Influence of pH and Temperature on Basaluminite Dissolution Rates

This is the author accepted manuscript. The final version is available from the American Chemical Society via the DOI in this record.The processes, rates, and controlling factors of basaluminite (Al4(SO4)(OH)10·4H2O) dissolution were assessed using batch dissolution experiments in both H2SO4 and HCl at pHs of 2.4, 2.9-3.1, 3.5-3.6 and 4.0-4.1, and temperatures of c. 279, 293, 303 and 312 K. Basaluminite dissolution is incongruent over most of the studied pH range, giving generally a lower Al/S ratio in solution than in the pristine basaluminite sample. The lower Al/S ratio may be at least partially explained by the preferential release of sulfate compared to Al from the dissolving basaluminite. The dissolution rates range between 10–7.6 and 10–9.1 mol·m−2 ·s −1 . At 291-293K, the slowest rates were observed at pH 4.1 in H2SO4 solutions, while at pH 3.0, the slowest rates were observed at 279 K in HCl solutions. Decreases in pH and increases in temperature increase dissolution rates. The influence of pH and temperature on the basaluminite dissolution rate, expressed as Al release, can be described by the following expression: = 107.3±0.5+ 0.64±0.04 −78±3⁄ Where rateAl is the basaluminite dissolution rate, based on the rate of Al release from dissolving basaluminite (in mol·m−2 ·s−1 ); aH+ is the activity of hydrogen ions in solution; R is the Universal gas constant (in kJ·mol−1 ·K−1 ) and T is temperature (in K). In light of the calculated value for the activation energy (78±3 kJ·mol−1 ), basaluminite dissolution appears to be surface-controlled. The reaction for basaluminite dissolution under the experimental conditions is proposed to be Al4(SO4)(OH)10·4H2O + 10 H +→ 4 Al3+ + SO4 2- + 14 H2O.We acknowledge funding for this study provided by the EC Marie Curie Intra-European Fellowship program (Project entitled ‘Reactivity of Aluminum Sulfate Minerals in Mine Wastes’; RASMIM) through a fellowship to P.A. We thank Gareth Tarbuck (UCL, London, UK) for help with the geochemical analyses and mineralogical determinations and their interpretation. We also thank the reviewers whose comments significantly improved the manuscript

Constraints on Association of Single-pulse Gamma-ray Bursts and Supernovae

We explore the hypothesis, similar to one recently suggested by Bloom and colleagues, that some nearby supernovae are associated with smooth, single-pulse gamma-ray bursts, possibly having no emission above ~ 300 keV. We examine BATSE bursts with durations longer than 2 s, fitting those which can be visually characterized as single-pulse events with a lognormal pulse model. The fraction of events that can be reliably ascertained to be temporally and spectrally similar to the exemplar, GRB 980425 - possibly associated with SN 1998bw - is 4/1573 or 0.25%. This fraction could be as high as 8/1573 (0.5%) if the dimmest bursts are included. Approximately 2% of bursts are morphologically similar to GRB 980425 but have emission above ~ 300 keV. A search of supernova catalogs containing 630 detections during BATSE's lifetime reveals only one burst (GRB 980425) within a 3-month time window and within the total 3-sigma BATSE error radius that could be associated with a type Ib/c supernova. There is no tendency for any subset of single-pulse GRBs to fall near the Supergalactic Plane, whereas SNe of type Ib/c do show this tendency. Economy of hypotheses leads us to conclude that nearby supernovae generally are not related to smooth, single-pulse gamma-ray bursts.Comment: 25 pages, 5 figure

Mitoxantrone is superior to doxorubicin in a multiagent weekly regimen for patients older than 60 with high-grade lymphoma: results of a BNLI randomized trial of PAdriaCEBO versus PMitCEBO

A prospective, multicenter, randomized trial was undertaken to compare the efficacy and toxicity of adriamycin with mitoxantrone within a 6-drug combination chemotherapy regimen for elderly patients (older than 60 years) with high-grade non-Hodgkin lymphoma (HGL) given for a minimum of 8 weeks. A total of 516 previously untreated patients aged older than 60 years were randomized to receive 1 of 2 anthracycline-containing regimens: adriamycin, 35 mg/m2 intravenously (IV) on day 1 (n = 259), or mitoxantrone, 7 mg/m2 IV on day 1 (n = 257); with prednisolone, 50 mg orally on days 1 to 14; cyclophosphamide, 300 mg/m2 IV on day 1; etoposide, 150 mg/m2 IV on day 1; vincristine, 1.4 mg/m2 IV on day 8; and bleomycin, 10 mg/m2 IV on day 8. Each 2-week cycle was administered for a minimum of 8 weeks in the absence of progression. Forty-three patients were ineligible for analysis. The overall and complete remission rates were 78% and 60% for patients receiving PMitCEBO and 69% and 52% for patients receiving PAdriaCEBO (P = .05, P = .12, respectively). Overall survival was significantly better with PMitCEBO than PAdriaCEBO (P = .0067). However, relapse-free survival was not significantly different (P = .16). At 4 years, 28% of PAdriaCEBO patients and 50% of PMitCEBO patients were alive (P = .0001). Ann Arbor stage III/IV, World Health Organization performance status 2-4, and elevated lactate dehydrogenase negatively influenced overall survival from diagnosis. In conclusion, the PMitCEBO 8-week combination chemotherapy regimen offers high response rates, durable remissions, and acceptable toxicity in elderly patients with HGL

Cold Molecule Spectroscopy for Constraining the Evolution of the Fine Structure Constant

