University of Bremen

About: University of Bremen is a education organization based out in Bremen, Germany. It is known for research contribution in the topics: Population & Glacial period. The organization has 14563 authors who have published 37279 publications receiving 970381 citations. The organization is also known as: Universität Bremen.

The ACOS CO 2 retrieval algorithm – Part II: Global X CO 2 data characterization

Abstract: . Here, we report preliminary estimates of the column averaged carbon dioxide (CO2) dry air mole fraction, XCO2, retrieved from spectra recorded over land by the Greenhouse gases Observing Satellite, GOSAT (nicknamed "Ibuki"), using retrieval methods originally developed for the NASA Orbiting Carbon Observatory (OCO) mission. After screening for clouds and other known error sources, these retrievals reproduce much of the expected structure in the global XCO2 field, including its variation with latitude and season. However, low yields of retrieved XCO2 over persistently cloudy areas and ice covered surfaces at high latitudes limit the coverage of some geographic regions, even on seasonal time scales. Comparisons of early GOSAT XCO2 retrievals with XCO2 estimates from the Total Carbon Column Observing Network (TCCON) revealed a global, −2% (7–8 parts per million, ppm, with respect to dry air) XCO2 bias and 2 to 3 times more variance in the GOSAT retrievals. About half of the global XCO2 bias is associated with a systematic, 1% overestimate in the retrieved air mass, first identified as a global +10 hPa bias in the retrieved surface pressure. This error has been attributed to errors in the O2 A-band absorption cross sections. Much of the remaining bias and spurious variance in the GOSAT XCO2 retrievals has been traced to uncertainties in the instrument's calibration, oversimplified methods for generating O2 and CO2 absorption cross sections, and other subtle errors in the implementation of the retrieval algorithm. Many of these deficiencies have been addressed in the most recent version (Build 2.9) of the retrieval algorithm, which produces negligible bias in XCO2 on global scales as well as a ~30% reduction in variance. Comparisons with TCCON measurements indicate that regional scale biases remain, but these could be reduced by applying empirical corrections like those described by Wunch et al. (2011b). We recommend that such corrections be applied before these data are used in source sink inversion studies to minimize spurious fluxes associated with known biases. These and other lessons learned from the analysis of GOSAT data are expected to accelerate the delivery of high quality data products from the Orbiting Carbon Observatory-2 (OCO-2), once that satellite is successfully launched and inserted into orbit.

Relationships between food consumption and living arrangements among university students in four European countries - A cross-sectional study

Abstract: The transition of young people from school to university has many health implications. Food choice at the university can differ because of childhood food consumption patterns, sex and the living arrangements. Food consumption may change especially if students are living away from home. We aimed to assess food consumption patterns among university students from four European countries and how they differ by their living arrangements. We analysed data from a cross-country survey assessing health and health behaviours of students. The sample comprised a total of 2402 first year undergraduate students from one university in each of the countries of Germany, Denmark, Poland and Bulgaria. Food consumption was assessed by means of a food frequency questionnaire with 9 food groups (indicators). Students’ food consumption patterns differed across the countries. Frequent consumption of unhealthy items was common. Bulgarian students reported most often frequent consumption of sweets and cakes and snacks (e.g. chips and fast food). Polish students reported the least frequent consumption of vegetables and a low consumption of fruits. Across all countries except Bulgaria, men reported substantially more often frequent consumption of snacks than women. Students living at parental home consumed more fruit, vegetables, and meat than those who resided outside of their family home in all studied countries. There was more variation with regard to cakes and salads with more frequent consumption of cakes among Bulgarian female students and Danish male students and more frequent consumption of salads among Danish female students not living at parental home, compared to students from other countries. Nutrition habits of university students differed across countries and by sex. Students living at parental home displayed more healthy nutrition habits, with some exceptions.

How do professional developers comprehend software

Abstract: Research in program comprehension has considerably evolved over the past two decades. However, only little is known about how developers practice program comprehension under time and project pressure, and which methods and tools proposed by researchers are used in industry. This paper reports on an observational study of 28 professional developers from seven companies, investigating how developers comprehend software. In particular we focus on the strategies followed, information needed, and tools used. We found that developers put themselves in the role of end users by inspecting user interfaces. They try to avoid program comprehension, and employ recurring, structured comprehension strategies depending on work context. Further, we found that standards and experience facilitate comprehension. Program comprehension was considered a subtask of other maintenance tasks rather than a task by itself. We also found that face-to-face communication is preferred to documentation. Overall, our results show a gap between program comprehension research and practice as we did not observe any use of state of the art comprehension tools and developers seem to be unaware of them. Our findings call for further careful analysis and for reconsidering research agendas.

Estimating global and North American methane emissions with high spatial resolution using GOSAT satellite data

Abstract: . We use 2009–2011 space-borne methane observations from the Greenhouse Gases Observing SATellite (GOSAT) to estimate global and North American methane emissions with 4° × 5° and up to 50 km × 50 km spatial resolution, respectively. GEOS-Chem and GOSAT data are first evaluated with atmospheric methane observations from surface and tower networks (NOAA/ESRL, TCCON) and aircraft (NOAA/ESRL, HIPPO), using the GEOS-Chem chemical transport model as a platform to facilitate comparison of GOSAT with in situ data. This identifies a high-latitude bias between the GOSAT data and GEOS-Chem that we correct via quadratic regression. Our global adjoint-based inversion yields a total methane source of 539 Tg a−1 with some important regional corrections to the EDGARv4.2 inventory used as a prior. Results serve as dynamic boundary conditions for an analytical inversion of North American methane emissions using radial basis functions to achieve high resolution of large sources and provide error characterization. We infer a US anthropogenic methane source of 40.2–42.7 Tg a−1, as compared to 24.9–27.0 Tg a−1 in the EDGAR and EPA bottom-up inventories, and 30.0–44.5 Tg a−1 in recent inverse studies. Our estimate is supported by independent surface and aircraft data and by previous inverse studies for California. We find that the emissions are highest in the southern–central US, the Central Valley of California, and Florida wetlands; large isolated point sources such as the US Four Corners also contribute. Using prior information on source locations, we attribute 29–44 % of US anthropogenic methane emissions to livestock, 22–31 % to oil/gas, 20 % to landfills/wastewater, and 11–15 % to coal. Wetlands contribute an additional 9.0–10.1 Tg a−1.

Networking strategies and methods for connecting theoretical approaches: first steps towards a conceptual framework

Abstract: The article contributes to the ongoing discussion on ways to deal with the diversity of theories in mathematics education research. It introduces and systematizes a collection of case studies using different strategies and methods for networking theoretical approaches which all frame (qualitative) empirical research. The term ‘networking strategies’ is used to conceptualize those connecting strategies, which aim at reducing the number of unconnected theoretical approaches while respecting their specificity. The article starts with some clarifications on the character and role of theories in general, before proposing first steps towards a conceptual framework for networking strategies. Their application by different methods as well as their contribution to the development of theories in mathematics education are discussed with respect to the case studies in the ZDM-issue.