Pluronic F-68 nanodots incorporating pyrimidine chromophores

We report the synthesis of nanosized particles based on bio-compatible polyethylene–polypropylene glycol (pluronic) materials. In aqueous solution, mini-emulsification of pluronic with two pyrimidine chromophores leads to nanoparticles with hydrodynamic radius below 100?nm. We have demonstrated that these probes exhibit a fast and fully reversible solvatochromic behaviour from yellow to purple when decreasing the pH solution. The average acidity constant of both dyes incorporated in pluronic mainly originate from the non-substituted pyrimidine (1,3-diazine) core. The close functionalization of the pyrimidine with pyridyl groups leads to a tridentate ligand suitable for metal cations complexation.

1,3- versus 1,4-[π4+π2] Cycloadditions between methyl glyoxylate oxime and cyclopentadiene or cyclopentene

The acid catalyzed cycloaddition reaction of methyl glyoxylate oxime with cyclopentadiene (CPD) afforded the corresponding aza-Diels–Alder adducts, the endo and exo isomers of (±)-methyl 2-hydroxy-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylates, and as the major product a 1,3-cycloadduct, methyl (1RS,4RS,5RS)-(2-oxa-3-azabicyclo[3.3.0]oct-7-ene)-4-carboxylate. The similar reaction using cyclopentene (CP) provided only the 1,3-cycloadduct methyl (1SR,4RS,5SR)-(2-oxa-3-azabicyclo[3.3.0]octane)-4-carboxylate. The influence of various parameters on the reaction outcome was studied and, based on the results obtained, a mechanism for the formation of both 1,3- and 1,4-cycloadducts is proposed. The structure of all adducts was confirmed by NMR spectroscopic data and/or by X-ray crystallography.     

Microscopic pressure-cooker model for studying molecules in confinement

A model for a system of a finite number of molecules in confinement is presented and expressions for determining the temperature, pressure, and volume of the system are derived. The present model is a generalisation of the Zwanzig–Langevin model because it includes pressure effects in the system. It also has general validity, preserves the ergodic hypothesis, and provides a formal framework for previous studies of hydrogen clusters in confinement. The application of the model is illustrated by an investigation of a set of prebiotic compounds exposed to varying pressure and temperature. The simulations performed within the model involve the use of a combination of molecular dynamics and density functional theory methods implemented on a computer system with a mixed CPU–GPU architecture.     

Pressure Effects on the Cooperative Jahn-Teller Distortion in AMnF 4 (A=Na,Tl)

This work investigates the Optical Absorption spectrum of the AMnF 4 layer perovskites of Mn 3+ , and its variation with the pressure. We show that the crystal-field transition energies and their pressure shifts provide a very useful information about the local structural changes in the \hbox{MnF}_6^{3-} complex and how it changes with the pressure, once the correlations between crystal-field electronic structure and coordination geometry around Mn 3+ has been established. Along this work we demonstrate that the equatorial and axial distances decrease from 1.844 to 1.813 + , and from 2.167 to 2.090 + , respectively, in the 0-100 kbar range, leading to a partial reduction of the Jahn-Teller distortion.     

Pressure Dependence on the Magnetic Structures of TbNi 1−x Cu x ( x =0.3 & 0.4) Using Neutron Techniques

In the TbNi 1 m x Cu x series, the Cu substitution has two main effects: the increase of the cell volume (～4.3% from TbNi to TbCu), and the increasing importance of antiferromagnetic interactions. In this sense, the magnetic structures of these compounds evolve from a non-collinear ferromagnetic (FM) arrangement to an incommensurate antiferromagnetic (AFM) one for Cu concentration larger than 35%. In this paper, we present the effects of pressure on the magnetic structures of the compounds which are closer to this critical concentration: TbNi 0.7 Cu 0.3 (FM) and TbNi 0.6 Cu 0.4 (AFM). It appears that a global antiferromagnetic behaviour is favoured by pressure.     

Is it possible to use Charge Transfer Bands to Measure Impurity-Ligand Distances? Experimental and Theoretical Results on Cu 2+ Doped (C 2 H 5 NH 3 ) 2 CdCl 4

The present work is focused on the effects produced by hydrostatic pressure on Cu 2+ (<100 ppm) doped (C 2 H 5 NH 3 ) 2 CdCl 4 single crystal. The energy E u ( ~ ) of the e u ( ~ ) M b 1 g (～ x 2 m y 2 ) charge-transfer transition of (C 2 H 5 NH 3 ) 2 CdCl 4 : Cu 2+ undergoes a red shift of 1400 cm m 1 on passing from ambient pressure to 40 kbar. To understand this fact theoretical calculations of the {\rm CuCl}^{4-}_{6} complex using four different methods have been carried out. Based on these calculations, it is concluded that the experimental red shift undergone by E u ( ~ ) can only be reasonably explained through a decrease of ～25 pm in R ax and an increase of ～7 pm in R eq leading to a decrement of the {\rm CuCl}^{4-}_{6} volume. Variations of any metal-halide distances down to 0.1 pm can be well detected through the shifts of the charge-transfer band energy upon pressure.     

On Urbanik's Axioms for Absolute Valued Algebras with Involution

Let W be an infinite word over finite alphabet A. We get combinatorial criteria of existence of interval exchange transformations that generate the word W.     

Asymptotic derivation of frictionless contact models for elastic rods on a foundation with normal compliance

Using asymptotic methods we derive some models for elastic rods in frictionless contact with a foundation with normal response. Starting from the three-dimensional problem we characterize the first terms of an asymptotic expansion of the solution taking the diameter of cross section as small parameter. Then we prove the convergence as this diameter tends to zero. In this way, we obtain and we mathematically justify a simplified model generalizing the best known classical models of such frictionless contact problems.     

On Lineability in Vector Integration

We prove the existence of infinite-dimensional linear spaces of Banach space-valued functions whose non-zero elements witness that two given notions of integrability are different: Bochner, Birkhoff, McShane, Pettis and Dunford integrability are considered.     

On the global convergence of a generalized iterative procedure for the minisum location problem with ℓ p distances for p > 2

This paper presents a procedure to solve the classical location median problem where the distances are measured with ? _p -norms with p > 2. In order to do that we consider an approximated problem. The global convergence of the sequence generated by this iterative scheme is proved. Therefore, this paper closes the still open question of giving a modification of the Weiszfeld algorithm that converges to an optimal solution of the median problem with ? _p norms and ${p \in (2, \infty)}$ . The paper ends with a computational analysis of the different provided iterative schemes.