| 1. |
- Amann, Peter, et al.
(författare)
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A dedicated photoelectron spectroscopy instrument for studies of catalytic reactions at pressures exceeding 1 bar
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Here, we present a new high-pressure x-ray photoelectron spectroscopy system dedicated to probing catalytic reactions under realistic conditions at pressures exceeding 1 bar. The instrument builds around the concept of a “virtual cell” in which a gasflow is directed onto the sample surface creating a local high pressure on top of the sample. This allows the instrument to maintain a low pressure of a few mbars in the main chamber, while simultaneously keeping a local pressure of around 1 bar. Synchrotron radiation based grazing incidence photoemission within ± 5° is used to enhance the surface sensitivity in the experiment. The aperture, separating the high-pressure region from the differential pumping of the electron spectrometer, consists of multiple, evenly spaced, mm sized holes matching the footprint of the x-ray beam on the sample surface. As the photo-emitted electrons are subject to strong scattering in the gas phase and the resulting signal is therefore highly dependent on the sample to aperture distance, the latter is controlled with high precision using a fully integrated manipulator that allows for sample movement with step sizes of 10 nm between 0 and –5 mm with very low vibrational amplitude. The instrumental features allows acquisition of metallic bulk spectra at He pressures up to 2.5 bar and also allows for following C1s spectra under realistic gas mixtures of CO + H2with various temperatures up to 500°C. This capability opens for studies of catalytic reactions in operandi.
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| 2. |
- Amann, Peter, et al.
(författare)
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A high-pressure x-ray photoelectron spectroscopy instrument for studies of industrially relevant catalytic reactions at pressures of several bars
- 2019
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 90:10
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Tidskriftsartikel (refereegranskat)abstract
- We present a new high-pressure x-ray photoelectron spectroscopy system dedicated to probing catalytic reactions under realistic conditions at pressures of multiple bars. The instrument builds around the novel concept of a "virtual cell" in which a gas flow onto the sample surface creates a localized high-pressure pillow. This allows the instrument to be operated with a low pressure of a few millibar in the main chamber, while simultaneously a local pressure exceeding 1 bar can be supplied at the sample surface. Synchrotron based hard x-ray excitation is used to increase the electron mean free path in the gas region between sample and analyzer while grazing incidence <5 degrees close to total external refection conditions enhances surface sensitivity. The aperture separating the high-pressure region from the differential pumping of the electron spectrometer consists of multiple, evenly spaced, micrometer sized holes matching the footprint of the x-ray beam on the sample. The resulting signal is highly dependent on the sample-to-aperture distance because photoemitted electrons are subject to strong scattering in the gas phase. Therefore, high precision control of the sample-to-aperture distance is crucial. A fully integrated manipulator allows for sample movement with step sizes of 10 nm between 0 and -5 mm with very low vibrational amplitude and also for sample heating up to 500 degrees C under reaction conditions. We demonstrate the performance of this novel instrument with bulk 2p spectra of a copper single crystal at He pressures of up to 2.5 bars and C1s spectra measured in gas mixtures of CO + H-2 at pressures of up to 790 mbar. The capability to detect emitted photoelectrons at several bars opens the prospect for studies of catalytic reactions under industrially relevant operando conditions.
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| 3. |
- Bäckström, Erik, 1983-, et al.
(författare)
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Storing keV negative ions for an hour : The lifetime of the metastable 2P1/2 level in 32S−
- 2015
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 114:14
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Tidskriftsartikel (refereegranskat)abstract
- We use a novel electrostatic ion storage ring to measure the radiative lifetime of the upper level in the 3p 5 P 2 o 1/2 →3p 5 P 2 o 3/2 spontaneous radiative decay in S − 32 to be 503±54 sec . This is by orders of magnitude the longest lifetime ever measured in a negatively charged ion. Cryogenic cooling of the storage ring gives a residual-gas pressure of a few times 10 −14 mbar at 13 K and storage of 10 keV sulfur anions for more than an hour. Our experimental results differ by 1.3σ from the only available theoretical prediction.
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| 4. |
- Chartkunchand, Kiattichart C., et al.
(författare)
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Dianion diagnostics in DESIREE : High-sensitivity detection of C-n(2-) from a sputter ion source
- 2018
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 89:3
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Tidskriftsartikel (refereegranskat)abstract
- A sputter ion source with a solid graphite target has been used to produce dianions with a focus on carbon cluster dianions, C-n(2-), with n = 7-24. Singly and doubly charged anions from the source were accelerated together to kinetic energies of 10 keV per atomic unit of charge and injected into one of the cryogenic (13 K) ion-beam storage rings of the Double ElectroStatic Ion Ring Experiment facility at Stockholm University. Spontaneous decay of internally hot C-n(2-) dianions injected into the ring yielded C-n(2-) anions with kinetic energies of 20 keV, which were counted with a microchannel plate detector. Mass spectra produced by scanning the magnetic field of a 90 degrees analyzing magnet on the ion injection line reflect the production of internally hot C-7(2-) - C-24(2-) dianions with lifetimes in the range of tens of microseconds to milliseconds. In spite of the high sensitivity of this method, no conclusive evidence of C-6(2-) was found while there was a clear C-7(2-) signal with the expected isotopic distribution. This is consistent with earlier experimental studies and with theoretical predictions. An upper limit is deduced for a C-6(2-) signal that is two orders-of-magnitude smaller than that for C-7(2-). In addition, CnO2- and CnCu2- dianions were detected.
