Extension of moment projection method to the fragmentation process

© 2017 Elsevier Inc. The method of moments is a simple but efficient method of solving the population balance equation which describes particle dynamics. Recently, the moment projection method (MPM) was proposed and validated for particle inception, coagulation, growth and, more importantly, shrinkage; here the method is extended to include the fragmentation process. The performance of MPM is tested for 13 different test cases for different fragmentation kernels, fragment distribution functions and initial conditions. Comparisons are made with the quadrature method of moments (QMOM), hybrid method of moments (HMOM) and a high-precision stochastic solution calculated using the established direct simulation algorithm (DSA) and advantages of MPM are drawn

Modelling of soot formation in a diesel engine with the moment projection method

© 2017 The Author(s). In this work, the recently developed moment projection method (MPM) is coupled with the Stochastic Reactor Model engine code to simulate the formation of soot in a direct injection diesel engine. The simulations take into account convective heat transfer, turbulent mixing, and adopts a detailed chemical mechanism so that the concentrations of soot precursors can be predicted. The soot model considered in this work is based on integration and modification of existing sub-models for soot inception, coagulation, condensation, surface growth and oxidation. The soot moment equations are solved using MPM which has been proven to be accurate and robust. A single-cylinder research version of the Great Wall 4D20 diesel engine with exhaust gas recirculation is modelled for two test cases with different injection timings, injection pressures and fuel consumptions. Simulations are fast (on the order of minutes) and comparison of computed and experimental pressure and heat release rate are in excellent agreement. The amount of soot produced is in qualitative agreement with measurements of diesel smoke opacity.This research is supported by the National Research Foundation, Prime Minister’s office, Singapore under its CREATE programme

A moment projection method for population balance dynamics with a shrinkage term

A new method of moments for solving the population balance equation is developed and presented. The moment projection method (MPM) is numerically simple and easy to implement and attempts to address the challenge of particle shrinkage due to processes such as oxidation, evaporation or dissolution. It directly solves the moment transport equation for the moments and tracks the number of the smallest particles using the algorithm by Blumstein and Wheeler (1973) [41]. The performance of the new method is measured against the method of moments (MOM) and the hybrid method of moments (HMOM). The results suggest that MPM performs much better than MOM and HMOM where shrinkage is dominant. The new method predicts mean quantities which are almost as accurate as a high-precision stochastic method calculated using the established direct simulation algorithm (DSA).This research is supported by the National Research Foundation, Prime Minister's Office, Singapore under its CREATE programme

Long-term follow-up in a randomised controlled trial of recombinant α2-interferon in Chinese patients with chronic hepatitis B infection

72 Chinese patients who had been positive for hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) for more than six months with stable serum hepatitis B virus DNA were randomised to receive recombinant α2-interferon at doses of 2.5, 5, or 10 x 106 U/m2 intramuscularly thrice weekly for 12-24 weeks, or no treatment. 6 (11%) of 54 treated and 1 (6%) of 18 control patients became HBeAg-negative at the end of therapy or after 24 weeks of follow-up. 9 (17%) of treated but none of the control patients became HBeAg-negative between completion of therapy and 12 months. Reactivation of HBV replication subsequently occurred in 7 (13%) of the treated patients and in 1 control. Thus, sustained clearance of HBeAg was achieved only in 8 (15%) of treated patients at 12 months. Between 12 and 24 months 3 (9%) of treated patients and 1 control became negative for HBeAg. None of the patients became HBsAg-negative. α2-interferon in the dose regimen used has little long-term effect in the suppression of HBV replication in Chinese patients with chronic HBV infection.link_to_subscribed_fulltex

Origin of triangular island shape and double-step bunching during GaN growth by molecular-beam epitaxy under excess Ga conditions

GaN homoepitaxial growth by molecular-beam epitaxy under both excess gallium (Ga) and excess nitrogen (N) conditions is investigated. Based on two-dimensional island shape and surface step structures, we suggest the growth is kinetic-limited under the excess-Ga condition but diffusion-limited in the excess-N regime. The triangular GaN islands and double step bunching seen on surfaces prepared under excess-Ga are attributed to a difference in adatom attachment and/or site exchange rates between A and B steps, which is induced by surfactant Ga adlayers on GaN(0001). © 2006 The American Physical Society.link_to_subscribed_fulltex

A new role for cathelicidin in ulcerative colitis in mice

Cathelicidin, an antimicrobial peptide of the innate immune system, modulates microbial growth, wound healing, and inflammation. However, its association with inflammatory bowel diseases (IBDs) is unknown. Our objective was to determine whether cathelicidin would exert a modulatory effect on the progression of IBD and, if so, investigate the mechanism of action through which this effect occurred. We evaluated the potential for a synthetic cathelicidin, the mouse cathelin-related antimicrobial peptide (mCRAMP), to prevent the initiation and promote the healing of lesions from inflammatory colitis that was experimentally induced in mice with dextran sulfate sodium (DSS). During the experiment, mCRAMP was given: (i) as a parallel treatment starting together with 3% DSS feeding, and (ii) as a posttreatment starting 7 days after 3% DSS feeding. The body weight, fecal microflora populations, clinical symptoms, and histologic findings of colonic tissues were measured. Relative gene expression of mucins (MUC1, MUC2, MUC3, and MUC4) in colonic tissues was determined by real-time polymerase chain reaction. Intrarectal administration of mCRAMP ameliorated DSS-induced colitis with negligible effects on mucosal healing. The peptide also significantly reduced the increased number of fecal microflora in colitis animals. It reversed the decline of colonic mucus thickness during colitis through upregulation of the expression of mucin genes. Treatment with mCRAMP also prevented colitis development by suppressing the induction of apoptosis by DSS. The current study demonstrates for the first time that intrarectal administration of cathelicidin may be a novel therapeutic option for IBDs. Copyright © 2007 by the Society for Experimental Biology and Medicine.link_to_subscribed_fulltex

