Sök uppsatser och vetenskapliga publikationer

(0.013 sekunder)
There is a wealth of studies of polychlorinated biphenyls (PCB) in surface water and biota of the Arctic Ocean. Still, there are no observation-based assessments of PCB distribution and inventories in and between the major Arctic Ocean compartments. Here, the first water column distribution of PCBs in the central Arctic Ocean basins (Nansen, Amundsen, and Makarov) is presented, demonstrating nutrient-like vertical profiles with 5-10 times higher concentrations in the intermediate and deep water masses than in surface waters. The consistent vertical profiles in all three Arctic Ocean basins likely reflect buildup of PCBs transported from the shelf seas and from dissolution and/or mineralization of settling particles. Combined with measurement data on PCBs in other Arctic Ocean compartments collected over the past decade, the total Arctic Ocean inventory of Sigma 7PCB was estimated to 182 +/- 40 t (+/- 1 standard error of the mean), with sediments (144 +/- 40 t), intermediate (5 +/- 1 t) and deep water masses (30 +/- 2 t) storing 98% of the PCBs in the Arctic Ocean. Further, we used hydrographic and carbon cycle parametrizations to assess the main pathways of PCBs into and out of the Arctic Ocean during the 20th century. River discharge appeared to be the major pathway for PCBs into the Arctic Ocean with 115 +/- 11 t, followed by ocean currents (52 +/- 17 t) and net atmospheric deposition (30 +/- 28 t). Ocean currents provided the only important pathway out of the Arctic Ocean, with an estimated cumulative flux of 22 +/- 10 t. The observation-based inventory of Sigma 7PCB of 182 +/- 40 t is consistent with the contemporary inventory based on cumulative fluxes for Sigma 7PCB of 173 +/- 36 t. Information on the concentration and distribution of PCBs in the deeper compartments of the Arctic Ocean improves our understanding of the large-scale fate of POPs in the Arctic and may also provide a means to test and improve models used to assess the fate of organic pollutants in the Arctic.
N/A / Link / Sobek , Anna / 2014

This thesis is based on two studies dealing with the computational investigation of asymmetric transfer hydrogenation reactions, in which hydrogen is transferred from a donor molecule (e.g. alcohol) to a substrate (ketone), via mediation of a metal-ligand catalyst complex. The catalysts, employing either rhodium or ruthenium in combination with pseudo-dipeptideligands, enantioselectively reduce acetophenone into the secondary alcohol. Stereochemically pure secondary alcohols are important intermediates in the synthesis of many pharmaceutical, agricultural and fine chemistry products. The demand for developing effective, mild and reproducible methods for making these alcohols is high.The present studies were made using density functional theory calculations, aiming at explaining the sources of enantioselectivity in the reactions. The calculations reproduce the trends in enantioselectivity quite satisfactorily. In the analysis of the obtained free energy graphs and the optimized geometries several factors that contribute to the enantioselectivity are identified
N/A / Link / Nordin , Mikael / 2014

Stockholms universitet Övrigt
N/A / Link / Hallengren , Anders / 2003

Certain membrane proteins involved in lipid synthesis can induce formation of new intracellular membranes in Escherichia coli, i.e., intracellular vesicles. Among those, the foreign monotopic glycosyltransferase MGS from Acholeplasma laidlawii triggers such massive lipid synthesis when overexpressed. To examine the mechanism behind the increased lipid synthesis, we investigated the lipid binding properties of MGS in vivo together with the correlation between lipid synthesis and MGS overexpression levels. A good correlation between produced lipid quantities and overexpressed MGS protein was observed when standard LB medium was supplemented with four different lipid precursors that have significant roles in the lipid biosynthesis pathway. Interestingly, this correlation was highest concerning anionic lipid production and at the same time dependent on the selective binding of anionic lipid molecules by MGS. A selective interaction with anionic lipids was also observed in vitro by P-31 NMR binding studies using bicelles prepared with E. coli lipids. The results clearly demonstrate that the discriminative withdrawal of anionic lipids, especially phosphatidylglycerol, from the membrane through MGS binding triggers an in vivo signal for cells to create a feed-forward stimulation of lipid synthesis in E. coil. By this mechanism, cells can produce more membrane surface in order to accommodate excessively produced MGS molecules, which results in an interdependent cycle of lipid and MGS protein synthesis.
N/A / Link / Ariöz , Candan / 2013

Stockholms universitet Övrigt
The modifiable areal unit problem (MAUP) is seldom accounted for in economic geography cluster studies. This issue is particularly problematic as clusters play such a central role in regional development policy. In this study, we tested for the appearance of the MAUP when examining workplace category clusters over three different administrative scales in Stockholm County, Sweden. The measures used were the standardised ratio, global autocorrelation, and local autocorrelation. We discovered not only that the appearance of clusters depended on the administrative unit scale but also that the location of the clusters, based on the local indicator of spatial association, fluctuated wildly over the various administrative scales. Thus, our conclusion was that the robustness and validity of workplace category clusters should always be challenged if the MAUP has not been taken into account, or at least tested for.
N/A / Link / Nielsen , Michael M. / 2014

