| 1. |
- Fu, Tian-Min, et al.
(författare)
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Protein preparation, crystallization and preliminary X-ray analysis of the C-terminal domain of human RSK1 serine/threonine protein kinase
- 2007
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Ingår i: Acta Crystallographica. Section F: Structural Biology and Crystallization Communications. - 2053-230X. ; 63:Pt 12, s. 8-1026
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Tidskriftsartikel (refereegranskat)abstract
- As a substrate of extracellular signal-related kinase (ERK), the p90 ribosome S6 kinase 1 (RSK1) is at the terminus of the Ras/ERK pathway. Residues 411-735 of human RSK1, covering the C-terminal serine/threonine kinase catalytic domain and the functionally important tail, were cloned into an Escherichia coli expression vector. The protein was expressed, purified and crystallized. The crystals diffracted to 2.7 A and belonged to space group P2(1), with unit-cell parameters a = 39.8, b = 143.8, c = 59.9 A, beta = 95.7 degrees.
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| 2. |
- Li, Xuemei, et al.
(författare)
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Perfluorooctanesulfonate and related fluorochemicals in the Amur tiger (Panthera tigris altaica) from China
- 2008
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 42:19, s. 7078-7083
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Tidskriftsartikel (refereegranskat)abstract
- Perfluorinated compounds (PFCs) are used in a variety of industrial applications. We tested the hypothesis that, in Amur tigers (Panthera tigris altaica), captivity in industrialized areas increases PFC levels, potentially presenting a health risk to these animals. Serum samples were collected from 100 tigers from industrialized or nonindustrialized regions in China with nonpoint sources of PFCs. Mean concentrations of PFCs in these samples ranged from 1.57 ± 0.83 ng/mL in nonindustrial Hailin to 4.31 ± 2.90 ng/mL in industrial Beijing. PFC concentrations were significantly higher in tigers from the industrial city of Harbin than those from Hailin (p < 0.05). Perfluorooctanesulfonate (PFOS) was the most abundant PFC in all tigers and increased with age, regardless of industrial/nonindustrial background (p < 0.01). However, PFOS concentrations were 2-4 orders of magnitude less than the current no-observed-effect level. In addition, overall PFC levels in Amur tigers were low compared with various species living in other countries, consistent with the relatively short history of PFC use in China. These results are consistent with the hypothesis that captivity in industrialized areas increases PFC levels in Amurtigers. They also suggestthat PFC accumulation will persist, and even increase, with continued use of PFCs in China.
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| 3. |
- Liu, Cong, et al.
(författare)
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Preparation, crystallization and preliminary X-ray analysis of protein YtlP from Bacillus subtilis
- 2006
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Ingår i: Acta Crystallographica. Section F: Structural Biology and Crystallization Communications. - 2053-230X. ; 62:10, s. 967-969
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Tidskriftsartikel (refereegranskat)abstract
- Bacillus subtilis YtlP is a protein that is predicted to belong to the bacterial and archael 2'-5' RNA-ligase family. It contains 183 residues and two copies of the HXTX sequence motif conserved among proteins belonging to this family. In order to determine the structure of YtlP and to compare it with the paralogue YjcG and identified 2'-5' RNA ligases, the gene ytlP was amplified from B. subtilis genomic DNA and cloned into expression vector pET-21a. The soluble protein was produced in Escherichia coli, purified to homogeneity and crystals suitable for X-ray analysis were obtained. The crystal diffracted to 2.0 angstrom and belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 34.16, b = 48.54, c = 105.75 angstrom.
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| 4. |
- Richards, Stephen, et al.
(författare)
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The genome of the model beetle and pest Tribolium castaneum.
