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Biomedical subjects

M Nobili

Publications and source records attributed to M Nobili.

At least 19 recordsLinked to original sources
PubMed2006

Brownian motion of an ellipsoid.

We studied the Brownian motion of isolated ellipsoidal particles in water confined to two dimensions and elucidated the effects of coupling between rotational and translational motion. By using digital video microscopy, we quantified the crossover from short-time anisotropic to long-time isotropic diffusion and directly measured probability distributions functions for displacements. We confirmed and interpreted our measurements by using Langevin theory and numerical simulations. Our theory and observations provide insights into fundamental diffusive processes, which are potentially useful for understanding transport in membranes and for understanding the motions of anisotropic macromolecules.

Journal Article↗
PubMed2006

A 2D spring model for the simulation of ultrasonic wave propagation in nonlinear hysteretic media.

A two-dimensional (2D) approach to the simulation of ultrasonic wave propagation in nonclassical nonlinear (NCNL) media is presented. The approach represents the extension to 2D of a previously proposed one dimensional (1D) Spring Model, with the inclusion of a PM space treatment of the intersticial regions between grains. The extension to 2D is of great practical relevance for its potential applications in the field of quantitative nondestructive evaluation and material characterization, but it is also useful, from a theoretical point of view, to gain a better insight of the interaction mechanisms involved. The model is tested by means of virtual 2D experiments. The expected NCNL behaviors are qualitatively well reproduced.

Journal Article↗
PubMed2005

Cracks and topological defects in lyotropic nematic gels.

We report on the effects of the coupling of nematic order and elasticity in anisotropic lyotropic gels consisting of large nematic domains of surfactant coated single wall carbon nanotubes embedded in a cross-linked N-isopropyl acrylamide polymer matrix. We observe the following striking features: (i) undulations and then cusping of the gel sidewalls, (ii) a nematic director field that evolves as the gel sidewalls deform, (iii) networks of surface cracks that are orthogonal to the nematic director field, and (iv) fissures at the sidewall cusps and associated topological defects that would not form in liquid nematics.

Anisotropy↗
PubMed2005

Dynamics of nematic liquid crystal disclinations: the role of the backflow.

We measure the electric-field-driven annihilation of nematic disclination pairs with strength +/- 1/2 in the 4-cyano-4'-n-pentylbiphenyl (5CB) liquid crystal. The use of a very weak azimuthal anchoring ensures a two-dimensional director field. The relaxation is governed by the formation of a pi wall connecting the two opposite charge defects. The +1/2 disclinations move almost twice as fast as the -1/2 disclinations. The simple used geometry allows a quantitative comparison with numerical studies based on the hydrodynamics of the tensorial order parameter. The simulations show that in the pi wall regime the symmetry breaking is due to the backflow and not to the elastic anisotropy.

Journal Article↗
PubMed2004

Progesterone supplement in pregnancy: an immunologic therapy?

One of the most interesting functions of the placenta is the regulation of the maternal immune response such that the fetal semi-allograft is tolerated during pregnancy. Trophoblasts are presumed to be essential to this phenomenon because they lie at the maternal-fetal interface, where they are in direct contact with cells of the maternal immune system. Trophoblasts do not express classic major histocompatibility complex (MHC) class II molecules. Surprisingly, cytotrophoblasts express more HLA-G, a MHC class Ib molecule, as they invade the uterus. Progesterone plays an important role in postovulatory regulation of the menstrual cycle. If fertilization occurs, progesterone supports implantation of the ovum and maintains the pregnancy. Progesterone has been named the 'hormone of pregnancy', because in preparing the endometrium for embryo implantation and facilitating endometrial development, it is critical to the very survival of a pregnancy. In addition, this key hormone inhibits the rejection of T cell-mediated tissue and also decreases myometrial activity and sensitivity throughout pregnancy. The cellular actions of progesterone are mediated through intracellular progesterone receptors (PRs), which are well studied gene regulators, not express classic major histocompatibility complex. The more used paradigm is relative to the alteration of relationship TH1/TH2, but the complexity of the respective distributions of cytokines at the materno-fetal interface, strongly suggest that, as useful as it certainly was for a while, the Th1/Th2 paradigm must now be considered as an oversimplification. Rather, the existing data point to sequential windows and are suggestive of a system where an extreme complexity is allied to very precise timing and tuning. They also suggest that the materno-fetal relationship is not simply maternal tolerance of a foreign tissue, but a series of intricate mutual cytokine interactions governing selective immune regulation and also control of the adhesion and vascularization processes during this dialogue. However, as shifting the immune response toward the Th2 pattern (IL-4, IL-5, IL-6) may benefit the fetus, whereas development of proinflammatory Th1 cells (secreting IL-2, IFN g, TNF a) may be harmful. Now we are working to open comprise the precise behaviour of NK populations, with the hope of obtaining a diagnostic test of the condition of abortion from 'immunological causes'.

