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Lewis
Terms modified by Lewis Selected AbstractsThe Late Prehistoric,Early Historic Game Sink in the Northwestern United StatesCONSERVATION BIOLOGY, Issue 1 2002R. Lee Lyman The number of big game killed by the Corps of Discovery in 1805,1806 and recorded by Lewis and Clark suggests that ungulates were abundant in central and eastern Montana and rare in western Montana, central Idaho, and southeastern Washington during the early nineteenth century. Paleoecologists Paul Martin and Chris Szuter conclude that this difference was a function of human predation. They support their conclusion that ungulates would have been abundant in southeastern Washington had humans not hunted them by arguing that the nineteenth-century livestock industry was successful without supplemental feeding. The livestock industry was, however, not consistently successful until artificial feeding was initiated. Archaeological data from eastern Washington indicate that ungulates have been taken by human hunters more frequently than small-mammal prey throughout the last 10,000 years and that ungulates decreased relative to small mammals coincident with changes in climate. Bison ( Bison bison) and elk (Cervus canadensis) were present in eastern Washington throughout the Holocene, but bison were abundant there only during a cooler and moister period; elk have been abundant only in the twentieth century, subsequent to transplants and the extermination of predators. Geographic variation in the abundance of bison across Montana, Idaho, and eastern Washington has been influenced by human predation but has also been influenced by biogeographic history, habitat differences, and climatic change. Resumen: Los datos históricos proveen información valiosa sobre las estructuras de los ecosistemas, sus funciones y procesos. El número de animales de caza grandes que fueron sacrificados por las tropas de descubrimiento en 1805-1806 y registradas por Lewis y Clark sugieren que los ungulados eran abundantes en Montana central y oriental y raros en Montana occidental, Idaho central y el sudeste de Washington durante los inicios del siglo diecinueve. Los paleontólogos Paul Martin y Chris Szuter concluyen que esta diferencia fue causada por la depredación humana. Ellos apoyan su conclusión de que los ungulados podrían haber sido abundantes en el sudeste de Washington si los humanos no los hubieran cazado argumentando que la industria de la ganadería del siglo diecinueve exitosa sin alimento suplementario. Sin embargo, la industria de la ganadería no fue consistentemente exitosa hasta que se inició la alimentación artificial. Los datos arqueológicos de Washington oriental indican que los ungulados fueron eliminados por los cazadores humanos mas frecuentemente que las presas pequeñas de mamíferos a lo largo de los últimos 10,000 años y que la disminución de ungulados, relativa a la de mamíferos pequeños coincidió con cambios en el clima. El bisonte (Bison bison) y el alce (Cervus canadiensis) estuvieron presentes en Washington oriental a lo largo del Holoceno, pero los bisontes fueron abundantes solo durante un periodo mas frío y húmedo; los alces habían sido abundantes solo en el siglo veinte subsecuente a los transplantes y a la exterminación de los depredadores. La variación en la abundancia de alces a lo largo de Montana, Idaho y el oriente de Washington estuvo influenciada por la depredación humana, pero también por la historia biogeográfica, las diferencias en hábitat y el cambio climático. [source] From the closed room to an opening sky: vectors of space in Eliot, Woolf, and LewisCRITICAL QUARTERLY, Issue 4 2007MICHAEL LEVENSON First page of article [source] Words, flies, Jews, Joyce, Joint: Wyndham Lewis and the unpublishing of obscenityCRITICAL QUARTERLY, Issue 4 2004Geoff Gilbert First page of article [source] Slavery, Memory, and Museum Display in Baltimore: The Great Blacks in Wax and the Reginald F. LewisCURATOR THE MUSEUM JOURNAL, Issue 2 2009Marcus Wood The analysis deals with the question by focusing on the radically contrasting museological, aesthetic, and ethical codes of the Great Blacks in Wax Museum, and the Reginald Lewis Museum, both situated in Baltimore, Maryland. Three key sites are isolated for discussion: the names of the museums, their approaches to the topic of the Middle Passage, and lynching. While both museums have made important cultural contributions to the public memorialization of highly charged subjects, the Great Blacks in Wax emerges as the more radical institution, closely