bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronic treatment with a novel γ‐secretase modulator, JNJ‐40418677, inhibits amyloid plaque formation in a mouse model of Alzheimer's disease
Authors: Van Broeck B , Chen J‐M , Tréton G , Desmidt M , Hopf C , Ramsden N , Karran E , Mercken M , Rowley A
Published: January 2011

BACKGROUND AND PURPOSE

γ‐Secretase modulators represent a promising therapeutic approach for Alzheimer's disease (AD) because they selectively decrease amyloid β 42 (Aβ42), a particularly neurotoxic Aβ species that accumulates in plaques in the brains of patients with AD. In the present study, we describe the in vitro and in vivo pharmacological properties of a potent novel γ‐secretase modulator, 2‐(S)‐(3,5‐bis(4‐(trifluoromethyl)phenyl)phenyl)‐4‐methylpentanoic acid (JNJ‐40418677).

EXPERIMENTAL APPROACH

The potency and selectivity of JNJ‐40418677 for Aβ reduction was investigated in human neuroblastoma cells, rat primary neurones and after treatment with single oral doses in non‐transgenic mouse brains. To evaluate the effect of JNJ‐40418677 on plaque formation, Tg2576 mice were treated from 6 until 13 months of age via the diet.

KEY RESULTS

JNJ‐40418677 selectively reduced Aβ42 secretion in human neuroblastoma cells and rat primary neurones, but it did not inhibit Notch processing or formation of other amyloid precursor protein cleavage products. Oral treatment of non‐transgenic mice with JNJ‐40418677 resulted in an excellent brain penetration of the compound and a dose‐ and time‐dependent decrease of brain Aβ42 levels. Chronic treatment of Tg2576 mice with JNJ‐40418677 reduced brain Aβ levels, the area occupied by plaques and plaque number in a dose‐dependent manner compared with transgenic vehicle‐treated mice.

CONCLUSIONS AND IMPLICATIONS

JNJ‐40418677 selectively decreased Aβ42 production, showed an excellent brain penetration after oral administration in mice and lowered brain Aβ burden in Tg2576 mice after chronic treatment. JNJ‐40418677 therefore warrants further investigation as a potentially effective disease‐modifying therapy for AD.
Characterization of the mechanisms of the increase in PPARδ expression induced by digoxin in the heart using the H9c2 cell line
Authors: Chen Zhih‐Cherng , Yu Bu‐Chin , Chen Li‐Jen , Cheng Kai‐Chun , Lin Hung Jung , Cheng Juei‐Tang
Published: January 2011

BACKGROUND AND PURPOSE

Digoxin has been used as an inotropic agent in heart failure for a long time. Troponin I (TnI) phosphorylation is related to cardiac contractility, and the genes are regulated by peroxisome proliferator‐activated receptors (PPARs). Our previous studies indicated that cardiac abnormality related to the depressed expression of PPARδ in the hearts of STZ rats is reversed by digoxin. However, the cellular mechanisms for this effect of digoxin have not been elucidated. The aim of the present study was to investigate possible mechanisms for this effect of digoxin using the H9c2 cell line cultured in high glucose (HG) conditions.

METHODS

The effects of digoxin on PPARδ expression, intracellular calcium and TnI phosphorylation were investigated in cultured H9c2 cells, maintained in a HG medium, by using Western blot analysis.

RESULTS

Digoxin increased PPARδ expression in H9c2 cells subjected to HG conditions, and increase the intracellular calcium concentration. This effect of digoxin was blocked by BAPTA‐AM at concentrations sufficient to chelate calcium ions. In addition, the calcineurin inhibitor cyclosporine A and KN93, an inhibitor of calcium/calmodulin‐dependent protein kinase, inhibited this action. Digoxin also increased TnI phosphorylation and this was inhibited when PPARδ was silenced by the addition of RNAi to the cells. Similar changes were observed on the contraction of H9c2 cells.

CONCLUSION

The results suggest that digoxin appears, through calcium‐triggered signals, to reverse the reduced expression of PPARδ in H9c2 cells caused by HG treatment.
Antimicrobial tolerance and the significance of persister cells in recalcitrant chronic wound biofilms
Authors: Percival Steven L. , Hill Katja E. , Malic Sladjana , Thomas David W. , Williams David W.
Published: January 2011

The application of antimicrobials in the management of wounds is a complex procedure requiring appropriate clinical decision making, judgment and a thorough understanding of antimicrobial therapies, together with their potential disadvantages. There is considerable direct and indirect evidence for the presence of bacterial biofilms in the chronic wound bed, and it has been demonstrated that bacteria within these biofilms may exhibit both specific and nonspecific antimicrobial tolerance. The antimicrobial tolerance of biofilms is a major concern in the treatment of both infected and nonhealing chronic wounds and an understanding of the mechanisms involved is of fundamental importance in managing wound infections and developing future wound management strategies. The aim of this review is therefore to provide an overview of our current understanding of the mechanisms by which bacteria in wound biofilms can resist conventional antibiotic and antibacterial therapies which is very important to wound healing.
Young Adult Couples’ Decision Making Regarding Emergency Contraceptive Pills
Authors: Beaulieu Richard , Kools Susan M. , Kennedy Holly Powell , Humphreys Janice
Published: January 2011

Purpose: Unintended pregnancy is a significant public health problem among young people worldwide. The purpose of this study was to explore and better understand the reasons for the apparent underuse of emergency contraceptive pills (ECP) in young people in coupled relationships.

