Influence of silica fume on mechanical and physical properties of recycled aggregate concrete

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Özgür Çakır

2015-08-01

Full Text Available Several studies related to sustainable concrete construction have encouraged development of composite binders, involving Portland cement, industrial by-products, and concrete mixes with partial replacement of natural aggregate with recycled aggregate. In this paper, the effects of incorporating silica fume (SF in the concrete mix design to improve the quality of recycled aggregates in concrete are presented. Portland cement was replaced with SF at 0%, 5% and 10%. Specimens were manufactured by replacing natural aggregates with recycled aggregates. Two size fractions (4/12 mm and 8/22 mm as recycled aggregates were used and four series of concrete mixtures were produced. In all concrete mixtures, a constant water/binder ratio at 0.50 was used and concrete mixtures with a target initial slump of S4 class (16–21 cm were prepared. Concrete properties were evaluated by means of compressive strength, tensile splitting strength, water absorption and ultrasonic pulse velocity and it was found that, using 10% SF as a cement replacement for recycled aggregate concretes enhanced the mechanical and physical properties of concrete. At all the test ages the tensile splitting strength gain of the natural aggregate concrete mixture (NA with and without SF was higher than that of the recycled concrete mixtures. Continuous and significant improvement in the tensile splitting strength of recycled aggregate concretes incorporating SF was observed. Similar to compressive strength test results, concrete incorporating 10% SF and containing 4/12 mm fraction recycled aggregates showed better performance among recycled aggregate concretes.

Flocculation kinetics and aggregate structure of kaolinite mixtures in laminar tube flow.

Science.gov (United States)

Vaezi G, Farid; Sanders, R Sean; Masliyah, Jacob H

2011-03-01

Flocculation is commonly used in various solid-liquid separation processes in chemical and mineral industries to separate desired products or to treat waste streams. This paper presents an experimental technique to study flocculation processes in laminar tube flow. This approach allows for more realistic estimation of the shear rate to which an aggregate is exposed, as compared to more complicated shear fields (e.g. stirred tanks). A direct sampling method is used to minimize the effect of sampling on the aggregate structure. A combination of aggregate settling velocity and image analysis was used to quantify the structure of the aggregate. Aggregate size, density, and fractal dimension were found to be the most important aggregate structural parameters. The two methods used to determine aggregate fractal dimension were in good agreement. The effects of advective flow through an aggregate's porous structure and transition-regime drag coefficient on the evaluation of aggregate density were considered. The technique was applied to investigate the flocculation kinetics and the evolution of the aggregate structure of kaolin particles with an anionic flocculant under conditions similar to those of oil sands fine tailings. Aggregates were formed using a well controlled two-stage aggregation process. Detailed statistical analysis was performed to investigate the establishment of dynamic equilibrium condition in terms of aggregate size and density evolution. An equilibrium steady state condition was obtained within 90 s of the start of flocculation; after which no further change in aggregate structure was observed. Although longer flocculation times inside the shear field could conceivably cause aggregate structure conformation, statistical analysis indicated that this did not occur for the studied conditions. The results show that the technique and experimental conditions employed here produce aggregates having a well-defined, reproducible structure. Copyright © 2011

Experimental investigation of asphalt mixture containing Linz-Donawitz steel slag

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Jens Groenniger

2017-08-01

Full Text Available Standard asphalt mixtures for road infrastructures consist of natural aggregate and bitumen. A number of research efforts have successfully investigated the possibility of replacing the conventional aggregate skeleton with industrial by-products such as slag originating from steel production process. However, little is known on the effect of steel slag on the mixtures performance properties such as resistance to low-temperature cracking and to permanent deformation, stiffness and fatigue. This paper presents a comprehensive investigation on the fundamental performance properties of different types of asphalt mixtures prepared with 100% LD slag aggregate and a conventional asphalt mixture containing natural Gabbro aggregate. Sophisticated testing methods were used to evaluate the key performance parameters for the set of asphalt mixtures investigated. In this study, low temperature cracking was addressed through thermal stress restrained specimen tests. Penetration tests and cyclic compression tests were used to evaluate the response of asphalt binder and asphalt mixture to permanent deformation due repeated loading, respectively. The cyclic indirect tensile test was selected for investigating both stiffness properties and fatigue resistance. For this purpose the complex stiffness modulus was measured to quantify material stiffness under different temperature and loading conditions providing information on the visco-elasto-plastic material behavior. Fatigue tests were used to determine the progressive and localized material damage caused by cyclic loading. The experimental results indicate that asphalt mixtures prepared with LD slag are suitable for asphalt pavement construction and that in most cases they perform better than conventional asphalt mixtures prepared with Gabbro aggregate.

Study on Concrete Containing Recycled Aggregates Immersed in Epoxy Resin

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Adnan Suraya Hani

2017-01-01

Full Text Available In recent decades, engineers have sought a more sustainable method to dispose of concrete construction and demolition waste. One solution is to crush this waste concrete into a usable gradation for new concrete mixes. This not only reduces the amount of waste entering landfills but also alleviates the burden on existing sources of quality natural concrete aggregates. There are too many kinds of waste but here constructions waste will be the priority target that should be solved. It could be managed by several ways such as recycling and reusing the concrete components, and the best choice of these components is the aggregate, because of the ease process of recycle it. In addition, recycled aggregates and normal aggregates were immersed in epoxy resin and put in concrete mixtures with 0%, 5%, 10% and 20% which affected the concrete mixtures properties. The strength of the concrete for both normal and recycled aggregates has increased after immersed the aggregates in epoxy resin. The percentage of water absorption and the coefficient of water permeability decreased with the increasing of the normal and the recycled aggregates immersed in epoxy resin. Generally the tests which have been conducted to the concrete mixtures have a significant results after using the epoxy resin with both normal and recycled aggregates.

Internal water curing with Liapor aggregates

DEFF Research Database (Denmark)

Lura, Pietro

2005-01-01

Internal water curing is a very efficient way to counteract self-desiccation and autogenous shrinkage in high performance concrete, thereby reducing the likelihood of early-age cracking. This paper deals with early-age volume changes and moisture transport in lightweight aggregate concrete realized...... with wet lightweight aggregates. Lightweight aggregate concrete mixtures with different degree of saturation and different particle size of the lightweight aggregates were studied and compared to normal weight concrete. Autogenous deformations, selfinduced stresses in fully restrained conditions, elastic...

Evaluation of Colemanite Waste as Aggregate Hot Mix Asphalt Concrete

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Nihat MOROVA

2015-09-01

Full Text Available In this study usability of waste colemanite which is obtained after cutting block colemanite for giving proper shape to blocks as an aggregate in hot mix asphalt. For this aim asphalt concrete samples were prepared with four different aggregate groups and optimum bitumen content was determined. First of all only limestone was used as an aggregate. After that, only colemanite aggregate was used with same aggregate gradation. Then, the next step of the study, Marshall samples were produced by changing coarse and fine aggregate gradation as limestone and colemanite and Marshall test were conducted. When evaluated the results samples which produced with only limestone aggregate gave the maximum Marshall Stability value. When handled other mixture groups (Only colemanite, colemanite as coarse aggregate-limestone as fine aggregate, colemanite as fine aggregate-limestone as coarse aggregate all groups were verified specification limits. As a result, especially in areas where there is widespread colemanite waste, if transportation costs did not exceed the cost of limestone, colemanite stone waste could be used instead of limestone in asphalt concrete mixtures as fine aggregate

Stripping in hot mix asphalt produced by aggregates from construction and demolition waste.

Science.gov (United States)

Pérez, I; Pasandín, A R; Gallego, J

2012-01-01

This paper analyses the effect of water on the durability of hot asphalt mixtures made with recycled aggregates from construction and demolition debris. Indirect tensile stress tests were carried out to evaluate stripping behaviour. The mixtures tested were fabricated with 0, 20, 40 and 60% recycled aggregates. Two types of natural aggregates were used: schist and calcite dolomite. An increase in the percentage of recycled aggregates was found to produce a decrease in the tensile stress ratio of the hot asphalt mixtures. To study this phenomenon, two and three factor analyses of variance (ANOVA) were performed with indirect tensile stress being used as the dependent variable. The factors studied were the percentage of recycled aggregates (0, 20, 40 and 60%), the moisture state (dry, wet) and the type of natural aggregate (schist, calcite). On the basis of the ANOVA results, it was found that the most important factor affecting resistance was the moisture state (dry, wet) of the specimens. The percentage of recycled aggregate also affected indirect tensile stress, especially in the dry state. The type of natural aggregate did not have a significant effect on indirect tensile stress. The hot asphalt mixture specimens made with different percentages of recycled aggregates from construction and demolition debris and of natural quarry aggregates showed poor stripping behaviour. This stripping behaviour can be related to both the poor adhesion of the recycled aggregates and the high absorption of the mortar of cement adhered to them.

The Effect of Morphological Characteristic of Coarse Aggregates Measured with Fractal Dimension on Asphalt Mixture’s High-Temperature Performance

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Hainian Wang

2016-01-01

Full Text Available The morphological properties of coarse aggregates, such as shape, angularity, and surface texture, have a great influence on the mechanical performance of asphalt mixtures. This study aims to investigate the effect of coarse aggregate morphological properties on the high-temperature performance of asphalt mixtures. A modified Los Angeles (LA abrasion test was employed to produce aggregates with various morphological properties by applying abrasion cycles of 0, 200, 400, 600, 800, 1000, and 1200 on crushed angular aggregates. Based on a laboratory-developed Morphology Analysis System for Coarse Aggregates (MASCA, the morphological properties of the coarse aggregate particles were quantified using the index of fractal dimension. The high-temperature performances of the dense-graded asphalt mixture (AC-16, gap-graded stone asphalt mixture (SAC-16, and stone mastic asphalt (SMA-16 mixtures containing aggregates with different fractal dimensions were evaluated through the dynamic stability (DS test and the penetration shear test in laboratory. Good linear correlations between the fractal dimension and high-temperature indexes were obtained for all three types of mixtures. Moreover, the results also indicated that higher coarse aggregate angularity leads to stronger high-temperature shear resistance of asphalt mixtures.

Partitioning the aggregation of parasites on hosts into intrinsic and extrinsic components via an extended Poisson-gamma mixture model.

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Justin M Calabrese

Full Text Available It is well known that parasites are often highly aggregated on their hosts such that relatively few individuals host the large majority of parasites. When the parasites are vectors of infectious disease, a key consequence of this aggregation can be increased disease transmission rates. The cause of this aggregation, however, is much less clear, especially for parasites such as arthropod vectors, which generally spend only a short time on their hosts. Regression-based analyses of ticks on various hosts have focused almost exclusively on identifying the intrinsic host characteristics associated with large burdens, but these efforts have had mixed results; most host traits examined have some small influence, but none are key. An alternative approach, the Poisson-gamma mixture distribution, has often been used to describe aggregated parasite distributions in a range of host/macroparasite systems, but lacks a clear mechanistic basis. Here, we extend this framework by linking it to a general model of parasite accumulation. Then, focusing on blacklegged ticks (Ixodes scapularis on mice (Peromyscus leucopus, we fit the extended model to the best currently available larval tick burden datasets via hierarchical Bayesian methods, and use it to explore the relative contributions of intrinsic and extrinsic factors on observed tick burdens. Our results suggest that simple bad luck-inhabiting a home range with high vector density-may play a much larger role in determining parasite burdens than is currently appreciated.

Evaluation of Skid Resistance of Wearing Course Made Of Stone Mastic Asphalt Mixture in Laboratory Conditions

Science.gov (United States)

Wasilewska, Marta

2017-10-01

This paper presents the comparison of skid resistance of wearing course made of SMA (Stone Mastic Asphalt) mixtures which differ in resistance to polishing of coarse aggregate. Dolomite, limestone, granite and trachybasalt were taken for investigation. SMA mixtures have the same nominal size of aggregate (11 mm) and very similar aggregate particle-size distribution in mineral mixtures. Tested SMA11 mixtures were designed according to EN 13108-5 and Polish National Specification WT-2: 2014. Evaluation of the skid resistance has been performed using the FAP (Friction After Polishing) test equipment also known as the Wehner/Schulze machine. Laboratory method enables to compare the skid resistance of different types of mixtures under specified conditions simulating polishing processes. Tests were performed on both the specimens made of each coarse aggregate and SMA11 mixtures containing these aggregates. Measuring of friction coefficient μm was conducted before and during polishing process up to 180 0000 passes of polishing head. Comparison of the results showed differences in sensitivity to polishing among particular mixtures which depend on the petrographic properties of rock used to produce aggregate. Limestone and dolomite tend to have a fairly uniform texture with low hardness which makes these rock types susceptible to rapid polishing. This caused lower coefficient of friction for SMA11 mixtures with limestone and dolomite in comparison with other test mixtures. These significant differences were already registered at the beginning of the polishing process. Limestone aggregate had lower value of μm before starting the process than trachybasalt and granite aggregate after its completion. Despite the differences in structure and mineralogical composition between the granite and trachybasalt, slightly different values of the friction coefficient at the end of polishing were obtained. Images of the surface were taken with the optical microscope for better

Performance evaluation of Louisiana superpave mixtures : tech summary.

Science.gov (United States)

2008-12-01

The primary objective of this research was to evaluate the fundamental engineering : properties and mixture performance of Superpave hot mix asphalt (HMA) mixtures : in Louisiana through laboratory mechanistic tests, aggregate gradation analysis, and...

Aggregation behavior of sodium lauryl ether sulfate with a positively bicharged organic salt and effects of the mixture on fluorescent properties of conjugated polyelectrolytes.

Science.gov (United States)

Tang, Yongqiang; Liu, Zhang; Zhu, Linyi; Han, Yuchun; Wang, Yilin

2015-02-24

The aggregation behavior of anionic single-chain surfactant sodium lauryl ether sulfate containing three ether groups (SLE3S) with positively bicharged organic salt 1,2-bis(2-benzylammoniumethoxy)ethane dichloride (BEO) has been investigated in aqueous solution, and the effects of the BEO/SLE3S aggregate transitions on the fluorescent properties of anionic conjugated polyelectrolyte MPS-PPV with a larger molecular weight and cationic conjugated oligoelectrolyte DAB have been evaluated. Without BEO, SLE3S does not affect the fluorescent properties of MPS-PPV and only affects the fluorescent properties of DAB at a higher SLE3S concentration. With the addition of BEO, SLE3S and BEO form gemini-like surfactant (SLE3S)2-BEO. When the BEO/SLE3S molar ratio is fixed at 0.25, with increasing the BEO/SLE3S concentration, the BEO/SLE3S mixture forms large, loosely arranged aggregates and then transforms to closely packed spherical aggregates and finally to long thread-like micelles. The photoluminescence (PL) intensity of MPS-PPV varies with the morphologies of the BEO/SLE3S aggregates, while the PL intensity of DAB is almost independent of the aggregate morphologies. The results demonstrate that gemini-like surfactants formed through intermolecular interactions can effectively adjust the fluorescent properties of conjugated polyelectrolytes.

Pervious concrete using fly ash aggregate as coarse aggregate-an experimental study

Science.gov (United States)

Dash, Subhakanta; Kar, Biswabandita; Mukherjee, Partha Sarathi

2018-05-01

The present study deals with the fabrication of pervious concrete from fly ash aggregates. The pervious concrete were obtained by the mixture of three different size fly ash aggregates (4.75 mm,9.5 mm,12.5 mm), Portland cement, water with little amount of sand or without sand. Admixtures like Silica fume(SF) and Super plasticizer are added to the mixture to enhance the strength of concrete. Trial being taken on preparation of Fly ash based pervious concrete (FPC) with different w/c ratio i.e. 0.30, 0.35 and 0.40 respectively. Tests such as porosity, permeability and compressive, strength are studied for this concrete material and the result concluded that the concrete when cured for 28 days its compressive strength falls in between 7.15 - 15.74 MPa and permeability 9.38 - 16.07 mm/s with porosity 27.59 - 34.05% and these are suited to be used as for use as an environment friendly concrete.

EAF Slag Aggregate in Roller-Compacted Concrete Pavement: Effects of Delay in Compaction

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My Ngoc-Tra Lam

2018-04-01

Full Text Available This study investigates the effect of delay in compaction on the optimum moisture content and the mechanical propertie s (i.e., compressive strength, ultrasonic pulse velocity, splitting tensile strength, and modulus of elasticity of roller-compacted concrete pavement (RCCP made of electric arc furnace (EAF slag aggregate. EAF slag with size in the range of 4.75–19 mm was used to replace natural coarse aggregate in RCCP mixtures. A new mixing method was proposed for RCCP using EAF slag aggregate. The optimum moisture content of RCCP mixtures in this study was determined by a soil compaction method. The Proctor test assessed the optimum moisture content of mixtures at various time after mixing completion (i.e., 0, 15, 30, 60, and 90 min. Then, the effect of delay in compaction on the mechanical properties of RCCP mixtures at 28 days of age containing EAF slag aggregate was studied. The results presented that the negative effect on water content in the mixture caused by the higher water absorption characteristic of EAF slag was mitigated by the new mixing method. The optimum water content and maximum dry density of RCCP experience almost no effect from the delay in compaction. The compressive strength and splitting tensile strength of RCCP using EAF slag aggregate fulfilled the strength requirements for pavement with 90 min of delay in compaction.

Atomic Force Microscope Imaging of the Aggregation of Mouse Immunoglobulin G Molecules

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Ke Xia

2003-01-01

Full Text Available Mouse immunoglobulin G (Ig G1 and the mixture of Ig G1 and Ig G2 deposited on mica were imaged with an atomic force microscope at room temperature and ambient pressure. At a concentration around 1.0mg/L, the molecules were well dispersed. 2~3 days after sample preparation, both Ig G1 and the mixture could self- assemble into different shapes and further form some types of local-ordered toroidal aggregations (monotoroidal, intercrossed toroidal, concentric toroidal, etc.. The number of monomers was not identical in the different toroidal aggregations but in a same circle, the shapes of polymer self-assembled by several monomolecules were found to be almost the same. There was difference between the aggregation behavior of Ig G1 and the mixture. The mechanism of Ig G molecule aggregation was ascribed to the “Y” shape and loops structure of Ig G molecule.

Blasted copper slag as fine aggregate in Portland cement concrete.

Science.gov (United States)

Dos Anjos, M A G; Sales, A T C; Andrade, N

2017-07-01

The present work focuses on assessing the viability of applying blasted copper slag, produced during abrasive blasting, as fine aggregate for Portland cement concrete manufacturing, resulting in an alternative and safe disposal method. Leaching assays showed no toxicity for this material. Concrete mixtures were produced, with high aggregate replacement ratios, varying from 0% to 100%. Axial compressive strength, diametrical compressive strength, elastic modulus, physical indexes and durability were evaluated. Assays showed a significant improvement in workability, with the increase in substitution of fine aggregate. With 80% of replacement, the concrete presented lower levels of water absorption capacity. Axial compressive strength and diametrical compressive strength decreased, with the increase of residue replacement content. The greatest reductions of compressive strength were found when the replacement was over 40%. For tensile strength by diametrical compression, the greatest reduction occurred for the concrete with 80% of replacement. After the accelerated aging, results of mechanic properties showed a small reduction of the concrete with blasted copper slag performance, when compared with the reference mixture. Results indicated that the blasted copper slag is a technically viable material for application as fine aggregate for concrete mixtures. Copyright © 2017 Elsevier Ltd. All rights reserved.

Natural aggregate totally replacement by mechanically treated concrete waste

Directory of Open Access Journals (Sweden)

Junak Jozef

2015-06-01

Full Text Available This paper presents the results obtained from the research focused on the utilization of crushed concrete waste aggregates as a partial or full replacement of 4/8 and 8/16 mm natural aggregates fraction in concrete strength class C 16/20. Main concrete characteristics such as workability, density and compressive strength were studied. Compressive strength testing intervals for samples with recycled concrete aggregates were 2, 7, 14 and 28 days. The amount of water in the mixtures was indicative. For mixture resulting consistency required slump grade S3 was followed. Average density of all samples is in the range of 2250 kg/m3 to 2350 kg/m3. The highest compressive strength after 28 days of curing, 34.68 MPa, reached sample, which contained 100% of recycled material in 4/8 mm fraction and 60% of recycled aggregates in 8/16 mm fraction. This achieved value was only slightly different from the compressive strength 34.41 MPa of the reference sample.

Recycled Concrete as Aggregate for Structural Concrete Production

OpenAIRE

Mirjana Malešev; Vlastimir Radonjanin; Snežana Marinković

2010-01-01

A comparative analysis of the experimental results of the properties of fresh and hardened concrete with different replacement ratios of natural with recycled coarse aggregate is presented in the paper. Recycled aggregate was made by crushing the waste concrete of laboratory test cubes and precast concrete columns. Three types of concrete mixtures were tested: concrete made entirely with natural aggregate (NAC) as a control concrete and two types of concrete made with natural fine and recycle...

Valorization of lignite combustion residues and ferroalumina in the production of aggregates.

Science.gov (United States)

Anagnostopoulos, I M; Stivanakis, V E; Angelopoulos, G N; Papamantellos, D C

2010-02-15

The present research study investigates the synergy of industrial solid by-products from lignite combustion (fly ash and bottom ash) and aluminum production (ferroalumina) in the production of lightweight aggregates (LWA). The process consists of two stages, pelletization and sintering. Bottom ash (BA) is used as the principal raw material in mixtures while ferroalumina (FAL) is added in lower percentages (5-30 wt%). BA carbon content is used as the fuel of sintering process in high temperatures, around 1250 degrees C, and gas generation is responsible for porous structure formation. Physical properties such as porosity, water absorption and bulk density, of sintering products are measured. Increase of FAL percentage in sintering mixtures results in decrease of porosity from 61% to 35% and of water absorption from 61% to 21% and in increase of bulk density from 1.02 g/cm(3) to 1.80 g/cm(3) of the produced aggregates. Aggregates produced by FAL addition up to 20 wt% are characterized as LWA. Aggregates formed are used in the production of concrete specimens. Compressive strength of concrete increases by increasing FAL addition in aggregates from 5 wt% to 15 wt% (highest strength value), while decrease by increasing FAL addition from 20 wt% to 30 wt%. FAL addition in lignite ashes sintering mixtures (up to 15 wt%) is considered as an important parameter for enhancing aggregates strength.

Cement treated recycled crushed concrete and masonry aggregates for pavements

NARCIS (Netherlands)

Xuan, D.X.

2012-01-01

This research is focusing on the characterization of the mechanical and deformation properties of cement treated mixtures made of recycled concrete and masonry aggregates (CTMiGr) in relation to their mixture variables. An extensive laboratory investigation was carried out, in which the mechanical

Recovery of MSWI and soil washing residues as concrete aggregates.

Science.gov (United States)

Sorlini, Sabrina; Abbà, Alessandro; Collivignarelli, Carlo

2011-02-01

The aim of the present work was to study if municipal solid waste incinerator (MSWI) residues and aggregates derived from contaminated soil washing could be used as alternative aggregates for concrete production. Initially, chemical, physical and geometric characteristics (according to UNI EN 12620) of municipal solid waste incineration bottom ashes and some contaminated soils were evaluated; moreover, the pollutants release was evaluated by means of leaching tests. The results showed that the reuse of pre-treated MSWI bottom ash and washed soil is possible, either from technical or environmental point of view, while it is not possible for the raw wastes. Then, the natural aggregate was partially and totally replaced with these recycled aggregates for the production of concrete mixtures that were characterized by conventional mechanical and leaching tests. Good results were obtained using the same dosage of a high resistance cement (42.5R calcareous Portland cement instead of 32.5R); the concrete mixture containing 400 kg/m(3) of washed bottom ash and high resistance cement was classified as structural concrete (C25/30 class). Regarding the pollutants leaching, all concrete mixtures respected the limit values according to the Italian regulation. Copyright © 2010 Elsevier Ltd. All rights reserved.

The optimization of concrete mixtures for use in highway applications

Science.gov (United States)

Moini, Mohamadreza

Portland cement concrete is most used commodity in the world after water. Major part of civil and transportation infrastructure including bridges, roadway pavements, dams, and buildings is made of concrete. In addition to this, concrete durability is often of major concerns. In 2013 American Society of Civil Engineers (ASCE) estimated that an annual investment of 170 billion on roads and 20.5 billion for bridges is needed on an annual basis to substantially improve the condition of infrastructure. Same article reports that one-third of America's major roads are in poor or mediocre condition [1]. However, portland cement production is recognized with approximately one cubic meter of carbon dioxide emission. Indeed, the proper and systematic design of concrete mixtures for highway applications is essential as concrete pavements represent up to 60% of interstate highway systems with heavier traffic loads. Combined principles of material science and engineering can provide adequate methods and tools to facilitate the concrete design and improve the existing specifications. In the same manner, the durability must be addressed in the design and enhancement of long-term performance. Concrete used for highway pavement applications has low cement content and can be placed at low slump. However, further reduction of cement content (e.g., versus current specifications of Wisconsin Department of Transportation to 315-338 kg/m 3 (530-570 lb/yd3) for mainstream concrete pavements and 335 kg/m3 (565 lb/yd3) for bridge substructure and superstructures) requires delicate design of the mixture to maintain the expected workability, overall performance, and long-term durability in the field. The design includes, but not limited to optimization of aggregates, supplementary cementitious materials (SCMs), chemical and air-entraining admixtures. This research investigated various theoretical and experimental methods of aggregate optimization applicable for the reduction of cement content

Reuse of steel slag in bituminous paving mixtures.

Science.gov (United States)

Sorlini, Sabrina; Sanzeni, Alex; Rondi, Luca

2012-03-30

This paper presents a comprehensive study to evaluate the mechanical properties and environmental suitability of electric arc furnace (EAF) steel slag in bituminous paving mixtures. A variety of tests were executed on samples of EAF slag to characterize the physical, geometrical, mechanical and chemical properties as required by UNI EN specifications, focusing additionally on the volumetric expansion associated with hydration of free CaO and MgO. Five bituminous mixtures of aggregates for flexible road pavement were designed containing up to 40% of EAF slag and were tested to determine Marshall stability and indirect tensile strength. The leaching behaviour of slag samples and bituminous mixtures was evaluated according to the UNI EN leaching test. The tested slag showed satisfactory physical and mechanical properties and a release of pollutants generally below the limits set by the Italian code. Tests on volume stability of fresh materials confirmed that a period of 2-3 months is necessary to reduce effects of oxides hydration. The results of tests performed on bituminous mixtures with EAF slag were comparable with the performance of mixtures containing natural aggregates and the leaching tests provided satisfactory results. Copyright © 2012 Elsevier B.V. All rights reserved.

The Influence of Moisture on the Performance of Polymer Fibre-Reinforced Asphalt Mixture

Directory of Open Access Journals (Sweden)

Kamaruddin Ibrahim

2016-01-01

Full Text Available A number of researches have been done worldwide to evaluate the damage caused by water in bituminous pavements. The use of the retained strength ratios obtained from laboratory moisture damage tests is a useful tool in making quantitative predictions of the related damage caused by water. This study involved laboratory work on the effect of water on the performance of bituminous mixtures. Comparisons are made between the performances of Hot-rolled Asphalt (HRA bituminous mixtures containing base bitumen of 50 pen grade to that of a polymer-fibre reinforced HRA mixture. Two types of polymer fibre were studied, namely polypropylene and polyester and these fibre were added in different concentrations in the bituminous mixtures. Changes in both the cohesive properties of the bitumen and the adhesion of the bitumen to the aggregate surface were observed as a result of exposing the bituminous mixtures to moisture. The effect of polymer fibre reinforcement in bituminous mixtures helps reduce the level of moisture damage. This was evident in the lower moisture susceptibility achieved in the polymer fibre reinforced bituminous mixtures as compared to the control mixture. The additional bitumen in the fibre reinforced mixtures also afforded an increased film thickness on the aggregate particles, thus affording additional protection of the mixtures from moisture. The reinforcement of polymer fibres in bituminous mixtures also acts to decrease the moisture sensitivity of the bitumen to aggregate bonding. This may be due to the strengthening of the wetted binder matrix that helps promote both adhesion and cohesion retention.

SGC Tests for Influence of Material Composition on Compaction Characteristic of Asphalt Mixtures

Directory of Open Access Journals (Sweden)

Qun Chen

2013-01-01

Full Text Available Compaction characteristic of the surface layer asphalt mixture (13-type gradation mixture was studied using Superpave gyratory compactor (SGC simulative compaction tests. Based on analysis of densification curve of gyratory compaction, influence rules of the contents of mineral aggregates of all sizes and asphalt on compaction characteristic of asphalt mixtures were obtained. SGC Tests show that, for the mixture with a bigger content of asphalt, its density increases faster, that there is an optimal amount of fine aggregates for optimal compaction and that an appropriate amount of mineral powder will improve workability of mixtures, but overmuch mineral powder will make mixtures dry and hard. Conclusions based on SGC tests can provide basis for how to adjust material composition for improving compaction performance of asphalt mixtures, and for the designed asphalt mixture, its compaction performance can be predicted through these conclusions, which also contributes to the choice of compaction schemes.

Single particle detection and characterization of synuclein co-aggregation

International Nuclear Information System (INIS)

Giese, Armin; Bader, Benedikt; Bieschke, Jan; Schaffar, Gregor; Odoy, Sabine; Kahle, Philipp J.; Haass, Christian; Kretzschmar, Hans

2005-01-01

Protein aggregation is the key event in a number of human diseases such as Alzheimer's and Parkinson's disease. We present a general method to quantify and characterize protein aggregates by dual-colour scanning for intensely fluorescent targets (SIFT). In addition to high sensitivity, this approach offers a unique opportunity to study co-aggregation processes. As the ratio of two fluorescently labelled components can be analysed for each aggregate separately in a homogeneous assay, the molecular composition of aggregates can be studied even in samples containing a mixture of different types of aggregates. Using this method, we could show that wild-type α-synuclein forms co-aggregates with a mutant variant found in familial Parkinson's disease. Moreover, we found a striking increase in aggregate formation at non-equimolar mixing ratios, which may have important therapeutic implications, as lowering the relative amount of aberrant protein may cause an increase of protein aggregation leading to adverse effects

Fission product release from core-concrete mixtures

International Nuclear Information System (INIS)

Roche, M.F.; Settle, J.; Leibowitz, L.; Johnson, C.E.; Ritzman, R.L.

1988-01-01

The objective of this research is to measure the amount of strontium, barium, and lanthanum that is vaporized from core-concrete mixtures. The measurements are being done using a transpiration method. Mixtures of limestone-aggregated concrete, urania doped with a small amount of La, Sr, Ba, and Zr oxides, and stainless steel were vaporized at 2150 K from a zirconia crucible into flowing He-6% H 2 -0.06% H 2 O (a partial molar free energy of oxygen of -420 kJ). The amounts that were vaporized was determined by weight change and by chemical analyses on condensates. The major phases present in the mixture were inferred from electron probe microanalysis (EPM). They were: (1) urania containing calcia and zirconia, (2) calcium zirconate, (3) a calcium magnesium silicate, and (4) magnesia. About 10% of the zirconia crucible was dissolved by the concrete-urania mixture during the experiment, which accounts for the presence of zirconia-containing major phases. To circumvent the problem of zirconia dissolution, we repeated the experiments using mixtures of the limestone-aggregate concrete and the doped urania in molybdenum crucibles. These studies show that thermodynamic calculations of the release of refractory fission products will yield release fractions that are a factor of sixteen too high if the effects of zirconate formation are ignored

Protein-peptide interactions in mixtures of whey peptides and whey proteins

NARCIS (Netherlands)

Creusot, N.; Gruppen, H.

2007-01-01

The effects of several conditions on the amounts and compositions of aggregates formed in mixtures of whey protein hydrolysate, made with Bacillus licheniformis protease, and whey protein isolate were investigated using response surface methodology. Next, the peptides present in the aggregates were

Study of mechanical properties and recommendations for the application of waste Bakelite aggregate concrete

OpenAIRE

Nopagon Usahanunth; Seree Tuprakay; Waranon Kongsong; Sirawan Ruangchuay Tuprakay

2018-01-01

Bakelite waste from industrial manufacturing may be a hazard to the environment and public health. The utilization of waste Bakelite (WB) to replace natural aggregates (NA), such as natural coarse aggregate (NCA) and natural fine aggregate (NFA), in concrete and mortar is an approach for reducing both waste plastic and natural material. This research examines the utilization of waste Bakelite aggregate (WBA) in concrete and mortar mixtures to form waste Bakelite aggregate concrete (WBAC) and ...

A phase field approach for multicellular aggregate fusion in biofabrication.

Science.gov (United States)

Yang, Xiaofeng; Sun, Yi; Wang, Qi

2013-07-01

We present a modeling and computational approach to study fusion of multicellular aggregates during tissue and organ fabrication, which forms the foundation for the scaffold-less biofabrication of tissues and organs known as bioprinting. It is known as the phase field method, where multicellular aggregates are modeled as mixtures of multiphase complex fluids whose phase mixing or separation is governed by interphase force interactions, mimicking the cell-cell interaction in the multicellular aggregates, and intermediate range interaction mediated by the surrounding hydrogel. The material transport in the mixture is dictated by hydrodynamics as well as forces due to the interphase interactions. In a multicellular aggregate system with fixed number of cells and fixed amount of the hydrogel medium, the effect of cell differentiation, proliferation, and death are neglected in the current model, which can be readily included in the model, and the interaction between different components is dictated by the interaction energy between cell and cell as well as between cell and medium particles, respectively. The modeling approach is applicable to transient simulations of fusion of cellular aggregate systems at the time and length scale appropriate to biofabrication. Numerical experiments are presented to demonstrate fusion and cell sorting during tissue and organ maturation processes in biofabrication.

Critical aggregates concentration of fatty esters present in biodiesel determined by turbidity and fluorescence.

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Froehner, Sandro; Sánez, Juan; Dombroski, Luiz Fernando; Gracioto, Maria Paula

2017-09-01

Biodiesel for combustible engine is available as mixture of fossil diesel and fatty esters obtained by transesterification of vegetable oils. The use of biodiesel reduces the amount of SO x , mainly. However, it was already observed that biodiesel has a different behavior in environment in cases of accidental spill and groundwater contamination. It was noticed that the biodegradation of hydrocarbons (cyclic and aliphatic) in the presence of biodiesel are speeded, although the mechanism is still unclear. Considering the chemical structure of fatty esters, it was investigated the formation of aggregates in water solution by fatty esters present in commercial biodiesel. In Brazil, biodiesel is composed by 95% of fossil diesel and 5% of fatty esters mixture. In this work, fatty esters were treated as neutral surfactant, i.e., it was treated as a molecule with polar and non-polar part. Turbidity and fluorescence were used to determine the critical aggregates concentration (CAC). Water solutions containing fatty esters were examined exploiting changes in turbidity and fluorescence intensity of pyrene. Abrupt changes were attributed to aggregates formation, following the same behavior of traditional amphiphilic compounds. It was determined the CAC for ethyl palmitate, ethyl stearate, ethyl oleate, and ethyl linoleate. The values of CAC for fatty esters varied from 1.91 to 4.27 μmol/L, while CAC for the mixture of esters (biodiesel) was 2.01 for methyl esters and 1.19 for ethyl esters, both prepared using soybean oil. The aggregates formation was also determined by fluorescence measurements considering the changes in intensity of peaks I and III of pyrene. Pyrene senses the changes in environment polarity. The values found of CAC by fluorescence for individual ethyl esters varied from 1.85 to 3.21 μmol/L, while mixtures of ethyl esters was 2.23 and 2.07 μmol/L for mixture of methyl esters. The results clearly showed that fatty esters form aggregates and might be

Utilization of cement treated recycled concrete aggregates as base or subbase layer in Egypt

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Ahmed Ebrahim Abu El-Maaty Behiry

2013-12-01

Full Text Available Recently, environmental protection has a great concern in Egypt where recycling of increased demolition debris has become a viable option to be incorporated into roads applications. An extensive laboratory program is conducted to study the feasibility of using recycled concrete aggregate (RCA mixed with traditional limestone aggregate (LSA which is currently being used in base or subbase applications in Egypt. Moreover, the influence of mixture variables on the mechanical properties of cement treated recycled aggregate (CTRA is investigated. Models to predict the compressive and tensile strengths based on mixture parameters are established. The results show that the adding of RCA improves the mechanical properties of the mixture where the unconfined compressive strength (UCS is taken as an important quality indicator. Variables influencing the UCS such as cement content, curing time, dry density play important roles to determine the performance of CTRA.

Usage of solar aggregate stockpiles in the production of hot mix asphalt

International Nuclear Information System (INIS)

Androjić, Ivica; Kaluđer, Gordana

2016-01-01

Highlights: • Low energy storage mineral mixtures. • The impact of models thermal insulation on the temperature of aggregate. • Effect of periods with no solar radiation on the aggregate accumulated heat. • Low energy storage saves energy for preheating mineral mixtures. - Abstract: The production process of hot mix asphalt (HMA) requires a considerable demand for thermal energy which is fed into the process of drying and heating of mineral mixture. An overview of solar aggregate stockpiles designed in order to reduce energy consumption is given. Solar stockpiles were designed with the primary goal of achieving as much accumulation of thermal energy obtained from solar radiation as possible during the exposure period. Models of solar stockpiles were made with a constant volume capacity, variable thermal insulation thickness in the range of 2, 5 and 10 cm, and a glass ceiling surface to allow the realisation of high solar transmission into the interior of a stockpile. Temperature measurement of the mineral mixture deposited in the solar models and of those exposed to external environmental conditions was conducted during the period from May to November, 2015. The results achieved indicate to the facts that there comes to the constant growth in warmth of mineral mixtures in insulated stockpiles for the duration of their exposure to solar radiation, that an increase in thermal insulation thickness leads to the quadratic functional dependence between the referred thickness and mixture temperature and, ultimately, that there comes to the exponential loss of an accumulated thermal energy in insulated models in the period with no effect of solar radiation.

The single scattering properties of the aerosol particles as aggregated spheres

International Nuclear Information System (INIS)

Wu, Y.; Gu, X.; Cheng, T.; Xie, D.; Yu, T.; Chen, H.; Guo, J.

2012-01-01

The light scattering and absorption properties of anthropogenic aerosol particles such as soot aggregates are complicated in the temporal and spatial distribution, which introduce uncertainty of radiative forcing on global climate change. In order to study the single scattering properties of anthorpogenic aerosol particles, the structures of these aerosols such as soot paticles and soot-containing mixtures with the sulfate or organic matter, are simulated using the parallel diffusion limited aggregation algorithm (DLA) based on the transmission electron microscope images (TEM). Then, the single scattering properties of randomly oriented aerosols, such as scattering matrix, single scattering albedo (SSA), and asymmetry parameter (AP), are computed using the superposition T-matrix method. The comparisons of the single scattering properties of these specific types of clusters with different morphological and chemical factors such as fractal parameters, aspect ratio, monomer radius, mixture mode and refractive index, indicate that these different impact factors can respectively generate the significant influences on the single scattering properties of these aerosols. The results show that aspect ratio of circumscribed shape has relatively small effect on single scattering properties, for both differences of SSA and AP are less than 0.1. However, mixture modes of soot clusters with larger sulfate particles have remarkably important effects on the scattering and absorption properties of aggregated spheres, and SSA of those soot-containing mixtures are increased in proportion to the ratio of larger weakly absorbing attachments. Therefore, these complex aerosols come from man made pollution cannot be neglected in the aerosol retrievals. The study of the single scattering properties on these kinds of aggregated spheres is important and helpful in remote sensing observations and atmospheric radiation balance computations.

Recycled Concrete as Aggregate for Structural Concrete Production

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Mirjana Malešev

2010-04-01

Full Text Available A comparative analysis of the experimental results of the properties of fresh and hardened concrete with different replacement ratios of natural with recycled coarse aggregate is presented in the paper. Recycled aggregate was made by crushing the waste concrete of laboratory test cubes and precast concrete columns. Three types of concrete mixtures were tested: concrete made entirely with natural aggregate (NAC as a control concrete and two types of concrete made with natural fine and recycled coarse aggregate (50% and 100% replacement of coarse recycled aggregate. Ninety-nine specimens were made for the testing of the basic properties of hardened concrete. Load testing of reinforced concrete beams made of the investigated concrete types is also presented in the paper. Regardless of the replacement ratio, recycled aggregate concrete (RAC had a satisfactory performance, which did not differ significantly from the performance of control concrete in this experimental research. However, for this to be fulfilled, it is necessary to use quality recycled concrete coarse aggregate and to follow the specific rules for design and production of this new concrete type.

Reuse of municipal solid wastes incineration fly ashes in concrete mixtures.

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Collivignarelli, Carlo; Sorlini, Sabrina

2002-01-01

This study is aimed at assessing the feasibility of concrete production using stabilized m.s.w. (municipal solid waste) incineration fly ashes in addition to natural aggregates. The tested fly ashes were washed and milled, then stabilized by a cement-lime process and finally were reused as a "recycled aggregate" for cement mixture production, in substitution of a natural aggregate (with dosage of 200-400 kg m(-3)). These mixtures, after curing, were characterized with conventional physical-mechanical tests (compression, traction, flexure, modulus of elasticity, shrinkage). In samples containing 200 kg(waste) m(-3)(concrete), a good compressive strength was achieved after 28 days of curing. Furthermore, concrete leaching behavior was evaluated by means of different leaching tests, both on milled and on monolithic samples. Experimental results showed a remarkable reduction of metal leaching in comparison with raw waste. In some cases, similar behavior was observed in "natural" concrete (produced with natural aggregates) and in "waste containing" concrete.

Aggregate assesment and durability evaluation of optimized graded concrete in the state of Oklahoma

Science.gov (United States)

Ghaeezadeh, Ashkan

This research is a part of a larger project that emphasizes on creating a more scientific approach to designing concrete mixtures for concrete pavements that use less cement and more aggregate which is called optimized graded concrete. The most challenging obstacle in optimized mixtures is reaching enough workability so that one doesn't have to add more cement or super-plasticizer to reach the desired level of flowability. Aggregate gradation and characteristics have found to be very important when it comes to the workabaility of optimized graded concrete. In this research a new automated method of aggregate assessment was used to compare the shape and the surface of different aggregates as well as their influence on the concrete flowability. At the end, the performance of optimized graded concrete against drying shrinkage and freezing and thawing condition were investigated.

Detection and aggregation of the antitumoral drug parietin in ethanol/water mixture and on plasmonic metal nanoparticles studied by surface-enhanced optical spectroscopy: Effect of pH and ethanol concentration

Science.gov (United States)

Lopez-Tobar, Eduardo; Verebova, Valeria; Blascakova, Ludmila; Jancura, Daniel; Fabriciova, Gabriela; Sanchez-Cortes, Santiago

2016-04-01

In the present paper, we have investigated the effect of ethanol in aqueous media, the pH and the presence of Ag nanoparticles (NPs) on the aggregation processes of the antitumoral anthraquinone parietin in aqueous media and on the metal surface. UV-visible absorption, fluorescence and Raman spectra of parietin were used for such purpose. The present study provides information about the deprotonation and molecular aggregation processes occurring in parietin under different environments: ethanol/water mixture and when adsorbed onto Ag nanoparticles. The effect of ethanol on the optical properties of parietin in alcohol-water mixtures was also investigated at different ethanol concentrations with the time. For the case of the adsorption and organization of parietin molecules on the surface of Ag NPs, special attention was paid to the use of surface-enhanced optical techniques, SEF (surface-enhanced fluorescence) and SERS (surface-enhanced Raman scattering), for the characterization of the parietin aggregates and the ionization of the molecule on the surface. In particular, we have studied the variation of the SEF signal with the pH, which depends on the molecular organization of the molecule on the surface. Furthermore, a detailed analysis of the SERS spectra at different pH was accomplished and the main Raman bands of the protonated, mono-deprotonated and di-deprotonated parietin were identified. Finally, the second ionization pK of parietin on metal NPs was deduced from the SERS spectra.

Automatic Control of the Concrete Mixture Homogeneity in Cycling Mixers

Science.gov (United States)

Anatoly Fedorovich, Tikhonov; Drozdov, Anatoly

2018-03-01

The article describes the factors affecting the concrete mixture quality related to the moisture content of aggregates, since the effectiveness of the concrete mixture production is largely determined by the availability of quality management tools at all stages of the technological process. It is established that the unaccounted moisture of aggregates adversely affects the concrete mixture homogeneity and, accordingly, the strength of building structures. A new control method and the automatic control system of the concrete mixture homogeneity in the technological process of mixing components have been proposed, since the tasks of providing a concrete mixture are performed by the automatic control system of processing kneading-and-mixing machinery with operational automatic control of homogeneity. Theoretical underpinnings of the control of the mixture homogeneity are presented, which are related to a change in the frequency of vibrodynamic vibrations of the mixer body. The structure of the technical means of the automatic control system for regulating the supply of water is determined depending on the change in the concrete mixture homogeneity during the continuous mixing of components. The following technical means for establishing automatic control have been chosen: vibro-acoustic sensors, remote terminal units, electropneumatic control actuators, etc. To identify the quality indicator of automatic control, the system offers a structure flowchart with transfer functions that determine the ACS operation in transient dynamic mode.

Sequence dependent aggregation of peptides and fibril formation

Science.gov (United States)

Hung, Nguyen Ba; Le, Duy-Manh; Hoang, Trinh X.

2017-09-01

Deciphering the links between amino acid sequence and amyloid fibril formation is key for understanding protein misfolding diseases. Here we use Monte Carlo simulations to study the aggregation of short peptides in a coarse-grained model with hydrophobic-polar (HP) amino acid sequences and correlated side chain orientations for hydrophobic contacts. A significant heterogeneity is observed in the aggregate structures and in the thermodynamics of aggregation for systems of different HP sequences and different numbers of peptides. Fibril-like ordered aggregates are found for several sequences that contain the common HPH pattern, while other sequences may form helix bundles or disordered aggregates. A wide variation of the aggregation transition temperatures among sequences, even among those of the same hydrophobic fraction, indicates that not all sequences undergo aggregation at a presumable physiological temperature. The transition is found to be the most cooperative for sequences forming fibril-like structures. For a fibril-prone sequence, it is shown that fibril formation follows the nucleation and growth mechanism. Interestingly, a binary mixture of peptides of an aggregation-prone and a non-aggregation-prone sequence shows the association and conversion of the latter to the fibrillar structure. Our study highlights the role of a sequence in selecting fibril-like aggregates and also the impact of a structural template on fibril formation by peptides of unrelated sequences.

Comparison of compressive strength of paving block with a mixture of Sinabung ash and paving block with a mixture of lime

Science.gov (United States)

Hastuty, I. P.; Sembiringand Nursyamsi, I. S.

2018-02-01

Paving block is one of the material used as the top layer of road structure besides asphalt and concrete paving block is usually made of mixed material such as Portland cement or other adhesive material, water, and aggregate. People nowadays prefer paving block compared to other pavement such as concrete or asphalt. Their interest toward the use of paving block increase because paving block is an eco-friendly construction which is very useful in helping soil water conservation, can be done faster, has easier installation and maintenance, has a variety of shades that increase the aesthetic value, also costs cheaper than the other. Preparation of the specimens with a mixture of Sinabung ash and a mixture of Sinabung ash and lime are implemented with a mixture ratio of cement : sand : stone ash is 1: 2 : 3. The mixture is used as a substitute material by reducing the percentage amount of the weight of the cement with the composition ratio variation based on the comparative volume category of the paving block aggregate, i.e. 0%, 5%, 10%, 15%, 20%, and 25%. The result of this research shows that the maximum compressive strength value is 42.27 Mpa, it was obtained from a mixture of 10% lime with curing time 28 days. The maximum compressive strength value which is obtained from the mixture of sinabung ash is 41.60 Mpa, it was obtained from a mixture of 15% sinabung ash. From the use of these two materials, paving blocks produced are classified as paving blocks quality A and B (350 - 400 Mpa) in accordance to specification from SNI 03-0691-1996.

Environmental performance and mechanical analysis of concrete containing recycled asphalt pavement (RAP) and waste precast concrete as aggregate.

Science.gov (United States)

Erdem, Savaş; Blankson, Marva Angela

2014-01-15

The overall objective of this research project was to investigate the feasibility of incorporating 100% recycled aggregates, either waste precast concrete or waste asphalt planning, as replacements for virgin aggregates in structural concrete and to determine the mechanical and environmental performance of concrete containing these aggregates. Four different types of concrete mixtures were designed with the same total water cement ratio (w/c=0.74) either by using natural aggregate as reference or by totally replacing the natural aggregate with recycled material. Ground granulated blast furnace slag (GGBS) was used as a mineral addition (35%) in all mixtures. The test results showed that it is possible to obtain satisfactory performance for strength characteristics of concrete containing recycled aggregates, if these aggregates are sourced from old precast concrete. However, from the perspective of the mechanical properties, the test results indicated that concrete with RAP aggregate cannot be used for structural applications. In terms of leaching, the results also showed that the environmental behaviour of the recycled aggregate concrete is similar to that of the natural aggregate concrete. Copyright © 2013 Elsevier B.V. All rights reserved.

Mechanical and radiation shielding properties of mortars with additive fine aggregate mine waste

International Nuclear Information System (INIS)

Gallala, Wissem; Hayouni, Yousra; Gaied, Mohamed Essghaier; Fusco, Michael; Alsaied, Jasmin; Bailey, Kathryn; Bourham, Mohamed

2017-01-01

Highlights: • Effectiveness of mine waste as additive fine aggregate has been investigated. • Experimental results are verified by computationally from composition of synthesized samples. • Work focuses on shielding materials for nuclear systems including spent fuel storage and drycasks. - Abstract: Incorporation of barite-fluorspar mine waste (BFMW) as a fine aggregate additive has been investigated for its effect on the mechanical and shielding properties of cement mortar. Several mortar mixtures were prepared with different proportions of BFMW ranging from 0% to 30% as fine aggregate replacement. Cement mortar mixtures were evaluated for density, compressive and tensile strengths, and gamma ray radiation shielding. The results revealed that the mortar mixes containing 25% BFMW reaches the highest compressive strength values, which exceeded 50 MPa. Evaluation of gamma-ray attenuation was both measured by experimental tests and computationally calculated using MicroShield software package, and results have shown that using BFMW aggregates increases attenuation coefficient by about 20%. These findings have demonstrated that the mine waste can be suitably used as partial replacement aggregate to improve radiation shielding as well as to reduce the mortar and concrete costs.

Osmotic properties of binary mixtures 1-butyl-1-methylpyrrolidinium dicyanamide and 1-methyl-3-octylimidazolium chloride with water: Effect of aggregation of ions

International Nuclear Information System (INIS)

Ahmed, Sayeed Ashique; Chatterjee, Aninda; Maity, Banibrata; Seth, Debabrata

2015-01-01

Graphical abstract: Osmotic properties of binary mixture of two ionic liquids (ILs): 1-butyl-1-methyl pyrrolidinium dicyanamide and 1-methyl-3-octylimidazolium chloride with water was reported by using vapour pressure osmometry (VPO) method. - Highlights: • Osmotic properties of binary mixture of ionic liquids (ILs) with water by using vapour pressure osmometry (VPO) method. • The experimental osmotic coefficients were well correlated by Archer extension of Pitzer model. • From the experimental osmotic coefficient data the critical micellar concentration (cmc) of the ILs in water was estimated. • Mean molar activity coefficient and the excess Gibbs free energy was determine for the (ILs + water) binary mixture. - Abstract: In this work, the osmotic properties of the binary mixture of ionic liquids (ILs) and water were studied by using vapour pressure osmometry (VPO) method. We have used two ILs: 1-butyl-1-methyl pyrrolidinium dicyanamide and 1-methyl-3-octylimidazolium chloride. The aqueous solution of NaCl was used as the reference solution to precisely measure the osmotic coefficients of the above systems. We have calculated the activity of water in the above systems and the change of vapour pressure of water due to the addition of ILs in water. The experimental osmotic coefficients were correlated by the Archer extension of Pitzer model. The parameters of this Archer extension of Pitzer model were found from this data fitting. From the experimental osmotic coefficient value we have estimated the critical micellar concentration (cmc) of ILs in water. The experimental values of osmotic coefficient in the above systems were compared with the literature and the reason of variation was explained, in terms of the aggregation of ILs in water

Mechanical properties of hot mix asphalt made with recycled aggregates from reclaimed construction and demolition debris

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Taibo, J.

2007-03-01

Full Text Available The mix design for asphalt mixtures containing recycled aggregates from construction and demolition debris was evaluated. The tests conducted to characterize the mechanical behaviour of these mixtures showed that the mechanical properties of mixtures with recycled and virgin aggregate are similar. The asphalt mixtures containing recycled aggregate proved to have lower resistance to water action. Nonetheless, recycled aggregate was found to be potentially usable in asphalt mixtures if higher quality materials are selected and such low resistance is corrected. This will call for expanding upon the preliminary work described in the present article.En este trabajo se dosificaron mezclas bituminosas fabricadas con áridos reciclados de residuos de construcción y demolición. Se realizaron una serie de ensayos que permitieron caracterizar el comportamiento mecánico de estas mezclas. Los parámetros mecánicos de las mezclas con áridos reciclados son similares a los de las mezclas fabricadas únicamente con áridos naturales de cantera. Sin embargo, las mezclas bituminosas con áridos reciclados tuvieron un mal comportamiento frente a la disminución de la resistencia por pérdida de cohesión por la acción del agua. No obstante, mediante la selección de materiales de mejor calidad y corrección de este mal comportamiento, existen posibilidades de utilizar áridos reciclados en mezclas bituminosas. Para ello será necesario ampliar la primera aproximación realizada en este artículo.

Improvement of Bearing Capacity in Recycled Aggregates Suitable for Use as Unbound Road Sub-Base

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Laura Garach

2015-12-01

Full Text Available Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates with lower densities, higher water absorption capacities, and lower mechanical strength than natural aggregates. In this paper, the mechanical behaviour and microstructural properties of natural aggregates, recycled concrete aggregates and mixed recycled aggregates were compared. Different specimens of unbound recycled mixtures demonstrated increased resistance properties. The formation of new cement hydrated particles was observed, and pozzolanic reactions were discovered by electronon microscopy in these novel materials. The properties of recycled concrete aggregates and mixed recycled aggregates suggest that these recycled materials can be used in unbound road layers to improve their mechanical behaviour in the long term.

Durability Indicators in High Absorption Recycled Aggregate Concrete

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Luis F. Jiménez

2015-01-01

Full Text Available The use of recycled aggregates in structural concrete production has the inconvenience of increasing the fluid transport properties, such as porosity, sorptivity, and permeability, which reduces the resistance against penetration of environmental loads such as carbon dioxide and chloride ion. In this paper, behavior of ten concrete mixtures with different percentages of coarse aggregate replacement was studied. The recycled material was recovered by crushing of concrete rubble and had high absorption values. The results showed that it is possible to achieve good resistance to carbonation and chloride penetration with up to 50% replacement of recycled coarse aggregate for 0.5 water/cement ratio. Finally, new indexes for porosity and sorptivity were proposed to assess the quality of concrete.

GRAVITY PIPELINE TRANSPORT FOR HARDENING FILLING MIXTURES

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Leonid KROUPNIK

2015-12-01

Full Text Available In underground mining of solid minerals becoming increasingly common development system with stowing hardening mixtures. In this case the natural ore array after it is replaced by an artificial excavation of solidified filling mixture consisting of binder, aggregates and water. Such a mixture is prepared on the surface on special stowing complexes and transported underground at special stowing pipelines. However, it is transported to the horizons of a few kilometers, which requires a sustainable mode of motion of such a mixture in the pipeline. Hardening stowing mixture changes its rheological characteristics over time, which complicates the calculation of the parameters of pipeline transportation. The article suggests a method of determining the initial parameters of such mixtures: the status coefficient, indicator of transportability, coefficient of hydrodynamic resistance to motion of the mixture. These indicators characterize the mixture in terms of the possibility to transport it through pipes. On the basis of these indicators is proposed methodology for calculating the parameters of pipeline transport hardening filling mixtures in drift mode when traffic on the horizontal part of the mixture under pressure column of the mixture in the vertical part of the backfill of the pipeline. This technique allows stable operation is guaranteed to provide pipeline transportation.

Use of Adhesion Promoters in Asphalt Mixtures

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Cihlářová Denisa

2018-03-01

Full Text Available The purpose of asphalt binder as a significant binder in road constructions is to permanently bind aggregates of different compositions and grain sizes. The asphalt binder itself does not have suitable adhesiveness, so after a period of time, bare grains can appear. This results in a gradual separation of the grains from an asphalt layer and the presence of potholes in a pavement. Adhesion promoters or adhesive agents are important and proven promoters in practice. They are substances mainly based on the fatty acids of polyamides which should increase the reliability of the asphalt’s binder adhesion to the aggregates, thus increasing the lifetime period of the asphalt mixture as well as its resistance to mechanical strain. The amount of a promoter or agent added to the asphalt mixture is negligible and constitutes about 0.3% of the asphalt’s binder weight. Nevertheless, even this quantity significantly increases the adhesive qualities of an asphalt binder. The article was created in cooperatation with the Slovak University of Technology, in Bratislava, Slovakia, and focuses on proving the new AD2 adhesive additive and comparing it with the Addibit and Wetfix BE promoters used on aggregates from the Skuteč - Litická and Bystřec quarries.

Acoustic emission monitoring of recycled aggregate concrete under bending

Science.gov (United States)

Tsoumani, A. A.; Barkoula, N.-M.; Matikas, T. E.

2015-03-01

The amount of construction and demolition waste has increased considerably over the last few years, making desirable the reuse of this waste in the concrete industry. In the present study concrete specimens are subjected at the age of 28 days to four-point bending with concurrent monitoring of their acoustic emission (AE) activity. Several concrete mixtures prepared using recycled aggregates at various percentages of the total coarse aggregate and also a reference mix using natural aggregates, were included to investigate their influence of the recycled aggregates on the load bearing capacity, as well as on the fracture mechanisms. The results reveal that for low levels of substitution the influence of using recycled aggregates on the flexural strength is negligible while higher levels of substitution lead into its deterioration. The total AE activity, as well as the AE signals emitted during failure, was related to flexural strength. The results obtained during test processing were found to be in agreement with visual observation.

Design Method for Proportion of Cement-Foamed Asphalt Cold Recycled Mixture

OpenAIRE

Li Junxiao; Fu Wei; Zang Hechao

2018-01-01

Through foaming experiment of Zhongtai AH-70 asphalt, the best foaming temperature water consumption and influence factors of foamed asphalt’s foaming features are determined; By designing the proportion of foamed asphalt cold in-place recycled mixture combined with the water stability experiment, for this mixture the best foamed asphalt addition is 3%, and proportion of the mixture is RAP: fine aggregate: cement=75:23:2. Using SEM technology, the mechanism of increasing on the intensity of f...

Design Method for Proportion of Cement-Foamed Asphalt Cold Recycled Mixture

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Li Junxiao

2018-01-01

Full Text Available Through foaming experiment of Zhongtai AH-70 asphalt, the best foaming temperature water consumption and influence factors of foamed asphalt’s foaming features are determined; By designing the proportion of foamed asphalt cold in-place recycled mixture combined with the water stability experiment, for this mixture the best foamed asphalt addition is 3%, and proportion of the mixture is RAP: fine aggregate: cement=75:23:2. Using SEM technology, the mechanism of increasing on the intensity of foamed asphalt mixture resulted by the addition of cement was analysed. This research provides reference for cement admixture’s formulation in the designing of foamed asphalt cold in-place recycled mixture.

High-speed centrifugation induces aggregation of extracellular vesicles.

