Subcomponent self-assembly of circular helical Dy6(L)6 and bipyramid Dy12(L)8 architectures directed via second-order template effects

In situ metal-templated (hydrazone) condensation also called subcomponent self-assembly of 4,6-dihydrazino-pyrimidine, o-vanillin and dysprosium ions resulted in the formation of discrete hexa- or dodecanuclear metallosupramolecular Dy₆(L)₆ or Dy₁₂(L)₈ aggregates resulting from second-order template effects of the base and the lanthanide counterions used in these processes. XRD analysis revealed unique circular helical or tetragonal bipyramid architectures in which the bis(hydrazone) ligand L adopts different conformations and shows remarkable differences in its mode of metal coordination. While a molecule of trimethylamine acts as a secondary template that fills the void of the Dy₆(L)₆ assembly, sodium ions take on this role for the formation of heterobimetallic Dy₁₂(L)₈ by occupying vacant coordination sites, thus demonstrating that these processes can be steered in different directions upon subtle changes of reaction conditions. Furthermore, Dy₆(L)₆ shows an interesting spin-relaxation energy barrier of 435 K, which is amongst the largest values within multinuclear lanthanide single-molecular magnets.

Subcomponent self-assembly gave access to Dy₁₂(L)₈ and Dy₆(L)₆ architectures via second-order template effects. The Dy₆(L)₆ assembly behaves as a single-molecule magnet exhibiting a high anisotropy barrier and butterfly-shaped magnetic hysteresis.     

Efficacy of cidofovir injection for the treatment of recurrent respiratory papillomatosis

To evaluate the efficacy of intralesional cidofovir injection for the treatment of recurrent respiratory papillomatosis (RRP). It is a prospective, open-label study design. This prospective study included 16 RRP patients, ages 9 to 68 years, who were treated with intralesional injections of cidofovir combined with surgical excision of RRP. The disease states of the patients pretreatment and posttreatment were assessed by assigning RRP severity scores, examining the need for any surgical excision of RRP, and evaluating the presence of RRP upon long-term follow-up. Sixteen patients were treated with cidofovir; however, three were lost to follow-up. Thirteen patients are the subjects of this report. This study group included three pediatric patients. Ten of thirteen patients (76.9%) responded to the treatment and are presently in remission. One patient did not respond, and two patients relapsed after initial success or had a partial response. The responders consisted of eight adults and two children. The mean number of injections the responders received was 3.5, and the average follow-up period of the responders was 25.4 months. No immediate complication of cidofovir treatment was evident. However, three patients were found to have significant vocal fold scarring after long-term follow-up. Cidofovir has been found to be efficacious in treating RRP. Further study regarding long-term follow-up and the assessment of possible side effects after cidofovir intralesional injection for RRP is required.     

General order Newton-Padé approximants for multivariate functions

Summary Padé approximants are a frequently used tool for the solution of mathematical problems. One of the main drawbacks of their use for multivariate functions is the calculation of the derivatives off(x ₁, ...,x _p ). Therefore multivariate Newton-Padé approximants are introduced; their computation will only use the value off at some points. In Sect. 1 we shall repeat the univariate Newton-Padé approximation problem which is a rational Hermite interpolation problem. In Sect. 2 we sketch some problems that can arise when dealing with multivariate interpolation. In Sect. 3 we define multivariate divided differences and prove some lemmas that will be useful tools for the introduction of multivariate Newton-Padé approximants in Sect. 4. A numerical example is given in Sect. 5, together with the proof that forp=1 the classical Newton-Padé approximants for a univariate function are obtained.     

Sur le théorème en moyenne d'Akcoglu-Sucheston

Sans résumé     

Glycol-cleavage reagents also act on stannylene derivatives.

The well-known cleavage reactions of vicinal diols by such reagents as Pb(OAc)₄, NaIO₄, PhI(OAc)₂ and Ph₃Bi^V-compounds have now been observed for the first time on covalent derivatives of these vicinal diols, their dibutylstannylenes.     

Spin chirality in a molecular dysprosium triangle: the archetype of the noncollinear ising model

Single crystal magnetic studies combined with a theoretical analysis show that cancellation of the magnetic moments in the trinuclear Dy3+ cluster [Dy{3}(mu{3}-OH)2L3Cl(H2O){5}]Cl{3}, resulting in a nonmagnetic ground doublet, originates from the noncollinearity of the single-ion easy axes of magnetization of the Dy3+ ions that lie in the plane of the triangle at 120 degrees one from each other. This gives rise to a peculiar chiral nature of the ground nonmagnetic doublet and to slow relaxation of the magnetization with abrupt accelerations at the crossings of the discrete energy levels.     

Multiscale experimental investigations about the cyclic behavior of the 304L SS

This work follows a series of experiments carried out earlier at INSA of Rouen (Hassan, T., Taleb, L., Krishna, S., 2008. Influence of non-proportional loading paths on ratcheting responses and simulations by two recent cyclic plasticity models. Int. J. Plast. 24, 1863–1889). It investigates the elastoplastic cyclic behavior of a 304L stainless steel at room temperature. In a first step the cross path effect on ratcheting is confirmed, as well as the crucial role of the loading path non-proportionality. Strain controlled tests are also conducted for different strain amplitudes and loading paths. Cross-hardening effect appears more important when the shearing sequence is followed by the axial one. Moreover for alternating axial and shearing cycles, this phenomenon occurs after each crossing sequence leading to a very significant strain hardening, at least of the same order as the one obtained after a circular strain path. Yet, the magnitude of the observed over hardening does not necessarily seem a function of the cumulated plastic strain.     

Direct observation of the preference of hole transfer over electron transfer for radical ion pair recombination in donor-bridge-acceptor molecules

Understanding how the electronic structures of electron donor-bridge-acceptor (D-B-A) molecules influence the lifetimes of radical ion pairs (RPs) photogenerated within them (D+*-B-A-*) is critical to designing and developing molecular systems for solar energy conversion. A general question that often arises is whether the HOMOs or LUMOs of D, B, and A within D+*-B-A-* are primarily involved in charge recombination. We have developed a new series of D-B-A molecules consisting of a 3,5-dimethyl-4-(9-anthracenyl)julolidine (DMJ-An) electron donor linked to a naphthalene-1,8:4,5-bis(dicarboximide) (NI) acceptor via a series of Phn oligomers, where n = 1-4, to give DMJ-An-Phn-NI. The photoexcited charge transfer state of DMJ-An acts as a high-potential photoreductant to rapidly and nearly quantitatively transfer an electron across the Phn bridge to produce a spin-coherent singlet RP 1(DMJ+*-An-Phn-NI-*). Subsequent radical pair intersystem crossing yields 3(DMJ+*-An-Phn-NI-*). Charge recombination within the triplet RP then gives the neutral triplet state. Time-resolved EPR spectroscopy shows directly that charge recombination of the RP initially produces a spin-polarized triplet state, DMJ-An-Phn-3*NI, that can only be produced by hole transfer involving the HOMOs of D, B, and A within the D-B-A system. After the initial formation of DMJ-An-Phn-3*NI, triplet-triplet energy transfer occurs to produce DMJ-3*An-Phn-NI with rate constants that show a distance dependence consistent with those determined for charge separation and recombination.