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The Square Kilometre Array (SKA) is a planned large radio interferometer designed to operate over a wide range of frequencies, and with an order of magnitude greater sensitivity and survey speed than any current radio telescope. The SKA will address many important topics in astronomy, ranging from planet formation to distant galaxies. However, in this work, we consider the perspective of the SKA as a facility for studying physics. We review four areas in which the SKA is expected to make major contributions to our understanding of fundamental physics: cosmic dawn and reionisation; gravity and gravitational radiation; cosmology and dark energy; and dark matter and astroparticle physics. These discussions demonstrate that the SKA will be a spectacular physics machine, which will provide many new breakthroughs and novel insights on matter, energy, and spacetime.
Optimism is associated with reduced cardiovascular disease risk; however, few prospective studies have considered optimism in relation to hypertension risk specifically. We investigated whether optimism was associated with a lower risk of developing hypertension in U.S. service members, who are more likely to develop high blood pressure early in life. We also evaluated race/ethnicity, sex and age as potential effect modifiers of these associations.
Participants were 103 486 hypertension-free U.S. Army active-duty soldiers (mean age 28.96 years, 61.76% White, 20.04% Black, 11.01% Hispanic, 4.09% Asian, and 3.10% others). We assessed optimism, sociodemographic characteristics, health conditions, health behaviours and depression status at baseline (2009–2010) via self-report and administrative records, and ascertained incident hypertension over follow-up (2010–2014) from electronic health records and health assessments. We used Cox proportional hazards regression models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), and adjusted models for a broad range of relevant covariates.
Over a mean follow-up of 3.51 years, 15 052 incident hypertension cases occurred. The highest v. lowest optimism levels were associated with a 22% reduced risk of developing hypertension, after adjusting for all covariates including baseline blood pressure (HR = 0.78; 95% CI = 0.74–0.83). The difference in hypertension risk between the highest v. lowest optimism was also maintained when we excluded soldiers with hypertension in the first two years of follow-up and, separately, when we excluded soldiers with prehypertension at baseline. A dose–response relationship was evident with higher optimism associated with a lower relative risk (p < 0.001). Higher optimism was consistently associated with a lower risk of developing hypertension across sex, age and most race/ethnicity categories.
In a diverse cohort of initially healthy male and female service members particularly vulnerable to developing hypertension, higher optimism levels were associated with reduced hypertension risk independently of sociodemographic and health factors, a particularly notable finding given the young and healthy population. Results suggest optimism is a health asset and a potential target for public health interventions.
The need for hollow microneedle arrays is important for both drug delivery and wearable sensor applications; however, their fabrication poses many challenges. Hollow metal microneedle arrays residing on a flexible metal foil substrate were created by combining additive manufacturing, micromolding, and electroplating approaches in a process we refer to as electromolding. A solid microneedle with inward facing ledge was fabricated with a two photon polymerization (2PP) system utilizing laser direct write (LDW) and then molded with polydimethylsiloxane. These molds were then coated with a seed layer of Ti/Au and subsequently electroplated with pulsed deposition to create hollow microneedles. An inward facing ledge provided a physical blocking platform to restrict deposition of the metal seed layer for creation of the microneedle bore. Various ledge sizes were tested and showed that the resulting seed layer void could be controlled via the ledge length. Mechanical properties of the PDMS mold was adjusted via the precursor ratio to create a more ductile mold that eliminated tip damage to the microneedles upon removal from the molds. Master structures were capable of being molded numerous times and molds were able to be reused. SEM/EDX analysis showed that trace amounts of the PDMS mold were transferred to the metal microneedle upon removal. The microneedle substrate showed a degree of flexibility that withstood over 100 cycles of bending from side to side without damaging. Microneedles were tested for their fracture strength and were capable of puncturing porcine skin and injecting a dye.
Following a marine oil spill, it is important to know where the oil goes, how it changes chemically, how long the oil persists in various environmental compartments such as water or sediments, and what biological resources are affected. As an oil spill progresses over time, the behavior of the oil and the impacted areas and levels of risk to people and biological resources such as fish and wildlife change. Scientific studies provide the most benefit to cleanup efforts and the protection of people and biological resources in the area when they are coordinated and focused on the most pressing questions based on the phase of the oil spill. Over several decades, previous marine oil spills have shown a consistent pattern; understanding this pattern can help predict where the oil will go, how it changes chemically, where it will persist, and what living things are likely to be affected. Similarly, this predictability, coupled with specific observations at each spill, can help to provide a framework for designing and conducting studies that can address key questions at critical junctures in the evolution of the spill.
