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Symptoms of sleep-disordered breathing in children, such as frequent snoring, apnoea and choking, may lead to health problems if untreated. The caregiver's level of awareness of these symptoms has been poorly studied. This study aimed to study healthcare provider contact related to sleep-disordered breathing symptoms in a population of children aged 0–11 years.
A total of 1320 children were randomly selected from a national database that included all children living in Sweden. Caregivers answered a questionnaire about sleep-disordered breathing symptoms during the last month and healthcare provider contact related to these symptoms.
A total of 754 answers were received. The prevalence of sleep-disordered breathing symptoms was 4.8 per cent. Of this subgroup, 69 per cent had not been in contact with a healthcare provider regarding their symptoms.
This study shows that sleep-disordered breathing in children is underestimated and that there is a need to increase caregiver and healthcare provider awareness of sleep-disordered breathing in children.
Photovoltaic (PV) systems are progressively used for decentralized electricity generation. To obtain the maximum yield from such systems, optimisation of all components is essential. In this contribution, we provide a comprehensive modelling and sizing of PV systems for any location. Three applications are here presented providing real time monitoring of PV potential, accurate prediction of yield taking into account thermodynamic temperature effects, optimization of modules orientation addressing the effects of shading and efficient sizing of inverter for a higher yield output. When combined, these models can accurately predict the real time performance of any PV system.
For increasing the awareness of photovoltaic (PV) conversion and its consumer developments, a PV-powered infotainment spot (information + entertainment) has been recently designed to be used in the campus of Delft University of Technology. This demonstrator provides information to people on campus via a rugged touchscreen that is powered only by solar energy. In this PV system, a 90-W rated flexible CIGS module was deployed as market alternative to rigid c-Si modules. A methodology to accurately estimate the irradiance on a curved plane was developed. Taking into account temperature, irradiance and shading effects, the energy production of the PV module was estimated to be 62 kWh/year. On the other hand, the load should exhibit an energy consumption of 19.3 kWh/year. By means of a 12-V DC mini grid, the excess energy was thus stored in a 120 Ah battery regulated via charge controller or made directly available with two ad-hoc USB ports for smartphone battery recharging. The realized prototype of the infotainment spot is potentially a completely autonomous small-scale PV system with zero loss of load probability.
A large outbreak of norovirus (NoV) gastroenteritis caused by contaminated municipal drinking water occurred in Lilla Edet, Sweden, 2008. Epidemiological investigations performed using a questionnaire survey showed an association between consumption of municipal drinking water and illness (odds ratio 4·73, 95% confidence interval 3·53–6·32), and a strong correlation between the risk of being sick and the number of glasses of municipal water consumed. Diverse NoV strains were detected in stool samples from patients, NoV genotype I strains predominating. Although NoVs were not detected in water samples, coliphages were identified as a marker of viral contamination. About 2400 (18·5%) of the 13 000 inhabitants in Lilla Edet became ill. Costs associated with the outbreak were collected via a questionnaire survey given to organizations and municipalities involved in or affected by the outbreak. Total costs including sick leave, were estimated to be ∼8 700 000 Swedish kronor (∼€0·87 million).
Atomistic modeling is used to study the role of different alloying additions to metallic U-Zr nuclear fuels in terms of their ability to reduce lanthanide migration to the outer surface of the fuel and thus reduce their interaction with cladding. The Bozzolo-Ferrante-Smith (BFS) method for alloys is used to examine the behavior of each addition, the resulting phase structure, and the evolution of the fuel surface. Different behaviors are observed for each of the additives (In, Tl, Ga, Sb, Pd), all a result of the competition between the formation of bulk precipitates and the tendency of each additive to segregate to the surface. For each case, characteristic temperatures are determined indicating the range of temperatures in which each additive performs a different role. Sb and Pd additives are determined to be the most effective additions, properly balancing their ability to bind lanthanides in the fuel with their own segregating tendencies.
Ecosystem ecology is to a great extent about mass balances of elements and their interactions. The fluxes of elements are strongly coupled to each other, and often one limiting element regulates the fluxes of the others. This chapter gives an introduction to the most important elements and to some key concepts or cornerstones: mass balance, limiting nutrients, optimality and steady state.
