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  • crystal structure
  • evolution
  • kinetics
  • morphology
  • Springer  (98)
  • 2000-2004
  • 1990-1994  (98)
  • 1991  (98)
Collection
Keywords
Publisher
Years
  • 2000-2004
  • 1990-1994  (98)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Variation between strains of the flour beetle Tribolium castaneum in relative performance on five flours (1991)
    Springer
    Entomologia experimentalis et applicata 60 (1991), S. 173-182 
    Details
    ISSN: 1570-7458
    Keywords: Genetics ; evolution ; host adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When populations are exposed to different environments, evolutionary processes can lead either to genetically differentiated strains or to the appearance of increased generalism at the individual level. For evolution to occur, genetic variability in performance in different environments is required. Here, intraspecific genetic variation across environments was estimated in the flour beetle Tribolium castaneum (Herbst) by comparing the responses of two strains of T. castaneum to different flour types. Replicated groups from each strain were allowed to develop on either the standard whole wheat medium or on one of four novel flours (wheat, rice, corn and oat). In several of the novel flours, clear differences in mean development time or population size of one or both strains were seen relative to performance in the standard medium. Moreover, the strains differed significantly in their phenotypic responses to the flours. One strain did particularly poorly on oat flour. Reduced oviposition, reduced larval survivorship and increased larval cannibalism were examined as possible causes of the low productivity on oat flour. These three factors accounted for about 70% of the reduction in population size when this strain oviposited and developed in oat flour. The difference between these two outbred strains in response to these five flours suggests that genetic variation in resource use is present within T. castaneum and may also be present within strains and natural populations in grain storage facilities. Such variation would permit an evolutionary response to selection in multiple environments (flours). This process has agricultural implications when several types of grain are stored in a single location because it could eventually lead to the evolution of highly generalized populations of T. castaneum, an important pest of stored products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00177038
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  • 2
    Electronic Resource
    Electronic Resource
    The structure of Mo4Cl8(PEt3)4: How unrecognized disorder previously reduced the quality of the refinement (1991)
    Springer
    Journal of cluster science 2 (1991), S. 121-129 
    Details
    ISSN: 1572-8862
    Keywords: Molybdenum tetranuclear cluster ; rectangular ; triethylphosphine ligand ; preparation ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The preparation and structure of the title compound were reported several years ago by McCarly and co-workers ((1978).J. Am. Chem. Soc. 100, 7900). Curiously, it was reported that refinement of the structure converged at exceptionally high figures of merit (R=0.126;R w =0.158), but no reason was given. In view of a recent observation in this laboratory (Chen and Cotton (1991).J. Am. Chem. Soc. 113, 5857) that a similar type of compound, [Re4Cl8(μ-O)2(μ-OMe)2]2− exhibited a subtle but elegant disorder, we reexamined the crystal structure of the title compound. It is found to have 92% of the Mo4 rectangles in one orientation (the only one previously included in the refinement) and 8% in an orientation perpendicular to the main one. In both orientations the ligand positions are approximately the same. The figures of merit are nowR=0.041;R w =0.064. The three structure parameters previously reported are now only slightly different: Mo-Mo=2.210(1) vs. 2.211(3) Å; Mo-Mo'=2.897(1) vs. 2.901(2) Å; angle Mo-Clb-Mo=74.2[8]° vs. 74.4(2)°. We report here the complete structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702953
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  • 3
    Electronic Resource
    Electronic Resource
    Using a morphological analyzer to teach theoretical morphology (1991)
    Springer
    Computers and the humanities 25 (1991), S. 281-287 
    Details
    ISSN: 1572-8412
    Keywords: computational ; computers ; linguistics ; morphology ; natural language processing ; parsing ; programming ; PROLOG ; recursion ; teaching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Media Resources and Communication Sciences, Journalism
    Notes: Abstract This paper presents the results of our experience in using an instructional morphological parser (IMP) as a teaching tool in two graduate level courses, one in theoretical morphology and the other in computational morphology. IMP was written in Waterloo PROLOG by the second author and is based on the UDICT morphology system (Byrd 1983). The courses were taught by the first author at the Graduate School of the City University of New York. We present a brief overview of computational morphology and discuss in detail the implementation we used for IMP. We then give an outline of the two courses with some speculation on the computational and linguistic concepts that our students learned. In particular, we discuss the problems we encountered in teaching the notion of recursion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120964
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  • 4
    Electronic Resource
    Electronic Resource
    Cell size of mammalian myocardia is not related to physiological demand (1991)
    Springer
    Cellular and molecular life sciences 47 (1991), S. 1070-1072 
    Details
    ISSN: 1420-9071
