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Bird strikes are a considerable hazard to the aviation industry, which has led airports to develop detailed management strategies to identify and reduce the risk of them. These strategies include plans to modify bird habitats in and around airports to limit the establishment of high-risk species. Although airports are generally located on the outskirts of towns and cities, they may be encroached on by urban sprawl. In this study, we examined how an urbanization gradient affects the bird community around an air force base in Cape Town (South Africa) and quantified how this could modify the hazard of bird–aircraft collision. We surveyed the bird community in and around the Air Force Base Ysterplaat across four seasons and categorized species based on their response to increased urbanization (urban avoiders, adapters and exploiters). By combining this with species-specific information on body size, flock size, flight behaviour and abundance, we showed that although urbanization affects bird composition, the overall hazard of bird–aircraft collision is consistent regardless of urban response. However, urbanization complicates mitigation in the matrix surrounding the airport and creates novel challenges for the management of bird hazards. Therefore, new bird hazard management strategies should be integrated within community-driven land-use planning to minimize the negative effects of bird–aircraft collisions.
Across the globe, the implementation of quality improvement science and collaborative learning has positively affected the care and outcomes for children born with CHD. These efforts have advanced the collective expertise and performance of inter-professional healthcare teams. In this review, we highlight selected quality improvement initiatives and strategies impacting the field of cardiovascular care and describe implications for future practice and research. The continued leveraging of technology, commitment to data transparency, focus on team-based practice, and recognition of cultural norms and preferences ensure the success of sustainable models of global collaboration.
The astrometric capability of the Hubble Space Telescope Planetary Camera (WF/PC1) is investigated, motivated by a study of the internal velocity distribution of globular clusters. The astrometric accuracy of the HST PC will be determined ultimately by 1) the accuracy to which the aberrated images can be ‘centered’, and 2) the accuracy to which the distortions across the PC field can be modeled. A series of overlapping exposures of two clusters, NGC 6752 and M15, are utilized to examine these issues.
We have made use of maximum-likelihood image reconstruction to address the first issue, with good success. Reconstruction improves both the detectability and precision of the image centers. A preliminary exploration of the second issue, that of modeling the distortion across the PC field, is also presented, using positions derived from the multiple overlapping exposures.
The Hubble Space Telescope, a large optical instrument having an aperture of 2.4 meters and a length of 8.8 meters has been developed by the U.S. National Aeronautics and Space Administration in cooperation with the European Space Agency. The Space Shuttle will be used to place the telescope in orbit. The primary astrometric instrument will be one of the three Fine Guidance Sensors which have the capability of measuring the position of one object with respect to another to an accuracy of ±0.″002. To facilitate use of the Hubble Space Telescope, observers will be provided with the Astrometric Data Reduction Software package. The variety of astrometric problems and the several modes of operation are mentioned as well as the cooperative program with the European astrometric satellite project HIPPARCOS.
A complex cerium bearing oxide, Gd2Ce2O7 was synthesized in order to simulate Pu in a fluorite derivative oxide. X-ray diffraction (XRD) data was collected using a lab diffractometer at room temperature and analyzed by Rietveld refinement method using the xnd program. The diffraction pattern obtained from the material could be indexed as a C-type cubic bixbyite crystal structure however several peaks showed peak broadening and could not be accounted for within the single-phase bixbyite model. A full pattern refinement, assuming a possible existence of short order disordered bixbyite regions within an average disordered fluorite phase gave a good fit with the experimental data, providing an estimate for correlation length of those bixbyite regions. Transmission electron microscopy confirms the existence of these correlated domains of disordered bixbyite type phase inside a defect fluorite lattice. Understanding the extent of these domains as a function of composition and the thermal history of the samples may have a profound effect on our understanding of miscibility gaps in Re2O3-CeO2 phase diagrams. These effects could be eventually exploited to design materials with increased radiation resistance, a desired feature for oxide matrices where actinides can be safely disposed.
Polymers and polymer nanocomposites have been studied under conditions of extremely high heating rates. Traditionally, these materials have been examined by the flammability research community using methods which have heating rates on the order of 10 degrees C/min. In this study, we have examined how polypropylene-nanoclay (montmorillonite) and polypropylene-carbon nanotube nanocomposites behave subjected to heating rates on the order of one million degrees C/min when irradiated with a 1064 nm Nd-YAG variable pulse millisecond laser. Time-resolved temperature data and mass loss data was collected for each sample as well as post-mortem surface characterization using spectroscopy and electron microscopy. The analysis shows that the nanospecies are effective in providing a protective barrier that decreases the amount of degradation and mass loss to the underlying polymer material. The effect is clearly seen after irradiating with a single pulse and multiple pulses. A comparison between the performance of the nanoclay and carbon nanotube composites is given.
The World Health Organization ‘Surgical Safety Checklist’ has been adopted by UK surgical units following National Patient Safety Agency guidance. Our aim was to assess compliance with our local version of this Checklist.
Otolaryngology trainee doctors prospectively assessed compliance with the local Checklist over a six-week period. A staff educational intervention was implemented and the audit was repeated 12 months later.
A total of 72 cases were assessed. The initial audit found that: 44 per cent of procedures were undocumented at ‘Sign in’; ‘Time out’ was inappropriately interrupted in 39 per cent of cases; the procedure started before Checklist completion in 33 per cent of cases; and the ‘Sign out’ was not read out in 94 per cent of cases and was not fully documented in 42 per cent of cases. Following education, re-audit indicated that overall compliance had improved from 63.7 per cent (±8.9 per cent standard error of the mean) to 90.4 per cent (±2.7 per cent standard error of the mean).
