2,053 research outputs found
Boundary layer flow control using the method of spanwise mean velocity gradient
No full textOver the last decade wind tunnel experiments and numerical simulations have shown that steady spanwise mean velocity gradients are able to attenuate the growth of different types of boundary layer disturbances if introduced in a controlled way. In this paper different techniques to setup the spanwise mean velocity variations are reviewed and their stabilizing effect leading to transition delay are quantified. This control strategy has potential to lead to an unforeseen positive impact on the broad spectrum of industrial applications where reducing drag is a daily challenge
Prosecutor v Hans Åkerberg Fransson (Case C-617/10), ECLI:EU:C:2013:105, [2013] 2 CMLR 46, 26 February 2013
No full textEssential Cases: EU Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Prosecutor v Hans Åkerberg Fransson (Case C-617/10), ECLI:EU:C:2013:105, [2013] 2 CMLR 46, 26 February 2013. The document also included supporting commentary from author Noreen O’Meara.</p
Transition and wavy walls: an experimental study: An experimental study
No full textA wide body of research exists which explores the effects of surface roughness or patterned wall shapes on instability growth and transition. Building on those works as well as recent experiments demonstrating passive laminar flow control using arrays of discrete roughness [3, 8], a set of spanwise-wavy walls is designed with the goal of suppressing instability growth in two-dimensional boundary layers. In a numerical investigation of Tollmien-Schlichting (TS) wave growth in the presence of streamwise boundary-layer streaks, Cossu and Brandt [1] found that stabilization of TS waves results from spanwise shear in the mean flow, which forms a negative contribution to production in the perturbation kinetic energy equation. Whereas previous efforts have employed streamwise vorticity developing in roughness wakes to provide the requisite mean-flow deformation, in this work stabilization is achieved through modulation of the no-slip surface. Miniature vortex generators (MVGs) have proven an effective means of producing streamwise streaks for transition delay [8], though relatively large streak amplitudes are necessary to counter their eventual decay through viscous dissipation. The notion motivating this work is that spanwise-wavy walls extended in the streamwise direction can produce a similar effect while avoiding bypass transition resulting from large-amplitude streamwise streaks. Toward that end, six wavy walls are used in a modular test model. When TS waves are excited upstream of the wavy walls, substantial delays in the onset of transition are observed for certain spanwise wavelengths compared with the flat-plate reference case
Temperature-Dependent Chiral-Induced Spin Selectivity Effect: Experiments and Theory
No full textThe theoretical explanation for the chiral-induced spin selectivity effect, in which electrons’ passage through a chiral system depends on their spin and the handedness of the system, remains incomplete. Although most experimental work was performed at room temperature, most of the proposed theories did not include vibrations. Here, we present temperature-dependent experiments and a theoretical model that captures all observations and provides spin polarization values that are consistent with the experimental results. The model includes the vibrational contribution to the spin orbit coupling. It highlights the importance of dissipation and the relation between the effect and the optical activity. The model explains the main features related to the chiral-induced spin selectivity effect and provides a new framework for future calculations and experiments
Coupled-cluster response theory for near-edge x-ray-absorption fine structure of atoms and molecules
