Wave chaos enhanced light trapping in optically thin solar cells.

Enhancing the energy output of solar cells increases their competitiveness as a source of energy. Producing thinner solar cells is attractive, but a thin absorbing layer demands excellent light management in order to keep transmission- and reflection-related losses of incident photons at a minimum. We maximize absorption by trapping light rays to make the mean average path length in the absorber as long as possible. In chaotic scattering systems, there are ray trajectories with very long lifetimes. In this paper, we investigate the scattering dynamics of waves in a model system using principles from the field of quantum chaotic scattering. We quantitatively find that the transition from regular to chaotic scattering dynamics correlates with the enhancement of the absorption cross section and propose the use of an autocorrelation function to assess the average path length of rays as a possible way to verify the light-trapping efficiency experimentally.

Chaos: A new mechanism for enhancing the optical generation rate in optically thin solar cells.

The photogenerated current of solar cells can be enhanced by light management with surface structures. For solar cells with optically thin absorbing layers, it is especially important to take advantage of this fact through light trapping. The general idea behind light trapping is to use structures, either on the front surface or on the back, to scatter light rays to maximize their path length in the absorber. In this paper, we investigate the potential of chaotic scattering for light trapping. It is well known that the trajectories close to the invariant set of a chaotic scatterer spend a very long time inside of the scatterer before they leave. The invariant set, also called the chaotic repeller, contains all rays of infinite length that never enter or leave the region of the scatterer. If chaotic repellers exist in a system, a chaotic dynamics is present in the scatterer. As a model system, we investigate an elliptical dome structure placed on top of an optically thin absorbing film, a system inspired by the chaotic Bunimovich stadium. A classical ray-tracing program has been developed to classify the scattering dynamics and to evaluate the absorption efficiency, modeled with Beer-Lambert's law. We find that there is a strong correlation between the enhancement of absorption efficiency and the onset of chaotic scattering in such systems. The dynamics of the systems was shown to be chaotic by their positive Lyapunov exponents and the noninteger fractal dimension of their scattering fractals.

Injection-associated pain in femoral arteriography: a European multicenter study comparing safety, tolerability, and efficacy of iodixanol and iopromide.

PURPOSE: To evaluate injection-associated pain, safety, and efficacy with the isotonic contrast medium iodixanol (Visipaque 270 mg I/ml) compared with iopromide (Ultravist 300 mg I/ml) in femoral arteriography. METHODS: A multicenter, double-blind, randomized, parallel-group clinical investigation was carried out in 54 hospitals in Europe. Of the patients evaluated, 1225 received iodixanol and 1227 iopromide in conventional and/or digital subtraction angiography. RESULTS: The iodixanol group reported statistically significantly less injection-associated pain (0.9%) than the iopromide group (9.5%) (p << 0.001). Further, 4.1% in the iodixanol group experienced pain and/or severe heat sensation vs 19. 8% in the iopromide group (p << 0.001). In the iodixanol group, 1.8% of the patients experienced contrast-related adverse events vs 2.4% in the iopromide group (p = NS). Overall diagnostic information was optimal for 94.1% in the iodixanol group and 95.3% in the iopromide group (p = NS). CONCLUSIONS: Iodixanol 270 mg I/ml causes significantly less injection-associated pain during femoral arteriography and is as safe and efficacious as iopromide 300 mg I/ml.

Increased postperinatal child mortality among children of mothers exposed to measles during pregnancy.

Previous studies of an urban and a rural epidemic in Guinea-Bissau have shown perinatal mortality to be statistically significantly higher among children whose mothers have been exposed to measles during pregnancy. After the epidemic in 1970 in Bandim, a district in the capital of Guinea-Bissau, such children also had a postperinatal childhood mortality risk (7 days to 5 years of age) of 0.229, compared with 0.134 for other children in the community. None of the mothers had developed clinical measles. In a Cox regression analysis adjusting for known background factors, the mortality hazard ratio between the exposed and the controls was found to be 2.0 (95% confidence interval 1.1-3.8). After a small rural measles epidemic in Quinhamel in 1983, the mortality hazard ratio for children of mothers exposed during pregnancy compared with controls was 1.7 (95% confidence interval 0.6-4.6). Exposure to measles or some concomitantly transmitted pathogen during fetal life may contribute to the high childhood mortality found in many developing countries.

