Semi-solid Phases Research Articles

Diversity of organic components in airborne waste discharged from sewer pipe repairs.

Air-discharged waste from commonly used trenchless technologies of sewer pipe repairs is an emerging and poorly characterized source of urban pollution. This study reports on the molecular-level characterization of the atmospherically discharged aqueous-phase waste condensate samples collected at four field sites of the sewer pipe repairs. The molecular composition of organic species in these samples was investigated using reversed-phase liquid chromatography coupled with a photodiode array detector and a high-resolution mass spectrometer equipped with interchangeable atmospheric pressure photoionization and electrospray ionization sources. The waste condensate components comprise a complex mixture of organic species that can partition between gas-, aqueous-, and solid-phases when water evaporates from the air-discharged waste. Identified organic species have broad variability in molecular weight, molecular structures, and carbon oxidation state, which also varied between the waste samples. All condensates contained complex mixtures of oxidized organics, N- and S-containing organics, condensed aromatics, and their functionalized derivatives that are directly released to the atmospheric environment during installations. Furthermore, semi-volatile, low volatility, and extremely low volatility organic compounds comprise 75-85% of the total compounds identified in the waste condensates. Estimates of the component-specific viscosities suggest that upon evaporation of water waste material would form the semi-solid and solid phases. The low volatilities and high viscosities of chemical components in these waste condensates will contribute to the formation of atmospheric secondary organic aerosols and atmospheric solid nanoplastic particles. Lastly, selected components expected in the condensates were quantified and found to be present at high concentrations (1-20 mg L-1) that may exceed regulatory limits.

Influence of hydrothermal pretreatment conditions, typology of anaerobic digestion system, and microbial profile in the production of volatile fatty acids from olive mill solid waste

This study aimed to investigate the production of biobased volatile fatty acids (VFAs) from pretreated olive mill solid waste (OMSW). Three hydrothermal pretreatment (HP) conditions (D1: 125 ºC, 53 min; D2: 161 ºC, 62 min; D3: 191 ºC, 83 min) were selected. The pretreated olive mill solid fraction (OMSF), pretreated olive mill liquid fraction (OMLF), and pretreated OMSW were evaluated as potential substrates for acidification in the anaerobic digestion (AD) in liquid (L-AD), semi-solid (Ss-AD), and solid (S-AD) phases. The best acidification efficiency (AE) observed in this study was 65%, for L-AD and HP condition D2 (161 ºC, 62 min). However, the HP condition D2 applied to the Ss-AD provided a VFA concentration of 18218 mg L−1, about 6-fold higher than that observed in the L-AD system. Polyphenols changed the profile of VFAs, increasing the production of longer chain VFAs in the L-AD and S-AD systems. Also, the influence of the typology of the AD system and HP severity on the microbial community was evaluated. Proteobacteria and Firmicutes were the most representative phyla in acidogenic fermentation of OMSW substrates and the genera Enterobacter, Pseudomonas, Achromobacter, Clostridium, Ochrobactrum, and Peptoclostridium played an important role in the pretreated OMSW fermentation and, consequently, in the VFAs production profile.

Ex Situ and In Situ Measurement of Water Activity with a MEMS Tensiometer.

Water acts as the solvent for natural biotic and abiotic processes and in many technological contexts. The availability of water to participate in chemical and physical processes is captured by thermodynamic variables which track the energetic state of water such as water activity and water potential. Our understanding of the energetic state of water in relevant processes is limited by a lack of sensors capable of providing accurate and reliable ex situ and in situ measurements of water activity. To address this technology gap, we present applications of a microtensiometer (μTM): a biomimetic microelectromechanical system (MEMS) sensor capable of measuring water activity in liquid, vapor, and semisolid (e.g., hydrogels, cheese) phases. We developed packaging, measurement systems, and methodology to enable us to make water activity measurements previously inaccessible to tensiometry. We present measurements in two contexts: (1) a small benchtop unit for ex situ measurements and (2) a probe format for in situ measurements. We demonstrate that the μTM can accurately measure water activity in a diversity of complex samples and agrees with chilled mirror hygrometry, an industry standard for water activity measurement.

