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Search Results: 1 - 10 of 2876 matches for " Sven Larsson "
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Lattice Enthalpy Drives Hubbard U to Zero  [PDF]
Sven Larsson
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.46A007
Abstract:

In the equation U = IA for the Mott energy, the electron-hole interaction of the successor state is missing. Adding the attractive term, the energy for disproportionation (Hubbard U), may adopt any sign. The missing term is related to the Born effect, the Madelung correction and the Lattice Enthalpy.

Phonons in Lattice and Structural Dynamics
Sven Larsson
Advances in Condensed Matter Physics , 2010, DOI: 10.1155/2010/627452
Abstract: The critical temperature ( ) of superconductivity in compounds is generally lower smaller with alkali atoms (A). Furthermore decreases with applied pressure. In the BCS model, these trends are explained by the lower density of states at the Fermi level for a decreased lattice constant (R). There is more than one counterexample, however, suggesting that BCS does not give the whole truth. The most important one is that the compound with the largest lattice constant, , is not superconducting at all at ambient pressure. In this paper we derive a novel model where a negative lattice contribution to Hubbard U, proportional to 1/R, is taken into account. It is possible to explain why compounds with A = Li, and Na have a low or are not superconducting at all, and why is superconducting only at applied pressure and then with the highest of all alkali fullerides. It is concluded that the density of states mechanism derived in the BCS model is in doubt. Nevertheless superconductivity in depends on electron-phonon coupling. The dominating phonon is the bond stretching phonon, a breathing phonon for the whole fullerene molecular ion. 1. Introduction The discoveries of conductivity and superconductivity (SC) in and were great events in science during the 1990s [1–5]. SC was later discovered in a number of other compounds, where A stand for alkali atoms: Li, Na, K, Rb, or Cs. Generally, increase of the lattice constant leads to a higher critical temperature . Some of the compounds (A = Li, Na) with the smallest lattice constants are not superconducting [6–8]. Only fullerides have proven to be superconducting (SC). Remarkably, the compound with the highest lattice constant does not follow this trend [9–11]. Disorder-free is an antiferromagnetic insulator at ambient pressure. However, already at the quite modest pressure of 3?kbar ( 3000?atm), it turns into a superconductor (SC) with the highest known for any fulleride [9–11]. At temperatures above passes directly into a semiconducting and antiferromagnetic phase. This system thus needs an explanation model which is not depending on the existence of free electrons, as in the BCS model. Takabayashi et al. further point out [11] that transfer from SC to antiferromagnetic phase appears to be “purely electronic”, thus seemingly explicable without resorting to nuclear dynamics. There are a number of peculiarities in experimental data in general, as summarized by Gunnarsson [12], Rosseinsky [13], Margadonna and Prassides [14], and Iwasa and Takenobu [15]. A widely accepted approach is to treat the metallic alkali fullerides
Mixed valence model for superconductivity
Larsson, Sven;
Brazilian Journal of Physics , 2003, DOI: 10.1590/S0103-97332003000400022
Abstract: superconductivity often occurs in crystals with one active electron per site with charge density wave (cdw) or spin density wave (sdw) as 'mother state'. it is proposed that superconductivity is possible when the differences in equilibrium geometry and energy between the diabatic cdw and sdw states are so small that there is interaction between them via the zero point vibrations. electron pairing in real space is directly related to oxidation states being different in two units. three valence states in succession have to be stable (ground state or low-energy excited states) and we therefore refer to this mixed valence model as the mv-3 model. examples are chosen from bismuthates, cuprates, and fullerides. the theory is simple and straightforward and offers solutions to other important problems as well, for example for a3c60(a = k; rb), that (1) there are no magnetic moments in crystal phase, and (2) that these systems are superconducting metals while a4c60 are insulators.
Mixed valence model for superconductivity
Larsson Sven
Brazilian Journal of Physics , 2003,
Abstract: Superconductivity often occurs in crystals with one active electron per site with charge density wave (CDW) or spin density wave (SDW) as 'mother state'. It is proposed that superconductivity is possible when the differences in equilibrium geometry and energy between the diabatic CDW and SDW states are so small that there is interaction between them via the zero point vibrations. Electron pairing in real space is directly related to oxidation states being different in two units. Three valence states in succession have to be stable (ground state or low-energy excited states) and we therefore refer to this mixed valence model as the MV-3 model. Examples are chosen from bismuthates, cuprates, and fullerides. The theory is simple and straightforward and offers solutions to other important problems as well, for example for A3C(6)0(A = K; Rb), that (1) there are no magnetic moments in crystal phase, and (2) that these systems are superconducting metals while A4C(6)0 are insulators.
