An arc control and protection system for the JET lower hybrid antenna based on an imaging system.

Arcs are the potentially most dangerous events related to Lower Hybrid (LH) antenna operation. If left uncontrolled they can produce damage and cause plasma disruption by impurity influx. To address this issue an arc real time control and protection imaging system for the Joint European Torus (JET) LH antenna has been implemented. The LH system is one of the additional heating systems at JET. It comprises 24 microwave generators (klystrons, operating at 3.7 GHz) providing up to 5 MW of heating and current drive to the JET plasma. This is done through an antenna composed of an array of waveguides facing the plasma. The protection system presented here is based primarily on an imaging arc detection and real time control system. It has adapted the ITER like wall hotspot protection system using an identical CCD camera and real time image processing unit. A filter has been installed to avoid saturation and spurious system triggers caused by ionization light. The antenna is divided in 24 Regions Of Interest (ROIs) each one corresponding to one klystron. If an arc precursor is detected in a ROI, power is reduced locally with subsequent potential damage and plasma disruption avoided. The power is subsequently reinstated if, during a defined interval of time, arcing is confirmed not to be present by image analysis. This system was successfully commissioned during the restart phase and beginning of the 2013 scientific campaign. Since its installation and commissioning, arcs and related phenomena have been prevented. In this contribution we briefly describe the camera, image processing, and real time control systems. Most importantly, we demonstrate that an LH antenna arc protection system based on CCD camera imaging systems works. Examples of both controlled and uncontrolled LH arc events and their consequences are shown.

Changes in food neophobia and dietary habits of international students.

BACKGROUND: International study is becoming more prevalent, yet aspects such as food neophobia often militate against visiting students consuming a nutritionally balanced diet. The present study aimed to evaluate the extent to which international post-graduate students experience food neophobia, how this might vary by nationality and other demographic characteristics, and how acculturation might manifest itself in students' dietary behaviour. METHODS: International students (n = 228) attending a Masters course were invited to complete a validated food neophobia and dietary habits questionnaire during their first week at university. The questionnaire was subsequently re-administered to the same students approximately 4 and 8 months later. RESULTS: In total, 226 usable responses were analysed (124, 58 and 44, respectively) for the first, second and final data collection. Perhaps surprisingly, the overall food neophobia scores increased from an mean (SD) initial value of 27.95 (16.95) to 33.67 (33.67) after 3 months, although, when comparing European and Asian students, only the former were significantly different (P < 0.05). Both Asian and European students reported small but not significant changes in their eating habits, although, after 3 months, significantly (P = <0.05) fewer changes were reported. No significant changes were reported in students' perceived healthiness of their diets either by nationality or over time. CONCLUSIONS: Understanding the complexities of food neophobia, other aspects of dietary change and at what point these changes might take place in the acculturation process when students arrive in the UK needs to be fully understood if a climate for positive learning is to be established.

Sensitivity analysis predicts that the ERK-pMEK interaction regulates ERK nuclear translocation.

Following phosphorylation, nuclear translocation of the mitogen-activated protein kinases (MAPKs), ERK1 and ERK2, is critical for both gene expression and DNA replication induced by growth factors. ERK nuclear translocation has therefore been studied extensively, but many details remain unresolved, including whether or not ERK dimerisation is required for translocation. Here, we simulate ERK nuclear translocation with a compartmental computational model that includes systematic sensitivity analysis. The governing ordinary differential equations are solved with the backward differentiation formula and decoupled direct methods. To better understand the regulation of ERK nuclear translocation, we use this model in conjunction with a previously published model of the ERK pathway that does not include an ERK dimer species and with experimental measurements of nuclear translocation of wild-type ERK and a mutant form, ERK1-4, which is unable to dimerise. Sensitivity analysis reveals that the delayed nuclear uptake of ERK1-4 compared to that of wild-type ERK1 can be explained by the altered interaction of ERK1-4 with phosphorylated MEK (MAPK/ERK kinase), and so may be independent of dimerisation. Our study also identifies biological experiments that can verify this explanation.

Stochastic simulations of ErbB homo and heterodimerisation: potential impacts of receptor conformational state and spatial segregation.

