Science.gov

Sample records for aggregate initial construction

  1. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1995-01-01

    Part of the 1994 Industrial Minerals Review. The production, consumption, and applications of construction aggregates are reviewed. In 1994, the production of construction aggregates, which includes crushed stone and construction sand and gravel combined, increased 7.7 percent to 2.14 Gt compared with the previous year. These record production levels are mostly a result of funding for highway construction work provided by the Intermodal Surface Transportation Efficiency Act of 1991. Demand is expected to increase for construction aggregates in 1995.

  2. Construction aggregates

    USGS Publications Warehouse

    Langer, W.H.; Tepordei, V.V.; Bolen, W.P.

    2000-01-01

    Construction aggregates consist primarily of crushed stone and construction sand and gravel. Total estimated production of construction aggregates increased in 1999 by about 2% to 2.39 Gt (2.64 billion st) compared with 1998. This record production level continued an expansion that began in 1992. By commodities, crushed stone production increased 3.3%, while sand and gravel production increased by about 0.5%.

  3. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1994-01-01

    Part of a special section on industrial minerals in 1993. The 1993 production of construction aggregates increased 6.3 percent over the 1992 figure, to reach 2.01 Gt. This represents the highest estimated annual production of combined crushed stone and construction sand and gravel ever recorded in the U.S. The outlook for construction aggregates and the issues facing the industry are discussed.

  4. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1996-01-01

    Part of the Annual Commodities Review 1995. Production of construction aggregates such as crushed stone and construction sand and gravel showed a marginal increase in 1995. Most of the 1995 increases were due to funding for highway construction work. The major areas of concern to the industry included issues relating to wetlands classification and the classification of crystalline silica as a probable human carcinogen. Despite this, an increase in demand is anticipated for 1996.

  5. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1993-01-01

    Part of a special section on the market performance of industrial minerals in 1992. Production of construction aggregates increased by 4.6 percent in 1992. This increase was due, in part, to the increased funding for transportation and infrastructure projects. The U.S. produced about 1.05 Gt of crushed stone and an estimated 734 Mt of construction sand and gravel in 1992. Demand is expected to increase by about 5 percent in 1993.

  6. Construction aggregates

    USGS Publications Warehouse

    Nelson, T.I.; Bolen, W.P.

    2007-01-01

    Construction aggregates, primarily stone, sand and gravel, are recovered from widespread naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Much smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical processes, glass production and many other products.

  7. Construction aggregates

    USGS Publications Warehouse

    Bolen, W.P.; Tepordei, V.V.

    2001-01-01

    The estimated production during 2000 of construction aggregates, crushed stone, and construction sand and gravel increased by about 2.6% to 2.7 Gt (3 billion st), compared with 1999. The expansion that started in 1992 continued with record production levels for the ninth consecutive year. By commodity, construction sand and gravel production increased by 4.5% to 1.16 Gt (1.28 billion st), while crushed stone production increased by 1.3% to 1.56 Gt (1.72 billion st).

  8. A look at construction aggregates production

    USGS Publications Warehouse

    Willett, Jason Christopher

    2009-01-01

    Construction aggregates are defined as the combination of crushed stone and construction sand and gravel. Aggregates are one of the most accessible natural resources on Earth and one of the fundamental building blocks of our society. They have been used from the earliest times of our civilization for a variety of applications that have increased in number and complexity with time and technological progress. Despite the relatively low but increasing unit value of its basic products, the construction aggregates industry is a major contributor to and an indicator of the economic well-being of the nation.

  9. The Nation's top 25 construction aggregates producers

    USGS Publications Warehouse

    Willett, Jason Christopher

    2013-01-01

    U.S. production of construction aggregates in 2011 was 2.17 billion short tons, valued at $17.2 billion, free on board (f.o.b.) at plant. Construction aggregates production decreased by 37 percent, and the associated value decreased by 25 percent, compared with the record highs reported in 2006. In 2011, construction aggregates production increased for the first time since 2006, owing to a very slight increase in the production of both construction sand and gravel and crushed stone. The average unit value, which is the f.o.b. at plant price of a ton of material, increased slightly, but is still less than the average unit value of two years prior.

  10. A brief review of the construction aggregates market

    USGS Publications Warehouse

    Willett, Jason Christopher

    2012-01-01

    The U.S. Geological Survey defines the construction aggregates industry as those companies that mine and process crushed stone and/or construction sand and gravel. Aggregates have been used from the earliest times of our civilization for a variety of purposes - construction being the major use. As construction aggregates, crushed stone and construction sand and gravel are the basic raw materials used to build the foundation for modern society. The widespread use of construction aggregates is the result of their general availability throughout the country and around the world along with their relatively low cost. Although construction aggregates have a low unit value, their widespread use makes them major contributors to, and indicators of, the economic well-being of the nation.

  11. Relationship between the initial rate of protein aggregation and the lag period for amorphous aggregation.

    PubMed

    Borzova, Vera A; Markossian, Kira A; Kurganov, Boris I

    2014-07-01

    Lag period is an inherent characteristic of the kinetic curves registered for protein aggregation. The appearance of a lag period is connected with the nucleation stage and the stages of the formation of folding or unfolding intermediates prone to aggregation (for example, the stage of protein unfolding under stress conditions). Discovering the kinetic regularities essential for elucidation of the protein aggregation mechanism comprises deducing the relationship between the lag period and aggregation rate. Fändrich proposed the following equation connecting the duration of the lag phase (tlag) and the aggregate growth rate (kg) in the amyloid fibrillation: kg=const/tlag. To establish the relationship between the initial rate of protein aggregation (v) and the lag period (t0) in the case of amorphous aggregation, the kinetics of dithithreitol-induced aggregation of holo-α-lactalbumin from bovine milk was studied (0.1M Na-phosphate buffer, pH 6.8; 37°C). The order of aggregation with respect to protein (n) was calculated from the dependence of the initial rate of protein aggregation on the α-lactalbumin concentration (n=5.3). The following equation connecting v and t0 has been proposed: v(1/n)=const/(t0-t0,lim), where t0,lim is the limiting value of t0 at high concentrations of the protein. PMID:24794200

  12. Shaping the Growth Behaviour of Biofilms Initiated from Bacterial Aggregates.

    PubMed

    Melaugh, Gavin; Hutchison, Jaime; Kragh, Kasper Nørskov; Irie, Yasuhiko; Roberts, Aled; Bjarnsholt, Thomas; Diggle, Stephen P; Gordon, Vernita D; Allen, Rosalind J

    2016-01-01

    Bacterial biofilms are usually assumed to originate from individual cells deposited on a surface. However, many biofilm-forming bacteria tend to aggregate in the planktonic phase so that it is possible that many natural and infectious biofilms originate wholly or partially from pre-formed cell aggregates. Here, we use agent-based computer simulations to investigate the role of pre-formed aggregates in biofilm development. Focusing on the initial shape the aggregate forms on the surface, we find that the degree of spreading of an aggregate on a surface can play an important role in determining its eventual fate during biofilm development. Specifically, initially spread aggregates perform better when competition with surrounding unaggregated bacterial cells is low, while initially rounded aggregates perform better when competition with surrounding unaggregated cells is high. These contrasting outcomes are governed by a trade-off between aggregate surface area and height. Our results provide new insight into biofilm formation and development, and reveal new factors that may be at play in the social evolution of biofilm communities. PMID:26934187

  13. Shaping the Growth Behaviour of Biofilms Initiated from Bacterial Aggregates

    PubMed Central

    Melaugh, Gavin; Hutchison, Jaime; Kragh, Kasper Nørskov; Irie, Yasuhiko; Roberts, Aled; Bjarnsholt, Thomas; Diggle, Stephen P.; Gordon, Vernita D.; Allen, Rosalind J.

    2016-01-01

    Bacterial biofilms are usually assumed to originate from individual cells deposited on a surface. However, many biofilm-forming bacteria tend to aggregate in the planktonic phase so that it is possible that many natural and infectious biofilms originate wholly or partially from pre-formed cell aggregates. Here, we use agent-based computer simulations to investigate the role of pre-formed aggregates in biofilm development. Focusing on the initial shape the aggregate forms on the surface, we find that the degree of spreading of an aggregate on a surface can play an important role in determining its eventual fate during biofilm development. Specifically, initially spread aggregates perform better when competition with surrounding unaggregated bacterial cells is low, while initially rounded aggregates perform better when competition with surrounding unaggregated cells is high. These contrasting outcomes are governed by a trade-off between aggregate surface area and height. Our results provide new insight into biofilm formation and development, and reveal new factors that may be at play in the social evolution of biofilm communities. PMID:26934187

  14. Development of construction materials using nano-silica and aggregates recycled from construction and demolition waste.

    PubMed

    Mukharjee, Bibhuti Bhusan; Barai, Sudhirkumar V

    2015-06-01

    The present work addresses the development of novel construction materials utilising commercial grade nano-silica and recycled aggregates retrieved from construction and demolition waste. For this, experimental work has been carried out to examine the influence of nano-silica and recycled aggregates on compressive strength, modulus of elasticity, water absorption, density and volume of voids of concrete. Fully natural and recycled aggregate concrete mixes are designed by replacing cement with three levels (0.75%, 1.5% and 3%) of nano-silica. The results of the present investigation depict that improvement in early days compressive strength is achieved with the incorporation of nano-silica in addition to the restoration of reduction in compressive strength of recycled aggregate concrete mixes caused owing to the replacement of natural aggregates by recycled aggregates. Moreover, the increase in water absorption and volume of voids with a reduction of bulk density was detected with the incorporation of recycled aggregates in place of natural aggregates. However, enhancement in density and reduction in water absorption and volume of voids of recycled aggregate concrete resulted from the addition of nano-silica. In addition, the results of the study reveal that nano-silica has no significant effect on elastic modulus of concrete. PMID:25986048

  15. PRODUCTION OF CONSTRUCTION AGGREGATES FROM FLUE GAS DESULFURIZATION SLUDGE

    SciTech Connect

    1998-12-01

    Through a cooperative agreement with DOE, the Research and Development Department of CONSOL Inc. (CONSOL R and D) is teaming with SynAggs, Inc. and Duquesne Light to design, construct, and operate a 500 lb/h continuous pilot plant to produce road construction aggregate from a mixture of wet flue gas desulfurization (FGD) sludge, fly ash, and other components. The proposed project is divided into six tasks: (1) Project Management; (2) Mix Design Evaluation; (3) Process Design; (4) Construction; (5) Start-Up and Operation; and (6) Reporting. In this quarter, Tasks 1 and 2 were completed. A project management plan (Task 1) was issued to DOE on October 22, 1998 . The mix design evaluation (Task 2) with Duquesne Light Elrama Station FGD sludge and Allegheny Power Hatfields Ferry Station fly ash was completed. Eight semi-continuous bench-scale tests were conducted to examine the effects of mix formulation on aggregate properties. A suitable mix formulation was identified to produce aggregates that meet specifications of the American Association of State High Transport Officials (AASHTO) as Class A aggregate for use in highway construction. The mix formulation was used in designing the flow sheet of the pilot plant. The process design (Task 3) is approximately 80% completed. Equipment was evaluated to comply with design requirements. The design for the curing vessel was completed by an outside engineering firm. All major equipment items for the pilot plant, except the curing vessel, were ordered. Pilot plant construction (Task 4) was begun in October. The Hazardous Substance Plan was issued to DOE. The Allegheny County (PA) Heat Department determined that an air emission permit is not required for operation of the pilot plant.

  16. A Generalized Eigensolver based on Smoothed Aggregation (GES-SA) for Initializing Smoothed Aggregation Multigrid (SA)

    SciTech Connect

    Brezina, M; Manteuffel, T; McCormick, S; Ruge, J; Sanders, G; Vassilevski, P S

    2007-05-31

    Consider the linear system Ax = b, where A is a large, sparse, real, symmetric, and positive definite matrix and b is a known vector. Solving this system for unknown vector x using a smoothed aggregation multigrid (SA) algorithm requires a characterization of the algebraically smooth error, meaning error that is poorly attenuated by the algorithm's relaxation process. For relaxation processes that are typically used in practice, algebraically smooth error corresponds to the near-nullspace of A. Therefore, having a good approximation to a minimal eigenvector is useful to characterize the algebraically smooth error when forming a linear SA solver. This paper discusses the details of a generalized eigensolver based on smoothed aggregation (GES-SA) that is designed to produce an approximation to a minimal eigenvector of A. GES-SA might be very useful as a standalone eigensolver for applications that desire an approximate minimal eigenvector, but the primary aim here is for GES-SA to produce an initial algebraically smooth component that may be used to either create a black-box SA solver or initiate the adaptive SA ({alpha}SA) process.

  17. Aggregates from natural and recycled sources; economic assessments for construction applications; a materials flow study

    USGS Publications Warehouse

    Wilburn, David R.; Goonan, Thomas G.

    1998-01-01

    Increased amounts of recycled materials are being used to supplement natural aggregates (derived from crushed stone, sand and gravel) in road construction. An understanding of the economics and factors affecting the level of aggregates recycling is useful in estimating the potential for recycling and in assessing the total supply picture of aggregates. This investigation includes a descriptive analysis of the supply sources, technology, costs, incentives, deterrents, and market relationships associated with the production of aggregates.

  18. 5 CFR 550.164 - Construction and computation of existing aggregate rates.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Construction and computation of existing aggregate rates. 550.164 Section 550.164 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL... Pay on An Annual Basis § 550.164 Construction and computation of existing aggregate rates....

  19. 5 CFR 550.164 - Construction and computation of existing aggregate rates.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Construction and computation of existing aggregate rates. 550.164 Section 550.164 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL... Pay on An Annual Basis § 550.164 Construction and computation of existing aggregate rates....

  20. PRODUCTION OF CONSTRUCTION AGGREGATES FROM FLUE GAS DESULFURIZATION SLUDGE

    SciTech Connect

    M.M. Wu; D.C. McCoy; R.O. Scandrol; M.L. Fenger; J.A. Withum; R.M. Statnick

    2000-05-01

    The three main conclusions of this report are: (1) The pilot plant successfully demonstrated the continuous, fully-integrated, long-term process operation, including the mixing, pelletizing, and curing steps for aggregate production. The curing vessel, which was designed for the pilot plant test, was operated in a mass flow mode and performed well during pilot plant operation. (2) The pilot plant test demonstrated process flexibility. The same equipment was used to produce lightweight, medium-weight, and road aggregates. The only change was the mix formulation. Aggregates were produced from a variety of mix designs and from FGD sludge with solids concentrations between 45.0% and 56.7% and moisture contents between 55.0% and 43.3%. (3) The pilot plant provided operating data and experience to design and cost a commercial plant, which was not part of the cooperative agreement.

  1. 75 FR 79404 - Controlled Substances: Established Initial Aggregate Production Quotas for 2011

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-20

    ... schedules I and II was published in the Federal Register (75 FR 56137). All interested persons were invited... Enforcement Administration Controlled Substances: Established Initial Aggregate Production Quotas for 2011 AGENCY: Drug Enforcement Administration (DEA), Justice. ACTION: Notice of aggregate production quotas...

  2. Recycling of construction debris as aggregate in the Mid-Atlantic Region, USA

    USGS Publications Warehouse

    Robinson, G.R., Jr.; Menzie, W.D.; Hyun, H.

    2004-01-01

    Reclaimed asphalt pavement (RAP) and portland cement concrete (RPCC) are abundant and available substitutes for natural aggregate in many areas. This paper presents an overview of factors that affect recycled aggregate cost, availability, and engineering performance, and the results of a survey of business practices in the Mid-Atlantic region. For RAP, processing costs are less than those for virgin natural aggregate. Use of efficient asphalt pavement stripping technology, on-site reclamation, and linked two-way transport of asphalt debris and processed asphalt paving mix between asphalt mix plants and paving sites has led to extensive recycling of asphalt pavement in the Mid-Atlantic region of the US. Most of the sites that recycle asphalt pavement (RAP) are located in or near urban areas close to important transportation corridors. RPCC is a viable aggregate source in urban settings where unit costs for processed aggregate from RPCC and natural aggregate are comparable. Disposal fees charged at RPCC recycling sites help defray processing costs and the significantly lower tipping fees at recycling sites versus landfill disposal sites encourage recycling of construction debris as aggregate. Construction contractors and construction debris recycling centers, many of which have the ability to crush and process concrete debris at the job site, produce most RPCC. Production of RPCC aggregate from construction debris that is processed on site using portable equipment moved to the construction site eliminates transportation costs for aggregate and provides an economic incentive for RPCC use. Processing costs, quality and performance issues, and lack of large quantities where needed limit RPCC use. Most RPCC suppliers in the Mid-Atlantic area are located in counties with population densities greater than 400 people/km2 (1036 people/mile2) and that have high unit-value costs and limited local availability of natural aggregate. ?? 2004 Published by Elsevier B.V.

  3. Aggregates: Waste and recycled materials; new rapid evaluation technology. Soils, geology, and foundations; materials and construction. Transportation research record

    SciTech Connect

    Not Available

    1994-01-01

    ;Contents: Engineering Properties of Shredded Tires in Lightweight Fill Applications; Using Recovered Glass as Construction Aggregate Feedstock; Utilization of Phosphogypsum-Based Slag Aggregate in Portland Cement Concrete Mixtures; Waste Foundry Sand in Asphalt Concrete; Toward Automating Size-Gradation Analysis of Mineral Aggregate; Evaluation of Fine Aggregate Angularity Using National Aggregate Association Flow Test; Siliceous Content Determination of Sands Using Automatic Image Analysis; and Methodology for Improvement of Oxide Residue Models for Estimation of Aggregate Performance Using Stoichiometric Analysis.

  4. The Physician Values in Practice Scale: Construction and Initial Validation

    ERIC Educational Resources Information Center

    Hartung, Paul J.; Taber, Brian J.; Richard, George V.

    2005-01-01

    Measures of values typically appraise the construct globally, across life domains or relative to a broad life domain such as work. We conducted two studies to construct and initially validate an occupation- and context-specific values measure. Study 1, based on a sample of 192 medical students, describes the initial construction and item analysis…

  5. Crushed cement concrete substitution for construction aggregates; a materials flow analysis

    USGS Publications Warehouse

    Kelly, Thomas

    1998-01-01

    An analysis of the substitution of crushed cement concrete for natural construction aggregates is performed by using a materials flow diagram that tracks all material flows into and out of the cement concrete portion of the products made with cement concrete: highways, roads, and buildings. Crushed cement concrete is only one of the materials flowing into these products, and the amount of crushed cement concrete substituted influences the amount of other materials in the flow. Factors such as availability and transportation costs, as well as physical properties, that can affect stability and finishability, influence whether crushed cement concrete or construction aggregates should be used or predominate for a particular end use.

  6. Physical mechanisms controlling the initiation of convective self-aggregation in a General Circulation Model

    NASA Astrophysics Data System (ADS)

    Coppin, David; Bony, Sandrine

    2015-12-01

    Cloud-resolving models have shown that under certain conditions, the Radiative-Convective Equilibrium (RCE) could become unstable and lead to the spontaneous organization of the atmosphere into dry and wet areas, and the aggregation of convection. In this study, we show that this "self-aggregation" behavior also occurs in nonrotating RCE simulations performed with the IPSL-CM5A-LR General Circulation Model (GCM), and that it exhibits a strong dependence on sea surface temperature (SST). We investigate the physical mechanisms that control the initiation of self-aggregation in this model, and their dependence on temperature. At low SSTs, the onset of self-aggregation is primarily controlled by the coupling between low-cloud radiative effects and shallow circulations and the formation of "radiatively driven cold pools" in areas devoid of deep convection, while at high SSTs it is primarily controlled by the coupling between surface fluxes and circulation within convective areas. At intermediate temperatures, the occurrence of self-aggregation is less spontaneous and depends on initial conditions, but it can arise through a combination of both mechanisms. Through their coupling to circulation and surface fluxes, the radiative effects of low-level clouds play a critical role in both initiation mechanisms, and the sensitivity of boundary layer clouds to surface temperature explains to a large extent the temperature dependence of convective self-aggregation. At any SST, the presence of cloud-radiative effects in the free troposphere is necessary to the initiation, growth, and maintenance of convective aggregation.

  7. Weighting and Aggregation in Composite Indicator Construction: A Multiplicative Optimization Approach

    ERIC Educational Resources Information Center

    Zhou, P.; Ang, B. W.; Zhou, D. Q.

    2010-01-01

    Composite indicators (CIs) have increasingly been accepted as a useful tool for benchmarking, performance comparisons, policy analysis and public communication in many different fields. Several recent studies show that as a data aggregation technique in CI construction the weighted product (WP) method has some desirable properties. However, a…

  8. 5 CFR 550.164 - Construction and computation of existing aggregate rates.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Construction and computation of existing aggregate rates. 550.164 Section 550.164 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PAY ADMINISTRATION (GENERAL) Premium Pay General Rules Governing Payments of Premium Pay on An Annual Basis §...

  9. 18 CFR 1304.9 - Initiation of construction.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 18 Conservation of Power and Water Resources 2 2012-04-01 2012-04-01 false Initiation of construction. 1304.9 Section 1304.9 Conservation of Power and Water Resources TENNESSEE VALLEY AUTHORITY APPROVAL OF CONSTRUCTION IN THE TENNESSEE RIVER SYSTEM AND REGULATION OF STRUCTURES AND OTHER...

  10. 18 CFR 1304.9 - Initiation of construction.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 18 Conservation of Power and Water Resources 2 2014-04-01 2014-04-01 false Initiation of construction. 1304.9 Section 1304.9 Conservation of Power and Water Resources TENNESSEE VALLEY AUTHORITY APPROVAL OF CONSTRUCTION IN THE TENNESSEE RIVER SYSTEM AND REGULATION OF STRUCTURES AND OTHER...

  11. 18 CFR 1304.9 - Initiation of construction.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 18 Conservation of Power and Water Resources 2 2010-04-01 2010-04-01 false Initiation of construction. 1304.9 Section 1304.9 Conservation of Power and Water Resources TENNESSEE VALLEY AUTHORITY APPROVAL OF CONSTRUCTION IN THE TENNESSEE RIVER SYSTEM AND REGULATION OF STRUCTURES AND OTHER...

  12. 18 CFR 1304.9 - Initiation of construction.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 18 Conservation of Power and Water Resources 2 2011-04-01 2011-04-01 false Initiation of construction. 1304.9 Section 1304.9 Conservation of Power and Water Resources TENNESSEE VALLEY AUTHORITY APPROVAL OF CONSTRUCTION IN THE TENNESSEE RIVER SYSTEM AND REGULATION OF STRUCTURES AND OTHER...

  13. The shakeout scenario: Meeting the needs for construction aggregates, asphalt, and concrete

    USGS Publications Warehouse

    Langer, W.H.

    2011-01-01

    An Mw 7.8 earthquake as described in the ShakeOut Scenario would cause significantdamage to buildings and infrastructure. Over 6 million tons of newly mined aggregate would be used for emergency repairs and for reconstruction in the five years following the event. This aggregate would be applied mostly in the form of concrete for buildings and bridges, asphalt or concrete for pavement, and unbound gravel for applications such as base course that goes under highway pavement and backfilling for foundations and pipelines. There are over 450 aggregate, concrete, and asphalt plants in the affected area, some of which would be heavily damaged. Meeting the increased demand for construction materials would require readily available permitted reserves, functioning production facilities, a supply of cement and asphalt, a source of water, gas, and electricity, and a trained workforce. Prudent advance preparations would facilitate a timely emergency response and reconstruction following such an earthquake. ?? 2011, Earthquake Engineering Research Institute.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Presently, about 90% of the aggregate production in Europe comes from naturally occurring resources: quarries and pits. Due to the increased demand for sand and gravel for construction purposes, not only in building but also in road construction, the last decade has seen a significant trend towards the use of more crushed rock aggregates. This resource has been more and more preferred to sand and gravel thanks to the significant technological development of its process and use phase. The performance of the aggregates is generally evaluated depending on three main factors: the geological origin (mineral composition, texture, structure, degree of weathering), the aggregate processing (crushing, sieving, washing, storing) and the user technology for a specific area of use (e.g. road construction, asphalt binders). Nevertheless climatic conditions should carefully be taken into account in application such as road construction. Large temperature gradients and high levels of humidity are known to significantly affect the performance of the material. Although the problem is, at least in the asphalt field, considered mostly from the binder point of view, this article aims to investigate the effect of aggregate properties on road performance in cold climatic conditions. Two different climatic areas will be taken into account: Norway and Spain. While both these countries are listed among the main European producers of aggregates, they represent significantly different climatic regions. While Norwegian weather is characterized by humid cold winters and relatively mild summers, Spain has temperate climate with cold regions in mountainous and internal areas. Both countries have been significantly affected by climate change with increasing temperature variations and instability. At the same time, similar winter maintenance measures, including the use of a considerable amount of solid and liquid chemicals to avoid ice formation (e.g. NaCl) and/or to provide better friction, are

  15. Polymer depletion-driven cluster aggregation and initial phase separation in charged nanosized colloids.

    PubMed

    Gögelein, Christoph; Nägele, Gerhard; Buitenhuis, Johan; Tuinier, Remco; Dhont, Jan K G

    2009-05-28

    We study polymer depletion-driven cluster aggregation and initial phase separation in aqueous dispersions of charge-stabilized silica spheres, where the ionic strength and polymer (dextran) concentration are systematically varied, using dynamic light scattering and visual observation. Without polymers and for increasing salt and colloid content, the dispersions become increasingly unstable against irreversible cluster formation. By adding nonadsorbing polymers, a depletion-driven attraction is induced, which lowers the stabilizing Coulomb barrier and enhances the cluster growth rate. The initial growth rate increases with increasing polymer concentration and decreases with increasing polymer molar mass. These observations can be quantitatively understood by an irreversible dimer formation theory based on the classical Derjaguin, Landau, Verwey, and Overbeek pair potential, with the depletion attraction modeled by the Asakura-Oosawa-Vrij potential. At low colloid concentration, we observe an exponential cluster growth rate for all polymer concentrations considered, indicating a reaction-limited aggregation mechanism. At sufficiently high polymer and colloid concentrations, and lower salt content, a gas-liquidlike demixing is observed initially. Later on, the system separates into a gel and fluidlike phase. The experimental time-dependent state diagram is compared to the theoretical equilibrium phase diagram obtained from a generalized free-volume theory and is discussed in terms of an initial reversible phase separation process in combination with irreversible aggregation at later times. PMID:19485479

  16. Hydrodynamics of cell-cell mechanical signaling in the initial stages of aggregation.

    PubMed

    Bouffanais, Roland; Yue, Dick K P

    2010-04-01

    Mechanotactic cell motility has recently been shown to be a key player in the initial aggregation of crawling cells such as leukocytes and amoebae. The effects of mechanotactic signaling in the early aggregation of amoeboid cells are here investigated using a general mathematical model based on known biological evidence. We elucidate the hydrodynamic fundamentals of the direct guiding of a cell through mechanotaxis in the case where one cell transmits a mechanotactic signal through the fluid flow by changing its shape. It is found that any mechanosensing cells placed in the stimulus field of mechanical stress are able to determine the signal transmission direction with a certain angular dispersion which does not preclude the aggregation from happening. The ubiquitous presence of noise is accounted for by the model. Finally, the mesoscopic pattern of aggregation is obtained which constitutes the bridge between, on one hand, the microscopic world where the changes in the cell shape occur and, on the other hand, the cooperative behavior of the cells at the mesoscopic scale. PMID:20481766

  17. In Situ Construction and Characterization of Chlorin-Based Supramolecular Aggregates in Tumor Cells.

    PubMed

    Liu, Wei-Jiao; Zhang, Di; Li, Li-Li; Qiao, Zeng-Ying; Zhang, Ju-Chen; Zhao, Ying-Xi; Qi, Guo-Bin; Wan, Dong; Pan, Jie; Wang, Hao

    2016-09-01

    We demonstrate in situ construction and characterization of supramolecular aggregates from chlorin p6 (Cp6) molecules in tumor cells. Fully deprotonated Cp6 molecules in neutral condition were partially protonated inside the acidic lysosomes of cells and significantly increased the hydrophobicity of them that resulted in simultaneous formation of J-type aggregates. Importantly, the formation of J-aggregates was fully characterized in artificial tissues by UV-vis, circular dichroism (CD) and transmission electron microscope (TEM) techniques. Compared to the monomers, the J-aggregates exhibited 55-fold enhanced thermal conversion efficiency (η) at the optimal excitation wavelength (690 nm). The remarkably increased heat effect contributed to the stronger photoacoustic (PA) signals, leading to at least 2 orders of magnitude increase of the tumor-to-normal tissue ratio (T/N), which was defined as the PA signal ratio between tumor site and surrounding normal tissue. We envision that this proof-of-concept study will open a new way to develop tumor environment-induced self-assembly for variable biomedical applications. PMID:27529787

  18. A GIS analysis of suitability for construction aggregate recycling sites using regional transportation network and population density features

    USGS Publications Warehouse

    Robinson, G.R., Jr.; Kapo, K.E.

    2004-01-01

    Aggregate is used in road and building construction to provide bulk, strength, support, and wear resistance. Reclaimed asphalt pavement (RAP) and reclaimed Portland cement concrete (RPCC) are abundant and available sources of recycled aggregate. In this paper, current aggregate production operations in Virginia, Maryland, and the District of Columbia are used to develop spatial association models for the recycled aggregate industry with regional transportation network and population density features. The cost of construction aggregate to the end user is strongly influenced by the cost of transporting processed aggregate from the production site to the construction site. More than 60% of operations recycling aggregate in the mid-Atlantic study area are located within 4.8 km (3 miles) of an interstate highway. Transportation corridors provide both sites of likely road construction where aggregate is used and an efficient means to move both materials and on-site processing equipment back and forth from various work sites to the recycling operations. Urban and developing areas provide a high market demand for aggregate and a ready source of construction debris that may be processed into recycled aggregate. Most aggregate recycling operators in the study area are sited in counties with population densities exceeding 77 people/km2 (200 people/mile 2). No aggregate recycling operations are sited in counties with less than 19 people/km2 (50 people/mile2), reflecting the lack of sufficient long-term sources of construction debris to be used as an aggregate source, as well as the lack of a sufficient market demand for aggregate in most rural areas to locate a recycling operation there or justify the required investment in the equipment to process and produce recycled aggregate. Weights of evidence analyses (WofE), measuring correlation on an area-normalized basis, and weighted logistic regression (WLR), are used to model the distribution of RAP and RPCC operations relative

  19. Personal Growth Initiative: The Construct and Its Measure.

    ERIC Educational Resources Information Center

    Robitschek, Christine

    1998-01-01

    The Personal Growth Initiative Scale (PGIS) assesses intentionality in personal growth. Three studies were undertaken to (1) investigate the PGI construct; (2) describe the development and factor structure of the PGIS; and (3) test the internal consistency, temporal stability, and convergent and discriminant validity of scores on the PGIS. (EMK)

  20. Microstructure of Concrete with Aggregates from Construction and Demolition Waste Recycling Plants.

    PubMed

    Bravo, Miguel; Santos Silva, António; de Brito, Jorge; Evangelista, Luís

    2016-02-01

    This paper intends to analyze the microstructure of concrete with recycled aggregates (RA) from construction and demolition waste from various Portuguese recycling plants. To that effect, several scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed. Various concrete mixes were evaluated in order to analyze the influence of the RA's collection point and consequently of their composition on the mixes' characteristics. Afterward all the mixes were subjected to the capillary water absorption test in order to quantitatively evaluate their porosity. Results from the SEM/EDS analysis were compared with those from capillary water absorption test. The SEM/EDS analysis showed that the bond capacity of aggregates to the new cement paste is greatly influenced by the RA's nature. On the other hand, there was an increase in porosity with the incorporation of RA. PMID:26700727

  1. Constructing compact and effective graphs for recommender systems via node and edge aggregations

    SciTech Connect

    Lee, Sangkeun; Kahng, Minsuk; Lee, Sang-goo

    2014-12-10

    Exploiting graphs for recommender systems has great potential to flexibly incorporate heterogeneous information for producing better recommendation results. As our baseline approach, we first introduce a naive graph-based recommendation method, which operates with a heterogeneous log-metadata graph constructed from user log and content metadata databases. Although the na ve graph-based recommendation method is simple, it allows us to take advantages of heterogeneous information and shows promising flexibility and recommendation accuracy. However, it often leads to extensive processing time due to the sheer size of the graphs constructed from entire user log and content metadata databases. In this paper, we propose node and edge aggregation approaches to constructing compact and e ective graphs called Factor-Item bipartite graphs by aggregating nodes and edges of a log-metadata graph. Furthermore, experimental results using real world datasets indicate that our approach can significantly reduce the size of graphs exploited for recommender systems without sacrificing the recommendation quality.

  2. Constructing compact and effective graphs for recommender systems via node and edge aggregations

    DOE PAGESBeta

    Lee, Sangkeun; Kahng, Minsuk; Lee, Sang-goo

    2014-12-10

    Exploiting graphs for recommender systems has great potential to flexibly incorporate heterogeneous information for producing better recommendation results. As our baseline approach, we first introduce a naive graph-based recommendation method, which operates with a heterogeneous log-metadata graph constructed from user log and content metadata databases. Although the na ve graph-based recommendation method is simple, it allows us to take advantages of heterogeneous information and shows promising flexibility and recommendation accuracy. However, it often leads to extensive processing time due to the sheer size of the graphs constructed from entire user log and content metadata databases. In this paper, we proposemore » node and edge aggregation approaches to constructing compact and e ective graphs called Factor-Item bipartite graphs by aggregating nodes and edges of a log-metadata graph. Furthermore, experimental results using real world datasets indicate that our approach can significantly reduce the size of graphs exploited for recommender systems without sacrificing the recommendation quality.« less

  3. Basic Oxygen Furnace steel slag aggregates for phosphorus treatment. Evaluation of its potential use as a substrate in constructed wetlands.

    PubMed

    Blanco, Ivan; Molle, Pascal; Sáenz de Miera, Luis E; Ansola, Gemma

    2016-02-01

    Basic Oxygen Furnace (BOF) steel slag aggregates from NW Spain were tested in batch and column experiments to evaluate its potential use as a substrate in constructed wetlands (CWs). The objectives of this study were to identify the main P removal mechanisms of BOF steel slag and determine its P removal capacity. Also, the results were used to discuss the suitability of this material as a substrate to be used in CWs. Batch experiments with BOF slag aggregates and increasing initial phosphate concentrations showed phosphate removal efficiencies between 84 and 99% and phosphate removal capacities from 0.12 to 8.78 mg P/g slag. A continuous flow column experiment filled with BOF slag aggregates receiving an influent synthetic solution of 15 mg P/L during 213 days showed a removal efficiency greater than 99% and a phosphate removal capacity of 3.1 mg P/g slag. In both experiments the main P removal mechanism was found to be calcium phosphate precipitation which depends on Ca(2+) and OH(-) release from the BOF steel slag after dissolution of Ca(OH)2 in water. P saturation of slag was reached within the upper sections of the column which showed phosphate removal capacities between 1.7 and 2.5 mg P/g slag. Once Ca(OH)2 was completely dissolved in these column sections, removal efficiencies declined gradually from 99% until reaching stable outlet concentrations with P removal efficiencies around 7% which depended on influent Ca(2+) for limited continuous calcium phosphate precipitation. PMID:26722756

  4. Mobile work platform for initial lunar base construction

    NASA Technical Reports Server (NTRS)

    Brazell, James W.; Maclaren, Brice K.; Mcmurray, Gary V.; Williams, Wendell M.

    1992-01-01

    Described is a system of equipment intended for site preparation and construction of a lunar base. The proximate era of lunar exploration and the initial phase of outpost habitation are addressed. Drilling, leveling, trenching, and cargo handling are within the scope of the system's capabilities. The centerpiece is a three-legged mobile work platform, named SKITTER. Using standard interfaces, the system is modular in nature and analogous to the farmer's tractor and implement set. Conceptually somewhat different from their Earthbound counterparts, the implements are designed to take advantage of the lunar environment as well as the capabilities of the work platform. The proposed system is mechanically simple and weight efficient.

  5. Quality assessment for recycling aggregates from construction and demolition waste: An image-based approach for particle size estimation.

    PubMed

    Di Maria, Francesco; Bianconi, Francesco; Micale, Caterina; Baglioni, Stefano; Marionni, Moreno

    2016-02-01

    The size distribution of aggregates has direct and important effects on fundamental properties of construction materials such as workability, strength and durability. The size distribution of aggregates from construction and demolition waste (C&D) is one of the parameters which determine the degree of recyclability and therefore the quality of such materials. Unfortunately, standard methods like sieving or laser diffraction can be either very time consuming (sieving) or possible only in laboratory conditions (laser diffraction). As an alternative we propose and evaluate the use of image analysis to estimate the size distribution of aggregates from C&D in a fast yet accurate manner. The effectiveness of the procedure was tested on aggregates generated by an existing C&D mechanical treatment plant. Experimental comparison with manual sieving showed agreement in the range 81-85%. The proposed technique demonstrated potential for being used on on-line systems within mechanical treatment plants of C&D. PMID:26706749

  6. Amphiphilic calixresorcinarene associates as effective solubilizing agents for hydrophobic organic acids: construction of nano-aggregates.

