1,721,318 research outputs found
Reconstructing the phylogeny of 21 completely sequenced arthropod species based on their motor proteins
Full text linkAbstract Background Motor proteins have extensively been studied in the past and consist of large superfamilies. They are involved in diverse processes like cell division, cellular transport, neuronal transport processes, or muscle contraction, to name a few. Vertebrates contain up to 60 myosins and about the same number of kinesins that are spread over more than a dozen distinct classes. Results Here, we present the comparative genomic analysis of the motor protein repertoire of 21 completely sequenced arthropod species using the owl limpet Lottia gigantea as outgroup. Arthropods contain up to 17 myosins grouped into 13 classes. The myosins are in almost all cases clear paralogs, and thus the evolution of the arthropod myosin inventory is mainly determined by gene losses. Arthropod species contain up to 29 kinesins spread over 13 classes. In contrast to the myosins, the evolution of the arthropod kinesin inventory is not only determined by gene losses but also by many subtaxon-specific and species-specific gene duplications. All arthropods contain each of the subunits of the cytoplasmic dynein/dynactin complex. Except for the dynein light chains and the p150 dynactin subunit they contain single gene copies of the other subunits. Especially the roadblock light chain repertoire is very species-specific. Conclusion All 21 completely sequenced arthropods, including the twelve sequenced Drosophila species, contain a species-specific set of motor proteins. The phylogenetic analysis of all genes as well as the protein repertoire placed Daphnia pulex closest to the root of the Arthropoda. The louse Pediculus humanus corporis is the closest relative to Daphnia followed by the group of the honeybee Apis mellifera and the jewel wasp Nasonia vitripennis. After this group the rust-red flour beetle Tribolium castaneum and the silkworm Bombyx mori diverged very closely from the lineage leading to the Drosophila species.</p
Classification of Students’ Conceptual Understanding in STEM Education using Their Visual Attention Distributions: A Comparison of Three Machine-Learning Approaches
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Förderung von Konzeptverständnis und Repräsentationskompetenz durch Tablet-PC-gestützte Videoanalyse
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Using Smartphones as Experimental Tools—a Follow-up: Cognitive Effects by Video Analysis and Reduction of Cognitive Load by Multiple Representations
Full text linkMobile devices (smartphones or tablets) as experimental tools (METs) offer inspiring possibilities for science education, but until now, there has been little research studying this approach. Previous research indicated that METs have positive effects on students’ interest and curiosity. The present investigation focuses on potential cognitive effects of METs using video analyses on tablets to investigate pendulum movements and an instruction that has been used before to study effects of smartphones’ acceleration sensors. In a quasi-experimental repeated-measurement design, a treatment group uses METs (TG, NTG = 23) and a control group works with traditional experimental tools (CG, NCG = 28) to study the effects on interest, curiosity, and learning achievement. Moreover, various control variables were taken into account. We suppose that pupils in the TG have a lower extraneous cognitive load and higher learning achievement than those in the CG working with traditional experimental tools. ANCOVAs showed significantly higher levels of learning achievement in the TG (medium effect size). No differences were found for interest, curiosity, or cognitive load. This might be due to a smaller material context provided by tablets, in comparison to smartphones, as more pupils possess and are familiar with smartphones than with tablets. Another reason for the unchanged interest might be the composition of the sample: While previous research showed that especially originally less-interested students profited most from using METs, the current sample contained only specialized courses, i.e., students with a high original interest, for whom the effect of METs on their interest is presumably smaller
Using Mobile Devices to Augment Inquiry-Based Learning Processes with Multiple Representations
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