Using screening test data to recognize reactive chemical hazards

The evaluation of reactive hazards is necessary for safe operations in the chemical process industries. An integral aspect of reactive hazard testing is the screening of chemicals to focus experimental efforts on the more hazardous chemicals. Screening is often performed using a Differential Scanning Calorimeter (DSC) or the Reactive System Screening Tool (RSST). The study of chemical incompatibility highlights the need for efficient screening techniques, since a large number of experiments must be performed at a reasonable cost and in a short period of time. A purpose of this paper is to present chemical incompatibility data measured using the RSST for di-tert-butyl peroxide (DTBP) in a variety of organic solvents. Analysis of the data with regard to the solvent functional groups was generalized to extend the measured data to compounds for which data are unavailable. Further, a classification for reactive chemicals is proposed that can serve as a guideline for selecting compositions for detailed testing.     

Evaluating Pollution Prevention Progress (P2P)

P2P (Pollution Prevention Progress) is a computer-based tool that supports the comparison of process and product alternatives in terms of environmental impacts. This tool provides screening-level information for use in process design and in product life cycle assessment (LCA). Twenty one impact categories and data for approximately 3,000 chemicals are represented in the default database of the new release, P2P Mark III. These data help identify which emissions may require further, more sophisticated, characterisation in the different impact categories. In this paper, we primarily focus on the persistence-bioaccumulation toxicity (PBT) methodology adopted for the classification of chemicals in the context of (eco-)toxicological impacts. This classification methodology is cross-compared with a characterisation approach that provides a more complete model-based representation of the source-to-effect (or environmental) mechanism, but for fewer chemicals. To ensure that the quantity of the emission, and not just chemical hazard, is taken into account the comparison is based on a case study for the production of BDO (1,4-butanediol). Insights are presented independently for both the chemical processing stage, as well as from a broader life cycle perspective. Software available from:     

Evaluation of full and degraded mission reliability and mission dependability for intermittently operated, multi-functional systems

Availability is one of the metrics often used in the evaluation of system effectiveness. Its use as an effectiveness metric is often dictated by the nature of the system under consideration. While some systems operate continuously, many others operate on an intermittent basis where each operational period may often involve a different set of missions. This is the most likely scenario for complex multi-functional systems, where each specific system mission may require the availability of a different combination of system elements. Similarly, for these systems, not only is it important to know whether a mission can be initiated, it is just as important to know whether the system is capable of completing such a mission. Thus, for these systems, additional measures become relevant to provide a more holistic assessment of system effectiveness. This paper presents techniques for the evaluation of both full and degraded mission reliability and mission dependability for coherent, intermittently operated multi-functional systems. These metrics complement previously developed availability and degraded availability measures of multi-functional systems, in the comprehensive assessment of system effectiveness.     

Hazard evaluation of chemicals for bulk marine shipment

For economic reasons most chemicals used in large quantities by industry are transported in tank vessels. These chemicals range in properties from essentially harmless to highly dangerous. Although the United States and IMCO require certain minimum data before classifying a new chemical to be transported in bulk, no formal system exists to correlate these data with specific shipboard requirements such as the location of the tank within the vessel, gauging and venting systems, or cargo overfill protection.Developing guidelines for the evaluation of chemicals is a two part problem. First, the inherent hazards of a chemical (the hazards of a product when it is released, without regard to its cargo containment system) must be investigated. In the second part of the evaluation, these hazards are then correlated with specific shipboards requirements as mentioned above. This paper outlines the essential elements for developing a comprehensive system of hazard evaluation for bulk liquid chemicals.     

