[en] Isospecific propylene polymerization behavior of meta- and para-Lewis base (E) functionalized unbridged zirconocenes ([1-(E_n-Ph)-3,4-Me₂C₅H₂]₂ZrCl₂, E = NMe₂, OMe; n = 1 or 2) was investigated under bulk conditions. Catalytic activity of the zirconocenes, and molecular weight and isotacticity of polypropylenes are found to be dependent on the position and number of the Lewis base functional groups in the zirconocenes. All the crude polypropylenes possess a broad molecular weight distribution and multi-melting transitions, indicating an involvement of multi-catalytic active species in the polymerization. The highest [mmmm] value of an isotactic portion of the polypropylenes reached 89%, which is higher than that (85%) from the well-known C₂-symmetric EBIZr (rac-Et(Ind)₂ZrCl₂) catalyst. These results support that the in situ generated, rigid rac-like cation-anion pair through the Lewis acid-base interactions between the functional groups of zirconocenes and methylaluminoxane anion is effective in the formation of isotactic polypropylene under bulk propylene polymerization conditions

[en] To assess the sizes and configurations of thermal zones after overlapping ablations using a coaxial radiofrequency (RF) electrode and multiple cannulae in ex-vivo bovine liver. For ablation procedures, a coaxial RF electrode and introducer set was used. Employing real-time ultrasound guidance and overlapping techniques in explanted, fresh bovine liver, we created five kinds of thermal zones with one (n=10), two (n=8), four (n=3), and six ablation spheres (n=3). Following ablation, MR images were obtained and the dimensions of all thermal zones were measured on the longitudinal or transverse section of specimens. The shape of the composite ablation zones was evaluated using three-dimensional MR image reconstruction. At gross pathologic examination of ten single-ablation zones (spheres), the long-axis (transverse) and short-axis lengths of zones ranged from 3.7 to 4.4 (mean, 4.1) cm and from 3.5 to 4.0 (mean, 3.7) cm, respectively. The long-axis (transverse) and short-axis lengths of double-ablation zones (cylinders) with 23% overlap ranged from 7.0 to 7.7 (mean, 7.3) cm and from 3.0 to 3.9 (mean, 3.5) cm, respectively; those with 58% overlap ranged from 6.0 to 6.4 (mean, 6.2) cm and from 3.8 to 4.6 (mean, 4.3) cm, respectively. The long-axis (diagonal) and short-axis lengths on a transverse section of four-ablation zones (cakes) ranged from 8.5 to 9.7 (mean, 9.1) cm and from 3.0 to 4.1 (mean, 3.7) cm, respectively. Gross pathologic examination of three composite six-ablation zones (spheres) showed that the long-axis (diagonal) and short-axis lengths of zones ranged from 9.0 to 9.9 (mean, 9.4) cm and from 6.8 to 7.5 (mean, 7.2) cm, respectively. T2-weighted MR images depicted low-signal thermal zones containing multiple curvilinear and spotty regions of hyperintensity. Using a coaxial RF electrode and multiple cannulae, together with ultrasound guidance and precise overlapping ablation techniques, we successfully created predictable thermal zones in ex-vivo bovine liver

[en] Highlights: • Applicability of TRTs is studied to assess in-situ CO₂ storage in a saline aquifer. • Three inverse models are evaluated to assess the overall thermal conductivity. • The nonlinear least square inverse model produces the least error in the assessment. The study aims to evaluate the method of Thermal Response Tests (TRTs) in assessing in-situ residual saturation of CO₂ storage in saline aquifers. Similar to TRTs, mathematically the same type of an exact analytical solution presented by Theis is well-established for the transient drawdown in an infinite uniform confined aquifer. With the change of supercritical CO₂ and saline water in pore space, the inverse models of temperature change over time either heating or cooling may lead to the detection of a change in thermal properties of fluids and sold matrix. In assessing the overall thermal conductivity using the three inverse models, the Wang model describes the saline aquifer of the interest structurally well among the chosen four conductivity models. The results of the Wang model and the arithmetic model showed almost insensitivity to the residual CO₂ saturation up to 50 percents in the estimation of the overall thermal conductivity, while they did a sensitivity to porosity variation of the same range. Accuracy analysis of the three inversion models showed that a developed nonlinear least square inverse model produces the least error in the estimation consistently with the wide range of the residual saturation variation of CO₂.

[en] These factors essential for the excellent physical properties are also responsible for the poor processibility of PE, hampering bulk production of the polymer. Thus, the enhancement of the processibility of metallocene-based PE without losing its excellent properties has become an important research subject in recent years with a particular focus on modulating MWD and introducing branches. The incidental observation of catalytic systems that gave PE with broad MWD is uncommon. But the control of MWD of PE has been approached by using a series of reactors under different polymerization conditions, employing different catalytic systems in one pot and designing metallocene precatalytic systems that can produce multi catalytic species during the polymerization process. The concept embodied in the design of the foregoing metallocene precatalytic systems includes Lewis acid-base interaction in dialkylamino substituted ansa-metallocene, in situ generation of different isomers for non-Cp type catalyst and the stepwise dissociation of chelate ligand in halfmetallocene catalyst. To date, the attempt to modulate MWD of PE based on the coupled use of those concepts has not been reported. Thus, we have developed a new Cp/non-Cp hybrid catalytic system that produces PE with multimodal MWD by employing 2-pyridinecarboxylate, a potential chelate ligand with multi Lewis base centers of N and O atoms, as a non-Cp ligand