Investigation into the Manufacture and Properties of Inhalable High-Dose Dry Powders Produced by Comilling API and Lactose with Magnesium Stearate.

PubMed

Lau, Michael; Young, Paul M; Traini, Daniela

2017-08-01

The aim of the study was to understand the impact of different concentrations of the additive material, magnesium stearate (MGST), and the active pharmaceutical ingredient (API), respectively, on the physicochemical properties and aerosol performance of comilled formulations for high-dose delivery. Initially, blends of API/lactose with different concentrations of MGST (1-7.5% w/w) were prepared and comilled by the jet-mill apparatus. The optimal concentration of MGST in comilled formulations was investigated, specifically for agglomerate structure and strength, particle size, uniformity of content, surface coverage, and aerosol performance. Secondly, comilled formulations with different API (1-40% w/w) concentrations were prepared and similarly analyzed. Comilled 5% MGST (w/w) formulation resulted in a significant improvement in in vitro aerosol performance due to the reduction in agglomerate size and strength compared to the formulation comilled without MGST. Higher concentrations of MGST (7.5% w/w) led to reduction in aerosol performance likely due to excessive surface coverage of the micronized particles by MGST, which led to failure in uniformity of content and an increase in agglomerate strength and size. Generally, comilled formulations with higher concentrations of API increased the agglomerate strength and size, which subsequently caused a reduction in aerosol performance. High-dose delivery was achieved at API concentration of >20% (w/w). The study provided a platform for the investigation of aerosol performance and physicochemical properties of other API and additive materials in comilled formulations for the emerging field of high-dose delivery by dry powder inhalation.

Comparison of the agglomeration behavior of thin metallic films on SiO2

NASA Astrophysics Data System (ADS)

Gadkari, P. R.; Warren, A. P.; Todi, R. M.; Petrova, R. V.; Coffey, K. R.

2005-07-01

The stability of continuous metallic thin films on insulating oxide surfaces is of interest to applications such as semiconductor interconnections and gate engineering. In this work, we report the study of the formation of voids and agglomeration of initially continuous Cu, Au, Ru and Pt thin films deposited on amorphous thermally grown SiO2 surfaces. Polycrystalline thin films having thicknesses in the range of 10-100 nm were ultrahigh vacuum sputter deposited on thermally grown SiO2 surfaces. The films were annealed at temperatures in the range of 150-800 °C in argon and argon+3% hydrogen gases. Scanning electron microscopy was used to investigate the agglomeration behavior, and transmission electron microscopy was used to characterize the microstructure of the as-deposited and annealed films. The agglomeration sequence in all of the films is found to follow a two step process of void nucleation and void growth. However, void growth in Au and Pt thin films is different from Cu and Ru thin films. Residual stress and adhesion were observed to play an important part in deciding the mode of void growth in Au and Pt thin films. Last, it is also observed that the tendency for agglomeration can be reduced by encapsulating the metal film with an oxide overlayer.

Alternating Field Electronanofluidization

NASA Astrophysics Data System (ADS)

Espin, M. J.; Valverde, J. M.; Quintanilla, M. A. S.; Castellanos, A.

2009-06-01

The use of fluidized beds to remove submicron particles from gases has been investigated since 1949. High efficiency removal was achieved in the 1970's by imposing an electric field on a fluidized bed of semi-insulating granules that were able to collect the charged pollutant entrained in the fluidizing gas. In spite of their extended use nowadays, the collection efficiency of electrofluidized beds (EFB) is still hindered by gas bypassing associated to gas bubbling and the consequent requirement of too high gas flow and pressure drop. In this paper we report on the electromechanical behavior of an EFB of insulating nanoparticles. When fluidized by gas, these nanoparticles form extremely porous light agglomerates of size of the order of hundreds of microns that allow for a highly expanded nonbubbling fluidized state at reduced gas flow. It is found that fluidization uniformity and bed expansion are additionally enhanced by an imposed AC electric field for field oscillation frequencies of several tens of hertzs and field strengths of the order of 1 kV/cm. For oscillation frequencies of the order of hertzs, or smaller, bed expansion is hindered due to electrophoretic deposition of the agglomerates onto the vessel walls, whereas for oscillation frequencies of the order of kilohertzs, or larger, electrophoresis is nullified and bed expansion is not affected. According to a proposed model, the size of nanoparticle agglomerates stems from the balance between shear, which depends on field strength, and van der Waals forces. The optimum field strength for enhancing bed expansion produces an electric force on the agglomerates similar to their weight force, while the oscillation velocity of the agglomerates is similar to the gas velocity.

The Self-energy Of Growing Aggregates: "Strength Regime"

NASA Astrophysics Data System (ADS)

Guimaraes, Ana H. F.; Spahn, F.; Seiss, M.; Brilliantov, N. V.

2009-09-01

The vivid appearance of the outer regions of Saturn's rings points to a balance of ongoing fragmentation and coagulation processes. This idea finds support especially in the F-ring, where collisional processes occur on an almost daily basis stirred by perturbations of the satellites Prometheus and Pandora, and in addition due the presence of putative moonlets. In order to quantify this balance in a kinetic theory we propose to calculate the resistivity of small agglomerates ("dynamic ephemeral bodies") against rupture due collisional processes and tidal pull. Earlies studies have shown that the resistivity of an aggregate is divided into two phases: "strength regime" and "gravitational regime". Early in their formation, small agglomerates are supported basically by their "glue" between the particles (adhesion) - "strength regime". For larger agglomerates the "gravitational regime" takes over provided their sizes to be bigger than a threshold in which the self-gravitational energy exceeds the adhesive binding energy, in this case the cluster's constituents are held together gravitationally. We calculated the self-energy caused by adhesion and gravity of ring's aggregates which has been considered as the threshold of impact energy or of tidal work to disrupt the agglomerate. Using a Ballistic Particle Cluster Aggregate Model (BPCA) we varied the densities of the aggregates and the size distribution of their constituents (1-10cm), calculated their self-energy and identified the transition between the "strength" to "gravitational regime". The transition between the regimes occurs at house-size aggregates (diameter of approximately 20m), a fact, that fits to the cut-off on the dense rings' main population (cm - 5m in size). Acknowledgments: A.H.F.G. thanks Dr. E. Vieira-Neto for the discussions, and also the DAAD and Uni-Potsdam for the financial support of this project.

Roller compaction: Effect of morphology and amorphous content of lactose powder on product quality.

PubMed

Omar, Chalak S; Dhenge, Ranjit M; Osborne, James D; Althaus, Tim O; Palzer, Stefan; Hounslow, Michael J; Salman, Agba D

2015-12-30

The effect of morphology and amorphous content, of three types of lactose, on the properties of ribbon produced using roller compaction was investigated. The three types of lactose powders were; anhydrous SuperTab21AN, α-lactose monohydrate 200 M, and spray dried lactose SuperTab11SD. The morphology of the primary particles was identified using scanning electron microscopy (SEM) and the powder amorphous content was quantified using NIR technique. SEM images showed that 21AN and SD are agglomerated type of lactose whereas the 200 M is a non-agglomerated type. During ribbon production, an online thermal imaging technique was used to monitor the surface temperature of the ribbon. It was found that the morphology and the amorphous content of lactose powders have significant effects on the roller compaction behaviour and on ribbon properties. The agglomerated types of lactose produced ribbon with higher surface temperature and tensile strength, larger fragment size, lower porosity and lesser fines percentages than the non-agglomerated type of lactose. The lactose powder with the highest amorphous content showed to result in a better binding ability between the primary particles. This type of lactose produced ribbons with the highest temperature and tensile strength, and the lowest porosity and amount of fines in the product. It also produced ribbon with more smooth surfaces in comparison to the other two types of lactose. It was noticed that there is a relationship between the surface temperature of the ribbon during production and the tensile strength of the ribbon; the higher the temperature of the ribbon during production the higher the tensile strength of the ribbon. Copyright © 2015 Elsevier B.V. All rights reserved.

Study of distribution of Carbon nanotube in Al-CNT nanocomposite synthesized via Spark-Plasma sintering

NASA Astrophysics Data System (ADS)

Maiti, A.; Laha, T.

2018-03-01

In the present study, first ever attempt has been made to develop physically functionalized multiwalled carbon nanotube (MWCNT) reinforced Al-11 5Si alloy nanocomposites synthesized via novel consolidation technique viz spark plasma sintering (SPS). There is a recent trend in employing carbon nanotubes (CNTs), an allotrope of carbon, as reinforcement for high strength structural metallic composite materials, as these cylindrical nano-fibers poses extremely unique mechanical properties such as very high elastic modulus (~ 300 GPa to 1.5 TPa) as well as tensile strength (~150 GPa). However, it has remained as an ever-existing problem to achieve a porosity-free nanocrystalline matrix with homogenously dispersed CNTs, owing to the very high coagulation tendency of CNTs. The gas-atomized, spherical Al-11.5Si alloy powders (1-8 μm) were subjected to high energy ball milling for the purpose of achieving nanocrystallinity in the powders. The improvement in MWCNT dispersion was effort by treating the MWCNTs with a physical surfactant, sodium dodecyl sulfate (SDS). The nano-grained ball-milled Al-Si powders with varying MWCNT content (0.5 and 1 wt%) were consolidated via spark plasma sintering in order to retain the nano-sized grains in the Al-Si matrix, attributed to the faster and highly effective sintering kinetics of the sintering techniques. FESEM study shows problem of MWCNT agglomeration persists by addition of non-SDS treated as pristine MWCNT in the composite. After treated with SDS, MWCNTs are well separated out from each other and as a result of that good morphological and mechanical property such as high hardness value obtained after analysis. Detailed TEM study of the 0.5wt% MWCNT reinforced SPS nanocomposite revealed that the distribution of CNTs in the matrix. Mechanical analysis study of the nanocomposite attributes higher hardness in case of SDS treated CNT reinforced nanocomposite owing to less agglomeration problem of the CNT in the matrix. Nano-tribological data attributed variation of surface roughness after consolidated by SPS.

The effect of agglomeration state of silver and titanium dioxide nanoparticles on cellular response of HepG2, A549 and THP-1 cells.

PubMed

Lankoff, Anna; Sandberg, Wiggo J; Wegierek-Ciuk, Aneta; Lisowska, Halina; Refsnes, Magne; Sartowska, Bożena; Schwarze, Per E; Meczynska-Wielgosz, Sylwia; Wojewodzka, Maria; Kruszewski, Marcin

2012-02-05

Nanoparticles (NPs) occurring in the environment rapidly agglomerate and form particles of larger diameters. The extent to which this abates the effects of NPs has not been clarified. The motivation of this study was to examine how the agglomeration/aggregation state of silver (20nm and 200nm) and titanium dioxide (21nm) nanoparticles may affect the kinetics of cellular binding/uptake and ability to induce cytotoxic responses in THP1, HepG2 and A549 cells. Cellular binding/uptake, metabolic activation and cell death were assessed by the SSC flow cytometry measurements, the MTT-test and the propidium iodide assay. The three types of particles were efficiently taken up by the cells, decreasing metabolic activation and increasing cell death in all the cell lines. The magnitude of the studied endpoints depended on the agglomeration/aggregation state of particles, their size, time-point and cell type. Among the three cell lines tested, A549 cells were the most sensitive to these particles in relation to cellular binding/uptake. HepG2 cells showed a tendency to be more sensitive in relation to metabolic activation. THP-1 cells were the most resistant to all three types of particles in relation to all endpoints tested. Our findings suggest that particle features such as size and agglomeration status as well as the type of cells may contribute to nanoparticles biological impact. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Silicon nitride having a high tensile strength

DOEpatents

Pujari, Vimal K.; Tracey, Dennis M.; Foley, Michael R.; Paille, Norman I.; Pelletier, Paul J.; Sales, Lenny C.; Willkens, Craig A.; Yeckley, Russell L.

1996-01-01

A silicon nitride ceramic comprising: a) inclusions no greater than 25 microns in length, b) agglomerates no greater than 20 microns in diameter, and c) a surface finish of less than about 8 microinches, said ceramic having a four-point flexural strength of at least about 900 MPa.

Fragmentation and bond strength of airborne diesel soot agglomerates

PubMed Central

Rothenbacher, Sonja; Messerer, Armin; Kasper, Gerhard

2008-01-01

Background The potential of diesel soot aerosol particles to break up into smaller units under mechanical stress was investigated by a direct impaction technique which measures the degree of fragmentation of individual agglomerates vs. impact energy. Diesel aerosol was generated by an idling diesel engine used for passenger vehicles. Both the aerosol emitted directly and aerosol that had undergone additional growth by Brownian coagulation ("aging") was investigated. Optionally a thermo-desoption technique at 280°C was used to remove all high-volatility and the majority of low-volatility HC adsorbates from the aerosol before aging. Results It was found that the primary soot agglomerates emitted directly from the engine could not be fragmented at all. Soot agglomerates permitted to grow additionally by Brownian coagulation of the primary emitted particles could be fragmented to a maximum of 75% and 60% respectively, depending on whether adsorbates were removed from their surface prior to aging or not. At most, these aged agglomerates could be broken down to roughly the size of the agglomerates from the primary emission. The energy required for a 50% fragmentation probability of all bonds within an agglomerate was reduced by roughly a factor of 2 when aging "dry" agglomerates. Average bond energies derived from the data were 0.52*10-16 and 1.2*10-16 J, respectively. This is about 2 orders of magnitude higher than estimates for pure van-der-Waals agglomerates, but agrees quite well with other observations. Conclusion Although direct conclusions regarding the behavior of inhaled diesel aerosol in contact with body fluids cannot be drawn from such measurements, the results imply that highly agglomerated soot aerosol particles are unlikely to break up into units smaller than roughly the size distribution emitted as tail pipe soot. PMID:18533015

Silicon nitride having a high tensile strength

DOEpatents

Pujari, V.K.; Tracey, D.M.; Foley, M.R.; Paille, N.I.; Pelletier, P.J.; Sales, L.C.; Willkens, C.A.; Yeckley, R.L.

1996-11-05

A silicon nitride ceramic is disclosed comprising: (a) inclusions no greater than 25 microns in length, (b) agglomerates no greater than 20 microns in diameter, and (c) a surface finish of less than about 8 microinches, said ceramic having a four-point flexural strength of at least about 900 MPa. 4 figs.

Processing of Aluminum-Graphite Particulate Metal Matrix Composites by Advanced Shear Technology

NASA Astrophysics Data System (ADS)

Barekar, N.; Tzamtzis, S.; Dhindaw, B. K.; Patel, J.; Hari Babu, N.; Fan, Z.

2009-12-01

To extend the possibilities of using aluminum/graphite composites as structural materials, a novel process is developed. The conventional methods often produce agglomerated structures exhibiting lower strength and ductility. To overcome the cohesive force of the agglomerates, a melt conditioned high-pressure die casting (MC-HPDC) process innovatively adapts the well-established, high-shear dispersive mixing action of a twin screw mechanism. The distribution of particles and properties of composites are quantitatively evaluated. The adopted rheo process significantly improved the distribution of the reinforcement in the matrix with a strong interfacial bond between the two. A good combination of improved ultimate tensile strength (UTS) and tensile elongation (ɛ) is obtained compared with composites produced by conventional processes.

Microstructure evolution and mechanical properties of nano-SiCp/AZ91 composite processed by extrusion and equal channel angular pressing (ECAP)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiao, X.G.; Ying, T.

Nano-SiCp/AZ91 magnesium matrix composite was fabricated by stir casting. The as-cast ingots were extruded at 350 °C, then processed by equal channel angular pressing (ECAP) at various temperatures (250 °C, 300 °C and 350 °C). Grains are significantly refined after the extrusion and the ECAP. A basal fibre texture was detected by neutron diffraction after the extrusion, which inclines about 45° to the extrusion direction (ED) after the ECAP. Nano-scaled SiC particles agglomerate in the as-cast composite. After the extrusion, the agglomeration tends to form continuous or discontinuous strips along the extrusion direction. By application of the ECAP, the agglomeratedmore » SiC particles are partly dispersed and the strips formed during the extrusion tend to be thinner and broken with the increasing pass number. The yield tensile strength (YTS) and the ultimate tensile strength (UTS) of the composite are dramatically increased after the extrusion. ECAP for one pass at various temperatures further increases the strength, however, the YTS decreases with the increasing ECAP temperature and the pass number. The Orowan equations predict the maximum YTS of the composite may be up to 400 MPa providing SiC particles are homogenously distributed in the matrix. - Highlights: •Nano-scaled SiC particles were successfully added into AZ91 by stirring casting. •Agglomeration of nano-particles were improved by extrusion and ECAP. •Yield strength of the composite is 328 MPa after one pass of ECAP. •Further ECAP process with optimized parameters may fully disperse nano-particles. •Yield strength is predicted to up to 400 MPa when particles are fully dispersed.« less

Transformation of CuO Nanoparticles in the Aquatic Environment: Influence of pH, Electrolytes and Natural Organic Matter

PubMed Central

Peng, Cheng; Shen, Chensi; Zheng, Siyuan; Yang, Weiling; Hu, Hang; Liu, Jianshe; Shi, Jiyan

2017-01-01

Many studies have shown the effect of solution chemistry on the environmental behavior of metal-based nanoparticles (NPs), except CuO NPs. Here, we investigated the agglomeration, sedimentation, dissolution, and speciation of CuO NPs by varying pH, ionic strength, ionic valence, and natural organic matter (NOM). The results showed that as the pH moved away from 6, the size of CuO agglomerates decreased, along with the enhanced NP suspension stabilization, due to the increase of electrostatic repulsive force. Increasing ionic strength and valence intensified the agglomeration and sedimentation of CuO NPs because of the compression of electrical double layers. The presence of humic acid and citric acid enhanced the dispersion and stabilization of CuO NP suspension, but l-cysteine showed a different impact. Decreasing pH, increasing ionic strength and all NOM improved the dissolution of CuO NPs, but the divalent electrolyte (CaCl2) inhibited the Cu2+ release from CuO NPs compared to the monovalent electrolyte (NaCl). In addition, X-ray absorption near edge structure (XANES) analysis demonstrated that the presence of l-cysteine transformed more than 30% of CuO NPs to Cu(I)-cysteine by coordinating with thiol group. This study can give us an in-depth understanding on the environmental behavior and fate of CuO NPs in the aquatic environment. PMID:29036921

Microstickies agglomeration by electric field.

PubMed

Du, Xiaotang Tony; Hsieh, Jeffery S

2016-01-01

Microstickies deposits on both paper machine and paper products when it agglomerates under step change in ionic strength, pH, temperature and chemical additives. These stickies increase the down time of the paper mill and decrease the quality of paper. The key property of microstickies is its smaller size, which leads to low removal efficiency and difficulties in measurement. Thus the increase of microstickies size help improve both removal efficiency and reduce measurement difficulty. In this paper, a new agglomeration technology based on electric field was investigated. The electric treatment could also increase the size of stickies particles by around 100 times. The synergetic effect between electric field treatment and detacky chemicals/dispersants, including polyvinyl alcohol, poly(diallylmethylammonium chloride) and lignosulfonate, was also studied.

Colloidal stability of carbonate-coated silver nanoparticles in synthetic and natural freshwater.

PubMed

Piccapietra, Flavio; Sigg, Laura; Behra, Renata

2012-01-17

To gain important information on fate, mobility, and bioavailability of silver nanoparticles (AgNP) in aquatic systems, the influence of pH, ionic strength, and humic substances on the stability of carbonate-coated AgNP (average diameter 29 nm) was systematically investigated in 10 mM carbonate and 10 mM MOPS buffer, and in filtered natural freshwater. Changes in the physicochemical properties of AgNP were measured using nanoparticle tracking analysis, dynamic light scattering, and ultraviolet-visible spectroscopy. According to the pH-dependent carbonate speciation, below pH 4 the negatively charged surface of AgNP became positive and increased agglomeration was observed. Electrolyte concentrations above 2 mM Ca(2+) and 100 mM Na(+) enhanced AgNP agglomeration in the synthetic media. In the considered concentration range of humic substances, no relevant changes in the AgNP agglomeration state were measured. Agglomeration of AgNP exposed in filtered natural freshwater was observed to be primarily controlled by the electrolyte type and concentration. Moreover, agglomerated AgNP were still detected after 7 days of exposure. Consequently, slow sedimentation and high mobility of agglomerated AgNP could be expected under the considered natural conditions. A critical evaluation of the different methods used is presented as well.

The effect of carbon black loading and structure on tensile property of natural rubber composite

NASA Astrophysics Data System (ADS)

Savetlana, S.; Zulhendri; Sukmana, I.; Saputra, F. A.

2017-07-01

Natural rubber composite has been continuously developed due to its advantages such as a good combination of strength and damping property. Most of carbon black (CB)/Natural Rubber (NR) composite were used as material in tyre industry. The addition of CB in natural rubber is very important to enhance the strength of natural rubber. The particle loading and different structure of CB can affect the composite strength. The effects of CB particle loading of 20, 25 and 30 wt% and the effects of CB structures of N220, N330, N550 and N660 series on tensile property of composite were investigated. The result shows that the tensile strength and elastic modulus of natural rubber/CB composite was higher than pure natural rubber. From SEM observation the agglomeration of CB aggregate increases with particle loading. It leads to decrease of tensile strength of composite as more particle was added. High structure of CB particle i.e. N220 resulted in highest tensile stress. In fact, composite reinforced by N660 CB particle shown a comparable tensile strength and elastic modulus with N220 CB particle. SEM observation shows that agglomeration of CB aggregates of N330 and N550 results in lower stress of associate NR/CB composite.

a Case Study: Exploring Industrial Agglomeration of Manufacturing Industries in Shanghai Using Duranton and Overman's K-Density Function

NASA Astrophysics Data System (ADS)

Tian, S.; Wang, J.; Gui, Z.; Wu, H.; Wang, Y.

2017-09-01

There has wide academic and policy attention on the issue of scale economy and industrial agglomeration, with most of the attention paid to industrial geography concentration. This paper adopted a scale-independent and distance-based measurement method, K-density function or known as Duranton and Overman (DO) index, to study the manufacturing industries localization in Shanghai, which is the most representative economic development zone in China and East Asia. The result indicates the industry has a growing tendency of localization, and various spatial distribution patterns in different distances. Furthermore, the class of industry also show significant influence on the concentration pattern. Besides, the method has been coded and published on GeoCommerce, a visualization and analysis portal for industrial big data, to provide geoprocessing and spatial decision support.

Surface functionalization of WS2 fullerene-like nanoparticles.

PubMed

Shahar, Chen; Zbaida, David; Rapoport, Lev; Cohen, Hagai; Bendikov, Tatyana; Tannous, Johny; Dassenoy, Fabrice; Tenne, Reshef

2010-03-16

WS(2) belongs to a family of layered metal dichalcogenide compounds that are known to form cylindrical (inorganic nanotubes-INT) and polyhedral nanostructures--onion or nested fullerene-like (IF) particles. The outermost layers of these IF nanoparticles can be peeled under shear stress, thus IF nanoparticles have been studied for their use as solid lubricants. However, the IF nanoparticles tend to agglomerate, presumably because of surface structural defects induced by elastic strain and curvature, a fact that has a deleterious effect on their tribological properties. In the present work, chemical modification of the IF-WS(2) surface with alkyl-silane molecules is reported. The surface-modified IF nanoparticles display improved dispersion in oil-based suspensions. The alkyl-silane coating reduces the IF-WS(2) nanoparticles' tendency to agglomerate and consequently improves the long-term tribological behavior of oil formulated with the IF additive.

Uniformly Dispersed and Re-Agglomerated Graphene Oxide-Based Cement Pastes: A Comparison of Rheological Properties, Mechanical Properties and Microstructure.

PubMed

Long, Wu-Jian; Li, Hao-Dao; Fang, Chang-Le; Xing, Feng

2018-01-09

The properties of graphene oxide (GO)-based cement paste can be significantly affected by the state of GO dispersion. In this study, the effects of uniformly dispersed and re-agglomerated GO on the rheological, mechanical properties and microstructure of cement paste were systematically investigated. Two distinct dispersion states can be achieved by altering the mixing sequence: Polycarboxylate-ether (PCE) mixed with GO-cement or cement mixed with GO-PCE. The experimental results showed that the yield stress and plastic viscosity increased with the uniformly dispersed GO when compared to those of re-agglomerated GO cement paste. Moreover, the 3-day compressive and flexural strengths of uniformly dispersed GO paste were 8% and 27%, respectively, higher than those of re-agglomerated GO pastes. The results of X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy analyses demonstrated that uniformly dispersed GO more effectively promotes the formation of hydration products in hardened cement paste. Furthermore, a porosity analysis using mercury intrusion porosimetry revealed that the homogeneous dispersion of GO can better inhibit the formation of large-size pores and optimize the pore size distribution at 3 and 7 days than the re-agglomerated GO.

Roll Compaction/Dry Granulation of Dibasic Calcium Phosphate Anhydrous-Does the Morphology of the Raw Material Influence the Tabletability of Dry Granules?

PubMed

Grote, Simon; Kleinebudde, Peter

2018-04-01

The influence of raw material particle morphology on the tabletabilty of dry granules was investigated. Therefore, dibasic calcium phosphate anhydrous was used as a model material. One milled grade, 2 agglomerated grades with different porosities, and a functionalized structure, that is, an agglomerate formed by very small primary particles, were included. Particle size, density, and specific surface area of raw materials were measured. The starting materials and 2 fractions of dry granules were compressed to tablets. The tabletability of granules was compared to that of the powders and the influence of specific compaction force, granule size, and lubrication on tablet tensile strength was evaluated. All materials showed a loss in tabletability induced by a previous compaction step but to a varying extent. Only in case of the functionalized calcium phosphate morphology, this effect depended on the specific compaction force. In contrast to the other materials, the tabletability of functionalized calcium phosphate was influenced by the granule size. This effect was not related to an overlubrication as internal and external lubrication resulted in similar tensile strengths. A clear influence of the particle morphology on tablet strength was demonstrated by the study. The functionalized structure showed aspects of a more plastic deformation behavior. The functionalized dibasic calcium phosphate and the more porous agglomerate performed as potential filler/binder in the field of roll compaction/dry granulation. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Origin of the Chemical and Kinetic Stability of Graphene Oxide

PubMed Central

Zhou, Si; Bongiorno, Angelo

2013-01-01

At moderate temperatures (≤ 70°C), thermal reduction of graphene oxide is inefficient and after its synthesis the material enters in a metastable state. Here, first-principles and statistical calculations are used to investigate both the low-temperature processes leading to decomposition of graphene oxide and the role of ageing on the structure and stability of this material. Our study shows that the key factor underlying the stability of graphene oxide is the tendency of the oxygen functionalities to agglomerate and form highly oxidized domains surrounded by areas of pristine graphene. Within the agglomerates of functional groups, the primary decomposition reactions are hindered by both geometrical and energetic factors. The number of reacting sites is reduced by the occurrence of local order in the oxidized domains, and due to the close packing of the oxygen functionalities, the decomposition reactions become – on average – endothermic by more than 0.6 eV. PMID:23963517

Characterization of desert sand as a sensible thermal energy storage medium

NASA Astrophysics Data System (ADS)

Diago, Miguel; Iniesta, Alberto Crespo; Delclos, Thomas; Soum-Glaude, Audrey; Shamim, Tariq; Calvet, Nicolas

2016-05-01

Desert sand from the United Arab Emirates (UAE) is considered as a possible sensible heat, thermal energy storage (TES) material. Its thermal stability, specific heat capacity and tendency to agglomerate are studied at high temperatures. The analyses show that it is possible to use desert sand as a TES material up to 800-1000 °C. Above 800 °C, weak agglomeration effects start to become significant. The samples become solid above 1000 °C. This may represent a major operating limit depending on the handling mechanism in place for the possible transport of the sand. The sand chemical composition is analyzed with the XRF and XRD techniques, which reveal the dominance of quartz and carbonates. Finally, the spectral absorptivity of the samples is measured before and after a thermal cycle, as it may be possible to use the desert sand not only as a TES material but also as a direct solar absorber.

Origin of the chemical and kinetic stability of graphene oxide.

PubMed

Zhou, Si; Bongiorno, Angelo

2013-01-01

At moderate temperatures (≤ 70°C), thermal reduction of graphene oxide is inefficient and after its synthesis the material enters in a metastable state. Here, first-principles and statistical calculations are used to investigate both the low-temperature processes leading to decomposition of graphene oxide and the role of ageing on the structure and stability of this material. Our study shows that the key factor underlying the stability of graphene oxide is the tendency of the oxygen functionalities to agglomerate and form highly oxidized domains surrounded by areas of pristine graphene. Within the agglomerates of functional groups, the primary decomposition reactions are hindered by both geometrical and energetic factors. The number of reacting sites is reduced by the occurrence of local order in the oxidized domains, and due to the close packing of the oxygen functionalities, the decomposition reactions become - on average - endothermic by more than 0.6 eV.

Investigation of a 2-step agglomeration process performed in a rotary processor using polyethylene glycol solutions as the primary binder liquid.

PubMed

Kristensen, Jakob

2006-10-27

The purpose of this research was to investigate the use of polyethylene glycol (PEG) solutions as the primary binder liquid in a 2-step agglomeration process performed in a rotary processor and characterize the resulting granules and their tableting characteristics. This was done by granulation of binary mixtures of microcrystalline cellulose (MCC) and either lactose, calcium phosphate, acetaminophen, or theophylline, in a 1:3 ratio, using a 50% (wt/wt) aqueous solution of PEG and water as the binder liquid. Formulations containing lactose were agglomerated using 5 different amounts of the PEG binder solution, giving rise to a PEG content in the range of 6% to 43% (wt/wt). The process outcome was characterized according to adhesion, yield, and water requirement, and the prepared granules were characterized according to size, size distribution, and flow properties as well as tableting properties. The agglomeration of all mixtures resulted in high yields of free-flowing agglomerates and gave rise to good reproducibility of the investigated agglomerate characteristics. The process allowed for the incorporation of 42.5% (wt/wt) PEG, which is higher than the percentage of PEG reported for other equipment. Tablets of sufficient strength could be prepared with all investigated excipients using 20% wt/wt PEG; higher PEG contents gave rise to adhesion and prolonged disintegration. In conclusion, agglomeration in a torque-controlled rotary processor using solutions of PEG as the primary binder liquid was found to be a robust process, suitable for the incorporation of high contents of PEG and/or drug compounds.

Mechanistic Studies of Superplasticity of Structural Ceramics

DTIC Science & Technology

1992-02-01

green compact, with a higher density and and most of Ine heavier transition-metal fewer defects and agglomerates, has a cations of the third row, is very...between 60% to 65% of the theoretical defects is merely one which mediates the above solid "elec- density. Samples of 2Y-TZP and other TZPs were prepared...trolyte," although any tendency toward binding between similarly, except for a smaller dopant concentration ot 0.6% point defects and dopants to form

Influence of pH and media composition on suspension stability of silver, zinc oxide, and titanium dioxide nanoparticles and immobilization of Daphnia magna under guideline testing conditions.

PubMed

Cupi, Denisa; Hartmann, Nanna B; Baun, Anders

2016-05-01

In aquatic toxicity testing of engineered nanoparticles (ENPs) the process of agglomeration is very important as it may alter bioavailability and toxicity. In the present study, we aimed to identify test conditions that are favorable for maintaining stable ENP suspensions. We evaluated the influence of key environmental parameters: pH (2-12) and ionic strength using M7, Soft EPA (S EPA) medium, and Very Soft EPA (VS EPA) medium; and observed the influence of these parameters on zeta potential, zeta average, and acute immobilization of Daphnia magna for three different ENPs. Despite being sterically stabilized, test suspensions of silver (Ag) ENPs formed large agglomerates in both VS EPA and M7 media; and toxicity was found to be higher in VS EPA medium due to increased dissolution. Low-agglomerate suspensions for zinc oxide (ZnO) could be obtained at pH 7 in VS EPA medium, but the increase in dissolution caused higher toxicity than in M7 medium. Titanium dioxide (TiO2) ENPs had a point of zero charge in the range of pH 7-8. At pH 7 in VS EPA, agglomerates with smaller hydrodynamic diameters (~200nm) were present compared to the high ionic strength M7 medium where hydrodynamic diameters reached micrometer range. The stable suspensions of TiO2 ENPs caused immobilization of D. magna, 48-h EC50 value of 13.7mgL(-1) (95% CI, 2.4mg-79.1mgL(-1)); whereas no toxicity was seen in the unstable, highly agglomerated M7 medium suspensions, 48-h EC50 >100mgL(-1). The current study provides a preliminary approach for methodology in testing and assessing stability and toxicity of ENPs in aquatic toxicity tests of regulatory relevance. Copyright © 2016 Elsevier Inc. All rights reserved.

Nanographene reinforced carbon/carbon composites

NASA Astrophysics Data System (ADS)

Bansal, Dhruv

Carbon/Carbon Composites (CCC) are made of carbon reinforcement in carbon matrix and have high thermal stability and fatigue resistance. CCC are used in nose cones, heat shields and disc brakes of aircrafts due to their exceptional mechanical properties at high temperature. The manufacturing process of CCC involves a carbonization stage in which unwanted elements, except carbon, are eliminated from the polymer precursor. Carbonization results in the formation of voids and cracks due to the thermal mismatch between the reinforcement and the matrix and expulsion of volatiles from the polymer matrix. Thermal cracks and voids decrease the density and mechanical properties of the manufactured CCC. In this work, Nanographene Platelets (NGP) were explored as nanofillers to fill the voids/cracks and reduce thermal shrinkage in CCC. They were first compared with Vapor Grown Carbon Nanofibers (VGCNF) by dispersion of different concentrations (0.5wt%, 1.5wt%, 3wt%) in resole-type phenolic resin and were characterized to explore their effect on rheology, heat of reaction and wetting behavior. The dispersions were then cured to form nanocomposites and were characterized for morphology, flexure and thermal properties. Finally, NGP were introduced into the carbon/carboncomposites in two stages, first by spraying in different concentrations (0.5wt%, 1.5wt%, 3wt%, 5wt %) during the prepreg formation and later during densification by directly mixing in the corresponding densification mix. The manufactured NGP reinforced CCC were characterized for microstructure, porosity, bulk density and mechanical properties (Flexure and ILSS) which were further cross-checked by non-destructive techniques (vibration and ultrasonic). In this study, it was further found that at low concentration (≤ 1.5 wt%) NGP were more effective in increasing the heat of reaction and in decreasing the viscosity of the phenolic resin. The decrease in viscosity led to better wetting properties of NGP / phenolic dispersions compared to VGCNF/phenolic dispersions. In nanocomposites, at low concentration (≤ 1.5 wt%), NGP were effective in increasing the flexure strength, char content and lowering the porosity and coefficient of thermal expansion of neat phenolic resin. At higher concentration (>1.5wt%), NGP had a tendency to agglomerate and lost their effectiveness. The behavior observed in nanocomposites continued in manufactured CCC. The highest Inter Laminar Shear Strength (ILSS), flexure strength/modulus, stiffness and density was observed at 1.5 wt% NGP. In CCC at concentrations > 1.5 wt%, the properties (ILSS, flexure, stiffness, density) decreased due to agglomeration but they were still higher compared to that of neat CCC (without NGP).

The equidistance tendency and its consequences : problems in depth perception.

DOT National Transportation Integrated Search

1965-04-01

The equidistance tendency is the tendency for objects or other inhomogeneities in the field-of-view to appear at the same distance as each other with the strength of this tendency being inversely related to directional separation. The evidence for th...

Graphite fiber surface treatment to improve impact strength and fracture resistance in subsequent composites

NASA Technical Reports Server (NTRS)

Paul, J. T., Jr.; Buntin, G. A.

1982-01-01

Graphite (or carbon) fiber composite impact strength improvement was attempted by modifying the fiber surface. Elastomeric particles were made into lattices and deposited ionically on surface treated graphite fiber in an attempt to prepare a surface containing discrete rubber particles. With hard, nonelastomeric polystyrene discrete particle coverage was achieved. All the elastomeric containing lattices resulted in elastomer flow and filament agglomeration during drying.

Influence of temperature and aging time on HA synthesized by the hydrothermal method.

PubMed

Kothapalli, C R; Wei, M; Legeros, R Z; Shaw, M T

2005-05-01

The influence of temperature and aging time on the morphology and mechanical properties of nano-sized hydroxyapatite (HA) synthesized by a hydrothermal method is reported here. The pre-mixed reactants were poured into a stirred autoclave and reacted at temperatures between 25-250 degrees C for 2-10 h. HA powders thus obtained were examined using X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (FESEM) and a particle size analyzer. It was found that the aspect ratio of the particles increased with the reaction temperature. The length of the HA particles increased with the reaction temperature below 170 degrees C, but it decreased when the temperature was raised above 170 degrees C. The agglomerates of HA particles were formed during synthesis, and their sizes were strongly dependent on reaction temperatures. As the reaction temperature increased, the agglomerate size decreased (p = 0.008). The density of the discs pressed from these samples reached 85-90% of the theoretical density after sintering at 1200 degrees C for 1 h. No decomposition to other calcium phosphates was detected at this sintering temperature. A correlation existed (p = 0.05) between the agglomerate sizes of HA particles synthesized at various conditions and their sintered densities. With the increase of the agglomerate size, the sintered density of the HA compact decreased. It was found that both the sintered density and flexural strength increased with increasing aging time and reaction temperature. A maximum flexural strength of 78 MPa was observed for the samples synthesized at 170 degrees C for 5 h with the predicted average at these conditions being 65 MPa. These samples attained an average sintered density of 88%.

Colloidal properties and stability of aqueous suspensions of few-layer graphene: Importance of graphene concentration

PubMed Central

Su, Yu; Yang, Guoqing; Lu, Kun; Petersen, Elijah J.; Mao, Liang

2017-01-01

Understanding the colloidal stability of graphene is essential for predicting its transport and ecological risks in aquatic environments. We investigated the agglomeration of 14C-labeled few-layer graphene (FLG) at concentrations spanning nearly four orders of magnitude (2 μg/L to 10 mg/L) using dynamic light scattering and sedimentation measurements. FLG agglomerates formed rapidly in deionized water at concentrations > 3 mg/L. From 1 mg/L to 3 mg/L, salt-induced agglomeration was decreased with dilution of FLG suspensions; the critical coagulation concentration of the more concentrated suspension (3 mg/L) was significantly lower than the dilute suspension (1 mg/L) in the presence of NaCl (1.6 mmol/L and 10 mmol/L, respectively). In contrast, FLG underwent slow agglomeration and settling at concentrations ≤ 0.1 mg/L in NaCl solutions and ambient waters with low ionic strength (< 10 mmol/L). Although salt-induced agglomeration led to 67 % reduction in number of small FLG (25 nm to 50 nm) according to atomic force microscopy characterization, transition from concentrated to dilute suspension retarded the removal of the small FLG. Additionally, the small FLG exhibited greater bioaccumulation in zebrafish embryo and stronger chorion penetration ability than larger ones. These findings suggest that FLG at more environmentally relevant concentration is relatively stable and may have implications for exposure of small FLG to ecological receptors. PMID:27720543

Method of preparing thin porous sheets of ceramic material

DOEpatents

Swarr, Thomas E.; Nickols, Richard C.; Krasij, Myron

1987-03-24

A method of forming thin porous sheets of ceramic material for use as electrodes or other components in a molten carbonate fuel cell is disclosed. The method involves spray drying a slurry of fine ceramic particles in liquid carrier to produce generally spherical agglomerates of high porosity and a rough surface texture. The ceramic particles may include the electrode catalyst and the agglomerates can be calcined to improve mechanical strength. After slurrying with suitable volatile material and binder tape casting is used to form sheets that are sufficiently strong for further processing and handling in the assembly of a high temperature fuel cell.

Method of preparing thin porous sheets of ceramic material

DOEpatents

Swarr, T.E.; Nickols, R.C.; Krasij, M.

1984-05-23

A method of forming thin porous sheets of ceramic material for use as electrodes or other components in a molten carbonate fuel cell is disclosed. The method involves spray drying a slurry of fine ceramic particles in liquid carrier to produce generally spherical agglomerates of high porosity and a rough surface texture. The ceramic particles may include the electrode catalyst and the agglomerates can be calcined to improve mechanical strength. After slurrying with suitable volatile material and binder tape casting is used to form sheets that are sufficiently strong for further processing and handling in the assembly of a high temperature fuel cell.

Development of Graphene Nanoplatelet-Reinforced AZ91 Magnesium Alloy by Solidification Processing

NASA Astrophysics Data System (ADS)

Kandemir, Sinan

2018-04-01

It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites.

Aerosil for the improvement of the flow behavior of powdered substances

NASA Technical Reports Server (NTRS)

1981-01-01

The tendency of powdered substances to agglomerate and stick together is studied. The highly dispersed silicic acid Aerosil (tradename) is studied as an agent to improve the free flowing characteristics of powdered materials. It was concluded that the use of Aerosil 200, Aerosil R 972, aluminum oxide C and sylicic acid D 17 as flow agents caused broad improvements in the flow properties of powders. Additionally, the sifting, dispersion, and spray behavior, as well as the grinding and air separation characteristics of powders were improved.

Consolidation of Partially Stabilized ZrO2 in the Presence of a Noncontacting Electric Field

NASA Astrophysics Data System (ADS)

Majidi, Hasti; van Benthem, Klaus

2015-05-01

Electric field-assisted sintering techniques demonstrate accelerated densification at lower temperatures than the conventional sintering methods. However, it is still debated whether the applied field and/or resulting currents are responsible for the densification enhancement. To distinguish the effects of an applied field from current flow, in situ scanning transmission electron microscopy experiments with soft agglomerates of partially stabilized yttria-doped zirconia particles are carried out. A new microelectromechanical system-based sample support is used to heat particle agglomerates while simultaneously exposing them to an externally applied noncontacting electric field. Under isothermal condition at 900 °C , an electric field strength of 500 V /cm shows a sudden threefold enhancement in the shrinkage of the agglomerates. The applied electrostatic potential lowers the activation energy for point defect formation within the space charge zone and therefore promotes consolidation. Obtaining similar magnitudes of shrinkage in the absence of any electric field requires a higher temperature and longer time.

Coupling of Acoustic Cavitation with Dem-Based Particle Solvers for Modeling De-agglomeration of Particle Clusters in Liquid Metals

NASA Astrophysics Data System (ADS)

Manoylov, Anton; Lebon, Bruno; Djambazov, Georgi; Pericleous, Koulis

2017-11-01

The aerospace and automotive industries are seeking advanced materials with low weight yet high strength and durability. Aluminum and magnesium-based metal matrix composites with ceramic micro- and nano-reinforcements promise the desirable properties. However, larger surface-area-to-volume ratio in micro- and especially nanoparticles gives rise to van der Waals and adhesion forces that cause the particles to agglomerate in clusters. Such clusters lead to adverse effects on final properties, no longer acting as dislocation anchors but instead becoming defects. Also, agglomeration causes the particle distribution to become uneven, leading to inconsistent properties. To break up clusters, ultrasonic processing may be used via an immersed sonotrode, or alternatively via electromagnetic vibration. This paper combines a fundamental study of acoustic cavitation in liquid aluminum with a study of the interaction forces causing particles to agglomerate, as well as mechanisms of cluster breakup. A non-linear acoustic cavitation model utilizing pressure waves produced by an immersed horn is presented, and then applied to cavitation in liquid aluminum. Physical quantities related to fluid flow and quantities specific to the cavitation solver are passed to a discrete element method particles model. The coupled system is then used for a detailed study of clusters' breakup by cavitation.

Polymer Nanocomposite Materials with High Dielectric Permittivity and Low Dielectric Loss Properties

NASA Astrophysics Data System (ADS)

Toor, Anju

Materials with high dielectric permittivity have drawn increasing interests in recent years for their important applications in capacitors, actuators, and high energy density pulsed power. Particularly, polymer-based dielectrics are excellent candidates, owing to their properties such as high breakdown strength, low dielectric loss, flexibility and easy processing. To enhance the dielectric permittivity of polymer materials, typically, high dielectric constant filler materials are added to the polymer. Previously, ferroelectric and conductive fillers have been mainly used. However, such systems suffered from various limitations. For example, composites based on ferroelectric materials like barium titanate, exhibited high dielectric loss, and poor saturation voltages. Conductive fillers are used in the form of powder aggregates, and they may show 10-100 times enhancement in dielectric constant, however these nanoparticle aggregates cause the dielectric loss to be significant. Also, agglomerates limit the volume fraction of fillers in polymer and hence, the ability to achieve superior dielectric constants. Thus, the aggregation of nanoparticles is a significant challenge to their use to improve the dielectric permittivity. We propose the use of ligand-coated metal nanoparticle fillers to enhance the dielectric properties of the host polymer while minimizing dielectric loss by preventing nanoparticle agglomeration. The focus is on obtaining uniform dispersion of nanoparticles with no agglomeration by utilizing appropriate ligands/surface functionalizations on the gold nanoparticle surface. Use of ligand coated metal nanoparticles will enhance the dielectric constant while minimizing dielectric loss, even with the particles closely packed in the polymer matrix. Novel combinations of materials, which use 5 nm diameter metal nanoparticles embedded inside high breakdown strength polymer materials are evaluated. High breakdown strength polymer materials are chosen to allow further exploration of these materials for energy storage applications. In summary, two novel nanocomposite materials are designed and synthesized, one involving polyvinylidene fluoride (PVDF) as the host polymer for potential applications in energy storage and the other with SU-8 for microelectronic applications. Scanning elec- tron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy and ultramicrotoming techniques were used for the material characterization of the nanocomposite materials. A homogeneous dispersion of gold nanoparticles with low particle agglomeration has been achieved. Fabricated nanoparticle polymer composite films showed the absence of voids and cracks. Also, no evidence of macro-phase separation of nanoparticles from the polymer phase was observed. This is important because nanoparticle agglomeration and phase separation from the polymer usually results in poor processability of films and a high defect density. Dielectric characterization of the nanocomposite materials showed enhancement in the dielectric constant over the base polymer values and low dielectric loss values were observed.

Assessment of Tablet Surface Hardness by Laser Ablation and Its Correlation With the Erosion Tendency of Core Tablets.

PubMed

Narang, Ajit S; Breckenridge, Lydia; Guo, Hang; Wang, Jennifer; Wolf, Abraham Avi; Desai, Divyakant; Varia, Sailesh; Badawy, Sherif

2017-01-01

Surface erosion of uncoated tablets results in processing problems such as dusting and defects during coating and is governed by the strength of particle bonding on tablet surface. In this study, the correlation between dusting tendency of tablets in a coating pan with friability and laser ablation surface hardness was assessed using tablets containing different concentrations of magnesium stearate and tartaric acid. Surface erosion propensity of different batches was evaluated by assessing their dusting tendency in the coating pan. In addition, all tablets were analyzed for crushing strength, friability, modified friability test using baffles in the friability apparatus, and weight loss after laser ablation. Tablets with similar crushing strength showed differences in their surface erosion and dusting tendency when rotated in a coating pan. These differences did not correlate well with tablet crushing strength or friability but did show reasonably good correlation with mass loss after laser ablation. These results suggest that tablet surface mass loss by laser ablation can be used as a minipiloting (small-scale) tool to assess tablet surface properties during early stages of drug product development to assess the risk of potential large-scale manufacturing issues. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Crystal morphology optimization of thiamine hydrochloride in solvent system: Experimental and molecular dynamics simulation studies

NASA Astrophysics Data System (ADS)

Yang, Yang; Han, Dandan; Du, Shichao; Wu, Songgu; Gong, Junbo

2018-01-01

Thiamine hydrochloride (THCL) was produced in methanol accompanied with agglomeration in industry, the plate like morphology of THCL in methanol was not deserve to have a good quality. Selecting a suitable solvent should be considered because solvent could be one of the essential factors to impact morphology. Methanol and methanol/ethyl acetate solvent (0.2 vol fraction of methanol) was selected as the solvent system in reactive crystallization of THCL. The experiment results show the THCL crystal morphology in methanol/ethyl acetate solvent system was granular and more regular than that in methanol. In order to explicate the different crystal morphology in different solvents, molecular dynamics (MD) simulation was introduced to simulate crystal morphology in different solvents. The attachment energy (AE) model was employed to investigate the morphology of THCL under vacuum conditions, methanol and methanol/ethyl acetate solvent conditions, respectively. The simulation crystal morphology was in a good agreement with that of experimented. The particle of THCL in methanol/ethyl acetate solvent has less tendency to agglomeration, and then it is favorable to the downstream process, such as filtration, storage and transportation.

Plasma-Sprayed Titania and Alumina Coatings Obtained from Feedstocks Prepared by Heterocoagulation with 1 wt.% Carbon Nanotube

NASA Astrophysics Data System (ADS)

Jambagi, Sudhakar C.; Agarwal, Anish; Sarkar, Nilmoni; Bandyopadhyay, P. P.

2018-05-01

Properties of plasma-sprayed ceramic coatings can be improved significantly by reinforcing such coatings with carbon nanotube (CNT). However, it is difficult to disperse CNT in the plasma spray feedstock owing to its tendency to form agglomerate. A colloidal processing technique, namely heterocoagulation, is effective in bringing about unbundling of CNT, followed by its homogeneous dispersion in the ceramic powder. This report deals with the mixing of micro-sized crushed titania and agglomerated alumina powders with CNT using the heterocoagulation technique. Heterocoagulation of titania was attempted with both cationic and anionic surfactants, and the latter was found to be more effective. Mixing of the oxides and carbon nanotube was also accomplished in a ball mill either in a dry condition or in alcohol, and powders thus obtained were compared with the heterocoagulated powder. The heterocoagulated powder has shown a more homogeneous dispersion of CNT in the oxide. The coatings produced from the heterocoagulated powder demonstrated improvement in hardness, porosity, indentation fracture toughness and elastic modulus. This is attributed to CNT reinforcement.

The effect of thermal treatment on the organization of copper and nickel nanoclusters synthesized from the gas phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gafner, Yu. Ya., E-mail: ygafner@khsu.ru; Gafner, S. L.; Chepkasov, I. V.

2010-10-15

The condensation of 85000 Cu or Ni atoms from the high-temperature gas phase has been simulated by molecular dynamics with the tight binding potential. The efect of the subsequent thermal treatment on the shape and structure of synthesized particles was studied by simulating their gradual heating in a range of 100-1200 K. Some tendencies are revealed that are characteristic of the influence of heat treatment on the nanoparticles synthesized from the gas phase. It is concluded that short-term heating leads to significant ordering of the internal structure in 70% of agglomerated nanoparticles with the predominant formation of spherical shapes. Inmore » order to explain this result, the main mechanisms of cluster formation from the gas phase have been analyzed and it is found that the agglomeration temperature plays the main role in the formation of clusters with unified shape and structure. This opens the fundamental possibility of obtaining Cu and Ni nanoclusters with preset size, shape, and structure and, hence, predictable physical properties.« less

Gasification of rice straw in a fluidized-bed gasifier for syngas application in close-coupled boiler-gasifier systems.

PubMed

Calvo, L F; Gil, M V; Otero, M; Morán, A; García, A I

2012-04-01

The feasibility and operation performance of the gasification of rice straw in an atmospheric fluidized-bed gasifier was studied. The gasification was carried out between 700 and 850 °C. The stoichiometric air-fuel ratio (A/F) for rice straw was 4.28 and air supplied was 7-25% of that necessary for stoichiometric combustion. Mass and power balances, tar concentration, produced gas composition, gas phase ammonia, chloride and potassium concentrations, agglomeration tendencies and gas efficiencies were assessed. Agglomeration was avoided by replacing the normal alumina-silicate bed by a mixture of alumina-silicate sand and MgO. It was shown that it is possible to produce high quality syngas from the gasification of rice straw. Under the experimental conditions used, the higher heating value (HHV) of the produced gas reached 5.1 MJ Nm(-3), the hot gas efficiency 61% and the cold gas efficiency 52%. The obtained results prove that rice straw may be used as fuel for close-coupled boiler-gasifier systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

Meat and bone meal as secondary fuel in fluidized bed combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

L. Fryda; K. Panopoulos; P. Vourliotis

2007-07-01

Meat and Bone Meal (MBM) was co-fired in a laboratory scale fluidized bed combustion (FBC) apparatus with two coals. Several fuel blends were combusted under different conditions to study how primary fuel substitution by MBM affects flue gas emissions as well as fluidized bed (FB) agglomeration tendency. MBM, being a highly volatile fuel, caused significant increase of CO emissions and secondary air should be used in industrial scale applications to conform to regulations. The high N-content of MBM is moderately reflected on the increase of nitrogen oxides emissions which are reduced by MBM derived volatiles. The MBM ash, mainly containingmore » bone material rich in Ca, did not create any noteworthy desulphurization effect. The observed slight decrease in SO{sub 2} emissions is predominantly attributed to the lower sulphur content in the coal/MBM fuel mixtures. The SEM/EDS analysis of bed material samples from the coal/MBM tests revealed the formation of agglomerates of bed material debris and ash with sizes that do not greatly exceed the original bed inventory and thus not problematic. 37 refs., 9 figs., 3 tabs.« less

A mixed solvent system for preparation of spherically agglomerated crystals of ascorbic acid.

PubMed

Ren, Fuzheng; Zhou, Yaru; Liu, Yan; Fu, Jinping; Jing, Qiufang; Ren, Guobin

2017-09-01

The objective of this research was to develop a novel solvent system to prepare spherically agglomerated crystals (SAC) of ascorbic acid with improved flowability for direct compression. A spherical agglomeration method was developed by selecting the mixed solvents (n-butyl and ethyl acetate) as a poor solvent and the process was further optimized by using triangular phase diagram and particle vision measurement. Physiochemical properties of SAC were characterized and compared with original drug crystals. It showed that amount of poor solvent, ratio of solvent mixture, and drug concentration are critical for preparation of SAC with desirable properties. The solid state of SAC was same as original crystals according to DSC, XRD, and FT-IR results. There was no significant difference in solubility and dissolution rate of drug between SAC and original crystals. The flowability and packability of SAC as well as the tensile strength and elastic recovery of tablets made from SAC were all significantly improved when compared with original crystals and tablets from crystals. It is concluded that the present method was suitable to prepare SAC of ascorbic acid for direct compression.

Effect of filler content on mechanical and dynamic mechanical properties of particulate biphasic calcium phosphate--polylactide composites.

PubMed

Bleach, N C; Nazhat, S N; Tanner, K E; Kellomäki, M; Törmälä, P

2002-04-01

A bioabsorbable self-reinforced polylactide/biphasic calcium phosphate (BCP) composite is being developed for fracture fixation plates. One manufacturing route is to produce preimpregnated sheets by pulling polylactide (PLA) fibres through a suspension of BCP filler in a PLA solution and compression moulding the prepreg to the desired shape. To aid understanding of the process, interactions between the matrix and filler were investigated. Composite films containing 0-0.25 volume fraction filler, produced by solvent casting, were analysed using SEM, tensile testing and dynamic mechanical analysis (DMA). Homogeneous films could be made, although some particle agglomeration was seen at higher filler volume fractions. As the filler content increased, the failure strain decreased due to a reduction in the amount of ductile polymer present and the ultimate tensile strength (UTS) decreased because of agglomeration and void formation at higher filler content. The matrix glass transition temperature increased due to polymer chain adsorption and immobilization onto the BCP particles. Complex damping mechanisms, such as particle-particle agglomeration, may exist at the higher BCP volume fractions.

Self-assembly of diphenylalanine with preclick components as capping groups.

PubMed

Gemma, Andrea; Mayans, Enric; Ballano, Gema; Torras, Juan; Díaz, Angélica; Jiménez, Ana I; Puiggalí, Jordi; Cativiela, Carlos; Alemán, Carlos

2017-10-11

Alkyne and azide, which are commonly used in the cycloaddition reaction recognized as "click chemistry", have been used as capping groups of two engineered diphenylalanine (FF) derivatives due to their ability to form weak intermolecular interactions (i.e. dipole-π and π-π stacking). In Poc-FF-N 3 , alkyne and azide act as N- and C-terminal capping groups, respectively, while such positions are exchanged in N 3 -FF-OPrp. The self-assembly of such two synthesized peptides has been extensively studied in their "pre-click" state, considering the influence of three different factors: the peptide concentration, the polarity of the medium, and the nature of the substrate. Poc-FF-N 3 assembles into microfibers that, depending on the medium and the substrate, can aggregate hierarchically in supramolecular structures with different morphologies. The most distinctive one corresponds to very stable birefringent dendritic-like microstructures, which are derived from the ordered agglomeration of microfibers. These branched supramolecular structures, which are observed under a variety of conditions, are relatively uncommon in short FF sequences. At the molecular level, Poc-FF-N 3 organizes in antiparallel β-sheets stabilized by N-HO intermolecular hydrogen bonds and re-enforced by weak interactions between the azide and alkyne groups of neighbouring molecules. In contrast, N 3 -FF-OPrp exhibits a very poor tendency to organize into structures with a well-defined morphology. Theoretical calculations on model complexes indicate that the tendency of the latter peptide to organize into small amorphous agglomerates is due to its poor ability to form specific intermolecular interactions in comparison with Poc-FF-N 3 . The implications of the weak interactions induced by the alkyne and azide groups, which strengthen peptidepeptide hydrogen bonds and π-ladders due to the stacked aromatic phenyl side groups, are discussed.

“Non-hydrolytic” sol–gel synthesis of molybdenum sulfides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leidich, Saskia; Buechele, Dominique; Lauenstein, Raphael

2016-10-15

Non-hydrolytic sol–gel reactions provide a low temperature solution based synthetic approach to solid-state materials. In this paper, reactions between molybdenum chloride and hexamethyldisilthiane in chloroform were explored, which gave access to both MoS{sub 2} and Mo{sub 2}S{sub 3} after heat treatment of as-recovered amorphous samples to 600–1000 °C. Interesting morphologies were obtained for MoS{sub 2}, ranging from fused spherical particles to well-defined nanoplatelets and nanoflakes. Both 2H- and 3R-MoS{sub 2} were observed, which formed thin hexagonal and triangular platelets, respectively. The platelets exhibited thicknesses of 10–30 nm, which corresponds to 15–50 MoS{sub 2} layers. No attempts to prevent agglomeration weremore » made, however, well separated platelets were observed for many samples. Heating at 1000 °C led to formation of Mo{sub 2}S{sub 3} for samples that showed well-defined MoS{sub 2} at lower temperatures, while less crystalline samples had a tendency to retain the MoS{sub 2} structure. - Graphical abstract: Overlay of variable pressure X-ray diffraction data of Al{sub 2}Mo{sub 3}O{sub 12} collected in a diamond anvil cell. Both subtle and discontinuous phase transitions are clearly observed. - Highlights: • Molybdenum sulfides were prepared by non-hydrolytic sol–gel chemistry. • Nanocrystalline 3R-MoS{sub 2} and 2H-MoS{sub 2}, and microcrystalline Mo{sub 2}S{sub 3} were obtained. • Particle morphology correlated strongly with crystalline phases. • Ultrathin platelets with limited tendency to agglomerate were recovered.« less

Micro/Nanomechanical characterization of multi-walled carbon nanotubes reinforced epoxy composite.

PubMed

Cui, Peng; Wang, Xinnan; Tangpong, X W

2012-11-01

In this paper, the mechanical properties of 1 wt.% multi-walled carbon nanotubes (MWCNTs) reinforced epoxy nanocomposites were characterized using a self-designed micro/nano three point bending tester that was on an atomic force microscope (AFM) to in situ observe MWCNTs movement on the sample surface under loading. The migration of an individual MWCNT at the surface of the nanocomposite was tracked to address the nanomechanical reinforcing mechanism of the nanocomposites. Through morphology analysis of the nanocomposite via scanning electron microscopy, AFM, and digital image correlation technique, it was found that the MWCNTs agglomerate and the bundles were the main factors for limiting the bending strength of the composites. The agglomeration/bundle effect was included in the Halpin-Tsai model to account for the elastic modulus of the nanocomposites.

Individualization as Driving Force of Clustering Phenomena in Humans

PubMed Central

Mäs, Michael; Flache, Andreas; Helbing, Dirk

2010-01-01

One of the most intriguing dynamics in biological systems is the emergence of clustering, in the sense that individuals self-organize into separate agglomerations in physical or behavioral space. Several theories have been developed to explain clustering in, for instance, multi-cellular organisms, ant colonies, bee hives, flocks of birds, schools of fish, and animal herds. A persistent puzzle, however, is the clustering of opinions in human populations, particularly when opinions vary continuously, such as the degree to which citizens are in favor of or against a vaccination program. Existing continuous opinion formation models predict “monoculture” in the long run, unless subsets of the population are perfectly separated from each other. Yet, social diversity is a robust empirical phenomenon, although perfect separation is hardly possible in an increasingly connected world. Considering randomness has not overcome the theoretical shortcomings so far. Small perturbations of individual opinions trigger social influence cascades that inevitably lead to monoculture, while larger noise disrupts opinion clusters and results in rampant individualism without any social structure. Our solution to the puzzle builds on recent empirical research, combining the integrative tendencies of social influence with the disintegrative effects of individualization. A key element of the new computational model is an adaptive kind of noise. We conduct computer simulation experiments demonstrating that with this kind of noise a third phase besides individualism and monoculture becomes possible, characterized by the formation of metastable clusters with diversity between and consensus within clusters. When clusters are small, individualization tendencies are too weak to prohibit a fusion of clusters. When clusters grow too large, however, individualization increases in strength, which promotes their splitting. In summary, the new model can explain cultural clustering in human societies. Strikingly, model predictions are not only robust to “noise”—randomness is actually the central mechanism that sustains pluralism and clustering. PMID:20975937

High performance SMC matrix for structural applications

NASA Astrophysics Data System (ADS)

Salard, T.; Lortie, F.; Gérard, J. F.; Peyre, C.

2016-07-01

Mechanical properties of a common SMC (Sheet Molding Compound) matrix constituted of a vinylester resin and a Low-Profile Additive (LPA) were compared to those of vinylester modified with core-shell rubber (CSR) particles. Valuable properties are brought by CSR, especially high impact strength, high fracture toughness with little loss in stiffness, in spite of the presence of CSR agglomerates in blends.

A micromechanical study of the damage mechanics of acrylic particulate composites under thermomechanical loading

NASA Astrophysics Data System (ADS)

Nie, Shihua

The main aim of this dissertation was to characterize the damage mechanism and fatigue behavior of the acrylic particulate composite. This dissertation also investigated how the failure mechanism is influenced by changes in certain parameters including the volume fraction of particle, the interfacial bonding strength, the stiffness and thickness of the interphase, and the CTE mismatch between the particle and the matrix. Monotonic uniaxial tensile and compressive testing under various temperatures and strain rates, isothermal low-cycle mechanical testing and thermal cycling of a plate with a cutout were performed. The influence of the interfacial bonding strength between the particle and the matrix on the failure mechanism of the ATH filled PMMA was investigated using in situ observations under uniaxial loading conditions. For composites with weak interfacial bonding, the debonding is the major damage mode. For composites with strong interfacial bonding, the breakage of the agglomerate of particles is the major damage mode. Experimental studies also demonstrated the significant influence of interfacial bonding strength on the fatigue life of the ATH filled PMMA. The damage was characterized in terms of the elastic modulus degradation, the load-drop parameter, the plastic strain range and the hysteresis dissipation. Identifying the internal state variables that quantify material degradation under thermomechanical loading is an active research field. In this dissertation, the entropy production, which is a measure of the irreversibility of the thermodynamic system, is used as the metric for damage. The close correlation between the damage measured in terms of elastic modulus degradation and that obtained from the finite element simulation results validates the entropy based damage evolution function. A micromechanical model for acrylic particulate composites with imperfect interfacial bonds was proposed. Acrylic particulate composites are treated as three-phase composites consisting of agglomerated particles, bulk matrix and an interfacial transition zone around the agglomerate. The influence of the interfacial bonding and the CTE mismatch between the matrix and the filler on the overall thermomechanical behavior of composites is studied analytically and experimentally. The comparison of analytical simulation with experimental data demonstrated the validity of the proposed micromechanical model for acrylic particulate composites with an imperfect interface. (Abstract shortened by UMI.)

Aggressive-antisocial boys develop into physically strong young men.

PubMed

Isen, Joshua D; McGue, Matthew K; Iacono, William G

2015-04-01

Young men with superior upper-body strength typically show a greater proclivity for physical aggression than their weaker male counterparts. The traditional interpretation of this phenomenon is that young men calibrate their attitudes and behaviors to their physical formidability. Physical strength is thus viewed as a causal antecedent of aggressive behavior. The present study is the first to examine this phenomenon within a developmental framework. We capitalized on the fact that physical strength is a male secondary sex characteristic. In two longitudinal cohorts of children, we estimated adolescent change in upper-body strength using the slope parameter from a latent growth model. We found that males' antisocial tendencies temporally precede their physical formidability. Boys, but not girls, with greater antisocial tendencies in childhood attained larger increases in physical strength between the ages of 11 and 17. These results support sexual selection theory, indicating an adaptive congruence between male-typical behavioral dispositions and subsequent physical masculinization during puberty. © The Author(s) 2015.

Modeling and experimental evaluation of the diffusion bonding of the oxide dispersion strengthened steel PM2000

NASA Astrophysics Data System (ADS)

Sittel, Wiebke; Basuki, Widodo W.; Aktaa, Jarir

2015-10-01

A modeling based optimization process of the solid state diffusion bonding is presented for joining ferritic oxide dispersion strengthened steels PM2000. An optimization study employing varying bonding temperatures and pressures results in almost the same strength and toughness of the bonded compared to the as received material. TEM investigations of diffusion bonded samples show a homogeneous distribution of oxide particles at the bonding seam similar to that in the bulk. Hence, no loss in strength or creep resistance due to oxide particle agglomeration is found, as verified by the mechanical properties observed for the joint.

Improved consolidation of silicon carbide

NASA Technical Reports Server (NTRS)

Freedman, M. R.; Millard, M. L.

1986-01-01

Alpha silicon carbide powder was consolidated by both dry and wet methods. Dry pressing in a double acting steel die yielded sintered test bars with an average flexural strength of 235.6 MPa with a critical flaw size of approximately 100 micro m. An aqueous slurry pressing technique produced sintered test bars with an average flexural strength of 440.8 MPa with a critical flaw size of approximately 25 micro m. Image analysis revealed a reduction in both pore area and pore size distribution in the slurry pressed sintered test bars. The improvements in the slurry pressed material properties are discussed in terms of reduced agglomeration and improved particle packing during consolidation.

Microexplosions and ignition dynamics in engineered aluminum/polymer fuel particles

DOE PAGES

Rubio, Mario A.; Gunduz, I. Emre; Groven, Lori J.; ...

2016-11-11

Aluminum particles are widely used as a metal fuel in solid propellants. However, poor combustion efficiencies and two-phase flow losses result due in part to particle agglomeration. Engineered composite particles of aluminum (Al) with inclusions of polytetrafluoroethylene (PTFE) or low-density polyethylene (LDPE) have been shown to improve ignition and yield smaller agglomerates in solid propellants, recently. Reductions in agglomeration were attributed to internal pressurization and fragmentation (microexplosions) of the composite particles at the propellant surface. We explore the mechanisms responsible for microexplosions in order to better understand the combustion characteristics of composite fuel particles. Single composite particles of Al/PTFE andmore » Al/LDPE with diameters between 100 and 1200 µm are ignited on a substrate to mimic a burning propellant surface in a controlled environment using a CO 2 laser in the irradiance range of 78–7700 W/cm 2. Furthermore, the effects of particle size, milling time, and inclusion content on the resulting ignition delay, product particle size distributions, and microexplosion tendencies are reported. For example particles with higher PTFE content (30 wt%) had laser flux ignition thresholds as low as 77 W/cm 2, exhibiting more burning particle dispersion due to microexplosions compared to the other materials considered. Composite Al/LDPE particles exhibit relatively high ignition thresholds compared to Al/PTFE particles, and microexplosions were observed only with laser fluxes above 5500 W/cm 2 due to low LDPE reactivity with Al resulting in negligible particle self-heating. However, results show that microexplosions can occur for Al containing both low and high reactivity inclusions (LDPE and PTFE, respectively) and that polymer inclusions can be used to tailor the ignition threshold. Furthermore, this class of modified metal particles shows significant promise for application in many different energetic materials that use metal fuels.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rubio, Mario A.; Gunduz, I. Emre; Groven, Lori J.

Aluminum particles are widely used as a metal fuel in solid propellants. However, poor combustion efficiencies and two-phase flow losses result due in part to particle agglomeration. Engineered composite particles of aluminum (Al) with inclusions of polytetrafluoroethylene (PTFE) or low-density polyethylene (LDPE) have been shown to improve ignition and yield smaller agglomerates in solid propellants, recently. Reductions in agglomeration were attributed to internal pressurization and fragmentation (microexplosions) of the composite particles at the propellant surface. We explore the mechanisms responsible for microexplosions in order to better understand the combustion characteristics of composite fuel particles. Single composite particles of Al/PTFE andmore » Al/LDPE with diameters between 100 and 1200 µm are ignited on a substrate to mimic a burning propellant surface in a controlled environment using a CO 2 laser in the irradiance range of 78–7700 W/cm 2. Furthermore, the effects of particle size, milling time, and inclusion content on the resulting ignition delay, product particle size distributions, and microexplosion tendencies are reported. For example particles with higher PTFE content (30 wt%) had laser flux ignition thresholds as low as 77 W/cm 2, exhibiting more burning particle dispersion due to microexplosions compared to the other materials considered. Composite Al/LDPE particles exhibit relatively high ignition thresholds compared to Al/PTFE particles, and microexplosions were observed only with laser fluxes above 5500 W/cm 2 due to low LDPE reactivity with Al resulting in negligible particle self-heating. However, results show that microexplosions can occur for Al containing both low and high reactivity inclusions (LDPE and PTFE, respectively) and that polymer inclusions can be used to tailor the ignition threshold. Furthermore, this class of modified metal particles shows significant promise for application in many different energetic materials that use metal fuels.« less

How the guest molecules in nanoporous Zn(II) metal-organic framework can prevent agglomeration of ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moeinian, Maryam; Akhbari, Kamran, E-mail: akhbari.k@khayam.ut.ac.ir

The host and the apohost framework of [Zn{sub 2}(BDC){sub 2}(H{sub 2}O){sub 2}·(DMF){sub 2}]{sub n} (1·2H{sub 2}O·2DMF), (BDC{sup 2−}=benzene-1,4-dicarboxylate and DMF=N,N-Dimethylformamide), were synthesized and subsequently used for preparation of ZnO nanomaterials. With calcination of the host framework of 1·2H{sub 2}O·2DMF, ZnO nanoparticles were obtained. By the same process on the apohost framework of 1, agglomerated nanoparticles of ZnO were formed. These nano-structures were characterized by X-ray powder diffraction (XRD) and Scanning electron microscopy (SEM). These results indicate that with removal of the guest DMF and coordinated H{sub 2}O molecules from the one-dimensional channels of 1·2H{sub 2}O·2DMF, the tendency of nanoparticles tomore » agglomerate increases and the role of this MOF in preparation of ZnO nanoparticles from this precursor was reduced. - Graphical abstract: Nano-porous zinc(II) MOF with guest DMF and coordinated H{sub 2}O molecules has been synthesized and characterized. The host and the apohost framework of it were used for preparation of ZnO nanomaterials. The role of these species in preparation of ZnO nanoparticles from the host framework is probably similar to the role of polymeric stabilizers in formation of nanoparticles. - Highlights: • Nanoparticles of ZnO were fabricated from nanoporous metal-organic framework. • The effect of guest DMF and coordinated H{sub 2}O molecules on this process was studied. • The effect of them in formation nanoparticle is similar to polymeric stabilizers.« less

Moving granular-bed filter development program, Option III: Development of moving granular-bed filter technology for multi-contaminant control. Task 14: Test plan; Topical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haas, J.C.; Olivo, C.A.; Wilson, K.B.

1994-04-01

An experimental test plan has been prepared for DOE/METC review and approval to develop a filter media suitable for multi-contaminant control in granular-bed filter (GBF) applications. The plan includes identification, development, and demonstration of methods for enhanced media morphology, chemical reactivity, and mechanical strength. The test plan includes media preparation methods, physical and chemical characterization methods for fresh and reacted media, media evaluation criteria, details of test and analytical equipment, and test matrix of the proposed media testing. A filter media composed of agglomerated limestone and clay was determined to be the best candidate for multi-contaminate control in GBF operation.more » The combined limestone/clay agglomerate has the potential to remove sulfur and alkali species, in addition to particulate, and possibly halogens and trace heavy metals from coal process streams.« less

Thermal and mechanical behaviour of sub micron sized fly ash reinforced polyester resin composite

NASA Astrophysics Data System (ADS)

Nantha Kumar, P.; Rajadurai, A.; Muthuramalingam, T.

2018-04-01

The utilization of particles reinforced resin matrix composites is being increased owing to its lower density and high strength to weight ratio. In the present study, an attempt has been made to synthesize fly ash particles reinforced polyester resin composite for engine cowling application. The thermal stability and mechanical behaviours such as hardness and flexural strength of the composite with 2, 3 and 4 weight % of reinforcement is studied and analyzed. The thermo gravimetric analysis indicates that the higher addition of reinforcement increases the decomposition temperature due to its refractory nature. It is also observed that the hardness increases with higher filler addition owing to the resistance of FA particles towards penetration. The flexural strength is found to increase up to the addition of 3% of FA particles, whereas the polyester resin composite prepared with 4% FA particles addition is observed to have low flexural strength owing to agglomeration of particles.

