| 1. |
- Erni, W., et al.
(author)
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Technical design report for the PANDA (AntiProton Annihilations at Darmstadt) Straw Tube Tracker
- 2013
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In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 49:2
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Journal article (peer-reviewed)abstract
- This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.
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| 2. |
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| 3. |
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| 4. |
- Makonyi, Karoly, et al.
(author)
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Evaluating vacuum phototriodes designed for the PANDA electromagnetic calorimeter
- 2014
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 763, s. 36-43
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Journal article (peer-reviewed)abstract
- In this work properties of a vacuum phototriode (VPT) and preamplifier unit designed for the electromagnetic calorimeter of the PANDA experiment being built at FAIR are investigated. With the use of lead tungstate and lanthanium bromide scintillators the VPT properties are studied at low photon energies, from tens of key in the lanthanium bromide measurements and between 10 MeV and 60 MeV in the lead tungstate measurements. At these energies the noise of the VPT unit can be expected to influence its performance significantly. It is shown that the noise contribution to the measured energy resolution, under optimal conditions, is consistent with a fluctuation of (one standard deviation) approximately 200 electrons at the VPT anode. For a lead tungstate crystal this is equivalent to a noise of 1.2 MeV. For lanthanium bromide this makes it possible to use VPTs for gamma ray spectroscopy above a few hundreds of keV without noticeable effects on the energy resolution compared to measurements with a standard photomultiplier.
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| 5. |
- Marcks von Wurtemberg, Klas, et al.
(author)
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The response of lead-tungstate scintillators (PWO) to photons with energies in the range 13 MeV-64 MeV
- 2012
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 679, s. 36-43
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Journal article (peer-reviewed)abstract
- The response of a matrix of 25 lead tungstate (PWO) scintillator detectors, operated at -25 degrees C, to photons in the range 13 MeV-64 MeV has been measured at the tagged-photon facility at MAX-lab, Lund. The tapered PWO crystals, each with a length of 200 mm and a cross-section of 24.4 x 24.4 mm(2) in the front end, read out by 19 mm photomultiplier tubes, were arranged in a 5 x 5 matrix. The response was measured for photons directed towards the centre of the central crystal as well as for photons directed towards the corner of the central crystal, where four crystals meet. The obtained energy resolution surpasses what has been published so far and is close to the limit given by Poisson statistics and escaped energy. For photons directed towards the centre(corner) of the central crystal the relative energy resolution, defined as (FWHM/2.35)/E-gamma, decreases from 7.3%(11.0%) at E-gamma = 13 MeV to 3.3%(3.6%) at E-gamma = 64 MeV. The reconstructed point of impact of a photon in this energy range is determined with an uncertainty (one standard deviation) of 7.3 +/- 0.1 mm.
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| 6. |
- Abata, E., et al.
(author)
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Study of energy response and resolution of the ATLAS barrel calorimeter to hadrons of energies from 20 to 350 GeV
- 2010
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 621:1-3, s. 134-150
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Journal article (peer-reviewed)abstract
- A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20-350 GeV and beam impact points and angles corresponding to pseudo-rapidity values in the range 0.2-0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit. (C) 2010 Published by Elsevier B.V.
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| 7. |
- Abelev, Betty, et al.
(author)
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Long-range angular correlations on the near and away side in p-Pb collisions at root S-NN=5.02 TeV
- 2013
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In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 29-41
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Journal article (peer-reviewed)abstract
- Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < P-T,P-assoc < P-T,P-trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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| 8. |
- Abelev, Betty, et al.
(author)
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Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV
- 2012
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In: Journal of High Energy Physics. - 1029-8479. ; :11
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Journal article (peer-reviewed)abstract
- The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.
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| 9. |
- Abelev, Betty, et al.
(author)
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Underlying Event measurements in pp collisions at root s=0.9 and 7 TeV with the ALICE experiment at the LHC
- 2012
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In: Journal of High Energy Physics. - 1029-8479. ; :7
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Journal article (peer-reviewed)abstract
- We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.
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| 10. |
- Adler, Jan-Olof, et al.
(author)
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The upgraded photon tagging facility at the MAX IV Laboratory
- 2013
-
In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 715, s. 1-10
-
Journal article (peer-reviewed)abstract
- A description is given of the upgraded photon tagging facility at the MAX IV Laboratory. Two magnetic spectrometers are used to momentum analyze post-bremsstrahlung electrons. The tagged photon range extends from 10 to 180 MeV with an energy resolution of about 300 keV. The system has been operated at rates up to 4 x 10(6) photons s(-1) MeV (-1). Different diagnostic tools are described as well as the experimental program.
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| 11. |
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| 12. |
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| 13. |
- Ganenko, V., et al.
(author)
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Linearly polarized photon beam at MAX-lab
- 2014
-
In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 763, s. 137-149
-
Journal article (peer-reviewed)abstract
- A linearly polarized photon beam has been produced at MAX-lab using the coherent bremsstrahlung of electrons with an energy of 192.6 MeV in a 0.1 mm thick diamond crystal. The intensity and shape of the coherent maxima and their dependence on the crystal orientation are similar to the features observed at higher electron energies (similar to 1 GeV) and are well described by coherent bremsstrahlung theory. The linear polarization of the uncollimated beam at the coherent peak energy approximate to 50-60 MeV is about 20% and can be increased to 40-45% if collimation of half the characteristic angle is used At present the degree of polarization is high enough to allow the study of polarization observables in photo-nuclear reactions at MAX-lab in the energy range from Giant Dipole Resonance up to approximate to 80 MeV. (C) 2014 Elsevier B.V. All rights reserved.
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| 14. |
- Gretarsdottir, Solveig, et al.
