On the variation of solar flare coronal x-ray source sizes with energy

Observations with {\em RHESSI} have enabled the detailed study of the structure of dense hard X-ray coronal sources in solar flares. The variation of source extent with electron energy has been discussed in the context of streaming of non-thermal particles in a one-dimensional cold-target model, and the results used to constrain both the physical extent of, and density within, the electron acceleration region. Here we extend this investigation to a more physically realistic model of electron transport that takes into account the finite temperature of the ambient plasma, the initial pitch-angle distribution of the accelerated electrons, and the effects of collisional pitch-angle scattering. The finite temperature results in the thermal diffusion of electrons, that leads to the observationally-inferred value of the acceleration region volume being an overestimate of its true value. The different directions of the electron trajectories, a consequence of both the non-zero injection pitch-angle and scattering within the target, cause the projected propagation distance parallel to the guiding magnetic field to be reduced, so that a one-dimensional interpretation can overestimate the actual density by a factor of up to $\sim 6$. The implications of these results for the determination of acceleration region properties (specific acceleration rate, filling factor, etc.) are discussed.Comment: 45 pages, 9 figures, accepted for publication in Ap

Determination of the total accelerated electron rate and power using solar flare hard X-ray spectra

Solar flare hard X-ray spectroscopy serves as a key diagnostic of the accelerated electron spectrum. However, the standard approach using the collisional cold thick-target model poorly constrains the lower-energy part of the accelerated electron spectrum, and hence the overall energetics of the accelerated electrons are typically constrained only to within one or two orders of magnitude. Here we develop and apply a physically self-consistent warm-target approach which involves the use of both hard X-ray spectroscopy and imaging data. The approach allows an accurate determination of the electron distribution low-energy cutoff, and hence the electron acceleration rate and the contribution of accelerated electrons to the total energy released, by constraining the coronal plasma parameters. Using a solar flare observed in X-rays by the {\em RHESSI} spacecraft, we demonstrate that using the standard cold-target methodology, the low-energy cutoff (and hence the energy content in electrons) is essentially undetermined. However, the warm-target methodology can determine the low-energy electron cutoff with $\sim$7\% uncertainty at the $3\sigma$ level and hence permits an accurate quantitative study of the importance of accelerated electrons in solar flare energetics.Comment: Accepted for publication in the Astrophysical Journal, 18 pages, 5 figure

Intestinal Dipeptide Absorption Is Preserved During Thermal Injury and Cytokine Treatment

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142293/1/jpen0520.pd

How Well has Land-Use Planning Worked Under Different Governance Regimes? A Case Study in the Portland, OR-Vancouver, WA Metropolitan Area, USA

We examine land use planning outcomes over a 30-year period in the Portland, OR-Vancouver, WA (USA) metropolitan area. The four-county study region enables comparisons between three Oregon counties subject to Oregon’s 1973 Land Use Act (Senate Bill 100) and Clark County, WA which implemented land use planning under Washington’s 1990 Growth Management Act. We describe county-level historical land uses from the mid-1970s to the mid-2000s, including low-density residential and urban development, both outside and inside of current urban growth boundaries. We use difference-in-differences models to test whether differences in the proportions of developed land resulting from implementation of urban growth boundaries are statistically significant and whether they vary between Oregon and Washington. Our results suggest that land use planning and urban growth boundaries now mandated both in Oregon and Washington portions of the study area have had a measurable and statistically significant effect in containing development and conserving forest and agricultural lands in the Portland-Vancouver metropolitan area. Our results also suggest, however, that these effects differ across the four study-area counties, likely owing in part to differences in counties’ initial levels of development, distinctly different land use planning histories, and how restrictive their urban growth boundaries were drawn

Downhill running impairs activation and strength of the elbow flexors

PURPOSE: The aim of this study was to determine if knee extensor injury induced by 1 h of downhill running attenuated force production in uninjured skeletal muscle (e.g., elbow flexors). METHODS: Recreationally active subjects (n = 12) completed a two group (injury vs control) repeated measures design with the injury group running downhill for 1 h and the control group performing only the measurement procedures. Strength and percent voluntary muscle activation were measured using an isokinetic dynamometer and electrical stimulation of the elbow flexors and knee extensors before and after a fatigue protocol at the following time points in relation to the downhill run: 15 min pre, 15 min post, 24 h post, and 48 h post. Blood samples were collected at the same time points to measure IL-1β and TNF-α concentrations. RESULTS: Knee extensor strength was significantly reduced by 53.5±9.9% immediately post-injury and remained reduced for up to 48 h in the injury group. Elbow flexor strength was significantly reduced immediately and 24 h post-injury by 13.2±3.9% and 17.3±4.0% respectively in the injury group. Elbow flexor electrically stimulated strength was not found to be different at any time point (P = 0.561). Elbow flexor activation was significantly reduced compared to control at 24 and 48 h post-injury by 22.9±9.1% and 13.5±5.7% respectively. No differences were observed in IL-1β or TNF-α between groups. CONCLUSION: A 1 h downhill run significantly injured the knee extensors. The elbow flexor muscles remained uninjured based on electrically stimulated strength, but voluntary strength of these muscles was impaired due to reduced activation. This suggests an injury to the knee extensors can impair strength in uninjured muscles by reducing voluntary activation. The mechanism behind this reduction remains undetermined. INDEX WORDS: Downhill running, Muscle injury, Central nervous system, Inflammatio

In-situ resonant band engineering of solution-processed semiconductors generates high performance n-type thermoelectric nano-inks.

