124 research outputs found
EmMa â ErzieherInnen machen Mathe
Die Ergebnisse zahlreicher Untersuchungen heben die Bedeutung frĂŒher mathematischer Bildungsprozesse eindrucksvoll hervor. So konnte gezeigt werden, dass Kinder ihre Schullaufbahn teilweise mit betrĂ€chtlichen mathematischen Erfahrungen beginnen (vgl. Fuson 1988; Hasemann 2003) diese allerdings sehr heterogen ausgeprĂ€gt sind (vgl. Krajewski 2003; GrĂŒĂing & Peter-Koop 2008). Es wurde ebenfalls festgestellt, dass das Vorwissen der Kinder bereits ein Jahr vor der Einschulung einen deutlicheren Einfluss auf die spĂ€teren Mathematikleistungen hat als z.B. Intelligenz (vgl. Dornheim 2008). Förderungen die von den Erziehenden der Kinder durchgefĂŒhrt werden, dabei methodisch alltagsintegriert und inhaltlich an den FĂ€higkeiten der Kinder anknĂŒpfen, wirken sich positiv und nachhaltig auf die mathematischen Kompetenzen der Kinder aus (vgl. GrĂŒĂing & Peter-Koop 2008; Gasteiger 2010). Ausgehend von diesen Befunden scheint es, auch um negative Erfahrungen in Bezug auf spĂ€teres Mathematiklernen zu vermeiden, notwendig und sinnvoll Kinder vorschulisch mathematisch anzuregen. Diese Aufgabe verlangt von den beteiligten Erziehenden neben einer kontinuierlichen Beobachtung und Dokumentation auch ein hohes MaĂ an Fachkompetenz und pĂ€dagogisch-didaktischer Handlungskompetenz (vgl. Gasteiger im Druck). Um Erziehende in Kindertageseinrichtungen, die im Rahmen ihrer Ausbildung kaum mathematikdidaktische Inhalte erarbeiten, bei dieser Aufgabe zu unterstĂŒtzen, bedarf es MaĂnahmen der Professionalisierung
Auf den PĂ€dagogen kommt es an â Zum möglichen Zusammenhang pĂ€dagogischer QualitĂ€t und mathematischer Basisfertigkeiten von Vorschulkindern
Polymers in disordered environments
Using a combination of analytical theory and newly developed numerical algorithms, we analyze the most pertinent conformational characteristics of three paradigmatic types of polymers in disordered environments: (i) flexible polymers in quenched, self-similar disorder as represented by a self-avoiding random walk on a critical percolation cluster, (ii) semiflexible polymers in quenched, steric disorder as represented by an equilibrium hard-disk fluid and (iii) semiflexible polymers subject to the random energy landscape that emerges from a surrounding network of similar semiflexible polymers
Molecular characterization of two new alternaviruses identified in members of the fungal family Nectriaceae
Since the first report in 2009, at least ten additional viruses have been identified and assigned to the proposed virus family Alternaviridae. Here we report two new mycoviruses tentatively assigned to this family, both identified as members of the fungal family Nectriaceae, which were isolated from surface-disinfected apple roots (Malus x domestica, Borkh.) affected by apple replant disease (ARD). ARD is a highly complex, worldwide-occurring disease resulting from plant reactions to a disturbed (micro)-biome and leads to high economic losses every year. The first alternavirus characterized in this study was identified in a Dactylonectria torresensis isolate. The virus was tentatively named dactylonectria torresensis alternavirus 1 (DtAV1) as the first member of the proposed new species Alternavirus dactylonectriae. The second virus was identified in an isolate of Ilyonectria robusta and was tentatively named ilyonectria robusta alternavirus 1 (IrAV1) as the first member of the proposed new species Alternavirus ilyonectriae. Full genomic sequences of the viruses were determined and are presented. Further, we found hints for putative components of a methyl transferase machinery using in silico approaches. This putative protein domain is encoded by segment 2. However, this result only establishes the basis for subsequent studies in which the function must be confirmed experimentally in vitro. Thus, this is the first study where a function is predicted to all three genomic segments within the group of the alternaviruses. These findings provide further insights into the virome of ARD-associated fungi and are therefore another brick in the wall of understanding the complexity of the disease
High Strain Rate and Stress-State-Dependent Martensite Transformation in AISI 304 at Low Temperatures
Deformation-induced martensitic transformation as the basis of a hardening process is dependent, among others, on the stress state. In applications such as cryogenic cutting, where a hardened martensitic subsurface can be produced in metastable austenitic steels, different stress states exist. Furthermore, cutting typically occurs at high strain rates greater than 103sâ1. In order to gain a deeper insight into the behavior of a metastable austenitic steel (AISI 304) upon cryogenic cutting, the influence of high strain rates under different loading conditions was analyzed. It was observed that higher strain rates lead to a decrease in the αâČ-martensite content if exposed to tensile loads due to generated adiabatic heat. Furthermore, a lath-like αâČ-martensite was induced. Under shear stress, no suppression of αâČ-martensite formation by higher strain rates was found. A lath αâČ-martensite was formed, too. In the specimens that were subjected exclusively to compressive loading, almost no αâČ-martensite was present. The martensitic surface generated by cutting experiments showed deformation lines in which αâČ-martensite was formed in a wave-like shape. As for the shear specimens, more αâČ-martensite was formed with increasing strain rate, i.e., force. Additionally, magnetic etching proved to be an effective method to verify the transformation of ferromagnetic αâČ-martensite
Non-destructive, Contactless and Real-Time Capable Determination of the 뱉-Martensite Content in Modified Subsurfaces of AISI 304
