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Self-reported activity restriction is an established correlate of depression in dementia caregivers (dCGs). It is plausible that the daily distribution of objectively measured activity is also altered in dCGs with depression symptoms; if so, such activity characteristics could provide a passively measurable marker of depression or specific times to target preventive interventions. We therefore investigated how levels of activity throughout the day differed in dCGs with and without depression symptoms, then tested whether any such differences predicted changes in symptoms 6 months later.
Design, setting, participants, and measurements:
We examined 56 dCGs (mean age = 71, standard deviation (SD) = 6.7; 68% female) and used clustering to identify subgroups which had distinct depression symptom levels, leveraging baseline Center for Epidemiologic Studies of Depression Scale–Revised Edition and Patient Health Questionnaire-9 (PHQ-9) measures, as well as a PHQ-9 score from 6 months later. Using wrist activity (mean recording length = 12.9 days, minimum = 6 days), we calculated average hourly activity levels and then assessed when activity levels relate to depression symptoms and changes in symptoms 6 months later.
Clustering identified subgroups characterized by: (1) no/minimal symptoms (36%) and (2) depression symptoms (64%). After multiple comparison correction, the group of dCGs with depression symptoms was less active from 8 to 10 AM (Cohen’s d ≤ −0.9). These morning activity levels predicted the degree of symptom change on the PHQ-9 6 months later (per SD unit β = −0.8, 95% confidence interval: −1.6, −0.1, p = 0.03) independent of self-reported activity restriction and other key factors.
These novel findings suggest that morning activity may protect dCGs from depression symptoms. Future studies should test whether helping dCGs get active in the morning influences the other features of depression in this population (i.e. insomnia, intrusive thoughts, and perceived activity restriction).
On August 25, 2017, Hurricane Harvey made landfall near Corpus Christi, Texas. The ensuing unprecedented flooding throughout the Texas coastal region affected millions of individuals.1 The statewide response in Texas included the sheltering of thousands of individuals at considerable distances from their homes. The Dallas area established large-scale general population sheltering as the number of evacuees to the area began to amass. Historically, the Dallas area is one familiar with “mega-sheltering,” beginning with the response to Hurricane Katrina in 2005.2 Through continued efforts and development, the Dallas area had been readying a plan for the largest general population shelter in Texas. (Disaster Med Public Health Preparedness. 2019;13:33–37)
Adélie penguins (Pygoscelis adeliae) are responding to ocean–climate variability throughout the marine ecosystem of the western Antarctic Peninsula (WAP) where some breeding colonies have declined by 80%. Nuclear and mitochondrial DNA (mtDNA) markers were used to understand historical population genetic structure and gene flow given relatively recent and continuing reductions in sea ice habitats and changes in numbers of breeding adults at colonies throughout the WAP. Genetic diversity, spatial genetic structure, genetic signatures of fluctuations in population demography and gene flow were assessed in four regional Adélie penguin colonies. The analyses indicated little genetic structure overall based on bi-parentally inherited microsatellite markers (FST =-0.006–0.004). No significant variance was observed in overall haplotype frequency (mtDNA ΦST =0.017; P=0.112). Some comparisons with Charcot Island were significant, suggestive of female-biased philopatry. Estimates of gene flow based on a two-population coalescent model were asymmetrical from the species’ regional core to its northern range. Breeding Adélie penguins of the WAP are a panmictic population and hold adequate genetic diversity and dispersal capacity to be resilient to environmental change.
Novel free boundary magnetohydrodynamic equilibrium states with spontaneous three-dimensional (3-D) deformations of the plasma–vacuum interface are computed. The structures obtained look like saturated ideal external kink/peeling modes. Large edge pressure gradients yield toroidal mode number
distortions when the edge bootstrap current is large and higher
corrugations when this current is small. Linear ideal MHD stability analyses confirm the nonlinear saturated ideal kink equilibrium states produced and we can identify the Pfirsch–Schlüter current as the main linear instability driving mechanism when the edge pressure gradient is large. The dominant non-axisymmetric component of this Pfirsch–Schlüter current drives a near resonant helical parallel current density ribbon that aligns with the near vanishing magnetic shear region caused by the edge bootstrap current. This current ribbon is a manifestation of the outer mode previously found on JET (Solano 2010). We claim that the equilibrium corrugations describe structures that are commonly observed in quiescent H-mode tokamak discharges.
