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J Andrieu

Publications and source records attributed to J Andrieu.

51 records · Page 3Linked to original sources
PubMed1967

[Serous otitis].

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Child↗
PubMedDate not supplied

Determination of mass and heat transfer parameters during freeze-drying cycles of pharmaceutical products.

The principal aim of this study was to evaluate the water vapour mass transfer resistance of the dried layer and the vial heat transfer coefficient values of a pharmaceutical product during the primary drying period. First, overall vial heat transfer coefficient values, Kv, were determined by a gravimetric method based on pure ice sublimation experiments. Thus, it was possible to set up a map of the total heat flux received by each vial throughout the plate surface of our pilot scale freeze-dryer. Important heterogeneities were observed for the vials placed at the plate edges and for the vials placed at the center of the plate. As well, the same gravimetric method was also used to precisely determine the influence of main lyophilization operating parameters (shelf temperature and gas total pressure) or the vial types and sizes on these overall heat transfer coefficient values. A semi-empirical relationship as a function of total gas pressure was proposed. The transient method by pressure rise analysis (PRA method) after interrupting the water vapour flow between the sublimation chamber and the condenser, previously set up and validated in our laboratory, was then extensively used with an amorphous BSA-based formulation to identify the dried layer mass transfer resistance values, Rp, the ice front temperature, and the total heat transfer coefficient values, Kv, with or without annealing treatment. It was proved that this method gave accurate and coherent data only during the first half of the sublimation period when the totality of the vials of the set was still sublimating. Thus, this rapid method allowed estimation of, on line and in situ, the sublimation front temperature and the characterization of the morphology and structure of the freeze-dried layer, all along the first part of the sublimation period. The estimated sublimation temperatures shown by the PRA model were about 2 degrees C lower than the experimental values obtained using thermocouples inserted inside the vial, in accordance with previous data given by this method for similar freeze-drying conditions. As well, by using this method we could confirm the homogenization of the dried layer porous structure by annealing treatment after the freezing step. Furthermore, frozen matrix structure analysis (mean pore diameter) using optical microscopy and mass transfer modelling of water vapour by molecular diffusion (Knudsen regime) allowed, in some cases, to predict the experimental values of this overall mass transfer resistance directly related to the freeze-dried cake permeability.

Algorithms↗
PubMedDate not supplied

Optimization of the freeze-drying cycle: adaptation of the pressure rise analysis model to non-instantaneous isolation valves.

The principal aim of this study is to extend to a pilot freeze-dryer equipped with a non-instantaneous isolation valve the previously presented pressure rise analysis (PRA) model for monitoring the product temperature and the resistance to mass transfer of the dried layer during primary drying. This method, derived from the original MTM method previously published, consists of interrupting rapidly (a few seconds) the water vapour flow from the sublimation chamber to the condenser and analysing the resulting dynamics of the total chamber pressure increase. The valve effect on the pressure rise profile observed during the isolation valve closing period was corrected by introducing in the initial PRA model a valve characteristic function factor which turned out to be independent of the operating conditions. This new extended PRA model was validated by implementing successively the two types of valves and by analysing the pressure rise kinetics data with the corresponding PRA models in the same operating conditions. The coherence and consistency shown on the identified parameter values (sublimation front temperature, dried layer mass transfer resistance) allowed validation of this extended PRA model with a non-instantaneous isolation valve. These results confirm that the PRA method, with or without an instantaneous isolation valve, is appropriate for on-line monitoring of product characteristics during freeze-drying. The advantages of PRA are that the method is rapid, non-invasive, and global. Consequently, PRA might become a powerful and promising tool not only for the control of pilot freeze-dryers but also for industrial freeze-dryers equipped with external condensers.

Algorithms↗
PubMedDate not supplied

Experimental study of the impact of annealing on ice structure and mass transfer parameters during freeze-drying of a pharmaceutical formulation.

The principal aim of this study is to evaluate the influence of annealing on structural properties and mass transfer parameters of a model formulation used for freeze-drying of pharmaceutical proteins. Characterization runs on ice morphology of the frozen material were performed in a cold chamber by direct optical microscopy using episcopic coaxial lighting. Consequently, it was possible to quantify the influence of annealing (temperature, duration) on ice morphology. Then, the pressure rise analysis method was used during primary drying to identify as a function of time both the dried layer mass transfer resistance values, R(p), and the sublimation front temperature, T(i), with or without annealing. Annealing turned out to accelerate sublimation rates by increasing ice crystal sizes of the frozen matrix, thus leading to lower values of R(p). Finally, secondary drying kinetics were studied by measuring the values of the desorption constant by a simple gravimetric method. In this study, annealing turned out to decrease desorption kinetics by a factor of two.

Chemistry, Pharmaceutical↗
PubMedDate not supplied

[Bacteroides infections].

The authors analyse 42 cases of bacteroides infection regrouping bacteremia and localised infection collected over a period of one year. The route of entry was almost always digestive. The prognosis seems mainly to depend on the background. The bacteriological diagnosis is now easy and germ-sensitivy is stereotyped.

Adolescent↗
PubMedDate not supplied

[Fulminating pneumococcal septicemia (author's transl)].

Two cases of fulminating pneumococcal septicemia (FSP) are reported, and 47 confirmed cases were discovered after a review of the published literature. The syndrome is that of a malignant infection with fever, collapse, and disseminated intravascular coagulation, with a rapid mortal outcome in most cases. Etiologically, FSP is usually the consequence of functional or anatomical asplenia, and the relative frequency of this affection after splenectomy following trauma confirms this observation. Lack of a splenic filter and a deficiency in the phagocytic system are the reasons for microbial proliferation in the blood, and the lymphocytic defence mechanisms are inactive because of the absence of any focus of infection.

Adult↗
PubMedDate not supplied

[Severe epistaxis caused by carotid artery rupture].

Epistaxis due to rupture of the carotid, usually occurs as a result of cranial or closed cranio-facial traumatism. Heamorrhage is secondary to the formation of post-traumatic arterial aneurysms or arterio-venous fistulas. Frequently, the lesion is along the intra-cavernous pathway of the internal carotid. Rupture of a spontaneous arterial aneurysm in the sphenoidal sinus is, however, extremely rare. Carotid arteriography is the main method of investigation, and this method alone is capable of detecting the carotid lesion. In addition to obvious cases, it should be requested in cases of severe, copious and recurrent epistaxis when interrogation of the patient reveals the merest hint of trauma, often a long time previously. Immediate treatment consists of anterior bilateral and naso-pharyngeal tampnage. This allows enough time for arteriography to be carried out under the most favourable conditions and also testing for carotid substitution. In order to ensure permanent thrombosis of the aneurysmal pocket or the arteriovenous fistula, most methods resolve themselves into occlusion of the carotid axis. Cervical ligature of the carotid on its own, and isolated trapping have given way to techniques employing either a combination of trapping and embolization, or the placing of a balloon probe without trapping. At present, Serbinenko is advocating using balloons released when arteriography is carried out, obliterating the fistula and left in position permanently. Finally, there is the method by which the sphenoidal sinus is approached para-lateronasally after ethmoidectomy: this is an effective method which is much less incursive than the endo-cranial approach.

Aneurysm↗