bluuebunny/crossref_metadata_2025 huggingface dataset:
Inactivation of the cannabinoid receptor CB1 prevents leukocyte infiltration and experimental fibrosis
Authors: Marquart Sieglinde , Zerr Pawel , Akhmetshina Alfiya , Palumbo Katrin , Reich Nicole , Tomcik Michal , Horn Angelika , Dees Clara , Engel Matthias , Zwerina Jochen , Distler Oliver , Schett Georg , Distler Jörg H. W.
Published: July 2010

Objective

Cannabinoids are derivates of the marijuana component Δ9‐tetrahydrocannabinol that exert their effects on mesenchymal cells and immune cells via CB1 and CB2 receptors. The aim of the present study was to evaluate the role of CB1 in systemic sclerosis.

Methods

CB1‐deficient (CB1−/−) mice and wild‐type littermates (CB1+/+mice) were injected with bleomycin. CB1 signaling was activated in vivo with the selective agonistN‐(2‐chloroethyl)‐5Z,8Z,11Z,14Z‐eicosatetraenamide (ACEA). Bone marrow transplantation experiments were performed to investigate whether the phenotype of CB1−/−mice was mediated by leukocytes or mesenchymal cells. The role of CB1 was also investigated in the TSK‐1 mouse model.

Results

CB1−/−mice were protected from bleomycin‐induced dermal fibrosis, with reduced dermal thickening, hydroxyproline content, and myofibroblast counts. Inactivation of CB1 decreased the number of infiltrating T cells and macrophages in lesional skin. In contrast, activation of CB1 with ACEA increased leukocyte infiltration and enhanced the fibrotic response to bleomycin. The phenotype of CB1−/−mice was mimicked by transplantation of CB1−/−mouse bone marrow into CB1+/+mice, demonstrating that CB1 exerts its profibrotic effects indirectly by regulating leukocyte infiltration. Consistently, knockdown of CB1 did not prevent fibrosis in the inflammation‐independent TSK‐1 mouse model.

Conclusion

We demonstrate that the cannabinoid receptor CB1 is crucial for leukocyte infiltration and secondary fibroblast activation and that inactivation of CB1 exerts potent antifibrotic effects in inflammation‐driven models of fibrosis.
The response of human anulus fibrosus cells to cyclic tensile strain is frequency‐dependent and altered with disc degeneration
Authors: Gilbert Hamish T. J. , Hoyland Judith A. , Millward‐Sadler Sarah J.
Published: July 2010

Objective

Mechanical loads are important for homeostasis of the intervertebral disc (IVD) cell matrix, with physiologic and nonphysiologic loads leading to matrix anabolism and catabolism, respectively. Previous investigations into the effects of load on disc cells have predominantly used animal models, with the limited number of human studies focusing primarily on nucleus pulposus cells. The aim of this study was to examine the effect of cyclic tensile strain (CTS) on human anulus fibrosus (AF) cells to ascertain whether the response was frequency‐dependent and to compare AF cells derived from nondegenerated and degenerated tissue samples.

Methods

AF cells were isolated from nondegenerated and degenerated human IVDs, expanded in monolayer, and cyclically strained for 20 minutes, applying 10% strain at a frequency of 1.0 Hz or 0.33 Hz with the use of a Flexcell strain device. Total RNA was extracted from the cells at baseline (control) and at 1, 3, and 24 hours following application of CTS. Real‐time quantitative polymerase chain reaction was used to analyze gene expression of matrix proteins (aggrecan, type I collagen, and type II collagen) and enzymes (matrix metalloproteinases [MMPs] 3, 9, 13, and ADAMTS‐4).

Results

The expression of catabolic genes (MMP‐3 and ADAMTS‐4) in AF cells derived from nondegenerated tissue decreased in response to 1.0 Hz of CTS, whereas changing the frequency to 0.33 Hz resulted in a shift toward matrix catabolism. Application of 1.0 Hz of CTS reduced anabolic gene expression (aggrecan and type I collagen) in AF cells derived from degenerated tissue, with 0.33 Hz of CTS resulting in increased catabolic gene expression.

Conclusion

The response of human AF cells to CTS is frequency‐dependent and is altered by degeneration.
Anticitrulline antibodies can be caused by homocitrulline‐containing proteins in rabbits
Authors: Turunen Sanna , Koivula Marja‐Kaisa , Risteli Leila , Risteli Juha
Published: July 2010

Objective

To clarify the possible roles of protein‐bound homocitrulline in causing an antibody response to citrulline and as a confounding factor in citrulline detection assays.

Methods

Native, carbamoylated, and citrullinated albumins were used for testing the specificity of commercial antibodies against modified citrulline by Western blot. Rabbits were immunized with human albumin and/or bone type I collagen, both of which were treated with cyanate to produce homocitrulline, or with citrullinated synthetic telopeptide of type I collagen. These antisera were tested for binding to cyclic citrullinated peptide 2 (CCP‐2), mutated citrullinated vimentin, and type I or II collagen telopeptides containing either citrulline or homocitrulline.

Results

Commercial antibodies that had been considered to be specific for chemically modified citrulline were found to recognize both homocitrulline‐ and citrulline‐containing albumins. The rabbits immunized with proteins containing homocitrulline produced high‐affinity antibodies against CCP‐2 and, to a lesser extent, against mutated citrullinated vimentin. The antisera also bound homocitrulline‐containing collagen telopeptides and, less strongly, citrulline‐containing telopeptides.

