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G Svensson

Publications and source records attributed to G Svensson.

At least 19 recordsLinked to original sources
PubMed2005

MEAD: an interdisciplinary study of the marine effects of atmospheric deposition in the Kattegat.

This paper summarises the results of the EU funded MEAD project, an interdisciplinary study of the effects of atmospheric nitrogen deposition on the Kattegat Sea between Denmark and Sweden. The study considers emissions of reactive nitrogen gases, their transport, transformations, deposition and effects on algal growth together with management options to reduce these effects. We conclude that atmospheric deposition is an important source of fixed nitrogen to the region particularly in summer, when nitrogen is the limiting nutrient for phytoplankton growth, and contributes to the overall eutrophication pressures in this region. However, we also conclude that it is unlikely that atmospheric deposition can, on its own, induce algal blooms in this region. A reduction of atmospheric nitrogen loads to this region will require strategies to reduce emissions of ammonia from local agriculture and Europe wide reductions in nitrous oxide emissions.

Agriculture↗
PubMed2005

Modelling non-structural best management practices--focus on reductions in stormwater pollution.

This paper describes a modelling approach for evaluating the efficiency of different non-structural best management practices for stormwater management. A scenario with a set of source reduction practices was simulated using the substance flow model SEWSYS for an urban catchment in the city of Göteborg, Sweden. The scenario is based on a hypothetical control program that includes prevention, education and regulations. The simulation shows relatively high reductions of copper and PAH, 77% and 50%, respectively. The reduction in copper is mainly due to less copper roof corrosion and brake wear, while reduced road wear has the greatest effect for PAH. An important result from this study is that the nonstructural BMPs applied did not give a sufficient reduction in pollution to meet the desirable environmental quality criteria. To meet these criteria, additional BMPs must be implemented, preferably a combination of both non-structural and structural measures.

Conservation of Natural Resources↗
PubMed2005

Modelling of different measures for improving removal in a stormwater pond.

The effect of retrofitting an existing pond on removal efficiency and hydraulic performance was modelled using the commercial software Mike21 and compartmental modelling. The Mike21 model had previously been calibrated on the studied pond. Installation of baffles, the addition of culverts under a causeway and removal of an existing island were all studied as possible improvement measures in the pond. The subsequent effect on hydraulic performance and removal of suspended solids was then evaluated. Copper, cadmium, BOD, nitrogen and phosphorus removal were also investigated for that specific improvement measure showing the best results. Outcomes of this study reveal that all measures increase the removal efficiency of suspended solids. The hydraulic efficiency is improved for all cases, except for the case where the island is removed. Compartmental modelling was also used to evaluate hydraulic performance and facilitated a better understanding of the way each of the different measures affected the flow pattern and performance. It was concluded that the installation of baffles is the best of the studied measures resulting in a reduction in the annual load on the receiving lake by approximately 8,000 kg of suspended solids (25% reduction of the annual load), 2 kg of copper (10% reduction of the annual load) and 600 kg of BOD (10% reduction of the annual load).

Models, Theoretical↗
PubMed2003

Modelling of temperature effects on removal efficiency and dissolved oxygen concentrations in stormwater ponds.

The performance of stormwater ponds, operated under winter conditions, was modelled using the commercial software Mike21 and MOUSE. Direct and indirect effects of changing temperature were investigated. The most important effect of winter conditions is the changed hydrology, characterised by long periods with no runoff followed by snowmelt events with large runoff volumes during several days. This gives lower removal efficiencies than during a period with the same precipitation but without winter conditions. For the concentration of dissolved oxygen, wind is an important factor. Consequently the most important effect of an ice cover on the pond is that it prevents the oxygenation effects of the wind. The direct temperature effects on the removal processes are negligible compared to the indirect effects in changed hydrology and forming of ice cover.

Climate↗
PubMed2002

Anatomical mismatch of the pulmonary autograft in the aortic root may be the cause of early aortic insufficiency after the Ross procedure.

