springer netherlands aug 1979 (9 risultati)

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -An analysis of the particular topics in biological control programmes all over the world indicates an increased interest in the utilization of aphid parasites. Besides the so-called traditional biological control of introduced aphids, there appears a situation which could perhaps be called a renaissance of biocontrol, i. e. the utilization of biotic agents against insecticide-resistant populations of aphid pests. The rapid increase in the amount of information as well as the necessity of syntheti cal papers are the well-known features in today's entomology. This requirement is much more topical in the groups where brief summarized information is needed for research workers in applied branches. The author has been well aware of all these difficulties and requirements owing to his own experience both in basic and applied research. Several years ago he decided to summarize our knowledge on the aphid parasites of the world by elaborating synthetical studies on the particular zoogeographical areas. These papers have been intended to represent annotated reviews of the parasite fauna, distribution, biologies and utilization in aphid pest management, with keys to genera and species, hos- parasite catalogue, and a list of references added. Naturally, these studies are only relatively updated, with respect to a certain deadline from which the research may be further continued. At present, the Far East Asian and the Mediterranean areas have been reviewed in this or at least in a similar manner. 128 pp. Englisch.

Buch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware 268 pp. Englisch.

Buch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware 158 pp. Englisch.

Buch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware Springer-Verlag GmbH, Tiergartenstr. 17, 69121 Heidelberg 268 pp. Englisch.

Buch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware Springer Verlag GmbH, Tiergartenstr. 17, 69121 Heidelberg 158 pp. Englisch.

Buch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -From their largely descriptive beginnings about a half century ago, studies on the ecology of small mammals have mushroomed in number, scope, content and complexity. Yet strangely, or perhaps not so strangely if one considers the extent and complexity of ecological interactions, the main problems for which the early workers sought answers still defy complete analysis, and basic hypotheses remain untested if not even untestable. The same holds true for so many branches of animal ecology that it seems to be the complexity of the concepts that frustrates efforts rather than the subject species. Like all branches of science, small mammal ecology has been subject to a series of fashionable approaches, one following another as tech nology penetrates previously impregnable regions. Doubtless the future development of our science will be punctuated by wave upon wave of new endeavour in whole fields that are perhaps even yet unidentified. Answers to the complex questions which ecologists ask do not come easily. Increasingly though, they arise in direct proportion to the efforts expended upon their elucidation. Many studies have achieved such a high level of elegance, in terms of manpower and apparatus, that there is a feeling that questions asked when such resources are unavailable are not worth asking. Nothing could be further from the truth. Many a complex model has failed fully to explain the phenomenon for which it was construc ted because of a lack of basic field data on the species' natural h~story. 404 pp. Englisch.

Buch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -A. Scope of the study 5 B. Background 6 C. Desert shru b rangelands 7 1. Definition 7 2. World distribution of desert shrub vegetation 8 3. Resource value of desert shrubs 12 D. Iraq, a brief introduction to the country 14 1. Environment 14 2. Population 17 3. Land use 18 4. Vegetation 19 I. INTRODUCTION I. A. Scope of the study The degradation of renewable natural resources in the arid areas of South West Asia has become a matter of great concern. Locally the effects of careless utili zation of the land and its resources had been felt long ago. It is, however, only relatively recently that the gravity of the situation is being generally and fully realised. It is now well understood that action is required to save what is left and possibly to restore what was once there. Such action requires organization and coordination, but above all knowledge of the present state of the resources and the impact of utilization processes. Part of this knowledge is already available. The problems are not confined to this part of the world's arid lands, but exist equally well elsewhere. Especially over the last decades an ever increasing number of studies have been published dealing with aspects of arid zone research. Problem analyses were followed by compila tions of knowledge in particular fields (White 1956; Hills 1966; Mc Ginnies et al. 1967, 1969, 1971;KauI1970;Clawsonetal. 460 pp. Englisch.

Buch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware -From their largely descriptive beginnings about a half century ago, studies on the ecology of small mammals have mushroomed in number, scope, content and complexity. Yet strangely, or perhaps not so strangely if one considers the extent and complexity of ecological interactions, the main problems for which the early workers sought answers still defy complete analysis, and basic hypotheses remain untested if not even untestable. The same holds true for so many branches of animal ecology that it seems to be the complexity of the concepts that frustrates efforts rather than the subject species. Like all branches of science, small mammal ecology has been subject to a series of fashionable approaches, one following another as tech nology penetrates previously impregnable regions. Doubtless the future development of our science will be punctuated by wave upon wave of new endeavour in whole fields that are perhaps even yet unidentified. Answers to the complex questions which ecologists ask do not come easily. Increasingly though, they arise in direct proportion to the efforts expended upon their elucidation. Many studies have achieved such a high level of elegance, in terms of manpower and apparatus, that there is a feeling that questions asked when such resources are unavailable are not worth asking. Nothing could be further from the truth. Many a complex model has failed fully to explain the phenomenon for which it was construc ted because of a lack of basic field data on the species' natural h~story.Springer Verlag GmbH, Tiergartenstr. 17, 69121 Heidelberg 404 pp. Englisch.

Buch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -The first four volumes of the series on 'Charged and Reactive Polymers' have been devoted to polymers in solution (Voh. I and II) or in gel and membrane forms (Vols. III and IV). In correlation with charges, other physical or chemical properties of macro molecules have been considered. Understanding of charge and hydrophobic effects is equally important for synthetic and biopolymers or their systems. Optically Active Polymers are related to problems of the same class, since optical activity is an inherent property of both natural macromolecules as well as a great variety of polymers synthesized in the Jast twenty years. Optical activity is a physical spectral property of chiral matter caused by asymmetrical configurations, conformations and structures which have no plane and no center of symmetry and consequently have two mirror image enantiomeric forms of inverse optical rotation. The racemic mixture of chiral enantiomers is optically inactive. The most common form of optical activity was first measured at a constant wavelength by the angle of rotation of linearly polarized light. More recently the measurements have been extended to the entire range of visible and attainable ultraviolet regions where electronic transitions are observed, giving rise to the ORD technique (Optical Rotatory Dispersion). The Cotton effects appear in the region of optically active absorption bands; outside of these bands the plain curve spectrum is also dependent on all the electronic transitions of the chromophores. 430 pp. Englisch.