| 1. |
- Adloff, C, et al.
(författare)
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Measurement and QCD analysis of neutral and charged current cross sections at HERA
- 2003
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 30:1, s. 1-32
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Tidskriftsartikel (refereegranskat)abstract
- The inclusive e(+)p single and double differential cross sections for neutral and charged current processes axe measured with the H1 detector at HERA. The data were taken in 1999 and 2000 at a centre-of-mass energy of roots = 319 GeV and correspond to an integrated luminosity of 65.2 pb(-1). The cross sections are measured in the range of four-momentum transfer squared Q(2) between 100 and 30 000 GeV2 and Bjorken x between 0.0013 and 0.65. The neutral current analysis for the new e(+)p data and the earlier e-p data taken in 1998 and 1999 is extended to small energies of the scattered electron and therefore to higher values of inelasticity y, allowing a determination of the longitudinal structure function F-L at high Q(2) (110 - 700 GeV2). A new measurement of the structure function x (F) over tilde (3) is obtained using the new e(+)p and previously published e p neutral current cross section data at high Q(2). These data together with H1 low Q(2) precision data are further used to perform new next-to-leading order QCD analyses in the framework of the Standard Model to extract flavour separated parton distributions in the proton.
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| 2. |
- Adloff, C, et al.
(författare)
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Measurement of D*(+/-) meson production and F-2(c) in deep-inelastic scattering at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 528:3-4, s. 199-214
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Tidskriftsartikel (refereegranskat)abstract
- The inclusive production of D*+/-(2010) mesons in deep-inelastic scattering is studied with the HI detector at HERA. In the kinematic region 1 < Q(2) < 100 GeV2 and 0.05 < y < 0.7 an e(+) p cross section for inclusive D*+/- meson production of 8.50 +/- 0.42(stat.)(-100)(+1.21)(syst.) nb is measured in the visible range p(tD*) > 1.5 GeV and eta(D*) < 1.5. Single and double differential inclusive D*+/- meson cross sections are compared to perturbative QCD calculations in two different evolution schemes, The charm contribution to the proton structure, F-c(2)(x, Q(2)), is determined by extrapolating the visible charm cross section to the full phase space. This contribution is found to rise from about 10% at Q(2) = 1.5 GeV2 to more than 25% at Q(2) = 60 GeV2 corresponding to x values ranging from 5 x 10(-5) to 3 x 10(-3). (C) 2002 Elsevier Science B.V. All rights reserved.
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| 3. |
- Adloff, C, et al.
(författare)
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Measurement of inclusive jet cross sections in photoproduction at HERA
- 2003
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 29:4, s. 497-513
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Tidskriftsartikel (refereegranskat)abstract
- Inclusive jet cross sections are measured in photoproduction at HERA using the H1 detector. The data sample of e(+)p --> e(+) + jet + X events in the kinematic range of photon virtualities Q(2) less than or equal to 1GeV(2) and photon-proton centre-of-mass energies 95 less than or equal to W-gammap less than or equal to 285GeV represents an integrated luminosity of 24.1pb(-1). Jets are defined using the inclusive k(perpendicular to) algorithm. Single- and multi-differential cross sections are measured as functions of jet transverse energy E-T(jet) and pseudorapidity eta(jet) in the domain 5 less than or equal to E-T(jet) less than or equal to 75GeV and -1 less than or equal to eta(jet) less than or equal to 2.5. The cross sections are found to be in good agreement with next-to-leading order perturbative QCD calculations corrected for fragmentation and underlying event effects. The cross section differential in E-T(jet), which varies by six orders of magnitude over the measured range, is compared with similar distributions from p (p) over bar colliders at equal and higher energies.
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| 4. |
- Adloff, C, et al.
(författare)
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Search for new physics in e +/- q contact interactions at HERA
- 2003
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 568:1-2, s. 35-47
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Tidskriftsartikel (refereegranskat)abstract
- Deep-inelastic e(+/-) p scattering at high squared momentum transfer Q(2) up to 30 000 GeV2 is used to search for eq contact interactions associated to scales far beyond the HERA centre of mass energy. The neutral current cross section measurements dsigma / dQ(2), corresponding to integrated luminosities of 16.4 pb(-1) of e(-) p data and 100.8 pb(-1) of e(+) p data, are well described by the Standard Model and are analysed to set constraints on new phenomena. For conventional contact interactions lower limits are set on compositeness scales A ranging between 1.6-5.5 TeV. Couplings and masses of leptoquarks and squarks in R-parity violating supersymmetry are constrained to M / lambda > 0.3-1.4 TeV. A search for low scale quantum gravity effects in models with large extra dimensions provides limits on the effective Planck scale of MS > 0.8 TeV. A form factor analysis yields a bound on the radius of light quarks of R-q < 1.0 10(-18) m. (C) 2003 Published by Elsevier B.V.
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| 5. |
- Andreev, V, et al.
