Depolarization and attenuation effects of radomes at 20 GHz

The problem of describing the attenuation and depolarization effects of a wet radome on a transmitted signal is considered by experiments carried out with two commonly used radome materials, ESSCOLAM-6 and ESSCOLAM-8. The results suggest that a two-component model of depolarization is required to account for the observed results. Predictions for the behavior of a complete radome are obtained, but full-scale testing with an operating radome to compare predicted and actual results remains to be done. An important conclusion is that while highly water-repellent radome materials are desirable from the point of view of attenuation experienced, they are not so desirable when considered in terms of the degree of depolarization introduced between orthogonally polarized signal components in frequency reuse systems     

Nanogram nitrite and nitrate determination in environmental and biological materials by vanadium (III) reduction with chemiluminescence detection

Nitrite in environmental water samples is reduced at room temperature to nitric oxide in acidic medium containing vanadium (III). Nitrate is also rapidly reduced after heating to 80-90 degrees C. Nitric oxide is removed from the reaction solution by scrubbing with helium carrier gas and is detected by means of a chemiluminescence NOx analyzer. Nanogram detection limits are obtained. The method has the advantage of not requiring highly acidic solutions for nitrate reduction and has been applied to the analysis of a variety of environmental waters, sediment, plant materials, and human urine and blood serum.     

Exploration of the two‐photon excitation spectrum of fluorescent dyes at wavelengths below the range of the Ti:Sapphire laser

We have studied the wavelength dependence of the two‐photon excitation efficiency for a number of common UV excitable fluorescent dyes; the nuclear stains DAPI, Hoechst and SYTOX Green, chitin‐ and cellulose‐staining dye Calcofluor White and Alexa Fluor 350, in the visible and near‐infrared wavelength range (540–800 nm). For several of the dyes, we observe a substantial increase in the fluorescence emission intensity for shorter excitation wavelengths than the 680 nm which is the shortest wavelength usually available for two‐photon microscopy. We also find that although the rate of photo‐bleaching increases at shorter wavelengths, it is still possible to acquire many images with higher fluorescence intensity. This is particularly useful for applications where the aim is to image the structure, rather than monitoring changes in emission intensity over extended periods of time. We measure the excitation spectrum when the dyes are used to stain biological specimens to get a more accurate representation of the spectrum of the dye in a cell environment as compared to solution‐based measurements.     

The role of state policies and programs in buffering the effects of poverty on children's immunization receipt

OBJECTIVES: This study assessed the influence of public policies on the immunization status of 2-year old children in the United States. METHODS: Up-to-dateness for the primary immunization series was assessed in a national sample of 8100 children from the 1988 National Maternal and Infant Health Survey and its 1991 Longitudinal Follow-Up. RESULTS: Documented immunization rates of this sample were 33% for poor children and 44% for others. More widespread Medicated coverage was associated with greater likelihood of up-to-dateness among poor children. Up-to-dateness was more likely for poor children with public rather than private sources of routine pediatric care, but all children living in states where most immunizations were delivered in the public sector were less likely to be up to date. Poor children in state with partial vaccine replacement programs were less likely to be up to date than those in free-market purchase states. CONCLUSIONS: While state policies can enhance immunization delivery for poor children, heavy reliance on public sector immunization does not ensure timely receipt of vaccines. Public- and private-sector collaboration is necessary to protect children from vaccine-preventable diseases.     

From expert-driven to user-oriented communication of infection control guidelines

Currently, infection control guidelines in hospitals and other health care institutions are more expert-driven than user-oriented. In order to enhance the usability of the expert-driven guideline format, we developed a website for the communication of existing guidelines that better fit the practical information needs of health care workers (HCWs). We employed a user-centered design process that involved two studies.In the initial study, 28 HCWs were asked to solve tasks using existing, paper-based infection control guidelines. In order to detect their strategies and problems, the participants were asked to think aloud. Usability problems occurred due to poorly structured information, insufficient quality of information, and a mismatch between experts’ and HCWs’ vocabulary. To overcome these shortcomings, three design principles were applied for communicating infection control guidelines: better navigation (the guidelines should be searchable in several ways); multimodality (the guidelines should not be presented as text only), and action-orientation (the guidelines should be presented as HCWs’ behaviors). A website was developed to meet these principles.In the second study, the same 28 HCWs completed tasks identical to those of the first study while thinking aloud, but this time using the website. The percentage of correctly completed tasks increased and the mean time for task completion decreased significantly. Also, respondents were more satisfied with the website than the paper-based guidelines. The number of problems due to poor information quality and a mismatch in vocabulary declined, although the number of structural problems increased. This can probably be explained by the fact that the navigation structure was user-generated (using Card Sort), in contrast to a standardized answer format based on common usability principles.Overall, we found that involving HCWs in the development process is important to create a sense of ownership and to foster the implementation of the guidelines, which might eventually result in compliance and reduce health care-associated infections. This paper outlines concrete steps for how to involve HCWs in the design process.     

The material basis for reduced mechanical properties in oim mice bones

Osteogenesis imperfecta (OI), a heritable disease caused by molecular defects in type I collagen, is characterized by skeletal deformities and brittle bones. The heterozygous and homozygous oim mice (oim/+ and oim/oim) exhibit mild and severe OI phenotypes, respectively, serving as controlled animal models of this disease. In the current study, bone geometry, mechanics, and material properties of 1-year-old mice were evaluated to determine factors that influence the severity of phenotype in OI. The oim/oim mice exhibited significantly smaller body size, femur length, and moment of area compared with oim/+ and wild-type (+/+) controls. The oim/oim femur mechanical properties of failure torque and stiffness were 40% and 30%, respectively, of the +/+ values, and 53% and 36% of the oim/+ values. Collagen content was reduced by 20% in the oim/oim compared with +/+ bone and tended to be intermediate to these values for the oim/+. Mineral content was not significantly different between the oim/oim and +/+ bones. However, the oim/oim ash content was significantly reduced compared with that of the oim/+. Mineral carbonate content was reduced by 23% in the oim/oim bone compared with controls. Mineral crystallinity was reduced in the oim/oim and oim/+ bone compared with controls. Overall, for the majority of parameters examined (geometrical, mechanical, and material), the oim/+ values were intermediate to those of the oim/oim and +/+, a finding that parallels the phenotypes of the mice. This provides evidence that specific material properties, such as mineral crystallinity and collagen content, are indicative and possibly predictive of bone fragility in this mouse model, and by analogy in human OI.