- 2008
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Ingår i: Nature. - 1476-4687. ; 452:7190, s. 949-55
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Tidskriftsartikel (refereegranskat)abstract
- Tribolium castaneum is a representative of earth’s most numerous eukaryotic order, a powerful model organism for the study of generalized insect development, and also an important pest of stored agricultural products. We describe its genome sequence here. This omnivorous beetle has evolved an ability to interact with a diverse chemical environment as evidenced by large expansions in odorant and gustatory receptors, as well as p450 and other detoxification enzymes. Developmental patterns in Tribolium are more representative of other arthropods than those found in Drosophila, a fact represented in gene content and function. For one, Tribolium has retained more ancestral genes involved in cell-cell communication than Drosophila, and some are expressed in the growth zone crucial for axial elongation in short germ development. Systemic RNAi in T. castaneum appears to use mechanisms distinct from those found in C. elegans, but nevertheless offers similar power for the elucidation of gene function and identification of targets for selective insect control.
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| 5. |
- Boonen, Steven, et al.
(författare)
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Safety and efficacy of teriparatide in elderly women with established osteoporosis: bone anabolic therapy from a geriatric perspective.
- 2006
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Ingår i: Journal of the American Geriatrics Society. - : Wiley. - 0002-8614 .- 1532-5415. ; 54:5, s. 782-9
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To assess the safety and efficacy of teriparatide in patients aged 75 and older and compare these findings with those of women younger than 75 using data from the Fracture Prevention Trial (FPT). DESIGN: The FPT was a randomized, multicenter, double-blind, placebo-controlled study. SETTING: The FPT multicenter international study. PARTICIPANTS: Postmenopausal women aged 42 to 86 were randomized to placebo (N=544) or teriparatide 20 mug (N=541) by daily self-injection for a median of 19 months. Patients received daily oral supplements of 1,000 mg calcium and 400 to 1,200 IU vitamin D. For this analysis, subgroups were defined according to patient age younger than 75 (N=841) and 75 and older (N=244). MEASUREMENTS: The effects of teriparatide on bone mineral density (BMD) of the lumbar spine and femoral neck; the incidence of new vertebral and new nonvertebral fragility fractures; bone turnover markers, including bone-specific alkaline phosphatase; and urinary deoxypyridinoline corrected for creatinine clearance, as well as the safety of teriparatide, were investigated. RESULTS: There were no significant treatment-by-age interactions for the bone turnover markers, femoral neck BMD, vertebral fractures, nonvertebral fragility fractures, height loss, hyperuricemia, or hypercalcemia. A significant treatment-by-age interaction for lumbar spine BMD (P=.08) was due to an increase in BMD observed in the placebo group aged 75 and older. There were no treatment-by-age interactions for important treatment-emergent adverse events (TEAEs), including back pain, nausea, leg cramps, and dizziness. The most important TEAEs in women aged 80 and older (23 patients from the placebo group and 25 patients from the teriparatide group) were also reviewed; no unexpected TEAEs were found in the patients treated with teriparatide. These results indicate that the clinical effects of teriparatide were consistent in the older and younger women. CONCLUSION: Age does not affect the safety and efficacy of teriparatide in postmenopausal women with osteoporosis.
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| 6. |
- Clark, Andrew G., et al.
(författare)
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Evolution of genes and genomes on the Drosophila phylogeny
- 2007
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 450:7167, s. 203-218
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Tidskriftsartikel (refereegranskat)abstract
- Comparative analysis of multiple genomes in a phylogenetic framework dramatically improves the precision and sensitivity of evolutionary inference, producing more robust results than single-genome analyses can provide. The genomes of 12 Drosophila species, ten of which are presented here for the first time (sechellia, simulans, yakuba, erecta, ananassae, persimilis, willistoni, mojavensis, virilis and grimshawi), illustrate how rates and patterns of sequence divergence across taxa can illuminate evolutionary processes on a genomic scale. These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution. Despite remarkable similarities among these Drosophila species, we identified many putatively non-neutral changes in protein-coding genes, non-coding RNA genes, and cis-regulatory regions. These may prove to underlie differences in the ecology and behaviour of these diverse species.