    PubMed

    Morozova, Ju E; Syakaev, V V; Kazakova, E Kh; Shalaeva, Ya V; Nizameev, I R; Kadirov, M K; Voloshina, A D; Zobov, V V; Konovalov, A I

    2016-07-01

    Here we represent the first example of the formation of mixed nanoscale associates, constructed from amphiphilic calixresorcinarenes and hydrophobic carboxylic acids including drugs. The amidoamino-calixresorcinarene self-associates effectively solubilize hydrophobic carboxylic acids - drugs such as naproxen, ibuprofen, ursodeoxycholic acid and aliphatic dodecanoic acid - with the formation of the mixed aggregates with the macrocycle/substrate stoichiometry from 1/1 to 1/7. The ionization of organic acids and the peripheral nitrogen atoms of the macrocycles with the subsequent inclusion of hydrophobic acids into the macrocycle self-associates is the driving force of solubilization. In some cases, this leads to the co-assembly of the macrocycle polydisperse associates into supramolecular monodisperse nanoparticles with the diameter of about 100 nm. The efficiency of drug loading into the nanoparticles is up to 45% and depends on the structure of organic acid. The dissociation of the mixed aggregates and release of organic acid are attained by decreasing pH. PMID:27252123

  7. Use of recycled aggregates from construction and demolition waste in geotechnical applications: A literature review.

    PubMed

    Cardoso, Rafaela; Silva, Rui Vasco; de Brito, Jorge; Dhir, Ravindra

    2016-03-01

    The use of recycled aggregates (RA) in construction constitutes a significant step towards a more sustainable society and also creates a new market opportunity to be exploited. In recent years, several case-studies have emerged in which RA were used in Geotechnical applications, such as filling materials and in unbound pavement layers. This paper presents a review of the most important physical properties of different types of RA and their comparison with natural aggregates (NA), and how these properties affect their hydraulic and mechanical behaviour when compacted. Specifically, the effects of compaction on grading size distribution curves and density are analysed, as well as the consequences of particle crushing on the resilient modulus, CBR and permeability. The paper also contains an analysis of the influence of incorporating different RA types on the performance of unbound road pavement layers as compared with those built with NA by means of the International Roughness Index and deflection values. The results collected from the literature indicate that the performance of most RA is comparable to that of NA and can be used in unbound pavement layers or in other applications requiring compaction. PMID:26748436

  8. Initial planetary base construction techniques and machine implementation

    NASA Technical Reports Server (NTRS)

    Crockford, William W.

    1987-01-01

    Conceptual designs of (1) initial planetary base structures, and (2) an unmanned machine to perform the construction of these structures using materials local to the planet are presented. Rock melting is suggested as a possible technique to be used by the machine in fabricating roads, platforms, and interlocking bricks. Identification of problem areas in machine design and materials processing is accomplished. The feasibility of the designs is contingent upon favorable results of an analysis of the engineering behavior of the product materials. The analysis requires knowledge of several parameters for solution of the constitutive equations of the theory of elasticity. An initial collection of these parameters is presented which helps to define research needed to perform a realistic feasibility study. A qualitative approach to estimating power and mass lift requirements for the proposed machine is used which employs specifications of currently available equipment. An initial, unmanned mission scenario is discussed with emphasis on identifying uncompleted tasks and suggesting design considerations for vehicles and primitive structures which use the products of the machine processing.

  9. A general ansatz for constructing quasi-diabatic states in electronically excited aggregated systems

    NASA Astrophysics Data System (ADS)

    Liu, Wenlan; Lunkenheimer, Bernd; Settels, Volker; Engels, Bernd; Fink, Reinhold F.; Köhn, Andreas

    2015-08-01

    We present a general method for analyzing the character of singly excited states in terms of charge transfer (CT) and locally excited (LE) configurations. The analysis is formulated for configuration interaction singles (CIS) singly excited wave functions of aggregate systems. It also approximately works for the second-order approximate coupled cluster singles and doubles and the second-order algebraic-diagrammatic construction methods [CC2 and ADC(2)]. The analysis method not only generates a weight of each character for an excited state, but also allows to define the related quasi-diabatic states and corresponding coupling matrix elements. In the character analysis approach, we divide the target system into domains and use a modified Pipek-Mezey algorithm to localize the canonical MOs on each domain, respectively. The CIS wavefunction is then transformed into the localized basis, which allows us to partition the wavefunction into LE configurations within domains and CT configuration between pairs of different domains. Quasi-diabatic states are then obtained by mixing excited states subject to the condition of maximizing the weight of one single LE or CT configuration (localization in configuration space). Different aims of such a procedure are discussed, either the construction of pure LE and CT states for analysis purposes (by including a large number of excited states) or the construction of effective models for dynamics calculations (by including a restricted number of excited states). Applications are given to LE/CT mixing in π-stacked systems, charge-recombination matrix elements in a hetero-dimer, and excitonic couplings in multi-chromophoric systems.

  10. A general ansatz for constructing quasi-diabatic states in electronically excited aggregated systems

    SciTech Connect

    Liu, Wenlan; Köhn, Andreas; Lunkenheimer, Bernd; Settels, Volker; Engels, Bernd; Fink, Reinhold F.

    2015-08-28

    We present a general method for analyzing the character of singly excited states in terms of charge transfer (CT) and locally excited (LE) configurations. The analysis is formulated for configuration interaction singles (CIS) singly excited wave functions of aggregate systems. It also approximately works for the second-order approximate coupled cluster singles and doubles and the second-order algebraic-diagrammatic construction methods [CC2 and ADC(2)]. The analysis method not only generates a weight of each character for an excited state, but also allows to define the related quasi-diabatic states and corresponding coupling matrix elements. In the character analysis approach, we divide the target system into domains and use a modified Pipek-Mezey algorithm to localize the canonical MOs on each domain, respectively. The CIS wavefunction is then transformed into the localized basis, which allows us to partition the wavefunction into LE configurations within domains and CT configuration between pairs of different domains. Quasi-diabatic states are then obtained by mixing excited states subject to the condition of maximizing the weight of one single LE or CT configuration (localization in configuration space). Different aims of such a procedure are discussed, either the construction of pure LE and CT states for analysis purposes (by including a large number of excited states) or the construction of effective models for dynamics calculations (by including a restricted number of excited states). Applications are given to LE/CT mixing in π-stacked systems, charge-recombination matrix elements in a hetero-dimer, and excitonic couplings in multi-chromophoric systems.

  11. Evaluating Aggregate Terrestrial Impacts of Road Construction Projects for Advanced Regional Mitigation

    NASA Astrophysics Data System (ADS)

    Thorne, James H.; Girvetz, Evan H.; McCoy, Michael C.

    2009-05-01

    This study presents a GIS-based database framework used to assess aggregate terrestrial habitat impacts from multiple highway construction projects in California, USA. Transportation planners need such impact assessment tools to effectively address additive biological mitigation obligations. Such assessments can reduce costly delays due to protracted environmental review. This project incorporated the best available statewide natural resource data into early project planning and preliminary environmental assessments for single and multiple highway construction projects, and provides an assessment of the 10-year state-wide mitigation obligations for the California Department of Transportation. Incorporation of these assessments will facilitate early and more strategic identification of mitigation opportunities, for single-project and regional mitigation efforts. The data architecture format uses eight spatial scales: six nested watersheds, counties, and transportation planning districts, which were intersected. This resulted in 8058 map planning units statewide, which were used to summarize all subsequent analyses. Range maps and georeferenced locations of federally and state-listed plants and animals and a 55-class landcover map were spatially intersected with the planning units and the buffered spatial footprint of 967 funded projects. Projected impacts were summarized and output to the database. Queries written in the database can sum expected impacts and provide summaries by individual construction project, or by watershed, county, transportation district or highway. The data architecture allows easy incorporation of new information and results in a tool usable without GIS by a wide variety of agency biologists and planners. The data architecture format would be useful for other types of regional planning.

  12. Correlation analysis between sulphate content and leaching of sulphates in recycled aggregates from construction and demolition wastes.

    PubMed

    Barbudo, Auxi; Galvín, Adela P; Agrela, Francisco; Ayuso, Jesús; Jiménez, Jose Ramón

    2012-06-01

    In some recycled aggregates applications, such as component of new concrete or roads, the total content of soluble sulphates should be measured and controlled. Restrictions are usually motivated by the resistance or stability of the new structure, and in most cases, structural concerns can be remedied by the use of techniques such as sulphur-resistant cements. However, environmental risk assessment from recycling and reuse construction products is often forgotten. The purpose of this study is to analyse the content of soluble sulphate on eleven recycled aggregates and six samples prepared in laboratory by the addition of different gypsum percentages. As points of reference, two natural aggregates were tested. An analysis of the content of the leachable amount of heavy metals regulated by European regulation was included. As a result, the correlation between solubility and leachability data allow suggest a limiting gypsum amount of 4.4% on recycled aggregates. This limit satisfies EU Landfill Directive criteria, which is currently used as reference by public Spanish Government for recycled aggregates in construction works. PMID:22410435

  13. Initial construction and validation of the Pathological Narcissism Inventory.

    PubMed

    Pincus, Aaron L; Ansell, Emily B; Pimentel, Claudia A; Cain, Nicole M; Wright, Aidan G C; Levy, Kenneth N

    2009-09-01

    The construct of narcissism is inconsistently defined across clinical theory, social-personality psychology, and psychiatric diagnosis. Two problems were identified that impede integration of research and clinical findings regarding narcissistic personality pathology: (a) ambiguity regarding the assessment of pathological narcissism vs. normal narcissism and (b) insufficient scope of existing narcissism measures. Four studies are presented documenting the initial derivation and validation of the Pathological Narcissism Inventory (PNI). The PNI is a 52-item self-report measure assessing 7 dimensions of pathological narcissism spanning problems with narcissistic grandiosity (Entitlement Rage, Exploitativeness, Grandiose Fantasy, Self-sacrificing Self-enhancement) and narcissistic vulnerability (Contingent Self-esteem, Hiding the Self, Devaluing). The PNI structure was validated via confirmatory factor analysis. The PNI correlated negatively with self-esteem and empathy, and positively with shame, interpersonal distress, aggression, and borderline personality organization. Grandiose PNI scales were associated with vindictive, domineering, intrusive, and overly-nurturant interpersonal problems, and vulnerable PNI scales were associated with cold, socially avoidant, and exploitable interpersonal problems. In a small clinical sample, PNI scales exhibited significant associations with parasuicidal behavior, suicide attempts, homicidal ideation, and several aspects of psychotherapy utilization. PMID:19719348

  14. Structural transformation of the amyloidogenic core region of TDP-43 protein initiates its aggregation and cytoplasmic inclusion.

    PubMed

    Jiang, Lei-Lei; Che, Mei-Xia; Zhao, Jian; Zhou, Chen-Jie; Xie, Mu-Yun; Li, Hai-Yin; He, Jian-Hua; Hu, Hong-Yu

    2013-07-01

    TDP-43 (TAR DNA-binding protein of 43 kDa) is a major deposited protein in amyotrophic lateral sclerosis and frontotemporal dementia with ubiquitin. A great number of genetic mutations identified in the flexible C-terminal region are associated with disease pathologies. We investigated the molecular determinants of TDP-43 aggregation and its underlying mechanisms. We identified a hydrophobic patch (residues 318-343) as the amyloidogenic core essential for TDP-43 aggregation. Biophysical studies demonstrated that the homologous peptide formed a helix-turn-helix structure in solution, whereas it underwent structural transformation from an α-helix to a β-sheet during aggregation. Mutation or deletion of this core region significantly reduced the aggregation and cytoplasmic inclusions of full-length TDP-43 (or TDP-35 fragment) in cells. Thus, structural transformation of the amyloidogenic core initiates the aggregation and cytoplasmic inclusion formation of TDP-43. This particular core region provides a potential therapeutic target to design small-molecule compounds for mitigating TDP-43 proteinopathies. PMID:23689371

  15. Effect of the slope and initial moisture content on soil loss, aggregate and particle size distribution

    NASA Astrophysics Data System (ADS)

    Szabó, Judit Alexandra; Jakab, Gergely; Szabó, Boglárka

    2015-04-01

    Soil structure degradation has effect through the soil water balance and nutrient supply on the agricultural potential of an area. The soil erosion process comprises two phases: detachment and transport by water. To study the transport phase nozzle type laboratory-scale rainfall simulator was used with constant 80 mmhr-1 intensity on an arable haplic Cambisol. Measuring the aggregate and particle size distribution of the soil loss gives a good approach the erosion process. The primary objective of this study was to examine the sediment concentration, and detect the quality and quantity change of the soil loss during a single precipitation under six treatment combinations (recently tilled and crusty soil surface on two different slope steepness, inland inundation and drought soil conditions). Soil loss were collected continually, and separated per aggregate size fractions with sieves in three rounds during a rain to measure the weights. The particle size distribution was measured with Horiba LA-950 particle size analyzer. In general the ratio of the macro aggregates decreases and the ratio of the micro aggregates and clay fraction increases in the sediment with time during the precipitation due to the raindrop impact. Sediment concentration depends on the slope steepness, as from steeper slopes the runoff can transport bigger amount of sediment, but from the tilled surface bigger aggregates were washing down. Micro aggregate fraction is one of the indicators of good soil structure. The degradation of micro aggregates occurs in steeper slopes and the most erosive time period depends on the micromorphology of the surface. And while the aggregate size distribution of the soil loss of the treatments shows high variety of distribution and differs from the original soil, the particle size distribution of each aggregate size fraction shows similar trends except the 50-250 µm fraction where the fine sand fraction is dominating instead of the loam. This anomaly may be

  16. The Work Cognition Inventory: Initial Evidence of Construct Validity

    ERIC Educational Resources Information Center

    Nimon, Kim; Zigarmi, Drea; Houson, Dobie; Witt, David; Diehl, Jim

    2011-01-01

    Contemporary literature lacks a comprehensive set of constructs that provides for understanding both the organizational and job factors that influence employee work passion. Through a detailed analysis of literature, this research identifies eight constructs that form the basis for the appraisal of an employee's work experience with the use of…

  17. Deriving Childhood Temperament Measures from Emotion-eliciting Behavioral Episodes: Scale Construction and Initial Validation

    PubMed Central

    Gagne, Jeffrey R.; Van Hulle, Carol A.; Aksan, Nazan; Essex, Marilyn J.; Goldsmith, H. Hill

    2010-01-01

    The authors describe the development and initial validation of a home-based version of the Laboratory Temperament Assessment Battery (Lab-TAB), which was designed to assess childhood temperament using a comprehensive series of emotion-eliciting behavioral episodes. This paper provides researchers with general guidelines for assessing specific behaviors using the Lab-TAB and for forming behavioral composites that correspond to commonly researched temperament dimensions. We used mother ratings and independent post-visit observer ratings to provide validity evidence in a community sample of 4.5 year-old children. 12 Lab-TAB behavioral episodes were employed, yielding 24 within-episode temperament components that collapsed into 9 higher-level composites (Anger, Sadness, Fear, Shyness, Positive Expression, Approach, Active Engagement, Persistence, and Inhibitory Control). These dimensions of temperament are similar to those found in questionnaire-based assessments. Correlations among the 9 composites were low to moderate, suggesting relative independence. As expected, agreement between Lab-TAB measures and post-visit observer ratings was stronger than agreement between the Lab-TAB and mother questionnaire. However, for Active Engagement and Shyness, mother ratings did predict child behavior in the Lab-TAB quite well. Findings demonstrate the feasibility of emotion-eliciting temperament assessment methodologies, suggest appropriate methods for data aggregation into trait-level constructs, and set some expectations for associations between Lab-TAB dimensions and the degree of cross-method convergence between the Lab-TAB and other commonly used temperament assessments. PMID:21480723

  18. The Construction and Initial Validation of the Work Volition Scale

    ERIC Educational Resources Information Center

    Duffy, Ryan D.; Diemer, Matthew A.; Perry, Justin C.; Laurenzi, Cathy; Torrey, Carrie L.

    2012-01-01

    This study constructed an instrument measuring work volition for adult populations, defined as the perceived capacity to make occupational choices despite constraints. In Study 1, an exploratory factor analysis produced a 3-factor structure containing subscales assessing general volition, financial constraints, and structural constraints. The full…

  19. Initial Construction and Validation of the Pathological Narcissism Inventory

    ERIC Educational Resources Information Center

    Pincus, Aaron L.; Ansell, Emily B.; Pimentel, Claudia A.; Cain, Nicole M.; Wright, Aidan G. C.; Levy, Kenneth N.

    2009-01-01

    The construct of narcissism is inconsistently defined across clinical theory, social-personality psychology, and psychiatric diagnosis. Two problems were identified that impede integration of research and clinical findings regarding narcissistic personality pathology: (a) ambiguity regarding the assessment of pathological narcissism vs. normal…

  20. Comparing MCDA Aggregation Methods in Constructing Composite Indicators Using the Shannon-Spearman Measure

    ERIC Educational Resources Information Center

    Zhou, P.; Ang, B. W.

    2009-01-01

    Composite indicators have been increasingly recognized as a useful tool for performance monitoring, benchmarking comparisons and public communication in a wide range of fields. The usefulness of a composite indicator depends heavily on the underlying data aggregation scheme where multiple criteria decision analysis (MCDA) is commonly used. A…

  1. Reframing the Practicum: Constructing Performative Space in Initial Teacher Education

    ERIC Educational Resources Information Center

    Wilson, Gary; I'Anson, John

    2006-01-01

    This paper points to a neglected dimension to Schon's work on the reflective practitioner: his distinctive characterisation of the practicum. We argue that Schon's understanding of the practicum is integrally related to his understanding of the reflective practitioner. The appropriation of the latter concept within programmes of initial teacher…

  2. Distributed microbially- and chemically-mediated redox processes controlling arsenic dynamics within Mn-/Fe-oxide constructed aggregates

    NASA Astrophysics Data System (ADS)

    Ying, Samantha C.; Masue-Slowey, Yoko; Kocar, Benjamin D.; Griffis, Sarah D.; Webb, Samuel; Marcus, Matthew A.; Francis, Christopher A.; Fendorf, Scott

    2013-03-01

    The aggregate-based structure of soils imparts physical heterogeneity that gives rise to variation in microbial and chemical processes which influence the speciation and retention of trace elements such as As. To examine the impact of distributed redox conditions on the fate of As in soils, we imposed various redox treatments upon constructed soil aggregates composed of ferrihydrite- and birnessite-coated sands presorbed with As(V) and inoculation with the dissimilatory metal reducing bacterium Shewanella sp. ANA-3. Aeration of the advecting solution surrounding the aggregates was varied to simulate environmental conditions. We find that diffusion-limited transport within high dissolved organic carbon environments allows reducing conditions to persist in the interior of aggregates despite aerated advecting external solutes, causing As, Mn, and Fe to migrate from the reduced aggregate interiors to the aerated exterior region. Upon transitioning to anoxic conditions in the external solutes, pulses of As, Mn and Fe are released into the advecting solution, while, conversely, a transition to aerated conditions in the exterior resulted in a cessation of As, Mn, and Fe release. Importantly, we find that As(III) oxidation by birnessite is appreciable only in the presence of O2; oxidation of As(III) to As(V) by Mn-oxides ceases under anaerobic conditions apparently as a result of microbially mediated Mn(IV/III) reduction. Our results demonstrate the importance of considering redox conditions and the physical complexity of soils in determining As dynamics, where redox transitions can either enhance or inhibit As release due to speciation shifts in both sorbents (solubilization versus precipitation of Fe and Mn oxides) and sorbates (As).

  3. Effect of initial temperature on water aggregation at a cold surface.

    PubMed

    Kier, Lemont B; Cheng, Chao-Kun

    2013-01-01

    Cellular automata models of water at two initial temperatures were created. Each model was exposed to a freezing surface. The formation of fully bonded water cells, f(4), was observed over time, beginning with a model of initially warm water and with initially cool water. The warm water formed more f(4) cells earlier than the initially cool water. A high percentage of f(4) cells is interpreted as the formation of ice. This is a model of the Mpemba effect. A description of the initial states for these two temperatures is offered in explanation of this effect. PMID:23341213

  4. 76 FR 11187 - Due Date of Initial Application Requirements for State Home Construction Grant

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-01

    ... assistance for a State home construction project (or acquisition of an existing facility to be used as a... Construction Grant AGENCY: Department of Veterans Affairs. ACTION: Proposed rule. SUMMARY: This document... must receive an initial application for a State Home Construction Grant in order for the application...

  5. Field site leaching from recycled concrete aggregates applied as sub-base material in road construction.

    PubMed

    Engelsen, Christian J; Wibetoe, Grethe; van der Sloot, Hans A; Lund, Walter; Petkovic, Gordana

    2012-06-15

    The release of major and trace elements from recycled concrete aggregates used in an asphalt covered road sub-base has been monitored for more than 4 years. A similar test field without an asphalt cover, directly exposed to air and rain, and an asphalt covered reference field with natural aggregates in the sub-base were also included in the study. It was found that the pH of the infiltration water from the road sub-base with asphalt covered concrete aggregates decreased from 12.6 to below pH 10 after 2.5 years of exposure, whereas this pH was reached within only one year for the uncovered field. Vertical temperature profiles established for the sub-base, could explain the measured infiltration during parts of the winter season. When the release of major and trace elements as function of field pH was compared with pH dependent release data measured in the laboratory, some similar pH trends were found. The field concentrations of Cd, Ni, Pb and Zn were found to be low throughout the monitoring period. During two of the winter seasons, a concentration increase of Cr and Mo was observed, possibly due to the use of de-icing salt. The concentrations of the trace constituents did not exceed Norwegian acceptance criteria for ground water and surface water Class II. PMID:22554532

  6. Highly selective fluorogenic multianalyte biosensors constructed via enzyme-catalyzed coupling and aggregation-induced emission.

    PubMed

    Wang, Xiaorui; Hu, Jinming; Zhang, Guoying; Liu, Shiyong

    2014-07-16

    The development of a highly selective and fast responsive fluorogenic biosensor for diverse analytes ranging from bioactive small molecules to specific antigens is highly desirable but remains a considerable challenge. We herein propose a new approach by integrating substrate-selective enzymatic reactions with fluorogens exhibiting aggregation-induced emission feature. Tyrosine-functionalized tetraphenylethene, TPE-Tyr, molecularly dissolves in aqueous media with negligible fluorescence emission; upon addition of horseradish peroxidase (HRP) and H2O2, effective cross-linking occurs due to HRP-catalyzed oxidative coupling of tyrosine moieties in TPE-Tyr. This leads to fluorescence emission turn-on and fast detection of H2O2 with high sensitivity and selectivity. As a validation of the new strategy's generality, we further configure it into the biosensor design for glucose through cascade enzymatic reactions and for pathologically relevant antigens (e.g., human carcinoembryonic antigen) by combining with the ELISA kit. PMID:24983204

  7. CONSTRUCTION PROGRESS PHOTO OF REMOTE ANALYTICAL FACILITY (CPP627) SHOWING INITIAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    CONSTRUCTION PROGRESS PHOTO OF REMOTE ANALYTICAL FACILITY (CPP-627) SHOWING INITIAL EXCAVATION. INL PHOTO NUMBER NRTS-54-10703. Unknown Photographer, 5/21/1954 - Idaho National Engineering Laboratory, Idaho Chemical Processing Plant, Fuel Reprocessing Complex, Scoville, Butte County, ID

  8. The Properties of Mortar Mixtures Blended with Natural, Crushed, and Recycled Fine Aggregates for Building Construction Materials

    SciTech Connect

    Yu, Myoung-Youl; Lee, Jae-Yong; Chung, Chul-Woo

    2012-01-12

    In this research, the possible applicability of fine aggregates blended with natural, crushed, and recycled fine aggregate are discussed. The fresh and hardened properties of mortar using blended fine aggregates are monitored depending on various blending ratio of fine aggregates. Newly developed ternary diagram was also utilized for better interpretation of the data. It was found that air content increased and unit weight decreased as recycled fine aggregate content increased. With moisture type processing of recycled fine aggregate, the mortar flow was not negatively affected by increase in the recycled fine aggregate content. The ternary diagram is found to be an effective graphical presentation tool that can be used for the quality evaluation of mortar using blended fine aggregate.

  9. Chapter K: Progress in the Evaluation of Alkali-Aggregate Reaction in Concrete Construction in the Pacific Northwest, United States and Canada

    USGS Publications Warehouse

    Shrimer, Fred H.

    2005-01-01

    The supply of aggregates suitable for use in construction and maintenance of infrastructure in western North America is a continuing concern to the engineering and resources-management community. Steady population growth throughout the region has fueled demand for high-quality aggregates, in the face of rapid depletion of existing aggregate resources and slow and difficult permitting of new sources of traditional aggregate types. In addition to these challenges, the requirement for aggregates to meet various engineering standards continues to increase. In addition to their physical-mechanical properties, other performance characteristics of construction aggregates specifically depend on their mineralogy and texture. These properties can result in deleterious chemical reactions when aggregate is used in concrete mixes. When this chemical reaction-termed 'alkali-aggregate reaction' (AAR)-occurs, it can pose a major problem for concrete structures, reducing their service life and requiring expensive repair or even replacement of the concrete. AAR is thus to be avoided in order to promote the longevity of concrete structures and to ensure that public moneys invested in infrastructure are well spent. Because the AAR phenomenon is directly related to the mineral composition, texture, and petrogenesis of the rock particles that make up aggregates, an understanding of the relation between the geology and the performance of aggregates in concrete is important. In the Pacific Northwest, some aggregates have a moderate to high AAR potential, but many others have no or only a low AAR potential. Overall, AAR is not as widespread or serious a problem in the Pacific Northwest as in other regions of North America. The identification of reactive aggregates in the Pacific Northwest and the accurate prediction of their behavior in concrete continue to present challenges for the assessment and management of geologic resources to the owners and operators of pits and quarries and to the

  10. Exploring Factors Influencing Collaborative Knowledge Construction in Online Discussions: Student Facilitation and Quality of Initial Postings

    ERIC Educational Resources Information Center

    Ioannou, Andri; Demetriou, Skevi; Mama, Maria

    2014-01-01

    Although lots of studies have investigated collaborative knowledge construction in online courses, the factors influencing this process are yet to be fully determined. This study provides quantitative and qualitative types of evidence on how (naturally emerged) student facilitation and quality of initial postings influence collaborative knowledge…

  11. Long-term survival of Escherichia coli in lightweight aggregate filter media of constructed wastewater treatment wetlands.

    PubMed

    Paruch, A M

    2011-01-01

    A laboratory scale experiment on the survival of Escherichia coli in samples of filter media from a horizontal subsurface flow constructed wetland treating domestic wastewater was performed. A concentration of E. coli was examined in samples collected from a wetland filter filled with lightweight aggregates (LWA). All samples testing positive for E. coli contamination were used to examine the effect of storage time on the survival of E. coli at three temperature regimes: cold (4°C), mild (10°C) and warm (22°C). It was found that the mild storage condition favoured the growth and survival of E. coli in the tested LWA media. The growth in samples of the uppermost layer of the media lasted for 5.5 months, during which E. coli reached a maximum concentration of 6.4×10(3) MPN/100 g dry matter in the media. It was also observed that E. coli had a greater capacity to survive for extended periods of time in samples collected from the upper layer of the LWA filter compared to samples taken from the deeper layers. The survival of E. coli in the shallowest samples of the wetland filter was remarkably long and unexpected, lasting for a period of over 14 months. PMID:21278480

  12. Brief summary of staffing levels at Fermilab during initial construction years

    SciTech Connect

    Livdahl, P.V.

    1983-11-01

    This paper very briefly summarizes the work of the various groups that were involved from the beginning through the end of the initial construction phase of the Fermilab project (defined here to be July 1, 1972) and the final construction or completion phase which is here defined as December 31, 1973. The numbers in this report have been gathered by examining the personnel records of Fermilab with the research being done by Chuck Marofske, the Head of Laboratory Services and his staff and by assembling information from the memories of people still with the laboratory in 1983. Since there was much mobility within the laboratory during the construction years and frequent reorganizations were the norm, the numbers presented herein can not be considered to be more accurate than about +- 5%.

  13. Conceptual design and analysis of roads and road construction machinery for initial lunar base operations

    NASA Astrophysics Data System (ADS)

    Sines, Jeffrey L.; Banks, Joel; Efatpenah, Keyanoush

    1990-06-01

    Recent developments have made it possible for scientists and engineers to consider returning to the Moon to build a manned lunar base. The base can be used to conduct scientific research, develop new space technology, and utilize the natural resources of the Moon. Areas of the base will be separated, connected by a system of roads that reduce the power requirements of vehicles traveling on them. Feasible road types for the lunar surface were analyzed and a road construction system was designed for initial lunar base operations. A model was also constructed to show the system configuration and key operating features. The alternate designs for the lunar road construction system were developed in four stages: analyze and select a road type; determine operations and machinery needed to produce the road; develop machinery configurations; and develop alternates for several machine components. A compacted lunar soil road was selected for initial lunar base operations. The only machinery required to produce this road were a grader and a compactor. The road construction system consists of a main drive unit which is used for propulsion, a detachable grader assembly, and a towed compactor.

  14. Conceptual design and analysis of roads and road construction machinery for initial lunar base operations

    NASA Technical Reports Server (NTRS)

    Sines, Jeffrey L.; Banks, Joel; Efatpenah, Keyanoush

    1990-01-01

    Recent developments have made it possible for scientists and engineers to consider returning to the Moon to build a manned lunar base. The base can be used to conduct scientific research, develop new space technology, and utilize the natural resources of the Moon. Areas of the base will be separated, connected by a system of roads that reduce the power requirements of vehicles traveling on them. Feasible road types for the lunar surface were analyzed and a road construction system was designed for initial lunar base operations. A model was also constructed to show the system configuration and key operating features. The alternate designs for the lunar road construction system were developed in four stages: analyze and select a road type; determine operations and machinery needed to produce the road; develop machinery configurations; and develop alternates for several machine components. A compacted lunar soil road was selected for initial lunar base operations. The only machinery required to produce this road were a grader and a compactor. The road construction system consists of a main drive unit which is used for propulsion, a detachable grader assembly, and a towed compactor.

  15. Staphylococcal enterotoxin B initiates protein kinase C translocation and eicosanoid metabolism while inhibiting thrombin-induced aggregation in human platelets.

    PubMed

    Tran, Uyen; Boyle, Thomas; Shupp, Jeffrey W; Hammamieh, Rasha; Jett, Marti

    2006-08-01

    Staphylococcal enterotoxin (SE) B, a heat-stable toxin secreted by Staphylococcus aureus, has been implicated in the pathogenesis and exacerbation of several critical illnesses. It has been hypothesized that enterotoxins may interact with blood products such as platelets, in addition to T-lymphocytes and renal proximal tubule cells. The aim of this present study was to elucidate whether SEB directly alters human platelet function. Human platelet rich plasma (PRP) was pre-incubated with SEA, SEB, SEC or TSST-1, (at various concentrations and incubation times). After incubation, PRP was exposed to thrombin and aggregation was assessed. Incubation with all toxins tested resulted in decreased aggregation, specifically; exposure to 10mu g/ml of SEB for 30 min caused a 20% decrease and a 49% decrease at 90 min. A similar reduction in aggregation was seen in samples incubated with phorbol myristate acetate, a known stimulator of protein kinase C (PKC). Further, platelets exposed to SEB exhibited an increased plasma membrane PKC activity. Sphingosine, an inhibitor of PKC proved to block the SEB-induced reduction in aggregation. SEB effects on platelet metabolism were investigated using high performance liquid chromatography showing up to a 2-fold increase of active metabolites lipoxin A4 and 12-HETE, as compared to control. These data indicate that SEB is able to induce platelet dysfunction, and these effects may be mediated through activation of PKC. PMID:16550298

  16. Recycled brake linings as partial aggregate substitute in asphalt paving. Construction and final report. Report for July 1992-August 1996

    SciTech Connect

    Miller, P.A.; Sukley, R.

    1996-09-01

    The purpose of this project was to evaluate the performance of asphalt containing various percentages of brake lining as an aggregate, and compare its performance to that of normal asphalt containing natural aggregate. This project is an effort to explore alternate ways to use waste product. Four test section of FB-2 Modified mix containing brake lining materials were placed in July 1992 along with one control section on SR 3022 in Mercer county. To date all sections are performing satisfactory, and Brake linings should be recommended as a viable partial replacement of aggregate in bituminous materials. This study only considered the performance of only off-spec brake linings, therefore, any performance data or enviromental effects of placement of used brake material should be addressed.

  17. nDEP-driven cell patterning and bottom-up construction of cell aggregates using a new bioelectronic chip.

    PubMed

    Menad, S; Franqueville, L; Haddour, N; Buret, F; Frenea-Robin, M

    2015-04-01

    Creating cell aggregates of controlled size and shape and patterning cells on substrates using a bottom-up approach constitutes important challenges for tissue-engineering applications and studies of cell-cell interactions. In this paper, we report nDEP (negative dielectrophoresis) driven assembly of cells as compact aggregates or onto defined areas using a new bioelectronic chip. This chip is composed of a quadripolar electrode array obtained using coplanar electrodes partially covered with a thin, micropatterned PDMS membrane. This thin PDMS layer was coated with poly-L-lysine and played the role of adhesive substrate for cell patterning. For the formation of detachable cell aggregates, the PDMS was not pretreated and cells were simply immobilized into assemblies maintained by cell-cell adhesion after the electric field removal. Cell viability after exposition to DEP buffer was also assessed, as well as cell spreading activity following DEP-driven assembly. PMID:25595475

  18. Initial Design and Construction of a Mobil Regenerative Fuel Cell System

    NASA Technical Reports Server (NTRS)

    Colozza, Anthony J.; Maloney, Thomas; Hoberecht, Mark (Technical Monitor)

    2003-01-01

    The design and initial construction of a mobile regenerative power system is described. The main components of the power system consists of a photovoltaic array, regenerative fuel cell and electrolyzer. The system is mounted on a modified landscape trailer and is completely self contained. An operational analysis is also presented that shows predicted performance for the system at various times of the year. The operational analysis consists of performing an energy balance on the system based on array output and total desired operational time.

  19. THE MURMANSK INITIATIVE - RF: COMPLETING CONSTRUCTION AND START-UP TESTING

    SciTech Connect

    CZAJKOWSKI,C.; BOWERMAN,B.S.; DYER,R.S.; SORLIE,A.A.; WESTER,D.

    1998-03-01

    The Murmansk Initiative - RF was instigated to address Russia's ability to meet the London Convention prohibiting ocean dumping of radioactive waste. The Initiative, under a trilateral agreement, will upgrade an existing low-level liquid radioactive waste treatment facility, increasing capacity from 1,200 m{sup 3}/year to 5,000 m{sup 3}/year, and expand the capability to treat liquids containing salt (up to 10 g/L). The three parties to the agreement, the Russian Federation, Norway, and the US, have split the costs for the project. All construction has been provided by Russia. Construction of mechanical systems (piping and valves, pumps, sorbent columns, settling tanks, surge tanks) is nearly complete, with instrumentation and control (I+C) systems the last to be installed. Delays to the I+C installation have occurred because changes in system specifications required some additional US-supplied computer control equipment to be purchased, and clearance through customs (both US and Russian) has been slow. Start-up testing has been limited to testing of some isolated sub-systems because of the delays in I+C installation. Final construction activities are also hampered by the current state of the Russian economy. The specific impact has been completion of the cementation unit, which was not funded under the trilateral agreement (but funded by the Russian government). Russian regulatory authorities have stated that final licensing for expanded capacity (5,000 m{sup 3}/year) will not be given until the cementation unit is on-line.

  20. The role of feedback mechanisms in the initial development of the constructed catchment Chicken Creek

    NASA Astrophysics Data System (ADS)

    Schaaf, Wolfgang; Hinz, Christoph; Gerwin, Werner; Zaplata, Markus; Hüttl, Reinhard F.

    2015-04-01

    Over a period of ten years, we investigated the initial development of the constructed catchment 'Chicken Creek', south of Cottbus, Germany (Gerwin et al., 2009). Since the boundary conditions and inner structures of the hillslope are well known and documented (Gerwin et al., 2011), the site offers unique possibilities to study the relevant processes of ecosystem development interacting with various structures and patterns. We observed considerable changes within the catchment (Elmer et al., 2013). Both internal and external factors could be identified as driving forces for the formation of structures and patterns in the artificial catchment. Initial structures formed by the construction process and initial substrate characteristics were decisive for the distribution and flow of water. External factors like episodic events triggered erosion and dissection during this initial phase, promoted by the low vegetation cover and the unconsolidated sandy substrate (Schaaf et al., 2013). With time, secondary structures and patterns evolved and became more and more important. Invading biota and vegetation succession initialized abiotic/biotic feedback mechanisms resulting in pattern and habitat formation, and generally in increased differentiation, heterogeneity and complexity that are typical characteristics of ecosystems (Schaaf et al., 2011). The processes and feedback mechanisms in the initial development of a new landscape may deviate in rates, intensity, and dominance from those known from mature ecosystems. It is therefore crucial to understand these early phases of ecosystem development and to disentangle the increasingly complex interactions between the evolving terrestrial and aquatic, biotic, and abiotic compartments of the system. Elmer M, Gerwin W, Schaaf W, Zaplata MK, Hohberg K, Nenov R, Bens O, Hüttl RF (2013): Dynamics of initial ecosystem development at the artificial catchment Chicken Creek, Lusatia, Germany. Environ Earth Sci 69, 491-505. Gerwin W

  1. Transport and Aggregation of Nanoparticles in Packed Beds: Effects of Pore Velocity and Initially-Fed Particle Size on Transient Particle Size Distributions

    NASA Astrophysics Data System (ADS)

    Pham, Ngoc; Papavassiliou, Dimitrios

    2015-11-01

    Aggregation of colloidal particles in flow through porous media has received careful consideration, as it reduces particle breakthrough due to pore clogging and sedimentation. Additionally, in unstable colloidal systems, deposition of colloidal aggregates on the pore surfaces can create sub-surfaces for further colloidal attachment. This phenomenon is known as ripening effect. In this study, transient particle size distributions of nano-particle systems, propagating in a bed packed with spheres are numerically investigated. In our simulation, only pair interactions are considered, and the aggregation rate is varied with the relative position of two particles in a pair. The packed bed consists of spheres of known size, randomly packed in a simulation box. To generate the velocity field of water inside the porous medium, the lattice Boltzmann method (LBM) is used. In conjunction with that, the trajectories of thousands of massless particles moving with the flow under convection and diffusion are recorded employing a Lagrangian framework. While pore clogging is neglected, we draw attention to the change of the distribution of particle size under different pore velocities and different initially-fed particle sizes.