Estimates of the excess length of stay (LOS) attributable to healthcare-associated infections (HAIs) in which total LOS of patients with and without HAIs are biased because of failure to account for the timing of infection. Alternate methods that appropriately treat HAI as a time-varying exposure are multistate models and cohort studies, which match regarding the time of infection. We examined the magnitude of this time-dependent bias in published studies that compared different methodological approaches.
We conducted a systematic review of the published literature to identify studies that report attributable LOS estimates using both total LOS (time-fixed) methods and either multistate models or matching patients with and without HAIs using the timing of infection.
Of the 7 studies that compared time-fixed methods to multistate models, conventional methods resulted in estimates of the LOS to HAIs that were, on average, 9.4 days longer or 238% greater than those generated using multistate models. Of the 5 studies that compared time-fixed methods to matching on timing of infection, conventional methods resulted in estimates of the LOS to HAIs that were, on average, 12.6 days longer or 139% greater than those generated by matching on timing of infection.
Our results suggest that estimates of the attributable LOS due to HAIs depend heavily on the methods used to generate those estimates. Overestimation of this effect can lead to incorrect assumptions of the likely cost savings from HAI prevention measures.
Infect. Control Hosp. Epidemiol. 2015;36(9):1089–1094
We detail the rich molecular story of NGC 1266, its serendipitous discovery within the ATLAS3D survey (Cappellari et al. 2011) and how it plays host to an AGN-driven molecular outflow, potentially quenching all of its star formation (SF) within the next 100 Myr. While major mergers appear to play a role in instigating outflows in other systems, deep imaging of NGC 1266 as well as stellar kinematic observations from SAURON, have failed to provide evidence that NGC 1266 has recently been involved in a major interaction. The molecular gas and the instantaneous SF tracers indicate that the current sites of star formation are located in a hypercompact disk within 200 pc of the nucleus (Fig. 1; SF rate ≈ 2 M⊙ yr−1). On the other hand, tracers of recent star formation, such as the Hβ absorption map from SAURON and stellar population analysis show that the young stars are distributed throughout a larger area of the galaxy than current star formation. As the AGN at the center of NGC 1266 continues to drive cold gas out of the galaxy, we expect star formation rates to decline as the star formation is ultimately quenched. Thus, NGC 1266 is in the midst of a key portion of its evolution and continued studies of this unique galaxy may help improve our understanding of how galaxies transition from the blue to the red sequence (Alatalo et al. 2011).
NGC 1266 is a nearby field galaxy observed as part of the ATLAS3D survey (Cappellari et al. 2011). NGC 1266 has been shown to host a compact (< 200 pc) molecular disk and a mass-loaded molecular outflow driven by the AGN (Alatalo et al. 2011). Very Long Basline Array (VLBA) observations at 1.65 GHz revealed a compact (diameter < 1.2 pc), high brightness temperature continuum source most consistent with a low-level AGN origin. The VLBA continuum source is positioned at the center of the molecular disk and may be responsible for the expulsion of molecular gas in NGC 1266. Thus, the candidate AGN-driven molecular outflow in NGC 1266 supports the picture in which AGNs do play a significant role in the quenching of star formation and ultimately the evolution of the red sequence of galaxies.
Hierarchically porous materials are of interest in a wide range of applications. If the materials are electronic, or ionic conductors, such materials are of interest as electrodes for use in fuel cells. Using hierarchically porous silica as templates, we have demonstrated the formation of hierarchically porous metal and metal oxide structures. Through the control of the synthesis conditions, we have produced partial replicas ca. 1 cubic centimeter in volume, in which two macroporous networks are separated by a nanoporous membrane. The macroporous network in the silica template is known to be bicontinuous. Our underlying model predicts that the second, induced, macroporous network should be similarly bicontinuous.
Micrometer resolution X-ray tomography of the whole sample confirms that the synthesis produces one bicontinuous macroporous network, and is consistent with the existence of a second set of macropores. Preliminary experiments were carried out using FIB/SEM serial tomography to image the second macropore network, however, the length scale of the structures is such that this approach it is unable to firmly establish that the second macropore network is bicontinuous throughout the entire sample volume.