Conclusion

Our findings demonstrate that homocitrulline, which is a structural analog of citrulline (longer by 1 carbon, and readily formed in the body), can be involved in raising citrulline‐recognizing antibodies in experimental animals and can cause false‐positive reactions in assays for citrulline.
Identification of the oxidative stress–related gene MSRA as a rheumatoid arthritis susceptibility locus by genome‐wide pathway analysis
Authors: Martín Jose‐Ezequiel , Alizadeh Behrooz Z. , González‐Gay Miguel A. , Balsa Alejandro , Pascual‐Salcedo Dora , Fernández‐Gutiérrez Benjamín , Raya Enrique , Franke Lude , van't Slot Ruben , Coenen Marieke J. H. , van Riel Piet , Radstake Timothy R. D. J. , Koeleman Bobby P. C. , Martín Javier
Published: July 2010

Objective

Genome‐wide association studies carried out in rheumatoid arthritis (RA) have led to the discovery of several genetic associations with this disease. Still, the current associated genetic variations can explain only part of the genetic risk involved in RA, and it is well recognized that these genome‐wide association studies are likely underpowered to detect all common disease variants. This study was undertaken to explore the genomic regions showing low‐significance associations in previous genome‐wide association studies of RA.

Methods

To reduce the false‐positive signal fraction, we exploited pathway analysis to prioritize regions containing genes most likely to be implicated in RA. We hypothesized that true disease genes would be in a similar pathway. Therefore, genes from similar pathways but located in different regions were prioritized for replication using Prioritizer software. A total of 384 genetic variants selected from previous RA genome‐wide association studies were tested in a Spanish case–control discovery cohort comprising 376 RA patients and 478 healthy controls for replication. Statistically significant associations were further validated in replication cohorts from Spain and The Netherlands. The study consisted of a total of 1,818 RA patients and 2,498 controls.

Results

We detected a novel genetic association between RA and the MSRA gene (rs10903323) in the Spanish combined population (P = 2.91 × 10−5, odds ratio [OR] 1.51). This association was further tested in our independent Dutch replication cohort. Combined analysis showed an overall association of MSRA with RA (P = 3.19 × 10−4, OR 1.28).

Conclusion

Our findings indicate that a novel association in the MSRA gene is related to oxidative stress and support the notion of a major role for this process in RA.
Anxiety and depressive symptoms in fibromyalgia are related to poor perception of health but not to pain sensitivity or cerebral processing of pain
Authors: Jensen Karin B. , Petzke Frank , Carville Serena , Fransson Peter , Marcus Hanke , Williams Steven C. R. , Choy Ernest , Mainguy Yves , Gracely Richard , Ingvar Martin , Kosek Eva
Published: July 2010

Objective

Mood disturbance is common among patients with fibromyalgia (FM), but the influence of psychological symptoms on pain processing in this disorder is unknown. We undertook the present study to investigate the differential effect of depressive symptoms, anxiety, and catastrophizing on 1) pain symptoms and subjective ratings of general health status and 2) sensitivity to pain and cerebral processing of pressure pain.

Methods

Eighty‐three women (mean ± SD age 43.8 ± 8.1 years) who fulfilled the American College of Rheumatology 1990 criteria for the classification of FM participated in the study. Patients rated pain intensity (100‐mm visual analog scale [VAS]), severity of FM (Fibromyalgia Impact Questionnaire), general health status (Short Form 36), depressive symptoms (Beck Depression Inventory), anxiety (State‐Trait Anxiety Inventory), and catastrophizing (Coping Strategies Questionnaire). Experimental pain in the thumb was induced using a computer‐controlled pressure stimulator. Event‐related functional magnetic resonance imaging was performed during administration of painful stimuli representing 50 mm on a pain VAS, as well as nonpainful pressures.

Results

A correlation analysis including all self‐ratings showed that depressive symptoms, anxiety, and catastrophizing scores were correlated with one another (P < 0.001), but did not correlate with ratings of clinical pain or with sensitivity to pressure pain. However, the subjective rating of general health was correlated with depressive symptoms and anxiety (P < 0.001). Analyses of imaging results using self‐rated psychological measures as covariates showed that brain activity during experimental pain was not modulated by depressive symptoms, anxiety, or catastrophizing.

Conclusion

Negative mood in FM patients can lead to a poor perception of one's physical health (and vice versa) but does not influence performance on assessments of clinical and experimental pain. Our data provide evidence that 2 partially segregated mechanisms are involved in the neural processing of experimental pain and negative affect.
Pathogenic role of CXCR7 in rheumatoid arthritis
Authors: Watanabe Kaori , Penfold Mark E. T. , Matsuda Akio , Ohyanagi Naho , Kaneko Kayoko , Miyabe Yoshishige , Matsumoto Kenji , Schall Thomas J. , Miyasaka Nobuyuki , Nanki Toshihiro
Published: July 2010

Objective

The interaction between CXCL12 and its receptor, CXCR4, in the synovium of patients with rheumatoid arthritis (RA) is important for local inflammatory cell recruitment, angiogenesis, and cytokine production. CXCR7 was recently identified as an alternative receptor for CXCL12. We undertook this study to analyze the expression of CXCR7 in RA synovium and the pathogenic role of the CXCL12/CXCR7 pathway in RA.

