A neglected GABAergic astrocyte: Calcium dynamics and involvement in seizure activity

Gamma-aminobutyric acid (GABA) contributes substantially to neurocognitive function as an important inhibitory neurotransmitter in the human cerebral cortex. However, the pathophysiology of disorders such as epilepsy are not well understood, since GABA agonists are not quite effective in treating epilepsy. Knowledge of the mechanism of action of GABA would contribute to review previously proposed anti-epileptic processes by GABA agonists. In this study based on recent experiments on GABAergic astrocytes, we developed a modified GABAergic astrocyte model, and successfully simulated a long-lasting Ca²⁺ oscillation in astrocytes after 0.5-s stimulation of GABAergic transmission. We then incorporated this GABAergic astrocyte model into a classical Ullah-Schiff seizure model and surprisingly found that this GABAergic astrocyte model functions to hinder the anti-epileptic action of GABA agonists, thereby explaining their low efficiency in previous experiments. These results also update our knowledge of the mechanism of action of GABA and the effects of astrocytes on physiological and pathological functions of the brain.     

Multi-objective robust design optimization of a novel negative Poisson’s ratio bumper system

Negative Poisson’s ratio (NPR) structure has outstanding performances in lightweight and energy absorption, and it can be widely applied in automotive industries. By combining the front anti-collision beam, crash box and NPR structure, a novel NPR bumper system for improving the crashworthiness is first proposed in the work. The performances of the NPR bumper system are detailed studied by comparing to traditional bumper system and aluminum foam filled bumper system. To achieve the rapid design while considering perturbation induced by parameter uncertainties, a multi-objective robust design optimization method of the NPR bumper system is also proposed. The parametric model of the bumper system is constructed by combining the full parametric model of the traditional bumper system and the parametric model of the NPR structure. Optimal Latin hypercube sampling technique and dual response surface method are combined to construct the surrogate models. The multi-objective robust optimization results of the NPR bumper system are then obtained by applying the multi-objective particle swarm optimization algorithm and six sigma criteria. The results yielded from the optimizations indicate that the energy absorption capacity is improved significantly by the NPR bumper system and its performances are further optimized efficiently by the multi-objective robust design optimization method.     

Path planning of a free-floating space robot based on the degree of controllability

An effective and more efficient path planning algorithm is developed for a kinematically non-redundant free-floating space robot (FFSR) system by proposing a concept of degree of controllability (DOC) for underactuated systems. The DOC concept is proposed for making full use of the internal couplings and then achieving a better control effect, followed by a certain definition of controllability measurement which measures the DOC, based on obtaining an explicit and finite equivalent affine system and singular value decomposition. A simple method for nilpotent approximation of the Lie algebra generated by the FFSR system is put forward by direct Taylor expansion when obtaining the equivalent system. Afterwards, a large-controllability-measurement (LCM) nominal path is searched by a weighted A* algorithm, and an optimal self-correcting method is designed to track the nominal path approximately, yielding an efficient underactuated path. The proposed strategy successfully avoids the drawback of inefficiency inherent in previous path-planning schemes, which is due to the neglect of internal couplings, and illustrative numerical examples show its efficacy.     

Performance evaluation of anti-radiation based on the gamma degradation process

In the environment of space radiation, the high-energy charged particles or high-energy photons acting on a spacecraft can cause either temporary device degradation or permanent failure. The traditional probability model is difficult to obtain reliable estimation of unit radiation resistance performance with small samples. Considering that different products will change differently after high-energy particle radiation, we construct a model based on the gamma degradation process. This model can efficiently describe the law of unit radiation resistance variation with the total radiation dose levels under the effect of the total dose and displacement damage. Finally, the proposed model is used to assess the anti-radiation performance of the N-channel power MOSFET device STRH60N20FSY3 produced by STM to obtain average unit radiation resistance, survival probability, survival function, etc.     

Damage localization for beams based on the wavelet correlation operator

The continuous wavelet transform (CWT) is one of the crucial damage identification tools in the vibration-based damage assessment. Because of the vanishing moment property, the CWT method is capable of featuring damage singularity in the higher scales, and separating the global trends and noise progressively. In the classical investigations about this issue, the localization property of the CWT is usually deemed as the most critical point. The abundant information provided by the scale-domain information and the corresponding effectiveness are, however, neglected to some extent. Ultimately, this neglect restricts the sufficient application of the CWT method in damage localization, especially in noisy conditions. In order to address this problem, the wavelet correlation operator is introduced into the CWT damage detection method as a post-processing. By means of the correlations among different scales, the proposed operator suppresses noise, cancels global trends, and intensifies the damage features for various mode shapes. The proposed method is demonstrated numerically with emphasis on characterizing damage in noisy environments, where the wavelet scale Teager-Kaiser energy operator is taken as the benchmark method for comparison. Experimental validations are conducted based on the benchmark data from composite beam specimens measured by a scanning laser vibrometer. Numerical and experimental validations/comparisons present that the introduction of wavelet correlation operator is effective for damage localization in noisy conditions.     