Theoretical Rational: In postmodern explications of grounded theory, social construction of realities and the influence of subjectivities on the meanings of experiences lead to the development of partial truths that may change with time, context, and situation.

Methods: Grounded theory methods guided semi‐structured face‐to‐face interviews and data analysis. Twenty‐two couples aged 18 to 25 years old were recruited through public notices.

Findings: Four salient and interrelated conditions were constructed to help explain the complexities involved in young couples decision making regarding ECP use: (a) the shifting locus of responsibility for contraceptive decision making: in a perfect world versus biological reality; (b) relationship power: control‐vulnerability continuum; (c) a woman's autonomy over her own body; and (d) conflicting views on ECP.

Conclusions: Healthcare professionals whose practice includes young people need to be aware of possible couple dynamics when discussing contraception. Clients in supportive relationships should be encouraged to engage in open communication with their partners about their contraception needs, including possible ECP use.

Clinical Relevance: The results of this study contribute to the body of knowledge with regard to decision making related to ECP use in young adults.
Randomized, Double-Blinded, Placebo-Controlled Crossover Trial of Treating Erectile Dysfunction with Sildenafil After Radiotherapy and Short-Term Androgen Deprivation Therapy: Results of RTOG 0215
Authors: Watkins Bruner Deborah , James Jennifer L. , Bryan Charlene J. , Pisansky Thomas M. , Rotman Marvin , Corbett Thomas , Speight Joycelyn , Byhardt Roger , Sandler Howard , Bentzen Søren , Kachnic Lisa , Berk Lawrence
Published: January 2011

Introduction

Erectile dysfunction (ED) may be the most commonly observed adverse event (AE) associated with the combination of radiation therapy (RT) and androgen deprivation therapy (ADT). A significant number of men are trying phosphodiesterase type 5 inhibitors (PDE5s) such as sildenafil to treat ED, yet sildenafil studies to date shed little light on the response to ED after ADT.

Aim

The purpose of this trial was to evaluate sildenafil in the treatment of ED in prostate cancer patients previously treated with external beam RT and neoadjuvant and concurrent ADT.

Methods

In this randomized, double-blinded crossover trial, eligible patients received RT/ADT for intermediate risk prostate cancer and currently had ED as defined by the International Index of Erectile Function (IIEF). Patients were randomized to 12 weeks of sildenafil or placebo followed by 1 week of no treatment then 12 weeks of the alternative. Treatment differences were evaluated using a marginal model for binary crossover data.

Main Outcome Measures

The primary end point was improved erectile function, as measured by the IIEF.

Results

The study accrued 115 patients and 61 (55%) completed all three IIEF assessments. Sildenafil effect was significant (P = 0.009) with a difference in probabilities of erectile response of 0.17 (95% confidence interval: 0.06, 0.29), and 0.21 (0.06, 0.38) for patients receiving ≤120 days of ADT. However, as few as 21% of patients had a treatment-specific response, only improving during sildenafil but not during the placebo phase.

Conclusions

This is the first controlled trial to suggest a positive sildenafil response for ED treatment in patients previously treated with RT/ADT, however, only a minority of patients responded to treatment. ADT duration may be associated with response and requires further study. The overall low response rate suggests the need for study of additional or preventative strategies for ED after RT/ADT for prostate cancer.
Pedophilic Behavior from Brain Disease
Authors: Mendez Mario , Shapira Jill S.
Published: January 2011

Introduction

Child molestation or other pedophilic behavior may result as a consequence of a brain disorder.

Aim

To characterize the mechanisms of pedophilic behavior associated with neurological diseases.

Methods

We report eight patients with pedophilic behavior as a manifestation of their brain disorder and review the literature.

Main Outcome Measures

The sexual, neuropsychiatric, and neurological aspects of a series of patients.

Results

All eight developed sexual behavior toward prepubescent children in mid- to late-life coincident with the development of a neurological disorder. Five had limited insight, anxiety, or concern for their behavior and tended to have frontal lobe executive deficits. Most of this group had frontally predominant disorders. Two others retained insight and concern in the context of marked hypersexuality. This second group had treated Parkinson’s disease and resembled reports of pedophilic behavior from subcortical lesions. The further presence of right temporal lobe-amygdala involvement may have predisposed to specific sexual preoccupation in some patients.

Conclusions

Brain disorders may release a predisposition to sexual attraction for children through disinhibition with frontal disease, sexual preoccupation with right temporal disease, or hypersexuality with subcortical disease in non-motor basal ganglia, hypothalamus, or septal nuclei. Differentiating these mechanisms of pedophilic behavior from brain disease could facilitate targeted interventions.
Does Metabolic Syndrome Impair Sexual Function in Middle- to Old-Aged Women?
Authors: Kim Yun Hwan , Kim Sun Mie , Kim Jin Ju , Cho In Seong , Jeon Myung Jae
Published: January 2011

Introduction

To date, there are few studies dealing with the impact of metabolic syndrome (MS) on female sexual function, and the association between MS and female sexual dysfunction (FSD) in middle- to old-aged women remains unclear.

