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101.
Stephen J. I. Shearan Jannick Jacobsen Prof. Ferdinando Costantino Dr. Roberto D'Amato Dr. Dmitri Novikov Prof. Norbert Stock Prof. Enrico Andreoli Dr. Marco Taddei 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(21):6579-6592
We report on the results of an in situ synchrotron powder X-ray diffraction study of the crystallisation in aqueous medium of two recently discovered perfluorinated CeIV-based metal–organic frameworks (MOFs), analogues of the already well investigated ZrIV-based UiO-66 and MIL-140A, namely, F4_UiO-66(Ce) and F4_MIL-140A(Ce). The two MOFs were originally obtained in pure form in similar conditions, using ammonium cerium nitrate and tetrafluoroterephthalic acid as reagents, and small variations of the reaction parameters were found to yield mixed phases. Here, we investigate the crystallisation of these compounds, varying parameters such as temperature, amount of the protonation modulator nitric acid and amount of the coordination modulator acetic acid. When only HNO3 is present in the reaction environment, only F4_MIL-140A(Ce) is obtained. Heating preferentially accelerates nucleation, which becomes rate determining below 57 °C. Upon addition of AcOH to the system, alongside HNO3, mixed-phased products are obtained. F4_UiO-66(Ce) is always formed faster, and no interconversion between the two phases occurs. In the case of F4_UiO-66(Ce), crystal growth is always the rate-determining step. A higher amount of HNO3 favours the formation of F4_MIL-140A(Ce), whereas increasing the amount of AcOH favours the formation of F4_UiO-66(Ce). Based on the in situ results, a new optimised route to achieving a pure, high-quality F4_MIL-140A(Ce) phase in mild conditions (60 °C, 1 h) is also identified. 相似文献
102.
Mushraf Hussain Maria Taddei Dr. Laura Bussotti Prof. Paolo Foggi Prof. Jianzhang Zhao Prof. Qingyun Liu Dr. Mariangela Di Donato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(68):15615-15627
Oxoverdazyl (Vz) radical units were covalently linked to the naphthalenediimide (NDI) chromophore to study the effect of the radical on the photophysical properties, especially the radical enhanced intersystem crossing (REISC), which is a promising approach to develop heavy-atom-free triplet photosensitizers. Rigid phenyl or ethynylphenyl linkers between the two moieties were used, thus REISC and formation of doublet (D1, total spin quantum number S=1/2) and quartet states (Q1, S=3/2) are anticipated. The photophysical properties of the dyads were studied with steady-state and femtosecond/nanosecond transient absorption (TA) spectroscopies and DFT computations. Femtosecond transient absorption spectra show a fast electron transfer (<150 fs), and ISC (ca. 1.4–1.85 ps) is induced by charge recombination (CR, in toluene). Nanosecond transient absorption spectra demonstrated a biexponential decay of the triplet state of the NDI moiety. The fast component (lifetime: 50 ns; population ratio: 80 %) is assigned to the D1→D0 decay, and the slow decay component (2.0 μs; 20 %) to the Q1→D0 ISC. DFT computations indicated ferromagnetic interactions between the radical and chromophore (J=0.07–0.13 eV). Reversible formation of the radical anion of the NDI moiety by photoreduction of the radical-NDI dyads in the presence of sacrificial electron donor triethanolamine (TEOA) is achieved. This work is useful for design of new triplet photosensitizers based on the REISC effect. 相似文献
103.
104.
Yepes PP Brannan T Huang J Mirkovic D Newhauser WD Taddei PJ Titt U 《Radiation measurements》2010,45(10):1367-1368
Treatment planning in proton therapy requires the calculation of absorbed dose distributions on beam shaping components and the patient anatomy. Analytical pencil-beam dose algorithms commonly used are not always accurate enough. The Monte Carlo approach is more accurate but extremely computationally intensive. The Fast Dose Calculator, a track-repeating algorithm, has been proposed as an alternative fast and accurate dose calculation. In this work FDC is applied to a proton therapy patient thoracic anatomy. 相似文献
105.
O. Adriani G. A. Bazilevskaya G. C. Barbarino T. R. Bellotti M. A. Bzheumikhova E. A. Bogomolov V. M. Boezio V. Bonvicini M. Bongi L. Bonechi S. Bottai A. Bruno A. Vacchi E. Vannuccini G. V. Vasiliev S. A. Voronov A. M. Galper L. A. Grishantseva G. Zampa N. Zampa V. G. Zverev M. Casolino T. D. Campana P. Carlson G. Castellini F. Cafagna A. N. Kvashnin S. V. Koldashov S. Yu. Krutkov A. A. Leonov V. V. Malakhov V. Malvezzi L. Marcelli W. Menn V. V. Mikhailov E. Mocchiutti S. Orsi G. Osteria P. Papini M. P. De Pascale T. P. Picozza M. Pearce G. De Rosa M. Ricci S. B. Ricciarini M. Simon N. De Simone R. Sparvoli P. Spillantini Yu. I. Stozhkov E. Taddei V. Di Felice D. Fedele P. Hofverberg Yu. T. Yurkin 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(3):364-366
Secondary electron and positron fluxes in the energy range from 3 MeV to 7 GeV were measured with the ARINA and PAMELA spectrometers onboard the Resurs-DK satellite launched on June 15, 2006 into an elliptical orbit with an inclination of 70.4° and an altitude of 350–600 km. It is shown that positrons dominate over electrons by a factor of up to 4–5 in the geomagnetic equator region (L < 1.2 and B > 0.25). 相似文献
106.
