Exploring the Effects of Residence Time on the Utility of Stable Isotopes and S/C Ratios as Proxies for Ocean Connectivity

Various geochemical proxies have been developed to determine if ancient sedimentary strata were deposited in marine or nonmarine environments. A critical parameter for proxy reliability is the residence time of aqueous species in seawater, which is rarely considered for proxies relying on stable isotopes and elemental abundance ratios. Differences in residence time may affect our ability to track geologically short-lived alternations between marine and nonmarine conditions. To test this effect for sulfur and nitrogen isotopes and sulfur/carbon ratios, we investigated a stratigraphic section in the Miocene Oberpullendorf Basin in Austria. Here, previous work revealed typical seawater-like rare earth element and yttrium (REY) systematics transitioning to nonmarine-like systematics. This shift was interpreted as a brief transition from an open marine depositional setting to a restricted embayment with a reduced level of exchange with the open ocean and possibly freshwater influence. Our isotopic results show no discernible response in carbonate-associated sulfate sulfur isotopes and carbon/sulfur abundance ratios during the interval of marine restriction inferred from the REY data, but nitrogen isotopes show a decrease by several permil. This observation is consistent with the much longer residence time of sulfate in seawater compared with REY and nitrate. Hence, this case study illustrates that the residence time is a key factor for the utility of seawater proxies. In some cases, it may make geochemical parameters more sensitive to marine water influx than paleontological observations, as in the Oberpullendorf Basin. Particular care is warranted in deep time, when marine residence times likely differ markedly from the modern

Administration of Steroids in Pediatric Cardiac Surgery: Impact on Clinical Outcome and Systemic Inflammatory Response

Cardiopulmonary bypass (CPB) is associated with a systemic inflammatory response. Pre-bypass steroid administration may modulate the inflammatory response, resulting in improved postoperative recovery. We performed a prospective study in the departments of cardiovascular surgery and pediatric intensive care medicine of two university hospitals that included 50 infants who underwent heart surgery. Patients received either prednisolone (30 mg/kg) added to the priming solution of the cardiopulmonary bypass circuit (steroid group) or no steroids (nonsteroid group). Clinical outcome parameters include therapy with inotropic drugs, oxygenation, blood lactate, glucose, and creatinine, and laboratory parameters of inflammation include leukocytes, C-reactive protein, and interleukin-8. Postoperative recovery (e.g., the number, dosage, and duration of inotropic drugs as well as oxygenation) was similar in patients treated with or without steroids when corrected for the type of cardiac surgery performed. After CPB, there was an inflammatory reaction, especially in patients with a long CPB time. Postoperative plasma levels of interleukin-8 were correlated with the duration of CPB time (r = 0.62, p < 0.001). Administration of steroids had no significant impact on the laboratory parameters of inflammation. Administration of prednisolone into the priming solution of the CPB circuit had no measurable influence on postoperative recovery and did not suppress the inflammatory respons

Experimental Evidence of Time Delay Induced Death in Coupled Limit Cycle Oscillators

Experimental observations of time delay induced amplitude death in a pair of coupled nonlinear electronic circuits that are individually capable of exhibiting limit cycle oscillations are described. In particular, the existence of multiply connected death islands in the parameter space of the coupling strength and the time delay parameter for coupled identical oscillators is established. The existence of such regions was predicted earlier on theoretical grounds in [Phys. Rev. Lett. 80, 5109 (1998); Physica 129D, 15 (1999)]. The experiments also reveal the occurrence of multiple frequency states, frequency suppression of oscillations with increased time delay and the onset of both in-phase and anti-phase collective oscillations.Comment: 4 aps formatted RevTeX pages; 6 figures; to appear in Phys. Rev. Let

Quasi-equilibria in one-dimensional self-gravitating many body systems

The microscopic dynamics of one-dimensional self-gravitating many-body systems is studied. We examine two courses of the evolution which has the isothermal and stationary water-bag distribution as initial conditions. We investigate the evolution of the systems toward thermal equilibrium. It is found that when the number of degrees of freedom of the system is increased, the water-bag distribution becomes a quasi-equilibrium, and also the stochasticity of the system reduces. This results suggest that the phase space of the system is effectively not ergodic and the system with large degreees of freedom approaches to the near-integrable one.Comment: 21pages + 7 figures (available upon request), revtex, submitted to Physical Review

The origin of rare alkali metals in geothermal fluids of southern Tibet, China: A silicon isotope perspective

Geothermal waters from the Semi, Dagejia and Kawu hot springs in the Shiquanhe-Yarlung Zangbo geothermal field of southern Tibet (China) are highly enriched in rare alkali metals (RAM). However, the enrichment mechanism is still hotly debated. Here, we report the first silicon isotope data of these geothermal waters to unravel the origin of the extreme RAM enrichments. Sinter precipitation in the spring vents and water-rock interaction in the deep reservoir controlled both the silicon budget and silicon isotope fractionation. The rates of water-rock interaction and sinter precipitation in three spring sites decrease in the sequences Semi > Kawu > Dagejia, and Dagejia > Kawu > Semi respectively. Silicon isotope fractionation during sinter precipitation (i.e. Δ30Siprecipitate-solution < -0.1‰) is less than that due to water-rock interaction (i.e. Δ30Sisolution-rocks at least as high as -0.47‰), which makes it possible to use the δ30Si signatures of springs to evaluate the intensity of water-rock interaction. Based on the available evidence, a conceptual model of RAM enrichment is proposed: (i) persistent magmatic activity in southern Tibet provided the initial enrichment of the RAM in host rocks and a heat sources for the deep reservoirs of geothermal systems; (ii) the high Cl- content and long residence time (thousands of years) promote the leaching of RAM from the silicate host rocks.National Key R&D Program of China [2017YFC0602405]; National Natural Science Foundation of China [41673001, 41872074, 41422302]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Coating Thin Mirror Segments for Lightweight X-ray Optics

