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Taschenbuch. Zustand: Neu. This item is printed on demand - Print on Demand Titel. Neuware -Classifications of periodic words and their application in group theory.- On the word problem for groups defined by periodic relations.- An application of the nilpotent quotient program.- Groups of exponent eight.- Finiteness proofs for groups of exponent 8.- Application of computers to questions like those of Burnside.- On certain groups of exponent eight generated by three involutions.- Generalized power laws.- Problems.Springer-Verlag KG, Sachsenplatz 4-6, 1201 Wien 280 pp. Englisch.…

Taschenbuch. Zustand: Neu. This item is printed on demand - Print on Demand Titel. Neuware -During the last decade and a half, studies of evolution and variation have been revolutionized by the introduction of the methods and concepts of molecular genetics. We can now construct reliable phylogenetic trees, even when fossil records are missing, by compara tive studies of protein or mRNA sequences. If, in addition, paleon tological information is available, we can estimate the rate at which genes are substituted in the species in the course of evolution. Through the application of electrophoretic methods, it has become possible to study intraspecific variation in molecular terms. We now know that an immense genetic variability exists in a sexually repro ducing species, and our human species is no exception. The mathematical theory of population genetics (particularly its stochastic aspects) in conjunction with these new developments led us to formulate the 'neutral theory' of molecular evolution, pointing out that chance, in the form of random gene frequency drift, is playing a much more important role than previously supposed. I believe that the traditional paradigm of neo-Darwinism needs drastic revision. Also, the importance of gene duplication in evolution, as first glimpsed by early Drosophila workers, has now been demonstrated by directly probing into genetic material. Recently, it has been discovered that some genes exist in large-scale repetitive structures, and that they are accompanied by newly described phenomena such as 'coincidental evolution'. Working out the population genetical consequences of multigene families is a fascinating subject, for which Dr. Ohta has been largely responsible.Springer-Verlag KG, Sachsenplatz 4-6, 1201 Wien 148 pp. Englisch.…

Taschenbuch. Zustand: Neu. This item is printed on demand - Print on Demand Titel. Neuware -N-nitroso-compounds form an important class of carcinogenic chemicals which may be of environmental importance (Druckrey et al. , 1967; Magee et al. , 1976; IARC, 1978). The mechanism by which these carcinogens initiate neoplastic growth is not well understood but there is substantial evidence favoring the hypothesis that the simple dialkylnitrosamines and alkylnitrosamides act by means of their conversion to al kylating agents. Alkylating species are generated from the nitrosamines by metabolic activation and from the nitrosamides by chemical decomposition at physiological pH. It is widely believed that DNA is the critical alkylation target. Alkylation takes place at at least 12 sites within the DNA molecule (Lawley, 1976; Singer, 1976; Pegg, 1977a). Al though alkylation at the 7-position of guanine is the most extensive reaction with the DNA bases and provides a reliable measurement of the degree of interaction with the carcinogen (Swann and Magee, 1968, 1971), recent experiments have suggested that alkylation of oxygen atoms may be the critical reaction (Goth and Rajewsky, 1974; Margison and Kleihues, 1975; Nicoll et aI. , 1975; Pegg, 1977a). These laboratories have observed a correlation between the production and persistence of 06-alkyl guanine and the occurrence oftumors in a variety of organs of rodents exposed to N-ni troso-carcinogens. It has, therefore, been suggested that the ability of tissues to catalyze the removal of 06-alkylguanine from DNA may provide a protective mechanism against carcinogenesis.Springer-Verlag GmbH, Tiergartenstr. 17, 69121 Heidelberg 348 pp. Englisch.…

Taschenbuch. Zustand: Neu. This item is printed on demand - Print on Demand Titel. Neuware -Fifty-two patients operated on for this type of spondylogenic myelo pathy by the anterior approach were reexamined. The male: female re lation was 2 : 1. Fifty percent were males in the 5th decade. About 20% had a congenital narrow spinal canal with an ap-diameter below the minimal standard values (3). The maximum of spondylogenic narrow ing was found between C4 and C6 in 2/3 of the cases. Results: good 44%, satisfactory 31%, unchanged 13%, deteriorated 12%, mortality O. The duration of the neurological symptoms before operation had no in fluence on the surgical results. Final neurological restitution was reached within 1 week to 3 months after the operation. The operative results in patients with congenital narrow spinal canal showed the same percentual distribution as the results of the entire group. No factors could be found to explain the groups of unsatisfactory results. References 1. DECKING, D. , STEEGE, W. ter: Rontgenologische ParametAr der Hals wirbelsaule im seitlichen Strahlengang. Die Wirbelsaule in Forschung und Praxis, ~ (1975) 2. HERRMANN, H. D. : Neurologie in Praxis und Klinik. HOPF, H. C. , POECK, K. , SCHLIACK, N. (Hrsg. ). Stuttgart: Thieme (in press) 3. PIEPGRAS, U. : Neuroradiologie. S. 88-89. Stuttgart: Thieme 1977 114 Classification and Prognosis of Cervical Myelopathy E. HAMEL, R. A FROWEIN, and A KARIMI-NEJAD Introduction Up to the present, 104 patients with cervical myelopathy caused by cervical disk lesions, have been operated on in our clinic.Springer-Verlag KG, Sachsenplatz 4-6, 1201 Wien 480 pp. Englisch. …

Taschenbuch. Zustand: Neu. This item is printed on demand - Print on Demand Titel. Neuware -Die Peristaltik zahlt zu dem jUngsten Zweig des Gesamtkomplexes der Durch stromung physiologischer GefaBe. Sowohl in der Biomechanik als auch in der Physiologie sind diesbezUglich umfangreiche Untersuchungen innerhalb der letzten fUnfzehn Jahre durchgefUhrt worden. Insbesondere wurde versucht, eine peristaltische Stromung im Experiment und als mathematisch- physika lisches Modell nachzubilden. Speziell in letzter Zeit sind umfangreiche experimentelle und zahlreiche theoretische Arbeiten veroffentlicht worden, wobei es auBerst schwierig und aufwendig ist, das Problem in voller All gemeinheit zu erfassen. Deshalb mUssen in den meisten Fallen Vereinfachungen getroffen werden, urn den Aufwand fUr die experimentellen und theoretischen Untersuchungen nicht zu groB werden zu lassen. Bisher scheint noch keine Veroffentlichung bekannt zu sein, die den Themen kreis Peristaltik in Ubersichtlicher Form darste11t. Mit diesem Buch soll versucht werden, diese LUcke zu sch1ieBen. Es 5011 eine Obersicht vermit teln bezUg1ich 1. der Beschreibung des Phanomens Peristaltik 2. des Auftretens der Peristaltik in der Physiologie 3. der experimente11en Untersuchungen in der Physiologie 4. der Nachbildung einer perista1tischen Stromung im Experiment 5. der theoretischen Mode11e zur Peristaltik 6. der Grundgleichungen derStromungs- und Elastomechanik 7. der Losungsmethoden der entsprechenden Gleichungen. In einem umfangreichen Literaturverzeichnis sind entsprechende Arbeiten, bzw. Aufsatze Uber die oben aufgefUhrten Punkte zu finden. Die einzelnen Kapite1 sind absichtlich re1ativ kurz geha1ten, da auf die entsprechende VI Literatur verwiesen werden kann. Die vorliegende Arbeit entstand am Institut fUr Mechanik (Prof. Dr.-lng.Springer-Verlag KG, Sachsenplatz 4-6, 1201 Wien 128 pp. Deutsch.…