Stochastic mean-square performance analysis of an adaptive Hammerstein filter

Journal ArticleAbstract-This paper presents an almost sure mean-square performance analysis of an adaptive Hammerstein filter for the case when the measurement noise in the desired response signal is a martingale difference sequence. The system model consists of a series connection of a memoryless nonlinearity followed by a recursive linear filter. A bound for the long-term time average of the squared a posteriori estimation error of the adaptive filter is derived using a basic set of assumptions on the operating environment. This bound consists of two terms, one of which is proportional to a parameter that depends on the step size sequences of the algorithm and the other that is inversely proportional to the maximum value of the increment process associated with the coefficients of the underlying system. One consequence of this result is that the long-term time average of the squared a posteriori estimation error can be made arbitrarily close to its minimum possible value when the underlying system is time-invariant

A stable adaptive Hammerstein filter employing partial orthogonalization of the input signals

Journal ArticleAbstract This paper presents an algorithm that adapts the parameters of a Hammerstein system model. Hammerstein systems are nonlinear systems that contain a static nonlinearity cascaded with a linear system. In this work, the static nonlinearity is modeled using a polynomial system and the linear filter that follows the nonlinerity is an infinite impulse response system. The adaptation of the nonlinear components is enhanced in the algorithm by orthogonalizing the inputs to the coefficients of the polynomial system. The linear system is implemented as a recursive higher-order filter. The step sizes associated with the recursive components are constrained in such a way as to guarantee bounded-input, bounded-output stability of the overall system. Experimental results included in the paper show that the algorithm performs well and always converges to the global minimum of the input signal is white

A stable adaptive Hammerstein filter employing partial orthogonalization of the input signals

Journal ArticleAbstract-This paper presents an algorithm that adapts the parameters of a Hammerstein system model. Hammerstein systems are nonlinear systems that contain a static nonlinearity cascaded with a linear system. In this paper, the static nonlinearity is modeled using a polynomial system, and the linear filter that follows the nonlinearity is an infinite-impulse response (IIR) system. The adaptation of the nonlinear components is improved by orthogonalizing the inputs to the coefficients of the polynomial system. The step sizes associated with the recursive components are constrained in such a way as to guarantee bounded-input bounded-output (BIBO) stability of the overall system. This paper also presents experimental results that show that the algorithm performs well in a variety of operating environments, exhibiting stability and global convergence of the algorithm

Identification of nonlinear, memoryless systems using chebyshev nodes

Journal ArticleABSTRACT This paper describes an approach for identification of static nonlinearities from input-output measurements. The approach is based on minimax approximation of memoryless nonlinear systems using Chebyshev polynomials. For memoryless nonlinear systems that are finite and continuous with finite derivatives, it is known that the error caused by the K th order Chebyshev approximation in a specified interval is bounded by a quantity that is proportional to the maximum value of the (K + 1) th derivative of the inputoutput relationship and decays exponentially with K. The method of the paper identifies the system by first estimating the system output at the Chebyshev nodes using localized linear model around the nodes, and then solving for the coefficients associated with the Chebyshev polynomials of the first kind

NMR evaluation of ammonium ion movement within a unimolecular G-quadruplex in solution

d[G4(T4G4)3] has been folded into a unimolecular G-quadruplex in the presence of 15NH4+ ions. NMR spectroscopy confirmed that its topology is the same as the solution state structure determined earlier by Wang and Patel (J. Mol. Biol., 1995; 251: 76–94) in the presence of Na+ ions. The d[G4(T4G4)3] G-quadruplex exhibits four G-quartets with three 15NH4+-ion-binding sites (O1, I and O2). Quantitative analysis utilizing 15NH4+ ions as a NMR probe clearly demonstrates that there is no unidirectional 15NH4+ ion movement through the central cavity of the G-quadruplex. 15NH4+ ions move back and forth between the binding sites within the G-quadruplex and exchange with ions in bulk solution. 15NH4+ ion movement is controlled by the thermodynamic preferences of individual binding sites, steric restraints of the G-quartets for 15NH4+ ion passage and diagonal versus edge-type arrangement of the T4 loops. The movement of 15NH4+ ions from the interior of the G-quadruplex to bulk solution is faster than exchange within the G-quadruplex. The structural details of the G-quadruplex define stiffness of individual G-quartets that intimately affects 15NH4+ ion movement. The stiffness of G-quartets and steric hindrance imposed by thymine residues in the loops contribute to the 5-fold difference in the exchange rate constants through the outer G-quartets

Computational design and characterization of nanobody-derived peptides that stabilize the active conformation of the β2-adrenergic receptor (β2-AR)

This study aimed to design and functionally characterize peptide mimetics of the nanobody (Nb) related to the β2-adrenergic receptor (β2-AR) (nanobody-derived peptide, NDP). We postulated that the computationally derived and optimized complementarity-determining region 3 (CDR3) of Nb is sufficient for its interaction with receptor. Sequence-related Nb-families preferring the agonist-bound active conformation of β2-AR were analysed using the informational spectrum method (ISM) and β2-AR:NDP complexes studied using protein-peptide docking and molecular dynamics (MD) simulations in conjunction with metadynamics calculations of free energy binding. The selected NDP of Nb71, designated P3, was 17 amino acids long and included CDR3. Metadynamics calculations yielded a binding free energy for the β2-AR:P3 complex of ΔG = (−7.23 ± 0.04) kcal/mol, or a Kd of (7.9 ± 0.5) μM, for T = 310 K. In vitro circular dichroism (CD) spectropolarimetry and microscale thermophoresis (MST) data provided additional evidence for P3 interaction with agonist-activated β2-AR, which displayed ~10-fold higher affinity for P3 than the unstimulated receptor (MST-derived EC50 of 3.57 µM vs. 58.22 µM), while its ability to inhibit the agonist-induced interaction of β2-AR with β-arrestin 2 was less evident. In summary, theoretical and experimental evidence indicated that P3 preferentially binds agonist-activated β2-AR. © 2019, The Author(s)

