Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits

We report new precision measurements of the properties of our Galaxy's supermassive black hole. Based on astrometric (1995-2007) and radial velocity (2000-2007) measurements from the W. M. Keck 10-meter telescopes, a fully unconstrained Keplerian orbit for the short period star S0-2 provides values for Ro of 8.0+-0.6 kpc, M_bh of 4.1+-0.6x10^6 Mo, and the black hole's radial velocity, which is consistent with zero with 30 km/s uncertainty. If the black hole is assumed to be at rest with respect to the Galaxy, we can further constrain the fit and obtain Ro = 8.4+-0.4 kpc and M_bh = 4.5+-0.4x10^6 Mo. More complex models constrain the extended dark mass distribution to be less than 3-4x10^5 Mo within 0.01 pc, ~100x higher than predictions from stellar and stellar remnant models. For all models, we identify transient astrometric shifts from source confusion and the assumptions regarding the black hole's radial motion as previously unrecognized limitations on orbital accuracy and the usefulness of fainter stars. Future astrometric and RV observations will remedy these effects. Our estimates of Ro and the Galaxy's local rotation speed, which it is derived from combining Ro with the apparent proper motion of Sgr A*, (theta0 = 229+-18 km/s), are compatible with measurements made using other methods. The increased black hole mass found in this study, compared to that determined using projected mass estimators, implies a longer period for the innermost stable orbit, longer resonant relaxation timescales for stars in the vicinity of the black hole and a better agreement with the M_bh-sigma relation.Comment: ApJ, accepted (26 pages, 16 figures, 7 tables

Identification of a Multipotent Self-Renewing Stromal Progenitor Population during Mammalian Kidney Organogenesis

Summary The mammalian kidney is a complex organ consisting of multiple cell types. We previously showed that the Six2-expressing cap mesenchyme is a multipotent self-renewing progenitor population for the main body of the nephron, the basic functional unit of the kidney. However, the cellular mechanisms establishing stromal tissues are less clear. We demonstrate that the Foxd1-expressing cortical stroma represents a distinct multipotent self-renewing progenitor population that gives rise to stromal tissues of the interstitium, mesangium, and pericytes throughout kidney organogenesis. Fate map analysis of Foxd1-expressing cells demonstrates that a small subset of these cells contributes to Six2-expressing cells at the early stage of kidney outgrowth. Thereafter, there appears to be a strict nephron and stromal lineage boundary derived from Six2-expressing and Foxd1-expressing cell types, respectively. Taken together, our observations suggest that distinct multipotent self-renewing progenitor populations coordinate cellular differentiation of the nephron epithelium and renal stroma during mammalian kidney organogenesis

A stated preference investigation of household demand for illegally hunted bushmeat in the Serengeti, Tanzania

This paper originates in a research project “Hunting for Sustainability” supported by the European Commission under the 7th Framework Programme for Research and Technological Development, and the research has been co-funded by Frankfurt Zoological Society.Illegal hunting for bushmeat is regarded as an important cause of biodiversity decline in Africa. We use a ‘stated preferences’ method to obtain information on determinants of demand for bushmeat and two other protein sources, fish and chicken, in villages around the Serengeti National Park, Tanzania. Our study focuses particularly on the impact of price changes, as anticipating and understanding the impact of price changes (whether caused by conservation interventions or market changes) on demand for bushmeat enables effective responses to be planned. We estimate the effects of changes in the price of bushmeat and in the prices of two substitute protein sources – fish and chicken – on household demand for bushmeat. Results suggest that increasing the availability of lower priced protein substitutes would reduce demand for bushmeat, and therefore, potentially pressure on wildlife populations. However, raising the price of bushmeat (e.g. as a result of reducing illegal hunting) would reduce household demand to a greater degree than equivalent decreases in the price of alternative protein sources. In both cases, elasticity of demand parameters are reported, which summarize the relative response to households to these alternative interventions. A 10% rise in bushmeat prices would reduce demand by around 6–7%, while a 10% fall in chicken or fish prices would reduce bushmeat demand by around 3–4%. The response to price changes varied between ethnic groups, and also according to household size (with the direction of the effect depending on whether the substitute was chicken or fish), but was not significantly affected by wealth or income.PostprintPeer reviewe

Six-minute walking test performance relates to neurocognitive abilities in preschoolers

This study investigated the relationship between six-minute walking test (6MWT) distance walked and preschool-aged children\u27s academic abilities, and behavioral and event-related potentials (ERP) indices of cognitive control. There were 59 children (25 females; age: 5.0 ± 0.6 years) who completed a 6MWT (mean distance: 449.6 ± 82.0 m) to estimate cardiorespiratory fitness. The Woodcock Johnson Early Cognitive and Academic Development Test evaluated academic abilities. A modified Eriksen flanker, hearts and flowers task, and auditory oddball task eliciting ERPs (N2, P3) assessed cognitive control. After adjusting for adiposity, diet, and demographics, linear regressions resulted in positive relationships between 6MWT distance and General Intellectual Ability (β = 0.25, Adj

Designing and Piloting a Tool for the Measurement of the Use of Pronunciation Learning Strategies

What appears to be indispensable to drive the field forward and ensure that research findings will be comparable across studies and provide a sound basis for feasible pedagogic proposals is to draw up a classification of PLS and design on that basis a valid and reliable data collection tool which could be employed to measure the use of these strategies in different groups of learners, correlate it with individual and contextual variables, and appraise the effects of training programs. In accordance with this rationale, the present paper represents an attempt to propose a tentative categorization of pronunciation learning strategies, adopting as a point of reference the existing taxonomies of strategic devices (i.e. O'Malley and Chamot 1990; Oxford 1990) and the instructional options teachers have at their disposal when dealing with elements of this language subsystem (e.g. Kelly 2000; Goodwin 2001). It also introduces a research instrument designed on the basis of the classification that shares a number of characteristics with Oxford's (1990) Strategy Inventory for Language Learning but, in contrast to it, includes both Likert-scale and open-ended items. The findings of a pilot study which involved 80 English Department students demonstrate that although the tool requires considerable refinement, it provides a useful point of departure for future research into PLS

Moderate-to-Vigorous Physical Activity is Related With Retinal Neuronal and Axonal Integrity in Persons With Multiple Sclerosis

Background Moderate-to-vigorous physical activity (MVPA) may confer benefits for axonal and/or neuronal integrity in adults with multiple sclerosis (MS). Purpose Examine the association between device-measured MVPA with optical coherence tomography (OCT) metrics of retinal nerve fiber layer (RNFL) thickness and total macular volume (TMV) in persons with and without MS. Methods Adults with MS (N = 41), along with sex-matched healthy control (HC) participants (N = 79), underwent measurements of retinal morphology via OCT and wore an accelerometer for a period of 7 days as a measure of MVPA. Results Persons with MS had significantly lower MVPA, RNFL thickness, and TMV compared with HCs. MVPA was correlated with RNFL (r = .38, P \u3c .01) thickness and TMV (r = .49, P \u3c .01). Hierarchical linear regression analyses indicated that addition of MVPA attenuated the Group effect on RNFL and TMV. MVPA accounted for 8% and 3% of the variance in TMV (β = .343, P \u3c .01) and RNFL thickness (β = .217, P = .03), respectively. Conclusion MVPA was positively associated with axonal and neuronal integrity assessed by OCT and partially explained group differences in those metrics. These results present possible future targets for MS management by increasing MVPA