The determination of optical absorption and scattering in translucent porcelain

Reflectance and transmittance theories have been used to calculate the optical absorption and scattering within materials. For these calculations, the incorporation of corrections for interfacial reflections has not been universally applied, and when corrections have been incorporated, the value used for the diffuse internal reflection coefficient has often been based on theoretical considerations. A method of incorporating interfacial-reflection corrections is presented. The importance of the incorporation of such corrections, with the proper value for the internal reflection coefficient, is clearly demonstrated for both reflectance and transmittance theories. The limitation of transmittance theory to materials with a scattering power (SX) of greater than 0.5 is also demonstrated for collimated illumination, unless an independent determination is made of the internal reflection coefficient.     

Origins of scaling in natural images

One of the most robust qualities of our visual world is the scale invariance of natural images. Not only has scaling been found in different visual environments, but the phenomenon also appears to be calibration-independent. This paper proposes a simple property of natural images which explains this robustness: they are collages of regions corresponding to statistically independent "objects". Evidence is provided for these objects having a power-law distribution of sizes within images, from which follows scaling in natural images. It is commonly suggested that scaling instead results from edges, each with power spectrum 1/k2. This hypothesis is refuted by example.     

Empirical development of brief smoking prevention videotapes which target African-American adolescents

Two studies are described which provide evaluations for two brief videotapes developed as supplemental materials in the prevention of tobacco use among African-American adolescents. One videotape (the "soap opera") provides a more general audience-oriented presentation of prevention material and it was filmed primarily at a shopping mall, whereas the other videotape (the "rap") provides a "hip-hop generation" presentation, and it was filmed primarily at an outdoor hangout. The first study compared the two videotapes against each other. The second study compared the two videotapes combined in the same presentation, controlling for order of presentation, against a discussion group control. The results of the two studies indicated few differences in receptivity to the two videotapes among primarily African-American and Latino young adolescents. The rap videotape was rated as more accurate in its depiction of the African-American lifestyle, although both videotapes were equally liked. When shown together, the videotapes were not found to be superior in decreasing behavioral intention to smoke compared to a discussion group control. No change in trial of smoking was observed within or across conditions measured over a pre-post summer interval. These data suggest that "culturally sensitive" videotapes have no more of a short-term effect on youth than do other types of brief interventions which involve minority implementers.     

Arrested pregnancy syndrome in Haiti: findings from a national survey

This report describes findings from a national survey of pregnant women in Haiti regarding the social epidemiology of pedisyon (perdition), or "arrested pregnancy syndrome," a condition believed to be associated with infertility. Data collected on mortality of respondents' sisters were used to indirectly measure the prevalence of this culture-bound syndrome in the adult female population and to compare its distribution in urban and rural areas. Perdition appears to be a fairly common event that affects a large proportion of Haitian women. Reported cases of pedisyon were significantly higher in urban areas, which also differed from rural areas on respondent education, economic status, use of prenatal care, and fertility. No differences were found on sociodemographic, health, or fertility variables when women reporting perdition deaths were compared with women who reported other sister deaths. The utility and limitations of the proxy respondent method are discussed. Possible explanations for the higher rate of pedisyon among urban Haitian women are discussed, and suggestions are made for future research on arrested pregnancy syndrome.     

A new method of acrylic cranioplasty

BACKGROUND: Previous acrylic cranioplasty techniques have relied on wire or suture fixation of the acrylic to the skull. A new methyl methacrylate cranioplasty technique, using acrylic with titanium plating, is described. METHODS: Titanium plates were bent into a "Z" shape and attached to the skull at the perimeter of the skull defect, extending into the defect. The acrylic was then poured into the defect and held in place during setting with a sheet of plastic. The plates are thereby embedded in the acrylic. RESULTS: Standard methyl methacrylate and titanium plates and screws were used to perform a new method of cranioplasty. CONCLUSIONS: A rigid, form-fitting, aesthetic construct can be easily and quickly created. This technique also offers the benefit of allowing secondary craniotomy, if necessary.