| 1. |
- Pham, M. K., et al.
(författare)
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A new reference material for radionuclides in the mussel sample from the Mediterranean Sea (IAEA-437)
- 2010
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 283:3, s. 851-859
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Tidskriftsartikel (refereegranskat)abstract
- A new Reference Material (RM) for radionuclides in mussel (Mytilus galloprovincialis) from the Mediterranean Sea (IAEA-437) is described and the results of the certification process are presented. Four radionuclides (K-40, U-234, U-238, and Pu239+240) have been certified, and information values on massic activities with 95% confidence intervals are given for nine radionuclides (Cs-137, Pb-210(Po-210), Ra-226, Ra-228, Th-228, Th-230, Th-232, U-235, and Am-241). Results for less frequently reported radionuclides (Sr-90, I-129, Pu-238, Pu-239, and Pu-240) are also reported. The RM can be used for quality assurance/quality control of the analysis of radionuclides in mussel samples, for the development and validation of analytical methods and for training purposes. The material is available in 200 g units.
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| 2. |
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| 3. |
- Merino, E. G., et al.
(författare)
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Molecular dynamics of poly(ATRIF) homopolymer and poly(AN-co-ATRIF) copolymer investigated by dielectric relaxation spectroscopy
- 2011
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 47:7, s. 1429-1446
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Tidskriftsartikel (refereegranskat)abstract
- Aiming to develop new dielectric polymers containing CN and F groups with strong dipole moments, a novel copolymer of acrylonitrile (AN) and 2,2,2-trifluoroethyl acrylate (ATRIF) was synthesized in acetonitrile by free radical process as well as the respective homopolymer (poly(ATRIF)). The copolymer's composition and microstructure were analyzed by FTIR, (1)H and (13)C NMR spectroscopy and SEC. The molar incorporation of AN determined in the copolymer by NMR was 58 mol%. Thermogravimetric analysis of poly(AN-co-ATRIF) copolymer showed good thermal stability comparatively to the fluorinated homopolymer. Both copolymer, poly(AN-co-ATRIF), and homopolymer, poly(ATRIF), were dielectrically characterized over a frequency range from 10(-1) to 10(6) Hz, and in a temperature range from 223 to 393 K. The dominating relaxation process detected in both materials is the alpha-relaxation, associated with the dynamic glass transition. A VFTH temperature dependence of the relaxation times (tau) was found for both materials, as characteristic of cooperative processes, from which the respective glass transition temperatures (T(g)(tau = 100 s)) were estimated, which differ similar to 40 K, the one of the copolymer being higher (307 K) in accordance to the calorimetric analysis. This effect was attributed to a higher stiffness of the backbone in the copolymer originated by the inclusion of the acrylonitrile groups. Both relaxation functions have the same breath of relaxation times allowing constructing a single master curve, indicating similar non-exponential character. A less fragile behavior was found for the copolymer. This was rationalized in a more straightforward way by the free volume approach instead from a correlation between fragility and intermolecular coupling. It was found that in the copolymer the free volume increases at a lower rate with the temperature increase. It was inferred from the VFTH temperature dependence of the dc conductivity and low values of the decoupling index that ion motion is significantly influenced by the dynamics of the alpha-process.
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| 7. |
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| 9. |
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| 10. |
- Billnert, Robert, 1981, et al.