(författare)
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Isolated electrons and muons in events with missing transverse momentum at HERA
- 2003
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 561:3-4, s. 241-257
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Tidskriftsartikel (refereegranskat)abstract
- A search for events with a high-energy isolated electron or muon and missing transverse momentum has been performed at the electron-proton collider HERA using an integrated luminosity of 13.6 pb(-1) in e(-) p scattering and 104.7 pb(-1) in e(+) p scattering. Within the Standard Model such events are expected to be mainly due to W boson production with subsequent leptonic decay. In e(-) p interactions one event is observed in the electron channel and none in the muon channel, consistent with the expectation of the Standard Model. In the e(+) p data a total of 18 events are seen in the electron and muon channels compared to an expectation of 12.4 +/- 1.7 dominated by W production (9.4 +/- 1.6). Whilst the overall observed number of events is broadly in agreement with the number predicted by the Standard Model, there is-an excess of events with transverse momentum of the hadronic system greater than 25 GeV with 10 events found compared to 2.9 +/- 0.5 expected. The results are used to determine the cross-section for events with an isolated electron or muon and missing transverse momentum. (C) 2003 Published by Elsevier Science B.V.
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| 6. |
- Adloff, C, et al.
(författare)
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Diffractive photoproduction of psi(2S) mesons at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 541:3-4, s. 251-264
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Tidskriftsartikel (refereegranskat)abstract
- Results on diffractive photoproduction of psi(2S) mesons are presented using data collected between 1996 and 2000 with the H1 detector at the HERA ep collider. The data correspond to an integrated luminosity of 77 pb(-1). The energy dependence of the diffractive psi(2S) cross section is found to be similar to or possibly somewhat steeper than that for J/psi mesons. The dependences of the elastic and proton dissociative psi(2S) photoproduction cross sections on the squared momentum transfer t at the proton vertex are measured. The t-dependence of the elastic channel, parametrised as e(bt), yields b(el)(psi(2S)) = (4.31 +/- 0.57 +/- 0.46) GeV-2, compatible with that of the J/psi. For the proton dissociative channel the result b(pd)(psi(2S)) = (0.59 +/- 0.13 +/- 0.12) GeV-2 is 2.3 standard deviations smaller than that measured for the J/psi. With proper account of the individual wavefunctions theoretical predictions based on perturbative QCD are found to describe the measurements well. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 7. |
- Adloff, C, et al.
(författare)
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Energy flow and rapidity gaps between jets in photoproduction at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 24:4, s. 517-527
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Tidskriftsartikel (refereegranskat)abstract
- Dijet events in photon-proton collisions in which there is a large pseudorapidity separation, Deltaeta > 2.5 between the two highest E-T jets are studied with the H1 detector at HERA. The inclusive dijet cross sections are measured as functions of the longitudinal momentum fractions of the proton and photon which participate in the production of the jets, x(p)(jets) and x(gamma)(jets) respectively, Deltaeta, the pseudorapidity P separation between the two highest E-T jets, and E-T(gap), the total summed transverse energy between the jets. Rapidity gap events are defined as events in which E-T(gap) is less than E-T(cut), for E-T(cut) varied between jets 0.5 and 2.0 GeV. The fraction of dijet events with a rapidity gap is measured differentially in Deltaeta, x(p)(jets) and x(gamma)(jets). An excess of events with rapidity gaps at low values of E-T(cut) is observed above the expectation from standard photoproduction processes. This excess can be explained by the exchange of a strongly interacting colour singlet object between the jets.
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| 8. |
- Adloff, C, et al.
(författare)
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Inelastic leptoproduction of J/psi mesons at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 25:1, s. 41-53
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Tidskriftsartikel (refereegranskat)abstract
- The leptoproduction of J/psi mesons is studied in inelastic reactions for four momentorri transfers 2 < Q(2) < 100GeV(2). The data were taken with the H1 detector at the electron proton collider HERA and correspond to an integrated luminosity of 77 pb(-1). Single differential and double differential cross sections are measured with increased precision compared with previous analyses. New leading order calculations within the non-relativistic QCD factorisation approach including colour octet and colour singlet contributions are compared with the data and are found to give a reasonable description of most distributions. An exception is the shape of the distribution in the J/psi fractional energy. z, which deviates significantly from that of the data. Comparisons with photoproduction are made and the polarisation of the produced J/psi meson is analysed.
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| 9. |
- Adloff, C, et al.
(författare)
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Inelastic photoproduction of J/psi mesons at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 25:1, s. 25-39
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Tidskriftsartikel (refereegranskat)abstract
- An analysis of inelastic photoproduction of J/psi mesons is presented using data collected at the ep collider HERA corresponding to an integrated luminosity of above 80 pb(-1), Differential and double I < P-t/psi(2) < differential cross sections are measured in a wide kinematic region: 60 < W-gammap < 260 GeV, 1 p(t,psi)(2) < 60 GeV2 and 0.05 < z < 0.9. where z is the fraction of the energy of the exchanged photon transferred to the J/psi meson in the rest frame of the target proton. Cross sections at z less than or similar to 0.3 are presented for the first time. Theoretical calculations within the Colour Singlet Model at NLO for direct photon processes are shown to give a good description of the data in the medium z region (0.3 < z < 0.9) up to the highest p(t,psi)(2) values. A calculation using a k(t) factorisation approach in LO in the Colour Singlet Model is also able to describe these data. The data in the full z range are also compared to LO calculations within a non-relativistic QCD framework including colour octet and colour singlet contributions for direct and resolved photons. It seems possible to reconcile data and theory with modest contributions from colour octet processes. The polarisation of the J/psi meson is measured as a function of z and p(t,psi) and is reasonably described by the theoretical predictions.