We report precise measurements of ground-state, $\lambda$-doublet microwave transitions in the hydroxyl radical molecule (OH). Utilizing slow, cold molecules produced by a Stark decelerator we have improved over the precision of the previous best measurement by twenty-five-fold for the F' = 2 $\to$ F = 2 transition, yielding (1 667 358 996 $\pm$ 4) Hz, and by ten-fold for the F' = 1 $\to$ F = 1 transition, yielding (1 665 401 803 $\pm$ 12) Hz. Comparing these laboratory frequencies to those from OH megamasers in interstellar space will allow a sensitivity of 1 ppm for $\Delta\alpha/\alpha$ over $\sim$$10^{10}$ years.Comment: This version corrects minor typos in the Zeeman shift discussio

The effect of topology on the structure and free energy landscape of DNA kissing complexes

We use a recently developed coarse-grained model for DNA to study kissing complexes formed by hybridization of complementary hairpin loops. The binding of the loops is topologically constrained because their linking number must remain constant. By studying systems with linking numbers -1, 0 or 1 we show that the average number of interstrand base pairs is larger when the topology is more favourable for the right-handed wrapping of strands around each other. The thermodynamic stability of the kissing complex also decreases when the linking number changes from -1 to 0 to 1. The structures of the kissing complexes typically involve two intermolecular helices that coaxially stack with the hairpin stems at a parallel four-way junction

Current status and developing recommendations of tailings dam failure

This is the final version of the article. Available from Hindawi Publishing Corporation via the DOI in this record.Tailings dam failure accidents with limited emergency response time and huge potential threats, can often lead to heavy casualties and serious financial losses. In recent years, the decreasing trend of tailings dam failure accidents evidences the development of modern technology and safety management. However, the frequency of major tailings dam failure accidents has increased, rather than decreased. The 2015 Samarco Accident in Brazil and the 2014 Mount Polley Accident in Canada, along with their disastrous consequences, once again sounded the alarm for the tailings ponds safety. China is now facing a complicated safety situation, with 8869 tailings ponds all over the country, including 1425 “Overhead Tailings Ponds” which represents the tailings ponds that located within 1 km upstream of residential area, workshops, schools or other important facilities. Based on a large amount of relevant research literatures, focusing on three main aspects of accident prevention and control which include safety monitoring, early-warning and emergency preparation, safety management codes and standards, the current status and frontier progress were reviewed in this paper. Furthermore, the relevant problems in China were discussed and several improvement recommendations were put forward, which could provide a reference for the tailings pond accident prevention theoretical research and technological innovation. The result shows: (1) the safety monitoring standards in China are relatively strict. However, the monitoring instruments are lack of the stability, reliability and practicability. Thus the development of specific devices and new technologies is urgently needed. (2) The current early-warning method is lack of diversity and reliability. And further interdisciplinary application of information technology is becoming the developing trend. (3) The emergency management and decision-making should be based on sufficient scientific proof. However the relevant research is limited by test methods and simulating algorithms. (4) China now has built a complete system of safety management codes and standards. But with shortcomings of safety level classification, life-cycle management, change management process, accident investigation and so on, there is still a long way to go

Gene-history correlation and population structure

Correlation of gene histories in the human genome determines the patterns of genetic variation (haplotype structure) and is crucial to understanding genetic factors in common diseases. We derive closed analytical expressions for the correlation of gene histories in established demographic models for genetic evolution and show how to extend the analysis to more realistic (but more complicated) models of demographic structure. We identify two contributions to the correlation of gene histories in divergent populations: linkage disequilibrium, and differences in the demographic history of individuals in the sample. These two factors contribute to correlations at different length scales: the former at small, and the latter at large scales. We show that recent mixing events in divergent populations limit the range of correlations and compare our findings to empirical results on the correlation of gene histories in the human genome.Comment: Revised and extended version: 26 pages, 5 figures, 1 tabl

First limits on the 3-200 keV X-ray spectrum of the quiet Sun using RHESSI

We present the first results using the Reuven Ramaty High-Energy Solar Spectroscopic Imager, RHESSI, to observe solar X-ray emission not associated with active regions, sunspots or flares (the quiet Sun). Using a newly developed chopping technique (fan-beam modulation) during seven periods of offpointing between June 2005 to October 2006, we obtained upper limits over 3-200 keV for the quietest times when the GOES12 1-8A flux fell below $10^{-8}$ Wm$^{-2}$. These values are smaller than previous limits in the 17-120 keV range and extend them to both lower and higher energies. The limit in 3-6 keV is consistent with a coronal temperature $\leq 6$ MK. For quiet Sun periods when the GOES12 1-8A background flux was between $10^{-8}$ Wm$^{-2}$ and $10^{-7}$ Wm$^{-2}$, the RHESSI 3-6 keV flux correlates to this as a power-law, with an index of $1.08 \pm 0.13$. The power-law correlation for microflares has a steeper index of $1.29 \pm 0.06$. We also discuss the possibility of observing quiet Sun X-rays due to solar axions and use the RHESSI quiet Sun limits to estimate the axion-to-photon coupling constant for two different axion emission scenarios.Comment: 4 pages, 3 figures, Accepted by ApJ letter

The Time Machine: A Simulation Approach for Stochastic Trees

In the following paper we consider a simulation technique for stochastic trees. One of the most important areas in computational genetics is the calculation and subsequent maximization of the likelihood function associated to such models. This typically consists of using importance sampling (IS) and sequential Monte Carlo (SMC) techniques. The approach proceeds by simulating the tree, backward in time from observed data, to a most recent common ancestor (MRCA). However, in many cases, the computational time and variance of estimators are often too high to make standard approaches useful. In this paper we propose to stop the simulation, subsequently yielding biased estimates of the likelihood surface. The bias is investigated from a theoretical point of view. Results from simulation studies are also given to investigate the balance between loss of accuracy, saving in computing time and variance reduction.Comment: 22 Pages, 5 Figure