of glucose (CMR(glc)) of the two sessions were generated. The averaged subtraction (second minus first session) and t-statistic images were generated, which were rendered into Talairach's stereotaxic coordinates and merged with the averaged magnetic resonance imaging (MRI) image. In the baseline-baseline group, regional K*, K(1)* and CMR(glc) in the first and second sessions were strongly correlated (r(2)=0.953, 0.935, and 0.951, respectively, n=330). In the baseline-stimulation group, significant increases in these estimates were obtained in the contralateral primary somatosensory cortex (SI) (from 3.43+/-0.78 to 4.02+/-1.01 ml/100 g/min for K*, 7.85+/-1.88 to 9.09+/-1.71 ml/100 g/min for K(1)*, and 280+/-5.9 to 32.3+/-5.5 mumol/100 g/min for CMR(glc)), while there were no significant changes in the ipsilateral SI (from 3.45+/-0.83 to 359+/-0.72 ml/100 g/min for K*, 8.17+/-2.33 to 837+/-1.75 ml/100 g/min for K(1 )* and 29.5+/-8.1 to 29.1+/-8.2 mumol/100 g/mln for CMR (glc)), Significant increases in K* and CMR(glc) in the contralateral SI were clearly demonstrated in the t-statistic image. In conclusion, the proposed method allows mapping of changes in cerebral glucose utilization during physiological stimulation of the brain, and will be useful for studying the relationship between neural activity and regional cerebral glucose metabolism.     

Selective recording of the canine hypoglossal nerve using a multicontact flat interface nerve electrode

A flat-interface nerve electrode (FINE) is presented as a potential solution for using multifascicle nerve recordings as part of a closed-loop control system. To investigate the ability of this electrode to achieve selective recordings at physiological signal-to-noise ratio (SNR), a finite-element model (FEM) of a beagle hypoglossal nerve with an implanted FINE was constructed. Action potentials (AP) were generated at various SNR levels and the performance of the electrode was assessed with a selectivity index (0 < or = SI < or = 1; ability of the electrode to distinguish two active sources). Computer simulations yielded a selective range (0.05 < or = SI < or = 0.76) that was 1) related to the interfiber distance and 2) used to predict the minimum interfiber distance (0.23 mm < or = d < or = 1.42 mm) for selective recording at each SNR. The SI was further evaluated using recorded compound APs elicited from electrically activating the branches of the beagle hypoglossal nerve. For all experiments (n = 7), the selectivity (SI = 0.45 +/- 0.16) was within the range predicted by the FEM. This study suggests that the FINE can record the activity from a multifasciculated nerve and, more importantly, distinguish neural signals from pairs of fascicles at physiologic SNR.     

Efficient,perfect polynomial random number generators

Let N be a positive integer and let P [x] be a polynomial that is nonlinear on the set _N of integers modulo N. If, by choosing x at random in an initial segment of _N , P(x) (mod N) appears to be uniformly distributed in _N to any polynomial-time observer, then it is possible to construct very efficient pseudorandom number generators that pass any polynomial-time statistical test. We analyse this generator from two points of view. A complexity theoretic analysis relates the perfectness of the generator to the security of the RSA-scheme. A statistical analysis proves that the least-significant bits of P(x) (mod N) are statistically random.This research was performed while C. P. Schnorr was visiting the Department of Computer Science of the University of Chicago, who also supported his research. A U.S. patent, based on this work, has been granted.     