(författare)
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New information on the characteristics of 1 in. x 1 in. cerium bromide scintillation detectors
- 2011
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 647:1, s. 94-99
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Tidskriftsartikel (refereegranskat)abstract
- In view of highly demanded new and accurate data on prompt gamma-ray emission in nuclear fission a major part of investigations is directed towards the selection of suitable detector systems. Here we have studied a new type of crystal scintillation detectors made from cerium bromide (CeBr(3)). For the first time a full characterization of such a detector is presented in terms of energy resolution, pulse-height linearity, intrinsic activity and intrinsic timing resolution. In particular the latter one is very important for prompt fission gamma-ray studies, because the presence of fast neutrons, emitted in fission too, requires the time-of-flight method for their discrimination. The energy resolution has been found to be comparable to that of cerium-doped LaCl(3):Ce detectors at an efficiency comparable to the one of a LaBr(3):Ce detector of the same size. The intrinsic activity of the CeBr(3) crystal was observed to be much lower compared to lanthanum halide crystals. The intrinsic timing resolution of a coaxial 1 in. x 1 in. sized detector was measured relative to that of a previously characterized LaCl(3):Ce detector and found to be (326 +/- 7) Ps at (60)Co energies, which is in between those of a LaBr(3):Ce and a LaCl(3):Ce detector of same size.
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| 11. |
- Billnert, Robert, 1981, et al.
(författare)
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Novel Scintillation Detectors for Prompt Fission γ-Ray Measurements
- 2012
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 31, s. 29-34
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Konferensbidrag (refereegranskat)abstract
- In this work we present first results from measurements of prompt fission γ-rays from the spontaneous fission in 252Cf. New and accurate data on corresponding γ-rays from the reactions 235U(nth,f) and 239Pu(nth,f) are highly demanded for the modeling of new Generation-IV nuclear reactor systems. For these experiments we employed scintillation detectors made out of new materials (LaBr3, LaCl3 and CeBr3), whose properties were necessary to know in order to obtain reliable results. Hence, we have characterized these detectors. In all the important properties these detectors outshine sodium-iodine detectors that where used in the 1970s, when the existing data had been acquired. Our finding is that the new generation of scintillation detectors is indeed promising, as far as an improved precision of the demanded data is concerned.
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| 12. |
- Eklund, Patrik, 1958-, et al.
(författare)
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The logic of geriatrics
- 2013
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Ingår i: The Journal of Nutrition, Health & Aging. - : Springer. - 1279-7707 .- 1760-4788. ; 17:1, s. 305-306
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Tidskriftsartikel (refereegranskat)
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| 13. |
- Engvall, Karin, et al.
(författare)
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A new multiple regression model to identify multi-family houses with a high prevalence of sick building symptoms "SBS", within the healthy sustainable house study in Stockholm (3H)
- 2010
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Ingår i: International Archives of Occupational and Environmental Health. - : Springer Science and Business Media LLC. - 0340-0131 .- 1432-1246. ; 83:1, s. 85-94
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSES: The aim was to develop a new model to identify residential buildings with higher frequencies of "SBS" than expected, "risk buildings". METHODS: In 2005, 481 multi-family buildings with 10,506 dwellings in Stockholm were studied by a new stratified random sampling. A standardised self-administered questionnaire was used to assess "SBS", atopy and personal factors. The response rate was 73%. Statistical analysis was performed by multiple logistic regressions. RESULTS: Dwellers owning their building reported less "SBS" than those renting. There was a strong relationship between socio-economic factors and ownership. The regression model, ended up with high explanatory values for age, gender, atopy and ownership. Applying our model, 9% of all residential buildings in Stockholm were classified as "risk buildings" with the highest proportion in houses built 1961-1975 (26%) and lowest in houses built 1985-1990 (4%). CONCLUSION: To identify "risk buildings", it is necessary to adjust for ownership and population characteristics.
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| 14. |
- Eriksson, Magnus G., et al.
