Improving optical contact for functional near‑infrared brain spectroscopy and imaging with brush optodes

A novel brush optode was designed and demonstrated to overcome poor optical contact with the scalp that can occur during functional near infrared spectroscopy (fNIRS) and imaging due to light obstruction by hair. The brush optodes were implemented as an attachment to existing commercial flat-faced (conventional) fiber bundle optodes. The goal was that the brush optodes would thread through hair and improve optical contact on subjects with dense hair. Simulations and experiments were performed to assess the magnitude of these improvements. FNIRS measurements on 17 subjects with varying hair colors (blonde, brown, and black) and hair densities (0–2.96 hairs/mm2) were performed during a finger tapping protocol for both flat and brush optodes. In addition to reaching a study success rate of almost 100% when using the brush optode extensions, the measurement setup times were reduced by a factor of three. Furthermore, the brush optodes enabled improvements in the activation signal-to-noise ratio (SNR) by up to a factor of ten as well as significant (p < 0.05) increases in the detected area of activation (dAoA). The measured improvements in SNR were matched by Monte Carlo (MC) simulations of photon propagation through scalp and hair. In addition, an analytical model was derived to mathematically estimate the observed light power losses due to different hair colors and hair densities. Interestingly, the derived analytical formula produced excellent estimates of the experimental data and MC simulation results despite several simplifying assumptions. The analytical model enables researchers to readily estimate the light power losses due to obstruction by hair for both flat-faced fiber bundles and individual fibers for a given subject

The potential for coral reef establishment through free-living stabilization

Corals thrive in a variety of environments, from low wave and tidal energy lagoons, to high energy tidal reef flats, but remain dependent upon suitable substrate. Herein we reviewed the phenomenon of free-living corals (coralliths), examined whether they have the capacity to create their own stable habitat in otherwise uninhabitable, poor substrate environments through 'free-living stabilization', and explore their potential ecological role on coral reefs. This stabilization could be achieved by coral settlement and survival on mobile substrate, with subsequent growth into free-living coralliths until a critical mass is reached that prevents further movement. This allows for secondary reef colonization by other coral species. To preliminarily test this hypothesis we provide evidence that the potential to support secondary coral colonisation increases with corallith size. Due to the limited diversity of corallith species observed here and in the literature, and the lack of physiological differences exhibited by coralliths here to static controls, it seems likely that only a small selection of coral species have the ability to form coralliths, and the potential to create their own stable habitat

The Lead-208(deuteron,triton)lead-207 Reaction With 15 To 25 Mev Deuterons.

PhDNuclear physicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/184472/2/6701782.pd

The Relationship Between Carbonate Chemistry and Calcification on the Florida Reef Tract, and in the Symbiotic Reef Coral, Acropora cervicornis

Increasing atmospheric carbon dioxide (pCO2) dissolves in the ocean, decreasing the calcium carbonate saturation state (Ωaragonite) and creating conditions unfavorable for calcification (G) in reef-building corals. Understanding the effects of ocean acidification on coral reefs requires a robust description of the relationship between Ω and calcification (Ω-G) at both the reef scale and at the organismal scale. To evaluate the Ω-G relationship on the reef, we conducted repeat surveys across 200 km of the Florida Reef Tract over a 2 year period. Results showed that net community calcification switches from positive in the summer to negative in the winter, indicating net dissolution and revealing that the reef tract is currently straddling the tipping point between reef growth and loss. To evaluate the Ω-G relationship at the organismal scale, we grew Acropora cervicornis under six CO2 levels, 2-3 times more than typically achieved in laboratory settings. The associated Ω stretched from current levels to highly undersaturated seawater, creating a robust test of linearity of the Ω-G relationship. Our results show that the Ω-G relationship is linear and maintained even in highly undersaturated seawater. The effect of pCO2 on calcification was also strongly mediated by heterotrophy, which significantly alleviated the effect of ocean acidification at all pCO2 levels. The obligate symbiont, Symbiodinium microadriaticum, also showed a significant response to increasing pCO2 and declined in density in both corals in the laboratory (A. cervicornis), and in corals at natural CO2 vents in the South Pacific (Acropora millepora and Pocillopora damicornis). This dissertation demonstrates that while heterotrophy can offset a significant portion of the negative effects of ocean acidification, coral calcification still declines in direct proportion to reductions in Ω. At the community level, evidence is presented that calcification on the Florida Reef Tract exists near the threshold for net carbonate accretion. Thus, while corals can utilize heterotrophic sources of nutrients to alleviate the effects of ocean acidification, it is unlikely to translate into net reef growth in the natural environment, where net annual dissolution is already occurring

Image quality assessment of LaBr3-based whole-body 3D PET scanners: a Monte Carlo evaluation. Phys Med Biol,

Abstract The main thrust for this work is the investigation and design of a wholebody PET scanner based on new lanthanum bromide scintillators. We use Monte Carlo simulations to generate data for a 3D PET scanner based on LaBr 3 detectors, and to assess the count-rate capability and the reconstructed image quality of phantoms with hot and cold spheres using contrast and noise parameters. Previously we have shown that LaBr 3 has very high light output, excellent energy resolution and fast timing properties which can lead to the design of a time-of-flight (TOF) whole-body PET camera. The data presented here illustrate the performance of LaBr 3 without the additional benefit of TOF information, although our intention is to develop a scanner with TOF measurement capability. The only drawbacks of LaBr 3 are the lower stopping power and photo-fraction which affect both sensitivity and spatial resolution. However, in 3D PET imaging where energy resolution is very important for reducing scattered coincidences in the reconstructed image, the image quality attained in a non-TOF LaBr 3 scanner can potentially equal or surpass that achieved with other high sensitivity scanners. Our results show that there is a gain in NEC arising from the reduced scatter and random fractions in a LaBr 3 scanner. The reconstructed image resolution is slightly worse than a high-Z scintillator, but at increased count-rates, reduced pulse pileup leads to an image resolution similar to that of LSO. Image quality simulations predict reduced contrast for small hot spheres compared to an LSO scanner, but improved noise characteristics at similar clinical activity levels

3d Image Reconstruction for PET by Multi-Slice Rebinning and Axial Filtering

Two different approaches are used at present to reconstruct from 3D coincidence data in PET. We refer to these approaches as the single-slice rebinning approach and the fully-3D approach. The single-slice rebinning approach involves geometrical approximations, but it requires the least possible amount of computation. Fully-3D reconstruction algorithms, both iterative and non-iterative, do not make such approximations, but require much more computation. Multi-slice rebinning with axial filtering is a new approach which attempts to achieve the geometrical accuracy of the fully-3D approach with the simplicity and modest amount of computation of the single-slice rebinning approach. The first step (multi-slice rebinning) involves rebinning of coincidence lines into a stack of 2D sinograms, where multiple sinograms are incremented for each oblique coincidence line. This operation is followed by an axial filtering operation, either before or after slice-by-slice reconstruction, to reduce the blurring in the axial direction. Tests with simulated and experimental data indicate that the new method has better geometrical accuracy than single-slice rebinning, at the cost of only a modest increase in computation. 11 refs