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| 7. |
- Edholm, Dan, 1972-
(författare)
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VEGFR-2 in Endothelial Differentiation and Vascular Organization
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The cardiovascular system is the first functional organ to develop during embryogenesis. As the embryo reaches above a certain size, passive diffusion of gases and nutrients is no longer compatible with efficient growth. During embryogenesis, endothelial progenitor cells (angioblasts) are recruited from the primitive streak mesoderm and instructed to express vascular endothelial growth factor receptor-2 (VEGFR-2). This thesis examines the roles played by VEGFR-2 in the events through which a subpopulation of embryonic stem (ES) cells differentiate into endothelial cells and form the vasculature. We show that ES cells gene targeted for VEGFR-2 (flk1-/-) develop immature endothelial cells (ECs), precursors, when differentiated in vitro as embryoid bodies (EBs). The flk1-/- ECs are unresponsive to VEGF-stimulation and consistently fail to form vessels. However, when co-cultured with wild type ES cells in chimeric EBs, flk1-/- endothelial precursors are guided by wild type ECs to form transient, chimeric vascular structures. Use of lentivirus in an add-back approach allowed reconstitution of VEGFR-2 expression in flk1-/- ES cells, and rescue of vasculogenesis and sprouting angiogenesis. We propose that recruitment to the endothelial lineage is not dependent on VEGFR-2, although this receptor tyrosine kinase appears indispensible for EC integrity, survival and for differentation of endothelial precursors into mature ECs formating a stable vasculature. Neuropilin-1 (NRP1) and heparan sulfate proteoglycans (HSPGs) function as co-receptors for VEGFs. The co-receptors influence, qualitatively and quantitatively, the intracellular signal relayed by VEGFR-2 but it is unclear how. We examined the contribution of NRP1 to VEGFR-2 signaling in EB cultures, in zebrafish and in mice. Only NRP1-binding VEGFs were able to promote sprouting angiogenesis and formation of properly branched vascular tubes, supported by pericytes. Downstream of VEGFR-2/NRP1 activation, we identified recruitment of p38MAPK in signal transduction regulating sprouting angiogenesis.
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| 8. |
- Elsik, Christine G., et al.
(författare)
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The Genome Sequence of Taurine Cattle : A Window to Ruminant Biology and Evolution
- 2009
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 324:5926, s. 522-528
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Tidskriftsartikel (refereegranskat)abstract
- To understand the biology and evolution of ruminants, the cattle genome was sequenced to about sevenfold coverage. The cattle genome contains a minimum of 22,000 genes, with a core set of 14,345 orthologs shared among seven mammalian species of which 1217 are absent or undetected in noneutherian (marsupial or monotreme) genomes. Cattle-specific evolutionary breakpoint regions in chromosomes have a higher density of segmental duplications, enrichment of repetitive elements, and species-specific variations in genes associated with lactation and immune responsiveness. Genes involved in metabolism are generally highly conserved, although five metabolic genes are deleted or extensively diverged from their human orthologs. The cattle genome sequence thus provides a resource for understanding mammalian evolution and accelerating livestock genetic improvement for milk and meat production.
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| 9. |
- Farahbakhshazad, Neda, et al.
(författare)
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Modeling biogeochemical impacts of alternative management practices for a row-crop field in Iowa
- 2008
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Ingår i: Agriculture, Ecosystems & Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 123:1-3, s. 30-48
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Tidskriftsartikel (refereegranskat)abstract
- The management of contemporary agriculture is rapidly shifting from single-goal to multi-goal strategies. The bottleneck of implementing the strategies is the capacity of predicting the simultaneous impacts of change in management practices on agricultural production, soil and water resources and environmental safety. Process-based models provide an opportunity to quantify the impacts of farm management options on various pools and fluxes of carbon (C) and nitrogen (N) in agroecosystems. The denitrification-decomposition or DNDC model was recently modified for simulating N cycling for the U.S. Midwestern agricultural systems. This paper reports a continuous effort on applying the model for estimating the impacts of alternative management practices (e.g., no-till, cover crop, change in fertilizer rate or timing) on agroecosystems in the Midwestern U.S. A typical row-crop field in Iowa was selected for the sensitivity tests. The modeled results were assessed with a focus on four major indicators of agro-ecosystems, namely crop yield, soil organic carbon (SOC) sequestration, nitrate-N leaching loss and nitrous oxide (N2O) emissions. The results indicated that no-till practice significantly increased SOC storage and reduced nitrate-N leaching rate, but slightly decreased crop yield and increased N2O emissions. By modifying the methods of fertilizer application in conjunction with the no-till practice, the disadvantages of no-till could be overcome. For example, increasing the fertilizing depth and using a nitrification inhibitor could substantially reduce N2O emissions and increase crop yield under the no-till conditions. This study revealed the complexity of impacts of the alternative farming management practices across different climate conditions, soil properties and management regimes. Process-based models can play an important role in quantifying the comprehensive effects of management alternatives on agricultural production and the environment.