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| 10. |
- Adloff, C, et al.
(författare)
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Measurement of dijet cross sections in photoproduction at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 25:1, s. 13-23
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Tidskriftsartikel (refereegranskat)abstract
- Dijet cross sections as functions of several jet observables are measured in photoproduction using the HI detector at HERA. The data sample comprises e(+)p data with an integrated luminosity of 319 pb(-1). Jets are selected using the inclusive k(perpendicular to) algorithm with a minimum transverse energy of 25 GeV for the leading jet. The phase space covers longitudinal proton momentum fraction x(p) and photon longitudinal momentum fraction x(gamma) in the ranges 0.05 < x(p) < 0.6 and 0.1 < x(gamma) < 1. The predict ions of next-to-leading order perturbative QCD, including recent photon and proton parton densities, are found to be compatible with the data in a wide kinematical range.
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| 11. |
- Adloff, C, et al.
(författare)
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Measurement of dijet electroproduction at small jet separation
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 24:1, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- Deep-inelastic scattering data in the range 150 < Q(2) < 35000 GeV2 are used to investigate the minimum jet separation necessary to allow accurate description of the rate of dijet production using next-to-leading order perturbative QCD calculations. The required jet separation is found to be small, allowing about 1/3 of DIS data to be classified as dijet, as opposed to approximately 1/10 with more typical jet analyses. A number of precision measurements made using this dijet sample are well described by the calculations. The data are also described by the combination of leading order matrix elements and parton showers, as implemented in the QCD based Monte Carlo model RAPGAP.
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| 12. |
- Adloff, C, et al.
(författare)
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Search for excited electrons at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 548:1-2, s. 35-44
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Tidskriftsartikel (refereegranskat)abstract
- A search for excited electron (e*) production is described in which the electroweak decays e* --> egamma, e* --> eZ and e* ---> nuW are considered. The data used correspond to an integrated luminosity of 120 pb(-1) taken in e(+/-)p collisions from 1994 to 2000 with the H1 detector at HERA at centre-of-mass energies of 300 and 318 GeV. No evidence for a signal is found. Mass dependent exclusion limits are derived for the ratio of the couplings to the compositeness scale, f/A. These limits extend the excluded region to higher masses than has been possible in previous direct searches for excited electrons. (C) 2002 Published by Elsevier Science B.V.
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| 13. |
- Adloff, C, et al.
(författare)
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Search for excited neutrinos at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 525:1-2, s. 9-16
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Tidskriftsartikel (refereegranskat)abstract
- We present a search for excited neutrinos using e(-) p data taken by the H1 experiment at HERA at a center-of-mass energy of 318 GeV with an integrated luminosity of 15 pb(-1). No evidence for excited neutrino production is found. Mass dependent exclusion limits are determined for the ratio of the coupling to the compositeness scale, f/Lambda, independently of the relative couplings to the SU(2) and U(1) gauge bosons. These limits extend the excluded region to higher masses than has been possible in previous searches at other colliders.
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| 14. |
- Adloff, C, et al.
(författare)
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Search for QCD instanton-induced processes in deep-inelastic scattering at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 25:4, s. 495-509
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Tidskriftsartikel (refereegranskat)abstract
- Signals of QCD instanton-induced processes are searched for in deep-inelastic scattering (DIS) at the electron-proton collider HERA in a kinematic region defined by the Bjorken-scaling variables x > 10(-3), 0.1 < y < 0.6 and photon virtualities 10 less than or similar to Q(2) < 100 GeV2. Several observables characterising hadronic final state properties of QCD instanton-induced events are exploited to identify a potentially instanton-enriched domain. While an excess of events with instanton-like topology is observed it cannot be claimed significant given the uncertainty of the standard DIS background simulation. Upper limits on the cross-section for instanton-induced processes of between 60 pb and 1000 pb are set dependent on the kinematic domain considered. The data do not exclude the cross-section predicted by instanton perturbation theory for small instanton sizes. At large instanton sizes a naive extrapolation of instanton perturbation theory yields a cross-section in the range of sensitivity of this study. Such a cross-section is not observed, in agreement with non-perturbative lattice simulations of the QCD vacuum.
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| 15. |
- Adloff, C, et al.
(författare)
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A measurement of the t dependence of the helicity structure of diffractive rho meson electroproduction at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 539:1-2, s. 25-39
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Tidskriftsartikel (refereegranskat)abstract
- The helicity structure of the diffractive electroproduction of rho mesons, e + p --> e + rho + Y, is studied in a previously unexplored region of large four-momentum transfer squared at the proton vertex, t: 0 < t' < 3 GeV2, where t' = - min. The data used are collected with the HI detector at HERA in the kinematic domain 2.5 < Q(2) < 60 GeV2, 40 < W < 120 GeV No t dependence of the r(00)(04) spin density matrix element is found. A significant t dependent helicity non-conservation from the virtual photon to the rho meson is observed for the spin density matrix element combinations r(00)(5) + 2r(11)(5) and r(00)(1) + 2r(11)(1). These t dependences are consistently described by a perturbative QCD model based on the exchange of two gluons.
