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Raising the bar for reading comprehension
No full textMechteld van Kuijk onderzocht de resultaten van een nascholingsprogramma van leerkrachten in het basisonderwijs voor het vak begrijpend lezen, het Streef Middenbouw-project. De groep 4- en 5-leerlingen presteerden aan het eind van het nascholingsjaar aanzienlijk beter op de Cito-toets voor begrijpend lezen dan vergelijkbare klassen met vergelijkbare leerlingen van wie de leerkrachten niet aan een project meededen. Het leverde bij de kinderen een voorsprong in leesvaardigheid op dat gelijk staat aan ruim een half jaar onderwijs. Bij toepassing in de klas van een aangeleerde instructietechniek, waarbij de leerkracht hardop denkend voordoet hoe hij/zij een leesstrategie toepast, gingen de leerlingen beter lezen.
Tijdens de nascholing stonden drie thema’s centraal namelijk 1) doelen gebaseerd op leerstandaarden, 2) opbrengstgericht werken en 3) effectieve instructie en vakspecifieke kennis voor begrijpend lezen. In het kader van deze thema’s zijn leerkrachten bezig geweest met de vragen 1) Wat is mijn koers?, 2) Lig ik met mijn leerlingen op koers? en 3) Hoe krijg ik mijn leerlingen op koers? Het nascholingsproject is uitgevoerd in het schooljaar 2011-2012. In totaal hebben 33 leerkrachten meegedaan aan de nascholing. Deze leerkrachten gaven les aan 451 leerlingen op 19 scholen in Noord-Nederland. Bijna tachtig procent van de Streef Middenbouw-leerlingen presteerde op of hoger dan het gewenste niveau. Uit klassenobservaties bleek wel dat nog niet alle elementen uit de nascholing even optimaal werden geïmplementeerd door de leerkrachten.
As reading constitutes an important basis for learning, working and living, an important goal of primary schools is to equip students with sufficient reading skills. In the research of Mechteld van Kuijk, it was investigated whether an evidence-based teacher Professional Development (PD) program would help to improve students’ reading comprehension skills. The PD program targeted second- and third-grade teachers (student age: 7 to 9 years old) due to concerns about reading performance in this age group. The participating teachers were supported in improving their practice with help of three components: 1) setting standards and performance goals for every student, 2) applying formative assessment and data use, and 3) acquiring relevant instructional skills and (content and curriculum) knowledge in reading comprehension. Using these components, the teachers focused on answering the questions 1) Where am I going?, 2) How am I going? and 3) How can I improve how I am going? The PD program was conducted in the school year of 2011-2012. In total, 33 second- and third-grade teachers (teaching 451 students in 19 schools) participated. It was found that students whose teachers participated in the PD program outperformed comparable students in comparable classes whose teachers did not participate in the program: this advantage was comparable to a little over 6 months of schooling. Almost 80 percent of students in the program performed at or above the desired level. Yet it was found that not all elements from the PD program were implemented by the participating teachers.
Good Vibrations – Effects of Whole Body Vibration on Attention in Healthy Individuals and Individuals with ADHD
No full textObjectives: Most of the current treatment strategies of ADHD are associated with a number of disadvantages which strengthen the need for alternative or additional approaches for the treatment of ADHD. In this respect, Whole Body Vibration (WBV) might be interesting as it was found to have beneficial effects on a variety of physiological measures. The present study explored the effects of WBV on attention of healthy individuals and adults diagnosed with ADHD.
Methods: Eighty-three healthy individuals and seventeen adults diagnosed with ADHD participated in the study. WBV treatment was applied passively, while participants were sitting on a chair which was mounted on a vibrating platform. A repeated measure design was employed in order to explore potential effects of WBV treatment on attention within subjects. Attention (i.e. inhibitory control) was measured with a color-word interference paradigm.
Results: A period of two minutes of WBV treatment had significant beneficial effects of small to medium size on attention of both healthy individuals and adults with ADHD. The effect of WBV treatment on attention did not differ significantly between groups.
Conclusions: WBV was demonstrated to improve cognitive performance of healthy individuals as well as of individuals with ADHD. WBV treatment is relatively inexpensive and easy to apply and might therefore be of potential relevance for clinical use. The application of WBV treatment as a cognitive enhancement strategy and as a potential treatment of cognitive impairments is discussed.
Stabilization of cyclohexanone monooxygenase by a computationally designed disulfide bond spanning only one residue
No full textEnzyme stability is an important parameter in biocatalytic applications, and there is a strong need for efficient methods to generate robust enzymes. We investigated whether stabilizing disulfide bonds can be computationally designed based on a model structure. In our approach, unlike in previous disulfide engineering studies, short bonds spanning only a few residues were included. We used cyclohexanone monooxygenase (CHMO), a Baeyer–Villiger monooxygenase (BVMO) from Acinetobacter sp. NCIMB9871 as the target enzyme. This enzyme has been the prototype BVMO for many biocatalytic studies even though it is notoriously labile. After creating a small library of mutant enzymes with introduced cysteine pairs and subsequent screening for improved thermostability, three stabilizing disulfide bonds were identified. The introduced disulfide bonds are all within 12 Å of each other, suggesting this particular region is critical for unfolding. This study shows that stabilizing disulfide bonds do not have to span many residues, as the most stabilizing disulfide bond, L323C–A325C, spans only one residue while it stabilizes the enzyme, as shown by a 6 °C increase in its apparent melting temperature.
