Showing papers by "Bengt Johansson published in 2015"

Long-Term Outcome of Mustard/Senning Correction for Transposition of the Great Arteries in Sweden and Denmark

Abstract: Background— The atrial switch operation, the Mustard or Senning operation, for the transposition of the great arteries (TGA) was introduced in the late 1950s and was the preferred surgery for TGA until the early 1990s. The Mustard and Senning operation involves extensive surgery in the atria and leaves the right ventricle as the systemic ventricle. The Mustard and Senning cohort is now well into adulthood and we begin to see the long-term outcome. Methods and Results— All the 6 surgical centers that performed Mustard and Senning operations in Sweden and Denmark identified all operated TGA patients. Information about death was obtained in late 2007 and early 2008 from the Danish and Swedish Centralised Civil Register by using the patients’ unique national Civil Registration Numbers. Four hundred sixty-eight patients undergoing the atrial switch operation were identified. Perioperative 30-day mortality was 20%, and 60% were alive after 30 years of follow-up. Perioperative mortality was significantly increased by the presence of a ventricular septal defect, left ventricular outflow obstruction, surgery early in the Mustard and Senning era. However, only pacemaker implantation is predictive of long-term outcome (hazard ratio, 1.90; 95% confidence interval, 1.05–3.46, P =0.04), once the TGA patient has survived the perioperative period. The risk of reoperation was correlated to the presence of associated defects and where the first Mustard/Senning operation was performed. Conclusions— The long-term survival of patients with Mustard and Senning correction for TGA appears to be primarily determined by factors in the right ventricle and tricuspid valve and not the timing of or the type of surgery in childhood. Cardiac function necessitating the implantation of a pacemaker is associated with an increase in mortality. # CLINICAL PERSPECTIVE {#article-title-24}

Effect of Pre-Chamber Volume and Nozzle Diameter on Pre-Chamber Ignition in Heavy Duty Natural Gas Engines

Abstract: It has previously been shown by the authors that the pre-chamber ignition technique operating with fuel-rich pre-chamber combustion strategy is a very effective means of extending the lean limit of combustion with excess air in heavy duty natural gas engines in order to improve indicated efficiency and reduce emissions. This article presents a study of the influence of pre-chamber volume and nozzle diameter on the resultant ignition characteristics. The two parameters varied are the ratio of pre-chamber volume to engine's clearance volume and the ratio of total area of connecting nozzle to the pre-chamber volume. Each parameter is varied in 3 steps hence forming a 3 by 3 test matrix. The experiments are performed on a single cylinder 2L engine fitted with a custom made pre-chamber capable of spark ignition, fuel injection and pressure measurement. The measured main and pre-chamber pressure data is then used to perform heat release analysis to understand combustion phenomenon in pre-chamber and the ignition and combustion of fuel-lean charge in main chamber that follows. Within the span of parameter variation, it has been observed that a larger pre-chamber provides higher ignition energy which results in shortened flame development angle and combustion duration. It is also observed that at a given pre-chamber volume, nozzle diameter mainly affects the combustion duration which may be due to difference in penetration depths of pre-chamber jets. The varied parameters seemed to have minor effect on NOx emissions. (Less)

Adults with complex congenital heart disease have impaired skeletal muscle function and reduced confidence in performing exercise training

Abstract: Background Adults with congenital heart disease (ACHD) usually have reduced aerobic exercise capacity compared with controls. However, their skeletal muscle function is less studied. Material and m ...

Double Compression Expansion Engine Concepts: A Path to High Efficiency

Abstract: Internal combustion engine (ICE) fuel efficiency is a balance between good indicated efficiency and mechanical efficiency. High indicated efficiency is reached with a very diluted air/fuel-mixture and high load resulting in high peak cylinder pressure (PCP). On the other hand, high mechanical efficiency is obtained with very low peak cylinder pressure as the piston rings and bearings can be made with less friction. This paper presents studies of a combustion engine which consists of a two stage compression and expansion cycle. By splitting the engine into two different cycles, high-pressure (HP) and low-pressure (LP) cycles respectively, it is possible to reach high levels of both indicated and mechanical efficiency simultaneously. The HP cycle is designed similar to today's turbo-charged diesel engine but with an even higher boost pressure, resulting in high PCP. To cope with high PCP, the engine needs to be rigid. The usage of higher piston ring tension and larger bearings are examples of measures to cope with higher PCP. These measures will cost in terms of friction. Hence, mechanical efficiency is not as good as other engine concepts with lower PCP. The low-pressure cycle on the other hand, uses a design more similar to current naturally aspirated (NA) spark ignited (SI) engines, but designed for even lower PCP. Because of this, the engine does not need to be as rigidly designed and the overall friction levels will be much lower. By combining these two engine philosophies, a total engine concept with both high indicated and mechanical efficiencies can be achieved. Simulations show net indicated efficiency above 60% and a brake efficiency of 56%. (Less)