New challenges in quantum chemistry: Quests for accurate calculations for large molecular systems

As quantum chemistry plays a more and more central role in many complicated chemical problems, it has become necessary to obtain accurate results for large molecular systems. Conventional quantum chemistry methods are either too expensive to apply to large systems or too approximate for the results to be reliable, and they fail to satisfy this requirement. A variety of different approaches is being developed with the aim of achieving this goal: local correlation methods; divide-and-conquer methods; linear-scaling density functional methods based on the fast multipole and other approximations; effective potential methods; and hybrid methods. ONIOM (our N-layered integrated molecular orbital plus molecular mechanics method), developed by the authors, is a hybrid method in which a large molecular system is divided into onion-skin-like layers, and different quantum chemistry/molecular mechanics methods are used for different parts of the system; the results are combined to extrapolatively estimate the results of high-level calculation for the real system. Several applications of ONIOM will be discussed.     

Integrating process safety with molecular modeling-based risk assessment of chemicals within the REACH regulatory framework: benefits and future challenges

Registration, evaluation and authorization of chemicals (REACH) represents a recent regulatory initiative by the European union commission to protect human health and the environment from potentially hazardous chemicals. Under REACH, all stakeholders must submit (thermo)physical, thermochemical, and toxicological data for certain chemicals. The commission's impact assessment studies estimate that the costs of REACH will be approximately 3-5 billion Euros. The present study advocates the systematic incorporation of computational chemistry and computer-assisted chemical risk assessment methods into REACH to reduce regulatory compliance costs. Currently powerful computer-aided ab initio techniques can be used to generate predictions of key properties of broad classes of chemicals, without resorting to costly experimentation and potentially hazardous testing. These data could be integrated into a centralized IT decision and compliance support system, and stored in a retrievable, easily communicable manner should new regulatory and/or production requirements necessitate the introduction of different uses of chemicals under different conditions. For illustration purposes, ab initio calculations are performed on heterocyclic nitrogen-containing compounds which currently serve as high energy density materials in the chemical industry. Since investigations of these compounds are still in their infancy, stability studies are imperative regarding their safe handling and storage, as well as registration under REACH.     

Modeling and Measuring All the Elements of an Ultrasonic Nondestructive Evaluation System II: Model-Based Measurements

In Part I: Modeling Foundations [1], a comprehensive model of an ultrasonic nondestructive evaluation (NDE) flaw measurement system was developed. Here, it will be shown that this comprehensive model can be used to completely characterize commercial measurement systems where all the elements of the system can be either modeled explicitly or measured, using purely electrical measurements. When combined, these models and measurements are shown to be able to predict accurately the measured signals in an ultrasonic test.     

Modeling and Measuring All the Elements of an Ultrasonic Nondestructive Evaluation System II: Model-Based Measurements

In Part I: Modeling Foundations [1], a comprehensive model of an ultrasonic nondestructive evaluation (NDE) flaw measurement system was developed. Here, it will be shown that this comprehensive model can be used to completely characterize commercial measurement systems where all the elements of the system can be either modeled explicitly or measured, using purely electrical measurements. When combined, these models and measurements are shown to be able to predict accurately the measured signals in an ultrasonic test.     

Modeling and Measuring All the Elements of an Ultrasonic Nondestructive Evaluation System II: Model-Based Measurements

Abstract

In Part I: Modeling Foundations [1], a comprehensive model of an ultrasonic nondestructive evaluation (NDE) flaw measurement system was developed. Here, it will be shown that this comprehensive model can be used to completely characterize commercial measurement systems where all the elements of the system can be either modeled explicitly or measured, using purely electrical measurements. When combined, these models and measurements are shown to be able to predict accurately the measured signals in an ultrasonic test.     

