bluuebunny/crossref_metadata_2025 huggingface dataset:
Biological differentiation at predynastic Naqada, Egypt: An analysis of dental morphological traits
Authors: Johnson Andrew L. , Lovell Nancy C.
Published: August 2005

Cemetery T at Naqada has been postulated as being the interment site of a predynastic royal or ruling elite due to its small, localized area and the richness of its burial goods. In order to examine possible biological differentiation between the individuals buried in Cemetery T and those buried in other, possibly lower status cemeteries at Naqada, nonmetric dental morphological data were analyzed using the Mean Measure of Divergence statistic. Results indicate that Cemetery T shows some biological distinction from both Cemetery B and the Great Cemetery. The size of the difference supports the archaeological interpretation that Cemetery T represents a ruling or elite segment (or lineage) of the local population at Naqada, rather than a ruling or elite immigrant population. Given the problem of small samples, however, this interpretation is tentative. © 1994 Wiley‐Liss, Inc.
Treponematosis and Lyme borreliosis connections: Explanation for Tchefuncte disease syndromes?
Authors: Lewis Barbara
Published: August 2005

A convergence of evidence from macroscopic, radiographic and histologic examination indicates that treponemal infection was present in the 16ST1 Tchefuncte Indian burial population, dated 500 B.C. to 300 A.D. Pattern and nature of lesions suggests that chronic infection induced by variants of the spirochete Treponema pallidum, causing endemic syphilis and/or yaws, resulted in third‐stage osseous response. It is suggested that Tchefuncte Indians acquired partial immunity to treponemal infection by exposure to a variant of the related spirochete, Borrelia burgdorferi, the causative agent of Lyme disease. Partial immunity would help explain the relatively mild expression of the treponemal disease process in the 16ST1 skeletal population and the apparent absence of venereal syphilis. Presence of the Borrelia burgdorferi spirochete might be linked to a single incidence of juvenile rheumatoid arthritis. © 1994 Wiley‐Liss, Inc.
Electromyography of back muscles during quadrupedal and bipedal walking in primates
Authors: Shapiro Liza J. , Jungers William L.
Published: August 2005

Despite the extensive electromyographic research that has addressed limb muscle function during primate quadrupedalism, the role of the back muscles in this locomotor behavior has remained undocumented. We report here the results of an electromyographic (EMG) analysis of three intrinsic back muscles (multifidus, longissimus, and iliocostalis) in the baboon (Papio anubis), chimpanzee (Pan troglodytes), and orangutan (Pongo pygmaeus) during quadrupedal walking. The recruitment patterns of these three back muscles are compared to those reported for the same muscles during nonprimate quadrupedalism. In addition, the function of the back muscles during quadrupedalism and bipedalism in the two hominoids is compared. Results indicate that the back muscles restrict trunk movements during quadrupedalism by contracting with the touchdown of one or both feet, with more consistent activity associated with touchdown of the contralateral foot. Moreover, despite reported differences in their gait preferences and forelimb muscle EMG patterns, primates and nonprimate mammals recruit their back muscles in an essentially similar fashion during quadrupedal walking. These quadrupedal EMG patterns also resemble those reported for chimpanzees, gibbons and humans (but not orangutans) walking bipedally. The fundamental similarity in back muscle function across species and locomotor behaviors is consistent with other data pointing to conservatism in the evolution of the neural control of tetrapod limb movement, but does not preclude the suggestion (based on forelimb muscle EMG and spinal lesion studies) that some aspects of primate neural circuitry are unique. © 1994 Wiley‐Liss, Inc.
Comparative locomotor ecology of gibbons and macaques: Selection of canopy elements for crossing gaps
Authors: Cannon Chuck H. , Leighton Mark
Published: August 2005

To examine functional questions of arboreal locomotor ecology, the selection of canopy elements by Bornean agile gibbons (Hylobates agilis) and long‐tailed macaques (Macaca fascicularis) was contrasted, and related to locomotor behaviors. The two species, and in some cases, the macaque sexes, varied in their use of most structural elements. Although both species traveled most frequently in the main canopy layer (macaques: 56%, gibbons: 48%), the gibbons strongly preferred the emergent canopy layer and traveled higher than the macaques (31 vs. 23 m above ground) in larger trees (48 vs. 26 cm dbh). Macaques preferred to cross narrower gaps (50% were in the class 0.1–0.5 m wide) than gibbons (42% were 1.6–3.0 m wide), consistent with the maximum gap width each crossed (3.5 m for macaques, 9 m for gibbons). Macaques could cross only 12% of the gaps encountered in the main canopy, and < 5% of the gaps in each of the other four layers. In contrast, all layers appear relatively continuous for gibbons. Specialized locomotor modes were used disproportionately at the beginning and end of travel segments, further indicating that behavior was organized around gap crossings. A model is defined, the Perceived Continuity Index (PCI), which predicts the relative use of canopy strata for each species, based on the percentage of gaps a species can cross, the frequency of gaps, and median length of continuous canopy structure in each canopy layer. The results support the hypothesis that locomotor behaviors, and strategies of selecting canopy strata for travel, are strongly constrained by wide gaps between trees and are ultimately based on selection for efficient direct line travel between distant points. © 1994 Wiley‐Liss, Inc.
Possible secular trend in the incidence of an anatomical variant: Median artery of the forearm
Authors: Henneberg M. , George B. J.
Published: August 2005

