Showing 1931 - 1940 of 2039 Items
Named Professorships at Bowdoin College
Date: 1976-01-01
Access: Open access
- Named Professorships at Bowdoin College (1976) is a study of the named professorial chairs and other endowed funds designated directly for faculty support.
Characterizing the influence of Atlantic water intrusion on water mass formation and phytoplankton distribution in Kongsfjorden, Svalbard
Date: 2019-12-01
Creator: Courtney M. Payne
Collin S. Roesler
Access: Open access
- Warm water intrusion into Arctic fjords is increasingly affecting polar ecosystems. This study investigated how Atlantic water intrusion and tidewater glacial melting impacted water mass formation and phytoplankton distribution in Kongsfjorden, Svalbard. Field data were collected over a 2-week period during the height of the melt season in August 2014 and were contextualized within an 18-year regional MODIS satellite record. Since 1998, intruding waters have warmed by 4–5.5 °C, which has prevented sea ice formation and changed the characteristics of fjord bottom waters. Modeled light fields suggest that suspended sediment in this glacial meltwater has reduced the euphotic zone close to the ice face, contributing to lower phytoplankton concentrations in both persistent and intermittently sediment-laden meltwater plumes. However, measurements collected close to terrestrially terminating glaciers indicate that turbidity is significantly lower in the meltwater plumes, resulting in deep euphotic zones and high phytoplankton concentrations. The results of this study support a three-part conceptual model of the effects of warm-water intrusion on water mass formation and primary production within 10 km of tidewater glaciers. Initially, warm water intrusion reduces sea ice coverage, which increases the euphotic depth and increases phytoplankton biomass. Warm water intrusions may also result in increased melting of tidewater glaciers, enhanced sediment release, reduction in euphotic depth and reduction in phytoplankton biomass. Ultimately, as tidewater glaciers retreat and become terrestrially terminating, the sediment load decreases, the euphotic zone again increases, and phytoplankton biomass increases.
Pandemic as method
Date: 2019-10-01
Creator: Belinda Kong
Access: Open access
- This essay deploys the concept of pandemic as a set of discursive relations rather than a neutral description of a natural phenomenon, arguing that pandemic discourse is a product of layered histories of power that in turn reproduces myriad forms of imperial and racial power in the new millennium. The essay aims to denaturalize the idea of infectious disease by reframing it as an assemblage of multiple histories of American geopower and biopower from the Cold War to the War on Terror. In particular, Asia and Asian bodies have been targeted by US discourses of infection and biosecurity as frontiers of bioterrorism and the diseased other. A contemporary example of this bioorientalism can be seen around the 2003 SARS epidemic, in which global discourses projected the source of contagion onto Asia and Asians. Pandemic as method can thus serve as a theoretical pathway for examining cultural concatenations of orientalism and biopower.
Where do the poor live in cities? Revisiting the role of public transportation on income sorting in US urban areas
Date: 2020-06-03
Creator: Erik Nelson
Access: Open access
- Glaeser et al. (2008) argue that the relative distribution of poor and rich households (HHs) in American cities is "strongly" explained by the spatial location of the cities' public transportation (PT) networks. Among their claims: 1) The broad distribution of poor and rich HHs in the typical American city is consistent with a basic monocentric city model that includes commute technology speeds; 2) Poor commuters will overwhelmingly transition from commuting by PT to car if they experience a substantial increase in their HH’s income; 3) areas in American cities that receive new PT infrastructure become poorer over time. Using 2017 data I find empirical evidence that partially or wholly contradicts these three claims. First, as of 2017, the observed concentration of poor HHs in the inner city and rich HHs in the suburbs of the US’ smaller cities cannot be explained by monocentric model that includes commute speeds. Second, as of 2017, significant increases in poor HHs’ incomes were not expected to lead to a "massive shift" towards car commuting in these HHs; most of these poor workers commute by car already. Third, using data from four cities that expanded their light-rail and rapid-bus network in the early 2000s, I find that neighborhoods surrounding new light-rail or rapid-bus stations either saw little change in their income patterns or became slightly richer after station opening. In conclusion, as of 2017, the spatial distribution of HH incomes within American urban areas is not as intricately linked to the location of PT networks as Glaeser et al. (2008) would have us believe. As an addendum to the analysis I add some thoughts on how the COVID-19 pandemic might affect commuting behavior and income distributions within urban areas over the next decade.