Aim

To evaluate the impact of MS on sexual function in middle- to old-aged women.

Methods

From May 2009 to January 2010, we performed a cross-sectional study of sexually active women (≥40 years old) who visited a health-screening clinic. Comprehensive history taking, anthropometric measurement, laboratory testing, and questionnaire administration were performed for each of the total 773 women enrolled.

Main Outcome Measures

The Female Sexual Function Index (FSFI) was used to assess the key dimensions of female sexual function.

Results

The median age of enrolled subjects was 48 (40–65) years, and the rates of MS and FSD were 12.2% (94/773) and 54.7% (423/773), respectively. We found that the demographics of women with and without MS (P < 0.05) differed significantly from one another in terms of age, menopausal status, body mass index, educational status, household income, and urinary incontinence (UI) symptoms, although their frequency of FSD was similar (52.1% vs. 55.1%). After adjusting clinical confounders, we found that only the pain domain score was significantly different between women with MS and without MS, while the total FSFI score and other constituent domain scores showed little difference between the two groups. However, in the multivariate logistic regression model, MS and most of its components were not associated with FSD; only age, menopausal status, smoking, depression, and symptomatic UI proved to be independent risk factors for FSD (P < 0.05).

Conclusions

Our study suggests that MS may have little impact on sexual function in middle- to old-aged women. Further studies with population-based and longitudinal design should be conducted to confirm this finding.
The Effect of Prolapse Surgery on Vaginal Sensibility
Authors: Lakeman Mariëlle M.E. , van der Vaart C. Huub , Laan Ellen , Roovers Jan-Paul W.R.
Published: January 2011

Introduction

Prolapse surgery has been shown to have major impact on sexual function. Since prolapse surgery not only influences psychological factors but might also influence physiological conditions such as vaginal innervation, there is a need for objective outcome measurements to better understand the effects of prolapse surgery on sexual function.

Aims

To assess the effects of prolapse surgery with or without stress incontinence surgery on vaginal sensibility and to assess the relationship between vaginal wall sensibility and sexual well-being.

Methods

This study was performed parallel to a randomized controlled trial comparing vaginal and abdominal prolapse surgery with or without incontinence surgery in women with uterine prolapse stage 2 or more.

Main Outcome Measures

Vaginal wall sensibility was defined as mean sensation threshold to electrical stimulation of the vaginal wall at four standardized places, measured before and 6 months after surgery. Higher sensation thresholds postsurgery relative to presurgery indicate diminished vaginal wall sensibility. Sexual function was assessed at the same time points using a questionnaire.

Results

Data on vaginal wall sensibility were obtained from 65 patients. The sensibility of the distal posterior (P = 0.02) and distal anterior (P = 0.10) vaginal wall decreased after vaginal surgery compared to abdominal surgery. Abdominal prolapse surgery with incontinence surgery decreased sensibility of the distal part of the anterior vaginal wall significantly more than abdominal prolapse surgery only (P = 0.01). Before surgery, vaginal wall sensibility was lower in women who reported vaginal dryness or anorgasmia. The presence of genital pain was associated with higher vaginal wall sensibility. Postoperative vaginal wall sensibility was similar in women with and without sexual problems.

Conclusion

Vaginal prolapse surgery as well as abdominal prolapse surgery with additional incontinence surgery resulted in decreased vaginal wall sensibility. This pilot study shows no influence of the decreased vaginal wall sensibility on sexual well-being. Larger studies are needed to better understand the association between changes in vaginal wall sensibility and changes in sexual well-being.
Model for Cameron-band emission in comets: a case for the EPOXI mission target comet 103P/Hartley 2
Authors: Bhardwaj Anil , Raghuram Susarla
Published: January 2011

The CO2 production rate has been derived in comets using Cameron-band (a3Π→X1Σ) emission of CO molecules, assuming that photodissociative excitation of CO2 is the main production mechanism of CO in the a3Π metastable state. We have developed a model for the production and loss of CO(a3Π), which has been applied to comet 103P/Hartley 2: the target of the EPOXI mission. Our model calculations show that photoelectron impact excitation of CO and dissociative excitation of CO2 can together contribute about 60–90 per cent to Cameron-band emission. The modelled brightness of (0–0) Cameron-band emission on comet Hartley 2 is consistent with Hubble Space Telescope observations for 3–5 per cent CO2 (depending on the model input solar flux) and 0.5 per cent CO relative to water, where the photoelectron impact contribution is about 50–75 per cent. We suggest that estimation of CO2 abundances on comets using Cameron-band emission may be reconsidered. We predict a height-integrated column brightness of the Cameron band of ∼1300 Rayleigh during the EPOXI mission encounter period.
GGR Biennial Review: Isotope Ratio Determination in the Earth and Environmental Sciences 2008–2009
Authors: Woodhead Jon D.
Published: January 2011