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| 5. |
- Chartkunchand, Kiattichart C., et al.
(författare)
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Radiative lifetimes of the bound excited states of Pt-
- 2016
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 94:3
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 American Physical Society.The intrinsic radiative lifetimes of the 5d106sS1/22 and 5d96s2 D3/22 bound excited states in the platinum anion Pt- have been studied at cryogenic temperatures at the Double ElectroStatic Ion Ring Experiment (DESIREE) facility at Stockholm University. The intrinsic lifetime of the higher-lying 5d106s S1/22 state was measured to be 2.54±0.10s, while only a lifetime in the range of 50-200 ms could be estimated for the 5d96s2 D3/22 fine-structure level. The storage lifetime of the Pt- ion beam was measured to be a little over 15 min at a ring temperature of 13K. The present study reports the lifetime of an atomic negative ion in an excited bound state with an electron configuration different from that of the ground state.
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| 6. |
- Eklund, Gustav, et al.
(författare)
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Cryogenic merged-ion-beam experiments in DESIREE : Final-state-resolved mutual neutralization of Li+ and D-
- 2020
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society (APS). - 2469-9926 .- 2469-9934. ; 102:1
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an experimental technique to study charge-and energy-flow processes in sub-eV collisions between oppositely charged, internally cold, ions of atoms, molecules, and clusters. Two ion beams are stored in separate rings of the cryogenic ion-beam storage facility DESIREE, and merged in a common straight section where a set of biased drift tubes is used to control the center-of-mass collision energy locally in fine steps. Here, we present measurements on mutual neutralization between Li+ and D- where a time-sensitive imaging-detector system is used to measure the three-dimensional distance between the neutral Li and D atoms as they reach the detector. This scheme allows for direct measurements of kinetic-energy releases, and here it reveals separate populations of the 3s state and the (3p + 3d) states in neutral Li while the D atom is left in its ground state 1s. The branching fraction of the 3s final state is measured to be 57.8 +/- 0.7% at a center-of-mass collision energy of 78 +/- 13 meV. The technique paves the way for studies of charge-, energy-, and mass-transfer reactions in single collisions involving molecular and cluster ions in well-defined quantum states.
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| 7. |
- Gatchell, Michael, et al.
(författare)
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Commissioning of the DESIREE storage rings - a new facility for cold ion-ion collisions
- 2014
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Ingår i: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013). - : Institute of Physics (IOP). ; 488:1
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Konferensbidrag (refereegranskat)abstract
- We report on the ongoing commissioning of the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. Beams of atomic carbon anions (C-) and smaller carbon anion molecules (C-2(-), C-3(-), C-4(-) etc.) have been produced in a sputter ion source, accelerated to 10 keV or 20 keV, and stored successfully in the two electrostatic rings. The rings are enclosed in a common vacuum chamber cooled to below 13 Kelvin. The DESIREE facility allows for studies of internally relaxed single isolated atomic, molecular and cluster ions and for collision experiments between cat-and anions down to very low center-of-mass collision energies (meV scale). The total thermal load of the vacuum chamber at this temperature is measured to be 32 W. The decay rates of stored ion beams have two components: a non-exponential component caused by the space charge of the beam itself which dominates at early times and an exponential term from the neutralization of the beam in collisions with residual gas at later times. The residual gas limited storage lifetime of carbon anions in the symmetric ring is over seven minutes while the 1/e lifetime in the asymmetric ring is measured to be about 30 seconds. Although we aim to improve the storage in the second ring, the number of stored ions are now sufficient for many merged beams experiments with positive and negative ions requiring milliseconds to seconds ion storage.
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| 8. |
- Gatchell, Michael, et al.
(författare)
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First results from the Double ElectroStatic Ion-Ring ExpEriment, DESIREE
- 2014
-
Ingår i: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013). - : Institute of Physics (IOP). ; 488
-
Konferensbidrag (refereegranskat)abstract
- We have stored the first beams in one of the rings of the double electrostatic ion-storage ring, DESIREE at cryogenic and at room temperature conditions. At cryogenic operations the following parameters are found. Temperature; T= 13K, pressure; p <10(-13) mbar, initial number of stored ions; N > 10(7) and storage lifetime of a C-2(-) beam; tau = 450 S.
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| 9. |
- Hartman, Henrik, et al.
