What do gas-rich galaxies actually tell us about modified Newtonian dynamics?

It has recently been claimed that measurements of the baryonic Tully-Fisher relation (BTFR), a power-law relationship between the observed baryonic masses and outer rotation velocities of galaxies, support the predictions of modified Newtonian dynamics for the slope and scatter in the relation, while challenging the cold dark matter (CDM) paradigm. We investigate these claims, and find that: 1) the scatter in the data used to determine the BTFR is in conflict with observational uncertainties on the data; 2) these data do not make strong distinctions regarding the best-fit BTFR parameters; 3) the literature contains a wide variety of measurements of the BTFR, many of which are discrepant with the recent results; and 4) the claimed CDM "prediction" for the BTFR is a gross oversimplification of the complex galaxy-scale physics involved. We conclude that the BTFR is currently untrustworthy as a test of CDM.Comment: 5 pages, 2 figures; minor revisions to match published versio

Precision cosmology defeats void models for acceleration

The suggestion that we occupy a privileged position near the centre of a large, nonlinear, and nearly spherical void has recently attracted much attention as an alternative to dark energy. Putting aside the philosophical problems with this scenario, we perform the most complete and up-to-date comparison with cosmological data. We use supernovae and the full cosmic microwave background spectrum as the basis of our analysis. We also include constraints from radial baryonic acoustic oscillations, the local Hubble rate, age, big bang nucleosynthesis, the Compton y-distortion, and for the first time include the local amplitude of matter fluctuations, \sigma_8. These all paint a consistent picture in which voids are in severe tension with the data. In particular, void models predict a very low local Hubble rate, suffer from an "old age problem", and predict much less local structure than is observed.Comment: 22 pages, 12 figures; v2 adds models in closed backgrounds; conclusions strengthened; version accepted to Phys. Rev.

Arcjet Testing and Thermal Model Development for Multilayer Felt Reusable Surface Insulation

Felt Reusable Surface Insulation was used extensively on leeward external surfaces of the Shuttle Orbiter, where the material is reusable for temperatures up to 670 K. For application on leeward surfaces of the Orion Multi-Purpose Crew Vehicle, where predicted temperatures reach 1620 K, the material functions as a pyrolyzing conformal ablator. An arcjet test series was conducted to assess the performance of multilayer Felt Reusable Surface Insulation at high temperatures, and a thermal-response, pyrolysis, and ablation model was developed. Model predictions compare favorably with the arcjet test dat

Success Nonetheless: Making public utilities work in small-scale democracies despite difficult social capital conditions

INTRODUCTION: The fate of societies and their governments intertwined. Academics and policy makers have long sought to understand how the attributes of a people translate to the form of government that arises and survives. In particular, they have explored which key social levers can increase the success rates of democracies. One branch of this research focussed on which societal conditions are conducive to the flourishing of democracy. Prominent scholars such as Huntington, Fukuyama and Sen explored whether formerly authoritarian societies could be remade into democratic communities, and how democracy could be maintained in societies where it was already established. This concern also extended to countries that have been longstanding members of the club of democracies, and asked whether on-going societal changes would have an impact on the endurance and effectiveness of democratic government. These efforts generated a long list of conditions that are deemed essential to the prosperity of democracy; ranging from social cohesion and civic traditions to stocks of interpersonal trust and active civil societies. This thesis does not aim to identify further conditions for democratic success. Rather it wants to document how democratic governments can perform well even if their societies do not meet the ideal requirements. Specifically, it investigates how democratic governments can be effective in delivering public services, even if the socio-cultural circumstances are adverse to democracy itself

Human Rights as a basis for Justice in the EU

© 2017 The Author(s). Justice is a contested concept. A more graspable understanding of it requires the context of ‘injustice’. As such, a main theme of this paper is the disjunction between, on the one hand, strong reactions to injustice and a desire for some effective dimension to the EU, some normative adhesive that might bind the EU as an ethical entity and on the other, the very great difficulty in identifying an enforceable concept of justice in an EU that continues to be driven by a market mentality. This paper also argues that it is the very sui generis, supranational status of the EU that creates particular obstacles to the realisation of a shared sense of justice. Due to this structural limitation, it is argued that any agreed concept of justice will remain minimalist. However, human rights remain a powerful symbolic and actual force for justice and a better focus for its achievement