Association between invasiveness, inflammatory reaction, desmoplasia and survival in colorectal cancer.

Five hundred and twenty seven colorectal carcinomas were reviewed histologically. A multivariate analysis (Cox) was used to test the prognostic importance of certain histological features (invasiveness, inflammatory reaction, and amount of fibrous tissue) at the tumour edge after allowance had been made for clinicopathological stage, tumour site, and histological type and grade. A poorly defined tumour border, lack of inflammatory reaction, and a pronounced fibrosis (desmoplasia) at the tumour edge were associated with unfavourable stage distributions, but each of these features also had an independent effect on prognosis.

Influence of mucinous components on survival in colorectal adenocarcinomas: a multivariate analysis.

Of 534 resected colorectal adenocarcinomas, 165 (31%) contained some mucinous components; these represented the main part of the tumour in 67 (13%). Of the mucin containing tumours, 63 (38%) were in the right colon compared with 50 (13%) of the non-mucinous ones (p less than 0.001). Patients with predominantly mucinous tumours were significantly older than those with non-mucinous tumours, and they tended to present with tumours at a more advanced stage. A multivariate analysis did not show any significant independent prognostic influence of the mucinous component except when this had a predominantly signet ring cell pattern.

Degree of differentiation in colorectal adenocarcinomas: a multivariate analysis of the influence on survival.

Three hundred and sixty eight resected colorectal adenocarcinomas were graded (WHO) retrospectively and the results correlated with estimated length of patient survival. In 30 (82%) of the tumours more than one degree of differentiation was found. Histological grade significantly influenced survival time when other explanatory variables such as tumour site and stage, age, and sex were adjusted for. The results suggested that three degrees of differentiation (well, moderate, and poor) are sufficient for the grading of colorectal carcinomas, and that grading should be based on the predominating degree of differentiation represented in the primary tumour.

Increased perinatal mortality among children of mothers exposed to measles during pregnancy.

A survey done after a severe epidemic of measles in an urban area of Guinea-Bissau has shown that children born to women exposed to measles during pregnancy had a perinatal mortality rate of 15%, compared with only 4% for other children in the community (OR = 4.2; 95% CI 2.1-8.5). None of the women had clinical evidence of measles. Adjusting for background variables, logistic regression analysis showed no tendency towards reduced risk of perinatal mortality among children of women exposed during pregnancy relative to controls. Both stillbirth and early neonatal mortality rates were increased. A similar tendency was found in a rural epidemic (OR = 9.5; 95% CI 2.6-35.1). Exposure during any trimester of fetal life increased the rate of perinatal mortality. The results suggest that exposure to measles virus or some concomitantly transmitted pathogen may contribute to the high perinatal mortality risk found in many developing countries. The possible long-term health consequences of exposure to measles virus should be considered when assessing the value of measles control programmes.

PIP: A survey done after a severe epidemic of measles in an urban area of Guinea-Bissau has shown that children born to women exposed to measles during pregnancy had a perinatal mortality rate of 15%, compared with only 4% for other children in the community (OR=4.2; 95% CI 2.1-8.5). None of the women had clinical evidence of measles. Adjusting for background variables, logistic regression analysis showed no tendency towards reduced risk of perinatal mortality among children of women exposed during pregnancy relative to controls. Both stillbirth and early neonatal mortality rates were increased. A similar tendency was found in a rural epidemic (OR=9.5; 95% CI 2.6-35.1). Exposure during any trimester of fetal life increased the rate of perinatal mortality. The results suggest that exposure to measles virus or some concomitantly transmitted pathogen may contribute to the high perinatal mortality risk found in many developing countries. The possible long-term health consequences of exposure to measles virus should be considered when assessing the value of measles control programs.

Tumour site: a prognostic factor in colorectal cancer? A multivariate analysis.

Data from 753 patients with single adenocarcinomas of the large intestine diagnosed and treated at Trondheim Regional and University Hospital between 1964 and 1978 were studied to determine the influence of tumour site on survival by adjusting for tumour stage, age, and sex. The Cox regression model was used. Although the clinicopathologic stage had the strongest association with prognosis, the tumour site independently influenced the mortality, which increased from the right colon via the transverse/left part of the colon to the rectum.