A flexible route to new spirodioxanes, oxathianes and morpholines

International audienceThis work describes a modular efficient route to 10-aza-4-thia-, 10-aza-4-oxa-, and 10-oxa-4-thia-1,7-dioxaspiro[5.5]undecanes. The synthetic pathway relies upon the iterative nucleophilic substitution of 1,3-dichloropropan-2-one O-benzyloxime by solketal derivatives. The oxime key-intermediates, submitted to an acidic deprotection–spiroacetalization process, afforded these original spiroketal compounds in three steps, few purifications, and very good yields

Hylomorphic solitons in the nonlinear Klein-Gordon equation

Roughly speaking a solitary wave is a solution of a field equation whose energy travels as a localised packet and which preserves this localisation in time. A soliton is a solitary wave which exhibits some strong form of stability so that it has a particle-like behaviour. In this paper we show a new mechanism which might produce solitary waves and solitons for a large class of equations, such as the nonlinear Klein-Gordon equation. We show that the existence of these kind of solitons, that we have called \emph{hylomorphic} solitons, depends on a suitable energy/charge ratio. We show a variational method that allows to prove the existence of hylomorphic solitons and that turns out to be very useful for numerical applications. Moreover we introduce some classes of nonlinearities which admit hylomorphic solitons of different shapes and with different relations between charge, energy and frequency.Comment: 23 page

Real-time imaging and tracking of microrobots in tissues using ultrasound phase analysis

Ultrasound B-mode imaging has been employed to monitor single agents and collective swarms of microrobots in vitro and ex vivo in controlled experimental conditions. However, low contrast and spatial resolution still limit the effective employment of such a method in a medical microrobotic scenario. Doppler-based ultrasound appears as a promising tool for tracking microrobots in echogenic and dynamic environments as biological tissues. In this Letter, we demonstrate that microrobot displacements can be used as a special signature for their visualization within echogenic media, where B-mode fails. To this aim, we induced vibrations of a magnetic soft microrobot through alternated magnetic fields and used ultrasound phase analysis to derive microrobot features such as size and position over time. By exploiting vibrations, we were able to perform imaging and tracking of a low contrast microrobot both in tissue-mimicking phantom and in chicken breast. The axial resolution was 38 μm, which is four times smaller than the B-mode resolution with the employed equipment. We also performed real-time tracking of the microrobot's positions along linear trajectories with a linear velocity up to 1 mm/s. Overall, the reported results pave the way for the application of the proposed approach for the robust monitoring of medical microrobots in tissue

Pulsatile Viscous Flows in Elliptical Vessels and Annuli: Solution to the Inverse Problem, with Application to Blood and Cerebrospinal Fluid Flow

We consider the fully-developed flow of an incompressible Newtonian fluid in a cylindrical vessel with elliptical cross-section and in an annulus between two confocal ellipses. Since flow rate is the main physical quantity which can be actually be derived from measurements, we address the extit {inverse problem} to compute the velocity field associated with a given, time-periodic flow rate. We propose a novel numerical strategy, which is nonetheless grounded on several analytical relations and which leads to the solution of systems of ordinary differential equations. Our method holds romise to be more amenable to implementation than previous ones based on challenging computation of Mathieu functions. We report numerical results based on measured data for human blood flow in the internal carotid artery, and cerebrospinal fluid flow in the upper cervical region of the human spine. Computational efficiency is shown, but the main goal of the present study is to provide an improved source of initial/boundary data, as well as a benchmark solution for pulsatile flows in elliptical sections and the proposed method has potential applications to bio-fluid dynamics investigations (e.g. to address aspects of relevant diseases), to biomedical applications (e.g. targeted drug delivery and energy harvesting for implantable devices), up to longer-term medical microrobotics applications

Flame-vortex interactions - Effects of buoyancy from microgravity imaging studies

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76483/1/AIAA-1997-669-671.pd

Retrieval of magnetic medical microrobots from the bloodstream

Untethered magnetic microrobots hold the potential to penetrate hard-to-reach areas of the human body and to perform therapy in a controlled way. In the past decade, impressive advancements have been made in this field but the clinical adoption of magnetoresponsive microrobots is still hampered by safety issues. A tool appointed for magnetic microrobots retrieval within body fluids could enable a real paradigm change, fostering their clinical translation.By starting from the general problem to retrieve magnetic microrobots injected into the bloodstream, the authors introduce a magnetic capture model that allows to design retrieval tools for magnetic cores of different diameters (down to 10 nm) and in different environmental conditions (fluid speed up to 7 cms-1). The model robustness is demonstrated by the design and testing of a retrieval catheter. In its optimal configuration, the catheter includes 27 magnets and fits a 12 F catheter. The model provides a good prediction of capture efficiency for 250 nm magnetic particles (experimental data: 77.6%, model prediction: 65%) and a very good prediction for 500 nm particles (experimental data: 93.6%, model prediction: 94%). The results support the proposed model-based design approach, which can be extended to retrieve other magnetoresponsive agents from body compartments

Biosensing platform combining label-free and labelled analysis using Bloch surface waves

Bloch surface waves (BSW) propagating at the boundary of truncated photonic crystals (1D-PC) have emerged as an attractive approach for label-free sensing in plasmon-like sensor configurations. Due to the very low losses in such dielectric thin film stacks, BSW feature very low angular resonance widths compared to the surface plasmon resonance (SPR) case. Besides label-free operation, the large field enhancement and the absence of quenching allow utilizing BSW coupled fluorescence detection to additionally sense the presence of fluorescent labels. This approach can be adapted to the case of angularly resolved resonance detection, thus giving rise to a combined label-free / labelled biosensor platform. It features a parallel analysis of multiple spots arranged as a one-dimensional array inside a microfluidic channel of a disposable chip. Application of such a combined biosensing approach to the detection of the Angiopoietin-2 cancer biomarker in buffer solutions is reported