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| 16. |
- Adloff, C, et al.
(författare)
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Measurement of inclusive jet cross-sections in deep-inelastic ep scattering at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 542:3-4, s. 193-206
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Tidskriftsartikel (refereegranskat)abstract
- A measurement of inclusive jet cross-sections in deep-inelastic ep scattering at HERA is presented based on data with an integrated luminosity of 21.1 pb(-1). The measurement is performed for photon virtualities Q(2) between 5 and 100 GeV2, differentially in Q(2), in the jet transverse energy E-T, in E-T(2)/Q(2) and in the pseudorapidity eta(lab). With the renormalization scale mu(R) = E-T, perturbative QCD calculations in next-to-leading order (NLO) give a good description of the data in most of the phase space. Significant discrepancies are observed only for jets in the proton beam direction with ET below 20 GeV and Q2 below 20 GeV2. This corresponds to the region in which NLO corrections are largest and further improvement of the calculations is thus of particular interest.
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| 17. |
- Adloff, C, et al.
(författare)
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Search for odderon-induced contributions to exclusive pi(0) photoproduction at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 544:1-2, s. 35-43
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Tidskriftsartikel (refereegranskat)abstract
- A search for contributions to the reaction ep --> epi(0)N* from photon-odderon fusion in the photoproduction regime at HERA is reported, at an average photon-proton centre-of-mass energy = 215 GeV. The measurement proceeds via detection of the pi(0) decay photons, a leading neutron from the N* decay, and the scattered electron. No pi(0) signal is observed and an upper limit on the cross section for the photon-odderon fusion process of sigma(gammap --> pi(0)N*) < 49 nb at the 95% confidence level is derived, integrated over the experimentally accessible range of the squared four-momentum transfer at the nucleon vertex 0.02 < < 0.3 GeV2. This excludes a recent prediction from a calculation based on a non-perturbative QCD model of a photon-odderon fusion cross section above 200 nb. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 18. |
- Aktas, A, et al.
(författare)
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Diffractive photoproduction of J/psi mesons with large momentum transfer at HERA
- 2003
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 568:3-4, s. 205-218
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Tidskriftsartikel (refereegranskat)abstract
- The diffractive photoproduction of J/psi mesons is measured with the HI detector at the ep collider HERA using an integrated luminosity of 78 pb(-1). The differential cross section dsigma(gammap --> J/psiY)/dt is studied in the range 2 < < 30 GeV2, where t is the square of the four-momentum transferred at the proton vertex. The cross section is also presented as a function of the photon-proton centre-of-mass energy W-gammap in three t intervals, spanning the range 50 < W-gammap < 200 GeV. A fast rise of the cross section with W-gammap is observed for each t range and the slope for the effective linear Pomeron trajectory is measured to be alpha' = -0.0135 +/- 0.0074(stat.) +/- 0.0051(syst.) GeV-2. The measurements are compared with perturbative QCD models based on BFKL and DGLAP evolution. The data are found to be compatible with s-channel helicity conservation. (C) 200 Published by Elsevier B.V.
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| 19. |
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| 20. |
- Manigart, S., et al.
(författare)
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The syndication of venture capital investments in Europe: evidence from five European countries
- 2002
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Ingår i: Frontiers of Entrepreneurship Research: Proceedings of the Twenty-Second Annual Entrepreneurship Research Conference. - 0910897239
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Konferensbidrag (refereegranskat)abstract
- Financial theory, resource-based theory and deal flow generation are used to explain synd ication practices among venture capitalists in Belgium, France, The Netherlands, Sweden and the UK. Similar motives drive syndication in the five countries: the desire to share risk and increase portfolio diversification is more important than the desire to access additional intangible resources or deal flow. When resource-based motives are more important, however, the propensity to syndicate increases. Syndication practices are more important in young venture capital (VC) firms and in VC firms with more portfolio companies.
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| 21. |
- Hesse, C, et al.