(författare)
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First storage of ion beams in the Double Electrostatic Ion-Ring Experiment : DESIREE
- 2013
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 84:5
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first storage of ion beams in the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. We have produced beams of atomic carbon anions and small carbon anion molecules (Cn-, n = 1, 2, 3, 4) in a sputter ion source. The ion beams were accelerated to 10 keV kinetic energy and stored in an electrostatic ion storage ring enclosed in a vacuum chamber at 13 K. For 10 keV C2- molecular anions we measure the residual-gas limited beam storage lifetime to be 448 s +/- 18 s with two independent detector systems. Using the measured storage lifetimes we estimate that the residual gas pressure is in the 10-14 mbar range. When high current ion beams are injected, the number of stored particles does not follow a single exponential decay law as would be expected for stored particles lost solely due to electron detachment in collision with the residual-gas. Instead, we observe a faster initial decay rate, which we ascribe to the effect of the space charge of the ion beam on the storage capacity.
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| 10. |
- Kamińska, Magdalena, et al.
(författare)
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Lifetime of the bound excited level in Ni
- 2016
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Ingår i: Physical Review A. - 1050-2947 .- 1094-1622. ; 93:1
-
Tidskriftsartikel (refereegranskat)abstract
- The intrinsic lifetime of the upper level in the bound-bound 3d(9) 4s(2) D-2(3/2) -> 3d(9) 4s(2) D-2(5/2) radiative transition in Ni- was measured to be 15.1 +/- 0.4 s. The experiment was performed at cryogenic temperatures in one of the ion-beam storage rings of the Double ElectroStatic Ion Ring ExpEriment facility at Stockholm University. The storage lifetime of the Ni- ion beam was measured to be close to 5 min at a ring temperature of 13 K.
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| 11. |
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| 12. |
- Kristiansson, Moa K., 1989-, et al.
(författare)
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High-precision electron affinity of oxygen
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Negative ions are important in many areas of science and technology, e.g., in interstellar chemistry, for accelerator-based radionuclide dating, and in anti-matter research. They are unique quantum systems where electron-correlation effects govern their properties. Atomic anions are loosely bound systems, which with very few exceptions lack optically allowed transitions. This limits prospects for high-resolution spectroscopy, and related negative-ion detection methods. Here, we present a method to measure negative ion binding energies with an order of magnitude higher precision than what has been possible before. By laser-manipulation of quantum-state populations, we are able to strongly reduce the background from photodetachment of excited states using a cryogenic electrostatic ion-beam storage ring where keV ion beams can circulate for up to hours. The method is applicable to negative ions in general and here we report an electron affinity of 1.461 112 972(87) eV for O-16. High-precision measurements are useful to find isotopic shifts and electron correlation. Here the authors measure electron affinity and hyperfine splitting of atomic oxygen with higher precision than previous studies.
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| 13. |
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| 14. |
- Schmidt, Henning, et al.
(författare)
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DESIREE as a new tool for interstellar ion chemistry
- 2008
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Ingår i: International Journal of Astrobiology. - 1473-5504 .- 1475-3006. ; 7:3-4, s. 205-208
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Tidskriftsartikel (refereegranskat)abstract
- A novel cryogenic electrostatic storage device consisting of two ion-beam storage rings with a common straight section for studies of interactions between oppositely charged ions at low and well-defined relative velocities is under construction at Stockholm University. Here we consider the prospect of using this new tool to measure cross-sections and rate coefficients for mutual neutralization reactions of importance in interstellar ion chemistry in general and specifically in cosmic pre-biotic ion chemistry.
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| 15. |
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| 16. |
- Schmidt-May, Alice F., 1988-, et al.
(författare)
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State-resolved mutual neutralization of 16O+ with 1H− and 2H− at collision energies below 100 meV
- 2024
-
Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 109:5
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Tidskriftsartikel (refereegranskat)abstract
- We measured the product-state distribution and its dependence on the hydrogen isotope for the mutual neutralization between 16O+ and 1,2H− at the double electrostatic ion-beam storage ring DESIREE for center-of-mass collision energies below 100 meV. We find at least six product channels into ground-state hydrogen and oxygen in different excited states. The majority of oxygen products populate terms corresponding to 2?22?3(4?∘)4? with 5S∘ as the main reaction product. We also observe product channels into terms corresponding to 2?22?3(4?)3?. Collisions with the heavier hydrogen isotope yield a branching into these lower excited states smaller than collisions with 1H−. The observed reaction products agree with the theoretical predictions. The detailed branching fractions, however, differ between the theoretical results, and none of them fully agree with the experiment.
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| 17. |
- Thomas, Richard D., et al.
(författare)
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DESIREE : Physics with cold stored ion beams
- 2015
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Ingår i: DR2013. - : EDP Sciences. ; 84, s. 01004-01004
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Konferensbidrag (refereegranskat)abstract
- Here we will briefly describe the commissioning of the Double ElectroStatic Ion Ring ExpEriment (DESIREE) facility at Stockholm University, Sweden. This device uses purely electrostatic focussing and deflection elements and allows ion beams of opposite charge to be confined under extreme high vacuum and cryogenic conditions in separate rings and then merged over a common straight section. This apparatus allows for studies of interactions between cations and anions at very low and well-defined centre-of-mass energies (down to a few meV) and at very low internal temperatures (down to a few K).
