Comonotone approximation with interpolation at the ends on an interval

Let a function f ∈ C[-1, 1], changes its monotonisity at the finite collection Y := {y1,… ,ys} of s points yi ∈ (-1, 1). For each n ≥ N(Y), we construct an algebraic polynomial Pn, of degree ≤ n, which is comonotone with f, that is changes its monotonisity at the same points yi as f, and |f(x)-Pn(x)|≤c(s)ω2(f,(√1-x2)/n), x∈[-1,1],where N(Y) is a constant depending only on Y, c(s) is a constant depending only on s and ω2 (f, t) is the second modulus of smoothness of f.     

Tailoring the polarity of polymer shell on BaTiO_3 nanoparticle surface for improved energy storage performance of dielectric polymer nanocomposites

Nanocomposites comprising flexible polymers and high dielectric constant inorganic nanoparticles are considered to be one of the promising candidates for electrostatic capacitor dielectrics.However,the effect of interfacial property on electrical ene rgy storage of dielectric polymer nanocomposites is still not clear.Herein,the role of the polarity of the interfacial region is investigated.For this purpose,three polymers with different polarity,polymethyl methacrylate(PMMA),polyglycidyl methacrylate,and polymethylsulfonyl ethyl methacrylate(PMSEMA) are attached onto BaTi03(BT) na noparticle surface via surface-initiated reversible addition-fragmentation chain transfer polymerization.It is found that the polarity of shell polymers shows an apparent effect on the dielectric and energy storage of dielectric polymer nanocomposites.For example,PMSEMA@BT(shell polymer possesses the highest polarity)increases dielectric loss and decreases the breakdown strength of the nanocomposites,leading to lower ene rgy storage capability.However,PMMA@BT(shell polymer possesses the lowest polarity) can induce higher breakdown strength of the nanocomposites.As a result,the PMMA@BT nanocomposite exhibits the highest electrical energy sto rage capability among the three nanocomposites.This re search provides new insight into the design of core-shell nanofillers for dielectric energy storage applications.     

Kinetic study on solute permeation at the interface of molecular aggregates by partial filling capillary electrophoresis

Moment analysis method using partial filling CE was developed for the kinetic study on solute permeation at the interface of spherical molecular aggregates. Moment equations for partial filling CE were developed by classifying CE systems into five categories according to the migration velocities of solute and molecular aggregate. The method was applied to the study on the dissolution of electrically neutral solutes into SDS micelles. Elution peaks were measured by partial filling CE while changing the concentration of SDS and the filling ratio of SDS micellar zone to the capillary (ϕ_M). Partition equilibrium constants (K_p) and rate constants of interfacial solute permeation of SDS micelles (k_in and k_out) were determined from the first absolute and second central moments of the elution peaks by using the moment equations. Their values were comparable irrespective of ϕ_M and were almost the same as those previously measured by complete filling CE. The positive correlation of K_p with the hydrophobicity of the solutes was explained in terms of the change in k_in and k_out. It was demonstrated that the moment analysis method using partial filling CE is effective for studying solute permeation kinetics at the interface of spherical molecular aggregates.     

Preparation of Low-dielectric Permittivity Polyimide Resins with High Surface Activity from Chemically Bonded Hyperbranched Polysiloxane

Thermosetting resin matrix is the key component of advanced wave-transparent composites,where low dielectric constant,excellent processability,high thermal stability,as well as good bonding ability are required for resins.Herein,we prepared a series of phenylethynyl terminated polyimide(PI)resins by grafting amine-functionalized hyperbranched polysiloxane(HBPSi)to PI chains during the in situ polymerization.The effects of HBPSi on the processability of oligomers,molecular packing,thermal stability,dielectric property and bonding ability to reinforce Kevlar fibers of the cured PI/HBPSi composite resins have been examined in detail.The dielectric constants of the cured composite resins were greatly reduced from 3.29 to 2.19 without compromising its processability and thermal stability.Meanwhile,the 10 wt％HBPSi-containing PI resin demonstrated better bonding ability to reinforce fibers with the interfacial shear strength(IFSS)of 37.64 MPa,compared with that of neat PI-6 matrix(27.34 MPa),and better adhesion to metal with the lap shear strength of 10.48 MPa,50％higher than that of neat resin PI-6(6.98 MPa).These resultant PI/HBPSi composite resins exhibit excellent comprehensive properties,indicating their great potential as low-dielectric constant resin matrix in radar radome.     

