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Full applicability of physics to human biology does not necessarily imply that one can uncover a comprehensive, algorithmic correlation between physical brain states and corresponding mental states. The argument takes into account that information processing is finite in principle in a finite world. Presumbly the brain-mind-relation cannot be resolved in all essential aspects, particularly when high degrees of abstraction or self-analytical processes are involved. Our conjecture plausibly unifies the universal validity of physics and a logical limitation of human thought, and it does not regard consciousness -the most basic human experience - as a marginal phenomenon. ++++ RATIO appeared up to 1987 in both a German and an English version. The German title of this article: Alfred Gierer, Der physikalische Grundlegungsversuch in der Biologie und das psychophysische Problem. RATIO XII, Heft 1, 1970, S. 40-54.
The introductory personal remarks refer to my motivations for choosing research projects, and for moving from physics to molecular biology and then to development, with Hydra as a model system. Historically, Trembley’s discovery of Hydra regeneration in 1744 was the begin¬ning of developmental biology as we understand it, with passionate debates about preformation versus de novo generation, mechanisms versus organisms. In fact, seemingly conflicting bottom-up and top-down concepts are both required in combination to understand development. In modern terms, this means analysing the molecules involved, as well as searching for physical principles underlying development within systems of molecules, cells and tissues. During the last decade, molecular biology has provided surprising and impressive evidence that the same types of mol¬ecules and molecular systems are involved in pattern formation in a wide range of organisms, including coelenterates like Hydra, and thus appear to have been “invented” early in evolution. Likewise, the features of certain systems, especially those of developmental regulation, are found in many different organisms. This includes the generation of spatial structures by the interplay of self-enhancing activation and “lateral” inhibitory effects of wider range, which is a main topic of my essay. Hydra regeneration is a particularly clear model for the formation of defined patterns within initially near-uniform tissues. In conclusion, this essay emphasizes the analysis of development in terms of physical laws, including the application of mathematics, and insists that Hydra was, and will continue to be, a rewarding model for understanding general features of embryogenesis and regeneration.
Within the sedimentation diagram of infective RNA preparations isolated from Tobacco Mosaic Virus, undegraded molecules form a sharp peak with a molecular weight corresponding to the total RNA content of the virus particle. Degradation kinetics by ribonuclease is of the linear, single-target type, indicating that the RNA is single-stranded. The intact RNA of a virus particle thus forms one big single-stranded molecule. Quantitative evaluation of the effect degradation by RNA-ase on the infectivity of the RNA shows that the integrity of the entire molecule is required for its biological activity.
Socioeconomic inequalities are functions not only of intrinsic differences between persons or groups, but also of the dynamics of their interactions. Inequalities can arise and become stabilized if there are advantages (such as generalized wealth including “human capital”) which are self-enhancing, whereas depletion of limiting resources is widely distributed. A recent theory of biological pattern formation has been generalized, adapted and applied to deal with this process. Applications include models for the non-Gaussian distribution of personal income and wealth, for overall economic growth in relation to inequalities and for effects of uncoupling strategies between developing and developed countries. Note added after publication: The equations (14) for the model of the income distribution, with its characteristic non-Gaussian extension towards higher incomes (fig.4), are closely related to the Fokker-Planck equation that is widely applied in many fields of physics.
Validity of physical laws for any aspect of brain activity and strict correlation of mental to physical states of the brain do not imply, with logical necessity, that a complete algorithmic theory of the mind-body relation is possible. A limit of decodability may be imposed by the finite number of possible analytical operations which is rooted in the finiteness of the world. It is considered as a fundamental intrinsic limitation of the scientific approach comparable to quantum indeterminacy and the theorems of logical undecidability. An analysis of these limits, applied to dispositions of future behaviour, suggests that limits of decodability of the psycho-physic relation may actually exist with respect to brain states with self-referential aspects, as they are involved in mental processes. Limits for an algorithmic theory of the mind-body problem suggested by this study are formally similar to other intrinsic limits of the scientific method such as quantum indeterminacy and mathematical undecidability which are also related to self-referential operations. At the metatheoretical level, hard sciences, despite their reliability, universality and objectivity, depend on metatheoretical presuppositions which allow for multiple philosophical interpretations.
