Biomedical subjects

B Eliasson

Publications and source records attributed to B Eliasson.

At least 19 recordsLinked to original sources

PubMed2006

Instability and dynamics of two nonlinearly coupled laser beams in a two-temperature electron plasma.

We consider nonlinear interactions between two colliding laser beams in an electron plasma, accounting for the relativistic electron mass increase in the laser fields and radiation pressure driven electron-acoustic (EA) perturbations that are supported by hot and cold electrons. By using the hydrodynamic and Maxwell equations, we obtain the relevant equations for nonlinearly coupled laser beams and EA perturbations. The coupled equations are then Fourier analyzed to obtain a nonlinear dispersion relation. The latter is numerically solved to show the existence of new classes of the parametric instabilities in the presence of two colliding laser beams in a two-electron plasma. The dynamics of nonlinearly coupled laser beams in our electron plasma is also investigated. The results should be useful in understanding the nonlinear propagation characteristics of multiple electromagnetic beams in laser-produced plasmas as well as in space plasmas.

Journal Article↗

PubMed2006

Instability and evolution of nonlinearly interacting water waves.

We consider the modulational instability of nonlinearly interacting two-dimensional waves in deep water, which are described by a pair of two-dimensional coupled nonlinear Schrödinger equations. We derive a nonlinear dispersion relation. The latter is numerically analyzed to obtain the regions and the associated growth rates of the modulational instability. Furthermore, we follow the long term evolution of the latter by means of computer simulations of the governing nonlinear equations and demonstrate the formation of localized coherent wave envelopes. Our results should be useful for understanding the formation and nonlinear propagation characteristics of large-amplitude freak waves in deep water.

Journal Article↗

PubMed2006

Formation and dynamics of dark solitons and vortices in quantum electron plasmas.

We present simulation studies of the formation and dynamics of dark solitons and vortices in quantum electron plasmas. The electron dynamics in the latter is governed by a pair of equations comprising the nonlinear Schrödinger and Poisson system of equations, which conserves the number of electrons as well as their momentum and energy. The present governing equations in one spatial dimension admit stationary solutions in the form a dark envelope soliton. The dynamics of the latter reveals its robustness. Furthermore, we numerically demonstrate the existence of cylindrically symmetric two-dimensional quantum electron vortices, which survive during collisions. The nonlinear structures presented here may serve the purpose of transporting information at quantum scales in ultracold micromechanical systems and dense plasmas, such as those created during intense laser-matter interactions.

Journal Article↗

PubMed2006

Obesity and cardiovascular risk factors in type 2 diabetes: results from the Swedish National Diabetes Register.

OBJECTIVES: To compare obese with normal and overweight type 2 diabetic patients regarding body mass index (BMI) and cardiovascular risk factors, and to analyse changes in weight versus risk factors. DESIGN AND SETTING: A cross-sectional study of 44 042 type 2 patients, and a 6-year prospective study of 4468 type 2 patients. RESULTS: Obese patients (BMI > or = 30 kg m(-2)), 37% of all patients, had high frequencies of hypertension (88%), hyperlipidaemia (81%) and microalbuminuria (29%). Only 11% had blood pressure <130/80 mmHg. Their ratio of triglycerides to HDL cholesterol was considerably elevated, whilst the mean total and LDL cholesterol were similar as in normal weight subjects. Obese patients had elevated odds ratios for hypertension, hyperlipidaemia and microalbuminuria: 2.1, 1.8 and 1.4 in the cross-sectional study, similarly confirmed in the prospective 6-year study. BMI was an independent predictor of these risk factors (P < 0.001), although only slightly associated with HbA1c and not with total or LDL cholesterol. A change in BMI during the prospective study was related to a change in HbA1c in patients treated with diet and oral hypoglycaemic agents (OHAs) but not with insulin. In all patients, an increase in BMI was related to the development of hypertension, and a change in BMI to change in blood pressure, also mostly confirmed when treated with diet, OHAs or insulin. CONCLUSIONS: The high frequencies of risk factors in obese type 2 patients implies an increased risk of cardiovascular disease and the need for therapeutic measures. The paradox that hypoglycaemic treatment accompanied by weight gain may increase cardiovascular risk factors seems to be verified here concerning hypertension but not concerning microalbuminuria.

Aged↗

PubMed2006

Pathogenesis and treatment of diabetic vascular disease - illustrated by two cases.

