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Stratification in randomization and analysis are widely employed to balance treatment groups in clinical trials. However, the potential power loss due to under-stratification or over-stratification has not been thoroughly evaluated in the typical setting of confirmatory clinical trials. In cases where there are too many strata and some have small sample sizes or a small number of events, it is common practice to combine these small strata during analysis. However, there is a lack of guidance on how those small strata should be combined. This paper presents extensive simulation studies to evaluate the impact of under-stratification or over-stratification on the power of survival analysis and the estimate of hazard ratio using stratified log-rank test and Cox PH model, respectively. The difference in power between stratified and unstratified log-rank tests is also investigated under different scenarios. Our results suggest that failing to consider prognostic stratification factors with strong effects, and/or accounting for non-prognostic factors such as noise and predictive factors, may reduce the power of the stratified log-rank test. Additionally, methods of combining small strata are explored and compared. [ABSTRACT FROM AUTHOR]

An ultra-wideband dual-polarized tightly coupled dipole array (TCDA) with 10:1 bandwidth is presented. Aimed at solving the ultra-wideband impedance matching problem between the antenna and free space, a novel meta-material wide-angle impedance matching (WAIM) layer is presented. The meta-WAIM utilized a structure of planar double layers with the elliptical split ring on top and the concentric split ring on the bottom, which improves the beam scanning ability over the high-frequency band. The dual-polarized dipoles are arranged as "egg-create" and fed by the integrated double-Y balun. A resistive frequency selective surface (FSS) is loaded between the dipole and ground plane to improve the active VSWR and lower the overall profile, simultaneously. The proposed antenna array can operate over a 10:1 bandwidth (0.2–2 GHz) with an active VSWR < {2.1, 2.7, 4} and average radiation efficiency > {71.6 %, 68.9 %, 60.3 %} for the scan up to {broadside, 45°, 60°}, respectively. The overall antenna profile is 95 mm, which is only 0.063λ L evaluated at the lowest operating frequency. A prototype of a 6 × 10 array is simulated, fabricated, and measured. Good agreement is achieved between the simulated and measured results. [ABSTRACT FROM AUTHOR]

• BCN was surface modified with two silane coupling agents. • Composites exhibited excellent properties before and after gamma irradiation. • The performance of composites can be improved by improving the interfacial compatibility. • Modified BCN could weaken oxidative degradation of EP under γ irradiation. Polymer matrix composites reinforced with boron nitride (BN) have attracted much attention in the nuclear industry due to their attractive properties. Nevertheless, the performance of such composites largely depends on matrix–filler interactions. Herein, carbon-doped boron nitride (BCN), modified by two silane coupling agents, was used to fabricate epoxy composites, and the effect of gamma irradiation on the properties of epoxy resin composites was investigated. The research showed that the modified BCN/epoxy composites prepared herein exhibited excellent mechanical and thermal properties before and after gamma irradiation. The tensile strength of the composites increased up to 63.1 MPa at 0.5 wt % loadings compared to neat epoxy (54.7 MPa). After irradiation at 900 kGy, the tensile strength of the composites was 32.5% higher than that of neat EP. This improvement was ascribed to the excellent compatibility of the modified BCN and epoxy. Moreover, the char yield and the glass transition temperature significantly increased with incorporation of modified BCN before and after irradiation. The mechanism for the enhanced performance was that the barrier consisting of BN protected the matrix from further oxidative degradation. This study suggested that functionalized BN more effectively enhanced epoxy properties before and after irradiation. [ABSTRACT FROM AUTHOR]

