Influence of Population Density on CO2 Emissions Eliminating the Influence of Climate

More than 50% of the world’s population lives in cities. Its buildings consume more than a third of the energy and generate 40% of the emissions. This makes cities in general and their buildings in particular priority points of attention for policymakers and utilities. This paper uses population density as a variable to know its influence on energy consumption and emissions produced in buildings. Furthermore, to show its effect more clearly, the influence of the climate was eliminated. The usual energy consumption in buildings is thermal and electrical. The study was carried out at the city level, both per inhabitant and per household. The area actually occupied by the city was considered. The proposed method was applied to the case of Spanish cities with more than 50,000 inhabitants. The results show that the higher the population density, the higher the energy consumption per inhabitant and household in buildings. The consumption of thermal energy is elastic, while that of electrical energy is inelastic, varying more than 100% between extreme groups. Regarding CO2 emissions, the higher the population density, the higher the emissions. Emissions of electrical origin barely vary by 2% and are greater than those of thermal origin. In addition, the proportion of emissions of electrical origin, with respect to the total, decreases with increasing population density from 74% to 55%. This research aims to help policymakers and utilities to take the appropriate measures that favor the use of renewable energies and reduce CO2 emissions.

Influence of Population Income on Energy Consumption and CO2 Emissions in Buildings of Cities

More than half of the world’s population lives in cities. A large part of the emissions and energy consumption corresponds to buildings, both in the residential sector and in the service sector. This means that a large part of the measures taken by governments to reduce energy consumption and greenhouse gas emissions are focused on this sector. With this background, this paper studies energy consumption in city buildings and the CO2 emissions they produce. It only makes use of publicly available data. The analysis is made from the point of view of income per inhabitant, and the results are obtained per inhabitant and household. To facilitate the analysis of the results, an index has been defined. The main contributions of this work are to analyze energy consumption and emissions due to buildings, study them from the point of view of the income of their inhabitants, and consider cities individually. The proposed methodology has been applied to the case of Spain. A total of 145 Spanish cities that have more than 50,000 inhabitants have been studied. The results show that the higher the income, the higher the consumption and emissions. Electricity consumptions are almost inelastic, while those of thermal origin are greatly influenced by the level of income. Regarding CO2 emissions, the percentage of emissions of electrical origin with respect to total emissions is higher than that of thermal origin. In addition, the lower the income, the higher the percentage of emissions of electrical origin.

Influence of Population Income and Climate on Air Pollution in Cities Due to Buildings: The Case of Spain

Half of the world’s population lives in cities. In addition, more than 40% of greenhouse gas emissions are produced in buildings in the residential and tertiary sectors. Therefore, cities, and in particular their buildings, have a great influence on these emissions. In fact, they are reflected in several of the United Nations’ Sustainable Development Goals. Any measure taken to reach these goals has a significant impact from the point of view of reducing greenhouse gases. An understanding of these goals is the basis of greenhouse gas mitigation. This work analyzed the CO2 emissions from the buildings in cities as a function of the economic income of their inhabitants. For this, databases published by official sources were used. The origins of the CO2 are usually emitted by buildings were analyzed—electrical and thermal, in the form of natural gas. Another variable that influences these emissions is climate. To study only the income variable, the influence of climate has been eliminated. Also, to facilitate analysis, an index has been introduced. As an example of application of the proposed methodology, Spanish cities with more than 50,000 inhabitants were studied. The analysis was carried out by household and by inhabitant. The results showed the following: the higher the income of the citizens, the higher the total and thermal emissions; thermal consumption is elastic, while electrical consumption is inelastic; emissions of electrical origin are almost constant; emissions from electrical energy are greater than those from thermal energy; as income increases, the ratio between emissions of electrical and thermal origin decreases.