(author)
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Genome-wide association study identifies a sequence variant within the DAB2IP gene conferring susceptibility to abdominal aortic aneurysm
- 2010
-
In: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 42:8, s. 71-692
-
Journal article (peer-reviewed)abstract
- We performed a genome-wide association study on 1,292 individuals with abdominal aortic aneurysms (AAAs) and 30,503 controls from Iceland and The Netherlands, with a follow-up of top markers in up to 3,267 individuals with AAAs and 7,451 controls. The A allele of rs7025486 on 9q33 was found to associate with AAA, with an odds ratio (OR) of 1.21 and P = 4.6 x 10(-10). In tests for association with other vascular diseases, we found that rs7025486[A] is associated with early onset myocardial infarction (OR = 1.18, P = 3.1 x 10(-5)), peripheral arterial disease (OR = 1.14, P = 3.9 x 10(-5)) and pulmonary embolism (OR = 1.20, P = 0.00030), but not with intracranial aneurysm or ischemic stroke. No association was observed between rs7025486[A] and common risk factors for arterial and venous diseases-that is, smoking, lipid levels, obesity, type 2 diabetes and hypertension. Rs7025486 is located within DAB2IP, which encodes an inhibitor of cell growth and survival.
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| 15. |
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| 16. |
- Hansen, Niklas, 1974-
(author)
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Arbetsvillkor i privat och offentlig sjukvård : Implikationer för personalens attityder och hälsa
- 2014
-
Doctoral thesis (other academic/artistic)abstract
- Omvandlingen av sjukvården mot marknadisering och nya driftsformer har huvudsakligen genomförts utifrån ekonomiska och politiska föresatser om ökad effektivitet och vårdkvalitet. Goda arbetsvillkor för personalen är en viktig förutsättning för förverkligandet av dessa mål. Givet det oklara kunskapsläget kring psykologiska implikationer av omställningen i välfärdssektorns styrning var syftet med avhandlingen att studera olika aspekter av arbetsvillkor samt arbetsrelaterade attityder och hälsa i privat, bolagiserad och förvaltningsdriven sjukvård. Det gjordes genom att undersöka hur krav och resurser i arbetet förhåller sig till uppkomsten och utbredningen av utbrändhet hos sjuksköterskor, betydelsen av kontroll i och över arbetet för de anställdas arbetstrivsel samt hur motivationsbaserade kognitioner av bemyndigande hos vårdpersonal förändras vid privatisering och relaterar till attityder och hälsa. De empiriska studierna inkluderade såväl tvärsnittliga som longitudinella enkätdata från tre svenska akutsjukhus med olika driftsform. Resultaten visade högre nivåer av utbrändhet hos sjuksköterskor i privat jämfört med förvaltningsdrivet sjukhus. För arbetstrivsel fanns ingen nivåskillnad mellan de tre driftsformerna. Krav i arbetet hängde samman med högre utbrändhetsnivåer och lägre arbetstrivsel. Flera resurser var förenade med lägre grad av utbrändhet medan kontroll hängde samman med högre trivsel. Vid en förändring från bolagiserad till privat driftsform var vårdpersonalens bemyndigande relativt stabilt. Dock fanns efter privatiseringen en tendens till standardisering då graden av bemyndigande blev mer lika. Likaså skedde en statusmässig differentiering i bemyndigande mellan yrkesgrupperna genom att flera med låg status fick mindre bemyndigande. Sammantaget pekar avhandlingen på fler likheter än skillnader mellan driftsformerna vilket antyder att driftsform tycks ha mindre betydelse för såväl nivå som betydelse av arbetsvillkor för personalens attityder och hälsa.
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| 17. |
- Helgadottir, Anna, et al.
(author)
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Apolipoprotein(a) Genetic Sequence Variants Associated With Systemic Atherosclerosis and Coronary Atherosclerotic Burden But Not With Venous Thromboembolism
- 2012
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In: Journal of the American College of Cardiology. - : Elsevier BV. - 0735-1097 .- 1558-3597. ; 60:8, s. 722-729
-
Journal article (peer-reviewed)abstract
- Objectives The purpose of this study is investigate the effects of variants in the apolipoprotein(a) gene (LPA) on vascular diseases with different atherosclerotic and thrombotic components. Background It is unclear whether the LPA variants rs10455872 and rs3798220, which correlate with lipoprotein(a) levels and coronary artery disease (CAD), confer susceptibility predominantly via atherosclerosis or thrombosis. Methods The 2 LPA variants were combined and examined as LPA scores for the association with ischemic stroke (and TOAST [Trial of Org 10172 in Acute Stroke Treatment] subtypes) (effective sample size [n(e)] = 9,396); peripheral arterial disease (n(e) = 5,215); abdominal aortic aneurysm (ne = 4,572); venous thromboembolism (ne = 4,607); intracranial aneurysm (ne = 1,328); CAD (n(e) = 12,716), carotid intima-media thickness (n = 3,714), and angiographic CAD severity (n = 5,588). Results LPA score was associated with ischemic stroke subtype large artery atherosclerosis (odds ratio [OR]: 1.27; p = 6.7 X 10(-4)), peripheral artery disease (OR: 1.47; p = 2.9 x 10(-14)), and abdominal aortic aneurysm (OR: 1.23; p = 6.0 x 10(-5)), but not with the ischemic stroke subtypes cardioembolism (OR: 1.03; p = 0.69) or small vessel disease (OR: 1.06; p = 0.52). Although the LPA variants were not associated with carotid intima-media thickness, they were associated with the number of obstructed coronary vessels (p = 4.8 x 10(-12)). Furthermore, CAD cases carrying LPA risk variants had increased susceptibility to atherosclerotic manifestations outside of the coronary tree (OR: 1.26; p = 0.0010) and had earlier onset of CAD (-1.58 years/allele; p = 8.2 x 10(-8)) than CAD cases not carrying the risk variants. There was no association of LPA score with venous thromboembolism (OR: 0.97; p = 0.63) or intracranial aneurysm (OR: 0.85; p = 0.15). Conclusions LPA sequence variants were associated with atherosclerotic burden, but not with primarily thrombotic phenotypes. (J Am Coll Cardiol 2012; 60: 722-9) (C) 2012 by the American College of Cardiology Foundation
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| 18. |
- Kallesoe, Christian, et al.
