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This chapter contains sections titled: Model Predictive Control: State-of-the-Art General Principle Dynamic Matrix Control Nonlinear MPC General Tuning Guideline of Nonlinear MPC Discretisation of Models: Orthogonal Collocation Method Pros and Cons of MPC Optimisation Example: Chaotic System Notes and References

Abstract Devonian–Mississippian strata in the northwestern region of the Western Canada sedimentary basin (WCSB) were investigated for shale gas potential. In the subsurface, thermally mature strata of the Besa River, Horn River, Muskwa, and Fort Simpson formations attain thicknesses of more than 1 km (0.6 mi), encompassing an area of approximately 125,000 km2 (48,300 mi2) and represent an enormous potential gas resource. Total gas capacity estimates range between 60 and 600 bcf/section. Of particular exploration interest are shales and mudrocks of the Horn River Formation (including the laterally equivalent lower Besa River mudrocks), Muskwa Formation, and upper Besa River Formation, which yield total organic carbon (TOC) contents of up to 5.7 wt.%. Fort Simpson shales seldom have TOC contents above 1 wt.%. Horn River and Muskwa formations have excellent shale gas potential in a region between longitudes 122°W and 123°W and latitudes 59°N and 60°N (National Topographic System [NTS] 94O08 to 94O15). In this area, which covers an areal extent of 6250 km2 (2404 mi2), average TOC contents are higher (>3 wt.% as determined by wire-line-log calibrations), and have a stratal thickness of more than 200 m (656 ft). Gas capacities are estimated to be between 100 and 240 bcf/section and possibly greater than 400 tcf gas in place. A substantial percentage of the gas capacity is free gas caused by high reservoir temperatures and pressures. Muskwa shales have adsorbed gas capacities ranging between 0.3 and 0.5 cm3/g (9.6–16 scf/t) at reservoir temperatures of 60–80°C (140–176°F), whereas Besa River mudrocks and shales have low adsorbed gas capacities of less than 0.01 cm3/g (0.32 scf/t; Liard Basin region) because reservoir temperatures exceed 130°C (266°F). Potential free gas capacities range from 1.2 to 9.5 cm3/g (38.4 to 304 scf/t) when total pore volumes (0.4–6.9%) are saturated with gas. The mineralogy has a major influence on total gas capacity. Carbonate-rich samples, indicative of adjacent carbonate platform and embayment successions, commonly have lower organic carbon content and porosity and corresponding lower gas capacity (<1% TOC and <1% porosity). Seaward of the carbonate Slave Point edge, Muskwa and lower Besa River mudrocks can be both silica and TOC rich (up to 92% quartz and 5 wt.% TOC) and most favorable for shale gas reservoir exploration because of possible fracture enhancement of the brittle organic- and siliceous-rich facies. However, an inverse relation between silica and porosity in some regions implies that zones with the best propensity for fracture completion may not provide optimal gas capacity, and a balance between favorable reservoir characteristics needs to be sought.

Abstract We describe a new method for predicting well-log properties from seismic data. The analysis data consist of a series of target logs from wells which tie a 3-D seismic volume. The target logs theoretically may be of any type; however, the greatest success to date has been in predicting porosity logs. From the 3-D seismic volume a series of sample-based attributes is calculated. The objective is to derive a multiattribute transform, which is a linear or nonlinear transform between a subset of the attributes and the target log values. The selected subset is determined by a process of forward stepwise regression, which derives increasingly larger subsets of attributes. An extension of conventional crossplotting involves the use of a convolutional operator to resolve frequency differences between the target logs and the seismic data. In the linear mode, the transform consists of a series of weights derived by least-squares minimization. In the nonlinear mode, a neural network is trained, using the selected attributes as inputs. Two types of neural networks have been evaluated: the multilayer feedforward network (MLFN) and the probabilistic neural network (PNN). Because of its mathematical simplicity, the PNN appears to be the network of choice. To estimate the reliability of the derived multiattribute transform, crossvalidation is used. In this process, each well is systematically removed from the training set, and the transform is rederived from the remaining wells. The prediction error for the hidden well is then calculated. The validation error, which is the average error for all hidden wells, is used as a measure of the likely prediction error when the transform is applied to the seismic volume. The method is applied to two real data sets. In each case, we see a continuous improvement in predictive power as we progress from single-attribute regression to linear multiattribute prediction to neural network prediction. This improvement is evident not only on the training data but, more importantly, on the validation data. In addition, the neural network shows a significant improvement in resolution over that from linear regression.

