State-of-science: situation awareness in individuals, teams and systems.

Our review addresses one of the most used, but debated, topics in Ergonomics: Situation Awareness (SA). We examine and elaborate upon key SA models. These models are divided into individual SA, team SA and systems SA categories. Despite, or perhaps because of, the debates surrounding SA it remains an enduring theme for research and practice in the domain of Ergonomics, now for over two decades. A contingent approach, which seeks to match different models of SA to different types of ergonomics problem, enables the differences between positions to be revealed and reconciled, and the practitioner guided towards optimum methodological solutions. Practitioner Summary: Measuring SA in individuals, teams and systems has become a key objective in Ergonomics. One single approach to SA does not fit all problems encountered. This review shows the importance of considering all three types of models and achieving a match between them and the problem at hand.

21st century trucking: A trajectory for ergonomics and road freight.

Over the past decade there has been significant pressure to minimise emissions and safety risks related to commercial driving. This pressure to meet the triple bottom line of cost, environment, and society has often resulted in the rapid application of vehicle technologies designed to mitigate undesired effects. Often the cognitive and behavioural effects of technologies on the commercial driver have not received in-depth analysis to determine comprehensive viability. As such, this paper aims to identify a timescale for implementation for future technologies for UK road freight, and likely associated human factors issues, improving upon the currently employed 'trial-and-error' approach to implementation which may carry high economic, environmental, safety-related risk. Thought experiments are carried out to broadly explore these future systems. Furthermore, this work aims to examine whether technology alone will be enough to meet future CO2 reduction targets, and assess the role of behavioural and systems interventions for future research.

British Dietetic Association evidence-based guidelines for the protein requirements of adults undergoing maintenance haemodialysis or peritoneal dialysis.

BACKGROUND: Existing nutritional guidelines suggest that protein requirements of adults with stage five chronic kidney disease undergoing haemodialysis (HD) or peritoneal dialysis (PD) are increased as a result of protein losses during dialysis. The present review aimed to update previous guidance and develop evidence-based practice guidelines on the protein requirements of adults undergoing maintenance dialysis. METHODS: Following a PICO approach (Participants or Population, Intervention or Exposure, Comparison and Outcome), four research questions were formulated to investigate the total protein requirement and protein quality required by adults undergoing HD and PD. A comprehensive, systematic review was undertaken using the databases Medline, EMBASE and the Cochrane Library from 2005 to September 2009 for HD studies and from 1997 to September 2009 for PD studies. RESULTS: The literature search yielded 2931 studies, which were assessed for inclusion. Following appraisal, 19 studies in HD and 18 studies in PD met the inclusion criteria and were systematically reviewed. Limited good quality evidence supports the recommendations that: (i) adults undergoing maintenance HD require a minimum protein intake of 1.1 g kg(-1) ideal body weight (IBW) per day; and (ii) adults undergoing maintenance PD require a minimum protein intake of 1.0-1.2 kg(-1) IBW per day, in conjunction with an adequate energy intake. There were no studies that addressed the quality of protein for either HD or PD. CONCLUSIONS: Evidence suggests that nutritional status may be maintained with lower protein intakes than previously recommended. However, the evidence base is limited and further randomised controlled trials are required to establish the optimal protein intake for dialysis patients.

Using cognitive work analysis to explore activity allocation within military domains.

Cognitive work analysis (CWA) is frequently advocated as an approach for the analysis of complex socio-technical systems. Much of the current CWA literature within the military domain pays particular attention to its initial phases; work domain analysis and contextual task analysis. Comparably, the analysis of the social and organisational constraints receives much less attention. Through the study of a helicopter mission planning system software tool, this paper describes an approach for investigating the constraints affecting the distribution of work. The paper uses this model to evaluate the potential benefits of the social and organisational analysis phase within a military context. The analysis shows that, through its focus on constraints, the approach provides a unique description of the factors influencing the social organisation within a complex domain. This approach appears to be compatible with existing approaches and serves as a validation of more established social analysis techniques. As part of the ergonomic design of mission planning systems, the social organisation and cooperation analysis phase of CWA provides a constraint-based description informing allocation of function between key actor groups. This approach is useful because it poses questions related to the transfer of information and optimum working practices.

