Showing papers by "ExxonMobil published in 2003"

PPARα Agonist-Induced Rodent Tumors: Modes of Action and Human Relevance

Abstract: Widely varied chemicals--including certain herbicides, plasticizers, drugs, and natural products--induce peroxisome proliferation in rodent liver and other tissues. This phenomenon is characterized by increases in the volume density and fatty acid oxidation of these organelles, which contain hydrogen peroxide and fatty acid oxidation systems important in lipid metabolism. Research showing that some peroxisome proliferating chemicals are nongenotoxic animal carcinogens stimulated interest in developing mode of action (MOA) information to understand and explain the human relevance of animal tumors associated with these chemicals. Studies have demonstrated that a nuclear hormone receptor implicated in energy homeostasis, designated peroxisome proliferator-activated receptor alpha (PPARalpha), is an obligatory factor in peroxisome proliferation in rodent hepatocytes. This report provides an in-depth analysis of the state of the science on several topics critical to evaluating the relationship between the MOA for PPARalpha agonists and the human relevance of related animal tumors. Topics include a review of existing tumor bioassay data, data from animal and human sources relating to the MOA for PPARalpha agonists in several different tissues, and case studies on the potential human relevance of the animal MOA data. The summary of existing bioassay data discloses substantial species differences in response to peroxisome proliferators in vivo, with rodents more responsive than primates. Among the rat and mouse strains tested, both males and females develop tumors in response to exposure to a wide range of chemicals including DEHP and other phthalates, chlorinated paraffins, chlorinated solvents such as trichloroethylene and perchloroethylene, and certain pesticides and hypolipidemic pharmaceuticals. MOA data from three different rodent tissues--rat and mouse liver, rat pancreas, and rat testis--lead to several different postulated MOAs, some beginning with PPARalpha activation as a causal first step. For example, studies in rodent liver identified seven "key events," including three "causal events"--activation of PPARalpha, perturbation of cell proliferation and apoptosis, and selective clonal expansion--and a series of associative events involving peroxisome proliferation, hepatocyte oxidative stress, and Kupffer-cell-mediated events. Similar in-depth analysis for rat Leydig-cell tumors (LCTs) posits one MOA that begins with PPARalpha activation in the liver, but two possible pathways, one secondary to liver induction and the other direct inhibition of testicular testosterone biosynthesis. For this tumor, both proposed pathways involve changes in the metabolism and quantity of related hormones and hormone precursors. Key events in the postulated MOA for the third tumor type, pancreatic acinar-cell tumors (PACTs) in rats, also begin with PPARalpha activation in the liver, followed by changes in bile synthesis and composition. Using the new human relevance framework (HRF) (see companion article), case studies involving PPARalpha-related tumors in each of these three tissues produced a range of outcomes, depending partly on the quality and quantity of MOA data available from laboratory animals and related information from human data sources.

Polyolefin adhesive compositions and articles made therefrom

Abstract: Embodiments of the present invention relate to article comprising 1) a functionalized component, 2) tackifier, and 3) an olefin polymer comprising one or more C3 to C40 olefins, optionally one or more diolefins, and less than 5 mole % of ethylene having a Dot T-Peel of 1 Newton or more, a branching index (g′) of 0.95 or less measured at the Mz of the polymer; and an Mw of 100,000 or less; where the functional component is selected from the group consisting of functionalized polymers, functionalized oligomers and beta nucleating agents; and where the Gardner color of the adhesive does not change by more than 7 Gardner units when the adhesive has been heat aged at 180° C. for 48 hours as compared to the Gardner color of the unaged composition.

Nucleation ability of multiwall carbon nanotubes in polypropylene composites

Abstract: The nonisothermal crystallization of multiwall carbon nanotube (MWNT)/isotactic polypropylene (iPP) nanocomposites was investigated The results derived from the differential scanning calorimetry curves (onset temperature, melting point, supercooling, peak temperature, half-time of crystallization, and enthalpy of crystallization) were compared with those of neat iPP The data were also processed according to Ozawa's theory and Dobreva's approach These results and X-ray diffraction data showed that the MWNTs acted as α-nucleating agents in iPP Accordingly, MWNT/iPP was significantly different from neat iPP: A fibrillar morphology was observed instead of the usual spherulites © 2003 Wiley Periodicals, Inc J Polym Sci Part B: Polym Phys 41: 520–527, 2003