Abstract Characterising the pore structure of gas shales is of critical importance to establish the original gas in place and flow characteristics of the rock matrix. Methods of measuring pore volume, pore size distribution, and sorptive capacity of shales, inherited from the coalbed methane and conventional reservoir rock analyses, although widely applied, are of limited value in characterising many shales Helium which is routinely used to measure shale skeletal and grain density, permeability and diffusivity, has greater access to the fine pore structure of shale than larger molecules such as methane. Utilizing gases other than He to measure porosity or flux requires corrections for sorption to be incorporated in the analyses. Since the permeability of shales vary by several orders of magnitude with effective stress, methods that do not consider effective stress such as crushed permeability, permeability from Hg porosimetry, and from desorption are of limited utility and may be at best instructional. For shales investigated to date, clay-rich rocks have higher porosity and permeability than biogenic silica-rich shales or carbonate-rich shales. Shales rich in detrital quartz have higher porosity and permeability than shales rich in biogenic quartz and hence simply knowing the mineralogy of a shale may not be diagnostic. The porosity of most shales is mainly dependent on the degree of pore volume development in pores less than 10 um. Quantifying total gas in place in shales by much of the industry using coal desorption methods and porosity and water saturation determinations, developed for conventional reservoir rocks, may lead to substantial errors. Canister ‘desorption' methods applied to gas shales routinely captures free and solution gas as well as sorbed gas which, if considered as only sorbed gas, results in a significant overestimation of gas in place. A proprietary method of analyses, referred to as MARIO, results in rigorous total gas in place determinations that avoids errors including those associated with molecular sieving and provides a maximum value of the sorbed gas contribution to total gas.

Here is a method for modifying an existing three-phase simulator so that it may be used to forecast miscible flood performance. The simulator is capable of modeling the essential features of miscible displacement while leaving the fine structure of unstable miscible flow unresolved, making it possible to represent the reservoir by a fairly coarse numerical grid. possible to represent the reservoir by a fairly coarse numerical grid. Introduction When designing or evaluating a miscible displacement project, one would like to be capable of accurately project, one would like to be capable of accurately forecasting reservoir performance for a variety of operating conditions. In the past, physical model studies have provided the bulk of the data used in these evaluations. Unfortunately, proper scaling of miscible displacement is difficult to obtain and model construction is time-consuming and expensive. Consequently, considerable effort has been devoted in recent years to the development of numerical reservoir simulators capable of predicting miscible flood performance. In this paper, a method is described for modifying an existing three-phase simulator so that it may be used to simulate miscible flooding. The model employed is unique in that the essential characteristics of miscible displacement are described without reproducing the fine structure of unstable frontal advance. This feature is of particular importance as it allows the reservoir to particular importance as it allows the reservoir to be represented by a fairly coarse numerical grid. We shall describe here three- and four-component versions of the miscible flood simulator. In the three-component version, wetting (water) and nonwetting (hydrocarbon) phases are considered with two-component miscible flow of oil and solvent in the hydrocarbon phase. With the four-component version, slug as well phase. With the four-component version, slug as well as continuous solvent injection may be examined. The validity of the miscible simulator is demonstrated by comparing predicted performance with experimental results from both linear and areal displacement in laboratory models. Predictions are also compared with reported results of miscible displacements carried out in a shallow, water-bearing reservoir. Finally, possible application of the simulator is demonstrated by its use in the evaluation of alternative flooding configurations and operational policies for a field example. policies for a field example. Simulator Requirements A common characteristic of miscible recovery processes is unstable frontal advance, in the form of either viscous fingering or gravity tonguing. These instabilities are the natural result of the highly adverse viscosify ratio and large density difference that generally exist between an oil and the displacing solvent. Fig. 1, for example, depicts the swept zone at solvent breakthrough for a five-spot pattern flood as actually observed in a Hele-Shaw (parallel plate) model. The model is simulating the miscible displacement of oil by solvent at an adverse mobility ratio of about 15. The effect that an unstable frontal advance exerts upon oil recovery might be considerably worse than actually observed if it were not for the fact that solvent disperses in the oil, which renders the effective viscosity and density differences less extreme than those of the pure components. Thus, a successful miscible-flood simulator should allow for the possibility of unstable frontal advance and must describe possibility of unstable frontal advance and must describe the dispersion phenomenon, at least as related to the determination of effective fluid properties. P. 874