Solid, Semisolid, and Liquid Phase States of Individual Submicrometer Particles Directly Probed Using Atomic Force Microscopy.

Currently, the impact of various phase states of aerosols on the climate is not well understood, especially for submicrometer sized aerosol particles that typically have extended lifetime in the atmosphere. This is largely due to the inherent size limitations present in current experimental techniques that aim to directly assess the phase states of fine aerosol particles. Herein we present a technique that uses atomic force microscopy to probe directly for the phase states of individual, submicrometer particles by using nanoindentation and nano-Wilhelmy methodologies as a function of relative humidity (RH) and ambient temperature conditions. When using these methodologies for substrate deposited individual sucrose particles, Young's modulus and surface tension can be quantified as a function of RH. We show that the force profiles collected to measure Young's modulus and surface tension can also provide both qualitative and quantitative assessments of phase states that accompany solid, semisolid, and liquid particle phases. Specifically, we introduce direct measurements of relative indentation depth and viscoelastic response distance on a single particle basis at a given applied force to quantitatively probe for the phase state as a function of RH and corresponding viscosity. Thus, we show that the three phase states and phase state transitions of sucrose can be identified and ultimately propose that this technique may also be used to study other atmospherically relevant systems.

Comparative performance of various smart aggregates during strength gain and damage states of concrete

Information regarding the early strength gain of fresh concrete determines the time for the removal of form work and the transfer of pre-stressing forces for pre-stressed concrete. An ultrasonic based non-destructive evaluation of early strength gain may not work for concrete in fluid and semi-solid phases. A possible alternative is a lead zirconate titanate (PZT)-based smart aggregate embedded in concrete, which can evaluate the micro-structural and rheological properties right from the fluid phase. A set of five smart aggregates embedded in a concrete cube were investigated for their suitability to evaluate electromechanical impedance (EMI) signatures. Cubes were loaded to failure and the EMI during progressive strength loss under compressive loads was studied. To show the generalized applicability of this, experimental results for the performance of typical smart aggregates on a larger specimen, namely a concrete beam, are also discussed. Different statistical metrics were examined computationally on a three peak admittance curve with a parametric variation of stiffness, damping and simple scaling. The root mean square deviation (RMSD), mean absolute percentage deviation (MAPD), cross correlation (CC) and modified cross correlation (MCC) were investigated, in addition to the rate of change of the RMSD. Variations between the reference and modified states were studied. Both stiffness and mass gains occur for the smart aggregates, resulting in an increase or decrease of frequency and amplitude peaks due to progressive C-S-H gel formation. The trend of increasing stiffness and the consequent rightward shift of the resonant peaks and decrease of damping, with the consequent upward shift of amplitudes that happens during curing and strength gain, was observed to be reversed during the application of damaging loads.

Influence of particle-phase state on the hygroscopic behavior of mixed organic–inorganic aerosols

