Notes

Numerous anterior choroidal veins as well as perioperative ischemic problems throughout unruptured anterior choroidal artery aneurysms treated with microsurgical trimming.
Treating multiple brain metastases with a single isocenter improves efficiency but requires margins to account for rotation induced shifts that increase with target-to-isocenter distance. A method to select the single isocenter position that minimizes the total volume of normal tissue treated during multi-target stereotactic radiosurgery (SRS) is presented. A statistical framework was developed to quantify the impact of uncertainties on planning target volumes (PTV). Translational and rotational shifts were modeled with independent, zero mean, Gaussian distributions in three dimensions added in quadrature. The standard deviations of errors were varied from 0.5-2.0 mm and 0.5°-2.0°. The volume of normal tissue treated due to margin expansions required to maintain a 95% probability of target coverage was computed. Tumors were modeled as 4-40 mm diameter spheres. Target separation distance was varied from 40-100 mm for two- and three-lesion scenarios. The percent increase in PTV was determined relative to an isocenter at the geometric centroid of the targets for the optimal isocenter that minimized the total normal tissue treated, and isocenters at the center-of-mass (COM) and center-of-surface-area (CSA). For two targets, isocenter placement at the optimal location, COM, and CSA, reduced the total margin versus an isocenter at midline up to 17.8%, 17.7%, and 17.8%, respectively, for 0.5 mm and 0.5° errors. For three targets, optimal isocenter placement reduced the margin volume up to 21%, 19%, and 14%, for uncertainties of (0.5 mm, 0.5°), (1.0 mm, 1.0°), and (2.0 mm, 2.0°), respectively. COM and CSA provide useful approximations to select the optimal isocenter for multi-target single-isocenter SRS for two or three targets with maximum dimensions ≤40 mm and separation distances ≤100 mm when uncertainties are ≤1.0 mm and ≤1.0°. CSA provides a more accurate approximation than COM. Optimal treatment isocenter selection for multiple targets of large size differences can significantly reduce total margin volume.The properties of the foot deployed in a bipedal robot that targets the rendering of a human-like dynamic gait are crucial. Firstly, it has to implement a set of mechanical mechanisms/properties that improve the efficiency of the locomotion. Secondly, it has to integrate a sensory system that captures the interaction with the ground with suitable precision. Both systems - the mechanical and the sensory system - have to be integrated as tightly as possible to keep the overall dimensions and weight low. Being the most distal element of the leg, especially the latter is crucial for favorable leg dynamics. Regarding the structural properties, a modern prosthetic foot poses a good solution and has hence been adopted in various bipeds. Their elaborated structures - mostly made from carbon fiber composites - are designed to imitate the mechanisms of the anthropomorphic counterpart. The following presents a concept to estimate the ground interaction based on the intrinsic deformation of a commercially available prosthesis. To measure the deformation, a strain gauges are applied to its main structural elements. Using this information, the center of pressure and the normal force acting on it are estimated. The performance of two approaches - linear regression and neural networks - is presented and compared. Finally, the accuracy of the strain- based estimation is evaluated in two experiments and compared to a conventional force/torque sensor ( FTS )-based system and a pressure insole. While the presented work is initially motivated by robotics research, it might as well be transferred to the design of a modern actively actuated prosthesis.This paper presents a generic method to reduce the radiofrequency (RF) induced heating of external fixation devices during magnetic resonance imaging (MRI) procedure. A simplified equivalent circuit model was developed to illustrate the interactions between the external fixation device and the MRI RF field. Carefully designed mechanical structures, which utilize capacitive reactance from the circuit model, were applied to the external fixation devices to mitigate the coupling between the external fixation device and the MRI RF field for RF-induced heating reduction. Both numerical and experimental studies were performed to demonstrate the validity of the circuit model and the effectiveness of the proposed method. Selleckchem Y-27632 By adding capacitive structures in both the clamp-pin and rod-clamp joints, the peak specific absorption rate averaged in 1 gram (SAR1g) near the pin tips were reduced from 760.4 W/kg to 12.0 W/kg at 1.5 T and 391.5 W/kg to 25.2 W/kg at 3 T from numerical simulations. Experimental results showed that RF-induced heating was reduced from 7.85 °C to 1.01 °C at 1.5 T and from 16.70 °C to 0.32 °C at 3 T for the external fixation device studied here. The carefully designed capacitive structures can be used to detune the coupling between the external fixation device and the MRI fields to reduce the RF-induced heating in the human body for both 1.5 T and 3 T MRI systems.A systematic study of electronic structure, mechanical and transport properties of RuV-based half-Heusler alloys (RuVZ, Z=As, P, Sb) have been presented using itab-itinitio Density Functional and Boltzmann transport theory. The electronic structures are obtained using generalized gradient approximation(GGA) with Perdew-Burke-Ernzerhof(PBE) functional. All the compounds are crystallized in face centered cubic(fcc) phase with space group #216. Our preliminary electronic structure simulations reveal that all the alloys are non-magnetic semiconductors. Additionally, the phonon dispersion and elastic constants (along with the related elastic moduli) also verify mechanical stability of the alloys. Due to strong dependence on the electronic bandgap in thermoelectric materials, we have estimated bandgap using more accurate hybrid functional i.e. Heyd-Scuseria-Ernzerhof(HSE). The transport coefficients (e.g. Seebeck, electrical conductivity, thermal conductivity due to electrons) are calculated by solving the Boltzmann transport equation for charge carriers as implemented in BoltztraP software under constant relaxation time approximation. The lattice thermal conductivity due to phonons is calculated using more reliable shengBTE code based upon the Boltzmann transport equation for phonons. We have calculated the more reliable value of the thermoelectric figure of merit, ZT (related to the conversion efficiency) for all the compounds. The obtained ZT for RuVAs, RuVP and RuVSb is 0.41(0.32), 0.21(0.16) and 0.70(0.61) for p(n)-type behavior at 900K. The corresponding carrier concentrations are also predicted. High value of ZT is obtained for RuVSb alloy due to low lattice thermal conductivity. Among these compounds, RuVSb emerged out as a most suitable candidate for thermoelectric power generation device. Minimum lattice thermal conductivity in theoretical limit along with the corresponding maximum value of ZT is also predicted in these alloys.
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