bluuebunny/crossref_metadata_2025 huggingface dataset:
A simple method for calibrating collagenase/pronase E ratio to optimize heart cell isolation
Authors: Le Guennec Jean‐Yves , Peineau Nicolas , Esnard Frédéric , Lacampagne Alain , Gannier Francois , Argibay Jorge , Gauthier Francis , Garnier Didier
Published: February 2012

Summary— A mixture of crude collagenase and non‐specific proteases has been used to isolate guinea pig ventricular heart cells. Measurements of collagenase activity with Wünsch's substrate and protein content with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) suggest that collagenase enzymes do not play a major role in heart cell isolation. On the other hand, an important factor in heart digestion seems to consist of some fractions of the proteases present in crude collagenase. It is also noted that crude collagenases do not present any sensitivity to added calcium but because this ion is important to obtain isolated cells its role is discussed. According to our results, the SDS‐PAGE method can be used to determine the appropriate enzyme concentrations to obtain calcium‐tolerant myocytes. These myocytes have electrophysiological properties as reported in the literature.
Tunic morphogenesis in the sea peach (Halocynthia papillosa, Ascidiacea, rochordata): Cellular events, the initiation of twisted fibrous arrangements and spine formation
Authors: Lübbering Birgit , Giraud‐Guille Marie‐Madeleine , Goffinet Gerard
Published: February 2012

Summary— The adult tunic of the sea peach (Halocynthia papillosa) shows a high degree of organisation. Tunic morphogenesis was monitored from the onset of tunic secretion until juveniles reached the age of 3 months. While some characteristics of the adult tunic are still missing, like certain types of intratunical cells and striated bodies, its main features have already developed by this time. Crucial events take place at or soon after the onset of metamorphosis (stage M 0). Cuticular spines cover the external surface of the juvenile. At least two types of intratunical cells enter the tunic and the fibrous material adopts a three‐dimensional twisted helicoidal architecture. The initiation of this helicoidal arrangement of fibrils directly after stage M 0 is discussed regarding accompanying developmental events. The existence of cells that penetrate the outer compartment of the tunic at the end of larval life is reported for the first time.
Bacteriocinogenesis in cells of Xenorhabdus nematophilus and Photorhabdus luminescens: Enterobacteriaceae associated with entomopathogenic nematodes
Authors: Baghdiguian Stephen , Boyer‐Giglio Marie‐Hélène , Thaler Jacques‐Olivier , Bonnot Guy , Boemare Noël
Published: February 2012

Summary— Xenorhabdus nematophilus FI strain and Photorhabdus luminescens NC19 strain produced bacteriocins after mitomycin C treatment and under natural conditions respectively. The ultrastructure of these two strains was described and compared to the ultrastructure of untreated or normal cells. After image processing of purified bacteriocins we found morphological homology in infected cells with protoplasmic rods in longitudinal section and hexagonal aggregates in transversal section. We concluded that these particular structures, so‐called ‘lattice structures’ and previously interpreted as ‘photosomes’, are in fact the early stages of in situ production of bacteriocins in these two bacterial genera. Natural occurrence of Photorhabdus spp bacteriocinogenesis was observed in other strains, while other lysogenic strains of Xenorhabdus spp are lysed after a mitomycin C treatment.
An evaluation of the potential of linear and nonlinear skin permeation models for the prediction of experimentally measured percutaneous drug absorption
Authors: Brown Marc B , Lau Chi-Hian , Lim Sian T , Sun Yi , Davey Neail , Moss Gary P , Yoo Seon-Hie , De Muynck Christian
Published: February 2012

Objectives

The developments in combinatorial chemistry have led to a rapid increase in drug design and discovery and, ultimately, the production of many potential molecules that require evaluation. Hence, there has been much interest in the use of mathematical models to predict dermal absorption. Therefore, the aim of this study was to test the performance of both linear and nonlinear models to predict the skin permeation of a series of 11 compounds.

Methods

The modelling in this study was carried out by the application of both quantitative structure permeability relationships and Gaussian process-based machine learning methods to predict the flux and permeability coefficient of the 11 compounds. The actual permeation of these compounds across human skin was measured using Franz cells and a standard protocol with high performance liquid chromatography analysis. Statistical comparison between the predicted and experimentally-derived values was performed using mean squared error and the Pearson sample correlation coefficient.

Key findings

The findings of this study would suggest that the models failed to accurately predict permeation and in some cases were not within two- or three-orders of magnitude of the experimentally-derived values. However, with this set of compounds the models were able to effectively rank the permeants.

Conclusions

Although not suitable for accurately predicting permeation the models may be suitable for determining a rank order of permeation, which may help to select candidate molecules for in-vitro screening. However, it is important to note that such predictions need to take into account actual relative drug candidate potencies.
Clove and eugenol in noncytotoxic concentrations exert immunomodulatory/anti-inflammatory action on cytokine production by murine macrophages
Authors: Bachiega Tatiana Fernanda , de Sousa João Paulo Barreto , Bastos Jairo Kenupp , Sforcin José Maurício
Published: February 2012

Objectives

The extract and essential oil of clove (Syzygium aromaticum) are widely used because of their medicinal properties. Eugenol is the most important component of clove, showing several biological properties. Herein we have analysed the immunomodulatory/anti-inflammatory effect of clove and eugenol on cytokine production (interleukin (IL)-1β, IL-6 and IL-10) in vitro.

