In this study which was part of the DISUM-project, 224 ninth graders from 14 German classes from middle track schools (Realschule) were asked about their enjoyment, interest, value and self-efficacy expectations concerning three types of mathematical problems: intra-mathematical problems, word problems and modelling problems. Enjoyment, interest, value and self-efficacy were assessed before and after a ten-lesson teaching unit promoting modelling competency related to the topics "Pythagoras' theorem" and "linear functions". The study aimed to answer the following research questions: (1) Do students' enjoyment, value, interest and self-efficacy expectations differ depending on the type of task? (2) Does the treatment of modelling problems in classroom instruction influence these variables? (3) Are there any differential effects for different ways of teaching modelling problems, including a "directive", teacher-centred instruction and an "operative-strategic", more studentcentred instruction emphasising group work and strategic scaffolding by the teacher? The findings show that there were no differences in students' enjoyment, interest, value and self-efficacy between the three types of tasks. However, teaching oriented towards modelling problems had positive effects on some of the student variables, with the student-centred teaching method producing the most beneficial effects.

As a first step to exploit the potential of Trichoderma reesei to produce hemicellulases, we have purified two endo-beta-1,4-xylanases (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) and cloned their genes. The enzymes were isolated from culture filtrates of T. reesei C30 grown on xylan as a carbon source, using two steps of cation exchange chromatography. They exhibited molecular weights of 19 (XYN I) and 21 (XYN II) kD, and isoelectric points of 5.2 and 9.0, respectively. These enzymes differed in their pH optimum for activity and affinity for xylan, and accounted for more than 90% of the total xylanolytic activity of the fungus. The purified enzymes were subjected to N-terminal sequence analysis, and after cleavage with trypsin and endoproteinase Glu-C the resulting peptides were sequenced. Oligonucleotides based on these sequences were used to clone gene fragments via PCR, and these were used as probes to isolate full-length copies of xyn1 and xyn2 from a lambda gene bank of T. reesei. The products of xyn1 and xyn2 share considerable homology, but the enzyme encoded by xyn2 appears to more closely resemble several other bacterial and fungal xylanases than does that of xyn1.

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In a study within the DISUM research project, we investigated the role that the construction of situation models plays as an essential prerequisite for understanding a given mathematical modelling task, using a sample of 21 9th grade classes (N = 416). Specific task characteristics, general mathematical competence, reading competence, and teacher interventions aiming at understanding the situation model were analyzed as crucial factors influencing students' ability to solve modelling tasks. The results show that: (1) strategies for constructing an adequate situation model have a significant influence on modelling competence, (2) mathematical reading competence and intra-mathematical competence can explain almost one third of the variance of the performance on the modelling test, (3) teacher interventions may encourage students to adopt strategies facilitating the construction of situation models, but an increase of modelling competence requires separate strategy training.Keywords Modelling competence · Reading comprehension · Situation model · Word problem · Teacher intervention Mathematics Subject Classification (2000) 97C30 · 97C70 · 97D40 · 97D70 · 97M10 Zusammenfassung Im Rahmen einer Studie des Forschungsprojekts DISUM wurde in 21 Realschulklassen der Jahrgangsstufe 9 (N = 416) untersucht, welche Rolle das Konstruieren des Situationsmodells als wesentliche Voraussetzung für das Verstehens einer gegebenen Aufgabenstellung bei der Bearbeitung von Modellierungsaufgaben spielt. Als zentrale Einflussfaktoren für die Modellierungskompetenz der Schüler wurden spezifische Aufgabeneigenschaften, die allgemeine mathematische Kompetenz und die Lesekompetenz identifiziert sowie Interventionen, mit denen Lehrpersonen auf das Verstehen einwirken. Dabei zeigen die Ergebnisse der vorliegenden Studie u.a., dass (1) Strategien zur Konstruktion eines adäquaten Situationsmodells einen signifikanten Einfluss auf die Modellierungskompetenz haben, (2) mathematische Lesekompetenz und innermathematische Kompetenzen knapp ein Drittel der Leistungsvarianz des Modellierungstests erklären können, (3) Lehrerinterventionen im Unterricht zwar die Anwendung solcher situationsmodellbezogener Strategien bei den Schülern anregen können, individuelle Leistungssteigerungen aber offenbar eines gesonderten Strategientrainings bedürfen.