O. Adriani G. A. Bazilevskaya G. C. Barbarino R. Bellotti M. Boezio E. A. Bogomolov L. Bonechi M. Bongi V. Bonvicini S. V. Borisov S. Bottai A. Bruno F. Cafagna D. Campana P. Carlson M. Casolino G. Castellini M. P. De Pascale G. De Rosa D. Fedele V. Di Felice A. M. Galper L. A. Grishantseva P. Hofverberg A. A. Leonov S. V. Koldashov S. Yu. Krutkov A. N. Kvashnin V. Malvezzi L. Marcelli W. Menn V. V. Mikhailov M. Minori E. Mocchiutti S. Orsi G. Osteria P. Papini M. Pearce P. Picozza M. Ricci S. B. Ricciarini M. Simon N. De Simone R. Sparvoli P. Spillantini Yu. I. Stozhkov E. Taddei A. Vacchi E. Vannuccini G. V. Vasil’ev S. A. Voronov Yu. T. Yurkin G. Zampa N. Zampa V. G. Zverev 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(5):568-570
The PAMELA experiment is being carried out on board the Russian satellite Resurs DK1 placed in the near-earth near-polar orbit on June 15, 2006. The apparatus comprising a silicon-strip magnetic spectrometer and an electromagnetic calorimeter allows measurement of electron and positron fluxes in cosmic rays in a wide energy interval from ~100 MeV to hundreds of GeV. The high-energy electron and positron separation technique is discussed and the data on positron-to-electron ratio in primary cosmic rays up to E ≈ 10 GeV from the 2006–2007 measurements are reported in this work. 相似文献
107.
Five sets of differently sterilised conventional ultra‐high molecular weight polyethylene (UHMWPE) and cross‐linked polyethylene (XLPE) acetabular cups were run for 5 million cycles on a hip joint simulator in order to evaluate their wear behaviour in relation to material properties (PE grade, conventional or cross‐linked) and sterilisation method (ethylene oxide (EtO) treatment or γ‐irradiation). Gravimetric measurements revealed that conventional UHMWPE wore significantly more than XLPE. The differences in wear behaviour could be partly related to the orthorhombic contents obtained by Raman spectroscopy in the unworn areas of the cups: XLPE cups showed a significantly higher crystallinity degree than the UHMWPE specimens. Raman analysis showed that wear testing did not significantly modify the orthorhombic content of any of the tested acetabular cups. However, the set of cups that showed the highest weight loss, i.e. γ‐sterilised PE GUR1020, appeared the most homogeneously polished upon wear testing; from a molecular point of view, only this set of cups showed a significant increase of the I1130/I1060 intensity ratio, suggesting the occurrence of chain orientation. On the other hand, XLPE cups, despite the lowest weight loss undergone, showed a decrease in the amorphous content upon wear testing as well as a limited orthorhombic → monoclinic transformation, which did not appear detrimental. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
108.
The trans diesters of 1,4-cyclohexanediol with a number of acetic acid analogues, CX3COOH, of varying steric hindrance and polarity (CX3 = Me, Et, iso-Pr, tert-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, CBr3) were synthesized, and the axial,axial/equatorial,equatorial conformational equilibria were studied by low-temperature 1H NMR spectroscopy in CD2Cl2. The structures and relative energies of the axial,axial and equatorial,equatorial conformers were calculated at both the MP2/6-311G* and the MP2/6-311+G* levels of theory, and it was only by including diffuse functions that a good correlation of deltaG(o)calcd vs deltaG(o)exptl could be obtained. Both the structures and the energy differences of the axial,axial and equatorial,equatorial conformers are discussed with respect to the established models of conformational analysis, viz., steric 1,3-diaxial and hyperconjugative interactions. Interestingly, the hyperconjugative interactions sigma(C-C)/sigma(C-H) --> sigma*(C-O), together with a steric effect which also destabilizes the equatorial,equatorial conformers on increasing bulk of the substituents, proved to dominate the position of the conformational equilibria. In addition, the preference of the axial,axial conformers with respect to their equatorial,equatorial analogues was greater than expected from the conformational energies of the corresponding substituents in the monosubstituted cyclohexyl esters. The reason for this very interesting and unexpected result is also discussed. 相似文献
109.
Giazotto F Taddei F Governale M Castellana C Fazio R Beltram F 《Physical review letters》2006,97(19):197001
A solid-state cooling principle based on magnetic-field-driven tunable suppression of Andreev reflection in superconductor/two-dimensional electron gas nanostructures is proposed. This cooling mechanism can lead to very large heat fluxes per channel up to 10;{4} times greater than currently achieved with superconducting tunnel junctions. This efficacy and its availability in a two-dimensional electron system make this method of particular relevance for the implementation of quantum nanostructures operating at cryogenic temperatures. 相似文献
110.
ZnBr2 in dichloromethane is a convenient reagent for mild and selective removal of the tert-butoxycarbonyl group from secondary amines. 相似文献