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Linares, Romain; Tan, Sisareuth; Gounou, Céline; Arraud, Nicolas; Brisson, Alain R

2015-01-01

Plasma and other body fluids contain cell-derived extracellular vesicles (EVs), which participate in physiopathological processes and have potential biomedical applications. In order to isolate, concentrate and purify EVs, high-speed centrifugation is often used. We show here, using electron microscopy, receptor-specific gold labelling and flow cytometry, that high-speed centrifugation induces the formation of EV aggregates composed of a mixture of EVs of various phenotypes and morphologies. The presence of aggregates made of EVs of different phenotypes may lead to erroneous interpretation concerning the existence of EVs harbouring surface antigens from different cell origins.

High-speed centrifugation induces aggregation of extracellular vesicles

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Romain Linares

2015-12-01

Full Text Available Plasma and other body fluids contain cell-derived extracellular vesicles (EVs, which participate in physiopathological processes and have potential biomedical applications. In order to isolate, concentrate and purify EVs, high-speed centrifugation is often used. We show here, using electron microscopy, receptor-specific gold labelling and flow cytometry, that high-speed centrifugation induces the formation of EV aggregates composed of a mixture of EVs of various phenotypes and morphologies. The presence of aggregates made of EVs of different phenotypes may lead to erroneous interpretation concerning the existence of EVs harbouring surface antigens from different cell origins.

Comparison Pore Aggregate Levels After Extraction With Solvents Pertamax Plus And Gasoline

Science.gov (United States)

Anggraini, Muthia

2017-12-01

Loss of asphalt content extraction results become problems in Field Work For implementing parties. The use of solvents with high octane (pertamax plus) for the extraction, dissolving the asphalt more than gasoline. By comparing the levels of aggregate pores after using solvent extraction pertamax plus compared to gasoline could answer that pertamax plus more solvent dissolves the bitumen compared to gasoline. This study aims to obtain comparative levels of porous aggregate mix AC-WC after using solvent extraction pertamax plus compared to gasoline. This study uses the aggregate that has been extracted from the production of asphalt mixtures, when finisher and after compaction field. The method used is the assay of coarse and fine aggregate pores, extraction of bitumen content to separate the aggregate with bitumen. Results of testing the total absorption after extraction using a solvent preta max plus in the production of asphalt mixtures 0.80%, while gasoline solvent 0.67% deviation occurs 0.13%. In the finisher after the solvent extraction preta max plus 0.77%, while 0.67% gasoline solvent occurs deviation of 0.1%. At the core after extraction and solvent pertamax plus 0.71%, while gasoline solvent 0.60% 0.11% deviation occurs. The total water absorption after extraction using a solvent pertamax plus greater than gasoline. This proves that the solvent dissolves pertamax plus more asphalt than gasoline.

Assessment of optimum threshold and particle shape parameter for the image analysis of aggregate size distribution of concrete sections

Science.gov (United States)

Ozen, Murat; Guler, Murat

2014-02-01

Aggregate gradation is one of the key design parameters affecting the workability and strength properties of concrete mixtures. Estimating aggregate gradation from hardened concrete samples can offer valuable insights into the quality of mixtures in terms of the degree of segregation and the amount of deviation from the specified gradation limits. In this study, a methodology is introduced to determine the particle size distribution of aggregates from 2D cross sectional images of concrete samples. The samples used in the study were fabricated from six mix designs by varying the aggregate gradation, aggregate source and maximum aggregate size with five replicates of each design combination. Each sample was cut into three pieces using a diamond saw and then scanned to obtain the cross sectional images using a desktop flatbed scanner. An algorithm is proposed to determine the optimum threshold for the image analysis of the cross sections. A procedure was also suggested to determine a suitable particle shape parameter to be used in the analysis of aggregate size distribution within each cross section. Results of analyses indicated that the optimum threshold hence the pixel distribution functions may be different even for the cross sections of an identical concrete sample. Besides, the maximum ferret diameter is the most suitable shape parameter to estimate the size distribution of aggregates when computed based on the diagonal sieve opening. The outcome of this study can be of practical value for the practitioners to evaluate concrete in terms of the degree of segregation and the bounds of mixture's gradation achieved during manufacturing.

Use of plastic waste (poly-ethylene terephthalate) in asphalt concrete mixture as aggregate replacement.

Science.gov (United States)

Hassani, Abolfazl; Ganjidoust, Hossein; Maghanaki, Amir Abedin

2005-08-01

One of the environmental issues in most regions of Iran is the large number of bottles made from poly-ethylene terephthalate (PET) deposited in domestic wastes and landfills. Due to the high volume of these bottles, more than 1 million m3 landfill space is needed for disposal every year. The purpose of this experimental study was to investigate the possibility of using PET waste in asphalt concrete mixes as aggregate replacement (Plastiphalt) to reduce the environmental effects of PET disposal. For this purpose the mechanical properties of plastiphalt mixes were compared with control samples. This study focused on the parameters of Marshall stability, flow, Marshall quotient (stability-to-flow ratio) and density. The waste PET used in this study was in the form of granules of about 3 mm diameter which would replace (by volume) a portion of the mineral coarse aggregates of an equal size (2.36-4.75 mm). In all prepared mixes the determined 6.6% optimum bitumen content was used. In this investigation, five different percentages of coarse aggregate replacement were used. The results showed that the aggregate replacement of 20% by volume with PET granules would result in a reduction of 2.8% in bulk compacted mix density. The value of flow in the plastiphalt mix was lower than that of the control samples. The results also showed that when PET was used as partial aggregate replacement, the corresponding Marshall stability and Marshall quotient were almost the same as for the control samples. According to most of specification requirement, these results introduce an asphalt mix that has properties that makes it suitable for practical use and furthermore, the recycling of PET for asphalt concrete roads helps alleviate an environmental problem and saves energy.

Ternary mixtures of alkyltriphenylphosphonium bromides (C12 TPB ...

Indian Academy of Sciences (India)

Administrator

Critical Micellar Concentrations (CMCs) by conductometry, but their ternary mixtures produce single ... efficiently quenched pyrene fluorescence; the performances of the homologues in this respect were assessed. Keywords ..... The shape of the amphiphile aggregates ..... Haque M E, Das A R and Moulik S P 1999 J. Colloid.

Properties of concretes produced with waste concrete aggregate

International Nuclear Information System (INIS)

Topcu, Ilker Bekir; Sengel, Selim

2004-01-01

An environmentally friendly approach to the disposal of waste materials, a difficult issue to cope with in today's world, would only be possible through a useful recycling process. For this reason, we suggest that clearing the debris from destroyed buildings in such a way as to obtain waste concrete aggregates (WCA) to be reused in concrete production could well be a partial solution to environmental pollution. For this study, the physical and mechanical properties along with their freeze-thaw durability of concrete produced with WCAs were investigated and test results presented. While experimenting with fresh and hardened concrete, mixtures containing recycled concrete aggregates in amounts of 30%, 50%, 70%, and 100% were prepared. Afterward, these mixtures underwent freeze-thaw cycles. As a result, we found out that C16-quality concrete could be produced using less then 30% C14-quality WCA. Moreover, it was observed that the unit weight, workability, and durability of the concretes produced through WCA decreased in inverse proportion to their endurance for freeze-thaw cycle

Ultrasonic and viscosimetric studies of samarium laurate in benzene-dimethylsulfoxide mixtures

International Nuclear Information System (INIS)

Mehrotra, K.N.; Anis, M.

1995-01-01

Ultrasonic and viscosity measurements of samarium laurate in benzene-DMSO mixtures of different compositions (7:3 and 1:1 V/V) have been used to determine the critical micelle concentration (CMC), soap-solvent interaction, and various acoustic parameters of the system. The values of critical micelle concentration increase with increasing amount of DMSO in the solvent mixtures. The viscosity results have been explained on the basis of equations proposed by Einstein, Vand. Moulik, and Jones-Dole. The values of CMC for samarium laurate obtained from the viscosity measurements are in agreement with the results obtained from ultrasonic measurements. The results show that the soap molecules do not aggregate appreciably below CMC there is a marked change in the aggregation behaviour at CMC. (author)

Reusing recycled aggregates in structural concrete

Science.gov (United States)

Kou, Shicong

The utilization of recycled aggregates in concrete can minimize environmental impact and reduce the consumption of natural resources in concrete applications. The aim of this thesis is to provide a scientific basis for the possible use of recycled aggregates in structure concrete by conducting a comprehensive programme of laboratory study to gain a better understanding of the mechanical, microstructure and durability properties of concrete produced with recycled aggregates. The study also explored possible techniques to of improve the properties of recycled aggregate concrete that is produced with high percentages (≧ 50%) of recycled aggregates. These techniques included: (a) using lower water-to-cement ratios in the concrete mix design; (b) using fly ash as a cement replacement or as an additional mineral admixture in the concrete mixes, and (c) precasting recycled aggregate concrete with steam curing regimes. The characteristics of the recycled aggregates produced both from laboratory and a commercially operated pilot construction and demolition (C&D) waste recycling plant were first studied. A mix proportioning procedure was then established to produce six series of concrete mixtures using different percentages of recycled coarse aggregates with and without the use of fly ash. The water-to-cement (binder) ratios of 0.55, 0.50, 0.45 and 0.40 were used. The fresh properties (including slump and bleeding) of recycled aggregate concrete (RAC) were then quantified. The effects of fly ash on the fresh and hardened properties of RAC were then studied and compared with those RAC prepared with no fly ash addition. Furthermore, the effects of steam curing on the hardened properties of RAC were investigated. For micro-structural properties, the interfacial transition zones of the aggregates and the mortar/cement paste were analyzed by SEM and EDX-mapping. Moreover, a detailed set of results on the fracture properties for RAC were obtained. Based on the experimental

Aggregate surface areas quantified through laser measurements for South African asphalt mixtures

CSIR Research Space (South Africa)

Anochie-Boateng, Joseph

2012-02-01

Full Text Available design. This paper introduces the use of a three-dimensional (3D) laser scanning method to directly measure the surface area of aggregates used in road pavements in South Africa. As an application of the laser-based measurements, the asphalt film...

Modification of strength properties of soil-aggregate system on ...

African Journals Online (AJOL)

Introduction. India is currently having a road network of 4.69 million kilometers. ... National Highways and State Highways, comprising only 3% of total road length, each carrying ... Two types of mixtures are specified in the code for soil – aggregate ..... performance of sabkha subgrade, Building and Environment, Vol. 41, No.

SHAPE CHARACTERIZATION OF CONCRETE AGGREGATE

Directory of Open Access Journals (Sweden)

Jing Hu

2011-05-01

Full Text Available As a composite material, the performance of concrete materials can be expected to depend on the properties of the interfaces between its two major components, aggregate and cement paste. The microstructure at the interfacial transition zone (ITZ is assumed to be different from the bulk material. In general, properties of conventional concrete have been found favoured by optimum packing density of the aggregate. Particle size is a common denominator in such studies. Size segregation in the ITZ among the binder particles in the fresh state, observed in simulation studies by concurrent algorithm-based SPACE system, additionally governs density as well as physical bonding capacity inside these shell-like zones around aggregate particles. These characteristics have been demonstrated qualitatively pertaining also after maturation of the concrete. Such properties of the ITZs have direct impact on composite properties. Despite experimental approaches revealed effects of aggregate grain shape on different features of material structure (among which density, and as a consequence on mechanical properties, it is still an underrated factor in laboratory studies, probably due to the general feeling that a suitable methodology for shape characterization is not available. A scientific argument hindering progress is the interconnected nature of size and shape. Presently, a practical problem preventing shape effects to be emphasized is the limitation of most computer simulation systems in concrete technology to spherical particles. New developments at Delft University of Technology will make it possible in the near future to generate jammed states, or other high-density fresh particle mixtures of non-spherical particles, which thereupon can be subjected to hydration algorithms. This paper will sketch the outlines of a methodological approach for shape assessment of loose (non-embedded aggregate grains, and demonstrate its use for two types of aggregate, allowing

Atomic force microscopy and Raman scattering spectroscopy studies on heat-induced fibrous aggregates of β-lactoglobulin

OpenAIRE

Ikeda, Shinya

2003-01-01

Nanometer-thick fibrous aggregates of β-lactoglobulin alone and its mixture with other globular proteins were formed by heating aqueous solutions at pH 2 with maintaining an effective level of electrostatic repulsion among denatured protein molecules. In atomic force microscopy (AFM) images, these fibrous aggregates appeared to be fairly uniform in width and height and composed of strings of globular elements. Fibrous aggregates formed in β-lactoglobulin individual systems were only slightly ...

Valorisation of different types of boron-containing wastes for the production of lightweight aggregates

International Nuclear Information System (INIS)

Kavas, T.; Christogerou, A.; Pontikes, Y.; Angelopoulos, G.N.

2011-01-01

Four boron-containing wastes (BW), named as Sieve (SBW), Dewatering (DBW), Thickener (TBW) and Mixture (MBW) waste, from Kirka Boron plant in west Turkey were investigated for the formation of artificial lightweight aggregates (LWA). The characterisation involved chemical, mineralogical and thermal analyses as well as testing of their bloating behaviour by means of heating microscopy. It was found that SBW and DBW present bloating behaviour whereas TBW and MBW do not. Following the above results two mixtures M1 and M2 were prepared with (in wt.%): 20 clay mixture, 40 SBW, 40 DBW and 20 clay mixture, 35 SBW, 35 DBW, 10 quartz sand, respectively. Two different firing modes were applied: (a) from room temperature till 760 deg. C and (b) abrupt heating at 760 deg. C. The obtained bulk density for M1 and M2 pellets is 1.2 g/cm 3 and 0.9 g/cm 3 , respectively. The analysis of microstructure with electron microscopy revealed a glassy phase matrix and an extended formation of both interconnected and isolated, closed pores. The results indicate that SBW and DBW boron-containing wastes combined with a clay mixture and quartz sand can be valorised for the manufacturing of lightweight aggregates.

Evaluation of the environmental, material, and structural performance of recycled aggregate concrete

Science.gov (United States)

Michaud, Katherine Sarah

Concrete is the most commonly used building material in the construction industry, and contributes to 52% of construction and demolition waste in Canada. Recycled concrete aggregate (RCA) is one way to reduce this impact. To evaluate the performance of coarse and granular (fine and coarse) RCA in structural concrete applications, four studies were performed: an environmental assessment, a material testing program, a shear performance study, and a flexural performance study. To determine the environmental benefits of recycled aggregate concrete (RAC), three case studies were investigated using different populations and proximities to city centres. Environmental modelling suggested that RCA replacement could result in energy savings and greenhouse gas emission reductions, especially in remote areas. Tests were performed to determine if the volumetric replacement of up to 30% coarse RCA and 20% granular RCA is suitable for structural concrete applications in Canada. Fresh, hardened, and durability properties were evaluated. All five (5) of the RCA mixes showed equivalent material performance to the control mixes and met the requirements for a structural concrete mix. The five (5) RAC mixes were also used in structural testing. One-way reinforced concrete slab specimens were tested to failure to evaluate the shear and flexural performance of the RAC members. Peak capacities of and crack formation within each member were analyzed to evaluate the performance of RAC compared to conventional concrete. The shear capacity of specimens made from four (4) of the five (5) RAC mixtures was higher or equivalent to the control specimens. Specimens of the concrete mixture containing the highest content of recycled aggregate, 20% volumetric replacement of granular RCA, had shear capacities 14.1% lower, and exhibited cracking at lower loads than the control. The average flexural capacities of all RAC specimens were within 3.7% of the control specimens. Results from this research

Heat-Induced Soluble Protein Aggregates from Mixed Pea Globulins and β-Lactoglobulin.

Science.gov (United States)

Chihi, Mohamed-Lazhar; Mession, Jean-luc; Sok, Nicolas; Saurel, Rémi

2016-04-06

The present work investigates the formation of protein aggregates (85 °C, 60 min incubation) upon heat treatment of β-lactoglobulin (βlg)-pea globulins (Glob) mixtures at pH 7.2 and 5 mM NaCl from laboratory-prepared protein isolates. Various βlg/Glob weight ratios were applied, for a total protein concentration of 2 wt % in admixture. Different analytical methods were used to determine the aggregation behavior of "mixed" aggregates, that is, surface hydrophobicity and also sulfhydryl content, protein interactions by means of SDS-PAGE electrophoresis, and molecule size distribution by DLS and gel filtration. The production of "mixed" thermal aggregates would involve both the formation of new disulfide bonds and noncovalent interactions between the denatured βlg and Glob subunits. The majority of "mixed" soluble aggregates displayed higher molecular weight and smaller diameter than those for Glob heated in isolation. The development of pea-whey protein "mixed" aggregates may help to design new ingredients for the control of innovative food textures.

Evaluation of open-graded friction course mixture : technical assistance report.

Science.gov (United States)

2004-10-01

Open-graded friction course (OGFC) is a porous, gap-graded, predominantly single size aggregate bituminous mixture that contains a high percentage of air voids. The high air void content and the open structure of this mix promote the effective draina...

Influence of uncoated and coated plastic waste coarse aggregates to concrete compressive strength

Directory of Open Access Journals (Sweden)

Purnomo Heru

2017-01-01

Full Text Available The use of plastic waste as coarse aggregates in concrete is part of efforts to reduce environmental pollution. In one hand the use of plastic as aggregates can provide lighter weight of the concrete than concrete using natural aggregates, but on the other hand bond between plastic coarse aggregates and hard matrix give low concrete compressive strength. Improvement of the bond between plastic coarse aggregate and hard matrix through a sand coating to plastic coarse aggregate whole surface is studied. Sand used to coat the plastic aggregates are Merapi volcanic sand which are taken in Magelang. Three mixtures of polypropylene (PP coarse plastic aggregates, Cimangkok river sand as fine aggregates, water and Portland Cement Composite with a water-cement ratio of 0.28, 0.3 and 0.35 are conducted. Compression test are performed on concrete cylindrical specimens with a diameter of 10 cm and a height of 20 cm. The results in general show that concrete specimens using plastic aggregates coated with sand have higher compressive strength compared to those of concrete specimens using plastic aggregates without sand coating. The bond improvement is indirectly indicated by the betterment of concrete compressive strength.

Nanocomposite metal/plasma polymer films prepared by means of gas aggregation cluster source

Energy Technology Data Exchange (ETDEWEB)

Polonskyi, O.; Solar, P.; Kylian, O.; Drabik, M.; Artemenko, A.; Kousal, J.; Hanus, J.; Pesicka, J.; Matolinova, I. [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, 18000 Prague 8 (Czech Republic); Kolibalova, E. [Tescan, Libusina trida 21, 632 00 Brno (Czech Republic); Slavinska, D. [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, 18000 Prague 8 (Czech Republic); Biederman, H., E-mail: bieder@kmf.troja.mff.cuni.cz [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, 18000 Prague 8 (Czech Republic)

2012-04-02

Nanocomposite metal/plasma polymer films have been prepared by simultaneous plasma polymerization using a mixture of Ar/n-hexane and metal cluster beams. A simple compact cluster gas aggregation source is described and characterized with emphasis on the determination of the amount of charged clusters and their size distribution. It is shown that the fraction of neutral, positively and negatively charged nanoclusters leaving the gas aggregation source is largely influenced by used operational conditions. In addition, it is demonstrated that a large portion of Ag clusters is positively charged, especially when higher currents are used for their production. Deposition of nanocomposite Ag/C:H plasma polymer films is described in detail by means of cluster gas aggregation source. Basic characterization of the films is performed using transmission electron microscopy, ultraviolet-visible and Fourier-transform infrared spectroscopies. It is shown that the morphology, structure and optical properties of such prepared nanocomposites differ significantly from the ones fabricated by means of magnetron sputtering of Ag target in Ar/n-hexane mixture.

Fresh and mechanical properties of self-compacting concrete with coarse aggregate replacement using Waste of Oil Palm Shell

Science.gov (United States)

Prayuda, Hakas; Saleh, Fadillawaty; Ilham Maulana, Taufiq; Monika, Fanny

2018-05-01

Self-compacting Concrete (SCC) is a real innovation that can solidify itself without the help of tools to ease field practice. In its implementation, SCC can use alternative materials to reduce waste, such as Oil Palm Shell (OPS). In this research, OPS used as a replacement of crushed stone as the main coarse aggregate. The concrete mixture used consists of cement, sand, crushed stone, OPS as a variation of aggregate substitutes, palm oil fuel ash, and superplasticizer. OPS used were variated with 0%, 5%, 10%, 25% and 50% of crushed stone aggregate weight with age up to 28 days. Tests were conducted on fresh and mechanical properties. From the results, it is known that replacement of aggregate using OPS meets fresh properties criteria and although the compressive strength of OPS concrete mixture is lower than normal SCC, OPS still can be an alternative in making SCC and reducing palm oil industrial waste.

New Sesquiterpenoids and Anti-Platelet Aggregation Constituents from the Rhizomes of Curcuma zedoaria.

Science.gov (United States)

Chen, Jih-Jung; Tsai, Tung-Han; Liao, Hsiang-Ruei; Chen, Li-Chai; Kuo, Yueh-Hsiung; Sung, Ping-Jyun; Chen, Chun-Lin; Wei, Chun-Sheng

2016-10-17

Two new sesquiterpenoids-13-hydroxycurzerenone ( 1 ) and 1-oxocurzerenone ( 2 )-have been isolated from the rhizomes of Curcuma zedoaria , together with 13 known compounds ( 3 - 15 ). The structures of two new compounds were determined through spectroscopic and MS analyses. Among the isolated compounds, 13-hydroxycurzerenone ( 1 ), 1-oxocurzerenone ( 2 ), curzerenone ( 3 ), germacrone ( 4 ), curcolone ( 5 ), procurcumenol ( 6 ), ermanin ( 7 ), curcumin ( 8 ), and a mixture of stigmast-4-en-3,6-dione ( 12 ) and stigmasta-4,22-dien-3,6-dione ( 13 ) exhibited inhibition (with inhibition % in the range of 21.28%-67.58%) against collagen-induced platelet aggregation at 100 μM. Compounds 1 , 5 , 7 , 8 , and the mixture of 12 and 13 inhibited arachidonic acid (AA)-induced platelet aggregation at 100 μM with inhibition % in the range of 23.44%-95.36%.

Investigations on Fresh and Hardened Properties of Recycled Aggregate Self Compacting Concrete

Science.gov (United States)

Revathi, P.; Selvi, R. S.; Velin, S. S.

2013-09-01

In the recent years, construction and demolition waste management issues have attracted the attention from researchers around the world. In the present study, the potential usage of recycled aggregate obtained from crushed demolition waste for making self compacting concrete (SCC) was researched. The barriers in promoting the use of recycled material in new construction are also discussed. In addition, the results of an experimental study involving the use of recycled concrete aggregate as coarse aggregates for producing self-compacting concrete to study their flow and strength characteristics are also presented. Five series of mixture were prepared with 0, 25, 50, 75, and 100 % coarse recycled aggregate adopting Nan Su's mix proportioning method. The fresh concrete properties were evaluated through the slump flow, J-ring and V-funnel tests. Compressive and tensile strengths were also determined. The results obtained showed that SCC could be successfully developed by incorporating recycled aggregates.

Performance on Water Stability of Cement-Foamed Asphalt Cold Recycled Mixture

Directory of Open Access Journals (Sweden)

Li Junxiao

2018-01-01

Full Text Available Through designing the mixture proportion of foamed asphalt cold in-place recycled mixture combined with the water stability experiment, it shows that the addition of cement can obviously improve foamed asphalt mixture’s water stability and the best cement admixture is between 1% ~ 2%; Using digital imaging microscope and SEM technology, the mechanism of increasing on the intensity of foamed asphalt mixture resulted by adding cement was analyzed. It revealed that the cement hydration products contained in the foamed asphalt mixture hydrolyzed into space mesh structure and wrapped up the aggregate particle, this is the main reason that the cement can enhance the mixture’s intensity as well as the water stability. This research provides reference for cement admixture’s formulation in the designing of foamed asphalt cold in-place recycled mixture.

Theoretical modeling of cationic surfactant aggregation at the silica/aqueous solution interface: Effects of pH and ionic strength

NARCIS (Netherlands)

Drach, M.; Andrzejewska, A.; Narkiewicz-Michalek, J.; Rudzinski, W.; Koopal, L.K.

2002-01-01

A theory of ionic surfactant aggregation on oppositely charged surfaces is presented. In the proposed model the adsorbed phase is considered as a mixture of singly dispersed surfactant molecules, monolayered and bilayered aggregates of various sizes and the ions of simple electrolyte added to the

Gas-particle partitioning of semivolatile organic compounds (SOCs) on mixtures of aerosols in a smog chamber.

Science.gov (United States)

Chandramouli, Bharadwaj; Jang, Myoseon; Kamens, Richard M

2003-09-15

The partitioning behavior of a set of diverse SOCs on two and three component mixtures of aerosols from different sources was studied using smog chamber experimental data. A set of SOCs of different compound types was introduced into a system containing a mixture of aerosols from two or more sources. Gas and particle samples were taken using a filter-filter-denuder sampling system, and a partitioning coefficient Kp was estimated using Kp = Cp/(CgTSP). Particle size distributions were measured using a differential mobility analyzer and a light scattering detector. Gas and particle samples were analyzed using GCMS. The aerosol composition in the chamber was tracked chemically using a combination of signature compounds and the organic matter mass fraction (f(om)) of the individual aerosol sources. The physical nature of the aerosol mixture in the chamber was determined using particle size distributions, and an aggregate Kp was estimated from theoretically calculated Kp on the individual sources. Model fits for Kp showed that when the mixture involved primary sources of aerosol, the aggregate Kp of the mixture could be successfully modeled as an external mixture of the Kp on the individual aerosols. There were significant differences observed for some SOCs between modeling the system as an external and as an internal mixture. However, when one of the aerosol sources was secondary, the aggregate model Kp required incorporation of the secondary aerosol products on the preexisting aerosol for adequate model fits. Modeling such a system as an external mixture grossly overpredicted the Kp of alkanes in the mixture. Indirect evidence of heterogeneous, acid-catalyzed reactions in the particle phase was also seen, leading to a significant increase in the polarity of the resulting aerosol mix and a resulting decrease in the observed Kp of alkanes in the chamber. The model was partly consistent with this decrease but could not completely explain the reduction in Kp because of

A statistical approach to optimizing concrete mixture design.

Science.gov (United States)

Ahmad, Shamsad; Alghamdi, Saeid A

2014-01-01

A step-by-step statistical approach is proposed to obtain optimum proportioning of concrete mixtures using the data obtained through a statistically planned experimental program. The utility of the proposed approach for optimizing the design of concrete mixture is illustrated considering a typical case in which trial mixtures were considered according to a full factorial experiment design involving three factors and their three levels (3(3)). A total of 27 concrete mixtures with three replicates (81 specimens) were considered by varying the levels of key factors affecting compressive strength of concrete, namely, water/cementitious materials ratio (0.38, 0.43, and 0.48), cementitious materials content (350, 375, and 400 kg/m(3)), and fine/total aggregate ratio (0.35, 0.40, and 0.45). The experimental data were utilized to carry out analysis of variance (ANOVA) and to develop a polynomial regression model for compressive strength in terms of the three design factors considered in this study. The developed statistical model was used to show how optimization of concrete mixtures can be carried out with different possible options.

A Statistical Approach to Optimizing Concrete Mixture Design

Directory of Open Access Journals (Sweden)

Shamsad Ahmad

2014-01-01

Full Text Available A step-by-step statistical approach is proposed to obtain optimum proportioning of concrete mixtures using the data obtained through a statistically planned experimental program. The utility of the proposed approach for optimizing the design of concrete mixture is illustrated considering a typical case in which trial mixtures were considered according to a full factorial experiment design involving three factors and their three levels (33. A total of 27 concrete mixtures with three replicates (81 specimens were considered by varying the levels of key factors affecting compressive strength of concrete, namely, water/cementitious materials ratio (0.38, 0.43, and 0.48, cementitious materials content (350, 375, and 400 kg/m3, and fine/total aggregate ratio (0.35, 0.40, and 0.45. The experimental data were utilized to carry out analysis of variance (ANOVA and to develop a polynomial regression model for compressive strength in terms of the three design factors considered in this study. The developed statistical model was used to show how optimization of concrete mixtures can be carried out with different possible options.

The effect of recycled concrete aggregate properties on the bond strength between RCA concrete and steel reinforcement

International Nuclear Information System (INIS)

Butler, L.; West, J.S.; Tighe, S.L.

2011-01-01

The purpose of this study was to investigate the influence that replacing natural coarse aggregate with recycled concrete aggregate (RCA) has on concrete bond strength with reinforcing steel. Two sources of RCA were used along with one natural aggregate source. Numerous aggregate properties were measured for all aggregate sources. Two types of concrete mixture proportions were developed replacing 100% of the natural aggregate with RCA. The first type maintained the same water-cement ratios while the second type was designed to achieve the same compressive strengths. Beam-end specimens were tested to determine the relative bond strength of RCA and natural aggregate concrete. On average, natural aggregate concrete specimens had bond strengths that were 9 to 19% higher than the equivalent RCA specimens. Bond strength and the aggregate crushing value seemed to correlate well for all concrete types.

An investigation of waste foundry sand in asphalt concrete mixtures.

Science.gov (United States)

Bakis, Recep; Koyuncu, Hakan; Demirbas, Ayhan

2006-06-01

A laboratory study regarding the reuse of waste foundry sand in asphalt concrete production by replacing a certain portion of aggregate with WFS was undertaken. The results showed that replacement of 10% aggregates with waste foundry sand was found to be the most suitable for asphalt concrete mixtures. Furthermore, the chemical and physical properties of waste foundry sand were analysed in the laboratory to determine the potential effect on the environment. The results indicated that the investigated waste foundry sand did not significantly affect the environment around the deposition

Parameters of Solidifying Mixtures Transporting at Underground Ore Mining

Directory of Open Access Journals (Sweden)

Golik Vladimir

2017-01-01

Full Text Available The article is devoted to the problem of providing mining enterprises with solidifying filling mixtures at underground mining. The results of analytical studies using the data of foreign and domestic practice of solidifying mixtures delivery to stopes are given. On the basis of experimental practice the parameters of transportation of solidifying filling mixtures are given with an increase in their quality due to the effect of vibration in the pipeline. The mechanism of the delivery process and the procedure for determining the parameters of the forced oscillations of the pipeline, the characteristics of the transporting processes, the rigidity of the elastic elements of pipeline section supports and the magnitude of vibrator’ driving force are detailed. It is determined that the quality of solidifying filling mixtures can be increased due to the rational use of technical resources during the transportation of mixtures, and as a result the mixtures are characterized by a more even distribution of the aggregate. The algorithm for calculating the parameters of the pipe vibro-transport of solidifying filling mixtures can be in demand in the design of mineral deposits underground mining technology.

Parameters of Solidifying Mixtures Transporting at Underground Ore Mining

Science.gov (United States)

Golik, Vladimir; Dmitrak, Yury

2017-11-01

The article is devoted to the problem of providing mining enterprises with solidifying filling mixtures at underground mining. The results of analytical studies using the data of foreign and domestic practice of solidifying mixtures delivery to stopes are given. On the basis of experimental practice the parameters of transportation of solidifying filling mixtures are given with an increase in their quality due to the effect of vibration in the pipeline. The mechanism of the delivery process and the procedure for determining the parameters of the forced oscillations of the pipeline, the characteristics of the transporting processes, the rigidity of the elastic elements of pipeline section supports and the magnitude of vibrator' driving force are detailed. It is determined that the quality of solidifying filling mixtures can be increased due to the rational use of technical resources during the transportation of mixtures, and as a result the mixtures are characterized by a more even distribution of the aggregate. The algorithm for calculating the parameters of the pipe vibro-transport of solidifying filling mixtures can be in demand in the design of mineral deposits underground mining technology.

Effect of the addition of CMC on the aggregation behaviour of proteins

Energy Technology Data Exchange (ETDEWEB)

Yu, H.; Sabato, S.F.; D' Aprano, G.; Lacroix, M. E-mail: monique.lacroix@inrs-iaf.uquebec.ca

2004-10-01

The effect of carboxymethylcellulose (CMC) on the aggregation of formulation based on calcium caseinate, commercial whey protein (WPC), and a 1:1 mixture of soy protein isolate (SPI) and whey protein isolate (WPI) was investigated. Protein aggregation could be observed upon addition of CMC, as demonstrated by size-exclusion chromatography. This aggregation behaviour was enhanced by means of physical treatments, such as heating at 90 deg. C for 30 min or gamma-irradiation at 32 kGy. A synergy resulted from the combination of CMC to gamma-irradiation in Caseinate/CMC and SPI/WPI/CMC formulations. Furthermore, CMC prevented precipitation in irradiated protein solutions for a period of more than 3 months at 4 deg. C.

Effect of the addition of CMC on the aggregation behaviour of proteins

International Nuclear Information System (INIS)

Yu, H.; Sabato, S.F.; D'Aprano, G.; Lacroix, M.

2004-01-01

The effect of carboxymethylcellulose (CMC) on the aggregation of formulation based on calcium caseinate, commercial whey protein (WPC), and a 1:1 mixture of soy protein isolate (SPI) and whey protein isolate (WPI) was investigated. Protein aggregation could be observed upon addition of CMC, as demonstrated by size-exclusion chromatography. This aggregation behaviour was enhanced by means of physical treatments, such as heating at 90 deg. C for 30 min or gamma-irradiation at 32 kGy. A synergy resulted from the combination of CMC to gamma-irradiation in Caseinate/CMC and SPI/WPI/CMC formulations. Furthermore, CMC prevented precipitation in irradiated protein solutions for a period of more than 3 months at 4 deg. C

Impact of Aggregate Gradation and Filler Type on Marshall Properties of Asphalt Concrete

Directory of Open Access Journals (Sweden)

saad I. Sarsam

2015-09-01

Full Text Available As asphalt concrete wearing course (ACWC is the top layer in the pavement structure, the material should be able to sustain stresses caused by direct traffic loading. The objective of this study is to evaluate the influence of aggregate gradation and mineral filler type on Marshall Properties. A detailed laboratory study is carried out by preparing asphalt mixtures specimens using locally available materials including asphalt binder (40-50 penetration grade, two types of aggregate gradation representing SCRB and ROAD NOTE 31 specifications and two types of mineral filler including limestone dust and coal fly ash. Four types of mixtures were prepared and tested. The first type included SCRB specification and limestone dust, the second type included SCRB specification and coal fly ash, the third types included ROAD NOTE 31 specification and limestone dust and the fourth type included ROAD NOTE 31 specification and coal fly ash. The optimum asphalt content of each type of mixtures was determined using Marshall Method of mix design. 60 specimen were prepared and tested with dimension of 10.16 cm in diameter and 6.35 cm in height. Results of this study indicated that aggregate gradation and filler type have a significant effect on optimum asphalt content and Marshall Properties. From the experimental data, it was observed that the value of Marshall Stability is comparatively higher when using fly ash as filler as compared to limestone dust.

Flexural Behavior of Corroded Reinforced Recycled Aggregate Concrete Beams

Directory of Open Access Journals (Sweden)

Taoping Ye

2018-01-01

Full Text Available Recycling concrete not only reduces the use of virgin aggregate but also decreases the pressure on landfills. As a result, recycled coarse aggregate (RCA is extensively recommended for new construction projects. However, the flexural behavior of corroded reinforced recycled aggregate concrete (RAC beams is uncertain. The experimental research presented in this paper was performed to investigate the flexural behavior of corroded reinforced RAC beams compared to that of corroded reinforced natural aggregate concrete (NAC beams and consequently explore the possibility of using RAC beams in corrosive environments. Four different percentages of RCA in total mass of coarse aggregate in concrete mixtures (0%, 33%, 66%, and 100% and two different concrete strengths (C30, C60 were the governing parameters. The electrochemical method was adopted to accelerate steel corrosion. Full-scale tests were performed on eight simply supported beams until the failure load was reached. Comparison of load-deflection behavior, crack patterns, failure modes, ductility, and ultimate flexural capacity of corroded reinforced NAC and RAC beams was made based on the experimental results obtained. The comparison results show that the flexural behavior of corroded reinforced RAC beams with an appropriate percentage of RCA is satisfactory compared to the behavior of NAC beams.

Density of asphalt paving mixtures: Measurements, variations, and influencing factors

International Nuclear Information System (INIS)

Solaimanian, M.

1990-01-01

The first part describes the results of a research study to determine the effectiveness of the Troxler Model 4640 Thin Lift Nuclear Density Gauge. The densities obtained from cores and the nuclear density gauge from seven construction projects were compared. A linear regression technique was used to investigate how well the core densities could be predicted from nuclear densities. Correlation coefficients were determined to indicate the degree of correlation between the core and nuclear densities. Using a statistical analysis technique, the range of differences between core and nuclear measurements was established for specified confidence levels for each project. Analysis of the data indicated that the accuracy of this gauge is highly material dependent. While acceptable results were obtained with limestone mixtures, the gauge did not perform satisfactorily with mixtures containing siliceous aggregate. The data presented in this paper indicate that the gauge could be used as a quality control tool provided that a calibration is developed for each project. The maximum theoretical specific gravities of asphalt-aggregate paving mixtures obtained from different methods were compared. The study included experimental work and analysis of the resulting data. The agreement between results obtained from the Texas C-14 method and the Rice method were excellent. Results obtained by backcalculating theoretical maximum densities from a single Rice test were also found to be satisfactory. Theoretical approach based on bulk specific gravity of aggregate is not recommended because of yielding significantly low theoretical maximum specific gravities and high relative densities. The last two parts summarize density levels and corresponding variations obtained from fifty-seven construction projects throughout the state of Texas

Development of Ecoefficient Engineered Cementitious Composites Using Supplementary Cementitious Materials as a Binder and Bottom Ash Aggregate as Fine Aggregate

Directory of Open Access Journals (Sweden)

Jin Wook Bang

2015-01-01

Full Text Available The purpose of this study is to develop ecoefficient engineered cementitious composites (ECC using supplementary cementitious materials (SCMs, including fly ash (FA and blast furnace slag (SL as a binder material. The cement content of the ECC mixtures was replaced by FA and SL with a replacement rate of 25%. In addition, the fine aggregate of the ECC was replaced by bottom ash aggregate (BA with a substitution rate of 10%, 20%, and 30%. The influences of ecofriendly aggregates on fresh concrete properties and on mechanical properties were experimentally investigated. The test results revealed that the substitution of SCMs has an advantageous effect on fresh concrete’s properties; however, the increased water absorption and the irregular shape of the BA can potentially affect the fresh concrete’s properties. The substitution of FA and SL in ECC led to an increase in frictional bond at the interface between PVA fibers and matrix, improved the fiber dispersion, and showed a tensile strain capacity ranging from 3.3% to 3.5%. It is suggested that the combination of SCMs (12.5% FA and 12.5% SL and the BA aggregate with the substitution rate of 10% can be effectively used in ECC preparation.

Performance Evaluation and Improving Mechanisms of Diatomite-Modified Asphalt Mixture.

Science.gov (United States)

Yang, Chao; Xie, Jun; Zhou, Xiaojun; Liu, Quantao; Pang, Ling

2018-04-27

Diatomite is an inorganic natural resource in large reserve. This study consists of two phases to evaluate the effects of diatomite on asphalt mixtures. In the first phase, we characterized the diatomite in terms of mineralogical properties, chemical compositions, particle size distribution, mesoporous distribution, morphology, and IR spectra. In the second phase, road performances, referring to the permanent deformation, crack, fatigue, and moisture resistance, of asphalt mixtures with diatomite were investigated. The characterization of diatomite exhibits that it is a porous material with high SiO₂ content and large specific surface area. It contributes to asphalt absorption and therefore leads to bonding enhancement between asphalt and aggregate. However, physical absorption instead of chemical reaction occurs according to the results of FTIR. The resistance of asphalt mixtures with diatomite to permanent deformation and moisture are superior to those of the control mixtures. But, the addition of diatomite does not help to improve the crack and fatigue resistance of asphalt mixture.

Performance Evaluation and Improving Mechanisms of Diatomite-Modified Asphalt Mixture

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Chao Yang

2018-04-01

Full Text Available Diatomite is an inorganic natural resource in large reserve. This study consists of two phases to evaluate the effects of diatomite on asphalt mixtures. In the first phase, we characterized the diatomite in terms of mineralogical properties, chemical compositions, particle size distribution, mesoporous distribution, morphology, and IR spectra. In the second phase, road performances, referring to the permanent deformation, crack, fatigue, and moisture resistance, of asphalt mixtures with diatomite were investigated. The characterization of diatomite exhibits that it is a porous material with high SiO2 content and large specific surface area. It contributes to asphalt absorption and therefore leads to bonding enhancement between asphalt and aggregate. However, physical absorption instead of chemical reaction occurs according to the results of FTIR. The resistance of asphalt mixtures with diatomite to permanent deformation and moisture are superior to those of the control mixtures. But, the addition of diatomite does not help to improve the crack and fatigue resistance of asphalt mixture.

Sintering study in vertical fixed bed reactor for synthetic aggregate production

International Nuclear Information System (INIS)

Quaresma, D.S.; Neves, A.S.S.; Melo, A.O.; Pereira, L.F.S.; Bezerra, P.T.S.; Macedo, E.N.; Souza, J.A.S.

2017-01-01

The synthetic aggregates are being employed in civil construction for the reduction of mineral extraction activities. Within this context, the recycling of industrial waste is the basis of the majority of processes to reduce the exploitation of mineral resources. In this work the sintering in a vertical fixed bed reactor for synthetic aggregate production using 20% pellets and 80% charcoal was studied. The pellets were prepared from a mixture containing clay, charcoal and fly ash. Two experiments varying the speed of air sucking were carried out. The material produced was analyzed by X-ray diffraction, scanning electron microscopy, measures of their ceramic properties, and particle size analysis. The results showed that the solid-state reactions, during the sintering process, were efficient and the produced material was classified as coarse lightweight aggregate. The process is interesting for the sintering of aggregates, and can be controlled by composition, particle size, temperature gradient and gaseous flow. (author)

The influence of aggregates type on W/C ratio on the strength and other properties of concrete

Science.gov (United States)

Malaiskiene, J.; Skripkiunas, G.; Vaiciene, M.; Karpova, E.

2017-10-01

The influence of different types of aggregates and W/C ratio on concrete properties is analysed. In order to achieve this aim, lightweight (with expanded clay aggregate) and normal concrete (with gravel aggregate) mixtures are prepared with different W/C ratios. Different W/C ratios are selected by reducing the amount of cement when the amount of water is constant. The following properties of concrete have been determined: density, compressive strength and water absorption. Additionally, the statistical data analysis is performed and influence of aggregate type and W/C ratio on concrete properties is determined. The empirical equations indicating dependence between concrete strength and W/C and strength of aggregate are obtained for normal concrete and light-weight concrete.

Influence of surface modified basalt fiber on strength of cinder lightweight aggregate concrete

Science.gov (United States)

Xiao, Liguang; Li, Jiheng; Liu, Qingshun

2017-12-01

In order to improve the bonding and bridging effect between volcanic slag lightweight aggregate concrete cement and basalt fiber, The basalt fiber was subjected to etching and roughening treatment by NaOH solution, and the surface of the basalt fiber was treated with a mixture of sodium silicate and micro-silica powder. The influence of modified basalt fiber on the strength of volcanic slag lightweight aggregate concrete was systematically studied. The experimental results show that the modified basalt fiber volcanic slag lightweight aggregate concrete has a flexural strength increased by 47%, the compressive strength is improved by 16% and the toughness is increased by 27% compared with that of the non-fiber.

Optimization of thermal neutron shield concrete mixture using artificial neural network

Energy Technology Data Exchange (ETDEWEB)

Yadollahi, A. [Engineering Department, Shahid Beheshti University, G.C., P.O. Box: 1983963113, Tehran (Iran, Islamic Republic of); Nazemi, E., E-mail: nazemi.ehsan@yahoo.com [Young Researchers and Elite Club, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Zolfaghari, A. [Engineering Department, Shahid Beheshti University, G.C., P.O. Box: 1983963113, Tehran (Iran, Islamic Republic of); Ajorloo, A.M. [Water and Environmental Engineering Department, Shahid Beheshti University, P.O. Box: 167651719, Tehran (Iran, Islamic Republic of)

2016-08-15

Highlights: • Colemanite was used in fabricating of thermal neutron shield concrete. • The Taguchi method was implemented to obtain the data set required for training the ANN. • Trained ANN predicted quality characteristics of thermal neutron shield. - Abstract: Colemanite is the most convenient boron mineral which has been widely used in construction of radiation shielding concrete in order to improve the capture of thermal neutrons. But utilization of Colemanite in radiation shielding concrete has a deleterious effect on both physical and mechanical properties. In the present work, Taguchi method and artificial neural network (ANN) were employed to find an optimal mixture of Colemanite based concrete in order to improve the boron content of concrete and increase thermal neutron absorption without violating the standards for physical and mechanical properties. Using Taguchi method for experimental design, 27 concrete samples with different mixtures were fabricated and tested. Water/cement ratio, cement quantity, volume fraction of Colemanite aggregate and silica fume quantity were selected as control factors, and compressive strength, ultrasonic pulse velocity and thermal neutron transmission ratio were considered as the quality responses. Obtained data from 27 experiments were used to train 3 ANNs. Four control factors were utilized as the inputs of 3 ANNs and 3 quality responses were used as the outputs, separately (each ANN for one quality response). After training the ANNs, 1024 different mixtures with different quality responses were predicted. At the final, optimum mixture was obtained among the predicted different mixtures. Results demonstrated that the optimal mixture of thermal neutron shielding concrete has a water–cement ratio of 0.38, cement content of 400 kg/m{sup 3}, a volume fraction Colemanite aggregate of 50% and silica fume–cement ratio of 0.15.

Optimization of thermal neutron shield concrete mixture using artificial neural network

International Nuclear Information System (INIS)

Yadollahi, A.; Nazemi, E.; Zolfaghari, A.; Ajorloo, A.M.

2016-01-01

Highlights: • Colemanite was used in fabricating of thermal neutron shield concrete. • The Taguchi method was implemented to obtain the data set required for training the ANN. • Trained ANN predicted quality characteristics of thermal neutron shield. - Abstract: Colemanite is the most convenient boron mineral which has been widely used in construction of radiation shielding concrete in order to improve the capture of thermal neutrons. But utilization of Colemanite in radiation shielding concrete has a deleterious effect on both physical and mechanical properties. In the present work, Taguchi method and artificial neural network (ANN) were employed to find an optimal mixture of Colemanite based concrete in order to improve the boron content of concrete and increase thermal neutron absorption without violating the standards for physical and mechanical properties. Using Taguchi method for experimental design, 27 concrete samples with different mixtures were fabricated and tested. Water/cement ratio, cement quantity, volume fraction of Colemanite aggregate and silica fume quantity were selected as control factors, and compressive strength, ultrasonic pulse velocity and thermal neutron transmission ratio were considered as the quality responses. Obtained data from 27 experiments were used to train 3 ANNs. Four control factors were utilized as the inputs of 3 ANNs and 3 quality responses were used as the outputs, separately (each ANN for one quality response). After training the ANNs, 1024 different mixtures with different quality responses were predicted. At the final, optimum mixture was obtained among the predicted different mixtures. Results demonstrated that the optimal mixture of thermal neutron shielding concrete has a water–cement ratio of 0.38, cement content of 400 kg/m 3 , a volume fraction Colemanite aggregate of 50% and silica fume–cement ratio of 0.15.

Studying the Physical Properties of Hma with Recycled Aggregate Subjected to Moisture

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Ahlam K. Razzaq

2018-01-01

Full Text Available As being exposed to water that exists on asphalt road, HMA that is created by utilizing a certain resources may require to be made strong due to the capability of that water to stop the covering to be attached to the aggregate, consequently, asphalt road layers will not be held jointly, this will have a negative influence on the asphalt that will be damaged quickly. Such phenomenon is known as "the erosion", which requires to be dealt with by, for example, improving asphalt layers by means of specific resources that assist in existence of water. Different ways in this work are employed to calculate the strength of various mixes via using used aggregate that is exposed to  saturation times, similarly, the importance of exploiting the anti-stripping as chemical addition is determined. Three kinds of HMA were exposed in the current study, 60% of the first kind were made of used aggregate taking from crushed pavement, and 60% of the second kind were taking from using aggregate that is part of concrete mix, while the third mixture has 10% of wax used as an addition by pavement weight. These mixtures were soaked in water bath of 25o C for various intervals of time that are (3, 7, 15, 28 days. Many investigations examinations had been as well executed, and then the outcomes were contrasted against standard pavement blend subjected to similar circumstances. Number of examinations were adopted in this study, these are (Marshall Stability and flow, mass thickness, roundabout elasticity, compressive quality, affectability to temperature, flexible modulus. The study achieved a good success as it makes important outcomes, the enhanced pavement showed strength against moisture damage while taking advantage of used aggregate of preceding blends, on other hand, the wax has affective role in raising these strengths in addition to develop the characteristics of HMA. 

Amplification of Chirality through Self-Replication of Micellar Aggregates in Water

KAUST Repository

Bukhriakov, Konstantin

2015-03-17

We describe a system in which the self-replication of micellar aggregates results in a spontaneous amplification of chirality in the reaction products. In this system, amphiphiles are synthesized from two "clickable" fragments: a water-soluble "head" and a hydrophobic "tail". Under biphasic conditions, the reaction is autocatalytic, as aggregates facilitate the transfer of hydrophobic molecules to the aqueous phase. When chiral, partially enantioenriched surfactant heads are used, a strong nonlinear induction of chirality in the reaction products is observed. Preseeding the reaction mixture with an amphiphile of one chirality results in the amplification of this product and therefore information transfer between generations of self-replicating aggregates. Because our amphiphiles are capable of catalysis, information transfer, and self-assembly into bounded structures, they present a plausible model for prenucleic acid "lipid world" entities. © 2015 American Chemical Society.

Effect of Fibers on Mixture Design of Stone Matrix Asphalt

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Yanping Sheng

2017-03-01

Full Text Available Lignin fibers typically influence the mixture performance of stone matrix asphalt (SMA, such as strength, stability, durability, noise level, rutting resistance, fatigue life, and water sensitivity. However, limited studies were conducted to analyze the influence of fibers on the percent voids in mineral aggregate in bituminous mixture (VMA during the mixture design. This study analyzed the effect of different fibers and fiber contents on the VMA in SMA mixture design. A surface-dry condition method test and Marshall Stability test were applied on the SMA mixture with four different fibers (i.e., flocculent lignin fiber, mineral fiber, polyester fiber, blended fiber. The test results indicated that the bulk specific gravity of SMA mixtures and asphalt saturation decreased with the increasing fiber content, whilst the percent air voids in bituminous mixtures (VV, Marshall Stability and VMA increased. Mineral fiber had the most obvious impact on the bulk specific gravity of bituminous mixtures, while flocculent lignin fiber had a minimal impact. The mixture with mineral fiber and polyester fiber had significant effects on the volumetric properties, and, consequently, exhibited better VMA over the conventional SMA mixture with lignin fiber. Modified fiber content range was also provided, which will widen the utilization of mineral fiber and polyester fiber in the applications of SMA mixtures. The mixture evaluation suggested no statistically significant difference between lignin fiber and polyester fiber on the stability. The mineral fiber required a much larger fiber content to improve the mixture performance than other fibers. Overall, the results can be a reference to guide SMA mixture design.

Effects of aggregate grading on the properties of steel fibre-reinforced concrete

Science.gov (United States)

Acikgens Ulas, M.; Alyamac, K. E.; Ulucan, Z. C.

2017-09-01

This study investigates the effects of changing the aggregate grading and maximum aggregate size (D max ) on the workability and mechanical properties of steel fibre-reinforced concrete (SFRC). Four different gradations and two different D max were used to produce SFRC mixtures with constant cement dosages and water/cement ratios. Twelve different concrete series were tested. To observe the properties of fresh concrete, slump and Ve-Be tests were performed immediately after the mixing process to investigate the effects of time on workability. The hardened properties, such as the compressive, splitting tensile and flexural strengths, were also evaluated. In addition, the toughness of the SFRC was calculated. Based on our test results, we can conclude that the grading of the aggregate and the D max have remarkable effects on the properties of fresh and hardened SFRC. In addition, the toughness of the SFRC was influenced by changing the grading of the aggregate and the D max .

Using a centrifuge for quality control of pre-wetted lightweight aggregate in internally cured concrete

Science.gov (United States)

Miller, Albert E.

Early age shrinkage of cementitious systems can result in an increased potential for cracking which can lead to a reduction in service life. Early age shrinkage cracking can be particularly problematic for high strength concretes, which are often specified due to their high strength and low permeability. However, these high strength concretes frequently exhibit a reduction in the internal relative humidity (RH) due to the hydration reaction (chemical shrinkage) and self-desiccation which results in a bulk shrinkage, termed autogenous shrinkage, which is substantial at early ages. Due to the low permeability of these concretes, standard external curing is not always efficient in addressing this reduction in internal RH since the penetration of water can be limited. Internal curing has been developed to reduce autogenous shrinkage. Internally cured mixtures use internal reservoirs filled with fluid (generally water) that release this fluid at appropriate times to counteract the effects of self-desiccation thereby maintaining a high internal RH. Internally cured concrete is frequently produced in North America using pre-wetted lightweight aggregate. One important aspect associated with preparing quality internally cured concrete is being able to determine the absorbed moisture and surface moisture associated with the lightweight aggregate which enables aggregate moisture corrections to be made for the concrete mixture. This thesis represents work performed to develop a test method using a centrifuge to determine the moisture state of pre-wetted fine lightweight aggregate. The results of the test method are then used in a series of worksheets that were developed to assist field technicians when performing the tests and applying the results to a mixture design. Additionally, research was performed on superabsorbent polymers to assess their ability to be used as an internal curing reservoir.

Concrete with onyx waste aggregate as aesthetically valued structural concrete

Science.gov (United States)

Setyowati E., W.; Soehardjono, A.; Wisnumurti

2017-09-01

The utillization of Tulungagung onyx stone waste as an aggregate of concrete mixture will improve the economic value of the concrete due to the brighter color and high aesthetic level of the products. We conducted the research of 75 samples as a test objects to measure the compression stress, splits tensile stress, flexural tensile stress, elasticity modulus, porosity modulus and also studied 15 test objects to identify the concrete micro structures using XRD test, EDAX test and SEM test. The test objects were made from mix designed concrete, having ratio cement : fine aggregate : coarse aggregate ratio = 1 : 1.5 : 2.1, and W/C ratio = 0.4. The 28 days examination results showed that the micro structure of Tulungagung onyx waste concrete is similar with normal concrete. Moreover, the mechanical test results proved that Tulungagung onyx waste concretes also have a qualified level of strength to be used as a structural concrete with higher aesthetic level.

Scattering and radiative properties of semi-external versus external mixtures of different aerosol types

International Nuclear Information System (INIS)

Mishchenko, Michael I.; Liu Li; Travis, Larry D.; Lacis, Andrew A.

2004-01-01

The superposition T-matrix method is used to compute the scattering of unpolarized light by semi-external aerosol mixtures in the form of polydisperse, randomly oriented two-particle clusters with touching components. The results are compared with those for composition-equivalent external aerosol mixtures, in which the components are widely separated and scatter light in isolation from each other. It is concluded that aggregation is likely to have a relatively weak effect on scattering and radiative properties of two-component tropospheric aerosols and can be replaced by the much simpler external-mixture model in remote sensing studies and atmospheric radiation balance computations

Discrete Element Method Modeling of the Rheological Properties of Coke/Pitch Mixtures.

Science.gov (United States)

Majidi, Behzad; Taghavi, Seyed Mohammad; Fafard, Mario; Ziegler, Donald P; Alamdari, Houshang

2016-05-04

Rheological properties of pitch and pitch/coke mixtures at temperatures around 150 °C are of great interest for the carbon anode manufacturing process in the aluminum industry. In the present work, a cohesive viscoelastic contact model based on Burger's model is developed using the discrete element method (DEM) on the YADE, the open-source DEM software. A dynamic shear rheometer (DSR) is used to measure the viscoelastic properties of pitch at 150 °C. The experimental data obtained is then used to estimate the Burger's model parameters and calibrate the DEM model. The DSR tests were then simulated by a three-dimensional model. Very good agreement was observed between the experimental data and simulation results. Coke aggregates were modeled by overlapping spheres in the DEM model. Coke/pitch mixtures were numerically created by adding 5, 10, 20, and 30 percent of coke aggregates of the size range of 0.297-0.595 mm (-30 + 50 mesh) to pitch. Adding up to 30% of coke aggregates to pitch can increase its complex shear modulus at 60 Hz from 273 Pa to 1557 Pa. Results also showed that adding coke particles increases both storage and loss moduli, while it does not have a meaningful effect on the phase angle of pitch.

Aggregate development in C 60/N-methyl-2-pyrrolidone solution and its mixture with water as revealed by extraction and mass spectroscopy

Science.gov (United States)

Kyzyma, O. A.; Korobov, M. V.; Avdeev, M. V.; Garamus, V. M.; Snegir, S. V.; Petrenko, V. I.; Aksenov, V. L.; Bulavin, L. A.

2010-06-01

The aggregate development in C 60/N-methyl-2-pyrrolidone (C 60/NMP) solution with time is studied by the extraction (hexane) and mass spectroscopy. It is shown that only molecular C 60 in NMP is extracted in hexane, which makes it possible to follow a change in the concentration of non-aggregated fullerene in C 60/NMP during the aggregate growth. It is concluded that almost all fullerene dissolved in NMP is in the aggregates after one month. The reorganization of the aggregates is detected when water is added to the aggregated solution C 60/NMP. Both methods prove that in this case individual fullerene molecules are detached from the aggregates, which contradicts somewhat to complete insolubility of C 60 in water.

Properties of concrete blocks prepared with low grade recycled aggregates.

Science.gov (United States)

Poon, Chi-Sun; Kou, Shi-cong; Wan, Hui-wen; Etxeberria, Miren

2009-08-01

Low grade recycled aggregates obtained from a construction waste sorting facility were tested to assess the feasibility of using these in the production of concrete blocks. The characteristics of the sorted construction waste are significantly different from that of crushed concrete rubbles that are mostly derived from demolition waste streams. This is due to the presence of higher percentages of non-concrete components (e.g. >10% soil, brick, tiles etc.) in the sorted construction waste. In the study reported in this paper, three series of concrete block mixtures were prepared by using the low grade recycled aggregates to replace (i) natural coarse granite (10mm), and (ii) 0, 25, 50, 75 and 100% replacement levels of crushed stone fine (crushed natural granite concrete blocks. Test results on properties such as density, compressive strength, transverse strength and drying shrinkage as well as strength reduction after exposure to 800 degrees C are presented below. The results show that the soil content in the recycled fine aggregate was an important factor in affecting the properties of the blocks produced and the mechanical strength deceased with increasing low grade recycled fine aggregate content. But the higher soil content in the recycled aggregates reduced the reduction of compressive strength of the blocks after exposure to high temperature due probably to the formation of a new crystalline phase. The results show that the low grade recycled aggregates obtained from the construction waste sorting facility has potential to be used as aggregates for making non-structural pre-cast concrete blocks.

