| 31. |
- Abdallah, J., et al.
(författare)
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Study of leading hadrons in gluon and quark fragmentation
- 2006
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 643:3-4, s. 147-157
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Tidskriftsartikel (refereegranskat)abstract
- The study of quark jets in e(+)e(-) reactions at LEP has demonstrated that the hadronisation process is reproduced well by the Lund string model. However. our understanding of gluon fragmentation is less complete. In this study enriched quark and gluon jet samples of different purities are selected in three-jet events from hadronic decays of the Z collected by the DELPHI experiment in the LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are defined by requiring a rapidity gap and their sum of charges is studied. An excess of leading systems with total charge zero is found for gluon jets in all cases, when compared to Monte Carlo simulations with JETSET (with and without Bose-Einstein correlations included) and ARIADNE. The corresponding leading systems of quark jets do not exhibit such an excess. The influence of the gap size and of the gluon purity on the effect is studied and a concentration of the excess of neutral leading systems at low invariant masses (less than or similar to 2 GeV/c(2)) is observed, indicating that gluon jets might have an additional hitherto undetected fragmentation mode via a two-gluon system. This could be an indication of a possible production of gluonic states as predicted by QCD.
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| 32. |
- Abdallah, J., et al.
(författare)
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Study of multi-muon bundles in cosmic ray showers detected with the DELPHI detector at LEP
- 2007
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Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 28:3, s. 273-286
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Tidskriftsartikel (refereegranskat)abstract
- The DELPHI detector at LEP has been used to measure multi-muon bundles originating from cosmic ray interactions with air. The cosmic events were recorded in "parasitic mode" between individual e(+)e(-) interactions and the total live time of this data taking is equivalent to 1.6 x 10(6) s. The DELPHI apparatus is located about 100 m underground and the 84 metres rock overburden imposes a cutoff of about 52 GeV/c on muon momenta. The data from the large volume Hadron Calorimeter allowed the muon multiplicity of 54,201 events to be reconstructed. The resulting muon multiplicity distribution is compared with the prediction of the Monte Carlo simulation based on CORSIKA/QGSJETOI. The model fails to describe the abundance of high multiplicity events. The impact of QGSJET internal parameters on the results is also studied.
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| 33. |
- Abdallah, J., et al.
(författare)
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Study of triple-gauge-boson couplings ZZZ, ZZ gamma and Z gamma gamma at LEP
- 2007
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 51:3, s. 525-542
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Tidskriftsartikel (refereegranskat)abstract
- Neutral triple-gauge-boson couplings ZZZ, ZZγ and Zγγ have been studied with the DELPHI detector using data at energies between 183 and 208 GeV. Limits are derived on these couplings from an analysis of the reactions e+e-→Zγ, using data from the final states γff̄, with f=q or ν, from e+e-→ZZ, using data from the four-fermion final states qq̄qq̄, qq̄μ+μ-, qq̄e+e-, qq̄νν̄, μ+μ-νν̄ and e+e-νν̄, and from e+e-→Zγ*, in which the final state γ is off mass-shell, using data from the four-fermion final states qq̄e+e- and qq̄μ+μ-. No evidence for the presence of such couplings is observed, in agreement with the predictions of the Standard Model.
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| 34. |
- Abdallah, J., et al.
(författare)
-
Study of W-boson polarisations and triple gauge boson couplings in the reaction e(+)e(-)-> W+W- at LEP 2
- 2008
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:54, s. 345-364
-
Tidskriftsartikel (refereegranskat)abstract
- A determination of the single W spin density matrix (SDM) elements in the reaction e(+)e(-) -> W+W--> l nu q (q) over bar (l=e/mu) is reported at centre-of-mass energies between 189 and 209GeV. The data sample used corresponds to an integrated luminosity of 520pb(-1) taken by DELPHI between 1998 and 2000. The single W SDM elements, rho(W +/-)(tau tau') (tau,tau'=+/- 1 or 0), are determined as a function of the W- production angle with respect to the e(-) beam direction and are obtained from measurements of the W decay products by the application of suitable projection operators, Lambda(tau tau'), which assume the V-A coupling of the W-boson to fermions. The measured SDM elements are used to obtain the fraction of longitudinally polarised Ws, with the result: sigma(L)/sigma(tot) = 24.9 +/- 4.5 (stat) +/- 2.2 (syst)% at a mean energy of 198 GeV. The SDM elements are also used to determine the triple gauge couplings Delta g(1)(Z), Delta kappa(gamma), lambda(gamma) and g(4)(Z), (kappa) over tilde (Z) and (lambda) over tilde (Z). For the CP-violating couplings the results of single parameter fits are: g(4)(Z) = -0.39(-0.20)(+0.19) (kappa) over tilde (Z) = -0.09(-0.05)(+0.08) (lambda) over tilde (Z) = -0.08 +/- 0.07. The errors are a combination of statistical and systematic errors. All results are consistent with the Standard Model.