This review documents developments and applications in the field of isotope ratio determination, as reflected in the literature for the Earth and environmental sciences for the years 2008 and 2009. The emphasis is predominantly on applications, reflecting the enormous diversity of problems to which isotopic analysis can now be applied, but viewed in the context of rapid development of new analytical methodologies as significant new drivers of research output.
Changes in immunological markers and influx of macrophages following trans‐scleral thermotherapy of uveal melanoma
Authors: Dennaoui Jihan , Bronkhorst Inge H. G. , Ly Long V. , de Wolff‐Rouendaal Didi , Keunen Jan E. E. , Schalij‐Delfos Nicoline E. , Jager Martine J.
Published: January 2011

Purpose:  In trans‐scleral thermotherapy (TSTT), heat is applied through the sclera in order to target an intraocular uveal melanoma. Previously, it had been shown that in uveal melanoma, hyperthermia and transpupillary thermotherapy influenced expression of immunologically relevant proteins, such as S100, HLA and heat‐shock proteins (HSPs). We investigated whether TSTT induced similar changes.

Methods:  Experimental TSTT was applied on eleven uveal melanomas prior to enucleation. Each tumour sample was processed for histopathological examination; immunohistochemical analysis was performed to determine expression of S100, HLA, HSPs and macrophage markers.

Results:  In TSTT‐treated areas, expression of S100 and different HSPs was lost, while an upregulated expression of HSP GP96 was observed at the border of these areas. Expression levels of HLA‐A and HLA‐B varied between tumours and were not influenced by TSTT. The borders of the TSTT‐treated areas showed high numbers of infiltrating macrophages, which were predominantly of the M2 phenotype.

Conclusion:  TSTT has an effect on immunological parameters with local loss of expression of HSPs and S100. The influx of M2 macrophages around the TSTT‐treated areas indicates the presence of an innate immune reaction against the induced necrosis, suggesting that TSTT‐treated tumour cells are removed by a macrophage‐mediated tissue repair mechanism.
Protein kinase A signalling is involved in the relaxant responses to the selective β-oestrogen receptor agonist diarylpropionitrile in rat aortic smooth muscle in vitro
Authors: Valero Marta S , Pereboom Desiree , Barcelo-Batllory Silvia , Brines Laia , Garay Ricardo P , Alda José O
Published: January 2011

Objectives

The oestrogen receptor β (ERβ) selective agonist diarylpropionitrile (DPN) relaxes endothelium-denuded rat aorta, but the signalling mechanism is unknown. The aim of this study was to assess whether protein kinase A (PKA) signalling is involved in DPN action.

Methods

cAMP was measured by radioimmunoassay, HSP20 phosphorylation by 2D gel electrophoresis with immunoblotting, and membrane potential and free cytosolic calcium by flow cytometry.

Key findings

DPN increased cAMP content and hyperpolarised cell membranes over the same range of concentrations as it relaxed phenylephrine-precontracted aortic rings (10–300 µM). DPN-induced vasorelaxation was largely reduced by the PKA inhibitors Rp-8-Br-cAMPS (8-bromoadenosine-3′, 5′-cyclic monophosphorothioate, Rp-isomer) and H-89 (N-(2-bromocynnamyl(amino)ethyl)-5-isoquinoline sulfonamide HCl) (−73%) and by the adenylate cyclase inhibitor MDL12330A (cis-N-(2-phenylcyclopentyl)-azacyclotridec-1-en-2-amine)) (−65.5%). Conversely, the PKG inhibitor Rp-8-Br-cGMP was inactive against DPN vasorelaxation. In aortic smooth muscle segments, DPN increased PKA-dependent HSP20 phosphorylation, an effect reversed by H-89. Relaxant responses to DPN were modestly antagonised (−23 to −48% reduction; n = 12 per compound) by the potassium channel inhibitors iberiotoxin, PNU-37883A, 4-aminopyridine, or BaCl2. All four potassium channel inhibitors together reduced DPN relaxation by 86 ± 9% (n = 12) and fully blocked DPN hyperpolarisation.

Conclusions

ERβ-dependent relaxation of rat aortic smooth muscle evokes an adenylate cyclase/cAMP/PKA signalling pathway, likely activating the cystic fibrosis transmembrane conductance regulator chloride channel and at least four potassium channels.
Collaboration in chronic care: unpacking the relationship of pharmacists and general medical practitioners in primary care
Authors: Dey Rosalind M , de Vries Michael J W , Bosnic-Anticevich Sinthia
Published: January 2011

Objectives

The objective of this research was to gain deeper understanding of the expectations, experiences and perceptions of Australian general medication practitioners (GPs) and pharmacists around collaboration in chronic illness (asthma) management in the primary care setting.

Methods

A qualitative research methodology utilising a semi-structured interview guide, based on theory and an empirical approach, was used to fulfill the objectives of this study. Face-to-face interviews with pharmacists (n = 18) and GPs (n = 7) were recorded, transcribed and coded for concepts and themes. Relationships between concepts and themes were examined and used to describe the nature of collaborative relationships in the primary care setting.

Key findings

A relationship between GPs and pharmacists currently exists although there is minimal collaboration and there are several areas of practice and patient care in which the two professional groups are mismatched. At the same time, this research uncovered key aspects of the GP–pharmacist relationship, which could be used to develop more collaborative relationships in the future. The findings from this study were evaluated in light of the Collaborative Working Relationships model and published literature.