Abstract. Recent work has demonstrated that organic and mixed organic–inorganic particles can exhibit multiple phase states depending on their chemical composition and on ambient conditions such as relative humidity (RH). To explore the extent to which water uptake varies with particle-phase behavior, hygroscopic growth factors (HGFs) of nine laboratory-generated, organic and organic–inorganic aerosol systems with physical states ranging from well-mixed liquids to phase-separated particles to viscous liquids or semi-solids were measured with the Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe at RH values ranging from 40 to 90%. Water-uptake measurements were accompanied by HGF and RH-dependent thermodynamic equilibrium calculations using the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model. In addition, AIOMFAC-predicted growth curves are compared to several simplified HGF modeling approaches: (1) representing particles as ideal, well-mixed liquids; (2) forcing a single phase but accounting for non-ideal interactions through activity coefficient calculations; and (3) a Zdanovskii–Stokes–Robinson-like calculation in which complete separation of the inorganic and organic components is assumed at all RH values, with water uptake treated separately in each of the individual phases. We observed variability in the characteristics of measured hygroscopic growth curves across aerosol systems with differing phase behaviors, with growth curves approaching smoother, more continuous water uptake with decreasing prevalence of liquid–liquid phase separation and increasing oxygen : carbon ratios of the organic aerosol components. We also observed indirect evidence for the dehydration-induced formation of highly viscous semi-solid phases and for kinetic limitations to the crystallization of ammonium sulfate at low RH for sucrose-containing particles. AIOMFAC-predicted growth curves are generally in good agreement with the HGF measurements. The performances of the simplified modeling approaches, however, differ for particles with differing phase states. This suggests that no single simplified modeling approach can be used to capture the water-uptake behavior for the diversity of particle-phase behavior expected in the atmosphere. Errors in HGFs calculated with the simplified models are of sufficient magnitude to produce substantial errors in estimates of particle optical and radiative properties, particularly for the assumption that water uptake is driven by absorptive equilibrium partitioning with ideal particle-phase mixing.

Multiphase chemistry at the atmosphere-biosphere interface influencing climate and public health in the anthropocene.

This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. Review pubs.acs.org/CR Multiphase Chemistry at the Atmosphere−Biosphere Interface Influencing Climate and Public Health in the Anthropocene Ulrich Po schl* and Manabu Shiraiwa* Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany air contaminants (SHCC) and their multiphase chemical interactions at the atmosphere−biosphere interface, including human lungs and skin, plant leaves, cryptogamic covers, soil, and aquatic surfaces. After an overview of different groups of SHCC, we address the chemical interactions of reactive oxygen species and reactive nitrogen species (ROS, RNS), primary biological and secondary organic aerosols (PBA, SOA), as well as carbonaceous combustion aerosols (CCA) including soot, black/elemental carbon, polycyclic aromatic hydrocarbons, and related compounds (PAH, PAC). ROS and RNS interact strongly with other SHCC and are central to both atmospheric and physiological processes and their coupling through the atmosphere−biosphere interface, for example, in the formation and aging of biogenic and combustion aerosols as well as in CONTENTS inflammatory and allergic immune responses triggered by air pollution. Deposition of atmospheric ROS/RNS and aerosols 1. Introduction and Motivation can damage biological tissues, modify surface microbiomes, and 2. Health- and Climate-Relevant Air Contaminants induce oxidative stress through Fenton-like reactions and 2.1. Reactive Oxygen and Nitrogen Species immune responses. The chemical mechanisms and kinetics are 2.2. Primary Biological Aerosols not yet fully elucidated, but the available evidence suggests that 2.3. Secondary Organic Aerosols multiphase processes are crucial for the assessment, prediction, 2.4. Carbonaceous Combustion Aerosols and handling of air quality, climate, and public health. Caution 2.5. Other Air Contaminants Linking Atmospher- should be taken to avoid that human activities shaping the ic and Physiological Chemistry Anthropocene create a hazardous or pathogenic atmosphere 3. Multiphase Chemical Reactions at Specific Bio- overloaded with allergenic, corrosive, toxic, or infectious logical Interfaces contaminants. 3.1. Lung Lining Fluid Multiphase chemistry deals with chemical reactions, trans- 3.2. Human Skin port processes, and transformations between gaseous, liquid, 3.3. Plant Surfaces and Cryptogamic Covers and solid matter. These processes are essential for Earth system 3.4. Soil and Aquatic Surfaces science and climate research as well as for life and health 4. Conclusions and Outlook sciences on molecular and global levels, bridging a wide range Author Information of spatial and temporal scales from below nanometers to Corresponding Authors thousands of kilometers and from less than nanoseconds to Notes years and millennia as illustrated in Figure 1. Biographies From a chemical perspective, life and the metabolism of most Acknowledgments living organisms can be regarded as multiphase processes References involving gases like oxygen and carbon dioxide; liquids like water, blood, lymph, and plant sap; and solid or semisolid substances like bone, tissue, skin, wood, and cellular 1. INTRODUCTION AND MOTIVATION membranes. Even primitive forms of life and metabolic activity Multiphase chemistry plays a vital role in the Earth system, under anaerobic conditions generally involve multiple liquid climate, and health. Chemical reactions, mass transport, and and solid or semisolid phases structured by cells, organelles, and phase transitions between gases, liquids, and solids are essential membranes. 2 On global scales, the biogeochemical cycling of for the interaction and coevolution of life and climate. chemical compounds and elements, which can be regarded as Knowledge of the mechanisms and kinetics of these processes the metabolism of planet Earth, also involves chemical is also required to address societally relevant questions of global reactions, mass transport, and phase transitions within and environmental change and public health in the Anthropocene, that is, in the present era of globally pervasive and steeply Special Issue: 2015 Chemistry in Climate increasing human influence on planet Earth. 1 In this work, we review the current scientific understanding and recent advances Received: September 1, 2014 in the investigation of short-lived health- and climate-relevant Published: April 9, 2015 © 2015 American Chemical Society DOI: 10.1021/cr500487s Chem. Rev. 2015, 115, 4440−4475