Methods

CXCR7 expression in RA synovial tissue was analyzed using immunohistochemistry, while expression of CXCR4 and CXCR7 on human umbilical vein endothelial cells (HUVECs) was examined using quantitative reverse transcription–polymerase chain reaction, and CXCR7 expression was also analyzed by flow cytometry. Tube formation and rat aortic ring angiogenesis assays were used to assess the effects of CCX733 (a CXCR7 antagonist) and AMD3100 (a CXCR4 antagonist) on CXCL12‐induced angiogenesis. The effect of anti‐CXCR4 monoclonal antibody (mAb) was also analyzed using a tube formation assay. The effects of CCX733 in a murine model of collagen‐induced arthritis (CIA) were also evaluated.

Results

CXCR7 was expressed on endothelial cells in RA synovium and also on unstimulated HUVECs. The expression of CXCR7 on HUVECs was markedly up‐regulated by interleukin‐1β (IL‐1β) stimulation, and this overexpression was further enhanced by CXCL12 treatment. Incubation with CXCL12 also promoted angiogenic activity, with addition of IL‐1β again augmenting the effect. CXCL12‐induced angiogenesis was inhibited by both CXCR4 and CXCR7 antagonists and by anti‐CXCR4 mAb. Furthermore, treatment with CCX733 significantly reduced the clinical arthritis scores and the numbers of vessels in the inflamed synovial tissue in mice with CIA.

Conclusion

CXCR7 and CXCR4 are both important for angiogenesis in RA synovium, making CXCR7 another potential target molecule for novel RA angiogenesis‐blocking therapies.
Students' illustrations of the human nervous system as a formative assessment tool
Authors: Ranaweera Sisika Priyani Nelum , Montplaisir Lisa Marie
Published: July 2010

The purpose of this study was to explore students' knowledge and learning of the human nervous system (HNS) in an introductory undergraduate Human Anatomy and Physiology course. Classroom observations, demographic data, a preinstructional unit test with drawings, and a postinstructional unit test with drawings were used to identify students' overall knowledge and learning during the unit of study. Quantitative and qualitative analysis indicate that students have an initially poor understanding of the nervous system with many prevailing alternative conceptions. These alternative conceptions include both structural and functional components and often incorporate colloquial use of language. Findings reveal students include the heart as a major component of the HNS, a reflex arc illustrated by the action rather than structure, and types of neurons (unipolar, bipolar, or multipolar) differentiated by charge or number of cell bodies rather than structural arrangement. Classroom instruction coupled with concurrent laboratory participation provided experiences for students to overcome some of their alternative conceptions. The finding of this research suggest that instructors should be aware of the students' prevailing alternative conceptions prior to instruction and that use of drawings as a formative assessment tool is an excellent way to collect such information. Anat Sci Educ 3:227–233, 2010. © 2010 American Association of Anatomists.
The record‐breaking cold temperatures during the winter of 2009/2010 in the Northern Hemisphere
Authors: Wang Chunzai , Liu Hailong , Lee Sang‐Ki
Published: July 2010

In this study, we show that the record‐breaking cold temperatures from North America to Europe and Asia during the period of 28 December 2009 to 13 January 2010 are associated with extremely negative values of the North Atlantic Oscillation (NAO) index, which produce northerly surface wind anomalies and cause the southward advection of the cold Arctic air. Corresponded to longer‐term variations of Pacific and Atlantic Sea Surface Temperatures (SSTs), the downward trend of the NAO has occurred since the early 1990s. It is speculated that if the downward trend of the NAO continues, more frequent cold outbreaks and heavy snow are likely in the coming years. Published 2010 by John Wiley and Sons, Ltd.
Optimization of silver cementation yield in fixed bed reactor using factorial design and central composite design
Authors: Yahiaoui I. , Aissani‐Benissad F. , Aït‐Amar H.
Published: July 2010

This work deals with cementation of silver onto iron grid in fixed bed reactor. The influence of several parameters is studied namely: initial concentration of silver [Ag+]0, flow rate, solution pH, and mass of iron. Moreover, their influence on the yield of the reaction of cementation is investigated statistically by the experimental design in view of industrial application. The estimation and the comparison of the parameter's effects are realised by using two‐level factorial design. The analysis of these effects permits to state that the most influential factor is the mass of iron with an effect of (+5.642), the second in the order is the initial concentration of silver ions (Ag+) with an effect of (+4.005), the third is the flow rate of the electrolytic solution with an effect of (+3.824). A central composite design methodology is employed to determine the optimum conditions for a silver cementation yield onto iron grid. For this end, the experimental results were approximated by a second‐order model as well as the surface contour plots and surface responses are drowned. The optimal conditions found for initial silver concentration, such as a flow rate, pH of the solution and mass of iron, are respectively: 21.25 mg/L, 4.43 L/min, 3.6 and 50 g. Under these conditions, the obtained silver cementation yield is 96.851%.
Interfacial area for concurrent gas–liquid upflow through packed bed
Authors: Raghavendra Rao A. V. , Kishore Kumar R. , Sankarshana T. , Khan Ahamed
Published: July 2010

Interfacial area is measured for a large range of column packing (Raschig rings, Intalox saddles, and two sizes of spheres) for concurrent gas–liquid upflow through packed bed covering bubble, pulse and early spray flow regimes using air–aqueous sodium sulfite solution. It was observed that the interfacial area increased with increase in fluids flow rate and decreased with the increase in the particle size for the same type of packing. A correlation (3 ≤ Rel ≤ 165, 0.5 ≤ Reg ≤ 210) was developed using present data (120 data points) and literature data (100 data points), which predict the interfacial area with an rms deviation of 16%.
Retrofit of absorption heat pumps into manufacturing processes: Implementation guidelines
Authors: Bakhtiari Bahador , Fradette Louis , Legros Robert , Paris Jean
Published: July 2010