OBJECTIVE: To provide a comprehensive review of the literature on the measurement, correlates, and health outcomes of medication adherence among community-dwelling older adults. DATA SOURCES: Searches of MEDLINE, PubMed, and International Pharmaceutical Abstracts databases for English-language literature (1966-December 2002) were conducted using one or more of the following terms: elderly, adherence/nonadherence, compliance/noncompliance, medication/drug, methodology/measurement, and hospitalization. STUDY SELECTION AND DATA EXTRACTION: From the above search, studies of medication adherence in community-dwelling seniors were selected for review along with relevant publications from the reference lists of articles identified in the initial database search. DATA SYNTHESIS: Although several methods are available for the assessment of adherence, accurate measurement continues to be difficult. The available evidence suggests that polypharmacy and poor patient-healthcare provider relationships (including the use of multiple providers) may be major determinants of nonadherence among older persons, with the impact of most sociodemographic factors being negligible. There is little consensus regarding other determinants of nonadherence. Relatively few high-quality investigations have examined the associations between nonadherence and subsequent health outcomes. Available data provide some support for increased health risks with nonadherence. However, interventions to improve adherence have seldom demonstrated positive effects on health outcomes. CONCLUSIONS: There are few empirical data to support a simple systematic descriptor of the nonadherent patient. The inconsistencies across studies may be attributable, in part, to the inherent difficulties involved in the measurement of a behavioral risk factor such as nonadherence. Future research in this area would be strengthened by incorporation of detailed assessments of patient-reported reasons for nonadherence, the appropriateness of drug regimens, and the effect of nonadherence on health outcomes.

Abstract This analysis draws together basic rock physics, amplitude variations with offset (AVO), and seismic amplitude inversion to discuss how fluid-factor discrimination can be performed using prestack seismic data. From both Biot and Gassmann theories for porous, fluid-saturated rocks, a general formula is first derived for fluid-factor discrimination given that both the P and S impedances are available. In essence, the two impedances are transformed so that they better differentiate between the fluid and rock matrix of the porous medium. This formula provides a more sensitive discriminator of the pore-fluid saturant than the acoustic impedance and is especially applicable in hard-rock environments. The formulation can be expressed with either the Lamé constants and density, or the bulk and shear moduli and density. Numerical and well-log examples illustrate the applicability of this approach. AVO inversion results are then incorporated to show how this method can be implemented using prestack seismic data. Finally, a shallow gas-sand example from Alberta and a well-log example from eastern Canada are shown to illustrate the technique.

Construction of physical maps of genomes by pulsed-field gel electrophoresis requires enzymes which cut the genome into an analyzable number of fragments; most produce too many fragments. The enzyme I-Ceu I, encoded by a mobile intron in the chloroplast 23S ribosomal RNA (rrl) gene of Chlamydomonas eugametos, cuts a 26-bp site in the rrl gene. This enzyme digests DNA of Salmonella typhimurium at seven sites, each corresponding to one of the rrl genes of the rrn operons, but at no other site. These seven fragments were located on the previously determined Xba I physical map, and the I-Ceu I sites, and thus the rrn genes of S. typhimurium, were mapped on the 4800-kb chromosome. Escherichia coli K-12 also yields seven fragments of sizes similar to those of S. typhimurium, indicating conservation of rrn genes and their location, and a chromosome size of 4600 kb. The sizes of the E. coli fragments are close to the size predicted from restriction maps and nucleotide sequence. The I-Ceu I maps of Salmonella enteritidis, Salmonella paratyphi A, B, C, and Salmonella typhi were deduced after digesting genomic DNA and I-Ceu I and probing with DNA of S. typhimurium; the data indicated strong conservation of rrn gene number and position and genome sizes up to 4950 kb. Digestion of DNA of other bacteria (species of Haemophilus, Neisseria, Proteus, and Pasteurella) suggested that only rrn genes are cut in all these species. I-Ceu I digestion followed by pulsed-field gel electrophoresis is a powerful tool for determining genome structure and evolution.

We review current knowledge of contaminant exposure and effects in Arctic biota.