Analysis of the Rheological Behaviour of Selected Semi-Solid Slag Systems in Blast Furnace Flow Conditions

Abstract The rheological properties of liquid and semi-solid systems of slag and hot metal in a blast furnace are extremely important from the perspective of their dripping in the unit. The rheological nature and the values of the dynamic viscosity coefficient of liquid and semi-solid phases - slag and hot metal - determine the permeability of the zones in which those systems exist. The modelling of dripping processes and e.g. static and dynamic holding/retention of liquid in the bed, requires an accurate description of the rheological behaviour of slag and iron systems. Determining the liquid flow through the lump bed of the blast furnace is based on the assumption that liquids in the unit in the whole range of their occurrence are similar to a Newtonian ideal liquid. This study presents an analysis of the findings of high-temperature rheometric measurements of CaO-SiO2-Al2O3-MgO systems, liquid, semi-solid slags of the blast furnace type doped with TiO2 and solids in the form of TiN. The tests were performed within a temperature range of 1310-1490°C. Also measurement results for glycerol solutions with concentrations of 86% and 100% at the ambient temperature, simulating blast furnace slags with various contents of solids - PC, anthracite - are presented.

High-Speed Synchrotron X-ray Imaging Studies of the Ultrasound Shockwave and Enhanced Flow during Metal Solidification Processes

The highly dynamic behavior of ultrasonic bubble implosion in liquid metal, the multiphase liquid metal flow containing bubbles and particles, and the interaction between ultrasonic waves and semisolid phases during solidification of metal were studied in situ using the complementary ultrafast and high-speed synchrotron X-ray imaging facilities housed, respectively, at the Advanced Photon Source, Argonne National Laboratory, US, and Diamond Light Source, UK. Real-time ultrafast X-ray imaging of 135,780 frames per second revealed that ultrasonic bubble implosion in a liquid Bi-8 wt pctZn alloy can occur in a single wave period (30 kHz), and the effective region affected by the shockwave at implosion was 3.5 times the original bubble diameter. Furthermore, ultrasound bubbles in liquid metal move faster than the primary particles, and the velocity of bubbles is 70 ~ 100 pct higher than that of the primary particles present in the same locations close to the sonotrode. Ultrasound waves can very effectively create a strong swirling flow in a semisolid melt in less than one second. The energetic flow can detach solid particles from the liquid–solid interface and redistribute them back into the bulk liquid very effectively.