Characterizing hydraulic fracturing fluid <Emphasis Type="Italic">greenness</Emphasis>: application of a hazard-based index approach

Growth of the unconventional gas industry is predicted to continue to be an important component of the global energy landscape. The rapid expansion of shale and tight gas development has raised many environmental and human health concerns, particularly in regards to ground and surface water contamination. The unconventional gas industry has begun to transition toward the use of hydraulic fracturing chemicals that pose minimal environmental and human health hazards in order to mitigate the risks associated with possible chemical containment failure. Integrated chemical hazard evaluation has been facilitated by an adapted index-based approach to combine noncommensurate multiparameter chemical hazard data into a single score value. Comparative analysis of existing chemical hazard index scoring systems as well as the formulation of a novel hydraulic fracturing fluid greenness assessment system revealed several important considerations for index development and application. Index scores calculated using the investigated index systems highlighted the need for informed, optimized hazard class selection as input for score determination, the maintenance of hazard category intensity during parameter transformation, as well as representative hazard class and chemical component mathematical weightings, and robust aggregation techniques for final score calculation. Continued research should work to model the combined hazard posed by individual chemicals while considering the effect of dilution as well as incorporate additional index metrics beyond hazard intensity. Fully disclosed index systems, applied with complete knowledge of their strengths and weaknesses, provide useful monitoring and communication tools to promote environmental-best practices in the unconventional gas industry.     

Mapping spatiotemporal molecular distributions using a microfluidic array

The spatial and temporal distributions of an extensive number of diffusible molecules drive a variety of complex functions. These molecular distributions often possess length scales on the order of a millimeter or less; therefore, microfluidic devices have become a powerful tool to study the effects of these molecular distributions in both chemical and biological systems. Although there exist a number of studies utilizing microdevices for the creation of molecular gradients, there are few, if any, studies focusing on the measurement of spatial and temporal distributions of molecular species created within the study system itself. Here we present a microfluidic device capable of sampling multiple chemical messengers in a spatiotemporally resolved manner. This device operates through spatial segregation of nanoliter-sized volumes of liquid from a primary sample reservoir into a series of analysis microchannels, where fluid pumping is accomplished via a system of passive microfluidic pumps. Subsequent chemical analysis within each microchannel, achieved via optical or bioanalytical methods, yields quantitative data on the spatial and temporal information for any analytes of interest existing within the sample reservoir. These techniques provide a simple, cost-effective route to measure the spatiotemporal distributions of molecular analytes, where the system can be tailored to study both chemical and biological systems.     

The development of the globally harmonized system (GHS) of classification and labelling of hazardous chemicals

The hazards of chemicals can be classified using classification criteria that are based on physical, chemical and ecotoxicological endpoints. These criteria may be developed be iteratively, based on scientific or regulatory processes. A number of national and international schemes have been developed over the past 50 years, and some, such as the UN Dangerous Goods system or the EC system for hazardous substances, are in widespread use. However, the unnecessarily complicated multiplicity of existing hazard classifications created much unnecessary confusion at the user level, and a recommendation was made at the 1992 Rio Earth summit to develop a globally harmonized chemical hazard classification and compatible labelling system, including material safety data sheets and easily understandable symbols, that could be used for manufacture, transport, use and disposal of chemical substances. This became the globally harmonized system for the Classification and Labelling of Chemicals (GHS). The developmental phase of the GHS is largely complete. Consistent criteria for categorising chemicals according to their toxic, physical, chemical and ecological hazards are now available. Consistent hazard communication tools such as labelling and material safety data sheets are also close to finalisation. The next phase is implementation of the GHS. The Intergovernmental Forum for Chemical Safety recommends that all countries implement the GHS as soon as possible with a view to have the system fully operational by 2008. When the GHS is in place, the world will finally have one system for classification of chemical hazards.     