Methods

Macrophages were incubated with clove or eugenol (5, 10, 25, 50 or 100 µg/well) for 24 h. Concentrations that inhibited the production of cytokines were used before or after incubation with lipopolysaccharide (LPS), to verify a preventive or therapeutic effect. Culture supernatants were harvested for measurement of cytokines by enzyme-linked immunosorbent assay.

Key findings

Clove (100 µg/well) inhibited IL-1β, IL-6 and IL-10 production and exerted an efficient action either before or after LPS challenge for all cytokines. Eugenol did not affect IL-1β production but inhibited IL-6 and IL-10 production. The action of eugenol (50 or 100 µg/well) on IL-6 production prevented efficiently effects of LPS either before or after its addition, whereas on IL-10 production it counteracted significantly LPS action when added after LPS incubation.

Conclusions

Clove exerted immunomodulatory/anti-inflammatory effects by inhibiting LPS action. A possible mechanism of action probably involved the suppression of the nuclear factor-κB pathway by eugenol, since it was the major compound found in clove extract.
Mechanisms of action of zinc on rat intestinal epithelial electrogenic ion secretion: insights into its antidiarrhoeal actions
Authors: Bzik Victoria A , Medani Mekki , Baird Alan W , Winter Desmond C , Brayden David J
Published: February 2012

Objectives

Zinc is a useful addition to oral rehydration therapy for acute diarrhoea. We have assessed the mechanism of its epithelial antisecretory action when intestinal epithelial tight junctions were pharmacologically opened.

Methods

Rat isolated ileal and colonic mucosae were mounted in Ussing chambers and exposed to ZnSO4 (Zn2+) in the presence of secretagogues and inhibition of short circuit current (Isc) was measured.

Key findings

Pre-incubation with basolateral but not apical Zn2+ reduced Isc stimulated by forskolin, carbachol and A23187. In the presence of the tight junction-opener, cytochalasin D, antisecretory effects of apically-applied Zn2+ were enabled in colon and ileum. The apparent permeability coefficient (Papp) of Zn2+ was increased 1.4- and 2.4-fold across rat ileum and colon, respectively, by cytochalasin D. Basolateral addition of Zn2+ also reduced the Isc stimulated by nystatin in rat colon, confirming K channel inhibition. In comparison with other inhibitors, Zn2+ was a relatively weak blocker of basolateral KATP and K Ca2+ channels. Exposure of ileum and colon to Zn2+ for 60 min had minimal effects on epithelial histology.

Conclusions

Antisecretory effects of Zn2+ on intestinal epithelia arose in part through nonselective blockade of basolateral K channels, which was enabled when tight junctions were open.
Formulation development of gastroretentive tablets of lamivudine using the floating-bioadhesive potential of optimized polymer blends
Authors: Singh Bhupinder , Garg Babita , Chaturvedi Subhash Chand , Arora Sharry , Mandsaurwale Rachana , Kapil Rishi , Singh Baljinder
Published: February 2012

Objectives

The current studies entail successful formulation of optimized gastroretentive tablets of lamivudine using the floating-bioadhesive potential of carbomers and cellulosic polymers, and their subsequent in-vitro and in-vivo evaluation in animals and humans.

Methods

Effervescent floating-bioadhesive hydrophilic matrices were prepared and evaluated for in-vitro drug release, floatation and ex-vivo bioadhesive strength. The optimal composition of polymer blends was systematically chosen using central composite design and overlay plots. Pharmacokinetic studies were carried out in rabbits, and various levels of in-vitro/in-vivo correlation (IVIVC) were established. In-vivo gamma scintigraphic studies were performed in human volunteers using 99mTc to evaluate formulation retention in the gastric milieu.

Key findings

The optimized formulation exhibited excellent bioadhesive and floatational characteristics besides possessing adequate drug-release control and pharmacokinetic extension of plasma levels. The successful establishment of various levels of IVIVC substantiated the judicious choice of in-vitro dissolution media for simulating the in-vivo conditions. In-vivo gamma scintigraphic studies ratified the gastroretentive characteristics of the optimized formulation with a retention time of 5 h or more.

Conclusions

Besides unravelling the polymer synergism, the study helped in developing an optimal once-a-day gastroretentive drug delivery system with improved bioavailability potential exhibiting excellent swelling, floating and bioadhesive characteristics.
A herbal-drug interaction study of keishi-bukuryo-gan, a traditional herbal preparation used for menopausal symptoms, in healthy female volunteers
Authors: Saruwatari Junji , Takaishi Chisato , Yoshida Kousuke , Takashima Ayaka , Fujimura Youhei , Umemoto Yuichiro , Abe Tomohiro , Kitamado Masataka , Shimomasuda Masatsugu , Muramoto Yousuke , Nakagawa Kazuko
Published: February 2012

Objectives

Many patients use herbal medicines to relieve menopausal symptoms. Keishi-bukuryo-gan contains five herbal components, and has been used for treating hypermenorrhoea, dysmenorrhoea and menopausal symptoms in Asian countries. In this study, we investigated the potential herb–drug interactions of keishi-bukuryo-gan in healthy female subjects.