  2. Construction of initial vortex-surface fields and Clebsch potentials for flows with high-symmetry using first integrals

    NASA Astrophysics Data System (ADS)

    He, Pengyu; Yang, Yue

    2016-03-01

    We report a systematic study on the construction of the explicit, general form of vortex-surface fields (VSFs) and Clebsch potentials in the initial fields with the zero helicity density and high symmetry. The construction methodology is based on finding independent first integrals of the characteristic equation of a given three-dimensional velocity-vorticity field. In particular, we derive the analytical VSFs and Clebsch potentials for the initial field with the Kida-Pelz symmetry. These analytical results can be useful for the evolution of VSFs to study vortical structures in transitional flows. Moreover, the generality of the construction method is discussed with the synthetic initial fields and the initial Taylor-Green field with multiple wavenumbers.

  3. Virtual Faces Expressing Emotions: An Initial Concomitant and Construct Validity Study

    PubMed Central

    Joyal, Christian C.; Jacob, Laurence; Cigna, Marie-Hélène; Guay, Jean-Pierre; Renaud, Patrice

    2014-01-01

    Background: Facial expressions of emotions represent classic stimuli for the study of social cognition. Developing virtual dynamic facial expressions of emotions, however, would open-up possibilities, both for fundamental and clinical research. For instance, virtual faces allow real-time Human–Computer retroactions between physiological measures and the virtual agent. Objectives: The goal of this study was to initially assess concomitants and construct validity of a newly developed set of virtual faces expressing six fundamental emotions (happiness, surprise, anger, sadness, fear, and disgust). Recognition rates, facial electromyography (zygomatic major and corrugator supercilii muscles), and regional gaze fixation latencies (eyes and mouth regions) were compared in 41 adult volunteers (20 ♂, 21 ♀) during the presentation of video clips depicting real vs. virtual adults expressing emotions. Results: Emotions expressed by each set of stimuli were similarly recognized, both by men and women. Accordingly, both sets of stimuli elicited similar activation of facial muscles and similar ocular fixation times in eye regions from man and woman participants. Conclusion: Further validation studies can be performed with these virtual faces among clinical populations known to present social cognition difficulties. Brain–Computer Interface studies with feedback–feedforward interactions based on facial emotion expressions can also be conducted with these stimuli. PMID:25324768

  4. Construction and initial validation of the Gendered Racial Microaggressions Scale for Black women.

    PubMed

    Lewis, Jioni A; Neville, Helen A

    2015-04-01

    The purpose of this study was to develop a measure of gendered racial microaggressions (i.e., subtle and everyday verbal, behavioral, and environmental expressions of oppression based on the intersection of one's race and gender) experienced by Black women by applying an intersectionality framework to Essed's (1991) theory of gendered racism and Sue, Capodilupo, et al.'s (2007) model of racial microaggressions. The Gendered Racial Microaggressions Scale (GRMS), was developed to assess both frequency and stress appraisal of microaggressions, in 2 separate studies. After the initial pool of GRMS items was developed, we received input from a community-based focus group of Black women and an expert panel. In Study 1, an exploratory factor analysis using a sample of 259 Black women resulted in a multidimensional scale with 4 factors as follows: (a) Assumptions of Beauty and Sexual Objectification, (b) Silenced and Marginalized, (c) Strong Black Woman Stereotype, and (d) Angry Black Woman Stereotype. In Study 2, results of confirmatory factor analyses using an independent sample of 210 Black women suggested that the 4-factor model was a good fit of the data for both the frequency and stress appraisal scales. Supporting construct validity, the GRMS was positively related to the Racial and Ethnic Microaggressions Scale (Nadal, 2011) and the Schedule of Sexist Events (Klonoff & Landrine, 1995). In addition, the GRMS was significantly related to psychological distress, such that greater perceived gendered racial microaggressions were related to greater levels of reported psychological distress. Implications for future research and practice are discussed. PMID:25867696

  5. Driving Cartilage Formation in High-Density Human Adipose-Derived Stem Cell Aggregate and Sheet Constructs Without Exogenous Growth Factor Delivery

    PubMed Central

    Dang, Phuong N.; Solorio, Loran D.

    2014-01-01

    An attractive cell source for cartilage tissue engineering, human adipose-derived stem cells (hASCs) can be easily expanded and signaled to differentiate into chondrocytes. This study explores the influence of growth factor distribution and release kinetics on cartilage formation within 3D hASC constructs incorporated with transforming growth factor-β1 (TGF-β1)-loaded gelatin microspheres. The amounts of microspheres, TGF-β1 concentration, and polymer degradation rate were varied within hASC aggregates. Microsphere and TGF-β1 loading concentrations were identified that resulted in glycosaminoglycan (GAG) production comparable to those of control aggregates cultured in TGF-β1-containing medium. Self-assembling hASC sheets were then engineered for the production of larger, more clinically relevant constructs. Chondrogenesis was observed in hASC-only sheets cultured with exogenous TGF-β1 at 3 weeks. Importantly, sheets with incorporated TGF-β1-loaded microspheres achieved GAG production similar to sheets treated with exogenous TGF-β1. Cartilage formation was confirmed histologically via observation of cartilage-like morphology and GAG staining. This is the first demonstration of the self-assembly of hASCs into high-density cell sheets capable of forming cartilage in the presence of exogenous TGF-β1 or with TGF-β1-releasing microspheres. Microsphere incorporation may bypass the need for extended in vitro culture, potentially enabling hASC sheets to be implanted more rapidly into defects to regenerate cartilage in vivo. PMID:24873753

  6. Construction of initial vortex-surface fields and Clebsch potentials for flows with high-symmetry using first integrals

    NASA Astrophysics Data System (ADS)

    He, Pengyu; Yang, Yue

    2015-11-01

    We develop a systematic methodology to construct the explicit, general form of vortex-surface fields (Yang and Pullin, J. Fluid Mech., 661, 2010) and Clebsch potentials based on first integrals of the characteristic equation of a given three-dimensional velocity-vorticity field. This methodology is successfully applied to the initial fields with the zero helicity density and high symmetry, e.g., initial fields with the Taylor-Green and the Kida-Pelz symmetries.

  7. The Community College Survey of Men: An Initial Validation of the Instrument's Non-Cognitive Outcomes Construct

    ERIC Educational Resources Information Center

    Wood, J. \\Luke; Harris, Frank, III.

    2013-01-01

    The purpose of this manuscript is to discuss the utility of the Community College Survey of Men (CCSM[c]), an instrument designed to examine predictors of student success for men in community colleges. The authors highlight initial validation results from a recent pilot of the CCSM[c], with a focus on the non-cognitive outcomes construct employed…

  8. Characterization and environmental risk assessment of heavy metals in construction and demolition wastes from five sources (chemical, metallurgical and light industries, and residential and recycled aggregates).

    PubMed

    Gao, Xiaofeng; Gu, Yilu; Xie, Tian; Zhen, Guangyin; Huang, Sheng; Zhao, Youcai

    2015-06-01

    Total concentrations of heavy metals (Cu, Zn, Pb, Cr, Cd, and Ni) were measured among 63 samples of construction and demolition (C&D) wastes collected from chemical, metallurgical and light industries, and residential and recycled aggregates within China for risk assessment. The heavy metal contamination was primarily concentrated in the chemical and metallurgical industries, especially in the electroplating factory and zinc smelting plant. High concentrations of Cd were found in light industry samples, while the residential and recycled aggregate samples were severely polluted by Zn. Six most polluted samples were selected for deep research. Mineralogical analysis by X-ray fluorescence (XRF) spectrometry and X-ray diffraction (XRD), combined with element speciation through European Community Bureau of Reference (BCR) sequential extraction, revealed that a relatively slight corrosion happened in the four samples from electroplating plants but high transfer ability for large quantities of Zn and Cu. Lead arsenate existed in the acid extractable fraction in CI7-8 and potassium chromium oxide existed in the mobility fraction. High concentration of Cr could be in amorphous forms existing in CI9. The high content of sodium in the two samples from zinc smelter plants suggested severe deposition and erosion on the workshop floor. Large quantities of Cu existed as copper halide and most of the Zn appeared to be zinc, zinc oxide, barium zinc oxide, and zincite. From the results of the risk assessment code (RAC), the samples from the electroplating factory posed a very high risk of Zn, Cu, and Cr, a high risk of Ni, a middle risk of Pb, and a low risk of Cd. The samples from the zinc smelting plant presented a high risk of Zn, a middle risk of Cu, and a low risk of Pb, Cr, Cd, and Ni. PMID:25601613

  9. Clarifying the Differences between Training, Development, and Enrichment: The Role of Institutional Belief Constructs in Creating the Purpose of Faculty Learning Initiatives

    ERIC Educational Resources Information Center

    Stabile, Christopher; Ritchie, William F.

    2013-01-01

    This article suggests that institutional attitude toward faculty learning initiatives, which is determined by its belief constructs, influences how faculty learning initiatives will be interpreted and applied. A construct is the organizing framework where an institution demonstrates its belief and values regarding faculty learning initiatives.…

  10. Numerical construction of initial data for Einstein's equations with static extension to space-like infinity

    NASA Astrophysics Data System (ADS)

    Doulis, Georgios; Rinne, Oliver

    2016-04-01

    We describe a numerical method to construct Cauchy data extending to space-like infinity based on Corvino's (2000) gluing method. Adopting the setting of Giulini and Holzegel (2005), we restrict ourselves here to vacuum axisymmetric spacetimes and glue a Schwarzschildean end to Brill-Lindquist data describing two non-rotating black holes. Our numerical implementation is based on pseudo-spectral methods and we carry out extensive convergence tests to check the validity of our numerical results. We also investigate the dependence of the total ADM mass on the details of the gluing construction.

  11. Career Adapt-Abilities Scale--China Form: Construction and Initial Validation

    ERIC Educational Resources Information Center

    Hou, Zhi-Jin; Leung, S. Alvin; Li, Xixi; Li, Xu; Xu, Hui

    2012-01-01

    The Career Adapt-Abilities Scale (CAAS)--China Form consists of four subscales, with six items each to measure Concern, Control, Curiosity, and Confidence as psychosocial resources for managing occupational transitions, developmental tasks, and work traumas. This study investigated the construction and validation of its Chinese Form. Results…

  12. Initiating Culturally Responsive Teaching for Identity Construction in the Malaysian Classrooms

    ERIC Educational Resources Information Center

    Idrus, Faizah

    2014-01-01

    This article presents evidence to the need for Culturally Responsive Teaching (CRT) to construct students' identity in the Malaysian classrooms. Since an important objective of education is to prepare individuals to exercise efficaciously in their environment, all students in multicultural society could benefit from exposure to CRT (Gay, 2000). In…

  13. Young workers in the construction industry and initial OSH-training when entering work life.

    PubMed

    Holte, Kari Anne; Kjestveit, Kari

    2012-01-01

    Studies have found that young workers are at risk for injuries. The risk for accidents is high within construction, indicating that young workers may be especially vulnerable in this industry. In Norway, it is possible to enter the construction industry as a full time worker at the age of 18. The aim of this paper was to explore how young construction workers are received at their workplace with regards to OHS-training. The study was designed as a qualitative case study. Each case consisted of a young worker or apprentice (< 25 years), a colleague, the immediate superior, the OHS manager, and a safety representative in the company. The interviews were recorded and analyzed through content analysis. The results showed that there were differences between large and small companies, where large companies had more formalized routines and systems for receiving and training young workers. These routines were however more dependent on requirements set by legislators and contractors more than by company size, since the legislation has different requirements with impact on OHS. PMID:22317356

  14. The Support Appraisal for Work Stressors Inventory: Construction and Initial Validation

    ERIC Educational Resources Information Center

    Lawrence, Sandra A.; Gardner, John; Callan, Victor J.

    2007-01-01

    In order to better understand the role of perceived available support in buffering the negative effects of workplace stressors, a new multidimensional measure of perceived available support, the SAWS, was developed. Initial item development and content validation were conducted, followed by scale evaluation and validation. Two samples of 190 and…

  15. Deriving Childhood Temperament Measures from Emotion-Eliciting Behavioral Episodes: Scale Construction and Initial Validation

    ERIC Educational Resources Information Center

    Gagne, Jeffrey R.; Van Hulle, Carol A.; Aksan, Nazan; Essex, Marilyn J.; Goldsmith, H. Hill

    2011-01-01

    The authors describe the development and initial validation of a home-based version of the Laboratory Temperament Assessment Battery (Lab-TAB), which was designed to assess childhood temperament with a comprehensive series of emotion-eliciting behavioral episodes. This article provides researchers with general guidelines for assessing specific…

  16. Psychosocial Costs of Racism to Whites Scale (PCRW): Construction and Initial Validation

    ERIC Educational Resources Information Center

    Spanierman, Lisa B.; Heppner, Mary J.

    2004-01-01

    This investigation reports on the development and initial validation of the Psychosocial Costs of Racism to Whites Scale (PCRW), which operationalizes the idea that racism has a host of psychosocial costs for White individuals. Data from 727 participants were collected in 3 interrelated studies that subjected the items to the rigors of both…

  17. Design, construction, and initial operation of the Los Alamos National Laboratory salt-gradient solar pond

    SciTech Connect

    Jones, G.F.; Meyer, K.A.; Hedstrom, J.C.; Dreicer, J.S.; Grimmer, D.P.

    1983-01-01

    A 232 m/sup 2/ solar pond was constructed at Los Alamos National Laboratory for the purpose of studying pond hydrodynamics on a large scale and to complement the flow visualization and one-dimensional pond simulator experiments that are ongoing at the Laboratory. Design methods and construction techniques, some of which are unique to this pond, are described in detail. The pond was excavated from a soft volcanic rock known as tuff; such rock forms a large fraction of the Los Alamos area surface geology. Because tuff has a small thermal conductivity, little insulation was required to reduce perimeter energy losses. In addition, the strength of tuff permitted the pond to be built with vertical side walls; this design eliminated local side wall convection in the gradient zone that is possible with sloping side walls. Instrumentation in the pond consists of traversing and fixed rakes of thermometers and salinity probes, an underwater pyranometer, and a weather station. The traversing rake is a wheeled trolley driven vertically on a rectangular rail. Installed on the trolley are coplanar platinum RTDs, a point conductivity probe, and an induction salinometer. The stationary rake supports 28 thermocouples and 28 sample-fluid withdrawal taps located every 10 cm. About 127 T of sodium chloride has been introduced and is nearly dissolved. A 120-cm-thick salinity gradient was established and the pond is heating. Preliminary results indicate a lower-convective-zone heating rate of 1.2/sup 0/C/day during the pond's first month of operation. Recommendations on pond design, construction, and instrumentation are presented.

  18. Mineral resource of the month: aggregates

    USGS Publications Warehouse

    Willett, Jason C.

    2012-01-01

    Crushed stone and construction sand and gravel, the two major types of natural aggregates, are among the most abundant and accessible natural resources on the planet. The earliest civilizations used aggregates for various purposes, mainly construction. Today aggregates provide the basic raw materials for the foundation of modern society.

  19. Joint approach for reducing eccentricity and spurious gravitational radiation in binary black hole initial data construction

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Szilágyi, Béla

    2013-10-01

    At the beginning of binary black hole simulations, there is a pulse of spurious radiation (or junk radiation) resulting from the initial data not matching astrophysical quasi-equilibrium inspiral exactly. One traditionally waits for the junk radiation to exit the computational domain before taking physical readings, at the expense of throwing away a segment of the evolution, and with the hope that junk radiation exits cleanly. We argue that this hope does not necessarily pan out, as junk radiation could excite long-lived constraint violation. Another complication with the initial data is that they contain orbital eccentricity that needs to be removed, usually by evolving the early part of the inspiral multiple times with gradually improved input parameters. We show that this procedure is also adversely impacted by junk radiation. In this paper, we do not attempt to eliminate junk radiation directly, but instead tackle the much simpler problem of ameliorating its long-lasting effects. We report on the success of a method that achieves this goal by combining the removal of junk radiation and eccentricity into a single procedure. Namely, we periodically stop a low resolution simulation; take the numerically evolved metric data and overlay it with eccentricity adjustments; run it through an initial data solver (i.e. the solver receives as free data the numerical output of the previous iteration); restart the simulation; repeat until eccentricity becomes sufficiently low; and then launch the high resolution “production run” simulation. This approach has the following benefits: (1) We do not have to contend with the influence of junk radiation on eccentricity measurements for later iterations of the eccentricity reduction procedure. (2) We reenforce constraints every time the initial data solver is invoked, removing the constraint violation excited by junk radiation previously. (3) The wasted simulation segment associated with the junk radiation’s evolution is

  20. Photophoretic force on aggregate grains

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin S.; Kimery, Jesse B.; Wurm, Gerhard; de Beule, Caroline; Kuepper, Markus; Hyde, Truell W.

    2016-01-01

    The photophoretic force may impact planetary formation by selectively moving solid particles based on their composition and structure. This generates collision velocities between grains of different sizes and sorts the dust in protoplanetary discs by composition. This numerical simulation studied the photophoretic force acting on fractal dust aggregates of μm-scale radii. Results show that aggregates tend to have greater photophoretic drift velocities than spheres of similar mass or radii, though with a greater spread in the velocity. While the drift velocities of compact aggregates continue to increase as the aggregates grow larger in size, fluffy aggregates have drift velocities which are relatively constant with size. Aggregates formed from an initially polydisperse size distribution of dust grains behave differently from aggregates formed from a monodisperse population, having smaller drift velocities with directions which deviate substantially from the direction of illumination. Results agree with microgravity experiments which show the difference of photophoretic forces with aggregation state.

  1. Modelling the initial structure dynamics of soil and sediment exemplified for a constructed hydrological catchment

    NASA Astrophysics Data System (ADS)

    Maurer, Thomas; Schneider, Anna; Gerke, Horst H.

    2016-04-01

    The structure of a hydrological catchment is determined by the geometry of the boundaries and the spatial distribution of soil and sediment properties. Models of the 3D subsurface structure and the soil heterogeneity have often been built based on geostatistical approaches and conditional simulations for spatial interpolation between measurements. Here, an alternative model was proposed that generated 3D subsurface structures by imitating basic structures resulting from mass distribution processes. Instead of directly assuming stochastic variations of the subsurface structure, the present approach assumed stochastic variations in parameters of the process-based algorithms of the generator models. The constructed hydrological catchment "Hühnerwasser" located in the Lower Lusatia region of Brandenburg, Germany, was used as an example for the development of such a 3D structure generator model. Boundary geometries and changes in the surface topography due to erosion and sedimentation processes were quantified on the basis of digital elevation models (DEMs) derived from aerial photographs and terrestrial laser scanning information. Basic sediment properties came i) from a geological model of the parent material at the outcrop site, ii) from actual soil sample measurements on-site, and iii) based on stochastic texture variations. Sediment distributions were generated according to construction processes such as sediment dumping, particle segregation, and soil compaction. The resulting internal structures reflect the formation of spoil cones and surface compaction by machinery. The simulated 3D model scenarios of soil texture and bulk density distributions were incorporated in a gridded 3D volume model using the 3D software tool GoCAD (Paradigm Ltd.). This 3D distributed solid phase structure of the catchment allowed for a more direct comparison with observations using minimal invasive methods. By including structural changes over time (e.g., derived from DEM

  2. Design, construction, and initial operation of the SNS MEBT chopper system

    SciTech Connect

    Hardekopf, R. A.

    2004-01-01

    The chopper system for the Spallation Neutron Source (SNS) provides a gap in the beans for clean extraction from the accumulator ring. It consists of a pre-chopper in the low-energy bean transport (LEBT) and a faster chopper in the medium-energy beam transport (MEBT). We report here on the final design, fabrication, installation, and first beans tests of the MEBT chopper. The traveling-wave deflector is a meander-line design that matches the propagation of the deflecting pulse with the velocity of the beam at 2.5 MeV, after the radio-frequency quadrupole (RFQ) acceleration stage. The pulses uses a series of fast-risetime MOSFET transistors to generate the deflecting pulses of +- 2.5 kV with rise and fall times of 10 ns. We describe the design and fabrication of the meander line and pulsers and report on the first operation during initial beam tests at SNS.

  3. Biogeochemistry in the initial phase of the constructed catchment Chicken Creek

    NASA Astrophysics Data System (ADS)

    Schaaf, Wolfgang; Claudia, Zönnchen

    2014-05-01

    We studied biogeochemical processes over a period of 8 years at the constructed catchment Chicken Creek, NE Germany. The site with a size of 6 ha and defined boundary conditions serves as a research infrastructure to study feedback mechansims during early ecosystem development. Gypsum dissolution and decalcification were important processes controlling soil solution and surface water composition and element budgets of the catchment. With invading vegetation, different patches formed. Element transformation within these patches was studied in controlled microcosm experiments using soil from the catchment and labelled plant litter of dominating species. Litter from Lotus corniculatus with low C/N ratio increased decalcification due to faster decomposition and nitrification. Potassium leached from litter was almost completely retained in the sandy soils. These results were not mere additive effects of parent materials plus plant litter, but reflect differences in biogeochemical process intensities and could result in an increasing heterogeneity of soil properties, nutrient availability, and element leaching fluxes with time. Similar trends were recorded at the field site. Compared the the low organic carbon contents in the soil (< 2 mg g-1), DOC concentrations were high. Both 14C dating of field samples and 13C labelling in the microcosms indicated that old inherited carbon was the main source of DOC.

  4. Weighted aggregation

    NASA Technical Reports Server (NTRS)

    Feiveson, A. H. (Principal Investigator)

    1979-01-01

    The use of a weighted aggregation technique to improve the precision of the overall LACIE estimate is considered. The manner in which a weighted aggregation technique is implemented given a set of weights is described. The problem of variance estimation is discussed and the question of how to obtain the weights in an operational environment is addressed.

  5. Black holes and fundamental fields in numerical relativity: Initial data construction and evolution of bound states

    NASA Astrophysics Data System (ADS)

    Okawa, Hirotada; Witek, Helvi; Cardoso, Vitor

    2014-05-01

    Fundamental fields are a natural outcome in cosmology and particle physics and might therefore serve as a proxy for more complex interactions. The equivalence principle implies that all forms of matter gravitate, and one therefore expects relevant, universal imprints of new physics in strong field gravity, such as that encountered close to black holes. Fundamental fields in the vicinities of supermassive black holes give rise to extremely long-lived, or even unstable, configurations, which slowly extract angular momentum from the black hole or simply evolve nonlinearly over long time scales, with important implications for particle physics and gravitational-wave physics. Here, we perform a fully nonlinear study of scalar-field condensates around rotating black holes. We provide novel ways to specify initial data for the Einstein—Klein—Gordon system, with potential applications in a variety of scenarios. Our numerical results confirm the existence of long-lived bar modes, which act as lighthouses for gravitational wave emission: the scalar field condenses outside the black hole geometry and acts as a constant frequency gravitational-wave source for very long time scales. This effect could turn out to be a potential signature of beyond standard model physics and also a promising source of gravitational waves for future gravitational-wave detectors.

  6. The design, construction, and initial operation of a closed-cycle, salt-gradient solar pond

    SciTech Connect

    Alagao, F.B.; Akbarzadeh, A.; Johnson, P.W. )

    1994-10-01

    In operation of a closed-cycle salt-gradient solar pond (CCSGSP) system, fresh or low salinity water is supplied at the surface of the solar pond (SP) as make-up for evaporation losses as well as for surface washing. In the present investigation the surface water is flushed to an evaporation pond (EP) and concentrated for reinjection at the bottom of the SP. A 20 m[sup 2] SP incorporating an EP for concentrating brine, has been established. Theoretical modelling of the CCSGSP is presented. Results from the initial operation of the SP show that wind action and convective mixing caused some erosion of the gradient layer thereby increasing the surface layer thickness. Salt flux to the surface was found to be approximately 19 kg/m[sup 2] per year. Sodium hypochlorite solution proved successful as shock treatment during severe algal bloom. The result of acidification w as less promising in maintaining pond clarity. Occasional addition of alum helped in settling some of the suspended particulates in the pond.

  7. An anticancer drug suppresses the primary nucleation reaction that initiates the production of the toxic Aβ42 aggregates linked with Alzheimer’s disease

    PubMed Central

    Habchi, Johnny; Arosio, Paolo; Perni, Michele; Costa, Ana Rita; Yagi-Utsumi, Maho; Joshi, Priyanka; Chia, Sean; Cohen, Samuel I. A.; Müller, Martin B. D.; Linse, Sara; Nollen, Ellen A. A.; Dobson, Christopher M.; Knowles, Tuomas P. J.; Vendruscolo, Michele

    2016-01-01

    The conversion of the β-amyloid (Aβ) peptide into pathogenic aggregates is linked to the onset and progression of Alzheimer’s disease. Although this observation has prompted an extensive search for therapeutic agents to modulate the concentration of Aβ or inhibit its aggregation, all clinical trials with these objectives have so far failed, at least in part because of a lack of understanding of the molecular mechanisms underlying the process of aggregation and its inhibition. To address this problem, we describe a chemical kinetics approach for rational drug discovery, in which the effects of small molecules on the rates of specific microscopic steps in the self-assembly of Aβ42, the most aggregation-prone variant of Aβ, are analyzed quantitatively. By applying this approach, we report that bexarotene, an anticancer drug approved by the U.S. Food and Drug Administration, selectively targets the primary nucleation step in Aβ42 aggregation, delays the formation of toxic species in neuroblastoma cells, and completely suppresses Aβ42 deposition and its consequences in a Caenorhabditis elegans model of Aβ42-mediated toxicity. These results suggest that the prevention of the primary nucleation of Aβ42 by compounds such as bexarotene could potentially reduce the risk of onset of Alzheimer’s disease and, more generally, that our strategy provides a general framework for the rational identification of a range of candidate drugs directed against neurodegenerative disorders. PMID:26933687

  8. An anticancer drug suppresses the primary nucleation reaction that initiates the production of the toxic Aβ42 aggregates linked with Alzheimer's disease.

    PubMed

    Habchi, Johnny; Arosio, Paolo; Perni, Michele; Costa, Ana Rita; Yagi-Utsumi, Maho; Joshi, Priyanka; Chia, Sean; Cohen, Samuel I A; Müller, Martin B D; Linse, Sara; Nollen, Ellen A A; Dobson, Christopher M; Knowles, Tuomas P J; Vendruscolo, Michele

    2016-02-01

    The conversion of the β-amyloid (Aβ) peptide into pathogenic aggregates is linked to the onset and progression of Alzheimer's disease. Although this observation has prompted an extensive search for therapeutic agents to modulate the concentration of Aβ or inhibit its aggregation, all clinical trials with these objectives have so far failed, at least in part because of a lack of understanding of the molecular mechanisms underlying the process of aggregation and its inhibition. To address this problem, we describe a chemical kinetics approach for rational drug discovery, in which the effects of small molecules on the rates of specific microscopic steps in the self-assembly of Aβ42, the most aggregation-prone variant of Aβ, are analyzed quantitatively. By applying this approach, we report that bexarotene, an anticancer drug approved by the U.S. Food and Drug Administration, selectively targets the primary nucleation step in Aβ42 aggregation, delays the formation of toxic species in neuroblastoma cells, and completely suppresses Aβ42 deposition and its consequences in a Caenorhabditis elegans model of Aβ42-mediated toxicity. These results suggest that the prevention of the primary nucleation of Aβ42 by compounds such as bexarotene could potentially reduce the risk of onset of Alzheimer's disease and, more generally, that our strategy provides a general framework for the rational identification of a range of candidate drugs directed against neurodegenerative disorders. PMID:26933687

  9. Implications of epidermal growth factor (EGF) induced egf receptor aggregation.

    PubMed Central

    Wofsy, C; Goldstein, B; Lund, K; Wiley, H S

    1992-01-01

    To investigate the role of receptor aggregation in EGF binding, we construct a mathematical model describing receptor dimerization (and higher levels of aggregation) that permits an analysis of the influence of receptor aggregation on ligand binding. We answer two questions: (a) Can Scatchard plots of EGF binding data be analyzed productively in terms of two noninteracting receptor populations with different affinities if EGF induced receptor aggregation occurs? No. If two affinities characterize aggregated and monomeric EGF receptors, we show that the Scatchard plot should have curvature characteristic of positively cooperative binding, the opposite of that observed. Thus, the interpretation that the high affinity population represents aggregated receptors and the low affinity population nonaggregated receptors is wrong. If the two populations are interpreted without reference to receptor aggregation, an important determinant of Scatchard plot shape is ignored. (b) Can a model for EGF receptor aggregation and EGF binding be consistent with the "negative curvature" (i.e., curvature characteristic of negatively cooperative binding) observed in most Scatchard plots of EGF binding data? Yes. In addition, the restrictions on the model parameters required to obtain negatively curved Scatchard plots provide new information about binding and aggregation. In particular, EGF binding to aggregated receptors must be negatively cooperative, i.e., binding to a receptor in a dimer (or higher oligomer) having one receptor already bound occurs with lower affinity than the initial binding event. A third question we consider is whether the model we present can be used to detect the presence of mechanisms other than receptor aggregation that are contributing to Scatchard plot curvature. For the membrane and cell binding data we analyzed, the best least squares fits of the model to each of the four data sets deviate systematically from the data, indicating that additional factors are

  10. Mineral of the month: aggregates

    USGS Publications Warehouse

    Tepordei, Valentin V.

    2005-01-01

    Natural aggregates, consisting of crushed stone, and sand and gravel, are a major contributor to economic health, and have an amazing variety of uses. Aggregates are among the most abundant mineral resources and are major basic raw materials used by construction, agriculture and other industries that employ complex chemical and metallurgical processes.

  11. Antisense Proline-Arginine RAN dipeptides linked to C9ORF72-ALS/FTD form toxic nuclear aggregates that initiate in vitro and in vivo neuronal death

    PubMed Central

    Wen, Xinmei; Tan, Wenzhi; Westergard, Thomas; Krishnamurthy, Karthik; ShamamandriMarkandaiah, Shashirekha; Shi, Yingxiao; Lin, Shaoyu; Shneider, Neil A.; Monaghan, John; Pandey, Udai B.; Pasinelli, Piera; Ichida, Justin K.; Trotti, Davide

    2015-01-01

    SUMMARY Expanded GGGGCC nucleotide repeats within the C9ORF72 gene are the most common genetic mutation associated with both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Sense and antisense transcripts of these expansions are translated to form five dipeptide repeat proteins (DRPs). We employed primary cortical and motor neuron cultures, live-cell imaging, and transgenic fly models and found that the arginine-rich dipeptides, in particular Proline-Arginine (PR), are potently neurotoxic. Factors that anticipated their neurotoxicity included aggregation in nucleoli, decreased number of processing bodies, and stress granules formation, implying global translational dysregulation as path accountable for toxicity. Nuclear PR aggregates were also found in human-induced motor neurons and postmortem spinal cord tissues from C9ORF72 ALS and ALS/FTD patients. Intronic G4C2 transcripts, but not loss of C9ORF72 protein, are also toxic to motor and cortical neurons. Interestingly, G4C2 transcript-mediated neurotoxicity synergizes with that of PR aggregates, suggesting convergence of mechanisms. PMID:25521377

  12. Constructing New Expertise: Private and Public Initiatives for Safe Food (Brussels in the First Half of the Nineteenth Century)

    PubMed Central

    Scholliers, Peter

    2014-01-01

    In 1856, the mayor of Brussels proposed the establishment of a municipal laboratory with a chemist to analyse food and beverages to restrain fraud. His proposal was accepted and a laboratory – possibly one of the first municipal laboratories in Europe – was set up. The laboratory still exists today. This paper aims at tracing the conditions in which it emerged, situating it within the laissez-faire context of the time. It was brought into existence by a liberal administration, in a period of little interventionism replete with unencumbered private interests (those of bakers, butchers, grocers, millers, pharmacists, doctors and so on). What will be considered here is the general mood with regard to food fraud, fair trade, correct price, and the quality of food in the first half of the nineteenth century. On a broader level, this contribution addresses the frictions between private and public initiative, while focusing on the process of construction of expertise. The paper makes use of contemporary documents such as reviews, newspapers, association reports and city council chronicles. PMID:25284894

  13. Constructing new expertise: private and public initiatives for safe food (Brussels in the first half of the nineteenth century).

    PubMed

    Scholliers, Peter

    2014-10-01

    In 1856, the mayor of Brussels proposed the establishment of a municipal laboratory with a chemist to analyse food and beverages to restrain fraud. His proposal was accepted and a laboratory - possibly one of the first municipal laboratories in Europe - was set up. The laboratory still exists today. This paper aims at tracing the conditions in which it emerged, situating it within the laissez-faire context of the time. It was brought into existence by a liberal administration, in a period of little interventionism replete with unencumbered private interests (those of bakers, butchers, grocers, millers, pharmacists, doctors and so on). What will be considered here is the general mood with regard to food fraud, fair trade, correct price, and the quality of food in the first half of the nineteenth century. On a broader level, this contribution addresses the frictions between private and public initiative, while focusing on the process of construction of expertise. The paper makes use of contemporary documents such as reviews, newspapers, association reports and city council chronicles. PMID:25284894

  14. Global kinetic analysis of seeded BSA aggregation.

    PubMed

    Sahin, Ziya; Demir, Yusuf Kemal; Kayser, Veysel

    2016-04-30

    Accelerated aggregation studies were conducted around the melting temperature (Tm) to elucidate the kinetics of seeded BSA aggregation. Aggregation was tracked by SEC-HPLC and intrinsic fluorescence spectroscopy. Time evolution of monomer, dimer and soluble aggregate concentrations were globally analysed to reliably deduce mechanistic details pertinent to the process. Results showed that BSA aggregated irreversibly through both sequential monomer addition and aggregate-aggregate interactions. Sequential monomer addition proceeded only via non-native monomers, starting to occur only by 1-2°C below the Tm. Aggregate-aggregate interactions were the dominant mechanism below the Tm due to an initial presence of small aggregates that acted as seeds. Aggregate-aggregate interactions were significant also above the Tm, particularly at later stages of aggregation when sequential monomer addition seemed to cease, leading in some cases to insoluble aggregate formation. The adherence (or non-thereof) of the mechanisms to Arrhenius kinetics were discussed alongside possible implications of seeding for biopharmaceutical shelf-life and spectroscopic data interpretation, the latter of which was found to often be overlooked in BSA aggregation studies. PMID:26970282

  15. A cognitive neuroscience-based computerized battery for efficient measurement of individual differences: standardization and initial construct validation.

    PubMed

    Gur, Ruben C; Richard, Jan; Hughett, Paul; Calkins, Monica E; Macy, Larry; Bilker, Warren B; Brensinger, Colleen; Gur, Raquel E

    2010-03-30

    There is increased need for efficient computerized methods to collect reliable data on a range of cognitive domains that can be linked to specific brain systems. Such need arises in functional neuroimaging studies, where individual differences in cognitive performance are variables of interest or serve as confounds. In genetic studies of complex behavior, which require particularly large samples, such trait measures can serve as endophenotypes. Traditional neuropsychological tests, based on clinical pathological correlations, are protracted, require extensive training in administration and scoring, and leave lengthy paper trails (double-entry for analysis). We present a computerized battery that takes an average of 1h and provides measures of accuracy and speed on 9 neurocognitive domains. They are cognitive neuroscience-based in that they have been linked experimentally to specific brain systems with functional neuroimaging studies. We describe the process of translating tasks used in functional neuroimaging to tests for assessing individual differences. Data are presented on each test with samples ranging from 139 (81 female) to 536 (311 female) of carefully screened healthy individuals ranging in age from 18 to 84. Item consistency was established with acceptable to high Cronbach alpha coefficients. Inter-item correlations were moderate to high within domain and low to nil across domains, indicating construct validity. Initial criterion validity was demonstrated by sensitivity to sex differences and the effects of age, education and parental education. These results encourage the use of this battery in studies needing an efficient assessment of major neurocognitive domains such as multi-site genetic studies and clinical trials. PMID:19945485

  16. Evaluation of the amyloid beta-GFP fusion protein as a model of amyloid beta peptides-mediated aggregation: a study of DNAJB6 chaperone

    PubMed Central

    Hussein, Rasha M.; Hashem, Reem M.; Rashed, Laila A.

