158 research outputs found
Author Correction: Kondo-like transport and magnetic field effect of charge carrier fluctuations in granular aluminum oxide thin films
No full textCorrection to: Scientific Reports https://doi.org/10.1038/s41598-018-32298-1, published online 17 September 2018
Unconventional magnetic field effect on noise properties of AlOx thin films in Kondo-like transport regime
No full textGranular aluminum oxide is an interesting material for application in quantum circuits. However, several issues regarding its normal state transport properties are still open. Here, detailed DC and noise transport measurements have been performed on thin films of granular Al oxide. The results evidence the presence of a Kondo-type resistivity increase at low temperatures, where specific excess 1/f noise is observed. The magnetic dependence of the excess noise further strengthens its connection with the Kondo mechanism
Current-Resistance Effects Inducing Nonlinear Fluctuation Mechanisms in Granular Aluminum Oxide Nanowires
No full textThe unusual superconducting properties of granular aluminum oxide have been recently investigated for application in quantum circuits. However, the intrinsic irregular structure of this material requires a good understanding of the transport mechanisms and, in particular, the effect of disorder, especially when patterned at the nanoscale level. In view of these aspects, electric transport and voltage fluctuations have been investigated on thin-film based granular aluminum oxide nanowires, in the normal state and at temperatures between 8 and 300 K. The nonlinear resistivity and two-level tunneling fluctuators have been observed. Regarding the nature of the noise processes, the experimental findings give a clear indication in favor of a dynamic random resistor network model, rather than the possible existence of a local ordering of magnetic origin. The identification of the charge carrier fluctuations in the normal state of granular aluminum oxide nanowires is very useful for improving the fabrication process and, therefore, reducing the possible sources of decoherence in the superconducting state, where quantum technologies that are based on these nanostructures should work
Structure and Properties of Precursor/Successor Complex and Transition State of the FeCl2+/Fe2+ Electron Self-Exchange Reaction via the Inner-Sphere Pathway
No full textThe electron self-exchange reaction FeCl(OH2)(5)(2+) + Fe(OH2)(6)(2+) -> Fe(OH2)(6)(2+) + FeCl(OH2)(5)(2+), proceeding via the inner-sphere pathway, was investigated with quantum chemical methods. Geometry and vibrational frequencies of the precursor/successor complex, (H2O)(5)(FeClFeII)-Cl-III(OH2)(5)(4+)/(H2O)(5)(FeClFeIII)-Cl-II(OH2)(5)(4+) (P/S), and the transition state, (H2O)(5)FeClFe(OH2)(5)(4+) (TS), were computed with the LC-BOP functional and CPCM hydration. Bent and linear structures were computed for the TS and P/S. The electronic coupling matrix element (H-ab) and the electronic energies were calculated with multistate extended general multiconfiguration quasi-degenerate second-order perturbation theory (XGMC-QDPT2) and spin-orbit configuration interaction (SO-CI). Since the Fe Fe distance changes considerably along the electron transfer step, the transformation P -> TS -> S, equations based on the hypothesis of a fixed donor-acceptor distance cannot be applied. Hence, the rate constant for the electron transfer step (k(et)) was calculated as described previously (Rotzinger, F. P. Inorg. Chem. 2014, 53, 9923). k(et) is very fast, similar to 9.4 x 10(8-)6.6 x 10(9) s(-1) at 0 degrees C. The experimental rate constant of the title reaction (k) is much slower and controlled by the formation of the precursor complex. The substitution of a water ligand by FeCl(OH2)(5)(2+) at Fe(OH2)(6)(2+) is rate-determining.LP
Kondo-like transport and magnetic field effect of charge carrier fluctuations in granular aluminum oxide thin films
