A review of offshore wind power development in the United Kingdom

Currently wind power is dominated by onshore wind farms. However, as the demand for power grows driven by security of energy supply issues, dwindling fossil fuel supplies and greenhouse gas emissions reduction targets, offshore wind power will develop rapidly because of the decline of viable onshore sites. The United Kingdom has a target of 21% renewable electricity by 2020 and this is expected to come mostly from wind power. Britain is the most active internationally in terms of offshore wind farm development with almost 48GW in some stage of development. In addition the Scottish Government, the Northern Ireland Executive and the Government of Ireland undertook the 'Irish-Scottish Links on Energy Study' (ISLES), which examined the feasibility of creating an offshore interconnected transmission network and subsea electricity grid based on renewable energy sources off the coast of western Scotland and the Irish Sea. The aim of this paper is to provide an appraisal of offshore wind power development with a focus on the United Kingdom. © 2013 IEEE.

Adaptive backstepping droop controller design for multi-terminal high-voltage direct current systems

Wind power is one of the most developed renewable energy resources worldwide. To integrate offshore wind farms to onshore grids, the high-voltage direct current (HVDC) transmission cables interfaced with voltage source converters (VSCs) are considered to be a better solution than conventional approaches. Proper DC voltage indicates successive power transfer. To connect more than one onshore grid, the DC voltage droop control is one of the most popular methods to share the control burden between different terminals. However, the challenges are that small droop gains will cause voltage deviations, while higher droop gain settings will cause large oscillations. This study aims to enhance the performance of the traditional droop controller by considering the DC cable dynamics. Based on the backstepping control concept, DC cables are modelled with a series of capacitors and inductors. The final droop control law is deduced step-by-step from the original remote side. At each step the control error from the previous step is considered. Simulation results show that both the voltage deviations and oscillations can be effectively reduced using the proposed method. Further, power sharing between different terminals can be effectively simplified such that it correlates linearly with the droop gains, thus enabling simple yet accurate system operation and control.

Digital Dermatitis in Dairy Cows: A Review of Risk Factors and Potential Sources of Between-Animal Variation in Susceptibility

Digital dermatitis (DD) is a bacterial disease that primarily affects the skin on the heels of cattle. It is a major cause of lameness in dairy cows and a significant problem for the dairy industry in many countries, causing reduced animal welfare and economic loss. A wide range of infection levels has been found on infected farms, prompting investigations into both farm level and animal level risk factors for DD occurrence. There also appears to be individual variation between animals in susceptibility to the disease. The identification of factors affecting individual variation in susceptibility to DD might allow changes in breeding policies or herd management which could be used to reduce DD prevalence. Factors mentioned in the literature as possibly influencing individual variation in susceptibility to DD include physical factors such as hoof conformation and properties of the skin, physiological factors such as the efficacy of the immune response, and behavioural factors such as standing half in cubicles. Further work is required to determine the influence of these factors, identify the genetic basis of variation, clarify the level of heritability of DD susceptibility and to determine how this is correlated with production and health traits currently used in breeding programmes.

Quantifying heritable variation in fitness-related traits of wild, farmed and hybrid Atlantic salmon families in a wild river environment

Farmed fish are typically genetically different from wild conspecifics. Escapees from fish farms may contribute one-way gene flow from farm to wild gene pools, which can depress population productivity, dilute local adaptations and disrupt coadapted gene complexes. Here, we reanalyse data from two experiments (McGinnity et al., 1997, 2003) where performance of Atlantic salmon (Salmo salar) progeny originating from experimental crosses between farm and wild parents (in three different cohorts) were measured in a natural stream under common garden conditions. Previous published analyses focussed on group-level differences but did not account for pedigree structure, as we do here using modern mixed-effect models. Offspring with one or two farm parents exhibited poorer survival in their first and second year of life compared with those with two wild parents and these group-level inferences were robust to excluding outlier families. Variation in performance among farm, hybrid and wild families was generally similar in magnitude. Farm offspring were generally larger at all life stages examined than wild offspring, but the differences were moderate (5–20%) and similar in magnitude in the wild versus hatchery environments. Quantitative genetic analyses conducted using a Bayesian framework revealed moderate heritability in juvenile fork length and mass and positive genetic correlations (>0.85) between these morphological traits. Our study confirms (using more rigorous statistical techniques) previous studies showing that offspring of wild fish invariably have higher fitness and contributes fresh insights into family-level variation in performance of farm, wild and hybrid Atlantic salmon families in the wild. It also adds to a small, but growing, number of studies that estimate key evolutionary parameters in wild salmonid populations. Such information is vital in modelling the impacts of introgression by escaped farm salmon.

