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Epidemiological studies have reported an association between air pollution and central nervous system disorders. However, its biological mechanisms are poorly understood. This study aimed to determine the effect of short-term environmental exposure to PM10 and associated heavy metals on changes in blood and urinary nervous markers in dusty conditions. A total of 44 healthy non-smokers were identified with a mean age of 36 years. Blood and urine samples were taken from these people 24 h before and after the dust storm to measure the biomarkers of the central nervous system. Cortisol, white blood cells (WBCs), neuron-specific enolase (NSE), and S100β were measured as blood markers, while vanillylmandelic acid (VMA) and homovanillic acid (HVA) were tracked as urine markers. These people had 7 h of environmental exposure in dusty conditions. Eleven heavy metals (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Co, Pb, and Zn) associated with PM10 were measured. The average PM10 concentration on dust days was 3.25 times higher than on normal days (309.81 μg m−3 vs. 86.11 μg m−3). The results of the statistical paired T-test showed that the mean S100β from pre-exposure to post-exposure increased by 5.85 ng L−1 (P ≤ 0.004). The NSE mean of the pre-exposure (3.37 ± 3.48 μg L−1) was significantly different from the NSE mean after exposure)4.15 ± 3.74 μg L−1 ((P = 0.002). The post-exposure WBC mean was 0.59 times higher than that before exposure, albeit not statistically significant (P = 0.269). The mean VMA after exposure increased by 0.55 mg g−1 CRT (Creatinine) compared to that before exposure. This difference was statistically significant (P = 0.000). Changes in S100β after exposure to dust storms had a high correlation with changes in Cr, Pb, and Fe metal concentrations, respectively (r = 0.81, r = 0.72, r = 0. 65). NSE changes were significantly associated with changes in Mn, Cd, and Fe (r = 0.71, r = 0.99, r = 0.71). Heavy metals associated with PM10 can damage neurons and astrocytes, promoting neuropsychiatric disorders in people with exposure.

Purpose : Memantine is an approved drug for the treatment of Alzheimer’s disease (AD). Autophagy, lysosome dysfunction, and sigma receptors have possible roles in the pathophysiology of AD. Therefore, we aimed to investigate the contribution of sigma receptors and lysosome inhibition to the neuroprotective effects of memantine against amyloid-beta (Aβ)-induced neurotoxicity in SH-SY5Y cells. Methods: We determined the neuroprotective effects of memantine (2.5 µM), dizocilpine (MK801, as a selective N-methyl-D-aspartate (NMDA) receptor antagonist) (5 μM) against Aβ25– 35 (2 μg/μL)-induced neurotoxicity. We used chloroquine (10, 20, and 40 μM) as a lysosome inhibitor and BD-1063 (1, 10, and 30 μM) as a selective sigma receptor antagonist. The MTT assay was used to measure the neurotoxicity in the SH-SY5Y cells. Data were analyzed using the one-way ANOVA. Results: Memantine (2.5 µM), dizocilpine (5 µM), chloroquine (10 and 20 µM) and BD-1063 (1, 10 and 30 µM) decreased the neurotoxic effects of Aβ on the SH-SY5Y cells. However, chloroquine (40 µM) increased the neurotoxic effects of Aβ. Cell viability in the cells treated with memantine + Aβ + chloroquine (10, 20, and 40 μM) was significantly lower than the memantine + Aβ-treated group. Moreover, cell viability in the memantine + Aβ group was higher than the memantine + Aβ + BD-1063 (10 and 30 μM) groups. Conclusion: The lysosomal and sigma receptors may contribute to the neuroprotective mechanism of memantine and other NMDA receptor antagonists. Moreover, the restoration of lysosomes function and the modulation of sigma receptors are potential targets in the treatment of AD.

