Compact stacked planar inverted-F antenna for passive deep brain stimulation implants

A compact meandered three-layer stacked circular planar inverted-F antenna is designed and simulated at the UHF band (902.75 – 927.25 MHz) for passive deep brain stimulation implants. The UHF band is used because it offers small antenna size, and high data rate. The top and middle radiating layers are meandered, and low cost substrate and superstrate materials are used to limit the radius and height of the antenna to 5 mm and 1.64 mm, respectively. A dielectric substrate of FR-4 of εr= 4.7 and δ= 0.018, and a biocompatible superstrate of silicone of er= 3.7 and d= 0.003 with thickness of 0.2 mm are used in the design. The resonance frequency of the proposed antenna is 918 MHz with a bandwidth of 24 MHz at return loss of −10 dB in free space. The antenna parameter such as 3D gain pattern of the designed antenna within a skin-tissue model is evaluated by using the finite element method. The compactness, wide bandwidth, round shape, and stable characteristics in skin make this antenna suitable for DBS. The feasibility of the wireless power transmission to the implant in the human head is also examined.

Spinoza/space/speed/sublime: Problems of philosophy and politics in the post-colonial fiction of Gerald Murnane

This article takes account of the ‘spontaneity’ of the post-colonial fiction of Gerald Murnane within the ‘dominating space’ of the philosophy of Spinoza. My use of Paul Carter’s terms here is strategic. The compact of fiction and philosophy in Murnane corresponds with the relationship of spontaneity to the dominating organization of desire in Carter’s rendering of an Aboriginal hunter. Carter’s phrase “‘a figure at once spontaneous and wholly dominated by the space of his desire’” worries Ken Gelder and Jane M. Jacobs, who suggest that it subjugates the formation of Aboriginal desire (incorporating spontaneity) to impulses of imperialism. The captivating immanence of Spinoza’s philosophy in Murnane’s fiction, which I will demonstrate with various examples, puts pressure on the fiction to occupy the same space as the space of the philosophy. Here is a clue to why Murnane’s post-colonial thematics have been little explored by critics with an interest in post-colonial politics. The desire of Spinoza’s philosophy creates a spatial textuality within which the spontaneity of Murnane’s fiction, to the degree that it maximizes or fills the philosophy, is minimized in its political effects. That is to say, the fiction shifts politics into an external space of what Roland Barthes calls “resistance or condemnation”. However, the different speeds (or timings) of Murnane and Spinoza, within the one space, mitigate this resistance of the outside, at least in respect of certain circumstances of post-coloniality. It is especially productive, I suggest, to engage Carter’s representation of an Aboriginal hunter through the compact of coincidental spaces and differential speeds created by Murnane’s fiction in Spinoza’s philosophy. This produces a ceaseless activation of desire and domination, evidenced in Murnane’s short story ‘Land Deal’, and indexed by a post-Romantic sublime. What limits the value of Murnane’s fiction in most contexts of post-colonial politics, is precisely what makes it useful in the matter of Carter’s Aboriginal hunter.

Development of a compact rectenna for wireless powering of a head-mountable deep brain stimulation device

Design of a rectangular spiral planar inverted-F antenna (PIFA) at 915 MHz for wireless power transmission applications is proposed. The antenna and rectifying circuitry form a rectenna, which can produce dc power from a distant radio frequency energy transmitter. The generated dc power is used to operate a low-power deep brain stimulation pulse generator. The proposed antenna has the dimensions of 10 mm × 12.5 mm × 1.5 mm and resonance frequency of 915 MHz with a measured bandwidth of 15 MHz at return loss of -10 dB. A dielectric substrate of FR-4 of εr = 4.8 and δ = 0.015 with thickness of 1.5 mm is used for both antenna and rectifier circuit simulation and fabrication because of its availability and low cost. An L-section impedance matching circuit is used between the PIFA and voltage doubler rectifier. The impedance matching circuit also works as a low-pass filter for elimination of higher order harmonics. Maximum dc voltage at the rectenna output is 7.5 V in free space and this rectenna can drive a deep brain stimulation pulse generator at a distance of 30 cm from a radio frequency energy transmitter, which transmits power of 26.77 dBm.

Distinct kinetics of molecular gelation in a confined space and its relation to the structure and property of thin gel films

Thin films of molecular gels formed in a confined space have potential applications in transdermal delivery, artificial skin, molecular electronics, etc. The microstructures and properties of thin gel films can be significantly different from those of their bulk counterparts. However, so far a comprehensive understanding of the effects of spatial confinement on the molecular gelation kinetics, fiber network structure and related mechanical properties is still lacking. In this work, using rheological techniques, we investigated the effect of one-dimensional confinement on the formation kinetics of fiber networks in the molecular gelation process. Fractal analyses of the kinetic information in terms of an extended Dickinson model enabled us to describe quantitatively the distinct kinetic signature of molecular gelation. The structural features derived from gelation kinetics support well the fractal patterns of the fiber networks acquired by optical and electron microscopy. With the kinetics-structure correlation, we can gain an in-depth understanding of the confinement-induced differences in the structure and consequently the mechanical properties of a model molecular gelling system. Particularly, the confinement induced structural transition, from a three-dimensional, dense and compact spherulitic network composed of highly branched fibers to a quasi-two-dimensional sparse spherulitic network composed of less branched fibers and entangled fibrils at the boundary areas, renders a gel film to become less stiff but more ductile. Our study suggests here a new strategy of engineering the fiber network microstructure to achieve functional gel films with unusual but useful properties.