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| 10. |
- Field, Dawn, et al.
(författare)
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The minimum information about a genome sequence (MIGS) specification.
- 2008
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Ingår i: Nature biotechnology. - : Springer Science and Business Media LLC. - 1546-1696 .- 1087-0156. ; 26:5, s. 541-7
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Tidskriftsartikel (refereegranskat)abstract
- With the quantity of genomic data increasing at an exponential rate, it is imperative that these data be captured electronically, in a standard format. Standardization activities must proceed within the auspices of open-access and international working bodies. To tackle the issues surrounding the development of better descriptions of genomic investigations, we have formed the Genomic Standards Consortium (GSC). Here, we introduce the minimum information about a genome sequence (MIGS) specification with the intent of promoting participation in its development and discussing the resources that will be required to develop improved mechanisms of metadata capture and exchange. As part of its wider goals, the GSC also supports improving the 'transparency' of the information contained in existing genomic databases.
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| 11. |
- Hedlin, Dan, 1960-, et al.
(författare)
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Future challenges of small area estimation
- 2006
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Ingår i: Statistics in transition. - Warsaw : Polish Statistical Association. - 1234-7655. ; 7:4, s. 759-769
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Tidskriftsartikel (refereegranskat)abstract
- A panel discussion session entitled as “Future Challenges of Small Area Estimation” was organized in the SAE2005 Conference, with Ray Chambers as the organizer and chair and Jan van den Brakel, Dan Hedlin, Marie Cruddas, Risto Lehtonen, Imbi Traat and Li-Chun Zhang as the discussants. The output of the panel discussion session is summarized in this paper. Each contributor is responsible of the respective piece of text; the paper has been edited by the chairman of the session.
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| 12. |
- Kawamura, Harukiyo, et al.
(författare)
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Neuropilin-1 in regulation of VEGF-induced activation of p38MAPK and endothelial cell organization
- 2008
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 112:9, s. 3638-49
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Tidskriftsartikel (refereegranskat)abstract
- Vascular endothelial growth factor (VEGF)-A regulates vascular development and angiogenesis. VEGF isoforms differ in ability to bind coreceptors heparan sulfate (HS) and neuropilin-1 (NRP1). We used VEGF-A165 (which binds HS and NRP1), VEGF-A121 (binds neither HS nor NRP1), and parapoxvirus VEGF-E-NZ2 (binds NRP1 but not HS) to investigate the role of NRP1 in organization of endothelial cells into vascular structures. All 3 ligands induced similar level of VEGFR-2 tyrosine phosphorylation in the presence of NRP1. In contrast, sprouting angiogenesis in differentiating embryonic stem cells (embryoid bodies), formation of branching pericyte-embedded vessels in subcutaneous matrigel plugs, and sprouting of intersegmental vessels in developing zebrafish were induced by VEGF-A165 and VEGF-E-NZ2 but not by VEGF-A121. Analyses of recombinant factors with NRP1-binding gain- and loss-of-function properties supported the conclusion that NRP1 is critical for VEGF-induced sprouting and branching of endothelial cells. Signal transduction antibody arrays implicated NRP1 in VEGF-induced activation of p38MAPK. Inclusion of the p38MAPK inhibitor SB203580 in VEGF-A165-containing matrigel plugs led to attenuated angiogenesis and poor association with pericytes. Our data strongly indicate that the ability of VEGF ligands to bind NRP1 influences p38MAPK activation, and formation of functional, pericyte-associated vessels.