(författare)
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One-pot enzymatic polycondensation to telechelic methacrylate-functional oligoesters used for film formation
- 2011
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Ingår i: POLYM CHEM. - Cambridge : ROYAL SOC CHEMISTRY. - 1759-9954 .- 1759-9962. ; 2:3, s. 714-719
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Tidskriftsartikel (refereegranskat)abstract
- Based on largely renewable monomers, an enzymatic one-pot polycondensation route towards functional oligomers with targeted molecular weights and end-groups was developed. This one-pot synthesis was performed by combining Candida antarctica lipase B (CALB), 2-hydroxyethyl methacrylate (HEMA), ethylene glycol, and divinyl adipate under reduced pressure (72 mbar) at 60 degrees C. The polymerization went to completion (>95% conversion for all monomers) within 24 h and the fraction of methacrylate end-groups was >90%. Three targeted dimethacrylate functional oligomers with molecular weights of 920, 1700 and 2500 g mol(-1) (degrees of polymerization 4, 8, and 13 respectively) were synthesized. The oligomer products were characterized by NMR, MALDI-TOF MS and SEC. The dimethacrylate functional oligomers were further UV homopolymerized or combined with a tetrathiol crosslinker to demonstrate the potential to produce novel networks with tunable thermal properties dependent on chain length of the telechelic building blocks. This research is the first to demonstrate methacrylate functionalization and condensation polymerization in a one step process, which expands the growing toolbox for polymer/material chemists towards an increased throughput in available macromonomers used in material design.
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| 15. |
- Fogelström, Linda, 1978-
(författare)
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Polymer Nanocomposites in Thin Film Applications
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The introduction of a nanoscopic reinforcing phase to a polymer matrix offers great possibilities of obtaining improved properties, enabling applications outside the boundaries of traditional composites. The majority of the work in this thesis has been devoted to polymer/clay nanocomposites in coating applications, using the hydroxyl-functional hyperbranched polyester Boltorn® as matrix and montmorillonite clay as nanofiller. Nanocomposites with a high degree of exfoliation were readily prepared using the straightforward solution-intercalation method with water as solvent. Hard and scratch-resistant coatings with preserved flexibility and transparency were obtained, and acrylate functionalization of Boltorn® rendered a UV-curable system with similar property improvements. In order to elucidate the effect of the dendritic architecture on the exfoliation process, a comparative study on the hyperbranched polyester Boltorn® and a linear analogue of this polymer was performed. X-ray diffraction and transmission electron microscopy confirmed the superior efficiency of the hyperbranched polymer in the preparation of this type of nanocomposites. Additionally, an objective of this thesis was to investigate how cellulose nanofibers can be utilized in high performance polymer nanocomposites. A reactive cellulose “nanopaper” template was combined with a hydrophilic hyperbranched thermoset matrix, resulting in a unique nanocomposite with significantly enhanced properties. Moreover, in order to fully utilize the great potential of cellulose nanofibers as reinforcement in hydrophobic polymer matrices, the hydrophilic surface of cellulose needs to be modified in order to improve the compatibility. For this, a grafting-from approach was explored, using ring-opening polymerization of ε-caprolactone (CL) from microfibrillated cellulose (MFC), resulting in PCL-modified MFC. It was found that the hydrophobicity of the cellulose surfaces increased with longer graft lengths, and that polymer grafting rendered a smoother surface morphology. Subsequently, PCL-grafted MFC film/PCL film bilayer laminates were prepared in order to investigate the interfacial adhesion. Peel tests demonstrated a gradual increase in the interfacial adhesion with increasing graft lengths.
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| 16. |
- Hult, Annika, et al.
(författare)
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Weak A phenotypes associated with novel ABO alleles carrying the A(2)-related 1061C deletion and various missense substitutions.