in touch with the dynamic and creative museum aesthetic of the wider Black Atlantic Diaspora, and of Brazil in particular. [source] Potential roles for BMP and Pax genes in the development of iris smooth muscleDEVELOPMENTAL DYNAMICS, Issue 2 2005Abbie M. Jensen Abstract The embryonic optic cup generates four types of tissue: neural retina, pigmented epithelium, ciliary epithelium, and iris smooth muscle. Remarkably little attention has focused on the development of the iris smooth muscle since Lewis ([1903] J. Am. Anat. 2:405,416) described its origins from the anterior rim of the optic cup neuroepithelium. As an initial step toward understanding iris smooth muscle development, I first determined the spatial and temporal pattern of the development of the iris smooth muscle in the chick by using the HNK1 antibody, which labels developing iris smooth muscle. HNK1 labeling shows that iris smooth muscle development is correlated in time and space with the development of the ciliary epithelial folds. Second, because neural crest is the only other neural tissue that has been shown to generate smooth muscle (Le Lievre and Le Douarin [1975] J. Embryo. Exp. Morphol. 34:125,154), I sought to determine whether iris smooth muscle development shares similarities with neural crest development. Two members of the BMP superfamily, BMP4 and BMP7, which may regulate neural crest development, are highly expressed by cells at the site of iris smooth muscle generation. Third, because humans and mice that are heterozygous for Pax6 mutations have no irides (Hill et al. [1991] Nature 354:522,525; Hanson et al. [1994] Nat. Genet. 6:168,173), I determined the expression of Pax6. I also examined the expression of Pax3 in the developing anterior optic cup. The developing iris smooth muscle coexpresses Pax6 and Pax3. I suggest that some of the eye defects caused by mutations in Pax6, BMP4, and BMP7 may be due to abnormal iris smooth muscle. Developmental Dynamics 232:385,392, 2005. © 2004 Wiley-Liss, Inc. [source] Contextualism, Scepticism, and the Problem of Epistemic DescentDIALECTICA, Issue 4 2001Duncan Pritchard Perhaps the most dominant anti-sceptical proposal in recent literature ,advanced by such figures as Stewart Cohen, Keith DeRose and David Lewis ,is the contextualist response to radical scepticism. Central to the contextualist thesis is the claim that, unlike other non-contextualist anti-sceptical theories, contextualism offers a dissolution of the sceptical paradox that respects our common sense epistemological intuitions. Taking DeRose's view as representative of the contextualist position, it is argued that instead of offering us an intuitive response to scepticism, contextualism is actually committed to a revisionist stance as regards our everyday usage of epistemic terms. In particular, it is argued that the thesis fails to present a satisfactory explication of a notion ,that of,epistemic descent', that is pivotal to the anti-sceptical import of the account. On the positive side, however, it is claimed that although the contextualist response to scepticism is ultimately unsatisfying, DeRose's theory does contain within it the framework for a completely different - and far more persuasive - account of the,phenomenology'of scepticism which runs along non-contextualist lines. [source] Lewis, Causality, and Possible WorldsDIALECTICA, Issue 2 2000Graham White First page of article [source] THE SCHOOL AS AN EXCEPTIONAL SPACE: RETHINKING EDUCATION FROM THE PERSPECTIVE OF THE BIOPEDAGOGICALEDUCATIONAL THEORY, Issue 2 2006Tyson E. LewisArticle first published online: 3 MAY 200 Agamben's theory of the camp provides a challenging, critical vantage point for looking at the ambiguities that emerge from the complex field of disciplinary procedures now prevalent in inner-city, low-income, minority schools, and helps to clarify what exactly is at stake in the symbolic and sometimes physical violence of schooling. Key to understanding the primary relation between camp and classroom is Agamben's framework of the biopolitical, which paradoxically includes life as a political concern through its exclusion from the political sphere. Here Lewis appropriates Agamben's terminology in order to theorize the biopedagogical, wherein educational life is included in schooling through its abandonment. For Lewis, the theory of the camp is necessary to recognizing how schools function and, in turn, how they could function differently. [source] Taxonomy of the genus Rhizophagus Herbst (Coleoptera: Monotomidae: Rhizophaginae) in KoreaENTOMOLOGICAL RESEARCH, Issue 