(author)
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Integration, gap formation, and sharpening of III-V heterostructure nanowires by selective etching
- 2010
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In: Journal of Vacuum Science and Technology B. - : American Vacuum Society. - 1520-8567. ; 28:1, s. 21-26
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Journal article (peer-reviewed)abstract
- Epitaxial growth of heterostructure nanowires allows for the definition of narrow sections with specific semiconductor composition. The authors demonstrate how postgrowth engineering of III-V heterostructure nanowires using selective etching can form gaps, sharpening of tips, and thin sections simultaneously on multiple nanowires. They investigate the potential of combining nanostencil deposition of catalyst, epitaxial III-V heterostructure nanowire growth, and selective etching, as a road toward wafer scale integration and engineering of nanowires with existing silicon technology. Nanostencil lithography is used for deposition of catalyst particles on trench sidewalls and the lateral growth of III-V nanowires is achieved from such catalysts. The selectivity of a bromine-based etch on gallium arsenide segments in gallium phosphide nanowires is examined, using a hydrochloride etch to remove the III-V native oxides. Depending on the etching conditions, a variety of gap topologies and tiplike structures are observed, offering postgrowth engineering of material composition and morphology.
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| 19. |
- Krarup, Anne L., et al.
(author)
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Randomised clinical trial: the efficacy of a transient receptor potential vanilloid 1 antagonist AZD1386 in human oesophageal pain.
- 2011
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In: Alimentary pharmacology & therapeutics. - : Wiley. - 1365-2036 .- 0269-2813. ; 33:10, s. 1113-22
-
Journal article (peer-reviewed)abstract
- Background Many patients with gastro-oesophageal reflux disease (GERD) are hypersensitive to heat and acid and may respond insufficiently to standard treatment. Antagonists of the heat and acid receptor ‘transient receptor potential vanilloid 1’(TRPV1) are a potential drug class for GERD treatment. Aim To investigate the effect of a TRPV1 antagonist (AZD1386) on experimentally induced oesophageal pain. Methods Twenty-two healthy men (20–31 years) participated in this randomised, placebo-controlled, double-blinded, crossover study examining the effects of a single-dose oral AZD1386 (30 and 95 mg). Subjects were block-randomised. On treatment days, participants were stimulated with painful heat, distension, electrical current and acid in the oesophagus. Heat and pressure pain on the forearm were somatic control stimuli. Data analysis: intention-to-treat. Results A total of 21 participants completed the protocol and 1 voluntarily discontinued. In the oesophagus, both 30 and 95 mg of AZD1386 increased pain thresholds to heat stimuli 23% [95% confidence interval (CI): 10–38%] and 28%, respectively (CI: 14–43%). The skin heat tolerance was increased 2.1 °C (CI: 1.1–3.2 °C) after 30 mg AZD1386 and 4.0 °C (CI: 3.0–5.0 °C) after 95 mg. Heat analgesia persisted for 2.5 h. Pain thresholds to the other stimuli were unaffected by AZD1386. 50% reported ‘feeling cold’ and body temperature increased in all subjects exposed to 30 and 95 mg AZD1386 (mean increase 0.4 ± 0.3 °C and 0.7 ± 0.3 °C, respectively, P < 0.05). Conclusions AZD1386 increased oesophageal and skin heat pain thresholds and had a safe adverse-event profile. This drug class may have a potential for treatment of GERD (ClinicalTrials.gov identifier: NCT00711048).
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| 20. |
- Krarup, Anne L., et al.
(author)
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Randomized clinical trial: inhibition of the TRPV1 system in patients with nonerosive gastroesophageal reflux disease and a partial response to PPI treatment is not associated with analgesia to esophageal experimental pain.
- 2013
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In: Scandinavian journal of gastroenterology. - : Informa UK Limited. - 1502-7708 .- 0036-5521. ; 48:3, s. 274-84
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Journal article (peer-reviewed)abstract
- Abstract Objective. Many patients with nonerosive reflux disease (NERD) have insufficient relief on proton pump inhibitors (PPIs). Some patients have a hypersensitive esophagus and may respond to transient receptor potential vanilloid 1 (TRPV1) antagonists. Aim. To investigate the effect of the TRPV1 antagonist AZD1386 on experimental esophageal pain in NERD patients. Material and methods. Enrolled patients had NERD and a partial PPI response (moderate-to-severe heartburn or regurgitation ≥3 days/week before enrolment despite ≥6 weeks' PPI therapy). Fourteen patients (21-69 years, 9 women) were block-randomized into this placebo-controlled, double-blinded, crossover study examining efficacy of a single dose (95 mg) of AZD1386. On treatment days, each participant's esophagus was stimulated with heat, distension, and electrical current at teaching hospitals in Denmark and Sweden. Heat and pressure pain served as somatic control stimuli. Per protocol results were analyzed. Results. Of 14 randomized patients, 12 were treated with AZD1386. In the esophagus AZD1386 did not significantly change the moderate pain threshold for heat [-3%, 95% confidence interval (CI), -22;20%], distension (-11%, 95% CI, -28;10%), or electrical current (6%, 95% CI, -10;25%). Mean cutaneous heat tolerance increased by 4.9°C (95% CI, 3.7;6.2°C). AZD1386 increased the maximum body temperature by a mean of 0.59°C (95% CI, 0.40-0.79°C), normalizing within 4 h. Conclusions. AZD1386 had no analgesic effect on experimental esophageal pain in patients with NERD and a partial PPI response, whereas it increased cutaneous heat tolerance. TRPV1 does not play a major role in heat-, mechanically and electrically evoked esophageal pain in these patients. ClinicalTrials.gov identifier: D9127C00002.
