bluuebunny/crossref_metadata_2025 huggingface dataset:
Syntheses, Structures, and Antimicrobial Activities of Light-Stable and Di- and Mononuclear Silver(I) Carboxylate Complexes Composed of Triphenylphosphine, and Chiral and Racemic Forms of 2-Pyrrolidone-5-carboxylic Acid (H2pyrrld). A Variety of Ag–O Bonding Modes in the Silver(I) Complexes Constructed with Hard Oxygen and Soft Phosphorus Atoms
Authors: Noguchi Ryusuke , Sugie Akiyoshi , Okamoto Yohei , Hara Akihiro , Nomiya Kenji
Published: October 2005

Using light-stable dimeric silver(I) carboxylate precursors {[Ag(Hpyrrld)]2}n formed with chiral and racemic forms of 2-pyrrolidone-5-carboxylic acid (H2pyrrld) ligand, six novel light-stable, triphenylphosphinesilver(I) complexes consisting of both a hard Lewis base (O atom) and a soft Lewis base (P atom) were prepared, i.e. [Ag2(R-Hpyrrld)2(H2O)(PPh3)2]·H2O (1), [Ag(R-Hpyrrld)(PPh3)2]2 (2), [Ag2(S-Hpyrrld)2(H2O)(PPh3)2]·H2O (3), [Ag(S-Hpyrrld)(PPh3)2]2 (4), {[Ag(R,S-Hpyrrld)(PPh3)]2}n (5), and [Ag(R,S-Hpyrrld)(PPh3)2] (6). Their solid-state and solution structures were unequivocally characterized with elemental analysis, TG/DTA, FTIR, X-ray structure analysis, molecular weight measurements in EtOH with the vaporimetric method, solution (1H, 13C, and 31P) NMR, and solid-state 31P CPMAS NMR spectroscopy. Two sets of the enantiomeric complexes were isolated as (1 and 3) and (2 and 4). X-ray crystallography revealed that these complexes possessed different Ag–O bonding modes, depending on the number of PPh3 ligands and the chirality of the Hpyrrld− ligand. The complexes 1–6 behaved as a monomeric species in EtOH and CD2Cl2. The antimicrobial activites by the silver(I) complexes in the water–suspension system against selected bacteria, yeast, and molds, were significantly correlated with the number of coordinating PPh3 ligands per silver(I) atom in the complexes.
Preparation of Silica Nanosprings Using Cationic Gelators as Template
Authors: Yang Yonggang , Fukui Hiroaki , Suzuki Masahiro , Shirai Hirofusa , Hanabusa Kenji
Published: October 2005

Cationic cyclo(dipeptide) gelators 10mimClO4, 11mimClO4, and 11pyClO4 were synthesized as templates for the sol–gel transcription reaction of alkoxysilanes. They were able to cause physical opaque gels in alcohols such as methanol, ethanol, and 1-propanol. Three-dimensional fibrous networks responsible for physical gelation were found in SEM images of gels. Sol–gel transcription reactions using the self-assemblies of three gelators as the templates were carried out in the presence of propylamine as a catalyst. When tetraethoxysilane (TEOS) was selected as a precursor, three kinds of morphologies, such as inner-helical nanotubes, right-handed nanobundles, and right-handed helical nanosprings were observed by electron microscopy. The helical nanosprings were preferentially formed as compared with nanotubes and nanobundles. On the other hand, the sol–gel polymerization of bis(triethoxysilyl)methane, 1,2-bis(triethoxysilyl)ethane, and 1,4-bis(triethoxysilyl)benzene as precursors gave nanoballs instead of tubular structures. When tetrabutylammonium fluoride (TBAF) was used as a catalyst, a helical tubular structure coated by silica nanoballs was identified.
High Tg Fluorene-based Hole-transporting Materials for Organic Light-emitting Diodes
Authors: Shao Ke-Feng , Li Ying-Feng , Yang Lian-Ming , Xu Xin-Jun , Yu Gui , Liu Yun-Qi
Published: October 2005

A new series of fluorene-based hole-transporting materials, 9,9-bis[4-(di-p-tolylamino)phenyl]-2,7-bis(diphenylamino)fluorene (1), 9,9-bis[4-(di-p-tolylamino)phenyl]-2,7-bis(di-p-tolylamino)fluorene (2), 9,9-bis[4-(di-p-tolylamino)phenyl]-2,7-bis(2-naphthylphenylamino)fluorene (3), and 9,9-bis[4-(di-p-tolylamino)phenyl]-2,7-bis(9-carbazolyl)fluorene (4), was prepared and employed in the fabrication of organic light-emitting devices (OLEDs). These materials were designed to have bulky triarylamine moieties at the C-9 position, which provides them with excellent thermal stability and high glass-transition temperatures (Tg = 139–171 °C). 1 and 3 are comparable to 1,4-bis(1-naphthylphenylamino)biphenyl (NPB) in terms of device performance (maximum luminence and current efficiency) in a standard hole-transporting layer (HTL)/tris(8-hydroxyquinolino)aluminum (Alq3) double-layer device, but are superior to NPB in terms of higher glass-transition temperatures (Tg = 139 and 145 °C, respectively), while 2 shows higher luminance and current efficiency as well as Tg (140 °C) than those of NPB (100 °C).
A Convenient Method for the Preparation of Alkyl Aryl Sulfides from Alcohols and (Chloromethylene)dimethylammonium Chloride
Authors: Kawano Yoshikazu , Kaneko Nobuya , Mukaiyama Teruaki
Published: October 2005