1 2007Sun-Jae PARK Abstract A taxonomic study of the genus Rhizophagus Herbst in Korea is presented. Three species ,Rhizophagus (Anomophagus) puncticollis Sahlberg, Rhizophagus (Rhizophagus) japonicus Reitter and Rhizophagus (Rhizophagus) nobilis Lewis , are recognized. The genus and species are recorded for the first time in Korea. A key, habitus photos, descriptions, and illustrations of diagnostic characters of known Korean Rhizophagus species are given. [source] A Taxonomic Review of the Genus Platydema Laporte and Brulle in Korea (Coleoptera, Tenebrionidae, Diaperinae)ENTOMOLOGICAL RESEARCH, Issue 1 2005Jin Ill KIM ABSTRACT Taxanomic review of Korean Platydema Laporte and Brulle of tribe Diaperini in Tenebrionidae is presented. Eight species including P. marseuli Lewis, 1894 recorded newly in Korea are described here. We provide a key to Korean species, diagnoses, lists of feeding fungi and photos for them. [source] Behavioral observation of two fungivorous beetles (Coleoptera: Tenebrionidae) on wood-decaying bracket fungus Cryptoporus volvatusENTOMOLOGICAL SCIENCE, Issue 1 2010Kohmei KADOWAKI Abstract The behavior of two sympatric beetles, Parabolitophagus felix Lewis and Ischnodactylus loripes Lewis (Tenebrionidae: Coleoptera), specialists of a bracket fungus Cryptoporus volvatus (Peck) Shear, was studied in Kyoto, central Japan. A sporocarp of C. volvatus has a distinct white volva, and a small elliptical ostiole near the base. Adults of two tenebrionids use the volval chambers of a sporocarp as mating space. Adults walked across closely located sporocarps infrequently on a tree at night (19.30,20.30 h). Field observation showed that the occupancy patterns of the volval chambers in the two species were temporally segregated: Parabolitophagus felix occupied them until May, while I. loripes occupied them in late May to early June [source] Dacie & Lewis: Practical HaematologyEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2006Ole Weis Bjerrum No abstract is available for this article. [source] Rat strain differences in peripheral and central serotonin transporter protein expression and functionEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003Francesca Fernandez Abstract Female Fischer 344 (F344) rats have been shown to display increased serotonin transporter (5-HTT) gene expression in the dorsal raphe, compared to female Lewis (LEW) rats. Herein, we explored, by means of synaptosomal preparations and in vivo microdialysis, whether central, but also peripheral, 5-HTT protein expression/function differ between strains. Midbrain and hippocampal [3H]paroxetine binding at the 5-HTT and hippocampal [3H]serotonin (5-HT) reuptake were increased in male and female F344 rats, compared to their LEW counterparts, these strain differences being observed both in rats of commercial origin and in homebred rats. Moreover, in homebred rats, it was found that these strain differences extended to blood platelet 5-HTT protein expression and function. Saturation studies of midbrain and hippocampal [3H]paroxetine binding at the 5-HTT, and hippocampal and blood platelet [3H]5-HT reuptake, also revealed significant strain differences in Bmax and Vmax values. Although F344 and LEW rats differ in the activity of the hypothalamo-pituitary-adrenal (HPA) axis, manipulations of that axis revealed that the strain differences in hippocampal [3H]paroxetine binding at 5-HTTs and [3H]5-HT reuptake were not accounted for by corticosteroids. Hippocampal extracellular 5-HT levels were reduced in F344 rats, compared to LEW rats, with the relative, but not the absolute, increase in extracellular 5-HT elicited by the local administration of citalopram being larger in F344 rats. Because the aforementioned strain differences did not lie in the coding sequences of the 5-HTT gene, our results open the promising hypothesis that F344 and LEW strains model functional polymorphisms in the promoter region of the human 5-HTT gene. [source] Strain differences in the behavioural outcome of neonatal ventral hippocampal lesions are determined by the postnatal environment and not genetic factorsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2001Graham K. Wood Abstract It has been demonstrated that not only do rats neonatally lesioned in the ventral hippocampus (VH) develop behavioural hypersensitivity to amphetamine postpubertally, but also that the expression of the sensitivity is strain specific. For example, excitotoxic VH lesions at postnatal day (PD) 7 lead to significant increases in amphetamine-induced locomotion in postpubertal