bluuebunny/crossref_metadata_2025 huggingface dataset:
DNA-templated Cooperative Formation of the Luminous Lanthanide Complex and Its Analytical Application to Gene Detection
Authors: Kitamura Yusuke , Ihara Toshihiro , Tsujimura Yusuke , Tazaki Masato , Jyo Akinori
Published: October 2005

Ethylenediamine tetraacetic acid (EDTA) and 1,10-phenanthrorine (phen) were covalently attached to the 5′ and 3′ ends of two different oligonucleotides (ODNs), respectively. The sequences of the ODN conjugates were designed to contiguously hybridize on the target DNA with their auxiliary units facing each other, providing a microenvironment to accommodate the lanthanide ions. The characteristic emissions of the Tb3+ and Eu3+ ions were clearly observed in the presence of the full-matched target DNA. On the other hand, the emissions from the mixed solutions with the mutant containing one base displacement were marginal.
Assessment of osteoarthritis after reconstruction of the anterior cruciate ligament
Authors: Hart A. J. , Buscombe J. , Malone A. , Dowd G. S. E.
Published: October 2005

We used single-photon emission computed tomography (SPECT) to determine the long-term risk of degenerative change after reconstruction of the anterior cruciate ligament (ACL). Our study population was a prospective series of 31 patients with a mean age at injury of 27.8 years (18 to 47) and a mean follow-up of ten years (9 to 13) after bone-patellar tendon-bone reconstruction of the ACL. The contralateral normal knee was used as a control. All knees were clinically stable with high clinical scores (mean Lysholm score, 93; mean Tegner activity score, 6). Fifteen patients had undergone a partial meniscectomy and ACL reconstruction at or before reconstruction of their ACL.

In the group with an intact meniscus, clinical symptoms of osteoarthritis (OA) were found in only one patient (7%), who was also the only patient with marked isotope uptake on the SPECT scan compatible with OA. In the group which underwent a partial meniscectomy, clinical symptoms of OA were found in two patients (13%), who were among five (31%) with isotope uptake compatible with OA. Only one patient (7%) in this group had evidence of advanced OA on plain radiographs.

The risk of developing OA after ACL reconstruction in this series is very low and lower than published figures for untreated ACL-deficient knees. There is a significant increase (p < 0.05) in degenerative change in patients who had a reconstruction of their ACL and a partial meniscectomy compared with those who had a reconstruction of their ACL alone.
Oxford medial unicompartmental knee arthroplasty in patients younger and older than 60 years of age
Authors: Price A. J. , Dodd C. A. F. , Svard U. G. C. , Murray D. W.
Published: October 2005

We present a comparison of the results of the Oxford unicompartmental knee arthroplasty in patients younger and older than 60 years of age. The ten-year all-cause survival of the < 60 years of age group (52) was 91% (95% confidence interval (CI) 12), while in the ≥ 60 years of age group (512), the figure was 96% (95% CI 3). For the younger group, the mean Hospital for Special Surgery score at ten-year follow-up (n = 21) was 94 of 100, compared with a mean of 86 of 100 for the older group (n = 135). The results show that the Oxford unicompartmental arthroplasty can achieve ten-year results that are comparable to total knee arthroplasty in patients < 60 years of age. We conclude that for patients aged over 50, age should not be considered a contraindication for this procedure.
Ten-year in vivo wear measurement of a fully congruent mobile bearing unicompartmental knee arthroplasty
Authors: Price A. J. , Short A. , Kellett C. , Beard D. , Gill H. , Pandit H. , Dodd C. A. F. , Murray D. W.
Published: October 2005

Polyethylene particulate wear debris continues to be implicated in the aetiology of aseptic loosening following knee arthroplasty. The Oxford unicompartmental knee arthroplasty employs a spherical femoral component and a fully congruous meniscal bearing to increase contact area and theoretically reduce the potential for polyethylene wear. This study measures the in vivo ten-year linear wear of the device, using a roentgenstereophotogrammetric technique.

In this in vivo study, seven medial Oxford unicompartmental prostheses, which had been implanted ten years previously were studied. Stereo pairs of radiographs were acquired for each patient and the films were analysed using a roentgen stereophotogrammetric analysis calibration and a computer-aided design model silhouette-fitting technique. Penetration of the femoral component into the original volume of the bearing was our estimate of linear wear. In addition, eight control patients were examined less than three weeks post-insertion of an Oxford prosthesis, where no wear would be expected. The control group showed no measured wear and suggested a system accuracy of 0.1 mm. At ten years, the mean linear wear rate was 0.02 mm/year.

The results from this in vivo study confirm that the device has low ten-year linear wear in clinical practice. This may offer the device a survival advantage in the long term.
Finite-element analysis of failure of the Capital Hip designs
Authors: Janssen D. , Aquarius R. , Stolk J. , Verdonschot N.
Published: October 2005

The Capital Hip implant was a Charnley-based system which included a flanged and a roundback stem, both of which were available in stainless steel and titanium. The system was withdrawn from the market because of its inferior performance. However, all four of the designs did not produce poor rates of survival. Using a simulated-based, finite-element analysis, we have analysed the Capital Hip system. Our aim was to investigate whether our simulation was able to detect differences which could account for the varying survival between the Capital Hip designs, thereby further validating the simulation.