No full textGranular aluminum oxide is an attractive material for superconducting quantum electronics. However, its low-temperature normal state transport properties are still not fully understood, while they could be related to the unconventional phenomenon of the superconductivity in this material. In order to obtain useful information on this aspect, a detailed study of charge carrier fluctuations has been performed in granular aluminum oxide films. The results of electric noise measurements indicate the presence of a Kondo-type spin-flip scattering mechanism for the conducting electrons in the normal state, at low temperatures. Moreover, the magnetic field dependence of the noise amplitude suggests that interface magnetic moments are the main source of fluctuations. The identification of the nature of fluctuation processes is a mandatory requirement for the improvement of quality and performance of quantum devices
Structure and Properties of Precursor/Successor Complex and Transition State of the FeCl<sup>2+</sup>/Fe<sup>2+</sup> Electron Self-Exchange Reaction via the Inner-Sphere Pathway
No full textThe electron self-exchange reaction <b>Fe</b>Cl(OH<sub>2</sub>)<sub>5</sub><sup>2+</sup> + Fe(OH<sub>2</sub>)<sub>6</sub><sup>2+</sup> → <b>Fe</b>(OH<sub>2</sub>)<sub>6</sub><sup>2+</sup> + FeCl(OH<sub>2</sub>)<sub>5</sub><sup>2+</sup>, proceeding via the inner-sphere pathway, was investigated
with quantum chemical methods. Geometry and vibrational frequencies
of the precursor/successor complex, (H<sub>2</sub>O)<sub>5</sub>Fe<sup>III</sup>ClFe<sup>II</sup>(OH<sub>2</sub>)<sub>5</sub><sup>4+</sup>/(H<sub>2</sub>O)<sub>5</sub>Fe<sup>II</sup>ClFe<sup>III</sup>(OH<sub>2</sub>)<sub>5</sub><sup>4+</sup> (P/S), and the transition state,
(H<sub>2</sub>O)<sub>5</sub>FeClFe(OH<sub>2</sub>)<sub>5</sub><sup>4+⧧</sup> (TS), were computed with the LC-BOP functional and
CPCM hydration. Bent and linear structures were computed for the TS
and P/S. The electronic coupling matrix element (<i>H</i><sub>ab</sub>) and the electronic energies were calculated with multistate
extended general multiconfiguration quasi-degenerate second-order
perturbation theory (XGMC-QDPT2) and spin–orbit configuration
interaction (SO-CI). Since the Fe···Fe distance changes
considerably along the electron transfer step, the transformation
P → TS → S, equations based on the hypothesis of a fixed
donor–acceptor distance cannot be applied. Hence, the rate
constant for the electron transfer step (<i>k</i><sub>et</sub>) was calculated as described previously (Rotzinger, F. P. <i>Inorg. Chem.</i> <b>2014</b>, <i>53</i>, 9923). <i>k</i><sub>et</sub> is very fast, ∼9.4 × 10<sup>8</sup>–6.6 × 10<sup>9</sup> s<sup>–1</sup> at 0 °C.
The experimental rate constant of the title reaction (<i>k</i>) is much slower and controlled by the formation of the precursor
complex. The substitution of a water ligand by FeCl(OH<sub>2</sub>)<sub>5</sub><sup>2+</sup> at Fe(OH<sub>2</sub>)<sub>6</sub><sup>2+</sup> is rate-determining
Titanium and Zirconium Ferrocene-Substituted Enolates and Their Reaction Products with Benzaldehyde and Acetophenone: Structural and Kinetic Studies of the Aldol Condensation Pathway
No full textThe reaction of acetyl- and propionylferrocene, [(RCOcp)(cp)Fe] (R = Me (1), Et (2)), with KH led to the isolation of the corresponding ion-pair enolates 3 and a in the solid state. When the deprotonation of 1 is carried out in the presence of 18-crown-6, the naked enolate 5, [(CH(2)COcp)(cp)Fe]K--(18-crown-6)(+)], was isolated. The potassium enolate 3 has been converted into the corresponding titanium and zirconium enolates via the reaction with (cp)(2)MCl(2) (M = Ti, Zr), while only 4 was converted into the analogous zirconium enolate. The following metal enolates have been isolated in good yield and as crystalline solids: [(cp)-Fe(cpC(CH2)O)M(cp)(2)(Cl)] (M = Ti (6), Zr (7)) and [(cp)Fe(cpC(CHMe)O)Zr(cp)(2)(Cl)] (8). Compounds 6 and 7 have been characterized by H-1 and C-13 NMR, and an X-ray crystal structure of 7 was obtained; compound 8 was characterized by H-1 NMR. The aldol reaction of 6 and 7 with benzaldehyde led to the corresponding metal aldol derivatives [(cp)Fe(cpC-(O)CH2C(H)(Ph)O)M(cp)(2)(Cl)] (M = Ti (9), Zr(10)). For compound 9 the solid-state structure and solution data are reported. Complex 9 undergoes a facile Ti-Cl ionization, leading to the cationic complex [(cp)Fe(cpC(O)CH2C(H)(Ph)O)Ti(cp)(2)](+)BPh(4)(-) (11). In complex 11, the aldol fragment forms a metallacycle where both oxygens are bonded to titanium. This structure mimics the bond connectivity of the generally proposed ''transition state'' of aldol reactions. The isolation of structurally well-defined titanium and zirconium enolates allowed us to carry out a kinetic investigation into the