- 2010
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Ingår i: Transfusion. - : Wiley. - 1537-2995 .- 0041-1132. ; 50, s. 1471-1486
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The 1061delC single-nucleotide polymorphism (SNP) has been reported mostly in the context of the common A(2)[A201] allele and typically produces an A(2) phenotype. This study evaluated new A(weak) alleles, each containing 1061delC. STUDY DESIGN AND METHODS: Twenty samples were referred to our laboratory for analysis due to suspected A(weak) phenotypes originally detected at the referring centers. ABO Exons 1 through 7 and flanking intronic regions were sequenced. A antigen expression on red blood cells was analyzed by flow cytometry. Plasma enzyme activity was studied in one case. Molecular three-dimensional modeling techniques studied the potential effects of amino acid changes on the resulting glycosyltransferases (GTs). RESULTS: Thirteen alleles were discovered, each featuring 1061delC with at least 1 of 12 additional SNPs in the coding region. One of these SNPs disrupts the translation initiation codon. Another constitutes the first reported change in the DVD motif. One SNP found in three alleles causes a substitution of one of the four amino acids that differentiates the wild-type A and B enzymes but plasma enzyme analysis by two methods showed only slightly decreased or normal A(2) activity. Flow cytometric analysis semiquantified the A antigen levels in 16 cases featuring 10 of the alleles and ranged from very weak to nearly A(2) levels. However, the majority of the samples displayed A(x)-like patterns. Molecular modeling of some of the GT variants indicated conformational changes that may explain the diminished A expression observed. CONCLUSION: Missense SNPs were identified in 13 novel A(2)-like alleles, which produced a variety of A subgroup phenotypes.
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| 17. |
- Hult, Francis M., et al.
(författare)
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Entextualising Ideologies about English and Multilingualism in a University Language Policy
- 2013
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Ingår i: The English Language in Teaching in European Higher Education, 19 April - 21 April 2013, Copenhagen. ; , s. 20-21
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Konferensbidrag (refereegranskat)abstract
- Contemporary multilingualism in Sweden led to the creation of a language law in 2009 (SFS 2009:600), making Swedish the official language and passing on the responsibility for protecting the continued use of Swedish in all domains of society to public sector institutions. Given the growing need for English in today’s globalized tertiary-level education and scientific research, Swedish universities now need to develop their own procedures and policies that attend both to the language law and to the need to be globalized.This paper, then, which reports on part of a larger ethnographic/discourse analytic project, examines how ideologies about English and multilingualism are entextualized in a language policy that was developed by a committee at a major Swedish university. Using nexus analysis (Scollon & Scollon, 2004), we map the discourses in place reflected in the policy in order to lift forward how core language ideologies are intertwined with institutional language planning. Analysis brings to light intertextual connections to language ideologies reflected in the national language law, in particular (i) ‘clear language’ in all the university’s communication regardless of language used and (ii) Swedish as the main language to be used in all official documents that have legal force. Moreover, the need to be globalized and accessible to non- Swedish-speaking individuals is to be met by Swedish-English bilingualism, resemiotized (Scollon & Scollon 2004) in the policy as ‘parallel language use’, in most of the university’s communication. Further, Swedish is stipulated as the main medium of instruction in first-cycle undergraduate courses, with growing use of English at the second- and third-cycle levels, and in the university’s research activities. Finally, reflecting Sweden’s linguistic hierarchy (Hult 2012), multilingualism was backgrounded in the policy text but still framed as important asset to the university.
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| 18. |
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| 19. |
- Hörder, Helena M, et al.
(författare)
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Home as a health promotion setting for older adults
- 2014
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Ingår i: Scandinavian Journal of Public Health. - : SAGE Publications. - 1403-4948 .- 1651-1905. ; 42:Suppl 15, s. 36-40
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Tidskriftsartikel (refereegranskat)abstract
- Background: The number and the proportion of older persons is growing in the Nordic Countries. The growth in the older population has a clear impact on the care system for older persons. One trend is to prioritise home care instead of care in institutions. Another trend is to emphasise preventive and health promotion care. As official guidelines in the Nordic countries state that home is the best place to grow old, it is essential that older persons keep their health and functional capacity in order to be able to live at home for as long as possible. As current policy emphasises living at home, home care, preventive work and health promotion it becomes essential to study the home as a health promotion setting. Objective: The aim of this study was to reach a new understanding of home as a health promotion setting for older persons. Study design: The method used was a literature reflection and analysis with a hermeneutical approach. Results: The results show that with increasing age the home environment becomes a crucial determinant for independence. The home environment supports the self as people age; it has associations with the past, can provide proximity to family, and a sense of being a part of neighbourhood life. Conclusions: Only by taking into consideration the meaning of home and the resources of the individual older person can home function as a true health promoting setting. If health personnel focus solely on risk prevention, they can neglect the perspectives of the older person, resulting in dis-empowerment not health promotion.
