bluuebunny/crossref_metadata_2025 huggingface dataset:
Pathway and kinetics of vitellogenin‐gold internalization in the Xenopus oocyte
Authors: Busson Sylvie , Ovtracht Ludmilla , Gounon Pierre
Published: February 2012

Summary— After in vitro incubation of Xenopus oocytes with vitellogenin (VTG)‐gold conjugate, the gold particles are distributed on the whole plasma membrane. Their concentration in coated pits still occurs at 0°C. At +20°C the label quickly (30 sec) appears in multi‐vesicular endosomes (MVE) which segregate together with primary endocytic vesicles into distinct clusters below the plasma membrane. From this step up to crystallization of the yolk platelets, the gold particles stay in the same compartment. During 5.5 h the label progressively increases along the MVE membrane, first (1.5 h) by fusion of primary endocytic vesicles with consecutively enlarging endosomes, then (4 h) by decreasing of the MVE membrane. As concerns the yolk platelet formation, concentration of primordial yolk platelets (PYP) occurs at 5.5 h from the incubation onset, the labeling of preexisting yolk platelets starts at 7 h, while crystallization of PYP begins only after 12–13 h.

Our results indicate that VTG receptors are not preclustered in coated pits and their lateral translation is not inhibited at 0°C. The yolk protein processing takes place within one compartment only. The VTG condensation begins with a long concentration phase of receptor‐VTG complexes still integrated in the endosome membrane. It occurs in MVE by: i) a repeated fusion of primary endocytic vesicles; ii) removing part of the endosome membrane by internal vesiculation. Fusion between endosomes occurs only after VTG has dissociated from its receptors and VTG dissociates only when when the density of the VTG‐receptor complexes in the endosome membrane is sufficient. Crystallization begins after a 7–8 h delay.

The endosome migration into the oocyte is also controlled by the binding of VTG to its receptors.

Our results also demonstrate that binding of VTG colloidal gold modifies neither the vitellogenic pathway nor the duration of the vitellogenin internalization. However when vitellogenin is bound to colloidal gold, dissociation of ligand‐receptor complexes is delayed because the amount of ligand in the incubation medium is necessarily low.
Characterization of human autoantibodies specific for lamin A
Authors: Courvalin Jean‐Claude , Chaudhary Nilabh , Danon Françoise , Brouet Jean‐Claude , Lassoued Kaiss
Published: February 2012

Summary— We have characterized human autoimmune polyclonal antibodies reactive with lamin A, a 74 kDa peripheral protein of the nuclear envelope. Unlike other known antibodies to lamin A, the antibodies described here do not crossreact with the structurally related lamin C. These antibodies feature only x light chains suggesting that their specificity is restricted to a limited number of epitopes. Based on the known amino acid sequence of human lamins A and C, the epitope(s) are most likely located in the 80 amino acid carboxyl tail of mature lamin A.
Effects of local anaesthetics (lidocaine) on the structure and function of ciliated respiratory epithelial cells
Authors: Verra Fernando , Escudier Estelle , Pinchon Marie‐Claire , Fleury Jocelyne , Bignon Jean , Bernaudin Jean‐François
Published: February 2012

Summary— Sampling for nasal or bronchial ciliated cells requires the use of anaesthetic agents, but such drugs may interfere with the morphological or functional results. Lidocaine is the most frequently used local anaesthetic. In order to study the morphological and functional effects of lidocaine hydrochloride, we designed an experimental study on ciliated cells from guinea pig and bovine trachea. On guinea pig tracheal specimens, different lidocaine concentrations (0.05, 0.25 and 1%) were tested. Tracheal rings were immersed in either culture medium alone (control) or in different lidocaine concentrations. Measurements of ciliary beat frequency (CBF) were performed by the stroboscopic method. Tracheal rings were consecutively incubated in culture medium alone and a second set of measurements was performed. Tracheal rings were studied by light microscopy after incubation in either 1% lidocaine or in culture medium alone. On bovine tracheal specimens, a coton wool swab impregnated with different lidocaine concentrations (0, 0.25, 1, 2.5 and 5%) was placed in contact with the tracheal mucosa. Three different kinds of samples were collected: the first one was used to study CBF, the second one (0.1 and 5%) was studied by scanning electron microscope (SEM) and the third (0.1 and 5%) by transmission electron microscopy (TEM). The results on guinea pig specimens show a significant but reversible CBF diminution for concentrations of 0.25 and 1% lidocaine and cellular lesions for the concentration of 1%. On bovine specimens a diminution in CBF for concentrations of 2.5 and 5% lidocaine was shown and the SEM study demonstrated obvious lesions on the epithelial surface treated with the 5% concentration. The TEM study showed morphological alterations on respiratory epithelium (deciliated areas, cytoplasmic vacuoles and mitochondrial swelling) for 5% lidocaine concentration. However the axonemal structure of cilia was normal for control and 5% concentration. We concluded that in vitro lidocaine can inhibit the CBF and that high concentrations of lidocaine can damage the respiratory epithelium but without modifications of the axonemal ultrastructure.
Permeability of the normal rat brain, spinal cord and dorsal root ganglia microcirculations to immunoglobulins G
Authors: Azzi Georges , Bernaudin Jean‐François , Bouchaud Claude , Bellon Blanche , Fleury‐Feith Jocelyne
Published: February 2012