This publication is a summary of the presentations given at the First JIM Grand Round held at the Sahlgrenska University Hospital on 15 March 2006. The Grand Round was based on two case reports; a patient with type 2 diabetes and pronounced macrovascular disease and another patient with early microvascular disease combined with the macrovascular complications. The pathogenesis of the vascular complications and the current treatment regimens were discussed in relation to the history and examinations performed in these patients.

Adiponectin↗

PubMed2005

Formation and dynamics of finite amplitude localized pulses in elastic tubes.

We present theoretical and simulation studies of the formation and dynamics of finite-amplitude localized pulses (solitary waves) of an incompressible fluid in an elastic tube. Starting from a set of hydrodynamic equations, we derive a Hamiltonian which represents the energy integral of our system. The energy integral is analyzed to obtain explicit profiles of finite-amplitude solitary pulses. Also studied are the excitation and dynamics of solitary pulses by using computer simulations. It is found that a train of solitary pulses can be excited by the nonlinear self-steepening at shock fronts. The relevance of our investigation to blood solitary waves in arteries is discussed.

Journal Article↗

PubMed2005

Solitary phase-space holes in pair plasmas.

We present theoretical and computer simulation studies of the formation and dynamics of solitary phase-space holes in pair plasmas, which can be applied to both electron-positron plasmas and to plasmas containing positively and negatively charged macro-ions or macro-particulates (charged dust grains). We apply our numerical treatment to the parameters used in a recent series of experiments in a pair ion plasma whose constituents are negatively and positively charged fullerene carbon nanotubes. New experiments should be conducted to confirm our theoretical and numerical predictions.

Journal Article↗

PubMed2005

Localization of intense electromagnetic waves in a relativistically hot plasma.

We consider nonlinear interactions between intense short electromagnetic waves (EMWs) and a relativistically hot electron plasma that supports relativistic electron holes (REHs). It is shown that such EMW-REH interactions are governed by a coupled nonlinear system of equations composed of a nonlinear Schro dinger equation describing the dynamics of the EMWs and the Poisson-relativistic Vlasov system describing the dynamics of driven REHs. The present nonlinear system of equations admits both a linearly trapped discrete number of eigenmodes of the EMWs in a quasistationary REH and a modification of the REH by large-amplitude trapped EMWs. Computer simulations of the relativistic Vlasov and Maxwell-Poisson system of equations show complex interactions between REHs loaded with localized EMWs.

Journal Article↗

PubMed2005

Microalbuminuria and risk factors in type 1 and type 2 diabetic patients.

A prospective study of normoalbuminuric diabetic patients was performed between 1997 and 2002 on 4097 type 1 and 6513 type 2 diabetic patients from the Swedish National Diabetes Register (NDR); mean study period, 4.6 years. The strongest independent baseline risk factors for the development of microalbuminuria (20-200 microg/min) were elevated HbA(1c) and diabetes duration in both types 1 and 2 diabetic patients. Other risk factors were high BMI, elevated systolic and diastolic BP in type 2 patients, and antihypertensive therapy in type 1 patients. A subsequent larger cross-sectional study in 2002 showed that established microalbuminuria was independently associated with HbA(1c), diabetes duration, systolic BP, BMI, smoking and triglycerides in types 1 and 2 diabetic patients, and also with HDL-cholesterol in type 2 patients. Relatively few types 1 and 2 patients with microalbuminuria achieved treatment targets of HbA(1c) < 6.5% (21-48%), BP < 130/85 mmHg (33-13%), cholesterol < 5 mmol/l (48-46%), triglycerides < 1.7 mmol/l (83-48%) and BMI < 25 kg/m(2) (50-18%), respectively. In conclusion, high HbA(1c), BP and BMI were independent risk factors for the development of microalbuminuria in types 1 and 2 diabetic patients. These risk factors as well as triglycerides, HDL-cholesterol and smoking were independently associated with established microalbuminuria. Treatment targets were achieved by a relatively few patients with microalbuminuria.

Adult↗

PubMed2005

Optimization of basal insulin delivery in Type 1 diabetes: a retrospective study on the use of continuous subcutaneous insulin infusion and insulin glargine.