Properties Improvement of Cast Stone Produced Using Recycled Glass Waste and Lightweight Aggregates

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Elham Abd AL-Majeed

2018-01-01

Full Text Available Cast stone (CS is a form of pre-cast concrete widely, used in architectural applications for decorating and building face in place of natural stone due its superior features. The present study was an attempt in using of local lightweight aggregate materials (LWAM as an alternative to percentage of coarse aggregate, and glass wastes as alternatives to percentages of fine aggregate in cast stone normal mixtures with white cement and plasticizer admixture. The CS products were cured after 24 hrs using of two different processes: water curing (at 23 C° for 3 days and steam curing (at 60 C° for 14 hrs. Then the products were characterized by tests of compressive strength, design, absorption, flexure strength and liner drying shrinkage. The addition of alternative materials was done by trial mixes (M0-M3 through 3 groups (A, B, and C according to standards. Group A: design of reference mixtures of CS with compressive strength of 46.3 MPa and the absorption of 6.19%, Group B: design of mixtures containing 50% LWA were 16% lighter than those of Group A with compressive strength of 43.6 MPa and 11% improvement in the absorption, Group C: design of mixtures containing (50 and 75% glass waste with compressive strength of (47.5-44.3 MPa and the absorption of (5.3-4.7%, respectively. The modified steam curing process (curing after 24 hrs casting done in this study could prove its effectiveness in the achievement of the required compressive strength in comparison with the normal process (direct curing after casting due to the effect of such new process in providing the more uniform distribution of the cement gel with good physical properties. Results from the flexural strength test could prove the achievement of the required levels (6.9 – 6.3 at 50 – 75% glass waste addition recorded in the standard.

Cosolvent effect on the dynamics of water in aqueous binary mixtures

Science.gov (United States)

Zhang, Xia; Zhang, Lu; Jin, Tan; Zhang, Qiang; Zhuang, Wei

2018-04-01

Water rotational dynamics in the mixtures of water and amphiphilic molecules, such as acetone and dimethyl sulfoxide (DMSO), measured by femtosecond infrared, often vary non-monotonically as the amphiphilic molecule's molar fraction changes from 0 to 1. Recent study has attributed the non-ideal water rotation with concentration in DMSO-water mixtures to different microscopic hydrophilic-hydrophobic segregation structure in water-rich and water-poor mixtures. Interestingly, the acetone molecule has very similar molecular structure to DMSO, but the extremum of the water rotational time in the DMSO-water mixtures significantly shifts to lower concentration and the rotation of water is much faster than those in acetone-water mixtures. The simulation results here shows that the non-ideal rotational dynamics of water in both mixtures are due to the frame rotation during the interval of hydrogen bond (HB) switchings. A turnover of the frame rotation with concentration takes place as the structure transition of mixture from the hydrogen bond percolation structure to the hydrophobic percolation structure. The weak acetone-water hydrogen bond strengthens the hydrophobic aggregation and accelerates the relaxation of the hydrogen bond, so that the structure transition takes places at lower concentration and the rotation of water is faster in acetone-water mixture than in DMSO-water mixture. A generally microscopic picture on the mixing effect on the water dynamics in binary aqueous mixtures is presented here.

Phytoplankton aggregate formation: observations of patterns and mechanisms of cell sticking and the significance of exopolymeric material

DEFF Research Database (Denmark)

Kiørboe, Thomas; Hansen, Jorgen L. S.

1993-01-01

are sticky in themselves, and coagulation depends on cell-cell sticking and does not involve mucus. Aggregates are composed solely of cells. Cells of the diatom Chaetoceros affinis, on the other hand, are not in themselves sticky. Transparent exopolymeric particles (TEP), produced by the diatom, cause...... the cells to aggregate and coagulation depends on TEP-cell rather than cell-cell sticking. Aggregates are formed of a mixture of mucus and cells. We found several species of diatoms and one flagellate species to produce copious amounts of TEP. TEP from some species (e.g. Coscinodiscus sp.) is sticky and may...

Aging Influence on Fatigue Characteristics of RAC Mixtures Containing Warm Asphalt Additives

Directory of Open Access Journals (Sweden)

Feipeng Xiao

2010-01-01

Full Text Available Aging is an important factor to affect the long-term performance of asphalt pavement. The fatigue life of a typical warm mix asphalt (WMA is generally related to various factors of rheological and mechanical properties of the mixture. The study of the fatigue behavior of the specific rubberized WMA is helpful in recycling the scrap tires and saving energy in terms of the conventional laboratory aging process. This study explores the utilization of the conventional fatigue analysis approach in investigating the cumulative dissipated, stiffness, and fatigue life of rubberized asphalt concrete mixtures containing the WMA additive after a long-term aging process. The aged beams were made with one rubber type (−40 mesh ambient crumb rubber, two aggregate sources, two WMA additives (Asphamin and Sasobit, and tested at 5 and 20ºC. A total of 55 aged fatigue beams were tested in this study. The test results indicated that the addition of crumb rubber extends the fatigue resistance of asphalt binder while WMA additive exhibits a negative effect. The study indicated that the WMA additive generally has an important influence on fatigue life. In addition, test temperature and aggregate source play an important role in determining the cumulative dissipated energy, stiffness, and fatigue life of an aged mixture.

An investigation on the use of shredded waste PET bottles as aggregate in lightweight concrete

International Nuclear Information System (INIS)

Akcaoezoglu, Semiha; Atis, Cengiz Duran; Akcaoezoglu, Kubilay

2010-01-01

In this work, the utilization of shredded waste Poly-ethylene Terephthalate (PET) bottle granules as a lightweight aggregate in mortar was investigated. Investigation was carried out on two groups of mortar samples, one made with only PET aggregates and, second made with PET and sand aggregates together. Additionally, blast-furnace slag was also used as the replacement of cement on mass basis at the replacement ratio of 50% to reduce the amount of cement used and provide savings. The water-binder (w/b) ratio and PET-binder (PET/b) ratio used in the mixtures were 0.45 and 0.50, respectively. The size of shredded PET granules used in the preparation of mortar mixtures were between 0 and 4 mm. The results of the laboratory study and testing carried out showed that mortar containing only PET aggregate, mortar containing PET and sand aggregate, and mortars modified with slag as cement replacement can be drop into structural lightweight concrete category in terms of unit weight and strength properties. Therefore, it was concluded that there is a potential for the use of shredded waste PET granules as aggregate in the production of structural lightweight concrete. The use of shredded waste PET granules due to its low unit weight reduces the unit weight of concrete which results in a reduction in the death weight of a structural concrete member of a building. Reduction in the death weight of a building will help to reduce the seismic risk of the building since the earthquake forces linearly dependant on the dead-weight. Furthermore, it was also concluded that the use of industrial wastes such as PET granules and blast-furnace slag in concrete provides some advantages, i.e., reduction in the use of natural resources, disposal of wastes, prevention of environmental pollution, and energy saving.

An investigation on the use of shredded waste PET bottles as aggregate in lightweight concrete.

Science.gov (United States)

Akçaözoğlu, Semiha; Atiş, Cengiz Duran; Akçaözoğlu, Kubilay

2010-02-01

In this work, the utilization of shredded waste Poly-ethylene Terephthalate (PET) bottle granules as a lightweight aggregate in mortar was investigated. Investigation was carried out on two groups of mortar samples, one made with only PET aggregates and, second made with PET and sand aggregates together. Additionally, blast-furnace slag was also used as the replacement of cement on mass basis at the replacement ratio of 50% to reduce the amount of cement used and provide savings. The water-binder (w/b) ratio and PET-binder (PET/b) ratio used in the mixtures were 0.45 and 0.50, respectively. The size of shredded PET granules used in the preparation of mortar mixtures were between 0 and 4 mm. The results of the laboratory study and testing carried out showed that mortar containing only PET aggregate, mortar containing PET and sand aggregate, and mortars modified with slag as cement replacement can be drop into structural lightweight concrete category in terms of unit weight and strength properties. Therefore, it was concluded that there is a potential for the use of shredded waste PET granules as aggregate in the production of structural lightweight concrete. The use of shredded waste PET granules due to its low unit weight reduces the unit weight of concrete which results in a reduction in the death weight of a structural concrete member of a building. Reduction in the death weight of a building will help to reduce the seismic risk of the building since the earthquake forces linearly dependent on the dead-weight. Furthermore, it was also concluded that the use of industrial wastes such as PET granules and blast-furnace slag in concrete provides some advantages, i.e., reduction in the use of natural resources, disposal of wastes, prevention of environmental pollution, and energy saving.

Modelling and Laboratory Studies on the Adhesion Fatigue Performance for Thin-Film Asphalt and Aggregate System

Directory of Open Access Journals (Sweden)

Dongsheng Wang

2014-01-01

Full Text Available Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more important effect on the adhesion performance comparing with aggregate. Basalt, which is regarded as hydrophobic aggregates with low silica content, has better adhesion performance to asphalt binder when compared with granite. The effects of aging on the adhesion fatigue performance are different for PG64-22 and rubber asphalt. Long-term aging is found to reduce the adhesion fatigue lives for rubber asphalt and aggregate system, while the effect of long-term aging for aggregate and PG64-22 binder system is positive. Generally the increased stress amplitude and test temperature could induce greater damage and lead to less fatigue lives for adhesion test system.

Studies for the stabilization of coal-oil mixtures. Final report, August 1978-May 1981

Energy Technology Data Exchange (ETDEWEB)

Botsaris, G.D.; Glazman, Y.M.; Adams-Viola, M.

1981-01-01

A fundamental understanding of the stabilization of coal-oil mixtures (COM) was developed. Aggregation of the coal particles was determined to control both the sedimentation and rheological properties of the COM. Sedimentation stability of COM prepared with coal, 80% < 200 mesh, is achieved by particle aggregation, which leads to the formation of a network of particles throughout the oil. The wettability of coal powders was evaluated by the Pickering emulsion test and a spherical agglomeration test to assess its effect on the stability of various COM formulations. Sedimentation stability of hydrophilic coal-oil-water mixtures (COWM) involves the formation of water bridges between the coal particles, while less stabilization of oleophilic COWM is achieved by the formation of an emulsion. Anionic SAA were least sensitive to the coal type and enhanced the aggregation stability of the suspension. The effect of cationic SAA, nonionic SAA and polymer additives depended upon the specific chemical structure of the SAA, the water content of the COM and the type of coal. The sedimentation stability of ultrafine COM was not directly due to the fineness of the powder but due to the formation of a network of flocculated particles.

Effect of Fly-Ash on Corrosion Resistance Characteristics of Rebar Embedded in Recycled Aggregate Concrete

Science.gov (United States)

Revathi, Purushothaman; Nikesh, P.

2018-04-01

In the frame of an extended research programme dealing with the utilization of recycled aggregate in concrete, the corrosion resistance characteristics of rebars embedded in recycled aggregate concrete is studied. Totally five series of concrete mixtures were prepared with fly-ash as replacement for cement in the levels of 10-30% by weight of cement. Corrosion studies by 90 days ponding test, linear polarization test and impressed voltage tests were carried out, in order to investigate whether corrosion behaviour of the rebars has improved due to the replacement of cement with fly-ash. Results showed that the replacement of cement with fly-ash in the range of 20-30% improves the corrosion resistance characteristics of recycled aggregate concrete.

Stability and Volumetric Properties of Asphalt Mixture Containing Waste Plastic

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Abd Kader Siti Aminah

2017-01-01

Full Text Available The objectives of this study are to determine the optimum bitumen content (OBC for every percentage added of waste plastics in asphalt mixtures and to investigate the stability properties of the asphalt mixtures containing waste plastic. Marshall stability and flow values along with density, air voids in total mix, voids in mineral aggregate, and voids filled with bitumen were determined to obtain OBC at different percentages of waste plastic, i.e., 4%, 6%, 8%, and 10% by weight of bitumen as additive. Results showed that the OBC for the plastic-modified asphalt mixtures at 4%, 6%, 8%, and 10% are 4.98, 5.44, 5.48, and 5.14, respectively. On the other hand, the controlled specimen’s shows better volumetric properties compared to plastic mixes. However, 4% additional of waste plastic indicated better stability than controlled specimen.

Qualitative criteria and thresholds for low noise asphalt mixture design

Science.gov (United States)

Vaitkus, A.; Andriejauskas, T.; Gražulytė, J.; Šernas, O.; Vorobjovas, V.; Kleizienė, R.

2018-05-01

Low noise asphalt pavements are cost efficient and cost effective alternative for road traffic noise mitigation comparing with noise barriers, façade insulation and other known noise mitigation measures. However, design of low noise asphalt mixtures strongly depends on climate and traffic peculiarities of different regions. Severe climate regions face problems related with short durability of low noise asphalt mixtures in terms of considerable negative impact of harsh climate conditions (frost-thaw, large temperature fluctuations, hydrological behaviour, etc.) and traffic (traffic loads, traffic volumes, studded tyres, etc.). Thus there is a need to find balance between mechanical and acoustical durability as well as to ensure adequate pavement skid resistance for road safety purposes. Paper presents analysis of the qualitative criteria and design parameters thresholds of low noise asphalt mixtures. Different asphalt mixture composition materials (grading, aggregate, binder, additives, etc.) and relevant asphalt layer properties (air void content, texture, evenness, degree of compaction, etc.) were investigated and assessed according their suitability for durable and effective low noise pavements. Paper concluded with the overview of requirements, qualitative criteria and thresholds for low noise asphalt mixture design for severe climate regions.

Crushed aggregate-betonite mixtures as backfill material for the Finnish repositories of low- and intermediate-level radioactive wastes

International Nuclear Information System (INIS)

Holopainen, P.; Pirhonen, V.; Snellman, M.

1984-03-01

Backfill materials consisting of three components: crushed rock aggregate, finely ground rock aggregate and bentonite (3 to 2 per cent of weight) were studied. The production and installation procedures of the material were evaluated. Laboratory tests were made to determine the hydraulic conductivity and swelling potential of the materials. Chemical tests were made on the different materials and groundwaters. Mineralogical changes of the clay fraction were estimated. (author)

On the interfacial interaction between bituminous binders and mineral surfaces as present in asphalt mixtures

Energy Technology Data Exchange (ETDEWEB)

Fischer, Hartmut R., E-mail: hartmut.fischer@tno.nl [TNO Technical Sciences, De Rondom 1, 5612 AP Eindhoven (Netherlands); Dillingh, E.C.; Hermse, C.G.M. [TNO Technical Sciences, De Rondom 1, 5612 AP Eindhoven (Netherlands)

2013-01-15

Highlights: Black-Right-Pointing-Pointer Direct measurement of the contact angle between different phases of the microstructure of bitumen and aggregate surfaces of different chemical nature using AFM. Black-Right-Pointing-Pointer Common schema of adhesion of bitumen on aggregates via asphaltene precipitation. Black-Right-Pointing-Pointer Surface roughness/porosity more important than chemical nature for strength of adhesion between aggregate and bitumen. - Abstract: The interfacial interaction between bituminous binders and several mineral surfaces of different chemical nature as present in asphalt mixtures has been investigated using atomic force microscopy. Several dry mineral surfaces display comparable wetting with respect to the different phases present in the micro-structure of bitumen, regardless of differences in their chemical nature. The peri/catana-phase shows a preferential wetting due to adsorption of asphaltene aggregates to the mineral surfaces.

On the interfacial interaction between bituminous binders and mineral surfaces as present in asphalt mixtures

International Nuclear Information System (INIS)

Fischer, Hartmut R.; Dillingh, E.C.; Hermse, C.G.M.

2013-01-01

Highlights: ► Direct measurement of the contact angle between different phases of the microstructure of bitumen and aggregate surfaces of different chemical nature using AFM. ► Common schema of adhesion of bitumen on aggregates via asphaltene precipitation. ► Surface roughness/porosity more important than chemical nature for strength of adhesion between aggregate and bitumen. - Abstract: The interfacial interaction between bituminous binders and several mineral surfaces of different chemical nature as present in asphalt mixtures has been investigated using atomic force microscopy. Several dry mineral surfaces display comparable wetting with respect to the different phases present in the micro-structure of bitumen, regardless of differences in their chemical nature. The peri/catana-phase shows a preferential wetting due to adsorption of asphaltene aggregates to the mineral surfaces.

Discrete Element Method Modeling of the Rheological Properties of Coke/Pitch Mixtures

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Behzad Majidi

2016-05-01

Full Text Available Rheological properties of pitch and pitch/coke mixtures at temperatures around 150 °C are of great interest for the carbon anode manufacturing process in the aluminum industry. In the present work, a cohesive viscoelastic contact model based on Burger’s model is developed using the discrete element method (DEM on the YADE, the open-source DEM software. A dynamic shear rheometer (DSR is used to measure the viscoelastic properties of pitch at 150 °C. The experimental data obtained is then used to estimate the Burger’s model parameters and calibrate the DEM model. The DSR tests were then simulated by a three-dimensional model. Very good agreement was observed between the experimental data and simulation results. Coke aggregates were modeled by overlapping spheres in the DEM model. Coke/pitch mixtures were numerically created by adding 5, 10, 20, and 30 percent of coke aggregates of the size range of 0.297–0.595 mm (−30 + 50 mesh to pitch. Adding up to 30% of coke aggregates to pitch can increase its complex shear modulus at 60 Hz from 273 Pa to 1557 Pa. Results also showed that adding coke particles increases both storage and loss moduli, while it does not have a meaningful effect on the phase angle of pitch.

Utilization of polyethylene terephthalate (PET) in bituminous mixture for improved performance of roads

Science.gov (United States)

Ahmad, A. F.; Razali, A. R.; Razelan, I. S. M.; Jalil, S. S. A.; Noh, M. S. M.; Idris, A. A.

2017-05-01

Plastic bottle for recycling can be found from the household waste stream, and most of them are made from Polyethylene Terephthalate. In this research, PET is utilized to explore the potential prospects to upgrade asphalt mixture properties. The objectives include deciding the best measure of PET to be used. For experimental, Marshall mix design was utilized to determine the ideal bitumen binder content and to test the modified mixture properties. The samples were created per the requirement for aggregate course wearing (ACW14) using the Standard Specification of Road Work (SSRW) in Malaysia. 20 samples were utilized to determine the binder content, and 30 samples were used to research the impact of modifying asphalt mixtures. 2%, 5%, 10%, 15% and 20% of PET by weight of the optimum binder content (4.8%) were tested. Optimum PET content is 10%, and the result shows a good stability with 16.824kN, 2.32g/cm3 bulk density, void filled with bitumen (VFB) with 71.35%, flow with 3.2248mm, air void (AV) with 4.53%, and void of mineral aggregate (VMA) with 15.15%. The outcomes showed that PET modifier gives better engineering properties. Therefore, 10% of PET by the weight of binder content was suggested as the best amount of the modifier.

Using of Glass Wastes as a Fine Aggregate in Concrete Mixture

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Mohammad F. Al-Deen

2013-04-01

Full Text Available In this study, the waste glass (WG is considered as a fine aggregate in the concretemixture. WG is used after grinding to size according to Iraqi sand specificationsNo.45. The waste glass has been used instead of sand in different proportions whichare 0%, 33%, 66% and 100%. The effects of WG on compressive strength of theconcrete and unit weight are analysed. As results of this study, WG is determined tohave a significant effect upon the reduction of its compressive strength and there is asignificant decreasing of its unit weight. As for cost analysis, it was determined tolower the cost of concrete production. This study was an environmental one inconsideration of the fact that WG could be used in the concrete as fine aggreagateswithout the need for a high cost or rigorous energy.

Effect of Natural Sand Percentages on Fatigue Life of Asphalt Concrete Mixture

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Nahla Yassub Ahmed

2016-03-01

Full Text Available The design of a flexible pavement requires the knowledge of the material properties which are characterized by stiffness and fatigue resistance. The fatigue resistance relates the number of load cycles to failure with the strain level applied to the asphalt mixture. The main objective of this research is the evaluation of the fatigue life of asphalt mixtures by using two types of fine aggregate having different percentages. In this study, two types of fine aggregate were used natural sand (desert sand and crushed sand. The crushed sand was replaced by natural sand (desert sand with different percentages (0%, 25%, 75% and 100% by the weight of the sand (passing sieve No.8 and retained on sieve No.200 and one type of binder (40/50 penetration from Al-Daurah refinery. The samples of beams were tested by four point bending beam fatigue test at the control strain mode (250, 500 and 750 microstrain while the loading frequency (5Hz and testing temperature (20oC according to (AASHTO T321. The experimental work showed that fatigue life (Nf and initial flexural stiffness increased when control strain decreased for asphalt mixtures. Acceptable fatigue life at 750 microstrain was obtained with asphalt concrete mixtures containing 100% crushed sand as well as asphalt concrete contained 25% natural sand. The asphalt concrete contained 100% and 75% of natural sand exhibited high fatigue life at low level of microstrain (250. The main conclusion of this study found that best proportion of natural sand to be added to an asphaltic concrete mixture is falling within the range (0% and 25% by weight of fraction (passing No.8 and retained on No.200 sieve .

Phase behaviour of oat β-glucan/sodium caseinate mixtures varying in molecular weight.

Science.gov (United States)

Agbenorhevi, Jacob K; Kontogiorgos, Vassilis; Kasapis, Stefan

2013-05-01

The isothermal phase behaviour at 5 °C of mixtures of sodium caseinate and oat β-glucan isolates varying in molecular weight (MW) was investigated by means of phase diagram construction, rheometry, fluorescence microscopy and electrophoresis. Phase diagrams indicated that the compatibility of the β-glucan/sodium caseinate system increases as β-glucan MW decreases. Images of mixtures taken at various biopolymer concentrations revealed phase separated domains. Results also revealed that at the state of thermodynamic equilibrium, lower MW samples yielded considerable viscosity in the mixture. At equivalent hydrodynamic volume of β-glucan in the mixtures, samples varying in molecular weight exhibited similar flow behaviour. A deviation dependent on the protein concentration was observed for the high MW sample in the concentrated regime due to the size of β-glucan aggregates formed. Results demonstrate that by controlling the structural features of β-glucan in mixtures with sodium caseinate, informed manipulation of rheological properties in these systems can be achieved. Copyright © 2012 Elsevier Ltd. All rights reserved.

Structure and stability of charged colloid-nanoparticle mixtures

Science.gov (United States)

Weight, Braden M.; Denton, Alan R.

2018-03-01

Physical properties of colloidal materials can be modified by addition of nanoparticles. Within a model of like-charged mixtures of particles governed by effective electrostatic interactions, we explore the influence of charged nanoparticles on the structure and thermodynamic phase stability of charge-stabilized colloidal suspensions. Focusing on salt-free mixtures of particles of high size and charge asymmetry, interacting via repulsive Yukawa effective pair potentials, we perform molecular dynamics simulations and compute radial distribution functions and static structure factors. Analysis of these structural properties indicates that increasing the charge and concentration of nanoparticles progressively weakens correlations between charged colloids. We show that addition of charged nanoparticles to a suspension of like-charged colloids can induce a colloidal crystal to melt and can facilitate aggregation of a fluid suspension due to attractive van der Waals interactions. We attribute the destabilizing influence of charged nanoparticles to enhanced screening of electrostatic interactions, which weakens repulsion between charged colloids. This interpretation is consistent with recent predictions of an effective interaction theory of charged colloid-nanoparticle mixtures.

Three Dimensional Digital Sieving of Asphalt Mixture Based on X-ray Computed Tomography

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Chichun Hu

2017-07-01

Full Text Available In order to perform three-dimensional digital sieving based on X-ray computed tomography images, the definition of digital sieve size (DSS was proposed, which was defined as the minimum length of the minimum bounding squares of all possible orthographic projections of an aggregate. The corresponding program was developed to reconstruct aggregate structure and to obtain DSS. Laboratory experiments consisting of epoxy-filled aggregate specimens were conducted to investigate the difference between mechanical sieve analysis and the digital sieving technique. It was suggested that concave surface of aggregate was the possible reason for the disparity between DSS and mechanical sieve size. A comparison between DSS and equivalent diameter was also performed. Moreover, the digital sieving technique was adopted to evaluate the gradation of stone mastic asphalt mixtures. The results showed that the closest proximity of the laboratory gradation curve was achieved by calibrated DSS, among gradation curves based on calibrated DSS, un-calibrated DSS and equivalent diameter.

Assessment of aggregates- cement paste border in concretes containing silica fume and fly ash

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Ali Sademomtazi

2017-12-01

Full Text Available The bond between aggregate and cement paste, called the interfacial transition zone (ITZ is an important parameter that effect on the mechanical properties and durability of concrete. Transition zone microstructure and porosity (pores of cement paste or concrete are affected by the type and properties of materials used which evaluated in this research. On the other hand, the use of efficient, low-cost and reliable method is particularly important for evaluating of concrete performance against the chloride ion penetration and its relationships with transition zone as a suitable index to assess the durability. So far, various methods to approach the electrical Indices are presented. In this research, the effect of pozzolanic materials fly ash (10%, 20% and 30% and silica fume (5% and 10% as substitute of cement by weight in binary and ternary mixtures on the fresh and hardened concrete properties were investigated. To determine mechanical properties, the compressive strength, splitting tensile strength and modulus of elasticity tests were performed. Also, water penetration depth, porosity, water sorptivity, specific electrical resistivity, rapid chloride penetration test (RCPT and rapid chloride migration test (RCMT tests were applied to evaluate concrete durability. To examine the border of aggregate and cement paste morphology of concrete specimens, scanning electron microscope images (SEM was used. The fresh concrete results showed that the presence of silica fume in binary and ternary mixtures reduced workability and air content but fly ash increased them. Adding silica fume to mixtures of containing flay ash while increasing mechanical strength reduced the porosity and pores to 18%. The presence of pozzolanic materials in addition to increasing bond quality and uniformity of aggregate-cement matrix border a considerably positive effect on the transport properties of concrete.

Coupling of demixing and magnetic ordering phase transitions probed by turbidimetric measurements in a binary mixture doped with magnetic nanoparticles

International Nuclear Information System (INIS)

Hernandez-Diaz, Lorenzo; Hernandez-Reta, Juan Carlos; Encinas, Armando; Nahmad-Molinari, Yuri

2010-01-01

We present a novel study on the effect of a magnetic field applied on a binary mixture doped with magnetic nanoparticles close to its demixing transition. Turbidity measurements in the Faraday configuration show that the effect of applying an external field produces changes in the critical opalescence of the mixture that allow us to track an aggregation produced by critical Casimir forces and a reversible aggregation due to the formation of chain-like flocks in response to the external magnetic field. The observation of a crossover of the aggregation curves through optical signals is interpreted as the evolution from low to high power dispersion nuclei due to an increase in the radius of the condensation seed brought about by Casimir or magnetic interactions. Finally, evidence of an enhanced magnetocaloric effect due to the coupling between mixing and ordering phase transitions is presented which opens up a nonsolid state approach of designing refrigerating cycles and devices.

Coupling of demixing and magnetic ordering phase transitions probed by turbidimetric measurements in a binary mixture doped with magnetic nanoparticles

Science.gov (United States)

Hernández-Díaz, Lorenzo; Hernández-Reta, Juan Carlos; Encinas, Armando; Nahmad-Molinari, Yuri

2010-05-01

We present a novel study on the effect of a magnetic field applied on a binary mixture doped with magnetic nanoparticles close to its demixing transition. Turbidity measurements in the Faraday configuration show that the effect of applying an external field produces changes in the critical opalescence of the mixture that allow us to track an aggregation produced by critical Casimir forces and a reversible aggregation due to the formation of chain-like flocks in response to the external magnetic field. The observation of a crossover of the aggregation curves through optical signals is interpreted as the evolution from low to high power dispersion nuclei due to an increase in the radius of the condensation seed brought about by Casimir or magnetic interactions. Finally, evidence of an enhanced magnetocaloric effect due to the coupling between mixing and ordering phase transitions is presented which opens up a nonsolid state approach of designing refrigerating cycles and devices.

Coupling of demixing and magnetic ordering phase transitions probed by turbidimetric measurements in a binary mixture doped with magnetic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Hernandez-Diaz, Lorenzo; Hernandez-Reta, Juan Carlos; Encinas, Armando; Nahmad-Molinari, Yuri, E-mail: yuri@ifisica.uaslp.m [Instituto de Fisica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi (Mexico)

2010-05-19

We present a novel study on the effect of a magnetic field applied on a binary mixture doped with magnetic nanoparticles close to its demixing transition. Turbidity measurements in the Faraday configuration show that the effect of applying an external field produces changes in the critical opalescence of the mixture that allow us to track an aggregation produced by critical Casimir forces and a reversible aggregation due to the formation of chain-like flocks in response to the external magnetic field. The observation of a crossover of the aggregation curves through optical signals is interpreted as the evolution from low to high power dispersion nuclei due to an increase in the radius of the condensation seed brought about by Casimir or magnetic interactions. Finally, evidence of an enhanced magnetocaloric effect due to the coupling between mixing and ordering phase transitions is presented which opens up a nonsolid state approach of designing refrigerating cycles and devices.

Aggregation of non-amphiphilic bathophenanthroline in the restricted geometry of Langmuir-Blodgett films with two different matrices

Energy Technology Data Exchange (ETDEWEB)

Pal, Ajitesh [Centre of Studies in Surface Science and Technology, School of Chemistry, Sambalpur University, Jyoti Vihar-768019, Orissa (India); Panigrahi, Simanchalo [Department of Physics, National Institute of Technology, Rourkela-788011, Orissa (India); Nath, Ranendu Kumar [Department of Chemistry, Tripura University, Suryamaninagar-799130, Tripura (India); Deb, Subrata [Department of Physics, Iswar Chandra Vidyasagar College, Belonia-799155, Tripura (India); Sinha, Tripurari Prasad [Department of Physics, Bose Institute, Kolkata-700009, West Bengal (India); Mishra, Bijay Kumar, E-mail: bijaym@hotmail.com [Centre of Studies in Surface Science and Technology, School of Chemistry, Sambalpur University, Jyoti Vihar-768019, Orissa (India)

2011-10-31

The behavior of binary mixed Langmuir monolayers from the mixture of non-amphiphilic bathophenanthroline (BPH) and behenic acid (BA)/poly(methyl methacrylate) (PMMA) spread on aqueous subphase was investigated on the basis of the analysis of surface pressure-average area per molecule ({pi}-A) isotherms complemented with UV-vis absorption spectroscopy and scanning electron microscopy. In addition, the miscibility of the components in the two investigated mixed systems (BPH/BA and BPH/PMMA) was also tested by using additivity and surface phase rules. The plots of area per molecule versus mole fraction suggest that BPH and BA are immiscible, whereas BPH and PMMA mixtures show non-ideal behavior at low surface pressures and complete miscibility or immiscibility at higher surface pressures. Spectroscopic study reveals that J-type of aggregates is formed in the mixed films. Scanning electron microscopic study supports the presence of aggregates.

Molecular Dynamics Simulation to Investigate the Interaction of Asphaltene and Oxide in Aggregate

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Rui Li

2016-01-01

Full Text Available The asphalt-aggregate interface interaction (AAI plays a significant role in the overall performances of asphalt mixture, which is caused due to the complicated physicochemical processes and is influenced by various factors, including the acid-base property of aggregates. In order to analyze the effects of the chemical constitution of aggregate on the AAI, the average structure C65H74N2S2 is selected to represent the asphaltene in asphalt and magnesium oxide (MgO, calcium oxide (CaO, aluminium sesquioxide (Al2O3, and silicon dioxide (SiO2 are selected to represent the major oxides in aggregate. The molecular models are established for asphaltene and the four oxides, respectively, and the molecular dynamics (MD simulation was conducted for the four kinds of asphaltene-oxide system at different temperatures. The interfacial energy in MD simulation is calculated to evaluate the AAI, and higher value means better interaction. The results show that interfacial energy between asphaltene and oxide reaches the maximum value at 25°C and 80°C and the minimum value at 40°C. In addition, the interfacial energy between asphaltene and MgO was found to be the greatest, followed by CaO, Al2O3, and SiO2, which demonstrates that the AAI between asphalt and alkaline aggregates is better than acidic aggregates.

Foam stabilization by solid particle aggregates

Energy Technology Data Exchange (ETDEWEB)

Guignot, S.; Faure, S. [CEA Marcoule, Lab. des Procedes Avances de Decontamination, 30 (France); Pitois, O. [UniversiteParis-Est Marne-La-Valle, Lab. Physique des Materiaux Divises et des Interfaces (LPMDI), 77 - Marne la Vallee (France)

2008-07-01

During the dismantling of nuclear facilities, radioactive deposits on exposed areas are removed and solubilized by successive rinses of reactive liquid. Using this liquid in a foam state reduces the amount of resulting wastes. During the required decontamination time (1 to 5 hours) the foam has to be sufficiently wet (1). In the Laboratory of Advanced Processes for Decontamination, new formulations are currently studied to slow down the drainage kinetics of these foams, by adding colloidal particles of hydrophilic fumed silica into the classical mixtures of well-defined non ionic foaming surfactants previously used (2). The objective of our study is to shed light on the foam surprising stability induced by these particles. The study focuses on drainage of foams generated by air sparging through a suspension lying on a porous glass. The foaming suspensions contain between 0 and 70 g.L-1 of a fumed silica (Aerosil 380) which is well-known to form gels for concentrations above 200 g.L{sup -1}. In the studied solutions this silica builds up into aggregates of dozens of microns, whose volume-averaged mean diameter after sonication is centred around 300 nm. Under gentle stirring, they display no sign of re-aggregation during 24 h. On a free drainage configuration, a foam that contains particles keeps a significant amount of its initial liquid: up to 60 % during up to 5 hours, in contrast to classical foams that drain out all of their liquid in about 20 minutes. From a rheological point of view, the most concentrated suspensions display a yield stress behaviour. This evidences the structuring of the aggregates into a coherent network that might explain the incomplete drainage of the solutions. For the lowest concentrated solutions, such rheological properties have not been observed although the corresponding foams can retain large amount of solution. This suggests that local concentrations of aggregates can rise owing to their retention by foam channels, until they form

Behavior of crushed rock aggregates used in road construction exposed to cold climate conditions

Science.gov (United States)

Kuznetsova, Elena; Pérez Fortes, Ana Patricia; Anastasio, Sara; Willy Danielsen, Svein

2016-04-01

carried out in both countries. The use of crushed aggregates in both the frost protection layer and asphalt layers is the main topic for our investigations. In existing standards there is large focus on mechanical properties of aggregates and their grain size distribution, but little focus on mineralogy and and its behaviour at low temperatures. With the purpose to study the effect of winter climatic conditions and the use of salts during winter maintenance, different samples of aggregates and asphalt mixtures used in Norwegian and Spanish roads were subjected to freeze-thaw cycles in the laboratory. To evaluate the impact of these cycles to the mechanical properties of the selected materials, Los Angeles test on aggregates and Cantabro test on asphalt have been done and compared with results from the same aggregates and asphalt mixtures but untreated in the laboratory. The results obtained were related to the petrographical analysis of the rocks that compose the aggregates in order to estimate the influence of the rock properties (mineralogy, texture and structure) in road materials behavior, especially when they are exposed to winter conditions.

Study of mechanical properties and recommendations for the application of waste Bakelite aggregate concrete

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Nopagon Usahanunth

2018-06-01

Full Text Available Bakelite waste from industrial manufacturing may be a hazard to the environment and public health. The utilization of waste Bakelite (WB to replace natural aggregates (NA, such as natural coarse aggregate (NCA and natural fine aggregate (NFA, in concrete and mortar is an approach for reducing both waste plastic and natural material. This research examines the utilization of waste Bakelite aggregate (WBA in concrete and mortar mixtures to form waste Bakelite aggregate concrete (WBAC and waste Bakelite mortar (WBM. The tests cover the physical and chemical properties of WBA, the mechanical properties of WBAC and WBM (including the extraction of chemical substances from WBA utilization to replace NCA and NFA, and recommendations for the application of replacement. The results indicate that WBA particles of different sizes can replace both fine and coarse natural aggregates. Its weight is less than natural aggregate but the absorption rate is higher. As for recommendations for the application, it was found that replacing 20% of NCA with waste Bakelite coarse aggregate in concrete (WBAC-RNCA was the most suitable proportion, owing to its mechanical properties and safety for the environment and public health, and because its material cost is acceptable. However, the use of waste Bakelite fine aggregate to replace NFA (WBAC-RNFA in concrete is not appropriate, because its mechanical properties are not sufficient, and it is considered unsafe for the environment and health. Moreover, WBM is not a suitable material for plastering work, since it may be a hazard to the environment and public health, and its cost is higher than conventional mortar. Keywords: Waste Bakelite, Aggregate, Concrete, Mortar

Molecular Approach to the Synergistic Effect on Astringency Elicited by Mixtures of Flavanols.

Science.gov (United States)

Ramos-Pineda, Alba María; García-Estévez, Ignacio; Brás, Natércia F; Martín Del Valle, Eva M; Dueñas, Montserrat; Escribano Bailón, María Teresa

2017-08-09

The interactions between salivary proteins and wine flavanols (catechin, epicatechin, and mixtures thereof) have been studied by HPLC-DAD, isothermal titration microcalorimetry, and molecular dynamics simulations. Chromatographic results suggest that the presence of these flavanol mixtures could facilitate the formation of precipitates to the detriment of soluble aggregates. Comparison between the thermodynamic parameters obtained showed remarkably higher negative values of ΔG in the system containing the mixture of both flavanols in comparison to the systems containing individual flavanols, indicating a more favorable scenario in the mixing system. Also, the apparent binding constants were higher in this system. Furthermore, molecular dynamics simulations suggested a faster and greater cooperative binding of catechin and epicatechin to IB7 14 peptides when both types of flavanols are present simultaneously in solution.

The influence of air-fuel ratio on mixture parameters in port fuel injection engines

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Adrian Irimescu

2008-10-01

Full Text Available Nowadays, research in the internal combustion engine field is focusing on detailed understanding of the processes that take place in certain parts of the aggregate, and can have a great influence on the engine’s performance and pollution levels. Such research is developed in this paper, in which using a numerical method based on the i-x air-fuel diagram, one can simulate a series of values for pressure, temperature and intake air humidity before and after mixture formation takes place in a spark ignition engine inlet port. The aim is to evaluate the final temperature of the air-fuel mixture near the inlet valve and evaluating the main factors of influence on the homogeneity of the mixture.

The effect of aggregate aspect ratio and temperature on the fracture toughness of a low cement refractory concrete

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Laura Brum Prata

2003-12-01

Full Text Available This work investigated the influence of the aggregate's aspect ratio on the fracture behavior of a low cement aluminum silicate refractory castable treated at two different temperatures (110 °C and 1000 °C. The aggregates were cylindrical pellets with an aspect ratio of 1, 2, 3 and 4, produced by extruding a mixture of clay and calcined alumina fired at 1600 °C for 4 h to yield mullite (3Al2O3.2SiO2. The behavior of the R-Curve and other relevant fracture parameters were evaluated based on the "Two Parameter Fracture Model" in a three-point flexure test of single-edge straight through notched specimens. The two temperature treatments produced different degrees of matrix-aggregate adhesion. The larger aspect ratio aggregates were found to promote toughening only in the dried condition, at 110 °C, while the specimens fired at 1000 °C for 4 h, regardless of their aggregate aspect ratio, displayed no significant toughening. The best results for fired samples, however, were obtained from specimens containing conventional angular aggregates.

SB certification handout material requirements, test methods, responsibilities, and minimum classification levels for mixture-based specification for flexible base.

Science.gov (United States)

2012-10-01

A handout with tables representing the material requirements, test methods, responsibilities, and minimum classification levels mixture-based specification for flexible base and details on aggregate and test methods employed, along with agency and co...

Use of additives to improve the capacity of bituminous mixtures to be heated by means of microwaves

International Nuclear Information System (INIS)

Gallego, J.; Val, M.A. del; Contreras, V.; Páez, A.

2017-01-01

This study examines the potential of adding electric arc furnace slag to bituminous mixtures to be heated by microwaves. The susceptibility of bituminous mixtures to microwave energy is limited and so, in order to improve the energy performance of the heating process, it is necessary to incorporate additives or components to the mixture so as to improve the capacity for microwave heating. The article presents the results of adding various components, (steel wool, scrap tire wire, silicon carbide, iron filings) and an alternative aggregate: electric arc furnace slag. According to the results obtained in the laboratory, slag addition of at least 5% by weight of the bituminous mixture represents the best option for both technical and economic reasons. The results may promote the valorization of this steel industry residue in bituminous mixtures by improving microwave heating response. [es

Investigation of Self Consolidating Concrete Containing High Volume of Supplementary Cementitious Materials and Recycled Asphalt Pavement Aggregates

Science.gov (United States)

Patibandla, Varun chowdary

The use of sustainable technologies such as supplementary cementitiuous materials (SCMs), and/or recycled materials is expected to positively affect the performance of concrete mixtures. However, it is important to study and qualify such mixtures and check if the required specifications of their intended application are met before they can be implemented in practice. This study presents the results of a laboratory investigation of Self Consolidating concrete (SCC) containing sustainable technologies. A total of twelve concrete mixtures were prepared with various combinations of fly ash, slag, and recycled asphalt pavement (RAP). The mixtures were divided into three groups with constant water to cementitiuous materials ratio of 0.37, and based on the RAP content; 0, 25, and 50% of coarse aggregate replaced by RAP. All mixtures were prepared to achieve a target slump flow equal to or higher than 500 mm (24in). A control mixture for each group was prepared with 100% Portland cement whereas all other mixtures were designed to have up to 70% of portland cement replaced by a combination of supplementary cementitiuous materials (SCMs) such as class C fly ash and granulated blast furnace slag. The properties of fresh concrete investigated in this study include flowability, deformability; filling capacity, and resistance to segregation. In addition, the compressive strength at 3, 14, and 28 days, the tensile strength, and the unrestrained shrinkage up to 80 days was also investigated. As expected the inclusion of the sustainable technologies affected both fresh and hardened concrete properties. Analysis of the experimental data indicated that inclusion of RAP not only reduces the ultimate strength, but it also affected the compressive strength development rate. Moreover, several mixes satisfied compressive strength requirements for pavements and bridges; those mixes included relatively high percentages of SCMs and RAP. Based on the results obtained in this study, it is not

Rydberg aggregates

Science.gov (United States)

Wüster, S.; Rost, J.-M.

2018-02-01

We review Rydberg aggregates, assemblies of a few Rydberg atoms exhibiting energy transport through collective eigenstates, considering isolated atoms or assemblies embedded within clouds of cold ground-state atoms. We classify Rydberg aggregates, and provide an overview of their possible applications as quantum simulators for phenomena from chemical or biological physics. Our main focus is on flexible Rydberg aggregates, in which atomic motion is an essential feature. In these, simultaneous control over Rydberg-Rydberg interactions, external trapping and electronic energies, allows Born-Oppenheimer surfaces for the motion of the entire aggregate to be tailored as desired. This is illustrated with theory proposals towards the demonstration of joint motion and excitation transport, conical intersections and non-adiabatic effects. Additional flexibility for quantum simulations is enabled by the use of dressed dipole-dipole interactions or the embedding of the aggregate in a cold gas or Bose-Einstein condensate environment. Finally we provide some guidance regarding the parameter regimes that are most suitable for the realization of either static or flexible Rydberg aggregates based on Li or Rb atoms. The current status of experimental progress towards enabling Rydberg aggregates is also reviewed.

Pre-Saturation Technique of the Recycled Aggregates: Solution to the Water Absorption Drawback in the Recycled Concrete Manufacture.

Science.gov (United States)

García-González, Julia; Rodríguez-Robles, Desirée; Juan-Valdés, Andrés; Morán-Del Pozo, Julia Mª; Guerra-Romero, M Ignacio

2014-09-01

The replacement of natural aggregates by recycled aggregates in the concrete manufacturing has been spreading worldwide as a recycling method to counteract the large amount of construction and demolition waste. Although legislation in this field is still not well developed, many investigations demonstrate the possibilities of success of this trend given that concrete with satisfactory mechanical and durability properties could be achieved. However, recycled aggregates present a low quality compared to natural aggregates, the water absorption being their main drawback. When used untreated in concrete mix, the recycled aggregate absorb part of the water initially calculated for the cement hydration, which will adversely affect some characteristics of the recycled concrete. This article seeks to demonstrate that the technique of pre-saturation is able to solve the aforementioned problem. In order to do so, the water absorption of the aggregates was tested to determine the necessary period of soaking to bring the recycled aggregates into a state of suitable humidity for their incorporation into the mixture. Moreover, several concrete mixes were made with different replacement percentages of natural aggregate and various periods of pre-saturation. The consistency and compressive strength of the concrete mixes were tested to verify the feasibility of the proposed technique.

Optimization the composition of sand-lime products modified of diabase aggregate

Science.gov (United States)

Komisarczyk, K.; Stępień, A.

2017-10-01

The problem of optimizing the composition of building materials is currently of great importance due to the increasing competitiveness and technological development in the construction industry. This phenomenon also applies to catalog sand-lime. The respective arrangement of individual components or their equivalents, and linking them with the main parameters of the composition of the mixture, i.e. The lime/sand/water should lead to the intended purpose. The introduction of sand-lime diabase aggregate is concluded with a positive effect of final products. The paper presents the results of optimization with the addition of diabase aggregate. The constant value was the amount of water, variable - the mass of the dry ingredients. The program of experimental studies was taken for 6 series of silicates made in industrial conditions. Final samples were tested for mechanical and physico-chemical expanding the analysis of the mercury intrusion porosimetry, SEM and XRD. The results show that, depending on the aggregate’s contribution, exhibit differences. The sample in an amount of 10% diabase aggregate the compressive strength was higher than in the case of reference sample, while modified samples absorbed less water.

Technical viability of self-compacting concretes with by-products from crushed coarse aggregate production

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Edgar Bacarji

Full Text Available Abstract The main objective of this work is to present the technical viability of Self Compacting Concretes (SCC containing by-products from crushed coarse aggregate production. For this purpose, a vast characterization of these by-products was made; six mixtures of SCC were produced using two different aggregates: granite and mica schist. The binder/dry aggregate (b/agg ratio by mass was 1:3. The following properties were analyzed: compressive strength, direct tensile strength, flexural tensile strength and splitting tensile strength. Granite presented the best mechanical performance. The replacement of natural sand by granite sand generated concretes with the same level of compressive strength and caused an increase in tensile strength values. The incorporation of silica fume into concrete with granite produced an increase of 17% in compressive strength. So, the use of these by-product materials can provide a technically feasible solution that is also consistent with the aims of sustainable development and preservation of the environment.

Aggregation in particle rich environments: a textural study of examples from volcanic eruptions, meteorite impacts, and fluidized bed processing

Science.gov (United States)

Mueller, Sebastian B.; Kueppers, Ulrich; Huber, Matthew S.; Hess, Kai-Uwe; Poesges, Gisela; Ruthensteiner, Bernhard; Dingwell, Donald B.

2018-04-01

Aggregation is a common process occurring in many diverse particulate gas mixtures (e.g. those derived from explosive volcanic eruptions, meteorite impact events, and fluid bed processing). It results from the collision and sticking of particles suspended in turbulent gas/air. To date, there is no generalized model of the underlying physical processes. Here, we investigate aggregates from 18 natural deposits (16 volcanic deposits and two meteorite impact deposits) as well as aggregates produced experimentally via fluidized bed techniques. All aggregates were analyzed for their size, internal structuring, and constituent particle size distribution. Commonalities and differences between the aggregate types are then used to infer salient features of the aggregation process. Average core to rim ratios of internally structured aggregates (accretionary lapilli) is found to be similar for artificial and volcanic aggregates but up to an order of magnitude different than impact-related aggregates. Rim structures of artificial and volcanic aggregates appear to be physically similar (single, sub-spherical, regularly-shaped rims) whereas impact-related aggregates more often show multiple or irregularly shaped rims. The particle size distributions (PSDs) of all three aggregate types are similar (< 200 μm). This proves that in all three environments, aggregation occurs under broadly similar conditions despite the significant differences in source conditions (particle volume fraction, particle size distribution, particle composition, temperature), residence times, plume conditions (e.g., humidity and temperature), and dynamics of fallout and deposition. Impact-generated and volcanic aggregates share many similarities, and in some cases may be indistinguishable without their stratigraphic context.

Pre-Saturation Technique of the Recycled Aggregates: Solution to the Water Absorption Drawback in the Recycled Concrete Manufacture †

Science.gov (United States)

García-González, Julia; Rodríguez-Robles, Desirée; Juan-Valdés, Andrés; Morán-del Pozo, Julia Mª; Guerra-Romero, M. Ignacio

2014-01-01

The replacement of natural aggregates by recycled aggregates in the concrete manufacturing has been spreading worldwide as a recycling method to counteract the large amount of construction and demolition waste. Although legislation in this field is still not well developed, many investigations demonstrate the possibilities of success of this trend given that concrete with satisfactory mechanical and durability properties could be achieved. However, recycled aggregates present a low quality compared to natural aggregates, the water absorption being their main drawback. When used untreated in concrete mix, the recycled aggregate absorb part of the water initially calculated for the cement hydration, which will adversely affect some characteristics of the recycled concrete. This article seeks to demonstrate that the technique of pre-saturation is able to solve the aforementioned problem. In order to do so, the water absorption of the aggregates was tested to determine the necessary period of soaking to bring the recycled aggregates into a state of suitable humidity for their incorporation into the mixture. Moreover, several concrete mixes were made with different replacement percentages of natural aggregate and various periods of pre-saturation. The consistency and compressive strength of the concrete mixes were tested to verify the feasibility of the proposed technique. PMID:28788188

On the mesoscopic origins of high viscosities in some polyelectrolyte-surfactant mixtures

Energy Technology Data Exchange (ETDEWEB)

Hoffmann, Ingo, E-mail: ingo.hoffmann@tu-berlin.de [Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 124, Sekr. TC 7, D-10623 Berlin (Germany); Institut Max von Laue-Paul Langevin (ILL), F-38042 Grenoble Cedex 9 (France); Farago, Bela; Schweins, Ralf; Falus, Peter; Sharp, Melissa [Institut Max von Laue-Paul Langevin (ILL), F-38042 Grenoble Cedex 9 (France); Prévost, Sylvain [Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 124, Sekr. TC 7, D-10623 Berlin (Germany); Helmholtz-Zentrum Berlin, D-14109 Berlin (Germany); Gradzielski, Michael, E-mail: michael.gradzielski@tu-berlin.de [Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 124, Sekr. TC 7, D-10623 Berlin (Germany)

2015-08-21

Oppositely charged polyelectrolyte (PE) surfactant mixtures allow the control of rheological parameters of a solution even at fairly low concentrations. For example, addition of 0.3 wt. % of anionic surfactant to a 1 wt. % solution of the polycation JR 400 increases the viscosity by 4 orders of magnitude. Recently, we could show that this increase is related to the formation of mixed, rod-like PE/surfactant aggregates which interconnect several polyelectrolyte chains [Hoffmann et al., Europhys. Lett. 104, 28001 (2013)]. In this paper, we refine our structural model of the aggregates to obtain a more consistent picture of their internal structure for different anionic surfactants. Combining small angle neutron scattering (SANS) and neutron spin-echo (NSE) allows us to determine the size of the aggregates. By comparing different contrasts, the internal structure of the aggregates can be elucidated and it is seen that the PE in the aggregates retains a relatively high freedom of movement. We proceeded to investigate the influence of the surfactant concentration and the surfactant type on structure and dynamics of the mixed aggregates. It is seen that the structural parameters of the aggregates depend very little on the surfactant concentration and headgroup. However, it is crucial to incorporate a sufficient amount of PE in the aggregates to increase the viscosity of the aggregates. By comparing viscous samples at 1 wt. % PE concentration with samples at a PE concentration of 0.3 wt. %, where no significant increase in viscosity is observed, we find that similar aggregates are formed already at this lower PE concentrations. However, the amount of PE incorporated in them is insufficient to interconnect several PE chains and therefore, they do not increase viscosity. So, our detailed investigation combining contrast variation SANS and NSE does not only allow to explain the viscosity behavior but also to deduced detailed information regarding the structures and

BEHAVIOR OF SURFACTANT MIXTURE AT SOLID/LIQUID AND OIL/LIQUID INTERFACE IN CHEMICAL FLOODING SYSTEMS

Energy Technology Data Exchange (ETDEWEB)

Prof. P. Somasundaran

2002-03-01

The aim of the project is to develop and evaluate efficient novel surfactant mixtures for enhanced oil recovery. Preliminary ultra-filtration tests suggest that two kinds of micelles may exist in binary surfactant mixtures at different concentrations. Due to the important role played in interfacial processes by micelles as determined by their structures, focus of the current work is on the delineation of the relationship between such aggregate structures and chemical compositions of the surfactants. A novel analytical centrifuge application is explored to generate information on structures of different surfactants aggregates. In this report, optical systems, typical output of the analytical ultracentrifuge results and four basic experiments are discussed. Initial sedimentation velocity investigations were conducted using nonyl phenol ethoxylated decyl ether (NP-10) to choose the best analytical protocol, calculate the partial specific volume and obtain information on sedimentation coefficient, aggregation mass of micelles. The partial specific volume was calculated to be 0.920. Four softwares: Optima{trademark} XL-A/XL-I data analysis software, DCDT+, Svedberg and SEDFIT, were compared for the analysis of sedimentation velocity experimental data. The sedimentation coefficient and aggregation number of NP-10 micelles obtained using the first three softwares at 25 C are 209, 127, and 111, respectively. The last one is closest to the result from Light Scattering. The reason for the differences in numbers obtained using the three softwares is discussed. Based on these tests, Svedberg and SEDFIT analysis are chosen for further studies. This approach using the analytical ultracentrifugation offers an unprecedented opportunity now to obtain important information on mixed micelles and their role in interfacial processes.

Some Properties of Emulsified Asphalt Paving Mixture at Iraqi Environmental Conditions

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Shakir.A.Al-Mishhadani* Hasan.H.Al-Baid

2014-04-01

Full Text Available Cold emulsified asphalt mixture is generally a mix made of emulsified asphalt withaggregate. Emulsified asphalt is manufactured from base asphalt, emulsifier agent and waterwith approximate percentage of 40% to 75% asphalt, 0.1% to 2.5% emulsifier and 25% to60% water plus some minor components. This study aims to use the cold emulsified asphaltmixtures for road construction and maintenance in Iraq as an alternative to the hot asphaltmixtures, due to its economical, practical and environmental advantages. This studyfocusedto test and evaluates the emulsified asphalt material properties to be used as paving mixture.The tested properties of emulsified asphalt mixture were bulk density, air voids, dry Marshallstability, wet Marshall stability, retained Marshall stability, flow tests and compared with thecommon used specification.The results indicate that the emulsified asphalt type cationic slowsetting low viscosity (CSS-1 is very suitable with quartz type of aggregate from Al-Nibaayquarry. From many trial mixes it is found that the best percentages of initial residual bitumencontent to produced adequateresults for coating test ,mixing ,compaction ,curing and Marshallstability were ranged from (2.5%, 3%,3.5%,4% and 4.5%, andthe optimum percentage is(3.5%.Finally it can be conducted that the emulsified asphalt mixture is a suitable alternativemixture to the hot asphalt mixture for road construction and maintenance in Iraq.  

Some Properties of Emulsified Asphalt Paving Mixture at Iraqi Environmental Conditions

Directory of Open Access Journals (Sweden)

Shakir.A.Al-Mishhadani

2014-02-01

Full Text Available Cold emulsified asphalt mixture is generally a mix made of emulsified asphalt withaggregate. Emulsified asphalt is manufactured from base asphalt, emulsifier agent and waterwith approximate percentage of 40% to 75% asphalt, 0.1% to 2.5% emulsifier and 25% to60% water plus some minor components. This study aims to use the cold emulsified asphaltmixtures for road construction and maintenance in Iraq as an alternative to the hot asphaltmixtures, due to its economical, practical and environmental advantages. This studyfocusedto test and evaluates the emulsified asphalt material properties to be used as paving mixture.The tested properties of emulsified asphalt mixture were bulk density, air voids, dry Marshallstability, wet Marshall stability, retained Marshall stability, flow tests and compared with thecommon used specification.The results indicate that the emulsified asphalt type cationic slowsetting low viscosity (CSS-1 is very suitable with quartz type of aggregate from Al-Nibaayquarry. From many trial mixes it is found that the best percentages of initial residual bitumencontent to produced adequateresults for coating test ,mixing ,compaction ,curing and Marshallstability were ranged from (2.5%, 3%,3.5%,4% and 4.5%, andthe optimum percentage is(3.5%.Finally it can be conducted that the emulsified asphalt mixture is a suitable alternativemixture to the hot asphalt mixture for road construction and maintenance in Iraq.

Protein aggregation in aqueous casein solution

International Nuclear Information System (INIS)

Yousri, R.M.

1980-01-01

From the vast amount of research efforts dealing with various aspects of radiation effects on foods and food components (11, 18, 5, 12, 19, 8, 9, 6, 13, 15, 17, 20), it is apparent up to now that much remains to be studied in depth, much may have to be added or corrected about radiation-induced physico-chemical changes in foods. A great many reactions that take place when foodstuffs are subjected to ionizing radiation are still not fully understood. The better understanding of some of the radiation-induced changes in pure proteins as such or in mixture with other food constituents could yield much data which could be meaningfully extrapolated to intact foods and consequently could help to improve the assessment of the wholesomeness of irradiated foods. It was the purpose of our investigations to elucidate some of the changes in the chemical structure of a pure protein (casein), irradiated as such or which added carbohydrate and/or lipid. The effect of subsequent storage of the irradiated solutions has been also examined. The formation of protein aggregates was studied by gel filtration technique. The application of thin-layer gel filtration, its speed and adaptability to very small samples facilitated the measurements of the extent of aggregation which occurred in protein molecules after irradiation. (orig.) [de

Adsorption of mixtures of poly(amidoamine) dendrimers and sodium dodecyl sulfate at the air-water interface.

Science.gov (United States)

Arteta, Marianna Yanez; Campbell, Richard A; Nylander, Tommy

2014-05-27

We relate the adsorption from mixtures of well-defined poly(amidoamine) (PAMAM) dendrimers of generations 4 and 8 with sodium dodecyl sulfate (SDS) at the air-water interface to the bulk solution properties. The anionic surfactant shows strong attractive interactions with the cationic dendrimers at pH 7, and electrophoretic mobility measurements indicate that the association is primarily driven by electrostatic interactions. Optical density measurements highlight the lack of colloidal stability of the formed bulk aggregates at compositions close to charge neutrality, the time scale of which is dependent on the dendrimer generation. Adsorption at the air-water interface was followed from samples immediately after mixing using a combination of surface tension, neutron reflectometry, and ellipsometry measurements. In the phase separation region for dendrimers of generation 4, we observed high surface tension corresponding to a depleted surfactant solution but only when the aggregates carried an excess of surfactant. Interestingly, these depleted adsorption layers contained spontaneously adsorbed macroscopic aggregates, and these embedded particles do not rearrange to spread monomeric material at the interface. These findings are discussed in relation to the interfacial properties of mixtures involving dendrimers of generation 8 as well as polydisperse linear and hyperbranched polyelectrolytes where there is polyelectrolyte bound to a surfactant monolayer. The results presented here demonstrate the capability of dendrimers to sequester anionic surfactants in a controllable manner, with potential applications as demulsification and antifoaming agents.

Aggregation and metal-complexation behaviour of THPP porphyrin in ethanol/water solutions as function of pH

Science.gov (United States)

Zannotti, Marco; Giovannetti, Rita; Minofar, Babak; Řeha, David; Plačková, Lydie; D'Amato, Chiara A.; Rommozzi, Elena; Dudko, Hanna V.; Kari, Nuerguli; Minicucci, Marco

2018-03-01

The effect of pH change on 5,10,15,20-Tetrakis(4-hydroxyphenyl)-21H,23H-porphine (THPP) with its aggregation as function of water-ethanol mixture was studied with UV-vis, fluorescence, Raman and computational analysis. In neutral pH, THPP was present as free-base and, increasing the water amount, aggregation occurred with the formation of H- and J-aggregates. The aggregation constant and the concentration of dimers were calculated, other information about the dimer aggregation were evaluated by computational study. In acidic pH, by the insertions of two hydrogens in the porphyrin rings, the porphyrin changed its geometry with a ring deformation confirmed by red-shifted spectrum and quenching in fluorescence; at this low pH, increasing the water amount, the acidic form (THPPH2)2 + resulted more stable due to a polar environment with stronger interaction by hydrogen bonding. In basic pH, reached by NH4OH, THPP porphyrin was able to react with alkali metals in order to form sitting-atop complex (M2THPP) confirmed by the typical absorption spectrum of metallo-porphyrin, Raman spectroscopy and by computational analysis.