(Chloromethylene)dimethylammonium chloride (Vilsmeier reagent), prepared easily from DMF and oxalyl chloride, works as an efficient condensation reagent for the thioetherification of alcohols in one-pot under mild conditions. Various alcohols are successively converted into the corresponding sulfides with inversion of configurations in moderate to high yields.
Mid-term wear characteristics of an uncemented acetabular component
Authors: Goosen J. H. M. , Verheyen C. C. P. M. , Tulp N. J. A.
Published: October 2005

We investigated the rate of polyethylene wear of a cementless acetabular component at different periods of follow-up in order to test the hypothesis than an irrecoverable deformation process (creep) was followed by an initially low, but gradually increasing wear rate. We studied prospectively 93 uncemented total hip arthroplasties in 83 patients (mean age 50 years (22 to 63)) with a mean follow-up of 8.2 years (3 to 12). We measured the penetration of the femoral head from radiographs taken immediately after surgery at three, six and nine years, or at the latest follow-up.

The median wear rate was 0.17 mm per year in the first three years, a finding which we considered to be caused by creep. Thereafter, the rate of wear declined to 0.07 mm per year (four- to six-year period) and then increased to 0.17 mm per year (seven to nine years) and 0.27 mm per year (more than nine years), which we considered to be a reflection of genuine polyethylene wear. After the nine-year follow-up the wear rates were higher in patients with marked osteolysis. We found no relationship between the inclination angle of the acetabular component or femoral head orientation and the rate of wear. No acetabular component required revision.
Operative treatment for hip subluxation in spinal muscular atrophy
Authors: Zenios M. , Sampath J. , Cole C. , Khan T. , Galasko C. S. B.
Published: October 2005

Subluxation of the hip is common in patients with intermediate spinal muscular atrophy. This retrospective study aimed to investigate the influence of surgery on pain and function, as well as the natural history of subluxed hips which were treated conservatively. Thirty patients were assessed clinically and radiologically. Of the nine who underwent surgery only one reported satisfaction and four had recurrent subluxation. Of the 21 patients who had no surgery, 18 had subluxation at the latest follow-up, but only one reported pain in the hip. We conclude that surgery for subluxation of the hip in these patients is not justified.
Tenodesis of the extensor carpi ulnaris for chronic, post-traumatic lunotriquetral instability
Authors: Shahane S. A. , Trail I. A. , Takwale V. J. , Stilwell J. H. , Stanley J. K.
Published: October 2005

We describe a technique of soft-tissue reconstruction which is effective for the treatment of chronic lunotriquetral instability. Part of extensor carpi ulnaris is harvested with its distal attachment preserved. It is passed through two drill holes in the triquetrum and sutured to itself. This stabilises the ulnar side of the wrist.

We have reviewed 46 patients who underwent this procedure for post-traumatic lunotriquetral instability with clinical signs suggestive of ulnar-sided carpal instability. Standard radiographs were normal. All patients had pre-operative arthroscopy of the wrist at which dynamic lunotriquetral instability was demonstrated. A clinical rating system for the wrist by the Mayo clinic was used to measure the outcome. In 19 patients the result was excellent, in ten good, in 11 satisfactory and in six poor. On questioning, 40 (87%) patients said that surgery had substantially improved the condition and that they would recommend the operation. However, six (13%) were unhappy with the outcome and would not undergo the procedure again for a similar problem. There were six complications, five of which related to pisotriquetral problems. The mean follow-up was 39.1 months (6 to 100). We believe that tenodesis of extensor carpi ulnaris is a very satisfactory procedure for isolated, chronic post-traumatic lunotriquetral instability in selected patients. In those with associated pathology, the symptoms were improved, but the results were less predictable.
Men and women have similar Q angles
Authors: Grelsamer R. P. , Dubey A. , Weinstein C. H.
Published: October 2005

The Q angle is an important determinant of patellar tracking, though its clinical relevance is debatable. One controversy centres around any possible differences in its value between men and women. The accepted, though unproven explanation, for the greater Q angle in women is that a woman has a wider pelvis. However, because of the long distance between the pelvis and patella, relative to the distance from the patella to the tibial tuberosity, large changes in the position of the anterior superior iliac spine are necessary to effect significant changes in the Q angle. In our study of 69 subjects, we did not find such large differences in the position of the anterior superior iliac spine, and found a mean difference of only 2.3° between the Q angles of men and women.

Furthermore, we found that men and women of equal height demonstrated similar Q angles, with taller people having slightly smaller Q angles. The slight difference in Q angles between men and women can be explained by the fact that men tend to be taller.
The validity of the mangled extremity severity score in the assessment of upper limb injuries
Authors: Togawa S. , Yamami N. , Nakayama H. , Mano Y. , Ikegami K. , Ozeki S.
Published: October 2005

The Mangled Extremity Severity Score (MESS) may be used to decide whether to perform amputation in patients with injuries involving a limb. A score of 7 points or higher indicates the need for amputation. We have treated three patients with a MESS of 7 points or higher, in two of which the injured limb was salvaged. This scoring system was originally devised to assess injuries to the lower limb. However, a MESS of 7 points as a justification for amputation does not appear appropriate when assessing injuries to the major vessels in the upper limb.
Sciatic nerve palsy secondary to postoperative haematoma in primary total hip replacement
Authors: Butt A. J. , McCarthy T. , Kelly I. P. , Glynn T. , McCoy G.
Published: October 2005

Sciatic nerve palsy is a recognised complication of primary total hip replacement. In our unit this complication was rare with an incidence of < 0.2% in the past ten years. We describe six cases of sciatic nerve palsy occurring in 355 consecutive primary total hip replacements (incidence 1.69%). Each of these palsies was caused by post-operative haematoma in the region of the sciatic nerve.