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| 13. |
- Li, Qiang, et al.
(författare)
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DNS of a spatially developing turbulent boundary layer with passive scalar transport
- 2009
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Ingår i: International Journal of Heat and Fluid Flow. - : Elsevier BV. - 0142-727X .- 1879-2278. ; 30:5, s. 916-929
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Tidskriftsartikel (refereegranskat)abstract
- A direct numerical simulation (DNS) of a spatially developing turbulent boundary layer over a flat plate under zero pressure gradient (ZPG) has been carried out. The evolution of several passive scalars with both isoscalar and isoflux wall boundary condition are computed during the simulation. The Navier-Stokes equations as well as the scalar transport equation are solved using a fully spectral method. The highest Reynolds number based on the free-stream velocity U-infinity and momentum thickness 0 is Re-0 = 830, and the molecular Prandtl numbers are 0.2, 0.71 and 2. To the authors' knowledge, this Reynolds number is to date the highest with such a variety of scalars. A large number of turbulence statistics for both flow and scalar fields are obtained and compared when possible to existing experimental and numerical simulations at comparable Reynolds number. The main focus of the present paper is on the statistical behaviour of the scalars in the outer region of the boundary layer, distinctly different from the channel-flow simulations. Agreements as well as discrepancies are discussed while the influence of the molecular Prandtl number and wall boundary conditions is also highlighted. A Pr scaling for various quantities is proposed in outer scalings. In addition, spanwise two-point correlation and instantaneous fields are employed to investigate the near-wall streak spacing and the coherence between the velocity and the scalar fields. Probability density functions (PDF) and joint probability density functions (JPDF) are shown to identify the intermittency both near the wall and in the outer region of the boundary layer. The present simulation data will be available online for the research community.
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| 14. |
- Li, Qiang, et al.
(författare)
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Simulations of heat transfer in a boundary layer subject to free-stream turbulence
- 2009
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Ingår i: 6th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2009. - : International Symposium on Turbulence and Shear Flow Phenomena, TSFP. ; , s. 195-200
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Konferensbidrag (refereegranskat)abstract
- The present study investigates the effects or the ambient, free-stream turbulence (FST) on the momentum and heat transfer in a turbulent flat-plate boundary layer via large-eddy simulations (LES) using the ADM-RT model. Due to a FST of 20%, the skin-friction coefficient c/and Stanton number St are substantially elevated up to 15% in the fully turbulent region. The depression of both the mean velocity and temperature profiles in the wake region due to the FST is observed, however, the influence on the wall-normal heat flux in the near-wall region is negligible. © 2009 International Symposium on Turbulence and Shear Flow Phenomena, TSFP09. All rights reserved.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Li, Xiujuan, et al.
(författare)
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Lentiviral rescue of vascular endothelial growth factor receptor-2 expression in flk1-/- embryonic stem cells shows early priming of endothelial precursors
- 2007
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Ingår i: Stem Cells. - : Oxford University Press (OUP). - 1066-5099 .- 1549-4918. ; 25:12, s. 2987-2995
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Tidskriftsartikel (refereegranskat)abstract
- The vascular endothelial growth factor ( VEGF) family and its receptors are important for vascular development and maintenance of blood vessels, as well as for angiogenesis, the formation of new vessels. Loss of VEGF receptor-2 (VEGFR-2; designated Flk-1 in mouse) results in arrest of vascular and hematopoietic development in vivo. We used lentiviral transduction to reconstitute VEGFR-2 expression in flk1-/- embryonic stem (ES) cells. VEGF-induced vasculogenesis and sprouting angiogenesis were rescued in transduced ES cultures differentiating in vitro as EBs. Although the transgene was expressed in the pluripotent stem cells and lacked linage restriction during differentiation, the extent of endothelial recruitment was similar to that in wild-type EBs. Reconstitution of VEGFR-2 in flk1-/- ES cells allowed only precommitted precursors to differentiate into functional endothelial cells able to organize into vascular structures. Chimeric EB cultures composed of wild-type ES cells mixed with flk1-/- ES cells or reconstituted VEGFR-2expressing ES cells were created. In the chimeric cultures, flk1-/- endothelial precursors were excluded from wild-type vessel structures, whereas reconstituted VEGFR-2-expressing precursors became integrated together with wild-type endothelial cells to form chimeric vessels. We conclude that maturation of endothelial precursors, as well as organization into vascular structures, requires expression of VEGFR-2.