Occurrence of a secular trend in the presence of a common anatomical variant—median artery of the forearm is studied. Data from the literature indicated the incidence of the median artery to be between 4.4 and 8.3% in adult cadavers studied before 1960 while our recent study found a frequency of 27.2%. In 224 adult and 60 infant cadavers of people born between 1900 and 1991 studied using a uniform method the incidence of the median artery in the birth cohort 1900–1910 was 15.0% of individuals, it rose to 29.7% in 1921–1930 and further to 38.1% in 1951–1960 to become 52.8% in 1980–1991. This trend is statistically significant. Since the median artery is deemed to dwindle away in most individuals around the 7th week of the intrauterine life, the increasing proportion of individuals who retain it into postnatal life may indicate a recent trend in human intrauterine development. © 1995 Wiley‐Liss, Inc.
Posterior dental size reduction in hominids: The Atapuerca evidence
Authors: De Castro José M. Bermúdez , Nicolas M. Elena
Published: August 2005

In order to reassess previous hypotheses concerning dental size reduction of the posterior teeth during Pleistocene human evolution, current fossil dental evidence is examined. This evidence includes the large sample of hominid teeth found in recent excavations (1984–1993) in the Sima de los Huesos Middle Pleistocene cave site of the Sierra de Atapuerca (Burgos, Spain). The lower fourth premolars and molars of the Atapuerca hominids, probably older than 300 Kyr, have dimensions similar to those of modern humans. Further, these hominids share the derived state of other features of the posterior teeth with modern humans, such as a similar relative molar size and frequent absence of the hypoconulid, thus suggesting a possible case of parallelism. We believe that dietary changes allowed size reduction of the posterior teeth during the Middle Pleistocene, and the present evidence suggests that the selective pressures that operated on the size variability of these teeth were less restrictive than what is assumed by previous models of dental reduction. Thus, the causal relationship between tooth size decrease and changes in food‐preparation techniques during the Pleistocene should be reconsidered. Moreover, the present evidence indicates that the differential reduction of the molars cannot be explained in terms of restriction of available growth space. The molar crown area measurements of a modern human sample were also investigated. The results of this study, as well as previous similar analyses, suggest that a decrease of the rate of cell proliferation, which affected the later‐forming crown regions to a greater extent, may be the biological process responsible for the general and differential dental size reduction that occurred during human evolution. © 1995 Wiley‐Liss, Inc.
Comparison of radiologic and gross examination for detection of cancer in defleshed skeletons
Authors: Rothschild Bruce M. , Rothschild Christine
Published: August 2005

The reliability of visual examination of defleshed bones was assessed for detection of postcranial metastatic disease in individuals known to have had cancer. This was compared with standard clinical radiologic techniques. The skeletons of 128 diagnosed cancer patients from an early 20th century autopsied skeletal collection (Hamann‐Todd Collection) were examined. Radiologic examination detected evidence of metastatic disease in 33 individuals, compared to 11 by visual examination of the postcranial skeletons. Four of these cases were detected by both techniques. Blastic lesions were most commonly overlooked on visual examination, because they were localized to trabecular (internal bone) structures. The ilium was the most commonly affected bone, with lytic or blastic lesions detected in 30 of 33 individuals. While the proximal femur was affected in only nine individuals, x‐ray of the proximal femur and ilium detected all individuals with postcranial evidence of metastatic disease. Skeletal distribution of metastases provides no clue to the location of origin or histologic subtype of the cancer. Survey of archeological human remains for metastatic cancer requires radiologic examination. Such skeletal surveys should x‐ray at least the ilia and femora. © 1995 Wiley‐Liss, Inc.
Kinetics of leaping primates: Influence of substrate orientation and compliance
Authors: Demes B. , Jungers W. L. , Gross T. S. , Fleagle J. G.
Published: August 2005

Our current knowledge about the forces leapers generate and absorb is very limited and based exclusively on rigid force platform measurements. In their natural environments, however, leapers take off and land on branches and tree trunks, and these may be compliant. We evaluated the influence of substrate properties on leaping kinetics in prosimian leapers by using a combined field and laboratory approach. Tree sway and the timing of takeoffs relative to the movements of trees were documented for animals under natural conditions in Madagascar. Field data collected on three species (Indriindri, Propithecus diadema, Propithecus verreauxi) indicate that in the majority of takeoffs, the substrate sways and the animals takeoff before the elastic rebound of the substrate. This implies that force is “wasted” to deform supports. Takeoff and landing forces were measured in an experimental setting with a compliant force pole at the Duke University Primate Center. Forces were recorded for 2 Propithecus verreauxi and 3 Hapalemur griseus. Peak takeoff forces were 9.6 (P. verreauxi) and 10.3 (H. griseus) times body weight, whereas peak landing forces were 6.7 (P. verreauxi) and 8.4 (H. griseus) times body weight. As part of the impulse generated does not translate into leaping distance but is used to deform the pole, greater effort is required to reach a given target substrate, and, consequently, takeoff forces are high. The landing forces, on the other hand, are damped by the pole/substrate yield that increases the time available for deceleration. Our results contrast with previous studies of leaping forces recorded with rigid platform measuring systems that usually report higher landing than takeoff forces. We conclude that 1) Leapers generate and are exposed to exceptionally high locomotory forces. The takeoff forces are higher than the landing forces when using compliant supports, indicating that the takeoff rather than the landing may be critical in interpreting leaping behavior and related aspects of muscu‐loskeletal design. 2) Large‐bodied vertical clingers and leapers do not usually take advantage of the elastic energy stored in substrates. Rather, force (and energy) is wasted to deform compliant supports. 3) A compliant force pole approximates the conditions faced by large‐bodied vertical clingers and leapers in the wild more closely than do rigid force platforms. © 1995 Wiley‐Liss, Inc.
Developmental, genetic, and environmental components of aerobic capacity at high altitude
Authors: Frisancho A. Roberto , Frisancho Hedy G. , Milotich Mark , Brutsaert Tom , Albalak Rachel , Spielvogel Hilde , Villena Mercedez , Vargas Enrique , Soria Rudy
Published: August 2005

