Three charge isomeric forms of vitellogenin are reported in the blood of estrogen-treated murrel, Channa punctatus on the basis of the results of native and SDS-PAGE, isoelectric focusing, and Ferguson plot analysis. Vitellogenin was induced in adult murrels by exogenous administration of estradiol-17beta and labelled with 32P in vivo. Labelled vitellogenin isolated from other plasma proteins on Ultrogel AcA 34 columns resolve into three bands on native-PAGE. Ferguson plot analysis reveals free electrophoretic mobilities of the three bands as 6.0, 4.5, and 3.7, which are very similar to the isoelectric point values of 5.9, 4.6, and 3.8, respectively. The apparent molecular weight of native murrel vitellogenin is 530 kDa. It consists of a single peptide with a molecular weight of 175 kDa. All the three bands on native PAGE resolves into a single peptide on SDS-PAGE. N-terminal amino acid sequence for murrel vitellogenin peptide is MKAVVLALLL. The protein phosphorus:lipid phosphorus ratio for murrel vitellogenin is 0.9. The total lipid content is 32.8%, consisting of 45% neutral lipids and 30% phospholipids. Phosphatidyl choline is the major phospholipid whereas triglycerides are the major neutral lipids. Results of these analytical analyses indicate that murrel native vitellogenin circulates as three charge isomers; poor in phosphorus but rich in lipids content.

A generalized approach, based on linear algebra, is described for processing exhaust gas analyser data. Systematic methods of deriving useful relationships from arbitrary data are proposed and used to produce several novel and useful results, as well as to show how existing relationships may be derived in forms that involve no approximations. The methods developed lend themselves to automatic real-time assessment of the consistency of gas analyser data, and in the case of inconsistencies, identifying plausible reasons. The approach is also used to develop methods to examine storage and release mechanisms within after-treatment devices, such as oxygen storage/release in three-way catalysts, soot oxidation in particle filters and water condensation/evaporation.

OBJECTIVE:In population-based studies performed on multiple continents during the past two decades, diabetes mellitus has been negatively associated with the prevalence and progression of abdominal aortic aneurysm (AAA) disease. We investigated the possibility that metformin, the primary oral hypoglycemic agent in use worldwide, may influence the progression of AAA disease. METHODS:Preoperative AAA patients with diabetes were identified from an institutional database. After tabulation of individual cardiovascular and demographic risk factors and prescription drug regimens, odds ratios for categorical influences on annual AAA enlargement were calculated through nominal logistical regression. Experimental AAA modeling experiments were subsequently performed in normoglycemic mice to validate the database-derived observations as well as to suggest potential mechanisms of metformin-mediated aneurysm suppression. RESULTS:Fifty-eight patients met criteria for study inclusion. Of 11 distinct classes of medication considered, only metformin use was negatively associated with AAA enlargement. This association remained significant after controlling for gender, age, cigarette smoking status, and obesity. The median enlargement rate in AAA patients not taking oral diabetic medication was 1.5 mm/y; by nominal logistic regression, metformin, hyperlipidemia, and age ≥70 years were associated with below-median enlargement, whereas sulfonylurea therapy, initial aortic diameter ≥40 mm, and statin use were associated with above-median enlargement. In experimental modeling, metformin dramatically suppressed the formation and progression, with medial elastin and smooth muscle preservation and reduced aortic mural macrophage, CD8 T cell, and neovessel density. CONCLUSIONS:Epidemiologic evidence of AAA suppression in diabetes may be attributable to concurrent therapy with the oral hypoglycemic agent metformin.

Certain H∞-control problems are considered and potential numerical difficulties are discussed. An alternative test for checking that the solution to an algebraic Riccati equation is positive semi-definite which is robust to rounding error even when the matrix is singular is presented. Finally the H∞ loop-shaping method is summarised and its numerical properties are shown to be satisfactory.

