New strategies in the synthesis of regioselectively trifluoromethyl- and trifluoromethoxy-substituted arenes as building blocks for biologically active molecules

Regioisomerically pure trifluoromethyl- and trifluoromethoxy-substituted aromatic and heteroaromatic aldehydes and carboxylic acids are valuable building blocks for the synthesis of biologically active molecules. They have been prepared by employing modern organometallic methods. On this basis, a novel access to 2,3-dihydro-5-(trifluoromethoxy)indole was developed which represents an intriguing example of how organometallic and radical chemistry can fecundate each other.     

Periodic solutions of non linear differential difference equations

In this paper we will be interested in the behaviour of long chains of coupled gravitational pendula. We will prove existence and uniqueness of periodic solutions for such chains under periodic forcing and will prove that under some smoothness assumptions the chain behaves as an uncoupled one. We will also analyse a more general class of differential difference equations and prove existence and unicity results for periodic solutions.Research partially supported by AFOSR under U.R.I, contract F49620-86-C-0131 to Northeastern University.     

Single–Step Synthesis of Nanocrystalline Doped-Lanthanum Hydroxide Materials from Heterometallic Alkoxides

The reactions between La₃(OBu^t)₉(HOBu^t)₂ and various trimethylsilylamide species M[N(SiMe₃)₂] _x(THF)_y (M = K, Ba, Pb) have been investigated as a means to acceed to heterometallic La-M species. The La-K derivative was used as synthon in metathesis reaction toward CuCl₂ in order to get an heterometallic La-Cu derivative. All compounds were characterized by elemental analysis, FT-IR, EPR and multinuclear NMR spectroscopies. Their hydrolyses at room temperature in THF led to nanocrystalline doped-lanthanum hydroxides. The as-prepared materials were characterized by elemental analysis, XRD and TEM. Their thermal behavior was studied by XRD and compared with that of yttrium derivatives.     

Highly metallized polymers: synthesis, characterization, and lithographic patterning of polyferrocenylsilanes with pendant cobalt, molybdenum, and nickel cluster substituents

High molecular weight, soluble, air- and moisture-stable, highly metallized (>25 wt% metal) polyferrocenylsilanes (PFS) [Fe(eta-C5H4)2Si(Me){Co2(CO)6C2Ph}]n (Co-PFS), [Fe(eta-C5H4)2Si(Me){Mo2-Cp2(CO)4C2Ph}]n (Mo-PFS), and [Fe(eta-C5H4)2Si(Me){Ni2Cp2C2Ph}]n (Ni-PFS) containing pendant cobalt, molybdenum, and nickel clusters, respectively, have been prepared via macromolecular clusterization of an acetylide-substituted PFS [Fe(eta-C5H4)2Si(Me)C(triple bond)CPh]n with [Co(2)(CO)8], [{MoCp(CO)(2)}2], or [{NiCp(CO)}2]. The extent of clusterization achieved was in the range of 70-75%. All three highly metallized polymers were demonstrated to function as negative-tone resists in electron-beam lithography, while Co-PFS and Mo-PFS were successfully patterned by UV-photolithography, allowing the fabrication of micron-sized bars, dots, and lines. These studies suggest that the highly metallized polymers may be useful in the fabrication of patterned arrays of alloy nanoparticles for both materials science and catalytic applications.     

Data completion via an energy error functional

We propose, in this Note, a new procedure for data completion based on the minimization of an energy like error functional. The efficiency of the proposed method is illustrated by a thermostatic application. To cite this article: S. Andrieux et al., C. R. Mecanique 333 (2005).     

Physicochemical and thermodynamic characterization of hydroxy pentacyclic triterpenoic acid/γ-cyclodextrin inclusion complexes

Hydroxy pentacyclic triterpenoic acids (HPTAs) have been described to exhibit numerous pharmacological properties. They also exhibit poor hydrosolubility, thus affecting their potential clinical interest. The association of these active substances with cyclodextrins could be employed to improve some properties such as bioavailability and activity. 1:1 Inclusion complexes of ursolic, oleanolic and betulinic acids with γ-cyclodextrin were evaluated by DSC and ¹H NMR spectroscopy. The apparent formation constants (K_f) of the formed complexes were determined using RP-HPLC. Thermodynamic parameters ΔGo, ΔHo and ΔSo were calculated with temperatures ranging from 25 to 45?°C to evaluate the complexation process. Finally the influence of γ-CD on the HPTA water solubility was investigated by phase-solubility studies.     

Rheological constitutive equation of solids: a link between models based on irreversible thermodynamics and on fractional order derivative equations

In this paper we focus on the rheological problem of defining a constitutive equation for viscoelastic materials. In this simple case, we show that writing the dissipative component of the observable response to a given excitation as the result of multiple internal processes working for equilibrium recovery (flux of internal hidden variables), can yield a recursive series in time. This can be obtained when use is made of the theorem of created entropy equipartition as a model for fluctuation regression. A distribution (spectrum) for relaxation times naturally follows. The model thus obtained reflects the concept of a hierarchically constrained dynamic behavior. The conclusion is that the operator of non-integer differentiation in time applied to field variables can also be recovered from pure thermodynamic considerations.     

GaN nanowires for piezoelectric generators

We demonstrate the high potential of GaN nanowires (NWs) to convert mechanical energy into electric energy. Using an atomic force microscope equipped with a Resiscope module, an average output voltage of –74 mV and a maximum of –443 mV ± 2% per NW were measured. This latter value is the highest reported so far for GaN NWs. By considering these output signals, we have estimated an average and a maximum power density generated by one layer of GaN NWs of the order of 5.9 mW/cm² and 130 mW/cm², respectively. These results offer promising prospects for the use of GaN NWs for high‐efficiency ultracompact piezogenerators. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)