Theoretical Investigation of the Viscous Damping Coefficient of Hydraulic Actuators

The viscous damping coefficient(VDC) of hydraulic actuators is crucial for system modeling,control and dynamic characteristic analysis.Currently,the researches on hydraulic actuators focus on behavior assessment,promotion of control performance and efficiency.However,the estimation of the VDC is difficult due to a lack of study.Firstly,using two types of hydraulic cylinders,behaviors of the VDC are experimentally examined with velocities and pressure variations.For the tested plunger type hydraulic cylinder,the exponential model B=αυ~(-β),(α0,β0)or B=α_1e~(-β_1υ)+α_2e~(-β_2υ)(α_1,α_20,β_1,β_20),fits the relation between the VDC and velocities for a given pressure of chamber with high precision.The magnitude of the VDC decreases almost linearly under certain velocities when increasing the chamber pressure from 0.6 MPa to 6.0 MPa.Furthermore,the effects of the chamber pressures on the VDC of piston and plunge type hydraulic cylinders are different due to different sealing types.In order to investigate the VDC of a plunger type hydraulic actuator drastically,a steady-state numerical model has been developed to describe the mechanism incorporating tandem seal lubrication,back-up ring related friction behaviors and shear stress of fluid.It is shown that the simulated results of VDC agree with the measured results with a good accuracy.The proposed method provides an instruction to predict the VDC in system modeling and analysis.     

Studies of the Influence of Temperature and the Energy State of the Surface Layer of Adsorbents on Wall Effects in Soap-Based Greases

This paper presents the results of studies of wall effects in commercial soap-based greases LT4-S2 and HUTPLEX EP-2, thickened with, respectively, lithium 12-hydroxystearate and overbased calcium sulfonate. The studies were conducted in the presence of five different materials: copper alloy C11000, bronze B476, EPDM rubber and PTFE and PU thermoplastics. The influence of the energy state of the surface layer of the adsorbents and temperature (ranging from ?20 to 60 °C) on the intensity of wall effects was investigated. Changes in the structural viscosity and shear stress in the boundary layer area in the greases and the soap-based thickener’s ability to adsorb on the surfaces of the adsorbents were determined by evaluating the rheological parameter plateau modulus.     

Extended bisection method for parameter identification of the transient heat conduction equation for thermo-elastic deformations during drilling

A new interdisciplinary approach is discribed to identifying unknown parameters using an extended version of the known interval bisection method. This developed method is based on the use of finite elements for calibrating the simulation calculation. The resulting thermo-elastic deformations which occur in drilling processes with impaired cooling lubrication are to be used as correction values for tool positioning in the NC control. Based on the strong impact on workpiece temperature of machining, a simulation approach is presented for calculating the temperature fields and their thermo-elastic consequences. In addition, methods are presented to correct these effects. This paper particularly deals with the temperature fields of drilling operations. Special attention is paid to the technique employed for iterative numerical determination of the unknown heat flux η _w and heat transfer coefficient \(\bar {\gamma }\) values. Finally, the data obtained from experiments are compared with those achieved by numerical simulation in order to verify the efficiency of simulation and determination of parameters.     

Ethik-Cafés in der geriatrischen Langzeitpflege: halten sie,was sie versprechen?

Definition of the problem Ethics cafés in long-term geriatric care are considered as ethical education. They allow the participants to have an open discourse in a casual setting about moral issues related to daily work. In the literature, various characteristics are attributed to ethics cafés, e.g., improving analytical skills and communication, increasing ethical sensitivity and authority for making decisions. These characteristics primarily result from theory-based models. Arguments The goal of this study is the empirical investigation of the effectiveness of ethics cafés in the Nursing Homes Mattenhof–Irchelpark, Zurich. Furthermore, the study examined whether the subjective evaluation of characteristics of nurses and other professional groups are different. To capture the characteristics, a questionnaire was constructed in which the participants rated 16 statements during the survey period. A 5-point Likert scale was used for the analysis. One subgroup distinguished between “nursing staff” and “non-nursing staff”. Conclusion The postulated characteristics were confirmed with a very high approval. Therefore, the ethics cafés provide important input which enable the staff to analyze more clearly in difficult situations or to let them decide ethically in a more sensitive manner and to justify decisions made. The interdisciplinary approach supports an understanding of the views and arguments among the various areas and hierarchies. The differences between the two professionals groups are partially highly significant. It can be noted that the assigned characteristics in the questionnaire are generally perceived stronger and more significantly by the nursing staff. Therefore, a distinction must be made when interpreting the results of this study concerning the participants.     

„Leben machen,sterben lassen“: Palliative Care und Biomacht

Definition of the problem This article takes a critical look at the current theory and practice of palliative care (PC), how it deals with death and dying, and the underlying guiding principle of a good death. Thereby, Foucault’s concept of biopower is utilized. Argument Because PC aims to facilitate a good death, manifold criteria and measures have been developed that help plan interventions and determine their success. In light of the concept of biopower, certain problematic aspects of this development become manifest that usually remain hidden in the bioethical discourse. Conclusion A goal of PC is to improve the quality of life of the dying and therefore not only treats physical symptoms but also psychological, social, and spiritual suffering; thus, it commits itself to maximizing life in a way that can become overdemanding for the individual and possibly does not satisfy the patient’s real needs.