Synthesis of organic-inorganic hybrids via a high-pressure-ramp process: the effect of inorganic nanoparticle loading on structural and photochromic properties.

Organic polymerization remains a limiting step in the preparation of organic-inorganic hybrid materials with a strong concentration of the inorganic component. In this work, a high-pressure-ramp process was applied to achieve pHEMA-TiO2 nanoparticulate solids with an unprecedentedly high concentration (12 mol l-1) of the inorganic component, which is four times higher than that obtained after radical polymerization induced thermally or by photons. The inorganic nanoparticles underwent morphological and structural changes with an increase of Ti concentration above 1.5 mol l-1: they slightly coarsen and crystallize into an anatase polymorph. The material possesses a strong photochromic response related to the electron-hole separation at the organic-inorganic interface and can store 1e- per 5 Ti atoms. The electron storage capacity of the titania nanoparticles decreases upon crystallization.

Experimental evidence of an electronic transition in CeP under pressure using Ce L3 XAS.

Cerium phosphide undergoes a unit-cell volume discontinuity without any structural phase transitions upon application of a high pressure of ∼10 GPa. This phenomenon is attributed to a change in the electronic charge distribution of the cerium in CeP, but to date no direct experimental verification for this hypothesis has been presented. Here, we report a Ce L3-edge X-ray absorption spectroscopy study under pressure, which provides direct compelling evidence of an electronic transition associated with the above-mentioned isostructural volume discontinuity. The present results should be relevant to the understanding of the phenomenon of pressure induced isostructural transitions involving unit-cell volume collapse.

A New Route for High-Purity Organic Materials: High-Pressure-Ramp-Induced Ultrafast Polymerization of 2-(Hydroxyethyl)Methacrylate.

The synthesis of highly biocompatible polymers is important for modern biotechnologies and medicine. Here, we report a unique process based on a two-step high-pressure ramp (HPR) for the ultrafast and efficient bulk polymerization of 2-(hydroxyethyl)methacrylate (HEMA) at room temperature without photo- and thermal activation or addition of initiator. The HEMA monomers are first activated during the compression step but their reactivity is hindered by the dense glass-like environment. The rapid polymerization occurs in only the second step upon decompression to the liquid state. The conversion yield was found to exceed 90% in the recovered samples. The gel permeation chromatography evidences the overriding role of HEMA2(••) biradicals in the polymerization mechanism. The HPR process extends the application field of HP-induced polymerization, beyond the family of crystallized monomers considered up today. It is also an appealing alternative to typical photo- or thermal activation, allowing the efficient synthesis of highly pure organic materials.

Laser-assisted high-pressure-induced polymerization of 2-(hydroxyethyl)methacrylate.

We report on a successful room-temperature polymerization of 2-(hydroxyethyl)methacrylate (HEMA) under high pressure. The polymerization is observed in a limited range of pressures 0.1 to 1.6 GPa without the use of any initiator. When the compressed sample is irradiated at 488 or 355 nm by a laser, the polymerization reaction rate is increased by a factor of 10 or 30, respectively. Moreover, the shift of the laser wavelength to the UV improves the polymerization yield of the recovered sample to 84%. The catalysis of the polymerization process by light results from a one-photon-assisted electron transfer to π* antibonding states of the monomer molecule. The observed polymerization is irreversible and almost complete, which makes this synthesis process suitable for applications.

Electronic structure of spinel-type nitride compounds Si3N4, Ge3N4, and Sn3N4 with tunable band gaps: application to light emitting diodes.

In this Letter using experimental and theoretical methods, we show that the solid solutions of group 14 nitrides having spinel structure (γ-M3N4 where M=Si, Ge, Sn) exhibit mainly direct electronic band gaps with values that span the entire visible wavelength region, making these hard and thermally stable materials suitable for optoelectronic devices and, in particular, lighting applications. Using the simulated band structure, we also calculate the exciton binding energy. The combination of large exciton binding energies and the tunable electronic band gaps in the visible range makes these binary spinel nitrides and their solid solutions a new class of multifunctional materials with optoelectronic properties that can be engineered to suit the desired application.

Academic models of clinical care for women: the National Centers of Excellence in Women's Health.

Between 1996 and 1999, 18 academic health centers were awarded the designation of National Center of Excellence (CoE) in Women's Health by the Office on Women's Health within the Department of Health and Human Services and were provided with seed monies to develop model clinical services for women. Although the model has evolved in various forms, core characteristics that each nationally designated CoE has adopted include comprehensive, women-friendly, women-focused, women-relevant, integrated, multidisciplinary care. The permanent success of these comprehensive clinical programs resides in the ability to garner support of leaders of the academic health centers who understand both the importance of multidisciplinary programs to the clinical care they provide women and the education they offer to the future providers of women's healthcare.

Women's health centers and minority women: addressing barriers to care. The National Centers of Excellence in Women's Health.

