| 1. |
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| 2. |
- Bolsman, Caspar T., et al.
(författare)
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The Use of Resonant Structures for Miniaturizing FMAVs
- 2007
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Ingår i: Proceedings of the 3rd US-European Competition and Workshop on Micro Air Vehicle Systems (MAV07) & European Micro Air Vehicle Conference and Flight Competition (EMAV2007), 17-21 September 2007, Toulouse, France. ; , s. 12-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of resonant structures in FMAVs is an idea inspired by nature. The application of resonancein an oscillating system requires a careful analysis of the involved structures in insects. The applicationof this concept in FMAVs yields opportunities for size reduction. As one moves away from standard constructionalprinciples. The latter become less feasible at the small scale. It is mandatory to include thecontrol mechanism in the design loop from the start. Control over wing kinematics in insects relies oncomplex wing root structures, for FMAVs other solutions are possible and needed. This article providesan overview on structures and their functions in insects and the engineering alternatives. Emphasis is ontechniques which are applicable in smaller designs. In particular, control mechanisms and thorax structuresare covered. Initial concepts are analyzed and presented based onmulti-body and FE representation.
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| 3. |
- Carlert, Sara, et al.
(författare)
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Predicting intestinal precipitation : a case example for a basic BCS class II drug
- 2010
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Ingår i: Pharmaceutical research. - : Springer Science and Business Media LLC. - 0724-8741 .- 1573-904X. ; 27:10, s. 2119-2130
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate the prediction accuracy of in vitro and in vitro/in silico methods for in vivo intestinal precipitation of basic BCS class II drugs in humans. METHODS: Precipitation rate of a model drug substance, AZD0865 (pKa = 6.1; log K(D) = 4.2), was investigated in vitro using simulated intestinal media, and calculations of the crystallization rates were made with a theoretical model. Human intestinal precipitation was estimated by analysis of pharmacokinetic data from clinical studies at different doses. RESULTS: All in vitro models predicted rapid drug precipitation, where the intestinal concentration of dissolved AZD0865 at the highest dose tested was expected to decrease to half after less than 20 min. However, there was no indication of precipitation in vivo in humans as there was a dose proportional increase in drug plasma exposure. The theoretical model predicted no significant precipitation within the range of expected in vivo intestinal concentrations. CONCLUSIONS: This study indicated that simple in vitro methods of in vivo precipitation of orally administered bases overpredict the intestinal crystalline precipitation in vivo in humans. Hydrodynamic conditions were identified as one important factor that needs to be better addressed in future in vivo predictive methods.
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| 4. |
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| 5. |
- Jonsén, Pär, et al.
(författare)
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A novel method for full-body modelling of grinding charges in tumbling mills
- 2012
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 33:S1, s. 2-12
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Tidskriftsartikel (refereegranskat)abstract
- The smoothed particle hydrodynamic (SPH) method is used to model a ball charge and its interaction with the mill structure, while the flexible rubber lifter and the lining are modelled with the finite element method (FEM). The adaptive nature of the SPH-method together with the non-connectivity between the particles results in a method that is able to handle very large deformations. This computational model makes it possible to predict the deflection and stresses of the lining in a pilot ball mill and the mechanical waves travelling in the mill system. It also makes it possible to predict e.g. charge pressure and von Mises’ stress within the charge and the contact forces between the charge and lining. The deflection profile of the lifters obtained from SPH–FEM simulation shows a reasonably good correspondence to pilot mill measurements as measured by an embedded strain gauge sensor.
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| 6. |
- Jonsén, Pär, et al.
(författare)
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A novel method for modelling of interactions between pulp, charge and mill structure in tumbling mills
- 2014
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 63, s. 65-72
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Tidskriftsartikel (refereegranskat)abstract
- Modelling the pulp fluid and its interaction with both the charge and the mill structure is an interesting challenge. The interaction is normally modelled with a combination of CFD and DEM, where the DEM particles (grinding balls) create the structure through which the fluid penetrates, and in its turn creates forces on the grinding balls. However, in a tumbling mill, many free surfaces are found and that limits the use of CFD. An alternative computational approach is here necessary.The smoothed particle hydrodynamic (SPH) method has earlier been used to model a ball charge and its interaction with the mill structure. In the present contribution, a SPH description of the pulp fluid is introduced. The lifters and the lining are still modelled with the finite element method (FEM), and the grinding balls with DEM. This combined computational model makes it possible to predict pressure within the pulp fluid. It is also possible to predict how the dampening effect of the pulp liquid is affected by its viscosity and density. The charge induced torque in a laboratory-scale ball mill is used for validation, and the mechanical shock waves travelling in the mill system are described
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| 7. |
- Jonsén, Pär, et al.