Summary— The distribution of blood‐borne immunoglobulins G (IgG) was studied in the cerebral cortex, pineal gland, spinal cord and dorsal root ganglia of normal Lewis rats using the detection of autologous anti‐horseradish peroxidase (HRP) antibodies. This detection was performed by means of light and electron microscopy. This study demonstrated that, in the cerebral cortex and the spinal cord microcirculations, endothelial cells are a restrictive barrier against IgG while IgG are able to diffuse into the perivascular parenchyma of the pineal gland and spinal ganglia.
Activity‐dependent plastic changes in the motor nerve terminals of the adult rat
Authors: Tomas Josep , Batlle Jordi , Fenoll Maria Rosa , Santafé Manel , Lanuza Maria Angel
Published: February 2012

Summary— Small and short‐lasting physiologic variations in the locomotor activity of normal adult rats can induce remodelling in the motor nerve endings of the fast extensor digitorum longus muscle. The specificity and relative importance of the different plastic adaptations occurring in the presynaptic axonal tree have been studied, in silver impregnated nerve endings, by using an automatic image analysis treatment of the nerve terminals' geometric properties and a discriminant analysis of the morphometric parameters. Changes observed, like selective length variations in certain terminal segments and positional rearrangements, agree with a mechanism of neural connectivity regulation in the adult that arises as a consequence of normal neuromuscular activity.
Micropillar Testing of Amorphous Silica
Authors: Lacroix Rémi , Chomienne Vincent , Kermouche Guillaume , Teisseire Jérémie , Barthel Etienne , Queste Samuel
Published: February 2012

Amorphous silica exhibits a complex mechanical response. The elastic regime is highly nonlinear while plastic flow does not conserve volume, resulting in densification. As a result the quantification of a reliable constitutive equation is a difficult task. We have assessed the potential of micropillar compression testing for the investigation of the micromechanical properties of amorphous silica. We have calculated the response of amorphous silica micropillars as predicted by finite element analysis. The results were compared to preliminary microcompression tests. In the calculations, an advanced constitutive law including plastic response, densification, and strain hardening was used. Special attention was paid to the evaluation of the impact of substrate compliance, pillar misalignment, and friction conditions. We find that amorphous silica is much more amenable than some metals to microcompression experiments due to a comparatively high ratio between yield stress and elastic modulus. The simulations are found to be very consistent with the experimental results. However, full agreement cannot be obtained without allowance for the nonlinear response of amorphous silica in the elastic regime.
Geolocation by light: accuracy and precision affected by environmental factors
Authors: Lisovski Simeon , Hewson Chris M. , Klaassen Raymond H. G. , Korner‐Nievergelt Fränzi , Kristensen Mikkel W. , Hahn Steffen
Published: February 2012

1. Geolocation by light allows for tracking animal movements, based on measurements of light intensity over time by a data‐logging device (‘geolocator’). Recent developments of ultra‐light devices (<2 g) broadened the range of target species and boosted the number of studies using geolocators. However, an inherent problem of geolocators is that any factor or process that changes the natural light intensity pattern also affects the positions calculated from these light patterns. Although the most important factors have been identified, estimation of their effect on the accuracy and precision of positions estimated has been lacking but is very important for the analyses and interpretation of geolocator data.

2. The ‘threshold method’ is mainly used to derive positions by defining sunrise and sunset times from the light intensity pattern for each recorded day. This method requires calibration: a predefined sun elevation angle for estimating latitude by fitting the recorded day/night lengths to theoretical values across latitudes. Therewith, almost constant shading can be corrected for by finding the appropriate sun elevation angle.

3. Weather, topography and vegetation are the most important factors that influence light intensities. We demonstrated their effect on the measurement of day/night length, time of solar midnight/noon and the resulting position estimates using light measurements from stationary geolocators at known places and from geolocators mounted on birds. Furthermore, we investigated the influence of different calibration methods on the accuracy of the latitudinal positions.

4. All three environmental factors can influence the light intensity pattern significantly. Weather and an animal’s behaviour result in increased noise in positioning, whereas topography and vegetation result in systematic shading and biased positions. Calibration can significantly shift the estimated latitudes and potentially increase the accuracy, but detailed knowledge about the particular confounding factors and the behaviour of the studied animal is crucial for the choice of the most appropriate calibration method.
Osteoarthritis of the knee and hip. Part II: therapy with ibuprofen and a review of clinical trials
Authors: Adatia Aleem , Rainsford K D , Kean Walter F
Published: February 2012

Objectives

We review the pharmacological properties and clinical evidence pertaining to the efficacy of ibuprofen as a first-line treatment in hip and knee osteoarthritis (OA). In the context of our previous paper's exploration of the aetiology and pathogenesis of OA as a basis for pharmacotherapy, we discuss the pharmacokinetics (PK) and clinical pharmacodynamics (PD) of ibuprofen relevant to OA.