Fischer rats, but not in Lewis rats. However, as it is likely that the effect of strain differences are due to a combination of genetics and environment, we examined the contributions of the environment of the pups in determining the behavioural outcome following neonatal VH lesions. Fisher and Lewis rat pups were cross-fostered at birth, and then at PD7 lesioned bilaterally in the VH with ibotenic acid. anova analysis of postpubertal amphetamine-induced locomotor data revealed a significant effect of the strain of the dams raising the pups but no effect of the strain of the pup. In addition, a post hoc analysis revealed that lesioned Fisher or Lewis rats raised by Fisher, but not those raised by Lewis, dams demonstrated amphetamine-induced hyperlocomotion relative to nonlesioned controls. Observations of the maternal behaviour of Fischer and Lewis dams revealed significant differences in the frequency of arched-back nursing between the two strains. Interestingly, a correlation of the frequency of arched back nursing vs novelty- or amphetamine-induced locomotion revealed that the lesioned rats were significantly more affected by increases in arched-back nursing compared to the controls. The results suggest that the genetic background of the pups does not significantly affect the behavioural outcome following neonatal VH lesions; however, the results do suggest an important role of early environmental variables on the behavioural outcome of neonatal VH lesions. [source] Quinean Scepticism About De Re Modality After David LewisEUROPEAN JOURNAL OF PHILOSOPHY, Issue 1 2007John Divers First page of article [source] DO RECENT FINDINGS IN PLANT MITOCHONDRIAL MOLECULAR AND POPULATION GENETICS HAVE IMPLICATIONS FOR THE STUDY OF GYNODIOECY AND CYTONUCLEAR CONFLICT?EVOLUTION, Issue 5 2008David E. McCauley The coexistence of females and hermaphrodites in plant populations, or gynodioecy, is a puzzle recognized by Darwin. Correns identified cytoplasmic inheritance of one component of sex expression, now known as cytoplasmic male sterility (CMS). Lewis established cytonuclear inheritance of gynodioecy as an example of genetic conflict. Although biologists have since developed an understanding of the mechanisms allowing the joint maintenance of CMS and nuclear male fertility restorer genes, puzzles remain concerning the inheritance of sex expression and mechanisms governing the origination of CMS. Much of the theory of gynodioecy rests on the assumption of maternal inheritance of the mitochondrial genome. Here we review recent studies of the genetics of plant mitochondria, and their implications for the evolution and transmission of CMS. New studies of intragenomic recombination provide a plausible origin for the chimeric ORFs that characterize CMS. Moreover, evidence suggests that nonmaternal inheritance of mitochondria may be more common than once believed. These findings may have consequences for the maintenance of cytonuclear polymorphism, mitochondrial recombination, generation of gynomonoecious phenotypes, and interpretation of experimental crosses. Finally we point out that CMS can alter the nature of the cytonuclear conflict that may have originally selected for uniparental inheritance. [source] Marker-assisted dissection of genetic influences on motor and neuroendocrine sensitization to cocaine in ratsGENES, BRAIN AND BEHAVIOR, Issue 3 2009L. F. Vendruscolo This study investigated genetic influences on behavioral and neuroendocrine responses to cocaine sensitization. We used male and female rats of the inbred strains Lewis (LEW) and spontaneously hypertensive rats (SHR), which display genetic differences in stress-related responses. The influence of two quantitative trait loci (QTL; Ofil1 and Ofil2 on chromosomes 4 and 7), which modulate stress reactivity in rats, on the effects of cocaine was also investigated through the use of recombinant lines (derived from a LEW × SHR intercross) selected by their genotype at Ofil1 and Ofil2. Animals were given repeated cocaine or saline injections and tested for locomotion (induction of sensitization). Two weeks later, all animals were challenged with cocaine, and locomotion and corticosterone levels were measured (expression of sensitization). Results indicated that male SHR rats showed more behavioral sensitization than LEW rats, whereas no strain differences in sensitization were seen among females. When challenged with cocaine, LEW and SHR rats of both sexes pretreated with cocaine showed behavioral sensitization compared with saline pretreated animals; however, only LEW