bluuebunny/crossref_metadata_2025 huggingface dataset:
A Numerical Simulation of Analysis of Backfiring Phenomena in a Hydrogen-Fueled Spark Ignition Engine
Authors: Subramanian K. A. , Salvi B. L.
Published: March 2016

Hydrogen utilization in spark ignition (SI) engines could reduce urban pollution including particulate matter as well as greenhouse gas emission. However, backfiring, which is an undesirable combustion process of intake charge in hydrogen-fueled SI engine with manifold-based injection, is one of the major technical issues in view of safety of engine operation. Backfiring occurs generally during suction stroke as the hydrogen–air charge interacts with residual gas, resulting in flame growth and propagation toward upstream of engine's intake manifold, resulting in stalling of engine operation and high risk of safety. This work is aimed at analysis of backfiring in a hydrogen-fueled SI engine. The results indicate that backfiring is mainly function of residual gas temperature, start of hydrogen injection timing, and equivalence ratio. Any hot-spot present in the cylinder would act as ignition source resulting in more chances of backfiring. In addition to this, computational fluid dynamics (CFD) analysis was carried out in order to assess flow characteristics of hydrogen and air during suction stroke in intake manifold. Furthermore, numerical analysis of intake charge velocity, flame speed (deflagration), and flame propagation (backfiring) toward upstream of intake manifold was also carried out. Some notable points of backfiring control strategy including exhaust gas recirculation (EGR) and retarded (late) hydrogen injection timing are emerged from this study for minimizing chance of backfiring. This study results are useful for development of dedicated SI engine for hydrogen fuel in the aspects of elimination of backfiring.
Engine
Capability Prediction for Spark Ignited Engine Fueled With
Syngas
Authors: Xu Hui , LaPointe Leon
A.
Published: March 2016

There are increasing interests in converting solid waste or lignocellulosic biomass into gaseous fuels and using reciprocating internal combustion engine to generate electricity. A widely used technique is gasification. Gasification is a process where the solid fuel and air are introduced to a partial oxidation environment, and generate combustible gaseous called synthesis gas or syngas. Converting solid waste into gaseous fuel can reduce landfill and create income for process owners. However, it can be very challenging to use syngas on a gaseous fueled spark ignited (SI) engine, such as a natural gas (NG) engine. NG engines are typically developed with pipeline quality natural gas (PQNG). NG engines can operate at lean burn spark ignited (LBSI), or stoichiometric with exhaust gas recirculation (EGR) spark ignited (SESI) conditions. This work discusses the LBSI engine condition. NG engines can perform very differently when fueled with nonstandard gaseous fuels such as syngas without appropriate tuning. It is necessary to evaluate engine performance in terms of combustion duration, relative knock propensity, and NOx emissions for such applications. Due to constraints in time and resources it is often not feasible to test such fuel blends in the laboratory. An analytical method is needed to predict engine performance in a timely manner. This study investigated the possibility of using syngas on an SI engine developed with PQNG. Engine performance was predicted using in house developed models and PQNG as the reference fuel. Laminar flame speed (LFS), adiabatic flame temperature (AFT), and auto-ignition interval (AI) are used to predict combustion duration, engine out NOx and engine knock propensity relative to NG at the target lambda values. Single cylinder research engine data obtained under lean burn conditions fueled with PQNG was selected as the baseline. LFS, AFT, and AI of syngas were computed at reference conditions. Lambda of operation was predicted for syngas to provide the same burn rate as NG at the reference lambda value for NG. Analysis shows that, using syngas at the selected lambda, the engine can have less engine out NOx emissions and less knock propensity relative to NG at the same speed and load. Modifications to fuel system components may be required to avoid engine derate.
Impact of Compressor Surge on Performance and Emissions of a Marine Diesel Engine
Authors: Vrettakos Nikolaos-Alexandros
Published: March 2016

The operation during compressor surge of a medium speed marine diesel engine was examined on a test bed. The compressor of the engine's turbocharger was forced to operate beyond the surge line, by injecting compressed air at the engine intake manifold, downstream of the compressor during steady-state engine operation. While the compressor was surging, detailed measurements of turbocharger and engine performance parameters were conducted. The measurements included the use of constant temperature anemometry for the accurate measurement of air velocity fluctuations at the compressor inlet during the surge cycles. Measurements also covered engine performance parameters such as in-cylinder pressure and the impact of compressor surge on the composition of the exhaust gas emitted from the engine. The measurements describe in detail the response of a marine diesel engine to variations caused by compressor surge. The results show that both turbocharger and engine performance are affected by compressor surge and fast Fourier transform (FFT) analysis proved that they oscillate at the same main frequency. Also, prolonged steady-state operation of the engine with this form of compressor surge led to a non-negligible increase of NOx emissions.
Evaluation of Tribological Properties of Organoclay Reinforced UHMWPE Nanocomposites
Authors: Mohammed Abdul Samad , Ali Annas bin , Nesar Merah
Published: March 2016