Key findings

Although widely used, the benefits and risks of ibuprofen, especially compared with other non-steroidal anti-inflammatory drugs (NSAIDs) and placebo, have only recently been evaluated in OA of the hip and knee in randomized-controlled clinical trials (RCT). The efficacy and occurrence of adverse reactions from ibuprofen was compared with placebo in a structural review of the literature and systematic review of RCTs in large-scale clinical trials. Ibuprofen has been found to result in approximately 50–60% improvement over placebo in WOMAC scores, including those reflecting inflammatory joint pain in knee and hip OA or other indices of pain, disability and impaired function. Mega-trials performed in comparison with the newer NSAIDs, the coxibs, have shown that ibuprofen has comparable therapeutic benefits and although serious gastrointestinal conditions are sometimes more frequent after short-term treatment, longer-term (several months) therapy in OA reduces the advantages of the coxibs over other NSAIDs including ibuprofen. Cardiovascular risk, though present with coxibs and some NSAIDs in OA, is lower or slightly so with ibuprofen compared with coxibs.

Ibuprofen is effective and relatively safe (especially at low over-the-counter doses and in the short term) for mild-to-moderate OA of the knee and hip. The PK properties of ibuprofen in OA (short plasma t½) confer advantages of this drug for OA, while evidence for clinically relevant PD benefits in joints of patients with OA, though limited, is suggestive of local anti-inflammatory activity.
Enhancement of anti-inflammatory and antinociceptive actions of red ginseng extract by fermentation
Authors: Jung Hyun-Joo , Choi Hojin , Lim Hye-Won , Shin Daehyun , Kim Hacksoo , Kwon Bin , Lee Jong Eun , Park Eun-Hee , Lim Chang-Jin
Published: February 2012

Objectives

This work aimed to compare some pharmacological properties of red ginseng extract (RG) and fermented red ginseng extract (FRG).

Methods

Antinociceptive activity was analysed using the acetic acid-induced abdominal constriction response. Anti-inflammatory activity was evaluated using acetic acid-induced vascular permeability and carrageenan-induced inflammation in the air pouch, and analysed through the measurement of nitrite content in the lipopolysaccharide (LPS)-stimulated macrophage cells. Anti-angiogenic activity was determined using the chick chorioallantoic membrane assay.

Key findings

In-vivo anti-inflammatory activity of FRG was stronger than that of RG in two animal models, vascular permeability and air-pouch models. In the vascular permeability model, the doses of RG and FRG required for half-maximal inhibition (IC50) were 181 and 59 mg/kg, respectively. FRG exhibited significantly stronger antinociceptive activity than RG. In the acetic acid-induced abdominal constriction response, the IC50 values of RG and FRG were 153 and 27 mg/kg, respectively. Although both RG and FRG were able to suppress production of nitric oxide in the LPS-stimulated RAW264.7 macrophage cells, the suppressive activity of FRG appeared to be stronger than that of RG. However, RG and FRG showed similar anti-angiogenic activity.

Conclusions

FRG possesses enhanced anti-inflammatory and antinociceptive activity but similar anti-angiogenic activity than RG.
Nitric oxide and passive limb movement: a new approach to assess vascular function
Authors: Trinity Joel D. , Groot H. Jonathan , Layec Gwenael , Rossman Matthew J. , Ives Stephen J. , Runnels Sean , Gmelch Ben , Bledsoe Amber , Richardson Russell S.
Published: February 2012

Key points 

Passive limb movement elicits a robust increase in limb blood flow (LBF) and limb vascular conductance (LVC) without a concomitant increase in skeletal muscle metabolism.

The peripheral vascular mechanisms associated with the increase in LBF and LVC are unknown.

Using an intra‐arterial infusion of NG‐monomethyl‐l‐arginine (l‐NMMA) to inhibit nitric oxide synthase (NOS) the hyperaemic and vasodilatory response to passive limb movement was attenuated by nearly 80%.

This finding demonstrates that the increases in LBF and LVC during passive limb movement are primarily NO dependent.

Passive limb movement appears to have significant promise as a new approach to assess NO‐mediated vascular function, an important predictor of cardiovascular disease risk.
Analysis of Constraint Configurations in Mechanical Assembly via Screw Theory
Authors: Rusli Leonard , Luscher Anthony , Schmiedeler James
Published: February 2012

The essential function of a mechanical assembly is the removal of degrees of freedom (DOF) to enable the transfer of load between two bodies. Assembly constraint features serve to provide this DOF removal, so their locations and orientations greatly affect the quality of an assembly as measured by its ability to resist relative motion between the parts. This paper addresses attachment-level design in which design decisions are made to establish the types, locations, and orientations of assembly features. The analysis methodology in this paper models assembly features such as point, pin, line, and plane constraints with equivalent first, second, and third order wrench systems. The set of relative motions to be evaluated is generated by composing from among these constraints a five-system pivot wrench combination to which a freedom screw motion is reciprocal. The effectiveness of each constraint to resist these motions is calculated as the ratio of the reaction forces at each resisting constraint to the input wrench magnitude. Based on these resistance values, multiple rating metrics are calculated to rate the overall assembly’s performance in resisting the motion. This work represents the first tool available to analyze a constraint configuration’s effectiveness to resist motion with a quantitative metric. Case studies are presented to demonstrate the utility of the analysis tool.
Analysis and Design of One Degree of Freedom Worm Robots for Locomotion on Rigid and Compliant Terrain
Authors: Zarrouk David , Shoham Moshe
Published: February 2012

