Defining a Discipline: George Gaylord Simpson and the Invention of Modern Paleontology

Kearney studies how the paleontologist George Gaylord Simpson worked to define his own field of evolutionary paleontology

The University of Pennsylvania\u27s Department of Mines, Arts, and Manufactures in Context

This paper argues that even though it was short-lived compared to its contemporary engineering schools, the University of Pennsylvania\u27s Department of Mines was an integral part of the changing energy landscape of 19th-century Pennsylvania. In addition to walking the reader through the history of Penn\u27s Department of Mines, the paper explains how the value of science lies not in the lone pursuit of knowledge for knowledge\u27s sake, but in its application to problems of economic importance, ultimately advocating the importance of the dissemination of knowledge

Tuzo Wilson in China: Tectonics, Diplomacy and Discipline During the Cold War

Canadian geophysicist John Tuzo Wilson\u27s transform fault concept was instrumental in unifying the various strands of evidence that together make up plate tectonic theory. Outside of his scientific research, Wilson was a tireless science administrator and promoter of international scientific cooperation. To that end, he travelled to China twice, once in 1958 as part of the International Geophysical Year and once again in 1971. Coming from a rare non-communist westerner in China both before and after the Cultural Revolution, Wilson\u27s travels constitute valuable temporal and spatial cross-sections of China as that nation struggled to define itself in relation to its past, to the Soviet Union which inspired its politics, and to the West through Wilson\u27s new science of plate tectonics. In so constructing these cross-sections, Wilson acts as a kind of cartographer of science, mapping the tectonic shifts during the Cold War, which revolutionized his understanding of the earth, of politics, and of the discipline of geophysics

Stage-discharge relationship in tidal channels

Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography: Methods 15 (2017): 394–407, doi:10.1002/lom3.10168.Long-term records of the flow of water through tidal channels are essential to constrain the budgets of sediments and biogeochemical compounds in salt marshes. Statistical models which relate discharge to water level allow the estimation of such records from more easily obtained records of water stage in the channel. Here we compare four different types of stage-discharge models, each of which captures different characteristics of the stage-discharge relationship. We estimate and validate each of these models on a two-month long time series of stage and discharge obtained with an Acoustic Doppler Current Profiler in a salt marsh channel. We find that the best performance is obtained by models that account for the nonlinear and time-varying nature of the stage-discharge relationship. Good performance can also be obtained from a simplified version of these models, which captures nonlinearity and nonstationarity without the complexity of the fully nonlinear or time-varying models.This research was supported by the National Science Foundation (awards OCE1354251, OCE1354494, and OCE1238212).2018-04-2

Appropriate timing of the 14 C-urea breath test to establish eradication of Helicobacter pylori infection

The aim of this study was to determine the performance characteristics of the 14 C-urea breath test (UBT) performed 2 wk after the completion of therapy for Helicobacter pylori using a 4 to 6 wk study as the gold standard. METHODS : Patients with active Helicobacter pylori infection at four medical centers received proton pump inhibitor-based triple or quadruple therapy for 10–14 days. Patients underwent the 14 C-UBT 2 and 4–6 wk after the completion of therapy. A positive test was defined as 14 CO 2 excretion of >200 dpm, a negative test as 50 but <200 dpm. Performance characteristics of the 2-wk UBT were calculated using the 4 to 6-wk result as a gold standard. RESULTS : Eighty-five patients were enrolled and 82 patients (mean ± SD age, 62 ± 15 yr; 15 women) completed the protocol. Four patients had equivocal UBT results and were excluded from the analysis. Of the 78 patients, 68 (87%) had a negative 4 to 6-wk UBT. The 2-week UBT yielded a sensitivity of 90% (95% confidence interval 72–100%), specificity of 99% (97–100%), and accuracy of 97% (93–100%). In patients with a persistently positive UBT, 14 CO 2 excretion at 2 wk was significantly lower than at 4–6 wk after therapy ( p = 0.03 ). CONCLUSIONS : A UBT performed 2 wk after therapy yielded results comparable to 4 to 6 wk testing. Further studies to evaluate the optimal time of confirmatory testing in the age of more effective proton pump inhibitor-based triple therapies are warranted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73434/1/j.1572-0241.2000.02005.x.pd

Vps27-Hse1 and ESCRT-I complexes cooperate to increase efficiency of sorting ubiquitinated proteins at the endosome

Ubiquitin (Ub) attachment to cell surface proteins causes their lysosomal degradation by incorporating them into lumenal membranes of multivesicular bodies (MVBs). Two yeast endosomal protein complexes have been proposed as Ub-sorting “receptors,” the Vps27-Hse1 complex and the ESCRT-I complex. We used NMR spectroscopy and mutagenesis studies to map the Ub-binding surface for Vps27 and Vps23. Mutations in Ub that ablate only Vps27 binding or Vps23 binding blocked the ability of Ub to serve as an MVB sorting signal, supporting the idea that both the Vps27-Hse1 and ESCRT-I complexes interact with ubiquitinated cargo. Vps27 also bound Vps23 directly via two PSDP motifs present within the Vps27 COOH terminus. Loss of Vps27-Vps23 association led to less efficient sorting into the endosomal lumen. However, sorting of vacuolar proteases or the overall biogenesis of the MVB were not grossly affected. In contrast, disrupting interaction between Vps27 and Hse1 caused severe defects in carboxy peptidase Y sorting and MVB formation. These results indicate that both Ub-sorting complexes are coupled for efficient recognition of ubiquitinated cargo

