The role of convexity in perceptual completion: beyond good continuation

Since the seminal work of the Gestalt psychologists, there has been great interest in understanding what factors determine the perceptual organization of images. While the Gestaltists demonstrated the significance of grouping cues such as similarity, proximity and good continuation, it has not been well understood whether their catalog of grouping cues is complete--in part due to the paucity of effective methodologies for examining the significance of various grouping cues. We describe a novel, objective method to study perceptual grouping of planar regions separated by an occluder. We demonstrate that the stronger the grouping between two such regions, the harder it will be to resolve their relative stereoscopic depth. We use this new method to call into question many existing theories of perceptual completion (Ullman, S. (1976). Biological Cybernetics, 25, 1-6; Shashua, A., & Ullman, S. (1988). 2nd International Conference on Computer Vision (pp. 321-327); Parent, P., & Zucker, S. (1989). IEEE Transactions on Pattern Analysis and Machine Intelligence, 11, 823-839; Kellman, P. J., & Shipley, T. F. (1991). Cognitive psychology, Liveright, New York; Heitger, R., & von der Heydt, R. (1993). A computational model of neural contour processing, figure-ground segregation and illusory contours. In Internal Conference Computer Vision (pp. 32-40); Mumford, D. (1994). Algebraic geometry and its applications, Springer, New York; Williams, L. R., & Jacobs, D. W. (1997). Neural Computation, 9, 837-858) that are based on Gestalt grouping cues by demonstrating that convexity plays a strong role in perceptual completion. In some cases convexity dominates the effects of the well known Gestalt cue of good continuation. While convexity has been known to play a role in figure/ground segmentation (Rubin, 1927; Kanizsa & Gerbino, 1976), this is the first demonstration of its importance in perceptual completion.     

Three-fold reduction in the prevalence of tuberculosis over 25 years in Indonesia.

BACKGROUND: Tuberculosis (TB) remains the principal cause of death from a curable infectious disease. Indonesia is estimated to have the third highest case load worldwide, but TB prevalence has not been measured for 25 years. METHODS: In 2004, 20000 households were selected in all 30 provinces. All adults (aged >/=15 years) in every household were screened for symptoms of pulmonary tuberculosis (PTB). Among those with symptoms, TB was diagnosed by sputum smear microscopy and sputum culture. RESULTS: Eighty adults were positive on at least two sputum smears (104 per 100000 population, 95%CI 66-142). Prevalence was lower in Central Indonesia (Java-Bali, 59/100000) than in the Western (Sumatra, 160/100000) or Eastern regions (189/100000), but the estimated 225000 prevalent cases were distributed evenly among the three regions. The national per capita prevalence in 2004 was lower than in 1979-1982 by a factor of three (3.1, 95%CI 1.2-4.9), and the total number of cases was lower by a factor of two. CONCLUSIONS: Although the 2004 national survey may have underestimated the prevalence of smear-positive TB in Indonesia, there is strong evidence that it fell markedly between 1979-1982 and 2004.     

Primary infection by Plasmodium falciparum or P. vivax in a cohort of Javanese migrants to Indonesian Papua

The clinical and parasitological characteristics of the first naturally acquired malarial infection have rarely been documented in humans. When 243 migrants from non-endemic Java were followed from the day of their arrival in Indonesian Papua, 217 (89%) were found to become infected with Plasmodium falciparum and/or P. vivax before they were lost to follow-up. The incidence of malarial infection in the children investigated (who were aged 6-10 years) was indistinguishable from that in the adults (aged >20 years), with 1.10 and 1.14 P. falciparum infections/person-year (relative risk=0.97; 95% confidence interval=0.72-1.29) and 1.47 and 1.49 P. vivax infections/person-year (relative risk=0.99; 95% confidence interval=0.72-1.29), respectively. During their first infections, the children had higher P. falciparum parasitaemias than the adults (with geometric means of 1318 and 759 parasites/microl, respectively; P=0.04) but similar P. vivax parasitaemias (with geometric means of 355 and 331 parasites/microl, respectively; P=0.76). At first infection, 56% of the subjects were febrile and 90% complained of symptoms. There were no differences between children and adults with respect to these two parameters, either for P. falciparum or P. vivax. These findings indicate that, with promptly diagnosed and treated uncomplicated malaria, migrant children and adults in north-eastern Indonesian Papua have an equal risk of malarial infection and of disease following their first infections with P. falciparum and P. vivax.     

The association between thrombotic and inflammatory biomarkers and lower‐extremity peripheral artery disease

Lower‐extremity peripheral artery disease (LEAD) is associated with increased rates of mortality and morbidity. The aim of this study was to evaluate the associations among inflammatory and thrombotic markers and lower‐extremity peripheral disease. A total of 280 patients were enrolled in this study. Of these patients, 152 patients had LEAD on peripheral angiography that was performed because of suspected lower‐extremity peripheral disease based on history, physical examination, and non‐invasive tests. The control group consisted of 128 patients without LEAD on peripheral angiography. Patients with LEAD were classified according to trans‐atlantic inter‐society consensus (TASC) II classification. Subsequently, patients in TASC A to B were defined as having mild to moderate peripheral artery disease, and those in TASC C to D were defined as having advanced peripheral artery disease. Thrombotic and inflammatory markers, such as the neutrophil‐to‐lymphocyte ratio (NLR), the high‐sensitivity C (hs‐C) reactive protein level, the monocyte‐to‐high‐density lipoprotein‐cholesterol ratio, the fibrinogen to albumin ratio (FAR), and whole‐blood viscosity at high shear rate (HSR) and low shear rate (LSR), were evaluated in this population. The NLR, the monocyte‐to‐high‐density lipoprotein‐cholesterol ratio, the FAR, and whole‐blood viscosity, both at a LSR and a HSR, were significantly higher in patients with lower‐extremity peripheral disease compared with patients without lower‐extremity peripheral disease. We determined that lower‐extremity peripheral disease severity was correlated with the NLR, monocyte‐to‐high‐density lipoprotein‐cholesterol ratio, FAR, whole‐blood viscosity at LSR, and whole‐blood viscosity at HSR (r = 0.719, P = .004; r = 0.25, P = .008; r = 0.691, P = .002; r = 0.546, P < .001; and r = 0.448, P = .001, respectively). However hs‐C reactive protein levels were similar between patients with or without LEAD (2.47 ± 1.32 1.61 ± 0.91 P = .685). In addition, there was no correlation between the severity of LEAD and hs‐C reactive levels. In this study, we determined that the levels of inflammatory and thrombotic biomarkers are elevated in peripheral artery disease, and these levels predict disease severity.     

Single coronary artery with anomalous origin of the right coronary artery from the left anterior descending artery with a unique proximal course

A 62-year-old man with hypertension and hypercholesterolemia was referred to our unit for evaluation of chest pain. A very rare variant of single coronary artery, in which the anomalous right coronary artery originated as a separate branch from the left anterior descending artery, was incidentally found on his coronary angiography. The anomalous right coronary artery in our case appears to be unique in that it courses intraseptally rather than rightwards proximally and has obstructive atherosclerotic lesions resulting in inferior ischemia. Moreover, the acute angle made by the anomalous right coronary artery to turn toward the atrioventricular groove may have reduced the flow velocity and contributed to the development of inferior ischemia.