Search

The growth mechanism and polymer density in conjugated polymer brush (CPB) films composed of poly(3-methylthiophene) (P3MT) are characterized. X-ray photoelectron spectroscopy experiments show that the initiation of aryl halide monolayers by Pd(PtBu3)2 produces disproportionated monolayer initiators. Unlike disproportionated species formed during the solution-phase initiation of aryl halides, which cannot mediate polymerization, the surface-bound initiators catalyze polymerization to form CPB films with a high grafting density (1.2 nm-2). Rutherford backscattering spectrometry (RBS) experiments show that P3MT CPB films have a characteristic monomer volume density (3.7 nm-3) that is indistinguishable from the volume density of spuncast poly(3-hexylthiophene) films. Using these RBS and XPS results, characteristics of P3MT CPB growth are obtained, including the turnover frequency (7.5 h-1) and polymer molecular weight (300 g/mol·nm).

The morphological, structural, and electrical properties of poly(3-methylthiophene) polymer brush films grown on indium tin oxide up to 120 nm thick are reported. Optical spectroscopy experiments indicate that the average orientation of polymer chains is nearly isotropic at thicknesses below 10 nm and above 30 nm, and exhibits mild vertical anisotropy in between. Atomic force microscopy shows that the film surfaces consist of column-shaped domains with an average cross-sectional area (2.3 × 10-3 μm2) and density (200 μm-2) that are independent of film thickness. Analysis of the contact between printed Au electrodes and the polymer brush film shows that a small fraction of the film surface (i.e., the tallest columns) makes contact with the electrodes. The measured bulk resistivity along the columns is 1.4 × 105 Ω·cm, 2 orders of magnitude lower than typical values for spuncast poly(3-alkylthiophene) films, while the resistance along individual polymer chains in the columns is estimated to be 360 GΩ/nm per molecule, comparable to molecular wires that exhibit charge transport by intramolecular processes. The enhanced conduction is likely due to additional intramolecular transport pathways enabled by the electrode-polymer brush-electrode device architecture, establishing conjugated polymer brushes as a platform for studying the interplay among synthesis, morphology, and charge transport phenomena.

The design of the system architecture has been a critical and relevant activity in the systems engineering discipline from several decades for the design of physical man-made systems [1]. However, a reduced set of design methods and complementary decision-making techniques have been consistently used with successful results [2–4].

Epitaxial films of CoxMnyGez grown on Ge (111) substrates by molecular-beam-epitaxy techniques have been investigated as a continuous function of composition using combinatorial synchrotron x-ray diffraction (XRD) and x-ray fluorescence (XRF) spectroscopy techniques. A high-resolution ternary epitaxial phase diagram is obtained, revealing a small number of structural phases stabilized over large compositional regions. Ordering of the constituent elements in the compositional region near the full Heusler alloy Co2MnGe has been examined in detail using both traditional XRD and a new multiple-edge anomalous diffraction (MEAD) technique. Multiple-edge anomalous diffraction involves analyzing the energy dependence of multiple reflections across each constituent absorption edge in order to detect and quantify the elemental distribution of occupation in specific lattice sites. Results of this paper show that structural and chemical ordering are very sensitive to the Co: Mn atomic ratio, such that the ordering is the highest at an atomic ratio of 2 but significantly reduced even a few percent off this ratio. The in-plane lattice is nearly coherent with that of the Ge substrate, while the approximately 2% lattice mismatch is accommodated by the out-of-plane tetragonal strain. The quantitative MEAD analysis further reveals no detectable amount (

Epitaxial growth and structural properties of Cox Mny Siz thin films on Ge (111) substrates, including the Heusler alloy Co2 MnSi (111), have been studied using combinatorial molecular beam epitaxy (MBE) techniques. In situ reflection high energy electron diffraction and ex situ x-ray diffraction experiments show that high quality coherent MBE growth with fcc (111) stacking can be achieved over a relatively large composition space that includes Co2 MnSi. The highest structural and chemical ordering is observed near the composition of Co0.63 Mn 0.14 Si0.23 rather than that at the Heusler stoichiometry of Co2 MnSi. The in-plane crystallographic axis of the fcc film exhibits a 60°rotation with respect to that of the Ge substrate. The rotation appears to be originated at the film-substrate interface, as a result of the symmetry and stacking of the Ge (111) surface reconstruction.

