Quantitative Study on the Influence of Bromide Ions toward the Reduction Kinetics for Size-Tunable Palladium Nanocubes.

During the preparation of nanocrystals, regulating the dosage of key additives in the reaction system and the reaction temperature commonly affects the sizes and morphologies of the products. Despite the fact that bromide ions play a pivotal role in the synthesis of palladium nanocubes (Pd NCs), there is still a lack of quantitative and in-depth research on how the ions affect the reduction kinetics of Pd precursors and further on products. In this work, Pd NCs with different sizes have been prepared under various reaction conditions coupled to a systematic mechanism study. Quantitative measurements demonstrate that the reduction processes could be considered quasi-first-order reactions, and the corresponding kinetic parameters have been obtained. Furthermore, a linear relationship is discovered between k and the average size (d) of Pd NCs. The investigation on the growth patterns of four chosen systems reveals that given reaction conditions lead to certain results with unique growth patterns.

Systematic Study on the Precursor Reduction Kinetics and Growth Pattern for Size-Tunable Palladium Nanocubes.

Unveiling the underlying chemistry during the growth of well-defined nanocrystals is a fundamental but challenging task in materials chemistry. Herein, Pd NCs with tunable sizes ranging from 4.5 to 23.5 nm have been synthesized in the presence of potassium acetate (KOAc). The Pd precursor variation trends of these preparation systems along with reaction time have been determined using a UV-vis spectrometer, and corresponding reduction kinetic parameters, including the apparent reduction rate constant (k) and activation energy (Ea), are calculated by regarding the reduction processes as quasi-first-order reactions. It is confirmed that the introduction of KOAc does not affect the value of the Ea of different reaction systems. The interrelationship of k, product size (d), and reaction temperature (T) is discussed in depth. Results indicate that the three parameters are closely related, and for given reaction systems, they are specified. With the careful investigation of six specific systems (reaction systems with 10 mM, 20 mM KOAc at 55 °C, with 5 mM, 10 mM KOAc at 65 °C, without KOAc at 75 °C, and with 5 mM KOAc at 85 °C), the growth pattern of Pd NCs is described with an empirical expression and is further confirmed as a synergistic result of k and T.

Controllable Deposition of Bi onto Pd for Selective Hydrogenation of Acetylene.

The rational regulation of catalyst active sites at atomic scale is a key approach to unveil the relationship between structure and catalytic performance. Herein, we reported a strategy for the controllable deposition of Bi on Pd nanocubes (Pd NCs) in the priority order from corners to edges and then to facets (Pd NCs@Bi). The spherical aberration-corrected scanning transmission electron microscopy (ac-STEM) results indicated that Bi2O3 with an amorphous structure covers the specific sites of Pd NCs. When only the corners and edges of the Pd NCs were covered, the supported Pd NCs@Bi catalyst exhibited an optimal trade-off between high conversion and selectivity in the hydrogenation of acetylene to ethylene under ethylene-rich conditions (99.7% C2H2 conversion and 94.3% C2H4 selectivity at 170 °C) with remarkable long-term stability. According to the H2-TPR and C2H4-TPD measurements, the moderate hydrogen dissociation and the weak ethylene adsorption are responsible for this excellent catalytic performance. Following these results, the selectively Bi-deposited Pd nanoparticle catalysts showed incredible acetylene hydrogenation performance, which provides a feasible perspective to design and develop highly selective hydrogenation catalysts for industrial applications.

Paraffin-Coated Hydrophobic Hemostatic Zeolite Gauze for Rapid Coagulation with Minimal Adhesion.

To solve the problem of strong adhesion and excessive blood loss caused by the use of hydrophilic zeolite gauze (Z-Gauze) in uncontrollable bleeding, we have modified the surface of commercial Z-Gauze with a paraffin coating and prepared a hydrophobic dressing PZ-Gauze. After paraffin coating, the adhesion of Z-Gauze was reduced without an obvious decrease in coagulation activity. The clotting time of the hydrophobic PZ-Gauze was reduced from 378.3 to 154.6 s compared with that of cotton gauze, and the peeling force was decreased from 348.8 to 84.7 mN compared with that of Z-Gauze. Besides, PZ-Gauze can efficiently cut down the blood loss during treatment. On the basis of in vitro and in vivo experiments, it is confirmed that surface hydrophobic modification does not change the procoagulant performance because of the maintained cation exchange capacity of zeolites, and the reduced blood loss as well as enhanced difficulty for fibrin adhesion is attributed to its hydrophobicity. This is different from the traditional gauze procoagulant theories, where gauze hydrophilicity and procoagulant performance are always positively correlated.