System and method for processing financial transactions using multi-payment preferences

Abstract: The invention relates generally to retail transactions (Fig. 1) and, more particularly, to retail transaction systems and methods employing consumer preferences applicable to the transaction for goods and services (12). Methods, systems and processes are provided in which a customer is identified and associated with a customer profile and/or a method of payment corresponding to the customer (16). The customer profile may comprise customer preferences with regard to at least one method of payment (16). Based on the customer profile and/or other preference or transaction criteria, a preferred method of payment may be determined for a specific transaction (14). The provided methods, systems and processes may be used merely to identify a customer or in combination with transaction payment (e.g., payment for goods, services, or other financial transaction). The methods, systems and processes may also be used in combination with a loyalty program with a specific merchant or an association of merchants participating in a combined customer loyalty program (15).

Plasticized polyolefin compositions

Abstract: The present invention relates to plasticized polyolefin compositions comprising a polyolefin and a non-functionalized hydrocarbon plasticizer.

Multiple catalyst system for olefin polymerization and polymers produced therefrom

Abstract: This invention relates to a polymer comprising one or more C3 to C40 olefins, optionally one or more diolefins, and less than 15 mole % of ehtylene, where the polymer has: a) a Dot T-Peel of 1 Newton or more; and b) a branching index (g') of 0.95 or less measured at the Mz of the polymer; c) an Mw of 100,000 or less and to a continuous process to produce a branched olefin polymer comprising 1) selecting a first catalyst component capable of producing a polymer having an Mw of 100,000 or less and a crystallinity of 5% or less under selected polymerization conditions; 2) selecting a second catalyst component capable of producing polymer having an Mw of 100,000 or less and a crystallinity of 20% or more at the selected polymerization conditions; 3) contacting the catalyst components in the presence of one or more activators with one or more C3 to C40 olefins, and, optionally one or more diolefins; 4) at a temperature of greater than 100°C; 5) at a residence time of 120 minutes or less; 6) wherein the ratio of the first catalyst to the second catalyst is from 1:1 to 50:1; 7) wherein the activity of the catalyst components is at least 100 kilograms of polymer per gram of the catalyst components; and wherein at least 20% of the olefins are converted to polymer.

Chemical Form and Distribution of Selenium and Sulfur in the Selenium Hyperaccumulator Astragalus bisulcatus

Abstract: In its natural habitat, Astragalus bisulcatus can accumulate up to 0.65% (w/w) selenium (Se) in its shoot dry weight. X-ray absorption spectroscopy has been used to examine the selenium biochemistry of A. bisulcatus. High concentrations of the nonprotein amino acid Se-methylseleno-cysteine (Cys) are present in young leaves of A. bisulcatus, but in more mature leaves, the Se-methylseleno-Cys concentration is lower, and selenate predominates. Seleno-Cys methyltransferase is the enzyme responsible for the biosynthesis of Se-methylseleno-Cys from seleno-Cys and S-methyl-methionine. Seleno-Cys methyltransferase is found to be expressed in A. bisulcatus leaves of all ages, and thus the biosynthesis of Se-methylseleno-Cys in older leaves is limited earlier in the metabolic pathway, probably by an inability to chemically reduce selenate. A comparative study of sulfur (S) and Se in A. bisulcatus using x-ray absorption spectroscopy indicates similar trends for oxidized and reduced Se and S species, but also indicates that the proportions of these differ significantly. These results also indicate that sulfate and selenate reduction are developmentally correlated, and they suggest important differences between S and Se biochemistries.

Structure of the first silicate molecular sieve with 18-ring pore openings, ECR-34.

Abstract: The three-dimensional microporosity of zeolite frameworks have allowed their widespread use in industry as heterogeneous catalysts, absorbents, and ion-exchangers. While the phosphate analogues of zeolites having up to 24 tetrahedral atoms in the pore openings are known, silicate-based zeolites have, until now, been limited to 14-membered ring pore openings. We now disclose the structure and characterization of the synthetic zeolite ECR-34, which can be prepared from a mixed alkali metal reaction gel containing tetraethylammonium (TEA) cations. Its structure has been determined from powder diffraction data and shows ECR-34 to be hexagonal with the dimensions a, b = 21.030(1) A, c = 8.530(1) A, containing one-dimensional, 18-ring pores with 10 A diameter free openings. ECR-34 is stable to 800 °C and is able to absorb and ion-exchange large organic molecules. The existence of ECR-34 suggests the potential of preparing other thermally stable silicate molecular sieves with extra-large pores.

