Multi-model ensemble predictions of atmospheric turbulence

Atmospheric turbulence is a major aviation hazard, costing the aviation industry millions of dollars each year through aircraft damage and injuries to passengers and crew. In this thesis we compare reanalysis data to climate model simulations to understand how well climate models predict the location of Clear-Air Turbulence (CAT). We then model how climate change will impact CAT on a global scale, in all four seasons and at multiple flight levels. This provides ample motivation for the second half of the thesis which aims to improve aviation turbulence forecasting by testing a multi-model ensemble forecast by combing the Met Office Global and Regional Ensemble Prediction System (MOGREPS-G) and the European Centre for Medium Range Weather Forecasting (ECMWF) Ensemble. The main results found are that climate models are able to skilfully predict the location of CAT, with the main uncertainty of the location of CAT coming from which turbulence index is the best and not from the use of a climate model. We also found CAT will increase globally in the future with climate change, for multiple aviation-relevant turbulence strength categories, at multiple flight levels and in all seasons. For ensemble forecasting we started with a single-diagnostic equally weighted multi-model ensemble and found it is at least as skilful as the single-model ensembles. This lack of significant improvement in the forecast skill could be because when increasing the forecast spread, we capture more turbulence events but also more false alarms. The relative economic value of the forecast is improved for the multi-model ensemble, particularly at low cost/loss ratios. Through combining two ensembles we gain consistency, gain more operational resilience and create one authoritative forecast whilst maintaining skill and increasing value. Extending this work further, it is found that these results apply more generally for multiple turbulence diagnostics, as the multi-model ensemble was more skilful than either of the single-model ensembles. When combining the predictors, the multi-diagnostic multi-model ensemble was more skilful than the two single-model ensembles. It was also found that an optimised 12-member ECMWF and MOGREPS-G multi-diagnostic ensemble was more skilful than the 51-member multi-diagnostic ensemble. What this therefore indicates is that a smaller ensemble spread for the individual diagnostics within a multidiagnostic ensemble is important for optimising operational forecasts in the future, which could reduce computational costs for turbulence forecasting

Estimativa do nível crítico de cobre para a soja, em solos do cerrado brasileiro.

A prática da monocultura de soja no Brasil, com o passar do tempo, pode diminuir o teor de matéria orgânica dos solos, sendo esse problema mais sério em solos arenosos. Isso tem aumentado a deficiência de certos micronutrientes, em especial o cobre (Cu). Além disso, a aplicação de adubos, muitas vezes em demasia e sem critério técnico, pode provocar problemas nutricionais de toxicidade ou deficiência desse micronutriente. Com a expansão da soja nas regiões de solos de Cerrado, passou-se para o cultivo em solos de textura média a arenosa, com teores de argila inferiores a 200 g.kg-1, CTC baixa e, originalmente, com baixo teor de Cu. Foram instalados experimentos, com a cultura da soja, em três solos do Cerrado: Latossolo Vermelho Amarelo (LVA) com 260 g.kg-1 de argila, no município de Tasso Fragoso, Latossolo Vermelho (LV) com 450 g.kg-1 de argila, no município de São Raimundo das Mangabeiras, ambos no sul do Estado do Maranhão e em Latossolo Vermelho (LV) com 550 g.kg-1 de argila, no município de Pedra Preta, sudeste do Estado do Mato Grosso, com seis doses de Cu (0; 1,25; 2,5; 5,0; 10 e 20 kg/ha), da fonte sulfato de cobre (30% de Cu) e seis níveis de saturação de bases (V%=30, 40, 50, 60, 70 e 80), com quatro repetições. Os valores estimados, acima dos quais não é esperada resposta à aplicação de cobre, são de 0,74 mg.dm-3 e 0,34 mg.dm-3 de Cu2+, pelos métodos Mehlich e DTPA, respectivamente. Portanto, as faixas de Cu no solo em mg.dm-3, para interpretação dos níveis do nutriente no solo são: para o Método Mehlich-1; Baixo 0,74. Para o Método DTPA; Baixo 0,34

Credimus

We believe that economic design and computational complexity---while already important to each other---should become even more important to each other with each passing year. But for that to happen, experts in on the one hand such areas as social choice, economics, and political science and on the other hand computational complexity will have to better understand each other's worldviews. This article, written by two complexity theorists who also work in computational social choice theory, focuses on one direction of that process by presenting a brief overview of how most computational complexity theorists view the world. Although our immediate motivation is to make the lens through which complexity theorists see the world be better understood by those in the social sciences, we also feel that even within computer science it is very important for nontheoreticians to understand how theoreticians think, just as it is equally important within computer science for theoreticians to understand how nontheoreticians think

Global response of clear-air turbulence to climate change

Clear-air turbulence (CAT) is one of the largest causes of weather-related aviation incidents. Here we use climate model simulations to study the impact that climate change could have on global CAT by the period 2050–2080. We extend previous work by analyzing eight geographic regions, two flight levels, five turbulence strength categories, and four seasons. We find large relative increases in CAT, especially in the midlatitudes in both hemispheres, with some regions experiencing several hundred per cent more turbulence. The busiest international airspace experiences the largest increases, with the volume of severe CAT approximately doubling over North America, the North Pacific, and Europe. Over the North Atlantic, severe CAT in future becomes as common as moderate CAT historically. These results highlight the increasing need to improve operational CAT forecasts and to use them effectively in flight planning, to limit discomfort and injuries among passengers and crew