Methods

Thirty-one healthy females (20–27 years) were studied to evaluate their baseline activity of cytochrome P450 (CYP) 1A2, CYP2D6, CYP3A, xanthine oxidase (XO) and N-acetyltransferase 2 (NAT2) based on the urinary metabolic indices of an 8-h urine sample collected after a 150-mg dose of caffeine and a 30-mg dose of dextromethorphan, and also the urinary excretion ratio of 6β-hydroxycortisol to cortisol. Thereafter, the subjects received 3.75 g of keishi-bukuryo-gan twice daily for seven days, and underwent the same tests on post-dose day 7.

Key findings

The geometric mean phenotypic index for CYP1A2 significantly decreased by 16% on day 7 compared with the baseline (P = 0.026). Keishi-bukuryo-gan did not alter the indices for CYP2D6, CYP3A, XO and NAT2.

Conclusions

Keishi-bukuryo-gan may inhibit the activity of CYP1A2, which is predominantly involved in oestrogen metabolism. However, TJ-25 is unlikely to participate in herb–drug interactions involving medications predominantly metabolized by CYP2D6, CYP3A, XO and NAT2.
The effect of poloxamer 407 on the functional properties of HDL in mice
Authors: Yasuda Tomoyuki , Johnston Thomas P , Shinohara Masakazu , Inoue Michihiko , Ishida Tatsuro
Published: February 2012

Objectives

There is an inverse relationship between high-density lipoprotein (HDL) and heart disease. HDL possesses not only both antioxidant and anti-inflammatory properties, but also anti-thrombotic and endothelial function-promoting qualities. However, it is not only the serum concentration of HDL that is important, but also the ‘functional’ quality of the HDL. The objective was to determine the functional status of HDL in a well-established mouse model of dyslipidaemia and atherosclerosis induced by the administration of a block copolymer (poloxamer 407; P-407).

Methods

C57BL/6 mice were administered a single intraperitoneal dose of P-407 (0.5 g/kg) and blood was collected at 24 h post-dosing. HDL was isolated from controls (control HDL) and P-407-treated (P-407 HDL) mice and used to test its anti-inflammatory properties in vitro. Additionally, antioxidant enzymes associated with HDL, namely, platelet activating factor-acetylhydrolase (PAF-AH) and paraoxonase (PON), were evaluated for any potential reduction in their biological activity.

Key findings

A single injection of P-407 in C57BL/6 mice resulted in a marked decrease in the levels of HDL-cholesterol and phospholipids. HDL particle size significantly increased, primarily due to remodelling of HDL with triglyceride. It was demonstrated that (i) long-chain saturated fatty acids were higher and the n-3/n-6 fatty acid ratio was significantly lower for P-407 HDL compared with control HDL, and (ii) P-407 HDL lost its capacity to inhibit tumour necrosis factor-α (TNF-α)-induced vascular cell adhesion molecule-1 (VCAM-1) expression compared with control HDL. Additionally, P-407 HDL was not able to neutralize lipopolysaccharide and inhibit subsequent TNF-α production compared with control HDL. The biological activity of platelet-activating factor acetylhydrolase (PAF-AH) and paraoxonase (PON) decreased in direct proportion to the circulating levels of both HDL-cholesterol and apolipoprotein (apoA-1).

Conclusions

Combination of previously reported findings in P-407-treated mice, such as (i) production of both oxidized LDL and malondialdehyde, and (ii) profound elevations in the soluble forms of intercellular adhesion molecule-1 (ICAM-1), VCAM-1, and E-selectin, with the present results, would strongly suggest that HDL in P-407-treated mice is rendered dysfunctional. Thus, these findings help to explain why P-407-treated mice begin to form aortic atherosclerotic lesions about one month after initiating P-407 treatment.
Platycodon grandiflorum modifies adipokines and the glucose uptake in high-fat diet in mice and L6 muscle cells
Authors: Ahn Young-Min , Kim Su Kang , Kang Ji-Suck , Lee Byung-Cheol
Published: February 2012

Objectives

Obesity and diabetes have become the most common human health problems worldwide. Obesity's contribution to type 2 diabetes might be due to dysregulation of adipokines and glucose uptake.

Methods

In this study, we performed in-vivo and in-vitro studies to evaluate the effects of Platycodon grandiflorum extract (PGE) on adipokines and glucose uptake. Before study, platycodin D concentrations were analysed by HPLC in PGE prepared in water, in 50% ethanol and in 80% ethanol, and we selected the 80% ethanol extract as the PGE for this study based on the HPLC results.

Key findings

We found that inclusion of PGE in the high-fat diet (HFD) markedly attenuated food intake, body weight, epididymal fat weight, adipocyte size and blood glucose levels by the oral glucose tolerance test in mice, and maintained serum levels of adiponectin, resistin, leptin, fructosamine and triglycerides. Gene expression analysis revealed that PGE up-regulated adiponectin, and down-regulated TNF-α and leptin in fat tissue. In L6 muscle cells in vitro, PGE increased insulin-stimulated glucose uptake.

