138 research outputs found
Viscosity Calculation for Binary Mixtures of Organic Solvents Based on Modified Eyring-Modified Two-Suffix-Margules (MTSM) Model
Recently, the Eyring-modified two-suffix-margules
(MTSM) model
for calculating viscosities of ionic liquid mixtures was proposed
by Atashrouz et al. (Atashrouz, S.; Zarghampour, M.; Abdolrahimi,
S.; Pazuki, G.; Nasernejad, B. <i>J. Chem. Eng. Data</i> <b>2014</b>, <i>59</i>, 3691ā3704). In this
work, a simple modification of the Eyring-MTSM model was presented
and applied to the viscosity calculation of binary mixtures of organic
solvents. The accuracy of the modified model was assessed by comparing
experimental viscosities at atmospheric pressure for 182 binary mixtures,
and the overall average relative deviation (ARD) between the calculated
results and literatures is 0.61%. In addition, the relationship between
the parameters in the model and the boiling point of mixtures was
established. Experimental viscosities containing 478 binary mixtures
were used to evaluate the reliability of the relations, and good agreement
was obtained between experimental and calculated values with ARD of
1.62%. Furthermore, the modified Eyring-MTSM model was extended to
the viscosities of high pressures. The ARD is 1.61% for the high-pressure
viscosities of 63 binary mixtures. The predictive ability of the model
was also tested, and the model is suitable for the prediction of the
homologous mixtures
Densities and excess molar volumes of the binary system <i>N</i>-methyldiethanolamine + (2-aminoethyl)ethanolamine and its ternary aqueous mixtures from 283.15 to 363.15 K
<p>Experimental density data of the binary mixtures of <i>N</i>-methyldiethanolamine + (2-aminoethyl)ethanolamine and the ternary mixtures of <i>N</i>-methyldiethanolamine + (2-aminoethyl)ethanolamine + water were reported at atmospheric pressure over the entire composition range at temperatures from 283.15 to 363.15Ā K. Density measurements were performed using an Anton Paar digital vibrating U-tube densimeter. Excess molar volumes were calculated from the experimental data and correlated as the Redlich-Kister equation for the binary mixtures, and as the Nagata-Tamura equation for the ternary mixtures. Several empirical models were applied to predict the excess molar volumes of ternary mixtures from the corresponding binary mixture values. It indicates that the best agreement with the experimental data was achieved by the Redlich-Kister, Kohler, and Jacob-Fitzner models.</p
High-Spin Iron(II) Alkynyl Complexes with NāHeterocyclic Carbene Ligation: Synthesis, Characterization, and Reactivity Study
High-spin
ironĀ(II) alkynyl complexes [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>ĀFeĀ(Cī¼CBu<sup><i>t</i></sup>)<sub>2</sub>]
(<b>1</b>) and [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeĀ(Cī¼CR)Ā(NHMes)]
(R = Bu<sup><i>t</i></sup> <b>2</b>, SiMe<sub>3</sub> <b>3</b>) bearing a monodentate N-heterocyclic carbene ligand
IPr<sub>2</sub>Me<sub>2</sub> (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene)
have been prepared by salt metathesis and/or amine elimination methods
and characterized by various spectroscopic methods. Complex <b>1</b> reacts with PMe<sub>3</sub> (4 equiv) and Bu<sup><i>t</i></sup>NC (4 equiv) to form <i>trans</i>-[(PMe<sub>3</sub>)<sub>4</sub>ĀFeĀ(Cī¼CBu<sup><i>t</i></sup>)<sub>2</sub>] (<b>4</b>) and [Ī·<sup>3</sup>-{(Bu<sup><i>t</i></sup>Cī¼C)Ā(Bu<sup><i>t</i></sup>)ĀCCĀ(IPr<sub>2</sub>Me<sub>2</sub>)ĀCĀ(NBu<sup><i>t</i></sup>)}ĀFeĀ(NCBu<sup><i>t</i></sup>)<sub>3</sub>]
(<b>5</b>), respectively. In contrast, the reactions of <b>1</b> with 4-Pr<sup><i>i</i></sup>-C<sub>6</sub>H<sub>4</sub>NCO and Pr<sup><i>i</i></sup>NCNPr<sup><i>i</i></sup> lead to the formation of the zwitterionic salts 4-Pr<sup><i>i</i></sup>-C<sub>6</sub>H<sub>4</sub>NCĀ(O)Ā(IPr<sub>2</sub>Me<sub>2</sub>) and (Pr<sup><i>i</i></sup>N)<sub>2</sub>CĀ(IPr<sub>2</sub>Me<sub>2</sub>), respectively. The interaction of <b>1</b> with I<sub>2</sub> gives Bu<sup><i>t</i></sup>Cī¼CCī¼CBu<sup><i>t</i></sup> and (IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeI<sub>2</sub>. The CĀ(sp)āCĀ(sp<sup>3</sup>) cross-coupling products <i>n</i>-C<sub>8</sub>H<sub>17</sub>Cī¼CBu<sup><i>t</i></sup> and <i>c</i>-C<sub>6</sub>H<sub>11</sub>Cī¼CBu<sup><i>t</i></sup> are formed in high yields when <b>1</b> is treated with
the corresponding alkyl halides <i>n</i>-C<sub>8</sub>H<sub>17</sub>X and <i>c</i>-C<sub>6</sub>H<sub>11</sub>X (X
= Br, Cl). The formation of the ring-opening product 7,7-dimethyloct-1-en-5-yne
in the reaction of <b>1</b> with cyclopropylmethyl bromide supports
the radical character of the cross-coupling reaction
Maximizing the Spread of Influence via Generalized Degree Discount
<div><p>It is a crucial and fundamental issue to identify a small subset of influential spreaders that can control the spreading process in networks. In previous studies, a degree-based heuristic called <i>DegreeDiscount</i> has been shown to effectively identify multiple influential spreaders and has severed as a benchmark method. However, the basic assumption of <i>DegreeDiscount</i> is not adequate, because it treats all the nodes equally without any differences. To consider a general situation in real world networks, a novel heuristic method named <i>GeneralizedDegreeDiscount</i> is proposed in this paper as an effective extension of original method. In our method, the status of a node is defined as a probability of not being influenced by any of its neighbors, and an index generalized discounted degree of one node is presented to measure the expected number of nodes it can influence. Then the spreaders are selected sequentially upon its generalized discounted degree in current network. Empirical experiments are conducted on four real networks, and the results show that the spreaders identified by our approach are more influential than several benchmark methods. Finally, we analyze the relationship between our method and three common degree-based methods.</p></div
The spreading influence of GeneralizedDegreeDiscount and three adaptive centrality-based methods under different effective spreading rates.