Analysis of Transmission Loss with Droop Control in a Multi-Terminal HVDC System

High Voltage Direct Current (HVDC) electric power transmission is a promising technology for integrating offshore wind farms and interconnecting power grids in different regions. In order to maintain the DC voltage, droop control has been widely used. Transmission line loss constitutes an import part of the total power loss in a multi-terminal HVDC scheme. In this paper, the relation between droop controller design and transmission loss has been investigated. Different MTDC layout configurations are compared to examine the effect of droop controller design on the transmission loss.

Major and trace elements in milk and Halloumi cheese as markers for authentication of goat feeding regimes and geographical origin

Sixty samples of milk, Halloumi cheese and local grazing plants (i.e. shrubs) were collected over a year from dairy farms located on three different locations of Cyprus. Major and trace elements were quantified using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Milk and Halloumi cheese produced in different geographical locations presented significant differences in the concentration of some of the elements analysed. Principal component analysis showed grouping of samples according to the region of production for both milk and cheese samples. These findings show that the assay of elements can provide useful fingerprints for the characterisation of dairy products.

Whole Genome Sequencing Reveals Local Transmission Patterns of Mycobacterium bovis in Sympatric Cattle and Badger Populations

Whole genome sequencing (WGS) technology holds great promise as a tool for the forensic epidemiology of bacterial pathogens. It is likely to be particularly useful for studying the transmission dynamics of an observed epidemic involving a largely unsampled 'reservoir' host, as for bovine tuberculosis (bTB) in British and Irish cattle and badgers. BTB is caused by Mycobacterium bovis, a member of the M. tuberculosis complex that also includes the aetiological agent for human TB. In this study, we identified a spatio-temporally linked group of 26 cattle and 4 badgers infected with the same Variable Number Tandem Repeat (VNTR) type of M. bovis. Single-nucleotide polymorphisms (SNPs) between sequences identified differences that were consistent with bacterial lineages being persistent on or near farms for several years, despite multiple clear whole herd tests in the interim. Comparing WGS data to mathematical models showed good correlations between genetic divergence and spatial distance, but poor correspondence to the network of cattle movements or within-herd contacts. Badger isolates showed between zero and four SNP differences from the nearest cattle isolate, providing evidence for recent transmissions between the two hosts. This is the first direct genetic evidence of M. bovis persistence on farms over multiple outbreaks with a continued, ongoing interaction with local badgers. However, despite unprecedented resolution, directionality of transmission cannot be inferred at this stage. Despite the often notoriously long timescales between time of infection and time of sampling for TB, our results suggest that WGS data alone can provide insights into TB epidemiology even where detailed contact data are not available, and that more extensive sampling and analysis will allow for quantification of the extent and direction of transmission between cattle and badgers. © 2012 Biek et al.