Cases, which were recognised early and surgically-evacuated promptly, showed earlier and more complete recovery. Those patients for whom the diagnosis was delayed, and who were therefore managed expectantly, showed little or no recovery. Unexpected pain and significant swelling in the buttock, as well as signs of sciatic nerve irritation, suggest the presence of haematoma in the region of the sciatic nerve.

It is, therefore, of prime importance to be vigilant for the features of a sciatic nerve palsy in the early post-operative period as, when recognised and treated early, the injury to the sciatic nerve may be reversed.
Queer Gardens: Mary Delany's Flowers and Friendships
Authors: Moore Lisa Lynne
Published: October 2005

This essay considers the work of Mary Granville Pendarves Delany (1700–1788) from the perspectives of lesbian studies and queer theory. Delany participated in communities of intimate women friends in eighteenth-century London and Dublin. These friendships fell along a continuum from sexual intimacy to chaste devotion; the first section of this essay explores these themes in Delany's writing. Next, comparing Delany's "improvements" at Delville and Bulstrode with a tradition of erotic garden design allows us to see Delany in the act of creating three-dimensional spaces for female intimacy. Finally, the essay suggests that Delany's famous botanical illustrations form part of an English Linnaean tradition that expresses human sexual variation via representations of the reproductive life of plants.
Why Don't They Just Get Married? Barriers to Marriage among the Disadvantaged
Authors: Edin Kathryn , Reed Joanna M
Published: October 2005

Kathryn Edin and Joanna Reed review recent research on social and economic barriers to marriage among the poor and discuss the efficacy of efforts by federal and state policymakers to promote marriage among poor unmarried couples, especially those with children, in light of these findings.
Gay Marriage, Same-Sex Parenting, and America's Children
Authors: Meezan William , Rauch Jonathan
Published: October 2005

Same-sex marriage, barely on the political radar a decade ago, is a reality in America. How will it affect the well-being of children? Some observers worry that legalizing same-sex marriage would send the message that same-sex parenting and opposite-sex parenting are interchangeable, when in fact they may lead to different outcomes for children.
Marriage as a Public Issue
Authors: Nock Steven L
Published: October 2005

Over the past fifty years, powerful cultural and social forces have made marriage less central to Americans' family lives. In reaction, the United States is now engaged in a wide-ranging debate about the place of marriage in contemporary society.
For Love and Money? The Impact of Family Structure on Family Income
Authors: Thomas Adam , Sawhill Isabel V
Published: October 2005

What do the half-century decline in U.S. marriage and the attendant rise in single parenthood mean for the economic well-being of children, especially children living in single-parent families?
Kommos: Further Iron Age Pottery
Authors: Johnston A. W. (Alan W.)
Published: October 2005

Excavations at Kommos, southern Crete, yielded large amounts of pottery of the Iron Age from levels of slight chronological significance. In this article the author deals with such material, expanding the ceramic aspects of deposition, largely adumbrated in previous publications concerned with stratigraphically significant material from the site. The sum of these publications should therefore constitute an adequate record of the Iron Age pottery from Kommos. The present article also includes pieces of individual interest, whether fully explicable or not, for the scrutiny of a wider public.
The Seder Beriyot in Byzantine-Era Piyyut
Authors: Rand Michael
Published: October 2005

In this article, I attempt to demonstrate the existence of an organic connection between the seder 'avoda, a piyyut type belonging to the liturgy of Yom Kippur, and the short introductory piyyut that frequently precedes it in liturgical practice-the seder beriyot. The connection is apparent on the thematic level, since the beginning of the seder 'avoda, together with the seder beriyot are both concerned with the story of creation. By means of an analysis of some of the formal properties of these two types, however, I argue that in addition to the thematic connection there exists a formal one as well, and that the seder beriyot grew out of the seder 'avoda through a process of internal differentiation that eventually led to the creation of a new piyyut type. In addition to this argument, I suggest that the introductory piyyut that sometimes precedes the seder 'olam in the liturgy of Shavuot was created by analogy to the seder beriyot.
Theories of Policy Diffusion Lessons from Latin American Pension Reform
Authors: Weyland Kurt
Published: October 2005

What accounts for the waves of policy diffusion that increasingly sweep across regions of the world? Why do many diverse countries adopt similar changes? Focusing on the spread of Chilean-style pension privatization in Latin America, this article assesses the relative merit of four theoretical explanations that scholars of diffusion have proposed. As the principal mechanism driving innovations' spread, these approaches emphasize external pressures, emanating especially from international financial institutions; the quest for symbolic or normative legitimacy; rational learning and cost-benefit calculation; and cognitive heuristics, respectively. The article assesses which one of these frameworks can best account for the three distinctive features of diffusion, namely its wavelike temporal pattern; its geographical clustering; and the spread of similarity amid diversity. While several approaches contribute to understanding policy diffusion, the analysis suggests that the cognitive-psychological framework offers a particularly persuasive account of the spread of pension reform.
FLOATING ON THE BORDERS OF EUROPE SOKUROV'S RUSSIAN ARK
Authors: Ravetto-Biagioli Kriss
Published: October 2005

