Future probabilistic hot summer years for overheating risk assessments

As the 2003 Paris heatwave showed, elevated temperatures in buildings can cause thousands of deaths. This makes the assessment of overheating risk a critical exercise. Unfortunately current methods of creating example weather time series for the assessment of overheating are based on a single weather variable, and hence on only one driver of discomfort or mortality. In this study, two alternative approaches for the development of current and future weather files are presented: one (pHSY-1) is based on Weighted Cooling Degree Hours (WCDH), the other (pHSY-2) is based on Physiologically Equivalent Temperature (PET). pHSY-1 and pHSY-2 files were produced for fourteen locations. These were then compared with the existing probabilistic future Design Summer Year (pDSY) and the probabilistic future Test Reference Year. It was found that both pHSY-1 and pHSY-2 are more robust than the pDSY. It is suggested that pHSY-1 could be used for assessing the severity and occurrence of overheating, while pHSY-2 could be used for evaluating thermal discomfort or heat stress. The results also highlight an important limitation in using different metrics to compare overheating years. If the weather year is created by a ranking of a single environmental variable, to ensure consistent results assessment of the building should be with a similar single metric (e.g. hours >28 °C or WCDH), if however the weather year is based upon several environmental variables then a composite metric (e.g. PET or Fanger’s PMV) should be used. This has important implications for the suitability of weather files for thermal comfort analysis.This research was supported by Engineering and Physical Science Research Council (EPSRC) via grants EP/M021890/1 and EP/M022099/1. All data created during this research are available from the University of Bath data archive at http://doi.org/10.15125/BATH-00190

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. Practical application: The measurements indicate that such a slab could be used as a practical replacement for perforated plasterboard or a tile-in-grid system. This would allow the slab to be tuned to the building’s acoustic performance and structural requirements. The approach has the potential to: (1) reduce the embodied and operational energy of buildings; (2) improve thermal comfort and (3) create a better acoustic environment in situations where surface robustness or longevity is important, for example public stairwells, pathways under roads and metro stations. </jats:p

Spinor Dark Energy and Cosmological Coincidence Problem

Recently, the so-called Elko spinor field has been proposed to be a candidate of dark energy. It is a non-standard spinor and has unusual properties. When the Elko spinor field is used in cosmology, its unusual properties could bring some interesting consequences. In the present work, we discuss the cosmological coincidence problem in the spinor dark energy models by using the dynamical system method. Our results show that the cosmological coincidence problem should be taken to heart in the investigations of spinor dark energy models.Comment: 9 pages, revtex4; v2: major revision, title changed, Phys. Lett. B in press; v3: published versio

Kerr-CFT From Black-Hole Thermodynamics

We analyze the near-horizon limit of a general black hole with two commuting killing vector fields in the limit of zero temperature. We use black hole thermodynamics methods to relate asymptotic charges of the complete spacetime to those obtained in the near-horizon limit. We then show that some diffeomorphisms do alter asymptotic charges of the full spacetime, even though they are defined in the near horizon limit and, therefore, count black hole states. We show that these conditions are essentially the same as considered in the Kerr/CFT corresponcence. From the algebra constructed from these diffeomorphisms, one can extract its central charge and then obtain the black hole entropy by use of Cardy's formula.Comment: 19 pages, JHEP3, no figures. V2: References added, small typos fixe

Measurement and analysis of air quality in temporary shelters on three continents

