Bowdoin College

About: Bowdoin College is a education organization based out in Brunswick, Maine, United States. It is known for research contribution in the topics: Population & Black hole. The organization has 1430 authors who have published 2811 publications receiving 82816 citations.

Text Chunking using Transformation-Based Learning

Abstract: Eric Brill introduced transformation-based learning and showed that it can do part-of-speech tagging with fairly high accuracy. The same method can be applied at a higher level of textual interpretation for locating chunks in the tagged text, including non-recursive ``baseNP'' chunks. For this purpose, it is convenient to view chunking as a tagging problem by encoding the chunk structure in new tags attached to each word. In automatic tests using Treebank-derived data, this technique achieved recall and precision rates of roughly 92% for baseNP chunks and 88% for somewhat more complex chunks that partition the sentence. Some interesting adaptations to the transformation-based learning approach are also suggested by this application.

Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps

Abstract: Soils and other unconsolidated deposits in the northern circumpolar permafrost region store large amounts of soil organic carbon (SOC). This SOC is potentially vulnerable to remobilization following soil warming and permafrost thaw, but SOC stock estimates were poorly constrained and quantitative error estimates were lacking. This study presents revised estimates of permafrost SOC stocks, including quantitative uncertainty estimates, in the 0–3 m depth range in soils as well as for sediments deeper than 3 m in deltaic deposits of major rivers and in the Yedoma region of Siberia and Alaska. Revised estimates are based on significantly larger databases compared to previous studies. Despite this there is evidence of significant remaining regional data gaps. Estimates remain particularly poorly constrained for soils in the High Arctic region and physiographic regions with thin sedimentary overburden (mountains, highlands and plateaus) as well as for deposits below 3 m depth in deltas and the Yedoma region. While some components of the revised SOC stocks are similar in magnitude to those previously reported for this region, there are substantial differences in other components, including the fraction of perennially frozen SOC. Upscaled based on regional soil maps, estimated permafrost region SOC stocks are 217 ± 12 and 472 ± 27 Pg for the 0–0.3 and 0–1 m soil depths, respectively (±95% confidence intervals). Storage of SOC in 0–3 m of soils is estimated to 1035 ± 150 Pg. Of this, 34 ± 16 Pg C is stored in poorly developed soils of the High Arctic. Based on generalized calculations, storage of SOC below 3 m of surface soils in deltaic alluvium of major Arctic rivers is estimated as 91 ± 52 Pg. In the Yedoma region, estimated SOC stocks below 3 m depth are 181 ± 54 Pg, of which 74 ± 20 Pg is stored in intact Yedoma (late Pleistocene ice- and organic-rich silty sediments) with the remainder in refrozen thermokarst deposits. Total estimated SOC storage for the permafrost region is ∼1300 Pg with an uncertainty range of ∼1100 to 1500 Pg. Of this, ∼500 Pg is in non-permafrost soils, seasonally thawed in the active layer or in deeper taliks, while ∼800 Pg is perennially frozen. This represents a substantial ∼300 Pg lowering of the estimated perennially frozen SOC stock compared to previous estimates.

The Political Relevance of Political Trust

Abstract: Scholars have debated the importance of declining political trust to the American political system. By primarily treating trust as a dependent variable, however, scholars have systematically underestimated its relevance. This study establishes the importance of trust by demonstrating that it is simultaneously related to measures of both specific and diffuse support. In fact, trust's effect on feelings about the incumbent president, a measure of specific support, is even stronger than the reverse. This provides a fundamentally different understanding of the importance of declining political trust in recent years. Rather than simply a reflection of dissatisfaction with political leaders, declining trust is a powerful cause of this dissatisfaction. Low trust helps create a political environment in which it is more difficult for leaders to succeed.

Development of short and very short forms of the Children's Behavior Questionnaire.

Abstract: Using data from 468 parents and taking into account internal consistency, breadth of item content, within-scale factor analysis, and patterns of missing data, we developed short (94 items, 15 scales) and very short (36 items, 3 broad scales) forms of the Children's Behavior Questionnaire (CBQ; Rothbart, Ahadi, & Hershey, 1994; Rothbart, Ahadi, Hershey, & Fisher, 2001), a well-established parent-report measure of temperament for children aged 3 to 8 years. We subsequently evaluated the forms with data from 1,189 participants. In mid/high-income and White samples, the CBQ short and very short forms demonstrated both satisfactory internal consistency and criterion validity, and exhibited longitudinal stability and cross-informant agreement comparable to that of the standard CBQ. Internal consistency was somewhat lower among African American and low-income samples for some scales. Very short form scales demonstrated acceptable internal consistency for all samples, and confirmatory factor analyses indicated marginal fit of the very short form items to a three-factor model.

Resurgent Mass Partisanship: The Role of Elite Polarization

Abstract: For the most part, scholars who study American political parties in the electorate continue to characterize them as weak and in decline. Parties on the elite level, however, have experienced a resurgence over the last two decades. Such a divergence between elite behavior and mass opinion is curious, given that most models of public opinion place the behavior of elites at their core. In fact, I find that parties in the electorate have experienced a noteworthy resurgence over the last two decades. Greater partisan polarization in Congress has clarified the parties’ ideological positions for ordinary Americans, which in turn has increased party importance and salience on the mass level. Although parties in the 1990s are not as central to Americans as they were in the 1950s, they are far more important today than in the 1970s and 1980s. The party decline thesis is in need of revision.