ErbB overexpression is linked to carcinogenesis. It is hypothesised that this is due to increased receptor density and receptor clustering, leading to increased receptor dimerisation and activation. Herein, spatial stochastic simulations have been performed to shed light receptor dimerisation processes. First, ligand-independent homodimerisation, is considered, based upon constitutive oligomerisation estimates (14%) in A431 cells that overexpress epidermal growth factor receptor (EGFR). When autocrine stimulation is blocked, ligand-independent EGFR activation is demonstrated by persistent, low levels of phosphorylation. The possibility that ligand-independent signalling is due to the fluctuation of EGFR conformation is considered. The agent-based model predicts the frequency (expressed as a probability) that uniformly distributed receptors would need to flux to the open conformation to reach 14% EGFR dimers at high receptor density. Simulations suggest that ligand-independent EGFR homodimerisation is highly density dependent, since collisions between 'open', dimerisation-competent receptors are a rare event at low receptor levels. Simulations that incorporate receptor clustering lower the threshold for homodimerisation of unoccupied receptors as well as the estimate of the probability for fluxing to the dimer-competent conformation. The impact of ErbB receptor clustering patterns on hetero and homodimerisation rates is also considered, using immunoelectron microscopy data derived from SKBR3 breast cancer cells that express ErbB2>>EGFR>ErbB3. Partial spatial segregation of ErbB receptors has a profound effect on simulated heterodimerisation rates. Despite the general assumption that ErbB2 is a preferred heterodimerising partner for other ErbBs, it is predicted that most ErbB2 will form homodimers. Overall, it is proposed that both receptor density and membrane spatial organisation contribute to the carcinogenesis process.

Hospital food service: a comparative analysis of systems and introducing the 'Steamplicity' concept.

BACKGROUND: Patient meals are an integral part of treatment hence the provision and consumption of a balanced diet, essential to aid recovery. A number of food service systems are used to provide meals and the Steamplicity concept has recently been introduced. This seeks, through the application of a static, extended choice menu, revised patient ordering procedures, new cooking processes and individual patient food heated/cooked at ward level, to address some of the current hospital food service concerns. The aim of this small-scale study, therefore, was to compare a cook-chill food service operation against Steamplicity. Specifically, the goals were to measure food intake and wastage at ward level; 'stakeholders' (i.e. patients, staff, etc.) satisfaction with both systems; and patients' acceptability of the food provided. METHOD: The study used both quantitative (self-completed patient questionnaires, n = 52) and qualitative methods (semi-structured interviews, n = 16) with appropriate stakeholders including medical and food service staff, patients and their visitors. RESULTS: Patients preferred the Steamplicity system overall and in particular in terms of food choice, ordering, delivery and food quality. Wastage was considerably less with the Steamplicity system, although care must be taken to ensure that poor operating procedures do not negate this advantage. When the total weight of food consumed in the ward at each meal is divided by the number of main courses served, at lunch, the mean intake with the cook-chill system was 202 g whilst that for the Steamplicity system was 282 g and for the evening meal, 226 g compared with 310 g. CONCLUSIONS: The results of this small study suggest that Steamplicity is more acceptable to patients and encourages the consumption of larger portions. Further evaluation of the Steamplicity system is warranted.

Sea-level performance in runners using altitude tents: a field study.

In this study of effects of simulated altitude exposure on sea-level performance, 10 competitive runners slept in a hypoxic environment achieved with tents for 9.8+/-1.3 h.d(-1) (mean+/-standard deviation) for 24 days-30 days at 2500-3500 m (PIO2=117-103 mmHg) above sea level. The altitude group and a control group of 10 runners performed usual training (PIO2=149 mmHg). At approximately 4-wk intervals before and after exposure both groups performed an incremental test for lactate threshold. The altitude group performed an additional test, a treadmill run to exhaustion lasting approximately 5 min. One week following exposure lactate threshold speed of the altitude group relative to the control group increased by 1.2% (90% likely limits +/-3.1%), but the effect became slightly negative after controlling for baseline differences in running speed between the groups. A 16% increase in time to exhaustion was observed in the altitude group, equivalent to a 1.9% (+/-1.4%) increase in speed in a time trial. Change in performance had an unclear relationship to total altitude exposure, genotype for angiotensin converting enzyme, and change in haemoglobin concentration. Our findings are consistent with little or no effect of use of altitude tents on sea-level performance.

A comparison of energy intake between eating positions in a NHS hospital--a pilot study.

Malnutrition and the under-consumption of food in hospitals is prevalent and in UK hospitals, the consumption of meals is mainly a solitude event, despite evidence to show that eating in the presence of others can actually increase food intake. Dietary data were collected for three consecutive 24 h periods (n=13) from patients who consumed their meals either in bed, at the side of the bed or in the presence of others. Results show a significant increase (p<0.05) in the mean daily energy intake for those sitting around a table in the presence of others. Although a small pilot study, the results confirm the value of social facilitation in improving the under-consumption of food when in hospital.

Suitability and utility of computational analysis tools: characterization of erythrocyte parameter variation.

