Eight-Channel Head Array and Control System for Parallel Transmit/Receive Magnetic Resonance Imaging

Interest in magnetic resonance imaging (MRI) at high fields strengths (3 Tesla and above) is driven by the associated improvements in signal-to-noise ratio and spectral resolution. In practice, however, technical challenges prevent these benefits from being straightforwardly realized. High fields are associated with an increase in frequency and a decrease in the radiofrequency (RF) wavelength. The shortened wavelength causes potential inhomogeneity in the transmit field of the RF coil, resulting in non-uniform excitations. Susceptibility effects are also more pronounced at high field strengths, and can cause local distortions in the field and create areas of signal dropout. Parallel transmit is one method in development to address these challenges at high fields. Parallel transmit involves using multiple independently driven channels with RF pulses varying in amplitude, phase, and pulse envelope to create desired transmit excitations. Parallel transmit has been implemented to create homogenous transmit patterns and compensate for magnetic susceptibility effects, but despite its proven usefulness, the technology has yet to receive widespread adoption. Few parallel transmit systems exist and little work has been done in the pre-clinical realm. Studies demonstrating the clinical benefits of parallel transmit constitute a gap in the current body of work. This works presents an approach to a parallel transmit array and control system that can be easily and safely integrated on a clinical whole-body scanner. The transmit array was designed for use with ultra-low output impedance amplifiers and demonstrates an array design with a simplified decoupling network augmented by amplifier decoupling in both transmit and receive. The control system was programmed in LabVIEW using off-the-shelf hardware to manage pulse playback, correct transmit chain non-linearities, monitor on-coil waveforms, and drive the transmit hardware. The transmit array was shown with well-isolated patterns, and parallel transmit capability was demonstrated. This work progressed the translation of experimental parallel transmit technology to pre-clinical use

Chains of Affection: The Structure of Adolescent Romantic and Sexual Networks

This article describes the structure of the adolescent romantic and sexual network in a population of over 800 adolescents residing in a midsized town in the midwestern United States. Precise images and measures of network structure are derived from reports of relationships that occurred over a period of 18 months between 1993 and 1995. The study offers a comparison of the structural characteristics of the observed network to simulated networks conditioned on the distribution of ties; the observed structure reveals networks characterized by longer contact chains and fewer cycles than expected. This article identifies the micromechanisms that generate networks with structural features similar to the observed network. Implications for disease transmission dynamics and social policy are explored

The Impact of an International Interprofessional Experience on Perceptions of Pharmacist-Physician Relationships

Objective. To assess the impact of this international interprofessional learning experience on perceptions of pharmacist-physician relationships and interprofessional teams. Methods. Medical and pharmacy students completed a one-week interprofessional medical mission experience in the Dominican Republic. Anonymous surveys were administered to 17 students before and after completion to measure perceptions of pharmacist-physician relationships and interprofessional teams. Responses were matched and changes in perceptions were analyzed using the Wilcoxon Signed Rank test. The SPICE-R2 instrument was administered after the experience to measure attitudes toward interprofessional teams. Results. Of the 17 participants, 100% responded to all surveys. Significant improvements were seen in the perception of pharmacists as an integral part of medical mission trips (P=0.035) and confidence in the ability to communicate with other healthcare disciplines (P=0.033). All students stated they would recommend this experience, and agreed that interprofessional experiences enhance their team work skills and should be incorporated into their education. Student comments supported that this was a meaningful and effective interprofessional experience. The results of the SPICE-R2 demonstrated positive attitudes about interprofessional teams, with all questions having a median score of “agree” or “strongly agree.” Conclusions. An international interprofessional experience improved the perception of pharmacist-physician relationships. The experience provided understanding of the other healthcare discipline, an appreciation for the importance of interprofessional teamwork, increased student confidence in communicating with the other discipline, and cultivated interest in future interprofessional collaboration

Effect of growth temperature on photosynthetic capacity and respiration in three ecotypes of Eriophorum vaginatum

Ecotypic differentiation in the tussock‐forming sedge Eriophorum vaginatum has led to the development of populations that are locally adapted to climate in Alaska\u27s moist tussock tundra. As a foundation species, E. vaginatum plays a central role in providing topographic and microclimatic variation essential to these ecosystems, but a changing climate could diminish the importance of this species. As Arctic temperatures have increased, there is evidence of adaptational lag in E. vaginatum, as locally adapted ecotypes now exhibit reduced population growth rates. Whether there is a physiological underpinning to adaptational lag is unknown. Accordingly, this possibility was investigated in reciprocal transplant gardens. Tussocks of E. vaginatum from sites separated by ~1° latitude (Coldfoot: 67°15′N, Toolik Lake: 68°37′, Sagwon: 69°25′) were transplanted into the Toolik Lake and Sagwon sites and exposed to either an ambient or an experimental warming treatment. Five tussocks pertreatment combination were measured at each garden to determine photosynthetic capacity (i.e., Vcmax and Jmax) and dark respiration rate (Rd) at measurement temperatures of 15, 20, and 25°C. Photosynthetic enhancements or homeostasis were observed for all ecotypes at both gardens under increased growth temperature, indicating no negative effect of elevated temperature on photosynthetic capacity. Further, no evidence of thermal acclimation in Rd was observed for any ecotype, and there was little evidence of ecotypic variation in Rd. As such, no physiological contribution to adaptational lag was observed given the increase in growth temperature (up to ~2°C) provided by this study. Despite neutral to positive effects of increased growth temperature on photosynthesis in E. vaginatum, it appears to confer no lasting advantage to the species