© 2015 SAE Japan. There is a trend towards increasing the degree of engine downsizing due to its potential for reducing fuel consumption and hence lowering CO2 emissions. However, downsizing introduces significant challenges for the engine airpath hardware and control, if driveability is to be maintained at an acceptable level. The transient response of the engine is affected by both the hardware selection and the associated controller. In order to understand the potential performance and limitations of the possible airpath hardware, a mean value model of the engine under consideration can be utilized. One benefit of these models is that they can be used as the basis of a model predictive controller which gives close to optimal performance with minimal tuning effort. In this paper we examine different two-stage series sequential turbocharger arrangements. The benefits of the mean value engine model, together with a model based controller are shown to observe the system and actuator constraints and demonstrate the best achievable performance for several configurations. This systematic approach to system evaluation is invaluable for comparing system performance without the risk of the controller prejudicing the result or requiring an excessive amount of tuning.

Real-time model predictive control (MPC) is used to experimentally assess the transient air-path performance of a two-stage serial variable geometry turbocharger (VGT) fitted to a light duty Diesel engine. The control model is based on a mean value engine model (MVEM) that is developed using data from the engine with a single stage turbocharger and modified to simulate the two-stage arrangement. A tip-in transient manoeuvre is used to assess system performance, in particular the boost-control where MPC is used to achieve close to optimal performance. This paper explores the improvement in transient performance when using two VGT turbochargers in series and considers where the differences between experiment and simulation occur.

Diabetes mellitus is a significant risk factor for arterial occlusive disease in many circulatory beds. Paradoxically, the risk for abdominal aortic aneurysm (AAA) disease is reduced in diabetic patients, and in patients with established AAA, diabetes is associated with reduced rates of aneurysm enlargement. The specific influences of hyperglycemia or its treatment on aneurysm pathogenesis remain poorly understood. We investigated the possibility that metformin, the most widely prescribed oral hypoglycemic agent worldwide, may independently limit AAA progression. After IRB approval, a health care system-wide database was retrospectively queried to identify diabetic AAA patients with at least two serial aortic diameter measurements prior to surgical repair. In this cohort, time-dependent aortic diameter enlargement was analyzed as a function of medication regimen. In parallel experiments, murine AAA models were created to assess the influence of metformin on aneurysm progression, using serial in vivo aortic diameter assessment during treatment and histologic analysis at euthanasia. Sixty-five diabetic AAA patients were identified as having at least two serial cross-sectional imaging studies spanning a period of at least 6 months. Average follow-up was 2.4 ± 2.1 years. When controlled for smoking status and gender, analyzed as a function of statin, angiotensin inhibition, α-/β- or calcium channel blocker status, insulin and oral hypoglycemic use, only metformin (Fig A and B) was negatively associated with aneurysm progression. In the mouse experiments, treatment with metformin dramatically suppressed the incidence and progression experimental aneurysms (Fig C and D). Histologically, metformin treatment preserved medial elastin content and smooth muscle cellularity, while reducing the density of aortic mural macrophages, CD8 T cells, and neovessels (data not shown). Metformin use may influence AAA progression. The negative association of diabetes mellitus with AAA prevalence and progression, confirmed in epidemiologic studies worldwide, may not be due to the consequences of hyperglycemia or insulin resistance alone.

Mean value engine models (MVEM) are well established for the study of IC engine air-path performance. Closed-loop control of the air-path is used to ensure the tracking of reference signals subject to constraints. To meet these requirements model predictive control (MPC) has been applied successfully to several air-path applications. This paper reports on the development of an MVEM and suitable MPC controller for transient performance evaluation which is then applied to the engine. A linearised prediction model is evaluated at each control time step, based on the current operating conditions, which ensures the model remains valid across a wide range of speeds and loads. This linearisation of the nonlinear model allows for the formulation of quadratic programming (QP) problems, which are efficiently solved as part of the proposed MPC algorithm. Special treatment in the measurement and calculation of the states and their derivatives is demonstrated to provide excellent tracking performance and a good match between the model and real-time experimental results. The systematic process of modelling coupled with MPC is shown to closely match test-bed performance, which verifies the methodology for studying air-path hardware alternatives.

