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  • 1
    Unknown
    Seasonal Forecasts, Climatic Change and Human Health : Health and Climate (2008)
    Springer
    Details
    Keywords: Assessment ; Malaria ; Public Health ; Scale ; Weather ; climate change ; public health policy ; temperature
    Description / Table of Contents: Awareness that many key aspects of public health are strongly influenced by climate is growing dramatically, driven by new research and experience and fears of climate change and the research needed to underpin policy developments in area is growing rapidly . This awareness has yet to translate into a practical use of climate knowledge by health policy-makers. Evidence based policy and practice is the mantra of the health sector. If climate scientists are to contribute effectively to health policy at local and global scales then careful empirical studies must be undertaken – focused on the needs of the public health policy and decision-makers. Results presented at the Wengen conference make clear that the science and art of integrating climate knowledge into the control of climate sensitive diseases on a year to year time frame as well as careful assessments of the potential impacts of climate change on health outcomes over longer time frames is advancing rapidly on many fronts. This includes advances in the empirical understanding of mechanisms, methodologies for modeling future impacts, new partnership developments between the health and climate community along with access to relevant data resources, and education and training. In a rapidly evolving field this book provides a snapshot of these emerging themes.
    Pages: Online-Ressource (X, 232 pages)
    ISBN: 9781402068775
    URL: https://doi.org/10.1007/978-1-4020-6877-5
    Language: English
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  • 2
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    The Pangenome (2021)
    Springer Nature | Springer
    Details
    Publication Date: 2024-04-05
    Description: This open access book offers the first comprehensive account of the pan-genome concept and its manifold implications. The realization that the genetic repertoire of a biological species always encompasses more than the genome of each individual is one of the earliest examples of big data in biology that opened biology to the unbounded. The study of genetic variation observed within a species challenges existing views and has profound consequences for our understanding of the fundamental mechanisms underpinning bacterial biology and evolution. The underlying rationale extends well beyond the initial prokaryotic focus to all kingdoms of life and evolves into similar concepts for metagenomes, phenomes and epigenomes. The book’s respective chapters address a range of topics, from the serendipitous emergence of the pan-genome concept and its impacts on the fields of microbiology, vaccinology and antimicrobial resistance, to the study of microbial communities, bioinformatic applications and mathematical models that tie in with complex systems and economic theory. Given its scope, the book will appeal to a broad readership interested in population dynamics, evolutionary biology and genomics.
    Keywords: Microbial Genetics and Genomics ; Evolutionary Biology ; Genetics and Population Dynamics ; Microbial Ecology ; Human Genetics ; Genetics and Genomics ; Comparative genomics ; Metagenomics ; Microbial Population Analysis ; Pangenome Profile ; Supra-Genome Analysis ; Adaptive Evolution ; Computational Tools ; Bioinformatic Genomics ; Core Dispensable Genome ; Selection, Recombination, Composition ; Acquired Resistance ; Bacterial Species Concept ; Genomic Diversity ; Bacterial Ecology, Microevolution ; Open Access ; Pan-metagenomics ; Pan-microbiomics ; Pan-epigenome ; Gene Transfer ; Pan-phenomes ; Microbiology (non-medical) ; Genetics (non-medical) ; Evolution ; Applied mathematics ; Ecological science, the Biosphere ; Medical genetics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSG Microbiology (non-medical) ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAJ Evolution ; thema EDItEUR::P Mathematics and Science::PB Mathematics::PBW Applied mathematics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAF Ecological science, the Biosphere ; thema EDItEUR::M Medicine and Nursing::MF Pre-clinical medicine: basic sciences::MFN Medical genetics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAK Genetics (non-medical)
    Language: English
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  • 3
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    Upper Ocean Temperatures Hit Record High in 2020 (2021)
    Springer
    Details
    Publication Date: 2021-05-12
    Description: The long-term warming of the ocean is a critical indicator of both the past and present state of the climate system. It also provides insights about the changes to come, owing to the persistence of both decadal variations and secular trends, which the ocean records extremely well (Hansen et al., 2011; IPCC, 2013; Rhein et al., 2013; Trenberth et al., 2016; Abram et al., 2019). It is well established that the emission of greenhouse gasses by human activities is mainly responsible for global warming since the industrial revolution (IPCC, 2013; Abram et al., 2019). The increased concentration of heat-trapping greenhouse gases in the atmosphere has interfered with natural energy flows. Currently there is an energy imbalance in the Earth’s climate system of almost 1 W m−2 (Trenberth et al., 2014; von Schuckmann et al., 2016, 2020a; Wijffels et al., 2016; Johnson et al., 2018; Cheng et al., 2019a; von Schuckmann et al., 2020a). Over 90% of this excess heat is absorbed by the oceans, leading to an increase of ocean heat content (OHC) and sea level rise, mainly through thermal expansion and melting of ice over land. These processes provide a useful means to quantify climate change. The first global OHC time series by Levitus et al. (2000) identified a robust long-term 0−3000 m ocean warming from 1948−98. Since then, many other analyses of global and regional OHC data have been performed. Here, we provide the first analysis of recent ocean heating, incorporating 2020 measurements through 2020 into our analysis.
    Description: Published
    Description: 523–530
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Keywords: ocean temperature ; climate change ; climate change
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Beyond one-way determinism: San Frediano's miracle and climate change in Central and Northern Italy in late antiquity (2021)
    Springer
    Details
    Publication Date: 2021-11-26
    Description: Integrating palaeoclimatological proxies and historical records, which is necessary to achieve a more complete understanding of climate impacts on past societies, is a challenging task, often leading to unsatisfactory and even contradictory conclusions. This has until recently been the case for Italy, the heart of the Roman Empire, during the transition between Antiquity and the Middle Ages. In this paper, we present new high-resolution speleothem data from the Apuan Alps (Central Italy). The data document a period of very wet conditions in the sixth c. AD, probably related to synoptic atmospheric conditions similar to a negative phase of the North Atlantic Oscillation. For this century, there also exist a significant number of historical records of extreme hydroclimatic events, previously discarded as anecdotal. We show that this varied evidence reflects the increased frequency of floods and extreme rainfall events in Central and Northern Italy at the time. Moreover, we also show that these unusual hydroclimatic conditions overlapped with the increased presence of "water miracles" in Italian hagiographical accounts and social imagination. The miracles, performed by local Church leaders, strengthened the already growing authority of holy bishops and monks in Italian society during the crucial centuries that followed the "Fall of the Roman Empire". Thus, the combination of natural and historical data allows us to show the degree to which the impact of climate variability on historical societies is determined not by the nature of the climatic phenomena per se, but by the culture and the structure of the society that experienced it.
    Description: Published
    Description: 25
    Description: 5A. Ricerche polari e paleoclima
    Description: JCR Journal
    Keywords: Precipitation ; Roman Empire ; miracles ; Social feedbacks ; Cultural change ; climate change
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
    Electronic Resource
    Electronic Resource
    Risk Perceptions, General Environmental Beliefs, and Willingness to Address Climate Change (1999)
    Springer
    Risk analysis 19 (1999), S. 461-471 
    Details
    ISSN: 1539-6924
    Keywords: Risk perceptions ; climate change ; knowledge ; environmental beliefs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The research reported here examines the relationship between risk perceptions and willingness to address climate change. The data are a national sample of 1225 mail surveys that include measures of risk perceptions and knowledge tied to climate change, support for voluntary and government actions to address the problem, general environmental beliefs, and demographic variables. Risk perceptions matter in predicting behavioral intentions. Risk perceptions are not a surrogate for general environmental beliefs, but have their own power to account for behavioral intentions. There are four secondary conclusions. First, behavioral intentions regarding climate change are complex and intriguing. People are neither “nonbelievers” who will take no initiatives themselves and oppose all government efforts, nor are they “believers” who promise both to make personal efforts and to vote for every government proposal that promises to address climate change. Second, there are separate demographic sources for voluntary actions compared with voting intentions. Third, recognizing the causes of global warming is a powerful predictor of behavioral intentions independent from believing that climate change will happen and have bad consequences. Finally, the success of the risk perception variables to account for behavioral intentions should encourage greater attention to risk perceptions as independent variables. Risk perceptions and knowledge, however, share the stage with general environmental beliefs and demographic characteristics. Although related, risk perceptions, knowledge, and general environmental beliefs are somewhat independent predictors of behavioral intentions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007004813446
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  • 6
    Electronic Resource
    Electronic Resource
    The Maillard reaction in vivo (1991)
    Springer
    European journal of nutrition 30 (1991), S. 29-45 
    Details
    ISSN: 1436-6215
    Keywords: advanced glycosylation endproducts (AGE) ; ag(e)ing ; aminoguanidine ; ascorbate ; autoxidation ; biomarker ; browning reaction ; chemical modification of proteins ; diabetes ; glycation ; glycoxidation ; nonenzymatic glycosylation ; oxidation ; Maillard reaction ; Aminoguanidin ; Ascorbat ; Autooxidation ; Biomarker ; Bräunungsreaktion ; chemische Veränderung vonProteinen ; Diabetes ; Glycosylierung ; Glycoxidation ; nichtenzymatische ; Glycosylierung ; Oxidation ; Maillardreaktion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Die Maillard- oder Bräunungsreaktion genannten Umsetzungen zwischen reduzierenden Zuckern und Eiweiß führen zur chemischen Zerstörung der Aminosäuren und zum Verlust der Proteinqualität während der Lebensmittelbearbeitung und -lagerung. Der vorliegende Beitrag zeigt Befunde auf, daß die Maillardreaktion auch im Gewebe des Menschen bei der Alterung von Proteinen mit langer biologischer Halbwertszeit auftritt. Die Konzentrationen an den sogenannten Amadori-Produkten, die im Initialstadium der Maillardreaktion aus Glucose und den Proteinen der Augenlinse oder dem Kollagen der Haut entstehen, erwiesen sich als relativ konstant, auch mit zunehmendem Alter. Die Produkte der Glycosylierung und nachfolgenden Oxidation der Proteine, auch Glycoxidationsprodukte genannt, häufen sich dagegen im Alter an, und zwar bei Diabetikern in vermehrtem Maße. Zu diesen Produkten gehören die Aminosäurenderivate N-(carboxymethyl)-lysin (CML), N-(carboxymethyl)-hydroxylysin (CMhL) sowie das fluoreszierende Quervernetzungsprodukt Pentosidin. Während diese Glycoxidationsprodukte in den Körpergeweben nur in Spuren vorkommen, gibt es deutliche Hinweise auf die Anwesenheit weiterer Bräunungsprodukte, deren Charakterisierung jedoch noch aussteht. Es werden Möglichkeiten zur „Entgiftung“ der reaktiven Zwischenprodukte aus der Maillardreaktion sowie zum Abbau extrem gebräunter Proteine diskutiert sowie neuere Möglichkeiten zur therapeutischen Modulierung fortgeschrittener Stadien der Maillardreaktion aufgezeigt.