Conclusions

We conclude that PGE may improve obesity in mice fed an HFD and glucose uptake in L6 muscle cells by modifying adipokines, and could offer clinical benefits as a supplement to treat obesity and diabetes.
Osteoarthritis of the knee and hip. Part I: aetiology and pathogenesis as a basis for pharmacotherapy
Authors: Adatia Aleem , Rainsford K D , Kean Walter F
Published: February 2012

Objectives

Osteoarthritis (OA) of the knee and hip is among the most frequent and debilitating arthritic conditions. Aside from surgical intervention in severe cases, conventional treatment involves relieving painful symptoms with non-steroidal anti-inflammatory drugs (NSAIDs), narcotic and non-narcotic (weak) analgesics and physical therapy. To obtain insight into the extent of pathological changes in hip and knee OA we reviewed current literature on the pathogenesis of this state as a basis for current pharmacotherapy options.

Key findings

Key features of the pathological joint changes in OA include: cartilage destruction by pro-inflammatory cytokines, matrix metalloproteinases and prostaglandins, which promote a catabolic environment; subchondral bone remodelling and resorption; hypertrophic differentiation of chondrocytes; neovascularisation of synovial tissue; and focal calcification of joint cartilage. Despite the central involvement of hyaline cartilage in OA pathogenesis, the source of pain likely stems from the richly innervated synovium, subchondral bone and periosteum components of the joint. Tissue damage during joint degeneration generates nociceptive stimuli. The presence of inflammatory mediators, including bradykinin, prostaglandins and leukotrienes, lowers the threshold of the Aδ and C pain fibres, resulting in a heightened response to painful stimuli.

It is our opinion that it is important to base and centre the management of OA patients on the severity of patient-important outcomes, rather than purely an assessment of damage to the joint. The joint damage, as interpreted from radiographs, is not necessarily representative of the symptoms experienced. The management of OA primarily comprises pharmacological therapy, surgical interventions and various non-pharmacological interventions.
Investigating paracetamol pharmacokinetics using venous and capillary blood and saliva sampling
Authors: Rittau Anneliese M , McLachlan Andrew J
Published: February 2012

Objective

The aim of this study was to develop, validate and apply a high performance liquid chromatography (HPLC) assay for analysis of paracetamol, paracetamol glucuronide and paracetamol sulfate in plasma (venous and capillary) and saliva to study paracetamol pharmacokinetics in healthy volunteers.

Methods

Samples were prepared using protein precipitation and analysed using reverse phase HPLC with UV detection. This assay was applied to venous and capillary plasma and saliva samples from 20 healthy volunteers after paracetamol 1 g four times daily for three days.

Key findings

The HPLC assay for paracetamol and its metabolites was found to be sensitive and selective in plasma and saliva samples over the range 0.05–50 mg/l with an inter- and intraday precision and accuracy within 11.2% and 11.1%, respectively. Mean recoveries for all analytes were > 88%. A study of paracetamol pharmacokinetics in healthy volunteers found close agreement between the sampling matrices for paracetamol and metabolites (metabolites were not detected in saliva). The value for area under the concentration–time curve over the 6 h dosing interval of venous plasma (45.3 ± 12.9 mg/l.h) was significantly higher than that observed for capillary plasma (33.8 ± 12.9 mg/l.h) or saliva (35.1 ± 9.4 mg/l.h; P > 0.01).

Conclusions

Capillary blood and saliva collection were found to be reliable sampling matrices for the evaluation of paracetamol pharmacokinetics, although paracetamol metabolites were not detected in saliva.
Copper‐dependent regulation of NMDA receptors by cellular prion protein: implications for neurodegenerative disorders
Authors: Stys Peter K. , You Haitao , Zamponi Gerald W.
Published: February 2012

Abstract  N‐Methyl‐d‐aspartate (NMDA) receptors mediate a wide range of important nervous system functions. Conversely, excessive NMDA receptor activity leads to cytotoxic calcium overload and neuronal damage in a wide variety of CNS disorders. It is well established that NMDA receptors are tightly regulated by a number of cell signalling pathways. Recently, it has been shown that NMDA receptor activity is modulated by cellular prion protein (PrPC) in a copper‐dependent manner. Here we give an overview of the current state of knowledge concerning the novel concept of potent modulation of this receptor's kinetics by copper ions, and the interplay between NMDA receptors and PrPC in the context of neurological diseases such as Alzheimer's disease, epilepsy, pain and depression.
Hybrid Transmission for Mobile Robot
Authors: Esmail Essam L.
Published: February 2012

This paper presents proposed designs of parallel hybrid transmissions with only one electric motor/generator (MG) and without any rotating clutches. The proposed motor/generator integrated hybrid transmission serves to regulate the engine’s effective gear ratio (engine rotational velocity versus vehicle velocity) by mixing the engine and electric motor powers through a power controlling device. The proposed design provides some of the benefits and flexibility of a power-split design but using conventional available components in a simpler mechanical layout that makes the design compact, mechanically simple, and operationally flexible. Three commonly used transmission gear sets are used for this purpose; Simpson, Ravigneaux, and Type-6206 gear sets. With an electronic control unit, eight major modes of operation including a regenerative braking capability are shown to be feasible in the proposed hybrid transmission; one electric motor mode, two engine modes, two engine/charge modes, and two power modes. Continuously variable transmission (CVT) capability is provided with the second engine/charge mode and with the second power mode. The second power mode can be further subdivided into three hybrid submodes that correspond to the direct drive, underdrive, and overdrive of a conventional automatic transmission. The feasibility of the proposed hybrid transmission is demonstrated with a numerical example employing conventional Ravigneaux gear train. The kinematics, static torque, and power flow relations for all operation modes are analyzed in detail.
Computational Synthesis of Product Architectures Based on Object-Oriented Graph Grammars
Authors: Helms Bergen , Shea Kristina
Published: February 2012

