Solutions to Wiener Filtering and Stationary LQG Problem via H₂ Control Theory - Part II : Discrete - Time System

This paper derives the solutions to the Wiener filtering and stationary LQG problem for a discrete-time system by applying the state-space techniques developed for H₂H∞ optimal controls. As mathematical preliminaries, we collect useful operations for the transfer function matrices. We also provide a new proof for the inner-outer factorization algorithm that appears in the discrete-time H₂ optimization

Parameter Identification of Image Models by the Recursive Maximum Likelihood Method

This paper considers the problem of identifying the blur parameters of the observed image. It is assumed that the original image is a sample from the homogeneous random field described by a two-dimensional (2-D) semicausal model, and that the point spread function (PSF) characterizing the image blur is symmetric. It is also assumed that the observation noise is negligibly small. By applying the discrete sine transform, we derive a set of nearly uncorrelated ARMA models, which are of non-minimum phase, for the blurred image. Although all-pass components of the MA part of the models can not be estimated, we show that the parameters of the non-minimum phase MA part can be restored by exploiting the fact that the PSF is symmetric. We develop a new algorithm for identifying the blur parameters of the image model from the MA parameters estimated by the recursive maximum likelihood (RML) method. Simulation studies are also included to show the feasibility of the algorithm

Solutions to Wiener Filtering and Stationary LQG Problems via H₂ Control Theory-Part I : Continuous-Time System

This paper derives solutions to the multivariable Wiener filtering and the stationary LQG problems using the H₂ optimal control theory and the state-space technique. Inner-outer factorization and spectral factorization results arising in H₂/H∞ optimal controls are also derived by the state-space technique

Parametrization of All Stable Unbiased ℋ∞ Estimators Based on Model Matching

This paper considers the H∞ estimation problem by using a model matching technique. For a given possibly unstable plant, the H∞ estimation problem is reduced to a standard model matching problem by introducing a class of all stable and unbiased estimators. Based on Nehari's theorem, a necessary and suffcient condition for the existence of a solution of the H∞ estimation problem is derived in terms of an H∞-type algebraic Riccati equation. The LFT representation of the class of all solutions is also developed

A Subspace Identification of δ-Operator State-Space Model

This paper derives a subspace identification algorithm for a δ-operator state-space model by using the methods due to Moonen et al. [11], [12], [21]. Since the δ-operator model converges to a continuous-time model as the sampling interval goes to zero, the algorithm obtained is applicable to the identification of continuous-time medels. A method of computing the state vector from the block Hankel matrix is developed. Simulation studies show the present algorithm provides good results for the case of a low N/S ratio. Improvement of the algorithm for the case of a higher N/S ratio remains to be done

Application of Maximum Likelihood Method to Boiler System Identification

A maximum likelihood (ML) method is applied to a boiler system identification. The mathematical model used in this paper is a discrete-time, singleinput and single-output (SISO), constant, linear system excited by an “innovation” process. Since the ML identification is reduced to a nonlinear optimization problem with equality constraints, the Davidon's conjugate gradient method is employed for numerical solutions. By using the given input/output data, the dynamics of the governor/steam pressure and the governor/steam temperature relations are identified as an SISO system, respectively. AIC and a test based on the innovation process are also applied for selecting an appropriate order of the assumed model

Expression of human mutant cyclin dependent kinase 4, Cyclin D and telomerase extends the life span but does not immortalize fibroblasts derived from loggerhead sea turtle (Caretta caretta)

Conservation of the genetic resources of endangered animals is crucial for future generations. The loggerhead sea turtle (Caretta caretta) is a critically endangered species, because of human hunting, hybridisation with other sea turtle species, and infectious diseases. In the present study, we established primary fibroblast cell lines from the loggerhead sea turtle, and showed its species specific chromosome number is 2n = 56, which is identical to that of the hawksbill and olive ridley sea turtles. We first showed that intensive hybridization among multiple sea turtle species caused due to the identical chromosome number, which allows existence of stable hybridization among the multiple sea turtle species. Expressions of human-derived mutant Cyclin-dependent kinase 4 (CDK4) and Cyclin D dramatically extended the cell culture period, when it was compared with the cell culture period of wild type cells. The recombinant fibroblast cell lines maintained the normal chromosome condition and morphology, indicating that, at the G1/S phase, the machinery to control the cellular proliferation is evolutionally conserved among various vertebrates. To our knowledge, this study is the first to demonstrate the functional conservation to overcome the negative feedback system to limit the turn over of the cell cycle between mammalian and reptiles. Our cell culture method will enable the sharing of cells from critically endangered animals as research materials

Drug retention of 7 biologics and tofacitinib in biologics-naïve and biologics-switched patients with rheumatoid arthritis: The ANSWER cohort study

Background: This multi-center, retrospective study aimed to clarify retention rates and reasons for discontinuation of 7 biological disease-modifying antirheumatic drugs (bDMARDs) and tofacitinib (TOF), one of the janus kinase inhibitors, in bDMARDs-naïve and bDMARDs-switched patients with rheumatoid arthritis (RA). Methods: This study assessed 3897 patients and 4415 treatment courses with bDMARDs and TOF from 2001 to 2019 (2737 bDMARDs-naïve courses and 1678 bDMARDs-switched courses [59.5% of switched courses were their second agent], female 82.3%, baseline age 57.4 years, disease duration 8.5 years; rheumatoid factor positivity 78.4%; Disease Activity Score in 28 joints using erythrocyte sedimentation rate 4.3; concomitant prednisolone [PSL] dose 6.1 mg/day [usage 42.4%], and methotrexate [MTX] dose 8.5 mg/week [usage 60.9%]). Treatment courses included abatacept (ABT; n = 663), adalimumab (ADA; n = 536), certolizumab pegol (CZP; n = 226), etanercept (ETN; n = 856), golimumab (GLM; n = 458), infliximab (IFX; n = 724), tocilizumab (TCZ; n = 851), and TOF (n = 101/only bDMARDs-switched cases). Drug discontinuation reasons (categorized into lack of effectiveness, toxic adverse events, non-toxic reasons, or remission) and rates were estimated at 36 months using Gray's test and statistically evaluated after adjusted by potential clinical confounders (age, sex, disease duration, concomitant PSL and MTX usage, starting date, and number of switched bDMARDs) using the Fine-Gray model. Results: Cumulative incidence of drug discontinuation for each reason was as follows: lack of effectiveness in the bDMARDs-naïve group (from 13.7% [ABT] to 26.9% [CZP]; P < 0.001 between agents) and the bDMARDs-switched group (from 18.9% [TCZ] to 46.1% [CZP]; P < 0.001 between agents); toxic adverse events in the bDMARDs-naïve group (from 4.6% [ABT] to 11.2% [ETN]; P < 0.001 between agents) and the bDMARDs-switched group (from 5.0% [ETN] to 15.7% [TOF]; P = 0.004 between agents); and remission in the bDMARDs-naïve group (from 2.9% [ETN] to 10.0% [IFX]; P < 0.001 between agents) and the bDMARDs-switched group (from 1.1% [CZP] to 3.3% [GLM]; P = 0.9 between agents). Conclusions: Remarkable differences were observed in drug retention of 7 bDMARDs and TOF between bDMARDs-naïve and bDMARDs-switched cases.Ebina K., Hirano T., Maeda Y., et al. Drug retention of 7 biologics and tofacitinib in biologics-naïve and biologics-switched patients with rheumatoid arthritis: The ANSWER cohort study. Arthritis Research and Therapy 22, 142 (2020); https://doi.org/10.1186/s13075-020-02232-w