Scaling limit of ballistic self-avoiding walk interacting with spatial random permutations

We consider nearest neighbour spatial random permutations on Zd. In this case, the energy of the system is proportional to the sum of all cycle lengths, and the system can be interpreted as an ensemble of edge-weighted, mutually self-avoiding loops. The constant of proportionality, α, is the order parameter of the model. Our first result is that in a parameter regime of edge weights where it is known that a single self-avoiding loop is weakly space filling, long cycles of spatial random permutations are still exponentially unlikely. For our second result, we embed a self-avoiding walk into a background of spatial random permutations, and condition it to cover a macroscopic distance. For large values of α (where long cycles are very unlikely) we show that this walk collapses to a straight line in the scaling limit, and give bounds on the fluctuations that are almost sufficient for diffusive scaling. For proving our results, we develop the concepts of spatial strong Markov property and iterative sampling for spatial random permutations, which may be of independent interest. Among other things, we use them to show exponential decay of correlations for large values of α in great generality

Interacting self-avoiding polygons

We consider a system of self-avoiding polygons interacting through a potential that penalizes or rewards the number of mutual touchings and we provide an exact computation of the critical curve separating a regime of long polygons from a regime of localized polygons. Moreover, we prove the existence of a sub-region of the phase diagram where the self-avoiding polygons are space filling and we provide a non-trivial characterization of the regime where the polygon length admits uniformly bounded exponential moments

Temperature- and light-induced relaxation of the electro-optic properties of poled side-chain copolymers

We report on the measurement of the time relaxation of the electro-optic properties of poled side-chin copolymers under illumination with absorbed laser radiation. Films of side- chain Disperse Red 1 substituted poly-Methyl-Methacrylate were sandwiched between ITO and gold electrodes and poled with a standard temperature/electric field cycle. The decay of the electro-optic properties, measured by means of the Teng and Man ellipsometric reflection technique at (lambda) equals 830nm, was measured for several intensities of a circular polarized absorbed laser beam, (lambda) equals 514.5nm, illuminating the sample. The relaxation shows a stretched exponential time dependence, with intensity dependent decay and stretching constants. The relaxation curves are compared with those obtained, for the same sample, in standard temperature stimulated non linear dielectric relaxation measurements

Role of M2 muscarinic receptor in epithelial ovarian carcinoma (EOC)

Role of M2 muscarinic receptor in epithelial ovarian carcinoma (EOC) Marilena Taggi1, M. Falcinelli1, V. Cacciamani1, V. Di Paolo1, A. M. Tata2 R. Canipari1 (1) Dipartimento SAIMLAL - Sezione di Istologia –Sapienza, Università di Roma; (2) Dip. Biologia e Biotecnologie Charles Darwin, Sapienza, Università di Roma Epithelial ovarian cancer (EOC) is one of the most common female cancer. EOC arises from the ovarian surface epithelium (OSE) which undergoes a process of injury-repair at each ovulation. In the ovary, a non-neuronal cholinergic system is present, and acetylcholine (ACh) is produced by granulosa cells and luteal cells. We have characterized the expression of muscarinic receptors in two human ovarian carcinoma cell lines (SKOV-3, TOV21-G) and in one immortalized ovarian surface epithelium cell line (i-120). We observed a lower expression of M2 muscarinic receptor subtype in cancer cells, compared to i-120. We investigated its role in the control of cell growth and survival. Treatment with arecaidine propargyl ester hydrobromide (APE), a selective M2 agonist, cell number decreases in a dose and time dependent manner. In the i-120 we observed high levels of cell death, which may be related to the high expression of M2 receptor. Conversely, in cancer cells, there is significantly lower cell death but the APE delays the cell cycle progression. These results suggest that M2 receptor has a negative role on cell growth/vitality, therefore, its downregulation may favor tumor progression

Charge injection and trapping effects in DPOP-PPV polymer films

We report on the measurement of the Kerr electro-optic susceptibility in DPOP-poly-phenylene-vinylene films sandwiched between indium tin oxide and metal electrodes. Such a polymer was designed and used for the application in third-order non-linear optical integrated devices. The results, obtained by means of non-linear reflectance ellipsometry, indicate the presence of charge injected and trapped in the polymer films under application of a dc voltage. The values of the Kerr χ(3) susceptibility and of the total voltage drop on the film are evaluated

Gastric cancer prevalence in patients with liver cirrhosis

An increased risk for gastric cancer in patients with liver cirrhosis has recently been reported in epidemiological studies. The present endoscopic study was performed to further evaluate whether people with cirrhosis are at increased risk for gastric cancer development. We reviewed the medical records of all cirrhotic patients referred to our Endoscopic Service for portal hypertension screening and, therefore, cases of latent gastric cancer were observed. For a comparison, the prevalence (age and sex standardized) of latent gastric cancer in the general population was estimated hypothesizing a latency period of 5 years. Overall, 1379 patients with cirrhosis were selected from a total of 15 791 endoscopically examined different patients observed during the period 1982-1997. Histological assessment revealed the presence of gastric cancer in 10 patients (9 males and 1 female). There was a significant 2.6-fold (P<0.01) increase in prevalence of gastric cancer compared with that expected in our cirrhotic patients. In conclusion, our findings confirm that liver cirrhosis would seem to be a risk factor for the development of gastric cancer. Other studies are needed to evaluate the pathogenic mechanisms involved

The activation of M2 muscarinic receptor inhibits cell growth and survival in human epithelial ovarian carcinoma

Ovarian cancer is the fifth leading cause of cancer-related deaths in females. Many ovarian tumor cell lines express muscarinic receptors (mAChRs), and their expression is correlated with reduced survival of patients. We have characterized the expression of mAChRs in two human ovarian carcinoma cell lines (SKOV-3, TOV-21G) and two immortalized ovarian surface epithelium cell lines (iOSE-120, iOSE-398). Among the five subtypes of mAChRs (M1–M5 receptors), we focused our attention on the M2 receptor, which is involved in the inhibition of tumor cell proliferation. Western blot analysis and real-time PCR analyses indicated that the levels of M2 are statistically downregulated in cancer cells. Therefore, we investigated the effect of arecaidine propargyl ester hydrobromide (APE), a preferential M2 agonist, on cell growth and survival. APE treatment decreased cell number in a dose and time-dependent manner by decreasing cell proliferation and increasing cell death. FACS and immunocytochemistry analysis have also demonstrated the ability of APE to accumulate the cells in G2/M phase of the cell cycle and to increase the percentage of abnormal mitosis. The higher level of M2 receptors in the iOSE cells rendered these cells more sensitive to APE treatment than cancer cells. The data here reported suggest that M2 has a negative role in cell growth/survival of ovarian cell lines, and its downregulation may favor tumor progression