Conclusions

A model for the development of GP–pharmacist relationship has been postulated which articulates the dynamic nature of professional relationship in primary care and highlights a pathway to more collaborative practice. Future research should focus on further developing this model.
Revealing Nonlinear Dynamics Phenomena in Mooring Due to Slowly-Varying Drift
Authors: Bernitsas Michael M. , Matsuura João Paulo J.
Published: January 2011

The effects of slowly-varying wave drift forces on the nonlinear dynamics of mooring systems have been studied extensively in the past 30 years. It has been concluded that slowly-varying wave drift may resonate with mooring system natural frequencies. In recent work, we have shown that this resonance phenomenon is only one of several possible nonlinear dynamic interactions between slowly-varying wave drifts and mooring systems. We were able to reveal new phenomena, based on the design methodology developed at the University of Michigan for autonomous mooring systems, and treating slowly-varying wave drift as an external time-varying force in systematic simulations. This methodology involves exhaustive search regarding the nonautonomous excitation, however, and approximations in defining response bifurcations. In this paper, a new approach is developed, based on the harmonic balance method, where the response to the slowly-varying wave drift spectrum is modeled by limit cycles of frequency, estimated from a limited number of simulations. Thus, it becomes possible to rewrite the nonautonomous system as autonomous and reveal stability properties of the nonautonomous response. Catastrophe sets of the symmetric principal equilibrium, serving as design charts, define regions in the design space where the trajectories of the mooring system are asymptotically stable, limit cycles, or nonperiodic. This methodology reveals and proves that mooring systems subjected to slowly-varying wave drift exhibit many nonlinear phenomena, which lead to motions with amplitudes two to three orders of magnitude larger than those resulting from linear resonance. A turret mooring system (TMS) is used to demonstrate the harmonic balance methodology developed. The produced catastrophe sets are then compared with numerical results obtained from systematic simulations of the TMS dynamics.
A Case Study in Optimization of Gait and Physical Parameters for a Snake-Inspired Robot Based on a Rectilinear Gait
Authors: Hopkins James K. , Spranklin Brent W. , Gupta Satyandra K.
Published: January 2011

Physical parameters of the constituent modules and gait parameters affect the overall performance of snake-inspired robots. Hence, a system-level optimization model needs to concurrently optimize the module parameters and the gait. Incorporating a physics-based model of rectilinear gaits in the system-level optimization model is a computationally challenging problem. This paper presents a case study to illustrate how metamodels of the precomputed optimal rectilinear gaits can be utilized to reduce the complexity of the system-level optimization model. An example is presented to illustrate the importance of concurrently optimizing the module parameters and the gait to obtain the optimal performance for a given mission.
On Line Screw Systems and Their Application to Flexure Synthesis
Authors: Su Hai-Jun , Tari Hafez
Published: January 2011

Motivated by the problem of synthesizing a pattern of flexures that provide a desired constrained motion, this paper presents a new screw theory that deals with “line screws” and “line screw systems.” A line screw is a screw with a zero pitch. The set of all line screws within a screw system is called a line variety. A general screw system of rank m is a line screw system if the rank of its line variety equals m. This paper answers two questions: (1) how to calculate the rank of a line variety for a given screw system and (2) how to algorithmically find a set of linearly independent lines from a given screw system. It has been previously found that a wire or beam flexure is considered a line screw, or more specifically a pure force wrench. By following the reciprocity and definitions of line screws, we have derived the necessary and sufficient conditions of line screw systems. When applied to flexure synthesis, we show that not all motion patterns can be realized with wire flexures connected in parallel. A computational algorithm based on this line screw theory is developed to find a set of admissible line screws or force wrenches for a given motion space. Two flexure synthesis case studies are provided to demonstrate the theory and the algorithm.
Correlation Between Speciated Hydrocarbon Emissions and Flame Ionization Detector Response for Gasoline/Alcohol Blends
Authors: Wallner Thomas
Published: January 2011

The U.S. Renewable Fuel Standard has made it a requirement to increase the production of ethanol and advanced biofuels to 36 billion gallons by 2022. Ethanol will be capped at 15 billion gallons, which leaves 21 billion gallons to come from other sources, such as butanol. Butanol has a higher energy density and lower affinity for water than ethanol. Moreover, alcohol fueled engines in general have been shown to positively affect engine-out emissions of oxides of nitrogen and carbon monoxide compared to their gasoline fueled counterparts. In light of these developments the variety and blend levels of oxygenated constituents is likely to increase in the foreseeable future. The effect on engine-out emissions for total hydrocarbons (THC) is less clear due to the relative insensitivity of the flame ionization detector (FID) toward alcohols and aldehydes. It is well documented that hydrocarbon (HC) measurement using a conventional FID in presence of oxygenates in the engine exhaust stream can lead to a misinterpretation of HC emissions trends for alcohol fuel blends. Characterization of the exhaust stream for all expected hydrocarbon constituents is required to accurately determine the actual concentration of unburned fuel components in the exhaust. In addition to a conventional exhaust emissions bench, this characterization requires supplementary instrumentation capable of hydrocarbon speciation and response factor independent quantification. Although required for certification testing, this sort of instrumentation is not yet widely available in engine development facilities. Therefore an attempt is made to empirically determine an oxygenate fuel, FID correction factor. Exhaust emissions of an engine fueled with several blends of gasoline and ethanol, n-Butanol and iso-Butanol were characterized using both a conventional FID and an FTIR. Based on these results, a response factor predicting the actual hydrocarbon emissions, based solely on FID results as a function of alcohol type and content, is presented. Finally the correlation derived from data presented in this study is compared to equations and results found in the literature.
Numerical Study on a Heavy Duty CI Engine to Achieve Ultra-Low Emissions
Authors: Koten H. , Yilmaz M. , Gul M. Z.
Published: January 2011