Computational design synthesis aims to iteratively and automatically generate solution spaces of standard and novel design alternatives to support the innovation process. New approaches are required to generate alternative solutions at the function and behavior level as well as to ease the computational modeling of design knowledge. This paper introduces the approach of object-oriented graph grammars for the computational synthesis of product models based on a Function–Behavior–Structure (FBS) representation. The approach combines the advantages of a generic and systematic design method with a highly computable graph representation and object-oriented concepts. Through this combination, advances in terms of extendibility, efficiency, and flexible formalization of declarative and procedural engineering knowledge are achieved. Validation of the method is given through the synthesis of hybrid powertrains. The generation of hybrid powertrain solution spaces is shown, especially focusing on the impact of an evolving vocabulary, or building blocks, for synthesis. Future work includes integrating search methods in the synthesis process along with quantitative evaluation using simulation methods.
Characterization of Gasoline and E85 Direct Injection Sprays in a Constant Volume Vessel Under Late Cycle Engine Conditions
Authors: Morgan Christopher J. , Arora Rajat , Nesbitt Jaclyn E. , Lee Seong-Young , Naber Jeffrey D.
Published: February 2012

Spray characteristics of a high pressure gasoline direct injector were studied in a constant volume optical combustion vessel over a range of charge gas composition, pressure and temperature conditions for gasoline and E85. The fuel injector was a Bosch GDI injector, with fuel delivery provided through a high pressure accumulator supply system. The conditions were selected to match those for late injection timing during the compression stroke. To simulate the in-cylinder conditions, the combustion chamber temperatures and pressures were varied from 30°C to 305°C and from 1.8 bar to 9.2 bar respectively. Injection pressure was held constant at 30 bar. Injector and thus initial fuel temperature was controlled independently of the ambient conditions at 50°C. Simultaneous images were taken using Schlieren, laser luminescence and Mie scattering diagnostics. It was found that penetration and spray angle are primarily dependent on charge density, and vaporization is dependent on both charge density and charge temperature. The gasoline sprays are shown to have increased vaporization and higher penetration in comparison to E85.
Comparisons of Global Heat Transfer Correlations for Conventional and High Efficiency Reciprocating Engines
Authors: Caton Jerald A.
Published: February 2012

Cylinder wall heat transfer is known to be an important process for internal combustion engines, and directly affects engine efficiency, performance and emissions. In some cases, up to third of the fuel energy is lost via heat transfer. Better understandings of the cylinder heat transfer should provide opportunities for improvements of engine efficiency and performance. The influence of various heat transfer correlations on engine efficiency and performance, total heat transfer and nitric oxide emissions is determined for conventional and high efficiency engines. These high efficiency engines are often based on “low temperature combustion” — and such engines have inherently lower heat transfer. At least some of the improvements associated with LTC engines are attributed to reduced heat losses. This work uses a thermodynamic engine cycle simulation and studies automotive engines. Both conventional and LTC engines are examined. As expected, engine performance and efficiency increase for reductions in the cylinder wall heat transfer. Although the heat transfer is lower for LTC engines compared to conventional engines, efficiency increases still are obtained as the cylinder wall heat transfer is reduced. In addition to the above, these assessments include the effects of the various heat transfer correlations on nitric oxide emissions and exergy destruction during the combustion process for both engines.
Design and Flow Analysis of a Novel Optically Accessible Heavy Duty Diesel Research Engine
Authors: Busch Stephen , Kleindienst Maurice , Dahnz Christoph , Wagner Uwe , Spicher Ulrich
Published: February 2012

A new single-cylinder optically accessible heavy duty diesel engine has been conceived and constructed at the Institut fu¨r Kolbenmaschinen. Rather than being made from a quartz glass cylinder, the cylinder liner of this engine is modified with three round, flat optical access ports to facilitate laser-optical measurements within the combustion chamber. The flat optical surfaces prove less problematic than a quartz glass cylinder in terms of internal reflections, cleaning procedures, cost, and robustness. A specially adapted piston facilitates the passage of the laser sheet into the piston bowl and provides a view into the bowl at top dead center. Computational fluid dynamics (CFD) simulations were performed in order to estimate the effects of the optically necessary piston and cylinder liner modifications on in-cylinder flow and to compare the flow characteristics with those simulated for a non-modified engine. Emphasis is placed on turbulence behavior before top dead center. The trade-offs and limitations inherent in the modified piston design are discussed in this context. Further optical investigations with this engine will provide insight into the mixture formation and combustion processes. In particular, the soot formation and oxidation processes will be studied under realistic engine operating conditions.
An Experimental and Modeling-Based Study Into the Ignition Delay Characteristics of Diesel Surrogate Binary Blend Fuels
Authors: Carr Matthew A. , Caton Patrick A. , Hamilton Leonard J. , Cowart Jim S. , Mehl Marco , Pitz William J.
Published: February 2012