The current study is aimed to investigate the tribological properties of ultrahigh molecular weight polyethylene (UHMWPE) reinforced with organoclay Cloisite (C15A). Nanocomposites are prepared using a high energy ball milling process followed by hot pressing. Three different loadings of 0.5 wt.%, 1.5 wt.%, and 3 wt.% of C15A, respectively, are used as reinforcement. Results from the ball-on-disk wear tests showed that nanocomposites reinforced with 1.5 wt.% of C15A exhibited best wear resistance and lower coefficient of friction (COF), with C15A reducing the wear rate by 41% and the COF by 38%, when compared to the pristine UHMWPE. These improvements are attributed to the uniform dispersion of the nanosized clay platelets preventing large-scale material removal and formation of a thin tenacious, continuous transfer film on the counterface for C15A organoclay composites. X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical profilometry are used to characterize the morphology of the nanocomposites and the wear tracks. SEM images of worn surfaces indicated more abrasive wear for the case of pristine UHMWPE as compared to organoclay composites.
In Situ Synthesis of Fe–TiC Nanocomposite Coating on CK45 Steel From Ilmenite Concentrate by Plasma-Spray Method
Authors: Firouzbakht Alireza , Razavi Mansour , Rahimipour Mohammad Reza
Published: March 2016

These days wear-resistant coatings including Fe–TiC composites because of their properties such as high melting point, hardness, and wear resistance are used in different fields such as aerospace, transport, cutting, and abrasive. In situ synthesis of Fe–TiC nanocomposite as a wear-resistant coating by the plasma-spray process is the purpose of this study. Ilmenite concentrate and carbon black were used as raw materials. Three kinds of powders with different conditions were prepared and sprayed on CK45 steel substrates in constant conditions. Microstructure, phase identification, wear resistance, and hardness of coated samples were determined. The results showed that activated sample was synthesized during the plasma spray, but in situ synthesize did not happen for inactive sample which was sprayed by plasma spray. Also, wear resistance and hardness tests showed by synthesis of Fe–TiC composite in coated samples, wear resistance, and hardness were increased.
Experimental quantification of the true efficiency of carbon nanotube thin-film thermophones
Authors: Bouman Troy M. , Barnard Andrew R. , Asgarisabet Mahsa
Published: March 2016

Carbon nanotube thermophones can create acoustic waves from 1 Hz to 100 kHz. The thermoacoustic effect that allows for this non-vibrating sound source is naturally inefficient. Prior efforts have not explored their true efficiency (i.e., the ratio of the total acoustic power to the electrical input power). All previous works have used the ratio of sound pressure to input electrical power. A method for true power efficiency measurement is shown using a fully anechoic technique. True efficiency data are presented for three different drive signal processing techniques: standard alternating current (AC), direct current added to alternating current (DCAC), and amplitude modulation of an alternating current (AMAC) signal. These signal processing techniques are needed to limit the frequency doubling non-linear effects inherent to carbon nanotube thermophones. Each type of processing affects the true efficiency differently. Using a 72 Wrms input signal, the measured efficiency ranges were 4.3 × 10−6 − 319 × 10−6, 1.7 × 10−6 − 308 × 10−6, and 1.2 × 10−6 – 228 × 10−6% for AC, DCAC, and AMAC, respectively. These data were measured in the frequency range of 100 Hz to 10 kHz. In addition, the effects of these processing techniques relative to sound quality are presented in terms of total harmonic distortion.
A Three-Wave Longitudinal Test of Self-Determination Theory’s Mediation Model of Engagement and Disaffection in Youth Sport
Authors: Curran Thomas , Hill Andrew P. , Ntoumanis Nikos , Hall Howard K. , Jowett Gareth E.
Published: March 2016

Research adopting self-determination theory (SDT) supports a mediation model whereby coach motivational styles (autonomy support and interpersonal control) predict athletes’ engagement and disaffection in youth sport via the satisfaction and frustration of psychological needs (autonomy, competence, and relatedness). Our study extends this research by examining SDT’s mediation model longitudinally with three waves of data. Two hundred fifty-two youth sports participants (Mage = 12.98; SD = 1.84; range = 11–17; female n = 67) completed measures of study variables at the start, middle, and end of a competitive soccer season. Cross-lagged path analyses revealed that associations between the two coach motivational styles and athletes’ engagement were mediated by psychological need satisfaction. Furthermore, a positive reciprocal association between psychological need satisfaction and engagement emerged over time. This study therefore supports the temporal assumptions underpinning SDT’s mediation model but, importantly, evidences a mutually reinforcing interplay between athletes’ psychological needs and their engaged behavior.
Controlling Coaching Behaviors and Athlete Burnout: Investigating the Mediating Roles of Perfectionism and Motivation
Authors: Barcza-Renner Kelly , Eklund Robert C. , Morin Alexandre J.S. , Habeeb Christine M.
Published: March 2016

This investigation sought to replicate and extend earlier studies of athlete burnout by examining athlete-perceived controlling coaching behaviors and athlete perfectionism variables as, respectively, environmental and dispositional antecedents of athlete motivation and burnout. Data obtained from NCAA Division I swimmers (n = 487) within 3 weeks of conference championship meets were analyzed for this report. Significant indirect effects were observed between controlling coaching behaviors and burnout through athlete perfectionism (i.e., socially prescribed, self-oriented) and motivation (i.e., autonomous, amotivation). Controlling coaching behaviors predicted athlete perfectionism. In turn, self-oriented perfectionism was positively associated with autonomous motivation and negatively associated with amotivation, while socially prescribed perfectionism was negatively associated with autonomous motivation and positively associated with controlled motivation and amotivation. Autonomous motivation and amotivation, in turn, predicted athlete burnout in expected directions. These findings implicate controlling coaching behaviors as potentially contributing to athlete perfectionism, shaping athlete motivational regulations, and possibly increasing athlete burnout.
The Effects of High- and Low-Anxiety Training on the Anticipation Judgments of Elite Performers
Authors: Alder David , Ford Paul R. , Causer Joe , Williams A. Mark
Published: March 2016

