Esterification of xylan with ibuprofen via activiation of the carboxylic acid with N,N′‐carbonyldiimidazole (CDI) yields products of high drug loadings. Subsequent sulfation of xylan ibuprofen esters ...using the gentle agent SO3/DMF was successfully carried out in order to modify hydrophobicity of the xylan esters. The structure of the novel xylan esters was evaluated by means of NMR spectroscopy. The resulting xylan derivatives self assemble into spherical nanoparticles with mean diameters ranging from 162 to 472 nm. Preliminary stability measurements indicate that hydrolytic stability decreases with increase in degree of substitution of sulfate groups. Thus, a new concept toward improved drug delivery from polysaccharide‐based nanoparticles can be established here.
Well defined xylan ibuprofen esters were prepared. Activation with N,N′‐carbonyldiimidazole and coupling of the anti‐inflammatory ibuprofen carboxylic acid at xylan proofed to be efficient in dimethylsulfoxide. The degree of substitution can be adjusted by variation of the ratios of ibuprofen and xylan. Subsequent sulfation of the xylan ibuprofen esters was performed to modify the polarity of products. The novel xylan derivatives were characterized by NMR spectroscopy. The xylan esters show nanoparticle formation behavior, with varying properties regarding size and stability in dependence of the polarity of the products.
Background
Fair comparisons of educational systems in large-scale assessments can be made only if the differences in curricula have little impact on the outcomes. This study investigated the ...sensitivity of science achievement rankings to varying degrees of curriculum implementation in the Trends in International Mathematics and Science Study (TIMSS).
Methods
Country-specific teacher-reported curriculum implementation profiles across the TIMSS science domains were charted including their within-country variability across the classrooms for 33 participating countries of TIMSS 2015. A sensitivity test compared the original ranking to TIMSS curriculum implementation scenarios (a least-possible, a most-possible, and more realistic country-specific median implementation).
Results
In contrast to expectations, no support was found for a positive relationship between opportunity to learn and science achievement at the between-country level or the within-country level, with only minor exceptions. The sensitivity analysis under different curriculum implementation scenarios also suggests little impact on the rank order of the countries.
Conclusions
Plausible explanations for this null finding are addressed; attention and research efforts should focus on improving the quality of curriculum implementation indicators in large-scale assessments.
► Chemical modification is most promising to design new xylan based materials. ► Own results in synthesis of non- and ionic xylan derivatives are mainly reviewed. ► The syntheses are described ...regarding control of substituent distribution. ► Properties of the derivatives are highlighted, e.g. formation of nanostructures. ► Application potential of the xylan derivatives is discussed.
The chemical modification of xylan is a promising path to new biopolymer ethers and esters with specific properties depending on the functional groups, the degree of substitution, and the substitution pattern. The reaction of 4-O-methylglucuronoxylan (GX) from birch with sodium monochloroacetate and 2,3-epoxypropyltrimethylammonium chloride in aqueous sodium hydroxide/slurry medium is described. The influence of the conditions of activation on product structure and properties are discussed in some detail. Methylation of GX was investigated under completely heterogeneous conditions or starting with dissolved polymer using methyl halides as reagents in the presence of NaOH. An activation of the biopolymer has been carried out before the reaction to enhance the accessibility of the reagents. Furthermore, novel xylan esters were efficiently synthesized by conversion of the hemicellulose with furan- and pyroglutamic acid as well as ibuprofen and N,N′-carbonyldiimidazole as activating agent under homogeneous conditions in dimethyl sulfoxide. This conditions are also appropriate to synthesize novel xylan ester containing xylan-4-N,N,N-trimethylammoniumbutyrate chloride moieties. Homogeneous syntheses of xylan sulfates could be carried out in a N,N-dimethylformamide (DMF)/LiCl as solvent applying sulfur trioxide complexes with DMF or pyridine. Advanced analytical techniques including NMR spectroscopy, HPLC, scanning electron microscopy, rheology, measurements of turbidity and surface tension allow description of structure–property-relationships; selected results will be briefly discussed. Xylan esters may form spherical nanoparticles of a size down to 60nm and a narrow particle size distribution applying a simple dialysis process and may be used for drug delivery applications. For cationic xylan derivatives a wide range of applications as paper strength additives, flocculation aids, and antimicrobial agents are proposed.
To improve the understanding of the drivers of interest, and its impact on other outcomes, researchers and educators need valid and informative measures capturing the different domains of interest. ...Answering the lack of interest measures in marketing education, we develop and psychometrically assess three instruments reflecting the theoretical notions of situational and individual interest: course interest, contents interest, and job interest. Drawing on a relatively large sample of Norwegian upper-secondary marketing classes (Nclasses = 22; Nstudents = 433), initial psychometric validation showed that each instrument has good unidimensionality, local item independence, measurement precision across the latent scales, and invariance across instructional approaches, gender, and parental education level. Furthermore, the interest instruments are related but distinct from each other and provide different information than measures of perceptions and achievement. We conclude this first steppingstone by showing the instruments’ information value and discussing future paths for strengthening the validity evidence.