Predicting mortality in acute ischaemic stroke treated with mechanical thrombectomy: analysis of a multicentre prospective registry.

OBJECTIVES: We aimed to determine predictors of mortality within 90 days and develop a simple score for patients with mechanical thrombectomy (MT). DESIGN: Analysis of a multicentre prospective registry. SETTING: In six participating centres, patients who had an acute ischaemic stroke (AIS) treated by MT between March 2017 and May 2018 were documented prospectively. PARTICIPANTS: 224 patients with AIS were treated by MT. RESULTS: Of 224 patients, 49 (21.9%) patients died, and 87 (38.8%) were independent. Variables associated with 90-day mortality were age, previous stroke, admission National Institutes of Health Stroke Scale (NIHSS), fasting blood glucose and occlusion site. Logistic regression identified four variables independently associated with 90-day mortality: age ≥80 years (OR 3.26, 95% CI 1.45 to 7.33), previous stroke (OR 2.33, 95% CI 1.04 to 5.21), admission NIHSS ≥18 (OR 2.37, 95% CI 1.13 to 4.99) and internal carotid artery or basilar artery occlusion (OR 2.92, 95% CI 1.34 to 6.40). Using these data, we developed predicting 90-day mortality of AIS with MT (PRACTICE) score ranging from 0 to 6 points. The receiver operator curve analysis found that PRACTICE score (area under the curve (AUC)=0.744, 95% CI 0.669 to 0.820) was numerically better than iScore (AUC=0.661, 95% CI 0.577 to 0.745) and Predicting Early Mortality of Ischemic Stroke score (AUC=0.638, 95% CI 0.551 to 0.725) for predicting 90-day mortality. CONCLUSIONS: We developed a simple score to estimate the 90-day mortality of patients who had an AIS treated with MT. But the score needs to be prospectively validated. TRIAL REGISTRATION NUMBER: Chinese Clinical Trial Registry (ChiCTR-OOC-17013052).

Outcome of endovascular treatment within and beyond 6 h without perfusion software.

Endovascular treatment (EVT) has been accepted as the standard of care for patients with acute ischemic stroke. The aim of the present study was to compare clinical outcomes of patients who received EVT within and beyond 6 h from symptom onset to groin puncture without perfusion software in Guangdong district, China. Between March 2017 and May 2018, acute ischemic stroke patients who received EVT from 6 comprehensive stroke centers, were enrolled into the registry study. In this subgroup study, we included all patients who had acute proximal large vessel occlusion in the anterior circulation. The demographic, clinical and neuroimaging data were collected from each center. A total of 192 patients were included in this subgroup study. They were divided into two groups: group A (n = 125), within 6 h; group B (n = 67), 6-24 h from symptom onset to groin puncture. There were no substantial differences between these two groups in terms of 90 days favorable outcome (modified Rankin scale [mRS] ≤ 2, P = 0.051) and mortality (P = 0.083), and the risk of symptomatic intracranial hemorrhage at 24 h (P = 0.425). The NIHSS (median 16, IQR12-20, group A; median 12, IQR8-18, group B; P = 0.009) and ASPECTS (median 10, IQR8-10, group A; median 9, IQR8-10, group B; P = 0.034) at baseline were higher in group A. The anesthesia method (general anesthesia, 21.3%, group A vs. 1.5% group B, P = 0.001) were also statistically different between the two groups. The NIHSS and ASPECTS were higher, and general anesthesia was also more widely used in group A. Clinical outcomes were not significantly different within 6 h versus 6-24 h from symptom onset to groin puncture in this real world study.

PdAgPt Corner-Satellite Nanocrystals in Well-Controlled Morphologies and the Structure-Related Electrocatalytic Properties.