Control of Metal Dispersion and Structure by Changes in the Solid-State Chemistry of Supported Cobalt Fischer–Tropsch Catalysts

Abstract: Controlling preparation variables in supported cobalt Fischer–Tropsch catalysts has a dramatic effect on the dispersion and distribution of cobalt, and determines how active and selective the resulting catalyst will be. We detail specific examples of catalyst synthesis strategies for modifying interactions between the support and the cobalt precursor, promoting reduction, stabilizing catalysts to high-temperature treatments, minimizing deleterious support metal interactions, and controlling the distribution of cobalt on large support particles. It is important to optimize the support and precursor interaction strength, so that it is strong enough to obtain good dispersion but not too strong to prevent low temperature reduction. We show examples in which formation of surface complexes and epitaxial matching of precursor and support structures improves dispersion dramatically. Reduction promoters can help in those cases where support–precursor interactions are too strong. We show how substitutions of silicon into a titania lattice stabilizes surface area and retards formation at high oxidation temperatures of cobalt ternary oxides that reduce only at very high temperatures—an important consideration if oxidative coke removal is necessary. In addition, surface treatment of TiO2 with an irreducible oxide like ZrO2 can inhibit deleterious support interactions that can block surface cobalt sites. Selectivity can also be dramatically altered by catalyst synthesis. We illustrate a case of large (2 mm) SiO2 particles onto which cobalt can be added either uniformly or in discrete eggshells, with the eggshell catalysts having substantially higher C5+ selectivity. These approaches can lead to optimal Fischer–Tropsch catalysts with high activity and C5+ selectivity, good physical integrity, and a long life.

On the implementation of perfectly matched layers in a three‐dimensional fourth‐order velocity‐stress finite difference scheme

Abstract: [1] Robust absorbing boundary conditions are central to the utility and advancement of 3-D numerical wave propagation methods. It is in general preferred that an absorbing boundary method be capable of broadband absorption, be efficient in terms of memory and computation time, and be widely stable in connection with sophisticated numerical schemes. Here we discuss these issues for a promising absorbing boundary method, perfectly matched layers (PML), as implemented in the widely used fourth-order accurate three-dimensional (3-D) staggered-grid velocity-stress finite difference (FD) scheme. Numerical results for point (explosive and double couple) and extended sources, velocity structures (homogeneous, 1-D and 3-D), and different thickness PML zones are excellent, in general, leaving no observable reflections in PML seismograms compared to the amplitudes of the primary phases. For both homogeneous half-space and 1-D models, typical amplitude reduction factors (with respect to the maximum trace amplitude) range between 1/100 and 1/625 for PML thicknesses of 5–20 nodes. A PML region of thickness 5 outperforms a simple exponential damping region of thickness 20 in a homogeneous half-space model by a factor of 3. We find that PML is effective across the simulation bandwidth. For example, permanent offset artifacts due to particularly poor absorption of long-period energy by the simple exponential damping are effectively absent when PML is used. The computational efficiency and storage requirements of PML, compared to the simple exponential damping, are reduced due to the need for only narrow absorbing regions. We also discuss stability and present the complete PML model for the 3-D velocity-stress system.

Bioremediation of Marine Oil Spills

Abstract: In the long run, biodegradation is the eventual fate of oil spilled at sea that cannot be collected or burnt. Stimulating this biodegradation is thus an important option for maximizing the removal of oil from the environment, and minimizing the environmental impact of a spill. For handling oil while it is still floating on the sea surface, dispersants are advantageous because they maximize the surface area available for microbial attack, and stimulate biodegradation. If oil beaches on a shoreline, it is likely that biodegradation is limited by nutrients such as nitrogen and phosphorus, and the careful application of fertilizers stimulates the biodegradation of residual beached oil. These approaches epitomize modern environmental technologies; working with natural phenomena to achieve a more rapid clean-up while minimizing undesirable environmental impacts of a spill. For handling oil while it is still floating on the sea surface, dispersants are advantageous because they maximize the surface area available for microbial attack, and stimulate biodegradation. If oil beaches on a shoreline, it is likely that biodegradation is limited by nutrients such as nitrogen and phosphorus, and the careful application of fertilizers stimulates the biodegradation of residual beached oil. These approaches epitomize modern environmental technologies; working with natural phenomena to achieve a more rapid clean-up while minimizing undesirable environmental impacts.

