| 1. |
- Augustyniak, W., et al.
(författare)
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Polarization of a stored beam by spin-filtering
- 2012
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 718:1, s. 64-69
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Tidskriftsartikel (refereegranskat)abstract
- The PAX Collaboration has successfully performed a spin-filtering experiment with protons at the COSY-ring. The measurement allowed the determination of the spin-dependent polarizing cross section, that compares well with the theoretical prediction from the nucleon-nucleon potential. The test confirms that spin-filtering can be adopted as a method to polarize a stored beam and that the present interpretation of the mechanism in terms of the proton-proton interaction is correct. The outcome of the experiment is of utmost importance in view of the possible application of the method to polarize a beam of stored antiprotons.
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| 2. |
- Oellers, D., et al.
(författare)
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New experimental upper limit of the electron-proton spin-flip cross-section
- 2014
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 759, s. 6-9
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Tidskriftsartikel (refereegranskat)abstract
- In a previous publication, measurements of the depolarization of a stored proton beam by interaction with a co-propagating unpolarized electron beam at low relative energy have been presented and an upper limit of about 3 x 10(7) b for the electron-proton spin flip cross-section was determined. A refined analysis presented in this paper reduces the previous upper limit by a factor of three by the introduction of a new procedure that, also makes use of non-identified particles.
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| 3. |
- Thörngren Engblom, Pia, et al.
(författare)
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Extensive high-precision studies of proton deuteron breakup reactions at COSY
- 2011
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Ingår i: Proceedings of Science. - : Sissa Medialab Srl.
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Konferensbidrag (refereegranskat)abstract
- We plan to measure the spin dependence of proton deuteron breakup at 30 and 49 MeV proton beam energy where previous measurements are few and limited. The physics objective is to test the predictive power of the chiral effective field theory in the three nucleon continuum by measuring analyzing powers and double spin observables with high precision over large areas of phase space at relevant energies for the theoretical interpretation. The experiment will be done at a newly installed and commissioned low-b section and interaction point in the COSY ring utilizing the PAX Multipurpose Detection System that is presently in the design stage.
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| 4. |
- Albèr, Cathrine, et al.
(författare)
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Effects of water gradients and use of urea on skin ultrastructure evaluated by confocal Raman microspectroscopy
- 2013
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Ingår i: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier. - 0005-2736 .- 1879-2642 .- 0006-3002. ; 1828:11, s. 2470-2478
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Tidskriftsartikel (refereegranskat)abstract
- The rather thin outermost layer of the mammalian skin, stratum corneum (SC), is a complex biomembrane which separates the water rich inside of the body from the dry outside. The skin surface can be exposed to rather extreme variations in ambient conditions (e.g. water activity, temperature and pH), with potential effects on the barrier function. Increased understanding of how the barrier is affected by such changes is highly relevant for regulation of transdermal uptake of exogenous chemicals. In the present study we investigate the effect of hydration and the use of a well-known humectant, urea, on skin barrier ultrastructure by means of confocal Raman microspectroscopy. We also perform dynamic vapor sorption (DVS) microbalance measurements to examine the water uptake capacity of SC pretreated with urea. Based on novel Raman images, constructed from 2D spectral maps, we can distinguish large water inclusions within the skin membrane exceeding the size of fully hydrated corneocytes. We show that these inclusions contain water with spectral properties similar to that of bulk water. The results furthermore show that the ambient water activity has an important impact on the formation of these water inclusions as well as on the hydration profile across the membrane. Urea significantly increases the water uptake when present in skin, as compared to skin without urea, and it promotes formation of larger water inclusions in the tissue. The results confirm that urea can be used as a humectant to increase skin hydration.
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| 5. |
- Albèr, Cathrine, et al.
(författare)
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Spatial imaging and evaluation of humectants impact on stratum corneum hydration with confocal Raman microscpectroscopy
- 2012
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Ingår i: International Journal of Cosmetic Science. - : John Wiley & Sons. - 0142-5463 .- 1468-2494. ; :34, s. 359-359
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Objective: Confocal Raman microspectroscopy (CRM) enables non-invasive depth-scanning of biological tissues. The technique has been used to obtain information about the molecular composition of the skin, tracking of externally applied compounds and to determine molecular concentration profiles. The objective of this study is to use CRM in order to evaluate the changes in stratum corneum hydration when applying polyethylene glycol and the humectants urea and glycerol, and thereby also varying the external chemical potential of water. In the present study we also utilize the advantages of CRM to create novel spatial high- resolution Raman images of stratum corneum. Methodology: Excised porcine skin membranes (500 nm in thickness) were equilibrated from the surface with phosphate buffered saline (PBS) together with different types of humectants using Franz cells. The Raman measurements were performed with a WITec alpha300 system (Ulm, Germany) equipped with a 532 nm laser. The change in stratum corneum hydration after treatment with different humectants was determined from the relative intensity of the water and protein spectra. Raman images were created along a cross section by integrating the Raman intensities for specific vibrational modes. Results and conclusions: The results show that the hydration profiles of stratum corneum correlates well with the gradient in water chemical potential created by the applied humectants, i.e. low molecular weight humectants enable increased hydration of stratum corneum compared to a high molecular weight, non-penetrating polyethylene glycol. In addition the novel results from the Raman imaging experiments illustrates that it is possible to distinguish between water rich domains and the extracellular lipid rich domains along a cross section of the intact skin membrane.