The functions of heterogeneous metallic nanocrystals (HMNCs) can be undoubtedly tuned by controlling their morphologies and compositions. As a less-studied kind of HMNCs, corner-satellite multi-metallic nanocrystals (CSMNCs) have great research value in structure-related electrocatalytic performance. In this work, PdAgPt corner-satellite nanocrystals with well-controlled morphologies and compositions have been developed by temperature regulation of a seed-mediated growth process. Through the seed-mediated growth, the morphology of PdAgPt products evolves from Pd@Ag cubes to PdAgPt corner-satellite cubes, and eventually to truncated hollow octahedra, as a result of the expansion of {111} facets in AgPt satellites. The growth of AgPt satellites exclusively on the corners of central cubes is realized with the joint help of Ag shell and moderate bromide, and hollow structures form only at higher reaction temperatures on account of galvanic displacement promoted by the Pd core. In view of the different performances of Pd and Pt toward formic acid oxidation (FAO), this structure-sensitive reaction is chosen to measure electrocatalytic properties of PdAgPt HMNCs. It is proven that PdAgPt CSMNCs display greatly improved activity toward FAO in direct oxidation pathway. In addition, with the help of AgPt heterogeneous shells, all PdAgPt HMNCs exhibit better durability than Pd cubes and commercial Pt.

Influence of Reduction Kinetics on the Preparation of Well-Defined Cubic Palladium Nanocrystals.

A facile synthesis strategy has been developed to synthesize palladium nanocubes with tunable size and well-controlled morphology. Through adjusting the dosages of acetate species (KOAc, NH4OAc, and HOAc), the sizes of well-defined Pd nanocubes are tuned. The reduction of Pd precursors, a first-order reaction, is influenceable by acetate species, and a quantitative relationship between cubic width and apparent reduction rate constant, which has been found to be an effective parameter to describe the growth process of Pd nanocubes, has been uncovered. The effect of apparent reduction rate constant on the growth of Pd nanocubes has been discussed, and the growth kinetics of Pd nanocubes is quantitatively depicted.

Novel Guanidinium-Based Ionic Liquids for Highly Efficient SO2 Capture.

The application of ionic liquids (ILs) for acidic gas absorption has long been an interesting and challenging issue. In this work, the ethyl sulfate ([C2OSO3](-)) anion has been introduced into the structure of guanidinium-based ILs to form two novel low-cost ethyl sulfate ILs, namely 2-ethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate ([C2(2)(C1)2(C1)2(3)gu][C2OSO3]) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate ([(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3]). The ethyl sulfate ILs, together with 2-ethyl-1,1,3,3-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide ([C2(2)(C1)2(C1)2(3)gu][NTf2]) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide ([(C2)2(2)(C1)2(C1)2(3)gu][NTf2]), are employed to evaluate the SO2 absorption and desorption performance. The recyclable ethyl sulfate ILs demonstrate high absorption capacities of SO2. At a low pressure of 0.1 bar and at 20 °C, 0.71 and 1.08 mol SO2 per mole of IL can be captured by [C2(2)(C1)2(C1)2(3)gu][C2OSO3] and [(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3], respectively. The absorption enthalpy for SO2 absorption with [C2(2)(C1)2(C1)2(3)gu][C2OSO3] and [(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3] are -3.98 and -3.43 kcal mol(-1), respectively. While those by [C2(2)(C1)2(C1)2(3)gu][NTf2] and [(C2)2(2)(C1)2(C1)2(3)gu][NTf2] turn out to be only 0.17 and 0.24 mol SO2 per mole of IL under the same conditions. It can be concluded that the guanidinium ethyl sulfate ILs show good performance for SO2 capture. Quantum chemistry calculations reveal nonbonded weak interactions between the ILs and SO2. The anionic moieties of the ILs play an important role in SO2 capture on the basis of the consistently experimental and computational results.

Dosimetric comparison of patient setup strategies in stereotactic body radiation therapy for lung cancer.