Hazardous odor markers from sewage wastewater: A step towards simultaneous assessment, dearomatization and removal

Odor emissions from Sewage Treatment Plants (STP) may be hazardous and cause nuisance in the surrounding area. Odor is generated by the mixture of volatile organic compounds present in the sewage gas, leachate and leachate treatment systems, sewage sludge and waste materials.This research aimed to develop a quantitative Odor Assessment and Control Scheme (OACS) by simultaneous use of human sensors and liquid phase adsorption. Assessment of odor intensity was accomplished by the standard Sniffer Panel method of Olfactometry. Psychophysical laws were applied and validated to evaluate odor concentrations in the semi-solid, liquid and gas phases. Parameters of these laws were estimated by a robust nonlinear least square technique. It was observed that Beidler's equation on intensity–concentration relationship for sewage could be suitable for samples carrying intense odor from trickling filter based STP. The temporal reduction in odor concentration correlated well with the reduction in the concentration of the most hazardous volatile organo-sulfur compounds (VOSCs) such as n-Propyl Mercaptan (1-Propanethiol), Ethyl-Methyl Sulphide (Methylthio Ethane) and 3,6 Dimethyl 2,4,5,7-tetrathiooctane (bis 1-[{methylthio}ethyl] disulphide).

Gas–particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology

Atmospheric aerosols, comprising organic compounds and inorganic salts, play a key role in air quality and climate. Mounting evidence exists that these particles frequently exhibit phase separation into predominantly organic and aqueous electrolyte-rich phases. As well, the presence of amorphous semi-solid or glassy particle phases has been established. Using the canonical system of ammonium sulfate mixed with organics from the ozone oxidation of α-pinene, we illustrate theoretically the interplay of physical state, non-ideality, and particle morphology affecting aerosol mass concentration and the characteristic timescale of gas-particle mass transfer. Phase separation can significantly affect overall particle mass and chemical composition. Semi-solid or glassy phases can kinetically inhibit the partitioning of semivolatile components and hygroscopic growth, in contrast to the traditional assumption that organic compounds exist in quasi-instantaneous gas-particle equilibrium. These effects have significant implications for the interpretation of laboratory data and the development of improved atmospheric air quality and climate models.

Phase of atmospheric secondary organic material affects its reactivity

The interconversion of atmospheric organic particles among solid, semisolid, and liquid phases is of keen current scientific interest, especially for particles of secondary organic material (SOM). Herein, the influence of phase on ammonia uptake and subsequent particle-phase reactions was investigated for aerosol particles of adipic acid and α-pinene ozonolysis SOM. The nitrogen content of the particles was monitored by online mass spectrometry for increasing ammonia exposure. Solid and semisolid adipic acid particles were inert to the ammonia uptake for low RH (< 5%). For the solid particles, ammonia exposure at high relative humidity (RH; > 94%) induced a first-order deliquescence phase transition into aqueous particles. Solid particles exposed to supersaturated (RH > 100%) conditions and cycled back to high RH (> 94%), thereby becoming acidic metastable particles, underwent a gradual second-order transition upon ammonia exposure to form aqueous, partially neutralized particles. For α-pinene SOM, ammonia exposure at low RH increased the particle-phase ammonium content by a small amount. Mass spectrometric observations suggest a mechanism of neutralization and co-condensation of acidic gas-phase species, consistent with a highly viscous semisolid upon which adsorption occurs. At high RH the ammonium content increased greatly, indicative of rapid diffusion and absorption in a liquid environment. The mass spectra indicated the production of organonitrogen compounds, possibly by particle-phase reactive chemistry. The present results demonstrate that phase can be a key regulator of the reactivity of atmospheric SOM particles.

Structuring oils without highly saturated fats – how far are we?