A note on terminology
When we talk about ecosystems we need to define the quantities of which they are made. We will refer to concrete, measured or calculated quantities, as stocks of elements. When we talk about these quantities in more abstract terms we use the terms pools or compartments. The movements of matter between pools will interchangeably be called flows or fluxes. The transfer of energy between compartments was previously a key study area in ecology. Today we stress movements of individual elements, in particular carbon, as this approach provides insights into more aspects of ecosystems functionality. Amounts of elements can be expressed either by mass or by number of moles. We will follow the convention in terrestrial ecosystem ecology and use mass units, unless otherwise stated, rather than the molar units that are common in aquatic ecology. The typical units are kg m−2 and Mg ha−1 (1 kg m−2 = 10 Mg ha−1) for stocks, and flows are per year or per day. Mass can also be expressed as dry weight (dw), when all water has been removed, or fresh weight (fw), when the sample is at its ambient water content. Dry weight is often replaced by its carbon content; if no measurements are available a carbon content of 50% can be assumed.
A major characteristic of terrestrial ecosystems is element cycles. We first discuss different modes of cycling based on the nature of the participating processes. Cycling is then presented for two different scales – local and global, respectively. The following elements are treated in detail: carbon, nitrogen, phosphorus, potassium, magnesium, calcium and sulfur. Cycling in a temperate Norway spruce forest gives an insight into details and a comparison of cycling characteristics of ecosystems of major biomes in different climates – arctic, boreal, temperate and tropical – provides the broad picture. Major methods for measuring the different elements are also presented.
A major function in terrestrial ecosystems is the cycling of nutrients or mineral elements. A number of processes are responsible for the gradual changes in organic and inorganic materials, which eventually lead to the release of elements in forms that can be taken up by plants; thus maintaining the production of plant matter and sustaining life for other organisms in the ecosystem. Components of these cycles were discussed in Chapters 6 and 7 in relation to plant growth and soil organic matter turnover. Here we will consider the complete cycles of the major elements.
Understanding the environment has always been important for mankind. In this section we briefly trace how this has led to the development of modern ecology. We will also define the scientific arena of ecology and in particular that of ecosystem ecology and how it relates to other scientific disciplines. Ecosystem ecology relies on some fundamental cornerstones: mass balance, limiting nutrients, optimality and steady state. These concepts are explained and used to demonstrate our philosophical attitude towards the discipline.
Understanding the present requires insights into the past. We will therefore briefly describe the development of ecology and ecosystem knowledge. In particular, we will follow how terrestrial ecosystem ecology has grown from early primitive ideas about Nature and how a natural science perspective gradually has become the foundation for investigating Nature and its function. From early ecology there has been a steady development, eventually leading to the introduction of the ecosystem concept. This development towards an independent discipline is, however, dependent on a number of basic disciplines. We see a number of ecological directions dealing with basic understanding, as well as applied questions, such as worldwide production of food and maintaining the ecosystems in a sustainable way. Major actors or profiles and their impact on the discipline are presented.
Mankind has always depended, and will always depend, on what Nature gives. We can read in historical documents how we have used plants and animals as the basis for our existence. In the Bible we meet the first professions of farming and cattle breeding. Medical plants are mentioned by Hippocrates (460–377 BC), as well as ideas about plant and animal life.
Ecology and ecosystems have many faces or directions. We explain the relations between different sub-disciplines. The scientific field dealing with structure, functions and dynamics of ecosystems is ecosystem ecology. The recent development of the field suggests that it should be considered as a discipline in its own right. A definition is given and its relation to other disciplines is discussed.
In the historical account on the development of ecology we learnt about the early origins of ecology and defined it as the mutual relationships between organisms and their physical environment. The discipline is complex and builds upon an integration of components from different disciplines, all depending on the focus of the problem to be investigated (Figure 2.1). The focus can shift from the organisms, biotic focus, to the physical environment, abiotic focus. The relations to other disciplines will then at the same time shift from biological to physical and chemical.
Wind, fire and herbivory are three major forces that alter the dynamics of ecosystems by modifying their element cycles and regulating ecosystem development, in particular returning mature ecosystems to earlier development stages.
Wind as an ecological factor acts in two ways. At moderate to low speed it has an indirect action by affecting the intensity of, for example, physiological processes. For plants, subtle winds, for example, modify the temperature of plants and other organisms. Transpiration can be increased, as well as carbon dioxide transport to plants, which stimulates photosynthesis (Chapter 5). At higher wind speeds the mechanical impact on the ecosystem is of particular interest for the dynamics of the ecosystem.