rats displayed an increase in the corticosterone levels. Ofil1 was found to influence the induction of sensitization in males and Ofil2 modulated the locomotor effect of cocaine in females. This study provides evidence of a genotype-dependent relationship between the induction and expression of cocaine sensitization, and between the behavioral and neuroendocrine responses induced by cocaine. Moreover, the Ofil1 and Ofil2 loci may contain one or more genes that control the behavioral effects of cocaine in rats. [source] Evidence for a female-specific effect of a chromosome 4 locus on anxiety-related behaviors and ethanol drinking in ratsGENES, BRAIN AND BEHAVIOR, Issue 6 2006L. F. Vendruscolo Previous studies using the inbred rat strains Lewis (LEW) and spontaneously hypertensive rats (SHR) led to the mapping of two quantitative trait loci, named Ofil1 (on chromosome 4 of the rat) and Ofil2 (on chromosome 7), for open-field inner locomotion, a behavioral index of anxiety. Studies using other strains showed that the region next to Ofil1 influences measures of not only anxiety but also ethanol consumption. In view of the high prevalence of psychiatric disorders such as anxiety and alcoholism, as well as the comorbidity between them, the present study was designed to better characterize the contribution of these two loci to complex emotional and consummatory responses. Rats deriving from an F2 intercross between the LEW and the SHR strains were selected according to their genotype at markers flanking the loci Ofil1 and Ofil2 and bred to obtain lines of rats homozygous LEW/LEW or SHR/SHR for each of the two loci, thus generating four genotypic combinations. These selected animals as well as purebred LEW and SHR rats of both sexes were submitted to a battery of tests including measures of locomotor activity, anxiety, sweet and bitter taste reinforcement and ethanol intake. Lewis rats displayed more anxiety-like behavior and less ethanol intake than SHR rats. Ofil1 (on chromosome 4) affected both the activity in the center of the open field and ethanol drinking in females only. These results suggest that Ofil1 contains either linked genes with independent influences on anxiety-related responses and ethanol drinking or a pleiotropic gene with simultaneous effects on both traits. [source] Common variations in the pretest environment influence genotypic comparisons in models of anxietyGENES, BRAIN AND BEHAVIOR, Issue 7 2005G. S. Izídio The behavioral characterization of rodent strains in different studies and laboratories can provide unreplicable results even when genotypes are kept constant and environmental control is maximized. In the present study, the influence of common laboratory environmental variables and their interaction with genotype on the results of behavioral tests of anxiety/emotionality were investigated. To this end, the inbred rat strains Lewis (LEW) and spontaneously hypertensive rats (SHR), which are known to differ for numerous emotionality-related behaviors, were tested in the open field (OF), elevated plus maze (EPM) and black/white box (BWB), while three environmental factors were systematically controlled and analyzed: (1) the experimenter handling the animal (familiar or unfamiliar); (2) the position of the home cage (top or bottom shelf of the rack) and (3) the behavioral state of the animal immediately before the test (arousal or rest). Experimenter familiarity did not alter the behavior of rats in the OF. Cage position, on the other hand, influenced the behavior in the OF and BWB, with rats housed in top cages appearing less anxious like than those housed in the bottom. In the BWB (but not in the OF), these effects were genotype dependent. Finally, the behavioral state of the animals prior to testing altered the results of the EPM in a strain-dependent manner, with some anxiety-related genotypic differences being found only among rats that were aroused in their home cages. This study showed that common variations in the laboratory environment interact with genotype in behavioral tests of anxiety/emotionality. Recognizing and understanding such variations can help in the design of more effective experiments. [source] The Local Shape of Revolution: Reflections on Quantitative Geography at Cambridge in the 1950s and 1960sGEOGRAPHICAL ANALYSIS, Issue 3 2008Peter Haggett The "quantitative revolution" in human geography which swept across so many universities in the 1950s and 1960s had its main diffusion centers in a few locations which were to have global significance. Two critical early centers