(författare)
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Development of physically based tumbling mill models
- 2014
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Ingår i: Proceedings of XXIII International Mineral Processing Congress. - Santiago : IMPC. - 9789569393150
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Konferensbidrag (refereegranskat)abstract
- Numerical modelling of grinding in tumbling mills is traditionally done with the discrete element method (DEM). The grinding balls are then represented by DEM particles and the mill structure is considered rigid. To include more physical phenomena several numerical methods can be combined. One important improvement is to include the mill structure response, using the finite element method (FEM). The interaction between charge and lining can then be studied in detail. The pulp can also be included using a particle-based continuum method e.g. smoothed particle method (SPH). The strength of SPH lies in modelling of free surface flows and very large deformations and it is suited to model simultaneous fluid and granular flow. Still, the coarse particles (grinding balls) in the charge are suitable to be model using DEM. Each of these methods has their strength and weaknesses, but combined they can successfully mimic the main features of the charge movement. With these numerical tools the complex interaction between the different components of the grinding process; pulp, charge, lining and the mechanical behaviour of the mill, can be studied together. This work will present novel numerical approaches to model, simulate and validate charge behaviour in tumbling mills. These numerical models give possibilities to better understand the physical and mechanical behaviour of particulate material systems during grinding in a tumbling mill. This is important in order to develop and optimise future high-capacity grinding circuits and save energy.
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| 8. |
- Jonsén, Pär, et al.
(författare)
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Modelling and validation of interactions between pulp, charge and mill structure in tumbling mills
- 2013
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Konferensbidrag (refereegranskat)abstract
- Modelling the pulp fluid and its interaction with both the charge and the mill structure is an interesting challenge. To close the gap between reality and numerical result in modelling of tumbling mills, physically realistic methods are a necessity. A problem is that tumbling mills often operate in a metastable state because of the difficulty to balance the rate of replenishment of large ore particles from the feed with the consumption in the charge. Understanding of the charge motion within the mill is of significance in mill optimisation. The comminution process is complex and to include all phenomena that occur in a single numerical model is today not possible. Therefore, limiting the modelling to the physical interaction between charge, mill structure and pulp liquid without simulating the actual crushing is the major goal in this work. The smoothed particle hydrodynamic (SPH) method has earlier been used to model a ball charge and its interaction with the mill structure. The mesh free formulation and the adaptive nature of the SPH method result in a method that handles extremely large deformations and thereby suits modelling of grinding charges and pulp liquids. In the present contribution, a SPH description of the pulp fluid is introduced. The lifters and the lining are still modelled with the finite element method (FEM), and the grinding balls with the discreet element method (DEM). This combined computational model makes it possible to predict pressure and shear stresses within the pulp fluid. It is also possible to predict how the dampening effect of the pulp liquid is affected by its viscosity and density. The charge induced torque in a laboratory-scale ball mill is used for validation, and the mechanical shock waves travelling in the mill system are described. The results from the coupled 3D SPH-DEM-FEM model show a fair estimation of the induced torque due to the charge motion in a tumbling mill. This is a good indication that the model is physically correct.
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| 9. |
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| 10. |
- Jonsén, Pär, et al.