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| 21. |
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| 22. |
- Ley, David, et al.
(author)
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Longitudinal infusion of insulin-like growth factor-I and IGF-binding protein-3 complex to five preterm infants: pharmacokinetics and short term safety.
- 2013
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In: Pediatric Research. - : Springer Science and Business Media LLC. - 0031-3998 .- 1530-0447. ; 63:1, s. 68-74
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Journal article (peer-reviewed)abstract
- Background:In preterm infants, low levels of insulin like growth factor-I (IGF-I) and IGF binding protein 3 (IGFBP-3) are associated with impaired brain growth and retinopathy of prematurity (ROP).Treatment with IGF-I/IGFBP-3 may be beneficial for brain development and decrease prevalence of ROP.Methods:In a phase II pharmacokinetic and safety study, five infants (3 girls) with a median (range) gestational age (GA) of 26+6 (26+0 - 27+2) weeks and birth weight (BW) of 990 (900-1212) g received continuous intravenous infusion of rhIGF-I/rhIGFBP-3. Treatment was initiated during the first postnatal day and continued for median (range) 168h (47-168) in doses between 21 - 111 µg/kg/24h.Results:Treatment with rhIGF-I/rhIGFBP-3 was associated with higher serum IGF-I and IGFBP-3 concentrations (p<0.001) than model-predicted endogenous levels. Out of 74 IGF-I samples measured during study drug infusion, 37 (50%) were within target range, 4 (5%) above and 33 (45%) were below. Predicted dose of rhIGF-I/rhIGFBP-3 to establish circulating levels of IGF-I within the intrauterine range in a 1000g infant was 75-100 µg/kg/24h. No hypoglycemia or other adverse effects were recorded.Conclusion:Continuous intravenous infusion of rhIGF-I/rhIGFBP-3 was effective in increasing serum concentrations of IGF-I and IGFBP-3. Administration during study was safe.Pediatric Research (2012); doi:10.1038/pr.2012.146.
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| 23. |
- Lindskog Stokland, Birgitta, 1959, et al.
(author)
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Changes in molar position with missing opposed and/or adjacent tooth: a 12-year study in women
- 2012
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In: Journal of Oral Rehabilitation. - 0305-182X. ; 39:2, s. 136-43
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Journal article (peer-reviewed)abstract
- Summary The aim of this study was to radiographically analyse long-term changes in (i) overeruption of unopposed molars and (ii) tipping of molars with a mesial edentulous space, and whether there is an interaction between the two events. A further aim was to analyse if loss of alveolar bone height might influence overeruption and tipping. The sample consisted of panoramic radiographs taken at an interval of 12years of 292 subjects from a prospective population study of women. The panoramic radiographs were scanned and analysed. Changes in tipping, overeruption and alveolar bone height of molars and control teeth were measured. The results showed that unopposed molars were more commonly found in the upper jaw and that unopposed molars showed 4·9 times higher risk of overeruption of ≥2mm (95% CI 1·5-15·3) than opposed molars during the 12-year observation period. The average overeruption for the unopposed molars was 4·5% (s.d. 7·6), which corresponds to approximately 0·9mm. The degree of overeruption increased with decreased bone support. Molars with a mesial edentulous space were most prevalent in the lower jaw, but neither an edentulous space nor alveolar bone level/bone level change were found to have a significant effect on tipping of the molars. The average mesial tipping was 0·8° (s.d. 5·6). In conclusion, unopposed molars showed a significantly increased risk for overeruption. Molars facing a mesial edentulous space showed a low risk for mesial tipping, but a significant interaction between overeruption and tipping was identified.
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| 24. |
- Lindskog Stokland, Birgitta, 1959, et al.
(author)
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Molar position associated with a missing opposed and/or adjacent tooth: a follow up study in women
- 2013
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In: Swedish Dental Journal. - 0347-9994. ; 37:2, s. 97-105
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Journal article (peer-reviewed)abstract
- The purpose of the study was to assess (i) the degree of overeruption of molars lacking opposed teeth and (ii) the inclination of molars with a mesial edentulous space and also to study (iii) changes during a 12 year period. The subject sample originated from the prospective population study of women in Gothenburg, Sweden where scanned panoramic radiographs taken with an interval of 12 years were analysed. Tipping as well as overeruption were scored on the two images according to a five-level scale. Sixty-seven subjects fulfilled the inclusion criteria at baseline and were referred to as "the non-extraction group". Further 35 subjects had lost the opposed and/or the adjacent tooth/teeth during the 12-year follow-up period: "the extraction-group". These groups were studied separately and a comparison between these groups was performed. The prevalence of molars tipped more than 15 degrees at baseline was 17.1 % in the upper jaw and 44.3 % in the lower jaw, in the non-extraction group. At baseline overeruption was seen in 25 % of the unopposed upper molars and none of lower molars in the non-extraction group. The prevalence of tipping and overeruption was statistical significant less in the extraction group (P<0.01), than in the non-extraction group at baseline, but at follow-up no statistical significant group differences existed. -The prevalence of tipped molars facing a mesial edentulous space and overerupted unopposed molars increased in adults during the 12-year period but the changes were small. -Overeruption and tipping is most pronounced immediately after extractions.