We examined the effects of high- versus low-anxiety conditions during video-based training of anticipation judgments using international-level badminton players facing serves and the transfer to high-anxiety and field-based conditions. Players were assigned to a high-anxiety training (HA), low-anxiety training (LA) or control group (CON) in a pretraining–posttest design. In the pre- and posttest, players anticipated serves from video and on court under high- and low-anxiety conditions. In the video-based high-anxiety pretest, anticipation response accuracy was lower and final fixations shorter when compared with the low-anxiety pretest. In the low-anxiety posttest, HA and LA demonstrated greater accuracy of judgments and longer final fixations compared with pretest and CON. In the high-anxiety posttest, HA maintained accuracy when compared with the low-anxiety posttest, whereas LA had lower accuracy. In the on-court posttest, the training groups demonstrated greater accuracy of judgments compared with the pretest and CON.
Number of Years of Team and Individual Sport Participation During Adolescence and Depressive Symptoms in Early Adulthood
Authors: Sabiston Catherine M. , Jewett Rachel , Ashdown-Franks Garcia , Belanger Mathieu , Brunet Jennifer , O’Loughlin Erin , O’Loughlin Jennifer
Published: March 2016

The purpose of this study was to examine the longitudinal and unique association between number of years of team sport and individual sport participation during adolescence and depressive symptoms during early adulthood. Adolescents (n = 860) reported team sport and individual sport participation in each year of secondary school for five years. Participants reported depressive symptoms using the Major Depression Inventory three years after secondary school. Multivariate linear regression was performed to model the associations of sport participation with depressive symptoms while controlling for sex, age, parent education, and baseline depressive symptoms. In the final model, adolescents who consistently participated in team sport during high school reported lower depression scores in early adulthood (β = −.09, p = .02). Number of years of individual sport participation was not statistically significantly associated with depressive symptoms in early adulthood. Based on these findings, team sport participation may protect against depressive symptoms in early adulthood. If this finding is replicated, strategies should be implemented to encourage and maintain team sport participation during adolescence. Further research is needed to understand the mechanisms that link team sport participation to lower depression.
Predicting Sport Experience During Training: The Role of Change-Oriented Feedback in Athletes’ Motivation, Self-Confidence and Needs Satisfaction Fluctuations
Authors: Carpentier Joëlle , Mageau Geneviève A.
Published: March 2016

Change-oriented feedback (COF) quality is predictive of between-athletes differences in their sport experience (Carpentier & Mageau, 2013). This study extends these findings by investigating how training-to-training variations in COF quality influence athletes’ training experience (within-athlete differences) while controlling for the impact of promotion-oriented feedback (POF). In total, 49 athletes completed a diary after 15 consecutive training sessions to assess COF and POF received during training, as well as situational outcomes. Multivariate multilevel analyses showed that, when controlling for covariates, COF quality during a specific training session is positively linked to athletes’ autonomous motivation, self-confidence and satisfaction of their psychological needs for autonomy and relatedness during the same session. In contrast, COF quantity is negatively linked to athletes’ need for competence. POF quality is a significant positive predictor of athletes’ self-confidence and needs for autonomy and competence. Contributions to the feedback and SDT literature, and for coaches’ training, are discussed.
Error Detection Is Critical for Visual-Motor Corrections
Authors: Sainburg Robert L. , Mutha Pratik K.
Published: March 2016

The target article (Smeets, Oostwoud Wijdenes, & Brenner, 2016) proposes that short latency responses to changes in target location during reaching reflect an unconscious, continuous, and incremental minimization of the distance between the hand and the target, which does not require detection of the change in target location. We, instead, propose that short-latency visuomotor responses invoke reflex- or startle-like mechanisms, an idea supported by evidence that such responses are both automatic and resistant to cognitive influences. In addition, the target article fails to address the biological underpinnings for the range of response latencies reported across the literature, including the circuits that might underlie the proposed sensorimotor loops. When considering the range of latencies reported in the literature, we propose that mechanisms grounded in neurophysiology should be more informative than the simple information processing perspective adopted by the target article.
l-glutamine and l-alanine supplementation increase glutamine-glutathione axis and muscle HSP-27 in rats trained using a progressive high-intensity resistance exercise
Authors: Leite Jaqueline Santos Moreira , Raizel Raquel , Hypólito Thaís Menezes , Rosa Thiago dos Santos , Cruzat Vinicius Fernandes , Tirapegui Julio
Published: March 2016