Worm-like robots for applications including maintenance of small pipes and medical procedures in biological vessels such as the intestines, urethra, and blood vessels, have been the focus of many studies in the last few decades. The robots must be small, reliable, energy efficient, and capable of carrying cargos such as cameras, biosensors, and drugs. In this study, worm locomotion along rigid and compliant terrain is analyzed, and a novel design of worm-like multicell robots actuated by a single motor is presented. The robots employ a screw-like axis for sequencing and coordination of the cells and clamps. This design allows for significant miniaturization and reduces complexity and cost. The design of the robots and analysis of their dynamics and power efficiency are described. Two earthworm and two inchworm prototypes were built to demonstrate their performance. The robots are capable of moving forward, backward, and vertically and consume low power, which allow them to climb for hundreds of meters using onboard batteries.
Laser Spark Plug Numerical Design Process With Experimental Validation
Authors: McIntyre Dustin L. , Woodruff Steven D.
Published: February 2012

This work reports the numerical modeling design procedure for a miniaturized laser spark plug. In previous work both side pumped and end pumped laser spark plugs were empirically designed and tested. Experimental data from the previous laser spark plug development cycles is compared to the output predicted by a known set of rate equations. The rate equations are used to develop interrelated inter cavity time dependent waveforms that are then used to identify key variables. These variables are then input to a set of secondary equations for determining the output pulse energy, output power, and output pulse width of the simulated laser system. The physical meaning and the operation of the rate equations is explained in detail. This paper concentrates on the process and decision points needed to successfully design a solid state passively Q-switched laser system, either side pumped or end pumped, that produces the appropriate output needed for use as a laser spark plug for internal combustion engines.
An Optimization Model for Plug-In Hybrid Electric Vehicles
Authors: Malikopoulos Andreas A. , Smith David E.
Published: February 2012

The necessity for environmentally conscious vehicle designs in conjunction with increasing concerns regarding U.S. dependency on foreign oil and climate change have induced significant investment towards enhancing the propulsion portfolio with new technologies. More recently, plug-in hybrid electric vehicles (PHEVs) have held great intuitive appeal and have attracted considerable attention. PHEVs have the potential to reduce petroleum consumption and greenhouse gas (GHG) emissions in the commercial transportation sector. They are especially appealing in situations where daily commuting is within a small amount of miles with excessive stop-and-go driving. The research effort outlined in this paper aims to investigate the implications of motor/generator and battery size on fuel economy and GHG emissions in a medium-duty PHEV. An optimization framework is developed and applied to two different parallel powertrain configurations, e.g., pre-transmission and post-transmission, to derive the optimal design with respect to motor/generator and battery size. A comparison between the conventional and PHEV configurations with equivalent size and performance under the same driving conditions is conducted thus allowing an assessment of the fuel economy and GHG emissions potential improvement. The post-transmission parallel configuration yields higher fuel economy and less GHG emissions compared to pre-transmission configuration partly attributable to the enhanced regenerative braking efficiency.
Equilibrium Chemistry Calculations for Assessment of NOx Abatement Strategies in IC Engines
Authors: Aithal S. M.
Published: February 2012

Nitrogen Enriched Air (NEA) has shown great potential in NOx reduction without the drawbacks of exhaust gas recirculation (EGR). Use of NEA in stationary natural gas engines has shown up to 70% NOx reduction with a modest 2% nitrogen enrichment. However, nitrogen enrichment beyond a point leads to degradation in engine performance in terms of power density, brake thermal efficiency and unburned hydrocarbons. Optimizing the nitrogen enrichment levels to reduce NOx without performance degradation of the engine would greatly benefit the advancement of the air separation membrane technology. Development of fast and robust modeling tools to compute the temporal variation of the incylinder engine pressure, temperature and NOx formation can aid experimental efforts in determining the optimum enrichment levels for a given engine operating condition. This work presents a methodology to compute engine-out NOx for engines with and without nitrogen enrichment. Temporal variation of in-cylinder engine pressure and temperature can be obtained by a solution of the energy equation. Using these temperature and pressure values, along with the instantaneous composition of the working fluid, one can evaluate the equilibrium concentration of the combustion products. Since the NOx formation freezes a few crank angle degrees after the completion of combustion, it is instructive to examine whether the equilibrium computation can provide a reasonable estimate of engine-out NOx. To this end, engine-out NOx computed by using the above-mentioned procedure was obtained as a function of equivalence ratio for cases with nitrogen enrichment of 2% and no nitrogen enrichment. The results showed that the equilibrium NOx concentrations a few crank angle degrees after end of combustion were close to those reported experimentally in stationary natural gas engines. These results suggest that it would be possible to use equilibrium chemistry computations to evaluate various NOx mitigation strategies.
Oxidative Stability of Algae Derived Methyl Esters Containing Varying Levels of Methyl Eicosapentaenoate and Methyl Docosahexaenoate
Authors: Bucy Harrison , Marchese Anthony J.
Published: February 2012