Evaluation of Asphalt Mixture Low-Temperature Performance in Bending Beam Creep Test.

Science.gov (United States)

Pszczola, Marek; Jaczewski, Mariusz; Rys, Dawid; Jaskula, Piotr; Szydlowski, Cezary

2018-01-10

Low-temperature cracking is one of the most common road pavement distress types in Poland. While bitumen performance can be evaluated in detail using bending beam rheometer (BBR) or dynamic shear rheometer (DSR) tests, none of the normalized test methods gives a comprehensive representation of low-temperature performance of the asphalt mixtures. This article presents the Bending Beam Creep test performed at temperatures from -20 °C to +10 °C in order to evaluate the low-temperature performance of asphalt mixtures. Both validation of the method and its utilization for the assessment of eight types of wearing courses commonly used in Poland were described. The performed test indicated that the source of bitumen and its production process (and not necessarily only bitumen penetration) had a significant impact on the low-temperature performance of the asphalt mixtures, comparable to the impact of binder modification (neat, polymer-modified, highly modified) and the aggregate skeleton used in the mixture (Stone Mastic Asphalt (SMA) vs. Asphalt Concrete (AC)). Obtained Bending Beam Creep test results were compared with the BBR bitumen test. Regression analysis confirmed that performing solely bitumen tests is insufficient for comprehensive low-temperature performance analysis.

Sample size choices for XRCT scanning of highly unsaturated soil mixtures

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Smith Jonathan C.

2016-01-01

Full Text Available Highly unsaturated soil mixtures (clay, sand and gravel are used as building materials in many parts of the world, and there is increasing interest in understanding their mechanical and hydraulic behaviour. In the laboratory, x-ray computed tomography (XRCT is becoming more widely used to investigate the microstructures of soils, however a crucial issue for such investigations is the choice of sample size, especially concerning the scanning of soil mixtures where there will be a range of particle and void sizes. In this paper we present a discussion (centred around a new set of XRCT scans on sample sizing for scanning of samples comprising soil mixtures, where a balance has to be made between realistic representation of the soil components and the desire for high resolution scanning, We also comment on the appropriateness of differing sample sizes in comparison to sample sizes used for other geotechnical testing. Void size distributions for the samples are presented and from these some hypotheses are made as to the roles of inter- and intra-aggregate voids in the mechanical behaviour of highly unsaturated soils.

Self-assembly in mixtures of sodium alkyl sulfates and alkyltrimethylammonium bromides : Aggregation behavior and catalytic properties

NARCIS (Netherlands)

Talhout, Reinskje; Engberts, BFN

1997-01-01

Two aqueous mixtures of cationic and anionic surfactants have been studied by means of conductometry, transmission electron microscopy, and microcalorimetry. Their catalytic effects on the decarboxylation of the kinetic probe 6-nitrobenzisoxazole-3-carboxylate (6-NBIC) were also examined in some

Marine Synechococcus Aggregation

Science.gov (United States)

Neuer, S.; Deng, W.; Cruz, B. N.; Monks, L.

2016-02-01

Cyanobacteria are considered to play an important role in the oceanic biological carbon pump, especially in oligotrophic regions. But as single cells are too small to sink, their carbon export has to be mediated by aggregate formation and possible consumption by zooplankton producing sinking fecal pellets. Here we report results on the aggregation of the ubiquitous marine pico-cyanobacterium Synechococcus as a model organism. We first investigated the mechanism behind such aggregation by studying the potential role of transparent exopolymeric particles (TEP) and the effects of nutrient (nitrogen or phosphorus) limitation on the TEP production and aggregate formation of these pico-cyanobacteria. We further studied the aggregation and subsequent settling in roller tanks and investigated the effects of the clays kaolinite and bentonite in a series of concentrations. Our results show that despite of the lowered growth rates, Synechococcus in nutrient limited cultures had larger cell-normalized TEP production, formed a greater volume of aggregates, and resulted in higher settling velocities compared to results from replete cultures. In addition, we found that despite their small size and lack of natural ballasting minerals, Synechococcus cells could still form aggregates and sink at measureable velocities in seawater. Clay minerals increased the number and reduced the size of aggregates, and their ballasting effects increased the sinking velocity and carbon export potential of aggregates. In comparison with the Synechococcus, we will also present results of the aggregation of the pico-cyanobacterium Prochlorococcus in roller tanks. These results contribute to our understanding in the physiology of marine Synechococcus as well as their role in the ecology and biogeochemistry in oligotrophic oceans.

INTERACTION’S EFFECT OF ORGANIC MATERIAL AND AGGREGATION ON EXTRACTION EFFICIENCY OF TPHS FROM PETROLEUM CONTAMINATED SOILS WITH MAE

Directory of Open Access Journals (Sweden)

H. Ganjidoust and Gh. Naghizadeh

2005-10-01

Full Text Available Microwave-Assisted Extraction (MAE is a type of low-temperature thermal desorption process that its numerous advantages have caused a wide spread use of it. Microwave heating is a potentially attractive technique as it provides volumetric heating process to improve heating efficiencies as compared with conventional techniques. The ability to rapidly heat the sample solvent mixture is inherent to MAE and the main advantage of this technique. Presently MAE has been shown to be one of the best technologies for removing environmental pollutants specially PAHs, phenols and PCBs from soils and sediments. Five different mixtures and types of aggregation (Sand, Top soil, Kaolinite besides three concentrations of crude oil as a contaminant (1000, 5000 and 10000 mg/L were considered. The results indicated that regardless of aggregation, the presence of humus component in soil reduces the efficiency. Minimum and maximum efficiencies were for sandy soil (containing organic components and kaolinite (without any organic content, respectively. According to the results of this research when some amount of humus and organic materials are available in the matrix, it causes the extraction efficiency to perform as a function of just humus materials but not aggregation. Increasing the concentration of crude oil reduced the efficiency with a sharp steep for higher concentration (5000-10000 mg/L and less steeper for lower concentration (1000-5000 mg/L. The concentration of the contaminant, works just as an independent function with extraction time and aggregation factors. The extraction period of 10 min. can be suggested as an optimum extraction time in FMAE for PAHs contaminated soils.

Discrepancies over the onset of surfactant monomer aggregation interpreted by fluorescence, conductivity and surface tension methods

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Maria de Fátima Carvalho Costa

1998-06-01

Full Text Available Molecular probe techniques have made important contributions to the determination of microstructure of surfactant assemblies such as size, stability, micropolarity and conformation. Conductivity and surface tension were used to determine the critical aggregation concentration (cac of polymer-surfactant complexes and the critical micellar concentration (cmc of aqueous micellar aggregates. The results are compared with those of fluorescent techniques. Several surfactant systems were examined, 1-butanol-sodium dodecylsulfate (SDS mixtures, solutions containing poly(ethylene oxide-SDS, poly(vinylpyrrolidone-SDS and poly(acrylic acid-alkyltrimethylammonium bromide complexes. We found differences between the cac and cmc values obtained by conductivity or surface tension and those obtained by techniques which use hydrophobic probe.

Laboratory evaluation of resistance to moisture damage in asphalt mixtures

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Ahmed Ebrahim Abu El-Maaty Behiry

2013-09-01

Full Text Available Moisture damage in asphalt mixtures refers to loss in strength and durability due to the presence of water. Egypt road network is showing severe deterioration such as raveling and stripping because the bond between aggregates and asphalt film is broken due to water intrusion. To minimize moisture damage, asphalt mixes are investigated to evaluate the effect of air voids, degree of saturation, media of attack and the conditioning period. Two medias of attack are considered and two anti-stripping additives are used (hydrated lime and Portland cement. The retained Marshall stability and tensile strength ratio are calculated to determine the resistance to moisture damage. The results showed that both lime and cement could increase Marshall stability, resilient modulus, tensile strength and resistance to moisture damage of mixtures especially at higher condition periods. Use of hydrated lime had better results than Portland cement.

An Image-Based Finite Element Approach for Simulating Viscoelastic Response of Asphalt Mixture

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Wenke Huang

2016-01-01

Full Text Available This paper presents an image-based micromechanical modeling approach to predict the viscoelastic behavior of asphalt mixture. An improved image analysis technique based on the OTSU thresholding operation was employed to reduce the beam hardening effect in X-ray CT images. We developed a voxel-based 3D digital reconstruction model of asphalt mixture with the CT images after being processed. In this 3D model, the aggregate phase and air void were considered as elastic materials while the asphalt mastic phase was considered as linear viscoelastic material. The viscoelastic constitutive model of asphalt mastic was implemented in a finite element code using the ABAQUS user material subroutine (UMAT. An experimental procedure for determining the parameters of the viscoelastic constitutive model at a given temperature was proposed. To examine the capability of the model and the accuracy of the parameter, comparisons between the numerical predictions and the observed laboratory results of bending and compression tests were conducted. Finally, the verified digital sample of asphalt mixture was used to predict the asphalt mixture viscoelastic behavior under dynamic loading and creep-recovery loading. Simulation results showed that the presented image-based digital sample may be appropriate for predicting the mechanical behavior of asphalt mixture when all the mechanical properties for different phases became available.

Investigation of Low-Temperature Behavior of Stone Mastic Asphalt Mixtures Modified with Paraffin and Crumb Rubber

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Baha Vural KÖK

2017-08-01

Full Text Available In hot mix asphalts at low temperatures, cracks occur due to thermal tension and these cracks cause water to leak inside the pavement and the pavement gets deformed sooner than expected. In order to improve the properties of bituminous mixtures, mostly polymer type additives are used in the modification of the bitumen. These types of improvements usually have positive effects on the high-temperature behavior of the mixture. In this study, semi-circular bending test, which is the most commonly used method in the literature to investigate the low-temperature behavior of bituminous mixtures, was performed. In the study, the resistance of stone mastic asphalt mixtures, which were prepared with modified bitumen with a constant 3% of paraffin and various amounts of crumb rubber, to crack formation and its movement was identified. As a result, it was concluded that the effects of additives on crack formation and its movement is varied and the relation between the fractured aggregate surface areas and the fracture toughness of the mixture can be determined by the image processing method.

A review of asphalt and asphalt mixture aging

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Wilmar Darío Fernández-Gómez

2013-01-01

Full Text Available This paper presents an extensive review of the pertinent literature regarding asphalt and asphalt mixture Aging. Aging affects flexible pavement performance and is produced by intrinsic and extrinsic variables as well as exposure time. Intrinsic variables include asphalt and aggregate properties, a mixture’s asphalt content, binder film thickness and air void content; extrinsic variables are associated with production (short-term aging and exposure to environmental field conditions (long-term aging. Taken together, both variables demonstrate that aging results from three distinct mechanisms: volatilisation, oxidation and steric hardening. Temperature, pressure and photo degradation treatments are used to simulate aging in the laboratory and empirical and semi-empirical models are created to represent and study aging. Aging increases asphalt complex modulus and decreases the phase angle. Mixtures become stiffer while fatigue life becomes reduced. Carbonyl and sulfoxide group formation in asphalt are often studied as such chemical changes show oxidation in aged asphalts. The prevailing models used to predict asphalt aging are discussed, though more comprehensive research into asphalt aging is still needed.

Experimental Study of Self-Compacting Mortar Incorporating Recycled Glass Aggregate

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Awetehagn Tuaum

2018-01-01

Full Text Available This experimental research is focused on the development of self-compacting mortar incorporating recycled glass aggregate (SCM-RGA as partial substitution of fine aggregate (wt 0%, 10%, 20%, 30%, 40% and 50%. The fresh and hardened mechanical properties as well as durability of SCM-RGA mixes were investigated. Limestone powder (LP was used as filler that constitutes 20% of the powder volume to reduce the amount of cement. The SCM-RGA mixtures were designed based on Japanese mix design method. The experimental test results showed that the slump flow of SCM-RGA mixes decreased and V-funnel flow time increased when the content of recycled glass aggregate (RGA increased. The bulk density, compressive strength, flexural strength, water absorption and sorptivity of SCM-RGA mixes were decreased as RGA content increased. Moreover, the accelerated mortar bar test results showed that the expansion due to alkali–silica reaction (ASR of SCM-RGA mixes increased as the content of RGA increased although the expansion of all mixes were within acceptable limit and potentially innocuous. In conclusion, up to 30% of RGA can be successfully integrated in SCM mixes that offers comparable strength performance, sorptivity enhancement and without long term detrimental ASR effect, and thus, contributes towards sustainable solid waste management, conservation of natural resources and environmental protection.

Defining and systematic analyses of aggregation indices to evaluate degree of calcium oxalate crystal aggregation

Science.gov (United States)

Chaiyarit, Sakdithep; Thongboonkerd, Visith

2017-12-01

Crystal aggregation is one of the most crucial steps in kidney stone pathogenesis. However, previous studies of crystal aggregation were rarely done and quantitative analysis of aggregation degree was handicapped by a lack of the standard measurement. We thus performed an in vitro assay to generate aggregation of calcium oxalate monohydrate (COM) crystals with various concentrations (25-800 µg/ml) in saturated aggregation buffer. The crystal aggregates were analyzed by microscopic examination, UV-visible spectrophotometry, and GraphPad Prism6 software to define a total of 12 aggregation indices (including number of aggregates, aggregated mass index, optical density, aggregation coefficient, span, number of aggregates at plateau time-point, aggregated area index, aggregated diameter index, aggregated symmetry index, time constant, half-life, and rate constant). The data showed linear correlation between crystal concentration and almost all of these indices, except only for rate constant. Among these, number of aggregates provided the greatest regression coefficient (r=0.997; pr=0.993; pr=‑0.993; pr=0.991; p<0.001 for both). These five indices are thus recommended as the most appropriate indices for quantitative analysis of COM crystal aggregation in vitro.

Sustainable aggregates production : green applications for aggregate by-products.

Science.gov (United States)

2015-06-01

Increased emphasis in the construction industry on sustainability and recycling requires production of : aggregate gradations with lower dust (cleaner aggregates) and smaller maximum sizeshence, increased : amount of quarry by-products (QBs). QBs ...

Effect of Lime Addition Methods on Performance Related Properties of Asphalt Concrete Mixture

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Amjad Hamd Khalil Albayati

2016-09-01

Full Text Available In the recent years, some of the newly constructed asphalt concrete pavements in Baghdad as well as other cities across Iraq showed premature failures with consequential negative impact on both roadway safety and economy. Frequently, load associated mode of failure (rutting and fatigue as well as, occasionally, moisture damage in some poorly drained sections are the main failure types found in those newly constructed road. In this research, hydrated lime was introduced into asphalt concrete mixtures of wearing course in two methods. The first one was the addition of dry lime on dry aggregate and the second one was the addition of dry lime on saturated surface dry aggregate moisturized by 2.0 to 3.0 percent of water. For each type of addition, five different percentages of lime as a partial replacement of ordinary limestone mineral filler were used; these were; 1.0, 1.5, 2.0, 2.5, and 3 percent by weight of aggregate besides a control mixture that did not contain lime. Marshall Mix design method was used and the performance properties of moisture damage, resilient modulus, permanent deformation and fatigue characteristics were evaluated using indirect tensile strength, uniaxial repeated loading and repeated flexural beam tests. Also, VESYS5W software was implemented to evaluate the pavements performance in terms of rut depth and fatigue area for a typical pavement structure. The main conclusion withdrawn from this research revealed that the use of 2.5 percent hydrated lime in dry addition method and wet addition method showed an improved fatigue and permanent deformation characteristics, lower moisture susceptibility and high resilient modulus.

Influence of Aggregate Wettability with Different Lithology Aggregates on Concrete Drying Shrinkage

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Yuanchen Guo

2015-01-01

Full Text Available The correlation of the wettability of different lithology aggregates and the drying shrinkage of concrete materials is studied, and some influential factors such as wettability and wetting angle are analyzed. A mercury porosimeter is used to measure the porosities of different lithology aggregates accurately, and the pore size ranges that significantly affect the drying shrinkage of different lithology aggregate concretes are confirmed. The pore distribution curve of the different coarse aggregates is also measured through a statistical method, and the contact angle of different coarse aggregates and concrete is calculated according to the linear fitting relationship. Research shows that concrete strength is determined by aggregate strength. Aggregate wettability is not directly correlated with concrete strength, but wettability significantly affects concrete drying shrinkage. In all types’ pores, the greatest impacts on wettability are capillary pores and gel pores, especially for the pores of the size locating 2.5–50 nm and 50–100 nm two ranges.

RELATIONSHIPS BETWEEN SOIL MICROBIAL BIOMASS, AGGREGATE STABILITY AND AGGREGATE ASSOCIATED-C: A MECHANISTIC APPROACH

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Patrizia Guidi

2014-01-01

Full Text Available For the identification of C pools involved in soil aggregation, a physically-based aggregate fractionation was proposed, and  additional pretreatments were used in the measurement of the 1-2 mm aggregate stability in order to elucidate the relevance of the role of soil microorganisms with respect to the different aggregate breakdown mechanisms. The study was carried out on three clay loam Regosols, developed on calcareous shales, known history of organic cultivation.Our results showed that the soil C pool controlling the process of stabilisation of aggregates was related to the microbial community. We identified the resistance to fast wetting as the major mechanism of aggregate stability driven by microorganims. The plausible hypothesis is that organic farming promotes fungi growth, improving water repellency of soil aggregates by fungal hydrophobic substances. By contrast, we failed in the identification of C pools controlling the formation of aggregates, probably because of the disturbance of mechanical tillage which contributes to the breakdown of soil aggregates.The physically-based aggregate fractionation proposed in this study resulted useful in the  mechanistically understanding of the role of microorganisms in soil aggregation and it might be suggested for studying the impact of management on C pools, aggregates properties and their relationships in agricultural soils.

Effect of Coating Palm Oil Clinker Aggregate on the Engineering Properties of Normal Grade Concrete

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Fuad Abutaha

2017-10-01

Full Text Available Palm oil clinker (POC is a waste material generated in large quantities from the palm oil industry. POC, when crushed, possesses the potential to serve as an aggregate for concrete production. Experimental investigation on the engineering properties of concrete incorporating POC as aggregate and filler material was carried out in this study. POC was partially and fully used to replace natural coarse aggregate. The volumetric replacements used were 0%, 20%, 40%, 60%, 80%, and 100%. POC, being highly porous, negatively affected the fresh and hardened concrete properties. Therefore, the particle-packing (PP method was adopted to measure the surface and inner voids of POC coarse aggregate in the mixtures at different substitution levels. In order to enhance the engineering properties of the POC concrete, palm oil clinker powder (POCP was used as a filler material to fill up and coat the surface voids of POC coarse, while the rest of the mix constituents were left as the same. Fresh and hardened properties of the POC concrete with and without coating were determined, and the results were compared with the control concrete. The results revealed that coating the surface voids of POC coarse with POCP significantly improved the engineering properties as well as the durability performance of the POC concrete. Furthermore, using POC as an aggregate and filler material may reduce the continuous exploitation of aggregates from primary sources. Also, this approach offers an environmental friendly solution to the ongoing waste problems associated with palm oil waste material.

Achieving Mixtures of Ultra-High Performance Concrete

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Mircea POPA

2013-07-01

Full Text Available Ultra-High Performance Concrete (UHPC is a relatively new concrete. According to [11] UHPC is that concrete which features compressive strength over C100/115 class. Up to this point standards for this type of concrete were not adopted, although its characteristic strength exceeds those specified in [33]. Its main property is high compressive strength. This provides the possibility of reducing the section of elements (beams or columns made of this type of concrete, while the load capacity remains high. The study consists in blending mixtures of UHPC made of varying proportions of materials. The authors have obtained strengths of up to 160 MPa. The materials used are: Portland cement, silica fume, quartz powder, steel fibers, superplasticiser, sand and crushed aggregate for concrete - andesite.

Minimizing the Moisture Damage and Drain down of Iraqi SMA Mixtures Using Waste Additives

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Ali Al-Hadidy

2013-04-01

Full Text Available This research deals with the viability of using polyester fiber (PF, crumb rubber tire (CRT and cellulose fiber (CF as stabilizing waste additives in producing Iraqi SMA mixtures that sustain drain down phenomenon and moisture damage sensitivity. Different ratios of these additives (0.1, 0.2, and 0.3% by weight of aggregate and filler were mixed with 40/50 paving asphalt by means of dry process. Unmodified and modified SMA mixtures were subjected to drain down, Marshall, static indirect tensile strength, tensile stiffness modulus, static compressive strength, tensile strength ratio and index of retained strength tests. A set of regression equations between these tests were established. In addition, an optimization table based on these tests, which can be used to select the type or amount of additive for any field applications has been determined and reported. The results indicated that the inclusion of these additives in SMA mixtures can satisfy the performance requirement of high temperature and much rain zone.

Patterns of [PSI+] aggregation allow insights into cellular organization of yeast prion aggregates

Science.gov (United States)

Tyedmers, Jens

2012-01-01

The yeast prion phenomenon is very widespread and mounting evidence suggests that it has an impact on cellular regulatory mechanisms related to phenotypic responses to changing environments. Studying the aggregation patterns of prion amyloids during different stages of the prion life cycle is a first key step to understand major principles of how and where cells generate, organize and turn-over prion aggregates. The induction of the [PSI+] state involves the actin cytoskeleton and quality control compartments such as the Insoluble Protein Deposit (IPOD). An initially unstable transitional induction state can be visualized by overexpression of the prion determinant and displays characteristic large ring- and ribbon-shaped aggregates consisting of poorly fragmented bundles of very long prion fibrils. In the mature prion state, the aggregation pattern is characterized by highly fragmented, shorter prion fibrils that form aggregates, which can be visualized through tagging with fluorescent proteins. The number of aggregates formed varies, ranging from a single large aggregate at the IPOD to multiple smaller ones, depending on several parameters discussed. Aggregate units below the resolution of light microscopy that are detectable by fluorescence correlation spectroscopy are in equilibrium with larger aggregates in this stage and can mediate faithful inheritance of the prion state. Loss of the prion state is often characterized by reduced fragmentation of prion fibrils and fewer, larger aggregates. PMID:22449721

Effect of aggregate graining compositions on skid resistance of Exposed Aggregate Concrete pavement

Science.gov (United States)

Wasilewska, Marta; Gardziejczyk, Wladysław; Gierasimiuk, Pawel

2018-05-01

The paper presents the evaluation of skid resistance of EAC (Exposed Aggregate Concrete) pavements which differ in aggregate graining compositions. The tests were carried out on concrete mixes with a maximum aggregate size of 8 mm. Three types of coarse aggregates were selected depending on their resistance to polishing which was determined on the basis of the PSV (Polished Stone Value). Basalt (PSV 48), gabbro (PSV 50) and trachybasalt (PSV 52) aggregates were chosen. For each type of aggregate three graining compositions were designed, which differed in the content of coarse aggregate > 4mm. Their content for each series was as follows: A - 38%, B - 50% and C - 68%. Evaluation of the skid resistance has been performed using the FAP (Friction After Polishing) test equipment also known as the Wehner/Schulze machine. Laboratory method enables to compare the skid resistance of different types of wearing course under specified conditions simulating polishing processes. In addition, macrotexture measurements were made on the surface of each specimen using the Elatexure laser profile. Analysis of variance showed that at significance level α = 0.05, aggregate graining compositions as well as the PSV have a significant influence on the obtained values of the friction coefficient μm of the tested EAC pavements. The highest values of the μm have been obtained for EAC with the lowest amount of coarse aggregates (compositions A). In these cases the resistance to polishing of the aggregate does not significantly affect the friction coefficients. This is related to the large areas of cement mortar between the exposed coarse grains. Based on the analysis of microscope images, it was observed that the coarse aggregates were not sufficiently exposed. It has been proved that PSV significantly affected the coefficient of friction in the case of compositions B and C. This is caused by large areas of exposed coarse aggregate. The best parameters were achieved for the EAC pavements

Concrete produced with recycled aggregates

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J. J. L. Tenório

Full Text Available This paper presents the analysis of the mechanical and durable properties of recycled aggregate concrete (RAC for using in concrete. The porosity of recycled coarse aggregates is known to influence the fresh and hardened concrete properties and these properties are related to the specific mass of the recycled coarse aggregates, which directly influences the mechanical properties of the concrete. The recycled aggregates were obtained from construction and demolition wastes (CDW, which were divided into recycled sand (fine and coarse aggregates. Besides this, a recycled coarse aggregate of a specific mass with a greater density was obtained by mixing the recycled aggregates of the CDW with the recycled aggregates of concrete wastes (CW. The concrete was produced in laboratory by combining three water-cement ratios, the ratios were used in agreement with NBR 6118 for structural concretes, with each recycled coarse aggregates and recycled sand or river sand, and the reference concrete was produced with natural aggregates. It was observed that recycled aggregates can be used in concrete with properties for structural concrete. In general, the use of recycled coarse aggregate in combination with recycled sand did not provide good results; but when the less porous was used, or the recycled coarse aggregate of a specific mass with a greater density, the properties of the concrete showed better results. Some RAC reached bigger strengths than the reference concrete.

Graph Aggregation

NARCIS (Netherlands)

Endriss, U.; Grandi, U.

Graph aggregation is the process of computing a single output graph that constitutes a good compromise between several input graphs, each provided by a different source. One needs to perform graph aggregation in a wide variety of situations, e.g., when applying a voting rule (graphs as preference

Processed bottom ash for replacing fine aggregate in making high-volume fly ash concrete

OpenAIRE

Antoni; Sulistio Aldi Vincent; Wahjudi Samuel; Hardjito Djwantoro; Hardjito Djwantoro

2017-01-01

Bottom ash is a coal plant by-product that is abundant and underutilized. There is the potential use of bottom ash as a fine aggregate replacement in concrete mixtures; however, the problems of water absorption and uniformity of quality of the material need to be overcome first. In this study, bottom ash was treated by sieve separation and pounding to smaller particle size for use as a sand substitute. The physical and chemical characteristics of bottom ash were tested after treatment includi...

Stiffness modulus of Polyethylene Terephthalate modified asphalt mixture: A statistical analysis of the laboratory testing results

International Nuclear Information System (INIS)

Baghaee Moghaddam, Taher; Soltani, Mehrtash; Karim, Mohamed Rehan

2015-01-01

Highlights: • Effect of PET modification on stiffness property of asphalt mixture was examined. • Different temperatures and loading amounts were designated. • Statistical analysis was used to find interactions between selected variables. • A good agreement between experimental results and predicted values was obtained. • Optimal amount of PET was calculated to achieve the highest mixture performance. - Abstract: Stiffness of asphalt mixture is a fundamental design parameter of flexible pavement. According to literature, stiffness value is very susceptible to environmental and loading conditions. In this paper, effects of applied stress and temperature on the stiffness modulus of unmodified and Polyethylene Terephthalate (PET) modified asphalt mixtures were evaluated using Response Surface Methodology (RSM). A quadratic model was successfully fitted to the experimental data. Based on the results achieved in this study, the temperature variation had the highest impact on the mixture’s stiffness. Besides, PET content and amount of stress showed to have almost the same effect on the stiffness of mixtures. The optimal amount of PET was found to be 0.41% by weight of aggregate particles to reach the highest stiffness value

Iterative Mixture Component Pruning Algorithm for Gaussian Mixture PHD Filter

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Xiaoxi Yan

2014-01-01

Full Text Available As far as the increasing number of mixture components in the Gaussian mixture PHD filter is concerned, an iterative mixture component pruning algorithm is proposed. The pruning algorithm is based on maximizing the posterior probability density of the mixture weights. The entropy distribution of the mixture weights is adopted as the prior distribution of mixture component parameters. The iterative update formulations of the mixture weights are derived by Lagrange multiplier and Lambert W function. Mixture components, whose weights become negative during iterative procedure, are pruned by setting corresponding mixture weights to zeros. In addition, multiple mixture components with similar parameters describing the same PHD peak can be merged into one mixture component in the algorithm. Simulation results show that the proposed iterative mixture component pruning algorithm is superior to the typical pruning algorithm based on thresholds.

p53 Aggregates penetrate cells and induce the co-aggregation of intracellular p53.

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Karolyn J Forget

Full Text Available Prion diseases are unique pathologies in which the infectious particles are prions, a protein aggregate. The prion protein has many particular features, such as spontaneous aggregation, conformation transmission to other native PrP proteins and transmission from an individual to another. Protein aggregation is now frequently associated to many human diseases, for example Alzheimer's disease, Parkinson's disease or type 2 diabetes. A few proteins associated to these conformational diseases are part of a new category of proteins, called prionoids: proteins that share some, but not all, of the characteristics associated with prions. The p53 protein, a transcription factor that plays a major role in cancer, has recently been suggested to be a possible prionoid. The protein has been shown to accumulate in multiple cancer cell types, and its aggregation has also been reproduced in vitro by many independent groups. These observations suggest a role for p53 aggregates in cancer development. This study aims to test the «prion-like» features of p53. Our results show in vitro aggregation of the full length and N-terminally truncated protein (p53C, and penetration of these aggregates into cells. According to our findings, the aggregates enter cells using macropinocytosis, a non-specific pathway of entry. Lastly, we also show that once internalized by the cell, p53C aggregates can co-aggregate with endogenous p53 protein. Together, these findings suggest prion-like characteristics for p53 protein, based on the fact that p53 can spontaneously aggregate, these aggregates can penetrate cells and co-aggregate with cellular p53.

New, rapid method to measure dissolved silver concentration in silver nanoparticle suspensions by aggregation combined with centrifugation

International Nuclear Information System (INIS)

Dong, Feng; Valsami-Jones, Eugenia; Kreft, Jan-Ulrich

2016-01-01

It is unclear whether the antimicrobial activities of silver nanoparticles (AgNPs) are exclusively mediated by the release of silver ions (Ag"+) or, instead, are due to combined nanoparticle and silver ion effects. Therefore, it is essential to quantify dissolved Ag in nanosilver suspensions for investigations of nanoparticle toxicity. We developed a method to measure dissolved Ag in Ag"+/AgNPs mixtures by combining aggregation of AgNPs with centrifugation. We also describe the reproducible synthesis of stable, uncoated AgNPs. Uncoated AgNPs were quickly aggregated by 2 mM Ca"2"+, forming large clusters that could be sedimented in a low-speed centrifuge. At 20,100g, the sedimentation time of AgNPs was markedly reduced to 30 min due to Ca"2"+-mediated aggregation, confirmed by the measurements of Ag content in supernatants with graphite furnace atomic absorption spectrometry. No AgNPs were detected in the supernatant by UV–Vis absorption spectra after centrifuging the aggregates. Our approach provides a convenient and inexpensive way to separate dissolved Ag from AgNPs, avoiding long ultracentrifugation times or Ag"+ adsorption to ultrafiltration membranes.

New, rapid method to measure dissolved silver concentration in silver nanoparticle suspensions by aggregation combined with centrifugation

Energy Technology Data Exchange (ETDEWEB)

Dong, Feng, E-mail: fengdongub@gmail.com [University of Birmingham, Institute of Microbiology and Infection, School of Biosciences (United Kingdom); Valsami-Jones, Eugenia [University of Birmingham, School of Geography, Earth and Environmental Sciences (United Kingdom); Kreft, Jan-Ulrich [University of Birmingham, Institute of Microbiology and Infection, School of Biosciences (United Kingdom)

2016-09-15

It is unclear whether the antimicrobial activities of silver nanoparticles (AgNPs) are exclusively mediated by the release of silver ions (Ag{sup +}) or, instead, are due to combined nanoparticle and silver ion effects. Therefore, it is essential to quantify dissolved Ag in nanosilver suspensions for investigations of nanoparticle toxicity. We developed a method to measure dissolved Ag in Ag{sup +}/AgNPs mixtures by combining aggregation of AgNPs with centrifugation. We also describe the reproducible synthesis of stable, uncoated AgNPs. Uncoated AgNPs were quickly aggregated by 2 mM Ca{sup 2+}, forming large clusters that could be sedimented in a low-speed centrifuge. At 20,100g, the sedimentation time of AgNPs was markedly reduced to 30 min due to Ca{sup 2+}-mediated aggregation, confirmed by the measurements of Ag content in supernatants with graphite furnace atomic absorption spectrometry. No AgNPs were detected in the supernatant by UV–Vis absorption spectra after centrifuging the aggregates. Our approach provides a convenient and inexpensive way to separate dissolved Ag from AgNPs, avoiding long ultracentrifugation times or Ag{sup +} adsorption to ultrafiltration membranes.

Inertial deposition of nanoparticle chain aggregates: Theory and comparison with impactor data for ultrafine atmospheric aerosols

International Nuclear Information System (INIS)

Barone, Teresa L.; Lall, Anshuman Amit; Zhu Yifang; Yu Rongchung; Friedlander, Sheldon K.

2006-01-01

mixture of diesel and internal combustion engine emissions. Aggregates collected at LAX were most likely present as a result of aircraft emissions. In both measurements, the aggregate aerodynamic diameters calculated from the primary particle diameter were fairly close to the stage cutoff diameter. The number of primary particles per aggregate varied one order of magnitude for particles depositing on the same stage. The average aggregate surface area per unit volume was 2.41 x 10 6 cm -1 and 2.59 x 10 6 cm -1 (50 nm d a,50 ) and 1.81 x 10 6 cm -1 and 1.68 x 10 6 cm -1 (75 nm d a,50 ) for near-freeway and LAX measurements, respectively. These preliminary measurements are consistent with values calculated from theory

Information Aggregation in Organizations

OpenAIRE

Schulte, Elisabeth

2006-01-01

This dissertation contributes to the analysis of information aggregation procedures within organizations. Facing uncertainty about the consequences of a collective decision, information has to be aggregated before making a choice. Two main questions are addressed. Firstly, how well is an organization suited for the aggregation of decision-relevant information? Secondly, how should an organization be designed in order to aggregate information efficiently? The main part deals with information a...

Recyclable Aggregates of Mesoporous Titania Synthesized by Thermal Treatment of Amorphous or Peptized Precursors

Directory of Open Access Journals (Sweden)

Maria Cristina Mascolo

2018-03-01

Full Text Available Recyclable aggregates of mesoporous titania with different anatase–rutile ratios have been prepared by thermal treatments of either amorphous or peptized precursors. These last two have been obtained by hydrolysis of either Ti(OC2H54 or of Ti(OC2H54 in mixture with 5 mol % Zr(OC3H74 at room temperature in the presence of NH4OH as a catalyzing agent. The anatase–rutile ratio, the recyclable aggregates of the nano-sized particles, the mesoporosity, the surface area and the crystallinity of the resulting crystallized products of titania can be controlled by the synthesis parameters including: concentration of ammonia catalyst, stirring time and concentration of the peptizing HNO3, drying method of peptized precursors, calcination temperature, and finally the ramp rate up to the titania crystallization temperature. A broad range of synthesis parameters control the crystal sizes of titania particles produced. This allows catalyst preparation with very different crystal size, surface area, anatase to rutile crystal ratio and various mesoporous structures. Drying by lyophilization of precursors reduce the aggregation of the primary particles giving micro-/macroporous structures.

A Novel Method to Quantify Soil Aggregate Stability by Measuring Aggregate Bond Energies

Science.gov (United States)

Efrat, Rachel; Rawlins, Barry G.; Quinton, John N.; Watts, Chris W.; Whitmore, Andy P.

2016-04-01

Soil aggregate stability is a key indicator of soil quality because it controls physical, biological and chemical functions important in cultivated soils. Micro-aggregates are responsible for the long term sequestration of carbon in soil, therefore determine soils role in the carbon cycle. It is thus vital that techniques to measure aggregate stability are accurate, consistent and reliable, in order to appropriately manage and monitor soil quality, and to develop our understanding and estimates of soil as a carbon store to appropriately incorporate in carbon cycle models. Practices used to assess the stability of aggregates vary in sample preparation, operational technique and unit of results. They use proxies and lack quantification. Conflicting results are therefore drawn between projects that do not provide methodological or resultant comparability. Typical modern stability tests suspend aggregates in water and monitor fragmentation upon exposure to an un-quantified amount of ultrasonic energy, utilising a laser granulometer to measure the change in mean weight diameter. In this project a novel approach has been developed based on that of Zhu et al., (2009), to accurately quantify the stability of aggregates by specifically measuring their bond energies. The bond energies are measured operating a combination of calorimetry and a high powered ultrasonic probe, with computable output function. Temperature change during sonication is monitored by an array of probes which enables calculation of the energy spent heating the system (Ph). Our novel technique suspends aggregates in heavy liquid lithium heteropolytungstate, as opposed to water, to avoid exposing aggregates to an immeasurable disruptive energy source, due to cavitation, collisions and clay swelling. Mean weight diameter is measured by a laser granulometer to monitor aggregate breakdown after successive periods of calculated ultrasonic energy input (Pi), until complete dispersion is achieved and bond

Strength and microstructure characteristics of the recycled rubber tire-sand mixtures as lightweight backfill.

Science.gov (United States)

Zhang, Tao; Cai, Guojun; Duan, Weihong

2018-02-01

The disposal of scrap rubber tires has induced critical environmental issue worldwide due to the rapid increase in the number of vehicles. Recycled scrap tires as a construction material in civil engineering have significant environmental benefits from a waste management perspective. A systematic study that deals with strength and microstructure characteristics of the rubber-sand mixtures is initiated, and mechanical response of the mixtures is discussed in this investigation. Experiments were conducted to evaluate the effects of rubber fraction on the basic properties including mass density (ρ), stress-strain characteristics, shear strength, and unconfined compression strength (q u ) of the rubber-sand mixtures. Additionally, scanning electron microscopy (SEM) was carried out to reveal the microstructure characteristics of the mixtures with various rubber fractions. A discussion on the micromechanics of the mixtures also was conducted. This study demonstrates that the ρ, friction angle, and q u decrease linearly with an increase in rubber fraction, whereas shear strain at peak increases. The stress-strain characteristics of the rubber-sand mixtures shift from brittle to ductile as the rubber fraction increase. These changes are attributed to remarkably lower stiffness and higher compressibility of the rubber particle compared with those of the conventional mineral aggregates. With an increase in the rubber fraction, the mechanical response of rubber-sand mixtures exhibits two types: sand-like material and rubber-like material. Rubber particle possesses the capacity to prevent the contacted sand particles from sliding at lower rubber fraction, whereas it transmits the applied loadings as the rubber fraction increased. This outcome reinforces the practicability of using recycled rubber tire-sand mixtures as a lightweight backfill in subbase/base applications.

Production of Controlled Low Strength Material Utilizing Waste Paper Sludge Ash and Recycled Aggregate Concrete

Directory of Open Access Journals (Sweden)

Azmi A. N.

2016-01-01

Full Text Available Recently, the best method to make the concrete industry more sustainable was using the waste materials to replace the natural resources. Currently waste paper sludge is a major economic and environmental problem in this country. In this research, the alternative method is to dwindle the usage of natural resources and the usage of cement in the construction. This method is to replace the usage of cement with the waste paper sludge ash (WPSA and to use the recycle aggregate collected from the construction is used. The WPSA has ingredient likely cement such as self-cementation but for a low strength. The research was conducted at heavy laboratory UITM Pulau Pinang. Meanwhile, the WPSA is collected at MNI Industries at Mentakab, Pahang. The recycle aggregate is a separated half, which were fine aggregate and the coarse aggregate with the specific size. In this research, the ratio is divided into two (2 which is 1:1 and 1:2 for the aggregate and difference percentage levels of WPSA. The percentage levels of WPSA that use in this research are 10%, 20%, 30%, 40%, 50%, and 60%. A total of 36 cubes were prepared. Aim of this research is to develop a simple design approach for the mixture proportioning of WPSA and recycle concrete aggregate (RCA within the concrete and to assess the effect of concrete mix with different percentage of WPSA and RCA ratio on the properties. It is found that the best design mix that achieves control low strength material (CLSM is on 30% of WPSA with the ratio 1:2 on day 28 of compression test.

Curcumin Attenuates Amyloid-β Aggregate Toxicity and Modulates Amyloid-β Aggregation Pathway.

Science.gov (United States)

Thapa, Arjun; Jett, Stephen D; Chi, Eva Y

2016-01-20

The abnormal misfolding and aggregation of amyloid-β (Aβ) peptides into β-sheet enriched insoluble deposits initiates a cascade of events leading to pathological processes and culminating in cognitive decline in Alzheimer's disease (AD). In particular, soluble oligomeric/prefibrillar Aβ have been shown to be potent neurotoxins. The naturally occurring polyphenol curcumin has been shown to exert a neuroprotective effect against age-related neurodegenerative diseases such as AD. However, its protective mechanism remains unclear. In this study, we investigated the effects of curcumin on the aggregation of Aβ40 as well as Aβ40 aggregate induced neurotoxicity. Our results show that the curcumin does not inhibit Aβ fibril formation, but rather enriches the population of "off-pathway" soluble oligomers and prefibrillar aggregates that were nontoxic. Curcumin also exerted a nonspecific neuroprotective effect, reducing toxicities induced by a range of Aβ conformers, including monomeric, oligomeric, prefibrillar, and fibrillar Aβ. The neuroprotective effect is possibly membrane-mediated, as curcumin reduced the extent of cell membrane permeabilization induced by Aβ aggregates. Taken together, our study shows that curcumin exerts its neuroprotective effect against Aβ induced toxicity through at least two concerted pathways, modifying the Aβ aggregation pathway toward the formation of nontoxic aggregates and ameliorating Aβ-induced toxicity possibly through a nonspecific pathway.

Role of calcium-enriched mixture in endodontics

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Pradeep Kabbinale

2015-01-01

Full Text Available Calcium-enriched mixture (CEM has been recently introduced as a hydrophilic tooth-colored cement. The CEM cement powder is composed of calcium oxide, calcium sulfate, phosphorus oxide, and silica as major elements. CEM is alkaline cement (pH~11 that releases calcium hydroxide (CH during and after setting. The physical properties of CEM, such as flow, film thickness, and primary setting time are favorable. This cement is biocompatible and induces formation of cementum, dentin, bone and periodontal tissues. This novel cement has an antibacterial effect comparable to CH and superior to mineral trioxide aggregate (MTA and sealing ability similar to MTA. Its clinical applications include pulp capping, pulpotomy, root-end filling and perforation repair. This review describes the composition, properties and clinical applications of CEM in endodontics.

High volume fly ash RCC for dams - I : mixture optimization and mechanical properties

Energy Technology Data Exchange (ETDEWEB)

Jacobsen, S. [PEAB Construction Co., Oslo (Norway); Lahus, O. [Norwegian Building Research Inst., Oslo (Norway)

2001-07-01

Roller compacted concretes (RCC) were developed for the Norwegian Skjerka hydropower project. RCCs were developed to have a high-volume fly ash content to address environmental issues, including the reduction of carbon dioxide emissions associated with dam construction. They also makes good use of waste product and conserve natural resources. This study examined a series of mixtures to determine the appropriateness of using RCC as a competing alternative to the traditional rock fill dam proposed for the Skjerka hydropower project. The main advantage of RCC is speed, allowing a relatively large dam to be constructed in just one summer season, saving financial costs and providing early return on the investment. In addition, fly ash can be used in the structure, using clean and renewable energy. Several procedures to proportion RCC mixtures were proposed, including the optimal paste volume method which is based on the assumption that an optimal RCC should have just enough paste to fill the space between particles when the granular skeleton has reached its maximum density under compaction. With this assumption, RCC tests began in 1998 in the laboratories of the Norwegian Building Research Institute. An ordinary portland cement was used and combined with ordinary low lime fly ash. Both coarse and fine aggregate were used. The tests determined the optimum paste-mortar ratio, the content of coarse aggregates and the production of specimens for test on hardened and fresh concrete. The study showed that the compressive strength of RCC increased with increasing cement/(cement + fly ash) ratio. The permeability coefficient decreased with increasing cement-content and increasing cement/(cement + fly ash) ratio due to the slow pozzolanic reaction of fly ash making a more open pore structure. It was concluded that an optimized mixture can result in a high performance RCC in terms of fresh and hardened concrete properties. 15 refs., 5 tabs., 11 figs.

Recycled aggregates concrete: aggregate and mix properties

Directory of Open Access Journals (Sweden)

González-Fonteboa, B.

2005-09-01

Full Text Available This study of structural concrete made with recycled concrete aggregate focuses on two issues: 1. The characterization of such aggregate on the Spanish market. This involved conducting standard tests to determine density, water absorption, grading, shape, flakiness and hardness. The results obtained show that, despite the considerable differences with respect to density and water absorption between these and natural aggregates, on the whole recycled aggregate is apt for use in concrete production. 2. Testing to determine the values of basic concrete properties: mix design parameters were established for structural concrete in non-aggressive environments. These parameters were used to produce conventional concrete, and then adjusted to manufacture recycled concrete aggregate (RCA concrete, in which 50% of the coarse aggregate was replaced by the recycled material. Tests were conducted to determine the physical (density of the fresh and hardened material, water absorption and mechanical (compressive strength, splitting tensile strength and modulus of elasticity properties. The results showed that, from the standpoint of its physical and mechanical properties, concrete in which RCA accounted for 50% of the coarse aggregate compared favourably to conventional concrete.

Se aborda el estudio de hormigones estructurales fabricados con áridos reciclados procedentes de hormigón, incidiéndose en dos aspectos: 1. Caracterización de tales áridos, procedentes del mercado español. Para ello se llevan a cabo ensayos de densidad, absorción, granulometría, coeficiente de forma, índice de lajas y dureza. Los resultados obtenidos han puesto de manifiesto que, a pesar de que existen diferencias notables (sobre todo en cuanto a densidad y absorción con los áridos naturales, las características de los áridos hacen posible la fabricación de hormigones. 2. Ensayos sobre propiedades básicas de los hormigones: se establecen parámetros de dosificaci

Towards General Temporal Aggregation

DEFF Research Database (Denmark)

Boehlen, Michael H.; Gamper, Johann; Jensen, Christian Søndergaard

2008-01-01

associated with the management of temporal data. Indeed, temporal aggregation is complex and among the most difficult, and thus interesting, temporal functionality to support. This paper presents a general framework for temporal aggregation that accommodates existing kinds of aggregation, and it identifies...

The effect of steel slag as a coarse aggregate and Sinabung volcanic ash a filler on high strength concrete

Science.gov (United States)

Karolina, R.; Putra, A. L. A.

2018-02-01

The Development of concrete technology is continues to grow. The requisite for efficient constructions that are often viewed in terms of concrete mechanical behavior, application on the field, and cost estimation of implementation increasingly require engineers to optimize construction materials, especially for concrete materials. Various types of concrete have now been developed according to their needs, such as high strength concrete. On high strength concrete design, it is necessary to consider several factors that will affect the reach of the quality strength, Those are cement, water cement ratio (w/c), aggregates, and proper admixture. In the use of natural mineral, it is important for an engineer to keep an eye on the natural conditions that have been explored. So the selection of aggregates as possible is a material that is not causing nature destruction. On this experiment the use of steel slag from PT.Growth Sumatra Industry as a substitute of coarse and fine aggregate, and volcanic ash of mount Sinabung as microsilka in concrete mixture substituted to create high strength concrete that is harmless for the environment. The use of mount sinabung volcanic ash as microsilika coupled with the use of Master Glenium Sky 8614 superplasticizer. This experiment intend to compare high strength concrete based slag steel as the main constituent aggregates and high strength concrete with a conventional mixture. The research result for 28 days old concrete shows that conventional concrete compressive strength is 67.567 MPa, slag concrete 75.958 Mpa, conventional tensile strength 5.435 Mpa while slag concrete 5.053 Mpa, conventional concrete bending strength 44064.96 kgcm while concrete slag 51473.94 kgcm and modulus of conventional concrete fracture 124.978 kg / cm2 while slag concrete 145.956 kg / cm2. Both concrete slump values shows similar results due to the use of superplasticizer.

Effect of solvent-controlled aggregation on the intrinsic emission properties of PAMAM dendrimers

International Nuclear Information System (INIS)

Jasmine, Maria J.; Kavitha, Manniledam; Prasad, Edamana

2009-01-01

Solvent-induced aggregation and its effect on the intrinsic emission properties of amine, hydroxy and carboxylate terminated, poly(amidoamine) (PAMAM) dendrimers have been investigated in glycerol, ethylene glycol, methanol, ethylene diamine and water. Altering the solvent medium induces remarkable changes in the intrinsic emission properties of the PAMAM dendrimers at identical concentration. Upon excitation at 370 nm, amine terminated PAMAM dendrimer exhibits an intense emission at 470 nm in glycerol, ethylene glycol as well as glycerol-water mixtures. Conversely, weak luminescence is observed for hydroxy and carboxylate terminated PAMAM dendrimers in the same solvent systems. When the solvent is changed to ethylene diamine, hydroxy terminated PAMAM exhibits intense blue emission at 425 nm. While the emission intensity is varied when the solvent milieu is changed, excited state lifetime values of PAMAM dendrimers remain independent of the solvent used. UV-visible absorption and dynamic light scattering (DLS) experiments confirm the formation of solvent-controlled dendrimer aggregates in the systems. Comparison of the fluorescence and DLS data reveals that the size distribution of the dendrimer aggregates in each solvent system is distinct, which control the intrinsic emission intensity from PAMAM dendrimers. The experimental results suggest that intrinsic emission intensity from PAMAM dendrimers can be regulated by proper selection of solvents at neutral conditions and room temperature

Dextrose-mediated aggregation of therapeutic monoclonal antibodies in human plasma: Implication of isoelectric precipitation of complement proteins.

Science.gov (United States)

Luo, Shen; Zhang, Baolin

2015-01-01

Many therapeutic monoclonal antibodies (mAbs) are clinically administered through intravenous infusion after mixing with a diluent, e.g., saline, 5% dextrose. Such a clinical setting increases the likelihood of interactions among mAb molecules, diluent, and plasma components, which may adversely affect product safety and efficacy. Avastin® (bevacizumab) and Herceptin® (trastuzumab), but not Remicade® (infliximab), were shown to undergo rapid aggregation upon dilution into 5% dextrose when mixed with human plasma in vitro; however, the biochemical pathways leading to the aggregation were not clearly defined. Here, we show that dextrose-mediated aggregation of Avastin or Herceptin in plasma involves isoelectric precipitation of complement proteins. Using mass spectrometry, we found that dextrose-induced insoluble aggregates were composed of mAb itself and multiple abundant plasma proteins, namely complement proteins C3, C4, factor H, fibronectin, and apolipoprotein. These plasma proteins, which are characterized by an isoelectronic point of 5.5-6.7, lost solubility at the resulting pH in the mixture with formulated Avastin (pH 6.2) and Herceptin (pH 6.0). Notably, switching formulation buffers for Avastin (pH 6.2) and Remicade (pH 7.2) reversed their aggregation profiles. Avastin formed little, if any, insoluble aggregates in dextrose-plasma upon raising the buffer pH to 7.2 or above. Furthermore, dextrose induced pH-dependent precipitation of plasma proteins, with massive insoluble aggregates being detected at pH 6.5-6.8. These data show that isoelectric precipitation of complement proteins is a prerequisite of dextrose-induced aggregation of mAb in human plasma. This finding highlights the importance of assessing the compatibility of a therapeutic mAb with diluent and human plasma during product development.

Proteins aggregation and human diseases

International Nuclear Information System (INIS)

Hu, Chin-Kun

2015-01-01

Many human diseases and the death of most supercentenarians are related to protein aggregation. Neurodegenerative diseases include Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), frontotemporallobar degeneration, etc. Such diseases are due to progressive loss of structure or function of neurons caused by protein aggregation. For example, AD is considered to be related to aggregation of Aβ40 (peptide with 40 amino acids) and Aβ42 (peptide with 42 amino acids) and HD is considered to be related to aggregation of polyQ (polyglutamine) peptides. In this paper, we briefly review our recent discovery of key factors for protein aggregation. We used a lattice model to study the aggregation rates of proteins and found that the probability for a protein sequence to appear in the conformation of the aggregated state can be used to determine the temperature at which proteins can aggregate most quickly. We used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that when the bending-angle dependent and torsion-angle dependent interactions are zero or very small, then protein chains tend to aggregate at lower temperatures. All atom models were used to identify a key peptide chain for the aggregation of insulin chains and to find that two polyQ chains prefer anti-parallel conformation. It is pointed out that in many cases, protein aggregation does not result from protein mis-folding. A potential drug from Chinese medicine was found for Alzheimer's disease. (paper)

Proteins aggregation and human diseases

Science.gov (United States)

Hu, Chin-Kun

2015-04-01

Many human diseases and the death of most supercentenarians are related to protein aggregation. Neurodegenerative diseases include Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), frontotemporallobar degeneration, etc. Such diseases are due to progressive loss of structure or function of neurons caused by protein aggregation. For example, AD is considered to be related to aggregation of Aβ40 (peptide with 40 amino acids) and Aβ42 (peptide with 42 amino acids) and HD is considered to be related to aggregation of polyQ (polyglutamine) peptides. In this paper, we briefly review our recent discovery of key factors for protein aggregation. We used a lattice model to study the aggregation rates of proteins and found that the probability for a protein sequence to appear in the conformation of the aggregated state can be used to determine the temperature at which proteins can aggregate most quickly. We used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that when the bending-angle dependent and torsion-angle dependent interactions are zero or very small, then protein chains tend to aggregate at lower temperatures. All atom models were used to identify a key peptide chain for the aggregation of insulin chains and to find that two polyQ chains prefer anti-parallel conformation. It is pointed out that in many cases, protein aggregation does not result from protein mis-folding. A potential drug from Chinese medicine was found for Alzheimer's disease.

A diethylhydroxylaminate based mixed lithium/beryllium aggregate

Energy Technology Data Exchange (ETDEWEB)

Berger, Raphael J.F. [Paris-Lodron Universitaet Salzburg (Austria). Fachbereich fuer Materialwissenschaften und Physik; Jana, Surajit [Asansol Girls College, West-Bengal (India). Dept. of Chemistry; Froehlich, Roland [Muenster Univ. (Germany). Organisch-Chemisches Inst.; Mitzel, Norbert W. [Bielefeld Univ. (Germany). Anorganische Chemie und Strukturchemie

2015-07-01

A mixed lithium/beryllium diethylhydroxylaminate compound containing {sup n}butyl beryllium units of total molecular composition {sup n}Be(ONEt{sub 2}){sub 2} [(LiONEt{sub 2}){sup 2} {sup n}BuBeONEt{sub 2}]{sub 2} (1) was isolated from a reaction mixture of {sup n}butyl lithium, N,N-diethylhydroxylamine and BeCl{sub 2} in diethylether/thf. The crystal structure of 1 has been determined by X-ray diffraction. The aggregate is composed of two ladder-type subunits connected in a beryllium-centered distorted tetrahedron of four oxygen atoms. Only the lithium atoms are engaged in coordination with the nitrogen donor atoms. The DFT calculations support the positional occupation determined for Li and Be in the crystal structure. The DFT and the solid-state structure are in excellent agreement, indicating only weak intermolecular interactions in the solid state. Structural details of metal atom coordination are discussed.

Effect of presence of benzene ring in surfactant hydrophobic chain on the transformation towards one dimensional aggregate

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Rabah A. Khalil

2015-07-01

Full Text Available The formation of wormlike micelle and the following significant changes in rheological properties suffer misunderstanding from both theoretical and fundamental aspects. Recently, we have introduced a theory for interpreting such important phenomenon which is referred to as critical intermolecular forces (CIF. The theory has stated that the hydrophobic effect is the main factor for the formation of worm-like aggregates. Therefore, it seems interesting to check out the validity of this new physical insight through investigating the presence of benzene ring as less hydrophobic group in contrast to that of alkyl in surfactant tail. The mixture of anionic sodium dodecylbenzenesulphonate (SDBS and cationic cetyltrimethylammonium bromide (CTAB shows a high dynamic viscosity peak at the ratio of 80/20 of 3 wt.% CTAB/SDBS indicating the formation of wormlike micelles. The thermodynamic properties have been evaluated for this mixture exhibiting good agreement with the rheological changes. Interestingly, the results show the presence of benzene ring (in SDBS causing a negative effect towards the formation of one dimensional aggregate in contrast to previous results which support the proposed CIF theory. The presence of nonionic surfactant TritonX-100 in binary and ternary systems of SDBS and CTAB prohibits the formation of wormlike micelles.

The transformation of waste Bakelite to replace natural fine aggregate in cement mortar

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Nopagon Usahanunth

2017-06-01

Full Text Available Bakelite material has been used to produce the various components for cars and consumer goods industry in Thailand. The growth of Bakelite consumption increases Bakelite waste. Bakelite waste is prohibited from disposing of direct landfilling and open burning because of the improper disposal and emission reasons. A large amount of this waste needs the large safe space of warehouse area for keeping which becomes a waste management problem. Size reduction by milling machine is helpful for waste handling and storing, however, the post-milling waste Bakelite plastic utilization shall be studied to maintain the waste storing capacity. There are some studies of the milling machine used for waste plastic size reduction. However, the particular study of milling machine application for waste size reduction and its milling waste utilization is still insufficient in Thailand. The purpose of this research is the use of waste Bakelite aggregate milling machine for Bakelite waste size reduction and use of the post-milling waste Bakelite as a fine aggregate to replace natural sand material in cement mortar. The waste Bakelite fine aggregate (WBFA was mixed in cement mortar mixture with the proportion 0% 20% 40% 60% 80% and 100% by volume for cement mortar sample preparation. The mortar sample was tested for compressive strength follow ASTM standard. The compressive test result of mortar samples will be compared between conventional mortar (0% WBFA and waste Bakelite mortar (WBM as well as comparing with the mortar standard. From an analysis of the sample test data found that the WBFA content in cement mortar mixture can predict the strength of WBM. The compressive strength of WBM at 28 days age with the fraction of WBFA is not exceeded 11.03%, and 23.08% respectively can be met the mortar standard according to the equation. The utilization of WBM to develop mortar non-structural mortar product can be usable from a technical point of view.

Use of Cement Kiln Dust, Blast Furnace Slag and Marble Sludge in the Manufacture of Sustainable Artificial Aggregates by Means of Cold Bonding Pelletization.

Science.gov (United States)

Colangelo, Francesco; Cioffi, Raffaele

2013-07-25

In this work, three different samples of solid industrial wastes cement kiln dust (CKD), granulated blast furnace slag and marble sludge were employed in a cold bonding pelletization process for the sustainable production of artificial aggregates. The activating action of CKD components on the hydraulic behavior of the slag was explored by evaluating the neo-formed phases present in several hydrated pastes. Particularly, the influence of free CaO and sulfates amount in the two CKD samples on slag reactivity was evaluated. Cold bonded artificial aggregates were characterized by determining physical and mechanical properties of two selected size fractions of the granules for each studied mixture. Eighteen types of granules were employed in C28/35 concrete manufacture where coarser natural aggregate were substituted with the artificial ones. Finally, lightweight concretes were obtained, proving the suitability of the cold bonding pelletization process in artificial aggregate sustainable production.