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| 20. |
- Lundberg, Pontus, 1982-
(författare)
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Designing Polymers for Biological Interfaces - From Antifouling to Drug Delivery
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Unspecific interactions, at the interface between a synthetic material and an aqueous biological environment, leading to irreversible protein adsorption can cause to undesired consequences. These include fouling of a boat hull or a triggered immune response. Thus, stealthy materials are a topic that has generated a great deal of interest in the scientific community. This work deals with the design of networks, nanoparticles, and surfaces containing poly(ethylene glycol) (PEG), known for its resistance to protein adsorption and non-toxic nature. Initially, PEG-based networks, hydrogels, were synthesized using photoinduced thiol-ene chemistry in order to afford coatings targeted for marine antifouling applications. By varying the length of the PEG chain, curing chemistry, cross-linker as well as hydrolytical stability, a library of hydrogel coatings was produced. The coatings were subsequently characterized with respect to curing efficiency, thermal and mechanical properties, and aqueous stability. Furthermore, the antifouling properties of coatings were evaluated using in vitro tests with proteins, marine bacteria, and diatoms. As a final test the coatings were evaluated in a four month field test. It was found that coatings comprising longer PEG chains displayed enhanced antifouling performance, compared to shorter PEGs. In addition, the choice of cross-linker, curing chemistry, and hydrolytical stability also affected the properties to a great extent. This thesis further deals with the design of amphiphilic linear dendritic hybrids, with PEG as the hydrophilic block. Using non-toxic 2,2-bis(methylol) propionic acid (bis-MPA) based dendrons, bearing click functional cores (alkyne or allyl) and peripheral hydroxyl groups, as macrointitiators for ring-opening polymerization of ε-caprolactone, a library of star branched materials was afforded. As a final step, click functional (azide or thiol) PEGs were attached using copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) or thiol-ene click chemistry. The size of the dendrons was varied from generation 0-4, along with variation of both poly(ε-caprolactone) (PCL) length and PEG length. The materials were designed in order to allow a study of the impact of the dendron generation. Finally, the hybrid materials were used for the preparation of micelles, as well as for the formation of honeycomb membranes. The micelles critical micelle concentration, size and drug loading capacity were shown to be highly dependent on the generation of the dendron. The generation of the dendron also had a profound effect on the ability of the hybrid materials to form ordered honeycomb membranes, and hybrid materials of the 3rd generation yielded the most highly ordered membranes.
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| 21. |
- Lundberg, Pontus, et al.
(författare)
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Poly(ethylene glycol)-Based Thiol-ene Hydrogel Coatings-Curing Chemistry, Aqueous Stability, and Potential Marine Antifouling Applications
- 2010
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 2:3, s. 903-912
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Tidskriftsartikel (refereegranskat)abstract
- Photocured thiol-ene hydrogel coatings based on poly(ethylene glycol) (PEG) were investigated for marine antifouling purposes. By varying the PEG length, vinylic end-group, and thiol cross-linker, a library of hydrogel coatings with different structural composition was efficiently accomplished, with or without ester linkages. The thiol-methacrylate and thiol-allyl systems were evaluated with respect to curing, degradation, as well as antifouling properties. Moth acrylate-based systems exhibited homopolymerization, whereas allyl-based systems reacted more selectively through thiol-ene couplings reaction. The ester-free hydrogels elucidated higher hydrolytic stability whereas longer PEG chains accelerated the degradation process. The antifouling properties were evaluated by protein adsorption With Bovine serum albumin (BSA) and bioassays with the marine bacteria, Cobetia marina, and the marine diatom, Amphora coffeaeformis; in all tests, longer PEG lengths improved the antifouling properties.
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| 22. |
- Lutter, G., et al.