    Notes: Summary The Maillard or browning reaction between reducing sugars and protein contributes to the chemical deterioration and loss of nutritional value of proteins during food processing and storage. This article presents and discusses evidence that the Maillard reaction is also involved in the chemical aging of long-lived proteins in human tissues. While the concentration of the Amadori adduct of glucose to lens protein and skin collagen is relatively constant with age, products of sequential glycation and oxidation of protein, termed glycoxidation products, accumulate in these long-lived proteins with advancing age and at an accelerated rate in diabetes. Among these products are the chemically modified amino acids, Nɛ-(carboxymethyl)lysine (CML), Nɛ-(carboxymethyl)hydroxylysine (CMhL), and the fluorescent crosslink, pentosidine. While these glycoxidation products are present at only trace levels in tissue proteins, there is strong evidence for the presence of other browning products which remain to be characterized. Mechanisms for detoxifying reactive intermediates in the Maillard reaction and catabolism of extensively browned proteins are also discussed, along with recent approaches for therapeutic modulation of advanced stages of the Maillard reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01910730
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  • 7
    Electronic Resource
    Electronic Resource
    Statistical validation of GCM-simulated climates for the U.S. Great Lakes and the C.I.S. Emba and Ural River basins (1992)
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 69-80 
    Details
    ISSN: 1436-3259
    Keywords: Hydrology ; global circulation models ; statistics ; climate change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Many researchers use outputs from large-scale global circulation models of the atmosphere to assess hydrological and other impacts associated with climate change. However, these models cannot capture all climate variations since the physical processes are imperfectly understood and are poorly represented at smaller regional scales. This paper statistically compares model outputs from the global circulation model of the Geophysical Fluid Dynamics Laboratory to historical data for the United States' Laurentian Great Lakes and for the Emba and Ural River basins in the Commonwealth of Independent States (C.I.S.). We use maximum entropy spectral analysis to compare model and data time series, allowing us to both assess statistical predictabilities and to describe the time series in both time and frequency domains. This comparison initiates assessments of the model's representation of the real world and suggests areas of model improvement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581676
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  • 8
    Electronic Resource
    Electronic Resource
    Can the theory of evolution be falsified? (1984)
    Springer
    Acta biotheoretica 33 (1984), S. 35-50 
    Details
    ISSN: 1572-8358
    Keywords: Evolution ; falsification ; Darwinism ; philosophy of science
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this paper we discuss the epistemological positions of evolution theories. A sharp distinction is made between the theory that species evolved from common ancestors along specified lines of descent (here called “the theory of common descent”), and the theories intended as causal explanations of evolution (e.g. Lamarck's and Darwin's theory). The theory of common descent permits a large number of predictions of new results that would be improbable without evolution. For instance, (a) phylogenetic trees have been validated now; (b) the observed order in fossils of new species discovered since Darwin's time could be predicted from the theory of common descent; (c) owing to the theory of common descent, the degrees of similarity and difference in newly discovered properties of more or less related species could be predicted. Such observations can be regarded as attempts to falsify the theory of common descent. We conclude that the theory of common descent is an easily-falsifiable & often-tested & still-not-falsified theory, which is the strongest predicate a theory in an empirical science can obtain. Theories intended as causal explanations of evolution can be falsified essentially, and Lamarck's theory has been falsified actually. Several elements of Darwin's theory have been modified or falsified: new versions of a theory of evolution by natural selection are now the leading scientific theories on evolution. We have argued that the theory of common descent and Darwinism are ordinary, falsifiable scientific theories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00045845
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  • 9
    Electronic Resource
    Electronic Resource
    Nonequilibrium thermodynamics and different axioms of evolution (1986)
    Springer
    Acta biotheoretica 35 (1986), S. 77-106 
    Details
    ISSN: 1572-8358
    Keywords: Evolution ; nonequilibrium thermodynamics ; boundary conditions models ; initial conditions models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Proponents of two axioms of biological evolutionary theory have attempted to find justification by reference to nonequilibrium thermodynamics. One states that biological systems and their evolutionary diversification are physically improbable states and transitions, resulting from a selective process; the other asserts that there is an historically constrained inherent directionality in evolutionary dynamics, independent of natural selection, which exerts a self-organizing influence. The first, the Axiom of Improbability, is shown to be nonhistorical and thus, for a theory of change through time, acausal. Its perception of the improbability of living states is at least partially an artifact of closed system thinking. The second, the Axiom of Historically Determined Inherent Directionality, is supported evidentially and has an explicit historical component. Historically constrained dynamic populations are inherently nonequilibrium systems. It is argued that living, evolving systems, when considered to be historically constrained nonequilibrium systems, do not appear improbable at all. Thus, the two axioms are not compatible. Instead, the Axiom of Improbability is considered to result from an unjustified attempt to extend the contingent proximal actions of natural selection into the area of historical, causal explanations. It is thus denied axiomatic status, and the effects of natural selection are subsumed as an additional level of constraint in an evolutionary theory derived from the Axiom of Historically Determined Inherent Directionality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00118368
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  • 10
    Electronic Resource
    Electronic Resource
    Some prerequisites for a study of the evolution of cognition in the animal kingdom (1996)
    Springer
    Acta biotheoretica 44 (1996), S. 37-57 
    Details
    ISSN: 1572-8358
    Keywords: Animal cognition ; Evolution ; Representation ; Computation ; Significance ; Phenomenology ; Autonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A distinction is made between two definitions of animal cognition: the one most frequently employed in cognitive sciences considers cognition as extracting and processing information; a more phenomenologically inspired model considers it as attributing to a form of the outside world a significance, linked to the state of the animal. The respective fields of validity of these two models are discussed along with the limitations they entail, and the questions they pose to evolutionary biologists are emphasized. This is followed by a presentation of a general overview of what might be the study of the evolution of knowledge in animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046434
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  • 11
    Electronic Resource
    Electronic Resource
    Oxidation of bridging groups by carboxylate coordinated ligands in palladium clusters (1992)
    Springer
    Journal of cluster science 3 (1992), S. 411-421 
    Details
    ISSN: 1572-8862
    Keywords: Palladium ; carbene ; oxidation ; phosphonate ; carboxylate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Thermolysis of tetranuclear palladium clusters Pd4(μ-Q)4 Pd4(μ-Q)4(μ-O2CR)4 (Q=CPh2 or CO;R=Me, CMe3, Ph, CH2Cl or CF3) has been found to involve innersphere oxidation of carbene or carbonyl ligands during which an oxygen atom transfer occurs from the carboxylate group to the carbene or carbonyl ligand. The thermolysis of the carbonyl clusters gives rise to the products of CO2 insertion into the C–H bond of benzene or toluene used as solvents forming benzoic acid from benzene and a mixture of phenylacetic and toluic acids from toluene. The reaction of [Pd(OAc)2(PPh3)]2 with HCO2H includes the transfer of an O atom from formate ligand to the P atom and cleavage of the P-Ph bond accompanied by transfer of the Ph group from PPh3 ligand to the palladium atom. The structure of the complex formed, [Pd(μ-O2PPh2)(C6H5)(PPh3)]2, has been resolved by X-ray analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702748
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  • 12
    Electronic Resource
    Electronic Resource
    Chemiluminescence in evaluating the thermal oxidative stability of acrylonitrile-butadiene-styrene (ABS) copolymers. II. ABS/polycarbonate (PC) blends (1993)
    Springer
    Journal of polymers and the environment 1 (1993), S. 275-279 
    Details
    ISSN: 1572-8900
    Keywords: Chemiluminescence ; oxidation ; stability ; acrylonitrile-butadiene-styrene (ABS) ; ABS/polycarbonate blend
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The thermal oxidative stability of various ABS/PC compounds was studied by means of the chemiluminescence technique. Similarly to pure ABS, Irganox 1076 and Irganox MD 1024 perform as moderate antioxidants in ABS/PC and (ABS/PC + lubricant) blends. Neither Tinuvin 144, Irgaphos 168, nor their mixture affects the durability of the ABS/PC blend. At the same time, (Irgaphos 168 + Tinuvin 144) in combination with Irganoxes was found to provide a noticeable enhancement in durability to the (ABS/PC + lubricant) system. Titanium dioxide pigments by themselves have only a slight influence on the oxidative stability of the ABS/PC blend. Durability of the (ABS/PC + pigment) and (ABS/PC + lubricant) systems was found to be the same and the overall protective effect of Irganox 1076 was similar in both the (ABS/PC + lubricant) and the (ABS/PC + lubricant + pigment) systems. Certain modifiers significantly improve the durability of the ABS/PC compounds, although their function may differ in the systems with and without pigments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01458294
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  • 13
    Electronic Resource
    Electronic Resource
    Chemiluminescence in evaluating the thermal oxidative stability of acrylonitrile-butadiene-styrene (ABS) copolymers. 1. Influence of stabilizers and lubricants (1993)
    Springer
    Journal of polymers and the environment 1 (1993), S. 107-110 
    Details
    ISSN: 1572-8900
    Keywords: Chemiluminescence ; oxidation ; stability ; acrylonitrile-butadiene-styrene (ABS)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The influence of lubricants, UV stabilizers, antioxidants, and metal deactivators on the resistance of ABS to thermal oxidation was studied by means of the chemiluminescence technique. Neither of the additives seems to affect significantly the induction period of oxidation. At the same time, the influence of various additives on the oxidation rate constant is remarkably different: the introduction of lubricants and UV stabilizers increases its value, while antioxidants and metal deactivators have the opposite effect. For the particular systems studied durability is decreased in samples containing the lubricant and UV stabilizers and increased in samples stabilized with the antioxidant and metal deactivator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01418203
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  • 14
    Electronic Resource
    Electronic Resource
    Carbon monoxide electrooxidation on porous Pt–Ru electrodes in sulphuric acid (1997)
    Springer
    Journal of applied electrochemistry 27 (1997), S. 1275-1282 
    Details
    ISSN: 1572-8838
    Keywords: Carbon monoxide ; Pt-Ru/C catalyst ; Tafel slopes ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract CO electrooxidation on a Pt–Ru/C catalyst was investigated in sulphuric acid electrolyte. The physico-chemical properties of the Pt–Ru/C catalyst were studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The influence of temperature, CO partial pressure and proton concentration on the electrochemical oxidation rate was investigated by steady-state galvanostatic polarization measurements. The apparent activation energy decreased from 70 to 30kJmol−1 as the overpotential increased from 0.5 to 0.9V vs NHE. The reaction order with respect to carbon monoxide increased, passing from 0.4 to 1, with the increase of the overpotential from 0.5 to 0.7V vs NHE; a reaction order close to −1 with respect to the protonic concentration was observed, irrespective of the potential. Tafel slopes of about 136mVdec−1 were determined for oxidation of CO and CO/N2 mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018492122263
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  • 15
    Electronic Resource
    Electronic Resource
    Characterization and stability of doped SnO2 anodes (1998)
    Springer
    Journal of applied electrochemistry 28 (1998), S. 607-612 
    Details
    ISSN: 1572-8838
    Keywords: SnO2 anodes ; doping ; high overvoltage anodes ; surface analysis ; oxidation ; water treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Doped tin dioxide electrodes have been prepared by a standard spray pyrolysis technique. The electrochemical behaviour of these electrodes has been investigated by cyclic voltammetry in sulphuric acid using the Fe2+/Fe3+ redox couple system as test reaction. Oxygen evolution has been used to study the stability of doped SnO2 electrodes. The SnO2 electrodes doped with antimony and platinum exhibit the highest stability. XPS analysis shows that the oxidation state of Sn, Sb and Pt are +4, +3 and +2, respectively, the probable species being SnO2, Sb2O3 and PtO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003250118996
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  • 16
    Electronic Resource
    Electronic Resource
    Phosphazene-bound Rose Bengal: A novel photosensitizer for singlet oxygen generation (1991)
    Springer
    Journal of inorganic and organometallic polymers and materials 1 (1991), S. 389-395 
    Details
    ISSN: 1572-8870
    Keywords: Poly(organophosphazenes) ; cyclophosphazenes ; Rose Bengal ; photosensitization ; singlet oxygen ; oxidation ; heterogeneous phase photosensitizer ; 1,3-diphenyl-isobenzofuran
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this paper we report the synthesis and the characterization of cyclo- and polyphosphazenes supporting Rose Bengal. These substrates are suitable for the photosensitized generation of singlet oxygen, both in homogeneous and in heterogeneous phase. The efficiency of1O2 production has been measured in homogeneous solution using, as photosensitizer, the cyclophosphazene-bound Rose Bengal and considering, as testing reaction, the oxidation of 1,3-diphenylisobenzofuran; it was found comparable to that of free Rose Bengal in the same experimental conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702501
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  • 17
    Electronic Resource
    Electronic Resource
    Biomass conversion: attempted electrooxidation of lignin for vanillin production (2000)
    Springer
    Journal of applied electrochemistry 30 (2000), S. 727-731 
    Details
    ISSN: 1572-8838
    Keywords: electrosynthesis ; oxidation ; lignin ; vanillin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electrochemical oxidative degradation of Kraft lignin was investigated in batch and flow cells on Pt, Au, Ni, Cu, DSA–O2 and PbO2 anodes. Production of vanillin was evaluated by means of formal kinetic analyses. Conversion and chemical yields were found to be dependent mainly on the applied current density, that is on the partial pressure of oxygen at the interface, while the nature of the electrode influenced the reaction rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004003613883
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  • 18
    Electronic Resource
    Electronic Resource
    Synthesis and crystal structure of 1-acetyl-3-bromo-3-phenylazetidine and 1-phenyl-2-(N-acetyl-N-formyl)-aminoethanone (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 119-123 
    Details
    ISSN: 1572-8854
    Keywords: Azetidine ; azetine ; ring opening ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 1-Acetyl-3-bromo-3-phenylazetidine (1), C11H12BrNO, has been synthesized and characterized by spectroscopic methods and single crystal X-ray analysis. It crystallizes in the space group P2 1/c with a = 8.633(1), b = 7.461(1), c = 17.204(1) Å, β = 98.403(7)°, V = 1096.2(2) Å3, Z = 4, D calc = 1.540 g cm−3. The azetidine ring is nearly planar since the four atoms are within ±0.039(5) Å of the mean square plane calculated for the heterocycle. The attempt to obtain a highly strained 2-azetine derivative from the above compound gave, surprisingly, 1-phenyl-2-(N-acetyl-N-formyl)-aminoethanone (2), C11H11NO3. This compound has been also characterized by spectroscopic methods and single crystal X-ray analysis. It crystallizes in the space group P212121, with a = 5.4719(3), b = 8.3205(6), c = 23.298(3) Å, V = 1060.7(2) Å3, Z = 4, D calc = 1.286 g cm−3. The aminoethanone residue is in a near planar conformation where the torsion angles are 7(2)° for N–C–C–=O and −173(2)° for N–C–C–C(Ph).
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    Oxidation of 3-methylindole catalyzed by cobalt(II)phthalocyanines covalently bound to polyorganosiloxane (1991)
    Springer
    Journal of inorganic and organometallic polymers and materials 1 (1991), S. 211-221 
    Details
    ISSN: 1572-8870
    Keywords: Polyorganosiloxane ; cobalt(II)phthalocyanine ; polymeric catalyst ; oxidation ; 3-methylindole ; polymer conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two kinds of cobalt(II)phthalocyanines covalently bound to polyorganosiloxane (POS) were prepared to be applied as catalysts for the oxidation of 3-methylindole in organic solvents. The catalytic activity of the POS whose carboxyl residues were methyl-esterified was high compared with that of the POS which has carboxyl residues. The former polymeric atalyst exhibited higher catalytic activity than monomolecular phthalocyanine, indicating an appearance of effects of polymer chains. The factors which influence the catalytic oxidation, e.g., polymer conformations, basicity of solvents, and equilibrium involving phthalocyanine monomer and the dimer, are discussed. It has become apparent that polymer conformation influences catalytic activity and that the catalytic activity of the POS, whose main chains are mobile, is high.
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    URL: http://dx.doi.org/10.1007/BF00701320
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    Chemiluminescence in evaluating thermal oxidative stability of acrylonitrile-butadiene-styrene (ABS) copolymers. III. Emulsion-grade products (1995)
    Springer
    Journal of polymers and the environment 3 (1995), S. 199-203 
    Details
    ISSN: 1572-8900
    Keywords: Chemiluminescence ; oxidation ; stability ; acrylonitrile-butadiene-styrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The thermal oxidative stability of various formulations based on emulsion-grade ABS was studied by the chemiluminescence technique. Emulsion products were found to be essentially less stable than ionic mass polymerization resins. Among the antioxidants studied, Santonox R is clearly more efficient than Irganox 1076 and Irganox 3114, and its superiority is reflected primarily in improved induction period values. The introduction of Tinuvin 770 and Tinuvin 328 UV stabilizers into emulsion resins does not change the durability of the products. In mixtures where both Irganox 1076 and UV stabilizers are present, a certain antagonistic effect was noted at high UV stabilizer concentrations.