Objectives: The current study aimed at evaluating testis parameters and spermatogenesis changes in male rats administrated by different busulfan doses and time to construct a subfertile animal model by stereological methods.Materials and Methods: In the present study, 150 male Wistar rats randomly divided into 5 groups. All experimental groups were treated by different concentrations of busulfan (0.0, 2.5, 5, 10, and 15 mg/kg). Rats were sacrificed 1, 15, and 30 days after busulfan treatment. The tissue processing was done for stereological study and the results were analyzed by the one-way ANOVA followed by the Duncan test. Results: The most stereological parameters such as testes weight and volume, tubules volume density, interstitial tissue (P

International audience; This study aimed to investigate the effects of short-term ambient environmental exposure to fine particles and heavy metals (HMs) on neural biomarkers of people within dust storm conditions. From 44 healthy volunteers, who had already been identified, blood and urine samples were taken 24 h before the dust storm. Their blood and urine samples were taken 24 h after exposure. Vanillylmandelic acid (VMA) and homovanillic acid (HVA) were measured as urine markers, while neuron-specific enolase (NSE), cortisol, S100 beta, and white blood cells (WBCs) were tracked as blood markers. Eleven HMs (Fe, Mn, Zn, Cr, Co, Al, Ni, Pb, Cd, As, and Cu) correlated with fine particles were measured in both normal and dusty days. The mean concentration of fine particles on normal and dusty days was 60.21 and 238.8 mu g m(-3), respectively. The mean value of the post-exposure NSE and S100 beta was 0.59 ng/L-1 (p = 0.002) and 5.61 ng/L-1 (p

Male infertility secondary to exposure to gonadotoxic agents during reproductive age is a concerning issue. The aim of this experimental study was to determine the effect of Loboob on sperm parameters.55 healthy rats were selected, weighted and divided into five groups consisting of 11 rats each. The control group received no medication. Rats in Treatment Group 1 received 10mg/kg Busulfan and rats in Treatment Groups 2, 3, and 4 received 35,70 and 140 mg/kg Loboob respectively in addition to 10mg/kg Busulfan. Finally, the sperm parameters and weights of the rats were compared using the Kolmogorov-Smirnov, non-parametric Kruskal-Wallis, and Dunn-Bonferroni tests.All sperm parameters and weights were significantly decreased among rats receiving Busulfan. All dosages of Loboob were effective to enhance the motility of slow spermatozoa, while only in the rats given 70 and 140 mg/kg of Loboob saw improvements in progressively motile sperm percentages (0.024 and 0.01, respectively). Loboob at a dosage of 140mg/kg improved sperm viability. It did not improve normal morphology sperm or decrease immotile sperm counts. Loboob did not affect mean rat weight.Loboob offered a dose-dependent protective effect on several sperm parameters in rats with busulfan-induced subfertility.

Purpose: Neuroinflammation was indicated in the pathophysiology of Alzheimer’s disease. Previous reports have also signified that spironolactone has anti-inflammatory effects. Therefore, the aim of this study was to assess the modulatory effects of spironolactone on neuroinflammation and memory loss in a rat model of Alzheimer’s disease. Methods: The β-amyloid protein fragment 25-35 (Aβ) was injected in the dorsal hippocampus (5μg/2.5μl each side) of male Sprague-Dawley rats for four consecutive days to induce memory impairment. Animals have intraperitoneally received spironolactone (10, 25, or 50 mg/kg, N=6/group) or vehicle for 14 days. The passive inhibitory avoidance and the novel recognition tests were used for memory evaluation. Neuroinflammation was assessed by measuring the level of Iba1 protein, a marker of microglial activation, using western immunoblotting. Results: Different doses of spironolactone showed no significant changes in latency times and discriminations ratios in passive inhibitory avoidance and novel recognition tests, respectively, as compared to vehicle. However, spironolactone-treated groups showed significantly lower Iba1 protein levels in comparison to the vehicle-treated group (p

