107 resultados para Nonlinear Dynamics and Control
Resumo:
Establishing how invasive species impact upon pre-existing species is a fundamental question in ecology and conservation biology. The greater white-toothed shrew (Crocidura russula) is an invasive species in Ireland that was first recorded in 2007 and which, according to initial data, may be limiting the abundance/distribution of the pygmy shrew (Sorex minutus), previously Ireland’s only shrew species. Because of these concerns, we undertook an intensive live-trapping survey (and used other data from live-trapping, sightings and bird of prey pellets/nest inspections collected between 2006 and 2013) to model the distribution and expansion of C. russula in Ireland and its impacts on Ireland’s small mammal community. The main distribution range of C. russula was found to be approximately 7,600 km2 in 2013, with established outlier populations suggesting that the species is dispersing with human assistance within the island. The species is expanding rapidly for a small mammal, with a radial expansion rate of 5.5 km/yr overall (2008–2013), and independent estimates from live-trapping in 2012–2013 showing rates of 2.4–14.1 km/yr, 0.5–7.1 km/yr and 0–5.6 km/yr depending on the landscape features present. S. minutus is negatively associated with C. russula. S. minutus is completely absent at sites where C. russula is established and is only present at sites at the edge of and beyond the invasion range of C. russula. The speed of this invasion and the homogenous nature of the Irish landscape may mean that S. minutus has not had sufficient time to adapt to the sudden appearance of C. russula. This may mean the continued decline/disappearance of S. minutus as C. russula spreads throughout the island.
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The Bronze Age in Britain was a time of major social and cultural changes, reflected in the division of the landscape into field systems and the establishment of new belief systems and ritual practices. Several hypotheses have been advanced to explain these changes, and assessment of many of them is dependent on the availability of detailed palaeoenvironmental data from the sites concerned. This paper explores the development of a later prehistoric landscape in Orkney, where a Bronze Age field system and an apparently ritually-deposited late Bronze Age axe head are located in an area of deep blanket peat from which high-resolution palaeoenvironmental sequences have been recovered. There is no indication that the field system was constructed to facilitate agricultural intensification, and it more likely reflects a cultural response to social fragmentation associated with a more dispersed settlement pattern. There is evidence for wetter conditions during the later Bronze Age, and the apparent votive deposit may reflect the efforts of the local population to maintain community integrity during a time of perceptible environmental change leading to loss of farmland. The study emphasises the advantages of close integration of palaeoenvironmental and archaeological data for interpretation of prehistoric human activity. The palaeoenvironmental data also provide further evidence for the complexity of prehistoric woodland communities in Orkney, hinting at greater diversity than is often assumed. Additionally, differing dates for woodland decline in the two sequences highlight the dangers of over-extrapolation from trends observed in a single pollen profile, even at a very local scale.
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Using ownership and control data for 890 firm‐years, this article examines the concentration of capital and voting rights in British companies in the second half of the nineteenth century. We find that both capital and voting rights were diffuse by modern‐day standards. However, this does not necessarily mean that there was a modern‐style separation of ownership from control in Victorian Britain. One major implication of our findings is that diffuse ownership was present in the UK much earlier than previously thought, and given that it occurred in an era with weak shareholder protection law, it somewhat undermines the influential law and finance hypothesis. We also find that diffuse ownership is correlated with large boards, a London head office, non‐linear voting rights, and shares traded on multiple markets.
Resumo:
The paper presents a conceptual discussion of the characterisation and phenomenology of passive intermodulation (PIM) by the localised and distributed nonlinearities in passive devices and antennas. The PIM distinctive nature and its impact on signal distortions are examined in comparison with similar effects in power amplifiers. The main features of PIM generation are discussed and illustrated by the example of PIM due to electro-thermal nonlinearity. The issues of measurement, discrimination and modelling of PIM generated by nonlinearities in passive RF components and antennas are addressed.
Resumo:
This paper presents the results of an investigation into the utility of remote sensing (RS) using meteorological satellites sensors and spatial interpolation (SI) of data from meteorological stations, for the prediction of spatial variation in monthly climate across continental Africa in 1990. Information from the Advanced Very High Resolution Radiometer (AVHRR) of the National Oceanic and Atmospheric Administration's (NOAA) polar-orbiting meteorological satellites was used to estimate land surface temperature (LST) and atmospheric moisture. Cold cloud duration (CCD) data derived from the High Resolution Radiometer (HRR) onboard the European Meteorological Satellite programme's (EUMETSAT) Meteosat satellite series were also used as a RS proxy measurement of rainfall. Temperature, atmospheric moisture and rainfall surfaces were independently derived from SI of measurements from the World Meteorological Organization (WMO) member stations of Africa. These meteorological station data were then used to test the accuracy of each methodology, so that the appropriateness of the two techniques for epidemiological research could be compared. SI was a more accurate predictor of temperature, whereas RS provided a better surrogate for rainfall; both were equally accurate at predicting atmospheric moisture. The implications of these results for mapping short and long-term climate change and hence their potential for the study anti control of disease vectors are considered. Taking into account logistic and analytical problems, there were no clear conclusions regarding the optimality of either technique, but there was considerable potential for synergy.
