Incompatible Components Research Articles

High‐ and Low‐Temperature I‐type Granites

Abstract: I– and S‐type granites differ in several distinctive ways, as a consequence of their derivation from contrasting source rocks. The more mafic granites, whose compositions are closest to those of the source rocks, are most readily classified as I– or S–type. As granites become more felsic, compositions of the two types converge towards those of lowest temperature silicate melts. While discrimination of the two is therefore more difficult for such felsic rocks, that in no way invalidates the twofold subdivision. If felsic granite melts undergo fractional crystallisation, the major element compositions are not affected to any significant extent, but the concentrations of trace elements can vary widely. For some trace elements, fractional crystallisation causes the trace element abundances to diverge, so the I– and S– type granites are again easily separated. Such fractionated S‐type granites can be distinguished, for example, by high P and low Th and Ce, relative to their I‐type analogues.Our observations in the Lachlan Fold Belt show that there is no genetic basis for subdividing peraluminous granites into more mafic and felsic varieties, as has been attempted elsewhere. The subdivision of felsic peraluminous granites into I– and S‐types is more appropriate, and mafic peraluminous granites are always S–type. In a given area, associated mafic and felsic S‐type granites are likely to be closely related in origin, with the former comprising both restite‐rich magmas and cumulate rocks, and the felsic granites corresponding to melts that may have undergone fractional crystallisation after prior restite separation.We propose a subdivision of I‐type granites into two groups, formed at high and low temperatures. The high‐temperature I–type granites formed from a magma that was completely or largely molten, and in which crystals of zircon were not initially present because the melt was undersaturated in zircon. In comparison with low‐temperature I–type granites, the compositions extend to lower SiO2 contents and the abundances of Ba, Zr and the rare earth elements initially increase with increasing SiO2 in the more mafic rocks. While the high‐temperature I–type granite magmas were produced by the partial melting of mafic source rocks, their low‐temperature analogues resulted from the partial melting of quartzofeldspathic rocks such as older tonalites. In that second case, the melt produced was felsic and the more mafic low‐temperature I–type granites have that character because of the presence of entrained and magmatically equilibrated restite.High temperature granites are more prospective for mineralisation, both because of that higher temperature and because they have a greater capacity to undergo extended fractional crystallisation, with consequent concentration of incompatible components, including H2O.

Chemical modification of polymer blends by reactive processing:In situ reactions of interlinking agents in PS/EPDM blends

Polystyrene (PS) and the ethylene–propylene–ethylidene norbornene terpolymer (EPDM) were melt-processed in the presence of multifunctional interlinking agents, divinylbenzene (DVB) and trimethylolpropane triacrylate (TRIS), in an internal mixer to promote functionalization of the polymers and target in situ formation of the interpolymer product via coreaction of the functionalities. This approach leads to effective in situ compatibilization of the otherwise incompatible polymer components of the blends. The weight ratio of PS/EPDM and the concentration of the interlinking agents were kept constant at 70/30 and 5%, respectively. The effect of varying the concentration of the free-radical initiator (a peroxide) and the method of its addition during melt processing on the overall reaction outcome was also examined. Changes in torque during the melt-processing operation was monitored. Sequential extraction of the polymer blends was used to separate and characterize the insoluble fraction (interpolymer). Changes in the thermal behavior (shifts in glass transition temperatures) of both the polymer blends and their insoluble fractions was investigated together with an examination of the morphology and mechanical properties of the reactively processed blends. It was found that the use of mixed reactive interlinking agents in a one-step reactive blending process and the enhancement of PS reactivity via preinitiation before addition of the reactive agents led to an increase in the extent of the coupling reaction between the functionalized PS and EPDM. This results in the formation of an “across-phase” interpolymer with an optimum composition that is responsible for the significant changes observed in the morphology and associated improvements in the mechanical properties of the blend samples. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1933–1951, 1998

The birth of the Earth's atmosphere: the behaviour and fate of its major elements