Eckhard Flöter The interest to structure oil-based products with materials different from highly saturated fats has increased significantly during the time when ‘fat technologists’ were busy to find solutions to reduce and widely eliminate trans fatty acids from our food products. Next to the trans fatty acid elimination the reduction of saturated fatty acids has become a generally acknowledged target. This is expressed in the FAO/WHO goal to limit the energy intake from saturated fatty acids to 10%. The motivation to develop alternative structuring technologies for soft-solid lipid phases could increase beyond current ‘low SaFA’-claims through ongoing discussions on the taxation of saturated fats in products as currently present in Denmark and additionally the risk that the application of natural saturated fatty acids, with palm oil as primary source, becomes more complicated. The latter could be either due to availability issues driven by competing usages or developments of the public opinion with regard to the consumption of tropical oils. As an alternative to replace saturated fats organogelators are now of considerable interest. In simple terms the desired organogelators are to vegetable oils the analogue of what gelatine and other biopolymers are with respect to the structuring of water. These structurants, preferentially applied at low concentration levels, deliver semi-solid lipid phases that have practically the same lipid nutritional profile as liquid oils. Oil structuring or organogelation is not new and the field of organogels outside food is highly active. Non-food applications cover optical materials, drug delivery systems, oil spill recovery techniques, and home and personal care products. Even though the limitation to edible applications reduces the number of candidate structuring materials the size of the haystack for searching some magic needles is still sizable. The scientific efforts of the past decade have not yet delivered a true breakthrough and hence the door for broad food applications of organogels is still closed. The structuring systems that have been studied can arbitrarily be categorized in three classes. First, there are the obvious one component systems familiar to the products considered such as waxes, fatty acids, fatty alcohols and mono- and diacylglycerols. These seem to deliver only limited, if at all, benefits over triacylglycerols. However, in this category of single structurants, materials such as ceramides and 12-hydroxystearic acid offer a clear SaFA benefit compared to structuring vegetable oils by fat crystals. Second, there is a class of composed structuring systems. These usually binary systems such as β-sitosterol and oryzanol, or fatty acids and fatty alcohol, the combination lecithin and sorbitolesters are unfortunately very prone to losing their structuring potential in product applications. This is for example due to either the presence of an oil-water interface or the formation of hydrates that tend to deplete the self-assembled structure in at least one of its components. Third, there is oil structuring through components that are alien to the products considered and mostly deliberately synthesized. Here, ethylcellulose and protein fibrils have to be mentioned. The field of edible oil structuring and the current status of different approaches has been reviewed and discussed repeatedly 1-3. Undoubtedly substantial progress has been made with respect to the number of different structuring systems and the comprehension of their mechanism of action. However, the step from gelling oil on the laboratory bench to deliver a robust structured lipid phase in a food product appears to be quite big. At first some structuring systems are just too costly or the availability of the necessary material is limited. Secondly, food products and their manufacturing processes appear to be quite hostile for oil structuring systems because oil–water interfaces, water activity levels or shear during manufacturing can be critical for the organogels. Additionally, the perceivable properties of gelled oils are different from conventional semi-solid lipid phases. Typically there will be no cooling sensation and also other product disintegration characteristics will change. This is understandably a major obstacle in any product development effort. However, the time might be ripe to selectively move oil structuring from the laboratory bench towards product development. Recently a good example of a successful product application was reported by Zetzl et al. 4. Here the domains of animal fat in Frankfurter sausages were substituted by pieces of ethylcellulose structured vegetable oil. Since it is unlikely that a single oil structuring system will be a general substitute for fat crystals one can expect different application specific structuring solutions varying from hybrid systems, combinations of saturated TAG and organogelators, to full replacement of the structuring fat. Finally, the future market success of organogel-based products will not only depend on the technical ability to formulate acceptable products, which is certainly easier for completely new ones without any reference perception, but also on the ‘consumer digestible’ communication concerning the structuring materials. Eckhard Flöter Editor

Formation of semi-solid lipid phases by aggregation of protein microspheres in water-in-oil emulsions