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| 18. |
- Thomas, Richard D., et al.
(författare)
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The double electrostatic ion ring experiment : A unique cryogenic electrostatic storage ring for merged ion-beams studies
- 2011
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 82:6, s. 065112-
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Tidskriftsartikel (refereegranskat)abstract
- We describe the design of a novel type of storage device currently under construction at Stockholm University, Sweden, using purely electrostatic focussing and deflection elements, in which ion beams of opposite charges are confined under extreme high vacuum cryogenic conditions in separate rings and merged over a common straight section. The construction of this double electrostatic ion ring experiment uniquely allows for studies of interactions between cations and anions at low and well-defined internal temperatures and centre-of-mass collision energies down to about 10 K and 10 meV, respectively. Position sensitive multi-hit detector systems have been extensively tested and proven to work in cryogenic environments and these will be used to measure correlations between reaction products in, for example, electron-transfer processes. The technical advantages of using purely electrostatic ion storage devices over magnetic ones are many, but the most relevant are: electrostatic elements which are more compact and easier to construct; remanent fields, hysteresis, and eddy-currents, which are of concern in magnetic devices, are no longer relevant; and electrical fields required to control the orbit of the ions are not only much easier to create and control than the corresponding magnetic fields, they also set no upper mass limit on the ions that can be stored. These technical differences are a boon to new areas of fundamental experimental research, not only in atomic and molecular physics but also in the boundaries of these fields with chemistry and biology. For examples, studies of interactions with internally cold molecular ions will be particular useful for applications in astrophysics, while studies of solvated ionic clusters will be of relevance to aeronomy and biology.
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| 19. |
- Andersson, Mathias H., et al.
(författare)
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Displacement effects of ship noise on fish population : FP7 - Collaborative Project n° 314227 WP 4: Sensitivity of marine life to shipping noise Task 4.2.1
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Ship induced noise is one of the major contributors to the elevated noise levels in the world’s oceans today. However, the knowledge about the impact on marine organisms is still scarce. Especially the effects on fish behaviour needs to be studied as fish are a fundamental part of the oceans ecosystem. Direct measurement of fish behaviour in the open sea area is technically difficult but needs to be done in order to estimate reaction thresholds and scales of any reaction. This experiment studies the long term behavioural reaction by wild cod (Gadus morhua) to ship noise and describes the character and scale of the reaction. This study took place on the Swedish west coast with a small local cod population and the area is normally without any large vessel traffic. For the ship disturbance, the Swedish Coast Guard ship KBV 032 was hired and passed thru the area nine times during three days. During the three days of ship noise exposure, the noise levels increased well above the ambient noise. The ship signature was what could be expected in terms of spectral level with most radiated noise energy between 100 - 500 Hz. The ship had a higher source level than expected (232 dB re 1μPa at 1 m, 10 - 300 Hz) but this was deliberate as the crew was asked to use the propellers in a non-optimal way to generate as much noise as possible. The result was a lot of broadband cavitation pulses generated by the ship. Then a noise footprint model was created and used in the estimates of received levels (exposure level) by the individual fish in the area based on the most probable location. It was clear in the transmission loss varied between the two sites where at the shallow site, the noise was attenuated more compared to the deep site. This is probably caused by the quite complicated propagation pattern. Also, the acoustically different bottom properties will affect the transmission loss in the area. In total, 39 cod (Gadus morhua) were caught by hand jigging and were fitted with internal acoustical tags. Bottom mounted receivers were deployed covering the area where the cod were known to inhabit. This study was designed to capture more large scale movements of hundreds of meters and not startle responses to the ship noise. Out of the 39 tagged fish, 17 and 18 fish met the set quality criterion for the short time behaviour analysis and 23 fish for long time behaviour to be included in the analysis. Some fish met the quality criteria for both the short and long term analysis. The other fish were either eaten by seals, caught by fishermen, left the area or had a malfunctioning tag. In general, the noticed reaction in terms of horizontal swimming were much smaller than expected and what the study was designed for. This results was surprising as the sound pressure levels the fish were exposed to would, based on the literature, cause a strong behaviour response in the fish. The movement was not in any large scale that would affect their energy consumption and affect their long term survival. This study was able to track fish with an accuracy of less than 10 m and estimates an interval of received noise level. This is one of the first studies of its kind that is tracking free swimming fish over a long period of time during an acoustic disturbance.
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| 20. |
-
Att välja trä
- 2020. - 10
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Samlingsverk (redaktörskap) (populärvet., debatt m.m.)
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| 21. |
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| 22. |
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| 23. |
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| 24. |
- Bladh, Oscar, et al.