New models of care delivery have been developed to better coordinate and integrate healthcare for women. In the United States, one of the challenges is to incorporate the needs of racial and ethnic minority populations into these newer care paradigms. This paper begins with a brief historical review of the experience of racial and ethnic minorities in the American healthcare system to provide a context for discussing barriers and limitations of more traditional models of women's healthcare. Specific approaches used by National Centers of Excellence in Women's Health are presented as examples of strategies that may be implemented by other communities to address these barriers.

Solidus of Earth's deep mantle

The solidus of a pyrolite-like composition, approximating that of the lower mantle, was measured up to 59 gigapascals by using CO2 laser heating in a diamond anvil cell. The solidus temperatures are at least 700 kelvin below the melting temperatures of magnesiowustite, which in the deep mantle has the lowest melting temperatures of the three major components-magnesiowustite, Mg-Si-perovskite, and Ca-Si-perovskite. The solidus in the deep mantle is more than 1500 kelvin above the average present-day geotherm, but at the core-mantle boundary it is near the core temperature. Thus, partial melting of the mantle is possible at the core-mantle boundary.

(Mg,Fe)SiO3-perovskite stability under lower mantle conditions

In three different experiments up to 100 gigapascals and 3000 kelvin, (Mg,Fe)SiO3-perovskite, the major component of the lower mantle, remained stable and did not decompose to its component oxides (Mg, Fe)O and SiO2. Perovskite was formed from these oxides when heated in a diamond anvil cell at pressures up to 100 gigapascals. Both MgSiO3 crystals and glasses heated to 3000 kelvin at 75 gigapascals also formed perovskite as a single phase, as evident from Raman spectra. Moreover, fluorescence measurements on chromium-doped samples synthesized at these conditions gave no indication of the presence of MgO.

Respiratory health of Hispanic migrant farm workers in Indiana.

The prevalence of respiratory disease in a Midwest Hispanic (mostly Mexican) migrant farm worker population was investigated. Chronic respiratory symptoms (cough, wheezing, sputum production) in adult workers (n = 354) were elevated (8.5%, 6.2%, 6.5%, respectively) and were accompanied by physiologic abnormalities as determined by pulmonary function testing. Over 15% of the adult cohort exhibited a FEV1/FVC < 75, and over 14% had FEF25-75 values which were less than 60% of predicted. The observed airflow obstruction of both large and small airways was not explained by cigarette usage (43%) in the adult cohort (current/past smokers). Tuberculin skin tests (TST) were positive (> or = 10 mm) in 55/195 men and 35/123 women for a total prevalence of 28.3%. No case of active tuberculosis (TB) was identified by either chest X-ray (CXR) or sputum cultures (in selected cases). In contrast to adult farm workers, who were predominantly born in Mexico (70%), only 36% of adolescent workers (age 11-18 years, n = 107) were born in Mexico with only 7.5% exhibiting TST positivity. Airflow obstruction of large airways (5.8%) and small airways (12.9%) were also less common in adolescents than adults. In summary, these studies document respiratory dysfunction in Hispanic migrant farm workers in Indiana and highlight the need to closely monitor the respiratory health of this high-risk population.

Incorporating mobile mammography units into primary care: focus group interviews among inner-city health center patients.

Mammography screening is underutilized, especially among women of lower socioeconomic status (SES). Mobile mammography units reduce cost and patient burden of mammography, and therefore might enhance screening rates among underserved populations. Few studies have explored factors associated with the acceptability of mobile mammography; none have targeted low-SES women. To explore these issues, we conducted focus group interviews in five university-affiliated urban primary-care clinics. The forty-three participants were 74% African-American, ranged in age from 40 to 70 years and most (67%) had household incomes below $15,000. A trained moderator led the groups of eight to 12 women through standardized, open-end interview questions exploring perceptions of mobile mammography. Findings suggest mammography vans are acceptable under only certain circumstances, including advance notice and assurance of privacy and quality. Convenience was important; 53% related being more likely to have mammograms if scheduled in conjunction with primary-care visits. Participants felt strongly that vans were inappropriate for public forums such as shopping centers. Association with primary-care health centers seemed to legitimize mammography vans and to allay concerns. If mammography screening is to become more widespread among low-income populations, these exploratory findings must be addressed in research and intervention development.

Melting of (Mg, Fe)SiO3-Perovskite to 625 Kilobars: Indication of a High Melting Temperature in the Lower Mantle.

The melting curves of two compositions of (Mg,Fe) SiO3-perovskite, the likely dominant mineral phase in the lower mantle, have been measured in a C02 laser-heated diamond cell with direct temperature measurements and in situ detection of melting. At 625 kilobars, the melting temperature is 5000 +/- 200 kelvin, independent of composition. Extrapolation to the core-mantle boundary pressure of 1.35 megabar with three different melting relations yields melting temperatures between 7000 and 8500 kelvin. Thus, the temperature at the base of the lower mantle, accepted to lie between 2550 and 2750 kelvin, is only at about one-third of the melting temperature. The large difference between mantle temperature and corresponding melting temperature has several important implications; particularly the temperature sensitivity of the viscosity is reduced thus allowing large lateral temperature variations inferred from seismic tomographic velocity anomalies and systematics found in measured velocity-density functions. Extensive melting of the lower mantle can be ruled out throughout the history of the Earth.