Stockholms universitet Övrigt
The main objects of this thesis are branched coverings obtained as projectionfrom a point in P^2. Our general goal is to understand how a givenmeromorphic function f: X -> P^1 can be induced from a compositionX --> C -> P^1, where C is a plane curve in  P^2 which is birationallyequivalent to the smooth curve X. In particular, we want to characterizemeromorphic functions on plane curves which are obtained in such a way.For instance, we want to describe the relations on branching points ofprojections of plane projective curves of degree d and enumerate such functions.To this end, in a series of two papers, we show that any degree d meromorphicfunction on a smooth projective plane curve C of degree d > 4 isisomorphic to a linear projection from a point p belonging to P^2 \ C to P^1. Secondly,we introduce a planarity filtration of the small Hurwitz space using theminimal degree of a plane curve such that a given meromorphic functioncan be fit into a composition X --> C -> P^1. Finally, we also introduce thenotion of plane Hurwitz numbers in this thesis.
978-91-7447-927-0 / Link / Ongaro , Jared / 2014

A novel top down approach was developed to fabricate dense ZrB2-SiC-BN (ZSN) composites with a fine-grained (<1 mu m) microstructure using coarse-grained (similar to 10 mu m) ZrN and Si precursors that reacted with fine (similar to 0.5 mu m) B4C powders at 1850 degrees C. The results show that the reaction and densification mechanisms acting during sintering could be separated or happen simultaneously by changing the pressure loading strategy. Loading cycles not only have a substantial influence on the microstructure homogeneity and the strength reliability of as sintered composites, but might alter the electric current path during the Spark Plasma Sintering process as well. A residual compressive stress of 361 MPa, generated upon the SiC grains in the ZSN composites, was measured by Raman spectroscopy. The fine SiC grains tended to form larger clusters in the dense microstructure if the loading cycle is inappropriate, which was further employed to interpret the observed scattering of strength values in one batch of ZSN. The 48ZrB(2)-24SiC-28BN (number in vol%) composite has an average strength of 473 MPa, which was 94% of that of in situ densified ZrB2-SiC ceramics (ZS). Considering the corresponding Youngs modulus was only half of that for ZS, the in situ ZSN composite owns a better mechanical strain tolerance.
N/A / Link / Zou , Ji / 2014

Stockholms universitet Övrigt
Pro-Am live video producers broadcast events on a regular basis. They are here selected for an ethnographic study since their continuous content generation can teach us something of what it takes for amateurs, who currently struggle with mastering the video medium, to become proficient producers. We learn from media theory that Pro- Ams are distinguished from professionals in terms of inherent skills and identities, and have therefore focused on these characteristics. We add to this research by showing on-going challenges that the former face in their production, i.e. how their learning practices, such as learning through instructions, are situated and related to particular settings. Learning and development of skills were done as organizations, rather than as individuals. Furthermore, the recurrent nature of both events and broadcasts appears to be an important condition for establishing the terms needed to carry out a production, and to learn the skills of a producer. This understanding may explain in part why accounts in previous research, of single users struggling with the affordances of live video, point to such difficulties in mastering the medium. The findings guide design to better support activities contiguous with the set-up of the production, rather than the broadcast per se. 
978-1-4503-2473-1 / Link / Juhlin , Oskar / 2014

N/A / Link / Gottlieb , Christian / 1994

Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database of approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general controls on wetland methane emissions from soil temperature, water table, and vegetation, but also show that these relationships are modified depending on wetland type (bog, fen, or swamp), region (subarctic to temperate), and disturbance. Fen methane flux was more sensitive to vegetation and less sensitive to temperature than bog or swamp fluxes. The optimal water table for methane flux was consistently below the peat surface in bogs, close to the peat surface in poor fens, and above the peat surface in rich fens. However, the largest flux in bogs occurred when dry 30-day averaged antecedent conditions were followed by wet conditions, while in fens and swamps, the largest flux occurred when both 30-day averaged antecedent and current conditions were wet. Drained wetlands exhibited distinct characteristics, e. g. the absence of large flux following wet and warm conditions, suggesting that the same functional relationships between methane flux and environmental conditions cannot be used across pristine and disturbed wetlands. Together, our results suggest that water table and temperature are dominant controls on methane flux in pristine bogs and swamps, while other processes, such as vascular transport in pristine fens, have the potential to partially override the effect of these controls in other wetland types. Because wetland types vary in methane emissions and have distinct controls, these ecosystems need to be considered separately to yield reliable estimates of global wetland methane release.
N/A / Link / Turetsky , Merritt R. / 2014