The aerobic capacity of 268 subjects (158 males and 110 females) was evaluated in La Paz, Bolivia situated at 3,750 m. The sample included 1) 39 high altitude rural natives (all male); 2) 67 high altitude urban natives (32 male, 35 female); 3) 69 Bolivians of foreign ancestry acclimatized to high altitude since birth (37 male, 32 female); 4) 50 Bolivians of foreign ancestry acclimatized to high altitude during growth (25 male, 25 female); and 5) 43 non‐Bolivians of either European or North American ancestry acclimatized to high altitude during adulthood (25 male, 18 female). Data analyses indicate that 1) high altitude urban natives, acclimatized to high altitude since birth or during growth, attained higher aerobic capacity than subjects acclimatized to high altitude during adulthood; 2) age at arrival to high altitude is inversely related to maximum oxygen consumption (V̇O2 max) expressed in terms L/min or ml/min/kg of lean body mass, but not in terms of ml/min/kg of body weight; 3) among subjects acclimatized to high altitude during growth, approximately 25% of the variability in aerobic capacity can be explained by developmental factors; 4) as inferred from evaluations of skin color reflectance and sibling similarities, approximately 20 to 25% of the variability in aerobic capacity at high altitude can be explained by genetic factors; 5) except among the non‐Bolivians acclimatized to high altitude during adulthood, the aerobic capacity of individuals with high occupational activity level is equal to the aerobic capacity of high altitude rural natives; and 6) the relationship between occupational activity level and aerobic capacity is much greater among subjects acclimatized to high altitude before the age of 10 years than afterwards. Together these data suggest that the attainment of normal aerobic capacity at high altitude is related to both developmental acclimatization and genetic factors but its expression is highly mediated by environmental factors, such as occupational activity level and body composition. © 1995 Wiley‐Liss, Inc.
Borinium‐, Borenium‐ und Boroniumionen: Synthese, Reaktivität, Anwendung
Authors: Piers Warren E. , Bourke Sara C. , Conroy Korey D.
Published: August 2005

Kationische Borverbindungen sind instabile und hoch elektrophile Spezies, die eine Schlüsselrolle in der Chemie des Bors einnehmen. Obwohl man sich schon sehr früh für die Chemie dieser Verbindungen interessierte, blieben die meisten bis in die jüngste Zeit hinein chemische Kuriositäten. Allerdings summierten sich auch allmählich die Hinweise auf ihr Potenzial als starke Elektrophile, und die Entwicklungen im Bereich der schwach koordinierenden Anionen ließen es lohnend erscheinen, dieses Teilgebiet der Borchemie genauer zu erforschen. Seit der letzten umfassenden Übersicht über kationische Borverbindungen sind fast 20 Jahre vergangen; die seit damals erzielten Fortschritte werden in diesem Aufsatz zusammengefasst.
The effect of swelling agents and characterization of polyurethane/polymer electrolytes/clay composites
Authors: Chiu Hsien‐Tang , Wu Jyh‐Horng
Published: August 2005

This study discusses the interaction model and characterization of a clay organic processed with different swelling agents blended with PU/polymer electrolytes. The change in d‐spacing of the clay and modified clay in the PU/polymer electrolytes blends was analyzed using X‐rays. A rigid‐body pendulum rheometer was used to determine the curing behavior of PU/polymer electrolytes matrix in the clay and modified clay with different proportions. Dynamic mechanical analysis has been applied to discuss the intermolecular interaction between clay and organoclay with different proportions and PU/polymer electrolytes blends. We have also analyzed the mechanical properties, stress, and strain. As a result, the compatibility of polymer electrolytes, clay, and organoclay is better. The swelling agent that intercalated among the layers of clay will be crowded out and adsorbed onto the surface of clay. The curing time, intermolecular interaction, thermal properties, and mechanical properties of composites were clearly influenced by the clay and swelling agent. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1206–1214, 2005
Effect of the network topology on the tensile strength of natural rubber vulcanizate at elevated temperature
Authors: González L. , Valentín J. L. , Fernández‐Torres A. , Rodríguez A. , Marcos‐Fernández A.
Published: August 2005