(författare)
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Measurement of apolipoprotein E (apoE) in cerebrospinal fluid
- 2000
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Ingår i: Neurochemical Research. - 1573-6903. ; 25:4, s. 511-517
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Tidskriftsartikel (refereegranskat)abstract
- Apolipoprotein E (apoE) is a protein involved in transport of lipids and has been implicated to play an important role in regeneration after nerve injury. Determination of apoE in cerebrospinal fluid (CSF) thus have a potential interest when studying different forms of brain damage and as a marker of ongoing regenerative processes in the brain. However, previous studies on CSF-ApoE in Alzheimer's disease (AD) have given inconclusive results. Such inconsistent results might be related to confounding factors interfering with sample handling and/or analyses, which have not been fully elucidated. We therefore examined different potential confounding factors for analyses of apoE in CSF and also developed a new enzyme linked immunosorbent assay (ELISA). The hydrophobic character of ApoE resulted in adsorption to different types of test tubes commonly used for collection of CSF at lumbar puncture, resulting in falsely low levels. This makes CSF handling critical, especially if samples are taken in different types of tubes, or is transferred to new tubes. Taking this confounding factors in consideration and analysing patient and control CSF handled in the same way and using the new ELISA, we could confirm our previous finding of reduced levels of ApoE in AD, (3.4 +/- 1.3 mg/l) compared with controls (4.5 +/- 2.7 mg/l) (p = 0.045). Both in the AD and in the control group, higher levels of CSF-ApoE was found in individuals possessing the ApoE4 alleles. Our results support that CSF-ApoE is reduced in AD, and that handling of CSF is a critical factor, which may explain the discrepant results from previous studies. Differences in the amount of patients and controls possessing the ApoE4 allele included might also increase the variance between different studies.
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| 22. |
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Andreasen, N, et al.
(författare)
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Evaluation of CSF-tau and CSF-Abeta42 as diagnostic markers for Alzheimer disease in clinical practice
- 2001
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Ingår i: Archives of Neurology. - 0003-9942. ; 58:3, s. 373-379
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To evaluate the diagnostic potential of cerebrospinal fluid (CSF) levels of tau and beta-amyloid protein ending at amino acid 42 (Abeta42) as biomarkers for Alzheimer disease (AD) in clinical practice. DESIGN: A 1-year prospective study. SETTING: Community population-based sample of all consecutive patients admitted for investigation of cognitive symptoms to the Pitea River Valley Hospital, Pitea, Sweden. PATIENTS: A total of 241 patients with probable AD (n = 105), possible AD (n = 58), vascular dementia (n = 23), mild cognitive impairment (n = 20), Lewy body dementia (n = 9), other neurological disorders (n = 3), and psychiatric disorders (n = 5) and nondemented individuals (n = 18). MAIN OUTCOME MEASURES: Cerebrospinal fluid tau and CSF-Abeta42 were assayed each week as routine clinical neurochemical analyses. Sensitivity and specificity were defined using the regression line from 100 control subjects from a multicenter study. Positive and negative predictive values were calculated for different prevalence rates of AD. RESULTS: We found increased CSF-tau and decreased CSF-Abeta42 levels in probable and possible AD. Sensitivity was 94% for probable AD, 88% for possible AD, and 75% for mild cognitive impairment, whereas specificity was 100% for psychiatric disorders and 89% for nondemented. Specificity was lower in Lewy body dementia (67%) mainly because of low CSF-Abeta42 levels and in vascular dementia (48%) mainly because of high CSF-tau levels. Sensitivity for CSF-tau and CSF-Abeta42 increased in patients with AD possessing the ApoE epsilon4 allele, approaching 100%. At a prevalence of AD of 45%, the positive predictive value was 90% and the negative predictive value was 95%. CONCLUSIONS: Cerebrospinal fluid tau and CSF-Abeta42 have so far been studied in research settings, under conditions providing data on the optimal performance. We examined a prospective patient sample, with assays run in clinical routine, giving figures closer to the true performance of CSF-tau and CSF-Abeta42. The predictive value for AD was greater than 90%. Therefore, these biomarkers may have a role in the clinical workup of patients with cognitive impairment, especially to differentiate early AD from normal aging and psychiatric disorders.
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| 27. |
- Bjarnadottir, M., et al.
(författare)
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The cerebral hemorrhage-producing cystatin C variant (L68Q) in extracellular fluids
- 2001
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Ingår i: Amyloid. - 1350-6129. ; 8:1, s. 41284-41284
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Tidskriftsartikel (refereegranskat)abstract
- A variant of the normal extracellular cysteine protease inhibitor cystatin C (L68Q-cystatin C), is the amyloid precursor in hereditary cystatin C amyloid angiopathy (HCCAA). It has been suggested that the mutation causes cellular entrapment of L68Q-cystatin C in vivo and that the variant protein is not secreted to extracellular fluids. In order to test this hypothesis, we used matrix-assisted laser desorption ionization time-of-flight mass spectrometry in an effort to demonstrate the presence of L68Q- along with wildtype cystatin C in plasma and cerebrospinal fluid (CSF) of HCCAA-patients. Plasma from all five investigated HCCAA-patients contained both L68Q- and wildtype cystatin C. The presence of approximately equal amounts of cystatin C dimers and monomers was demonstrated in plasma from HCCAA-patients, whereas only monomers could be found in normal plasma. L68Q-wildtype-cystatin C heterodimers seem to be present in the dimeric cystatin C population. CSF from six HCCAA-patients also contained cystatin C-dimers and monomers, bur the dimeric fraction was minute. CSF from control patients did not contain dimeric cystatin C. These results suggest that the milieu of L68Q-cystatin C is important for its stability and dimerization status and that certain milieus might hinder its further development into oligomers, amyloid fibrils and other precipiting aggregates.
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| 28. |
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| 29. |
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| 30. |
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| 31. |
- Davidsson, P, et al.