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| 25. |
- Lund, Magnus, et al.
(author)
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Characteristics of summer-time energy exchange in a high Arctic tundra heath 2000-2010
- 2014
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In: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 66
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Journal article (peer-reviewed)abstract
- Global warming will bring about changes in surface energy balance of Arctic ecosystems, which will have implications for ecosystem structure and functioning, as well as for climate system feedback mechanisms. In this study, we present a unique, long-term (2000-2010) record of summer-time energy balance components (net radiation, R-n; sensible heat flux, H; latent heat flux, LE; and soil heat flux, G) from a high Arctic tundra heath in Zackenberg, Northeast Greenland. This area has been subjected to strong summer-time warming with increasing active layer depths (ALD) during the last decades. We observe high energy partitioning into H, low partitioning into LE and high Bowen ratio (beta = H/LE) compared with other Arctic sites, associated with local climatic conditions dominated by onshore winds, slender vegetation with low transpiration activity and relatively dry soils. Surface saturation vapour pressure deficit (D-s) was found to be an important variable controlling within-year surface energy partitioning. Throughout the study period, we observe increasing H/R-n and LE/R-n and decreasing G/R-n and beta, related to increasing ALD and decreasing soil wetness. Thus, changes in summer-time surface energy balance partitioning in Arctic ecosystems may be of importance for the climate system.
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| 26. |
- Margaryan, Ashot, et al.
(author)
-
Low-Pressure MWPC System for the detection of Alpha-Particles and Fission Fragments
- 2010
-
In: Armenian Journal of Physics. - 1829-1171. ; 3:4, s. 282-291
-
Journal article (peer-reviewed)abstract
- A low-pressure, position-sensitive, multi-wire proportional chamber (LPMWPC) system with an active area 12×12 cm 2 for the detection of heavy nuclear fragments, has been developed for use in tagged photon beam experiments. The LPMWPC system can be operated in single as well as double step operational modes. In the case of double step operational mode with a high gas amplification factor, signals from α-particles reside well above the electronic noise. Typical energy loss spectra of alpha particles and fission fragments (FF) obtained from a 252 Cf source are shown and discussed. The pulse height distributions of α-particles have a Landau distribution shape, while the pulse height distribution of FFs differs from Gaussian shape. It has long tails at both low-and high-energy sides. The average pulse height ratio of alpha particles and FF's is close to the theoretical value and amounts to about 1/80.
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| 27. |
- Myers, L. S., et al.
(author)
-
Compton scattering from C-12 using tagged photons in the energy range 65-115 MeV
- 2014
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 89:3
-
Journal article (peer-reviewed)abstract
- Elastic scattering of photons from C-12 has been investigated using quasimonoenergetic tagged photons with energies in the range 65-115 MeV at laboratory angles of 60 degrees, 120 degrees, and 150 degrees. at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed to provide an estimate of the sensitivity of the C-12(gamma,gamma)C-12 cross section to the bound- nucleon polarizabilities.
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| 28. |
- Myers, L S, et al.
(author)
-
Measurement of compton scattering from the deuteron and an improved extraction of the neutron electromagnetic polarizabilities.
- 2014
-
In: Physical Review Letters. - 1079-7114. ; 113:26
-
Journal article (peer-reviewed)abstract
- The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data-and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here, we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world data set. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using chiral effective field theory with dynamical Δ(1232) degrees of freedom shows the data are consistent with and within the world data set. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities, and combining them with a recent result for the proton, we obtain the neutron polarizabilities as α_{n}=[11.55±1.25(stat)±0.2(BSR)±0.8(th)]×10^{-4} fm^{3} and β_{n}=[3.65∓1.25(stat)±0.2(BSR)∓0.8(th)]×10^{-4} fm^{3}, with χ^{2}=45.2 for 44 degrees of freedom.
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| 29. |
-
Ojämlikhetens nya geografi. Texter om stadens och rummets förändringar under den globala kapitalismen
- 2011
-
Editorial collection (other academic/artistic)abstract
- Vem har rätt till staden i en tid präglad av ökad ojämlikhet, gentrifiering och konkurrens städer emellan? Hur har nyliberalismen berett rum för kapitalismen genom att frånta människor deras platser och rättigheter? Vilka är förutsättningarna för samhällsförändring? I Ojämlikhetens nya geografi analyserar kulturgeografen David Harvey den globala kapitalismens nya rumslighet och den ojämlikhet som den skapar. Han diskuterar hur vår kunskap om dessa processer kan bidra till att både stärka jämlikheten och förbättra miljön. Boken innehåller några av Harveys mest betydande texter och teorier. Här finns både nyskrivet och äldre material från ett författarskap som under fyra årtionden gett oss viktiga inblickar i kapitalismens rumsliga dimension.
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| 30. |
- Preston, M. F., et al.
(author)
-
Tests of the Monte Carlo Simulation of the Photon-Tagger Focal-Plane Electronics at the MAX IV Laboratory
- 2014
-
In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 744, s. 17-17
-
Journal article (peer-reviewed)abstract
- Rate-dependent effects in the electronics used to instrument the tagger focal plane at the MAX IV Laboratory were recently investigated using the novel approach of Monte Carlo simulation to allow for normalization of high-rate experimental data acquired with single-hit time-to-digital converters (TDCs). The instrumentation of the tagger focal plane has now been expanded to include multi-hit TDCs. The agreement between results obtained from data taken using single-hit and multi-hit TDCs demonstrate a thorough understanding of the behavior of the detector system.
