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排序方式: 共有317条查询结果,搜索用时 15 毫秒
31.
Dr. Colm Browne William J. Ramsay Dr. Tanya K. Ronson John Medley‐Hallam Prof. Jonathan R. Nitschke 《Angewandte Chemie (International ed. in English)》2015,54(38):11122-11127
The subcomponent self‐assembly of a bent dialdehyde ligand and different cationic and anionic templates led to the formation of two new metallosupramolecular architectures: a FeII4L6 molecular rectangle was isolated following reaction of the ligand with iron(II) tetrafluoroborate, and a M5L6 trigonal bipyramidal structure was constructed from either zinc(II) tetrafluoroborate or cadmium(II) trifluoromethanesulfonate. The spatially constrained arrangement of the three equatorial metal ions in the M5L6 structures was found to induce small‐molecule transformations. Atmospheric carbon dioxide was fixed as carbonate and bound to the equatorial metal centers in both the Zn5L6 and Cd5L6 assemblies, and sulfur dioxide was hydrated and bound as the sulfite dianion in the Zn5L6 structure. Subsequent in situ oxidation of the sulfite dianion resulted in a sulfate dianion bound within the supramolecular pocket. 相似文献
32.
Julia Novak Barbara Kensington-Miller Tanya Evans 《International Journal of Mathematical Education in Science & Technology》2017,48(5):647-658
This paper describes students’ perspectives of a one-off flipped lecture in a large undergraduate mathematics service course. The focus was on calculating matrix determinants and was designed specifically to introduce debate and argumentation into a mathematics lecture. The intention was to promote a deeper learning and understanding through engagement with the added hope of instilling some passion for the subject. During the lecture, students were asked to vote with their feet, literally moving around the lecture theatre to form groups according to their shared favourite technique for calculating matrix determinants. Group discussions were then followed by a whole class debate facilitated by the lecturers, before they wrapped up the lecture by resolving the professional disagreements that had come to light during the debate. Following the lecture, data on student perspectives was gathered using both surveys and focus groups. Within this paper, we share the data and reveal the interesting results that emerged from our analysis. Despite remaining unconvinced as to whether flipped lectures are better for learning, students reported greater engagement and increased understanding of the material covered. 相似文献
33.
Henkelis JJ Ronson TK Harding LP Hardie MJ 《Chemical communications (Cambridge, England)》2011,47(23):6560-6562
Crystalline M(3)L(2) complexes with either single cage or triply interlocking [2]catenane chiral structures are formed the self-assembly of host-like ligands with transition metals. 相似文献
34.
R. Andrew Sims Pankaj Kadwani Heike Ebendorff-Heideprem Lawrence Shah Tanya M. Monro Martin Richardson 《Applied physics. B, Lasers and optics》2013,111(2):299-304
We report femtosecond pulse generation and chirped pulse amplification in Tm:fiber. A mode-locked oscillator operating in the soliton regime produced 800 fs pulses with 5 nm spectral bandwidth, at 40 pJ pulse energy. This oscillator seeded a pre-amplifier that utilizes a Raman soliton self-frequency shift to produce wavelength tunable pulses with 3 nJ energy, reduced pulse duration of 150 fs, and increased bandwidth of 30 nm. For further amplification, the pulses were stretched up to 160 ps using a chirped Bragg grating (CBG). Stretched pulses were amplified to 85 nJ after compression in single-mode Tm:fiber and recompressed with the CBG as short as 400 fs. Compressed pulses were coupled into a highly nonlinear tellurite fiber to investigate the potential of this ultrashort pulse 2-μm fiber source as a pump for mid-IR supercontinuum generation. 相似文献
35.