The epitaxial growth of (FeCo)x Ge1-x films on Ge and GaAs (001) substrates has been studied systematically with x in the range between 0 and 17 at. %, using combinatorial molecular beam epitaxy (MBE) techniques. Complementary doping using the two transition metal dopants into Ge (001) during MBE growth is shown to produce high quality coherent epitaxial films for transition metal concentrations as high as 11 at. %. As the doping level increases, rough growth occurs, which is accompanied by an increasing amount of stacking faults along the 〈111〉 directions. The crystal lattice that resulted from the rough growth exhibits a large out-of-plane tetragonal distortion. There are no detectable secondary phases up to a combined transition metal concentration of 17 at. %. The behaviors are shown to be invariant with respect to the choice of substrates.

The authors report a study of structural and chemical disorders in a ternary combinatorial epitaxial film of Cox Mny Ge1-x-y in the composition range that includes the Heusler alloy Co2 MnGe, using microbeam anomalous x-ray diffraction techniques. The structural and chemical ordering of the alloy has been found to be extremely stable over a large composition range, while elemental site swapping and sublattice vacancies have been identified. A model of anomalous diffraction around the Co and Ge edges is presented and shown to make possible the identification and quantification of these disorders in an epitaxial film.

The National Retail Data Monitor (NRDM) is a public health surveillance tool that collects and analyzes daily sales data for over-the-counter (OTC) health-care products. NRDM collects sales data for selected OTC health-care products in near real time from15,000 retail stores and makes them available to public health officials. NRDM is one of the first examples of a national data utility for public health surveillance that collects, redistributes, and analyzes daily sales-volume data of selected health-care products, thereby reducing the effort for both data providers and health departments.

To assess the value of ICD-9 coded chief complaints for early detection of epidemics, we measured sensitivity, positive predictive value, and timeliness of Influenza detection using a respiratory set (RS) of ICD-9 codes and an Influenza set (IS). We also measured inherent timeliness of these data using the cross-correlation function. We found that, for a one-year period, the detectors had sensitivity of 100% (1/1 epidemic) and positive predictive values of 50% (1/2) for RS and 25% (1/4) for IS. The timeliness of detection using ICD-9 coded chief complaints was one week earlier than the detection using Pneumonia and Influenza deaths (the gold standard). The inherent timeliness of ICD-9 data measured by the cross-correlation function was two weeks earlier than the gold standard.

We have grown epitaxial thin films of c-axis oriented metastable four-layered hexagonal BaRuO3 on a (111) SrTiO3 substrate by 90° off-axis sputtering techniques. X-ray diffraction and transmission electron microscopy reveal that the films are single domains of c-axis four-layered hexagonal structures with an in-plane epitaxial arrangement of BaRuO3 [2110]||SrTiO3[110]. Surfaces with smooth terraces having a step height of a half unit cell (~4.7 Å) have been observed by scanning tunneling microscopy. The in-plane electrical resistivity of the films is metallic, with a room temperature value of 810 muOmega cm and slightly curved temperature dependence. Their magnetic susceptibility is Pauli paramagnetic. The metastable layered metallic oxide can be used for understanding new solid-state phenomena and device applications.

DMS is a Web-based disease-management system, which facilitates easy access for users and close connection to hospital information systems, based on clinical practice guidelines. Currently we are prototyping DMS in the area of hyperlipidemia management. However our approach is general. For each office visit, DMS generates an encounter form with recommendations based on the National Cholesterol Education Program (NCEP) guidelines. In between visits, DMS provides email notifications to clinicians about delinquent laboratory studies and recommendations for patient management based on recently available information. By reviewing previous efforts for implementing NCEP guidelines and some of the pitfalls that were encountered, we first constructed DMS for hyperlipidemia management. A detailed description of DMS is provided in this paper.

We have investigated the thermal conductivity of single-crystal Ba1-xKxBiO3 (BKBO). The measured temperature and field dependences reveal that both electrons and phonons contribute to the thermal conduction of BKBO in both the normal and the superconducting states, and that the phonon mean free path can be manipulated by potassium doping concentration. The potassium-underdoped samples exhibit a suppression of phonon diffusivity, and consequently a more pronounced electronic contribution, indicating that the statistical fluctuation of potassium concentration may lead to an increase of defect density. The field-dependent thermal conductivity of BKBO in the superconducting state exhibits scaling behavior, which indicates the presence of an unconventional superconducting gap.