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 (K_St) 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.     

The trials and tribulations of a robotic screening core

It is well recognized within the pharmaceutical industry that high throughput screening is a valuable and rapid tool to identify novel chemical compounds that may lead to tomorrow''s drugs. High throughput screening involves testing as many chemical compounds as quickly as possible against a defined molecular or cellular ‘target’ (for example an enzyme) in the hope that interacting compounds may provide significant therapeutic benefits.At Wyeth-Ayerst Research, a Robotics and Automation Research Core Group has been established which serves as the in-house resource for high throughput screening. The robotics group has three missions: (1) develop and perform high throughput screens for customers in all therapeutic departments in the company; (2) educate customers in issues related to screen design; and (3) help customers to bring automated workstations into their laboratories. The mission, therefore, requires the effective use of automation, as well as building a strong collaboration with customers.The challenges that have been faced fall into two categories: technology limiting and customer relations. Technological challenges arise because it is necessary to develop and implement assays with very different formats and biochemical endpoints within extremely shortened time frames. The primary means to meet these challenges is with flexible robotics and flexible people. Challenges in the area of customer relations include setting realistic expectations, maintaining a sense of collaboration (and not merely service), educating investigators as to how to deal with the huge amount of data generated and seeking feedback. Effective and frequent communication, and an awareness of each individual''s perspective, are essential to provide the most appropriate service.     

Traumatic brain injury and memory: The role of hippocampal atrophy.

In traumatically brain-injured (TBI) patients (n?=?83), memory performance was examined on the Warrington Recognition Memory Test, Rey-Osterrieth Complex Figure, and the Logical Memory and Visual Reproduction subtests of the Wechsler Memory Scale-Revised in relationship to time postinjury and structural changes based on MRI volumetry, including hippocampus volume. Significant trauma-induced changes were observed, including hippocampal atrophy. Structure-function relationships generally became significant only after 90 days postinjury. Memory tended to relate more to the degree of hippocampal atrophy, particularly left hippocampus, than to nonspecific indicators such as the temporal horns or the ventricle-to-brain ratio. A stronger relationship with left versus right hippocampus was evident for measures of verbal and supposedly nonverbal memory. These results are discussed with regard to the role the hippocampus may play in a neural system of memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Formal methods integration for the specification of dependable distributed systems

This paper describes a real-world case study in the specification and analysis of dependable distributed systems. The case study is an automated transport system with safety requirements. In order to manage the complexity of the problem of specifying the dynamic behavior of the whole system, a compositional approach is used, based on the integration of the trace logic of the Communicating Sequential Processes (CSP) theory, and stochastic Petri nets (SPNs). It is argued that the integration of different formal methods is a useful approach in the definition of practical engineering methodologies for the specification, design and analysis of complex dependable distributed systems.