Cryogenic turning can be used to produce deformation-induced martensite in metastable austenitic steels. Martensite exhibits a higher hardness than austenite and increases the wear resistance of the workpiece. In order to reliably induce a desired martensite content in the subsurface zone during the turning process, a non-destructive, contactless and real-time testing method is necessary. Eddy current testing is an electromagnetic method that is non-destructive, non-contact and real-time capable. Furthermore, eddy current testing has been integrated into production processes many times. Eddy current testing can be used to detect the transformation of paramagnetic austenite to ferromagnetic αâČ-martensite based on the change in magnetic and electrical properties. Thus, the newly formed subsurface can be characterized and the manufacturing process can be monitored. The objective of this study was to understand the correlation of eddy current testing signals with newly formed αâČ-martensite in the subsurface of AISI 304 and to quantify the amount formed. The measurements were performed within a machining center. Several methods for reference measurement of martensite content are known in the literature. However, depending on the method used, large discrepancies may occur between the determined contents. Therefore, different analytical methods were used for reference measurements to determine the total martensite content in the subsurface. Metallographic sections, magnetic etching, Mössbauer spectroscopy, and X-ray diffraction with two different analytical methods were employed. Based on the correlation between the eddy current testing signals and the αâČ-martensite content in the subsurface, process control of the manufacturing process can be achieved in the future
The population biology of the living coelacanth studied over 21Â years
Between 1986 and 2009 nine submersible and
remote-operated vehicle expeditions were carried out to
study the population biology of the coelacanth Latimeria
chalumnae in the Comoro Islands, located in the western
Indian Ocean. Latimeria live in large overlapping home
ranges that can be occupied for as long as 21 years. Most
individuals are confined to relatively small home ranges,
resting in the same caves during the day. One hundred and
forty five coelacanths are individually known, and we
estimate the total population size of Grande Comore as
approximately 300â400 adult individuals. The local population
inhabiting a census area along an 8-km section of
coastline remained stable for at least 18 years. Using
LASER-assisted observations, we recorded length frequencies
between 100 and 200 cm total length and did not
encounter smaller-bodied individuals (\100 cm total
length). It appears that coelacanth recruitment in the
observation areas occur mainly by immigrating adults. We
estimate that the mean numbers of deaths and newcomers
are 3â4 individuals per year, suggesting that longevity may
exceed 100 years. The domestic fishery represents a threat
to the long-term survival of coelacanths in the study area.
Recent changes in the local fishery include a decrease in
the abundance of the un-motorized canoes associated with
exploitation of coelacanths and an increase in motorized
canoes. Exploitation rates have fallen in recent years, and
by 2000, had fallen to lowest ever reported. Finally, future
fishery developments are discussed
Non-destructive Evaluation of Workpiece Properties along the Hybrid Bearing Bushing Process Chain
To combine the advantages of two materials, hybrid bulk metal workpieces are attractive for subsequent processes such as metal forming. However, hybrid materials rely on the initial bond strength for the effective transfer of applied loads. Thus, a non-destructive evaluation of the bonding along the production process chain is of high interest. To evaluate to what extent non-destructive testing can be employed to monitor the bonding quality between the joining partners steel and aluminum and to characterize the age hardening condition of the aluminum component, ultrasonic testing and electrical conductivity measurements were applied. It was found that a lateral angular co-extrusion process can create homogeneous bonding although the electrical conductivity of the aluminum is altered during processing. A previous bonding before the subsequent die forging process leads to a sufficient bonding in areas with little deformation and is therefore, advantageous compared to unjoined semi-finished products, which do not form a bonding if the deformation ratio is too small. An influence of the subsequent heat treatment on the bonding is not visible in the ultrasonic testing signals though a homogenized electrical conductivity can be detected, which indicates uniform artificial aging conditions of the aluminum allo
Genetic Survey of Psilocybe Natural Products
Psilocybe magic mushrooms are best known for their main natural product, psilocybin, and its dephosphorylated congener, the psychedelic metabolite psilocin. Beyond tryptamines, the secondary metabolome of these fungi is poorly understood. The genomes of five species ( P. azurescens , P. cubensis , P.â
cyanescens , P. mexicana , and P. serbica ) were browsed to understand more profoundly common and speciesâspecific metabolic capacities. The genomic analyses revealed a much greater and yet unexplored metabolic diversity than evident from parallel chemical analyses. P. cyanescens and P. mexicana were identified as aeruginascin producers. Lumichrome and verpacamide A were also detected as Psilocybe metabolites. The observations concerning the potential secondary metabolome of this fungal genus support pharmacological and toxicological efforts to find a rational basis for yet elusive phenomena, such as paralytic effects, attributed to consumption of some magic mushrooms
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