    2015-01-01

    Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized by the accumulation and aggregation of extracellular amyloid β (Aβ) peptides and intracellular aggregation of hyper-phosphorylated tau protein. Recent evidence indicates that accumulation and aggregation of intracellular amyloid β peptides may also play a role in disease pathogenesis. This would suggest that intracellular Heat Shock Proteins (HSP) that maintain cellular protein homeostasis might be candidates for disease amelioration. We recently found that DNAJB6, a member of DNAJ family of heat shock proteins, effectively prevented the aggregation of short aggregation-prone peptides containing large poly glutamines (associated with CAG repeat diseases) both in vitro and in cells. Moreover, recent in vitro data showed that DNAJB6 can delay the aggregation of Aβ42 peptides. In this study, we investigated the ability of DNAJB6 to prevent the aggregation of extracellular and intracellular Aβ peptides using transfection of human embryonic kidney 293 (HEK293) cells with Aβ-green fluorescent protein (GFP) fusion construct and performing western blotting and immunofluorescence techniques. We found that DNAJB6 indeed suppresses Aβ-GFP aggregation, but not seeded aggregation initiated by extracellular Aβ peptides. Unexpectedly and unlike what we found for peptide-mediated aggregation, DNAJB6 required interaction with HSP70 to prevent the aggregation of the Aβ-GFP fusion protein and its J-domain was crucial for its anti-aggregation effect. In addition, other DNAJ proteins as well as HSPA1a overexpression also suppressed Aβ-GFP aggregation efficiently. Our findings suggest that Aβ aggregation differs from poly glutamine (Poly Q) peptide induced aggregation in terms of chaperone handling and sheds doubt on the usage of Aβ-GFP fusion construct for studying Aβ peptide aggregation in cells. PMID:26283911

  17. Assessing relationships among properties of demolished concrete, recycled aggregate and recycled aggregate concrete using regression analysis.

    PubMed

    Tam, Vivian W Y; Wang, K; Tam, C M

    2008-04-01

    Recycled demolished concrete (DC) as recycled aggregate (RA) and recycled aggregate concrete (RAC) is generally suitable for most construction applications. Low-grade applications, including sub-base and roadwork, have been implemented in many countries; however, higher-grade activities are rarely considered. This paper examines relationships among DC characteristics, properties of their RA and strength of their RAC using regression analysis. Ten samples collected from demolition sites are examined. The results show strong correlation among the DC samples, properties of RA and RAC. It should be highlighted that inferior quality of DC will lower the quality of RA and thus their RAC. Prediction of RAC strength is also formulated from the DC characteristics and the RA properties. From that, the RAC performance from DC and RA can be estimated. In addition, RAC design requirements can also be developed at the initial stage of concrete demolition. Recommendations are also given to improve the future concreting practice. PMID:17764837

  18. Aqueous-based immobilization of initiator and surface-initiated ATRP to construct hemocompatible surface of poly (styrene-b-(ethylene-co-butylene)-b-styrene) elastomer.

    PubMed

    Hou, Jianwen; Shi, Qiang; Stagnaro, Paola; Ye, Wei; Jin, Jing; Conzatti, Lucia; Yin, Jinghua

    2013-11-01

    Surface-initiated atom transfer radical polymerization (SI-ATRP) is a versatile tool for surface functionalization in a well-controlled manner. However, surface modification of styrenic thermoplastic elastomers (STPEs) faces a great challenge because immobilization of typical ATRP initiators onto STPEs needs to be carried out in organic solvent, which dissolves and destroys the STPEs film. In this work, a simple aqueous-based route is developed to immobilize ATRP initiators, Br, onto the surface of styrene-b-(ethylene-co-butylene)-b-styrene elastomer (SEBS), chosen as a model copolymer of STPEs. In such a way, functional polymer brushes of ethylene glycol methyl ether methacrylate (OEGMA) are successfully prepared from the surface of SEBS. Kinetic investigations show an approximately linear relationship between grafting density and reaction time, indicating the growth of chains is coincident with a "controlled" process. CBr bonds directly connected to benzene rings on the SEBS-Br surfaces are demonstrated to be effective initiation sites for SI-ATRP. The even coverage of the surface by well-defined P(OEGMA) brushes enable SEBS films to exhibit excellent resistance to protein adsorption and platelet adhesion as well as low hemolysis ratio. This work not only manipulates the SEBS surface to substantially improve its biocompatibility, but paves a way to facilitate SI-ATRP on the surface of styrene-based block copolymers (SBCs). PMID:23838201

  19. A construct for building the capacity of community-based initiatives in racial and ethnic communities: a qualitative cross-case analysis.

    PubMed

    Goodman, Robert M

    2009-01-01

    This article reports on a qualitative cross-case study that compares patterns of implementation across community-based public health initiatives resulting in a construct for building the capacity of such initiatives in racial and ethnic communities. By specifying which capacities provide optimum leverage, community initiatives may increase precision in developing intervention strategies that focus on those pivotal capacities that are necessary for producing desired outcomes. First, community capacity is defined and briefly contrasted with social capital. Then the research method is described from which the capacity construct is derived. The study reveals several capacities of community-based initiatives that are crucial in distinguishing highly successful initiatives from those that had greater difficulty in realizing their goals. Leadership was the most important capacity that distinguished highly and less successful initiatives. Organizing capacity, or the propensity to provide structure, operational procedures, oversight, and activity formation were also critical in leveraging community action and desired outcomes. The study concludes that developing high levels of community capacity where it can produce the most strategic advantage is a promising pathway for mitigating antagonistic social factors. PMID:19202401

  20. From Aggregate Availability to Sustainability in California

    NASA Astrophysics Data System (ADS)

    Testa, S. M.; Parrish, J. G.

    2012-12-01

    California leads the nation in the production of sand and gravel, and ranks second behind Texas in the production of portland cement. Prior to 1960, the California Geological Survey (CGS, formerly the Division of Mines and Geology) and the State Mining and Geology Board (SMGB, formerly State Mining Board) placed an emphasis "in obtaining and providing information of benefit to the State's mineral industry". By the late 1960s, the Division initiated activities in the area of geologic hazards, and also expressed concern over the loss of aggregate resources via urbanization, which were among the state's most valuable mineral resource. Under the California Surface Mining and Reclamation Act of 1975 (SMARA), the State Geologist classifies mineral resources solely on geologic factors, and without regard to existing land use and land ownership. Following classification, the SMGB may consider "designating" such lands should the classified area contain mineral resources of regional or statewide economic significance and that may be needed to meet future demands. In 1979, the classification of aggregate resources in the three-county area of Los Angeles, Orange, and Ventura, was completed, with designation of such resources in Los Angeles County in 1981. Maps and descriptions of the designated mineral lands were placed in the California Public Resources Code and officially transmitted to those county and city governments having permitting authority over the use of those lands. In 1999, the SMGB in concert with CGS implemented the SMARA Regional Synthesis Map series, with the first (and last) of the series covering the Los Angeles Basin. This map was very useful for regional planners and the general citizenry since it provided a broader perspective not readily apparent in the smaller scale Production-Consumption (P-C) regional maps. CGS's statewide Aggregate Availability Map, commonly referred to as Map Sheet 52, was developed in 2002 and updated in 2006. The purpose of Map 52

  1. Optimization of a polyglutamine aggregation inhibitor peptide (QBP1) using a thioflavin T fluorescence assay.

    PubMed

    Hamuro, Lora; Zhang, Guangtao; Tucker, Timothy J; Self, Christopher; Strittmatter, Warren J; Burke, James R

    2007-10-01

    Polyglutamine protein aggregates are a hallmark of several neurodegenerative diseases, including Huntington's disease, and increasing evidence suggests that reducing or inhibiting aggregation produces a therapeutic benefit in animal models of disease. Part of the challenge in designing compounds that interfere with protein aggregation is having a sensitive and consistent in vitro assay that allows for efficient screening and lead optimization. Here we describe a simplified polyglutamine assay that uses a soluble, pathological-length polyglutamine construct (62 glutamines [Q62]) fused to glutathione-S-transferase (GST) and measure aggregate formation with fluorescence generated by thioflavin T binding. Controlled release of Q62 from GST using proteolytic cleavage resulted in time-dependent aggregate formation that was not observed for a non-pathological-length GST-Q19 construct. Cleavage of the polyglutamine domain from GST increased the rate of Q62 aggregation from days to hours, significantly decreasing the time for compound analysis. Controlled aggregate formation combined with the fluorescence sensitivity of the dye thioflavin T allowed us to screen a series of peptide analogs for lead optimization of a previously identified peptide aggregation inhibitor, QBP1. QBP1 analogs showed the greatest inhibitory potency when added prior to Q62 aggregate initiation, suggesting that the mechanism of inhibition was interference with early formed aggregates that were not detectable by ultraviolet or dye binding. The assay detected activities that differed by three orders of magnitudes with Z' = 0.56, which is suitable for high-throughput screening and allowed us to do lead optimization of QBP1 analogs for pharmacophore model building. PMID:17939755

  2. New developments in sampling and aggregation for remotely sensed surveys

    NASA Technical Reports Server (NTRS)

    Feiveson, A. H. (Principal Investigator)

    1979-01-01

    Sampling techniques used to construct large area crop estimates are briefly reviewed. Problem areas in sampling and aggregation are covered. The natural sampling strategy, two phase sampling, weighted aggregation, and multiyear estimation are among the topics discussed.

  3. Logical-Mathematical Constructions in an Initial Course at the University: A View of Their Syntactic, Semantic and Pragmatic Aspects

    ERIC Educational Resources Information Center

    Falsetti, Marcela; Alvarez, Marisa

    2015-01-01

    We present an analysis of students' formal constructions in mathematics regarding to syntactic, semantic and pragmatic aspects. The analyzed tasks correspond to students of the Course of Mathematics for the admission to the university. Our study was qualitative, consisted in the identification, analysis and interpretation, focused in logic…

  4. Choosing Aggregation Rules for Composite Indicators

    ERIC Educational Resources Information Center

    Munda, Giuseppe

    2012-01-01

    From a formal point of view, a composite indicator is an aggregate of all dimensions, objectives, individual indicators and variables used for its construction. This implies that what defines a composite indicator is the set of properties underlying its mathematical aggregation convention. In this article, I try to revise the theoretical debate on…

  5. Dielectric measurement method for real-time monitoring of initial hardening of backfill materials used for underground construction

    NASA Astrophysics Data System (ADS)

    Karlovšek, Jurij; Schwing, Moritz; Chen, Zhen; Wagner, Norman; Williams, David J.; Scheuermann, Alexander

    2016-04-01

    The broadband dielectric measurement method based on the vector network analysis technique, in combination with an open-ended coaxial probe, was applied to the determination of the dielectric relaxation behaviour of one- and two-component backfilling grout materials in the frequency range from 40 MHz to 2 GHz. The cement hydration process and the gelling of commercial grouts was monitored in real-time to investigate the application of non-destructive testing methods in the tunnelling industry. It was found that the time-dependent dielectric relaxation behaviour can accurately reveal the different stages of the hydration process and delineate the start of gel hardening. These measurement results demonstrate the practicability of the real-time dielectric measurement method to determine the broadband dielectric parameters of conventional backfill materials used in underground construction to determine construction integrity using non-destructive testing methods.

  6. The constructed catchment 'Chicken Creek' - a landscape observatory to analyze processes and feedback mechanisms during initial ecosystem development

    NASA Astrophysics Data System (ADS)

    Elmer, Michael; Schaaf, Wolfgang; Gerwin, Werner; Hinz, Christoph

    2014-05-01

    We investigated the initial development of the landscape observatory 'Chicken Creek', Germany, an artificial catchment with well known boundary conditions and inner structures (Gerwin et al., 2011). Over a period of nine years, we observed considerable changes within the site (Elmer et al., 2013). Both internal and external factors could be identified as driving forces for the formation of structures and patterns in the catchment. Over time, secondary structures and patterns evolved and became more and more important. Invading biota and vegetation succession initialized feedback mechanisms resulting in pattern and habitat formation as well as in increased differentiation, heterogeneity and complexity that are typical characteristics of ecosystems (Schaaf et al., 2013). The processes and feedback mechanisms in the initial development of a new landscape may deviate in rates, intensity, and dominance from those known from mature ecosystems. It is therefore crucial to understand these early phases of ecosystem development and to disentangle the increasingly complex interactions between the evolving terrestrial and aquatic, biotic, and abiotic compartments of the system. Elmer M, Gerwin W, Schaaf W, Zaplata MK, Hohberg K, Nenov R, Bens O, Hüttl RF (2013): Dynamics of initial ecosystem development at the artificial catchment Chicken Creek, Lusatia, Germany. Environ Earth Sci 69, 491-505. Gerwin W, Schaaf W, Biemelt D, Winter S, Fischer A, Veste M, Hüttl RF (2011): Overview and first results of ecological monitoring at the artificial watershed Chicken Creek (Germany). Phys Chem Earth 36, 61-73. Schaaf W, Elmer M, Fischer A, Gerwin W, Nenov R, Pretsch H, Seifert S, Winter S, Zaplata MK (2013): Monitoring the formation of structures and patterns during initial development of an artificial catchment. Environ Monit Assess 185, 5965-5986.

  7. Role of Multicellular Aggregates in Biofilm Formation

    PubMed Central

    Kragh, Kasper N.; Hutchison, Jaime B.; Melaugh, Gavin; Rodesney, Chris; Roberts, Aled E. L.; Irie, Yasuhiko; Jensen, Peter Ø.; Diggle, Stephen P.; Allen, Rosalind J.

    2016-01-01

    ABSTRACT In traditional models of in vitro biofilm development, individual bacterial cells seed a surface, multiply, and mature into multicellular, three-dimensional structures. Much research has been devoted to elucidating the mechanisms governing the initial attachment of single cells to surfaces. However, in natural environments and during infection, bacterial cells tend to clump as multicellular aggregates, and biofilms can also slough off aggregates as a part of the dispersal process. This makes it likely that biofilms are often seeded by aggregates and single cells, yet how these aggregates impact biofilm initiation and development is not known. Here we use a combination of experimental and computational approaches to determine the relative fitness of single cells and preformed aggregates during early development of Pseudomonas aeruginosa biofilms. We find that the relative fitness of aggregates depends markedly on the density of surrounding single cells, i.e., the level of competition for growth resources. When competition between aggregates and single cells is low, an aggregate has a growth disadvantage because the aggregate interior has poor access to growth resources. However, if competition is high, aggregates exhibit higher fitness, because extending vertically above the surface gives cells at the top of aggregates better access to growth resources. Other advantages of seeding by aggregates, such as earlier switching to a biofilm-like phenotype and enhanced resilience toward antibiotics and immune response, may add to this ecological benefit. Our findings suggest that current models of biofilm formation should be reconsidered to incorporate the role of aggregates in biofilm initiation. PMID:27006463

  8. Modifiers of mutant huntingtin aggregation

    PubMed Central

    Teuling, Eva; Bourgonje, Annika; Veenje, Sven; Thijssen, Karen; de Boer, Jelle; van der Velde, Joeri; Swertz, Morris; Nollen, Ellen

    2011-01-01

    Protein aggregation is a common hallmark of a number of age-related neurodegenerative diseases, including Alzheimer’s, Parkinson’s, and polyglutamine-expansion disorders such as Huntington’s disease, but how aggregation-prone proteins lead to pathology is not known. Using a genome-wide RNAi screen in a C. elegans-model for polyglutamine aggregation, we previously identified 186 genes that suppress aggregation. Using an RNAi screen for human orthologs of these genes, we here present 26 human genes that suppress aggregation of mutant huntingtin in a human cell line. Among these are genes that have not been previously linked to mutant huntingtin aggregation. They include those encoding eukaryotic translation initiation, elongation and translation factors, and genes that have been previously associated with other neurodegenerative diseases, like the ATP-ase family gene 3-like 2 (AFG3L2) and ubiquitin-like modifier activating enzyme 1 (UBA1). Unravelling the role of these genes will broaden our understanding of the pathogenesis of Huntington’s disease. PMID:21915392

  9. 76 FR 65537 - Controlled Substances: Proposed Aggregate Production Quotas for 2012

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-21

    ... Enforcement Administration Controlled Substances: Proposed Aggregate Production Quotas for 2012 AGENCY: Drug...: This notice proposes initial year 2012 aggregate production quotas for controlled substances in....S.C. 826) requires that the Attorney General establish aggregate production quotas for each...

  10. 75 FR 56137 - Controlled Substances: Proposed Aggregate Production Quotas for 2011

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-15

    ... Enforcement Administration Controlled Substances: Proposed Aggregate Production Quotas for 2011 AGENCY: Drug Enforcement Administration (DEA), Justice. ACTION: Notice of proposed year 2011 aggregate production quotas. SUMMARY: This notice proposes initial year 2011 aggregate production quotas for controlled substances...

  11. Continental aggregation, subduction initiation, and plume generation

    NASA Astrophysics Data System (ADS)

    Heron, P. J.; Lowman, J. P.

    2013-12-01

    Several processes unfold during the supercontinent cycle, more than one of which might result in an elevation in subcontinental mantle temperatures through the generation of mantle plumes. Paleogeographic plate reconstructions have indicated that sub-continental mantle upwellings appear below large continents that are extensively ringed by subduction zones. Moreover, several numerical simulations of supercontinent formation and dispersal attribute the genesis of sub-continental plumes to the generation of subduction zones on the edges of the supercontinent, rather than resulting from continental insulation. However, the role of the location of downwellings in producing a return-flow upwelling, and on increasing sub-continental mantle temperatures, is not fully understood. In this mantle convection study, we examine the evolution of mantle dynamics after supercontinent accretion over a subduction zone (analogous to the formation of Pangea) for a range of continental coverage. We present 2D and 3D Cartesian geometry mantle convection simulations, featuring geotherm- and pressure-dependent viscosity with thermally and mechanically distinct oceanic and continental plates. Through changing the size of the continent we are able to analyze the factors involved in the generation of mantle plumes in purely thermal convection. Furthermore, we change the upper and lower mantle viscosity to determine their relation to plume formation in vigorous mantle convection simulations. Elevated sub-continental temperatures are analyzed in relation to continental coverage to further understand the influence of continental tectonics on the thermal evolution of the mantle.

  12. Natural aggregates of the conterminous United States

    USGS Publications Warehouse

    Langer, William H.

    1988-01-01

    Crushed stone and sand and gravel are the two main sources of natural aggregates. These materials are commonly used construction materials and frequently can be interchanged with one another. They are widely used throughout the United States, with every State except two producing crushed stone. Together they amount to about half the mining volume in the United States. Approximately 96 percent of sand and gravel and 77 percent of the crushed stone produced in the United States are used in the construction industry. Natural aggregates are widely distributed throughout the United States in a variety of geologic environments. Sand and gravel deposits commonly are the results of the weathering of bedrock and subsequent transportation and deposition of the material by water or ice (glaciers). As such, they commonly occur as river or stream deposits or in glaciated areas as glaciofluvial and other deposits. Crushed stone aggregates are derived from a wide variety of parent bedrock materials. Limestone and other carbonates account for approximately three quarters of the rocks used for crushed stone, with granite and other igneous rocks making up the bulk of the remainder. Limestone deposits are widespread throughout the Central and Eastern United States and are scattered in the West. Granites are widely distributed in the Eastern and Western United States, with few exposures in the Midwest. Igneous rocks (excluding granites) are largely concentrated in the Western United States and in a few isolated localities in the East. Even though natural aggregates are widely distributed throughout the United States, they are not universally available for consumptive use. Some areas are devoid of sand and gravel, and potential sources of crushed stone may be covered with sufficient unconsolidated material to make surface mining impractical. In some areas many aggregates do not meet the physical property requirements for certain uses, or they may contain mineral constituents that react

  13. Aggregated Recommendation through Random Forests

    PubMed Central

    2014-01-01

    Aggregated recommendation refers to the process of suggesting one kind of items to a group of users. Compared to user-oriented or item-oriented approaches, it is more general and, therefore, more appropriate for cold-start recommendation. In this paper, we propose a random forest approach to create aggregated recommender systems. The approach is used to predict the rating of a group of users to a kind of items. In the preprocessing stage, we merge user, item, and rating information to construct an aggregated decision table, where rating information serves as the decision attribute. We also model the data conversion process corresponding to the new user, new item, and both new problems. In the training stage, a forest is built for the aggregated training set, where each leaf is assigned a distribution of discrete rating. In the testing stage, we present four predicting approaches to compute evaluation values based on the distribution of each tree. Experiments results on the well-known MovieLens dataset show that the aggregated approach maintains an acceptable level of accuracy. PMID:25180204

  14. Aggregated recommendation through random forests.

    PubMed

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

    2014-01-01

    Aggregated recommendation refers to the process of suggesting one kind of items to a group of users. Compared to user-oriented or item-oriented approaches, it is more general and, therefore, more appropriate for cold-start recommendation. In this paper, we propose a random forest approach to create aggregated recommender systems. The approach is used to predict the rating of a group of users to a kind of items. In the preprocessing stage, we merge user, item, and rating information to construct an aggregated decision table, where rating information serves as the decision attribute. We also model the data conversion process corresponding to the new user, new item, and both new problems. In the training stage, a forest is built for the aggregated training set, where each leaf is assigned a distribution of discrete rating. In the testing stage, we present four predicting approaches to compute evaluation values based on the distribution of each tree. Experiments results on the well-known MovieLens dataset show that the aggregated approach maintains an acceptable level of accuracy. PMID:25180204

  15. Supporting residents’ expression of sexuality: the initial construction of a sexuality assessment tool for residential aged care facilities

    PubMed Central

    2014-01-01

    Background Sexuality is a key component of quality of life and well-being and a need to express one’s sexuality continues into old age. Staff and families in residential aged care facilities often find expressions of sexuality by residents, particularly those living with dementia, challenging and facilities often struggle to address individuals’ needs in this area. This paper describes the development of an assessment tool which enables residential aged care facilities to identify how supportive their organisation is of all residents’ expression of their sexuality, and thereby improve where required. Methods Multi-phase design using qualitative methods and a Delphi technique. Tool items were derived from the literature and verified by qualitative interviews with aged care facility staff, residents and families. The final item pool was confirmed via a reactive Delphi process. Results A final item pool of sixty-nine items grouped into seven key areas allows facilities to score their compliance with the areas identified as being supportive of older people’s expression of their sexuality in a residential aged care environment. Conclusions The sexuality assessment tool (SexAT) guides practice to support the normalization of sexuality in aged care homes and assists facilities to identify where enhancements to the environment, policies, procedures and practices, information and education/training are required. The tool also enables facilities to monitor initiatives in these areas over time. PMID:24980463

  16. Waves and aggregation patterns in myxobacteria

    NASA Astrophysics Data System (ADS)

    Igoshin, Oleg A.; Welch, Roy; Kaiser, Dale; Oster, George

    2004-03-01

    Under starvation conditions, a population of myxobacteria aggregates to build a fruiting body whose shape is species-specific and within which the cells sporulate. Early in this process, cells often pass through a "ripple phase" characterized by traveling linear, concentric, and spiral waves. These waves are different from the waves observed during slime mold aggregation that depend on diffusible morphogens, because myxobacteria communicate by direct contact. The difference is most dramatic when waves collide: rather than annihilating one another, myxobacterial waves appear to pass through one another unchanged. Under certain conditions, the spacing and location of the nascent fruiting bodies is determined by the wavelength and pattern of the waves. Later in fruiting body development, waves are replaced by streams of cells that circulate around small initial aggregates enlarging and rounding them. Still later, pairs of motile aggregates coalesce to form larger aggregates that develop into fruiting bodies. Here we present a mathematical model that quantitatively explains these wave and aggregation phenomena.

  17. A review of volcanic ash aggregation

    NASA Astrophysics Data System (ADS)

    Brown, R. J.; Bonadonna, C.; Durant, A. J.

    2012-01-01

    Most volcanic ash particles with diameters <63 μm settle from eruption clouds as particle aggregates that cumulatively have larger sizes, lower densities, and higher terminal fall velocities than individual constituent particles. Particle aggregation reduces the atmospheric residence time of fine ash, which results in a proportional increase in fine ash fallout within 10-100 s km from the volcano and a reduction in airborne fine ash mass concentrations 1000 s km from the volcano. Aggregate characteristics vary with distance from the volcano: proximal aggregates are typically larger (up to cm size) with concentric structures, while distal aggregates are typically smaller (sub-millimetre size). Particles comprising ash aggregates are bound through hydro-bonds (liquid and ice water) and electrostatic forces, and the rate of particle aggregation correlates with cloud liquid water availability. Eruption source parameters (including initial particle size distribution, erupted mass, eruption column height, cloud water content and temperature) and the eruption plume temperature lapse rate, coupled with the environmental parameters, determines the type and spatiotemporal distribution of aggregates. Field studies, lab experiments and modelling investigations have already provided important insights on the process of particle aggregation. However, new integrated observations that combine remote sensing studies of ash clouds with field measurement and sampling, and lab experiments are required to fill current gaps in knowledge surrounding the theory of ash aggregate formation.

  18. Bioconductive 3D nano-composite constructs with tunable elasticity to initiate stem cell growth and induce bone mineralization.

    PubMed

    Sagar, Nitin; Khanna, Kunal; Sardesai, Varda S; Singh, Atul K; Temgire, Mayur; Kalita, Mridula Phukan; Kadam, Sachin S; Soni, Vivek P; Bhartiya, Deepa; Bellare, Jayesh R

    2016-12-01

    Bioactive 3D composites play an important role in advanced biomaterial design to provide molecular coupling and improve integrity with the cellular environment of the native bone. In the present study, a hybrid lyophilized polymer composite blend of anionic charged sodium salt of carboxymethyl chitin and gelatin (CMChNa-GEL) reinforced with nano-rod agglomerated hydroxyapatite (nHA) has been developed with enhanced biocompatibility and tunable elasticity. The scaffolds have an open, uniform and interconnected porous structure with an average pore diameter of 157±30μm and 89.47+0.03% with four dimensional X-ray. The aspect ratio of ellipsoidal pores decrease from 4.4 to 1.2 with increase in gelatin concentration; and from 2.14 to 1.93 with decrease in gelling temperature. The samples were resilient with elastic stain at 1.2MPa of stress also decreased from 0.33 to 0.23 with increase in gelatin concentration. The crosslinker HMDI (hexamethylene diisocyanate) yielded more resilient samples at 1.2MPa in comparison to glutaraldehyde. Increased crosslinking time from 2 to 4h in continuous compression cycle show no improvement in maximum elastic stain of 1.2MPa stress. This surface elasticity of the scaffold enables the capacity of these materials for adherent self renewal and cultivation of the NTERA-2 cL.D1 (NT2/D1), pluripotent embryonal carcinoma cell with biomechanical surface, as is shown here. Proliferation with MG-63, ALP activity and Alizarin red mineralization assay on optimized scaffold demonstrated ***p<0.001 between different time points thus showing its potential for bone healing. In pre-clinical study histological bone response of the scaffold construct displayed improved activity of bone regeneration in comparison to self healing of control groups (sham) up to week 07 after implantation in rabbit tibia critical-size defect. Therefore, this nHA-CMChNa-GEL scaffold composite exhibits inherent and efficient physicochemical, mechanical and biological

  19. Commercial Demonstration of the Manufactured Aggregate Processing Technology Utilizing Spray Dryer Ash

    SciTech Connect

    Milton Wu; Paul Yuran

    2006-12-31

    Universal Aggregates LLC (UA) was awarded a cost sharing Co-operative Agreement from the Department of Energy (DOE) through the Power Plant Improvement Initiative Program (PPII) to design, construct and operate a lightweight aggregate manufacturing plant at the Birchwood Power Facility in King George, Virginia in October 2001. The Agreement was signed in November 2002. The installation and start-up expenses for the Birchwood Aggregate Facility are $19.5 million. The DOE share is $7.2 million (37%) and the UA share is $12.3 million (63%). The original project team consists of UA, SynAggs, LLC, CONSOL Energy Inc. and P. J. Dick, Inc. Using 115,000 ton per year of spray dryer ash (SDA), a dry FGD by-product from the power station, UA will produce 167,000 tons of manufactured lightweight aggregate for use in production of concrete masonry units (CMU). Manufacturing aggregate from FGD by-products can provide an economical high-volume use and substantially expand market for FGD by-products. Most of the FGD by-products are currently disposed of in landfills. Construction of the Birchwood Aggregate Facility was completed in March 2004. Operation startup was begun in April 2004. Plant Integration was initiated in December 2004. Integration includes mixing, extrusion, curing, crushing and screening. Lightweight aggregates with proper size gradation and bulk density were produced from the manufacturing aggregate plant and loaded on a stockpile for shipment. The shipped aggregates were used in a commercial block plant for CMU production. However, most of the production was made at low capacity factors and for a relatively short time in 2005. Several areas were identified as important factors to improve plant capacity and availability. Equipment and process control modifications and curing vessel clean up were made to improve plant operation in the first half of 2006. About 3,000 tons of crushed aggregate was produced in August 2006. UA is continuing to work to improve plant

  20. Ash Aggregates in Proximal Settings

    NASA Astrophysics Data System (ADS)

    Porritt, L. A.; Russell, K.

    2012-12-01

    early pyroclastic phase of the formation of Kima'Kho, a tuya in northern B.C., Canada produced a subaqueous pyroclastic cone which became emergent during the latter stages of formation. Armoured lapilli are pervasive within the emergent upper third of the sequence. No other types of ash aggregates have been observed. Petrographic and textural analysis of the armoured lapilli shows them to comprise a central 2-30 mm-sized, juvenile, vesiculated pyroclast, concentrically coated by mm-scale layers of 10-250 μm sized ash particles. At Kima'Kho, the armoured lapilli are shown to be a direct indicator of fallout from a sustained plume attended by concomitant production of pyroclastic density currents. The size and internal structure of the armoured lapilli provide constraints on the nature of the initial explosive phase of eruption at Kima'Kho. Their proximity to the vent also indicates rapid aggregation within the eruption plume. Within both sequences rapid aggregation of ash particles occurred in proximity to the vent. However, the conditions were substantially different leading to the production of armoured lapilli (no accretionary lapilli) at Kima'Kho and diverse ash aggregates but no armoured lapilli at A418. Here we investigate vent-proximal ash aggregation and the specific conditions which lead to the formation of coated ash pellets and armoured lapilli.

  1. Bouncing behavior of microscopic dust aggregates

    NASA Astrophysics Data System (ADS)

    Seizinger, A.; Kley, W.

    2013-03-01

    Context. Bouncing collisions of dust aggregates within the protoplanetary disk may have a significant impact on the growth process of planetesimals. Yet, the conditions that result in bouncing are not very well understood. Existing simulations studying the bouncing behavior used aggregates with an artificial, very regular internal structure. Aims: Here, we study the bouncing behavior of sub-mm dust aggregates that are constructed applying different sample preparation methods. We analyze how the internal structure of the aggregate alters the collisional outcome and we determine the influence of aggregate size, porosity, collision velocity, and impact parameter. Methods: We use molecular dynamics simulations where the individual aggregates are treated as spheres that are made up of several hundred thousand individual monomers. The simulations are run on graphic cards (GPUs). Results: Statistical bulk properties and thus bouncing behavior of sub-mm dust aggregates depend heavily on the preparation method. In particular, there is no unique relation between the average volume filling factor and the coordination number of the aggregate. Realistic aggregates bounce only if their volume filling factor exceeds 0.5 and collision velocities are below 0.1 ms-1. Conclusions: For dust particles in the protoplanetary nebula we suggest that the bouncing barrier may not be such a strong handicap in the growth phase of dust agglomerates, at least in the size range of ≈100 μm.

  2. Development of Arsenic and Iron Biogeochemical Gradients upon Anaerobiosis at Soil Aggregate Scale

    NASA Astrophysics Data System (ADS)

    Masue-Slowey, Y.; Pallud, C.; Bedore, P.; Tufano, K.; Fendorf, S.

    2008-12-01

    In aerated soils, As release is limited due to the strong interaction between As(V) and soil minerals. However, under anaerobic conditions, As desorption is stimulated by As(V) reduction to As(III) and reductive dissolution/transformation of Fe (hydr)oxides, common hosts of As. The effect of As(V) and Fe(III) reduction on As release has been extensively studied in laboratory batch and column systems; correlation of apparent Fe and As reduction, with concomitant release to pore water, has also been noted under field conditions. What remains unresolved is the coupling of biogeochemical and physical processes that ultimately control As transport within structured media such as soils. Soils are heterogeneous porous media that are comprised of individual aggregates having pores that are dominated by diffusive (aggregate interiors) or advective (aggregate exteriors) transport. As a consequence of physical and chemical differences in the interior and the exterior of aggregates, As(III,V) and Fe(II,III) chemical gradients develop. Here, we examine As release from constructed aggregates exposed to fluctuating redox conditions. Artificial aggregates were made with As(V) adsorbed ferrihydrite-coated sand homogeneously inoculated with Shewanella sp. ANA-3 (model As(V) and Fe(III) reducer) and then fused using an agarose binder into spheres. Aggregates were placed in a flow reactor and saturated flow of aerobic or anaerobic artificial groundwater media was initiated. Redox fluctuated in select systems to examine changes in chemical gradient under changing aeration status. Our results show that within aerated solutions, oxidized aggregate exteriors provide a "gprotective barrier"h against As release despite anoxia within diffusively constrained aggregate interiors. During a transition to anaerobic conditions in advective zones, however, As is released and transport is promoted. Our study illustrates the microscale variation in biogeoechemical processes within soils and the

  3. Platelet aggregation test

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003669.htm Platelet aggregation test To use the sharing features on this page, please enable JavaScript. The platelet aggregation blood test checks how well platelets , a ...

  4. Thermodynamics of Protein Aggregation

    NASA Astrophysics Data System (ADS)

    Osborne, Kenneth L.; Barz, Bogdan; Bachmann, Michael; Strodel, Birgit

    Amyloid protein aggregation characterizes many neurodegenerative disorders, including Alzheimer's, Parkinson's, and Creutz- feldt-Jakob disease. Evidence suggests that amyloid aggregates may share similar aggregation pathways, implying simulation of full-length amyloid proteins is not necessary for understanding amyloid formation. In this study we simulate GNNQQNY, the N-terminal prion-determining domain of the yeast protein Sup35 to investigate the thermodynamics of structural transitions during aggregation. We use a coarse-grained model with replica-exchange molecular dynamics to investigate the association of 3-, 6-, and 12-chain GNNQQNY systems and we determine the aggregation pathway by studying aggregation states of GN- NQQNY. We find that the aggregation of the hydrophilic GNNQQNY sequence is mainly driven by H-bond formation, leading to the formation of /3-sheets from the very beginning of the assembly process. Condensation (aggregation) and ordering take place simultaneously, which is underpinned by the occurrence of a single heat capacity peak only.

  5. Platelet aggregation test

    MedlinePlus

    The platelet aggregation blood test checks how well platelets , a part of blood, clump together and cause blood to clot. ... Decreased platelet aggregation may be due to: Autoimmune ... Fibrin degradation products Inherited platelet function defects ...

  6. Local stereo matching with adaptive shape support window based cost aggregation.

    PubMed

    Xu, Yafan; Zhao, Yan; Ji, Mengqi

    2014-10-10

    Cost aggregation is the most important step in a local stereo algorithm. In this work, a novel local stereo-matching algorithm with a cost-aggregation method based on adaptive shape support window (ASSW) is proposed. First, we compute the initial cost volume, which uses both absolute intensity difference and gradient similarity to measure dissimilarity. Second, we apply an ASSW-based cost-aggregation method to get the aggregated cost within the support window. There are two main parts: at first we construct a local support skeleton anchoring each pixel with four varying arm lengths decided on color similarity; as a result, the support window integral of multiple horizontal segments spanned by pixels in the neighboring vertical is established. Then we utilize extended implementation of guided filter to aggregate cost volume within the ASSW, which has better edge-preserving smoothing property than bilateral filter independent of the filtering kernel size. In this way, the number of bad pixels located in the incorrect depth regions can be effectively reduced through finding optimal support windows with an arbitrary shape and size adaptively. Finally, the initial disparity value of each pixel is selected using winner takes all optimization and post processing symmetrically, considering both the reference and the target image, is adopted. The experimental results demonstrate that the proposed algorithm achieves outstanding matching performance compared with other existing local algorithms on the Middlebury stereo benchmark, especially in depth discontinuities and piecewise smooth regions. PMID:25322396

  7. Microbial aggregates in anaerobic wastewater treatment.

    PubMed

    Kosaric, N; Blaszczyk, R

    1990-01-01

    sludge. Methanogenic bacterial aggregates have been successfully applied in many full scale installations, especially for sugar beet, potato, pulp and paper mill, and other soluble wastes. The UASB reactors used for these treatments are simple in construction and handling which result in rather low total costs. A further and wider application of UASB reactors and methanogenic aggregates for various industrial wastewaters is expected. PMID:2291438

  8. Tracking the monthly changes of dissolved organic matter composition in a newly constructed reservoir and its tributaries during the initial impounding period.