Thermal and mechanical properties of TPU/PBT reinforced by carbon fiber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Jintao; Liu, Huanyu; Lu, Xiang

2016-03-09

In this study, thermal, mechanical properties and processability were performed on a series of carbon fiber (CF) filled thermoplastic polyurethane (TPU)/poly (butylene terephthalate) (PBT) composites to identify the effect of CF weight fraction on the properties of TPU/PBT. Scanning Electronic Microscope (SEM) show that CFs are uniformly dispersed in TPU/PBT matrix and there are no agglomerations. Melt flow index (MFI) show that the melt viscosity increased with the CF loading. Thermogravimetric analysis (TGA) revealed that the introduction of CF into organic materials tend to improve their thermal stability. The mechanical properties indicated that tensile strength and modulus, flexural strength andmore » modulus, improved with an increase in CF loading, but the impact strength decreased by the loading of CF.« less

Structure–property relationships in hybrid dental nanocomposite resins containing monofunctional and multifunctional polyhedral oligomeric silsesquioxanes

PubMed Central

Wang, Weiguo; Sun, Xiang; Huang, Li; Gao, Yu; Ban, Jinghao; Shen, Lijuan; Chen, Jihua

2014-01-01

Organic-inorganic hybrid materials, such as polyhedral oligomeric silsesquioxanes (POSS), have the potential to improve the mechanical properties of the methacrylate-based composites and resins used in dentistry. In this article, nanocomposites of methacryl isobutyl POSS (MI-POSS [bears only one methacrylate functional group]) and methacryl POSS (MA-POSS [bears eight methacrylate functional groups]) were investigated to determine the effect of structures on the properties of dental resin. The structures of the POSS-containing networks were determined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Monofunctional POSS showed a strong tendency toward aggregation and crystallization, while multifunctional POSS showed higher miscibility with the dimethacrylate monomer. The mechanical properties and wear resistance decreased with increasing amounts of MI-POSS, indicating that the MI-POSS agglomerates act as the mechanical weak point in the dental resins. The addition of small amounts of MA-POSS improved the mechanical and shrinkage properties. However, samples with a higher MA-POSS concentration showed lower flexural strength and flexural modulus, indicating that there is a limited range in which the reinforcement properties of MA-POSS can operate. This concentration dependence is attributed to phase separation at higher concentrations of POSS, which affects the structural integrity, and thus, the mechanical and shrinkage properties of the dental resin. Our results show that resin with 3% MA-POSS is a potential candidate for resin-based dental materials. PMID:24550674

Structure-property relationships in hybrid dental nanocomposite resins containing monofunctional and multifunctional polyhedral oligomeric silsesquioxanes.

PubMed

Wang, Weiguo; Sun, Xiang; Huang, Li; Gao, Yu; Ban, Jinghao; Shen, Lijuan; Chen, Jihua

2014-01-01

Organic-inorganic hybrid materials, such as polyhedral oligomeric silsesquioxanes (POSS), have the potential to improve the mechanical properties of the methacrylate-based composites and resins used in dentistry. In this article, nanocomposites of methacryl isobutyl POSS (MI-POSS [bears only one methacrylate functional group]) and methacryl POSS (MA-POSS [bears eight methacrylate functional groups]) were investigated to determine the effect of structures on the properties of dental resin. The structures of the POSS-containing networks were determined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Monofunctional POSS showed a strong tendency toward aggregation and crystallization, while multifunctional POSS showed higher miscibility with the dimethacrylate monomer. The mechanical properties and wear resistance decreased with increasing amounts of MI-POSS, indicating that the MI-POSS agglomerates act as the mechanical weak point in the dental resins. The addition of small amounts of MA-POSS improved the mechanical and shrinkage properties. However, samples with a higher MA-POSS concentration showed lower flexural strength and flexural modulus, indicating that there is a limited range in which the reinforcement properties of MA-POSS can operate. This concentration dependence is attributed to phase separation at higher concentrations of POSS, which affects the structural integrity, and thus, the mechanical and shrinkage properties of the dental resin. Our results show that resin with 3% MA-POSS is a potential candidate for resin-based dental materials.

Effect of cellulose nanocrystals (CNC) particle morphology on dispersion and rheological and mechanical properties of polypropylene/CNC nanocomposites.

PubMed

Khoshkava, Vahid; Kamal, Musa R

2014-06-11

Polypropylene (PP) nanocomposites containing spray-dried cellulose nanocrystals (CNC), freeze-dried CNC, and spray-freeze-dried CNC (CNCSFD) were prepared via melt mixing in an internal batch mixer. Polarized light, scanning electron, and atomic force microscopy showed significantly better dispersion of CNCSFD in PP/CNC nanocomposites compared with the spray-dried and freeze-dried CNCs. Rheological measurements, including linear and nonlinear viscoelastic tests, were performed on PP/CNC samples. The microscopy results were supported by small-amplitude oscillatory shear tests, which showed substantial rises in the magnitudes of key rheological parameters of PP samples containing CNCSFD. Steady-shear results revealed a strong shear thinning behavior of PP samples containing CNCSFD. Moreover, PP melts containing CNCSFD exhibited a yield stress. The magnitude of the yield stress and the degree of shear thinning behavior increased with CNCSFD concentration. It was found that CNCSFD agglomerates with a weblike structure were more effective in modifying the rheological properties. This effect was attributed to better dispersion of the agglomerates with the weblike structure. Dynamic mechanical analysis showed considerable improvement in the modulus of samples containing CNCSFD agglomerates. The percolation mechanical model with modified volume percolation threshold and filler network strength values and the Halpin-Kardos model were used to fit the experimental results.

Mixing of nanosize particles by magnetically assisted impaction techniques

NASA Astrophysics Data System (ADS)

Scicolone, James V.

Nanoparticles and nanocomposites offer unique properties that arise from their small size, large surface area, and the interactions of phases at their interfaces, and are attractive for their potential to improve performance of drugs, biomaterials, catalysts and other high-value-added materials. However, a major problem in utilizing nanoparticles is that they often lose their high surface area due to grain growth. Creating nanostructured composites where two or more nanosized constituents are intimately mixed can prevent this loss in surface area, but in order to obtain homogeneous mixing, de-agglomeration of the individual nanoparticle constituents is necessary. Due to high surface area, nano-particles form very large, fractal agglomerates. The structure of these agglomerates can have a large agglomerate composed of sub-agglomerates (SA), which itself consists of primary agglomerates (PA), that contain chain or net like nano-particle structures; typically sub-micron size. Thus the final agglomerate has a hierarchical, fractal structure, and depending upon the forces applied, it could break down to a certain size scale. The agglomerates can be fairly porous and fragile or they could be quite dense, based on primary particle size and its surface energy. Thus depending upon the agglomerate strength at different length scales, one could achieve deagglomeration and subsequent mixing at varying length scale. A better understanding of this can have a major impact on the field of nano-structured materials; thus the long term objective of this project is to gain fundamental understanding of deagglomeration and mixing of nano-agglomerates. Dry mixing is in general not effective in achieving desired mixing at nanoscale, whereas wet mixing suffers from different disadvantages like nanomaterial of interest should be insoluble, has to wet the liquid, and involves additional steps of filtration and drying. This research examines the use of environmentally friendly a novel approach based on use of small magnetic particles as mixing media is introduced that achieves a high-degree of mixing at scales of about a micron. The method is tested for binary mixture of alumina/silica and silica/titania. Various parameters such as processing time, size of the magnets, and magnetic particle to powder mixed ratio are considered. Experiments are carried out in batch containers in liquid and dry mediums, as well as a fluidized bed set-up. Homogeneity of Mixing (HoM), defined as the compliment of the Intensity of Segregation, was evaluated at the micron scale through field-emission scanning electron microscopy (FESEM) and the energy dispersive x-ray spectroscopy (EDS). Secondary electron images, along with elemental mappings, were used to visualize the change in agglomerate sizes. Compositional percent data of each element were obtained through an EDS spatial distribution point analysis and used to obtain quantitative analysis on the homogeneity of the mixture. The effect of magnet impaction on mixing quality was examined on the HoM of binary mixtures. The research shows that HoM improved with magnetically assisted impaction mixing techniques indicating that the HoM depends on the product of processing time with the number of magnets. In a fluidized bed set-up, MAIM not only improved dispersion, but it was also found that the magnetic particles served to break down the larger agglomerates, to reduce the minimum fluidization velocity, to delay the onset of bubbling, and to convert the fluidization behavior of ABF powder to APF. Thus MAIM techniques may be used to achieve mixing of nanopowders at a desired HoM through adjusting the number of magnets and processing time; and its inherent advantages are its simplicity, an environmentally benign operation, and reduced cost as compared with wet mixing techniques.

Association among components of resilience and workplace violence-related depression among emergency department nurses in Taiwan: a cross-sectional study.

PubMed

Hsieh, Hsiu-Fen; Chen, Yao-Mei; Wang, Hsiu-Hung; Chang, Shu-Chen; Ma, Shu-Ching

2016-09-01

This correlation study examined the relationship among recently workplace violence, depressive tendency, social support, and resilience of victimised nurses, and we also tried to identify protective factors and potential targets for preventive interventions for these nurses. Workplace violence in hospitals negatively affects occupational health and safety of medical professionals, especially for emergency department nurses. A cross-sectional, correlation research design was applied. Hierarchical regression was used to examine data which were collected from June 2013 to December 2013 from emergency departments in Taiwan. One hundred and eighty nurses were recruited from two hospitals. Structured interviews and questionnaires were applied to collect data, including the Social Support Scale, the Resilience Scale and the Center for Epidemiologic Studies Depression. A total of 159 (88·33%) nurses had suffered from physical or verbal violence by patients or their family. Resilience and peer support were significantly higher in the group without depressive tendency. Components of resilience of personal strength, social competence, structure style and religious beliefs were significant factors which accounted for 46·0% of variance in depressive tendency. Three of the five components of resilience: personal strength, social competence and structured style were found to have profounder effects against depressive tendency than peer support. Hospital managers should establish a safer working environment for emergency department nurses and reinforce their resilience against depression when they encounter workplace violence. This study showed that three of the five components of resilience: personal strength, social competence and structured style are protective factors against depressive tendency in victimised nurses. Improving these three components with coping and problem-solving skills by healthcare manager would be effective measures for enhancing their resilience in situations of workplace violence. © 2016 John Wiley & Sons Ltd.

Hydrophobic agglomeration of apatite fines induced by sodium oleate in aqueous solutions

NASA Astrophysics Data System (ADS)

Yang, Bingqiao; Huang, Pengliang; Song, Shaoxian; Luo, Huihua; Zhang, Yi

2018-06-01

In this work, the hydrophobic agglomeration of apatite fines induced by sodium oleate in aqueous solutions has been investigated through the measurement of agglomeration degree and fractal dimension. The results showed that the agglomeration degree of apatite fines and agglomerates morphology was strongly depended on sodium oleate concentration, pH, stirring speed and time. Better agglomeration degree and more regular agglomerates were achieved at sodium oleate concentration of 5 × 10-5 mol/L under neutral condition. The critical stirring speed for agglomerates rupture was 1000 rev/min, above which, prolonged stirring time would cause breakage and restructure of the agglomerates after a certain stirring time, resulting in lower agglomeration degree and more regular agglomerates. The agglomeration degree of apatite fines could be greatly enhanced with the addition of emulsified kerosene, but only if the apatite surface was hydrophobic enough.

Effect of Strength Enhancement of Soil Treated with Environment-Friendly Calcium Carbonate Powder

PubMed Central

Park, Kyungho; Jun, Sangju; Kim, Daehyeon

2014-01-01

This study aims to investigate the effects of the strength improvement of soft ground (sand) by producing calcium carbonate powder through microbial reactions. To analyze the cementation effect of calcium carbonate produced through microbial reaction for different weight ratios, four different types of specimens (untreated, calcium carbonate, cement, and calcium carbonate + cement) with different weight ratios (2%, 4%, 6%, and 8%) were produced and cured for a period of 3 days, 7 days, 14 days, 21 days, and 28 days to test them. The uniaxial compression strength of specimens was measured, and the components in the specimen depending on the curing period were analyzed by means of XRD analysis. The result revealed that higher weight ratios and longer curing period contributed to increased strength of calcium carbonate, cement, and calcium carbonate + cement specimens. The calcium carbonate and the calcium carbonate + cement specimens in the same condition showed the tendency of decreased strength approximately 3 times and two times in comparison with the 8% cement specimens cured for 28 days, but the tendency of increased strength was approximately 4 times and 6 times in comparison with the untreated specimen. PMID:24688401

Effect of strength enhancement of soil treated with environment-friendly calcium carbonate powder.

PubMed

Park, Kyungho; Jun, Sangju; Kim, Daehyeon

2014-01-01

This study aims to investigate the effects of the strength improvement of soft ground (sand) by producing calcium carbonate powder through microbial reactions. To analyze the cementation effect of calcium carbonate produced through microbial reaction for different weight ratios, four different types of specimens (untreated, calcium carbonate, cement, and calcium carbonate + cement) with different weight ratios (2%, 4%, 6%, and 8%) were produced and cured for a period of 3 days, 7 days, 14 days, 21 days, and 28 days to test them. The uniaxial compression strength of specimens was measured, and the components in the specimen depending on the curing period were analyzed by means of XRD analysis. The result revealed that higher weight ratios and longer curing period contributed to increased strength of calcium carbonate, cement, and calcium carbonate + cement specimens. The calcium carbonate and the calcium carbonate + cement specimens in the same condition showed the tendency of decreased strength approximately 3 times and two times in comparison with the 8% cement specimens cured for 28 days, but the tendency of increased strength was approximately 4 times and 6 times in comparison with the untreated specimen.

Study to minimize hydrogen embrittlement of ultrahigh-strength steels

NASA Technical Reports Server (NTRS)

Elsea, S. T.; Fletcher, E. E.; Groeneveld, T. P.

1967-01-01

Hydrogen-stress cracking in high-strength steels is influenced by hydrogen content of the material and its hydrogen absorption tendency. Non-embrittling cleaning, pickling, and electroplating processes are being studied. Protection from this hydrogen embrittlement is important to the aerospace and aircraft industries.

Crack nucleation using combined crystal plasticity modelling, high-resolution digital image correlation and high-resolution electron backscatter diffraction in a superalloy containing non-metallic inclusions under fatigue

PubMed Central

Zhang, Tiantian; Britton, Ben; Shollock, Barbara; Dunne, Fionn

2016-01-01

A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) resolution-electron backscatter diffraction (HR-EBSD) and high (spatial) resolution-digital image correlation (HR-DIC) strain measurement techniques. Experimentally, this sample has been subjected to heat treatment leading to the establishment of residual (elastic) strains local to the agglomerate and subsequently loaded under conditions of low cyclic fatigue. The full thermal and mechanical loading history was reproduced within the model. HR-EBSD and HR-DIC elastic and total strain measurements demonstrate qualitative and quantitative agreement with crystal plasticity results. Crack nucleation by interfacial decohesion at the nickel matrix/agglomerate inclusion boundaries is observed experimentally, and systematic modelling studies enable the mechanistic basis of the nucleation to be established. A number of fatigue crack nucleation indicators are also assessed against the experimental results. Decohesion was found to be driven by interface tensile normal stress alone, and the interfacial strength was determined to be in the range of 1270–1480 MPa. PMID:27279765

Crack nucleation using combined crystal plasticity modelling, high-resolution digital image correlation and high-resolution electron backscatter diffraction in a superalloy containing non-metallic inclusions under fatigue

NASA Astrophysics Data System (ADS)

Zhang, Tiantian; Jiang, Jun; Britton, Ben; Shollock, Barbara; Dunne, Fionn

2016-05-01

A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) resolution-electron backscatter diffraction (HR-EBSD) and high (spatial) resolution-digital image correlation (HR-DIC) strain measurement techniques. Experimentally, this sample has been subjected to heat treatment leading to the establishment of residual (elastic) strains local to the agglomerate and subsequently loaded under conditions of low cyclic fatigue. The full thermal and mechanical loading history was reproduced within the model. HR-EBSD and HR-DIC elastic and total strain measurements demonstrate qualitative and quantitative agreement with crystal plasticity results. Crack nucleation by interfacial decohesion at the nickel matrix/agglomerate inclusion boundaries is observed experimentally, and systematic modelling studies enable the mechanistic basis of the nucleation to be established. A number of fatigue crack nucleation indicators are also assessed against the experimental results. Decohesion was found to be driven by interface tensile normal stress alone, and the interfacial strength was determined to be in the range of 1270-1480 MPa.

Concurrent agglomeration and straining govern the transport of 14C-labeled few-layer graphene in saturated porous media.

PubMed

Su, Yu; Gao, Bin; Mao, Liang

2017-05-15

Deposition of graphene on environmental surfaces will dictate its transport and risks. In this work, the deposition, mobilization, and transport of 14 C-labeled few-layer graphene (FLG) in saturated quartz sand were systematically examined. Increasing solution ionic strength (IS) (1-100 mmol/L NaCl) resulted in greater retention of FLG (33-89%) in the sand and more hyper-exponential distribution of FLG along the sand column. Only a small fraction (≤7.4%) of the retained FLG was remobilized due to perturbation of IS by deionized water. These results indicate that trapping in pore spaces (i.e., physical straining) plays a dominant role in FLG deposition rather than attachment onto the surfaces of the sand. When IS, FLG input concentration, and flow velocity favor particle-particle interaction over particle-collector interaction, concurrent agglomeration within the pores promotes straining. In addition, electrostatic and steric repulsion that derived from the adsorbed organic macromolecules on FLG effectively reduced agglomeration and thereby enhanced transport and release of FLG. Moreover, the recovery of FLG (that deposited at 100 mmol/L NaCl) in the effluent reached 33% after speeding up the deionized water flushing rate. These findings highlight the need for FLG management in view of variations in transport behavior when assessing water quality and associated risks. Copyright © 2017 Elsevier Ltd. All rights reserved.

Agglomeration of SRC residues. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Theodore, F.W.; Wasson, G.E.

1982-01-01

EPRI contracted with CCDC to agglomerate Kerr-McGee ash concentrate and determine whether the agglomerates could be used as a fixed-bed gasifier feed. Briquettes were produced from Kerr-McGee ash concentrate which met CCDC's strength criteria for handling as feed to a fixed-bed gasifier. In addition, when shock heated under conditions simulating gasifier conditions, strong coke was produced demonstrating that the briquettes will not disintegrate during the initial temperature shock when charged to the gasifier. The conclusion of this study is that briquettes produced from the Kerr-McGee ash concentrate studied could be considered as feed for a fixed-bed gasifier. The CO/sub 2/-carbonmore » reactivity of the briquettes had values between a typical eastern and western coal. In the case of a dry bottom gasifier where the reactivity is important, it is not clear-cut whether the ash concentrate briquettes would be an economical feed. A closer inspection by a gasifier manufacturer is needed to resolve this issue. Since higher gasification temperatures are used in a slagging gasifier, the reactivity question is eliminated and the briquettes should be considered as a feed. This study does not deal with the exact design of a gasifier since this is a function of the type used. The gasifier manufacturer should be considered in future work for their input on critical design considerations i.e. stirrer design, etc.« less

Isometric strength ratios of the hip musculature in females with patellofemoral pain: a comparison to pain-free controls.

PubMed

Magalhães, Eduardo; Silva, Ana Paula M C C; Sacramento, Sylvio N; Martin, RobRoy L; Fukuda, Thiago Y

2013-08-01

The purpose of the study was to compare hip agonist-antagonist isometric strength ratios between females with patellofemoral pain (PFP) syndrome and pain-free control group. One hundred and twenty females between 15 and 40 years of age (control group: n = 60; PFP group: n = 60) participated in the study. Hip adductor, abductor, medial rotator, lateral rotator, flexor, and extensor isometric strength were measured using a hand-held dynamometer. Comparisons in the hip adductor/abductor and medial/lateral rotator and flexor/extensor strength ratios were made between groups using independent t-tests. Group comparisons also were made between the anteromedial hip complex (adductor, medial rotator, and flexor musculature) and posterolateral hip complex (abductor, lateral rotator, and extensor musculature). On average, the hip adductor/abductor isometric strength ratio in the PFP group was 23% higher when compared with the control group (p = 0.01). The anteromedial/posterolateral complex ratio also was significantly higher in the PFP group (average 8%; p = 0.04). No significant group differences were found for the medial/lateral rotator ratio and flexor/extensor strength ratios. The results of this study demonstrate that females with PFP have altered hip strength ratios when compared with asymptomatic controls. These strength imbalances may explain the tendency of females with PFP to demonstrate kinematic tendencies that increase loading on the patellofemoral joint (i.e., dynamic knee valgus).

Mechanical behavior of glass/epoxy composite laminate with varying amount of MWCNTs under different loadings

NASA Astrophysics Data System (ADS)

Singh, K. K.; Rawat, Prashant

2018-05-01

This paper investigates the mechanical response of three phased (glass/MWCNTs/epoxy) composite laminate under three different loadings. Flexural strength, short beam strength and low-velocity impact (LVI) testing are performed to find an optimum doping percentage value for maximum enhancement in mechanical properties. In this work, MWCNTs were used as secondary reinforcement for three-phased composite plate. MWCNT doping was done in a range of 0–4 wt% of the thermosetting matrix system. Symmetrical design eight layered glass/epoxy laminate with zero bending extension coupling laminate was fabricated using a hybrid method i.e. hand lay-up technique followed by vacuum bagging method. Ranging analysis of MWCNT mixing highlighted the enhancement in flexural, short beam strength and improvement in damage tolerance under LVI loading. While at higher doping wt%, agglomeration of MWCNTs are observed. Results of mechanical testing proposed an optimized doping value for maximum strength and damage resistance of the laminate.

Long-term biopersistence of tangled oxidized carbon nanotubes inside and outside macrophages in rat subcutaneous tissue

NASA Astrophysics Data System (ADS)

Sato, Yoshinori; Yokoyama, Atsuro; Nodasaka, Yoshinobu; Kohgo, Takao; Motomiya, Kenichi; Matsumoto, Hiroaki; Nakazawa, Eiko; Numata, Tomoko; Zhang, Minfang; Yudasaka, Masako; Hara, Hideyuki; Araki, Rikita; Tsukamoto, Osamu; Saito, Hiroaki; Kamino, Takeo; Watari, Fumio; Tohji, Kazuyuki

2013-08-01

Because of their mechanical strength, chemical stability, and low molecular weight, carbon nanotubes (CNTs) are attractive biological implant materials. Biomaterials are typically implanted into subcutaneous tissue or bone; however, the long-term biopersistence of CNTs in these tissues is unknown. Here, tangled oxidized multi-walled CNTs (t-ox-MWCNTs) were implanted into rat subcutaneous tissues and structural changes in the t-ox-MWCNTs located inside and outside of macrophages were studied for 2 years post-implantation. The majority of the large agglomerates were present in the intercellular space, maintained a layered structure, and did not undergo degradation. By contrast, small agglomerates were found inside macrophages, where they were gradually degraded in lysosomes. None of the rats displayed symptoms of cancer or severe inflammatory reactions such as necrosis. These results indicate that t-ox-MWCNTs have high biopersistence and do not evoke adverse events in rat subcutaneous tissue in vivo, demonstrating their potential utility as implantable biomaterials.

Effect of nano/micro B4C and SiC particles on fracture properties of aluminum 7075 particulate composites under chevron-notch plane strain fracture toughness test

NASA Astrophysics Data System (ADS)

Morovvati, M. R.; Lalehpour, A.; Esmaeilzare, A.

2016-12-01

Reinforcing aluminum with SiC and B4C nano/micro particles can lead to a more efficient material in terms of strength and light weight. The influence of adding these particles to an aluminum 7075 matrix is investigated using chevron-notch fracture toughness test method. The reinforcing factors are type, size (micro/nano), and weight percent of the particles. The fracture parameters are maximum load, notch opening displacement, the work up to fracture and chevron notch plane strain fracture toughness. The findings demonstrate that addition of micro and nano size particles improves the fracture properties; however, increasing the weight percent of the particles leads to increase of fracture properties up to a certain level and after that due to agglomeration of the particles, the improvement does not happen for both particle types and size categories. Agglomeration of particles at higher amounts of reinforcing particles results in improper distribution of particles and reduction in mechanical properties.

Structural and electronic properties of copper-doped chalcogenide glasses

NASA Astrophysics Data System (ADS)

Guzman, David M.; Strachan, Alejandro

2017-10-01

Using ab initio molecular dynamics based on density functional theory, we study the atomic and electronic structure, and transport properties of copper-doped germanium-based chalcogenide glasses. These mixed ionic-electronic conductor materials exhibit resistance or threshold switching under external electric field depending on slight variations of chemical composition. Understanding the origin of the transport character is essential for the functionalization of glassy chalcogenides for nanoelectronics applications. To this end, we generated atomic structures for GeX3 and GeX6 (X = S, Se, Te) at different copper concentrations and characterized the atomic origin of electronic states responsible for transport and the tendency of copper clustering as a function of metal concentration. Our results show that copper dissolution energies explain the tendency of copper to agglomerate in telluride glasses, consistent with filamentary conduction. In contrast, copper is less prone to cluster in sulfides and selenides leading to hysteresisless threshold switching where the nature of transport is dominated by electronic midgap defects derived from polar chalcogen bonds and copper atoms. Simulated I -V curves show that at least 35% by weight of copper is required to achieve the current demands of threshold-based devices for memory applications.

Pairing tendencies in a two-orbital Hubbard model in one dimension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Niravkumar D.; Nocera, Adriana; Alvarez, Gonzalo

The recent discovery of superconductivity under high pressure in the ladder compound BaFe2S3 has opened a new field of research in iron-based superconductors with focus on quasi-one-dimensional geometries. In this publication, using the density matrix renormalization group technique, we study a two-orbital Hubbard model defined in one-dimensional chains. Our main result is the presence of hole binding tendencies at intermediate Hubbard U repulsion and robust Hund coupling JH / U = 0.25. Binding does not occur either in weak coupling or at very strong coupling. The pair-pair correlations that are dominant near half-filling, or of similar strength as the chargemore » and spin correlation channels, involve hole-pair operators that are spin singlets, use nearest-neighbor sites, and employ different orbitals for each hole. As a result, the Hund coupling strength, presence of robust magnetic moments, and antiferromagnetic correlations among them are important for the binding tendencies found here.« less

Characterization of sintered SiC by using NDE

NASA Technical Reports Server (NTRS)

Baaklini, George Y.

1988-01-01

Capabilities of projection microfocus X-radiography and of ultrasonic velocity and attenuation for characterizing silicon carbide specimens were assessed. Silicon carbide batches covered a range of densities and different microstructural characteristics. Room-temperature, four-point flexural strength tests were conducted. Fractography was used to identify types, sizes, and locations of fracture origins. Fracture toughness values were calculated from fracture strength and flaw characterization data. Detection capabilities of radiography for fracture-causing flaws were evaluated. Applicability of ultrasonics for verifying material strength and toughness was examined. Radiography proved useful in detecting high-density inclusions and isolated voids, but failed in detecting surface and subsurface agglomerates and large grains as fracture origins. Ultrasonic velocity dependency on density was evident. Attenuation dependency on density and mean pore size was clearly demonstrated. Understanding attenuation as a function of toughness was limited by shortcomings in K sub IC determination.

Wear characterization of nano-hydroxyapatite with addition of titanium (HA-Ti)

NASA Astrophysics Data System (ADS)

Rosmamuhamadani, R.; Arawi, A. Z. O.; Talari, M. K.; Mahat, M. M.; Bonnia, N. N.; Sabrina; Yahaya, M.; Sulaiman, S.; Ismail, M. I. S.

2018-04-01

Hydroxyapatite (Ca10 (PO4)6(OH)2, HA), is an attractive material of an inorganic compound whose chemical composition and crystallographic structures are similar to the composition of the bone. A natural source such as egg shells is composed of 94 wt. % of calcium carbonate (CaCO3), which can be calcined as calcium oxide (CaO) by the calcinations process. The efficient temperature to produce CaO is 900 °C for 2 hours. The synthesis of nano-HA was done by the mixing the diammonium phosphate (DAP) and calcium hydroxide (Ca(OH)2) and subjected into a microwave for 30 minutes at 1100 W irradiation power. Ball milling process was used for 30 minutes to mix the nano-HA with different compositions of titanium. These were pressed to form pallets by hand hydraulic pump (force=2300 psi). The pallets then were sintered at 1200 °C with the heating rate of 3 °C/min for 2 hours. The pallets were tested by several mechanical testing including hardness, compression strength and wear. From the results, HA-25wt. %Ti composite gave the highest hardness, compression and coefficient of friction for wear test values which were 89.6 Hv, 82.5MPa and 0.76μ respectively. It showed that by adding Ti to nano-HA, the mechanical properties of nano-HA could be enhanced. The microstructure analyses by optical micrograph showed that nano-HA-Ti particles displayed shape likes needle morphology. The particles showed the high tendency to form the agglomerations.

Influence of PVP in magnetic properties of NiSn nanoparticles prepared by polyol method

NASA Astrophysics Data System (ADS)

Bobadilla, L. F.; García, C.; Delgado, J. J.; Sanz, O.; Romero-Sarria, F.; Centeno, M. A.; Odriozola, J. A.

2012-11-01

The influence of PVP on the magnetic properties of NiSn nanoparticles prepared by polyol method has been studied. NiSn nanoparticles exhibit superparamagnetic behavior although there is a ferromagnetic contribution due to particles agglomerated below the blocking temperature. The particle size is controlled by the addiction of PVP in varying amounts. The addition of PVP also favours the particles isolation, narrow the particle size distribution and decrease the interparticle interaction strength increasing the superparamagnetic contribution.

Formation of polymer micro-agglomerations in ultralow-binder-content composite based on lunar soil simulant

NASA Astrophysics Data System (ADS)

Chen, Tzehan; Chow, Brian J.; Zhong, Ying; Wang, Meng; Kou, Rui; Qiao, Yu

2018-02-01

We report results from an experiment on high-pressure compaction of lunar soil simulant (LSS) mixed with 2-5 wt% polymer binder. The LSS grains can be strongly held together, forming an inorganic-organic monolith (IOM) with the flexural strength around 30-40 MPa. The compaction pressure, the number of loadings, the binder content, and the compaction duration are important factors. The LSS-based IOM remains strong from -200 °C to 130 °C, and is quite gas permeable.

Influence of stabilizers on the physicochemical characteristics of inhaled insulin powders produced by supercritical antisolvent process.

PubMed

Kim, Yong Ho; Sioutas, Constantinos; Shing, Katherine S

2009-01-01

To examine the effect of stabilizers on aerosol physicochemical characteristics of inhaled insulin particles produced using a supercritical fluid technology. Insulin with stabilizers such as mannitol and trehalose was micronized by aerosol solvent extraction system (ASES). The supercritically-micronized insulin particles were characterized for size, shape, aerosol behavior, crystallinity and secondary structure. Experimental results indicated that when insulin was incorporated with the most commonly used stabilizer mannitol (insulin/mannitol: 15/85 wt.%, designated IM), the particles formed were irregular and needle-shaped and had a tendency to agglomerate. With the incorporation of a second stabilizer trehalose (insulin/mannitol/trehalose: 15/70/15 wt.%, designated IMT), the particles were relatively uniform, more spherical, less cohesive, and less agglomerated in an air flow, when compared to IM particles. The mass median aerodynamic diameter of the IMT particles was 2.32 mum which is suitable for use in inhalation therapy. In vitro deposition test using micro-orifice uniform deposit impactor showed 69 +/- 7 wt.% of the IMT particles was deposited in stage 3, 4, 5 and 6 while 41 +/- 15 wt.% of the IM particles was deposited in the same stages. In terms of insulin stability, secondary structures of insulin particles were not adversely affected by the ASES processing studied here. When properly formulated (as in IMT particles), ASES process can produce particles with appropriate size and size distribution suitable for pulmonary insulin delivery.

Graphene-Reinforced Aluminum Matrix Composites: A Review of Synthesis Methods and Properties

NASA Astrophysics Data System (ADS)

Chen, Fei; Gupta, Nikhil; Behera, Rakesh K.; Rohatgi, Pradeep K.

2018-06-01

Graphene-reinforced aluminum (Gr-Al) matrix nanocomposites (NCs) have attracted strong interest from both research and industry in high-performance weight-sensitive applications. Due to the vastly different bonding characteristics of the Al matrix (metallic) and graphene (in-plane covalent + inter-plane van der Waals), the graphene phase has a general tendency to agglomerate and phase separate in the metal matrix, which is detrimental for the mechanical and chemical properties of the composite. Thus, synthesis of Gr-Al NCs is extremely challenging. This review summarizes the different methods available to synthesize Gr-Al NCs and the resulting properties achieved in these NCs. Understanding the effect of processing parameters on the realized properties opens up the possibility of tailoring the synthesis methods to achieve the desired properties for a given application.

An Experimental Investigation of Sewage Sludge Gasification in a Fluidized Bed Reactor

PubMed Central

Calvo, L. F.; García, A. I.; Otero, M.

2013-01-01

The gasification of sewage sludge was carried out in a simple atmospheric fluidized bed gasifier. Flow and fuel feed rate were adjusted for experimentally obtaining an air mass : fuel mass ratio (A/F) of 0.2 < A/F < 0.4. Fuel characterization, mass and power balances, produced gas composition, gas phase alkali and ammonia, tar concentration, agglomeration tendencies, and gas efficiencies were assessed. Although accumulation of material inside the reactor was a main problem, this was avoided by removing and adding bed media along gasification. This allowed improving the process heat transfer and, therefore, gasification efficiency. The heating value of the produced gas was 8.4 MJ/Nm, attaining a hot gas efficiency of 70% and a cold gas efficiency of 57%. PMID:24453863

Graphene-Reinforced Aluminum Matrix Composites: A Review of Synthesis Methods and Properties

NASA Astrophysics Data System (ADS)

Chen, Fei; Gupta, Nikhil; Behera, Rakesh K.; Rohatgi, Pradeep K.

2018-03-01

Graphene-reinforced aluminum (Gr-Al) matrix nanocomposites (NCs) have attracted strong interest from both research and industry in high-performance weight-sensitive applications. Due to the vastly different bonding characteristics of the Al matrix (metallic) and graphene (in-plane covalent + inter-plane van der Waals), the graphene phase has a general tendency to agglomerate and phase separate in the metal matrix, which is detrimental for the mechanical and chemical properties of the composite. Thus, synthesis of Gr-Al NCs is extremely challenging. This review summarizes the different methods available to synthesize Gr-Al NCs and the resulting properties achieved in these NCs. Understanding the effect of processing parameters on the realized properties opens up the possibility of tailoring the synthesis methods to achieve the desired properties for a given application.

The use of AntiMisting Kerosene (AMK) in turbojet engines

NASA Technical Reports Server (NTRS)

Schmidt, H. W.

1981-01-01

The effect of antimisting kerosene (AMK) flow characteristics on fan jet engines and the impact of degradation requirements on the fuel system was evaluated. It was determined from the present program that AMK fuel cannot be used without predegradation, although some degradation occurs throughout the fuel feed system, expecially in the fuel pumps. There is a tendency toward FM-9 AMK additive agglomeration and gel formation when the liquid flows at a critical velocity through very small passages. The data indicate this phenomenon to be a function of the degree of degradation, the passage size, the differential pressure, the fluid temperature, and the accumulated flow time. Additionally, test results indicate that the long term cumulative effects of this phenomenon may require more degradation than the theoretical requirement determined from short term tests.

Synthesis and characterization of dextran-coated iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Predescu, Andra Mihaela; Matei, Ecaterina; Berbecaru, Andrei Constantin; Pantilimon, Cristian; Drăgan, Claudia; Vidu, Ruxandra; Predescu, Cristian; Kuncser, Victor

2018-03-01

Synthesis and characterization of iron oxide nanoparticles coated with a large molar weight dextran for environmental applications are reported. The first experiments involved the synthesis of iron oxide nanoparticles which were coated with dextran at different concentrations. The synthesis was performed by a co-precipitation technique, while the coating of iron oxide nanoparticles was carried out in solution. The obtained nanoparticles were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectrometry, Fourier transform infrared spectroscopy and superconducting quantum interference device magnetometry. The results demonstrated a successful coating of iron oxide nanoparticles with large molar weight dextran, of which agglomeration tendency depended on the amount of dextran in the coating solution. SEM and TEM observations have shown that the iron oxide nanoparticles are of about 7 nm in size.

Influence of brazing conditions on the strength of brazed joints of alumina dispersion-strengthened copper to 316 stainless steel

NASA Astrophysics Data System (ADS)

Nishi, H.; Kikuchi, K.

1998-10-01

Brazing of alumina dispersion-strengthened copper (DS Cu) to 316 stainless steel were conducted in order to investigate the influence of filler metals and brazing conditions on the joint strength. The brazing were performed with a silver-base (BAg-8) and three kinds of gold-base (BAu-2,4,11) filler metals with varying brazing joint clearance and brazing time. The filler metal had a greater effect on the joint strength than the brazing joint clearance and brazing time. The joint with BAu-2 was superior to the joint with other filler metals. The tensile strength of the joint with BAu-2 was as large as that of DS Cu, however, the Charpy and low cycle fatigue strength were lower than those of DS Cu. The DS Cu melted near the brazed zone, consequently recrystallization and agglomeration of alumina occurred in the diffusion layer for all filler metals. The grain size after the recrystallization was small in order of BAu-2, BAu-4 and BAu-11, that was in accordance with the order of the brazing temperature. The excellent fracture strength for the joint with BAu-2 was attributed to the smallest grain size.

The missing piece in the puzzle: Prediction of aggregation via the protein-protein interaction parameter A∗2.

PubMed

Koepf, Ellen; Schroeder, Rudolf; Brezesinski, Gerald; Friess, Wolfgang

2018-07-01

The tendency of protein pharmaceuticals to form aggregates is a major challenge during formulation development, as aggregation affects quality and safety of the product. In particular, the formation of large native-like particles in the context of liquid-air interfacial stress is a well-known but not fully understood problem. Focusing on the two most fundamental criteria of protein formulation affecting protein-protein interaction, the impact of pH and ionic strength on the interaction parameter A ∗ 2 and its link to aggregation upon mechanical stress was investigated. A ∗ 2 of two monoclonal antibodies (mABs) and a polyclonal IgG was determined using dynamic light scattering and was correlated to the number of particles formed upon shaking in vials analyzed by visual inspection, turbidity analysis, light obscuration and micro-flow imaging. A good correlation between aggregation induced by interfacial stress and formulation pH was given. It could be shown that A ∗ 2 was highest for mAB 1 and lowest for IgG, what was in good accordance with the number of particles formed. Shaking of IgG resulted in overall higher numbers of particles compared to the two mABs. A ∗ 2 decreased and particle numbers increased with increasing pH. Different to pH, ionic strength only slightly affected A ∗ 2 . Nevertheless, at high ionic (100 mM) strength the samples exhibited more pronounced particle formation, particularly of large particles >25 µm, which was most pronounced at high pH. Protein solutions were identified to form continuous films with an inhomogeneous protein distribution at the liquid-air interface. These areas of agglomerated, native-like protein material can be transferred into the bulk solution by compression-decompression of the interface. Whether or not those clusters lead to the appearance of large protein aggregates or fall apart depends on the attractive or repulsive forces between protein molecules. Thus, protein aggregation due to interfacial stress is correlated with the protein-protein interactions as determined by A ∗ 2 . This enables to differentiate different antibodies according to their propensity to form particles upon mechanical stress and to identify optimum formulation conditions. Copyright © 2018 Elsevier B.V. All rights reserved.

In vitro dosimetry of agglomerates

NASA Astrophysics Data System (ADS)

Hirsch, V.; Kinnear, C.; Rodriguez-Lorenzo, L.; Monnier, C. A.; Rothen-Rutishauser, B.; Balog, S.; Petri-Fink, A.

2014-06-01

Agglomeration of nanoparticles in biological fluids is a pervasive phenomenon that leads to difficulty in the interpretation of results from in vitro exposure, primarily due to differing particokinetics of agglomerates to nanoparticles. Therefore, well-defined small agglomerates were designed that possessed different particokinetic profiles, and their cellular uptake was compared to a computational model of dosimetry. The approach used here paves the way for a better understanding of the impact of agglomeration on the nanoparticle-cell interaction.Agglomeration of nanoparticles in biological fluids is a pervasive phenomenon that leads to difficulty in the interpretation of results from in vitro exposure, primarily due to differing particokinetics of agglomerates to nanoparticles. Therefore, well-defined small agglomerates were designed that possessed different particokinetic profiles, and their cellular uptake was compared to a computational model of dosimetry. The approach used here paves the way for a better understanding of the impact of agglomeration on the nanoparticle-cell interaction. Electronic supplementary information (ESI) available: ITC data for tiopronin/Au-NP interactions, agglomeration kinetics at different pHs for tiopronin-coated Au-NPs, UV-Vis spectra in water, PBS and DMEM and temporal correlation functions for single Au-NPs and corresponding agglomerates, calculation of diffusion and sedimentation parameters, modelling of relative cell uptake based on the ISDD model and cytotoxicity of single Au-NPs and their agglomerates, and synthesis and cell uptake of large spherical Au-NPs. See DOI: 10.1039/c4nr00460d

A systematic and mechanistic evaluation of aspartic acid as filler for directly compressed tablets containing trimethoprim and trimethoprim aspartate.

PubMed

ElShaer, Amr; Hanson, Peter; Mohammed, Afzal R

2013-04-01

The generally accepted paradigm of 'inert' and 'mono functional' excipient in dosage form has been recently challenged with the development of individual excipients capable of exhibiting multiple functions (e.g. binder-disintegrants, surfactant which affect P-gp function). The proposed study has been designed within the realm of multifunctionality and is the first and novel investigation towards evaluation of aspartic acid as a filler and disintegration enhancing agent for the delivery of biopharmaceutical class IV model drug trimethoprim. The study investigated powder characteristics using angle of repose, laser diffractometry and scanning electron microscopy (SEM). The prepared tablets were characterised using Heckel analysis, disintegration time and tensile strength measurements. Although Heckel analysis revealed that both TMP and TMP aspartate salt have high elasticity, the salt form produced a stronger compact which was attributed to the formation of agglomerates. Aspartic acid was found to have high plasticity, but its incorporation into the formulations was found to have a negative impact on the compaction properties of TMP and its salt. Surface morphology investigations showed that mechanical interlocking plays a vital role in binding TMP crystals together during compaction, while the small particle size of TMP aspartate agglomerates was found to have significant impact on the tensile strength of the tablets. The study concluded that aspartic acid can be employed as filler and disintegrant and that compactability within tablets was independent of the surface charge of the excipients. Copyright © 2012 Elsevier B.V. All rights reserved.

Release, transport and toxicity of engineered nanoparticles.

PubMed

Soni, Deepika; Naoghare, Pravin K; Saravanadevi, Sivanesan; Pandey, Ram Avatar

2015-01-01

Recent developments in nanotechnology have facilitated the synthesis of novel engineered nanoparticles (ENPs) that possess new and different physicochemical properties. These ENPs have been ex tensive ly used in various commercial sectors to achieve both social and economic benefits. However. the increasing production and consumption of ENPs by many different industries has raised concerns about their possible release and accumulation in the environment. Released EN Ps may either remain suspended in the atmosphere for several years or may accumulate and eventually be modified int o other substances. Settled nanoparticles can he easily washed away during ra in s. and therefore may easily enter the food chain via water and so il. Thus. EN Ps can contaminate air. water and soil and can subsequently pose adverse risks to the health of different organisms. Studies to date indicate that ENP transport to and within the ecosystem depend on their chemical and physical properties (viz .. size. shape and solubility) . Therefore. the EN Ps display variable behavior in the environment because of their individual properties th at affect their tendency for adsorption, absorption, diffusional and colloidal interaction. The transport of EN Ps also influences their fate and chemical transformation in ecosystems. The adsorption, absorption and colloidal interaction of ENPs affect their capacity to be degraded or transformed, whereas the tendency of ENPs to agglomerate fosters their sedimentation. How widely ENPs are transported and their environmental fate influence how tox ic they may become to environmental organisms. One barrier to fully understanding how EN Ps are transformed in the environment and how best to characterize their toxicity, is related to the nature of their ultrafine structure. Experiments with different animals, pl ants, and cell lines have revealed that ENPs induce toxicity via several cellular pathways that is linked to the size. shape. surface area, agglomeration state. and sur face charge of the ENP involved. Future research is needed to elucidate the mechanisms by which nanoparticles act to induce their tox ic effects aft er they reach various ecosystems. Moreover. work is needed to develop a holistic approach for better understanding the effects that ENPs produce at the cellular and genetic level.

Recovery Act: Novel Oxygen Carriers for Coal-fueled Chemical Looping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Wei-Ping; Cao, Yan

2012-11-30

Chemical Looping Combustion (CLC) could totally negate the necessity of pure oxygen by using oxygen carriers for purification of CO{sub 2} stream during combustion. It splits the single fuel combustion reaction into two linked reactions using oxygen carriers. The two linked reactions are the oxidation of oxygen carriers in the air reactor using air, and the reduction of oxygen carriers in the fuel reactor using fuels (i.e. coal). Generally metal/metal oxides are used as oxygen carriers and operated in a cyclic mode. Chemical looping combustion significantly improves the energy conversion efficiency, in terms of the electricity generation, because it improvesmore » the reversibility of the fuel combustion process through two linked parallel processes, compared to the conventional combustion process, which is operated far away from its thermo-equilibrium. Under the current carbon-constraint environment, it has been a promising carbon capture technology in terms of fuel combustion for power generation. Its disadvantage is that it is less mature in terms of technological commercialization. In this DOE-funded project, accomplishment is made by developing a series of advanced copper-based oxygen carriers, with properties of the higher oxygen-transfer capability, a favorable thermodynamics to generate high purity of CO{sub 2}, the higher reactivity, the attrition-resistance, the thermal stability in red-ox cycles and the achievement of the auto-thermal heat balance. This will be achieved into three phases in three consecutive years. The selected oxygen carriers with final-determined formula were tested in a scaled-up 10kW coal-fueled chemical looping combustion facility. This scaled-up evaluation tests (2-day, 8-hour per day) indicated that, there was no tendency of agglomeration of copper-based oxygen carriers. Only trace-amount of coke or carbon deposits on the copper-based oxygen carriers in the fuel reactor. There was also no evidence to show the sulphidization of oxygen carriers in the system by using the high-sulfur-laden asphalt fuels. In all, the scaled-up test in 10 kW CLC facility demonstrated that the preparation method of copper-based oxygen carrier not only help to maintain its good reactivity, also largely minimize its agglomeration tendency.« less

Determination of Uniaxial Compressive Strength of Ankara Agglomerate Considering Fractal Geometry of Blocks

NASA Astrophysics Data System (ADS)

Coskun, Aycan; Sonmez, Harun; Ercin Kasapoglu, K.; Ozge Dinc, S.; Celal Tunusluoglu, M.

2010-05-01

The uniaxial compressive strength (UCS) of rock material is a crucial parameter to be used for design stages of slopes, tunnels and foundations to be constructed in/on geological medium. However, preparation of high quality cores from geological mixtures or fragmented rocks such as melanges, fault rocks, coarse pyroclastic rocks, breccias and sheared serpentinites is often extremely difficult. According to the studies performed in literature, this type of geological materials may be grouped as welded and unwelded birmocks. Success of preparation of core samples from welded bimrocks is slightly better than unwelded ones. Therefore, some studies performed on the welded bimrocks to understand the mechanical behavior of geological mixture materials composed of stronger and weaker components (Gokceoglu, 2002; Sonmez et al., 2004; Sonmez et al., 2006; Kahraman, et al., 2008). The overall strength of bimrocks are generally depends on strength contrast between blocks and matrix; types and strength of matrix; type, size, strength, shape and orientation of blocks and volumetric block proportion. In previously proposed prediction models, while UCS of unwelded bimrocks may be determined by decreasing the UCS of matrix considering the volumetric block proportion, the welded ones can be predicted by considering both UCS of matrix and blocks together (Lindquist, 1994; Lindquist and Goodman, 1994; Sonmez et al., 2006 and Sonmez et al., 2009). However, there is a few attempts were performed about the effect of blocks shape and orientation on the strength of bimrock (Linqduist, 1994 and Kahraman, et al., 2008). In this study, Ankara agglomerate, which is composed of andesite blocks and surrounded weak tuff matrix, was selected as study material. Image analyses were performed on bottom, top and side faces of cores to identify volumetric block portions. In addition to the image analyses, andesite blocks on bottom, top and side faces were digitized for determination of fractal dimensions. To determine fractal dimensions of more than hundred andesite blocks in cores, a computer program namely FRACRUN were developed. Fractal geometry has been used as practical and popular tool to define particularly irregular shaped bodies in literature since the theory of fractal was developed by Mandelbrot (1967) (Hyslip and Vallejo, 1997; Kruhl and Nega, 1996; Bagde etal., 2002; Gulbin and Evangulova, 2003; Pardini, 2003; Kolay and Kayabali, 2006; Hamdi, 2008; Zorlu, 2009 and Sezer, 2009). Although there are some methods to determine fractal dimensions, square grid-cell count method for 2D and segment count method for 1D were followed in the algorithm of FRACRUN. FRACRUN has capable of determine fractal dimensions of many closed polygons on a single surface. In the study, a database composed of uniaxial compressive strength, volumetric block proportion, fractal dimensions and number of blocks for each core was established. Finally, prediction models were developed by regression analyses and compared with the empirical equations proposed by Sonmez et al. (2006). Acknowledgement This study is a product of ongoing project supported by TUBITAK (The Scientific and Technological Research Council of Turkey - Project No: 108Y002). References Bagde, M.N., Raina, A.K., Chakraborty, A.K., Jethwa, J.L., 2002. Rock mass characterization by fractal dimension. Engineering Geology 63, 141-155. Gokceoglu, C., 2002. A fuzzy triangular chart to predict the uniaxial compressive strength of the Ankara agglomerates from their petrographic composition. Engineering Geology, 66 (1-2), 39-51. Gulbin, Y.L., Evangulova, E.B., 2003. Morphometry of quartz aggregates in granites: fractal images referring to nucleation and growth processes. Mathematical Geology 35 (7), 819-833 Hamdi, E., 2008. A fractal description of simulated 3D discontinuity networks. Rock Mechanics and Rock Engineering 41, 587-599. Hyslip, J.P., Vallejo, L.E., 1997. Fractals analysis of the roughness and size distribution of granular materials. Engineering Geology 48, 231-244. Kahraman, S., Alber, M., Fener, M. and Gunaydin, O. 2008. Evaluating the geomechanical properties of Misis fault breccia (Turkey). Int. J. Rock Mech. Min. Sci, 45, (8), 1469-1479. Kolay, E., Kayabali, K., 2006. Investigation of the effect of aggregate shape and surface roughness on the slake durability index using the fractal dimension approach. Engineering Geology 86, 271-294. Kruhl, J.H., Nega, M., 1996. The fractal shape of sutured quartz grain boundaries: application as a geothermometer. Geologische Rundschau 85, 38-43. Lindquist E.S. 1994. The strength, deformation properties of melange. PhD thesis, University of California, Berkeley, 1994. 264p. Lindquist E.S. and Goodman R.E. 1994. The strength and deformation properties of the physical model m!elange. In: Nelson PP, Laubach SE, editors. Proceedings of the First North American Rock Mechanics Conference (NARMS), Austin, Texas. Rotterdam: AA Balkema; 1994. Pardini, G., 2003. Fractal scaling of surface roughness in artificially weathered smectite rich soil regoliths. Geoderma 117, 157-167. Sezer E., 2009. A computer program for fractal dimension (FRACEK) with application on type of mass movement characterization. Computers and Geosciences (doi:10.1016/j.cageo.2009.04.006). Sonmez H, Tuncay E, and Gokceoglu C., 2004. Models to predict the uniaxial compressive strength and the modulus of elasticity for Ankara Agglomerate. Int. J. Rock Mech. Min. Sci., 41 (5), 717-729. Sonmez, H., Gokceoglu, C., Medley, E.W., Tuncay, E., and Nefeslioglu, H.A., 2006. Estimating the uniaxial compressive strength of a volcanic bimrock. Int. J. Rock Mech. Min. Sci., 43 (4), 554-561. Zorlu K., 2008. Description of the weathering states of building stones by fractal geometry and fuzzy inference system in the Olba ancient city (Southern Turkey). Engineering Geology 101 (2008) 124-133.

Human Strength Capabilities for the Operation of Parachute Ripcords and Riser Releases

DTIC Science & Technology

1983-10-01

Parachutes Human Strength Ripcords Isometric Force Riser Releases Anthropometry 0 24 SITRACT (Con i, e on reveres. id. If neceay and Identify by block numb... Anthropometry . . . .. .. ... .. 41 DISCUSSIONS . . . . . . . . . . . . . 43 Other Studies . . . . . . . . . 44 CONCLUSIONS AND RECOMMENDATIONS...tendency to produce greater forces. Anthropometry . Results of the anthropometric measurements are given in Table 11, listing the means, standard

Fuel agglomerates and method of agglomeration

DOEpatents

Wen, Wu-Wey

1986-01-01

Solid fuel agglomerates are prepared of particulate coal or other carbonaceous material with a binder having a high humic acid or humate salt content. The humic acid is extracted from oxidized carbonaceous material with a mild aqueous alkali solution of, for instance, ammonia. The particulate material is blended with the extract which serves as the binder for the agglomerates. The water-resistant agglomerates are formed such as by pelletizing, followed by drying to remove moisture and solidify the humic acid binder throughout the agglomerate.

Aluminum agglomeration involving the second mergence of agglomerates on the solid propellants burning surface: Experiments and modeling

NASA Astrophysics Data System (ADS)

Ao, Wen; Liu, Xin; Rezaiguia, Hichem; Liu, Huan; Wang, Zhixin; Liu, Peijin

2017-07-01

The agglomeration of aluminum particles usually occurs on the burning surface of aluminized composite propellants. It leads to low propellant combustion efficiency and high two-phase flow losses. To reach a thorough understanding of aluminum agglomeration behaviors, agglomeration processes, and particles size distribution of Al/AP/RDX/GAP propellants were studied by using a cinephotomicrography experimental technique, under 5 MPa. Accumulation, aggregation, and agglomeration phenomena of aluminum particles have been inspected, as well as the flame asymmetry of burning agglomerates. Results reveals that the dependency of the mean and the maximum agglomeration diameter to the burning rate and the virgin aluminum size have the same trend. A second-time mergence of multiple agglomerates on the burning surface is unveiled. Two typical modes of second mergence are concluded, based upon vertical and level movement of agglomerates, respectively. The latter mode is found to be dominant and sometimes a combination of the two modes may occur. A new model of aluminum agglomeration on the burning surface of composite propellants is derived to predict the particulates size distribution with a low computational amount. The basic idea is inspired from the well-known pocket models. The pocket size of the region formed by adjacent AP particles is obtained through scanning electron microscopy of the propellant cross-section coupled to an image processing method. The second mergence mechanism, as well as the effect of the burning rate on the agglomeration processes, are included in the present model. The mergence of two agglomerates is prescribed to occur only if their separation distance is less than a critical value. The agglomerates size distribution resulting from this original model match reasonably with the experimental data. Moreover, the present model gives superior results for mean agglomeration diameter compared to common empirical and pocket models. The average prediction error is lower than 5% for the four propellants tested. Results of this study are expected to provide better insight and enrich in the theoretical frame of aluminum agglomeration.

Impact of chemistry on Standard High Solids Vessel Design mixing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poirier, M.

2016-03-02

The plan for resolving technical issues regarding mixing performance within vessels of the Hanford Waste Treatment Plant Pretreatment Facility directs a chemical impact study to be performed. The vessels involved are those that will process higher (e.g., 5 wt % or more) concentrations of solids. The mixing equipment design for these vessels includes both pulse jet mixers (PJM) and air spargers. This study assesses the impact of feed chemistry on the effectiveness of PJM mixing in the Standard High Solids Vessel Design (SHSVD). The overall purpose of this study is to complement the Properties that Matter document in helping tomore » establish an acceptable physical simulant for full-scale testing. The specific objectives for this study are (1) to identify the relevant properties and behavior of the in-process tank waste that control the performance of the system being tested, (2) to assess the solubility limits of key components that are likely to precipitate or crystallize due to PJM and sparger interaction with the waste feeds, (3) to evaluate the impact of waste chemistry on rheology and agglomeration, (4) to assess the impact of temperature on rheology and agglomeration, (5) to assess the impact of organic compounds on PJM mixing, and (6) to provide the technical basis for using a physical-rheological simulant rather than a physical-rheological-chemical simulant for full-scale vessel testing. Among the conclusions reached are the following: The primary impact of precipitation or crystallization of salts due to interactions between PJMs or spargers and waste feeds is to increase the insoluble solids concentration in the slurries, which will increase the slurry yield stress. Slurry yield stress is a function of pH, ionic strength, insoluble solids concentration, and particle size. Ionic strength and chemical composition can affect particle size. Changes in temperature can affect SHSVD mixing through its effect on properties such as viscosity, yield stress, solubility, and vapor pressure, or chemical reactions that occur at high temperatures. Organic compounds will affect SHSVD mixing through their effect on properties such as rheology, particle agglomeration/size, particle density, and particle concentration.« less

ILLUMINATING THE ROLE OF AGGLOMERATES ON CRITICAL PHYSICOCHEMICAL PROPERTIES OF AMORPHOUS CALCIUM PHOSPHATE COMPOSITES

PubMed Central

O’Donnell, J.N.R.; Antonucci, J.M.; Skrtic, D.

2009-01-01

Water sorption (WS), mechanical strength, and ion release of polymeric composites formulated with 40 % as-made or milled amorphous calcium phosphate (ACP) are compared after 1, 2 and 3 months of aqueous exposure. Ethoxylated bisphenol A dimethacrylate, triethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate and methacryloxyethyl phthalate comprised the resin. The WS (mass %) peaked at 3 months. WS of as-made ACP composites was significantly higher than WS of milled ACP composites and copolymers. Both composite groups experienced decreases in biaxial flexural strength (BFS) with water aging, with milled ACP composites retaining a significantly higher BFS throughout immersion. Ion release was moderately reduced in milled ACP composites, though they remained superior to as-made ACP composites due to significantly lower WS and higher BFS after prolonged aqueous exposure. PMID:19774100

Mechanical strength of [HA/Bioplastic/Sericin] composite part printed by bioprinter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tontowi, Alva Edy, E-mail: alvaedytontowi@ugm.ac.id; Setiawan, Agris

The aim of this research was to determine the effect of hydroxyapatite (HA) content in printed biocomposite to its mechanical strength. The biocomposite paste was prepared by composing HA, bioplastic and sericin with various ratios of [HA/Bioplastic]: 40/60, 50/50, 60,40 and 70/30. Sericin of 0.3% weight was added to the biocomposite. Mechanical test was conducted to observe tensile (ASTM D 638 type 4) and flexural strength (ASTM D 790). Both type of specimens were fabricated using 3D Printer. Printing process parameter (infill speed, print speed and layer height) were set up as 60 mm/s, 10 mm/s, 0.35 mm, respectively. Resultsmore » showed that biocomposite with [HA/Biplastic]. weight ratio of 60/40(w/w) has an optimum tensile (3.89 ± 1.26 MPa) and flexural strength (2.51 ± 0.45 MPa). Scanning electron microscope observation indicated that microstructure of specimen was influenced by the percentage of the hydroxyapatite. There was no agglomeration of HA particle within the composite.« less

Ethanol at levels produced by Saccharomyces cerevisiae during wheat dough fermentation has a strong impact on dough properties.

PubMed

Jayaram, Vinay B; Rezaei, Mohammad N; Cuyvers, Sven; Verstrepen, Kevin J; Delcour, Jan A; Courtin, Christophe M

2014-09-24

Yeast's role in bread making is primarily the fermentative production of carbon dioxide to leaven the dough. Fermentation also impacts dough matrix rheology, thereby affecting the quality of the end product. Surprisingly, the role of ethanol, the other yeast primary metabolite, has been ill studied in this context. Therefore, this study aims to assess the potential impact of ethanol on yeastless dough extensibility and spread and gluten agglomeration at concentrations at which it is produced in fermenting dough, i.e., up to 60 mmol per 100 g of flour. Reduced dough extensibility and dough spread were observed upon incorporation of ethanol in the dough formula, and were more pronounced for a weak than for a strong flour. Uniaxial and biaxial extension tests showed up to 50% decrease in dough extensibility and a dough strength increase of up to 18% for 60 mmol of ethanol/100 g of flour. Ethanol enhanced gluten agglomeration of a weak flour. Sequential extraction of flour in increasing ethanol concentrations showed that better gluten-solvent interaction is a possible explanation for the changed dough behavior.

Incorporation of the Fe3O4 and SiO2 nanoparticles in epoxy-modified silicone resin as the coating for soft magnetic composites with enhanced performance

NASA Astrophysics Data System (ADS)

Luo, Dahao; Wu, Chen; Yan, Mi

2018-04-01

Three inorganic-organic hybrids have been designed by incorporating epoxy-modified silicone resin (ESR) with SiO2, Fe3O4 and their mixture in the application as the coating of Fe soft magnetic composites (SMCs). The introduced SiO2 nanoparticles are well dispersed in the ESR, while the Fe3O4 tends to agglomerate or even separate from the ESR. Simultaneous addition of the SiO2 and Fe3O4 gives rise to satisfactory distribution of both nanoparticles and optimized magnetic performance of the SMCs with high permeability (124.6) and low loss (807.8 mW/cm3). On one hand, introduction of the ferromagnetic Fe3O4 reduces the magnetic dilution effect, which is beneficial for improved magnetization and permeability. On the other hand, SiO2 incorporation prevents the agglomeration of the Fe3O4 nanoparticles and gives rise to increased electrical resistivity for reduced core loss as well as enhanced mechanical strength of the SMCs.

Mobility and settling rate of agglomerates of polydisperse nanoparticles.

PubMed

Spyrogianni, Anastasia; Karadima, Katerina S; Goudeli, Eirini; Mavrantzas, Vlasis G; Pratsinis, Sotiris E

2018-02-14

Agglomerate settling impacts nanotoxicology and nanomedicine as well as the stability of engineered nanofluids. Here, the mobility of nanostructured fractal-like SiO 2 agglomerates in water is investigated and their settling rate in infinitely dilute suspensions is calculated by a Brownian dynamics algorithm tracking the agglomerate translational and rotational motion. The corresponding friction matrices are obtained using the HYDRO++ algorithm [J. G. de la Torre, G. del Rio Echenique, and A. Ortega, J. Phys. Chem. B 111, 955 (2007)] from the Kirkwood-Riseman theory accounting for hydrodynamic interactions of primary particles (PPs) through the Rotne-Prager-Yamakawa tensor, properly modified for polydisperse PPs. Agglomerates are generated by an event-driven method and have constant mass fractal dimension but varying PP size distribution, mass, and relative shape anisotropy. The calculated diffusion coefficient from HYDRO++ is used to obtain the agglomerate mobility diameter d m and is compared with that from scaling laws for fractal-like agglomerates. The ratio d m /d g of the mobility diameter to the gyration diameter of the agglomerate decreases with increasing relative shape anisotropy. For constant d m and mean d p , the agglomerate settling rate, u s , increases with increasing PP geometric standard deviation σ p,g (polydispersity). A linear relationship between u s and agglomerate mass to d m ratio, m/d m , is revealed and attributed to the fast Brownian rotation of such small and light nanoparticle agglomerates. An analytical expression for the u s of agglomerates consisting of polydisperse PPs is then derived, u s =1-ρ f ρ p g3πμmd m (ρ f is the density of the fluid, ρ p is the density of PPs, μ is the viscosity of the fluid, and g is the acceleration of gravity), valid for agglomerates for which the characteristic rotational time is considerably shorter than their settling time. Our calculations demonstrate that the commonly made assumption of monodisperse PPs underestimates u s by a fraction depending on σ p,g and agglomerate mass mobility exponent. Simulations are in excellent agreement with deposition rate measurements of fumed SiO 2 agglomerates in water.

Mobility and settling rate of agglomerates of polydisperse nanoparticles

NASA Astrophysics Data System (ADS)

Spyrogianni, Anastasia; Karadima, Katerina S.; Goudeli, Eirini; Mavrantzas, Vlasis G.; Pratsinis, Sotiris E.

2018-02-01

Agglomerate settling impacts nanotoxicology and nanomedicine as well as the stability of engineered nanofluids. Here, the mobility of nanostructured fractal-like SiO2 agglomerates in water is investigated and their settling rate in infinitely dilute suspensions is calculated by a Brownian dynamics algorithm tracking the agglomerate translational and rotational motion. The corresponding friction matrices are obtained using the HYDRO++ algorithm [J. G. de la Torre, G. del Rio Echenique, and A. Ortega, J. Phys. Chem. B 111, 955 (2007)] from the Kirkwood-Riseman theory accounting for hydrodynamic interactions of primary particles (PPs) through the Rotne-Prager-Yamakawa tensor, properly modified for polydisperse PPs. Agglomerates are generated by an event-driven method and have constant mass fractal dimension but varying PP size distribution, mass, and relative shape anisotropy. The calculated diffusion coefficient from HYDRO++ is used to obtain the agglomerate mobility diameter dm and is compared with that from scaling laws for fractal-like agglomerates. The ratio dm/dg of the mobility diameter to the gyration diameter of the agglomerate decreases with increasing relative shape anisotropy. For constant dm and mean dp, the agglomerate settling rate, us, increases with increasing PP geometric standard deviation σp,g (polydispersity). A linear relationship between us and agglomerate mass to dm ratio, m/dm, is revealed and attributed to the fast Brownian rotation of such small and light nanoparticle agglomerates. An analytical expression for the us of agglomerates consisting of polydisperse PPs is then derived, us=(1/-{ρf/ρp})g 3 π μ m/dm (ρf is the density of the fluid, ρp is the density of PPs, μ is the viscosity of the fluid, and g is the acceleration of gravity), valid for agglomerates for which the characteristic rotational time is considerably shorter than their settling time. Our calculations demonstrate that the commonly made assumption of monodisperse PPs underestimates us by a fraction depending on σp,g and agglomerate mass mobility exponent. Simulations are in excellent agreement with deposition rate measurements of fumed SiO2 agglomerates in water.

Enhanced mechanical properties of graphene/copper nanocomposites using a molecular-level mixing process.

PubMed

Hwang, Jaewon; Yoon, Taeshik; Jin, Sung Hwan; Lee, Jinsup; Kim, Taek-Soo; Hong, Soon Hyung; Jeon, Seokwoo

2013-12-10

RGO flakes are homogeneously dispersed in a Cu matrix through a molecular-level mixing process. This novel fabrication process prevents the agglomeration of the RGO and enhances adhesion between the RGO and the Cu. The yield strength of the 2.5 vol% RGO/Cu nanocomposite is 1.8 times higher than that of pure Cu. The strengthening mechanism of the RGO is investigated by a double cantilever beam test using the graphene/Cu model structure. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A comparative study of the influence of alpha-lactose monohydrate particle morphology on granule and tablet properties after roll compaction/dry granulation.

PubMed

Grote, Simon; Kleinebudde, Peter

2018-05-29

The influence of particle morphology and size of alpha-lactose monohydrate on dry granules and tablets was studied. Four different morphologies were investigated: Two grades of primary crystals, which differed in their particle size and structure (compact crystals vs. agglomerates). The materials were roll compacted at different specific compaction forces and changes in the particle size distribution and the specific surface area were measured. Afterwards, two fractions of granules were pressed to tablets and the tensile strength was compared to that from tablets compressed from the raw materials. The specific surface area was increased induced by roll compaction/dry granulation for all materials. At increased specific compaction forces, the materials showed sufficient size enlargement. The morphology of lactose determined the strength of direct compressed tablets. In contrast, the strength of granule tablets was leveled by the previous compression step during roll compaction/dry granulation. Thus, the tensile strength of tablets compressed directly from the powder mixtures determined whether materials exhibited a loss in tabletability after roll compaction/dry granulation or not. The granule size had only a slight influence on the strength of produced tablets. In some cases, the fraction of smaller granules showed a higher tensile strength compared to the larger fraction.

Staged mold for encapsulating hazardous wastes

DOEpatents

Unger, Samuel L.; Telles, Rodney W.; Lubowitz, Hyman R.

1990-01-01

A staged mold for stabilizing hazardous wastes for final disposal by molding an agglomerate of the hazardous wastes and encapsulating the agglomerate. Three stages are employed in the process. In the first stage, a first mold body is positioned on a first mold base, a mixture of the hazardous wastes and a thermosetting plastic is loaded into the mold, the mixture is mechanically compressed, heat is applied to cure the mixture to form a rigid agglomerate, and the first mold body is removed leaving the agglomerate sitting on the first mold base. In the second stage, a clamshell second mold body is positioned around the agglomerate and the first mold base, a powdered thermoplastic resin is poured on top of the agglomerate and in the gap between the sides of the agglomerate and the second mold body, the thermoplastic is compressed, heat is applied to melt the thermoplastic, and the plastic is cooled jacketing the agglomerate on the top and sides. In the third stage, the mold with the jacketed agglomerate is inverted, the first mold base is removed exposing the former bottom of the agglomerate, powdered thermoplastic is poured over the former bottom, the first mold base is replaced to compress the thermoplastic, heat is applied to melt the new thermoplastic and the top part of the jacket on the sides, the plastic is cooled jacketing the bottom and fusing with the jacketing on the sides to complete the seamless encapsulation of the agglomerate.

Staged mold for encapsulating hazardous wastes

DOEpatents

Unger, Samuel L.; Telles, Rodney W.; Lubowitz, Hyman R.

1988-01-01

A staged mold for stabilizing hazardous wastes for final disposal by molding an agglomerate of the hazardous wastes and encapsulating the agglomerate. Three stages are employed in the process. In the first stage, a first mold body is positioned on a first mold base, a mixture of the hazardous wastes and a thermosetting plastic is loaded into the mold, the mixture is mechanically compressed, heat is applied to cure the mixture to form a rigid agglomerate, and the first mold body is removed leaving the agglomerate sitting on the first mold base. In the second stage, a clamshell second mold body is positioned around the agglomerate and the first mold base, a powdered thermoplastic resin is poured on top of the agglomerate and in the gap between the sides of the agglomerate and the second mold body, the thermoplastic is compressed, heat is applied to melt the thermoplastic, and the plastic is cooled jacketing the agglomerate on the top and sides. In the third stage, the mold with the jacketed agglomerate is inverted, the first mold base is removed exposing the former bottom of the agglomerate, powdered thermoplastic is poured over the former bottom, the first mold base is replaced to compress the thermoplastic, heat is applied to melt the new thermoplastic and the top part of the jacket on the sides, the plastic is cooled jacketing the bottom and fusing with the jacketing on the sides to complete the seamless encapsulation of the agglomerate.

Method for encapsulating hazardous wastes using a staged mold

DOEpatents

Unger, Samuel L.; Telles, Rodney W.; Lubowitz, Hyman R.

1989-01-01

A staged mold and method for stabilizing hazardous wastes for final disposal by molding an agglomerate of the hazardous wastes and encapsulating the agglomerate. Three stages are employed in the process. In the first stage, a first mold body is positioned on a first mold base, a mixture of the hazardous wastes and a thermosetting plastic is loaded into the mold, the mixture is mechanically compressed, heat is applied to cure the mixture to form a rigid agglomerate, and the first mold body is removed leaving the agglomerate sitting on the first mold base. In the second stage, a clamshell second mold body is positioned around the agglomerate and the first mold base, a powdered thermoplastic resin is poured on top of the agglomerate and in the gap between the sides of the agglomerate and the second mold body, the thermoplastic is compressed, heat is applied to melt the thermoplastic, and the plastic is cooled jacketing the agglomerate on the top and sides. In the third stage, the mold with the jacketed agglomerate is inverted, the first mold base is removed exposing the former bottom of the agglomerate, powdered thermoplastic is poured over the former bottom, the first mold base is replaced to compress the thermoplastic, heat is applied to melt the new thermoplastic and the top part of the jacket on the sides, the plastic is cooled jacketing the bottom and fusing with the jacketing on the sides to complete the seamless encapsulation of the agglomerate.

Estimating conformation content of a protein using citrate-stabilized Au nanoparticles

NASA Astrophysics Data System (ADS)

Deka, Jashmini; Paul, Anumita; Chattopadhyay, Arun

2010-08-01

Herein we report the use of the optical properties of citrate-stabilized gold nanoparticles (Au NPs) for estimation of native or denatured conformation content in a mixture of a protein in solution. The UV-vis extinction spectrum of citrate-stabilized Au NPs is known to broaden differently in the presence of native and denatured states of α-amylase, bovine serum albumin (BSA) or amyloglucosidase (AMG). On the other hand, herein we show that when a mixture of native and denatured protein was present in the medium, the broadening of the spectrum differed for different fractional content of the conformations. Also, the total area under the extinction spectrum varied linearly with the change in the mole fraction content of a state and for a constant total protein concentration. Transmission electron microscopy (TEM) measurements revealed different levels of agglomeration for different fractional contents of the native or denatured state of a protein. In addition, time-dependent denaturation of a protein could be followed using the present method. The rate constants calculated for denaturation indicated a possible fast change in conformation of a protein before complete thermal denaturation. The observations have been explained based on the changes in extinction coefficient (thereby oscillator strength) upon interaction of citrate-stabilized NPs with proteins being in different states and levels of agglomeration.Herein we report the use of the optical properties of citrate-stabilized gold nanoparticles (Au NPs) for estimation of native or denatured conformation content in a mixture of a protein in solution. The UV-vis extinction spectrum of citrate-stabilized Au NPs is known to broaden differently in the presence of native and denatured states of α-amylase, bovine serum albumin (BSA) or amyloglucosidase (AMG). On the other hand, herein we show that when a mixture of native and denatured protein was present in the medium, the broadening of the spectrum differed for different fractional content of the conformations. Also, the total area under the extinction spectrum varied linearly with the change in the mole fraction content of a state and for a constant total protein concentration. Transmission electron microscopy (TEM) measurements revealed different levels of agglomeration for different fractional contents of the native or denatured state of a protein. In addition, time-dependent denaturation of a protein could be followed using the present method. The rate constants calculated for denaturation indicated a possible fast change in conformation of a protein before complete thermal denaturation. The observations have been explained based on the changes in extinction coefficient (thereby oscillator strength) upon interaction of citrate-stabilized NPs with proteins being in different states and levels of agglomeration. Electronic supplementary information (ESI) available: Additional UV-vis and fluorescence spectra and graphs based on UV-vis studies. See DOI: 10.1039/c0nr00154f

Magnetic Thermometer: Thermal effect on the Agglomeration of Magnetic Nanoparticles by Magnetic field

NASA Astrophysics Data System (ADS)

Jin, Daeseong; Kim, Hackjin

2018-03-01

We have investigated the agglomeration of magnetite nanoparticles in the aqueous solution under magnetic field by measuring temporal change of magnetic weight. The magnetic weight corresponds to the force due to the magnetization of magnetic materials. Superparamagnetic magnetite nanoparticles are synthesized and used in this work. When the aqueous solution of magnetite nanoparticle is placed under magnetic field, the magnetic weight of the sample jumps instantaneously by Neel and Brown mechanisms and thereafter increases steadily following a stretched exponential function as the nanoparticles agglomerate, which results from the distribution of energy barriers involved in the dynamics. Thermal motions of nanoparticles in the agglomerate perturb the ordered structure of the agglomerate to reduce the magnetic weight. Fluctuation of the structural order of the agglomerate by temperature change is much faster than the formation of agglomerate and explained well with the Boltzmann distribution, which suggests that the magnetic weight of the agglomerate works as a magnetic thermometer.

In-line agglomeration degree estimation in fluidized bed pellet coating processes using visual imaging.