CFD Simulations of Pre-Chamber Jets' Mixing Characteristics in a Heavy Duty Natural Gas Engine

Abstract: The effect of pre-chamber volume and nozzle diameter on performance of pre-chamber ignition device in a heavy duty natural gas engine has previously been studied by the authors. From the analysis of recorded pre- and main chamber pressure traces, it was observed that a pre-chamber with a larger volume reduced flame development angle and combustion duration while at a given pre-chamber volume, smaller nozzle diameters provided better ignition in the main chamber. The structure of pre-chamber jet and its mixing characteristics with the main chamber charge are believed to play a vital role, and hence CFD simulations are performed to study the fluid dynamic aspects of interaction between the pre-chamber jet and main chamber charge during the period of flame development angle, i.e. before main chamber ignition. It has been observed that jets from a larger pre-chamber penetrates through the main chamber faster due to higher momentum and generates turbulence in the main chamber earlier. At a given pre-chamber volume, smaller nozzle diameter causes higher velocity jet also causing high turbulence built up and better distribution of active species from the pre-chamber into the main chamber. (Less)

The level of physical exercise is associated with self-reported health status (EQ-5D) in adults with congenital heart disease

Abstract: BACKGROUND: The prognosis in adults with congenital aortic valve disease is usually favourable; nevertheless, a number of medical and social factors might hamper long-term prognosis and quality of ...

Death from Nitrous Oxide.

Abstract: Nitrous oxide is an inflammable gas that gives no smell or taste. It has a history of abuse as long as its clinical use, and deaths, although rare, have been reported. We describe two cases of accidental deaths related to voluntary inhalation of nitrous oxide, both found dead with a gas mask covering the face. In an attempt to find an explanation to why the victims did not react properly to oncoming hypoxia, we performed experiments where a test person was allowed to breath in a closed system, with or without nitrous oxide added. Vital signs and gas concentrations as well as subjective symptoms were recorded. The experiments indicated that the explanation to the fact that neither of the descendents had reacted to oncoming hypoxia and hypercapnia was due to the inhalation of nitrous oxide. This study raises the question whether nitrous oxide really should be easily, commercially available.

High-Speed Particle Image Velocimetry Measurement of Partially Premixed Combustion (PPC) in a Light Duty Engine for Different Injection Strategies

Abstract: It has been proven that partially premixed combustion (PPC) has the capability of high combustion efficiency with low soot and NOx emissions, which meet the requirements of increasingly restricted emission regulations. In order to obtain more homogenous combustion and longer ignition delay in PPC, different fuel injection strategies were employed which could affect the fuel air mixing and control the combustion. In the present work, a light duty optical diesel engine was used to conduct high speed particle image velocimetry (PIV) for single, double and triple injections with different timings. A quartz piston and a cylinder liner were installed in the Bowditch configuration to enable optical access. The geometry of the quartz piston crown is based on the standard diesel combustion chamber design for this commercial passenger car engine, including a re-entrant bowl shape. The severe image distortions caused by the optical piston shape are minimized through recordings of reference targets and an image dewarping algorithm. To the authors knowledge this is the first time the flow field inside such realistic re-entrant piston bowl has been mapped through high speed PIV. PRF 70 was used as fuel in these measurements. The in-cylinder flow field was evaluated and investigated with high temporal and spatial resolution to provide additional understanding of the fuel air mixing process. Formation of the vortices and turbulence enhance the air fuel interaction. The vector field of 40 consecutive cycles, mean velocity, and turbulence kinetic energy were calculated and evaluated. All the results based on PIV experiment also provide a quantitative dataset being useful for model validation of the computational fluid dynamics (CFD) simulation of this PPC engine.

Effects of Injection Strategies on Fluid Flow and Turbulence in Partially Premixed Combustion (PPC) in a Light Duty Engine

Abstract: Partially premixed combustion (PPC) is used to meet the increasing demands of emission legislation and to improve fuel efficiency. With gasoline fuels, PPC has the advantage of a longer premixed duration of the fuel/air mixture, which prevents soot formation. In addition, the overall combustion stability can be increased with a longer ignition delay, providing proper fuel injection strategies. In this work, the effects of multiple injections on the generation of in-cylinder turbulence at a single swirl ratio are investigated. High-speed particle image velocimetry (PIV) is conducted in an optical direct-injection (DI) engine to obtain the turbulence structure during fired conditions. Primary reference fuel (PRF) 70 (30% n-heptane and 70% iso-octane) is used as the PPC fuel. In order to maintain the in-cylinder flow as similarly as possible to the flow that would exist in a production engine, the quartz piston retains a realistic bowl geometry. The distortion caused by the complex shape of the optical piston is corrected by an advanced image-dewarping algorithm. The in-cylinder charge motion is evaluated and investigated over a range of crank angles in the compression and expansion strokes in order to understand the turbulence level, especially the late-cycle turbulence. The results show the spatial and temporal development of the flow-field structures in the piston bowl. The PIV data, obtained in the vertical plan, are used to calculate the ensemble average velocity turbulent kinetic energy (TKE), cycle-resolved turbulence, and mean velocity of the instantaneous fluid motion.