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    URL: http://dx.doi.org/10.1007/BF02068674
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    The oxidation of Cu(I) in electrolyte solutions (1988)
    Springer
    Journal of solution chemistry 17 (1988), S. 581-599 
    Details
    ISSN: 1572-8927
    Keywords: Copper ; oxidation ; NaCl solutions ; ionic strength ; speciation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rates of oxidation of Cu(I) in air saturated solutions was measured as a function of pH, temperature (5–45°C), and ionic strength (0.5 to 6m) in NaCl and NaCl−NaClO4 solutions. In pure NaCl solutions, the effect of pH is independent of ionic strength and temperature. The overall rate constant is given by logk=12.32+0.12(pH)−2064/T−3.69I1/2+ 0.73I The energy of activitation was 39±2 kJ-mol−1 and is independent of ionic strength. At a constant ionic strength (I=1, 3 and 6m) in NaCl−NaClO4 mixtures the Cl− dependence of the rates is attributed to the oxidation of the various forms of Cu(I) in the solution. The rate constants for the oxidation of the various species are found to be functions of ionic strength. At a constant ionic strength (I=1) in NaCl−NaClO4 solutions, the effect of temperature is independent of the chloride concentration. The effect of Mg2+ and HCO 3 − on the oxidation rate was determined as a function of chloride concentration (1 to 6m) at 25°C and pH=8. The addition of Mg2+ causes the rate to decrease and the addition of HCO 3 − causes the rate to increase. The possible causes of these effects are discussed. Empirical equations for the rate of oxidation of Cu(I) in Na-Mg-Cl-HCO3 solutions as a function of composition are used to make reliable estimates of the oxidation in seawater and Red Sea waters.
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    Effect of ionic strength and ionic interactions on the oxidation of Fe(II) (1989)
    Springer
    Journal of solution chemistry 18 (1989), S. 585-599 
    Details
    ISSN: 1572-8927
    Keywords: Fe(II) ; oxidation ; ionic strength ; NaCl ; NaClO4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rates of oxidation of Fe(II) in NaCl and NaClO 4 solutions were studied as a function of pH (6 to 9), temperature (5 to 25°C), and ionic strength (0 to 6m). The rates are second order with respect to [H+] or [OH−] and independent of ionic strength and temperature. The overall rate of the oxidation is given by $$d[Fe(II)]/dt = - k[Fe(II)][OH^ - ]^2 [O_2 ]$$ where [OH−]=K W * /[H+](K W * is the stoichiometric dissociation constant for water) and [O 2 ] is the molal concentration of the oxygen. The experimental results were fitted to equations of the form $$log{\text{ }}k = log{\text{ }}k_0 + {\rm A}\sqrt {\rm I} + {\rm A}\sqrt {\rm I} /T + CI$$ where log k0=21.56−1545/T, A=0.470, B=−646, and C=0.723 (σ=0.07) for NaCl; A=−1.638, B=0, and C=0.836 (σ=0.11) for NaClO 4 . The lower results in NaCl at higher ionic strengths are attributed to the formation of FeCl+ that has a slower rate of oxidation. The kinetic results giveβ FeCl = 1.2 ± 0.5, which is in reasonable agreement with literature data. Measurements of the effect of various ions on the rates were studied at constant ionic strength. The results were in the order HCO 3 − 〉Br−〉ClO 4 − 〉Cl−〉NO 3 − 〉SO 4 2− 〉B(OH) 4 − and were attributed to the relative strength of the interactions of Fe 2+ with these anions. The strong interactions of Fe 2+ with SO 4 2− and B(OH) 4 − were used to estimate the stability constants, logβ FeSO 4 = 1.8 ± 0.1 and logβ FeB(OH) 4 = 3.2 ± 0.1, which are in reasonable agreement with literature data.
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    Effect of ionic interactions on the oxidation of Fe(II) with H2O2 in aqueous solutions (1991)
    Springer
    Journal of solution chemistry 20 (1991), S. 1079-1092 
    Details
    ISSN: 1572-8927
    Keywords: Fe(II) ; oxidation ; H2O2 ; ionic strength ; NaCl ; NaClO4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of Fe(II) with H2O2 has been measured in NaCl and NaClO4 solutions as a function of pH, temperature T (K) and ionic strength (M, mol-L−1). The rate constants, k (M−1-sec−1), d[Fe(II)]/DT=-k[Fe(II)][2O2] at pH=6.5 have been fitted to equations of the form log k = log k0+ AI 1/2+BI+CI 1/2/T Where log k0=15.53-3425/T in water; A=−2.3, −1.35; B=0.334, 0.180; and C=391, 235, respectively, for NaCl (σ=0.09) and NaClO4 (σ =0.08). Measurements made in NaCl solutions with added anions yield rates in the order B(OH) 4 − 〉HCO 3 − 〉ClO 4 − 〉Cl−〉NO 3 − 〉SO 4 2− and are attributed to the relative strength of the interactions of Fe2+ or FeOH+ with these anions. The FeB(OH) 4 + species is more reactive while the FeCO 3 0 , FeCl+, FeNO 3 + and FeSO 4 0 species are less reactive than the FeOH+ ion pair. The general trend is similar to our earlier studies of the oxidation of Fe(II) with O2 except for B(OH) 4 − . The effect of pH on the logk was found to be a quadratic function of the concentration of H+ or OH− from pH=4 to 8. These results have been attributed to the different rate constants for Fe2+ (k0) and FeOH+ (k1) which are related to the measured k by, k=k0αFe + k1αFeOH, where αi is the molar fraction of species i. The rates increase due to the greater reactivity of FeOH+ compared to Fe2+. k0 is independent of composition and ionic strength but k1 is a function of ionic strength and composition due to the interactions of FeOH+ with various anions.
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    Preparation and characterization of bimodal porous carbons derived from a styrene-divinylbenzene copolymer (1997)
    Springer
    Adsorption 3 (1997), S. 67-79 
    Details
    ISSN: 1572-8757
    Keywords: porous carbons ; activation ; oxidation ; surface oxygen groups ; LTPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A styrene/divinylbenzene copolymer has been used as precursor for making porous carbons with bimodal pore size distributions (i.e., with both microporosity and mesoporosity). Pretreatment of the as-received copolymer by mild oxidation in air, significantly increased the carbon yield after carbonization. Reactivity studies of the polymer-based chars to CO2 clearly show the influences of some important factors such as carbonization temperature, heating rate, soak time on char reactivities. Bimodal porous carbons were prepared by carbonization of the preoxidized styrene/divinylbenzene copolymer in N2, followed by activation in CO2 at different temperatures to different levels of burnoff. The pore structures of the porous carbons produced have been characterized by various techniques such as gas adsorption and mercury porosimetry. The surfaces of the porous carbons produced, and a commercial carbon adsorbent, have been modified with HNO3 and H2O2 treatment at various conditions. Characterization of the surface oxygen functionality, both quantitatively and qualitatively, has been achieved using techniques such as Linear Temperature Programed Desorption (LTPD) and selective neutralization of bases.
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    The Influence of Catalyst Composition on the Oxidation Process of Carbonado Type Synthesized Polycrystalline Diamonds (1997)
    Springer
    Advanced performance materials 4 (1997), S. 297-304 
    Details
    ISSN: 1572-8765
    Keywords: carbonado ; diamond ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of carbonado type synthesized polycrystalline diamonds produced from graphite together with catalytic Ni-Mo alloy doped with TiB2 and BNcub was investigated. It was found that the addition of these boron compounds increases the oxidation resistance of the carbonado type synthesized polycrystalline diamonds. The oxidation mechanism acting on the carbonado type synthesized polycrystalline diamonds and the role of boron compounds in increasing the resistance to the oxygen reaction are discussed.
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    URL: http://dx.doi.org/10.1023/A:1008677105534
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    Mechanism for the formation of carbon dioxide in the catalytic oxidation of carbon monoxide and methane on silica (1992)
    Springer
    Catalysis letters 13 (1992), S. 283-288 
    Details
    ISSN: 1572-879X
    Keywords: Silica ; oxidation ; methane ; carbon monoxide ; carbon dioxide ; labelled reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of carbon monoxide to carbon dioxide is shown to be catalyzed at 850 K or above over almost all lattice oxygen atoms on the surface of silica prepared by the sol-gel method from ethyl orthosilicate under conditions which yield high selectivity to carbon dioxide in the oxidation of methane.
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    The partial oxidation of some cyclohexenes and branched chain olefins over a silver catalyst (1992)
    Springer
    Catalysis letters 16 (1992), S. 149-158 
    Details
    ISSN: 1572-879X
    Keywords: Silver ; oxidation ; cyclohexenes ; branched chain olefins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of some cyclic and branched chain olefins over a silver catalyst effective for the conversion of ethylene to ethylene oxide has been investigated in a steady state flow system. The reaction of cyclohexene produces benzene and that of both 1-methylcyclohexene and 4-methylcyclohexene yields toluene. The selectivity to aromatics exceeds 20% for fractional conversions below 0.2, but it can be improved to almost 50% by inclusion of an optimum quantity of dichloroethane in the feed. Styrene is oxidised more slowly than the cyclohexenes and only carbon dioxide and water are produced. The oxidation of 3,3-dimethyl-1-butene and 3-methyl-1-butene occurs much faster than that of the cyclic molecules and some of the corresponding epoxides are produced. The selectivity with the dimethyl-butene is 9–13% for conversions to 0.2. The methylbutene requires a higher temperature for reaction and the epoxide yield is lower. Factors influencing reactivity and product distribution are discussed.
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    Factors affecting bioleaching kinetics of sulfide ores using acidophilic micro-organisms (1999)
    Springer
    BioMetals 12 (1999), S. 1-10 
    Details
    ISSN: 1572-8773
    Keywords: acidophilic ; strain ; oxidation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Recovery of metal values from sulfide ores by use of acidophilic microorganisms is gaining importance. A number of commercial/pilot plants are setup to find out the techno-economic feasibility of the overall process. The main drawback in the process is the slow kinetics of dissolution of metal values from the sulfide ores. To make the technology e attractive the kinetics should be improved considerably. There are various factors which determine the overall kinetics such as bacterial activity and concentration, iron and sulfur oxidation, oxygen consumption, reactor design and nature of ore. A brief review has been made dealing with the above parameters
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    The molecular structures and reactivity of V2O5/TiO2/SiO2 catalysts (1992)
    Springer
    Catalysis letters 13 (1992), S. 9-19 
    Details
    ISSN: 1572-879X
    Keywords: Vanadia ; titania ; silica ; Raman ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of V2O5/TiO2/SiO2 catalysts were structurally investigated byin situ Raman spectroscopy and chemically probed by methanol oxidation in order to determine the molecular structure-reactivity relationships of the V2O5/TiO2/SiO2 catalysts. Only surface TiO x species are present on the 3% TiO2/SiO2 catalysts, and the surface TiO x species as well as bulk TiO2 (anatase) particles coexist on the 40% TiO2/SiO2 catalyst. The deposition of 1–3% vanadium oxide onto 3% TiO2/SiO2 and 4% vanadium oxide onto 40% TiO2/SiO2 forms only a surface vanadium oxide phase.In situ Raman studies reveal that the surface vanadium oxide species preferentially exist on the titania sites of the TiO2/SiO2 system. The interaction between the surface vanadia and the surface titania overlayer on SiO2 increases the methanol oxidation reactivity by two orders of magnitude relative to V2O5/SiO2. In the presence of bulk TiO2 (anatase) particles on the SiO7 support, the reactivity of the surface vanadia further increases by an order magnitude relative to the catalysts containing only surface titania, and is close to that of surface vanadia on bulk TiO2. This suggests that the surface VO x -TiO2 (bulk) interactions results in a more active site than the surface VO x -TiO x -SiO2 interactions. In addition, the V2O5/TiO2/SiO2 catalysts exhibit high selectivity towards HCHO because redox sites are predominant on the surface of these catalysts with essentially no acid site present.
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    URL: http://dx.doi.org/10.1007/BF00770942
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    High yield synthesis of propanal from methane and air (1992)
    Springer
    Catalysis letters 13 (1992), S. 341-347 
    Details
    ISSN: 1572-879X
    Keywords: Methane ; oxidation ; oxidative coupling ; hydroformylation ; propanal ; catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract High yield synthesis of propanal from methane and air can be obtained in a single pass at atmospheric pressure. Three catalytic processes are combined to give 13% yield of propanal based on total methane input. Ethene is made from the oxidative coupling reaction and carbon monoxide and hydrogen is generated from partial oxygenation of methane. These gases are combined and passed to a hydroformylation catalyst to give liquid propanal. The unreacted methane is inert in the hydroformylation stage, while oxygen deactivates the catalyst readily. The results imply that propanal can be obtained, in good yield, from methane and air provided that total oxygen conversion is achieved. The yield of propanal from the three combined processes can be substantially higher than that of ethene from the oxidative coupling reaction. Thus, higher yields of a condensible and oxygenated product are obtained.
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    Preparation of small α-iron particles from an amorphous Fe91Zr9 alloy (1989)
    Springer
    Catalysis letters 3 (1989), S. 191-195 
    Details
    ISSN: 1572-879X
    Keywords: Iron ; zirconium ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Small α-iron particles with diameter less than 10 nm and enlarged lattice constant have been obtained by low temperature oxidation and reduction of an amorphous Fe91Zr9 alloy.In-situ X-ray diffraction has been used to study the transformation of the alloy at 300 °C which is far below the crystallization temperature. Scanning electron microscopy showed that the reacted sample consisted mainly of aggregates of small iron particles. This might offer a promising method for the effective preparation of heterogeneous catalysts.
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    Selective oxidation of secondary amines over titanium silicalite molecular sieves, TS-1 and TS-2 (1996)
    Springer
    Catalysis letters 37 (1996), S. 213-216 
    Details
    ISSN: 1572-879X
    Keywords: titanium silicalites ; oxidation ; amines ; hydrogen peroxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Titanium silicalite molecular sieves, TS-1 and TS-2 having MFI and MEL structures, respectively, catalyze the oxidation of secondary amines to the corresponding hydroxylamines using hydrogen peroxide as the oxidant. Higher concentrations of H2O2 lead to further oxidation of hydroxylamine to nitrone. Diffuse reflectance spectroscopy shows the formation of a titanium peroxo complex upon addition of hydrogen peroxide to the TS-1 catalyst. The titanium peroxo complex oxidizes the substrate and reforms to a titanyl group.
