Unraveling the Dose-response Puzzle of L. monocytogenes: A Mechanistic Approach

Food-borne disease outbreaks caused by Listeria monocytogenes continue to impose heavy burdens on public health in North America and globally. To explore the threat L. monocytogenes presents to the elderly, pregnant woman and immuno-compromised individuals, many studies have focused on in-host infection mechanisms and risk evaluation in terms of dose-response outcomes. However, the connection of these two foci has received little attention, leaving risk prediction with an insufficient mechanistic basis. Consequently, there is a critical need to quantifiably link in-host infection pathways with the dose-response paradigm. To better understand these relationships, we propose a new mathematical model to describe the gastro-intestinal pathway of L. monocytogenes within the host. The model dynamics are shown to be sensitive to inoculation doses and exhibit bi-stability phenomena. Applying the model to guinea pigs, we show how it provides useful tools to identify key parameters and to inform critical values of these parameters that are pivotal in risk evaluation. Our preliminary analysis shows that the effect of gastro-environmental stress, the role of commensal microbiota and immune cells are critical for successful infection of L. monocytogenes and for dictating the shape of the dose-response curves

Assessing effects of idling of a diesel engine operated with optimized blend of palm and mustard biodiesel

Palm is an edible feedstock which is immensely popular in Malaysia as an alternative fuel which can substitute diesel fuel. However, use of Palm biodiesel in diesel engine have a negative effect on food security, thus, in this study authors used Mustard biodiesel, which has poor fuel properties, with Palm biodiesel to produce an optimum blend. This blend will have better fuel properties compared to Mustard biodiesel and will help eliminate dependency of Palm biodiesel. To ensure that optimized blend achieves better fuel properties MATLAB optimization tool was used to find out the optimum blend ratio. Linear relationship among the fuel properties was considered for MATLAB coding. The resultant optimum blend is represented by PM. Optimum blend revealed improved fuel properties compared to mustard biodiesel. Fuel consumption and exhaust emission of diesel engine operated by the produced optimized blend blends at high idling conditions with and without a turbocharger installed, were evaluated. Optimized blend achieved lower CO, HC and NOX emission compared to Mustard biodiesel blends and also improved fuel consumption at idling conditions. When the engine was turbocharged it further decreased CO, HC and fuel consumption, but significantly increased NOX emission.</p

Current state and perspectives on transesterification of triglycerides for biodiesel production

Triglycerides are the main constituents of lipids, which are the fatty acids of glycerol. Natural organic triglycerides (viz. virgin vegetable oils, recycled cooking oils, and animal fats) are the main sources for biodiesel production. Biodiesel (mono alkyl esters) is the most attractive alternative fuel to diesel, with numerous environmental advantages over petroleum-based fuel. The most practicable method for converting triglycerides to biodiesel with viscosities comparable to diesel fuel is transesterification. Previous research has proven that biodiesel–diesel blends can operate the compression ignition engine without the need for significant modifications. However, the commercialization of biodiesel is still limited due to the high cost of production. In this sense, the transesterification route is a crucial factor in determining the total cost of biodiesel production. Homogenous base-catalyzed transesterification, industrially, is the conventional method to produce biodiesel. However, this method suffers from limitations both environmentally and economically. Although there are review articles on transesterification, most of them focus on a specific type of transesterification process and hence do not provide a comprehensive picture. This paper reviews the latest progress in research on all facets of transesterification technology from reports published by highly-rated scientific journals in the last two decades. The review focuses on the suggested modifications to the conventional method and the most promising innovative technologies. The potentiality of each technology to produce biodiesel from low-quality feedstock is also discussed.</p

Impact of fatty acid composition and physicochemical properties of Jatropha and Alexandrian laurel biodiesel blends: An analysis of performance and emission characteristics

This experimental investigation deals with the effects of fatty acid methyl ester (FAME) composition and the physicochemical properties of biodiesel on engine performance and emissions. FAME compositions have a considerable influence on the physical and chemical properties of biodiesel, such as density, viscosity, heating value, cetane number (CN), oxidation stability, and cold flow properties. The performance and emissions of a four-cylinder turbocharged diesel engine were studied under varying speeds and full load condition. For this investigation, 10% and 20% blends of Jatropha (Jatropha curcas), Alexandrian laurel (Calophyllum inophyllum), and palm biodiesels (JB, ALB, and PB, respectively) were used, and the results were compared with that of the B5 fuel (95% diesel and 5% palm biodiesel). The content of saturated fatty acid (methyl palmitate) for ALB and JB was found to be 23.3% and 20.4% higher respectively than that for PB. In total, PB showed 19.8% higher saturation than JB, while ALB showed 7.3% higher saturation than JB because of their higher content of longer chain saturated fatty acid (methyl stearate). The CNs of all three biodiesels increased with the increase of carbon chain length and saturation level, whereas iodine value and saponification value decreased with the increase of saturation level. An average of 2.8% and 4.5% brake power reduction were observed in the case of 10% and 20% biodiesel blends respectively. Brake specific fuel consumption increased in the range of 6%–20% compared with B5 fuel, whereas carbon monoxide and hydrocarbon emissions decreased significantly. Nitrogen oxide emissions increased in the range of 9%–23% for the 10% and 20% biodiesel blends with respect to B5 fuel.</p

State‐of‐the‐art of establishing test procedures for real driving gaseous emissions from light‐ and heavy‐duty vehicles

Air pollution caused by vehicle emissions has raised serious public health concerns. Vehicle emissions generally depend on many factors, such as the nature of the vehicle, driving style, traffic conditions, emission control technologies, and operational conditions. Concerns about the certification cycles used by various regulatory authorities are growing due to the difference in emission during certification procedure and Real Driving Emissions (RDE). Under laboratory condi-tions, certification tests are performed in a ‘chassis dynamometer’ for light‐duty vehicles (LDVs) and an ‘engine dynamometer’ for heavy‐duty vehicles (HDVs). As a result, the test drive cycles used to measure the automotive emissions do not correctly reflect the vehicle’s real‐world driving pattern. Consequently, the RDE regulation is being phased in to reduce the disparity between type approval and vehicle’s real‐world emissions. According to this review, different variables such as traffic signals, driving dynamics, congestions, altitude, ambient temperature, and so on have a ma-jor influence on actual driving pollution. Aside from that, cold‐start and hot‐start have been shown to have an effect on on‐road pollution. Contrary to common opinion, new technology such as start-stop systems boost automotive emissions rather than decreasing them owing to unfavourable conditions from the point of view of exhaust emissions and exhaust after‐treatment systems. In addi-tion, the driving dynamics are not represented in the current laboratory‐based test procedures. As a result, it is critical to establish an on‐road testing protocol to obtain a true representation of vehic-ular emissions and reduce emissions to a standard level. The incorporation of RDE clauses into certification procedures would have a positive impact on global air quality.</p