We created finite-element models of reconstructions with the flanged and roundback Capital Hips. A loading history was applied representing normal walking and stair-climbing, while we monitored the formation of fatigue cracks in the cement.

Corresponding to the clinical findings, our simulation was able to detect the negative effects of the titanium material and the flanged design in the Capital Hip system. Although improvements could be made by including the effect of the roughness of the surface of the stem, our study increased the value of the model as a predictive tool for determining failure of an implant.
Osteolysis in a surface-cemented, primary, modular Freeman-Samuelson total knee replacement
Authors: Arora J. , Ogden A. C.
Published: October 2005

We analysed at a mean follow-up of 7.25 years the clinical and radiological outcome of 117 patients (125 knees) who had undergone a primary, cemented, modular Freeman-Samuelson total knee replacement. While the tibial and femoral components were cemented, the patellar component was uncemented. A surface-cementing technique was used to secure the tibial components. A total of 82 knees was available for radiological assessment. Radiolucent lines were seen in 41 knees (50%) and osteolytic lesions were seen in 13 knees (16%). Asymptomatic, rotational loosening of the patellar implant was seen in four patients and osteolysis was more common in patients with a patellar resurfacing. Functional outcome scores were available for 41 patients (41 knees, 35%) and the mean Western Ontario McMasters Universities score was 77.5 (sd 19.5) and the cumulative survival was 93.4% at ten years with revision for aseptic loosening as an endpoint. Increased polyethylene wear from modular components, a rotationally-loose patella, and the surface-cementing technique may have contributed to the high rate of osteolysis seen in our study.
The use of a virtual three-dimensional model to evaluate the intraosseous space available for percutaneous screw fixation of acetabular fractures
Authors: Attias N. , Lindsey R. W. , Starr A. J. , Borer D. , Bridges K. , Hipp J. A.
Published: October 2005

We created virtual three-dimensional reconstruction models from computed tomography scans obtained from patients with acetabular fractures. Virtual cylindrical implants were placed intraosseously in the anterior column, the posterior column and across the dome of the acetabulum. The maximum diameter which was entirely contained within the bone was determined for each position of the screw. In the same model, the cross-sectional diameters of the columns were measured and compared to the maximum diameter of the corresponding virtual implant.

We found that the mean maximum diameter of virtual implant accommodated by the anterior columns was 6.4 mm and that the smallest diameter of the columns was larger than the maximum diameter of the equivalent virtual implant.

This study suggests that the size of the screw used for percutaneous fixation of acetabular fractures should not be based solely on the measurement of cross-sectional diameter and that virtual three-dimensional reconstructions might be useful in pre-operative planning.
A completely shattered tibia
Authors: John V. Z. , Alagappan M. , Devadoss S. , Devadoss A.
Published: October 2005

Despite advances in reconstructive surgery, salvage of mangled extremities still requires long periods of treatment with many operations that can be taxing both to the surgeon and the patient. Attempts at reconstruction of severely shattered limbs necessitate counselling with regard to the protracted course of treatment and associated morbidity as well as problems which may require abandoning of the procedure and secondary amputation. We report the successful salvage of a severely comminuted and open fracture of the tibia in a 32-year-old man.
The incidence of Perthes’ disease in Southwest Scotland
Authors: Pillai A. , Atiya S. , Costigan P. S.
Published: October 2005

We have investigated the annual incidence of Perthes’ disease in Dumfries and Galloway (Southwest Scotland), in relation to the population density and socio-economic status. The incidence of Perthes’ disease in rural Scotland is comparable with that in urban areas (15.4 per 100 000). There was a direct association between the incidence of Perthes’ disease and deprivation scores, with the highest incidence in the most deprived areas. A higher incidence of Perthes’ disease was noted in areas with a lower population density compared with those with a higher density. We found no correlation between population density and deprivation scores for individual electoral wards within the region.
The effect of hip resurfacing on oxygen concentration in the femoral head
Authors: Steffen R. T. , Smith S. R. , Urban J. P. G. , McLardy-Smith P. , Beard D. J. , Gill H. S. , Murray D. W.
Published: October 2005

We inserted an electrode up the femoral neck into the femoral head of ten patients undergoing a metal-on-metal hip resurfacing arthroplasty through a posterior surgical approach and measured the oxygen concentration during the operation. In every patient the blood flow was compromised during surgery, but the extent varied. In three patients, the oxygen concentration was zero at the end of the procedure. The surgical approach caused a mean 60% drop (p < 0.005) in oxygen concentration while component insertion led to a further 20% drop (p < 0.04). The oxygen concentration did not improve significantly on wound closure. This study demonstrates that during hip resurfacing arthroplasty, patients experience some compromise to their femoral head blood supply and some have complete disruption.
Race as Class
Authors: Gans Herbert J.
Published: October 2005

Why does the idea of race continue to exert so much influence in the United States? Because the skin colors and other physical features used to define race were selected precisely because they mirror the country's socioeconomic pecking order.
Breaking the Last Taboo: Interracial Marriage in America
Authors: Qian Zhenchao
Published: October 2005