(författare)
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Modelling of internal stresses in grinding charges
- 2011
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Ingår i: Particle-based Methods – Fundamentals and Applications. - Barcelona : International Center for Numerical Methods in Engineering (CIMNE). - 9788489925670 ; , s. 757-768
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Physically realistic methods are a necessity to close the gap between reality and numerical result in modelling of tumbling mills. A problem is that tumbling mills often operate in a metastable state because of the difficulty to balance the rate of replenishment of large ore particles from the feed with the consumption in the charge. Understanding of the charge motion within the mill is of significance in mill optimisation. Both the breakage of ore particles and the wear of liners/ball media are closely linked to the charge motion. In this work, a ball charge and its interaction with the mill structure is modelled with the smoothed particle hydrodynamic (SPH) method. The mesh free formulation and the adaptive nature of the SPH method result in a method that handles extremely large deformations and thereby suits modelling of grinding charges and pulp liquids. The flexible rubber lifter and the lining are modelled with the finite element method (FEM). A hyper-elastic model governs the elastic behaviour of the rubber.The comminution process is complex and to include all phenomena that occur in a single numerical model is today not possible. Therefore, modelling the physical interaction between charge, mill structure and pulp liquid is the major goal in this work. The SPH-FEM model can predict responses of the mill structure e.g. stress and strain. All parts of the mill system will affect its response and the model gives the opportunity to study the influence of the mill structure and e.g. pressure and shear stresses in the charge. This computational model also makes it possible to predict, the contact forces for varying mill dimensions, liner combinations and pulp densities. By comparing numerical results with experimental measurement from grinding in a pilot mill equipped with an instrumented rubber lifter a validation is done. The deflection profile of the lifters obtained from SPH-FEM simulation shows a reasonably good correspondence to pilot mill measurements as measured by an embedded strain gauge sensor. This model gives information on the grinding process in tumbling mills and better correlation with experimental measurements.
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| 11. |
- Jonsén, Pär, et al.
(författare)
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Modelling of physical interactions between pulp, charge and mill structure in tumbling mills
- 2015
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Konferensbidrag (refereegranskat)abstract
- To develop a tumbling mill model that includes the pulp fluid and its simultaneous interactions with both the charge and the mill structure is an interesting challenge. The interactions have previously been modelled for dry grinding with a combination of discrete element method (DEM) or smoothedparticle hydrodynamics (SPH) together with the finite element method (FEM). In such combination the DEM particles or SPH particles represent the grinding balls and FEM is used to model the mill structure. In this work, the previous model is extended to include fluids using SPH. Wet milling with water and a magnetite pulp, for graded and mono-size charges are numerically modelled and validated. The charge behaviour and its interaction with the mill structure are studied. An important part of the model is the coupling between DEM and SPH elements. Sliding and impact along the contacting interfaces are important for the response of the model. In the present work, the contact between the grinding balls and the pulp is realized using a penalty based “nodes to node” contact. The combined SPH-DEM-FEM model presented here can predict responses from the mill structure, as well as the pulp liquid flow and pressure. Validation is conducted by comparing numerical results with experimental measurements from grinding in an instrumented small-scale batch ball millequipped with an accurate torque meter. The simulated charge movement is also compared with high speed video of the charge movement for a number of cases. In conclusion, the SPH-DEM-FEM can predict the charge movement and driving torque with good agreement compared to experimental measurement for a wet tumbling mill process. In addition, the presented methodology is generic and can as well be applied to dry or wet stirred media mills of various configurations
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| 12. |
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| 13. |
- Jonsén, Pär, et al.
(författare)
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Novel simulation methods for mill charges
- 2011
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Ingår i: Conference in minerals engineering. - Luleå : Luleå tekniska universitet. - 9789174392203
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 14. |
- Jonsén, Pär, et al.
(författare)
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Simulation of charge and structure behaviour in a tumbling mill
- 2011
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Ingår i: 8th European LD-DYNA Users Conference May 23-24, 2011, Strasbourg.
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Konferensbidrag (refereegranskat)abstract
- For a long time discrete element methods (DEM) has been used as simulation tools to gain insight into particulate flow processes. The mechanical behaviour in tumbling mills is complex. To include all phenomena that occur in a single numerical model is today not possible. A common approach is to model milling charges using the DEM assuming a rigid mill structure. To close the gap between reality and numerical models in milling, more physically realistic methods have to be used. In this work, the finite element method (FEM) and the smoothed particle hydrodynamic (SPH) method are used together to model a ball mill charge in a tumbling mill. The mesh free formulation and the adaptive nature of the SPH method result in a method that handles extremely large deformations and thereby suits for modelling of grinding charges. The flexible rubber lifter and the lining are modelled with the finite element method. The mill structure consists of rubber lifter and liners and a mantel made of solid steel. For the elastic behaviour of the rubber, a Blatz-Ko hyper-elastic model is used. The supplier of the lining provided experimental data for the rubber. The deflection profile of the lifters obtained from SPH-FEM simulation shows a reasonably good correspondence to pilot mill measurements as measured by an embedded strain gauge sensor. This computational model makes it possible to predict charge pressure and shear stresses within the charge. It is also possible to predict contact forces for varying mill dimensions and liner combinations.