Maintaining the Strength of American Capitalism

The American economic system has always been the foundation of our national strength. But this foundation is showing cracks—from high levels of income inequality, declining economic mobility, and persistent economic insecurity among low- and middle-income Americans.Many now conclude that our economic system is broken. Recent polling data show that trust in capitalism is declining, especially among younger people. A 2018 Gallup poll found that less than half of respondents (45%) ages 18-29 held positive views of capitalism. This shift represents a 20-point decline since 2010 in the share of young adults' who held positive views of capitalism.The upshot is clear: American capitalism is in trouble. We need to strengthen our system to ensure that more people participate in our economic success. This means updating and adjusting our policies to ensure the outcomes of our market-based economy are consistent with fundamental American values of freedom, opportunity, and equality.Doing so isn't just an imperative for economic reasons. We believe that strengthening capitalism is as important for the health of the American economy as it is for the strength of our democracy. High levels of economic inequality will only contribute to increasing political dysfunction.The essays contained in this volume seek to clarify the lines of debate on some of the greatest economic policy challenges of our time and present evidence- based analysis on how to address them. It examines the hypothesis that growing market concentration is inhibiting a dynamic and competitive economy. Next, it examines the health of America's fiscal situation and what it implies about the continued strength of our market-based economy. Finally, it takes a hard look at recent policy proposals that would dramatically raise taxes on the rich and expand access to public benefit programs in response to high levels of income inequality and declining economic mobility.The perspectives presented in this volume are not intended to represent the consensus view of Aspen Economic Strategy Group members. Our goal is to equip policymakers with the best analysis available to better inform decision making and to help Americans better understand the difficult trade-offs our leaders face in making such decisions.There is no single solution to the challenges facing the American economy. The important role of evidence-based policies with bipartisan appeal, however, is difficult to overstate. This volume cannot claim to represent the end of thinking on ways to strengthen American capitalism, but we believe it provides a useful start

Astronomical X-Ray Optics Using Mono-Crystalline Silicon: High Resolution, Light Weight, and Low Cost

X-ray astronomy critically depends on X-ray optics. The capability of an X-ray telescope is largelydetermined by the point-spread function (PSF) and the photon-collection area of its mirrors, the same astelescopes in other wavelength bands. Since an X-ray telescope must be operated above the atmosphere inspace and that X-rays reflect only at grazing incidence, X-ray mirrors must be both lightweight and thin, bothof which add significant technical and engineering challenge to making an X-ray telescope. In this paper wereport our effort at NASA Goddard Space Flight Center (GSFC) of developing an approach to making an Xraymirror assembly that can be significantly better than the mirror assembly currently flying on the ChandraX-ray Observatory in each of the three aspects: PSF, effective area per unit mass, and production cost per uniteffective area. Our approach is based on the precision polishing of mono-crystalline silicon to fabricate thinand lightweight X-ray mirrors of the highest figure quality and micro-roughness, therefore, having thepotential of achieving diffraction-limited X-ray optics. When successfully developed, this approach will makeimplementable in the 2020s and 2030s many X-ray astronomical missions that are currently on the drawingboard, including sounding rocket flights such as OGRE, Explorer class missions such as STAR-X andFORCE, Probe class missions such as AXIS, TAP, and HEX-P, as well as large missions such as Lynx

Kinematic Alignment and Bonding of Silicon Mirrors for High-Resolution Astronomical X-Ray Optics

Optics for the next generation's high-resolution, high throughput x-ray telescope requires fabrication of well-formed lightweight mirror segments and their integration at arc-second precision. Recent advances in the fabrication of silicon mirrors developed at NASA/Goddard prompted us to develop a new method of mirror alignment and integration. In this method, stiff silicon mirrors are aligned quasi-kinematically and are bonded in an interlocking fashion to produce a "meta-shell" with large collective area. We address issues of aligning and bonding mirrors with this method and show a recent result of 4 seconds-of-arc for a single pair of mirrors tested at soft x-rays

Sea Level Rise and the Dynamics of the Marsh-Upland Boundary

During sea level rise, salt marshes transgress inland invading low-lying forests, agricultural fields, and suburban areas. This transgression is a complex process regulated by infrequent storms that flood upland ecosystems increasing soil salinity. As a result upland vegetation is replaced by halophyte marsh plants. Here we present a review of the main processes and feedbacks regulating the transition from upland ecosystems to salt marshes. The goal is to provide a process-based framework that enables the development of quantitative models for the dynamics of the marsh-upland boundary. Particular emphasis is given to the concept of ecological ratchet, combining the press disturbance of sea level rise with the pulse disturbance of storms