The influence of network topology on tensile strength at elevated temperature of natural rubber compounds vulcanized with different systems was studied. The tensile strength behavior of natural rubber at high strain is attributed to the capacity to crystallize on stretching. Variation of this property with the temperature and/or crosslink density was related, not only with the nature of the crosslinks, but also with their spatial distribution. In this sense, measurements of the freezing point depression of cyclohexane imbibed in the rubber matrix were used to evaluate the spatial distribution of the crosslinks. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1219–1223, 2005
Design‐based stereological analysis of the lung parenchymal architecture and alveolar type II cells in surfactant protein A and D double deficient mice
Authors: Jung Anja , Allen Lennell , Nyengaard Jens R. , Gundersen Hans Jørgen G. , Richter Joachim , Hawgood Samuel , Ochs Matthias
Published: August 2005

Alveolar epithelial type II cells synthesize and secrete surfactant. The surfactant‐associated proteins A and D (SP‐A and SP‐D), members of the collectin protein family, participate in pulmonary immune defense, modulation of inflammation, and surfactant metabolism. Both proteins are known to have overlapping as well as distinct functions. The present study provides a design‐based stereological analysis of adult mice deficient in both SP‐A and SP‐D (A−D−) with special emphasis on parameters characterizing alveolar architecture and surfactant‐producing type II cells. Compared to wild‐type, A−D− mice have fewer and larger alveoli, an increase in the number and size of type II cells, as well as more numerous and larger alveolar macrophages. More surfactant‐storing lamellar bodies are seen in type II cells, leading to a threefold increase in the total volume of lamellar bodies per lung, but the mean volume of a single lamellar body remains constant. These results demonstrate that chronic deficiency of SP‐A and SP‐D in mice leads to parenchymal remodeling, type II cell hyperplasia and hypertrophy, and disturbed intracellular surfactant metabolism. The design‐based stereological approach presented here provides a framework for the quantitative lung structure analysis in gene‐manipulated mice as well as in human lung disease. © 2005 Wiley‐Liss, Inc.
Exploring the rabbit hole of possibilities by myself or with my group: The benefits and liabilities of activating counterfactual mind‐sets for information sharing and group coordination
Authors: Liljenquist Katie A. , Galinsky Adam D. , Kray Laura J.
Published: August 2005

The current experiment explored the effect of activating a counterfactual mind‐set on the discussion of unique information and group judgment accuracy. Evidence suggests that a counterfactual mind‐set is characterized by a focused, analytic mental state and, when activated at the group level, improves group judgment accuracy in the murder mystery paradigm (a hidden profile task). We hypothesized that the beneficial effect of the counterfactual mind‐set would only help group problem‐solving tasks if the mind‐set had been activated at the group level, allowing the analytical mind‐set to play out in an atmosphere of synergistic coordination. In contrast, if this highly focused mental state is activated at the individual level, it could impair group judgment quality because inwardly focused analytical individuals may fail to coordinate their behavior with other group members. Consistent with our hypothesis, activating a counterfactual mind‐set at the individual level had a debilitating effect on the group judgment task, whereas activating a counterfactual mind‐set at the group level had a facilitative effect, increasing information sharing, synergistic coordination and judgment accuracy. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis of poly(Pro–Hyp–Gly)n by direct polycondensation of (Pro–Hyp–Gly)n, where n = 1, 5, and 10, and stability of the triple‐helical structure
Authors: Kishimoto Takahiro , Morihara Yasushi , Osanai Michinori , Ogata Shin‐ichi , Kamitakahara Masanobu , Ohtsuki Chikara , Tanihara Masao
Published: August 2005

Pro–Hyp–Gly is a characteristic amino acid sequence found in fibrous collagens, and (Pro–Hyp–Gly)10, which has been widely used as a collagen‐model peptide, forms a stable triple‐helical structure. Here, we synthesized polypeptides consisting of the Pro–Hyp–Gly sequence by direct polycondensation of (Pro–Hyp–Gly)n, where n = 1, 5, and 10, using 1‐hydroxybenzotriazole and 1‐ethyl‐3‐(3‐dimethyl‐aminopropyl)‐carbodiimide hydrochloride in both phosphate buffer (pH = 7.4) and dimethylsulfoxide (DMSO) solutions for 48 h at 20°C. The reaction of (Pro–Hyp–Gly)5 and (Pro–Hyp–Gly)10 in DMSO successfully gave polypeptides with molecular weights over 10,000, whereas low molecular weight products were obtained by reaction in phosphate buffer (pH = 7.4). In contrast, Pro–Hyp–Gly at a concentration of 50 mg/mL in phosphate buffer (pH = 7.4) gave polypeptides with molecular weights over 10,000. The Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR) spectra of poly(Pro–Hyp–Gly)10 revealed that the polymerization of (Pro–Hyp–Gly)10 described in this report had no side reactions. Each polypeptide obtained shows a collagen‐like triple‐helical structure, and the triple‐helical structures of poly(Pro–Hyp–Gly) and poly(Pro–Hyp–Gly)10 were stable up to T = 80°C, which suggests that the high molecular weight promotes stability of the triple‐helical structure, in addition to the high Hyp content. Furthermore, transmission electron microscopy (TEM) observations show that poly(Pro–Hyp–Gly)10 aggregates to form nanofiber‐like structures about 10 nm in width, which suggests that a Pro–Hyp–Gly repeating sequence contains enough information for triple‐helix formation, and for subsequent nanofiber‐like structure formation. © 2005 Wiley Periodicals, Inc. Biopolymers 79: 163–172, 2005