Influence of the Population Density of Cities on Energy Consumption of Their Households

36% of the energy consumed and 40% of emissions are due to buildings in the residential and tertiary sectors. These antecedents have forced governments to focus on saving energy and reducing emissions in this sector. To help government decision-making and facilitate energy planning for utilities, this work analyzes the energy consumption that occurs in city buildings. The information used to carry it out is publicly accessible. The study is carried out from the point of view of the population density of the cities, and these are analyzed individually. Furthermore, the area actually occupied by the city has been considered. The results are studied by inhabitant and household. The proposed method has been applied to the case of Spanish cities with more than 50,000 inhabitants. The results show that the higher the population density, the higher the energy consumption. This occurs both per inhabitant and per household. Furthermore, the consumption of electrical energy is inelastic, which is not the case with the consumption of thermal origin.

Thermal Flows

Flows of thermal origin and heat transfer problems are central in a variety of disciplines and industrial applications [...]

Statistics of pathogenic bacteria in the search of host cells

A crucial phase in the infection process, which remains poorly understood, is the localization of suitable host cells by bacteria. It is often assumed that chemotaxis plays a key role during this phase. Here, we report a quantitative study on how Salmonella Typhimurium search for T84 human colonic epithelial cells. Combining time-lapse microscopy and mathematical modeling, we show that bacteria can be described as chiral active particles with strong active speed fluctuations, which are of biological, as opposed to thermal, origin. We observe that there exists a giant range of inter-individual variability of the bacterial exploring capacity. Furthermore, we find Salmonella Typhimurium does not exhibit biased motion towards the cells and show that the search time statistics is consistent with a random search strategy. Our results indicate that in vitro localization of host cells, and also cell infection, are random processes, not involving chemotaxis, that strongly depend on bacterial motility parameters.

Gate Control of Superconductivity in Mesoscopic All-Metallic Devices

The possibility to tune, through the application of a control gate voltage, the superconducting properties of mesoscopic devices based on Bardeen–Cooper–Schrieffer metals was recently demonstrated. Despite the extensive experimental evidence obtained on different materials and geometries, a description of the microscopic mechanism at the basis of such an unconventional effect has not been provided yet. This work discusses the technological potential of gate control of superconductivity in metallic superconductors and revises the experimental results, which provide information regarding a possible thermal origin of the effect: first, we review experiments performed on high-critical-temperature elemental superconductors (niobium and vanadium) and show how devices based on these materials can be exploited to realize basic electronic tools, such as a half-wave rectifier. Second, we discuss the origin of the gating effect by showing gate-driven suppression of the supercurrent in a suspended titanium wire and by providing a comparison between thermal and electric switching current probability distributions. Furthermore, we discuss the cold field-emission of electrons from the gate employing finite element simulations and compare the results with experimental data. In our view, the presented data provide a strong indication regarding the unlikelihood of the thermal origin of the gating effect.

Microbial community composition is linked to Sphagnum acclimation to warming

<p>Peatlands store about third of the terrestrial carbon (C) and exert long-term climate cooling. Dominant plant genera in acidic peatlands, <em>Sphagnum</em> mosses, are main contributors to net primary productivity. Through associative relationships with diverse microbial organisms (microbiome), <em>Sphagnum</em> mosses control major biogeochemical processes, namely uptake, storage and potential release of carbon and nitrogen. Climate warming is expected to negatively impact C accumulation in peatlands and alter nutrient cycling, however <em>Sphagnum</em>-dominated peatland resilience to climate warming may depend on <em>Sphagnum</em>-microbiome associations. The ability of the microbiome to rapidly acclimatize to warming may aid <em>Sphagnum</em> exposed to elevated temperatures through host-microbiome acquired thermotolerance. We investigated the role of the microbiome on <em>Sphagnum</em>’s ability to acclimate to elevated temperatures using a microbiome-transfer approach to test: a) whether the thermal origin of the microbiome influences acclimation of <em>Sphagnum</em> growth and b) if microbial benefits to <em>Sphagnum</em> growth depend on donor <em>Sphagnum</em> species.</p><p>            Using a full-factorial design, microbiomes were separated from <em>Sphagnum</em> “donor” species from four different peatlands across a wide range of thermal environments (11.4-27°C). The microbiomes were transferred onto germ-free “recipient” <em>Sphagnum</em> species in the laboratory and exposed to a range of experimental temperatures (8.5 – 26.5°C) for growth analysis over 4 weeks.</p><p>            Normalized growth rates were maximized for plants that received a microbiome from a matched “donor” and with a similar origin temperature (ΔT<sub>treatment-origin</sub>: 0.3±0.9°C [±standard error], p = 0.73). For non-matched “donor-recipient” <em>Sphagnum</em> pairs, ΔT<sub>treatment-origin</sub> was slightly negative with -4.1±2.1°C (p = 0.06). The largest growth rate of the “recipient” was measured when grown with a microbiome from a matching “donor” <em>Sphagnum</em> species and was 252% and 48% larger than the maximum growth rate of the germ-free <em>Sphagnum</em> and the non-matched “donor-recipient” <em>Sphagnum</em> pairs, respectively.</p><p>            Our results suggest that the composition of the <em>Sphagnum</em> microbiome plays a critical role in host plant temperature acclimation. We found that microbially-provided benefits to the host plant were most pronounced when: 1) the thermal origin of the microbiome is similar to experimental temperatures, and 2) when donor and recipient <em>Sphagnum</em> species are the same. Together, these results suggest that <em>Sphagnum</em> temperature acclimation can be modulated, in part, by microbial interactions and may potentially play a role in peatland resilience to climate warming.</p>