AIMS: To compare the effects on glycaemic control after using continuous subcutaneous insulin infusion (CSII) or insulin glargine. METHODS: Data were obtained from 17 diabetes outpatient clinics in Sweden, employing the same diabetes data management system. Type 1 diabetic patients using multiple dose injections were included prior to starting on either CSII (n = 563) or glargine (n = 513). The median duration of therapy was 25 months for CSII and 6 months for glargine. The comparison between the treatment modalities was carried out by multiple regression analysis and logistic regression analysis in an attempt at reducing the influence of confounding factors. RESULTS: The mean HbA1c decrease was 0.59 +/- 1.19% for CSII and 0.20 +/- 1.07% for glargine (P < 0.001, when assessed by logistic regression). An additional 0.1% lower HbA1c would be expected if glargine had been optimized with basal insulin 40-60% of the daily dose. The more pronounced effect of CSII was achieved with a lower daily dosage of insulin. In a multiple regression analysis with a change of HbA1c as the dependent variable, the following variables were significant: choice of treatment (P < 0.001), HbA1c prior to treatment (P < 0.001) and BMI prior to treatment (P < 0.01). CONCLUSION: Both regimes improved metabolic control, but CSII resulted in significantly higher reduction in HbA1c than after insulin glargine treatment, particularly in those individuals who had higher levels of HbA1c at baseline.

Adult↗

PubMed2005

The gap between guidelines and reality: Type 2 diabetes in a National Diabetes Register 1996-2003.

Guidelines for the treatment of risk factors in diabetes care have been updated recently, due to indisputable results from clinical end-point trials. This study evaluates risk factor control compared with current national and international targets during the period 1996-2003 in Type 2 diabetes (DM2). Patients were registered in primary-care and hospital outpatient clinics using computer software, or via the Internet. The clinical characteristics of the patients, treatment, HbA(1c), and risk factors were reported after screening by local methods. The numbers of cases of DM2 reported were 17547 in 1996 and 57119 in 2003. The mean HbA(1c) decreased from 7.8 to 7.2%, while blood pressure decreased from 150/82 to 143/78 mmHg during the same period. Longitudinal analysis of results was performed in 5356 patients repeatedly reported, showing slightly lower effects. The new European treatment targets of HbA(1c)< or = 6.1%, blood pressure < 130/80 mmHg and total cholesterol < 4.5 mmol/l were attained by 16, 13 and 28% of the patients in 2003, respectively. The prevalence of the metabolic syndrome in 2003 was 77%. Aspirin was prescribed in 36% of cases. Lipid-lowering, anti-hypertensive drugs, and treatment with oral hypoglycaemic agents in combination with insulin were increasingly employed during the period studied. Risk factor control in DM2 reported to the National Diabetes Register (NDR) is slowly improving, although multiple risk factors and the metabolic syndrome are found in most patients. The majority of subjects do not achieve current target levels for HbA(1c), blood pressure and blood lipids. Thus, giving up smoking and increased use of aspirin are called for, as well as more aggressive treatment of hyperglycaemia, elevated blood pressure and blood lipid levels, in accordance with updated international guidelines.

Administration, Oral↗

PubMed2004

Electron acceleration to energies beyond GeV by a relativistic ion beam instability.

Synchrotron emission suggests the presence of TeV electrons at various astrophysical objects. We propose a mechanism for the acceleration of electrons to ultrahigh energies (UHE) by intense electrostatic waves (ESWs). The latter are driven by dense proton beams that move at relativistic speeds relative to a background plasma and the electrons are accelerated by their nonlinear interaction with the ESWs. We follow the evolution of the wave instability by means of particle-in-cell (PIC) simulations. After the instability has saturated, we obtain spatially confined electron voids in which secondary instabilities develop due to resonant interactions between the beams and the background protons, generating intense ESWs which accelerate electrons to ultrarelativistic speeds within times of a few hundred inverse plasma frequencies.

Journal Article↗

PubMed2004

Dynamics of electron holes in an electron-oxygen-ion plasma.

The dynamics of electron holes (EHs) in an electron-oxygen-ion plasma is studied by means of Vlasov simulations. It is found that EHs are attracted by ion density maxima but repelled by ion density minima. Standing EHs repel ions owing to the positive EH potential, creating an ion density cavity which ejects the EH, which propagates away from the cavity with a constant speed. On the other hand, propagating EHs can be trapped at ion density maxima. The results of our simulations will help in understanding the nonlinear dynamics of EHs in space and laboratory plasmas.