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Interfacial areas and gas hold‐ups at elevated pressures in a mechanically agitated gas‐liquid reactor
Authors: Oyevaar Martin , Zijl Ad , Westerterp Roel
Published: August 2005

Interfacial areas and gas hold‐ups were determined at pressures of up to 1.7 MPa in a glass vessel, 88 mm in diameter and of standard geometry. Superficial gas velocities between 0.25 and 2.0 cm/s were used and the stirring speed varied between 4 and 30 rps. The interfacial areas were determined by the chemical method, using the model reaction between CO2 and aqueous diethanolamine (DEA). Hold‐ups were determined by observation of differences in height. In contrast to literature indications, the gas hold‐up was found to be independent of reactor pressure. This is also true for the interfacial area.
Engineering aspects and applications of crossflow microfiltration
Authors: Ripperger Siegfried
Published: August 2005

Crossflow microfiltration (CMF) is a pressure driven membrane process for the separation of suspended microparticles, bacteria and emulsion droplets. The fluid to be filtered flows in parallel to the membrane surface and restricts the formation of a filter cake. This contribution explains the basic process characteristics and the combination of the crossflow technique with other membrane cleaning methods (periodic backflushing, chemical cleaning). Special attention is paid to the influence of different process parameters on the flux through the membrane. The principle of plant design and different operation modes are described. Engineering aspects such as hydrodynamics, energy requirement and selection of construction materials are discussed in some detail.
The influence of stress and attrition on crystal size distribution
Authors: Pohlisch Joachim , Mersmann Alfons
Published: August 2005

An important parameter influencing the crystal size distribution in mass crystallization from solution is the mechanical stress exerted on crystals in the crystallizer. This contribution presents the study of the influence of mechanical stress and attrition of the system potassium nitrate‐water in an FC‐crystallizer and in various draft‐tube crystallizers, fitted with different types of impellers. The intensity of stress is a newly defined variable which is used to describe the level of stress in crystallizers. The reduction of crystal size by attrition is described by the linear attrition rate. The influence of impeller design and crystal hold‐up on crystal size distribution and scale‐up rules is discussed.
Attrition and secondary nucleation in crystallizers
Authors: Mersmann Alfons , Sangl Reinhard , Kind Matthias , Pohlisch Joachim
Published: August 2005

The mean crystal size of coarse crystalline products is determined by secondary nucleation and crystal growth. Secondary unclei are mainly produced by contacts of crystals with parts of the crystallizer or with other crystals. As a consequence, attrition effects are very important. In this paper, a model is proposed in order to calculate the attrition rate of crystals, depending on the physical properties of the crystalline product, the geometry of the crystallizer and on the operating conditions such as the stirrer speed or the suspension density. The effective rate of secondary nucleation can be expressed in terms of the attrition rate by introducing effective values for number and size of attrition particles. Finally, a scale‐up criterion based on this model is derived. This criterion allows to predict effective rates of secondary nucleation and mean crystal sizes if data obtained in a laboratory crystallizer are available.
Theoretical and experimental study of sedimentation in vertical flow tanks
Authors: Horn Eva‐Maria , Wiesmann Udo
Published: August 2005

Settling characteristics of four different suspensions were measured by batch settling tests (glass spheres in glycerol‐water mixtures and CaCO3) and by continuous settling test in a bench‐scale vertical flow tank (activated sludge and kaolin in water), including the measurement of solids concentrations inside the tank. The characteristics could be described by different correlation functions which now include all the information about the settling behaviour of ideal suspensions. Continuous settling experiments in a bench‐scale vertical flow tank were carried out with the same four material systems. These results correspond with sufficient accuracy to those from the theory of limiting flux if the settling characteristics determined earlier are considered.
Effect of combustion air preheating on NOx emissions from gas burners in high‐temperature industrial applications
Authors: Flamme Michael , Beckervordersandforth Christian Paul , Kremer Hans
Published: August 2005

NOx emissions from different commercial gas burners for metal heat treatment applications were measured for a research project of the Gaswärme‐Institut. The burners, rated at up to 50 kW, were installed for the tests in a laboratory combustion chamber operated at temperatures of up to 1400°C. The air for combustion was preheated to maximum temperature of 600°C. Following the tests, the potentials of different NOx control techniques were investigated. Methods explored included staged combustion air injection, staged fuel injection and fuel gas injection into the flue for NOx reduction. The results showed that it is feasible to reduce the NOx content of flue gases by as much as 90%.
Thermal deactivation of heterogeneous catalyst, part 1. The theta‐rule ‐ a critical review
Authors: Kral Hans
Published: August 2005

