Composition of the Earth's inner core from high-pressure sound velocity measurements in Fe-Ni-Si alloys

Editor: R.D. van der Hilst Keywords: Fe-Ni-Si alloy aggregate compressional and shear sound velocities high pressure inner core light elements We performed room-temperature sound velocity and density measurements on a polycrystalline alloy, Fe 0.89 Ni 0.04 Si 0.07 , in the hexagonal close-packed (hcp) phase up to 108 GPa. Over the investigated pressure range the aggregate compressional sound velocity is ∼ 9% higher than in pure iron at the same density. The measured aggregate compressional (V P ) and shear (V S ) sound velocities, extrapolated to core densities and corrected for anharmonic temperature effects, are compared with seismic profiles. Our results provide constraints on the silicon abundance in the core, suggesting a model that simultaneously matches the primary seismic observables, density, P-wave and S-wave velocities, for an inner core containing 4 to 5 wt.% of Ni and 1 to 2 wt.% of Si

Redesigning axial-axial (biaxial) cruciform specimens for very high cycle fatigue ultrasonic testing machines

The necessity to increase performances in terms of lifetime and security in mechanical components or structures is the motivation for intense research in fatigue. Applications range from aeronautics to medical devices. With the development of new materials, there is no longer a fatigue limit in the classical sense, where it was accepted that the fatigue limit is the stress level such that there is no fracture up to 1E7 cycles. The recent development of ultrasonic testing machines where frequencies can go as high as 20 kHz or over enabled tests to be extended to ranges larger than 1E9 in just a few days. This area of studies is now known as Very High Cycle Fatigue (VHCF). On the other hand, most of the existing test equipment in the market for both classical and VHCF are uniaxial test machines. However, critical components used in Engineering applications are usually subjected to complex multi-axial loading conditions. In this paper, it is presented the methodology to redesigning existing cruciform test specimens that can be used to create an in-plane biaxial state of stress when used in ‘uniaxial’ VHCF ultrasonic testing machines (in this case, the term ‘uniaxial’ is used not because of the state of stress created at the centre of the specimen, but because of the direction at which the load is applied). The methodology is explained in such a way that it can be expanded to other existing designs, namely cruciform designs, that are not yet used in VHCF. Also, although the approach is presented in simple and logical terms, it may not be that obvious for those who have a more focused approach on fatigue rather than on modal analysis. It is expected that by contributing to bridging the gap between the sciences of modal analysis and fatigue, this research will help and encourage others exploiting new capabilities in VHCF

Association of sarcopenia with incident osteoporosis: a prospective study of 168,682 UK biobank participants

Background: Sarcopenia often co-occurs with osteoporosis in cross-sectional studies. However, this association has rarely been studied in prospective studies. This study aimed to investigate the association between sarcopenia categories—along with its individual components—and incident osteoporosis in both middle-aged and older men and women from the UK Biobank study. Methods: A total of 168,682 participants (48.8% women, aged 37 to 70 years at baseline) were included in this prospective study. Categories of sarcopenia (pre-sarcopenia and sarcopenia), and its individual components, were defined according to the EWGSOP2 criteria (2019). Associations with incident osteoporosis by sex were investigated using Cox-proportional hazard models adjusted for socio-demographic, lifestyle and health-related factors, and morbidity count. Associations between categories of sarcopenia and incident osteoporosis were also investigated by age-groups and subtype of osteoporosis (with and without pathological fractures). Results: After a median follow-up of 7.4 years, 6296 participants were diagnosed with osteoporosis. When the analyses were adjusted for a range of relevant confounding factors, pre-sarcopenia was associated with 1.3-times higher risk of osteoporosis in men (HR: 1.30 [95% CI: 1.03 to 1.63]) but not in women, and sarcopenia was associated with 1.66-times increased osteoporosis risk in women (HR: 1.66 [95% CI: 1.33 to 2.08]) but not in men compared with people without sarcopenia or pre-sarcopenia. A similar magnitude of associations was found in osteoporosis without pathological fractures but weaker for those with pathological fractures. Within the individual components, low muscle mass (HRwomen: 1.36 [95% CI: 1.22 to 1.51] and HRmen: 3.07 [95% CI: 1.68 to 5.59]), followed by slow gait speed (HRwomen: 1.30 [95% CI: 1.17 to 1.45] and HRmen: 1.70 [95% CI: 1.43 to 2.02]), were associated with a higher risk of incident osteoporosis in both sexes. Low grip strength was associated with a higher risk of incident osteoporosis in men (HR: 1.38 [95% CI: 1.15 to 1.65]), but not in women. No significant interaction between the exposures and incident osteoporosis by age groups were identified. Conclusions: Our findings demonstrated that pre-sarcopenic men and sarcopenic women had a higher risk of developing osteoporosis even after adjustment for a large range of potential confounders. Considering that sarcopenia could be prevented, health interventions to improve physical capability may delay or prevent the onset of osteoporosis