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| 31. |
- Sarwar, Nadeem, et al.
(author)
-
Interleukin-6 receptor pathways in coronary heart disease : a collaborative meta-analysis of 82 studies
- 2012
-
In: The Lancet. - New York, NY, USA : Elsevier. - 0140-6736 .- 1474-547X. ; 379:9822, s. 1205-1213
-
Journal article (peer-reviewed)abstract
- Background: Persistent inflammation has been proposed to contribute to various stages in the pathogenesis of cardiovascular disease. Interleukin-6 receptor (IL6R) signalling propagates downstream inflammation cascades. To assess whether this pathway is causally relevant to coronary heart disease, we studied a functional genetic variant known to affect IL6R signalling. Methods: In a collaborative meta-analysis, we studied Asp358Ala (rs2228145) in IL6R in relation to a panel of conventional risk factors and inflammation biomarkers in 125 222 participants. We also compared the frequency of Asp358Ala in 51 441 patients with coronary heart disease and in 136 226 controls. To gain insight into possible mechanisms, we assessed Asp358Ala in relation to localised gene expression and to postlipopolysaccharide stimulation of interleukin 6. Findings: The minor allele frequency of Asp358Ala was 39%. Asp358Ala was not associated with lipid concentrations, blood pressure, adiposity, dysglycaemia, or smoking (p value for association per minor allele >= 0.04 for each). By contrast, for every copy of 358Ala inherited, mean concentration of IL6R increased by 34.3% (95% CI 30.4-38.2) and of interleukin 6 by 14.6% (10.7-18.4), and mean concentration of C-reactive protein was reduced by 7.5% (5.9-9.1) and of fibrinogen by 1.0% (0.7-1.3). For every copy of 358Ala inherited, risk of coronary heart disease was reduced by 3.4% (1.8-5.0). Asp358Ala was not related to IL6R mRNA levels or interleukin-6 production in monocytes. Interpretation: Large-scale human genetic and biomarker data are consistent with a causal association between IL6R-related pathways and coronary heart disease.
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| 32. |
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| 33. |
- Wallberg, Petra, et al.
(author)
-
Evaluation of Swedish National Screening Studies 2007-2012
- 2014
-
Reports (other academic/artistic)abstract
- IVL Swedish Environmental Research Institute has made an assessment of the need for follow-up of Swedish national screening studies performed during the years 2007-2012. Defined tasks were to select approximately 25 substances for risk evaluation and to identity if there is a need for a more in-depth evaluation for any of these substances, and to select approximately 8 screening studies where there are needs for follow-up studies. Forty screening studies were performed during the selected time period and the total number of screened substances amounted to 540 individual chemical substances, groups of substances and metals. Substances not prioritized for risk evaluation were: classical well known substances ( e.g . PCBs, dioxins, metals) and their metabolites; substances with low detection frequency in biotic < 50%; substances listed on as a priority substance within the Water Framework Directive (WFD) and substances treated as a group rather than as individuals ( e.g . unintentionally produced substances). Finally 22 substances remained for risk evaluation. Two brominated flame retardants (HBB and PBEB), two UV-filters (OTNE and AC) and one benzotriazole (UV 327) were suggested to be considered for an in depth evaluation. The screening studies not recommended for follow-up were: studies where a follow-up already had been done; studies concerning priority substances in the WFD; studies where the authors concluded that the substances do not pose a risk or that no issues remain at present; studies where follow-up studies, research projects and/or literature reviews are ongoing, and studies where method development is ongoing or needed before further screening can be performed. Six studies were not prioritized for a new screening but need to be considered further. Finally, the studies selected to be prioritized for further screening included the following substances; UV-filters, pharmaceuticals, fragrances, benzothiazoles and benzotriazoles, platinum group metals, organophosphate esters, metabolites of PAHs and phthalates in urine, and antioxidants and their degradation products.
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| 34. |
- Wallberg, Petra, et al.
(author)
-
Evaluation of Swedish National Screening Studies 2007-2012 Assessment of the Need for Follow-up
- 2014
-
Reports (other academic/artistic)abstract
- In October 2013 the Swedish Environmental Research Institute IVL were assigned by the Swedish EPA to make an assessment of the need for further follow-up of Swedish national screening studies performed during the years 2007-2012. Defined tasks were to: Select approximately 25 substances for risk evaluation and to identity if there is a need for a more in-depth evaluation for any of these substances. Select approximately 8 screening studies where there are needs for follow-up studies and rank them in order of preference. The need for method development should also be identified.Forty screening studies were performed during the selected time period and the total number of screened substances amounted to 540 individual chemical substances, groups of substances and metals (Appendix 1, Table 1). For the Swedish EPA it was important that each step in the selection procedure was accounted for in the report.The first set criteria for reduction of substances not relevant forrisk evaluation were: Classical well known substances (e.g. PCBs, dioxins, metals) or are metabolites. Substances with low detection frequency in biotic samples including humans, < 50%. Priority substances within the Water Framework Directive (WFD) and therefore considered as well known Substances that should be treated as a group rather than as individual compounds,e.g. unintentionally produced substances.After this selection step, 22 substances remained on the list (Table 3). Two brominated flame retardants (HBB and PBEB), two UV-filters (OTNE and AC) and one benzotriazole (UV 327) was suggested for an in depth evaluation.The forty screening studies were evaluated for follow up (Table 2). The set of criteria for studies not selected for a follow-up were: A follow up study has already been performed (7 studies). The screening study concerned priority substances within the WFD (2 studies). The screening showed that the substances do not pose any risk or that no issues remain at present (5 studies). Follow-up studies, research projects and/or literature reviews are ongoing (9 studies). Method development is ongoing or needed before further screening (2 studies).Evaluation of Swedish National Screening Studies 2007-2012 IVL report B2159 Assement of the Need for Follow-upSix studies were not prioritized for a new screening but needs to be considered (see Appendix 3, Table 1 for comments). Finally, nine studies, of which two