This study examines the combustion characteristics of a binary mixture surrogate for possible future diesel fuels using both a single-cylinder research engine and a homogeneous reactor model using detailed chemical reaction kinetics. Binary mixtures of a normal straight-chain alkane (pure n-hexadecane, also known as n-cetane, C16H34) and an alkyl aromatic (toluene, C7H8) were tested in a single-cylinder research engine. Pure n-hexadecane was tested as a baseline reference, followed by 50%, 70%, and 80% toluene in hexadecane blends. Testing was conducted at fixed engine speed and constant indicated load. As references, two conventional petroleum-based fuels (commercial diesel and US Navy JP-5 jet fuel) and five synthetic Fischer-Tropsch-based fuels were also tested. The ignition delay of the binary mixture surrogate increased with increasing toluene fraction and ranged from approximately 1.3 ms (pure hexadecane) to 3.0 ms (80% toluene in hexadecane). While ignition delay changed substantially, the location of 50% mass fraction burned did not change as significantly due to a simultaneous change in the premixed combustion fraction. Detailed chemical reaction rate modeling using a constant pressure, adiabatic, homogeneous reactor model predicts a chemical ignition delay with a similar trend to the experimental results, but shorter overall magnitude. The difference between this predicted homogeneous chemical ignition delay and the experimentally observed ignition delay is defined as the physical ignition delay due to processes such as spray formation, entrainment, mixing, and vaporization. On a relative basis, the addition of 70% toluene to hexadecane causes a nearly identical relative increase in both physical and chemical ignition delay of approximately 50%. The chemical kinetic model predicts that, even though the addition of toluene delays the global onset of ignition, the initial production of reactive precursors such as HO2 and H2O2 may be faster with toluene due to the weakly bound methyl group. However, this initial production is insufficient to lead to wide-scale chain branching and ignition. The model predicts that the straight-chain alkane component (hexadecane) ignites first, causing the aromatic component to be consumed shortly thereafter. Greater ignition delay observed with the high toluene fraction blends is due to consumption of OH radicals by toluene. Overall, the detailed kinetic model captures the experimentally observed trends well and may be able to provide insight as to the relationship between bulk properties and physical ignition delay.
Quick Response Fuel Injector for Direct-Injection Gasoline Engines
Authors: Abe Motoyuki , Maekawa Noriyuki , Yasukawa Yoshihito , Ishikawa Tohru , Namaizawa Yasuo , Ehara Hideharu
Published: February 2012

We developed a new injector for direct injection gasoline engines that reduce the exhaust emissions and help to reduce fuel consumption. The newly developed actuator in this injector has two features. One is a bounce-less valve closing mechanism, and the second is quick-response moving parts. The first feature, the bounce-less valve closing mechanism, can prevent ejecting a coarse droplet, which causes unburned gas emission. The new actuation mechanism realizes the bounce-less valve closing. We analyzed the valve motion and injection behavior. The second feature, the quick response actuator, achieves a smaller minimum injection quantity. This feature assists in reducing the fuel consumption under low load engine conditions. The closing delay time of the needle valve is the dominant factor of the minimum injection quantity because the injection quantity is controlled by the duration time of the valve opening. The new actuator movements can be operated with a shorter closing delay time. The closing delay time is caused by a magnetic delay and kinematic delay. A compact magnetic circuit of the actuator reduces the closing delay time by 26%. In addition, the kinematic delay was improved when the hydraulic resistance was reduced by 9%. As a result, the new injector realizes reduction of the minimum injection quantity by 25% compared to a conventional injector.
Dynamic Modeling of a Variable Displacement Vane Pump Within an Engine Oil Circuit
Authors: Geist Bruce , Resh William
Published: February 2012

Automakers and the car-buying public maintain a strong and continuing interest in enhanced vehicle efficiency. Ideally, adaptively controlled oil pumps supply only enough flow within an engine to satisfy its performance requirements. Any extra flow wastes energy. In order to better understand how to improve engine and engine oil circuit efficiency, and to assess pump stability, a detailed dynamic model of a variable displacement vane pump (VDVP) is developed. This detailed pump model is mated to a simplified engine oil circuit model. This marriage allows for a detailed prediction of pump response under various simulated engine operating conditions. The VDVP modeled here adapts its pump chamber volumes according to 1) the feedback oil pressure provided from the engine oil circuit and 2) according to the sizing and installed compression loading of an internal spring. Many phenomena such as internal leakage from one pump chamber volume to another, variable oil conditions such as aeration and viscosity, as well as variations in choice for the internal spring rate and preload can be investigated for their effects on oil pump behavior and performance within the simplified oil circuit.
Controlling Gasoline Low Temperature Combustion by Diesel Micro Pilot Injection
Authors: Eichmeier Johannes , Wagner Uwe , Spicher Ulrich
Published: February 2012