1-D engine simulation models are widely used for the analysis and verification of air-path design concepts to assess performance and therefore determine suitable hardware. The transient response is a key driver in the selection process which in most cases requires closed loop control of the model to ensure operation within prescribed physical limits and tracking of reference signals. Since the controller effects the system performance a systematic procedure which achieves close-to-optimal performance is desired, if the full potential of a given hardware configuration is to be properly assessed. For this purpose a particular implementation of Model Predictive Control (MPC) based on a corresponding Mean Value Engine Model (MVEM) is reported here. The MVEM is linearised on-line at each operating point to allow for the formulation of quadratic programming (QP) problems, which are solved as the part of the proposed MPC algorithm. The MPC output is used to control a 1-D engine model. The closed loop performance of such a system is benchmarked against the solution of a related optimal control problem (OCP). The system is also tested for operation at high altitude conditions to demonstrate the ability of the controller to respect specified physical constraints. As an example this study is focused on the transient response of a light-duty automotive Diesel engine. For the cases examined the proposed controller design gives a more systematic procedure than other ad hoc approaches that require considerable tuning effort.

A key challenge in achieving good transient performance of highly boosted engines is the difficulty of accelerating the turbocharger from low air flow conditions (turbo lag). Multi-stage turbocharging, electric turbocharger assistance, electric compressors and hybrid powertrains are helpful in the mitigation of this deficit, but these technologies add significant cost and integration effort. Air-assist systems have the potential to be more cost-effective. Injecting compressed air into the intake manifold has received considerable attention, but the performance improvement offered by this concept is severely constrained by the compressor surge limit. The literature describes many schemes for generating the compressed gas, often involving significant mechanical complexity and/or cost. In this paper we demonstrate a novel exhaust assist system in which a reservoir is charged during braking. Experiments have been conducted using a 2.0 litre light-duty Diesel engine equipped with exhaust gas recirculation (EGR) and variable geometry turbine (VGT) coupled to an AC transient dynamometer, which was controlled to mimic engine load during in-gear braking and acceleration. The experimental results confirm that the proposed system reduces the time to torque during the 3rd gear tip-in by around 60%. Such a significant improvement was possible due to the increased acceleration of turbocharger immediately after the tip-in. Injecting the compressed gas into the exhaust manifold circumvents the problem of compressor surge and is the key enabler of the superior performance of the proposed concept. Copyright © 2013 SAE International.

Self-excited oscillation is becoming a major issue in low-emission, lean partially premixed combustion systems, and active control has been shown to be a feasible method to suppress such instabilities. A number of robust control methods are employed to obtain a feedback controller and it is observed that the robustness to system uncertainty is significantly better for a low complexity controller in spite of the norms being similar. Moreover, we demonstrate that closed-loop stability for such a complex system can be proved via use of the integral quadratic constraint method. Open- and closed-loop nonlinear simulations are provided.

Universal exhaust gas oxygen sensors (UEGOs) are in widespread use in internal combustion engines where they are used to measure lambda (the non-dimensional air-fuel ratio) and oxygen concentration (X-O2). The sensors are used on production engines and for research and development. In a previous paper, a model of the UEGO sensor was presented, based on a solution of the Stefan-Maxwell equations for an axisymmetric geometry, and it was shown that for a known gas composition, predictions of the sensor response agreed well with experiment. In the present paper, the more 'practical' problem is addressed: how well can such a model predict. and X-O2 based on the sensor response? For IC engine applications, a chemistry model is required in order to predict lambda, and such a model is also desirable for an accurate prediction of X-O2. A fast (matrix exponential) method of solving the Stefan-Maxwell equations is also introduced, which offers the possibility of a near real-time computation of lambda and X-O2, with application, for example, to bench instruments. Extensive results are presented showing how the interpretation of the UEGO response may be compromised by uncertainties. These uncertainties may relate not only to the sensor itself, such as temperature, pressure and mean pore diameter, but also the chemistry model.