Abstract The accretion of the major volatiles of the Earth is described in the frame of the integral Enstatite Chondrite model [Javoy, M., 1995. The integral Enstatite Chondrite model of the Earth. G.R. Lett., 22, 2219–2222.]. The accretion of the Earth–Moon system takes place inside an inner solar system dominated by EH type material, at temperatures ≥1000°C. A late evolution of that system brings back some unmodified CI material at the end of the accretion on the edge of the inner zone where the Earth resides. This is the cause of a late veneer deposit weighing ∼1.4 per mil of the Earth mass. Following this model the upper and lower mantle are decoupled and the volatile evolution concerns essentially the Upper Earth (UE) (upper mantle+crust+ocean–atmosphere) with negligible contributions from the lower mantle. The main features are the following: (a) the bulk of the primary reduced material, constituting more than 99.8% of the total mass of the planet brought an isotopically light component corresponding to 6% of the hydrogen, 48% of the carbon and 70% of the nitrogen of the UE. (b) the late veneer (7.5 per mil of the UE's, 1.4 per mil of the bulk Earth's mass) of CI (or cometary) composition supplied an isotopically heavy component of H and N corresponding to 94% of the hydrogen, 52% of the carbon and 30% of the nitrogen. (c) the availability of oxygen in the UE results first from the partial reduction of silicon during the upper mantle–lower mantle–core differentiation (Javoy, 1995) bringing ∼7.5% FeO in the upper mantle. Then, the extra oxidizing reservoir due to the CI veneer creates the right proportion of FeIII in that primarily FeII system and explains the current 2.5% Fe3+/Fe2+ presently observed in the upper mantle. (d) atmospheric radiogenic argon is derived essentially from the outgassing of the UE which contains ∼450 ppm of potassium. The present distribution of the major volatiles in the UE corresponds to a negligible supply from the lower mantle. Measured in units of the superficial reservoirs (oceans, atmosphere, crustal carbon), the contents of the upper mantle are the following: water: 0.21 ocean masses, nitrogen: ∼10 atmosphere masses, carbon: 5.4 crustal carbon masses. This corresponds to a very significant trapping of carbon and nitrogen by the mantle during the Earth's history, whereas water repartition stayed about unchanged and strongly favoured the superficial reservoir. That difference between carbon and water is due to the fact that the major part of subducted water from oceanic crust escapes via arc volcanism. There is another very significant difference between carbon and nitrogen; the present outgassing and subducting fluxes of carbon are both mass- and isotopically-equilibrated, whereas there is still a gross isotopic disequilibrium for nitrogen, with the large, isotopically-heavy, subducted flux still outweighing the small, isotopically-light, outgassed flux. This is due to the fact that while carbon and water are essentially incompatible components, nitrogen is a compatible element because of the presence of very stable mantle nitrides (probably osbornite) or of nitride ions substituting oxygen in silicates.

Jadeite, albite and nepheline as inclusions in spinel of chromitite from Hess Deep, equatorial Pacific: their genesis and implications for serpentinite diapir formation

Polymineralic inclusions which consist of a few grains of diopside, enstatite, jadeite, nepheline, albite, pargasite, phlogopites and olivine were found in chromian spinel in a chromitite pod and in troctolite from Hess Deep, equatorial Pacific. The inclusion mineral suite in chromitite is characterized by Na-Al silicates, such as jadeite, nepheline and albite. Jadeite and nepheline commonly coexist with enstatite, and tend to occur as interstitial grains between subhedral enstatite (or other minerals) and host spinel. Albite, diopside and enstatite occur as equant inclusions. The mafic minerals in the inclusions have similar chemistry to those found in the troctolite and dunite. The modes of occurrence and mineral chemistry of the inclusions are controlled by magmatic precipitation, and subsequent reequilibration due to decrease of temperature in the uppermost mantle. The mafic minerals in spinel inclusions were crystallized from a melt enriched in Cr and some incompatible components formed by melt-mantle interaction process mixed to various extent with subsequently supplied more primary melt. Albite and nepheline could also be formed at the magmatic stage. Jadeite was formed by a subsolidus reaction of albite and nepheline at low temperatures (250–300 °C) at slightly less than 3 kbar. This requires a remarkable temperature decrease, at least locally, of the uppermost mantle and crust. The Hess Deep rocks were formed in the uppermost mantle beneath a spreading-ridge axis at more than 1000 °C, and were transposed outwards from the axis by corner flow. At the off-ridge conditions, the rocks were cooled and serpentinized by circulation of sea water at the mantle depth to form jadeite in chromitite. The serpentinized portion could have risen as a kind of serpentinite diapir through the thin crust up to the ocean floor.

