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11.
Leanne Jill Rylands Don Shearman 《International Journal of Mathematical Education in Science & Technology》2018,49(8):1133-1147
This paper considers the effects of both free optional mathematics learning support and engagement on the mathematics performance in a foundation mathematics subject of a cohort of engineering students entering university with poor mathematical skills. New engineering students were directed to either a foundation or standard mathematics subject based on the results of a placement test. For students in the foundation subject, it was found that high levels of learning support were associated with greater improvement over the semester. Some form of learning support was used by 57.9% of the students, a reasonably high proportion of the cohort. Some factors for this high level of use of learning support are considered. One possible factor, the placement test, appears to have had a positive effect. Engagement in the subject activities as measured by tutorial attendance and learning management system use was found to have a positive association with final mark. Students who utilized a high level of learning support were more likely to be more engaged with the subject, making it impossible to draw conclusions about improvements being solely due to the use of learning support. 相似文献
12.
Jan C. A. Boeyens Leanne M. Cook Tak-ho Ngoi David H. Reid 《Journal of chemical crystallography》1996,26(3):215-218
The crystal structure of two isomeric oximes, C11N10N2OS have been studied by X-ray diffraction. The open-chain thiocyanato derivative is somewhat'less dense and crystallizes with the orthorhombic space group Pbcn;a,b,c=18.718(1), 10.601(3), 11.528(1) Å,Z=8. The heterocyclic isomer occurs as pseudo-orthorhombic (Cmma)twinned crystals of space group P21/n, a, b, c, =12.11(1), 7.46(1), 12.12(1) Å, 100.09(1)o,Z=4. Twinning occurs as a result of the near-equality of the monoclinica andc cell constants. 相似文献
13.
Britcher L Barnes TJ Griesser HJ Prestidge CA 《Langmuir : the ACS journal of surfaces and colloids》2008,24(15):7625-7627
Porous silicon has received considerable interest in recent years in a range of biomedical applications, with its performance determined by surface chemistry. In this work, we investigate the PEGylation of porous silicon wafers using click chemistry. The porous silicon wafer surface chemistry was monitored at each stage of the reaction via photoacoustic Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, whereas sessile drop contact angle and model protein adsorption measurements were used to characterize the final PEGylated surface. This work highlights the simplicity of click-chemistry-based functionalization in tailoring the porous silicon surface chemistry and controlling protein-porous silicon interactions. 相似文献
14.
Allendorf MD Houk RJ Andruszkiewicz L Talin AA Pikarsky J Choudhury A Gall KA Hesketh PJ 《Journal of the American Chemical Society》2008,130(44):14404-14405
In this work we demonstrate the concept of stress-induced chemical detection using metal-organic frameworks (MOFs) by integrating a thin film of the MOF HKUST-1 with a microcantilever surface. The results show that the energy of molecular adsorption, which causes slight distortions in the MOF crystal structure, can be converted to mechanical energy to create a highly responsive, reversible, and selective sensor. This sensor responds to water, methanol, and ethanol vapors, but yields no response to either N2 or O2. The magnitude of the signal, which is measured by a built-in piezoresistor, is correlated with the concentration and can be fitted to a Langmuir isotherm. Furthermore, we show that the hydration state of the MOF layer can be used to impart selectivity to CO2. Finally, we report the first use of surface-enhanced Raman spectroscopy to characterize the structure of a MOF film. We conclude that the synthetic versatility of these nanoporous materials holds great promise for creating recognition chemistries to enable selective detection of a wide range of analytes. 相似文献
15.
Poli MA Rivera VR Neal DD Baden DG Messer SA Plakas SM Dickey RW Said KE Flewelling L Green D White J 《Journal of AOAC International》2007,90(1):173-178
A new competitive electrochemiluminescence-based immunoassay for the type-2 brevetoxins in oyster extracts was developed. The assay was verified by spiking known amounts of PbTx-3 into 80% methanol extracts of Gulf Coast oysters. We also provide preliminary data demonstrating that 100% acetone extracts, aqueous homogenates, and the clinical matrixes urine and serum can also be analyzed without significant matrix interferences. The assay offers the advantages of speed ( 2 h analysis time); simplicity (only 2 additions, one incubation period, and no wash steps before analysis); low limit of quantitation (conservatively, 50 pg/mL = 1 ng/g tissue equivalents); and a stable, nonradioactive label. Due to the variety of brevetoxin metabolites present and the lack of certified reference standards for liquid chromatography-mass spectrometry confirmation, a true validation of brevetoxins in shellfish extracts is not possible at this time. However, our assay correlated well with another brevetoxin immunoassay currently in use in the United States. We believe this assay could be useful as a regulatory screening tool and could support pharmacokinetic studies in animals and clinical evaluation of neurotoxic shellfish poisoning victims. 相似文献
16.