Physics communication and peer assessment in a reformed introductory mechanics classroom

We designed and implemented a set of introductory mechanics laboratory exercises featuring real-world data-gathering, computational modeling, and video lab reports with peer assessment. Our goal in developing a peer assessment system was to create a valid substitute for instructor grading which could operate at scale, and to achieve learning goals related to student scientific communication and critique. We found our peer assessment system to be an adequate replacement for instructor grading of these lab report videos, and discovered that students learned to produce more expert-like assessments as the semester progressed, as demonstrated by a substantial rise in student-expert rating agreement. Further investigation showed that this improvement in accuracy was related, at least in part, to the completeness (but not necessarily the correctness) of students' explanations of physics phenomena in their lab report videos. At the beginning of the semester, this completeness had no effect on the ratings which students would give each others' videos; at the end of the semester, explanation completeness was strongly correlated with lower student ratings. This correspondence between salutary communicative practices and peer assessment behavior indicates that our introduction of peer assessment was indeed effective at achieving communication-oriented learning goals. Students' retrospective accounts of their experiences with peer assessment also produced some themes and trends that seemed to be corroborated in our quantitative research. All this work together, both quantitative and qualitative, will serve as a basis for continued research into modeling student engagement with peer assessment in the introductory physics classroom.Ph.D

Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming - April 1993

Large coal resources occur in the Upper Cretaceous Williams Fork Formation and lower Tertiary Fort Union Formation in the eastern part of the Sand Wash Basin. These coals are mainly subbituminous to high-volatile B bituminous and have average gas contents of less than 100 to 200 ft3/ton (<3.12 to 6.24 m3/t). Coalbed methane resources total xx Tcf (x.xx Tm3) and are xx.xx Tcf (xxx Bm3) at drilling depths of less than 6,000 ft (<1,830 m). More than 85 percent of them are in the Williams Fork. The basin's cumulative gas/water ratio is approximately 15 ft3/bbl (2.7 m3/m3). To date, low gas content and high water production have limited coalbed methane activity in the basin. Steep structural dip and coal distribution have restricted exploration to the eastern margins of the basin. Prospective Williams Fork and Fort Union coals, respectively, lie basinward in association with the Cedar Mountain fault system and westward along Cherokee Arch into the Powder Wash field area. High productivity requires that permeability, ground-water flow direction, coal distribution and rank, gas content, and structural grain be synergistically combined. That synergism explains prolific and marginal production in the San Juan and Sand Wash Basins, respectively. On the basis of a comparison between the basins, a basin-scale coalbed methane productivity model is proposed whose essential elements are: ground-water flow through thick coals of high rank, perpendicular to no-flow boundaries and conventional trapping along them.Bureau of Economic Geolog

Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming

Geologic and hydrologic analysis of the Upper Cretaceous Mesaverde Group shows that the major controls on the production of coalbed methane are: structural configuration, coal occurrence, gas content, hydrodynamics, and water production. Steep structural dip (500 ft/mi) and coal occurrence limit economic exploration to the eastern and southeastern margins of the basin. Coal resources occur mainly in the lower Williams Fork Formation (upper Mesaverde) in the eastern part of the basin. Most coal beds are high-volatile C to B bituminous rank and have gas contents of less than 200 scf/ton. Moreover, Williams Fork coals do not extend westward to the area of highest thermal maturity. Thus, they could not serve as conduits for long-distance migration of gas. Regionally, groundwater flows westward from an eastern recharge area across an area of low thermal maturity up the coal-rank gradient. Consequently, only a relatively small volume of gas may be available to be swept basinward for conventional trapping. The most prospective areas lie basinward, northwest of Craig, Colorado, on the upflow, downward side of a major fault zone. Gas contents in some coal beds on the downthrown side of the fault exceed 400 scf/ton. The Mesaverde is a thick, regionally interconnected aquifer system of high transmissivity, yielding large volumes of water. Paradoxically, coalbed permeabilities of 10's to 1,000's of md may be too high for economic gas production. To date, high water production and low gas content at the basin margins have limited coalbed activity in the Sand Wash Basin. Major Tertiary coal resources occur in the lower part of the Paleocene Fort Union Formation.Bureau of Economic Geolog

Distance information transmission using first order reflections

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (p. 114-116).by Douglas S. Brungart.M.S