Hydroxyethylstarch sedimentation by gravity ex vivo for red cell reduction of granulocyte apheresis components

BACKGROUND When selecting only leukocyte compatible donors, the requirement of ABO compatibility limits the investigation and application of granulocyte transfusion therapy by reducing the pool of potential donors. Ex vivo hetastarch (HES) sedimentation was evaluated as a method of red blood cell (RBC) reduction of granulocyte components. The objective was to determine if this procedure consistently resulted in reduction of component packed RBC (PRBC) volume to < 5 ml, the range acceptable for infusion of ABO incompatible blood components based on guidelines set forth by the American Association of Blood Banks (AABB). STUDY DESIGN AND METHODS: HLA-matched, ABO-compatible sibling marrow donors were selected to donate granulocyte components, which were transfused into the allogeneic bone marrow transplant (BMT) recipient as prophylaxis against infection. Three granulocyte components were collected from each of 5 donors receiving G-CSF (daily × 5). Leukapheresis (LA) began 1 day after the first G-CSF dose (Day 1), and was repeated on Days 3 and 5. LA were performed using a continuous-flow blood cell separator, with 7L blood processed during each procedure. RBC sedimentation was facilitated by administration of a 6% HES solution to the donor line. The 5 granulocyte components collected on Day 1 were not manipulated after collection. The 10 components collected on Days 3 and 5 were manipulated by ex vivo gravity sedimentation for 60 minutes followed by transfer of the buffy coat (red cell poor [RCP] fraction) to a transfer bag with residual RBCs retained in the collection bag (red cell rich [RCR] fraction). The PRBC volume and cellular composition of the components and fractions were determined. RESULTS: When data for the 10 manipulated components were combined, the fraction of the components with < 5 ml PRBC was 0.4 in the RCP and 0.1 in the RCR fractions. All unmanipulated components contained > 5 ml PRBC. The mean PRBC volume (ml) of the RCP and RCR fractions were 6.3 and 16.4, respectively (P = .06). The mean number of RBC (×1011) in the RCP and the RCR fractions were .41 and 1.73, respectively (P = .03). The average proportion of cells in the manipulated components lost to the RCR fraction was 19.2% of granulocytes and 18.6% of platelets. CONCLUSION: Ex vivo HES sedimentation, as performed, significantly reduced the number of RBCs from granulocyte components, but did not consistently result in PRBC volumes in the RCP fraction within the range acceptable for infusion of ABO incompatible blood components based on the AABB guidelines. Moreover, significant numbers of granulocytes were lost to the RCR fraction. J. Clin. Apheresis 13:56–61, 1998. © 1998 Wiley-Liss, Inc.

Hydroxyethylstarch sedimentation by gravity ex vivo for red cell reduction of granulocyte apheresis components.

When selecting only leukocyte compatible donors, the requirement of ABO compatibility limits the investigation and application of granulocyte transfusion therapy by reducing the pool of potential donors. Ex vivo hetastarch (HES) sedimentation was evaluated as a method of red blood cell (RBC) reduction of granulocyte components. The objective was to determine if this procedure consistently resulted in reduction of component packed RBC (PRBC) volume to < 5 ml, the range acceptable for infusion of ABO incompatible blood components based on guidelines set forth by the American Association of Blood Banks (AABB). HLA-matched, ABO-compatible sibling marrow donors were selected to donate granulocyte components, which were transfused into the allogeneic bone marrow transplant (BMT) recipient as prophylaxis against infection. Three granulocyte components were collected from each of 5 donors receiving G-CSF (daily x 5). Leukapheresis (LA) began 1 day after the first G-CSF dose (Day 1), and was repeated on Days 3 and 5. LA were performed using a continuous-flow blood cell separator, with 7L blood processed during each procedure. RBC sedimentation was facilitated by administration of a 6% HES solution to the donor line. The 5 granulocyte components collected on Day 1 were not manipulated after collection. The 10 components collected on Days 3 and 5 were manipulated by ex vivo gravity sedimentation for 60 minutes followed by transfer of the buffy coat (red cell poor [RCP] fraction) to a transfer bag with residual RBCs retained in the collection bag (red cell rich [RCR] fraction). The PRBC volume and cellular composition of the components and fractions were determined. When data for the 10 manipulated components were combined, the fraction of the components with < 5 ml PRBC was 0.4 in the RCP and 0.1 in the RCR fractions. All unmanipulated components contained > 5 ml PRBC. The mean PRBC volume (ml) of the RCP and RCR fractions were 6.3 and 16.4, respectively (P = .06). The mean number of RBC (x10(11)) in the RCP and the RCR fractions were .41 and 1.73, respectively (P = .03). The average proportion of cells in the manipulated components lost to the RCR fraction was 19.2% of granulocytes and 18.6% of platelets. Ex vivo HES sedimentation, as performed, significantly reduced the number of RBCs from granulocyte components, but did not consistently result in PRBC volumes in the RCP fraction within the range acceptable for infusion of ABO incompatible blood components based on the AABB guidelines. Moreover, significant numbers of granulocytes were lost to the RCR fraction.