ABSTRACT This paper analyzes how Aleksandr Sokurov's Russian Ark treats the complex relationship of Russia and Europe, considering their history not as a fact but as a poetic construction. The film demonstrates how nostalgia for an imaginary past often produces various forms of historical erasure and national myths of origin.
Expression of vascular endothelial growth factor (VEGF) and its receptors in thyroid carcinomas of follicular origin: a potential autocrine loop
Authors: Vieira Joaquim Miguel , Santos Susana C Rosa , Espadinha Carla , Correia Isabel , Vag Tibor , Casalou Cristina , Cavaco Branca Maria , Catarino Ana Luiísa , Dias Sérgio , Leite Valeriano
Published: October 2005

Objective: The aim of this study was to clarify the role of vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) pathways in thyroid tumourigenesis.

Methods: We examined VEGF, VEGFR-1 and VEGFR-2 expression on 34 papillary thyroid carcinomas (PTCs), 18 follicular thyroid carcinomas (FTCs), eight poorly differentiated thyroid carcinomas (PDTCs) and on a thyroid tumour-derived cell line (NPA′87) by immunohistochemistry, reverse transcriptase PCR, immunofluorescence and Western blotting.

Results: We have demonstrated that VEGF expression was significantly (P < 0.05) more prevalent in PTCs (79%) than in FTCs (50%) or PDTCs (37%). Similarly, 76% of PTCs, 83% of FTCs and 25% of PDTCs expressed VEGFR-1, whereas 68% of PTCs, 56% of FTCs and 37% of PDTCs expressed VEGFR-2. Coexpression of VEGF and its receptors was observed in 50% of PTCs, 39% of FTCs and 12% of PDTCs, raising the possibility that VEGF may signal in an autocrine loop in these neoplasias, as observed previously for other types of cancer. In agreement with the idea that autocrine VEGF signalling plays an important role in thyroid carcinogenesis, the blockade of either VEGF or its receptors with neutralizing antibodies significantly reduced cell viability and increased apoptosis levels of the VEGFR-positive thyroid tumour cell line NPA′87.

Conclusions: Our results highlight a previously undefined VEGF autocrine action in thyroid carcinomas which could play a crucial role in tumour cell survival and could represent a useful therapeutic target for thyroid tumours.
Thyroid hormone increases mannan-binding lectin levels
Authors: Riis Anne Lene Dalkjær , Hansen Troels Krarup , Thiel Steffen , Gravholt Claus Højbjerg , Gjedde Signe , Gormsen Lars Christian , Jørgensen Jens Otto Lunde , Weeke Jørgen , Møller Niels
Published: October 2005

Background: Recent studies have indicated the existence of causal links between the endocrine and immune systems and cardiovascular disease. Mannan-binding lectin (MBL), a protein of the innate immune system, may constitute a connection between these fields.

Methods: To test whether thyroid hormone regulates MBL levels, we studied eight patients with Graves’ hyperthyroidism before and after methimazole therapy, eight healthy subjects before and after short-term experimental hyperthyroidism, and eight hypothyroid patients with chronic auto-immune thyroiditis before and after L-thyroxine substitution.

Results: In all hyperthyroid patients, MBL levels were increased – median (range), 1886 ng/ml (1478–7344) – before treatment and decreased to 954 ng/ml (312–3222) after treatment (P = 0.01, paired comparison: Wilcoxon’s signed ranks test). The healthy subjects had MBL levels of 1081 ng/ml (312–1578). Administration of thyroid hormones to these persons induced mild hyperthyroidism and increased MBL levels significantly to 1714 ng/ml (356–2488) (P = 0.01). Two of the eight hypothyroid patients had undetectably low levels of MBL both before and after L-thyroxine substitution. The other six hypothyroid patients had decreased levels of MBL of 145 ng/ml (20–457) compared with 979 ng/ml (214–1533) after L-thyroxine substitution (P = 0.03, paired comparison: Wilcoxon’s signed ranks test).

Conclusion: Our data show that thyroid hormone increases levels of MBL. MBL is part of the inflammatory complement system, and this modulation of complement activation may play a role in the pathogenesis of a number of key components of thyroid diseases.
The expression of wild-type pendrin (SLC26A4) in human embryonic kidney (HEK 293 Phoenix) cells leads to the activation of cationic currents
Authors: Dossena Silvia , Maccagni Antonella , Vezzoli Valeria , Bazzini Claudia , Garavaglia Maria Lisa , Meyer Giuliano , Fürst Johannes , Ritter Markus , Fugazzola Laura , Persani Luca , Zorowka Patrick , Storelli Carlo , Beck-Peccoz Paolo , Bottà Guido , Paulmichl Markus
Published: October 2005

Objective: The SLC26A4 protein (pendrin) seems to be involved in the exchange of chloride with other anions, therefore being responsible for iodide organification in the thyroid gland and the conditioning of the endolymphatic fluid in the inner ear. Malfunction of SLC26A4 leads to Pendred syndrome, characterized by mild thyroid dysfunction often associated with goiter and/or prelingual deafness. The precise function of the SLC26A4 protein, however, is still elusive. An open question is still whether the SLC26A4-induced ion exchange mechanism is electrogenic or electroneutral. Recently, it has been shown that human pendrin expressed in monkey cells leads to chloride currents.