Next generations lightweight, high resolution, high throughput optics for x-ray astronomy requires integration of very thin mirror segments into a lightweight telescope housing without distortion. Thin glass substrates with linear dimension of 200 mm and thickness as small as 0.4 mm can now be fabricated to a precision of a few arc-seconds for grazing incidence optics. Subsequent implementation requires a distortion-free deposition of metals such as iridium or platinum. These depositions, however, generally have high coating stresses that cause mirror distortion. In this paper, we discuss the coating stress on these thin glass mirrors and the effort to eliminate their induced distortion. It is shown that balancing the coating distortion either by coating films with tensile and compressive stresses, or on both sides of the mirrors is not sufficient. Heating the mirror in a moderately high temperature turns out to relax the coated films reasonably well to a precision of about a second of arc and therefore provide a practical solution to the coating problem

The Coupled Electronic-Ionic Monte Carlo Simulation Method

Quantum Monte Carlo (QMC) methods such as Variational Monte Carlo, Diffusion Monte Carlo or Path Integral Monte Carlo are the most accurate and general methods for computing total electronic energies. We will review methods we have developed to perform QMC for the electrons coupled to a classical Monte Carlo simulation of the ions. In this method, one estimates the Born-Oppenheimer energy E(Z) where Z represents the ionic degrees of freedom. That estimate of the energy is used in a Metropolis simulation of the ionic degrees of freedom. Important aspects of this method are how to deal with the noise, which QMC method and which trial function to use, how to deal with generalized boundary conditions on the wave function so as to reduce the finite size effects. We discuss some advantages of the CEIMC method concerning how the quantum effects of the ionic degrees of freedom can be included and how the boundary conditions can be integrated over. Using these methods, we have performed simulations of liquid H2 and metallic H on a parallel computer.Comment: 27 pages, 10 figure

Experimental investigation of the elasticity of the human diaphragm

<p>Abstract</p> <p>Background</p> <p>Traumatic diaphragmatic ruptures affect mainly the left side. In an experimental study in human corpses we examined the stretch behaviour of the left and right diaphragmatic halves.</p> <p>Methods</p> <p>In a total of 8 male and 8 female corpses each diaphragmatic half was divided into 4 different segments. Each segments stretch behaviour was investigated. In steps of 2 N the stretch was increased up to 24 N.</p> <p>Results</p> <p>In the female the left diaphragm showed a stronger elasticity compared to the right. Additionally the left diaphragm in females showed a higher elasticity in comparison to the left in males. Traumatic diaphragmatic ruptures affect mostly the central tendineous part or the junction between tendineous and muscular part of the diaphragmatic muscle. Accordingly we found a lower elasticity in these parts compared with the other diaphragmatic segments.</p> <p>Conclusion</p> <p>In summary it can be said that albeit some restrictions we were able to determine the elasticity of different diaphragmatic segments quantitatively and reproduceably with our presented method. Thereby a comparison of results of different diaphragmatic segments as well as of both diaphragmatic halves and of both genders was possible</p

Administration of Steroids in Pediatric Cardiac Surgery: Impact on Clinical Outcome and Systemic Inflammatory Response

Cardiopulmonary bypass (CPB) is associated with a systemic inflammatory response. Pre-bypass steroid administration may modulate the inflammatory response, resulting in improved postoperative recovery. We performed a prospective study in the departments of cardiovascular surgery and pediatric intensive care medicine of two university hospitals that included 50 infants who underwent heart surgery. Patients received either prednisolone (30 mg/kg) added to the priming solution of the cardiopulmonary bypass circuit (steroid group) or no steroids (nonsteroid group). Clinical outcome parameters include therapy with inotropic drugs, oxygenation, blood lactate, glucose, and creatinine, and laboratory parameters of inflammation include leukocytes, C-reactive protein, and interleukin-8. Postoperative recovery (e.g., the number, dosage, and duration of inotropic drugs as well as oxygenation) was similar in patients treated with or without steroids when corrected for the type of cardiac surgery performed. After CPB, there was an inflammatory reaction, especially in patients with a long CPB time. Postoperative plasma levels of interleukin-8 were correlated with the duration of CPB time (r = 0.62, p < 0.001). Administration of steroids had no significant impact on the laboratory parameters of inflammation. Administration of prednisolone into the priming solution of the CPB circuit had no measurable influence on postoperative recovery and did not suppress the inflammatory respons

Solid molecular hydrogen: The Broken Symmetry Phase

By performing constant-pressure variable-cell ab initio molecular dynamics simulations we find a quadrupolar orthorhombic structure, of $Pca2_1$ symmetry, for the broken symmetry phase (phase II) of solid H2 at T=0 and P =110 - 150 GPa. We present results for the equation of state, lattice parameters and vibronic frequencies, in very good agreement with experimental observations. Anharmonic quantum corrections to the vibrational frequencies are estimated using available data on H2 and D2. We assign the observed modes to specific symmetry representations.Comment: 5 pages (twocolumn), 4 Postscript figures. To appear in Phys. Rev. Let