(författare)
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Comparison of SARS-CoV-2 spike-specific IgA and IgG in nasal secretions, saliva and serum
- 2024
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Ingår i: Frontiers in Immunology. - : FRONTIERS MEDIA SA. - 1664-3224. ; 15
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: Several novel vaccine platforms aim at mucosal immunity in the respiratory tract to block SARS-CoV-2 transmission. Standardized methods for mucosal sample collection and quantification of mucosal antibodies are therefore urgently needed for harmonized comparisons and interpretations across mucosal vaccine trials and real-world data. Methods: Using commercial electrochemiluminescence antibody panels, we compared SARS-CoV-2 spike-specific IgA and IgG in paired saliva, nasal secretions, and serum from 1048 healthcare workers with and without prior infection. Results: Spike-specific IgA correlated well in nasal secretions and saliva (r>0.65, p<0.0001), but the levels were more than three-fold higher in nasal secretions as compared to in saliva (p<0.01). Correlations between the total population of spike-specific IgA and spike-specific secretory IgA (SIgA) were significantly stronger (p<0.0001) in nasal secretions (r=0.96, p<0.0001) as opposed to in saliva (r=0.77, p<0.0001), and spike-specific IgA correlated stronger (p<0.0001) between serum and saliva (r=0.73, p<0.001) as opposed to between serum and nasal secretions (r=0.54, p<0.001), suggesting transudation of monomeric spike specific IgA from the circulation to saliva. Notably, spike-specific SIgA had a markedly higher SARS-CoV-2 variant cross-binding capacity as compared to the total population of spike specific IgA and IgG in both nasal secretions, saliva and serum, (all p<0.0001), which emphasizes the importance of taking potential serum derived monomeric IgA into consideration when investigating mucosal immune responses. Discussion: Taken together, although spike-specific IgA can be reliably measured in both nasal secretions and saliva, our findings imply an advantage of higher levels and likely also a larger proportion of SIgA in nasal secretions as compared to in saliva. We further corroborate the superior variant cross-binding capacity of SIgA in mucosal secretions, highlighting the potential protective benefits of a vaccine targeting the upper respiratory tract.
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| 25. |
- Bladh, Oscar, et al.
(författare)
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Comparison of SARS-CoV-2 spike-specific IgA and IgG in nasal secretions, saliva and serum
- 2024
-
Ingår i: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 15
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: Several novel vaccine platforms aim at mucosal immunity in the respiratory tract to block SARS-CoV-2 transmission. Standardized methods for mucosal sample collection and quantification of mucosal antibodies are therefore urgently needed for harmonized comparisons and interpretations across mucosal vaccine trials and real-world data.Methods: Using commercial electrochemiluminescence antibody panels, we compared SARS-CoV-2 spike-specific IgA and IgG in paired saliva, nasal secretions, and serum from 1048 healthcare workers with and without prior infection.Results: Spike-specific IgA correlated well in nasal secretions and saliva (r>0.65, p<0.0001), but the levels were more than three-fold higher in nasal secretions as compared to in saliva (p<0.01). Correlations between the total population of spike-specific IgA and spike-specific secretory IgA (SIgA) were significantly stronger (p<0.0001) in nasal secretions (r=0.96, p<0.0001) as opposed to in saliva (r=0.77, p<0.0001), and spike-specific IgA correlated stronger (p<0.0001) between serum and saliva (r=0.73, p<0.001) as opposed to between serum and nasal secretions (r=0.54, p<0.001), suggesting transudation of monomeric spike specific IgA from the circulation to saliva. Notably, spike-specific SIgA had a markedly higher SARS-CoV-2 variant cross-binding capacity as compared to the total population of spike specific IgA and IgG in both nasal secretions, saliva and serum, (all p<0.0001), which emphasizes the importance of taking potential serum derived monomeric IgA into consideration when investigating mucosal immune responses.Discussion: Taken together, although spike-specific IgA can be reliably measured in both nasal secretions and saliva, our findings imply an advantage of higher levels and likely also a larger proportion of SIgA in nasal secretions as compared to in saliva. We further corroborate the superior variant cross-binding capacity of SIgA in mucosal secretions, highlighting the potential protective benefits of a vaccine targeting the upper respiratory tract.
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| 26. |
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| 27. |
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| 28. |
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| 29. |
- Blom, Hans, et al.
(författare)
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Flocculate removal after alkaline lysis in plasmid DNA production.
- 2010
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Ingår i: Vaccine. - : Elsevier BV. - 0264-410X .- 1873-2518. ; 29:1, s. 6-10
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Tidskriftsartikel (refereegranskat)abstract
- Alkaline lysis is the most commonly used method following harvest of bacterial cells for production of plasmid DNA. The method was originally developed for laboratory scale experiments and has shown to be challenging at larger scales. A major problem prior to further downstream processing is the risk of filter clogging without efficient removal of the flocculate that occurs after neutralization. For this purpose we here present a scalable method where the clarification of alkaline lysate is greatly simplified. Through a rapid procedure, involving the addition of ammonium hydrogen carbonate to the neutralized alkaline lysate, the flocculate is lifted to the surface of the solution by the released carbon dioxide and ammonium. After this step a clarified solution can be drained from the bottom of the vessel. The procedure does not impact pH, plasmid DNA concentration or the ratio of open circular to supercoiled plasmid DNA in the solution.