Use of Cement Kiln Dust, Blast Furnace Slag and Marble Sludge in the Manufacture of Sustainable Artificial Aggregates by Means of Cold Bonding Pelletization

Directory of Open Access Journals (Sweden)

Raffaele Cioffi

2013-07-01

Full Text Available In this work, three different samples of solid industrial wastes cement kiln dust (CKD, granulated blast furnace slag and marble sludge were employed in a cold bonding pelletization process for the sustainable production of artificial aggregates. The activating action of CKD components on the hydraulic behavior of the slag was explored by evaluating the neo-formed phases present in several hydrated pastes. Particularly, the influence of free CaO and sulfates amount in the two CKD samples on slag reactivity was evaluated. Cold bonded artificial aggregates were characterized by determining physical and mechanical properties of two selected size fractions of the granules for each studied mixture. Eighteen types of granules were employed in C28/35 concrete manufacture where coarser natural aggregate were substituted with the artificial ones. Finally, lightweight concretes were obtained, proving the suitability of the cold bonding pelletization process in artificial aggregate sustainable production.

Denitrification in Soil Aggregate Analogues-Effect of Aggregate Size and Oxygen Diffusion

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Steffen Schlüter

2018-04-01

Full Text Available Soil-borne nitrous oxide (N2O emissions have a high spatial and temporal variability which is commonly attributed to the occurrence of hotspots and hot moments for microbial activity in aggregated soil. Yet there is only limited information about the biophysical processes that regulate the production and consumption of N2O on microscopic scales in undisturbed soil. In this study, we introduce an experimental framework relying on simplified porous media that circumvents some of the complexities occuring in natural soils while fully accounting for physical constraints believed to control microbial activity in general and denitrification in particular. We used this framework to explore the impact of aggregate size and external oxygen concentration on the kinetics of O2 consumption, as well as CO2 and N2O production. Model aggregates of different sizes (3.5 vs. 7 mm diameter composed of porous, sintered glass were saturated with a defined growth medium containing roughly 109 cells ml−1 of the facultative anaerobic, nosZ-deficient denitrifier Agrobacterium tumefaciens with N2O as final denitrification product and incubated at five different oxygen levels (0–13 vol-%. We demonstrate that the onset of denitrification depends on the amount of external oxygen and the size of aggregates. Smaller aggregates were better supplied with oxygen due to a larger surface-to-volume ratio, which resulted in faster growth and an earlier onset of denitrification. In larger aggregates, the onset of denitrification was more gradual, but with comparably higher N2O production rates once the anoxic aggregate centers were fully developed. The normalized electron flow from the reduced carbon substrate to N-oxyanions (edenit-/etotal- ratio could be solely described as a function of initial oxygen concentration in the headspace with a simple, hyperbolic model, for which the two empirical parameters changed with aggregate size in a consistent way. These findings confirm the

Oil-Price Shocks: Beyond Standard Aggregate Demand/Aggregate Supply Analysis.

Science.gov (United States)

Elwood, S. Kirk

2001-01-01

Explores the problems of portraying oil-price shocks using the aggregate demand/aggregate supply model. Presents a simple modification of the model that differentiates between production and absorption of goods, which enables it to better reflect the effects of oil-price shocks on open economies. (RLH)

Mixture

Directory of Open Access Journals (Sweden)

Silva-Aguilar Martín

2011-01-01

Full Text Available Metals are ubiquitous pollutants present as mixtures. In particular, mixture of arsenic-cadmium-lead is among the leading toxic agents detected in the environment. These metals have carcinogenic and cell-transforming potential. In this study, we used a two step cell transformation model, to determine the role of oxidative stress in transformation induced by a mixture of arsenic-cadmium-lead. Oxidative damage and antioxidant response were determined. Metal mixture treatment induces the increase of damage markers and the antioxidant response. Loss of cell viability and increased transforming potential were observed during the promotion phase. This finding correlated significantly with generation of reactive oxygen species. Cotreatment with N-acetyl-cysteine induces effect on the transforming capacity; while a diminution was found in initiation, in promotion phase a total block of the transforming capacity was observed. Our results suggest that oxidative stress generated by metal mixture plays an important role only in promotion phase promoting transforming capacity.

Photo-induced reorganization of molecular packing of amphi-PIC J-aggregates (single J-aggregate spectroscopy)

International Nuclear Information System (INIS)

Malyukin, Yu.V.; Sorokin, A.V.; Yefimova, S.L.; Lebedenko, A.N.

2005-01-01

Confocal luminescence microscopy has been used to excite and collect luminescence from single amphi-PIC J-aggregate. Two types of J-aggregates have been revealed in the luminescence image: bead-like J-aggregates, which diameter is less than 1 μm and rod-like ones, which length is about 3 μm and diameter is less than 1 μm. It has been found that single rod-like and bead-like J-aggregates exhibit different luminescence bands with different decay parameters. At the off-resonance blue tail excitation, the J-aggregate exciton luminescence disappeared within a certain time period and a new band appeared, which cannot be attributed to the monomer emission. The luminescence image shows that the J-aggregate is not destroyed. However, J-aggregate storage in darkness does not recover its exciton luminescence

Studies on recycled aggregates-based concrete.

Science.gov (United States)

Rakshvir, Major; Barai, Sudhirkumar V

2006-06-01

Reduced extraction of raw materials, reduced transportation cost, improved profits, reduced environmental impact and fast-depleting reserves of conventional natural aggregates has necessitated the use of recycling, in order to be able to conserve conventional natural aggregate. In this study various physical and mechanical properties of recycled concrete aggregates were examined. Recycled concrete aggregates are different from natural aggregates and concrete made from them has specific properties. The percentages of recycled concrete aggregates were varied and it was observed that properties such as compressive strength showed a decrease of up to 10% as the percentage of recycled concrete aggregates increased. Water absorption of recycled aggregates was found to be greater than natural aggregates, and this needs to be compensated during mix design.

Risk assessment by percolation leaching tests of extensive green roofs with fine fraction of mixed recycled aggregates from construction and demolition waste.

Science.gov (United States)

López-Uceda, Antonio; Galvín, Adela P; Ayuso, Jesús; Jiménez, José Ramón; Vanwalleghem, Tom; Peña, Adolfo

2018-03-19

Extensive green roofs are urban construction systems that provide thermal regulation and sound proofing for the buildings involved, in addition to providing an urban heat island mitigation or water retention. On the other hand, policies towards reduction of energy consumption, a circular economy and sustainability are core in the European Union. Motivated by this, an experimental study was carried out to evaluate the environmental risk assessment according to release levels of polluting elements on leachates of different green roof substrate mixtures based on recycled aggregates from construction and demolition waste through (i) the performance in laboratory of two procedures: compliance and percolation tests and (ii) an upscaled experimental leaching test for long-term on-site prediction. Four plots were built on a building roof and covered with autochthonous Mediterranean plants in Córdoba, South of Spain. As growing substrate, four mixtures were used of a commercial growing substrate with different proportions of a fine mixed recycled aggregate ranging from 0 to 75% by volume. The results show that these mixtures were classified as non-hazardous materials according to legal limits of the Landfill Directive 2003/33/CE. The release levels registered in extensive green roofs were lower compared to the laboratory test data. This shows how laboratory conditions can overestimate the potential pollutant effect of these materials compared to actual conditions.

Warm mix asphalt: Chemical additives’ effects on bitumen properties and limestone aggregates mixture compactibility

Directory of Open Access Journals (Sweden)

Raul Pereira

2018-05-01

Full Text Available Asphalt industries consume large amounts of fuels and emit pollutant gases into the atmosphere. Warm mix asphalt is the most recognized way to minimize these negative impacts, which have given rise to numerous issues related to their performance and the materials used. In this study, the basic and rheological properties of three different bituminous binders, modified with two different chemical additives, were evaluated, determining their behaviour and susceptibility to modification. The results showed that, although chemical additives do not affect the binder by reducing its viscosity, they act on the mixture, allowing to improve its compactability and, consequently, reduce the required production and compaction temperatures. Keywords: Warm mix asphalt, Bitumen, Chemical additives, Behaviour, Additive-binder interaction, Road pavements

Investigation of Physico-Chemical Properties of Sand-Lime Products Modified of Diabase Aggregate and Chalcedonite Meal

Science.gov (United States)

Dachowski, Ryszard; Komisarczyk, Katarzyna

2017-10-01

In the era of rapid development in the construction industry, particular attention is focused on harmless and natural materials. Some of the best materials for building masonry walls are sand-lime products. Silicates are obtained from a mixture of quartz, sand and a small amount of water. They emerge as a result of the hydrothermal treatment conducted under high pressure and at a temperature of app. 203 °C. Silicates were modified of different kinds of aggregates, glass or plastics, and the content of dry ingredients was changed because of this fact. The paper describes the studies where the combination of diabase aggregate and chalcedonite meal was used. Microstructure of the products was analyzed with the use of mercury intrusion porosimetry, SEM and XRD methods. Variable content of chalcedonite meal changes the internal structure and the physico-chemical properties.

An exact approach for aggregated formulations

DEFF Research Database (Denmark)

Gamst, Mette; Spoorendonk, Simon; Røpke, Stefan

Aggregating formulations is a powerful approach for problems to take on tractable forms. Aggregation may lead to loss of information, i.e. the aggregated formulation may be an approximation of the original problem. In branch-and-bound context, aggregation can also complicate branching, e.g. when...... optimality cannot be guaranteed by branching on aggregated variables. We present a generic exact solution method to remedy the drawbacks of aggregation. It combines the original and aggregated formulations and applies Benders' decomposition. We apply the method to the Split Delivery Vehicle Routing Problem....

Properties of Concrete with Tire Derived Aggregate Partially Replacing Coarse Aggregates.

Science.gov (United States)

Siringi, Gideon; Abolmaali, Ali; Aswath, Pranesh B

2015-01-01

Tire derived aggregate (TDA) has been proposed as a possible lightweight replacement for mineral aggregate in concrete. The role played by the amount of TDA replacing coarse aggregate as well as different treatment and additives in concrete on its properties is examined. Conventional concrete (without TDA) and concrete containing TDA are compared by examining their compressive strength based on ASTM C39, workability based on ASTM C143, splitting tensile strength based on ASTM C496, modulus of rupture (flexural strength) based on ASTM C78, and bond stress based on ASTM C234. Results indicate that while replacement of coarse aggregates with TDA results in reduction in strength, it may be mitigated with addition of silica fume to obtain the desired strength. The greatest benefit of using TDA is in the development of a higher ductile product while utilizing recycled TDA.

Protein aggregate turbidity: Simulation of turbidity profiles for mixed-aggregation reactions.

Science.gov (United States)

Hall, Damien; Zhao, Ran; Dehlsen, Ian; Bloomfield, Nathaniel; Williams, Steven R; Arisaka, Fumio; Goto, Yuji; Carver, John A

2016-04-01

Due to their colloidal nature, all protein aggregates scatter light in the visible wavelength region when formed in aqueous solution. This phenomenon makes solution turbidity, a quantity proportional to the relative loss in forward intensity of scattered light, a convenient method for monitoring protein aggregation in biochemical assays. Although turbidity is often taken to be a linear descriptor of the progress of aggregation reactions, this assumption is usually made without performing the necessary checks to provide it with a firm underlying basis. In this article, we outline utilitarian methods for simulating the turbidity generated by homogeneous and mixed-protein aggregation reactions containing fibrous, amorphous, and crystalline structures. The approach is based on a combination of Rayleigh-Gans-Debye theory and approximate forms of the Mie scattering equations. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

Aggregates from mineral wastes

Directory of Open Access Journals (Sweden)

Baic Ireneusz

2016-01-01

Full Text Available The problem concerning the growing demand for natural aggregates and the need to limit costs, including transportation from remote deposits, cause the increase in growth of interest in aggregates from mineral wastes as well as in technologies of their production and recovery. The paper presents the issue related to the group of aggregates other than natural. A common name is proposed for such material: “alternative aggregates”. The name seems to be fully justified due to adequacy of this term because of this raw materials origin and role, in comparison to the meaning of natural aggregates based on gravel and sand as well as crushed stones. The paper presents characteristics of the market and basic application of aggregates produced from mineral wastes, generated in the mining, power and metallurgical industries as well as material from demolished objects.

Aggregated Computational Toxicology Online Resource

Data.gov (United States)

U.S. Environmental Protection Agency — Aggregated Computational Toxicology Online Resource (AcTOR) is EPA's online aggregator of all the public sources of chemical toxicity data. ACToR aggregates data...

Processed bottom ash for replacing fine aggregate in making high-volume fly ash concrete

Directory of Open Access Journals (Sweden)

Antoni

2017-01-01

Full Text Available Bottom ash is a coal plant by-product that is abundant and underutilized. There is the potential use of bottom ash as a fine aggregate replacement in concrete mixtures; however, the problems of water absorption and uniformity of quality of the material need to be overcome first. In this study, bottom ash was treated by sieve separation and pounding to smaller particle size for use as a sand substitute. The physical and chemical characteristics of bottom ash were tested after treatment including water absorption, sieve analysis, and fineness modulus. Highvolume fly ash (HVFA mortar specimens were made and the compressive strength and flowability test using bottom ash after treatment are compared with that of the sand specimen. Low water to cementitious ratio was used to ensure higher strength from the cementitious paste and superplasticizer demand was determined for each treatment. The result showed that bottom ash can be used as fine aggregate replacement material. Sieve separation of the bottom ash could produce 75% of the compressive strength compared with the control sand specimen, whereas pounded bottom ash could have up to 96% of the compressive strength of the control specimen. A 28-day compressive strength of 45 MPa was achievable with 100% replacement of fine aggregate with bottom ash.

Aggregation and pH-temperature phase behavior for aggregates of an IgG2 antibody.

Science.gov (United States)

Sahin, Erinc; Weiss, William F; Kroetsch, Andrew M; King, Kevin R; Kessler, R Kendall; Das, Tapan K; Roberts, Christopher J

2012-05-01

Monomer unfolding and thermally accelerated aggregation kinetics to produce soluble oligomers or insoluble macroscopic aggregates were characterized as a function of pH for an IgG2 antibody using differential scanning calorimetry (DSC) and size-exclusion chromatography (SEC). Aggregate size was quantified via laser light scattering, and aggregate solubility via turbidity and visual inspection. Interestingly, nonnative oligomers were soluble at pH 5.5 above approximately 15°C, but converted reversibly to visible/insoluble particles at lower temperatures. Lower pH values yielded only soluble aggregates, whereas higher pH resulted in insoluble aggregates, regardless of the solution temperature. Unlike the growing body of literature that supports the three-endotherm model of IgG1 unfolding in DSC, the results here also illustrate limitations of that model for other monoclonal antibodies. Comparison of DSC with monomer loss (via SEC) from samples during thermal scanning indicates that the least conformationally stable domain is not the most aggregation prone, and that a number of the domains remain intact within the constituent monomers of the resulting aggregates. This highlights continued challenges with predicting a priori which domain(s) or thermal transition(s) is(are) most relevant for product stability with respect to aggregation. Copyright © 2012 Wiley Periodicals, Inc.

Properties of Concrete with Tire Derived Aggregate Partially Replacing Coarse Aggregates

Science.gov (United States)

Siringi, Gideon; Abolmaali, Ali; Aswath, Pranesh B.

2015-01-01

Tire derived aggregate (TDA) has been proposed as a possible lightweight replacement for mineral aggregate in concrete. The role played by the amount of TDA replacing coarse aggregate as well as different treatment and additives in concrete on its properties is examined. Conventional concrete (without TDA) and concrete containing TDA are compared by examining their compressive strength based on ASTM C39, workability based on ASTM C143, splitting tensile strength based on ASTM C496, modulus of rupture (flexural strength) based on ASTM C78, and bond stress based on ASTM C234. Results indicate that while replacement of coarse aggregates with TDA results in reduction in strength, it may be mitigated with addition of silica fume to obtain the desired strength. The greatest benefit of using TDA is in the development of a higher ductile product while utilizing recycled TDA. PMID:26161440

Properties of Concrete with Tire Derived Aggregate Partially Replacing Coarse Aggregates

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Gideon Siringi

2015-01-01

Full Text Available Tire derived aggregate (TDA has been proposed as a possible lightweight replacement for mineral aggregate in concrete. The role played by the amount of TDA replacing coarse aggregate as well as different treatment and additives in concrete on its properties is examined. Conventional concrete (without TDA and concrete containing TDA are compared by examining their compressive strength based on ASTM C39, workability based on ASTM C143, splitting tensile strength based on ASTM C496, modulus of rupture (flexural strength based on ASTM C78, and bond stress based on ASTM C234. Results indicate that while replacement of coarse aggregates with TDA results in reduction in strength, it may be mitigated with addition of silica fume to obtain the desired strength. The greatest benefit of using TDA is in the development of a higher ductile product while utilizing recycled TDA.

Optimal mixture experiments

CERN Document Server

Sinha, B K; Pal, Manisha; Das, P

2014-01-01

The book dwells mainly on the optimality aspects of mixture designs. As mixture models are a special case of regression models, a general discussion on regression designs has been presented, which includes topics like continuous designs, de la Garza phenomenon, Loewner order domination, Equivalence theorems for different optimality criteria and standard optimality results for single variable polynomial regression and multivariate linear and quadratic regression models. This is followed by a review of the available literature on estimation of parameters in mixture models. Based on recent research findings, the volume also introduces optimal mixture designs for estimation of optimum mixing proportions in different mixture models, which include Scheffé’s quadratic model, Darroch-Waller model, log- contrast model, mixture-amount models, random coefficient models and multi-response model.  Robust mixture designs and mixture designs in blocks have been also reviewed. Moreover, some applications of mixture desig...

Flow regime and deposition pattern of evaporating binary mixture droplet suspended with particles.

Science.gov (United States)

Zhong, Xin; Duan, Fei

2016-02-01

The flow regimes and the deposition pattern have been investigated by changing the ethanol concentration in a water-based binary mixture droplet suspended with alumina nanoparticles. To visualize the flow patterns, Particle Image Velocimetry (PIV) has been applied in the binary liquid droplet containing the fluorescent microspheres. Three distinct flow regimes have been revealed in the evaporation. In Regime I, the vortices and chaotic flows are found to carry the particles to the liquid-vapor interface and to promote the formation of particle aggregation. The aggregates move inwards in Regime II as induced by the Marangoni flow along the droplet free surface. Regime III is dominated by the drying of the left water and the capillary flow driving particles radially outward is observed. The relative weightings of Regimes I and II, which are enhanced with an increasing load of ethanol, determine the motion of the nanoparticles and the formation of the final drying pattern.

Evaluation and Study the Effect of Additives and Other Factors on Tensile Strength of Asphalt Paving Mixtures

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Hanaa Khaleel A. Al-Baiti

2012-03-01

Full Text Available The resistance of asphaltic concrete to cracking is dependent upon its tensile strength and flexibility characteristics. Also the low tensile strength has recognized as a major contributor to other performance problems. The fatigue life of mixtures decreases exponentially with decreasing of tensile strength. This trend is justified by the loss in stiffness and thereby initiating cracks and stripping. The main objective of this research is intended to study the effect of different variables related with the used materials and the external conditions on the tensile strength and predict a model of indirect tensile strength in asphalt concrete paving materials under the local prevailing conditions and investigate the effect of percent of additives of (Polyestrene resins and Hydrated Lime to enhance the resistance ability of asphalt concrete mixture against distresses. The main affected factors; soaking, asphalt content, compaction, aggregate maximum size and temperature, influence on the indirect tensile strength and presented through a statistics analysis model for tensile strength in asphalt mixture

Aggregation effects on tritium-based mean transit times and young water fractions in spatially heterogeneous catchments and groundwater systems

Science.gov (United States)

Stewart, Michael K.; Morgenstern, Uwe; Gusyev, Maksym A.; Małoszewski, Piotr

2017-09-01

Kirchner (2016a) demonstrated that aggregation errors due to spatial heterogeneity, represented by two homogeneous subcatchments, could cause severe underestimation of the mean transit times (MTTs) of water travelling through catchments when simple lumped parameter models were applied to interpret seasonal tracer cycle data. Here we examine the effects of such errors on the MTTs and young water fractions estimated using tritium concentrations in two-part hydrological systems. We find that MTTs derived from tritium concentrations in streamflow are just as susceptible to aggregation bias as those from seasonal tracer cycles. Likewise, groundwater wells or springs fed by two or more water sources with different MTTs will also have aggregation bias. However, the transit times over which the biases are manifested are different because the two methods are applicable over different time ranges, up to 5 years for seasonal tracer cycles and up to 200 years for tritium concentrations. Our virtual experiments with two water components show that the aggregation errors are larger when the MTT differences between the components are larger and the amounts of the components are each close to 50 % of the mixture. We also find that young water fractions derived from tritium (based on a young water threshold of 18 years) are almost immune to aggregation errors as were those derived from seasonal tracer cycles with a threshold of about 2 months.

Kinetics of aggregation with choice.

Science.gov (United States)

Ben-Naim, E; Krapivsky, P L

2016-12-01

We generalize the ordinary aggregation process to allow for choice. In ordinary aggregation, two random clusters merge and form a larger aggregate. In our implementation of choice, a target cluster and two candidate clusters are randomly selected and the target cluster merges with the larger of the two candidate clusters. We study the long-time asymptotic behavior and find that as in ordinary aggregation, the size density adheres to the standard scaling form. However, aggregation with choice exhibits a number of different features. First, the density of the smallest clusters exhibits anomalous scaling. Second, both the small-size and the large-size tails of the density are overpopulated, at the expense of the density of moderate-size clusters. We also study the complementary case where the smaller candidate cluster participates in the aggregation process and find an abundance of moderate clusters at the expense of small and large clusters. Additionally, we investigate aggregation processes with choice among multiple candidate clusters and a symmetric implementation where the choice is between two pairs of clusters.

Kinetic Behaviors of Catalysis-Driven Growth of Three-Species Aggregates on Base of Exchange-Driven Aggregations

International Nuclear Information System (INIS)

Sun Yunfei; Chen Dan; Lin Zhenquan; Ke Jianhong

2009-01-01

We propose a solvable aggregation model to mimic the evolution of population A, asset B, and the quantifiable resource C in a society. In this system, the population and asset aggregates themselves grow through self-exchanges with the rate kernels K 1 (k, j) = K 1 kj and K 2 (k, j) = K 2 kj, respectively. The actions of the population and asset aggregations on the aggregation evolution of resource aggregates are described by the population-catalyzed monomer death of resource aggregates and asset-catalyzed monomer birth of resource aggregates with the rate kernels J 1 (k, j) = J 1 k and J 2 (k, j) = J 2 k, respectively. Meanwhile, the asset and resource aggregates conjunctly catalyze the monomer birth of population aggregates with the rate kernel I 1 (k, i, j) = I 1 ki μ j η , and population and resource aggregates conjunctly catalyze the monomer birth of asset aggregates with the rate kernel I 2 (k, i, j) = I 2 ki v j η . The kinetic behaviors of species A, B, and C are investigated by means of the mean-field rate equation approach. The effects of the population-catalyzed death and asset-catalyzed birth on the evolution of resource aggregates based on the self-exchanges of population and asset appear in effective forms. The coefficients of the effective population-catalyzed death and the asset-catalyzed birth are expressed as J 1e = J 1 /K 1 and J 2e = J 2 /K 2 , respectively. The aggregate size distribution of C species is found to be crucially dominated by the competition between the effective death and the effective birth. It satisfies the conventional scaling form, generalized scaling form, and modified scaling form in the cases of J 1e 2e , J 1e = J 2e , and J 1e > J 2e , respectively. Meanwhile, we also find the aggregate size distributions of populations and assets both fall into two distinct categories for different parameters μ, ν, and η: (i) When μ = ν = η = 0 and μ = ν = 0, η = 1, the population and asset aggregates obey the generalized

Wasteless combined aggregate-coal-fired steam-generator/melting-converter

International Nuclear Information System (INIS)

Pioro, L.S.; Pioro, I.L.

2003-01-01

A method of reprocessing coal sludge and ash into granulate for the building industry in a combined wasteless aggregate-steam-generator/melting-converter was developed and tested. The method involves melting sludge and ash from coal-fired steam-generators of power plants in a melting-converter installed under the steam-generator, with direct sludge drain from the steam generator combustion chamber. The direct drain of sludge into converter allows burnup of coal with high ash levels in the steam-generator without an additional source of ignition (natural gas, heating oil, etc.). Specific to the melting process is the use of a gas-air mixture with direct combustion inside a melt. This feature provides melt bubbling and helps to achieve maximum heat transfer from combustion products to the melt, to improve mixing, to increase rate of chemical reactions and to improve the conditions for burning the carbon residue from the sludge and ash. The 'gross' thermal efficiency of the combined aggregate is about 93% and the converter capacity is about 18 t of melt in 100 min. The experimental data for different aspects of the proposed method are presented. The effective ash/charging materials feeding system is also discussed. The reprocessed coal ash and sludge in the form of granules can be used as fillers for concretes and as additives in the production of cement, bricks and other building materials

The Importance of Superplastizer Dosage in the Mix Design of Lightweight Aggregate Concrete Reinforced With Plypropylene Fiber

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Shafigh Payam

2016-01-01

Full Text Available This paper reports the results of a study conducted to investigate the effect of superplasticizer (SP dosage on the slump, density, compressive strength and splitting tensile strength under different curing conditions of a lightweight aggregate concrete reinforced with polypropylene (PP fiber. The lightweight aggregate used in this study was oil palm shell, which is an agricultural solid waste, originating from the palm oil industry. The results indicated that an increase in superplasticizer increased the workability, however, all the mechanical properties declined significantly. The reduction in the 28-day compressive and splitting tensile strengths was about 14. This study showed that although additional SP can improve the workability of the concrete, it may have a negative effect on the other properties of concrete. Therefore, the SP dosage in concrete mixtures containing PP fiber should be limited to a certain amount.

Phase behavior of diblock copolymer/star-shaped polymer thin film mixtures.

Science.gov (United States)

Zhao, Junnan; Sakellariou, Georgios; Green, Peter F

2016-05-07

We investigated the phase behavior of thin film, thickness h≈ 100 nm, mixtures of a polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer with star-shaped polystyrene (SPS) molecules of varying functionalities f, where 4 ≤f≤ 64, and molecular weights per arm Marm. The miscibility of the system and the surface composition varied appreciably with Marm and f. For large values of Marm, regardless of f, the miscibility of the system was qualitatively similar to that of linear chain PS/PS-b-P2VP mixtures - the copolymer chains aggregate to form micelles, each composed of an inner P2VP core and PS corona, which preferentially segregate to the free surface. On the other hand, for large f and small Marm, SPS molecules preferentially resided at the free surface. Moreover, blends containing SPS molecules with the highest values of f and lowest values of Marm were phase separated. These observations are rationalized in terms of competing entropic interactions and the dependence of the surface tension of the star-shaped molecules on Marm and f.

Research on Judgment Aggregation Based on Logic

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Li Dai

2014-05-01

Full Text Available Preference aggregation and judgment aggregation are two basic research models of group decision making. And preference aggregation has been deeply studied in social choice theory. However, researches of social choice theory gradually focus on judgment aggregation which appears recently. Judgment aggregation focuses on how to aggregate many consistent logical formulas into one, from the perspective of logic. We try to start with judgment aggregation model based on logic and then explore different solutions to problem of judgment aggregation.

Quantitative analysis of the effect of zidovudine, efavirenz, and ritonavir on insulin aggregation by multivariate curve resolution alternating least squares of infrared spectra

International Nuclear Information System (INIS)

Martí-Aluja, Idoia; Ruisánchez, Itziar; Larrechi, M. Soledad

2013-01-01

Highlights: ► The structure of insulin can be changed via interaction with antiretroviral drugs. ► The chemical interaction promotes the formation of aggregates. ► This drug effect was evaluated by MCR-ALS coupled to IR spectroscopy. ► Formation of aggregates was favourable if drugs were able to form hydrogen bonds. ► Higher drug concentrations favoured formation of amorphous aggregates. - Abstract: Quantification of the effect of antiretroviral drugs on the insulin aggregation process is an important area of research due to the serious metabolic diseases observed in AIDS patients after prolonged treatment with these drugs. In this work, multivariate curve resolution alternating least squares (MCR-ALS) was applied to infrared monitoring of the insulin aggregation process in the presence of three antiretroviral drugs to quantify their effect. To evidence concentration dependence in this process, mixtures at two different insulin:drug molar ratios were used. The interaction between insulin and each drug was analysed by 1 H NMR spectroscopy. In all cases, the aggregation process was monitored during 45 min by infrared spectroscopy. The aggregates were further characterised by scanning electron microscopy (SEM). MCR-ALS provided the spectral and concentration profiles of the different insulin–drug conformations that are involved in the process. Their feasible band boundaries were calculated using the MCR-BANDS methodology. The kinetic profiles describe the aggregation pathway and the spectral profiles characterise the conformations involved. The retrieved results show that each of the three drugs modifies insulin conformation in a different way, promoting the formation of aggregates. Ritonavir shows the strongest promotion of aggregation, followed by efavirenz and zidovudine. In the studied concentration range, concentration dependence was only observed for zidovudine, with shorter aggregation time obtained as the amount of zidovudine increased. This factor

Sintering study in vertical fixed bed reactor for synthetic aggregate production; Estudo da sinterizacao em reator vertical de leito fixo para producao de agregado sintetico

Energy Technology Data Exchange (ETDEWEB)

Quaresma, D.S.; Neves, A.S.S.; Melo, A.O.; Pereira, L.F.S.; Bezerra, P.T.S.; Macedo, E.N.; Souza, J.A.S., E-mail: danysq@gmail.com [Universidade Federal do Para (UFPA), Belem, PA (Brazil). Faculdade de Engenharia Quimica

2017-04-15

The synthetic aggregates are being employed in civil construction for the reduction of mineral extraction activities. Within this context, the recycling of industrial waste is the basis of the majority of processes to reduce the exploitation of mineral resources. In this work the sintering in a vertical fixed bed reactor for synthetic aggregate production using 20% pellets and 80% charcoal was studied. The pellets were prepared from a mixture containing clay, charcoal and fly ash. Two experiments varying the speed of air sucking were carried out. The material produced was analyzed by X-ray diffraction, scanning electron microscopy, measures of their ceramic properties, and particle size analysis. The results showed that the solid-state reactions, during the sintering process, were efficient and the produced material was classified as coarse lightweight aggregate. The process is interesting for the sintering of aggregates, and can be controlled by composition, particle size, temperature gradient and gaseous flow. (author)

Influence of bagasse ash and recycled concrete aggregate on hardened properties of high-strength concrete

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P. Rattanachu

2018-04-01

Full Text Available This research aimed to use of bagasse ash as a cement replacement in high-strength recycled aggregate concrete (HS-RAC. Crushed limestone was replaced with 100% recycled concrete aggregate (RCA and the ground bagasse ash (GBA was used to partially replace ordinary Portland cement (OPC at 20, 35 and 50%wt of binder to cast HS-RAC. The results indicated that the replacing of crushed limestone with RCA had a negative impact on the properties of the concrete. Increasing the amount of GBA in HS-RAC resulted in a decrease in density and an increase in the volume of permeable pore space. The concrete mixtures prepared with 20%wt GBA replacement of OPC promoted greater the compressive strength than the conventional concrete (CT concrete at 90 days or more. HS-RAC with GBA (up to 50% was more durable in terms of chloride ion penetration resistance, although it had lower compressive strength than the CT concrete.

Investigation on the Combined Effect of Fibers and Cement on the Mechanical Performance of Foamed Bitumen Mixtures Containing 100% RAP

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Ehsan Ashouri Taziani

2016-01-01

Full Text Available Concerns about virgin aggregate sources and increasing demands for construction materials of transport infrastructures as the key parameters in development are the most important reasons, which convinced pavement engineers to develop new methods in order to use higher amount of recycled asphalt pavement (RAP. One of the common methodologies to produce mixtures containing RAP is foamed bitumen mix (FBM. In addition, according to previous research studies, incorporating various types of fibers and hydraulic binders such as cement could significantly improve the mechanical performance of mixtures. The present research study evaluated FBM containing 100% RAP and two types of fiber and Portland cement. Dynamic modulus, unconfined dynamic creep compression, and indirect tensile strength were evaluated in the laboratory at optimum moisture content, which was investigated in this research. Both types of fiber and cement proved to enhance specific properties of mixtures.

Iron-reducing bacteria accumulate ferric oxyhydroxide nanoparticle aggregates that may support planktonic growth.

Science.gov (United States)

Luef, Birgit; Fakra, Sirine C; Csencsits, Roseann; Wrighton, Kelly C; Williams, Kenneth H; Wilkins, Michael J; Downing, Kenneth H; Long, Philip E; Comolli, Luis R; Banfield, Jillian F

2013-02-01

Iron-reducing bacteria (FeRB) play key roles in anaerobic metal and carbon cycling and carry out biogeochemical transformations that can be harnessed for environmental bioremediation. A subset of FeRB require direct contact with Fe(III)-bearing minerals for dissimilatory growth, yet these bacteria must move between mineral particles. Furthermore, they proliferate in planktonic consortia during biostimulation experiments. Thus, a key question is how such organisms can sustain growth under these conditions. Here we characterized planktonic microbial communities sampled from an aquifer in Rifle, Colorado, USA, close to the peak of iron reduction following in situ acetate amendment. Samples were cryo-plunged on site and subsequently examined using correlated two- and three-dimensional cryogenic transmission electron microscopy (cryo-TEM) and scanning transmission X-ray microscopy (STXM). The outer membranes of most cells were decorated with aggregates up to 150 nm in diameter composed of ∼3 nm wide amorphous, Fe-rich nanoparticles. Fluorescent in situ hybridization of lineage-specific probes applied to rRNA of cells subsequently imaged via cryo-TEM identified Geobacter spp., a well-studied group of FeRB. STXM results at the Fe L(2,3) absorption edges indicate that nanoparticle aggregates contain a variable mixture of Fe(II)-Fe(III), and are generally enriched in Fe(III). Geobacter bemidjiensis cultivated anaerobically in the laboratory on acetate and hydrous ferric oxyhydroxides also accumulated mixed-valence nanoparticle aggregates. In field-collected samples, FeRB with a wide variety of morphologies were associated with nano-aggregates, indicating that cell surface Fe(III) accumulation may be a general mechanism by which FeRB can grow while in planktonic suspension.

Heating of Porous Icy Dust Aggregates

Energy Technology Data Exchange (ETDEWEB)

Sirono, Sin-iti [Earth and Environmental Sciences, Nagoya University, Tikusa-ku, Furo-cho, Nagoya 464-8601 (Japan)

2017-06-10

At the beginning of planetary formation, highly porous dust aggregates are formed through coagulation of dust grains. Outside the snowline, the main component of an aggregate is H{sub 2}O ice. Because H{sub 2}O ice is formed in amorphous form, its thermal conductivity is extremely small. Therefore, the thermal conductivity of an icy dust aggregate is low. There is a possibility of heating inside an aggregate owing to the decay of radionuclides. It is shown that the temperature increases substantially inside an aggregate, leading to crystallization of amorphous ice. During the crystallization, the temperature further increases sufficiently to continue sintering. The mechanical properties of icy dust aggregates change, and the collisional evolution of dust aggregates is affected by the sintering.

Synergy of aggregation pheromone with methyl (E,E,Z)-2,4,6-decatrienoate in attraction of brown marmorated stink bug, Halyomorpha halys

Science.gov (United States)

The male-produced aggregation pheromone of the brown marmorated stink bug ((BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae)), recently identified as a mixture of (3S,6S,7R,10S)-10,11-epoxy-1-bisabolen-3-ol and (3S,6S,7R,10R)-10,11-epoxy-1-bisabolen-3-ol, offers new opportunities for manage...

Contributory Factors Related to Permanent Deformation of Hot Asphalt Mixtures

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Alaa Husein Abd

2017-03-01

Full Text Available Permanent deformation (Rutting of asphalt pavements which appears in many roads in Iraq, have caused a major impact on pavement performance by reducing the useful service life of pavement and creating services hazards for highway users. The main objective of this research is investigating the effect of some contributory factors related to permanent deformation of asphalt concrete mixture. To meet the objectives of this research, available local materials are used including asphalt binder, aggregates, mineral filler and modified asphalt binder. The Superpave mix design system was adopted with varying volumetric compositions. The Superpave Gyratory Compactor was used to compact 24 asphalt concrete cylindrical specimens. To collect the required data and investigate the development of permanent deformation in asphalt concrete under repeated loadings, Wheel-Tracking apparatus has been used in a factorial testing program during which 44 slab samples; with dimensions of 400×300×50 mm; were tested to simulate . actual pavement. Based on wheel-tracking test results, it has been concluded that increasing the compaction temperature from 110 to 150ºC caused a decreasing in permanent deformation by 20.5 and 15.6 percent for coarse and fine gradation control asphalt mixtures respectively. While the permanent deformation decreased about 21.3 percent when the compaction temperature is increased from 110 to 150ºC for coarse gradation asphalt mixtures modified with styrene butadiene styrene SBS with 3 percent by asphalt binder weight.

GENERAL: Kinetic Behaviors of Catalysis-Driven Growth of Three-Species Aggregates on Base of Exchange-Driven Aggregations

Science.gov (United States)

Sun, Yun-Fei; Chen, Dan; Lin, Zhen-Quan; Ke, Jian-Hong

2009-06-01

We propose a solvable aggregation model to mimic the evolution of population A, asset B, and the quantifiable resource C in a society. In this system, the population and asset aggregates themselves grow through self-exchanges with the rate kernels K1(k, j) = K1kj and K2(k, j) = K2kj, respectively. The actions of the population and asset aggregations on the aggregation evolution of resource aggregates are described by the population-catalyzed monomer death of resource aggregates and asset-catalyzed monomer birth of resource aggregates with the rate kernels J1(k, j) = J1k and J2(k, j) = J2k, respectively. Meanwhile, the asset and resource aggregates conjunctly catalyze the monomer birth of population aggregates with the rate kernel I1(k, i, j) = I1kiμjη, and population and resource aggregates conjunctly catalyze the monomer birth of asset aggregates with the rate kernel I2(k, i, j) = I2kivjη. The kinetic behaviors of species A, B, and C are investigated by means of the mean-field rate equation approach. The effects of the population-catalyzed death and asset-catalyzed birth on the evolution of resource aggregates based on the self-exchanges of population and asset appear in effective forms. The coefficients of the effective population-catalyzed death and the asset-catalyzed birth are expressed as J1e = J1/K1 and J2e = J2/K2, respectively. The aggregate size distribution of C species is found to be crucially dominated by the competition between the effective death and the effective birth. It satisfies the conventional scaling form, generalized scaling form, and modified scaling form in the cases of J1e J2e, respectively. Meanwhile, we also find the aggregate size distributions of populations and assets both fall into two distinct categories for different parameters μ, ν, and η: (i) When μ = ν = η = 0 and μ = ν = 0, η = 1, the population and asset aggregates obey the generalized scaling forms; and (ii) When μ = ν = 1, η = 0, and μ = ν = η = 1, the

Model for amorphous aggregation processes

Science.gov (United States)

Stranks, Samuel D.; Ecroyd, Heath; van Sluyter, Steven; Waters, Elizabeth J.; Carver, John A.; von Smekal, Lorenz

2009-11-01

The amorphous aggregation of proteins is associated with many phenomena, ranging from the formation of protein wine haze to the development of cataract in the eye lens and the precipitation of recombinant proteins during their expression and purification. While much literature exists describing models for linear protein aggregation, such as amyloid fibril formation, there are few reports of models which address amorphous aggregation. Here, we propose a model to describe the amorphous aggregation of proteins which is also more widely applicable to other situations where a similar process occurs, such as in the formation of colloids and nanoclusters. As first applications of the model, we have tested it against experimental turbidimetry data of three proteins relevant to the wine industry and biochemistry, namely, thaumatin, a thaumatinlike protein, and α -lactalbumin. The model is very robust and describes amorphous experimental data to a high degree of accuracy. Details about the aggregation process, such as shape parameters of the aggregates and rate constants, can also be extracted.

Characterization and influence of fine recycled aggregates on masonry mortars properties

Directory of Open Access Journals (Sweden)

Saiz-Martínez, P.

2015-09-01

Full Text Available This research aims to study mechanical behaviour and relevant properties of masonry mortars fabricated using fine recycled aggregate in different mixture proportions. Fine recycled aggregates samples originated from the ceramic and concrete recycling process and coming from two recycling plants of Madrid region have been used. Tests were performed using 1:3:0.5 volumetric cement-to-aggregate-to-water ratio. Standardized sand with fine recycled aggregate replacement percentages were: 10%, 15%, 25%, 35% and 45%. A continuous size distribution curve can be observed and the main crystalline phases determined have been quartz, calcite and gypsum. Compressive strength, shrinkage and bond strength tests revealed poorer performance of recycled mortars compared to the conventional mortars; however, specific values are within the limits established by the manufacturers and standards. This study shows that cement-based mortars prepared with volumetric ratio 1:3:0.5 may contain up to 45% of fine recycled aggregates, without their properties being affected and without presenting significant losses.Esta investigación estudia el comportamiento mecánico y las propiedades más relevantes de los morteros de albañilería fabricados usando arenas recicladas en diferentes proporciones. Muestras pertenecientes a la línea de reciclaje cerámica y de hormigón proceden de dos centrales de reciclaje de la Comunidad de Madrid. Los ensayos se realizaron con una dosificación 1:3:0,5. Los porcentajes de arena reciclada fueron: 10%, 15%, 25%, 35% y 45%. Se observa una línea granulométrica continua y las principales fases cristalinas encontradas son cuarzo, calcita y yeso. Los ensayos de resistencia a compresión, retracción y adherencia muestran un peor comportamiento en los morteros reciclados frente a los morteros elaborados con arena normalizada, aunque dentro de los límites establecidos por normativas y fabricantes. Se deduce que, los morteros de alba

A comparative study on the aggregating effects of guanidine thiocyanate, guanidine hydrochloride and urea on lysozyme aggregation

Energy Technology Data Exchange (ETDEWEB)

Emadi, Saeed, E-mail: emadi@iasbs.ac.ir; Behzadi, Maliheh

2014-08-08

Highlights: • Lysozyme aggregated in guanidine thiocyanate (1.0 and 2.0 M). • Lysozyme aggregated in guanidine hydrochloride (4 and 5 M). • Lysozyme did not aggregated at any concentration (0.5–5 M) of urea. • Unfolding pathway is more important than unfolding per se in aggregation. - Abstract: Protein aggregation and its subsequent deposition in different tissues culminate in a diverse range of diseases collectively known as amyloidoses. Aggregation of hen or human lysozyme depends on certain conditions, namely acidic pH or the presence of additives. In the present study, the effects on the aggregation of hen egg-white lysozyme via incubation in concentrated solutions of three different chaotropic agents namely guanidine thiocyanate, guanidine hydrochloride and urea were investigated. Here we used three different methods for the detection of the aggregates, thioflavin T fluorescence, circular dichroism spectroscopy and atomic force microscopy. Our results showed that upon incubation with different concentrations (0.5, 1.0, 2.0, 3.0, 4.0, 5.0 M) of the chemical denaturants, lysozyme was aggregated at low concentrations of guanidine thiocyanate (1.0 and 2.0 M) and at high concentrations of guanidine hydrochloride (4 and 5 M), although no fibril formation was detected. In the case of urea, no aggregation was observed at any concentration.

Stability studies of colloidal silica dispersions in binary solvent mixtures

International Nuclear Information System (INIS)

Bean, Keith Howard

1997-01-01

A series of monodispersed colloidal silica dispersions, of varying radii, has been prepared. These particles are hydrophilic in nature due to the presence of surface silanol groups. Some of the particles have been rendered hydrophobic by terminally grafting n-alkyl (C 18 ) chains to the surface. The stability of dispersions of these various particles has been studied in binary mixtures of liquids, namely (i) ethanol and cyclohexane, and (ii) benzene and n-heptane. The ethanol - cyclohexane systems have been studied using a variety of techniques. Adsorption excess isotherms have been established and electrophoretic mobility measurements have been made. The predicted stability of the dispersions from D.V.L.O. calculations is compared to the observed stability. The hydrophilic silica particles behave as predicted by the calculations, with the zeta potential decreasing and the van der Waals attraction increasing with increasing cyclohexane concentration. The hydrophobic particles behave differently than expected, and the stability as a function of solvent mixture composition does not show a uniform trend. The effect of varying the coverage of C 18 chains on the surface and the effect of trace water in the systems has also been investigated. Organophilic silica dispersions in benzene - n-heptane solvent mixtures show weak aggregation and phase separation into a diffuse 'gas-like' phase and a more concentrated 'liquid-like' phase, analogous to molecular condensation processes. Calculations of the van der Waals potential as a function of solvent mixture composition show good agreement with the observed stability. Determination of the number of particles in each phase at equilibrium allows the energy of flocculation to be determined using a simple thermodynamic relationship. Finally, the addition of an AB block copolymer to organophilic silica particles in benzene n-heptane solvent mixtures has been shown to have a marked effect on the dispersion stability. This stability

Influence of granitic aggregates from Northeast Brazil on the alkali-aggregate reaction

Energy Technology Data Exchange (ETDEWEB)

Gomes Neto, David de Paiva; Santana, Rodrigo Soares de; Barreto, Ledjane Silva, E-mail: pvgomes@uol.com.br [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Dept. de Ciencias dos Materiais e Engenharia; Conceicao, Herbert; Lisboa, Vinicios Anselmo Carvalho [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Dept. de Geologia

2014-08-15

The alkali-aggregate reaction (AAR) in concrete structures is a problem that has concerned engineers and researchers for decades. This reaction occurs when silicates in the aggregates react with the alkalis, forming an expanded gel that can cause cracks in the concrete and reduce its lifespan. The aim of this study was to characterize three coarse granitic aggregates employed in concrete production in northeastern Brazil, correlating petrographic analysis with the kinetics of silica dissolution and the evolution of expansions in mortar bars, assisted by SEM/EDS, XRD, and EDX. The presence of grains showing recrystallization into individual microcrystalline quartz subgrains was associated with faster dissolution of silica and greater expansion in mortar bars. Aggregates showing substantial deformation, such as stretched grains of quartz with strong undulatory extinction, experienced slower dissolution, with reaction and expansion occurring over longer periods that could not be detected using accelerated tests with mortar bars. (author)

Evaluation of permanent deformation characteristics of unmodified and Polyethylene Terephthalate modified asphalt mixtures using dynamic creep test

International Nuclear Information System (INIS)

Baghaee Moghaddam, Taher; Soltani, Mehrtash; Karim, Mohamed Rehan

2014-01-01

Highlights: • Waste PET was utilized as modifier in asphalt mixture. • Deformation characteristics of asphalt mixtures were assessed. • Dynamic creep test was conducted at different temperatures and stress levels. • Permanent deformation models were introduced. - Abstract: One of the major types of plastics that can be found in Municipal Solid Waste (MSW) is Polyethylene Terephthalate (PET) which is a non-biodegradable semi-crystalline thermoplastic polymer, and is considered as polyester material. Generating large amount of waste PET, mainly as bottles, would cause environmental hazards by disposing in landfills. This paper aims to evaluate effects of utilizing waste PET flakes as modifier in asphalt mixture as an alternative solution to overcome the potential risks arise from producing large amount of waste PET as well as evaluating the deformation characteristics of unmodified and PET modified asphalt mixtures. To achieve this aim, different percentages of PET were designated for this investigation, namely: 0%, 0.2%, 0.4%, 0.6%, 0.8% and 1% by weight of aggregate particles, and dynamic creep test was performed at different stress levels (300 kPa and 400 kPa) and temperatures (10 °C, 25 °C and 40 °C). Consequently, Zhou three-stage model was developed. The results showed that permanent deformation characteristics of asphalt mixture were considerably improved by utilization of PET modification, when the permanent strain was remarkably decreased in PET modified mixture compared to the conventional mixture at all stress levels and temperatures. Besides, based on Zhou model, it was concluded that elastic and visco-elastic properties of asphalt mixture were improved by application of PET modification

Fractal Aggregates in Tennis Ball Systems

Science.gov (United States)

Sabin, J.; Bandin, M.; Prieto, G.; Sarmiento, F.

2009-01-01

We present a new practical exercise to explain the mechanisms of aggregation of some colloids which are otherwise not easy to understand. We have used tennis balls to simulate, in a visual way, the aggregation of colloids under reaction-limited colloid aggregation (RLCA) and diffusion-limited colloid aggregation (DLCA) regimes. We have used the…

A Functional Reference Architecture for Aggregators

DEFF Research Database (Denmark)

Bondy, Daniel Esteban Morales; Heussen, Kai; Gehrke, Oliver

2015-01-01

Aggregators are considered to be a key enabling technology for harvesting power system services from distributed energy resources (DER). As a precondition for more widespread use of aggregators in power systems, methods for comparing and validating aggregator designs must be established. This paper...... proposes a functional reference architecture for aggregators to address this requirement....

Aggregation server for grid-integrated vehicles

Science.gov (United States)

Kempton, Willett

2015-05-26

Methods, systems, and apparatus for aggregating electric power flow between an electric grid and electric vehicles are disclosed. An apparatus for aggregating power flow may include a memory and a processor coupled to the memory to receive electric vehicle equipment (EVE) attributes from a plurality of EVEs, aggregate EVE attributes, predict total available capacity based on the EVE attributes, and dispatch at least a portion of the total available capacity to the grid. Power flow may be aggregated by receiving EVE operational parameters from each EVE, aggregating the received EVE operational parameters, predicting total available capacity based on the aggregated EVE operational parameters, and dispatching at least a portion of the total available capacity to the grid.

Sand Cement Brick Containing Recycled Concrete Aggregate as Fine-Aggregate Replacement

Directory of Open Access Journals (Sweden)

Sheikh Khalid Faisal

2017-01-01

Full Text Available Nowadays, the usage amount of the concrete is increasing drastically. The construction industry is a huge consumer of natural consumer. It is also producing the huge wastage products. The usage of concrete has been charged to be not environmentally friendly due to depletion of reserve natural resources, high energy consumption and disposal issues. The conservation of natural resources and reduction of disposal site by reuse and recycling waste material was interest possibilites. The aim of this study is to determine the physical and mechanical properties of sand cement brick containing recycled concrete aggregate and to determine the optimum mix ratio containing recycled concrete aggregate. An experiment done by comparing the result of control specimen using 100% natural sand with recycled concrete aggregate replacement specimen by weight for 55%, 65%, and 75%. The sample was tested under density, compressive strength, flexural strength and water absorption to study the effect of using recycled concrete aggregate on the physical and mechanical properties of bricks. The result shows that the replacement of natural sand by recycled concrete aggregate at the level of 55% provide the highest compressive and flexural strength compared to other percentage and control specimen. However, if the replacement higher than 55%, the strength of brick was decreased for compressive and flexural strength, respectively. The relationship of compressive-flexural strength is determined from statistical analysis and the predicted result can be obtained by using equation ff,RCA = 0.5375 (fc0.3272.

Aggregation effects on tritium-based mean transit times and young water fractions in spatially heterogeneous catchments and groundwater systems

Directory of Open Access Journals (Sweden)

M. K. Stewart

2017-09-01

Full Text Available Kirchner (2016a demonstrated that aggregation errors due to spatial heterogeneity, represented by two homogeneous subcatchments, could cause severe underestimation of the mean transit times (MTTs of water travelling through catchments when simple lumped parameter models were applied to interpret seasonal tracer cycle data. Here we examine the effects of such errors on the MTTs and young water fractions estimated using tritium concentrations in two-part hydrological systems. We find that MTTs derived from tritium concentrations in streamflow are just as susceptible to aggregation bias as those from seasonal tracer cycles. Likewise, groundwater wells or springs fed by two or more water sources with different MTTs will also have aggregation bias. However, the transit times over which the biases are manifested are different because the two methods are applicable over different time ranges, up to 5 years for seasonal tracer cycles and up to 200 years for tritium concentrations. Our virtual experiments with two water components show that the aggregation errors are larger when the MTT differences between the components are larger and the amounts of the components are each close to 50 % of the mixture. We also find that young water fractions derived from tritium (based on a young water threshold of 18 years are almost immune to aggregation errors as were those derived from seasonal tracer cycles with a threshold of about 2 months.

Aggregation pheromone of coconut rhinoceros beetle,Oryctes rhinoceros (L.) (coleoptera: Scarabaeidae).

Science.gov (United States)

Hallett, R H; Perez, A L; Gries, G; Gries, R; Pierce, H D; Yue, J; Oehlschlager, A C; Gonzalez, L M; Borden, J H

1995-10-01

Male coconut rhinoceros beetles,Oryctes rhinoceros (L.), produce three sex-specific compounds, ethyl 4-methyloctanoate, ethyl 4-methylheptanoate, and 4-methyloctanoic acid, the first of which is an aggregation pheromone. Synthesis of these compounds involving conjugate addition of organocuprates to ethyl acrylate is reported. In field trapping experiments, (4S)-ethyl 4-methyloctanoate and the racemic mixture were equally attractive and 10 times more effective in attracting beetles than ethyl chrysanthemumate, a previously recommended attractant. Ethyl 4-methylheptanoate was as attractive as ethyl chrysanthemumate and more attractive than 4-methyloctanoic acid, but further studies are required before it can be classed as an aggregation pheromone. Compared to ethyl 4-methyloctanoate alone, combinations of the three male-produced compounds did not increase attraction, whereas addition of freshly rotting oil palm fruit bunches to pheromone-baited traps significantly enhanced attraction. With increasing dose, captures ofO. rhinoceros increased, but doses of 6, 9, and 18 mg/day were competitive with 30 mg/day lures. Newly designed vane traps were more effective in capturing beetles than were barrier or pitfall traps. Results of this study indicate that there is potential for using ethyl 4-methyloctanoate in operational programs to controlO. rhinoceros in oil palm plantations.

Research of Deformation of Clay Soil Mixtures Mixtures

OpenAIRE

Romas Girkontas; Tadas Tamošiūnas; Andrius Savickas

2014-01-01

The aim of this article is to determine clay soils and clay soils mixtures deformations during drying. Experiments consisted from: a) clay and clay mixtures bridges (height ~ 0,30 m, span ~ 1,00 m); b) tiles of clay and clay, sand and straw (height, length, wide); c) cylinders of clay; clay and straw; clay, straw and sand (diameter; height). According to the findings recommendations for clay and clay mixtures drying technology application were presented. During the experiment clay bridge bear...

Observing Convective Aggregation

Science.gov (United States)

Holloway, Christopher E.; Wing, Allison A.; Bony, Sandrine; Muller, Caroline; Masunaga, Hirohiko; L'Ecuyer, Tristan S.; Turner, David D.; Zuidema, Paquita

2017-11-01

Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network.

Deciding which chemical mixtures risk assessment methods work best for what mixtures

International Nuclear Information System (INIS)

Teuschler, Linda K.

2007-01-01

The most commonly used chemical mixtures risk assessment methods involve simple notions of additivity and toxicological similarity. Newer methods are emerging in response to the complexities of chemical mixture exposures and effects. Factors based on both science and policy drive decisions regarding whether to conduct a chemical mixtures risk assessment and, if so, which methods to employ. Scientific considerations are based on positive evidence of joint toxic action, elevated human exposure conditions or the potential for significant impacts on human health. Policy issues include legislative drivers that may mandate action even though adequate toxicity data on a specific mixture may not be available and risk assessment goals that impact the choice of risk assessment method to obtain the amount of health protection desired. This paper discusses three important concepts used to choose among available approaches for conducting a chemical mixtures risk assessment: (1) additive joint toxic action of mixture components; (2) toxicological interactions of mixture components; and (3) chemical composition of complex mixtures. It is proposed that scientific support for basic assumptions used in chemical mixtures risk assessment should be developed by expert panels, risk assessment methods experts, and laboratory toxicologists. This is imperative to further develop and refine quantitative methods and provide guidance on their appropriate applications. Risk assessors need scientific support for chemical mixtures risk assessment methods in the form of toxicological data on joint toxic action for high priority mixtures, statistical methods for analyzing dose-response for mixtures, and toxicological and statistical criteria for determining sufficient similarity of complex mixtures

What favors convective aggregation and why?

Science.gov (United States)

Muller, Caroline; Bony, Sandrine

2015-07-01

The organization of convection is ubiquitous, but its physical understanding remains limited. One particular type of organization is the spatial self-aggregation of convection, taking the form of cloud clusters, or tropical cyclones in the presence of rotation. We show that several physical processes can give rise to self-aggregation and highlight the key features responsible for it, using idealized simulations. Longwave radiative feedbacks yield a "radiative aggregation." In that case, sufficient spatial variability of radiative cooling rates yields a low-level circulation, which induces the upgradient energy transport and radiative-convective instability. Not only do vertically integrated radiative budgets matter but the vertical profile of cooling is also crucial. Convective aggregation is facilitated when downdrafts below clouds are weak ("moisture-memory aggregation"), and this is sufficient to trigger aggregation in the absence of longwave radiative feedbacks. These results shed some light on the sensitivity of self-aggregation to various parameters, including resolution or domain size.

Structural transition in aqueous lipid/bile salt [DPPC/NaDC] supramolecular aggregates: SANS and DLS study

International Nuclear Information System (INIS)

Kiselev, M.A.; Janich, M.; Hildebrand, A.; Strunz, P.; Neubert, R.H.H.; Lombardo, D.

2013-01-01

Highlights: • Self-assembly in model DPPC lipids and NaDC bile salt by SANS and DLS experiments. • Bile salt creates structural interference against cohesive tendency of DPPC bilayers. • NaDC steric interactions cause transition toward different supramolecular structures. - Abstract: Small angle neutron scattering (SANS) and dynamic light scattering (DLS) were used to study different aggregation states in sodium deoxycholate (NaDC)-phosphatidylcholine systems at T = 60 °C. Size and shape of the aggregates investigated as a function of the NaDC bile salt concentration (at the constant DPPC concentration of 6 mM) indicate a strong dependence of the size and morphology of the generated aggregates on the relative amount of NaDC bile salt. More specifically large occupied area of the bile salt induces a steric interaction which promotes the transition toward a variety of supramolecular structures ranging from ellipsoidal vesicles, ribbon-like structures, up to final spherical mixed micelles at the large amount of bile salt of 10 mM NaDC. The findings of the obtained results give important insight for understanding the formation of different topologies in aqueous lipid–bile salt mixtures as well as stimulate new routes for liposome reconstitution–solubilisation processes suitable for technological applications

Synthesis of new N-heteroaromatic attached tetraphenylethene based luminogens having aggregation induced emission and their applications in organic light emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Odabas, Serhat [Department of Chemistry, Middle East Technical University, 06800 Ankara (Turkey); The Scientific and Technological Research Council of Turkey (TUBITAK), Marmara Research Center, Institute of Chemical Technology, P.K. 21, 41470 Gebze, Kocaeli (Turkey); Tekin, Emine [The Scientific and Technological Research Council of Turkey (TUBITAK), Marmara Research Center, Material Institute, P.K. 21, 41470 Gebze, Kocaeli (Turkey); Turksoy, Figen, E-mail: figen.turksoy@tubitak.gov.tr [The Scientific and Technological Research Council of Turkey (TUBITAK), Marmara Research Center, Institute of Chemical Technology, P.K. 21, 41470 Gebze, Kocaeli (Turkey); Tanyeli, Cihangir, E-mail: tanyeli@metu.edu.tr [Department of Chemistry, Middle East Technical University, 06800 Ankara (Turkey)

2016-08-15

Aggregation induced emission is an auxiliary property that can eliminate the aggregation caused quenching effect. It is a common undesired emission characteristic of most bulky aromatic molecules. Tetraphenylethene, with its unique features, is the most commonly studied molecule having aggregation induced emission property. In this work four N heteroaromatic attached tetraphenylethene derivatives were synthesized via inexpensive C–N bond formation reactions. The synthesized luminogens showed good thermal properties, having high Td values between 366 °C and 505 °C. All four tetraphenylethene derivatives exhibited excellent aggregation induced emission properties and there was an up to 200-fold increase in their fluorescence intensities. According to the time-resolved emission decay experimental analyses, all four luminogens showed two relaxation pathways in a THF – water mixture (10–90%). Non-doped turquoise and light green OLED devices using the synthesized luminogens as a light emitting layer exhibited a maximum brightness up to 2600 cd/m{sup 2}, a maximum current efficiency up to 3.6 cd/A, turn-on voltages between 7.0 and 10.0 V, and external quantum efficiencies up to 1.5%. - Highlights: • A series of N-heterocyclic attached tetraphenylethene cored luminogens are synthesized and characterized. • Excellent thermal and aggregation induced emission properties are observed. • OLEDs are fabricated using synthesized luminogens as non-doped emitting layers.

