Magnetic and Mössbauer spectroscopy studies of nanocrystalline iron oxide aerogels

A sol-gel synthesis was used to produce iron oxide aerogels. These nanocrystalline aerogels have a pore-solid structure similar to silica aerogels but are composed entirely of iron oxides. Mössbauer experiments and x-ray diffraction showed that the as-prepared aerogel is an amorphous or poorly crystalline iron oxide, which crystallized as a partially oxidized magnetite during heating in argon. After further heat treatment in air, the nanocrystallites are fully converted to maghemite. The particles are superparamagnetic at high temperatures, but the magnetic properties are strongly influenced by magnetic interactions between the particles at lower temperatures

First observation of rotational structures in Re 168

The first rotational sequences have been assigned to the odd-odd nucleus Re168. Coincidence relationships of these structures with rhenium x rays confirm the isotopic assignment, while arguments based on the γ-ray multiplicity (K-fold) distributions observed with the new bands lead to the mass assignment. Configurations for the two bands were determined through analysis of the rotational alignments of the structures and a comparison of the experimental B(M1)/B(E2) ratios with theory. Tentative spin assignments are proposed for the πh11/2νi13/2 band, based on energy level systematics for other known sequences in neighboring odd-odd rhenium nuclei, as well as on systematics seen for the signature inversion feature that is well known in this region. The spin assignment for the πh11/2ν(h9/2/f7/2) structure provides additional validation of the proposed spins and configurations for isomers in the Au176 → Ir172→Re168 α-decay chain

Multiple band structures in 169,170Re: Search for the wobbling mode in 169Re, and residual-interaction analysis of structures in 170Re

Although the observation of wobbling was once thought to be possibly confined to lutetium isotopes in N≈94 nuclei, the identification of this exotic collective mode in 167Ta has raised the question of the role of the proton Fermi surface with regard to this phenomenon. To investigate this issue, an experiment was performed to populate high-spin states in the N=94 nucleus 169Re. The heavy-ion reaction 55Mn+118Sn was used in conjunction with Gammasphere to detect the emitted γ rays. More than 130 new transitions were added to the 169Re level scheme, including the first identification of the πi13/2 rotational sequence in this nucleus. This configuration is the structure on which all known wobbling sequences are based, but no wobbling band was observed, likely owing to the fact that the πi13/2 sequence is located at a relatively high energy in comparison with the other structures found in 169Re. Nine decay sequences are now established in this nucleus and are described within the context of the cranked shell model. In addition, significant extension of the level scheme of the odd-odd 170Re nucleus was possible and a discussion of the residual interactions for the πh 9/2νi13/2 and πi13/2νi13/2 configurations in this region is given as well

High-spin structure of odd-odd Re 172

A significant extension of the level scheme for the odd-odd nucleus Re172 was accomplished through the use of the Gammasphere spectrometer. States up to a tentative spin assignment of 39 were observed and two new structures were identified. Configuration assignments are proposed based on alignment properties and observed band crossings

Possible deformation evolution in the πi13/2 structure of 171Re

The phenomenon of wobbling can only occur for a nuclear shape with stable triaxial deformation. To date, only a few examples of this exotic collective mode have been observed in lutetium and tantalum isotopes. A search for a wobbling sequence was performed in 171Re to determine if this feature can be observed in Z>73 nuclei. No evidence was found for wobbling; however, an interaction between the πi13/2 sequence and another positive-parity band may give an indication on why wobbling may not occur in this nucleus. The level scheme for 171Re was significantly extended and interpretations for the decay sequences are proposed within the context of the cranked shell model

The Earth: Plasma Sources, Losses, and Transport Processes

This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, 1999) are addressed

Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990-2015: A systematic analysis for the Global Burden of Disease Study 2015

Background: The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 provides an up-to-date synthesis of the evidence for risk factor exposure and the attributable burden of disease. By providing national and subnational assessments spanning the past 25 years, this study can inform debates on the importance of addressing risks in context. Methods: We used the comparative risk assessment framework developed for previous iterations of the Global Burden of Disease Study to estimate attributable deaths, disability-adjusted life-years (DALYs), and trends in exposure by age group, sex, year, and geography for 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks from 1990 to 2015. This study included 388 risk-outcome pairs that met World Cancer Research Fund-defined criteria for convincing or probable evidence. We extracted relative risk and exposure estimates from randomised controlled trials, cohorts, pooled cohorts, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. We developed a metric that allows comparisons of exposure across risk factors—the summary exposure value. Using the counterfactual scenario of theoretical minimum risk level, we estimated the portion of deaths and DALYs that could be attributed to a given risk. We decomposed trends in attributable burden into contributions from population growth, population age structure, risk exposure, and risk-deleted cause-specific DALY rates. We characterised risk exposure in relation to a Socio-demographic Index (SDI). Findings: Between 1990 and 2015, global exposure to unsafe sanitation, household air pollution, childhood underweight, childhood stunting, and smoking each decreased by more than 25%. Global exposure for several occupational risks, high body-mass index (BMI), and drug use increased by more than 25% over the same period. All risks jointly evaluated in 2015 accounted for 57·8% (95% CI 56·6–58·8) of global deaths and 41·2% (39·8–42·8) of DALYs. In 2015, the ten largest contributors to global DALYs among Level 3 risks were high systolic blood pressure (211·8 million [192·7 million to 231·1 million] global DALYs), smoking (148·6 million [134·2 million to 163·1 million]), high fasting plasma glucose (143·1 million [125·1 million to 163·5 million]), high BMI (120·1 million [83·8 million to 158·4 million]), childhood undernutrition (113·3 million [103·9 million to 123·4 million]), ambient particulate matter (103·1 million [90·8 million to 115·1 million]), high total cholesterol (88·7 million [74·6 million to 105·7 million]), household air pollution (85·6 million [66·7 million to 106·1 million]), alcohol use (85·0 million [77·2 million to 93·0 million]), and diets high in sodium (83·0 million [49·3 million to 127·5 million]). From 1990 to 2015, attributable DALYs declined for micronutrient deficiencies, childhood undernutrition, unsafe sanitation and water, and household air pollution; reductions in risk-deleted DALY rates rather than reductions in exposure drove these declines. Rising exposure contributed to notable increases in attributable DALYs from high BMI, high fasting plasma glucose, occupational carcinogens, and drug use. Environmental risks and childhood undernutrition declined steadily with SDI; low physical activity, high BMI, and high fasting plasma glucose increased with SDI. In 119 countries, metabolic risks, such as high BMI and fasting plasma glucose, contributed the most attributable DALYs in 2015. Regionally, smoking still ranked among the leading five risk factors for attributable DALYs in 109 countries; childhood underweight and unsafe sex remained primary drivers of early death and disability in much of sub-Saharan Africa. Interpretation: Declines in some key environmental risks have contributed to declines in critical infectious diseases. Some risks appear to be invariant to SDI. Increasing risks, including high BMI, high fasting plasma glucose, drug use, and some occupational exposures, contribute to rising burden from some conditions, but also provide opportunities for intervention. Some highly preventable risks, such as smoking, remain major causes of attributable DALYs, even as exposure is declining. Public policy makers need to pay attention to the risks that are increasingly major contributors to global burden. Funding: Bill & Melinda Gates Foundation