Objectives The aim of this study was to evaluate the antiepileptic effects of opipramol, a sigma receptor agonist, diazepam, ketamine, an N-methyl-d-Aspartate (NMDA) receptor antagonist, and dantrolene, a ryanodine receptor antagonist, against caffeine-induced seizures in mice.Methods We used caffeine (1000 mg/kg) intraperitoneally for inducing clonic and tonic-clonic seizures in male albino Swiss strain of mice. We used opipramol in three different doses (10, 20 and 50 mg/kg), ketamine (50 mg/kg), dantrolene (40 mg/kg), opipramol (20 mg/kg) plus ketamine (50 mg/kg), opipramol (20 mg/kg) plus dantrolene (40 mg/kg), diazepam (5 mg/kg as a positive control) and the vehicle 30 min before injecting caffeine. We recorded the onset of clonic, tonic-clonic seizures and the time of death of animals after using caffeine.Results Animals treated with opipramol at a dose of 50 mg/kg or diazepam had a higher onset of clonic seizure compared with the vehicle-treated group. Dantrolene alone or with opipramol (20 mg/kg) increased the latency of clonic seizure compared with the control group. Opipramol (20 and 50 mg/kg), diazepam, ketamine alone or with opipramol, and dantrolene plus opipramol increased the latency of tonic-clonic seizures in mice. All the treatments except opipramol (10 mg/kg) and dantrolene alone increased the latency of death of animals.Conclusion Opipramol attenuated seizures produced by high doses of caffeine. Moreover, the activation of sigma receptors and inhibition of ryanodine receptors may produce synergistic effects against caffeine-induced seizures. Our study may imply that different mechanisms such as inhibition of gamma-aminobutyric acid-A receptors, activation of NMDA and ryanodine receptors may contribute to the caffeine-induced seizures.

This paper investigates the effect of factors on Farmers Adaptation Behavior in Water Scarcity Conditions in Rural Communities of Sabzevar, Iran. A survey questionnaire was used for collecting data, the study population was 120 farmers in rural Sabzevar County selected based on the Cochran formula. A questionnaire was designed for the target group for the measurement of on farm adaptation behavior in water scarcity conditions. Research models were drawn using structural equation modeling and the relationships between latent variables and indicators. The findings indicate that there is a significant relationship between awareness and adaptation behavior. Meanwhile, there is a significant relationship among network and media on farmer's perception about water scarcity and their activities toward better management of water in the critical condition. There are also significant relationships among perception and awareness with intention however, intention do not effect on adaptation behavior strongly. In other words, even the that means farmers had information about crisis, they are not able to have not operational plans to confront the water scarcity conditions. Keywords: Farmers adaptation behavior, Water scarcity, Rural communities, Iran

Objectives The aim of this study was to investigate the potential effects of Sargassum oligocystum extract on the pentylenetetrazole (PTZ) seizure and the contribution of antioxidant capacity of this alga to its antiepileptic effect.Methods A dose of 100 mg/kg PTZ was used to induce the seizure in the male albino mice. Extract of Sargassum oligocystum in four doses (100, 200, 400 and 600 mg/kg), diazepam (5 mg/kg) and the vehicle were used 30 min before the injection of PTZ (n = 8). The onsets of clonic and tonic-clonic seizures, as well as the latency of death of animals, were recorded and the total antioxidant capacity (TAC), Superoxide dismutase (SOD) activity and catalase level were measured. Data were analyzed using one-way ANOVA or Kruskal-Wallis tests.Results Sargassum oligocystum extract at the doses of 400 and 600 mg/kg significantly increased the latency of clonic and tonic-clonic seizures. Also, at the doses of 100, 200 and 400 mg/kg significantly increased the TAC. Moreover, Sargassum oligocystum at the doses of 200 and 400 mg/kg increased the SOD activity and at the doses of 400 and 600 mg/kg increased the catalase level in neural cells compared with the vehicle-treated group.Conclusion Sargassum oligocystum extract inhibited PTZ-induced seizure. Attenuation of oxidative stress may partly be responsible for the anticonvulsant effects of this alga in the PTZ-induced seizures. Therefore, marine algae, especially Sargassum oligocystum, may be a valuable target to discover new antiepileptic drugs.