    Keywords: Cell size ; cross sectional area ; myofibril ; mitochondria ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Morphological characteristics of myocardial ventricular myocytes have been evaluated from 5 mammalian orders with resting heart rates ranging from 51 to 475 bpm. The purpose was to determine if morphological characteristics of the myocardia are related to the functional demand imposed on the cell as represented by the resting heart rate. Cell size is a constant among mammals of different sizes which have different physiological demands. In contrast, there is more mitochondrial area and less myofibrillar area per cell in animals with rapidly beating hearts than in animals with slower heart rates. Additionally, the mean cross sectional area of individual myofibrils is 30% larger in the cow as compared to the mouse. These findings combined with our previous studies indicate that the different functional requirements of myocardia from different mammalian orders are satisfied by intracellular adaptations of both a structural and biochemical nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01923345
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  • 5
    Electronic Resource
    Electronic Resource
    Evolution: Teleology or chance? (1991)
    Springer
    Journal for general philosophy of science 22 (1991), S. 133-141 
    Details
    ISSN: 1572-8587
    Keywords: evolution ; teleology ; chance ; purpose ; anthropomorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Philosophy , Nature of Science, Research, Systems of Higher Education, Museum Science
    Notes: Summary Revaluation of the problem of natural teleology seems an important precondition for elucidating our environmental crisis and for formulating an ‘ecological ethics’, because it calls for a recognition of an intrinsic value in nature and organisms. Therefore, it is necessary to show that the concept of natural teleology is not in contradiction with scientific theories, in particular not with the theory of evolution. In this paper I shall argue that there is a fundamental misunderstanding about the concepts of teleology and chance in modern thinking. This as a result of a radical transformation of the Aristotelian concept of teleology by Christian theologians during the Middle Ages. This confusion resulted in the rejection of teleology from evolution and in an exaggeration of the role of chance. However, not a solution for the problem of teleology is given here, but only an attempt to prove that neither the fossil-record, nor the role of chance in evolution can give adequate arguments for the negation of teleology in evolution. That is not to say that, therefore there exists teleology in evolution, but the problem of teleology in nature cannot, be solved by the scientific theory of evolution, but only be elucidated by philosophical analysis. At the end of the paper it is argued that teleology must be rather presupposed in evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01801253
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  • 6
    Electronic Resource
    Electronic Resource
    The characterization of high-tech materials: Perspectives, challenges, trends (1991)
    Springer
    Microchimica acta 104 (1991), S. 177-214 
    Details
    ISSN: 1436-5073
    Keywords: atomic structure ; crystal structure ; microstructure ; constructions ; topochemistry ; graphite ; glassy carbon ; pyrolytic carbon ; microelectronics ; carriers of information ; refractory metal alloys ; life time ; recrystallization ; fatigue ; photon probe techniques ; electron probe techniques ; ion probe techniques ; electrical field probes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract From the Stone Age on, developmental periods of mankind carry the names of materials. Materials determine the applicability of key technologies and these are in turn of major significance for the economic success and the social development in modern society. Today's high-tech materials are the consequence of an improved understanding of the structure and composition of matter and of the interplay of microstructure and minor and trace constituents. We can distinguish four basic dimensional structural categories of materials: (a) the atomic structure level; (b) the crystal, glassy or amorphous structural level; (c) the microstructural level; (d) the level of constructions. As an example, these structural levels are described in some detail for graphite, a material used extensively throughout Analytical Chemistry. Decisive differences at the microstructural level result in graphitic materials with very varying properties: polycrystalline electrographite, glassy carbon, and pyrolytic graphite. Examples for the use of these materials in ETAAS are discussed. Structural features together with topochemical and trace chemical characteristics are studied today by a wide variety of analytical instrumentation and methods of modern materials analysis which can be grouped into four categories of techniques: (a) photon probe techniques; (b) electron probe techniques; (c) ion probe techniques; (d) electrical field probes. The most important of those techniques are discussed shortly with respect to their main characteristics as lateral and depth resolution, detection sensitivity, additional bonding or structural information, depth profiling possibilities etc. The constructions are the ultimate level of a materials structure. Structures of microelectronic components reach dimensionally into the domain of microstructure whereas constructions in heavy industry are of meter-ton dimensions. Progress in the use of materials as carriers of information is visualized by a morphological comparison of the sound tracks of conventional records with the information imprinted in optical discs. It is important to conceive materials as dynamic systems with limited lifetime. Fatigue and recrystallization are prominent relevant phenomena which must be studied by microstructural and topochemical methods. Dispersion strengthened microalloys like TZM, HT-molybdenum and NS-tungsten are discussed as examples how materials can be improved with respect to their extended use under extreme conditions. Again, a thorough structural and topochemical characterization was the basis of a successful respective materials development although a multitude of relevant topochemical questions still remain to be solved. Lifetime investigations are an essential tool of materials development as well as quality control. Relevant investigations for various tube materials for ETAAS are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01245508