Effect of growth temperature on photosynthetic capacity and respiration in three ecotypes of Eriophorum vaginatum

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ecology and Evolution 8 (2018): 3711-3725, doi:10.1002/ece3.3939.Ecotypic differentiation in the tussock‐forming sedge Eriophorum vaginatum has led to the development of populations that are locally adapted to climate in Alaska's moist tussock tundra. As a foundation species, E. vaginatum plays a central role in providing topographic and microclimatic variation essential to these ecosystems, but a changing climate could diminish the importance of this species. As Arctic temperatures have increased, there is evidence of adaptational lag in E. vaginatum, as locally adapted ecotypes now exhibit reduced population growth rates. Whether there is a physiological underpinning to adaptational lag is unknown. Accordingly, this possibility was investigated in reciprocal transplant gardens. Tussocks of E. vaginatum from sites separated by ~1° latitude (Coldfoot: 67°15′N, Toolik Lake: 68°37′, Sagwon: 69°25′) were transplanted into the Toolik Lake and Sagwon sites and exposed to either an ambient or an experimental warming treatment. Five tussocks pertreatment combination were measured at each garden to determine photosynthetic capacity (i.e., Vcmax and Jmax) and dark respiration rate (Rd) at measurement temperatures of 15, 20, and 25°C. Photosynthetic enhancements or homeostasis were observed for all ecotypes at both gardens under increased growth temperature, indicating no negative effect of elevated temperature on photosynthetic capacity. Further, no evidence of thermal acclimation in Rd was observed for any ecotype, and there was little evidence of ecotypic variation in Rd. As such, no physiological contribution to adaptational lag was observed given the increase in growth temperature (up to ~2°C) provided by this study. Despite neutral to positive effects of increased growth temperature on photosynthesis in E. vaginatum, it appears to confer no lasting advantage to the species.Division of Polar Programs Grant Numbers: 1417645, 1417763, 1418010; West Chester University, Department of Biolog

Femtosecond-laser-induced delamination and blister formation in thermal oxide films on silicon (100)

Silicon (100) substrates with thermal oxide films of varying thickness were irradiated with single and multiple 150 fs150fs laser pulses at normal and non-normal incidences. A range of laser fluence was found in which a blister or domelike feature was produced where the oxide film was delaminated from the substrate. At normal and non-normal incidences blister features were observed for samples with 54, 147, and 1200 nm1200nm of thermal oxide. The blister features were analyzed with optical and atomic force microscopy. In addition, the time frame for blister growth was obtained using pump-probe imaging techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87772/2/153121_1.pd

Constraining the Carbon Budget of Peat Ecosystems: Application of Stoichiometry and Enthalpy Balances

We consider how the stoichiometry and energy content of organic matter reservoirs and fluxes through and from a peatland enable the fluxes and storage of carbon within a peatland to be constrained. We include the elemental composition of the above- and below-ground biomass, litter, the peat profile, and the dissolved and particulate organic matter within a blanket bog in northern England for which the C budget has previously been measured. The study shows, based only on the elemental composition, and calculation of oxidation and energy contents, that: (a) Dissolved organic carbon (DOC) in first-order streams is significantly more oxidized than in peat pore water but that there was no significant difference in organic carbon oxidation state down the peat profile; (b) The occurrence and speciation of N uptake and release in the peatland with N used and recycled can be predicted; (c) The relatively high oxidation state of DOC in stream water acts as an endpoint for peat-forming reactions; (d) Methanogenesis does not result in deep peat formation as its requirement for energy consumes too much organic matter to form residual peat at depth; (e) Sulfate reduction does occur during the formation of deep peat; (f) Organic matter elemental composition could be constrained to within three bounding equations though the proportions of carbon species could not be specified. (g) The formation of deep peat in this catchment could only be achieved if the dissolved organic matter (DOM) in the peat pore water is the dominant electron acceptor and energy source in the production of residual organic matter; however, it is unclear as to the flux of DOM up or down the peat profile

A new globular cluster black hole in NGC 4472

We discuss CXOU~1229410+075744, a new black hole candidate in a globular cluster in the elliptical galaxy NGC~4472. By comparing two Chandra observations of the galaxy, we find a source that varies by at least a factor of 4, and has a peak luminosity of at least $2\times10^{39}$ ergs/sec. As such, the source varies by significantly more than the Eddington luminosity for a single neutron star, and is a strong candidate for being a globular cluster black hole. The source's X-ray spectrum also evolves in a manner consistent with what would be expected from a single accreting stellar mass black hole. We consider the properties of the host cluster of this source and the six other strong black hole X-ray binary candidates, and find that there is suggestive evidence that black hole X-ray binary formation is favored in bright and metal rich clusters, just as is the case for bright X-ray sources in general.Comment: 6 pages, one 2-panel figure, 2 tables; accepted to MNRA