Integration of absorption heat pumps (AHP) in industrial processes has not yet been fully exploited due to the lack of clear implementation guidelines for this technology. In this work, a systematic methodology for the integration of AHPs in a process has been developed and is presented. Guidelines are formulated for the proper selection of heat sources and sinks that will maximise the benefit derived from heat pumping while respecting process constraints and operating requirements of the AHP. The principles of AHP operation and its efficient process integration are thus described. The methodology relies on data extracted from a Pinch Analysis of the plant. The advantages and outputs of the methodology are illustrated using an AHP implementation in a Kraft pulping process. Two realistic implementation options are presented along with their detailed design and preliminary economic evaluation.
Modelling and control of different types of polymerization processes using neural networks technique: A review
Authors: Noor R. A. Mat , Ahmad Z. , Don M. Mat , Uzir M. H.
Published: July 2010

Polymerization process can be classified as a nonlinear type process since it exhibits a dynamic behaviour throughout the process. Therefore, it is highly complicated to obtain an accurate mechanistic model from the nonlinear process. This predicament always been a “wall” to researchers to be able to devise an optimal process model and control scheme for such a system. Neural networks have succeeded the other modelling and control methods especially in coping with nonlinear process due to their very conciliate characteristics. These characteristics are further explained in this work. The predicament that is encountered by researchers nowadays is lack of data which consequently lead to an imprecise mechanistic model that scarcely conforms to the desired process. The implementations of the neural network model not only restrict to polymerization reactor but to other difficult‐to‐measure parameters such as polymer quality, polymer melts index and mixture of initiators. This work is aimed to manifest ascendancy of neural networks in modelling and control of polymerization process.
A kinetics study in CSTR using simultaneous temperature scanning and composition modulation: The alkaline hydrolysis of ethyl acetate
Authors: Jaree Attasak , Nuammaneerat Chonthida
Published: July 2010

This work presents a new technique for reaction kinetic studies of liquid phase reactions in a CSTR. By simultaneously varying the reaction temperature (temperature scanning—TS) and reactant feed concentration (composition modulation—CM) while recording the output concentration, the technique allows, through the least‐square fitting of computer‐generated model data to the experimental time‐series, to obtain from a single experiment the reaction orders as well as both Arrhenius parameters. The alkaline hydrolysis of ethyl acetate was chosen to illustrate the technique, assuming a rate law in the form of a simple power law. The set of parameters that resulted in the minimum sum of squared errors was selected. These values were very close to those reported in literature. The technique saves much time and experimental resources.
On MHD heat and mass transfer over a moving vertical plate with a convective surface boundary condition
Authors: Makinde O. D.
Published: July 2010

In this paper, the magnetohydrodynamics (MHD) boundary layer flow with heat and mass transfer over a moving vertical plate in the presence of magnetic field and a convective heat exchange at the surface with the surrounding has been studied. The similarity solution is used to transform the system of partial differential equations, describing the problem under consideration, into a boundary value problem of coupled ordinary differential equations, and an efficient numerical technique is implemented to solve the reduced system. The results are presented graphically and the conclusion is drawn that the flow field and other quantities of physical interest are significantly influenced by these parameters.
Computer calculation of heat capacity of natural gases over a wide range of pressure and temperature
Authors: Dranchuk P. M. , Abou‐Kassem J. H.
Published: July 2010

This paper presents a method whereby specific heats or heat capacities of natural gases, both sweet and sour, at elevated pressures and temperatures may be made suitable to modern day machine calculation. The method involves developing (1) a correlation for ideal isobaric heat capacity as a function of gas gravity and pseudo reduced temperature over the temperature range of 300 to 1500 K and (2) a mathematical equation for the isobaric heat capacity departure based on accepted thermodynamic principles applied to an equation of state that adequately describes the behavior of gases to which the Standing and Katz Z factor correlation applies. The heat capacity departure equation is applicable over the range of 0.2 ≤ Pr ≤ 15 and 1.05 ≤ Tr ≤ 3. The significance of the method presented here lies in its utility and adaptability to computer applications.
Hydrogenation of carbon dioxide on iron catalysts doubly promoted with manganese and potassium
Authors: Lee Jyh‐Fu , Chern Wen‐Shing , Lee Min‐Dar , Dong Teng‐Yuan
Published: July 2010

The effect of addition of manganese and potassium promoters onto iron catalysts for hydrogenation of carbon dioxide was investigated. Catalyst characterizations were performed using BET surface area measurement, carbon monoxide chemisorption, temperature‐programmed reduction and Mössbauer spectroscopy. It was noted that metallic iron catalysts were carburized to θ‐Fe3C and χ‐Fe5C2 as well as oxidized to Fe3O4 during the course of reaction. The promotional effect of manganese was reflected in stabilization of catalytic behavior owing to a higher resistance to bulk oxidation. However, the distribution of hydrocarbon products did not change significantly in the presence of manganese promoter. With further addition of potassium promoter, the bulk phase was more likely to transform to carbides, and the selectivity toward olefins and long‐chain hydrocarbons was remarkably enhanced.
A study of the pressure balance around the loop of a circulating fluidized bed
Authors: Rhodes M. J. , Laussmann P.
Published: July 2010