(författare)
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Differential increase in cerebrospinal fluid-acetylcholinesterase after treatment with acetylcholinesterase inhibitors in patients with Alzheimer's disease
- 2001
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Ingår i: Neuroscience Letters. - 0304-3940. ; 300:3, s. 157-160
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Tidskriftsartikel (refereegranskat)abstract
- The clinical significance and the effects of pharmacological treatment of patients with Alzheimer's disease (AD) were evaluated by measurement of acetylcholinesterase (AChE) in the cerebrospinal fluid (CSF). CSF-AChE of AD patients was lower, not significantly, compared with controls. However, CSF-AChE was significantly increased after treatment of AD patients with AChE inhibitors (donepezil and galantamine). The increase was higher in patients treated with donezepil than in those treated with galantamine, which might be related to different mechanisms for the substances. The increase was also dose-dependent, and was especially marked in patients showing a clinical response. These data suggest that CSF biomarkers are capable not only of identifying a biochemical effect of drugs, but also of differentiating between different compounds in a dose-dependent manner.
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| 32. |
- Davidsson, P, et al.
(författare)
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Reduced expression of amyloid precursor protein, presenilin-1 and rab3a in cortical brain regions in Alzheimer's disease
- 2001
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Ingår i: Dementia and geriatric cognitive disorders. - : S. Karger AG. - 1420-8008 .- 1421-9824. ; 12:4, s. 243-250
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Tidskriftsartikel (refereegranskat)abstract
- To study the role of amyloid precursor protein (APP) in the pathogenesis of Alzheimer’s disease (AD), the level of APP was analysed by quantitative immunoblotting in 6 AD patients and 6 age-matched controls in 9 brain regions. These were associative cortices (orbital frontal cortex, inferior temporal cortex, inferior parietal cortex), primary cortex (occipital cortex), limbic structures (anterior cingulate gyrus, hippocampus), subcortical structures (putamen, thalamus) and cerebellum. To assess a potential relationship between APP and presenilin-1 (PS-1) and/or synaptic proteins, the levels of PS-1 and rab3a, a specific synaptic vesicle protein, were also determined in the same tissue samples. The level of APP was almost the same in the association cortical regions, primary cortex, and limbic structures and in the subcortical structures, while the lowest level was found in the cerebellum. There were more marked differences in the level of PS-1 and rab3a between different brain regions. The highest levels of PS-1 and rab3a were found in the association cortical areas, while intermediate levels were found in primary cortex, limbic structures and subcortical structures. As for APP, the lowest level was found in cerebellum. We found significantly reduced levels of all three proteins in the association cortices and in hippocampus in AD. Our data show that the protein levels are reduced in specific areas, restricted to neuronal populations that are known to degenerate in AD. Due to the similarity of the expression of APP, PS-1 and rab3a, it is tempting to speculate whether there is a functional relationship between these proteins.
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| 33. |
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| 34. |
- Davidsson, P, et al.
(författare)
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The business platform : Developing an instrument to gauge and to assist the development of young firms
- 2003
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Ingår i: Journal of small business management (Print). - 0047-2778 .- 1540-627X. ; 41:1, s. 1-26
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Tidskriftsartikel (refereegranskat)abstract
- The research presented here addresses the following problems we perceive in research on the development of young firms. First, we feel there is a lack of holistic yet quantifiable and generalizable ways in which to assess the state of newly started firms. Quantitative research typically relies on additive models that are unable to explain more than half of the outcome variance at the most. Holistic approaches tend to be qualitative and therefore have unknown generalizability. Second, we feel there is a lack of action-oriented assessment models that are firmly anchored in research. Research models typically take a passive prediction position and often build on relationships that give little hands-on advice to managers. Numerous practical tools for assessing and developing firms during their early development can be found in how-to literature, but these typically are not anchored in systematic research and therefore have unknown validity. Hence, what we set out to do in the research presented in this article is to develop a quantifiable, holistic, and research-based instrument for assessing and assisting the development of young firms.
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| 35. |
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| 36. |
- Gutierrez, P, et al.
(författare)
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An investigation of errors in estimates of the cometary nuclei active area fractions
- 2003
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 401:2, s. 755-761
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Tidskriftsartikel (refereegranskat)abstract
- Active area fractions of cometary nuclei are often estimated by comparing the observed water production rates with theoretical rates obtained by applying the fast rotator or subsolar point approximations to spherical model nuclei. Any discrepancy between observed and theoretical production rates is interpreted as a certain degree of dust mantling (or in some cases hyper activity) of the object. We here investigate the typical errors introduced in such active area fraction estimates by the usage of oversimplified spherical model nuclei. This is done by first calculating the production rates of slowly rotating irregular model bodies with different activity patterns on their surfaces and arbitrary spin axis orientations, for which solar illumination is treated properly. Next, the production rates of the spherical model objects under averaged insolation are compared to the production rates of the complex model objects in an attempt to recover the known active area fraction of the latter bodies. We then find that the fast rotator and subsolar point approximations generally yield large over- and underestimates of the active area fraction, depending on the characteristics of the simulated complex nuclei. Acceptable relative errors ( <100%) only occur at small heliocentric distances, and the subsolar point approximation yields somewhat better results than the fast rotator approximation.