Thermal deactivation can be described either by deactivation kinetics or by the isokinetic effect. The latter expression is used synonymously with the “compensation effect” and the “Theta‐Rule”. An examination of the original literature shows that only the compensation effect is applicable to thermal deactivation but not the Theta‐Rule. The introduction of the preparation temperature as a parameter of the compensation effect results in a “modified Theta‐Rule”, which describes the experimental data and is proposed for the non‐separable kinetics. The consequence of the observed deviations from the validity range of the Theta‐Rule is that the activation energy cannot be used as a universal activity criterion.
Heat transfer between particle beds and submerged surfaces
Authors: Molerus Otto , Scheuring Horst
Published: August 2005

Theoretical modelling of heat transfer to particle beds comprises two sequential steps: transfer from the heating surface to contacting particles followed by transfer to the interior of the bed. Two different limiting case can be formulated for the second step: unmixed and homogeneously mixed bed. In the case, heat is transferred gradually via a repeated sequence of heat transfer in the gap between adjacent particles and conduction in the particulate material. In the second case, heat is transferred to the interior of the bed by mixing of particles which have previously attained the temperature of the heating surface. On the other hand, the mixing motion maintains a homogeneous lower temperature throughout the bed. Theory predicts a significant and easily measurable difference in the behaviour of heat transfer coefficients for the two regimes at long contact times t: unmixed beds ∝ \documentclass{article}\pagestyle{empty}\begin{document}$$ \sqrt t $$\end{document} and homogeneously mixed beds ∝ 1/t. For short times t, both regimes show the same behaviour, namely of t.

From a theoretical standpoint, it makes sense to differentiate further between the behaviour patterns of unmixed beds: at long times t, instantaneous heat transfer coefficients are independent of heat transfer form the heating surface to adjacent particles. Comparison with experimental result from literature shows that the derived models, which are consistent, are suitable for describing the heat transfer from submerged surfaces to unmixed and mixed beds of particles.
The role of energy dissipation in contacting and mixing devices
Authors: Villermaux Jacques
Published: August 2005

The aim of the present paper is the discussion of the relevance of power dissipation as a criterion for the understanding and prediction of transfer and mixing efficiencies in contactors and chemical reactors. After reviewing the approach of Le Goff to the energetic efficiency of exchangers, based on the deviations from Chilton‐Colburn analogy, the following processes are studied: mass transfer between a flowing fluid and a reactive solid surface, transfer to a fixed object in a stirred vessel, macro‐ and micromixing of miscible fluids, and mass transfer in fluid‐fluid contractors (especially gas‐liquid reactors). It is concluded from the various examples that a direct relationship between the dissipated power and intensity of transfer or mixing can be established only under the two following conditions: local values must be considered at the point where the actual transfer and mixing occur, and not average values over the whole device, and power dissipation must be coupled to transfer or mixing and appear physically as the driving force of the process.
Mass transfer behaviour of gas‐liquid jet loop reactors
Authors: Warnecke Hans‐Joachim , Geisendörfer Matthias , Hempel Dietmar Christian
Published: August 2005

A special type of jet loop reactor (JLR), designed for continuous operation and short residence times was investigated with regard to its mass transfer behaviour, described by the volumetric mass transfer coefficient kLa. The jet stream and superficial gas velocities are varied in two JLRs of different sizes, equipped with different nozzles. Fully desalinated water, 0.08 molar NaCI solution and solutions of different concentration of carboxymethyl cellulose (CMC) are used as the liquid phase. A steady‐state physical method is employed to determine kLa: air oxygen is purged from the liquid phase by gaseous nitrogen. The measurements show that the reactor is characterized by high power density and high mass transfer performance. No limit of mass transfer capacity was observed in the chosen ranges of volumetric gas and liquid flow rates, i.e. at a given jet stream velocity, the relationship between kLa and the superficial gas velocity is nearly linear. The investigations show that the mass transfer contributed by the jet stream largely depends on liquid phase composition.
Modelling of multiphase detonations with drop disintegration ‐ description of thermal detonations
Authors: Carachalios Constantinos , Unger Hermann , Bürger Manfred
Published: August 2005

A model is presented which consists of steady‐state and transient codes for the description of reacting multiphase flow fields, including hydrodynamic fragmentation of liquid drops in relative flows. An application of this model for the description of large scale melt‐coolant interactions (thermal detonations) is described. A simulation of two‐phase chemical detonations, especially those with hydrodynamic disintegration of liquid fuel drops in the reaction zone, is possible, in principle, within the framework of the modeling.
Model discrimination and parameter estimation in the kinetic study of methanol synthesis
Authors: Xu Jianguo , Rickert Thomas , Hoffmann Ulrich
Published: August 2005

The new model discrimination method is based on the correlation coefficient test of experimental data sets for different reactions, without requiring a prior parameter estimation. The new parameter estimation method reduces by n the number of dimensions to be tested, compared to the classical method where n is the number of independent reactions in the system. This has reduced the computation time for most complex reactions to a level, comparable to that needed for single reactions. The example used is the kinetic study of methanol synthesis in which the formation rates of methanol, methane, ethanol and ethane are considered. Two adequately accurate models were obtained from an extensive range of plausible models by using the new model discrimination and parameter estimation method with a relatively small computation effort.
Kinetic investigation of methacrylic acid synthesis on hetropoly‐compounds
Authors: Haeberle Thomas , Emig Gerhard
Published: August 2005