Global observations of 3D mantle attenuation using normal modes

<div> <div> <div> <p>Seismic tomographic models based solely on wave velocities are unable to distinguish between a temperature or compositional origin for Earth’s 3D structure variations, such as the Large Low Shear Velocity Provinces (LLSVPs) beneath the lower mantle of Africa and the Pacific. Seismic attenuation or damping is able able to provide additional information that may help to unravel the origin of the LLSVPs, which is fundamental to understand mantle convection evolution. For example, a thermal origin for the LLSVPs will point to them being short-lived anomalies, whereas a compositional origin will point to them being long-lived, forming mantle 'anchors' and influencing the pattern of mantle convection for a large part of Earth’s history. Seismic attenuation is able to make that distinction, because it is directly sensitive to temperature variations. So far, global 3D attenuation models have only been available for the upper mantle, with only two regional body waves studies exploring the lower mantle (Lawrence and Wysession, 2006; Hwang and Ritsema, 2011).<br>Here, we use normal mode data to measure elastic splitting functions (dependent on velocity and density) and anelastic splitting functions (dependent on attenuation). The advantage of normal modes is that they allow us to include focussing and scattering due to the velocity structure without the need for approximations, because we measure the elastic splitting function jointly with the anelastic splitting function. In our measurements for upper mantle sensi- tive modes, we find anti-correlation between the elastic and anelastic splitting functions, suggesting a thermal origin for low velocity spreading ridges, and agreeing with previous studies. On the other hand, for lower mantle sensitive modes, we find correlation, suggesting the averagely attenuating LLSVPs are surrounded by strongly attenuating regions potentially due to the presence of post-perovskite.</p> </div> </div> </div>

Insight into Thermal Stress Distribution and Required Reinforcement Reducing Early-Age Cracking in Mass Foundation Slabs

The heat released during cement hydration results in temperature-induced non-uniform volume changes in concrete structures. As a consequence, tensile thermal stresses of significant values may occur. The level of these stresses can be lowered by using various technological measures during the construction process and a proper concrete mix composition. Nevertheless, the application of an appropriate reinforcement is a reliable method for controlling the width and spacing of possible cracks. The rules for calculating this reinforcement are not precisely detailed in the standards devoted to concrete structures. Additionally, the correct calculation of the reinforcement requires the identification of the tensile stress distribution in a mass slab. The presented study provides insight into stress distribution and relevant reinforcement for controlling early-age cracks of thermal origin. The existing standards and guidelines are discussed and clarified. The possible paths for calculating the reinforcement are proposed through the example of mass foundation slabs with different levels of external restraints. The results indicate a significant impact of the calculation method as well as the restraint conditions of the slab on the area of required reinforcement.