The past decade has witnessed the emergence of a new phenomenon in marketing practice and research in terms of the rapid and widespread diffusion of information technology. Of particular interest in the marketing literature is the notion of interactivity within and among firms and customers. To better understand how IT-enabled interactivity impacts contemporary marketing practice, this paper synthesizes the extant and emerging literature to develop two related conceptual frameworks useful for discussion and empirical investigation. Building on an established conceptualization of marketing practices that comprises four different approaches (Transaction, Database, Interaction, and Network marketing), the first framework introduces a fifth approach: e-Marketing. The second framework relates these five marketing approaches to three distinct roles for information technology in the organization. Implications are offered for both managers and researchers.

The world's first commercial scale post-combustion coal fired carbon capture and storage project was started in September of this year at the SaskPower Boundary Dam Power Station in Estevan, Saskatchewan. Above and beyond being the process licensor, technology provider and amine supplier for both the flue gas desulphurization and CO2 capture processes, Shell Cansolv has provided a multitude of products and services to SaskPower for this first-of-a-kind achievement. Shell Cansolv's contribution spanned from the supply of modular amine filtration and amine purification units to overall process performance optimization, going through operator training, support of plant commissioning and start-up and review of standard operating procedures. This project will be a milestone for the fossil fuel power industry worldwide, as it will prove the viability of large scale CO2 capture and demonstrate that carbon capture can be brought successfully to commercial scale.

This paper presents the comparison of three different strategies for the control of a doubly fed induction generator (DFIG) in wind energy conversion systems (WECS). Three of the most widespread and well-performing control approaches are implemented in an experimental setup based on a digital signal processor (DSP), namely, vector control, direct torque control, and direct power control. Said control methods are reviewed and their performances analyzed and compared on the basis of simulations and experimental results. The qualitative and quantitative comparison results thus obtained are likely to be of great interest to engineers and researches involved in the field of DFIG-based WECS.

ABSTRACT A new pressure-pulse decay method is presented to measure permeabilities of tight rock samples. Existing pressure-pulse methods yield pressure decays which are either slow or difficult to analyse. Often approximations are made which may yield considerable errors in the derived permeability values. The new method is simple and enables very fast and accurate permeability measurements. The exact solution of the differential equation describing the decay curve resulting from a pressure-pulse measurement was analysed in detail. This showed how the decay curve is influenced by various parameters in the design of the pressure-pulse permeameter. In this way various existing designs could be compared. Furthermore, the analysis showed how a pressure-pulse permeameter should be designed such that the measured decay is fast and simple to analyse. Also an approximate solution was obtained which is accurate to within 0.3% of the exact solution which is much more difficult to handle. Using this solution a new and simple analysis procedure was developed. Combining the new design with the new analysis method results in an elegant method for fast and accurate pressure-pulse measurements.

Abstract A major stream of post‐consumer plastics is a commingled blend of polyethylenes and polypropylenes, which usually exhibits lower performance compared with that of the homopolymers due to the incompatible nature of polyethylenes and polypropylenes. Various studies have been carried out to characterize the structure, morphology, mechanical, thermal, and rheological behavior of this blend. The effect of processing, modification, and compatibilization have also been studied by various workers. This article is a review of the work done on polyethylene–polypropylene blends to help in the understanding of this important blend. © 1994 John Wiley & Sons, Inc.