The major volatile elements of the Earth: Their origin, behavior, and fate

Stable isotope constraints impose a heterogeneous accretion of the earth's volatiles: the primary, reduced material, 99.8% of the planet, brought 6% of the hydrogen, 48% of the carbon and 70% of the nitrogen of the Upper Earth (upper mantle, crust, ocean‐atmosphere). A late veneer (1.4 per mil of the bulk Earth's mass), of CI composition, supplied 94% of the hydrogen, 52% of the carbon and 30% of the nitrogen.The present distribution of the major volatiles in the Upper Earth corresponds to a negligible supply from the lower mantle. Measured in units of the superficial reservoirs the upper mantle contains: 0.21 ocean masses of water, ∼10 atmosphere masses of nitrogen, 5.4 crustal carbon masses of carbon.This corresponds to a very significant trapping of carbon and nitrogen by the mantle during the Earth's history, whereas water repartition stayed about unchanged and strongly favoured the superficial reservoir. There is, however, a very significant difference between carbon and nitrogen, the present outgassing and subducting fluxes of carbon being equilibrated both in masses and isotopically, whereas there is still a gross isotopic disequilibrium for nitrogen, the large, isotopically heavy, subducted flux, still outweighing the small, isotopically light, outgassed flux.This is due to the fact that, while carbon and water are essentially incompatible components, nitrogen is a compatible element because of the presence of very stable mantle nitrides (probably osbornite).

Composites via heterogeneous crosslinking of concentrated emulsions

Polymer composites based on an epoxy resin oligomer, an amine terminated oligomer or maleic anhydride, and one or several monomers among styrene, methyl methacrylate, butyl methacrylate, glycidyl methacrylate, and acrylonitrile have been prepared using the concentrated emulsion pathway. Each of the components of the composite was first transformed in a concentrated emulsion in which water with a low volume fraction was the continuous phase. The concentrated emulsions containing monomers were partially polymerized (to ensure their stability during the subsequent heating) before being mixed with one or two concentrated emulsions, each containing one of the above mentioned oligomers. The mixture of concentrated emulsions was subjected to heating for the complete polymerization of the monomer and for the reaction between the epoxy resin and the amine terminated oligomer or the maleic anhydride to occur. The reaction generates a crosslinking among the cells of the concentrated emulsions (heterogeneous crosslinking) and thus achieves compatibilization among various incompatible components. The composites were characterized using Fourier transform infra-red spectroscopy, differential scanning calorimetry, swelling, as well as solubility measurements. Tensile measurements showed that the components of the composites were compatibilized and that the latter possess excellent mechanical properties.

Clathrate formation in the liquid phase of (C4H9)4NF−NH4F−H2O

At a certain concentration of NH4F, the solid allocyric solutions of the (C4H9)4NF−NH4F−H2O system stratify into two liquid phases in the process of melting. The mutual solubility of the liquids decreases at elevated temperatures. The boundary surface of the stratification region was determined The solubility isotherms (27 and 30°C) of the stratification region are investigated by the solubility method This relatively rare mutual sulubility of liquids (retrograde solubility) is associated with clathrate formation in the liquid phase. Near the melting points of the solid clathrate solutions, both in the liquid and solid phases the tetrabutylammonium cation evidently forms surrounding cavities bounded by water and ammonium fluoride molecules linked by hydrogen bonds. The clathrate-like components of the solution are structurally compatible with “water-like” and “organic” components, i.e., they are homogenizing components. At higher temperatures, the homogenizing clathrate-like structures break down, and the structurally incompatible solution components stratify into two phases.

