Experimental and Numerical Investigation of Therapeutic Ultrasound Angioplasty

Therapeutic ultrasound angioplasty is an emerging minimally invasive cardiovascular surgical procedure that involves the delivery of ultrasonic displacements to the distal-tip of small diameter wire waveguides. The ultrasonic distal-tip displacements affect atherosclerotic plaque and thrombus by direct contact ablation, pressure wave components and cavitation, in addition to an acoustic streaming event around the distal-tip. This study uses experimental and numerical methods to investigate ultrasonic displacements in wire waveguides and the effect the distal-tip displacements have on the surrounding fluid. An experimental therapeutic ultrasound wire waveguide apparatus is described that delivers displacements to the distal-tip of 1.0 mm and tapered 0.35 mm diameter nickel-titanium (NiTi) waveguides. The operating frequency of the apparatus has been experimentally determined to be 23.5 kHz and for the power settings tested delivers displacements of up to 85 µm peak-to-peak (p-p) to the distal-tip of 1.0 mm diameter waveguides. The apparatus has been shown to directly ablate calcified materials with a stiffer response when compared with atherosclerotic plaques and to generate cavitation and acoustic streaming. A coupled fluid-structure numerical model of the waveguide and fluid surrounding the distal-tip has been developed that predicts the waveguide displacements and stresses along the entire length of the wire waveguide. The structural results of the model have been validated against experimental measurements of the displacements of the waveguide with the inclusion of a constant damping value of 4.5%. The fluid results of the model predict the pressure amplitudes developed in the surrounding fluid and compare closely with values reported in literature. The model predicts the distal-tip displacements required to cause cavitation, a major disruptive event, and has been compared with experimental observations made with the ultrasonic wire waveguide apparatus. The waveguide numerical model will prove a valuable design tool in the further development and improvement of this emerging cardiovascular technology

Photon pair-state preparation with tailored spectral properties by spontaneous four-wave mixing in photonic-crystal fiber

We study theoretically the generation of photon pairs by spontaneous four-wave mixing (SFWM) in photonic crystal optical fiber. We show that it is possible to engineer two-photon states with specific spectral correlation (``entanglement'') properties suitable for quantum information processing applications. We focus on the case exhibiting no spectral correlations in the two-photon component of the state, which we call factorability, and which allows heralding of single-photon pure-state wave packets without the need for spectral post filtering. We show that spontaneous four wave mixing exhibits a remarkable flexibility, permitting a wider class of two-photon states, including ultra-broadband, highly-anticorrelated states.Comment: 17 pages, 7 figures, submitte

Prospective Study of Early MRI Appearances following Flow- Diverting Stent Placement for Intracranial Aneurysms

ABSTRACT BACKGROUND AND PURPOSE: MR imaging findings of aneurysm enlargement, aneurysm wall enhancement, perianeurysmal edema, and embolic phenomena following deployment of flow-diverting stents may be relevant to those patients who subsequently experience procedure-related intracranial hemorrhage. We sought to document the routine early postoperative MR imaging findings following flow-diverting stent insertion

Long-lived driven solid-state quantum memory

We investigate the performance of inhomogeneously broadened spin ensembles as quantum memories under continuous dynamical decoupling. The role of the continuous driving field is two-fold: first, it decouples individual spins from magnetic noise; second and more important, it suppresses and reshapes the spectral inhomogeneity of spin ensembles. We show that a continuous driving field, which itself may also be inhomogeneous over the ensemble, can enhance the decay of the tails of the inhomogeneous broadening distribution considerably. This fact enables a spin ensemble based quantum memory to exploit the effect of cavity protection and achieve a much longer storage time. In particular, for a spin ensemble with a Lorentzian spectral distribution, our calculations demonstrate that continuous dynamical decoupling has the potential to improve its storage time by orders of magnitude for the state-of-art experimental parameters

A Patient-Centered Description of Severe Asthma:Patient Understanding Leading to Assessment for a Severe Asthma Referral (PULSAR)

BACKGROUND: Although severe asthma can be life-threatening, many patients are unaware they have this condition. OBJECTIVES: Patient Understanding Leading to Assessment for a Severe Asthma Referral (PULSAR) is a novel, multidisciplinary working group aiming to develop and disseminate a global, patient-centered description of severe asthma to improve patient understanding of severe asthma and effect a change in patient behavior whereby patients are encouraged to visit their healthcare professional, when appropriate. METHODS: Current definitions from patient organization websites, asthma guidelines, and medication information for key asthma drugs were assessed and informed a multidisciplinary working group, convened to identify common concepts and terminology used to define severe asthma. A patient-centered description of severe asthma and patient checklist were drafted based on working-group discussions and reviewed by an external behavioral scientist for patient understanding and relevance. These were tested using an online US/Canadian survey. RESULTS: The patient-centered description of severe asthma and patient checklist were reviewed and re-drafted by the authors. The text was simplified following the behavioral-scientist review. The survey (n = 153) included 105 patients with severe asthma. Of those with severe asthma, 92.2% of patients reported that the description was consistent with their experiences of severe asthma and 92.6% of patients reported that the PULSAR initiative would encourage them to visit their healthcare provider. CONCLUSION: A patient-centered description of severe asthma has been developed and tested using patients with severe asthma; this description will allow patients to assess whether they might have severe asthma and prompt them to visit their healthcare provider, if appropriate