The simultaneous reduction of fuel consumption and pollutant emissions, namely NOx and soot, is the predominant goal in modern engine development. In this context, low temperature combustion concepts are believed to be the most promising approaches to resolve the above mentioned conflict of goals. Disadvantageously these combustion concepts show high peak pressures or high rates of pressure rise due to early ignition and high reaction rates especially at high loads. Furthermore, there are still challenges in controlling combustion phasing. In this context using a small amount of pilot Diesel injected directly into the combustion chamber to ignite a highly diluted gasoline air mixture can overcome the aforementioned difficulties. As the gasoline does not ignite without the Diesel, the pilot injection timing can be used to control combustion phasing. By increasing dilution even high loads with low rates of pressure rise and without knocking are possible. This paper shows the results of experimental investigations carried out on a heavy duty boosted single cylinder Diesel engine. Based on the indicated cylinder pressure, the combustion process is characterised by performing knock analyses as well as thermodynamic analyses. Furthermore an optically accessible engine has been set up to investigate both the Diesel injection and the combustion process by means of digital high speed imaging. Together with the thermodynamic analyses the results of these optical investigations make up the base for the presented theoretical model of this combined Diesel gasoline combustion process. To show the load potential of this Dual-Fuel-CAI concept, the engine was operated at 2100 1/min with an IMEP of 19 bar. NOx emissions did not exceed 0.027 g/kWh.
The Spray and Engine Combustion Performances of Ethanol-Biodiesel Fuel Blends
Authors: Lee Po-I , Matsumoto Atsushi , Zheng Yi , Xie Xingbin , Lai Ming-Chia
Published: February 2012

Some research has studied the effects of ethanol blended diesel (E-diesel) on emissions due to the availability of ethanol. However, a co-solvent or emulsifier is needed to provide better mixing of these two fuels, which would complicate the production process. In recent years, researchers have reported that biodiesel is a good co-solvent in terms of its miscibility with ethanol. Therefore, the present study utilizes the name “E-Biodiesel” representing the blend of ethanol and biodiesel as an alternative fuel. In this paper, the effects of blending ratios (B100, B80E20, and B60E40) of ethanol-biodiesel on viscosity, spray vaporization, engine combustion, and exhaust emissions are investigated. The viscosity measurements show that appropriate ethanol-biodiesel blends could approach the viscosity of ultra-low sulfur diesel (ULSD). The effect of blends on fuel spray structure is investigated by using two single-hole injectors with different nozzle orifice diameters (80μm and 150 μm) and high-speed Schlieren imaging. The results indicate that different patterns of spray vaporization are observed due to the addition of ethanol at different ambient pressure. The combustion and emission tests are carried out in a multi-cylinder high-speed diesel engine, and the effects of E-Biodiesel are significant with respect to the power output, fuel consumption, and emissions. As a result, nitrogen oxides (NOX) and particulate matter (PM) could be reduced simultaneously by the adjustment of injection timing and exhaust gas recirculation (EGR). Therefore, with proper blending ratios of biodiesel and ethanol, E-biodiesel could be considered viable as an alternative fuel in the future.
Multi-Cycle Torsional Vibration Simulation With AVL EXCITE Designer
Authors: Parikyan Tigran
Published: February 2012

Traditionally, torsional vibration analysis (TVA) programs operating in frequency domain, consider only one 2- or 4-stroke engine cycle to simulate a steady-state dynamics of the powertrain. There are, however, some phenomena which cannot be revealed during a single-cycle simulation. First such case is related to propeller drives. If the transmission ratio between internal combustion engine and propeller shaft is not synchronized with the number of propeller blades, then low-frequency fluctuations of vibration magnitude (beats) are induced, which can only be seen if multiple engine cycles are analyzed. Second case refers to simulation of random misfiring. Although an isolated event, it has an influence on the system dynamics beyond the engine cycle where it happens, and therefore requires considering multiple cycles. The paper shows how these two cases are dealt with, using AVL software EXCITE Designer.
Exhaust Emissions Characterization of a Turbocharged 2-Stroke Tier 0+ Locomotive Engine: NOx, PM, SOF and SOF Composition
Authors: Bohac Stanislav V. , Feiler Eric , Bradbury Ian
Published: February 2012

This study presents a detailed exhaust emission characterization of an EMD 2-Stroke turbocharged line haul locomotive diesel engine fitted with an early-development Tier 0+ emissions kit. The objective of this work is to use emissions characterization to gain insight into engine operation and mechanisms of pollutant formation for this family of engine, and identify areas of potential future engine emissions improvement. Results show that at the notches tested (notches 3–8) the largest contributor to PM mass is insolubles (mostly elemental carbon), but that the soluble component of PM, comprising 14–32% of PM, is also significant. GC-FID analysis of the soluble portion shows that it is composed of 55–77% oil-like C22-C30+ hydrocarbons, with the remainder being fuel-like C9-C21 hydrocarbons. The emissions characterization suggests that advancing combustion timing should be effective in reducing PM mass by reducing the insoluble portion (elemental carbon) of PM at all notches. NOx will likely increase, but the current level of NOx is sufficiently below Tier 0+ limits to allow a moderate increase. Reducing engine oil consumption should also reduce PM mass at all notches, although to a smaller degree than measures that reduce the insoluble portion of PM.
NO2 Reaction Pathways With NH3 on an Fe-Zeolite SCR Catalyst
Authors: Smith Michael A. , Depcik Christopher D. , Klinkert Stefan , Hoard John W. , Bohac Stanislav V. , Assanis Dionissios N.
Published: February 2012