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| 15. |
- Jonsén, Pär, et al.
(författare)
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Validation of a model for physical interactions between pulp, charge and mill structure in tumbling mills
- 2015
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 73, s. 77-84
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Tidskriftsartikel (refereegranskat)abstract
- Modelling the pulp fluid and its simultaneous interactions with both the charge and the mill structure is an interesting challenge. The interactions have previously been modelled for dry grinding with a combination of discrete element method (DEM), smoothed particle hydrodynamics (SPH) and the finite element method (FEM), where the DEM particles or SPH particles represent the grinding balls and FEM is used to model the mill structure. In this work, the previous model is extended to include fluids with SPH. Wet milling with water and a magnetite pulp, for graded and mono-size charges are numerically modelled and validated. The internal working of the charge and the physical interaction between the charge and the mill structure is studied. The combined SPH–DEM–FEM model presented here can predict the classical DEM results, but can also predict responses from the mill structure, as well as the pulp liquid flow and pressure. Validation is conducted by comparing numerical results with experimental measurements from grinding in an instrumented small-scale batch ball mill equipped with an accurate torque metre. The simulated charge movement is also compared with high speed video of the charge movement for a number of cases. Numerical results are in good agreement with experimental measurements
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| 16. |
- Jonsén, Pär, et al.
(författare)
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Validation of tumbling mill charge induced torque as predicted by simulations
- 2013
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Ingår i: 2013 SME Annual Meeting & Exhibit (SME 2013) and CMA 115th National Western Mining Conference. - Denver, CO, USA : Society for Mining, Metalurgy and Exploration. ; , s. 728-733
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Konferensbidrag (refereegranskat)abstract
- Understanding mill charge motion is important. In the charge, the centre of gravity is shifted from the rotational centre of the mill system, and its motion is induced by rotation of the mill, while at the same time the charge creates a torque into the mill system. Breakage of ore particles and wear of liners/ball media are closely linked to the motion. To study these phenomena in a physically correct manner, numerical models for different parts of the mill system are needed. Validations of such models are scarce, because of the difficulty to measure in a tumbling mill. Experimental measurements in a lab mill were done for diverse load cases: varying feed materials, mill fillings, mill speeds and pulp liquids. The mill is set up to directly measure the charge-induced torque. The accuracy is good with relative uncertainty smaller than ±2% for relevant load cases. A full three dimensional numerical model of the whole mill is used to predict induced torque. Agreement between predicted and measured torque at steady-state is good. In addition, the model can accurately predict the mill start-up behaviour for torque and mill power. This proves that the model is physically correct, and can be used for full-scale mills.
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| 17. |
- Jonsén, Pär, et al.
(författare)
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Validation of tumbling mill charge induced torque as predicted by simulations
- 2013
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Ingår i: Minerals & metallurgical processing. - : Springer Science and Business Media LLC. - 0747-9182. ; 30:4, s. 220-225
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Tidskriftsartikel (refereegranskat)abstract
- Understanding mill charge motion is important. In the charge, the center of gravity is shifted from the rotational center of the mill system, and its motion is induced by rotation of the mill, while at the same time the charge creates a torque into the mill system. Breakage of ore particles and wear of liners/ball media are closely linked to this motion. To study these phenomena in a physically correct manner, numerical models for different parts of the mill system are needed. Validations of such models are scarce, because of the difficulty to measure inside a tumbling mill.Experimental measurements in a lab mill were done for a number of load cases: varying feed material, mill filling, mill speed and pulp liquid. The mill is set up to measure the charge-induced torque. The accuracy is good with relative uncertainty smaller than ±2% for relevant load cases.A full three dimensional numerical model of the whole mill is used to predict induced torque. Agreement between predicted and measured torque at steady-state is good. In addition, the model can accurately predict the mill start-up behavior for torque and mill power. This proves that the model is physically correct, and can be used for modeling large-scale mills.