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| 19. |
- Liu, Bingbing, et al.
(författare)
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Effects of silver films with different nano-particle sizes on SERS of single-walled carbon nanotubes
- 2005
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Ingår i: Chemical Journal of the Chinese Universities. - 0251-0790. ; 26:10, s. 1930-1933
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Tidskriftsartikel (refereegranskat)abstract
- Surface-enhanced Raman scattering (SERS) spectra of single-walled carbon nanotubes (SWCNTs) on silver films with different nano-particle sizes from 20 to 100 nm deposited on quartz and glass substrates were studied systematically. The characteristic Raman spectral features of SWCNT G-band and D-band were analyzed. The two bands show a similar tendency with the change of nano-particle size of silver on quartz and glass substrates. The position and the intensity of the G-band are less sensitive to the films' silver particle sizes in the studied range, indicating that hexagonal carbon rings are stable and have a weak interaction with silver films. The shape of the D-band depends on the silver size. The smaller the silver particle size, the more the contribution of high frequency vibrations to the D-band, indicating that disorder carbon has a strong interaction with the active silver films.
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| 20. |
- Schlatter, Philip, et al.
(författare)
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High-Reynolds number turbulent boundary layers studied by numerical simulation
- 2009
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Ingår i: Bulletin of the American Physical Society. - : APS Physics.
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Konferensbidrag (refereegranskat)abstract
- Direct and large-eddy simulations (DNS and LES) of spatially developing high-Reynolds number turbulent boundary layers (Reθ up to 4300) under zero pressure gradient are studied. The inflow of the computational domain and the tripping of the boundary layer is located at low Reynolds numbers Reθ 350, a position where natural transition to turbulence can be expected. The simulation thus includes the spatial evolution of the boundary layer for an extended region, providing statistics and budget terms at each streamwise position. The data is obtained with up to O(10^10) grid points using a parallelised, fully spectral method. The DNS and LES results are critically evaluated and validated, in comparison with other relevant data, e.g. the experiments by "Osterlund et al. (1999). Quantities difficult or even impossible to measure, e.g. pressure fluctuations and complete Reynolds stress budgets, shall be discussed. In addition, special emphasis is put on a further quantification of the large-scale structures appearing in the flow, and their relation to other wall-bounded flow as e.g. channel flow. The results clearly show that with today's computer power Reynolds numbers relevant for industrial applications can be within reach for DNS/LES.
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| 21. |
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| 22. |
- Schlatter, Philipp, et al.
(författare)
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Turbulent boundary layers up to Re-theta=2500 studied through simulation and experiment
- 2009
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Ingår i: Physics of fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 21:5, s. 051702-
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Tidskriftsartikel (refereegranskat)abstract
- Direct numerical simulations (DNSs) and experiments of a spatially developing zero-pressure-gradient turbulent boundary layer are presented up to Reynolds number Re-theta=2500, based on momentum thickness theta and free-stream velocity. For the first time direct comparisons of DNS and experiments of turbulent boundary layers at the same (computationally high and experimentally low) Re-theta are given, showing excellent agreement in skin friction, mean velocity, and turbulent fluctuations. These results allow for a substantial reduction of the uncertainty of boundary-layer data, and cross validate the numerical setup and experimental technique. The additional insight into the flow provided by DNS clearly shows large-scale turbulent structures, which scale in outer units growing with Re-theta, spanning the whole boundary-layer height.
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| 23. |
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| 24. |
- Zhang, Xuanjun, et al.