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| 35. |
- Abdallah, J., et al.
(författare)
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Z gamma* production in e(+) e(-) interactions at root s=183-209 GeV
- 2007
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 51:3, s. 503-523
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of Z gamma* production are presented using data collected by the DELPHI detector at centre-of-mass energies ranging from 183 to 209 GeV, corresponding to an integrated luminosity of about 667 pb(-1). The measurements cover a wide range of the possible final state four-fermion configurations: hadronic and leptonic (e(+) e(-) q (q) over bar, mu(+) mu(-) q (q) over bar ,q (q) over barv (v) over bar), fully leptonic (l(+) l(-) l' (+) l'(-)) and fully hadronic. nal states (q (q) over barq (q) over bar, with a low mass q (q$) over bar pair). Measurements of the Z gamma* cross-section for the various. nal states have been compared with the Standard Model expectations and found to be consistent within the errors. In addition, a total cross-section measurement of the l(+) l(-) l'(+)l'(-) cross-section is reported, and found to be in agreement with the prediction of the Standard Model.
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| 36. |
- Abdurahman, Samir, 1965-, et al.
(författare)
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Isolation and characterization of a small antiretroviral molecule affecting HIV-1 capsid morphology
- 2009
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Ingår i: Retrovirology. - : Springer Science and Business Media LLC. - 1742-4690. ; 6, s. 34-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Formation of an HIV-1 particle with a conical core structure is a prerequisite for the subsequent infectivity of the virus particle. We have previously described that glycineamide (G-NH2) when added to the culture medium of infected cells induces non-infectious HIV-1 particles with aberrant core structures. Results: Here we demonstrate that it is not G-NH2 itself but a metabolite thereof that displays antiviral activity. We show that conversion of G-NH2 to its antiviral metabolite is catalyzed by an enzyme present in bovine and porcine but surprisingly not in human serum. Structure determination by NMR suggested that the active G-NH2 metabolite was alpha-hydroxy-glycineamide (alpha-HGA). Chemically synthesized alpha-HGA inhibited HIV-1 replication to the same degree as G-NH2, unlike a number of other synthesized analogues of G-NH2 which had no effect on HIV-1 replication. Comparisons by capillary electrophoresis and HPLC of the metabolite with the chemically synthesized alpha-HGA further confirmed that the antiviral G-NH2-metabolite indeed was alpha-HGA. Conclusion: alpha-HGA has an unusually simple structure and a novel mechanism of antiviral action. Thus, alpha-HGA could be a lead for new antiviral substances belonging to a new class of anti-HIV drugs, i.e. capsid assembly inhibitors.
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| 37. |
- Abelson, Anna-Karin, et al.
(författare)
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No evidence of association between genetic variants of the PDCD1 ligands and SLE
- 2007
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Ingår i: Genes and Immunity. - : Springer Science and Business Media LLC. - 1466-4879 .- 1476-5470. ; 8:1, s. 69-74
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Tidskriftsartikel (refereegranskat)abstract
- PDCD1, an immunoreceptor involved in peripheral tolerance has previously been shown to be genetically associated with systemic lupus erythematosus (SLE). PDCD1 has two ligands whose genes are located in close proximity on chromosome 9p24. Our attention was drawn to these ligands after finding suggestive linkage to a marker (gata62f03, Z=2.27) located close to their genes in a genome scan of Icelandic families multiplex for SLE. Here, we analyse Swedish trios (N=149) for 23 single nucleotide polymorphisms (SNPs) within the genes of the PDCD1 ligands. Initially, indication of association to eight SNPs was observed, and these SNPs were therefore also analysed in Mexican trios (N=90), as well as independent sets of patients and controls from Sweden (152 patients, 448 controls) and Argentina (288 patients, 288 controls). We do not find support for genetic association to SLE. This is the first genetic study of SLE and the PDCD1 ligands and the lack of association in several cohorts implies that these genes are not major risk factors for SLE.