The rotary Atkinson cycle engine includes two modes of combustion: combustion initiation and propagation in ignition chamber and then flame jet entrainment and propagation in expansion chamber. The turbulent flame propagation model is a predictive model for SI engines which could be developed for this type of combustion for the rotary Atkinson engine similar to the congenital engine with pre-chamber; in split combustion chamber SI engines, small amount of fuel is burned in pre-chamber while the fuel burned in ignition chamber of rotary Atkinson cycle is considerable. In this study a mathematical modeling of spherical flame propagation inside ignition chamber and new combined conical flame and spherical flame propagation model of a new two-stroke Atkinson cycle SI engine will be presented. The mathematical modeling is carried out using two-zone combustion analysis and the model also is validated against experimental tests and compared with previous study using non-predictive Weibe function model.

Summary Objectives There are some reports, particularly case studies about adverse effects of performance-enhancing drugs on the renal function. However, there is very limited information about performance-enhancing drugs effects on the renal function. Therefore, the aim of this study was to use a simple screening test to evaluate side effects of performance-enhancing drugs on the kidney among bodybuilding athletes in the south of Iran, Bushehr. Equipment and methods Personal information was collected via a face-to-face interview using a survey containing athlete's characteristics, exercise patterns and state of the performance-enhancing drug use. The bodybuilding athletes were classified according to the state of performance-enhancing drug use in the three stages as follows: (1) current performance-enhancing drug users, (2) non-current performance-enhancing drug users and (3) non-user athletes. The creatinine and blood urea nitrogen levels were measured as the main indices of renal function. Results The mean creatinine levels were significantly different among three studied groups (F = 7.35, df = 2, P 0.05). After adjusting for age, body mass index, alcohol and supplement use, the glomerular filtration rate levels of the current users were significantly lower than the non-current user and the non-user athletes. Moreover, the prevalence of acute kidney injury among the current users was significantly higher than the non-current and the non-user athletes (X2 = 10.40, df = 4, P

ObjectiveThe exact pathophysiology of bipolar disorder (BD) is not yet fully understood, and there are many questions in this area which should be answered. This review aims to discuss the roles of glial cells in the pathophysiology of BD and their contribution to the mechanism of action of mood-stabilising drugs.MethodsWe critically reviewed the most recent advances regarding glial cell roles in the pathophysiology and treatment of BD and the neuroprotective and neurotrophic effects of these cells.ResultsPostmortem studies revealed a decrease in the glial cell number or density in the specific layers of prefrontal and anterior cingulate cortex in the patients with BD, whereas there was no difference in other brain regions, such as entorhinal cortex, amygdala and hippocampus. Astrocytes and oligodendrocytes were the most important glial types that were responsible for the glial reduction, but microglia activation rather than loss may be implicated in BD. The decreased number or density of glial cells may contribute to the pathological changes observed in neurons in the patients with BD. Alteration of specific neurotrophic factors such as glial cell line-derived neurotrophic factor and S100B may be an important feature of BD. Glial cells mediate the therapeutic effects of mood-stabilising agents in the treatment of BD.ConclusionRecent studies provide important evidence on the impairment of glial cells in the pathophysiology and treatment of BD. However, future controlled studies are necessary to elucidate different aspects of glial cells contribution to BD, and the mechanism of action of mood-stabilising drugs.

This study aimed to investigate the effects of sigma receptor modulators, opipramol and BD-1063, on epileptogenesis in pentylenetetrazole (PTZ)-kindling model of epilepsy. Mice (n = 6/group) were received PTZ (30 mg/kg), PTZ plus opipramol (5 or 10 mg/kg), PTZ plus opipramol (5 mg/kg) plus BD-1063 (5 mg/kg, a selective sigma-1 receptor antagonist), and PTZ plus BD-1063 on alternate days for 15 days. Opipramol (5 and 10 mg/kg) + PTZ groups became fully kindled and had higher seizure scores compared to the PTZ group. In contrast, the PTZ plus BD-1063 and the PTZ plus opipramol (5 mg/kg) plus BD-1063 group did not show full kindling. These findings indicate that opipramol has a pro-convulsant effect, which is possibly mediated through activation of sigma-1 receptors.

