Ozone measurements from the Balloon Intercomparison Campaign     

D. Robbins  J. Waters  P. Zimmermann  R. Jarnot  J. Hardy  H. Pickett  S. Pollitt  W. Traub  K. Chance  N. Louisnard  W. Evans  J. Kerr 《Journal of Atmospheric Chemistry》1990,10(2):181-218

Measurements of the Balloon Intercomparison Campaign (BIC), conducted during fall, 1982 (BIC-1) and summer, 1983 (BIC-2), are reported. Results of five remote and two in situ techniques agree (with a few exceptions) within 95% confidence level uncertainties and generally within 15% above 20 km. Weighted mean profiles, which best represent conditions during the capaign, are used as a comparison standard. Accuracies of experiments indicated by BIC generally confirm estimated uncertainites for ECC sondes, UV photometry, and microwave emission experiments, are somewhat better for far IR emission and IR absorption experiments, and are somewhat worse for IR emission and solar UV absorption experiments. The large collection of BIC measurements confirms a problem reported earlier with current theoretical modeling of ozone near 40 km where transport is negligible and the chemistry is believed to be simpler.  相似文献   

Fate of Benzalkonium Chloride in a Sewage Sludge Low Temperature Conversion Process Investigated by LC‐LC/ESI‐MS/MS     

Heike Sütterlin  Rainer Trittler  Sebastian Bojanowski  Ernst A. Stadlbauer  Klaus Kümmerer 《洁净——土壤、空气、水》2007,35(1):81-87

Thermocatalytic low temperature conversion (LTC) is a new method for the disposal of sewage sludge. Using this method, sludge is converted into a residual solid (coal) along with reaction water, oil, and non‐condensable gases. The oil can be used as an energy source and the coal as a substitute for charcoal. To this end, it is important to determine whether there are any easily available contaminants present in the coal generated by the process. Contaminants that can be strongly sorbed by sewage sludge solids are, e. g., pharmaceuticals and disinfectants. As an example the fate of the persistent and strong adsorbing disinfectant benzalkonium chloride (BAC) has been investigated within the LTC process. The sewage sludge was spiked with BAC and then subjected to the LTC process. The resulting coal was extracted and analyzed using LC‐LC/ESI‐MS/MS (ion trap). BAC could not be detected in the LTC coal, although it could be extracted from the spiked sludge before the LTC treatment. It can thus be concluded that the investigated compound is not easily available in the coal, and hence that its use does not present a risk.  相似文献   

Beyond the headlines: changing patterns in international student enrollment in the United States     

Heike C. Alberts 《GeoJournal》2007,68(2-3):141-153

In the aftermath of the terrorist attacks of September 11, 2001, newspapers and magazines reported a dramatic decline in the enrollment of international students at US universities. Many of these articles blamed this decrease on the difficulties of getting a visa to the US and expressed concern about the potential impact on the US education system and economy. A look beyond the headlines, however, reveals that this decline cannot be attributed exclusively to the heightened security measures, as student numbers from some countries had already begun to decline before 2001 or continue to increase despite the changed regulations. Therefore, other factors also play a role in explaining the diverse migration patterns—most notably increasing competition from other host countries and changing economic and educational conditions in sending countries. Since international students often stay in their host countries after the completion of their degrees, the United States has a strong interest in continuing to attract international students as potential highly skilled immigrants. In order to achieve this, changes need to be implemented at the government level as well as at individual universities.  相似文献   

Vegetative Reproduction in Posidonia oceanica     

Heike  Molenaar Alexandre  Meinesz 《Marine Ecology》1992,13(2):175-185

Abstract. An investigation was conducted on transplantation in the Mediterranean seagrass, Posidonia oceanica. The effects of rhizome length and season of transplantation were investigated over the first year of growth in relation to survival and development in orthotropic shoots. Twelve batches, each composed of 36 transplants bearing one leaf bundle, were detached and planted at the same site and depth. They were fixed horizontally to mesh supports. These twelve batches, comprising three classes of rhizome length (10, 15, and 20 cm), were transplanted at four times of year. Mortality was highest for transplants made in early summer, when temperatures exceeded 20°C, and lowest for those made in autumn. Although initial rhizome length had no discernible effect on subsequent mortality, it was positively related to the length of the necrosed portion one year later. The most successful transplants, made in autumn with 10 to 15 cm long rhizomes, gave survival rates of 92 to 97%. These results should help to develop transplantation techniques for restoring damaged sites.  相似文献   

Introduction: Toward More Inclusive and Comparative Perspectives in the Histories of Geographical Knowledge     

Heike Jöns  Janice Monk  Innes M. Keighren 《The Professional geographer》2017,69(4):655-660