A Novel Animal Model of Borrelia recurrentis Louse-Borne Relapsing Fever Borreliosis Using Immunodeficient Mice
Christer Larsson,Jenny Lundqvist,Nico van Rooijen,Sven Bergstr?m
PLOS Neglected Tropical Diseases , 2009, DOI: 10.1371/journal.pntd.0000522
Abstract: Louse-borne relapsing fever (LBRF) borreliosis is caused by Borrelia recurrentis, and it is a deadly although treatable disease that is endemic in the Horn of Africa but has epidemic potential. Research on LBRF has been severely hampered because successful infection with B. recurrentis has been achieved only in primates (i.e., not in other laboratory or domestic animals). Here, we present the first non-primate animal model of LBRF, using SCID (-B, -T cells) and SCID BEIGE (-B, -T, -NK cells) immunocompromised mice. These animals were infected with B. recurrentis A11 or A17, or with B. duttonii 1120K3 as controls. B. recurrentis caused a relatively mild but persistent infection in SCID and SCID BEIGE mice, but did not proliferate in NUDE (-T) and BALB/c (wild-type) mice. B. duttonii was infectious but not lethal in all animals. These findings demonstrate that the immune response can limit relapsing fever even in the absence of humoral defense mechanisms. To study the significance of phagocytic cells in this context, we induced systemic depletion of such cells in the experimental mice by injecting them with clodronate liposomes, which resulted in uncontrolled B. duttonii growth and a one-hundred-fold increase in B. recurrentis titers in blood. This observation highlights the role of macrophages and other phagocytes in controlling relapsing fever infection. B. recurrentis evolved from B. duttonii to become a primate-specific pathogen that has lost the ability to infect immunocompetent rodents, probably through genetic degeneration. Here, we describe a novel animal model of B. recurrentis based on B- and T-cell-deficient mice, which we believe will be very valuable in future research on LBRF. Our study also reveals the importance of B-cells and phagocytes in controlling relapsing fever infection.
Symptoms induced by environmental irritants and health-related quality of life in patients with chronic cough - A cross-sectional study
Ewa Ternesten-Hasséus, Sven Larsson, Eva Millqvist
Cough , 2011, DOI: 10.1186/1745-9974-7-6
Abstract: Our main aim was to analyse, in a group of patients with chronic cough, the presence of symptoms induced by environmental factors such as chemicals, scents, and cold air, and to measure the social and emotional influences of these symptoms in relation to quality of life. A second aim was to pilot-test a Swedish translation of a cough-specific questionnaire.A total of 119 patients with chronic cough were asked to answer three different questionnaires: a local symptom questionnaire, the Chemical Sensitivity Scale for Sensory Hyperreactivity (CSS-SHR), and the Nottingham Health Profile (NHP). In addition, a Swedish version of the Hull Airway Reflux Questionnaire (HARQ) was developed and answered by a subgroup of patients and healthy controls.Sixty-two patients (52%) with mean cough duration of 10.6 years answered the local symptom questionnaire, the CSS-SHR, and the NHP. Of these, 39 (63%) claimed to have cough and other symptoms induced by chemicals and scents. Compared to population-based findings, the patients scored higher on the CSS-SHR, and the CSS-SHR score was significantly higher among chemical-sensitive individuals (p < 0.001). The NHP showed that the patients had a significantly reduced quality of life, which was most pronounced among chemical-sensitive individuals. The 31 patients who answered the HARQ had significantly higher scores (p < 0.0001) than 59 healthy controls.Among patients with chronic cough, a majority claimed that environmental factors induced coughing. Both the CSS-SHR and the HARQ score systems seem to be valuable instruments in the mapping of cough patients, supporting the novel paradigm of a cough hypersensitivity syndrome. Our results emphasize that cough is a substantial burden to the patient, influencing daily living and quality of life.Cough is an essential protective physiological mechanism to prevent food, liquid, dust, and chemicals from reaching the lower airways, but it is also a symptom of many inflammatory diseases of the lungs
A gender difference in circulating neutrophils in malnourished patients with COPD
Sven Larsson, Anita Nordenson, Pernilla Glader, et al
International Journal of Chronic Obstructive Pulmonary Disease , 2011, DOI: http://dx.doi.org/10.2147/COPD.S15351
Abstract: gender difference in circulating neutrophils in malnourished patients with COPD Original Research (3331) Total Article Views Authors: Sven Larsson, Anita Nordenson, Pernilla Glader, et al Published Date January 2011 Volume 2011:6 Pages 83 - 88 DOI: http://dx.doi.org/10.2147/COPD.S15351 Sven Larsson1, Anita Nordenson1, Pernilla Glader1, Shigemi Yoshihara2, Anders Lindén1, Frode Slinde3 1Department of Internal Medicine/Respiratory Medicine and Allergology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden; 2Department of Pediatrics, Dokkyo Medical University, Tochigi, Japan; 3Department of Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden Background: Circulating markers of inflammation in chronic obstructive pulmonary disease (COPD) may correlate to disease progression and extrapulmonary complications such as malnourishment. However, surprisingly little is known about gender-related differences for circulating inflammatory markers in COPD. Purpose: To characterize differences in circulating markers of inflammation in malnourished female and male patients with COPD. Subjects: Thirty female and 11 male patients with a clinical diagnosis of COPD and malnourishment were examined. A group of control subjects