Millions of displaced people are housed in shelters that generally consist of a single room, meaning that activities including cooking, sleeping and socializing all take place in the same space. Therefore, indoor air quality can be poor, resulting in estimated 20,000 displaced people dying prematurely every year. Very few studies considered the issue and all within one country. This paper describes the first comprehensive study investigating air quality in shelters by looking at Volatile Organic Compounds (VOCs), Particulate Matter (PM), and CO2 in ten locations within Peru, Ethiopia, Djibouti, Jordan, Turkey and Bangladesh. It has the aim of: (i) discovering how widespread the issue is, (ii) identifying some of the causes, (iii) whether it is linked to cultural and behavioural factors, (iv) location and climate, or (v) shelters’ materials or design. Results revealed very harmful levels of pollutants that are often linked to excess mortality - with total VOC concentrations as high as 102400 µgm-3 and PM over 3000 µgm-3. The reasons for these concentrations were complex, multifaceted and setting-specific. However, it was an issue in both simple self-built shelters and mass-manufactured designs, and across all climates and cultures. In all cases, conditions could be greatly improved by improving airflow as windows were frequently blocked for various reasons. Therefore, airflow should be explicitly considered, whilst being cognisant of the local context; and when cooking is likely to occur indoors, chimneys must be fitted

Gravitational Collapse of Phantom Fluid in (2+1)-Dimensions

This investigation is devoted to the solutions of Einstein's field equations for a circularly symmetric anisotropic fluid, with kinematic self-similarity of the first kind, in $(2+1)$-dimensional spacetimes. In the case where the radial pressure vanishes, we show that there exists a solution of the equations that represents the gravitational collapse of an anisotropic fluid, and this collapse will eventually form a black hole, even when it is constituted by the phantom energy.Comment: 10 page

Automatic mapping of atoms across both simple and complex chemical reactions

Mapping atoms across chemical reactions is important for substructure searches, automatic extraction of reaction rules, identification of metabolic pathways, and more. Unfortunately, the existing mapping algorithms can deal adequately only with relatively simple reactions but not those in which expert chemists would benefit from computer&apos;s help. Here we report how a combination of algorithmics and expert chemical knowledge significantly improves the performance of atom mapping, allowing the machine to deal with even the most mechanistically complex chemical and biochemical transformations. The key feature of our approach is the use of few but judiciously chosen reaction templates that are used to generate plausible &quot;intermediate&quot; atom assignments which then guide a graph-theoretical algorithm towards the chemically correct isomorphic mappings. The algorithm performs significantly better than the available state-of-the-art reaction mappers, suggesting its uses in database curation, mechanism assignments, and - above all - machine extraction of reaction rules underlying modern synthesis-planning programs

Gravitational collapse with tachyon field and barotropic fluid

A particular class of space-time, with a tachyon field, \phi, and a barotropic fluid constituting the matter content, is considered herein as a model for gravitational collapse. For simplicity, the tachyon potential is assumed to be of inverse square form i.e., V(\phi) \sim \phi^{-2}. Our purpose, by making use of the specific kinematical features of the tachyon, which are rather different from a standard scalar field, is to establish the several types of asymptotic behavior that our matter content induces. Employing a dynamical system analysis, complemented by a thorough numerical study, we find classical solutions corresponding to a naked singularity or a black hole formation. In particular, there is a subset where the fluid and tachyon participate in an interesting tracking behaviour, depending sensitively on the initial conditions for the energy densities of the tachyon field and barotropic fluid. Two other classes of solutions are present, corresponding respectively, to either a tachyon or a barotropic fluid regime. Which of these emerges as dominant, will depend on the choice of the barotropic parameter, \gamma. Furthermore, these collapsing scenarios both have as final state the formation of a black hole.Comment: 18 pages, 7 figures. v3: minor changes. Final version to appear in GR

Sex-Differential Herbivory in Androdioecious Mercurialis annua

Males of plants with separate sexes are often more prone to attack by herbivores than females. A common explanation for this pattern is that individuals with a greater male function suffer more from herbivory because they grow more quickly, drawing more heavily on resources for growth that might otherwise be allocated to defence. Here, we test this ‘faster-sex’ hypothesis in a species in which males in fact grow more slowly than hermaphrodites, the wind-pollinated annual herb Mercurialis annua. We expected greater herbivory in the faster-growing hermaphrodites. In contrast, we found that males, the slower sex, were significantly more heavily eaten by snails than hermaphrodites. Our results thus reject the faster-sex hypothesis and point to the importance of a trade-off between defence and reproduction rather than growth