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| 30. |
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| 31. |
- Blom, Kristin, et al.
(författare)
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Eosinophil associated genes in the inflammatory bowel disease 4 region : Correlation to inflammatory bowel disease revealed
- 2012
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Ingår i: World Journal of Gastroenterology. - : Baishideng Publishing Group Inc.. - 1007-9327 .- 2219-2840. ; 18:44, s. 6409-6419
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Tidskriftsartikel (refereegranskat)abstract
- AIM: To study the association between inflammatory bowel disease (IBD) and genetic variations in eosinophil protein X (EPX) and eosinophil cationic protein (ECP). METHODS: DNA was extracted from ethylene diamine tetraacetic acid blood of 587 patients with Crohn's disease (CD), 592 with ulcerative colitis (UC) and 300 healthy subjects. The EPX405 (G > C, rs2013109), ECP434 (G > C, rs2073342) and ECP562 (G > C, rs2233860) gene polymorphisms were analysed, by the 5'-nuclease allelic discrimination assay. For determination of intracellular content of EPX and ECP in granulocytes, 39 blood samples was collected and extracted with a buffer containing cetyltrimethylammonium bromide. The intracellular content of EPX was analysed using an enzyme-linked immunosorbent assay. The intracellular content of ECP was analysed with the UniCAP (R) system as described by the manufacturer. Statistical tests for calculations of results were chi(2) test, Fisher's exact test, ANOVA, Student-Newman-Keuls test, and Kaplan-Meier survival curve with Log-rank test for trend, the probability values of P < 0.05 were considered statistically significant. RESULTS: The genotype frequency for males with UC and with an age of disease onset of >= 45 years (n = 57) was for ECP434 and ECP562, GG = 37%, GC = 60%, CC = 4% and GG = 51%, GC = 49%, CC = 0% respectively. This was significantly different from the healthy subject's genotype frequencies of ECP434 (GG = 57%, GC = 38%, CC = 5%; P = 0.010) and ECP562 (GG = 68%, GC = 29 /0,CC = 3%; P = 0.009). The genotype frequencies for females, with an age of disease onset of >= 45 years with CD (n = 62), was for the ECP434 and ECP562 genotypes GG = 37%, GC = 52%, CC = 11% and GG = 48%, GC = 47% and CC = 5% respectively. This was also statistically different from healthy controls for both ECP434 (P = 0.010) and ECP562 (P = 0.013). The intracellular protein concentration of EPX and ECP was calculated in mu g/10(6) eosinophils and then correlated to the EPX 405 genotypes. The protein content of EPX was highest in the patients with the CC genotype of EPX405 (GG = 4.65, GC = 5.93, and CC = 6.57) and for ECP in the patients with the GG genotype of EPX405 (GG = 2.70, GC = 2.47 and CC = 1.90). ANOVA test demonstrated a difference in intracellular protein content for EPX (P = 0.009) and ECP (P = 0.022). The age of disease onset was linked to haplotypes of the EPX405, ECP434 and ECP562 genotypes. Kaplan Maier curve showed a difference between haplotype distributions for the females with CD (P = 0.003). The highest age of disease onset was seen in females with the EPX405CC, ECP434GC, ECP562CC haplotype (34 years) and the lowest in females with the EPX405GC, ECP434GC, ECP562GG haplotype (21 years). For males with UC there was also a difference between the highest and lowest age of the disease onset (EPX405CC, ECP434CC, ECP562CC, mean 24 years vs EPX405GC, ECP434GC, ECP562GG, mean 34 years, P = 0.0009). The relative risk for UC patients with ECP434 or ECP562-GC/CC genotypes to develop dysplasia/cancer was 2.5 (95%CI: 1.2-5.4, P = 0.01) and 2.5 (95%CI: 1.1-5.4, P = 0.02) respectively, compared to patients carrying the GG-genotypes. CONCLUSION: Polymorphisms of EPX and ECP are associated to IBD in an age and gender dependent manner, suggesting an essential role of eosinophils in the pathophysiology of IBD.
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| 32. |
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| 33. |
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| 34. |
- Blom, Martin, et al.
(författare)
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Företaget och dess roll(er) i samhället - fallet Findus
- 2016
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Ingår i: Organisation & Samhälle. - Stockholm. - 2001-9114 .- 2002-0287. ; :2, s. 4-9
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Man kan se nedläggningen av Findus i Bjuv på många olika sätt och ur flera olika perspektiv.
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| 35. |
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| 36. |
- Blom, Martin, et al.