The first formed tooth serves as a signalling centre to induce the formation of the dental row in zebrafish
Date: 2019-06-12
Creator: Yann Gibert
Eric Samarut
Megan K. Ellis
William R. Jackman
Vincent, Laudet
Access: Open access
- The diversity of teeth patterns in actinopterygians is impressive with tooth rows in many locations in the oral and pharyngeal regions. The first-formed tooth has been hypothesized to serve as an initiator controlling the formation of the subsequent teeth. In zebrafish, the existence of the first tooth (named 4 V1) is puzzling as its replacement is induced before the opening of the mouth. Functionally, it has been shown that 4 V1 formation requires fibroblast growth factor (FGF) and retinoic acid (RA) signalling. Here, we show that the ablation of 4 V1 prevents the development of the dental row demonstrating its dependency over it. If endogenous levels of FGF and RA are restored after 4 V1 ablation, embryonic dentition starts again by de novo formation of a first tooth, followed by the dental row. Similarly, induction of anterior ectopic teeth induces subsequent tooth formation, demonstrating that the initiator tooth is necessary and sufficient for dental row formation, probably via FGF ligands released by 4 V1 to induce the formation of subsequent teeth. Our results show that by modifying the formation of the initiator tooth it is possible to control the formation of a dental row. This could help to explain the diversity of tooth patterns observed in actinopterygians and more broadly, how diverse traits evolved through molecular fine-tuning.
Does Productivity Respond to Exchange Rate Appreciations? A Theoretical and Empirical Investigation
Date: 2010-12-15
Creator: Yao Tang
Access: Open access
- Although real currency appreciations pose direct difficulties for exporters and import-competing firms as they will face more intense competition, is it possible that such competition spurs firms to improve productivity? To answer this question, the paper first constructs a theoretical model to show how the competitive pressures of currency appreciations induce firms to improve productivity by adopting new technologies. In addition, the model predicts that during appreciations there will be a positive relation between market concentration and improvements in productivity for industries highly exposed to trade, because the marginal benefits of productivity improvement will be bigger for firms with a larger market share. The paper then examines Canadian manufacturing data from 1997 to 2006, and finds evidence consistent with model predictions. I find that growth rates of labor productivity were on average higher during the Canadian dollar appreciation between 2002 and 2006, after controlling for industry characteristics. Within the group of highly traded Canadian industries, the more concentrated ones experienced larger growth in labor productivity.
Recruiting the Host's Immune System to Target Helicobacter pylori's Surface Glycans
Date: 2013-04-01
Creator: Pornchai Kaewsapsak
Onyinyechi Esonu
Danielle H. Dube
Access: Open access
- Due to the increased prevalence of bacterial strains that are resistant to existing antibiotics, there is an urgent need for new antibacterial strategies. Bacterial glycans are an attractive target for new treatments, as they are frequently linked to pathogenesis and contain distinctive structures that are absent in humans. We set out to develop a novel targeting strategy based on surface glycans present on the gastric pathogen Helicobacter pylori (Hp). In this study, metabolic labeling of bacterial glycans with an azide-containing sugar allowed selective delivery of immune stimulants to azide-covered Hp. We established that Hp's surface glycans are labeled by treatment with the metabolic substrate peracetylated N-azidoacetylglucosamine (Ac4GlcNAz). By contrast, mammalian cells treated with Ac4GlcNAz exhibited no incorporation of the chemical label within extracellular glycans. We further demonstrated that the Staudinger ligation between azides and phosphines proceeds under acidic conditions with only a small loss of efficiency. We then targeted azide-covered Hp with phosphines conjugated to the immune stimulant 2,4-dinitrophenyl (DNP), a compound capable of directing a host immune response against these cells. Finally, we report that immune effector cells catalyze selective damage in vitro to DNP-covered Hp in the presence of anti-DNP antibodies. The technology reported herein represents a novel strategy to target Hp based on its glycans. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.