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91.
This paper investigates teachers’ and students’ perceptions concerning the impact of using tablet devices for teaching and learning purposes. An explorative focus group study was conducted with teachers (n = 18) and students (n = 39) in a secondary school that has implemented tablet devices since 2012. The general finding of this study shows that the use of tablet devices in the classroom setting has an impact on both teaching and learning practices. The results suggest that teachers can be divided into two categories: the innovative teachers and the instrumental teachers. Innovative teachers attempt to shift from a teacher-centered to a learning-centered approach. They have changed their teaching style by transforming lessons in accordance with the advantages tablet computers can offer. Instrumental teachers seem to use the device as a ‘book behind glass’. The distinction between the two groups has consequences for both the way courses are given and how students experience them. In general, the introduction of tablet devices entails a shift in the way students learn, as the devices provide interactive, media-rich, and exciting new environments. The results of this study indicate that policy makers should consider introducing technical and pedagogical support in order to facilitate both teachers’ and students’ understanding of the full potential of this kind of technology in education. 相似文献
92.
93.
Goey AK Sparidans RW Meijerman I Rosing H Schellens JH Beijnen JH 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2011,879(1):41-48
Echinacea purpurea is one of the most popular herbal medicines and is known for its immunostimulatory effects. Alkylamides are the main lipophilic components of E. purpurea that contribute to its pharmacological actions. For quantification in human plasma of one of these alkylamides, undeca-2-ene-8,10-diynoic acid isobutylamide, a sensitive LC-MS/MS assay has been developed and validated. Plasma samples were pretreated using liquid-liquid extraction with a mixture of diethyl ether and n-hexane (50:50, v/v). Dried extracts were reconstituted in 50 μL of acetonitrile-water (50:50, v/v) after which 15 μL of sample was injected into the HPLC system. HPLC was performed using a Polaris 3 C18-A column (50 mm×2 mm ID) and isocratic elution with acetonitrile-water (50:50, v/v) containing 0.1% formic acid at a flow rate of 0.3 mL/min. Subsequently, electrospray ionization in the positive ion mode followed by tandem mass spectrometry was performed for detection. The total run time was 3 min. The assay was validated over a concentration range from 0.05 to 50 ng/mL for undeca-2-ene-8,10-diynoic acid isobutylamide, with 0.05 ng/mL being the lower limit of quantification using 1.0 mL plasma samples. Inter-assay inaccuracy (±12.7%), within-day and between-day precisions (CV≤8.23%) were acceptable. Further, undeca-2-ene-8,10-diynoic acid isobutylamide was found to be chemically stable under relevant conditions. Finally, the applicability of this assay has been successfully demonstrated in a pharmacokinetic experiment in which a human volunteer ingested a commercial extract of E. purpurea. 相似文献
94.
Carola W.N. Damen Han Speijer Jan H.M. Schellens Hilde Rosing 《Analytical biochemistry》2009,393(1):73-57
For the bioanalysis of therapeutic monoclonal antibodies in biological matrices, immunoassays—especially enzyme-linked immunosorbent assays (ELISAs)—are the most widely used techniques. Although ELISAs are very sensitive, the obtained sensitivity is not always sufficient. In this study, we have investigated the possibilities of performing a precipitate-enhanced immunoassay (PEIA) with ellipsometric detection for the bioanalysis of the therapeutic monoclonal antibody trastuzumab. Hydrophobic silicon slides were coated with anti-idiotype trastuzumab antibodies. Trastuzumab in serum samples could bind to this primary catcher, and biotinylated anti-idiotype antibodies were used for detection. After binding of streptavidin-poly-horseradish peroxidase (HRP), the precipitating substrate 3,3′-diaminobenzidine tetrahydrochloride (DAB) was added. Precipitation speed was analyzed using a novel prototype eight-cell ellipsometer, and calibration curves were obtained by plotting this speed versus the trastuzumab concentration. Results demonstrate that the PEIA is at least four times more sensitive than the same ELISA using the chromogenic substrate 3,5,3′,5′-tetramethylbenzidine (TMB) instead of precipitating DAB. The calibration range of the assay is 11 to 700 pg/ml. Serum samples are diluted 10 times prior to incubation corresponding to 110 to 7000 pg/ml in undiluted serum. Validation results demonstrate that these low concentrations can be analyzed accurately and precisely. In addition, samples of a patient treated with trastuzumab were analyzed with both the PEIA and the ELISA. Results demonstrate excellent correlation (r = 0.984) between the methods. Thus, when more sensitivity is required than in a conventional immunoassay, a PEIA with ellipsometric detection may be a useful alternative. The prototype ellipsometer is still in development, and from the data obtained in this study, improvements will be implemented. 相似文献
95.