(författare)
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Företagets roller i samhället
- 2016. - 1
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Varför finns egentligen företag? Vilka roller spelar de i samhället?Vårt svar är att företag samtidigt spelar flera olika roller och i boken presenteras och diskuteras några av dessa.Utgångspunkten är de många offentliga sammanhang där företag och företagande diskuteras och där olika, ibland sinsemellan motstridiga, roller bildar utgångspunkten. Dessa roller har alla sitt stöd i vetenskaplig teori liksom i olika ideologier, något som också tas upp i boken. Splittringen i synen på företag som fenomen och vilka roller de spelar i samhället får också konsekvenser i förhållande till dagsaktuell politisk debatt.Boken riktar sig främst till studenter på universitet och högskola som precis påbörjat sina akademiska studier i företagsekonomi,men också till mer erfarna studenter som börjat reflektera över fenomenet företag. Nyfikna personer inom näringsliv och politik bör också finna boken stimulerande och intressant.Syftet med boken är att ge en tankeväckande introduktion till några av de perspektiv som finns på företag och den mångfald av teorier som betonar och stödjer dessa olika perspektiv.Ambitionen är också att bidra till en mer nyanserad syn på fenomenet företag och vilka roller de spelar och därmed bidra till en mer konstruktiv debatt i de sammanhang där företag och företagande åberopas.
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| 37. |
- Blom, Martin, et al.
(författare)
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How to understand and handle divergent views on the need for leadership interventions: a social constructionist approach
- 2016
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Konferensbidrag (refereegranskat)abstract
- This paper addresses the challenge of how to understand and handle divergent views on the need for leadership interventions between managers and subordinates. Recent popular discourses of leadership, such as the authentic leadership perspective, privileges the potential leader himself or herself as the origin of leadership. This perspective thereby neglects the view of the followers and the essentially socially constructed relationship between leaders and followers. Based upon a critique against essentialist views of leadership such as authentic leadership we suggest a model on how to analyse divergent views between leaders and followers and its implications regarding managerial discretion regarding leadership initiatives.
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| 38. |
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| 39. |
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| 40. |
- Blom, Martin, et al.
(författare)
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Strategy consultants doing strategy : How status and visibility affect strategizing
- 2013
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Ingår i: African Journal of Business Management. - : Academic Journals. - 1993-8233. ; 7:14, s. 1144-1160
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Tidskriftsartikel (refereegranskat)abstract
- Strategy consultants form a highly influential group of strategy practitioners, yet surprisingly neglected within strategy studies. Therefore, we aim to contribute our own understanding to the term, strategy consultants and discuss the characteristics of strategy work. We do this from the perspective of strategy-as-practice and direct our attention to the praxis and practices of strategy consultants. Our study builds upon extensive empirical material, including first hand observations of strategy consulting work being performed. Based upon results from a grounded theory analysis (early- and intermediate stages), we claim that strategy consulting work differs substantially depending on the roles that are constituted by the interaction and relation with the client. We suggest four metaphors to categorize these roles and discuss their characteristics and implications for strategizing activities.
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| 41. |
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| 42. |
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| 43. |
- Blom, Martin, et al.
(författare)
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The (In)voluntary follower
- 2020
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Ingår i: Leadership. - : Sage Publications. - 1742-7150 .- 1742-7169. ; 16:2, s. 163-179
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Tidskriftsartikel (refereegranskat)abstract
- An important assumption when it comes to leader-follower relationships is that compliance and subordination are basically voluntary. In this article, we problematize and develop this assumption and discuss different circumstances in which voluntariness in terms of followership may be compromised. Based on this discussion, we also suggest a tentative model of follower voluntariness, indicating dimensions in which voluntariness can be infringed upon and followership corroded and when it might be more productive to depict an asymmetrical relationship as something else than followership.
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| 44. |
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| 45. |
- Blom, Åsa, et al.
(författare)
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Above Ground Durability of Swedish Softwood
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes aspects of durability of Swedish softwood in above ground applications. The thesis consists of a summary of nine papers, which all aim to explain the existing variation in above ground microbial durability and moisture sensitivity of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris). The methods used were two field tests, one accelerated durability test, and three water permeability tests. The main conclusions made in the study were that Norway spruce sapwood is more susceptible to discolouring fungi than heartwood. With respect to Scots pine, the only important factor for its natural durability above ground was whether the samples consisted of heartwood or of sapwood. There was also no systematic variation between pine heartwood from different stand origins in above ground conditions. Origin had no influence on durability in practice for neither spruce nor pine. Furthermore, in contradiction with traditional thinking, annual ring width and density had no influence on durability in any of the tests. The material came from two different samplings. The ‘old’ material was sampled in the beginning of the 1980s and consisted of Scots pine and Norway spruce from three different origins: the north, the central area, and the south of Sweden. The material was subjected to different handling conditions and surface and end-grain treatments. The ‘old’ material was used in a large above ground field test, carried out between 1985 and 1994. Unfortunately, the spruce sapwood and heartwood was not separated in this field test. In the field trial with the ‘old’ material, the most important factor for the durability of Norway spruce was the samples’ surface- and end-grain treatment. It was also observed that