Aggregates of previously isolated cells of Hydra are capable, under suitable solvant conditions, of regeneration forming complete animals. In a first stage, ecto- and endodermal cells sort out, producing the bilayered hollow structure characteristic of Hydra tissue; thereafter, heads are formed (even if the original cell preparation contained no head cells), eventually leading to the separation of normal animals with head, body column and foot. Hydra appears to be the highest type of organism that allows for regeneration of the entire structure from random cell aggregates. The system is particularly useful for studying cell interactions, tissue polarity, pattern formation, and cell differentiation.
Psychology's territories - historical and contemporary perspective from different disciplines
(2007)
What determines the territories of psychology? How have the boundaries of psychological research and practice been developed in history, and how might or should they be changed nowadays? This volume presents new approaches to these questions, resulting from a three-year collaboration among internationally known psychologists, neuroscientists, social scientists and historians and philosophers of science from Germany and the United States under the auspices of the Berlin-Brandenburg Academy of Sciences and Humanities. The authors reflect critically on traditional and current views of psychology on the basis of focused historical and contemporary case studies of three broad topic areas: How have psychological concepts been used in disciplines such as psychology, philosophy, or neuroscience, as well as in daily life? Has the use of instruments in psychological research expanded or restricted the discipline’s reach? And how have applications of psychological thinking and research worked in practical contexts? The volume thus presents essays that investigate the separations as well as the interactions between psychology and its neighboring disciplines and, moreover, essays that try to overcome disciplinary distinctions in exemplary ways. The contributions aim to make historical and philosophical studies of psychology relevant to contemporary concerns, and to show how psychology can profit from better interdisciplinary cooperation, thus improving mutual understanding between different scientific cultures.
The generation of viral mutants in vitro was demonstrated by treatment of the isolated RNA of Tobacco Mosaic Virus by nitrous acid. This agent causes deaminations converting cytosine into uracil, and adenine into hypoxanthine. Our assay for mutagenesis was the production of local lesions on a tobacco variety on which the untreated strain produces systemic infections only. A variety of different mutants are generated in this way. Quantitative analysis of the kinetics of mutagenesis leads to the conclusion that alteration of a single out of the 6000 nucleotides of the viral RNA is sufficient for causing a mutation.
The development of modern science has depended strongly on specific features of the cultures involved; however, its results are widely and transculturally accepted and applied. The science and technology of electricity, for example, emerged as a specific product of post-Renaissance Europe, rooted in the Greek philosophical tradition that encourages explanations of nature in theoretical terms. It did not evolve in China presumably because such encouragement was missing. The transcultural acceptance of modern science and technology is postulated to be due, in part, to the common biological dispositions underlying human cognition, with generalizable capabilities of abstract, symbolic and strategic thought. These faculties of the human mind are main prerequisites for dynamic cultural development and differentiation. They appear to have evolved up to a stage of hunters and gatherers perhaps some 100 000 years ago. However, the extent of the correspondence between some constructions of the human mind and the order of nature, as revealed by science, is a late insight of the last two centuries. Unless we subscribe to extreme forms of constructivism or historical relativism, we may take the success and the formal structure of science as indications of a close, intrinsic relation between the physical and the mental, between the order of nature and the structure of human cognition. At the metatheoretical level, however, modern science is consistent with philosophical and cultural diversity.
Non-Oberbeck-Boussinesq (NOB) effects on the Nusselt number Nu and Reynolds number Re in strongly turbulent Rayleigh-Benard convection in liquids were investigated both experimentally and theoretically. In the experiment, the heat current, the temperature difference, and the temperature at the horizontal mid-plane were measured. Three cells of different heights L, all filled with water and all with aspect ratio T close to 1 were used. For each L, about 1.5 decades in Ra were covered, together spanning the ränge 108 < Ra < 1011. For the largest temperature difference between the bottom and top plates of ? = 40K the kinematic viscosity and the thermal expansion coefficient, due to their temperature dependence, varied by more than a factor of two. The Oberbeck-Boussinesq (OB) approximation of temperature independent material parameters thus was no longer valid. The ratio Ï? of the temperature drops across the bottom and top thermal boundary layers became as small as Ï? = 0.83, as compared to the ratio Ï? = 1 in the OB case. Nevertheless, the Nusselt number Nu was found to be only slightly smaller (at most 1.4%) than in the next larger cell with the same Rayleigh number, where the material parameters were still nearly height-independent. The Reynolds numbers in the OB and NOB case agreed with each other within the experimental resolution of about 2%, showing that NOB effects for this parameter were small as well. Thus Nu and Re are rather insensitive against even significant deviations from OB conditions. Theoretically, we first account for the robustness of Nu with respect to NOB corrections: the NOB effects in the top boundary layer cancel those which arise in the bottom boundary layer as long as they are linear in the temperature difference ?. The net effects on Nu are proportional to ?2 and thus increase only slowly and still remain minor despite drastic material parameter changes. We then extend the Prandtl-Blasius boundary-layer theory to NOB Rayleigh-Benard flow with temperature dependent viscosity and thermal diffusivity. This allows the calculation of the shift of the bulk temperature, the temperature drops across the boundary layers, and the ratio Ï? without introducing any fitting parameter. The calculated quantities are in very good agreement with experiment. When in addition we use the experimental finding that for water the sum of the top and bottom thermal boundary-layer widths (based on the slopes of the temperature profiles at the plates) remains unchanged under NOB effects within experimental resolution, the theory also gives the measured small Nusseltnumber reduction for the NOB case. In addition, it predicts an increase by about 0.5% of the Reynolds number, which is also consistent with the experimental data. By theoretically studying hypothetical liquids with only one of the material parameters being temperature dependent, we shed further light on the origin of NOB corrections in water: While the NOB deviation of x from its OB value Ï? = 1 mainly originates from the temperature dependence of the viscosity, the NOB correction of the Nusselt number primarily originates from the temperature dependence of the thermal diffusivity. Finally, we give the predictions from our theory for the NOB corrections if glycerol is used as operating liquid.
