Simulation of four stroke engine cycle for a 4 - valve pentroof engine in KIVA 3VR2

The main purpose of this project is to understand the process of engine simulation using the open source CFD code called KIVA. This report mainly discusses the simulation of the 4-valve Pentroof engine through KIVA 3VR2. KIVA is an open source FORTRAN code which is used to solve the fluid flow field in the engines with the transient 2D and 3D chemically reactive flow with spray. It also focuses on the complete procedure to simulate an engine cycle starting from pre- processing until the final results. This report will serve a handbook for the using the KIVA code.

Cell replacement therapy for intracerebral hemorrhage

Intracerebral hemorrhage (ICH), for which no effective treatment strategy is currently available, constitutes one of the most devastating forms of stroke. As a result, developing therapeutic options for ICH is of great interest to the medical community. The 3 potential therapies that have the most promise are cell replacement therapy, enhancing endogenous repair mechanisms, and utilizing various neuroprotective drugs. Replacement of damaged cells and restoration of function can be accomplished by transplantation of cells derived from different sources, such as embryonic or somatic stem cells, umbilical cord blood, and genetically modified cell lines. Early experimental data showing the benefits of cell transplantation on functional recovery after ICH have been promising. Nevertheless, several studies have focused on another therapeutic avenue, investigating novel ways to activate and direct endogenous repair mechanisms in the central nervous system, through exposure to specific neuronal growth factors or by inactivating inhibitory molecules. Lastly, neuroprotective drugs may offer an additional tool for improving neuronal survival in the perihematomal area. However, a number of scientific issues must be addressed before these experimental techniques can be translated into clinical therapy. In this review, the authors outline the recent advances in the basic science of treatment strategies for ICH.

Current trends in hormone replacement therapy: perceptions and usage

OBJECTIVE: To determine whether physicians' confidence in the use of hormone replacement therapy (HRT) for climacteric symptoms has been affected by the negative media interpretation of data from landmark studies investigating HRT usage such as the Women's Health Initiative (WHI) study. METHODS: A structured questionnaire was completed via the internet by European and US gynecologists, obstetrician/gynecologists and general practitioners - all experienced in treating women with climacteric symptoms. RESULTS: Six hundred physicians completed the survey in six countries. Overall, 98% agreed that the menopause significantly affects quality of life and 97% considered that the majority/all of their patients experienced positive benefits from HRT. Most physicians (90%) believed the benefits of HRT outweigh the risks in suitable patients, and 92% would prescribe HRT for themselves/spouse/family. For treatment of atrophic vaginitis, 86% agreed that local estrogen was the most effective course of action. While 82% of participants were aware of the latest recommendations on low-dose HRT, and estrogen dose in particular, 67% cited lowering the progestogen dose as important. With regard to the recent negative media coverage on HRT, 78% of physicians felt this was unjustified. CONCLUSIONS: These results provide reassurance that health-care professionals in Europe and the US, experienced in treating women with climacteric symptoms, have not lost confidence in HRT. Despite a consensus on the importance of lowering the dose of HRT and a focus on estrogen, there remains a need to heighten prescribers' awareness on the pivotal role that a lower progestogen dose plays in optimizing the risk-benefit profile.

DEVELOPMENT OF A PREDICTIVE COMBUSTION MODEL OF A SPARK IGNITED ENGINE WITH GASOLINE DIRECT INJECTION, VARIABLE VALVE TIMING, DURATION AND LIFT TECHNOLOGIES

There is a need by engine manufactures for computationally efficient and accurate predictive combustion modeling tools for integration in engine simulation software for the assessment of combustion system hardware designs and early development of engine calibrations. This thesis discusses the process for the development and validation of a combustion modeling tool for Gasoline Direct Injected Spark Ignited Engine with variable valve timing, lift and duration valvetrain hardware from experimental data. Data was correlated and regressed from accepted methods for calculating the turbulent flow and flame propagation characteristics for an internal combustion engine. A non-linear regression modeling method was utilized to develop a combustion model to determine the fuel mass burn rate at multiple points during the combustion process. The computational fluid dynamic software Converge ©, was used to simulate and correlate the 3-D combustion system, port and piston geometry to the turbulent flow development within the cylinder to properly predict the experimental data turbulent flow parameters through the intake, compression and expansion processes. The engine simulation software GT-Power © is then used to determine the 1-D flow characteristics of the engine hardware being tested to correlate the regressed combustion modeling tool to experimental data to determine accuracy. The results of the combustion modeling tool show accurate trends capturing the combustion sensitivities to turbulent flow, thermodynamic and internal residual effects with changes in intake and exhaust valve timing, lift and duration.

Resuspension of the aortic valve in acute type A dissection: long-term results

BACKGROUND AND AIM OF THE STUDY: Preservation of the aortic valve during the repair of acute type A aortic dissection (AADA) is a viable option to prevent lifelong oral anticoagulation. The study aim was to assess aortic valve function following resuspension and supracoronary ascending aortic grafting. METHODS: Among a collective of 210 consecutive patients undergoing surgery for AADA, 140 (66.7%) with resuspension of the aortic valve and supracoronary ascending graft were analyzed. Of these patients, 83 (59.3%) had a complete follow up (mean 61.2 +/- 40.8 months), with 65 of the subgroup (78.3%) being followed by computed tomography scanning and echocardiography. RESULTS: Reoperation due to severe aortic valve regurgitation was required in seven patients (10.8%). The perioperative characteristics were similar in these patients; notably, no significant difference was evident with regards to the aortic annulus diameter and the severity of regurgitation at the time of surgery. The left ventricular mass index was significantly higher in patients requiring reoperation due to aortic valve regurgitation (219.3 +/- 146.6 versus 123.9 +/- 146.6 g/m2; p <0.05). None of the patients died as a result of reoperation. CONCLUSION: The long-term functional results following resuspension of the aortic valve in AADA were very good. A close echocardiographic follow up was necessary, as reoperation of the aortic valve was required in more than 10% of the collective, with an average follow up of five years. Reoperation was mainly related to secondary dilatation of the aortic root.

Tricuspid valve regurgitation attributable to endomyocardial biopsies and rejection in heart transplantation

In the present report the prevalence, severity, and risk factors of tricuspid valve regurgitation (TR) in 251 heart transplant recipients have been analyzed retrospectively. Tricuspid valve function was studied by color-flow Doppler echocardiogram and annual heart catheterization. The presence or severity of TR was graded on a scale from 0 (no TR) to 4 (severe). Additional postoperative data included rate of rejection, number of endomyocardial biopsies, incidence of transplant vasculopathy, and preoperative and postoperative hemodynamics. The incidence of grade 3 TR increases from 5% at 1 year to 50% at 4 years after transplantation. Multivariate analysis showed rate of rejection and donor heart weight to be significant risk factors. The ischemic intervals as well as the preoperative and postoperative pulmonary hemodynamics did not affect the severity or prevalence of TR. These results indicate that various factors appear to have an impact on the development of TR and that the prevalence might be lowered by a reduction of the number of biopsies performed and when possible, oversizing of donor hearts.

Clinical and hemodynamic predictors of natriuretic peptide elevation among aortic valve disease patients

We investigated the relative contribution of hemodynamic and clinical factors to serum natriuretic peptide elevation in seventy-one patients with either aortic stenosis or aortic regurgitation. We found that pulmonary hypertension, heart failure and renal failure are the most powerful independent predictors of natriuretic peptide elevation in patients with aortic valve disease, irrespective of the type or severity of valvular lesion itself.