Estimation of Mycobacterium avium subsp. paratuberculosis load in raw bulk tank milk in Emilia-Romagna Region (Italy) by qPCR

Consumption of milk and dairy products is considered one of the main routes of human exposure to Mycobacterium avium subsp. paratuberculosis (MAP). Quantitative data on MAP load in raw cows’ milk are essential starting point for exposure assessment. Our study provides this information on a regional scale, estimating the load of MAP in bulk tank milk (BTM) produced in Emilia-Romagna region (Italy). The survey was carried out on 2934 BTM samples (88.6% of the farms herein present) using two different target sequences for qPCR (f57 and IS900). Data about the performances of both qPCRs are also reported, highlighting the superior sensitivity of IS900-qPCR. Seven hundred and eighty-nine samples tested MAP-positive (apparent prevalence 26.9%) by IS900 qPCR. However, only 90 of these samples were quantifiable by qPCR. The quantifiable samples contained a median load of 32.4 MAP cells mL−1 (and maximum load of 1424 MAP cells mL−1). This study has shown that a small proportion (3.1%) of BTM samples from Emilia-Romagna region contained MAP in excess of the limit of detection (1.5 × 101 MAP cells mL−1), indicating low potential exposure for consumers if the milk subsequently undergoes pasteurization or if it is destined to typical hard cheese production.

Use of bacterial whole-genome sequencing to investigate local persistence and spread in bovine tuberculosis

Mycobacterium bovis is the causal agent of bovine tuberculosis, one of the most important diseases currently facing the UK cattle industry. Here, we use high-density whole genome sequencing (WGS) in a defined sub-population of M. bovis in 145 cattle across 66 herd breakdowns to gain insights into local spread and persistence. We show that despite low divergence among isolates, WGS can in principle expose contributions of under-sampled host populations to M. bovis transmission. However, we demonstrate that in our data such a signal is due to molecular type switching, which had been previously undocumented for M. bovis. Isolates from farms with a known history of direct cattle movement between them did not show a statistical signal of higher genetic similarity. Despite an overall signal of genetic isolation by distance, genetic distances also showed no apparent relationship with spatial distance among affected farms over distances <5 km. Using simulations, we find that even over the brief evolutionary timescale covered by our data, Bayesian phylogeographic approaches are feasible. Applying such approaches showed that M. bovis dispersal in this system is heterogeneous but slow overall, averaging 2 km/year. These results confirm that widespread application of WGS to M. bovis will bring novel and important insights into the dynamics of M. bovis spread and persistence, but that the current questions most pertinent to control will be best addressed using approaches that more directly integrate WGS with additional epidemiological data.

Wave Fields around Wave Energy Converter Arrays

Wave energy converters, by their nature, extract large amounts of energy
from incident waves. If the industry is to progress such that wave energy
becomes a significant provider of power in the future, large wave farms will
be required. Presently, consenting for these sites is a long and problematic
process, mainly due to a lack of knowledge of the potential environmental
impacts. Accurate numerical modelling of the effect of wave energy extraction
on the wave field and subsequent evaluation of changes to coastal
processes is therefore required. Modelling the wave field impact is also
necessary to allow optimum wave farm configurations to be determined.
This thesis addresses the need for more accurate representation of wave
energy converters in numerical models so that the effect on the wave field,
and subsequently the coastal processes, may be evaluated. Using a hybrid
of physical and numerical modelling (MIKE21 BW and SW models) the
effect of energy extraction and operation of a WEC array on the local wave
climate has been determined.
The main outcomes of the thesis are: an improved wave basin facility, in
terms of wave climate homogeneity, reducing the standard deviation of wave
amplitude by up to 50%; experimental measurement of the wave field around
WEC arrays, showing that radiated waves account for a significant proportion
of the wave disturbance; a new representation method of WECs for use
with standard numerical modelling tools, validated against experimental
results.
The methodology and procedures developed here allow subsequent evaluation
of changes to coastal processes and sediment transport due to WEC
arrays.

