Controlling solid-state microstructure of semi-crystalline polymers through chemical design of chains: a study of model polyesters

Doctorat en sciences (sciences chimiques) (CHIM 3)--UCL, 200

In Stent Re-Stenosis After Carotid Artery Stenting.

A 62 year old man underwent endovascular right hemisphere thrombectomy for an ischaemic stroke. […

Pyogenic Ventriculitis Caused by Listeria Monocytogenes.

In case of meningitis, intraventricular sediments showing diffusion restriction on brain magnetic resonance imaging are highly suggestive of pyogenic ventriculitis for which early diagnosis is crucial for appropriate treatment

Characterization of long-chain aliphatic polyesters: Crystalline and supramolecular structure of PE22,4 elucidated by X-ray scattering and nuclear magnetic resonance

The crystalline packing and the phase structure of a long-chain aliphatic polyester, (O(CH2)(22)-OOCCH2CH2CO)(n), PE22,4, have been studied in molecular detail by small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) experiments as well as various solid-state nuclear magnetic resonance (NMR) methods, in particular two-dimensional double-quantum spectroscopy (DOQSY) NMR. The volume crystallinity is 73 +/- 3% according to quantitative C-13 NMR and SAXS analyses. The DOQSY NMR spectra show signal characteristic of trans ester groups incorporated into straight poly(methylene) chains, as expected on the basis of WAXD. DOQSY spectra of singly (COO)-C-13-labeled diesters prove close proximity of ester groups in neighboring chains, confirming the ester layering deduced from SAXS, with three diester layers per crystallite. SAXS shows a 37 degrees chain tilt with respect to the diester layers and crystallite surface, and the DOQSY NMR spectra confirm the resulting significant displacement of ester groups along neighboring chains. The data suggest a alpha beta(22) tilting of the chain axes. NMR detects no significant disorder along the chain axes; this suggests that the disappearance of (h, k, l not equal 0) reflections in WAXD is due to the small crystallite thickness, which is 5.6 +/- 0.5 nm according to SAXS. The DOQSY NMR patterns show that the planes of the chains are far from the perpendicular relative orientation found in orthorhombic polyethylene, constraining the angle between the (normals to the) O-C = O ester planes to 55 degrees +/- 20 degrees. DOQSY NMR also indicates that similar to 1/3 of the COO groups directly at the crystalline-amorphous interface are disordered. The chain loops in the amorphous phase contain only 6% of the esters and thus mostly consist of the C-22 Polymethylene section of one C-26 repeat unit. The C-22 loops connect similar to 71% of the ends of crystalline stems, while 9% are terminated by chain ends and 20% are connected to a loose loop or tie molecule. NMR relaxation measurements confirm that, in spite of the relatively small fraction of ester groups among the poly(methylene) chains, they strongly suppress the fast 180 degrees chain flips observed in polyethylene crystallites

No benefit from 3-months valganciclovir prophylaxis vs preemptive treatment in heart transplantation: should we extend the prophylaxis to 200 days or beyond?

Aim: Cytomegalovirus (CMV) is the main opportunistic pathogen in solid organ transplantation and has a major impact on outcome both by its direct and indirect effects. Both prophylactic and preemptive strategies have been described. We reviewed our 20-year experience both in term of CMV infection and in term of its potential influence of long-term complications such as acute cellular rejection and coronary artery disease. Methods: Retrospective single-center study of heart transplants recipients from 1995 to 2015. Out of 305 patients (310 Tx), 231 met our inclusion’s criteria. All CMV seropositive recipients benefited from the preemptive strategy, as did the high-risk group (seronegative recipient/seropositive donor) from 1995 to 2004. From 2005 to 2015, the later group received 3 months anti-CMV prophylaxis. End-points of this study were CMV infection, acute rejection, cardiac allograft vasculopathy (CAV) and patient survival. Results: 32% of our patients developed CMV infection during the follow-up, the majority within the first 6 months after transplantation. Overall, 11.2% of our patients developed CMV disease (10.4% in seropositive patients vs 32.4% in high-risk patients, p=0.001). The 3-month prophylaxis significantly delayed the occurrence of CMV infection but had no beneficial effect on its incidence. CMV infection did not influence the rate of acute cellular rejection within the first year (3A or higher: 10.4%), nor on the occurrence of CAV (24 % at 10yr). The median survival time of our cohort was 15 years. CMV infection had no impact on survival, though patients with CMV disease had a non-significant decrease in survival time (9.9yrs, p=0.15). Conclusion: Anti-CMV prophylaxis for 3 months delayed CMV infection but with a tendency to increase the incidence of CMV disease. This study could not demonstrate any pejorative effect of CMV on rejection nor on chronic allograft vasculopathy. Additional studies should be done with longer prophylaxis in heart transplant recipients since favorable data were demonstrated in other solid organ transplantation