Curcumin inhibits aggregation of alpha-synuclein.

Science.gov (United States)

Pandey, Neeraj; Strider, Jeffrey; Nolan, William C; Yan, Sherry X; Galvin, James E

2008-04-01

Aggregation of amyloid-beta protein (Abeta) is a key pathogenic event in Alzheimer's disease (AD). Curcumin, a constituent of the Indian spice Turmeric is structurally similar to Congo Red and has been demonstrated to bind Abeta amyloid and prevent further oligomerization of Abeta monomers onto growing amyloid beta-sheets. Reasoning that oligomerization kinetics and mechanism of amyloid formation are similar in Parkinson's disease (PD) and AD, we investigated the effect of curcumin on alpha-synuclein (AS) protein aggregation. In vitro model of AS aggregation was developed by treatment of purified AS protein (wild-type) with 1 mM Fe3+ (Fenton reaction). It was observed that the addition of curcumin inhibited aggregation in a dose-dependent manner and increased AS solubility. The aggregation-inhibiting effect of curcumin was next investigated in cell culture utilizing catecholaminergic SH-SY5Y cell line. A model system was developed in which the red fluorescent protein (DsRed2) was fused with A53T mutant of AS and its aggregation examined under different concentrations of curcumin. To estimate aggregation in an unbiased manner, a protocol was developed in which the images were captured automatically through a high-throughput cell-based screening microscope. The obtained images were processed automatically for aggregates within a defined dimension of 1-6 microm. Greater than 32% decrease in mutant alpha-synuclein aggregation was observed within 48 h subsequent to curcumin addition. Our data suggest that curcumin inhibits AS oligomerization into higher molecular weight aggregates and therefore should be further explored as a potential therapeutic compound for PD and related disorders.

Adsorption properties of biologically active derivatives of quaternary ammonium surfactants and their mixtures at aqueous/air interface. I. Equilibrium surface tension, surfactant aggregation and wettability.

Science.gov (United States)

Rojewska, Monika; Biadasz, Andrzej; Kotkowiak, Michał; Olejnik, Anna; Rychlik, Joanna; Dudkowiak, Alina; Prochaska, Krystyna

2013-10-01

The adsorption properties of surfactant mixtures containing two types of quaternary derivatives of lysosomotropic substances: alkyl N,N-dimethylalaninates methobromides and alkyl N,N-dimethylglycinates methobromides were studied. Quantitative and qualitative description of the adsorption process was carried out on the basis of experimentally obtained equilibrium surface tension isotherms. The results indicated that most of the systems studied revealed synergistic effect both in adsorption and wetting properties. In vitro studies on human cancer cells were undertaken and the data obtained showed that the mixtures suppressed the cancer cells' proliferation more effectively than individual components. Results of preliminary research on the interaction of catanionic mixtures with phospholipids suggested a possibility of a strong penetration of cell membranes by the mixtures investigated. Copyright © 2013 Elsevier B.V. All rights reserved.

Platelet activation and aggregation

DEFF Research Database (Denmark)

Jensen, Maria Sander; Larsen, O H; Christiansen, Kirsten

2013-01-01

This study introduces a new laboratory model of whole blood platelet aggregation stimulated by endogenously generated thrombin, and explores this aspect in haemophilia A in which impaired thrombin generation is a major hallmark. The method was established to measure platelet aggregation initiated...

Role of Multicellular Aggregates in Biofilm Formation

Directory of Open Access Journals (Sweden)

Kasper N. Kragh

2016-03-01

Full Text Available In traditional models of in vitro biofilm development, individual bacterial cells seed a surface, multiply, and mature into multicellular, three-dimensional structures. Much research has been devoted to elucidating the mechanisms governing the initial attachment of single cells to surfaces. However, in natural environments and during infection, bacterial cells tend to clump as multicellular aggregates, and biofilms can also slough off aggregates as a part of the dispersal process. This makes it likely that biofilms are often seeded by aggregates and single cells, yet how these aggregates impact biofilm initiation and development is not known. Here we use a combination of experimental and computational approaches to determine the relative fitness of single cells and preformed aggregates during early development of Pseudomonas aeruginosa biofilms. We find that the relative fitness of aggregates depends markedly on the density of surrounding single cells, i.e., the level of competition for growth resources. When competition between aggregates and single cells is low, an aggregate has a growth disadvantage because the aggregate interior has poor access to growth resources. However, if competition is high, aggregates exhibit higher fitness, because extending vertically above the surface gives cells at the top of aggregates better access to growth resources. Other advantages of seeding by aggregates, such as earlier switching to a biofilm-like phenotype and enhanced resilience toward antibiotics and immune response, may add to this ecological benefit. Our findings suggest that current models of biofilm formation should be reconsidered to incorporate the role of aggregates in biofilm initiation.

Pre-aggregation for Probability Distributions

DEFF Research Database (Denmark)

Timko, Igor; Dyreson, Curtis E.; Pedersen, Torben Bach

Motivated by the increasing need to analyze complex uncertain multidimensional data (e.g., in order to optimize and personalize location-based services), this paper proposes novel types of {\\em probabilistic} OLAP queries that operate on aggregate values that are probability distributions...... and the techniques to process these queries. The paper also presents the methods for computing the probability distributions, which enables pre-aggregation, and for using the pre-aggregated distributions for further aggregation. In order to achieve good time and space efficiency, the methods perform approximate...... multidimensional data analysis that is considered in this paper (i.e., approximate processing of probabilistic OLAP queries over probability distributions)....

Dynamic and thermodynamic characteristics associated with the glass transition of amorphous trehalose-water mixtures.

Science.gov (United States)

Weng, Lindong; Elliott, Gloria D

2014-06-21

The glass transition temperature Tg of biopreservative formulations is important for predicting the long-term storage of biological specimens. As a complementary tool to thermal analysis techniques, which are the mainstay for determining Tg, molecular dynamics simulations have been successfully applied to predict the Tg of several protectants and their mixtures with water. These molecular analyses, however, rarely focused on the glass transition behavior of aqueous trehalose solutions, a subject that has attracted wide scientific attention via experimental approaches. Important behavior, such as hydrogen-bonding dynamics and self-aggregation has yet to be explored in detail, particularly below, or in the vicinity of, Tg. Using molecular dynamics simulations of several dynamic and thermodynamic properties, this study reproduced the supplemented phase diagram of trehalose-water mixtures (i.e., Tg as a function of the solution composition) based on experimental data. The structure and dynamics of the hydrogen-bonding network in the trehalose-water systems were also analyzed. The hydrogen-bonding lifetime was determined to be an order of magnitude higher in the glassy state than in the liquid state, while the constitution of the hydrogen-bonding network exhibited no noticeable change through the glass transition. It was also found that trehalose molecules preferred to form small, scattered clusters above Tg, but self-aggregation was substantially increased below Tg. The average cluster size in the glassy state was observed to be dependent on the trehalose concentration. Our findings provided insights into the glass transition characteristics of aqueous trehalose solutions as they relate to biopreservation.

Interplay of sequence, topology and termini charge in determining the stability of the aggregates of GNNQQNY mutants: a molecular dynamics study.

Directory of Open Access Journals (Sweden)

Alka Srivastava

Full Text Available This study explores the stabilities of single sheet parallel systems of three sequence variants of 1GNNQQNY7, N2D, N2S and N6D, with variations in aggregate size (5-8 and termini charge (charged or neutral. The aggregates were simulated at 300 and 330 K. These mutations decrease amyloid formation in the yeast prion protein Sup35. The present study finds that these mutations cause instability even in the peptide context. The protonation status of termini is found to be a key determinant of stabilities; other determinants are sequence, position of mutation and aggregate size. All systems with charged termini are unstable, whereas both stable and unstable systems are found when the termini are neutral. When termini are charged, the largest stable aggregate for the N2S and N6D systems has 3 to 4 peptides whereas N2D mutation supports oligomers of larger size (5-and 6-mers as well. Mutation at 2nd position (N2S and N2D results in fewer H-bonds at the mutated as well as neighboring (Gly1/Gln4 positions. However, no such effect is found if mutation is at 6th position (N6D. The effect of Asn→Asp mutation depends on the position and termini charge: it is more destabilizing at the 2nd position than at the 6th in case of neutral termini, however, the opposite is true in case of charged termini. Appearance of twist in stable systems and in smaller aggregates formed in unstable systems suggests that twist is integral to amyloid arrangement. Disorder, dissociation or rearrangement of peptides, disintegration or collapse of aggregates and formation of amorphous aggregates observed in these simulations are likely to occur during the early stages of aggregation also. The smaller aggregates formed due to such events have a variety of arrangements of peptides. This suggests polymorphic nature of oligomers and presence of a heterogeneous mixture of oligomers during early stages of aggregation.

Discrete stochastic charging of aggregate grains

Science.gov (United States)

Matthews, Lorin S.; Shotorban, Babak; Hyde, Truell W.

2018-05-01

Dust particles immersed in a plasma environment become charged through the collection of electrons and ions at random times, causing the dust charge to fluctuate about an equilibrium value. Small grains (with radii less than 1 μm) or grains in a tenuous plasma environment are sensitive to single additions of electrons or ions. Here we present a numerical model that allows examination of discrete stochastic charge fluctuations on the surface of aggregate grains and determines the effect of these fluctuations on the dynamics of grain aggregation. We show that the mean and standard deviation of charge on aggregate grains follow the same trends as those predicted for spheres having an equivalent radius, though aggregates exhibit larger variations from the predicted values. In some plasma environments, these charge fluctuations occur on timescales which are relevant for dynamics of aggregate growth. Coupled dynamics and charging models show that charge fluctuations tend to produce aggregates which are much more linear or filamentary than aggregates formed in an environment where the charge is stationary.

Investigation on the Combined Effect of Fibers and Cement on the Mechanical Performance of Foamed Bitumen Mixtures Containing 100% RAP

OpenAIRE

Ehsan Ashouri Taziani; Emanuele Toraldo; Filippo Giustozzi; Maurizio Crispino

2016-01-01

Concerns about virgin aggregate sources and increasing demands for construction materials of transport infrastructures as the key parameters in development are the most important reasons, which convinced pavement engineers to develop new methods in order to use higher amount of recycled asphalt pavement (RAP). One of the common methodologies to produce mixtures containing RAP is foamed bitumen mix (FBM). In addition, according to previous research studies, incorporating various types of fiber...

Prediction of the aggregation propensity of proteins from the primary sequence: aggregation properties of proteomes.

Science.gov (United States)

Castillo, Virginia; Graña-Montes, Ricardo; Sabate, Raimon; Ventura, Salvador

2011-06-01

In the cell, protein folding into stable globular conformations is in competition with aggregation into non-functional and usually toxic structures, since the biophysical properties that promote folding also tend to favor intermolecular contacts, leading to the formation of β-sheet-enriched insoluble assemblies. The formation of protein deposits is linked to at least 20 different human disorders, ranging from dementia to diabetes. Furthermore, protein deposition inside cells represents a major obstacle for the biotechnological production of polypeptides. Importantly, the aggregation behavior of polypeptides appears to be strongly influenced by the intrinsic properties encoded in their sequences and specifically by the presence of selective short regions with high aggregation propensity. This allows computational methods to be used to analyze the aggregation properties of proteins without the previous requirement for structural information. Applications range from the identification of individual amyloidogenic regions in disease-linked polypeptides to the analysis of the aggregation properties of complete proteomes. Herein, we review these theoretical approaches and illustrate how they have become important and useful tools in understanding the molecular mechanisms underlying protein aggregation. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

RasC is required for optimal activation of adenylyl cyclase and Akt/PKB during aggregation.

Science.gov (United States)

Lim, C J; Spiegelman, G B; Weeks, G

2001-08-15

Disruption of Dictyostelium rasC, encoding a Ras subfamily protein, generated cells incapable of aggregation. While rasC expression is enriched in a cell type-specific manner during post-aggregative development, the defect in rasC(-) cells is restricted to aggregation and fully corrected by application of exogenous cAMP pulses. cAMP is not produced in rasC(-) cells stimulated by 2'-deoxy-cAMP, but is produced in response to GTPgammaS in cell lysates, indicating that G-protein-coupled cAMP receptor activation of adenylyl cyclase is regulated by RasC. However, cAMP-induced ERK2 phosphorylation is unaffected in rasC(-) cells, indicating that RasC is not an upstream activator of the mitogen-activated protein kinase required for cAMP relay. rasC(-) cells also exhibit reduced chemotaxis to cAMP during early development and delayed response to periodic cAMP stimuli produced by wild-type cells in chimeric mixtures. Furthermore, cAMP-induced Akt/PKB phosphorylation through a phosphatidylinositide 3-kinase (PI3K)-dependent pathway is dramatically reduced in rasC(-) cells, suggesting that G-protein-coupled serpentine receptor activation of PI3K is regulated by RasC. Cells lacking the RasGEF, AleA, exhibit similar defects as rasC(-) cells, suggesting that AleA may activate RasC.

Evaluation system for CO2 emission of hot asphalt mixture

Directory of Open Access Journals (Sweden)

Bo Peng

2015-04-01

Full Text Available The highway construction industry plays an important role in economic and development, but is also a primary source of carbon emission. Accordingly, with the global climate change, energy conservation and reduction of carbon emissions have become critical issues in the highway construction industry. However, to date, a model for the highway construction industry has not been established. Hence, to implement a low-carbon construction model for highways, this study divided asphalt pavement construction into aggregate stacking, aggregate supply, and other stages, and compiled a list of energy consumption investigation. An appropriate calculation model of CO2 emission was then built. Based on the carbon emission calculation model, the proportion of carbon emissions in each stage was analyzed. The analytic hierarchy process was used to establish the system of asphalt pavement construction with a judgment matrix, thereby enabling calculation of the weight coefficient of each link. In addition, the stages of aggregate heating, asphalt heating, and asphalt mixture mixing were defined as key stages of asphalt pavement construction. Carbon emissions at these stages accounted for approximately 90% of the total carbon emissions. Carbon emissions at each stage and their impact on the environment were quantified and compared. The energy saving construction schemes as well as the environmental and socioeconomic benefits were then proposed. Through these schemes, significant reductions in carbon emissions and costs can be achieved. The results indicate that carbon emissions reduce by 32.30% and 35.93%, whereas costs reduce by 18.58% and 6.03%. The proposed energy-saving and emission reduction scheme can provide a theoretical basis and technical support for the development of low-carbon highway construction.

Understanding curcumin-induced modulation of protein aggregation.

Science.gov (United States)

Ahmad, Basir; Borana, Mohanish S; Chaudhary, Ankur P

2017-07-01

Curcumin, a diarylheptanoid compound, found in spice turmeric is known to alter the aggregation of proteins and reduce the toxicity of the aggregates. This review looks at the molecular basis of modulating protein aggregation and toxicity of the aggregates. Foremost, we identify the interaction of curcumin and its derivatives with proteins/peptides and the effect of their interaction on the conformational stability and unfolding/folding pathway(s). The unfolding/folding processes generate partially folded/unfolded intermediate, which serve as aggregation precursor state. Secondly, we discuss the effect of curcumin binding on the kinetics parameters of the aggregation process, which give information about the mechanism of the aggregation inhibition. We describe, in addition, that curcumin can accelerate/promote fibril formation by binding to oligomeric intermediate(s) accumulated in the aggregation pathway. Finally, we discuss the correlation of curcumin-induced monomeric and/or oligomeric precursor states with aggregate structure and toxicity. On the basis of these discussions, we propose a model describing curcumin-induced inhibition/promotion of formation of amyloid-like fibrils. Copyright © 2016 Elsevier B.V. All rights reserved.

Customer Aggregation: An Opportunity for Green Power?

Energy Technology Data Exchange (ETDEWEB)

Holt, E.; Bird, L.

2001-02-26

We undertook research into the experience of aggregation groups to determine whether customer aggregation offers an opportunity to bring green power choices to more customers. The objectives of this report, therefore, are to (1) identify the different types of aggregation that are occurring today, (2) learn whether aggregation offers an opportunity to advance sales of green power, and (3) share these concepts and approaches with potential aggregators and green power advocates.

Transportation and utilization of aggregates for road construction

Science.gov (United States)

Fladvad, Marit; Wigum, Børge Johannes; Aurstad, Joralf

2017-04-01

Road construction relies on non-renewable aggregate resources as the main construction material. Sources for high-quality aggregate resources are scattered, and requirements for aggregate quality can cause long transport distances between quarry and road construction site. In European countries, the average aggregate consumption per capita is 5 tonnes per year (European Aggregates Association, 2016), while the corresponding figure for Norway is 11 tonnes (Neeb, 2015). Half the Norwegian aggregate production (sand, gravel and crushed rock) is used for road construction. In Norway, aggregate resources have been considered abundant. However, stricter requirement for aggregate quality, and increased concern for sustainability and environmental issues have spurred focus on reduction of transport lengths through better utilization of local aggregate materials. In this research project, information about pavement design and aggregate quality requirements were gathered from a questionnaire sent to selected experts from the World Road Organization (PIARC), European Committee for Standardization (CEN), and Nordic Road Association (NVF). The gathered data was compared to identify differences and similarities for aggregate use in the participating countries. Further, the data was compared to known data from Norway regarding: - amount of aggregates required for a road structure - aggregate transport lengths and related costs A total of 18 countries participated in the survey, represented by either road authorities, research institutions, or contractors. There are large variations in practice for aggregate use among the represented countries, and the selection of countries is sufficient to illustrate a variety in pavement designs, aggregate sizes, and quality requirements for road construction. There are considerable differences in both pavement thickness and aggregate sizes used in the studied countries. Total thicknesses for pavement structures varies from 220 mm to 2400 mm

Aggregated particles caused by instrument artifact

Science.gov (United States)

Pierce, Ashley M.; Loría-Salazar, S. Marcela; Arnott, W. Patrick; Edwards, Grant C.; Miller, Matthieu B.; Gustin, Mae S.

2018-04-01

Previous studies have indicated that superaggregates, clusters of aggregates of soot primary particles, can be formed in large-scale turbulent fires. Due to lower effective densities, higher porosity, and lower aerodynamic diameters, superaggregates may pass through inlets designed to remove particles 2.5 µm in aerodynamic diameter were collected on 36 out of 158 sample days. On preliminary analysis, it was thought that these aggregated particles were superaggregates, depositing past PM10 (particles wind speeds, as well as the use of generators on site. Samples with aggregated particles, referred to as aggregates, were analyzed using a scanning electron microscope for size and shape and energy dispersive X-ray spectroscopy was used for elemental analysis. It was determined, based on the high amounts of aluminum present in the aggregate samples, that a sampling artifact associated with the sample inlet and prolonged, high wind events was the probable reason for the observed aggregates.

Performance estimation for concretes made with recycled aggregates of construction and demolition waste of some Brazilian cities

Directory of Open Access Journals (Sweden)

Antonio Eduardo Bezerra Cabral

2012-12-01

Full Text Available The aim of this paper is to verify the influence of composition variability of recycled aggregates (RA of construction and demolition wastes (CDW on the performance of concretes. Performance was evaluated building mathematical models for compressive strength, modulus of elasticity and drying shrinkage. To obtain such models, an experimental program comprising 50 concrete mixtures was carried out. Specimens were casted, tested and results for compressive strength, modulus of elasticity and drying shrinkage were statistically analyzed. Models inputs are CDW composition observed at seven Brazilian cities. Results confirm that using RA from CDW for concrete building is quite feasible, independently of its composition, once compressive strength and modulus of elasticity still reached considerable values. We concluded the variability presented by recycled aggregates of CDW does not compromise their use for concrete building. However, this information must be used with caution, and experimental tests should always be performed to certify concrete properties.

The alkali–aggregate reaction for various aggregates used in concrete

Directory of Open Access Journals (Sweden)

Calderón, V.

2010-09-01

Full Text Available The aim of this work is to contribute to the knowledge of the interactions between aggregates and the components of the interstitial phase of concrete and to determine whether those aggregates that are subsequently used in the manufacture of concrete are reagents and are therefore likely to undergo a progressive deterioration of their initial properties. An initial petrographic study of each aggregate is performed in order to be able to determine its subsequent behaviour and reactivity under the influence of various factors. The potential reactivity of different silicaceous aggregates (slates, gneiss, hornfels, granites, quartzite and serpentine is then determined by a chemical method for evaluating the potential reactivity of aggregates and an accelerated method in mortar specimens, and finally the surface reactivity is investigated. The results of these studies suggest that some aggregates are able to react with the components of the interstitial phase of concrete. The existence of this kind of interaction is confirmed by the results of the surface investigations before and after the basic reaction.

Este trabajo pretende contribuir al conocimiento de las reacciones de interacción entre los áridos y los componentes de la fase intersticial del hormigón y determinar si estos áridos, empleados posteriormente en la fabricación del hormigón, son reactivos y por tanto susceptibles de provocar una disminución progresiva de sus propiedades iniciales. Para la caracterización de cada árido se ha realizado un estudio petrográfico, fundamental a la hora de determinar su posterior comportamiento en términos de reactividad frente a diversos factores. Seguidamente, se ha analizado la reactividad potencial de diferentes áridos silicatados (pizarras, gneis, corneanas, granitos, cuarcita y serpentina mediante los dos métodos normalizados existentes: el método químico para la determinación de la reactividad potencial de áridos y

Information Aggregation and Investment Decisions

OpenAIRE

Christian Hellwig; Aleh Tsyvinski; Elias Albagli

2010-01-01

This paper studies an environment in which information aggregation interacts with investment decisions. The first contribution of the paper is to develop a tractable model of such interactions. The second contribution is to solve the model in closed form and derive a series of implications that result from the interplay between information aggregation and the value of market information for the firms' decision problem. We show that the model generates an information aggregation wedge between ...

Lightweight concrete with Algerian limestone dust. Part II: study on 50% and 100% replacement to normal aggregate at timely age

Directory of Open Access Journals (Sweden)

S. Kitouni

2015-12-01

Full Text Available Abstract A control lightweight concrete (LWC mixture made with 50% and 100% of limestone as a replacement of coarse aggregates in weight was prepared. Limestone is used for economical and environmental concern. The concrete samples were cured at 65% relative humidity at 20 ºC. The compressive and flexural tensile strengths, elastic modulus and Poisson's ratio of hardened concrete were measured. Laboratory compressive and tensile strength tests results showed that LWC can be produced by the use of limestone. The aim of this study is twofold: one is to design a lightweight concrete with the use of limestone that will provide an advantage of reduction in dead weight of a structure; and second is to obtain a more economical LWC mixture with the use of limestone.

Production of lightweight aggregates from washing aggregate sludge and fly ash

Science.gov (United States)

González-Corrochano, Beatriz; Alonso-Azcárate, Jacinto; Rodas, Magdalena

2010-05-01

Increasing generation of wastes is one of the main environmental problems in industrialised countries. Heat treatment at high temperatures can convert some types of wastes into ceramic products with a wide range of microstructural features and properties (Bethanis et al., 2004). A lightweight aggregate (LWA) is a granular material with a bulk density (bd) not exceeding 1.20 g/cm3 or with a particle density not exceeding 2.00 g/cm3 (UNE-EN-13055-1, 2003). They have become a focus of interest because the low particle density and the low bulk density entail a decrease in the load transmitted to the ground, and less work and effort are required to transport them (De' Gennaro et al., 2004). The benefits associated with these low densities, which are due to the formation of voids and pores, are very good thermal and acoustic insulation and materials with a good resistance to fire (Benbow, 1987; Fakhfakh et al., 2007). The objective was to recycle fly ash, used motor oil from cars and mineral wastes from washing aggregate sludge, in order to obtain a usable material such as lightweight aggregates, and also to ensure that they are of good quality for different applications. Raw materials have been physically, chemically and mineralogically characterized. On the basis of the results obtained, they were mixed, milled to a grain size of less than 200 μm (Yasuda, 1991), formed into pellets, pre-heated for 5 min and sintered in a rotary kiln at 1150°C, 1175°C, 1200°C and 1225°C for 10 and 15 min at each temperature (Theating). Effects of raw material characteristics, heating temperature and dwell time on the following LWAs properties were determined: loss on ignition (LOI), bloating index (BI), loose bulk density (bd), apparent and dry particle density (ad, dd), voids (H), water absorption (WA24h) and compressive strength (S). The products obtained were lightweight aggregates in accordance with norm UNE-EN-13055-1 (bd ≤1.20 g/cm3 or particle density ≤2.00 g/cm3). LWAs

Recycling ground granulated blast furnace slag as cold bonded artificial aggregate partially used in self-compacting concrete.

Science.gov (United States)

Gesoğlu, Mehmet; Güneyisi, Erhan; Mahmood, Swara Fuad; Öz, Hatice Öznur; Mermerdaş, Kasım

2012-10-15

Ground granulated blast furnace slag (GGBFS), a by-product from iron industry, was recycled as artificial coarse aggregate through cold bonding pelletization process. The artificial slag aggregates (ASA) replaced partially the natural coarse aggregates in production of self-compacting concrete (SCC). Moreover, as being one of the most widely used mineral admixtures in concrete industry, fly ash (FA) was incorporated as a part of total binder content to impart desired fluidity to SCCs. A total of six concrete mixtures having various ASA replacement levels (0%, 20%, 40%, 60%, and 100%) were designed with a water-to-binder (w/b) ratio of 0.32. Fresh properties of self-compacting concretes (SCC) were observed through slump flow time, flow diameter, V-funnel flow time, and L-box filling height ratio. Compressive strength of hardened SCCs was also determined at 28 days of curing. It was observed that increasing the replacement level of ASA resulted in decrease in the amount of superplasticizer to achieve a constant slump flow diameter. Moreover, passing ability and viscosity of SCC's enhanced with increasing the amount of ASA in the concrete. The maximum compressive strength was achieved for the SCC having 60% ASA replacement. Copyright © 2012 Elsevier B.V. All rights reserved.

Fly ash aggregates. Vliegaskunstgrind

Energy Technology Data Exchange (ETDEWEB)

1983-03-01

A study has been carried out into artificial aggregates made from fly ash, 'fly ash aggregates'. Attention has been drawn to the production of fly ash aggregates in the Netherlands as a way to obviate the need of disposal of fly ash. Typical process steps for the manufacturing of fly ash aggregates are the agglomeration and the bonding of fly ash particles. Agglomeration techniques are subdivided into agitation and compaction, bonding methods into sintering, hydrothermal and 'cold' bonding. In sintering no bonding agent is used. The fly ash particles are more or less welded together. Sintering in general is performed at a temperature higher than 900 deg C. In hydrothermal processes lime reacts with fly ash to a crystalline hydrate at temperatures between 100 and 250 deg C at saturated steam pressure. As a lime source not only lime as such, but also portland cement can be used. Cold bonding processes rely on reaction of fly ash with lime or cement at temperatures between 0 and 100 deg C. The pozzolanic properties of fly ash are used. Where cement is applied, this bonding agent itself contributes also to the strength development of the artificial aggregate. Besides the use of lime and cement, several processes are known which make use of lime containing wastes such as spray dry absorption desulfurization residues or fluid bed coal combustion residues. (In Dutch)

Solution self-assembly and adsorption at the air-water interface of the monorhamnose and dirhamnose rhamnolipids and their mixtures.

Science.gov (United States)

Chen, M L; Penfold, J; Thomas, R K; Smyth, T J P; Perfumo, A; Marchant, R; Banat, I M; Stevenson, P; Parry, A; Tucker, I; Grillo, I

2010-12-07

The self-assembly in solution and adsorption at the air-water interface, measured by small-angle neutron scattering, SANS, and neutron reflectivity, NR, of the monorhamnose and dirhamnose rhamnolipids (R1, R2) and their mixtures, are discussed. The production of the deuterium-labeled rhamnolipids (required for the NR studies) from a Pseudomonas aeruginosa culture and their separation into the pure R1 and R2 components is described. At the air-water interface, R1 and R2 exhibit Langmuir-like adsorption isotherms, with saturated area/molecule values of about 60 and 75 Å(2), respectively. In R1/R2 mixtures, there is a strong partitioning of R1 to the surface and R2 competes less favorably because of the steric or packing constraints of the larger R2 dirhamnose headgroup. In dilute solution (<20 mM), R1 and R2 form small globular micelles, L(1), with aggregation numbers of about 50 and 30, respectively. At higher solution concentrations, R1 has a predominantly planar structure, L(α) (unilamellar, ULV, or bilamellar, BLV, vesicles) whereas R2 remains globular, with an aggregation number that increases with increasing surfactant concentration. For R1/R2 mixtures, solutions rich in R2 are predominantly micellar whereas solutions rich in R1 have a more planar structure. At an intermediate composition (60 to 80 mol % R1), there are mixed L(α)/L(1) and L(1)/L(α) regions. However, the higher preferred curvature associated with R2 tends to dominate the mixed R1/R2 microstructure and its associated phase behavior.

Macrophage triggering by aggregated immunoglobulins. II. Comparison of IgE and IgG aggregates or immune complexes.

Science.gov (United States)

Pestel, J; Dessaint, J P; Joseph, M; Bazin, H; Capron, A

1984-01-01

Macrophages incubated with complexed or aggregated IgE released beta-glucuronidase (beta-G) within 30 min. In contrast in the presence of aggregated or complexed IgG, macrophages liberated equivalent amount of beta-G only after 6 h incubation. In addition the rapid macrophage stimulation induced by aggregated IgE was also followed by a faster 3H-glucosamine incorporation when compared to the delayed activation caused by aggregated IgG. However, macrophages stimulated either by IgG or by IgE oligomers produced the same percentage of plasminogen activator at 24 h. In contrast, while the interaction between macrophages and aggregated IgE was only followed by a peak of cyclic GMP and a beta-G release during the first 30 min of incubation, the interaction between macrophages and IgG oligomers was accompanied by a simultaneous increase of cyclic GMP and AMP nucleotides and by an absence of beta-G exocytosis. Moreover, the beta-G release induced by aggregated IgE was increased when macrophages were preincubated with aggregated IgG. This additive effect was not observed in the reverse situation. Finally macrophages activated by IgG oligomers were demonstrated to exert a cytotoxic effect on tumour cells and to kill schistosomula in the presence of a low level of complement. Taken together these results underline the peculiar ability of aggregated or complexed IgE to trigger rapidly the macrophage activation compared to aggregated IgG and can explain the important role of complexed IgE in some macrophage dependent cytotoxicity mechanisms (i.e. in parasitic diseases). PMID:6088135

Microfluidic magnetic switching valves based on aggregates of magnetic nanoparticles: Effects of aggregate length and nanoparticle sizes

Energy Technology Data Exchange (ETDEWEB)

Jiemsakul, Thanakorn [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), 111 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Nueng, Amphoe Khlong Luang, Pathum Thani 12120 (Thailand); Manakasettharn, Supone, E-mail: supone@nanotec.or.th [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), 111 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Nueng, Amphoe Khlong Luang, Pathum Thani 12120 (Thailand); Kanharattanachai, Sivakorn; Wanna, Yongyuth [College of Nanotechnology, King Mongkut' s Institute of Technology Ladkrabang, Chalongkrung Road, Bangkok 10520 (Thailand); Wangsuya, Sujint [College of Nanotechnology, King Mongkut' s Institute of Technology Ladkrabang, Chalongkrung Road, Bangkok 10520 (Thailand); Faculty of Science, Mahidol University, 272 Rama VI Road, Ratchathewi District, Bangkok 10400 (Thailand); Pratontep, Sirapat [College of Nanotechnology, King Mongkut' s Institute of Technology Ladkrabang, Chalongkrung Road, Bangkok 10520 (Thailand)

2017-01-15

We demonstrate microfluidic switching valves using magnetic nanoparticles blended within the working fluid as an alternative microfluidic flow control in microchannels. Y-shaped microchannels have been fabricated by using a CO{sub 2} laser cutter to pattern microchannels on transparent poly(methyl methacrylate) (PMMA) sheets covered with thermally bonded transparent polyvinyl chloride (PVC) sheets. To examine the performance of the microfluidic magnetic switching valves, an aqueous magnetic nanoparticle suspension was injected into the microchannels by a syringe pump. Neodymium magnets were then employed to attract magnetic nanoparticles and form an aggregate that blocked the microchannels at a required position. We have found that the maximum volumetric flow rate of the syringe pump that the magnetic nanoparticle aggregate can withstand scales with the square of the external magnetic flux density. The viscosity of the fluid exhibits dependent on the aggregate length and the size of the magnetic nanoparticles. This microfluidic switching valve based on aggregates of magnetic nanoparticles has strong potentials as an on-demand flow control, which may help simplifying microfluidic channel designs. - Highlights: • We demonstrate microfluidic switching valves based on aggregates of magnetic particles. • Maximum flow rate that the aggregate can withstand scales with the square of the external magnetic flux density. • Aggregates with smaller magnetic nanoparticle size can withstand higher flow rate. • Aggregate length exhibits a linear dependence with flow resistance of a viscous fluid.

Measurement and correlation of excess molar volumes for mixtures of 1-propanol and aromatic hydrocarbons

International Nuclear Information System (INIS)

Gahlyan, Suman; Rani, Manju; Maken, Sanjeev Kumar; Lee, Inkyu; Moon, Il

2015-01-01

Excess molar volumes (V m E ) have been measured at 303.15 K for 1-propanol+benzene or toluene or o- or m- or p-xylene mixtures using V-shape dilatometer. The V m E values, for an equimolar composition, vary in the order: benzene>toluene-m-xylene>o-xylene>p-xylene. The V m E data have been used to calculate partial molar volumes, excess partial molar volumes, and apparent molar volumes of 1-propanol and aromatic hydrocarbons over the entire range of composition. The excess volume data have also been interpreted in terms of graph-theoretical approach and Prigogine-Flory-Patterson theory (PFP). While PFP theory fails to predict the V m E values for systems with s-shaped V m E versus x 1 graph, the V m E values calculated by graph theory compare reasonably well with the corresponding experimental values. This graph theory analysis has further yielded information about the state of aggregation of pure components as well as of the mixtures

Macroeconomic susceptibility, inflation, and aggregate supply

Science.gov (United States)

Hawkins, Raymond J.

2017-03-01

We unify aggregate-supply dynamics as a time-dependent susceptibility-mediated relationship between inflation and aggregate economic output. In addition to representing well various observations of inflation-output dynamics this parsimonious formalism provides a straightforward derivation of popular representations of aggregate-supply dynamics and a natural basis for economic-agent expectations as an element of inflation formation. Our formalism also illuminates questions of causality and time-correlation that challenge central banks for whom aggregate-supply dynamics is a key constraint in their goal of achieving macroeconomic stability.

Aggregated recommendation through random forests.

Science.gov (United States)

Zhang, Heng-Ru; Min, Fan; He, Xu

2014-01-01

Aggregated recommendation refers to the process of suggesting one kind of items to a group of users. Compared to user-oriented or item-oriented approaches, it is more general and, therefore, more appropriate for cold-start recommendation. In this paper, we propose a random forest approach to create aggregated recommender systems. The approach is used to predict the rating of a group of users to a kind of items. In the preprocessing stage, we merge user, item, and rating information to construct an aggregated decision table, where rating information serves as the decision attribute. We also model the data conversion process corresponding to the new user, new item, and both new problems. In the training stage, a forest is built for the aggregated training set, where each leaf is assigned a distribution of discrete rating. In the testing stage, we present four predicting approaches to compute evaluation values based on the distribution of each tree. Experiments results on the well-known MovieLens dataset show that the aggregated approach maintains an acceptable level of accuracy.

Microbial properties of soil aggregates created by earthworms and other factors: spherical and prismatic soil aggregates from unreclaimed post-mining sites

Energy Technology Data Exchange (ETDEWEB)

Frouz, J.; Kristufek, V.; Liveckova, M.; van Loo, D.; Jacobs, P.; Van Hoorebeke, L. [Charles University of Prague, Prague (Czech Republic). Inst. of Environmental Studies

2011-01-15

Soil aggregates between 2 and 5 mm from 35- and 45-year-old unreclaimed post-mining sites near Sokolov (Czech Republic) were divided into two groups: spherical and prismatic. X-ray tomography indicated that prismatic aggregates consisted of fragments of claystone bonded together by amorphous clay and roots while spherical aggregates consisted of a clay matrix and organic fragments of various sizes. Prismatic aggregates were presumed to be formed by plant roots and physical processes during weathering of Tertiary mudstone, while earthworms were presumed to contribute to the formation of spherical aggregates. The effects of drying and rewetting and glucose addition on microbial respiration, microbial biomass, and counts of bacteria in these aggregates were determined. Spherical aggregates contained a greater percentage of C and N and a higher C-to-N ratio than prismatic ones. The C content of the particulate organic matter was also higher in the spherical than in the prismatic aggregates. Although spherical aggregates had a higher microbial respiration and biomass, the growth of microbial biomass in spherical aggregates was negatively correlated with initial microbial biomass, indicating competition between bacteria. Specific respiration was negatively correlated with microbial biomass. Direct counts of bacteria were higher in spherical than in prismatic aggregates. Bacterial numbers were more stable in the center than in the surface layers of the aggregates. Transmission electron microscopy indicated that bacteria often occurred as individual cells in prismatic aggregates but as small clusters of cells in spherical aggregates. Ratios of colony forming units (cultivatable bacteria) to direct counts were higher in spherical than in prismatic aggregates. Spherical aggregates also contained faster growing bacteria.

I-optimal mixture designs

OpenAIRE

GOOS, Peter; JONES, Bradley; SYAFITRI, Utami

2013-01-01

In mixture experiments, the factors under study are proportions of the ingredients of a mixture. The special nature of the factors in a mixture experiment necessitates specific types of regression models, and specific types of experimental designs. Although mixture experiments usually are intended to predict the response(s) for all possible formulations of the mixture and to identify optimal proportions for each of the ingredients, little research has been done concerning their I-optimal desi...

Glycation precedes lens crystallin aggregation

International Nuclear Information System (INIS)

Swamy, M.S.; Perry, R.E.; Abraham, E.C.

1987-01-01

Non-enzymatic glycosylation (glycation) seems to have the potential to alter the structure of crystallins and make them susceptible to thiol oxidation leading to disulfide-linked high molecular weight (HMW) aggregate formation. They used streptozotocin diabetic rats during precataract and cataract stages and long-term cell-free glycation of bovine lens crystallins to study the relationship between glycation and lens crystallin aggregation. HMW aggregates and other protein components of the water-soluble (WS) and urea-soluble (US) fractions were separated by molecular sieve high performance liquid chromatography. Glycation was estimated by both [ 3 H]NaBH 4 reduction and phenylboronate agarose affinity chromatography. Levels of total glycated protein (GP) in the US fractions were about 2-fold higher than in the WS fractions and there was a linear increase in GP in both WS and US fractions. This increase was parallelled by a corresponding increase in HMW aggregates. Total GP extracted by the affinity method from the US fraction showed a predominance of HMW aggregates and vice versa. Cell-free glycation studies with bovine crystallins confirmed the results of the animals studies. Increasing glycation caused a corresponding increase in protein insolubilization and the insoluble fraction thus formed also contained more glycated protein. It appears that lens protein glycation, HMW aggregate formation, and protein insolubilization are interrelated

Reuse of industrial sludge as construction aggregates.

Science.gov (United States)

Tay, J H; Show, K Y; Hong, S Y

2001-01-01

Industrial wastewater sludge and dredged marine clay are high volume wastes that needed enormous space at landfill disposal sites. Due to the limitation of land space, there is an urgent need for alternative disposal methods for these two wastes. This study investigates the possibility of using the industrial sludge in combination with marine clay as construction aggregates. Different proportions of sludge and clay were made into round and angular aggregates. It was found that certain mix proportions could provide aggregates of adequate strength, comparable to that of conventional aggregates. Concrete samples cast from the sludge-clay aggregates yield compressive strengths in the range of 31.0 to 39.0 N/mm2. The results showed that the round aggregates of 100% sludge and the crush aggregates of sludge with up to 20% clay produced concrete of compressive strengths which are superior to that of 38.0 N/mm2 for conventional aggregate. The study indicates that the conversion of high volume wastes into construction materials is a potential option for waste management.

Silt-clay aggregates on Mars

International Nuclear Information System (INIS)

Greeley, R.

1979-01-01

Viking observations suggest abundant silt and clay particles on Mars. It is proposed that some of these particles agglomerate to form sand size aggregates that are redeposited as sandlike features such as drifts and dunes. Although the binding for the aggregates could include salt cementation or other mechanisms, electrostatic bonding is considered to be a primary force holding the aggregates together. Various laboratory experiments conducted since the 19th century, and as reported here for simulated Martian conditions, show that both the magnitude and sign of electrical charges on windblown particles are functions of particle velocity, shape and composition, atmospheric pressure, atmospheric composition, and other factors. Electrical charges have been measured for saltating particles in the wind tunnel and in the field, on the surfaces of sand dunes, and within dust clouds on earth. Similar, and perhaps even greater, charges are proposed to occur on Mars, which could form aggregates of silt and clay size particles. Electrification is proposed to occur within Martian dust clouds, generating silt-clay aggregates which would settle to the surface where they may be deposited in the form of sandlike structures. By analog, silt-clay dunes are known in many parts of the earth where silt-clay aggregated were transported by saltation and deposited as 'sand.' In these structures the binding forces were later destroyed, and the particles reassumed the physical properties of silt and clay, but the sandlike bedding structure within the 'dunes' was preserved. The bedding observed in drifts at the Viking landing site is suggested to result from a similar process involving silt-clay aggregates on Mars

Exploring the early steps of aggregation of amyloid-forming peptide KFFE

International Nuclear Information System (INIS)

Wei Guanghong; Mousseau, Normand; Derreumaux, Philippe

2004-01-01

It has been shown recently that even a tetrapeptide can form amyloid fibrils sharing all the characteristics of amyloid fibrils built from large proteins. Recent experimental studies also suggest that the toxicity observed in several neurodegenerative diseases, such as Alzheimer's disease and Creutzfeldt-Jakob disease, is not only related to the mature fibrils themselves, but also to the soluble oligomers formed early in the process of fibrillogenesis. This raises the interest in studying the early steps of the aggregation process. Although fibril formation follows the nucleation-condensation process, characterized by the presence of lag phase, the exact pathways remain to be determined. In this study, we used the activation-relaxation technique and a generic energy model to explore the process of self-assembly and the structures of the resulting aggregates of eight KFFE peptides. Our simulations show, starting from different states with a preformed antiparallel dimer, that eight chains can self-assemble to adopt, with various orientations, four possible distant oligomeric well-aligned structures of similar energy. Two of these structures show a double-layer β-sheet organization, in agreement with the structure of amyloid fibrils as observed by x-ray diffraction; another two are mixtures of dimers and trimers. Our results also suggest that octamers are likely to be below the critical size for nucleation of amyloid fibrils for small peptides

Exploring the early steps of aggregation of amyloid-forming peptide KFFE

Energy Technology Data Exchange (ETDEWEB)

Wei Guanghong [Departement de Physique and Regroupement Quebecois sur les Materiaux de Pointe, Universite de Montreal, CP 6128, succursale centre-ville, Montreal, QC, H3C 3J7 (Canada); Mousseau, Normand [Departement de Physique and Regroupement Quebecois sur les Materiaux de Pointe, Universite de Montreal, CP 6128, succursale centre-ville, Montreal, QC, H3C 3J7 (Canada); Derreumaux, Philippe [Laboratoire de Biochimie, Theorique, UPR 9080 CNRS, IBPC, Universite Paris 7 Denis-Diderot, 13 rue Pierre et Marie Curie, 75005 Paris (France)

2004-11-10

It has been shown recently that even a tetrapeptide can form amyloid fibrils sharing all the characteristics of amyloid fibrils built from large proteins. Recent experimental studies also suggest that the toxicity observed in several neurodegenerative diseases, such as Alzheimer's disease and Creutzfeldt-Jakob disease, is not only related to the mature fibrils themselves, but also to the soluble oligomers formed early in the process of fibrillogenesis. This raises the interest in studying the early steps of the aggregation process. Although fibril formation follows the nucleation-condensation process, characterized by the presence of lag phase, the exact pathways remain to be determined. In this study, we used the activation-relaxation technique and a generic energy model to explore the process of self-assembly and the structures of the resulting aggregates of eight KFFE peptides. Our simulations show, starting from different states with a preformed antiparallel dimer, that eight chains can self-assemble to adopt, with various orientations, four possible distant oligomeric well-aligned structures of similar energy. Two of these structures show a double-layer {beta}-sheet organization, in agreement with the structure of amyloid fibrils as observed by x-ray diffraction; another two are mixtures of dimers and trimers. Our results also suggest that octamers are likely to be below the critical size for nucleation of amyloid fibrils for small peptides.

Aggregating and Disaggregating Flexibility Objects

DEFF Research Database (Denmark)

Siksnys, Laurynas; Valsomatzis, Emmanouil; Hose, Katja

2015-01-01

In many scientific and commercial domains we encounter flexibility objects, i.e., objects with explicit flexibilities in a time and an amount dimension (e.g., energy or product amount). Applications of flexibility objects require novel and efficient techniques capable of handling large amounts...... and aiming at energy balancing during aggregation. In more detail, this paper considers the complete life cycle of flex-objects: aggregation, disaggregation, associated requirements, efficient incremental computation, and balance aggregation techniques. Extensive experiments based on real-world data from...

Mixtures of latex particles and the surfactant of opposite charge used as interface stabilizers--influence of particle contact angle, zeta potential, flocculation and shear energy.

Science.gov (United States)

Deleurence, Rémi; Parneix, Caroline; Monteux, Cécile

2014-09-28

We investigate the stabilization of air-water interfaces by mixtures of negatively charged latex particles (sulfate polystyrene) and cationic surfactants (alkyl trimethylammonium bromides). First we report results concerning the binding of surfactant molecules to the latex particles. As the surfactant concentration increases, the charge of the particles reverses, from negative to positive, because CnTAB first binds electrostatically to the latex particles and then through hydrophobic interaction with the monolayer already adsorbed on the particles as well as directly with the hydrophobic surface of the latex. Over a large range of surfactant concentrations around the charge inversion, a strong flocculation is observed and 100 μm large aggregates form in the suspension. Unlike previous studies published on mixtures of inorganic particles with oppositely charged surfactants, we show that we can vary the sign of the zeta potential of the particles without changing the contact angle of the particles over a large range of surfactant concentrations. Indeed, the latex particles that we study are more hydrophobic than inorganic particles, hence adding moderate concentrations of the surfactant results in a weak variation of the contact angle while the charge of the particles can be reversed. This enables decoupling of the effect of zeta potential and contact angle on the interfacial properties of the mixtures. Our study shows that the contact angle and the charge of the particles are not sufficient parameters to control the foam properties, and the key-parameters are the flocculation state and the shear energy applied to produce the foam. Indeed, flocculated samples, whatever the sign of the zeta potential, enable production of a stable armour at the interface. The large aggregates do not adsorb spontaneously at the interface because of their large size, however when a large shear energy is used to produce the foam very stable foam is obtained, where particles are trapped

CPAD, Curated Protein Aggregation Database: A Repository of Manually Curated Experimental Data on Protein and Peptide Aggregation.

Science.gov (United States)

Thangakani, A Mary; Nagarajan, R; Kumar, Sandeep; Sakthivel, R; Velmurugan, D; Gromiha, M Michael

2016-01-01

Accurate distinction between peptide sequences that can form amyloid-fibrils or amorphous β-aggregates, identification of potential aggregation prone regions in proteins, and prediction of change in aggregation rate of a protein upon mutation(s) are critical to research on protein misfolding diseases, such as Alzheimer's and Parkinson's, as well as biotechnological production of protein based therapeutics. We have developed a Curated Protein Aggregation Database (CPAD), which has collected results from experimental studies performed by scientific community aimed at understanding protein/peptide aggregation. CPAD contains more than 2300 experimentally observed aggregation rates upon mutations in known amyloidogenic proteins. Each entry includes numerical values for the following parameters: change in rate of aggregation as measured by fluorescence intensity or turbidity, name and source of the protein, Uniprot and Protein Data Bank codes, single point as well as multiple mutations, and literature citation. The data in CPAD has been supplemented with five different types of additional information: (i) Amyloid fibril forming hexa-peptides, (ii) Amorphous β-aggregating hexa-peptides, (iii) Amyloid fibril forming peptides of different lengths, (iv) Amyloid fibril forming hexa-peptides whose crystal structures are available in the Protein Data Bank (PDB) and (v) Experimentally validated aggregation prone regions found in amyloidogenic proteins. Furthermore, CPAD is linked to other related databases and resources, such as Uniprot, Protein Data Bank, PUBMED, GAP, TANGO, WALTZ etc. We have set up a web interface with different search and display options so that users have the ability to get the data in multiple ways. CPAD is freely available at http://www.iitm.ac.in/bioinfo/CPAD/. The potential applications of CPAD have also been discussed.

Contrasting self-aggregation over land and ocean surfaces

Science.gov (United States)

Inda Diaz, H. A.; O'Brien, T. A.

2017-12-01

The spontaneous organization of convection into clusters, or self-aggregation, demonstrably changes the nature and statistics of precipitation. While there has been much recent progress in this area, the processes that control self-aggregation are still poorly understood. Most of the work to date has focused on self-aggregation over ocean-like surfaces, but it is particularly pressing to understand what controls convective aggregation over land, since the associated change in precipitation statistics—between non-aggregated and aggregated convection—could have huge impacts on society and infrastructure. Radiative-convective equilibrium (RCE), has been extensively used as an idealized framework to study the tropical atmosphere. Self-aggregation manifests in numerous numerical models of RCE, nevertheless, there is still a lack of understanding in how it relates to convective organization in the observed world. Numerous studies have examined self-aggregation using idealized Cloud Resolving Models (CRMs) and General Circulation Models over the ocean, however very little work has been done on RCE and self-aggregation over land. Idealized models of RCE over ocean have shown that aggregation is sensitive to sea surface temperature (SST), more intense precipitation occurs in aggregated systems, and a variety of feedbacks—such as surface flux, cloud radiative, and upgradient moisture transport— contribute to the maintenance of aggregation, however it is not clear if these results apply over land. Progress in this area could help relate understanding of self-aggregation in idealized simulations to observations. In order to explore the behavior of self-aggregation over land, we use a CRM to simulate idealized RCE over land. In particular, we examine the aggregation of convection and how it compares with aggregation over ocean. Based on previous studies, where a variety of different CRMs exhibit a SST threshold below which self-aggregation does not occur, we hypothesize

Mechanisms of browning development in aggregates of marine organic matter formed under anoxic conditions: A study by mid-infrared and near-infrared spectroscopy

Science.gov (United States)

Mecozzi, Mauro; Acquistucci, Rita; Nisini, Laura; Conti, Marcelo Enrique

2014-03-01

In this paper we analyze some chemical aspects concerning the browning development associated to the aggregation of marine organic matter (MOM) occurring in anoxic conditions. Organic matter samples obtained by the degradation of different algal samples were daily taken to follow the evolution of the aggregation process and the associated browning process. These samples were examined by Fourier transform mid infrared (FTIR) and Fourier transform near infrared (FTNIR) spectroscopy and the colour changes occurring during the above mentioned aggregation process were measured by means of Colour Indices (CIs). Spectral Cross Correlation Analysis (SCCA) was applied to correlate changes in CI values to the structural changes of MOM observed by FTIR and FTNIR spectra which were also submitted to Two-Dimensional Hetero Correlation Analysis (2HDCORR). SCCA results showed that all biomolecules present in MOM aggregates such as carbohydrates, proteins and lipids are involved in the browning development. In particular, SCCA results of algal mixtures suggest that the observed yellow-brown colour can be linked to the development of non enzymatic (i.e. Maillard) browning reactions. SCCA results for MOM furthermore suggest that aggregates coming from brown algae also showed evidence of browning related to enzymatic reactions. In the end 2HDCORR results indicate that hydrogen bond interactions among different molecules of MOM can play a significant role in the browning development.

Light-induced aggregation of microbial exopolymeric substances.

Science.gov (United States)

Sun, Luni; Xu, Chen; Zhang, Saijin; Lin, Peng; Schwehr, Kathleen A; Quigg, Antonietta; Chiu, Meng-Hsuen; Chin, Wei-Chun; Santschi, Peter H

2017-08-01

Sunlight can inhibit or disrupt the aggregation process of marine colloids via cleavage of high molecular weight compounds into smaller, less stable fragments. In contrast, some biomolecules, such as proteins excreted from bacteria can form aggregates via cross-linking due to photo-oxidation. To examine whether light-induced aggregation can occur in the marine environment, we conducted irradiation experiments on a well-characterized protein-containing exopolymeric substance (EPS) from the marine bacterium Sagitulla stellata. Our results show that after 1 h sunlight irradiation, the turbidity level of soluble EPS was 60% higher than in the dark control. Flow cytometry also confirmed that more particles of larger sized were formed by sunlight. In addition, we determined a higher mass of aggregates collected on filter in the irradiated samples. This suggests light can induce aggregation of this bacterial EPS. Reactive oxygen species hydroxyl radical and peroxide played critical roles in the photo-oxidation process, and salts assisted the aggregation process. The observation that Sagitulla stellata EPS with relatively high protein content promoted aggregation, was in contrast to the case where no significant differences were found in the aggregation of a non-protein containing phytoplankton EPS between the dark and light conditions. This, together with the evidence that protein-to-carbohydrate ratio of aggregates formed under light condition is significantly higher than that formed under dark condition suggest that proteins are likely the important component for aggregate formation. Light-induced aggregation provides new insights into polymer assembly, marine snow formation, and the fate/transport of organic carbon and nitrogen in the ocean. Copyright © 2017 Elsevier Ltd. All rights reserved.

The effect of electrolytes on the aggregation kinetics of titanium dioxide nanoparticle aggregates

International Nuclear Information System (INIS)

Shih Yanghsin; Zhuang Chengming; Tso Chihping; Lin Chenghan

2012-01-01

Metal oxide nanoparticles (NPs) are receiving increasing attention due to their increased industrial production and potential hazardous effect. The process of aggregation plays a key role in the fate of NPs in the environment and the resultant health risk. The aggregation of commercial titanium dioxide NP powder (25 nm) was investigated with various environmentally relevant solution chemistries containing different concentrations of monovalent (Na + , K + ) and divalent (Ca 2+ ) electrolytes. Titanium dioxide particle size increased with the increase in ion concentration. The stability of titanium dioxide also depended on the ionic composition. Titanium dioxide aggregated to a higher degree in the presence of divalent cations than monovalent ones. The attachment efficiency of NPs was constructed through aggregation kinetics data, from which the critical coagulation concentrations for the various electrolytes are determined (80, 19, and 1 meq/L for Na + , K + , and Ca 2+ , respectively). Our results suggest that titanium dioxide NP powders are relatively unstable in water and could easily be removed by adding multivalent cations so hazardous potentials decrease in aquatic environment.

Aggregated particles caused by instrument artifact

Directory of Open Access Journals (Sweden)

A. M. Pierce

2018-04-01

Full Text Available Previous studies have indicated that superaggregates, clusters of aggregates of soot primary particles, can be formed in large-scale turbulent fires. Due to lower effective densities, higher porosity, and lower aerodynamic diameters, superaggregates may pass through inlets designed to remove particles  <  2.5 µm in aerodynamic diameter (PM2.5. Ambient particulate matter samples were collected at Peavine Peak, NV, USA (2515 m northwest of Reno, NV, USA from June to November 2014. The Teledyne Advanced Pollution Instrumentation (TAPI 602 BetaPlus particulate monitor was used to collect PM2.5 on two filter types. During this time, aggregated particles  >  2.5 µm in aerodynamic diameter were collected on 36 out of 158 sample days. On preliminary analysis, it was thought that these aggregated particles were superaggregates, depositing past PM10 (particles  <  10 µm in aerodynamic diameter pre-impactors and PM2.5 cyclones. However, further analysis revealed that these aggregated particles were dissimilar to superaggregates observed in previous studies, both in morphology and in elemental composition. To determine if the aggregated particles were superaggregates or an instrument artifact, samples were investigated for the presence of certain elements, the occurrence of fires, high relative humidity and wind speeds, as well as the use of generators on site. Samples with aggregated particles, referred to as aggregates, were analyzed using a scanning electron microscope for size and shape and energy dispersive X-ray spectroscopy was used for elemental analysis. It was determined, based on the high amounts of aluminum present in the aggregate samples, that a sampling artifact associated with the sample inlet and prolonged, high wind events was the probable reason for the observed aggregates.

Concrete Waste Recycling Process for High Quality Aggregate

International Nuclear Information System (INIS)

Ishikura, Takeshi; Fujii, Shin-ichi

2008-01-01

Large amount of concrete waste generates during nuclear power plant (NPP) dismantling. Non-contaminated concrete waste is assumed to be disposed in a landfill site, but that will not be the solution especially in the future, because of decreasing tendency of the site availability and natural resources. Concerning concrete recycling, demand for roadbeds and backfill tends to be less than the amount of dismantled concrete generated in a single rural site, and conventional recycled aggregate is limited of its use to non-structural concrete, because of its inferior quality to ordinary natural aggregate. Therefore, it is vital to develop high quality recycled aggregate for general uses of dismantled concrete. If recycled aggregate is available for high structural concrete, the dismantling concrete is recyclable as aggregate for industry including nuclear field. Authors developed techniques on high quality aggregate reclamation for large amount of concrete generated during NPP decommissioning. Concrete of NPP buildings has good features for recycling aggregate; large quantity of high quality aggregate from same origin, record keeping of the aggregate origin, and little impurities in dismantled concrete such as wood and plastics. The target of recycled aggregate in this development is to meet the quality criteria for NPP concrete as prescribed in JASS 5N 'Specification for Nuclear Power Facility Reinforced Concrete' and JASS 5 'Specification for Reinforced Concrete Work'. The target of recycled aggregate concrete is to be comparable performance with ordinary aggregate concrete. The high quality recycled aggregate production techniques are assumed to apply for recycling for large amount of non-contaminated concrete. These techniques can also be applied for slightly contaminated concrete dismantled from radiological control area (RCA), together with free release survey. In conclusion: a technology on dismantled concrete recycling for high quality aggregate was developed

Cholesterol impairment contributes to neuroserpin aggregation

Science.gov (United States)

Giampietro, Costanza; Lionetti, Maria Chiara; Costantini, Giulio; Mutti, Federico; Zapperi, Stefano; La Porta, Caterina A. M.

2017-03-01

Intraneural accumulation of misfolded proteins is a common feature of several neurodegenerative pathologies including Alzheimer’s and Parkinson’s diseases, and Familial Encephalopathy with Neuroserpin Inclusion Bodies (FENIB). FENIB is a rare disease due to a point mutation in neuroserpin which accelerates protein aggregation in the endoplasmic reticulum (ER). Here we show that cholesterol depletion induced either by prolonged exposure to statins or by inhibiting the sterol reg-ulatory binding-element protein (SREBP) pathway also enhances aggregation of neuroserpin proteins. These findings can be explained considering a computational model of protein aggregation under non-equilibrium conditions, where a decrease in the rate of protein clearance improves aggregation. Decreasing cholesterol in cell membranes affects their biophysical properties, including their ability to form the vesicles needed for protein clearance, as we illustrate by a simple mathematical model. Taken together, these results suggest that cholesterol reduction induces neuroserpin aggregation, even in absence of specific neuroserpin mutations. The new mechanism we uncover could be relevant also for other neurodegenerative diseases associated with protein aggregation.