A potassium-based polymer mud has been used successfully for controlling troublesome shales in many wells around the world. Shale stability results by combining potassium chloride with a high-molecular-weight, partially hydrolyzed polyacrylamide. Field application of the polyacrylamide/ potassium-chloride mud has been successful in stabilizing hard, sloughing potassium-chloride mud has been successful in stabilizing hard, sloughing shales in Canada and in reducing shale-related hole problems in several offshore areas. Introduction Drilling water-sensitive shales with conventional waterbase muds frequently results in increased costs arising from shale-related hole problems. These problems can range from minor annoyances, in which case they are generally ignored, to situations where further drilling is impossible and the well is sidetracked or abandoned. Darley and Chenevert were instrumental in determining basic mechanisms that cause shales to become unstable when exposed to water-base fluids. Various solutions have been suggested for dealing with troublesome shales encountered when drilling. Guidelines for choosing muds for drilling various types of shales have been presented by Kelly and by Allred and McCaleb . Oil-base fluids have been used successfully to drill water-sensitive formations; however, the use of oil-base muds is expensive and presents environmental problems, particularly for presents environmental problems, particularly for offshore use. A recent advance in drilling-fluid technology is the introduction of water-base muds containing potassium salts. The ability of potassium ions to reduce the swelling tendencies of shales has been studied by O'Brien and Chenevert, who also found that the use of certain polymers in combination with potassium ions showed promise as the basis of potassium ions showed promise as the basis of shale-protective drilling fluids. Mondshine presented data on the development of a potassium-chloride/ potassium-lignite system for stabilizing potassium-lignite system for stabilizing water-sensitive shales. This paper discusses the development of a potassium-based polymer mud that has been successful potassium-based polymer mud that has been successful in controlling troublesome shales in many wells around the world. Shale stability is achieved by combining potassium chloride with a high-molecular-weight, potassium chloride with a high-molecular-weight, partially hydrolyzed polyacrylamide.* Results of a partially hydrolyzed polyacrylamide.* Results of a laboratory evaluation of the shale-stabilizing ability of a number of polymers in combination with potassium chloride are presented. Information concerning formulation, handling, and treatment of the system is given, along with results of field application of the polyacrylamide/potassium-chloride mud in a variety of polyacrylamide/potassium-chloride mud in a variety of shales and geographical locations. Laboratory Evaluation of Shale-Stabilizing Fluids Test Equipment and Procedures The laboratory equipment used for evaluating the shale-protective ability of water-base fluids is the mud triaxial tester described by Darley. A schematic drawing of the tester is shown in Fig. 1. The mud triaxial tester allows mud to flow through a simulated borehole (1/4 in. in diameter) in the shale test specimen (1 in. thick × 2 in. in diameter) while the shale is under stress. Axial and radial stresses can be varied independently, although standard procedure is to set them equal. JPT P. 719

Summary The first exploration-and-production downhole field trial of distributed acoustic sensing (DAS) fiber-optic technology was conducted during the completion of a tight gas well in February 2009. DAS is a novel technology that allows the detection, discrimination, and location of acoustic events on a standard telecom single-mode fiber several kilometers long. Using a combination of the measurement of backscattered light and advanced signal processing, the DAS interrogator system segregates the fiber into an array of individual microphones. To date, the technology has been applied mainly in the defense and security industries. One of the most exciting applications for downhole application of DAS is in the area of hydraulic fracturing of tight-sand and shale-gas reservoirs. Balancing the cost of hydraulic-fracture stimulation with the production benefit is crucial in tight-sand and shale-gas developments because, after drilling costs, the completion is the largest single cost component of the well. Recordings can be made while tools are run in hole, bridge plugs are set and perforations are shot and during the fracture-stimulation treatment. The technology is sufficiently reliable and sensitive to detect and monitor these in-well activities. The fidelity of the recordings made during hydraulic-fracturing and flowback operations provides a step-change improvement in the ability to perform real-time and post-job diagnostics and analyses of the stimulation. The different case studies presented in this paper will illustrate how, even in its earliest form, DAS has the potential to enhance the capability of monitoring and understanding in-wellbore activities. The technology enables the optimization of hydraulic-fracturing design and execution, which can drive down completion costs and lead to increased well productivity and ultimate recovery.

Abstract A field experiment was carried out to measure hydraulic fracture growth in naturally fractured rock. Hydraulic fracture interactions with pre-existing natural fractures, shear zones, veins, and adjacent hydraulic fractures were measured and mapped during the project. Tiltmeter and microseismic arrays were installed to test the performance of these monitoring methods in determining the fracture geometry, which was eventually revealed by the mine-through mapping. The physically mapped fractures were oriented approximately horizontally, perpendicular to the minimum stress direction. They crossed natural fractures and shear zones, but were offset by some shear zones, most often oriented with an approximate 45° dip. The analysis of the tiltmeter data correctly predicted fractures to be horizontal. Microseismic monitoring, although a proven method for imaging hydraulic fractures, did not resolve the fracture orientation or size for conditions at the E48 Northparkes site because of a lack of recorded micro-seismic events. The hydraulic fractures grew through solid rock, along natural fractures and stepped along inclined shear zones. Proppant was distributed throughout the fractures, including in the offset portions. Initial modeling indicates higher treatment pressure and slower extension rate for a stepped 2D hydraulic fracture compared to a straight fracture.