Leanne James Muhammet Kose Ted Metcalfe Vickie McKee 《Journal of chemical crystallography》2011,41(4):577-581
Abstract
The title complex, [Ba(L1)(μ1,2-ClO4)]2(ClO4)2 (where L1 = 5,17-dihydroxy-3,7,15,19,25,26-hexa-azatricyclo(19.3.1.19,13)hexacosa-1(25),2,7,9(26),10,12,14,19,21,23-decaene), was synthesised by a Schiff base condensation of 2,6-diformylpyridine with 1,3-diaminopropan-2-ol in dry methanol using barium(II) as template ion. The complex was characterised by IR, 1H NMR, mass spectrometry, elemental analysis and X-ray crystallography. The structure was solved in the triclinic space group P [`\text1] {\bar{\text{1}}} with a = 8.4587(9), b = 8.7360(9), c = 17.7722(19) ?, α = 79.786(2), β = 88.780(2), γ = 83.048(2)°, V = 1283.0(2) ?3, Z = 1 and R1 = 0.0433. The macrocycle is folded and the complex dimerises via perchlorate anions which bridge the barium ions, and this interaction is supported by hydrogen bonding between neighbouring alcohol groups. The dimers are further linked into chains via intermolecular O–H···OClO3 hydrogen bonds. 相似文献17.
Pugh D Bloor LG Parkin IP Carmalt CJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(19):6079-6087
The donor-functionalised alkoxides {Me(3-x)N(CH(2)CH(2)O)(x)} (L(x); x = 1, 2) have been used to form gallium hydride complexes [{GaH(2)(L(1))}(2)] and [{GaH(L(2))}(2)] that are stable and isolable at room temperature. Along with a heteroleptic gallium tris(alkoxide) complex [Ga(L(1))(3)] and the dimeric complex [{GaMe(L(2))}(2)], these compounds have been used as single-source precursors for the deposition of Ga(2)O(3) by aerosol-assisted chemical vapour deposition (AACVD) with toluene as solvent. The resulting films were mostly transparent, indicating low levels of carbon contamination, and they were also mainly amorphous. However, [Ga(L(1))(3)] did contain visibly crystalline material deposited at a substrate temperature of 450?°C, by far the lowest ever observed for the CVD of gallium oxide. 相似文献
18.
Geert-Jan Boons Peter Grice Ray Leslie Steven V Ley Lam Lung Yeung 《Tetrahedron letters》1993,34(52):8523-8526
The reactivity of dispiroketal protected thioglycosides makes them useful new precursors for oligossaccharide synthesis as is illustrated by the preparation of a protected pentasaccharide unit common to the variant surface glycoprotein of Trypanosoma brucei. 相似文献
19.
A high pressure microwave discharge source operating with a dilute mixture of O2 in Ne has been used to produce a supersonic nozzle beam of O atoms seeded in Ne. This low energy supersonic O atom beam has been used to study the reactive scattering of O atoms with Cl2 and CS2 molecules at an initial translational energy E = 13 kJ mol?1. The results are compared with rective scattering from the same reactions using a high energy O atom beam formed by seeding O atoms in He. The O + Cl2 reaction proceeds via a short-lived collision complex where the lifetime of the collision complex depends upon the initial translational energy. However the O + CS2 reaction follows a stripping mechanism which is unaffected by initial translational energy. 相似文献
20.
A high pressure microwave discharge source operating with a dilute mixture of O2 in He has been used to produce a supersonic nozzle beam of O atoms seeded in He. This source has been used to study the reactive scattering of O atoms with Cl2 and CS2 molecules at an initial translational energy E = 38 kJ mol?1. Velocity distribution of reactive scattering were measured over a wide angular range by cross-correlation time-of-flight analysis. The O + Cl2 reaction proceeds via a short-lived collision complex while the O + CS2 reaction follows a stripping mechanism. 相似文献