<p>The numbers of spreaders are 100 in all networks, and the results are obtained by averaging over 200 implementations of the SIR model.</p
Dually Heterogeneous Hydrogels via Dynamic and Supramolecular Cross-Links Tuning Discontinuous Spatial Ruptures
Biological
tissues are often highly and multiply heterogeneous
in both structure and composition, but the integrity of multiheterogeneity
in artificial materials is still a big challenge. Herein, dually heterogeneous
hydrogels were constructed with two distinct strategies via dynamic
bonds and supramolecular cross-links. The hydrogels showed discontinuous
spatial ruptures, and the mechanical behaviors of hydrogels could
be tuned. The primary heterogeneity resulted from a nonuniform distribution
of dynamic and/or static cross-links. The presence of only primary
heterogeneity within hydrogels led to uneven mechanical properties
that were represented by discontinuous spatial ruptures during the
stretching the hydrogel and therefore caused the necking deformation.
Further introduction of the secondary heterogeneity by incorporating
anisotropic cellulose nanocrystals (CNC) into the hydrogels allowed
the adjustment of the necking phenomenon. Moreover, distinct CNC with
diverse surface functionalities exhibited different effects: the āactiveā
CNC with surface-attached dynamic bonds retarded the necking propagation,
while the āneutralā CNC without further surface modification
promoted the extension of necking points. Thus, the regulation of
deformation and fracture mode of hydrogels was achieved by the synergy
of dually heterogeneous structure
The spreading influence of nine methods on four networks under different effective spreading rates.
<p>The parameters are <i>Ī»</i> = 1.1, <i>q</i> = 1/ā©<i>k</i>āŖ for all networks, and all results are obtained by averaging over 200 implementations of the SIR model.</p
The similarities between <i>GeneralizedDegreeDiscount</i> and <i>Degree</i>, <i>SingleDiscount</i>, <i>DegreeDiscount</i>.
<p>The fraction of spreaders is 1%.</p
Monomeric Bis(anilido)iron(II) Complexes with <i>N</i>āHeterocyclic Carbene Ligation: Synthesis, Characterization, and Redox Reactivity toward Aryl Halides
Using monodentate <i>N</i>-heterocyclic carbenes
as the ancillary ligands, seven monomeric bisĀ(anilido)ĀironĀ(II) complexes
[(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeĀ(NHAr)<sub>2</sub>]
(IPr<sub>2</sub>Me<sub>2</sub> = 2,5-diisopropyl-3,4-dimethylimidazol-1-ylidene;
Ar = Ph, C<sub>6</sub>H<sub>4</sub>-2-Pr<sup><i>i</i></sup>, Mes, C<sub>6</sub>H<sub>3</sub>-2,6-Cl<sub>2</sub>, Dipp) and [(IPr)ĀFeĀ(NHAr)<sub>2</sub>] (IPr = 2,5-diĀ(2,6-diisopropylphenyl)Āimidazol-1-ylidene;
Ar = C<sub>6</sub>H<sub>3</sub>-2,6-Cl<sub>2</sub>, Dipp) have been
prepared by the one-pot reactions of [FeĀ(Mes)<sub>2</sub>]<sub>2</sub> with the corresponding <i>N</i>-heterocyclic carbenes,
and anilines. These high-spin diamido complexes have been fully characterized
by <sup>1</sup>H NMR, solution magnetic susceptibility, UVāvis,
IR, X-ray diffraction, cyclic voltammetry, as well as elemental analysis.
The strong affinity of the <i>N</i>-heterocyclic carbene
ligands toward ferrous centers, and the steric protection exerted
by the NHC ligands are the key factors to stabilize these bisĀ(anilido)Āiron
complexes in a monomeric manner. Reactivity studies revealed the four-coordinate
complex [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeĀ(NHMes)<sub>2</sub>] can react with 1 equiv of 1-iodo-3,5-dimethylbenzene or
1-bromo-3,5-dimethylbenzene in C<sub>6</sub>D<sub>6</sub> and THF-d<sub>8</sub> to furnish 1-C<sub>6</sub>D<sub>5</sub>-3,5-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>, and 5-D-1,3-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>, respectively. Under similar conditions, the three-coordinate
compound [(IPr)ĀFeĀ(NHDipp)<sub>2</sub>] is inert toward these halides
The diagram of <i>DegreeDiscount</i>.
<p>Nodes filled by gray denote the selected spreaders, and others denote normal nodes.</p
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