In this study we investigated the chronic effects of oral l-glutamine and l-alanine supplementation, either in their free or dipeptide form, on glutamine-glutathione (GLN-GSH) axis and cytoprotection mediated by HSP-27 in rats submitted to resistance exercise (RE). Forty Wistar rats were distributed into 5 groups: sedentary; trained (CTRL); and trained supplemented with l-alanyl-l-glutamine, l-glutamine and l-alanine in their free form (GLN+ALA), or free l-alanine (ALA). All trained animals were submitted to a 6-week ladder-climbing protocol. Supplementations were offered in a 4% drinking water solution for 21 days prior to euthanasia. Plasma glutamine, creatine kinase (CK), myoglobin (MYO), and erythrocyte concentration of reduced GSH and glutathione disulfide (GSSG) were measured. In tibialis anterior skeletal muscle, GLN-GSH axis, thiobarbituric acid reactive substances (TBARS), and the expression of heat shock factor 1 (HSF-1), 27-kDa heat shock protein (HSP-27), and glutamine synthetase were determined. In CRTL animals, high-intensity RE reduced muscle glutamine levels and increased GSSG/GSH rate and TBARS, as well as augmented plasma CK and MYO levels. Conversely, l-glutamine–supplemented animals showed an increase in plasma and muscle levels of glutamine, with a reduction in GSSG/GSH rate, TBARS, and CK. Free l-alanine administration increased plasma glutamine concentration and lowered muscle TBARS. HSF-1 and HSP-27 were high in all supplemented groups when compared with CTRL (p < 0.05). The results presented herein demonstrate that l-glutamine supplemented with l-alanine, in both a free or dipeptide form, improve the GLN-GSH axis and promote cytoprotective effects in rats submitted to high-intensity RE training.
An optimizing process of profiled cross-sectional aluminum alloy porthole die extrusion using response surface methodology
Authors: Zhou Fujian , Li Feng , Shi Liansheng , Jiang Hongwei
Published: March 2016

The porthole die extrusion process of profiled cross-section hollow aluminum alloy is influenced by numerous factors, which brings inconvenience to the process design. In this paper, 7075 aluminum alloy is taken as an example, the fitting model of the ultimate load is analyzed by variance and regression analysis using response surface method (RSM). The influences of extrusion speed, friction factor and initial temperature on the change of extruded ultimate load are investigated systematically, and the important influence factors (initial temperature [Formula: see text] friction factor [Formula: see text] extrusion speed) to the load are determined eventually. By comparison, the error between the ultimate load model obtained after fitting and the calculated value is only 2.4%, further verifying the reliability of this model. The optimal objective is to minimize the ultimate load, then the optimum technological parameters are obtained by optimizing the process, where the initial temperature, the extrusion speed and the friction factor are 430[Formula: see text]C, 2.28[Formula: see text]mm/s and 0.31, respectively. The results provide a theoretical basis for the scientific design of the porthole die extrusion process of profiled cross-section hollow aluminum alloy.
Analytic solutions and Darboux transformation to a new Hamiltonian lattice hierarchy
Authors: Tian Shou-Fu , Zhou Fu-Bao , Zhou Sheng-Wu , Zhang Tian-Tian
Published: March 2016

In this paper, a new Hamiltonian lattice hierarchy is analytically investigated, which can be reduced to some classic integrable lattice hierarchies, such as Ablowitz–Ladik hierarchy, Volterra hierarchy and multi-Hamiltonian lattice hierarchy, etc. By choosing the auxiliary problem [Formula: see text], we present a Darboux transformation (DT) to the new discrete matrix spectral problem. As its applications, a series of analytical solutions are generated in a recursive manner. Finally, the graphical analysis of these analytical solutions are presented, respectively. The DT of other lattice hierarchies can be also constructed in this method.
Chaos theory perspective for industry clusters development
Authors: Yu Haiying , Jiang Minghui , Li Chengzhang
Published: March 2016

Industry clusters have outperformed in economic development in most developing countries. The contributions of industrial clusters have been recognized as promotion of regional business and the alleviation of economic and social costs. It is no doubt globalization is rendering clusters in accelerating the competitiveness of economic activities. In accordance, many ideas and concepts involve in illustrating evolution tendency, stimulating the clusters development, meanwhile, avoiding industrial clusters recession. The term chaos theory is introduced to explain inherent relationship of features within industry clusters. A preferred life cycle approach is proposed for industrial cluster recessive theory analysis. Lyapunov exponents and Wolf model are presented for chaotic identification and examination. A case study of Tianjin, China has verified the model effectiveness. The investigations indicate that the approaches outperform in explaining chaos properties in industrial clusters, which demonstrates industrial clusters evolution, solves empirical issues and generates corresponding strategies.
Adsorption and Conformational Evolution of Alpha-Helical BSA Segments on Graphene: A Molecular Dynamics Study
Authors: Yeo Jingjie , Cheng Yuan , Han You Ting , Zhang Yingyan , Guan Guijian , Zhang Yong-Wei
Published: March 2016

Molecular dynamics (MD) simulations are performed to investigate the adsorption mechanics and conformational dynamics of single and multiple bovine serum albumin (BSA) peptide segments on single-layer graphene through analysis of parameters such as the root-mean-square displacements, number of hydrogen bonds, helical content, interaction energies, and motions of mass center of the peptides. It is found that for the single segment system, destabilization of the helical structures in the form of the reduction in hydrogen bond numbers and [Formula: see text]-helical content of the peptides occurred due to the strong interactions between BSA peptides and graphene. Similar destabilizations of the individual segments in the multi-segment system can occur as well, albeit with greater complexity and in a lesser degree due to the inter-segment interactions. Alleviation of decreases in the total helical content in the multi-segment system indicates protective capabilities of segment–segment interactions, which weaken their interactions with graphene. Diffusive motion upon adsorption of the segment(s) onto graphene is found to be highly confined, and the distance traversed by each segment in the multi-segment system was more significant than that in the single segment system, similarly attributable to reductions in their interactions with graphene due to inter-segment interactions.
Power Efficient Hardware Transactional Memory
Authors: Do Sang Wook Stephen , Dubois Michel
Published: March 2016