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  • 7
    Electronic Resource
    Electronic Resource
    Quantitative aspects of cellular turnover (1991)
    Springer
    Antonie van Leeuwenhoek 60 (1991), S. 175-191 
    Details
    ISSN: 1572-9699
    Keywords: growing systems ; kinetics ; murein wall ; nucleic acid ; protein ; turnover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Living organisms do not just grow by synthesizing cellular components. As part of the necessary steps for existence, some components are degraded after synthesis. Even for bacteria in balanced, exponential growth some substances, under some conditions, are turned over. In other phases of growth turnover can be much more extensive, but it is still selective. This review covers studies with animals as a way to put the studies on microorganisms in perspective. The history, the mathematics, and experimental design of turnover experiments are reviewed. The important conclusion is that most of the proteins during balanced growth are very stable in bacteria, although ribosomal proteins are degraded under starvation conditions. Another generalization is that the process of wall enlargement in general is associated with obligatory turnover of the peptidoglycan.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00430364
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  • 8
    Electronic Resource
    Electronic Resource
    Ergatoid queens and intercastes in ants: Two distinct adult forms which look morphologically intermediate between workers and winged queens (1991)
    Springer
    Insectes sociaux 38 (1991), S. 1-15 
    Details
    ISSN: 1420-9098
    Keywords: Reproduction ; caste ; morphology ; Ponerinae ; Leptothoracini
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The term “ergatogyne” is used in ants to describe permanently-wingless female adults which are “morphologically intermediate” between workers and winged queens. This definition is ambiguous because there are two distinct categories of “ergatogynes”: ergatoid queens and intercastes. Both have an external appearance (ocelli and alitrunk structure) which combines traditional queen and worker characters, and thus can be confused if they both function as reproductives — however intercastes in most species cannot reproduce. Ergatoid queens have replaced winged queens in a substantial number of species. They are sometimes externally similar to conspecific workers, especially in various ponerine species which exhibit limited size dimorphism between castes. Ergatoid queens retain the specialized attributes of a reproductive caste, including larger ovaries, and they are always the functional egg-layers in a colony. In contrast, conspecific intercastes represent various graded stages in a series connecting workers and winged queens, and they occur together with the queens. These hybrid phenotypes result from deviations from the normal pattern of caste differentiation during larval development. Intercastes generally lack a spermatheca and have no reproductive function; however they can mate in a few leptothoracine ants, and then reproduce instead of winged queens in a proportion of colonies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01242708
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  • 9
    Electronic Resource
    Electronic Resource
    Polymorphism in the giant cocoa termite,Neotermes papua (Desneux) (1991)
    Springer
    Insectes sociaux 38 (1991), S. 263-272 
    Details
    ISSN: 1420-9098
    Keywords: Isoptera ; Kalotermitidae ; Neotermes papua ; termites ; caste differentiation ; division of labour ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The direct development ofNeotermes papua (Isoptera: Kalotermitidae) comprises four larval and three nymphal instars before the alate. The first five instars can be easily characterized. The second stage nymphs come morphologically close to the pseudergates, characterized by reduced wing buds. These nymphs can moult stationarily, i.e. with little morphological change, or to presoldiers, or proceed to the alate via the third nymphal stage. Pseudergates originate through a late and reversible deviation from the straight development to the alate. Presoldiers may derive from several stages, up to the last nymphal one; their production is subject to an inhibition by extant soldiers. This developmental schema is congruent with those described in other Kalotermitidae and the Termopsidae. By pinpointing the existence of a large pool of pluripotent individuals, in which the penultimate nymphal stage mingles with pseudergates, the present study also reveals a great similarity betweenNeotermes andProrhinotermes, and suggests that this developmental schema might be generally applicable to termites devoid of a permanent worker caste.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01314912
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  • 10
    Electronic Resource
    Electronic Resource
    A comparison of pyridoxal 5′-phosphate dependent decarboxylase and transaminase enzymes at a molecular level (1991)
    Springer
    Cellular and molecular life sciences 47 (1991), S. 1104-1118 
    Details
    ISSN: 1420-9071
    Keywords: Transaminase ; decarboxylase ; serine hydroxymethyltransferase ; pyridoxal 5′-phosphate ; enzyme mechanism ; stereochemistry ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Pyridoxal 5′-phosphate is a coenzyme for a number of enzymes which catalyse reactions at Cα of amino acid substrates including transaminases, decarboxylases and serine hydroxymethyltransferase. Using the X-ray coordinates for a transaminase, aspartate aminotransferase, and the results of stereochemical and mechanistic studies for decarboxylases and serine hydroxymethyltransferase, an active-site structure for the decarboxylase group is constructed. The structure of the active-site is further refined through active-site pyridoxyllysine peptide sequence comparison and a 3-D catalytic mechanism for the L-α-amino acid decarboxylases is proposed. The chemistry of serine hydroxymethyltransferase is re-examined in the light of the proposed decarboxylase mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01918374
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