Interracial marriages are becoming more common, but skin color still matters in America. As minorities—especially Asian and Hispanic Americans—move up the ladder and integrate neighborhoods, they increasingly marry whites. Still, strong racial identities and lingering prejudice, particularly toward African Americans, limit this most intimate form of integration.
Race and the Social Science of Sincerity
Authors: Jackson John L.
Published: October 2005

Why does one child raised in the same socioeconomic setting as his peer succeed where his peer fails? The concepts of authenticity and sincerity suggest contrasting answers.
DOING NOTHING: Harry Langdon and the Performance of Absence
Authors: Rapf Joanna E.
Published: October 2005

ABSTRACT Doing Nothing: Harry Langdon and The Performance of Absence. Where most comedians of the silent era did things, Harry Langdon's trick was to do nothing. His is a comedy of absence, surreal in its exploration of repressed desire that is perversely shown in his relationship with vamps. With long, slow takes he enacts a dark, subtle humor with contemporary resonance.
Lost on Pleasure Islands: Storytelling in Disney's Silly Symphonies
Authors: Merritt Russell
Published: October 2005

ABSTRACT Disney broke away from gag-centered cartoons in favor of fantasy narrative in his Silly Symphony cartoon series, produced in the 1930s. In landmark Symphonies such as The Ugly Duckling, Babes in the Woods, Lullaby Land, Who Killed Cock Robin?, and Three Little Pigs he explores with remarkable potency the inner life of the child—dramatizing the child's issues of separation, sense of shame, struggle to control impulses, fear of annihilation, and love of adventure.
Shift from Conn’s syndrome to Cushing’s syndrome in a recurrent adrenocortical carcinoma
Authors: Barzon L , Masi G , Fincati K , Pacenti M , Pezzi V , Altavilla G , Fallo F , Palù G
Published: October 2005

Objective: Adrenocortical tumors may originate from the zona glomerulosa, zona fasciculata, or zona reticularis and be associated with syndromes due to overproduction of mineralocorticoids, glucocorticoids, or androgens respectively. We report an unusual case of recurrent adrenocortical carcinoma (ACC), which seems to contradict the paradigm of functional adrenal zonation.

Case report: A male patient presented with severe primary aldosteronism due to an ACC, which relapsed after adrenalectomy and adjuvant mitotane therapy. After removal of the tumor recurrence and eight cycles of chemotherapy with etoposide, doxorubicin and cisplatin, the patient presented again with ACC masses, but in association with overt Cushing’s syndrome and normal aldosterone levels.

Methods and results: Extensive pathologic examination showed that this shift in steroid hormone production was paralleled by an attenuation of tumor cell atypia and polymorphism, whereas gene expression profile analysis demonstrated a change in expression of adrenal steroidogenic enzymes. Moreover, cancer progression was associated with overexpression of the inhibin-α subunit, which could have contributed to the phenotypic changes.

Conclusions: This case of recurrent ACC demonstrates that adrenocortical cells can reverse their differentiation program during neoplastic progression and change their specific hormone synthesis, as a consequence of modifications in the expression profile of steroidogenic enzymes and cofactors. We hypothesize that this shift in steroid hormone secretion is a consequence of chromosome amplification induced by chemotherapy. These findings, besides opening new perspectives to study adrenocortical cell plasticity and potential, demonstrate how conventional clinical and pathologic evaluation can be combined with genomic analysis in order to dissect thoroughly the biology of cancer.
Efficacy and safety of Monascus purpureus Went rice in subjects with hyperlipidemia
Authors: Lin Cheng-Chieh , Li Tsai-Chung , Lai Ming-May
Published: October 2005

Objective: The purpose of this study was to assess the lipid-lowering effect of Monascus purpureus Went rice on serum lipids in patients with hyperlipidemia, and to assess its safety by reporting adverse events and clinical laboratory measurements.

Design and methods: This was a randomized, double-blind, placebo-controlled study. In all, 79 patients (aged 23–65 years) with a mean baseline low-density lipoprotein cholesterol (LDL-C) level of 5.28 mmol/l (203.9 mg/dl) received a twice daily dose of placebo or Monascus purpureus Went rice (600 mg) for 8 weeks.

Results: At week 8, Monascus purpureus Went rice therapy reduced LDL-C by 27.7%, total cholesterol by 21.5%, triglycerides by 15.8% and apolipoprotein B by 26.0%. High-density lipoprotein cholesterol and apolipoprotein A-I levels were increased by 0.9 and 3.4% respectively (not significant). No patient in the Monascus purpureus Went rice treatment group had an alanine aminotransferase (ALT), aspartate aminotransferase (AST) or creatine phosphokinase (CPK) measurement that was ≥ 3 times the upper limit of normal at week 4 and week 8.

Conclusion: Monascus purpureus Went rice significantly reduced LDL-C, total cholesterol, triglycerides and apolipoprotein B levels, and was well tolerated in patients with hyperlipidemia. However, this study only provides data from an 8-week trial and long-term safety and efficacy data are needed.
The tumour necrosis factor (TNF)-α system is activated in accordance with pulse pressure in normotensive subjects with type 1 diabetes mellitus
Authors: González-Clemente J M , Giménez-Pérez G , Richart C , Broch M , Caixàs A , Megia A , Giménez-Palop O , Simón I , Mauricio D , Vendrell J
Published: October 2005

Objective: Pulse pressure (PP) and inflammation are important predictors of cardiovascular disease (CVD), even in the normotensive. The age-related increase in PP can be diagnosed up to 20 years earlier in subjects with type 1 diabetes mellitus (T1DM) than in the general population. Some evidence suggests that PP can stimulate inflammation. Our aim was to study the relationship between PP and plasma inflammatory proteins in normotensive subjects with T1DM.