We report the results of epitaxial growth experiments on AlxGa1−xN (0≤ x ≤ 1) on Si(111) and sapphire substrates aimed at understanding the origin and elimination of cracking. We describe growth procedures resulting in thick layers of AlxGa1−xN, grown by gas source molecular beam epitaxy with ammonia, that are free of cracks. In GaN layers with the thickness of ∼2.5 µm, we find the background electron concentration of (1-2)×1016 cm−3 and mobility of (800±100) cm2/Vs. In AlxGa1−xN (0.2 < x < 0.6) with the film thickness of 0.5-0.7 µm the electron concentration of (2-3)×1016 cm−3 is obtained. Low background concentrations in GaN allow for formation of p-n junctions by doping with Mg. Light emitting diodes with the peak emission at 380 nm have been demonstrated.
Thermal conductivity, electrical resistivity, Seebeck coefficient and thermal expansion data were obtained on well-annealed Ni3Al containing 24 and 25 at. % Al. The results span the temperature range 300 to 1000 K. The expansion coefficients did not vary with composition and increased with temperature, reaching values of aIout 17 × 10−6 K−1 at 1000 K. The thermal conductivity and electrical resistivity changed rapidly with composition, and the thermal conductivity of 24 at. % Al is as much as 30% lower than that for stoichiometric Ni3A1. The electronic Lorenz function of Ni3Al was obtained by subtracting the estimated phonon conductivity component and found to be within about 5% of the Sommerfeld prediction from 300 to 1000 K. The electrical resistivity results for stoichiometric Ni 3Al are influenced by the loss of ferromagnetic order at lower temperatures and are not adequately described by the Bloch-Grüneisen equation.
High-temperature, light-weight materials represent enabling technology in the continued evolution of high-performance aerospace vehicles and propulsion systems being pursued by the U.S. Air Force. In this regard, titanium aluminide matrix composites appear to offer unique advantages in terms of a variety of weightspecific properties at high temperatures. However, a key requirement for eventual structural use of these materials is a balance of mechanical properties that can be suitably exploited by aircraft and engine designers without compromising reliability. An overview of the current capability of titanium aluminide composites is presented, with an effort to assess the balance of properties offered by this class of materials. Emphasis is given to life-limiting cyclic and monotonic properties and the roles of high-temperature, time-dependent deformation and environmental effects. An attempt is made to assess the limitations of currently available titanium aluminide composites with respect to application needs and to suggest avenues for improvements in key properties.
Unidirectionally-reinforced Timetal® 21S composite specimens were subjected to elevated temperature heat treatments. The SiC fibers were then chemically extracted from the matrix, and their tensile strengths were measured at room temperature. A Weibull statistical analysis of fiber strength distribution was performed to compare the Weibull parameters of fibers from the as-consolidated and heat-treated composites. Fractographic analysis of the tested fibers was used to identify the flaws which caused failure in each condition. Surface flaws were found to initiate low strength failures in all conditions, and the number of surface initiated failures increased with an increase in severity of heat-treatment. A relationship between the fiber/matrix chemical reaction and surface flaw development is demonstrated. A fracture mechanics analysis that explains the relationship between surface flaw size, fiber fracture toughness, and the measured tensile strengths is suggested.
Polycrystalline, stoichiometric β- silicon carbide fiber tow suitable for ceramic or metallic matrix composite use has been prepared using a polymer precursor route to obtain textile grade, weavable fibers. Individual filaments have a diameter of 10 μm, an average tensile strength of up to 3.4 GPa (500 ksi), an elastic modulus up to 430 GPa (62 msi) and a density > 3.1 g/cm3. Crystallites average about 60 nm by x-ray line broadening. The SiC fiber shows improved mechanical and thermal stability properties, especially in an inert atmosphere, as compared to commercial polymer-derived SiC ceramic fibers. Thermochemical and mechanical properties, as well as fractography and microstructure will be presented.
