1,632 research outputs found
Unraveling the Helix Nebula: Its Structure and Knots
Through HST imaging of the inner part of the main-ring of the Helix Nebula
together with CTIO 4-m images of the fainter outer parts, we have an
unprecedented-quality view of the nearest bright planetary nebula. These images
have allowed determination that the main-ring of the nebula is composed of an
inner-disk of about 499\arcsec diameter (0.52 pc) surrounded by an outer-ring
(in reality a torus) of 742\arcsec diameter (0.77 pc) whose plane is highly
inclined to the plane of the disk. This outer-ring is surrounded by an
outermost-ring of 1500\arcsec (1.76 pc) diameter which is flattened on the side
colliding with the ambient interstellar medium. The inner-disk has an extended
distribution of low density gas along its rotational axis of symmetry and the
disk is optically thick to ionizing radiation, as is the outer-ring.
Published radial velocities of the knots provides support for the
two-component structure of the main-ring of the nebula and to the idea that the
knots found there are expanding along with the nebular material from which it
recently originated. There is a change in the morphology of the knots as a
function of the distance from the local ionization front. This supports a
scenario in which the knots are formed in or near the ionization front and are
then sculpted by the stellar radiation from the central star as the ionization
front advances beyond them.Comment: 30 pages, 20 figures, many figures have reduce fidelity for astroph
preprint. Note: URLs in preprint were change
Oral Cannabidiol Does Not Produce a Signal for Abuse Liability in Frequent Marijuana Smokers
BackgroundâCannabidiol (CBD) is a naturally occurring constituent of the marijuana plant. In the past few years, there has been great interest in the therapeutic effects of isolated CBD and it is currently being explored for numerous disease conditions (e.g., pain, epilepsy, cancer, various drug dependencies). However, CBD remains a Schedule I drug on the U.S. Controlled Substances Act (CSA). Despite its status, there are no well-controlled data available regarding its abuse liability.
MethodsâHealthy, frequent marijuana users (n=31) were enrolled in this within subject, randomized, placebo-controlled, double-blind, multisite study that administered oral cannabidiol (0, 200, 400, 800 mg) alone and in combination with smoked marijuana (0.01%, 5.3-5.8% THC). Participants received one dose combination across 8 once-weekly outpatient sessions (7.5 hrs). The primary findings on the drug interaction effects were previously reported (Haney et al., 2016). The present study is a secondary analysis of the data to examine the abuse liability profile of oral cannabidiol (200, 400, 800 mg) in comparison to oral placebo and active smoked marijuana (5.3-5.8% THC).
ResultsâActive marijuana reliably produced abuse-related subjective effects (e.g., high) (p \u3c .05). However, CBD was placebo-like on all measures collected (p \u3e .05).
ConclusionsâOverall, CBD did not display any signals of abuse liability at the doses tested and these data may help inform U.S. regulatory decisions regarding CBD schedule on the CSA
The speaking vocabulary of grade two
Thesis (M.A.)--Boston Universit
[OII] as a Star Formation Rate Indicator
We investigate the [OII] emission-line as a star formation rate (SFR)
indicator using integrated spectra of 97 galaxies from the Nearby Field
Galaxies Survey (NFGS). The sample includes all Hubble types and contains SFRs
ranging from 0.01 to 100 Msun/yr. We compare the Kennicutt [OII] and H-alpha
SFR calibrations and show that there are two significant effects which produce
disagreement between SFR[OII] and SFR(H-alpha): reddening and metallicity.