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    Transient experiments on the selective oxidation of methane to formaldehyde over V2O5/SiO2 studied in the temporal-analysis-of-products reactor (1993)
    Springer
    Catalysis letters 21 (1993), S. 209-214 
    Details
    ISSN: 1572-879X
    Keywords: Methane ; formaldehyde ; oxidation ; vanadium oxide ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Methane oxidation to formaldehyde was studied over a vanadium oxide catalyst supported on silica at 630 °C using the technique known as temporal analysis of products with sequential pulsing of methane and oxygen. This work shows that methane interacts very weakly and oxygen very strongly with the catalyst surface and it is concluded that the initial activation of methane involves an adsorbed oxygen species. Methyl radicals formed in the first step subsequently extract lattice oxygen to yield formaldehyde.
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    Novel iron meso-nitrooctaethylporphine complexes for the catalytic reaction of alkanes with molecular oxygen (1994)
    Springer
    Catalysis letters 24 (1994), S. 79-83 
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    ISSN: 1572-879X
    Keywords: Metallonitroporphines ; oxidation ; isobutane ; propane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Introducing nitro groups into themeso-positions of a metalloporphyrin converts a catalytically inactive complex into a highly active catalyst for the oxidation of alkanes with molecular oxygen. The degree of nitration correlates with both the Fe(III)/Fe(II) reduction potential and the catalytic activity.
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    Catalytic oxidation of cyclohexene with molecular oxygen by polyoxometalate-intercalated hydrotalcites (1996)
    Springer
    Catalysis letters 40 (1996), S. 43-45 
    Details
    ISSN: 1572-879X
    Keywords: oxidation ; cyclohexene ; polyoxometalate-intercalated hydrotalcite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyclohexene was oxidized with molecular oxygen over transition-metal-substituted polyoxometalate-intercalated hydrotalcites to produce 2-cyclohexene-1-one and 2-cyclohexene-1-ol with high selectivity under mild reaction conditions.
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    A broad spectrum catalytic system for removal of toxic organics from water by deep oxidation using dioxygen as the oxidant (1996)
    Springer
    Catalysis letters 40 (1996), S. 95-99 
    Details
    ISSN: 1572-879X
    Keywords: palladium metal ; oxidation ; toxic organics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In water, metallic palladium was found to catalyze the deep oxidation of a wide variety of functional organics by dioxygen at 80–90°C in the presence of carbon monoxide. Several classes of organic compounds were examined: benzene, phenol and substituted phenols, aliphatic and aromatic halogenated compounds, organophosphorus, and organosulfur compounds. In every case, deep oxidation to carbon monoxide, carbon dioxide, and water occurred in high yields, resulting in up to several hundred turnovers over a 24 h period. Since the heterogeneous catalyst can be removed by simple filtration, simultaneous water purification and contaminant destruction becomes feasible. For those substrates that are insoluble in pure water, a mixture of water and perfluorobutyric acid was successfully employed as the solvent.
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    X-ray photoelectron spectroscopy of Pd/γ-alumina and Pd foil after catalytic methane oxidation (1995)
    Springer
    Catalysis letters 34 (1995), S. 31-40 
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    ISSN: 1572-879X
    Keywords: palladium ; PdO ; alumina ; methane ; oxidation ; carbon ; XPS ; ellipsometry ; structure sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Samples of palladium supported onγ-alumina and a palladium foil were used as catalysts for methane oxidation at 550° C. The samples were quenched quickly in the reaction chamber to room temperature in flowing Ar and then transferred in vacuo for XPS analysis. Structure sensitivity was manifest from an increase in PdO stability and a decrease in carbon deposition relative to Pd with increasing particle size. The results were compared with recent ellipsometric data.
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    Mo incorporation in MCM-41 type zeolite (1998)
    Springer
    Catalysis letters 52 (1998), S. 25-29 
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    ISSN: 1572-879X
    Keywords: metallosilicate ; mesoporous ; MCM-41 ; Mo-MCM-41 ; catalysis ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mo-incorporated MCM-41 has been prepared by direct hydrothermal synthesis. XRD and N2-adsorption measurements showed the characteristics of MCM-41. IR, FT-Raman and UV-VIS DR spectroscopic analyses gave the evidences for the incorporation of Mo in the framework of MCM-41. They are found to be stable and active for cyclohexanol and cyclohexane oxidation reactions with H2O2 as oxidant. Activity of this system has been compared with that of Ti-MCM-41 and molybdena impregnated on pure siliceous MCM-41.
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    Alkene selectivity enhancement in the oxidation of propane on calcium-based catalysts (1999)
    Springer
    Catalysis letters 59 (1999), S. 67-72 
    Details
    ISSN: 1572-879X
    Keywords: propane ; oxidation ; calcium-based catalysts ; tetrachloromethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of propane has been investigated in the presence and absence of tetrachloromethane (TCM) on calcium hydroxyapatite (CaHAp), Ca3(PO4)2, CaSO4 and CaO at 723 K. In the absence of TCM, the conversion of C3H8 on CaHAp was 7.7–9.2% during 6 h on-stream while that on Ca3(PO4)2, CaSO4 and CaO was 0.6, 0 and 0.2–0.4%, respectively. The principal products on all catalysts in the absence of TCM were CO and CO2 with small selectivities to C3H6 and C2H4 (both 5–6%) observed on CaHAp. Upon addition of TCM, the selectivity to C3H6 on all catalysts and the conversion of C3H8 on CaSO4 increased while, with increasing time-on-stream, the changes in the conversion and selectivity were dependent upon the nature of the catalysts. XPS and XRD analyses provide evidence for the presence of chlorine in the surface and/or bulk of three of the catalysts, suggesting that chlorinated species on the solids play a role in the selectivity enhancement, but the absence of chlorine from the sulphate demonstrates the dissimilarities of the catalysts in their abilities to sorb and decompose TCM.
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    Synergistic effects in the oxidation of methane on strontium and lead hydroxyapatites (1999)
    Springer
    Catalysis letters 57 (1999), S. 161-165 
    Details
    ISSN: 1572-879X
    Keywords: methane ; oxidation ; strontium hydroxyapatite ; lead hydroxyapatite ; tetrachloromethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of methane has been investigated on lead hydroxyapatite (PbHAp), strontium hydroxyapatite (SrHAp) and their binary mixtures at 873 K. PbHAp showed no activity for the oxidation of methane, while SrHAp produced carbon monoxide selectively at 2–4% conversion. On binary mixtures of the hydroxyapatites the conversion of methane and the selectivity to C2 compounds reached values higher than those of the separate constituents of the mixture. With tetrachloromethane in the feed stream a similar synergistic effect was observed with conversions of methane and selectivities to CH3Cl higher on the binary mixtures than those on either SrHAp or PbHAp. The strontium-containing hydroxyapatite appears to play a crucial role in the activation of methane, while the presence of the lead-containing analogue is apparently required for the minimization of undesirable processes involving methyl radicals.
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    The partial oxidation of norbornene over a silver catalyst under steady state conditions (1991)
    Springer
    Catalysis letters 9 (1991), S. 133-143 
    Details
    ISSN: 1572-879X
    Keywords: Norbornene ; oxidation ; silver ; norbornene epoxide ; 3-cyclohexene-1-carboxyaldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The continuous oxidation of norbornene (C7H10) by molecular oxygen over a silver catalyst at 500–573 K has been investigated. In contrast to that observed during the temperature programmed reaction of norbornene and oxygen adsorbed on Ag(110) no norbornene epoxide is formed. Instead benzene is the sole partial oxidation product. A stable selectivity of 20 to 25% with fractional conversions up to 0.8 at 573 K could be obtained by inclusion of 15 to 30 ppm dichloroethane in the feed. Separate experiments withexo-norbornene epoxide showed that in the absence of oxygen it was almost completely isomerised to 3-cyclohexene-1-carboxyaldehyde with production of lesser amounts of norcamphor and norbornene. With oxygen present carbon dioxide and small amounts of benzene were also produced. It is concluded that norbornene epoxide cannot be a gas phase intermediate in the production of benzene from norbornene.
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    Oxidation of acrolein on a multicomponent oxide catalyst (1992)
    Springer
    Catalysis letters 15 (1992), S. 401-404 
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    ISSN: 1572-879X
    Keywords: Acrylic acid ; oxidation ; mixed oxides ; acrolein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Catalytic oxidation of acrolein to acrylic acid has been studied and the optimum composition of the multicomponent catalyst Mo a V b Cu c Fe d O x has been found. The reaction kinetics has been measured.
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    Silicoaluminophosphate number eighteen (SAPO-18): a new microporous solid acid catalyst (1994)
    Springer
    Catalysis letters 28 (1994), S. 241-248 
    Details
    ISSN: 1572-879X
    Keywords: coke ; zeolites ; catalyst regeneration ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract SAPO-18, which has a microporous framework structure related to, but crystallographically distinct from, that of the solid acid catalyst SAPO-34, was synthesized hydrothermally from a silicoaluminophosphate gel containing N,N-diisopropylethylamine as a structuredirecting template. Although both materials have similar Si/(Si + Al + P) ratios, the content of Brønsted acid sites in SAPO-18 is considerably less than that in SAPO-34. As catalysts for methanol conversion to light olefins, SAPO-18 and SAPO-34 have closely similar initial activity and selectivity, but the lifetime of SAPO-18 is distinctly superior to that of SAPO-34.
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    Effect of fluorination of alumina support on activity of platinum catalysts for complete oxidation of benzene (1997)
    Springer
    Catalysis letters 49 (1997), S. 155-161 
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    ISSN: 1572-879X
    Keywords: fluorination ; alumina ; platinum catalysts ; oxidation ; oxidation of benzene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Platinum supported on fluorinated alumina is more active for the total oxidation of benzene than is the catalyst with the same Pt loading supported on hydrophilic unfluorinated alumina. The Pt-F/alumina catalyst contains well-dispersed small Pt particles, in contrast to Pt/alumina. The high dispersion is a consequence of a strong metal-support interaction.
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    Fischer-Tropsch synthesis over iron catalysts (1990)
    Springer
    Catalysis letters 7 (1990), S. 241-251 
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    ISSN: 1572-879X
    Keywords: Fischer-Tropsch synthesis ; iron based catalysts ; Fe ; Co ; Ru catalysts ; fixed bed reactors ; fluidized bed reactors ; sulfur poisoning ; oxidation ; coke fouling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Because of the decreased profitability of making synthetic fuels, Sasol intends expanding its production of the higher valued chemicals, in particular waxes and olefins. The advantages and disadvantages of using Fe, Co and Ru catalysts are discussed from the point of view of costs, availability, product selectivity, activity and sensitivity to poisons. The loss of activity and selectivity of iron based catalysts in both fixed and fluidized bed reactors is discussed. The main contributing factors are sulfur poisoning, oxidation and coke fouling. In fixed bed reactors sulfur poisoning and “coke” laydown deactivates the front end of the bed while hydrothermal sintering/oxidation deactivates the back end. In fluidized beds the deposition of large amounts of Boudouard carbon doesnot markedly lower the activity. The smaller catalyst particles end up consisting of small iron carbide entities embedded in a matrix of carbon. The larger catalyst particles consist of cores of inert magnetite surrounded by the carbide/carbon matrix. FT reactor development at Sasol is briefly reviewed.
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    A new process for acetic acid production by direct oxidation of ethylene (1999)
    Springer
    Catalysis surveys from Japan 3 (1999), S. 55-60 
    Details
    ISSN: 1572-8803
    Keywords: acetic acid ; oxidation ; Pd ; heteropoly acid ; ethylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new process for acetic acid production by direct oxidation of ethylene which was established and commercialized is described. The catalyst system consisting of Pd and heteropoly acid exhibits excellent activity and selectivity. The addition of Se or Te to the catalyst system is effective to suppress the formation of carbon dioxide. This new process is applicable to a plant of a wide range of size corresponding to the local demand. Because this new process produces little waste water, it is very friendly to the environment.
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    Oxidation and reduction effects of propane–oxygen on Pd–chlorine/alumina catalysts (2000)
    Springer
    Catalysis letters 64 (2000), S. 163-169 
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    ISSN: 1572-879X
    Keywords: oxidation ; reduction of palladium catalysts ; chlorine effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pd–chloride precursor salt was used to prepare Pd/Al2O3 catalysts. TPSR measurements showed three distinct reactions for the oxidation of propane on palladium surface under excess of hydrocarbon: complete oxidation, steam reforming and propane hydrogenolysis. Propane oxidation on palladium catalysts was related to the Pd2+ sites observed on Pd/Al2O3 through infrared of adsorbed carbon monoxide. In fresh catalysts reduced by H2, the IR spectra showed the linear and bridge adsorbed CO species on the Pd0 surface. After propane reaction, a new band at 2130 cm-1 related to CO adsorption on Pd2+ species was noted. Carbon monoxide species adsorbed on Pd0 were also observed in all samples after reaction. Our results suggest surface ratios of Pd0/PdO during the propane oxidation. On the other hand, time on stream conversions of the complete oxidation of propane were affected by either the water generated during the reaction or added as a reactant at 10 vol%. The water generated by the reaction helped to eliminate chlorine residues in the form of oxychloride species leading to an increasing of the activity. However, the presence of water into the reaction mixture caused a strong decreasing of the activity. The inhibition mechanism of propane oxidation in the presence of water consisted in the dissociative adsorption of water on palladium sites with the possible formation of palladium hydroxide (Pd–OH) at the surface, diminishing the number of active surface sites. Dynamic fluctuations into the reaction conditions supported the idea that a pseudo‐equilibrium adsorption–desorption of water was reached. After water removal or increasing in the reaction temperature the equilibrium was shifted to the direction of OH–Pd decomposition. This behavior suggests that the inhibitory effect of water is a reversible phenomenon, being a function of the amount of water and the reaction temperature.
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    Preparation of Polyuronic Acid from Cellulose by TEMPO-mediated Oxidation (1998)
    Springer
    Cellulose 5 (1998), S. 153-164 
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    ISSN: 1572-882X
    Keywords: cellulose ; TEMPO ; polyglucuronic acid ; degree of polymerization ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Various cellulose samples were oxidized by 2,2,6,6,-tetramethylpipelidine-1-oxyl radical (TEMPO)-NaBr-NaClO systems, and the effects of oxidation conditions on chemical structures and degrees of polymerization of the products obtained were studied. In the case of regenerated and mercerized celluloses, almost all C6 primary alcohol groups were selectively oxidized to carboxyl groups, and water-soluble polyglucuronic acid (cellouronic acid) sodium salts were obtained almost quantitatively; the degrees of polymerization were influenced greatly by the amount of TEMPO added, and the oxidation time and temperatures. Cellouronic acids prepared from mercerized linter and kraft pulps had size exclusion chromatograms with two separate peaks due to higher and lower molecular weight fractions. On the other hand, only small amounts of carboxyl groups were introduced into native cellulose samples. Since polyglucuronic acids prepared from cellulose by the TEMPO–NaBr– NaClO systems regularly consist of the glucuronic acid repeating unit, differing from the conventional water-soluble cellulose derivatives, they may open new fields of cellulose utilization.