Transactional Memory (TM) is no longer just an academic interest as industry has started to adopt the idea in its commercial products. In this paper, we propose Dynamic Transaction Issue (DTI), a new scheme that can be easily implemented on top of existing Hardware TM (HTM) systems, provided additional messages. Instead of wasting power and energy in transaction aborts, Dynamic Transaction Issue puts a processor core into a low-power state when there is a reasonable suspicion that the current transaction running on it will be aborted soon in the future.

We have implemented Dynamic Transaction Issue on a cycle-accurate simulator of a multicore processor system with out-of-order superscalar cores, augmented with a power package and a TM package which add accurate dynamic power estimates and a TM framework to the simulator. Our simulation results show that Dynamic Transaction Issue can achieve energy savings up to 37% from the energy consumption of a base machine with no mechanism to suppress useless aborts. We also compare Dynamic Transaction Issue with various alternative hardware TM mechanisms.
Cache-aware real-time scheduling simulator
Authors: Tran Hai Nam , Singhoff Frank , Rubini Stéphane , Boukhobza Jalil
Published: March 2016

Evaluating cache related preemption delay (CRPD) in preemptive scheduling context of Real-Time Embedded System (RTES) stays an open issue despite of its practical importance. Indeed, various parameters should be taken into account such as memory layout, cache utilization, processor utilization, priority assignment and scheduling algorithm. In state-of-the-art work, dependencies amongst those parameters are not investigated with precision because of the lack of scheduling analysis tool taking them into account. In this article, we present a tool to investigate and evaluate scheduling analysis of RTES with cache memory and various scheduling parameters. The work consists in modeling guidelines and implementation of a cache-aware scheduling simulator. Implementation is made in Cheddar, an open-source scheduling analyzer, which is freely available to researchers and practitioners. Experiments are conducted in order to illustrate applicability and performance of our tool. Furthermore, we discuss about implementation issues, problems raised and lessons learned from those experiments.
Exploring storage bottlenecks in Linux-based embedded systems
Authors: Joyce Russell , Audsley Neil
Published: March 2016

With recent advances in non-volatile memory technologies and embedded hardware, large, high-speed persistent-storage devices can now realistically be used in embedded systems. Traditional models of storage systems, including the implementation in the Linux kernel, assume the performance of storage devices to be far slower than CPU and system memory speeds, encouraging extensive caching and buffering over direct access to storage hardware. In an embedded system, however, processing and memory resources are limited while storage hardware can still operate at full speed, causing this balance to shift, and leading to the observation of performance bottlenecks caused by the operating system rather than the speed of storage devices themselves.

In this paper, we present performance and profiling results from high-speed storage devices attached to a Linux-based embedded system, showing that the kernel's standard file I/O operations are inadequate for such a set-up, and that `direct I/O' may be preferable for certain situations. Examination of the results identifies areas where potential improvements may be made in order to reduce CPU load and increase maximum storage throughput.
Endoscopic Pancreatic Stenting in Pancreatic Cancer
Authors: Costamagna Guido , Alevras Petros , Palladino Francesco , Rainoldi Fernando , Mutignani Massimiliano , Morganti Alessio
Published: March 2016

Most pancreatic carcinomas are unresectable at the time of diagnosis; therefore, palliative treatment is very often the main concern of clinicians in this setting. The main symptoms resulting in the need for palliation in pancreatic cancer are obstructive jaundice, duodenal obstruction and pain. Therapeutic endoscopy plays a major role in the palliation of obstructive jaundice by stent placement into the biliary ducts. Initial experience has also been gained recently with endoscopic placement of expandable metallic stents to treat gastric outlet obstruction. Much less is known about the possible role of endoscopic pancreatic stenting in patients with unresectable pancreatic carcinoma. The main indication for pancreatic ductal stenting is ‘obstructive’ pain related to meals in patients with dilated main pancreatic duct beyond the stricture and intraluminal brachyradiotherapy. The technique of endoscopic pancreatic stenting does not substantially differ from that applied on the biliary tree. When technically possible, placement of 10 French plastic stents is preferred. According to the authors’ indications, only about 15% of patients with advanced pancreatic cancer (55 of 355 in the present study) may potentially benefit from this technique. Pancreatic stenting may be obtained in more than 80% of these selected patients, with low morbidity (less than 10%) and no procedure-related mortality. According to the authors of the present and other studies reported in the literature, about 60% of patients treated because of ‘obstructive’ pain become symptom-free, and another 20% to 25% significantly reduce the amount of analgesic drugs required. Intraluminal brachyradiotherapy with 192iridium in the main pancreatic duct is a feasible and safe method to deliver high radiation doses to the tumour while sparing adjacent organs. Brachyradiotherapy may be performed alone or in conjunction with external beam radiotherapy. Because of the small number of patients suitable for this treatment, only a multicentre study will be able to detect whether intraluminal brachyradiotherapy in pancreatic cancer may have any positive impact on survival.
Determinants of Ethnic or Geographical Differences in Infectivity and Transmissibility ofHelicobacter pylori
Authors: Fallone Carlo A
Published: March 2016