This article puts to work a Deleuzio-Guattarian methodology of cartography using data from a pilot study of young schoolgirls' school-related ill-health and well-being. Doing a cartography means setting up a map of various kinds of data produced by a multiplicity of desiring agents in various power-producing fields such as medicine, psychology, popular science, media, as well as narrative data from young girls and the two researchers themselves. Together, these data make up a wider machinic assemblage of Public Health in Sweden. As researchers, we understand ourselves as co-productive of this machinic assemblage that, in turn, is productive of a multiplicity of different Bodies without Organs (BwOs) that young schoolgirls fabricate for themselves. The analysis will show the specific types of BwOs that are fabricated, how they are fabricated, the modes of desire that come to pass on them, and thus what kinds of subjectivities of schoolgirls might be produced.
N/A / Link / Taguchi , Hillevi Lenz / 2014

Symmetrical and unsymmetrical diaryliodonium triflates have been synthesized from both electron-deficient and electron-rich arenes and aryl iodides with mCPBA and triflic acid. A thorough investigation of the optimization, scope and limitations has resulted in an improved one-pot protocol that is fast, high-yielding, and operationally simple. The reaction has been extended to the direct synthesis of symmetrical iodonium salts from iodine and arenes, conveniently circumventing the need for aryl iodides.
N/A / Link / Bielawski , Marcin / 2007

Södertörns högskola Övrigt
N/A / Link / Marklund , Carl / 2002

In this thesis we investigate the moduli space M3[2] of curves of genus 3 equipped with a symplectic level 2 structure. In particular, we are interested in the cohomology of this space. We obtain cohomological information by decomposing M3[2] into a disjoint union of two natural subspaces, Q[2] and H3[2], and then making S7- resp. S8-equivariantpoint counts of each of these spaces separately.
978-91-7447-923-2 / Link / Bergvall , Olof / 2014

Södertörns högskola Samhällsvetenskap
91-89658-05-1 / Link / Jacobsson , Kerstin / 2002

Södertörns högskola Samhällsvetenskap
978-91-89140-71-4 / Link / Jacobsson , Kerstin / 2010

Stockholms universitet Övrigt
Interaction of supernova (SN) ejecta with the optically thick circumstellar medium (CSM) of a progenitor star can result in a bright, long-lived shock-breakout event. Candidates for such SNe include Type IIn and superluminous SNe. If some of these SNe are powered by interaction, then there should be a specific relation between their peak luminosity, bolometric light-curve rise time, and shock-breakout velocity. Given that the shock velocity during shock breakout is not measured, we expect a correlation, with a significant spread, between the rise time and the peak luminosity of these SNe. Here, we present a sample of 15 SNe IIn for which we have good constraints on their rise time and peak luminosity from observations obtained using the Palomar Transient Factory. We report on a possible correlation between the R-band rise time and peak luminosity of these SNe, with a false-alarm probability of 3%. Assuming that these SNe are powered by interaction, combining these observables and theory allows us to deduce lower limits on the shock-breakout velocity. The lower limits on the shock velocity we find are consistent with what is expected for SNe (i.e., similar to 10(4) km s(-1)). This supports the suggestion that the early-time light curves of SNe IIn are caused by shock breakout in a dense CSM. We note that such a correlation can arise from other physical mechanisms. Performing such a test on other classes of SNe ( e. g., superluminous SNe) can be used to rule out the interaction model for a class of events.
N/A / Link / Ofek , Eran O. / 2014

In this note, the authors describe the MULTIBIODOSE software, which has been created as part of the MULTIBIODOSE project. The software enables doses estimated by networks of laboratories, using up to five retrospective (biological and physical) assays, to be combined to give a single estimate of triage category for each individual potentially exposed to ionizing radiation in a large scale radiation accident or incident. The MULTIBIODOSE software has been created in Java. The usage of the software is based on the MULTIBIODOSE Guidance: the program creates a link to a single SQLite database for each incident, and the database is administered by the lead laboratory. The software has been tested with Java runtime environment 6 and 7 on a number of different Windows, Mac, and Linux systems, using data from a recent intercomparison exercise. The Java program MULTIBIODOSE_1.0.jar is freely available to download from http://www.multibiodose.eu/software or by contacting the software administrator: MULTIBIODOSE-software@gmx.com.
N/A / Link / Ainsbury , Elizabeth A. / 2014