Microalgae is currently receiving strong consideration as a potential biofuel feedstock to help meet the advanced biofuels mandate of the 2007 Energy Independence and Security Act because of its theoretically high yield (gallons/acre/year) in comparison to current terrestrial feedstocks. Microalgae lipids can be converted into a variety of biofuels including fatty acid methyl esters (e.g. biodiesel), renewable diesel, renewable gasoline or synthetic paraffinic aviation kerosene. For algal methyl ester biodiesel, fuel properties will be directly related to the fatty acid composition of the lipids produced by the given microalgae strain. Several microalgae species under consideration for wide scale cultivation, such as Nannochloropsis, produce lipids with fatty acid compositions containing substantially higher quantities of long chain-polyunsaturated fatty acids (LC-PUFA) in comparison to terrestrial feedstocks. It is expected that increased levels of LC-PUFA will be problematic in terms of meeting all of the current ASTM specifications for biodiesel. For example, it is well known that oxidative stability decreases with increasing levels of LC-PUFA. However, these same LC-PUFA fatty acids, such as eicosapentaenoic acid (EPA: C20:5) and docosahexaenoic acid (DHA: C22:6) are known to have high nutritional value thereby making separation of these compounds economically attractive. Given the uncertainty in the future value of these LC-PUFA compounds and the economic viability of the separation process, the goal of this study was to examine the oxidative stability of algal methyl esters with varying levels of EPA and DHA. Tests were conducted using a Metrohm 743 Rancimat with automatic induction period determination following ASTM D6751 and EN 14214 standards, which call for induction periods of at least 3 hours and 6 hours, respectively. Tests were conducted at a temperature of 110°C and airflow of 10 L/h with model algal methyl ester compounds synthesized from various sources to match the fatty acid compositions of several algae strains subjected to varying removal amounts of roughly 0 to 100 percent LC-PUFA. In addition, tests were also conducted with real algal methyl esters produced from multiple sources. The bis-allylic position equivalent (BAPE) was calculated for each fuel sample to quantify the level of unsaturation. The induction period was then plotted as a function of BAPE, which showed that the oxidative stability varied exponentially with the amount of LC-PUFA. The results suggest that removal of 45 to 65 percent of the LC-PUFA from Nannochloropsis-based algal methyl esters would be sufficient for meeting existing ASTM specifications for oxidative stability.
The Influence of Peanut Fatty Acid Methyl Ester Blends on Combustion in an Indirect Injection Diesel Engine
Authors: Soloiu Valentin , Lewis Jeffery , Covington April , Vlcek Brian , Schmidt Norman
Published: February 2012

The project investigates the effects of peanut FAME on diesel engine combustion and thermal efficiency. The cold flow properties and viscosity were tested and were found that the cloud point (CP) and pour point (PP) of peanut FAME were 17°C and 8°C respectively, and was able to achieve CP of 0°C when blended 20:80 (wt%) with diesel No. 2 (P20). The dynamic viscosity of peanut FAME was 4.2cP (P100) and 2.85cP at 54°C (P20), both fuels are within the ASTM standard for biodiesel. The lower heating value (LHV) of peanut FAME was 37.10MJ/kg (P100) and 41.3MJ/kg (P20) compared to 41.7MJ/kg for diesel No.2 (D100), which supports the usage of peanut FAME in compression ignition engines. At residence time of 5ms from start of injection, P50 has shown positive combustion characteristics with ignition delay of 1.072ms at 2600rpm, 4.78 bmep (100% load). The P50 heat release displayed similar development compared with diesel No. 2, where premixed phase combined with diffusion combustion and reaching a maximum of 20.0J/CAD, which was higher than 17.5J/CAD for D100. Convection flux for both D100 and P50 had values of 1.4MW/m2. The total heat flux, calculated by Annand model, produced maximum values of 2.1MW/m2 for D100 compared with 2.3MW/m2 for the P50. The mechanical efficiency was only a 4% loss when observing the transition from D100 to P50. These findings support peanut FAME as a viable option when blended and used with diesel engines in order to meet the standards set forth by the RSF-2 and EISA allowing the U.S. to decrease foreign energy dependency and benefiting society through a cleaner burning fuel than is currently in use.
Ignition by Shielded Glow Plug in Natural Gas Fueled Direct Injection Engines
Authors: Fabbroni Mark , Wallace James S.
Published: February 2012

Injected natural gas requires some form of ignition assist in order to ignite in the time available in a diesel engine combustion chamber. A glow plug — a heated surface — is one form of ignition assist. Ignition by glow plug results in a single site of ignition from which the flame must propagate to other jets in the ignition pattern. The goal of this work was to determine what factors affect how the flame propagates from this initial ignition site to the remaining unburned mixture. The combustion of natural gas jets under diesel engine conditions was studied over a range of temperatures with a glow plug shield using a CFR engine as a rapid compression device. The results showed that of all the factors considered it is the inter-related geometries of the injection pattern, combustion chamber, and glow plug shield that are most dominant in controlling combustion rates and fuel utilization, because those factors determine the distribution of fuel in the combustion chamber. Ignition of adjacent gas jets requires a flammable path between jets, which is achieved: 1) through mixing between the entrainment regions of adjacent jets and 2) through mixing along the cylinder wall of adjacent jets that are spreading along the wall. Ignition by either of both of these pathways can provide high fuel utilization and combustion rates and low combustion variability. Autoignition of an adjacent jet due to heat release from ignition of the first jet was not observed in these experiments with two jets.
Emissions From Various Biodiesel Sources Compared to a Range of Diesel Fuels in DPF Equipped Diesel Engines
Authors: Williams Aaron , Burton Jonathan , Christensen Earl , McCormick Robert L. , Tester John
Published: February 2012