The prevalence ofHelicobacter pyloriinfection is variable in different countries. There are two distinct patterns ofH pyloriprevalence with respect to age depending on the geographical region studied. The first pattern is widespread infection early in childhood with elevated prevalence rates of close to 80% throughout adulthood, and the second is increasing prevalence with age. This variability in pattern suggests a difference in infectivity or transmissibility ofH pyloriinfection. Potential determinants of these differences are reviewed including environmental, bacterial and host factors. The most important determinant is likely socioeconomic class, which affects living conditions and sanitation, thus altering exposure to the bacterium. Host factors also play a role, perhaps via host receptors forH pylori. Bacterial factors may also contribute, although compelling evidence is lacking.
Local and Systemic Antibody Responses in Humans withHelicobacter pyloriInfection
Authors: Blanchard Thomas G , Nedrud John G , Czinn Steven J
Published: March 2016

Immunization can prevent or cure an otherwise chronic helicobacter infection in several animal models despite the chronic nature of natural helicobacter infections. Differences in the antigenic specificity of the antibodies may contribute to the protection observed in these experimental animals. The goal of the present study was to compare the local and systemic antibody responses of humans with chronicHelicobacter pyloriinfection with those of an individual with spontaneous resolution of infection to find an immunological correlate of protection. Spontaneous resolution of infection was accompanied by a change in immunoblot profiles. Whereas a broad range ofH pyloriantigens was recognized in chronically infected patients (including the patient who ultimately cleared the infection spontaneously), resolution of infection in the absence of therapeutic agents resulted in the recognition of only several immunodominant antigens. The most dominant antigen was approximately 66 kDa in molecular mass. Immunoblot analysis demonstrated that these antibodies were specific for the structural subunits of the urease enzyme. These studies suggest that the success of antihelicobacter immunization may be due to the ability of vaccination to induce an immune response against antigens that are normally not immunodominant during the course of infection.
Oral Tolerance: A New Tool for the Treatment of Gastrointestinal Inflammatory Disorders and Liver-Directed Gene Therapy
Authors: Ilan Yaron
Published: March 2016

Oral tolerance is a method of downregulating an immune response by feeding antigens. The use of oral tolerance toward adenoviruses and colitis-extracted proteins for long term gene therapy and alleviation of experimental colitis, and the mechanisms of tolerance induction are presented. Adenoviruses are efficient vectors in liver-directed gene therapy; however, the antiviral immune response precludes the ability to achieve long term gene expression and prohibits the ability to reinject the recombinant virus. Oral tolerance induction via feeding of viral-extracted proteins prevented the antiadenoviral humoral and cellular immune responses, thus enabling long term gene therapy using these viruses. Moreover, pre-existing immune response to the virus was overcome by tolerance induction, enabling prolonged gene expression in a presensitized host. Inflammatory bowel diseases are immune-mediated disorders where an imbalance between proinflammatory (T helper cell type 1) and anti-inflammatory (T helper cell type 2) cytokines are thought to play a role in the pathogenesis. In the experimental colitis model, the feeding of colitis-extracted proteins downregulated the anticolon immune response. Tolerance induction toward colitis-extracted proteins ameliorated colonic inflammation as shown by decreased diarrhea and reduction of colonic ulcerations, intestinal and peritoneal adhesions, wall thickness and edema. Histological parameters for colitis were markedly improved in tolerized animals. In both models, tolerized animals developed an increase in transforming growth factor-beta, interleukin-4 and interleukin-10, and a decrease in the mRNA of interferon-gamma lymphocytes and serum levels. Adoptive transfer of tolerized lymphocytes enabled the transfer of tolerance toward adenoviruses and colon-extracted proteins. Thus, oral tolerance induces suppressor lymphocytes that mediate immune response downregulation by induction of a shift from a proinflammatory T helper cell type 1 to an anti-inflammatory T helper cell type 2 immune response.
Endoscopic Mucosal Resection Using a Cap: Techniques for Use and Preventing Perforation
Authors: Inoue Haruhiro , Kawano Tatsuyuki , Tani Masao , Takeshita Kimiya , Iwai Takehisa
Published: March 2016

Endoscopic mucosal resection (EMR) is one of several local treatments that provide a specimen for histopathological analysis. The authors developed a technique of EMR using a transparent plastic cap (EMRC) in 1992. By using the EMRC procedure, any part of the gastrointestinal tract mucosa can be easily accessed. The technical details of EMRC are described. The authors have performed EMR in 380 cases of gastrointestinal lesions. The most serious complication may be perforation. Two perforations (one in the esophagus and one in the colon) have occurred. By evaluating recorded videotapes, it was determined that the lack of submucosal saline injection was the major cause. Therefore, large volume injection, which creates a large bleb and potentially reduces the risk of perforation, is recommended. Furthermore, target mucosa should be strangulated at the middle part of the created bleb (never strangulated at the base). Particularly in the colon, injecting a sufficient volume of saline and controlling the power of suction are extremely important, because the cap on the colonoscope is relatively large in size.
Colorectal Cancer Screening: A Guide to the Guidelines
Authors: Rex Douglas K
Published: March 2016