Differences in the ionization state of the ISM do not contribute significantly
to the observed difference between SFR([OII]) and SFR(H-alpha) for the NFGS
galaxies with metallicities log(O/H)12>8.5. The Kennicutt [OII]-SFR relation
assumes a typical reddening for nearby galaxies; in practice, the reddening
differs significantly from sample to sample. We derive a new SFR([OII])
calibration which does not contain a reddening assumption. Our new SFR([OII])
calibration also provides an optional correction for metallicity. Our SFRs
derived from [OII] agree with those derived from H-alpha to within 0.03-0.05
dex. We apply our SFR([OII]) calibration with metallicity correction to two
samples: high-redshift 0.8<z<1.6 galaxies from the NICMOS H-alpha survey, and
0.5<z<1.1 galaxies from the Canada-France Redshift Survey. The SFR([OII]) and
SFR(H-alpha) for these samples agree to within the scatter observed for the
NFGS sample, indicating that our SFR([OII]) relation can be applied to both
local and high-z galaxies. Finally, we apply our SFR([OII]) to estimates of the
cosmic star formation history. After reddening and metallicity corrections, the
star formation rate densities derived from [OII] and H-alpha agree to within
30%.Comment: 34 pages, 19 figures. To be published in the April 2004 issue of the
Astronomical Jourma
Permeability-porosity relationships in seafloor vent deposits : dependence on pore evolution processes
Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): B05208, doi:10.1029/2006JB004716.Systematic laboratory measurements of permeability and porosity were conducted on three large vent structures from the Mothra Hydrothermal vent field on the Endeavor segment of the Juan de Fuca Ridge. Geometric means of permeability values obtained from a probe permeameter are 5.9 Ă 10â15 m2 for Phang, a tall sulfide-dominated spire that was not actively venting when sampled; 1.4 Ă 10â14 m2 for Roane, a lower-temperature spire with dense macrofaunal communities growing on its sides that was venting diffuse fluid of <300°C; and 1.6 Ă 10â14 m2 for Finn, an active black smoker with a well-defined inner conduit that was venting 302°C fluids prior to recovery. Twenty-three cylindrical cores were then taken from these vent structures. Permeability and porosity of the drill cores were determined on the basis of Darcy's law and Boyle's law, respectively. Permeability values range from âŒ10â15 to 10â13 m2 for core samples from Phang, from âŒ10â15 to 10â12 m2 for cores from Roane, and from âŒ10â15 to 3 Ă 10â13 m2 for cores from Finn, in good agreement with the probe permeability measurements. Permeability and porosity relationships are best described by two different power law relationships with exponents of âŒ9 (group I) and âŒ3 (group II). Microstructural analyses reveal that the difference in the two permeability-porosity relationships reflects different mineral precipitation processes as pore space evolves within different parts of the vent structures, either with angular sulfide grains depositing as aggregates that block fluid paths very efficiently (group I), or by late stage amorphous silica that coats existing grains and reduces fluid paths more gradually (group II). The results suggest that quantification of permeability and porosity relationships leads to a better understanding of pore evolution processes. Correctly identifying permeability and porosity relationships is an important first step toward accurately estimating fluid distribution, flow rate, and environmental conditions within seafloor vent deposits, which has important consequences for chimney growth and biological communities that reside within and on vent structures.Support from the
National Science Foundation under grants NSF OCE-9986456 (W.Z. and
M.K.T.) and NSF OCE-0327488 (P.R.C.) is gratefully acknowledged. We
also thank the WHOI summer student fellowship for providing support to
H.G
Measuring the capability to raise revenue process and output dimensions and their application to the Zambia revenue authority
The worldwide diffusion of the good governance agenda and new public management has triggered a renewed focus on state capability and, more specifically, on the capability to raise revenue in developing countries. However, the analytical tools for a comprehensive understanding of the capability to raise revenue remain underdeveloped. This article aims at filling this gap and presents a model consisting of the three process dimensions âinformation collection and processingâ, âmerit orientationâ and âadministrative accountabilityâ. âRevenue performanceâ constitutes the fourth capability dimension which assesses tax administrationâs output. This model is applied to the case of the Zambia Revenue Authority. The dimensions prove to be valuable not only for assessing the how much but also the how of collecting taxes. They can be a useful tool for future comparative analyses of tax administrationsâ capabilities in developing countries.Die weltweite Verbreitung der Good-Governance- und New-Public-Management-Konzepte hat zu einer zunehmenden Konzentration auf staatliche LeistungsfĂ€higkeit und, im Besonderen, auf die LeistungsfĂ€higkeit der Steuererhebung in EntwicklungslĂ€ndern gefĂŒhrt. Allerdings bleiben die analytischen Werkzeuge fĂŒr ein umfassendes VerstĂ€ndnis von LeistungsfĂ€higkeit unterentwickelt. Dieser Artikel stellt hierfĂŒr ein Modell vor, das die drei Prozess-Dimensionen âSammeln und Verarbeiten von Informationenâ, âLeistungsorientierung der Mitarbeiterâ und âVerantwortlichkeit der Verwaltungâ beinhaltet. âEinnahmeperformanzâ ist die vierte Dimension und erfasst den Output der Steuerverwaltung. Das mehrdimensionale Modell wird fĂŒr die Analyse der LeistungsfĂ€higkeit der Steuerbehörde Zambias (Zambia Revenue Authority) genutzt. Es erweist sich nicht nur fĂŒr die Untersuchung des Wieviel, sondern auch des Wie des Erhebens von Steuern als wertvoll. Die vier Dimensionen können in Zukunft zur umfassenden und vergleichenden Analyse der LeistungsfĂ€higkeit verschiedener Steuerverwaltungen in EntwicklungslĂ€ndern genutzt werden
Cooperation between Referees and Authors Increases Peer Review Accuracy
Peer review is fundamentally a cooperative process between scientists in a community who agree to review each other's work in an unbiased fashion. Peer review is the foundation for decisions concerning publication in journals, awarding of grants, and academic promotion. Here we perform a laboratory study of open and closed peer review based on an online game. We show that when reviewer behavior was made public under open review, reviewers were rewarded for refereeing and formed significantly more cooperative interactions (13% increase in cooperation, Pâ=â0.018). We also show that referees and authors who participated in cooperative interactions had an 11% higher reviewing accuracy rate (Pâ=â0.016). Our results suggest that increasing cooperation in the peer review process can lead to a decreased risk of reviewing errors
"An Impediment to Living Life": Why and How Should We Measure Stiffness in Polymyalgia Rheumatica?