Disturbances are a major factor influencing the species composition of ecosystems – wind is no exception (Pickett & White 1985). Extremely high wind speeds usually occur on sea coasts and in mountains. Lowlands may also experience extreme situations or catastrophic events such as tornados and hurricanes. Forests close to the coast in wind-exposed situations are always suppressed and further inland the height increases. The trees lean in the prevailing wind direction. The wind also transports salt, which is deposited on the leaves and has a negative effect on the vegetation. In mountains the wind, together with temperature and snow cover, determines the level of the tree limit.
We discuss here different concepts of the stability of ecosystems and how they are related to the populations composing the ecosystem. It is possible that in the end stability of ecosystem processes comes at the expense of the stability of the individual species within the ecosystem.
Species and ecosystems
The importance of the identity of the species forming an ecosystem is far from a resolved issue. In certain respects the exact identities of the species matter little because they all perform the same functions: plants photosynthesise, whilst fungi and bacteria decompose organic matter in the soil. In other respects the identity of the species is crucial because only certain species can perform specific and important functions. Examples of such species, keystone species, are nitrogen fixers and nitrifiers. The stability, whatever is implied in that term, may also depend on the identity and diversity of species.
Concepts of stability
An ecosystem can be stable or unstable with respect to disturbances in several senses. We will discuss the most important ones. A convenient analogue for understanding ecological stability is a ball in a landscape with hills and valleys (Figure 8.1). Note that the terminology in this area is sometimes confusing and different schools may use different terms for the same property or the same term for different properties (Peterson et al. 1998). First of all, the question is whether an ecosystem returns to the same state as before a disturbance. The ability to recover after a disturbance is often referred to as resilience (this term is sometimes used for the rate of return and then called engineering resilience as opposed to ecological resilience as used here). A more technical way of expressing resilience is to look at the range over which the system can be disturbed and still return to its initial state, its basin of attraction.
Air pollution in the form of sulfur dioxide, nitrogen oxides and ozone affects ecosystems, both vegetation and soil. The immediate effects are physiological damage to vegetation and soil organisms, whereas long-term effects occur through changes in soil chemistry, in particular the loss of base cations. To identify the limits to which ecosystems can support the impacts of air pollutants, the concepts of critical levels and critical loads have been developed.
Today's awareness of air pollution and its effects follows observations in early industrialisation when, for example, roasting of iron ore containing sulfur resulted in drastic effects on the surroundings, with the death of vegetation. Our modern society, with combustion of fossil fuels containing sulfur and nitrogen at levels not compatible with a clean environment, has then delivered further unpleasant surprises, e.g. ‘dead’ lakes and now also a changing climate. This chapter deals with the effects of air pollution on forests – an area which has been the focus of research for a long time at the home institute of the authors.
Two major features of the terrestrial ecosystems have been dealt with so far, structure and function. A third major feature is dynamics, development and changes over time, and also the reaction of the ecosystems to perturbations – natural or man-made. It is a question of the stability of ecosystems and their ability to accommodate changes. Changes occur on different temporal and spatial scales. There are changes at the global scale, which have occurred since the Earth's early history, as well as those occurring in recent times. The very early history of the Earth has a flavour of ‘science fiction’ and today we have the issue of ‘climate change’, which is experienced as dramatic and to some extent uncertain.
Dead organic matter from plants, litter, has to be decomposed in order to release its content of elements for use by other plants. This chapter discusses how the release of different elements is related and the factors regulating the release. A simple mathematical model provides a framework that lets us identify how different properties of the decomposer organisms, mainly bacteria and fungi, control the rate and fate of the decomposition process.
Litter and soil organic matter
Litter and soil organic matter represent different forms of a continuous transition of organic matter from newly shed, or even still attached, plant tissue or tissues from other living organisms, to an amorphous mixture of organic compounds. Since soils (with litters and soil organic matter) in general contain more of the most important elements than other stores in global element cycles (see Figures 9.21–9.24), the dynamics of soil pools are critical for the functioning of the element cycles. For simplicity, in this chapter we will include litters in soil organic matter, SOM for brevity (see Chapter 4 and the partitioning of soils into horizons).