Specific heat measurements and structural investigation of CeCu6 - xSnx compounds

International audienceThe evolution of the crystal structure and some magnetic properties of the heavy-fermion material CeCu6 - xSnx (x = 0, 0.25, 0.65, 0.75, 0.85 and 1.0) has been studied by powder neutron diffraction and by specific heat measurements. The substitution of Cu by Sn suppresses the temperature induced orthorhombic to monoclinic transition, known to occur in the pure CeCu6 phase. No structural phase transition has been observed in these samples as a function of x but the cell volume increases considerably in an anisotropic way. Sn occupies preferentially the special Cu crystallographic site which is next to each of the four Ce atoms in the unit cell. The transition to antiferromagnetic order, characterizing the samples with higher x, is sensitive to both x and magnetic field. The results are discussed in the context of the competition between Kondo and RKKY interactions in disordered or not heavy-fermion systems and reveal an interesting interplay between composition, structure and magnetism in CeCu6 - xSnx

Evaluation of Human Telomeric G-Quadruplexes: The Influence of Overhanging Sequences on Quadruplex Stability and Folding

To date, various G-quadruplex structures have been reported in human telomeric sequences. Human telomeric repeats can form many topological structures depending on conditions and on base modification; parallel, antiparallel, and hybrid forms. The effect of salts and some specific ligands on conformational switches between different conformers is known, but the influence of protruding sequences has rarely been discussed. In this paper, we analyze different quadruplex-forming oligomers derived from human telomeric sequences which contain 3′- and 5′-protruding nucleotides, not usually associated with the G-quadruplex motif. The study was performed using electrophoresis, CD, and UV spectroscopies. The major findings are (i) protruding nucleotides destabilize the G-quadruplex structure, and (ii) overhanging sequences influence the folding of the quadruplex

Accuracy of 3-Dimensional Transoesophageal Echocardiography in Assessment of Prosthetic Mitral Valve Dehiscence with Comparison to Anatomical Specimens

The evolution of echocardiography from 2-Dimensional Transthoracic Echo through to real time 3-Dimensional Transoesophageal Echo has enabled more accurate visualisation and quantification of valvular disorders especially prosthetic mitral valve paravalvular regurgitation. However, validation of accuracy is rarely confirmed by surgical or post-mortem specimens. We present a case directly comparing different echocardiographic modality images to post mortem specimens in a patient with prosthetic mitral valve paravalvular regurgitation

Differences in Elementary Students’ Self-Regulated Processes for Computer Versus Printed Reading Assignments

The purpose of this study was to investigate metacognitive self-regulated learning (SRL) differences in computer- and paper-based reading assignments across elementary students. Students in two after-school programs in a southeastern U.S. public school district were recruited. The final sample consisted of 48 students in Grades 2–5 who participated in two counterbalanced conditions involving a computer- and a paper-based reading assignment. The study employed a 2 x 4 (condition-by-grade) mixed-model analysis of variance (ANOVA) and followup tests to examine metacognitive SRL differences between conditions and grades. The results indicate that elementary students used various metacognitive SRL skills across both conditions. The mixed-model ANOVA results show a significant interaction in control processes in paper-based reading for students in fifth grade, a significant main effect of condition in evaluation practices in computer-based reading for all grades, and a significant main effect of condition in conditional knowledge in the paper reading assignment for all grades. The results suggest that students can benefit from focused instruction to apply metacognitive SRL skills between the two reading formats. Keywords: self-regulated learning, metacognition, online reading, reading strategies, elementary grade

A novel approach to administration of peptides in women: Systemic absorption of a GnRH agonist via transvaginal ring delivery system

trans-Epithelial delivery of medication across the vagina has proven successful for administration of small, lipophilic molecules such as sex steroids. However, little information is available regarding the vaginal delivery of larger and more polar molecules that currently require parenteral administration because the vaginal epithelium is perceived as a barrier to absorption of larger molecular weight (MW) molecules. Six healthy women underwent administration of 18 or 36 mg of leuprolide, a GnRH agonist and a larger MW peptide, via a novel ethylene vinyl acetate (EVA) ring transvaginal drug delivery system (TVDS). Serum levels rose within 8 h following insertion: low dose at 310 pg/ml and high dose at 1220 pg/ml, i.e. levels typically following parenteral injections of leuprolide. GnRHa biological activity was validated by secretion of gonadotropins and sex steroids. These results demonstrate that the non-keratinized vaginal epithelium permits a rapid absorption of a biologically active peptide and that there is significant potential for a novel TVDS to deliver peptides and possibly other macromolecules therapeutically. Significance statement Current routes of administration of medications can include oral, subcutaneous, intravenous, intramuscular, transcutaneous, etc. Many of these approaches have limitations, including pain, poor tolerability, lack of adherence, and inadequate delivery. Peptides, in particular, cannot typically be given orally because they are broken down in the intestinal tract before they are absorbed. While the skin is an attractive way to deliver medications, its superb intrinsic barrier function often makes this route untenable at times. The vaginal epithelium, in contrast, is not keratinized and can allow absorption of other molecules. In this study, we demonstrate that a novel transvaginal drug delivery system (TVDS) is capable of delivering peptide therapeutics to women in a non-parenteral fashion as demonstrated by both blood levels and biologic effects of its delivery. Keywords: Intravaginal Ring; EVA; GnRH Agonist; Peptide; Phase 1; Transepithelia