The Atkinson cycle provides the potential to increase the efficiency of SI engines using overexpansion concept. This also will suggest decrease in CO2 generation by internal combustion engine. In this study a mathematical modeling of complete thermodynamic cycle of a new two-stroke Atkinson cycle SI engine will be presented. The mathematical modeling is carried out using two-zone combustion analysis in order to make the model predict exhaust emission so that its values could be compared with the values of conventional SI engine. The model also is validated against experimental tests in that increase in efficiency is achieved compared to conventional SI engines.

Acute pancreatitis (AP) causes morbidity and mortality. The aim of the present study was to investigate the protective effect of tropisetron against AP induced by cerulein. Cerulein (50μg/kg, 5 doses) was used to induce AP in mice. Six hours after final cerulein injection, animals were decapitated. Hepatic/pancreatic enzymes in the serum, pancreatic content of malondialdehyde (MDA), pro-inflammatory cytokines and myeloperoxidase (MPO) activity were measured. Tropisetron significantly attenuated pancreatic injury markers and decreased the amount of elevated serum amylase, lipase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), MPO activities and pro-inflammatory cytokines levels caused by AP in mice. Tropisetron didn't affect the pancreatic levels of MDA. Our results suggest that tropisetron could attenuate cerulein-induced AP by combating inflammatory signaling. Further clinical studies are needed to confirm its efficacy in patients with AP.

Inflammatory bowel disease (IBD) is a chronic inflammation of the gastrointestinal (GI) tract. Tropisetron, a selective 5-HT3 receptor antagonist, is highly used to counteract chemotherapy-induced emesis. Previous studies revealed the anti-inflammatory properties of this drug. The aim of this study was to evaluate the role of peroxisome proliferator-activated receptor gamma (PPARγ) receptor in the protective effect of tropisetron in an animal model of ulcerative colitis. Experimental colitis was induced by a single intra-colonic instillation of 4% (V/V) acetic acid in male rats. Tropisetron (3 mg/kg) and GW9662 (PPARγ antagonist) (5 mg/kg) were given twice daily for 2 days after colitis induction. Forty-eight hours after induction of colitis, colon was removed and macroscopic and microscopic features were given. Moreover, colonic concentrations of malondialdehyde (MDA), nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) levels, myeloperoxidase (MPO), and PPARγ activity were assessed. Both macroscopic and histopathological features of colonic injury were markedly ameliorated by tropisetron. Likewise, levels of NO, MDA, TNF-α, and IL-1β diminished significantly (p

At high altitudes, power of an internal combustion engine reduces due to air density reduction. In turbocharged diesel engine this issue affects the performance of the compressor and can result in unstable operation of the turbocharger if the power is not decreased by engine actuator. Mainly for testing the effects of altitude in the test room, air throttle valve and combustion air handling unit were used to reduce the suction air pressure. Easier and cheaper solution to consider effect of altitude on engine performance is to mask part of the air filter to reduce the suction pressure. In this paper, pressure drop against 0%, 26%, 52%, 66% and 74% of air filter hole’s masking for different mass flow rates has been studied by computational fluid dynamics. The analysis output mass flow rate-pressure diagram for the air filter, will be used as input data in the GT-Power software which is a one-dimensional computational fluid dynamics software and the effect of masking on altitude and performance at different revolutions per minute of the engine is investigated. Also, an experimental and computational fluid dynamics study was carried out to predict altitude against different proportions of air filter hole’s masking at 1000 rpm. The predicted results are validated by comparing with those of experimental data. A good agreement between the predicted and experimental values ensures the accuracy of the numerical predictions with the present work.

