A medical information system for monitoring respiratory function and related nonlinear dynamics

In this paper the nonlinear effects in the respiratory systems at low frequencies are measured and evaluated in healthy children and healthy adults. To this aim forced oscillations technique (FOT) has been used to non-invasively measure the lung tissue mechanics. FOT does not require any special effort from the patient in contrast with standardized tests where maneuvers are necessary. Hence, FOT is an ideal lung function test for extreme ages, more specifically children and elderly, given the simpleness of measurement technique. Hitherto, measurements at low frequencies (i.e. close to the breathing frequency similar to 0.3 Hz) have been invasively performed in sacrificed animals and on anesthetized humans. Here we measure in the frequency interval 0.1-2 Hz a total number of 94 volunteers (37 adults with ages between 25-35 years and 57 children with ages between 8-11 years). To evaluate the nonlinear contributions of the respiratory tissue, a novel T-index has been introduced. We have tested the hypothesis whether the nonlinear distortions are changing with growth/development of the respiratory tree and aim to quantify its dependence to biometric values. The results obtained indicate that the proposed index can differentiate between the two analyzed groups and that there is a dependence to age, height and weight. A medical information system may use this information to update predictions of respiratory function and provide aid in decision-making process of drug therapy

Model based control strategies for a class of nonlinear mechanical sub-systems

This paper presents a comparison between various control strategies for a class of mechanical actuators common in heavy-duty industry. Typical actuator components are hydraulic or pneumatic elements with static non-linearities, which are commonly referred to as Hammerstein systems. Such static non-linearities may vary in time as a function of the load and hence classical inverse-model based control strategies may deliver sub-optimal performance. This paper investigates the ability of advanced model based control strategies to satisfy a tolerance interval for position error values, overshoot and settling time specifications. Due to the presence of static non-linearity requiring changing direction of movement, control effort is also evaluated in terms of zero crossing frequency (up-down or left-right movement). Simulation and experimental data from a lab setup suggest that sliding mode control is able to improve global performance parameters

On the potential of using fractional-order systems to model the respiratory impedance

This contribution provides an analysis of the human respiratory system in frequency domain by means of estimating the respiratory impedance. Further on, analysis of several models for human respiratory impedance is done, leading to the conclusion that a fractional model gives a better description of the impedance than the classical theory of integer-order systems. A mathematical analysis follows, starting from the conclusions obtained heuristically. Correlation to the physiological characteristics of the respiratory system is discussed

Some frequency domain considerations upon human respiratory mechanics

The aim of this paper is to present a brief analysis of recent results considering human respiratory mechanics. The final purpose of the investigation is to provide a fast method for identification of airway mechanics, in order to assist the medical staff in obtaining a diagnosis of the patient within the context of performing routine evaluation of the respiratory function. Considerations are made with respect to the future potential of the method as a screening technique on a large number of populations

The inhibition of adenylate kinase by 2,4-thiazolidinedione evaluated by protein-ligand docking

Due to its crucial role in nucleotide metabolism, adenylate kinase deserves a special attention in screening of potential inhibitors. Herein, we report the assessment of the relative orientation of the ligand 2,4-thiazolidinedione to adenylate kinase crystallized in closed conformation. Protein-ligand docking was performed to estimate the binding energy and inhibition constant of 2,4-thiazolidinedione to the adenylate kinases’ active sites from different organisms. Our results revealed the best orientation of 2,4-thiazolidinedione is with Gram-positive and acid fast bacteria adenylate kinase – Ki = 0.76±0.1 mM and binding energy -4.26±0.08 kcal/mol. Human adenylate kinases display unfavourable interactions, the binding affinity fluctuating among Ki=0.84 mM and 8.8 mM (3.88±3.51); the energy binding -3.56±0.57. From the three human adenylate kinases analysed, only isoenzyme 2 shows a binding conformation similar to its counterpart from E. coli. Adenylate kinase - this small enzyme needed for survival of every organisms - interacts differently with 2,4-thiazolidinedione, this selectivity being the most important evidence of the present study