Methods: We overexpressed the human SLC26A4 isoform in HEK293 Phoenix cells and measured cationic and anionic currents by the patch-clamp technique in whole cell configuration.

Results: Here we show that human pendrin expressed in human cells does not lead to the activation of chloride currents, but, in contrast, leads to an increase of cationic currents.

Conclusion: Our experiments suggest that the SLC26A4-induced chloride transport is electroneutral when expressed in human cellular systems.
Control of a Biped Robot by Total Rate of Angular Momentum Using the Task Function Approach
Authors: Rojas-Estrada J. A. , Marot J. , Sardain P. , Bessonnet G.
Published: October 2005

In this work we address the control problem of biped robots by using the task function approach. A problem arrives when one of the feet is in contact with the ground, which presents imperfections. There is then the possibility that the biped robot undergoes a fall. It is difficult to track any trajectory due to the presence of unevenness on the ground. What we propose is to use the task function approach combined with the application of the total rate of angular momentum to obtain a control law for the ankle. By this technique, the tracking becomes more smooth and the balance is assured. The control law proposed allows the upper part of the robot to be controlled independently since only the ankle actuators are concerned. We enounce the formal problem and present some simulations with real parameters of a 21 degrees of freedom biped robot.
Do You Hear Voices? A Study of the Symbolic Reading Inventory
Authors: Baer Allison L.
Published: October 2005

In an effort to make reading more visible and find out what goes on in the minds of adolescent readers, the author led a group of seventh‐grade students in creating Symbolic Reading Inventories. The students created “snapshot” scenes from the books they were reading and placed themselves, as readers, in or around the picture.

Reading is a complex puzzle made up of myriad pieces, some that fall easily into place and others that struggle to find some kind of fit. To make matters even more interesting, reading is an invisible process, deeply personal between the reader and the text. In interviewing chosen students, the author found that, in general, they were able to suspend reality and actively place themselves in the created scenes. In particular, the students engaged their imaginations, entering the text as they heard, saw, and felt aspects from chosen scenes. Not only did they bring life to the text, but they also brought their own lives to the text as they were actively engaged in creating meaning. Based on this information, the author encourages educators to provide situations that move our students from the commonplace to the extraordinary.
Kinetic Evaluation of Carbon Formation in Steam/CO2-Natural Gas Reformers. Influence of the Catalyst Activity and Alkalinity
Authors: Snoeck Joost-Willem , Froment Gilbert , Fowles Martin
Published: October 2005

The production of synthesis gas with a low H2/CO ratio from natural gas requires recycling the produced CO2, but this enhances the risk of carbon formation. A simulation model for steam/CO2 reformers comprising detailed kinetics of the main reactions but also of the carbon formation and gasification was used to evaluate the potential of carbon formation in the bulk gas phase and inside the catalyst particles along the reactor tube. Simulation results are presented for a number of cases with varying amounts of CO2 in the feed. The model permits an accurate determination of the minimum amount of steam or the maximum amount of CO2 that can be tolerated in the feed. Thermodynamic and kinetic criteria are compared, and a strategy for the evaluation of the risk of carbon formation is proposed. The importance of the activity level of the catalyst and of its alkalinity is also illustrated.
Valorization of Polyolefin/LCO Blend over HZSM-5 Zeolites
Authors: Arandes José M. , Ereña Javier , Olazar Martin , Bilbao Javier , de la Puente Gabriela
Published: October 2005

The cracking of low density polyethylene (PE) and of polypropylene (PP) dissolved in LCO (light cycle oil, product of a commercial FCC unit) is studied in the 450-550 ºC range, by using a reactor simulating a FCC riser. The reaction was carried out on catalysts prepared based on HZSM-5 zeolites with different Si/Al ratio The results are explained by the shape selectivity of the HZSM-5 zeolite and by the total acidity, which decreases as the Si/Al ratio of the zeolite is increased. A feed with polyolefin content higher than 5 wt% limits the conversion of LCO. The cracking on HZSM-5 zeolite catalysts of PE/LCO and PP/LCO blends produces a yield of C5-C12 fraction, which is highly aromatic and with a high content of styrene, and a low yield of C1 and C2 gases and of coke. A feed made up of polyolefins and LCO contributes to increasing the yield of light olefins, of which the concentration of ethylene increases with temperature. When compared to the coke selectivity of LCO cracking, a feed with PP contributes to increasing it, whereas PE decreases it.
Applications of the Non-Dominated Sorting Genetic Algorithm (NSGA) in Chemical Reaction Engineering
Authors: Nandasana Anjana D , Ray Ajay Kumar , Gupta Santosh K.
Published: October 2005