One approach for nitrogen oxides (NOx) emission control of medium duty diesel engines is through the use of a combination Lean NOx Trap and Selective Catalytic Reduction (LNT-SCR) catalyst system. In this system, part of the NOx conversion occurs via an NH3 SCR catalyst that is dependent on the NO2 to NOx ratio of the feed gas with NO2 being a more advantageous oxidizer. One benefit of using this system is the conversion of NO to NO2 over the LNT which increases the NO2:NOx ratio of the feed gas to the SCR catalyst. An experimental study has been performed to investigate the NO2-NH3 reaction for an Fe-based zeolite SCR catalyst using a bench top flow reactor. The increase in NO2 concentration at the inlet of the SCR results in the formation of large quantities of N2O from 200°C to 400°C. Further experiments determined that N2O and NH3 react above 350°C. This has led to a hypothesis that one primary SCR reaction (Slow SCR) can be replaced with two reaction steps featuring NH3, NO2, and N2O. As a result, this paper proposes five NOx reduction reactions as part of a global mechanism, which would account for the observed experimental behavior.
Numerical Analysis of Biogas Composition Effects on Combustion Parameters and Emissions in Biogas Fueled HCCI Engines for Power Generation
Authors: Bedoya Iva´n D. , Saxena Samveg , Cadavid Francisco J. , Dibble Robert W.
Published: February 2012

This study investigates the effects of biogas composition on combustion stability for a purely biogas fueled HCCI engine. Biogas is one of the most promising renewable fuels for Combined Heat and Power systems driven by internal combustion engines. However, the high content of CO2 in biogas composition leads to low thermal efficiencies in spark ignited and dual fuel compression ignited engines. The study is divided into two parts: first experimental results on a biogas-fueled HCCI engine are used to validate a numerical model, and second the model is used to investigate how biogas composition impacts combustion stability. In the first part of the study, experimental analysis of a 4 cylinder, 1.9 L Volkswagen TDI Diesel engine running with biogas in HCCI mode has shown high gross indicated mean effective pressure (close to 8 bar), high gross indicated efficiency (close to 45%) and ultra-low NOx emissions below the US2010 limit (0.27 g/kWh). An inlet absolute pressure of 2 bar and inlet temperature of 473 K (200°C) were required for allowing HCCI combustion with a biogas composition of 60% CH4 and 40% CO2 on a volumetric basis. However, slight changes in inlet pressure and temperature caused large changes in cycle-to-cycle variations at low equivalence ratios and large changes in ringing intensity at high equivalence ratios. A numerical model is validated against these experimental results. In the second part of the study, the numerical results for varied biogas composition show that at high load limit, higher contents of CH4 in biogas composition allow advanced combustion and increased burning rates of the biogas air mixture. Higher contents of CO2 in biogas composition allow lowered ringing intensities with moderate decrease in the indicated efficiency and power output. NOx emissions are not highly affected by biogas composition, while CO and HC emissions tend to increase with higher contents of CO2. According with the numerical results, biogas composition is an effective strategy to control the onset of combustion and combustion phasing of HCCI engines running biogas, allowing more stabilized combustion at low equivalence ratios and safe operation at high equivalence ratios. The main advantages of using biogas fueled HCCI engines in CHP systems are the low sensitivity of power output and indicated efficiency to biogas composition, as well as the ultra low NOx emissions achieved for all tested compositions.
Knock in Various Combustion Modes in a Gasoline-Fueled Automotive Engine
Authors: Vavra Jiri , Bohac Stanislav V. , Manofsky Laura , Lavoie George , Assanis Dennis N.
Published: February 2012

Homogeneous charge compression ignition (HCCI) offers great potential for improved fuel economy and dramatically reduced NOx emissions, compared to typical spark ignition (SI) combustion. However the benefits of HCCI are limited to low and medium loads by the simultaneous occurrence of combustion instability and knock at a maximum load that is too low for conventional SI combustion. To provide smooth operation in the intermediate range between HCCI and SI requires alternative combustion strategies. One such strategy is spark-assisted compression ignition (SACI) which uses a spark plug to initiate a flame which consumes a portion of the mixture, followed by autoignition of the remaining charge. This moderates the rapid heat release and allows higher loads to be achieved without exceeding knock and stability limits. In a recent study we have explored this region and have found that spark assist at first dramatically reduces knock as load is raised above the HCCI limit; however with further load increase, knock returns, but in a form which resembles spark ignited knock rather than the HCCI knock. This study investigates in detail the knocking conditions observed in that work. The objectives of this study are twofold: first, to explore the differences between the two forms of knock; and second, to apply and compare a number of commonly used metrics for knock and noise over the range of HCCI, SACI and SI combustion. Experimental data were acquired on a single-cylinder DI research engine equipped with a fully flexible valve actuation (FFVA) system and fueled by research-grade gasoline. Cycle to cycle results based on filtered pressure traces are shown and compared with a number of knock measures including a widely used correlation for ringing intensity for HCCI combustion. Although based on a limited set of data, the results identify important qualitative features of the two forms of knock and point out significant differences among the knock metrics. The results suggest that further investigations are needed to fully understand both the knocking phenomenon and how best to quantify it.