The antiemetic and gastroprokinetic drug metoclopramide is a weak substrate of the blood-brain barrier (BBB) efflux transporter P-gp and displays central nervous system (CNS) side effects (extrapyramidal symptoms, tardive dyskinesia), which occur with a higher incidence in elderly people. WHAT QUESTION DID THIS STUDY ADDRESS? We performed [ 11 C]metoclopramide positron emission tomography scans in young and elderly healthy men, both after administration of a microdose and therapeutic dose of metoclopramide, to investigate whether differences in brain distribution of metoclopramide may explain its CNS side effects.
The method of intramolecular force compensation forms a new approach for reducing the response time of hydrogel-based chemical sensors and improving their long-term stability. The principle is based on a single bisensitive hydrogel, that fulfills both the function of a sensor and an actuator. This paper presents the measuring principle, the required bisensitive hydrogel and a sensor setup. The results show the desired bisensitivity of the sensor to the temperature and ion concentration as well as the successful reduction of the response time by more than 50 % compared to the conventional deflection method. The continuous sensor operation with the application of varying measuring solvents indicates a negligibly low hysteresis behaviour.
A main characteristic of hydrogels is their multisensitivity, i.e., the material's capability to respond to multiple stimuli such as temperature, chemical concentration or light. Most modeling approaches to swelling in the literature deal with the monosensitive behavior of hydrogels. Herein, two approaches to the modeling of multisensitive sensors and actuators are proposed: the N‐field method and the trajectory method. They are derived using experimental data of the bisensitive hydrogel [net‐P(AMPS‐co‐NiPAAm)]‐sipn‐PAMPS. It is sensitive to sodium salt concentration and temperature. For the trajectory method, the procedure for the generalized representation of the material behavior is presented. Applying the Temperature Expansion Model, this is implemented in Abaqus and the results of verification simulations are given. The trajectory method is capable of representing the multisensitive behavior of hydrogels. The method is easy to implement in commercial Finite Element tools based on the free‐swelling data of the material. Simulation results of the free swelling are in excellent agreement with the given calibration data. The obtained swelling behavior can be combined with mechanical loads and arbitrary boundary conditions to form more complex setups. The current work allows a deeper understanding of complex multifunctional materials, such as hydrogels, and their application in sensor or actuator devices.
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