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| 37. |
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| 38. |
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| 39. |
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| 40. |
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| 41. |
- Olsson, A, et al.
(författare)
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Measurement of alpha- and beta-secretase cleaved amyloid precursor protein in cerebrospinal fluid from Alzheimer patients
- 2003
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Ingår i: Experimental Neurology. - 0014-4886. ; 183, s. 74-
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Tidskriftsartikel (refereegranskat)abstract
- One of the major histopathological hallmarks of Alzheimer's disease (AD) is redundant senile plaques mainly composed of beta-amyloid (Abeta) aggregates. Alternative cleavage of the amyloid precursor protein (APP), occurring in both normal and AD subjects, results in the generation and secretion of soluble APP (sAPP) and Abeta. We examined the cerebrospinal fluid (CSF) for alpha- and beta-secretase cleaved sAPP (alpha-sAPP and beta-sAPP) in 81 sporadic AD patients, 19 patients with mild cognitive impairment, and 42 healthy controls by using newly developed sandwich enzyme-linked immunosorbent assay methods. We found that neither the level of CSF-alpha-sAPP nor CSF-beta-sAPP differed between sporadic AD patients and healthy controls. These findings further support the conclusion that there is no change in APP expression in sporadic AD. However, the level of CSF-beta-sAPP was significantly increased in patients with mild cognitive impairment compared to controls. We also investigated the relationship between the CSF level of alphabeta-sAPP and Abeta(42) and the apoE epsilon4 (apoFA.) allele. Significantly lower levels of CSF-alpha-sAPP were found in AD patients possessing one or two apoE4 alleles than in those not possessing the apoE4 allele. Neither the levels of CSF-beta-sAPP nor CSF-Abeta(42) differed when comparing ApoE4 allele-positive with allele-negative individuals. (C) 2003 Elsevier Science (USA). All rights reserved.
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| 42. |
- Parnetti, L, et al.
(författare)
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Cerebrospinal fluid levels of biomarkers and activity of acetylcholinesterase (AChE) and butyrylcholinesterase in AD patients before and after treatment with different AChE inhibitors
- 2002
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Ingår i: Neurological Sciences. - : Springer Science and Business Media LLC. - 1590-1874 .- 1590-3478. ; 23, s. 95-96
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Tidskriftsartikel (refereegranskat)abstract
- In order to evaluate the biochemical effects of long-term treatment with inhibitors of acetylcholinesterase (AChE) in patients with Alzheimer's disease (AD), we measured the activities of AChE and butyry1cholinesterase (BuChe) and the concentrations of beta-amyloid (1-42), tau and phosphorylated tau proteins in the cerebrospinal fluid (CSF). A total of 91 patients suffering from probable AD of mild to moderate degree were treated for 6 months with donepezil (n=59), galantamine (n=15), rivastigmine (n=10), or placebo (n=7). AChE activity in CSF was significantly increased after treatment with donepezil and galantamine; the opposite was observed in the rivastigmine-treated group. Untreated patients did not show any AChE activity variation. BuChE did not show any change in any of the groups studied. Mean values of beta-amyloid(1-42), total tau and phosphorylated tau also did not vary significantly. We conclude that AChE inhibitors induce different effects on CSF AChE activity, while other CSF biomarkers are not significantly affected by treatment.
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| 43. |
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| 44. |
- Sjogren, M, et al.
(författare)
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CSF levels of tau, beta-amyloid(1-42) and GAP-43 in frontotemporal dementia, other types of dementia and normal aging
- 2000
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Ingår i: Journal of Neural Transmission. - : Springer Science and Business Media LLC. - 0300-9564 .- 1435-1463. ; 107:5, s. 563-579
-
Tidskriftsartikel (refereegranskat)abstract
- Cerebrospinal fluid (CSF) levels of tau, beta-amyloid(1-42) and growth-associated protein 43 (GAP-43) were studied in patients with frontotemporal dementia (FTD; n = 17), Alzheimer's disease (AD; n = 60), subcortical white-matter dementia (SWD; n = 24), Parkinson's disease (PD; n = 23) and dysthymia (n = 19) and in age-matched controls (n = 32). CSF-tau was significantly increased only in AD, and CSF-beta-amyloid(1-42) was significantly decreased in AD and SWD as compared to controls, and in AD compared to FTD. CSF-GAP-43 was significantly decreased only in PD. The GAP-43/tau ratio was decreased in all the patient groups except the dysthymia group compared to controls. A positive correlation was found between CSF-GAP-43 and CSF-tau in all groups. The results suggest normal levels of CSF-tau and CSF-beta-amyloid(1-42) in FTD, which will aid in the clinical separation of FTD from AD. In SWD, decreased levels of CSF-beta-amyloid(1-42) suggest concomitant involvement of vascular and amyloid protein mechanisms.
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| 45. |
- Sjogren, M, et al.