PubMed

Mehle, Andraž; Kitak, Domen; Podrekar, Gregor; Likar, Boštjan; Tomaževič, Dejan

2018-05-09

Agglomeration of pellets in fluidized bed coating processes is an undesirable phenomenon that affects the yield and quality of the product. In scope of PAT guidance, we present a system that utilizes visual imaging for in-line monitoring of the agglomeration degree. Seven pilot-scale Wurster coating processes were executed under various process conditions, providing a wide spectrum of process outcomes. Images of pellets were acquired during the coating processes in a contactless manner through an observation window of the coating apparatus. Efficient image analysis methods were developed for automatic recognition of discrete pellets and agglomerates in the acquired images. In-line obtained agglomeration degree trends revealed the agglomeration dynamics in distinct phases of the coating processes. We compared the in-line estimated agglomeration degree in the end point of each process to the results obtained by the off-line sieve analysis reference method. A strong positive correlation was obtained (coefficient of determination R 2 =0.99), confirming the feasibility of the approach. The in-line estimated agglomeration degree enables early detection of agglomeration and provides means for timely interventions to retain it in an acceptable range. Copyright © 2018 Elsevier B.V. All rights reserved.

A model to estimate the size of nanoparticle agglomerates in gas-solid fluidized beds

NASA Astrophysics Data System (ADS)

de Martín, Lilian; van Ommen, J. Ruud

2013-11-01

The estimation of nanoparticle agglomerates' size in fluidized beds remains an open challenge, mainly due to the difficulty of characterizing the inter-agglomerate van der Waals force. The current approach is to describe micron-sized nanoparticle agglomerates as micron-sized particles with 0.1-0.2-μm asperities. This simplification does not capture the influence of the particle size on the van der Waals attraction between agglomerates. In this paper, we propose a new description where the agglomerates are micron-sized particles with nanoparticles on the surface, acting as asperities. As opposed to previous models, here the van der Waals force between agglomerates decreases with an increase in the particle size. We have also included an additional force due to the hydrogen bond formation between the surfaces of hydrophilic and dry nanoparticles. The average size of the fluidized agglomerates has been estimated equating the attractive force obtained from this method to the weight of the individual agglomerates. The results have been compared to 54 experimental values, most of them collected from the literature. Our model approximates without a systematic error the size of most of the nanopowders, both in conventional and centrifugal fluidized beds, outperforming current models. Although simple, the model is able to capture the influence of the nanoparticle size, particle density, and Hamaker coefficient on the inter-agglomerate forces.

Process and apparatus for coal hydrogenation

DOEpatents

Ruether, John A.

1988-01-01

In a coal liquefaction process an aqueous slurry of coal is prepared containing a dissolved liquefaction catalyst. A small quantity of oil is added to the slurry and then coal-oil agglomerates are prepared by agitation of the slurry at atmospheric pressure. The resulting mixture of agglomerates, excess water, dissolved catalyst, and unagglomerated solids is pumped to reaction pressure and then passed through a drainage device where all but a small amount of surface water is removed from the agglomerates. Sufficient catalyst for the reaction is contained in surface water remaining on the agglomerates. The agglomerates fall into the liquefaction reactor countercurrently to a stream of hot gas which is utilized to dry and preheat the agglomerates as well as deposit catalyst on the agglomerates before they enter the reactor where they are converted to primarily liquid products under hydrogen pressure.

Bed material agglomeration during fluidized bed combustion. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, R.C.; Dawson, M.R.; Smeenk, J.L.

The purpose of this project is to determine the physical and chemical reactions which lead to the undesired agglomeration of bed material during fluidized bed combustion of coal and to relate these reactions to specific causes. A survey of agglomeration and deposit formation in industrial fluidized bed combustors (FBCs) indicate that at least five boilers were experiencing some form of bed material agglomeration. Deposit formation was reported at nine sites with deposits most commonly at coal feed locations and in cyclones. Other deposit locations included side walls and return loops. Three general types of mineralogic reactions were observed to occurmore » in the agglomerates and deposits. Although alkalies may play a role with some {open_quotes}high alkali{close_quotes} lignites, we found agglomeration was initiated due to fluxing reactions between iron (II) from pyrites and aluminosilicates from clays. This is indicated by the high amounts of iron, silica, and alumina in the agglomerates and the mineralogy of the agglomerates. Agglomeration likely originated in the dense phase of the FBC bed within the volatile plume which forms when coal is introduced to the boiler. Secondary mineral reactions appear to occur after the agglomerates have formed and tend to strengthen the agglomerates. When calcium is present in high amounts, most of the minerals in the resulting deposits are in the melilite group (gehlenite, melilite, and akermanite) and pyroxene group (diopside and augite). During these solid-phase reactions, the temperature of formation of the melilite minerals can be lowered by a reduction of the partial pressure of CO{sub 2} (Diopside + Calcite {r_arrow}Akermanite).« less

Investigation of the influence of humidity on the ultrasonic agglomeration of submicron particles in diesel exhausts.

PubMed

Riera-Franco de Sarabia, E; Elvira-Segura, L; González-Gómez, I; Rodríguez-Maroto, J J; Muñoz-Bueno, R; Dorronsoro-Areal, J L

2003-06-01

Removing very fine particles in the 0.01-1 micro m range generated in diesel combustion is important for air pollution abatement because of the impact such particles have on the environment. By forming larger particles, acoustic agglomeration of submicron particles is presented as a promising process for enhancing the efficiency of the current filtration systems for particle removal. Nevertheless, some authors have pointed out that acoustic agglomeration is much more efficient for larger particles than for smaller particles. This paper studies the effect of humidity on the acoustic agglomeration of diesel exhausts particles in the nanometer size range at 21 kHz. For the agglomeration tests, the experimental facility basically consists of a pilot scale plant with a diesel engine, an ultrasonic agglomeration chamber a dilution system, a nozzle atomizer, and an aerosol sampling and measuring station. The effect of the ultrasonic treatment, generated by a linear array of four high-power stepped-plate transducers on fumes at flow rates of 900 Nm(3)/h, was a small reduction in the number concentration of particles at the outlet of the chamber. However, the presence of humidity raised the agglomeration rate by decreasing the number particle concentration by up to 56%. A numerical study of the agglomeration process as a linear combination of the orthokinetic and hydrodynamic agglomeration coefficients resulting from mutual radiation pressure also found that acoustic agglomeration was enhanced by humidity. Both results confirm the benefit of using high-power ultrasound together with humidity to enhance the agglomeration of particles much smaller than 1 micro m.

Automatic approach/avoidance tendencies towards food and the course of anorexia nervosa.

PubMed

Neimeijer, Renate A M; de Jong, Peter J; Roefs, Anne

2015-08-01

The aim of the present study was to investigate the role of automatic approach/avoidance tendencies for food in Anorexia Nervosa (AN). We used a longitudinal approach and tested whether a reduction in eating disorder symptoms is associated with enhanced approach tendencies towards food and whether approach tendencies towards food at baseline are predictive for treatment outcome after one year follow up. The Affective Simon Task-manikin version (AST-manikin) was administered to measure automatic approach/avoidance tendencies towards high-caloric and low-caloric food in young AN patients. Percentage underweight and eating disorder symptoms as indexed by the EDE-Q were determined both during baseline and at one year follow up. At baseline anorexia patients showed an approach tendency for low caloric food, but not for high caloric food, whereas at 1 year follow up, they have an approach tendency for both high and low caloric food. Change in approach bias was neither associated with change in underweight nor with change in eating disorder symptoms. Strength of approach/avoidance tendencies was not predictive for percentage underweight. Although approach tendencies increased after one year, approach tendencies were neither associated with concurrent change in eating disorder symptoms nor predictive for treatment success as indexed by EDE-Q. This implicates that, so far, there is no reason to add a method designed to directly target approach/avoidance tendencies to the conventional approach to treat patients with a method designed to influence the more deliberate processes in AN. Copyright © 2015 Elsevier Ltd. All rights reserved.

[The effect of 24 weeks of moderate-to-high intensity strength training on the elderly].

PubMed

Solà Serrabou, Marta; López del Amo, José Luis; Valero, Oliver

2014-01-01

Strength programs have been seen to be useful in minimizing the effects of sarcopenia, although intervention protocols may vary in their content and characteristics. The aim of this study was to demonstrate the influence of a particular strength protocol for the elderly. A total of 35 individuals took part in the study, with 18 in the exercise group (4 men and 14 women), and 17 in the control group (4 men and 13 women). The average age was 73. The exercise group carried out a strength training program at moderate to high intensity over 24 weeks. Strength was evaluated using the chair stand test, 2-minute step and 2 vertical jumps-squat jump (SJ), and countermovement jump (CMJ). Falls in both groups were also compared before and after the intervention, as well as their relationship with the chair stand variable. A tendency towards improvement was observed in all tests, with the exception of CMJ; while the control group showed a tendency in the opposite direction. Contrast between the two groups at the end of the intervention was notable in all the tests. An inverse relationship between the chair stand strength variable and the number of falls was evident. According to the results achieved, the training was perceived to exercise a positive influence on both the strength of the elderly people and a reduction of the number of falls. The gap between the two groups widened towards the end of the intervention. Copyright © 2013 SEGG. Published by Elsevier Espana. All rights reserved.

Method for providing improved solid fuels from agglomerated subbituminous coal

DOEpatents

Janiak, Jerzy S.; Turak, Ali A.; Pawlak, Wanda; Ignasiak, Boleslaw L.

1989-01-01

A method is provided for separating agglomerated subbituminous coal and the heavy bridging liquid used to form the agglomerates. The separation is performed by contacting the agglomerates with inert gas or steam at a temperature in the range of 250.degree. to 350.degree. C. at substantially atmospheric pressure.

Co-milled API-lactose systems for inhalation therapy: impact of magnesium stearate on physico-chemical stability and aerosolization performance.

PubMed

Lau, Michael; Young, Paul M; Traini, Daniela

2017-06-01

Particle micronization for inhalation can impart surface disorder (amorphism) of crystalline structures. This can lead to stability issues upon storage at elevated humidity from recrystallization of the amorphous state, which can subsequently affect the aerosol performance of the dry powder formulation. The aim of this study was to investigate the impact of an additive, magnesium stearate (MGST), on the stability and aerosol performance of co-milled active pharmaceutical ingredient (API) with lactose. Blends of API-lactose with/without MGST were prepared and co-milled by the jet-mill apparatus. Samples were stored at 50% relative humidity (RH) and 75% RH for 1, 5, and 15 d. Analysis of changes in particle size, agglomerate structure/strength, moisture sorption, and aerosol performance were analyzed by laser diffraction, scanning electron microscopy (SEM), dynamic vapor sorption (DVS), and in-vitro aerodynamic size assessment by impaction. Co-milled formulation with MGST (5% w/w) led to a reduction in agglomerate size and strength after storage at elevated humidity compared with co-milled formulation without MGST, as observed from SEM and laser diffraction. Hysteresis in the sorption/desorption isotherm was observed in the co-milled sample without MGST, which was likely due to the recrystallization of the amorphous regions of micronized lactose. Deterioration in aerosol performance after storage at elevated humidity was greater for the co-milled samples without MGST, compared with co-milled with MGST. MGST has been shown to have a significant impact on co-milled dry powder stability after storage at elevated humidity in terms of physico-chemical properties and aerosol performance.

Powder agglomeration in a microgravity environment

NASA Technical Reports Server (NTRS)

Cawley, James D.

1994-01-01

This is the final report for NASA Grant NAG3-755 entitled 'Powder Agglomeration in a Microgravity Environment.' The research program included both two types of numerical models and two types of experiments. The numerical modeling included the use of Monte Carlo type simulations of agglomerate growth including hydrodynamic screening and molecular dynamics type simulations of the rearrangement of particles within an agglomerate under a gravitational field. Experiments included direct observation of the agglomeration of submicron alumina and indirect observation, using small angle light scattering, of the agglomeration of colloidal silica and aluminum monohydroxide. In the former class of experiments, the powders were constrained to move on a two-dimensional surface oriented to minimize the effect of gravity. In the latter, some experiments involved mixture of suspensions containing particles of opposite charge which resulted in agglomeration on a very short time scale relative to settling under gravity.

Nature of hydrogen embrittlement of steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Archakov, Yu. I.; Grebeshkova, I.D.

1986-01-01

The hydrogen embrittlement of metals is the result of the origin and development of microcracks, which are formed as the result of the occurence of internal stresses. The specific feature of the appearance of hydrogen embrittlement are the result of the physical properties of the metals and the character of their interaction with hydrogen. The tendency of metals toward hydrogen embrittlement is determined by the following characteristics: their capacity to dissolve hydrogen and its maximum solubility; the chemical activity of the metals and other phases in relation to hydrogen, that is, the capacity toward hydride formation and failure of themore » carbided sand oxides, and the tendency of the metal toward the occurence and propagation of cracks. The authors cite and discuss two general forms of action of hydrogen on metals, the physical action of hydrogen on metals and the physicochemical action when chemical interaction of hydrogen with the different phases and the individual components of the alloy on the surface and in the volume occurs. The tendency toward hydrogen embrittlement is shown to increase with an increase in the strength of the steel. In addition to the strength, this characteristic also depends upon the chemical composition and structural condition of the steel.« less

Strategies to optimize the biocompatibility of iron oxide nanoparticles - ;SPIONs safe by design;

NASA Astrophysics Data System (ADS)

Janko, Christina; Zaloga, Jan; Pöttler, Marina; Dürr, Stephan; Eberbeck, Dietmar; Tietze, Rainer; Lyer, Stefan; Alexiou, Christoph

2017-06-01

Various nanoparticle systems have been developed for medical applications in recent years. For constant improvement of efficacy and safety of nanoparticles, a close interdisciplinary interplay between synthesis, physicochemical characterizations and toxicological investigations is urgently needed. Based on combined toxicological data, we follow a ;safe-by design; strategy for our superparamagnetic iron oxide nanoparticles (SPION). Using complementary interference-free toxicological assay systems, we initially identified agglomeration tendencies in physiological fluids, strong uptake by cells and improvable biocompatibility of lauric acid (LA)-coated SPIONs (SPIONLA). Thus, we decided to further stabilize those particles by an artificial protein corona consisting of serum albumin. This approach finally lead to increased colloidal stability, augmented drug loading capacity and improved biocompatibility in previous in vitro assays. Here, we show in whole blood ex vivo and on isolated red blood cells (RBC) that a protein corona protects RBCs from hemolysis by SPIONs.

Spatiotemporal Analysis of the Ebola Hemorrhagic Fever in West Africa in 2014

NASA Astrophysics Data System (ADS)

Xu, M.; Cao, C. X.; Guo, H. F.

2017-09-01

Ebola hemorrhagic fever (EHF) is an acute hemorrhagic diseases caused by the Ebola virus, which is highly contagious. This paper aimed to explore the possible gathering area of EHF cases in West Africa in 2014, and identify endemic areas and their tendency by means of time-space analysis. We mapped distribution of EHF incidences and explored statistically significant space, time and space-time disease clusters. We utilized hotspot analysis to find the spatial clustering pattern on the basis of the actual outbreak cases. spatial-temporal cluster analysis is used to analyze the spatial or temporal distribution of agglomeration disease, examine whether its distribution is statistically significant. Local clusters were investigated using Kulldorff's scan statistic approach. The result reveals that the epidemic mainly gathered in the western part of Africa near north Atlantic with obvious regional distribution. For the current epidemic, we have found areas in high incidence of EVD by means of spatial cluster analysis.

The effect of doped zinc on the structural properties of nano-crystalline (Se0.8Te0.2)100-xZnx

NASA Astrophysics Data System (ADS)

Kumar, Arun; Singh, Harkawal; Gill, P. S.; Goyal, Navdeep

2016-05-01

The effect of metallic zinc (Zn) on the structural properties of (Se0.8Te0.2)1-XZnX (x=0, 2, 6, 8, 10) samples analyzed by X-ray Diffraction (XRD). The presence of sharp peaks in XRD patterns confirmed the crystalline nature of the samples and is indexed in orthorhombic crystal structure. XRD studies predicts that the average particle size of all the samples are about 46.29 nm, which is less than 100 nm and hence have strong tendency of agglomeration. Williamson-Hall plot method was used to evaluate the lattice strain. The dislocation density and no. of unit cells of the samples were calculated which show the inverse relation with each other. Morphology index derived from FWHM of XRD data explains the direct relationship with the particle size.

Empowering Head Start African American and Latino Families: Promoting Strengths-Based Parenting Characteristics through Child Parent Relationship Training--An Evidence-Based Group Parenting Program

ERIC Educational Resources Information Center

Sheely-Moore, Angela I.; Ceballos, Peggy L.

2011-01-01

With the tendency of low-income African American and Latino children identified at-risk for school readiness and school success compared to their early-childhood counterparts, Head Start personnel are challenged to examine the role of family strengths in the promotion of academic success for these populations. This article provides a rationale for…

Molten salt based nanofluids based on solar salt and alumina nanoparticles: An industrial approach

NASA Astrophysics Data System (ADS)

Muñoz-Sánchez, Belén; Nieto-Maestre, Javier; Guerreiro, Luis; Julia, José Enrique; Collares-Pereira, Manuel; García-Romero, Ana

2017-06-01

Thermal Energy Storage (TES) and its associated dispatchability is extremely important in Concentrated Solar Power (CSP) plants since it represents the main advantage of CSP technology in relation to other renewable energy sources like photovoltaic (PV). Molten salts are used in CSP plants as a TES material because of their high operational temperature and stability of up to 600°C. Their main problems are their relative poor thermal properties and energy storage density. A simple cost-effective way to improve the thermal properties of molten salts is to dope them with nanoparticles, thus obtaining the so-called salt-based nanofluids. Additionally, the use of molten salt based nanofluids as TES materials and Heat Transfer Fluid (HTF) has been attracting great interest in recent years. The addition of tiny amounts of nanoparticles to the base salt can improve its specific heat as shown by different authors1-3. The application of these nano-enhanced materials can lead to important savings on the investment costs in new TES systems for CSP plants. However, there is still a long way to go in order to achieve a commercial product. In this sense, the improvement of the stability of the nanofluids is a key factor. The stability of nanofluids will depend on the nature and size of the nanoparticles, the base salt and the interactions between them. In this work, Solar Salt (SS) commonly used in CSP plants (60% NaNO3 + 40% KNO3 wt.) was doped with alumina nanoparticles (ANPs) at a solid mass concentration of 1% wt. at laboratory scale. The tendency of nanoparticles to agglomeration and sedimentation is tested in the molten state by analyzing their size and concentration through the time. The specific heat of the nanofluid at 396 °C (molten state) is measured at different times (30 min, 1 h, 5 h). Further research is needed to understand the mechanisms of agglomeration. A good understanding of the interactions between the nanoparticle surface and the ionic media would provide the tools to avoid agglomeration and sedimentation.

Mechanical Properties and Durability of Ultra High Strength Concrete Incorporating Multi-Walled Carbon Nanotubes

PubMed Central

Lu, Liulei; Ouyang, Dong; Xu, Weiting

2016-01-01

In this work, the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties and durability of ultra high strength concrete (UHSC) is reported. First, the MWCNTs were dispersed by a nano sand-mill in the presence of a surfactant in water. The UHSC specimens were prepared with various amounts of MWCNTs, ranging from 0% to 0.15% by weight of cement (bwoc). Results indicated that use of an optimal percentage of MWCNTs (0.05% bwoc) caused a 4.63% increase in compressive strength and a 24.0% decrease in chloride diffusion coefficient of UHSC at 28 days curing. Moreover, the addition of MWCNTs also improved the flexural strength and deformation ability. Furthermore, a field-emission scanning electron microscopy (FE-SEM) was used to observe the dispersion of MWCNTs in the cement matrix and morphology of the hardened cement paste containing MWCNTs. FE-SEM observation revealed that MWCNTs were well dispersed in the matrix and no agglomerate was found and the reinforcing effect of MWCNTs on UHSC was thought to be pulling out and microcrack bridging of MWCNTs, which transferred the load in tension. PMID:28773541

Mechanical Properties and Durability of Ultra High Strength Concrete Incorporating Multi-Walled Carbon Nanotubes.

PubMed

Lu, Liulei; Ouyang, Dong; Xu, Weiting

2016-05-27

In this work, the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties and durability of ultra high strength concrete (UHSC) is reported. First, the MWCNTs were dispersed by a nano sand-mill in the presence of a surfactant in water. The UHSC specimens were prepared with various amounts of MWCNTs, ranging from 0% to 0.15% by weight of cement (bwoc). Results indicated that use of an optimal percentage of MWCNTs (0.05% bwoc) caused a 4.63% increase in compressive strength and a 24.0% decrease in chloride diffusion coefficient of UHSC at 28 days curing. Moreover, the addition of MWCNTs also improved the flexural strength and deformation ability. Furthermore, a field-emission scanning electron microscopy (FE-SEM) was used to observe the dispersion of MWCNTs in the cement matrix and morphology of the hardened cement paste containing MWCNTs. FE-SEM observation revealed that MWCNTs were well dispersed in the matrix and no agglomerate was found and the reinforcing effect of MWCNTs on UHSC was thought to be pulling out and microcrack bridging of MWCNTs, which transferred the load in tension.

Properties of Powder Composite Polyhydroxybutyrate-Chitosan-Calcium Phosphate System

NASA Astrophysics Data System (ADS)

Medvecky, L.; Stulajterova, R.; Giretova, M.; Faberova, M.

2017-12-01

Prepared powder polyhydroxybutyrate - chitosan - calcium phosphate composite system with 10 wt % of biopolymer component can be utilized as biocement which is characterized by the prolonged setting time and achieves wash out resistance after 5 minutes of setting. The origin powder tetracalcium phosphate/nanomonetite agglomerates were coated with the thin layer of biopolymer which decelerates both the transformation rate of calcium phosphates and hardening process of composites. The porosity of hardened composite was around 62% and the compressive strength (8 MPa) was close to trabecular bone. No cytotoxicity of composite resulted from live/dead staining of osteoblasts cultured on substrates.

Effects of Al(OH)O nanoparticle agglomerate size in epoxy resin on tension, bending, and fracture properties

NASA Astrophysics Data System (ADS)

Jux, Maximilian; Finke, Benedikt; Mahrholz, Thorsten; Sinapius, Michael; Kwade, Arno; Schilde, Carsten

2017-04-01

Several epoxy Al(OH)O (boehmite) dispersions in an epoxy resin are produced in a kneader to study the mechanistic correlation between the nanoparticle size and mechanical properties of the prepared nanocomposites. The agglomerate size is set by a targeted variation in solid content and temperature during dispersion, resulting in a different level of stress intensity and thus a different final agglomerate size during the process. The suspension viscosity was used for the estimation of stress energy in laminar shear flow. Agglomerate size measurements are executed via dynamic light scattering to ensure the quality of the produced dispersions. Furthermore, various nanocomposite samples are prepared for three-point bending, tension, and fracture toughness tests. The screening of the size effect is executed with at least seven samples per agglomerate size and test method. The variation of solid content is found to be a reliable method to adjust the agglomerate size between 138-354 nm during dispersion. The size effect on the Young's modulus and the critical stress intensity is only marginal. Nevertheless, there is a statistically relevant trend showing a linear increase with a decrease in agglomerate size. In contrast, the size effect is more dominant to the sample's strain and stress at failure. Unlike microscaled agglomerates or particles, which lead to embrittlement of the composite material, nanoscaled agglomerates or particles cause the composite elongation to be nearly of the same level as the base material. The observed effect is valid for agglomerate sizes between 138-354 nm and a particle mass fraction of 10 wt%.

Low-rank coal oil agglomeration product and process

DOEpatents

Knudson, Curtis L.; Timpe, Ronald C.; Potas, Todd A.; DeWall, Raymond A.; Musich, Mark A.

1992-01-01

A selectively-sized, raw, low-rank coal is processed to produce a low ash and relative water-free agglomerate with an enhanced heating value and a hardness sufficient to produce a non-decrepitating, shippable fuel. The low-rank coal is treated, under high shear conditions, in the first stage to cause ash reduction and subsequent surface modification which is necessary to facilitate agglomerate formation. In the second stage the treated low-rank coal is contacted with bridging and binding oils under low shear conditions to produce agglomerates of selected size. The bridging and binding oils may be coal or petroleum derived. The process incorporates a thermal deoiling step whereby the bridging oil may be completely or partially recovered from the agglomerate; whereas, partial recovery of the bridging oil functions to leave as an agglomerate binder, the heavy constituents of the bridging oil. The recovered oil is suitable for recycling to the agglomeration step or can serve as a value-added product.

Low-rank coal oil agglomeration product and process

DOEpatents

Knudson, C.L.; Timpe, R.C.; Potas, T.A.; DeWall, R.A.; Musich, M.A.

1992-11-10

A selectively-sized, raw, low-rank coal is processed to produce a low ash and relative water-free agglomerate with an enhanced heating value and a hardness sufficient to produce a non-degradable, shippable fuel. The low-rank coal is treated, under high shear conditions, in the first stage to cause ash reduction and subsequent surface modification which is necessary to facilitate agglomerate formation. In the second stage the treated low-rank coal is contacted with bridging and binding oils under low shear conditions to produce agglomerates of selected size. The bridging and binding oils may be coal or petroleum derived. The process incorporates a thermal deoiling step whereby the bridging oil may be completely or partially recovered from the agglomerate; whereas, partial recovery of the bridging oil functions to leave as an agglomerate binder, the heavy constituents of the bridging oil. The recovered oil is suitable for recycling to the agglomeration step or can serve as a value-added product.

High concentration agglomerate dynamics at high temperatures.

PubMed

Heine, M C; Pratsinis, S E

2006-11-21

The dynamics of agglomerate aerosols are investigated at high solids concentrations that are typical in industrial scale manufacture of fine particles (precursor mole fraction larger than 10 mol %). In particular, formation and growth of fumed silica at such concentrations by chemical reaction, coagulation, and sintering is simulated at nonisothermal conditions and compared to limited experimental data and commercial product specifications. Using recent chemical kinetics for silica formation by SiCl4 hydrolysis and neglecting aerosol polydispersity, the evolution of the diameter of primary particles (specific surface area, SSA), hard- and soft-agglomerates, along with agglomerate effective volume fraction (volume occupied by agglomerate) is investigated. Classic Smoluchowski theory is fundamentally limited for description of soft-agglomerate Brownian coagulation at high solids concentrations. In fact, these high concentrations affect little the primary particle diameter (or SSA) but dominate the soft-agglomerate diameter, structure, and volume fraction, leading to gelation consistent with experimental data. This indicates that restructuring and fragmentation should affect product particle characteristics during high-temperature synthesis of nanostructured particles at high concentrations in aerosol flow reactors.

Multifrequency scanning probe microscopy study of nanodiamond agglomerates

NASA Astrophysics Data System (ADS)

Aravind, Vasudeva; Lippold, Stephen; Li, Qian; Strelcov, Evgheny; Okatan, Baris; Legum, Benjamin; Kalinin, Sergei; Clarion University Team; Oak Ridge National Laboratory Team

Due to their rich surface chemistry and excellent mechanical properties and non-toxic nature, nanodiamond particles have found applications such as biomedicine, tribology and lubrication, targeted drug delivery systems, tissue scaffolds and surgical implants. Although single nanodiamond particles have diameters about 4-5nm, they tend to form agglomerates. While these agglomerates can be useful for some purposes, many applications of nanodiamonds require single particle, disaggregated nanodiamonds. This work is oriented towards studying forces and interactions that contribute to agglomeration in nanodiamonds. In this work, using multifrequency scanning probe microscopy techniques, we show that agglomerate sizes can vary between 50-100nm in raw nanodiamonds. Extremeties of particles and Interfaces between agglomerates show dissipative forces with scanning probe microscope tip, indicating agglomerates could act as points of increased adhesion, thus reducing lubricating efficiency when nanodiamonds are used as lubricant additives. This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

Microbial effects on colloidal agglomeration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hersman, L.

1995-11-01

Colloidal particles are known to enhance the transport of radioactive metals through soil and rock systems. This study was performed to determine if a soil microorganism, isolated from the surface samples collected at Yucca Mountain, NV, could affect the colloidal properties of day particles. The agglomeration of a Wyoming bentonite clay in a sterile uninoculated microbial growth medium was compared to the agglomeration in the medium inoculated with a Pseudomonas sp. In a second experiment, microorganisms were cultured in the succinate medium for 50 h and removed by centrifugation. The agglomeration of the clay in this spent was compared tomore » sterile uninoculated medium. In both experiments, the agglomeration of the clay was greater than that of the sterile, uninoculated control. Based on these results, which indicate that this microorganism enhanced the agglomeration of the bentonite clay, it is possible to say that in the presence of microorganisms colloidal movement through a rock matrix could be reduced because of an overall increase in the size of colloidal particle agglomerates. 32 refs.« less

Method for recovering light hydrocarbons from coal agglomerates

DOEpatents

Huettenhain, Horst; Benz, August D.; Getsoian, John

1991-01-01

A method and apparatus for removing light hydrocarbons, such as heptane, from coal agglomerates includes an enclosed chamber having a substantially horizontal perforate surface therein. The coal agglomerates are introduced into a water bath within the chamber. The agglomerates are advanced over the surface while steam is substantially continuously introduced through the surface into the water bath. Steam heats the water and causes volatilization of the light hydrocarbons, which may be collected from the overhead of the chamber. The resulting agglomerates may be collected at the opposite end from the surface and subjected to final draining processes prior to transportation or use.

Metal-based nanoparticles in soil: fate, behavior, and effects on soil invertebrates.

PubMed

Tourinho, Paula S; van Gestel, Cornelis A M; Lofts, Stephen; Svendsen, Claus; Soares, Amadeu M V M; Loureiro, Susana

2012-08-01

Metal-based nanoparticles (NPs) (e.g., silver, zinc oxide, titanium dioxide, iron oxide) are being widely used in the nanotechnology industry. Because of the release of particles from NP-containing products, it is likely that NPs will enter the soil compartment, especially through land application of sewage sludge derived from wastewater treatment. This review presents an overview of the literature dealing with the fate and effects of metal-based NPs in soil. In the environment, the characteristics of NPs (e.g., size, shape, surface charge) and soil (e.g., pH, ionic strength, organic matter, and clay content) will affect physical and chemical processes, resulting in NP dissolution, agglomeration, and aggregation. The behavior of NPs in soil will control their mobility and their bioavailability to soil organisms. Consequently, exposure characterization in ecotoxicological studies should obtain as much information as possible about dissolution, agglomeration, and aggregation processes. Comparing existing studies is a challenging task, because no standards exist for toxicity tests with NPs. In many cases, the reporting of associated characterization data is sparse, or missing, making it impossible to interpret and explain observed differences in results among studies. Copyright © 2012 SETAC.

Agglomerates, smoke oxide particles, and carbon inclusions in condensed combustion products of an aluminized GAP-based propellant

NASA Astrophysics Data System (ADS)

Ao, Wen; Liu, Peijin; Yang, Wenjing

2016-12-01

In solid propellants, aluminum is widely used to improve the performance, however the condensed combustion products especially the large agglomerates generated from aluminum combustion significantly affect the combustion and internal flow inside the solid rocket motor. To clarify the properties of the condensed combustion products of aluminized propellants, a constant-pressure quench vessel was adopted to collect the combustion products. The morphology and chemical compositions of the collected products, were then studied by using scanning electron microscopy coupled with energy dispersive (SEM-EDS) method. Various structures have been observed in the condensed combustion products. Apart from the typical agglomerates or smoke oxide particles observed before, new structures including the smoke oxide clusters, irregular agglomerates and carbon-inclusions are discovered and investigated. Smoke oxide particles have the highest amount in the products. The highly dispersed oxide particle is spherical with very smooth surface and is on the order of 1-2 μm, but due to the high temperature and long residence time, these small particles will aggregate into smoke oxide clusters which are much larger than the initial particles. Three types of spherical agglomerates have been found. As the ambient gas temperature is much higher than the boiling point of Al2O3, the condensation layer inside which the aluminum drop is burning would evaporate quickly, which result in the fact that few "hollow agglomerates" has been found compared to "cap agglomerates" and "solid agglomerates". Irregular agglomerates usually larger than spherical agglomerates. The formation of irregular agglomerates likely happens by three stages: deformation of spherical aluminum drops; combination of particles with various shape; finally production of irregular agglomerates. EDS results show the ratio of O to Al on the surface of agglomerates is lower in comparison to smoke oxide particles. C and O account for most element compositions for all the carbon inclusions. The rough, spherical, strip shape and flake shape carbon-inclusions are believed to be derived from the degradation products of the binder or oxidizer, while the fiber silk is possibly the combustion product of fiber inside the heat insulation layer of the propellants. Images of products at different pressures reveal high pressure reduces the degree of agglomeration. The chemical compositions, size range and content of all the observed structures are given in this paper. Results of our study are expected to provide better insight in the working process of solid rocket motor.

Novel Binders and Methods for Agglomeration of Ore

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. K. Kawatra; T. C. Eisele; K. A. Lewandowski

2006-09-30

Heap leaching is one of the methods being used to recover metal from low grade ore deposits. The main problem faced during heap leaching is the migration of fine grained particles through the heap, forming impermeable beds which result in poor solution flow. The poor solution flow leads to less contact between the leach solution and the ore, resulting in low recovery rates. Agglomeration of ore into coarse, porous masses prevents fine particles from migrating and clogging the spaces and channels between the larger ore particles. Currently, there is one facility in the United States which uses agglomeration. This operationmore » agglomerates their ore using leach solution (raffinate), but is still experiencing undesirable metal recovery from the heaps due to agglomerate breakdown. The use of a binder, in addition to the leach solution, during agglomeration would help to produce stronger agglomerates that did not break down during processing. However, there are no known binders that will work satisfactorily in the acidic environment of a heap, at a reasonable cost. As a result, operators of many facilities see a large loss of process efficiency due to their inability to take advantage of agglomeration. Increasing copper recovery in heap leaching by the use of binders and agglomeration would result in a significant decrease in the amount of energy consumed. Assuming that 70% of all the leaching heaps would convert to using agglomeration technology, as much as 1.64*10{sup 12} BTU per year would be able to be saved if a 25% increase in copper recovery was experienced, which is equivalent to saving approximately 18% of the energy currently being used in leaching heaps. For every week a leach cycle was decreased, a savings of as much as 1.23*10{sup 11} BTU per week would result. This project has identified several acid-resistant binders and agglomeration procedures. These binders and experimental procedures will be able to be used for use in improving the energy efficiency of heap leaching.« less

Micro Structural, Optical and Magnetic Properties of Co-SiO2 Nanocomposite Synthesized by Sol-Gel Technique

NASA Astrophysics Data System (ADS)

Saha, Mrinal; Mukherjee, Soumya; Gayen, Arup; Mukherjee, Siddhartha

2017-04-01

Co-SiO2 nano composite has been synthesized via sol-gel technique using dextrose [C6H12O6] as a reducer and tetraethyl orthosilicate [Si(OCH2CH3)4] as oxide forming agent, respectively. The dried gel has been subsequently calcined at different temperature (850 and 900 °C) for 30 min in an inert atmosphere by N2 purging. The synthesized materials have been characterized by X-ray diffraction, high resolution transmission microscope, Fourier transform infrared spectroscopy, UV-Vis spectroscopy, scanning electron microscope, field emission microscope, atomic force microscope and physical property measurement system. The crystallite sizes of the face centered cubic cobalt nano composite materials have been found to be in the range of 14-28 nm. The crystallite size of the material found to be increased at higher calcination temperature due to the grain growth. The surface morphology of the obtained material has been found to be agglomerated but spherical in nature. This agglomeration tendency could be attributed to magnetic interaction between particles, large surface area as well as high surface energy. The band gap value of the obtained material has been determined to be 1.92 eV. The saturation magnetization (Ms) and the coercivity (Hc) of the composite material were found to be 29.45 emu g-1and 23.2 Oe, respectively. This technique has thus been found to be a convenient and effective method to prepare pure metallic cobalt nanoparticles with uniform size and homogeneous distribution throughout the matrix.

Effect of silica nanoparticles with variable size and surface functionalization on human endothelial cell viability and angiogenic activity

NASA Astrophysics Data System (ADS)

Guarnieri, Daniela; Malvindi, Maria Ada; Belli, Valentina; Pompa, Pier Paolo; Netti, Paolo

2014-02-01

Silica nanoparticles could be promising delivery vehicles for drug targeting or gene therapy. However, few studies have been undertaken to determine the biological behavior effects of silica nanoparticles on primary endothelial cells. Here we investigated uptake, cytotoxicity and angiogenic properties of silica nanoparticle with positive and negative surface charge and sizes ranging from 25 to 115 nm in primary human umbilical vein endothelial cells. Dynamic light scattering measurements and nanoparticle tracking analysis were used to estimate the dispersion status of nanoparticles in cell culture media, which was a key aspect to understand the results of the in vitro cellular uptake experiments. Nanoparticles were taken up by primary endothelial cells in a size-dependent manner according to their degree of agglomeration occurring after transfer in cell culture media. Functionalization of the particle surface with positively charged groups enhanced the in vitro cellular uptake, compared to negatively charged nanoparticles. However, this effect was contrasted by the tendency of particles to form agglomerates, leading to lower internalization efficiency. Silica nanoparticle uptake did not affect cell viability and cell membrane integrity. More interestingly, positively and negatively charged 25 nm nanoparticles did not influence capillary-like tube formation and angiogenic sprouting, compared to controls. Considering the increasing interest in nanomaterials for several biomedical applications, a careful study of nanoparticle-endothelial cells interactions is of high relevance to assess possible risks associated to silica nanoparticle exposure and their possible applications in nanomedicine as safe and effective nanocarriers for vascular transport of therapeutic agents.

Modeling of Particle Agglomeration in Nanofluids

NASA Astrophysics Data System (ADS)

Kanagala, Hari Krishna

Nanofluids are colloidal dispersions of nano sized particles (<100nm in diameter) in dispersion mediums. They are of great interest in industrial applications as heat transfer fluids owing to their enhanced thermal conductivities. Stability of nanofluids is a major problem hindering their industrial application. Agglomeration and then sedimentation are some reasons, which drastically decrease the shelf life of these nanofluids. Current research addresses the agglomeration effect and how it can affect the shelf life of a nanofluid. The reasons for agglomeration in nanofluids are attributable to the interparticle interactions which are quantified by the various theories. By altering the governing properties like volume fraction, pH and electrolyte concentration different nanofluids with instant agglomeration, slow agglomeration and no agglomeration can be produced. A numerical model is created based on the discretized population balance equations which analyses the particle size distribution at different times. Agglomeration effects have been analyzed for alumina nanoparticles with average particle size of 150nm dispersed in de-ionized water. As the pH was moved towards the isoelectric point of alumina nanofluids, the particle size distribution became broader and moved to bigger sizes rapidly with time. Particle size distributions became broader and moved to bigger sizes more quickly with time with increase in the electrolyte concentration. The two effects together can be used to create different temporal trends in the particle size distributions. Faster agglomeration is attributed to the decrease in the electrostatic double layer repulsion forces which is due to decrease in the induced charge and the double layer thickness around the particle. Bigger particle clusters show lesser agglomeration due to reaching the equilibrium size. The procedures and processes described in this work can be used to generate more stable nanofluids.

Consolidation of Hierarchy-Structured Nanopowder Agglomerates and Its Application to Net-Shaping Nanopowder Materials

PubMed Central

Lee, Jai-Sung; Choi, Joon-Phil; Lee, Geon-Yong

2013-01-01

This paper provides an overview on our recent investigations on the consolidation of hierarchy-structured nanopowder agglomerates and related applications to net-shaping nanopowder materials. Understanding the nanopowder agglomerate sintering (NAS) process is essential to processing of net-shaped nanopowder materials and components with small and complex shape. The key concept of the NAS process is to enhance material transport through controlling the powder interface volume of nanopowder agglomerates. Based upon this concept, we have suggested a new idea of full density processing for fabricating micro-powder injection molded part using metal nanopowder agglomerates produced by hydrogen reduction of metal oxide powders. Studies on the full density sintering of die compacted- and powder injection molded iron base nano-agglomerate powders are introduced and discussed in terms of densification process and microstructure. PMID:28788317

Problems of Research, Projects and Mechanisms for Their Implementation in Chelyabinsk City Agglomeration

NASA Astrophysics Data System (ADS)

Bolshakov, V. V.

2017-11-01

The article analyzes the research and design methods of urban agglomerations in the context of the Chelyabinsk agglomeration from the point of view of correctness, objectivity and consistency of the results obtained. The completed and approved project of the Chelyabinsk agglomeration is analysed to provide architectural and planning solutions for sustainable social and economic development according to the theories that have been formed to date. The possibility of effectuation and implementation of the approved project of the Chelyabinsk agglomeration taking in account existing specific natural, historical and socio-economic factors characteristic for the territory under consideration is examined. The authors draw the conclusions the project of the Chelyabinsk agglomeration has been developed in line with the town-planning solutions that do not reflect modern approaches based on the competitive advantages of territories and do not form a space providing transition to a modernized and innovative economy. Specific town-planning decisions have a weak justification and an undeveloped methodology for pre-project analysis and methodology for designing urban agglomerations because of absence of a full study of the phenomenon of urban agglomeration and processes occurring in it today. It is necessary to continue research in the field of development of the Chelyabinsk agglomeration with the use of a logical and objective methodology to analyze the territory and design which can lead to the formation of an urban-planning information model that reflects all the system processes and allows for predicting project solutions.

Evaluation and characterization during the anaerobic digestion of high-strength kitchen waste slurry via a pilot-scale anaerobic membrane bioreactor.

PubMed

Xiao, Xiaolan; Huang, Zhenxing; Ruan, Wenquan; Yan, Lintao; Miao, Hengfeng; Ren, Hongyan; Zhao, Mingxing

2015-10-01

The anaerobic digestion of high-strength kitchen waste slurry via a pilot-scale anaerobic membrane bioreactor (AnMBR) was investigated at two different operational modes, including no sludge discharge and daily sludge discharge of 20 L. The AnMBR provided excellent and reliable permeate quality with high COD removal efficiencies over 99%. The obvious accumulations of long chain fatty acids (LCFAs) and Ca(2+) were found in the anaerobic digester by precipitation and agglomeration. Though the physicochemical process contributed to attenuating the free LCFAs toxicity on anaerobic digestion, the digestion efficiency was partly influenced for the low bioavailability of those precipitates. Moreover, higher organic loading rate (OLR) of 5.8 kg COD/(m(3) d) and digestion efficiency of 78% were achieved as the AnMBR was stably operated with sludge discharge, where the membrane fouling propensity was also alleviated, indicating the crucial significance of SRT control on the treatment of high-strength kitchen waste slurry via AnMBRs. Copyright © 2015 Elsevier Ltd. All rights reserved.

The Effect of Small Additions of Carbon Nanotubes on the Mechanical Properties of Epoxy Polymers under Static and Dynamic Loads

NASA Astrophysics Data System (ADS)

Tarasov, A. E.; Badamshina, E. R.; Anokhin, D. V.; Razorenov, S. V.; Vakorina, G. S.

2018-01-01

The results of measurements of the mechanical characteristics of cured epoxy composites containing small and ultrasmall additions of single-walled carbon nanotubes in the concentration range from 0 to 0.133 wt % under static and dynamic loads are presented. Static measurements of strength characteristics have been carried out under standard test conditions. Measurements of the Hugoniot elastic limit and spall strength were performed under a shock wave loading of the samples at a deformation rate of (0.8-1.5) ß 105 s-1 before the fracture using explosive devices by recording and subsequent analyzing the evolution of the full wave profiles. It has been shown that agglomerates of nanotubes present in the structure of the composites after curing cause a significant scatter of the measured strength parameters, both in the static and in the dynamic test modes. However, the effects of carbon nanotube additions in the studied concentration interval on the physical and mechanical characteristics of the parameters were not revealed for both types of loading.

The Feeling of Action Tendencies: On the Emotional Regulation of Goal-Directed Behavior

PubMed Central

Lowe, Robert; Ziemke, Tom

2011-01-01

In this article, we review the nature of the functional and causal relationship between neurophysiologically/psychologically generated states of emotional feeling and action tendencies and extrapolate a novel perspective. Emotion theory, over the past century and beyond, has tended to regard feeling and action tendency as independent phenomena: attempts to outline the functional and causal relationship that exists between them have been framed therein. Classically, such relationships have been viewed as unidirectional, but an argument for bidirectionality rooted in a dynamic systems perspective has gained strength in recent years whereby the feeling–action tendency relationship is viewed as a composite whole. On the basis of our review of somatic–visceral theories of feelings, we argue that feelings are grounded upon neural-dynamic representations (elevated and stable activation patterns) of action tendency. Such representations amount to predictions updated by cognitive and bodily feedback. Specifically, we view emotional feelings as minimalist predictions of the action tendency (what the agent is physiologically and cognitively primed to do) in a given situation. The essence of this point is captured by our exposition of action tendency prediction–feedback loops which we consider, above all, in the context of emotion regulation, and in particular, of emotional regulation of goal-directed behavior. The perspective outlined may be of use to emotion theorists, computational modelers, and roboticists. PMID:22207854

Growth and form of planetary seedlings: results from a sounding rocket microgravity aggregation experiment.

PubMed

Krause, Maya; Blum, Jürgen

2004-07-09

In a second microgravity experiment on the formation of dust agglomerates by Brownian motion-induced collisions we find that the agglomerates have fractal dimensions as low as 1.4. Because of much better data, we are now able to derive the diffusion constant of the agglomerates as a function of mass, to show that a power law with an exponent of 1.7 describes the temporal evolution of the mean agglomerate mass very well and to prove that the collision cross section is proportional to the geometrical cross section. In addition to that we derived the universal mass-distribution function of the agglomerates.

Development and Application of Agglomerated Multigrid Methods for Complex Geometries

NASA Technical Reports Server (NTRS)

Nishikawa, Hiroaki; Diskin, Boris; Thomas, James L.

2010-01-01

We report progress in the development of agglomerated multigrid techniques for fully un- structured grids in three dimensions, building upon two previous studies focused on efficiently solving a model diffusion equation. We demonstrate a robust fully-coarsened agglomerated multigrid technique for 3D complex geometries, incorporating the following key developments: consistent and stable coarse-grid discretizations, a hierarchical agglomeration scheme, and line-agglomeration/relaxation using prismatic-cell discretizations in the highly-stretched grid regions. A signi cant speed-up in computer time is demonstrated for a model diffusion problem, the Euler equations, and the Reynolds-averaged Navier-Stokes equations for 3D realistic complex geometries.

Communication — Modeling polymer-electrolyte fuel-cell agglomerates with double-trap kinetics

DOE PAGES

Pant, Lalit M.; Weber, Adam Z.

2017-04-14

A new semi-analytical agglomerate model is presented for polymer-electrolyte fuel-cell cathodes. The model uses double-trap kinetics for the oxygen-reduction reaction, which can capture the observed potential-dependent coverage and Tafel-slope changes. An iterative semi-analytical approach is used to obtain reaction rate constants from the double-trap kinetics, oxygen concentration at the agglomerate surface, and overall agglomerate reaction rate. The analytical method can predict reaction rates within 2% of the numerically simulated values for a wide range of oxygen concentrations, overpotentials, and agglomerate sizes, while saving simulation time compared to a fully numerical approach.

Experimental study of acoustic agglomeration and fragmentation on coal-fired ash

NASA Astrophysics Data System (ADS)

Shen, Guoqing; Huang, Xiaoyu; He, Chunlong; Zhang, Shiping; An, Liansuo; Wang, Liang; Chen, Yanqiao; Li, Yongsheng

2018-02-01

As the major part of air pollution, inhalable particles, especially fine particles are doing great harm to human body due to smaller particle size and absorption of hazardous components. However, the removal efficiency of current particles filtering devices is low. Acoustic agglomeration is considered as a very effective pretreatment technique for removing particles. Fine particles collide, agglomerate and grow up in the sound field and the fine particles can be removed by conventional particles devices easily. In this paper, the agglomeration and fragmentation of 3 different kinds of particles with different size distributions are studied experimentally in the sound field. It is found that there exists an optimal frequency at 1200 Hz for different particles. The agglomeration efficiency of inhalable particles increases with SPL increasing for the unimodal particles with particle diameter less than 10 μm. For the bimodal particles, the optimal SPLs are 115 and 120 dB with the agglomeration efficiencies of 25% and 55%. A considerable effectiveness of agglomeration could only be obtained in a narrow SPL range and it decreases significantly over the range for the particles fragmentation.

Low-rank coal oil agglomeration

DOEpatents

Knudson, Curtis L.; Timpe, Ronald C.

1991-01-01

A low-rank coal oil agglomeration process. High mineral content, a high ash content subbituminous coals are effectively agglomerated with a bridging oil which is partially water soluble and capable of entering the pore structure, and usually coal derived.

The Magnet Cove Rutile Company mine, Hot Spring County, Arkansas

USGS Publications Warehouse

Kinney, Douglas M.

1949-01-01

The Magnet Cove Rutile Company mine was mapped by the U.S. Geological Survey in November 1944. The pits are on the northern edge of Magnet Cove and have been excavated in the oxidized zone of highly weathered and altered volcanic agglomerate. The agglomerate is composed of altered mafic igneous rocks in a matrix of white to gray clay, a highly altered tuff. The agglomerate appears layered and is composed of tuffaceous clay material below and igneous blocks above. The agglomerate is cut by aplite and lamprophyre dikes. Alkalic syenite dikes crop out on the ridge north of the pits. At the present stage of mine development the rutile seems to be concentrated in a narrow zone beneath the igneous blocks of the agglomerate. Rutile, associated with calcite and pyrite, occurs as disseminated acicular crystals and discontinuous vein-like masses in the altered tuff. Thin veins of rutile locally penetrate the mafic igneous blocks of the agglomerate.

Individual differences in Affective Neuroscience Personality Scale (ANPS) primary emotional traits and depressive tendencies.

PubMed

Montag, Christian; Widenhorn-Müller, Katharina; Panksepp, Jaak; Kiefer, Markus

2017-02-01

The present study investigated individual differences in the Affective Neuroscience Personality Scales (ANPS), representing measures of primary emotional systems, and depressive tendencies in two independent samples. In order to be able to find support for a continuum model with respect to the relation of strength in the cross-species "affective neuroscience" taxonomy of primary emotional systems, we investigated ANPS measured personality traits in a psychologically mostly healthy population (n=614 participants) as well as a sample of clinically depressed people (n=55 depressed patients). In both normal and depressed samples robust associations appeared between higher FEAR and SADNESS scores and depressive tendencies. A similar - albeit weaker - association was observed with lower SEEKING system scores and higher depressive tendencies, an effect again seen in both samples. The study is of cross-sectional nature and therefore only associations between primary emotional systems and depressive tendencies were evaluated. These results show that similar associations between ANPS monitored primary emotional systems and tendencies toward depression can be observed in both healthy and depressed participants. This lends support for a continuum of affective changes accompanying depression, potentially reflecting differences in specific brain emotional system activities in both affectively normal as well as clinically depressed individuals. Copyright © 2016 Elsevier Inc. All rights reserved.

Does intrinsic motivation strengthen physical activity habit? Modeling relationships between self-determination, past behaviour, and habit strength.

PubMed

Gardner, Benjamin; Lally, Phillippa

2013-10-01

Habit formation is thought to aid maintenance of physical activity, but little research is available into determinants of habit strength aside from repeated performance. Previous work has shown that intrinsically motivated physical activity, underpinned by inherent satisfaction derived from activity, is more likely to be sustained. We explored whether this might reflect a tendency for self-determined activity to become more strongly habitual. A sample of 192 adults aged 18-30 completed measures of motivational regulation, intention, behaviour, and habit strength. Results showed that self-determined regulation interacted with past behaviour in predicting habit strength: prior action was more predictive of habit strength among more autonomously motivated participants. There was an unexpected direct effect of self-determined regulation on habit strength, independently of past behaviour. Findings offer possible directions for future habit formation work.

Correlating bilayer tablet delamination tendencies to micro-environmental thermodynamic conditions during pan coating.

PubMed

Zacour, Brian M; Pandey, Preetanshu; Subramanian, Ganeshkumar; Gao, Julia Z; Nikfar, Faranak

2014-06-01

The objective of this study was to determine the impact that the micro-environment, as measured by PyroButton data loggers, experienced by tablets during the pan coating unit operation had on the layer adhesion of bilayer tablets in open storage conditions. A full factorial design of experiments (DOE) with three center points was conducted to study the impact of final tablet hardness, film coating spray rate and film coating exhaust temperature on the delamination tendencies of bilayer tablets. PyroButton data loggers were placed (fixed) at various locations in a pan coater and were also allowed to freely move with the tablet bed to measure the micro-environmental temperature and humidity conditions of the tablet bed. The variance in the measured micro-environment via PyroButton data loggers accounted for 75% of the variance in the delamination tendencies of bilayer tablets on storage (R(2 )= 0.75). A survival analysis suggested that tablet hardness and coating spray rate significantly impacted the delamination tendencies of the bilayer tablets under open storage conditions. The coating exhaust temperature did not show good correlation with the tablets' propensity to crack indicating that it was not representative of the coating micro-environment. Models created using data obtained from the PyroButton data loggers outperformed models created using primary DOE factors in the prediction of bilayer tablet strength, especially upon equipment or scale transfers. The coating micro-environment experienced by tablets during the pan coating unit operation significantly impacts the strength of the bilayer interface of tablets on storage.

The role of vision, speed, and attention in overcoming directional biases during arm movements.

PubMed

Dounskaia, Natalia; Goble, Jacob A

2011-03-01

Previous research has revealed directional biases (preferences to select movements in specific directions) during horizontal arm movements with the use of a free-stroke drawing task. The biases were interpreted as a result of a tendency to generate motion at either the shoulder or elbow (leading joint) and move the other (subordinate) joint predominantly passively to avoid neural effort for control of interaction torque. Here, we examined influence of vision, movement speed, and attention on the directional biases. Participants performed the free-stroke drawing task, producing center-out strokes in randomly selected directions. Movements were performed with and without vision and at comfortable and fast pace. A secondary, cognitive task was used to distract attention. Preferred directions remained the same in all conditions. Bias strength mildly increased without vision, especially during fast movements. Striking increases in bias strength were caused by the secondary task, pointing to additional cognitive load associated with selection of movements in the non-preferred directions. Further analyses demonstrated that the tendency to minimize active interference with interaction torque at the subordinate joint matched directional biases in all conditions. This match supports the explanation of directional biases as a result of a tendency to minimize neural effort for interaction torque control. The cognitive load may enhance this tendency in two ways, directly, by reducing neural capacity for interaction torque control, and indirectly, by decreasing capacity of working memory that stores visited directions. The obtained results suggest strong directional biases during daily activities because natural arm movements usually subserve cognitive tasks.

Engineering and Technical Education in Russia, in Numbers

ERIC Educational Resources Information Center

Aref'ev, A. L.; Aref'ev, M. A.

2013-01-01

An analysis of the main tendencies in the development of engineering and technical education in Russia during the last 100 years shows that earlier strengths have been lost, and that currently technical education in Russia is far behind modern world standards.

Composite propellant combustion with low aluminum agglomeration

NASA Astrophysics Data System (ADS)

Mullen, Jessica Christine

Aluminum behavior---accumulation, agglomeration and ignition---is studied in a unique, wide-distribution, ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellant formulation that results in low Al agglomeration, even at low pressures (1--30 atm). Variations in formulation---such as fine-AP/binder ratio, Al particle size, Al loading, coarse-AP size---are also examined. A fuel-rich, oxygenated binder matrix highly loaded with fine (2-mum) AP (FAP) at 75/25:FAP/binder (by mass) is found to have premixed flame conditions that produce minimal agglomeration (without ignition) of 15-mum Al. Coarse AP (CAP) is added to the system in the form of either particles (200 or 400 mum) or pressed-AP laminates (simulated CAP). In the 2-D laminate system the CAP/oxyfuel-matrix flame structure is seen to be similar to that previously described for non-aluminized laminates with split (diffusion) and merged (partially-premixed) flame regimes, depending on pressure and fuel-matrix thickness. Both laminate and particulate systems show that with CAP present, Al can agglomerate more extensively on CAP via lateral surface migration from fuel matrix to the CAP region. The particulate CAP system also shows that Al can accumulate/agglomerate via settling on CAP from above (in the direction of burning). Both systems, but more clearly the 2-D laminates, show that with CAP present, Al is ignited by the outer CAP/fuel-matrix canopy flames. Thus, a propellant formulation is proposed for reducing overall Al agglomeration through intrinsically reduced agglomeration in the fuel-matrix and a reduced number of CAP-particle agglomerates via higher FAP/CAP ratio.

Low-rank coal oil agglomeration

DOEpatents

Knudson, C.L.; Timpe, R.C.

1991-07-16

A low-rank coal oil agglomeration process is described. High mineral content, a high ash content subbituminous coals are effectively agglomerated with a bridging oil which is partially water soluble and capable of entering the pore structure, and is usually coal-derived.

Modeling of particle agglomeration in nanofluids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishna, K. Hari; Neti, S.; Oztekin, A.

2015-03-07

Agglomeration strongly influences the stability or shelf life of nanofluid. The present computational and experimental study investigates the rate of agglomeration quantitatively. Agglomeration in nanofluids is attributed to the net effect of various inter-particle interaction forces. For the nanofluid considered here, a net inter-particle force depends on the particle size, volume fraction, pH, and electrolyte concentration. A solution of the discretized and coupled population balance equations can yield particle sizes as a function of time. Nanofluid prepared here consists of alumina nanoparticles with the average particle size of 150 nm dispersed in de-ionized water. As the pH of the colloid wasmore » moved towards the isoelectric point of alumina nanofluids, the rate of increase of average particle size increased with time due to lower net positive charge on particles. The rate at which the average particle size is increased is predicted and measured for different electrolyte concentration and volume fraction. The higher rate of agglomeration is attributed to the decrease in the electrostatic double layer repulsion forces. The rate of agglomeration decreases due to increase in the size of nano-particle clusters thus approaching zero rate of agglomeration when all the clusters are nearly uniform in size. Predicted rates of agglomeration agree adequate enough with the measured values; validating the mathematical model and numerical approach is employed.« less

Spatial Linkage and Urban Expansion: AN Urban Agglomeration View

NASA Astrophysics Data System (ADS)

Jiao, L. M.; Tang, X.; Liu, X. P.

2017-09-01

Urban expansion displays different characteristics in each period. From the perspective of the urban agglomeration, studying the spatial and temporal characteristics of urban expansion plays an important role in understanding the complex relationship between urban expansion and network structure of urban agglomeration. We analyze urban expansion in the Yangtze River Delta Urban Agglomeration (YRD) through accessibility to and spatial interaction intensity from core cities as well as accessibility of road network. Results show that: (1) Correlation between urban expansion intensity and spatial indicators such as location and space syntax variables is remarkable and positive, while it decreases after rapid expansion. (2) Urban expansion velocity displays a positive correlation with spatial indicators mentioned above in the first (1980-1990) and second (1990-2000) period. However, it exhibits a negative relationship in the third period (2000-2010), i.e., cities located in the periphery of urban agglomeration developing more quickly. Consequently, the hypothesis of convergence of urban expansion in rapid expansion stage is put forward. (3) Results of Zipf's law and Gibrat's law show urban expansion in YRD displays a convergent trend in rapid expansion stage, small and medium-sized cities growing faster. This study shows that spatial linkage plays an important but evolving role in urban expansion within the urban agglomeration. In addition, it serves as a reference to the planning of Yangtze River Delta Urban Agglomeration and regulation of urban expansion of other urban agglomerations.

Magnetic Cloud Field Intensities and Solar Wind Velocities

NASA Technical Reports Server (NTRS)

Gonzalez, Walter D.; Clau de Gonzalez, Alicia D.; Tsurutani, Bruce T.; Arballo, John K.

1997-01-01

For the sets of magnetic clouds studied in this work we have shown that there is a general relationship between their magnetic fields strength and velocities. With a clear tendency that the faster the speed of the cloud the higher the magnetic field.

Nanoparticle transport in water-unsaturated porous media: effects of solution ionic strength and flow rate

NASA Astrophysics Data System (ADS)

Prédélus, Dieuseul; Lassabatere, Laurent; Louis, Cédric; Gehan, Hélène; Brichart, Thomas; Winiarski, Thierry; Angulo-Jaramillo, Rafael

2017-03-01

This paper presents the influence of ionic strength and flow on nanoparticle (NP) retention rate in an unsaturated calcareous medium, originating from a heterogeneous glaciofluvial deposit of the region of Lyon (France). Laboratory columns 10 cm in diameter and 30 cm in length were used. Silica nanoparticles (Au-SiO2-FluoNPs), with hydrodynamic diameter ranging from 50 to 60 nm and labeled with fluorescein derivatives, were used to simulate particle transport, and bromide was used to characterize flow. Three flow rates and five different ionic strengths were tested. The transfer model based on fractionation of water into mobile and immobile fractions was coupled with the attachment/detachment model to fit NPs breakthrough curves. The results show that increasing flow velocity induces a decrease in nanoparticle retention, probably as the result of several physical but also geochemical factors. The results show that NPs retention increases with ionic strength. However, an inversion of retention occurs for ionic strength >5.10-2 M, which has been scarcely observed in previous studies. The measure of zeta potential and DLVO calculations show that NPs may sorb on both solid-water and air-water interfaces. NPs size distribution shows the potential for nanoparticle agglomeration mostly at low pH, leading to entrapment in the soil pores. These mechanisms are highly sensitive to both hydrodynamic and geochemical conditions, which explains their high sensitivity to flow rates and ionic strength.

Comments on an Analytical Thermal Agglomeration for Problems with Surface Growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hodge, N. E.

2017-03-22

Up until Dec 2016, the thermal agglomeration was very heuristic, and as such, difficult to define. The lack of predictability became problematic, and the current notes represent the first real attempt to systematize the specification of the agglomerated process parameters.

Simulation of deterministic energy-balance particle agglomeration in turbulent liquid-solid flows

NASA Astrophysics Data System (ADS)

Njobuenwu, Derrick O.; Fairweather, Michael

2017-08-01

An efficient technique to simulate turbulent particle-laden flow at high mass loadings within the four-way coupled simulation regime is presented. The technique implements large-eddy simulation, discrete particle simulation, a deterministic treatment of inter-particle collisions, and an energy-balanced particle agglomeration model. The algorithm to detect inter-particle collisions is such that the computational costs scale linearly with the number of particles present in the computational domain. On detection of a collision, particle agglomeration is tested based on the pre-collision kinetic energy, restitution coefficient, and van der Waals' interactions. The performance of the technique developed is tested by performing parametric studies on the influence of the restitution coefficient (en = 0.2, 0.4, 0.6, and 0.8), particle size (dp = 60, 120, 200, and 316 μm), Reynolds number (Reτ = 150, 300, and 590), and particle concentration (αp = 5.0 × 10-4, 1.0 × 10-3, and 5.0 × 10-3) on particle-particle interaction events (collision and agglomeration). The results demonstrate that the collision frequency shows a linear dependency on the restitution coefficient, while the agglomeration rate shows an inverse dependence. Collisions among smaller particles are more frequent and efficient in forming agglomerates than those of coarser particles. The particle-particle interaction events show a strong dependency on the shear Reynolds number Reτ, while increasing the particle concentration effectively enhances particle collision and agglomeration whilst having only a minor influence on the agglomeration rate. Overall, the sensitivity of the particle-particle interaction events to the selected simulation parameters is found to influence the population and distribution of the primary particles and agglomerates formed.

Successfully use agglomeration for size enlargement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pietsch, W.

1996-04-01

The processing of fine and ultrafine particles by size enlargement finds an ever increasing application. At the same time, undesirable agglomeration such as buildup, caking, bridging, and uncontrolled aggregation of fine particles can occur during processing and handling of these particulate solids. This article will provide a survey of the phenomena of agglomeration and discuss the unit operation of size enlargement by agglomeration. This article is also an invitation, particularly to young engineers, to become interested in agglomeration. Considering that mechanical process technologies are requiring more energy every year than any other group of consumers and efficiencies are typically inmore » the single digits or teens at best, considerable rewards can be expected from the development of scientifically modified, more energy-efficient methods and equipment.« less

Influence of daylight on the fate of silver and zinc oxide nanoparticles in natural aquatic environments.

PubMed

Odzak, Niksa; Kistler, David; Sigg, Laura

2017-07-01

Nanoparticles, such as silver (Ag-NP) and zinc oxide (ZnO-NP), are increasingly used in many consumer products. These nanoparticles (NPs) will likely be exposed to the aquatic environment (rain, river, lake water) and to light (visible and UV) in the products where they are applied, or after those products are discharged. Dissolution of Ag-NP and ZnO-NP is an important process because the dissolved Ag + and Zn 2+ are readily available and toxic for aquatic organisms. The objective of this study was to investigate the role of daylight (UV and visible) for the fate of engineered Ag-NP and ZnO-NPs in different types of natural waters. Ag-NP and ZnO-NP were exposed to rainwater, river Rhine, and lake waters (Greifen, Lucerne, Cristallina, Gruère) under different light conditions (no light, UV 300-400 nm and visible light 400-700 nm) for up to 8 days. Stronger agglomeration of Ag-NP was observed in the waters with higher ionic strength in comparison to those with lower ionic strength. Visible light tended to increase the dissolution of Ag-NP under most natural water conditions in comparison to dark conditions, whereas UV-light led to decreased dissolved Ag + after longer exposure time. These effects illustrate the dynamic interactions of Ag-NP with light, which may lead both to increased oxidation and to increased reduction of Ag + by organic compounds under UV-light. In the case of ZnO-NP, agglomeration occurred at higher ionic strength, but the effects of pH were predominant for dissolution, which occurred up to concentrations close to the solubility limit of ZnO(s) at pH around 8.2 and to nearly complete dissolution of ZnO-NP at lower pH (pH 4.8-6.5), with both visible and UV-light facilitating dissolution. This study thus shows that light conditions play an important role in the dissolution processes of nanoparticles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Study on mechanical and ablative properties of EPDM/OMMT thermal insulating nanocomposites.

PubMed

Gao, Guoxin; Zhang, Zhicheng; Li, Xuefei; Meng, Qingjie; Zheng, Yuansuo; Jin, Zhihao

2010-11-01

In order to enhance the elongation at break, the ablation resistant properties as well as the tensile strength of the thermal insulating materials, organo-montmorillonite (OMMT) was introduced into the short aramid fibers reinforced Ethylene-Propylene-Diene Monomer (EPDM) based nanocomposites. The effects of OMMT content on the mechanical and ablative properties of the nanocomposites were investigated systematically. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirm that EPDM-matrix has been intercalated into OMMT interlayers after a mixing process on a two-roll mill. The brittle fracture of nanocomposites also indicates that OMMT can lubricate aramid fiber to weaken the interfacial adhesive strength between the fibers and the matrix. As a result, the tensile strength and elongation at break are both improved sharply with OMMT content increasing from 1 phr to 7 phr. However, thanks to the inevitable agglomeration of OMMT with high loading inside the nanocomposites, the tensile strength and elongation at break reduce gently once OMMT is over 7 phr. Furthermore, the ablation resistant properties are improved greatly by increasing OMMT from 1 phr to 11 phr. Therefore, the optimal content of OMMT is 7-11 phr for the thermal insulating nanocomposites with big elongation and excellent ablation resistant properties.

A MODEL FOR FINE PARTICLE AGGLOMERATION IN CIRCULATING FLUIDIZED BED ABSORBERS

EPA Science Inventory

A model for fine particle agglomeration in circulating fluidized bed absorbers (CFBAS) has been developed. It can model the influence of different factors on agglomeration, such as the geometry of CFBAs, superficial gas velocity, initial particle size distribution, and type of ag...

Urban Planning Problems of Agglomerations

NASA Astrophysics Data System (ADS)

Olenkov, V. D.; Tazeev, N. T.

2017-11-01

The article explores the state of the air basin of the Chelyabinsk agglomeration and gives the examples of solutions for the pollution problems from the point of view of city planning. The main features and structure of the modern urban agglomerations are considered, the methods for determining their boundaries are studied and the main problems are identified. The study of the boundaries and territorial structure of the Chelyabinsk urban agglomeration is conducted, and a general description of the territory is given. The data on the change in the volume of pollutant emissions into the atmosphere and the index of atmospheric pollution for the period 2003-2015 are given basing on the annual comprehensive reports regarding the state of the environment. The review of the world experience of city-planning actions on the decision of ecological problems is carried out. The most suitable ways for the ecological problems solving in the Chelyabinsk agglomeration are considered. The authors give recommendations for the ecological situation improving in the territory of the Chelyabinsk agglomeration.

Morphological characterization of diesel soot agglomerates based on the Beer-Lambert law

NASA Astrophysics Data System (ADS)

Lapuerta, Magín; Martos, Francisco J.; José Expósito, Juan

2013-03-01

A new method is proposed for the determination of the number of primary particles composing soot agglomerates emitted from diesel engines as well as their individual fractal dimension. The method is based on the Beer-Lambert law and it is applied to micro-photographs taken in high resolution transmission electron microscopy. Differences in the grey levels of the images lead to a more accurate estimation of the geometry of the agglomerate (in this case radius of gyration) than other methods based exclusively on the planar projections of the agglomerates. The method was validated by applying it to different images of the same agglomerate observed from different angles of incidence, and proving that the effect of the angle of incidence is minor, contrary to other methods. Finally, the comparisons with other methods showed that the size, number of primary particles and fractal dimension (the latter depending on the particle size) are usually underestimated when only planar projections of the agglomerates are considered.

Nanoparticle agglomeration in an evaporating levitated droplet for different acoustic amplitudes

NASA Astrophysics Data System (ADS)

Tijerino, Erick; Basu, Saptarshi; Kumar, Ranganathan

2013-01-01

Radiatively heated levitated functional droplets with nanosilica suspensions exhibit three distinct stages namely pure evaporation, agglomeration, and finally structure formation. The temporal history of the droplet surface temperature shows two inflection points. One inflection point corresponds to a local maximum and demarcates the end of transient heating of the droplet and domination of vaporization. The second inflection point is a local minimum and indicates slowing down of the evaporation rate due to surface accumulation of nanoparticles. Morphology and final precipitation structures of levitated droplets are due to competing mechanisms of particle agglomeration, evaporation, and shape deformation. In this work, we provide a detailed analysis for each process and propose two important timescales for evaporation and agglomeration that determine the final diameter of the structure formed. It is seen that both agglomeration and evaporation timescales are similar functions of acoustic amplitude (sound pressure level), droplet size, viscosity, and density. However, we show that while the agglomeration timescale decreases with initial particle concentration, the evaporation timescale shows the opposite trend. The final normalized diameter can be shown to be dependent solely on the ratio of agglomeration to evaporation timescales for all concentrations and acoustic amplitudes. The structures also exhibit various aspect ratios (bowls, rings, spheroids) which depend on the ratio of the deformation timescale (tdef) and the agglomeration timescale (tg). For tdef

Novel Binders and Methods for Agglomeration of Ore

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. K. Kawatra; T. C. Eisele; K. A. Lewandowski

2006-03-31

Many metal extraction operations, such as leaching of copper, leaching of precious metals, and reduction of metal oxides to metal in high-temperature furnaces, require agglomeration of ore to ensure that reactive liquids or gases are evenly distributed throughout the ore being processed. Agglomeration of ore into coarse, porous masses achieves this even distribution of fluids by preventing fine particles from migrating and clogging the spaces and channels between the larger ore particles. Binders are critically necessary to produce agglomerates that will not break down during processing. However, for many important metal extraction processes there are no binders known that willmore » work satisfactorily at a reasonable cost. A primary example of this is copper heap leaching, where there are no binders currently encountered in this acidic environment process. As a result, operators of many facilities see a large loss of process efficiency due to their inability to take advantage of agglomeration. The large quantities of ore that must be handled in metal extraction processes also means that the binder must be inexpensive and useful at low dosages to be economical. The acid-resistant binders and agglomeration procedures developed in this project will also be adapted for use in improving the energy efficiency and performance of a broad range of mineral agglomeration applications, particularly heap leaching. The active involvement of our industrial partners will help to ensure rapid commercialization of any agglomeration technologies developed by this project.« less

Novel Binders and Methods for Agglomeration of Ore

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. K. Kawatra; T. C. Eisele; J. A. Gurtler

2005-09-30

Many metal extraction operations, such as leaching of copper, leaching of precious metals, and reduction of metal oxides to metal in high-temperature furnaces, require agglomeration of ore to ensure that reactive liquids or gases are evenly distributed throughout the ore being processed. Agglomeration of ore into coarse, porous masses achieves this even distribution of fluids by preventing fine particles from migrating and clogging the spaces and channels between the larger ore particles. Binders are critically necessary to produce agglomerates that will not break down during processing. However, for many important metal extraction processes there are no binders known that willmore » work satisfactorily at a reasonable cost. A primary example of this is copper heap leaching, where there are no binders currently encountered in this acidic environment process. As a result, operators of many facilities see a large loss of process efficiency due to their inability to take advantage of agglomeration. The large quantities of ore that must be handled in metal extraction processes also means that the binder must be inexpensive and useful at low dosages to be economical. The acid-resistant binders and agglomeration procedures developed in this project will also be adapted for use in improving the energy efficiency and performance of a broad range of mineral agglomeration applications, particularly heap leaching. The active involvement of our industrial partners will help to ensure rapid commercialization of any agglomeration technologies developed by this project.« less

Hydrodynamic Characteristics and Strength Analysis of a Novel Dot-matrix Oscillating Wave Energy Converter

NASA Astrophysics Data System (ADS)

Shao, Meng; Xiao, Chengsi; Sun, Jinwei; Shao, Zhuxiao; Zheng, Qiuhong

2017-12-01

The paper analyzes hydrodynamic characteristics and the strength of a novel dot-matrix oscillating wave energy converter, which is in accordance with nowadays’ research tendency: high power, high efficiency, high reliability and low cost. Based on three-dimensional potential flow theory, the paper establishes motion control equations of the wave energy converter unit and calculates wave loads and motions. On this basis, a three-dimensional finite element model of the device is built to check its strength. Through the analysis, it can be confirmed that the WEC is feasible and the research results could be a reference for wave energy’s exploration and utilization.

Personality and Career Decision Making.

ERIC Educational Resources Information Center

Malik, Har G. S.

The hypotheses tested that (1) anxiety and (2) extraversion (exvia) would be negatively related to career making ability. Variables defined as contributing to anxiety included ego weakness, excitability, low superego strength, threat sensitivity and high ergic tension. Extraversion was considered the "general tendency to social interaction" with…

Rock geochemistry in the Mahd adh Dhahab district, Kingdom of Saudi Arabia

USGS Publications Warehouse

Worl, R.G.; Doebrich, J.L.; Allen, M.S.; Afifi, A.M.; Ebens, R.J.

