Les vascularites du système nerveux central (SNC) peuvent rapidement engager le pronostic vital ou être responsables de séquelles neurologiques définitives. Compte tenu des performances limitées des ...différents outils diagnostiques (tomodensitométrie, imagerie par résonance magnétique, angiographie conventionnelle, biopsie cérébrale), les vascularites cérébrales primitives sont particulièrement difficiles à diagnostiquer. Elles ne doivent pas être confondues avec les angéites d’origine infectieuse ou néoplasique, les maladies systémiques, mais aussi les vasculopathies cérébrales non inflammatoires, au premier rang desquelles figure le syndrome de vasoconstriction cérébrale réversible. Malgré les progrès de la neuro-imagerie et la publication récente de quelques grandes séries de vascularite primitive du SNC, cette entité rare reste un cadre nosologique hétérogène et un défi diagnostique et thérapeutique. Des travaux prospectifs multidisciplinaires sont donc indispensables pour améliorer la prise en charge des patients chez qui un diagnostic de vascularite du système nerveux central est suspecté.
Central nervous system (CNS) vasculitides are a heterogeneous group of diseases that can lead to severe disability and death. Given the poor performance of available diagnostic procedures (magnetic resonance imaging, angiography and brain biopsy), the diagnosis of isolated CNS vasculitis is challenging. Differential diagnosis includes secondary CNS vasculitides (infection, cancer, drug exposure or systemic inflammatory disorders) and several non-inflammatory cerebral vasculopathies, such as the reversible cerebral vasoconstriction syndrome. Despite recent advances in neuroradiology and the publication of large retrospective case series, primary angiitis of the CNS remains a heterogeneous and challenging nosological entity. Prospective interdisciplinary studies are necessary to improve our approach to these patients.
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Silica–polystyrene hybrid nanoparticles were synthesized by Pickering emulsion polymerization. The coupling effect of initiator type and silica surface charge was studied to exhibit ...the predominant role of electrostatic interactions in the synthesis mechanisms.
Non-ionic hydrophobic initiator (2,2′-azobis(2-methylpropionitrile), AIBN) or anionic hydrophilic initiator (sodium persulfate, NaPS), and positively or negatively charged silica were used as reactants with styrene for Pickering emulsion polymerization. Their interactions were evaluated by Zeta potential measurements. The droplet size and the stability of the Pickering emulsions, and the hybrid particle morphology, surface coverage, size and agglomeration were evaluated by laser granulometry and microscopy.
Similar surface charge between negatively charged silica particles and an anionic initiator led to strong repulsions and thus to non-covered polystyrene nanoparticles. With positively charged silica, a high decoration was obtained due to attractive interactions between the inorganic and the organic phases, but a strong agglomeration was also observed. The use of a non-ionic initiator led to a homogeneous coverage with negatively charged silica. With positively charged silica micronic sizes were formed by following two different mechanisms. These data, by enriching the existing literature, led to a more complete and robust description of the emulsion polymerization synthesis for hybrid nanostructures.
This paper proposes a comparative study of two techniques of granulation of a submicronic alumina powder with high binder content slurries, by spray drying and freeze granulation for the preparation ...of mixed granules. First, the viscosity and flow index of the suspensions are given as a function of dispersant, solid and binder contents versus alumina content, and the data are analysed in order to give a predictive model in a wide range. Suspensions with varying viscosities (7–208 mPa.s), densities (1.31–1.76) and surface tensions (23–40 mN/m) were then granulated. The first observations reveal the importance of the content and the molar mass of the binder: when they are too high, the freeze granulation fails and filaments are produced instead of granules due to extensive stretching of the molecular chains of the binder during spraying. Then through a theoretical analysis of the phenomena leading to granulation, an original dimensionless number is proposed to describe the evolution of the granule size as a function of suspension formulation. This number is related to the Reynolds and Weber number and is able to predict the granule size over a wide range (20–500 μm for freeze granulation, and 5–30 μm for spray drying). Spray drying leads to smaller granules with various shapes, from full shape to hollow or donut-like, whereas freeze granulation leads to bigger but spherical granules with a microporosity, and a size easier to predict as no drying shrinkage is observed.
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•Spray drying and freeze granulation are compared in terms of granule size.•A dimensionless number is calculated to predict the freeze-dried granule size.•Freeze granulation leads to full, porous and spherical granules.
