Plant-symbiotic fungi as chemical engineers: multi-genome analysis of the Clavicipitaceae reveals dynamics of alkaloid Loci

The fungal family Clavicipitaceae includes plant symbionts and parasites that produce several psychoactive and bioprotective alkaloids. The family includes grass symbionts in the epichloae clade (Epichloë and Neotyphodium species), which are extraordinarily diverse both in their host interactions and in their alkaloid profiles. Epichloae produce alkaloids of four distinct classes, all of which deter insects, and some—including the infamous ergot alkaloids—have potent effects on mammals. The exceptional chemotypic diversity of the epichloae may relate to their broad range of host interactions, whereby some are pathogenic and contagious, others are mutualistic and vertically transmitted (seed-borne), and still others vary in pathogenic or mutualistic behavior. We profiled the alkaloids and sequenced the genomes of 10 epichloae, three ergot fungi (Claviceps species), a morning-glory symbiont (Periglandula ipomoeae), and a bamboo pathogen (Aciculosporium take), and compared the gene clusters for four classes of alkaloids. Results indicated a strong tendency for alkaloid loci to have conserved cores that specify the skeleton structures and peripheral genes that determine chemical variations that are known to affect their pharmacological specificities. Generally, gene locations in cluster peripheries positioned them near to transposon-derived, AT-rich repeat blocks, which were probably involved in gene losses, duplications, and neofunctionalizations. The alkaloid loci in the epichloae had unusual structures riddled with large, complex, and dynamic repeat blocks. This feature was not reflective of overall differences in repeat contents in the genomes, nor was it characteristic of most other specialized metabolism loci. The organization and dynamics of alkaloid loci and abundant repeat blocks in the epichloae suggested that these fungi are under selection for alkaloid diversification. We suggest that such selection is related to the variable life histories of the epichloae, their protective roles as symbionts, and their associations with the highly speciose and ecologically diverse cool-season grasses

Application of a loss causation model to the Westray mine explosion

On 9 May 1992 an underground explosion destroyed the Westray coal mine located in Plymouth, Nova Scotia, Canada. Twenty-six miners were killed. This paper attempts to resolve the multiple layers of accident causation by systematic application of a loss causation model. Immediate and basic causes having their origin in lack of management control are identified. The analysis helps to identify the lessons to be learned from this disaster, the two most important of which are the need for a rigorous loss management system and an appropriate attitude toward industrial safety

Overpressure Effects

Explosions produce pressure waves which expand in the atmosphere. When impacting industrial equipment, domino effects may be caused if the equipment content is flammable or toxic. A detailed analysis of these scenarios requires complex computational tecniques based on finite element analysis. Simplified methodologies have been developed in the past years for land use planning and quantitative risk assessment. These approaches are based on the definition of probability functions and threshold values for the occurrence of loss of containment from damaged systems and rely on the prediction of peak overpressure with respect to distance from the explosion source and on the structural category of the target equipment. \ua9 2013 Elsevier B.V. All rights reserved

Inherent Safety Implementation Throughout the Process Design Lifecycle

The applicability of inherent safety throughout the different steps of the engineering design and management lifecycle is discussed in the present paper. The concept of a design space as a representation of different stages and levels of the safety design process is introduced. This provides a framework for a systematic, step-by-step safety analysis of the process design and also to recognize the opportunity to implement inherently safer design. Further, the selection and design of add-on safety strategies and implementation of risk control measures through engineered (active or passive) or procedural approaches using inherent safety principles is described. A procedural methodology is suggested to support the application of the described approach, resulting in a tool suitable for inherent safety implementation throughout the process design lifecycle. Application of the proposed approach is demonstrated through use of an industrial example

Modelling of the effect of size on flocculent dust explosions

The effect of size on the severity of explosions involving flocculent materials has been simulated by means of a model previously developed for spherical particles and here extended to the cylindrical geometry of flock. The model consists of the identification of the regime (internal and external heating, pyrolysis/devolatilization reaction, and volatiles combustion) controlling the explosion by the evaluation of dimensionless numbers (Bi, Da, Th and Pc) and then of the estimation of the deflagration index as a function of flocculent size. The model has been validated by means of explosion data of polyamide 6.6 (nylon) at varying diameter and length. The comparison between model and experimental data show a fairly good agreement. �� 2013 Elsevier Ltd. All rights reserved