Pressure measurements around the loop of a circulating fluidized bed with 152 mm ID riser and L‐valve fecuer were analysed to determine the effect of operating parameters (superficial gas velocity in the range 2.2 ‐ 4.0 m/s, solids circulation flux in the range 5 ‐ 50 kg/m2 · s and solids inventory, in the range 80 ‐ 180 kg) on the components of the pressure balance. The riser pressure drop, and hence, riser solids holdup were not affected by changes in the inventory of solids in the system, provided riser superficial gas velocity and solid circulation flux were held constant. The mean suspension concentration in the riser was found to be directly proportional to the ratio of solids flux to superficial gas velocity (G / U) in the riser.
Optimal stationary states in thermalhydraulics: Total reflux condensation
Authors: Venugopalan D. , Girard R. , Kirkaldy J. S.
Published: July 2010

Reflux condensation in a weakly fluctuating stationary mode can be classified with dissipative. pattern‐forming structures. In those states which possess a single phase region topping the two‐phase region the steady state conservation equations do not uniquely determine the length of the two‐phase column. This degeneracy can be removed in accord with the principle of maximum path probability by optimizing the rate of entropy production. Models of reflux condensers with one and several cooling jackets which possess a maximal state are presented. The model predicts the general features of the experimental data without recourse to empirical correlations.
Modeling of solid—liquid adsorption: Effects of adsorbent loads on model parameters
Authors: Leitão Anabela , da Conceição Euridice , Santos Rosalinda , Rodrigues Alirio
Published: July 2010

The adsorption of cobalt phthalocyanine dye onto activated carbon in a continuous stirred tank adsorber was studied.

The variables investigated were: adsorbent mass, adsorbent particle size and fluid flowrate.

Several models based on film, pore and surface diffusion were constructed and fitted to the experimental data.

Experimental results showed: (i) the increasing importance of the film mass transfer resistance for increasing adsorbent loads; (ii) the increasing importance of the surface diffusion mechanism for increasing adsorbent loads; and (iii) the better discrimination among different models for higher adsorbent loads and lower flowrate.
Adsorption of water vapour on activated alumina. I —‐ equilibrium behaviour
Authors: Desai R. , Hussain M. , Ruthven D. M.
Published: July 2010

Equilbrium isotherms are reported for adsorption of water vapour on several different activated alumina adsorbents. The experimentally measured isotherms represent the sum of the contributions from water vapour held in several ways but these contributions can be resolved by detailed analysis. The individual isotherms conform closely to simple idealized models (Langmuir for chemisorption, BET for physisorption), thus providing a rational basis on which to compare different samples and the effects of different regeneration procedures. The apparent complexity in the behaviour of these systems arises from the superposition of the different contributions, the relative importance of which depends upon the nature of the sample and the regeneration conditions. By contrast, the behaviour of the resolved isotherms is relatively straightforward.
Adsorption on activated alumina. II — kinetic behaviour
Authors: Desai R. , Hussain M. , Ruthven D. M.
Published: July 2010

The kinetics of adsorption of water vapour, dimethyl ether, isobutylene, and methanol on activated alumina have been investigated by gravimetric uptake rate and breakthrough curve measurements. Intraparticle diffusivities were determined by matching the experimental response curves to appropriate theoretical models. At low concentration the kinetic‐behaviour is straightforward. The sorption rate is controlled by macropore diffusion with contributions from both the Knudsen and molecular mechanisms, depending on the conditions. For water vapour at higher pressures beyond the point of inflection of the isotherm there appears to be a significant contribution from surface diffusion.
Characterization of the reactivity of limestones with SO2 in a fluidized bed reactor
Authors: Garciá‐Labiano F. , Adánez J. , Rubiera F. , Fuertes A. B. , Pis J. J.
Published: July 2010

The reaction between SO2 and calcined limestone particles has been studied in a fluidized bed combustor. Measurements of sorbent reactivity with SO2 were made for small batches of limestone injected into the combustor. Simultaneous continuous combustion of bituminous coal provided conditions like those of a boiler for study of the sulphation reaction. A semi‐empirical rate model of the CaO‐SO2 reaction has been developed. External mass transfer of SO2, diffusion within the particles and chemical reaction are taken into account. The limestone reactivity with SO2 is characterized by two parameters which are dependent on the temperature and sorbent particle size.

A model for predicting the limestone requirements in a fluidized bed boiler has been developed. Parameters from the batch experiments are included. The predictions for sulfur retention agree with the experimental results. In addition, effects of operating conditions (gas velocity, recycle, limestone particle size) on the retention of SO2 were simulated using the model.
The movement of solids through flighted rotating drums. Part II solids‐gas interaction and model validation
Authors: Sherritt Richard G. , Caple Rod , Behie Leo A. , Mehrotra Anil K.
Published: July 2010

A residence time model for a rotating drum with lifting flights which includes axial displacement of airborne particles due to the drag of the gas stream has been developed in Part I of this study (Sherritt et al., 1993). Because the particles fall in curtains, the equations for single particle drag overestimated the effect of the gas stream on the displacement of the falling particles. In this paper, large scale wind tunnel experiments, which involved pouring a curtain of particles into a gas stream, indicated that the shielding effect of the curtain could be represented by a lower‐than‐average gas velocity within the curtain. The magnitude of the curtain shielding effect is related to the flight discharge rate, the fall distance and the flight length. Incorporating the results of the experiments into the residence time model provides a significant improvement on the effect of the gas velocity, and hence the best model available, especially for industrial‐scale equipment.
Measurement of gas and liquid flows in stirred tank reactors with multiple agitators
Authors: Manikowski M. , Bodemeier S. , Lübbert A. , Bujalski W. , Nienow A. W.
Published: July 2010