Ground motion scaling methods for different site conditions and structure characteristics

Abstract: Non-linear dynamic time-history analyses conducted as part of a performance-based seismic design approach often require that the ground motion records are scaled to a specified level of seismic intensity. Recent research has demonstrated that certain ground motion scaling methods can introduce a large scatter in the estimated seismic demands. The resulting demand estimates may be biased, leading to designs with significant uncertainty and unknown margins of safety, unless a relatively large ensemble of ground motion records is used. This paper investigates the effectiveness of seven ground motion scaling methods in reducing the scatter in estimated peak lateral displacement demands. Non-linear single-degree-of-freedom systems and non-linear multi-degree-of-freedom systems are considered with different site conditions (site soil profile and epicentral distance) and structural characteristics (yield strength, period, and hysteretic behavior). It is shown that scaling methods that work well for ground motions representative of stiff soil and far-field conditions lose their effectiveness for soft soil and near-field conditions for a wide range of structural characteristics. Copyright © 2003 John Wiley & Sons, Ltd.

Capturing pressure‐dependence in automated mechanism generation: Reactions through cycloalkyl intermediates

Abstract: Chemical kinetic mechanisms for gas-phase processes (including combustion, pyrolysis, partial oxidation, or the atmospheric oxidation of organics) will often contain hundreds of species and thousands of reactions. The size and complexity of such models, and the need to ensure that important pathways are not left out, have inspired the use of computer tools to generate such large chemical mechanisms automatically. But the models produced by existing computerized mechanism generation codes, as well as a great many large mechanisms generated by hand, do not include pressure-dependence in a general way. This is due to the difficulty of computing the large number of k(T, P) estimates required. Here we present a fast, automated method for computing k(T, P) on-the-fly during automated mechanism generation. It uses as its principal inputs the same high-pressure-limit rate estimation rules and group-additivity thermochemistry estimates employed by existing computerized mechanism-generation codes, and automatically identifies the important chemically activated intermediates and pathways. We demonstrate the usefulness of this approach on a series of pressure-dependent reactions through cycloalkyl radical intermediates, including systems with over 90 isomers and 200 accessible product channels. We test the accuracy of these computer-generated k(T, P) estimates against experimental data on the systems H + cyclobutene, H + cyclopentene, H + cyclohexene, C2H3 + C2H4, and C3H5 + C2H4, and make predictions for temperatures and pressures where no experimental data are available. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 95–119, 2003

Correlation of Material and Processing Time Scales with Structure Development in Isotactic Polypropylene Crystallization

Abstract: The influence of average molar mass and shear on the crystallization of isotactic polypropylene (iPP) has been studied. The Weissenberg number, a dimensionless parameter consisting of the product of the shear rate and a characteristic relaxation time (γ0λr), provides a criterion to locate the morphological transition from spherulitic to extended growth. The Weissenberg criterion applies to polymers of high and of low molecular weight. This is attributed to the importance of the initial nucleation process. Comparison of materials of different molar masses and various shear histories is allowed by the introduction of the normalized crystallization time τ, which is the ratio of the experimental time and a characteristic crystallization time λVvmax that needs to be defined from the several possible choices. Rheological and rheooptical experiments furnish the material characteristic relaxation and crystallization time scales, respectively. The time λVvmax, defined with light scattering as the moment at maximu...

Small Angle X-Ray Scattering for Sub-100 nm Pattern Characterization

Abstract: Characterization of sub-100 nm photolithographic patterns with nanometer scale resolution is demonstrated using small angle x-ray scattering. The transmission scattering geometry employed potentially enables high throughput measurements for future technology nodes of the semiconductor industry, organic and inorganic nanoscale devices, and three-dimensional structures. The method is demonstrated through the characterization of a series of polymer photoresist gratings using a synchrotron x-ray source. Quantities, such as periodicity and line width, are extracted using minimal modeling. Additional quantities and the potential of a laboratory-based x-ray system are briefly discussed.

Pressure swing reforming

Abstract: Synthesis gas is produced though a cyclic method where the first step of the cycle includes reforming a hydrocarbon feed over a catalyst to synthesis gas in a first zone of a bed and the second step reheats this first zone. A hydrocarbon feed is introduced to a bed along with CO2 and optionally steam where it is reformed into synthesis gas. The synthesis gas is collected at a second zone of the bed and an oxygen-containing gas is then introduced to this second zone of the bed and combusted with a fuel, thereby reheating the first zone to sufficient reforming temperatures. Additionally, a non-combusting gas can also be introduced to the second zone to move heat from the second zone to the first zone.