1987-01-01

Anomalous values of gold, silver, lead, and to a lesser extent copper and zinc in surface rock samples clearly delineated the northern mineralized zone in the upper agglomerate, and an east-vein area and west-vein area of the southern mineralized zone in the lower agglomerate. A third geochemically anomalous area occurs farther to the west in the lower agglomerate, suggesting that mineralization may have extended at least to this area along the lower agglomerate-lower tuff contact, and possibly even further to the west.

Search for the contamination source of butyltin compounds in wine: agglomerated cork stoppers.

PubMed

Jiang, Gui-Bin; Liu, Ji-Yan; Zhou, Qun-Fang

2004-08-15

A possible butyltin contamination source in wine was studied in this paper. Agglomerated cork stoppers, which were produced in Portugal, Spain, and Italy, used in wine bottles were examined. The domestic cork products, cork granules, and mucus used for cork products were also analyzed. The levels of mono- and dibutyltin compounds in corks were found in the range from <0.0024 to 3.3 and from <0.0029 to 6.7 microg of Sn/g, respectively. A low level of tributyltin contamination was also found in 2 of 31 tested samples. The presence of butyltin compounds in agglomerated cork stoppers was confirmed by GC-MS. Experimental results indicated that all overseas agglomerated cork stoppers studied contained mono- and/or dibutyltins. Butyltins were not detected in cork granules, mucus, most of the natural cork stoppers, and domestic agglomerated cork products. The concentrations of mono- and dibutyltins increased with the time in a 30-day experiment, showing that butyltin compounds can leach from agglomerated cork to the wine. When the butyltin concentrations in wine samples were compared with their levels in the corresponding agglomerated cork stoppers, a correlation was found. The potential harm of such food contamination was evaluated by the toxic research of butyltin compounds using Daphnia sp. as the experimental model.

Centrifugal air-assisted melt agglomeration for fast-release "granulet" design.

PubMed

Wong, Tin Wui; Musa, Nafisah

2012-07-01

Conventional melt pelletization and granulation processes produce round and dense, and irregularly shaped but porous agglomerates respectively. This study aimed to design centrifugal air-assisted melt agglomeration technology for manufacture of spherical and yet porous "granulets" for ease of downstream manufacturing and enhancing drug release. A bladeless agglomerator, which utilized shear-free air stream to mass the powder mixture of lactose filler, polyethylene glycol binder and poorly water-soluble tolbutamide drug into "granulets", was developed. The inclination angle and number of vane, air-impermeable surface area of air guide, processing temperature, binder content and molecular weight were investigated with reference to "granulet" size, shape, texture and drug release properties. Unlike fluid-bed melt agglomeration with vertical processing air flow, the air stream in the present technology moved centrifugally to roll the processing mass into spherical but porous "granulets" with a drug release propensity higher than physical powder mixture, unprocessed drug and dense pellets prepared using high shear mixer. The fast-release attribute of "granulets" was ascribed to porous matrix formed with a high level of polyethylene glycol as solubilizer. The agglomeration and drug release outcomes of centrifugal air-assisted technology are unmet by the existing high shear and fluid-bed melt agglomeration techniques. Copyright © 2012 Elsevier B.V. All rights reserved.

Light scattering by low-density agglomerates of micron-sized grains with the PROGRA2 experiment

NASA Astrophysics Data System (ADS)

Hadamcik, E.; Renard, J.-B.; Lasue, J.; Levasseur-Regourd, A. C.; Blum, J.; Schraepler, R.

2007-07-01

This work was carried out with the PROGRA2 experiment, specifically developed to measure the angular dependence of the polarization of light scattered by dust particles. The samples are small agglomerates of micron-sized grains and huge, low number density agglomerates of the same grains. The constituent grains (spherical or irregularly shaped) are made of different non-absorbing and absorbing materials. The small agglomerates, in a size range of a few microns, are lifted by an air draught. The huge centimeter-sized agglomerates, produced by random ballistic deposition of the grains, are deposited on a flat surface. The phase curves obtained for monodisperse, micron-sized spheres in agglomerates are obviously not comparable to the ‘smooth’ phase curves obtained by remote observations of cometary dust or asteroidal regoliths but they are used for comparison with numerical calculations to a better understanding of the light scattering processes. The phase curves obtained for irregular grains in agglomerates are similar to those obtained by remote observations, with a negative branch at phase angles smaller than 20° and a maximum polarization decreasing with increasing albedo. These results, coupled with remote observations in the solar system, should provide a better understanding of the physical properties of solid particles and their variation in cometary comae and asteroidal regoliths.

Characterization of Propylene Glycol-Mitigated Freeze/Thaw Agglomeration of a Frozen Liquid nOMV Vaccine Formulation by Static Light Scattering and Micro-Flow Imaging.

PubMed

Mensch, Christopher D; Davis, Harrison B; Blue, Jeffrey T

2015-01-01

The purpose of this work was to investigate the susceptibility of an aluminum adjuvant and an aluminum-adjuvanted native outer membrane vesicle (nOMV) vaccine formulation to freeze/thaw-induced agglomeration using static light scattering and micro-flow Imaging analysis; and to evaluate the use of propylene glycol as a vaccine formulation excipient by which freeze/thaw-induced agglomeration of a nOMV vaccine formulation could be mitigated. Our results indicate that including 7% v/v propylene glycol in an nOMV containing aluminum adjuvanted vaccine formulation, mitigates freeze/thaw-induced agglomeration. We evaluated the effect of freeze-thawing on an aluminum adjuvant and an aluminum adjuvanted native outer membrane vesicle (nOMV) vaccine formulation. Specifically, we characterized the freeze/thaw-induced agglomeration through the use of static light scattering, micro-flow imaging, and cryo-electron microscopy analysis. Further, we evaluated the use of 0-9% v/v propylene glycol as an excipient which could be included in the formulation for the purpose of mitigating the agglomeration induced by freeze/thaw. The results indicate that using 7% v/v propylene glycol as a formulation excipient is effective at mitigating agglomeration of the nOMV vaccine formulation, otherwise induced by freeze-thawing. © PDA, Inc. 2015.

NOVEL BINDERS AND METHODS FOR AGGLOMERATION OF ORE

DOE Office of Scientific and Technical Information (OSTI.GOV)

S.K. Kawatra; T.C. Eisele; J.A. Gurtler

2005-04-01

Many metal extraction operations, such as leaching of copper, leaching of precious metals, and reduction of metal oxides to metal in high-temperature furnaces, require agglomeration of ore to ensure that reactive liquids or gases are evenly distributed throughout the ore being processed. Agglomeration of ore into coarse, porous masses achieves this even distribution of fluids by preventing fine particles from migrating and clogging the spaces and channels between the larger ore particles. Binders are critically necessary to produce agglomerates that will not breakdown during processing. However, for many important metal extraction processes there are no binders known that will workmore » satisfactorily. Primary examples of this are copper heap leaching, where there are no binders that will work in the acidic environment encountered in this process. As a result, operators of many facilities see large loss of process efficiency due to their inability to take advantage of agglomeration. The large quantities of ore that must be handled in metal extraction processes also means that the binder must be inexpensive and useful at low dosages to be economical. The acid-resistant binders and agglomeration procedures developed in this project will also be adapted for use in improving the energy efficiency and performance of a broad range of mineral agglomeration applications, particularly heap leaching.« less

Novel Binders and Methods for Agglomeration of Ore

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. K. Kawatra; T. C. Eisele; J. A. Gurtler

2004-03-31

Many metal extraction operations, such as leaching of copper, leaching of precious metals, and reduction of metal oxides to metal in high-temperature furnaces, require agglomeration of ore to ensure that reactive liquids or gases are evenly distributed throughout the ore being processed. Agglomeration of ore into coarse, porous masses achieves this even distribution of fluids by preventing fine particles from migrating and clogging the spaces and channels between the larger ore particles. Binders are critically necessary to produce agglomerates that will not break down during processing. However, for many important metal extraction processes there are no binders known that willmore » work satisfactorily. A primary example of this is copper heap leaching, where there are no binders that will work in the acidic environment encountered in this process. As a result, operators of acidic heap-leach facilities see a large loss of process efficiency due to their inability to take advantage of agglomeration. The large quantities of ore that must be handled in metal extraction processes also means that the binder must be inexpensive and useful at low dosages to be economical. The acid-resistant binders and agglomeration procedures developed in this project will also be adapted for use in improving the energy efficiency and performance of other agglomeration applications, particularly advanced primary ironmaking.« less

The mechanical properties of nanofilled resin-based composites: characterizing discrete filler particles and agglomerates using a micromanipulation technique.

PubMed

Curtis, Andrew R; Palin, William M; Fleming, Garry J P; Shortall, Adrian C C; Marquis, Peter M

2009-02-01

To assess the mechanical properties of discrete filler particles representative of several inorganic fillers in modern dental resin-based composites (RBCs) and to assess the validity of a novel micromanipulation technique. RBCs with microhybrid (Filtek Z250), 'nanohybrid' (Grandio) and 'nanofilled' (Filtek Supreme), filler particle morphologies were investigated. Filler particles were provided by the manufacturer or separated from the unpolymerized resin using a dissolution technique. Filler particles (n=30) were subjected to compression using a micromanipulation technique between a descending glass probe and a glass slide. The number of distinct fractures particles underwent was determined from force/displacement and stress/deformation curves and the force at fracture and pseudo-modulus of stress was calculated. Agglomerated fillers ('nanoclusters') exhibited up to four distinct fractures, while spheroidal and irregular particles underwent either a single fracture or did not fracture following micromanipulation. Z-tests highlighted failure of nanoclusters to be significant compared with spheroidal and irregular particles (P<0.05). The mean force at first fracture of the nanoclusters was greater (1702+/-909 microN) than spheroidal and irregular particles (1389+/-1342 and 1356+/-1093 microN, respectively). Likewise, the initial pseudo-modulus of stress of nanoclusters (797+/-555 MPa) was also greater than spheroidal (587+/-439 MPa) or irregular (552+/-275 MPa) fillers. The validity of employing the micromanipulation technique to determine the mechanical properties of filler particulates was established. The 'nanoclusters' exhibited a greater tendency to multiple fractures compared with conventional fillers and possessed a comparatively higher variability of pseudo-modulus and load prior to and at fracture, which may modify the damage tolerance of the overall RBC system.

The influence of bacteria on struvite crystal habit and its importance in urinary stone formation

NASA Astrophysics Data System (ADS)

Clapham, L.; McLean, R. J. C.; Nickel, J. C.; Downey, J.; Costerton, J. W.

1990-07-01

Infection-induced urinary stones form as a result of a urinary tract infection by urease-producing bacteria. These stones are not totally crystalline in nature but rather consist of an agglomeration of bacteria, organic matrix, and crystal of struvite (MgNH 4PO 4· 6H 2O). Crystal formation is related to the ability of the bacteria to effect an increase in the urine pH. Another equally important bacterial role lies in their formation of a 'biofilm' which later becomes the organic matrix constituent of the stone. Results of the present in vitro study indicate that crystals are formed more readily if produced within the bacterial biofilm than in the surrounding urine. It is proposed that supersaturation, due in part to a bacterial-induced pH increase and in part to the metal binding tendency of the biofilm, leads to crystal formation via a gel growth mechanism within the biofilm itself. In time further bacterial cell division, microcolony.

Full allogeneic fusion of embryos in a holothuroid echinoderm.

PubMed

Gianasi, Bruno L; Hamel, Jean-François; Mercier, Annie

2018-05-30

Whole-body chimaeras (organisms composed of genetically distinct cells) have been directly observed in modular/colonial organisms (e.g. corals, sponges, ascidians); whereas in unitary deuterostosmes (including mammals) they have only been detected indirectly through molecular analysis. Here, we document for the first time the step-by-step development of whole-body chimaeras in the holothuroid Cucumaria frondosa , a unitary deuterostome belonging to the phylum Echinodermata. To the best of our knowledge, this is the most derived unitary metazoan in which direct investigation of zygote fusibility has been undertaken. Fusion occurred among hatched blastulae, never during earlier (unhatched) or later (larval) stages. The fully fused chimaeric propagules were two to five times larger than non-chimaeric embryos. Fusion was positively correlated with propagule density and facilitated by the natural tendency of early embryos to agglomerate. The discovery of natural chimaerism in a unitary deuterostome that possesses large externally fertilized eggs provides a framework to explore key aspects of evolutionary biology, histocompatibility and cell transplantation in biomedical research. © 2018 The Author(s).

Design of Magnetic Gelatine/Silica Nanocomposites by Nanoemulsification: Encapsulation versus in Situ Growth of Iron Oxide Colloids

PubMed Central

Allouche, Joachim; Chanéac, Corinne; Brayner, Roberta; Boissière, Michel; Coradin, Thibaud

2014-01-01

The design of magnetic nanoparticles by incorporation of iron oxide colloids within gelatine/silica hybrid nanoparticles has been performed for the first time through a nanoemulsion route using the encapsulation of pre-formed magnetite nanocrystals and the in situ precipitation of ferrous/ferric ions. The first method leads to bi-continuous hybrid nanocomposites containing a limited amount of well-dispersed magnetite colloids. In contrast, the second approach allows the formation of gelatine-silica core-shell nanostructures incorporating larger amounts of agglomerated iron oxide colloids. Both magnetic nanocomposites exhibit similar superparamagnetic behaviors. Whereas nanocomposites obtained via an in situ approach show a strong tendency to aggregate in solution, the encapsulation route allows further surface modification of the magnetic nanocomposites, leading to quaternary gold/iron oxide/silica/gelatine nanoparticles. Hence, such a first-time rational combination of nano-emulsion, nanocrystallization and sol-gel chemistry allows the elaboration of multi-component functional nanomaterials. This constitutes a step forward in the design of more complex bio-nanoplatforms. PMID:28344239

Design of Magnetic Gelatine/Silica Nanocomposites by Nanoemulsification: Encapsulation versus in Situ Growth of Iron Oxide Colloids.

PubMed

Allouche, Joachim; Chanéac, Corinne; Brayner, Roberta; Boissière, Michel; Coradin, Thibaud

2014-07-31

The design of magnetic nanoparticles by incorporation of iron oxide colloids within gelatine/silica hybrid nanoparticles has been performed for the first time through a nanoemulsion route using the encapsulation of pre-formed magnetite nanocrystals and the in situ precipitation of ferrous/ferric ions. The first method leads to bi-continuous hybrid nanocomposites containing a limited amount of well-dispersed magnetite colloids. In contrast, the second approach allows the formation of gelatine-silica core-shell nanostructures incorporating larger amounts of agglomerated iron oxide colloids. Both magnetic nanocomposites exhibit similar superparamagnetic behaviors. Whereas nanocomposites obtained via an in situ approach show a strong tendency to aggregate in solution, the encapsulation route allows further surface modification of the magnetic nanocomposites, leading to quaternary gold/iron oxide/silica/gelatine nanoparticles. Hence, such a first-time rational combination of nano-emulsion, nanocrystallization and sol-gel chemistry allows the elaboration of multi-component functional nanomaterials. This constitutes a step forward in the design of more complex bio-nanoplatforms.

"Non-hydrolytic" sol-gel synthesis of molybdenum sulfides

NASA Astrophysics Data System (ADS)

Leidich, Saskia; Buechele, Dominique; Lauenstein, Raphael; Kluenker, Martin; Lind, Cora

2016-10-01

Non-hydrolytic sol-gel reactions provide a low temperature solution based synthetic approach to solid-state materials. In this paper, reactions between molybdenum chloride and hexamethyldisilthiane in chloroform were explored, which gave access to both MoS2 and Mo2S3 after heat treatment of as-recovered amorphous samples to 600-1000 °C. Interesting morphologies were obtained for MoS2, ranging from fused spherical particles to well-defined nanoplatelets and nanoflakes. Both 2H- and 3R-MoS2 were observed, which formed thin hexagonal and triangular platelets, respectively. The platelets exhibited thicknesses of 10-30 nm, which corresponds to 15-50 MoS2 layers. No attempts to prevent agglomeration were made, however, well separated platelets were observed for many samples. Heating at 1000 °C led to formation of Mo2S3 for samples that showed well-defined MoS2 at lower temperatures, while less crystalline samples had a tendency to retain the MoS2 structure.

Dynamics of Lysozyme in a Glycerol-Water system

NASA Astrophysics Data System (ADS)

Ghatty, Pavan; Carri, Gustavo

2007-03-01

Bio-preservation of proteins is of great commercial and academic interest. A variety of sugars have been found to be effective in preserving the structure of proteins. This has been attributed and in some cases proved to their ability to form strong hydrogen bonds with proteins thus restricting their motion. The work presented here explores the hypothesis that glycerol, a tri-alcohol curbs the motion of protein. We have carried out a 10ns Molecular Dynamics simulation to study the phenomenon. The structure of Lysozyme (PDB code 193L) has been studied in three solutions of 10, 20 and 30 % by weight of glycerol in water. Glycerol molecules in all three solutions have shown a tendency to agglomerate around the protein. Strong hydrogen bonding has also been observed between glycerol molecules and the protein. With increasing time, the g(r) of glycerol molecules around proteins shows two peaks with increasing prominence suggesting the movement of glycerol cluster to positions closer to the protein surface.

A Critical Study of Agglomerated Multigrid Methods for Diffusion

NASA Technical Reports Server (NTRS)

Nishikawa, Hiroaki; Diskin, Boris; Thomas, James L.

2011-01-01

Agglomerated multigrid techniques used in unstructured-grid methods are studied critically for a model problem representative of laminar diffusion in the incompressible limit. The studied target-grid discretizations and discretizations used on agglomerated grids are typical of current node-centered formulations. Agglomerated multigrid convergence rates are presented using a range of two- and three-dimensional randomly perturbed unstructured grids for simple geometries with isotropic and stretched grids. Two agglomeration techniques are used within an overall topology-preserving agglomeration framework. The results show that multigrid with an inconsistent coarse-grid scheme using only the edge terms (also referred to in the literature as a thin-layer formulation) provides considerable speedup over single-grid methods but its convergence deteriorates on finer grids. Multigrid with a Galerkin coarse-grid discretization using piecewise-constant prolongation and a heuristic correction factor is slower and also grid-dependent. In contrast, grid-independent convergence rates are demonstrated for multigrid with consistent coarse-grid discretizations. Convergence rates of multigrid cycles are verified with quantitative analysis methods in which parts of the two-grid cycle are replaced by their idealized counterparts.

A Critical Study of Agglomerated Multigrid Methods for Diffusion

NASA Technical Reports Server (NTRS)

Thomas, James L.; Nishikawa, Hiroaki; Diskin, Boris

2009-01-01

Agglomerated multigrid techniques used in unstructured-grid methods are studied critically for a model problem representative of laminar diffusion in the incompressible limit. The studied target-grid discretizations and discretizations used on agglomerated grids are typical of current node-centered formulations. Agglomerated multigrid convergence rates are presented using a range of two- and three-dimensional randomly perturbed unstructured grids for simple geometries with isotropic and highly stretched grids. Two agglomeration techniques are used within an overall topology-preserving agglomeration framework. The results show that multigrid with an inconsistent coarse-grid scheme using only the edge terms (also referred to in the literature as a thin-layer formulation) provides considerable speedup over single-grid methods but its convergence deteriorates on finer grids. Multigrid with a Galerkin coarse-grid discretization using piecewise-constant prolongation and a heuristic correction factor is slower and also grid-dependent. In contrast, grid-independent convergence rates are demonstrated for multigrid with consistent coarse-grid discretizations. Actual cycle results are verified using quantitative analysis methods in which parts of the cycle are replaced by their idealized counterparts.

Friction Stir Welding of Al Alloy 2219-T8: Part II-Mechanical and Corrosion

NASA Astrophysics Data System (ADS)

Kang, Ju; Feng, Zhi-Cao; Li, Ji-Chao; Frankel, G. S.; Wang, Guo-Qing; Wu, Ai-Ping

2016-09-01

In Part I of this series, abnormal agglomerations of θ particles with size of about 100 to 1000 µm were observed in friction stir welded AA2219-T8 joints. In this work, the effects of these agglomerated θ particles on the mechanical and corrosion properties of the joints are studied. Tensile testing with in situ SEM imaging was utilized to monitor crack initiation and propagation in base metal and weld nugget zone (WNZ) samples. These tests showed that cracks initiated in the θ particles and at the θ/matrix interfaces, but not in the matrix. The WNZ samples containing abnormal agglomerated θ particles had a similar ultimate tensile stress but 3 pct less elongation than other WNZ samples with only normal θ particles. Measurements using the microcell technique indicated that the agglomerated θ particles acted as a cathode causing the dissolution of adjacent matrix. The abnormal θ particle agglomerations led to more severe localized attack due to the large cathode/anode ratio. Al preferential dissolution occurred in the abnormal θ particle agglomerations, which was different from the corrosion behavior of normal size θ particles.

Recovery of hazardous semiconductor-industry sludge as a useful resource.

PubMed

Lee, Tzen-Chin; Liu, Feng-Jiin

2009-06-15

Sludge, a solid waste recovered from wastewater of semiconductor-industries composes of agglomerates of nano-particles like SiO(2) and CaF(2). This sludge deflocculates in acidic and alkaline aqueous solutions into nano-particles smaller than 100 nm. Thus, this sludge is potentially hazardous to water resources when improperly dumped. It can cause considerable air-pollution when fed into rotary-kilns as a raw material for cement production. In this study, dried and pulverized sludge was used to replace 5-20 wt.% Portland cement in cement mortar. The compressive strength of the modified mortar was higher than that of plain cement mortar after curing for 3 days and more. In particular, the strength of mortar with 10 wt.% substitution improved by 25-35% after curing for 7-90 days. TCLP studies reveal no detectable release of heavy metals. Preliminary studies showed that nano-particles deflocculated from the sludge, when cured for up to 3 days retain in the modified mortar their nano-size, which become large-sized hydration compounds that contribute to the final mortar strength. Semiconductor sludge can thus be utilized as a useful resource to replace portion of cement in cement mortar, thereby avoiding their potential hazard on the environment.

Structure, mechanical and thermal behaviour of mixtures of polyester resin and dental ceramic waste

NASA Astrophysics Data System (ADS)

Peña Rodríguez, G.; Martínez Maldonado, L.; Dulce Moreno, H. J.

2016-02-01

The tensile strength and bending strength, structure and thermal behaviour of mixtures of polyester resin (P-2000) and powders (ASTM sieve 200, <75μm) of dental ceramic wastes (dentals impressions, alginate and gypsum) was reported. The samples consisted of mixtures with percentage weights of 50-50%, 60-40%, 70-30%, 80-20%, 90-10%, where the resin was the majority phase, the Mekc (4% wt) was used as catalyst. The structure was studied using SEM and XRD, the thermal behaviour using DSC, TGA and DMA, while the mechanical strength was tested using standards ASTM D790 and D638. Irregular morphology and presence of small agglomerations was observed, with particle sizes between 29.63 and 38.67μm, the presence of different phases of calcium sulphate was found, and that to the increasing the concentration of the powder, the materials becomes more crystalline, increasing its density. An average service temperature of 69.15±4.60°C was found. Vickers hardness values are reported in ranges from 18.65 to 27.96. Considering the elastic modules was established that the materials become more rigid by having more powder concentration.

Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials

NASA Astrophysics Data System (ADS)

Herbold, E. B.; Nesterenko, V. F.; Benson, D. J.; Cai, J.; Vecchio, K. S.; Jiang, F.; Addiss, J. W.; Walley, S. M.; Proud, W. G.

2008-11-01

The variation of metallic particle size and sample porosity significantly alters the dynamic mechanical properties of high density granular composite materials processed using a cold isostatically pressed mixture of polytetrafluoroethylene (PTFE), aluminum (Al), and tungsten (W) powders. Quasistatic and dynamic experiments are performed with identical constituent mass fractions with variations in the size of the W particles and pressing conditions. The relatively weak polymer matrix allows the strength and fracture modes of this material to be governed by the granular type behavior of agglomerated metal particles. A higher ultimate compressive strength was observed in relatively high porosity samples with small W particles compared to those with coarse W particles in all experiments. Mesoscale granular force chains of the metallic particles explain this unusual phenomenon as observed in hydrocode simulations of a drop-weight test. Macrocracks forming below the critical failure strain for the matrix and unusual behavior due to a competition between densification and fracture in dynamic tests of porous samples were also observed. Numerical modeling of shock loading of this granular composite material demonstrated that the internal energy, specifically thermal energy, of the soft PTFE matrix can be tailored by the W particle size distribution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liuyun, Jiang, E-mail: jlytxg@163.com; Chengdong, Xiong; Lixin, Jiang

Graphical abstract: Effect of n-HA content on the isothermal crystallization, morphology and mechanical property of n-HA/PLGA composites was studied in details. The results showed that the addition of higher content of g-n-HA was favorable to promote the crystallization better in g-n-HA/PLGA composites, but it could also cause more agglomeration in PLGA matrix, as a result of worse mechanical properties, and the addition content of 3 wt% g-n-HA to PLGA matrix was an appropriate proportion, which had the highest bending strength among these g-n-HA/PLGA composites, and it might be potential to be used in biomedical fields in future. Highlights: ► Themore » effect of n-HA content on the n-HA/PLGA composites was studied in detail. ► Isothermal crystallization, microstructure and mechanical property were studied. ► The relation between n-HA content and properties of n-HA/PLGA composite was found. ► An appropriate proportion of n-HA in n-HA/PLGA composite was obtained. - Abstract: A serials of g-n-HA/PLGA composites with surface-modified g-n-HA of 1%, 3%, 6%, 10% and 15% in weight were prepared by solution mixing. The isothermal crystallization, morphology and mechanical property of g-n-HA/PLGA composites were investigated by differential scanning calorimeter (DSC), scanning electron microscope (SEM) and electromechanical universal tester. The results showed that Avrami equation was suitable for describing the isothermal crystallization process in this system, and the crystallization rate of g-n-HA/PLGA composites containing more than 3 wt% g-n-HA was basically accord with the relational expression of T{sub 110} {sub °C} > T{sub 105°C} > T{sub 115°C} > T{sub 120°C}. Moreover, at the same Tc, crystallization rate was greatly enhanced with the increasing of g-n-HA acting as nucleate. However, the addition of higher content of g-n-HA would cause more agglomeration in PLGA matrix, so that the mechanical properties of g-n-HA/PLGA composites would gradually decrease. In conclusion, the addition of higher content of g-n-HA was favorable to promote the crystallization better in g-n-HA/PLGA composites, but it could also cause more agglomeration in PLGA matrix, result in worse mechanical properties, and the addition content of 3 wt% g-n-HA to PLGA matrix was an appropriate proportion, which had the highest bending strength among these g-n-HA/PLGA composites, and it might be potential to be used in biomedical fields in future.« less

Dynamic forces on agglomerated particles caused by high-intensity ultrasound.

PubMed

Knoop, Claas; Fritsching, Udo

2014-03-01

In this paper the acoustic forces on particles and agglomerates caused by high-intensity ultrasound in gaseous atmosphere are derived by means of computational fluid dynamics (CFD). Sound induced forces cause an oscillating stress scenario where the primary particles of an agglomerate are alternatingly pressed together and torn apart with the frequency of the applied wave. A comparison of the calculated acoustic forces with respect to the inter particle adhesion forces from Van-der-Waals and liquid bridge interactions reveals that the separation forces may reach the same order of magnitude for 80 μm sized SiO2-particles. Hence, with finite probability acoustically agitated gases may de-agglomerate/disperse solid agglomerate structures. This effect is confirmed by dispersion experiments in an acoustic particle levitation setup. Copyright © 2013 Elsevier B.V. All rights reserved.

Cost-effectiveness of conservation payment schemes for species with different range sizes.

PubMed

Drechsler, Martin; Smith, Henrik G; Sturm, Astrid; Wätzold, Frank

2016-08-01

Payments to compensate landowners for carrying out costly land-use measures that benefit endangered biodiversity have become an important policy instrument. When designing such payments, it is important to take into account that spatially connected habitats are more valuable for many species than isolated ones. One way to incentivize provision of connected habitats is to offer landowners an agglomeration bonus, that is, a bonus on top of payments they are receiving to conserve land if the land is spatially connected. Researchers have compared the cost-effectiveness of the agglomeration bonus with 2 alternatives: an all-or-nothing, agglomeration payment, where landowners receive a payment only if the conserved land parcels have a certain level of spatial connectivity, and a spatially homogeneous payment, where landowners receive a payment for conserved land parcels irrespective of their location. Their results show the agglomeration bonus is rarely the most cost-effective option, and when it is, it is only slightly better than one of the alternatives. This suggests that the agglomeration bonus should not be given priority as a policy design option. However, this finding is based on consideration of only 1 species. We examined whether the same applied to 2 species, one for which the homogeneous payment is best and the other for which the agglomeration payment is most cost-effective. We modified a published conceptual model so that we were able to assess the cost-effectiveness of payment schemes for 2 species and applied it to a grassland bird and a grassland butterfly in Germany that require the same habitat but have different spatial-connectivity needs. When conserving both species, the agglomeration bonus was more cost-effective than the agglomeration and the homogeneous payment; thus, we showed that as a policy the agglomeration bonus is a useful conservation-payment option. © 2016 Society for Conservation Biology.

Microstructure, mechanical and tribological performance of hybrid A359/(SiC  +  Si3N4) composites for automotive applications

NASA Astrophysics Data System (ADS)

Shalaby, Essam A. M.; Churyumov, Alexander Yu

2017-11-01

In this study, microstructure analysis, yield strength at high temperatures and wear rate of hybrid A359/(SiC  +  Si3N4) composites were investigated. Different weight percent of (SiC  +  Si3N4) particles were introduced to synthesis the composites using stir/squeeze process. XRD, SEM, TEM and EDS were utilized to investigate the distribution of particles throughout the matrix, and the interfacial reaction at matrix/particle interface. It confirmed the existence of MgAl2O4 which enhances the wettability between the particles and the matrix, and the absence of particle agglomeration. The (SiC  +  Si3N4) addition not only enhances the hardness measurements but also leads to a reduction in the dendritic arm spacing (DAS). Moreover, it develops the wear performance and the yield strength at high temperatures. The developed composites provide a promising material suitable for automotive industries.

Improved silicon nitride for advanced heat engines

NASA Technical Reports Server (NTRS)

Yeh, H. C.; Wimmer, J. M.; Huang, H. H.; Rorabaugh, M. E.; Schienle, J.; Styhr, K. H.

1985-01-01

The AiResearch Casting Company baseline silicon nitride (92 percent GTE SN-502 Si sub 3 N sub 4 plus 6 percent Y sub 2 O sub 3 plus 2 percent Al sub 2 O sub 3) was characterized with methods that included chemical analysis, oxygen content determination, electrophoresis, particle size distribution analysis, surface area determination, and analysis of the degree of agglomeration and maximum particle size of elutriated powder. Test bars were injection molded and processed through sintering at 0.68 MPa (100 psi) of nitrogen. The as-sintered test bars were evaluated by X-ray phase analysis, room and elevated temperature modulus of rupture strength, Weibull modulus, stress rupture, strength after oxidation, fracture origins, microstructure, and density from quantities of samples sufficiently large to generate statistically valid results. A series of small test matrices were conducted to study the effects and interactions of processing parameters which included raw materials, binder systems, binder removal cycles, injection molding temperatures, particle size distribution, sintering additives, and sintering cycle parameters.

Electrostatic formation of liquid marbles and agglomerates

NASA Astrophysics Data System (ADS)

Liyanaarachchi, K. R.; Ireland, P. M.; Webber, G. B.; Galvin, K. P.

2013-07-01

We report observations of a sudden, explosive release of electrostatically charged 100 μm glass beads from a particle bed. These cross an air gap of several millimeters, are engulfed by an approaching pendant water drop, and form a metastable spherical agglomerate on the bed surface. The stability transition of the particle bed is explained by promotion of internal friction by in-plane electrostatic stresses. The novel agglomerates formed this way resemble the "liquid marbles" formed by coating a drop with hydrophobic particles. Complex multi-layered agglomerates may also be produced by this method, with potential industrial, pharmaceutical, environmental, and biological applications.

Experiment Investigation of the Influencing Factors on Bed Agglomeration During Fluidized-Bed Gasification of Biomass Fuels

NASA Astrophysics Data System (ADS)

Chen, Y. Q.; Chen, H. P.; Yang, H. P.; Wang, X. H.; Zhang, S. H.

With the depleting of fossil fuel and environmental polluting increasing, the utilization of biomass resources caught increasing concern. Biomass gasification in fluidized bed, as one promising technology, developed quickly. However, serious agglomeration was displayed as biomass ash reacted with bed material (silica sand) at higher temperature. It hindered the wide utilization of CFB gasifier. The objective ofthis work is to investigate the agglomeration behavior between biomass ash and silica sand, and catch the inherent mechanism. Firstly, the influence of ash compounds on the agglomeration behavior was analyzed with biomass ash and synthesis ash compounds addition in fixed bed as ash sample mixed with bed material evenly before every trial. The reaction temperature was set 850°C that is the operated temperature for many fluidized bed gasificated biomass fuels. Then the influence of reaction time was analyzed. The characteristics of the agglomerated silica sand particles were analyzed by the XRD. Finally, it was simulated with HSC computer mode based on thermodynamic equilibrium. It was observed that when the ratio of the biomass ash to the silica sand was above 0.2, the agglomeration was observed. With the increase of the reaction time, more silica sand particles agglomerated with the biomass ash. There are two kinds of silicate eutecticum investigated by the XRD. It is of great significance for the running ofCFB biomass gasifier and the development ofbiomass utilization technology.

Mechanical particle coating using polymethacrylate nanoparticle agglomerates for the preparation of controlled release fine particles: The relationship between coating performance and the characteristics of various polymethacrylates.

PubMed

Kondo, Keita; Kato, Shinsuke; Niwa, Toshiyuki

2017-10-30

We aimed to understand the factors controlling mechanical particle coating using polymethacrylate. The relationship between coating performance and the characteristics of polymethacrylate powders was investigated. First, theophylline crystals were treated using a mechanical powder processor to obtain theophylline spheres (<100μm). Second, five polymethacrylate latexes were powdered by spray freeze drying to produce colloidal agglomerates. Finally, mechanical particle coating was performed by mixing theophylline spheres and polymethacrylate agglomerates using the processor. The agglomerates were broken under mechanical stress to coat the spheres effectively. The coating performance of polymethacrylate agglomerates tended to increase as their pulverization progressed. Differences in the grindability of the agglomerates were attributed to differences in particle structure, resulting from consolidation between colloidal particles. High-grindability agglomerates exhibited higher pulverization as their glass transition temperature (T g ) increased and the further pulverization promoted coating. We therefore conclude that the minimization of polymethacrylate powder by pulverization is an important factor in mechanical particle coating using polymethacrylate with low deformability. Meanwhile, when product temperature during coating approaches T g of polymer, polymethacrylate was soften to show high coating performance by plastic deformation. The effective coating by this mechanism may be accomplished by adjusting the temperature in the processor to the T g . Copyright © 2017 Elsevier B.V. All rights reserved.

The Heavy Metal Subculture and Suicide.

ERIC Educational Resources Information Center

Stack, Steven; And Others

1994-01-01

Assessed relationship between heavy metal music and suicide with data on heavy metal magazine subscriptions and youth suicide in 50 states. Found that, controlling for other predictors of suicide, greater strength of metal subculture, higher youth suicide rate, suggests that music perhaps nurtures suicidal tendencies already present in subculture.…

Change in fibrinolytic activity under the influence of a constant magnetic field. [blood coagulation normilization in heart patients

NASA Technical Reports Server (NTRS)

Yepishina, S. G.

1974-01-01

The fibrinolytic activity of plasma changes under the influence of a constant magnetic field (CMF) with a strength of 250 or 2500 oersteds. CMF shows a tendency toward normalization of fibrinolytic processes in the presence of pathological disturbances in fibrinolysis activation.

Science Lives: School Choices and "Natural Tendencies"

ERIC Educational Resources Information Center

Salehjee, Saima; Watts, Mike

2015-01-01

An analysis of 12 semi-structured interviews with university-based scientists and non-scientists illustrates their life journeys towards, or away from, science and the strengths and impact of life occurrences leading them to choose science or non-science professions. We have adopted narrative approaches and used Mezirow's transformative learning…

Through Technology Leverage and Risk Avoidance

ERIC Educational Resources Information Center

Sugasawa, Yoshio; Shinomiya, Takeshi

2010-01-01

Companies make concerted efforts to survive in a radically changing global society with the advent of a highly-networked and information-rich society that is featured by intense market competition. Manufacturing industries in particular have a tendency to rely on technological development strengths as a means of survival in a highly globalised and…

Method of separating and de-watering fine particles

DOEpatents

Yoon, Roe-Hoan

2016-12-13

A process for cleaning and dewatering hydrophobic particulate materials is presented. The process is performed in two steps: 1) agglomeration of the hydrophobic particles in a first hydrophobic liquid/aqueous mixture; followed by 2) dispersion of the agglomerates in a second hydrophobic liquid to release the water trapped within the agglomerates along with the entrained hydrophilic particles.

Overpopulated, Underdeveloped Urban Agglomerations: Tomorrow’s Unstable Operating Environment

DTIC Science & Technology

2012-05-08

DATES COVERED (From - To) 4. TITLE AND SUBTITLE Overpopulated , Underdeveloped Urban Agglomerations: Tomorrow’s 5a. CONTRACT NUMBER...ABSTRACT This paper asserts that a unique future operational environment is developing: overpopulated , underdeveloped urban agglomerations. A...proposed definition for this operating environment is (or would be) an overpopulated urban area which is located within a developing or underdeveloped

High strength yttria-reinforced HA scaffolds fabricated via honeycomb ceramic extrusion.

PubMed

Elbadawi, M; Shbeh, M

2018-01-01

The present study investigated the effects of hydroxyapatite (HA) reinforced with yttria on porous scaffolds fabricated via honeycomb ceramic extrusion. Yttria was selected as it has been demonstrated to toughen other ceramics. Moreover, yttria has been surmised to suppress dehydroxylation in HA, a characteristic that prefigures decomposition thereof during sintering into mechanically weaker phases. However, the compressive strength of yttria-reinforced hydroxyapatite (Y-HA) porous scaffolds has hitherto not been reported. Y-HA was synthesised by calcining a commercially available HA with 10wt% yttria at 1000°C. Y-HA was then fabricated into porous scaffolds using an in-house honeycomb extruder, and subsequently sintered at 1200 and 1250°C. The results were compared to the uncalcined as-received commercial powder (AR-HA) and calcined pure HA powder at 1000°C (C-HA). It was discovered that calcination alone caused marked improvements to the stoichiometry, thermal stability, porosity and compressive strength of scaffolds. The improvements were ascribed to the calcined powders with less susceptibility to both agglomeration and enhanced densification. Still, differences were observed between C-HA and Y-HA at 1250°C. The compressive strength increased from 105.9 to 127.3MPa, a larger microporosity was descried and the HA matrix in Y-HA was more stoichiometric. The latter was confirmed by XRD and EDS analyses. Therefore, it was concluded that the reinforcing of hydroxyapatite with yttria improved the compressive strength and suppressed dehydroxylation of porous HA scaffolds. In addition, the compressive strength achieved demonstrated great potential for load-bearing application. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dielectric breakdown in silica-amorphous polymer nanocomposite films: the role of the polymer matrix.

PubMed

Grabowski, Christopher A; Fillery, Scott P; Westing, Nicholas M; Chi, Changzai; Meth, Jeffrey S; Durstock, Michael F; Vaia, Richard A

2013-06-26

The ultimate energy storage performance of an electrostatic capacitor is determined by the dielectric characteristics of the material separating its conductive electrodes. Polymers are commonly employed due to their processability and high breakdown strength; however, demands for higher energy storage have encouraged investigations of ceramic-polymer composites. Maintaining dielectric strength, and thus minimizing flaw size and heterogeneities, has focused development toward nanocomposite (NC) films; but results lack consistency, potentially due to variations in polymer purity, nanoparticle surface treatments, nanoparticle size, and film morphology. To experimentally establish the dominant factors in broad structure-performance relationships, we compare the dielectric properties for four high-purity amorphous polymer films (polymethyl methacrylate, polystyrene, polyimide, and poly-4-vinylpyridine) incorporating uniformly dispersed silica colloids (up to 45% v/v). Factors known to contribute to premature breakdown-field exclusion and agglomeration-have been mitigated in this experiment to focus on what impact the polymer and polymer-nanoparticle interactions have on breakdown. Our findings indicate that adding colloidal silica to higher breakdown strength amorphous polymers (polymethyl methacrylate and polyimide) causes a reduction in dielectric strength as compared to the neat polymer. Alternatively, low breakdown strength amorphous polymers (poly-4-vinylpyridine and especially polystyrene) with comparable silica dispersion show similar or even improved breakdown strength for 7.5-15% v/v silica. At ∼15% v/v or greater silica content, all the polymer NC films exhibit breakdown at similar electric fields, implying that at these loadings failure becomes independent of polymer matrix and is dominated by silica.

Compression Properties and Electrical Conductivity of In-Situ 20 vol.% Nano-Sized TiCx/Cu Composites with Different Particle Size and Morphology

PubMed Central

Zhang, Dongdong; Bai, Fang; Sun, Liping; Wang, Yong; Wang, Jinguo

2017-01-01

The compression properties and electrical conductivity of in-situ 20 vol.% nano-sized TiCx/Cu composites fabricated via combustion synthesis and hot press in Cu-Ti-CNTs system at various particles size and morphology were investigated. Cubic-TiCx/Cu composite had higher ultimate compression strength (σUCS), yield strength (σ0.2), and electric conductivity, compared with those of spherical-TiCx/Cu composite. The σUCS, σ0.2, and electrical conductivity of cubic-TiCx/Cu composite increased by 4.37%, 20.7%, and 17.8% compared with those of spherical-TiCx/Cu composite (526 MPa, 183 MPa, and 55.6% International Annealed Copper Standard, IACS). Spherical-TiCx/Cu composite with average particle size of ~94 nm exhibited higher ultimate compression strength, yield strength, and electrical conductivity compared with those of spherical-TiCx/Cu composite with 46 nm in size. The σUCS, σ0.2, and electrical conductivity of spherical-TiCx/Cu composite with average size of ~94 nm in size increased by 17.8%, 33.9%, and 62.5% compared with those of spherical-TiCx/Cu composite (417 MPa, 121 MPa, and 40.3% IACS) with particle size of 49 nm, respectively. Cubic-shaped TiCx particles with sharp corners and edges led to stress/strain localization, which enhanced the compression strength of the composites. The agglomeration of spherical-TiCx particles with small size led to the compression strength reduction of the composites. PMID:28772859

Effect of the aggregate morphology on the dispersability of MWCNTs in polymer melts

NASA Astrophysics Data System (ADS)

de Luna, M. Salzano; Tito, A.; Citterio, A.; Mazzocchia, C.; Acierno, D.; Filippone, G.

2012-07-01

Polystyrene nanocomposites filled with multi-walled carbon nanotubes have been prepared through a masterbatch melt mixing method and subjected to morphological, rheological and dielectrical analyses. The role of the structure of the initial aggregates has been investigated by comparing commercially available and synthesized MWCNTs prepared through fluidized bed chemical vapor deposition method and purified through a scalable one-pot route. Electron microscopy analyses reveal a less compact structure of the synthesized particles, in which the nanotubes are arranged in less entangled bundles. This reduces the strength of the initial agglomerates, thus enhancing their dispersability inside the host polymer by means of melt compounding as confirmed by both rheological and dielectrical measurements.

Morphological characteristics of mechanochemically synthesized Fe/Ti composites

NASA Astrophysics Data System (ADS)

Grigor'eva, T. F.; Kovaleva, S. A.; Kiseleva, T. Yu.; Vosmerikov, S. V.; Devyatkina, E. T.; Pastukhov, E. A.; Lyakhov, N. Z.

2016-08-01

The joint mechanical activation of chemically interacting iron and titanium has been studied by X-ray diffraction and atomic force microscopy. It is shown that chemically interacting metals Fe and Ti do not form any intermetallic compounds or solid solutions upon intense mechanical activation in a high-energy planetary mill. The products of mechanical activation are Fe/Ti mechanocomposites, in which titanium is distributed over the iron grain surface. An increase in the mechanical activation time leads to the agglomeration of powders and the formation of particles with a wide size range (5-25 μm). The iron crystallite sizes and the level of microstresses are reduced, indicating a decrease in the particle strength.

Degradation Mechanisms in Solid-Oxide Fuel and Electrolyzer Cells: Analytical Description of Nickel Agglomeration in a Ni /Y S Z Electrode

NASA Astrophysics Data System (ADS)

Kröll, L.; de Haart, L. G. J.; Vinke, I.; Eichel, R.-A.

2017-04-01

The microstructural evolution of a porous electrode consisting of a metal-ceramic matrix, consisting of nickel and yttria-stabilized zirconia (Y S Z ), is one of the main degradation mechanisms in a solid-oxide cell (SOC), in either fuel cell or electrolyzer mode. In that respect, the agglomeration of nickel particles in a SOC electrode leads to a decrease in the electronic conductivity as well as in the active catalytic area for the oxidation-reduction reaction of the fuel-water steam. An analytical model of the agglomeration behavior of a Ni /Y S Z electrode is proposed that allows for a quantitative description of the nickel agglomeration. The accuracy of the model is validated in terms of a comparison with experimental degradation measurements. The model is based on contact probabilities of nickel clusters in a porous network of nickel and Y S Z , derived from an algorithm of the agglomeration process. The iterative algorithm is converted into an analytical function, which involves structural parameters of the electrode, such as the porosity and the nickel content. Furthermore, to describe the agglomeration mechanism, the influence of the steam content and the flux rate are taken into account via reactions on the nickel surface. In the next step, the developed agglomeration model is combined with the mechanism of the Ostwald ripening. The calculated grain-size growth is compared to measurements at different temperatures and under low flux rates and low steam content, as well as under high flux rates and high steam content. The results confirm the necessity of connecting the two mechanisms and clarify the circumstances in which the single processes occur and how they contribute to the total agglomeration of the particles in the electrode.

Explore the influence of agglomeration on electrochemical performance of an amorphous MnO2/C composite by controlling drying process

NASA Astrophysics Data System (ADS)

Cui, Mangwei; Kang, Litao; Shi, Mingjie; Xie, Lingli; Wang, Xiaomin; Zhao, Zhe; Yun, Shan; Liang, Wei

2017-09-01

Amorphous MnO2/C composite is prepared by a facile redox reaction between potassium permanganate (KMnO4) and commercial black pen ink. Afterwards, two different drying processes, air drying or freeze drying, are employed to adjust the agglomeration state of particles in samples and explore its influence on capacitive performance. Experimental results indicate that the air-dried sample demonstrates much better cycling stability than the freeze-dried one (capacity retention at 5000 cycles: 70.9 vs. 60.7%), probably because of the relatively strong agglomeration between particles in this sample. Nevertheless, strong agglomeration seems to deteriorate the specific capacitance (from 492 down to 440.5 F/g at 1 A/g) due to the decrease of porosity and specific surface area. This study suggests that agglomeration of primary particles plays an important role to balance the specific capacitance and cycling stability for electrode materials.

Investigation of Kevlar fabric-based materials for use with inflatable structures

NASA Technical Reports Server (NTRS)

Niccum, R. J.; Munson, J. B.; Rueter, L. L.

1977-01-01

Design, manufacture and testing of laminated and coated composite materials incorporating a structural matrix of Kevlar are reported. The practicality of using Kevlar in aerostat materials is demonstrated, and data are provided on practical weaves, lamination and coating particulars, rigidity, strength, weight, elastic coefficients, abrasion resistance, crease effects, peel strength, blocking tendencies, helium permeability, and fabrication techniques. Properties of the Kevlar-based materials are compared with conventional Dacron-reinforced counterparts. A comprehensive test and qualification program is discussed, and considerable quantitative biaxial tensile and shear test data are provided.

Improved silicon carbide for advanced heat engines

NASA Technical Reports Server (NTRS)

Whalen, T. J.; Winterbottom, W. L.

1986-01-01

Work performed to develop silicon carbide materials of high strength and to form components of complex shape and high reliability is described. A beta-SiC powder and binder system was adapted to the injection molding process and procedures and process parameters developed capable of providing a sintered silicon carbide material with improved properties. The initial effort has been to characterize the baseline precursor materials (beta silicon carbide powder and boron and carbon sintering aids), develop mixing and injection molding procedures for fabricating test bars, and characterize the properties of the sintered materials. Parallel studies of various mixing, dewaxing, and sintering procedures have been carried out in order to distinguish process routes for improving material properties. A total of 276 MOR bars of the baseline material have been molded, and 122 bars have been fully processed to a sinter density of approximately 95 percent. The material has a mean MOR room temperature strength of 43.31 ksi (299 MPa), a Weibull characteristic strength of 45.8 ksi (315 MPa), and a Weibull modulus of 8.0. Mean values of the MOR strengths at 1000, 1200, and 14000 C are 41.4, 43.2, and 47.2 ksi, respectively. Strength controlling flaws in this material were found to consist of regions of high porosity and were attributed to agglomerates originating in the initial mixing procedures. The mean stress rupture lift at 1400 C of five samples tested at 172 MPa (25 ksi) stress was 62 hours and at 207 MPa (30 ksi) stress was 14 hours. New fluid mixing techniques have been developed which significantly reduce flaw size and improve the strength of the material. Initial MOR tests indicate the strength of the fluid-mixed material exceeds the baseline property by more than 33 percent.

Calcium silicate cement sorbent for H/sub 2/S removal and improved gasification processes. Annual progress report, October 1, 1981-September 30, 1982

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, H.J.; Steinberg, M.

1982-10-01

Commercial calcium silicate bearing Portland cement type III (PC III), in the form of agglomerated cement sorbent (ACS) pellets, is being investigated for in-situ desulfurization of fuel gases and for improved coal gasification. The preparation procedure and conditions for pelletizing agglomerated cement sorbent (ACS) by a low energy, low cost agglomeration technique have been modified using a two-stage pelletization procedure, which yields ACS pellets of greater mechanical strength. A 40 mm ID bench scale fluidized bed gasifier (FBG) was used to determine sulfur removal efficiency of ACS pellets as well as their attrition resistance, using a simulated gas mixture. Thesemore » tests show that 90% or more of the sulfur removal from the gas is achieved until 35% of the ACS pellet is sulfidated and that it has excellent attrition resistance (less than 0.1% wt loss) during cyclic tests excluding the first conditioning cycle. The gasification of coal by partial oxidation with air to low Btu gas was conducted in a 1-inch bench scale FBG unit by our collaborator, the Foster Wheeler Corporation (FWC). At temperatures between 800/sup 0/C and 950/sup 0/C the efficiency of coal gasification is improved by as much as 40% when ACS pellets are used compared to the use of Greer limestone. At the same time the sulfur removal efficiency is increased from 50 to 65% with Greer limestone to over 95% with the ACS pellets. The test on sulfur fixation characteristics of the sorbent in the 1-inch FBG unit using a simulated gas also shows that the ACS pellet is much more reactive toward H/sub 2/S than Greer limestone. The ability of ACS pellets to simultaneously desulfurize and improve the gasification efficiency of coal in FBG justifies further investigation.« less

Scale effects on the transverse tensile strength of graphite epoxy composites

NASA Technical Reports Server (NTRS)

Obrien, T. Kevin; Salpekar, Satish A.

1992-01-01

The influence of material volume on the transverse tensile strength of AS4/3501-6 graphite epoxy composites was investigated. Tensile tests of 90 degree laminates with 3 different widths and 5 different thicknesses were conducted. A finite element analysis was performed to determine the influence of the grip on the stress distribution in the coupons and explain the tendency for the distribution of failure locations to be skewed toward the grip. Specimens were instrumented with strain gages and extensometers to insure good alignment and to measure failure strains. Data indicated that matrix dominated strength properties varied with the volume of material that was stressed, with the strength decreasing as volume increased. Transverse strength data were used in a volumetric scaling law based on Weibull statistics to predict the strength of 90 degree laminates loaded in three point bending. Comparisons were also made between transverse strength measurements and out-of-plane interlaminar tensile strength measurements from curved beam bending tests. The significance of observed scale effects on the use of tests for material screening, quality assurance, and design allowables is discussed.

Engineering development of selective agglomeration: Task 5, Bench- scale process testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1991-09-01

Under the overall objectives of DOE Contract ``Engineering Development of Selective Agglomeration,`` there were a number of specific objectives in the Task 5 program. The prime objectives of Task 5 are highlighted below: (1) Maximize process performance in pyritic sulfur rejection and BTU recovery, (2) Produce a low ash product, (3) Compare the performance of the heavy agglomerant process based on diesel and the light agglomerant process using heptane, (4) Define optimum processing conditions for engineering design, (5) Provide first-level evaluation of product handleability, and (6) Explore and investigate process options/ideas which may enhance process performance and/or product handleability.

Engineering development of selective agglomeration: Task 5, Bench- scale process testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1991-09-01

Under the overall objectives of DOE Contract Engineering Development of Selective Agglomeration,'' there were a number of specific objectives in the Task 5 program. The prime objectives of Task 5 are highlighted below: (1) Maximize process performance in pyritic sulfur rejection and BTU recovery, (2) Produce a low ash product, (3) Compare the performance of the heavy agglomerant process based on diesel and the light agglomerant process using heptane, (4) Define optimum processing conditions for engineering design, (5) Provide first-level evaluation of product handleability, and (6) Explore and investigate process options/ideas which may enhance process performance and/or product handleability.

Process and apparatus for coal hydrogenation

DOEpatents

Ruether, John A.; Simpson, Theodore B.

1991-01-01

In a coal liquefaction process an aqueous slurry of coal is prepared containing a dissolved liquefaction catalyst. A small quantity of oil is added to the slurry and then coal-oil agglomerates are prepared by agitation of the slurry at atmospheric pressure. The resulting mixture is drained of excess water and dried at atmospheric pressure leaving catalyst deposited on the agglomerates. The agglomerates then are fed to an extrusion device where they are formed into a continuous ribbon of extrudate and fed into a hydrogenation reactor at elevated pressure and temperature. The catalytic hydrogenation converts the extrudate primarily to liquid hydrocarbons in the reactor. The liquid drained in recovering the agglomerates is recycled.

In Situ Observations of Agglomeration of Non-metallic Inclusions at Steel/Ar and Steel/Slag Interfaces by High-Temperature Confocal Laser Scanning Microscope: A Review

NASA Astrophysics Data System (ADS)

Mu, Wangzhong; Dogan, Neslihan; Coley, Kenneth S.

2018-05-01

The agglomeration behavior of non-metallic inclusions in the steelmaking process is important for controlling the cleanliness of the steel. In this work, the observation of agglomeration behaviors of inclusions at steel/Ar and steel/slag interfaces using a high-temperature confocal laser scanning microscope (HT-CLSM) is summarized. This HT-CLSM technique has been applied to observe phase transformation during solidification and heat treatment and the engulfment and pushing behavior of inclusions in front of the solidified interface. In the current work, the inclusion agglomeration behavior at steel/Ar and steel/slag interfaces is summarized and discussed. Subsequently, the development of the theoretical work investigating inclusion agglomeration at steel/Ar and steel/slag interfaces including the initial capillary force model and Kralchevsky-Paunov model is described. Finally, the Kralchevsky-Paunov model is applied to investigating nitride inclusion agglomeration at high-manganese steel/Ar interfaces. This work aims to give a critical review of the application of HT-CLSM in secondary refining as well as a better control of inclusion elimination for clean steel production.

Influences of Different Components on Agglomeration Behavior of MoS2 During Oxidation Roasting Process in Air

NASA Astrophysics Data System (ADS)

Wang, Lu; Zhang, Guo-Hua; Wang, Jing-Song; Chou, Kuo-Chih

2016-08-01

An agglomeration of the furnace charge always takes place during the oxidation roasting process of molybdenite concentrate (with the main component of MoS2) in multiple hearth furnaces, which greatly affects the production process and furnace service life. In the present work, a preliminary study about the influence of various components on the agglomeration phenomenon of pure MoS2 have been carried out. The results show that reaction temperature, impurity content, and air flow rate have significant effects on the agglomeration extent. Meanwhile, the impurity type added into the pure MoS2 plays a crucial role. It was found that CaO and MgO have a stronger sulfur-fixing effect and that the desulphurization of the roasted product was uncompleted. It was also concluded that the agglomeration is due to the formation of low-melting-point eutectics, including that between MoO3 and impurities and that between MoO3 and Mo4O11. It is suggested that decreasing the impurities contents, especially K, Cu, Pb, and Fe, is an effective method for reducing the extent of agglomeration.

Theranostic potential of gold nanoparticle-protein agglomerates

NASA Astrophysics Data System (ADS)

Sanpui, Pallab; Paul, Anumita; Chattopadhyay, Arun

2015-11-01

Owing to the ever-increasing applications, glittered with astonishing success of gold nanoparticles (Au NPs) in biomedical research as diagnostic and therapeutic agents, the study of Au NP-protein interaction seems critical for maximizing their theranostic efficiency, and thus demands comprehensive understanding. The mutual interaction of Au NPs and proteins at physiological conditions may result in the aggregation of protein, which can ultimately lead to the formation of Au NP-protein agglomerates. In the present article, we try to appreciate the plausible steps involved in the Au NP-induced aggregation of proteins and also the importance of the proteins' three-dimensional structures in the process. The Au NP-protein agglomerates can potentially be exploited for efficient loading and subsequent release of various therapeutically important molecules, including anticancer drugs, with the unique opportunity of incorporating hydrophilic as well as hydrophobic drugs in the same nanocarrier system. Moreover, the Au NP-protein agglomerates can act as `self-diagnostic' systems, allowing investigation of the conformational state of the associated protein(s) as well as the protein-protein or protein-Au NP interaction within the agglomerates. Furthermore, the potential of these Au NP-protein agglomerates as a novel platform for multifunctional theranostic application along with exciting future-possibilities is highlighted here.

NOVEL BINDERS AND METHODS FOR AGGLOMERATION OF ORE

DOE Office of Scientific and Technical Information (OSTI.GOV)

S.K. Kawatra; T.C. Eisele; J.A. Gurtler

2004-04-01

Many metal extraction operations, such as leaching of copper, leaching of precious metals, and reduction of metal oxides to metal in high-temperature furnaces, require agglomeration of ore to ensure that reactive liquids or gases are evenly distributed throughout the ore being processed. Agglomeration of ore into coarse, porous masses achieves this even distribution of fluids by preventing fine particles from migrating and clogging the spaces and channels between the larger ore particles. Binders are critically necessary to produce agglomerates that will not break down during processing. However, for many important metal extraction processes there are no binders known that willmore » work satisfactorily. Primary examples of this are copper heap leaching, where there are no binders that will work in the acidic environment encountered in this process, and advanced ironmaking processes, where binders must function satisfactorily over an extraordinarily large range of temperatures (from room temperature up to over 1200 C). As a result, operators of many facilities see a large loss of process efficiency due to their inability to take advantage of agglomeration. The large quantities of ore that must be handled in metal extraction processes also means that the binder must be inexpensive and useful at low dosages to be economical. The acid-resistant binders and agglomeration procedures developed in this project will also be adapted for use in improving the energy efficiency and performance of a broad range of mineral agglomeration applications, particularly heap leaching and advanced primary ironmaking.« less

The agglomeration state of nanoparticles can influence the mechanism of their cellular internalisation.

PubMed

Halamoda-Kenzaoui, Blanka; Ceridono, Mara; Urbán, Patricia; Bogni, Alessia; Ponti, Jessica; Gioria, Sabrina; Kinsner-Ovaskainen, Agnieszka

2017-06-26

Significant progress of nanotechnology, including in particular biomedical and pharmaceutical applications, has resulted in a high number of studies describing the biological effects of nanomaterials. Moreover, a determination of so-called "critical quality attributes", that is specific physicochemical properties of nanomaterials triggering the observed biological response, has been recognised as crucial for the evaluation and design of novel safe and efficacious therapeutics. In the context of in vitro studies, a thorough physicochemical characterisation of nanoparticles (NPs), also in the biological medium, is necessary to allow a correlation with a cellular response. Following this concept, we examined whether the main and frequently reported characteristics of NPs such as size and the agglomeration state can influence the level and the mechanism of NP cellular internalization. We employed fluorescently-labelled 30 and 80 nm silicon dioxide NPs, both in agglomerated and non-agglomerated form. Using flow cytometry, transmission electron microscopy, the inhibitors of endocytosis and gene silencing we determined the most probable routes of cellular uptake for each form of tested silica NPs. We observed differences in cellular uptake depending on the size and the agglomeration state of NPs. Caveolae-mediated endocytosis was implicated particularly in the internalisation of well dispersed silica NPs but with an increase of the agglomeration state of NPs a combination of endocytic pathways with a predominant role of macropinocytosis was noted. We demonstrated that the agglomeration state of NPs is an important factor influencing the level of cell uptake and the mechanism of endocytosis of silica NPs.

Effects of upper-body sprint-interval training on strength and endurance capacities in female cross-country skiers

PubMed Central

Vandbakk, Kristine; Welde, Boye; Kruken, Andrea Hovstein; Baumgart, Julia; Ettema, Gertjan; Karlsen, Trine; Sandbakk, Øyvind

2017-01-01

This study compared the effects of adding upper-body sprint-intervals or continuous double poling endurance training to the normal training on maximal upper-body strength and endurance capacity in female cross-country skiers. In total, 17 female skiers (age: 18.1±0.8yr, body mass: 60±7 kg, maximal oxygen uptake (VO2max): 3.30±0.37 L.min-1) performed an 8-week training intervention. Here, either two weekly sessions of six to eight 30-s maximal upper-body double poling sprint-intervals (SIG, n = 8) or 45–75 min of continuous low-to-moderate intensity double poling on roller skis (CG, n = 9) were added to their training. Before and after the intervention, the participants were tested for physiological and kinematical responses during submaximal and maximal diagonal and double poling treadmill roller skiing. Additionally, we measured maximal upper-body strength (1RM) and average power at 40% 1RM in a poling-specific strength exercise. SIG improved absolute VO2max in diagonal skiing more than CG (8% vs 2%, p<0.05), and showed a tendency towards higher body-mass normalized VO2max (7% vs 2%, p = 0.07). Both groups had an overall improvement in double poling peak oxygen uptake (10% vs 6% for SIG and CG) (both p<0.01), but no group-difference was observed. SIG improved 1RM strength more than CG (18% vs 10%, p<0.05), while there was a tendency for difference in average power at 40% 1RM (20% vs 14%, p = 0.06). Oxygen cost and kinematics (cycle length and rate) in double poling and diagonal remained unchanged in both groups. In conclusion, our study demonstrates that adding upper-body sprint-interval training is more effective than continuous endurance training in improving upper-body maximal strength and VO2max. PMID:28241030

Development of a fluidized bed agglomeration modeling methodology to include particle-level heterogeneities in ash chemistry and granular physics

NASA Astrophysics Data System (ADS)

Khadilkar, Aditi B.

The utility of fluidized bed reactors for combustion and gasification can be enhanced if operational issues such as agglomeration are mitigated. The monetary and efficiency losses could be avoided through a mechanistic understanding of the agglomeration process and prediction of operational conditions that promote agglomeration. Pilot-scale experimentation prior to operation for each specific condition can be cumbersome and expensive. So the development of a mathematical model would aid predictions. With this motivation, the study comprised of the following model development stages- 1) development of an agglomeration modeling methodology based on binary particle collisions, 2) study of heterogeneities in ash chemical composition and gaseous atmosphere, 3) computation of a distribution of particle collision frequencies based on granular physics for a poly-disperse particle size distribution, 4) combining the ash chemistry and granular physics inputs to obtain agglomerate growth probabilities and 5) validation of the modeling methodology. The modeling methodology comprised of testing every binary particle collision in the system for sticking, based on the extent of dissipation of the particles' kinetic energy through viscous dissipation by slag-liquid (molten ash) covering the particles. In the modeling methodology developed in this study, thermodynamic equilibrium calculations are used to estimate the amount of slag-liquid in the system, and the changes in particle collision frequencies are accounted for by continuously tracking the number density of the various particle sizes. In this study, the heterogeneities in chemical composition of fuel ash were studied by separating the bulk fuel into particle classes that are rich in specific minerals. FactSage simulations were performed on two bituminous coals and an anthracite to understand the effect of particle-level heterogeneities on agglomeration. The mineral matter behavior of these constituent classes was studied. Each particle class undergoes distinct transformations of mineral matter at fluidized bed operating temperatures, as determined by using high temperature X-ray diffraction, thermo-mechanical analysis and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). For the incorporation of a particle size distribution, bottom ash from an operating plant was divided into four size intervals and the system granular temperatures and dynamic bed height were computed using MFIX, a CFD simulation software. The kinetic theory of granular flow was used to obtain a distribution of binary collision frequencies for the entire particle size distribution. With this distribution of collision frequencies, which is computed based on hydrodynamics and granular physics of the poly-disperse system, as the particles grow, defluidize and decrease in number, the collision frequency also decreases. Under the conditions studied, the growth rate in the latter half of the run decreased to almost 1/5th the initial rate, with this decrease in collision frequency. This interdependent effect of chemistry and physics-based parameters, at the particle-level, was used to predict the agglomerate growth probabilities of Pittsburgh No. 8, Illinois No. 6 and Skidmore anthracite coals in this study, to illustrate the utility of the modeling methodology. The study also showed that agglomerate growth probability significantly increased above 15 to 20 wt. % slag. It was limited by ash chemistry at levels below this amount. Ash agglomerates were generated in a laboratory-scale fluidized bed combustor at Penn State to support the proposed agglomerate growth mechanism. This study also attempted to gain a mechanistic understanding of agglomerate growth with particle-level initiation occurring at the relatively low operating temperatures of about 950 °C, found in some fluidized beds. The results of this study indicated that, for the materials examined, agglomerate growth in fluidized bed combustors and gasifiers is initiated at the particle-level by low-melting components rich in iron- and calcium-based minerals. Although the bulk ash chemical composition does not indicate potential for agglomeration, study of particle-level heterogeneities revealed that agglomeration can begin at lower temperatures than the fluidized bed operating temperatures of 850 °C. After initiation at the particle-level, more slag is observed to form from alumino-silicate components at about 50 to 100 °C higher temperatures caused by changes in the system, and agglomerate growth propagates in the bed. A post-mortem study of ash agglomerates using SEM-EDX helped to identify stages of agglomerate growth. Additionally, the modeling methodology developed was used to simulate agglomerate growth in a laboratory-scale fluidized bed combustor firing palm shells (biomass), reported in the literature. A comparison of the defluidization time obtained by simulations to the experimental values reported in the case-study was made for the different operating conditions studied. This indicated that although the simulation results were comparable to those reported in the case study, modifications such as inclusion of heat transfer calculations to determine particle temperature resulting from carbon conversion would improve the predictive capabilities. (Abstract shortened by ProQuest.).

Maternal Mind-Mindedness and Children's Behavioral Difficulties: Mitigating the Impact of Low Socioeconomic Status

ERIC Educational Resources Information Center

Meins, Elizabeth; Centifanti, Luna C. Munoz; Fernyhough, Charles; Fishburn, Sarah

2013-01-01

Relations between mothers' tendency to comment appropriately on their 8-month-olds' internal states (mind-mindedness) and children's behavioral difficulties (Strengths and Difficulties Questionnaire) at ages 44 and 61 months were investigated in a socially diverse sample (N = 171, 88 boys). Controlling for maternal depressive symptoms, perceived…

Instructional Coach Weighs 3 Types of Data to Get Triple-Strength Feedback

ERIC Educational Resources Information Center

Boehle, Monica

2014-01-01

This article describes three types of data that can impact how instructional coaches face the challenges in measuring the impact of their work with teachers on student learning. Descriptions of the three types of data--"shifts in teacher reflective tendencies," "the use of student performance as an indicator of success," and…

Grieving in the Muscogee Creek Tribe

ERIC Educational Resources Information Center

Walker, Andrea C.

2008-01-01

A qualitative, collective case study explores grieving in the Muscogee Creek tribe. Data from interviews with 27 participants, all adult members of the tribe, reveal tendencies in patterns of grieving. Commonalities include (a) individual strength and certainty of recovery; (b) focus on giving to others in the family and coping as a family unit;…

Cue Strength as a Moderator of the Testing Effect: The Benefits of Elaborative Retrieval

ERIC Educational Resources Information Center

Carpenter, Shana K.

2009-01-01

The current study explored the elaborative retrieval hypothesis as an explanation for the testing effect: the tendency for a memory test to enhance retention more than restudying. In particular, the retrieval process during testing may activate elaborative information related to the target response, thereby increasing the chances that activation…

Contest experience and body size affect different types of contest decisions.

PubMed

Chen, Yu-Ju; Hsu, Yuying

2016-11-01

This study examined the relative importance of contest experience and size differences to behavioral decisions over the course of contests. Using a mangrove rivulus fish, Kryptolebias marmoratus, we showed that although contest experience and size differences jointly determined contest outcomes, they affected contestants' interactions at different stages of contests. Contest experience affected behavioral decisions at earlier stages of contests, including the tendency and latency to launch attacks, the tendency to escalate contests into mutual attacks and the outcome of non-escalated contests. Once contests were escalated into mutual attacks, the degree of size difference affected the fish's persistence in escalation and chance of winning, but contest experience did not. These results support the hypothesis that contest experience modifies individuals' estimation of their fighting ability rather than their actual strength. Furthermore, (1) in contests between two naïve contestants, more than 60 % of fish that were 2-3 mm smaller than their opponent escalated the contest to physical fights, even though their larger opponents eventually won 92 % of escalated fights and (2) fish with a losing experience were very likely to retreat in the face of an opponent 2-3 mm smaller than them without escalating. The result that a 2-3 mm size advantage could not offset the influence of a losing experience on the tendency to escalate suggests that, as well as depending on body size, the fish's physical strength is influenced by other factors which require further investigation.

Research approach and first results on agglomerate compaction in protoplanetary dust simulation in the Cloud Manipulation System

NASA Astrophysics Data System (ADS)

Vedernikov, Andrei; Blum, Jurgen; Ingo Von Borstel, Olaf; Schraepler, Rainer; Balapanov, Daniyar; Cecere, Anselmo

2016-07-01

Nanometre and micrometre-sized solid particles are ubiquitous in space and on Earth - from galaxies, interstellar space, protoplanetary and debris disks to planetary rings and atmospheres, planetary surfaces, comets, interplanetary space, Earth's atmosphere. Apparently, the most intriguing problem in the picture of the formation of planets is the transition from individual microscopic dust grains to kilometre-sized planetesimals. Revealing the mechanisms of this transition is one of the main tasks of the European Space Agency's project Interaction in Cosmic and Atmospheric Particle Systems (ICAPS). It was found that Brownian motion driven agglomeration could not provide the transition within reasonable time scale. As a result, at this stage top scientific goals shifted towards forced agglomeration and concentration of particles, targeting revealing the onset of compaction, experimental study of the evolution of fractal dimensions, size and mass distribution, occurrence of bouncing. The main tasks comprise 1) development of the rapid agglomeration model 2) development of the experimental facilities creating big fractal-type agglomerates from 10 to 1000 μm from a cloud of micrometre-size grains; 3) experimental realization of the rapid agglomeration in microgravity and ground conditions; and 4) in situ investigation of the morphology, mobility, mechanical and optical properties of the free-floating agglomerates, including investigation of thermophoresis, photophoresis of the agglomerates and of the two-phase flow phenomena. To solve the experimental part of the tasks we developed a Cloud Manipulation System, realized as a breadboard (CMS BB) for long duration microgravity platforms and a simplified laboratory version (CMS LV) mostly oriented on short duration microgravity and ground tests. The new system is based on the use of thermophoresis, most favourable for cloud manipulation without creating additional particle-particle forces in the cloud with a possibility of growing single agglomerate out of the whole cloud. The cloud manipulation system additionally provides temperature stabilization or, on the contrary, high temperature variation in the observation volume; formation of controlled temperature gradients, intensive three-dimensional periodic shear flow or three-dimensional gas density pulsations of the contraction-expansion type; application of electrostatic gradients including electro dynamic balancing; imposing of photophoretic force, etc. Their choice and/or combination depend upon particular experimental task. Experiments on forced agglomeration in short duration microgravity conditions of the Bremen drop tower succeeded in rapid growth of extended agglomerates, formation of complex three-dimensional cloud patterns, allowed observing controlled cloud displacement, cloud trapping, particle separation with respect to their electrical charge. The breadboard (CMS BB) and the laboratory version of the Cloud Manipulation System (CMS LV) are new types of scientific instrument with high scientific potential. ESA PRODEX program, the Belgian Federal Science Policy Office, DLR project 50WM1223, ZARM Drop Tower Operation and Service Company Ltd. are greatly acknowledged.

Controlling adsorption and passivation properties of bovine serum albumin on silica surfaces by ionic strength modulation and cross-linking.

PubMed

Park, Jae Hyeon; Sut, Tun Naw; Jackman, Joshua A; Ferhan, Abdul Rahim; Yoon, Bo Kyeong; Cho, Nam-Joon

2017-03-29

Understanding the physicochemical factors that influence protein adsorption onto solid supports holds wide relevance for fundamental insights into protein structure and function as well as for applications such as surface passivation. Ionic strength is a key parameter that influences protein adsorption, although how its modulation might be utilized to prepare well-coated protein adlayers remains to be explored. Herein, we investigated how ionic strength can be utilized to control the adsorption and passivation properties of bovine serum albumin (BSA) on silica surfaces. As protein stability in solution can influence adsorption kinetics, the size distribution and secondary structure of proteins in solution were first characterized by dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), and circular dichroism (CD) spectroscopy. A non-monotonic correlation between ionic strength and protein aggregation was observed and attributed to colloidal agglomeration, while the primarily α-helical character of the protein in solution was maintained in all cases. Quartz crystal microbalance-dissipation (QCM-D) experiments were then conducted in order to track protein adsorption onto silica surfaces as a function of ionic strength, and the measurement responses indicated that total protein uptake at saturation coverage is lower with increasing ionic strength. In turn, the QCM-D data and the corresponding Voigt-Voinova model analysis support that the surface area per bound protein molecule is greater with increasing ionic strength. While higher protein uptake under lower ionic strengths by itself did not result in greater surface passivation under subsequent physiologically relevant conditions, the treatment of adsorbed protein layers with a gluteraldehyde cross-linking agent stabilized the bound protein in this case and significantly improved surface passivation. Collectively, our findings demonstrate that ionic strength modulation influences BSA adsorption uptake on account of protein spreading and can be utilized in conjunction with covalent cross-linking strategies to prepare well-coated protein adlayers for improved surface passivation.

High thermally stable Ni /Ag(Al) alloy contacts on p-GaN

NASA Astrophysics Data System (ADS)

Chou, C. H.; Lin, C. L.; Chuang, Y. C.; Bor, H. Y.; Liu, C. Y.