Background: The level of serum uric acid, as an important endogenous antioxidant, may be correlated to the different phases of mood disorders. Objectives: The aim of this study was to compare serum uric acid levels before and after treatment in patients with acute mania and depression. Patients and Methods: We measured serum uric acid in 33 manic and 10 depressed hospitalized patients, both before and after treatment. Mood disorder was diagnosed according to the DSM-IV criteria. Manic or depressive scores were measured with the Young Mania Rating Scale or the Hamilton Depression Rating Scale, respectively. Uric acid levels were compared in the acute and remission phases of the mood disorder, and the relationship of uric acid levels with the onset of response was analyzed. Results: Serum uric acid levels were increased after bipolar disorder treatment. Serum uric acid levels were increased after bipolar disorder treatment. Moreover, depressed patients with lower uric acid levels had a faster onset of response. The uric acid levels in the acute mania patients were higher than in the acute depression patients. Conclusions: The remission phase, in comparison to acute mania or depression, had higher levels of uric acid. Moreover, lower serum uric acid may correlate to a faster response in depressed patients. These results may support the roles of the purinergic system and of oxidative stress in the treatment of mood disorders.

In this paper, a discrete-time piecewise affine (PWA) model has been proposed for a nonlinear model of boiler–turbine unit using plant operating points. PWA model is one of the main classes of hybrid systems being equivalent to some other hybrid modeling frameworks such as mixed logical dynamical (MLD) model. In order to control the system, a model predictive control (MPC) strategy in explicit form has been used which calculates the control law as an affine function of system states. In this method, the computation of MPC is moved off-line. The off-line control law is easier to implement reducing to a look-up table in comparison with the on-line approach. Finally, the explicit model predictive control performance has been compared with the linear controller obtained using H∞ approach. The results are illustrated by simulations. They show that the explicit MPC method has suitably improved the system performance, especially the quantity of control efforts is smaller and without saturation compared with that of H∞ control system.

The purpose of this study is to investigate the effect of injection parameters on a heavy duty diesel engine performance and emission characteristics. In order to analyze the injection and spray characteristics of diesel fuel with employing high-pressure common-rail injection system, the injection characteristics such as injection delay, injection duration, and injection rate and number of nozzle holes were investigated by using a quasi-dimensional model. In the present work, the variety of injection rate is performed at various injection parameters where as performance and emission of the engine will be simulated subsequently. Finally the best injection system for a high efficiency and low NO x emission heavy duty diesel engine was investigated.

HCCI is considered a very promising solution to reduce engine pollutant emissions, however so far only experimental prototypes have been inspired by this concept. HCCI combustion of both DME and n -heptane fuels display a distinct two-stage ignition reaction with the first stage taking place at fairly low temperatures and the second stage taking place at high temperatures. The second stage is responsible for the main stage of the heat release process. In this study, a single-zone, zero-dimensional, thermo-kinetic combustion model has been developed. MATLAB software is used to predict engine performance characteristics of HCCI engines using two types of diesel fuel: Dimethyl ether and n -heptane. The effects of intake temperature and pressure, fuel loading and addition of EGR gases on auto-ignition characteristics, optimum combustion phasing, and performance of the HCCI engines are considered in this study.

Objective(s): The neuroprotective effect of lithium has been attributed to its therapeutic action. However, the role of glial cells particularly astrocytes, and the possible interactions between neurons and astrocytes in neuroprotective effects of lithium have been disregarded. Thus, the aim of this study was to evaluate the direct effects of lithium on brain derived neurotrophic factor (BDNF) and glial cell line derived neurotrophic factor (GDNF) in rat primary neuronal, astrocytes, and mixed neuro-astroglial cultures to assess the possible effects of lithium on astrocytes and neuro-astroglia interactions. Materials and Methods: Rat primary astrocyte, neuronal and mixed neuro-astrocyte cultures were prepared from cortices of 18-day embryos. Cell cultures were exposed to lithium (1 mM) or vehicle for 1 day (acute) or 7 days (chronic). BDNF and GDNF mRNA and protein levels were determined by RT-PCR and ELISA, respectively. Results: Chronic but not acute lithium treatment increased intracellular BDNF and GDNF protein levels in rat primary neuronal and astrocyte cultures, respectively (P