Modelling the effect of particle size on dust explosions

The recent concept of inherent safety uses the properties of a material or process to eliminate or reduce the risk thus removing or minimizing the hazard at the source as opposed to accept the hazard and looking to mitigate the effects. In this framework the control of particle size in dust explosion prevention and mitigation is recognized as a major inherent safety methodology. Indeed, the increase of particle size may allow significant reduction of particle reaction rate eventually reducing the risk. In this paper a novel model is developed to quantify the effect of particle size on dust reactivity in an explosion phenomenon. The model takes into account all of the steps involved in a dust explosion: internal and external heating, devolatilization reaction and volatiles combustion. Varying the dust size can establish different regimes depending on the values of the characteristic time of each step and of several dimensionless numbers (Damköhler number, Da; Biot number, Bi; thermal Thiele number, Th). Results from the model are reported in terms of the deflagration index (KSt) as a function of dust diameter in all regimes and at varying Da, Th and Bi. Comparison with experimental data from polyethylene explosion tests shows promising results. Finally, the results of the model are presented in the form of a dust explosion regime diagram, which is helpful to make a draft evaluation of the role of dust size on explosion behavior and severity. © 2009 Elsevier Ltd. All rights reserved

Safety Assessment in Plant Layout Design using Indexing Approach: Implementing Inherent Safety Perspective. Part 1 \u2013 Guideword applicability and method description

Layout planning plays a key role in the inherent safety performance of process plants since this design feature controls the possibility of accidental chain-events and the magnitude of possible consequences. A lack of suitable methods to promote the effective implementation of inherent safety in layout design calls for the development of new techniques and methods. In the present paper, a safety assessment approach suitable for layout design in the critical early phase is proposed. The concept of inherent safety is implemented within this safety assessment; the approach is based on an integrated assessment of inherent safety guideword applicability within the constraints typically present in layout design. Application of these guidewords is evaluated along with unit hazards and control devices to quantitatively map the safety performance of different layout options. Moreover, the economic aspects related to safety and inherent safety are evaluated by the method. Specific sub-indices are developed within the integrated safety assessment system to analyze and quantify the hazard related to domino effects. The proposed approach is quick in application, auditable and shares a common framework applicable in other phases of the design lifecycle (e.g. process design). The presentwork is divided in two parts: Part 1 (current paper) presents the application of inherent safety guidelines in layout design and the index method for safety assessment; Part 2 (accompanying paper) describes the domino hazard sub-index and demonstrates the proposed approach with a case study, thus evidencing the introduction of inherent safety features in layout design

Multimedia fate of oil spills in a marine environment - an integrated modelling approach

A fugacity-based methodology is presented to predict the fate of spilled oil in the marine environment. In the proposed methodology, oil weathering processes are coupled with a level IV (dynamic) fugacity-based model. A two~compartment system, comprised of water and sediment, is used to explore the fate of oil in a marine environment.Peer reviewed: YesNRC publication: Ye

Determination of Hybrid Mixture Explosion Severity

This paper presents four different approaches for determining the consequences of hybrid mixture explosions. Experimental work has been completed using a Siwek 20-L chamber for polyethylene alone, and for the ethylene/polyethylene, hexane/polyethylene, and propane/ polyethylene hybrid mixture systems. Empirical relationships for the hybrid mixtures were developed by modeling the explosion phenomena as being dependent on the burning velocity of the admixed gas. Fundamental thermo-kinetic modeling of the polyethylene and various hydrocarbon/polyethylene systems has resulted in excellent agreement with the experimental results in terms of the size-normalized maximum rate of pressure rise. CFD modeling of the mixtures investigated experimentally has been conducted with the GexCon code DESC (Dust Explosion Simulation Code); the preliminary results are promising in terms of consequence prediciton