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    Preparation of metallosilicates with zeolite structure by atom-planting method (1998)
    Springer
    Catalysis surveys from Japan 2 (1998), S. 121-132 
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    ISSN: 1572-8803
    Keywords: zeolite ; metallosilicate ; atom-planting ; modification ; catalysis ; acidity ; shape-selective alkylation ; oxidation ; hydrogen peroxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Atom-planting, a useful method to prepare some metallosilicates having zeolitic structure, was proposed. By treatment of highly siliceous zeolite with metal chloride vapor at selected temperature, metal cation could be introduced into the defect sites (hydroxyl nests) of zeolite framework. By the atom-planting method, some metallosilicates which are difficult to be synthesized by hydrothermal synthesis could be prepared. The vapor phase shape-selective alkylation of ethylbenzene with ethanol, and the liquid phase selective oxidation with hydrogen peroxide on the metallosilicates prepared by atom-planting method were reviewed.
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    Steady-state conversion of methane to C4+ aliphatic products in high yields using an integrated recycle reactor system (2000)
    Springer
    Catalysis letters 66 (2000), S. 1-4 
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    ISSN: 1572-879X
    Keywords: methane ; oxidation ; aliphatic hydrocarbons ; zeolite ; recycle reactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Conversion of methane in high yields to C4+ nonaromatic hydrocarbons was demonstrated in a recycle system. The principal components of the recycle system included an oxidative coupling reactor with a Mn/Na2WO4/SiO2 catalyst at 800°C for conversion of methane to ethylene, and a reactor with an H-ZSM-5 zeolite at 275°C for subsequent conversion of ethylene to higher hydrocarbons. Total yields of C4+ products were in the range of 60–80%, and yields of C4+ nonaromatic hydrocarbons were in the range of 50–60%.
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    Benzylacetate synthesis by oxyacetoxylation of toluene on Pd–Bi binary catalyst (2000)
    Springer
    Topics in catalysis 13 (2000), S. 243-248 
    Details
    ISSN: 1572-9028
    Keywords: oxidation ; oxyacetoxylation ; alloy ; palladium ; bismuth ; benzylacetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Benzylacetate synthesis from toluene, acetic acid and oxygen on Pd–Bi binary catalyst was studied in the liquid phase. By incorporation of Bi with Pd, both the activity and selectivity were improved. Especially better stability was obtained with the catalyst having Pd/Bi = 3. Deactivation of the catalyst was investigated in detail by XRD, XPS, TEM, elemental analysis, EPMA and so on. Comparing the used catalyst with the fresh one, it was indicated that the main cause of deactivation was the dissolution of Pd into the reaction mixture from the most outer surface of the catalyst. By adopting proper reaction conditions to prevent the Pd dissolution, the catalyst having Pd/Bi = 3 was suggested to be used as an industrial catalyst.
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    The chemisorption of nitric oxide and the oxidation of ammonia at Cu(110) surfaces: a X-ray photoelectron spectroscopy (XPS) and scanning tunnelling microscopy (STM) study (2000)
    Springer
    Topics in catalysis 14 (2000), S. 101-109 
    Details
    ISSN: 1572-9028
    Keywords: nitric oxide ; ammonia ; oxidation ; X-ray photoelectron spectroscopy ; scanning tunnelling microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dissociative chemisorption of nitric oxide at Cu(110) has been shown to result in rapid ordering of oxygen adatoms as (2×1)O chains oriented along the 〈100〉 direction while the associated nitrogen adatoms are mainly disordered at 295 K. Surface diffusion of the N adatoms, following bond cleavage, is activated and ordering of the (2×3)N strings occurs on heating to 430 K. A number of distinct reaction pathways have been isolated during the oxidation of ammonia resulting in the formation of either chemisorbed imide or nitrogen adatoms. The latter depending on temperature, may exhibit a (2×3)N, a (3×3)N or both structures may exist simultaneously. The concentration of nitrogen in the complete (2×3)N structure has been determined to be 6.6×1014 cm-2, with only a 25% decrease in nitrogen concentration leading to the transformation to the (3×3)N structure. The oxygen atoms at a Cu(110)–O overlayer, and present at the ends of the (2×1) strings terminating in steps, show specific reactivity when exposed to ammonia at 375 K resulting in the “decoration” of the steps with imide species while the oxygens within the (2×1) strings remain unreactive.
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    Direct liquid‐phase side‐chain oxidation of alkylbenzenes over 2 catalyst (2000)
    Springer
    Catalysis letters 65 (2000), S. 181-183 
    Details
    ISSN: 1572-879X
    Keywords: alkylbenzene ; toluene ; ethylbenzene ; xylene ; mesitylene ; p‐ethyltoluene ; cumene ; p‐cymene ; oxidation ; palladium ; 1,10‐phenanthroline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Only the side‐chain oxidation of alkylbenzenes (R–C6H3–R′–R″ R=H, Me, Et, Pri R′=H, Me; and R″=H, Me) by oxygen (35–50 atm, 200)C° is promoted in the presence of [Pd(phen)(OAc)2].
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    Catalysis by porous heteropoly compounds (1998)
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    Catalysis surveys from Japan 2 (1998), S. 31-44 
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    ISSN: 1572-8803
    Keywords: porous heteropoly compounds ; Pt-promoted heteropoly compounds ; shape selectivity ; water-tolerant catalyst ; hydrogenation ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper attempts to review recent works on catalysis of porous heteropoly compounds. The salts of heteropolyacids having Keggin structure with large cations like Cs+ are porous materials. For Cs hydrogen salts, the pore width can be controlled by the Cs content. Cs2.5H0.5PW12O40 has the largest amount of protons on the surface among the acidic Cs salts and possesses pores with bimodal distribution in the micro and meso region. Efficient performances were demonstrated for acid-catalyzed reactions such as skeletal isomerization of η-butane in solid-gas system, alkylation and acylation in solid-liquid system, and hydrolysis and hydration in solid-water system. A microporous salt, Cs2.2H0.8PW12O40, exhibited reactant shape selectivity towards direct decomposition of esters. Furthermore, an ultramicroporous bifunctional catalyst, Pt–Cs2.1H0.9PW12O40 of which the pore width is around 5 Å, exhibits reactant shape selectivity for hydrogenation of alkenes and oxidation of hydrocarbons, and product shape selectivity for skeletal isomerization of η-butane.
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    The structural basis for the enhanced oxygenase activity of copper acetate dimers encapsulated in zeolites (2000)
    Springer
    Topics in catalysis 11-12 (2000), S. 359-367 
    Details
    ISSN: 1572-9028
    Keywords: zeozyme ; encapsulated complexes ; copper acetate ; copper dimers ; enzyme mimic ; EPR of copper ; tyrosinase ; oxidation ; oxygenase ; tyrosine oxidation ; phenol oxidation ; hydroxylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxygenase mimicking activity of copper acetate dimers in the regioselective ortho-hydroxylation of L-tyrosine to L-dopa is enhanced on encapsulation in zeolite Y. The structure and magnetic properties of the catalytic active site were characterized by EPR spectroscopy. The spectra of this “zeozyme” reveal the presence of (1) copper acetate dimers in the supercages and (2) isolated Cu(II) ions in the sodalite cages of the zeolite. There are significant differences in the EPR spectra of the “neat” and encapsulated complexes: on encapsulation in zeolite, the Cu–Cu exchange coupling constant, −, increases to 310 from 259 cm−1 for the “neat” complex (i.e., by about 19.7%). Simultaneously the Cu–Cu separation in the dimer, estimated indirectly from the exchange coupling constant, shortens to 2.40 Å in the encapsulated state from 2.64 Å in the “neat” complex. There is, hence, a relatively greater overlap of the metal orbitals of the dimer copper atoms inside the restricted confines of the zeolite cages. The consequent, enhanced, trans axial lability of the phenolate and dioxygen ligands promotes the catalytic oxygenase activity of copper acetate dimers on encapsulation in zeolites. A causal relationship between changes in the structural features of an active site on encapsulation in the zeolite and the corresponding catalytic activity has, thus, been established.
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    On the possible role of montmorillonites in prebiotic peptide formation (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 1033-1039 
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    ISSN: 1434-4475
    Keywords: Prebiotic peptide formation ; Evolution ; Clay catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Fähigkeit von Tonmineralien der Montmorillonitklasse zur Katalyse von Peptidbildungsreaktionen aus Aminosäuren in wäßriger Lösung wurde am Beispiel von Glyzin und Kupfer sowie Kalzium und Morillonit untersucht. Experimente mit Verdampfungszyklen haben gezeigt, daß kleinere Mengen von Di- und Tripeptiden aus der Aminosäure gebildet werden. Die weitere Polymerisation von Dipeptiden hingegen scheint wesentlich leichter in diesem Reaktionssystem zu verlaufen als der Anfangsschritt der Bildung des Dipeptides. Eine mögliche Rolle von Tonmineralien in der präbiotischen Peptidevolution kann daher in der Verlängerung von Peptidketten gesehen werden. Kupferionen in der Tonmatrix zeigen keinerlei Vorteile gegenüber den üblichen Kalziumionen, die in natürlichem Montmorillonit vorkommen.
    Notes: Summary The ability of montmorillonite clay minerals for catalyzing peptide formation from amino acids in aqueous solution has been investigated using glycine and Cu2+ and Ca2+ containing montmorillonites as reaction systems. Evaporation cycle experiments showed that minor amounts of di- and tripeptide are formed from the amino acid. Further polymerization of dipeptide, however, seems to be more favoured by this reaction system than the initial step of dipeptide formation, and a possible role of clays in prebiotic peptide evolution could be seen therefore in the prolongation of peptide chains. Cu2+ ions in the clay matrix did not show any advantage over the usual Ca2+ ions embedded in natural montmorillonite.
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    Purification and characterization of an ADP-dependent phosphofructokinase from Thermococcus zilligii (1999)
    Springer
    Extremophiles 3 (1999), S. 121-129 
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    ISSN: 1433-4909
    Keywords: Key words Thermococcus ; Pyrococcus ; Thermophilic ; Phosphofructokinase ; Evolution ; ADP ; Glycolysis ; ATP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ADP-dependent phosphofructokinase (PFK) from Thermococcus zilligii has been purified 950 fold; it had a specific activity of 190 U mg−1. The enzyme required Mg2+ ions for optimal activity and was specific for ADP. The forward reaction kinetics were hyperbolic for both cosubstrates (pH optimum of 6.4), and the apparent K m values for ADP and fructose-6-phosphate were 0.6 mM (apparent V max of 243 U mg−1) and 1.47 mM (apparent V max of 197 U mg−1), respectively. Significantly, the enzyme is indicated to be nonallosteric but was slightly activated by some monovalent cations including Na+ and K+. The protein had a subunit size of 42.2 kDa and an estimated native molecular weight of 66 kDa (gel filtration). Maximal reaction rates for the reverse reaction were attained at pH 7.5–8.0, and the apparent K m values for fructose-1,6-bisphosphate and AMP were 0.56 mM (apparent V max of 2.9 U mg−1) and 12.5 mM, respectively. The biochemical characteristics of this unique ADP-dependent enzymatic activity are compared to ATP and pyrophosphate-dependent phosphofructokinases.
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    Isolation of a chymotrypsinogen B-like enzyme from the archaeon Natronomonas pharaonis and other halobacteria (1999)
    Springer
    Extremophiles 3 (1999), S. 153-161 
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    ISSN: 1433-4909
    Keywords: Key wordsNatronomonas pharaonis ; Natronobacteria ; Archaea ; Serine protease ; Chymotrypsinogen ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A protease of a molecular mass of approximately 30 kDa was isolated and purified from the haloalkaliphilic archaeon Natronomonas (formerly Natronobacterium) pharaonis. The enzyme hydrolyzed synthetic peptides, preferentially at the carboxyl terminus of phenylalanine or leucine, as well as large proteins. Hydrolysis occurred over the range of pH from 6 to 12, with an optimum at pH 10. The temperature optimum was 61°C. The enzyme was nearly equally active over the range of salt concentration from 0.5 to 4 M (NaCl or KCl). A strong cross-reaction with a polyclonal antiserum against human chymotrypsin was observed. Enzymatic activity was inhibited by typical serine protease inhibitors. There was significant homology between N-terminal and internal sequences from autolytic fragments and the sequence of bovine chymotrypsinogen B; the overall amino acid composition was similar to that of vertebrate chymotrypsinogens. Evidence for a zymogen-like processing of the protease was obtained. Cell extracts from other halobacteria exhibited similar proteolytic activity and immunoreactivity. The data suggested a widespread distribution of a chymotrypsinogen B-like protease among halo- and haloalkaliphilic Archaea.
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    Fluctuating rates of evolution (1985)
    Springer
    Cellular and molecular life sciences 41 (1985), S. 1080-1082 
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    ISSN: 1420-9071
    Keywords: Evolution ; evolutionary rate ; stasis ; brain ; encephalization ; body size ; fitness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Constant evolutionary rates are possible only in verylarge populations, where natural selection does not exhaust varition because mutation supplies fresh variability. In a small population where a small number of genes influence an integrated system like brain and body size which have an allometric relationship, variation is removed rapidly under natural selection, This occurs even when the final fitness of the population is not optimal.