(författare)
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Cytoskeleton proteins in CSF distinguish frontotemporal dementia from AD
- 2000
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Ingår i: Neurology. - 1526-632X. ; 54:10, s. 1960-1964
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE AND BACKGROUND: To investigate the CSF levels of tau and the light neurofilament protein (NFL) in patients with frontotemporal dementia (FTD) and other common dementia disorders as well as normal control subjects. Both proteins have been implicated in the pathophysiology of FTD. METHODS: CSF levels of tau and NFL were investigated in 18 patients with FTD, 21 patients with early-onset AD (EAD), 21 patients with late-onset AD (LAD), and 18 age-matched control subjects. RESULTS: Mean +/- SD CSF NFL levels were increased in patients with FTD (1442 +/- 1183 pg/mL; p < 0.05) and LAD (1006 +/- 727 pg/mL; p < 0.001) compared with control subjects (241 +/- 166 pg/mL) and in LAD compared with EAD (498 +/- 236 pg/mL; p < 0.05), and tended to be increased in FTD compared with EAD. CSF tau levels were increased in EAD (751 +/- 394 pg/mL; p < 0.01) and LAD (699 +/- 319 pg/mL; p < 0.01) compared with control subjects (375 +/- 170 pg/mL), and in EAD (p < 0.001) and LAD (p < 0. 01) compared with FTD (354 +/- 140 pg/mL). CSF NFL correlated positively with degree of cognitive impairment in FTD (r = 0.59; p < 0.05) and LAD (r = 0.61; p < 0.01). No significant differences were found in CSF NFL or CSF tau when comparing patients who did and did not possess the APOE-epsilon4 allele within each diagnostic group. CONCLUSION: The results suggest a differential involvement of these cytoskeleton proteins in FTD and EAD, with NFL primarily involved in the pathophysiology of FTD and tau in that of EAD. The increase in CSF NFL found in LAD might reflect the white-matter degeneration found in a proportion of LAD cases.
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| 46. |
- Sjogren, M., et al.
(författare)
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Decreased CSF-ß-amyloid 42 in Alzheimer's disease and amyotrophic lateral sclerosis may reflect mismetabolism of ß-amyloid induced by disparate mechanisms
- 2002
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Ingår i: Dementia and Geriatric Cognitive Disorders. - : S. Karger AG. - 1420-8008 .- 1421-9824. ; 13:2, s. 112-118
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Tidskriftsartikel (refereegranskat)abstract
- Both tau and ß-amyloid 42 (Aß42) have been implicated in Alzheimer's disease (AD) and tau alone in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). These proteins can be measured in the cerebrospinal fluid (CSF), differences from normal CSF levels may reflect pathophysiological mechanisms. Using ELISAs, we investigated the levels of total CSF-tau (here referred to as tau), phosphorylated CSF-tau (phospho-tau), and Aß42 in patients with AD (n = 19), FTD (n = 14), ALS (n = 11) and Parkinson's disease (PD, n = 15) and in age-matched controls (n = 17). Both CSF-tau and CSF-phosphotau were increased in AD compared with FTD (p < 0.001), ALS (p < 0.001), PD (p < 0.001) and controls (p < 0.001). CSF-Aß42 was markedly decreased in AD and ALS (both p < 0.001) and slightly decreased in FTD (p < 0.01) and PD (p < 0.05) compared with controls. Using CSF-phosphotau may improve the differentiation of AD from FTD and ALS in clinical praxis. Furthermore, decreased CSF-Aß42 levels may be common in neurode-generative disorders possibly reflecting changes in the metabolism of ß-amyloid or axonal degeneration. Copyright © 2002 S. Karger AG, Basel.
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| 47. |
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| 48. |
- Sjögren, M, et al.
(författare)
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CSF levels of tau, beta-amyloid and GAP-43 in frontotemporal 1-42 dementia, other types of dementia and normal aging
- 2000
-
Ingår i: Journal of neural transmission. - 0300-9564 .- 1435-1463. ; 107:5, s. 563-579
-
Tidskriftsartikel (refereegranskat)abstract
- Cerebrospinal fluid (CSF) levels of tau, ▀-amyloid1-42 and growth-associated protein 43 (GAP-43) were studied in patients with frontotemporal dementia (FTD, n = 17), Alzheimer's disease (AD, n = 60), subcortical white-matter dementia (SWD, n = 24), Parkinson's disease (PD, n = 23) and dysthymia (n = 19) and in age-matched controls (n = 32). CSF-tau was significantly increased only in AD, and CSF-▀-amyloid1-42 was significantly decreased in AD and SWD as compared to controls, and in AD compared to FTD. CSF-GAP-43 was significantly decreased only in PD. The GAP-43/tau ratio was decreased in all the patient groups except the dysthymia group compared to controls. A positive correlation was found between CSF-GAP-43 and CSF-tau in all groups. The results suggest normal levels of CSF-tau and CSF-▀-amyloid1-42 in FTD, which will aid in the clinical separation of FTD from AD. In SWD, decreased levels of CSF-▀-amyloid1-42 suggest concomitant involvement of vascular and amyloid protein mechanisms.
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| 49. |
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| 50. |
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