Screening for Familial Thoracic Aortic Aneurysms with Aortic Imaging Does Not Detect All Potential Carriers of the Disease.

Abstract: Background: About 20% of patients with thoracic aortic aneurysm or dissection (TAAD) have a first-degree relative with a similar disease. The familial form (FTAAD) of the disease is inherited in an ...

Sensitivity Analysis of Partially Premixed Combustion (PPC) for Control Purposes

Abstract: Partially Premixed Combustion (PPC) is a promising advanced combustion mode for future engines In order to investigate the sensitivity of PPC to exhaust gas recirculation (EGR) rate, intake gas temperature, intake gas pressure, and injection timing, these parameters were swept individually at three different loads in a single cylinder diesel engine with gasoline-like fuelA factor of sensitivity was defined to indicate the combustion's controllability and sensitivity to inlet gas parameters and injection timings Through analysis of experimental results, a control window of inlet gas parameters and injection timings is obtained at different loads in PPC mode from 5 bar to 10 bar IMEPg load at 1200 rpmTo further study the PPC controllability with injection timing, main injection timing was adjusted to sustain steady combustion phasing subject to perturbation of inlet gas state Experimental results show that the main injection timing can resist the interference of intake parameters and maintain constant combustion phasing Injection timing control is a promising approach to maintain high engine efficiency and low emission levels during transient operation (Less)

Ischemic heart disease among subjects with and without chronic obstructive pulmonary disease – ECG-findings in a population-based cohort study

Abstract: Cardiovascular comorbidity in COPD is common and contributes to increased mortality. A few population-based studies indicate that ischemic electrocardiogram (ECG)-changes are more prevalent in COPD, while others do not. The aim of the present study was to estimate the presence of ischemic heart disease (IHD) in a population-based COPD-cohort in comparison with subjects without COPD. All subjects with obstructive lung function (COPD, n = 993) were identified together with age- and sex-matched controls (non-COPD, n = 993) from population-based cohorts examined in 2002–04. In 2005, data from structured interview, spirometry and ECG were collected from 1625 subjects. COPD was classified into GOLD 1–4 after post-bronchodilator spirometry. Ischemic ECG-changes, based on Minnesota-coding, were classified according to the Whitehall criteria into probable and possible IHD. Self-reported IHD was equally common in COPD and non-COPD, and so were probable and possible ischemic ECG-changes according to Whitehall. After excluding subjects with restrictive spirometric pattern from the non-COPD-group, similar comparison with regard to presence of IHD performed between those with COPD and those with normal lung-function did neither show any differences. There was a significant association between self-reported IHD (p = 0.007) as well as probable ischemic ECG-changes (p = 0.042), and increasing GOLD stage. In COPD there was a significant association between level of FEV1 percent of predicted and self-reported as well as probable ischemic ECG-changes, and this association persisted for self-reported IHD also after adjustment for sex and age. In this population-based study, self-reported IHD and probable ischemic ECG-changes were associated with COPD disease severity assessed by spirometry.

An internal combustion engine system and a method for an internal combustion engine system

Abstract: The invention provides an internal combustion engine system (1) comprising - at least one combustor (3), and - a first expander (4) arranged to receive exhaust gases from at least one of the at least one combustor (3), and to expand and extract energy from the exhaust gases, - characterized in that the system comprises a second expander (5) arranged to receive exhaust gases from the first expander (4), and to expand and extract energy from the exhaust gases.

An internal combustion engine system and an exhaust treatment unit for such a system

Abstract: The invention provides an internal combustion engine system comprising - a compressor (3) arranged to compress air, - at least one combustor (4), at least one of the at least one combustor (4) being arranged to receive the compressed air, and - an exhaust treatment device (8) arranged to process exhaust gases produced by at least one of the at least one combustor (4), - characterized in that the system comprises a heat exchanger (6) arranged to receive the compressed air from the compressor (3) before it reaches the at least one of the at least one combustor (4), and that the heat exchanger (6) is arranged to transfer heat from the compressed air to the exhaust treatment device (8).

Increased endurance capacity in adults with complex congenital heart disease after home-based interval exercise training on ergometer cycle

Abstract: Increased endurance capacity in adults with complex congenital heart disease after home-based interval exercise training on ergometer cycle