Generalized M-2M Mapping Scheme for SLM and PTS Based OFDM Systems Without Side-Information

Orthogonal frequency division multiplexing (OFDM) is an attractive multicarrier modulation scheme, but it suffers from the problem of high peak-to-average power ratio (PAPR). Selected mapping (SLM) and partial transmit sequences (PTS) are two well known, distortion-less techniques with good PAPR reduction capabilities. But, both the methods require side information (SI) about the phase rotation factors to recover the original data signal at the receiving end. The transmission of SI not only results in data rate loss but also, in BER performance degradation if SI gets corrupted over the channel. In this paper we have proposed a new mapping scheme, named “ $M\text{- }2M$ Mapping scheme” for SLM and PTS based methods to completely eliminate the requirement of SI at the receiver. In this scheme $M$ data points are mapped to the constellation points of 2M-ary modulation scheme using (1, j) as the phase rotation factors. Some criteria are suggested with which the method is applied for different constellation sizes, $M=4$ to $M=16$ . The method can be easily coupled with conventional SLM and PTS techniques. When compared with the existing methods like multi point square mapping, which do not need SI, our technique is scalable and provides good PAPR reduction capability with consistent BER performance.     

Glucose effectiveness and insulin sensitivity from the minimalmodels: consequences of undermodeling assessed by Monte Carlo simulation

The unlabeled (cold) minimal model (MM) and the labeled (hot) minimal model (HMM) are a powerful tool to investigate in vivo metabolism from a standard intravenous glucose tolerance test (IVGTT) or hot IVGTT (HIVGTT). They allow to estimate metabolic indexes of the glucose-insulin system, namely glucose effectiveness (GE) and insulin sensitivity (IS) (of uptake and production those of MM, and of uptake only these of HMM). Here, the consequences of the single-compartment glucose kinetics approximation used in the MM's are investigated via Monte Carlo simulation, using a physiologic reference model (RM) of the system, RM allows to generate noisy synthetic plasma concentrations of glucose, tracer glucose, and insulin during IVGTT and HIVGTT, which are then analyzed with MM and HMM. The MM and HMM CE and IS are then compared with the RM ones. Results of 400 runs show that: (1) correlation of MM GE with the RM index is weak; (2) MM IS is well correlated with the RM index, but severely underestimates it; (3) HMM clearance rate is correlated with RM clearance; and (4) HMM IS is well correlated and only slightly overestimates the RM index. These results demonstrate that GE of MM is most affected by the single-compartment approximation and the indexes of HMM are more robust than those of MM     

Voice low tone to high tone ratio: a potential quantitative index for vowel [a:] and its nasalization

Hypernasality is associated with various diseases and interferes with speech intelligibility. A recently developed quantitative index called voice low tone to high tone ratio (VLHR) was used to estimate nasalization. The voice spectrum is divided into low-frequency power (LFP) and high-frequency power (HFP) by a specific cutoff frequency (600 Hz). VLHR is defined as the division of LFP into HFP and is expressed in decibels. Voice signals of the sustained vowel [a :] and its nasalization in eight subjects with hypernasality were collected for analysis of nasalance and VLHR. The correlation of VLHR with nasalance scores was significant (r = 0.76, p < 0.01), and so was the correlation between VLHR and perceptual hypernasality scores (r = 0.80, p < 0.01). Simultaneous recordings of nasal airflow temperature with a thermistor and voice signals in another 8 healthy subjects showed a significant correlation between temperature rate of nasal airflow and VLHR (r = 0.76, p < 0.01), as well. We conclude that VLHR may become a potential quantitative index of hypernasal speech and can be applied in either basic or clinical studies.     