Most of the chemical reaction engineering optimization problems encounters more than one objective functions. A considerable amount of research has been reported on the multiobjective optimization of various chemical reactors using various non-dominated sorting genetic algorithms. This is reviewed in this paper. The introduction of the topic is given at the beginning, followed by the description of multi-objective optimization and Pareto set. We have then discussed various non-dominated sorting genetic algorithms and its applications in chemical reaction engineering. Some comments are also made on the future research direction in this area.
The Catalytic Evaluation of Structured Zeolite Catalysts
Authors: Möller Klaus P , Hedlund Jonas L. L. , Öhrman Olov , Msimang Velaphi
Published: October 2005

ZSM-5 films, with thicknesses between 150 and 2300 nm, supported on 3 mm diameter alumina beads are characterised in terms of their catalytic activity and selectivity for tri-isopropylbenzene cracking and para-xylene isomerisation at 450 °C. A reaction-diffusion model adequately represents the experimental data and is used to estimate intrinsic reactivity and diffusion properties of the zeolite films. Results show that the external activity, overall activity and the diffusivity increase with increasing film thickness. The variation in reactivity and diffusivity, when compared to physio-chemical data, are a result of structural defects and non-homogeneities of the zeolite film. The measured diffusivities are within an order of magnitude of those extrapolated from literature. Thick zeolite films have the largest Thiele modulus as the increase in zeolite film thickness dominates over the structural defects. The largest selectivity improvements are observed for thick zeolite films.
Estimation of Cumene Cracking Reaction-Diffusion Model Parameters: Uniqueness and Parametric Sensitivity Analysis
Authors: Schwan Peter , Möller Klaus P
Published: October 2005

The pulse response of cumene cracking over ZSM5 extrudates has been measured using a Jetloop recycle reactor. A model assuming first order irreversible reaction with constant macro-pore diffusivity and linear adsorption was used to describe the response curves of the reactants and products. The model parameters adsorption, diffusion and reaction rate are in general highly correlated. Relationships for regions of parameter insensitivity and correlation functions between dependent parameters are given. With the aid of independent measurement of adsorption, a sensitivity analysis and a similarity analysis between equations, it was possible to reduce the 7 parameter model into a 2 parameter model for conditions of strong diffusion limitation observed in these experiments. Although good model fits could be achieved, a high degree of uncertainty in the parameter estimates remained, which reflects the high correlation of the physical parameters. Comparison with steady state results shows that the transient diffusivity for cumene is approximately equal to the Knudsen diffusivity, but an order of magnitude lower than the steady state diffusivity. The transient Thiele modulus for cumene was an order of magnitude higher than the steady state value.
Oxygen Distribution in Packed Bed Membrane Reactors For Partial Oxidation Systems and its Effect On Product Selectivity
Authors: Kuerten U. , van Sint Annaland Martin , Kuipers J.A.M.
Published: October 2005

Packed bed membrane reactors (PBMRs) are currently considered for the distributive addition of oxygen in partial oxidation systems. Among other advantages the decreased oxygen concentrations in the PBMR can result in improved product selectivities for reaction systems in which the oxygen dependency of the target product formation is less pronounced than that of the waste product formation. Oxidative dehydrogenation (ODH) of methanol to formaldehyde (Diakov et al., 2002) and ethylbenzene to styrene (Shakhnovich et al., 1984) are industrially relevant examples of such a kinetic system.To achieve considerable selectivity improvements the oxygen concentration should be kept small compared to hydrocarbon concentrations. However, a decrease of the oxygen concentration is accompanied with a decrease in the effectiveness of the catalyst particles since the intraparticle oxygen concentration gradients (and not the hydrocarbon concentration gradients) predominantly determine the actual activity and product selectivities of the catalyst, rendering the common effectiveness factors inapplicable for the modeling of a PBMR.Furthermore, concentration profiles over the radius of the packed bed can emerge, if the radial mass transport rate of oxygen from the membrane wall to the center of the bed is insufficient compared to the local oxygen consumption rate. If the transmembrane flux is dominated by convective transport as typical with porous membranes, the radial oxygen concentration profiles result in increased product losses, and the use of a one-dimensional reactor model may result in an overestimation of the product selectivity.In this paper the effect of limitations of the oxygen mass transport in a PBMR  i.e. intraparticle and from the membrane to the centerline of the packed bed  have been discussed for the ODH of methanol and ethylbenzene.
Bubble Behaviour in Three Phase Capillary Microreactors
Authors: Simmons Mark J , Wong David C Y , Travers Paul J , Rothwell James S
Published: October 2005

Two-phase flow characteristics in vertical capillary downflow were investigated in order to obtain understanding of the behaviour of three-phase monolith reactors. Experiments were conducted using air and dyed water in round and square capillary tubes of 2 mm and 3 mm diameter. The flow regimes and transitions observed were recorded using high speed videography and this data was used to produce flow maps for each tube. The gas and liquid superficial velocities used ranged from 0.001 to 10 m/s and 0.0001 to 1 m/s respectively. The flow regimes and their transitions were found to be a strong function of tube geometry and surface tension effects, and some differences were observed between capillaries of round and square section. This has significant implications for the design of microchannel reactors. Annular, slug-annular, slug, bubbly and churn flow regimes were observed in the round tubes; channelling/irregular flow was observed in the square tubes in place of annular and slug-annular flow.
Formulation of Reduced-Order Models for the Dynamic and Stability Analyses of Autothermal Radial Flow Reactors
Authors: Bartels Malte , Gatica Jorge E. , Pedernera Marisa , Schbib Noemí Susana , Borio Daniel Oscar
Published: October 2005