(författare)
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Radiopurity of a CeBr3 crystal used as scintillation detector
- 2013
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 703, s. 158-162
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Tidskriftsartikel (refereegranskat)abstract
- Cerium bromide (CeBr3) has recently been shown to exhibit several properties making it a suitable material as a scintillation detector in nuclear physics applications. The intrinsic activity of gamma-ray emitting radionuclides in a 38.1 mm x 38.1 mm (diameter x height) crystal of CeBr3 was investigated. The measurements were carried out in the HADES underground laboratory located 225 m underground. Two primordial radionuclides were detected; Ac-227 (and its daughters) with massic activity of 0.30 +/- 0.02 Bq/kg and La-138 with massic activity of 7.4 +/- 1.0 mBq/kg. Two activation products were also detected; Ce-139 and Br-82. Their massic activities (assuming a homogeneous distribution in the crystal) just before taking the CeBr3 crystal underground were 4.3 +/- 0.3 mBq/kg and 18 +/- 4 mBq/kg correspondingly. None of the other common primordial radionuclides (K-49, Ra-226, Ra-228, Th-228, and U-235) were detected and their detection limits were below 2 mBq/kg except for U-238 for which the upper limit was 135 mBq/kg and Pb-210 with an upper limit of 600 mBq/kg.
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| 23. |
- Marton, Z., et al.
(författare)
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Mutations in the stereospecificity pocket and at the entrance of the active site of Candida antarctica lipase B enhancing enzyme enantioselectivity
- 2010
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Ingår i: Journal of Molecular Catalysis B. - : Elsevier BV. - 1381-1177 .- 1873-3158. ; 65:1-4, s. 11-17
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Tidskriftsartikel (refereegranskat)abstract
- Two different parts of Candida antarctica lipase B (stereospecificity pocket at the bottom of the active site and hydrophobic tunnel leading to the active site) were redesigned by single- or double-point mutations, in order to better control and improve enzyme enantioselectivity toward secondary alcohols. Single-point isosteric mutations of Ser47 and Thr42 situated in the stereospecificity pocket gave rise to variants with doubled enantioselectivity toward pentan-2-ol, in solid/gas reactor. Besides, the width and shape of the hydrophobic tunnel leading to the active site was modified by producing the following single-point mutants: Ile189Ala, Leu278Val and Ala282Leu. For each of these variants a significant modification of enantioselectivity was observed compared to wild-type enzyme, indicating that discrimination of the enantiomers by the enzyme could also arise from their different accessibilities from the enzyme surface to the catalytic site. (C) 2010 Elsevier B.V. All rights reserved.
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| 24. |
- Montanez, Maria I., et al.
(författare)
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Accelerated Growth of Dendrimers via Thiol-Ene and Esterification Reactions
- 2010
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 43:14, s. 6004-6013
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Tidskriftsartikel (refereegranskat)abstract
- By taking advantage of the orthogonal nature of thiol-ene coupling and anhydride based esterification reactions, a facile and chemoselective strategy to dendritic macromolecules has been developed The ability to interchange growth steps based on thiol-ene and anhydride chemistry allows the synthesis of fifth-generation dendrimers in only five steps and under benign reaction conditions In addition, the presented coupling chemistries eliminate the traditional need for protection/deprotection steps and afford dendrimers in high yield and purity The modularity of this strategy coupled with the latent reactivity of the alkene/hydroxyl chain ends was demonstrated by using different cores (alkene and hydroxyl functional), various AB(2) and CD2 monomers and a range of chain end groups As a result, three dendritic libraries were prepared which exhibited tunability of both the chemical functionality and physical properties including the fabrication of PEG hydrogels.
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| 25. |
- Steinmetz, Erik M, 1984, et al.