concerns fragrances, where prioritized for further screening.Below the screening studies are listed and commented in priority order where the first three are of most relevance. (See the report for each screening study for a more extended presentation.)National screening, 2009, UV filtersThe screening results show that the occurrence of UV-filters is widespread in surface water from background areas and in the urban environment. Several of the included UV-filters pose a potential risk to the environment. The highest concentrations occur during the reproductive season and the use is not likely to decrease. The industry of personal care products may be perceptive to new information on risks concerning these substances. A new screening should therefore be preceded by a review on use, ecotoxicity and persistence of UV filters.National screening, 2010, PharmaceuticalsThere is an increasing amount of evidence that pharmaceuticals may cause effects in the environment. Three pharmaceutical substances are on the watch-list within the WFD. Thus, more data is requested concerning environmental concentrations. The results in the screening show that removal rates of some pharmaceuticals in WWTP are difficult to determine. Method development and a follow-up screening would contribute to a better assessment of predicted environmental concentrations. Furthermore, the knowledge of the fate of pharmaceuticals in sewage sludge, in soil receiving sludge amendments and subsequent uptake in biota is limited. In a recent screening conducted in Norway the authors highlighted the number of pharmaceuticals detected in prawns, fish and birds (> 30; Miljødirektoratet 2013).National screening, 2008, Musk substances and metabolitesNational screening, 2011 Fragances; OTNE, acetyl cedrene and diphenyleterFragrance substances and their metabolites are widespread in the environment and were detected in surface water, sediment, fish, soil (to which sludge has been amended) and in breast milk. Many of these substances can bioaccumlate and the data indicate that these substances are persistent and that atmospheric long range transport occurs. Ecotoxicological data are limited for many of these substances. A new screening should be preceded by a literature review regarding usage and relevant substances. Fragrances that have been reported to occur in human samples should be included, and screening in human breast milk repeated. Furthermore, we suggest that the air compartment should be included.National screening, 2011 Benzothiazoles, benzenediamines, dicyclohexylamine and benzotriazolesA widespread occurrence of benzotriazoles was reported, both at background and urban areas. However, as no ecotoxicity data were found, no assessment of risk could be made.The result of the screening was also reflected by analytical challenges of these substances. Benzothiazoles and benzotriazoles have recently been reported in different matrixes in a non-target screening in Norway (Miljødirektoratet, 2013).A follow up screening is recommended, but before the need for method development should be assessed.National screening, 2007, Platinum group metalsThe screening study included the platinum group elements (PGEs) platinum (Pt), palladium (Pd) and rhodium (Rh). Pd was almost consistently detected in the biological samples (fish, moose, cow, white tailed eagle and plants). The concentrations of Pd in groundwater were higher than in run-off water ponds. The authors concluded that the results in this study do not indicate that PGEs pose a risk to humans or the aquatic ecosystem, but that this conclusion is based on lack of reference values and proper risk assessments for humans as well as biota.National screening, 2007, Organophosphate esters in human breast milk and fish in Swedish lakes and coastal areasThe results from this study indicate that environmental load of organophosphate esters (OP) are high and that there is chronic exposure of OP. The authors concluded that the knowledge of the effects and the fate of these substances is limited and that more information on sources, degradation and uptake in biota is needed. A literature survey is suggested before decision on the selection of substances and environmental matrices for a follow up. Air and dust are likely to be important exposure routes for humans.National screening, 2008, Exposure and effect screening in urine of womenThe results show that urine is a good matrix for human biomonitoring of many organic chemicals and metals. The authors suggested follow-up studies on a selection of PAHs and phthalate metabolites and a larger test group could better establish factors influencing metabolite concentration in urine. We suggest that based on the outcome of other screening studies, also metabolites of other organic chemicals and metals,e.g. silver and metabolites of fragrances, should be considered.National screening, 2007, Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionateAvailable data for the aquatic environment indicates that octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate has low acute toxicity but no chronic tests have been done, and, thus, it is not possible to determine the risk. Given the persistent properties and the large production volume a follow up study is recommended, also including degradation products. It may be of interest to also include other antioxidants of similar chemical structure and their degradation products.
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| 35. |
- Walther, Charles, et al.
(author)
-
Biphasic, Hyperdiploid Breast Tumors in Children: A Distinct Entity?
- 2012
-
In: Journal of Pediatric Hematology/Oncology. - 1536-3678.
-
Journal article (peer-reviewed)abstract
- BACKGROUND:: The differentiation between a giant fibroadenoma and a phyllodes tumor can be a precarious diagnostic task. However, the distinction between the 2 lesions is important to make, especially since the latter can be malignant and consequently the prognoses differ. PROCEDURE:: We used various genetic approaches to study a breast tumor showing features of both entities in a 10-year-old girl with a congenital cerebral malformation and diabetes mellitus. RESULTS:: Cytogenetic analysis of cultured tumor cells from 3 different samples revealed a hyperdiploid karyotype: 50-54,XX,+5,+13,+17,+18,+19,+20,+21. High-resolution single nucleotide polymorphism array analysis not only confirmed the trisomies, but also revealed uniparental disomy (UPD) for chromosomes 10, 11, and 22. A consequence of UPD11 was a homozygous deletion in chromosome band 11p15 affecting the PARVA gene; this gene was hemizygously lost in constitutional DNA. Extended analysis of the family revealed that the deletion was inherited, but it did not segregate with breast tumors or congenital malformations. CONCLUSIONS:: Combined with the literature data, the findings in the present case strongly suggest that biphasic tumors with high hyperdiploid karyotypes constitute a distinct clinicomorphologic subgroup of benign breast tumors, being particularly common among young children.