(författare)
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Anion-Directed Assembly of Macrocycle and Helix
- 2006
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 6:6, s. 1440-1444
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembly of the flexible ligand N,N‘-bis(3-pyridylmethyl)thiourea (bpt) with ZnCl2 and CdCl2 in the absence and presence of KSCN yielded a short series of novel complexes (1−4) with macrocyclic, helical, double-helical, and 1D polymeric structures. Different metal ions, hydrogen bonds, and counteranions play significant roles in the final crystal structures. The NCS- anion was found to favor the formation of helical structures, whereas the Cl- anion favored macrocycle formation in the present system. Photoluminescence (PL) measurement results revealed that complex 2 (Zn(bpt)(SCN)2) with a helical structure exhibits enhanced emissions compared to those of the ligand and other complexes. The anion-directed assembly as well as the interesting emissions may provide useful information for further design of metal−organic compounds with novel structures and properties.
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| 25. |
- Zhang, Xuanjun, et al.
(författare)
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Dichlorobis(phenothiazine-S)palladium(II)
- 2005
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Ingår i: Acta Crystallographica Section E. - 1600-5368. ; E61, s. m603-m605
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Tidskriftsartikel (refereegranskat)abstract
- In the title complex, [PdCl2(C12H9NS)2], the Pd atom lies on a center of inversion and is coordinated by two chloride anions and two S atoms from two phenothiazine ligands, forming a square-planar PdCl2S2 geometry. In the crystal structure, a one-dimensional polymer structure is constructed via N-H...Cl and N-H...N hydrogen bonds.
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| 26. |
- Zhang, Xuanjun, et al.
(författare)
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From Large 3D Assembly to Highly Dispersed Spherical Assembly: Weak- and Strong- Coordination Mediated Self-Aggregation of Au Colloids
- 2006
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Ingår i: New Journal of Chemistry. - : RSC Publishing. - 1144-0546 .- 1369-9261. ; 30, s. 706-711
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Tidskriftsartikel (refereegranskat)abstract
- Distinctly different 3D assemblies of 1.6 nm Au nanoparticles are constructed based on weak and strong coordination strategies. Reduction of KAuCl4 with NaBH4 in the presence of newly-synthesized 4-(4-phenylmethanethiol)-2,2′:6′,2′′-terpyridine (1) yields functionalized Au nanoparticles which assemble in situ into large 3D aggregates via weak coordination between alkali metal ions and terpyridine attached to separated particles. These assemblies are disassembled into individual nanoparticles via addition of DMF solvent and further reassembled into highly dispersed 3D spherical nanostructures via addition of Co2+ (strong coordination with 1). Wide and small angle XRD measurements show that the assemblies are formed from small Au nanoparticles, consistent with TEM results. It is significant that the large aggregates formed in situ can be directly transformed into nearly monodispersed 3D spherical assemblies via strong coordination (with Co2+), presenting the first example of a direct transformation of one 3D nanonetwork into another distinctly different 3D nanonetwork. The controlled assembly and disassembly processes are accompanied by distinct shifts in the surface plasmon resonance.
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| 27. |
- Zhang, Xuanjun, et al.
(författare)
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Metal-Compound-Induced Vesicles as Efficient Directors for Rapid Synthesis of Hollow Alloy Spheres†
- 2006
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Ingår i: Angewandte Chemie International Edition. - : Wiley-VCH Verlagsgesellschaft. - 1433-7851 .- 1521-3773. ; 45:36, s. 5971-5974
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Tidskriftsartikel (refereegranskat)abstract
- Hollow alloy: Vesicles formed from tetrabutylammonium bromide and metal compounds act as efficient directors for the rapid synthesis of a variety of binary, ternary, and quaternary intermetallic materials with hollow structures. In this way, different metals were co-alloyed on the vesicle surface to produce hollow alloy spheres containing more than two kinds of metals.
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| 28. |
- Zhou, Xiao-Ping, et al.