Investigating Tools used to Analyse the Impact of a Wave Farm on the surrounding Wave Field

For wave energy to become commercially viable, it is predicted that wave energy converters (WECs) will need to be installed in large wave farms. This will required an extensive environmental impact study. Assessments of impacts of these sites requires prior numerical modelling however the available tools have not been fully validated.
This project investigates the area surrounding an array of five scaled WEC models using experimental techniques. It then assesses the suitability of numerical tools to be validated with this experimental data. Validated numerical tools could then be used to predict parameters relating to the models such as reflection and transmission coefficients.
The physical aspect of this project was conducted in the Portaferry wave basin owned by Queen’s University Belfast. The device studied was a bottom hinged oscillating wave surge converter (OWSC) which penetrates the surface (similar to the Oyster device). The models were tested at 40th scale.

A Review of Numerical Modelling of Wave Energy Converter Arrays

Large-scale commercial exploitation of wave energy is certain to require the deployment of wave energy converters (WECs) in arrays, creating ‘WEC farms���. An understanding of the hydrodynamic interactions in such arrays is essential for determining optimum layouts of WECs, as well as calculating the area of ocean that the farms will require. It is equally important to consider the potential impact of wave farms on the local and distal wave climates and coastal processes; a poor understanding of the resulting environmental impact may hamper progress, as it would make planning consents more difficult to obtain. It is therefore clear that an understanding the interactions between WECs within a farm is vital for the continued development of the wave energy industry.To support WEC farm design, a range of different numerical models have been developed, with both wave phase-resolving and wave phase-averaging models now available. Phase-resolving methods are primarily based on potential flow models and include semi-analytical techniques, boundary element methods and methods involving the mild-slope equations. Phase-averaging methods are all based around spectral wave models, with supra-grid and sub-grid wave farm models available as alternative implementations.The aims, underlying principles, strengths, weaknesses and obtained results of the main numerical methods currently used for modelling wave energy converter arrays are described in this paper, using a common framework. This allows a qualitative comparative analysis of the different methods to be performed at the end of the paper. This includes consideration of the conditions under which the models may be applied, the output of the models and the relationship between array size and computational effort. Guidance for developers is also presented on the most suitable numerical method to use for given aspects of WEC farm design. For instance, certain models are more suitable for studying near-field effects, whilst others are preferable for investigating far-field effects of the WEC farms. Furthermore, the analysis presented in this paper identifies areas in which the numerical modelling of WEC arrays is relatively weak and thus highlights those in which future developments are required.

Factores que influenciam o peso e crescimento de cabritos da raça Murciana-granadina, em aleitamento artificial

A exploração caprina de leite tem evoluído no sentido de alguma intensificação, com recurso a raças de elevado potencial produtivo, de que é exemplo a raça Murciana- Granadina. O leite constitui a principal fonte de receita destas explorações. Complementarmente, vendem animais para carne e, as de melhor nível genético, animais para reprodutores. Analisaram-se os pesos de 241 cabritos da raça Murciana-Granadina, numa exploração comercial, com o objectivo de quantificar os pesos e crescimento de cabritos, e identificar os factores que os influenciam. Os cabritos foram aleitados artificialmente, em regime ad libitum, com leite de substituição comercial, dispondo ainda de concentrado comercial, feno de luzerna e palha. Os cabritos foram pesados ao nascimento e, posteriormente, semanalmente, até aos 60 dias de idade. Calcularam-se os respetivos pesos ajustados, bem como os ganhos médios diários, a diferentes idades padrão. Procedeu-se a uma análise de variância com um modelo linear que incluiu os efeitos da época de parto, tipo de parto, sexo e idade da cabra. Foram registados pesos superiores nos partos simples e duplos, relativamente aos triplos, e nos machos, relativamente às fêmeas. Os ganhos médios diários, a partir do mês de idade, registaram valores inferiores na época inverno-primavera, comparativamente com a época primavera-verão. Dairy goat farming has evolved towards intensification, with increased use of high milk-yielding breeds, including the Murciano-Granadina breed. Milk is the main source of farm income. Secondary income sources are the sale of animals for meat and, in genetically superior herds, the sale of breeding animals. The weights of 241 commercial farms artificially reared Murciano-Granadina kids were analyzed with the objective of quantifying weight and growth and identifying variation factors. Kids were artificially reared to weaning, on ad libitum commercial milk replacer, commercial concentrate, lucerne hay and straw. Kids were weighed at birth and at weekly intervals until 60 days of age. Age adjusted weights and growth-rates were calculated. A variance analysis was performed with a model including the effects of season of birth, number of kids per kidding, sex and age of dam. Single and twin-born kids had higher weights than triplets, and males had higher weights than females. Average daily gain after one month of age was lower for kids born in winter-spring than for those born in spring-summer