No full textBased on an asymmetric Lanczos-chain subspace algorithm, damped coupled cluster linear response functions have been implemented for the hierarchy of coupled cluster (CC) models including CC with single excitations (CCS), CC2, CC with single and double excitations (CCSD), and CCSD with noniterative triple corrected excitation energies CCSDR(3). This work is a first step toward the extension of these theoretical electronic structure methods of well-established high accuracy in UV-vis absorption spectroscopies to applications concerned with x-ray radiation. From the imaginary part of the linear response function, the near K-edge x-ray absorption spectra of neon, water, and carbon monoxide are determined and compared with experiment. Results at the CCSD level show relative peak intensities in good agreement with experiment with discrepancies in transition energies due to incomplete treatment of electronic relaxation and correlation that amount to 1-2 eV. With inclusion of triple excitations, errors in energetics are less than 0.9 eV and thereby capturing 90%, 95%, and 98% of the relaxation-correlation energies for C, O, and Ne, respectively.Funding Agencies|EU|254326|Swedish Research Council|621-2010-5014|National Supercomputer Centre (NSC), Sweden|
Carbon X-ray absorption spectra of fluoroethenes and acetone: A study at the coupled cluster, density functional, and static-exchange levels of theory
No full textNear carbon K-edge X-ray absorption fine structure spectra of a series of fluorine-substituted ethenes
and acetone have been studied using coupled cluster and density functional theory (DFT) polarization
propagator methods, as well as the static-exchange (STEX) approach. With the complex polarization
propagator (CPP) implemented in coupled cluster theory, relaxation effects following the
excitation of core electrons are accounted for in terms of electron correlation, enabling a systematic
convergence of these effects with respect to electron excitations in the cluster operator. Coupled
cluster results have been used as benchmarks for the assessment of propagator methods in DFT as
well as the state-specific static-exchange approach. Calculations on ethene and 1,1-difluoroethene
illustrate the possibility of using nonrelativistic coupled cluster singles and doubles (CCSD) with
additional effects of electron correlation and relativity added as scalar shifts in energetics. It has
been demonstrated that CPP spectra obtained with coupled cluster singles and approximate doubles
(CC2), CCSD, and DFT (with a Coulomb attenuated exchange-correlation functional) yield excellent
predictions of chemical shifts for vinylfluoride, 1,1-difluoroethene, trifluoroethene, as well as good
spectral features for acetone in the case of CCSD and DFT. Following this, CPP-DFT is considered to
be a viable option for the calculation of X-ray absorption spectra of larger π-conjugated systems, and
CC2 is deemed applicable for chemical shifts but not for studies of fine structure features. The CCSD
method as well as the more approximate CC2 method are shown to yield spectral features relating
to π*-resonances in good agreement with experiment, not only for the aforementioned molecules
but also for ethene, cis-1,2-difluoroethene, and tetrafluoroethene. The STEX approach is shown to
underestimate π*-peak separations due to spectral compressions, a characteristic which is inherent
to this method
Coupled cluster study of near-edge x-ray absorption spectra
No full textCoupled cluster methods are considered among the most accurate tools in
electronic structure theory to obtain ground state properties and spectroscopic
properties. Nonetheless, their application to the high-energy region, specifically
to describe the core-excitation phenomena that are behind spectroscopic
techniques like XAS and XCD are very limited.
We present here an implementation of damped response theory based on an
asymmetric Lanczos algorithm within Coupled Cluster theory for the CCS, CC2
and CCSD approximations, We apply it to the simulation of the K-edge X-ray
absorption spectra of the closed-shell 10-electron systems Neon, CH4, H2O, HF
and NH3. The effect of triple excitations on the excitation energies is estimated
by means of the CCSDR(3) approximation. Results are compared with
experiment as well as results obtained with other computational methods, in
particular the Hartree-Fock STEX approach
Job strain in relation to body mass index: pooled analysis of 160,000 adults from 13 cohort studies.