The effect of inhibiting protein glycosylation was studied in nongrowing mycelia and protoplasts of Trichoderma reesei which secreted two endoglucanases (I and II) upon addition of sophorose. Tunicamycin (40 μg∙mL−1) inhibited incorporation of N-acetylglucosamine into secreted protein, but had no effect on secretion of total protein or endoglucanases. The secreted endoglucanases I and II exhibited relative molecular masses of 58 and 45 kilodaltons, respectively, irrespective of the presence of tunicamycin. On the other hand 2-deoxy-D-glucose inhibited the biosynthesis of extracellular as well as intracellular protein over a wide range of concentrations; at 50 μg∙mL−1, however, it inhibited the synthesis of extracellular protein more strongly. The synthesis of endoglucanases I and II was decreased accordingly under these conditions. SDS–PAGE did not reveal the secretion of endoglucanases with smaller molecular weights. When the two endoglucanases were purified and subjected to Endo H treatment or β-elimination, the former had no detectable effect, whereas the latter released all carbohydrate from the protein. Nevertheless, endoglucanases I and II contained 1.3 and 0.5 mol of glucosamine per mol enzyme, respectively. It is concluded that endoglucanases I and II from T. reesei contain mainly O-linked neutral carbohydrate, which is required for their secretion.

The qualitative and quantitative monosaccharide spectra of purified yeast cell walls revealed that there are three phylogenetically distinct lineages of sterigma-forming basidiomycetous yeasts: (i) Kurtzmanomyces and Sterigmatomyces species, which contain high levels of mannose; (ii) Tilletiopsis species, which contain glucose, galactose, and small amounts of mannose; and (iii) Fellomyces, Kockovaella, Sterigmatosporidium, and Tsuchiyaea species, which appear to be closely related on the basis of their high levels of glucose and the presence of xylose. The yeast cell wall neutral sugars of Sporobolomyces antarcticus and Sterigmatomyces aphidis were similar to those of members of the genus Tilletiopsis. However, the possibility that these taxa are conspecific was eliminated by the results of a random amplified polymorphic DNA (RAPD) analysis. The conspecificity of Mrakia jiigida and Mrakia nivalis, the conspecificity of Mrakia gelida and Mrakia stokesii, and the conspecificity of Sterigmatomyces halophilus and Sterigmatomyces indicus were confirmed by RAPD analysis results. RAPD analysis was found to be a simple and highly sensitive method which can be used to differentiate species at the DNA level; it can replace nuclear DNA-nuclear DNA hybridization experiments for species identification, characterization, and delimitation.The genus Mrakia was proposed for Leucosporidium fngidum as a new genus of the Filobasidiaceae by Yamada and Komagata (51). The following four species that formerly had been placed in the genus Leucosporidium were transferred to the genus Mrakia: Mrakia Jizgida, Mrakia gelida, Mrakia nivalis, and Mrakia stokesii (7, 8, 51). A homothallic, apomictic life cycle, self-sporulating simple holobasidia bearing terminal, sessile basidiospores, fermentation of sugars, the presence of ubiquinone Q-8, production of extracellular amyloid compounds, and yeast cell walls containing xylose are the most distinctive features of Mrakia species (14,26,32,51). The fact that the genus Mrakia should be separated from phragmobasidial, smut-like Leucosporidium species (31) has been corroborated by the results of determinations of parts of the 18s and 26s rRNA sequences (6, 9,48) and ultrastructural septa1 pore data (37).The Mrakia species originally defined on the basis of their ability to ferment glucose and their ability to utilize nitrate or various carbon compounds (cellobiose, maltose, maltose, melibiose, raffinose) for growth (7, 8) turned out to be questionable taxa after investigations of the electrophoretic enzyme patterns (39, 52) and parts of the 18s and 26s rRNA sequences (6, 9, 48). The electrophoretic enzyme patterns (52) suggested that M. nivalis and M. stokesii are synonyms of M. fngida and M. gelida, respectively.The genus Sterigmatomyces was introduced by Fell (5) for nonfilamentous, yeast-like fungi that are characterized by a unique method of cell division. The yeast cells produce one or more sterigmata, each of which gives rise to a single conidium.