Representing situation awareness in collaborative systems: a case study in the energy distribution domain.

The concept of distributed situation awareness (DSA) is currently receiving increasing attention from the human factors community. This article investigates DSA in a collaborative real-world industrial setting by discussing the results derived from a recent naturalistic study undertaken within the UK energy distribution domain. The results describe the DSA-related information used by the networks of agents involved in the scenarios analysed, the sharing of this information between the agents and the salience of different information elements used. Thus, the structure, quality and content of each network's DSA is discussed, along with the implications for DSA theory. The findings reinforce the notion that when viewing situation awareness (SA) in collaborative systems, it is useful to focus on the coordinated behaviour of the system itself, rather than on the individual as the unit of analysis and suggest that the findings from such assessments can potentially be used to inform system, procedure and training design. SA is a critical commodity for teams working in industrial systems and systems, procedures and training programmes should be designed to facilitate efficient system SA acquisition and maintenance. This article presents approaches for describing and understanding SA during real-world collaborative tasks, the outputs from which can potentially be used to inform system, training programmes and procedure design.

Changing drivers' minds: the evaluation of an advanced driver coaching system.

This paper reports on the study of an advanced driver coaching system. The study distinguishes between different types of post-licensure programmes in order to explore a system based on a model of identifying and responding to hazards, called 'information, position, speed, gear and acceleration' (IPSGA). Previous literature has been sceptical about the benefits of advanced driver education; thus, the current study was designed to control for the effects of coaching drivers in the 'IPSGA' system (the treatment group) against the effects of being accompanied (control group 1), as well as the mere effects of time (control group 2). Measures were taken before the driver coaching began (as a baseline measure) and again after 8 weeks (to see if any changes had occurred). These measures included driver knowledge via a post-drive interview, observations of driving skill and driver attitude using a locus of control scale. The results suggest that advanced driver coaching using the IPSGA system had a beneficial effect on all of these measures. Drivers in the coaching condition improved their situation awareness, driving skills and reduced attributions of external locus of control. The study lends support to the case for one-to-one individualized driver coaching using a systematic model of driving.

Inhibition of maize leaf phosphoenolpyruvate carboxylase by diethyl oxaloacetate.

Diethyl oxaloacetate was found to be a competitive inhibitor of maize leaf phosphoenolpyruvate carboxylase activity with respect to the substrate phosphoenolpyruvate. The Ki values, based on total diethyl oxaloacetate, decreased with increasing pH, while the Ki values, based on the enol tautomer (average of 4 µM), were similar and independent of pH. The results suggest that inhibition is dependent on the enol tautomer. Diethyl oxaloacetate was a weak inhibitor following treatment of the enzyme with dithiothreitol; inhibition could be restored by treatment with diamide, indicating inhibition depends on the reduction state of thiol groups on the enzyme.

ATP-dependent activation of a new form of spinach leaf 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase.

A novel form of 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase that possesses little 2-kinase or bisphosphatase activity as isolated has been partially purified from spinach (Spinacia oleracea L.) leaves. However, the new form can be activated by pretreatment with Mg X ATP at room temperature. After ATP activation, the fructose 2,6-bisphosphatase activity has a Michaelis constant for fructose 2,6-bisphosphate of about 1 mM, and is inhibited by high substrate concentrations (greater than 2 mM) and both end products. The kinase/phosphatase activity ratio of the new form was dependent on pH and varied from 0.3 at pH 7.0 to 5.0 at pH 8.2. In contrast, the previously characterized form of the enzyme (which is isolated in an active form and is unaffected by preincubation with Mg X ATP) had an activity ratio of about 2 that was insensitive to pH over the range tested. The ATP-dependent activation of the new enzyme form was stimulated by fructose 6-phosphate and inhibited by glucose 6-phosphate. These results explain why activation is not observed during assay of this enzyme, and indicate that the activation process may be regulated by metabolites. Collectively, these data provide further evidence for the existence, in spinach leaves, of two molecular forms of the enzyme which exhibit different kinetic properties.