Resumo:
Contested Open Spaces?: Access and control issues in Tundikhel, Kathmandu
Public spaces play a role of political, economic and cultural transformation of cities and the impact of these transformations on the nature of public space.
Urban open space(s) in Kathmandu have been an important part of the city’s urbanism. Historically they have played an important role in the city as spaces for religious, cultural, social and political and military activities during the 300 years of unified monarchy. Throughout the civil war period (Maoist insurgency between 1996 and 2006) they became material locations for political activities, and a site for protests and dharnas. In post-conflict Kathmandu, especially since the abolition of Monarchy in May 28, 2008, these spaces are increasingly seen being claimed by street hawkers, informal sellers and individuals reflecting a new set of users and functions, whereas a significant part of Tundikhel still remains under the military occupation posing important questions around access, identity and control of an important space.
Public spaces are broadly defined as crossroads where different paths and trajectories meet, sometimes overlapping and other times colliding (Madanipour, 2003). Using Tudikhel in Kathmandu, this research examines the increasing collision and contestations witnessed through social, political and neoliberal interactions. It explores how spaces are constantly
contested, negotiated and as a result reshaped through these interactions. It is observed that multiple forces are at play to gain control and access of this important open space, leading to increasing fragmentation of the space, and erosion of its historic significance both as cultural venue and a symbol of democracy in modern Nepal. It is argued that increasing disconnection of Tudikhel from wider urban setting has contributed to exacerbation of these contestations
Resumo:
High-affinity nitrate transport was examined in intact hyphae of Neurospora crassa using electrophysiological recordings to characterize the response of the plasma membrane to NO3 - challenge and to quantify transport activity. The NO3 --associated membrane current was determined using a three electrode voltage clamp to bring membrane voltage under experimental control and to compensate for current dissipation along the longitudinal cell axis. Nitrate transport was evident in hyphae transferred to NO3 --free, N-limited medium for 15 hr, and in hyphae grown in the absence of a nitrogen source after a single 2-min exposure to 100 μM NO3 -. In the latter, induction showed a latency of 40-80 min and rose in scalar fashion with full transport activity mensurable approx. 100 min after first exposure to NO3 -; it was marked by the appearance of a pronounced sensitivity of membrane voltage to extracellular NO3 - additions which, after induction, resulted in reversible membrane depolarizations of (+)54-85 mV in the presence of 50 μM NO3 -; and it was suppressed when NH4 +, was present during the first, inductive exposure to NO3 -. Voltage clamp measurements carried out immediately before and following NO3 - additions showed that the NO3 --evoked depolarizations were the consequence of an inward-directed current that appeared in parallel with the depolarizations across the entire range of accessible voltages -400 to +100 mV). Measurements of NO3 - uptake using NO3 --selective macroelectrodes indicated a charge stoichiometry for NO3 - transport of 1(+):1(NO3 -) with common K(m) and J(max) values around 25 μM and 75 pmol NO3 - cm-2sec-1, respectively, and combined measurements of pH(o) and [NO3 -](o) showed a net uptake of approx. 1 H+ with each NO3 - anion. Analysis of the NO3 - current demonstrated a pronounced voltage sensitivity within the normal physiological range between -300 and -100 mV as well as interactions between the kinetic parameters of membrane voltage, pH(o) and [NO3 -](o). Increasing the bathing pH from 5.5 to 8.0 reduced the current and the associated membrane depolarizations 2- to 4-fold. At a constant pH(o) of 6.1, driving the membrane voltage from -350 to -150 mV resulted in an approx. 3-fold reduction in the maximum current and a 5-fold rise in the apparent affinity for NO3 -. By contrast, the same depolarization effected an approx. 20% fall in the K(m) for transport as a function in [H+](o). These, and additional results are consistent with a charge-coupling stoichiometry of 2(H+) per NO anion transported across the membrane, and implicate a carrier cycle in which NO binding is kinetically adjacent to the rate-limiting step of membrane charge transit. The data concur with previous studies demonstrating a pronounced voltage-dependence to high-affinity NO3 - transport system in Arabidopsis, and underline the importance of voltage as a kinetic factor controlling NO3 - transport; finally, they distinguish metabolite repression of NO3 - transport induction from its sensitivity to metabolic blockade and competition with the uptake of other substrates that draw on membrane voltage as a kinetic substrate.
