281 research outputs found
A differential equation model for the description of the fast fluorescence rise (O-I-D-P-transient) in leaves
No full textBaake E, Strasser RJ. A differential equation model for the description of the fast fluorescence rise (O-I-D-P-transient) in leaves. PHYSIOLOGIA PLANTARUM. 1989;76
A differential equation model for the description of the fast fluorescence rise (O-I-D-P-transient) in leaves
No full textBaake E, Strasser RJ. A differential equation model for the description of the fast fluorescence rise (O-I-D-P-transient) in leaves. In: Baltscheffsky M, ed. Current Research in Photosynthesis. Dordrecht: Kluwer; 1990: 443-449
Author comment on RC4: 'Review of Strasser et al.: Rofental catchment', Adam Winstral, 02 Oct 2017
No full textThe New Paternalism
No full textThe author argues that the belief that patient autonomy has great
moral value has justified a new form of medical paternalism which can have
effects similar to those of the old rejected form. He cites the argument that
"all illness represents a state of diminished autonomy" and that therefore
autonomy is not overridden when physicians make all decisions. Another view
is that, in some situations, withholding information may prevent patient
deterioration and loss of autonomy. Abridgement of present autonomy, then, is
permissible if it promotes future autonomy. Strasser also rejects physician
decision making based on patients' previously communicated values or on the
theory that patient values are important but not decisive. He concludes that
if we "allow paternalistic practices, then we should admit that we are denying
autonomy in light of some other good rather than claim that, somehow, we are
respecting autonomy by abridging it." (KIE abstract
Plant stress analysis: application of prompt, delayed chlorophyll fluorescence and 820 nm modulated reflectance. Insights from independent experiments.
No full textNine short-term independent studies were carried out with two M-PEA units on several plant species differing in their functional traits (woody evergreen, woody deciduous, herbaceous) and exposed to different kind of abiotic stress (drought, salt, ozone, UV radiation). Aim of the study is to check the consistency of plant responses, assessed through three sets of simultaneously measured signals: Prompt Fluorescence (PF), Delayed Fluorescence (DF) and Modulated Reflectance of 820 nm light (MR). The decrease of FV/FM and F0, the increase of VJ and VI were the most common responses related to PF parameters. The decrease of vox and vred as well the increase of MRmin were common response of MR. DF showed species-treatment specific behaviors. The Principal Component Analysis (PCA) suggests that the combination of PF and MR parameters represents a powerful tool for plant stress phenotyping, whereas MR parameters are linked to physiological strategies, related to different functional groups, to cope with stress factors
The covariance structure of conditional maximum likelihood estimates
No full textIn this paper we consider conditional maximum likelihood (cml) estimates for
item parameters in the Rasch model under random subject parameters. We give
a simple approximation for the asymptotic covariance matrix of the cml-estimates.
The approximation is stated as a limit theorem when the number of item parameters
goes to infinity. The results contain precise mathematical information on the order
of approximation.
The results enable the analysis of the covariance structure of cml-estimates when
the number of items is large. Let us give a rough picture. The covariance matrix has
a dominating main diagonal containing the asymptotic variances of the estimators.
These variances are almost equal to the efficient variances under ml-estimation when
the distribution of the subject parameter is known. Apart from very small numbers
n of item parameters the variances are almost not affected by the number n. The
covariances are more or less negligible when the number of item parameters is large.
Although this picture intuitively is not surprising it has to be established in precise
mathematical terms. This has been done in the present paper.
The paper is based on previous results [5] of the author concerning conditional
distributions of non-identical replications of Bernoulli trials. The mathematical background
are Edgeworth expansions for the central limit theorem. These previous results
are the basis of approximations for the Fisher information matrices of cmlestimates.
The main results of the present paper are concerned with the approximation
of the covariance matrices.