Controlled aggregation of protein microspheres in water-in-oil (W/O) emulsions was used to form semi-solid lipid materials. The aqueous phase consisted of 10wt% whey protein isolate (WPI) in buffer solution (pH 7.0, 100mM NaCl). The oil phase consisted of a lipophilic nonionic surfactant (8 wt % polyglycerol polyricinoleate, PGPR) dispersed in a liquid oil (soybean oil). Lipid phases containing protein microspheres were formed by homogenization of the oil and aqueous phases to form a W/O emulsion followed by heating (90°C for 30min) to promote gelation of the WPI in the aqueous phase. Temperature-scanning dynamic shear measurements showed that the W/O emulsions underwent an irreversible liquid-to-solid transition when heated above the thermal denaturation temperature of WPI, which was attributed to protein gelation and microsphere aggregation. Optical microscopy indicated that a three-dimensional network of aggregated protein microspheres was formed at high aqueous phase contents (>30 wt %). Shear rheology measurements (shear stress versus shear rate) indicated that these structured emulsions were non-ideal plastic-like materials. The apparent shear viscosity increased with thermal treatment, increasing aqueous phase content, and decreasing shear rate. The structured W/O emulsions developed in this study may be useful materials for the development of foods with highly viscous or gel-like lipid phases, but low saturated or trans-fat contents.

Gas uptake and chemical aging of semisolid organic aerosol particles.

Organic substances can adopt an amorphous solid or semisolid state, influencing the rate of heterogeneous reactions and multiphase processes in atmospheric aerosols. Here we demonstrate how molecular diffusion in the condensed phase affects the gas uptake and chemical transformation of semisolid organic particles. Flow tube experiments show that the ozone uptake and oxidative aging of amorphous protein is kinetically limited by bulk diffusion. The reactive gas uptake exhibits a pronounced increase with relative humidity, which can be explained by a decrease of viscosity and increase of diffusivity due to hygroscopic water uptake transforming the amorphous organic matrix from a glassy to a semisolid state (moisture-induced phase transition). The reaction rate depends on the condensed phase diffusion coefficients of both the oxidant and the organic reactant molecules, which can be described by a kinetic multilayer flux model but not by the traditional resistor model approach of multiphase chemistry. The chemical lifetime of reactive compounds in atmospheric particles can increase from seconds to days as the rate of diffusion in semisolid phases can decrease by multiple orders of magnitude in response to low temperature or low relative humidity. The findings demonstrate that the occurrence and properties of amorphous semisolid phases challenge traditional views and require advanced formalisms for the description of organic particle formation and transformation in atmospheric models of aerosol effects on air quality, public health, and climate.

MUC2, MUC5AC and MUC5B in the mucus of a patient with pseudomyxoma peritonei: Biochemical and immunohistochemical study

A 58-year-old man with a 1 year history of progressive abdominal distension underwent a laparotomy for pseudomyxoma peritonei. The mucin was identified and characterized in the present study. Approximately 6 L of crude mucus in the sol (highly viscous) and gel (semisolid) phases was obtained from the patient's peritoneal cavity. The sol material was briefly homogenized followed by slow stirring at dilutions of up to 1:10 with 6 mol/L guanidinium chloride and proteolytic inhibitors for periods of up to 48 h. Preparative and analytical gel filtration on Sepharose 2B showed some PAS-positive material eluting in the void volume accompanied by equal or larger amounts of protein in the void and included volumes of the columns. Sodium dodecylsulfate-polyacrylamide gel electrophoresis of purified mucin on a 4-20% gradient gel showed PAS-positive material on the top of the running gel and a distinct smaller-sized species of mucin of higher electrophoretic mobility with background material in between the large and small mucin. Western blot (confirmed by immunohistochemical analysis) after agarose gel electrophoresis showed the presence of MUC2, MUC5AC and MUC5B in the mucus. There was no MUC1, MUC1core or MUC6 in the tissue. Histopathological examination confirmed a mucinous appendicular adenocarcinoma. Histology showed the mucin to be predominantly of the sulfated and non-sulfated acidic type. Serine, threonine and proline comprised 21.6% of the total amino acid composition of the sample. The viscous nature of the material is due to the presence of three gel-forming mucins and possibly to its high content of protein.

