Dynamic radial positioning of a hydrodynamically focused particle stream enabled by a three-dimensional microfluidic nozzle.

The ability to confine flows and focus particle streams has become an integral component of the design of microfluidic systems for the analysis of a wide range of samples. Presented here is the implementation of a 3D microfluidic nozzle capable of both focusing particles as well as dynamically positioning those particles in selected flow lamina within the downstream analysis channel. Through the independent adjustment of the three sheath inlet flows, the nozzle controlled the size of a focused stream for 6, 10, and 15 µm polystyrene microparticles. Additional flow adjustment allowed the nozzle to dynamically position the focused particle stream to a specific area within the downstream channel. This unique ability provides additional capability and sample flexibility to the system. In order to gain insight into the fluidic behavior of the system, experimental conditions and results were duplicated within 4.75 µm using a COMSOL Multiphysics(®) model to elucidate the structure, direction, proportion, and fate of fluid lamina throughout the nozzle region. The COMSOL Multiphysics model showed that the position and distribution of particles upon entering the nozzle have negligible influence over its focusing ability, extending the experimental results into a wider range of particle sizes and system flow rates. These results are promising for the application of this design to allow for a relatively simple, fast, fully fluidically controlled nozzle for selective particle focusing and positioning for further particle analysis and sorting.

[Effectiveness of sodium hyaluronate in patients with gonarthrosis: randomized comparative study]. / Efectividad del hialuronato de sodio en pacientes con gonartrosis, estudio comparativo y aleatorizado.

INTRODUCTION: Hyaluronic acid is a major component of synovial fluid and cartilage; it plays an essential role in joint function. This concept is based on the hypothesis that intraarticular sodium hyaluronate injections improve articular function upon restoring synovial fluid viscosupplementation and promoting endogenous synthesis. MATERIAL AND METHODS: Forty randomly selected patients older than 50 years of age, with a diagnosis of gonarthrosis, standard treatment-naïve, were divided into two 20-patient groups. The first group was treated with five 2.5 ml doses of hyaluronic acid, at one dose per week. The second group was treated with a single 2 ml dose of intraarticular methylprednisolone. A survey containing the Womac functional scale and the pain visual analogue scale was applied to both groups before and 3 months after treatment. RESULTS: A statistically significant reduction in pain (visual analogue scale) was observed 3 months after treatment in group H (1.6 +/- 0.88) and group M (2.95 +/- 1.84), as well as a functional post-treatment improvement in the Womac scale. Results for post-treatment pain were 5.43 +/- 1.05 for group H and 7.86 +/- 0.77 for group M; results for post-treatment stiffness were 3.05 +/- 0.82 for group H and 3.7 +/- 0.85 for group M; and finally for post-treatment functional capacity the results were 12.25 +/- 0.82 for group H and 18.95 +/- 0.85 for group M. CONCLUSION: Intraarticular sodium hyaluronate is more effective for pain and function than methylprednisolone. However, it involves higher costs than conservative treatment and fewer costs than surgical treatment, as well as the discomfort resulting from repeated intraarticular injections and the possibility of anaphylactic reaction.

Fiber based optical trapping of aerosols.

We present the use of optical fibers to form a counter-propagating optical trap as a means of manipulating both solid and liquid aerosols. We explore the use of single and multimode fibers to achieve trapping of various particles in air, present the trapping properties of the different fiber types and compare the observed trends to those predicted by theory. Using fibers, we are able to hold suspended particles for extended periods of time and to precisely manipulate them over distances of several hundred microns. We discuss the difficulties and advantages of each fiber configuration and conclude with a demonstration that fiber based trapping offers a good candidate for studying optical binding in air.

White light propagation invariant beams.

Propagation invariant light fields such as Bessel light beams are of interest in a variety of current areas such as micromanipulation of atoms and mesoscopic particles, laser plasmas, and the study of optical angular momentum. Considering the optical fields as a superposition of conical waves, we discuss how the coherence properties of light play a key role in their formation. As an example, we show that Bessel beams can be created from temporally incoherent broadband light sources including a halogen bulb. By using a supercontinuum source we elucidate how the beam behaves as a function of bandwidth of the incident light field.