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Rainfall erosivities as defined by the R factor from the universal soil loss equation were determined for all events during a two-year period at the station La Cuenca in western Amazonia. Three methods based on a power relationship between rainfall amount and erosivity were then applied to estimate event and daily rainfall erosivities from the respective rainfall amounts. A test of the resulting regression equations against an independent data set proved all three methods equally adequate in predicting rainfall erosivity from daily rainfall amount. We recommend the Richardson model for testing in the Amazon Basin, and its use with the coefficient from La Cuenca in western Amazonia.
This paper presents a new methodology for examining the phenomenon of subitizing. Subjects were presented with a standard numerosity-detection task but for a range of presentation times to allow Task-Accuracy Functions to be computed for individual subjects. The data appear to show a continuous change in processing for numerosities from 2 to 5 when the data are aggregated across subjects. At the level of individual subjects, there appear to be qualitative shifts in enumeration processing after 3 or 4 objects. The approach used in this experiment may be used to test the claim that subitizing is a distinct enumeration process that can be used for small numbers of objects.
Arbeitszeit und Wertewandel
(1993)
Inhalt: 1. Arbeitszeit und Wertwandel als personal- und tarifpolitische Kategorien 1.1. Dauer und Lage der Arbeitszeit als Reflex von Wertvorstellungen 1.2. Wertewandel als Ergebnis der Veränderung der Arbeitszeit 1.3. Personal- und tarifpolitische Konsequenzen 2. Zur Diskussion des Wertewandels in der Arbeitswelt 2.1. Ansichten über den Verlauf des Wertewandels 2.2. Ansichten über die Ursachen des Wertewandels 2.3. Ansichten über die Auswirkungen des Wertewandels 3. Wertvorstellungen der Arbeitnehmer zur Arbeitszeitgestaltung 3.1. Wünsche zur Arbeitszeitverkürzung 3.2. Wünsche zur Umgestaltung der Arbeitszeit 4. Personal- und tarifpolitische Gestaltungsfelder 4.1. Arbeitszeit und Wertewandel aus der Sicht der Tarifpartner 4.2. Arbeitszeit und Wertewandel aus betrieblicher Sicht 4.3. Arbeitszeit und Wertewandel als individuelles Problem
Prostaglandin (PG)F₂α has previously been shown to increase glucose output from perfused livers and isolated hepatocytes, where it stimulated glycogen phosphorylase via an inositol-trisphosphatedependent signal pathway. In this study, PGF₂α binding sites on hepatocyte plasma membranes, that might represent the putative receptor, were characterized. Binding studies could not be performed with intact hepatocytes, because PGF₂α accumulated within the cells even at 4°C. The intracellular accumulation was an order of magnitude higher than binding to plasma membranes. Purified hepatocyte plasma membranes had a high-affinity/low-capacity and a low-affinity/highcapacity binding'site for PGF₂α. The respective binding constants for the high-affinity site were Kd = 3 nM and Bmax = 6 fmol/mg membrane protein, and for the low-affinity site Kd = 426 nM and Bmax = 245 fmol/mg membrane protein. Specific PGF₂α binding to the low-affinity site, but not to the high-affinity site, could be enhanced most potently by GTP[γS] followed by GDP[ϐS] and GTP, but not by ATP[γS] or GMP. PGF₂α competed most potently with [³H]PGF₂α for specific binding to hepatocyte plasma membranes, followed by PGD₂ and PGE₂. Since the low-affinity PGF₂α-binding site had a Kd in the concentration range in which PG had previously been shown to be half-maximally active, and since this binding site showed a sensitivity to GTP, it is concluded that it might represent the receptor involved in the PGF₂α signal chain in hepatocytes. A biological function of the high-affinity site is currently not known.
Die vorliegende Arbeit berichtet über die Entwicklung des „Fragebogen zum Studieninteresse" (FSI) und seine testtheoretische Überprüfung. An der Untersuchung nahmen 298 Studenten verschiedener Studiengänge teil. Ausgehend von einer 27 Items umfassenden Version verblieben aufgrund von Faktorenanalyse und Rasch- Skalierung 18 Items, die eine eindimensionale Skala bilden. Die interne Konsistenz (Alpha) des revidierten FSI beträgt .90, die Test-Retest-Reliabilität .67 (Zeitspanne: 2 Jahre). Zur Prüfung der Validität des revidierten FSI wurde eine Reihe weiterer Variablen erhoben (z.B. intrinsische motivationale Orientierung, Tätigkeitszentrierung, Extraversion, Verwendung von Lernstrategien, Studienleistung). Die Ergebnisse zeigen, daß der FSI in ausreichendem Maße konvergente, diskriminante und kriteriumsbezogene Validität besitzt.