The use of fenestrated and branched endovascular aneurysm repair for juxtarenal and thoracoabdominal aneurysms: a systematic review and cost-effectiveness analysis.

BACKGROUND: Patients with large abdominal aortic aneurysms (AAAs) are usually offered reparative treatment given the high mortality risk. There is uncertainty about how to treat juxtarenal AAAs (JRAAAs) or thoracoabdominal aortic aneurysms (TAAAs). Endovascular repair of an abdominal aortic aneurysm (EVAR) is often seen as safer and easier than open surgical repair (OSR). However, endovascular treatment of JRAAAs or TAAAs requires specially manufactured stent grafts, with openings to allow blood to reach branches of the aorta. Commissioners are receiving increasing requests for fenestrated EVAR (fEVAR) and branched EVAR (bEVAR), but it is unclear whether or not the extra cost of fEVAR or bEVAR is justified by advantages for patients. OBJECTIVE(S): To assess the clinical effectiveness, safety and cost-effectiveness of fEVAR and bEVAR in comparison with conventional treatment (i.e. no surgery) or OSR for two populations: JRAAAs and TAAAs. DATA SOURCES: Resources were searched from inception to October 2013, including MEDLINE (OvidSP), EMBASE (OvidSP) and the Cochrane Central Register of Controlled Trials (Wiley) and, additionally, for cost-effectiveness, NHS Economic Evaluation Database (NHS EED; Wiley) and EconLit (EBSCOhost). Conference abstracts were also searched. REVIEW METHODS: Studies were included based on an intervention of either fEVAR or bEVAR and a comparator of either OSR or no surgery. For clinical effectiveness, observational studies were excluded only if they were not comparative, i.e. explicitly selected on the basis of prognosis. RESULTS: For clinical effectiveness, searches retrieved 5253 records before deduplication. Owing to overlap between the databases, 1985 duplicate records were removed. Of the remaining 3268 records, based on titles and abstracts, 3244 records were excluded, leaving 24 publications to be ordered. All 24 studies were excluded as none of them satisfied the inclusion criteria. Sixteen studies were excluded on study design, six on intervention and two on comparator. Five out of 16 studies excluded on study design reported a comparison. However, all of the studies acknowledged that they had groups that were not comparable at baseline given that they had selectively assigned younger, fitter patients to OSR. Therefore, these studies were considered 'non-comparative'. For cost-effectiveness, searches identified 104 references before deduplication. Owing to overlap between the databases, 34 duplicate records were removed. Of the remaining 70 records, seven were included for the full assessment based on initial screening. After a full-text review, no studies were included. Because of the lack of clinical effectiveness evidence and difficulty in estimating costs given the rapidly changing and variable technology, a cost-effectiveness analysis (CEA) was not performed. Instead a detailed description of modelling methods was provided. CONCLUSIONS: Despite a thorough search, no studies could be found that met the inclusion criteria. All studies that compared either fEVAR or bEVAR with either OSR or no surgery explicitly selected patients based on prognosis, i.e. essentially the populations for each comparator were not the same. Despite not being able to conduct a CEA, we have provided detailed methods for the conduct if data becomes available. FUTURE WORK: We recommend at least one clinical trial to provide an unbiased estimate of effect for fEVAR/bEVAR compared with OSR or no surgery. This trial should also collect data for a CEA. STUDY REGISTRATION: This study is registered as PROSPERO CRD42013006051. FUNDING: The National Institute for Health Research Health Technology Assessment programme