2007-01-01

Ag agglomeration was found to occur at Ni /Ag to p-GaN contacts after annealing at 500°C. This Ag agglomeration led to the poor thermal stability showed by the Ni /Ag contacts in relation to the reflectivity and electrical properties. However, after alloying with 10at.% Al by e-gun deposition, the Ni /Ag(Al) p-GaN contacts were found to effectively retard Ag agglomeration thereby greatly enhancing the thermal stability. Based on the x-ray photoelectron spectroscopy analysis, the authors believe that the key for the retardation of Ag agglomeration was the formation of ternary Al-Ni-O layer at p-GaN interface.

Magnetic agglomeration method for size control in the synthesis of magnetic nanoparticles

DOEpatents

Huber, Dale L [Albuquerque, NM

2011-07-05

A method for controlling the size of chemically synthesized magnetic nanoparticles that employs magnetic interaction between particles to control particle size and does not rely on conventional kinetic control of the reaction to control particle size. The particles are caused to reversibly agglomerate and precipitate from solution; the size at which this occurs can be well controlled to provide a very narrow particle size distribution. The size of particles is controllable by the size of the surfactant employed in the process; controlling the size of the surfactant allows magnetic control of the agglomeration and precipitation processes. Agglomeration is used to effectively stop particle growth to provide a very narrow range of particle sizes.

High thermally stable Ni/Ag(Al) alloy contacts on p-GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chou, C. H.; Lin, C. L.; Chuang, Y. C.

2007-01-08

Ag agglomeration was found to occur at Ni/Ag to p-GaN contacts after annealing at 500 degree sign C. This Ag agglomeration led to the poor thermal stability showed by the Ni/Ag contacts in relation to the reflectivity and electrical properties. However, after alloying with 10 at. % Al by e-gun deposition, the Ni/Ag(Al) p-GaN contacts were found to effectively retard Ag agglomeration thereby greatly enhancing the thermal stability. Based on the x-ray photoelectron spectroscopy analysis, the authors believe that the key for the retardation of Ag agglomeration was the formation of ternary Al-Ni-O layer at p-GaN interface.

Agglomeration of nano- and microplastic particles in seawater by autochthonous and de novo-produced sources of exopolymeric substances.

PubMed

Summers, Stephen; Henry, Theodore; Gutierrez, Tony

2018-05-01

Microplastics (<5 mm) have often been studied under in-vitro conditions where plastics have been investigated in isolation. However, in the natural environment microplastics readily form agglomerates conferring the particles with properties different to their pristine counterparts. Here, we examined the interaction of exopolymers with polystyrene nanoplastics and microplastics. Formation of plastic agglomerates was examined using simulated sea surface conditions. Flow cytometry coupled with microscopy revealed that nano- and microplastic particle spheres form agglomerates in seawater with a mucilagenous material and an associated microbial community. To characterise this material, differential staining methods revealed it to be glycoprotein in composition. Exposing increasing concentrations of a marine bacterial glycoprotein EPS to nano- or microplastics revealed that these types of polymers contribute to the formation and abundance of plastic agglomerates. This work highlights the importance of EPS on the fate of plastic and future research should take this into account when evaluating the impact of plastics. Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.

Effect of a Dispersant Agent in Fine Coal Recovery from Washery Tailings by Oil Agglomeration (Preliminary Study)

NASA Astrophysics Data System (ADS)

Yasar, Özüm; Uslu, Tuncay

2017-12-01

Among the fine coal cleaning methods, the oil agglomeration process has important advantages such as high process recovery, more clean product, simple dewatering stage. Several coal agglomeration studies have been undertaken recently and effects of different variables on the process performance have been investigated. However, unlike flotation studies, most of the previous agglomeration studies have not used dispersing agents to minimize slime coating effects of clays. In this study, agglomeration process was applied for recovery of fine coals from coal washery tailings containing remarkable amount of fine coal. Negative effect of fine clays during recovery was tried to be eliminated by using dispersing agent instead of de-sliming. Although ash reductions over 90 % were achieved, performance remained below expectations in terms of combustible matter recovery. However, this study is a preliminary one. It is considered that more satisfied results will be obtained in the next studies by changing the variables such as solid ratio, oil dosage, dispersant type and dosage.

Agglomeration of dust in convective clouds initialized by nuclear bursts

NASA Astrophysics Data System (ADS)

Bacon, D. P.; Sarma, R. A.

Convective clouds initialized by nuclear bursts are modeled using a two-dimensional axisymmetric cloud model. Dust transport through the atmosphere is studied using five different sizes ranging from 1 to 10,000 μm in diameter. Dust is transported in the model domain by advection and sedimentation. Water is allowed to condense onto dust particles in regions of supersaturation in the cloud. The agglomeration of dust particles resulting from the collision of different size dust particles is modeled. The evolution of the dust mass spectrum due to agglomeration is modeled using a numerical scheme which is mass conserving and has low implicit diffusion. Agglomeration moves mass from the small particles with very small fall velocity to the larger sizes which fall to the ground more readily. Results indicate that the dust fallout can be increased significantly due to this process. In preliminary runs using stable and unstable environmental soundings, at 30 min after detonation the total dust in the domain was 11 and 30%, respectively, less than a control case without agglomeration.

Nanoparticle agglomerates of fluticasone propionate in combination with albuterol sulfate as dry powder aerosols

PubMed Central

El-Gendy, Nashwa; Pornputtapitak, Warangkana; Berkland, Cory

2015-01-01

Particle engineering strategies remain at the forefront of aerosol research for localized treatment of lung diseases and represent an alternative for systemic drug therapy. With the hastily growing popularity and complexity of inhalation therapy, there is a rising demand for tailor-made inhalable drug particles capable of affording the most proficient delivery to the lungs and the most advantageous therapeutic outcomes. To address this formulation demand, nanoparticle agglomeration was used to develop aerosols of the asthma therapeutics, fluticasone or albuterol. In addition, a combination aerosol was formed by drying agglomerates of fluticasone nanoparticles in the presence of albuterol in solution. Powders of the single drug nanoparticle agglomerates or of the combined therapeutics possessed desirable aerodynamic properties for inhalation. Powders were efficiently aerosolized (~75% deposition determined by cascade impaction) with high fine particle fraction and rapid dissolution. Nanoparticle agglomeration offers a unique approach to obtain high performance aerosols from combinations of asthma therapeutics. PMID:21964203

Predicting the Agglomeration of Cohesive Particles in a Gas-Solid Flow and its Effect on the Solids Flow

NASA Astrophysics Data System (ADS)

Kellogg, Kevin; Liu, Peiyuan; Lamarche, Casey; Hrenya, Christine

2017-11-01

In flows of cohesive particles, agglomerates will readily form and break. These agglomerates are expected to complicate how particles interact with the surrounding fluid in multiphase flows, and consequently how the solids flow. In this work, a dilute flow of particles driven by gas against gravity is studied. A continuum framework, composed of a population balance to predict the formation of agglomerates, and kinetic-theory-based balances, is used to predict the flow of particles. The closures utilized for the birth and death rates due to aggregation and breakage in the population balance take into account how the impact velocity (the granular temperature) affects the outcome of a collision as aggregation, rebound, or breakage. The agglomerate size distribution and solids velocity predicted by the continuum framework are compared to discrete element method (DEM) simulations, as well to experimental results of particles being entrained from the riser of a fluidized bed. Dow Corning Corporation.

Role of Solvents in Improvement of Dissolution Rate of Drugs: Crystal Habit and Crystal Agglomeration

PubMed Central

Maghsoodi, Maryam

2015-01-01

Crystallization is often used for manufacturing drug substances. Advances of crystallization have achieved control over drug identity and purity, but control over the physical form remains poor. This review discusses the influence of solvents used in crystallization process on crystal habit and agglomeration of crystals with potential implication for dissolution. According to literature it has been known that habit modification of crystals by use of proper solvents may enhance the dissolution properties by changing the size, number and the nature of crystal faces exposed to the dissolution medium. Also, the faster dissolution rate of drug from the agglomerates of crystals compared with the single crystals may be related to porous structure of the agglomerates and consequently their better wettability. It is concluded from this review that in-depth understanding of role of the solvents in crystallization process can be applied to engineering of crystal habit or crystal agglomeration, and predictably dissolution improvement in poorly soluble drugs. PMID:25789214

Colloidal aspects and packing behaviour of charged microparticulates in high efficiency ion chromatography.

PubMed

Wahab, M Farooq; Pohl, Christopher A; Lucy, Charles A

2012-12-28

The development of small particles in ion chromatography (IC) is a recent phenomenon. Very few studies are available on packing polymeric particles bearing ionizable functional groups. This study explores the colloidal and rheological properties that govern slurry packing to form high efficiency IC columns. The polymeric substrate used was non-porous 4.4 μm sulfonated ethylvinylbenzene–divinylbenzene (1.4 mequiv. SO(3)H/g resin) with 55% crosslink. We developed simple tests optical microscopy and sedimentation tests for predicting the quality of packed columns. The negatively charged particles (zeta potential: −52 mV in water) behave like colloids. The influence of counter-ion charge (Al(3+), Mg(2+), Na(+)) and ionic strength on column efficiency followed the Schulze–Hardy rule. Highly flocculating slurries give poorly packed columns with N ~ 900 whereas under non-agglomerating slurry conditions efficiencies up to N > 10,000 can be achieved. A non-agglomerating slurry also shows non-Newtonian behaviour, specifically shear thickening. Packing at lower flow rate (<1 mL/min) or higher temperature (>50 °C) reduces the shear thickening and produces higher efficiency columns. The packed sulfonated resin column is coated with 72 nm quaternary ammonium bearing latex (AS4A) and used in the separation of F(−), Cl(−), NO(2)(−), Br(−), and NO(3)(−) yielding a reduced plate height of 1.9 under optimum conditions.

On-chip free-flow magnetophoresis: continuous flow separation of magnetic particles and agglomerates.

PubMed

Pamme, Nicole; Manz, Andreas

2004-12-15

The separation of magnetic microparticles was achieved by on-chip free-flow magnetophoresis. In continuous flow, magnetic particles were deflected from the direction of laminar flow by a perpendicular magnetic field depending on their magnetic susceptibility and size and on the flow rate. Magnetic particles could thus be separated from each other and from nonmagnetic materials. Magnetic and nonmagnetic particles were introduced into a microfluidic separation chamber, and their deflection was studied under the microscope. The magnetic particles were 2.0 and 4.5 microm in diameter with magnetic susceptibilities of 1.12 x 10(-4) and 1.6 x 10(-4) m(3) kg(-1), respectively. The 4.5-microm particles with the larger susceptibility were deflected further from the direction of laminar flow than the 2.0-microm magnetic particles. Nonmagnetic 6-microm polystyrene beads, however, were not deflected at all. Furthermore, agglomerates of magnetic particles were found to be deflected to a larger extent than single magnetic particles. The applied flow rate and the strength and gradient of the applied magnetic field were the key parameters in controlling the deflection. This separation method has a wide applicability since magnetic particles are commonly used in bioanalysis as a solid support material for antigens, antibodies, DNA, and even cells. Free-flow magnetophoretic separations could be hyphenated with other microfluidic devices for reaction and analysis steps to form a micro total analysis system.

Modeling Europa's Ice-Ocean Interface

NASA Astrophysics Data System (ADS)

Elsenousy, A.; Vance, S.; Bills, B. G.

2014-12-01

This work focuses on modeling the ice-ocean interface on Jupiter's Moon (Europa); mainly from the standpoint of heat and salt transfer relationship with emphasis on the basal ice growth rate and its implications to Europa's tidal response. Modeling the heat and salt flux at Europa's ice/ocean interface is necessary to understand the dynamics of Europa's ocean and its interaction with the upper ice shell as well as the history of active turbulence at this area. To achieve this goal, we used McPhee et al., 2008 parameterizations on Earth's ice/ocean interface that was developed to meet Europa's ocean dynamics. We varied one parameter at a time to test its influence on both; "h" the basal ice growth rate and on "R" the double diffusion tendency strength. The double diffusion tendency "R" was calculated as the ratio between the interface heat exchange coefficient αh to the interface salt exchange coefficient αs. Our preliminary results showed a strong double diffusion tendency R ~200 at Europa's ice-ocean interface for plausible changes in the heat flux due to onset or elimination of a hydrothermal activity, suggesting supercooling and a strong tendency for forming frazil ice.

Investigation of Kevlar fabric based materials for use with inflatable structures

NASA Technical Reports Server (NTRS)

Niccum, R. J.; Munson, J. B.

1974-01-01

Design, manufacture and testing of laminated and coated composite materials incorporating a structural matrix of Kevlar are reported in detail. The practicality of using Kevlar in aerostat materials is demonstrated and data are provided on practical weaves, lamination and coating particulars, rigidity, strength, weight, elastic coefficients, abrasion resistance, crease effects, peel strength, blocking tendencies, helium permeability, and fabrication techniques. Properties of the Kevlar based materials are compared with conventional, Dacron reinforced counterparts. A comprehensive test and qualification program is discussed and quantitative biaxial tensile and shear test data are provided. The investigation shows that single ply laminates of Kevlar and plastic films offer significant strength to weight improvements, are less permeable than two ply coated materials, but have a lower flex life.

Flotation of oil-agglomerated coal for ash and pyrite removal -- Simultaneous grinding and agglomeration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, S.; Perkson, A.; Trass, O.

1996-12-31

Oil agglomeration is an excellent technique for the beneficiation of fine coal. For separation of the spherical agglomerates by screening, a high level of oil must be used, however. When the subsequent separation is done by flotation, this disadvantage is eliminated. Better pyrite removal is also possible. In this paper, such a fine coal beneficiation process, also called hydrophobic flocculation-flotation (HFF), is described. It features low non-polar oil consumption, intensive mechanical energy input, and smaller agglomerates or looser flocs. This process can be simplified by grinding the coal in water with small amounts of oil added. The excess grinding energymore » is then used for agglomerating the coal. The Prince coal from Nova Scotia contained 13.3% ash and 3.3% total sulfur, 1.4% pyritic. After four stages of flotation, ash and pyrite removal were 93% and 66% respectively, with 87% combustibles recovery. The parameters affecting the HFF process, such as particle size, dosage of non-polar oil, pH value of the slurry and duration of agitation, were investigated. Simultaneous grinding and agglomeration (SGA) utilizing the Szego Mill was also explored at the very low oil levels used. The intensive agitation/preconditioning step prior to flotation was eliminated. When the other parameters established from the sequential process were used with the SGA process, virtually identical beneficiation results were obtained, but with slightly lower combustibles recovery. While further testing is required to properly optimize the SGA process conditions, significant equipment simplification and energy savings are possible.« less

The Physics of Protoplanetesimal Dust Agglomerates. VIII. Microgravity Collisions between Porous SiO{sub 2} Aggregates and Loosely Bound Agglomerates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whizin, Akbar D.; Colwell, Joshua E.; Blum, Jürgen, E-mail: Akbar.Whizin@ucf.edu

2017-02-10

We performed laboratory experiments colliding 0.8–1.0 mm and 1.0–1.6 mm SiO{sub 2} dust aggregates with loosely bound centimeter-sized agglomerates of those aggregates in microgravity. This work builds on previous microgravity laboratory experiments examining the collisional properties of porous loosely bound dust aggregates. In centimeter-sized aggregates, surface forces dominate self-gravity and may play a large role in aggregate growth beyond this size range. We characterize the properties of protoplanetary aggregate analogs to help place constraints on initial formation mechanisms and environments. We determined several important physical characteristics of these aggregates in a large number of low-velocity collisions. We observed low coefficientsmore » of restitution and fragmentation thresholds near 1 m s{sup −1} for 1–2 cm agglomerates, which are in good agreement with previous findings in the literature. We find the accretion efficiency for agglomerates of loosely bound aggregates to be higher than that for just aggregates themselves. We find sticking thresholds of 6.6 ± 2 cm s{sup −1}, somewhat higher than those in similar studies, which have observed few aggregates stick at speeds of under 3 cm s{sup −1}. Even with highly dissipative collisions, loosely bound agglomerates have difficulty accreting beyond centimeter-sized bodies at typical collision speeds in the disk. Our results indicate agglomerates of porous aggregates have slightly higher sticking thresholds than previously thought, allowing possible growth to decimeter-sized bodies if velocities are low enough.« less

Novel Binders and Methods for Agglomeration of Ore

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. K. Kawatra; T. C. Eisele; K. A. Lewandowski

2006-12-31

Many metal extraction operations, such as leaching of copper, leaching of precious metals, and reduction of metal oxides to metal in high-temperature furnaces, require agglomeration of ore to ensure that reactive liquids or gases are evenly distributed throughout the ore being processed. Agglomeration of ore into coarse, porous masses achieves this even distribution of fluids by preventing fine particles from migrating and clogging the spaces and channels between the larger ore particles. Binders are critically necessary to produce agglomerates that will not break down during processing. However, for many important metal extraction processes there are no binders known that willmore » work satisfactorily. Primary examples of this are copper heap leaching, where there are no binders that will work in the acidic environment encountered in this process, and advanced ironmaking processes, where binders must function satisfactorily over an extraordinarily large range of temperatures (from room temperature up to over 1200 C). As a result, operators of many facilities see a large loss of process efficiency due to their inability to take advantage of agglomeration. The large quantities of ore that must be handled in metal extraction processes also means that the binder must be inexpensive and useful at low dosages to be economical. The acid-resistant binders and agglomeration procedures developed in this project will also be adapted for use in improving the energy efficiency and performance of a broad range of mineral agglomeration applications, particularly heap leaching and advanced primary ironmaking. This project has identified several acid-resistant binders and agglomeration procedures that can be used for improving the energy efficiency of heap leaching, by preventing the ''ponding'' and ''channeling'' effects that currently cause reduced recovery and extended leaching cycle times. Methods have also been developed for iron ore processing which are intended to improve the performance of pellet binders, and have directly saved energy by increasing filtration rates of the pelletization feed by as much as 23%.« less

Characterization of multiwalled carbon nanotube-polymethyl methacrylate composite resins as denture base materials.

PubMed

Wang, Russell; Tao, Junliang; Yu, Bill; Dai, Liming

2014-04-01

Most fractures of dentures occur during function, primarily because of the flexural fatigue of denture resins. The purpose of this study was to evaluate a polymethyl methacrylate denture base material modified with multiwalled carbon nanotubes in terms of fatigue resistance, flexural strength, and resilience. Denture resin specimens were fabricated: control, 0.5 wt%, 1 wt%, and 2 wt% of multiwalled carbon nanotubes. Multiwalled carbon nanotubes were dispersed by sonication. Thermogravimetric analysis was used to determine quantitative dispersions of multiwalled carbon nanotubes in polymethyl methacrylate. Raman spectroscopic analyses were used to evaluate interfacial reactions between the multiwalled carbon nanotubes and the polymethyl methacrylate matrix. Groups with and without multiwalled carbon nanotubes were subjected to a 3-point-bending test for flexural strength. Resilience was derived from a stress and/or strain curve. Fatigue resistance was conducted by a 4-point bending test. Fractured surfaces were analyzed by scanning electron microscopy. One-way ANOVA and the Duncan tests were used to identify any statistical differences (α=.05). Thermogravimetric analysis verified the accurate amounts of multiwalled carbon nanotubes dispersed in the polymethyl methacrylate resin. Raman spectroscopy showed an interfacial reaction between the multiwalled carbon nanotubes and the polymethyl methacrylate matrix. Statistical analyses revealed significant differences in static and dynamic loadings among the groups. The worst mechanical properties were in the 2 wt% multiwalled carbon nanotubes (P<.05), and 0.5 wt% and 1 wt% multiwalled carbon nanotubes significantly improved flexural strength and resilience. All multiwalled carbon nanotubes-polymethyl methacrylate groups showed poor fatigue resistance. The scanning electron microscopy results indicated more agglomerations in the 2% multiwalled carbon nanotubes. Multiwalled carbon nanotubes-polymethyl methacrylate groups (0.5% and 1%) performed better than the control group during the static flexural test. The results indicated that 2 wt% multiwalled carbon nanotubes were not beneficial because of the inadequate dispersion of multiwalled carbon nanotubes in the polymethyl methacrylate matrix. Scanning electron microscopy analysis showed agglomerations on the fracture surface of 2 wt% multiwalled carbon nanotubes. The interfacial bonding between multiwalled carbon nanotubes and polymethyl methacrylate was weak based on the Raman data and dynamic loading results. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Recent Advances in Agglomerated Multigrid

NASA Technical Reports Server (NTRS)

Nishikawa, Hiroaki; Diskin, Boris; Thomas, James L.; Hammond, Dana P.

2013-01-01

We report recent advancements of the agglomerated multigrid methodology for complex flow simulations on fully unstructured grids. An agglomerated multigrid solver is applied to a wide range of test problems from simple two-dimensional geometries to realistic three- dimensional configurations. The solver is evaluated against a single-grid solver and, in some cases, against a structured-grid multigrid solver. Grid and solver issues are identified and overcome, leading to significant improvements over single-grid solvers.

Effect of composition on physical properties of food powders

NASA Astrophysics Data System (ADS)

Szulc, Karolina; Lenart, Andrzej

2016-04-01

The paper presents an influence of raw material composition and technological process applied on selected physical properties of food powders. Powdered multi-component nutrients were subjected to the process of mixing, agglomeration, coating, and drying. Wetting liquids ie water and a 15% water lactose solution, were used in agglomeration and coating. The analyzed food powders were characterized by differentiated physical properties, including especially: particle size, bulk density, wettability, and dispersibility. The raw material composition of the studied nutrients exerted a statistically significant influence on their physical properties. Agglomeration as well as coating of food powders caused a significant increase in particle size, decreased bulk density, increased apparent density and porosity, and deterioration in flowability in comparison with non-agglomerated nutrients.

Study on spatial-temporal change of Changsha-Zhuzhou-Xiangtan urban agglomeration based on DMSP / OLS night light data

NASA Astrophysics Data System (ADS)

Li, Mao; Li, Lel-in

2018-03-01

For the sake of curbing the spreading of Changsha-Zhuzhou-Xiangtan urban agglomeration and spatial disorder in the process of urbanization development on the regional bearing capacity of land resources and ecological environment and assisting to plan the integration process of ChangZhuTan,this paper uses the DMSP/OLS night light data of Chang ZhuTan in 1992 to 2013 to invert the urbanization process index of ChangZhuTan urban agglomeration. Based on the two scales of time and space, this paper analyzes the average index of lights, the speed of urban expansion and urban compactness index et al and studies the temporal and spatial characteristics of ChangZhuTan urban agglomeration in this period.

Development of the fine-particle agglomerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feldman, P.; Balasic, P.

1999-07-01

This paper presents the current status of the commercial development of a new technology to more efficiently control fine particulate emissions. The technology is based on an invention by Environmental Elements Corporation (EEC) which utilizes laminar flow to promote contact of fine submicron particles with larger particles to form agglomerates prior to their removal in a conventional particulate control device, such as an ESP. As agglomerates the particles are easily captured in the control device, whereas a substantial amount would pass through if allowed to remain as fine particles. EEC has developed the laminar-flow agglomerator technology through the laboratory proof-of-conceptmore » stage, which was funded by a DOE SBIR grant, to pilot-scale and full-scale demonstrations.« less

Evolution of genuine cross-correlation strength of focal onset seizures.

PubMed

Müller, Markus F; Baier, Gerold; Jiménez, Yurytzy López; Marín García, Arlex O; Rummel, Christian; Schindler, Kaspar

2011-10-01

To quantify the evolution of genuine zero-lag cross-correlations of focal onset seizures, we apply a recently introduced multivariate measure to broad band and to narrow-band EEG data. For frequency components below 12.5 Hz, the strength of genuine cross-correlations decreases significantly during the seizure and the immediate postseizure period, while higher frequency bands show a tendency of elevated cross-correlations during the same period. We conclude that in terms of genuine zero-lag cross-correlations, the electrical brain activity as assessed by scalp electrodes shows a significant spatial fragmentation, which might promote seizure offset.

How dangerous are mobile phones, transmission masts, and electricity pylons?

PubMed

Wood, A W

2006-04-01

Electrical power and mobile communications deliver enormous benefit to society, but there are concerns whether the electric and magnetic field (EMF) emissions associated with the delivery of this benefit are linked to cancer or other health hazards. This article reviews the strength of the available epidemiological and laboratory evidence and notes that this falls short of what is normally required to establish a causal link. However, because of scientific uncertainty a cautious approach is often advocated, but here, too, there may be a tendency to judge these risks more harshly than those in other areas with similar strength of evidence.

Carbon nanotubes: properties, synthesis, purification, and medical applications

PubMed Central

2014-01-01

Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering. PMID:25170330

Carbon nanotubes: properties, synthesis, purification, and medical applications

NASA Astrophysics Data System (ADS)

Eatemadi, Ali; Daraee, Hadis; Karimkhanloo, Hamzeh; Kouhi, Mohammad; Zarghami, Nosratollah; Akbarzadeh, Abolfazl; Abasi, Mozhgan; Hanifehpour, Younes; Joo, Sang Woo

2014-08-01

Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering.

Carbon nanotubes: properties, synthesis, purification, and medical applications.

PubMed

Eatemadi, Ali; Daraee, Hadis; Karimkhanloo, Hamzeh; Kouhi, Mohammad; Zarghami, Nosratollah; Akbarzadeh, Abolfazl; Abasi, Mozhgan; Hanifehpour, Younes; Joo, Sang Woo

2014-01-01

Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering.

[Relationship Between Child Behavior and Emotional Problems and School Based Effort Avoidance].

PubMed

Weber, Hanna Maria; Büttner, Peter; Rücker, Stefan; Petermann, Franz

2015-01-01

The present study has examined the relationship between school based effort avoidance tendencies and problem behavior in children aged 9 to 16 years. Effort avoidance tendencies were assessed in 367 children with and without child care. Teachers and social workers rated children on behavioral and emotional problems with the Strengths and Difficulties Questionnaire (SDQ). Results confirmed significant but low correlations between teacher ratings of behavior and emotional problems in children and selected subscales of self-reported effort avoidance in school, especially for children in child care institutions. For them "conduct problems" were significantly correlated with three of the four subscales and the total sum score of effort avoidance whereas "hyperactivity" was the only scale which was significantly associated with the fourth subscale. In the school sample only "hyperactivity" and "peer problems" were significantly correlated with one subscale of school-based effort avoidance. The findings suggest that more problem behavior is in relation to more school based effort avoidance tendencies.

Volume labeling with Alexa Fluor dyes and surface functionalization of highly sensitive fluorescent silica (SiO2) nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Wei; Nallathamby, Prakash D.; Foster, Carmen M.; Morrell-Falvey, Jennifer L.; Mortensen, Ninell P.; Doktycz, Mitchel J.; Gu, Baohua; Retterer, Scott T.

2013-10-01

A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of <15%. In comparison with conventional surface tagged particles created by post-synthesis modification, this process maintains the physical and surface chemical properties that have the most pronounced effect on colloidal stability and interactions with their surroundings. These volume-labeled nanoparticles have proven to be extremely robust, showing excellent signal strength, negligible photobleaching, and minimal loss of functional organic components. The native or ``free'' surface of the volume-labeled particles can be altered to achieve a specific surface functionality without altering fluorescence. Their utility was demonstrated for visualizing the association of surface-modified fluorescent particles with cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems.A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of <15%. In comparison with conventional surface tagged particles created by post-synthesis modification, this process maintains the physical and surface chemical properties that have the most pronounced effect on colloidal stability and interactions with their surroundings. These volume-labeled nanoparticles have proven to be extremely robust, showing excellent signal strength, negligible photobleaching, and minimal loss of functional organic components. The native or ``free'' surface of the volume-labeled particles can be altered to achieve a specific surface functionality without altering fluorescence. Their utility was demonstrated for visualizing the association of surface-modified fluorescent particles with cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems. Electronic supplementary information (ESI) available: Cell culture preparation for dose/response imaging experiments. See DOI: 10.1039/c3nr02639f

Characteristics of epoxy resin/SiO2 nanocomposite insulation: effects of plasma surface treatment on the nanoparticles.

PubMed

Yan, Wei; Phung, B T; Han, Zhao Jun; Ostrikov, Kostya

2013-05-01

The present study compares the effects of two different material processing techniques on modifying hydrophilic SiO2 nanoparticles. In one method, the nanoparticles undergo plasma treatment by using a custom-developed atmospheric-pressure non-equilibrium plasma reactor. With the other method, they undergo chemical treatment which grafts silane groups onto their surface and turns them into hydrophobic. The treated nanoparticles are then used to synthesize epoxy resin-based nanocomposites for electrical insulation applications. Their characteristics are investigated and compared with the pure epoxy resin and nanocomposite fabricated with unmodified nanofillers counterparts. The dispersion features of the nanoparticles in the epoxy resin matrix are examined through scanning electron microscopy (SEM) images. All samples show evidence that the agglomerations are smaller than 30 nm in their diameters. This indicates good dispersion uniformity. The Weibull plot of breakdown strength and the recorded partial discharge (PD) events of the epoxy resin/plasma-treated hydrophilic SiO2 nanocomposite (ER/PTI) suggest that the plasma-treated specimen yields higher breakdown strength and lower PD magnitude as compared to the untreated ones. In contrast, surprisingly, lower breakdown strength is found for the nanocomposite made by the chemically treated hydrophobic particles, whereas the PD magnitude and PD numbers remain at a similar level as the plasma-treated ones.

The Contribution of Distance Education in Providing Education for a Just Social Order.

ERIC Educational Resources Information Center

Rumble, Greville

Concerned with the means by which distance education programs can be used to further social justice in various parts of the world, this paper considers both the generally recognized strengths of and some potential problems in three aspects of such programs--access, curriculum, and a monopolistic tendency. It draws on the experience of the…

Chaos or transformation? Managing innovation.

PubMed

Manion, J

1993-05-01

Nurse innovation is the key to transformation of the healthcare organization and the healthcare system. This article offers the nurse executive and the leadership team a way to assess innovative tendencies of their department or organization and determine where strengths and trouble spots exist. The author discusses a five-phase innovation management process with suggested interventions for each phase.

Educational Decentralization and Its Implications for Governance: Explaining the Differences in the Four Asian Newly Industrialized Economies

ERIC Educational Resources Information Center

Lo, William Yat Wai

2010-01-01

This paper views seeking the optimal balance between state strengths and the scope of state functions for "good governance" as the formation of a homogenization-heterogenization matrix of policy initiatives in different social settings. Homogenization refers to a global tendency for institutional changes and governance framework to…

Thermomechanical treatment of 2124 PM aluminum alloys with low and high dispersoid levels

NASA Technical Reports Server (NTRS)

Sarkar, B.; Lisagor, W. B.

1986-01-01

The effects of thermomechanical treatment (TMT) on the mechanical properties and metallurgical structure of 2124 powder metallurgy aluminum alloys prepared from rapidly solidified powders were investigated. The alloys were prepared by using a standard canning/vacuum degassing/hot consolidation/extrusion sequence. Two compositions, with manganese contents of 0.5 and 1.5 percent, were investigated to examine the effects of low and high dispersoid levels. The results indicate that significant improvements in strength can be accomplished through TMT for this PM alloy system with little loss in toughness. The increase in strength observed is attributed to the presence of much finer, more homogeneous S-prime precipitation than that observed without TMT. Rolling deformation at room temperature resulted in some tendency for nonuniform (planar) deformation and resulted in slightly lower notch strength values. The lower notch strengths observed in the higher manganese composition were attributed to the coarser, more dense dispersoids observed in this material.

Investigation of nanoparticle agglomeration on the effective thermal conductivity of a composite material

NASA Astrophysics Data System (ADS)

Webb, Anthony J.

Phase Change Materials (PCMs), like paraffin wax, can be used for passive thermal management of portable electronics if their overall bulk thermal conductivity is increased through the addition of highly conducting nanoparticles. Finite Element Analysis (FEA) is used to investigate the influence of nanoparticle agglomeration on the overall conductive thermal transport in a nanoenhanced composite by dictating the thermal conductivity of individual elements according to their local inclusion volume fraction and characteristics inside a low conducting PCM matrix. The inclusion density distribution is dictated by an agglomeration factor, and the effective thermal conductivity of each element is calculated from the nanoparticle volume fraction using a method similar to the Representative Volume Element (RVE) methodology. FEA studies are performed for 2-D and 3-D models. In the 2-D model, the grain boundary is fixed at x = 0 for simplicity. For the 3-D model, the grain boundary geometry is randomly varied. A negligible 2-D effect on thermal transport in the 2-D model is seen, so a 1-D thermal resistance network is created for comparison, and the results agree within 4%.The influence of the agglomeration factor and contact Biot number on the overall bulk thermal conductivity is determined by applying Fourier's Law on the entire simulated composite. For the 2-D and 3-D models with a contact Biot number above 1, the overall bulk thermal conductivity decreases prior to the percolation threshold being met and then increases with increasing agglomeration. Finally, a MatlabRTM based image processing tool is created to estimate the agglomeration factor based on an experimental image of a nanoparticle distribution, with a calculated approximate agglomeration value of Beta*L = 5 which results in a bulk thermal conductivity of 0.278 W/(m-K).

PM2.5, Population Exposure and Economic Effects in Urban Agglomerations of China Using Ground-Based Monitoring Data

PubMed Central

Shen, Yonglin

2017-01-01

This paper adopts the PM2.5 concentration data obtained from 1497 station-based monitoring sites, population and gross domestic product (GDP) census data, revealing population exposure and economic effects of PM2.5 in four typical urban agglomerations of China, i.e., Beijing-Tianjin-Hebei (BTH), the Yangtze River delta (YRD), the Pearl River delta (PRD), and Chengdu-Chongqing (CC). The Cokriging interpolation method was used to estimate the PM2.5 concentration from station-level to grid-level. Next, an evaluation was conducted mainly at the grid-level with a cell size of 1 × 1 km, assisted by the urban agglomeration scale. Criteria including the population-weighted mean, the cumulative percent distribution and the correlation coefficient were applied in our evaluation. The results showed that the spatial pattern of population exposure in BTH was consistent with that of PM2.5 concentration, as well as changes in elevation. The topography was also an important factor in the accumulation of PM2.5 in CC. Moreover, the most polluted urban agglomeration based on the population-weighted mean was BTH, while the least was PRD. In terms of the cumulative percent distribution, only 0.51% of the population who lived in the four urban agglomerations, and 2.33% of the GDP that was produced in the four urban agglomerations, were associated with an annual PM2.5 concentration smaller than the Chinese National Ambient Air Quality Standard of 35 µg/m3. This indicates that the majority of people live in the high air polluted areas, and economic development contributes to air pollution. Our results are supported by the high correlation between population exposure and the corresponding GDP in each urban agglomeration. PMID:28671643

Use of mesophilic and thermophilic bacteria for the improvement of copper extraction from a low-grade ore

NASA Astrophysics Data System (ADS)

Darezereshki, E.; Schaffie, M.; Lotfalian, M.; Seiedbaghery, S. A.; Ranjbar, M.

2011-04-01

Bioleaching was examined for copper extraction from a low grade ore using mesophilic and moderate thermophilic bacteria. Five equal size columns were used for the leaching of the ore. Sulfuric acid solution with a flow rate of 3.12 L·m-2·h-1 and pH 1.5 passed through each column continuously for 90 d. In the first and the second column, bioleaching was performed without agglomeration of the ore and on the agglomerated ore, respectively. 28wt% of the copper was extracted in the first column after 40 d, while this figure was 38wt% in the second column. After 90 d, however, the overall extractions were almost the same for both of them. Bioleaching with mesophilic bacteria was performed in the third column without agglomeration of the ore and in the fourth column on the agglomerated ore. After 40 d, copper extractions in the third and the fourth columns were 62wt% and 70wt%, respectively. Copper extractions were 75wt% for both the columns after 90 d. For the last column, bioleaching was performed with moderate thermophilic bacteria and agglomerated ore. Copper extractions were 80wt% and 85wt% after 40 and 90 d, respectively. It was concluded that crushing and agglomeration of the ore using bacteria could enhance the copper extraction considerably.

Temperature-Switchable Agglomeration of Magnetic Particles Designed for Continuous Separation Processes in Biotechnology.

PubMed

Paulus, Anja S; Heinzler, Raphael; Ooi, Huey Wen; Franzreb, Matthias

2015-07-08

The purpose of this work was the synthesis and characterization of thermally switchable magnetic particles for use in biotechnological applications such as protein purification and enzymatic conversions. Reversible addition-fragmentation chain-transfer polymerization was employed to synthesize poly(N-isopropylacrylamide) brushes via a "graft-from" approach on the surface of magnetic microparticles. The resulting particles were characterized by infrared spectroscopy and thermogravimetric analysis and their temperature-dependent agglomeration behavior was assessed. The influence of several factors on particle agglomeration (pH, temperature, salt type, and particle concentration) was evaluated. The results showed that a low pH value (pH 3-4), a kosmotropic salt (ammonium sulfate), and a high particle concentration (4 g/L) resulted in improved agglomeration at elevated temperature (40 °C). Recycling of particles and reversibility of the temperature-switchable agglomeration were successfully demonstrated for ten heating-cooling cycles. Additionally, enhanced magnetic separation was observed for the modified particles. Ionic monomers were integrated into the polymer chain to create end-group functionalized particles as well as two- and three-block copolymer particles for protein binding. The adsorption of lactoferrin, bovine serum albumin, and lysozyme to these ion exchange particles was evaluated and showed a binding capacity of up to 135 mg/g. The dual-responsive particles combined magnetic and thermoresponsive properties for switchable agglomeration, easy separability, and efficient protein adsorption.

The effects of mindfulness-based cognitive therapy on affective memory recall dynamics in depression: a mechanistic model of rumination.

PubMed

van Vugt, Marieke Karlijn; Hitchcock, Peter; Shahar, Ben; Britton, Willoughby

2012-01-01

converging research suggests that mindfulness training exerts its therapeutic effects on depression by reducing rumination. Theoretically, rumination is a multifaceted construct that aggregates multiple neurocognitive aspects of depression, including poor executive control, negative and overgeneral memory bias, and persistence or stickiness of negative mind states. Current measures of rumination, most-often self-reports, do not capture these different aspects of ruminative tendencies, and therefore are limited in providing detailed information about the mechanisms of mindfulness. we developed new insight into the potential mechanisms of rumination, based on three model-based metrics of free recall dynamics. These three measures reflect the patterns of memory retrieval of valenced information: the probability of first recall (Pstart) which represents initial affective bias, the probability of staying with the same valence category rather than switching, which indicates strength of positive or negative association networks (Pstay), and probability of stopping (Pstop) or ending recall within a given valence, which indicates persistence or stickiness of a mind state. We investigated the effects of Mindfulness-Based Cognitive Therapy (MBCT; N = 29) vs. wait-list control (N = 23) on these recall dynamics in a randomized controlled trial in individuals with recurrent depression. Participants completed a standard laboratory stressor, the Trier Social Stress Test, to induce negative mood and activate ruminative tendencies. Following that, participants completed a free recall task consisting of three word lists. This assessment was conducted both before and after treatment or wait-list. while MBCT participant's Pstart remained relatively stable, controls showed multiple indications of depression-related deterioration toward more negative and less positive bias. Following the intervention, MBCT participants decreased in their tendency to sustain trains of negative words and increased their tendency to sustain trains of positive words. Conversely, controls showed the opposite tendency: controls stayed in trains of negative words for longer, and stayed in trains of positive words for less time relative to pre-intervention scores. MBCT participants tended to stop recall less often with negative words, which indicates less persistence or stickiness of negatively valenced mental context. MBCT participants showed a decrease in patterns that may perpetuate rumination on all three types of recall dynamics (Pstart, Pstay, and Pstop), compared to controls. MBCT may weaken the strength of self-perpetuating negative associations networks that are responsible for the persistent and "sticky" negative mind states observed in depression, and increase the positive associations that are lacking in depression. This study also offers a novel, objective method of measuring several indices of ruminative tendencies indicative of the underlying mechanisms of rumination.

Mechanical and morphological properties of polypropylene/nano α-Al2O3 composites.

PubMed

Mirjalili, F; Chuah, L; Salahi, E

2014-01-01

A nanocomposite containing polypropylene (PP) and nano α-Al2O3 particles was prepared using a Haake internal mixer. Mechanical tests, such as tensile and flexural tests, showed that mechanical properties of the composite were enhanced by addition of nano α-Al2O3 particles and dispersant agent to the polymer. Tensile strength was approximately ∼ 16% higher than pure PP by increasing the nano α-Al2O3 loading from 1 to 4 wt% into the PP matrix. The results of flexural analysis indicated that the maximum values of flexural strength and flexural modulus for nanocomposite without dispersant were 50.5 and 1954 MPa and for nanocomposite with dispersant were 55.88 MPa and 2818 MPa, respectively. However, higher concentration of nano α-Al2O3 loading resulted in reduction of those mechanical properties that could be due to agglomeration of nano α-Al2O3 particles. Transmission and scanning electron microscopic observations of the nanocomposites also showed that fracture surface became rougher by increasing the content of filler loading from 1 to 4% wt.

Directional Agglomeration Multigrid Techniques for High Reynolds Number Viscous Flow Solvers

NASA Technical Reports Server (NTRS)

1998-01-01

A preconditioned directional-implicit agglomeration algorithm is developed for solving two- and three-dimensional viscous flows on highly anisotropic unstructured meshes of mixed-element types. The multigrid smoother consists of a pre-conditioned point- or line-implicit solver which operates on lines constructed in the unstructured mesh using a weighted graph algorithm. Directional coarsening or agglomeration is achieved using a similar weighted graph algorithm. A tight coupling of the line construction and directional agglomeration algorithms enables the use of aggressive coarsening ratios in the multigrid algorithm, which in turn reduces the cost of a multigrid cycle. Convergence rates which are independent of the degree of grid stretching are demonstrated in both two and three dimensions. Further improvement of the three-dimensional convergence rates through a GMRES technique is also demonstrated.

Directional Agglomeration Multigrid Techniques for High-Reynolds Number Viscous Flows

NASA Technical Reports Server (NTRS)

Mavriplis, Dimitri J.

1998-01-01

A preconditioned directional-implicit agglomeration algorithm is developed for solving two- and three-dimensional viscous flows on highly anisotropic unstructured meshes of mixed-element types. The multigrid smoother consists of a pre-conditioned point- or line-implicit solver which operates on lines constructed in the unstructured mesh using a weighted graph algorithm. Directional coarsening or agglomeration is achieved using a similar weighted graph algorithm. A tight coupling of the line construction and directional agglomeration algorithms enables the use of aggressive coarsening ratios in the multigrid algorithm, which in turn reduces the cost of a multigrid cycle. Convergence rates which are independent of the degree of grid stretching are demonstrated in both two and three dimensions. Further improvement of the three-dimensional convergence rates through a GMRES technique is also demonstrated.

New measurements of photospheric magnetic fields in late-type stars and emerging trends

NASA Technical Reports Server (NTRS)

Saar, S. H.; Linsky, J. L.

1986-01-01

The magnetic fields of late-type stars are measured using the method of Saar et al. (1986). The method includes radiative transfer effects and compensation for line blending; the photospheric magnetic field parameters are derived by comparing observed and theoretical line profiles using an LTE code that includes line saturation and full Zeeman pattern. The preliminary mean active region magnetic field strengths (B) and surface area coverages for 20 stars are discussed. It is observed that there is a trend of increasing B towards the cooler dwarfs stars, and the linear correlation between B and the equipartition value of the magnetic field strength suggests that the photospheric gas pressure determines the photospheric magnetic field strengths. A tendency toward larger filling factors at larger stellar angular velocities is also detected.

Effect of bending on the room-temperature tensile strengths of structural ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jenkins, M.G.

1992-01-01

Results for nearly fifty, room-temperature tensile tests conducted on two advanced, monolithic silicon nitride ceramics are evaluated for the effects of bending and application of various Weibull statistical analyses. Two specimen gripping systems (straight collet and tapered collet) were evaluated for both success in producing gage section failures and tendency to minimize bending at failure. Specimen fabrication and grinding technique consderations are briefly reviewed and related to their effects on successful tensile tests. Ultimate tensile strengths are related to the bending measured at specimen failure and the effects of the gripping system on bending are discussed. Finally, comparisons are mademore » between the use of censored and uncensored data sample sets for determining the maximum likelihood estimates of the Weibull parameters from the tensile strength distributions.« less

Effect of bending on the room-temperature tensile strengths of structural ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jenkins, M.G.

1992-07-01

Results for nearly fifty, room-temperature tensile tests conducted on two advanced, monolithic silicon nitride ceramics are evaluated for the effects of bending and application of various Weibull statistical analyses. Two specimen gripping systems (straight collet and tapered collet) were evaluated for both success in producing gage section failures and tendency to minimize bending at failure. Specimen fabrication and grinding technique consderations are briefly reviewed and related to their effects on successful tensile tests. Ultimate tensile strengths are related to the bending measured at specimen failure and the effects of the gripping system on bending are discussed. Finally, comparisons are mademore » between the use of censored and uncensored data sample sets for determining the maximum likelihood estimates of the Weibull parameters from the tensile strength distributions.« less

Investigation of the interaction of ferromagnetic fluids with proteins by dynamic light scattering

NASA Astrophysics Data System (ADS)

Velichko, Elena; Nepomnyashchaya, Elina; Dudina, Alina; Pleshakov, Ivan; Aksenov, Evgenii

2018-04-01

In this article the interaction between ionically stabilized magnetic nanoparticles and blood serum albumin proteins in liquid medium are discussed. Some distributions of nanoparticles' agglomerate sizes in solutions of albumin molecules, magnetic nanoparticles and their mixtures both under the influence of magnetic field and free from it are presented. It is shown that magnetic nanoparticles interact with albumin molecules, forming agglomerates. It is also shown that at the influence of magnetic field sizes of agglomerates increase proportionally to the magnetic field density.

Transport and Deposition of Welding Fume Agglomerates in a Realistic Human Nasal Airway.

PubMed

Tian, Lin; Inthavong, Kiao; Lidén, Göran; Shang, Yidan; Tu, Jiyuan

2016-07-01

Welding fume is a complex mixture containing ultra-fine particles in the nanometer range. Rather than being in the form of a singular sphere, due to the high particle concentration, welding fume particles agglomerate into long straight chains, branches, or other forms of compact shapes. Understanding the transport and deposition of these nano-agglomerates in human respiratory systems is of great interest as welding fumes are a known health hazard. The neurotoxin manganese (Mn) is a common element in welding fumes. Particulate Mn, either as soluble salts or oxides, that has deposited on the olfactory mucosa in human nasal airway is transported along the olfactory nerve to the olfactory bulb within the brain. If this Mn is further transported to the basal ganglia of the brain, it could accumulate at the part of the brain that is the focal point of its neurotoxicity. Accounting for various dynamic shape factors due to particle agglomeration, the current computational study is focused on the exposure route, the deposition pattern, and the deposition efficiency of the inhaled welding fume particles in a realistic human nasal cavity. Particular attention is given to the deposition pattern and deposition efficiency of inhaled welding fume agglomerates in the nasal olfactory region. For particles in the nanoscale, molecular diffusion is the dominant transport mechanism. Therefore, Brownian diffusion, hydrodynamic drag, Saffman lift force, and gravitational force are included in the model study. The deposition efficiencies for single spherical particles, two kinds of agglomerates of primary particles, two-dimensional planar and straight chains, are investigated for a range of primary particle sizes and a range of number of primary particles per agglomerate. A small fraction of the inhaled welding fume agglomerates is deposited on the olfactory mucosa, approximately in the range 0.1-1%, and depends on particle size and morphology. The strong size dependence of the deposition in olfactory mucosa on particle size implies that the occupation deposition of welding fume manganese can be expected to vary with welding method. © The Author 2016. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Adaptations in humans for assessing physical strength from the voice

PubMed Central

Sell, Aaron; Bryant, Gregory A.; Cosmides, Leda; Tooby, John; Sznycer, Daniel; von Rueden, Christopher; Krauss, Andre; Gurven, Michael

2010-01-01

Recent research has shown that humans, like many other animals, have a specialization for assessing fighting ability from visual cues. Because it is probable that the voice contains cues of strength and formidability that are not available visually, we predicted that selection has also equipped humans with the ability to estimate physical strength from the voice. We found that subjects accurately assessed upper-body strength in voices taken from eight samples across four distinct populations and language groups: the Tsimane of Bolivia, Andean herder-horticulturalists and United States and Romanian college students. Regardless of whether raters were told to assess height, weight, strength or fighting ability, they produced similar ratings that tracked upper-body strength independent of height and weight. Male voices were more accurately assessed than female voices, which is consistent with ethnographic data showing a greater tendency among males to engage in violent aggression. Raters extracted information about strength from the voice that was not supplied from visual cues, and were accurate with both familiar and unfamiliar languages. These results provide, to our knowledge, the first direct evidence that both men and women can accurately assess men's physical strength from the voice, and suggest that estimates of strength are used to assess fighting ability. PMID:20554544

Streptomycin-loaded PLGA-alginate nanoparticles: preparation, characterization, and assessment

NASA Astrophysics Data System (ADS)

Asadi, Asadollah

2014-04-01

The aim of this study was to formulate and characterize streptomycin-loaded PLGA-alginate nanoparticles for their potential therapeutic use in Salmonella subsp. enterica ATCC 14028 infections. The streptomycin nanoparticle was prepared by solvent diffusion method, and the other properties such as size, zeta potential, loading efficacy, release kinetics, and antimicrobial strength were evaluated. The survey shows that nanoparticles may serve as a carrier of streptomycin and may provide localized antibacterial activity in the treatment of Salmonellosis. Electron microscopy showed spherical particles with indentations. The average size of the nanoparticles was 90 nm. At pH 7.2, the release kinetics of streptomycin from the nanoparticles was successfully illustrated as an initial burst defined by a first order equation that after this stage, it has a drastic tendency to obtain steady state. Nevertheless, nanoparticles showed loading efficacy nearly about 70-75 %. In addition, the tendency of concentration of streptomycin released from nanoparticles to reach antibacterial activity was similar to that of free streptomycin against PLGA-alginate, but it had threefold more antimicrobial strength in comparison with free streptomycin. This work shows the potential use of streptomycin-loaded PLGA-alginate nanoparticles and its capability.

Influence of Surface Properties of Filtration-Layer Metal Oxide on Ceramic Membrane Fouling during Ultrafiltration of Oil/Water Emulsion.

PubMed

Lu, Dongwei; Zhang, Tao; Gutierrez, Leo; Ma, Jun; Croué, Jean-Philippe

2016-05-03

In this work, ceramic ultrafiltration membranes deposited with different metal oxides (i.e., TiO2, Fe2O3, MnO2, CuO, and CeO2) of around 10 nm in thickness and similar roughness were tested for O/W emulsion treatment. A distinct membrane fouling tendency was observed, which closely correlated to the properties of the filtration-layer metal oxides (i.e., surface hydroxyl groups, hydrophilicity, surface charge, and adhesion energy for oil droplets). Consistent with the distinct bond strength of the surface hydroxyl groups, hydrophilicity of these common metal oxides is quite different. The differences in hydrophilicity consequently lead to different adhesion of these metal oxides toward oil droplets, consistent with the irreversible membrane fouling tendency. In addition, the surface charge of the metal oxide opposite to that of emulsion can help to alleviate irreversible membrane fouling in ultrafiltration. Highly hydrophilic Fe2O3 with the lowest fouling tendency could be a potential filtration-layer material for the fabrication/modification of ceramic membranes for O/W emulsion treatment. To the best of our knowledge, this is the first study clearly showing the correlations between surface properties of filtration-layer metal oxides and ceramic membrane fouling tendency by O/W emulsion.

Acoustic agglomeration methods and apparatus

NASA Technical Reports Server (NTRS)

Barmatz, M. B. (Inventor)

1984-01-01

Methods are described for using acoustic energy to agglomerate fine particles on the order of one micron diameter that are suspended in gas, to provide agglomerates large enough for efficient removal by other techniques. The gas with suspended particles, is passed through the length of a chamber while acoustic energy at a resonant chamber mode is applied to set up one or more acoustic standing wave patterns that vibrate the suspended particles to bring them together so they agglomerate. Several widely different frequencies can be applied to efficiently vibrate particles of widely differing sizes. The standing wave pattern can be applied along directions transversed to the flow of the gas. The particles can be made to move in circles by applying acoustic energy in perpendicular directions with the energy in both directions being of the same wavelength but 90 deg out of phase.

A comparison of dispersing media for various engineered carbon nanoparticles.

PubMed

Buford, Mary C; Hamilton, Raymond F; Holian, Andrij

2007-07-27

With the increased manufacture and use of carbon nanoparticles (CNP) there has been increasing concern about the potential toxicity of fugitive CNP in the workplace and ambient environment. To address this matter a number of investigators have conducted in vitro and in vivo toxicity assessments. However, a variety of different approaches for suspension of these particles (culture media, Tween 80, dimethyl sulfoxide, phosphate-buffered saline, fetal calf serum, and others), and different sources of materials have generated potentially conflicting outcomes. The quality of the dispersion of nanoparticles is very dependent on the medium used to suspend them, and this then will most likely affect the biological outcomes. In this work, the distributions of different CNP (sources and types) have been characterized in various media. Furthermore, the outcome of instilling the different agglomerates, or size distributions, was examined in mouse lungs after one and seven days. Our results demonstrated that CNP suspended in serum produced particle suspensions with the fewest large agglomerates, and the most uniform distribution in mouse lungs. In addition, no apparent clearance of instilled CNP took place from lungs even after seven days. This work demonstrates that CNP agglomerates are present in all dispersing vehicles to some degree. The vehicle that contains some protein, lipid or protein/lipid component disperses the CNP best, producing fewer large CNP agglomerates. In contrast, vehicles absent of lipid and protein produce the largest CNP agglomerates. The source of the CNP is also a factor in the degree of particle agglomeration within the same vehicle.

A discrete element and ray framework for rapid simulation of acoustical dispersion of microscale particulate agglomerations

NASA Astrophysics Data System (ADS)

Zohdi, T. I.

2016-03-01

In industry, particle-laden fluids, such as particle-functionalized inks, are constructed by adding fine-scale particles to a liquid solution, in order to achieve desired overall properties in both liquid and (cured) solid states. However, oftentimes undesirable particulate agglomerations arise due to some form of mutual-attraction stemming from near-field forces, stray electrostatic charges, process ionization and mechanical adhesion. For proper operation of industrial processes involving particle-laden fluids, it is important to carefully breakup and disperse these agglomerations. One approach is to target high-frequency acoustical pressure-pulses to breakup such agglomerations. The objective of this paper is to develop a computational model and corresponding solution algorithm to enable rapid simulation of the effect of acoustical pulses on an agglomeration composed of a collection of discrete particles. Because of the complex agglomeration microstructure, containing gaps and interfaces, this type of system is extremely difficult to mesh and simulate using continuum-based methods, such as the finite difference time domain or the finite element method. Accordingly, a computationally-amenable discrete element/discrete ray model is developed which captures the primary physical events in this process, such as the reflection and absorption of acoustical energy, and the induced forces on the particulate microstructure. The approach utilizes a staggered, iterative solution scheme to calculate the power transfer from the acoustical pulse to the particles and the subsequent changes (breakup) of the pulse due to the particles. Three-dimensional examples are provided to illustrate the approach.

Particle agglomeration and fuel decomposition in burning slurry droplets

NASA Astrophysics Data System (ADS)

Choudhury, P. Roy; Gerstein, Melvin

In a burning slurry droplet the particles tend to agglomerate and produce large clusters which are difficult to burn. As a consequence, the combustion efficiency is drastically reduced. For such a droplet the nonlinear D2- t behavior associated with the formation of hard to burn agglomerates can be explained if the fuel decomposes on the surface of the particles. This paper deals with analysis and experiments with JP-10 and Diesel #2 slurries prepared with inert SiC and Al 2O 3 particles. It provides direct evidence of decomposed fuel residue on the surface of the particles heated by flame radiation. These decomposed fuel residues act as bonding agents and appear to be responsible for the observed agglomeration of particles in a slurry. Chemical analysis, scanning electron microscope photographs and finally micro-analysis by electron scattering clearly show the presence of decomposed fuel residue on the surface of the particles. Diesel #2 is decomposed relatively easily and therefore leaves a thicker deposit on SiC and forms larger agglomerates than the more stable JP-10. A surface reaction model with particles heated by flame radiation is able to describe the observed trend of the diameter history of the slurry fuel. Additional experiments with particles of lower emissivity (Al 2O 3) and radiation absorbing dye validate the theoretical model of the role of flame radiation in fuel decomposition and the formation of agglomerates in burning slurry droplets.

Characterisation of the de-agglomeration effects of bovine serum albumin on nanoparticles in aqueous suspension.

PubMed

Tantra, Ratna; Tompkins, Jordan; Quincey, Paul

2010-01-01

This paper describes the use of nanoparticle characterisation tools to evaluate the interaction between bovine serum albumin (BSA) and dispersed nanoparticles in aqueous media. Dynamic light scattering, zeta-potential measurements and scanning electron microscopy were used to probe the state of zinc oxide (ZnO) and titanium dioxide (TiO(2)) nanoparticles in the presence of various concentrations of BSA, throughout a three-day period. BSA was shown to adhere to ZnO but not to TiO(2). The adsorption of BSA led to subsequent de-agglomeration of the sub-micron ZnO clusters into smaller fragments, even breaking them up into individual isolated nanoparticles. We propose that certain factors, such as adsorption kinetics of BSA on to the surface of ZnO, as well as the initial agglomerated state of the ZnO, prior to BSA addition, are responsible for promoting the de-agglomeration process. Hence, in the case of TiO(2) we see no de-agglomeration because: (a) the nanoparticles are more highly agglomerated to begin with and (b) BSA does not adsorb effectively on the surface of the nanoparticles. The zeta-potential results show that, for either ZnO or TiO(2), the presence of BSA resulted in enhanced stability. In the case of ZnO, the enhanced stability is limited to BSA concentrations below 0.5 wt.%. Steric and electrostatic repulsion are thought to be responsible for improved stability of the dispersion.

Water-extractable and water-unextractable arabinoxylans affect gluten agglomeration behavior during wheat flour gluten-starch separation.

PubMed

Frederix, Sofie A; Van Hoeymissen, Klaartje E; Courtin, Christophe M; Delcour, Jan A

2004-12-29

Water-extractable arabinoxylan (WE-AX) of variable molecular weight (MW) and water-unextractable arabinoxylan (WU-AX) were added to wheat flour to study their effect on gluten agglomeration in a dough and batter gluten-starch separation process with recovery of gluten from the batter with a set of vibrating sieves (400, 250, and 125 microm). Low MW WE-AX had almost no impact on the distribution of the gluten on the different sieves. High MW WE-AX decreased yields of the largest (400 microm sieve) gluten aggregates, more than their medium MW counterparts, indicating the importance of AX MW for their effect on gluten interactions. Correlations between the total level of gluten protein recovered on the three sieves and the batter extract viscosity as well as between the proportion of gluten protein recovered on the 400 microm sieve to that on the three sieves and the batter extract viscosity pointed to the importance of viscosity as an indicator for gluten agglomeration, as did the fact that another viscosity increasing plant polysaccharide (guar gum) also negatively influenced gluten agglomeration. However, the obtained data cannot rule out that AX and guar gum also exert steric effects on gluten agglomeration. WU-AX, present as discrete cell wall fragments, had a negative impact on the level of large gluten aggregates. Taken together, the results show that both native WE-AX and WU-AX detrimentally impact gluten agglomeration.

Development of a lauric acid/albumin hybrid iron oxide nanoparticle system with improved biocompatibility

PubMed Central

Zaloga, Jan; Janko, Christina; Nowak, Johannes; Matuszak, Jasmin; Knaup, Sabine; Eberbeck, Dietmar; Tietze, Rainer; Unterweger, Harald; Friedrich, Ralf P; Duerr, Stephan; Heimke-Brinck, Ralph; Baum, Eva; Cicha, Iwona; Dörje, Frank; Odenbach, Stefan; Lyer, Stefan; Lee, Geoffrey; Alexiou, Christoph

2014-01-01

The promising potential of superparamagnetic iron oxide nanoparticles (SPIONs) in various nanomedical applications has been frequently reported. However, although many different synthesis methods, coatings, and functionalization techniques have been described, not many core-shell SPION drug delivery systems are available for clinicians at the moment. Here, bovine serum albumin was adsorbed onto lauric acid-stabilized SPIONs. The agglomeration behavior, zeta potential, and their dependence on the synthesis conditions were characterized with dynamic light scattering. The existence and composition of the core-shell-matrix structure was investigated by transmission electron microscopy, Fourier transform infrared spectroscopy, and zeta potential measurements. We showed that the iron oxide cores form agglomerates in the range of 80 nm. Moreover, despite their remarkably low tendency to aggregate even in a complex media like whole blood, the SPIONs still maintained their magnetic properties and were well attractable with a magnet. The magnetic properties were quantified by vibrating sample magnetometry and a superconducting quantum interference device. Using flow cytometry, we further investigated the effects of the different types of nanoparticle coating on morphology, viability, and DNA integrity of Jurkat cells. We showed that by addition of bovine serum albumin, the toxicity of nanoparticles is greatly reduced. We also investigated the effect of the particles on the growth of primary human endothelial cells to further demonstrate the biocompatibility of the particles. As proof of principle, we showed that the hybrid-coated particles are able to carry payloads of up to 800 μg/mL of the cytostatic drug mitoxantrone while still staying colloidally stable. The drug-loaded system exhibited excellent therapeutic potential in vitro, exceeding that of free mitoxantrone. In conclusion, we have synthesized a biocompatible ferrofluid that shows great potential for clinical application. The synthesis is straightforward and reproducible and thus easily translatable into a good manufacturing practice environment. PMID:25364244

Preparation and Characterization of Chitosan-coated Fe3O4 Nanoparticles using Ex-Situ Co-Precipitation Method and Tripolyphosphate/Sulphate as Dual Crosslinkers

NASA Astrophysics Data System (ADS)

Wulandari, Ika O.; Mardila, Vita T.; Santjojo, D. J. Djoko H.; Sabarudin, Akhmad

2018-01-01

The unique properties of nanomaterial provide great opportunities to develop in several fields. Several types of nanoparticles have been proven beneficial for biomedical and therapeutic agent development. Particularly for clinical use, nanoparticles must be biocompatible and non-toxic. Iron oxide nanoparticles consist of either magnetite (Fe3O4) or maghemite (γ-Fe2O3) was eligible to use for in vivo application including targeting drug delivery. Due to their distinct properties, these nanoparticles could be directed to the specific target under external magnetic field. However, nanoparticles have a tendency to form agglomeration. Therefore, surface modification was required to reduce the agglomeration. In this study, nanoparticles of Fe3O4 were produced and coated by biomaterial (chitosan) using ex-situ co-precipitation method. Nanoparticles of Fe3O4 were synthesized by adding ammonia water into iron ferric and ferrous solution. Synthesis process of Fe3O4 was conducted prior to adding chitosan. Chitosan was then cross-linked by a combination of tripolyphosphate/sulphate. The different composition ratio and crosslinking time provide the different physical and magnetic characteristics of nanoparticles. Particle and crystallite size was determined by using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) respectively, whereas magnetic characteristic was determined by Electron Spin Resonance (ESR). The results showed that the ratio enhancement between chitosan: Fe3O4 increase the particle size, while decreased the crystallite size. Morphology and particle size were influenced by the ratio of crosslinkers. It was found that the higher tripolyphosphate content was contributed to the small size and more spherical morphology. In addition, the influence of crosslinking time toward crystallite size was determined by altering stirring time. The longer duration of crosslinking time, provide the larger crystallite size of chitosan-Fe3O4. There was an interesting correlation between particle size and amount of Fe3O4 phase with ESR curve.

Multilaboratory study of the shifts in the IEP of anatase at high ionic strengths.

PubMed

Kosmulski, Marek; Dukhin, Andrei S; Priester, Torsten; Rosenholm, Jarl B

2003-07-01

The zeta-potentials of anatase at pH 2-11 in 0.1, 0.3, 0.5, and 1 moldm(-3) NaI were studied using the DT 1200 in three laboratories. At [NaI]=1 moldm(-3) the zeta-potentials were positive over the entire pH range. The previously observed tendency of the isoelectric point of anatase to shift to high pH at high ionic strength (M. Kosmulski, J.B. Rosenholm, J. Phys. Chem. 100 (1996) 11681) and the salt specificity of this effect were confirmed. The zeta-potentials obtained in different laboratories using DT 1200 are consistent within 3 mV.

Two-stage agglomeration of fine-grained herbal nettle waste

NASA Astrophysics Data System (ADS)

Obidziński, Sławomir; Joka, Magdalena; Fijoł, Olga

2017-10-01

This paper compares the densification work necessary for the pressure agglomeration of fine-grained dusty nettle waste, with the densification work involved in two-stage agglomeration of the same material. In the first stage, the material was pre-densified through coating with a binder material in the form of a 5% potato starch solution, and then subjected to pressure agglomeration. A number of tests were conducted to determine the effect of the moisture content in the nettle waste (15, 18 and 21%), as well as the process temperature (50, 70, 90°C) on the values of densification work and the density of the obtained pellets. For pre-densified pellets from a mixture of nettle waste and a starch solution, the conducted tests determined the effect of pellet particle size (1, 2, and 3 mm) and the process temperature (50, 70, 90°C) on the same values. On the basis of the tests, we concluded that the introduction of a binder material and the use of two-stage agglomeration in nettle waste densification resulted in increased densification work (as compared to the densification of nettle waste alone) and increased pellet density.

Production of aluminum--silicon alloy and ferrosilicon and commercial purity aluminum by the direct reduction process. First interim technical report, Phase B, September 1--November 30, 1978

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruno, M.J.

1978-12-01

The parameters of charge content, reaction temperatures and residence time were studied in a bench reactor concerning the production of Al--Si and Fe--Si alloys. Results confirmed that minimum final stage reaction temperature is 1950 to 2000/sup 0/C. Residence time varied with initial charge concentration. Fe/sub 2/O/sub 3/ additions to the charge produced a significant increase in metallic yield. A burden preparation procedure was developed for making acceptable agglomerates containing Fe/sub 2/O/sub 3/, bauxite, clay and coke. Particle size distribution of starting materials was correlated with agglomerate strength. A new bench scale reactor was designed and built to facilitate semi-continuous operation,more » using O/sub 2/ injection to burn coke supporting the burden, resulting in burden movement. In a number of runs bridging of the burden material occurred due to condensation of volatilized sub-oxides in the cooler zones of the reactor. The reactor operated smoothly as an iron blast furnace at 1500/sup 0/C, demonstrating the validity of the equipment and test procedures. Initial construction of pilot reactor VSR-1 was completed. Bench scale fractional crystallizer runs were continued to determine the impurity effects of Fe up to 6.9% and Ti up to 1.25% on alloy product concentration and yield. High levels of impurities formed intermetallic complexes with Al and reduced product yield.« less

The role of interstitial binding in radiation induced segregation in W-Re alloys

NASA Astrophysics Data System (ADS)

Gharaee, Leili; Marian, Jaime; Erhart, Paul

2016-07-01

Due to their high strength and advantageous high-temperature properties, tungsten-based alloys are being considered as plasma-facing candidate materials in fusion devices. Under neutron irradiation, rhenium, which is produced by nuclear transmutation, has been found to precipitate in elongated precipitates forming thermodynamic intermetallic phases at concentrations well below the solubility limit. Recent measurements have shown that Re precipitation can lead to substantial hardening, which may have a detrimental effect on the fracture toughness of W alloys. This puzzle of sub-solubility precipitation points to the role played by irradiation induced defects, specifically mixed solute-W interstitials. Here, using first-principles calculations based on density functional theory, we study the energetics of mixed interstitial defects in W-Re, W-V, and W-Ti alloys, as well as the heat of mixing for each substitutional solute. We find that mixed interstitials in all systems are strongly attracted to each other with binding energies of -2.4 to -3.2 eV and form interstitial pairs that are aligned along parallel first-neighbor <111 > strings. Low barriers for defect translation and rotation enable defect agglomeration and alignment even at moderate temperatures. We propose that these elongated agglomerates of mixed-interstitials may act as precursors for the formation of needle-shaped intermetallic precipitates. This interstitial-based mechanism is not limited to radiation induced segregation and precipitation in W-Re alloys but is also applicable to other body-centered cubic alloys.

Formation mechanism of shock-induced particle jetting.

PubMed

Xue, K; Sun, L; Bai, C

2016-08-01

The shock dissemination of granular rings or shells is characterized by the formation of coherent particle jets that have different dimensions from those associated with the constituent grains. In order to identify the mechanisms governing the formation of particle jets, we carry out the simulations of the shock dispersal of quasi-two-dimensional particle rings based on the discrete-element method. The evolution of the particle velocities and contact forces on the time scales ranging from microseconds to milliseconds reveals a two-stage development of particle jets before they are expelled from the outer surface. Much effort is made to understand the particle agglomeration around the inner surface that initiates the jet formation. The shock interaction with the innermost particle layers generates a heterogeneous network of force chains with clusters of strong contacts regularly spaced around the inner surface. Momentum alongside the stresses is primarily transmitted along the strong force chains. Therefore, the clustering of strong force chains renders the agglomeration of fast-moving particles connected by strong force chains. The fast-moving particle clusters subsequently evolve into the incipient particle jets. The following competition among the incipient jets that undergo unbalanced growth leads to substantial elimination of the minor jets and the significant multiplication of the major jets, the number of jets thus varying with time. Moreover, the number of jets is found to increase with the strength of the shock loading due to an increased number of jets surviving the retarding effect of major jets.

Leukocyte Agglomeration Reaction in Diagnosis of Allergy Reactions from Antibiotics,

DTIC Science & Technology

tested in a clinic on 80 patients with serious allergic anamnesis . The results of the studies indicate that the leukocyte agglomeration reaction is a highly sensitive immunological indicator of hypersensitivity to antibiotics.

METALLOGRAPHIC STUDIES OF SPUTNIK 4 FRAGMENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kammerer, O.F.; Sadofsky, J.; Gurinsky, D.H.

1963-09-01

Metallographic analyses were performed on a fragment of steel recovered after the disintegration of Sputnik 4 and on a melted agglomerate found on the fragment. The examination indicated that the material was a hot-rolled carbon steel similar in hardness to a structural steel with a tensile strength of 3.8 to 4.1 x 10/sup 10/ dynes/cm/sup 2/. The major portion of the fragment exhibited a banded structure characteristic of hot-rolled material. The upper surface was probably heated to the melting point which resulted in the formation of a narrow band similar to an as-cast Widmannstaettn microstructure. The melted material at themore » bottom of the specimen was a porous mass containing several different varieties of inclusions and compounds. (auth)« less

Chemical Characterization of Bed Material Coatingsby LA-ICP-MS and SEM-EDS

NASA Astrophysics Data System (ADS)

Piispanen, M. H.; Mustonen, A. J.; Tiainen, M. S.; Laitinen, R. S.

Bed material coatings and the consequent agglomeration of bed material are main ash-related problems in FB-boilers. The bed agglomeration is a particular problem when combusting biofuels and waste materials. Whereas SEM-EDS together with automated image processing has proven to be a convenient method to study compositional distribution in coating layers and agglomerates, it is a relatively expensive technique and is not necessarily widely available. In this contribution, we explore the suitability of LA-ICP-MS to provide analogous information of the bed.

A pocket model for aluminum agglomeration in composite propellants

NASA Technical Reports Server (NTRS)

Cohen, N. S.

1981-01-01

This paper presents a model for the purpose of estimating the fraction of aluminum powder that will form agglomerates at the surface of deflagrating composite propellants. The basic idea is that the fraction agglomerated depends upon the amount of aluminum that melts within effective binder pocket volumes framed by oxidizer particles. The effective pocket depends upon the ability of ammonium perchlorate modals to encapsulate the aluminum and provide a local temperature sufficient to ignite the aluminum. Model results are discussed in the light of data showing effects of propellant formulation variables and pressure.

Photovoltaic's silica-rich waste sludge as supplementary cementitious material (SCM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quercia, G., E-mail: g.quercia@tue.nl; Eindhoven University of Technology, Department of the Built Environment, P.O. Box 513, 5600 MB Eindhoven; Putten, J.J.G. van der

2013-12-15

Waste sludge, a solid recovered from wastewater of photovoltaic-industries, composes of agglomerates of nano-particles like SiO{sub 2} and CaCO{sub 3}. This sludge deflocculates in aqueous solutions into nano-particles smaller than 1 μm. Thus, this sludge constitutes a potentially hazardous waste when it is improperly disposed. Due to its high content of amorphous SiO{sub 2}, this sludge has a potential use as supplementary cementitious material (SCM) in concrete. In this study the main properties of three different samples of photovoltaic's silica-rich waste sludge (nSS) were physically and chemically characterized. The characterization techniques included: scanning electron microscopy (SEM), X-ray energy dispersive spectroscopymore » (EDS), X-ray diffraction (XRD), nitrogen physical adsorption isotherm (BET method), density by Helium pycnometry, particle size distribution determined by laser light scattering (LLS) and zeta-potential measurements by dynamic light scattering (DLS). In addition, a dispersability study was performed to design stable slurries to be used as liquid additives for the concrete production on site. The effects on the hydration kinetics of cement pastes by the incorporation of nSS in the designed slurries were determined using an isothermal calorimeter. A compressive strength test of standard mortars with 7% of cement replacement was performed to determine the pozzolanic activity of the waste nano-silica sludge. Finally, the hardened system was fully characterized to determine the phase composition. The results demonstrate that the nSS can be utilized as SCM to replace portion of cement in mortars, thereby decreasing the CO{sub 2} footprint and the environmental impact of concrete. -- Highlights: •Three different samples of PV nano-silica sludge (nSS) were fully characterized. •nSS is composed of agglomerates of nano-particles like SiO{sub 2} and CaCO{sub 3}. •Dispersability studies demonstrated that nSS agglomerates are broken to nano-size. •nSS can be classified as a pozzolanic material with activity index higher than 100. •nSS can be use as a potential SCM to partly replace cement in concrete.« less

The improved dissolution performance of a post processing treated spray-dried crystalline solid dispersion of poorly soluble drugs.