DCE-MRI定量参数对子宫内膜癌的诊断价值及与临床病理因素的相关性

本文选取了子宫内膜癌患者108例作为观察组,另选取子宫内膜良性病变患者105例作为对照组,均行DCE-MRI检查后发现,观察组容量转移常数(K trans)、速率常数(K ep)、血管外细胞外间隙容积比值(V e)高于对照组(P<0.05);K trans、K ep、V e值联合诊断子宫内膜癌的曲线下面积(AUC)为0.841;K trans、K ep、V e值与临床分期、肌层浸润程度呈正相关,与分化程度呈负相关(P<0.05)。本研究结果提示DCE-MRI定量参数对子宫内膜癌具有一定鉴别诊断价值,有助于进一步区分子宫内膜癌患者肌层浸润程度、临床分期、分化程度。     

Unexpected Radical Telomerisation of Vinylidene Fluoride with 2-Mercaptoethanol

The radical telomerisation of vinylidene fluoride (VDF) with 2-mercaptoethanol as chain transfer agent (CTA) was studied to synthesise fluorinated telomers which bear a hydroxy end-group, such as H(VDF)_nS(CH₂)₂OH, under thermal (di-tert-butyl peroxide as the initiator) or photochemical initiations. A careful structural study of a typical H-VDF-S(CH₂)₂OH telomer was performed by ¹H and ¹⁹F NMR spectroscopy. These analytical methods allowed us to explore the selective addition of the thiyl radical onto the hydrogenated side of VDF, and the telomer containing one VDF unit was obtained selectively. Surprisingly, for higher [VDF]_o initial concentrations, a monoadduct telomer was produced as well as PVDF homopolymer. This feature was related to the fast consumption of the CTA. The kinetics of radical telomerisation led to a quite high transfer constant of the CTA (40 at 140 °C) that evidences the formation of a monoadduct as the only telomer formed.     

Thermodynamic studies on protonation constant of adenosine and guanosine at different temperatures and ionic strengths

Stepwise protonation constants of two purine nucleosides (adenosine and guanosine) were determined at different temperatures (293.15 to 308.15) and various ionic strengths (0.101 to 3.503 mol · kg⁻¹ NaClO₄) using a combination of potentiometric and spectrophotometric method. The thermodynamic parameters (i.e. enthalpy change, ΔH, and entropy change, ΔS) of the protonations were calculated at different temperatures using van’t Hoff and virial equations. The dependence of the protonation constant on ionic strength is modeled by a Debye–Hückel type equation and discussed. Finally, the protonation constants of the nucleosides and the enthalpy change of protonations were determined at zero ionic strength.     

Anharmonic Effect of the Unimolecular Isomerization/Decomposition of Benzyne

The anharmonic and harmonic rate constants were calculated for the unimolecular decomposition of o‐benzyne, the isomerization of o‐benzyne to m‐benzyne, the isomerization of m‐benzyne to p‐benzyne and unimolecular decomposition of p‐benzyne by using the Rice–Ramsperger–Kassel–Marcus (RRKM) theory respectively, in the canonical and microcanonical systems. The geometry and the vibrational frequencies were calculated by MP2 and B3LYP methods with 6‐311G(d,p) basis set and the barrier energies were corrected using CBS‐QB3 theory. The anharmonic effect on the reactions was also examined. Comparison of results for the decompositions of benzyne indicate that both in microcanonical and canonical cases, the anharmonic effect on the decomposition of the o‐C₆H₄ and p‐C₆H₄ are significant, while the anharmonic effect on the two isomerizations are not pronounced.     

环烷酸对油水界面膜流变性质的影响研究

研究了环烷酸对油水界面膜界面张力、弹性模量、损耗模量以及界面膜破裂速率常数的影响,同时对环烷酸与沥青质之间的相互作用进行了测定。结果表明,环烷酸使得原油油水界面张力下降;弹性模量随着环烷酸加量以及振荡频率的增加都分别逐渐增大,并且最终都趋于平衡;在任何振荡频率值时,损耗模量都随着环烷酸加量先增大后减小;当环烷酸加量增加时,界面膜破裂速率常数降低。环烷酸与沥青质之间存在相互作用,随着环烷酸加量的增加,其对沥青质界面膜弹性模量的影响与对原油界面膜弹性模量的影响相似,表明环烷酸主要是通过与沥青质相互作用而促进乳状液稳定性的。