The effect of species diversity on metal adsorption onto bacteria

In this study, we measure proton, Pb, and Cd adsorption onto the bacteria Deinococcus radiodurans, Thermus thermophilus, Acidiphlium angustum, Flavobacterium aquatile, and Flavobacterium hibernum, and we calculate the thermodynamic stability constants for the important surface complexes. These bacterial species represent a wide genetic diversity of bacteria, and they occupy a wide range of habitats. All of the species, except for A. angustum, exhibit similar proton and metal uptake. The only species tested that exhibits significantly different protonation behavior is A. angustum, an acidophile that grows at significantly lower pH than the other species of this study. We demonstrate that a single, metal-specific, surface complexation model can be used to reasonably account for the acid/base and metal adsorption behaviors of each species. We use a four discrete site non-electrostatic model to describe the protonation of the bacterial functional groups, with averaged pK_a values of 3.1 ± 0.3, 4.8 ± 0.2, 6.7 ± 0.1, and 9.2 ± 0.3, and site concentrations of (1.0 ± 0.17) × 10⁻⁴, (9.0 ± 3.0) × 10⁻⁵, (4.6 ± 1.8) × 10⁻⁵, and (6.1 ± 2.3) × 10⁻⁵ mol of sites per gram wet mass of bacteria, respectively. Adsorption of Cd and Pb onto the bacteria can be accounted for by the formation of complexes with each of the bacterial surface sites. The average log stability constants for Cd complexes with Sites 1-4 are 2.4 ± 0.4, 3.2 ± 0.1, 4.4 ± 0.1, and 5.3 ± 0.1, respectively. The average log stability constants for Pb complexes with Sites 1-4 are 3.3 ± 0.2, 4.5 ± 0.3, 6.5 ± 0.1, and 7.9 ± 0.5, respectively. This study demonstrates that a wide range of bacteria exhibit similar proton and metal adsorption behaviors, and that a single set of averaged acidity constants, site concentrations, and stability constants for metal-bacterial surface complexes yields a reasonable model for the adsorption behavior of many of these species. The differences in adsorption behavior that we observed for A. angustum demonstrate that genetic differences do exist between the cell wall functional group chemistries of some bacterial species, and that significant exceptions to the typical bacterial adsorption behavior do exist.     

Overbreak and underbreak in underground openings Part 2: causes and implications

Summary The newly developed light sectioning method has been used to investigate some of the causes and costs of overbreak and underbreak. Investigations at the Aquamilpa Hydroelectric Project in Mexico have shown decreased overbreak and increased underbreak as a result of increased rock quality and decreased explosive energy. A new measure of explosive energy, the perimeter powder factor (PPF), has been defined and shown to be useful in the context of tunnel-wall rock damage. Tentative results indicate that explosive energy (PPF) may be a more important factor in producing underbreak, whereas rock quality may be a greater factor in producing overbreak. A site-specific equation is given for predicting overbreak or underbreak as a function of rock quality and explosive energy, with an evaluation of the cost of underbreak and overbreak.     

Optimal placement of dampers and actuators based on stochastic approach

A general method is developed for optimal application of dampers and actuators by installing them at optimal location on seismic-resistant structures. The study includes development of a statistical criterion, formulation of a general optimization problem and establishment of a solution procedure. Numerical analysis of the seismic response in time-history of controlled structures is used to verify the proposed method for optimal device application and to demonstrate the effectiveness of seismic response control with optimal device location. This study shows that the proposed method for the optimal device application is simple and general, and that the optimally applied dampers and actuators are very efficient for seismic response reduction.     

The age of glacier peak tephra in west-central Montana

At Sheep Mountain Bog, near Missoula, Montana, a late-glacial tephra, that probably fell in late summer, is preserved as an 8-mm-thick graded bed overlain by another 8 mm of redeposited ash mixed with lake deposits. Sediment surrounding the ash was ¹⁴C dated to about 11,200 yr B.P. Electron-microprobe analyses of the volcanic glass and hornblende phenocrysts from this ash layer indicate that they are similar in major-element chemistry to those of Glacier Peak layer G previously considered to be about 12,000 yr old or older.     

Laboratory tests as a basis for the control of sewage sludge dumping at sea

Toxicity and bioaccumulation studies were carried out on a number of UK sewage sludges to determine whether laboratory experiments could be used to regulate sludge dumping at sea. Whilst the acute toxicity of sewage sludges to adult marine organisms was generally low, shrimp larvae were found to be up to 500 times more sensitive than adults of the same species. No significant bioaccumulation of mercury or cadmium could be detected following up to 60 days exposure of fish, shrimps and mussels to the most heavily contaminated sludges available, although there was some uptake of lead, zinc and copper.     

Secular resonance,solar spin down,and the orbit of Mercury

A mechanism capable of accounting for the large mean eccentricity (0.175) and inclination (7°.2) of Mercury is discussed. Provided the gravitational field of the rapidly rotating primordial Sun had a sufficiently large second degree harmonic (i.e., J₂ ? order 10^?3), subsequent solar spin down would drive the orbit of Mercury through two secular resonances with Venus, one involving the precession of the line of apsides, the other one involving the regression of the nodal line. Resonance passage generates contributions to the eccentricity and inclination that are proportional to the square root of the characteristic solar spin down time. We find that an initial solar rotation l period of $\text{P ? 5}\text{1}\text{2}\text{hr}$ guarantees passage through resonance and that a spin down time of $\text{τ = Ω|dΩ/dt|}{}^{\mathrm{?1}}$ of order 10⁶ years could have produced the observed eccentricity and inclination. Such a primordial rotation rate is comparable to the measured rotations of very young stars and the spin down time appears consistent with the time scale derived for magnetic braking of the Sun's rotation by an intense solar wind during a T-Tauri stage of solar evolution.     

“Washed away”—assessing community perceptions of flooding and prevention strategies: a North Queensland example

This article explored the perceptions of residents of a regional city in North Queensland of how to remain safe during flood events. It also explored reasons for and how to prevent risk-taking behaviour in floodwater using the protection motivation theory (PMT). PMT is a psychological theory which has recently been applied to assess behaviour during floods and was used as a framework to analyse the themes of responses to the online survey. The online survey was conducted prior to the wet season of 2011/2012 with 130 Townsville residents participating. The results indicate that about half of respondents (55 %) had some experience with floods of which driving through floodwater (38 %) was the most common type of flood experience listed and was more common amongst male respondents. Respondents’ advice to keep friends and family safe during floods was consistent with “coping appraisal”, which would improve their ability to cope with the flood. Prior experiences with floodwater influenced the reasons given for why people drive through floodwater and were taken to be indicative of an actor/observer bias. Respondents who had experience driving through floodwater (the actors) indicate how the context of the situation can influence decision-making, whereas those respondents who had no personal experience of driving through floodwater (the observers) were more likely to cite low perceived vulnerability of harm as a motivator. Prevention strategies focused on structural mechanisms to block access, information provision and punishment of offenders. It is suggested that in communities which regularly experience flooding, timely and context-specific reminders of the dangers inherent in floodwater along with the type, effectiveness and cost of protective action could minimise the public’s contact with floodwater and prove useful regardless of past experiences.