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    Serological and genetical studies on the evolution of substrate specificity of flavone glycosyltransferase genes inSilene (1987)
    Springer
    Cellular and molecular life sciences 43 (1987), S. 202-205 
    Details
    ISSN: 1420-9071
    Keywords: Evolution ; substrate specificity ; serological homologies ; flavone biosynthesis ; Silene ; glycosyltransferases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The variation in flavone glycosylation patterns inSilene is the result of the expression of six genetic loci, which control either the presence of allozymes differing in substrate specificity or isozymes regulated differently during development. Serological studies showed that at least three of these six loci are evolutionarily related. The genetic mechanisms leading to these complicated variation patterns and the role of this polymorphism for the plant in its interaction with the environment are discussed.
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    Inference of ground surface temperature history from subsurface temperature data: Interpreting ensembles of borehole logs (1996)
    Springer
    Pure and applied geophysics 147 (1996), S. 537-550 
    Details
    ISSN: 1420-9136
    Keywords: Borehole temperature ; climate change ; inversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Ground surface temperature histories (GSTHs) inferred from borehole temperaturedepth (T-z) data are often degraded, to a various extent, by random or systematic noise in theT-z data and in the measurements of thermophysical properties of the earth. To minimize the effects of noise, and hence improve the fidelity of the inferred GSTH, a plausible approach is to perform a simultaneous inversion, of theT-z logs in a region, or alternatively, to invert the individualT-z logs and then average the resulting GSTHs. Averaging and simultaneous inversion are conceptually different: whereas an averaging can always be peformed, a simultaneous inversion is predicated on the assumption of a common transient component of the GSTH in all theT-z logs. In this work we examine and compare the two approaches, using a time domain inverse formulation based on the method of least squares. We consider a set of scenarios: (a) multipleT-z logs from a single borehole, (b) multiple boreholes from a single site, (c) multiple boreholes in similar climatological settings, and (d) multiple boreholes in different climatological settings. We show that for (a), (b) and (c), averaging and simultaneous inversion yield nearly identical results. For boreholes in different settings, the assumption of a common transient GSTH may be invalid and averaging and simultaneous inversion give divergent results.
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    The effect of oxide structure and cation reduction potential of vanadates on the selective oxidative dehydrogenation of butane and propane (1992)
    Springer
    Catalysis letters 12 (1992), S. 45-50 
    Details
    ISSN: 1572-879X
    Keywords: Propane ; butane ; alkane ; oxidation ; dehydrogenation ; vanadates ; cation reduction potential ; oxide structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidative dehydrogenation of butane over a series of orthovanadates of cations of different reduction potentials showed a correlation that the selectivity for dehydrogenation decreased with increasing ease of reduction of the cation. The highest selectivity was observed on Mg orthovanadate. Mg pyrovanadate was nonselective for butane oxidation, but was as selective as Mg orthovanadate in propane oxidation. These results were interpreted by the different structures of the two Mg vanadates.
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    The ozone sensitized oxidative conversion of methane to methanol and ethane to ethanol (1992)
    Springer
    Catalysis letters 16 (1992), S. 217-221 
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    ISSN: 1572-879X
    Keywords: Methane ; ethane ; methanol ; ethanol ; ozone ; oxygen atom ; oxidation ; sensitization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction of O2, O3, and CH4 or C2H6 of 7.76, 0.24 and 92% of the hydrocarbon respectively (residence time of 8.8 min) at 1 atm, and 400 °C for CH4 and 300 °C for C2H6 gave CO, CO2, H2O, CH2O and CH3OH from CH4 and in addition CH4, C2H4, CH3CHO and C2H5OH from C2H6. No reaction occurred when O3 was absent indicating that the partial oxidation was sensitized (initiated) by the oxygen atoms formed by the decomposition of ozone.
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    The influence of sulfur dioxide on propane oxidation activity over supported platinum and palladium (1994)
    Springer
    Catalysis letters 30 (1994), S. 41-51 
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    ISSN: 1572-879X
    Keywords: propane ; oxidation ; platinum ; palladium ; sulfur dioxide ; alumina ; zirconia ; activity ; acidity ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Earlier studies have shown that sulfur dioxide and metal-support interaction can strongly influence propane oxidation over platinum. In particular, oxidation activity is enhanced when platinum is supported on sulfated γ-alumina or zirconia compared to γ-alumina. Therefore, it is of interest to compare the performance of palladium under the same experimental conditions. Four model catalysts were examined: Pt/γ-alumina, Pt/zirconia, Pd/γ-alumina and Pd/zirconia. The metal loading was kept at or below 0.05 wt% to emphasize changes in activity attributable to metal-support interaction. Reaction rates were measured with and without sulfur dioxide. Surface sulfation was analyzed by measuring acid strength and evaluating spectra obtained by Fourier-transform infrared spectroscopy. In contrast to platinum, sulfation does not promote propane oxidation on Pd/γ-alumina, and Pd/zirconia is less active than Pd/γ-alumina.
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    Multiple steady-states for the oxidation of aqueous ethanol with oxygen on a carbon supported platinum catalyst (1994)
    Springer
    Catalysis letters 30 (1994), S. 269-277 
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    ISSN: 1572-879X
    Keywords: aqueous ethanol ; multiple steady-state ; oxidation ; platinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The selective oxidation of aqueous ethanol by dioxygen over a platinum on carbon catalyst was investigated in a three-phase continuously stirred tank reactor at a total pressure of 600 kPa, a temperature of 323 K, a pH of 8.4, and a catalyst concentration of 2.3 kg m−3. Multiple steady-states were obtained by systematic changes in the start-up procedure and variation of the feed concentration of ethanol and partial oxygen pressure in the reactor. The ethanol feed concentration was varied from 100 to 2500 mol m−3 and the partial oxygen pressure from 8 to 120 kPa. On the time scale of the experiments, i.e. 21 ks, two steady-states of the net disappearance rate of ethanol are observed in the ethanol feed concentration range from 500 to 2500 mol m−3 at a partial oxygen pressure of 58 kPa and in the range of partial pressure of oxygen from 8 to 120 kPa at an ethanol feed concentration of 500 mol m−3. Three steady-states are observed in the feed ethanol concentration range from 200 to 400 mol m−3 and a partial oxygen pressure of 58 kPa.
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    Photocatalytic oxidation of substituted toluenes with irradiated TiO2 semiconductor. Effect of zeolite (1995)
    Springer
    Catalysis letters 33 (1995), S. 395-400 
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    ISSN: 1572-879X
    Keywords: TiO2 ; heterogeneous photocatalysis ; oxidation ; substituted toluenes ; zeolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Photocatalytic oxidation of substituted toluenes was investigated on irradiated TiO2 and TiO2 combined with HY15 and HY20 zeolites. In all cases the oxidation occurred in the first step exclusively on either one substituent or the other, but never on both simultaneously. In the presence of a zeolite, photooxidation conversion was higher than that obtained without zeolite.
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    Study of the deactivation mechanism of Al2O3-supported cobalt Fischer-Tropsch catalysts (1995)
    Springer
    Catalysis letters 34 (1995), S. 269-284 
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    ISSN: 1572-879X
    Keywords: Fischer-Tropsch synthesis ; cobalt catalysts ; deactivation ; oxidation ; reduction ; promoters ; rhenium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of water on alumina-supported cobalt catalysts has been studied. The deactivation of supported Co catalysts was studied in a fixed-bed reactor using synthesis gas feeds containing different concentrations of water vapour. Supporting model studies were carried out using H2O/H2 feeds in conjunction with XPS and gravimetry. Rapid deactivation occurs on Re-promoted CO/Al2O3 catalysts when H2/CO/H2O feeds are used, whereas unpromoted CO/Al2O3 shows more stable activity. The results from the gravimetric studies suggest that only a small fraction of the bulk cobalt metal initially present reoxidizes to cobalt oxide during reaction. However, the XPS results indicate significant reoxidation of surface cobalt atoms or highly dispersed cobalt phases, which is likely to be the cause of the observed deactivation. Rhenium is shown to have a marked effect on the extent of reoxidation of alumina-supported cobalt catalysts.
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    Oxidative dehydrogenation of ethane over La1−xSrxFeO3−δ perovskite oxides (1996)
    Springer
    Catalysis letters 38 (1996), S. 189-195 
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    ISSN: 1572-879X
    Keywords: perovskite ; La1−xSrxFeO3−δ ; dehydrogenation ; oxidation ; ethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Catalysts of the composition La1−xSrxFeO3−δ, 0⩽x ⩽1, have been tested for the oxidative dehydrogenation of ethane in the temperature range 300–800°C. The catalyst is active above 400°C, giving a maximum yield of 37% ethylene at 650°C. Above 650°C, synthesis gas was formed together with methane, suggesting that the reforming reaction and thermal cracking of ethane took place. The catalytic data are compared to conductivity measurements on the same material, and a good correlation between the activity and p-type conductivity has been found. In the phase diagram for the system LaFeO3-SrFeO3−δ, a phase separation to two types of (La, Sr)FeO3−δ perovskites was observed in the La/Sr binary composition in the temperature range below 800°C. The phase separation can elucidate the dependency of the catalytic activity on its p-type conductivity.
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    Inhibition of CO oxidation on hydroxyapatite by tetrachloromethane (1996)
    Springer
    Catalysis letters 39 (1996), S. 205-208 
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    ISSN: 1572-879X
    Keywords: oxidation ; hydroxyapatite ; carbon monoxide ; inhibition ; tetrachloromethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The introduction of tetrachloromethane (TCM) into the feedstream of CO and O2 inhibits the formation of CO2 on hydroxyapatite. TCM interacts with the surface of hydroxyapatite to form its chlorinated analogue, chlorapatite, which suppresses the oxidation of CO to CO2. Thus, in the oxidative coupling of methane the beneficial effects of the addition of TCM to the feedstream result, at least in part, from the suppression of the further oxidation of CO.
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    Oxidation of Cl-modified Ag(111) under UHV conditions and ethylene adsorption on the oxidized surface (1994)
    Springer
    Catalysis letters 26 (1994), S. 109-121 
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    ISSN: 1572-879X
    Keywords: Cl-modified Ag(111) ; oxidation ; phonons ; ethylene adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Oxidation of Cl-modified Ag(111) under UHV conditions was investigated using AES, ISS and HREELS. The results showed that Cl-modified Ag(111) can be easily oxidized at 550 K by 1 × 10−6 mbar oxygen which was also heated to 550 K. With HREELS two fundamental vibrations at 600 and 1000 cm−1 were detected for silver oxide and the multiple losses and combination excitations as well. Ethylene adsorption on the oxide was analyzed by HREELS. Surface hydroxyl species was formed at 230 K and stable to above 300 K, which is attributed to silver oxide. Ethylidyne was suggested to form concurrently with hydroxyl species.
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    Pyrene oxidation as a model reaction for characterizing the mechanism of coke oxidation on Y zeolites (1994)
    Springer
    Catalysis letters 28 (1994), S. 53-59 
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    ISSN: 1572-879X
    Keywords: coke ; zeolites ; catalyst regeneration ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The same effect of temperature on the production of CO, CO2 and H2O was found during oxidative treatment of HY zeolites either impregnated with pyrene or coked. Therefore, pyrene oxidation can be used to specify the mechanism of coke oxidation. Three types of reactions can be distinguished: (a) condensation of polyaromatic molecules, (b) oxidation of polyaromatics into aldehydes, ketones, acids and anhydrides and (c) decarbonylation or decarboxylation of oxygenated compounds, all these reactions involving protonic sites.
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    Platinum deactivation: in situ EXAFS during aqueous alcohol oxidation reaction (1998)
    Springer
    Catalysis letters 55 (1998), S. 141-145 
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    ISSN: 1572-879X
    Keywords: platinum ; EXAFS ; catalysis ; catalyst deactivation ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract With a new set‐up for in situ EXAFS spectroscopy the state of a carbon‐supported platinum catalyst during aqueous alcohol oxidation has been observed. The catalyst deactivation during platinum‐catalysed cyclohexanol oxidation is caused by platinum surface oxide formation. The detected Pt–O co‐ordination at 2.10 Å during exposure to nitrogen‐saturated cyclohexanol solution is different from what is observed for the pure oxidised platinum surface (2.06 Å).
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    Insights into surface reactivity: formic acid oxidation on Cu(110) studied using STM and a molecular beam reactor (1998)
    Springer
    Catalysis letters 56 (1998), S. 77-83 
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    ISSN: 1572-879X
    Keywords: catalysis ; combustion ; oxidation ; formic acid ; STM ; molecular beams ; surface diffusion ; surface reactivity ; active sites ; reconstruction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using a combination of STM and molecular beam reactor data we summarise some important features of a model reaction (formic acid oxidation on Cu(110)) which is of general significance to surface reactivity and to catalysis. Three such features are highlighted here. The first concerns the role of weakly held species (possibly physisorbed) in surface reactions. These species, although of very short lifetime on the surface, can, nevertheless, diffuse over long distances to “find” a sparse distribution of active sites. Thus a very low coverage of oxygen on the surface of Cu(110) increases the sticking probability of all the formic acid molecules which strike the surface to high value (0.82), even though the clean surface is relatively unreactive. The important concept here is the “diffusion circle” or “collection zone” which represents the area of surface visited by the molecule in its short sojourn in the weakly held state. The second theme concerns the concept of the “flexible surface”. We show that the involvement of surface atoms in reactions directs the structure and reactivity for a particular reaction. For formic acid oxidation the liberation of Cu atoms during the removal of oxygen as water leads to gross restructuring of the surface and can lead to “compression” of one reactant (the oxygen in this case) into a lower area, higher local coverage, unreactive state (the c(6×2) oxygen structure). Thirdly, and finally, it is proposed that, for many surface reactions, the surface acts in an analogous way to a solvent, supporting a “dissolved” (highly mobile and fluxional) phase of intermediates at low coverage, which crystallise out above a critical coverage (the 2D “solubility limit”).
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    A study of “superacidic” MoO3/ZrO2 catalysts for methane oxidation (1999)
    Springer
    Catalysis letters 57 (1999), S. 109-113 
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    ISSN: 1572-879X
    Keywords: superacid ; zirconia ; molybdenum oxide ; methane ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of zirconia-supported molybdenum oxide catalysts with different molybdenum loadings prepared using conditions reported to generate “superacidity” have been evaluated for their performance as catalysts for methane oxidation. A marked dependence of Mo content on activity has been observed, with the most active material being that with intermediate molybdenum content. 5 wt% MoO3/ZrO2 compares favourably with ZrxCe1-xO2 for methane combustion. The presence of MoO3 is observed to stabilise the tetragonal polymorph of ZrO2 and, as Mo content is increased, dispersed MoO3 crystallites are formed as evidenced by Raman spectroscopy. Temperature-programmed reduction studies evidence differences in the reduction behaviour of the materials as a function of loading. The results indicate that molybdenum oxide supported on monoclinic zirconia gives rise to the most active catalyst. It is tentatively suggested that the formation of a MoO3 monolayer during reaction may be of importance.