Thermomechanical finite-element model of shell behavior in continuous casting of steel

A coupled finite-element model, CON2D, has been developed to simulate temperature, stress, and shape development during the continuous casting of steel, both in and below the mold. The model simulates a transverse section of the strand in generalized plane strain as it moves down at the casting speed. It includes the effects of heat conduction, solidification, nonuniform superheat dissipation due to turbulent fluid flow, mutual dependence of the heat transfer and shrinkage on the size of the interfacial gap, the taper of the mold wall, and the thermal distortion of the mold. The stress model features an elastic-viscoplastic creep constitutive equation that accounts for the different responses of the liquid, semisolid, delta-ferrite, and austenite phases. Functions depending on temperature and composition are employed for properties such as thermal linear expansion. A contact algorithm is used to prevent penetration of the shell into the mold wall due to the internal liquid pressure. An efficient two-step algorithm is used to integrate these highly nonlinear equations. The model is validated with an analytical solution for both temperature and stress in a solidifying slab. It is applied to simulate continuous casting of a 120 mm billet and compares favorably with plant measurements of mold wall temperature, total heat removal, and shell thickness, including thinning of the corner. The model is ready to investigate issues in continuous casting such as mold taper optimization, minimum shell thickness to avoid breakouts, and maximum casting speed to avoid hot-tear crack formation due to submold bulging.

The influence of oxygen tension on the long-term growth in vitro of haematopoietic progenitor cells from human cord blood.

Growth of low density human cord blood cells in long-term suspension culture was evaluated at incubation conditions of 5% carbon dioxide in approximately 20% (normal incubator) oxygen tension or in 5% (low) oxygen tension. During the first 5 weeks there was no difference in the numbers of morphologically recognizable cells grown at either oxygen tension, while growth was superior from weeks 5 to 8 at approximately 20% oxygen tension. For the first 5 weeks, growth of granulocyte-macrophage progenitors (CFU-GM) was superior at 5% oxygen tension during the long-term and semi-solid culture phases and least impressive in the long-term and semi-solid cultures incubated at approximately 20% oxygen. This trend was reversed after 5 weeks and after 8 weeks there were no detectable CFU-GM in suspension cultures at 5% oxygen while steady state levels of CFU-GM were maintained for greater than 12 weeks in suspension cultures at approximately 20% oxygen. Semi-solid cultures for erythroid (BFU-E) and multipotential (CFU-GEMM) progenitors were incubated at approximately 20% oxygen only. During the first 4 weeks, the growth of BFU-E and CFU-GEMM was superior at 5% oxygen during long-term culture. Numbers of these cells decreased by week 5 and at this time growth was better in the long-term cultures grown at approximately 20% oxygen. By week 6, no BFU-E or CFU-GEMM were detectable. Thus, growth of cord blood at low oxygen tension gives an initial enhancement in output of progenitor cells, but this appears to be at the expense of continued production.

Thermodynamics of distribution of salicylates in semi-solid ointment bases.

The distribution behavior of salicylic acid and its various esters (methyl, ethyl, phenyl, and glycol) between different semisolid vehicles (PEG, Carbopol 940, Plastibase) and non-miscible second phases has been examined over a range of temperature. The derived thermodynamics data can be used to discuss drug-vehicle interactions and changes in the thermodynamic activity of the solute. Salicylic acid interacts little, if at all, with inert materials such as Plastibase (mineral oil thickened with polyethylene) but together with its esters shows strong interaction with PEG. An increased interaction with increase in molecular weight (ethylene oxide content) of PEG is demonstrated. The salicylate esters have a lower affinity for Carbopol gels than for PEG because of entropy effects. Glycol salicylate in Carbopol gels demonstrates anomalous behavior. The relevance of the data to studies on drug release, and in particular the evaluation of rheological factors, is discussed.