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| 18. |
- Nilsson, Magnus, et al.
(författare)
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A 9-band WCDMA/EDGE transceiver supporting HSPA evolution
- 2011
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Ingår i: [Host publication title missing]. - 0193-6530. ; , s. 366-368
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Konferensbidrag (refereegranskat)abstract
- The future of cellular radio ICs lies in the integration of an ever-increasing number of bands and channel bandwidths. This paper presents a transceiver together with the associated discrete front-end components. The transceiver supports 4 EDGE bands and 9 WCDMA bands (l-VI and Vlll-X), while the radio can be configured to simultaneously support the 4 EDGE bands and up to 5 WCDMA bands: 3 high bands (HB) and 2 low bands (LB). The RX is a SAW-less homodyne composed of a main RX and a diversity RX. To reduce package complexity with so many bands, we chose to minimize the number of ports by using single-ended RF interfaces for both RX and TX. This saves seve ral package pins, but requires careful attention to grounding. The main RX has 8 LNA ports and the diversity RX has 5, with some LNAs supporting multiple bands. On the TX side, 2 ports are used for all EDGE bands and 4 for the WCDMA bands.
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| 19. |
- Pålsson, Birger, et al.
(författare)
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Partial splenic embolization as pretreatment for antiviral therapy in hepatitis C virus infection
- 2005
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Ingår i: European Journal of Gastroenterology and Hepathology. - 1473-5687. ; 17:11, s. 1153-1155
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Tidskriftsartikel (refereegranskat)abstract
- Antiviral therapy in hepatitis C virus (HCV) infection is limited by haematological side-effects, especially thrombocytopenia and leucopenia. The pancytopenia associated with liver cirrhosis has multifactorial causes, but hypersplenism seems to be a major contributor, especially regarding thrombocytopenia. The use of PSE as a 'Pretreatment' in order to make more patients with HCV-induced cirrhosis and pancytopenia suitable for antiviral therapy using ribavirin and pegylated interferon is a new, promising concept. The setting needs further investigation in prospective, longitudinal studies, in order to evaluate safety, define patient selection criteria, the timing between the PSE procedure and the antiviral therapy and to evaluate the long-term results. The setting needs further investigation in prospective, longitudinal studies, in order to evaluate safety, define patient selection criteria, the timing between the PSE procedure and the antiviral therapy and to evaluate the long-term results.
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| 20. |
- Pålsson, Erik, 1975, et al.
(författare)
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Markers of glutamate signaling in cerebrospinal fluid and serum from patients with bipolar disorder and healthy controls
- 2015
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Ingår i: European Neuropsychopharmacology. - : Elsevier BV. - 0924-977X. ; 25:1, s. 133-140
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Tidskriftsartikel (refereegranskat)abstract
- Glutamate is the major excitatory neurotransmitter in the brain. Aberrations in glutamate signaling have been linked to the pathophysiology of mood disorders. Increased plasma levels of glutamate as well as higher glutamine+glutamate levels in the brain have been demonstrated in patients with bipolar disorder as compared to healthy controls. In this study, we explored the glutamate hypothesis of bipolar disorder by examining peripheral and central levels of amino acids related to glutamate signaling. A total of 215 patients with bipolar disorder and 112 healthy controls from the Swedish St. Goran bipolar project were included in this study. Glutamate, glutamine, glycine, L-serine and D-serine levels were determined in serum and in cerebrospinal fluid using high performance liquid chromatography with fluorescence detection. Serum levels of glutamine, glycine and D-serine were significantly higher whereas L-serine levels were lower in patients with bipolar disorder as compared to controls. No differences between the patient and control group in amino acid levels were observed in cerebrospinal fluid. The observed differences in serum amino acid levels may be interpreted as a systemic aberration in amino acid metabolism that affects several amino acids related to glutamate signaling. (C) 2014 Elsevier B.V. and ECNP. All rights reserved.
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