Fractographic analysis of SCS-6/Ti-24Al-11 Nb(a/o) (Ti-24-11 hereafter) and SCS-6/Ti-1 5V- 3Cr-3Al-3Sn(w/o) (Ti-15-3 hereafter) composites subjected to fatigue crack growth conditions indicates that the interface is prone to wear damage as a result of fiber/matrix sliding. In this study, the effect of fatigue loading on the integrity of the Interface was studied by using fiber pushout testing to compare the interfacial shear strength of composite specimens in the asreceived condition with specimens that were previously subjected to fatigue loading. Fatigue loading was also simulated by pushing fibers back and forth (multiple reverse pushouts). It was concluded that interfacial sliding during fatigue loading results in interfacial damage and degradation of the interfacial shear strength. Tensile testing of extracted fibers exposed to fatigue-induced interfacial damage was also performed to determine the effect of interface damage on the fiber strength. Interfacial damage also resulted in decreased fiber strength of the SCS-6 fiber. Fracture and wear of the outer carbon coatings on the SCS-6 fiber is the main contributing factor in the deterioration of these interfaces.
Processing routes for fabrication of continuous fiber, intermetallic-matrix composites are reviewed. These methods include conventional and isostatic hot pressing of layups of matrix material (e.g. foil or powder cloth) and fiber mats; consolidation of monotapes made by techniques such as arc, plasma, vapor, or electron beam deposition or tape casting; and liquid metal infiltration-base methods. The advantages and disadvantages of the various methods are discussed. Particular attention is focussed on HIP consolidation via foil-fiber-foil techniques. Process modeling techniques to assess the effects of pressure, temperature, and time on consolidation behavior are described. By this means, maps to delineate the interaction of process variables in such methods can be developed and applied for process optimization.
Model high-melting point Nb3Al + Nb intermetallic composites have been fabricated in situ by vacuum hot pressing and reaction sintering elemental powders mixed in the ratio Nb + 7wt. % Al. In both cases, microstructures feature islands of ductile Nb solid solution (∼20 vol. %) in a brittle Nb3Al intermetallic matrix. Thermal treatment for 24 h at 1800°C results in a lamellar microstructure containing a uniform and fine distribution of filamentary Nb in a Nb3Al matrix following the massive peritectic transformation. In this paper, the fatigue and fracture resistance of these two microstructures are examined and compared to pure Nb3Al and Nb. Preliminary results suggest that the Nb phase can provide significant toughening to Nb3Al via crack bridging, plastic stretching and interfacial debonding mechanisms. Measured plane-strain fracture toughness values for the as hot-pressed and fully-aged microstructures are ∼6–8 Mpa√m compared to √fm for pure Nb3Al. However, under cyclic loading, the composites tend to show a strong dependence on applied stress-intensity level; fatigue thresholds range between 2–3 Mpa√m.
Strength degradation of single crystal Al2O3 fibers due to the effect of fiber/matrix interaction and processing of NiAl and superalloy matrix composites, was investigated. Strength loss was quantified by tensile testing fibers that were exposed to the matrix alloy using two different methods. In one method, the fibers were incorporated into a composite by either the Powder Cloth (P-C) or binderless powder technique. The fibers were then extracted from the composite by chemical dissolution of the matrix and subsequently tensile tested and examined by scanning electron microscopy. In the other method, fibers were sputter-coated with a similar matrix composition and heat-treated to simulate conditions similar to those experienced during composite powder fabrication methods. In the sputter coating method, the contribution of fiber-matrix reaction on fiber strength loss was isolated from the effects of the various mechanical loads which are present during powder fabrication. For all matrices studied, significant strength loss was observed both in fibers extracted from composites and in fibers sputter-coated and annealed. Although surface ridges and pores were observed on the degraded fibers, it remains uncertain whether these features were responsible for the strength loss.
A new sol/gel fiber which exhibits exceptional high temperature properties was recently developed at 3M. This fiber has the composition 85% Al2O3-15% SiO2 (85A-15S). High temperature tensile strength and creep properties were measured in the temperature range 1000°C – 1300°C. The creep rate for the 85A-15S fibers was three orders of magnitude less than single phase polycrystalline alumina fibers such as Nextel 610, and 90% of room tensile strength was retained at 1250°C. These exceptional high temperature properties were attributed to a unique, two-phase microstructure consisting of globular and elongated grains of a-Al2O3 and mullite (3Al2O3-2SiO2). The room temperature single filament strength of the 85% Al2O3-15% SiO2 fibers was 2130 MPa, and the elastic modulus was 260 GPa.