The purpose of this study was to measure the impact of various sources of petroleum-based and bio-based diesel fuels on regulated emissions and fuel economy in diesel particulate filter (DPF) equipped diesel engines. Two model year 2008 diesel engines were tested with nine fuels including a certification ultra-low sulfur diesel (ULSD), local ULSD, high aromatic ULSD, low aromatic ULSD, and twenty percent blends of biodiesel derived from algae, camelina, soy, tallow, and yellow grease. Regulated emissions were measured over the heavy duty diesel transient test cycle. Measurements were also made of DPF-out particle size distribution and total particle count from a 13-mode steady state test using a fast mobility particle sizer. Test engines were a 2008 Cummins ISB and a 2008 International Maxx Force 10, both equipped with actively regenerated DPFs. Fuel consumption was roughly 2% greater over the transient test cycle for the B20 blends versus certification ULSD in both engines, consistent with the slightly lower energy content of biodiesel. Unlike studies conducted on older model engines, these engines equipped with diesel oxidation catalysts and DPFs showed small or no measurable fuel effect on the tailpipe emissions of total hydrocarbons (THC), carbon monoxide (CO) and particulate matter (PM). No differences in particle size distribution or total particle count were seen in a comparison of certification ULSD and B20 soy, with the exception of engine idling conditions where B20 produced a small reduction in the number of nucleation mode particles. In the Cummins engine, B20 prepared from algae, camelina, soy, and tallow resulted in an approximately 2.5% increase in nitrogen oxides (NOx) compared to the base fuel. The International engine demonstrated a higher degree of variability for NOx emissions, and fuel effects could not be resolved (p > 0.05). The group of petroleum diesel test fuels produced a range of NOx emissions very similar to that caused by blending of biodiesel. Test cycles where an active regeneration of the DPF occurred resulted in a nearly threefold increase in NOx emissions and a 15% increase in fuel consumption. The full quantification of DPF regeneration events further complicates the accurate calculation of fuel impacts on emissions and fuel consumption.
Effect of Hydrocarbon Emissions From PCCI-Type Combustion on the Performance of Selective Catalytic Reduction Catalysts
Authors: Prikhodko Vitaly Y. , Pihl Josh A. , Lewis Samuel A. , Parks James E.
Published: February 2012

Core samples cut from full size commercial Fe- and Cu-zeolite SCR catalysts were exposed to a slipstream of raw engine exhaust from a 1.9-liter 4-cylinder diesel engine operating in conventional and PCCI combustion modes. Subsequently, the NOx reduction performance of the exposed catalysts was evaluated on a laboratory bench-reactor fed with simulated exhaust. The Fe-zeolite NOx conversion efficiency was significantly degraded, especially at low temperatures (<250°C), after the catalyst was exposed to the engine exhaust. The degradation of the Fe-zeolite performance was similar for both combustion modes. The Cu-zeolite was much more resistant to HC fouling than the Fe-zeolite catalyst. In the case of the Cu-zeolite, PCCI exhaust had a more significant impact than the exhaust from conventional combustion on the NOx conversion efficiency. For all cases, the clean catalyst performance was recovered after heating to 600°C. GC-MS analysis of the HCs adsorbed to the catalyst surface provided insights into the observed NOx reduction performance trends.
An Investigation Into the Causes of Transient Particulate Matter Spikes in Production Diesel Engines
Authors: Brahma Indranil
Published: February 2012

Particulate matter spikes occurring during transient engine operation have important health implications. This paper investigates the root cause of particulate matter spikes in modern electronically controlled diesel engines that impose strict fuel-Oxygen ratio limits during the turbocharger lag period. It is proposed that these spikes can be significantly reduced by improved estimation of transient charge flow through the engine. Through transient data analysis and with the aid of transient data based empirical models, it has been shown that the fuel-Oxygen ratio restrictions imposed by contemporary engine controllers are ineffective during transients because of temporary but large differences between exhaust and intake manifold pressures during aggressive transients resulting in inaccurate volumetric efficiency and charge flow estimation. Steady state experiments with artificially generated high engine manifold pressure differentials have been conducted to support this hypothesis. The engine manifold pressure differential hypothesis is a consequence of previous investigations to explain the baffling inability of empirical data based models to predict the magnitudes of transient particulate matter spikes. Accurate volumetric efficiency estimation during transients can make the fuel-Oxygen ratio limits more effective at reducing opacity spikes. It would also make model based transient calibration more useful by increasing the accuracy of particulate matter models and by directing any dynamic optimization process to mould calibratable surfaces to minimize engine manifold pressure differential spikes. Fuel efficiency benefits due to lower pumping losses during transients and lower regeneration penalties would also result.
Development of a Common Rail Diesel Engine Combustion Model for ROHR Real-Time Estimation
Authors: Ponti Fabrizio , Ravaglioli Vittorio , De Cesare Matteo
Published: February 2012