Design: This was a cross-sectional study of a group of normotensive (<140/80 mmHg) subjects diagnosed with T1DM 14 years before. None of them had clinically proven CVD or inflammatory conditions or were on antiplatelet, antihypertensive, anti-inflammatory or lipid-lowering treatment.

Methods: The following information was recorded: sex, age, body-mass index (BMI), waist-to-hip ratio (WHR), systolic blood pressure (SBP), diastolic blood pressure (DBP), PP, mean blood pressure (MBP), smoking, alcohol intake, insulin dose, lipid profile, HbA1c, microvascular complications, and plasma concentrations of soluble receptor types 1 and 2 of tumour necrosis factor (TNF)-α (sTNFR1 and sTNFR2, respectively), interleukin-6, C-reactive protein, adiponectin and leptin.

Results: A total of 112 subjects were evaluated (aged 27.4±6.6 years, 52.7% women, BMI: 20.4±2.7 kg/m2, WHR: 0.82±0.09, SBP: 112±12 mmHg, DBP: 68±9 mmHg, PP: 45±9 mmHg, MBP: 82±9 mmHg, HbA1c: 8.2% (7.3–9.0%), 41.1% microvascular complications). After adjusting for potential confounders, only inflammatory markers of the TNF-α system correlated significantly with PP (Pearson correlation coefficient between sTNFR1 and PP: r = 0.215, P = 0.030; and between PP and sTNFR2: r = 0.238, P = 0.020).

Conclusion: In normotensive subjects with T1DM after 14 years of diagnosis, the activation of the TNF-α system is positively associated with PP levels. This finding might suggest a pathogenic role of the TNF-α system in the development of cardiovascular disease in T1DM.
Interdependence of lean body mass and total body water, but not quality of life measures, during low dose GH replacement in GH-deficient adults
Authors: Mukherjee Annice , Adams Judith E , Smethurst Linda , Shalet Stephen M
Published: October 2005

Lean body mass (LBM) and total body water (TBW) are reduced in GH-deficient (GHD) adults and alter with GH replacement. Whether these parameters are interdependent and whether alterations in their homeostasis contribute to the perceived quality of life (QOL) deficit in GHD remains unclear. In this study, IGF-I, body composition by whole-body dual-energy X-ray absorptiometry, TBW by deuterium dilution (D2O) and two validated QOL instruments - psychological general well-being schedule (PGWB, generic, 6 domains; lower score worse QOL) and assessment of GH deficiency in adults (AGHDA, disease orientated; higher score worse QOL) were studied at baseline and after 3 and 6 months of GH replacement in thirty GHD adults. Patients with diabetes insipidus, and cardiac and renal failure were excluded. Median age-adjusted IGF-I standard deviation score increased from −3.40 (−6.40 to −1.60) to −0.2 (−1.88 to 0.78) (P < 0.0001) at a median daily GH dose of 0.4 mg. During treatment, LBM increased from 47.4 ± 10.7 kg at baseline to 49.5 ± 10.8 kg at 6 months (P = 0.0008), and fat mass decreased from 28.0 ± 12.1 kg at baseline to 27.2 ± 12.6 kg at 6 months (P = 0.0004). A non-significant trend towards an increase in TBW was observed (mean 1.7 kg, P = 0.08). The PGWB score increased from 62.9 ± 20.6 to 73.7 ± 21.7 (P = 0.0006). The AGHDA score decreased from 13.7 ± 7.3 to 8.75 ± 7.75 (P = 0.0002). At each time point, a linear correlation between LBM and TBW was demonstrated, defined by TBW = (0.972 × LBM)–10.6. However, only a weakly positive correlation existed between the percentage changes in these variables (R = 0.40, P = 0.04). No correlations were demonstrated between QOL measures and body composition. The change in LBM with physiological GH replacement correlates weakly with change in TBW, therefore factors other than TBW may also contribute to the LBM changes. Improved QOL with GH replacement is not explained by favourable changes in body composition.
Self‐Tuning Insulin Adjustment Algorithm for Type 1 Diabetic Patients based on Multi‐Doses Regime
Authors: Campos-Delgado D. U. , Femat R. , Hernández-Ordoñez M. , Gordillo-Moscoso A.
Published: October 2005

A self‐tuning algorithm is presented for on‐line insulin dosage adjustment in type 1 diabetic patients (chronic stage). The algorithm suggested does not need information of the patient insulin–glucose dynamics (model‐free). Three doses are programmed daily, where a combination of two types of insulin: rapid/short and intermediate/long acting is injected into the patient through a subcutaneous route. The doses adaptation is performed by reducing the error in the blood glucose level from euglycemics. In this way, a total of five doses are tuned per day: three rapid/short and two intermediate/long, where there is large penalty to avoid hypoglycemic scenarios. Closed‐loop simulation results are illustrated using a detailed nonlinear model of the subcutaneous insulin–glucose dynamics in a type 1 diabetic patient with meal intake.
The Imposter: A Motivational Strategy to Encourage Reading in Adolescents
Authors: Curran Michael J. , Smith Elizabeth C.
Published: October 2005

The Imposter is a strategy that encourages a focused approach to reading among adolescents. Contradictions or other types of conceptual flaws are inserted into a reading passage. The reader, knowing that flaws are hidden in the text, attempts to discover the errors. The reader then justifies his or her identification of flaws based on the concepts developed in the reading. In other words, the reader must demonstrate why the identified aspect or passage does not fit with the rest of the text.