Numerically well-conditioned state-space realisations for all-pass systems, such as Padé approximations to exp(-s), are derived that can be computed using exact integer arithmetic. This is then applied to the a series of functions of exp(-s). It is also shown that the H-infinity norm of the transfer function from the input to the state of a balanced realisation of the Padé approximation of exp(-s) is unity.

Delivering acceptable low end torque and good transient response is a significant challenge for all turbocharged engines. As downsized gasoline engines and Diesel engines make up a larger and larger proportion of the light-duty engines entering the market, the issue takes on greater significance. Several schemes have been proposed to improve torque response in highly boosted engines, including the use of electrical assist turbochargers and compressed air assist. In this paper we examine these methods with respect to their effectiveness in improving transient response and their relative performance along with some of the practical considerations for real world application. Results shown in this paper are from 1-D simulations using the Ricardo WAVE software package. The simulation model is based on a production light-duty Diesel engine modified to allow the introduction of compressed air at various points in the air-path as well as direct torque application to the turbocharger shaft (such as might be available from an electrical assist turbocharger). Whilst the 1-D simulation software provides a suitable environment for investigating the various boost assistance options, the overall air path performance also depends upon the control system. The introduction of boost assistance complicates the control in two significant ways: the system may run into constraints (such as compressor surge) that are not encountered in normal operation and the assistance introduces an additional control input. Production engine controllers are usually based on gain-scheduled PID control and extensive calibration. For this study, the non-linear nature of the engine together with the multiple configurations considered and the slower than real-time execution of 1-D models makes such an approach time consuming. Moreover, an ad-hoc approach would leave some doubt as to the fairness of comparisons between the different boost-assist options. Model Predictive Control has been shown to offer a convenient approach to controlling the 1-D simulations in a close to optimal manner for a typical Diesel VGT-EGR air path configuration. We show that the same technique can be applied to all the considered assistance methods with only modest calibration effort required. Copyright © 2012 SAE International.

Active control has been shown as a feasible technology for suppressing thermoacoustic instability in continuous combustion systems, and the control strategy design is substantially dependent on the reliability of the flame model. In this paper, refinement of G-equation flame model for the dynamics of lean premixed combustion is investigated. Precisely, the dynamics between the flame speed Su and equivalence ratio φ are proposed based on numerical calculations and physical explanations. Finally, the developed model is tested on one set of experimental data.

We discuss solvability issues of ℋ − /ℋ 2/∞ optimal fault detection problems in the most general setting. A solution approach is presented which successively reduces the initial problem to simpler ones. The last computational step generally may involve the solution of a non-standard ℋ − /ℋ 2/∞ optimization problem for which we discuss possible solution approaches. Using an appropriate definition of the ℋ − -index, we provide a complete solution of this problem in the case of ℋ 2 -norm. Furthermore, we discuss the solvability issues in the case of ℋ ∞ -norm.

Common-rail fuel injection systems on modern light duty diesel engines are effectively able to respond instantaneously to changes in the demanded injection quantity. In contrast, the air-system is subject to significantly slower dynamics, primarily due to filling/emptying effects in the manifolds and turbocharger inertia. The behaviour of the air-path in a diesel engine is therefore the main limiting factor in terms of engine-out emissions during transient operation. This paper presents a simple mean-value model for the air-path during throttled operation, which is used to design a feed-forward controller that delivers very rapid changes in the in-cylinder charge properties. The feed-forward control action is validated using a state-of-the-art sampling system that allows true cycle-by-cycle measurement of the in-cylinder CO2 concentration. © 2011 SAE International.

It is well known that self-excited oscillation is becoming a major issue in low emission, premixed combustion system. The mechanism of this phenomenon is the interaction between the unsteady heat release and the acoustic waves. Acoustic waves produce fluctuations in heat release, for instance by perturbing the equivalence ratio or flame shape. These heat fluctuations will in turn generate more acoustic waves and in some situations self-excited oscillations can happen. A kinematic heat release model with time-varying delays is proposed and linearized, both the the fully and imperfectly premixed situations are calculated and compared. A simplified acoustic model is developed and the coupling model between the heat release and acoustic model is established. Comparison is made between the theory and experiment.