Enthalpic interaction of diblock copolymers with immiscible polymer blend components

An attempt is made to extend the model of Leibler for the emulsifying activity and interfacial properties of A-b-B diblock copolymers in incompatible blends of the homopolymers A and B-which are identical with the respective copolymer components- to enthalpically interacting C-b-D diblock copolymers, the block C being thermodynamically compatible with A and D with B. Due to the attractive enthalpic interaction the A/C-b-D/B compatibilized blends are promising for optimum phase adhesion (bold types for thermodynamically compatible partners). Thus, the extended model for a plane interfacial layer includes the enthalpic interaction of the compatible polymer pairs beside the entropic effects. The approach starts with the equillibrium supposition, not taking into consideration enthalpy driven migration effects of the block copolymer from the bulk to the interface, The model confirms a dominant role of the enthalpic interaction between blocks of the diblock copolymer and the respective homopolymers to the compatibilization of incompatible blend components. It is applicable also for blends compatibilized with block copolymers of unfavourable repulsive type interaction, A/C-b-D/B, and for blend systems with mixed type interactions, e. g. A/C-b-B/B or A/C-b-D/B.

Electronic verification of donor-recipient compatibility: the computer crossmatch.

This article describes standard operating procedures (SOPs) for a computer crossmatch to replace the immediate-spin crossmatch for ABO incompatibility between patient blood samples submitted for pretransfusion testing and the blood component selected for transfusion. These SOPs were developed following recent changes to the Standards for Blood Banks and Transfusion Services of the American Association of Blood Banks (AABB). SOPs were developed, utilizing currently available software, for pretransfusion testing. The SOP for donor unit processing entails bar code entry of the unit number, component name, and ABO/Rh type; computer entry and interpretation of serologic reactions; warning of discrepancies between bar code-entered blood type and result interpretation; and quarantine of the donor unit in such instances. The SOP for patient sample testing requires bar code entry of specimen accession number, which accesses patient demographics; computer entry and interpretation of ABO/Rh tests; repeat blood typing at the time of crossmatch if only one patient blood type is on record; and warning if there are nonconcordant current and historical blood types. The computer crossmatch SOP requires bar code entry of specimen accession and donor unit numbers; release of group O red cells pending resolution of discrepancies; and immediate-spin crossmatch during computer downtime. Tables validated on-site prompt warning messages and prevent both computer crossmatch and release if blood components of the wrong ABO type are selected. These SOPs meet the requirements of the 15th edition of the AABB Standards. Projected annual time savings at this institution are > 100,000 workload recording units. Further benefits include reduced patient sample volume requirements, less handling of biohazardous material, and elimination of unwanted positive or negative reactions associated with the immediate-spin crossmatch. Release of incompatible blood components when the wrong patient blood type is on record is addressed by requiring the use of group O red cells in the absence of two concordant blood types, one of which must be from a current sample. A combination of existing computer programs and carefully developed SOPs can provide a safe and efficient means of detecting donor-recipient incompatibility without performance of serologic crossmatch.

Treating excess disabilities in special care units: A review of interventions

There is a predictable decline in functioning among individuals with progressive dementias. In addition, independent of the disease process, there can be “excess disabilities” due to incompatible components of the social and physical environment. We review the nature and sources of these excess disabilities and examine the literature on ameliorative interventions in special care units.

Real-Time Cell Control for Flexible Manufacturing

Flexible Manufacturing C ells (FMCs) may be considered the most significant development in small batch manufacturing. Setting up and operating costs prove to be the most major hinderance to large scale implementation and use of the FMCs, particularly by small and medium size industries. Incompatibility between the different components constituting the cells, and the lack of a unified language/approach to programming and coordinating it, is cited as the cause of the complexity of setting up and subsequent operating the cells. An object oriented software environment, Uniset, is being developed at the University of Ottawa to address the shortcomings of setting-up and operating FMCs comprising incompatible components from different suppliers. The environment provides the users with a consistent platform to configure, program, simulate, and control an FMC irrespective of the nature of its constituents. This paper presents the object oriented cell representation approach, and the interaction between the objects in Uniset. This approach allows the development of task/high level cell programs, and the simulation and verification of these programs. Real-time cell control and coordination in Uniset benefit a great deal from the object based method of representation.