The effect of inelastic processes on tunneling

We study an electron that interacts with phonons or other linear or nonlinear excitations as it resonantly tunnels. The method we use is based on mapping a many-body problem in a large variational space exactly onto a one-body problem. The method is conceptually simpler than previous Green's function approaches, and allows the essentially exact numerical solution of much more general problems. We solve tunneling problems with transverse channels, multiple sites coupled to phonons, and multiple phonon degrees of freedom and excitations.Comment: 12 pages, REVTex, 4 figures in compressed tar .ps forma

Liraglutide Improved Cardiometabolic Parameters More in Obese than in Non-obese Patients with Type 2 Diabetes: A Real-World 18-Month Prospective Study

Introduction The glucagon-like peptide-1 agonist (GLP1-RA) liraglutide is currently approved for the treatment of both obesity and type 2 diabetes (T2DM). We investigated whether the effect of this agent on cardiometabolic parameters in subjects with T2DM varied in relation to the concomitant presence of obesity. Methods One hundred thirty-five subjects (78 men and 57 women; age: 62 +/- 10 years) naive to incretin-based therapies were treated with low-dose liraglutide (1.2 mg/day) as an add-on to metformin for 18 months. Patients were divided into two subgroups based on their body-mass index (BMI): (a) obese (BMI >= 30) and (b) non-obese (BMI < 30). Clinical and laboratory analyses were assessed at baseline and every 6 months. Results During follow-up, significant improvements were seen in both groups in fasting glycemia, glycated hemoglobin, waist circumference, and carotid intima-media thickness (cIMT), while body weight, BMI, total cholesterol, and low-density lipoprotein cholesterol decreased significantly in obese subjects only. Correlation analysis revealed that changes in subclinical atherosclerosis (assessed by cIMT) were associated with changes in triglycerides (r = 0.488, p < 0.0001) in the obese group only. Conclusion Liraglutide had beneficial actions on glycemic parameters and cardiometabolic risk factors in both non-obese and obese patients with T2DM, with a greater efficacy in the latter. These findings reinforce the benefits of liraglutide for the cardiometabolic outcomes of obese patients with T2DM in the real-world setting. This has critical importance during the current pandemic, since patients with diabetes and obesity are exposed globally to the most severe forms of COVID-19, related complications, and death

Applying Frostbuster in protecting orchards from frost

Posljednjih je godina relativno velika učestalost pojave kasnoproljetnih mrazova u trajnim nasadima. Intenzitet pojave mraza za vrijeme cvatnje voćaka bio je takav da su voćari ostali bez cjelokupnog uroda, a posljedice su se osjetile duže vrijeme. Sustav navodnjavanja kišenjem u dobroj mjeri može biti učinkovit način zaštite od mraza, ali ima dosta nedostataka jer dolazi do pucanja grana zbog velike količine leda, tlo u nasadu je potpuno raskvašeno pa je otežan prohod traktora, a često se javljaju i bolesti u nasadu. Primjena suvremenog stroja „Frostbuster“ tijekom cvatnje voćaka (jabuka, kruška, breskva, marelica, trešnja, šljiva) osigurava pouzdanu i učinkovitu zaštitu od mraza na površini od 8 do 10 hektara.In the last years there has been a relatively high incidence of late spring frost in permanent plantations. The intensity of frost appearance during flowering of fruit trees was such that fruit growers lost their complete yield and the consequences were felt for a longer period of time. The system of sprinkler irrigation can to a great extent be an effective way of protection against frost, but it also has a lot of disadvantages due to the fact that many branches break because of a large quantity of ice, plantation soil is completely leached so passability for tractors is difficult, and diseases often appear in a plantation. The application of a modern machine Frostbuster during flowering of fruit trees (apples, pears, peaches, apricots, cherries, plums, etc.) ensures a reliable and effective protection against frost at the area of 8 to 10 hectares

Molecular velocity auto-correlation of simple liquids observed by NMR MGSE method

The velocity auto-correlation spectra of simple liquids obtained by the NMR method of modulated gradient spin echo show features in the low frequency range up to a few kHz, which can be explained reasonably well by a $t^{-3/2}$ long time tail decay only for non-polar liquid toluene, while the spectra of polar liquids, such as ethanol, water and glycerol, are more congruent with the model of diffusion of particles temporarily trapped in potential wells created by their neighbors. As the method provides the spectrum averaged over ensemble of particle trajectories, the initial non-exponential decay of spin echoes is attributed to a spatial heterogeneity of molecular motion in a bulk of liquid, reflected in distribution of the echo decays for short trajectories. While at longer time intervals, and thus with longer trajectories, heterogeneity is averaged out, giving rise to a spectrum which is explained as a combination of molecular self-diffusion and eddy diffusion within the vortexes of hydrodynamic fluctuations.Comment: 8 pages, 6 figur