Mechanical properties of recycled concrete with demolished waste concrete aggregate and clay brick aggregate

Science.gov (United States)

Zheng, Chaocan; Lou, Cong; Du, Geng; Li, Xiaozhen; Liu, Zhiwu; Li, Liqin

2018-06-01

This paper presents an experimental investigation on the effect of the replacement of natural coarse aggregate (NCA) with either recycled concrete aggregate (RCA) or recycled clay brick aggregate (RBA) on the compressive strengths of the hardened concrete. Two grades (C25 and C50) of concrete were investigated, which were achieved by using different water-to-cement ratios. In each grade concrete five different replacement rates, 0%, 25%, 50%, 75% and 100% were considered. In order to improve the performance of the recycled aggregates in the concrete mixes, the RCA and RBA were carefully sieved by using the optimal degradation. In this way the largest reduction in the 28-day compressive strength was found to be only 7.2% and 9.6% for C25 and C50 recycled concrete when the NCA was replaced 100% by RCA, and 11% and 13% for C25 and C50 recycled concrete when the NCA was replaced 100% by RBA. In general, the concrete with RCA has better performance than the concrete with RBA. The comparison of the present experimental results with those reported in literature for hardened concrete with either RCA or RBA demonstrates the effectiveness in improving the compressive strength by using the optimal gradation of recycled aggregates.

Compressive strength improvement for recycled concrete aggregate

Directory of Open Access Journals (Sweden)

Mohammed Dhiyaa

2018-01-01

Full Text Available Increasing amount of construction waste and, concrete remnants, in particular pose a serious problem. Concrete waste exist in large amounts, do not decay and need long time for disintegration. Therefore, in this work old demolished concrete is crashed and recycled to produce recycled concrete aggregate which can be reused in new concrete production. The effect of using recycled aggregate on concrete compressive strength has been experimentally investigated; silica fume admixture also is used to improve recycled concrete aggregate compressive strength. The main parameters in this study are recycled aggregate and silica fume admixture. The percent of recycled aggregate ranged from (0-100 %. While the silica fume ranged from (0-10 %. The experimental results show that the average concrete compressive strength decreases from 30.85 MPa to 17.58 MPa when the recycled aggregate percentage increased from 0% to 100%. While, when silica fume is used the concrete compressive strength increase again to 29.2 MPa for samples with 100% of recycled aggregate.

Liquids and liquid mixtures

CERN Document Server

Rowlinson, J S; Baldwin, J E; Buckingham, A D; Danishefsky, S

2013-01-01

Liquids and Liquid Mixtures, Third Edition explores the equilibrium properties of liquids and liquid mixtures and relates them to the properties of the constituent molecules using the methods of statistical thermodynamics. Topics covered include the critical state, fluid mixtures at high pressures, and the statistical thermodynamics of fluids and mixtures. This book consists of eight chapters and begins with an overview of the liquid state and the thermodynamic properties of liquids and liquid mixtures, including vapor pressure and heat capacities. The discussion then turns to the thermodynami

Pore structure of natural and regenerated soil aggregates

DEFF Research Database (Denmark)

Naveed, Muhammad; Arthur, Emmanuel; de Jonge, Lis Wollesen

2014-01-01

Quantitative characterization of aggregate pore structure can reveal the evolution of aggregates under different land use and management practices and their effects on soil processes and functions. Advances in X-ray Computed Tomography (CT) provide powerful means to conduct such characterization....... This study examined aggregate pore structure of three differently managed same textured Danish soils (mixed forage cropping, MFC; mixed cash cropping, MCC; cereal cash cropping, CCC) for (i) natural aggregates, and (ii) aggregates regenerated after 20 months of incubation. In total, 27 aggregates (8-16 mm...... pore diameter of 200 and 170 Hm, respectively. Pore shape analysis indicated that CCC and MFC aggregates had an abundance of rounded and elongated pores, respectively, and those of MCC were in-between CCC and MFC. Aggregate pore structure development in the lysimeters was nearly similar irrespective...

Ratio-Based Gradual Aggregation of Data

DEFF Research Database (Denmark)

Iftikhar, Nadeem

2012-01-01

cause data management and data storage issues. However, non-flexible and ineffective means of data aggregation not only reduce performance of database queries but also lead to erroneous reporting. This paper presents flexible and effective ratio-based methods for gradual data aggregation in databases....... Gradual data aggregation is a process that reduces data volume by converting the detailed data into multiple levels of summarized data as the data gets older. This paper also describes implementation strategies of the proposed methods based on standard database technology.......Majority of databases contain large amounts of data, gathered over long intervals of time. In most cases, the data is aggregated so that it can be used for analysis and reporting purposes. The other reason of data aggregation is to reduce data volume in order to avoid over-sized databases that may...

Aggregation of flexible polyelectrolytes: Phase diagram and dynamics.

Science.gov (United States)

Tom, Anvy Moly; Rajesh, R; Vemparala, Satyavani

2017-10-14

Similarly charged polymers in solution, known as polyelectrolytes, are known to form aggregated structures in the presence of oppositely charged counterions. Understanding the dependence of the equilibrium phases and the dynamics of the process of aggregation on parameters such as backbone flexibility and charge density of such polymers is crucial for insights into various biological processes which involve biological polyelectrolytes such as protein, DNA, etc. Here, we use large-scale coarse-grained molecular dynamics simulations to obtain the phase diagram of the aggregated structures of flexible charged polymers and characterize the morphology of the aggregates as well as the aggregation dynamics, in the presence of trivalent counterions. Three different phases are observed depending on the charge density: no aggregation, a finite bundle phase where multiple small aggregates coexist with a large aggregate and a fully phase separated phase. We show that the flexibility of the polymer backbone causes strong entanglement between charged polymers leading to additional time scales in the aggregation process. Such slowing down of the aggregation dynamics results in the exponent, characterizing the power law decay of the number of aggregates with time, to be dependent on the charge density of the polymers. These results are contrary to those obtained for rigid polyelectrolytes, emphasizing the role of backbone flexibility.

Nickel aggregates produced by radiolysis

International Nuclear Information System (INIS)

Marignier, J.L.; Belloni, J.

1988-01-01

Nickel aggregates with subcolloidal size and stable in water have been synthesized by inhibiting the corrosion by the medium. The protective effect of the surfactant is discussed in relation with the characteristics of various types of polyvinyl alcohol studied. The reactivity of aggregates towards oxidizing compounds, nitro blue tetrazolium, methylene blue, silver ions, oxygen, methylviologen, enables an estimation of the redox potential of nickel aggregates (E = - 04 ± 0.05 V). It has been applied to quantitative analysis of the particles in presence of nickel ions. 55 refs [fr

Aggregation Algorithms in Heterogeneous Tables

Directory of Open Access Journals (Sweden)

Titus Felix FURTUNA

2006-01-01

Full Text Available The heterogeneous tables are most used in the problem of aggregation. A solution for this problem is to standardize these tables of figures. In this paper, we proposed some methods of aggregation based on the hierarchical algorithms.

Small file aggregation in a parallel computing system

Science.gov (United States)

Faibish, Sorin; Bent, John M.; Tzelnic, Percy; Grider, Gary; Zhang, Jingwang

2014-09-02

Techniques are provided for small file aggregation in a parallel computing system. An exemplary method for storing a plurality of files generated by a plurality of processes in a parallel computing system comprises aggregating the plurality of files into a single aggregated file; and generating metadata for the single aggregated file. The metadata comprises an offset and a length of each of the plurality of files in the single aggregated file. The metadata can be used to unpack one or more of the files from the single aggregated file.

Broadband dynamics in neat 4-methyl-3-heptanol and in mixtures with 2-ethyl-1-hexanol

DEFF Research Database (Denmark)

Hecksher, Tina; Olsen, Niels Boye; Bauer, S

2013-01-01

place on similar time scales in contrast to the situation for the structural isomer 2-ethyl-1-hexanol (2E1H) [S. Schildmann et al. , J. Chem. Phys.135, 174511 (2011)]. This indicates a very weak decoupling of Debye-like and structural relaxation which was further probed using volume expansivity...... experiments. Shear viscosity as well as diffusometry measurements were performed and the data were analyzed in terms of the Debye-Stokes-Einstein equations. In mixtures of 4M3H with 2E1H the Debye-like process becomes much stronger and for 2E1H mole fraction of more than 25% the behavior of this alcohol...... is rapidly approached. This finding is interpreted to indicate that the ring-like supramolecular structures in 4M3H become energetically unfavorable when adding 2E1H, an alcohol that tends to form chain-like molecular aggregates. The concentration dependence of the Kirkwood factor in these mixtures displays...

ALPHA-SYNUCLEIN STRUCTURE, AGGREGATION AND MODULATORS

Directory of Open Access Journals (Sweden)

Pinakin K. Makwana

2016-06-01

Full Text Available Alpha-synuclein is an intrinsically unstructured protein, involved in various neurodegenerative disorders. In vitro/in vivo experiments, as well as genetic mutation studies establish a direct link between alphasynuclein and synucleinopathies. Due to its natively unfolded state, alpha synuclein can adopt numerous conformations upon interaction with its partners and cellular factors, offering explanation for its diverse interactions. Aggregated form of alpha-synuclein has been observed in the brain of patients with synucleinopathies, a hallmark of neurodegeneration, and cell death has been attributed to aggregation induced toxicity. The process of aggregation involves nucleation, followed by intermediate oligomeric states, and finally the fibrillar amyloids. Of the various conformations/species that alpha-synuclein assumes before it transforms into mature amyloid fibrils, the oligomeric species is the most toxic. Thus, an effective way to limit disease progression is by modifying/slowing down protein aggregation/deposition in the brain. Various small natural products, synthetic chemicals, peptides and antibodies specific to alpha-synuclein have been designed/identified to reduce its rate of aggregation. Unfortunately, not even a handful of the molecules have cleared the clinical trials. Even today, medications available for Parkinson’s patients are mostly the drugs that adjust for loss of dopamine in the brain, and hence do not stop the progression of the disease or cure the symptoms. Thus, more molecular level studies are warranted to fully elucidate the process of alpha-synuclein aggregation, which in turn could help in identifying novel therapeutics and preventives. The present review summarizes the insights gained into the structure, in vitro aggregation and inhibitors/modulators of alpha-synuclein aggregation, that can be used to design better and effective inhibitors against the diseases.

A general mixture theory. I. Mixtures of spherical molecules

Science.gov (United States)

Hamad, Esam Z.

1996-08-01

We present a new general theory for obtaining mixture properties from the pure species equations of state. The theory addresses the composition and the unlike interactions dependence of mixture equation of state. The density expansion of the mixture equation gives the exact composition dependence of all virial coefficients. The theory introduces multiple-index parameters that can be calculated from binary unlike interaction parameters. In this first part of the work, details are presented for the first and second levels of approximations for spherical molecules. The second order model is simple and very accurate. It predicts the compressibility factor of additive hard spheres within simulation uncertainty (equimolar with size ratio of three). For nonadditive hard spheres, comparison with compressibility factor simulation data over a wide range of density, composition, and nonadditivity parameter, gave an average error of 2%. For mixtures of Lennard-Jones molecules, the model predictions are better than the Weeks-Chandler-Anderson perturbation theory.

Mechanical Dissociation of Platelet Aggregates in Blood Stream

Science.gov (United States)

Hoore, Masoud; Fedosov, Dmitry A.; Gompper, Gerhard; Complex; Biological Fluids Group Team

2017-11-01

von Willebrand factor (VWF) and platelet aggregation is a key phenomenon in blood clotting. These aggregates form critically in high shear rates and dissolve reversibly in low shear rates. The emergence of a critical shear rate, beyond which aggregates form and below which they dissolve, has an interesting impact on aggregation in blood flow. As red blood cells (RBCs) migrate to the center of the vessel in blood flow, a RBC free layer (RBC-FL) is left close to the walls into which the platelets and VWFs are pushed back from the bulk flow. This margination process provides maximal VWF-platelet aggregation probability in the RBC-FL. Using mesoscale hydrodynamic simulations of aggregate dynamics in blood flow, it is shown that the aggregates form and grow in RBC-FL wherein shear rate is high for VWF stretching. By growing, the aggregates penetrate to the bulk flow and get under order of magnitude lower shear rates. Consequently, they dissolve and get back into the RBC-FL. This mechanical limitation for aggregates prohibits undesired thrombosis and vessel blockage by aggregates, while letting the VWFs and platelets to aggregate close to the walls where they are actually needed. The support by the DFG Research Unit FOR 1543 SHENC and CPU time Grant by the Julich Supercomputing Center are acknowledged.

Learning about individuals' health from aggregate data.

Science.gov (United States)

Colbaugh, Rich; Glass, Kristin

2017-07-01

There is growing awareness that user-generated social media content contains valuable health-related information and is more convenient to collect than typical health data. For example, Twitter has been employed to predict aggregate-level outcomes, such as regional rates of diabetes and child poverty, and to identify individual cases of depression and food poisoning. Models which make aggregate-level inferences can be induced from aggregate data, and consequently are straightforward to build. In contrast, learning models that produce individual-level (IL) predictions, which are more informative, usually requires a large number of difficult-to-acquire labeled IL examples. This paper presents a new machine learning method which achieves the best of both worlds, enabling IL models to be learned from aggregate labels. The algorithm makes predictions by combining unsupervised feature extraction, aggregate-based modeling, and optimal integration of aggregate-level and IL information. Two case studies illustrate how to learn health-relevant IL prediction models using only aggregate labels, and show that these models perform as well as state-of-the-art models trained on hundreds or thousands of labeled individuals.

Efficient clustering aggregation based on data fragments.

Science.gov (United States)

Wu, Ou; Hu, Weiming; Maybank, Stephen J; Zhu, Mingliang; Li, Bing

2012-06-01

Clustering aggregation, known as clustering ensembles, has emerged as a powerful technique for combining different clustering results to obtain a single better clustering. Existing clustering aggregation algorithms are applied directly to data points, in what is referred to as the point-based approach. The algorithms are inefficient if the number of data points is large. We define an efficient approach for clustering aggregation based on data fragments. In this fragment-based approach, a data fragment is any subset of the data that is not split by any of the clustering results. To establish the theoretical bases of the proposed approach, we prove that clustering aggregation can be performed directly on data fragments under two widely used goodness measures for clustering aggregation taken from the literature. Three new clustering aggregation algorithms are described. The experimental results obtained using several public data sets show that the new algorithms have lower computational complexity than three well-known existing point-based clustering aggregation algorithms (Agglomerative, Furthest, and LocalSearch); nevertheless, the new algorithms do not sacrifice the accuracy.

The effect of particle shape and size distribution on the acoustical properties of mixtures of hemp particles.

Science.gov (United States)

Glé, Philippe; Gourdon, Emmanuel; Arnaud, Laurent; Horoshenkov, Kirill-V; Khan, Amir

2013-12-01

Hemp concrete is an attractive alternative to traditional materials used in building construction. It has a very low environmental impact, and it is characterized by high thermal insulation. Hemp aggregate particles are parallelepiped in shape and can be organized in a plurality of ways to create a considerable proportion of open pores with a complex connectivity pattern, the acoustical properties of which have never been examined systematically. Therefore this paper is focused on the fundamental understanding of the relations between the particle shape and size distribution, pore size distribution, and the acoustical properties of the resultant porous material mixture. The sound absorption and the transmission loss of various hemp aggregates is characterized using laboratory experiments and three theoretical models. These models are used to relate the particle size distribution to the pore size distribution. It is shown that the shape of particles and particle size control the pore size distribution and tortuosity in shiv. These properties in turn relate directly to the observed acoustical behavior.

Customer Aggregation: An Opportunity for Green Power?; TOPICAL

International Nuclear Information System (INIS)

Holt, E.; Bird, L.

2001-01-01

We undertook research into the experience of aggregation groups to determine whether customer aggregation offers an opportunity to bring green power choices to more customers. The objectives of this report, therefore, are to (1) identify the different types of aggregation that are occurring today, (2) learn whether aggregation offers an opportunity to advance sales of green power, and (3) share these concepts and approaches with potential aggregators and green power advocates

Concrete manufacture with un-graded recycled aggregates

OpenAIRE

Richardson, Alan; Coventry, Kathryn; Graham, Sue

2009-01-01

Purpose – The purpose of this paper is to investigate whether concrete that includes un-graded recycled aggregates can be manufactured to a comparable strength to concrete manufactured from virgin aggregates. \\ud \\ud Design/methodology/approach – A paired comparison test was used to evaluate the difference between concrete made with virgin aggregates (plain control) and concrete including recycled waste. Un-graded construction demolition waste and un-graded ground glass were used as aggregate...

Coupling of aggregation and immunogenicity in biotherapeutics: T- and B-cell immune epitopes may contain aggregation-prone regions.

Science.gov (United States)

Kumar, Sandeep; Singh, Satish K; Wang, Xiaoling; Rup, Bonita; Gill, Davinder

2011-05-01

Biotherapeutics, including recombinant or plasma-derived human proteins and antibody-based molecules, have emerged as an important class of pharmaceuticals. Aggregation and immunogenicity are among the major bottlenecks during discovery and development of biotherapeutics. Computational tools that can predict aggregation prone regions as well as T- and B-cell immune epitopes from protein sequence and structure have become available recently. Here, we describe a potential coupling between aggregation and immunogenicity: T-cell and B-cell immune epitopes in therapeutic proteins may contain aggregation-prone regions. The details of biological mechanisms behind this observation remain to be understood. However, our observation opens up an exciting potential for rational design of de-immunized novel, as well as follow on biotherapeutics with reduced aggregation propensity.

A turbulence model in mixtures. First part: Statistical description of mixture

International Nuclear Information System (INIS)

Besnard, D.

1987-03-01

Classical theory of mixtures gives a model for molecular mixtures. This kind of model is based on a small gradient approximation for concentration, temperature, and pression. We present here a mixture model, allowing for large gradients in the flow. We also show that, with a local balance assumption between material diffusion and flow gradients evolution, we obtain a model similar to those mentioned above [fr

Detection of ubiquitinated huntingtin species in intracellular aggregates

Directory of Open Access Journals (Sweden)

Katrin eJuenemann

2015-01-01

Full Text Available Protein conformation diseases, including polyglutamine diseases, result from the accumulation and aggregation of misfolded proteins. Huntington’s disease is one of nine diseases caused by an expanded polyglutamine repeat within the affected protein and is hallmarked by intracellular inclusion bodies composed of aggregated N-terminal huntingtin fragments and other sequestered proteins. Fluorescence microscopy and filter trap assay are conventional methods to study protein aggregates, but cannot be used to analyze the presence and levels of post-translational modifications of aggregated huntingtin such as ubiquitination. Ubiquitination of proteins can be a signal for degradation and intracellular localization, but also affects protein activity and protein-protein interactions. The function of ubiquitination relies on its mono- and polymeric isoforms attached to protein substrates. Studying the ubiquitination pattern of aggregated huntingtin fragments offers an important possibility to understand huntingtin degradation and aggregation processes within the cell. For the identification of aggregated huntingtin and its ubiquitinated species, solubilization of the cellular aggregates is mandatory. Here we describe methods to identify post-translational modifications such as ubiquitination of aggregated mutant huntingtin. This approach is specifically described for use with mammalian cell culture and is suitable to study other disease-related proteins prone to aggregate.

Microstructural characterization of concrete prepared with recycled aggregates.

Science.gov (United States)

Guedes, Mafalda; Evangelista, Luís; de Brito, Jorge; Ferro, Alberto C

2013-10-01

Several authors have reported the workability, mechanical properties, and durability of concrete produced with construction waste replacing the natural aggregate. However, a systematic microstructural characterization of recycled aggregate concrete has not been reported. This work studies the use of fine recycled aggregate to replace fine natural aggregate in the production of concrete and reports the resulting microstructures. The used raw materials were natural aggregate, recycled aggregate obtained from a standard concrete, and Portland cement. The substitution extent was 0, 10, 50, and 100 vol%; hydration was stopped at 9, 24, and 96 h and 28 days. Microscopy was focused on the cement/aggregate interfacial transition zone, enlightening the effect of incorporating recycled aggregate on the formation and morphology of the different concrete hydration products. The results show that concretes with recycled aggregates exhibit typical microstructural features of the transition zone in normal strength concrete. Although overall porosity increases with increasing replacement, the interfacial bond is apparently stronger when recycled aggregates are used. An addition of 10 vol% results in a decrease in porosity at the interface with a corresponding increase of the material hardness. This provides an opportunity for development of increased strength Portland cement concretes using controlled amounts of concrete waste.

Core-size regulated aggregation/disaggregation of citrate-coated gold nanoparticles (5-50 nm) and dissolved organic matter: Extinction, emission, and scattering evidence

Science.gov (United States)

Esfahani, Milad Rabbani; Pallem, Vasanta L.; Stretz, Holly A.; Wells, Martha J. M.

2018-01-01

mixtures of CT-GNP-5 or -10 with DOM, whereas emissions for mixtures of CT-GNP-30 or -50 with DOM were enhanced at the surface plasmon resonance (SPR) wavelength. The emission spectra (ultraviolet range) for protein-like constituents of DOM were quenched. Resonance Rayleigh scattering (RRS) was more intense for the CT-GNP-30 and -50 than for the CT-GNP-5 and -10 controls. Intensity-based DLS particle size distributions (PSDs) of DOM controls, CT-GNP-5 and -10 nm controls, and 5- and 10 nm GNP-DOM mixtures exhibited multimodal aggregation. Analyses of CT-GNP-5 and CT-GNP-10 nm mixtures with DOM indicated overcoating of DOM molecules occurred in close proximity (systems.

Investigation on Tensile Strength Ratio (TSR Specimen to Predict Moisture Sensitivity of Asphalt Pavements Mixture and Using Polymer to Reduce Moisture Damage

Directory of Open Access Journals (Sweden)

Mohammed Aziz Hameed Al-Shaybani

2017-05-01

Full Text Available Moisture damage of asphalt concrete is defined as losing the strength and Permanence caused by the active presence of moisture.The most common technique to reduce moisture damage is using modifiers with the asphalt binder or the aggregate.The goal of this study was to explore the effect of various modifiers of polymer on the moisture susceptibility mixture of asphaltic concrete pavement. Modifiers included in this research selected two kinds of polymers Crumb Rubber No 50 (CR No 50 and Methyl Methacrylates (MMA(which are available in the local markets in Iraq and have been used in three percentages for each type. These percentages are (5, 10 and 15% for (CR No 50 and (2.5, 5 and 7.5(% for (MMA.Each type of these polymers is blended with asphalt by wet process at constant blending times for a suitable range of temperatures. The experimental works showed that all polymers modified mixtures have indirect tensile strength higher than control asphalt mixtures, its about (2-15 %, dependent on different type of polymer and polymer concentration under predicted suitable blending time.Test results of indirect tensile strength indicated betterment in modifying the proprieties of mixture, the increased resistance mixture of asphalt concrete pavement versus moisture damage, and reduced the effect of water on asphalt concrete properties. The final result is the addition of (10% CR No 50 and (5% MMA to asphalt mixtures showed an improved mixture of asphalt concrete properties and produced strong mixtures for road construction.One model is predicted for tensile strength ratio [TSR]to estimate the effects of polymer modification on moisture susceptibility mixture of asphalt concrete.

Modeling photopolarimetric characteristics of comet dust as a polydisperse mixture of polyshaped rough spheroids

Science.gov (United States)

Kolokolova, L.; Das, H.; Dubovik, O.; Lapyonok, T.

2013-12-01

It is widely recognized now that the main component of comet dust is aggregated particles that consist of submicron grains. It is also well known that cometary dust obey a rather wide size distribution with abundant particles whose size reaches dozens of microns. However, numerous attempts of computer simulation of light scattering by comet dust using aggregated particles have not succeeded to consider particles larger than a couple of microns due to limitations in the memory and speed of available computers. Attempts to substitute aggregates by polydisperse solid particles (spheres, spheroids, cylinders) could not consistently reproduce observed angular and spectral characteristics of comet brightness and polarization even in such a general case as polyshaped (i.e. containing particles of a variety of aspect ratios) mixture of spheroids (Kolokolova et al., In: Photopolarimetry in Remote Sensing, Kluwer Acad. Publ., 431, 2004). In this study we are checking how well cometary dust can be modeled using modeling tools for rough spheroids. With this purpose we use the software package described in Dubovik et al. (J. Geophys. Res., 111, D11208, doi:10.1029/2005JD006619d, 2006) that allows for a substantial reduction of computer time in calculating scattering properties of spheroid mixtures by means of using pre-calculated kernels - quadrature coefficients employed in the numerical integration of spheroid optical properties over size and shape. The kernels were pre-calculated for spheroids of 25 axis ratios, ranging from 0.3 to 3, and 42 size bins within the size parameter range 0.01 - 625. This software package has been recently expanded with the possibility of simulating not only smooth but also rough spheroids that is used in present study. We consider refractive indexes of the materials typical for comet dust: silicate, carbon, organics, and their mixtures. We also consider porous particles accounting on voids in the spheroids through effective medium approach. The

UTILITARIAN OPACITY MODEL FOR AGGREGATE PARTICLES IN PROTOPLANETARY NEBULAE AND EXOPLANET ATMOSPHERES

International Nuclear Information System (INIS)

Cuzzi, Jeffrey N.; Davis, Sanford S.; Estrada, Paul R.

2014-01-01

As small solid grains grow into larger ones in protoplanetary nebulae, or in the cloudy atmospheres of exoplanets, they generally form porous aggregates rather than solid spheres. A number of previous studies have used highly sophisticated schemes to calculate opacity models for irregular, porous particles with sizes much smaller than a wavelength. However, mere growth itself can affect the opacity of the medium in far more significant ways than the detailed compositional and/or structural differences between grain constituents once aggregate particle sizes exceed the relevant wavelengths. This physics is not new; our goal here is to provide a model that provides physical insight and is simple to use in the increasing number of protoplanetary nebula evolution and exoplanet atmosphere models appearing in recent years, yet quantitatively captures the main radiative properties of mixtures of particles of arbitrary size, porosity, and composition. The model is a simple combination of effective medium theory with small-particle closed-form expressions, combined with suitably chosen transitions to geometric optics behavior. Calculations of wavelength-dependent emission and Rosseland mean opacity are shown and compared with Mie theory. The model's fidelity is very good in all comparisons we have made except in cases involving pure metal particles or monochromatic opacities for solid particles with sizes comparable to the wavelength

Experimental and numerical modeling of chloride diffusivity in hardened cement concrete considering the aggregate shapes and exposure-duration effects

Directory of Open Access Journals (Sweden)

Wu Jie

Full Text Available This paper presents an experimental and numerical model describing the effects of the aggregate shapes and exposure duration of chloride diffusion into cement-based materials. A simple chloride diffusion test was performed on a concrete specimen composed of a mixture of cement mortar with crushed granites and round gravels. A simulation was done and the numerical model developed was applied to the matrix at the meso-scale level and the chloride diffusivity was investigated at 30, 60, and 90 days. The experimental and simulation results showed that the aggregate shape and the exposure duration of chloride diffusing into concrete are of high significance. It was indicated that the model with crushed granite presents a good resistance against chloride ingress, while the model with rounded gravels shows some sensitivity to the chloride penetration. It was also found out that when the time dependence of the diffusion coefficient is not taken into account, the diffusion rate will be overestimated. The meso-scale model developed in this study also provides a new method applied in the analysis of the chloride and water transport that causes damage to concrete considering the particle inclusion and the diffusion duration. Keywords: Meso-scale modeling, Chloride diffusivity, Concrete, Effects of aggregates shape and exposure duration, FEM

The alkali-aggregate reaction - concrete microstructure evolution

International Nuclear Information System (INIS)

Regourd, M.; Hornain, H.; Poitevin, P.

1981-01-01

The alkali-aggregate reaction has been studied by scanning electron microscopy and energy dispersive X-ray analysis, electron probe microanalysis, and X-ray diffraction in concretes containing glass aggregates or hornfels and greywacke aggregates. The surface reaction of the natural aggregates in alkaline solutions has been analysed by X-ray photo-electron spectrometry. The study of concretes with glass aggregates stored at 20 degrees Celcius and 100 percent relative humidity has revealed, irrespective of alkali content and type of cement, the formation of a gel containing SiO 2 , Na 2 O, CaO, MgO and Al 2 O 3 . Under heat and pressure (210 degrees Celcius at MPa for 48 hours), the gel crystallizes and yields silicates not very different from tobermorite found in autoclaved normal concretes but cotaining Na and K in solid solutions. The alkali reaction in two natural aggregate concretes, is also shown by the formation of gels and silicate crystals. The progressive structuring of the gels in silicate crystals is promoted by an increase in temperature. Ettringite and Ca(OH) 2 reinforce the alkali-aggregate reaction which may be looked upon as a hydration reaction, partially of the pozzolanic type

Collective Rationality in Graph Aggregation

NARCIS (Netherlands)

Endriss, U.; Grandi, U.; Schaub, T.; Friedrich, G.; O'Sullivan, B.

2014-01-01

Suppose a number of agents each provide us with a directed graph over a common set of vertices. Graph aggregation is the problem of computing a single “collective” graph that best represents the information inherent in this profile of individual graphs. We consider this aggregation problem from the

21 CFR 1303.11 - Aggregate production quotas.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Aggregate production quotas. 1303.11 Section 1303.11 Food and Drugs DRUG ENFORCEMENT ADMINISTRATION, DEPARTMENT OF JUSTICE QUOTAS Aggregate Production and Procurement Quotas § 1303.11 Aggregate production quotas. (a) The Administrator shall determine...

High performance of treated and washed MSWI bottom ash granulates as natural aggregate replacement within earth-moist concrete.

Science.gov (United States)

Keulen, A; van Zomeren, A; Harpe, P; Aarnink, W; Simons, H A E; Brouwers, H J H

2016-03-01

Municipal solid waste incineration bottom ash was treated with specially designed dry and wet treatment processes, obtaining high quality bottom ash granulate fractions (BGF) suitable for up to 100% replacement of natural gravel in concrete. The wet treatment (using only water for separating and washing) significantly lowers the leaching of e.g. chloride and sulfate, heavy metals (antimony, molybdenum and copper) and dissolved organic carbon (DOC). Two potential bottom ash granulate fractions, both in compliance with the standard EN 12620 (aggregates for concrete), were added into earth-moist concrete mixtures. The fresh and hardened concrete physical performances (e.g. workability, strength and freeze-thaw) of high strength concrete mixtures were maintained or improved compared with the reference mixtures, even after replacing up to 100% of the initial natural gravel. Final element leaching of monolithic and crushed granular state BGF containing concretes, showed no differences with the gravel references. Leaching of all mixtures did not exceed the limit values set by the Dutch Soil Quality Degree. In addition, multiple-life-phase emission (pH static test) for the critical elements of input bottom ash, bottom ash granulate (BGF) and crushed BGF containing concrete were assessed. Simulation pH lowering or potential carbonation processes indicated that metal (antimony, barium, chrome and copper) and sulfate element leaching behavior are mainly pH dominated and controlled, although differ in mechanism and related mineral abundance. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of clustering structure on volumetric properties of amino acids in (DMSO + water) mixtures

International Nuclear Information System (INIS)

Huang Aimin; Liu Chunli; Ma Lin; Tong Zhangfa; Lin Ruisen

2012-01-01

Graphical abstract: Together with static light scattering measurement, volumetric properties of glycine, L-alanine and L-serine were determined and utilized to reveal the microscopic solvent structure of (DMSO + water) mixtures and its influence on the interaction between DMSO and amino acids from a clustering point of view. The results demonstrated that the interaction between amino acids and DMSO was greatly related to the clustering structure of the mixed solvent and that amino acids interacted with already established solvent clusters. Hydrophobic aggregating of DMSO lead to a decrease in the hydrophobic effect of DMSO and the hydrophobic–hydrophilic and hydrophobic–hydrophobic interaction with amino acids, which was reflected by the solvation of proteins. Highlights: ► Determine volumetric properties of three amino acids in aqueous DMSO in details. ► Static light scattering measurement for clustering structure of aqueous DMSO. ► Volumetric behaviour of amino acids depends on clustering structure of aqueous DMSO. ► Clustering structure of aqueous DMSO influences solvation of protein and cellulose. - Abstract: For a better understanding on the functions of DMSO in biological systems at a relatively lower concentration, apparent molar volumes of three typical amino acids, glycine, L-alanine and L-serine in (DMSO + water) mixtures were determined and the transfer volumes from water to the mixtures were evaluated. Together with static light scattering measurement, the results were utilised to reveal the microscopic solvent structure of (DMSO + water) mixtures and its influence on the interaction between DMSO and amino acids from a clustering point of view. The results demonstrate that the interaction between amino acids and DMSO is greatly related to the clustering structure of the mixed solvent and that amino acids interacted with already established solvent clusters. The linear dependence of transfer volume of amino acids on DMSO concentration up to 2

Dynamic depletion attraction between colloids suspended in a phase-separating binary liquid mixture

International Nuclear Information System (INIS)

Araki, Takeaki; Tanaka, Hajime

2008-01-01

Understanding interactions between colloids (or nanoparticles) immersed in a phase-separating binary mixture is of both fundamental and technological importance. Here we report a novel type of interparticle attractive interaction of a purely dynamic origin, which is found by a coarse-grained numerical simulation. Due to surface wetting effects, there are strong diffusion fluxes towards particles just after the initiation of phase separation of the matrix binary liquid mixture. The flux in the region between particles soon becomes weaker than that in the other regions since the depletion zones formed around particles overlap selectively between the particles. The resulting imbalance of the diffusion flux induces interparticle attractive interactions, i.e., the osmotic force pushes particles closer. We confirm that this wetting-induced 'dynamic' depletion force can be stronger than a van der Waals force and a capillary force that is induced by the interfacial tension, and thus plays a dominant role in the early stage of particle aggregation. We note that this novel interaction originating from the momentum conservation law may be generic to particles acting as diffusional sinks or sources. (fast track communication)

Comminution and sizing processes of concrete block waste as recycled aggregates.

Science.gov (United States)

Gomes, P C C; Ulsen, C; Pereira, F A; Quattrone, M; Angulo, S C

2015-11-01

Due to the environmental impact of construction and demolition waste (CDW), recycling is mandatory. It is also important that recycled concrete aggregates (RCA) are used in concrete to meet market demands. In the literature, the influence of RCAs on concrete has been investigated, but very limited studies have been conducted on how the origin of concrete waste and comminution processes influence RCA characteristics. This paper aims to investigate the influence of three different comminution and sizing processes (simple screening, crushing and grinding) on the composition, shape and porosity characteristics of RCA obtained from concrete block waste. Crushing and grinding implies a reduction of RCA porosity. However, due to the presence of coarse quartz rounded river pebbles in the original concrete block mixtures, the shape characteristics deteriorated. A large amount of powder (<0.15 mm) without detectable anhydrous cement was also generated. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rapid Myoglobin Aggregation through Glucosamine-Induced α-Dicarbonyl Formation.

Science.gov (United States)

Hrynets, Yuliya; Ndagijimana, Maurice; Betti, Mirko

2015-01-01

The extent of glycation and conformational changes of horse myoglobin (Mb) upon glycation with N-acetyl-glucosamine (GlcNAc), glucose (Glc) and glucosamine (GlcN) were investigated. Among tested sugars, the rate of glycation with GlcN was the most rapid as shown by MALDI and ESI mass spectrometries. Protein oxidation, as evaluated by the amount of carbonyl groups present on Mb, was found to increase exponentially in Mb-Glc conjugates over time, whereas in Mb-GlcN mixtures the carbonyl groups decreased significantly after maximum at 3 days of the reaction. The reaction between GlcN and Mb resulted in a significantly higher amount of α-dicarbonyl compounds, mostly glucosone and 3-deoxyglucosone, ranging from and 27 to 332 mg/L and from 14 to 304 mg/L, respectively. Already at 0.5 days, tertiary structural changes of Mb-GlcN conjugate were observed by altered tryptophan fluorescence. A reduction of metmyoglobin to deoxy-and oxymyoglobin forms was observed on the first day of reaction, coinciding with the greatest amount of glucosone produced. In contrast to native α-helical myoglobin, 41% of the glycated protein sequence was transformed into a β-sheet conformation, as determined by circular dichroism spectropolarimetry. Transmission electron microscopy demonstrated that Mb glycation with GlcN causes the formation of amorphous or fibrous aggregates, started already at 3 reaction days. These aggregates bind to an amyloid-specific dye thioflavin T. With the aid of α-dicarbonyl compounds and advanced products of reaction, this study suggests that the Mb glycation with GlcN induces the unfolding of an initially globular protein structure into amyloid fibrils comprised of a β-sheet structure.

Mechanical properties of concrete containing recycled concrete aggregate (RCA) and ceramic waste as coarse aggregate replacement

Science.gov (United States)

Khalid, Faisal Sheikh; Azmi, Nurul Bazilah; Sumandi, Khairul Azwa Syafiq Mohd; Mazenan, Puteri Natasya

2017-10-01

Many construction and development activities today consume large amounts of concrete. The amount of construction waste is also increasing because of the demolition process. Much of this waste can be recycled to produce new products and increase the sustainability of construction projects. As recyclable construction wastes, concrete and ceramic can replace the natural aggregate in concrete because of their hard and strong physical properties. This research used 25%, 35%, and 45% recycled concrete aggregate (RCA) and ceramic waste as coarse aggregate in producing concrete. Several tests, such as concrete cube compression and splitting tensile tests, were also performed to determine and compare the mechanical properties of the recycled concrete with those of the normal concrete that contains 100% natural aggregate. The concrete containing 35% RCA and 35% ceramic waste showed the best properties compared with the normal concrete.

Logic-based aggregation methods for ranking student applicants

Directory of Open Access Journals (Sweden)

Milošević Pavle

2017-01-01

Full Text Available In this paper, we present logic-based aggregation models used for ranking student applicants and we compare them with a number of existing aggregation methods, each more complex than the previous one. The proposed models aim to include depen- dencies in the data using Logical aggregation (LA. LA is a aggregation method based on interpolative Boolean algebra (IBA, a consistent multi-valued realization of Boolean algebra. This technique is used for a Boolean consistent aggregation of attributes that are logically dependent. The comparison is performed in the case of student applicants for master programs at the University of Belgrade. We have shown that LA has some advantages over other presented aggregation methods. The software realization of all applied aggregation methods is also provided. This paper may be of interest not only for student ranking, but also for similar problems of ranking people e.g. employees, team members, etc.

Measurement and correlation of excess molar volumes for mixtures of 1-propanol and aromatic hydrocarbons

Energy Technology Data Exchange (ETDEWEB)

Gahlyan, Suman; Rani, Manju; Maken, Sanjeev Kumar [Deenbandhu Chhotu Ram University of Science and Technology, Murthal (India); Lee, Inkyu; Moon, Il [Yonsei University, Seoul (Korea, Republic of)

2015-01-15

Excess molar volumes (V{sub m}{sup E} ) have been measured at 303.15 K for 1-propanol+benzene or toluene or o- or m- or p-xylene mixtures using V-shape dilatometer. The V{sub m}{sup E} values, for an equimolar composition, vary in the order: benzene>toluene-m-xylene>o-xylene>p-xylene. The V{sub m}{sup E} data have been used to calculate partial molar volumes, excess partial molar volumes, and apparent molar volumes of 1-propanol and aromatic hydrocarbons over the entire range of composition. The excess volume data have also been interpreted in terms of graph-theoretical approach and Prigogine-Flory-Patterson theory (PFP). While PFP theory fails to predict the V{sub m}{sup E} values for systems with s-shaped V{sub m}{sup E} versus x{sub 1} graph, the V{sub m}{sup E} values calculated by graph theory compare reasonably well with the corresponding experimental values. This graph theory analysis has further yielded information about the state of aggregation of pure components as well as of the mixtures.

Topics in Probabilistic Judgment Aggregation

Science.gov (United States)

Wang, Guanchun

2011-01-01

This dissertation is a compilation of several studies that are united by their relevance to probabilistic judgment aggregation. In the face of complex and uncertain events, panels of judges are frequently consulted to provide probabilistic forecasts, and aggregation of such estimates in groups often yield better results than could have been made…

Thermophoretic aggregation of particles in a protoplanetary disc

Science.gov (United States)

Smith, Francis J.

2018-04-01

Thermophoresis causes particles to move down a temperature gradient to a cooler region of a neutral gas. An example is the temperature gradient in the gas around a large cold object, such as an aggregate of particles, cooled by radiation in a protoplanetary disc. Particles near this aggregate move down the temperature gradient to the aggregate, equivalent to the particles being attracted to it by an inter-particle thermophoretic force. This force is proportional to the temperature difference between gas and aggregate, to the gas density and to the cross-section of the aggregate. The force can be large. For example, calculations based on the equations of motion of the interacting particles show that it can be large enough in an optically thin environment to increase the rate of aggregation by up to six orders of magnitude when an aggregate radius lies between 0.1 μm and 1 mm. From 1 mm to about 10 cm aggregates drift inwards through the gas too quickly for the thermophoretic attraction to increase aggregation significantly; so they grow slowly, causing an observed accumulation of particles at these sizes. Particles above 10 cm move more quickly, causing aggregation due to collisions, but also causing fragmentation. However, calculations show that fragmenting particles and bouncing particles in inelastic collisions often have low enough relative velocities that thermophoresis brings them together again. This allows particles to grow above 1 m, which is otherwise difficult to explain.

Aggregates in monoclonal antibody manufacturing processes.

Science.gov (United States)

Vázquez-Rey, María; Lang, Dietmar A

2011-07-01

Monoclonal antibodies have proved to be a highly successful class of therapeutic products. Large-scale manufacturing of pharmaceutical antibodies is a complex activity that requires considerable effort in both process and analytical development. If a therapeutic protein cannot be stabilized adequately, it will lose partially or totally its therapeutic properties or even cause immunogenic reactions thus potentially further endangering the patients' health. The phenomenon of protein aggregation is a common issue that compromises the quality, safety, and efficacy of antibodies and can happen at different steps of the manufacturing process, including fermentation, purification, final formulation, and storage. Aggregate levels in drug substance and final drug product are a key factor when assessing quality attributes of the molecule, since aggregation might impact biological activity of the biopharmaceutical. In this review it is analyzed how aggregates are formed during monoclonal antibody industrial production, why they have to be removed and the manufacturing process steps that are designed to either minimize or remove aggregates in the final product. Copyright © 2011 Wiley Periodicals, Inc.

Towards constraint-based aggregation of energy flexibilities

DEFF Research Database (Denmark)

Valsomatzis, Emmanouil; Pedersen, Torben Bach; Abello, Alberto

2016-01-01

present the problem of aggregating energy flexibilities taking into account grid capacity limitations and introduce a heuristic aggregation technique. We show through an experimental setup that our proposed technique, compared to a baseline approach, not only leads to a valid unit commitment result......The aggregation of energy flexibilities enables individual producers and/or consumers with small loads to directly participate in the emerging energy markets. On the other hand, aggregation of such flexibilities might also create problems to the operation of the electrical grid. In this paper, we...

Mixture for plugging absorption zones

Energy Technology Data Exchange (ETDEWEB)

Sitinkov, G V; Kovalenko, N G; Makarov, L V; Zinnatulchin, Ts Kh

1981-01-17

A mixture is proposed for plugging absorption zones. The mixture contains synthetic polymer and a solvent. So as to increase the penetrability of the mixture through a reduction in its viscosity and an increase in insulation properties, the compound contains either Capron or Neilon as the synthetic polyamide resin polmyer, and concentrated chloride as the solvent. The mixture is prepared in a special AzINMASh-30 unit (acid cart). After the mixture has been produced, it is injected into the borehole by means of an acid cart pump. So as to prevent coaggulation at the point when the mixture in injected into the stratum through tubes, the mixture is placed betwen chemically inert fluids, for example, a clay mortar. The inert and compressed fluids are injected by means of a cementing unit. The entire process of production and application of the mixture is simple and fully automated through the use of well-known equipment.

Aspects Concerning the Use of Recycled Concrete Aggregates

Science.gov (United States)

Robu, I.; Mazilu, C.; Deju, R.

2016-11-01

Natural aggregates (gravel and crushed) are essential non-renewable resources which are used for infrastructure works and civil engineering. Using recycled concrete aggregates (RCA) is a matter of high priority in the construction industry worldwide. This paper presents a study on the use of recycled aggregates, from a concrete of specified class, to acquire new cement concrete with different percentages of recycled aggregates.

Sustainable normal and high strength recycled aggregate concretes using crushed tested cylinders as coarse aggregates

Directory of Open Access Journals (Sweden)

Bilal S. Hamad

2017-12-01

Full Text Available The paper reports on a research program that was designed at the American University of Beirut (AUB to investigate the fresh and hardened mechanical properties of a high performance concrete mix produced with partial or full substitution of crushed natural lime-stone aggregates with recycled aggregates from crushed tested cylinders in batching plants. Choosing crushed cylinders as source of recycling would result in reusing portion of the waste products of the concrete production industry. An extensive concrete batching and testing program was conducted to achieve two optimum normal and high strength concrete mixes. The variables were the nominal concrete strength (28 or 60 MPa and the percentage replacement of natural coarse aggregates with recycled aggregates from crushed tested cylinders (0, 20, 40, 60, 80, or 100%. Normal strength tested cylinders were used as source of the recycled aggregates for the normal strength concrete (NSC mix and high strength tested cylinders were used for the high strength concrete (HSC mix. Tests on the trial batches included plastic state slump and hardened state mechanical properties including cylinder compressive strength, cylinder splitting tensile strength, modulus of elasticity, and standard beams flexural strength. The results indicated no significant effect on the slump and around 10% average reduction in the hardened mechanical properties for both investigated levels of concrete compressive strength.

An exact approach for aggregated formulations

DEFF Research Database (Denmark)

Gamst, Mette; Spoorendonk, Simon

Aggregating formulations is a powerful approach for transforming problems into taking more tractable forms. Aggregated formulations can, though, have drawbacks: some information may get lost in the aggregation and { put in a branch-and-bound context { branching may become very di_cult and even....... The paper includes general considerations on types of problems for which the method is of particular interest. Furthermore, we prove the correctness of the procedure and consider how to include extensions such as cutting planes and advanced branching strategies....

Live Cell Characterization of DNA Aggregation Delivered through Lipofection.

Science.gov (United States)

Mieruszynski, Stephen; Briggs, Candida; Digman, Michelle A; Gratton, Enrico; Jones, Mark R

2015-05-27

DNA trafficking phenomena, such as information on where and to what extent DNA aggregation occurs, have yet to be fully characterised in the live cell. Here we characterise the aggregation of DNA when delivered through lipofection by applying the Number and Brightness (N&B) approach. The N&B analysis demonstrates extensive aggregation throughout the live cell with DNA clusters in the extremity of the cell and peri-nuclear areas. Once within the nucleus aggregation had decreased 3-fold. In addition, we show that increasing serum concentration of cell media results in greater cytoplasmic aggregation. Further, the effects of the DNA fragment size on aggregation was explored, where larger DNA constructs exhibited less aggregation. This study demonstrates the first quantification of DNA aggregation when delivered through lipofection in live cells. In addition, this study has presents a model for alternative uses of this imaging approach, which was originally developed to study protein oligomerization and aggregation.

Retiring the Short-Run Aggregate Supply Curve

Science.gov (United States)

Elwood, S. Kirk

2010-01-01

The author argues that the aggregate demand/aggregate supply (AD/AS) model is significantly improved--although certainly not perfected--by trimming it of the short-run aggregate supply (SRAS) curve. Problems with the SRAS curve are shown first for the AD/AS model that casts the AD curve as identifying the equilibrium level of output associated…

Performance of Hot Mix Asphalt Mixture Incorporating Kenaf Fibre

Science.gov (United States)

Hainin, M. R.; Idham, M. K.; Yaro, N. S. A.; Hussein, S. O. A. E.; Warid, M. N. M.; Mohamed, A.; Naqibah, S. N.; Ramadhansyah, P. J.

2018-04-01

Kenaf fibre has been recognised to increase the strength of concrete, but its application in asphalt concrete is still unanswered. This research investigated the performance of Hot Mix Asphalt (HMA) incorporated with different percentages of kenaf fibre (0.1 %, 0.2% and 0.3% by weight of dry aggregate) in term of resilient modulus, rutting performance using Asphalt Pavement analyser (APA) and moisture damage using the Modified Lottman test (AASHTO-T283). The fibre was interweaved to a diameter of about 5-10 mm and length of 30 mm which is three times the nominal maximum aggregate size used in the mix. Asphaltic mixtures of asphalt concrete (AC) 10 were prepared and compacted using Marshall compactor which were subsequently tested to evaluate the resilient modulus and moisture susceptibility. Twelve cylindrical specimens (150mm diameter) from AC10, two control samples with two modified ones for each percentage of kenaf fibres compacted using Gyratory compactor were used for rutting test using APA. The laboratory results reveal that the addition of kenaf fibres slightly reduce the resilient modulus of the mixes and that asphaltic mix with 0.3% kenaf fibre can mitigate both rutting and moisture damage which makes the pavement more sustain to the loads applied even in the presence of water. 0.3% kenaf fibre content is considered to be the optimal content which had the least rut depth and the highest TSR of 81.07%. Based on grid analysis, addition of 0.3% kenaf fibre in asphaltic concrete was recommended in modifying the samples.

Aggregate material formulated with MSWI bottom ash and APC fly ash for use as secondary building material.

Science.gov (United States)

del Valle-Zermeño, R; Formosa, J; Chimenos, J M; Martínez, M; Fernández, A I

2013-03-01

The main goal of this paper is to obtain a granular material formulated with Municipal Solid Waste Incineration (MSWI) bottom ash (BA) and air pollution control (APC) fly ash to be used as secondary building material. Previously, an optimum concrete mixture using both MSWI residues as aggregates was formulated. A compromise between the environmental behavior whilst maximizing the reuse of APC fly ash was considered and assessed. Unconfined compressive strength and abrasion resistance values were measured in order to evaluate the mechanical properties. From these results, the granular mixture was not suited for certain applications owing to the high BA/APC fly ash content and low cement percentages used to reduce the costs of the final product. Nevertheless, the leaching test performed showed that the concentrations of all heavy metals were below the limits established by the current Catalan legislation for their reutilization. Therefore, the material studied might be mainly used in embankments, where high mechanical properties are not needed and environmental safety is assured. Copyright © 2012 Elsevier Ltd. All rights reserved.

Measurement of platelet aggregation, independently of patient platelet count

DEFF Research Database (Denmark)

Vinholt, P J; Frederiksen, H; Hvas, A-M

2017-01-01

with collagen-related peptide). Platelet aggregation had a negative predictive value of 100% for a bleeding tendency among patients. Conclusion The established platelet aggregation assay was applicable for thrombocytopenic patients, and improved the identification of bleeding risk.......Essentials •Platelet function may influence bleeding risk in thrombocytopenia, but useful tests are needed. •A flow cytometric platelet aggregation test independent of the patient platelet count was made. •Platelet aggregation was reduced in thrombocytopenic patients with hematological cancer....... •High platelet aggregation ruled out bleeding tendency in thrombocytopenic patients. Summary Background Methods for testing platelet aggregation in thrombocytopenia are lacking. Objective To establish a flow-cytometric test of in vitro platelet aggregation independently of the patient's platelet count...

Environmentalism and natural aggregate mining

Science.gov (United States)

Drew, L.J.; Langer, W.H.; Sachs, J.S.

2002-01-01

Sustaining a developed economy and expanding a developing one require the use of large volumes of natural aggregate. Almost all human activity (commercial, recreational, or leisure) is transacted in or on facilities constructed from natural aggregate. In our urban and suburban worlds, we are almost totally dependent on supplies of water collected behind dams and transported through aqueducts made from concrete. Natural aggregate is essential to the facilities that produce energy-hydroelectric dams and coal-fired powerplants. Ironically, the utility created for mankind by the use of natural aggregate is rarely compared favorably with the environmental impacts of mining it. Instead, the empty quarries and pits are seen as large negative environmental consequences. At the root of this disassociation is the philosophy of environmentalism, which flavors our perceptions of the excavation, processing, and distribution of natural aggregate. The two end-member ideas in this philosophy are ecocentrism and anthropocentrism. Ecocentrism takes the position that the natural world is a organism whose arteries are the rivers-their flow must not be altered. The soil is another vital organ and must not be covered with concrete and asphalt. The motto of the ecocentrist is "man must live more lightly on the land." The anthropocentrist wants clean water and air and an uncluttered landscape for human use. Mining is allowed and even encouraged, but dust and noise from quarry and pit operations must be minimized. The large volume of truck traffic is viewed as a real menace to human life and should be regulated and isolated. The environmental problems that the producers of natural aggregate (crushed stone and sand and gravel) face today are mostly difficult social and political concerns associated with the large holes dug in the ground and the large volume of heavy truck traffic associated with quarry and pit operations. These concerns have increased in recent years as society's demand for

Component effects in mixture experiments

International Nuclear Information System (INIS)

Piepel, G.F.

1980-01-01

In a mixture experiment, the response to a mixture of q components is a function of the proportions x 1 , x 2 , ..., x/sub q/ of components in the mixture. Experimental regions for mixture experiments are often defined by constraints on the proportions of the components forming the mixture. The usual (orthogonal direction) definition of a factor effect does not apply because of the dependence imposed by the mixture restriction, /sup q/Σ/sub i=1/ x/sub i/ = 1. A direction within the experimental region in which to compute a mixture component effect is presented and compared to previously suggested directions. This new direction has none of the inadequacies or errors of previous suggestions while having a more meaningful interpretation. The distinction between partial and total effects is made. The uses of partial and total effects (computed using the new direction) in modification and interpretation of mixture response prediction equations are considered. The suggestions of the paper are illustrated in an example from a glass development study in a waste vitrification program. 5 figures, 3 tables

Equivalence of truncated count mixture distributions and mixtures of truncated count distributions.

Science.gov (United States)

Böhning, Dankmar; Kuhnert, Ronny

2006-12-01

This article is about modeling count data with zero truncation. A parametric count density family is considered. The truncated mixture of densities from this family is different from the mixture of truncated densities from the same family. Whereas the former model is more natural to formulate and to interpret, the latter model is theoretically easier to treat. It is shown that for any mixing distribution leading to a truncated mixture, a (usually different) mixing distribution can be found so that the associated mixture of truncated densities equals the truncated mixture, and vice versa. This implies that the likelihood surfaces for both situations agree, and in this sense both models are equivalent. Zero-truncated count data models are used frequently in the capture-recapture setting to estimate population size, and it can be shown that the two Horvitz-Thompson estimators, associated with the two models, agree. In particular, it is possible to achieve strong results for mixtures of truncated Poisson densities, including reliable, global construction of the unique NPMLE (nonparametric maximum likelihood estimator) of the mixing distribution, implying a unique estimator for the population size. The benefit of these results lies in the fact that it is valid to work with the mixture of truncated count densities, which is less appealing for the practitioner but theoretically easier. Mixtures of truncated count densities form a convex linear model, for which a developed theory exists, including global maximum likelihood theory as well as algorithmic approaches. Once the problem has been solved in this class, it might readily be transformed back to the original problem by means of an explicitly given mapping. Applications of these ideas are given, particularly in the case of the truncated Poisson family.

Soil aggregate stability and rainfall-induced sediment transport on field plots as affected by amendment with organic matter inputs

Science.gov (United States)

Shi, Pu; Arter, Christian; Liu, Xingyu; Keller, Martin; Schulin, Rainer

2017-04-01

Aggregate stability is an important factor in soil resistance against erosion, and, by influencing the extent of sediment transport associated with surface runoff, it is thus also one of the key factors which determine on- and off-site effects of water erosion. As it strongly depends on soil organic matter, many studies have explored how aggregate stability can be improved by organic matter inputs into the soil. However, the focus of these studies has been on the relationship between aggregate stability and soil organic matter dynamics. How the effects of organic matter inputs on aggregate stability translate into soil erodibility under rainfall impacts has received much less attention. In this study, we performed field plot experiments to examine how organic matter inputs affect aggregate breakdown and surface sediment transport under field conditions in artificial rainfall events. Three pairs of plots were prepared by adding a mixture of grass and wheat straw to one of plots in each pair but not to the other, while all plots were treated in the same way otherwise. The rainfall events were applied some weeks later so that the applied organic residues had sufficient time for decomposition and incorporation into the soil. Surface runoff rate and sediment concentration showed substantial differences between the treatments with and without organic matter inputs. The plots with organic inputs had coarser and more stable aggregates and a rougher surface than the control plots without organic inputs, resulting in a higher infiltration rate and lower transport capacity of the surface runoff. Consequently, sediments exported from the amended plots were less concentrated but more enriched in suspended particles (selective sediment transport. In contrast to the amended plots, there was an increase in the coarse particle fraction (> 250 µm) in the runoff from the plots with no organic matter inputs towards the end of the rainfall events due to emerging bed-load transport

Effects of vegetation restoration on the aggregate stability and distribution of aggregate-associated organic carbon in a typical karst gorge region

Science.gov (United States)

Tang, F. K.; Cui, M.; Lu, Q.; Liu, Y. G.; Guo, H. Y.; Zhou, J. X.

2015-08-01

Changes in soil utilization significantly affect aggregate stability and aggregate-associated soil organic carbon (SOC). A field investigation and indoor analysis were conducted in order to study the soil aggregate stability and organic carbon distribution in the water-stable aggregates (WSA) of the bare land (BL), grassland (GL), shrubland (SL), and woodland (WL) in a typical karst gorge region. The results indicated that the BL, GL, SL, and WL were dominated by particles with sizes > 5 mm under dry sieving treatment, and that the soil aggregate contents of various sizes decreased as the particle size decreased. In addition, the BL, GL, SL, and WL were predominantly comprised of WSA sieving treatment, and that the WSA contents initially increased, then decreased, and then increased again as the particle size decreased. Furthermore, at a soil depth of 0-60 cm, the mean weight diameter (MWD), geometrical mean diameter (GMD), and fractal dimensions (D) of the dry aggregates and water-stable aggregates in the different types of land were ranked, in descending order, as WL > GL > SL > BL. The contents of WSA > 0.25 mm, MWD and GMD increased significantly, in that order, and the percentage of aggregate destruction (PAD) and fractal dimensions decreased significantly as the soil aggregate stability improved. The results of this study indicated that, as the SOC contents increased after vegetation restoration, the average SOC content of WL was 2.35, 1.37, and 1.26 times greater than that in the BL, GL, and SL, respectively. The total SOC and SOC associated in WSA of various sizes were the highest at a soil depth of 0-20 cm. In addition, the SOC contents of the WSA increased as the soil aggregate sizes decreased. The SOC contents of the WSA aggregates aggregate SOC contents. The woodland and grassland facilitated WSA stability and SOC protection, thus, promoting the natural restoration of vegetation by reducing artificial disturbances could effectively restore the ecology

The Mechanisms of Aberrant Protein Aggregation

Science.gov (United States)

Cohen, Samuel; Vendruscolo, Michele; Dobson, Chris; Knowles, Tuomas

2012-02-01

We discuss the development of a kinetic theory for understanding the aberrant loss of solubility of proteins. The failure to maintain protein solubility results often in the assembly of organized linear structures, commonly known as amyloid fibrils, the formation of which is associated with over 50 clinical disorders including Alzheimer's and Parkinson's diseases. A true microscopic understanding of the mechanisms that drive these aggregation processes has proved difficult to achieve. To address this challenge, we apply the methodologies of chemical kinetics to the biomolecular self-assembly pathways related to protein aggregation. We discuss the relevant master equation and analytical approaches to studying it. In particular, we derive the underlying rate laws in closed-form using a self-consistent solution scheme; the solutions that we obtain reveal scaling behaviors that are very generally present in systems of growing linear aggregates, and, moreover, provide a general route through which to relate experimental measurements to mechanistic information. We conclude by outlining a study of the aggregation of the Alzheimer's amyloid-beta peptide. The study identifies the dominant microscopic mechanism of aggregation and reveals previously unidentified therapeutic strategies.