Combustion control is a crucial aspect in modern Diesel engines control strategies, mainly due to the requests to increase efficiency and maintain pollutant emissions within the values bounded by standard regulations. In order to perform an accurate combustion control, modern “closed loop” control algorithms require the evaluation of a large number of quantities that provide information about combustion process effectiveness. This work presents a methodology that allows real-time estimation of energy released, during the combustion process, in a Common Rail Multi-Jet Diesel engine. This procedure can be divided in two main steps. The first step consists in the development of a zero-dimensional combustion model based on the linear combination of a proper number of Wiebe functions. In this case, a zero-dimensional approach has been chosen, because it is accurate enough for this analysis and requires low computational efforts. Once the combustion model has been developed, it can be used to determine Rate of Heat Release (RoHR) and the angular position in which 50% of fuel burned within an engine cycle is reached (MFB50). The second section of this work describes the relationships existing between injection parameters (such as Start of Injection, injected fuel quantities, rail pressure...) and the Wiebe parameters identified in the first step of the procedure. The above mentioned relationships have been used to set up correlations that allow estimating Wiebe parameters, therefore ROHR and MFB50, starting from injection parameters. The results obtained in MFB50 estimation are particularly emphasized, because real-time knowledge of this quantity is necessary to feedback a control algorithm for optimal combustion positioning. This work is based on several experimental tests performed on a 2.2 liters Common Rail Multi-Jet Diesel engine. First, experimental tests have been carried out to identify the combustion model and the correlations existing between Wiebe parameters and injection parameters. Then, in order to determine the accuracy of the approach, the complete estimation methodology has been applied to the engine under study. This work describes a methodology for real-time estimation of several quantities that provide important information about combustion process effectiveness (useful, for example, in modern low temperature combustion control systems). No extra cost is needed, because the methodology requires no additional sensor.
The Effect of Intake Valve Deactivation on Lean Stratified Charge Combustion at an Idling Condition of a Spark-Ignition Direct-Injection (SIDI) Engine
Authors: Grover Ronald O. , Chang Junseok , Masters Edward R. , Najt Paul , Singh Aditya
Published: February 2012

A combined experimental and analytical study was carried out to understand the improvement in combustion performance of a 4-valve SIDI wall-guided engine operating at lean, stratified idle with enhanced in-cylinder charge motion by deactivating one of the two intake valves. A fully warmed-up engine was operated at low speed, light load by injecting the fuel from a pressure-swirl injector during the compression stroke to produce a stratified fuel cloud surrounding the spark plug at the time of ignition. Steady state flow-bench measurements and CFD calculations showed that valve deactivation primarily increased the in-cylinder swirl intensity as compared with opening both intake valves. Engine dynamometer measurements showed an increase in charge motion led to improved combustion stability, increased combustion efficiency, lower fuel consumption, and higher dilution tolerance. A CFD study was conducted using in-house models of spray and combustion to simulate the engine operating with and without valve deactivation. The computations demonstrated that the improved combustion was primarily driven by higher laminar flame speeds through enhanced mixing of internal residual gases, better containment of the fuel cloud within the piston bowl, and higher post-flame diffusion burn rates during the initial, main, and late stages of the combustion process, respectively.
Development of a Partially-Premixed Combustion Strategy for a Low-Emission, Direct Injection High Efficiency Natural Gas Engine
Authors: Munshi S. R. , McTaggart-Cowan G. P. , Huang J. , Hill P. G.
Published: February 2012

A heavy-duty engine was modified to operate on natural gas using a partially-premixed charge strategy. The 15 L engine used a production natural gas fuelling system which was capable of providing direct injections of natural gas and diesel at high pressure during the intake stroke and around TDC of the compression stroke. The engine’s compression ratio was reduced to 15.3:1 to maximize load without exceeding the peak cylinder pressure or encountering knock. A multi-mode strategy for the natural gas injection was used: at part-load the injection occurred during the intake stroke, generating a premixed charge, while at high load a second injection was added around TDC to generate a non-premixed combustion phase. Using this strategy, loads up to 19 bar BMEP were achieved with brake efficiencies of nearly 40% and NOx emissions below 0.29 g/kWh. The key parameters needed to achieve the target load without knock were EGR level, premixed EQR, and intake manifold temperature. At high load, smoke emissions were significant, while at part load, high efficiency and low NOx were achieved but unburned fuel emissions increased. CFD simulation results indicated that the part-load barriers were a result of slow flame propagation through the lean premixed mixture. The modelling suggested that methods to overcome this could include partial-premixing and increased turbulence during the later stages of the combustion.
Simulation Based Development of Combustion Concepts for Large Diesel Engines
Authors: Engelmayer Michael , Wimmer Andreas , Pirker Gerhard , Pemp Bernhard , Hirschl Gernot
Published: February 2012

