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Biomedical subjects

A Redaelli

Publications and source records attributed to A Redaelli.

24 records · Page 2Linked to original sources
PubMedDate not supplied

Mesh updating in fluid-structure interactions in biomechanics: an iterative method based on an uncoupled approach.

In this study, a computational uncoupled approach to fluid-structure interaction problems in biofluid mechanics is presented. It is based on the finite element method and is applied to study the local fluid dynamics in two specific situations: the left ventricular ejection phase and the motion of an isolated red blood cell along a small artery. Particularly, the focus is on the algorithms developed to deal with mesh updating, because both examined districts are characterized by geometrical deformations of the fluid domain edges. This is currently a challenging issue in the application of computational fluid dynamics techniques to living systems, especially to the cardiovascular system. Although the chosen approach uses a commercial computational fluid dynamics package for the solution of the fluid domain, original algorithms have been developed to perform the boundary displacement calculations correctly, as well as the corresponding mesh updating. Results are reported and compared with available data in the literature pertinent to the two studied problems.

Algorithms↗
PubMedDate not supplied

[Laparoscopic versus conventional surgery in the treatment of colorectal diseases].

The aim of the study was to compare the results obtained with laparoscopic (LPS) and laparotomic (LPT) colorectal resection after our initial experience with the laparoscopic technique. Fifty-six patients were submitted to colorectal resection, 26 with the LPS and 30 with the LPT technique. Eighteen patients out of 26 in the LPS group and 22/30 in the LPT group had malignancies. All resections were performed with a curative intent. The mean operating time was 220 min in the LPS group and 208 min in the LPT group. Mean blood loss was 287 ml and 312 ml, respectively (blood transfusions were needed in 1/26 and in 7/30 patients). The rates of major complications were 9.5% and 5.7%, respectively. There was no mortality. The conversion rate for the LPS group was 19.2%. In the cancer patients, no significant difference was observed between the two groups as regards postoperative staging. The mean length of specimens and the mean distance of the tumours from the resection margins were adequate. The mean number of lymph nodes harvested was 11.8 in the LPS group as against 18.5 in the LPT group. No early recurrences were observed. Resumption of gastrointestinal function was faster in the LPS patients who underwent the surgical procedure under general anaesthesia associated with epidural anaesthesia/postoperative analgesia. In conclusion, these preliminary results indicate that laparoscopic colorectal surgery is feasible and that the resections in cancer patients appear to be oncologically adequate. Long-term follow-up is needed for reliable assessment of oncological outcomes.

Adenocarcinoma↗
PubMedDate not supplied

Proteins, nucleic acids and genetic codes.

On the basis of the previous article (Morchio and Traverso [1999]), we discuss the possible interactions between the first proteic fragments developed in the hydrophobic layer made of hydrocarbons, which would have covered the surface of the primitive seas, and the nitrogenous bases, particularly the pyrimidinic ones, which would have found in such hydrophobic layer favourable conditions to their prebiotic synthesis. These interactions would have presumably brought, on the basis of the physicochemical laws, at the moment the only ones at work, to the linkage of various bases and so to the construction of the first nucleic acid chains (most likely RNA). Interestingly enough this result would have been obtained by inserting two more bases between those hydrogen bound to the amino acids and this might have been the ground for the future "triplets". These interactions might have been particularly significant because of two important consequences: the birth of a rough genetic code and the starting of interactions of the co-operative type between bases and amino acids that would have made the growth of both proteic and nucleic acid fragments easier and faster. We conclude that the development of the genetic code was neither a "frozen accident" nor an occurrence directed by any information flow.

Genetic Code↗