Water and air are the first environmental media affected during the early phase of any marine spill. Animal and plant life (or “biological resources”) can be affected immediately – as can humans involved in spill cleanup. The initial exposures to the chemicals in petroleum and the resulting effects can be acute, but short-lived. This is because once the spilled oil is no longer moving on or in the water, concentrations of harmful chemicals decrease rapidly owing to dilution, dispersion, and degradation (collectively known as “weathering”). Likewise, the evaporation of the volatile hydrocarbon components of fuels or crude oil immediately following a spill first increases, then decreases. By contrast, the effects on shoreline biological resources from oil that reaches land may persist. The last area potentially to be affected is bottom sediments, where oil can be transported before or after it reaches land (Chapter 4).
Most oil tanker accidents occur near land. So when a marine oil spill occurs, it is usually not long before the spilled oil reaches shorelines. The shoreline is where the potential for harm to the environment and biological resources is the greatest, and where media attention and public concerns usually focus. Therefore, it is essential to determine the distribution, amount, composition, and fate of spilled oil on shorelines. This information forms the foundation for management decisions about cleanup during the early phases of the spill, assessments of long-term exposure and injury to biological resources, and long-term restoration strategies after the initial cleanup.
In this chapter, we consider the fate of shoreline oil following the Exxon Valdez oil spill, beginning with oil coming ashore in Prince William Sound (PWS) in 1989. This chapter picks up where Chapter 3 left off, describing where the oil was deposited, why some locations were oiled more than others, and how oil disappeared over time and why, in a few isolated locations, it persisted.
Coastal shorelines teem with life. The intersection of the land with the sea, combined with tidal fluctuations and coastal currents, creates an array of habitats that supports an amazing diversity of plants and animals – limpets, starfish, anemones, crabs, rockweed, eelgrass, snails, tubeworms, and the like – that live on the surface and in the sediments of the intertidal zone. When floating oil from a marine oil spill strikes a shoreline, the potential effects on these organisms (the shoreline biota) may be severe. Even species that are not directly affected by spill may suffer its effects if the shoreline prey on which they feed are diminished. Understanding how a spill affects the shoreline biota is therefore important to assessing the potential effects on the broader shoreline and coastal ecosystems.
During the Exxon Valdez spill, oil first spread over shorelines in Prince William Sound (PWS) and later extended outside of PWS to the Kenai Peninsula, Kodiak Island, and Alaska Peninsula (see Map 1, p. v). The effects of the spill and the need to respond rapidly were of enormous concern, particularly within PWS, where oil quantities and potential toxicity were greatest. In this chapter, we discuss three major programs undertaken to assess the effects of the Exxon Valdez oil spill on shoreline biota in PWS, including studies to determine the effects of intensive cleanup efforts.
We present the adaptive optics assisted, near-infrared VLTI instrument GRAVITY for precision narrow-angle astrometry and interferometric phase referenced imaging of faint objects. With its two fibers per telescope beam, its internal wavefront sensors and fringe tracker, and a novel metrology concept, GRAVITY will not only push the sensitivity far beyond what is offered today, but will also advance the astrometric accuracy for UTs to 10 μas. GRAVITY is designed to work with four telescopes, thus providing phase referenced imaging and astrometry for 6 baselines simultaneously. Its unique capabilities and sensitivity will open a new window for the observation of a wide range of objects, and — amongst others — will allow the study of motion within a few times the event horizon size of the Galactic Center black hole.
Miller (1977) hypothesizes that dispersion of investor opinion in the presence of short-sale constraints leads to stock price overvaluation. However, previous empirical tests of Miller's hypothesis examine the valuation effects of only one of these two necessary conditions. We examine the valuation effects of the interaction between differences of opinion and shortsale constraints. We find robust evidence of significant overvaluation for stocks that are subject to both conditions simultaneously. Stocks are not systematically overvalued when either one of these two conditions is not met.
Co/Pt thin film multilayers with strong perpendicular anisotropy and out-of-plane coercivities of 5-11 kOe were magnetically altered in areas of local ion beam interaction. The ion irradiations were performed by ion projection through silicon stencil masks fabricated by silicon on insulator (SOI) membrane technology. The ion projector at the Fraunhofer Institute for Silicon Technology (ISiT) was operated at 73 keV ion energy and with a 8.7- fold demagnification. After exposure to 3 × 1014Ar+/ cm2 magnetic islands smaller than 100 nm in diameter were resolved in the Co/Pt multilayersby means of magnetic force microscopy. The impact of different ion species (He+, Ar+ and Xe+) and ion energies (10 – 200 keV) on the multilayer structure was evaluated using Monte Carlo simulations. The ballistic interface intermixing was used to predict magnetic coercivity changes for various irradiation conditions. The simulations revealed that with 73 keV Ar+ and Xe+ ions the irradiation dose could be reduced by a factor of 100 and 400 respectively in comparison to 73 keV He+which was verified in the experiments. X-ray reflectivity measurements confirmed that the Co/Pt superlattice structure is slightly weakened during the irradiation and that the surface smoothness of the media is preserved. Using the Ion Projection Process Development Tool (PDT) at IMS-Vienna concentric data tracks including head positioning servo informations were patterned onto a 1” IBM microdrive™ glass disk which was coated with Co/Pt multilayers. In a single exposure step several tracks within an exposure field of 17 mm in diameter were structured by 2 × 1015He+/ cm2 at 45 keV using a 4- fold demagnification set-up.