This article suggests several guidelines for implementing the strategy. The Imposter has wide applicability in subject matter text as well as across reading levels. Four examples are given—including readings from mathematics, chemistry, art, and English literature—which demonstrate not only the content and reading level of the passage, but also the degree of subtlety involved in the inserted flaw.
Teaching Queer‐Inclusive English Language Arts
Authors: Blackburn Mollie V. , Buckley JF
Published: October 2005

The authors argue for teaching queer‐inclusive English language arts (ELA). They report on a study that surveyed high school personnel across the United States, revealing that very few people in charge of ELA curricula value such inclusion. In response to these findings, the authors offer “images of the possible” in which texts and methods that could be used in queer‐inclusive ELA curricula are suggested. They advocate for teaching ELA that represents diverse people, including those who are lesbian, gay, bisexual, transgendered, and questioning, in a range of positionalities, as both insiders and outsiders in various texts. Such a curriculum is one way for all high school students to experience themselves amid “otherness,” or to experience the “other” in their midst. It is the vehicle for, and the echo of, a varied and varying society—a thesis‐antithesis dialectic that eschews synthesis. In order to accomplish this, teachers must educate students to examine and experience the multiple and mutable constituents of identity and culture, of which sexuality is a critical, but hardly constant, constituent.
Pedagogy of the Obsessed
Authors: Trier James
Published: October 2005

The author examines his obsession with a variety of media culture texts—films, television programs, visual ads in magazines and on billboards, music CDs, comic books, video games, websites—an obsession that manifests itself most pervasively in collecting “video texts.” Among the over 1,000 video texts collected are more than 100 school films, many of which were used for various critical pedagogical projects designed around selected media texts. The author explains how his use of these video texts was radically transformed when he began using selected segments from a wide range of them to create “videocompilations” and “videocollages.” He argues that even though we live in a media‐saturated society (a typically negative phrase within media‐literacy discourses), there exist many opportunities for educators to use media texts for productive pedagogical purposes.
Modeling of Autothermal Steam Methane Reforming in a Fluidized Bed Membrane Reactor
Authors: Dogan Meltem , Posarac Dusko , Grace John , Adris Alaa-Eldin M. , Lim C. Jim
Published: October 2005

Fluidized bed reactors for steam methane reforming, with and without immersed membrane surfaces for withdrawal of hydrogen, are modeled with oxygen added in order to provide the endothermic heat required by the reforming reactions. Porous alumina, palladium and palladium-coated high-flux tubes are investigated as separation materials, the latter two being permselective. Hydrogen yield and permeate hydrogen molar flow are predicted to decrease with increasing oxygen flow, and to increase with temperature. When the steam-to-carbon ratio increases, permeate hydrogen yield decreases slightly, while the total hydrogen yield increases for all configurations. The flow of oxygen required to achieve autothermal conditions depends on such factors as the reactor temperature, steam-to-carbon ratio and preheating of the feed.
Application of Computational Fluid Dynamics to Multiphase Flow in Bubble Columns
Authors: Bertola Francesco , Vanni Marco , Baldi Giancarlo
Published: October 2005

The application of Computational Fluid Dynamics (CFD) to the simulation of bubble columns devices is discussed. A comparison between different modeling approaches has been carried out in order to understand which is the present ability of CFD codes to predict the flow in a gasliquid system. The effect of different options of simulation, such as 2D and 3D grids with different density of cells, order of discretization, turbulence closure, has been studied for systems characterized by different values of gas hold-up. The analysis is restricted to bubbly flow conditions. Eulerian-Eulerian two fluid models have been used to describe both the timedependent motion of the bubble plume and the time-averaged flow pattern in the column. The systems considered are those experimentally characterized by the group of Eigenberger (Becker et al., 1994), by Mudde et al. (1997), by the group of Dudukovic (Sanyal et al., 1999) and by Ho Yu and Kim (1991).
Modeling of the Catalytic Distillation Process for the Synthesis of Ethyl Cellosolve Using A Three-Phase Nonequilibrium Model
Authors: Zheng Yuxiang , Ng Flora T. T. , Rempel Garry L.
Published: October 2005

The catalytic distillation (CD) process for the synthesis of ethyl cellosolve from ethanol and ethylene oxide on molecular sieve catalyst NKC-01 in a 200 mm CD pilot column was simulated using the three-phase nonequilibrium model which was developed in our laboratory. The main feature of this model is that the actual rates for transport and reaction are used and the stage efficiency or HETP (height equivalent to a theoretical plate) is not required. The effect of multicomponent mass and heat transfer between vapor and liquid phases as well as between liquid and solid (catalyst) phases was taken into account according to the Maxwell-Stefan equations. The Newton-Raphson method was used to solve the model equations. The simulation profiles of the temperature and composition along the column are in good agreement with the pilot CD plant data obtained for the synthesis of ethyl cellosolve. Good agreement between model predictions and experimental data is also obtained for the yield and selectivity of the ethyl cellosolve. This model could be extended to simulate other CD processes and commercial scale CD plants.
Performance Enhancement of Photocatalytic Reactor Utilizing Flow Instability
Authors: Mehrotra Kanheya , Ray Ajay Kumar
Published: October 2005