The kinetics of heterogeneously catalyzed methacrylic acid synthesis from isobutyric acid has been investigated. Initial catalyst screening pointed to 10‐molybdo‐2‐vanado‐phosphoric acid and its Cs‐salts as the most promising catalysts. A model describing the reaction behaviour of all the different hetropoly‐compounds used in this work was developed. A relationship was found between model parameters and composition of different catalysts. First insight was gained into the catalyst deactivation phenomena. Deactivation appears to be caused mainly by loss of molybdenum with simultaneous collapse of the Keggin structure.
Less known behaviour of gas‐solid reactions: The expanding core model in catalytic and non‐catalytic systems
Authors: Doraiswamy Laxmangudi K. , Gokarn Ashok N.
Published: August 2005

Gas‐solid reactions cover a wide spectrum of industrial products. Over the years, many conceptual models have been developed to describe the progress of a gas‐solid reaction starting outside the solid particle as well as that occurring throughout the particle. But the behaviour of a reaction, initiated inside the pellet, is less known. In this paper, a brief outline is given of this relatively rare but important mode of gas‐solid reaction. The causes of this relatively less known behaviour and characteristic features of five typical systems displaying it are discussed.
Reversible absorption of nitric oxide in low volatile organic liquids containing cupric halides
Authors: Gestrich Wolfgang
Published: August 2005

The absorption of nitric oxide (NO) in phosphoric acid esters and polyethylene glycol ethers which contain cupric halides has been investigated. Due to high solubility of cupric halides and high equilibrium constants of formed nitrosyl complexes, the effective solubility of nitric oxide can be enhanced to about 100‐fold its solubility in the salt‐free organic liquid which itself amounts to only about 5‐fold the NO‐solubility in water. Calculations taking into account flue gas conditions indicate that the required gas‐liquid ratio in industrial absorption processes will lie in the normal range of flue gas scrubbing processes, namely in the region of 400:1 to 1000:1 in volume. Thus, such a reversible absorption process could a viable alternative to SCR‐processes in flue gas denitrification.
Heat transfer to submerged surfaces in coarse‐grained pressurized fluidized beds and fixed beds
Authors: Schweinzer Jürgen , Molerus Otto
Published: August 2005

This contribution reports on the theory underlying a uniform representation of heat transfer to submerged surfaces in fixed bed reactors and of gas convective part of heat transfer in fluidized beds with coarse‐grained bulk solids and/or at elevated pressure. Based on an analysis of the pressure drop behaviour of fixed bed percolation at different gas pressures and with different bulk solids, a new dimensionless pressure drop parameter was developed. Fixed bed heat transfer data are very well correlated by this new dimensionless number. As soon as fluid throughput is in excess of minimum fluidization velocity, the pressure drop parameter transforms into the well‐known Archimedes number. These two dimensionless numbers are connected by the condition of equilibrium for pressure drop and mass of practices in a fluidized bed. This equilibrium is fulfilled as soon as fluidization commences. Up to now, the Archimedes number has been generally accepted as the significant parameter, determining the gas convective part of heat transfer in fluidized beds; however, without any physical interpretation of this parameter. Introduction of the pressure drop number, which is consistent with the Archimedes number, reduces the heat transfer behaviour to pressure drop characteristics. The usefulness of this concept is proven by the comparison of experimental results and prediction.
Selective hydrogenation: Kinetic investigation of 1, 3‐cyclo‐octadiene and cyclo‐octene hydrogenation
Authors: Hass Thomas , Gaube Johann
Published: August 2005

The vapour phase hydrogenation of 1,3‐cyclo‐octadiene (COD) over Pd on alumina has been studied in the gas phase, using a recycle reactor. The dependences of COD hydrogenation rates and those of the consecutive cyclo‐octene (COE) hydrogenation on the reaction conditions are well described by a model which takes into account mass transfer in the porous layer of palladium. The kinetics of the COE hydrogenation is of a Langmuir‐Hinshelwood type. The hydrogenation of COD is of first order with respect to hydrogen. The reaction order with respect to COD is −0.15. If the catalyst surface is completely covered by COD, the hydrogenation of COE is totally suppressed. This indicates a much stronger adsorption of COD than of COE. Hydrogenation of COE can only occur in the innermost part of the pores when the transport of COD by diffusion is insufficient to supply the entire active surface of the catalyst. This happens if the ratio P/PCOD exceeds 2/φ2 with φ being the Thiele's modulus. This relationship permits a simple evaluation of the effective diffusion coefficient in the porous Pd‐layer.
Absorption process for the removal of organic solvents from exhaust air
Authors: Geisthardt Klaus , Holtze Jürgen , Ludwig Rolf , Pilhofer Theo
Published: August 2005

It is shown in this report that, under certain conditions, cleaning of exhaust air by absorption presents an interesting alternative to the existing methods. In particular, this process can be used with advantage for small quantities of exhaust air, high and strongly fluctuating solvent concentrations and solvent mixtures such as those occurring in batch operation. A washing agent was employed which had not been previously used for this purpose. Its properties, which were investigated in the laboratory, were confirmed during a 15‐months' trial period in a semi‐industrial plant. The process and plant were optimized for practical use. Through its option of solvent recovery from exhaust air, this physical absorption process contributes to environmental control.
The pressure ratio of critical two‐phase flows
Authors: Hardekopf Friedhelm , Mewes Dieter
Published: August 2005