On the Inability of Markov Models to Capture Criticality in Human Mobility

We examine the non-Markovian nature of human mobility by exposing the inability of Markov models to capture criticality in human mobility. In particular, the assumed Markovian nature of mobility was used to establish a theoretical upper bound on the predictability of human mobility (expressed as a minimum error probability limit), based on temporally correlated entropy. Since its inception, this bound has been widely used and empirically validated using Markov chains. We show that recurrent-neural architectures can achieve significantly higher predictability, surpassing this widely used upper bound. In order to explain this anomaly, we shed light on several underlying assumptions in previous research works that has resulted in this bias. By evaluating the mobility predictability on real-world datasets, we show that human mobility exhibits scale-invariant long-range correlations, bearing similarity to a power-law decay. This is in contrast to the initial assumption that human mobility follows an exponential decay. This assumption of exponential decay coupled with Lempel-Ziv compression in computing Fano's inequality has led to an inaccurate estimation of the predictability upper bound. We show that this approach inflates the entropy, consequently lowering the upper bound on human mobility predictability. We finally highlight that this approach tends to overlook long-range correlations in human mobility. This explains why recurrent-neural architectures that are designed to handle long-range structural correlations surpass the previously computed upper bound on mobility predictability

An Evaluation of the Return to Practice Programme (Nursing) at City University of London (2017-2018)

In response to concerns over a predicted chronic nursing shortage recent focus has been placed on Return to Practice (RTP) programmes, which aim to increase the nursing workforce by enabling former nurses to return to the profession. In order to encourage former nurses to return to practice, it is important to understand the motivations, expectations and experiences of current returnees by evaluating RTP programmes. Aims: To evaluate the RTP programme by exploring the views and experiences of returnees to nursing, and of the nursing staff who support them. Methods: This was a mixed methods study: an electronic survey of all students currently or recently on the RTP programme at City, University of London; and interviews with a range of stakeholders, including returnees, mentors and senior managers, at North East London Foundation Trust (NELFT). Descriptive statistics were used to summarise quantitative responses to the survey and Framework method was employed to analyse qualitative data. Results: Seventy-four responses to the survey were received; eight interviews were carried out with returnees, and five with NELFT staff. Overall, data suggests that the programme has been very successful: most views were positive, many were very positive. Though returnees found the course fairly challenging, they also found it largely fit for purpose. There were many useful suggestions about how to improve and promote the programme. There were also some reservations about the organisation of placements and of mentorship arrangements, the latter largely due to the difficulty of arranging for time for returnees and their mentors to work together. Recommendations: RTP programmes should be continued and if possible expanded. Wider advertising, ideally involving successful RTP returnees, should be used to attract more recruits, and funding for returnees should be maintained or increased. Higher Education Institutions (HEIs) should offer support to enable RTP nurses to return to study and to achieve their academic objectives as smoothly as possible. This may include responding to the individual learning needs of RTP nurses and allowing flexibility for students who need longer for private study. National Health Service (NHS) Trusts/Boards should ensure that Human Resource (HR) departments are willing and able to deal quickly with arrangements for employed RTP students. Processes for arranging placements should include realistic timetables for Disclosure and Barring Service (DBS) checks to be carried out. NHS providers should consider the suggestion that returnees can arrange their own placements if they wish. NHS providers should make even greater efforts to ensure that front-line staff understand the position of RTP nursing students, what they can expect from them and what their responsibilities to them are. Recent RTP graduates should be encouraged and enabled to support future RTP students. As champions of the programme, they should support the Trust in clarifying to existing staff what RTP students need and can be permitted to do

Inductively coupled plasmas sustained by an internal oscillating current

A global electromagnetic model of an inductively coupled plasma sustained by an internal oscillating current sheet in a cylindrical metal vessel is developed. The electromagnetic field structure, profiles of the rf power transferred to the plasma electrons, electron/ion number density, and working points of the discharge are studied, by invoking particle and power balance. It is revealed that the internal rf current with spatially invariable phase significantly improves the radial uniformity of the electromagnetic fields and the power density in the chamber as compared with conventional plasma sources with external flat spiral inductive coils. This configuration offers the possibility of controlling the rf power deposition in the azimuthal direction

Cisternal Organization of the Endoplasmic Reticulum during Mitosis

The endoplasmic reticulum (ER) of animal cells is a single, dynamic, and continuous membrane network of interconnected cisternae and tubules spread out throughout the cytosol in direct contact with the nuclear envelope. During mitosis, the nuclear envelope undergoes a major rearrangement, as it rapidly partitions its membrane-bound contents into the ER. It is therefore of great interest to determine whether any major transformation in the architecture of the ER also occurs during cell division. We present structural evidence, from rapid, live-cell, three-dimensional imaging with confirmation from high-resolution electron microscopy tomography of samples preserved by high-pressure freezing and freeze substitution, unambiguously showing that from prometaphase to telophase of mammalian cells, most of the ER is organized as extended cisternae, with a very small fraction remaining organized as tubules. In contrast, during interphase, the ER displays the familiar reticular network of convolved cisternae linked to tubules