Activity of maize leaf phosphoenolpyruvate carboxylase in relation to tautomerization and nonenzymatic decarboxylation of oxaloacetate.

The keto form of oxaloacetate (OAA), a product of phosphoenolpyruvate carboxylase (PEPC) activity, can undergo various nonenzymatic conversions which make conventional methods of assaying the enzyme difficult, because the products may either act as inhibitors or go undetected. In studies with PEPC isolated from leaves of maize, an assay coupled with reduction of OAA to malate was compared with product analysis using high-performance liquid chromatography and an assay based on Pi release. The results show that activity of the enzyme in the assay coupled to malate dehydrogenase is underestimated, to varying extents, depending on magnesium concentration, buffer, and pH. In the assay coupled to malate dehydrogenase, inaccuracies occur due to conversion of the keto form of OAA to the enol form, which is not utilized as a substrate, and due to loss of OAA by decarboxylation to pyruvate. The assay based on Pi formation is considered to give the true rate of catalysis. With this assay the pH optimum is 7.8, compared to 8.3-8.5 for the assay coupled to malate dehydrogenase. The metal enol complex of oxaloacetate (M-OAAenol) is an inhibitor of PEPC and conditions which are favorable for forming this tautomer, high pH with divalent metal ions or high concentrations of Tris buffer at a pH below its pKa value, limit catalysis. Glycine stimulates enzyme activity, and it may have its effect by preventing the formation of the hydrated M-OAAenol complex and maintaining more of the OAA in the keto form. This interpretation is consistent with glycine stimulation of malate synthesis in the assay of PEPC coupled to malate dehydrogenase, with glycine stimulation of the decarboxylation of OAA, and with a reduction in the level of the M-OAAenol complex in the presence of glycine.

Catalytic activity of maize leaf phosphoenolpyruvate carboxylase in relation to oligomerization.

The relationship between the state of oligomerization and activity of purified maize leaf phosphoenolpyruvate carboxylase using size exclusion high performance liquid chromatography was examined. Maximum activities of 35 to 38 micromoles per minute per milligram protein were found when 100% of the enzyme was in its tetrameric form. The effects of the sulfhydryl group modifiers CuCl(2) and p-chloromercuribenzoate on enzyme inhibition and the state of aggregation of the protein complex were examined. Aggregation of the enzyme is temperature and pH sensitive with low temperature and high pH favoring depolymerization. Stability of the tetrameric form is largely dependent upon histidyl residues, and to some extent this explains the biphasic response of enzyme activity to changes in MgCl(2) concentrations. Modification of the tetramer's histidyl residues by the inhibitor diethylpyrocarbonate (0.125 millimolar) results in its dissociation to the dimeric form and loss of activity. Subsequent treatment with 0.4 molar hydroxylamine results in reassociation to the tetramer and restoration of enzymic activity.

Characterization of the transport of oxaloacetate by pea leaf mitochondria.

Mitochondria isolated from pea (Pisum sativum L.) leaves are able to transport the keto acid, oxaloacetate, from the reaction medium into he mitochondrial matrix at high rates. The rate of uptake by the mitochondria was measured as the rate of disappearance of oxaloacetate from the reaction medium as it was reduced by matrix malate dehydrogenase using NADH provided by glycine oxidation. The oxaloacetate transporter was identifed as being distinct from the dicarboxylate and the alpha-ketoglutarate transporters because of its inhibitor sensitivities and its inability to interact with other potential substrates. Phthalonate and phthalate were competitive inhibitors of oxaloacetate transport with K(i) values of 60 micromolar and 2 millimolar, respectively. Butylmalonate, an inhibitor of the dicarboxylate and alpha-ketoglutarate transporters, did not alter the rate of oxaloacetate transport. In addition, a 1000-fold excess of malate, malonate, succinate, alpha-ketoglutarate, or phosphate had little effect on the rate of oxaloacetate transport. The K(m) for the oxaloacetate transporter was about 15 micromolar with a maximum velocity of over 500 nanomoles per milligram mitochondrial protein/min at 25 degrees C. No requirement for a counter ion to move against oxaloacetate was detected and the highest rates of uptake occurred at alkaline pH values. An equivalent transporter has not been reported in animal mitochondria.