A New Approach to the SCI Journal Citation Reports,a System for Evaluating Scientific Journals

The Science Citation Index, Journal Citation Reports (JCR), published by the Institute for Scientific Information (ISI) and designed to rank, evaluate, categorize and compare journals, is used in a wide scientific context as a tool for evaluating researchers and research work, through the use of just one of its indicators, the impact factor. With the aim of obtaining an overall and synthetic perspective of impact factor values, we studied the frequency distributions of this indicator using the box-plot method. Using this method we divided the journals listed in the JCR into five groups (low, lower central, upper central, high and extreme). These groups position the journal in relation to its competitors. Thus, the group designated as extreme contains the journals with high impact factors which are deemed to be prestigious by the scientific community. We used the JCR data from 1996 to determine these groups, firstly for all subject categories combined (all 4779 journals) and then for each of the 183 ISI subject categories. We then substituted the indicator value for each journal by the name of the group in which it was classified. The journal group may differ from one subject category to another. In this article, we present a guide for evaluating journals constructed as described above. It provides a comprehensive and synthetic view of two of the most used sections of the JCR. It makes it possible to make more accurate and complete judgements on and through the journals, and avoids an oversimplified view of the complex reality of the world of journals. It immediately reveals the scientific subject category where the journal is best positioned. Also, whereas it used to be difficult to make intra- and interdisciplinary comparisons, this is now possible without having to consult the different sections of the JCR. We construct this guide each year using indicators published in the JCR by the ISI.     

Comparisons between drum–buffer–rope and material requirements planning: a case study

Drum–Buffer–Rope (DBR) is an alternative approach to manufacturing planning and control that is not as formally tested as Material Requirements Planning (MRP) systems which have traditionally been around for years. Yet, some reports indicate very good performance for DBR and the associated use of synchronous manufacturing principles. But how do these systems compare and relate to one another? Based on our experiences of studying a Bearing Manufacturing Company that actually made the transition from an MRP system to a DBR system, we conduct simulation-based experiments in this paper with the objective of providing a more formal comparison between these two systems than what has been offered in prior literature. To our knowledge, this is the only study of its kind that uses a real-world setting to evaluate key differences and convergence points between comprehensive MRP and DBR systems. Our results show that even though the MRP and DBR systems position inventory differently and provide different dynamic responses to customer demand, there are several operating policies that can be implemented in either system. While the DBR performance in our simulation model was clearly superior to a nominal MRP implementation, we show that even within the constraints of the structural design of MRP system, policy modification based on DBR principles can significantly reduce these performance differences. This finding has an important implication for practising managers who need not necessarily switch from a MRP system to a DBR type of a system (as was done by our case-study firm) in order to take advantage of attractive features of the DBR system. Future researchers can use our study to understand more fully how these Structural Design and Operating Policy differences can be further exploited to implement unique systems that combine the best features of both DBR and MRP systems.     

Recognition and interpretation of interacting and non-interacting features using spatial decomposition and Hamiltonian path search

Since it is a complex task to formalize the feature recognition problem explicitly, a large variety of systems has been developed. One of the problems these systems have to overcome is the recognition and interpretation of interacting features. A fair success has been achieved in surface based methods to recognize certain classes of interacting features. However the problem remains for general cases of interacting features. Recently much effort has been focused on the volumetric approach. We present here the current state of a volumetric feature recognition method. The system considers interacting features in prismoidal parts and it operates in two stages: (1) recognition of regions of interest: a spatial decomposition of the space bounded by a predefined circumscribing volume is performed. A ‘cell evaluated and directed adjacency graph’ is then established. This graph is traversed to identify cavity volumes. (2) interpretation: cavity volumes made up of more than one cell can be produced by different machining operations. A graph-based decomposition method and Hamiltonian path search are combined to generate interpretations which correspond to optimal machining. The system CEDAG developed in this work uses a cell-face directed graph and contrasts the face-edge and edge-vertex graphs encountered in most conventional graph-based recognition methods.     

Technological applications of functionalized polymers

In most of the major applications of polymeric materials their mechanical properties are often of paramount importance. Even in such applications as electrical insulators their stiffness, cut and abrasion resistance will be of importance as well as their low conductivity. Now, polymers containing specific functional groups are being utilized in analytical and many synthetic organic chemical procedures [1–4], in biologically and pharmacologically active systems, in food additives, and in the field of agricultural chemicals [5]. Following their successful applications in the laboratory and industrial processes, the introduction of active functional groups, other than those previously discussed, into polymers will be discussed in the present article. It is meant only to illustrate selected aspects of more general areas of polymers in the technological uses based on their specific active functional groups, in additon to the advantageous properties of the polymeric material.     