The gas flow in a 3:1 aspect ratio vessel agitated by triple Rushton turbines has been measured by an ultrasound Doppler probe and by means of residence time studies. Strong recirculation around each impeller is found which fits in well with the compartmentalisation found in earlier liquid mixing studies. Surprisingly, when two axial A315 impellers above a Rushton turbine were used, gas recirculation around each impeller was still found. Study of the liquid phase mixing by a decolourisation technique confirmed that the gas flow essentially destroyed the strong axial liquid flow expected. Indeed, even under unaerated conditions, compartmentalisation was found between each impeller.
Effect of restrictive diffusion on hydrodesulfurization of heavy residue oils over CoMo/Al2O3
Authors: Chen Yu‐Wen , Tsai Ming‐Chang , Li Chiuping , Kang Ben‐Chang
Published: July 2010

The effect of the ratio of reactant molecular diameter to catalyst pore diameter (λ) on the restrictive diffusion under hydrodesulfurization (HDS) reactions of heavy residue oils over CoMo/Al2O3 catalysts was investigated. A series of Al2O3 with various pore structures were used as supports of CoMo sulfide. The HDS reaction was carried out in a semi‐batch Carberry type reactor at 648 K and 10.3 MPa. Two empirical correlations for restrictive diffusion under HDS reaction conditions were developed depending on the value of λ. The results showed that the restrictive diffusion effect under HDS reaction conditions is severe for the lower values of λ. However, this effect seems not prominent for higher values of λ. The order of the magnitude of the effective diffusivity was in the range of 10−6‐10−7 cm2/s for the sulfur‐containing compounds of residue oil in CoMo/Al2O3 catalysts at 648 K.
Effect of Technological Factors on Electrochemical Hydrogenation of Lignin
Authors: Zhang Jianan , Zhang Xiaoyong , Xie Dongming , Liu Dehua , Li Zuohu
Published: July 2010

Lignin properties were improved by electrochemical hydrogenation. Various technological factors, such as cathode materials, temperature and concentrations of water, solvent, substrate, on the electrochemical hydrogenation of lignin in divided electrolytic cell were studied. The results showed that the hydrogen content (H %) and ratio of hydrogen to carbon (H/C) of hydrogenated lignin (HL) increased by 1.7 % and 0.04, respectively, and the softening point (SP) decreased by 24°C in comparison with lignin raw material. It was feasible for lignin to be electrochemically hydrogenated.
Flocculation Monitoring: Focused Beam Reflectance Measurement as a Measurement Tool
Authors: Blanco A , Fuente E , Negro C , Tijero J
Published: July 2010

A methodology to study flocculation processes and floc properties using a non‐imaging scanning laser microscope is presented in this paper. This methodology allows us to study floc stability and resistance to shear forces, re‐flocculation tendency and reversibility of the flocs. Furthermore, optimal dosage of any polymer and the associated flocculation mechanism can be determined. In order to illustrate the technique, some examples applied to flocculation in papermaking are described. Although in this paper all the examples have been applied to papermaking, the developed methodology can be used in any process in which flocculation phenomena is involved.
Determination of the Optimum Conditions for Zinc Extraction from Ore Containing Sphalerite by HCL Solutions
Authors: Ata Osman Nuri , Yeşilyurt Murat , Çolak Sabri , Beşe Ayşe Vildan
Published: July 2010

The Taguchi method has been used to determine optimum conditions for the zinc and iron extraction from ore containing sphalerite by HCI solutions. After determining the important parameters in extraction efficiency, an experimental series with two steps was carried out. The optimum conditions for the first series of experiments were found to be reaction temperature 90°C, solid‐to‐liquid ratio 0.091 g/mL, acid concentration 25 mass%, particle size ‐100+200 mesh, stirring speed 300 rpm and reaction time 120 min. Under these conditions, zinc extraction efficiency from ore was approximately 60%. The optimum conditions for the second series of experiments were found to be reaction temperature 90°C, acid concentration 32.5 mass%, solid‐to‐liquid ratio 0.1 g/mL, and reaction time 180 min. Under these conditions, zinc extraction efficiency from the ore was approximately 100%. Alternative working conditions reducing the total cost were also determined.
Measuring Volumetric Phase Fractions in a Gas‐Solid‐Liquid Stirred Tank Reactor Using an Impedance Probe
Authors: Brunazzi Elisabetta , Festa Umberto Di , Galletti Chiara , Merello Cesare , Paglianti Alessandro , Pintus Sandro
Published: July 2010

A probe based on the measurement of the electrical impedance has been developed to determine the phase hold‐ups in gas‐solid‐liquid stirred tank reactors. The idea was to take advantage of the complex nature of electrical impedance to derive two independent data (conductance and capacitance) from one measurement. Particular attention has been paid to the calibration of the probe and two semi‐empirical equations have been given to relate measurement to hold‐ups. Subsequently, experiments were performed on three‐phase and two‐phase (gas‐liquid and solid‐liquid) systems and the results have been critically analysed.
Diagnosis of Solid Distribution in Vessels Stirred with Multiple PBTs and Comparison of Two Modelling Approaches
Authors: Montante Giuseppina , Pinelli Davide , Magelli Franco
Published: July 2010