A detailed analysis has been performed for a heterogeneous photocatalytic Taylor vortex reactor that uses flow instability to recirculate fluid continually from the vicinity of the rotating inner cylindrical surface (coated with catalyst) to the stationary outer cylindrical surface of an annulus. A detailed time accurate computation when the reactor is started impulsively shows the different stages of flow evolution and the effects of finite length of the reactor in creating eddies, the overall effects of which shows very high efficiency of photocatalytic conversion. The physical arrangement considered is such that pollutant degradation is maximized by a combination of the controlled periodic illumination effect and the motion of fluid particles in a specific regime of centrifugal instability. It was found out that optimum Reynolds's number is 380 as the system reaches steady state faster, number of vortices per unit length is more, vortices move faster towards center from end, and the magnitude of both axial and radial component of velocity is more than at higher or lower value of Reynolds's number.
Modeling of Membrane Reactor
Authors: Hoff Karl A. , Poplsteinova Jana , Jakobsen Hugo A. , Falk-Pedersen Olav , Juliussen Olav , Svendsen Hallvard F.
Published: October 2005

A two-dimensional model for a membrane reactor used for the absorption of CO2 into amines was developed and two solution procedures were tested for the combined diffusion-reaction problem. The method of lines/finite difference method is the fastest and most stable, but conservation of mass is not guaranteed. The finite volume method needs very good initial estimates to converge, and is much slower. This shows a potential problem in the use of commercial CFD-codes for coupled fluid dynamic, diffusion, and chemical reaction problems. The model has been validated with respect to effects of steep wall diffusivity profiles, membrane pore penetration, and available gas/liquid contact area. The agreement between simulated and experimental absorption fluxes is very good, and the experimental unit is found to have good sensitivity for obtaining kinetic and diffusion parameters.
Gas Holdup Characteristics in a Tapered Bubble Column
Authors: Zhang Kai , Zhao Yulong , Zhang Bijiang
Published: October 2005

Gas holdup characteristics were explored experimentally in a tapered bubble column of 3.00m height. The internal diameter increased from 0.10 m at the bottom to 0.20 m at the top. Two gas holdup characteristic parameters investigated were local gas holdup and overall gas holdup. Local gas holdup was measured by pressure drop method whilst overall gas holdup was measured by both pressure drop and bed expansion techniques. Axial gas holdup profile decreased from the bottom to the top in the range of the experiments. Overall gas holdup reached a maximum in transitional regime for either the gas-liquid system or the gas-liquid-solid system with low slurry concentration, but increased monotonically for gas-liquid-solid system with high slurry concentration. Overall gas holdup decreased with increasing static slurry height or solid concentration. The effect of particle diameter on gas holdup was too insignificant to be considered. Experiments were carried out in a cylindrical column to compare the difference between cylindrical and tapered bubble columns. Moreover, an empirical correlation was presented to estimate overall gas holdup in the tapered slurry bubble column (TSBC).
Gas Dispersion and Bubble-to-Emulsion Phase Mass Exchange in a Gas-Solid Bubbling Fluidized Bed: A Computational and Experimental Study
Authors: Patil Dhaneshwar J. , van Sint Annaland Martin , Kuipers J.A.M.
Published: October 2005

Knowledge of gas dispersion and mass exchange between the bubble and the emulsion phases is essential for a correct prediction of the performance of fluidized beds, particularly when catalytic reactions take place. Test cases of single rising bubble and a bubbling fluidized bed operated with a jet without a chemical reaction were studied in order to obtain fundamental insights in the prevailing mass transfer phenomena. Numerical simulations were carried out to predict the dispersion of tracer gas using a two-fluid model based on Kinetic Theory of Granular Flow (KTGF). The simulations of a single-bubble rising through an incipiently fluidized bed revealed that the assumptions often made in phenomenological models in the derivation of correlations for the mass transfer coefficient, mainly that the bubble diameter remains constant and that the tracer concentration is uniform in the bubble, are not valid. The predicted bubble-to-emulsion phase mass transfer coefficient showed good agreement with the estimated values from the literature correlations assuming additive convection-diffusion transport for different bubble sizes and different particle sizes, indicating the importance of the convective distribution even for relatively small particles. Experiments were carried out to measure the steady state concentration profiles of a tracer gas in a pseudo two-dimensional bubbling fluidized bed operated with a jet. The simulated steady state concentration profiles of the tracer gas agreed well the experimental measurements. The radial convection of the gas is significantly influenced by the bubble throughflow and therefore depends upon the particle and bubble size. The experimental comparison of theoretical results was extended to study the influence of the jet velocity and the particle diameter on the radial dispersion of the tracer gas in the bed.
Modelling of a Reverse Flow Catalytic Membrane Reactor for the Partial Oxidation of Methane
Authors: Smit J. , van Sint Annaland M. , Kuipers J.A.M.
Published: October 2005