The two most recent guidelines for colorectal cancer screening are those of the Agency for Healthcare Policy and Research, and the American Cancer Society. The guidelines are similar in many regards and reflect current literature, consensus opinion and compromise between members of multidisciplinary panels. The emphasis of both guidelines is to increase the options available for colorectal cancer screening. Increasing choice should expand the attractiveness of colorectal cancer screening to more patients and physicians, and the development of guidelines should help compel payers to provide reimbursement for colorectal cancer screening. These guidelines are summarized and evaluated as they pertain to colorectal cancer screening.
Helicobacter pyloriInfection and Childhood Recurrent Abdominal Pain: Lack of Evidence for a Cause and Effect Relationship
Authors: Macarthur Colin
Published: March 2016

BACKGROUND: Recurrent abdominal pain is a common complaint among children and adolescents. Apley’s criteria – at least three discrete episodes of abdominal pain of sufficient severity to interrupt normal activities that occur over a period of three or more months - are often used to define this chronic pain syndrome.

OBJECTIVE: To summarize the extent and quality of the published evidence for a cause-and-effect relationship betweenHelicobacter pyloriinfection and childhood recurrent abdominal pain.

MATERIALS AND METHODS: The MEDLINE bibliographic database (January 1983 to July 1998) was searched to identify pertinent (English language) studies. The search was restricted to prospective, controlled studies reporting empirical data on children up to 18 years of age.

RESULTS: Six studies were identified. Five of the six were case-control studies, while the remaining study assessed the effectiveness of antibiotic therapy. Only one study was community based, with the remaining studies conducted in the tertiary hospital setting. The evidence for a causal relationship was inconsistent; of the five case-control studies reviewed, the odds ratios ranged from 0.32 to 1.80. Two studies demonstrated statistically significant results; however, the findings were conflicting. The only treatment trial was limited because of methodological flaws.

CONCLUSIONS: Current evidence suggests no association betweenH pyloriinfection and recurrent abdominal pain in children. The evidence to date indicates that routine investigation forH pyloriinfection in children who present with the classical symptoms of recurrent abdominal pain based on Apley’s criteria is not warranted.
Clinical Implication of Vascular Cell Adhesion Molecule‐1 and Very Late Activation Antigen‐4 Interaction, and Matrix Metalloproteinase‐2 Production in Patients with Liver Disease
Authors: Haruta Ikuko , Tokushige Katsutoshi , Komatsu Tatsuji , Ikeda Ikuo , Yamauchi Katsumi , Hayashi Naoaki
Published: March 2016

OBJECTIVES: To clarify the role of adhesion molecule in liver cell injury.

PATIENTS AND METHODS: The serum levels of soluble vascular cell adhesion molecule‐1 (sVCAM‐1), and the expression of VCAM‐1 and its ligand, very late activation antigen‐4 (VLA‐4), were examined in patients with various liver diseases. In addition, the presence of matrix metalloproteinase‐2 (MMP‐2) was investigated because the release of MMP‐2 is thought to be mediated by VLA‐4‐positive cells. sVCAM‐1 and MMP‐2 were measured by ELISA assay, and VCAM‐1 and VLA‐4 were studied by immunohistological methods.

RESULTS: In acute hepatitis (AH) patients, the serum level of sVCAM‐1 was significantly elevated compared with that in other cohorts. VCAM‐1 was expressed on sinusoidal lining cells but not on hepatocytes. In patients with chronic liver disease, sVCAM‐1 levels rose in concert with the progression of chronic hepatitis (CH), and VCAM‐1 was also expressed. VLA‐4 was detected in both mononuclear cells and Kupffer cells in AH livers, but mainly in Kupffer cells in patients with CH. In AH patients, MMP‐2 levels were similar to those in control subjects, but in CH and liver cirrhosis patients, MMP‐2 level was elevated in association with CH progression.

CONCLUSIONS: The immune response through the VCAM‐1 and VLA‐4 pathways is important in hepatocyte injury, especially in AH patients, to attach VLA‐4‐positive mononuclear cells to VCAM‐1‐positive sinusoidal lining cells. The distribution of VLA‐4‐positive cells differs between AH and CH patients. VLA‐4‐positive Kupffer cells in chronic liver diseases might be involved in the progression of CH, perhaps through the mechanism of upregulation of MMP‐2 production.
What Do We Do about Helicobacter pylori?
Authors: Hawkey CJ
Published: March 2016

Heliobacter pylori and nonsteroidal anti‐inflammatory drugs (NSAIDs) cause ulcers by different mechanisms. Under some circumstances, patients infected with H pylori may be less prone to NSAID‐associated ulcers than those who are H pylori‐negative. Eradication trials have yielded differing results. However, those who have studied patients who have a past history of ulcer disease and are already established on NSAIDs have shown no benefit from H pylori eradication.
Is Light‐Induced Fluorescence Better Than the Endoscopist’s Eye?
Authors: Marcon Norman E
Published: March 2016