Changes in the electron transport chain of pea leaf mitochondria metabolizing malate.

Pea leaf mitochondria showed complex kinetics for malate metabolism. O2 uptake increased as malate concentration increased from 0 to 10 mM, reached a plateau between 10 and 20 mM malate, and then increased again up to 40 mM malate. Analysis of the products of malate oxidation by high-performance liquid chromatography revealed that the first phase of O2 uptake coincided with the synthesis of both pyruvate and oxalacetate (OAA) while the second phase of O2 uptake at higher malate levels usually occurred with a large increase in OAA formation. The biphasic response in O2 uptake and the changing ratios of pyruvate and OAA synthesis did not appear to be the direct result of the differing Km values of malate dehydrogenase and malic enzyme. Rather, they resulted from thermodynamic properties of these two malate oxidases and the kinetics of the two NADH dehydrogenases found in plant mitochondria. At low malate concentrations the rotenone-sensitive NADH dehydrogenase was active and could accept electrons from both malate oxidases. This NADH dehydrogenase became saturated at about 10 mM malate. At higher malate concentrations the rotenone-insensitive NADH dehydrogenase was increasingly important and its increased electron transport capacity was best exploited by malate dehydrogenase. At the higher malate concentrations an increasing portion of the electrons from malate reduce O2 through the alternative oxidase. Although this coincided with the second phase of malate-dependent O2 uptake it was not required for this phase to be seen.

Simultaneous oxidation of glycine and malate by pea leaf mitochondria.

Mitochondria isolated from pea leaves (Pisum sativum L.) readily oxidized malate and glycine as substrates. The addition of glycine to mitochondria oxidizing malate in state 3 diminished the rate of malate oxidation. When glycine was added to mitochondria oxidizing malate in state 4, however, the rate of malate oxidation was either unaffected or stimulated. The reason both glycine and malate can be metabolized in state 4 appears to be that malate only used part of the electron transport capacity available in these mitochondria in this state. The remaining electron transport capacity was used by glycine, thus allowing both substrates to be oxidized simultaneously. This can be explained by differential use of two NADH dehydrogenases by glycine and malate and an increase in alternate oxidase activity upon glycine addition. These results help explain why photorespiratory glycine oxidation and its associated demand for NAD do not inhibit citric acid cycle function in leaves.

Photophosphorylation in isolated maize bundle sheath chloroplasts and cells.

Isolated maize bundle sheath chloroplasts showed substantial rates of noncyclic photophosphorylation. A typical rate of phosphorylation coupled to whole-chain electron transport (methylviologen or ferricyanide as acceptor) was 60 mumol per hour per milligram chlorophyll) with a coupling efficiency (P/e(2)) of 0.6. Partial electron transport reactions driven by photosystem I or II supported phosphorylation with P/e(2) values of 0.2 to 0.3. Thus, two sites of phosphorylation seem to be associated with the photosynthetic chain in much the same way as in spinach chloroplasts.Isolated bundle sheath cells were capable of photosynthetic electron transport with membrane permeant electron carriers (but not with ferricyanide) at rates which were similar to those found in isolated chloroplasts. ATP formation also occurred during electron transport when ADP and phosphate were present in the cell suspension. The rates of photophosphorylation reactions in cells were about 30 to 40% of those found in isolated chloroplasts (maximum rate in cells 80 mumoles ATP per hour per milligram chlorophyll with diaminodurene as electron carrier), with the exception of endogenous photophosphorylation (photophosphorylation without added electron carriers) whose rate was three to four times higher in cells than in chloroplasts. The endogenous photophosphorylation in cells appeared to be coupled to pseudo-cyclic, rather than cyclic, electron transport. It was accompanied by O(2) uptake (when the catalase inhibitor KCN was present), was sensitive to dichlorophenyldimethylurea and methylamine, but was totally insensitive to 20 micromolar antimycin which completely inhibited succinate-supported oxidative phosphorylation in the cells. The implications of these and other phenomena associated with photophosphorylation in bundle sheath cells are discussed.