The features of solids concentration distribution were investigated in two baffled vessels of different scale. The vessels were of high aspect ratio and were stirred with multiple PBTs. Both steady‐ and unsteady‐state experiments were performed. The experimental data were compared with the previsions of the one‐dimensional sedimentation‐dispersion model and of CFD tools. The former approach provides good estimates only of the average, steady‐state vertical profiles, while the latter describes the local variations much more accurately. Both approaches give fairly good estimates of the transient solids concentration distribution. The dynamic CFD simulations allowed us also to tune the value of the turbulent Schmidt number as a relevant parameter. Finally, both simulation approaches have confirmed that the particle settling velocity in a stirred liquid is a correct parameter to be used instead of the terminal settling velocity.
Experimental Analysis of Hydrodynamics Induced by a Moritz HAS Impeller in Laminar and Turbulent Regimes
Authors: Escudié Renaud , Liné Alain , Kiener Pierre
Published: July 2010

The hydrodynamics induced by a Moritz HAS impeller are investigated using the PIV technique. The purpose of this study is to extend the knowledge of this kind of impeller, well known in turbulent flow, to the transition regime and laminar flow. Measurements of instantaneous velocity fields are synchronized with the position of the blade of the impeller. The periodic motion induced by the impeller blade rotation is measured by this conditional averaging. A triple decomposition is used to analyze the levels of turbulent kinetic energy and periodic kinetic energy induced by the impeller. In a turbulent regime, the impeller induces axial flow: the magnitude of periodic fluctuation is low compared to the turbulent one. In a laminar regime, the impeller induces a tangential‐radial discharge flow, and periodic velocity fluctuations are limited to the vicinity of the impeller.
The Effect of Adding Phosphate on the Size of Extremely Fine Needle‐like Lepidocrocite Particles Prepared by Oxidizing an Aqueous Suspension of Ferrous Hydroxide
Authors: Mihara Naoki , Kawasaki Hiroyuki , Kumazawa Hidehiro , Choi Woo‐Sik , Kwak Jung‐Sup , Choi Hee‐Kyu
Published: July 2010

Extremely fine particles of needle‐like lepidocrocite (γ‐FeOOH) were synthesized by the oxidation of aqueous suspensions of ferrous hydroxide using a bubble column with draft tube at a constant temperature of 30°C, and the effects of the reaction conditions or the oxidation rate were investigated in order to determine the parameters that control the particle size. When the concentration of oxygen in the feed stream was varied under a constant gas velocity, the mean size based on the major axis of a needle‐like particle decreased from 0.7 µm to 0.4 µm with increasing oxidation rate. By adding of NaH2PO4 to an aqueous Fe(OH)2 suspension, in concentrations up to 1.0 mol/m3 during the air oxidation, and up to 0.9 mol/m3 during the oxidation with 30% and 50% O2, the major axis could be reduced to ca. 0.3 µm with the minor axis and the oxidation rate remained almost unchanged.
Settling Velocities of Polydisperse Concentrated Suspensions
Authors: Ha Zhanyao , Liu Shijie
Published: July 2010

A model for particle settling velocities in polydisperse suspensions is proposed alongside normalized particle self and interaction mobilities. The model predictions are compared with other models (Davis and Gecol, 1994; and Al‐Naafa and Selim, 1989), as well as published experimental data. A general agreement was found between the current model and the existing data for binary dispersed particle systems except for one case where ΦL is fixed. For ternary dispersed particle systems, predictions from both the A‐S model and the current model agree well with the existing data. With the improved sedimentation coefficients, the D‐G model also produces satisfactory results.
Some Issues on Core‐Annulus and Cluster Models of Circulating Fluidized Bed Reactors
Authors: Bi Hsiaotao T.
Published: July 2010

The one‐dimensional cluster model and the core‐annulus model are examined based on existing correlations. The core‐annulus model is found to give reasonable agreement with ozone decomposition data when the effective interphase mass transfer rate constant is equal to about 0.1 1/s, which is one order smaller than the reported values based on gas tracer tests. The prediction from the core‐annulus model that the reactor performance decreases with increasing the riser diameter is found to be inconsistent with limited experimental data The one‐dimensional cluster model predicts that a riser reactor performs very close to the pseudo‐homogeneous plug flow reactor because of the high mass transfer rate between the cluster and the dilute phase. The improvement of model predictions lies in the better characterization of the cluster shape, size and the mass transfer rate between the cluster and the dilute phases.
Modelling the Effective Thermal Conductivity in Polydispersed Bed Systems: A Unified Approach using the Linear Packing Theory and Unit Cell Model
Authors: Gupta Murlidhar , Yang Jin , Roy Christian
Published: July 2010

A comprehensive, unified approach, using the Linear Packing Theory and Unit Cell Model, is proposed for calculating of the effective thermal conductivity of polydispersed packed beds. In this new approach, the effect of packing density is incorporated by the use of (i) an initial porosity to take into account the packing of mono‐sized particles, and (ii) the packing size ratio as a measure of the particle‐particle interaction. The proposed approach was validated with the experimental measurements of binary and ternary beds. This new approach demonstrates that the effective thermal conductivity of beds composed of polydispersed particles can be simulated for any composition without the need to measure the in situ porosity.
Multicriteria Optimization of a High‐Yield Pulping Process
Authors: Thibault Jules , Lanouette Robert , Fonteix Christian , Kiss Laszlo N.
Published: July 2010