    PubMed

    Chen, Meilian; He, Wei; Choi, Ilhwan; Hur, Jin

    2016-01-01

    Understanding the roles of inland reservoirs becomes increasingly important with respect to global carbon cycling as well as water resource management due to the unprecedented demand for construction in recent decades. In this study, the dissolved organic matter (DOM) quantity and quality in a newly constructed dam reservoir and its tributaries were monitored monthly during the initial impounding period (July to November 2014) using a size exclusion chromatography (SEC) with online organic carbon detector (OCD). The highest values were observed in the month of August with the highest precipitation for the bulk dissolved organic carbon (DOC), specific UV absorbance (SUVA), and most of the assigned size fractions (except for biopolymers) in the tributaries, indicating that allochthonous sources of DOM were dominant in the feeding stream waters of the reservoir. The bulk DOC and high molecular weight humic substance fraction (∼1 kDa) were generally co-varied with the monthly precipitation in the tributaries, while building blocks (350-500 Da), and low molecular weight (LMW) acids and neutrals showed different trends. In a dam site, the smaller molecular fractions became more abundant during the dry season (September to November), presumably due to the in-reservoir processes such as photo- and bio-degradation. Our results also revealed that storms mobilized a large amount of highly aromatic soil-derived DOM to the reservoir. A depth profile at the dam site showed the water is well mixed up to a depth of ∼20 m. The SEC-OCD data coupled with non-metric multidimensional scaling provided a clear visualization of the spatiotemporal variations in DOM composition, which shed new light on the DOM composition formed in a newly constructed dam reservoir and also on the strategies for future water treatment options. PMID:26358212

  9. Environmentalism and natural aggregate mining

    USGS Publications Warehouse

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

    2002-01-01

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

  10. Competitive aggregation dynamics using phase wave signals.

    PubMed

    Sakaguchi, Hidetsugu; Maeyama, Satomi

    2014-10-21

    Coupled equations of the phase equation and the equation of cell concentration n are proposed for competitive aggregation dynamics of slime mold in two dimensions. Phase waves are used as tactic signals of aggregation in this model. Several aggregation clusters are formed initially, and target patterns appear around the localized aggregation clusters. Owing to the competition among target patterns, the number of the localized aggregation clusters decreases, and finally one dominant localized pattern survives. If the phase equation is replaced with the complex Ginzburg-Landau equation, several spiral patterns appear, and n is localized near the center of the spiral patterns. After the competition among spiral patterns, one dominant spiral survives. PMID:24956327

  11. Aggregate structure, morphology and the effect of aggregation mechanisms on viscosity at elevated protein concentrations.

    PubMed

    Barnett, Gregory V; Qi, Wei; Amin, Samiul; Neil Lewis, E; Roberts, Christopher J

    2015-12-01

    Non-native aggregation is a common issue in a number of degenerative diseases and during manufacturing of protein-based therapeutics. There is a growing interest to monitor protein stability at intermediate to high protein concentrations, which are required for therapeutic dosing of subcutaneous injections. An understanding of the impact of protein structural changes and interactions on the protein aggregation mechanisms and resulting aggregate size and morphology may lead to improved strategies to reduce aggregation and solution viscosity. This report investigates non-native aggregation of a model protein, α-chymotrypsinogen, under accelerated conditions at elevated protein concentrations. Far-UV circular dichroism and Raman scattering show structural changes during aggregation. Size exclusion chromatography and laser light scattering are used to monitor the progression of aggregate growth and monomer loss. Monomer loss is concomitant with increased β-sheet structures as monomers are added to aggregates, which illustrate a transition from a native monomeric state to an aggregate state. Aggregates grow predominantly through monomer-addition, resulting in a semi-flexible polymer morphology. Analysis of aggregation growth kinetics shows that pH strongly affects the characteristic timescales for nucleation (τn) and growth (τg), while the initial protein concentration has only minor effects on τn or τg. Low-shear viscosity measurements follow a common scaling relationship between average aggregate molecular weight (Mw(agg)) and concentration (σ), which is consistent with semi-dilute polymer-solution theory. The results establish a link between aggregate growth mechanisms, which couple Mw(agg) and σ, to increases in solution viscosity even at these intermediate protein concentrations (less than 3w/v %). PMID:26284891

  12. Users’ Support as a Social Resource in Educational Services: Construct Validity and Measurement Invariance of the User-Initiated Support Scale (UISS)

    PubMed Central

    Loera, Barbara; Martini, Mara; Viotti, Sara; Converso, Daniela

    2016-01-01

    Social support is an important resource for reducing the risks of stress and burnout at work. It seems to be particularly helpful for educational and social professionals. The constant and intense relationships with users that characterize this kind of service can be very demanding, increasing stress and leading to burnout. While significant attention has been paid to supervisors and colleagues in the literature, users have rarely been considered as possible sources of social support. The only exception is the Zimmermann et al.’s (2011) research, focused on customer support as a resource for workers’ well-being. This paper proposes the validation of the customer-initiated support scale developed by Zimmermann et al. (2011), translated into Italian and focused on educational services users (children’s parents), to measure the user support perceived by workers: the User-Initiated Support Scale (UISS). In Study 1 (105 teachers), which specifically involved educators and kindergarten teachers, the items and scale properties were preliminarily examined using descriptive analyses and exploratory factor analysis (EFA). In Study 2 (304 teachers), the construct and criterion validity and scale dimensionality were analyzed using confirmatory factor analysis (CFA). In Study 3 (304 teachers from Study 2 and 296 educators), measurement invariance (MI) was tested. The EFA results from Study 1 showed a one-factor solution (explained variance, 67.2%). The scale showed good internal coherence (alpha = 0.88). The CFA in Study 2 validated the one-factor solution (comparative fit index = 0.987; standardized root mean square residual = 0.054). Bivariate correlations confirmed construct validity; the UISS was positively associated (convergent) with user gratitude, and not associated (divergent) with disproportionate customer expectations. Regarding the criterion validity test, the UISS was strongly correlated with burnout and job satisfaction. The analysis of MI performed on the

  13. Users' Support as a Social Resource in Educational Services: Construct Validity and Measurement Invariance of the User-Initiated Support Scale (UISS).

    PubMed

    Loera, Barbara; Martini, Mara; Viotti, Sara; Converso, Daniela

    2016-01-01

    Social support is an important resource for reducing the risks of stress and burnout at work. It seems to be particularly helpful for educational and social professionals. The constant and intense relationships with users that characterize this kind of service can be very demanding, increasing stress and leading to burnout. While significant attention has been paid to supervisors and colleagues in the literature, users have rarely been considered as possible sources of social support. The only exception is the Zimmermann et al.'s (2011) research, focused on customer support as a resource for workers' well-being. This paper proposes the validation of the customer-initiated support scale developed by Zimmermann et al. (2011), translated into Italian and focused on educational services users (children's parents), to measure the user support perceived by workers: the User-Initiated Support Scale (UISS). In Study 1 (105 teachers), which specifically involved educators and kindergarten teachers, the items and scale properties were preliminarily examined using descriptive analyses and exploratory factor analysis (EFA). In Study 2 (304 teachers), the construct and criterion validity and scale dimensionality were analyzed using confirmatory factor analysis (CFA). In Study 3 (304 teachers from Study 2 and 296 educators), measurement invariance (MI) was tested. The EFA results from Study 1 showed a one-factor solution (explained variance, 67.2%). The scale showed good internal coherence (alpha = 0.88). The CFA in Study 2 validated the one-factor solution (comparative fit index = 0.987; standardized root mean square residual = 0.054). Bivariate correlations confirmed construct validity; the UISS was positively associated (convergent) with user gratitude, and not associated (divergent) with disproportionate customer expectations. Regarding the criterion validity test, the UISS was strongly correlated with burnout and job satisfaction. The analysis of MI performed on the Study 3

  14. Salient latent constructs underlying smoking initiation and continuous use by student-smokers of Huazhong University of Science and Technology, China.

    PubMed

    Turkson, Anthony J; Wang, Xiang J; Gobah, Freeman F K

    2015-03-01

    The factor analysis model was used to parsimoniously reduce the number of variables that influence smoking among students to salient factors that cut across continents, race, and sociocultural settings among university students in China. Stratified random sampling and snowball techniques were employed to obtain the sample. A Likert-type questionnaire was used to collect data. The results revealed that of the 39 variables identified to influence smoking, 34 were retained and regrouped in terms of common features they share into 13 salient factors that accounted for 58% of variances in the original variables. The predominant hidden construct was influence by association. The other 12 factors were labeled and ordered as follows: emotional needs, family history, addiction, peer pressure, lack of full realization of the consequences of their action as regards the expense of smoking, social needs, advertisement, psychological needs, self-image, environmental factors, ineffective policies, and underestimation of health risks. Irrespective of regional demarcations, factors that influence smoking initiation and continuous use are same. PMID:22186389

  15. Thermal Aggregation of Recombinant Protective Antigen: Aggregate Morphology and Growth Rate

    PubMed Central

    Belton, Daniel J.; Miller, Aline F.

    2013-01-01

    The thermal aggregation of the biopharmaceutical protein recombinant protective antigen (rPA) has been explored, and the associated kinetics and thermodynamic parameters have been extracted using optical and environmental scanning electron microscopies (ESEMs) and ultraviolet light scattering spectroscopy (UV-LSS). Visual observations and turbidity measurements provided an overall picture of the aggregation process, suggesting a two-step mechanism. Microscopy was used to examine the structure of aggregates, revealing an open morphology formed by the clustering of the microscopic aggregate particles. UV-LSS was used and developed to elucidate the growth rate of these particles, which formed in the first stage of the aggregation process. Their growth rate is observed to be high initially, before falling to converge on a final size that correlates with the ESEM data. The results suggest that the particle growth rate is limited by rPA monomer concentration, and by obtaining data over a range of incubation temperatures, an approach was developed to model the aggregation kinetics and extract the rate constants and the temperature dependence of aggregation. In doing so, we quantified the susceptibility of rPA aggregation under different temperature and environmental conditions and moreover demonstrated a novel use of UV spectrometry to monitor the particle aggregation quantitatively, in situ, in a nondestructive and time-resolved manner. PMID:23476645

  16. Aggregate size distribution of the soil loss

    NASA Astrophysics Data System (ADS)

    Szabó, Judit Alexandra; Jakab, Gergely; Szabó, Boglárka; Józsa, Sándor; Szalai, Zoltán; Centeri, Csaba

    2016-04-01

    In agricultural areas the soil erosion and soil loss estimation is vital information in long-term planning. During the initial period of the erosion a part of the soil particles and aggregates get transportable and nutrients and organic matter could be transported due to the effect of water or wind. This preliminary phase was studied with laboratory-scale rainfall simulator. Developed surface crust and aggregate size composition of the runoff was examined in six different slope-roughness-moisture content combination of a Cambisol and a Regosol. The ratio of micro- and macro aggregates in the runoff indicate the stability of the aggregates and determine the transport capacity of the runoff. Both soil samples were taken from field where the water erosion is a potential hazard. During the experiment the whole amount of runoff and sediment was collected through sieve series to a bucket to separate the micro- and macro aggregates. In case of both samples the micro aggregates dominate in the runoff and the runoff rates are similar. Although the runoff of the Regosol - with dominant >1000μm macro aggregate content - contained almost nothing but <50μm sized micro aggregates. Meanwhile the runoff of the Cambisol - with more balanced micro and macro aggregate content - contained dominantly 50-250μm sized micro aggregates and in some case remarkable ratio 250-1000μm sized macro aggregates. This difference occurred because the samples are resistant against drop erosion differently. In case of both sample the selectivity of the erosion and substance matrix redistribution manifested in mineral crusts in the surface where the quartz deposited in place while the lighter organic matter transported with the sediment. The detachment of the aggregates and the redistribution of the particles highly effect on the aggregate composition of the runoff which is connected with the quality of the soil loss. So while the estimation of soil loss quantity is more or less is easy, measuring

  17. Aggregations in Flatworms.

    ERIC Educational Resources Information Center

    Liffen, C. L.; Hunter, M.

    1980-01-01

    Described is a school project to investigate aggregations in flatworms which may be influenced by light intensity, temperature, and some form of chemical stimulus released by already aggregating flatworms. Such investigations could be adopted to suit many educational levels of science laboratory activities. (DS)

  18. Geobotanical remote sensing for determination of aggregate source material

    NASA Technical Reports Server (NTRS)

    Minor, Timothy; Mouat, David; Myers, Jeff

    1988-01-01

    Aggregate source material suitable for facility and roadbed construction is often a very limited and highly valuable resource. The location of suitable source material is crucial to construction operations once facility requirements are established. The application of airborne and spaceborne remote sensing to terrain information requirements has proved attractive because of the rapid processing time and extensive spatial coverage associated with remotely gathered imagery. Source material identification may be improved by the remote sensing of vegetation associated with the material, particularly in areas of high vegetative cover. A research study employing remote sensing techniques was initiated to determine if vegetation could be used to discriminate parent materials for suitability as aggregate source material. Two test sites representing potential alluvial and residual source areas were selected in a semiarid region of Central California. Methods developed for the study included field observations of vegetation characteristics associated with the two parent material types along with the analysis of Thematic Mapper Simulator data flown over the test sites. The most useful images were those composites that included bands from two of the techniques (i.e., a Perpendicular Vegetation Index (PVI) band combined with principal components bands).

  19. Collision simulation of sintered dust aggregates

    NASA Astrophysics Data System (ADS)

    Sirono, Sin-iti; Ueno, Haruta

    Collisional evolution of dust aggregates is the initial process of the planet formation. Sticking velocity, below which collisional sticking of an aggregate happens, is a crucial quantity in the collisional evolution. In the standard model of protoplanetary nebula, the maximum collisional velocity is around 50m/s. Therefore, if a planetesimal is formed through direct collisional sticking, the sticking velocity should be higher than 50m/s. Even if a planetesimal is formed by other mechanism such as anticyclonic vortices, substantial growth of an aggregate is required because the motion of an aggregate should be decoupled from that of gas. Collisional simulation of icy dust aggregates (Wada et al. 2009, ApJ 702, 1490) showed that the sticking velocity was larger than 50m/s and planetesimal formation by collisional sticking was possible. However, sintering of ice proceeds in a wide area of a protoplanetary nebula (Sirono 2011, ApJ 765, 50). Sintering enlarges a neck, connection between adjacent dust grains, and changes the mechanical properties of a dust aggregate. Here we performed collisional simulations between sintered dust aggregates taking account of sintering. We found that the sticking velocity was decreased substantially down to 20m/s. This result suggests that a planetesimal is not formed by direct collisional sticking and that the planetesimal formation proceeded in particular regions in a protoplanetary nebula.

  20. Comparative Aggregate Patterns of Grade Retention Rates.

    ERIC Educational Resources Information Center

    Morris, Don R.

    A search for patterns in grade retention rates across grades 1-12 to construct simulation research models is described in this paper. Aggregate data from Shepard and Smith (1989) on grade retention rates from 12 American states for the year 1979-80 and from 11 states for 1985-86 were examined for across-grade patterns, supplemented by Dade County…

  1. Charged Dust Aggregate Interactions

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin; Hyde, Truell

    2015-11-01

    A proper understanding of the behavior of dust particle aggregates immersed in a complex plasma first requires a knowledge of the basic properties of the system. Among the most important of these are the net electrostatic charge and higher multipole moments on the dust aggregate as well as the manner in which the aggregate interacts with the local electrostatic fields. The formation of elongated, fractal-like aggregates levitating in the sheath electric field of a weakly ionized RF generated plasma discharge has recently been observed experimentally. The resulting data has shown that as aggregates approach one another, they can both accelerate and rotate. At equilibrium, aggregates are observed to levitate with regular spacing, rotating about their long axis aligned parallel to the sheath electric field. Since gas drag tends to slow any such rotation, energy must be constantly fed into the system in order to sustain it. A numerical model designed to analyze this motion provides both the electrostatic charge and higher multipole moments of the aggregate while including the forces due to thermophoresis, neutral gas drag, and the ion wakefield. This model will be used to investigate the ambient conditions leading to the observed interactions. This research is funded by NSF Grant 1414523.

  2. Kinetics of Thermal Denaturation and Aggregation of Bovine Serum Albumin

    PubMed Central

    Borzova, Vera A.; Markossian, Kira A.; Chebotareva, Natalia A.; Kleymenov, Sergey Yu.; Poliansky, Nikolay B.; Muranov, Konstantin O.; Stein-Margolina, Vita A.; Shubin, Vladimir V.; Markov, Denis I.; Kurganov, Boris I.

    2016-01-01

    Thermal aggregation of bovine serum albumin (BSA) has been studied using dynamic light scattering, asymmetric flow field-flow fractionation and analytical ultracentrifugation. The studies were carried out at fixed temperatures (60°C, 65°C, 70°C and 80°C) in 0.1 M phosphate buffer, pH 7.0, at BSA concentration of 1 mg/ml. Thermal denaturation of the protein was studied by differential scanning calorimetry. Analysis of the experimental data shows that at 65°C the stage of protein unfolding and individual stages of protein aggregation are markedly separated in time. This circumstance allowed us to propose the following mechanism of thermal aggregation of BSA. Protein unfolding results in the formation of two forms of the non-native protein with different propensity to aggregation. One of the forms (highly reactive unfolded form, Uhr) is characterized by a high rate of aggregation. Aggregation of Uhr leads to the formation of primary aggregates with the hydrodynamic radius (Rh,1) of 10.3 nm. The second form (low reactive unfolded form, Ulr) participates in the aggregation process by its attachment to the primary aggregates produced by the Uhr form and possesses ability for self-aggregation with formation of stable small-sized aggregates (Ast). At complete exhaustion of Ulr, secondary aggregates with the hydrodynamic radius (Rh,2) of 12.8 nm are formed. At 60°C the rates of unfolding and aggregation are commensurate, at 70°C the rates of formation of the primary and secondary aggregates are commensurate, at 80°C the registration of the initial stages of aggregation is complicated by formation of large-sized aggregates. PMID:27101281

  3. Aggregate and the environment

    USGS Publications Warehouse

    Langer, William H.; Drew, Lawrence J.; Sachs, J.S.

    2004-01-01

    This book is designed to help you understand our aggregate resources-their importance, where they come from, how they are processed for our use, the environmental concerns related to their mining and processing, how those concerns are addressed, and the policies and regulations designed to safeguard workers, neighbors, and the environment from the negative impacts of aggregate mining. We hope this understanding will help prepare you to be involved in decisions that need to be made-individually and as a society-to be good stewards of our aggregate resources and our living planet.

  4. Protein Colloidal Aggregation Project

    NASA Technical Reports Server (NTRS)

    Oliva-Buisson, Yvette J. (Compiler)

    2014-01-01

    To investigate the pathways and kinetics of protein aggregation to allow accurate predictive modeling of the process and evaluation of potential inhibitors to prevalent diseases including cataract formation, chronic traumatic encephalopathy, Alzheimer's Disease, Parkinson's Disease and others.

  5. Particle aggregation mechanisms in ionic liquids.

    PubMed

    Szilagyi, Istvan; Szabo, Tamas; Desert, Anthony; Trefalt, Gregor; Oncsik, Tamas; Borkovec, Michal

    2014-05-28

    Aggregation of sub-micron and nano-sized polystyrene latex particles was studied in room temperature ionic liquids (ILs) and in their water mixtures by time-resolved light scattering. The aggregation rates were found to vary with the IL-to-water molar ratio in a systematic way. At the water side, the aggregation rate is initially small, but increases rapidly with increasing IL content, and reaches a plateau value. This behaviour resembles simple salts, and can be rationalized by the competition of double-layer and van der Waals forces as surmised by the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO). At the IL side, aggregation slows down again. Two generic mechanisms could be identified to be responsible for the stabilization in ILs, namely viscous stabilization and solvation stabilization. Viscous stabilization is important in highly viscous ILs, as it originates from the slowdown of the diffusion controlled aggregation due to the hindrance of the diffusion in a viscous liquid. The solvation stabilization mechanism is system specific, but can lead to a dramatic slowdown of the aggregation rate in ILs. This mechanism is related to repulsive solvation forces that are operational in ILs due to the layering of the ILs close to the surfaces. These two stabilization mechanisms are suspected to be generic, as they both occur in different ILs, and for particles differing in surface functionalities and size. PMID:24727976

  6. Aggregation of commercial heparin samples in storage.

    PubMed

    Racey, T J; Rochon, P; Awang, D V; Neville, G A

    1987-04-01

    The size distribution of heparin aggregates in commercial heparin preparations was examined with the technique of quasi-elastic light scattering. The size distributions were initially examined to determine if any relationship existed between the physical state of the heparin preparation, its age, and its biological activity. It was found that commercial heparin samples change their aggregation state in storage. The amount of aggregation appears to be related to the amount of time in storage and to the storage history. Storage of the samples under conditions of refrigeration and handling represents the storage history that most noticeably increases the aggregation state of the heparin preparations. These aggregates, once formed, appear to be stable. The biological activity of the heparin samples (as measured by the official test) was found to still fall within the accepted limits, independent of the aggregation state of the samples. It is not known what effect, if any, a change in the physical state of the commercial preparation should have on its biological activity. PMID:3598891

  7. Ion-specific aggregation of hydrophobic particles.

    PubMed

    López-León, Teresa; Ortega-Vinuesa, Juan Luis; Bastos-González, Delfina

    2012-06-18

    This work shows that colloidal stability and aggregation kinetics of hydrophobic polystyrene (PS) nanospheres are extremely sensitive to the nature of the salt used to coagulate them. Three PS latices and four aggregating electrolytes, which all share the same cation (Na(+)) but have various anions located at different positions in the classical Hofmeister series depending on their kosmotropic or chaotropic character, are used. The present study focuses on analyzing different aggregating parameters, such as critical coagulation concentrations (CCC), cluster size distributions (CSD), initial kinetic constants K(11), and fractal dimensions of the aggregates d(f). While aggregation induced by SO(4)(2-) and Cl(-) behaved according to the predictions of the classical Derjaguin-Landau-Verwey-Overbeek theory, important discrepancies are found with NO(3)(-), which become dramatic when using SCN(-). These discrepancies among the anions were far more significant when they acted as counterions rather than as co-ions. While SO(4)(2-) and Cl(-) trigger fast diffusion-limited aggregation, SCN(-) gives rise to a stationary cluster size distribution in a few aggregation times when working with cationic PS particles. Clear differences are found among all analyzed parameters (CCC, CSD, K(11), and d(f)), and the experimental findings show that particles aggregate in potential wells whose depth is controlled by the chaotropic character of the anion. This paper presents new experimental evidence that may help to understand the microscopic origin of Hofmeister effects, as the observations are consistent with appealing theoretical models developed in the last few years. PMID:22556130

  8. Microstructural characterization of concrete prepared with recycled aggregates.

    PubMed

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

    2013-10-01

    Several authors have reported the workability, mechanical properties, and durability of concrete produced with construction waste replacing the natural aggregate. However, a systematic microstructural characterization of recycled aggregate concrete has not been reported. This work studies the use of fine recycled aggregate to replace fine natural aggregate in the production of concrete and reports the resulting microstructures. The used raw materials were natural aggregate, recycled aggregate obtained from a standard concrete, and Portland cement. The substitution extent was 0, 10, 50, and 100 vol%; hydration was stopped at 9, 24, and 96 h and 28 days. Microscopy was focused on the cement/aggregate interfacial transition zone, enlightening the effect of incorporating recycled aggregate on the formation and morphology of the different concrete hydration products. The results show that concretes with recycled aggregates exhibit typical microstructural features of the transition zone in normal strength concrete. Although overall porosity increases with increasing replacement, the interfacial bond is apparently stronger when recycled aggregates are used. An addition of 10 vol% results in a decrease in porosity at the interface with a corresponding increase of the material hardness. This provides an opportunity for development of increased strength Portland cement concretes using controlled amounts of concrete waste. PMID:23673273

  9. 200 North Aggregate Area source AAMS report

    SciTech Connect

    Not Available

    1993-06-01

    This report presents the results of an aggregate area management study (AAMS) for the 200 North Aggregate Area in the 200 Areas of the US Department of Energy (DOE) Hanford Site in Washington State. This scoping level study provides the basis for initiating Remedial Investigation/Feasibility Study (RI/FS) activities under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) or Resource Conservation and Recovery Act (RCRA) Facility Investigations (RFI) and Corrective Measures Studies (CMS) under RCRA. This report also integrates select RCRA treatment, storage, or disposal (TSD) closure activities with CERCLA and RCRA past practice investigations.

  10. Technology meets aggregate

    SciTech Connect

    Wilson, C.; Swan, C.

    2007-07-01

    New technology carried out at Tufts University and the University of Massachusetts on synthetic lightweight aggregate has created material from various qualities of fly ash from coal-fired power plants for use in different engineered applications. In pilot scale manufacturing tests an 'SLA' containing 80% fly ash and 20% mixed plastic waste from packaging was produced by 'dry blending' mixed plastic with high carbon fly ash. A trial run was completed to produce concrete masonry unit (CMU) blocks at a full-scale facility. It has been shown that SLA can be used as a partial substitution of a traditional stone aggregate in hot asphalt mix. 1 fig., 2 photos.

  11. Ralstonia insidiosa induces cell aggregation by Listeria monocytogenes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biofilm formation is an important strategy for foodborne bacterial pathogens to survive in stressful environments such as fresh produce processing facilities. Bacterial cell aggregation strongly promotes the initiation of microcolonies and the formation of biofilms on abiological surfaces. We previ...

  12. Reduction in soil aggregation in response to dust emission processes

    NASA Astrophysics Data System (ADS)

    Swet, Nitzan; Katra, Itzhak

    2016-09-01

    Dust emission by aeolian (wind) soil erosion depends on the topsoil properties of the source area, especially on the nature of the aggregates where most dust particles are held. Although the key role of soil aggregates in dust emission, the response of soil aggregation to aeolian processes and its implications for dust emission remain unknown. This study focuses on aggregate size distribution (ASD) analyses before and after in-situ aeolian experiments in semiarid loess soils that are associated with dust emission. Wind tunnel simulations show that particulate matter (PM) emission and saltation rates depend on the initial ASD and shear velocity. Under all initial ASD conditions, the content of saltator-sized aggregates (63-250 μm) increased by 10-34% due to erosion of macro-aggregates (> 500 μm), resulting in a higher size ratio (SR) between the saltators and macro-aggregates following the aeolian erosion. The results revealed that the saltator production increases significantly for soils that are subjected to short-term (anthropogenic) disturbance of the topsoil. The findings highlight a decrease in soil aggregation for all initial ASD's in response to aeolian erosion, and consequently its influence on the dust emission potential. Changes in ASD should be considered as a key parameter in dust emission models of complex surfaces.

  13. Orbital Aggregation and Space Infrastructure Systems (OASIS)

    NASA Technical Reports Server (NTRS)

    Troutman, Patrick A.; Mazanek, Daniel D.; Stillwagen, Frederic H.; Antol, Jeffrey; Sarver-Verhey, Timothy R.; Chato, David J.; Saucillo, Rudolf J.; Blue, Douglas R.; Carey, David; Krizan, Shawn A.

    2002-01-01

    This paper summarizes the results of a NASA lead study performed to identify synergistic opportunities and concepts between human exploration initiatives and commercialization of space. The goal of this initiative, called Orbital Aggregation & Space Infrastructure Systems (OASIS), is to develop an in-space architecture and associated concepts that provide common infrastructure for enabling a large class of space missions. The concepts include communications, navigation and power systems, propellant modules, tank farms, habitats, and in-space transportation systems using several propulsion technologies. OASIS features in-space aggregation of systems and resources in support of mission objectives. The concepts feature a high level of reusability and are supported by inexpensive launch of propellant and logistics payloads from the Earth/moon system. Industry, NASA and other users could share infrastructure costs. The anticipated benefits of synergistic utilization of space infrastructure are reduced mission costs and increased mission flexibility for future space exploration and commercialization initiatives.

  14. Under Construction: Benchmark Assessments and Common Core Math Implementation in Grades K-8. Formative Evaluation Cycle Report for the Math in Common Initiative, Volume 1

    ERIC Educational Resources Information Center

    Flaherty, John, Jr.; Sobolew-Shubin, Alexandria; Heredia, Alberto; Chen-Gaddini, Min; Klarin, Becca; Finkelstein, Neal D.

    2014-01-01

    Math in Common® (MiC) is a five-year initiative that supports a formal network of 10 California school districts as they implement the Common Core State Standards in mathematics (CCSS-M) across grades K-8. As the MiC initiative moves into its second year, one of the central activities that each of the districts is undergoing to support CCSS…

  15. Chemotaxis Control of Transient Cell Aggregation

    PubMed Central

    2015-01-01

    Chemotaxis affords motile cells the ability to rapidly respond to environmental challenges by navigating cells to niches favoring growth. Such a property results from the activities of dedicated signal transduction systems on the motility apparatus, such as flagella, type IV pili, and gliding machineries. Once cells have reached a niche with favorable conditions, they often stop moving and aggregate into complex communities termed biofilms. An intermediate and reversible stage that precedes commitment to permanent adhesion often includes transient cell-cell contacts between motile cells. Chemotaxis signaling has been implicated in modulating the transient aggregation of motile cells. Evidence further indicates that chemotaxis-dependent transient cell aggregation events are behavioral responses to changes in metabolic cues that temporarily prohibit permanent attachment by maintaining motility and chemotaxis. This minireview discusses a few examples illustrating the role of chemotaxis signaling in the initiation of cell-cell contacts in bacteria moving via flagella, pili, or gliding. PMID:26216846

  16. A stab in the dark: Design and construction of a novel device for conducting incised knife trauma investigations and its initial test.

    PubMed

    Humphrey, Caitlin; Kumaratilake, Jaliya; Henneberg, Maciej

    2016-05-01

    Knife attacks are commonly seen in Australia and other countries. During forensic investigations the force with which a wound was inflicted is often questioned. The ability to examine resultant trauma and particular weapons at different forces with an experimental device may lead to better interpretations of knife wounds. The objective of this study is to design, construct and test a device to analyse the characteristics and forces involved in knife attacks, particularly incised wounds. The mechanical variables (e.g. force, angle, knife geometry) involved in knife attacks have been considered to design and construct a suitable device which allows these variables to be systematically controlled and varied. A device was designed and constructed from mild steel. This included a pivoting arm and instrumented knife holder. The arm has adjustable angle and weight so that knives can be operated at different calculated forces. A device was successfully constructed and the repeatability of incised knife trauma and its characteristics in skeletal tissues were investigated. A device which allows reproducible and controlled experiments with knife wounds will be advantageous to forensic investigations. In particular, in determining forces and types of weapons associated with particular wounds, identifying or eliminating suspected weapons and more accurately answering the common question: How much force would be required to cause that particular wound. This could help to characterise the perpetrator. The device can be altered to be used in the future to investigate trauma caused by other weapons. PMID:27061866

  17. Aggregates, broccoli and cauliflower

    NASA Astrophysics Data System (ADS)

    Grey, Francois; Kjems, Jørgen K.

    1989-09-01

    Naturally grown structures with fractal characters like broccoli and cauliflower are discussed and compared with DLA-type aggregates. It is suggested that the branching density can be used to characterize the growth process and an experimental method to determine this parameter is proposed.

  18. Identifying protein aggregation mechanisms and quantifying aggregation rates from combined monomer depletion and continuous scattering.

    PubMed

    Barnett, Gregory V; Drenski, Michael; Razinkov, Vladimir; Reed, Wayne F; Roberts, Christopher J

    2016-10-15

    Parallel temperature initial rates (PTIR) from chromatographic separation of aggregating protein solutions are combined with continuous simultaneous multiple sample light scattering (SMSLS) to make quantitative deductions about protein aggregation kinetics and mechanisms. PTIR determines the rates at which initially monomeric proteins are converted to aggregates over a range of temperatures, under initial-rate conditions. Using SMSLS for the same set of conditions provides time courses of the absolute Rayleigh scattering ratio, IR(t), from which a potentially different measure of aggregation rates can be quantified. The present report compares these measures of aggregation rates across a range of solution conditions that result in different aggregation mechanisms for anti-streptavidin (AS) immunoglobulin gamma-1 (IgG1). The results illustrate how the two methods provide complementary information when deducing aggregation mechanisms, as well as cases where they provide new mechanistic details that were not possible to deduce in previous work. Criteria are presented for when the two techniques are expected to give equivalent results for quantitative rates, the potential limitations when solution non-idealities are large, as well as a comparison of the temperature dependence of AS-IgG1 aggregation rates with published data for other antibodies. PMID:27510552

  19. Cluster-cluster aggregation simulation in a concentrated suspension.

    PubMed

    Kusaka, Yasuyuki; Fukasawa, Tomonori; Adachi, Yasuhisa

    2011-11-01

    The collision radius of a floc is an indispensable parameter for the precise description of the rate of aggregation during the development of particle flocs with a wide size distribution. Herein, we report on the characteristics of the collision radius of fractal aggregates formed by off-lattice diffusion-limited cluster-cluster aggregation (DLCCA) simulations, and discuss aggregation kinetics based on the value of the estimated collision radius. The collision radius has a fractal relationship with the number of primary particles that compose the floc. Further, the obtained fractal dimensions of flocs increase from the normally accepted value of 1.6-1.8 to a value of ~2.5 when the initial volume fraction is above 8%. From an assessment of the partial radial distribution function of the particles, the increase of the fractal dimensions determined by the collision radius can be attributed to a change in the spatial distribution of neighboring particles. The DLCCA simulation also reveals an apparent increase in the rate of aggregation upon an increase in the initial volume fraction. For a relatively low initial volume fraction, the enhancement of the aggregation rate is expressed by a population balance equation taking into account additional factors, i.e., transient collision flux among particles/flocs, excluded volumes, and polydispersed features of flocs. However, for cases with high initial volume fractions, the population balance model that accounts for these three factors overestimates the aggregation rate, which supports the concept of a caging effect. PMID:21840531

  20. Aggregation kinetics and structure of cryoimmunoglobulins clusters

    NASA Astrophysics Data System (ADS)

    Spirito, M. De; Chiappini, R.; Bassi, F. Andreasi; Stasio, E. Di; Giardina, B.; Arcovito, G.

    2002-02-01

    Cryoimmunoglobulins are pathological antibodies characterized by a temperature-dependent reversible insolubility. Rheumatoid factors (RF) are immunoglobulins possessing anti-immunoglobulin activity and usually consist of an IgM antibody that recognizes IgG as antigen. These proteins are present in sera of patients affected by a large variety of different pathologies, such as HCV infection, neoplastic and autoimmune diseases. Aggregation and precipitation of cryoimmunoglobulins, leading to vasculiti, are physical phenomena behind such pathologies. A deep knowledge of the physico-chemical mechanisms regulating such phenomena plays a fundamental role in biological and clinical applications. In this work, a preliminary investigation of the aggregation kinetics and of the final macromolecular structure of the aggregates is presented. Through static light scattering techniques, the gyration radius Rg and the fractal dimension Dm of the growing clusters have been determined. However, while the initial aggregation mechanism could be described using the universal reaction-limited cluster-cluster aggregation (RLCCA) theory, at longest times from the beginning of the process, the RLCCA theory fails and a restructuring of clusters is observed together with an increase of the cluster fractal dimension Dm up to a value Dm∼3. The time tn, at which the restructuring takes place, and the final cluster size can be modulated by varying the quenching temperature.

  1. Determination of the dynamic elastic constants of recycled aggregate concrete

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    Nowadays, construction and demolition waste constitutes a major portion of the total solid waste production in the world. Due to both environmental and economical reasons, an increasing interest concerning the use of recycled aggregate to replace aggregate from natural sources is generated. This paper presents an investigation on the properties of recycled aggregate concrete. Concrete mixes are prepared using recycled aggregates at a substitution level between 0 and 100% of the total coarse aggregate. The influence of this replacement on strengthened concrete's properties is being investigated. The properties estimated are: density and dynamic modulus of elasticity at the age of both 7 and 28 days. Also, flexural strength of 28 days specimens is estimated. The determination of the dynamic elastic modulus was made using the ultrasonic pulse velocity method. The results reveal that the existence of recycled aggregates affects the properties of concrete negatively; however, in low levels of substitution the influence of using recycled aggregates is almost negligible. Concluding, the controlled use of recycled aggregates in concrete production may help solve a vital environmental issue apart from being a solution to the problem of inadequate concrete aggregates.

  2. Construct validity of adolescents' self-reported big five personality traits: importance of conceptual breadth and initial validation of a short measure.