Depressurization of a pressure vessel, containing a liquid or a gas is limited by the maximum possible mass flux. This flux occurs at a certain drop in pressure. The ratio of ambient pressure to that inside the vessel must be less than a certain critical value. The critical pressure ratio depends on the thermodynamic state of the fluid inside the vessel and on the geometry of the outlet cross‐section. The outlet can be a pipeline, a safety valve or a rupture disk. The results of known theoretical and experimental work are presented. In previous experiments, saturated liquids, two‐phase flows or pure vapours were examined. In order to predict the critical pressure ratio, certain assumptions are necessary. These are derived for three well‐defined cross‐sections of the vessel outlet.
Effects of pretreatments on semi‐continuous anaerobic digestion of wheat straw
Authors: Tosun Ayşe , Selçuk Nevin , Soyupak Selçuk
Published: August 2005

The effects of alkali treatment, nitrogen supplement and hydraulic retention time on methane production rate from semi‐continuous anaerobic digestion of 5% wheat straw‐water mixtures were investigated. The experiments were carried out in laboratory scale fermenters, fed with 1 1 of basic, alkali treated and nitrogen supplemented 5% wheat straw‐water mixtures, respectively, and maintained at 55 °C. Digestion experiments were performed for hydraulic retention times of 8, 10 and 15 days. The amount and composition of produced gas were measured until steady state was attained in each run. The steady‐state methane production rates were found to increase with hydraulic retention time and with the type of slurry in the following order; basic, nitrogen supplemented and alkali treated slurry. Data obtained from the experiments were employed to determine the kinetics of methane production from anaerobic digestion of wheat straw, for the assessment of pretreatment effects on process kinetics. The predicted methane production rates were found to be in a reasonably good agreement with the measurements.
A new model of the effect of stirring intensity on the rate of secondary nucleation
Authors: Ploß Reinhard , Mersmann Alfons
Published: August 2005

Secondary nucleation in industrial crystallizers depends on both supersaturation and mechanical stress by stirring. Most models which consider mechanical stress assume that nucleation is proprotional to the energy transferred to the crystals during collisions. This is not based on any physical relationship and, in addition, the models do not satisfactorily reproduce the experimental results. Own model, based on the theory of Hertz/Huber, which accounts for the stress of the crystals caused by impact, gave better results. This well‐known and proven theory allows the calculation of the volume abraded during collisions between crystals and stirrer or walls. Introducing a nucleate efficienncy, the effect of mechanical stress on the rate of secondary nucleation, due to stirring intensity and crystallizer size, can be determined.
A new particle size effect
Authors: Kral Hans
Published: August 2005

The sintering effect of highly dispersed metals is the reason for the following phenomena: thermal deactivation, particle size effect, separable or non‐separable kinetics and the isokinetic relationship ( = compensation effect). A comparison of these phenomena reveals a contradiction which can be reconciled by a new particle size effect. This effect is characterized in the following way: The dependence of specific activity on particle size is always connected with a variation of the activation energy, caused by the particle size distribution. Therefore, this effect is referred to as the partical size and distribution effect, P.S.D.E. This new concept describes all the observed phenomena of the conventional partical size effect. Moreover, it is consistent with similar effects such as non‐separable kinetics and the isokinetic relationship. In consequence, the method of isothermal measurement of specific activity is inadequate.
Reduction of energy requirements in distillation
Authors: Stichlmair Johann , Stemmer Ansgar
Published: August 2005

Distillation has been, up to now, the standard method for separating fluid mixtures in the process industry and the consensus is that it will remain so for years to come. The only disadvantage of distillation is its high energy requirement. In the following, it will be demonstrated on the example of an ideal ternary mixture, how the energy requirement of distillation process can be reduced. Very effective are some modifications of single columns, optimization of column sequences and direct or indirect column coupling. It will be shown that, just by column coupling, the energy requirement can be reduced to a third.
Venturi scrubber calculation and optimization
Authors: Haller Heinz , Muschelknautz Edgar , Schultz Tilman
Published: August 2005

Collection efficiency and pressure loss of a venturi scrubber can usually be determined from the calculation models of Barth and Calvert. However, this only leads to reasonable results if the droplets are uniformly distributed throughout each cross‐section of the washing zone. In this work, a two‐zone models is developed which allows the calculation of the venturi scrubber at operating conditions with a non‐uniform droplet distribution. The scrubber geometry is also taken into account. A venturi scrubber was developed on the basis of this new model. Its energy consumption is significantly lower than the well‐Known optimum characteristic of Wicke and Holzer. For ideal operating conditions, a new optimum characteristic is given which should be the aim of future optimizations.
Mass transfer and chemical reaction in fluid two‐phase systems
Authors: Langemann Horst , Brandt Hermann , Neumann Martin , Wüllner Gerhard , Voigt Markus
Published: August 2005

Steady‐state concentrations of the transferred reactant in the bulk phase and the non‐flowing diffusion boundary layer of an isothermal, isobaric two‐phase reactor with an irreversible first‐order reaction and constant composition of one phase.