were the University of Washington in the Pacific Northwest and Lund University in southern Sweden. But the experience of change was different in different locations as the general forces of perturbation sweeping around academia were translated into local eddies with local repercussions. Here, small and somewhat random quirks at the outset, led eventually to fundamental divergences between adoption and rejection. The theme is illustrated by reference to changes which occurred at Cambridge, one of England's two oldest universities, as seen from the perspective of someone who,as undergraduate, graduate student, and later, faculty member,was caught up in these changes and took some small part in propagating them. Special attention is given to the role of two environmental scientists, Vaughan Lewis and Richard Chorley, in introducing changes and the way in which later developments in human geography drew on preceding experiences in physical geography. The reasons behind the "Cambridge variant" and the questions of how intellectual DNA is passed across the generations are discussed. [source] Printed Origami Structures (Adv. Mater.ADVANCED MATERIALS, Issue 20 201020/2010) Bok Y. Ahn, Jennifer Lewis, and co-workers report on p.,2251 a new method for creating complex 3D structures that combines direct-write assembly with a wet-folding origami technique. Planar lattices composed of a titanium hydride ink are printed, and then folded, rolled, or molded into the desired shape. These 3D objects are then transformed into metallic or ceramic structures by thermal annealing. [source] The Ideal Explanatory Text in History: A Plea for EcumenismHISTORY AND THEORY, Issue 3 2004Tor Egil Førland ABSTRACT This article presents Peter Railton's analysis of scientific explanation and discusses its application in historiography. Although Railton thinks covering laws are basic in explanation, his account is far removed from Hempel. The main feature of Railton's account is its ecumenism. The "ideal explanatory text," a central concept in Railton's analysis, has room for not only causal and intentional, but also structural and functional explanations. The essay shows this by analyzing a number of explanations in history. In Railton's terminology all information that reduces our insecurity as to what the explanandum is due is explanatory. In the "encyclopedic ideal explanatory text," different kinds of explanation converge in the explanandum from different starting points. By incorporating pragmatic aspects, Railton's account is well suited to show how explanations in historiography can be explanatory despite their lack of covering laws or tendency statements. Railton's account is also dynamic, showing how the explanatory quest is a never-ending search for better illumination of the ideal explanatory text. Railton's analysis is briefly compared to, and found compatible with, views on explanation presented by David Lewis, C. Behan McCullagh, and R. G. Collingwood. Confronted with Hans-Georg Gadamer's hermeneutics and Donald Davidson's insistence on the indeterminacy of interpretation, the essay suggests that the objectivity of the ideal explanatory text should be regarded as local, limited to the description under which the action is seen. [source] Searching for Sacajawea: Whitened Reproductions and Endarkened RepresentationsHYPATIA, Issue 2 2007Wanda Pillow Pillow's aim is to demonstrate how representations of Sacajawea have shifted in writings about the Lewis and Clark expedition in ways that support manifest destiny and white colonial projects. This essay begins with a general account of Sacajawea. The next section uses two novels (one hundred years apart) to make the case that shifts in the representation of this important historical figure serve similar purposes. There is some attention to white suffragist representations, but the central contrast is between manifest destiny and multiculturalism. The final section addresses the important question of whether it is possible for feminists to theorize Sacajawea in ways that are not co-opted by colonial projects. [source] Lewis and Sumner syndrome following infliximab treatment in Crohn's disease: A report of 2 casesINFLAMMATORY BOWEL DISEASES, Issue 9 2010Stephane Nancey MD First page of article [source] The journal Communications in Numerical Methods in Engineering with Biomedical Applications becomes the International Journal for Numerical Methods in Biomedical Engineering (IJNMBE) from 1st January 2010INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 16 2009Perumal Nithiarasu Editor