Our completed audit cycle demonstrated a significant improvement in Checklist compliance following educational intervention. We discuss barriers to compliance, as well as strategies for quality improvement, and we call for other surgeons to similarly publish their Checklist experience and assess its impact on surgical outcomes.
We report results of experimental studies on the behavior of Np during aqueous corrosion of unirradiated Np-bearing U oxides. Np-doped U oxides were reacted in humid air at 90°C and 150°C for several weeks within sealed stainless-steel vessels. Reacted solids were examined by scanning and transmission electron microscopies (SEM and TEM), electron energy-loss spectroscopy (EELS), and X-ray powder diffraction (XRD). Dehydrated schoepite, (UO2)O0.25-z(OH)1.5+2z (0 ≤z ≤0.15), is the predominant U(VI) compound formed in these experiments. Preliminary EELS analysis on crushed grains verify that dehydrated schoepite formed at 150°C contains up to approximately 2 wt.% Np, corresponding to a maximum Np:U molar ratio of approximately 1:40. These are maximum values because the degree to which surface-sorbed Np is present on the grains analyzed is not yet known. Crystalline NpO2 also precipitated during these experiments, and the concentration of Np in dehydrated schoepite may represent the maximum amount of Np that can be incorporated into dehydrated schoepite under the experimental conditions.
The quantity, radioactivity, and isotopic characteristics of the spent fission fuel from a hybrid fusion-fission system capable of extremely high burnups are described. The waste generally has higher activity per unit mass of heavy metal, but much lower activity per unit energy generated. The very long-term radioactivity is dominated by fission products. Simple scaling calculations suggest that the dose from a repository containing such waste would be dominated by 129I, 135Cs, and 242Pu. Use of such a system for generating energy would greatly reduce the need for repository capacity
In this work, the influence of surrounding ambient atmosphere on the stability of electroluminescent (EL) porous Si (PS) diodes fabricated from anodic oxidation of epitaxially grown p-type layers on n-type Si substrates is investigated. These structures are characterized using photoluminescence (PL), electroluminescence (EL), and infrared (IR) spectrosopies, as well as scanning electron microscopy (SEM). Such structures yield orange emission with maxima near 620 nm upon the application of moderate applied voltages (3-7 V). In strong oxidizing environments, EL intensity degrades completely within 30 minutes; in contrast, the integrated intensity remains essentially unchanged in the same timeframe in the presence of a vigorous flow of inert gases such as nitrogen and argon. Infrared spectroscopic studies strongly suggest that electroluminescence degradation is related to porous silicon surface oxidation.
Photoresist polymer coatings in the film-substratum systems usually generate selfinduced residual stress during processing. It is believed that the residual stress is the driving force for buckling, cracking and delamination of the polymer coatings. Analysis of the residual stress development during processing is of great interest and practical importance.
Holographic interferometry technique has been developed for the direct measurements of general 2-dimensional stresses in thin films.[l] It turns out that it is a powerful technique to analyze residual stress development in polymer coatings during processing. By directly measuring the residual stress for each processing stage, the history of residual stress evolution can be closely followed and the residual stresses generated from different origins can be separated. By varying UV curing dosage, thermal curing temperature and the sequence of thermal and UV curing procedures, different residual stresses from various processing conditions can be comprehensively analyzed. Combining these data with mechanical properties of the coating offers valuable information for better understanding of the processing mechanism and enables one to optimize processing conditions for the best product capability.
This paper describes the fabrication method and initial characterization of self-assembled mesoscale arrays of quantum-confined CdS nanoparticles using DNA as a template for the overall shape. Three DNAs were used: the circular and linear forms of the plasmid pUCLeu4, and circular φ×174 RF II. In all three cases, the mesoscale lengths are consistent with the A-form of DNA. The structural signatures and crystallography were confirmed using conventional and high resolution transmission electron microscopy, and electron diffraction. Optical spectroscopy demonstrated that the particles display quantum-confinement effects. This research is a fundamental demonstration of the power of combining biochemical and solid-state processing techniques.
We describe here the use of calixarenes, methylene (-CH2-) linked phenolic macrocyclic molecules, to stabilize the formation of quantum-confined (Q-) CdS clusters. Specifically, we focus on the use of an amino-derivatized calixarene, para-[(dimethylamino)- methyl]calixarene, to stabilize Q-CdS clusters which have been characterized by High Resolution TEM (HREM), as well as absorption and emission spectroscopies. Under typical preparative conditions, an average particle diameter of 36 Å is obtained. HREM, in combination with Selected Area Diffraction (SAD), confirms the structure of the clusters as zinc blende CdS. Spectroscopic studies using absorption and emission methods indicate that both particle size and cluster photophysics are sensitive to the ratio of CdS to calixarene.
Deposition of a rare earth salt layer on a silicon substrate with subsequent spark processing yields a porous Si layer and SiO 2 cap doped with the rare earth ion. We have characterized luminescent Er-doped porous SiO2 on Si by scanning electron microscopy, energy dispersive Xray spectroscopy, as well as visible and near IR photoluminescence (PL) spectroscopies. Energydispersive x-ray maps indicate that the erbium concentration in the porous layer can be controlled by varying the molarity of the erbium solution deposited on the substrate prior to spark processing. Visible PL measurements reveal that the concentration of Er3+ is proportional to the resultant intensity of the visible fluorescence transitions; however, for the near IR fluorescence peak at 1.54 gim, self-quenching due to erbium clustering occurs at higher concentrations. Erbium-doped porous silicon layers can also be obtained by diffusion of an erbium salt into porous silicon formed by anodic etching of Si in hydrofluoric acid. Densification of the porous Si layers through high temperature oxidation after erbium diffusion forms erbium-doped SiO2 layers.