Objectives: To explore patientsâ concepts of stiffness in polymyalgia rheumatica (PMR), and how they think stiffness should be measured. Methods: Eight focus groups were held at three centres involving 50 patients with current/previous PMR. Each group had at least one facilitator and one rapporteur making field notes. An interview schedule was used to stimulate discussion. Interviews were recorded, transcribed and analysed using an inductive thematic approach. Results: Major themes identified were: symptoms: pain, stiffness and fatigue; functional impact; impact on daily schedule; and approaches to measurement. The common subtheme for the experience of stiffness was âdifficulty in movingâ, and usually considered as distinct from the experience of pain, albeit with a variable overlap. Some participants felt stiffness was the âoverwhelmingâ symptom, in that it prevented them carrying out âfundamental activitiesâ and âgenerally living lifeâ. Diurnal variation in stiffness was generally described in relation to the daily schedule but was not the same as stiffness severity. Some participants suggested measuring stiffness using a numeric rating scale or a Likert scale, while others felt that it was more relevant and straightforward to measure difficulty in performing everyday activities rather than about stiffness itself. Conclusions: A conceptual model of stiffness in PMR is presented where stiffness is an important part of the patient experience and impacts on their ability to live their lives. Stiffness is closely related to function and often regarded as interchangeable with pain. From the patientsâ perspective, visual analogue scales measuring pain and stiffness were not the most useful method for reporting stiffness; participants preferred numerical rating scales, or assessments of function to reflect how stiffness impacts on their daily lives. Assessing function may be a pragmatic solution to difficulties in quantifying stiffness
APOÎ4 Lowers Energy Expenditure in Females and Impairs Glucose Oxidation by Increasing Flux through Aerobic Glycolysis
BACKGROUND: Cerebral glucose hypometabolism is consistently observed in individuals with Alzheimer\u27s disease (AD), as well as in young cognitively normal carriers of the Î4 allele of Apolipoprotein E (APOE), the strongest genetic predictor of late-onset AD. While this clinical feature has been described for over two decades, the mechanism underlying these changes in cerebral glucose metabolism remains a critical knowledge gap in the field.
METHODS: Here, we undertook a multi-omic approach by combining single-cell RNA sequencing (scRNAseq) and stable isotope resolved metabolomics (SIRM) to define a metabolic rewiring across astrocytes, brain tissue, mice, and human subjects expressing APOE4.
RESULTS: Single-cell analysis of brain tissue from mice expressing human APOE revealed E4-associated decreases in genes related to oxidative phosphorylation, particularly in astrocytes. This shift was confirmed on a metabolic level with isotopic tracing of 13C-glucose in E4 mice and astrocytes, which showed decreased pyruvate entry into the TCA cycle and increased lactate synthesis. Metabolic phenotyping of E4 astrocytes showed elevated glycolytic activity, decreased oxygen consumption, blunted oxidative flexibility, and a lower rate of glucose oxidation in the presence of lactate. Together, these cellular findings suggest an E4-associated increase in aerobic glycolysis (i.e. the Warburg effect). To test whether this phenomenon translated to APOE4 humans, we analyzed the plasma metabolome of young and middle-aged human participants with and without the Î4 allele, and used indirect calorimetry to measure whole body oxygen consumption and energy expenditure. In line with data from E4-expressing female mice, a subgroup analysis revealed that young female E4 carriers showed a striking decrease in energy expenditure compared to non-carriers. This decrease in energy expenditure was primarily driven by a lower rate of oxygen consumption, and was exaggerated following a dietary glucose challenge. Further, the stunted oxygen consumption was accompanied by markedly increased lactate in the plasma of E4 carriers, and a pathway analysis of the plasma metabolome suggested an increase in aerobic glycolysis.
CONCLUSIONS: Together, these results suggest astrocyte, brain and system-level metabolic reprogramming in the presence of APOE4, a \u27Warburg like\u27 endophenotype that is observable in young females decades prior to clinically manifest AD
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