OBJECTIVE: Early aortic insufficiency can be a problem after the Ross procedure. Anatomical mismatch and an inexact surgical technique may lead to distortion of the normal pulmonary valve geometry and subsequent incorrect leaflet coaptation and valve insufficiency. In this study, we assessed the efficacy of changing and improving the surgical technique to minimize the early pulmonary autograft valve failure. The modifications and the strategy are discussed. METHODS: From January 1995 to February 1999, a total of 77 adults underwent the Ross procedure for aortic valve replacement at Sahlgrenska University Hospital. The operative technique used was full free-standing aortic root replacement with a pulmonary autograft in all cases. In the first 24 cases, the diameter of the pulmonary roots was seldom measured, eye-balling was used to exclude anatomical mismatch due to a dilated aortic root, and only one attempt of correction was made, which failed. In the other 53 cases, the technique was improved by: (1) reducing the aortic anulus diameter in cases with moderate dilatation; (2) excluding cases with severe dilatation of the aortic annulus; (3) adjusting the diameter of the sinotubular junction of the aorta to the diameter of the sinotubular junction of the pulmonary artery; (4). reimplanting the left ostium in the autograft, and (5) changing the proximal anastomosis technique. RESULTS: In this study, we had an early aortic incompetence of grade 2 in eight patients among the first 24 patients. In the other 53 patients, postoperative echocardiography at 1 week revealed aortic insufficiency of grade 2 in two patients. CONCLUSIONS: Aortic insufficiency after the Ross procedure can be minimized by patient selection, intraoperative correction of anatomical mismatch and improved surgical technique.

Adolescent↗
PubMed2002

Detection and prevention of hepatitis C in dialysis patients and renal transplant recipients. A long-term follow up (1989-January 1997).

BACKGROUND: Hepatitis C is frequent problem in dialysis wards. DESIGN: A long time (1989-97) follow up of hepatitis C virus (HCV) infection in a Swedish nephrology unit was performed with anti-HCV screening, confirmatory antibody tests, viral RNA detection and molecular characterization. Case histories were reviewed with focus, onset of infection, liver morbidity and mortality. RESULTS: In October 1991, 10% (19 of 184) of the patients in the unit (haemodialysis-, peritoneal dialysis and transplanted patients) were verified or suspected HCV carriers, whilst the number at the end of 1996 was 8%, (13 of 157). Most patients were infected before 1991 but only in one case from a known HCV-infected blood donor. No new HCV infections associated with haemodialysis occurred during the study period. A total of 13 of 24 viremic patients had HCV genotype 2b, a pattern suggesting nosocomial transmission. This was further supported by phylogenetic analysis of HCV viral isolates in seven. HCV viremia was also common in patients with an incomplete anti-HCV antibody pattern as 8 of the 12 indeterminant sera were HCV-RNA positive. CONCLUSIONS: Awareness, prevention, identification of infected patients and donor testing limited transmission. Indeterminant recombinant immunoblot assays (RIBA)-results should be regarded with caution as a result of the relative immunodeficiency in uremic patients. Our data indicate nosocomial transmission in several patients.

Adolescent↗
PubMed2002

Metal content and particle size distribution of street sediments and street sweeping waste.

During recent years the interest in street sweeping as a pollutant control measure has increased. For planning of street sweeping programs and disposal of street sweeping waste there is a need to investigate the composition of street sweeping waste and the effect of street sweeping on the remaining sediments on the street. Particle size distribution and heavy metal concentration has been measured for street sweeping waste, street sediments before sweeping and remaining sediments after sweeping. The results show that the concentrations of heavy metals are a function of particle diameter and proportional to the inverse of the particle diameter, i.e. the highest concentrations are found in finest fractions. Regression equations for metal concentrations as a function of particle diameter are presented. According to Swedish guidelines for environmental quality of contaminated sites, heavy metal concentration in the sweeping waste can not be considered as a serious problem. The largest amount of metals and sediment is found in the sandy fractions (0.125-0.5 mm). The street sweeper is more effective in removing coarse sediments than fine. This means that the street sediments after sweeping are finer than the sediments before.

Cities↗
PubMed2001

Important pressure recovery in patients with aortic stenosis and high Doppler gradients.