Thermoelectric devices possess enormous potential to reshape the global energy landscape by converting waste heat into electricity, yet their commercial implementation has been limited by their high cost to output power ratio. No single "champion" thermoelectric material exists due to a broad range of material-dependent thermal and electrical property optimization challenges. While the advent of nanostructuring provided a general design paradigm for reducing material thermal conductivities, there exists no analogous strategy for homogeneous, precise doping of materials. Here, we demonstrate a nanoscale interface-engineering approach that harnesses the large chemically accessible surface areas of nanomaterials to yield massive, finely-controlled, and stable changes in the Seebeck coefficient, switching a poor nonconventional p-type thermoelectric material, tellurium, into a robust n-type material exhibiting stable properties over months of testing. These remodeled, n-type nanowires display extremely high power factors (~500 µW m-1K-2) that are orders of magnitude higher than their bulk p-type counterparts

Mechanisms by which sialylated milk oligosaccharides impact bone biology in a gnotobiotic mouse model of infant undernutrition

Undernutrition in children is a pressing global health problem, manifested in part by impaired linear growth (stunting). Current nutritional interventions have been largely ineffective in overcoming stunting, emphasizing the need to obtain better understanding of its underlying causes. Treating Bangladeshi children with severe acute malnutrition with therapeutic foods reduced plasma levels of a biomarker of osteoclastic activity without affecting biomarkers of osteoblastic activity or improving their severe stunting. To characterize interactions among the gut microbiota, human milk oligosaccharides (HMOs), and osteoclast and osteoblast biology, young germ-free mice were colonized with cultured bacterial strains from a 6-mo-old stunted infant and fed a diet mimicking that consumed by the donor population. Adding purified bovine sialylated milk oligosaccharides (S-BMO) with structures similar to those in human milk to this diet increased femoral trabecular bone volume and cortical thickness, reduced osteoclasts and their bone marrow progenitors, and altered regulators of osteoclastogenesis and mediators of Th2 responses. Comparisons of germ-free and colonized mice revealed S-BMO-dependent and microbiota-dependent increases in cecal levels of succinate, increased numbers of small intestinal tuft cells, and evidence for activation of a succinate-induced tuft cell signaling pathway linked to Th2 immune responses. A prominent fucosylated HMO, 2'-fucosyllactose, failed to elicit these changes in bone biology, highlighting the structural specificity of the S-BMO effects. These results underscore the need to further characterize the balance between, and determinants of, osteoclastic and osteoblastic activity in stunted infants/children, and suggest that certain milk oligosaccharides may have therapeutic utility in this setting

Long-term, treatment-free survival in select patients with distant metastatic papillary thyroid cancer

Well-differentiated thyroid carcinoma (WDTC) generally has a favorable prognosis. However, patients with distant metastatic disease experience progression of disease with a higher mortality. A subset of patients not previously described may challenge the conventional dogma regarding the progressive nature of all metastatic WDTC. Through analysis of our database, we identified patients with distant metastatic WDTC and persistent, minimally progressive disease. In all patients, persistent metastatic disease was confirmed via tissue biopsy, abnormal PET scan, and/or biochemical elevations in thyroglobulin or antibody levels. Progression of disease was monitored clinically and with repeat imaging. We describe five patients with WDTC and pulmonary metastases, aged 8–43 years at diagnosis. All patients underwent initial surgery and radioactive iodine (RAI) ablation, with some receiving multiple treatments. Persistent pulmonary metastatic disease was confirmed over decades (mean 22 years, range 8–42 years) with minimal progression despite no further treatment beyond thyroid hormone suppression. Persistent disease was biopsy-proven in all patients at a mean of 9.6 years from last RAI treatment. All patients had elevated thyroglobulin or anti-thyroglobulin antibody levels, while three demonstrated metabolically active disease with positive FDG uptake on PET scan, and one patient with persistent radioactive iodine avid pulmonary metastasis 36 years after her last RAI treatment. This case series demonstrates that some patients with distant metastases, even if metabolically active and radioactive iodine resistant, remain stable for decades without further treatment. Clinical awareness of such patients and continual reassessment of disease risk following initial therapy are crucial as aggressive treatment may not be necessary