Modern and Cenozoic records of seawater magnesium from foraminiferal Mg isotopes

Magnesium is an element critically involved in the carbon cycle, because weathering of Ca-Mg silicates removes atmospheric CO2 into rivers, and formation of Ca-Mg carbonates in the oceans removes carbon from the ocean-atmosphere system. Hence the Mg cycle holds the potential to provide valuable insights into Cenozoic climate-system history, and the shift during this time from a greenhouse to icehouse state. We present Mg isotope ratios for the past 40 Myr using planktic foraminifers as an archive. Modern foraminifera, which discriminate against elemental and isotopically heavy Mg during calcification, show no correlation between the Mg isotope composition (δ26Mg, relative to DSM-3) and temperature, Mg / Ca or other parameters such as carbonate saturation (ΔCO3). However, inter-species isotopic differences imply that only well-calibrated single species should be used for reconstruction of past seawater. Seawater δ26Mg inferred from the foraminiferal record decreased from ~0‰ at 15 Ma, to −0.83‰ at the present day, which coincides with increases in seawater lithium and oxygen isotope ratios. It strongly suggests that neither Mg concentrations nor isotope ratios are at steady state in modern oceans, given its ~10 Myr residence time. From these data, we have developed a dynamic box model to understand and constrain changes in Mg sources to the oceans (rivers) and Mg sinks (dolomitisation and hydrothermal alteration). Our estimates of seawater Mg concentrations through time are similar to those independently determined by pore waters and fluid inclusions. Modelling suggests that dolomite formation and the riverine Mg flux are the primary controls on the δ26Mg of seawater, while hydrothermal Mg removal and the δ26Mg of rivers are more minor controls. Using Mg riverine flux and isotope ratios inferred from the 87Sr / 86Sr record, the modelled Mg removal by dolomite formation shows minima in the Oligocene and at the present day (with decreasing trends from 15 Ma), both coinciding with rapid decreases in global temperatures

Psychological Health and Smoking in Young Adulthood

Introduction: Young adulthood is a critical time for the emergence of risk behaviors including smoking. Psychological health is associated with smoking, but studies rarely track both over time. We used longitudinal data to assess whether average patterns of psychological health influenced average patterns of smoking and whether short-term fluctuations in psychological health influenced fluctuations in smoking. Method: Young adults aged 18–30 from the Panel Study of Income Dynamics were followed from 2007 to 2013, and mean trajectories of smoking were modeled. Psychological health variables included ever having a mental health diagnosis and time-varying distress. Results: In regression models, individuals with poorer psychological health (higher distress or a diagnosis) were more likely to be smokers and to smoke greater number of cigarettes. The association of diagnosis with number of cigarettes smoked increased with age. Conclusions: Smoking-related interventions should target individuals with poorer psychological health, even if they have no formal mental health diagnosis

Josephson vortices and solitons inside pancake vortex lattice in layered superconductors

In very anisotropic layered superconductors a tilted magnetic field generates crossing vortex lattices of pancake and Josephson vortices (JVs). We study the properties of an isolated JV in the lattice of pancake vortices. JV induces deformations in the pancake vortex crystal, which, in turn, substantially modify the JV structure. The phase field of the JV is composed of two types of phase deformations: the regular phase and vortex phase. The phase deformations with smaller stiffness dominate. The contribution from the vortex phase smoothly takes over with increasing magnetic field. We find that the structure of the cores experiences a smooth yet qualitative evolution with decrease of the anisotropy. At large anisotropies pancakes have only small deformations with respect to position of the ideal crystal while at smaller anisotropies the pancake stacks in the central row smoothly transfer between the neighboring lattice positions forming a solitonlike structure. We also find that even at high anisotropies pancake vortices strongly pin JVs and strongly increase their viscous friction.Comment: 22 pages, 11 figures, to appear in Phys. Rev.

Phase Transitions in Isolated Vortex Chains

In very anisotropic layered superconductors (e.g. Bi$_2$Sr$_2$CaCu$_2$O$_x$) a tilted magnetic field can penetrate as two co-existing lattices of vortices parallel and perpendicular to the layers. At low out-of-plane fields the perpendicular vortices form a set of isolated vortex chains, which have recently been observed in detail with scanning Hall-probe measurements. We present calculations that show a very delicate stability of this isolated-chain state. As the vortex density increases along the chain there is a first-order transition to a buckled chain, and then the chain will expel vortices in a continuous transition to a composite-chain state. At low densities there is an instability towards clustering, due to a long-range attraction between the vortices on the chain, and at very low densities it becomes energetically favorable to form a tilted chain, which may explain the sudden disappearance of vortices along the chains seen in recent experiments.Comment: 9 pages, 10 figure

Microcantilever Studies of Angular Field Dependence of Vortex Dynamics in BSCCO

Using a nanogram-sized single crystal of BSCCO attached to a microcantilever we demonstrate in a direct way that in magnetic fields nearly parallel to the {\it ab} plane the magnetic field penetrates the sample in the form of Josephson vortices rather than in the form of a tilted vortex lattice. We further investigate the relation between the Josephson vortices and the pancake vortices generated by the perpendicular field component.Comment: 5 pages, 8 figure

Attitudes towards potential new tobacco control regulations among U.S. adults

Favorable attitudes towards tobacco control policies can facilitate their implementation and success. We examined attitudes toward four potential U.S. Federal tobacco regulations (banning menthol from cigarettes, reducing nicotine levels in cigarettes, banning candy and fruit flavored electronic cigarettes, and banning candy and fruit flavored little cigars and cigarillos) and associations with individual and state variables. A nationally representative phone survey of 4337 adults assessed attitudes toward potential policies. Weighted logistic regression was used to assess relationships between attitudes and demographic factors, smoking behavior, beliefs about the government (knowledge, trust, and credibility), exposure to tobacco control campaigns, and state variables from the US Centers for Disease Control and Prevention (CDC) State Tobacco Activities Tracking and Evaluation (STATE) System. Most respondents supported three out of four policies. Respondents that were female, non-white, Latino, living below the poverty line, had less than high school education, were of older age, did not smoke, had higher trust in government, and were exposed to national tobacco control campaigns had higher odds of expressing favorable attitudes toward potential new tobacco regulations than did their counterparts. No state-level effects were found. While differences in attitudes were observed by individual demographic characteristics, behaviors, and beliefs, a majority of participants supported most of the potential new tobacco regulations surveyed