The development of low-emission combustion concepts for large Diesel engines requires a specially adapted methodology. In all phases of the development process, it is essential that appropriate tools are used so that an optimized solution can be found within a short time. This paper will describe the methodology used for developing combustion concepts for large Diesel engines. In general, the development of a combustion concept for Diesel engines comprises the definition of the system (e.g. combustion chamber geometry, injection system, EGR system and charging system) and the calibration of engine parameters (e.g. injection parameters, EGR rate, charge pressure, excess air ratio and valve timing) for an application and its emission scenario. In the present case, the main objective was to develop concepts for applications to comply with emissions standards according to EU Stage III B and US EPA Tier 4. To this end, the LEC has developed the LDM method (LEC Development Methodology). This method is based on the intensive interaction of simulation with experimental investigations on single-cylinder research engines. As part of this development methodology, 3D CFD simulation as well as 0D and 1D engine cycle calculation are employed. Another approach used to handle the complexity of the systems is Design of Experiments (DoE) for simulation and experimental work. While 3D CFD simulation is used to optimize the details of the combustion and pollutant formation processes in the combustion chamber, 0D and 1D engine cycle simulation is applied to select the concepts and to pre-optimize important engine parameters. One great advantage of 0D and 1D models is their short calculation time, which allows the investigation of a great amount of variations in parameters. In order to apply the methodology, it must be guaranteed that the results from tests on the single-cylinder engine (SCE) can be transferred to the multi-cylinder engine (MCE). Therefore, it is necessary that the boundary conditions of the SCE are comparable to those of the MCE. Not only the same thermal boundary conditions but also the same conditions at the beginning of the high-pressure cycle (charge composition, pressure and temperature) must be maintained. The SCE measurement results that are generated serve to verify and calibrate the simulation models and deliver the necessary boundary conditions for further simulations. All in all, the paper comprises an evaluation of the different simulation models used and the applied development methodology in order to optimize fuel consumption and to reduce the emissions of large Diesel engines.
A Study on the Performance and Emissions Characteristics of a DI Compression Ignition Engine Operated With LPG and DTBP Blending Fuels
Authors: Kang Hoin , Caton Jerald A. , Lee Seangwock , Lee Seokhwan , Oh Seungmook
Published: February 2012

LPG (Liquefied Petroleum Gas) has been widely used as an alternative fuel for gasoline and diesel vehicles in light of clean fuel and diversity of energy resources. But conventional LPG vehicles using carburetors or MPI fuel injection systems can’t satisfy the emissions regulations and CO2 targets of the future. Therefore, it is essential to develop LPG engines of spark ignition or compression ignition type such that LPG fuel is directly injected into the combustion chamber under high pressure. A compression ignition engine using LPG is the ideal engine with many advantages of fuel economy, heat efficiency and low CO2, even though it is difficult to develop due to the unique properties of LPG. This paper reports on numerical and experimental studies related to LPG fuel for a compression ignition engine. The numerical analysis is conducted to study the combustion chamber shape with CATIA and to analyze the spray and fluid behaviors with FLUENT for diesel and LPG (n-butane 100%) fuels. In one experimental study, a constant volume chamber is used to observe the spray formation for the chamber pressure 0 to 3MPa and to analyze the flame process, P-V diagram, heat release rate and emissions through the combustion of LPG fuel with the cetane additive DTBP (Di-tert-butyl peroxide) 5 to 15 wt% at 25MPa of fuel injection pressure. In engine bench tests, experiments were performed to find the optimum injection timing, lambda, COV and emissions for the LPG fuel with the cetane additive DTBP 5 to 15 wt% at 25MPa fuel injection pressure and 1500 rpm. The penetration distance of LPG (n-butane 100%) was shorter than that of diesel fuel and LPG was sensitive to the chamber pressure. The ignition delay was in inverse proportion to the ambient pressure linearly. In the engine bench tests, the optimum injection timing of the test engine to the LPG fuel with DTBP 15 wt% was about BTDC 12° CA at all loads and 1500 rpm. An increasing of DTBP blending ratio caused the promotion of flame and fast burn and this lead to reduce HC and CO emissions, on the other hand, to increase NOx and CO2 emissions.
MK-4815, a Potential New Oral Agent for Treatment of Malaria
Authors: Powles Mary Ann , Allocco John , Yeung Lai , Nare Bakela , Liberator Paul , Schmatz Dennis
Published: February 2012

Malaria continues to have a significant impact on the health of the developing world. Efforts to combat this disease now focus on combination therapy in order to stem the emergence of resistant parasites. Continued efforts are needed to discover and develop new agents for use in combination antimalarial regimens. MK-4815 is a small molecule with antimalarial activity that was identified from a large pharmaceutical compound collection using a semiautomated version of a well-established
in vitro
assay for the erythrocytic stages of
Plasmodium falciparum. In vitro
studies indicate that the compound selectively accumulates in infected red blood cells and is most effective against the metabolically active late trophozoite/early schizont stages. A variety of drug-resistant field isolates of
P. falciparum
were found to be as sensitive to MK-4815 as the wild-type lines. MK-4815 is orally active in a
P. berghei
mouse model of acute malaria. In this model, where untreated animals succumb to infection 10 to 12 days postinfection, MK-4815 was completely curative when given as a single dose of 50 mg/kg, 2 doses of 25 mg/kg, or 4.5 doses of 12.5 mg/kg. In pharmacokinetic studies with mice and rhesus monkeys, MK-4815 demonstrated oral bioavailability and low clearance. In addition, MK-4815 is inexpensive to synthesize, an important characteristic for providing affordable antimalaria therapy to the developing world. The attractive biological and pharmaceutical profile of MK-4815 demonstrates its potential for use in combination with other agents in the fight against malaria.