196,245 research outputs found
Protein HU binds specifically to kinked DNA
No full textWe have purified the main four-way junction DNA-binding protein of Escherichia coli, and have found it to be the well-known HU protein. HU protein recognizes with high-affinity one of the angles present in the junction, a molecule with the shape of an X. Other DNA structures characterized by sharp bends or kinks, like bulged duplex DNAs containing unpaired bases, are also bound. HU protein appears to inhibit cruciform extrusion from supercoiled inverted repeat (palindromic) DNA, either by constraining supercoiling or by trapping a metastable interconversion intermediate. All these properties are analogous to the properties of the mammalian chromatin protein HMG1. We suggest that HU is a prokaryotic HMG1-like protein rather than a histone-like protein
Verification of Programs with Exceptions Through Operator Precedence Automata
No full textOperator Precedence Languages are one of the most expressive classes of context-free languages that enable Model Checking. Recently, the First-Order complete Precedence Oriented Temporal Logic (POTL) has been introduced for expressing properties on models defined through Operator Precedence Automata (OPA), a variant of Pushdown Automata for OPLs; moreover, an efficient tool called Precedence Oriented Model Checker (POMC) was devised for POTL. We propose here the core algorithms of POMC for on-the-fly depth-first exploration of the search space: for OPA, a reachability algorithm; for their ω -word variant, a fair-cycle detection algorithm. We have refined the tool with a user-friendly DSL called MiniProc for expressing procedural code with exceptions. We show how the expressiveness of POMC can be used to verify programs which make use of exceptions, thus overcoming the limits of LTL-based Model Checking. We demonstrate the effectiveness of POMC through a case study
Evaluation of cell proliferation and degeneration in one case of lymphoma: effects of hyperthermic treatment.
No full textRisk assessment of buried natural gas pipelines. Critical aspects of event tree analysis
No full textThe safety aspects of pipelines conveying hazardous materials are not included neither under the umbrella of Seveso Directives aiming at preventing major accidents at industrial facilities, nor in other EU legislation such as the Pressure Equipment Directive (PED). A review of relevant past accidents can provide statistical evidence on the extent to which pipelines present a risk potentially comparable to that of Seveso installations and on the degree to which the pipeline hazards are adequately controlled. Starting from evidence that in the last decades, the international natural gas market has been growing at a very high rate and continues to exhibit an increasing trend, in this paper we focus on consequences deriving from accidents on high pressure buried Natural Gas Pipelines (NGP) and related probabilities of the various outcomes. The paper focuses on a novel Event Tree framework, to overcome the limitations of the amply applied over-conservative IP UKOOA approach. In order to evidence the capability of the approach, the use of refined PET is exemplified by means of a real case-study of a high pressure buried NG pipeline, contrasting the actual results with those obtained by conventional methods, in terms of evolving scenario probability and damage. Conclusions are drawn about the effective application of the framework within risk assessment and related uncertainties in pipeline accident modelling
Human and organizational factor risk assessment in process industry and a risk assessment methodology (MEDIA) to incorporate human and organizational factors
No full textHuman and organizational factors (HOF) contribute to large number of accidents in process industries, therefore it is of prime importance to include HOF into risk assessment. In this paper, a newly developed methodology "Method for Error Deduction and Incident Analysis (MEDIA)" is presented. MEDIA is a taxonomy based HOF assessment methodology which can be used to quantify the HOF risk based on an accidental database (EMARS). Primarily, MEDIA analyzes different organizational characteristics and their effect on human action's outcome. This methodology also accounts for available risk reduction factors and critically of human action failure
Statistical analysis of past accidents and a methodology (MEDIA) for Human and Organizational Factors assessment in process industries
No full textThis paper presents a statistical analysis of past accidents occurred between 1983-2013 reported to European Major Accidental Reporting System (EMARS) across seven industries for Human and Organizational Factor (HOF) assessment. The main purpose of this analysis is to provide guidelines for the HOF analysis and its quantification in chemical process industries. Five identified organizational factors have been chosen as performance shaping factors for human actions/interventions which are quantified using analysis of past accidents. The relation between organizational and human factors is developed and quantified using a newly developed methodology MEDIA. A case study is carried out for a pig launcher that is widely used in oil and gas facilities during pigging operations. Failure Mode, Effects and Criticality Analysis (FMECA) approach is used to identify the potentially critical human actions/ interventions based on guided brainstorming. After that, these identified actions/interventions analyzed using conventional FMECA approach and MEDIA. FMECA can provides a qualitative results, while MEDIA can provides quantitative results and also demonstrates the influence of an organization on human reliability. © 2015 Taylor & Francis Group
Critical aspects of natural gas pipelines risk assessments. A case-study application on buried layout