Over the past three decades, feminist historiography of geography has begun to situate women's contribution to the production of geographical knowledge within the histories of geography, at times against the conviction of skeptical colleagues. In this Focus Section introduction, we renew Domosh's (1991a Domosh, M. 1991a. Beyond the frontiers of geographical knowledge. Transactions of the Institute of British Geographers 16 (4): 488–90.[Crossref], [Web of Science ®] , [Google Scholar], 1991b ———. 1991b. Toward a feminist historiography of geography. Transactions of the Institute of British Geographers 16 (1): 95–104.[Crossref], [Web of Science ®] , [Google Scholar]) call for creating more inclusive feminist histories of geography by situating the three focus section articles on the careers and contributions of women in twentieth-century geographical practice and knowledge production in the United Kingdom and the United States within wider debates about diverse, unfamiliar, and previously hidden aspects of geographical knowledge production. We argue that feminist historiography of geography and feminist historical geography could benefit from continuously diversifying inclusive and comparative research perspectives, and from unlocking diverse archives, to enhance understanding of why and how some male and some female gatekeepers have been more supportive of women than others.  相似文献   

Feminizing the University: The Mobilities,Careers, and Contributions of Early Female Academics in the University of Cambridge, 1926–1955     

Heike Jöns 《The Professional geographer》2017,69(4):670-682

This article examines the role of early female academics at the University of Cambridge in the production and dissemination of knowledge between 1926 and 1955. A statistical comparison of women's use of academic leave of absence with that of their male colleagues reveals that, across disciplines, women were less integrated into (inter)national knowledge networks and thus less visible in their epistemic communities than men because women focused their academic leaves more on research, rarely attended conferences, traveled overseas less often than men, and went more frequently to destinations within Europe than the United States as the new economic hegemon. Biographical case studies of these early female academics demonstrate the importance, variously, of their upper middle-class background, academic excellence, and familial and nonfamilial patronage in developing their careers, overcoming multiple hurdles, and producing intellectual contributions of equal quality to that of their male peers. Conceptually, this article calls for the inclusion of academic travelers from disciplines other than geography into feminist histories of geographical knowledge and argues that rather than stereotyping gender differences, greater comparative research on the experiences of female and male academics is needed to understand the mechanisms of gender inequality within the university.  相似文献   

Effects of Tidal Flooding on Juvenile Willows     

Heike Markus-Michalczyk  Dieter Hanelt  Kai Jensen 《Estuaries and Coasts》2016,39(2):397-405

Tidal wetlands are affected by sea level rise. In the tidal freshwater stretches of estuaries in the temperate zone, willows (Salix spp.) form tidal freshwater forests above the mean high water level. Willows tolerance to prolonged periodic flooding in riverine systems is well documented, whereas effects of tidal flooding on willows are largely unknown. Flooding stress may play a major role in regeneration failure of willows in tidal forest stands along estuarine shores, and juvenile willows might be specifically affected by partial or total submergence. To assess the tolerance of juvenile willows to tidal flooding, we conducted a mesocosm experiment with cuttings from Salix alba and Salix viminalis, which are both characteristic species for tidal freshwater forests in Europe. Cuttings originating from either fresh or brackish tidal forest stands were grown under four tidal treatments with up to a tidal flooding of 60 cm. A general tolerance to a tidal flooding of 60 cm was observed in chlorophyll fluorescence, growth rates, and biomass production in both willow species. Overall, S. alba showed higher leaf and shoot growth, whereas S. viminalis produced more biomass. S. alba with brackish origin performed worst with increasing tidal flooding, suggesting a possible pre-weakening due to stressful site conditions in tidal wetlands at the estuarine brackish stretch. This study demonstrates that juvenile willows of S. alba and S. viminalis tolerate tidal flooding of up to 60 cm. It is concluded that tidal inundation acts as a stress by causing submergence and soil anaerobiosis, but may also act as a subsidy by reestablishing aerobic conditions and thus maintaining willows performance. Therefore, we suggest investigations on Salix tidal flooding tolerance and possible effects of willows on tidal wetland accretion under estuarine field conditions.  相似文献   

A bridge over troubled waters? Systems theory and dialogue in geography     

Heike Egner  Kirsten von Elverfeldt 《Area》2009,41(3):319-328

In physical geography, systems are seen as a unity of parts and relationships, whereas human geographers using a second-order sociological systems approach define systems in terms of the difference between system and environment. Starting from this, dialogue between physical and human geographers using terms derived from systems theory is mostly in vain. This article explores some of the consequences that follow for dialogue in geography: the differences in defining systems, in the understanding of processes, the problem of system borders, the inconsistent understanding of the 'environment' itself as well as the different epistemology that comes with it (or leads to it). The article tries to bring systems theory back into geography with the decisive aim of enhancing the potentials for interaction between human and physical geographers and, therefore, to explore the possibility of connecting the social with the physical world – deviating from systems theory.  相似文献   

Utilisation of terrestrial carbon by osmotrophic algae     

Jörg Tittel  Ines Wiehle  Nicola Wannicke  Heike Kampe  Juergen Poerschmann  Jutta Meier  Norbert Kamjunke 《Aquatic Sciences - Research Across Boundaries》2009,71(1):46-54

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Transition from symmetry to asymmetry during continental rifting: an example from the Bight Basin–Terre Adélie (Australian and Antarctic conjugate margins)     

Nicolas Espurt  Jean‐Paul Callot  François Roure  Jennifer M. Totterdell  Heike I. M. Struckmeyer  Roland Vially 《地学学报》2012,24(3):167-180

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