Theoretical interpretation of scanning tunneling microscopy images: Application to the molybdenum disulfide family of transition metal dichalcogenides

We have performed ab initio quantum mechanical calculations to describe scanning tunneling microscopy (STM) images of MoS_2 and MoTe_2. These results indicate that the interpretation of the STM images of these and related materials depends sensitively on experimental conditions. For example, determining whether the maximum tunneling current correlates to the top atom (S or Te) or to the second‐layer atom (Mo) requires information on the tip‐sample separation. Based on these results we discuss some STM experimental procedures which would allow assignment of the chemical identity of STM spots with greater certainty

The repulsive and feeding-deterrent effects of electropositive metals on juvenile sandbar sharks (Carcharhinus plumbeus)

Reducing shark bycatch and depredation (i.e., damage caused by sharks to gear, bait, and desired fish species) in pelagic longline fisheries targeting tunas and swordfish is a priority. Electropositive metals (i.e., a mixture of the lanthanide elements lanthanum, cerium, neodymium, and praseodymium) have been shown to deter spiny dogfish (Squalus acanthias, primarily a coastal species) from attacking bait, presumably because of interactions with the electroreceptive system of this shark. We undertook to determine the possible effectiveness of electropositive metals for reducing the interactions of pelagic sharks with longline gear, using sandbar sharks (Carcharhinus plumbeus, family Carcharhinidae) as a model species. The presence of electropositive metal deterred feeding in groups of juvenile sandbar sharks and altered the swimming patterns of individuals in the absence of food motivation (these individuals generally avoided approaching electropositive metal closer than ~100 cm). The former effect was relatively short-lived however; primarily (we assume) because competition with other individuals increased feeding motivation. In field trials with bottom longline gear, electropositive metal placed within ~10 cm of the hooks reduced the catch of sandbar sharks by approximately two thirds, compared to the catch on hooks in the proximity of plastic pieces of similar dimensions. Electropositive metals therefore appear to have the potential to reduce shark interactions in pelagic longline fisheries, although the optimal mass, shape, composition, and distance to baited hooks remain to be determined

A new route to exposed thermal mass: Sound absorbing poured concrete

This paper investigates the novel possibility of utilising the structural concrete floor slab as a means of providing additional mid to low frequency sound absorption through the addition of cavities on the ceiling side, formed using flexible formwork, acting as Helmholtz resonators. Mid to low frequency sound absorption in rooms is typically achieved through the use of perforated plasterboard or a suspended tile-in-grid system. Such an approach can separate the room from the thermal mass of the ceiling above, leading to higher peak temperatures or increased cooling load. Suspended ceilings can also increase the embodied energy of the building and limit the potential for stack effect ventilation by reducing room height. In this work, frequency dependent absorption coefficients of perforated concrete samples were measured using an impedance tube test. The results were found to agree with a theoretical analysis, suggesting that it would be relatively easy to predict the performance of perforations of other depths and diameters including those targeted at absorbing higher frequencies

Folkecology and commons management in the Maya Lowlands

Three groups living off the same rainforest habitat manifest strikingly distinct behaviors, cognitions, and social relationships relative to the forest. Only the area's last native Maya reveal systematic awareness of ecological complexity involving animals, plants, and people and practices clearly favoring forest regeneration. Spanish-speaking immigrants prove closer to native Maya in thought, action, and social networking than do immigrant Maya. There is no overriding "local," "Indian," or "immigrant" relationship to the environment. Results indicate that exclusive concern with rational self-interest and institutional constraints do not sufficiently account for commons behavior and that cultural patterning of cognition and access to relevant information are significant predictors. Unlike traditional accounts of relations between culture, cognition, and behavior, the models offered are not synthetic interpretations of people's thoughts and behaviors but are emergent cultural patterns derived statistically from measurements of individual cognitions and behaviors.cognitive models / commons tragedy / culture consensus / social networks / sustainable agroforestry

Prefix-Tree Decoding for Predicting Mass Spectra from Molecules

Computational predictions of mass spectra from molecules have enabled the discovery of clinically relevant metabolites. However, such predictive tools are still limited as they occupy one of two extremes, either operating (a) by fragmenting molecules combinatorially with overly rigid constraints on potential rearrangements and poor time complexity or (b) by decoding lossy and nonphysical discretized spectra vectors. In this work, we use a new intermediate strategy for predicting mass spectra from molecules by treating mass spectra as sets of molecular formulae, which are themselves multisets of atoms. After first encoding an input molecular graph, we decode a set of molecular subformulae, each of which specify a predicted peak in the mass spectrum, the intensities of which are predicted by a second model. Our key insight is to overcome the combinatorial possibilities for molecular subformulae by decoding the formula set using a prefix tree structure, atom-type by atom-type, representing a general method for ordered multiset decoding. We show promising empirical results on mass spectra prediction tasks

The importance of thermal modelling and prototyping in shelter design:Transforming shelter design for the displaced

More than 9 million people live in shelters globally, often in extremely hot climates. The thermal performance of shelters is often overlooked in the design process, despite being a consideration second only to safety in surveys of camp dwellers. Indeed, indoor temperatures exceeding 40 °C have been recorded. To aid in improving conditions, we examine the roles building simulation and prototyping could play in forecasting shelter thermal performance as part of a new shelter design process. The thermal performance of seven prototypes, built in the refugee camp of Azraq, was monitored during the hot season to test the suitability of four design approaches: (1) “blind” (uncalibrated) models, (2) calibrated models, (3) on-site prototypes and (4) off-site prototypes. These included the original shelter and six design alternatives implementing different overheating countermeasures. The results demonstrate that blind models are sensitive to the judgement of uncertainties but were still qualitatively useful. Model calibration vastly improves the agreement and significantly enhances forecasts of performance for the design alternatives, which remained similar across examined climates. We therefore conclude that simulation and prototyping, either on-site or off-site, should be adopted within the shelter design process before mass deployment, to create better living conditions for their dwellers