    PubMed

    Morizot, Julien

    2014-10-01

    While there are a number of short personality trait measures that have been validated for use with adults, few are specifically validated for use with adolescents. To trust such measures, it must be demonstrated that they have adequate construct validity. According to the view of construct validity as a unifying form of validity requiring the integration of different complementary sources of information, this article reports the evaluation of content, factor, convergent, and criterion validities as well as reliability of adolescents' self-reported personality traits. Moreover, this study sought to address an inherent potential limitation of short personality trait measures, namely their limited conceptual breadth. In this study, starting with items from a known measure, after the language-level was adjusted for use with adolescents, items tapping fundamental primary traits were added to determine the impact of added conceptual breadth on the psychometric properties of the scales. The resulting new measure was named the Big Five Personality Trait Short Questionnaire (BFPTSQ). A group of expert judges considered the items to have adequate content validity. Using data from a community sample of early adolescents, the results confirmed the factor validity of the Big Five structure in adolescence as well as its measurement invariance across genders. More important, the added items did improve the convergent and criterion validities of the scales, but did not negatively affect their reliability. This study supports the construct validity of adolescents' self-reported personality traits and points to the importance of conceptual breadth in short personality measures. PMID:24619971

  3. Hierarchically Fourier-aggregated signals and generalized coherence of the noise in the GPS time series

    NASA Astrophysics Data System (ADS)

    Lyubushin, Alexey

    2016-04-01

    A new method for joint analysis of big number of time series is presented. The method is based on using of Fourier-aggregated signals and it has a purpose to detect time intervals and frequency bands when there is a coherence between noise components of all time series. An aggregated signal (AS) is constructed in two stages. At the 1st stage, initial multidimensional time series is substituted by time series of the same dimensionality but composed of so-called canonical components. The canonical components accumulate signals that are common for all initial components and are free of local variations that are specific for individual scalar time series only. At the 2nd stage, the common signals are amplified by constructing a single scalar time series, their first principal component. Thus, an AS is the first principal component of canonical components. In the case when there is a monitoring system with big number of recording stations all stations are split into a number of clusters with moderate number (10-20) of stations within each clusters. For all clusters AS are calculated which could be called AS of the 1st order. The technique of the 1st order AS computing provides estimating in moving time window and gives a possibility to take into account gaps in registration. If the number of the 1st order aggregation clusters is still big they could be split into 2nd order aggregation clusters and the 1st order AS could be aggregated more into 2nd order AS. At any stage of aggregation a multiple spectral coherence measures could be calculated which present time-frequency diagrams for evolution of coherence between noise components of time series. The elaborated method was applied to daily 3-components GPS time series from the networks in the USA (4512 stations) and in Europe (2122 stations). The multiple coherence measure estimated for different combinations of AS of the 1st and 2nd orders inside regions of USA and Europe and between them extracted essential peaks of

  4. Acoustic emission monitoring of recycled aggregate concrete under bending

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  5. Influence of porosity on collisions between dust aggregates

    NASA Astrophysics Data System (ADS)

    Gunkelmann, Nina; Ringl, Christian; Urbassek, Herbert M.

    2016-04-01

    Context. Collisions between dust particles may lead to agglomerate growth or fragmentation, depending on the porosity of the dust and the collision velocity. Aims: We study the effect of agglomerate porosity and collision velocity on aggregate fragmentation and agglomeration. Methods: Granular-mechanics simulations are used to study the outcome of head-on dust aggregate collisions. The aggregates are composed of silica grains of 0.76 μm radius and have filling factors of between 0.08 and 0.21. The simulations incorporate repulsive and viscoelastic, dissipative normal forces, and intergrain adhesion. The tangential forces are composed of gliding, rolling, and torsional friction. To study the effect of aggregate porosity, we prepared spherical aggregates with identical radius but differing particle numbers. Results: The threshold velocity for agglomerate fragmentation decreases with the porosity of the aggregates. Porous aggregates tend to fragment more easily, and the fragments are irregularly shaped. In the agglomeration regime, the merged aggregate is more compact than the initial collision partners. The collision velocity at which compaction is highest is independent of the initial porosity.

  6. [The formation of the influenza virus aggregates, enriched with hemagglutinin].

    PubMed

    Prokudina, E N; Semenova, N P; Chumakov, V M; Rudneva, I A; Iamnikova, S S

    2002-01-01

    The formation of electrostatic aggregates was studied by analysis of two types of virus-containing liquids: initial warm liquid collected at temperature 37 degrees and the same liquid stored over the night at temperature 4 degrees C. The formation of virus aggregates was revealed at 4 degrees C. The aggregates formed at temperature 4 degrees C had a relatively high HA/NP ratio in comparison with unassociated virus analyzed at 37 degrees. HA-enriched aggregates were found in the precipitate formed under short-term high-speed centrifugation as well as in "heavy arm" of the virus profile in the saccharose gradient. Aggregates formed at 4 degrees C dissociated at 37 degrees. The ability to form aggregates is reversible and correlates with the virus concentration. It is shown also that virus containing liquid contains heterogenic structures with molecular weight under 2000 kD having HA involved in the forming aggregates enriching HA. Possible nature of low-molecular HA-containing structures involved in the aggregates and nature of relations stabilizing aggregates are discussed. PMID:12271719

  7. Proteins aggregation and human diseases

    NASA Astrophysics Data System (ADS)

    Hu, Chin-Kun

    2015-04-01

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

  8. Comparative environmental assessment of natural and recycled aggregate concrete.

    PubMed

    Marinković, S; Radonjanin, V; Malešev, M; Ignjatović, I

    2010-11-01

    Constant and rapid increase in construction and demolition (C&D) waste generation and consumption of natural aggregate for concrete production became one of the biggest environmental problems in the construction industry. Recycling of C&D waste represents one way to convert a waste product into a resource but the environment benefits through energy consumption, emissions and fallouts reductions are not certain. The main purpose of this study is to determine the potentials of recycled aggregate concrete (concrete made with recycled concrete aggregate) for structural applications and to compare the environmental impact of the production of two types of ready-mixed concrete: natural aggregate concrete (NAC) made entirely with river aggregate and recycled aggregate concrete (RAC) made with natural fine and recycled coarse aggregate. Based on the analysis of up-to-date experimental evidence, including own tests results, it is concluded that utilization of RAC for low-to-middle strength structural concrete and non-aggressive exposure conditions is technically feasible. The Life Cycle Assessment (LCA) is performed for raw material extraction and material production part of the concrete life cycle including transport. Assessment is based on local LCI data and on typical conditions in Serbia. Results of this specific case study show that impacts of aggregate and cement production phases are slightly larger for RAC than for NAC but the total environmental impacts depend on the natural and recycled aggregates transport distances and on transport types. Limit natural aggregate transport distances above which the environmental impacts of RAC can be equal or even lower than the impacts of NAC are calculated for the specific case study. PMID:20434898

  9. Aggregation methodology for the circum-arctic resource appraisal

    USGS Publications Warehouse

    Schuenemeyer, John H.; Gautier, Donald L.

    2009-01-01

    This paper presents a methodology that intends to aggregate the results of a recent assessment of undiscovered conventional oil and gas resources of the Arctic by the U.S. Geological Survey. The assessment occurred in 48 geologically defined regions called assessment units. The methodology includes using assessor specified pair-wise correlations as the basis to construct a correlation matrix. Sampling from this matrix generates more realistic uncertainty estimates of aggregated resources than if assumptions of total independence or total dependence are made. The latter two assumptions result in overly narrow or overly broad estimates. Aggregation results for resources in regions north of the Arctic Circle are presented.

  10. Dynamics of fire ant aggregations

    NASA Astrophysics Data System (ADS)

    Tennenbaum, Michael; Hu, David; Fernandez-Nieves, Alberto

    Fire ant aggregations are an inherently active system. Each ant harvests its own energy and can convert it into motion. The motion of individual ants contributes non-trivially to the bulk material properties of the aggregation. We have measured some of these properties using plate-plate rheology, where the response to an applied external force or deformation is measured. In this talk, we will present data pertaining to the aggregation behavior in the absence of any external force. We quantify the aggregation dynamics by monitoring the rotation of the top plate and by measuring the normal force. We then compare the results with visualizations of 2D aggregations.

  11. Dielectric approach to investigation of erythrocyte aggregation. II. Kinetics of erythrocyte aggregation-disaggregation in quiescent and flowing blood.

    PubMed

    Pribush, A; Meiselman, H J; Meyerstein, D; Meyerstein, N

    2000-01-01

    A method based on dielectric properties of dispersed systems was applied to investigate the kinetics of RBC aggregation and the break-up of the aggregates. Experimentally, this method consists of measuring the capacitance at a frequency in the beginning of the beta-dispersion. Two experimental protocols were used to investigate the aggregation process. In the first case, blood samples were fully dispersed and then the flow was decreased or stopped to promote RBC aggregation. It was found that the initial phases of RBC aggregation are not affected by the shear rate. This finding indicates that RBC aggregation is a slow coagulation process. In the second case, RBCs aggregated under flow conditions at different shear rates and after the capacitance reached plateau levels, the flow was ceased. The steady-state capacitance of the quiescent blood and the kinetics of RBC aggregation after stoppage of shearing depend on the prior shear rate. To clarify the reasons for this effect, the kinetics of the disaggregation process was studied. In these experiments, time courses of the capacitance were recorded under different flow conditions and then a higher shear stress was applied to break up RBC aggregates. It was found that the kinetics of the disaggregation process depend on both the prior and current shear stresses. Results obtained in this study and their analysis show that the kinetics of RBC aggregation in stasis consists of two consecutive phases: At the onset, red blood cells interact face-to-face to form linear aggregates and then, after an accumulation of an appropriate concentration of these aggregates, branched rouleaux are formed via reactions of ends of the linear rouleaux with sides of other rouleaux (face-to-side interactions). Branching points are broken by low shear stresses whereas dispersion of the linear rouleaux requires significantly higher energy. PMID:11204548

  12. Cycloid Motions of Aggregates in a Dust Plasma

    NASA Astrophysics Data System (ADS)

    Feng, Fan; Zhang, Yongliang; Yan, Jia; Liu, Fucheng; Dong, Lifang; He, Yafeng

    2016-01-01

    Hypocycloid and epicycloid motions of aggregates consisted of one large and one small grains are experimentally observed in an rf dust plasma. The cycloid motions are regarded as combination of a primary circle and a secondary circle. Measurements with high spatiotemporal resolution show that the secondary circle is determined by the initial angle velocity of the dropped aggregate. The primary circle originates from the asymmetry of the aggregate. The small grain in the aggregate always leads the large one as they travelling, which results from the difference of the natural frequency of the two grains. Comparative experiments with regular microspheres show that the cycloid motions are distinctive features of aggregates immersed in a plasma. supported by National Natural Science Foundation of China (Nos. 11205044, 11405042), the Natural Science Foundation of Hebei Province, China (Nos. A2011201006, A2012201015), the Research Foundation of Education Bureau of Hebei Province, China (Nos. Y2012009, ZD2015025), and the Midwest Universities Comprehensive Strength Promotion Project of China

  13. Tau Aggregation Propensity Engrained in Its Solution State.

    PubMed

    Eschmann, Neil A; Do, Thanh D; LaPointe, Nichole E; Shea, Joan-Emma; Feinstein, Stuart C; Bowers, Michael T; Han, Songi

    2015-11-12

    A peptide fragment of the human tau protein which stacks to form neat cross β-sheet fibrils, resembling that found in pathological aggregation, (273)GKVQIINKKLDL(284) (here "R2/WT"), was modified with a spin-label at the N-terminus. With the resulting peptide, R2/G273C-SL, we probed events at time scales spanning seconds to hours after aggregation is initiated using transmission electron microscopy (TEM), thioflavin T (THT) fluorescence, ion mobility mass spectrometry (IMMS), electron paramagnetic resonance (EPR), and Overhauser dynamic nuclear polarization (ODNP) to determine if deliberate changes to its conformational states and population in solution influence downstream propensity to form fibrillar aggregates. We find varying solution conditions by adding the osmolyte urea or TMAO, or simply using different buffers (acetate buffer, phosphate buffer, or water), produces significant differences in early monomer/dimer populations and conformations. Crucially, these characteristics of the peptide in solution state before aggregation is initiated dictate the fibril formation propensity after aggregation. We conclude the driving forces that accelerate aggregation, when heparin is added, do not override the subtle intra- or interprotein interactions induced by the initial solvent conditions. In other words, the balance of protein-protein vs protein-solvent interactions present in the initial solution conditions is a critical driving force for fibril formation. PMID:26484390

  14. Making Graphene Resist Aggregation

    NASA Astrophysics Data System (ADS)

    Luo, Jiayan

    Graphene-based sheets have stimulated great interest in many scientific disciplines and shown promise for wide potential applications. Among various ways of creating single atomic layer carbon sheets, a promising route for bulk production is to first chemically exfoliate graphite powders to graphene oxide (GO) sheets, followed by reduction to form chemically modified graphene (CMG). Due to the strong van der Waals attraction between graphene sheets, CMG tends to aggregate. The restacking of sheets is largely uncontrollable and irreversible, thus it reduces their processability and compromises properties such as accessible surface area. Strategies based on colloidal chemistry have been applied to keep CMG dispersed in solvents by introducing electrostatic repulsion to overcome the van der Waals attraction or adding spacers to increase the inter-sheet spacing. In this dissertation, two very different ideas that can prevent CMG aggregation without extensively modifying the material or introducing foreign spacer materials are introduced. The van der Waals potential decreases with reduced overlapping area between sheets. For CMG, reducing the lateral dimension from micrometer to nanometer scale should greatly enhance their colloidal stability with additional advantages of increased charge density and decreased probability to interact. The enhanced colloidal stability of GO and CMG nanocolloids makes them especially promising for spectroscopy based bio-sensing applications. For potential applications in a compact bulk solid form, the sheets were converted into paper-ball like structure using capillary compression in evaporating aerosol droplets. The crumpled graphene balls are stabilized by locally folded pi-pi stacked ridges, and do not unfold or collapse during common processing steps. They can tightly pack without greatly reducing the surface area. This form of graphene leads to scalable performance in energy storage. For example, planer sheets tend to aggregate and

  15. Structure of Viral Aggregates

    NASA Astrophysics Data System (ADS)

    Barr, Stephen; Luijten, Erik

    2010-03-01

    The aggregation of virus particles is a particular form of colloidal self-assembly, since viruses of a give type are monodisperse and have identical, anisotropic surface charge distributions. In small-angle X-ray scattering experiments, the Qbeta virus was found to organize in different crystal structures in the presence of divalent salt and non-adsorbing polymer. Since a simple isotropic potential cannot explain the occurrence of all observed phases, we employ computer simulations to investigate how the surface charge distribution affects the virus interactions. Using a detailed model of the virus particle, we find an asymmetric ion distribution around the virus which gives rise to the different phases observed.

  16. Construction of a Gene Knockout System for Application in Paenibacillus alvei CCM 2051T, Exemplified by the S-Layer Glycan Biosynthesis Initiation Enzyme WsfP▿

    PubMed Central

    Zarschler, Kristof; Janesch, Bettina; Zayni, Sonja; Schäffer, Christina; Messner, Paul

    2009-01-01

    The gram-positive bacterium Paenibacillus alvei CCM 2051T is covered by an oblique surface layer (S-layer) composed of glycoprotein subunits. The S-layer O-glycan is a polymer of [→3)-β-d-Galp-(1[α-d-Glcp-(1→6)]→4)-β-d-ManpNAc-(1→] repeating units that is linked by an adaptor of -[GroA-2→OPO2→4-β-d-ManpNAc-(1→4)]→3)-α-l-Rhap-(1→3)-α-l-Rhap-(1→3)-α-l-Rhap-(1→3)-β-d-Galp-(1→ to specific tyrosine residues of the S-layer protein. For elucidation of the mechanism governing S-layer glycan biosynthesis, a gene knockout system using bacterial mobile group II intron-mediated gene disruption was developed. The system is further based on the sgsE S-layer gene promoter of Geobacillus stearothermophilus NRS 2004/3a and on the Geobacillus-Bacillus-Escherichia coli shuttle vector pNW33N. As a target gene, wsfP, encoding a putative UDP-Gal:phosphoryl-polyprenol Gal-1-phosphate transferase, representing the predicted initiation enzyme of S-layer glycan biosynthesis, was disrupted. S-layer protein glycosylation was completely abolished in the insertional P. alvei CCM 2051T wsfP mutant, according to sodium dodecyl sulfate-polyacrylamide gel electrophoresis evidence and carbohydrate analysis. Glycosylation was fully restored by plasmid-based expression of wsfP in the glycan-deficient P. alvei mutant, confirming that WsfP initiates S-layer protein glycosylation. This is the first report on the successful genetic manipulation of bacterial S-layer protein glycosylation in vivo, including transformation of and heterologous gene expression and gene disruption in the model organism P. alvei CCM 2051T. PMID:19304819

  17. Construction of a gene knockout system for application in Paenibacillus alvei CCM 2051T, exemplified by the S-layer glycan biosynthesis initiation enzyme WsfP.

    PubMed

    Zarschler, Kristof; Janesch, Bettina; Zayni, Sonja; Schäffer, Christina; Messner, Paul

    2009-05-01

    The gram-positive bacterium Paenibacillus alvei CCM 2051T is covered by an oblique surface layer (S-layer) composed of glycoprotein subunits. The S-layer O-glycan is a polymer of [-->3)-beta-D-Galp-(1[alpha-D-Glcp-(1-->6)]-->4)-beta-D-ManpNAc-(1-->] repeating units that is linked by an adaptor of -[GroA-2-->OPO2-->4-beta-D-ManpNAc-(1-->4)]-->3)-alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->3)-beta-D-Galp-(1--> to specific tyrosine residues of the S-layer protein. For elucidation of the mechanism governing S-layer glycan biosynthesis, a gene knockout system using bacterial mobile group II intron-mediated gene disruption was developed. The system is further based on the sgsE S-layer gene promoter of Geobacillus stearothermophilus NRS 2004/3a and on the Geobacillus-Bacillus-Escherichia coli shuttle vector pNW33N. As a target gene, wsfP, encoding a putative UDP-Gal:phosphoryl-polyprenol Gal-1-phosphate transferase, representing the predicted initiation enzyme of S-layer glycan biosynthesis, was disrupted. S-layer protein glycosylation was completely abolished in the insertional P. alvei CCM 2051T wsfP mutant, according to sodium dodecyl sulfate-polyacrylamide gel electrophoresis evidence and carbohydrate analysis. Glycosylation was fully restored by plasmid-based expression of wsfP in the glycan-deficient P. alvei mutant, confirming that WsfP initiates S-layer protein glycosylation. This is the first report on the successful genetic manipulation of bacterial S-layer protein glycosylation in vivo, including transformation of and heterologous gene expression and gene disruption in the model organism P. alvei CCM 2051T. PMID:19304819

  18. A quantitative assay for intercellular aggregation

    NASA Technical Reports Server (NTRS)

    Neelamegham, S.; Zygourakis, K.; McIntire, L. V. (Principal Investigator)

    1997-01-01

    In an earlier communication (Munn et al., J Immunol. Methods 166: 11-25, 1993), we presented the initial development of a quantitative assay for monitoring the rates of cellular aggregation based on digital image processing and video microscopy. This study describes some important enhancements and modifications to the procedure. A new index is introduced to characterize the three-dimensional morphology of the aggregates. This index is based on temporal changes in the projected area of the cells and cell aggregates during the course of the experiment. By drawing an analogy with the kinetic theory of gases, we have also introduced a procedure to normalize for variations in cell seeding density among different experiments. In addition, the image analysis technique has been improved by introducing a background subtraction algorithm to remove illumination defects and an adaptive segmentation procedure. These improvements allowed us to completely automate the image analysis procedure, thus minimizing user intervention and improving the reproducibility of the measurements. The enhanced visual assay is evaluated using some recent results from our studies on homotypic lymphocyte aggregation.

  19. Aggregation Trade Offs in Family Based Recommendations

    NASA Astrophysics Data System (ADS)

    Berkovsky, Shlomo; Freyne, Jill; Coombe, Mac

    Personalized information access tools are frequently based on collaborative filtering recommendation algorithms. Collaborative filtering recommender systems typically suffer from a data sparsity problem, where systems do not have sufficient user data to generate accurate and reliable predictions. Prior research suggested using group-based user data in the collaborative filtering recommendation process to generate group-based predictions and partially resolve the sparsity problem. Although group recommendations are less accurate than personalized recommendations, they are more accurate than general non-personalized recommendations, which are the natural fall back when personalized recommendations cannot be generated. In this work we present initial results of a study that exploits the browsing logs of real families of users gathered in an eHealth portal. The browsing logs allowed us to experimentally compare the accuracy of two group-based recommendation strategies: aggregated group models and aggregated predictions. Our results showed that aggregating individual models into group models resulted in more accurate predictions than aggregating individual predictions into group predictions.

  20. Design, Construction, and Initial Test of High Spatial Resolution Thermometry Arrays for Detection of Surface Temperature Profiles on SRF Cavities in Super Fluid Helium

    SciTech Connect

    Ari Palczewski, Rongli Geng, Grigory Eremeev

    2011-07-01

    We designed and built two high resolution (0.6-0.55mm special resolution [1.1-1.2mm separation]) thermometry arrays prototypes out of the Allen Bradley 90-120 ohm 1/8 watt resistor to measure surface temperature profiles on SRF cavities. One array was designed to be physically flexible and conform to any location on a SRF cavity; the other was modeled after the common G-10/stycast 2850 thermometer and designed to fit on the equator of an ILC (Tesla 1.3GHz) SRF cavity. We will discuss the advantages and disadvantages of each array and their construction. In addition we will present a case study of the arrays performance on a real SRF cavity TB9NR001. TB9NR001 presented a unique opportunity to test the performance of each array as it contained a dual (4mm separation) cat eye defect which conventional methods such as OST (Oscillating Superleak second-sound Transducers) and full coverage thermometry mapping were unable to distinguish between. We will discuss the new arrays ability to distinguish between the two defects and their preheating performance.

  1. Beliefs about emotions as a metacognitive construct: initial development of a self-report questionnaire measure and preliminary investigation in relation to emotion regulation.

    PubMed

    Manser, Rachel; Cooper, Myra; Trefusis, Jo

    2012-01-01

    Metacognitive theory, amongst other theories, gives an important role to beliefs about mental states, including beliefs about emotions, in the maintenance of distress. Mentalization theory as well as the dialectical behaviour therapy and emotion-focused therapy literature specifies particular beliefs thought to be related to emotion dysregulation and therefore to a label of borderline personality disorder. The current study aimed to develop a questionnaire to measure the beliefs about emotions as specified by this literature and to test the relationship of this new measure to various aspects of emotion regulation in a non-clinical sample of 289 participants. A factor analysis extracted six factors, which described beliefs about emotions as (a) overwhelming and uncontrollable; (b) shameful and irrational; (c) invalid and meaningless; (d) useless; (e) damaging; and (f) contagious. The final measure showed some promising psychometric properties. All of the questionnaire subscales were related to aspects of emotion dysregulation including distress, borderline personality disorder symptoms and behaviours associated with dysregulation of emotion, suggesting that beliefs about emotions could be an important metacognitive construct involved in the ability to regulate emotions. Beliefs about emotions may be a useful direct or indirect target for treatment of difficulties regulating emotions, and this could be achieved through the use of various therapeutic modalities. PMID:21374759

  2. Important features of Sustainable Aggregate Resource Management

    USGS Publications Warehouse

    Solar, Slavko V.; Shields, Deborah J.; Langer, William H.

    2004-01-01

    Every society, whether developed, developing or in a phase of renewal following governmental change, requires stable, adequate and secure supplies of natural resources. In the latter case, there could be significant need for construction materials for rebuilding infrastructure, industrial capacity, and housing. It is essential that these large-volume materials be provided in a rational manner that maximizes their societal contribution and minimizes environmental impacts. We describe an approach to resource management based on the principles of sustainable developed. Sustainable Aggregate Resource Management offers a way of addressing the conflicting needs and interests of environmental, economic, and social systems. Sustainability is an ethics based concept that utilizes science and democratic processes to reach acceptable agreements and tradeoffs among interests, while acknowledging the fundamental importance of the environment and social goods. We discuss the features of sustainable aggregate resource management.

  3. Cu nanoclusters with aggregation induced emission enhancement.

    PubMed

    Jia, Xiaofang; Li, Jing; Wang, Erkang

    2013-11-25

    A facile and versatile method for preparing water-soluble, stable, luminescent Cu nanoclusters (NCs) via the process of size-focusing etching from nonluminescent nanocrystals is presented. Using glutathione as a model ligand, the smallest cluster, Cu2 , is selectively synthesized to form a nearly monodisperse product, eliminating the need for tedious size fractionation. Evolution of photoluminescence and absorption spectra reveal that the formation of stable cluster species occurs through surface etching. Intriguingly, the as-prepared CuNCs exhibit an aggregation-induced emission enhancement effect. The CuNCs emit a faint light when dispersed in aqueous solution, but generate a striking fluorescence intensity enhancement upon aggregation. Armed with these attractive properties, the emissive CuNCs are expected to open new opportunities for the construction of light-emitting diodes, chemosensors, and bioimaging systems. PMID:23670847

  4. Extracellular Monomeric Tau Protein Is Sufficient to Initiate the Spread of Tau Protein Pathology*

    PubMed Central

    Michel, Claire H.; Kumar, Satish; Pinotsi, Dorothea; Tunnacliffe, Alan; St. George-Hyslop, Peter; Mandelkow, Eckhard; Mandelkow, Eva-Maria; Kaminski, Clemens F.; Kaminski Schierle, Gabriele S.

    2014-01-01

    Understanding the formation and propagation of aggregates of the Alzheimer disease-associated Tau protein in vivo is vital for the development of therapeutics for this devastating disorder. Using our recently developed live-cell aggregation sensor in neuron-like cells, we demonstrate that different variants of exogenous monomeric Tau, namely full-length Tau (hTau40) and the Tau-derived construct K18 comprising the repeat domain, initially accumulate in endosomal compartments, where they form fibrillar seeds that subsequently induce the aggregation of endogenous Tau. Using superresolution imaging, we confirm that fibrils consisting of endogenous and exogenous Tau are released from cells and demonstrate their potential to spread Tau pathology. Our data indicate a greater pathological risk and potential toxicity than hitherto suspected for extracellular soluble Tau. PMID:24235150

  5. Thermodynamically reversible generalization of diffusion limited aggregation.

    PubMed

    D'Souza, R M; Margolus, N H

    1999-07-01

    We introduce a lattice gas model of cluster growth via the diffusive aggregation of particles in a closed system obeying a local, deterministic, microscopically reversible dynamics. This model roughly corresponds to placing the irreversible diffusion limited aggregation model (DLA) in contact with a heat bath. Particles release latent heat when aggregating, while singly connected cluster members can absorb heat and evaporate. The heat bath is initially empty, hence we observe the flow of entropy from the aggregating gas of particles into the heat bath, which is being populated by diffusing heat tokens. Before the population of the heat bath stabilizes, the cluster morphology (quantified by the fractal dimension) is similar to a standard DLA cluster. The cluster then gradually anneals, becoming more tenuous, until reaching configurational equilibrium when the cluster morphology resembles a quenched branched random polymer. As the microscopic dynamics is invertible, we can reverse the evolution, observe the inverse flow of heat and entropy, and recover the initial condition. This simple system provides an explicit example of how macroscopic dissipation and self-organization can result from an underlying microscopically reversible dynamics. We present a detailed description of the dynamics for the model, discuss the macroscopic limit, and give predictions for the equilibrium particle densities obtained in the mean field limit. Empirical results for the growth are then presented, including the observed equilibrium particle densities, the temperature of the system, the fractal dimension of the growth clusters, scaling behavior, finite size effects, and the approach to equilibrium. We pay particular attention to the temporal behavior of the growth process and show that the relaxation to the maximum entropy state is initially a rapid nonequilibrium process, then subsequently it is a quasistatic process with a well defined temperature. PMID:11969759

  6. Taurine and platelet aggregation

    SciTech Connect

    Nauss-Karol, C.; VanderWende, C.; Gaut, Z.N.

    1986-03-01

    Taurine is a putative neurotransmitter or neuromodulator. The endogenous taurine concentration in human platelets, determined by amino acid analysis, is 15 ..mu..M/g. In spite of this high level, taurine is actively accumulated. Uptake is saturable, Na/sup +/ and temperature dependent, and suppressed by metabolic inhibitors, structural analogues, and several classes of centrally active substances. High, medium and low affinity transport processes have been characterized, and the platelet may represent a model system for taurine transport in the CNS. When platelets were incubated with /sup 14/C-taurine for 30 minutes, then resuspended in fresh medium and reincubated for one hour, essentially all of the taurine was retained within the cells. Taurine, at concentrations ranging from 10-1000 ..mu..M, had no effect on platelet aggregation induced by ADP or epinephrine. However, taurine may have a role in platelet aggregation since 35-39% of the taurine taken up by human platelets appears to be secreted during the release reaction induced by low concentrations of either epinephrine or ADP, respectively. This release phenomenon would imply that part of the taurine taken up is stored directly in the dense bodies of the platelet.

  7. Contrasting effects of nanoparticle-protein attraction on amyloid aggregation

    PubMed Central

    Radic, Slaven; Davis, Thomas P; Ke, Pu Chun; Ding, Feng

    2015-01-01

    Nanoparticles (NPs) have been experimentally found to either promote or inhibit amyloid aggregation of proteins, but the molecular mechanisms for such complex behaviors remain unknown. Using coarse-grained molecular dynamics simulations, we investigated the effects of varying the strength of nonspecific NP-protein attraction on amyloid aggregation of a model protein, the amyloid-beta peptide implicated in Alzheimer's disease. Specifically, with increasing NP-peptide attraction, amyloid aggregation on the NP surface was initially promoted due to increased local protein concentration on the surface and destabilization of the folded state. However, further increase of NP-peptide attraction decreased the stability of amyloid fibrils and reduced their lateral diffusion on the NP surface necessary for peptide conformational changes and self-association, thus prohibiting amyloid aggregation. Moreover, we found that the relative concentration between protein and NPs also played an important role in amyloid aggregation. With a high NP/protein ratio, NPs that intrinsically promote protein aggregation may display an inhibitive effect by depleting the proteins in solution while having a low concentration of the proteins on each NP's surface. Our coarse-grained molecular dynamics simulation study offers a molecular mechanism for delineating the contrasting and seemingly conflicting effects of NP-protein attraction on amyloid aggregation and highlights the potential of tailoring anti-aggregation nanomedicine against amyloid diseases. PMID:26989481

  8. The feeding practices and structure questionnaire: construction and initial validation in a sample of Australian first-time mothers and their 2-year olds

    PubMed Central

    2014-01-01

    Background Early feeding practices lay the foundation for children’s eating habits and weight gain. Questionnaires are available to assess parental feeding but overlapping and inconsistent items, subscales and terminology limit conceptual clarity and between study comparisons. Our aim was to consolidate a range of existing items into a parsimonious and conceptually robust questionnaire for assessing feeding practices with very young children (<3 years). Methods Data were from 462 mothers and children (age 21–27 months) from the NOURISH trial. Items from five questionnaires and two study-specific items were submitted to a priori item selection, allocation and verification, before theoretically-derived factors were tested using Confirmatory Factor Analysis. Construct validity of the new factors was examined by correlating these with child eating behaviours and weight. Results Following expert review 10 factors were specified. Of these, 9 factors (40 items) showed acceptable model fit and internal reliability (Cronbach’s α: 0.61-0.89). Four factors reflected non-responsive feeding practices: ‘Distrust in Appetite’, ‘Reward for Behaviour’, ‘Reward for Eating’, and ‘Persuasive Feeding’. Five factors reflected structure of the meal environment and limits: ‘Structured Meal Setting’, ‘Structured Meal Timing’, ‘Family Meal Setting’, ‘Overt Restriction’ and ‘Covert Restriction’. Feeding practices generally showed the expected pattern of associations with child eating behaviours but none with weight. Conclusion The Feeding Practices and Structure Questionnaire (FPSQ) provides a new reliable and valid measure of parental feeding practices, specifically maternal responsiveness to children’s hunger/satiety signals facilitated by routine and structure in feeding. Further validation in more diverse samples is required. PMID:24898364

  9. Properties of concrete blocks prepared with low grade recycled aggregates.

    PubMed

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

    2009-08-01

    Low grade recycled aggregates obtained from a construction waste sorting facility were tested to assess the feasibility of using these in the production of concrete blocks. The characteristics of the sorted construction waste are significantly different from that of crushed concrete rubbles that are mostly derived from demolition waste streams. This is due to the presence of higher percentages of non-concrete components (e.g. >10% soil, brick, tiles etc.) in the sorted construction waste. In the study reported in this paper, three series of concrete block mixtures were prepared by using the low grade recycled aggregates to replace (i) natural coarse granite (10mm), and (ii) 0, 25, 50, 75 and 100% replacement levels of crushed stone fine (crushed natural granite <5mm) in the concrete blocks. Test results on properties such as density, compressive strength, transverse strength and drying shrinkage as well as strength reduction after exposure to 800 degrees C are presented below. The results show that the soil content in the recycled fine aggregate was an important factor in affecting the properties of the blocks produced and the mechanical strength deceased with increasing low grade recycled fine aggregate content. But the higher soil content in the recycled aggregates reduced the reduction of compressive strength of the blocks after exposure to high temperature due probably to the formation of a new crystalline phase. The results show that the low grade recycled aggregates obtained from the construction waste sorting facility has potential to be used as aggregates for making non-structural pre-cast concrete blocks. PMID:19398196

  10. Holographic characterization of protein aggregates

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Zhong, Xiao; Ruffner, David; Stutt, Alexandra; Philips, Laura; Ward, Michael; Grier, David

    Holographic characterization directly measures the size distribution of subvisible protein aggregates in suspension and offers insights into their morphology. Based on holographic video microscopy, this analytical technique records and interprets holograms of individual aggregates in protein solutions as they flow down a microfluidic channel, without requiring labeling or other exceptional sample preparation. The hologram of an individual protein aggregate is analyzed in real time with the Lorenz-Mie theory of light scattering to measure that aggregate's size and optical properties. Detecting, counting and characterizing subvisible aggregates proceeds fast enough for time-resolved studies, and lends itself to tracking trends in protein aggregation arising from changing environmental factors. No other analytical technique provides such a wealth of particle-resolved characterization data in situ. Holographic characterization promises accelerated development of therapeutic protein formulations, improved process control during manufacturing, and streamlined quality assurance during storage and at the point of use. Mrsec and MRI program of the NSF, Spheryx Inc.

  11. Impact of gravity processes on the initial post-rift stages of construction and evolution of a continental margin: Insights from the eastern Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Baurion, Celine; Gorini, Christian; Leroy, Sylvie; Migeon, Sebastien; Lucazeau, Francis; Bache, Francois; Zaragosi, Sebastien; Smit, Jeroen; Al-Toubi, Khalfan; dos Reis, Antonio

    2013-04-01

    The study of the post-rift sediment architecture and continental slope morphology leads to a reconstruction of the initial stages of formation and evolution of gravity-driven processes on the northern margin of the eastern Gulf of Aden. The slope-related features and associated deposits in the deep basin along this young passive margin are investigated through the analysis of a set of seismic-reflection and multibeam bathymetry data. This study demonstrates how preconditioning and triggering factors (tectonics, climate and eustatic variations) can interact and control the margin morphology and post-rift sediment architecture in a source-to-sink perspective. The combined geomorphological and stratigraphic study of this margin allows us to identify three morphological domains inherited from the structural segmentation. The monsoon climate combined with a major eustatic lowstand is proposed as the most likely set of factors preconditioning slope destabilisation on the whole margin. These factors also enhance the effect of the late post-rift uplift of the eastern morphological domain of the studied margin. The formation and distribution of the slope-related features are thus mainly controlled by active faults on the continental slope and the potential effect of bottom currents at the base of the continental slope. The oversteepening of the continental slope in the eastern domain of the studied margin is probably the main triggering factor controlling the generation of failure processes and subsequent canyon formation by upslope erosion. The analysis of canyon location and morphology along the uplifted part of the continental slope reveals the long-term influence of secondary slope-related features, contour currents and turbidite flows on the development of canyons. As a consequence of the late post-rift uplift that only affected the eastern part of the studied margin, huge volumes of sediment were accumulated in mass-transport complexes at the foot of numerous slope

  12. Production of manufactured aggregates from flue gas desulfurization by-products

    SciTech Connect

    Wu, M.M.; McCoy, D.C.; Fenger, M.L.; Scandrol, R.O.; Winschel, R.A.; Withum, J.A.; Statnick, R.M.

    1999-07-01

    CONSOL R and D has developed a disk pelletization process to produce manufactured aggregates from the by-products of various technologies designed to reduce sulfur emissions produced from coal utilization. Aggregates have been produced from the by-products of the Coolside and LIMB sorbent injection, the fluidized-bed combustion (FBC), spray dryer absorption (SDA), and lime and limestone wet flue gas desulfurization (FGD) processes. The aggregates produced meet the general specifications for use as road aggregate in road construction and for use as lightweight aggregate in concrete masonry units. Small field demonstrations with 1200 lb to 5000 lb of manufactured aggregates were conducted using aggregates produced from FBC ash and lime wet FGD sludge in road construction and using aggregates made from SDA ash and lime wet FGD sludge to manufacture concrete blocks. The aggregates for this work were produced with a bench-scale (200--400 lb batch) unit. In 1999, CONSOL R and D constructed and operated a 500 lb/hr integrated, continuous pilot plant. A variety of aggregate products were produced from lime wet FGD sludge. The pilot plant test successfully demonstrated the continuous, integrated operation of the process. The pilot plant demonstration was a major step toward commercialization of manufactured aggregate production from FGD by-products. In this paper, progress made in the production of aggregates from dry FGD (Coolside, LIMB, SDA) and FBC by-products, and lime wet FGD sludge is discussed. The discussion covers bench-scale and pilot plant aggregate production and aggregate field demonstrations.

  13. Compressive strength and hydration processes of concrete with recycled aggregates

    SciTech Connect

    Koenders, Eduardus A.B.; Pepe, Marco; Martinelli, Enzo

    2014-02-15

    This paper deals with the correlation between the time evolution of the degree of hydration and the compressive strength of Recycled Aggregate Concrete (RAC) for different water to cement ratios and initial moisture conditions of the Recycled Concrete Aggregates (RCAs). Particularly, the influence of such moisture conditions is investigated by monitoring the hydration process and determining the compressive strength development of fully dry or fully saturated recycled aggregates in four RAC mixtures. Hydration processes are monitored via temperature measurements in hardening concrete samples and the time evolution of the degree of hydration is determined through a 1D hydration and heat flow model. The effect of the initial moisture condition of RCAs employed in the considered concrete mixtures clearly emerges from this study. In fact, a novel conceptual method is proposed to predict the compressive strength of RAC-systems, from the initial mixture parameters and the hardening conditions. -- Highlights: •The concrete industry is more and more concerned with sustainability issues. •The use of recycled aggregates is a promising solution to enhance sustainability. •Recycled aggregates affect both hydration processes and compressive strength. •A fundamental approach is proposed to unveil the influence of recycled aggregates. •Some experimental comparisons are presented to validate the proposed approach.