Der Vortrag über den im Titel „Naturwissenschaft und Menschenbild“ umschriebenen Problemkreis, der natur- und kulturwissenschaftliche Aspekte betrifft, bildete den Abschluss des Symposiums über das Thema „Wie entstehen neue Qualitäten in komplexen Systemen“ am 18. Dezember 1998 in Berlin zum 50-jährigen Gründungsjubiläum der Max-Planck-Gesellschaft. Schwerpunkte sind Reichweite und Grenzen naturwissenschaftlicher Erklärung von Bewusstsein, evolutionsbiologische Grundlagen von Kooperativität und Empathie, sowie die kulturellen Verallgemeinerungs- und Gestaltungsmöglichkeiten biologisch angelegter Fähigkeiten, insbesondere was die Aktivierung der fragilen und begrenzten, aber durchaus realen und wichtigen Ressource „Gemeinsinn“ angeht.
Abstract (ger): Die Flüssigkeitsschichten, die um ein sich bewegendes Molekül herumfließen, haben infolge der endlichen Abmessungen der Flüssigkeitsmolekeln eine endliche Dicke. Die Berücksichtigung dieses Umstandes führt zu einer Modifikation der Stokesschen Gesetze der Kontinuumstheorie für den Zusammenhang zwischen Reibung und Viskosität. Es ergibt sich die richtige Größenordnung und ungefähr die richtige Radienabhängigkeit der beobachteten Mikroreibung, und zwar sowohl für die Rotation als auch für die Translation.
Die Entstehung der modernen Naturwissenschaften beruhte auf sehr spezifischen Merkmalen der daran beteiligten Kulturen, und doch sind ihre Erkenntnisse und Ergebnisse transkulturell und weltweit akzeptiert. So waren die Elektrizitätslehre und die Elektrotechnik spezifische Produkte der europäischen Kultur der Neuzeit, die ihrerseits auf einer bestimmten Sequenz und Kombination kultureller und interkultureller Entwicklungen bis zurück zur altgriechischen Philosophie aufbauten. Sie entstanden nicht in China, wo die Kraft des theoretischen Denkens nicht in gleicher Weise eingeschätzt wurde. Warum wurden dann aber moderne Wissenschaft und Technik transkulturell wirksam? Ein Hauptgrund dafür dürfte darin bestehen, daß die zugrunde liegenden kognitiven Fähigkeiten - Fähigkeiten der Abstraktion, des symbolischen und strategischen Denkens - auf einer biologischen Basis beruhen, die der gesamten heutigen Spezies Mensch gemeinsam ist. Gegenstand wissenschaftlicher Erkenntnis sind aber auch die prinzipiellen Grenzen der Erkenntnis; sie bedingen, daß naturwissenschaftliches Denken, das seine eigenen Grenzen kritisch reflektiert, auf der metatheoretischen Ebene mit verschiedenen philosophischen und kulturellen Interpretationen des Menschen und der Welt vereinbar ist. Dazu gehören auch religiöse Interpretationen, die die Ordnung der Natur mit dem menschlichen Geist verbinden und es dem Menschen aufgeben, diese Ordnung mit Hilfe seines Denkens zu erleben und zu erfahren.