Pressure recovery has been described in aortic stenosis and may explain the difference occasionally observed between Doppler- and catheter-measured gradients. A narrow ascending aorta (AA) and moderately severe stenosis favors pressure recovery. The aims of this study were to investigate the degree to which these conditions are present in patients with aortic stenosis and high Doppler gradients and to evaluate the magnitude of pressure recovery. One hundred sixteen patients were examined with Doppler echocardiography before aortic valve replacement. Patients with a maximum gradient >70 mm Hg (n = 81) were included. The diameter of the AA was measured and compared with the diameter in an age- and body size-matched group of normal controls (n = 23). Pressure recovery was estimated from a previously validated equation by measuring the maximum Doppler gradient, the effective orifice area (EOA), and the diameter of the AA. The diameter of the AA was similar for patients (mean 3.0 cm, range 2.1 to 4.1) and normal controls (mean 3.0 cm, range 2.3 to 3.5). The maximum Doppler gradient was 107 mm Hg (range 71 to 170) and the EOA was 0.6 cm(2) (range 0.2 to 1.3). The calculated pressure recovery was 18 mm Hg (range 6 to 37), which gives a net gradient of 89 mm Hg (range 51 to 151). Twenty-three percent had a net gradient <70 mm Hg. A cutoff of EOA/AA diameter at >0.2 cm identified 84% of patients (16 of 19) with a net gradient <70 mm Hg. In conclusion, we found that important pressure recovery can be expected in most patients with aortic stenosis and high Doppler gradients. Pressure recovery may explain why some patients with high Doppler gradients are asymptomatic. Also, pressure recovery is a factor to consider in patients with atypical symptomatology and high Doppler gradients when one must decide on valvular replacement.

Aortic Valve↗
PubMed2001

KSbO(Ge0.32Si0.68)O4, a KTP isomorph.

A structural model of potassium antimony germanate/silicate (0.32/0.68), KSbO(Ge(0.32)Si(0.68))O(4), has been determined at room temperature. KSbO(Ge(0.32)Si(0.68))O(4) belongs to the KTiOPO(4) (KTP) isomorphic family and is composed of SbO(6) octahedra (site symmetry -1 and 2) arranged in helical chains bridged by (Ge/Si)O(4) tetrahedra. Germanium and silicon have a similar distribution in the crystallographically independent tetrahedra (site symmetry 2). The structure contains large cavities occupied by the K atom. Two partially occupied potassium positions have been identified 1.273 (8) A apart, with an indication of a third potassium position between them. At room temperature, KSbO(Ge(0.32)Si(0.68))O(4) crystallizes in the paraelectric phase of space group Pnan. This phase is found at elevated temperatures for almost all KTiOPO(4) isomorphic compounds and KSbO(Ge(0.32)Si(0.68))O(4) is the second isomorph that is paraelectric at room temperature.

Journal Article↗
PubMed2001

A database generator for human brain imaging.

Sharing scientific data containing complex information requires new concepts and new technology. NEUROGENERATOR is a database generator for the neuroimaging community. A database generator is a database that generates new databases. The scientists submit raw PET and fMRI data to NEUROGENERATOR, which then processes the data in a uniform way to create databases of homogeneous data suitable for data sharing, met-analysis and modelling the human brain at the systems level. These databases are then distributed to the scientists.

Brain↗
PubMed2001

Dual-energy X-ray absorptiometry registers bone mineral in the liver.

OBJECTIVE: To analyse the difference in bone mineral content (BMC) between the left and right trunk generally obtained by dual-energy X-ray absorptiometry (DXA) by creating identical images over the liver region and the contralateral side. PATIENTS AND DESIGN: Fifty-four patients were selected at random from 1,722 subjects examined by DXA because of osteoporosis. Another five patients were selected who had been followed for osteoporosis by repeated DXA two to five times at intervals from 2 to 36 months. One healthy volunteer was followed for one day by means of DXA total body measurements. All protocols were analysed with respect to BMC, fat mass (FM) and lean tissue mass (LTM) of the imaged trunk and liver. RESULTS: BMC of the right trunk exceeded that of the left trunk in 78% of the investigated subjects. The right (liver) image dominated in all 81 investigations calculated from 60 subjects. There were intraindividual short- and longterm variations between repeated DXA examinations. The amounts of FM and LTM were distributed symmetrically between the right and left trunk. CONCLUSIONS: DXA registers BMC in the liver, which explains the general dominance of the right trunk. The absorption over the liver region varies in the same individual in repeated measurements at intervals of hours to months.

Absorptiometry, Photon↗
PubMed2001

A TiP(2)O(7) superstructure.

A room-temperature structural model of titanium pyrophosphate, TiP(2)O(7), has been determined from synchrotron X-ray data. The structure consists of TiO(6) octahedra and PO(4) tetrahedra sharing corners in a three-dimensional network. The PO(4) tetrahedra form P(2)O(7) groups connecting the TiO(6) octahedra. The 3 x 3 x 3 superstructure differs substantially from the parent AB(2)O(7) structure. The P--O--P bonding angles of the pyrophosphate group are between 141.21 (12) and 144.51 (13) degrees for those groups not located on the threefold axis. The individual TiO(6) octahedra and PO(4) tetrahedra are somewhat distorted.