Numerical illustrations of the results and numerical experiments based on the
results are presented in Strasser, [6]. (author's abstract
Opportunistic survival strategy of<i>Welwitschia mirabilis</i>: recent anatomical and ecophysiological studies elucidating stomatal behaviour and photosynthetic potential
Get PDFWe present new findings on leaf and stomatal apparatus anatomy and ecophysiology of Welwitschia mirabilis Hook.f. that are relevant to survival in the desert. We show that the structure of the stomatal apparatus with thin areas in the guard cell walls is a key feature enabling an opportunistic survival strategy through reversible quick switch-over from water conservation to CO2assimilation. Desert environment and greenhouse data demonstrated that stomatal conductance increased almost immediately after dawn to reach a maximum within approximately an hour, whereupon a steep decrease occurred. After discontinuation of induced drought in potted plants, fast recovery of stomatal conductance occurred while copious new root hairs developed within 50 h. Stomatal limitation proved to be the main photosynthetic constraint under induced drought. Under severe drought stress, biochemical limitation came into play. Chlorophyll fluorescence data of in-situ plants showed that the photosynthetic potential of leaf tissue is highest near the basal meristem, but although it decreases with age, it retains activity up to the leaf apex at the end of the green part. The photosynthetic potential of potted plants was optimal at 20 °C, analogous to mesophytic plants. Our data confirms our hypothesis that leaf surface and stomatal structure play a crucial role in moisture conservation and moderating leaf temperature for desert survival.</jats:p
Author comment on RC2: 'Review of : “The Rofental: a high Alpine research basin (1890 m – 3770m a.s.l.) in the Ötztal Alps (Austria) with over 150 years of hydro-meteorological and glaciological observations” by Ulrich Strasser et. al.', Stefan Poh
No full textLe syllogisme pratique et son importance pour les sciences humaines
No full textThe author sketches the motives which led to attempts to conceive of an analytical theory of action. He also points to the old problem of the « Geisteswissenschaften », a problem Popper and Hempel were unable to deal with. In this context von Wright's essay on Explanation and Understanding merits attention because this scholar tries to give a synthesis of what he calls the « Galilean » and the « Aristotelian tradition » in Occidental thought. Within the latter the idea of the « practical syllogism » plays an important role. Thomas Aquinas' and Kant's conception of the « syllogismus practicus » are compared with von Wright's ideas. It appears that the logical reflection concerning an action is not on a footing with the action itself, since the action as such is directed towards its goal and since immediate directedness prevents reflection. The author, therefore, proposes to speak of « teleological reasoning » rather than of « practical syllogisms ». Interpreting Max Weber's notion of « Zweckrationalität » the author shows that the appropriate character of the means respective to their end constitutes a first instrument which enables the scientist to interprete human actions. The end may be choosen quite subjectively, the means too, but the adequacy or inadequacy of the means as related to their end can be evaluated in an objective manner. Teleological reasoning, therefore, may ensure a minimum of rationality in the scientific interpretation of human action. Von Wright is right in rejecting methodological dualism as advocated in the 19th century by Droysen and Dilthey. History, psychology, sociology are not simply « hermeneutical sciences ». « Nature » (as opposed to « culture ») plays a decisive role in the life of human individuals and groups. Nature as such cannot be interpreted in an anthropomorphic way, it can only be described by stating law-like regularities. Human sciences, therefore, cannot do without causal research. Scientifically speaking an interpretative theory has the status of a hypothesis. It is not a demonstration in the sense of natural science, it is a reconstruction ex post facto. The author proposes not to speak of « truth » in his context but rather of « plausibility ». An interpretative theory may be called « plausible », when it is elucidating, when it makes us understand the relations between many particular facts, when in its light certain regularities become intelligible. An interpretation which has none of these qualities is to be considered as « non plausible ». If it is incompatible with one of the facts known the interpretative theory is « false ».L'A. esquisse les motifs qui ont mené à essayer de concevoir une théorie analytique de l'action. Il mentionne aussi la vieille question des « Geisteswissenschaften », que Popper et Hempel ont été incapables de traiter. C'est pourquoi l'ouvrage de von Wright, Explanation and Understanding, mérite notre attention : cet auteur essaie de faire une synthèse de ce qu'il appelle les traditions « galiléenne » et « aristotélicienne » dans la pensée occidentale. Dans cette tradition-ci, l'idée du « syllogisme pratique » joue un rôle important. Les conceptions du « syllogisme pratique » selon S. Thomas et Kant sont comparées avec les idées de von Wright. Il en ressort que la réflexion logique à propos d'une action n'est pas sur le même plan que l'action elle-même, puisque l'action en tant que telle est dirigée vers son but et que cette application immédiate empêche la réflexion. L'A., en conséquence, propose de parler de « raisonnement téléologique » plutôt que de « syllogisme pratique ». Interprétant la notion weberienne de « Zweckrationalität », l'A. montre que le caractère approprié des moyens par rapport à la fin constitue un premier instrument qui permet à l'homme de science d'interpréter les actions humaines. La fin peut être choisie de manière tout à fait subjective, les moyens aussi, mais l'adéquation ou l'inadéquation des moyens à leur fin peut être évaluée de manière objective. Le raisonnement téléologique, par conséquent, peut assurer un minimum de rationalité dans l'interprétation scientifique des actions humaines. Von Wright est en droit de rejeter le dualisme méthodologique invoqué au XIXe siècle par Droysen et Dilthey. L'histoire, la psychologie et la sociologie ne sont pas de simples « sciences herméneutiques ». La « nature » (en tant qu'opposée à la « culture ») joue un rôle décisif dans la vie des êtres et des groupes humains. La nature en tant que telle ne peut être interprétée d'une manière anthropomorphique, elle peut seulement être décrite en établissant des régularités ressemblant à des lois. Les sciences humaines ne peuvent donc se passer de la recherche des causes. Scientifiquement parlant, une théorie interprétative a le statut d'une hypothèse. Ce n'est pas une démonstration comme dans les sciences de la nature, c'est une reconstruction ex post facto. L'A. propose de ne pas parler de « vérité » dans ce contexte, mais plutôt de « plausibilité ». Une théorie interprétative peut être appelée « plausible », quand elle éclaire, quand elle nous fait comprendre les relations entre plusieurs faits particuliers, quand à sa lumière des régularités deviennent intelligibles. Une interprétation qui n'a aucune de ces qualités ne peut pas être considérée comme « plausible ». Si la théorie interprétative est incompatible avec l'un des faits, elle est « fausse ».Strasser Stephan. Le syllogisme pratique et son importance pour les sciences humaines. In: Revue Philosophique de Louvain. Quatrième série, tome 81, n°49, 1983. pp. 82-102
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