Electrochemical compressor driven metal hydride heat pump

In this study, a new metal hydride heat pump system driven by an electrochemical compressor was proposed. The system uses the electrochemical compressor to generate absorption heating and desorption cooling in two identical LaNi₅ reactors operating at different pressure levels. A thermodynamic model was developed to predict the system performance in terms of various parameters. Modeling shows EC compression efficiency has a great impact on system performance. The system is suitable for cooling application less than 200 W where mechanical compressors are the most inefficient. The high compression efficiency of electrochemical compressor could potentially make the cooling system more competitive than existing metal hydride heat pump systems.     

Development and Characterization of a 96-Well Exposure System for Safety Assessment of Nanomaterials

In this study, a 96-well exposure system for safety assessment of nanomaterials is developed and characterized using an air–liquid interface lung epithelial model. This system is designed for sequential nebulization. Distribution studies verify the reproducible distribution over all 96 wells, with lower insert-to-insert variability compared to non-sequential application. With a first set of chemicals (TritonX), drugs (Bortezomib), and nanomaterials (silver nanoparticles and (non-)fluorescent crystalline nanocellulose), sequential exposure studies are performed with human lung epithelial cells followed by quantification of the deposited mass and of cell viability. The developed exposure system offers for the first time the possibility of exposing an air–liquid interface model in a 96-well format, resulting in high-throughput rates, combined with the feature for sequential dosing. This exposure system allows the possibility of creating dose-response curves resulting in the generation of more reliable cell-based assay data for many types of applications, such as safety analysis. In addition to chemicals and drugs, nanomaterials with spherical shapes, but also morphologically more complex nanostructures can be exposed sequentially with high efficiency. This allows new perspectives on in vivo-like and animal-free approaches for chemical and pharmaceutical safety assessment, in line with the 3R principle of replacing and reducing animal experiments.     

Gradients in polymeric materials

In this paper we consider the structure and properties of polymeric materials possessing spatial gradients as well as potential applications of such materials.These gradients may be generated by varying the chemical nature of the monomers, the molecular constitution of the polymers and the supramolecular structure or morphology of the polymers. Gradients in each of these categories are possible for single-phase as well as heterophase systems. Such gradients are associated with gradients in properties.The properties considered are chemical, mechanical, biomedical and transport properties. Structural gradients in the polymeric system may lead to a desired gradient in a single property, or to a combination of more than one property which may assume optimum values in different regions of the material. In the latter case, one of the properties is frequently related to mechanical integrity.Possible applications of gradient polymeric systems include platic gasoline tanks, biomedical implants, and damping materials for a wide frequency range.     

AMCXO and its test system

In this paper, we introduce a novel temperature compensated crystal oscillator--analog memory compensated crystal oscillator (AMCXO), a microcomputer compensated crystal oscillator (MCXO) based on an analogue approach, and we compare the performance between MCXO and AMCXO, and analyze the necessity of developing AMCXO. Both AMCXO and MCXO, combined with their test systems, use computers to generate the control signals used for the compensated crystal oscillators according to temperature variation. However, the execution devices are much different from each other in the practical temperature compensated crystal oscillators. A MCXO uses a set of digital units, including a microprocessor, to realize the compensation. For it, equations or tables are used to express the relationship between the control signal and temperature. An AMCXO uses an analogue memory, which has the same functions as the digital units of MCXO. For AMCXO, a curve or figure based on the equations or tables is used to express the same relationship. Their test systems have obvious distinctions in temperature experiment, data acquisition, and processing. A better performance will be obtained by using a more complicated AMCXO test system, and the cost can be reduced at the same time.