No full textThe safety aspects of pipelines conveying hazardous materials are included neither under the umbrella of Seveso Directives aiming at preventing major accidents at industrial facilities, nor in other EU legislations, such as the Pressure Equipment Directive (PED). Starting from evidence that in the last decades the international natural gas market has been growing at a very high rate and continues to exhibit an increasing trend, in this paper we focus on consequences deriving from accidents on high pressure buried Natural Gas Pipelines (NGP) and related probabilities of the various outcomes. A survey on historical accidents occurred on NG pipelines in the USA, Canada and EU allowed the attainment of significant statistics concerning the main factors responsible for the accident evolution, namely failure mode, immediate and root cause, evolving scenario, degree of confinement produced by the surroundings and ignition timing. In this paper, we focus on a refined Event Tree framework, to overcome the limitations of the amply applied over-conservative IP UKOOA approach. In order to evidence the capability of the approach, the use of refined PET is exemplified by means of a real case-study of a high pressure buried NG pipeline, contrasting the actual results with those obtained by conventional methods, in terms of evolving scenario probability and damage. Conclusions are drawn about the effective application of the framework within risk assessment and the uncertainties and sensitivities in the pipeline accident modelling
Behavioural responses related to increasing core body temperature of grazing dairy cows experiencing moderate heat stress
No full textExposure to direct solar radiation, high ambient temperature, lack of wind movement, coupled with own metabolic heat production, makes grazing dairy cows vulnerable to heat stress. In pastures, it would be beneficial to monitor heat stress by observable changes in behaviour. We hypothesised that grazing dairy cows exhibit behavioural changes due to increasing heat load in temperate climate. Over two consecutive summers, 38 full-time grazing Holstein dairy cows were investigated in 12 experimental periods of up to 3 consecutive days where the cows were repeatedly exposed to various levels of moderate heat load determined by the comprehensive climate index (CCI). The CCI defines the ambient climate conditions, combining air temperature, relative humidity, solar radiation and wind speed. Vaginal temperature (VT) was automatically measured as an indicator of heat stress. In addition, as a less invasive method, we investigated if reticular temperature (RET) can be indicative of heat stress on pastures. Walking activity, lying-, feeding, and ruminating durations were recorded continuously with sensors. Respiration rate (RR), proximity to and competition at the water trough, social licking, self-licking, inter-individual distance, and fly intensity were directly observed. Data were analysed in the morning (0900–1100 h) and during the hottest time of day when cows were on pasture (1230–1430 h). The VT and RET showed similar patterns in relation to the CCI, suggesting that RET can be suitable for continuous monitoring of heat stress on pastures. In the morning, the cow’s VT and RET did not relevantly react to the CCI. During the period 1230–1430 h, the cow’s mean VT (mean vaginal temperature (VTMEAN); range: 37.7–40.3 °C) and mean RET (mean reticular temperature; range: 37.0–41.1 °C) were positively related to the mean CCI (mean comprehensive climate index) in this period (mean ± SD: 25.9 ± 5.71 °C). For cows with greater VTMEAN, an increased mean RR and decreased durations of walking, lying, feeding, and ruminating were found. These cows were also more likely to be in proximity to the water trough and to have small inter-individual distances. Changes in these traits seem to reflect behavioural adaptations to heat stress in a temperate climate and could be used to detect the heat stress in individual dairy cows on pastures
Human and organizational factors assessment and their use as potential safety barriers
No full textThis paper presents a statistical analysis of past accidents that occurred between 1988 and 2012 reported to the European Commission's Major Accident Reporting System (eMARS) focusing on human and organizational factor (HOF) assessment. The main purpose of this analysis is to provide guidelines for the HOF analysis and its quantification for accident risk assessment in chemical process industries. In this analysis both operational and diagnostic layers are considered with respect to human actions. For the purpose of this analysis, five identified organizational factors have been selected as Performance Shaping Factors (PSF) for human actions/interventions. The SPAR- H model has been applied to evaluate the affect of PSFs on the human reliability. The overall framework has been modeled by using a newly developed approach, the Method for Error Deduction and Incident Analysis (MEDIA). In MEDIA new HOF action- based taxonomies have also been developed. By using a score method it is possible to identify the most critical PSF for human reliability, which should be improved in order to improve the overall human reliability
A Model Checker for Operator Precedence Languages
No full textThe problem of extending model checking from finite state machines to procedural programs has fostered much research toward the definition of temporal logics for reasoning on context-free structures. The most notable of such results are temporal logics on Nested Words, such as CaRet and NWTL. Recently, Precedence Oriented Temporal Logic (POTL) has been introduced to specify and prove properties of programs coded trough an Operator Precedence Language (OPL). POTL is complete w.r.t. the FO restriction of the MSO logic previously defined as a logic fully equivalent to OPL. POTL increases NWTL's expressive power in a perfectly parallel way as OPLs are more powerful that nested words.In this article, we produce a model checker, named POMC, for OPL programs to prove properties expressed in POTL. To the best of our knowledge, POMC is the first implemented and openly available model checker for proving tree-structured properties of recursive procedural programs. We also report on the experimental evaluation we performed on POMC on a nontrivial benchmark
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