Nicotine promotes colon tumor growth and angiogenesis through β-adrenergic activation

Cigarette smoking is a putative environmental risk factor for colon cancer. Nicotine, an active alkaloid in tobacco, has been implicated in carcinogenesis. In the present study, we demonstrated that oral nicotine administration (50 or 200 μg/ml) for 25 days stimulated growth of human colon cancer xenograft in nude mice. It also increased vascularization in the tumors and elevated cotinine and adrenaline plasma levels. β-Adrenoceptors, cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), and vascular endothelial growth factor (VEGF) in tumor tissues were also increased by nicotine. I.p. injection of β1-selective antagonist (atenolol, 5 or 10 mg/kg) or β2-selective antagonist (ICI 118,551, 5, or 10 mg/kg) blocked the nicotine-stimulated tumor growth dose dependently, in which β2-selective antagonist produced a more prominent effect. β-Adrenoceptors blockade also abrogated the stimulatory action of nicotine on microvessel densities as well as cell expression of COX-2, PGE2, and VEGF, in which β2-selective antagonist produced a significant effect. These findings provide a direct evidence that nicotine can enhance colon tumor growth mediated partly by stimulation of β-adrenoceptors, preferentially the β2-adrenoceptors. Activation of β-adrenoceptors and the subsequent stimulation of COX-2, PGE2, and VEGF expression is perhaps an important mechanism in the tumorigenic action of nicotine on colon tumor growth. These data suggest that β-adrenoceptors play a modulatory role in the development of colon cancer and partly elucidate the carcinogenic action of cigarette smoke. © The Author 2007. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved.link_to_subscribed_fulltex

Nicotine promotes cell proliferation via α7-nicotinic acetylcholine receptor and catecholamine-synthesizing enzymes-mediated pathway in human colon adenocarcinoma HT-29 cells

Cigarette smoking has been implicated in colon cancer. Nicotine is a major alkaloid in cigarette smoke. In the present study, we showed that nicotine stimulated HT-29 cell proliferation and adrenaline production in a dose-dependent manner. The stimulatory action of nicotine was reversed by atenolol and ICI 118,551, a β1- and β2-selective antagonist, respectively, suggesting the role of β-adrenoceptors in mediating the action. Nicotine also significantly upregulated the expression of the catecholamine-synthesizing enzymes [tyrosine hydroxylase (TH), dopamine-β-hydroxylase (DβH) and phenylethanolamine N-methyltransferase]. Inhibitor of TH, a rate-limiting enzyme in the catecholamine-biosynthesis pathway, reduced the actions of nicotine on cell proliferation and adrenaline production. Expression of α7-nicotinic acetylcholine receptor (α7-nAChR) was demonstrated in HT-29 cells. Methyllycaconitine, an α7-nAChR antagonist, reversed the stimulatory actions of nicotine on cell proliferation, TH and DβH expression as well as adrenaline production. Taken together, through the action on α7-nAChR nicotine stimulates HT-29 cell proliferation via the upregulation of the catecholamine-synthesis pathway and ultimately adrenaline production and β-adrenergic activation. These data reveal the contributory role α7-nAChR and β-adrenoceptors in the tumorigenesis of colon cancer cells and partly elucidate the carcinogenic action of cigarette smoke on colon cancer. © 2007 Elsevier Inc. All rights reserved.link_to_subscribed_fulltex

α-Interferon treatment in Chinese patients with chronic hepatitis B

α-Interferon has been shown to be the most promising antiviral agent in the treatment of chronic hepatitis B virus infection in Caucasian patients. The experience with recombinant interferon alfa-2a and alfa-2b in four randomized controlled trials in Chinese adults and children is reviewed here. α-Interferon alone has little long-term benefit in the treatment of Chinese patients with chronic hepatitis B virus infection, especially in patients who have normal or near normal serum aminotransferase levels. The response in patients with elevated aminotransferase levels appears to be better. The poor antiviral response in patients with normal aminotransferase levels is probably due to immunological tolerance to HBV induced by exposure to the virus in early life. Prednisone pretreatment does not seem to have any additional benefit to using interferon alone in these patients, while the effect in patients with elevated aminotransferase levels remains to be proven.link_to_subscribed_fulltex

Erratum: Shift of homeostasis from parenchymal regeneration to fibroblast proliferation induced by lipopolysaccharide-activated macrophages in gastric mucosal healing in vitro (Wound Repair and Regeneration (March/April 2007) 15, 2, (221))

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