Systems engineering can provide insights into multivariate regulatory networks and pooling in complex biological networks that cannot be fully interpreted through experiments alone. Herein, we analyzed the use of phase planes, modal and time-lagged correlation (TLC) analyses of the human erythrocyte to explore the utility of these techniques for understanding the effect of single parameter changes on the behavior of a metabolic network. Specifically, several parameters in key regulatory steps in erythrocyte glycolysis, Rapoport-Leubering bypass, pentose phosphate pathway, adenosine metabolism, and membrane transport were perturbed. The most sensitive parameters were identified based on the steady-state metabolite concentration changes and were explored further. Modal analysis identified relevant time scales for each parameter change. These time scales were further explored using phase plane and TLC analyses. Phase plane and TLC both inferred pooling changes, while TLC also identified changes in the regulatory network structure that resulted from various parameter changes. Each method has strengths and weaknesses for exploring and gaining insight into complex biological networks.

Quantitative analysis of Escherichia coli metabolic phenotypes within the context of phenotypic phase planes.

In silico models of Escherichia coli metabolism have been developed to predict metabolic behavior and propose experimentally testable hypotheses. However, a thorough assessment of the metabolic phenotype requires well-designed experimentation and reproducible experimental techniques. A method for the quantitative analysis of E. coli metabolism in vivo within the framework of in silico phenotypic phase plane analysis is presented. Using this approach, we have quantitatively studied E. coli metabolism in various environmental conditions and nutritional media. Our experimental methodology, in combination with steady-state metabolic models, can be used to study biological properties and evaluate the metabolic capabilities of microbes.

Fruit and vegetables--attitudes and knowledge of primary school children.

OBJECTIVES: To evaluate whether children, aged 8-11 years could correctly identify commonly available fruit and vegetables; to assess the acceptability of these; and to gain a broad understanding of children's perceptions of 'healthy eating'. METHODS: Fruit and vegetables used were those readily available in retail outlets in the UK. Data were collected from three year-groups (n = 221) using a questionnaire supported by semistructured interviews and discussions. RESULTS: Overall, fruit was more popular than vegetables and recognition of fruit better; melons being the least well identified. Recognition of vegetables increased with age; the least well identified being cabbage which was confused with lettuce by 32, 16 and 17% of pupils in their respective age groups. Most children (75%) were familiar with the term healthy eating, citing school (46%) as the most common source of information. Pupils showed an awareness and understanding of current recommendations for a balanced diet, although the message has become confused. CONCLUSIONS: If fresh fruit and vegetables are to form part of a balanced diet, the 'health message' needs to be clear. Fruit is well liked; vegetables are less acceptable with many being poorly recognized, factors which need to be addressed.

The complete phosphotransferase system in Escherichia coli.

We here tabulate and describe all currently recognized proteins of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) and their homologues encoded within the genomes of sequenced E. coli strains. There are five recognized Enzyme I homologues and six recognized HPr homologues. A nitrogen-metabolic PTS phosphoryl transfer chain encoded within the rpoN and ptsP operons and a tri-domain regulatory PTS protein encoded within the dha (dihydroxyacetone catabolic) operon, probably serve regulatory roles exclusively. In addition to several additional putative regulatory proteins, there are 21 (and possibly 22) recognized Enzyme II complexes. Of the 21 Enzyme II complexes, 7 belong to the fructose (Fru) family, 7 belong to the glucose (Glc) family, and 7 belong to the other PTS permease families. All of these proteins are briefly described, and phylogenetic data for the major families are presented.

Dynamic simulation of the human red blood cell metabolic network.

We have developed a Mathematica application package to perform dynamic simulations of the red blood cell (RBC) metabolic network. The package relies on, and integrates, many years of mathematical modeling and biochemical work on red blood cell metabolism. The extensive data regarding the red blood cell metabolic network and the previous kinetic analysis of all the individual components makes the human RBC an ideal 'model' system for mathematical metabolic models. The Mathematica package can be used to understand the dynamics and regulatory characteristics of the red blood cell.

Metabolic modeling of microbial strains in silico.

The large volume of genome-scale data that is being produced and made available in databases on the World Wide Web is demanding the development of integrated mathematical models of cellular processes. The analysis of reconstructed metabolic networks as systems leads to the development of an in silico or computer representation of collections of cellular metabolic constituents, their interactions and their integrated function as a whole. The use of quantitative analysis methods to generate testable hypotheses and drive experimentation at a whole-genome level signals the advent of a systemic modeling approach to cellular and molecular biology.

In silico predictions of Escherichia coli metabolic capabilities are consistent with experimental data.