An Asymmetrical Glycerol Diether Bolalipid with Protonable Phosphodimethylethanolamine Headgroup: The Impact of pH on Aggregation Behavior and Miscibility with DPPC

Directory of Open Access Journals (Sweden)

Thomas Markowski

2017-11-01

Full Text Available Investigations regarding the self-assembly of (bolaphospholipids in aqueous media are crucial to understand the complex relationship between chemical structure of lipids and the shape and size of their aggregates in water. Here, we introduce a new asymmetrical glycerol diether bolaphospholipid, the compound Me2PE-Gly(2C16C32-OH. This bolalipid contains a long (C32 ω-hydroxy alkyl chain bond to glycerol in the sn-3 position, a C16 alkyl chain at the sn-2 position, and a protonable phosphodimethylethanolamine (Me2PE headgroup at the sn-1 position of the glycerol. The aggregation behavior of this bolalipid was studied as a function of temperature and pH using transmission electron microscopy (TEM, differential scanning calorimetry (DSC, and Fourier transform infrared (FTIR spectroscopy. We show that this bolalipid aggregates into condensed lamellar sheets in acidic milieu and in large sheet-like aggregates at neutral pH-value. By contrast, at a pH-value of 10, where the Me2PE headgroup is only partially protonated, small lipid disks with diameter 50–100 nm were additionally found. Moreover, the miscibility of this asymmetrical bolalipid with the bilayer-forming phosphatidylcholine DPPC was investigated by means of DSC and TEM. The incorporation of bolalipids into phospholipid membranes could result in stabilized liposomes applicable for drug delivery purposes. We show that mixtures of DPPC and Me2PE-Gly(2C16C32-OH form large lamellar aggregates at pH of 5, 7, and 10. However, closed lipid vesicles (liposomes with an increased thermal stability were not found.

Salt-induced aggregation of stiff polyelectrolytes

International Nuclear Information System (INIS)

Fazli, Hossein; Mohammadinejad, Sarah; Golestanian, Ramin

2009-01-01

Molecular dynamics simulation techniques are used to study the process of aggregation of highly charged stiff polyelectrolytes due to the presence of multivalent salt. The dominant kinetic mode of aggregation is found to be the case of one end of one polyelectrolyte meeting others at right angles, and the kinetic pathway to bundle formation is found to be similar to that of flocculation dynamics of colloids as described by Smoluchowski. The aggregation process is found to favor the formation of finite bundles of 10-11 filaments at long times. Comparing the distribution of the cluster sizes with the Smoluchowski formula suggests that the energy barrier for the aggregation process is negligible. Also, the formation of long-lived metastable structures with similarities to the raft-like structures of actin filaments is observed within a range of salt concentration.

Suspensions of colloidal particles and aggregates

CERN Document Server

Babick, Frank

2016-01-01

This book addresses the properties of particles in colloidal suspensions. It has a focus on particle aggregates and the dependency of their physical behaviour on morphological parameters. For this purpose, relevant theories and methodological tools are reviewed and applied to selected examples. The book is divided into four main chapters. The first of them introduces important measurement techniques for the determination of particle size and interfacial properties in colloidal suspensions. A further chapter is devoted to the physico-chemical properties of colloidal particles—highlighting the interfacial phenomena and the corresponding interactions between particles. The book’s central chapter examines the structure-property relations of colloidal aggregates. This comprises concepts to quantify size and structure of aggregates, models and numerical tools for calculating the (light) scattering and hydrodynamic properties of aggregates, and a discussion on van-der-Waals and double layer interactions between ...

Thermophysical properties of binary mixtures of {ionic liquid 2-hydroxy ethylammonium acetate + (water, methanol, or ethanol)}

International Nuclear Information System (INIS)

Alvarez, Victor H.; Mattedi, Silvana; Martin-Pastor, Manuel; Aznar, Martin; Iglesias, Miguel

2011-01-01

Research highlights: → This paper reports the density and speed of sound data of binary mixtures {2-hydroxy ethylammonium acetate + (water, or methanol, or ethanol)} measured between the temperatures (298.15 and 313.15) K at atmospheric pressure. → The aggregation, dynamic behavior, and hydrogen-bond network were studied using thermo-acoustic, X-ray, and NMR techniques. → The Peng-Robinson equation of state, coupled with the Wong-Sandler mixing rule using the COSMO-SAC model predicted the density of the solutions with relative mean deviations below than 3.0%. - Abstract: In this work, density and speed of sound data of binary mixtures of an ionic liquid consisting of {2-hydroxy ethylammonium acetate (2-HEAA) + (water, methanol, or ethanol)} have been measured throughout the entire concentration range, from the temperature of (288.15 to 323.15) K at atmospheric pressure. The excess molar volumes, variations of the isentropic compressibility, the apparent molar volume, isentropic apparent molar compressibility, and thermal expansion coefficient were calculated from the experimental data. The excess molar volumes were negative throughout the whole composition range. Compressibility data in combination with low angle X-ray scattering and NMR measurements proved that the presence of micelles formed due to ion pair interaction above a critical concentration of the ionic liquid in the mixtures. The Peng-Robinson equation of state coupled with the Wong-Sandler mixing rule and COSMO-SAC model was used to predict densities and the calculated deviations were lower than 3%, for binary mixtures in all composition range.

ARK: Aggregation of Reads by K-Means for Estimation of Bacterial Community Composition.

Science.gov (United States)

Koslicki, David; Chatterjee, Saikat; Shahrivar, Damon; Walker, Alan W; Francis, Suzanna C; Fraser, Louise J; Vehkaperä, Mikko; Lan, Yueheng; Corander, Jukka

2015-01-01

Estimation of bacterial community composition from high-throughput sequenced 16S rRNA gene amplicons is a key task in microbial ecology. Since the sequence data from each sample typically consist of a large number of reads and are adversely impacted by different levels of biological and technical noise, accurate analysis of such large datasets is challenging. There has been a recent surge of interest in using compressed sensing inspired and convex-optimization based methods to solve the estimation problem for bacterial community composition. These methods typically rely on summarizing the sequence data by frequencies of low-order k-mers and matching this information statistically with a taxonomically structured database. Here we show that the accuracy of the resulting community composition estimates can be substantially improved by aggregating the reads from a sample with an unsupervised machine learning approach prior to the estimation phase. The aggregation of reads is a pre-processing approach where we use a standard K-means clustering algorithm that partitions a large set of reads into subsets with reasonable computational cost to provide several vectors of first order statistics instead of only single statistical summarization in terms of k-mer frequencies. The output of the clustering is then processed further to obtain the final estimate for each sample. The resulting method is called Aggregation of Reads by K-means (ARK), and it is based on a statistical argument via mixture density formulation. ARK is found to improve the fidelity and robustness of several recently introduced methods, with only a modest increase in computational complexity. An open source, platform-independent implementation of the method in the Julia programming language is freely available at https://github.com/dkoslicki/ARK. A Matlab implementation is available at http://www.ee.kth.se/ctsoftware.

Experiments with Mixtures Designs, Models, and the Analysis of Mixture Data

CERN Document Server

Cornell, John A

2011-01-01

The most comprehensive, single-volume guide to conducting experiments with mixtures"If one is involved, or heavily interested, in experiments on mixtures of ingredients, one must obtain this book. It is, as was the first edition, the definitive work."-Short Book Reviews (Publication of the International Statistical Institute)"The text contains many examples with worked solutions and with its extensive coverage of the subject matter will prove invaluable to those in the industrial and educational sectors whose work involves the design and analysis of mixture experiments."-Journal of the Royal S

Path coupling and aggregate path coupling

CERN Document Server

Kovchegov, Yevgeniy

2018-01-01

This book describes and characterizes an extension to the classical path coupling method applied to statistical mechanical models, referred to as aggregate path coupling. In conjunction with large deviations estimates, the aggregate path coupling method is used to prove rapid mixing of Glauber dynamics for a large class of statistical mechanical models, including models that exhibit discontinuous phase transitions which have traditionally been more difficult to analyze rigorously. The book shows how the parameter regions for rapid mixing for several classes of statistical mechanical models are derived using the aggregate path coupling method.

Entanglement dynamics of J-aggregate systems

Energy Technology Data Exchange (ETDEWEB)

Thilagam, A, E-mail: Thilagam.Lohe@unisa.edu.au [Information Technology, Engineering and the Environment, Mawson Institute, University of South Australia, South Australia 5095 (Australia)

2011-04-01

The entanglement dynamics of one-dimensional J-aggregate systems are examined using entanglement measures such as the von Neumann entropy and Wootters concurrence. The effect of dispersion and resonance terms associated with the exciton-phonon interaction are analyzed using Green's function formalism. A probability propagator term, derived using the Markovian approximation, presents J-aggregate systems as potential channels for large scale energy propagation for a select range of parameters. We highlight the role of a critical number of coherently coupled monomer sites and two-exciton states in determining superradiance in J-aggregate systems.

Preliminary studies on steel slag as a substitute for coarse aggregate on concrete

Directory of Open Access Journals (Sweden)

Karolina Rahmi

2017-01-01

Full Text Available The development of science and technology in the field of construction that is rapidly increasing, is always followed by the growing community needs for infrastructure facilities, such as buildings, bridges and other construction. One of the key element in that development is concrete. Due to the rapid development of science and technology in the field of construction, it’s required a building material which has better advantage than the materials of the existing building. To obtain a better building materials, one alternative is the use of waste as aggregate in concrete mixture. In this study the authors using waste steel waste (steel slag as a substitute for coarse aggregate. Steel slag used is steel waste from PT. Growth Sumatra Industry. The gravel substitution variations is 0%, 15%, and 25% and the testing was done by the slump test, compressive strength and flexural strength of concrete. From the test results obtained optimum compressive strength variation occurs in 25% substitution of steel slag gravel amounted to 40.481 MPa, whereas for the optimum bending capacity contained in variations of 25% substitution of steel slag gravel amounted to 19.592 N / mm2. And for optimum slump value obtained on the variation of normal concrete. This shows the workability of the concrete normally higher than the other variation.

Strengths and Failure Characteristics of Self-Compacting Concrete Containing Recycled Waste Glass Aggregate

Directory of Open Access Journals (Sweden)

Rahman Khaleel AL-Bawi

2017-01-01

Full Text Available The effects of different proportions of green-colored waste glass (WG cullet on the mechanical and fracture properties of self-compacting concrete (SCC were experimentally investigated. Waste bottles were collected, washed, crushed, and sieved to prepare the cullet used in this study. Cullet was incorporated at different percentages (0%, 20%, 40%, 60%, 80%, and 100% by weight instead of natural fine aggregate (NFA and/or natural coarse aggregate (NCA. Three SCC series were designed with a constant slump flow of 700±30 mm, total binder content of 570 kg/m3 and at water-to-binder (w/b ratio of 0.35. Moreover, fly ash (FA was used in concrete mixtures at 20% of total binder content. Mechanical aspects such as compressive, splitting tensile, and net flexural strengths and modulus of elasticity of SCC were investigated and experimentally computed at 28 days of age. Moreover, failure characteristics of the concretes were also monitored via three-point bending test on the notched beams. The findings revealed that the mechanical properties as well as fracture parameters were adversely influenced by incorporating of WG cullet. However, highest reduction of compressive strength did not exceed 43% recorded at 100% WG replacement level. Concretes containing WG showed less brittle behavior than reference concrete at any content.

Strain-dependent profile of misfolded prion protein aggregates.

Science.gov (United States)

Morales, Rodrigo; Hu, Ping Ping; Duran-Aniotz, Claudia; Moda, Fabio; Diaz-Espinoza, Rodrigo; Chen, Baian; Bravo-Alegria, Javiera; Makarava, Natallia; Baskakov, Ilia V; Soto, Claudio

2016-02-15

Prions are composed of the misfolded prion protein (PrP(Sc)) organized in a variety of aggregates. An important question in the prion field has been to determine the identity of functional PrP(Sc) aggregates. In this study, we used equilibrium sedimentation in sucrose density gradients to separate PrP(Sc) aggregates from three hamster prion strains (Hyper, Drowsy, SSLOW) subjected to minimal manipulations. We show that PrP(Sc) aggregates distribute in a wide range of arrangements and the relative proportion of each species depends on the prion strain. We observed a direct correlation between the density of the predominant PrP(Sc) aggregates and the incubation periods for the strains studied. The relative presence of PrP(Sc) in fractions of different sucrose densities was indicative of the protein deposits present in the brain as analyzed by histology. Interestingly, no association was found between sensitivity to proteolytic degradation and aggregation profiles. Therefore, the organization of PrP molecules in terms of the density of aggregates generated may determine some of the particular strain properties, whereas others are independent from it. Our findings may contribute to understand the mechanisms of strain variation and the role of PrP(Sc) aggregates in prion-induced neurodegeneration.

Balancing energy flexibilities through aggregation

DEFF Research Database (Denmark)

Valsomatzis, Emmanouil; Hose, Katja; Pedersen, Torben Bach

2014-01-01

One of the main goals of recent developments in the Smart Grid area is to increase the use of renewable energy sources. These sources are characterized by energy fluctuations that might lead to energy imbalances and congestions in the electricity grid. Exploiting inherent flexibilities, which exist...... in both energy production and consumption, is the key to solving these problems. Flexibilities can be expressed as flex-offers, which due to their high number need to be aggregated to reduce the complexity of energy scheduling. In this paper, we discuss balance aggregation techniques that already during...... aggregation aim at balancing flexibilities in production and consumption to reduce the probability of congestions and reduce the complexity of scheduling. We present results of our extensive experiments....

SHAPE ANALYSIS OF FINE AGGREGATES USED FOR CONCRETE

Directory of Open Access Journals (Sweden)

Huan He

2016-12-01

Full Text Available Fine aggregate is one of the essential components in concrete and significantly influences the material properties. As parts of natures, physical characteristics of fine aggregate are highly relevant to its behaviors in concrete. The most of previous studies are mainly focused on the physical properties of coarse aggregate due to the equipment limitations. In this paper, two typical fine aggregates, i.e. river sand and crushed rock, are selected for shape characterization. The new developed digital image analysis systems are employed as the main approaches for the purpose. Some other technical methods, e.g. sieve test, laser diffraction method are also used for the comparable references. Shape characteristics of fine aggregates with different origins but in similar size ranges are revealed by this study. Compared with coarse aggregate, fine grains of different origins generally have similar shape differences. These differences are more significant in surface texture properties, which can be easily identified by an advanced shape parameter: bluntness. The new image analysis method is then approved to be efficient for the shape characterization of fine aggregate in concrete.

Perception of trigeminal mixtures.

Science.gov (United States)

Filiou, Renée-Pier; Lepore, Franco; Bryant, Bruce; Lundström, Johan N; Frasnelli, Johannes

2015-01-01

The trigeminal system is a chemical sense allowing for the perception of chemosensory information in our environment. However, contrary to smell and taste, we lack a thorough understanding of the trigeminal processing of mixtures. We, therefore, investigated trigeminal perception using mixtures of 3 relatively receptor-specific agonists together with one control odor in different proportions to determine basic perceptual dimensions of trigeminal perception. We found that 4 main dimensions were linked to trigeminal perception: sensations of intensity, warmth, coldness, and pain. We subsequently investigated perception of binary mixtures of trigeminal stimuli by means of these 4 perceptual dimensions using different concentrations of a cooling stimulus (eucalyptol) mixed with a stimulus that evokes warmth perception (cinnamaldehyde). To determine if sensory interactions are mainly of central or peripheral origin, we presented stimuli in a physical "mixture" or as a "combination" presented separately to individual nostrils. Results showed that mixtures generally yielded higher ratings than combinations on the trigeminal dimensions "intensity," "warm," and "painful," whereas combinations yielded higher ratings than mixtures on the trigeminal dimension "cold." These results suggest dimension-specific interactions in the perception of trigeminal mixtures, which may be explained by particular interactions that may take place on peripheral or central levels. © The Author 2014. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Self-aggregation of magnetic semiconductor EuS nanocrystals

International Nuclear Information System (INIS)

Tanaka, Atsushi; Hasegawa, Yasuchika; Kamikubo, Hironari; Kataoka, Mikio; Kawai, Tsuyoshi

2009-01-01

Controlled formation of aggregates having organized structure of cube-shaped EuS nanocrystals is reported. The EuS aggregates in liquid media (methanol) were obtained by means of van der Waals interaction between EuS nanocrystals. The packing structure of the EuS aggregates is characterized with transmission electron microscopy (TEM) and small angle X-ray scattering measurements (SAXS). TEM image indicates the EuS nanocrystals form self-aggregated 2D orthogonal lattice structure. The diffraction peak of (111) of SAXS profile shows that the cube-shaped EuS form 3D cubic superlattice. We successfully demonstrated that the aggregates of cube-shaped EuS nanocrystals formed cubic stacking structure.

Spatial Mixture Modelling for Unobserved Point Processes: Examples in Immunofluorescence Histology.

Science.gov (United States)

Ji, Chunlin; Merl, Daniel; Kepler, Thomas B; West, Mike

2009-12-04

We discuss Bayesian modelling and computational methods in analysis of indirectly observed spatial point processes. The context involves noisy measurements on an underlying point process that provide indirect and noisy data on locations of point outcomes. We are interested in problems in which the spatial intensity function may be highly heterogenous, and so is modelled via flexible nonparametric Bayesian mixture models. Analysis aims to estimate the underlying intensity function and the abundance of realized but unobserved points. Our motivating applications involve immunological studies of multiple fluorescent intensity images in sections of lymphatic tissue where the point processes represent geographical configurations of cells. We are interested in estimating intensity functions and cell abundance for each of a series of such data sets to facilitate comparisons of outcomes at different times and with respect to differing experimental conditions. The analysis is heavily computational, utilizing recently introduced MCMC approaches for spatial point process mixtures and extending them to the broader new context here of unobserved outcomes. Further, our example applications are problems in which the individual objects of interest are not simply points, but rather small groups of pixels; this implies a need to work at an aggregate pixel region level and we develop the resulting novel methodology for this. Two examples with with immunofluorescence histology data demonstrate the models and computational methodology.

Modelling The Effects of Aggregate Size on Alkali Aggregate Reaction Expansion

Directory of Open Access Journals (Sweden)

N. Z. Sekrane

2014-06-01

Full Text Available This work aims at developing models to predict the potential expansion of concrete containing alkali-reactive aggregates. The paper gives measurements in order to provide experimental data concerning the effect of particle size of an alkali-reactive siliceous limestone on mortar expansion. Results show that no expansion was measured on the mortars using small particles (0.5-1.0 mm while the particles (1.0–2.0 mm gave the largest expansions (0.217%. Two models are proposed, the first one studies the correlations between the measured expansions and the size of aggregates, the second one calculates the thickness of the porous zone necessary to take again all the volume of the gel created.

Complex mixtures, complex responses: Assessing pharmaceutical mixtures using field and laboratory approaches

Science.gov (United States)

Schoenfuss, Heiko L.; Furlong, Edward T.; Phillips, Patrick J.; Scott, Tia-Marie; Kolpin, Dana W.; Cetkovic-Cvrlje, Marina; Lesteberg, Kelsey E.; Rearick, Daniel C.

2016-01-01

Pharmaceuticals are present in low concentrations (pharmaceutical formulation facilities. Using existing concentration data, the authors assessed pharmaceuticals in laboratory exposures of fathead minnows (Pimephales promelas) and added environmental complexity through effluent exposures. In the laboratory, larval and mature minnows were exposed to a simple opioid mixture (hydrocodone, methadone, and oxycodone), an opioid agonist (tramadol), a muscle relaxant (methocarbamol), a simple antidepressant mixture (fluoxetine, paroxetine, venlafaxine), a sleep aid (temazepam), or a complex mixture of all compounds. Larval minnow response to effluent exposure was not consistent. The 2010 exposures resulted in shorter exposed minnow larvae, whereas the larvae exposed in 2012 exhibited altered escape behavior. Mature minnows exhibited altered hepatosomatic indices, with the strongest effects in females and in mixture exposures. In addition, laboratory-exposed, mature male minnows exposed to all pharmaceuticals (except the selective serotonin reuptake inhibitor mixture) defended nest sites less rigorously than fish in the control group. Tramadol or antidepressant mixture exposure resulted in increased splenic T lymphocytes. Only male minnows exposed to whole effluent responded with increased plasma vitellogenin concentrations. Female minnows exposed to pharmaceuticals (except the opioid mixture) had larger livers, likely as a compensatory result of greater prominence of vacuoles in liver hepatocytes. The observed alteration of apical endpoints central to sustaining fish populations confirms that effluents containing waste streams from pharmaceutical formulation facilities can adversely impact fish populations but that the effects may not be temporally consistent. The present study highlights the importance of including diverse biological endpoints spanning levels of biological organization and life stages when assessing contaminant interactions.

Nonequimolar Mixture of Organic Acids and Bases: An Exception to the Rule of Thumb for Salt or Cocrystal.

Science.gov (United States)

Pratik, Saied Md; Datta, Ayan

2016-08-04

Formation of salt and/or cocrystal from organic acid-base mixtures has significant consequences in the pharmaceutical industry and its related intellectual property rights (IPR). On the basis of calculations using periodic dispersion corrected DFT (DFT-D2) on formic acid-pyridine adduct, we have demonstrated that an equimolar stoichiometric ratio (1:1) exists as a neutral cocrystal. On the other hand, the nonequimolar stoichiometry (4:1) readily forms an ionic salt. While the former result is in agreement with the ΔpKa rule between the base and the acid, the latter is not. Calculations reveal that, within the equimolar manifold (n:n; n = 1-4), the mixture exists as a hydrogen bonded complex in a cocrystal-like environment. However, the nonequimolar mixture in a ratio of 5:1 and above readily forms salt-like structures. Because of the cooperative nature of hydrogen bonding, the strength of the O-H···N hydrogen bond increases and eventually transforms into O(-)···H-N(+) (complete proton transfer) as the ratio of formic acid increases and forms salt as experimentally observed. Clearly, an enhanced polarization of formic acid on aggregation increases its acidity and, hence, facilitates its transfer to pyridine. Motion of the proton from formic acid to pyridine is shown to follow a relay mechanism wherein the proton that is far away from pyridine is ionized and is subsequently transferred to pyridine via hopping across the neutral formic acid molecules (Grotthuss type pathway). The dynamic nature of protons in the condensed phase is also evident for cocrystals as the barrier of intramolecular proton migration in formic acid (leading to tautomerism), ΔH(⧧)tautomer = 17.1 kcal/mol in the presence of pyridine is half of that in free formic acid (cf. ΔH(⧧)tautomer = 34.2 kcal/mol). We show that an acid-base reaction can be altered in the solid state to selectively form a cocrystal or salt depending on the strength and nature of aggregation.

Model of fractal aggregates induced by shear

Directory of Open Access Journals (Sweden)

Wan Zhanhong

2013-01-01

Full Text Available It is an undoubted fact that particle aggregates from marine, aerosol, and engineering systems have fractal structures. In this study, fractal geometry is used to describe the morphology of irregular aggregates. The mean-field theory is employed to solve coagulation kinetic equation of aggregates. The Taylor-expansion method of moments in conjunction with the self-similar fractal characteristics is used to represent the particulate field. The effect of the target fractal dimensions on zeroth-order moment, second-order moment, and geometric standard deviation of the aggregates is explored. Results show that the developed moment method is an efficient and powerful approach to solving such evolution equations.

Towards Better Understanding of Concrete Containing Recycled Concrete Aggregate

Directory of Open Access Journals (Sweden)

Hisham Qasrawi

2013-01-01

Full Text Available The effect of using recycled concrete aggregates (RCA on the basic properties of normal concrete is studied. First, recycled aggregate properties have been determined and compared to those of normal aggregates. Except for absorption, there was not a significant difference between the two. Later, recycled aggregates were introduced in concrete mixes. In these mixes, natural coarse aggregate was partly or totally replaced by recycled aggregates. Results show that the use of recycled aggregates has an adverse effect on the workability and air content of fresh concrete. Depending on the water/cement ratio and on the percent of the normal aggregate replaced by RCA, the concrete strength is reduced by 5% to 25%, while the tensile strength is reduced by 4% to 14%. All results are compared with previous research. As new in this research, the paper introduces a simple formula for the prediction of the modulus of elasticity of RCA concrete. Furthermore, the paper shows the variation of the air content of RAC.

Microbial Ecology of Soil Aggregation in Agroecosystems

Science.gov (United States)

Hofmockel, K. S.; Bell, S.; Tfailly, M.; Thompson, A.; Callister, S.

2017-12-01

Crop selection and soil texture influence the physicochemical attributes of the soil, which structures microbial communities and influences soil C cycling storage. At the molecular scale, microbial metabolites and necromass alter the soil environment, which creates feedbacks that influence ecosystem functions, including soil C accumulation. By integrating lab to field studies we aim to identify the molecules, organisms and metabolic pathways that control carbon cycling and stabilization in bioenergy soils. We investigated the relative influence of plants, microbes, and minerals on soil aggregate ecology at the Great Lakes Bioenergy Research experiment. Sites in WI and MI, USA have been in corn and switchgrass cropping systems for a decade. By comparing soil aggregate ecology across sites and cropping systems we are able to test the relative importance of plant, microbe, mineral influences on soil aggregate dynamics. Soil microbial communities (16S) differ in diversity and phylogeny among sites and cropping systems. FT-ICR MS revealed differences in the molecular composition of water-soluble fraction of soil organic matter for cropping systems and soil origin for both relative abundance of assigned formulas and biogeochemical classes of compounds. We found the degree of aggregation, measured by mean weighted diameter of aggregate fractions, is influenced by plant-soil interactions. Similarly, the proportion of soil aggregate fractions varied by both soil and plant factors. Differences in aggregation were reflected in differences in bacterial, but not fungal community composition across aggregate fractions, within each soil. Scanning electron microscopy revealed stark differences in mineral-organic interactions that influence the microbial niche and the accessibility of substrates within the soil. The clay soils show greater surface heterogeneity, enabling interactions with organic fraction of the soil. This is consistent with molecular data that reveal differences

The Field Emission Properties of Graphene Aggregates Films Deposited on Fe-Cr-Ni alloy Substrates

Directory of Open Access Journals (Sweden)

Zhanling Lu

2010-01-01

Full Text Available The graphene aggregates films were fabricated directly on Fe-Cr-Ni alloy substrates by microwave plasma chemical vapor deposition system (MPCVD. The source gas was a mixture of H2 and CH4 with flow rates of 100 sccm and 12 sccm, respectively. The micro- and nanostructures of the samples were characterized by Raman scattering spectroscopy, field emission scanning electron microscopy (SEM, and transparent electron microscopy (TEM. The field emission properties of the films were measured using a diode structure in a vacuum chamber. The turn-on field was about 1.0 V/m. The current density of 2.1 mA/cm2 at electric field of 2.4 V/m was obtained.

Cooperative structural transitions in amyloid-like aggregation

Science.gov (United States)

Steckmann, Timothy; Bhandari, Yuba R.; Chapagain, Prem P.; Gerstman, Bernard S.

2017-04-01

Amyloid fibril aggregation is associated with several horrific diseases such as Alzheimer's, Creutzfeld-Jacob, diabetes, Parkinson's, and others. Although proteins that undergo aggregation vary widely in their primary structure, they all produce a cross-β motif with the proteins in β-strand conformations perpendicular to the fibril axis. The process of amyloid aggregation involves forming myriad different metastable intermediate aggregates. To better understand the molecular basis of the protein structural transitions and aggregation, we report on molecular dynamics (MD) computational studies on the formation of amyloid protofibrillar structures in the small model protein ccβ, which undergoes many of the structural transitions of the larger, naturally occurring amyloid forming proteins. Two different structural transition processes involving hydrogen bonds are observed for aggregation into fibrils: the breaking of intrachain hydrogen bonds to allow β-hairpin proteins to straighten, and the subsequent formation of interchain H-bonds during aggregation into amyloid fibrils. For our MD simulations, we found that the temperature dependence of these two different structural transition processes results in the existence of a temperature window that the ccβ protein experiences during the process of forming protofibrillar structures. This temperature dependence allows us to investigate the dynamics on a molecular level. We report on the thermodynamics and cooperativity of the transformations. The structural transitions that occurred in a specific temperature window for ccβ in our investigations may also occur in other amyloid forming proteins but with biochemical parameters controlling the dynamics rather than temperature.

Aggregate formation in 3D turbulent-like flows

NARCIS (Netherlands)

Dominguez, A.; Aartrijk, van M.; Castello, Del L.; Clercx, H.J.H.; Geurts, B.; Clercx, H

2006-01-01

Aggregate formation is an important process in industrial and environ mental turbulent flows. Two examples in the environmental area, where turbulent aggregate formation takes place, are raindrop formation in clouds and Marine Snow (aggregate) formation in the upper layer in the oceans. The

Engineering Performance of Polyurethane Bonded Aggregates

Directory of Open Access Journals (Sweden)

Haimin WU

2017-08-01

Full Text Available In this paper the engineering performance of polyurethane (PUR bonded aggregate were studied. The engineering performance, including compressive and flexural mechanical properties, void ratio, and coefficient of permeability were determined through laboratory tests. Moreover, the effects of two different curing conditions on the compressive strength properties of a PUR bonded aggregate were also evaluated. The compressive strengths of PUR bonded aggregates were found to be lower than that of conventional porous concrete, which is a commonly used cushion material. However, experimental results indicated a higher void ratio and coefficient of permeability, lower elasticity modulus, better toughness, and stronger adaptability to flexural deformation compared to porous concrete. Consequently, PUR bonded aggregate is a better solution than porous concrete when used as the cushion material of a geomembrane surface barrier for a high rock-fill dam.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.15798

SHAPE ANALYSIS OF FINE AGGREGATES USED FOR CONCRETE

OpenAIRE

HE, Huan; Courard, Luc; Pirard, Eric; Michel, Frédéric

2016-01-01

Fine aggregate is one of the essential components in concrete and significantly influences the material properties. As parts of natures, physical characteristics of fine aggregate are highly relevant to its behaviors in concrete. The most of previous studies are mainly focused on the physical properties of coarse aggregate due to the equipment limitations. In this paper, two typical fine aggregates, i.e. river sand and crushed rock, are selected for shape characterization. The new developed d...

Grouting mixture

Energy Technology Data Exchange (ETDEWEB)

Klyusov, A A; Bakshutov, V S; Kulyavtsev, V A

1980-10-23

A grouting mixture is proposed for low-temperature boreholes. The mixture contains cement, beta gypsum polyhydrate, and calcium chloride, so as to increase the water resistance and strength properties of expanding brick at conditions from 20 to -5/sup 0/ C, the components are in the following ratios: (by wt.-%): cement, 77.45-88.06; beta gypsum polyhydrate, 9.79-19.36; calcium chloride, 2.15-3.19. Grouting mortar for cold boreholes serves as the cement.

Probabilistic Analysis of Structural Member from Recycled Aggregate Concrete

Science.gov (United States)

Broukalová, I.; Šeps, K.

2017-09-01

The paper aims at the topic of sustainable building concerning recycling of waste rubble concrete from demolition. Considering demands of maximising recycled aggregate use and minimising of cement consumption, composite from recycled concrete aggregate was proposed. The objective of the presented investigations was to verify feasibility of the recycled aggregate cement based fibre reinforced composite in a structural member. Reliability of wall from recycled aggregate fibre reinforced composite was assessed in a probabilistic analysis of a load-bearing capacity of the wall. The applicability of recycled aggregate fibre reinforced concrete in structural applications was demonstrated. The outcomes refer to issue of high scatter of material parameters of recycled aggregate concretes.

Liver tissue engineering based on aggregate assembly: efficient formation of endothelialized rat hepatocyte aggregates and their immobilization with biodegradable fibres

International Nuclear Information System (INIS)

Pang, Y; Shinohara, M; Komori, K; Sakai, Y; Montagne, K

2012-01-01

To realize long-term in vitro culture of hepatocytes at a high density while maintaining a high hepatic function for aggregate-based liver tissue engineering, we report here a novel culture method whereby endothelialized rat hepatocyte aggregates were formed using a PDMS microwell device and cultured in a perfusion bioreactor by introducing spacers between aggregates to improve oxygen and nutrient supply. Primary rat hepatocyte aggregates around 100 µm in diameter coated with human umbilical vein endothelial cells were spontaneously and quickly formed after 12 h of incubation, thanks to the continuous supply of oxygen by diffusion through the PDMS honeycomb microwell device. Then, the recovered endothelialized rat hepatocyte aggregates were mixed with biodegradable poly-l-lactic acid fibres in suspension and packed into a PDMS-based bioreactor. Perfusion culture of 7 days was successfully achieved with more than 73.8% cells retained in the bioreactor. As expected, the fibres acted as spacers between aggregates, which was evidenced from the enhanced albumin production and more spherical morphology compared with fibre-free packing. In summary, this study shows the advantages of using PDMS-based microwells to form heterotypic aggregates and also demonstrates the feasibility of spacing tissue elements for improving oxygen and nutrient supply to tissue engineering based on modular assembly. (paper)

Aggregate formation in 3D turbulent-like flows

NARCIS (Netherlands)

Dominguez, A.; Clercx, H.J.H.

2006-01-01

Aggregate formation is an important process in industrial and environmental turbulent flows. In oceans turbulence play an important role on Marine Snow (aggregate) formation. For a proper description, the study of aggregate formation in turbulent flows requires a particle based model i.e. following

The proteome of neurofilament-containing protein aggregates in blood

Directory of Open Access Journals (Sweden)

Rocco Adiutori

2018-07-01

Full Text Available Protein aggregation in biofluids is a poorly understood phenomenon. Under normal physiological conditions, fluid-borne aggregates may contain plasma or cell proteins prone to aggregation. Recent observations suggest that neurofilaments (Nf, the building blocks of neurons and a biomarker of neurodegeneration, are included in high molecular weight complexes in circulation. The composition of these Nf-containing hetero-aggregates (NCH may change in systemic or organ-specific pathologies, providing the basis to develop novel disease biomarkers. We have tested ultracentrifugation (UC and a commercially available protein aggregate binder, Seprion PAD-Beads (SEP, for the enrichment of NCH from plasma of healthy individuals, and then characterised the Nf content of the aggregate fractions using gel electrophoresis and their proteome by mass spectrometry (MS. Western blot analysis of fractions obtained by UC showed that among Nf isoforms, neurofilament heavy chain (NfH was found within SDS-stable high molecular weight aggregates. Shotgun proteomics of aggregates obtained with both extraction techniques identified mostly cell structural and to a lesser extent extra-cellular matrix proteins, while functional analysis revealed pathways involved in inflammatory response, phagosome and prion-like protein behaviour. UC aggregates were specifically enriched with proteins involved in endocrine, metabolic and cell-signalling regulation. We describe the proteome of neurofilament-containing aggregates isolated from healthy individuals biofluids using different extraction methods.

Influence of velocity gradient on optimisation of the aggregation process and properties of formed aggregates. Part 2. Quantification of the influence of agitation intensity and time on the properties of formed aggregates

Czech Academy of Sciences Publication Activity Database

Polášek, Pavel

2011-01-01

Roč. 59, č. 3 (2011), s. 196-205 ISSN 0042-790X R&D Projects: GA ČR GA103/07/1016 Institutional research plan: CEZ:AV0Z20600510 Keywords : inline high density suspension (IHDS) formation process * aggregation phases * aggregate properties * compactness * relative density of aggregates Subject RIV: BK - Fluid Dynamics Impact factor: 0.340, year: 2011

Soil aggregation under different management systems

Directory of Open Access Journals (Sweden)

Cibele Mascioli Rebello Portella

2012-12-01

Full Text Available Considering that the soil aggregation reflects the interaction of chemical, physical and biological soil factors, the aim of this study was evaluate alterations in aggregation, in an Oxisol under no-tillage (NT and conventional tillage (CT, since over 20 years, using as reference a native forest soil in natural state. After analysis of the soil profile (cultural profile in areas under forest management, samples were collected from the layers 0-5, 5-10, 10-20 and 20-40 cm, with six repetitions. These samples were analyzed for the aggregate stability index (ASI, mean weighted diameter (MWD, mean geometric diameter (MGD in the classes > 8, 8-4, 4-2, 2-1, 1-0.5, 0.5-0.25, and < 0.25 mm, and for physical properties (soil texture, water dispersible clay (WDC, flocculation index (FI and bulk density (Bd and chemical properties (total organic carbon - COT, total nitrogen - N, exchangeable calcium - Ca2+, and pH. The results indicated that more intense soil preparation (M < NT < PC resulted in a decrease in soil stability, confirmed by all stability indicators analyzed: MWD, MGD, ASI, aggregate class distribution, WDC and FI, indicating the validity of these indicators in aggregation analyses of the studied soil.

Aggregation of natively folded proteins: a theoretical approach

International Nuclear Information System (INIS)

Trovato, Antonio; Maritan, Amos; Seno, Flavio

2007-01-01

The reliable identification of β-aggregating stretches in protein sequences is essential for the development of therapeutic agents for Alzheimer's and Parkinson's diseases, as well as other pathological conditions associated with protein deposition. While the list of aggregation related diseases is growing, it has also been shown that many proteins that are normally well behaved can be induced to aggregate in vitro. This fact suggests the existence of a unified framework that could explain both folding and aggregation. By assuming this universal behaviour, we have recently introduced an algorithm (PASTA: prediction of amyloid structure aggregation), which is based on a sequence-specific energy function derived from the propensity of two residue types to be found paired in neighbouring strands within β-sheets in globular proteins. The algorithm is able to predict the most aggregation-prone portions of several proteins initially unfolded, in excellent agreement with experimental results. Here, we apply the method to a set of proteins which are known to aggregate, but which are natively folded. The quality of the prediction is again very high, corroborating the hypothesis that the amyloid structure is stabilized by the same physico-chemical determinants as those operating in folded proteins

Protein aggregation and misfolding: good or evil?

Science.gov (United States)

Pastore, Annalisa; Temussi, Pierandrea

2012-06-01

Protein aggregation and misfolding have important implications in an increasing number of fields ranging from medicine to biology to nanotechnology and material science. The interest in understanding this field has accordingly increased steadily over the last two decades. During this time the number of publications that have been dedicated to protein aggregation has increased exponentially, tackling the problem from several different and sometime contradictory perspectives. This review is meant to summarize some of the highlights that come from these studies and introduce this topical issue on the subject. The factors that make a protein aggregate and the cellular strategies that defend from aggregation are discussed together with the perspectives that the accumulated knowledge may open.

Protein aggregation and misfolding: good or evil?

International Nuclear Information System (INIS)

Pastore, Annalisa; Temussi, Pierandrea

2012-01-01

Protein aggregation and misfolding have important implications in an increasing number of fields ranging from medicine to biology to nanotechnology and material science. The interest in understanding this field has accordingly increased steadily over the last two decades. During this time the number of publications that have been dedicated to protein aggregation has increased exponentially, tackling the problem from several different and sometime contradictory perspectives. This review is meant to summarize some of the highlights that come from these studies and introduce this topical issue on the subject. The factors that make a protein aggregate and the cellular strategies that defend from aggregation are discussed together with the perspectives that the accumulated knowledge may open. (topical review)

A study of radiative properties of fractal soot aggregates using the superposition T-matrix method

International Nuclear Information System (INIS)

Li Liu; Mishchenko, Michael I.; Patrick Arnott, W.

2008-01-01

We employ the numerically exact superposition T-matrix method to perform extensive computations of scattering and absorption properties of soot aggregates with varying state of compactness and size. The fractal dimension, D f , is used to quantify the geometrical mass dispersion of the clusters. The optical properties of soot aggregates for a given fractal dimension are complex functions of the refractive index of the material m, the number of monomers N S , and the monomer radius a. It is shown that for smaller values of a, the absorption cross section tends to be relatively constant when D f f >2. However, a systematic reduction in light absorption with D f is observed for clusters with sufficiently large N S , m, and a. The scattering cross section and single-scattering albedo increase monotonically as fractals evolve from chain-like to more densely packed morphologies, which is a strong manifestation of the increasing importance of scattering interaction among spherules. Overall, the results for soot fractals differ profoundly from those calculated for the respective volume-equivalent soot spheres as well as for the respective external mixtures of soot monomers under the assumption that there are no electromagnetic interactions between the monomers. The climate-research implications of our results are discussed

Characterization of fine aggregates in concrete by different experimental approaches

OpenAIRE

He, Huan; Courard, Luc; Pirard, Eric; Michel, Frédéric

2011-01-01

Being its major component, aggregate can occupy up to three-quarter of the volume of concrete. The structure of aggregate formed in hardened state impacts largely on mechanical and durability properties of concrete. On another hand, physical characteristics of aggregate are primarily assumed to be relevant to granular behavior of aggregate. Therefore, characterization of aggregate is of high relevance to concrete studies. In this study, different types of fine aggregate used in concrete, name...

Efficient external memory structures for range-aggregate queries

DEFF Research Database (Denmark)

Agarwal, P.K.; Yang, J.; Arge, L.

2013-01-01

We present external memory data structures for efficiently answering range-aggregate queries. The range-aggregate problem is defined as follows: Given a set of weighted points in Rd, compute the aggregate of the weights of the points that lie inside a d-dimensional orthogonal query rectangle. The...

Experimental study on kinetics oil oil-suspended particulate matter aggregation

International Nuclear Information System (INIS)

Sun, J.; Environment Canada, Ottawa, ON; Khelifa, A.; Wang, Z.; Brown, C.; Fieldhouse, B.; Yang, C.; Zheng, X.; Wong, S.; So, L.C.

2009-01-01

Past studies of oil spills have shown that oil suspended particulate matter aggregates (OSAs) play a role in enhancing the natural cleansing of oiled shorelines. OSAs result from aggregation between suspended oil droplets and suspended particulate matter (SPM) in aquatic environments. During this process, oil dispersion into the water column is significantly increased since the surface of the oil droplet is surrounded by sediment particles. In addition, the accelerated biodegradation of the oil can be attributed to the greater oil-water contact area. This study focused on the kinetic aspects of OSA formation, with particular reference to the time scale of this process and its significance to oil dispersion following oil spills in water. A laboratory study was conducted to measure the time scale of OSA formation and its variations with mixing conditions. A reciprocating shaker and various oil/sediment mixtures were used to prepare the OSAs. Standard reference material 1941b was used as the natural sediment mixed with Arabian medium crude and artificial seawater under various mixing energies. The sediment-to-oil ratio remained constant for all experiments. Gas chromatography-flame ionization detection (GC-FID) analysis was used to measure the total petroleum hydrocarbons (TPH) trapped in negatively buoyant OSAs. Results showed that the TPH in OSAs increased exponentially with shaking time and reached an equilibrium value within 3 hours. The equilibrium decreased from 3 hours to 1.3 hours when the shaking rate increased from 2.0 to 2.3 Hz. It was concluded that high mixing energy enhances OSA formation and shortens the time for OSA formation. 42 refs., 6 tabs., 5 figs

Experimental study on kinetics oil oil-suspended particulate matter aggregation

Energy Technology Data Exchange (ETDEWEB)

Sun, J. [Ocean Univ. of China, Qingdoa (China). Environmental Science and Engineering Inst.; Environment Canada, Ottawa, ON (Canada). Emergencies Science and Technology Section, Emergencies, Operational Analytical Laboratories and Research Support Division; Khelifa, A.; Wang, Z.; Brown, C.; Fieldhouse, B.; Yang, C. [Environment Canada, Ottawa, ON (Canada). Emergencies Science and Technology Section, Emergencies, Operational Analytical Laboratories and Research Support Division; Zheng, X. [Ocean Univ. of China, Qingdoa (China). Environmental Science and Engineering Inst.; Wong, S. [Ottawa Univ., ON (Canada). Dept. of Chemistry; So, L.C. [Waterloo Univ., ON (Canada). Faculty of Engineering

2009-07-01

Past studies of oil spills have shown that oil suspended particulate matter aggregates (OSAs) play a role in enhancing the natural cleansing of oiled shorelines. OSAs result from aggregation between suspended oil droplets and suspended particulate matter (SPM) in aquatic environments. During this process, oil dispersion into the water column is significantly increased since the surface of the oil droplet is surrounded by sediment particles. In addition, the accelerated biodegradation of the oil can be attributed to the greater oil-water contact area. This study focused on the kinetic aspects of OSA formation, with particular reference to the time scale of this process and its significance to oil dispersion following oil spills in water. A laboratory study was conducted to measure the time scale of OSA formation and its variations with mixing conditions. A reciprocating shaker and various oil/sediment mixtures were used to prepare the OSAs. Standard reference material 1941b was used as the natural sediment mixed with Arabian medium crude and artificial seawater under various mixing energies. The sediment-to-oil ratio remained constant for all experiments. Gas chromatography-flame ionization detection (GC-FID) analysis was used to measure the total petroleum hydrocarbons (TPH) trapped in negatively buoyant OSAs. Results showed that the TPH in OSAs increased exponentially with shaking time and reached an equilibrium value within 3 hours. The equilibrium decreased from 3 hours to 1.3 hours when the shaking rate increased from 2.0 to 2.3 Hz. It was concluded that high mixing energy enhances OSA formation and shortens the time for OSA formation. 42 refs., 6 tabs., 5 figs.

Effect of fly ash on the strength of porous concrete using recycled coarse aggregate to replace low-quality natural coarse aggregate

Science.gov (United States)

Arifi, Eva; Cahya, Evi Nur; Christin Remayanti, N.

2017-09-01

The performance of porous concrete made of recycled coarse aggregate was investigated. Fly ash was used as cement partial replacement. In this study, the strength of recycled aggregate was coMPared to low quality natural coarse aggregate which has high water absorption. Compression strength and tensile splitting strength test were conducted to evaluate the performance of porous concrete using fly ash as cement replacement. Results have shown that the utilization of recycled coarse aggregate up to 75% to replace low quality natural coarse aggregate with high water absorption increases compressive strength and splitting tensile strength of porous concrete. Using fly ash up to 25% as cement replacement improves compressive strength and splitting tensile strength of porous concrete.

Cellular Handling of Protein Aggregates by Disaggregation Machines.

Science.gov (United States)

Mogk, Axel; Bukau, Bernd; Kampinga, Harm H

2018-01-18

Both acute proteotoxic stresses that unfold proteins and expression of disease-causing mutant proteins that expose aggregation-prone regions can promote protein aggregation. Protein aggregates can interfere with cellular processes and deplete factors crucial for protein homeostasis. To cope with these challenges, cells are equipped with diverse folding and degradation activities to rescue or eliminate aggregated proteins. Here, we review the different chaperone disaggregation machines and their mechanisms of action. In all these machines, the coating of protein aggregates by Hsp70 chaperones represents the conserved, initializing step. In bacteria, fungi, and plants, Hsp70 recruits and activates Hsp100 disaggregases to extract aggregated proteins. In the cytosol of metazoa, Hsp70 is empowered by a specific cast of J-protein and Hsp110 co-chaperones allowing for standalone disaggregation activity. Both types of disaggregation machines are supported by small Hsps that sequester misfolded proteins. Copyright © 2018 Elsevier Inc. All rights reserved.

Signature of an aggregation-prone conformation of tau

Science.gov (United States)

Eschmann, Neil A.; Georgieva, Elka R.; Ganguly, Pritam; Borbat, Peter P.; Rappaport, Maxime D.; Akdogan, Yasar; Freed, Jack H.; Shea, Joan-Emma; Han, Songi

2017-03-01

The self-assembly of the microtubule associated tau protein into fibrillar cell inclusions is linked to a number of devastating neurodegenerative disorders collectively known as tauopathies. The mechanism by which tau self-assembles into pathological entities is a matter of much debate, largely due to the lack of direct experimental insights into the earliest stages of aggregation. We present pulsed double electron-electron resonance measurements of two key fibril-forming regions of tau, PHF6 and PHF6*, in transient as aggregation happens. By monitoring the end-to-end distance distribution of these segments as a function of aggregation time, we show that the PHF6(*) regions dramatically extend to distances commensurate with extended β-strand structures within the earliest stages of aggregation, well before fibril formation. Combined with simulations, our experiments show that the extended β-strand conformational state of PHF6(*) is readily populated under aggregating conditions, constituting a defining signature of aggregation-prone tau, and as such, a possible target for therapeutic interventions.

Molecular investigation on the binding of Cd(II) by the binary mixtures of montmorillonite with two bacterial species

Energy Technology Data Exchange (ETDEWEB)

Du, Huihui; Qu, ChenChen; Liu, Jing; Chen, Wenli; Cai, Peng; Shi, Zhihua; Yu, Xiao-Ying; Huang, Qiaoyun

2017-10-01

Bacteria and phyllosilicate commonly coexist in the natural environment, producing various bacteria–clay complexes that are capable of immobilizing heavy metals, such as cadmium, via adsorption. However, the molecular binding mechanisms of heavy metals on these complex aggregates still remain poorly understood. This study investigated Cd adsorption on Gram-positive B. subtilis, Gram-negative P. putida and their binary mixtures with montmorillonite (Mont) using the Cd K-edge x-ray absorption spectroscopy (XAS) and isothermal titration calorimetry (ITC). We observed a lower adsorptive capacity for P. putida than B. subtilis, whereas P. putida–Mont and B. subtilis–Mont mixtures showed nearly identical Cd adsorption behaviors. EXAFS fits and ITC measurements demonstrated more phosphoryl binding of Cd in P. putida. The decreased coordination of C atoms around Cd and the reduced adsorption enthalpies and entropies for the binary mixtures compared to that for individual bacteria suggested that the bidentate Cd-carboxyl complexes in pure bacteria systems were probably transformed into monodentate complexes that acted as ionic bridging structure between bacteria and motmorillonite. This study clarified the binding mechanism of Cd at the bacteria–phyllosilicate interfaces from a molecular and thermodynamic view, which has an environmental significance for predicting the chemical behavior of trace elements in complex mineral–organic systems.

Growth hormone aggregates in the rat adenohypophysis

Science.gov (United States)

Farrington, M.; Hymer, W. C.

1990-01-01

Although it has been known for some time that GH aggregates are contained within the rat anterior pituitary gland, the role that they might play in pituitary function is unknown. The present study examines this issue using the technique of Western blotting, which permitted visualization of 11 GH variants with apparent mol wt ranging from 14-88K. Electroelution of the higher mol wt variants from gels followed by their chemical reduction with beta-mercaptoethanol increased GH immunoassayability by about 5-fold. With the blot procedure we found 1) that GH aggregates greater than 44K were associated with a 40,000 x g sedimentable fraction; 2) that GH aggregates were not present in glands from thyroidectomized rats, but were in glands from the thyroidectomized rats injected with T4; 3) that GH aggregates were uniquely associated with a heavily granulated somatotroph subpopulation isolated by density gradient centrifugation; and 4) that high mol wt GH forms were released from the dense somatotrophs in culture, since treatment of the culture medium with beta-mercaptoethanol increased GH immunoassayability by about 5-fold. Taken together, the results show that high mol wt GH aggregates are contained in secretory granules of certain somatotrophs and are also released in aggregate form from these cells in vitro.

Aggregate Supply and Potential Output

OpenAIRE

Razin, Assaf

2004-01-01

The New-Keynesian aggregate supply derives from micro-foundations an inflation-dynamics model very much like the tradition in the monetary literature. Inflation is primarily affected by: (i) economic slack; (ii) expectations; (iii) supply shocks; and (iv) inflation persistence. This paper extends the New Keynesian aggregate supply relationship to include also fluctuations in potential output, as an additional determinant of the relationship. Implications for monetary rules and to the estimati...

Targeting Protein Aggregation for the Treatment of Degenerative Diseases

Science.gov (United States)

Eisele, Yvonne S.; Monteiro, Cecilia; Fearns, Colleen; Encalada, Sandra E.; Wiseman, R. Luke; Powers, Evan T.; Kelly, Jeffery W.

2015-01-01

The aggregation of specific proteins is hypothesized to underlie several degenerative diseases, collectively called amyloid disorders. However, the mechanistic connection between the process of protein aggregation and tissue degeneration is not yet fully understood. Here, we review current and emerging strategies to ameliorate aggregation-associated degenerative disorders, with a focus on disease-modifying strategies that prevent the formation of and/or eliminate protein aggregates. Persuasive pharmacologic and genetic evidence now support protein aggregation as the cause of post-mitotic tissue dysfunction or loss. However, a more detailed understanding of the factors that trigger and sustain aggregate formation, as well as the structure-activity relationships underlying proteotoxicity are needed to develop future disease-modifying therapies. PMID:26338154

Extending Practical Pre-Aggregation in On-Line Analytical Processing

DEFF Research Database (Denmark)

Pedersen, Torben Bach; Jensen, Christian Søndergaard; Dyreson, Curtis E.

On-Line Analytical Processing (OLAP) based on a dimensional view of data is being used increasingly in traditional business applications as well as in applications such as health care for the purpose of analyzing very large amounts of data. Pre-aggregation, the prior materialization of aggregate...... select combinations of aggregates and then re-use these for efficiently computing other aggregates. However, this re-use of aggregates is contingent on the dimension hierarchies and the relationships between facts and dimensions satisfying stringent constraints. This severely limits the scope...

Aggregate assessments support improved operational decision making

International Nuclear Information System (INIS)

Bauer, R.

2003-01-01

At Darlington Nuclear aggregate assessment of plant conditions is carried out in support of Operational Decision Making. This paper discusses how aggregate assessments have been applied to Operator Workarounds leading to improved prioritisation and alignment of work programs in different departments. As well, aggregate assessment of plant and human performance factors has been carried out to identify criteria which support conservative decision making in the main control room during unit transients. (author)

Aggregated nanoplatelets: optical properties and optically induced deaggregation

International Nuclear Information System (INIS)

Jayabalan, J; Singh, Asha; Chari, Rama; Srivastava, Himanshu; Srivastava, A K; Mukhopadhyay, P K; Oak, S M

2008-01-01

A study of aggregation and laser-induced deaggregation of silver nanospheres and nanoplatelets in colloidal form is presented. Changes in the extinction spectrum caused by aggregation are explained using a two-particle approximation. In the case of platelets, controlled laser irradiation is shown to reverse the aggregation process.

Aggregated nanoplatelets: optical properties and optically induced deaggregation

Energy Technology Data Exchange (ETDEWEB)

Jayabalan, J; Singh, Asha; Chari, Rama [Laser Physics Application Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Srivastava, Himanshu; Srivastava, A K [Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Mukhopadhyay, P K; Oak, S M [Solid State Laser Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)], E-mail: jjaya@cat.ernet.in

2008-11-05

A study of aggregation and laser-induced deaggregation of silver nanospheres and nanoplatelets in colloidal form is presented. Changes in the extinction spectrum caused by aggregation are explained using a two-particle approximation. In the case of platelets, controlled laser irradiation is shown to reverse the aggregation process.

Viral Aggregation: Impact on Virus Behavior in the Environment.

Science.gov (United States)

Gerba, Charles P; Betancourt, Walter Q

2017-07-05

Aggregates of viruses can have a significant impact on quantification and behavior of viruses in the environment. Viral aggregates may be formed in numerous ways. Viruses may form crystal like structures and aggregates in the host cell during replication or may form due to changes in environmental conditions after virus particles are released from the host cells. Aggregates tend to form near the isoelectric point of the virus, under the influence of certain salts and salt concentrations in solution, cationic polymers, and suspended organic matter. The given conditions under which aggregates form in the environment are highly dependent on the type of virus, type of salts in solution (cation, anion. monovalent, divalent) and pH. However, virus type greatly influences the conditions when aggregation/disaggregation will occur, making predictions difficult under any given set of water quality conditions. Most studies have shown that viral aggregates increase the survival of viruses in the environment and resistance to disinfectants, especially with more reactive disinfectants. The presence of viral aggregates may also result in overestimation of removal by filtration processes. Virus aggregation-disaggregation is a complex process and predicting the behavior of any individual virus is difficult under a given set of environmental circumstances without actual experimental data.

A brief review of the construction aggregates market

Science.gov (United States)

Willett, Jason Christopher

2012-01-01

The U.S. Geological Survey defines the construction aggregates industry as those companies that mine and process crushed stone and/or construction sand and gravel. Aggregates have been used from the earliest times of our civilization for a variety of purposes - construction being the major use. As construction aggregates, crushed stone and construction sand and gravel are the basic raw materials used to build the foundation for modern society. The widespread use of construction aggregates is the result of their general availability throughout the country and around the world along with their relatively low cost. Although construction aggregates have a low unit value, their widespread use makes them major contributors to, and indicators of, the economic well-being of the nation.

Synthetic Co-Attractants of the Aggregation Pheromone of the Date Palm Root Borer Oryctes agamemnon.

Science.gov (United States)

Hasni, Narjes; Pinier, Centina; Imed, Cheraief; Ouhichi, Monêem; Couzi, Philippe; Chermiti, Brahim; Frérot, Brigitte; Saïd, Imen; Rochat, Didier

2017-07-01

Laboratory and field investigations to identify and evaluate plant co-attractants of the aggregation pheromone of the date palm pest Oryctes agamemnon are reported. Volatiles emitted by freshly cut palm core and palm core with feeding males, were collected, analyzed by gas chromatography coupled to mass spectrometry and evaluated in olfactometers alone or combined with synthetic pheromone. A collection of palm odor without male effluvia was attractive alone and enhanced attraction to synthetic pheromone in an olfactometer similar to that to a collection of palm odor emitted with feeding males and containing natural pheromone. Behavioral responses to collections of palm volatiles were correlated to the amount of volatiles material in them. Enhancement of the attractiveness of the pheromone was not correlated to chemicals specific to beetle feeding. The chemicals common to the active collections extracts were benzoate esters, mostly ethyl benzoate, anisole derivatives and sesquiterpenes. Blends of the most abundant components of the extracts were evaluated for enhancement of the attractiveness of pheromone (1 μg) in olfactometers at 1 or 10 μg doses. The mixtures were further evaluated by field trapping in Tunisia at 3-10 mg/day using reference (6 mg/day) or experimental pheromone formulations. A mixture of ethyl benzoate, 4-methylanisole and farnesol (1:1:1 w/w at 6.5 mg/day) enhanced captures in pheromone baited traps in 2014 and 2015 and this mixture was as active as the natural palm bait. The practical prospect of the result for the management for O. agamemnon, and other palm beetles is discussed.

PE859, a novel tau aggregation inhibitor, reduces aggregated tau and prevents onset and progression of neural dysfunction in vivo.

Directory of Open Access Journals (Sweden)

Michiaki Okuda

Full Text Available In tauopathies, a neural microtubule-associated protein tau (MAPT is abnormally aggregated and forms neurofibrillary tangle. Therefore, inhibition of the tau aggregation is one of the key approaches for the treatment of these diseases. Here, we have identified a novel tau aggregation inhibitor, PE859. An oral administration of PE859 resulted in the significant reduction of sarkosyl-insoluble aggregated tau along with the prevention of onset and progression of the motor dysfunction in JNPL3 P301L-mutated human tau transgenic mice. These results suggest that PE859 is useful for the treatment of tauopathies.

Strength of masonry blocks made with recycled concrete aggregates