Isolation of Aeromonas hydrophila in piglets

The production of Alentejano breed pig started a recovery two decades ago due to increasing demand for gourmet products. These pigs are raised in rotational semi-extensive or extensive outdoor production systems in the “Montado” (green and cork oak forest), grazing and feeding acorns and other associated food resources. Bacteria of the genus Aeromonas are considered as emerging pathogens of importance for man and animals, but its involvement in swine is not well documented. In the context of a study made at the University of Évora to assess the specific diseases of Alentejano swine, diseased piglets from two farms were submitted for pathological and bacteriological examinations. Pathological examinations revealed changes characteristic of septicemia, and Aeromonas hydrophila was isolated in pure culture from multiple organs of piglets from both farms. Antibiotic sensitivity tests showed that the isolates from one of the farms were susceptible to gentamicin, oxitetracycline, neomycin, enrofloxacin, colistin sulfate, trimethoprim, ceftiofur, and amoxicillin plus clavulanic acid. In contrast, the A. hydrophila isolated in the other farm was resistant to all drugs tested but enrofloxacin. This is the first report in the world showing the relationship between septicemia and A. hydrophila infection in piglets. The importance of this finding is further reinforced by the fact that these bacteria can be highly resistant to antimicrobial agents.

Pesquisa de Campylobacter fetus em amostras prepuciais de touros da região do Alentejo

A bactéria Campylobacter fetus divide-se em duas subespécies C. fetus fetus (Cff) e C. fetus venerealis (Cfv). Cfv é o agente patogénico responsável pela campilobacteriose genital bovina (CGB), uma doença que provoca infertilidade em vacas. Cff pode provocar abortos esporádicos, mas não provoca CGB. Neste trabalho procedeu-se à pesquisa de C. fetus por imunofluorescência direta (IFD) em 117 amostras prepuciais, recolhidas por raspagem, de touros pertencentes a 25 explorações na região do Alentejo. A prevalência real de CGB na amostra, considerando a sensibilidade e especificidade do teste, foi de 52,89% de animais e 80% de explorações. Foi também realizada uma comparação entre dois testes de diagnóstico de CGB, a IFD e o isolamento bacteriológico. O isolamento bacteriológico foi difícil de executar e a presença de bactérias contaminantes foi bastante problemática, levando a resultados falso-negativos. A sua correlação com a IFD foi muito baixa, tendo esta revelado ser muito mais sensível; #### Abstract Search for Campylobacter fetus in preputial samples of bulls from Alentejo region The bacteria Campylobacter fetus comprises two subspecies, C. fetus fetus (Cff) and C. fetus venerealis (Cfv). Cfv is the pathogen responsible for bovine genital campylobacteriosis (BGC), a disease that causes infertility in cows. Cff may lead to sporadic miscarriages, but does not cause BGC. In this work we searched for C. fetus by direct immunofluorescence (DIF) in 117 preputial samples, collected by scraping, from bulls from Alentejo region. The actual prevalence of BGC, considering the sensitivity and specificity of the test was 52.89% of animals and 80 % of farms. It was also performed a comparison between two BGC diagnostic tests, bacterial isolation and DIF. The bacterial isolation was difficult to perform and the presence of bacterial contaminants was very problematic, leading to false-negative results. The presence of bacterial contaminants in bacterial isolation was problematic, leading to false-negative results. Its correlation with DIF was quite low, and DIF proved to be much more sensitive.