| 1. |
- Riise, Gerdt C., 1956, et al.
(författare)
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The intrabronchial microbial flora in chronic bronchitis patients: a target for N-acetylcysteine therapy?
- 1994
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Ingår i: Eur Respir J. - 0903-1936. ; 7:1, s. 94-101
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Tidskriftsartikel (refereegranskat)abstract
- Chronic bronchitis is common among smokers, often together with recurrent infectious exacerbations. Streptococcus pneumoniae and Haemophilus influenzae are the pathogens traditionally considered most important. N-acetylcysteine (NAC) treatment has been shown to reduce the number of infectious exacerbations in patients with chronic bronchitis. The mechanism behind this is unknown. We attempted to characterize the intrabronchial bacterial flora in patients with chronic bronchitis in an infection-free interval, and to determine whether pharmacological and immunological factors effected the bacterial occurrence. Twenty two smokers with non-obstructive chronic bronchitis, 19 smokers with chronic bronchitis and chronic obstructive pulmonary disease (COPD) and 14 healthy nonsmokers underwent bronchoscopy. To obtain uncontaminated intrabronchial samples, a protected specimen brush was used. Quantitative bacterial cultures and virus isolations were performed. Significantly positive bacterial cultures (> 1,000 colony-forming units (cfu).ml-1) were found only in the patients. S. pneumoniae and H. influenzae were found in five patients, and only in the patients without NAC treatment. The most common bacterium was alpha-haemolytic streptococcus. Negative cultures were more common in the healthy controls. Of the various factors examined, only NAC medication had an influence on bacterial numbers. Significantly fewer patients with NAC medication had positive cultures (3 out of 16) than in the group of patients without NAC therapy (15 out of 21). Our results confirm that chronic bronchitis in smokers leads to increased intrabronchial bacterial colonization. We could also confirm that 1,000 cfu.ml-1 is an adequate cut-off level for significant bacterial growth when using the protected specimen brush. NAC medication was associated with low bacterial numbers.
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| 2. |
- Asadzadeh, Mohammad, 1952, et al.
(författare)
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The discrete ordinates method for the neutron transport equation in an infinite cylindrical domain
- 1992
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Ingår i: Mathematical Models and Methods in Applied Science. ; 2:3, s. 317-338
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Tidskriftsartikel (refereegranskat)abstract
- We prove a regularity result for a Fredholm integral equation with weakly singular kernel, arising in connection with the neutron transport equation in an infinite cylindrical domain. The theorem states that the solution has almost two derivatives in L1, and is proved using Besov space techniques. This result is applied in the error analysis of the discrete ordinates method for the numerical solution of the neutron transport equation. We derive an error estimate in the L1-norm for the scalar flux, and as a consequence, we obtain an error bound for the critical eigenvalue.
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| 3. |
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| 4. |
- Brockstedt, Sara, et al.
(författare)
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Vertical field MR imaging of upper thorax and spine in small children. Evaluation of a new surface coil
- 1993
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Ingår i: Acta Radiologica. - 1600-0455. ; 34:6, s. 549-553
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Tidskriftsartikel (refereegranskat)abstract
- To improve image quality in a vertical field MR imaging unit, operating at low field strength (0.3 T), we have designed a half-elliptical coil for use in the upper thoracic region of small children. Our intention was also to shorten the examination time, which until now has been long, because several scans with different coils have been necessary to cover the thoracic region. The experimental coil is designed so that a child's shoulders fit into the central region. The coil consists of 2 serially connected cable-loops, mounted on a foam rubber vest. The coil performance was tested in a phantom and improvements relative to standard coils were demonstrated in in vivo studies. The results indicate that by using the half-elliptical coil, the signal-to-noise (S/N) ratio can be improved by a factor of 2 to 3 in the thoracic region of a child.
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| 5. |
- Cronqvist, Mats, et al.
(författare)
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Evaluation of time-of-flight and phase-contrast MRA sequences at 1.0 T for diagnosis of carotid artery disease. I. A phantom and volunteer study
- 1996
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Ingår i: Acta Radiologica. - 1600-0455. ; 37:3 Pt 1, s. 267-277
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE AND MATERIAL: The aim of this work was, firstly, to compare different manufacturer-provided MRA sequences in a 1.0 T MR unit, with respect to the visibility of an artificial stenosis in a flow phantom and, secondly, to evaluate the same sequences in healthy volunteers with respect to S/N ratio levels and practical in vivo implementation routines. METHODS: The studied sequences were 2D and 3D TOF and sequences with an acquisition time of approximately 10 min. Quantitative signal evaluation was made using single transverse partitions in all phantom experiments. MIP angiograms and MPR reconstructions were made for visual inspection of image quality. In vivo, the images were individually evaluated by visual inspection by experienced neuroradiologists. RESULTS: In the evaluation of the grade and length of a stenosis, a combination of MIP and MPR was seen to be the optimal and necessary procedure. A shortening of TE played an important and significant role in the visualization of the poststenotic flow in the phantom using TOF MRA. However, the shortest TE values gave poor S/N ratio in vivo. The good results achieved in the phantom studies for 3D phase-contrast were somewhat reversed in the volunteer studies, whereas 3D TOF sequences showed good results in both the phantom and the volunteer studies.