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    Partial oxidation of methane to synthesis gas (1990)
    Springer
    Catalysis letters 6 (1990), S. 181-186 
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    ISSN: 1572-879X
    Keywords: Metals for catalysis “syngas” ; oxidation ; nickel ; platinum group metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Partial oxidation of methane to synthesis gas has been carried out over a number of transition metal catalysts under a range of conditions. It is found that the metals Ni, Ru, Rh, Pd, Ir and Pt, either supported on alumina or present in mixed metal oxide precursors, will bring the system to equilibrium. The yield of CO and H2 improves with increasing temperature in the range 650–1050 K, and decreases with increasing pressure between 1 and 20 atm. An excellent yield (∼92%) is obtained with a 4∶2∶1 N2∶CH4∶O2 ratio at 1050 K and atmospheric pressure, with a space velocity of 4×104 hour−1.
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    Formation of a liquid film of AgNO3 on a silver surface (2000)
    Springer
    Catalysis letters 64 (2000), S. 113-118 
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    ISSN: 1572-879X
    Keywords: X‐ray photoelectron spectroscopy (XPS) ; scanning electron microscopy (SEM) ; silver ; oxidation ; surface chemical reaction ; NO ; NO x
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The behavior of a AgNO3/Ag2O/Ag “sandwich” upon heating in vacuum was studied by in situ X‐ray photoelectron spectroscopy (XPS) and ex situ scanning electron microscopy (SEM). The AgNO3/Ag2O/Ag “sandwich” was prepared by exposure of a silver foil to a NO : O2 mixture. The upper layer of the “sandwich” consists of AgNO3 crystals of a mean size between 0.1 and 0.4 μm. Heating at 550 K in vacuum results in melting of the AgNO3 crystals. A liquid film of AgNO3, readily wetting the silver, covers the surface. Cooling below the melting point of AgNO3 leads to the agglomeration of silver nitrate to long islands with a size reaching a few tens of micrometers (μm). The possible effects of AgNO3 liquid‐phase formation on surface processes are discussed.
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    Effect of the catalyst supports on the removal of perchloroethylene (PCE) over chromium oxide catalysts (2000)
    Springer
    Catalysis letters 64 (2000), S. 201-207 
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    ISSN: 1572-879X
    Keywords: chlorinated hydrocarbons ; chromia ; titania ; alumina ; CVOCs ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of perchloroethylene (PCE) was investigated over chromium oxide catalysts supported on TiO2, Al2O3, SiO2, SiO2–Al2O3 and activated carbon. The phase of chromium oxide on the catalyst surface is critical for the oxidation of PCE. The catalytic activity of PCE removal enhances as the formation of Cr(VI) species on the catalyst surface increases. The surface area and the type of the catalyst supports were also essential for high performance in the PCE oxidation. In addition, the structure of Cr(VI) on the catalyst surface also plays an important role for the decomposition of PCE. The polymerized Cr(VI) mainly formed by the interaction of metals with the support is the active reaction site for the present reaction system. CrOx/TiO2 reveals the strongest PCE removal activity among the catalysts examined in the present study.
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    Effects of SO2 on the alkane activity of three-way catalysts (1991)
    Springer
    Catalysis letters 11 (1991), S. 183-190 
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    ISSN: 1572-879X
    Keywords: Three-way catalysts ; sulphur dioxide ; poisoning ; promotion ; oxidation ; steam reforming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Over current Pt-Rh/CeO2-Al2O3 catalysts, the conversion of alkanes occurs by two principal mechanisms: direct oxidation (HC + O2) and steam reforming (HC+H2O). Sulphur dioxide can influence both these mechanisms. Direct oxidation, which predominates when the exhaust-gas is fuel-lean, ispromoted by the adsorption of SOx species by the support. Under fuel-rich atmospheres, the presence of SO2 severelyinhibits steam reforming. The poisoning is associated with the formation of S2− on the platinum and of SO 4 2− on the support, but there is no indication of S-species being retained by the rhodium. It is proposed that each of the two mechanisms is sensitive to a different type of interaction at the metal-support interface. Direct oxidation is enhanced by the transfer of electrons from the precious metal to the support; steam reforming occurs at interfacial sites, which can be blocked by adsorbed SOx species.
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    Oxidation of methanol at copper surfaces (1996)
    Springer
    Catalysis letters 37 (1996), S. 79-87 
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    ISSN: 1572-879X
    Keywords: methanol ; oxidation ; copper ; electron spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The role of preadsorbed oxygen present at Cu(111), Cu(110) and polycrystalline surfaces in the oxidation of methanol has been investigated by X-ray and electron energy loss spectroscopies. In addition to the well established formation of methoxy species and its subsequent decomposition and desorption as formaldehyde, a second reaction pathway to surface formate is present. The latter is temperature dependent being undetectable at 260 K at a polycrystalline surface but occurs at a significant rate at 295 K and above. The limitations of experimental data for methanol oxidation by temperature programmed desorption and molecular beam techniques are discussed.
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    Synergistic effects during CO oxidation over mixed oxides. Study of (Fe2O3+SnO2) and (Mn2O3+SnO2) systems (1996)
    Springer
    Catalysis letters 37 (1996), S. 181-185 
    Details
    ISSN: 1572-879X
    Keywords: synergistic effect ; carbon monoxide ; oxidation ; mixed oxides ; iron oxide ; tin oxide ; manganese oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Based on the comparative evaluation of the catalytic activity of Fe2O3, Mn2O3 and SnO2 and their mixed oxides (Fe2O3+SnO2) and (Mn2O3+SnO2), it is shown that the system (Mn2O3+SnO2) shows strong synergistic effects during CO oxidation reaction. Such effects are not observed for the analogous system (Fe2O3+SnO2). Based on the calcination and reduction behaviour of these two mixed oxide systems and the redox potentials of the involved cations, the possible reasons for the observance of synergistic effects for the (Mn2O3+SnO2) system are discussed.
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    Non-uniform surface kinetics with two types of sites: the case of ethanol oxidation on molybdenum oxide (1996)
    Springer
    Catalysis letters 39 (1996), S. 67-71 
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    ISSN: 1572-879X
    Keywords: non-uniform surface ; kinetics ; ethanol ; oxidation ; molybdenum oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Temkin's theory of rates of catalytic reactions on non-uniform surfaces is extended to the MoO3-catalyzed oxidation of ethanol to acetaldehyde. Two types of sites are assumed to be present, an oxygen atom site that can be modeled with uniform properties and a metal atom site characterized by non-uniform properties both for ethanol chemisorption to an ethoxide intermediate and the conversion of this intermediate to acetaldehyde. The rate-limiting step is the cleavage of a C-H bond in the absorbed ethoxide intermediate. Non-uniform surface kinetics leads to a kinetic rate expression of the form $$v = kP_{C_2 H_5 OH}^{1 - m} P_{O_2 }^{(1 - m)/4} P_{H_2 O}^{ - (1 - m)/2} $$ . Such a rate expression, withm=0.14, is shown to provide a good fit to kinetic data for the selective oxidation of ethanol on a silica supported molybdenum oxide catalyst.
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    Kinetics of the gas-solid heterogeneous photocatalytic oxidation of trichloroethylene by near UV illuminated titanium dioxide (1990)
    Springer
    Catalysis letters 4 (1990), S. 345-354 
    Details
    ISSN: 1572-879X
    Keywords: Ultraviolet heterogeneous photocatalysis ; oxidation ; trichloroethylene ; titania ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Kinetics of the gas/solid heterogeneous photocatalytic oxidation of dilute trichloroethylene (TCE) vapors by ultraviolet-illuminated titanium dioxide have been determined using a fixed-bed dynamic photoreactor. Reaction rate dependences on inlet TCE, oxygen and water vapor concentrations were found to consist of both reactant sensitive and insensitive regions. In the reactant sensitive regions, measured limiting apparent reaction rate orders for TCE, oxygen and water vapor are 0.8, 1.7 and — 3, respectively. Water vapor in the reactant stream lowersinitial reaction rates relative to corresponding water free conditions, but is required to sustain photocatalytic activity for extended periods of time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00765320
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    Baeyer-Villiger rearrangement catalysed by titanium silicate molecular sieve (TS-1)/H2O2 system (1996)
    Springer
    Catalysis letters 40 (1996), S. 47-50 
    Details
    ISSN: 1572-879X
    Keywords: Baeyer-Villiger ; titanium silicate molecular sieve ; oxidation ; rearrangement ; titanium peroxo ; triphase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Titanium silicate molecular sieve TS-1 has been found to be an efficient catalyst for Baeyer-Villiger (BV) oxidation of cyclic and aromatic ketones under triphase conditions (solid catalyst along with two immiscible liquid reactants in the absence of any cosolvent), using dilute H2O2. Reactions studied are the oxidation of cyclohexanone and acetophenone. Whereas in the case of cyclohexane,ε-caprolactone, a BV product along with hydroxy and diketones is formed, in the case of acetophenone, phenyl acetate, a BV product along witho- andp-hydroxyacetophenone is formed. The acidic nature of titanium peroxo species, stabilised by water, is proposed to be responsible for such reactions under triphasic reaction conditions.
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    URL: http://dx.doi.org/10.1007/BF00807456
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    Platinum particle size effect on the oxidative dehydrogenation of aqueous ethanol (1996)
    Springer
    Catalysis letters 36 (1996), S. 31-36 
    Details
    ISSN: 1572-879X
    Keywords: ethanol ; kinetics ; oxidation ; oxydehydrogenation ; platinum ; structure sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of the platinum particle size was investigated for the catalytic oxidative dehydrogenation of aqueous ethanol to ethanal at a temperature of 303 K, an ethanol concentration of 260 mol m−3, a partial oxygen pressure 60 kPa, a pH of 9, and an ethanal and ethanoate concentration of 20 mol m−3. A particle size effect on the turnover frequency was observed but only for particle sizes smaller than 2 nm. Hence, the reaction shows a limited structure sensitivity.
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    URL: http://dx.doi.org/10.1007/BF00807202
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    Perfluoroalkylporphyrin complexes as active catalysts for the reaction of isobutane with oxygen and the decomposition of tert-butyl hydroperoxide (1996)
    Springer
    Catalysis letters 36 (1996), S. 69-73 
    Details
    ISSN: 1572-879X
    Keywords: oxidation ; metalloporphyrins ; hydroperoxide decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new family of metalloporphyrin complexes having perfluoroalkyl groups in the meso-positions of the ring are active catalysts for the oxidation of isobutane to tert-butyl alcohol, TBA, and for the decomposition of tert-butyl hydroperoxide to TBA. This discovery extends the limited number of meso-substituents that can be used to enhance catalytic activity and fits the postulate that groups that withdraw electrons from the porphyrin periphery give rise to active catalysts for alkane oxidation. The perfluoroalkyl groups also confer oxidative stability, hydrophobicity and lower cost to the catalyst.
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    URL: http://dx.doi.org/10.1007/BF00807207
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    The preparation and characterisation of nanometre platinum colloids on silicon wafers as model catalysts (1998)
    Springer
    Catalysis letters 50 (1998), S. 49-57 
    Details
    ISSN: 1572-879X
    Keywords: model catalysts ; spin coating ; Pt colloid ; AFM ; XPS ; Si wafer ; particle size ; oxidation ; reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Platinum particles of 2 nm diameter have been immobilised on oxidised silicon wafers by spin coating with colloidal solutions and characterised by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The coverage and dispersion of the Pt colloids on the Si wafer are controlled by varying the concentration and the spin speed. Under optimal conditions mono-dispersed Pt colloids on silicon wafers are prepared. For the Pt colloids immobilised on the Si wafer, the majority of the stabilising ligands are removed through a reduction (with H2 at 200°C) or an oxidation (in air at 300°C) procedure. AFM showed that particle sizes are retained after the reduction procedure, while significant sintering occurs after oxidation. The mechanism of ligand removal was studied using an in situ XPS reaction cell.
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    URL: http://dx.doi.org/10.1023/A:1019062901616
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    The CO2–CeO2 interaction and its role in the CeO2 reactivity (1998)
    Springer
    Catalysis letters 56 (1998), S. 199-202 
    Details
    ISSN: 1572-879X
    Keywords: cerium ; gas carbonic ; propane ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The interaction between CO2 and CeO2 and its role in the surface reactivity of alumina-supported cerium oxide has been studied by programmed thermodesorption (TPD) of CO2 and FTIR spectroscopy. The performance of Ce/Al2O3 systems was then analyzed for the propane oxidation in presence of CO2. The results have shown that the catalytic activity decreased when carbonate species are formed at the surface of CeO2. This behavior was attributed to the presence of CO2 from three different sources: contamination before use, during the handling of the samples, contamination proceeding from the reactants and from CO2 produced by the reaction itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019098121432
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    Effect of chloride on sintering of Pt/Al2O3 catalysts (1991)
    Springer
    Catalysis letters 8 (1991), S. 327-333 
    Details
    ISSN: 1572-879X
    Keywords: Platinum ; alumina ; oxichloride ; oxidation ; sintering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Reduced Pt/Al2O3 catalysts with different chloride contents were treated at different temperatures under oxygen flow. TPR and TPD studies of oxidized species show that at low Cl/Pt atomic ratio (⩽1) PtO2 is formed at low temperature (400–500 K) and is totally decomposed (900 K) yielding reduced metallic Pt and inducing metal sintering. At high Cl/Pt atomic ratio (⩾6) formation of stable (up to 1000 K) platinum oxichloride avoids metal sintering.
