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Gravitational waves from coalescing neutron stars encode information about nuclear matter at extreme densities, inaccessible by laboratory experiments. The late inspiral is influenced by the presence of tides, which depend on the neutron star equation of state. Neutron star mergers are expected to often produce rapidly rotating remnant neutron stars that emit gravitational waves. These will provide clues to the extremely hot post-merger environment. This signature of nuclear matter in gravitational waves contains most information in the 2–4 kHz frequency band, which is outside of the most sensitive band of current detectors. We present the design concept and science case for a Neutron Star Extreme Matter Observatory (NEMO): a gravitational-wave interferometer optimised to study nuclear physics with merging neutron stars. The concept uses high-circulating laser power, quantum squeezing, and a detector topology specifically designed to achieve the high-frequency sensitivity necessary to probe nuclear matter using gravitational waves. Above 1 kHz, the proposed strain sensitivity is comparable to full third-generation detectors at a fraction of the cost. Such sensitivity changes expected event rates for detection of post-merger remnants from approximately one per few decades with two A+ detectors to a few per year and potentially allow for the first gravitational-wave observations of supernovae, isolated neutron stars, and other exotica.
Introduction: Smokers with depressive and alcohol use disorders report more severe tobacco abstinence effects (e.g., tobacco withdrawal and craving, mood and sleep disturbance), but less is known about abstinence effects among smokers with subclinical features of these disorders.
Aims: The time-course and severity of acute abstinence effects were evaluated in smokers with and without subclinical depressive symptoms (DEP) and with and without subclinical alcohol consumption (ALC). Methods: Participants (N = 106) received smoking cessation counselling and were contingently compensated for biochemically-verified smoking abstinence. Abstinence effects were assessed pre-quit and daily for eight days post-quit.
Results/Findings: Seventy-four participants (70%) achieved eight-day continuous smoking abstinence. Generalised estimating equations revealed that time and DEP group significantly interacted to predict change in Wisconsin Smoking Withdrawal Scale (WSWS) Anxiety (Wald = 21.18, p < .01) and Questionnaire of Smoking Urges Relief from Negative Affect (Wald = 20.12, p < .01) subscale scores. Time and ALC group significantly interacted to predict change in Profile of Mood States (POMS) Fatigue subscale score (Wald = 19.78, p < .01). Compared to non-DEP smokers, DEP smokers reported higher mean post-quit scores on several measures of abstinence effects, including WSWS Sadness and POMS Total; however, pre-quit differences between DEP groups may have confounded post-quit differences.
Conclusions: Smokers with subclinical depressive symptoms endorsed high levels of abstinence effects, but it was unclear if these were related to the absence of tobacco. Smokers with subclinical alcohol consumption did not endorse high levels of abstinence effects but abstinence-related fatigue took longer to improve.
Although chemical vapor deposited mullite (3Al2O3•2SiO2) environmental barrier coatings have shown promise in protecting Si-based substrates for gas-turbine applications, there is concern that the silica content within the mullite coating itself might be susceptible to hot-corrosion and recession during long term exposure to corrosive atmospheres. There is thus a strong motivation to substantially reduce or even virtually eliminate the silica from the surface of the mullite coatings that are in direct contact with atmospheres containing corrosive oxides and steam. Functionally graded mullite (3Al2O3•2SiO2) coatings have been grown for Si-based substrates and the composition has been tailored in these coatings, with the Al/Si ratio being stoichiometric (∼ 3) at the coating/substrate interface for coefficient of thermal expansion (CTE) match, and increasing monotonically towards the outer coating surface. These functionally graded coatings have some of the highest Al-rich mullite reported to date at the coating surface. At these extremely high Al/Si ratios, mullite structure breaks down and the formation of a nano-sized high-alumina rich phase occurs. High-resolution transmission electron microscopy has been used to characterize the structure and composition of high alumina mullite and will be discussed.
Functionally graded mullite (3Al2O3.2SiO2) coatings were deposited on SiC substrates by Chemical Vapor Deposition (CVD) using the AlCl3-SiCl4-CO2-H2 system. It was found that due to preferential adsorption, coatings on SiC started off being Si-rich, while coatings on alumina substrates started out being Al-rich. In either case, if the coating composition was not close to stoichiometric mullite, the microstructure consisted ofg-Al2O3 nanocrystallites imbedded in a vitreous SiO2-rich matrix (nanocrystalline microstructure). On grading the composition, mullite grains nucleated when the composition of the growing nanocrystalline coatings reached a narrow surface composition range of Al/Si molar ratio of 2.9-3.4. Once nucleated, columnar mullite grains could be graded to highly nonstoichiometric Al-rich compositions. However, if the nucleated mullite grains were graded to be Si-rich, the mullite structure could not be sustained, and the coating reverted back to the nanocrystalline microstructure. This phenomenon is explained on the basis of the linkage of coordination polyhedra in the atomic structure of mullite.
Dense, uniform, and adherent chemically vapor-deposited mullite coatings were deposited on SiC substrates using the AlCl3–SiCl4–H2–CO2 system. Typical coating morphology consisted of a thin interfacial layer of γ–Al2O3 nanocrystallites embedded within a vitreous SiO2-based matrix. When a critical Al/Si ratio of 3.2 ± 0.29 was reached within this nanocrystalline layer, mullite crystals nucleated and grew as columnar grains. The thickness of the nanocrystalline layer decreased as the input AlCl3/SiCl4 ratio was increased. In all cases, the Al/Si composition in the coating increased from the coating/substrate interface to the coating surface. Critical factors leading to the nucleation and growth of mullite crystals are discussed in this article.
Mullite (3Al2O3.2SiO2) is an ideal candidate for coatings on SiC due to its toughness, corrosion resistance and coefficient of thermal expansion (CTE) match. We have deposited alternating layers of Al2O3 and SiO2 followed by post deposition heat treatment to induce mullite formation at the interface. We found that the devitrification of silica to cristobalite led to spallation of the multilayered coatings due to the fracture within the crystalline silica layers. To understand this transformation better, we studied the effect of pressure and temperature on devitrification of silica in both bulk and in coating form. We have demonstrated that the difference in specific volumes of the two phases plays a key role in the vitreous to crystalline transformation in silica.
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