PURPOSE: In this work, the authors retrospectively compared the accumulated dose over the treatment course for stereotactic body radiation therapy (SBRT) of lung cancer for three patient setup strategies. METHODS: Ten patients who underwent lung SBRT were selected for this study. At each fraction, patients were immobilized using a vacuum cushion and were CT scanned. Treatment plans were performed on the simulation CT. The planning target volume (PTV) was created by adding a 5-mm uniform margin to the internal target volume derived from the 4DCT. All plans were normalized such that 99% of the PTV received 60 Gy. The plan parameters were copied onto the daily CT images for dose recalculation under three setup scenarios: skin marker, bony structure, and soft tissue based alignments. The accumulated dose was calculated by summing the dose at each fraction along the trajectory of a voxel over the treatment course through deformable image registration of each CT with the planning CT. The accumulated doses were analyzed for the comparison of setup accuracy. RESULTS: The tumor volume receiving 60 Gy was 91.7 ± 17.9%, 74.1 ± 39.1%, and 99.6 ± 1.3% for setup using skin marks, bony structures, and soft tissue, respectively. The isodose line covering 100% of the GTV was 55.5 ± 7.1, 42.1 ± 16.0, and 64.3 ± 7.1 Gy, respectively. The corresponding average biologically effective dose of the tumor was 237.3 ± 29.4, 207.4 ± 61.2, and 258.3 ± 17.7 Gy, respectively. The differences in lung biologically effective dose, mean dose, and V20 between the setup scenarios were insignificant. CONCLUSIONS: The authors' results suggest that skin marks and bony structure are insufficient for aligning patients in lung SBRT. Soft tissue based alignment is needed to match the prescribed dose delivered to the tumors.

Dosimetric impact of breathing motion in lung stereotactic body radiotherapy treatment using intensity modulated radiotherapy and volumetric modulated arc therapy [corrected].

PURPOSE: The objective of this study was to investigate the influence of tumor motion on dose delivery in stereotactic body radiotherapy (SBRT) for lung cancer, using fixed field intensity- modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). METHODS AND MATERIALS: For each of 10 patients with stage I/II non-small-cell pulmonary tumors, a respiration-correlated four-dimensional computed tomography (4DCT) study was carried out. The internal target volume was delineated on the maximum intensity projection CT, which was reconstructed from the 4DCT dataset. A 5-mm margin was used for generation of the planning target volume. VMAT and five-field IMRT plans were generated using Pinnacle(3) SmartArc and direct machine parameter optimization, respectively. All plans were generated for an Elekta Synergy linear accelerator using 6-MV photons. Simulation was performed to study the interplay between multileaf collimator (MLC) sequences and target movement during the delivery of VMAT and IMRT. For each plan, 4D dose was calculated using deformable image registration of the 4DCT images. Target volume coverage and doses to critical structures calculated using 4D methodology were compared with those calculated using 3D methodology. RESULTS: For all patients included in this study, the interplay effect was found to present limited impact (less than 1% of prescription) on the target dose distribution, especially for SBRT, in which fewer fractions (three fractions) are delivered. Dose to the gross tumor volume (GTV) was, on average, slightly decreased (1% of prescription) in the 4D calculation compared with the 3D calculation. The motion impact on target dose homogeneity was patient-dependent and relatively small. CONCLUSIONS: Both VMAT and IMRT plans experienced negligible interplay effects between MLC sequence and tumor motion. For the most part, the 3D doses to the GTV and critical structures provided good approximations of the 4D dose calculations.

A two-stage sequential linear programming approach to IMRT dose optimization.

The conventional IMRT planning process involves two stages in which the first stage consists of fast but approximate idealized pencil beam dose calculations and dose optimization and the second stage consists of discretization of the intensity maps followed by intensity map segmentation and a more accurate final dose calculation corresponding to physical beam apertures. Consequently, there can be differences between the presumed dose distribution corresponding to pencil beam calculations and optimization and a more accurately computed dose distribution corresponding to beam segments that takes into account collimator-specific effects. IMRT optimization is computationally expensive and has therefore led to the use of heuristic (e.g., simulated annealing and genetic algorithms) approaches that do not encompass a global view of the solution space. We modify the traditional two-stage IMRT optimization process by augmenting the second stage via an accurate Monte Carlo-based kernel-superposition dose calculations corresponding to beam apertures combined with an exact mathematical programming-based sequential optimization approach that uses linear programming (SLP). Our approach was tested on three challenging clinical test cases with multileaf collimator constraints corresponding to two vendors. We compared our approach to the conventional IMRT planning approach, a direct-aperture approach and a segment weight optimization approach. Our results in all three cases indicate that the SLP approach outperformed the other approaches, achieving superior critical structure sparing. Convergence of our approach is also demonstrated. Finally, our approach has also been integrated with a commercial treatment planning system and may be utilized clinically.