Abstract Communications in Numerical Methods in Engineering, founded by Roland W. Lewis in 1985, will change its title to the ,International Journal for Numerical Methods in Biomedical Engineering' and has a revised Aims and Scope. Copyright © 2009 John Wiley & Sons, Ltd. [source] The journal Communications in Numerical Methods in Engineering with Biomedical Applications becomes the International Journal for Numerical Methods in Biomedical Engineering (IJNMBE) from 1st January 2010INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 11 2009Perumal Nithiarasu Editor Abstract Communications in Numerical Methods in Engineering, founded by Roland W. Lewis in 1985, will change its title to the ,International Journal for Numerical Methods in Biomedical Engineering' and has a revised Aims and Scope. Copyright © 2009 John Wiley & Sons, Ltd. [source] Catalytic cracking, dehydrogenation, and aromatization of isobutane over Ga/HZSM-5 and Zn/HZSM-5 at low pressuresINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 8 2002Yanping Sun Isobutane cracking, dehydrogenation, and aromatization over Ga/HZSM-5 and Zn/HZSM-5 has been investigated in a Knudsen cell reactor and the kinetics of the primary reaction steps for isobutene and propene formation have been accurately determined. Although cracking is the dominant reaction channel, with propene and methane being primary products, methane formation is significantly less than propene formation. This indicates that a proportion of the cracking proceeds via Lewis acid attack at CC bonds, and not just via alkanium ion formation at Bronsted acid sites. This is particularly apparent over Zn/HZSM-5. Intrinsic rate constants for cracking, calculated from the rate of propene formation, are and for dehydrogenation, calculated from the rate of isobutene formation, are Large preexponential factors for cracking and dehydrogenation over Ga/HZSM-5 indicate that either the coverage of active sites is significantly less than the coverage of exposed sites or the intrinsic reaction step involves a large entropy change between reactant and transition state. For Zn/HZSM-5 the small preexponential factors suggest either small entropy changes during activation, perhaps initiated by Lewis acid sites, or a steady-state distribution of active and exposed sites is rapidly reached. Differences in intrinsic activation energies may reflect the ratio of Lewis and Bronsted acid sites on the respective catalyst surfaces. Aromatization is more prolific over Ga/HZSM-5 than over Zn/HZSM-5 under the low-pressure conditions. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 467,480, 2002 [source] Modelling of air drying of fresh and blanched sweet potato slicesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2010Kolawole O. Falade Summary Effects of blanching, drying temperatures (50,80 °C) and thickness (5, 10 and 15 mm) on drying characteristics of sweet potato slices were investigated. Lewis, Henderson and Pabis, Modified Page and Page models were tested with the drying patterns. Page and Modified Page models best described the drying curves. Moisture ratio vs. drying time profiles of the models showed high correlation coefficient (R2 = 0.9864,0.9967), and low root mean squared error (RMSE = 0.0018,0.0130) and chi-squared (,2 = 3.446 × 10,6,1.03 × 10,2). Drying of sweet potato was predominantly in the falling rate period. The temperature dependence of the diffusion coefficient (Deff) was described by Arrhenius relationship. Deff increased with increasing thickness and air temperature. Deff of fresh and blanched sweet potato slices varied between 6.36 × 10,11,1.78 × 10,9 and 1.25 × 10,10,9.75 × 10,9 m2 s,1, respectively. Activation energy for moisture diffusion of the slices ranged between 11.1 and 30.4 kJ mol,1. [source] Geometric control of mechanical systems: modelling, analysis, and design for simple mechanical control systems, Francesco Bullo and Andrew D. Lewis, Springer, New York, NY, 2005INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 11 2006Stefano Stramigioli No abstract is available for this article. [source] Room Temperature Lewis Base-Catalyzed Alumination of Terminal AlkynesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Yuhan Zhou Abstract An efficient and mild access to mixed dimethylalkynylaluminum reagents has been developed via a direct Lewis base-catalyzed alumination of terminal alkynes by trimethylaluminum. The use of bis(trimethylsilyl)methylamine enables the metalation at room temperature with only 1% of catalyst loading. [source] | |||||||||||||||||||||||||||||||