Journal Article↗
PubMed2000

The Harvard Joint Center for Radiation Therapy, 1968-1999: a unique concept and its relationship to the prevailing times in academic medicine.

PURPOSE: Institutional structure, function, and philosophy reflect the organizational needs, and tend to mirror societal values of the times. For many years, the field of radiation oncology had among its major academic centers, an organization that served as a model for collaboration among health care institutions in an effort to serve the common good of its patients, hospitals, professional colleagues, and community. For over three decades, the Joint Center for Radiation Therapy (JCRT) was a leader in developing new organizational approaches for academic and clinical radiation oncology through the philosophy of collaboration in patient care, education, and research. METHODS AND RESULTS: In tracing the development and changes in organizational philosophy and structure of the JCRT, one can see the impact on academic oncology and cancer care through the emergence of both radiation and medical oncology as independent subspecialties, the importance of the National Cancer Act of 1971 accompanied by the growth of the NIH research and training programs and, more recently, the effect of the changing attitudes and approaches of hospitals, academicians, practitioners, and policy makers to health care delivery, structures, and cooperation. CONCLUSION: Lessons learned from the 31-year history of the JCRT may help provide organizational insight useful in guiding academic oncology and academic medical centers through periods of change.

Boston↗
PubMed2000

A single-crystal neutron diffraction study of RbTiOAsO(4).

A rubidium titanyl arsenate single-crystal has been studied by neutron diffraction (lambda = 1.207 A). The polished sample used was 5 x 3 x 2 mm and was cut from a crystal made by top-seeded solution growth. The crystal showed severe extinction. It was, however, possible to obtain a structural model with well defined oxygen sites and reasonable anisotropic displacement parameters.

Journal Article↗
PubMed2000

Insulin(GIK) improves myocardial metabolism in patients during blood cardioplegia.

The aim of this study was to test the hypothesis that abnormalities of myocardial substrate metabolism during blood cardioplegic aortic cross-clamping and early reperfusion are attenuated further by insulin(GIK) than by alpha-ketoglutarate enrichment of blood cardioplegia alone. Twenty-eight males (47 to 78 years) undergoing coronary artery bypass grafting (CABG) participated in a prospective, controlled, randomized study. All patients had alpha-ketoglutarate-enriched blood cardioplegia. Insulin(GIK) was infused in 13 patients during aortic cross-clamping. Insulin(GIK) prevented lactate release during cardioplegia (1.5+/-15 vs -44+/-14 micromol/min, p = 0.04), and a significant extraction of lactate was induced shortly after declamping the aorta (15+/-3 vs 2+/-1%, p = 0.001). Free fatty acid uptake was reduced after cardioplegic cross-clamping (5.7+/-1.6 vs 16.0+/-3.8 micromol/min, p = 0.02). More positive/less negative levels of alanine, aspartate, glutamine, glycine, ornithine, taurine and tyrosine were found in all the insulin-treated patients. We conclude that insulin(GIK) attenuates abnormalities of myocardial substrate metabolism during blood cardioplegic aortic cross-clamping and early reperfusion further than is obtained with alpha-ketoglutarate enrichment of blood cardioplegia alone.

Aged↗
PubMed2000

Dopant positions in strontium/chromium- and barium-doped KTP, determined with synchrotron X-radiation

Structure factors for strontium/chromium- (Sr/Cr) and barium- (Ba) doped potassium titanyl phosphate (KTiOPO(4), KTP) were measured with focused synchrotron X-radiation [0.75000 (9) A] using a fast avalanche photodiode counter. Space group Pna2(1), Z = 8, a = 12.786 (2), b = 6.3927 (8), c = 10.5585 (9) A, T = 293 (1) K, R = 0.028 (SrCrKTP); a = 12.851 (6), b = 6.418 (3), c = 10.620 (5) A, T = 120 (1) K, R = 0.031 (BaKTP). The refinement of the dopant positions showed that Ba(2+) is positioned in the larger of the two K cavities of KTP, while the smaller Sr(2+) ion is located in both. Split positions are found for the strontium dopant in both cavities and they are located in the positive c direction from the potassium cation. The chromium dopant has two different oxidation states, namely +III and +VI; in both states the dopant is located inside the TiO(6) octahedra. The two structures show slightly less distorted TiO(6) octahedra than pure KTP.

Journal Article↗