Photosynthetic electron transport in isolated maize bundle sheath cells.

Fragments of bundle sheath strands, free of mesophyll cells and showing a chlorophyll a/b ratio of 6.0 to 6.6 were prepared from Zea mays by a mechanical method. They were unable to photoreduce ferricyanide but were able to photoreduce the membrane-permeant 2,5-dimethylquinone at a rate of 250 to 420 microequivalents per hour per mg chlorophyll (mueq/hr . mg Chl) at 21 C. In the presence of the catalase inhibitor KCN, methylviologen catalyzed a Mehler reaction at a rate of 120 to 180 mueq/hr . mg Chl. This was increased to 200 to 350 mueq/hr . mg Chl when the uncoupler methylamine was added. The rate of endogenous pseudocyclic electron flow, detected as a Mehler reaction, was also considerable (100 to 150 mueq/hr . mg Chl with methylamine). Diaminodurene supported a high rate of photosystem I-mediated electron flow to methylviologen (400 to 750 mueq/hr . mg Chl).When the tissue fragments were illuminated in a weakly buffered suspension, a reversible rise in the medium pH was observed which apparently originated from H(+) translocation in the thylakoids. The kinetics of the pH changes was rather slow (t((1/2)) > 15 seconds for pH rise; > 30 seconds for dark decay) but the extent of H(+) uptake was substantial (0.1 to 0.3 mueq/mg Chl). All of the electron transport reactions tested, including partial reactions which involve only photosystem I or photosystem II, invariably supported H(+) uptake. This suggests that two sites of energy conservation are associated with the photosynthetic chain in the bundle sheath chloroplasts (as in spinach chloroplasts) and that both of these sites are functional in vivo. The pH changes observed in the absence of exogenous electron carriers were abolished by 3-(3,4-dichlorophenyl)-1,1-dimethylurea or by anaerobiosis, indicating that the underlying endogenous electron transport was strictly a pseudocyclic reaction. There was no evidence of endogenous cyclic electron flow which might contribute to the energy metabolism of the bundle sheath cells.

Electrochemical analysis of the carboxy-14C-labelled aliphatic carboxylic acid metabolites resulting from tracer studies.

14C02 output from carboxy-14C-labelled aliphatic carboxylic acids is measured in the micro-scale Kolbe reaction. Irrespective of whether rats were dosed with 1,1-dichloro[1-14C]ethylene or with chloro[1-14C]acetic acid, 1 mol.equiv. of the resulting thio[14C]diglycollic acid yields by electrolysis approx. 0.7 equiv. of 14CO2, which is interpreted in terms of the labelling of one of the carboxylic acid groups of thiodiglycollic acid. This observation provides important evidence concerning thiodiglycollic acid biosynthesis from 1.1-dichloroethylene.

An outbreak of infantile gastroenteritis due to E. coli 0142.

Twelve cases of gastroenteritis caused by Escherichia coli 0142K86H6 are described. Ten of these cases were clearly involved in an outbreak of cross infection. The other two cases yielded interesting information on infection with E. coli. 0142. Five cases, two being fatal, required repeated intravenous infusion, and one further infant required parenteral replacement therapy on a single occasion only. Cross infection occurred at the primary site-a ward partitioned into cubicles-despite full barrier nursing techniques. Infection spread also to two other wards, and resulted from transfer of latently infected cases. Illness in several infants was protracted and debilitating because of the relapsing nature of the infection. The pathology of the two fatalities is reported briefly.