A comparative kinetic study of modified Pt(dppf)Cl2 complexes and their interactions with L-cys and L-met

With the success of cisplatin (cis-diamminedichloroplatinum(II)), strong interest has developed in the application of inorganic metal complexes to the treatment of cancer. Research has focused on platinum(II) complexes with a variety of spectator ligands that provide novel physicochemical properties. In this paper we report a kinetic study of 1',1'-bis(diphenylphosphino)ferrocenedichloroplatinum(II) and two related compounds with either an acetate or amide ester substituent attached to the cyclopentadienyl ring. For all compounds the reactivity towards L-cysteine and L-methionine in aqueous solution has been investigated (25 degrees C, I= 0.010 M and pseudo-first-order conditions). For the reactions with l-cysteine and l-methionine the reactions proceeded via a steady-state aquated intermediate to form mono (0.92(2)-3.25(4)) x 10(-3) s(-1)) and bis adducts (0.97(2)-3.67(4)) x 10(-4) s(-1)). For reactions with l-cysteine, direct reactions with the starting complex also contributed (mono adduct: 0.36(2)-1.41(4) M(-1) s(-1), bis adduct: 0.080(1)-0.96(1) M(-1) s(-1)). The attached substituents were found to have a significant effect upon the reaction kinetics, with the substituted complexes found to have increased reactivity. It is proposed that the increased reactivity stems from hydrogen bonding between the substituent and the entering ligand and subsequent outer-sphere complex stabilisation. Evidence in support of this theory was obtained form measurements in dichloromethane with 1-propanethiol as the entering ligand. The reactivity of the dppf containing complexes was also compared to that of cisplatin (mono adduct: (0.170(1)-0.175(1)) x 10(-3) s(-1), bis adduct: (0.183(1)-0.397(1)) x 10(-4) s(-1)) and found to be significantly enhanced.     

Limit equilibrium analysis and the minimum thickness of circular masonry arches to withstand lateral inertial loading

In this paper, we compute the location of the imminent hinges and the minimum thickness, t, of a circular masonry arch with mid-thickness radius, R, and embracing angle, β, which can just sustain its own weight together with a given level of a horizontal ground acceleration, ε g. Motivated from the recent growing interest in identifying the limit equilibrium states of historic structures in earthquake prone areas, this paper shows that the value of the minimum horizontal acceleration that is needed to convert an arch with slenderness (t/R, β) into a four-hinge mechanism depends on the direction of the rupture at the imminent hinge locations. This result is obtained with a variational formulation and the application of the principle of stationary potential energy, and it is shown that a circular arch becomes a mechanism with vertical ruptures when subjected to a horizontal ground acceleration that is slightly lower than the horizontal acceleration needed to create a mechanism with radial ruptures. The paper explains that the multiplicity on the solution for the minimum uplift acceleration is a direct consequence of the multiple possible ways that a masonry arch with finite thickness may rupture at a given location. The paper further confirms that the results obtained with commercially available distinct element software are in very good agreement with the rigorous solution.     

Comparison of Li+‐ion conductivity in linear and crosslinked poly(ethylene oxide)

Polymer electrolytes are of tremendous importance for applications in modern lithium‐ion (Li⁺‐ion) batteries due to their satisfactory ion conductivity, low toxicity, reduced flammability, as well as good mechanical and thermal stability. In this study, the Li⁺‐ion conductivity of well‐defined poly(ethylene oxide) (PEO) networks synthesized via copper(I)‐catalyzed azide–alkyne cycloaddition is investigated by electrochemical impedance spectroscopy after addition of different lithium salts. The ion conductivity of the network electrolytes increases with increasing molar mass of the PEO chains between the junction points which is completely opposite to the behavior of their respective uncrosslinked linear precursors. Obviously, this effect is directly related to the segmental mobility of the PEO chains. Furthermore, the ion conductivity of the network electrolytes under investigation increases also with increasing size of the anion of the added lithium salt due to a weaker anti‐plasticizing effect of the more bulky anions. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 21–28     

Design and validation of a nonlinear vibration absorber to attenuate torsional oscillations of propulsion systems

Nonlinear Dynamics - Recent developments in propulsion systems to improve energy efficiency and reduce hazardous emissions often lead to severe torsional oscillations and aggravated noise....     

A Complete Foliation of Schwarzschild Spacetime by Free Falling Hypersurfaces

Free falling hypersurfaces in the Schwarzschild geometry have been studied to provide a complete foliation of spacetime. The hypersurfaces do not cross into the maximally extended spacetime and are well behaved everywhere except at the singularity r =0 the mean extrinsic curvature becomes infinity.     

Experimental Observation of Bright and Dark Solitons Mode-Locked with Zirconia-Based Erbium-Doped Fiber Laser

We demonstrate the generation of dark and bright solitons with our homemade zirconia-based erbium-doped fiber and graphene oxide(GO) saturable absorber in anomalous dispersion region.The GO is fabricated using an abridged Hummer's method,which is combined with polyethylene oxide to produce a composite film.The film is sandwiched between two optical ferrules and embedded in the laser cavity to enhance its birefringence and nonlinearity.The self-starting bright soliton is easily generated at pump power of 78 mW with the whole length cavity of 14.7 m.The laser produces the bright pulse train with repetition rate,pulse width,pulse energy and central wavelength being 13.9 MHz,0.6 ps,2.74 p J and 1577.46 nm,respectively.Then,by adding the 10 m of single mode fiber into the laser cavity,dark soliton pulse is produced.For the formation of dark pulse train,the measured repetition rate,pulse width,pulse energy and central wavelength are 8.3 MHz,20 ns and 4.98 p J and1596.82 nm,respectively.Both pulses operate in the anomalous region.