Richard S. Conroy

Recent Advances in Wearable Sensors for Health Monitoring

Wearable sensor technology continues to advance and provide significant opportunities for improving personalized healthcare. In recent years, advances in flexible electronics, smart materials, and low-power computing and networking have reduced barriers to technology accessibility, integration, and cost, unleashing the potential for ubiquitous monitoring. This paper discusses recent advances in wearable sensors and systems that monitor movement, physiology, and environment, with a focus on applications for Parkinsons disease, stroke, and head and neck injuries.

In vivo labeling of adult neural progenitors for MRI with micron sized particles of iron oxide: quantification of labeled cell phenotype.

The subventricular zone (SVZ) is a continual source of neural progenitors throughout adulthood. Many of the animal models designed to study the migration of these cells from the ventricle to places of interest like the olfactory bulb or an injury site require histology to localize precursor cells. Here, it is demonstrated that up to 30% of the neural progenitors that migrate along the rostral migratory stream (RMS) in an adult rodent can be labeled for MRI via intraventricular injection of micron sized particles of iron oxide (MPIOs). The precursors migrating from the SVZ along the RMS were found to populate the olfactory bulb with all three types of neural cells; neurons, oligodendrocytes, and astrocytes. In all cases 10-30% of these cells were labeled in the RMS en route to the olfactory bulb. Ara-C, an anti-mitotic agent, eliminated precursor cells at the SVZ, RMS, and olfactory bulb and also eliminated the MRI detection of the precursors. This indicates that the MRI signal detected is due to progenitor cells that leave the SVZ and is not due to non-specific diffusion of MPIOs. Using MRI to visualize neural progenitor cell behavior in individual animals during plasticity or disease models should be a useful tool, especially in combination with other information that MRI can supply.

Diffusion-controlled optical elements for optofluidics

Diffusion at the interface between two streams of liquids with different refractive indices, flowing laminarly, creates a controllable concentration gradient and a corresponding refractive index gradient. Using flow rate to change the time over which diffusion occurs in a liquid-liquid (L2) optical waveguide, we demonstrate an optical splitter and a wavelength filter. The optical splitter comprises two parallel L2 waveguides which smoothly merge into a single L2 waveguide by diffusion. The wavelength filter comprises an optical splitter in which the two L2 waveguides contain an absorbing dye.

Measurement of the phase diagram of DNA unzipping in the temperature-force plane.

We separate double stranded lambda phage DNA by applying a fixed force at a constant temperature ranging from 15 to 50 degrees C, and measure the minimum force required to separate the two strands. The measurements also offer information on the free energy of double stranded DNA (dsDNA) at temperatures where dsDNA does not thermally denature in the absence of force. While parts of the phase diagram can be explained using existing models and free energy parameters, others deviate significantly. Possible reasons for the deviations between theory and experiment are considered.

Blue microchip laser fabricated from Nd:YAG and KNbO3

A Nd:YAG/KNbO(3) composite-material microchip laser has generated blue radiation at 473 nm with output powers of 1 mW when diode laser pumped and 9 mW when Ti:sapphire laser pumped. The fundamental radiation generated by the quasi-three-level (4)F(3/2)-(4)I(9/2) transition in Nd:YAG at 946 nm was frequency doubled in KNbO(3) angle cut to be type I critically phase matched at 45 degrees C. Despite the normally isotropic nature of Nd:YAG, the fundamental is emitted linearly polarized and orthogonal to the linearly polarized blue radiation.

Ipsilateral cortical fMRI responses after peripheral nerve damage in rats reflect increased interneuron activity

In the weeks following unilateral peripheral nerve injury, the deprived primary somatosensory cortex (SI) responds to stimulation of the ipsilateral intact limb as demonstrated by functional magnetic resonance imaging (fMRI) responses. The neuronal basis of these responses was studied by using high-resolution fMRI, in vivo electrophysiological recordings, and juxtacellular neuronal labeling in rats that underwent an excision of the forepaw radial, median, and ulnar nerves. These nerves were exposed but not severed in control rats. Significant bilateral increases of fMRI responses in SI were observed in denervated rats. In the healthy SI of the denervated rats, increases in fMRI responses were concordant with increases in local field potential (LFP) amplitude and an increased incidence of single units responding compared with control rats. In contrast, in the deprived SI, increases in fMRI responses were associated with a minimal change in LFP amplitude but with increased incidence of single units responding. Based on action potential duration, juxtacellular labeling, and immunostaining results, neurons responding to intact forepaw stimulation in the deprived cortex were identified as interneurons. These results suggest that the increases in fMRI responses in the deprived cortex reflect increased interneuron activity.

The Diuretic Effect in Human Subjects of an Extract of Taraxacum officinale Folium over a Single Day

BACKGROUND Taraxacum officinale (L.) Weber (Asteraceae) has been extensively employed as a diuretic in traditional folk medicine and in modern phytotherapy in Europe, Asia, and the Americas without prior clinical trial substantiation. OBJECTIVES In this pilot study, a high-quality fresh leaf hydroethanolic extract of the medicinal plant T. officinale (dandelion) was ingested by volunteers to investigate whether an increased urinary frequency and volume would result. DESIGN Volume of urinary output and fluid intake were recorded by subjects. Baseline values for urinary frequency and excretion ratio (urination volume:fluid intake) were established 2 days prior to dandelion dosing (8 mL TID) and monitored throughout a 1-day dosing period and 24 hours postdosing. RESULTS For the entire population (n = 17) there was a significant (p < 0.05) increase in the frequency of urination in the 5-hour period after the first dose. There was also a significant (p < 0.001) increase in the excretion ratio in the 5-hour period after the second dose of extract. The third dose failed to change any of the measured parameters. CONCLUSIONS Based on these first human data, T. officinale ethanolic extract shows promise as a diuretic in humans. Further studies are needed to establish the value of this herb for induction of diuresis in human subjects.

Controlled transport of magnetic particles using soft magnetic patterns

Inspired by magnetic bubble memory technology, we demonstrate the temporal and spatial manipulation of superparamagnetic beads guided by soft magnetic patterns in a rotating magnetic field. Soft magnetic structures allow complex and repetitive tasks to be performed. As a demonstration, we show cyclic capture and release of antibodies from different microfluidic streams.

Fabrication of planar optical waveguides by electrical microcontact printing

We describe the fabrication by electrical microcontact printing of optical waveguides and splitters made of poly(4-vinylphenol) doped with phloxine B, permitting inexpensive, rapid prototyping over large areas and construction of integrated, multi-level devices.

Guiding effects in Nd:YVO/sub 4/ microchip lasers operating well above threshold

Guiding of the transverse mode in Nd:YVO/sub 4/ microchip lasers is examined both experimentally and theoretically at pump powers well above threshold. It is found that thermal changes in the cavity geometry induced by intense diode pumping can be well understood using a simple model. However, an understanding of these effects is not sufficient to explain the nature of the transverse mode. Gain-related guiding effects are found to play an important role even at pump powers well above threshold. For a 0.5-mm-thick microchip laser, a difference of around 30% is observed between the minimum beam waist expected due to thermal guiding and the measured beam waist. The gain-related effects are described theoretically and their importance is demonstrated experimentally.