Biogeochemical cycling of zinc and its isotopes in the Southern Ocean
No full textWe report Zn concentration and isotope data for seawater samples from the Atlantic sector of the Southern Ocean, collected during the IPY/GEOTRACES ANT-XXIV/III cruise along the Greenwich Zero Meridian. Data are reported for the full depth range of the water column at three stations, as well as a transect of surface samples, using a new analytical approach that is presented in detail here.
Zn concentrations increase with depth, though due to proximity to upwelling sites, surface concentrations are not as low as in some parts of the ocean such as further northward into the Sub-Antarctic Zone. For two depth profiles south of the Polar Front Zone, the physical stratification of the upper water column is reflected in sudden near-surface changes in Zn concentration with depth. In contrast, beneath 100–300 m Zn concentrations barely change with depth. Zn isotopic data beneath 1000 m, for the Southern Ocean data presented here as well as published data from the North Atlantic and North Pacific, are strikingly homogeneous, with an average δ66Zn = +0.53 ± 0.14‰ (2SD, 2SE = 0.03, n = 21). The surface Southern Ocean is more variable, with δ66Zn ranging from 0.07‰ to 0.80‰. Between the two is a thin horizon at 40–80 m which, in the Southern Ocean as well as the North Atlantic and North Pacific, is characterised by distinctly light isotopic signatures, with δ66Zn about 0.3‰ lower than surface waters.
Strong correlations between Si and Zn concentrations seen here and elsewhere, coupled to the lack of any systematic relationship between Si and Zn isotopes in the Southern Ocean, suggest that the removal of Zn associated with diatom opal involves little or no isotopic fractionation. Regeneration of this Zn also explains the homogeneous Zn isotopic composition of the global deep ocean so far sampled. However, the low Zn content of opal requires that deep ocean Zn does not directly come from the opal phase itself, but rather from associated organic material external to the diatom frustule during growth. Experimental data are consistent with little or no fractionation during incorporation of Zn into this material. On the other hand, the light zinc at 40–80 m is most consistent with the regeneration of an intra-cellular pool that both culturing experiments and field data suggest will be isotopically light. The data thus imply two processes by which Zn is taken up in the surface ocean, that these pools have very different regeneration lengthscales, and that physical mixing of the oceans cannot eradicate their isotopic signatures. Finally, the deep δ66Zn ocean value is significantly higher than the current best estimate of the input to the oceans. The most obvious candidate for the required light sink is the survival of some of the cellular Zn to be buried in sediment.
Industry structure and collusion with uniform yardstick competition: theory and experiments
No full textWe study cartel stability in an industry that is subject to uniform yardstick regulation. In a theoretical model, we show that the number of symmetric firms does not affect collusion. In a laboratory experiment, however, we do find an effect. If anything, increasing the number of firms facilitates collusion. Our theory suggests that an increase in heterogeneity increases the regulated price if firms do not collude, but also makes collusion harder, rendering the net effect ambiguous. Our experiment suggests that the effect of collusion is stronger.
Anomalous scaling of spin accumulation in ferromagnetic tunnel devices with silicon and germanium
No full textThe magnitude of spin accumulation created in semiconductors by electrical injection of spin-polarized electrons from a ferromagnetic tunnel contact is investigated, focusing on how the spin signal detected in a Hanle measurement varies with the thickness of the tunnel oxide. An extensive set of spin-transport data for Si and Ge magnetic tunnel devices reveals a scaling with the tunnel resistance that violates the core feature of available theories, namely, the linear proportionality of the spin voltage to the injected spin current density. Instead, an anomalous scaling of the spin signal with the tunnel resistance is observed, following a power law with an exponent between 0.75 and 1 over 6 decades. The scaling extends to tunnel resistance values larger than 10^9 Ω μm2, far beyond the regime where the classical impedance mismatch or back flow into the ferromagnet play a role. This scaling is incompatible with existing theory for direct tunnel injection of spins into the semiconductor. It also demonstrates conclusively that the large spin signal does not originate from two-step tunneling via localized states near the oxide/semiconductor interface. Control experiments show that spin accumulation in localized states within the tunnel barrier or artifacts are also not responsible. Altogether, the scaling results suggest that, contrary to all existing descriptions, the spin signal is proportional to the applied bias voltage, rather than the (spin) current.
Sensory ecology of Ruffs (Philomachus pugnax): Why feed by day on night-active worms?
No full textDe begeleider en/of auteur heeft geen toestemming gegeven tot het openbaar maken van de scriptie.
The supervisor and/or the author did not authorize public publication of the thesis.