No full textBackground. Evidence of an association between job strain and obesity is mixed, mostly limited to small-scale studies, and does not distinguish between categories of underweight or obesity sub-classes. Objectives. To examine the association between job strain and body mass index (BMI) in a large adult population. Methods. We performed a pooled cross-sectional analysis based on individual-level data from 13 European studies resulting in a total of 161,746 participants (49% men, mean age 43.7 years). Longitudinal analysis with a median follow-up of 4 years was possible in 4 cohort studies (N=42,222). Results. Of the participants, 86,429 were normal weight (BMI 18.5 - 24.9 kg/m2), 2149 underweight (BMI 35 kg/m2) obese. In all, 27,010 (17%) participants reported job strain. In cross-sectional analyses, we found increased odds of job strain among underweight (odds ratio 1.12, 95% confidence interval 1.00 to 1.25), obese class I (1.07, 95% confidence interval 1.02 to 1.12) and classes II-III participants (1.14, 95% confidence interval 1.01 to 1.28) as compared with normalweight participants. In longitudinal analysis, both weight gain and weight loss were related to the onset of job strain during follow-up. Conclusions. In an analysis of European data, we found both weight gain and weight loss to be associated with the onset of job strain, a finding which is consistent with the 'U'-shaped cross-sectional association between job strain and BMI.0Corresponding authors: Solja Nyberg Finnish Institute of Occupational Health Topeliuksenkatu 41 a A, 00250 Helsinki, Finland Email: [email protected] Tel. +358 30 474 2639 Mika Kivimaki University College London Department of Epidemiology and Public Health 1-19 Torrington Place WC1E 6BT London The UK Email: [email protected]: ar.jinfo:eu-repo/semantics/publishedAuthors list: Solja T. Nyberg,1 Katriina Heikkilä,1 Eleonor I. Fransson,2 3 Lars Alfredsson,2 Dirk De Bacquer,4 Jakob B. Bjorner,5 Sébastien Bonenfant,6 7 Marianne Borritz,8 Hermann Burr,9 Annalisa Casini,10 Els Clays,4 Nico Dragano,11 Raimund Erbel,12 Goedele A. Geuskens,13 Marcel Goldberg,6 7 Wendela E. Hooftman,13 Irene L. Houtman,13 Karl-Heinz Jöckel,11 France Kittel,10 Anders Knutsson,14 Markku Koskenvuo,15 Constanze Leineweber,16 Thorsten Lunau,11 Ida E.H. Madsen,5 Linda L. Magnusson Hanson,16 Michael G. Marmot,17 Martin L. Nielsen,18 Maria Nordin,19 Tuula Oksanen,20 21 Jaana Pentti,20 Reiner Rugulies,5 22 Johannes Siegrist,23 Sakari Suominen,24 25 Jussi Vahtera,20 24 26 Marianna Virtanen,1 Peter Westerholm,27 Hugo Westerlund,16 17 28 Marie Zins,6 7 Jane E. Ferrie,17 29 Töres Theorell,16 Andrew Steptoe,17 Mark Hamer,17 Archana Singh-Manoux,7 17 G. David Batty,17 30 and Mika Kivimäki1 17 31; for the IPD-Work Consortium 1. Finnish Institute of Occupational Health, Helsinki, Finland 2. Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden 3. School of Health Sciences, Jönköping University, Jönköping, Sweden 4. Department of Public Health, Ghent University, Ghent, Belgium 5. National Research Centre for the Working Environment, Copenhagen, Denmark 6. Versailles-Saint Quentin University, Versailles, France 7. Inserm U1018, Centre for Research in Epidemiology and Population Health, Villejuif, France 8. Department of Occupational Medicine, Bispebjerg University Hospital, Copenhagen, Denmark 9. Centre for Maritime Health and Safety, Esbjerg, Denmark 10. School of Public Health, Université Libre de Bruxelles, Brussels, Belgium 11. Institute for Medical Informatics, Biometry, and Epidemiology, University Duisburg-Essen, Essen, Germany 12. Department of Cardiology, West-German Heart Center Essen, University Duisburg-Essen, Essen, Germany 13. TNO, Hoofddorp, The Netherlands 14. Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden 15. Department of Public Health, University of Helsinki, Helsinki, Finland 16. Stress Research Institute, Stockholm University, Stockholm, Sweden 17. Epidemiology and Public Health, University College London, London, UK 18. Department of Occupational and Environmental Medicine, Bispebjerg University Hospital, Copenhagen, Denmark 19. Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, Umeå University, Umeå, Sweden 20. Finnish Institute of Occupational Health, Turku, Finland 21. Harvard School of Public Health, Department of Society, Human Development and Health, Boston, USA 22. Department of Public Health and Department of Psychology, University of Copenhagen, Copenhagen, Denmark 23. Department of Medical Sociology, University of Düsseldorf, Düsseldorf, Germany 24. Department of Public Health, University of Turku, Turku, Finland 25. Folkhälsan Research Center, Helsinki, Finland 26. Turku University Hospital, Turku, Finland 27. Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden 28. Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden 29. School of Community and Social Medicine, University of Bristol, Bristol, UK 30. Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK 31. Department of Behavioral Sciences, University of Helsinki, Helsinki, Finlan
From 1p3 to PI3K - Studies of neuroblastoma
No full textNeuroblastoma (NB) is a tumor of the sympathetic nervous system and is the most common extra-cranial tumor of childhood, accounting for 7% of all pediatric malignancies. Despite recent advances in therapeutics, outcome is still fatal for patients with aggressive NB and side-effects of treatment are severe. These are important reasons to gain further knowledge of the biology behind NB.