In der vorliegenden Arbeit wird argumentiert, daß das Erleben von „Flow" im Prozeß des Lernens für das Entstehen von intrinsischer Lernmotivation und für die kognitive Entwicklung der Schüler von entscheidender Bedeutung ist. Die FIow-Theorie von M. Csikszentmihalyi wird ausführlich dargestellt und ihre Relevanz für den Lernprozeß erläutert. Es werden zwei empirische Studien berichtet, die die Auswirkungen des Flow-Erlebens auf schulisches Lernen belegen. Schließlich wird der Versuch gemacht, Folgerungen für die pädagogische Praxis abzuleiten.
Die Arbeit hat die Inhalte der Verbalflexion im Französischunterricht an Deutschsprachige und ihre Progression zum Gegenstand. Es wird ein von unbeabsichtigten Lücken freies und zugleich auf ein Minimum beschränktes System von temporalen und modalen Kategorien, Verbklassen und Regeln zur Bildung der zusammengesetzten Tempora und Modi sowie zur Angleichung des Participe passé vorgeschlagen. Die Notwendigkeit, die sprachlichen Lehrinhalte zu reduzieren, ohne die Äußerungsmöglichkeiten der Schüler auf bestimmte Themen, Situationen oder Absichten zu beschränken, wird belegt durch Lücken, z.T. überhöhte, z.T. in anderer Hinsicht korrekturbedürftige Pensen in Grammatiken für den Französischunterricht, in Lehrplänen und Lehrwerken. Der zweite Teil der Arbeit enthält präzise Empfehlungen für die chronologische Anordnung und Gruppierung der Lehrinhalte, da den Lehrplan- und Lehrwerkautoren bisher auch für die Planung der Progression verläßliche Grundlagen fehlten. Insgesamt soll die Arbeit einen nicht zeitgebundenen Beitrag zur Planung des Französischunterrichts und zugleich eine Dokumentation des Forschungsstandes darstellen, der in Schulgrammatiken, Lehrplänen und Lehrwerken der letzten 30 Jahre erreicht wurde.
Prostaglandin E₂ has been reported both to stimulate glycogen-phosphorylase activity (glycogenolytic effect) and to inhibit the glucagon-stimulated glycogen-phosphorylase activity (antiglycogenolytic effect) in rat hepatocytes. It was the purpose of this study to resolve this apparent contradiction and to characterize the signalling pathways and receptor subtypes involved in the opposing prostaglandin E₂ actions. Prostaglandin E₂ (10 μM) increased glucose output, glycogen-phosphorylase activity and inositol trisphosphate formation in hepatocyte cell culture andor suspension. In the same systems, prostaglandin E₂ decreased the glucagon-stimulated (1 nM) glycogen-phosphorylase activity and cAMP formation. The signalling pathway leading to the glycogenolytic effect of PGE₂ was interrupted by incubation of the hepatocytes with 4P-phorbol 12-myristate 13-acetate (100 nM) for 10 min, while the antiglycogenolytic effect of prostaglandin E₂ was not attenuated. The signalling pathway leading to the antiglycogenolytic effect of prostaglandin E₂ was interrupted by an incubation of cultured hepatocytes with pertussis toxin (100 ng/ml) for 18 h, whereas the glycogenolytic effect of prostaglandin E₂ was enhanced. The EP₁/EP₃ prostaglandin-E₂-receptor-specific prostaglandin E₂ analogue Sulproston had a stronger glycogenolytic potency than the EP₃ prostaglandin-E₂-receptor-specific prostaglandin E₂ analogue Misoprostol. The antiglycogenolytic potency of both agonists was equal. It is concluded that the glycogenolytic and the antiglycogenolytic effects of prostaglandin E₂ are mediated via different signalling pathways in hepatocytes possibly involving EP₁ and EP₃ prostaglandin E₂ receptors, respectively.
Excerpt: The writings from the thirteenth century called by Gershom Scholem the "Writings of the 'lyyun circle" are one of the most intriguing chapters of early kabbalah - this I need not to elaborate on as it is a well known fact to anyone whoever had read these texts or the literature about them. When reading these texts, one gets the impression as if the authors had at hand a box full of terms and phrases into which everybody could just stick his hand and take terms and phrases out of it in order to arrange them according to his own taste, disregarding the meaning they have in the writings of his fellow kabbalists. The result was, that we now have before us a large number of varying mosaic pictures in which we detect again and again the same mosaic pebbles, however composed differently.