Deterministic tests for detecting singleV-coupling faults in RAMs

We consider the problem of detecting singleV-coupling faults (as defined by Nair, Thatte, and Abraham) inn×1 random-access memories (RAMs). First we derive a lower bound of 2 ^V–2 nlog₂ n+(2 ^V +3)n on the length of any test that detects all singleV-coupling faults, for 2V47 andn=2 ^e wheree{8,...,34}. In the derivation we make use of a family of binary codes which we call (n, )-exhaustive codes. We then describe a procedure which, given any (n, V–1)-exhaustive code, constructs a test that detects all singleV-coupling faults, fornV>2. Following this approach, optimal (n,1)- and (n, 2)-exhaustive codes are used to construct S2CTEST and S3CTEST, which are efficient tests of length 10n and 4nlog₂ n+18n that detect all single 2- and 3-coupling faults, respectively. S3CTEST is roughly five times shorter, for current RAM capacities, than Papachristou and Sahgal's test of length 24n[log₂ n]+n. Codes generated according to Tang and Chen are used similarly to construct S4CTEST and S5CTEST, which are tests of approximate length 8.6n(log₂ n)^1.585 and 9.6n(log₂ n)^2.322 that detect all single 4- and 5-coupling faults, respectively. S5CTEST has the interesting property of being able to detect all single physical neighborhood pattern-sensitive faults without requiring the mapping from logical cell addresses to physical cell locations. S5CTEST also detects the scrambled pattern-sensitive fault recently proposed by Franklin and Saluja; moreover, the new test is approximately fourteen times shorter (for 1 and 4 Mbit RAMs) than the test they describe.This work was supported by operating grants from the Central Research Fund of the University of Alberta and the Natural Sciences and Engineering Research Council of Canada under grant OGP0105567.     

Experimental evidence of improved transthoracic defibrillation with electroporation-enhancing pulses

There is considerable work on defibrillation wave form optimization. This paper determines the impedance changes during defibrillation, then uses that information to derive the optimum defibrillation wave form. METHODS PART I: Twelve guinea pigs and six swine were used to measure the current wave form for square voltage pulses of a strength which would defibrillate about 50% of the time. In guinea pigs, electrodes were placed thoracically, abdominally and subcutaneously using two electrode materials (zinc and steel) and two electrode pastes (Core-gel and metallic paste). RESULTS PART I: The measured current wave form indicated an exponentially increasing conductance over the first 3 ms, consistent with enhanced electroporation or another mechanism of time-dependent conductance. We fit this current with a parallel conductance composed of a time-independent component (g0 = 1.22 +/- 0.28 mS) and a time-dependent component described by g delta (1-e(-t/tau)), where g delta = 0.95 +/- 0.20 mS and tau = 0.82 +/- 0.17 ms in guinea pigs using zinc and Cor-gel. Different electrode placements and materials had no significant effect on this fit. From our fit, we determined the stimulating wave form that would theoretically charge the myocardial membrane to a given threshold using the least energy from the defibrillator. The solution was a very short, high voltage pulse followed immediately by a truncated ascending exponential tail. METHODS PART II: The optimized wave forms and similar nonoptimized wave forms were tested for efficacy in 25 additional guinea pigs and six additional swine using methods similar to Part I. RESULTS PART II: Optimized wave forms were significantly more efficacious than similar nonoptimized wave forms. In swine, a wave form with the short pulse was 41% effective while the same wave form without the short pulse was 8.3% effective (p < 0.03) despite there being only a small difference in energy (111 J versus 116 CONCLUSIONS: We conclude that a short pulse preceding a defibrillation pulse significantly improves efficacy, perhaps by enhancing electroporation.     

A note on the semiconductor current flow equations

The current flow equations for nondegenerate and degenerate semiconductors at low temperature are discussed in terms of the Boltzmann transport equation. It is shown that the diffusion current in an inhomogeneous but isotropic semiconductor must be expressed as q.D(r). ∇n(r) where n(r) is the carrier (electron) concentration and D(r) is a spatially varying diffusion "constant." Some formulas which have been given for semiconductor device parameters, i.e., the emitter efficiency for heavily doped transistors when expressed as a ratio of resistivities, could be rigorously developed if the diffusion current were expressible as q.∇[D(r)n(r)]. However, this form is not consistent with the transport equation from which D(r) can be defined and evaluated.     