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| 36. |
- Wang-Hansen, Carolin, 1982, et al.
(author)
-
Characterization of particulate matter from direct injected gasoline engines
- 2013
-
In: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 56:1-8, s. 446-451
-
Journal article (peer-reviewed)abstract
- The reactivity and reaction kinetics of particulate matter (PM) from direct injected gasoline (GDI) engines has been studied by O2 and NO2 based temperature programmed and isothermal step-response experiments, and the PM nano-structure has been characterized using HRTEM. The reactivity of the PM samples collected in filters during on-road driving was found to increase in the following order: Printex U\diesel\gasoline PI & gasoline DI\ethanol for O2 based combustion. The activation energies for O2 and NO2 based oxidation of PM collected from a GDI engine in an engine bench set-up was estimated to 146 and 71 kJ/mol respectively, which is comparable to corresponding values reported for diesel and model soot. Similar nano-structure features (crystallites plane dimensions, curvature and relative orientation) as observed for diesel soot were observed for gasoline PM.
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| 37. |
- Wang-Hansen, Carolin, 1982, et al.
(author)
-
Experimental Method for Kinetic Studies of Gas-Solid Reactions: Oxidation of Carbonaceous Matter
- 2011
-
In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:32, s. 16098-16108
-
Journal article (peer-reviewed)abstract
- A methodology comprising careful consideration of sample preparation, reactor design, experimental procedures, and data evaluation routines for precise analysis of the kinetics of gas␣solid reactions, specifically the oxidation of carbonaceous materials, has been developed and validated. The wellcontrolled solvent-free deposition of the carbonaceous material onto cordierite monolith substrates ensures experimental stud- ies in the absence of diffusion limitations, temperature gradients, and hot zones. These critical aspects are supported also by theoretical considerations. Temperature-programmed oxida- tion and isothermal oxygen step-response experiments in a continuous gas-flow reactor using a homogeneous synthetic carbon- black material demonstrate excellent reproducibility, and the conversion profiles agree well with previously reported data. An independent set of global kinetic parameters was estimated for each 5% subconversion interval using linear regression such that the conversion dependence of each parameter could be analyzed separately and compared to previously published data. The results show that the evolution of reactive carbons cannot be described with a single global reaction order. This is supported by intermittent ex situ measurements of the specific surface area of the carbon-black material during the course of isothermal oxidation, which reveals a developing microporous structure at high conversions. Physically the changes in carbon reaction order are interpreted as changes in fraction of accessible reactive carbon atoms during progressing oxidation. Moreover, at high conversions, the carbon reaction order approaches 0.7 implying not only that the evolution of the concentration of reactive carbon atoms is proportional to the external surface area of shrinking spheres but also that these spheres have approximately the same size.
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| 38. |
- Wiman, Magnus, et al.
(author)
-
Cellulose accessibility determines the rate of enzymatic hydrolysis of steam-pretreated spruce.
- 2012
-
In: Bioresource Technology. - : Elsevier BV. - 1873-2976 .- 0960-8524. ; 126C, s. 208-215
-
Journal article (peer-reviewed)abstract
- Spruce chips steam-pretreated at various conditions, according to a central composite design, were used for investigating the influence of pretreatment conditions on enzymatic hydrolysis, accounting for the individual effects of pretreatment temperature (194-220°C), time (3-11min) and sulfur dioxide uptake (0.7-2.5%). The materials were analyzed for several surface characteristics, including IR absorption, enzyme adsorption capacity, total surface area, cellulosic surface area, and cellulosic pore sizes. This work showed a clear correlation between rate of enzymatic hydrolysis and specific surface area. Although the lignin content of the particle surface increased at higher pretreatment temperature and residence time, the initial rate of enzymatic hydrolysis increased. Enzyme adsorption measurements and staining methods revealed that the higher rate of hydrolysis of these materials was due to increased accessibility of the cellulose. An accessible cellulose fraction is thus more important than a low surface lignin content for the enzymatic hydrolysis of steam-pretreated spruce.
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| 39. |
- Yasin, Zafar, et al.
(author)
-
Applicability of Parallel Plate Avalanche Counters to Spontaneous Fission from Cf-252
- 2012
-
In: International Journal of Modern Physics E. - 0218-3013. ; 21:4
-
Journal article (peer-reviewed)abstract
- The construction and performance of the parallel plate avalanche counters (PPACs) using a spontaneous fission source Cf-252 is described in this paper. The parallel plate circular electrodes are made of aluminum foils having a thickness less than ten microns. After fabrication, the detectors and the source are mounted inside a reaction chamber, the source between the two detectors. A low pressure is created inside the chamber using isobutane (C4H10) and a high voltage is applied to the electrodes. The detectors are first operated at different pressures and voltages to find the optimum values of the pressure and the voltage. This is necessary to avoid the sparking threshold, to achieve a good time resolution and to keep the gain of the detectors high and constant. The. PPACs are operated in 2 pi- and 4 pi-geometries. In 4 pi-geometry the detectors are allowed to function in coincidence and noncoincidence mode. The resulting pulse height and the time spectra are studied using the computer code ROOT and some conclusions are drawn from these analyses. The pulse height spectrum shows a clear separation between the fission fragments and the alpha particles and the time spectrum indicates a good intrinsic time resolution, 0.76 ns.
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| 40. |
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