Increase in prostanoid formation in rat liver macrophages (Kupffer cells) by human anaphylatoxin C3a
(1993)
Human anaphylatoxin C3a increases glycogenolysis in perfused rat liver. This action is inhibited by prostanoid synthesis inhibitors and prostanoid antagonists. Because prostanoids but not anaphylatoxin C3a can increase glycogenolysis in hepatocytes, it has been proposed that prostanoid formation in nonparenchymal cells represents an important step in the C3a-dependent increase in hepatic glycogenolysis. This study shows that (a) human anaphylatoxin C3a (0.1 to 10 mug/ml) dose-dependently increased prostaglandin D2, thromboxane B, and prostaglandin F2alpha formation in rat liver macrophages (Kupffer cells); (b) the C3a-mediated increase in prostanoid formation was maximal after 2 min and showed tachyphylaxis; and (c) the C3a-elicited prostanoid formation could be inhibited specifically by preincubation of C3a with carboxypeptidase B to remove the essential C-terminal arginine or by preincubation of C3a with Fab fragments of a neutralizing monoclonal antibody. These data support the hypothesis that the C3a-dependent activation of hepatic glycogenolysis is mediated by way of a C3a-induced prostanoid production in Kupffer cells.
Die gegenwärtig diskutierten Verfahren zur Erfassung von Lernstrategien, Lernstilen und Lernorientierungen können in zwei Gruppen unterteilt werden. Die erste Gruppe ist induktiv konstruiert worden und hat auf der Grundlage von Interviewstudien relativ globale Lernermerkmale postuliert. Typisch für diese Verfahren ist auch die Integration motivationaler und kognitiver Komponenten des Lernverhaltens. Die zweite Gruppe zeichnet sich durch ein deduktives Vorgehen aus. Ausgehend von kognitionspsychologischen Modellen des Lernprozesses sowie verschiedenen Motivationstheorien wurden differenzierte Tragebögen zu Lernstrategien undmotivationalen Merkmalen entwickelt. Die kognitiven und motivationalen Komponenten sind dabei strikt getrennt worden. Der vorliegende Artikel stellt beide Gruppen von Verfahren anhand ausgewählter Beispiele dar und diskutiert ihre Vor- und Nachteile.
In perfused rat livers, infusion of prostaglandin F₂α (PGF₂α) or noradrenaline increased glucose and lactate output and reduced flow. Glucagon increased glucose output and decreased lactate output without influence on flow. Infusion of phorbol 13-myristate 14-acetate (PMA) for 20 min prior to these stimuli strongly inhibited the metabolic and hemodynamic effects of noradrenaline, reduced the metabolic actions of PGF₂α but did not alter the effects of glucagon. In isolated rat hepatocytes PGF₂α, noradrenaline and glucagon activated glycogen phosphorylase but only PGF₂α and noradrenaline increased intracellular inositol 1,4,5-1risphosphalc (InsP₃). The noradrenaline- or PGF₂α-elicited activation of glycogen phosphorylase and increase in InsP₃ were largely reduced after preincubation of the cells for 10 min with PMA, whereas the glucagon-mediated enzyme activation was not affected. In contra\t to PMA, the phorbol ester 4a-phorbol 13,14-didecanoate. which does not activate protein kinase C, did not attenuate the PGF₂α- and noradrenaline-elicited stimulation of glucose output, glycogen phosphorylase and InsP, formation. Stimulation of InsP₃ formation by AlF₄⁻, which activates phospholipase C independently of the receptor, was not attenuated by prior incubation with PMA. Plasma membranes purified from isolated hepatocytes had both a high-capacity, low-affinity and a low-capacity, high-affinity binding site for PGF₂α. The Kd of the high-capacity, low-affinity binding site was close to the concentration of PGF₂α that increased glycogen phosphorylase activity halfmaximally. Binding to the high-capacity, low-affinity binding site was enhanced by guanosine 5'- 0-(3-thio)triphosphate (GTP[S]). This high-capacity, low-affinity site might thus represent the receptor. The Bmax and Kd of the high-capacity site, as well as the enhancement by GTP[S] of PGF₂α binding to this site, remained unaffected by PMA pretreatment. It is concluded that, in hepatocytes, activation of protein kinase C by PMA interrupted the InsP₃-mediated signal pathway from PGF₂α via a PGF₂α receptor and phospholipase C to glycogen phosphorylase at a point distal of the receptor prior to phospholipase C.