This article describes measurements of the surge voltage characteristics from a number of motors driven by inverter-fed drives (IFDs). The measurements were done with both laboratory and purpose-built instrumentation. Further, we discuss why certain surges deteriorate the insulation, and we give guidelines for determining which motors may be at risk of failure from IFD voltage surges. The effect of these surges on stator windings is also included, as well as means to determine if a motor installed in a severe surge environment will fail.

The first commercial post combustion CO2 capture plant, based on regenerable amine technology, designed by Shell Cansolv was started successfully in Q3, 2013. Subsequently, the plant conceded 72 hrs warranty test run and since then, the CO2 capture plant has been running smoothly. The plant performance met requirements for a successful warranty test run and in most cases results were considerably better than expected. The CO2 capture facility is designed to capture 170 tonnes of CO2/day from a gas-fired boiler's emissions, however, due to boiler limitations, the plant is running at a capacity of 120 tonnes of CO2/day. The capture facility is equipped with a prescrubber followed by an absorber and water wash on the capture side. CO2 was captured using counter current exchange with the Cansolv DC-103 solvent, which was regenerated in the stripper. At normal operation, the average CO2 capture was maintained at around 90%, however, CO2 capture as high as 98% is achieved. The average specific steam consumption over the Performance Test period was noticed as <1.05 kg of steam/per kg of CO2 captured. The average CO2 product purity was greater than 99.0%, more specifically as high as 99.8%. The capture unit is equipped with a semi-batch thermal reclaimer (TR) unit to remove ionic and non-ionic degradation products from DC-103 solvent. The average amine recovery from thermal reclaimer unit was 99.75% with a maximum of 99.8%. The CO2 capture performance, energy consumption, Amine recovery from Thermal Reclaimer, and operational philosophy exercised at the CO2 capture plant will help Shell Cansolv to optimize the design of the CO2 Capture unit further. Learning's from first commercial CO2 capture plant will help Shell Cansolv to successful start-up of upcoming commercial projects.

Groups of 70 male and 70 female Charles River CD-1 mice were exposed whole body to styrene vapor at 0, 20, 40, 80 or 160 ppm 6 h per day 5 days per week for 98 weeks (females) or 104 weeks (males). The mice were observed daily; body weights, food and water consumption were measured periodically, a battery of hematological and clinical pathology examinations were conducted at weeks 13, 26, 52, 78 and 98 (females)/104 (males). Ten mice of each gender per group were pre-selected for necropsy after 52 and 78 weeks of exposure and the survivors of the remaining 50 of each gender per group were necropsied after 98 or 104 weeks. An extensive set of organs from the control and high-exposure mice were examined histopathologically, whereas target organs, gross lesions and all masses were examined in all other groups. Styrene had no effect on survival in males. Two high-dose females died (acute liver toxicity) during the first 2 weeks; the remaining exposed females had a slightly higher survival than control mice. Levels of styrene and styrene oxide (SO) in the blood at the end of a 6 h exposure during week 74 were proportional to exposure concentration, except that at 20 ppm the SO level was below the limit of detection. There were no changes of toxicological significance in hematology, clinical chemistry, urinalysis or organ weights. Mice exposed to 80 or 160 ppm gained slightly less weight than the controls. Styrene-related non-neoplastic histopathological changes were found only in the nasal passages and lungs. In the nasal passages of males and females at all exposure concentrations, the changes included respiratory metaplasia of the olfactory epithelium with changes in the underlying Bowman's gland; the severity increased with styrene concentration and duration of exposure. Loss of olfactory nerve fibers was seen in mice exposed to 40, 80 or 160 ppm. In the lungs, there was decreased eosinophilia of Clara cells in the terminal bronchioles and bronchiolar epithelial hyperplasia extending into alveolar ducts. Increased tumor incidence occurred only in the lung. The incidence of bronchioloalveolar adenomas was significantly increased in males exposed to 40, 80 or 160 ppm and in females exposed to 20, 40 and 160 ppm. The increase was seen only after 24 months. In females exposed to 160 ppm, the incidence of bronchiolo-alveolar carcinomas after 24 months was significantly greater than in the controls. No difference in lung tumors between control and styrene-exposed mice was seen in the intensity or degree of immunostaining, the location of tumors relative to bronchioles or histological type (papillary, solid or mixed). It appears that styrene induces an increase in the number of lung tumors seen spontaneously in CD-1 mice.