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| 38. |
- Abrahamsson, Maria, et al.
(författare)
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Steric influence on the excited-state lifetimes of ruthenium complexes with bipyridyl-alkanylene-pyridyl ligands.
- 2008
-
Ingår i: Inorganic Chemistry. - : ACS. - 0020-1669 .- 1520-510X. ; 47:9, s. 3540-3548
-
Tidskriftsartikel (refereegranskat)abstract
- The structural effect on the metal-to-ligand charge transfer (MLCT) excited-state lifetime has been investigated in bis-tridentate Ru(II)-polypyridyl complexes based on the terpyridine-like ligands [6-(2,2'-bipyridyl)](2-pyridyl)methane (1) and 2-[6-(2,2'-bipyridyl)]-2-(2-pyridyl)propane (2). A homoleptic ([Ru(2)(2)](2+)) and a heteroleptic complex ([Ru(ttpy)(2)](2+)) based on the new ligand 2 have been prepared and their photophysical and structural properties studied experimentally and theoretically and compared to the results for the previously reported [Ru(1)(2)](2+). The excited-state lifetime of the homoleptic Ru-II complex with the isopropylene-bridged ligand 2 was found to be 50 times shorter than that of the corresponding homoleptic Ru-II complex of ligand 1, containing a methylene bridge. A comparison of the ground-state geometries of the two homoleptic complexes shows that steric interactions involving the isopropylene bridges make the coordination to the central Ru-II ion less octahedral in [Ru(2)(2)](2+) than in [Ru(1)(2))(2+). Calculations indicate that the structural differences in these complexes influence their ligand field splittings as well as the relative stabilities of the triplet metal-to-ligand charge transfer ((MLCT)-M-3) and metal-centered ((MC)-M-3) excited states. The large difference in measured excited-state lifetimes for the two homoleptic Ru-II complexes is attributed to a strong influence of steric interactions on the ligand field strength, which in turn affects the activation barriers for thermal conversion from (MLCT)-M-3 states to short-lived (MC)-M-3 states.
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| 39. |
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| 40. |
- Acosta, Stefan, et al.
(författare)
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Fatal colonic ischaemia : A population-based study
- 2006
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Ingår i: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 0036-5521 .- 1502-7708. ; 41:11, s. 1312-1319
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. To estimate the incidence of fatal colonic ischaemia (CI) and the cause-specific mortality of CI, and to describe the localization and extension of colonic infarction and quantify the risk factors associated with CI. Material and methods. Between 1970 and 1982 the autopsy rate in Malmo, Sweden, was 87%, creating the possibilities for a population-based study. Out of 23,446 clinical autopsies, 997 cases were coded for intestinal ischaemia in a database. In addition, 7569 forensic autopsy protocols were analysed. In a case-control study nested in the clinical autopsy cohort, four CI-free controls, matched for gender, age at death and year of death, were identified for each fatal CI case in order to evaluate the risk factors. Results. The cause-specific mortality ratio was 1.7/1000 autopsies. The overall incidence of autopsy-verified fatal CI was 1.7/100,000 person years, increasing with age up to 23/100,000 person years in octogenarians. Fatal cardiac failure (odds ratio (OR) 5.2), fatal valvular disease (OR 4.3), previous stroke (OR 2.5) and recent surgery (OR 3.4) were risk factors for fatal CI. Narrowing/occlusion of the inferior mesenteric artery (IMA) at the aortic origin was present in 68% of the patients. The most common segments affected by transmural infarctions were the sigmoid (83%) and the descending (77%) colon. Conclusions. Heart failure, atherosclerotic occlusion/stenoses of the IMA and recent surgery were the main risk factors causing colonic hypoperfusion and infarction. Segments of transmural infarctions were observed within the left colon in 94% of the patients. Awareness of the diagnosis and its associated cardiac comorbidities might help to improve survival.
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