  14. Aggregation dynamics of rigid polyelectrolytes

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    Similarly charged polyelectrolytes are known to attract each other and aggregate into bundles when the charge density of the polymers exceeds a critical value that depends on the valency of the counterions. The dynamics of aggregation of such rigid polyelectrolytes are studied using large scale molecular dynamics simulations. We find that the morphology of the aggregates depends on the value of the charge density of the polymers. For values close to the critical value, the shape of the aggregates is cylindrical with height equal to the length of a single polyelectrolyte chain. However, for larger values of charge, the linear extent of the aggregates increases as more and more polymers aggregate. In both the cases, we show that the number of aggregates decrease with time as power laws with exponents that are not numerically distinguishable from each other and are independent of charge density of the polymers, valency of the counterions, density, and length of the polyelectrolyte chain. We model the aggregation dynamics using the Smoluchowski coagulation equation with kernels determined from the molecular dynamics simulations and justify the numerically obtained value of the exponent. Our results suggest that once counterions condense, effective interactions between polyelectrolyte chains short-ranged and the aggregation of polyelectrolytes are diffusion-limited.

  15. Checking for reversibility of aggregation of UV-irradiated glycogen phosphorylase b under crowding conditions.

    PubMed

    Eronina, Tatiana B; Mikhaylova, Valeriya V; Chebotareva, Natalia A; Makeeva, Valentina F; Kurganov, Boris I

    2016-05-01

    It is believed that the initial stages of protein aggregation are reversible and can be reversed by simple dilution, whereas prolonged exposure to factors responsible for denaturing proteins (for example, to elevated temperatures) results in the formation of irreversible aggregates. A new approach has been developed to discriminate the stage of the formation of reversible aggregates. Aggregation of UV-irradiated glycogen phosphorylase b (UV-Phb) was studied at 10, 25 and 37°C in the presence of crowders (polyethylene glycol and Ficoll-70) using dynamic light scattering and analytical ultracentrifugation (pH 6.8; 0.1M NaCl). The dilution of the protein solution in the course of aggregation at 10°C results in the breakdown of protein aggregates suggesting that the aggregation process is reversible. When aggregation of UV-Phb is studied at 37°C, reversibility is lacking. Chemical chaperones (arginine, proline) induce the breakdown of protein aggregates of UV-Phb formed at 10°C. In the experiments carried out at 37°C in the presence of crowder the addition of arginine results in disintegration of protein aggregates only at early stages of the aggregation process. It is assumed that general pathway of protein aggregation includes the formation of reversible, completely dissociable, partly dissociable and irreversible aggregates. PMID:26853826

  16. Crushed aggregates for roads and their properties for frost protection

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Elena; Willy Danielsen, Svein

    2015-04-01

    Crushed aggregates for roads and their properties for frost protection Elena Kuznetsova, NTNU and Svein Willy Danielsen, SINTEF With natural (fluvial, glaciofluvial) sand/gravel resources being rapidly depleted in many countries, the last decade has seen a significant trend towards using more alternative materials for construction purpose. In Norway the development and implementation of crushed aggregate technology has been the most important way to get around the problem with increased resource scarcity. Today Norway is one the European countries with the highest percentage of crushed/manufactured aggregates. A crushed product will reveal a different particle size distribution, a sharper, more angular particle shape, and not least - a significantly different mineral composition. The latter may often be characterised by more polymineral composition, and it will also much more depend on the local bedrock. When handled with care and knowledge, these differences can give the user a lot of new opportunities relating to materials design. Norwegian road construction practice has changed significantly during the last 40 years due to the replacement of gravel by crushed rock materials in the granular layers of the pavements. The use of non-processed rock materials from blasting was allowed in the subbase layer until 2012. This was a reason for a lot of problems with frost heaving due to inhomogeneity of this material, and in practice it was difficult to control the size of large stones. Since 2012 there is a requirement that rock materials for use in the subbase layer shall be crushed (Handbook N200, 2014). During the spring 2014 The Norwegian Public Roads Administration introduced a new handbook with requirements for roads construction in Norway, including new specifications for the frost protection layer. When pavements are constructed over moist and/or frost susceptible soils in cold and humid environments, the frost protection layer also becomes a very important part

  17. Force aggregation using genetic algortihms

    NASA Astrophysics Data System (ADS)

    Shea, Peter J.; Peterson, John; Alexander, Kathleen; Azevedo, Alcino

    2004-01-01

    A surveillance system needs to accurately locate and identify not only single targets, but also groups of targets engaged in a common activity. Most existing tracking systems are capable of tracking individual targets quite accurately; however, they fail to use information related to group behavior in order to improve these estimates. Furthermore, in wide area surveillance situations a military operator is required to sort through hundreds to thousands of individual targets in order to develop an understanding of the situation. Having the ability to collapse the behavior of individual targets into a common, coordinated motion can greatly enhance the productively and situational awareness of the operator. Our long-term approach to solving this problem is to develop an understanding of how to define a group and then to understand the inter-relationships between the various characteristics that describe a group. Then using this information, we will be able to partition the set of target into groups that can be aggregated over the entire military force hierarchy. This goal of this paper is to describe an approach that is based upon genetic algorithms for solving the military force hierarchy problem. This paper will describe the underlying genetic algorithm, scoring function, and some initial results.

  18. Force aggregation using genetic algortihms

    NASA Astrophysics Data System (ADS)

    Shea, Peter J.; Peterson, John; Alexander, Kathleen; Azevedo, Alcino

    2003-12-01

    A surveillance system needs to accurately locate and identify not only single targets, but also groups of targets engaged in a common activity. Most existing tracking systems are capable of tracking individual targets quite accurately; however, they fail to use information related to group behavior in order to improve these estimates. Furthermore, in wide area surveillance situations a military operator is required to sort through hundreds to thousands of individual targets in order to develop an understanding of the situation. Having the ability to collapse the behavior of individual targets into a common, coordinated motion can greatly enhance the productively and situational awareness of the operator. Our long-term approach to solving this problem is to develop an understanding of how to define a group and then to understand the inter-relationships between the various characteristics that describe a group. Then using this information, we will be able to partition the set of target into groups that can be aggregated over the entire military force hierarchy. This goal of this paper is to describe an approach that is based upon genetic algorithms for solving the military force hierarchy problem. This paper will describe the underlying genetic algorithm, scoring function, and some initial results.

  19. Self-Aggregation of Convection in Long Channel Geometry

    NASA Astrophysics Data System (ADS)

    Wing, A. A.; Cronin, T.

    2014-12-01

    Cloud cover and relative humidity in the tropics are strongly influenced by organized atmospheric convection, which occurs across a range of spatial and temporal scales. One mode of organization that is found in idealized numerical simulations is "self-aggregation", a spontaneous transition from randomly distributed convection to organized convection despite homogeneous boundary conditions. We explore the influence of domain geometry on the mechanisms and temperature-dependence of self-aggregation of tropical convection. Specifically, the System for Atmospheric Modeling is used to perform 3-d simulations of radiative-convective equilibrium in a non-rotating framework, with interactive radiation and surface fluxes and fixed sea surface temperature. The results of simulations employing a highly elongated 3-d channel domain, in which self-aggregation takes the form of multiple moist and dry bands, are compared to that of a square domain, in which self-aggregation takes the form of a single moist cluster. For both domain types, and across a range of temperatures, we characterize the fundamental physical mechanisms that lead to self-aggregation as well as its growth rate and spatial scale. The variance budget equation for the vertically integrated frozen moist static energy is used to quantify the mechanisms governing self-aggregation and characterize its time scale. We find that diabatic processes dominate the evolution of self-aggregation in the elongated channel simulations. In contrast, in the square domain simulations, similar diabatic processes dominate the initial stages of aggregation but up-gradient advection by the circulation plays a role in the later stages. Self-aggregation occurs across a much wider range of temperatures with elongated channel geometry than with square geometry. As the sea surface temperature is increased in the channel simulations, the aggregated state is characterized by smaller spatial scales and more regularity. An advantage of the

  20. Self-aggregation of convection in long channel geometry

    NASA Astrophysics Data System (ADS)

    Wing, Allison; Cronin, Timothy

    2015-04-01

    Self-aggregation is the spontaneous transition in numerical simulations from randomly distributed convection to organized convection despite homogeneous boundary conditions. We explore the influence of domain geometry on the mechanisms and temperature-dependence of self-aggregation of tropical convection. Specifically, the System for Atmospheric Modeling is used to perform 3-d simulations of radiative-convective equilibrium in a non-rotating framework, with interactive radiation and surface fluxes and fixed sea surface temperature. The results of simulations employing a highly elongated 3-d channel domain, in which self-aggregation takes the form of multiple moist and dry bands, are compared to that of a square domain, in which self-aggregation takes the form of a single moist cluster. For both domain types, and across a range of temperatures, we characterize the fundamental physical mechanisms that lead to self-aggregation as well as its growth rate and spatial scale. The variance budget equation for the vertically integrated frozen moist static energy is used to quantify the mechanisms governing self-aggregation and characterize its time scale. We find that diabatic processes dominate the evolution of self-aggregation in the elongated channel simulations. In contrast, in the square domain simulations, similar diabatic processes dominate the initial stages of aggregation but up-gradient advection by the circulation plays a role in the later stages. Self-aggregation occurs across a much wider range of temperatures with elongated channel geometry than with square geometry. As the sea surface temperature is increased in the channel simulations, the aggregated state is characterized by smaller spatial scales and more regularity. An advantage of the channel geometry is that a separation distance between convectively active regions can be defined, which is a prerequisite for developing a spatial scaling theory.

  1. Measuring and modeling hemoglobin aggregation below the freezing temperature.

    PubMed

    Rosa, Mónica; Lopes, Carlos; Melo, Eduardo P; Singh, Satish K; Geraldes, Vitor; Rodrigues, Miguel A

    2013-08-01

    Freezing of protein solutions is required for many applications such as storage, transport, or lyophilization; however, freezing has inherent risks for protein integrity. It is difficult to study protein stability below the freezing temperature because phase separation constrains solute concentration in solution. In this work, we developed an isochoric method to study protein aggregation in solutions at -5, -10, -15, and -20 °C. Lowering the temperature below the freezing point in a fixed volume prevents the aqueous solution from freezing, as pressure rises until equilibrium (P,T) is reached. Aggregation rates of bovine hemoglobin (BHb) increased at lower temperature (-20 °C) and higher BHb concentration. However, the addition of sucrose substantially decreased the aggregation rate and prevented aggregation when the concentration reached 300 g/L. The unfolding thermodynamics of BHb was studied using fluorescence, and the fraction of unfolded protein as a function of temperature was determined. A mathematical model was applied to describe BHb aggregation below the freezing temperature. This model was able to predict the aggregation curves for various storage temperatures and initial concentrations of BHb. The aggregation mechanism was revealed to be mediated by an unfolded state, followed by a fast growth of aggregates that readily precipitate. The aggregation kinetics increased for lower temperature because of the higher fraction of unfolded BHb closer to the cold denaturation temperature. Overall, the results obtained herein suggest that the isochoric method could provide a relatively simple approach to obtain fundamental thermodynamic information about the protein and the aggregation mechanism, thus providing a new approach to developing accelerated formulation studies below the freezing temperature. PMID:23808610

  2. Aggregate of nanoparticles: rheological and mechanical properties

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Wu, Xiaojun; Yang, Wei; Zhai, Yuanming; Xie, Banghu; Yang, Mingbo

    2011-12-01

    The understanding of the rheological and mechanical properties of nanoparticle aggregates is important for the application of nanofillers in nanocompoistes. In this work, we report a rheological study on the rheological and mechanical properties of nano-silica agglomerates in the form of gel network mainly constructed by hydrogen bonds. The elastic model for rubber is modified to analyze the elastic behavior of the agglomerates. By this modified elastic model, the size of the network mesh can be estimated by the elastic modulus of the network which can be easily obtained by rheology. The stress to destroy the aggregates, i.e., the yield stress ( σ y ), and the elastic modulus ( G') of the network are found to be depended on the concentration of nano-silica ( ϕ, wt.%) with the power of 4.02 and 3.83, respectively. Via this concentration dependent behavior, we can extrapolate two important mechanical parameters for the agglomerates in a dense packing state ( ϕ = 1): the shear modulus and the yield stress. Under large deformation (continuous shear flow), the network structure of the aggregates will experience destruction and reconstruction, which gives rise to fluctuations in the viscosity and a shear-thinning behavior.

  3. Peptide aggregation in neurodegenerative disease.

    PubMed

    Murphy, Regina M

    2002-01-01

    In the not-so-distant past, insoluble aggregated protein was considered as uninteresting and bothersome as yesterday's trash. More recently, protein aggregates have enjoyed considerable scientific interest, as it has become clear that these aggregates play key roles in many diseases. In this review, we focus attention on three polypeptides: beta-amyloid, prion, and huntingtin, which are linked to three feared neurodegenerative diseases: Alzheimer's, "mad cow," and Huntington's disease, respectively. These proteins lack any significant primary sequence homology, yet their aggregates possess very similar features, specifically, high beta-sheet content, fibrillar morphology, relative insolubility, and protease resistance. Because the aggregates are noncrystalline, secrets of their structure at nanometer resolution are only slowly yielding to X-ray diffraction, solid-state NMR, and other techniques. Besides structure, the aggregates may possess similar pathways of assembly. Two alternative assembly pathways have been proposed: the nucleation-elongation and the template-assisted mode. These two modes may be complementary, not mutually exclusive. Strategies for interfering with aggregation, which may provide novel therapeutic approaches, are under development. The structural similarities between protein aggregates of dissimilar origin suggest that therapeutic strategies successful against one disease may have broad utility in others. PMID:12117755

  4. Topics in Probabilistic Judgment Aggregation

    ERIC Educational Resources Information Center

    Wang, Guanchun

    2011-01-01

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

  5. Flocculation characteristics of freshly eroded aggregates

    NASA Astrophysics Data System (ADS)

    Manning, Andrew; Wendling, Valentin; Gratiot, Nicolas; Legout, Cedric; Michallet, Herve

    2014-05-01

    had Ws of 0.4-0.5 mm/s, an order of magnitude slower than the peak sample Ws of 5.8 mm/s. These fast settling aggregates spanned the macrofloc (> 160 microns) and microfloc transition from 100-220 microns, representing over half the SSC. The majority of the microflocs (< 160 microns) exhibited effective densities between 160-1600 kg/m^-3, which suggests that some degree of flocculation has occurred. Furthermore, there are highly porous macroflocs demonstrating effective densities < 40 kg/m^-3; these flocs fell at a Ws of about 1 mm/s and represented ~4% of the total SSC. A key fundamental research question to be addressed in this study was: do aggregates rapidly turn into flocs? The initial results indicate that aggregates do not easily/rapidly turn into flocs. However, despite their poor kinetics, particles were undoubtedly aggregated. The aggregation index was measured to be of 50% for badlands materials. The behaviour of the soils differ significantly from those observed for estuarine muds, floc size and settling velocity increases with suspended sediment concentration, where as the soils tested did not.

  6. Mechanics of fire ant aggregations

    NASA Astrophysics Data System (ADS)

    Tennenbaum, Michael; Liu, Zhongyang; Hu, David; Fernandez-Nieves, Alberto

    2016-01-01

    Fire ants link their bodies to form aggregations; these can adopt a variety of structures, they can drip and spread, or withstand applied loads. Here, by using oscillatory rheology, we show that fire ant aggregations are viscoelastic. We find that, at the lowest ant densities probed and in the linear regime, the elastic and viscous moduli are essentially identical over the spanned frequency range, which highlights the absence of a dominant mode of structural relaxation. As ant density increases, the elastic modulus rises, which we interpret by alluding to ant crowding and subsequent jamming. When deformed beyond the linear regime, the aggregation flows, exhibiting shear-thinning behaviour with a stress load that is comparable to the maximum load the aggregation can withstand before individual ants are torn apart. Our findings illustrate the rich, collective mechanical behaviour that can arise in aggregations of active, interacting building blocks.

  7. Mechanics of fire ant aggregations.

    PubMed

    Tennenbaum, Michael; Liu, Zhongyang; Hu, David; Fernandez-Nieves, Alberto

    2016-01-01

    Fire ants link their bodies to form aggregations; these can adopt a variety of structures, they can drip and spread, or withstand applied loads. Here, by using oscillatory rheology, we show that fire ant aggregations are viscoelastic. We find that, at the lowest ant densities probed and in the linear regime, the elastic and viscous moduli are essentially identical over the spanned frequency range, which highlights the absence of a dominant mode of structural relaxation. As ant density increases, the elastic modulus rises, which we interpret by alluding to ant crowding and subsequent jamming. When deformed beyond the linear regime, the aggregation flows, exhibiting shear-thinning behaviour with a stress load that is comparable to the maximum load the aggregation can withstand before individual ants are torn apart. Our findings illustrate the rich, collective mechanical behaviour that can arise in aggregations of active, interacting building blocks. PMID:26501413

  8. Molecular aggregation of humic substances

    USGS Publications Warehouse

    Wershaw, R. L.

    1999-01-01

    Humic substances (HS) form molecular aggregates in solution and on mineral surfaces. Elucidation of the mechanism of formation of these aggregates is important for an understanding of the interactions of HS in soils arid natural waters. The HS are formed mainly by enzymatic depolymerization and oxidation of plant biopolymers. These reactions transform the aromatic and lipid plant components into amphiphilic molecules, that is, molecules that consist of separate hydrophobic (nonpolar) and hydrophilic (polar) parts. The nonpolar parts of the molecules are composed of relatively unaltered segments of plant polymers and the polar parts of carboxylic acid groups. These amphiphiles form membrane-like aggregates on mineral surfaces and micelle-like aggregates in solution. The exterior surfaces of these aggregates are hydrophilic, and the interiors constitute separate hydrophobic liquid-like phases.

  9. Imbibition kinetics of spherical aggregates

    NASA Astrophysics Data System (ADS)

    Hébraud, Pascal; Lootens, Didier; Debacker, Alban

    The imbibition kinetics of a millimeter-sized aggregate of 300 nm diameter colloidal particles by a wetting pure solvent is studied. Three successive regimes are observed : in the first one, the imbibition proceeds by compressing the air inside the aggregate. Then, the solvent stops when the pressure of the compressed air is equal to the Laplace pressure at the meniscus of the wetting solvent in the porous aggregate. The interface is pinned and the aggregate slowly degases, up to a point where the pressure of the entrapped air stops decreasing and is controlled by the Laplace pressure of small bubbles. Depending on the curvature of the bubble, the system may then be in an unstable state. The imbibition then starts again, but with an inner pressure in equilibrium with these bubbles. This last stage leads to the complete infiltration of the aggregate.

  10. Immunogenicity of Therapeutic Protein Aggregates.

    PubMed

    Moussa, Ehab M; Panchal, Jainik P; Moorthy, Balakrishnan S; Blum, Janice S; Joubert, Marisa K; Narhi, Linda O; Topp, Elizabeth M

    2016-02-01

    Therapeutic proteins have a propensity for aggregation during manufacturing, shipping, and storage. The presence of aggregates in protein drug products can induce adverse immune responses in patients that may affect safety and efficacy, and so it is of concern to both manufacturers and regulatory agencies. In this vein, there is a lack of understanding of the physicochemical determinants of immunological responses and a lack of standardized analytical methods to survey the molecular properties of aggregates associated with immune activation. In this review, we provide an overview of the basic immune mechanisms in the context of interactions with protein aggregates. We then critically examine the literature with emphasis on the underlying immune mechanisms as they relate to aggregate properties. Finally, we highlight the gaps in our current understanding of this issue and offer recommendations for future research. PMID:26869409

  11. Helical Folding Competing with Unfolded Aggregation in Phenylene Ethynylene Foldamers.

    PubMed

    Luo, Zhouyang; Zhu, Ningbo; Zhao, Dahui

    2016-07-25

    The folding and aggregation behavior of a pair of oligo(phenylene ethynylene) (OPE) foldamers are investigated by means of UV/Vis absorption and circular dichroism spectroscopy. With identical OPE backbones, two foldamers, 1 with alkyl side groups and 2 with triethylene glycol side chains, manifest similar helical conformations in solutions in n-hexane and methanol, respectively. However, disparate and competing folding and aggregation processes are observed in alternative solvents. In cyclohexane, oligomer 1 initially adopts the helical conformation, but the self-aggregation of unfolded chains, as a minor component, gradually drives the folding-unfolding transition eventually to the unfolded aggregate state completely. In contrast, in aqueous solution (CH3 OH/H2 O) both folded and unfolded oligomer 2 appear to undergo self-association; aggregates of the folded chains are thermodynamically more stable. In solutions with a high H2 O content, self-aggregation among unfolded oligomers is kinetically favored; these oligomers very slowly transform into aggregates of helical structures with greater thermodynamic stability. The folded-unfolded conformational switch thus takes place with the free (nonaggregated) molecules, and the very slow folding transition is due to the low concentration of molecularly dispersed oligomers. PMID:27374725

  12. One-dimensional model of yeast prion aggregation

    NASA Astrophysics Data System (ADS)

    Kunes, K. C.; Cox, D. L.; Singh, R. R. P.

    2005-11-01

    Mammalian prion proteins (PrP) are of significant public health interest. Yeasts have proteins, which can undergo similar reconformation and aggregation processes to PrP, without posing a threat to the organism. These yeast “prions,” such as SUP35, are simpler to experimentally study and model. Recent in vitro studies of the SUP35 protein found long aggregates, pure exponential growth of the misfolded form, and a lag time which depended weakly on the monomer concentration. To explain this data, we have extended a previous model of aggregation kinetics along with a stochastic approach. We assume reconformation only upon aggregation and include aggregate fissioning and an initial nucleation barrier. We find that for sufficiently small nucleation rates or seeding by a small number of preformed nuclei, the models achieve the requisite exponential growth, long aggregates, and a lag time which depends weakly on monomer concentration. The spread in aggregate sizes is well described by the Weibull distribution. All these properties point to the preeminent role of fissioning in the growth of misfolded proteins.

  13. Changes in soil aggregation and dust emission potential in response to aeolian processes

    NASA Astrophysics Data System (ADS)

    swet, Nitzan; Katra, Itzhak

    2016-04-01

    Aeolian (wind) dust emission has high environmental and socioeconomic significances due to loss of natural soil and air pollution. Dust emission involves complex interactions between the airflow and the soil surface. The soil aggregates were dust particles are held determine the topsoil erodibility in aeolian erosion. Although the key role of soil aggregation in dust emission mechanisms, information on changes in soil aggregate size distribution (ASD) due to aeolian erosion is lucking. This study is focused on quantitative ASD analyses before and after aeolian processes (saltation). Aeolian experiments and soil analyses were conducted on semiarid loess topsoils with different initial conditions of aggregation. The results show that saltation rates and PM emissions depend on the initial ASD and shear velocity. In all initial soil conditions, the content of aggregates at saltator-sized 63-250 μm was increased by 10-34 % following erosion of macro-aggregates > 500 μm. It revealed that the aggregate-saltator production increases with the shear velocity (up to 0.61 m s-1) for soils with available macro-aggregates. The findings highlight the dynamics in soil aggregation in response to aeolian transport and therefore its significance for determining the mechanisms of dust emission from soil aggregates.

  14. Perspectives on Preference Aggregation.

    PubMed

    Regenwetter, Michel

    2009-07-01

    For centuries, the mathematical aggregation of preferences by groups, organizations, or society itself has received keen interdisciplinary attention. Extensive theoretical work in economics and political science throughout the second half of the 20th century has highlighted the idea that competing notions of rational social choice intrinsically contradict each other. This has led some researchers to consider coherent democratic decision making to be a mathematical impossibility. Recent empirical work in psychology qualifies that view. This nontechnical review sketches a quantitative research paradigm for the behavioral investigation of mathematical social choice rules on real ballots, experimental choices, or attitudinal survey data. The article poses a series of open questions. Some classical work sometimes makes assumptions about voter preferences that are descriptively invalid. Do such technical assumptions lead the theory astray? How can empirical work inform the formulation of meaningful theoretical primitives? Classical "impossibility results" leverage the fact that certain desirable mathematical properties logically cannot hold in all conceivable electorates. Do these properties nonetheless hold true in empirical distributions of preferences? Will future behavioral analyses continue to contradict the expectations of established theory? Under what conditions do competing consensus methods yield identical outcomes and why do they do so? PMID:26158988

  15. Photocontrolled micellar aggregation of amphiphilic DNA-azobenzene conjugates.

    PubMed

    Gu, Renpeng; Lamas, Joseph; Rastogi, Shiva K; Li, Xiaopeng; Brittain, William; Zauscher, Stefan

    2015-11-01

    We demonstrate the reversible micellar aggregation of a DNA-azobenzene conjugate in aqueous conditions, in which the photoisomerization of the initially apolar trans-azobenzene moiety to the polar cis isomer causes disassembly of the aggregates. The molecular basis for this phenomena is a change in the hydrophobic/hydrophilic balance of the conjugate as the more polar cis azobenzene isomer is formed upon exposure to 365 nm irradiation. The conjugates were prepared by copper-free Click chemistry between an azide-modified, 53-base ssDNA and a cyclooctyne derivative of azobenzene. The photocontrolled aggregation of the conjugate was studied by dynamic light scattering and atomic force microscopy. The reversible micellar aggregation for a DNA-azobenzene conjugate has not been previously reported and holds promise for photocontrolled drug delivery applications. PMID:26247877

  16. Electrophoretic interactions and aggregation of colloidal biological particles

    NASA Technical Reports Server (NTRS)

    Davis, Robert H.; Nichols, Scott C.; Loewenberg, Michael; Todd, Paul

    1994-01-01

    The separation of cells or particles from solution has traditionally been accomplished with centrifuges or by sedimentation; however, many particles have specific densities close to unity, making buoyancy-driven motion slow or negligible, but most cells and particles carry surface charges, making them ideal for electrophoretic separation. Both buoyancy-driven and electrophoretic separation may be influenced by hydrodynamic interactions and aggregation of neighboring particles. Aggregation by electrophoresis was analyzed for two non-Brownian particles with different zeta potentials and thin double layers migrating through a viscous fluid. The results indicate that the initial rate of electrophoretically-driven aggregation may exceed that of buoyancy-driven aggregation, even under conditions in which buoyancy-driven relative motion of noninteracting particles is dominant.

  17. Effects of chemical mechanical planarization slurry additives on the agglomeration of alumina nanoparticles II: aggregation rate analysis.

    PubMed

    Brahma, Neil; Talbot, Jan B

    2014-04-01

    The aggregation rate and mechanism of 150 nm alumina particles in 1mM KNO3 with various additives used in chemical mechanical planarization of copper were investigated. The pH of each suspension was ∼8 such that the aggregation rate was slow enough to be measured and analyzed over ∼120 min. In general, an initial exponential growth was observed for most suspensions indicating reaction-limited aggregation. After aggregate sizes increase to >500 nm, the rate followed a power law suggesting diffusion-limited aggregation. Stability ratios and fractal dimension numbers were also calculated to further elucidate the aggregation mechanism. PMID:24491325

  18. Making Comparisons of Demographic Aggregates more Meaningful: A Case of Life Expectancies and Total Fertility Rates

    ERIC Educational Resources Information Center

    Mishra, Udaya S.

    2006-01-01

    With the recent emphasis on human development, development researchers are making frequent use of aggregate demographic measures in describing development experiences and more so while linking health and development. And it is often seen that comparison of these demographic aggregates across space and time is naive given their complex construct on…

  19. A population balance equation model of aggregation dynamics in Taxus suspension cell cultures

    PubMed Central

    Kolewe, Martin E.; Roberts, Susan C.; Henson, Michael A.

    2011-01-01

    The nature of plant cells to grow as multicellular aggregates in suspension culture has profound effects on bioprocess performance. Recent advances in the measurement of plant cell aggregate size allow for routine process monitoring of this property. We have exploited this capability to develop a conceptual model to describe changes in the aggregate size distribution that are observed over the course of a Taxus cell suspension batch culture. We utilized the population balance equation framework to describe plant cell aggregates as a particulate system, accounting for the relevant phenomenological processes underlying aggregation, such as growth and breakage. We compared model predictions to experimental data to select appropriate kernel functions, and found that larger aggregates had a higher breakage rate, biomass was partitioned asymmetrically following a breakage event, and aggregates grew exponentially. Our model was then validated against several data sets with different initial aggregate size distributions and was able to quantitatively predict changes in total biomass and mean aggregate size, as well as actual size distributions. We proposed a breakage mechanism where a fraction of biomass was lost upon each breakage event, and demonstrated that even though smaller aggregates have been shown to produce more paclitaxel, an optimum breakage rate was predicted for maximum paclitaxel accumulation. We believe this is the first model to use a segregated, corpuscular approach to describe changes in the size distribution of plant cell aggregates, and represents an important first step in the design of rational strategies to control aggregation and optimize process performance. PMID:21910121

  20. A population balance equation model of aggregation dynamics in Taxus suspension cell cultures.

    PubMed

    Kolewe, Martin E; Roberts, Susan C; Henson, Michael A

    2012-02-01

    The nature of plant cells to grow as multicellular aggregates in suspension culture has profound effects on bioprocess performance. Recent advances in the measurement of plant cell aggregate size allow for routine process monitoring of this property. We have exploited this capability to develop a conceptual model to describe changes in the aggregate size distribution that are observed over the course of a Taxus cell suspension batch culture. We utilized the population balance equation framework to describe plant cell aggregates as a particulate system, accounting for the relevant phenomenological processes underlying aggregation, such as growth and breakage. We compared model predictions to experimental data to select appropriate kernel functions, and found that larger aggregates had a higher breakage rate, biomass was partitioned asymmetrically following a breakage event, and aggregates grew exponentially. Our model was then validated against several datasets with different initial aggregate size distributions and was able to quantitatively predict changes in total biomass and mean aggregate size, as well as actual size distributions. We proposed a breakage mechanism where a fraction of biomass was lost upon each breakage event, and demonstrated that even though smaller aggregates have been shown to produce more paclitaxel, an optimum breakage rate was predicted for maximum paclitaxel accumulation. We believe this is the first model to use a segregated, corpuscular approach to describe changes in the size distribution of plant cell aggregates, and represents an important first step in the design of rational strategies to control aggregation and optimize process performance. PMID:21910121

  1. Constructing Traversable Wormholes: An Initial Value Approach

    SciTech Connect

    Delgado, J. Estevez; Garcia, N. Montelongo; Zannias, T.

    2009-05-01

    We set up a formalism that generates R{sup 2}xS{sup 2} static wormhole spacetimes (M,g). We are assuming that the magnitude of the timelike Killing vector field is uniform over the throat but its gradients is non vanishing on the throat. These conditions imply that a vicinity of the throat can be foliated by a family of closed regular two surfaces and relative to this foliation a (2+1+1) decompositions of G{sub {mu}}{sub v} = k-circumflex T{sub {mu}}{sub v} yields a set of constraints eqs and a set of dynamical eqs that propagated the intrinsic metric, extrinsic curvature as well as the matter variables of the throat.

  2. Lightweight alumina refractory aggregate. Phase 2, Pilot scale development

    SciTech Connect

    Swansiger, T.G.; Pearson, A.

    1994-11-01

    Kilogram quantities of refractory aggregate were prepared from both a paste and a pelletized form of extruder feed material in both bench and pilot-scale equipment. The 99{sup +} % alumina aggregate exhibited a bulk density approaching 2.5 g/cm{sup 3} and a fired strength slightly lower than fused alumina. Based on initial evaluation by two refractory manufacturers in brick or castable applications, the new aggregate offered adequate strength with thermal conductivity reductions up to 34%, depending on the temperature and application of the new aggregate in these initial trials. The new aggregate was simply substituted for Tabular{trademark} in the refractory formulation. Thus, there is room for improvement through formulation optimization with the lightweight aggregate. The new aggregate offers a unique combination of density, strength, and thermal properties not available in current aggregate. To this point in time, technical development has led to a pelletized formulation with borderline physical form leaving the Eirich mixer. The formulation requires further development to provide more latitude for the production of pelletized material without forming paste, while still reducing the bulk density slightly to reach the 2.5 g/cm{sup 3} target. The preferred, pelletized process flowsheet was outlined and a preliminary economic feasibility study performed based on a process retrofit into Alcoa`s Arkansas tabular production facilities. Based on an assumed market demand of 20,000 mt/year and an assumed selling price of $0.65/lb (25% more than the current selling price of Tabular{trademark}, on a volume basis), economics were favorable. Decision on whether to proceed into Phase 3 (full- scale demonstration) will be based on a formal market survey in 1994 October.

  3. Impact of aggregate size and structure on the photocatalytic properties of TiO2 and ZnO nanoparticles.

    PubMed

    Jassby, David; Farner Budarz, Jeffrey; Wiesner, Mark

    2012-07-01

    Aggregation of photocatalytic semiconductors was determined to reduce the generation of free hydroxyl radicals in aqueous suspensions in a fashion dependent on aggregate size and structure. Static light scattering measurements were used to follow temporal changes in the fractal dimension of aggregating TiO(2) and ZnO nanoparticles. At length scales comparable to nanoparticle size, the structure of aggregated TiO(2) nanoparticles was independent of particle stability and the associated aggregation rate, consistent with the fused nature of TiO(2) primary particles in the initial suspension. In contrast, ZnO aggregates were characterized by smaller fractal dimensions when ionic strength, and the resulting aggregation rate, were increased. The photocatalytic activity of ZnO and TiO(2) in generating free hydroxyl radicals varied with aggregate structure and size, consistent with theory that predicts reduced reactivity as aggregates become larger and more dense. PMID:22225505

  4. Cellular pattern formation during Dictyostelium aggregation

    NASA Astrophysics Data System (ADS)

    Höfer, Thomas; Sherratt, Jonathan A.; Maini, Philip K.

    The development of multicellularity in the life cycle of Dictyostelium discoideum provides a paradigm model system for biological pattern formation. Previously, mathematical models have shown how a collective pattern of cell communication by waves of the messenger molecule cyclic adenosine 3‧5‧-monophosphate (cAMP) arises from excitable local cAMP kinetics and cAMP diffusion. Here we derive a model of the actual cell aggregation process by considering the chemotactic cell response to cAMP and its interplay with the cAMP dynamics. Cell density, which previously has been treated as a spatially homogeneous parameter, is a crucial variable of the aggregation model. We find that the coupled dynamics of cell chemotaxis and cAMP reaction-diffusion lead to the break-up of the initially uniform cell layer and to the formation of the striking cell stream morphology which characterizes the aggregation process in situ. By a combination of stability analysis and two-dimensional simulations of the model equations, we show cell streaming to be the consequence of the growth of a small-amplitude pattern in cell density forced by the large-amplitude cAMP waves, thus representing a novel scenario of spatial patterning in a cell chemotaxis system. The instability mechanism is further analysed by means of an analytic caricature of the model, and the condition for chemotaxis-driven instability is found to be very similar to the one obtained for the standard (non-oscillatory) Keller-Segel system. The growing cell stream pattern feeds back into the cAMP dynamics, which can explain in some detail experimental observations on the time evolution of the cAMP wave pattern, and suggests the characterization of the Dictyostelium aggregation field as a self-organized excitable medium.

  5. Aggregate driver model to enable predictable behaviour

    NASA Astrophysics Data System (ADS)

    Chowdhury, A.; Chakravarty, T.; Banerjee, T.; Balamuralidhar, P.

    2015-09-01

    The categorization of driving styles, particularly in terms of aggressiveness and skill is an emerging area of interest under the broader theme of intelligent transportation. There are two possible discriminatory techniques that can be applied for such categorization; a microscale (event based) model and a macro-scale (aggregate) model. It is believed that an aggregate model will reveal many interesting aspects of human-machine interaction; for example, we may be able to understand the propensities of individuals to carry out a given task over longer periods of time. A useful driver model may include the adaptive capability of the human driver, aggregated as the individual propensity to control speed/acceleration. Towards that objective, we carried out experiments by deploying smartphone based application to be used for data collection by a group of drivers. Data is primarily being collected from GPS measurements including position & speed on a second-by-second basis, for a number of trips over a two months period. Analysing the data set, aggregate models for individual drivers were created and their natural aggressiveness were deduced. In this paper, we present the initial results for 12 drivers. It is shown that the higher order moments of the acceleration profile is an important parameter and identifier of journey quality. It is also observed that the Kurtosis of the acceleration profiles stores major information about the driving styles. Such an observation leads to two different ranking systems based on acceleration data. Such driving behaviour models can be integrated with vehicle and road model and used to generate behavioural model for real traffic scenario.