The short paper introduces the concept of possible branches of double-stranded DNA (later sometimes called palindromes): Certain sequences of nucleotides may be followed, after a short unpaired stretch, by a complementary sequence in reversed order, such that each DNA strand can fold back on itself, and the DNA assumes a cruciform or tree-like structure. This is postulated to interact with regulatory proteins.
Upon separation of the protein from the nucleic acid component of tobacco mosaic virus by phenol, using a fast and gentle procedure, the nucleic acid is infective in assays on tobacco leaves. A series of qualitative and quantitative control experiments demonstrates that the biological activity cannot depend on residual proteins in the preparation, but is a property of isolated nucleic acid which is thus the genetic material of the virus.
In dem Buch über „Wissenschaft und Menschenbild“ werden verschiedene Wege zu einem Verständnis unserer Spezies „Mensch“ begangen: Zum einen zeigt uns die Geschichte und die geistige Struktur der modernen Naturwissenschaft sowohl die umfassende Reichweite als auch die prinzipiellen Grenzen menschlicher Erkenntnis auf, und zwar wohl besser und genauer als jede andere Kulturleistung. Zum anderen ergibt die Evolutions- und die Gehirnbiologie Einsichten in menschliche Grundfähigkeiten wie Sprache, Selbstrepräsentation und strategisches Denken. Sie sind Ergebnisse genetischer Evolution, bildeten aber dann die Voraussetzung dynamischer kultureller Entwicklung, die nicht mehr auf genetischen Änderungen beruht. Die moderne Wissenschaft ist, indem sie ihre eigenen Grenzen begründet, offen für verschiedene, natürlich nicht für alle kulturellen und philosophischen Interpretationen des Menschen und der Welt. Menschliches Bewusstsein ist ein Ergebnis der Evolution des Gehirns, und doch ist die Gehirn-Geist-Beziehung aus entscheidungstheoretischen Gründen vermutlich nicht vollständig dekodierbar. Eine wesentliche Fähigkeit unserer Spezies Mensch ist kognitionsgestützte Empathie. Sie entstand vielleicht im Kontext der Evolution strategischen Denkens, indem sie es erleichtert, das Verhalten anderer vorherzusehen, ist aber auch Motivation für altruistisches Verhalten. Stereotype Kontroversen zwischen Sozialwissenschaftlern und Soziobiologen erscheinen heute eher überflüssig; es gibt eine, wenn auch begrenzte, biologische Basis auch für freundliche menschliche Eigenschaften wie Kooperativität und Vertrauen und nicht nur für Egoismus. Moralische Vorstellungen sollten die biologischen Grundlagen menschlichen Verhaltens respektieren: Gemeinwohl ist eine durchaus reale, aber doch begrenzte Ressource unserer Spezies „Mensch“. Sie ist eher behutsam zu aktivieren, und moralische Überforderungen sind kontraproduktiv.
Understanding cooperative human behaviour depends on insights into the biological basis of human altruism, as well as into socio-cultural development. In terms of evolutionary theory, kinship and reciprocity are well established as underlying cooperativeness. Reasons will be given suggesting an additional source, the capability of a cognition-based empathy that may have evolved as a by-product of strategic thought. An assessment of the range, the intrinsic limitations, and the conditions for activation of human cooperativeness would profit from a systems approach combining biological and socio-cultural aspects. However, this is not yet the prevailing attitude among contemporary social and biological scientists who often hold prejudiced views of each other's notions. It is therefore worth noticing that the desirable integration of aspects has already been attempted, in remarkable and encouraging ways, in the history of thought on human nature. I will exemplify this with the ideas of the fourteenth century Arab-Muslim historian Ibn Khaldun. He set out to explicate human cooperativeness - "asabiyah" - as having a biological basis in common descent, but being extendable far beyond within social systems, though in a relatively unstable and attenuated fashion. He combined psychological and material factors in a dynamical theory of the rise and decline of political rulership, and related general social phenomena to basic features of human behaviour influenced by kinship, expectation of reciprocity, and empathic emotions.
This is the invited evening lecture of the biannual workshop on hydroid development of 1999. Its topic is the role of hydra as a rather puristic model for the de-novo generation of spatial patterns in development, and our work in this field. Emphasis is placed not only on experimental studies, but also on theoretical analysis, because the understanding of spatial order requires a systems approach involving the combination of knowledge on molecules, cells and tissues with mathematical analysis, laws and facts.