Pressure drop coefficients for elliptic and circular sections in one, two and three-row arrangements of plate fin and tube heat exchangers

The objective of the present work is the experimental determination of pressure drop coefficients (loss coefficients) for elliptic and circular sections in one, two and three-row arrangements of plate fin and tube heat exchangers. The experiments permitted to correlate the dimensionless loss coefficient with the flow Reynolds number in the rectangular channel formed by the plate fins. The experimental technique consisted of the measurement of the longitudinal pressure distribution along the flow channel, for several values of air mass flow rate. The total number of data runs, each one characterized by the flow Reynolds number, was 216. The present geometry is used in compact heat exchangers for air conditioning systems, heaters, radiators, and others. Also, it is verified the influence of the utilization of elliptic tubes, instead of circular ones, in the pressure drop. The measurements were performed for Reynolds numbers ranging from 200 to 1900.

Culture of bovine ovarian follicle wall sections maintained the highly estrogenic profile under basal and chemically defined conditions

Follicle cultures reproduce in vitro the functional features observed in vivo. In a search for an ideal model, we cultured bovine antral follicle wall sections (FWS) in a serum-free defined medium (DM) known to induce 17β-estradiol (E2) production, and in a nondefined medium (NDM) containing serum. Follicles were sectioned and cultured in NDM or DM for 24 or 48 h. Morphological features were determined by light microscopy. Gene expression of steroidogenic enzymes and follicle-stimulating hormone (FSH) receptor were determined by RT-PCR; progesterone (P4) and E2 concentrations in the media were measured by radioimmunoassay. DM, but not NDM, maintained an FWS morphology in vitro that was similar to fresh tissue. DM also induced an increase in the expression of all steroidogenic enzymes, except FSH receptor, but NDM did not. In both DM and NDM, there was a gradual increase in P4 throughout the culture period; however, P4 concentration was significantly higher in NDM. In both media, E2 concentration was increased at 24 h, followed by a decrease at 48 h. The E2:P4 ratio was higher in DM than in NDM. These results suggest that DM maintains morphological structure, upregulates the expression of steroidogenic enzyme genes, and maintains steroid production with a high E2:P4 ratio in FWS cultures.

Comment on devient un dessinateur / par E. Viollet le Duc

Collection : Bibliothèque des professions industrielles, commerciales et agricoles ; 2

Hymne à Ammon-Ra : des papyrus égyptiens du musée de Boulaq / trad. et comment. par Eugène Grébaut,...

[Hymne à Amon (français). 1870]

Comités d'entreprises, délégués du personnel, sections syndicales (Ed. à jour au 1er mars 1971)

Collection : Journal officiel de la République française ; 1183

« L'Istoire royale », ou « Livre traittant comment par la vaillance de trois jeunes princes le royaulme de Naples fut jadis delivré du povoir des Sarrasins... grossé par DAVID AUBERT ».

Commençant par : « Les fais des anciens doit l'on voulontiers lire... » et finissant par : «... et trouvay escript au dessoubz : C'est le livre et histoire royal. Le present livre fut grossé... en la ville de Sesdin, par David Aubert, l'an de l'Incarnation N. S. J. C. 1463 » .