Gas-To-Liquid (GTL) processes have great potential as alternative to conventional oil and coal processing for the production of liquid fuels. In GTL-processes the partial oxidation of methane (POM) is combined with the Fischer-Tropsch reaction. An important part of the investment costs of a conventional GTL-plant is related to cryogenic air separation. These costs could be substantially reduced by separating air with recently developed oxygen perm-selective perovskite membranes, which operate at similar temperatures as a POM reactor. Integration of these membranes in the POM reactor seems very attractive because oxygen reacts at the membrane surface resulting in a high driving force over the membrane increasing the oxygen permeation.Because the POM-reaction is only slightly exothermic, the natural gas and air feed have to be preheated to high operating temperatures to obtain high syngas yields and because the Fischer-Tropsch reactor operates at much lower temperatures, recuperative heat exchange is essential for an air-based POM process. External heat transfer at elevated temperatures is expensive and therefore recuperative heat exchange is preferably carried out inside the reactor, which can be achieved with the reverse flow concept. To combine the POM reaction, air separation and recuperative heat exchange in a single apparatus a novel, multi-functional reactor is proposed, called the Reverse Flow Catalytic Membrane Reactor (RFCMR). In this reactor a relatively uniform temperature profile should be established at the membrane section and the temperature fronts should be located in the inert in- and outlet sections.To study the RFCMR concept, reactor models have been developed assuming a shell-and-tube geometry, based on models that are commonly used to describe conventional reverse flow reactors. Simulations of the novel reactor concept revealed that a small amount of methane has to combusted on the air side to create the reverse flow behaviour. Also a small amount of steam has to be injected distributively along the perovskite membrane section to maintain the centre of the reactor at nearly isothermal conditions. With these modifications it was found that the desired temperature profile could indeed be created in the RFCMR and that high overall syngas yields can be achieved.
Simulation and Design of a Non-adiabatic Multiphase Microreactor
Authors: Schuster Andreas , Lakshmanan Ramachandran , Ponton Jack , Sefiane Khellil
Published: October 2005

We have identified a novel, multiphase microreactor configuration for the direct fluorination of toluene. With this reactor the fluorine and toluene are separated by a macroporous membrane impregnated with a solid Lewis acid catalyst, which influences the fluorine directly when being absorbed into the liquid phase. Reaction occurs in the membrane adjacent to the gas-phase. According to the literature fluorine is turned into an electrophile in the presence of acidic catalysts improving the selectivity towards monofluorinated products. The direct fluorination of toluene is a very fast and exothermic reaction and therefore heat management is of great importance to avoid thermal runaway. Also, the selectivity of the process deteriorates at elevated temperatures due to increasing radical reactions.To address this issue a detailed model of the heat and mass transfer has been developed. The catalytic membrane is modelled as an idealised system and the porosity, tortuosity and catalytic activity are parameters in a sensitivity analysis to obtain bench-mark values for the reactor performance and the membrane design. The software package FEMLAB has been employed to solve the partial differential equations simultaneously by means of the finite element technique.The performance of the membrane reactor configuration is compared to a falling film microreactor. It is shown that the membrane reactor has great potential to improve the selectivity of the direct fluorination reaction towards mono-fluorinated products by means of a thin solid acid catalyst layer. The influence of the reactor size and the aspect ratio on the temperature in the reaction plane and hot spot formation is studied. With the falling film reactor rising channel size results in increasingly prominent hot spot formation and the selectivity towards monofluorinated products deteriorates. The membrane supports the heat removal because the reaction plane is located inside the solid grid. In this manner the membrane catalyst increases the selectivity of the process and also shifts the optimal operation temperature to higher values towards room temperature. Higher production rate per channel can be achieved requiring less cooling.
Low-Carbon Monoxide Hydrogen by Sorption-Enhanced Reaction
Authors: Harrison Douglas P , Peng Zhiyong
Published: October 2005

Hydrogen is an increasingly important chemical raw material and a probable future primary energy carrier. In many current and anticipated applications the carbon monoxide impurity level must be reduced to low-ppmv levels to avoid poisoning catalysts in downstream processes. Methanation is currently used to remove carbon monoxide in petroleum refining operations while preferential oxidation (PROX) is being developed for carbon monoxide control in fuel cells. Both approaches add an additional step to the multi-step hydrogen production process, and both inevitably result in hydrogen loss. The sorption enhanced process for hydrogen production, in which steam-methane reforming, water-gas shift, and carbon dioxide removal reactions occur simultaneously in the presence of a nickel-based reforming catalyst and a calcium-based carbon dioxide sorbent, is capable of producing high purity hydrogen containing minimal carbon monoxide in a single processing step. The process also has the potential for producing pure CO2 that is suitable for subsequent use or sequestration during the sorbent regeneration step. The current research on sorption-enhanced production of low-carbon monoxide hydrogen is an extension of previous research in this laboratory that proved the feasibility of producing 95+% hydrogen (dry basis), but without concern for the carbon monoxide concentration. This paper describes sorption-enhanced reaction conditions  temperature, feed gas composition, and volumetric feed rate  required to produce 95+% hydrogen containing low carbon monoxide concentrations suitable for direct use in, for example, a proton exchange membrane fuel cell.
Bubble Size Reduction in a Fluidized Bed by Electric Fields
Authors: Kleijn van Willigen Flip , van Ommen J. Ruud , van Turnhout Jan , van den Bleek Cor
Published: October 2005