Abortion, Habitual↗
PubMed2003

Azimuthal anchoring energy at the interface between a nematic liquid crystal and a PTFE substrate.

The azimuthal anchoring energy of the nematic liquid crystal 4-pentyl-4'-cyanobiphenil (5CB) on a poly(tetrafluoroethylene) (teflon, PTFE) film is measured for the first time. The PTFE film is deposed using the Wittmann and Smith technique which consists on rubbing a bar of this polymer against a glass substrate at a controlled temperature and pressure. Measurements of the azimuthal anchoring energy are made with a reflectometric technique which provides high accuracy and sensitivity. The dependence of the azimuthal anchoring energy on temperature and on the rubbing pressure is investigated. The extrapolation length remains virtually constant in the whole temperature range of the nematic phase except for an increase of 25% close to the clearing temperature. The azimuthal anchoring energy is somewhat strong and increases with increasing the deposition pressure of PTFE. The observation of a relevant pre-transitional anisotropy of the reflection coefficients in the isotropic phase proves that the surface interactions favor an excess of orientational order. Ageing of the anchoring energy and gliding of the easy axis are experimentally observed. Both these phenomena suggest the presence of an anisotropic adsorbed layer of nematic molecules on the PTFE film.

Journal Article↗
PubMed2002

Anchoring screening of defects interaction in a nematic liquid crystal.

The relaxation dynamic of a dipole of +1/2 and -1/2 parallel disclination lines in a confined geometry is measured. The confinement and the planar anchoring conditions force the disclinations to be normal to the glass plates. In a first asymptotic regime, the direct elastic interaction between disclination is completely screened out by the anchoring energy. In a second regime, corresponding to the final annihilation steps, the dynamic follows the square-root law predicted by de Gennes for two isolated and parallel disclinations. The annihilation dynamic, in the asymptotic regime, is in good agreement with an elastic model based on an electrostatic analogy.

Journal Article↗
PubMed1997

[Intestinal invagination in childhood: our experience].

The Authors report their experience in the treatment of twenty-one patients with intussusception operated in the Paediatric Surgery Division ASL FG/3 between January 1988 and December 1994. Eighty-nine percent of the patients were between 2 and 12 months of age, with a peak between 2 and 6 months (60%). Ultrasound allowed to identify the pathological picture in forty-two percent of the cases and diagnosis was confirmed by barium enema. In 8 patients a pathology more or less responsible of the intussusception or associated with it was detected. The time between the onset of symptoms and admission as well as the relation between intestinal resection and duration of symptomatology were analyzed. The resection rate was maximal (55%) in those patients presenting symptoms beyond 25 hours. Intestinal resection was performed in 9 patients (47%): 6 ileo-colic; 1 ileo-colic resection extended to the splenic flexure; and 2 ileo-ileal ones. In this series no postoperative complications or recurrences or deaths were registered. Long term results proved that ileo-colic resection, even in few-months old infants, is well tolerated.

Child↗
PubMed1997

[Meckel's diverticulum in childhood. The authors' own experience].

Meckel's diverticulum occurs in approximately 2 percent of the population and may present at any age. Although Meckel's diverticulum may produce an intestinal obstruction or perforation, simulating an appendicitis, hemorrhage is its most important clinical presentation. From 1989 to 1994, Meckel's diverticulum was discovered in ten children at laparotomy. Three cases were asymptomatic, representing an incidental finding at laparotomy. Of the seven symptomatic patients, four presented with bowel obstruction (intussusception), three had rectal bleeding one of whom had diverticulitis. Contrast studies--in gastrointestinal hemorrhage--were not helpful in establishing the diagnosis; colonoscopy and gastroscopy ruled out other causes of bleeding. Five of seven symptomatic patients had an intestinal resection while two a diverticulectomy after assessment that the ulcer did not require resection. No postoperative morbidity and mortality is reported in either groups. A Meckel's diverticulum found incidentally at laparotomy should be always resected as the risk of complication is high and that of resection low.

Adolescent↗
PubMed1991

[Detoxification from opiates through hospitalization: the long-term results. A longitudinal study of 104 admissions in 1982-1986].

One hundred and four drug addicts admitted to hospital during the period 1982-1986 were studied in order to evaluate whether detoxification from opiates in a protected environment had positive long-term results, namely a definitive rejection of the world of drugs. A follow-up of this population was carried out at the start of the current year and approximately 20% were found to be drug-free. Accumulated experience leads to the conclusion that hospitalisation may have a positive long-term outcome if a subject with proven motivation to "give up" is carefully selected, and if the subject is then inserted in a broader social health project.

Follow-Up Studies↗