In this paper, preliminary results about both the chemical and physical behaviours of hemp fibres in calcium rich medium are presented. The influence of hemp fibres introduction in Portland cement ...pastes on the setting time has been investigated. It seems that pectin contained in the fibres can form complex molecules with calcium ions and could be responsible for the observed delay. The role of fibres surface treatment has been also studied. Chemical attack of the fibres surface by an alkaline and calcium rich solution degrades hemicelluloses contained in the fibres and seems to roughen the surface. This surface modification seems to play a major role in the strengthening of the cement/fibres interface. These results show that hemp fibres introduced in cement pastes exhibit a typical composite behaviour compared to cement sample, which lead to an improvement of the mechanical properties.
MOX fuels are used in nuclear reactors. To ensure the manufacture of MOX, wet processes are investigated. Freeze granulation of water-based powder suspension seems a promising way to yield homogenous ...and easy-to-press UO2-PuO2 granules. These granules are expected to form dense and homogenous pellets by uniaxial pressing. Granules and pellet properties are affected by suspension formulation and atomization conditions. Therefore, these conditions must be studied and optimized to produce granules with good processability and thus MOX pellets with compliant density, homogeneity and absence of defects. In this scope, key properties of water-based suspensions of UO2 and PuO2 surrogate powders, TiO2 and Y2O3 respectively, were firstly studied to assess their suitability for the freeze granulation process. These properties were compared to those of UO2 and PuO2 suspensions to verify and confirm the correctness in the choice of surrogate powders. Then, the freeze granulation process itself was investigated focusing on TiO2-Y2O3 suspensions.
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Pickering emulsions stabilized with a natural silicate mineral, halloysite, were dried by freeze granulation in order to prepare porous granules. Different formulations were studied, ...by varying the pH of the suspension, the ionic strength and with the addition of organic binders (poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG)). To get a better understanding and control on the process, the objective was to correlate the formulation and the emulsion behavior to the morphology and size of the granules. This study highlights the predominant role of electrostatic interactions on the emulsions. Their stability is improved if the dispersion of solid particles in the continuous phase is relatively limited, with medium zeta potential absolute values. Freeze granulation of emulsions prepared at different ionic strength and pH led to similar granules, with an internal porosity attributed to the low solid fraction. The addition of organic additives PVA and PEG led to a better conservation of the structure, with fewer broken fragments and a larger porosity, attributed to a higher cohesion of these emulsions during the spray freezing and the lyophilisation steps.
To determine the frequency and risk factors of venous thromboembolic events (VTE) in Wegener's granulomatosis (WG), microscopic polyangiitis (MPA) and, the so far unstudied, Churg-Strauss syndrome ...(CSS) and polyarteritis nodosa (PAN).
Retrospective, systematic analysis and comparisons were made between the characteristics of patients in the VTE group and non-VTE group. 1130 patients with WG, MPA, CSS or PAN were identified from the French Vasculitis Study Group cohort.
During a mean follow-up of 58.4 (45.8) months, 83 VTE occurred in 74 (6.5%) patients, with a median vasculitis-VTE diagnosis interval of 5.8 months (-3 to +156). VTE occurred in seven of 285 (2.5%) patients with PAN, 19 of 232 (8.2%) with CSS, 30 of 377 (8%) with WG and 18 of 236 (7.6%) with MPA. Multivariate analysis retained age, male sex or previous VTE or stroke with motor deficit as being associated with a higher VTE risk. The adjusted odds ratio (95% confidence interval) for VTE was 2.88 (1.27 to 6.50) for patients with WG, MPA or CSS compared with PAN (p = 0.01).
Our results suggest that, like WG and MPA, patients with CSS are at a greater risk of VTE, than those with PAN. The reasons for this difference remain to be elucidated.
The development of Generation IV sodium-cooled fast reactors (SFR) is currently studied by several countries, France in particular. To manufacture the UO2-PuO2 fuels for these new types of reactors, ...new innovative wet colloidal processing routes are investigated. Among these wet colloidal processes, some involve at first the preparation of high solid content water-based suspensions. This key step needs to be investigated in order to obtain highly and easily processable suspensions, featuring optimal viscosity and dispersion state. The structures and properties for all intermediate and final products involved in such ceramic manufacturing processes are heavily affected by these suspension characteristics. Therefore, they are critical to ensure a compliant final product (i.e. fuel pellets) with the required density, homogeneity, mechanical strength and absence of defects. In this scope, preparation process of such suspensions was developed by the use of UO2 and PuO2 surrogating (i.e. mimicking) powders, TiO2 and Y2O3 respectively.
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