Do tumors in the lung deform during normal respiration? An image registration investigation.

PURPOSE: The purpose of this study was to investigate whether lung tumors may be described adequately using a rigid body assumption or whether they deform during normal respiration. METHODS AND MATERIALS: Thirty patients with early stage non-small-cell lung cancer underwent four-dimensional (4D) computed tomography (CT) simulation. The gross tumor volume (GTV) was delineated on the 4D CT images. Image registration was performed in the vicinity of the GTV. The volume of interest for registration was the GTV and minimal volume of surrounding non-GTV tissue. Three types of registration were performed: translation only, translation + rotation, and deformable. The GTV contour from end-inhale was mapped to end-exhale using the registration-derived transformation field. The results were evaluated using three metrics: overlap index (OI), root-mean-squared distance (RMS), and Hausdorff distance (HD). RESULTS: After translation only image registration, on average OI increased by 21.3%, RMS and HD reduced by 1.2 mm and 2.0 mm, respectively. The succeeding increases in OI after translation + rotation and deformable registration were 1.1% and 1.4% respectively. The succeeding reductions in RMS were 0.1 mm and 0.2 mm respectively. No reduction in HD was observed after translation + rotation and deformable image registration compared with translation only registration. The difference in the results from the three registration scenarios was independent of GTV size and motion amplitude. CONCLUSIONS: The primary effect of normal respiration on lung tumors was the translation of tumors. Rotation and deformation of lung tumors was determined to be minimal.

An evaluation of planning techniques for stereotactic body radiation therapy in lung tumors.

PURPOSE: To evaluate four planning techniques for stereotactic body radiation therapy (SBRT) in lung tumors. METHODS AND MATERIALS: Four SBRT plans were performed for 12 patients with stage I/II non-small-cell lung cancer under the following conditions: (1) conventional margins on free-breathing CT (plan 1), (2) generation of an internal target volume (ITV) using 4DCT with beam delivery under free-breathing conditions (plan 2), (3) gating at end-exhale (plan 3), and (4) gating at end-inhale (plan 4). Planning was performed following the RTOG 0236 protocol with a prescription dose of 54 Gy (3 fractions). For each plan 4D dose was calculated using deformable-image registration. RESULTS: There was no significant difference in tumor dose delivered by the 4 plans. However, compared with plan 1, plans 2-4 reduced total lung BED by 1.9+/-1.2, 3.1+/-1.6 and 3.5+/-2.1 Gy, reduced mean lung dose by 0.8+/-0.5, 1.5+/-0.8, and 1.6+/-1.0 Gy, reduced V20 by 1.5+/-1.0%, 2.7+/-1.4%, and 2.8+/-1.8%, respectively, with p<0.01. Compared with plan 2, plans 3-4 reduced lung BED by 1.2+/-1.0 and 1.6+/-1.5 Gy, reduced mean lung dose by 0.6+/-0.5 and 0.8+/-0.7 Gy, reduced V20 by 1.2+/-1.1% and 1.3+/-1.5%, respectively, with p<0.01. The differences in lung BED, mean dose and V20 of plan 4 compared with plan 3 were insignificant. CONCLUSIONS: Tumor dose coverage was statistically insignificant between all plans. However, compared with plan 1, plans 2-4 significantly reduced lung doses. Compared with plan 2, plan 3-4 also reduced lung toxicity. The difference in lung doses between plan 3 and plan 4 was not significant.

Effect of ultrasound probe on dose delivery during real-time ultrasound-guided tumor tracking.

Ultrasound is a noninvasive and less costly modality for real-time imaging of soft tissues. It has the capability of tracking soft tissue at levels of submillimeter precision even in the presence of radiation beams. The effect of a transducer on radiation dose is not fully known. The best imaging location for an ultrasound transducer happens to coincide with the path of an anterior-posterior beam in intensity modulated radiation therapy (IMRT). This study indicates a significant change in dose when this juxtaposition occurs. If the anterior-posterior beam is avoided in IMRT planning, however, the effect of the transducer on radiotherapy is found to be negligible.