PubMed

Chan, Siok-Yee; Toh, Seok-Ming; Khan, Nasir Hayat; Chung, Yin-Ying; Cheah, Xin-Zi

2016-11-01

Solution-mediated transformation has been cited as one of the main problems that deteriorate dissolution performances of solid dispersion (SD). This is mainly attributed by the recrystallization tendency of poorly soluble drug. Eventually, it will lead to extensive agglomeration which is a key process in reducing the dissolution performance of SD and offsets the true benefit of SD system. Here, a post-processing treatment is suggested in order to reduce the recrystallization tendency and hence bring forth the dissolution advantage of SD system. The current study investigates the effect of a post processing treatment on dissolution performance of SD in comparison to their performances upon production. Two poorly soluble drugs were spray dried into SD using polyvinyl alcohol (PVA) as hydrophilic carrier. The obtained samples were post processing treated by exposure to high humidity, i.e. 75% RH at room temperature. The physical properties and release rate of the SD system were characterized upon production and after the post-processing treatment. XRPD, Infrared and DSC results showed partial crystallinity of the fresh SD systems. Crystallinity of these products was further increased after the post-processing treatment at 75% RH. This may be attributed to the high moisture absorption of the SD system that promotes recrystallization process of the drug. However, dissolution efficiencies of the post-treated systems were higher and more consistent than the fresh SD. The unexpected dissolution trend was further supported by the results intrinsic dissolution and solubility studies. An increase of crystallinity in a post humidity treated SD did not exert detrimental effect to their dissolution profiles. A more stabilized system with a preferable enhanced dissolution rate was obtained by exposing the SD to a post processing humidity treatment.

Reasons and remedies for the agglomeration of multilayered graphene and carbon nanotubes in polymers

PubMed Central

Atif, Rasheed

2016-01-01

Summary One of the main issues in the production of polymer nanocomposites is the dispersion state of filler as multilayered graphene (MLG) and carbon nanotubes (CNTs) tend to agglomerate due to van der Waals forces. The agglomeration can be avoided by using organic solvents, selecting suitable dispersion and production methods, and functionalizing the fillers. Another proposed method is the use of hybrid fillers as synergistic effects can cause an improvement in the dispersion state of the fillers. In this review article, various aspects of each process that can help avoid filler agglomeration and improve dispersion state are discussed in detail. This review article would be helpful for both current and prospective researchers in the field of MLG- and CNT-based polymer nanocomposites to achieve maximum enhancement in mechanical, thermal, and electrical properties of produced polymer nanocomposites. PMID:27826492

Investigation of smooth specimen scc test procedures; variations in environment, specimen size, stressing frame, and stress state. [for high strength aluminum alloys

NASA Technical Reports Server (NTRS)

Lifka, B. W.; Sprowls, D. O.; Kelsey, R. A.

1975-01-01

The variables studied in the stress-corrosion cracking performance of high strength aluminum alloys were: (1) corrosiveness of the environment, (2) specimen size and stiffness of the stressing system, (3) interpretation of transgranular cracking, and (4) interaction of the state of stress and specimen orientation in a product with an anisotropic grain structure. It was shown that the probability of failure and time to fracture for a specimen loaded in direct tension are influenced by corrosion pattern, the stressing assembly stiffness, and the notch tensile strength of the alloy. Results demonstrate that the combination of a normal tension stress and a shear stress acting on the plane of maximum susceptibility in a product with a highly directional grain cause the greatest tendency for stress-corrosion cracking.

Improving UV Resistance of High Performance Fibers

NASA Astrophysics Data System (ADS)

Hassanin, Ahmed

High performance fibers are characterized by their superior properties compared to the traditional textile fibers. High strength fibers have high modules, high strength to weight ratio, high chemical resistance, and usually high temperature resistance. It is used in application where superior properties are needed such as bulletproof vests, ropes and cables, cut resistant products, load tendons for giant scientific balloons, fishing rods, tennis racket strings, parachute cords, adhesives and sealants, protective apparel and tire cords. Unfortunately, Ultraviolet (UV) radiation causes serious degradation to the most of high performance fibers. UV lights, either natural or artificial, cause organic compounds to decompose and degrade, because the energy of the photons of UV light is high enough to break chemical bonds causing chain scission. This work is aiming at achieving maximum protection of high performance fibers using sheathing approaches. The sheaths proposed are of lightweight to maintain the advantage of the high performance fiber that is the high strength to weight ratio. This study involves developing three different types of sheathing. The product of interest that need be protected from UV is braid from PBO. First approach is extruding a sheath from Low Density Polyethylene (LDPE) loaded with different rutile TiO2 % nanoparticles around the braid from the PBO. The results of this approach showed that LDPE sheath loaded with 10% TiO2 by weight achieved the highest protection compare to 0% and 5% TiO2. The protection here is judged by strength loss of PBO. This trend noticed in different weathering environments, where the sheathed samples were exposed to UV-VIS radiations in different weatheromter equipments as well as exposure to high altitude environment using NASA BRDL balloon. The second approach is focusing in developing a protective porous membrane from polyurethane loaded with rutile TiO2 nanoparticles. Membrane from polyurethane loaded with 4% rutile TiO2 nanoparticles showed excellent protection of braid from PBO. Only 7.5% strength loss was observed. To optimize the degree of protection of the sheath loaded with UV blocker particles, computational models were developed to optimize the protective layer thickness/weight and the amount of UV particles that provide the maximum protection with lightest weight of the protective layer and minimum amount of UV particles. The simulated results were found to be higher that the experimental results due to the tendency of nanoparticles to be agglomerated in real experiments. The third approach to achieve a maximum protection with the minimum weight added is constructing a sleeve from SpectraRTM (Ultra High Molecular Weight Polyethylene (UHMWPE) high performance fiber), which is known to resist UV, woven fabric. Covering the braid from PBO fiber with Spectra RTM woven fabric provide hybrid structure with two compatible components that can share the load and thus maintain the high strength to weight ratio. Although the SpectraRTM fabric had maximum cover factor, 20 % of visible light and about 15 % of UV were able to penetrate the fabric. This transmittance of UV-VIS light negatively affected the protection performance of the SpectraRTM woven fabric layer. It is thought that SpectraRTM fabric be coated with a thin layer (mentioned earlier) containing UV blocker for additional protection while maintain strength contribution to the hybrid structure. To maximize the strength to weight ratio of the hybrid structure (with core from PBO braid and sheath from SpectraRTM woven fabric) an established finite element model was utilized. The theoretical results using the finite element theory indicated that by controlling the bending rigidity of the filling yarn of the SpectraRTM fabric, the extension at peak load of woven fabric in warp direction (loading direction) could be controlled to match the braid extension at peak load. The match in the extension at peak load of the two components of the hybrid structure allowed the maximum strength to weight ratio. Thus, the SpectraRTM woven layer could achieve both the protection from UV and the load share in the hybrid structure.

A comparison of dispersing media for various engineered carbon nanoparticles

PubMed Central

Buford, Mary C; Hamilton, Raymond F; Holian, Andrij

2007-01-01

Background With the increased manufacture and use of carbon nanoparticles (CNP) there has been increasing concern about the potential toxicity of fugitive CNP in the workplace and ambient environment. To address this matter a number of investigators have conducted in vitro and in vivo toxicity assessments. However, a variety of different approaches for suspension of these particles (culture media, Tween 80, dimethyl sulfoxide, phosphate-buffered saline, fetal calf serum, and others), and different sources of materials have generated potentially conflicting outcomes. The quality of the dispersion of nanoparticles is very dependent on the medium used to suspend them, and this then will most likely affect the biological outcomes. Results In this work, the distributions of different CNP (sources and types) have been characterized in various media. Furthermore, the outcome of instilling the different agglomerates, or size distributions, was examined in mouse lungs after one and seven days. Our results demonstrated that CNP suspended in serum produced particle suspensions with the fewest large agglomerates, and the most uniform distribution in mouse lungs. In addition, no apparent clearance of instilled CNP took place from lungs even after seven days. Conclusion This work demonstrates that CNP agglomerates are present in all dispersing vehicles to some degree. The vehicle that contains some protein, lipid or protein/lipid component disperses the CNP best, producing fewer large CNP agglomerates. In contrast, vehicles absent of lipid and protein produce the largest CNP agglomerates. The source of the CNP is also a factor in the degree of particle agglomeration within the same vehicle. PMID:17655771

Ion Pairing and Diffusion in Magnesium Electrolytes Based on Magnesium Borohydride.

PubMed

Samuel, Devon; Steinhauser, Carl; Smith, Jeffrey G; Kaufman, Aaron; Radin, Maxwell D; Naruse, Junichi; Hiramatsu, Hidehiko; Siegel, Donald J

2017-12-20

One obstacle to realizing a practical, rechargeable magnesium-ion battery is the development of efficient Mg electrolytes. Electrolytes based on simple Mg(BH 4 ) 2 salts suffer from poor salt solubility and/or low conductivity, presumably due to strong ion pairing. Understanding the molecular-scale processes occurring in these electrolytes would aid in overcoming these performance limitations. Toward this goal, the present study examines the solvation, agglomeration, and transport properties of a family of Mg electrolytes based on the Mg(BH 4 ) 2 salt using classical molecular dynamics. These properties were examined across five different solvents (tetrahydrofuran and the glymes G1-G4) and at four salt concentrations ranging from the dilute limit up to 0.4 M. Significant and irreversible salt agglomeration was observed in all solvents at all nondilute Mg(BH 4 ) 2 concentrations. The degree of clustering observed in these divalent Mg systems is much larger than that reported for electrolytes containing monovalent cations, such as Li. The salt agglomeration rate and diffusivity of Mg 2+ were both observed to correlate with solvent self-diffusivity: electrolytes using longer- (shorter-) chain solvents had the lowest (highest) Mg 2+ diffusivity and agglomeration rates. Incorporation of Mg 2+ into Mg 2+ -BH 4 - clusters significantly reduces the diffusivity of Mg 2+ by restricting displacements to localized motion within largely immobile agglomerates. Consequently, diffusion is increasingly impeded with increasing Mg(BH 4 ) 2 concentration. These data are consistent with the solubility limitations observed experimentally for Mg(BH 4 ) 2 -based electrolytes and highlight the need for strategies that minimize salt agglomeration in electrolytes containing divalent cations.

Comparing effectiveness of rhamnolipid biosurfactant with a quaternary ammonium salt surfactant for hydrate anti-agglomeration.

PubMed

York, J Dalton; Firoozabadi, Abbas

2008-01-24

Natural gas is projected to be the premium fuel of the 21st century because of availability, as well as economical and environmental considerations. Natural gas is coproduced with water from the subsurface forming gas hydrates. Hydrate formation may result in shutdown of onshore and offshore operations. Industry practice has been usage of alcohols--which have undesirable environmental impacts--to affect bulk-phase properties and inhibit hydrate formation. An alternative to alcohols is changing the surface properties through usage of polymers and surfactants, effective at 0.5-3 wt % of coproduced water. One group of low-dosage hydrate inhibitors (LDHI) are kinetic inhibitors, which affect nucleation rate and growth. A second group of LDHI are anti-agglomerants, which prevent agglomeration of small hydrate crystallites. Despite great potential, reported work on hydrate anti-agglomeration is very limited. In this paper, our focus is on the use of two vastly different surfactants as anti-agglomerants. We use a model oil, water, and tetrahydrofuran as a hydrate-forming species. We examine the effectiveness of a quaternary ammonium salt (i.e., quat). Visual observation measurements show that a small concentration of the quat (0.01%) can prevent agglomeration. However, a quat is not a green chemical and therefore may be undesirable. We show that a rhamnolipid biosurfactant can be effective to a concentration of 0.05 wt %. One difference between the two surfactants is the stability of the water-in-oil emulsions created. The biosurfactant forms a less stable emulsion, which makes it very desirable for hydrate application.

Impact of agglomeration state of nano- and submicron sized gold particles on pulmonary inflammation

PubMed Central

2010-01-01

Background Nanoparticle (NP) toxicity testing comes with many challenges. Characterization of the test substance is of crucial importance and in the case of NPs, agglomeration/aggregation state in physiological media needs to be considered. In this study, we have addressed the effect of agglomerated versus single particle suspensions of nano- and submicron sized gold on the inflammatory response in the lung. Rats were exposed to a single dose of 1.6 mg/kg body weight (bw) of spherical gold particles with geometric diameters of 50 nm or 250 nm diluted either by ultrapure water or by adding phosphate buffered saline (PBS). A single dose of 1.6 mg/kg bw DQ12 quartz was used as a positive control for pulmonary inflammation. Extensive characterization of the particle suspensions has been performed by determining the zetapotential, pH, gold concentration and particle size distribution. Primary particle size and particle purity has been verified using transmission electron microscopy (TEM) techniques. Pulmonary inflammation (total cell number, differential cell count and pro-inflammatory cytokines), cell damage (total protein and albumin) and cytotoxicity (alkaline phosphatase and lactate dehydrogenase) were determined in bronchoalveolar lavage fluid (BALF) and acute systemic effects in blood (total cell number, differential cell counts, fibrinogen and C-reactive protein) 3 and 24 hours post exposure. Uptake of gold particles in alveolar macrophages has been determined by TEM. Results Particles diluted in ultrapure water are well dispersed, while agglomerates are formed when diluting in PBS. The particle size of the 50 nm particles was confirmed, while the 250 nm particles appear to be 200 nm using tracking analysis and 210 nm using TEM. No major differences in pulmonary and systemic toxicity markers were observed after instillation of agglomerated versus single gold particles of different sizes. Both agglomerated as well as single nanoparticles were taken up by macrophages. Conclusion Primary particle size, gold concentration and particle purity are important features to check, since these characteristics may deviate from the manufacturer's description. Suspensions of well dispersed 50 nm and 250 nm particles as well as their agglomerates produced very mild pulmonary inflammation at the same mass based dose. We conclude that single 50 nm gold particles do not pose a greater acute hazard than their agglomerates or slightly larger gold particles when using pulmonary inflammation as a marker for toxicity. PMID:21126342

Partisan strength, political trust and generalized trust in the United States: An analysis of the General Social Survey, 1972-2014.

PubMed

Hooghe, Marc; Oser, Jennifer

2017-11-01

The literature on political parties suggests that strong partisan identities are associated with citizens' effective interaction with the political system, and with higher levels of political trust. Traditionally, party identity therefore is seen as a mechanism that allows for political integration. Simultaneously, however, political parties have gained recent attention for their role in promoting societal polarization by reinforcing competing and even antagonistic group identities. This article uses General Social Survey data from 1972 - 2014 to investigate the relationship between partisan strength and both political and generalized trust. The findings show that increases in partisan strength are positively related to political trust, but negatively related to generalized trust. This suggests that while partisan strength is indeed an important linkage mechanism for the political system, it is also associated with a tendency toward social polarization, and this corrosive effect thus far has not gained sufficient attention in literature on party identity. Copyright © 2017 Elsevier Inc. All rights reserved.

Characteristics of upper limb muscular strength in male wheelchair tennis players

PubMed Central

Moon, Hyo-Bin; Park, Seung-Jae; Kim, Al-Chan; Jang, Jee-Hun

2013-01-01

The purpose of this study was to identify the characteristics of muscular strength in upper limb and to present the preliminary information for development of sports injury prevention program and exercise rehabilitation program in wheelchair tennis players. Participants were 12 male wheelchair tennis players. Muscular strength was measured in shoulder and elbow joints with isokinetic dynamometer. Ipsilateral (IR) and bilateral (BR) balance ratio were calculated with isokinetic strength at 60°/sec. As a result, extension strength (ES) was significantly higher than flexion strength (FS) (P< 0.001), and IR in both sides and BR in ES were maintained within normal range whereas BR in FS was lower than normal range in shoulder joint. In elbow joint FS was significantly higher than ES (P< 0.05), and IR and BR were lower than normal range. Consequently, the different tendency in IR between shoulder and elbow joints and lower IR and BR in elbow joints could be the characteristics in male wheelchair tennis players. It is suggested that flexor strengthening program in nondominant shoulder joint, extensor strengthening program in both elbow joint, and flexor strengthening program in non-dominant elbow joint should be introduced for male wheelchair tennis players. PMID:24278887

Operational source receptor calculations for large agglomerations

NASA Astrophysics Data System (ADS)

Gauss, Michael; Shamsudheen, Semeena V.; Valdebenito, Alvaro; Pommier, Matthieu; Schulz, Michael

2016-04-01

For Air quality policy an important question is how much of the air pollution within an urbanized region can be attributed to local sources and how much of it is imported through long-range transport. This is critical information for a correct assessment of the effectiveness of potential emission measures. The ratio between indigenous and long-range transported air pollution for a given region depends on its geographic location, the size of its area, the strength and spatial distribution of emission sources, the time of the year, but also - very strongly - on the current meteorological conditions, which change from day to day and thus make it important to provide such calculations in near-real-time to support short-term legislation. Similarly, long-term analysis over longer periods (e.g. one year), or of specific air quality episodes in the past, can help to scientifically underpin multi-regional agreements and long-term legislation. Within the European MACC projects (Monitoring Atmospheric Composition and Climate) and the transition to the operational CAMS service (Copernicus Atmosphere Monitoring Service) the computationally efficient EMEP MSC-W air quality model has been applied with detailed emission data, comprehensive calculations of chemistry and microphysics, driven by high quality meteorological forecast data (up to 96-hour forecasts), to provide source-receptor calculations on a regular basis in forecast mode. In its current state, the product allows the user to choose among different regions and regulatory pollutants (e.g. ozone and PM) to assess the effectiveness of fictive emission reductions in air pollutant emissions that are implemented immediately, either within the agglomeration or outside. The effects are visualized as bar charts, showing resulting changes in air pollution levels within the agglomeration as a function of time (hourly resolution, 0 to 4 days into the future). The bar charts not only allow assessing the effects of emission reduction measures but they also indicate the relative importance of indigenous versus imported air pollution. The calculations are currently performed weekly by MET Norway for the Paris, London, Berlin, Oslo, Po Valley and Rhine-Ruhr regions and the results are provided free of charge at the MACC website (http://www.gmes-atmosphere.eu/services/aqac/policy_interface/regional_sr/). A proposal to extend this service to all EU capitals on a daily basis within the Copernicus Atmosphere Monitoring Service is currently under review. The tool is an important example illustrating the increased application of scientific tools to operational services that support Air Quality policy. This paper will describe this tool in more detail, focusing on the experimental setup, underlying assumptions, uncertainties, computational demand, and the usefulness for air quality for policy. Options to apply the tool for agglomerations outside the EU will also be discussed (making reference to, e.g., PANDA, which is a European-Chinese collaboration project).

The Effects of Mindfulness-Based Cognitive Therapy on Affective Memory Recall Dynamics in Depression: A Mechanistic Model of Rumination

PubMed Central

van Vugt, Marieke Karlijn; Hitchcock, Peter; Shahar, Ben; Britton, Willoughby

2012-01-01

Objectives: converging research suggests that mindfulness training exerts its therapeutic effects on depression by reducing rumination. Theoretically, rumination is a multifaceted construct that aggregates multiple neurocognitive aspects of depression, including poor executive control, negative and overgeneral memory bias, and persistence or stickiness of negative mind states. Current measures of rumination, most-often self-reports, do not capture these different aspects of ruminative tendencies, and therefore are limited in providing detailed information about the mechanisms of mindfulness. Methods: we developed new insight into the potential mechanisms of rumination, based on three model-based metrics of free recall dynamics. These three measures reflect the patterns of memory retrieval of valenced information: the probability of first recall (Pstart) which represents initial affective bias, the probability of staying with the same valence category rather than switching, which indicates strength of positive or negative association networks (Pstay), and probability of stopping (Pstop) or ending recall within a given valence, which indicates persistence or stickiness of a mind state. We investigated the effects of Mindfulness-Based Cognitive Therapy (MBCT; N = 29) vs. wait-list control (N = 23) on these recall dynamics in a randomized controlled trial in individuals with recurrent depression. Participants completed a standard laboratory stressor, the Trier Social Stress Test, to induce negative mood and activate ruminative tendencies. Following that, participants completed a free recall task consisting of three word lists. This assessment was conducted both before and after treatment or wait-list. Results: while MBCT participant’s Pstart remained relatively stable, controls showed multiple indications of depression-related deterioration toward more negative and less positive bias. Following the intervention, MBCT participants decreased in their tendency to sustain trains of negative words and increased their tendency to sustain trains of positive words. Conversely, controls showed the opposite tendency: controls stayed in trains of negative words for longer, and stayed in trains of positive words for less time relative to pre-intervention scores. MBCT participants tended to stop recall less often with negative words, which indicates less persistence or stickiness of negatively valenced mental context. Conclusion: MBCT participants showed a decrease in patterns that may perpetuate rumination on all three types of recall dynamics (Pstart, Pstay, and Pstop), compared to controls. MBCT may weaken the strength of self-perpetuating negative associations networks that are responsible for the persistent and “sticky” negative mind states observed in depression, and increase the positive associations that are lacking in depression. This study also offers a novel, objective method of measuring several indices of ruminative tendencies indicative of the underlying mechanisms of rumination. PMID:23049507

The structure of hydrophobic gas diffusion electrodes.

NASA Technical Reports Server (NTRS)

Giner, J.

1972-01-01

The 'flooded agglomerate' model of the Teflon-bonded gas diffusion electrode is discussed. A mathematical treatment of the 'flooded agglomerate' model is given; it can be used to predict the performance of the electrode as a function of measurable physical parameters.

Growth and form of planetary seedlings: results from a microgravity aggregation experiment.

PubMed

Blum, J; Wurm, G; Kempf, S; Poppe, T; Klahr, H; Kozasa, T; Rott, M; Henning, T; Dorschner, J; Schräpler, R; Keller, H U; Markiewicz, W J; Mann, I; Gustafson, B A; Giovane, F; Neuhaus, D; Fechtig, H; Grün, E; Feuerbacher, B; Kochan, H; Ratke, L; El Goresy, A; Morfill, G; Weidenschilling, S J; Schwehm, G; Metzler, K; Ip, W H

2000-09-18

The outcome of the first stage of planetary formation, which is characterized by ballistic agglomeration of preplanetary dust grains due to Brownian motion in the free molecular flow regime of the solar nebula, is still somewhat speculative. We performed a microgravity experiment flown onboard the space shuttle in which we simulated, for the first time, the onset of free preplanetary dust accumulation and revealed the structures and growth rates of the first dust agglomerates in the young solar system. We find that a thermally aggregating swarm of dust particles evolves very rapidly and forms unexpected open-structured agglomerates.

Quantitative characterization of nanoparticle agglomeration within biological media

NASA Astrophysics Data System (ADS)

Hondow, Nicole; Brydson, Rik; Wang, Peiyi; Holton, Mark D.; Brown, M. Rowan; Rees, Paul; Summers, Huw D.; Brown, Andy

2012-07-01

Quantitative analysis of nanoparticle dispersion state within biological media is essential to understanding cellular uptake and the roles of diffusion, sedimentation, and endocytosis in determining nanoparticle dose. The dispersion of polymer-coated CdTe/ZnS quantum dots in water and cell growth medium with and without fetal bovine serum was analyzed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. Characterization by TEM of samples prepared by plunge freezing the blotted solutions into liquid ethane was sensitive to the dispersion state of the quantum dots and enabled measurement of agglomerate size distributions even in the presence of serum proteins where DLS failed. In addition, TEM showed a reduced packing fraction of quantum dots per agglomerate when dispersed in biological media and serum compared to just water, highlighting the effect of interactions between the media, serum proteins, and the quantum dots. The identification of a heterogeneous distribution of quantum dots and quantum dot agglomerates in cell growth medium and serum by TEM will enable correlation with the previously reported optical metrology of in vitro cellular uptake of this quantum dot dispersion. In this paper, we present a comparative study of TEM and DLS and show that plunge-freeze TEM provides a robust assessment of nanoparticle agglomeration state.

Examining the effects of urban agglomeration polders on flood events in Qinhuai River basin, China with HEC-HMS model.

PubMed

Gao, Yuqin; Yuan, Yu; Wang, Huaizhi; Schmidt, Arthur R; Wang, Kexuan; Ye, Liu

2017-05-01

The urban agglomeration polders type of flood control pattern is a general flood control pattern in the eastern plain area and some of the secondary river basins in China. A HEC-HMS model of Qinhuai River basin based on the flood control pattern was established for simulating basin runoff, examining the impact of urban agglomeration polders on flood events, and estimating the effects of urbanization on hydrological processes of the urban agglomeration polders in Qinhuai River basin. The results indicate that the urban agglomeration polders could increase the peak flow and flood volume. The smaller the scale of the flood, the more significant the influence of the polder was to the flood volume. The distribution of the city circle polder has no obvious impact on the flood volume, but has effect on the peak flow. The closer the polder is to basin output, the smaller the influence it has on peak flows. As the level of urbanization gradually improving of city circle polder, flood volumes and peak flows gradually increase compared to those with the current level of urbanization (the impervious rate was 20%). The potential change in flood volume and peak flow with increasing impervious rate shows a linear relationship.

A complex network approach for nanoparticle agglomeration analysis in nanoscale images

NASA Astrophysics Data System (ADS)

Machado, Bruno Brandoli; Scabini, Leonardo Felipe; Margarido Orue, Jonatan Patrick; de Arruda, Mauro Santos; Goncalves, Diogo Nunes; Goncalves, Wesley Nunes; Moreira, Raphaell; Rodrigues-Jr, Jose F.

2017-02-01

Complex networks have been widely used in science and technology because of their ability to represent several systems. One of these systems is found in Biochemistry, in which the synthesis of new nanoparticles is a hot topic. However, the interpretation of experimental results in the search of new nanoparticles poses several challenges. This is due to the characteristics of nanoparticle images and due to their multiple intricate properties; one property of recurrent interest is the agglomeration of particles. Addressing this issue, this paper introduces an approach that uses complex networks to detect and describe nanoparticle agglomerates so to foster easier and more insightful analyses. In this approach, each detected particle in an image corresponds to a vertice and the distances between the particles define a criterion for creating edges. Edges are created if the distance is smaller than a radius of interest. Once this network is set, we calculate several discrete measures able to reveal the most outstanding agglomerates in a nanoparticle image. Experimental results using images of scanning tunneling microscopy (STM) of gold nanoparticles demonstrated the effectiveness of the proposed approach over several samples, as reflected by the separability between particles in three usual settings. The results also demonstrated efficacy for both convex and non-convex agglomerates.

Direct numerical simulations of agglomeration of circular colloidal particles in two-dimensional shear flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Young Joon, E-mail: yjchoi@uvic.ca; Djilali, Ned, E-mail: ndjilali@uvic.ca

2016-01-15

Colloidal agglomeration of nanoparticles in shear flow is investigated by solving the fluid-particle and particle-particle interactions in a 2D system. We use an extended finite element method in which the dynamics of the particles is solved in a fully coupled manner with the flow, allowing an accurate description of the fluid-particle interfaces without the need of boundary-fitted meshes or of empirical correlations to account for the hydrodynamic interactions between the particles. Adaptive local mesh refinement using a grid deformation method is incorporated with the fluid-structure interaction algorithm, and the particle-particle interaction at the microscopic level is modeled using the Lennard-Jonesmore » potential. Motivated by the process used in fabricating fuel cell catalysts from a colloidal ink, the model is applied to investigate agglomeration of colloidal particles under external shear flow in a sliding bi-periodic Lees-Edwards frame with varying shear rates and particle fraction ratios. Both external shear and particle fraction are found to have a crucial impact on the structure formation of colloidal particles in a suspension. Segregation intensity and graph theory are used to analyze the underlying agglomeration patterns and structures, and three agglomeration regimes are identified.« less

Properties of poly(lactic acid)/hydroxyapatite composite through the use of epoxy functional compatibilizers for biomedical application.

PubMed

Monmaturapoj, Naruporn; Srion, Autcharaporn; Chalermkarnon, Prasert; Buchatip, Suthawan; Petchsuk, Atitsa; Noppakunmongkolchai, Warobon; Mai-Ngam, Katanchalee

2017-08-01

A composite of 70/30 poly(lactic acid)/hydroxyapatite was systematically prepared using various amounts of glycidyl methacrylate as reactive compatibilizer or Joncryl ADR®-4368 containing nine glycidyl methacrylate functions as a chain extension/branching agent to improve the mechanical and biological properties for suitable usage as internal bone fixation devices. The effect of glycidyl methacrylate/Joncryl on mechanical properties of poly(lactic acid)/hydroxyapatite was investigated through flexural strength. Cell proliferation and differentiation of osteoblast-like MC3T3-E1 cells cultured on the composite samples were determined by Alamar Blue assay and alkaline phosphatase expression, respectively. Result shows that flexural strength tends to decrease, as glycidyl methacrylate content increases except for 1 wt.% glycidyl methacrylate. With an addition of dicumyl peroxide, the flexural strength shows an improvement than that of without dicumyl peroxide probably due to the chemical bonding of the hydroxyapatite and poly(lactic acid) as revealed by FTIR and NMR, whereas the composite with 5 wt.% Joncryl shows the best result, as the flexural strength increases getting close to pure poly(lactic acid). The significant morphology change could be seen in composite with Joncryl where the uniform agglomeration of hydroxyapatite particles oriented in poly(lactic acid) matrix. Addition of the epoxy functional compatibilizers at suitable percentages could also have benefits to cellular attachment, proliferation, differentiation and mineralization. So that, this poly(lactic acid)/hydroxyapatite composite could be a promising material to be used as internal bone fixation devices such as screws, pins and plates.

Colloidal Mechanisms of Gold Nanoparticle Loss in Asymmetric Flow Field-Flow Fractionation.

PubMed

Jochem, Aljosha-Rakim; Ankah, Genesis Ngwa; Meyer, Lars-Arne; Elsenberg, Stephan; Johann, Christoph; Kraus, Tobias

2016-10-07

Flow field-flow fractionation is a powerful method for the analysis of nanoparticle size distributions, but its widespread use has been hampered by large analyte losses, especially of metal nanoparticles. Here, we report on the colloidal mechanisms underlying the losses. We systematically studied gold nanoparticles (AuNPs) during asymmetrical flow field-flow fractionation (AF4) by systematic variation of the particle properties and the eluent composition. Recoveries of AuNPs (core diameter 12 nm) stabilized by citrate or polyethylene glycol (PEG) at different ionic strengths were determined. We used online UV-vis detection and off-line elementary analysis to follow particle losses during full analysis runs, runs without cross-flow, and runs with parts of the instrument bypassed. The combination allowed us to calculate relative and absolute analyte losses at different stages of the analytic protocol. We found different loss mechanisms depending on the ligand. Citrate-stabilized particles degraded during analysis and suffered large losses (up to 74%). PEG-stabilized particles had smaller relative losses at moderate ionic strengths (1-20%) that depended on PEG length. Long PEGs at higher ionic strengths (≥5 mM) caused particle loss due to bridging adsorption at the membrane. Bulk agglomeration was not a relevant loss mechanism at low ionic strengths ≤5 mM for any of the studied particles. An unexpectedly large fraction of particles was lost at tubing and other internal surfaces. We propose that the colloidal mechanisms observed here are relevant loss mechanisms in many particle analysis protocols and discuss strategies to avoid them.

Transport and abatement of fluorescent silica nanoparticle (SiO2 NP) in granular filtration: effect of porous media and ionic strength

NASA Astrophysics Data System (ADS)

Zeng, Chao; Shadman, Farhang; Sierra-Alvarez, Reyes

2017-03-01

The extensive production and application of engineered silica nanoparticles (SiO2 NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO2 NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO2 NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO2 filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO2 NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO2 NP filtration.

Strength and Stiffness Development in Soft Soils: A FESEM aided Soil Microstructure Viewpoint

NASA Astrophysics Data System (ADS)

Wijeyesekera, D. C.; Ho, M. H.; Bai, X.; Bakar, I.

2016-07-01

This paper opens with an overview of the debatable definition of soft soil that goes beyond a (CH) organic / inorganic clay and OH peat to include weakly cemented periglacial deposits of loess and alike. It then outlines the findings obtained from stiffness test on cement-stabilised soft clay. The findings are complemented with a microstructure viewpoint obtained using field emission scanning electron microscope (FESEM). Research also comprised of making cylindrical stabilised clay samples, prepared in the laboratory with various rubber chips contents and cement, and then aged for 28 days. The samples were then subjected to unconfined compressive strength (UCS) test and observations were also made of its microstructure using the FESEM. The impact of the soil microstructure on the stiffness result was studied both with the stabilized soil and also of some of the natural undisturbed loess soils. Sustainability aspect and the potential of the use of rubber chips and sand as additives to cement stabilisation are also discussed. The overall test results indicated that rubber chips and sand contributed to the improvement in unconfined compressive strength (qu). The derogatory influence of moisture on the stiffness of the stabilised clay was studied simultaneously. SEM micrographs are presented that show bonding of cement, rubber chips/ sand and soft clay, granular units and aggregated / agglomerated units in loess. The paper concludes with observations on the dependence of soil microstructure on the soil strength and deformability and even collapsibility of the loess. Current practices adopted as engineering solutions to these challenging soils are outlined.

Effect of mixing geopolymer and peat on bearing capacity in Ogan Komering Ilir (OKI) by California bearing ratio (CBR) test

NASA Astrophysics Data System (ADS)

Raharja, Danang S.; Hadiwardoyo, Sigit P.; Rahayu, Wiwik; Zain, Nasuhi

2017-06-01

Geopolymer is binder material that consists of solid material and the activator solution. Geopolymer material has successfully replaced cement in the manufacture of concrete with aluminosilicate bonding system. Geopolymer concrete has properties similar to cement concrete with high compressive strength, low shrinkage value, relatively low creep value, as well as acid-resistant. Based on these, the addition of polymers in peat soils is expected to improve the bearing capacity of peat soils. A study on the influence of geopolymer addition in peat soils was done by comparing before and after the peat soil was mixed with geopolymer using CBR (California Bearing Ratio) test in unsoaked and soaked conditions. 10% mixture content of the peat dry was used, weighted with a variety of curing time 4 hours, 5 days, and 10 days. There were two methods of mixing: first, peat was mixed with fly ash geopolymer activators and mixed solution (waterglass, NaOH, water), and second, peat was mixed with fly ash and mixed geopolymer (waterglass, NaOH, water, fly ash). Changes were observed in specific gravity, dry density, acidity (pH), and the microscopic structure with Scanning Electron Microscope (SEM). Curing time did not significantly affect the CBR value. It even shows a tendency to decline with longer curing time. The first type mixture obtained CBR value of: 5.4% for 4 hours curing, 4.6% for 5 days curing and 3.6% for 10 days curing. The second type mixture obtained CBR value of: 6.1% for 4 hours curing, 5.2% for 5 days curing and 5.2% for 10 days curing. Furthermore, the specific gravity value, dry density, pH near neutral and swelling percentage increased. From both variants, the second type mixture shows better results than the first type mixture. The results of SEM (Scanning Electron Microscopy) show the structure of the peat which became denser with the fly ash particles filling the peat microporous. Also, the reaction of fly ash with geopolymer is indicated by the solid agglomerates that are larger than normal fly ash particle size.

Climatology of the Auroral Electrojets Derived From the Along-Track Gradient of Magnetic Field Intensity Measured by POGO, Magsat, CHAMP, and Swarm

NASA Astrophysics Data System (ADS)

Smith, A. R. A.; Beggan, C. D.; Macmillan, S.; Whaler, K. A.

2017-10-01

The auroral electrojets (AEJs) are complex and dynamic horizontal ionospheric electric currents which form ovals around Earth's poles, being controlled by the morphology of the main magnetic field and the energy input from the solar wind interaction with the magnetosphere. The strength and location of the AEJ varies with solar wind conditions and the solar cycle but should also be controlled on decadal timescales by main field secular variation. To determine the AEJ climatology, we use data from four polar Low Earth Orbit magnetic satellite missions: POGO, Magsat, CHAMP, and Swarm. A simple estimation of the AEJ strength and latitude is made from each pass of the satellites, from peaks in the along-track gradient of the magnetic field intensity after subtracting a core and crustal magnetic field model. This measure of the AEJ activity is used to study the response in different sectors of magnetic local time (MLT) during different seasons and directions of the interplanetary magnetic field (IMF). We find a season-dependent hemispherical asymmetry in the AEJ response to IMF By, with a tendency toward stronger (weaker) AEJ currents in the north than the south during By>0 (By<0) around local winter. This effect disappears during local summer when we find a tendency toward stronger currents in the south than the north. The solar cycle modulation of the AEJ and the long-term shifting of its position and strength due to the core field variation are presented as challenges to internal field modeling.

Friction-Stir Welding - Heavy Inclusions in Bi-metallic welds of Al 2219/2195

NASA Technical Reports Server (NTRS)

Rietz, Ward W., Jr.

2008-01-01

Heavy Inclusions (HI) were detected for the first time by radiographic examination in aluminum alloy 2219forging/2195plate (advancing/retreating side) Friction Sir Welds (FSW) for the Space Shuttle External Tank (ET) Program. Radiographic HI indications appear as either small (approx.0.005"-0.025") individual particles or clusters of small particles. Initial work was performed to verify that the HI was not foreign material or caused by FSW pin tool debris. That and subsequent elemental analysis determined that the HI were large agglomerations of Al2Cu (theta phase), which is the strengthening precipitate in Al2219. A literature search on that subject determined that the agglomeration of phase has also been found in Al2219 bead on plate FSW [Ref. 1]. Since this was detected in ET space flight hardware, an investigative study of the effect of agglomerated theta phase particles in FSW Al2219f/2195p was performed. Numerous panels of various lengths were welded per ET weld procedures and radiographically inspected to determine if any HI was detected. Areas that had HI were sampled for room temperature and cyclic cryogenic (-423F) tensile testing and determined no significant adverse affect on mechanical properties when compared to test specimens without HI and historical data. Fracture surface examination using the Scanning Electron Microscope (SEM) revealed smaller phase agglomerations undetectable by radiographic inspection dispersed throughout the Al2219f/2195p FSW. This indicates that phase agglomeration is inherent to the Al2219f/2195p FSW process and only rarely creates agglomerations large enough to be detected by radiography. HI has not been observed in FSW of plate to plate material for either Al2219 or AL2195.

Bed material agglomeration during fluidized bed combustion. Technical progress report, 1 July, 1993--30 September, 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, R.C.; Dawson, M.R.; Noble, S.D.

Agglomerates formed in laboratory coal combustion tests were analyzed to determine the chemical and mineral reactions which lead to the cohesion of bed particles. Combustion tests were conducted at 75, 90, 100, and 120% theoretical air values. The test at 75% theoretical air resulted in the formation of bed agglomerates within 30 minutes. Agglomerates which formed at the lower theoretical air values were compared to unagglomerated bed samples by X-ray diffraction analyses. Polished thin sections of the agglomerates were made for optical and scanning electron microscopy. The results of these analyses indicate there were, in a broad sense, two typesmore » of mineralogic reactions which lead to the cohesion of bed particles in the agglomerates. One mechanism of cohesion resulted from the melting of bed particles to form a viscous material which bridged other bed particles. Based on the chemical composition of the glass (which resulted from the melt), this material was probably derived from aluminosilicate minerals in the sand bed or from clays within the coal. Because of the high iron content in these glasses (4 to 5 wt%), it is likely that iron pyrites in the coal were involved in fluxing reactions. In addition, MgO appears to be relatively high in the glasses. It is suspected that Ca-Mg carbonates (dolomite) from the bed sand are also involved in mineralogic reactions with the aluminosilicate melt. The second type of mineralogic reaction appears to be a reaction involving calcium and magnesium with other bed particles and with the aluminosilicate melt to form new mineral phases. Although the composition of these phases is somewhat variable, some resemble single-chain silicates or pyroxenes.« less

About the relevance of waviness, agglomeration, and strain on the electrical behavior of polymer composites filled with carbon nanotubes evaluated by a Monte-Carlo simulation

NASA Astrophysics Data System (ADS)

Román, Sebastián; Lund, Fernando; Bustos, Javier; Palza, Humberto

2018-01-01

In several technological applications, carbon nanotubes (CNT) are added to a polymer matrix in order to develop electrically conductive composite materials upon percolation of the CNT network. This percolation state depends on several parameters such as particle characteristics, degree of dispersion, and filler orientation. For instance, CNT aggregation is currently avoided because it is thought that it will have a negative effect on the electrical behavior despite some experimental evidence showing the contrary. In this study, the effect of CNT waviness, degree of agglomeration, and external strain, on the electrical percolation of polymer composites is studied by a three dimensional Monte-Carlo simulation. The simulation shows that the percolation threshold of CNT depends on the particle waviness, with rigid particles displaying the lowest values. Regarding the effect of CNT dispersion, our numerical results confirm that low levels of agglomeration reduce the percolation threshold of the composite. However, the threshold is shifted to larger values at high agglomeration states because of the appearance of isolated areas of high CNT concentrations. These results imply, therefore, an optimum of agglomeration that further depends on the waviness and concentration of CNT. Significantly, CNT agglomeration can further explain the broad percolation transition found in these systems. When an external strain is applied to the composites, the percolation concentration shifts to higher values because CNT alignment increases the inter-particle distances. The strain sensitivity of the composites is affected by the percolation state of CNT showing a maximum value at certain filler concentration. These results open up the discussion about the relevance in polymer composites of the dispersion state of CNT and filler flexibility towards electrically conductive composites.

Size-segregated urban aerosol characterization by electron microscopy and dynamic light scattering and influence of sample preparation

NASA Astrophysics Data System (ADS)

Marvanová, Soňa; Kulich, Pavel; Skoupý, Radim; Hubatka, František; Ciganek, Miroslav; Bendl, Jan; Hovorka, Jan; Machala, Miroslav

2018-04-01

Size-segregated particulate matter (PM) is frequently used in chemical and toxicological studies. Nevertheless, toxicological in vitro studies working with the whole particles often lack a proper evaluation of PM real size distribution and characterization of agglomeration under the experimental conditions. In this study, changes in particle size distributions during the PM sample manipulation and also semiquantitative elemental composition of single particles were evaluated. Coarse (1-10 μm), upper accumulation (0.5-1 μm), lower accumulation (0.17-0.5 μm), and ultrafine (<0.17 μm) PM fractions were collected by high volume cascade impactor in Prague city center. Particles were examined using electron microscopy and their elemental composition was determined by energy dispersive X-ray spectroscopy. Larger or smaller particles, not corresponding to the impaction cut points, were found in all fractions, as they occur in agglomerates and are impacted according to their aerodynamic diameter. Elemental composition of particles in size-segregated fractions varied significantly. Ns-soot occurred in all size fractions. Metallic nanospheres were found in accumulation fractions, but not in ultrafine fraction where ns-soot, carbonaceous particles, and inorganic salts were identified. Dynamic light scattering was used to measure particle size distribution in water and in cell culture media. PM suspension of lower accumulation fraction in water agglomerated after freezing/thawing the sample, and the agglomerates were disrupted by subsequent sonication. Ultrafine fraction did not agglomerate after freezing/thawing the sample. Both lower accumulation and ultrafine fractions were stable in cell culture media with fetal bovine serum, while high agglomeration occurred in media without fetal bovine serum as measured during 24 h.

De-agglomeration Effect of the US Pharmacopeia and Alberta Throats on Carrier-Based Powders in Commercial Inhalation Products.

PubMed

Leung, Sharon Shui Yee; Tang, Patricia; Zhou, Qi Tony; Tong, Zhenbo; Leung, Cassandra; Decharaksa, Janwit; Yang, Runyu; Chan, Hak-Kim

2015-11-01

The US pharmacopeia (USP) and Alberta throats were recently reported to cause further de-agglomeration of carrier-free powders emitted from some dry powder inhalers (DPIs). This study assessed if they have similar influences on commercially available carrier-based DPIs. A straight tube, a USP throat, and an Alberta throat (non-coated and coated) were used for cascade impaction testing. Aerosol fine particle fraction (FPF ≤ 5 μm) was computed to evaluate throat-induced de-agglomeration. Computational fluid dynamics are employed to simulate airflow patterns and particle trajectories inside the USP and Alberta throats. For all tested products, no significant differences in the in vitro aerosol performance were observed between the USP throat and the straight tube. Using fine lactose carriers (<10 μm), Symbicort(®) and Oxis(™) showed minimal impaction inside the Alberta throat and resulted in similar FPF among all induction ports. For products using coarse lactose carriers (>10 μm), impaction frequency and energy inside the Alberta throat were significant. Further de-agglomeration was noted inside the non-coated Alberta throat for Seretide(®) and Spiriva(®), but agglomerates emitted from Relenza(®), Ventolin(®), and Foradil(®) did not further break up into smaller fractions. The coated Alberta throat considerably reduced the FPF values of these products due to the high throat retention, but they generally agreed better with the in vivo data. In conclusion, depending on the powder formulation (including carrier particle size), the inhaler, and the induction port, further de-agglomeration could happen ex-inhaler and create differences in the in vitro measurements.

Novel Injectable Calcium Phosphate Bone Cement from Wet Chemical Precipitation Method

NASA Astrophysics Data System (ADS)

Hablee, S.; Sopyan, I.; Mel, M.; Salleh, H. M.; Rahman, M. M.; Singh, R.

2017-06-01

Calcium phosphate cement has been prepared via chemical precipitation method for injectable bone filling materials. Calcium hydroxide, Ca(OH)2, and diammonium hydrogen phosphate, (NH4)2HPO4, were used as calcium and phosphorus precursors respectively. The synthesized powder was mixed with water at different powder-to-liquid (P/L) ratios, which was adjusted at 0.8, 0.9, 1.0, 1.1 and 1.2. The influence of P/L ratio on the injectability, setting time and mechanical strength of calcium phosphate cement paste has been evaluated. The synthesized powder appeared as purely hydroxyapatite with nanosized and agglomerated spherical particles. All cement pastes show excellent injectability except for the paste with P/L ratio 1.2. Calcium phosphate cement with P/L ratio 1.1 shows the ideal cement for bone filler application with good injectability, the initial and final setting times of 30 min and 160 min, and the compression strength of 2.47 MPa. The result indicated that the newly developed calcium phosphate cement is physically suitable for bone filler application. This paper presents our investigation on the effect of P/L ratio on the handling and mechanical properties of calcium phosphate cement prepared via wet chemical precipitation method.

Mechanical and Morphological Properties of Polypropylene/Nano α-Al2O3 Composites

PubMed Central

Mirjalili, F.; Chuah, L.; Salahi, E.

2014-01-01

A nanocomposite containing polypropylene (PP) and nano α-Al2O3 particles was prepared using a Haake internal mixer. Mechanical tests, such as tensile and flexural tests, showed that mechanical properties of the composite were enhanced by addition of nano α-Al2O3 particles and dispersant agent to the polymer. Tensile strength was approximately ∼16% higher than pure PP by increasing the nano α-Al2O3 loading from 1 to 4 wt% into the PP matrix. The results of flexural analysis indicated that the maximum values of flexural strength and flexural modulus for nanocomposite without dispersant were 50.5 and 1954 MPa and for nanocomposite with dispersant were 55.88 MPa and 2818 MPa, respectively. However, higher concentration of nano α-Al2O3 loading resulted in reduction of those mechanical properties that could be due to agglomeration of nano α-Al2O3 particles. Transmission and scanning electron microscopic observations of the nanocomposites also showed that fracture surface became rougher by increasing the content of filler loading from 1 to 4% wt. PMID:24688421

OXIDATIVE STRESS AND LIPID MEDIATORS INDUCED IN ALVEOLAR MACHROPHAGES BY ULTRAFINE PARTICLES

EPA Science Inventory

In ambient aerosols, ultrafine particles (UFP) and their agglomerates are considered to be major factors contributing to adverse health effects. Reactivity of agglomerated UFP of elemental carbon (EC), Printex 90, Printex G, and diesel exhaust particles (DEP) was evaluated by the...

Assessment of morphological and functional changes in organs of rats after intramuscular introduction of iron nanoparticles and their agglomerates.

PubMed

Sizova, Elena; Miroshnikov, Sergey; Yausheva, Elena; Polyakova, Valentina

2015-01-01

The research was performed on male Wistar rats based on assumptions that new microelement preparations containing metal nanoparticles and their agglomerates had potential. Morphological and functional changes in tissues in the injection site and dynamics of chemical element metabolism (25 indicators) in body were assessed after repeated intramuscular injections (total, 7) with preparation containing agglomerate of iron nanoparticles. As a result, iron depot was formed in myosymplasts of injection sites. The quantity of muscle fibers having positive Perls' stain increased with increasing number of injections. However, the concentration of the most chemical elements and iron significantly decreased in the whole skeletal muscle system (injection sites are not included). Consequently, it increased up to the control level after the sixth and the seventh injections. Among the studied organs (liver, kidneys, and spleen), Caspase-3 expression was revealed only in spleen. The expression had a direct dependence on the number of injections. Processes of iron elimination from preparation containing nanoparticles and their agglomerates had different intensity.

Effect of whey protein agglomeration on spray dried microcapsules containing Saccharomyces boulardii.

PubMed

Duongthingoc, Diep; George, Paul; Katopo, Lita; Gorczyca, Elizabeth; Kasapis, Stefan

2013-12-01

This work investigates the effect of whey protein agglomeration on the survivability of Saccharomyces boulardii within spray dried microcapsules. It attempts to go beyond phenomenological observations by establishing a relationship between physicochemical characteristics of the polymeric matrix and its effect on probiotic endurance upon spray drying. It is well known that this type of thermal shock has lethal consequences on the yeast cells. To avoid such undesirable outcome, we take advantage of the early agglomeration phenomenon observed for whey protein by adjusting the pH value of preparations close to isoelectric point (pH 4-5). During the subsequent process of spray drying, development of whey protein agglomerates induces formation of an early crust, and the protein in this molten globular state creates a cohesive network encapsulating the yeast cells. It appears that the early crust formation at a given sample pH and temperature regime during spray drying benefits the survivability of S. boulardii within microcapsules. Copyright © 2013. Published by Elsevier Ltd.

Diamond-like-carbon nanoparticle production and agglomeration following UV multi-photon excitation of static naphthalene/helium gas mixtures

NASA Astrophysics Data System (ADS)

Walsh, A. J.; Tielens, A. G. G. M.; Ruth, A. A.

2016-07-01

We report the formation of nanoparticles with significant diamond character after UV multi-photon laser excitation of gaseous naphthalene, buffered in static helium gas, at room temperature. The nanoparticles are identified in situ by their absorption and scattering spectra between 400 and 850 nm, which are modeled using Mie theory. Comparisons of the particles' spectroscopic and optical properties with those of carbonaceous materials indicate a sp3/sp2 hybridization ratio of 8:1 of the particles formed. The particle extinction in the closed static (unstirred) gas-phase system exhibits a complex and quasi-oscillatory time dependence for the duration of up to several hours with periods ranging from seconds to many minutes. The extinction dynamics of the system is based on a combination of transport features and particle interaction, predominantly agglomeration. The relatively long period of agglomeration allows for a unique analysis of the agglomeration process of diamond-like carbon nanoparticles in situ.

Experiment and simulation study on alkalis transfer characteristic during direct combustion utilization of bagasse.

PubMed

Liao, Yanfen; Cao, Yawen; Chen, Tuo; Ma, Xiaoqian

2015-10-01

Bagasse is utilized as fuel in the biggest biomass power plant of China, however, alkalis in the fuel created severe agglomeration and slagging problems. Alkalis transfer characteristic, agglomeration causes in engineering practice, additive improvement effects and mechanism during bagasse combustion were investigated via experiments and simulations. Only slight agglomeration occurs in ash higher than 800°C. Serious agglomeration in practical operation should be attributed to the gaseous alkalis evaporating at high temperature and condensing on the cooler grain surfaces in CFB. It can be speculated that ash caking can be avoided with temperature lower than 750°C and heating surface corrosion caused by alkali metal vapor can be alleviated with temperature lower than 850°C. Kaolin added into the bagasse has an apparent advantage over CaO additive both in enhancing ash fusion point and relieving alkali-chloride corrosion by locking alkalis in dystectic solid compounds over the whole temperature range. Copyright © 2015 Elsevier Ltd. All rights reserved.

Research on curing behavior of concrete with anti-frost admixtures at subzero temperature

NASA Astrophysics Data System (ADS)

Ionov, Yulian; Kramar, Ludmila; Kirsanova, Alena; Kolegova, Irina

2017-01-01

The purpose of this paper is research on curing behavior of cold-weather concrete with anti-frost admixtures. During the study derivative thermal and X-ray phase analyses were performed and tests were carried out according to the standard GOST technique. The research results obtained reveal the peculiarities of cement hydration and concrete curing at subzero temperatures. The influence of subzero temperatures and anti-frost admixtures on hydrated phases of hardened cement paste and concrete strength formation was studied. It is found that cold-weather concrete does not cure at subzero temperatures, but when defrosting it attains 80 to 85% of its grade strength by the 28th day. Concrete achieves its grade strength when curing in normal conditions in 60 days only. Freezing concrete with anti-frost admixtures results in increase of calcium hydroxide content in hardened cement paste immediately when produced and has increased tendency of concrete to carbonation.

The evolution of conformist transmission in social learning when the environment changes periodically.

PubMed

Nakahashi, Wataru

2007-08-01

Conformity is often observed in human social learning. Social learners preferentially imitate the majority or most common behavior in many situations, though the strength of conformity varies with the situation. Why has such a psychological tendency evolved? I investigate this problem by extending a standard model of social learning evolution with infinite environmental states (Feldman, M.W., Aoki, K., Kumm, J., 1996. Individual versus social learning: evolutionary analysis in a fluctuating environment. Anthropol. Sci. 104, 209-231) to include conformity bias. I mainly focus on the relationship between the strength of conformity bias that evolves and environmental stability, which is one of the most important factors in the evolution of social learning. Using the evolutionarily stable strategy (ESS) approach, I show that conformity always evolves when environmental stability and the cost of adopting a wrong behavior are small, though environmental stability and the cost of individual learning both negatively affect the strength of conformity.

Preferential rifting of continents - A source of displaced terranes

NASA Technical Reports Server (NTRS)

Vink, G. E.; Morgan, W. J.; Zhao, W.-L.

1984-01-01

Lithospheric rifting, while prevalent in the continents, rarely occurs in oceanic regions. To explain this preferential rifting of continents, the total strength of different lithospheres is compared by integrating the limits of lithospheric stress with depth. Comparisons of total strength indicate that continental lithosphere is weaker than oceanic lithosphere by about a factor of three. Also, a thickened crust can halve the total strength of normal continental lithosphere. Because the weakest area acts as a stress guide, any rifting close to an ocean-continent boundary would prefer a continental pathway. This results in the formation of small continental fragments or microplates that, once accreted back to a continent during subduction, are seen as displaced terranes. In addition, the large crustal thicknesses associated with suture zones would make such areas likely locations for future rifting episodes. This results in the tendency of new oceans to open along the suture where a former ocean had closed.

On the Da Vinci size effect in tensile strengths of nanowires: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Zhao, Ziyu; Liu, Jinxing; Soh, Ai Kah

2018-01-01

In recent decades, size effects caused by grain size, strain gradient, typical defects etc., have been widely investigated. Nevertheless, the dependence of tensile strength on the specimen length, addressed by Da Vinci around 500 hundred years ago, has received rather limited attention, even though it is one unavoidable question to answer if people attempt to bring materials' amazing nano-scale strengths up to macro-level. Therefore, we make efforts to study tensile behaviors of copper nanowires with a common cross-section and various lengths by employing the molecular dynamics simulations. Surprisingly, a strong size effect of Da Vinci type indeed arises. We have shown the influences of lattice orientation, temperature and prescribed notch on such a Da Vinci size effect. Two different theoretical explanations are briefly proposed for a qualitative understanding. Finally, a simple scaling rule is summarized to cover the tendencies observed.

Slip-activated surface creep with room-temperature super-elongation in metallic nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Li; Sansoz, Frederic; He, Yang

2016-11-28

Atom diffusion assisted by surfaces or interfaces (e.g. Coble creep) has been known to be the origin of large creep rates and superplastic softening in nanosized crystals at low temperature. By contrast, source-limited crystal slip in defect-free nanostructures engenders important strengths, but also premature plastic instability and low ductility. Here, using in-situ transmission electron microscopy, we report a slip-activated surface creep mechanism that suppresses the tendency towards plastic instability without compromising the strength, resulting in ultra-large room-temperature plasticity in face-centered-cubic silver nanocrystals. This phenomenon is shown experimentally and theoretically to prevail over a material-dependent range of diameters where surface dislocationmore » nucleation becomes a stimulus to diffusional creep. This work provides new fundamental insight into coupled diffusive-displacive deformation mechanisms maximizing ductility and strength simultaneously in nanoscale materials.« less

Surfactant Effects on Structure and Mechanical Properties of Ultrahigh-Molecular-Weight Polyethylene/Layered Silicate Composites.

PubMed

Nikiforov, Leonid A; Okhlopkova, Tatinana A; Kapitonova, Iullia V; Sleptsova, Sardana A; Okhlopkova, Aitalina A; Shim, Ee Le; Cho, Jin-Ho

2017-12-05

In this study, the reinforcement of ultrahigh-molecular-weight polyethylene (UHMWPE) with biotite was investigated. The biotite filler was mechanically activated with different dry surfactants to improve its compatibility with UHMWPE and decrease agglomeration among biotite particles. Alkyldimethylbenzylammonium chloride (ADBAC) and cetyltrimethylammonium bromide (CTAB) were selected as cationic surfactants. The tensile strength of composites containing 1 wt % of CTAB-treated biotite was increased by 30% relative to those with untreated biotite, but was unchanged with ADBAC treatment of the same biotite content. The stereochemistry of the surfactant may be critical to the composite structure and mechanical properties of the material. The stereochemistry of CTAB was preferable to that of ADBAC in enhancing mechanical properties because the stereochemistry of ADBAC impedes favorable interactions with the biotite surface during mechanical activation.

Peculiarities of hydration of Portland cement with synthetic nano-silica

NASA Astrophysics Data System (ADS)

Kotsay, Galyna

2017-12-01

Application of nano-materials in cement products significantly, improves their properties. Of course, the effectiveness of the materials depends on their quantity and the way they are introduced into the system. So far, amongst nano-materials used in construction, the most preferred was nano-silica. This research investigated the effect of synthetic precipitated nano-silica on the cement hydration as well as, on the physical and mechanical properties of pastes and mortars. Obtained results showed that admixture of nano-silica enhanced flexural and compressive strength of cement after 2 and 28 days, however, only when admixture made up 0.5% and 1.0%. On the other hand, the use of nano-silica in the amount 2% had some limitations, due to its ability to agglomerate, which resulted in deterioration of the rheological and mechanical properties.

High volume production of nanostructured materials

DOEpatents

Ripley, Edward B [Knoxville, TN; Morrell, Jonathan S [Knoxville, TN; Seals, Roland D [Oak Ridge, TN; Ludtka, Gerard M [Oak Ridge, TN

2009-10-13

A system and method for high volume production of nanoparticles, nanotubes, and items incorporating nanoparticles and nanotubes. Microwave, radio frequency, or infrared energy vaporizes a metal catalyst which, as it condenses, is contacted by carbon or other elements such as silicon, germanium, or boron to form agglomerates. The agglomerates may be annealed to accelerate the production of nanotubes. Magnetic or electric fields may be used to align the nanotubes during their production. The nanotubes may be separated from the production byproducts in aligned or non-aligned configurations. The agglomerates may be formed directly into tools, optionally in compositions that incorporate other materials such as abrasives, binders, carbon-carbon composites, and cermets.

Methods for high volume production of nanostructured materials

DOEpatents

Ripley, Edward B [Knoxville, TN; Morrell, Jonathan S [Knoxville, TN; Seals, Roland D [Oak Ridge, TN; Ludtka, Gerald M [Oak Ridge, TN

2011-03-22

A system and method for high volume production of nanoparticles, nanotubes, and items incorporating nanoparticles and nanotubes. Microwave, radio frequency, or infrared energy vaporizes a metal catalyst which, as it condenses, is contacted by carbon or other elements such as silicon, germanium, or boron to form agglomerates. The agglomerates may be annealed to accelerate the production of nanotubes. Magnetic or electric fields may be used to align the nanotubes during their production. The nanotubes may be separated from the production byproducts in aligned or non-aligned configurations. The agglomerates may be formed directly into tools, optionally in compositions that incorporate other materials such as abrasives, binders, carbon-carbon composites, and cermets.

Effects of pigeon pea and plantain starches on the compressional, mechanical, and disintegration properties of paracetamol tablets.

PubMed

Dare, Kunle; Akin-Ajani, Dorothy O; Odeku, Oluwatoyin A; Itiola, Oludele A; Odusote, Omotunde M

2006-03-01

A study has been made of the effects of pigeon pea starch obtained from the plant Cajanus cajan (L) Millisp. (family Fabaceae) and plantain starch obtained from the unripe fruit of Musa paradisiaca L. (family Musaceae) on the compressional, mechanical, and disintegration properties of paracetamol tablets in comparison with official corn starch BP. Analysis of compressional properties was done by using density measurements, and the Heckel and Kawakita equations, whereas the mechanical properties of the tablets were evaluated by using tensile strength (T--a measure of bond strength) and brittle fracture index (BFI--a measure of lamination tendency). The ranking for the mean yield pressure, P(y), for the formulations containing the different starches was generally corn < pigeon pea < plantain starch while the ranking for P(k), an inverse measure of the amount of plasticity, was pigeon pea < plantain < corn starch, which indicated that formulations containing corn starch generally exhibited the fastest onset of plastic deformation, whereas those formulations containing pigeon pea starch exhibited the highest amount of plastic deformation during tableting. The tensile strength of the tablets increased with increase in concentration of the starches while the Brittle Fracture Index decreased. The ranking for T was pigeon pea > plantain > corn starch while the ranking for BFI was corn > plantain > pigeon pea starch. The bonding capacity of the formulations was in general agreement with the tensile strength results. The disintegration time (DT) of the formulation increased with concentration of plantain and corn starches but decreased with concentration of pigeon pea starch. The general ranking of DT values was plantain < pigeon pea < corn starch. Notably, formulations containing pigeon pea starch exhibited the highest bond strength and lowest brittleness, suggesting the usefulness of pigeon pea starch in producing strong tablets with minimal lamination tendency. Plantain starch, on the other hand, would be more useful where faster disintegration of tablet is desired. The results show that the starches could be useful in various formulations depending on the intended use of the tablets with the implication that the experimental starches can be developed for commercial purposes.

Dielectric relaxation of near-percolated carbon nanofiber polypropylene composites

NASA Astrophysics Data System (ADS)

Paleo, A. J.; Zille, A.; Van Hattum, F. W.; Ares-Pernas, A.; Agostinho Moreira, J.

2017-07-01

In this work, the morphological, structural and dielectric analysis of near-percolated polypropylene (PP) composites containing carbon nanofibers (CNF) processing by melt-mixing are investigated. Whereas the morphological analysis shows that CNF exhibit some tendency to agglomerate within the PP matrix, the structural analysis showed first a general decrease in the intensity of the IR bands as a consequence of the interaction between carbon nanofibers and PP matrix and second an increase of the crystallinity degree of the PP/CNF composites when compared to the pure PP. The dielectric analysis demonstrates enhanced dielectric constants (from 2.97 for neat polymer to 9.7 for 1.9 vol% loaded composites at 200 Hz) and low dielectric losses. Furthermore, the dielectric relaxation for composites with concentrations in the vicinity of percolation is evidenced and well described by the generalized polydispersive Cole-Cole model from which the values of static dielectric constant (εs) , high frequency dielectric constant (ε∞) , distribution of relaxation time (α) and mean relaxation time (τo), are determined, suggesting that this latter analysis constitutes a strong tool for understanding the relationships between microstructure and dielectric properties in this type of polymer composites.

Mixed matrix membrane incorporated with large pore size halloysite nanotubes (HNT) as filler for gas separation: experimental.

PubMed

Hashemifard, S A; Ismail, A F; Matsuura, T

2011-07-15

This study investigated the gas separation and transport properties of asymmetric mixed matrix membranes (MMM) fabricated from polyetherimide (PEI); Ultem 1000 incorporated with raw and modified halloysite nanotubes (HNT) as filler. The modified HNTs; S-HNTs were prepared by treating HNTs with N-β-(aminoethyl)-γ-aminopropyltrimethoxy silane (AEAPTMS). FESEM, XRD, FTIR, TGA, DSC and pure gas permeation testing were used to characterise the S-HNTs and the fabricated MMMs. In the first part of the experiments, the effect of dope preparation factors such as: ultrasonic sonication period, filler wetting period and priming period were investigated. In the second part, the influence of silane concentration on the fabricated MMMs was studied. Results showed that, increasing the silane concentration, led to higher tendency in HNT agglomeration which resulted in poor separation properties but permeability enhancement. In the last part, the effect of S-HNTs loading was experienced. Our observations showed that the dispersion of nanoparticles decreased with an increase in the S-HNTs loading. Accordingly, 0.5% loading of silylated-HNT yielded the optimum MMMs in terms of permeability (27% increase) and selectivity (8% increase). Copyright © 2011 Elsevier Inc. All rights reserved.

Organosilylated complex [Eu(TTA)3(Bpy-Si)]: a bifunctional moiety for the engeneering of luminescent silica-based nanoparticles for bioimaging.

PubMed

Duarte, Adriana P; Mauline, Léïla; Gressier, Marie; Dexpert-Ghys, Jeannette; Roques, Christine; Caiut, José Maurício A; Deffune, Elenice; Maia, Danielle C G; Carlos, Iracilda Z; Ferreira, Antonio A P; Ribeiro, Sidney J L; Menu, Marie-Joëlle

2013-05-14

A new highly luminescent europium complex with the formula [Eu(TTA)3(Bpy-Si)], where TTA stands for the thenoyltrifluoroacetone, (C4H3S)COCH2COCF3, chelating ligand and Bpy-Si, Bpy-CH2NH(CH2)3Si(OEt)3, is an organosilyldipyridine ligand displaying a triethoxysilyl group as a grafting function has been synthesized and fully characterized. This bifunctional complex has been grafted onto the surface of dense silica nanoparticles (NPs) and on mesoporous silica microparticles as well. The covalent bonding of [Eu(TTA)3(Bpy-Si)] inside uniform Stöber silica nanoparticles was also achieved. The general methodology proposed could be applied to any silica matrix, allowed high grafting ratios that overcome chelate release and the tendency to agglomerate. Luminescent silica-based nanoparticles SiO2-[Eu(TTA)3(Bpy-Si)], with a diameter of 28 ± 2 nm, were successfully tested as a luminescent labels for the imaging of Pseudomonas aeruginosa biofilms. They were also functionalized by a specific monoclonal antibody and subsequently employed for the selective imaging of Escherichia coli bacteria.

Underwater microwave ignition of hydrophobic thermite powder enabled by the bubble-marble effect

NASA Astrophysics Data System (ADS)

Meir, Yehuda; Jerby, Eli

2015-08-01

Highly energetic thermite reactions could be useful for a variety of combustion and material-processing applications, but their usability is yet limited by their hard ignition conditions. Furthermore, in virtue of their zero-oxygen balance, exothermic thermite reactions may also occur underwater. However, this feature is also hard to utilize because of the hydrophobic properties of the thermite powder, and its tendency to agglomerate on the water surface rather than to sink into the water. The recently discovered bubble-marble (BM) effect enables the insertion and confinement of a thermite-powder batch into water by a magnetic field. Here, we present a phenomenon of underwater ignition of a thermite-BM by localized microwaves. The thermite combustion underwater is observed in-situ, and its microwave absorption and optical spectral emission are detected. The vapour pressure generated by the thermite reaction is measured and compared to theory. The combustion products are examined ex-situ by X-ray photo-electron spectroscopy which verifies the thermite reaction. Potential applications of this underwater combustion effect are considered, e.g., for detonation, wet welding, thermal drilling, material processing, thrust generation, and composite-material production, also for other oxygen-free environments.

Underwater microwave ignition of hydrophobic thermite powder enabled by the bubble-marble effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meir, Yehuda; Jerby, Eli, E-mail: jerby@eng.tau.ac.il

Highly energetic thermite reactions could be useful for a variety of combustion and material-processing applications, but their usability is yet limited by their hard ignition conditions. Furthermore, in virtue of their zero-oxygen balance, exothermic thermite reactions may also occur underwater. However, this feature is also hard to utilize because of the hydrophobic properties of the thermite powder, and its tendency to agglomerate on the water surface rather than to sink into the water. The recently discovered bubble-marble (BM) effect enables the insertion and confinement of a thermite-powder batch into water by a magnetic field. Here, we present a phenomenon ofmore » underwater ignition of a thermite-BM by localized microwaves. The thermite combustion underwater is observed in-situ, and its microwave absorption and optical spectral emission are detected. The vapour pressure generated by the thermite reaction is measured and compared to theory. The combustion products are examined ex-situ by X-ray photo-electron spectroscopy which verifies the thermite reaction. Potential applications of this underwater combustion effect are considered, e.g., for detonation, wet welding, thermal drilling, material processing, thrust generation, and composite-material production, also for other oxygen-free environments.« less

Activation of Molecular Oxygen Using Durable Cobalt Encapsulated with Nitrogen-Doped Graphitic Carbon Shells for Aerobic Oxidation of Lignin-Derived Alcohols.

PubMed

Sun, Yuxia; Ma, Hong; Luo, Yang; Zhang, Shujing; Gao, Jin; Xu, Jie

2018-03-26

It has long been a challenge for activating O 2 by transition-metal nanocatalysts, which might lose activity due to strong tendency for oxidation. Herein, O 2 could be activated by durable encapsulated cobalt nanoparticles (NPs) with N-doped graphitic carbon shells (Co@N-C), but not by encapsulated cobalt NPs with graphitic carbon, exposed cobalt NPs supported on activated carbon, or N-doped carbon. Electron paramagnetic resonance, real-time in situ FTIR spectroscopy, and mass spectrometry measurements demonstrated the generation of the highly active superoxide radical, O 2 .- . This unique ability enables Co@N-C to afford an excellent catalytic performance in model aerobic oxidation of monomeric lignin-derived alcohols. Further analysis elucidated that encapsulated cobalt and nitrogen-doped graphitic carbon might contribute to the capacity through influencing the electronic properties of outer layers. Moreover, through isolation by N-doped graphitic carbon shells, the inner metallic cobalt NPs are inaccessible in term of either alcohols or oxygenated products, and a distinctive resistance to leaching and agglomeration has been achieved. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Brief Research Review for Improvement Methods the Wettability between Ceramic Reinforcement Particulate and Aluminium Matrix Composites

NASA Astrophysics Data System (ADS)

Razzaq, Alaa Mohammed; Majid, Dayang Laila Abang Abdul; Ishak, M. R.; B, Uday M.

2017-05-01

The development of new methods for addition fine ceramic powders to Al aluminium alloy melts, which would lead to more uniform distribution and effective incorporation of the reinforcement particles into the aluminium matrix alloy. Recently the materials engineering research has moved to composite materials from monolithic, adapting to the global need for lightweight, low cost, quality, and high performance advanced materials. Among the different methods, stir casting is one of the simplest ways of making aluminium matrix composites. However, it suffers from poor distribution and combination of the reinforcement ceramic particles in the metal matrix. These problems become significantly effect to reduce reinforcement size, more agglomeration and tendency with less wettability for the ceramic particles in the melt process. Many researchers have carried out different studies on the wettability between the metal matrix and dispersion phase, which includes added wettability agents, fluxes, preheating the reinforcement particles, coating the reinforcement particles, and use composting techniques. The enhancement of wettability of ceramic particles by the molten matrix alloy and the reinforcement particles distribution improvement in the solidified matrix is the main objective for many studies that will be discussed in this paper.

How Does the Concentration of Determinants Affect Industrial Innovation Performance? - An Empirical Analysis of 23 Chinese Industrial Sectors.

PubMed

Huang, Shansong; Bai, Yang; Tan, Qingmei

2017-01-01

The agglomeration of innovation determinants has a significant influence on the innovation performance of industries and enterprises. Such an effect has received less attention in empirical research studies. This study involves a survey of the agglomeration effect of two important innovation determinants, R&D investment and R&D personnel, and its influence on innovation performance from the perspective of the industrial level. We analysed the agglomeration features based on the panel data of 23 Chinese industrial sectors from 2001~2013. An interpretation model is proposed to examine the agglomeration effect on innovation performance for 4 industrial groups: state-owned enterprises, individual enterprises, foreign-owned enterprises and enterprises as a whole. We found two main results. First, the agglomeration of determinants has a clear positive effect on the innovation performance of all 4 groups but affects individual enterprises more significantly, followed by state-owned and foreign-owned enterprises. Second, the state-owned enterprises show a much higher concentration of R&D investment and R&D personnel than other groups. However, the induced innovation efficiency in the state-owned enterprises is worse than in the individual enterprises. The advantage of resources and capital does not translate into corresponding innovation output. The privately owned small and medium-sized enterprises (SMEs) show a high capability of technological innovation and mercerization but have limited innovation resources.

How Does the Concentration of Determinants Affect Industrial Innovation Performance? – An Empirical Analysis of 23 Chinese Industrial Sectors

PubMed Central

Huang, Shansong; Bai, Yang; Tan, Qingmei

2017-01-01

The agglomeration of innovation determinants has a significant influence on the innovation performance of industries and enterprises. Such an effect has received less attention in empirical research studies. This study involves a survey of the agglomeration effect of two important innovation determinants, R&D investment and R&D personnel, and its influence on innovation performance from the perspective of the industrial level. We analysed the agglomeration features based on the panel data of 23 Chinese industrial sectors from 2001~2013. An interpretation model is proposed to examine the agglomeration effect on innovation performance for 4 industrial groups: state-owned enterprises, individual enterprises, foreign-owned enterprises and enterprises as a whole. We found two main results. First, the agglomeration of determinants has a clear positive effect on the innovation performance of all 4 groups but affects individual enterprises more significantly, followed by state-owned and foreign-owned enterprises. Second, the state-owned enterprises show a much higher concentration of R&D investment and R&D personnel than other groups. However, the induced innovation efficiency in the state-owned enterprises is worse than in the individual enterprises. The advantage of resources and capital does not translate into corresponding innovation output. The privately owned small and medium-sized enterprises (SMEs) show a high capability of technological innovation and mercerization but have limited innovation resources. PMID:28099452

Nanoparticle growth and surface chemistry changes in cell-conditioned culture medium.

PubMed

Kendall, Michaela; Hodges, Nikolas J; Whitwell, Harry; Tyrrell, Jess; Cangul, Hakan

2015-02-05

When biomolecules attach to engineered nanoparticle (ENP) surfaces, they confer the particles with a new biological identity. Physical format may also radically alter, changing ENP stability and agglomeration state within seconds. In order to measure which biomolecules are associated with early ENP growth, we studied ENPs in conditioned medium from A549 cell culture, using dynamic light scattering (DLS) and linear trap quadrupole electron transfer dissociation mass spectrometry. Two types of 100 nm polystyrene particles (one uncoated and one with an amine functionalized surface) were used to measure the influence of surface type. In identically prepared conditioned medium, agglomeration was visible in all samples after 1 h, but was variable, indicating inter-sample variability in secretion rates and extracellular medium conditions. In samples conditioned for 1 h or more, ENP agglomeration rates varied significantly. Agglomerate size measured by DLS was well correlated with surface sequestered peptide number for uncoated but not for amine coated polystyrene ENPs. Amine-coated ENPs grew much faster and into larger agglomerates associated with fewer sequestered peptides, but including significant sequestered lactose dehydrogenase. We conclude that interference with extracellular peptide balance and oxidoreductase activity via sequestration is worthy of further study, as increased oxidative stress via this new mechanism may be important for cell toxicity. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Agglomeration of Celecoxib by Quasi Emulsion Solvent Diffusion Method: Effect of Stabilizer.