Two decades of ocean CO2 sink and variability

Abstract: Atmospheric CO 2 has increased at a nearly identical average rate of 3.3 and 3.2 Pg C yr −1 for the decades of the 1980s and the 1990s, in spite of a large increase in fossil fuel emissions from 5.4 to 6.3 Pg C yr −1 . Thus, the sum of the ocean and land CO 2 sinks was 1 Pg C yr −1 larger in the 1990s than in to the 1980s. Here we quantify the ocean and land sinks for these two decades using recent atmospheric inversions and ocean models. The ocean and land sinks are estimated to be, respectively, 0.3 (0.1 to 0.6) and 0.7 (0.4 to 0.9) Pg C yr −1 larger in the 1990s than in the 1980s. When variability less than 5 yr is removed, all estimates show a global oceanic sink more or less steadily increasing with time, and a large anomaly in the land sink during 1990–1994. For year-to-year variability, all estimates show 1/3 to 1/2 less variability in the ocean than on land, but the amplitude and phase of the oceanic variability remain poorly determined. A mean oceanic sink of 1.9 Pg C yr −1 for the 1990s based on O 2 observations corrected for ocean outgassing is supported by these estimates, but an uncertainty on the mean value of the order of ±0.7 Pg C yr −1 remains. The difference between the two decades appears to be more robust than the absolute value of either of the two decades. DOI: 10.1034/j.1600-0889.2003.00043.x

The Effect of Sea Level, Climate, and Shelf Physiography on the Development of Incised-Valley Complexes: A Modern Example From the East China Sea

Abstract: Analysis of high-resolution seismic reflection and sonar data from the East China Sea (ECS) continental shelf reveals the presence of an extremely broad (> 330 km) and deep (maximum incision of 72 m) incised-valley complex whose development and subsequent fill is constrained to the end of the last glacial cycle ( 20,000 yr BP to present). Results from this study indicate that sea-level change, climate-controlled discharge and sediment supply, and shelf physiography were important factors in the development and subsequent fill of the ECS incised- valley complex. For example, wet climatic conditions during the initial Marine Oxygen Isotope Stage (MIS) 2 fall of sea level promoted fluvial erosion of the exposed shelf. However, the trend toward drier conditions during the MIS 2 fall of sea level slowed the overall development of the incised-valley complex to the point where only minor incision occurred during the maximum lowstand. Furthermore, the low-gradient morphology of the exposed outer shelf diminished the ability of fluvial systems to incise. Instead, fluvial systems migrated laterally, creating a shallow ( 300 km) incised-valley system on the outer shelf. During the late MIS 2 rise of sea level, accommodation was generated within the flooded reaches of the valley complex. However, arid climatic conditions that prevailed at this time resulted in minor sediment delivery to the transgressive shoreline via the incised-valley complex. Thus, the upper part of the drowned lowstand fluvial deposits were exposed at the sea floor and reworked into a valley-wide tidal-bar and tidal sheet complex. Wetter climatic conditions during middle to late MIS 1 resulted in abundant sediment delivery to the drowned parts of the valley complex (estuary) and buried lowstand fluvial deposits below the depth of tidal ravinement, where they remained undisturbed. Current sequence stratigraphic models can be applied to the late Quaternary stratigraphic secession of the ECS. However, these models are too simplistic because they rely largely on rates and directions of sea-level change to explain stratal architectures. Although the extent and rate of sea-level change is extremely important, this study shows that high-frequency climate change and shelf physiography also play important roles in the development of stratigraphic architectures. These factors are particularly important for the development of incised valleys, where they directly influence incised-valley morphology and facies distributions.

New technique for dating igneous sills

Abstract: Three-dimensional seismic interpretation of Tertiary sills within the northeast Atlantic margin demonstrates that shallow-level ( 20 km long. The fill of the minibasin is dated biostratigraphically as 54.6–55 Ma, which fits well with radiometric dates for the timing of intrusion of sills around this basin (ca. 53–55 Ma). The recognition and dating of onlap-fill seismic reflector packages that are delimited by forced folds form a new and useful method for dating shallow-level igneous intrusions in sedimentary basins, a method that provides independent constraints on radiometric dating techniques. Similar forced folds are recognized from other basins that have shallow-level sills, suggesting that the technique presented here may be similarly applicable in comparable geologic settings.