Modified Closed-form Dispersion and Loss Models of Slot-Line with Conductor Thickness

The CAD oriented closed-form models are presented to compute frequency and conductor thickness dependent effective relative permittivity and characteristic impedance of a slot-line with finite conductor thickness in the range 3 μm–50 μm. The models have average accuracy about 2% against the full-wave results from different sources in the frequency range 2 GHz–60 GHz, \( 2.22 \leqslant {\varepsilon_r} \leqslant 20 \), \( {{0.02 \leqslant {\text{w}}} \mathord{\left/{\vphantom {{0.02 \leqslant {\text{w}}} {\text{h}}}} \right.} {\text{h}}} \leqslant 1.0 \), \( {{{{0.01 \leqslant h} \mathord{\left/{\vphantom {{0.01 \leqslant h} {{\lambda_0} \leqslant 0.25}}} \right.} {{\lambda_0} \leqslant 0.25}}} \mathord{\left/{\vphantom {{{{0.01 \leqslant h} \mathord{\left/{\vphantom {{0.01 \leqslant h} {{\lambda_0} \leqslant 0.25}}} \right.} {{\lambda_0} \leqslant 0.25}}} {\sqrt {\left( {{\varepsilon_{\text{r}}} - 1} \right)} }}} \right.} {\sqrt {\left( {{\varepsilon_{\text{r}}} - 1} \right)} }} \). The models to compute the dielectric and conductor losses are also presented that show close agreement with the results of the spectral domain analysis. The average deviations for the dielectric and conductor losses are 0.011 Np/m and 0.143 Np/m against the results of SDA in the frequency range 2 GHz–30 GHz for narrow to wide slot-width.     

Composition and parameters of domains resulting from spinodal decomposition of quaternary alloys in epitaxial GaInP/Ga x In1 ? x As y P1 ? y /GaInP/GaAs(001) heterostructures

Structural and optical properties of two- and three-layer epitaxial heterostructures containing GaInP/Ga _x In_{1 − x} As _y P_{1 − y} quaternary alloy layers were studied. Domain formation due to spinodal decomposition of the quaternary alloy was detected in three-layer heterostructures. As a result, an additional long-wavelength band appears in the photoluminescence spectra, and an additional doublet of the line appears in X-ray diffraction patterns of the (006) line. The domain composition was determined on the basis of Vegard’s law and the Kouphal equation. Original Russian Text ? E.P. Domashevskaya, N.N. Gordienko, N.A. Rumyantseva, B.L. Agapov, P.V. Seredin, L.A. Bityutskaya, I.N. Arsent’ev, L.S. Vavilova, I.S. Tarasov, 2008, published in Fizika i Tekhnika Poluprovodnikov, 2008, Vol. 42, No. 9, pp. 1086–1093.     

Method for three-dimensional data registration from disparate imaging modalities in the NOGA Myocardial Viability Trial

Region-by-region comparison of data concerning left ventricular (LV) status is difficult to perform quantitatively if the data was acquired from disparate imaging modalities. We validated a method for comparing measurements obtained by electromechanical mapping (EMM) catheter with dobutamine stress echocardiography (DSE) via biplane contrast ventriculography, with the assistance of three-dimensional (3-D) echocardiographic data. The ventriculograms were traced and the borders were used to reconstruct the LV in 3-D with the aid of a database of 3-D echocardiographic studies. The 3-D LV was oriented to the EMM data based on the body coordinates and then manually scaled and translated to fit. The EMM data were mapped to the 3-D surface. The 3-D surface was divided into the 16 regions defined for echocardiographic assessment. The mean EMM value for local linear shortening, a parameter of function, was computed in each segment. The EMM and semiquantitative echocardiographic assessments of regional myocardial function were compared by segment, and the volume of the 3-D LV was compared with the volume computed from the ventriculogram. The volume of the 3-D surface correlated closely with that of the ventriculogram (r = 0.97, SEE = 27.4 ml) but with a significant overestimation of 63 +/- 35 ml. There was a highly significant (p < 0.0001) agreement in regional function between EMM and echo. Local linear shortening correlated significantly (p < 0.0001) with echocardiographic severity of wall motion, averaging 9.5 +/- 6.5, 8.1 +/- 5.4, 5.9 +/- 4.8, and 6.2 +/- 3.3 in segments read as normal, hypokinetic, akinetic, and dyskinetic, respectively. The method presented is valid for comparing cardiac parameters derived from disparate image data on a region-by-region basis by employing anatomic landmarks on 3-D reconstructions of the LV endocardial surface.     