The goal of this study is to find out effects of the injection parameters on the combustion process for a single cylinder of a nine-liter six cylinder diesel engine. Partially premixed compression ignition (PPCI) cases are compared for improvements on the combustion chamber design of the engine to achieve near zero particulate matter (PM) and NOx emissions for homogenous charge compression ignition (HCCI) engine. Therefore combustion simulations of the engine have been performed to find out flow development and emission generation in the cylinder. Moreover, the interaction of air motion with high-pressure fuel spray injected directly into the cylinder has also been analyzed. Finally, a comparison has been made considering the performance of the engine for various configurations such as compression ratio, injection timing, cone angle and bowl geometry. The results are widely in agreement qualitatively with the previous similar experimental and computational studies in the literature.
Fuel-Line Stationary Waves and Variability in CI Combustion During Complex Injection Strategies
Authors: Michailidis A. D. , Stobart R. K. , McTaggart-Cowan G. P.
Published: January 2011

This study investigated the effects of increased injection regime complexity on injector and combustion stability in a naturally aspirated single cylinder diesel engine equipped with a common rail fuel injection system and an instrumented injector. The injection regimes investigated included a single injection, a main injection with a pilot, and a split-main with a pilot. Injector performance was found to be very stable over all injection regimes and did not contribute to variations in combustion stability. Cylinder pressure variation during the initiation of combustion was identified as a potential method of identifying the start of combustion phasing and compared to current methods. Three series of tests were conducted at various speeds and injection pressures to demonstrate the influence of multi-pulse injection phasing on combustion stability and total fuel consumption. These results demonstrate that the presence of a stationary wave in the high-pressure fuel line, induced by an early injection, can dramatically affect the amount of fuel injected in subsequent injections within the same cycle.
Effect of Swirl and Injection Pressure on Performance and Emissions of JP-8 Fueled High Speed Single Cylinder Diesel Engine
Authors: Nargunde Jagdish , Jayakumar Chandrasekharan , Sinha Anubhav , Henein Naeim A. , Bryzik Walter , Sattler Eric
Published: January 2011

An investigation was conducted on a 0.42 liter single cylinder diesel engine equipped with a common rail fuel injection system to evaluate the influence of the swirl motion on JP-8 fuel combustion. Engine tests were performed under steady state conditions of 5 bar IMEP and 1500 RPM. Two different swirl ratios of 1.44 and 7.12 were applied at injection pressures ranging from 400 to 1200 bar. The apparent rate of heat release (ARHR) curve is analyzed to determine the effect of swirl on combustible mixture formation, auto-ignition, premixed and diffusion controlled combustion fractions. An attempt is made to correlate between the swirl ratio and different combustion and emissions parameters at different injection pressures. The emissions included the gaseous fractions and particulates. Two types of particulate matter were measured: Accumulation mode particles (AMPs) and Nucleation mode particles (NMPs). The results indicate that ignition delay duration of JP-8 increases as the swirl ratio increases influencing the overall combustion process and engine out emissions.
Development of an Exhaust Manifold Design Optimization for Cylinder Scavenging and Turbocharger Performance
Authors: Grauer Diana K. , Chapman Kirby S.
Published: January 2011

This paper presents an investigation into the NOX reduction role played by the exhaust manifold of large-bore two stroke cycle engines by exploring the impact of the exhaust manifold design on turbocharger and engine operation. Exhaust manifold performance is defined as the ability of the exhaust manifold to: 1) optimize cylinder scavenging efficiency; and 2) minimize the pressure differential between the compressor discharge and the turbine inlet by exploiting the blow-down pressure pulses and minimizing the static pressure gradient along the exhaust manifold. Pressure pulses in the exhaust manifold have been identified as a plausible mechanism that hinders efficient cylinder scavenging and turbocharger operating range. While modifying the ports and manifold may not be cost effective, a complete understanding of and the ability to address the impact of these pressure waves on turbocharger performance and scavenging efficiency will lead to more reliable engine upgrade projects as the industry approaches the 0.5 g/bhp-hr engine. The research team chose “available energy,” or the amount of mechanical and thermal energy available to the turbocharger turbine for operation as the parameter for defining optimal exhaust manifold design parameters. This allowed the research team to: 1) investigate energy losses in the candidate Clark TLA-6 exhaust removal system on a component basis, and 2) translate the mitigation of these losses into expanded turbocharger operating range. The end point of the project was a set of exhaust manifold design guidelines aimed at maximizing turbocharger performance by way of the defined metrics, scavenging efficiency and waste-gate margin.
A Simulation Study Quantifying the Effects of Drive Cycle Characteristics on the Performance of a Pneumatic Hybrid Bus
Authors: Trajkovic Sasa , Tunesta˚l Per , Johansson Bengt
Published: January 2011