Ronson TK Adams H Harding LP Pope SJ Sykes D Faulkner S Ward MD 《Dalton transactions (Cambridge, England : 2003)》2007,(10):1006-1022
A set of three potentially bridging ligands containing two tridentate chelating N,N',O-donor (pyrazole-pyridine-amide) donors separated by an o, m, or p-phenylene spacer has been prepared and their coordination chemistry with lanthanide(III) ions investigated. Ligand L(1) (p-phenylene spacer) forms complexes with a 2:3 M:L ratio according to the proportions used in the reaction mixture; the Ln(2)(L(1))(3) complexes contain two 9-coordinate Ln(III) centres with all three bridging ligands spanning both metal ions, and have a cylindrical (non-helical) 'mesocate' architecture. The 1:1 complexes display a range of structural types depending on the conditions used, including a cyclic Ln(4)(L(1))(4) tetranuclear helicate, a Ln(2)(L(1))(2) dinuclear mesocate, and an infinite one-dimensional coordination polymer in which metal ions and bridging ligands alternate along the sequence. ESMS studies indicate that the 1:1 complexes form a mixture of oligonuclear species {Ln(L(1))}(n) in solution (n up to 5) which are likely to be cyclic helicates. In contrast, ligands L(2) and L(3) (with o- and m-phenylene spacers, respectively) generally form dinuclear Ln(2)L(2) Ln(III) complexes in which the two ligands may be arranged in a helical or non-helical architecture about the two metal ions. These complexes also contain an additional exogenous bidentate bridging ligand, either acetate or formate, which has arisen from hydrolysis of solvent molecules promoted by the Lewis-acidity of the Ln(III) ions. Luminescence studies on some of the Nd(III) complexes showed that excitation into ligand-centred pi-pi* transitions result in the characteristic near-infrared luminescence from Nd(III) at 1060 nm. 相似文献
36.
Tanya M RamondGustavo E Davico Fredrik HellbergFredrik Svedberg Peter SalénPatrick Söderqvist W.Carl Lineberger 《Journal of Molecular Spectroscopy》2002,216(1):1-14
The 364-nm negative ion photoelectron spectra of XO and OXO molecules (X=Ni, Pd, and Pt) are reported. The spectra yield the electron affinities (EAs): EA(NiO)=1.455±0.005 eV; EA(PdO)=1.672±0.005 eV; EA(PtO)=2.172±0.005 eV; EA(ONiO)=3.043±0.005 eV; EA(OPdO)=3.086±0.005 eV; EA(OPtO)=2.677±0.005 eV. In addition, for the diatomics, transitions from the anion X?2Π3/2 and X?′2Π1/2 states into neutral X?3Σ−, 3Π, and for NiO and PdO, 1Π, are assigned. Several states have been reassigned from those in the existing literature. Anion 2Π3/2-2Π1/2 spin-orbit splittings are measured, as are neutral 3Π2-3Π1 spin-orbit splittings: the XO 3Π 2-3Π1 splittings increase from 405±30 cm−1 (NiO) to 805±30 cm−1 (PdO) to 3580±40 cm−1 (PtO). A bond length shortening of 0.03±0.01 Å is measured upon electron detachment from NiO−, resulting in an anion bond length of 1.66±0.01 Å. The bond length does not change upon electron detachment from PdO− using 3.4-eV photons. The Pt-O bond length decreases by 0.035±0.010 Å in the 3Π1←2Π3/2 transition. The spectrum of OPtO displays a significantly more extended vibrational progression than those of ONiO or OPdO, and the O-Pt bond length is found to decrease by 0.07±0.01 Å upon electron detachment. The spectra support the view that the Ni-O bond is largely ionic, the Pd-O bond is somewhat less so, and the Pt-O bond displays a substantial covalent character. 相似文献
37.
As a result of flight noise measurements made at various locations in the cabin of the standard lined/no interior Westwind model 1124 business executive jet, it was possible to develop an empirical method for predicting the overall sound pressure level (OASPL) at any required location in the cabin. The cabin overall sound level in decibels (linear) may be found from nomographs related to aircraft altitude, mach number or velocity. The noise spectrum at any location may be found from a reference spectrum shape corrected for local parameters. The accuracy of the prediction method, verified by additional tests, was found to be ± 1 dB. 相似文献
38.
Tanya Tsoncheva Mika Linden Jessica Rosenholm Christo Minchev 《Reaction Kinetics and Catalysis Letters》2005,86(2):275-280
Summary Ni-modifiedlarge poremesoporous silicasarecharacterized by XRD, N2physisorption and TPR with H2. Theeffectof the supportpore structure on their catalytic behaviorin methanol decomposition to H2, CO and CH4is studied. 相似文献
39.
40.
It is shown that the lower bound in the uncertainty relation for joint position-momentum measurements is twice as large as that in the usual Heisenberg uncertainty principle for separate measurements. 相似文献