(författare)
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Communication analysis for centralized intersection crossing coordination
- 2014
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Ingår i: Proc. 11th International Symposium on Wireless Communications Systems. - 9781479958634 ; , s. 813-818
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Konferensbidrag (refereegranskat)abstract
- Coordination of autonomous cooperative vehicles is an important challenge for future intelligent transportation systems. In particular, coordination to cross intersections captures the inherent and connected challenges among control and communication. While intersection coordination and vehicular wireless communication have both received extensive treatment in their respective communities, few works consider their interaction. We provide a communication system analysis for the specific problem of centralized intersection crossing coordination, leading to design guidelines for both uplink (whereby vehicles send intentions to the central controller) and downlink (where the controller prescribes vehicles of safe control actions).
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| 26. |
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| 27. |
- Thuresson, Britt, et al.
(författare)
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A novel B(weak) hybrid allele lacks three enhancer repeats but generates normal ABO transcript levels.
- 2012
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Ingår i: Vox Sanguinis. - : Wiley. - 1423-0410 .- 0042-9007. ; 102:1, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- Background and Objectives Weak expression of A/B histo-blood group antigens is often explained by single nucleotide substitutions at the ABO locus. However, hybrid alleles containing segments from different ABO alleles can result in unexpected phenotypes and may complicate genotype analysis. We investigated the basis of weak B phenotype in a referred sample. Materials and Methods A healthy young woman was serologically phenotyped as AB(weak) and RBCs were characterized by flow cytometry. All seven ABO exons, five introns plus the 5'-region including the CCAAT-binding factor/Nuclear Factor Y (CBF/NF-Y) binding enhancer were sequenced. ABO transcript levels were measured in fresh peripheral blood samples. Expression of B antigen was semiquantified following transfection of HeLa cells. Results A new B(weak) allele with 53G>T resulted in a characteristic pattern of moderately weakened B antigen expression on RBCs. Its sequence revealed a novel hybrid between O(2) [O03] and B [B101] alleles with a crossingover region in intron 4 as defined by allele-specific polymorphisms. B transcript levels were similar to normal controls despite the O(2) -related single CBF/NF-Y-binding 43-bp motif in the enhancer region. Expression of the glycosyltransferase including the O(2) -specific Arg18Leu substitution resulted in a slight decrease in B-antigen-positive cells. Conclusion We describe here the first hybrid between an O(2) and a B allele and characterized the associated decrease in B antigen expression. Although it lacks three enhancer repeat units compared to common B alleles, the resulting transcript level was unaltered. This study challenges previous suggestions that the number of 43-bp motifs in the ABO enhancer determines transcription rates in erythroid cells.
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| 28. |
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| 29. |
- Wolofsky, Kayla T., et al.
(författare)
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ABO Blood Groups Influence Macrophage-mediated Phagocytosis of Plasmodium falciparum-infected Erythrocytes
- 2012
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Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 8:10
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Tidskriftsartikel (refereegranskat)abstract
- Erythrocyte polymorphisms associated with a survival advantage to Plasmodium falciparum infection have undergone positive selection. There is a predominance of blood group O in malaria-endemic regions, and several lines of evidence suggest that ABO blood groups may influence the outcome of P. falciparum infection. Based on the hypothesis that enhanced innate clearance of infected polymorphic erythrocytes is associated with protection from severe malaria, we investigated whether P. falciparum-infected O erythrocytes are more efficiently cleared by macrophages than infected A and B erythrocytes. We show that human macrophages in vitro and mouse monocytes in vivo phagocytose P. falciparum-infected O erythrocytes more avidly than infected A and B erythrocytes and that uptake is associated with increased hemichrome deposition and high molecular weight band 3 aggregates in infected O erythrocytes. Using infected A(1), A(2), and O erythrocytes, we demonstrate an inverse association of phagocytic capacity with the amount of A antigen on the surface of infected erythrocytes. Finally, we report that enzymatic conversion of B erythrocytes to type as O before infection significantly enhances their uptake by macrophages to observed level comparable to that with infected O wild-type erythrocytes. These data provide the first evidence that ABO blood group antigens influence macrophage clearance of P. falciparum-infected erythrocytes and suggest an additional mechanism by which blood group O may confer resistance to severe malaria.
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