(författare)
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Anion-p-Interaction-Directed Self-Assembly of Ag(I) Coordination Networks
- 2007
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 7:3, s. 485-487
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Tidskriftsartikel (refereegranskat)abstract
- Reactions of AgX with 2,4,6-tri(2-pyridyl)-1,3,5-trazine (tpt) yielded three 3D highly symmetric isostructural coordination polymers (X = ClO4-, BF4-, and PF6-) and a dimer (X = CF3COO-), respectively. In the coordination polymers, anion−π interactions are found between the multiatomic anions and tpt ligands. Systematic variation including synthetic methods, ratios of reactants, and solvents provides synthetic evidence proving that anion−π interactions play a decisive role in assembly of the coordination polymers.
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| 29. |
- Zhou, Xiao-Ping, et al.
(författare)
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Cu(I) or Cu(I)-Cu(II) Mixed-Valence Complexes of 2,4,6-Tri(2-pyridyl)-1,3,5-triazine: Syntheses, Structures, and Theoretical Study of the Hydrolytic Reaction Mechanism
- 2006
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 45:18, s. 7119-7125
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Tidskriftsartikel (refereegranskat)abstract
- The reactions of 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tpt) with copper(I) halides under solvothermal or traditional conditions yielded two polymeric Cu(I) complexes [Cu2I2(tpt)]n (1) and [Cu3I3(tpt)]n (2), one mixed-valence Cu(I)−Cu(II) complex [Cu4Cl2I4(tpt)2] (3), and two Cu(II) complexes [CuBr(bpca)] (4) and [CuI(bpca)] (5) (bpca = bis(2-pyridylcarbonyl)amine). Complex 1 is a zigzag chain with tpt in a bis-bipyridine-like coordination mode, whereas complex 2 with tpt chelating three Cu(I) cations is a ladderlike coordination polymer. Complex 3 is mixed-valence, with Cu(I) in a distorted tetrahedral geometry and Cu(II) in a distorted square pyramidal geometry, forming a ladderlike supramolecular chain. Complexes 4 and 5 are the products of in situ hydrolysis of tpt involving the oxidation of Cu(I). The synthesis and characterization of complex 1, 2, and 5 indicated that Cu(I) cannot promote the hydrolysis of tpt. The theoretical study shows that the main effect for hydrolysis of tpt is the electron-withdrawing effect of metal ions.
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- Zhou, Xiao-ping, et al.
(författare)
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Syntheses of supramolecular CuCN complexes by decomposing CuSCN: a general route to CuCN coordination polymers?
- 2006
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Ingår i: Dalton Transactions. - : RSC Publishing. - 1477-9226 .- 1477-9234. ; :20, s. 2435-2443
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Tidskriftsartikel (refereegranskat)abstract
- The solvothermal reaction of CuSCN with 1,2-bis(diphenylphosphino)ethane (dppe) yielded a coordination polymer, which was characterized to be a complex of CuCN and 1,2-bis(diphenylthiophosphinyl)ethane (dppeS2): [(CuCN)2(dppeS2)]n (1). The identification of complex 1 reveals that CuSCN was decomposed and the sulfur was transferred to dppe, and represents a new example of the transformation of inorganic sulfur to organic sulfur. The weak coordination interactions between CuCN and dppeS2 indicate that dppeS2 may be substituted by ligands with strong coordination ability. The ligand 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tpt) was chosen as a substitute ligand. Three novel CuCN coordination polymers of tpt were synthesized and characterized: [Cu2(CN)2(tpt)]n (2) with a 3-D (10,3)-a network, [Cu2(CN)2(tpt)]n (3) and [Cu2(SCN)(CN)(tpt)]n (4) both with a 2-D (6,3) network, and only complex 2 can be obtained from CuCN directly. Interestingly, compounds 2 and 3 are genuine high-dimensional supramolecular isomers. During the syntheses of 2-4, single crystals of dppeS2 were isolated, which indicates it was substituted by tpt ligand and also confirmed the transformation of sulfur from CuSCN to dppe. The transformation of sulfur can be observed only when the temperature is relative high (>160 degrees C). At 140 degrees C, complex 5 containing only CuSCN was attained and no dppeS2 has been monitored in the resulting filtrate.
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