PubMed

Maghsoodi, Maryam; Nokhodchi, Ali

2016-12-01

Purpose: The quasi-emulsion solvent diffusion (QESD) has evolved into an effective technique to manufacture agglomerates of API crystals. Although, the proposed technique showed benefits, such as cost effectiveness, that is considerably sensitive to the choice of a stabilizer, which agonizes from a absence of systemic understanding in this field. In the present study, the combination of different solvents and stabilizers were compared to investigate any connections between the solvents and stabilizers. Methods: Agglomerates of celecoxib were prepared by QESD method using four different stabilizers (Tween 80, HPMC, PVP and SLS) and three different solvents (methyl acetate, ethyl acetate and isopropyl acetate). The solid state of obtained particles was investigated by differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectroscopy. The agglomerated were also evaluated in term of production yield, distribution of particles and dissolution behavior. Results: The results showed that the effectiveness of stabilizer in terms of particle size and particle size distribution is specific to each solvent candidate. A stabilizer with a lower HLB value is preferred which actually increased its effectiveness with the solvent candidates with higher lipophilicity. HPMC appeared to be the most versatile stabilizer because it showed a better stabilizing effect compared to other stabilizers in all solvents used. Conclusion: This study demonstrated that the efficiency of stabilizers in forming the celecoxib agglomerates by QESD was influenced by the HLB of the stabilizer and lipophilicity of the solvents.

The Effect of a Tectonic Stress Field on Coal and Gas Outbursts

PubMed Central

An, Fenghua; Cheng, Yuanping

2014-01-01

Coal and gas outbursts have always been a serious threat to the safe and efficient mining of coal resources. Ground stress (especially the tectonic stress) has a notable effect on the occurrence and distribution of outbursts in the field practice. A numerical model considering the effect of coal gas was established to analyze the outburst danger from the perspective of stress conditions. To evaluate the outburst tendency, the potential energy of yielded coal mass accumulated during an outburst initiation was studied. The results showed that the gas pressure and the strength reduction from the adsorbed gas aggravated the coal mass failure and the ground stress altered by tectonics would affect the plastic zone distribution. To demonstrate the outburst tendency, the ratio of potential energy for the outburst initiation and the energy consumption was used. Increase of coal gas and tectonic stress could enhance the potential energy accumulation ratio, meaning larger outburst tendency. The component of potential energy for outburst initiation indicated that the proportion of elastic energy was increased due to tectonic stress. The elastic energy increase is deduced as the cause for a greater outburst danger in a tectonic area from the perspective of stress conditions. PMID:24991648

An evaluation of fatigue limit of notched specimen of a C/C composite

NASA Astrophysics Data System (ADS)

Makabe, C.; Fujikawa, M.; Ferdous, M. S.

2018-06-01

The fatigue strengths in notched specimens of carbon fiber reinforced carbon composites (C/C composites) were investigated. The fatigue limit was measured by S-N curves and load increase tests. The value of fatigue limit obtained by those methods was almost the same. Slits of several sizes were cut on both sides of a test section, and different sizes of slit length were chosen. Also, specimens with blunt-notches were used to compare the fatigue strength. The weakest fatigue limit was obtained in the case of specimens with blunt-notches. However, the stress concentration factor of those is smaller than that of slit specimens. The relationships between fatigue strengths and specimen shapes were analyzed by stress distribution. The effect of slit configuration on fatigue strength was then discussed regarding the experimental consequences. Consequently, it was discussed that the fatigue strength of the present specimens was determined depending on the damage conditions in the vicinity of the notch and on the crack initiation behavior. It is expected that the tendency of the S-N curve and fatigue limit was related to the shear damage and shear mode of the crack growth.

Coal beneficiation by gas agglomeration

DOEpatents

Wheelock, Thomas D.; Meiyu, Shen

2003-10-14

Coal beneficiation is achieved by suspending coal fines in a colloidal suspension of microscopic gas bubbles in water under atmospheric conditions to form small agglomerates of the fines adhered by the gas bubbles. The agglomerates are separated, recovered and resuspended in water. Thereafter, the pressure on the suspension is increased above atmospheric to deagglomerate, since the gas bubbles are then re-dissolved in the water. During the deagglomeration step, the mineral matter is dispersed, and when the pressure is released, the coal portion of the deagglomerated gas-saturated water mixture reagglomerates, with the small bubbles now coming out of the solution. The reagglomerate can then be separated to provide purified coal fines without the mineral matter.

Continuous air agglomeration method for high carbon fly ash beneficiation

DOEpatents

Gray, McMahon L.; Champagne, Kenneth J.; Finseth, Dennis H.

2000-01-01

The carbon and mineral components of fly ash are effectively separated by a continuous air agglomeration method, resulting in a substantially carboree mineral stream and a highly concentrated carbon product. The method involves mixing the fly ash comprised of carbon and inorganic mineral matter with a liquid hydrocarbon to form a slurry, contacting the slurry with an aqueous solution, dispersing the hydrocarbon slurry into small droplets within the aqueous solution by mechanical mixing and/or aeration, concentrating the inorganic mineral matter in the aqueous solution, agglomerating the carbon and hydrocarbon in the form of droplets, collecting the droplets, separating the hydrocarbon from the concentrated carbon product, and recycling the hydrocarbon.

Exploring factors influencing the strength of the safety-in-numbers effect.

PubMed

Elvik, Rune

2017-03-01

Several studies have found a so-called safety-in-numbers effect for vulnerable road users. This means that when the number of pedestrians or cyclists increases, the number of accidents involving these road users and motor vehicles increases less than in proportion to the number of pedestrians or cyclists. In other words, travel becomes safer for each pedestrian or cyclist the more pedestrians or cyclists there are. This finding is highly consistent, but estimates of the strength of the safety-in-numbers effect vary considerably. This paper shows that the strength of the safety-in-numbers effect is inversely related to the number of pedestrians and cyclists. A stronger safety-in-numbers is found when there are few pedestrians or cyclists than when there are many. This finding is counterintuitive and one would expect the opposite relationship. The relationship between the ratio of the number of motor vehicles to the number of pedestrians or cyclists and the strength of the safety-in-numbers effect is ambiguous. Possible explanations of these tendencies are discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

GABE: A Cloud Brokerage System for Service Selection, Accountability and Enforcement

ERIC Educational Resources Information Center

Sundareswaran, Smitha

2014-01-01

Much like its meteorological counterpart, "Cloud Computing" is an amorphous agglomeration of entities. It is amorphous in that the exact layout of the servers, the load balancers and their functions are neither known nor fixed. Its an agglomerate in that multiple service providers and vendors often coordinate to form a multitenant system…

Scanning Electron Microscope Studies on Aggregation Characteristics of Alumina Nanofluids

DTIC Science & Technology

2013-08-01

acoustic cavitation refers to the formation, growth and implosive collapse of bubbles in a liquid due to ultrasound that passes through the liquid...1 2.0 THEORY: ACOUSTIC CAVITATION AND AGGLOMERATION...be achieved to maximize the overall thermal conductivity of the nanofluid. 2.0 THEORY: ACOUSTIC CAVITATION AND AGGLOMERATION The phenomenon of

Preparation, mechanical strengths, and thermal

NASA Astrophysics Data System (ADS)

Inoue, A.; Furukawa, S.; Hagiwara, M.; Masumoto, T.

1987-05-01

Ni-based amorphous wires with good bending ductility have been prepared for Ni75Si8B17 and Ni78P12B10 alloys containing 1 to 2 at. pct Al or Zr by melt spinning in rotating water. The enhancement of the wire-formation tendency by the addition of Al has been clarified to be due to the increase in the stability of the melt jet through the formation of a thin A12O3 film on the outer surface. The maximum wire diameter is about 190 to 200 μm for the Ni-Si (or P)-B-Al alloys and increases to about 250 μm for the Ni-Si-B-Al-Cr alloys containing 4 to 6 at. pct Cr. The tensile fracture strength and fracture elongation are 2730 MPa and 2.9 pct for (Ni0.75Si0.08B0.17 99Al1) wire and 2170 MPa and 2.4 pct for (Ni0.78P0.12B0.1)99Al1 wire. These wires exhibit a fatigue limit under dynamic bending strain in air with a relative humidity of 65 pct; this limit is 0.50 pct for a Ni-Si-B-Al wire, which is higher by 0.15 pct than that of a Fe75Si10B15 amorphous wire. Furthermore, the Ni-base wires do not fracture during a 180-deg bending even for a sample annealed at temperatures just below the crystallization temperature, in sharp contrast to high embrittlement tendency for Fe-base amorphous alloys. Thus, the Ni-based amorphous wires have been shown to be an attractive material similar to Fe- and Co-based amorphous wires because of its high static and dynamic strength, high ductility, high stability to thermal embrittlement, and good corrosion resistance.

[Carbon footprint of buildings in the urban agglomeration of central Liaoning, China].

PubMed

Shi, Yu; Yun, Ying Xia; Liu, Chong; Chu, Ya Qi

2017-06-18

With the development of urbanization in China, buildings consumed lots of material and energy. How to estimate carbon emission of buildings is an important scientific problem. Carbon footprint of the central Liaoning agglomeration was studied with carbon footprint approach, geographic information system (GIS) and high-resolution remote sensing (HRRS) technology. The results showed that the construction carbon footprint coefficient of central Liaoning urban agglomeration was 269.16 kg·m -2 . The approach of interpreting total building area and spatial distribution with HRRS was effective, and the accuracy was 89%. The extraction approach was critical for total carbon footprint and spatial distribution estimation. The building area and total carbon footprint of central Liaoning urban agglomeration in descending order was Shenyang, Anshan, Fushun, Liao-yang, Yingkou, Tieling and Benxi. The annual average increment of footprint from 2011 to 2013 in descending order was Shenyang, Benxi, Fushun, Anshan, Tieling, Yingkou and Liaoyang. The accurate estimation of construction carbon footprint spatial and its distribution was of significance for the planning and optimization of carbon emission reduction.

Gasification of palm empty fruit bunch in a bubbling fluidized bed: a performance and agglomeration study.

PubMed

Lahijani, Pooya; Zainal, Zainal Alimuddin

2011-01-01

Gasification of palm empty fruit bunch (EFB) was investigated in a pilot-scale air-blown fluidized bed. The effect of bed temperature (650-1050 °C) on gasification performance was studied. To explore the potential of EFB, the gasification results were compared to that of sawdust. Results showed that maximum heating values (HHV) of 5.37 and 5.88 (MJ/Nm3), dry gas yield of 2.04 and 2.0 (Nm3/kg), carbon conversion of 93% and 85 % and cold gas efficiency of 72% and 71 % were obtained for EFB and sawdust at the temperature of 1050 °C and ER of 0.25. However, it was realized that agglomeration was the major issue in EFB gasification at high temperatures. To prevent the bed agglomeration, EFB gasification was performed at temperature of 770±20 °C while the ER was varied from 0.17 to 0.32. Maximum HHV of 4.53 was obtained at ER of 0.21 where no agglomeration was observed. Copyright © 2010 Elsevier Ltd. All rights reserved.

Assessment of Morphological and Functional Changes in Organs of Rats after Intramuscular Introduction of Iron Nanoparticles and Their Agglomerates

PubMed Central

Sizova, Elena; Miroshnikov, Sergey; Yausheva, Elena; Polyakova, Valentina

2015-01-01

The research was performed on male Wistar rats based on assumptions that new microelement preparations containing metal nanoparticles and their agglomerates had potential. Morphological and functional changes in tissues in the injection site and dynamics of chemical element metabolism (25 indicators) in body were assessed after repeated intramuscular injections (total, 7) with preparation containing agglomerate of iron nanoparticles. As a result, iron depot was formed in myosymplasts of injection sites. The quantity of muscle fibers having positive Perls' stain increased with increasing number of injections. However, the concentration of the most chemical elements and iron significantly decreased in the whole skeletal muscle system (injection sites are not included). Consequently, it increased up to the control level after the sixth and the seventh injections. Among the studied organs (liver, kidneys, and spleen), Caspase-3 expression was revealed only in spleen. The expression had a direct dependence on the number of injections. Processes of iron elimination from preparation containing nanoparticles and their agglomerates had different intensity. PMID:25789310

Nifedipine Nanoparticle Agglomeration as a Dry Powder Aerosol Formulation Strategy

PubMed Central

Plumley, Carl; Gorman, Eric M.; Munson, Eric J.; Berkland, Cory

2009-01-01

Efficient administration of drugs represents a leading challenge in pulmonary medicine. Dry powder aerosols are of great interest compared to traditional aerosolized liquid formulations in that they may offer improved stability, ease of administration, and simple device design. Particles 1–5 µm in size typically facilitate lung deposition. Nanoparticles may be exhaled as a result of their small size; however, they are desired to enhance the dissolution rate of poorly soluble drugs. Nanoparticles of the hypertension drug nifedipine were co-precipitated with stearic acid to form a colloid exhibiting negative surface charge. Nifedipine nanoparticle colloids were destabilized by using sodium chloride to disrupt the electrostatic repulsion between particles as a means to achieve the agglomerated nanoparticles of a controlled size. The aerodynamic performance of agglomerated nanoparticles was determined by cascade impaction. The powders were found to be well suited for pulmonary delivery. In addition, nanoparticle agglomerates revealed enhanced dissolution of the drug species suggesting the value of this formulation approach for poorly water soluble pulmonary medicines. Ultimately, nifedipine powders are envisioned as an approach to treat pulmonary hypertension. PMID:19015016

Study on GIS Visualization in Evaluation of the Human Living Environment in Shenyang-Dalian Urban Agglomeration

PubMed Central

Hou, Kang; Zhou, Jieting; Li, Xuxiang; Ge, Shengbin

2016-01-01

Analysis of human living environmental quality of Shenyang-Dalian urban agglomerations has important theoretical and practical significance in rapid development region. A lot of investigations have been carried for Shenyang-Dalian urban agglomerations, including 38 counties. Based on the carrying capacity of resources, natural and socioeconomic environmental factors and regional changes of human living environmental evaluation are analyzed with the application of geographic information systems (GIS) software. By using principal component analysis (PCA) model and natural breaks classification (NBC) method, the evaluation results are divided into five categories. The results show that the human living environmental evaluation (HLEE) indexes of Dalian, Shenyang, and Liaoyang are higher than other counties. Among these counties, the human living environmental evaluation (HLEE) indexes of coastal counties are significantly higher than inland counties. The range of the human living environmental evaluation index in most of the study area is at III, IV, and V levels, accounting for 80.01%. Based on these results, it could illustrate the human living environment is in relatively suitable condition in Shenyang-Dalian urban agglomeration. PMID:27200212

Application of acoustic agglomeration to enhance air filtration efficiency in air-conditioning and mechanical ventilation (ACMV) systems.

PubMed

Ng, Bing Feng; Xiong, Jin Wen; Wan, Man Pun

2017-01-01

The recent episodes of haze in Southeast Asia have caused some of the worst regional atmospheric pollution ever recorded in history. In order to control the levels of airborne fine particulate matters (PM) indoors, filtration systems providing high PM capturing efficiency are often sought, which inadvertently also results in high airflow resistance (or pressure drop) that increases the energy consumption for air distribution. A pre-conditioning mechanism promoting the formation of particle clusters to enhance PM capturing efficiency without adding flow resistance in the air distribution ductwork could provide an energy-efficient solution. This pre-conditioning mechanism can be fulfilled by acoustic agglomeration, which is a phenomenon that promotes the coagulation of suspended particles by acoustic waves propagating in the fluid medium. This paper discusses the basic mechanisms of acoustic agglomeration along with influencing factors that could affect the agglomeration efficiency. The feasibility to apply acoustic agglomeration to improve filtration in air-conditioning and mechanical ventilation (ACMV) systems is investigated experimentally in a small-scale wind tunnel. Experimental results indicate that this novel application of acoustic pre-conditioning improves the PM2.5 filtration efficiency of the test filters by up to 10% without introducing additional pressure drop. The fan energy savings from not having to switch to a high capturing efficiency filter largely outstrip the additional energy consumed by the acoustics system. This, as a whole, demonstrates potential energy savings from the combined acoustic-enhanced filtration system without compromising on PM capturing efficiency.

Application of acoustic agglomeration to enhance air filtration efficiency in air-conditioning and mechanical ventilation (ACMV) systems

PubMed Central

Xiong, Jin Wen; Wan, Man Pun

2017-01-01

The recent episodes of haze in Southeast Asia have caused some of the worst regional atmospheric pollution ever recorded in history. In order to control the levels of airborne fine particulate matters (PM) indoors, filtration systems providing high PM capturing efficiency are often sought, which inadvertently also results in high airflow resistance (or pressure drop) that increases the energy consumption for air distribution. A pre-conditioning mechanism promoting the formation of particle clusters to enhance PM capturing efficiency without adding flow resistance in the air distribution ductwork could provide an energy-efficient solution. This pre-conditioning mechanism can be fulfilled by acoustic agglomeration, which is a phenomenon that promotes the coagulation of suspended particles by acoustic waves propagating in the fluid medium. This paper discusses the basic mechanisms of acoustic agglomeration along with influencing factors that could affect the agglomeration efficiency. The feasibility to apply acoustic agglomeration to improve filtration in air-conditioning and mechanical ventilation (ACMV) systems is investigated experimentally in a small-scale wind tunnel. Experimental results indicate that this novel application of acoustic pre-conditioning improves the PM2.5 filtration efficiency of the test filters by up to 10% without introducing additional pressure drop. The fan energy savings from not having to switch to a high capturing efficiency filter largely outstrip the additional energy consumed by the acoustics system. This, as a whole, demonstrates potential energy savings from the combined acoustic-enhanced filtration system without compromising on PM capturing efficiency. PMID:28594862

Development of advanced fluid-bed agglomeration and cyclonic incineration for simultaneous waste disposal and energy recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rehmat, A.; Khinkis, M.

The Institute of Gas Technology (IGT) is currently developing a two-stage fluidized-bed/cyclonic agglomerating incineration system for waste disposal that is based on combining the fluidized-bed agglomeration/incineration and cyclonic combustion techologies. Both technologies have been developed individually at IGT over many years. This combination has resulted in a unique and extremely flexible incinerator for solid, liquid, and gaseous wastes including municipal sludges. The system can operate over a wide range of conditions in the first stage, from low temperature (desorption) to high temperature (agglomeration), including gasification of wastes. In the combined system, solid, liquid, and gaseous organic wastes are incinerated withmore » ease and great efficiency (>99.99% destruction and removal efficiency (DRE)), while solid inorganic contaminants contained within a glassy matrix are rendered benign and suitable for disposal in an ordinary landfill. The heat generated within the incinerator can be recovered using the state-of-the-art boilers. The development of the two-stage incinerator is a culmination of extensive research and development efforts on each stage of the incinerator. The variety of data obtained with solid, liquid, and gaseous wastes for both stages includes agglomeration of ash, incineration and reclamation of used blast grit and foundry sand, partial combustion of carbonaceous fuels, in-situ desulfurization, combustion of low-Btu gases, incineration of industrial wastewater, and incineration of carbon tetrachloride. 5 refs., 7 figs., 12 tabs.« less

Advanced Multi-phase Flow CFD Model Development for Solid Rocket Motor Flowfield Analysis

NASA Technical Reports Server (NTRS)

Liaw, Paul; Chen, Yen-Sen

1995-01-01

A Navier-Stokes code, finite difference Navier-Stokes (FDNS), is used to analyze the complicated internal flowfield of the SRM (solid rocket motor) to explore the impacts due to the effects of chemical reaction, particle dynamics, and slag accumulation on the solid rocket motor (SRM). The particulate multi-phase flowfield with chemical reaction, particle evaporation, combustion, breakup, and agglomeration models are included in present study to obtain a better understanding of the SRM design. Finite rate chemistry model is applied to simulate the chemical reaction effects. Hermsen correlation model is used for the combustion simulation. The evaporation model introduced by Spalding is utilized to include the heat transfer from the particulate phase to the gase phase due to the evaporation of the particles. A correlation of the minimum particle size for breakup expressed in terms of the Al/Al2O3 surface tension and shear force was employed to simulate the breakup of particles. It is assumed that the breakup occurs when the Weber number exceeds 6. A simple L agglomeration model is used to investigate the particle agglomeration. However, due to the large computer memory requirements for the agglomeration model, only 2D cases are tested with the agglomeration model. The VOF (Volume of Fluid) method is employed to simulate the slag buildup in the aft-end cavity of the redesigned solid rocket motor (RSRM). Monte Carlo method is employed to calculate the turbulent dispersion effect of the particles. The flowfield analysis obtained using the FDNS code in the present research with finite rate chemical reaction, particle evaporation, combustion, breakup, agglomeration, and VOG models will provide a design guide for the potential improvement of the SRM including the use of materials and the shape of nozzle geometry such that a better performance of the SRM can be achieved. The simulation of the slag buildup in the aft-end cavity can assist the designer to improve the design of the RSRM geometry.

Development of an electrochemical process for production of nano-copper oxides: Agglomeration kinetics modeling.

PubMed

Shahcheraghi, Seyed Hadi; Schaffie, Mahin; Ranjbar, Mohammad

2018-06-01

The main objective of this study was the development of a simple, clean, and industrial applicable electrochemical process for production of high pure nano-copper oxides from mining and industrial resources (e.g., ore, spent, slag and wastewater). To conduct the proposed process, a special set up containing an electrochemical cell in an ultrasonic system (28 kHz and 160 W) was proposed. Accordingly, using this set up and applying appropriate voltage (≈ 5 V) at 25 °C, in the presence of N 2 gas, the simultaneous anode dissolution and nano-copper oxides formation (≈ 24 nm) can be occurred, rapidly (less than 45 min). Then, the effect of N 2 gas and free radicals generated by ultrasonic irradiation was studied. The results showed, in the absence of ultrasonic irradiation and N 2 , an increase of electrolyte pH from 6.42 to 10.92, a decrease of electrolyte Eh from 285 mV to -1.14 V, and formation of copper nanoparticles. While, in the presence of ultrasonic and N 2 , the CuO nanoparticles were formed due to presence of H 2 O 2 generated by interaction of free radicals. Moreover, a novel method for kinetics modeling of nanoparticles agglomeration was proposed according to distributed activation energy model and Arrhenius parameters variation. The results showed that, in the absence of ultrasonic irradiation, the nanoparticle agglomerates were firstly formed (interface controlled mechanism) and then, the diffusion of nanoparticle agglomerates was occurred (diffusion controlled mechanism). Therefore, the control of nanoparticles size and shape may be impossible without surfactant. Also, in the presence of ultrasonic irradiation, the whole of agglomeration process followed interface controlled mechanism. Therefore, using ultrasonic irradiation, the nanoparticles shape and size don't change due to prevention of agglomerates diffusion. Copyright © 2018 Elsevier B.V. All rights reserved.

Monte Carlo Simulation of Nanoparticle Encapsulation in Flames

NASA Technical Reports Server (NTRS)

Sun, Z.; Huertas, J. I.; Axelbaum, R. L.

1999-01-01

Two critical challenges facing the application of flames for synthesis of nanopowder materials are: (1) overcoming formation of agglomerates and (2) ensuring that the highly reactive nanopowders that are synthesized in flames can be produced in such a manner that their purity is maintained during subsequent processing. Agglomerates are produced in flames because particle formation occurs in a high temperature and high number density environment. They are undesirable in most advanced applications of powders. For example, agglomerates have a deleterious effect on compaction density, leading to voids when nanopowders are consolidated. Efforts to avoid agglomeration in flames without substantially reducing particle number density and, consequently, production rate, have had limited success. Powder purity must also be maintained during subsequent handling of nanopowders and this poses a significant challenge for any synthesis route because nanopowders, particularly metals and non-oxide ceramic powders, are inherently reactive. Impurities acquired during handling of nanopowders have slowed the advancement of the nanostructured materials industry. One promising approach that has been proposed to address these problems is nano-encapsulation. In this approach, the core particles are encapsulated in a removable material while they are within the flame but before excessive agglomeration has occurred. Condensation can be very rapid so that core particles are trapped within the condensed material and agglomeration is limited. Nano-encapsulation also addresses the handling concerns for post-synthesis processing. Results have shown that when nano-encapsulated powders are exposed to atmosphere the core particles are protected from oxidation and/or hydrolysis. Thus, handling of the powders does not require extreme care. If, for example, at the time of consolidation the encapsulation material is removed by vacuum annealing, the resulting powder remains unagglomerated and free of impurities. In this work, we described a novel aerosol model that has been developed to simulate particle encapsulation in flames. The model will ultimately be coupled to a one-dimensional spherical flame code and compared to results from microgravity flame experiments.

Phosphate-enhanced cytotoxicity of zinc oxide nanoparticles and agglomerates.

PubMed

Everett, W Neil; Chern, Christina; Sun, Dazhi; McMahon, Rebecca E; Zhang, Xi; Chen, Wei-Jung A; Hahn, Mariah S; Sue, H-J

2014-02-10

Zinc oxide (ZnO) nanoparticles (NPs) have been found to readily react with phosphate ions to form zinc phosphate (Zn3(PO4)2) crystallites. Because phosphates are ubiquitous in physiological fluids as well as waste water streams, it is important to examine the potential effects that the formation of Zn3(PO4)2 crystallites may have on cell viability. Thus, the cytotoxic response of NIH/3T3 fibroblast cells was assessed following 24h of exposure to ZnO NPs suspended in media with and without the standard phosphate salt supplement. Both particle dosage and size have been shown to impact the cytotoxic effects of ZnO NPs, so doses ranging from 5 to 50 μg/mL were examined and agglomerate size effects were investigated by using the bioinert amphiphilic polymer polyvinylpyrrolidone (PVP) to generate water-soluble ZnO ranging from individually dispersed 4 nm NPs up to micron-sized agglomerates. Cell metabolic activity measures indicated that the presence of phosphate in the suspension media can led to significantly reduced cell viability at all agglomerate sizes and at lower ZnO dosages. In addition, a reduction in cell viability was observed when agglomerate size was decreased, but only in the phosphate-containing media. These metabolic activity results were reflected in separate measures of cell death via the lactate dehydrogenase assay. Our results suggest that, while higher doses of water-soluble ZnO NPs are cytotoxic, the presence of phosphates in the surrounding fluid can lead to significantly elevated levels of cell death at lower ZnO NP doses. Moreover, the extent of this death can potentially be modulated or offset by tuning the agglomerate size. These findings underscore the importance of understanding how nanoscale materials can interact with the components of surrounding fluids so that potential adverse effects of such interactions can be controlled. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Temperature-Triggered Protein Adsorption on Polymer-Coated Nanoparticles in Serum.

PubMed

Koshkina, Olga; Lang, Thomas; Thiermann, Raphael; Docter, Dominic; Stauber, Roland H; Secker, Christian; Schlaad, Helmut; Weidner, Steffen; Mohr, Benjamin; Maskos, Michael; Bertin, Annabelle

2015-08-18

The protein corona, which forms on the nanoparticle's surface in most biological media, determines the nanoparticle's physicochemical characteristics. The formation of the protein corona has a significant impact on the biodistribution and clearance of nanoparticles in vivo. Therefore, the ability to influence the formation of the protein corona is essential to most biomedical applications, including drug delivery and imaging. In this study, we investigate the protein adsorption on nanoparticles with a hydrodynamic radius of 30 nm and a coating of thermoresponsive poly(2-isopropyl-2-oxazoline) in serum. Using multiangle dynamic light scattering (DLS) we demonstrate that heating of the nanoparticles above their phase separation temperature induces the formation of agglomerates, with a hydrodynamic radius of 1 μm. In serum, noticeably stronger agglomeration occurs at lower temperatures compared to serum-free conditions. Cryogenic transmission electron microscopy (cryo-TEM) revealed a high packing density of agglomerates when serum was not present. In contrast, in the presence of serum, agglomerated nanoparticles were loosely packed, indicating that proteins are intercalated between them. Moreover, an increase in protein content is observed upon heating, confirming that protein adsorption is induced by the alteration of the surface during phase separation. After cooling and switching the surface back, most of the agglomerates were dissolved and the main fraction returned to the original size of approximately 30 nm as shown by asymmetrical flow-field flow fractionation (AF-FFF) and DLS. Furthermore, the amounts of adsorbed proteins are similar before and after heating the nanoparticles to above their phase-separation temperature. Overall, our results demonstrate that the thermoresponsivity of the polymer coating enables turning the corona formation on nanoparticles on and off in situ. As the local heating of body areas can be easily done in vivo, the thermoresponsive coating could potentially be used to induce the agglomeration of nanoparticles and proteins and the accumulation of nanoparticles in a targeted body region.

Electrospray methodologies for characterization and deposition of nanoparticles

NASA Astrophysics Data System (ADS)

Modesto Lopez, Luis Balam

Electrospray is an aerosolization method that generates highly charged droplets from solutions or suspensions and, after a series of solvent evaporation -- droplet fission cycles, it results in particles carrying multiple charges. Highly charged particles are used in a variety of applications, including particle characterization, thin film deposition, nanopatterning, and inhalation studies among several others. In this work, a soft X-ray photoionization was coupled with an electrospray to obtain monodisperse, singly charged nanoparticles for applications in online size characterization with electrical mobility analysis. Photoionization with the soft X-ray charger enhanced the diffusion neutralization rate of the highly charged bacteriophages, proteins, and solid particles. The effect of nanoparticle surface charge and nanoparticle agglomeration in liquids on the electrospray process was studied experimentally and a modified expression to calculate the effective electrical conductivity of nanosuspensions was proposed. The effective electrical conductivity of TiO2 nanoparticle suspensions is strongly dependent on the electrical double layer and the agglomeration dynamics of the particles; and such dependence is more remarkable in liquids with low ionic strength. TiO2 nanoparticle agglomerates with nearly monodisperse sizes in the nanometer and submicrometer ranges were generated, by electrospraying suspensions with tuned effective electrical conductivity, and used to deposit photocatalytic films for water-splitting. Nanostructured films of iron oxide with uniform distribution of particles over the entire deposition area were formed with an electrospray system. The micro-Raman spectra of the iron oxide films showed that transverse and longitudinal optical modes are highly sensitive to the crystallize size of the electrospray-deposited films. The fabrication of films of natural light-harvesting complexes, with the aim of designing biohybrid photovoltaic devices, was explored with an electrospray. The ability to charge chlorosomes with large number of charges allowed their ballistic deposition onto TiO2 nanostructured columnar films simultaneously maintaining their light-harvesting properties. Single units of natural light-harvesting complexes were isolated in charged electrospray droplets for subsequent size characterization. The charge distribution of natural light-harvesting complexes, aerosolized with a collision nebulizer, was determined with tandem differential mobility analysis. It was found that nebulized light-harvesting complexes were multiply charged; hence they have potential applications in the deposition of functional films using electric fields. The studies conducted as part of this dissertation addressed fundamental issues in the characterization and deposition of nanoparticle suspensions and elucidated applications of the electrospray technique, particularly for solar energy utilization.

Inclusion evolution in molten and solidifying steel

NASA Astrophysics Data System (ADS)

Wang, Yan

Cleanliness, with respect to impurities and nonmetallic inclusions in the melt, is an important issue in steel production. The commercial interest in controlling steel cleanliness has been growing rapidly, because clean steel exhibits a highly attractive combination of corrosion resistance, good formability, pleasing appearance, and a wide range of strength levels. In order to satisfy the requirements for the degree of cleanliness in steel, controlling the size distribution, chemistry and shape of inclusions are of great importance in the steelmaking process. A knowledge of the formation of nonmetallic inclusions and their chemical and morphological evolution during the steelmaking and casting process is necessary in order to minimize the inclusion size and also try to promote potentially beneficial properties of inclusions, such as grain-refining. In this research, the evolution of inclusions in molten and solidifying steels was investigated through in-situ observations using a high temperature Confocal Scanning Laser Microscope (CSLM). The study focused on solid Al2O3 and liquid Al 2O3-CaO inclusions on low carbon steel melt surfaces. Firstly, the agglomeration and clustering of inclusions on steel surfaces were quantified and compared to predictions according to capillary depression driven attraction forces. A strong agglomeration was observed between the solid Al2O33 particle pairs. However, the liquid Al 2O3-CaO inclusions were not prone to agglomeration due to their lens-like morphology, which causes the absence of capillary force. Secondly, the pushing vs. engulfment and entrapment of both liquid Al 2O3-CaO and solid Al2O3 inclusions by advancing planar and cellular delta-ferrite solidification fronts was studied and compared to model predictions based on the force balances acting on the inclusions at the solid/melt interface. The critical velocity, above which the inclusions get engulfed, was observed to be slower at the cellular front than at the planar interface for liquid Al2O3-CaO inclusions. This indicates that these inclusions tend to more easily get engulfed at inter-cellular boundaries. However, there was no appreciable difference observed about the critical velocity for the large solid Al2O 3 inclusion clusters at the cellular boundary with that at the planar interface. The pushed liquid Al2O3-CaO inclusions were subject to a chemical and morphological change during solidification. (Abstract shortened by UMI.)

Influence de la taille de depart, de l'etat d'agglomeration et de la dose de nanoparticules de dioxyde de titane (TiO2) inhalees sur la reponse pulmonaire chez le rat

NASA Astrophysics Data System (ADS)

Noel, Alexandra

It is estimated that by 2014 more than 10 million jobs related to the nanotechnology field will be created worldwide. It is therefore important to investigate the possible health effects caused by nanoparticles (NP). Due to their small size, NP (< 100 nm) can coagulate quickly, which promotes their entry into the body in the form of agglomerates. However, few studies have evaluated their pulmonary toxicity, considering the physicochemical properties of NP, as well as the size of the agglomerates formed in the aerosols. The objective of this study is to evaluate the influence of the agglomeration state of three different primary particle sizes (5, 10-30 and 50 nm) of titanium dioxide (TiO2) NP on the pulmonary toxicity of male rats (F344) exposed to aerosols at 2, 7 or 20 mg/m3 for 6 hours. In an inhalation chamber, six groups of rats (n = 6 per group) were acutely exposed by nose-only inhalation to aerosols with a 5-nm primary particle size, produced in the form of small agglomerates (< 100 nm) (SA) or large agglomerates (> 100 nm) (LA) at 2, 7 and 20 mg/m3. Similarly, four other groups of rats were exposed to aerosols at 20 mg/m 3 with a primary particle size of 10-30 and 50 nm. The different aerosols were generated by nebulization of suspensions or by dry dispersion. For each mass concentration, one group of control rats (n = 6 per group) was exposed to compressed air under the same conditions. The size, shape, structure and agglomeration state of NP in both the bulk powders and the generated aerosols were characterized by transmission electron microscopy and using an electrical low pressure impactor. Mass concentrations were determined by gravimetric measurements. The animals were sacrificed 16 hours after the end of exposure, and analysis of the bronchoalveolar lavage fluids was used to measure markers of inflammatory (total and differential cell counts, as well as various cytokines: IL-1alpha, IL-6, MIP-1alpha, MCP-1 and TNF-alpha), cytotoxicity (lactate dehydrogenase (LDH), alkaline phosphatase and total protein concentration) and oxidative stress (heme oxygenase-1, glutathione and 8-isoprostane) effects. Lung sections were also analyzed for histopathology. The influence of the agglomeration state of TiO2 NP (5 nm) could not be determined at 2 mg/m3. For mass concentrations of 7 and 20 mg/m3, our results showed that an acute inflammatory response (increase in the number of neutrophils) was induced following exposure to LA aerosols. In addition to this response, exposure to SA aerosols resulted in a significant increase in 8-isoprostane and LDH. At 20 mg/m3, the cytotoxic effects were greater after exposure to the 5-nm NP in the SA aerosol. Given the significant work done to generate and characterize aerosols, this study showed that TiO2 NP use different mechanisms to induce their pulmonary toxicity as a function of their primary particle size and their agglomeration state.

Preparation of high performance NBR/HNTs nanocomposites using an electron transferring interaction method

NASA Astrophysics Data System (ADS)

Yang, Shuyan; Zhou, Yanxue; Zhang, Peng; Cai, Zhuodi; Li, Yangping; Fan, Hongbo

2017-12-01

Interfacial interaction is one of the key factors to improve comprehensive properties of polymer/inorganic filler nanocomposites. In this work, a new interfacial interaction called electron transferring interaction is reported in the nitrile-butadiene rubber/halloysite nanotubes (NBR/HNTs) nanocomposites. The X-ray photoelectron spectroscopy (XPS) and in-situ controlling temperature Fourier transform infrared spectroscopy (FTIR) have confirmed that electrons of electron-rich -CN groups in NBR can transfer to the electron-deficiency aluminum atoms of HNTs, which packs a part of NBR molecules onto the surface of HNTs to form bound rubber and stabilize the homogeneous dispersion of HNTs with few agglomeration as revealed by scanning electron microscope (SEM) and dynamic mechanical analysis (DMA) performances, even at high HNTs addition, resulting in high light transmittance. The tensile strength of NBR/30wt%HNTs nanocomposites is about 291% higher than pure NBR, without sacrificing the elongation at break.

Numerical modelling of powder caking at REV scale by using DEM

NASA Astrophysics Data System (ADS)

Guessasma, Mohamed; Silva Tavares, Homayra; Afrassiabian, Zahra; Saleh, Khashayar

2017-06-01

This work deals with numerical simulation of powder caking process caused by capillary condensation phenomenon. Caking consists in unwanted agglomeration of powder particles. This process is often irreversible and not easy to predict. To reproduce mechanism involved by caking phenomenon we have used the Discrete Elements Method (DEM). In the present work, we mainly focus on the role of capillary condensation and subsequent liquid bridge formation within a granular medium exposed to fluctuations of ambient relative humidity. Such bridges cause an attractive force between particles, leading to the formation of a cake with intrinsic physicochemical and mechanical properties. By considering a Representative Elementary Volume (REV), the DEM is then performed by means of a MULTICOR-3D software tacking into account the properties of the cake (degree of saturation) in order to establish relationships between the microscopic parameters and the macroscopic behaviour (tensile strength).

Modeling of magnetic particle orientation in magnetic powder injection molding

NASA Astrophysics Data System (ADS)

Doo Jung, Im; Kang, Tae Gon; Seul Shin, Da; Park, Seong Jin

2018-03-01

The magnetic micro powder orientation under viscous shear flow has been analytically understood and characterized into a new analytical orientation model for a powder injection molding process. The effects of hydrodynamic force from the viscous flow, external magnetic force and internal dipole-dipole interaction were considered to predict the orientation under given process conditions. Comparative studies with a finite element method proved the calculation validity with a partial differential form of the model. The angular motion, agglomeration and magnetic chain formation have been simulated, which shows that the effect of dipole-dipole interaction among powders on the orientation state becomes negligible at a high Mason number condition and at a low λ condition (the ratio of external magnetic field strength and internal magnetic moment of powder). Our developed model can be very usefully employed in the process analysis and design of magnetic powder injection molding.

Struvite-based fertilizer and its physical and chemical properties.

PubMed

Latifian, Maryam; Liu, Jing; Mattiasson, Bo

2012-12-01

This study describes a method to formulate struvite fine powder into pellets that are easy to spread on agricultural land. To evaluate the quality of produced pellets, some chemical and physical properties commonly measured for fertilizers were tested. The findings indicated that the salt index and heavy metal content ofstruvite pellets were significantly lower than those of commercial NPK fertilizers. In addition, the percentage of nutrient released from struvite pellets after 105 days was in the range of 9.6-23.2, 8.4-26.7 and 11.3-32.6% for nitrogen, phosphorous and magnesium, respectively, which is considerably lower than that of commercial NPK fertilizer. Among different formulations between struvite crystals and binders, starch and bentonite were the most efficient in agglomerating struvite powder, leading to an increase in the crush strength to over the recommended limit of >2.5 kgf for fertilizer hardness.

Tensile, swelling and morphological properties of bentonite-filled acrylonitrile butadiene rubber composites

NASA Astrophysics Data System (ADS)

Lotfi, Muhamad Nadhli Amin; Ismail, Hanafi; Othman, Nadras

2017-10-01

Tensile, swelling and morphological properties of bentonite filled acrylonitrile butadiene rubber (NBR/Bt) composites were studied. The experiments were conducted at room temperature by using two rolled mill, universal testing machine (INSTRON), and American Standard Testing Method (ASTM) D471 for compounding, tensile testing, and swelling test, respectively. Results obtained indicated that a better tensile strength, elongation at break and tensile modulus were recorded as compared to the pure NBR particularly up to 90 phr of Bt loading. However, swelling (%) exhibited the opposite trend where the liquid uptake by the composites was indirectly proportional with the increasing of Bt loading. Scanning electron microscopy (SEM) used on the tensile fractured surface of the NBR/Bt composites have shown that the fillers were well embedded in the NBR matrix, for Bt loading up to 90 phr. The agglomeration of fillers occurred for Bt loading exceeding 90 phr.

Comparison of quasistatic to impact mechanical properties of multiwall carbon nanotube/polycarbonate composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brühwiler, Paul A.; Barbezat, Michel; Necola, Adly

2010-10-22

We report the quasistatic tensile and impact penetration properties (falling dart test) of injection-molded polycarbonate samples, as a function of multiwall carbon nanotube (MWNT) concentration (0.0-2.5%). The MWNT were incorporated by dilution of a commercial MWNT/polycarbonate masterbatch. The stiffness and quasistatic yield strength of the composites increased approximately linearly with MWNT concentration in all measurements. The energy absorbed in fracture was, however, a negative function of the MWNT concentration, and exhibited different dependencies in quasistatic and impact tests. Small-angle x-ray scattering (SAXS) showed that the dispersion of the MWNT was similar at all concentrations. The negative effects on energy absorptionmore » are attributed to agglomerates remaining in the samples, which were observed in optical microscopy and SAXS. Overall, there was a good correspondence between static and dynamic energy absorption.« less

Resin-dentin bond stability and physical characterization of a two-step self-etching adhesive system associated with TiF4.

PubMed

Torres, Gabriele Barbosa; da Silva, Tânia Mara; Basting, Rosanna Tarkany; Bridi, Enrico Coser; França, Fabiana Mantovani Gomes; Turssi, Cecilia Pedroso; do Amaral, Flávia Lucisano Botelho; de Paiva Gonçalves, Sérgio Eduardo; Basting, Roberta Tarkany

2017-10-01

To evaluate the bond strength to superficial (SD) and deep (DD) dentin after the use of 2.5% (T2.5%) or 4% (T4%) titanium tetrafluoride (TiF 4 ) in aqueous solution as a dentin pretreatment, or when incorporated into the primer (T2.5%P and T4%P) of an adhesive system (Clearfil SE Bond/CL). Degree of conversion (DC), particle size (PS), polydispersity index (PI) and zeta potential (ZP) of the solutions were evaluated. Fifty molars were sectioned longitudinally to obtain two slices of each tooth, which were demarcated into SD and DD. Treatments were applied (n=10): CL; T2.5%; T4%; T2.5%P; T4%P. After 24h or 180days storage, microshear bond strength tests were performed. The DC values of T2.5%P and T4%P were evaluated by FTIR. PS, PI and ZP were measured using dynamic light scattering. Analysis of mixed models showed significant effect of concentration of TiF 4 * solution * storage time (p=0.0075). There were higher bond strength values in SD than in DD (p=0.0105) for all treatments in both times. The failure mode showed adhesive failures in the majority of groups, irrespective of depth and time (p=0.3746). The bond strength values were not affected by treatments. Lower average particle size was observed for T2.5%P and T4%P at baseline. T2.5% and T4% showed a trend towards agglomeration. Higher bond strength values were achieved at SD for all treatments and times. The failure modes observed were adhesive. TiF 4 incorporation did not affect DC. T2.5%P and T4%P presented excellent stability over time. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Char binder for fluidized beds

DOEpatents

Borio, Richard W.; Accortt, Joseph I.

1981-01-01

An arrangement that utilizes agglomerating coal as a binder to bond coal fines and recycled char into an agglomerate mass that will have suitable retention time when introduced into a fluidized bed 14 for combustion. The simultaneous use of coal for a primary fuel and as a binder effects significant savings in the elimination of non-essential materials and processing steps.

Long Life Na/NiCl2 Cells

NASA Technical Reports Server (NTRS)

Bugga, Ratnakumar V. (Inventor); Surampudi, Subbarao (Inventor); Halpert, Gerald (Inventor)

1996-01-01

The premature capacity failure of Na/NiCl2 secondary cells due to agglomeration of nickel particles on the surface of the NiCl2 cathode is prevented by addition of a minor amount such as 10 percent by weight of a transition metal such as Co, Fe or Mn to the cathode. The chlorides of the transition metals have lower potentials than nickel chloride and chlorinate during charge. A uniform dispersion of the transition metals in the cathodes prevents agglomeration of nickel, maintains morphology of the electrode, maintains the electrochemical area of the electrode and thus maintains capacity of the electrode. The additives do not effect sintering. The addition of sulfur to the liquid catholyte is expected to further reduce agglomeration of nickel in the cathode.

Construction Land Expansion and Transfer of Gravity Center from 1984 to 2016 : A study on Beijing - Tianjin - Hebei Urban Agglomeration

NASA Astrophysics Data System (ADS)

Lv, Jinxia; Jiang, Weiguo

2017-04-01

With the economic development and technological innovation, urban planning and construction has already broken through the shackles of the natural conditions such as topography and geomorphology, and the social factors such as politics and location have been affected by the urbanization process in the process of urbanization. At the same time, the synergies between urban development and local economy, national policy, industrial distribution and so on are also paid more attention. As the third pole of Chinese economy after the Pearl River Delta and the Yangtze River Delta, the Beijing-Tianjin-Hebei Metropolis Circle has attracted extensive attention on experts and scholars in its urban development and location. In recent years, studies on urban development have not only analyzed the spatial characteristics of urban or urban agglomerations, but also discussed the relationship between urban development and certain elements or phenomena. This paper presents a multi-threshold and multi-feature extraction method for building land using the optical characteristics of different landforms, based on Landsat remote sensing images from 1984 to 2016. The method selected Automated Water Extraction Index (AWEI), Normalized Difference Vegetation Index (NDVI), Soil Extraction Index (SOEI) and Normalized Difference Built-up Index (BUEI) to extract the construction land. It is an example study area of Beijing to extract the construction land in 30 years and to do a examine research. Using the ArcGIS software to calculate, we can get the coordinates of the city center of gravity in Beijing in various years. It can be seen that the center of gravity of built-up area and the movement of the center of gravity in Beijing. The results showed that the construction land in Beijing has an increasing tendency in recent 30 years. The main characteristic of expansion is the way of high-speed outward development. From 1984 to 1999, the center of gravity of the city shifted to the northeast, and from 2000 to 2016 the center of gravity shifted to the southeast. In the further study, we would do a research in the whole area in Beijing-Tianjin-Hebei and pay more attention to built-up land expansion prediction.

Fracture strength testing of crowns made of CAD/CAM composite resins.

PubMed

Okada, Ryota; Asakura, Masaki; Ando, Akihiro; Kumano, Hirokazu; Ban, Seiji; Kawai, Tatsushi; Takebe, Jun

2018-03-28

The purpose of this study was to ascertain whether computer aided design/computer aided manufacturing (CAD/CAM) composite resin crowns have sufficient strength to withstand the bite force of the molar teeth. The null hypothesis was that the fracture strength of CAD/CAM composite resin crowns is lower than the average maximum bite force of the molar tooth. The crowns, which shape is the right maxillary first molar, were fabricated using four CAD/CAM blanks made of composite resins (Block HC: HC, KZR-CAD HR: HR, KZR-CAD HR2: HR2, Avencia Block: AVE) and one CAD/CAM blank made of lithium disilicate glass-ceramic (IPS e.max CAD: IPS), which was used as a control. Fracture strength of fabricated crowns bonded to metal abutment and biaxial flexural strength of the materials were evaluated. The results of fracture strength test and biaxial flexural strength test showed different tendencies. The fracture strength of CAD/CAM composite resin crowns except HC ranged from 3.3kN to 3.9kN, and was similar to that of IPS (3.3kN). In contrast, biaxial flexural strength of CAD/CAM composite resins ranged from 175MPa to 247MPa, and was significantly lower than that of IPS (360MPa). All CAD/CAM composite resin crowns studied presented about 3-4 times higher fracture strength than the average maximum bite force of the molar tooth (700-900N), which result leads to the conclusion that CAD/CAM composite resin crowns would have sufficient strength to withstand the bite force of the molar teeth. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

The effects of excess calcium on the handling and mechanical properties of hydrothermal derived calcium phosphate bone cement

NASA Astrophysics Data System (ADS)

Razali, N. N.; Sukardi, M. A.; Sopyan, I.; Mel, M.; Salleh, H. M.; Rahman, M. M.

2018-01-01

The objective of this study is to determine the effects of excess calcium on the handling and mechanical properties of hydrothermal derived calcium phosphate cement (CPC) for bone filling applications. Hydroxyapatite powder was synthesized via hydrothermal method using calcium oxide, CaO and ammonium dihydrogen phosphate, NH4H2PO4 as the calcium and phosphorus precursors respectively. The effects of calcium excess were evaluated by varying the CaO content at 0, 5 and 15 mole %. The precursors were then refluxed in distilled water at 90-100°C and dried overnight until the calcium phosphate powder was formed. CPC was then produced by mixing the synthesized powder with distilled water at the powder-to-liquid (P/L) ratio of 1.5. The result from the morphological properties of CPC shows the increase in agglomeration and particles size with 5 mole % of calcium excess but decreased with 15 mole % of calcium excess in CPC. This result was in agreement with the compressive strength result where the CPC increased its strength with 5 mole % of calcium excess but reduced with 15 mole % of calcium excess. The excess in calcium precursor also significantly improved the setting time but reduced the injectability of CPC.

Preparation and characterization of bagasse/HDPE composites using multi-walled carbon nanotubes.

PubMed

Ashori, Alireza; Sheshmani, Shabnam; Farhani, Foad

2013-01-30

This article presents the preparation and characterization of bagasse/high density polyethylene (HDPE) composites. The effects of multi-walled carbon nanotubes (MWCNTs), as reinforcing agent, on the mechanical and physical properties were also investigated. In order to increase the interphase adhesion, maleic anhydride grafted polyethylene (MAPE) was added as a coupling agent to all the composites studied. In the sample preparation, MWCNTs and MAPE contents were used as variable factors. The morphology of the specimens was characterized using scanning electron microscopy (SEM) technique. The results of strength measurement indicated that when 1.5 wt% MWCNTs were added, tensile and flexural properties reached their maximum values. At high level of MWCNTs loading (3 or 4 wt%), increased population of MWCNTs lead to agglomeration and stress transfer gets blocked. The addition of MWCNTs filler slightly decreased the impact strength of composites. Both mechanical and physical properties were improved when 4 wt% MAPE was applied. SEM micrographs also showed that the surface roughness improved with increasing MAPE loading from 0 to 4 wt%. The improvement of physicomechanical properties of composites confirmed that MWCNTs have good reinforcement and the optimum synergistic effect of MWCNTs and MAPE was achieved at the combination of 1.5 and 4 wt%, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effects of content and surface hydrophobic modification of BaTiO3 on the cooling properties of ASA (acrylonitrile-styrene-acrylate copolymer)

NASA Astrophysics Data System (ADS)

Xiang, Bo; Zhang, Jun

2018-01-01

For the field of cool material, barium titanate (BaTiO3, BT) is still a new member that needs to be further studied. Herein, the effects of both content and surface hydrophobic modification of BT on the cooling properties of acrylonitrile-styrene-acrylate copolymer (ASA) were detailedly investigated, aiming to fabricate composited cool material. Butyl acrylate (BA) was employed to convert the surface of BT from hydrophilic to hydrophobic. The addition of unmodified BT could significantly improve the solar reflectance of ASA, especially when the addition amount is 3 vol%, the near infrared (NIR) reflectance increased from 22.02 to 72.60%. However, serious agglomeration occurred when the addition amount increased to 5 vol% and therefore led to a relatively smaller increase in solar reflectance and an obvious decline in impact strength. After surface hydrophobic modification, the modified BT (M-BT) presented better dispersibility in ASA matrix, which contributed to the improvement of both solar reflectance and impact strength. In addition, the temperature test provided a more sufficient and intuitive way to evaluate the cooling effect of the composited cool materials, and a significant decrease (over 10 °C) could be achieved in the temperature test when M-BT particles were introduced.

Succinic acid in levels produced by yeast (Saccharomyces cerevisiae) during fermentation strongly impacts wheat bread dough properties.

PubMed

Jayaram, Vinay B; Cuyvers, Sven; Verstrepen, Kevin J; Delcour, Jan A; Courtin, Christophe M

2014-05-15

Succinic acid (SA) was recently shown to be the major pH determining metabolite produced by yeast during straight-dough fermentation (Jayaram et al., 2013), reaching levels as high as 1.6 mmol/100 g of flour. Here, the impact of such levels of SA (0.8, 1.6 and 2.4 mmol/100 g flour) on yeastless dough properties was investigated. SA decreased the development time and stability of dough significantly. Uniaxial extension tests showed a consistent decrease in dough extensibility upon increasing SA addition. Upon biaxial extension in the presence of 2.4 mmol SA/100 g flour, a dough extensibility decrease of 47-65% and a dough strength increase of 25-40% were seen. While the SA solvent retention capacity of flour increased with increasing SA concentration in the solvent, gluten agglomeration decreased with gluten yield reductions of over 50%. The results suggest that SA leads to swelling and unfolding of gluten proteins, thereby increasing their interaction potential and dough strength, but simultaneously increasing intermolecular electrostatic repulsive forces. These phenomena lead to the reported changes in dough properties. Together, our results establish SA as an important yeast metabolite for dough rheology. Copyright © 2013 Elsevier Ltd. All rights reserved.

Molecules coating magnetic nanoparticles for oil-field applications

NASA Astrophysics Data System (ADS)

Zuluaga, Sebastian; Manchanda, Priyanka; Pantelides, Sokrates

Magnetic nanoparticles have recently attracted significant attention in scientific and industrial communities due to their use in the fields of catalysis, spintronics, biomedical applications, and oil recovery and reservoir characterization. However, these nanoparticles have to be protected with a coating layer of molecules that prevents the nanoparticles from oxidation, which is known to occur in air, and from agglomeration into larger nanoparticles. Therefore, the binding of the molecules to the nanoparticles is critical before a large scale implementation can be done. Here we report results of density functional theory calculations on several molecules (methylamine, acetic acid, boronic acid, ethyl phosphate, and ethyl trihydroxysilane) and magnetic nanoparticles (Fe3O4, NiFe2O4, and Fe3C). We focus on two main points: 1) the bond strength between the organic molecule and the nano particle, and 2) how, H2O and H+ in the oil well may facilitate the desorption of the molecules. The results show that H+ and H2O molecules facilitate the desorption of molecules reducing the bond strength by several eV. On the other hand, the results allow us to identify and design molecules that exhibit the best performance in protecting each nanoparticle. Supported by a Grant from the Petroleum Institute, Abu Dhabi.

DEVELOPMENT OF A FABRICATION PROCESS FOR SOL-GEL/METAL HYDRIDE COMPOSITE GRANULES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, E; Eric Frickey, E; Leung Heung, L

An external gelation process was developed to produce spherical granules that contain metal hydride particles in a sol-gel matrix. Dimensionally stable granules containing metal hydrides are needed for applications such as hydrogen separation and hydrogen purification that require columns containing metal hydrides. Gases must readily flow through the metal hydride beds in the columns. Metal hydrides reversibly absorb and desorb hydrogen and hydrogen isotopes. This is accompanied by significant volume changes that cause the metal hydride to break apart or decrepitate. Repeated cycling results in very fine metal hydride particles that are difficult to handle and contain. Fine particles tendmore » to settle and pack making it more difficult to flow gases through a metal hydride bed. Furthermore, the metal hydrides can exert a significant force on the containment vessel as they expand. These problems associated with metal hydrides can be eliminated with the granulation process described in this report. Small agglomerates of metal hydride particles and abietic acid (a pore former) were produced and dispersed in a colloidal silica/water suspension to form the feed slurry. Fumed silica was added to increase the viscosity of the feed slurry which helped to keep the agglomerates in suspension. Drops of the feed slurry were injected into a 27-foot tall column of hot ({approx}70 C), medium viscosity ({approx}3000 centistokes) silicone oil. Water was slowly evaporated from the drops as they settled. The drops gelled and eventually solidified to form spherical granules. This process is referred to as external gelation. Testing was completed to optimize the design of the column, the feed system, the feed slurry composition, and the operating parameters of the column. The critical process parameters can be controlled resulting in a reproducible fabrication technique. The residual silicone oil on the surface of the granules was removed by washing in mineral spirits. The granules were dried in air at 40 C. The granules were heated to 230 C for 30 minutes in argon to remove the remaining water and organic materials. The resulting product was spherical composite granules (100 to 2000 micron diameter) with a porous silica matrix containing small agglomerates of metal hydride particles. Open porosity in the silica matrix allows hydrogen to permeate rapidly through the matrix but the pores are small enough to contain the metal hydride particles. Additional porosity around the metal hydride particles, induced using abietic acid as a pore former, allows the particles to freely expand and contract without fracturing the brittle sol-gel matrix. It was demonstrated that the granules readily absorb and desorb hydrogen while remaining integral and dimensionally stable. Microcracking was observed after the granules were cycled in hydrogen five times. The strength of the granules was improved by coating them with a thin layer of a micro-porous polymer sol-gel that would allow hydrogen to freely pass through the coating but would filter out metal hydride poisons such as water and carbon monoxide. It was demonstrated that if a thin sol-gel coating was applied after the granules were cycled, the coating not only improved the strength of the granules but the coated granules retained their strength after additional hydrogen cycling tests. This additional strength is needed to extend the lifetime of the granules and to survive the compressive load in a large column of granules. Additional hydrogen adsorption tests are planned to evaluate the performance of coated granules after one hundred cycles. Tests will also be performed to determine the effects of metal hydride poisons on the granules. The results of these tests will be documented in a separate report. The process that was developed to form these granules could be scaled to a production process. The process to form granules from a mixture of metal hydride particles and pore former such as abietic acid can be scaled up using commercial granulators. The current laboratory-scale external gelation column produces approximately one gram of granules per hour. To increase the production output from a single column, multiple feed injection systems in a larger diameter column could be used.« less

Spherical agglomerates of pure drug nanoparticles for improved pulmonary delivery in dry powder inhalers

NASA Astrophysics Data System (ADS)

Hu, Jun; Dong, Yuancai; Pastorin, Giorgia; Ng, Wai Kiong; Tan, Reginald B. H.

2013-04-01

The aim of this study was to produce micron-sized spherical agglomerates of pure drug nanoparticles to achieve improved aerosol performance in dry powder inhalers (DPIs). Sodium cromoglicate was chosen as the model drug. Pure drug nanoparticles were prepared through a bottom-up particle formation process, liquid antisolvent precipitation, and then rapidly agglomerated into porous spherical microparticles by immediate (on-line) spray drying. Nonporous spherical drug microparticles with similar geometric size distribution were prepared by conventional spray drying of the aqueous drug solution, which together with the mechanically micronized drug particles were used as the control samples. The three samples were characterized by field emission scanning electron microscopy, laser diffraction, Brunauer-Emmett-Teller analysis, density measurement, powder X-ray diffraction, and in vitro aerosol deposition measurement with a multistage liquid impinger. It was found that drug nanoparticles with a diameter of 100 nm were precipitated and agglomerated into highly porous spherical microparticles with a volume median diameter ( D 50 %) of 2.25 ± 0.08 μm and a specific surface area of 158.63 ± 3.27 m2/g. In vitro aerosol deposition studies showed the fine particle fraction of such spherical agglomerates of drug nanoparticles was increased by more than 50 % in comparison with the control samples, demonstrating significant improvements in aerosol performance. The results of this study indicated the potential of the combined particle engineering process of liquid antisolvent precipitation followed by immediate (on-line) spray drying in the development of novel DPI drug products with improved aerosol performance.

Quantum dot agglomerates in biological media and their characterization by asymmetrical flow field-flow fractionation.

PubMed

Moquin, Alexandre; Neibert, Kevin D; Maysinger, Dusica; Winnik, Françoise M

2015-01-01

The molecular composition of the biological environment of nanoparticles influences their physical properties and changes their pristine physicochemical identity. In order to understand, or predict, the interactions of cells with specific nanoparticles, it is critical to know their size, shape, and agglomeration state not only in their nascent state but also in biological media. Here, we use asymmetrical flow field-flow fractionation (AF4) with on-line multiangle light scattering (MALS), dynamic light scattering (DLS) and UV-Visible absorption detections to determine the relative concentration of isolated nanoparticles and agglomerates in the case of three types of semi-conductor quantum dots (QDs) dispersed in Dulbecco's Modified Eagle Media (DMEM) containing 10% of fetal bovine serum (DMEM-FBS). AF4 analysis also yielded the size and size distribution of the agglomerates as a function of the time of QDs incubation in DMEM-FBS. The preferred modes of internalization of the QDs are assessed for three cell-types, N9 microglia, human hepatocellular carcinoma cells (HepG2) and human embryonic kidney cells (Hek293), by confocal fluorescence imaging of live cells, quantitative determination of the intracellular QD concentration, and flow cytometry. There is an excellent correlation between the agglomeration status of the three types of QDs in DMEM-FBS determined by AF4 analysis and their preferred mode of uptake by the three cell lines, which suggests that AF4 yields an accurate description of the nanoparticles as they encounter cells and advocates its use as a means to characterize particles under evaluation. Copyright © 2014 Elsevier B.V. All rights reserved.

Ultrasonication effects on thermal and rheological properties of carbon nanotube suspensions

PubMed Central

2012-01-01

The preparation of nanofluids is very important to their thermophysical properties. Nanofluids with the same nanoparticles and base fluids can behave differently due to different nanofluid preparation methods. The agglomerate sizes in nanofluids can significantly impact the thermal conductivity and viscosity of nanofluids and lead to a different heat transfer performance. Ultrasonication is a common way to break up agglomerates and promote dispersion of nanoparticles into base fluids. However, research reports of sonication effects on nanofluid properties are limited in the open literature. In this work, sonication effects on thermal conductivity and viscosity of carbon nanotubes (0.5 wt%) in an ethylene glycol-based nanofluid are investigated. The corresponding effects on the agglomerate sizes and the carbon nanotube lengths are observed. It is found that with an increased sonication time/energy, the thermal conductivity of the nanofluids increases nonlinearly, with the maximum enhancement of 23% at sonication time of 1,355 min. However, the viscosity of nanofluids increases to the maximum at sonication time of 40 min, then decreases, finally approaching the viscosity of the pure base fluid at a sonication time of 1,355 min. It is also observed that the sonication process not only reduces the agglomerate sizes but also decreases the length of carbon nanotubes. Over the current experimental range, the reduction in agglomerate size is more significant than the reduction of the carbon nanotube length. Hence, the maximum thermal conductivity enhancement and minimum viscosity increase are obtained using a lengthy sonication, which may have implications on application. PMID:22333487

Role of adsorption in combined membrane fouling by biopolymers coexisting with inorganic particles.

PubMed

Chen, Xu-di; Wang, Zhi; Liu, Dan-Yang; Xiao, Kang; Guan, Jing; Xie, Yuefeng F; Wang, Xiao-Mao; Waite, T David

2018-01-01

This study was conducted in order to obtain a better understanding of the combined fouling by biopolymers coexisting with inorganic particles from the aspects of fouling index, fouling layer structure and biopolymer-particle interactions. Calcium alginate was used as the model biopolymer and Fe 2 O 3 , Al 2 O 3 , kaolin, and SiO 2 were used as model inorganic particles. Results showed that the combined fouling differed greatly among the four types of inorganic particles. The differences were attributed particularly to the different adsorption capacities for calcium alginate by the particles with this capacity decreasing in the order of Fe 2 O 3 , Al 2 O 3 , kaolin and SiO 2 . Particle size measurement and electron microscopic observation indicated the formation of agglomerates between calcium alginate and those inorganic particles exhibiting strong adsorption capacity. A structure was proposed for the combined fouling layer comprised of a backbone cake layer of alginate-inorganic particle agglomerates with the pores partially filled with discontinuous calcium alginate gels. The filterability of the fouling layer was primarily determined by the abundance of the gels. The strength of physical interaction between calcium alginate and each type of inorganic particle was calculated from the respective surface energies and zeta potentials. Calculation results showed that the extent of physical interaction increased in the order of Al 2 O 3 , Fe 2 O 3 , kaolin and SiO 2 , with this order differing from that of adsorption capacity. Chemical interactions may also play an important role in the adsorption of alginate and the consequent combined fouling. High-resolution XPS scans revealed a slight shift of electron binding energies when alginate was adsorbed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Toward Semistructural Cellulose Nanocomposites: The Need for Scalable Processing and Interface Tailoring.

PubMed

Ansari, Farhan; Berglund, Lars A

2018-04-11

Cellulose nanocomposites can be considered for semistructural load-bearing applications where modulus and strength requirements exceed 10 GPa and 100 MPa, respectively. Such properties are higher than for most neat polymers but typical for molded short glass fiber composites. The research challenge for polymer matrix biocomposites is to develop processing concepts that allow high cellulose nanofibril (CNF) content, nanostructural control in the form of well-dispersed CNF, the use of suitable polymer matrices, as well as molecular scale interface tailoring to address moisture effects. From a practical point of view, the processing concept needs to be scalable so that large-scale industrial processing is feasible. The vast majority of cellulose nanocomposite studies elaborate on materials with low nanocellulose content. An important reason is the challenge to prevent CNF agglomeration at high CNF content. Research activities are therefore needed on concepts with the potential for rapid processing with controlled nanostructure, including well-dispersed fibrils at high CNF content so that favorable properties are obtained. This perspective discusses processing strategies, agglomeration problems, opportunities, and effects from interface tailoring. Specifically, preformed CNF mats can be used to design nanostructured biocomposites with high CNF content. Because very few composite materials combine functional and structural properties, CNF materials are an exception in this sense. The suggested processing concept could include functional components (inorganic clays, carbon nanotubes, magnetic nanoparticles, among others). In functional three-phase systems, CNF networks are combined with functional components (nanoparticles or fibril coatings) together with a ductile polymer matrix. Such materials can have functional properties (optical, magnetic, electric, etc.) in combination with mechanical performance, and the comparably low cost of nanocellulose may facilitate the use of large nanocomposite structures in industrial applications.

Volume Labeling with Alexa-Fluor Dyes and Surface Functionalization of Highly Sensitive Fluorescent SiO2 Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wei; Foster, Carmen M; Morrell-Falvey, Jennifer L

2013-01-01

A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and amore » polydispersity of <15%. In comparison with conventional surface tagged particles created by post-synthesis modification, this process maintains the physical and surface chemical properties that have the most pronounced effect on colloidal stability and interactions with their surroundings. These volume-labeled nanoparticles have proven to be extremely robust, showing excellent signal strength, negligible photobleaching, and minimal loss of functional organic components. The native or free surface of the volume-labeled particles can be altered to achieve a specific surface functionality without altering fluorescence. Their utility was demonstrated for visualizing the association of surface modified fluorescent particles with cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems.« less

Process for removing pyritic sulfur from bituminous coals

DOEpatents

Pawlak, Wanda; Janiak, Jerzy S.; Turak, Ali A.; Ignasiak, Boleslaw L.

1990-01-01

A process is provided for removing pyritic sulfur and lowering ash content of bituminous coals by grinding the feed coal, subjecting it to micro-agglomeration with a bridging liquid containing heavy oil, separating the microagglomerates and separating them to a water wash to remove suspended pyritic sulfur. In one embodiment the coal is subjected to a second micro-agglomeration step.

Do Universities Generate Agglomeration Spillovers? Evidence from Endowment Value Shocks. NBER Working Paper No. 15299

ERIC Educational Resources Information Center

Kantor, Shawn; Whalley, Alexander

2009-01-01

In this paper we quantify the extent and magnitude of agglomeration spillovers from a formal institution whose sole mission is the creation and dissemination of knowledge--the research university. We use the fact that universities follow a fixed endowment spending policy based on the market value of their endowments to identify the causal effect…

Efficient solid rocket propulsion for access to space

NASA Astrophysics Data System (ADS)

Maggi, Filippo; Bandera, Alessio; Galfetti, Luciano; De Luca, Luigi T.; Jackson, Thomas L.

2010-06-01

Space launch activity is expected to grow in the next few years in order to follow the current trend of space exploitation for business purpose. Granting high specific thrust and volumetric specific impulse, and counting on decades of intense development, solid rocket propulsion is a good candidate for commercial access to space, even with common propellant formulations. Yet, some drawbacks such as low theoretical specific impulse, losses as well as safety issues, suggest more efficient propulsion systems, digging into the enhancement of consolidated techniques. Focusing the attention on delivered specific impulse, a consistent fraction of losses can be ascribed to the multiphase medium inside the nozzle which, in turn, is related to agglomeration; a reduction of agglomerate size is likely. The present paper proposes a model based on heterogeneity characterization capable of describing the agglomeration trend for a standard aluminized solid propellant formulation. Material microstructure is characterized through the use of two statistical descriptors (pair correlation function and near-contact particles) looking at the mean metal pocket size inside the bulk. Given the real formulation and density of a propellant, a packing code generates the material representative which is then statistically analyzed. Agglomerate predictions are successfully contrasted to experimental data at 5 bar for four different formulations.

Do we still need cities? Evidence on rates of innovation from count data models of metropolitan statistical area patents.

PubMed

Sedgley, Norman; Elmslie, Bruce

2011-01-01

Evidence of the importance of urban agglomeration and the offsetting effects of congestion are provided in a number of studies of productivity and wages. Little attention has been paid to this evidence in the economic growth literature, where the recent focus is on technological change. We extend the idea of agglomeration and congestion effects to the area of innovation by empirically looking for a nonlinear link between population density and patent activity. A panel data set consisting of observations on 302 USA metropolitan statistical areas (MSAs) over a 10-year period from 1990 to 1999 is utilized. Following the patent and R&D literature, models that account for the discreet nature of the dependent variable are employed. Strong evidence is found that agglomeration and congestion are important in explaining the vast differences in patent rates across US cities. The most important reason cities continue to exist, given the dramatic drop in transportation costs for physical goods over the last century, is probably related to the forces of agglomeration as they apply to knowledge spillovers. Therefore, the empirical investigation proposed here is an important part of understanding the viability of urban areas in the future.

Development of Impregnated Agglomerate Pelletization (IAP) process for fabrication of (Th,U)O 2 mixed oxide pellets

NASA Astrophysics Data System (ADS)

Khot, P. M.; Nehete, Y. G.; Fulzele, A. K.; Baghra, Chetan; Mishra, A. K.; Afzal, Mohd.; Panakkal, J. P.; Kamath, H. S.

2012-01-01

Impregnated Agglomerate Pelletization (IAP) technique has been developed at Advanced Fuel Fabrication Facility (AFFF), BARC, Tarapur, for manufacturing (Th, 233U)O 2 mixed oxide fuel pellets, which are remotely fabricated in hot cell or shielded glove box facilities to reduce man-rem problem associated with 232U daughter radionuclides. This technique is being investigated to fabricate the fuel for Indian Advanced Heavy Water Reactor (AHWR). In the IAP process, ThO 2 is converted to free flowing spheroids by powder extrusion route in an unshielded facility which are then coated with uranyl nitrate solution in a shielded facility. The dried coated agglomerate is finally compacted and then sintered in oxidizing/reducing atmosphere to obtain high density (Th,U)O 2 pellets. In this study, fabrication of (Th,U)O 2 mixed oxide pellets containing 3-5 wt.% UO 2 was carried out by IAP process. The pellets obtained were characterized using optical microscopy, XRD and alpha autoradiography. The results obtained were compared with the results for the pellets fabricated by other routes such as Coated Agglomerate Pelletization (CAP) and Powder Oxide Pelletization (POP) route.

Control of nanoparticle agglomeration through variation of the time-temperature profile in chemical vapor synthesis

NASA Astrophysics Data System (ADS)

Djenadic, Ruzica; Winterer, Markus

2017-02-01

The influence of the time-temperature history on the characteristics of nanoparticles such as size, degree of agglomeration, or crystallinity is investigated for chemical vapor synthesis (CVS). A simple reaction-coagulation-sintering model is used to describe the CVS process, and the results of the model are compared to experimental data. Nanocrystalline titania is used as model material. Titania nanoparticles are generated from titanium-tetraisopropoxide (TTIP) in a hot-wall reactor. Pure anatase particles and mixtures of anatase, rutile (up to 11 vol.%), and brookite (up to 29 vol.%) with primary particle sizes from 1.7 nm to 10.5 nm and agglomerate particle sizes from 24.3 nm to 55.6 nm are formed depending on the particle time-temperature history. An inductively heated furnace with variable inductor geometry is used as a novel system to control the time-temperature profile in the reactor externally covering a large wall temperature range from 873 K to 2023 K. An appropriate choice of inductor geometry, i.e. time-temperature profile, can significantly reduce the degree of agglomeration. Other particle characteristics such as crystallinity are also substantially influenced by the time-temperature profile.

Further observations on OCOM MOX fuel: microstructure in the vicinity of the pellet rim and fuel — cladding interaction

NASA Astrophysics Data System (ADS)

Walker, C. T.; Goll, W.; Matsumura, T.

1997-06-01

The fuel investigated was manufactured by Siemens-KWU and irradiated at low rating in the KWO reactor in Germany. The MOX agglomerates in the cold outer region of the fuel shared several common features with the high burn-up structure at the rim of UO 2 fuel. It is proposed that in both cases the mechanism producing the microstructure change is recrystallisation. Further, it is shown that surface MOX agglomerates do not noticeably retard cladding creepdown although they swell into the gap. The contracting cladding appears able to push the agglomerates back into the fuel. The thickness of the oxide layer on the inner cladding surface increased at points where contact with surface MOX agglomerates had occurred. Despite this, the mean thickness of the oxide did not differ significantly from that found in UO 2 fuel rods of like design. It is judged that the high burn-up structure will form in the UO 2 matrix when the local burn-up there reaches 60 to 80 GWd/tM. Limiting the MOX scrap addition in the UO 2 matrix will delay its formation.

Helium shell flashes and evolution of accreting white dwarfs

NASA Astrophysics Data System (ADS)

Fujimoto, M. Y.; Sugimoto, D.