Aims: The objective of this thesis was to explore genes and gene products that might contribute to initiation and progression of NB and possibly also other malignancies. Main focus has been on the chromosomal region 1p36.2-3 and participants of the PI3K/Akt signaling pathway.
Results: Real-time expression analysis of 30 genes at 1p36.2-3 showed that TNFRSF9 and PIK3CD were down regulated in 1p-deleted compared to non-deleted NB tumors. Studies of the same region showed four genes (ERRFI, CASZ1, RBP7 and PIK3CD) possibly regulated by epigenetically means. Bisulphite sequencing of these four genes in NB cell lines and primary tumors showed that methylation probably is not involved but that histone deacetylation could be implicated in their regulation. Some rare sequence variants were also identified in ERRFI and PIK3CD. PIK3CD encodes a catalytic subunit of the phosphatidylinositol 3-kinase (PI3K) that is involved in activation of Akt. Analysis of mRNA levels in a set of 88 genes associated to PI3K/Akt signaling showed that PDGFRA, PIK3R1, PIK3CD, PRKCBI, PRKCZ and EIF4EBP1 were differentially expressed comparing stage 1-2 to stage 4 NB. At the protein level a stage-dependent expression of the different catalytic isoforms were detected, where levels of p110α were higher in stage 4 tumors compared to stage 1-2, while the opposite was seen for p110δ. Stage 4 NB also had higher levels of phosphorylated Akt (T308 and S473) compared to low stage NB. Furthermore, levels of phosphorylated Akt T308 showed inverse correlation to protein levels of the tumor suppressor Pten.
We have also identified a novel splice variant p37δ, encoded by PIK3CD. Usage of an alternative donor site leads to truncation in the RAS-binding domain and loss of the catalytic domain. Despite the truncation, p37δ interact with RAS and there is a strong correlation between protein levels of p37δ and RAS in primary cells. Expression of p37δ is increased in human cancers of the ovaries and colon and ubiquitous expression of the human p37δ in Drosophila increased the body size of the fly. Furthermore, over-expression of p37δ in HEK-293 and mouse embryonic fibroblasts increased proliferation and invasive properties compared to controls, indicating a role in tumorgenicity.
Conclusion: Analysis of expression levels of genes and proteins could be used for pinpointing important genes and pathways. This thesis has added more knowledge about the genes at 1p36.2-3, a region commonly deleted in NB, as well as the PI3K/Akt signaling in NB. We have also described a new splice variant of p110δ that is expressed in human cancer and increases proliferation in vitro and in vivo
Nation-wide clear-cut mapping in Sweden using ALOS PALSAR strip images
No full textAdvanced Land Observing Satellite (ALOS) Phased Array L-band type Synthetic Aperture Radar (PALSAR) backscatter images with 50 m pixel size (strip images) at HV-polarization were used to map clear-cuts at a regional and national level in Sweden. For a set of 31 clear-cuts, on average 59.9% of the pixels within each clear-cut were correctly detected. When compared with a one-pixel edge-eroded version of the reference dataset, the accuracy increased to 88.9%. With respect to statistics from the Swedish Forest Agency, county-wise clear-felled areas were underestimated by the ALOS PALSAR dataset (between 25% and 60%) due to the coarse resolution. When compared with statistics from the Swedish National Forest Inventory, the discrepancies were larger, partly due to the estimation errors from the plot-wise forest inventory data. In Sweden, for the time frame of 2008–2010, the total area felled was estimated to be 140,618 ha, 172,532 ha and 194,586 ha using data from ALOS PALSAR, the Swedish Forest Agency and the Swedish National Forest Inventory, respectively. ALOS PALSAR strip images at HV-polarization appear suitable for detection of clear-felled areas at a national level; nonetheless, the pixel size of 50 m is a limiting factor for accurate delineation of clear-felled areas
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