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    URL: http://dx.doi.org/10.1007/BF00764194
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    A new strategy for alkane oxidation with O2 using N‐hydroxyphthalimide (NHPI) as a radical catalyst (1999)
    Springer
    Catalysis surveys from Japan 3 (1999), S. 27-35 
    Details
    ISSN: 1572-8803
    Keywords: oxidation ; oxygen ; alkane ; N‐hydroxyphthalimide ; radical catalyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A practical catalytic method to convert alkanes into the corresponding oxygen‐containing compounds with O2 under mild conditions using N‐hydroxyphthalimide (NHPI) in the presence or absence of a transition metal was developed. Thus, cyclohexane was successfully converted into adipic acid in good conversion and selectivity by a combined catalytic system consisting of NHPI and Mn(acac)2. Lower alkane such as isobutane was converted into t‐butyl alcohol (83%) under 10 atm of air by NHPI‐Co(OAc)2 system. Alkylbenzene such as toluene was oxidized to benzoic acid in high yield (81%) under normal temperature and pressure of dioxygen in the presence of a catalytic amount of NHPI and Co(OAc)2. ESR measurements showed that phthalimide‐N‐oxyl generated from NHPI under dioxygen atmosphere is a key species in this oxidation and functions as a radical catalyst.
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    URL: http://dx.doi.org/10.1023/A:1019059315516
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    Bleaching of cellulose by hydrogen peroxide (1995)
    Springer
    Cellulose 2 (1995), S. 265-272 
    Details
    ISSN: 1572-882X
    Keywords: Hydrogen peroxide ; oxycellulose ; bleaching ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Peroxides are important bleaching agents, industrially, for cellulosic products. They are also used in detergents. Peroxides can degrade cellulose as well as decolorize it and remove stains. Both free radicals and perhydroxyl anions have been suggested as the intermediates in the reactions occurring between cellulosic products and hydrogen peroxide. The proposed mechanisms are reviewed with emphasis primarily on cotton cellulose. Further work is required to establish unequivocally the mechanism of degradation and decolorization of cellulose products.
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    URL: http://dx.doi.org/10.1007/BF00811817
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    Die biotheoretischen Mängel der Evolutionären Erkenntnistheorie (1990)
    Springer
    Journal for general philosophy of science 21 (1990), S. 309-328 
    Details
    ISSN: 1572-8587
    Keywords: Evolution ; evolutionäre Erkenntnistheorie ; Organismus ; Autonomie ; Abbildungskritik
    Source: Springer Online Journal Archives 1860-2000
    Topics: Philosophy , Nature of Science, Research, Systems of Higher Education, Museum Science
    Notes: Summary The concept of evolutionary epistemology has been critically discussed by philosophers who have mainly pointed to unacceptable philosophical tenets (cf. Vittorio Hösle, this Journal, Vol. 19 (1988), pp. 348–377). However, as most philosophers are extremely reluctant to critically treat the biological theories on which the ideas of evolutionary epistemology are based, the invalid concepts of adaption escaped their critical scrutiny. Therefore the influence of preconceived biological theories on the biological basis of evolutionary epistemology and the distorting consequences on the philosophical level could not be elaborated. The following context sketches a new view of organismic reasoning and its impact on evolutionary aspects of epistemology. The basic theorem of adaptation is shown to be unacceptable and invalid if organisms are conceived as autonomous entities which can only evolve according to their specific internal organismic properties.
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    URL: http://dx.doi.org/10.1007/BF01801041
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    Multiple class I loci expressed by the quail Mhc (1999)
    Springer
    Immunogenetics 49 (1999), S. 456-460 
    Details
    ISSN: 1432-1211
    Keywords: Key words Antigen processing ; Evolution ; Cell surface molecules ; Mhc ; Class I antigens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/s002510050519
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    Identification and characterization of a fish natural resistance-associated macrophage protein (NRAMP) cDNA (1999)
    Springer
    Immunogenetics 50 (1999), S. 60-66 
    Details
    ISSN: 1432-1211
    Keywords: Key words NRAMP ; Fish ; Carp ; Evolution ; Expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The mouse Lsh/Ity/Bcg locus regulates natural resistance to intracellular pathogens, and the Nramp1 gene was isolated as its candidate. Nramp is part of a small family of at least two genes, Nramp1 and Nramp2. In the present study, a full-length cDNA for carp NRAMP has been isolated and characterized. Nucleotide and predicted amino acid sequence analysis indicate that the carp NRAMP encodes a 548 amino acid membrane protein with 12 putative transmembrane domains, two N-linked glycosylation sites, and an evolutionarily conserved consensus transport motif. The peptide sequence identity among carp and human NRAMP2 is 78%, and 65% with human NRAMP1. Reverse transcription-polymerase chain reaction revealed that carp NRAMP is ubiquitously expressed. Phylogenetic analysis, using neigbor-joining, showed that the carp NRAMP protein clustered together with mammalian NRAMP2 proteins.
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    URL: http://dx.doi.org/10.1007/s002510050686
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    Diversity and evolution of T-cell receptor variable region genes in mammals and birds (1999)
    Springer
    Immunogenetics 50 (1999), S. 301-308 
    Details
    ISSN: 1432-1211
    Keywords: Key words T-cell receptors ; Variable region genes ; Evolution ; Phylogeny ; Diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The receptor of a T lymphocyte (TCR) recognizes nonself antigens in the company of major histocompatibility complex (MHC) molecules presented to it by the antigen-presenting cell. The variable region of TCR is encoded by either a concatenation of variable region (TCR-V), diversity region (TCR-D), and joining region (TCR-J) genes, or a concatenation of TCR-V and TCR-J genes. The TCR-V genes exist as a multigene family in vertebrate species. Here we study the evolutionary relationships of TCR-V genes from humans, sheep, cattle, rabbits, mice, and chicken. These six species can be classified into two groups according to the frequency of γδ T-cells in their peripheral T-cell populations. The "γδ low" group of species includes humans and mice, in which γδ T-cells constitute very limited portion of the T-cell population. The "γδ high" group includes sheep, cattle, rabbits, and chicken, in which γδ T-cells comprise up to 60% of the T-cell population. Here, we compiled TCR-V sequences from the six species and conducted a phylogenetic analysis. We identified various TCR-V gene subgroups based on the analysis. We found that humans and mice have representatives from nearly all of the subgroups identified, while other species have lost subgroups to different extent. Therefore, the γδ low species have a high degree of diversity of TCR-V genes, while γδ high species all have limited diversity of TCR-V genes. This pattern is similar to that found for immunoglobulin variable region (IGV) genes.
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    URL: http://dx.doi.org/10.1007/s002510050606
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    Marsupial light chains: IGK with four V families in the opossum Monodelphis domestica (1999)
    Springer
    Immunogenetics 50 (1999), S. 329-335 
    Details
    ISSN: 1432-1211
    Keywords: Key words Marsupials ; Light chains ; Variable regions ; IGK ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  A full-length and several partial cDNAs encoding IGK light chains from the marsupial South American opossum, Monodelphis domestica, were isolated and characterized. Using these clones as a starting point, the expressed IGKV repertoire was sampled by anchored polymerase chain reaction using an IGKC-specific primer. Based on nucleotide sequences of twenty unique, expressed IGKV-J combinations, there are at least four IGKV families and two J segments. Southern blot analysis revealed each IGK-V family contains multiple gene segments totaling at least thirty-five IGKV in the opossum genome. No evidence for particular, recurrent IGKV-J combinations in the opossum IGK repertoire was seen, rather the V-J combinations appeared random and diverse. Each of the four IGKV families appear more closely related to V segments from placental mammals than to each other, suggesting the duplication of the IGKV families prior to the separation of marsupials and placental mammals more than one-hundred-million years ago. Overall, the complexity of opossum light chain V segments appears greater than that found in the heavy chain, and light chains are likely to contribute significantly to Ig diversity in this species.With this report, the homologues encoding all three classes of eutherian Ig chains, IGH, IGL, and IGK, have been described in a non-placental mammal.
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    URL: http://dx.doi.org/10.1007/s002510050609
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    Major histocompatibility complex-linked MIC genes in rhesus macaques and other primates (1999)
    Springer
    Immunogenetics 50 (1999), S. 358-362 
    Details
    ISSN: 1432-1211
    Keywords: Key words MHC ; MIC ; Nonhuman primates ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/s002510050614
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    Class I and class II MHC bind self peptide sets that are strikingly different in their evolutionary characteristics (2000)
    Springer
    Immunogenetics 51 (2000), S. 8-15 
    Details
    ISSN: 1432-1211
    Keywords: Key words Antigen presentation ; Autoimmune disease ; Evolution ; MHC ; Self peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Comparison of peptides eluted from human class I and class II major histocompatibility complex (MHC) molecules and the proteins from which they are derived (source proteins) revealed that class I MHC bind peptides derived from proteins that are highly conserved, hydrophilic, and universally expressed, while the peptides themselves are hydrophobic and even more conserved than their source proteins. In contrast, source proteins for class II-bound peptides were not significantly more conserved than a random sample of proteins. Class II-bound peptides were generally more conserved than their source proteins but were significantly less conserved than class I-bound peptides. The characteristics of class I-bound peptides can probably be explained by the selectivity of processing and transport of peptides for binding by class I, while the relative lack of selectivity of peptide binding for class II may explain the high incidence of autoimmune diseases associated with alleles of these molecules.
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    URL: http://dx.doi.org/10.1007/s002510050002
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    Molecular and functional characterization of a fish inducible-type nitric oxide synthase (2000)
    Springer
    Immunogenetics 51 (2000), S. 339-346 
    Details
    ISSN: 1432-1211
    Keywords: Key words iNOS ; Fish ; Parasite ; Evolution ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Using an oligonucleotide primer based on a partial goldfish inducible nitric oxide synthase (iNOS) sequence, a complete carp iNOS cDNA was isolated from an activated carp phagocyte cDNA library. Nucleotide and predicted amino acid sequence analysis indicate that carp iNOS encodes a 1127-amino acid protein with 57% sequence identity to human iNOS. Like mammalian NOSs, carp iNOS protein contains putative binding sites for heme, tetrahydrobiopterin, calmodulin, flavine mononucleotide, flavine adenine dinucleotide, and NADPH. Phylogenetic analysis, using neighbor joining, showed that the carp iNOS protein clustered together with the other vertebrate iNOS proteins. Inducibility of carp iNOS was confirmed by reverse transcription-polymerase chain reaction after stimulation of carp phagocytes with lipopolysaccharide or the protozoan blood flagellate Trypanoplasma borreli. These stimulators produced high amounts of nitric oxide that were toxic for T. borreli in vitro. The nuclear transciption factor NF-κB was shown to play a role in the induction of iNOS transcription.
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    URL: http://dx.doi.org/10.1007/s002510050628
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    Major histocompatibility complex class I diversity in a West African chimpanzee population: implications for HIV research (2000)
    Springer
    Immunogenetics 51 (2000), S. 398-409 
    Details
    ISSN: 1432-1211
    Keywords: Key words HLA ; Patr class I molecules ; Evolution ; Polymorphism ; AIDS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Human immunodefiency virus (HIV) poses a major threat to humankind. And though, like humans, chimpanzees are susceptible to HIV infection, they are considered to be resistant to the development of the acquired immune deficiency syndrome (AIDS). Little is known about major histocompatibility complex (MHC) class I diversity in chimpanzee populations and, moreover, whether qualitative aspects of Patr class I molecules may control resistance to AIDS. To address these questions, we assayed MHC class I diversity in a West African chimpanzee population and in some animals from other subspecies of chimpanzee. Application of different techniques allowed the detection of 17 full-length Patr-A, 19 Patr-B, and 10 Patr-C alleles. All Patr-A alleles cluster only into the HLA-A1/A3/A11 family, which supports the idea that chimpanzees have experienced a reduction in their repertoire of A locus alleles. The Patr-B alleles do not cluster in the same lineages as their human equivalents, due to frequent exchange of polymorphic sequence motifs. Furthermore, polymorphic motifs may have been exchanged between Patr-A and Patr-B loci, resulting in convergence. With regard to evolutionary stability, the Patr-C locus is more similar to the Patr-A locus than it is to the Patr-B locus. Despite the relatively low number of animals analyzed, humans and chimpanzees were ascertained as sharing similar degrees of diversity at the contact residues constituting the B and F pockets in the peptide-binding side of MHC class I molecules. Our results indicate that within a small sample of a West African chimpanzee population, a high degree of Patr class I diversity is encountered. This is in agreement with the fact that chimpanzees display more mitochondrial DNA variation than humans. In addition, population analyses demonstrated that particular Patr-B molecules, with the capacity to bind conserved HIV-1 epitopes, are characterized by high gene frequencies. These findings have important implications for evaluating immune responses in HIV vaccine studies and, more importantly, may help in understanding the relative resistance of chimpanzees to AIDS.
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    URL: http://dx.doi.org/10.1007/s002510050638
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    Is a mutator analogous to the Ig hypermutator of the sheep ileal Peyer's patch active on MHC class I genes in the germ line? (2000)
    Springer
    Immunogenetics 51 (2000), S. 462-472 
    Details
    ISSN: 1432-1211
    Keywords: Key words HLA genes ; IgV genes ; Evolution ; Gene conversion ; Sheep ileal Peyer's patch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Polymorphic sequence variation in the peptide-binding domains of MHC class I molecules appears to have been driven largely by the constructive action of natural selection on the specificity of the peptide-binding groove. Similar features are displayed by the variable domains of immunoglobulins generated in the sheep ileal Peyer's patch, but in this case there is evidence that the action of a targeted hypermutator acting on a selected substrate rather than antigen-driven selection is responsible for the pattern of variation in the system. Such a hypermutator acting in the germ line would not only mimic the action of natural selection but also, by convergent mutation, generate similar patterns of variation in unrelated alleles that could be interpreted as evidence for short-tract gene conversion. We analyzed human class I MHC alleles in the light of these data, but failed to find evidence of the action of a similar hypermutator. A search for other mutationally driven patterns of variation also failed, even in hypervariable residues from parsimonious phylogenies. Single-nucleotide variation at these residues is also frequent in recent allelic variants, but the data are as consistent with short-tract gene conversion as with base mutation. We conclude that the patterns of allelic variation in MHC molecules are not driven by mutational pressure, but rather by conventional mutational processes, accompanied by short-tract gene conversion and intense natural selection.
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    URL: http://dx.doi.org/10.1007/s002510050645
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