The source of hydrogen sulfide in anoxic sediment

Putrefactive hydrogen sulfide production in the upper 4 cm of sediment in two small freshwater and eutrophic Southeast Michigan, U.S.A., lakes ranged from 0.13 to 1.51 with an average of 0.46 mg S l-1 day-1. Sulfate reductive production of hydrogen sulfide at the same sites ranged from 0.7 to 3.2 with an average of 1.54 mg S l-1 day-1. Putrefactive hydrogen sulfide production represented 5.1-53% (average of 18.3-27.6%) of the total hydrogen sulfide produced at the two lakes over an April-October study period. 35S labeled substrates were used to estimate hydrogen sulfide production rates.Proteolytic bacteria averaged 2.2 x 104 cells ml-1 sediment whereas sulfate reducers averaged 4.8 x 102 cells ml-1 sediment. Putrefactive hydrogen sulfide production correlated highly with numbers of proteolytic bacteria (r2 = 0.84) but the correlation between sulfate reduction and sulfate reducing bacteria was low (r2 = 0.13).Interstitial soluble inorganic sulfate, protein and organic carbon were not closely correlated with hydrogen sulfide production rates or bacteria enumeration results. Natural substrate concentrations (Sn) used to estimate hydrogen sulfide production were supported by kinetic bioassay results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25926/1/0000489.pd

Discovery of Highly Blueshifted Broad Balmer and Metastable Helium Absorption Lines in a Tidal Disruption Event

We report the discovery of nonstellar hydrogen Balmer and metastable helium absorption lines accompanying a transient, high-velocity (0.05c) broad absorption line (BAL) system in the optical spectra of the tidal disruption event (TDE) AT2018zr (z = 0.071). In the Hubble Space Telescope UV spectra, absorption of high- and low-ionization lines is also present at this velocity, making AT2018zr resemble a low-ionization BALQSO. We conclude that these transient absorption features are more likely to arise in fast outflows produced by the TDE than absorbed by the unbound debris. In accordance with the outflow picture, we are able to reproduce the flat-topped Hα emission in a spherically expanding medium without invoking the typical prescription of an elliptical disk. We also report the appearance of narrow (~1000 kms^(−1)) N III λ4640, He II λ4686, Hα, and Hβ emission in the late-time optical spectra of AT2018zr, which may be a result of UV continuum hardening at late times, as observed by Swift. Including AT2018zr, we find a high association rate (three out of four) of BALs in the UV spectra of TDEs. This suggests that outflows may be ubiquitous among TDEs and less sensitive to viewing angle effects compared to QSO outflows

Dealing with Time in Health Economic Evaluation: Methodological Issues and Recommendations for Practice

Time is an important aspect of health economic evaluation, as the timing and duration of clinical events, healthcare interventions and their consequences all affect estimated costs and effects. These issues should be reflected in the design of health economic models. This article considers three important aspects of time in modelling: (1) which cohorts to simulate and how far into the future to extend the analysis; (2) the simulation of time, including the difference between discrete-time and continuous-time models, cycle lengths, and converting rates and probabilities; and (3) discounting future costs and effects to their present values. We provide a methodological overview of these issues and make recommendations to help inform both the conduct of cost-effectiveness analyses and the interpretation of their results. For choosing which cohorts to simulate and how many, we suggest analysts carefully assess potential reasons for variation in cost effectiveness between cohorts and the feasibility of subgroup-specific recommendations. For the simulation of time, we recommend using short cycles or continuous-time models to avoid biases and the need for half-cycle corrections, and provide advice on the correct conversion of transition probabilities in state transition models. Finally, for discounting, analysts should not only follow current guidance and report how discounting was conducted, especially in the case of differential discounting, but also seek to develop an understanding of its rationale. Our overall recommendations are that analysts explicitly state and justify their modelling choices regarding time and consider how alternative choices may impact on results

THE ROLE OF NONCOGNITIVE SKILLS IN EXPLAINING COGNITIVE TEST SCORES

"This article examines whether noncognitive skills-measured both by personality traits and by economic preference parameters-influence cognitive tests' performance. The basic idea is that noncognitive skills might affect the effort people put into a test to obtain good results. We experimentally varied the rewards for questions in a cognitive test to measure to what extent people are sensitive to financial incentives. To distinguish increased mental effort from extra time investments, we also varied the questions' time constraints. Subjects with favorable personality traits such as high performance motivation and an internal locus of control perform relatively well in the absence of rewards, consistent with a model in which trying as hard as you can is the best strategy. In contrast, favorable economic preference parameters (low discount rate, low risk aversion) are associated with increases in time investments when incentives are introduced, consistent with a rational economic model in which people only invest when there are monetary returns. The main conclusion is that individual behavior at cognitive tests depends on noncognitive skills. "("JEL "J20, J24) Copyright (c) 2008 Western Economic Association International.