In the study presented in this paper, the effect of different vehicle driving cycles on the pneumatic hybrid has been investigated. The pneumatic hybrid powertrain has been modeled in GT-Power and validated against experimental data. The GT-Power engine model has been linked with a MATLAB/simulink vehicle model. The engine in question is a single-cylinder Scania D12 diesel engine, which has been converted to work as a pneumatic hybrid. The base engine model, provided by Scania, is made in GT-power and it is based on the same engine configuration as the one used in real engine testing. Earlier studies have shown a great reduction in fuel consumption with the pneumatic hybrid compared to conventional vehicles of today. However, most of these studies have been completely of theoretical nature. In this paper, the engine model is based on and verified against experimental data, and therefore more realistic results can be expected. The intent with the vehicle driving cycle simulation is to investigate the potential of a pneumatic hybrid bus regarding reduction in fuel consumption (FC) compared to a traditional internal combustion engine (ICE) powered bus. The results show that the improvement in fuel economy due to pneumatic hybridization varies heavily with choice of drive cycle. The New York bus drive cycle shows a reduction of up to 58% for the pneumatic hybrid while the FIGE drive cycle only shows a reduction of 8%. What all cycles have in common is that the main part of the fuel consumption reduction comes from the start/stop-functionality, while regenerative braking only account for a modest part of up to about 12% of the fuel consumption. The results also show that the optimal pressure tank volume varies with drive cycles, ranging from 60 to over 500 liters.
Computational and Experimental Analysis of Direct CNG Injection and Mixture Formation in a Spark Ignition Research Engine
Authors: Baratta Mirko , Catania Andrea E. , Pesce Francesco C.
Published: January 2011

Direct injection (DI) of compressed natural gas (CNG) under high pressure conditions is a topic of great interest, owing to its potential for improving SI engine performance and fuel consumption. However, relevant technical difficulties have yet to be resolved in order to stabilize combustion process, especially for stratified engine operating conditions. The present paper is focused on experimental and numerical investigations of the jet formation and fuel-air mixing process in a research optical-access single-cylinder engine. The engine is based on the multi-cylinder engine under development within the European Community (EC) VII Framework Program (FP) InGAS Integrated Project, and features a centrally mounted poppet-valve injector on a pent-roof combustion chamber with a bowl in piston. Experimental investigations were made by means of the planar laser-induced fluorescence technique, and revealed a cycle-to-cycle jet shape variability. In particular, for specific cylinder pressure values at the start of injection, the jet can adhere to chamber walls for a relevant number of cycles, leading to an ‘umbrella-like’ shape. This can change the mixing capabilities of the combustion chamber and cause instabilities in the combustion process. The mentioned behaviour is strongly dependent not only on the injection and cylinder pressures, but also on important design parameters, such as needle cone angle and in-chamber injector protrusion. For this reason, in order to obtain a deep insight into the injected gas behaviour on an average cycle basis, the experimental investigation was supported by a numerical analysis. Simulations were carried out by an optimized variable-density finite-volume numerical model which was built within the Star-CD environment. A previously developed and validated ‘virtual injector’ model was implemented. The outcomes of the numerical model were compared to laser-induced fluorescence images, for both stratified- and homogeneous-charge engine operating conditions and a good agreement was obtained, substantiating the reliability of the applied computational model. Then, the effects of the injector protrusion in the combustion chamber and of injection timing were analyzed, and their impact on jet stability and mixture-formation process was analyzed.
The Impacts of Mid-Level Alcohol Content in Gasoline on SIDI Engine-Out and Tailpipe Emissions
Authors: He Xin , Ireland John C. , Zigler Bradley T. , Ratcliff Matthew A. , Knoll Keith E. , Alleman Teresa L. , Luecke Jon H. , Tester John T.
Published: January 2011

The influences of ethanol and iso-butanol on gasoline engine performance, engine-out and tailpipe emissions were studied using a General Motors (GM) 2.0L turbocharged gasoline spark ignition direct injection (SIDI) engine. U.S. federal certification gasoline (E0), two ethanol-blended fuels (E10 and E20), and 11.7% iso-butanol blended fuels were tested. Fourier-Transform Infrared (FTIR) spectroscopy was used to measure non-regulated species including methane, ethylene, acetylene, formaldehyde, acetaldehyde, isobutylene, 1,3-butadiene, n-pentane, and iso-octane. A Fast Mobility Particle Sizer (FMPS) spectrometer was used to measure the particle number (PN) size distribution in the range from 5.6 to 560 nm. The regulated emissions total hydrocarbon (THC), carbon monoxide (CO), and oxides of nitrogen (NOx) were also measured. Both engine-out and tailpipe emissions results are presented as functions of alcohol content. In general, the alcohols tested reduced total PN emissions, with iso-butanol demonstrating the greatest reduction. Increasing ethanol content and iso-butanol increased formaldehyde emissions, with iso-butanol exhibiting the highest increase. Iso-butanol increased iso-butylene emission; however, it reduced emissions of 1,3-butadiene. Within the context of this study, the alcohols did not significantly change the other regulated emissions.
Gas Quality Sensor to Improve Biogas-Fueled CHP/DG
Authors: Zelepouga Serguei , Gnatenko Vitaly , Pratapas John M. , Jangale Vilas V. , Saveliev Alexei
Published: January 2011