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| 6. |
- Crouzeix, Michel, et al.
(författare)
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The stability of rational approximations of analytic semigroups
- 1993
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Ingår i: BIT Numer. Math.. - 0006-3835 .- 1572-9125. ; 33:1, s. 74-84
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Tidskriftsartikel (refereegranskat)abstract
- This paper contains two new characterizations of generators of analytic semigroups of linear operators in a Banach space. These characterizations do not require use of complex numbers. One is used to give a new proof that strongly elliptic second order partial differential operators generate analytic semigroups inL p , 1
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| 7. |
- Elliott, Charles M., et al.
(författare)
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Error estimates with smooth and nonsmooth data for a finite element method for the Cahn-Hilliard equation
- 1992
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Ingår i: Math. Comp.. - 0025-5718 .- 1088-6842. ; 58:198
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Tidskriftsartikel (refereegranskat)abstract
- A finite element method for the Cahn-Hilliard equation (a semilinear parabolic equation of fourth order) is analyzed, both in a spatially semidiscrete case and in a completely discrete case based on the backward Euler method. Error bounds of optimal order over a finite time interval are obtained for solutions with smooth and nonsmooth initial data. A detailed study of the regularity of the exact solution is included. The analysis is based on local Lipschitz conditions for the nonlinearity with respect to Sobolev norms, and the existence of a Ljapunov functional for the exact and the discretized equations is essential. A result concerning the convergence of the attractor of the corresponding approximate nonlinear semigroup (upper semicontinuity with respect to the discretization parameters) is obtained as a simple application of the nonsmooth data error estimate.
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| 8. |
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| 9. |
- Gustavsson, Carl Gunnar, et al.
(författare)
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Blood viscosity in relation to blood haemoglobin concentration in healthy subjects and in patients with different cardiovascular diseases
- 1994
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Ingår i: Clinical Hemorheology. - New York, USA : Pergamon Press. - 0271-5198. ; 14:5, s. 677-683
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Blood viscosity was measured at different shear rates using a rotational viscometer, and the correlation between blood viscosity and blood haemoglobin concentration was studied. In 10 healthy controls correlation coefficients were: 0,966 at shear rate 40,0 s-1, 0,931 at 19,6 s-l, 0,817 at 2,3 s-1 and 0,816 at 0,8 s-l , p<0,01 to p < 0,001. The regression lines for these relationships were then applied to the patient groups to calculate what blood viscosity should be predicted solely from the individual haemoglobin concentration, "predicted blood viscosity". In 34 patients with cardiovascular diseases (20 patients with coronary artery disease (CAD), 8 patients with idiopathic dilated cardiomyopathy and 6 patients with primary pulmonary hypertension) the correlation between blood viscosity and haemoglobin concentration was less good, for the total patient material 0,748 to 0,613, p < 0,001 at all shear rates, and for the CAD patients 0,664 to 0,428, p < 0,05 at 3 out of 4 shear rates. Apparently the poorer correlation in the patients was due to a larger influence from factors unrelated to haemoglobin concentration/haematocrit, as the quotients between individually measured and predicted blood viscosity correlated with measured blood viscosity when the haematocrit factor had been eliminated by in vitro standardisation of sample haematocrits to 45%. Key words: Blood viscosity; Haemorheology; Haemoglobin concentration; Microcirculation.
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| 10. |
- Gustavsson, Carl Gunnar, et al.
(författare)
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Changed blood rheology in patients with idiopathic dilated cardiomyopathy
- 1994
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Ingår i: Angiology. - New York, USA : Westminster Publications, Inc.. - 0003-3197 .- 1940-1574. ; 45:2, s. 107-111
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Rheologic properties of blood were studied in 8 patients with dilated cardiomyopathy (DCM) and in 10 healthy subjects. Whole-blood viscosity was measured at four different shear rates, by means of a computer-controlled rotational viscometer. The patients had significantly higher blood viscosity at all shear rates, both at their natural hematocrits and after an in vitro adjustment of sample hematocrits to 45%. Erythrocyte filterability (5 μm pore size) was significantly lower, fibrinogen concentration significantly higher, and HDLcholesterol concentration significantly lower in the patient group. No significant differences were found regarding hematocrit, mean corpuscular volume, haemoglobin concentration, leukocyte count and filterability (8 μm pore size), plasma viscosity, and total cholesterol concentration. The measured hemorheologic abnormalities may contribute to the previously reported reduction of coronary blood flow reserve in DCM patients and to myocardial microcirculatory disturbances, which have been suggested as a cause for DCM.
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