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The electron dynamics in a planar coil inductively coupled plasma (ICP) system with a capacitively biased electrode is investigated using space and phase resolved optical emission spectroscopy. The two power source frequencies are exact multiple of each other and phase-locked. In this configuration, the system is investigated when the coil is operated in both E-mode and H-mode. The results show that in a phase synchronized RF biased ICP, the electrode bias power couples with the capacitive contribution of the coil, in both E-mode and H-modes, similar to dual-frequency capacitively coupled plasmas (2f-CCPs). It is also demonstrated that in H-mode, the phase between the electrode bias frequency and the ICP coil frequency influences the electron heating, similar to the electrical asymmetry effect in 2f-CCPs.
Resumo:
This paper reports on a research project designed to discover what schools are teaching in Religious Education in Northern Ireland and what procedures are in place to maintain standards in the delivery of the subject. A search through literature shows that little research has been carried out to determine what is being taught in Religious Education in Northern Ireland. It also indicates that there are very weak systems of control to measure the effectiveness or quality of what is delivered. A survey of the websites of all Post-Primary schools in the region was used to provide some answers to the basic question of what is being taught in RE. Using content and discourse analysis of these alongside supporting documentary sources (textbooks and exam specifications), it is possible to get a clearer picture of how the Northern Ireland Core Syllabus for Religious Education and any additional curricular elements are delivered in schools. The findings show that a significant minority of schools do not publicly articulate what pupils do in religious education. In situations where the content of religious education is made clear, some definite trends are evident. Despite the existence of a statutory core syllabus, there is significant variation in what is taught in schools. The content is most divergent from the syllabus in relation to the teaching of World Religions at Key Stage 3 and at Key Stage 4 whole elements of the syllabus are neglected due to limited conformity between the syllabus and exam specifications. These results raise important questions about the systems of regulation and control of the subject in the region. In law the subject is exempt from formal inspection by the local inspection authority; instead, a form of inspection is allowed for by the Christian churches who design the syllabus, but it is a process that is either entirely neglected or entirely unreported in situations where it does occur. It is argued that these findings raise questions of more general concern for this and other regions in Europe where the teaching of religious education is largely unregulated. For example, to what extent should states take an interest in what is taught in religious education, how it is delivered, what values it promotes and how standards of teaching and learning in the subject are upheld?
Resumo:
The dynamics of self-generated magnetic B-fields produced following the interaction of a high contrast, high intensity (I > 1019W cm-2) laser beam with thin (3 μm thick) solid (Al or Au) targets is investigated experimentally and numerically. Two main sources drive the growth of B-fields on the target surfaces. B-fields are first driven by laser-generated hot electron currents that relax over ∼10-20 ps. Over longer timescales, the hydrodynamic expansion of the bulk of the target into vacuum also generates B-field induced by non-collinear gradients of density and temperature. The laser irradiation of the target front side strongly localizes the energy deposition at the target front, in contrast to the target rear side, which is heated by fast electrons over a much larger area. This induces an asymmetry in the hydrodynamic expansion between the front and rear target surfaces, and consequently the associated B-fields are found strongly asymmetric. The sole long-lasting (>30 ps) B-fields are the ones growing on the target front surface, where they remain of extremely high strength (∼8-10 MG). These B-fields have been recently put by us in practical use for focusing laser-accelerated protons [B. Albertazzi et al., Rev. Sci. Instrum. 86, 043502 (2015)]; here we analyze in detail their dynamics and structure.
Resumo:
In Italy, standards for the management of free-roaming dogs (FRDs) are defined by regional norms, generating a high variability of approaches around the country. Despite efforts carried out by the competent authorities, FRDs are still a reality impacting upon animal health and welfare and public costs. A similar scenario can be found in many other Mediterranean and Balkan counties. Here we present 14 years of data (2000–2013) retrieved from the admission dog registry of a public shelter (PS) responsible for the collection of stray dogs from one Italian province. The aim of this retrospective study was to describe the local FRD population, identifying its source and to evaluate the effectiveness of the actions implemented by the local authorities. In the investigated period, 7,475 dogs were admitted to the PS. Despite the intense sterilisation plan (mean 381.7 sterilisations per year), the overall number of dogs entering PS did not decrease consistently across the years. Results highlighted a lack of responsibility of owners by failing to sterilise and identify their dogs and allowing intact animals to roam free, therefore producing uncontrolled and unwanted litters. The current dog population management strategy, based on both sheltering and capture-neuter-release programmes, is insufficient to tackle the straying phenomenon. Educational and sterilisation programmes should be an integral part of a successfully implemented FRD control plan. Our results provide further insight on free-roaming dog population dynamics and control systems, and may have important implications for many other local contexts across Europe trying to overcome the straying phenomenon.
Resumo:
This is an analysis of the case law of the European Court of Human Rights on the obligation on States to plan and control the use of potentially lethal force by their police and military personnel. It illustrates the Court's attachment to the strict or careful scrutiny test and suggests how the Court might want to develop its jurisprudence in the future.