untreated spruce showed better durability than samples that were painted but without proper end-grain treatment. Samples originating from one of the stands were more sensitive towards air-drying than samples from the other two, which was reflected in a higher average moisture content and mass loss for the untreated samples. With respect to Scots pine, the most important factor was whether the sample consisted of heartwood or of sapwood. The heartwood samples were durable irrespective of their previous treatment. The Scots pine sapwood samples, on the other hand, had a very fluctuating moisture content if they were not surface- and end-painted. This was also reflected in higher mass losses in these samples. Even when properly surface- and end grain treated, the sapwood samples did not perform as well as the heartwood samples. The ‘new’ material consisted of Scots pine taken from six different stands, and Norway spruce from five different stands, all from areas in southern Sweden. The sampling was performed in order to achieve a large variation in wood properties. Thus, logs from areas with different climate and growth conditions were collected. This material was used for laboratory tests, and also for the second field test, which was evaluated after a test period of two years. In the second field test untreated Scots pine and Norway spruce samples from the ‘new’ material were investigated. Effects of origin and different tree diameters were examined. Furthermore, Scots pine was separated to heartwood and sapwood, and Norway spruce to mature and juvenile wood. The Norway spruce samples were sawn with vertical or horizontal annual rings. For the Norway spruce in the second field test, vertical annual rings were shown to be very beneficial for avoiding crack formation, while samples with horizontal annual rings displayed a large number of cracks. Despite this, the larger number of cracks did not result in a higher moisture content or more fungal discoloration. Juvenile wood had a slightly higher average discolouring fungal growth grading than the other spruce samples. For Scots pine, the only factor of importance was whether the samples consisted of heartwood or of sapwood. Annual ring width, density and origin had no significant effect on either fungal growth or moisture uptake. This observation held for both Norway spruce samples and Scots pine samples. An accelerated test was run in order to investigate Norway spruce sapwood and heartwood with respect to their differences in durability towards discolouring fungi and moisture uptake. The Mycologg method was used to accelerate fungal growth during a number of forced moisture cycles. The results showed that sapwood was much more sensitive to discolouring fungi than heartwood. Sapwood also recorded a higher average moisture content than heartwood. The differences that were observed between the types of samples were not due to annual ring width, density or origin. It was observed that Norway spruce sapwood samples and heartwood samples showed differences in liquid water permeability. This observation was made especially evident in a droplet absorption test. Water droplets were absorbed much faster on the sapwood samples in comparison with the heartwood samples. This higher affinity to water suggested that a sapwood surface would reach a higher moisture content than a heartwood surface. This observation provides a major explanation of why the sapwood samples showed poorer durability towards discolouring fungi in the Mycologg trials.
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| 46. |
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| 47. |
- Blom, Åsa, et al.
(författare)
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Durability of Untreated Norway Spruce (Picea abies) Exposed Outdoors Above Ground for Nine Years.
- 2004
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 58:2, s. 167-172
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Tidskriftsartikel (refereegranskat)abstract
- Moisture dynamics and durability during weather exposure as affected by origin and production method were studied for nine years on 113 untreated spruce samples. The moisture content was measured on 67 occasions. The weight loss was determined for each sample at the end of the sampling period. The most important factors, affecting both moisture content and weight loss, were origin and drying technique. The samples originating from central Sweden had the best durability, followed by the southern stand, while the northern stand had the lowest durability in terms of weight loss. Airdrying had a negative impact on the performance of samples from all three stands, but to different degrees. Samples from the northern stand were most sensitive to airdrying, in terms of both weight loss and moisture content, followed by the southern stand, while the central stand was least sensitive. Why the samples from the northern stand were more sensitive to airdrying and showed the largest weight losses is unknown; it can only be suggested that the origin of the wood can be of importance for the durability.
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| 48. |
- Blom, Åsa, et al.
(författare)
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Mass loss and moisture dynamics of Scots pine (Pinus sylvestris L.) exposed outdoors above ground in Sweden.
- 2005
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 59:2, s. 183-189
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Tidskriftsartikel (refereegranskat)abstract
- The durability of 566 Scots pine (Pinus sylvestris) samples was tested during a period of 9 years of exposure to weather in Sweden. The parameters investigated were heartwood/sapwood, origin, surface treatment, end-seal, storage and drying method, annual ring width and density. The weight was measured on 67 occasions during 9 years in order to assess the moisture content of the samples. The mass loss was determined for each sample at the end of the trial. Sapwood had a higher moisture uptake and a higher mass loss compared with heartwood. Even if sapwood was painted with an impermeable paint and then end-sealed, it still had higher average moisture content than heartwood. The results also demonstrated that sapwood was more sensitive to different handling conditions than heartwood. Sapwood was sensitive to air-drying and water storage, which was evident in the higher moisture uptake. In terms of mass loss, some differences were evident but they were not statistically significant due to the large standard deviation of the sapwood samples from water-stored logs. The only positive influence of water storage was on samples end-dipped in oil. One explanation could be that water storage led to increased permeability due to bacterial attack, which in turn enhanced the penetration of the oil. Heartwood had low and stable moisture dynamics during the test period, almost independent of treatment or handling conditions. No correlation with moisture uptake or mass loss was evident among annual ring width, origin or density.
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| 49. |
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| 50. |
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