Stockholms universitet Övrigt
We investigate seawater intrusion in three prominent Mediterranean aquifers that are subject to intensive exploitation and modified hydrologic regimes by human activities: the Nile Delta, Israel Coastal and Cyprus Akrotiri aquifers. Using a generalized analytical sharp interface model, we review the salinization history and current status of these aquifers, and quantify their resilience/vulnerability to current and future seawater intrusion forcings. We identify two different critical limits of seawater intrusion under groundwater exploitation and/or climatic stress: a limit of well intrusion, at which intruded seawater reaches key locations of groundwater pumping, and a tipping point of complete seawater intrusion upto the prevailing groundwater divide of a coastal aquifer. Either limit can be reached, and ultimately crossed, under intensive aquifer exploitation and/or climate-driven change. We show that seawater intrusion vulnerability for different aquifer cases can be directly compared in terms of normalized intrusion performance curves. The site-specific assessments show that: a) the intruding seawater currently seriously threatens the Nile Delta Aquifer, b) in the Israel Coastal Aquifer the sharp interface toe approaches the well location and c) the Cyprus Akrotiri Aquifer is currently somewhat less threatened by increased seawater intrusion.
N/A / Link / Mazi , Aikaterini / 2014

978-0-8122-4594-3 / Link / Klein , Barbro / 2014

978-91-88568-52-6 / Link / Andersson , Roger / 2011

Stockholms universitet Övrigt
Borosilicate zeolites with CHA-type framework are synthesized hydrothermally by using N,N,N-trimethylcyclohexylammonium hydroxide as structure directing agent. The use of this cation induces an increase of boron content in the CHA-type zeolites, and the Si/B ratios of the as-synthesized samples is in the range of 11.8-6.9. Rietveld refinements of the calcinated samples reveal a contraction of unit cells with the increase of boron content, and the 8-ring opening window of cha cavity becomes narrower. B-11 MAS NMR shows that all the boron atoms are incorporated into the framework as tetrahedral BO4 units in the as-synthesized samples. The thermal stability of these CHA-type borosilicates decreases with the increase of boron content, and the framework can retain up to 800 degrees C. These borosilicates, with the BET surfaces of 583-632 m(2)/g, show a high adsorption capacity for H-2 at 77 K, 900 mmHg and a preferential adsorption for CO2 at 273 K. This selective adsorption property enables CHA-type borosilicates to be potential materials as CO2 adsorbent.
N/A / Link / Liang , Jie / 2014

Södertörns högskola Etnologi
N/A / Link / Lilja , Agneta / 2009

The cell envelope of Escherichia coli, as for all living cells, is a magnificent semi-permeable membrane barrier that facilitates protection as well as enables fundamental contact with the exterior world. The envelope comprises a mixture of phospholipids, organized in two bilayers, which are stabilized by a rigid peptidoglycan layer. There are also a large number of proteins, which can be lipid-integrated or attached. Infact, it is anticipated that approximately 30-40% of the cellular proteome of E. coli could be associated with the envelope. These proteins are involved in the transport of small molecules and nutrients, the biogenesis of the envelope, metabolism, signaling, channeling and cellular movement and attachment.The focus of this thesis is to understand the cell envelope of E. coli by understanding the proteins it holds. Three main questions have been addressed: 1) Which proteins are present? 2) How do these proteins interact? 3) How are the interactions brought about? To answer these questions we have designed and optimized methods suitable for proteome-wide separation, visualization and characterization of membrane proteins and protein complexes. We present reference proteome and interactome maps of the envelope, which further our understanding of the assembly and composition of the cell envelope. In many instances our studies have provided a first step towards understanding protein function(s) and for carrying out meaningful biochemical and structural analysis. We have also developed parallel approaches, which have enabled us to dissect the assembly process for two specific membrane protein complexes, a homo-dimer of penicillin binding protein 5 and the respiratory oxidase cytochrome bo3. These studies have extended our understanding of the relationship between structure and function of protein complexes.
978-91-7447-118-2 / Link / Stenberg Bruzell , Filippa / 2010

Stockholms universitet Övrigt
91-1-897562-3 / Link / Ramberg , Jan / 1990

Stockholms universitet Övrigt
The Swedish East India Company has been studied mainly from an economic standpoint, but throughout the eighteenth century its employees played a crucial role in Swedish knowledge production on China. This article studies travel writings, speeches, and eulogies by the employees of the Swedish East India Company, noting in which ways they produced knowledge on China, and discusses reasons for choosing these particular ways. The company employees' production of knowledge is found to have strong links with their constructions of masculinity. Consequently, this article discusses the political implications of a connection between masculinity and knowledge for men employed in a non-colonial East India Company from a militarily weak country, and the role that the perceived and presented knowledge of China and its inhabitants played in this intertwining of gender construction, natural history, and power.
N/A / Link / Hellman , Lisa / 2014

Stockholms universitet Övrigt
978-91-88568-59-5 / Link / Odelman , Eva / 2014

Stockholms universitet Övrigt
978-1-137-30035-5 / Link / Christensen , Miyase / 2014