Degree of melting and source composition of Cenozoic basalts in southwest Japan: Evidence for mantle upwelling by flux melting

Based on a study of Cenozoic basalts in southwest Japan where mantle upwelling is considered to have occurred, the degree of melting for primary magmas and weight fractions of residual phases are quantitatively estimated using mass balances for major and compatible components among magma, residual phases and source. Assemblage and composition of the residual phases are obtained from melting experiments of primary magmas, and various source compositions were assumed. The calculation shows an increase of degree of melting toward the upwelling center from approximately 4 to 20%. This is consistent with a change in the residue from a spinel Iherzolite to a harzburgite, which was determined by melting experiments. We also obtain constraints on the source composition. Peridotite with more than 3.0 wt % Al2O3 and 2.0 wt % CaO and a high Al2O3/CaO ratio of approximately 1.5 is suitable as a source. Incompatible element concentrations of the source for Cenozoic basalts in southwest Japan are calculated assuming a batch melting model. At the center of upwelling, the source is anomalously enriched in incompatible elements (up to 200 times compared with primitive mantle model) excepting Nb, while that of upwelling margin has primitive or slightly enriched concentrations. These variations can be explained by addition of fluid (flux melting) and subsequent upwelling of enriched material from the deep mantle (e.g., lower‐upper mantle boundary or core‐mantle boundary). The flux melting model also explains the low potential temperature of approximately 1300 °C of the upwelling mantle. Cenozoic volcanism in southwest Japan may have been caused with a plume with abundant volatile and incompatible components rather than a plume of anomalously high temperature (e.g., Hawaii).

Stratification and phase separation in block copolymer coatings

Stratification, i.e. spontaneous formation of separate layers from a liquid coating containing inherently incompatible resinous components, provides a means of improving the adhesion of coatings. For mixtures of conventional homogeneous resins, surface and interface tensions are considered to be the driving forces for self-stratification, leading to films with separation patterns somewhere between purely spinodal decomposition textures and neatly separated A/B double layers. Inherently domain-forming block copolymers mixed with partly compatible resins give various different separation patterns ranging from ABA-sandwich structures to physically interpenetrating networks of co-continuous phases with homogeneous layers — sometimes monomolecular ones — at film surfaces. Besides tailoring adhesion to difficult substrates, block copolymer binders offer chances to achieve new interesting mechanical property profiles as required, e.g. for coatings for plastics or for stone chip-resistant surfacers useful in the automotive industry. The temperature-dependence of mechanical properties is significantly reduced in comparison with conventional homogeneous coating binders.

Crystallization and melting behaviour in block copolymers of poly(ethylene oxide) with amorphous components. The influence of compatibility

AbstractBy means of DSC, connections between melt crystallization (Tc) and melting temperatures (Tm) of block copolymers have been studied as depending on the compatibility of the block copolymer components. As examples for a compatible and an incompatible system, the systems poly(ethylene oxide) (PEO, crystalline)‐poly(methyl methacrylate) (PMMA, amorphous) and PEO/poly(tert.‐butyl methacrylate) (PTBMA, amorphous), respectively, were used. The compatibility of both systems is described. In block copolymers of compatible components, Tc depends on the composition, but it is less than in comparable blends. Provided a sufficient crystallization time is available, Tm is, in effect, only dependent on the PEO molecular weight. In block copolymers of incompatible components both Tc and Tm were strongly determined by molecular weights of all blocks of both components and, connected with that, by PEO domain sizes. Tc vs. Tm diagrams are presented and discussed.

Functional polypropylene blend compatibilizers

AbstractSolid phase dispersants, often referred to as blend compatibilizers, are the key components of high‐value‐in‐use polypropylene blends with unusual property combinations. In multiphase polypropylene blends, functional blend compatibilizers enhance the dispersion of incompatible polymeric blend components, in particular of polar polymers, fibers or fillers, and improve the interfacial adhesion between polymer matrix and dispersed phases. Some of the major synthetic routes to functional polypropylene blend compatibilizers are discussed. A novel range of monofunctional polypropylenes containing a variety of functional endgroups, e.g., anhydrides, esters, amines, carboxylic acids, silanes, boranes, alcohols, and thiols, has been derived from mono‐olefin‐terminated polypropylenes. These olefinic polypropylene intermediates have been prepared with soluble metallocene catalysts which give excellent control of polypropylene molecular weight, molecular weight distribution, microstructure, and olefinic endgroups. Thiol‐terminated isotactic polypropylenes have been used as polymeric chain transfer agents in styrene and styrene/acrylonitrile polymerization to form novel polypropylene‐block‐polystyrene and polypropylene‐block‐poly(styrene‐co‐acrylonitrile) block copolymers. In the case of poly(styrene‐co‐acrylonitrile) blends with polypropylene morphological studies demonstrate the efficiency of propylene block copolymer blend compatibilizers.