Today, renewable fuels such as biogas are being used to fuel combined heat and power (CHP) and distributed generation (DG) systems. The composition of biogas delivered to power generation equipment varies depending upon the origin of the anaerobic digestion process and site-specific factors. For improved process control and optimum utilization of CHP/DG systems, the biogas composition needs to be monitored. A new apparatus has been developed for characterization of hydrocarbon fuel mixtures. The method utilizes near infrared absorption spectroscopy to monitor composition and heating value of landfill gas, natural gas, and other hydrocarbon fuel gases. The measurement is virtually instantaneous. A commercialized version of this sensor is expected to cost less than half the price of gas chromatographs, which are widely used in the gas industry today.
Quasi-Two-Zone Modeling of Diesel Ignition Delay in Pilot-Ignited Partially Premixed Low Temperature Natural Gas Combustion
Authors: Jha Saroj Kumar , Krishnan Sundar Rajan , Srinivasan Kalyan Kumar
Published: January 2011

This paper presents simulated ignition delay (ID) results for diesel ignition in a pilot-ignited partially premixed, low temperature natural gas (NG) combustion engine. Lean premixed low temperature NG combustion was achieved using small pilot diesel sprays (2–3% of total fuel energy) injected over a range of injection timings (BOIs ∼ 20°–60° BTDC). Modeling IDs at advanced BOIs (50°–60° BTDC) presented unique challenges. In this study a single-component droplet evaporation model was used in conjunction with a modified version of the Shell autoignition (SAI) model to obtain ID predictions of pilot diesel over the range of BOIs (20°-60° BTDC). A detailed uncertainty analysis of several model parameters revealed that Aq and Eq, which affect chain initiation reactions, were the most important parameters (among a few others) for predicting IDs at very lean equivalence ratios. The ID model was validated (within ± 10 percent error) against experimentally measured IDs from a single-cylinder engine at 1700 rpm, BMEP = 6 bar, and intake manifold temperature (Tin) of 75°C. For BOIs close to TDC (e.g., 20° BTDC), the contribution of diesel evaporation times (Δθevap) and droplet diameters to predicted IDs were more significant compared to advanced BOIs (e.g., 60° BTDC). Increasing Tin (the most sensitive experimental input variable affecting predicted IDs), led to a reduction in both the physical and chemical components of ID. Hot EGR led to shorter predicted and measured IDs over the range of BOIs, except 20° BTDC. In general, the thermal effects of hot EGR were found to be more pronounced than either dilution or chemical effects for most BOIs. Finally, uncertainty analysis results also indicated that ID predictions were most sensitive to model parameters AP3, Aq, and Af1, and Eq, which affected chain initiation and propagation reactions and also contributed the most to overall uncertainties in IDs.
Investigation and Demonstration of a Small Intermittent Internal Combustion Heavy-Fueled Engine
Authors: Clark David A. , Owen Albert K. , Kascak Albert F. , Porter Brian J.
Published: January 2011

Since 2004, the Department of Defense (DoD) has had the stated goal of transitioning all engine systems to use a single fuel — JP-8. This “one fuel forward” initiative simplifies logistical issues, improves safety, and increases combat effectiveness. To improve technologies required to run Intermittent Internal Combustion (IIC) engines on lower volatility heavy fuels, the US Army Vehicle Technology Directorate (VTD) acquired and tested a small IIC engine and developed procedures allowing the operation of this engine on JP-8. The program consisted of engine simulation, engine testing and flight demonstration. Several strategies are presented to enhance the engine operation based on thermal management techniques and fuel injection.
Misfire Detection for Spark Ignition Engines Based Upon Cycle-by-Cycle Exhaust Temperature Sensing
Authors: Gardiner David P.
Published: January 2011

Misfiring is a serious issue for large spark-ignited industrial natural gas engines because it increases fuel consumption and emissions and can ultimately lead to engine damage. Continuous misfiring of an engine cylinder can often be diagnosed based upon vibration measurements or conventional exhaust temperature measurements. The aim of the research described in this paper was to develop a means of detecting not only frequent misfiring of a cylinder, but also isolated, individual misfires. This would make it possible to detect problems early in the progression from sporadic misfire events to the onset of continuous misfiring. The approach used in the study is based upon the sensing of cycle-by-cycle fluctuations in the exhaust temperature from each cylinder. Proprietary circuitry and signal processing techniques are used to extract high frequency temperature information from durable sheathed thermocouples similar to those commonly used for these types of engines. These signal fluctuations can be used to detect momentary drops in exhaust temperature that occur as unburned mixture from a misfire exits the cylinder. The system was developed and validated through engine dynamometer tests using an automotive engine equipped with laboratory-grade cylinder pressure sensors for reference measurements. Further testing was conducted using a medium speed stationary natural gas engine. In both cases, the system was shown to be able to detect and count individual and consecutive misfire events.