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Integration of magnetic resonance imaging (MRI) and positron emission tomography (PET) into a simultaneous device calls for adaptations of the radio frequency (RF) shielding concept. Conventional PET module housings fully encase the entire PET detector to reduce mutual interference. mTOR inhibitor Excluding passive components, i.e. scintillators, from the housings, offers integration advantages, e.g. by reducing the overall housing volume or utilizing bigger scintillators. However, locating the scintillator outside of the RF shielding requires an optically transparent RF shielding interface between the scintillators and the photodetector to close the aperture. Therefore, a careful evaluation and selection of RF materials is essential to ensure an excellent PET/MRI system performance. To this end, we examined 10 materials (coated glasses, coated foils, meshes). The shielding effectiveness (SE) was evaluated at 100 and 300 MHz. PET performance was tested for single event registration and coincident events by integrating the material into the PET detector stack between the digital silicon photomultiplier photodetector array and one-to-one coupled scintillator. We determined photon attenuation (PA), energy resolution (dE/E), and coincidence resolving time (CRT) and compared to reference measurements for each material group. MRI compatibility was assessed by analyzing the material influence on the main magnetic field (B0) homogeneity. The coated glasses and foils exhibited SEs of up to 25 dB at 300 MHz. Both had a PA 58% with a higher impact on dE/E and CRT. Only one mesh affected B0homogeneity. Overall, we recommend the coated foil HS 9400 for integration concepts as it exhibited a good performance with SE = 25 dB, PA = 22%, resulting in a PET performance of dE/E = 12% and CRT = 274 ps.Objective.Developments in electroencephalography (EEG) technology have allowed the use of the brain-computer interface (BCI) outside dedicated labratories. In order to achieve long-term monitoring and detection of EEG signals for BCI application, dry electrodes with good signal quality and high bio compatibility are essential. In 2016, we proposed a flexible dry electrode made of silicone gel and Ag flakes, which showed good signal quality and mechanical robustness. However, the Ag components used in our previous design made the electrode too expensive for commercial adaptation.Approach.In this study, we developed an affordable dry electrode made of silicone gel, metal flakes and graphene/GO based on our previous design. Two types of electrodes with different graphene/GO proportions were produced to explore how the amount of graphene/GO affects the electrode.Main results.During our tests, the electrodes showed low impedance and had good signal correlation to conventional wet electrodes in both the time and frequency domains. The graphene/GO electrode also showed good signal quality in eyes-open EEG recording. We also found that the electrode with more graphene/GO had an uneven surface and worse signal quality. This suggests that adding too much graphene/GO may reduce the electrods' performance. Furthermore, we tested the proposed dry electrodes' capability in detecting steady state visually evoked potential. We found that the dry electrodes can reliably detect evoked potential changes even in the hairy occipital area.Significance.Our results showed that the proposed electrode has good signal quality and is ready for BCI applications.Graphene, as a typical two-dimensional material, is popular in the design of nanodevices. The interlayer relative sliding of graphene sheets can significantly affect the effective bending stiffness of the few-layered graphene. For restricting the relative sliding, we adopted the atomic shot peening method to bond the graphene sheets together by ballistic C60 fullerenes from its two surfaces. Collision effects are evaluated via molecular dynamics simulations. Results obtained indicate that the fullerenes' incident velocity has an interval, in which the graphene sheet can be bonded after collision while no atoms on the fullerenes escaping from the graphene ribbon after collision. The limits of the interval increase with the layer number. Within a few picoseconds of collision, a stable carbon network is produced at an impacted area. The graphene sheets are bonded via the network and cannot slide relatively anymore. Conclusions are drawn to show the way of potential applications of the method in manufacturing a new graphene-based two-dimensional material that has a high out-of-plane bending stiffness.We experimentally demonstrate the transmission of electrons through different number (1, 2, and 5) of suspended graphene layers at electron energies between 20 and 250 eV. Electrons with initial energies lower than 40 eV are generated using silicon field emitter arrays with 1μm pitch, and accelerated towards the graphene layers supported by a silicon nitride grid biased at voltages from -20 to 200 V. We measured significant increase in current collected at the anode with the presence of graphene, which is attributed to the possible generation of secondary electrons by primary electrons impinging on the graphene membrane. Highest output current was recorded with monolayer graphene at approximately 90 eV, with up to 1.7 times the incident current. The transparency of graphene to low-energy electrons and its impermeability to gas molecules could enable low-voltage field emission electron sources, which often require ultra-high vacuum, to operate in a relatively poor vacuum environment.Islet encapsulation in membrane-based devices could allow for transplantation of donor islet tissue in the absence of immunosuppression. To achieve long-term survival of islets, the device should allow rapid exchange of essential nutrients and be vascularized to guarantee continued support of islet function. Recently, we have proposed a membrane-based macroencapsulation device consisting of a microwell membrane for islet separation covered by a micropatterned membrane lid. The device can prevent islet aggregation and support functional islet survivalin vitro. Here, based on previous modeling studies, we develop an improved device with smaller microwell dimensions, decreased spacing between the microwells and reduced membrane thickness and investigate its performancein vitroandin vivo. This improved device allows for encapsulating higher islet numbers without islet aggregation and by applying anin vivoimaging system we demonstrate very good perfusion of the device when implanted intraperitoneally in mice. Besides, when it is implanted subcutaneously in mice, islet viability is maintained and a vascular network in close proximity to the device is developed.
Here's my website: https://www.selleckchem.com/products/a-674563.html
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