A significant goal in the post-genome era is to relate the annotated genome sequence to the physiological functions of a cell. Working from the annotated genome sequence, as well as biochemical and physiological information, it is possible to reconstruct complete metabolic networks. Furthermore, computational methods have been developed to interpret and predict the optimal performance of a metabolic network under a range of growth conditions. We have tested the hypothesis that Escherichia coli uses its metabolism to grow at a maximal rate using the E. coli MG1655 metabolic reconstruction. Based on this hypothesis, we formulated experiments that describe the quantitative relationship between a primary carbon source (acetate or succinate) uptake rate, oxygen uptake rate, and maximal cellular growth rate. We found that the experimental data were consistent with the stated hypothesis, namely that the E. coli metabolic network is optimized to maximize growth under the experimental conditions considered. This study thus demonstrates how the combination of in silico and experimental biology can be used to obtain a quantitative genotype-phenotype relationship for metabolism in bacterial cells.

Flux-balance analysis of mitochondrial energy metabolism: consequences of systemic stoichiometric constraints.

Mitochondrial metabolism is a critical component in the functioning and maintenance of cellular organs. The stoichiometry of biochemical reaction networks imposes constraints on mitochondrial function. A modeling framework, flux-balance analysis (FBA), was used to characterize the optimal flux distributions for maximal ATP production in the mitochondrion. The model predicted the expected ATP yields for glucose, lactate, and palmitate. Genetic defects that affect mitochondrial functions have been implicated in several human diseases. FBA can characterize the metabolic behavior due to genetic deletions at the metabolic level, and the effect of mutations in the tricarboxylic acid (TCA) cycle on mitochondrial ATP production was simulated. The mitochondrial ATP production is severely affected by TCA-cycle mutations. In addition, the model predicts the secretion of TCA-cycle intermediates, which is observed in clinical studies of mitochondriopathies such as those associated with fumarase deficiency. The model provides a systemic perspective to characterize the effect of stoichiometric constraints and specific metabolic fluxes on mitochondrial function.

A preliminary assessment of two hospital food service systems using parameters of food safety and consumer opinion.

The goal of any hospital caterer should be to provide food that meets nutritional requirements, satisfies the patient, improves morale and is microbiologically safe. Food distribution to hospital wards plays a critical role. The aim of this study was to compare two hospital food service systems using parameters of food safety and consumer opinion. An NHS hospital was selected where food delivery was due to change from a plated system to a cafeteria trolley system. Samples (50 g) of dishes (n = 27) considered to be high-risk were collected for three consecutive days from breakfast, lunch and supper meals. The samples were taken from a pre-ordered tray (similar to that of a patient) in the plated system and from the trolley on the ward in the cafeteria system of meal delivery (approximately six months after its introduction). Consumer opinions cards (n = 180) were distributed and interviews also conducted. Microbiologically, the quality of food items delivered by both systems was satisfactory. However, concern was raised with the plated system, not for hot foods cooling down but for chilled foods warming up and being sustained in ambient conditions. Overall consumer satisfaction and experience was enhanced with the trolley system. Food was hotter and generally perceived to be of a better quality. Satisfaction with cold desserts was not dependent on the delivery system.

Robustness analysis of the Escherichia coli metabolic network.

Genomic, biochemical, and strain-specific data can be assembled to define an in silico representation of the metabolic network for a select group of single cellular organisms. Flux-balance analysis and phenotypic phase planes derived therefrom have been developed and applied to analyze the metabolic capabilities and characteristics of Escherichia coli K-12. These analyses have shown the existence of seven essential reactions in the central metabolic pathways (glycolysis, pentose phosphate pathway, tricarboxylic acid cycle) for the growth in glucose minimal media. The corresponding seven gene products can be grouped into three categories: (1) pentose phosphate pathway genes, (2) three-carbon glycolytic genes, and (3) tricarboxylic acid cycle genes. Here we develop a procedure that calculates the sensitivity of optimal cellular growth to altered flux levels of these essential gene products. The results indicate that the E. coli metabolic network is robust with respect to the flux levels of these enzymes. The metabolic flux in the transketolase and the tricarboxylic acid cycle reactions can be reduced to 15% and 19%, respectively, of the optimal value without significantly influencing the optimal growth flux. The metabolic network also exhibited robustness with respect to the ribose-5-phosphate isomerase, and the ribose-5-phosephate isomerase flux was reduced to 28% of the optimal value without significantly effecting the optimal growth flux. The metabolic network exhibited limited robustness to the three-carbon glycolytic fluxes both increased and decreased. The development presented another dimension to the use of FBA to study the capabilities of metabolic networks.