Autothermal radial flow reactors typically consist of a reactor setup of multiple catalyst-beds with internal heat exchange. These reactors are widely used because of their high efficiency due to the internal heat exchange, and radial flow arrangements are preferred due to their low pressure drops. Although an efficient multi-functional reactor arrangement, this setup has shown to provide for an additional destabilizing mechanism via the heat feedback. Thus, additional stability considerations are necessary when operating autothermal or non-adiabatic reactors at high conversions. This work proposes the formulation of a simplified model to investigate the effect of the heat transfer feedback on the stability of autothermal radial flow reactors. The present work focuses on a lumping approach to reduce the order of a complex distributed parameter system. The model is complex enough so as to preserve the intricacies of this reactor arrangement, but still yield a tractable dynamic formulation. The industrial ammonia synthesis process has been chosen as a case study to illustrate the proposed methodology. The lumped model predictions are qualitatively compared against numerical simulations of a detailed mathematical model.
CFD Simulation of Reaction and Heat Transfer Near the Wall of a Fixed Bed
Authors: Dixon Anthony G. , Nijemeisland Michiel , Stitt Hugh
Published: October 2005

Modeling of fluid flow, heat transfer and reaction in fixed beds is an essential part of their design. This is especially critical for highly endothermic or exothermic reactions in low tube-to-particle diameter ratio (N) tubes, such as are used in steam reforming and partial oxidation. In the simulations a near-wall section of an entire bed is used to create a simulation geometry that can be handled in the available computational domain. A full bed model was also available for validation of the wall-segment model. In the wall-segment approach a section of the bed is modeled in more detail, allowing for a relatively smaller control volume size and a more detailed view of the flow and heat transfer patterns. A simple model of a steam reforming process is used in the CFD simulation to incorporate the effect of reaction rate on temperature profiles in the bed. Simulations were performed under realistic industrial conditions of high temperature, pressure and gas flow rate, with gas properties corresponding to those of steam reforming. A constant wall heat flux was imposed, and various shapes of particles studied with heat sinks on the surface to simulate the reforming endothermic reaction, which is mainly confined to the surface of the pellet. Results will be presented showing the existence and effect of temperature profiles on the catalyst particles, and the effect on the local heat transfer rates of different gas compositions, corresponding to conditions at different locations along the catalyst tube. Local deactivation of catalyst particles can also lead to wall hot spots, or 'giraffe-necking' which can be well-reproduced by the simulations.
Gas and Solid Mixing in High-Density CFB Risers
Authors: Bi Xiaotao T
Published: October 2005

Both gas and solids mixing and dispersion in circulating fluidized beds have been studied using steady and unsteady state tracer techniques. Most studies, however, have been conducted in CFB risers with relatively low solids circulation rates. In recent years, the high density and high solids flux CFB riser has received increasing attention due to its applications in catalytic cracking of crude oil and potential applications in catalytic reactions requiring high catalyst-to-reactant loading ratios. In view of the significantly different flow structure in high-density and high solid flux risers where annulus solids downward flow is no longer present as revealed in some recent studies, this paper analyzed the similarity and differences of gas and solids mixing behaviour between low density and high density CFB risers based on the data recently collected in our lab and data reported in the literature. It is shown that there exists a clear transition of both gas and solids axial mixing behaviour when the flow structure changes from low density to high density operating conditions, in correspondence to the disappearance of solids downward flow near the wall region. In the low density CFB risers with solids flux lower than ~250 kg/m2s, both gas and solids axial dispersion and backmixing increased with increasing solids flux and solids concentration. Beyond the transition to the dense suspension upflow regime, however, both gas and solids axial dispersions tend to decrease with increasing solids flux, indicating the development of gas and solids flow toward the plug flow resulting from the disappearance of solids downflow in the near wall region. Radial dispersion of gas and solids, on the other hand, showed a continuous decrease over a wide range of solids fluxes within both the low density and high density flow regions, indicating a reduced lateral exchange of gas and particles with increasing solids fluxes.
Kinetic Study of Batch Biodegradation of Diapers
Authors: Espinosa Rosa M. , Delfin-Alcalá Irma , Turpin Sylvie , Contreras Jose Luis
Published: October 2005

The biodegradation of mixtures of diapers crumbled with residuals of pruning of gardens in a cylindrical batch reactor with agitation was studied. The weight of diapers was varied among 15 to 47%, grass 31% and sawdust the rest. The reaction temperature increased from 20 to 64°C as a result of biologic activity and it diminished up to 25°C in 3 weeks. The source genesis of the batch leaching liquid began with a pH of 7 and to the third day it went down to 5.6 due to the hydrolisis of organic compounds. The nitrogen contents increased from 1% up to 2.1% after 28 days due to the loss of CO2. Sawdust concentrations no more than 20% were suitable for the biodegradation reaction. The variation of the content of organic matter in function of the time was described using a kinetics of first order and the reaction model solid-gas of waning nucleus until 30 days in which the chemical reaction controled. After this time a diffusion process seemed to be more important.
Phenomenology of NOx Adsorber Catalysts
Authors: Daw C.Stuart , Lenox Katey E , Chakravarthy Kalyana , Epling William E , Campbell Greg
Published: October 2005