without evidence of COPD was recruited for comparison of some variables. Methods: Blood samples were drawn, and the following parameters were studied: leukocytes and differential counts, C-reactive protein (CRP), tumor necrosis factor-α, interleukin (IL)-6 and IL-8, myeloperoxidase (MPO), neutrophil elastase (NE), intracellular adhesion molecule-1, vascular endothelial adhesion molecule-1, and E-selectin. Results: The mean neutrophil concentration was significantly (P = 0.019) higher in female (4.5 × 109/L) than in male patients with COPD (3.5 × 109/L) and significantly higher than in female control subjects (3.1 × 109/L) (P , 0.01, n = 85). The mean CRP values were considerably higher in female (4.9 mg/mL) than in male patients with COPD (1.5 mg/mL), but the difference was not statistically significant (P = 0.20). The mean concentrations of IL-6 and IL-8 tended to be higher in female than in male patients with COPD, but these differences did not reach statistical significance either (P . 0.05). Confounding factors (smoking, medication) could not explain the gender differences noted. The concentrations of MPO and NE displayed a strong correlation (r = 0.89; P , 0.01, n = 41) but revealed no gender differences. The latter was true for concentrations of adhesion molecules as well. Conclusions: Our study puts forward evidence of a gender-related difference in systemic inflammation in malnourished patients with COPD in terms of circulating neutrophils being more abundant in female patients. Among these female patients, there was also a trend toward an increase in two neutrophil-mobilizing cytokines. New and better-powered studies are warranted to confirm and characterize this pote
A gender difference in circulating neutrophils in malnourished patients with COPD
Sven Larsson,Anita Nordenson,Pernilla Glader,et al
International Journal of COPD , 2011,
Abstract: Sven Larsson1, Anita Nordenson1, Pernilla Glader1, Shigemi Yoshihara2, Anders Lindén1, Frode Slinde31Department of Internal Medicine/Respiratory Medicine and Allergology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden; 2Department of Pediatrics, Dokkyo Medical University, Tochigi, Japan; 3Department of Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, SwedenBackground: Circulating markers of inflammation in chronic obstructive pulmonary disease (COPD) may correlate to disease progression and extrapulmonary complications such as malnourishment. However, surprisingly little is known about gender-related differences for circulating inflammatory markers in COPD.Purpose: To characterize differences in circulating markers of inflammation in malnourished female and male patients with COPD.Subjects: Thirty female and 11 male patients with a clinical diagnosis of COPD and malnourishment were examined. A group of control subjects without evidence of COPD was recruited for comparison of some variables.Methods: Blood samples were drawn, and the following parameters were studied: leukocytes and differential counts, C-reactive protein (CRP), tumor necrosis factor-α, interleukin (IL)-6 and IL-8, myeloperoxidase (MPO), neutrophil elastase (NE), intracellular adhesion molecule-1, vascular endothelial adhesion molecule-1, and E-selectin.Results: The mean neutrophil concentration was significantly (P = 0.019) higher in female (4.5 × 109/L) than in male patients with COPD (3.5 × 109/L) and significantly higher than in female control subjects (3.1 × 109/L) (P , 0.01, n = 85). The mean CRP values were considerably higher in female (4.9 mg/mL) than in male patients with COPD (1.5 mg/mL), but the difference was not statistically significant (P = 0.20). The mean concentrations of IL-6 and IL-8 tended to be higher in female than in male patients with COPD, but these differences did not reach statistical significance either (P . 0.05). Confounding factors (smoking, medication) could not explain the gender differences noted. The concentrations of MPO and NE displayed a strong correlation (r = 0.89; P , 0.01, n = 41) but revealed no gender differences. The latter was true for concentrations of adhesion molecules as well.Conclusions: Our study puts forward evidence of a gender-related difference in systemic inflammation in malnourished patients with COPD in terms of circulating neutrophils being more abundant in female patients. Among these female patients, there was also a trend toward an increase in two neutroph
Two-photon Franson-type interference experiments are not tests of local realism
Jan-Ake Larsson,Sven Aerts,Marek Zukowski
Physics , 1998,
Abstract: We report a local hidden-variable model which reproduces quantum predictions for the two-photon interferometric experiment proposed by Franson [Phys. Rev. Lett. 62, 2205 (1989)]. The model works for the ideal case of full visibility and perfect detection efficiency. This result changes the interpretation of a series of experiments performed in the current decade.
Two-photon Franson-type experiments and local realism
Sven Aerts,Paul Kwiat,Jan-Ake Larsson,Marek Zukowski
Physics , 1999, DOI: 10.1103/PhysRevLett.83.2872
Abstract: The two-photon interferometric experiment proposed by Franson [Phys. Rev. Lett. 62, 2205 (1989)] is often treated as a "Bell test of local realism". However, it has been suggested that this is incorrect due to the 50% postselection performed even in the ideal gedanken version of the experiment. Here we present a simple local hidden variable model of the experiment that successfully explains the results obtained in usual realizations of the experiment, even with perfect detectors. Furthermore, we also show that there is no such model if the switching of the local phase settings is done at a rate determined by the internal geometry of the interferometers.
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