While recognizing advanced tumours with endoscopy does not generally pose a challenge, cure rates are relatively low, depending on the size and stage of the tumour. Screening tests for cancer are advantageous for diagnosing cancers before the date after which a cure is no longer an option. Many gastrointestinal cancers are diagnosed after the date on which a cure is possible. The present article discusses some of the limitations of conventional white light endoscopy in screening and presents some of the fluorescent‐based diagnostics that are being investigated as complements to white light endoscopy. Autofluorescence and fluorescence due to exogenous photosensitizers or precursors are two sources of fluorescence that are being studied. Preliminary results of current investigations are presented, and future research directions are described.
Phlegmonous Gastritis Following Coronary Bypass Surgery
Authors: Radhi J , Kamouna M , Nyssen J
Published: March 2016

Phlegmonous gastritis is a rare, rapidly progressive and potentially fatal gastric bacterial infection. A case of phlegmonous gastritis following a coronary bypass surgery is described. This condition was not diagnosed premortem due to the nonspecific nature of the gastrointestinal symptoms. Upper gastrointestinal endoscopy may be of value in establishing the diagnosis in emergencies with culture of gastric aspirate and biopsy.
GB Virus C Infection: Clinical Significance
Authors: Meng Xiang Wei , Komatsu Masafumi , Ohshima Shigetoshi , Nakane Kunio , Fujii Tomoo , Goto Takashi , Yoneyama Kazuo , Kuramitsu Tomoyuki , Mukaide Motokazu
Published: March 2016

GB virus C (GBV-C) RNA positivity rates were examined in serum specimens from 231 patients with liver disease (23 patients with hepatitis B, 175 patients with hepatitis C, five patients with hepatitis B virus plus hepatitis C virus coinfection, and 28 patients with non-A, non-B, non-C hepatitis) to clarify the clinical significance of this virus. GBV-C RNA was detected in none of 12 patients with fulminant hepatitis, one of two patients with acute hepatitis positive for hepatitis B surface antigen and one of four patients with acute non-A, non-B, non-C hepatitis. Pathogenetic involvement of GBV-C was suspected in some patients in the latter group. Among patients with the non-B, non-C type of chronic disease, one of seven with cirrhosis (14%) and none with chronic hepatitis or hepatocellular carcinoma were GBV-C-positive. In chronic hepatitis C patients who had received interferon treatment, no difference was found in clinical findings, alanine aminotransferase (ALT) concentrations, histology or response to interferon between 11 patients who were GBV-C RNA-positive and 101 patients who were GBV-C RNA-negative. Moreover, changes in ALT after interferon therapy showed no relation to positivity for GBV-C RNA. On the basis of these findings, GBV-C appears to be an unlikely cause of initiation or progression of chronic hepatic diseases.
New Photosensitizers for Photodynamic Therapy in Gastroenterology
Authors: Bown SG , Rogowska AZ
Published: March 2016

Most applications of photodynamic therapy (PDT) in gastroenterology to date have used porfimer sodium as the photosensitizing agent. For destroying small lesions in the wall of the gastrointestinal tract in inoperable patients, it has proved to be most effective, but attempts to achieve circumferential mucosal ablation, as in the treatment of Barrett’s esophagus, have led to a high incidence of strictures, and all patients have cutaneous photosensitivity, which can last up to three months. Two new photosensitizers are of particular interest to gastroenterologists. PDT with metatetrahydroxyphenyl chlorin produces a similar biological effect as PDT with porfimer sodium, but the light doses required are much smaller, and cutaneous photosensitivity lasts only two to three weeks. Further, it can be used with percutaneous light delivery to destroy localized pancreatic cancers. The photosensitizing agent 5‐amino levulinic acid, converted in vivo into the photoactive derivative protoporphyrin IX, sensitizes the mucosa much more than the underlying layers. This makes it feasible to destroy areas of abnormal mucosa without damaging the underlying muscle and is, therefore, better for treating Barrett’s esophagus. Detailed clinical studies are required to establish the real role of PDT with the use of these and other new photosensitizers.
Intestinal Permeability before and after Ibuprofen in Families of Children with Crohn’s Disease
Authors: Zamora Samuel A , Hilsden Robert J , Meddings Jon B , Butzner J Decker , Scott R Brent , Sutherland Lloyd R
Published: March 2016

BACKGROUND: Members of a subset of first-degree relatives of adults with Crohn’s disease have been shown to have an increased baseline intestinal permeability and/or an exaggerated increase in intestinal permeability after the administration of acetylsalicylic acid.

PURPOSE: To determine intestinal permeability in unaffected first-degree relatives of children with Crohn’s disease before and after the administration of an ibuprofen challenge.

METHODS: Lactulose-mannitol ratios, a measure of intestinal permeability, were determined in 14 healthy control families (41 subjects) and 14 families with a child with Crohn’s disease (36 relatives, 14 probands) before and after ingestion of ibuprofen. An upper reference limit was defined using the control group as mean ± 2 SD.

RESULTS: The proportion of healthy, first-degree relatives with an exaggerated response to ibuprofen (20%, 95% CI 7% to 33%) was significantly higher than controls (P=0.003). The exaggerated response was more common among siblings than among parents of pediatric probands.

CONCLUSIONS: Members of a subset of first-degree relatives of children with Crohn’s disease have an exaggerated increase in intestinal permeability after ibuprofen ingestion. These findings are compatible with there being a genetic link between abnormalities of intestinal permeability and Crohn’s disease.