In this study, nanoindentation and nanoscratch testing were used to determine the effects of annealing and long term aging on the properties and fracture resistance of thin tantalum nitride resistor films on aluminum nitride substrates. These films were sputter-deposited to a thickness of 440 nm. Some films were left in the as-deposited condition while others were annealed or annealed and then aged. X-ray diffraction revealed that sputter deposition created high compressive residual stresses in the as-deposited films which were partially relieved by annealing. Subsequent aging of the annealed films had no effect on residual stress levels. Nanoindentation showed that mechanical properties were unchanged after annealing and after annealing and aging. However, nanoscratch testing showed that annealing markedly reduced the susceptibility to catastrophic failure with no further changes discernible after aging.
We are studying the boron nitride system by using a pulsed excimer laser to ablate from hexagonal BN (hBN) targets to form cubic BN (cBN) films. We are depositing BN films on heated (25 - 800°C) Si (100) surfaces and are using a broad-beam ion source operated with Ar and N2 source gasses to produce BN films with a high percentage of sp3-bonded cBN. In order to understand and optimize the growth and nucleation of cBN films, parametric studies of the growth parameters have been performed. The best films to date show >85% sp3-bonded BN as determined from Fourier-transform infrared (FTIR) reflection spectroscopy. High resolution transmission electron microscopy (TEM) and selected area electron diffraction confirm the presence of cBN in these samples. The films are polycrystalline and show grain sizes up to 30- 40 nm. We find from both the FTIR and TEM analyses that the cBN content in these films evolves with growth time. Initially, the films are deposited as hBN and the cBN nucleates on this hBN underlayer. Importantly, the position of the cBN IR phonon also changes with growth time. Initially this mode appears near 1130 cm-1 and the position decreases with growth time to a constant value of 1085 cm-1. Since in bulk cBN this IR mode appears at 1065 cm-1, a large compressive stress induced by the ion bombardment is suggested. In addition, we report on the variation in cBN percentage with temperature.
We are studying the boron nitride system by using a pulsed excimer laser to ablate from hexagonal BN (hBN) targets to form cubic BN (cBN) films. We are depositing BN films on heated (600°C) silicon (100) surfaces in a flowing (0- 10 sccm) ambient background gas of either NH3 or N2 of varying partial pressure (0–100 m Torr). Infrared (IR) reflection spectroscopy indicates the films have short-range hexagonal order. Some films grown at low laser energy densities have shown the cubic phase in IR transmission. Auger electron spectroscopy (AES) indicates the films are nitrogen deficient, which is linked to changes in the target stoichiometry with increasing laser fluence. Raman spectroscopy on the films shows only a strong background luminescence suggesting a high concentration of defects associated with the nitrogen vacancies. Atomic force microscopy (AFM) of the films shows a surface morphology that roughens as the growth rate increases. In order to improve the film stoichiometry it was necessary to actively enhance the nitrogen content of the films. It was found that bombarding films during growth with ions from an ion gun filled with NH3 gas increased the N/B ratio but did not enhance the cubic phase. RF biasing the substrate gave films which showed both cubic and hexagonal features in IR reflection. High resolution transmission electron microscopy (TEM) confirms the presence of cBN grains of ∼ 200Å size in films grown with an RF bias.
The use of high-intensity, 8Kw, x-ray sources (Rigaku rotating-anode generator and wide - angle goniometer for this study) provides both opportunities and challenges. With high - intensity x-ray sources, detection limits can be lowered significantly while still offering count times of practical duration. On the other hand, the availability of high intensity x-ray sources puts greater demands on information extraction procedures and on the mechanical preciseness of sample containment and support. In particular we addressed the use of a cylindrical aluminum sample cell with a 0.010’’ polycrystalline (cold rolled) beryllium window electron –beam welded to an aluminum frame. See Figure 1. This cell permitted analysis of various air-sensitive specimens. The sample was pressed against the back of the beryllium window by a spring-loaded backing plate.
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