High‐Performing Monometallic Cobalt Layered Double Hydroxide Supercapacitor with Defined Local Structure

Through a topochemical oxidative reaction (TOR) under air, a β‐Co(OH)₂ brucite type structure is converted into a monometallic Co^IICo^III–CO₃ layered double hydroxide (LDH). The structural and morphological characterizations are performed using powder X‐ray diffraction, Fourier‐transformed IR spectroscopy, and scanning and transmission electron microscopy. The local structure is scrutinized using an extended X‐ray absorption fine structure, X‐ray absorption near‐edge structure, and pair distribution function analysis. The chemical composition of pristine material and its derivatives (electrochemically treated) are identified by thermogravimetry analysis for the bulk and X‐ray photoelectron spectroscopy for the surface. The electrochemical behavior is investigated on deposited thin films in aqueous electrolyte (KOH) by cyclic voltammetry and electrochemical impedance spectroscopy, and their capacitive properties are further investigated by Galvanostatic cycling with potential limitation. The charge capacity is found to be as high as 1490 F g^?1 for Co^IICo^III–CO₃ LDH at a current density of 0.5 A g^?1. The performances of these materials are described using Ragone plots, which finally allow us to propose them as promising supercapacitor materials. A surface‐to‐bulk comparison using the above characterization techniques gives insight into the cyclability and reversibility limits of this material.     

Image overlay guidance for needle insertion in CT scanner

We present an image overlay system to aid needle insertion procedures in computed tomography (CT) scanners. The device consists of a display and a semitransparent mirror that is mounted on the gantry. Looking at the patient through the mirror, the CT image appears to be floating inside the patient with correct size and position, thereby providing the physician with two-dimensional (2-D) "X-ray vision" to guide needle insertions. The physician inserts the needle following the optimal path identified in the CT image rendered on the display and, thus, reflected in the mirror. The system promises to reduce X-ray dose, patient discomfort, and procedure time by significantly reducing faulty insertion attempts. It may also increase needle placement accuracy. We report the design and implementation of the image overlay system followed by the results of phantom and cadaver experiments in several clinical applications.