Although there are numerous studies on the development of teachers’ professional digital competence, only a few have studied the intermediate levels of the education system and its impact over time. ...A structural merger of three Norwegian municipalities allowed for a natural field experiment involving two school districts. In the present study, we explored potential differences in early and late adopter effects on teachers from school districts. Survey data were collected to assess teacher-level perceptions of organisational support and access to collaborative professional communities. Teachers also rated themselves according to the Technological, Pedagogical, and Content Knowledge (TPACK) framework for digital competence and answered questions to assess their level of student-centred teaching beliefs. The data were analysed using Structural Equation Model (SEM) to explore associations between study variables and patterns of differences between school districts. The results indicate that municipality- or school district-level initiatives have influenced the behaviour of school management and in the teacher community, and possibly result in a more student-centred teaching style in the classroom. The present paper adds new insights into how teachers and schools are influenced by the intermediate levels of the education system. The findings from our study may thus be of interest to researchers exploring the professional development of digital competence for teachers and schools. Moreover, as we highlight how school districts approach and support schools in the implementation of one-to-one coverage of digital devices in schools, we bring updated knowledge to this research field.
•A structural merger of municipalities allowed for a natural field experiment.•We explored potential differences in early and late adopter effects on teachers.•Findings indicate a more student-centred teaching style in the classroom over time.•The paper shows that intermediate levels of education system impact professional development of digital competence.
Background
The development and promotion of educational games are still outpacing knowledge of these games' effects, raising calls for evidence of benefits and challenges. Studies suggest that ...students and teachers like games, but the payoff of the investment in terms of increased motivation and achievement remains unclear.
Objectives
This study investigates the pure effect of a marketing simulation game on motivation, perceived learning and achievement, above and beyond regular student‐active instruction.
Methods
We applied a randomized, controlled experiment in a marketing course in upper‐secondary schools (Nclasses = 22; Nstudents = 433) comparing a collaborative–competitive marketing simulation game with regular, case‐based, student‐active instruction on three groups of outcome measures: motivation, perceived ability, and achievement. Additionally, students and teachers provided quantitative and qualitative feedback on game experiences.
Results and Conclusions
We showcase the importance of a robust study design with valid compound instruments. Moreover, investigations of the game implementation and experiences reveal insights about intervention timing, differential negative consequences by gender and need for reflection opportunities. We find no clear evidence of positive or negative effects of the game, despite students' and teachers' satisfaction.
Implications
Beyond the effect evaluation, we offer recommendations to researchers and developers of educational games about scaffolding, timing and teacher competence building.
Lay Description
What is already known about this topic
Some curricula contains many terms and complex knowledge links.
Simulation games are a popular remedy for these challenges.
Prior studies have relied on users' satisfaction with the game and unrealistic comparisons.
What this paper adds
This experiment compares game usage and regular student‐active instruction.
They use various measures of satisfaction, motivation, perceived learning and achievement.
The game has no effect on main outcomes.
Implications for practice and/or policy
Game implementation requires digitally acquainted and trained teachers.
Uncritical game design and use may motivate competitive boys over collaborative girls.
This study offers curriculum developers, teachers, and science education researchers a fine-grained profile on strengths and weaknesses in specific science domains and topics. The study involved a ...representative sample of 3844 Norwegian pupils in grade 8. Their responses on 216 TIMSS items in 18 topics from 4 science domains were modelled in a hierarchical item response model. An internal comparison identified topics that were relatively harder or easier compared to other topics for Norwegian pupils, and an external comparison identified topics that were relatively harder or easier for the Norwegian pupils compared with the average of TIMSS participating countries. Interpretation of the profile necessitates contextualisation; hence, these strengths and weaknesses, as well as their plausible explanations and possible implications, are discussed from the perspectives of curriculum development, teacher training, and science education research.
Low molecular weight xylan was modified at the reducing end with mono and bifunctional amines. Characterization by means of elemental analysis, nmr spectroscopy and mass spectrometry proved the ...success of the highly selective reaction. Modified xylan containing amino groups at the reducing end are capable to react with unmodified xylan and cellodextrins. The structure of the products obtained was proved by NMR spectroscopy. Size exclusion chromatography and mass spectrometry verified the increased molar mass of the head-head linked polysaccharides.
Homogeneous Sulfation of Xylan from Different Sources Daus, Stephan; Petzold-Welcke, Katrin; Kötteritzsch, Manuela ...
Macromolecular materials and engineering,
June 16, 2011, Letnik:
296, Številka:
6
Journal Article
Recenzirano
Xylan sulfates have been prepared under homogeneous reaction conditions in DMF/LiCl applying SO3/pyridine and SO3/DMF. The degree of substitution (DSSulfate) of the products obtained was determined ...by elemental analysis. DSSulfate reached values of up to 1.90 applying a molar ratio of 3 mol sulfating agent per anhydroxylose unit. The structure of the xylans and of the xylan sulfates was studied in detail by one‐ and two‐dimensional NMR spectroscopy and MALDI‐TOF mass spectrometry.
The sulfation of xylan was studied with the objective to obtain well‐characterized potentially bioactive xylan derivatives. Xylans from different plant sources were characterized prior to sulfation. The homogeneous derivatization of these xylans applying SO3‐complexes as sulfating agents was carried out in DMF/LiCl for the first time. It appeared that the DS value of the products can be controlled by varying the amount of the sulfating reagent in relation to the AXU. Structural differences between the xylan sulfates were confirmed by NMR spectroscopy and MALDI‐TOF mass spectrometry. The observed characteristics of xylan sulfates will support future investigations on structure–activity relationships.
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