1982-06-01

The evolution of accreting white dwarfs is investigated from the onset of accretion through the helium shell flash. Properties of the helium shell flashes are studied by means of a generalized theory of shell flash and by numerical computations, and it is found that the shell flash grows up to the strength of a supernova explosion when the mass of the helium zone is large enough on a massive white dwarf. Although accretion onto a hot white dwarf causes a weaker shell flash than those onto cool ones, a strong tendency exists for the strength to be determined mainly by the accretion rate. For fast accretion, the shell flashes are weak and triggered recurrently, while for slow accretion the helium shell flash, once triggered, develops into a detonation supernova.

Transport characteristics of nanoparticle-based ferrofluids in a gel model of the brain

PubMed Central

Basak, Soubir; Brogan, David; Dietrich, Hans; Ritter, Rogers; Dacey, Ralph G; Biswas, Pratim

2009-01-01

A current advance in nanotechnology is the selective targeting of therapeutics by external magnetic field-guided delivery. This is an important area of research in medicine. The use of magnetic forces results in the formation of agglomerated structures in the field region. The transport characteristics of these agglomerated structures are explored. A nonintrusive method based on in situ light-scattering techniques is used to characterize the velocity of such particles in a magnetic field gradient. A transport model for the chain-like agglomerates is developed based on these experimental observations. The transport characteristics of magnetic nanoparticle drug carriers are then explored in gel-based simulated models of the brain. Results of such measurements demonstrate decreased diffusion of magnetic nanoparticles when placed in a high magnetic field gradient. PMID:19421367

KISS: Kinetics and Structure of Superagglomerates Produced by Silane and Acetylene

NASA Technical Reports Server (NTRS)

Mulholland, G. W.; Yang, J. C.; Scott, J. H.; Sivithanu, Y.

2001-01-01

The objective of this study is to understand the process of gas phase agglomeration leading to superagglomerates and a gel-like structure for microgravity (0-g) silane and acetylene flames. Ultimately one would apply this understanding to predicting flame conditions that could lead to the gas phase production of an aero-gel. The approach is to burn acetylene and silane and to analyze the evolution of the soot and silica agglomerates. Acetylene is chosen because it has one of the highest soot volume fractions and there is evidence of super agglomerates being formed in laminar acetylene flames. Silane has the advantage that silica particles are the major combustion product resulting in a particle volume fraction a factor of ten greater than that for a carbonaceous smoke.

Mechanical Properties in a Bamboo Fiber/PBS Biodegradable Composite

NASA Astrophysics Data System (ADS)

Ogihara, Shinji; Okada, Akihisa; Kobayashi, Satoshi

In recent years, biodegradable plastics which have low effect on environment have been developed. However, many of them have lower mechanical properties than conventional engineering plastics. Reinforcing them with a natural fiber is one of reinforcing methods without a loss of their biodegradability. In the present study, we use a bamboo fiber as the reinforcement and polybutylenesuccinate (PBS) as the matrix. We fabricate long fiber unidirectional composites and cross-ply laminate with different fiber weight fractions (10, 20, 30, 40 and 50wt%). We conduct tensile tests to evaluate the mechanical properties of these composites. In addition, we measure bamboo fiber strength distribution. We discuss the experimentally-obtained properties based on the mechanical properties of the constituent materials. Young's modulus and tensile strength in unidirectional composite and cross-ply laminate increase with increasing fiber weight fraction. However, the strain at fracture showed decreasing tendency. Young's modulus in fiber and fiber transverse directions are predictable by the rules of mixture. Tensile strength in fiber direction is lower than Curtin's prediction of strength which considers distribution of fiber strength. Young's modulus in cross-ply laminate is predictable by the laminate theory. However, analytical prediction of Poisson's ratio in cross-ply laminate by the laminate theory is lower than the experimental results.

Restrained shrinkage cracking of cementitious composites containing soft PCM inclusions: A paste (matrix) controlled response

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Zhenhua; Falzone, Gabriel; Das, Sumanta

The addition of phase change materials (PCMs) has been proposed as a way to mitigate thermal cracking in cementitious materials. However, the addition of PCMs, i.e., soft inclusions, degrades the compressive strength of cementitious composites. From a strength-of-materials viewpoint, such reductions in strength are suspected to increase the tendency of cementitious materials containing PCMs to crack under load (e.g., volume instability-induced stresses resulting from thermal and/or hygral deformations). Based on detailed assessments of free and restrained shrinkage, elastic modulus, and tensile strength, this study shows that the addition of PCMs does not alter the cracking sensitivity of the material. Inmore » fact, the addition of PCMs (or other soft inclusions) enhances the cracking resistance as compared to a plain cement paste or composites containing equivalent dosages of (stiff) quartz inclusions. This is because composites containing soft inclusions demonstrate benefits resulting from crack blunting and deflection, and improved stress relaxation. As a result, although the tensile stress at failure remains similar, the time to failure (i.e., macroscopic cracking) of PCM-containing composites is considerably extended. More generally, the outcomes indicate that dosages of soft(er) inclusions, and the resulting decrease in compressive strength does not amplify the cracking risk of cementitious composites.« less

Study on identically voided pervious concrete made with different sized aggregates

NASA Astrophysics Data System (ADS)

Kastro Kiran, V.; Anand, K. B.

2018-02-01

Pervious concrete (PC) is also known as no fines concrete and has been found to be a reliable stormwater management tool. As a substitution for conventional impervious pavement, PC usage has been increasing during recent years. PC made with different sized aggregate shows different void ratios and changed properties. As void ratio plays a notable role on strength and permeability of PC, this study aims to focus on properties of PC at identical void ratio of 20%, made using aggregates of three size ranges, viz., 4.75-6mm, 10-12.5mm, and 10-20mm. Appropriate alternatives were used to maintain the identical void ratio. As the permeation capacity of PC gets reduced due to the clogging tendency, the life of PC will also get reduced. Hence, to make the PC to sustain for a long time it is necessary to study the clogging behavior. This study investigates the tendency of PC for clogging and the potential for regaining the permeability through de-clogging methods. Clogging tendency of PC is studied by using two sizes (coarse and fine) of clog particles and the changes in permeability are observed. Efficiency of declogging methods like pressure washing and vacuum suction on PC with different sized aggregates are also evaluated.

Accounting for occurrences: a new view of the use of contingency information in causal judgment.

PubMed

White, Peter A

2008-01-01

When people make causal judgments from contingency information, a principal aim is to account for occurrences of the outcome. When 2 causes are under consideration, the capacity of either to account for occurrences is judged from how likely the cause is to be present when the outcome occurs and from the rate at which the outcome occurs when that cause alone is present, which gives an estimate of the strength of the cause. These propositions are formalized in a weighted averaging model, which successfully predicted several judgmental phenomena not predicted by other models of causal judgment. These include a tendency for judgment of one cause (A) to be reduced as the number of occurrences of when only the other one (B) increases and a tendency for A to receive higher judgments than B if A is better able to account for occurrences than B is even if B has a higher contingency with the outcome than A does. Overshadowing, a tendency for judgments of B to be depressed if A has a higher contingency, is weak or absent when B is better able to account for occurrences than A. Results of several experiments support these and related predictions derived from the accounting for occurrences hypothesis. PsycINFO Database Record (c) 2008 APA, all rights reserved.

The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 2, Section 2: Strength and Fracture Resistance

DTIC Science & Technology

1989-10-15

tensions of. the integral equawin methods used in these earlier papers. Cook and Erdogan (1972) and Erdogan and Diniakolo (1973) investigate the...main crack impinging the interface at right angles. Additional work along these same lines is reported by Lu and Erdogan (1963). The tendency for a...crack approaching an interface or a free surface at 3n oblique unlet to be deflected one way or the other has been elucidated by itudics or Erdogan and

Effect of nano-oxide concentration on the mechanical properties of a maxillofacial silicone elastomer.

PubMed

Han, Ying; Kiat-amnuay, Sudarat; Powers, John M; Zhao, Yimin

2008-12-01

Contemporary silicone-based elastomeric prostheses tend to degrade over time because of the effect of mechanical loading. Little has been reported on how the mechanical properties of a maxillofacial prosthetic elastomer may be affected by the addition of nanosized oxide particles used as an opacifier. The purpose of this study was to evaluate the effect of different concentrations of nanosized oxides of various composition on the mechanical properties of a commercially available silicone elastomer. Nanosized oxides (Ti, Zn, or Ce) were added in various concentrations (0.5%, 1.0%, 1.5%, 2.0%, 2.5%, or 3.0% by weight) to a commercial silicone elastomer (A-2186), commonly used for fabricating extraoral maxillofacial prostheses. Silicone elastomer A-2186 without nanosized oxides served as a control group. Specimens (n=5) were polymerized according to manufacturer's recommendations and tested for tensile strength (ASTM D412) and tear strength (ASTM D624), and percent elongation in a universal testing machine. Uniformity of particle dispersion within the processed elastomer was assessed using scanning electron microscopic imaging. For each property, a 2-way ANOVA was performed evaluating the effect of oxide type and strength, and Fisher's PLSD test was used for pairwise comparisons (alpha=.05). SEM examination indicated that all 3 nanosized oxides distribute evenly throughout the silicone specimens, except for the 3.0% group, which are partly agglomerated. The 2.0% and 2.5% groups of all nanosized oxides demonstrated significantly higher tensile and tear strengths and percent elongation (P<.001) than the control group. CeO(2) had significantly lower tensile strength than TiO2 and ZnO (P<.05). The ZnO group had significantly higher tear strength than TiO(2) and CeO(2) (P <.05). Most of specimens became somewhat harder when compared with the control group. CeO(2) group had significantly higher Shore A hardness than TiO(2) and ZnO (P<.001). There was no significant difference of percent elongation among the type of nanosized oxides. Incorporation of Ti, Zn, or Ce nano-oxides at concentrations of 2.0% and 2.5% improved the overall mechanical properties of the silicone A-2186 maxillofacial elastomer.

Pulmonary toxicity and fate of agglomerated 10 and 40 nm aluminum oxyhydroxides following 4-week inhalation exposure of rats: toxic effects are determined by agglomerated, not primary particle size.

PubMed

Pauluhn, Jürgen

2009-05-01

Inhaled polydisperse micronsized agglomerated particulates composed of nanosized primary particles may exert their pulmonary toxicity in either form, depending on whether these tightly associated structures are disintegrated within the biological system or not. This hypothesis was tested in a rat bioassay using two calcined aluminum oxyhydroxides (AlOOH) consisting of primary particles in the range of 10-40 nm. Male Wistar rats were nose-only exposed to 0.4, 3, and 28 mg/m(3) in two 4-week (6 h/day, 5 days/week) inhalation studies followed by a 3-month postexposure period. The respective mass median aerodynamic diameter (MMAD) of agglomerated particles in inhalation chambers was 1.7 and 0.6 mum. At serial sacrifices, pulmonary toxicity was characterized by bronchoalveolar lavage (BAL) and histopathology. The retention kinetics of aluminum (Al) was determined in lung tissue, BAL cells, and selected extrapulmonary organs, including lung-associated lymph nodes (LALNs). Significant changes in BAL, lung, and LALN weights occurred at 28 mg/m(3). Histopathology revealed alveolar macrophages with enlarged and foamy appearance, increased epithelial cells, inflammatory cells, and focal septal thickening. The determination of aluminum in lung tissue shows that the cumulative lung dose was higher following exposure to AlOOH-40 nm/MMAD-0.6 mum than to AlOOH-10 nm/MMAD-1.7 mum, despite identical exposure concentrations. The associated pulmonary inflammatory response appears to be principally dependent on the agglomerated rather than primary particle size. Despite high lung burdens, conclusively increased extrapulmonary organ burdens did not occur at any exposure concentration and postexposure time point. Particle-induced pulmonary inflammation was restricted to cumulative doses exceeding approximately 1 mg AlOOH/g lung following 4-week exposure at 28 mg/m(3). It is concluded that the pulmonary toxicity of nanosized, agglomerated AlOOH particles appears to be determined by the size of agglomerated rather than primary particles, whereas the clearance half-time of particles appears to increase with decreased primary particle size. However, in regard to toxicokinetics, this outcome is highly contingent upon the total lung burden and especially whether overloading or non-overloading conditions were attained or not. In order to reliably demonstrate retention-related different characteristics in toxicity and fate of poorly soluble (nano)particles postexposure periods of at least 3 months appear to be indispensible.

Microgravity Superagglomerates Produced By Silane And Acetylene

NASA Technical Reports Server (NTRS)

Gokoglu, Suleyman (Technical Monitor); Bundy, Matthew; Mulholland, George W.; Manzello, Samuel; Yang, Jiann; Scott, John Henry; Sivathanu, Yudaya

2003-01-01

The size of the agglomerates produced in the upper portion of a flame is important for a variety of applications. Soot particle size and density effect the amount of radiative heat transfer from a fire to its surroundings. Particle size determines the lifetime of smoke in a building or in the atmosphere, and exposure hazard for smoke inhaled and deposited in the lungs. The visibility through a smoke layer and dectectability of the smoke are also greatly affected by agglomerate size. Currently there is limited understanding of soot growth with an overall dimension of 10 m and larger. In the case of polystyrene, smoke agglomerates in excess of 1 mm have been observed raining out from large fires. Unlike hydrocarbon fuels, silane has the advantage that silica particles are the major combustion product resulting in a particle volume fraction a factor of ten greater than that for a carbonaceous smoke. There are two very desirable properties of silica aero-gels that are important for both space and earth based applications. The first important property is its inertness to most oxidizing and reducing atmospheres. Therefore, silica aero-gels make excellent fire ablatives and can be used in very demanding applications. The second important property is that silica aero-gels are expected to have very high porosity (greater than 0.999), making them lightweight and ideal for aerospace applications. The added benefit of the high porosity is that they can be used as extremely efficient filters for many earth based applications as well. Evidence of the formation of superagglomerates in a laminar acetylene/air diffusion flame was found by Sorensen et al. [1]. An interconnecting web of super-agglomerates was observed to span the width of the soot plume in the region just above the flame tip and described as a gel state. It was observed that this gel state immediately breaks up into agglomerates as larges as 100 m due to buoyancy induced turbulence. Large soot agglomerates were observed in microgravity butane jet diffusion flames by Ito et al.[2]. Several other works to date have studied the effect of flame structure on soot volume fraction and agglomeration size in a microgravity environment.[3-4]. In microgravity the absence of buoyant convective flows increases the residence time in the flame and causes a broadening of the high temperature region in the flame. Both of these factors play a significant role in gas phase radiation and soot formation

Approach and Withdrawal Tendencies during Written Word Processing: Effects of Task, Emotional Valence, and Emotional Arousal

PubMed Central

Citron, Francesca M. M.; Abugaber, David; Herbert, Cornelia

2016-01-01

The affective dimensions of emotional valence and emotional arousal affect processing of verbal and pictorial stimuli. Traditional emotional theories assume a linear relationship between these dimensions, with valence determining the direction of a behavior (approach vs. withdrawal) and arousal its intensity or strength. In contrast, according to the valence-arousal conflict theory, both dimensions are interactively related: positive valence and low arousal (PL) are associated with an implicit tendency to approach a stimulus, whereas negative valence and high arousal (NH) are associated with withdrawal. Hence, positive, high-arousal (PH) and negative, low-arousal (NL) stimuli elicit conflicting action tendencies. By extending previous research that used several tasks and methods, the present study investigated whether and how emotional valence and arousal affect subjective approach vs. withdrawal tendencies toward emotional words during two novel tasks. In Study 1, participants had to decide whether they would approach or withdraw from concepts expressed by written words. In Studies 2 and 3 participants had to respond to each word by pressing one of two keys labeled with an arrow pointing upward or downward. Across experiments, positive and negative words, high or low in arousal, were presented. In Study 1 (explicit task), in line with the valence-arousal conflict theory, PH and NL words were responded to more slowly than PL and NH words. In addition, participants decided to approach positive words more often than negative words. In Studies 2 and 3, participants responded faster to positive than negative words, irrespective of their level of arousal. Furthermore, positive words were significantly more often associated with “up” responses than negative words, thus supporting the existence of implicit associations between stimulus valence and response coding (positive is up and negative is down). Hence, in contexts in which participants' spontaneous responses are based on implicit associations between stimulus valence and response, there is no influence of arousal. In line with the valence-arousal conflict theory, arousal seems to affect participants' approach-withdrawal tendencies only when such tendencies are made explicit by the task, and a minimal degree of processing depth is required. PMID:26779067

Approach and Withdrawal Tendencies during Written Word Processing: Effects of Task, Emotional Valence, and Emotional Arousal.

PubMed

Citron, Francesca M M; Abugaber, David; Herbert, Cornelia

2015-01-01

The affective dimensions of emotional valence and emotional arousal affect processing of verbal and pictorial stimuli. Traditional emotional theories assume a linear relationship between these dimensions, with valence determining the direction of a behavior (approach vs. withdrawal) and arousal its intensity or strength. In contrast, according to the valence-arousal conflict theory, both dimensions are interactively related: positive valence and low arousal (PL) are associated with an implicit tendency to approach a stimulus, whereas negative valence and high arousal (NH) are associated with withdrawal. Hence, positive, high-arousal (PH) and negative, low-arousal (NL) stimuli elicit conflicting action tendencies. By extending previous research that used several tasks and methods, the present study investigated whether and how emotional valence and arousal affect subjective approach vs. withdrawal tendencies toward emotional words during two novel tasks. In Study 1, participants had to decide whether they would approach or withdraw from concepts expressed by written words. In Studies 2 and 3 participants had to respond to each word by pressing one of two keys labeled with an arrow pointing upward or downward. Across experiments, positive and negative words, high or low in arousal, were presented. In Study 1 (explicit task), in line with the valence-arousal conflict theory, PH and NL words were responded to more slowly than PL and NH words. In addition, participants decided to approach positive words more often than negative words. In Studies 2 and 3, participants responded faster to positive than negative words, irrespective of their level of arousal. Furthermore, positive words were significantly more often associated with "up" responses than negative words, thus supporting the existence of implicit associations between stimulus valence and response coding (positive is up and negative is down). Hence, in contexts in which participants' spontaneous responses are based on implicit associations between stimulus valence and response, there is no influence of arousal. In line with the valence-arousal conflict theory, arousal seems to affect participants' approach-withdrawal tendencies only when such tendencies are made explicit by the task, and a minimal degree of processing depth is required.

Shoulder muscle strength in paraplegics before and after kayak ergometer training.

PubMed

Bjerkefors, Anna; Jansson, Anna; Thorstensson, Alf

2006-07-01

The purpose was to investigate if shoulder muscle strength in post-rehabilitated persons with spinal cord injury (SCI) was affected by kayak ergometer training and to compare shoulder strength in persons with SCI and able-bodied persons. Ten persons with SCI (7 males and 3 females, injury levels T3-T12) performed 60 min kayak ergometer training three times a week for 10 weeks with progressively increased intensity. Maximal voluntary concentric contractions were performed during six shoulder movements: flexion and extension (range of motion 65 degrees ), abduction and adduction (65 degrees ), and external and internal rotation (60 degrees ), with an angular velocity of 30 degrees s(-1). Position specific strength was assessed at three shoulder angles (at the beginning, middle and end of the range of motion) in the respective movements. Test-retests were performed for all measurements before the training and the mean intraclass correlation coefficient was 0.941 (95% CI 0.928-0.954). There was a main effect of kayak ergometer training with increased shoulder muscle strength after training in persons with SCI. The improvements were independent of shoulder movement, and occurred in the beginning and middle positions. A tendency towards lower shoulder muscle strength was observed in the SCI group compared to a matched reference group of able-bodied persons. Thus, it appears that post-rehabilitated persons with SCI have not managed to fully regain/maintain their shoulder muscle strength on a similar level as that of able-bodied persons, and are able to improve their shoulder muscle strength after a period of kayak ergometer training.

Why Does the Spatial Agglomeration of Firms Benefit Workers? Examining the Role of Organizational Diversity in U.S. Industries and Labor Markets

ERIC Educational Resources Information Center

Fullerton, Andrew S.; Villemez, Wayne J.

2011-01-01

Several recent studies across the social sciences show that the spatial agglomeration of employment in a local labor market benefits both firms and workers in terms of better firm performance and higher wages. Drawing from the organizational ecology perspective, we argue that workers receive higher wages in large industrial clusters and urban…

Size and weight graded multi-ply laminar electrodes

DOEpatents

Liu, Chia-Tsun; Demczyk, Brian G.; Rittko, Irvin R.

1984-01-01

An electrode is made comprising a porous backing sheet, and attached thereto a catalytically active layer having an electrolyte permeable side and a backing layer contacting side, where the active layer comprises a homogeneous mixture of active hydrophobic and hydrophilic agglomerates with catalyst disposed equally throughout the active layer, and where the agglomerate size increases from the electrolyte permeable side to the backing sheet contacting side.

Influence of different fillers on the properties of an experimental vinyl polysiloxane.

PubMed

Meincke, Débora Könzgen; Ogliari, Aline de Oliveira; Ogliari, Fabrício Aulo

2016-01-01

The aim of the study was to evaluate the effect of the incorporation of different fillers on an experimental vinyl polysiloxane (VPS) at two different concentrations, 20% and 40%. Different fillers were added to an experimental VPS. The study was developed in two stages: (i) incorporation of fillers in different concentrations: (a) 20 wt% fillers, and (b) 40 wt%. The fillers were added to experimental VPS and mixed with a speed mixer; (ii) characterization of experimental VPS; after the base paste and catalyst paste were mixed, the experimental VPS was used to make specimens specifically for each test, which were stored at 23°C for 24 hours. The tests were designed according to the specific standardization for the analysis of tensile strength, detail reproduction, Shore A hardness, and elastic recovery. For analysis of filler size pattern, scanning electron microscopy at 1500× magnification was used. The aerosil OX-50 40% (AE), and pure aluminum hydroxide 40% (PAH) groups presented the highest tensile strength and Shore A hardness values. However, those were the only groups that did not present continuous detail reproduction of an intersection of 20 μm line. The elastic recovery was not statistically significant. The undesirable characteristics of VPS (lowest Shore A hardness and tensile strength) were observed when it was added to the composition of acrylic polymer (AP) and fiberglass (FG) in both concentrations, 20% and 40%. In groups AE and PAH, agglomerates of nanofillers were shown in SEM micrography, while the other groups presented different shapes and fillers sizes.

The Physics of Protoplanetesimal Dust Agglomerates. IX. Mechanical Properties of Dust Aggregates Probed by a Solid-projectile Impact

NASA Astrophysics Data System (ADS)

Katsuragi, Hiroaki; Blum, Jürgen

2017-12-01

Dynamic characterization of mechanical properties of dust aggregates has been one of the most important problems to quantitatively discuss the dust growth in protoplanetary disks. We experimentally investigate the dynamic properties of dust aggregates by low-speed (≤slant 3.2 m s-1) impacts of solid projectiles. Spherical impactors made of glass, steel, or lead are dropped onto a dust aggregate with a packing fraction of ϕ = 0.35 under vacuum conditions. The impact results in cratering or fragmentation of the dust aggregate, depending on the impact energy. The crater shape can be approximated by a spherical segment and no ejecta are observed. To understand the underlying physics of impacts into dust aggregates, the motion of the solid projectile is acquired by a high-speed camera. Using the obtained position data of the impactor, we analyze the drag-force law and dynamic pressure induced by the impact. We find that there are two characteristic strengths. One is defined by the ratio between impact energy and crater volume and is ≃120 kPa. The other strength indicates the fragmentation threshold of dynamic pressure and is ≃10 kPa. The former characterizes the apparent plastic deformation and is consistent with the drag force responsible for impactor deceleration. The latter corresponds to the dynamic tensile strength to create cracks. Using these results, a simple model for the compaction and fragmentation threshold of dust aggregates is proposed. In addition, the comparison of drag-force laws for dust aggregates and loose granular matter reveals the similarities and differences between the two materials.

Preparation and characterization of jackfruit seed starch/poly (vinyl alcohol) (PVA) blend film

NASA Astrophysics Data System (ADS)

Sarifuddin, N.; Shahrim, N. A.; Rani, N. N. S. A.; Zaki, H. H. M.; Azhar, A. Z. A.

2018-01-01

From the environmental point of view, biodegradable materials have been rapidly developed in the past years. PVA is one of the biodegradable synthetic polymers commonly used, but its degradation rate is slow. As an alternative to reduce plastic waste and accelerate the degradation process, PVA frequently blended with other natural polymers to improve its biodegradability. The natural polymer such as starch has high potential in enhancing PVA biodegradability by blending both components. The usage of starch extracted from agriculture wastes such as jackfruit seed is quite promising. In this study, jackfruit seed starch (JFSS)/poly (vinyl alcohol) (PVA) blend films were prepared using the solution casting method. The effect of starch content on the mechanical (tensile strength and elongation to break %) and physical properties of the tested films were investigated. The optimum tensile strength was obtained at 10.45 MPa when 4 wt. % of starch added to the blend. But, decreasing trend of tensile strength was found upon increasing the amount of starch beyond 4 wt. % in starch/PVA blend films. Nevertheless, elongation at break decreases with the increase in starch content. The mechanical properties of the blend films are supported by the Field Emission Scanning Electron Microscopy (FESEM), in which the native JFSS granules are wetted by PVA continuous phase with good dispersion and less agglomeration. The incorporation of JFSS in PVA has also resulted in the appearance of hydrogen bond peak, which evidenced by Fourier Transform Infrared (FTIR). Additionally, the biodegradation rate of JFSS/PVA was evaluated through soil burial test.

Monte Carlo Simulation of Nanoparticle Encapsulation in Flames

NASA Technical Reports Server (NTRS)

Sun, Z.; Huertas, J. I.; Axelbaum, R. L.

1999-01-01

Gas-phase combustion (flame) synthesis has been an essential industrial process for producing large quantities of powder materials such as carbon black, titanium dioxide, and silicon dioxide. Flames typically produce simple oxides, with carbon black being the noted exception because the oxides of carbon are gaseous and are easily separated from the particulate matter that is formed during fuel pyrolysis. Furthermore, the powders produced in flames are usually agglomerated, nanometer-sized particles (nanoparticles). This composition and morphology is acceptable for many applications. However, the present interest in nanoparticles for advanced materials application has led to efforts to employ flames for the synthesis of unagglomerated nanoparticles (2 to 100 nm) of metals and non-oxide ceramics. Sodium-halide chemistry has proven to be viable for producing metals and non-oxide ceramics in flames. Materials that have been produced to date include Si (Calcote and Felder, 1993), TiN, TiB2, TiC, TiSi2, SiC, B4C (Glassman et al, 1993) Al, W, Ti, TiB2, AlN, and W-Ti and Al-AlN composites (DuFaux and Axelbaum, 1995, Axelbaum et al 1996,1997). Many more materials are possible. The main challenge that faces application of flame synthesis for advanced materials is overcoming formation of agglomerates in flames (Brezinsky, 1997). The high temperatures and high number densities in the flame environment favor the formation of agglomerates. Agglomerates must be avoided for many reasons. For example, when nanopowders are consolidated, agglomerates have a deleterious effect on compaction density, leading to voids in the final part. Efforts to avoid agglomeration in flames without substantially reducing particle number density and, consequently, production rate, have had limited success. Another critical challenge that faces all synthesis routes for nanopowders is ensuring that the powders are high purity and that the process is scaleable. Though the containerless, high temperature environment of a flame is excellent for producing high-purity simple compounds, ultrafine metals and non-oxide ceramic powders are inherently reactive in the presence of oxygen and/or moisture. Thus, the handling of these powders after synthesis poses a challenging problem. Impurities acquired during handling of nanoparticles have plagued the advancement of nanostructured materials technology.

Appendix D: Use of wave scenarios to assess potential submerged oil mat (SOM) formation along the coast of Florida and Alabama

USGS Publications Warehouse

Dalyander, P. Soupy; Long, Joseph W.; Plant, Nathaniel G.; Thompson, David M.

2013-01-01

During the Deepwater Horizon oil spill, oil in the surf zone mixed with sediment in the surf zone to form heavier-than-water sediment oil agglomerates of various size, ranging from small (cm-scale) pieces (surface residual balls, SRBs) to large mats (100-m scale, surface residue mats, SR mats). Once SR mats formed in the nearshore or in the intertidal zone, they may have become buried by sand moving onshore or alongshore. To assist in locating possible sites of buried oil, wave scenarios previously developed by the U.S. Geological Survey (USGS) were used to determine the depths at which surface oil had the potential to mix with suspended sediment. For sediment to mix with floating oil and form an agglomerate of sufficient density to sink to the seafloor, either the water must be very shallow (e.g., within the swash zone) or sediment must be suspended to the water surface in sufficient concentrations to create a denser-than-sea water agglomerate. The focus of this study is to analyze suspended sediment mixing with surface oil in depths beyond the swash zone, in order to define the seaward limit of mat formation. A theoretical investigation of sediment dynamics in the nearshore zone revealed that non-breaking waves do not suspend enough sediment to the surface to form sinking sand/oil agglomerates. For this study, it was assumed that the cross-shore distribution of potential agglomerate formation is associated with the primary breaker line, and the presence of plunging breakers, over the time frame of oiling. The potential locations of submerged oil mats (SOMs) are sites where (1) possible agglomerate formation occurred, where (2) sediment accreted post-oiling and buried the SOM, and where (3) the bathymetry has not subsequently eroded to re-expose any mat that may have formed at that site. To facilitate identification of these locations, the range of water level variation over the time frame of oiling was also prescribed, which combined with the wave-breaking depth analysis and pre-oiling bathymetry would identify the potential geographic locations of SOMs.

Investigation of Aerosol Surface Area Estimation from Number and Mass Concentration Measurements: Particle Density Effect

PubMed Central

Ku, Bon Ki; Evans, Douglas E.

2015-01-01

For nanoparticles with nonspherical morphologies, e.g., open agglomerates or fibrous particles, it is expected that the actual density of agglomerates may be significantly different from the bulk material density. It is further expected that using the material density may upset the relationship between surface area and mass when a method for estimating aerosol surface area from number and mass concentrations (referred to as “Maynard’s estimation method”) is used. Therefore, it is necessary to quantitatively investigate how much the Maynard’s estimation method depends on particle morphology and density. In this study, aerosol surface area estimated from number and mass concentration measurements was evaluated and compared with values from two reference methods: a method proposed by Lall and Friedlander for agglomerates and a mobility based method for compact nonspherical particles using well-defined polydisperse aerosols with known particle densities. Polydisperse silver aerosol particles were generated by an aerosol generation facility. Generated aerosols had a range of morphologies, count median diameters (CMD) between 25 and 50 nm, and geometric standard deviations (GSD) between 1.5 and 1.8. The surface area estimates from number and mass concentration measurements correlated well with the two reference values when gravimetric mass was used. The aerosol surface area estimates from the Maynard’s estimation method were comparable to the reference method for all particle morphologies within the surface area ratios of 3.31 and 0.19 for assumed GSDs 1.5 and 1.8, respectively, when the bulk material density of silver was used. The difference between the Maynard’s estimation method and surface area measured by the reference method for fractal-like agglomerates decreased from 79% to 23% when the measured effective particle density was used, while the difference for nearly spherical particles decreased from 30% to 24%. The results indicate that the use of particle density of agglomerates improves the accuracy of the Maynard’s estimation method and that an effective density should be taken into account, when known, when estimating aerosol surface area of nonspherical aerosol such as open agglomerates and fibrous particles. PMID:26526560

Investigation of Aerosol Surface Area Estimation from Number and Mass Concentration Measurements: Particle Density Effect.

PubMed

Ku, Bon Ki; Evans, Douglas E

2012-04-01

For nanoparticles with nonspherical morphologies, e.g., open agglomerates or fibrous particles, it is expected that the actual density of agglomerates may be significantly different from the bulk material density. It is further expected that using the material density may upset the relationship between surface area and mass when a method for estimating aerosol surface area from number and mass concentrations (referred to as "Maynard's estimation method") is used. Therefore, it is necessary to quantitatively investigate how much the Maynard's estimation method depends on particle morphology and density. In this study, aerosol surface area estimated from number and mass concentration measurements was evaluated and compared with values from two reference methods: a method proposed by Lall and Friedlander for agglomerates and a mobility based method for compact nonspherical particles using well-defined polydisperse aerosols with known particle densities. Polydisperse silver aerosol particles were generated by an aerosol generation facility. Generated aerosols had a range of morphologies, count median diameters (CMD) between 25 and 50 nm, and geometric standard deviations (GSD) between 1.5 and 1.8. The surface area estimates from number and mass concentration measurements correlated well with the two reference values when gravimetric mass was used. The aerosol surface area estimates from the Maynard's estimation method were comparable to the reference method for all particle morphologies within the surface area ratios of 3.31 and 0.19 for assumed GSDs 1.5 and 1.8, respectively, when the bulk material density of silver was used. The difference between the Maynard's estimation method and surface area measured by the reference method for fractal-like agglomerates decreased from 79% to 23% when the measured effective particle density was used, while the difference for nearly spherical particles decreased from 30% to 24%. The results indicate that the use of particle density of agglomerates improves the accuracy of the Maynard's estimation method and that an effective density should be taken into account, when known, when estimating aerosol surface area of nonspherical aerosol such as open agglomerates and fibrous particles.

Synthesis and Characterization of Yttria-Stabilized Zirconia Nanoparticles Doped with Ytterbium and Gadolinium: ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3

NASA Astrophysics Data System (ADS)

Bahamirian, M.; Hadavi, S. M. M.; Rahimipour, M. R.; Farvizi, M.; Keyvani, A.

2018-06-01

Defect cluster thermal barrier coatings (TBCs) are attractive alternatives to Yttria-stabilized zirconia (YSZ) in advanced applications. In this study, YSZ nanoparticles doped with ytterbium and gadolinium (ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3 (ZGYbY)) were synthesized through a chemical co-precipitation and calcination method, and characterized by in situ high-temperature X-ray diffraction analysis in the temperature range of 25 °C to 1000 °C (HTK-XRD), thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). Precise cell parameters of t-prime phase and the best zirconia phase for TBC applications were calculated by Cohen's and Rietveld refinement methods. Optimum crystallization temperature of the precursor powder was found to be 1000 °C. Furthermore, FE-SEM results for the calcined ZGYbY powders indicated orderly particles of uniform shape and size with a small tendency toward agglomeration. Average lattice thermal expansion coefficient in the temperature range of 25 °C to 1000 °C was determined to be 31.71 × 10-6 K-1.

Synthesis and Characterization of Yttria-Stabilized Zirconia Nanoparticles Doped with Ytterbium and Gadolinium: ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3

NASA Astrophysics Data System (ADS)

Bahamirian, M.; Hadavi, S. M. M.; Rahimipour, M. R.; Farvizi, M.; Keyvani, A.

2018-03-01

Defect cluster thermal barrier coatings (TBCs) are attractive alternatives to Yttria-stabilized zirconia (YSZ) in advanced applications. In this study, YSZ nanoparticles doped with ytterbium and gadolinium (ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3 (ZGYbY)) were synthesized through a chemical co-precipitation and calcination method, and characterized by in situ high-temperature X-ray diffraction analysis in the temperature range of 25 °C to 1000 °C (HTK-XRD), thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). Precise cell parameters of t-prime phase and the best zirconia phase for TBC applications were calculated by Cohen's and Rietveld refinement methods. Optimum crystallization temperature of the precursor powder was found to be 1000 °C. Furthermore, FE-SEM results for the calcined ZGYbY powders indicated orderly particles of uniform shape and size with a small tendency toward agglomeration. Average lattice thermal expansion coefficient in the temperature range of 25 °C to 1000 °C was determined to be 31.71 × 10-6 K-1.

Hydrogen storage and hydrolysis properties of core-shell structured Mg-MFx (M=V, Ni, La and Ce) nano-composites prepared by arc plasma method

NASA Astrophysics Data System (ADS)

Mao, Jianfeng; Zou, Jianxin; Lu, Chong; Zeng, Xiaoqin; Ding, Wenjiang

2017-10-01

In this work, core-shell structured Mg-MFx (M = V, Ni, La and Ce) nano-composites are prepared by using arc plasma method. The particle size distribution, phase components, microstructures, hydrogen sorption properties of these composites and hydrolysis properties of their corresponding hydrogenated powders are carefully investigated. It is shown that the addition of MFx through arc plasma method can improve both the hydrogen absorption kinetics of Mg and the hydrolysis properties of corresponding hydrogenated powders. Among them, the Mg-NiF2 composite shows the best hydrogen absorption properties at relatively low temperatures, which can absorb 3.26 wt% of H2 at 373 K in 2 h. Such rapid hydrogen absorption rate is mainly due to the formation of Mg2Ni and MgF2 on Mg particles during arc evaporation and condensation. In contrast, measurements also show that the hydrogenated Mg-VF3 composite has the lowest peak desorption temperature and the fastest hydrolysis rate among all the hydrogenated Mg-MFx composites. The less agglomeration tendency of Mg particles and VO2 covered on MgH2 particles account for the reduced hydrogen desorption temperature and enhanced hydrolysis rate.

Study on the Mechanical Properties of Bionic Coupling Layered B4C/5083Al Composite Materials

PubMed Central

Zhao, Qian; Liang, Yunhong; Liu, Qingping; Zhang, Zhihui; Yu, Zhenglei; Ren, Luquan

2018-01-01

Based on microstructure characteristics of Meretrix lusoria shell and Rapana venosa shell, bionic coupling layered B4C/5083Al composites with different layered structures and hard/soft combination models were fabricated via hot pressed sintering. The simplified bionic coupling models with hard and soft layers were similar to layered structure and hardness tendency of shells, guiding the bionic design and fabrication. B4C/5083Al composites with various B4C contents and pure 5083Al were treated as hard and soft layers, respectively. Hot pressed sintering maintained the designed bionic structure and enhanced high bonding strength between ceramics and matrix. Compared with B4C/5083Al composites, bionic layered composites exhibited high mechanical properties including flexural strength, fracture toughness, compressive strength and impact toughness. The hard layers absorbed applied loads in the form of intergranular fracture. Besides connection role, soft layers restrained slabbing phenomenon and reset extension direction of cracks among layers. The coupling functions of bionic composites proved the feasibility and practicability of bionic fabrication, providing a new method for improvement of ceramic/Al composite with properties of being lightweight and high mechanical strength. PMID:29701707

Testing of advanced liquefaction concepts in HTI Run ALC-1: Coal cleaning and recycle solvent treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robbins, G.A.; Winschel, R.A.; Burke, F.P.

In 1991, the Department of Energy initiated the Advanced Liquefaction Concepts Program to promote the development of new and emerging technology that has potential to reduce the cost of producing liquid fuels by direct coal liquefaction. Laboratory research performed by researchers at CAER, CONSOL, Sandia, and LDP Associates in Phase I is being developed further and tested at the bench scale at HTI. HTI Run ALC-1, conducted in the spring of 1996, was the first of four planned tests. In Run ALC-1, feed coal ash reduction (coal cleaning) by oil agglomeration, and recycle solvent quality improvement through dewaxing and hydrotreatmentmore » of the recycle distillate were evaluated. HTI`s bench liquefaction Run ALC-1 consisted of 25 days of operation. Major accomplishments were: 1) oil agglomeration reduced the ash content of Black Thunder Mine coal by 40%, from 5.5% to 3.3%; 2) excellent coal conversion of 98% was obtained with oil agglomerated coal, about 3% higher than the raw Black Thunder Mine coal, increasing the potential product yield by 2-3% on an MAF coal basis; 3) agglomerates were liquefied with no handling problems; 4) fresh catalyst make-up rate was decreased by 30%, with no apparent detrimental operating characteristics, both when agglomerates were fed and when raw coal was fed (with solvent dewaxing and hydrotreating); 5) recycle solvent treatment by dewaxing and hydrotreating was demonstrated, but steady-state operation was not achieved; and 6) there was some success in achieving extinction recycle of the heaviest liquid products. Performance data have not been finalized; they will be available for full evaluation in the new future.« less

Muscle hypertrophy, strength development, and serum hormones during strength training in elderly women with fibromyalgia.

PubMed

Valkeinen, H; Häkkinen, K; Pakarinen, A; Hannonen, P; Häkkinen, A; Airaksinen, O; Niemitukia, L; Kraemer, W J; Alén, M

2005-01-01

To examine the effects of strength training on maximal force, cross-sectional area (CSA), and electromyographic (EMG) activity of muscles and serum hormone concentrations in elderly females with fibromyalgia (FM). Twenty-six patients with FM were randomly assigned to a training (FMT; n = 13; mean age 60 years) or a control (FMC; n = 13; 59 years) group. FMT performed progressive strength training twice a week for 21 weeks. The measurements included maximal isometric and concentric leg extension forces, EMG activity of the vastus lateralis and medialis, CSA of the quadriceps femoris, and serum concentrations of testosterone (T), free testosterone (FT), growth hormone (GH), insulin-like growth factor-1 (IGF-1), dehydroepiandrosterone sulfate (DHEAS), and cortisol. Subjectively perceived symptoms of FM were also assessed. All patients were able to complete the training. In FMT strength training led to increases of 36% (p<0.001) and 33% (p<0.001) in maximal isometric and concentric forces, respectively. The CSA increased by 5% (p<0.001) and the EMG activity in isometric action by 47% (p<0.001) and in concentric action by 57% (p<0.001). Basal serum hormone concentrations remained unaltered during strength training. The subjective perceived symptoms showed a minor decreasing tendency (ns). No statistically significant changes occurred in any of these parameters in FMC. Progressive strength training increases strength, CSA, and voluntary activation of the trained muscles in elderly women with FM, while the measured basal serum hormone concentrations remain unaltered. Strength training benefits the overall physical fitness of the patients without adverse effects or any exacerbation of symptoms and should be included in the rehabilitation programmes of elderly patients with FM.

Study of the effects of Shockwaves on Nano fluids

NASA Astrophysics Data System (ADS)

Shreekhar; Akhil, Mohan; Ram, Sai; Gopaiah, Venkata; Koundinya, Sandeep; Nagaraja, S. R.

2018-02-01

Nanofluids are fluids with nanoparticles dispersed in them. Due to the presence of Nano particles, these fluids exhibit unique properties that can used in various applications such as heat exchangers and in medical fields. However, due to agglomeration, the size of these particle increases, reducing their efficiency. In order to break the agglomeration, we are passing shockwaves in the fluid. Shockwaves theoretically carry energy which can be used to break the agglomerating particles. In this paper, silver nanoparticles were synthesized using silver nitrate. Tri sodium citrate was used as the reducing agent. Shock waves were passed to the fluid containing silver Nano particles. The changes in the Nano fluid was measured by a UV-Vis Spectrophotometer. With each shock passed, the fluid’s absorbance and wavelength peak was measured and compared with Nano fluid without shock.

Development of clean coal and clean soil technologies using advanced agglomeration technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ignasiak, B.; Pawlak, W.; Szymocha, K.

1990-04-01

The specific objectives of the bituminous coal program were to explore and evaluate the application of advanced agglomeration technology for: (1)desulphurization of bituminous coals to sulphur content acceptable within the current EPA SO{sub 2} emission guidelines; (2) deashing of bituminous coals to ash content of less than 10 percent; and (3)increasing the calorific value of bituminous coals to above 13,000 Btu/lb. (VC)

Experimental Evaluation of a Carbon Slurry Droplet Combustion Model

DTIC Science & Technology

1981-12-14

the increased mass and energy transport due to the flow percolating through the open porous structure of the carbon agglomerate. Two separate models...catalysts. Transport-rate enhancement factors were also employed in the carbon-agglomerate reaction analysis to account for the increased mass and energy ...D Effective binary diffusivity Ei Activation energy h Heat transfer coefficient H2 Diatomic hydrogen H20 Water i Enthalpy if Enthalpy of formation

Gas-diffusion microextraction coupled with spectrophotometry for the determination of formaldehyde in cork agglomerates.

PubMed

Brandão, Pedro F; Ramos, Rui M; Valente, Inês M; Almeida, Paulo J; Carro, Antonia M; Lorenzo, Rosa A; Rodrigues, José A

2017-04-01

In this work, a simple methodology was developed for the extraction and determination of free formaldehyde content in cork agglomerate samples. For the first time, gas-diffusion microextraction was used for the extraction of volatile formaldehyde directly from samples, with simultaneous derivatization with acetylacetone (Hantzsch reaction). The absorbance of the coloured solution was read in a spectrophotometer at 412 nm. Different extraction parameters were studied and optimized (extraction temperature, sample mass, volume of acceptor solution, extraction time and concentration of derivatization reagent) by means of an asymmetric screening. The developed methodology proved to be a reliable tool for the determination of formaldehyde in cork agglomerates with the following suitable method features: low LOD (0.14 mg kg -1 ) and LOQ (0.47 mg kg -1 ), r 2  = 0.9994, and intraday and interday precision of 3.5 and 4.9%, respectively. The developed methodology was applied to the determination of formaldehyde in different cork agglomerate samples, and contents between 1.9 and 9.4 mg kg -1 were found. Furthermore, formaldehyde was also determined by the standard method EN 717-3 for comparison purposes; no significant differences between the results of both methods were observed. Graphical abstract Representation of the GDME system and its main components.

Phloem ultrastructure and pressure flow: Sieve-Element-Occlusion-Related agglomerations do not affect translocation.

PubMed

Froelich, Daniel R; Mullendore, Daniel L; Jensen, Kåre H; Ross-Elliott, Tim J; Anstead, James A; Thompson, Gary A; Pélissier, Hélène C; Knoblauch, Michael

2011-12-01

Since the first ultrastructural investigations of sieve tubes in the early 1960s, their structure has been a matter of debate. Because sieve tube structure defines frictional interactions in the tube system, the presence of P protein obstructions shown in many transmission electron micrographs led to a discussion about the mode of phloem transport. At present, it is generally agreed that P protein agglomerations are preparation artifacts due to injury, the lumen of sieve tubes is free of obstructions, and phloem flow is driven by an osmotically generated pressure differential according to Münch's classical hypothesis. Here, we show that the phloem contains a distinctive network of protein filaments. Stable transgenic lines expressing Arabidopsis thaliana Sieve-Element-Occlusion-Related1 (SEOR1)-yellow fluorescent protein fusions show that At SEOR1 meshworks at the margins and clots in the lumen are a general feature of living sieve tubes. Live imaging of phloem flow and flow velocity measurements in individual tubes indicate that At SEOR1 agglomerations do not markedly affect or alter flow. A transmission electron microscopy preparation protocol has been generated showing sieve tube ultrastructure of unprecedented quality. A reconstruction of sieve tube ultrastructure served as basis for tube resistance calculations. The impact of agglomerations on phloem flow is discussed.

Carbon, oxygen and their interaction with intrinsic point defects in solar silicon ribbon material: A speculative approach

NASA Technical Reports Server (NTRS)

Goesele, U.; Ast, D. G.

1983-01-01

Some background information on intrinsic point defects is provided and on carbon and oxygen in silicon in so far as it may be relevant for the efficiency of solar cells fabricated from EFG ribbon material. The co-precipitation of carbon and oxygen and especially of carbon and silicon self interstitials are discussed. A simple model for the electrical activity of carbon-self-interstitial agglomerates is presented. The self-interstitial content of these agglomerates is assumed to determine their electrical activity and that both compressive stresses (high self-interstitial content) and tensile stresses (low self-interstitial content) give rise to electrical activity of the agglomerates. The self-interstitial content of these carbon-related agglomerates may be reduced by an appropriate high temperature treatment and enhanced by a supersaturation of self-interstitials generated during formation of the p-n junction of solar cells. Oxygen present in supersaturation in carbon-rich silicon may be induced to form SiO, precipitates by self-interstitials generated during phosphorus diffusion. It is proposed that the SiO2-Si interface of the precipates gives rise to a continuum of donor stables and that these interface states are responsible for at least part of the light inhancement effects observed in oxygen containing EFG silicon after phosphorus diffusion.

Kinetics of Polymer-Fullerene Phase Separation during Solvent Annealing Studied by Table-Top X-ray Scattering.

PubMed

Vegso, Karol; Siffalovic, Peter; Jergel, Matej; Nadazdy, Peter; Nadazdy, Vojtech; Majkova, Eva

2017-03-08

Solvent annealing is an efficient way of phase separation in polymer-fullerene blends to optimize bulk heterojunction morphology of active layer in polymer solar cells. To track the process in real time across all relevant stages of solvent evaporation, laboratory-based in situ small- and wide-angle X-ray scattering measurements were applied simultaneously to a model P3HT:PCBM blend dissolved in dichlorobenzene. The PCBM molecule agglomeration starts at ∼7 wt % concentration of solid content of the blend in solvent. Although PCBM agglomeration is slowed-down at ∼10 wt % of solid content, the rate constant of phase separation is not changed, suggesting agglomeration and reordering of P3HT molecular chains. Having the longest duration, this stage most affects BHJ morphology. Phase separation is accelerated rapidly at concentration of ∼25 wt %, having the same rate constant as the growth of P3HT crystals. P3HT crystallization is driving force for phase separation at final stages before a complete solvent evaporation, having no visible temporal overlap with PCBM agglomeration. For the first time, such a study was done in laboratory demonstrating potential of the latest generation table-top high-brilliance X-ray source as a viable alternative before more sophisticated X-ray scattering experiments at synchrotron facilities are performed.

Combustion of metal agglomerates in a solid rocket core flow

NASA Astrophysics Data System (ADS)

Maggi, Filippo; Dossi, Stefano; DeLuca, Luigi T.

2013-12-01

The need for access to space may require the use of solid propellants. High thrust and density are appealing features for different applications, spanning from boosting phase to other service applications (separation, de-orbiting, orbit insertion). Aluminum is widely used as a fuel in composite solid rocket motors because metal oxidation increases enthalpy release in combustion chamber and grants higher specific impulse. Combustion process of metal particles is complex and involves aggregation, agglomeration and evolution of reacting particulate inside the core flow of the rocket. It is always stated that residence time should be enough in order to grant complete metal oxidation but agglomerate initial size, rocket grain geometry, burning rate, and other factors have to be reconsidered. New space missions may not require large rocket systems and metal combustion efficiency becomes potentially a key issue to understand whether solid propulsion embodies a viable solution or liquid/hybrid systems are better. A simple model for metal combustion is set up in this paper. Metal particles are represented as single drops trailed by the core flow and reacted according to Beckstead's model. The fluid dynamics is inviscid, incompressible, 1D. The paper presents parametric computations on ideal single-size particles as well as on experimental agglomerate populations as a function of operating rocket conditions and geometries.

Synthesis of crystalline and amorphous, particle-agglomerated 3-D nanostructures of Al and Si oxides by femtosecond laser and the prediction of these particle sizes

NASA Astrophysics Data System (ADS)

Sivayoganathan, Mugunthan; Tan, Bo; Venkatakrishnan, Krishnan

2012-11-01

We report a single step technique of synthesizing particle-agglomerated, amorphous 3-D nanostructures of Al and Si oxides on powder-fused aluminosilicate ceramic plates and a simple novel method of wafer-foil ablation to fabricate crystalline nanostructures of Al and Si oxides at ambient conditions. We also propose a particle size prediction mechanism to regulate the size of vapor-condensed agglomerated nanoparticles in these structures. Size characterization studies performed on the agglomerated nanoparticles of fabricated 3-D structures showed that the size distributions vary with the fluence-to-threshold ratio. The variation in laser parameters leads to varying plume temperature, pressure, amount of supersaturation, nucleation rate, and the growth rate of particles in the plume. The novel wafer-foil ablation technique could promote the possibilities of fabricating oxide nanostructures with varying Al/Si ratio, and the crystallinity of these structures enhances possible applications. The fabricated nanostructures of Al and Si oxides could have great potentials to be used in the fabrication of low power-consuming complementary metal-oxide-semiconductor circuits and in Mn catalysts to enhance the efficiency of oxidation on ethylbenzene to acetophenone in the super-critical carbon dioxide.

Synthesis of crystalline and amorphous, particle-agglomerated 3-D nanostructures of Al and Si oxides by femtosecond laser and the prediction of these particle sizes.

PubMed

Sivayoganathan, Mugunthan; Tan, Bo; Venkatakrishnan, Krishnan

2012-11-09

We report a single step technique of synthesizing particle-agglomerated, amorphous 3-D nanostructures of Al and Si oxides on powder-fused aluminosilicate ceramic plates and a simple novel method of wafer-foil ablation to fabricate crystalline nanostructures of Al and Si oxides at ambient conditions. We also propose a particle size prediction mechanism to regulate the size of vapor-condensed agglomerated nanoparticles in these structures. Size characterization studies performed on the agglomerated nanoparticles of fabricated 3-D structures showed that the size distributions vary with the fluence-to-threshold ratio. The variation in laser parameters leads to varying plume temperature, pressure, amount of supersaturation, nucleation rate, and the growth rate of particles in the plume. The novel wafer-foil ablation technique could promote the possibilities of fabricating oxide nanostructures with varying Al/Si ratio, and the crystallinity of these structures enhances possible applications. The fabricated nanostructures of Al and Si oxides could have great potentials to be used in the fabrication of low power-consuming complementary metal-oxide-semiconductor circuits and in Mn catalysts to enhance the efficiency of oxidation on ethylbenzene to acetophenone in the super-critical carbon dioxide.

Synthesis of crystalline and amorphous, particle-agglomerated 3-D nanostructures of Al and Si oxides by femtosecond laser and the prediction of these particle sizes

PubMed Central

2012-01-01

We report a single step technique of synthesizing particle-agglomerated, amorphous 3-D nanostructures of Al and Si oxides on powder-fused aluminosilicate ceramic plates and a simple novel method of wafer-foil ablation to fabricate crystalline nanostructures of Al and Si oxides at ambient conditions. We also propose a particle size prediction mechanism to regulate the size of vapor-condensed agglomerated nanoparticles in these structures. Size characterization studies performed on the agglomerated nanoparticles of fabricated 3-D structures showed that the size distributions vary with the fluence-to-threshold ratio. The variation in laser parameters leads to varying plume temperature, pressure, amount of supersaturation, nucleation rate, and the growth rate of particles in the plume. The novel wafer-foil ablation technique could promote the possibilities of fabricating oxide nanostructures with varying Al/Si ratio, and the crystallinity of these structures enhances possible applications. The fabricated nanostructures of Al and Si oxides could have great potentials to be used in the fabrication of low power-consuming complementary metal-oxide-semiconductor circuits and in Mn catalysts to enhance the efficiency of oxidation on ethylbenzene to acetophenone in the super-critical carbon dioxide. PMID:23140103

Phloem Ultrastructure and Pressure Flow: Sieve-Element-Occlusion-Related Agglomerations Do Not Affect Translocation[W

PubMed Central

Froelich, Daniel R.; Mullendore, Daniel L.; Jensen, Kåre H.; Ross-Elliott, Tim J.; Anstead, James A.; Thompson, Gary A.; Pélissier, Hélène C.; Knoblauch, Michael

2011-01-01

Since the first ultrastructural investigations of sieve tubes in the early 1960s, their structure has been a matter of debate. Because sieve tube structure defines frictional interactions in the tube system, the presence of P protein obstructions shown in many transmission electron micrographs led to a discussion about the mode of phloem transport. At present, it is generally agreed that P protein agglomerations are preparation artifacts due to injury, the lumen of sieve tubes is free of obstructions, and phloem flow is driven by an osmotically generated pressure differential according to Münch’s classical hypothesis. Here, we show that the phloem contains a distinctive network of protein filaments. Stable transgenic lines expressing Arabidopsis thaliana Sieve-Element-Occlusion-Related1 (SEOR1)–yellow fluorescent protein fusions show that At SEOR1 meshworks at the margins and clots in the lumen are a general feature of living sieve tubes. Live imaging of phloem flow and flow velocity measurements in individual tubes indicate that At SEOR1 agglomerations do not markedly affect or alter flow. A transmission electron microscopy preparation protocol has been generated showing sieve tube ultrastructure of unprecedented quality. A reconstruction of sieve tube ultrastructure served as basis for tube resistance calculations. The impact of agglomerations on phloem flow is discussed. PMID:22198148

Development of materials for the removal of metal ions from radioactive and non-radioactive waste streams

NASA Astrophysics Data System (ADS)

Hasan, Md. Shameem

Nuclear wastes that were generated during cold-war era from various nuclear weapon programs are presently stored in hundreds of tanks across the United States. The composition of these wastes is rather complex containing both radionuclides and heavy metals, such as 137Cs, 90Sr, Al, Pb, Cr, and Cd. In this study, chitosan based biosorbents were prepared to adsorb some of these metal ions. Chitosan is a partially acetylated glucosamine biopolymer encountered in the cell walls of fungi. In its natural form this material is soft and has a tendency to agglomerate or form gels. Various methods were used to modify chitosan to avoid these problems. Chitosan is generally available commercially in the form of flakes. For use in an adsorption system, chitosan was made in the form of beads to reduce the pressure drop in an adsorption column. In this research, spherical beads were prepared by mixing chitosan with perlite and then by dropwise addition of the slurry mixture into a NaOH precipitation bath. Beads were characterized using Fourier Transform InfraRed Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy dispersive spectroscopy (EDS), Tunneling Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), and Thermogravimetric Analysis (TGA). The SEM, EDS, and TEM data indicated that the beads were porous in nature. The TGA data showed that bead contained about 32% chitosan. The surface area, pore volume, and porosity of the beads were determined from the BET surface area that was measured using N2 as adsorbate at 77K. Adsorption and desorption of Cr(VI), Cr(III), Cd(II), U(VI), Cu(II), from aqueous solutions of these metal ions were studied to evaluate the adsorption capacities of the beads for these metals ions. Equilibrium adsorption data of these metals on the beads were found to correlate well with the Langmuir isotherm equation. Chitosan coated perlite beads had negligible adsorption capacity for Sr(II) and Cs(I). It was found that Fullers earth had very good capacity for these two metals. However, the mechanical strength of Fullers earth granules available commercially was not sufficient for use in a column. In this study chitosan was used as a binder to make Fullers earth beads and were used for adsorption of Cs(I) and Sr(II). (Abstract shortened by UMI.)

The influences of calcia silica contents to the compressive strength of the Al-7000 aluminium foam

NASA Astrophysics Data System (ADS)

Sutarno; Soepriyanto, S.; Korda, A. A.; Dirgantara, T.

2016-08-01

This experiment evaluated the effect of calcia alumina and alumina silica that formed as side products involved in metal mixture of aluminium foam. These compounds are formed from additional calcium carbonate and silica in the mixture. Calcium carbonate (CaCO3) roles as a blowing agent source of carbon dioxide (CO2). The formation of calcia alumina (CaO.Al2O3) is desired to improve the viscosity and to strengthen of cell wall of aluminium foam. However, Al-7000 aluminium foam showed a decrease tendency of compressive strength probably due to existence of alumina silica (3Al2O3.SiO2) in the metal mixture. In this case, the silica that thermally combines with alumina compound may degrade the metal mixture of aluminium foam structure.

Individual differences in the strength of taxonomic versus thematic relations

PubMed Central

Mirman, Daniel; Graziano, Kristen M.

2011-01-01

Knowledge about word and object meanings can be organized taxonomically (fruits, mammals, etc.) based on shared features, or thematically (eating breakfast, taking a dog for a walk, etc.) based on participation in events or scenarios. An eye-tracking study showed that both kinds of knowledge are activated during comprehension of a single spoken word, even when the listener is not required to perform any active task. The results further revealed that an individual’s relative activation of taxonomic relations compared to thematic relations predicts that individual’s tendency to favor taxonomic over thematic relations when asked to choose between them in a similarity judgment task. These results argue that individuals differ in the relative strengths of their taxonomic and thematic semantic knowledge and suggest that meaning information is organized in two parallel, complementary semantic systems. PMID:22201413

Imaging Local Magnetic Domain Rearrangement in Strained LaCoO3 Thin Films Using Magnetic Force Microscopy

NASA Astrophysics Data System (ADS)

Berg, Morgann; Leon, Neliza; Posadas, Agham; Lee, Alfred; Kim, Jeehoon; de Lozanne, Alex; Demkov, Alex

2012-02-01

Previous studies we have conducted on thin films of lanthanum cobaltate (LCO) under tensile strain have revealed a tendency toward local magnetic domain rearrangement into streak-like configurations near the ferromagnetic to paramagnetic phase transition. Moreover, the persistence of these streak-like characteristics to lower temperatures after field-cooling appears to be linked to the strength of the applied magnetic field in which these films are field-cooled. This tendency has not yet been verified for thin films of LCO under compressive strain which could indicate whether this magnetic domain rearrangement is intrinsic to thin film samples of LCO or is merely an effect of tensile strain. Using magnetic force microscopy, we investigate the microscale magnetic properties of a thin film of LCO under compressive strain, prepared by molecular beam epitaxy and deposited on a lanthanum aluminate substrate. We observe these properties across a wide temperature range and compare our results to global magnetic characteristics of this film as measured by a SQUID magnetometer.

Acculturative Stress, Psychological Distress, and Religious Coping Among Latina Young Adult Immigrants

PubMed Central

Da Silva, Nicole; Dillon, Frank R.; Rose Verdejo, Toni; Sanchez, Mariana; De La Rosa, Mario

2017-01-01

Religion is a source of strength in Latina/o culture during challenging life transitions, such as the immigration process. Guided by a sociological stress–process model, this study examines relations between dimensions of religious coping, acculturative stress, and psychological distress among 530 young Latina women (ages 18–23 years) who recently immigrated to the United States (i.e., approximately 12 months prior to assessment). Higher levels of acculturative stress were associated with higher levels of psychological distress. Negative religious coping (i.e., the tendency to struggle with faith) moderated the relation between acculturative stress and psychological distress. Participants experiencing higher levels of acculturative stress reported greater psychological distress when they indicated more negative religious coping. Positive religious coping (i.e., the tendency to relate to faith with comfort and certainty) was not linked with acculturative stress or psychological distress. Implications for culturally tailored counseling interventions for this underserved and understudied population are discussed. PMID:29033462

Fracture strength of different soldered and welded orthodontic joining configurations with and without filling material.

PubMed

Bock, Jens Johannes; Bailly, Jacqueline; Gernhardt, Christian Ralf; Fuhrmann, Robert Andreas Werner

2008-01-01

The aim of this study was to compare the mechanical strength of different joints made by conventional brazing, TIG and laser welding with and without filling material. Five standardized joining configurations of orthodontic wire in spring hard quality were used: round, cross, 3 mm length, 9 mm length and 7 mm to orthodontic band. The joints were made by five different methods: brazing, tungsten inert gas (TIG) and laser welding with and without filling material. For the original orthodontic wire and for each kind of joint configuration or connecting method 10 specimens were carefully produced, totalizing 240. The fracture strengths were measured with a universal testing machine (Zwick 005). Data were analyzed by ANOVA (p=0.05) and Bonferroni post hoc test (p=0.05). In all cases, brazing joints were ruptured on a low level of fracture strength (186-407 N). Significant differences between brazing and TIG or laser welding (p<0.05, Bonferroni post hoc test) were found in each joint configuration. The highest fracture strength means were observed for laser welding with filling material and 3 mm joint length (998 N). Using filling materials, there was a clear tendency to higher mean values of fracture strength in TIG and laser welding. However, statistically significant differences were found only in the 9-mm long joints (p<0.05, Bonferroni post hoc test). In conclusion, the fracture strength of welded joints was positively influenced by the additional use of filling material. TIG welding was comparable to laser welding except for the impossibility of joining orthodontic wire with orthodontic band.

FRACTURE STRENGTH OF DIFFERENT SOLDERED AND WELDED ORTHODONTIC JOINING CONFIGURATIONS WITH AND WITHOUT FILLING MATERIAL

PubMed Central

Bock, Jens Johannes; Bailly, Jacqueline; Gernhardt, Christian Ralf; Fuhrmann, Robert Andreas Werner

2008-01-01

The aim of this study was to compare the mechanical strength of different joints made by conventional brazing, TIG and laser welding with and without filling material. Five standardized joining configurations of orthodontic wire in spring hard quality were used: round, cross, 3 mm length, 9 mm length and 7 mm to orthodontic band. The joints were made by five different methods: brazing, tungsten inert gas (TIG) and laser welding with and without filling material. For the original orthodontic wire and for each kind of joint configuration or connecting method 10 specimens were carefully produced, totalizing 240. The fracture strengths were measured with a universal testing machine (Zwick 005). Data were analyzed by ANOVA (p=0.05) and Bonferroni post hoc test (p=0.05). In all cases, brazing joints were ruptured on a low level of fracture strength (186-407 N). Significant differences between brazing and TIG or laser welding (p<0.05, Bonferroni post hoc test) were found in each joint configuration. The highest fracture strength means were observed for laser welding with filling material and 3 mm joint length (998 N). Using filling materials, there was a clear tendency to higher mean values of fracture strength in TIG and laser welding. However, statistically significant differences were found only in the 9-mm long joints (p<0.05, Bonferroni post hoc test). In conclusion, the fracture strength of welded joints was positively influenced by the additional use of filling material. TIG welding was comparable to laser welding except for the impossibility of joining orthodontic wire with orthodontic band. PMID:19089229

Steric stabilization of nonaqueous silicon slips. I - Control of particle agglomeration and packing. II - Pressure casting of powder compacts

NASA Technical Reports Server (NTRS)

Kerkar, Awdhoot V.; Henderson, Robert J. M.; Feke, Donald L.

1990-01-01

The application of steric stabilization to control particle agglomeration and packing of silicon powder in benzene and trichloroethylene is reported. The results provide useful guidelines for controlling unfavorable particle-particle interactions during nonaqueous processing of silicon-based ceramic materials. The application of steric stabilization to the control and improvement of green processing of nonaqueous silicon slips in pressure consolidation is also demonstrated.

Coal hydrogenation and deashing in ebullated bed catalytic reactor

DOEpatents

Huibers, Derk T. A.; Johanson, Edwin S.

1983-01-01

An improved process for hydrogenation of coal containing ash with agglomeration and removal of ash from an ebullated bed catalytic reactor to produce deashed hydrocarbon liquid and gas products. In the process, a flowable coal-oil slurry is reacted with hydrogen in an ebullated catalyst bed reaction zone at elevated temperature and pressure conditions. The upward velocity and viscosity of the reactor liquid are controlled so that a substantial portion of the ash released from the coal is agglomerated to form larger particles in the upper portion of the reactor above the catalyst bed, from which the agglomerated ash is separately withdrawn along with adhering reaction zone liquid. The resulting hydrogenated hydrocarbon effluent material product is phase separated to remove vapor fractions, after which any ash remaining in the liquid fraction can be removed to produce substantially ash-free coal-derived liquid products.

On the Morphology of a Growing City: A Heuristic Experiment Merging Static Economics with Dynamic Geography.

PubMed

Delloye, Justin; Peeters, Dominique; Thomas, Isabelle

2015-01-01

In this paper, we aim at exploring how individual location decisions affect the shape of a growing city and, more precisely, how they may add up to a configuration that diverges from equilibrium configurations formulated ex-ante. To do so, we provide a two-sector city model merging a static equilibrium analysis with agent-based simulations. Results show that under strong agglomeration effects, urban development is monotonic and ends up with circular, monocentric long-term configurations. For low agglomeration effects however, elongated and multicentric urban configurations may emerge. The occurrence and underlying dynamics of these configurations are also discussed regarding commuting costs and the distance-decay of agglomeration economies between firms. To sum up, our paper warns urban planning policy makers against the difference that may stand between appropriate long-term perspectives, represented here by analytic equilibrium configurations, and short-term urban configurations, simulated here by a multi-agent system.

How much drinking water can be saved by using rainwater harvesting on a large urban area? application to Paris agglomeration.

PubMed

Belmeziti, Ali; Coutard, Olivier; de Gouvello, Bernard

2014-01-01

This paper is based on a prospective scenario of development of rainwater harvesting (RWH) on a given large urban area (such as metropolitan area or region). In such a perspective, a new method is proposed to quantify the related potential of potable water savings (PPWS) indicator on this type of area by adapting the reference model usually used on the building level. The method is based on four setting-up principles: gathering (definition of buildings-types and municipalities-types), progressing (use of an intermediate level), increasing (choice of an upper estimation) and prioritizing (ranking the stakes of RWH). Its application to the Paris agglomeration shows that is possible to save up to 11% of the total current potable water through the use of RWH. It also shows that the residential sector offers the most important part because it holds two-thirds of the agglomeration PPWS.

Bending analysis of agglomerated carbon nanotube-reinforced beam resting on two parameters modified Vlasov model foundation

NASA Astrophysics Data System (ADS)

Ghorbanpour Arani, A.; Zamani, M. H.

2018-06-01

The present work deals with bending behavior of nanocomposite beam resting on two parameters modified Vlasov model foundation (MVMF), with consideration of agglomeration and distribution of carbon nanotubes (CNTs) in beam matrix. Equivalent fiber based on Eshelby-Mori-Tanaka approach is employed to determine influence of CNTs aggregation on elastic properties of CNT-reinforced beam. The governing equations are deduced using the principle of minimum potential energy under assumption of the Euler-Bernoulli beam theory. The MVMF required the estimation of γ parameter; to this purpose, unique iterative technique based on variational principles is utilized to compute value of the γ and subsequently fourth-order differential equation is solved analytically. Eventually, the transverse displacements and bending stresses are obtained and compared for different agglomeration parameters, various boundary conditions simultaneously and variant elastic foundation without requirement to instate values for foundation parameters.

Method and system for producing metallic iron nuggets

DOEpatents

Iwasaki, Iwao; Kiesel, Richard F.; Englund, David J; Hendrickson, Dave

2012-12-18

A method and system for producing metallic iron nuggets may include providing multiple layers of agglomerates, such as briquettes, balls and extrusions, of a reducible mixture of reducing material (such as carbonaceous material) and of a reducible iron bearing material (such as iron oxide) on a hearth material layer (such as carbonaceous material) and providing a coarse overlayer of carbonaceous material over at least some of the agglomerates. Heating the agglomerates of reducible mixture to 1425.degree. C. or 1400.degree. C. or 1375.degree. C. results in formation of an intermediate product of one or more metallic iron nuggets, which may have a sulfur content of less than 0.03%, and slag, which may have less than 5% mass MgO, which may have a ratio of percent by weight sulfur in the slag over percent by weight sulfur in the metallic nuggets of at least about 12 or at least about 15.

Production of iron from metallurgical waste

DOEpatents

Hendrickson, David W; Iwasaki, Iwao

2013-09-17

A method of recovering metallic iron from iron-bearing metallurgical waste in steelmaking comprising steps of providing an iron-bearing metallurgical waste containing more than 55% by weight FeO and FeO equivalent and a particle size of at least 80% less than 10 mesh, mixing the iron-bearing metallurgical waste with a carbonaceous material to form a reducible mixture where the carbonaceous material is between 80 and 110% of the stoichiometric amount needed to reduce the iron-bearing waste to metallic iron, and as needed additions to provide a silica content between 0.8 and 8% by weight and a ratio of CaO/SiO.sub.2 between 1.4 and 1.8, forming agglomerates of the reducible mixture over a hearth material layer to protect the hearth, heating the agglomerates to a higher temperature above the melting point of iron to form nodules of metallic iron and slag material from the agglomerates by melting.

Dust recycling technology in Kimitsu Works

NASA Astrophysics Data System (ADS)

Oda, Hiroshi; Ibaraki, Tetsuharu

Dust recycling technology by the rotary hearth furnace has been applied at Nippon Steel‧s Kimitsu Works since 2000. The dust and sludge with iron oxide and carbon are agglomerated into shaped articles and the iron oxide is reduced in a high temperature atmosphere. Zinc and other impurities in the dust and sludge are expelled and exhausted into off gas. The DRI pellets made from the dust and sludge have 70% metallization and are strong enough for being recycled to the blast furnaces. No.1 plant, which was constructed in May 2000 and has an agglomeration method of pelletizing, recycles mainly dry dusts. No.2 plant, which was constructed in December 2002 and has an agglomeration method of extrusion, recycles mainly sludge. The combination of the two plants is a solution for recycling various kinds of dusts and sludge emitted in a large scale steel works as Kimitsu Works

Solid Hydrogen Experiments for Atomic Propellants: Image Analyses

NASA Technical Reports Server (NTRS)

Palaszewski, Bryan

2002-01-01

This paper presents the results of detailed analyses of the images from experiments that were conducted on the formation of solid hydrogen particles in liquid helium. Solid particles of hydrogen were frozen in liquid helium, and observed with a video camera. The solid hydrogen particle sizes, their agglomerates, and the total mass of hydrogen particles were estimated. Particle sizes of 1.9 to 8 mm (0.075 to 0.315 in.) were measured. The particle agglomerate sizes and areas were measured, and the total mass of solid hydrogen was computed. A total mass of from 0.22 to 7.9 grams of hydrogen was frozen. Compaction and expansion of the agglomerate implied that the particles remain independent particles, and can be separated and controlled. These experiment image analyses are one of the first steps toward visually characterizing these particles, and allow designers to understand what issues must be addressed in atomic propellant feed system designs for future aerospace vehicles.

Size control of Au NPs supported by pH operation

NASA Astrophysics Data System (ADS)

Ichiji, Masumi; Akiba, Hiroko; Hirasawa, Izumi

2017-07-01

Au NPs are expected to become useful functional particles, as particle gun used for plant gene transfer and also catalysts. We have studied PSD (particle size distribution) control of Au NPs by reduction crystallization. Previous study found out importance of seeds policy and also feeding profile. In this paper, effect of pH in the reduction crystallization was investigated to clarify the possibility of Au NPs PSD control by pH operation and also their growth process. Au NPs of size range 10-600 nm were obtained in single-jet system using ascorbic acid (AsA) as a reducing agent with adjusting pH of AsA. Au NPs are found to grow in the process of nucleation, agglomeration, agglomeration growth and surface growth. Au NPs tend to grow by agglomeration and become larger size in lower pH regions, and to grow only by surface growth and become smaller size in higher pH regions.

Asphaltene dispersants as demulsification aids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manek, M.B.

1995-11-01

Destabilization of petroleum asphaltenes may cause a multitude of problems in crude oil recovery and production. One major problem is their agglomeration at the water-oil interface of crude oil emulsions. Once agglomeration occurs, destabilized asphaltenes can form a thick pad in the dehydration equipment, which significantly reduces the demulsification rate. Certain polymeric dispersants increase asphaltene solubilization in hydrocarbon media, and when used in conjunction with emulsion breakers, facilitate the demulsification process. Two case studies are presented that demonstrate how asphaltene dispersants can efficiently inhibit pad formation and help reduce demulsifier dosage. Criteria for dispersant application and selection are discussed, whichmore » include the application of a novel laboratory technique to assess asphaltene stabilization in the crude oil. The technique monitors asphaltene agglomeration while undergoing titration with an incompatible solvent (precipitant). The method was used to evaluate stabilization of asphaltenes in the crude oil and to screen asphaltene dispersants.« less