ABSTRACT: BACKGROUND: Solution-based targeted genomic enrichment (TGE) protocols permit selective sequencing of genomic regions of interest on a massively parallel scale. These protocols could be improved by: 1) modifying or eliminating time consuming steps; 2) increasing yield to reduce input DNA and excessive PCR cycling; and 3) enhancing reproducible. RESULTS: We developed a solution-based TGE method for downstream Illumina sequencing in a non-automated workflow, adding standard Illumina barcode indexes during the post-hybridization amplification to allow for sample pooling prior to sequencing. The method utilizes Agilent SureSelect baits, primers and hybridization reagents for the capture, off-the-shelf reagents for the library preparation steps, and adaptor oligonucleotides for Illumina paired-end sequencing purchased directly from an oligonucleotide manufacturing company. CONCLUSIONS: This solution-based TGE method for Illumina sequencing is optimized for small- or medium-sized laboratories and addresses the weaknesses of standard protocols by reducing the amount of input DNA required, increasing capture yield, optimizing efficiency, and improving reproducibility. 相似文献
96.
97.
Sparidans RW Crul M Schellens JH Beijnen JH 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2002,780(2):423-430
An isocratic bio-analytical assay for the nucleotide gemcitabine triphosphate (2',2'-difluorodeoxycytidine 5'-triphosphate, dFdCTP) in human white blood cells (leukocytes) has been developed and validated. The method is based on ion-exchange liquid chromatography and ultraviolet detection (275 nm). dFdCTP is isolated from the matrix by extraction with perchloric acid while the sample is chilled on ice. After neutralization with potassium hydroxide and removal of the potassium perchlorate precipitate, with the sample still chilled on ice, the mixture is injected into the chromatograph. The method has been validated in the range 0.4-20 microM, 0.4 microM (approximately 20 pmol/10(6) cells) being the lower limit of quantification, using erythrocytes as a substitute for leukocytes. Precisions and accuracies both meet the current requirements for a bioanalytical assay. The stability of dFdCTP in intact mononuclear blood cells on ice is strongly limited (half-life approximately 100 min) and after freezing the half-life of the analyte in the cellular lysate is approximately 30 min. On the other hand, no degradation was observed for dFdCTP for at least approximately 24 h in perchloric acid extracts on ice or in neutralized extracts at ambient temperature. The applicability of the assay was demonstrated in white blood cells of a patient with advanced non-small cell lung cancer receiving i.v. gemcitabine. 相似文献
98.
Carbohydrate recognition by proteins is a key event in many biological
processes. Concanavalin A is known to specifically recognize the
pentasaccharide core (beta-GlcNAc-(1-->2)-alpha- Man-(1-->3)-[beta-
GlcNAc-(1-->2)-alpha-Man-(1-->6)]-Man) of N-linked oligosaccharides
with a Ka of 1.41 x 10(6 )M-1. We have determined the structure of
concanavalin A bound to beta-GlcNAc-(1-->2)-alpha-Man-(1-->3)-[beta-
GlcNAc-(1-->2)-alpha-Man- (1-->6)]-Man to 2.7A. In six of eight
subunits there is clear density for all five sugar residues and a well
ordered binding site. The pentasaccharide adopts the same conformation in
all eight subunits. The binding site is a continuous extended cleft on the
surface of the protein. Van der Waals interactions and hydrogen bonds
anchor the carbohydrate to the protein. Both GlcNAc residues contact the
protein. The GlcNAc on the 1-->6 arm of the pentasaccharide makes
particularly extensive contacts and including two hydrogen bonds. The
binding site of the 1-->3 arm GlcNAc is much less extensive.