Cumulate nodules as evidence for convective fractionation in a phonolite magma chamber

The physical mechanism by which chemical zonation develops in magma chambers has been controversial partly because unambiguous geological constraints have been lacking. The 11,000 years B.P. eruption of Laacher See Volcano produced a zoned tephra deposit and also ejected crystal-rich nodules which provide a snapshot of the materials crystallising at the magma chamber margins. New data on petrography and chemical compositions of nodules, their cumulate minerals and interstitial glasses are used to deduce the chemical evolution of the phonolite melt due to fractional crystallisation of the mineral assemblages. These data, together with those on the vertical zonation of the melt in the bulk of the chamber, are shown to be consistent with a model of stratification of the chamber by convective fractionation, in which a thin boundary layer of residual melt from fractional crystallisation ascends at the chamber side and accumulates at the roof. Crystallisation could have provided buoyancy to drive convection by enriching incompatible volatile components (mainly water) in the residual melt. Available fluid dynamic studies of single- and double-diffusive boundary layers are used to assess convection in the Laacher See chamber. The boundary layer is likely to have been: (1) laminar, which implies that the density gradient in the chamber steepened upwards; (2) in the counterflow regime, in which compositional and thermal layers flow in opposite directions; and (3) thin (≲ 10 cm), estimated from theory for a flat wall, suggesting that wall morphology could be important in determining boundary layer characteristics. Estimates of mass transfer rates due to this mechanism suggest that the chamber could have become stratified in a time of the order of 10 3 years.

The emergent syntax of pre-sentential turn openings

Spoken French contains a rich variety of pre-sentential discourse particles playing structural, interactional and pragmatic roles. In 65% of some 3700 utterances in classroom discussions and ordinary conversations, of both native and non-native French speakers, we find intonationally unitary turn-openings containing up to five of these particles. Distributional analysis reveals strong ordering constraints among the particles, with eight paradigmatic ‘slots’ available. The first two positions structure the transition from hearer's to speaker's roles ( hmhm…, ah bon…). Usually, the following two positions allow a bi-morphemic reaction ( mais oui…, ben non…) to the interactional and illocutionary validity of the preceding turn, while the fifth and sixth slots contain analogous reactions to its informative content. The remaining slots contain tag-like elements which play a largely prosodic role. Quantitative analysis of particle co-occurrence is based on the null hypothesis that occurrences in different slots are statistically independent. A comparison of observed versus predicted frequencies detects particle combinations used more, or less, than could be accounted for by the frequencies of their individual components, suggesting emergent collocations, and functionally incompatible components, respectively. Finally, we give a brief analysis of the semantic-pragmatic functions of some particle combinations.

Deformation behavior of HDPE/(PEC/PS)/SEBS blends

AbstractImmiscible blends of high density polyethylene (HDPE) and an amorphous glassy phase consisting of either pure polystyrene (PS) or a miscible blend of PS and a polyether copolymer (PEC) were compatibilized with various amounts of a styrene‐hydrogenated butadiene block copolymer (SEBS). PEC is structurally similar to poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). Using a liquid displacement stress dilatometer, the volume change of samples during uniaxial mechanical straining was determined and related to the various modes of deformation. Blends were fabricated by both injection and compression molding. Miscible PEC and PS blends were found to undergo a craze to shear yielding transition between 40 and 60% PS, which occurred at higher PS concentrations as SEBS was added. Blends with a HDPE matrix and a dispersed glassy phase showed reduced volume dilatation on adding SEBS, indicating better interfacial adhesion between the incompatible blend components. Increases in the sample volume were substantially less in blends with a PEC/PS glassy phase instead of pure PS, suggesting more effective compatibilization by the SEBS copolymer in blends with PEC. This trend is presumed to stem from an exothermic heat of mixing between the PS endblocks of SEBS and the PEC‐rich phases in the blend. Microscopic evidence of the improved adhesion and modes of deformation agrees with the results obtained by dilatometry. The volume dilatation of compression‐molded materials do not seem to be similarly affected by the composition of the glassy phase which may reflect morphological differences between injection‐and compression‐molded blends.