Journal Article↗

PubMed2004

Dust acoustic shock waves.

It is shown that nonlinear equations governing the dynamics of large amplitude nondispersive dust acoustic waves admit nonstationary dust acoustic shock waves. Analytical and numerical results for the latter are presented, and the relevance of our investigation to laboratory experiments is discussed.

Journal Article↗

PubMed2004

Production of nonisothermal electrons and Langmuir waves because of colliding ion holes and trapping of plasmons in an ion hole.

We present new simulation studies exhibiting production of nonisothermal electron distributions and Langmuir waves by colliding ion holes and trapping of plasmons in an ion hole. We find that, during head-on ion hole collisions, streams of accelerated electrons are produced by the electrostatic potentials supporting the ion holes. Subsequently, Langmuir waves are excited by a two-stream instability involving energetic electron beams. The resulting Langmuir waves can be trapped in an ion hole. The present ion-hole-Langmuir wave interactions are unique kinetic phenomena which can be dealt with a Vlasov code, which we developed recently. The results can have relevance to the understanding of particle and field data that are forthcoming from different spacecraft missions in Earth's auroral ionosphere and the magnetosphere.

Journal Article↗

PubMed2004

Modulational and filamentational instabilities of intense photon pulses and their dynamics in a photon gas.

It is shown that an intense photon pulse interacting nonlinearly with sound waves in a photon gas is subjected to modulational and filamentational instabilities. Starting from a new set of coupled equations governing nonlinear photon-photon interactions, we derive a dispersion relation which depicts the temporal and spatial amplification rates of the modulational and filamentational instabilities. The long term behavior of the modulationally unstable waves renders collapse of a photon beam as well as the formation of cylindrically symmetric photonic solitons. The results can have relevance to the understanding of the nonlinear photonic pulse propagation in astrophysical environments as well as in forthcoming intense laser-matter interaction experiments.

Journal Article↗

PubMed2004

Connecting shock velocities to electron-injection mechanisms.

Electrons can be accelerated by their interaction with nonlinearly saturated electrostatic waves up to speeds with which they can undergo diffusive acceleration across supernova remnant shocks. Here, we model this wave-electron interaction by particle-in-cell and Vlasov simulations. We find that the lifetime of the saturated wave is considerably longer in the Vlasov simulation, due to differences in how these simulation methods approximate the plasma. Electron surfing acceleration which requires a stable saturated wave may thus be more important for electron acceleration at shocks than previously thought. For beam speeds above a critical value, which we estimate here, both simulation codes exclude surfing acceleration due to a rapid wave collapse.

Journal Article↗

PubMed2004

Smoking is associated with increased HbA1c values and microalbuminuria in patients with diabetes--data from the National Diabetes Register in Sweden.

OBJECTIVES: The aim was to examine trends in the proportion of smoking in diabetes patients, and to study associations between smoking, glycaemic control, and microalbuminuria. METHODS: Smoking habits were reported to the Swedish National Diabetes Register (NDR), with data from hospitals and primary health care. Patient characteristics included were age, gender, type of treatment, diabetes duration, HbA1c, BMI, blood pressure, antihypertensive and lipid-lowering drugs, and microalbuminuria. RESULTS: The proportion of smokers in type 1 diabetes was 12-15% during 1996-2001, it was high in females<30 years (12-16%), and was higher in the age group 30-59 years (13-17%) than in older (6-9%) patients. The corresponding proportion of smoking in type 2 diabetes was 10-12%, higher in those less than 60 years of age (17-22%) than in older (7-9%) patients. Smoking type 1 and type 2 patients in 2001 had higher mean HbA1c but lower mean BMI values than non-smokers. Smokers also had higher frequencies of microalbuminuria, in both type 1 (18 vs 14%) and type 2 (20% vs 13%) diabetes. Multiple logistic regression analyses disclosed that smoking was independently associated with elevated HbA1c levels (p<0.001) and microalbuminuria (p<0.001), but negatively with BMI (p<0.001), in both type 1 and type 2 diabetes. CONCLUSIONS: Smoking in patients with diabetes was widespread, especially in young female type 1, and in middle-aged type 1 and type 2 diabetes patients, and should be the target for smoking cessation campaigns. Smoking was associated with both poor glycaemic control and microalbuminuria, independently of other study characteristics.

Adult↗