Search results for "ELF"

Fine-Tuning the Dimerization of Tetraureacalix[4]arenes

2010

Calix[4]arenes substituted by four urea residues at their wide rim form hydrogen-bonded homo- and heterodimeric capsules in apolar solvents. If urea groups are covalently connected to loops or substituted by bulky residues, the dimerization may be restricted to those pairs in which the loops do not overlap and for which the residues are small enough to pass the loops. In the present study, we describe the dimerization properties of tetraureas with one, two (adjacent or opposite), three, or four loops and those bearing (additionally) up to four residues of different size: a = tolyl, b = 3,5-di-tertbutylphenyl, c = 4-propyloxy-3,5-di-(tert-butylphenyl)phenyl, and d=4-[tris-(4-tert-butylphenyl…

Towards multifunctional magnetic systems through molecular-programmed self assembly of Re(IV) metalloligands

2015

Abstract The molecular-programmed approach based on the use as ligands of tailor-made metalloligands containing stable six-coordinate rhenium(IV) as paramagnetic centres is presented in this review article. A relatively large amount of spin density is covalent-delocalized away from the rhenium to the peripheral atoms of the ligands in the case of the Re(IV) metalloligands, as shown by polarized neutron diffraction experiments and density functional theory calculations. This feature accounts for the significant through space-magnetic interactions that occur in most of its mononuclear species and more interestingly it also explains the strengthening of the magnetic interactions in the heterom…

Dynamic formation of hybrid peptidic capsules by chiral self-sorting and self-assembly.

2014

Owing to their versatility and biocompatibility, peptide-based self-assembled structures constitute valuable targets for complex functional designs. It is now shown that artificial capsules based on β-barrel binding motifs can be obtained by means of dynamic covalent chemistry (DCC) and self-assembly. Short peptides (up to tetrapeptides) are reversibly attached to resorcinarene scaffolds. Peptidic capsules are thus selectively formed in either a heterochiral or a homochiral way by simultaneous and spontaneous processes, involving chiral sorting, tautomerization, diastereoselective induction of inherent chirality, and chiral self-assembly. Self-assembly is shown to direct the regioselectivit…

Noncovalentπ⋅⋅⋅π-Stacked Exo-Functional Nanotubes: Subtle Control of Resorcinarene Self-Assembly

2004

General occurrence of polar twisted minima in the ionic singlet excited surfaces of polyenes

1982

Except for a few cases, the lowest closed shell SCF solutions for the twisted geometries of polyenes involves delocalized nonpolarized MO’s, and represents a meaningless mixture of radicalar gound state and ionic excited states. Higher (quasi) solutions allow a realistic approach of the polarized ionic states. Orthogonality to the radicalar ground state may be imposed without important loss of energy. Further extensive CI does not modify significantly the situation. These statements are illustrated through ab initio calculations of butadiene and hexatriene. This approach allows us to show that slight distortions stablize polar minima even in ’’homosymmetric’’ molecules such as all‐trans hex…

Temperature and polymer crosslinking degree influence on drug transfer from alpha,beta-polyasparthydrazide hydrogel to model membranes. A calorimetri…

1998

Abstract A non-steroidal anti-inflammatory drug, diflunisal, has been chosen as drug model to be incorporated in α , β -polyasparthydrazide (PAHy) matrices to study the effect of polymer crosslinking degrees on the release processes from hydrogel ( X =0.4 and X =0.8) to a model membrane represented by unilamellar vesicles of dipalmitoylphosphatidylcholine. The technique employed to monitor these processes was differential scanning calorimetry that appears to be particularly suitable to follow the transfer kinetics of a drug from a controlled release system to void biomembrane model. The drug release from the two PAHy hydrogels differently crosslinked by glutaraldehyde to the lipidic model w…

Determination of single crystal elastic constants in textured polycrystalline materials: inverse approach coupling x-ray diffraction and self consist…

2004

La diffraction des rayons X couplee a l'utilisation d'un modele polycristallin (modele auto-coherent) est utilisee pour determiner les constantes d'elasticite monocristallines d'un materiau polycristallin texture. En effet, la connaissance du tenseur de rigidite elastique cijkl d'un solide est fondamentale pour les etudes s'attachant a la comprehension des proprietes mecaniques de la matiere (approches theoriques ou experimentales). Si, d'autres techniques permettent de determiner le tenseur d'elasticite d'un materiau (ultrasons par exemple), elles necessitent souvent l'utilisation d'un monocristal. Ceci n'est pas toujours realisable, en particulier pour des alliages de concentrations varia…

Static and dynamic screening effects in the electrostatic self-assembly of nano-particles.

2014

In the description of charge screening in the electrostatic self-assembly of nanoparticles (molecules) embedded into a polar solvent, the static screening effects (a contribution associated with the rapid spatial redistribution of small and highly mobile ions of a solvent) are traditionally treated phenomenologically, using the Yukawa short-range potential for describing the interaction between these particles. However, this model has a limited range of applicability being valid only for infinitely diluted systems and high salt concentrations. During a slow self-assembling process with nanoparticle formation, very dense structural elements (aggregates) are formed, in which the distances bet…

Self-adjuvanting C18 lipid vinil sulfone-PP2A vaccine: study of the induced immunomodulation against

2017

Despite the importance of the adjuvant in the immunization process, very few adjuvants merge with the antigens in vaccines. A synthetic self-adjuvant oleic-vinyl sulfone (OVS) linked to the catalytic region of recombinant serine/threonine phosphatase 2A from the nematode Angiostrongylus costaricensis (rPP2A) was used for intranasal immunization in mice previously infected with Trichuris muris. The animal intranasal immunization with rPP2A-OVS showed a reduction of 99.01% in the number of the nematode eggs and 97.90% in adult. The immunohistochemical analysis of the intestinal sections showed that in immunized animals with lipopeptide the mucus was significantly higher than in the other expe…

Visible but unreported: a case for the "not serious enough" cases of child maltreatment.

1995

This study examined the psychosocial characteristics of cases of child maltreatment labelled as "not serious enough." The sample consisted of cases of suspected physical abuse (N = 48), neglect (N = 13), and psychological maltreatment (N = 8) identified by teachers, and a nonabused comparison group (N = 283). Characteristics of children and their parents were evaluated at three ecological levels: individual, family, and social. Results indicated a poor personal and social adjustment of the children in the maltreatment groups, and suggest that the definition of cases of maltreatment as not serious enough does not represent the psychological reality of these children. Discriminant analysis in…