Oligosaccharide recognition by Con A occurs through specific protein
carbohydrate interactions and does not require recruitment of adventitious
water molecules. The beta-GlcNAc-(1-->2)-Man glycosidic linkage PSI
torsion angle on the 1-->6 arm is rotated by over 50 degrees from that
observed in solution. This rotation is coupled to disruption of
interactions at the monosaccharide site. We suggest destabilization of the
monosaccharide site and the conformational strain reduces the free energy
liberated by additional interactions at the 1-->6 arm GlcNAc site.
相似文献
99.
van Hoek AH; van Alen TA; Sprakel VS; Hackstein JH; Vogels GD 《Molecular biology and evolution》1998,15(9):1195-1206
The 18S and 5.8S rDNA genes and the internal transcribed spacers ITS-1 and
ITS-2 of ciliates living in the hindgut of frogs, millipedes, and
cockroaches were analyzed in order to study the evolution of intestinal
protists. All ciliates studied here belong to the genus Nycrotherus.
Phylogenetic analysis revealed that these ciliates from a monophyletic
group that includes the distantly related anaerobic free-living
heterotrichous ciliates Metopus palaeformis and Metopus contortus. The
intestinal ciliates from the different vertebrate and invertebrate hosts
are clearly divergent at the level of their rDNA repeats. This argues for
the antiquity of the associations and a predominantly vertical
transmission. This mode of transmission seems to be controlled primarily by
the behavior of the host. The different degrees of divergence between
ciliates living in different strains of one and the same cockroach species
most likely reflect the different geographical origins of the hosts. In
addition, host switches must have occurred during the evolution of
cockroaches, since identical ciliates were found only in distantly related
hosts. These phenomena prevent the reconstruction of potential cospeciation
events.
相似文献
100.
X-ray microanalysis of colloidal-gold-labelled lysosomes in rat liver sinusoidal cells after incubation for acid phosphatase activity 总被引:1,自引:0,他引:1
W. C. de Bruijn J. P. M. Schellens J. M. H. van Buitenen J. van der Meulen 《Histochemistry and cell biology》1980,66(2):137-148
Summary The lysosomal apparatus of the Kupffer and endothelial cells of the sinusoidal lining of the rat liver was found to take up colloidal-gold particles with a mean diameter of 5 nm, prepared according to a modified method. After incubation of the glutaraldehyde-perfusion-fixed tissue in a lead-containing medium for the demonstration of acid phosphatase activity, a reaction product was observed in the gold-loaded lysosomes. By X-ray microanalysis of such lysosomes, the presence of osmium, gold and lead was detected qualitatively in the unstained sections from the tissue, which after the incubation had been post-fixed with an OsO4-solution to which K4Fe(CN)6 had been added to enhance the contrast. The quantitative computer-assisted processing of the X-ray microanalytical data from such lysosomes enabled to determine the gold-to-lead ratio and the individual gold and lead peak intensities derived from both the M and L values in the spectra. On the basis of these results and those obtained similarly in control lysosomes containing either only gold or only lead phosphate precipitate, it was found that only the L values were reliable, whereas the M values from the same lysosomal spectra were unrealistic, due to deconvolution problems in the computer programs applied. Based upon the L values it was found that among the population of lysosomes in single Kupffer cells, studied after a 60-min interval between the injection of the gold colloid and fixation, three types of lysosomal contents could be quantitated by X-ray microanalysis, viz. one type with only gold, one with only lead, one with gold and lead, in various ratios. This quantitative approach might make it possible to detect variations in lysosomal composition associated with ageing.The unit for analytical electron microscopy was established by collaboration between: the Erasmus University of Rotterdam (W.C. de Bruijn), the University of Leiden, and the Organization for Health Research TNO. The analytical electron microscope was purchased with funds from the Netherlands Organization for Pure Scientific Research (ZWO) 相似文献