Guidelines for developing and using quantitative structure-activity relationships.

Abstract: Numerous quantitative structure-activity relationships (QSARs) have been developed to predict properties, fate, and effects of mostly discrete organic chemicals. As the demand for different types of regulatory testing increases and the cost of experimental testing escalates, there is a need to evaluate the use of QSARs and provide some guidance to avoid their misuse, especially as QSARs are being considered for regulatory purposes. This paper provides some guidelines that will promote the proper development and use of QSARs. While this paper uses examples of QSARs to predict toxicity, the proposed guidelines are applicable to QSARs used to predict physical or chemical properties, environmental fate, ecological effects and health effects.

Combined cracking and selective hydrogen combustion for catalytic cracking

Abstract: A catalyst system and process for combined cracking and selective hydrogen combustion of hydrocarbons are disclosed. The catalyst system contains at least one solid acid component and at least one metal-based component which consists of (a) oxygen and/or sulfur and (b) a metal combination selected from the group consisting of: i) at least one metal from Group 3 and at least one metal from Groups 4-15 of the Periodic Table of the Elements; ii) at least one metal from Groups 5-15 of the Periodic Table of the Elements, and at least one metal from at least one of Groups 1, 2, and 4 of the Periodic Table of the Elements; iii) at least one metal from Groups 1 and 2, at least one metal from Group 3, and at least one metal from Groups 4-15 of the Periodic Table of the Elements; and iv) two or more metals from Groups 4-15 of the Periodic Table of the Elements, wherein the at least one of oxygen and sulfur is chemically bound both within and between the metals and, optionally, (3) at least one of at least one support, at least one filler and at least one binder. The process is such that the yield of hydrogen is less than the yield of hydrogen when contacting the hydrocarbons with the solid acid component alone. Further, the emissions of NOx from the regeneration cycle of the catalyst system are reduced.

Time-scales of Differentiation from Mafic Parents to Rhyolite in North American Continental Arcs

Abstract: Young rhyolites and associated lavas andmagmatic enclaves from the Katmai---Novarupta volcanic system (Alaskan Peninsula), and the Crater Lake and Medicine Lake volcanic system (Cascades) were analyzed for U and Th isotope abundances, as well as major and trace element concentrations, to investigate the time-scales of the processes that lead to rhyolite generation in continental arcs. Basalts and basaltic andesites typically migrate from the mantle to the surface within several thousand years. Variations in (Th)/(Th) and (U)/(Th) ratios with SiO2 concentrations in intermediate lavas appear to result from crystal fractionation combined with assimilation of recently crystallized magmas. These data also suggest that 10---10 years of mafic magmatism are required at a volcanic center to generate silicic andesites and dacites. Rhyolite genesis involves varying proportions of crystal fractionation of intermediate magmas and assimilation of crust. The nearequilibrium (U)/(Th) ratios for all of the rhyolites suggest an average time since U was last fractionated from Th for the constituents making up these rhyolites of 410 years. Therefore, the residence times of continental magmas and their entrained crystals appear to increase by a minimum of 2---3 orders of magnitude with increasing SiO2 concentrations from basalt to rhyolite.

Continuous slurry polymerization volatile removal

Abstract: A process/apparatus is disclosed for continuously separating a liquid medium comprising diluent and unreacted monomers from a polymerization effluent comprising diluent, unreacted monomers and polymer solids, comprising a continuous discharge of the polymerization effluent from a slurry reactor through a discharge valve and transfer conduit into a first intermediate pressure flash tank with a conical bottom defined by substantially straight sides inclined at an angle to that of horizontal equal to or greater than the angle of slide of the slurry/polymer solids and an exit seal chamber of such diameter (d) and length (l) as to maintain a desired volume of concentrated polymer solids/slurry in the exit seal chamber such as to form a pressure seal while continuously discharging a plug flow of concentrated polymer solids/slurry bottom product of said first flash tank from the exit seal chamber through a seal chamber exit reducer with inclined sides defined by substantially straight sides inclined at an angle to that of horizontal equal to or greater than the angle of slide of the polymer solids which remain after removal of about 50 to 100% of the inert diluent therefrom to a second flash tank at a lower pressure.