This work deals with the application of a multicriteria optimization technique for the optimization of a jack pine pulping process, which has a large number of input and output variables. The optimization process is mainly comprised of two steps: reduction of the volume of the search space and determination of good compromise solutions. In the first step, the Pareto domain is approximated by a large number of possible solutions. The optimization technique uses the concept of preference, indifference and veto to determine the best solutions. Results show that an optimal solution zone can be defined and zones of decreasing preference can be drawn.
Spout Shape Predictions in Spouted Beds
Authors: Zanoelo Éverton F. , Rocha Sandra C. S.
Published: July 2010

A theoretical study to predict spout‐annulus interface variation with bed level for different column geometries of spouted beds is proposed. A previous mathematical model (Krzywanski et al., 1989), developed for spout shape predictions in two‐dimensional spouted beds, is here proposed to be applied also for cylindrical, conical or cone‐based cylindrical columns. Its predictions depend on the average spout diameter and on the spout expansion angle. While there exists empirical equations available to estimate the first model parameter, the second one requires a rigorous stress analysis of the particles at the entrance of the bed. To avoid this difficulty, this work proposes a simple mathematical strategy to calculate the spout expansion angle. The reliability of this approach was checked by comparison with several experimental results obtained in cone‐based cylindrical (Lim et al., 1974; Wu et al., 1987; He et al., 1998) and rectangular (Zanoelo, 1994) spouted beds.
Wall Effects for the Free Rise of Solid Spheres in Moderately Viscous Liquids
Authors: Dewsbury Kevin H. , Tzounakos Aristotelis , Karamanev Dimitre G. , Margaritis Argyrios
Published: July 2010

For the first time ever, the influence of wall effects on the free rise of a buoyant solid sphere in a square column in a non‐Newtonian (pseudoplastic) fluid was determined. It was found that in most cases, as the column width decreased, the terminal rise velocity of the sphere would decrease as well. It was also discovered that wall effects could change the rising sphere trajectory. Spheres that displayed a spiraling trajectory in larger columns would display a more linear trajectory in smaller columns. Occasionally, due to this change in trajectory, the solid sphere terminal velocity would increase as the column width decreased. This phenomenon (the positive wall effect) has not been reported for falling spheres in Newtonian or non‐Newtonian fluids.
Gas—Liquid Flow Through Helical Coils in Horizontal Orientation
Authors: Mandal Sailendra Nath , Das Sudip Kumar
Published: July 2010

Experimental investigations have been carried out to evaluate the two‐phase pressure drop and the holdup for gas‐Newtonian liquid flow through helical coils. 24 helical coils and three different liquids were used for the experiments. Empirical correlations have been developed to predict the two‐phase friction factor and the liquid holdup as functions of various physical and dynamic variables of the system. Statistical analysis of the correlations suggests that they are of acceptable accuracy.
Drop Deformation and Breakup Mechanisms in Viscoelastic Model Fluid Systems and Polymer Blends
Authors: Mighri Frej , Huneault Michel A.
Published: July 2010

This paper reviews the dispersion mechanisms in viscoelastic systems under relatively high shear rate conditions. In particular, two non‐Newtonian deformation and breakup mechanisms were revealed by flow visualization in a transparent Couette shearing setup. The first one is the dispersed droplet elongation perpendicular to the flow direction. This was observed only for viscoelastic drops and had been associated to normal force buildup in the droplet. The second deformation/breakup mechanism was observed in very high viscosity ratio polymer systems. It consists in erosion at the drop surface. Clouds of very small ribbons and sheets were developed around the drop then stretched and finally broken into very small droplets, rapidly distributed in the matrix.
Online Light Scattering Measurements as a Means to Assess Influence of Extrusion Parameters on Non‐reactive Polymer Blend Morphology: Experimental Procedure and Preliminary Results
Authors: Serra Christophe , Schlatter Guy , Bouquey Michel , Muller René , Terrisse Jean
Published: July 2010

The influence of extrusion parameters on the morphology of non‐reactive blends has been investigated by means of online light‐scattering measurements. A light‐scattering device was especially designed to be mounted on a twin screw extruder at different locations along the barrel. The obtained light‐scattering patterns were interpreted with respect to the variation of the processing parameters. Preliminary results show that there is little effect of the rotational speed, position along the screw and feed throughput on the morphology but a quite noticeable effect of the blend composition. These results were confirmed by SEM micrographs.
Evolution of Chemistry, Morphology and Rheology of Various Polymer Systems along a Twin‐Screw Extruder
Authors: Covas José A. , Carneiro Olga S. , Maia João M. , Filipe Susana A. , Machado Ana V.
Published: July 2010

Intermeshing twin‐screw extruders have been recently identified as useful in special application niches such as the extrusion of PVC dry blends (counter‐rotating machines) and compounding operations (co‐rotating machines). Thus, it is of interest to study the mechanical and/or chemical effects that occur along the screw axis of the extruders, since they will dictate the characteristics and performance of the final material. This work aims at illustrating the usefulness of a simple experimental tool recently developed for the study of the physical, chemical and morphological evolution along the extruder of polymer based systems, data being presented and discussed for a number of composites and blends.