Renormalization group approach to chaotic strings

Coupled map lattices of weakly coupled Chebychev maps, so-called chaotic strings, may have a profound physical meaning in terms of dynamical models of vacuum fluctuations in stochastically quantized field theories. Here we present analytic results for the invariant density of chaotic strings, as well as for the coupling parameter dependence of given observables of the chaotic string such as the vacuum expectation value. A highly nontrivial and selfsimilar parameter dependence is found, produced by perturbative and nonperturbative effects, for which we develop a mathematical description in terms of suitable scaling functions. Our analytic results are in good agreement with numerical simulations of the chaotic dynamics.Comment: 36 pages, 18 figures - v2 contains slightly more than the published versio

A Family of Right Coideal Subalgebras of U_q(sl_(n+1))

The presented thesis describes a new family of spherical right coideal subalgebras of quantum universal enveloping algebras of type A_n. The description of the spherical right coideal subalgebras is given in terms of PBW-type elements. The representation theory is derived from quantum universal enveloping algebras of type A_n. The resulting quantum homogeneous space is compared with an already known one

Investigating Emerging Biomedical Practices. Zones of Awkward Engagement on Different Scales

This special issue of Science, Technology, & Human Values critically explores a new stage in which the life sciences and biomedical practices have entered. This new stage is marked by postgenomic developments and an increased interest of life sciences in the everyday lives of people outside laboratories and clinical settings. Furthermore, particular attention is given to many chronic and degenerative disorders such as cardiovascular disease, Alzheimer’s disease, or developmental disorders. These developments coincide—or have become entangled—with a new set of interests that an anthropologically inclined science and technology studies (STS) is bringing to the analyses of biomedical practices. An increased interest is observed in the anthropologically inclined STS in studying phenomena on different scales and in exploring fields that are not readily dominated by technoscientific rationality in practice. The introduction to the special issue examines briefly these developments and situates them in a broader genealogy of different movements that have taken place in the anthropologically inclined subfield of STS since the late 1970s and early 1980s.Peer Reviewe

Ist die Aktivierung organischer Nitrate beim Menschen von Cytochrom P-450 abhängig?

Zahlreiche Hypothesen zur Bioaktivierung organischer Nitrate, welche nach etablierter Meinung als "Prodrug" anzusehen sind, wurden in den letzten Jahren formuliert. Nach Laboruntersuchungen an LLC-PK1 Nierenepithelzellen von Schweinen deu­tete vieles auf eine Cytochrom P-450-vermittelte Metabolisierung zu Stickstoffmon­oxid als aktives Spaltprodukt hin. In der vorliegenden Studie wurden zwölf gesunde männliche Probanden im Alter zwischen 23 und 29 Jahren randomisiert zwei Gruppen zugeteilt, welche jeweils vier Tage mit täglich 800 mg Cimetidin Cytochrom P-450-Hemmstoff bzw. mit Placebo behandelt wurden. Die Untersuchungen fanden im Einfachblindverfahren statt, es handelt sich um einen Parallelgruppenvergleich mit intraindividuellem Crossover. Zwischen beiden Behandlungsphasen wurde eine siebentägige Auswaschphase festgelegt. Es sollte anschließend untersucht werden, ob die gefäßdilatierende Wirkung nach sublingualer Applikation von 1,6 mg Glyceroltrinitrat in der Cimetidingruppe abge­schwächt nachweisbar ist. Zu diesem Zweck wurden am vierten Tag beider Behandlungsphasen verschiedene hämodynamische Parameter vor und während eines Zeitraums von 25 Minuten nach Verabreichung von 1,6 mg GTN bestimmt: Es wurde sonografisch der Durchmesser der Vena portae, fingerpulsplethysmografisch der a/b-Quotient, der Blutdruck nach Riva-Rocci und palpatorisch die Pulsfrequenz ermittelt und dokumentiert. Cimetidin hatte in dieser Untersuchung keinen Einfluss auf die vaskuläre Wirkung von Glyceroltrinitrat. Die ermittelte prozentuale Zunahme des Durchmessers der Pfortader betrug 5,0% ± 2,58% (Placebo) bzw. 5,21% ± 4,2% (Cimetidin). Bei der Analyse der a/b-Quotien­ten beobachteten wir bei beiden Gruppen eine deutliche Steigerung gegenüber den Ausgangswerten: Placebo: 99,0% ± 53,8%, Cimetidin: 79,2% ± 44,7%. Die hä­modynamischen Parameter Blutdruck und Herzfrequenz zeigten im Vergleich beider Behandlungsphasen einen nahezu identischen Kurvenverlauf mit nur geringem initialen Blutdruckabfall und Herzfrequenzsteigerung innerhalb der ersten fünf Minuten. Bezüglich aller erhobenen Parameter war zwischen beiden Gruppen kein signifikanter Unterschied erkennbar. Die Hypothese einer durch Cimetidin hemmbaren, Cytochrom P-450 abhängigen Metabolisierung von Glyceroltrinitrat kann mit den gewählten Meßmethoden an gesunden Probanden nicht unterstützt werden.Numerous hypotheses of the bioactivation of organic nitrates, generally considered to be "prodrugs", have come up during the last years. Studies of porcine LLC-PK1 nephritic epithelial cells have indicated a cytochrome P-450 induced metabolism to nitrous oxide as an active decay product. In this study twelve healthy male probands, aged between 23 and 29, were randomly divided into two groups, each treated with 800 mg cimetidine per day as a cytochrome P-450 inhibitor and with placebos, respectively, during a period of four days. The investigation was performed as a simple blind study, comparing parallel groups with intra-individual cross-over. Between two treatments a wash-out period of seven days was imposed on the probands. Subsequently the probands treated with cimetidine were examined for a reduced effect in vessel dilatation after sublingual administration of 1.6 mg glyceryl trinitrate (GTN). Therefore, on the fourth day of both treatments the following hemodynamic quantities were determined prior to the administration of 1.6 mg GTN and during a period of 25 minutes following the administration: the diameter of the vena portae by sonography, the finger-pulse a/b ratio by plethysmography, the blood-pressure after Riva-Rocci, and the palpated pulse frequency were measured and documented. In this study, cimetidine did not influence the vascular effect of glyceryl trinitrate. The increase of the portal vein's diameter was determined to be 5.0 % ± 2.58 % (placebo), and 5.2 % ± 4.2 % (cimetidine), respectively. In the analysis of the a/b ratios, a clear increase was observed in both groups: 99 % ± 54 % (placebo), and 79 % ± 45 % (cimetidine). The hemodynamic quantities, blood-pressure and pulse frequency, showed an almost identical development in both treatments, with only a small blood-pressure decrease and pulse frequency increase within the first five minutes. With regard to the measured quantities there was no significant difference perceptible between the two groups. The hypothesis of a cytochrome P-450 dependent glyceryl trinitrate metabolism, which is able to be inhibited by cimetidine, cannot be supported with these methods of measurement chosen in case of healthy probands

The Problem of Expertise

The problem of expertise plays a key role in current scientific and political debates. Dominant approaches to expertise are focused on knowledge as an idealistic content. Given the partial inadequacy of these perspectives, an amended theoretical and methodological approach is needed. This paper aims then at sketching a relational conceptualization of expertise. At this purpose, the connections between recent anthropological theories and pragmatist theories will be highlighted