Lean phase operation of lean NOx adsorbers or lean NOx traps (LNTs) is analyzed using data from highly controlled isothermal bench-flow experiments on Pt/K/Al2O3 catalysts. Simulated diesel exhaust was used for inflow in the experiments. Pt promotes the oxidation of NO, the primary component of engine-out NOx, to NO2 which is more easily adsorbed and stored as KNO3. While the presence of Pt was found to be essential for capturing the NOx from the exhaust, it was seen that the NOx storage efficiency did not increase indefinitely with increasing Pt loading. Pt loading at a given temperature of operation is optimal when the rate of NO oxidation to NO2 is nearly equal to the NO2 adsorption rate at the sorbent sites. The NOx storage efficiency seems to be kinetically limited at lower temperatures and equilibrium limited at higher temperatures. When the lean/NOx capture operation was started from a fully regenerated condition, the NOx storage efficiency under most conditions was found to be independent of the reductant mixture used for regenerating the catalyst. The experiments also indicate the possibility of a significant NOx reduction reaction even under the highly oxidizing conditions. This reduction reaction seems to be of fractional order and is more significant at lower temperatures. More detailed analysis of the outflow from the reactor using Fourier-Transform-Infrared (FTIR) spectroscopy is being planned to identify the final product of this reduction reaction.
Simulations of Reacting Fluidized Beds Using an Agent-Based Bubble Model
Authors: Pannala S. , Daw C.Stuart , Halow John
Published: October 2005

We apply a low-order dynamical model for simulating the conversion of bubbling bed reactors. The model includes mass-transfer and first-order reactions between the gas and solids and accounts for upward motion and interactions between bubbles. On a time-average basis, we get reasonably good agreement between the model and experimental measurements from an ozone decomposition reactor. The collective result of the bubble dynamics is a type of global emergent behavior characterized by the formation of a pulsing central channel of high void fraction and high gas flow. These pulsations appear to be similar in character to those typically seen in dynamic pressure measurements of bubbling beds. We use our model to explore the impact of these pulsations on reactor conversion.
Catalysis Engineering on Three Levels
Authors: Moulijn Jacob A. , Perez-Ramirez Javier , van Diepen Annelies , Kreutzer Michiel T. , Kapteijn Freek
Published: October 2005

The relevance of levels in space and time for chemical engineering are discussed. Catalysis Engineering is introduced as an emerging new discipline. In Catalysis Engineering three levels can be distinguished: the microlevel focusing on molecules and catalytic sites, the mesolevel focusing on the catalyst particle and the catalytic reactor, and the macrolevel considering the process as an integrated entity. On the level of particle and reactor fascinating developments are visible in the field of structuring of the space. A good example is the monolithic reactor. With the hydrogenation of alpha-methylstyrene as an example, it will be shown that structured reactors allow decoupling of hydrodynamics and chemical kinetics. This implies an extra degree of freedom. From a chemical engineering point of view the intrinsic scaleability of these reactors is intriguing. A case study on nitrous oxide abatement exemplifies the three-level catalysis engineering approach.
An Engineering Model for the Scale-Up and Design of Photocatalytic Reactors
Authors: Zhang Zisheng Jason , Anderson William A , Moo-Young Murray
Published: October 2005

Work is presented on the modeling and design of fixed-film photocatalytic reactors based on reaction kinetics data from a simple flat-plate photoreactor, local mass transfer rates and local radiation energy absorption rates on the surfaces of catalyst films, and an engineering model. The degradation of 4-chlorophenol in the flat plate reactor was examined experimentally for the purpose of model fitting, using fluorescent lamps as the illumination source. Using this information, the performance of several solar illuminated corrugated plate reactors with different structural parameters was calculated with the model.
Conversion of Synthesis Gas into Light Hydrocarbons. Modelling of the Catalytic Reaction Network
Authors: Hagey Louis , de Lasa Hugo Ignacio
Published: October 2005

This study considers a bi-functional catalyst for the conversion of synthesis gas into valuable light hydrocarbons. Catalysts are tested in a well-mixed Berty reactor. The effects of phosphorous additions on the overall catalyst performance including C5+ fractions and hydrocarbon yields are evaluated. The data obtained is very useful for establishing the validity of a kinetic model based on the gas phase observable species and to determine the various kinetic parameters of this model using statistical methods.
Pressure Effects on Gas-Solid Fluidized Bed Behavior
Authors: Sidorenko Igor , Rhodes Martin J
Published: October 2005

The purpose of this paper is to review the state of our knowledge of the effects of operating pressure on the hydrodynamic behavior of fluidized beds. With the development of coal combustion and gasification fluidized bed processes in the early 1970s, many academic and industrial researchers have studied the effect of pressure on fluidized bed behaviour. This review covers experimental and theoretical studies of effects of elevated operating pressure on fluidization, published in the literature before August, 2002.The review begins with the discussion of the effect of pressurized conditions on non-bubbling fluidization and several methods for better prediction of minimum fluidization velocity at elevated pressure are presented. The effects of pressure on non-bubbling bed expansion in the region between minimum fluidization and minimum bubbling velocities are considered and areas of uncertainty or disagreement are highlighted. The influence of pressure on the dynamics of gas bubbles and bubbling bed expansion is described next. In addition to fundamental hydrodynamics of fluidization, bed-to-surface heat transfer, jet penetration, solids mixing and particle entrainment are mentioned.