NaK(E)态的离解和Na(3PJ)精细结构分支比

研究了Na(3S) +K(4S) +nhν→Na(3PJ) +K(4S) +(n - 1 )hν过程 ,激光频率ν调到Na共振跃迁的两翼 ,分支比定义为I(D1 ) /I(D2 ) ,I(D1 ) ,I(D2 )分别是NaD1 ,D2 线的强度 ,在K密度 2～ 8× 1 0 2 0 m-3 范围内 ,测量了从Na共振跃迁的蓝翼 30 0cm-1 到红翼 1 0 0cm-1 的分支比 ,得到了离解率之比和精细结构转移截面 ,在近翼 ,分支比与ν有很大的关系。用对Na3PJ 态共振激发的方法 ,也得到了精细结构转移截面 ,对结果进行了讨论     

Domain Specific Reconfigurable Processing Core Architecture for Digital Filtering Applications

This paper presents a reconfigurable processing core architecture targeted for digital filtering applications. The architecture can be configured to execute linear phase FIR filter, DLMS adaptive FIR filter, (I)FFT, and 2D-(I)DCT with high performance and low energy consumption by reducing heavy routing resources used extensively in other reconfigurable architectures. The pipeline depth of the multipliers in the processing core is locally controlled so that power consumption is reduced by minimizing unnecessary register switching is saved. We have shown that the proposed processing core consumes less energy and has better or comparable performance than that of the existing reconfigurable architectures proposed in academia and industry, that have been tailored for these applications. The circuit is designed in 0.35-m CMOS processing technology with 3.3 V supply voltage.Sangjin Hong received the B.S. and M.S. degrees in EECS from the University of California, Berkeley and his Ph.D in EECS from the University of Michigan, Ann Arbor. He is currently with the department of Electrical and Computer Engineering at Stony Brook University - State University of New York. Before joining SUNY, he has worked at Ford Aerospace Corp. Computer Systems Division as a systems engineer. He also worked at Samsung Electronics in Korea as a technical consultant. His current research interests are in the areas of low power reconfigurable SoC design and optimization for DSP and wireless communication systems. He has served as a member of technical committee and track chair for numerous IEEE technical conferences.Shu-Shin Chin was born in Kaohsiung, Taiwan, ROC, in 1974. He received his M.S. and Ph.D degrees in electrical and computer engineering from Stony Brook University—State University of New Yorkin 1999 and 2004, respectively. His research interests include low-power digital circuits, and coarse-grained reconfigurable architectures for high-performance DSP systems.     

The efficiency of computing the reliability of k-out-of n systems

It is shown that the algorithm of R.S. Barlow and K.D. Heidtmann (ibid., vol.R-33, p.322-3, Oct. 1984) is more computationally efficient than those reported by S.P. Jain and K. Gopal (ibid., vol.R-34, p.144-6, June 1985) and S. Rai et al. (ibid., vol.R-36, p.261-5, June 1987). Efficiency is measured here by the number of multiplications     