The reduction of the size of bubbles can improve both selectivity and conversion in gas-solid fluidized beds. Results are reported of the reduction of bubble size by the application of electric fields to uncharged, polarizable particles in fluidized beds. It is shown how average bubble diameters can be drastically reduced, with little change of the bed expansion. A literature review shows that to maintain smooth fluidization, electric fields in the direction of the gas flow, with a relatively low alternating frequency, are optimal. To measure average bubble diameters, a spectral decomposition technique of pressure fluctuation time series is used. Using this method, based on non-intrusive measurements, a characteristic length scale for bubble diameters can be found. It is shown experimentally, using video analysis, that this length scale is of constant proportionality for a given bed material and bed dimensions. The proportionality of the length scale to bubble diameter is independent of measuring height or gas velocity. With this, we have a tool for measuring bubble diameters in both 2-D and 3-D fluidized beds. Electric fields were applied to fluidized beds using thin wire electrodes placed inside the column. Both 2-D and 3-D columns were tested over a range of frequencies and field strengths. For Geldart A glass beads, an optimal range was determined at 5-20 Hz and 400-1600 V/cm fields. The reduction of bubble diameter was measured to be up to 25% for this system. Larger Geldart B glass particles show a larger reduction of bubble diameters - up to 85%. For these particles, the optimal frequency was at a higher range, 20-70 Hz. At higher frequencies (up to 100 Hz), bubble size reduction is less, but still substantial. Experiments in the 3-D column using Geldart A particles show a similar reduction in bubble diameters.
Development of a Catalytic Candle Filter for One-Step Tar and Particle Removal in Biomass Gasification Gas
Authors: Engelen Karen , Zhang Yuhong , Baron Gino V
Published: October 2005

Renewable energy generation from biomass (e.g. wood, agricultural wastes) by gasification is attractive because it can be used for efficient energy production on both small and large scale. Unfortunately, biomass gasification gas contains unwanted impurities, such as condensable tars and ash particles that need to be removed to avoid damaging of the downstream equipment.This work reports on the performance of a novel catalytic candle filter for the integrated high temperature removal of tars and particles from the biomass gasification gas. The catalytic candle filters that are under development are alumina ceramic filters that contain a suitable nickel-based tar cracking catalyst in their pores. This not only avoids mass transfer limitations occurring in packed beds of such catalysts, but also yields a reduced investment cost for the cleanup step.Different nickel-based catalysts have been developed and impregnated in the pores of the alumina support. Nickel is efficient for tar removal, but is sensitive to sulfur poisoning by the biomass gasification gas that typically contains 20-200 ppm H2S. To enhance the resistance to sulfur poisoning CaO or MgO was added to the nickel and also the number of active nickel sites was increased by the deposition of a highly dispersed secondary alumina layer in the large pores of the primary support.Small-scale porous alumina filter discs were tested on their sulfur poisoning resistance under lab conditions using a simulated biomass gasification gas containing benzene and naphthalene as model compounds. At typical conditions, such as a filtration velocity of 2.5 cm/s and a H2S-content of 100 ppm, naphthalene conversions of 99.89% were obtained with a Ni/MgO-activated filter disc with increased surface of the support.
Use of Different Numerical Solution Approaches for a Three-Phase Slurry Catalytic Reactor Model
Authors: Barreira Mardonny Nazareno , Vasco de Toledo Eduardo Coselli , Maciel Filho Rubens , Enrique Maria das Graças
Published: October 2005

In this paper two different numerical approaches are used to find out the steady-state solution for multiphase chemical reactors. Such systems are distributed parameter systems and the steady-state formulation problem leads to a system of nonlinear algebraic equations. The problem is to solve the equations in a robust way so that reliable predictions can be made. Bearing this in mind in this work two methods are implement and their performances compared, to know the Orthogonal Collocation Method e the Finite Volume Method. The results show that in spite of good qualitative agreement in the predictions the latter approaches in more suitable to have a direct solution of the steady-state model of the reactor.
Control and Optimization of a Three Phase Industrial Hydrogenation Reactor
Authors: Rezende Mylene Cristina , Costa Aline Carvalho , Maciel Filho Rubens
Published: October 2005

Three phase catalytic reactors are very important industrial reactors with complex steady state and dynamic behavior. In fact, the interaction among the gas, solid and liquid phases with the kinetic, mass and heat transfer mechanisms lead the system to have a challenging behavior. That is the case for the o-cresol hydrogenation to obtain 2-methyl-cyclohexanol, which is carried out in a three phase catalyst slurry reactor. A determinist mathematical model was developed using the mass and energy conservation equations for each phase, so that a system of differential equations is generated. In order to identify some suitable control structures an extensive dynamic behavior analysis was carried out. The controller implemented was a multivariable predictive controller based on the philosophy of Dynamic Matrix Control (DMC). The problem of optimization was solved through non-linear programming making use of the Successive Quadratic Programming (SQP) algorithm.