Genetic polymorphism of CYP2A6 gene is a major causal factor in the large interindividual differences in nicotine metabolism. It may have an impact on smoking behavior and smoke-related cancer susceptibility. Until now, there are no reports of CYP2A6 allele frequencies in Iranian population.In the present study, we investigated the frequencies of CYP2A6 alleles in 250 male Iranians. CYP2A6*2, CYP2A6*4, CYP2A6*9, and CYP2A6*12 were determined by allele-specific polymerase chain reaction.Frequencies of *2, *4, *9, and *12 alleles were 2.2%, 0.95%, 12.4%, and 1.34%, respectively.These results showed that the distribution of CYP2A6 alleles in Iranian population was different from those reported previously for other ethnic groups. This highlights the importance of conducting further studies to investigate the implications on smoking dependence and cancer in Iranians.

Knock is well recognized as a destructive phenomenon to be avoided when running dual fuel engines. Typically, it occurs at high loads and high ambient temperatures and its onset has always been difficult to predict, particularly where multiple fuels are present. In a dual fuel engine, knock can occur from either the diesel or the gaseous fuel and it is recognised that the ratio of diesel fuel mass to gaseous fuel mass is an important index in determining which type of knock is predominant. This paper describes the development of a two-zone predictive model for the onset of knock in a dual fuel engine. Prediction of spark knock onset is the main objective of present work. A 9-step short mechanism with 11 chemical species, developed specifically for modelling dual fuel operation, is used to determine the chemical reactivity of the end-gas zone. The contribution of pilot diesel fuel combustion is taken into account by a heat release model. Chemical equilibrium is assumed for the burned gas zone. Simulation results predict the point of knock-limited BMEP and its dependency on operating parameters such as air intake temperature, boost pressure, start of pilot fuel injection timing and compression ratio. The results were first validated against some published engine analysis data and also some in-house performance prediction data. Secondly, a known dual-fuel development engine was simulated. Finally, the performance of an engine which had been converted from diesel to dual fuel during its service life was modeled but commercial constraints prevent the identification of this engine within this paper. However, good agreement with existing performance data was demonstrated in all these cases.

HCCI engines have low emission and high efficiency values compared to the conventional internal combustion engines. These engines can operate on most alternative fuels such as dimethyl ether (DME), which has been tested as a possible diesel fuel for its simultaneously reduced NOx and PM emissions. HCCI combustion of both DME and n-heptane fuels display a distinct two-stage ignition reaction with the first stage taking place at fairly low temperatures and the second stage taking place at high temperatures. The second stage is responsible for the main stage of the heat release process. In this study, a single-zone, zero-dimensional, thermo-kinetic combustion model has been developed. MATLAB software is used to predict engine performance characteristics of HCCI engines using two types of diesel fuel: Dimethyl ether and N-heptane. The effects of intake temperature and pressure, fuel loading and addition of EGR gases on auto-ignition characteristics, optimum combustion phasing, and performance of the HCCI engines are considered in this study. Simultaneous effects of these variables for finding the most appropriate regime of HCCI engine operation, considering knock and misfire boundaries, are also investigated.Copyright © 2008 by ASME

Homogenous Charge Compression Ignition (HCCI) is a mode of combustion in IC engines in which premixed fuel and air is ignited spontaneously. There is a belief that there is a great potential to improve fuel consumption and reduce NOx emissions using HCCI. In this study, a single zone, zero dimensional, thermo-kinetic model has been developed and a computer program with MATLAB software is used to predict engine performance characteristics. This model has been used to predict the principal parameters of controlling auto-ignition to acceptable level and this work leads to achieving the working region with two limitations for knock and misfire. The cycle is simulated with premixed blend of methane and DME with air. To highlight the importance of using HCCI engines instead of conventional diesel engines, an ISO continuous operation cycle (COP) and prime power cycle (PRP) has been investigated. Also NOx level are compared in a diesel engine working as a conventional diesel and in HCCI mode.Copyright © 2006 by ASME