Capacity and lattice strategies for canceling known interference

We consider the generalized dirty-paper channel Y=X+S+N,E{X/sup 2/}/spl les/P/sub X/, where N is not necessarily Gaussian, and the interference S is known causally or noncausally to the transmitter. We derive worst case capacity formulas and strategies for "strong" or arbitrarily varying interference. In the causal side information (SI) case, we develop a capacity formula based on minimum noise entropy strategies. We then show that strategies associated with entropy-constrained quantizers provide lower and upper bounds on the capacity. At high signal-to-noise ratio (SNR) conditions, i.e., if N is weak relative to the power constraint P/sub X/, these bounds coincide, the optimum strategies take the form of scalar lattice quantizers, and the capacity loss due to not having S at the receiver is shown to be exactly the "shaping gain" 1/2log(2/spl pi/e/12)/spl ap/ 0.254 bit. We extend the schemes to obtain achievable rates at any SNR and to noncausal SI, by incorporating minimum mean-squared error (MMSE) scaling, and by using k-dimensional lattices. For Gaussian N, the capacity loss of this scheme is upper-bounded by 1/2log2/spl pi/eG(/spl Lambda/), where G(/spl Lambda/) is the normalized second moment of the lattice. With a proper choice of lattice, the loss goes to zero as the dimension k goes to infinity, in agreement with the results of Costa. These results provide an information-theoretic framework for the study of common communication problems such as precoding for intersymbol interference (ISI) channels and broadcast channels.     

X-ray metrology for high-k atomic layer deposited HfxZr1−xO2 films

Hafnium-based dielectrics are the most promising material for SiO₂ replacement in future nodes of CMOS technology. While devices that utilize HfO₂ gate dielectrics suffer from lower carrier mobility and degraded reliability, our group has recently reported improved device characteristics with a modified Hf_xZr_1−xO₂ [R.I. Hegde, D.H. Triyoso, P.J. Tobin, S. Kalpat, M.E. Ramon, H.-H. Tseng, J.K. Schaeffer, E. Luckowski, W.J. Taylor, C.C. Capasso, D.C. Gilmer, M. Moosa, A. Haggag, M. Raymond, D. Roan, J. Nguyen, L.B. La, E. Hebert, R. Cotton, X.-D. Wang, S. Zollner, R. Gregory, D. Werho, R.S. Rai, L. Fonseca, M. Stoker, C. Tracy, B.W. Chan, Y.H. Chiu, B.E. White, Jr., in: Technical Digest - International Electron Devices Meet, vol. 39, 2005, D.H. Triyoso, R.I. Hegde, J.K. Schaeffer, D. Roan, P.J. Tobin, S.B. Samavedam, B.E. White, Jr., R. Gregory, X.-D. Wang, Appl. Phys. Lett. 88 (2006) 222901]. These results have lead to evaluation of X-ray reflectivity (XRR) for monitoring high-k film thickness and control of Zr addition to HfO₂ using measured film density. In addition, a combination of XRR and spectroscopic ellipsometry (SE) is shown to be a fast and non-intrusive method to monitor thickness of interfacial layer between high-k and the Si substrate.     

Nonlinear transient chirp signal modeling of the aortic and pulmonary components of the second heart sound

This paper describes a new approach based on the time-frequency representation of transient nonlinear chirp signals for modeling the aortic (A2) and the pulmonary (P2) components of the second heart sound (S2). It is demonstrated that each component is a narrow-band signal with decreasing instantaneous frequency defined by its instantaneous amplitude and its instantaneous phase. Each component is also a polynomial phase signal, the instantaneous phase of which can be accurately represented by a polynomial having an order of thirty. A dechirping approach is used to obtain the instantaneous amplitude of each component while reducing the effect of the background noise. The analysis-synthesis procedure is applied to 32 isolated A2 and 32 isolated P2 components recorded in four pigs with pulmonary hypertension. The mean +/- standard deviation of the normalized root-mean-squared error (NRMSE) and the correlation coefficient (rho) between the original and the synthesized signal components were: NRMSE = 2.1 +/- 0.3% and rho = 0.97 +/- 0.02 for A2 and NRMSE = 2.52 +/- 0.5% and rho = 0.96 +/- 0.02 for P2. These results confirm that each component can be modeled as mono-component nonlinear chirp signals of short duration with energy distributions concentrated along its decreasing instantaneous frequency.