reaction of 7 with acetophenone. The reaction was carried out in C6D6 at temperatures from 283 to 340 K. The reaction is second order (first order in each reactant), and the following activation parameters have been obtained: Delta H-double dagger = 44.4 +/- 1.7 kJ mol(-1), Delta S-double dagger greater than or equal to -150 +/- 6 J mol(-1) K-1, and Delta G(298)(double dagger) = 89.0 +/- 2.4 kJ mol(-1). A similar study with 4-fluoroacetophenone gave Delta H-double dagger = 33.0 +/- 4.6 kJ mol(-1), Delta S-double dagger greater than or equal to -189 +/- 15 J mol(-1) K-1, and Delta G(298)(double dagger) = 89.2 +/- 6.4 kJ mol(-1). The reaction rate at 320 K determined with 4-chloro-, 4-methyl-, and 4-nitroacetophenone allowed the determination of a Hammett plot with rho = 0.42 +/- 0.9. This value is implicit for a carbon-carbon bond-forming, rate-limiting step. Complexes 7 and 9 have been characterized by X-ray analysis
sj-docx-3-cpa-10.1177_07067437211070656 - Supplemental material for “One Degree of Separation”: A Mixed-Methods Evaluation of Canadian Mental Health Care User and Provider Experiences With Remote Care During COVID-19
No full textSupplemental material, sj-docx-3-cpa-10.1177_07067437211070656 for “One Degree of Separation”: A Mixed-Methods Evaluation of Canadian Mental Health Care User and Provider Experiences With Remote Care During COVID-19 by Amanda K. Ceniti, Wegdan R. Abdelmoemin, Keith Ho, Yudi Kang, Franca Placenza, Rachel Laframboise, Venkat Bhat, Jane A. Foster, Benicio N. Frey, Raymond W. Lam, Roumen Milev, Susan Rotzinger, Claudio N. Soares, Rudolf Uher and Sidney H. Kennedy in The Canadian Journal of Psychiatry</p
Zirconium-Assisted Aldol Condensation Reactions of Amido Enolates: Structural and Kinetic Analysis of the Reaction of N,N-Diphenylacetamide and N,N-Diphenylpropionamide Enolates with Benzaldehyde and p-Substituted Acetophenones
No full textThe deprotonation of N,N-diphenyl amides with LDA and subsequent reaction with [(cp)(2)ZrCl2] (cp = eta(5)-C5H5) allowed the enolate complexes [{Ph(2)NC(CH2)O}Zr(cp)(2)(Cl)] (5) and [{Ph(2)NC(CHCH3)O}Zr(cp)(2)(Cl)] (6) to be isolated. The crystal structure of 6 is reported. Reaction of 5 with [Cr(CO)(5)]. THF gave [Ph(2)NC{CH2Cr(CO)(5)}{OZr(Cl)(cp)(2)}] (7), an 0- and C-bonded dimetallic amido enolate. Reaction of 5 and 6 with benzaldehyde gave the corresponding aldol products 8 and 9; according to previous reports, the conversion of 6 into 9 is syn selective. Reaction of 6 with acetophenone followed by addition of silver triflate gave the complex [Ph(2)NC(=O)CH(CH3)C(Me)(Ph)OZr(cp)(2)(Cl)(OSO2CF3)] (11) as a diastereoisomeric mixture in the ratio anti:syn = 65:35. The crystal structure of sym-11 is reported. This cyclic complex mimics the postulated cyclic transition state of the aldol reaction mediated by zirconium amide enolates. A kinetic investigation of the reaction of 6 with acetophenone was performed and gave the following activation parameters: Delta H-double dagger = 38.3 +/- 0.9 kJ mol(-1); Delta S-double dagger greater than or equal to -181 +/- 3 J mol(-1) K-1; Delta G(298)(double dagger) = 92.2 +/- 1.2 kJ mol(-1). A similar study with 4-fluoroacetophenone gave Delta H-double dagger = 43.5 +/- 1.3 kJ mol(-1), Delta S-double dagger greater than or equal to -167 +/- 4 J mol(-1) K-1, and Delta G(298)(double dagger) = 93.3 +/- 1.8 kJ mol(-1). The reaction rate at 320 K determined with 4-chloro-, 4-methyl-, and 4-nitroacetophenone allowed the determination of a Hammett plot with rho = 0.41. This value is implicit of a carbon-carbon bond-forming, rate-limiting step
sj-docx-2-cpa-10.1177_07067437211070656 - Supplemental material for “One Degree of Separation”: A Mixed-Methods Evaluation of Canadian Mental Health Care User and Provider Experiences With Remote Care During COVID-19
No full textSupplemental material, sj-docx-2-cpa-10.1177_07067437211070656 for “One Degree of Separation”: A Mixed-Methods Evaluation of Canadian Mental Health Care User and Provider Experiences With Remote Care During COVID-19 by Amanda K. Ceniti, Wegdan R. Abdelmoemin, Keith Ho, Yudi Kang, Franca Placenza, Rachel Laframboise, Venkat Bhat, Jane A. Foster, Benicio N. Frey, Raymond W. Lam, Roumen Milev, Susan Rotzinger, Claudio N. Soares, Rudolf Uher and Sidney H. Kennedy in The Canadian Journal of Psychiatry</p
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