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| 6. |
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| 7. |
- Kren, F., et al.
(författare)
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Exclusive measurements of pp -> d pi(+)pi(0) : Double-pionic fusion without ABC effect
- 2010
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 684:2-3, s. 110-113
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Tidskriftsartikel (refereegranskat)abstract
- Exclusive measurements of the reaction pp -> d pi(+)pi(0) have been carried out at T-p = 1.1 GeV at the CELSIUS storage ring using the WASA detector. The isovector pi(+)pi(0) channel exhibits no enhancement at low invariant pi pi masses, i.e. no ABC effect. Therefore this most basic isovector double-pionic fusion reaction qualifies as an ideal test case for the conventional t-channel Delta Delta excitation process. Indeed, the obtained differential distributions reveal the conventional t-channel Delta Delta mechanism as the appropriate reaction process, which also accounts for the observed energy dependence of the total cross section.
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| 8. |
- Petrén, Henrik, et al.
(författare)
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eta-meson production in proton-proton collisions at excess energies of 40 and 72 MeV
- 2010
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 82:5, s. 055206-
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Tidskriftsartikel (refereegranskat)abstract
- The production of eta mesons in proton-proton collisions has been studied using the WASA detector at the CELSIUS storage ring at excess energies of Q = 40 MeV and Q = 72 MeV. The eta was detected through its 2 gamma decay in a near-4 pi electromagnetic calorimeter, whereas the protons were measured by a combination of straw chambers and plastic scintillator planes in the forward hemisphere. About 6.9 x 10(4) and 9.3 x 10(4) events were found at Q = 40 MeV and Q = 72 MeV, respectively, with background contributions of less than 5%. A simple parametrization of the production cross section in terms of low partial waves was used to evaluate the acceptance corrections. Strong evidence was found for the influence of higher partial waves. The Dalitz plots show the presence of p waves in both the pp and the eta {pp} systems and the angular distributions of the eta in the center-of-mass frame suggest the influence of d-wave eta mesons.
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| 9. |
- Schonning, K., et al.
(författare)
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The pd -> He-3 eta pi(0) reaction at T-p=1450 MeV CELSIUS/WASA Collaboration
- 2010
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 685:1, s. 33-37
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Tidskriftsartikel (refereegranskat)abstract
- The cross section for the pd -> He-3 eta pi(0) reaction has been measured at a beam energy of 1450 MeV using the WASA detector at the CELSIUS storage ring. The He-3 was detected in coincidence with four photons from the decays of the two mesons. The data indicate that the production mechanism involves the formation of the Delta(1232) isobar. Although the beam energy does not allow the full peak of this resonance to be seen, the invariant mass distributions Of all three pairs of final particles are well reproduced by a phase space Monte Carlo simulation weighted with the p-wave factor of the square of the pi(0) momentum in the He-3 pi(0) system.
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| 10. |
- Schönning, Karin, et al.
(författare)
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Production of eta and 3 pi mesons in the pd -> (HeX)-He-3 reaction at 1360 and 1450 MeV
- 2010
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 45:1, s. 11-21
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Tidskriftsartikel (refereegranskat)abstract
- The cross-sections of the pd -> He-3 eta, pd -> He-3 pi(0)pi(0)pi(0) and pd -> He-3 pi(+)pi(-)pi(0) reactions have been measured at the beam kinetic energies T-p = 1360 MeV and T-p = 1450 MeV using the CELSIUS/WASA detector setup. At both energies, the differential cross-section d sigma/d Omega of the eta meson in the pd -> He-3 eta reaction shows a strong forward-backward asymmetry in the CMS. The ratio between the pd -> He-3 pi(+)pi(-)pi(0) and pd -> He-3 pi(0)pi(0)pi(0) cross-sections has been analysed in terms of isospin amplitudes. The reconstructed invariant-mass distributions of the pi pi, He-3 pi and (3)He2 pi systems provide hints on the role of nucleon resonances in the 3 pi production process.
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