This article investigated the solubility of platinum group metals (PGMs) in sodium borosilicate glass and its effect on the viscosity and electrical conductivity of melts. The role of PGMs in the viscosity and electrical conductivity of melts was examined using the rotating cylinder method and impedance spectroscopy, respectively. Moreover, XRD, XPS, and SEM were used to measure the phase compositions, valence states, and microstructures, respectively, of the glass samples with different PGMs contents. The results showed that the solubility of Pd and Rh in sodium borosilicate glass was estimated to be less than 110 ppm by weight. The higher concentrations of Pd and Rh resulted in Pd-rich and Rh-rich inclusions in the glass matrix, which eventually agglomerated to form metallic Pd, Rh and Rh 2 O 3. The evolution of viscosity and electrical conductivity with different temperatures followed the Arrhenius equation with a fairly good linear relationship between ln η and ln κ. • The solubility of PGMs in borosilicate glass was less than 110 ppm by weight. • The aggregation and crystallization trends of PGMs in glass were investigated. • The temperature dependence of viscosity and conductivity of glass melts obeyed Arrhenius equation at high temperature region. • The viscous/electrical activation energy of glass melts containing 0–1 wt% PGMs was calculated. • The impact of PGMs concentration on the structure of PGMs aggregates had a nonlinear threshold effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • This review focuses on representative works involving Ni-, Pd-, Fe-, and Co-based catalysts with high thermal stability for ethylene polymerization in the past five years. • Classified by the ligand structure, polymerization performance parameters under elevated temperatures are discussed. • Primary approaches to develop thermally robust late transition metal catalysts are outlined. • Designability and logicality of research should be highly improved to clarify the relationship between ligand structure and thermal stability, and the combination of experimental results and theoretical calculations may be helpful. Since the pioneering work of highly active α -diimine palladium/nickel catalysts in 1995 by Brookhart, late transition metal catalysts have been extensively and deeply investigated. Although late transition metal catalysts continue to emerge with unique catalytic properties, they still encounter many formidable challenges in the process of industrialization. One of the biggest obstacles is that the traditional late transition metal catalysts typically show poor thermal stability and thus are inapplicable to industrial polymerization conditions. In recent years, numerous thermally robust late transition metal catalysts have been constantly developed to enhance the possibility of their industrial application. This review focuses on representative works involving Ni-, Pd-, Fe-, and Co-based catalysts with high thermal stability for ethylene polymerization in the past five years. Classified by the ligand structure, polymerization performance parameters under elevated temperatures including catalytic activity and polyethylene properties are summarized and discussed. It reveals that thermally stable α -diimine palladium/nickel catalysts may be the most promising candidate for industrialization. This is due to their good balance between catalytic activities and molecular weights of produced polyethylene. Furthermore, primary approaches to develop thermally robust late transition metal catalysts are outlined, which sheds light on the rational design and application of catalysts with desirable polymerization performance. As one of the most useful methods for improving the thermal stability of catalysts, steric effect can effectively suppress chain transfer and catalyst decomposition and/or deactivation process by blocking the axial coordination sites of the active metal center. Noted that most previously reported thermal stable catalysts have been developed by trial-and-error method, thus a regular understanding of the structure–property relationship of catalysts is required. To achieve the objective of industrialization, the thermal stability of late transition metal catalysts deserves more attention and is expected to achieve a further breakthrough. [ABSTRACT FROM AUTHOR]

Purpose Elbasvir (MK-8742) and grazoprevir (MK-5172; Merck & Co, Inc, Kenilworth, New Jersey) are hepatitis C virus (HCV)-specific inhibitors of the nonstructural protein 5A phosphoprotein and the nonstructural protein 3/4A protease, respectively. The aims of these studies were to evaluate the antiviral activity and safety of different doses of elbasvir or grazoprevir each administered as monotherapy to participants infected with either HCV genotype (GT) 1 or GT3. Methods These 2 double-blind, randomized, placebo-controlled, sequential-panel, multiple ascending dose studies were conducted to assess the safety and pharmacodynamics of 5 days of once-daily elbasvir or 7 days of once-daily grazoprevir in adult male participants chronically infected with either HCV GT1 or GT3. Findings Oral administration of elbasvir or grazoprevir once daily exhibited potent antiviral activity in participants with chronic GT1 or GT3 HCV infections. HCV RNA levels declined rapidly (within 1 day for elbasvir and 2 days for grazoprevir). At 50 mg of elbasvir once daily, the mean maximum reductions in HCV RNA from baseline were 5.21, 4.17, and 3.12 log 10 IU/mL for GT1b-, GT1a-, and GT3-infected participants, respectively. At 100 mg of grazoprevir once daily, the mean maximum reductions in HCV RNA from baseline were 4.74 and 2.64 log 10 IU/mL for GT1- and GT3-infected participants. Implications The results in the elbasvir monotherapy study showed that 10 to 50 mg of elbasvir was associated with a rapid decline in HCV viral load; the results in the grazoprevir monotherapy study suggest that doses of 50 mg of grazoprevir and higher are on the maximum response plateau of the dose–response curve for GT1-infected participants. The results of these proof-of-concept studies provided preliminary data for the selection of the dosages of elbasvir and grazoprevir to test in Phase II and III clinical studies. ClinicalTrials.gov identifiers: NCT00998985 (Protocol 5172-004) and NCT01532973 (Protocol 8742-002). [ABSTRACT FROM AUTHOR]