  6. Production of lightweight aggregate from industrial waste and carbon dioxide.

    PubMed

    Gunning, Peter J; Hills, Colin D; Carey, Paula J

    2009-10-01

    The concomitant recycling of waste and carbon dioxide emissions is the subject of developing technology designed to close the industrial process loop and facilitate the bulk-re-use of waste in, for example, construction. The present work discusses a treatment step that employs accelerated carbonation to convert gaseous carbon dioxide into solid calcium carbonate through a reaction with industrial thermal residues. Treatment by accelerated carbonation enabled a synthetic aggregate to be made from thermal residues and waste quarry fines. The aggregates produced had a bulk density below 1000 kg/m(3) and a high water absorption capacity. Aggregate crushing strengths were between 30% and 90% stronger than the proprietary lightweight expanded clay aggregate available in the UK. Cast concrete blocks containing the carbonated aggregate achieve compressive strengths of 24 MPa, making them suitable for use with concrete exposed to non-aggressive service environments. The energy intensive firing and sintering processes traditionally required to produce lightweight aggregates can now be augmented by a cold-bonding, low energy method that contributes to the reduction of green house gases to the atmosphere. PMID:19577916

  7. An in vivo platform for identifying inhibitors of protein aggregation

    PubMed Central

    Mahood, Rachel A.; Jackson, Matthew P.; Revill, Charlotte H.; Foster, Richard J.; Smith, D. Alastair; Ashcroft, Alison E.; Brockwell, David J.; Radford, Sheena E.

    2015-01-01

    Protein aggregation underlies an array of human diseases, yet only one small molecule therapeutic has been successfully developed to date. Here, we introduce an in vivo system, based on a β-lactamase tripartite fusion construct, capable of identifying aggregation-prone sequences in the periplasm of Escherichia coli and inhibitors that prevent their aberrant self-assembly. We demonstrate the power of the system using a range of proteins, from small unstructured peptides (islet amyloid polypeptide and amyloid β) to larger, folded immunoglobulin domains. Configured in a 48-well format, the split β-lactamase sensor readily differentiates between aggregation-prone and soluble sequences. Performing the assay in the presence of 109 compounds enabled a rank ordering of inhibition and revealed a new inhibitor of IAPP aggregation. This platform can be applied to both amyloidogenic and other aggregation-prone systems, independent of sequence or size, and can identify small molecules or other factors able to ameliorate or inhibit protein aggregation. PMID:26656088

  8. An in vivo platform for identifying inhibitors of protein aggregation.

    PubMed

    Saunders, Janet C; Young, Lydia M; Mahood, Rachel A; Jackson, Matthew P; Revill, Charlotte H; Foster, Richard J; Smith, D Alastair; Ashcroft, Alison E; Brockwell, David J; Radford, Sheena E

    2016-02-01

    Protein aggregation underlies an array of human diseases, yet only one small-molecule therapeutic targeting this process has been successfully developed to date. Here, we introduce an in vivo system, based on a β-lactamase tripartite fusion construct, that is capable of identifying aggregation-prone sequences in the periplasm of Escherichia coli and inhibitors that prevent their aberrant self-assembly. We demonstrate the power of the system using a range of proteins, from small unstructured peptides (islet amyloid polypeptide and amyloid β) to larger, folded immunoglobulin domains. Configured in a 48-well format, the split β-lactamase sensor readily differentiates between aggregation-prone and soluble sequences. Performing the assay in the presence of 109 compounds enabled a rank ordering of inhibition and revealed a new inhibitor of islet amyloid polypeptide aggregation. This platform can be applied to both amyloidogenic and other aggregation-prone systems, independent of sequence or size, and can identify small molecules or other factors able to ameliorate or inhibit protein aggregation. PMID:26656088

  9. Aggregate breakdown of nanoparticulate titania

    NASA Astrophysics Data System (ADS)

    Venugopal, Navin

    Six nanosized titanium dioxide powders synthesized from a sulfate process were investigated. The targeted end-use of this powder was for a de-NOx catalyst honeycomb monolith. Alteration of synthesis parameters had resulted principally in differences in soluble ion level and specific surface area of the powders. The goal of this investigation was to understand the role of synthesis parameters in the aggregation behavior of these powders. Investigation via scanning electron microscopy of the powders revealed three different aggregation iterations at specific length scales. Secondary and higher order aggregate strength was investigated via oscillatory stress rheometry as a means of simulating shear conditions encountered during extrusion. G' and G'' were measured as a function of the applied oscillatory stress. Oscillatory rheometry indicated a strong variation as a function of the sulfate level of the particles in the viscoelastic yield strengths. Powder yield stresses ranged from 3.0 Pa to 24.0 Pa of oscillatory stress. Compaction curves to 750 MPa found strong similarities in extrapolated yield point of stage I and II compaction for each of the powders (at approximately 500 MPa) suggesting that the variation in sulfate was greatest above the primary aggregate level. Scanning electron microscopy of samples at different states of shear in oscillatory rheometry confirmed the variation in the linear elastic region and the viscous flow regime. A technique of this investigation was to approach aggregation via a novel perspective: aggregates are distinguished as being loose open structures that are highly disordered and stochastic in nature. The methodology used was to investigate the shear stresses required to rupture the various aggregation stages encountered and investigate the attempt to realign the now free-flowing constituents comprising the aggregate into a denser configuration. Mercury porosimetry was utilized to measure the pore size of the compact resulting from

  10. Monosized aggregates -- A new model

    SciTech Connect

    Gopal, M.

    1997-08-01

    For applications requiring colloidal particles, it is desirable that they be monosized to better control the structure and the properties. In a number of systems, the monosized particles come together to form aggregates that are also monosized. A model is presented here to explain the formation of these monosized aggregates. This is of particular importance in the fields of ceramics, catalysis, pigments, pharmacy, photographic emulsions, etc.

  11. Polarimetric Models of Circumstellar Discs Including Aggregate Dust Grains

    NASA Astrophysics Data System (ADS)

    Mohan, Mahesh

    The work conducted in this thesis examines the nature of circumstellar discs by investigating irradiance and polarization of scattered light. Two circumstellar discs are investigated. Firstly, H-band high contrast imaging data on the transitional disc of the Herbig Ae/Be star HD169142 are presented. The images were obtained through the polarimetric differential imaging (PDI) technique on the Very Large Telescope (VLT) using the adaptive optics system NACO. Our observations use longer exposure times, allowing us to examine the edges of the disc. Analysis of the observations shows distinct signs of polarization due to circumstellar material, but due to excessive saturation and adaptive optics errors further information on the disc could not be inferred. The HD169142 disc is then modelled using the 3D radiative transfer code Hyperion. Initial models were constructed using a two disc structure, however recent PDI has shown the existence of an annular gap. In addition to this the annular gap is found not to be devoid of dust. This then led to the construction of a four-component disc structure. Estimates of the mass of dust in the gap (2.10E-6 Msun) are made as well as for the planet (1.53E-5 Msun (0.016 Mjupiter)) suspected to be responsible for causing the gap. The predicted polarization was also estimated for the disc, peaking at ~14 percent. The use of realistic dust grains (ballistic aggregate particles) in Monte Carlo code is also examined. The fortran code DDSCAT is used to calculate the scattering properties for aggregates which are used to replace the spherical grain models used by the radiative transfer code Hyperion. Currently, Hyperion uses four independent elements to define the scattering matrix, therefore the use of rotational averaging and a 50/50 percent population of grains and their enantiomers were explored to reduce the number of contributing scattering elements from DDSCAT. A python script was created to extract the scattering data from the DDSCAT

  12. Molecular dynamics studies of protein folding and aggregation

    NASA Astrophysics Data System (ADS)

    Ding, Feng

    This thesis applies molecular dynamics simulations and statistical mechanics to study: (i) protein folding; and (ii) protein aggregation. Most small proteins fold into their native states via a first-order-like phase transition with a major free energy barrier between the folded and unfolded states. A set of protein conformations corresponding to the free energy barrier, Delta G >> kBT, are the folding transition state ensemble (TSE). Due to their evasive nature, TSE conformations are hard to capture (probability ∝ exp(-DeltaG/k BT)) and characterize. A coarse-grained discrete molecular dynamics model with realistic steric constraints is constructed to reproduce the experimentally observed two-state folding thermodynamics. A kinetic approach is proposed to identify the folding TSE. A specific set of contacts, common to the TSE conformations, is identified as the folding nuclei which are necessary to be formed in order for the protein to fold. Interestingly, the amino acids at the site of the identified folding nuclei are highly conserved for homologous proteins sharing the same structures. Such conservation suggests that amino acids that are important for folding kinetics are under selective pressure to be preserved during the course of molecular evolution. In addition, studies of the conformations close to the transition states uncover the importance of topology in the construction of order parameter for protein folding transition. Misfolded proteins often form insoluble aggregates, amyloid fibrils, that deposit in the extracellular space and lead to a type of disease known as amyloidosis. Due to its insoluble and non-crystalline nature, the aggregation structure and, thus the aggregation mechanism, has yet to be uncovered. Discrete molecular dynamics studies reveal an aggregate structure with the same structural signatures as in experimental observations and show a nucleation aggregation scenario. The simulations also suggest a generic aggregation mechanism

  13. Model for amorphous aggregation processes

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  14. Glycation precedes lens crystallin aggregation

    SciTech Connect

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

    1987-05-01

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

  15. Kinetic model for erythrocyte aggregation.

    PubMed

    Bertoluzzo, S M; Bollini, A; Rasia, M; Raynal, A

    1999-01-01

    It is well known that light transmission through blood is the most widely utilized method for the study of erythrocyte aggregation. The curves obtained had been considered empirically as exponential functions. In consequence, the process becomes characterized by an only parameter that varies with all the process factors without discrimination. In the present paper a mathematical model for RBC aggregation process is deduced in accordance with von Smoluchowski's theory about the kinetics of colloidal particles agglomeration. The equation fitted the experimental pattern of the RBC suspension optical transmittance closely and contained two parameters that estimate the most important characteristics of the aggregation process separately, i.e., (1) average size of rouleaux at equilibrium and (2) aggregation rate. The evaluation of the method was assessed by some factors affecting erythrocyte aggregation, such as temperature, plasma dilutions, Dextran 500, Dextran 70 and PVP 360, at different media concentrations, cellular membrane alteration by the alkylating agent TCEA, and decrease of medium osmolarity. Results were interpreted considering the process characteristics estimated by the parameters, and there were also compared with similar studies carried out by other authors with other methods. This analysis allowed us to conclude that the equation proposed is reliable and useful to study erythrocyte aggregation. PMID:10660481

  16. Analysis of aggregation of platelets in thrombosis

    NASA Astrophysics Data System (ADS)

    Ahuja, Suresh

    Platelets are key players in thrombus formation by first rolling over collagen bound von Willebrand factor followed by formation of a stable interaction with collagen. The first adhered platelets bind additional platelets until the whole injury is sealed off by a platelet aggregate. The coagulation system stabilizes the formed platelet plug by creating a tight fibrin network, and then wound contraction takes place because of morphological changes in platelets. Coagulation takes place by platelet activation and aggregation mainly through fibrinogen polymerization into fibrin fibers. The process includes multiple factors, such as thrombin, plasmin, and local shear-rate which regulate and control the process. Coagulation can be divided into two pathways: the intrinsic pathway and the extrinsic pathway. The intrinsic pathway is initiated by the exposure of a negatively charged. It is able to activate factor XII, using a complex reaction that includes prekallikrein and high-molecular-weight kininogen as cofactors.. Thrombin is the final enzyme that is needed to convert fibrinogen into fibrin. The extrinsic pathway starts with the exposure of tissue factor to the circulating blood, which is the major initiator of coagulation. There are several feedback loops that reinforce the coagulation cascade, resulting in large amounts of thrombin. It is dependent on the presence of pro-coagulant surfaces of cells expressing negatively charged phospholipids--which include phosphatidylserine (PS)--on their outer membrane. PS-bearing surfaces are able to increase the efficiency of the reactions by concentrating and co-localizing coagulation factors.. Aggregation of platelets are analyzed and compared to adhesion of platelet to erythrocyte and to endothelial cells. This abstract is replacing MAR16-2015-020003.

  17. A Novel Energy-Efficient MAC Aware Data Aggregation Routing in Wireless Sensor Networks.

    PubMed

    Lin, Frank Yeong-Sung; Yen, Hong-Hsu; Lin, Shu-Ping

    2009-01-01

    Embedding data-aggregation capabilities into sensor nodes of wireless networks could save energy by reducing redundant data flow transmissions. Existing research describes the construction of data aggregation trees to maximize data aggregation times in order to reduce data transmission of redundant data. However, aggregation of more nodes on the same node will incur significant collisions. These MAC (Media Access Control) layer collisions introduce additional data retransmissions that could jeopardize the advantages of data aggregation. This paper is the first to consider the energy consumption tradeoffs between data aggregation and retransmissions in a wireless sensor network. By using the existing CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) MAC protocol, the retransmission energy consumption function is well formulated. This paper proposes a novel non-linear mathematical formulation, whose function is to minimize the total energy consumption of data transmission subject to data aggregation trees and data retransmissions. This solution approach is based on Lagrangean relaxation, in conjunction with optimization-based heuristics. From the computational experiments, it is shown that the proposed algorithms could construct MAC aware data aggregation trees that are up to 59% more energy efficient than existing data aggregation algorithms. PMID:22573969

  18. Paradoxical Acceleration of Dithiothreitol-Induced Aggregation of Insulin in the Presence of a Chaperone

    PubMed Central

    Bumagina, Zoya; Gurvits, Bella; Artemova, Natalya; Muranov, Konstantin; Kurganov, Boris

    2010-01-01

    The kinetics of dithiothreitol (DTT)-induced aggregation of human recombinant insulin and the effect of α-crystallin, a representative of the family of small heat shock proteins, on the aggregation process have been studied using dynamic light scattering technique. Analysis of the distribution of the particles by size measured in the course of aggregation showed that the initial stage of the aggregation process was the stage of formation of the start aggregates with a hydrodynamic radius (Rh) of about 90 nm. When studying the effect of α-crystallin on the rate of DTT-induced aggregation of insulin, it was demonstrated that low concentrations of α-crystallin dramatically accelerated the aggregation process, whereas high concentrations of α-crystallin suppressed insulin aggregation. In the present study, at the molar stoichiometric ratio (insulin:α-crystallin) less than 1:0.5, a pronounced accelerating effect of α-crystallin was observed; whereas a ratio exceeding the value of 1:0.6 caused suppression of insulin aggregation. The mechanisms underlying the dual effect of α-crystallin have been proposed. It is assumed that heterogeneous nucleation occurring on the surface of the α-crystallin particle plays the key role in the paradoxical acceleration of insulin aggregation by α-crystallin that may provide an alternative biologically significant pathway of the aggregation process. PMID:21151456

  19. Fluorescence spectroscopy in probing spontaneous and induced aggregation amongst size-selective gold nanoclusters

    NASA Astrophysics Data System (ADS)

    Rahman, Dewan S.; Ghosh, Sujit Kumar

    2014-06-01

    Gold nanoparticles have been synthesized by borohydride reduction using poly(N-vinyl 2-pyrrolidone) as the stabilizing agent in aqueous medium in the size regime of 1-5 nm. Aggregation amongst these polymer-stabilized gold nanoparticles has been accomplished by the controlled addition of hydrazine or aggregation may occur spontaneously (devoid of any chemicals) that is ubiquitous to nanoparticulate systems. Now, fluorescencein isothiocyanate (FITC), a prototype molecular probe has been employed in understanding the physical principles of aggregation phenomenon of the size-selective gold nanoparticles undergoing spontaneous and induced-aggregation under stipulated conditions. It is seen that there is enhancement of fluorescence intensity of FITC in the presence of both spontaneously and induced-aggregated gold nanoclusters as compared to free FITC. Interestingly, it is observed that the fluorescence sensitivity is able to distinguish seven different sizes of the gold nanoparticles in the aggregates and maximum enhancement of intensity arises at higher concentration with increase in size of gold particles within the aggregates. With increase in concentration of gold nanoparticle aggregates, the intensity increases, initially, reaches a maximum at a threshold concentration and then, gradually decreases in the presence of both spontaneously and induced-aggregated gold particles. However, the salient feature of physical significance is that the maximum enhancement of intensity with time has remained almost same for induced-aggregated gold while decreases exponentially with spontaneously aggregated gold particles.

  20. Kinetic Model for 1D aggregation of yeast ``prions''

    NASA Astrophysics Data System (ADS)

    Kunes, Kay; Cox, Daniel; Singh, Rajiv

    2004-03-01

    Mammalian prion proteins (PrP) are of public health interest because of mad cow and chronic wasting diseases. Yeast have proteins which can undergo similar reconformation and aggregation processes to PrP; yeast forms are simpler to experimentally study and model. Recent in vitro studies of the SUP35 protein(1), showed long aggregates and pure exponential growth of the misfolded form. To explain this data, we have extended a previous model of aggregation kinetics(2). The model assumes reconformation only upon aggregation, and includes aggregate fissioning and an initial nucleation barrier. We find for sufficiently small nucleation rates or seeding by small dimer concentrations that we can achieve the requisite exponential growth and long aggregates. We will compare to a more realistic stochastic kinetics model and present prelimary attempts to describe recent experiments on SUP35 strains. *-Supported by U.S. Army Congressionally Mandated Research Fund. 1) P. Chien and J.S. Weissman, Nature 410, 223 (2001); http://online.kitp.ucsb.edu/online/bionet03/collins/. 2) J. Masel, V.A.> Jansen, M.A. Nowak, Biophys. Chem. 77, 139 (1999).

  1. Lysozyme Aggregation and Fibrillation Monitored by Dynamic Light Scattering

    NASA Astrophysics Data System (ADS)

    Nemzer, Louis; Flanders, Bret; Schmit, Jeremy; Sorensen, Christopher

    2012-02-01

    The aggregation of amyloidogenic proteins provides a rich phase space with significant biomedical implications, including a link with several age-related diseases. We employed dynamic light scattering to monitor the aggregation of lysozyme, a model protein, from a monomeric state until the formation of micron-sized fibrils. For an aqueous lysozyme solution buffered at pH 2, the auto-correlation function of the scattered light intensity was found to be well-fit by a single exponential function with decay time τ = 1/(2Dq^2) = 0.25 ms, which corresponds to a mean hydrodynamic radius (RH) of 2.2 nm, very likely generated by monomers. Ethanol (4% v/v final concentration) induced a partial unfolding, to RH = 4.6 nm. The subsequent addition of 70 mM KCl was found to shrink the size back to RH = 2.5 nm, as expected when a denatured protein refolds due to partial screening of the intramolecular repulsion. However, further aggregation was not observed. At pH 4, using a low-salt acetate buffer, more ethanol (10% v/v) was required to initiate unfolding, but once it occurred, larger aggregates formed. These results are consistent with the model that partial unfolding, which exposes beta-motif secondary structure, is a prerequisite for aggregation and fibrillation, but the aggregation fate depends on the protein charge state (pH) and screening (salt concentration).

  2. Smooth muscle titin forms in vitro amyloid aggregates.

    PubMed

    Bobylev, Alexandr G; Galzitskaya, Oxana V; Fadeev, Roman S; Bobyleva, Liya G; Yurshenas, Darya A; Molochkov, Nikolay V; Dovidchenko, Nikita V; Selivanova, Olga M; Penkov, Nikita V; Podlubnaya, Zoya A; Vikhlyantsev, Ivan M

    2016-07-01

    Amyloids are insoluble fibrous protein aggregates, and their accumulation is associated with amyloidosis and many neurodegenerative diseases, including Alzheimer's disease. In the present study, we report that smooth muscle titin (SMT; 500 kDa) from chicken gizzard forms amyloid aggregates in vitro This conclusion is supported by EM data, fluorescence analysis using thioflavin T (ThT), Congo red (CR) spectroscopy and X-ray diffraction. Our dynamic light scattering (DLS) data show that titin forms in vitro amyloid aggregates with a hydrodynamic radius (Rh) of approximately 700-4500 nm. The initial titin aggregates with Rh approximately 700 nm were observed beyond first 20 min its aggregation that shows a high rate of amyloid formation by this protein. We also showed using confocal microscopy the cytotoxic effect of SMT amyloid aggregates on smooth muscle cells from bovine aorta. This effect involves the disorganization of the actin cytoskeleton and result is cell damage. Cumulatively, our results indicate that titin may be involved in generation of amyloidosis in smooth muscles. PMID:27129292

  3. Crystal aggregation in kidney stones; a polymer aggregation problem?

    NASA Astrophysics Data System (ADS)

    Wesson, J.; Beshensky, A.; Viswanathan, P.; Zachowicz, W.; Kleinman, J.

    2008-03-01

    Kidney stones most frequently form as aggregates of calcium oxalate monohydrate (COM) crystals with organic layers between them, and the organic layers contain principally proteins. The pathway leading to the formation of these crystal aggregates in affected people has not been identified, but stone forming patients are thought to have a defect in the structure or distribution of urinary proteins, which normally protect against stone formation. We have developed two polyelectrolyte models that will induce COM crystal aggregation in vitro, and both are consistent with possible urinary protein compositions. The first model was based on mixing polyanionic and polycationic proteins, in portions such that the combined protein charge is near zero. The second model was based on reducing the charge density on partially charged polyanionic proteins, specifically Tamm-Horsfall protein, the second most abundant protein in urine. Both models demonstrated polymer phase separation at solution conditions where COM crystal aggregation was observed. Correlation with data from other bulk crystallization measurements suggest that the anionic side chains form critical binding interactions with COM surfaces that are necessary along with the phase separation process to induce COM crystal aggregation.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  5. Security Analysis of the Unrestricted Identity-Based Aggregate Signature Scheme

    PubMed Central

    Lee, Kwangsu; Lee, Dong Hoon

    2015-01-01

    Aggregate signatures allow anyone to combine different signatures signed by different signers on different messages into a short signature. An ideal aggregate signature scheme is an identity-based aggregate signature (IBAS) scheme that supports full aggregation since it can reduce the total transmitted data by using an identity string as a public key and anyone can freely aggregate different signatures. Constructing a secure IBAS scheme that supports full aggregation in bilinear maps is an important open problem. Recently, Yuan et al. proposed such a scheme and claimed its security in the random oracle model under the computational Diffie-Hellman assumption. In this paper, we show that there is an efficient forgery on their IBAS scheme and that their security proof has a serious flaw. PMID:25993247

  6. Growth and Destruction from Low-Velocity Dust Aggregate Collisions

    NASA Astrophysics Data System (ADS)

    Dove, Adrienne; Colwell, J.; Vamos, C.

    2012-10-01

    By exploring a variety of impactor densities and velocities, we can observe the ranges over which growth, compaction, or erosion occur for cm-sized aggregates. Evolution of proto-planetary and planetary ring systems is driven by collisions between objects that are likely to themselves be formed from aggregates of smaller particles. In these collisional systems, impacts between objects may occur at very low velocities, much less than 1 m/s. Low-velocity impacts may play a critical role in the growth of larger aggregates. In planetary ring systems and circumplanetary disks, collisions between aggregates or dust-covered objects release dust that is a more visible tracer of the underlying parent population of massive objects. We have designed and built an apparatus to simulate these low-velocity collisions in a laboratory vacuum environment. In our experiment, one aggregate is launched upward by a spring launching mechanism, while another is dropped from directly above the launcher to create the impact. Impact velocities are controlled by initial spring launch velocity, masses of the particles, and timing of the collisions. Initially, we use JSC-1 lunar regolith simulant to create the aggregates; the simulant can be packed to different densities to control the mass and porosity of the impactors. A high-speed digital video camera is used to record the impacts to observe the behavior of both impactors and the resulting ejecta material. By exploring a variety of impactor densities and velocities, we can observe the ranges over which grow, compaction, or erosion occur for cm-sized aggregates.

  7. A Protein Aggregation Based Test for Screening of the Agents Affecting Thermostability of Proteins

    PubMed Central

    Eronina, Tatyana; Borzova, Vera; Maloletkina, Olga; Kleymenov, Sergey; Asryants, Regina; Markossian, Kira; Kurganov, Boris

    2011-01-01

    To search for agents affecting thermal stability of proteins, a test based on the registration of protein aggregation in the regime of heating with a constant rate was used. The initial parts of the dependences of the light scattering intensity (I) on temperature (T) were analyzed using the following empiric equation: I = Kagg(T−T0)2, where Kagg is the parameter characterizing the initial rate of aggregation and T0 is a temperature at which the initial increase in the light scattering intensity is registered. The aggregation data are interpreted in the frame of the model assuming the formation of the start aggregates at the initial stages of the aggregation process. Parameter T0 corresponds to the moment of the origination of the start aggregates. The applicability of the proposed approach was demonstrated on the examples of thermal aggregation of glycogen phosphorylase b from rabbit skeletal muscles and bovine liver glutamate dehydrogenase studied in the presence of agents of different chemical nature. The elaborated approach to the study of protein aggregation may be used for rapid identification of small molecules that interact with protein targets. PMID:21760963

  8. Fractal Aggregates in Tennis Ball Systems

    ERIC Educational Resources Information Center

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

    2009-01-01

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

  9. Aggregation of regularized solutions from multiple observation models

    NASA Astrophysics Data System (ADS)

    Chen, Jieyang; Pereverzyev, Sergiy, Jr.; Xu, Yuesheng

    2015-07-01

    Joint inversion of multiple observation models has important applications in many disciplines including geoscience, image processing and computational biology. One of the methodologies for joint inversion of ill-posed observation equations naturally leads to multi-parameter regularization, which has been intensively studied over the last several years. However, problems such as the choice of multiple regularization parameters remain unsolved. In the present study, we discuss a rather general approach to the regularization of multiple observation models, based on the idea of the linear aggregation of approximations corresponding to different values of the regularization parameters. We show how the well-known linear functional strategy can be used for such an aggregation and prove that the error of a constructive aggregator differs from the ideal error value by a quantity of an order higher than the best guaranteed accuracy from the most trustable observation model. The theoretical analysis is illustrated by numerical experiments with simulated data.

  10. On the radiative properties of soot aggregates part 1: Necking and overlapping

    NASA Astrophysics Data System (ADS)

    Yon, J.; Bescond, A.; Liu, F.

    2015-09-01

    There is a strong interest in accurately modelling the radiative properties of soot aggregates (also known as black carbon particles) emitted from combustion systems and fires to gain improved understanding of the role of black carbon to global warming. This study conducted a systematic investigation of the effects of overlapping and necking between neighbouring primary particles on the radiative properties of soot aggregates using the discrete dipole approximation. The degrees of overlapping and necking are quantified by the overlapping and necking parameters. Realistic soot aggregates were generated numerically by constructing overlapping and necking to fractal aggregates formed by point-touch primary particles simulated using a diffusion-limited cluster aggregation algorithm. Radiative properties (differential scattering, absorption, total scattering, specific extinction, asymmetry factor and single scattering albedo) were calculated using the experimentally measured soot refractive index over the spectral range of 266-1064 nm for 9 combinations of the overlapping and necking parameters. Overlapping and necking affect significantly the absorption and scattering properties of soot aggregates, especially in the near UV spectrum due to the enhanced multiple scattering effects within an aggregate. By using correctly modified aggregate properties (fractal dimension, prefactor, primary particle radius, and the number of primary particle) and by accounting for the effects of multiple scattering, the simple Rayleigh-Debye-Gans theory for fractal aggregates can reproduce reasonably accurate radiative properties of realistic soot aggregates.

  11. On the dynamics of the TPPS4 aggregation in aqueous solutions: successive formation of H and J aggregates.

    PubMed

    Aggarwal, Lucimara P F; Borissevitch, Iouri E

    2006-01-01

    The dynamics of aggregation of meso-tetrakis (p-sulfonatofenyl) porphyrin (TPPS4) in function of its concentration, pH and ionic strength was studied by optical absorption, fluorescence and resonance light scattering (RLS) techniques. In the region of pH, where TPPS4 exists in biprotonated form, the addition of NaCl induces the TPPS4 aggregation due to the formation of the "cloud" of counter ions around the TPPS4 molecule thus reducing electrostatic repulsion between the porphyrin molecules. The formation of this "cloud" shifts the pKa value to acid region (from 5.0 in the absence of salt to 4.5 at [NaCl] = 0.4 M), reduces the TPPS4 absorption in all spectral range and quantum yield and lifetime of fluorescence (from 0.27 to 0.17 and from 4.00+/-0.04 to 3.00+/-0.03 ns in the absence of salt and in the presence of NaCl, respectively). The aggregation process involves two successive stages: initially H aggregates are formed, which in time are transformed in J ones. The existence of these two stages was confirmed by the fluorescence and RLS data. The kinetics of the formation of J aggregates is characterized by the induction time t1 and the average growth time t2, which depend on both TPPS4 and salt concentrations. The induction period t1 appears as a result of initial formation of H aggregates and their successive transformation in J ones. At very high TPPS4 concentrations, the J aggregates are united in more complex structures such as hollow cylinders or helixes. PMID:15955725

  12. Aggregation operations for multiaspect fuzzy soft sets

    NASA Astrophysics Data System (ADS)

    Sulaiman, Nor Hashimah; Mohamad, Daud

    2015-10-01

    Multiaspect fuzzy soft set (MAFSS) is one of the generalized forms of fuzzy soft sets. In this paper, we introduce two types of aggregation operations for MAFSSs, namely the weighted arithmetic mean (WAM)-based MAFSS aggregation, and the ordered weighted aggregation (OWA)-based MAFSS aggregation. The applicability of the two MAFSS-aggregation operations is illustrated with numerical examples in group decision making.

  13. Two solvable systems of coagulation equations with limited aggregations

    NASA Astrophysics Data System (ADS)

    Bertoin, Jean

    2009-11-01

    We consider two simple models for the formation of polymers where at the initial time, each monomer has a certain number of potential links (called arms in the text) that are consumed when aggregations occur. Loosely speaking, this imposes restrictions on the number of aggregations. The dynamics of concentrations are governed by modifications of Smoluchowski's coagulation equations. Applying classical techniques based on generating functions, resolution of quasi-linear PDE's, and Lagrange inversion formula, we obtain explicit solutions to these non-linear systems of ODE's. We also discuss the asymptotic behavior of the solutions and point at some connexions with certain known solutions to Smoluchowski's coagulation equations with additive or multiplicative kernels.

  14. Evaporation effects in elastocapillary aggregation

    NASA Astrophysics Data System (ADS)

    Vella, Dominic; Hadjittofis, Andreas; Singh, Kiran; Lister, John

    2015-11-01

    We consider the effect of evaporation on the aggregation of a number of elastic objects due to a liquid's surface tension. In particular, we consider an array of spring-block elements in which the gaps between blocks are filled by thin liquid films that evaporate during the course of an experiment. Using lubrication theory to account for the fluid flow within the gaps, we study the dynamics of aggregation. We find that a non-zero evaporation rate causes the elements to aggregate more quickly and, indeed, to contact within finite time. However, we also show that the number of elements within each cluster decreases as the evaporation rate increases. We explain these results quantitatively by comparison with the corresponding two-body problem and discuss their relevance for controlling pattern formation in carbon nanotube forests.

  15. Molecular Aggregation in Disodium Cromoglycate

    NASA Astrophysics Data System (ADS)

    Singh, Gautam; Agra-Kooijman, D.; Collings, P. J.; Kumar, Satyendra

    2012-02-01

    Details of molecular aggregation in the mesophases of the anti-asthmatic drug disodium cromoglycate (DSCG) have been studied using x-ray synchrotron scattering. The results show two reflections, one at wide angles corresponding to π-π stacking (3.32 å) of molecules, and the other at small angles which is perpendicular to the direction of molecular stacking and corresponds to the distance between the molecular aggregates. The latter varies from 35 - 41 å in the nematic (N) phase and 27 -- 32 å in the columnar (M) phase. The temperature evolution of the stack height, positional order correlations in the lateral direction, and orientation order parameter were determined in the N, M, and biphasic regions. The structure of the N and M phases and the nature of the molecular aggregation, together with their dependence on temperature and concentration, will be presented.

  16. A plant cell model of polyglutamine aggregation: Identification and characterisation of macromolecular and small-molecule anti-protein aggregation activity in vivo.

    PubMed

    Liu, Guobao; Hu, Yueming; Tunnacliffe, Alan; Zheng, Yizhi

    2015-08-10

    In vitro studies have shown that LEA proteins from plants and invertebrates protect and stabilise other proteins under conditions of water stress, suggesting a role in stress tolerance. However, there is little information on LEA protein function in whole plants or plant cells, particularly with respect to their anti-aggregation activity. To address this, we expressed in tobacco BY-2 suspension cells an aggregation-prone protein based on that responsible for Huntington's disease (HD). In HD, abnormally long stretches of polyglutamine (polyQ) in huntingtin (Htt) protein cause aggregation of Htt fragments within cells. We constructed stably transformed BY-2 cell lines expressing enhanced green fluorescent protein (EGFP)-HttQ23 or EGFP-HttQ52 fusion proteins (encoding 23 or 52 glutamine residues, pertaining to the normal and disease states, respectively), as well as an EGFP control. EGFP-HttQ52 protein aggregated in the cytoplasm of transformed tobacco cells, which showed slow growth kinetics; in contrast, EGFP-HttQ23 or EGFP did not form aggregates and cells expressing these constructs grew normally. To test the effect of LEA proteins on protein aggregation in plant cells, we constructed cell lines expressing both EGFP-HttQ52 and LEA proteins (PM1, PM18, ZLDE-2 or AavLEA1) or a sHSP (PM31). Of these, AavLEA1 and PM31 reduced intracellular EGFP-HttQ52 aggregation and alleviated the associated growth inhibition, while PM18 and ZLDE-2 partially restored growth rates. Treatment of EGFP-HttQ52-expressing BY2 cells with the polyphenol epigallocatechin-3-gallate (EGCG) also reduced EGFP-HttQ52 aggregation and improved cell growth rate. The EGFP-HttQ52 cell line therefore has potential for characterising both macromolecular and small molecule inhibitors of protein aggregation in plant cells. PMID:26003885

  17. Data relationship degree-based clustering data aggregation for VANET

    NASA Astrophysics Data System (ADS)

    Kumar, Rakesh; Dave, Mayank

    2016-03-01

    Data aggregation is one of the major needs of vehicular ad hoc networks (VANETs) due to the constraints of resources. Data aggregation in VANET can reduce the data redundancy in the process of data gathering and thus conserving the bandwidth. In realistic applications, it is always important to construct an effective route strategy that optimises not only communication cost but also the aggregation cost. Data aggregation at the cluster head by individual vehicle causes flooding of the data, which results in maximum latency and bandwidth consumption. Another approach of data aggregation in VANET is sending local representative data based on spatial correlation of sampled data. In this article, we emphasise on the problem that recent spatial correlation data models of vehicles in VANET are not appropriate for measuring the correlation in a complex and composite environment. Moreover, the data represented by these models is generally inaccurate when compared to the real data. To minimise this problem, we propose a group-based data aggregation method that uses data relationship degree (DRD). In the proposed approach, DRD is a spatial relationship measurement parameter that measures the correlation between a vehicle's data and its neighbouring vehicles' data. The DRD clustering method where grouping of vehicle's data is done based on the available data and its correlation is presented in detail. Results prove that the representative data using proposed approach have a low distortion and provides an improvement in packet delivery ratio and throughput (up to of 10.84% and 24.82% respectively) as compared to the other state-of-the-art solutions like Cluster-Based Accurate Syntactic Compression of Aggregated Data in VANETs.

  18. Experimental investigation and population balance equation modeling of solid lipid nanoparticle aggregation dynamics.

    PubMed

    Yang, Yihui; Corona, Alessandro; Henson, Michael A

    2012-05-15

    Solid lipid nanoparticles (SLNs) have applications in drug delivery and the encapsulation of bioactive, lipophilic compounds. However, SLNs tend to aggregate when stored due to the lipid crystals undergoing a polymorphic transformation from the unstable α form to the stable β form. We developed a population balance equation (PBE) model for prediction of average polymorph content and aggregate size distribution to better understand this undesirable behavior. Experiments with SLNs stored at room temperature showed that polymorphic transformation was the rate determining step for our system, SLNs with smaller initial size distributions aggregated more rapidly, and aggregates contained particles with both α and β crystals. Using parameter values estimated from our data, the PBE model was able to capture the bimodal nature of aggregate size distributions, the α-to-β polymorph ratio, and the faster aggregation dynamics of SLNs with smaller initial size distributions. However, the model was unable to adequately capture the fast disappearance rate of primary particles, the broad size distributions of formed aggregates, and the significant α content of aggregating particles. These discrepancies suggest that a PBE model which accounts for polymorph content as an internal variable along with aggregate size may be required to better reproduce experimental observations. PMID:22405582

  19. Colloidal Recycling: Reconfiguration of Random Aggregates into Patchy Particles.

    PubMed

    Meester, Vera; Verweij, Ruben W; van der Wel, Casper; Kraft, Daniela J

    2016-04-26

    The key ingredients to the successful bottom-up construction of complex materials are believed to be colloids with anisotropic shapes and directional, or patchy, interactions. We present an approach for creating such anisotropic patchy particles based on reconfiguring randomly shaped aggregates of colloidal spheres. While colloidal aggregates are often undesirable in colloidal dispersions due to their random shapes, we exploit them as a starting point to synthesize patchy particles. By a deliberate destabilization of the colloidal particles, diffusion-limited aggregation is induced which partitions the particles into randomly shaped aggregates with controlled size distribution. We achieve a reconfiguration of the aggregates into uniform structures by swelling the polymer spheres with an apolar solvent. The swelling lowers the attractive van der Waals forces, lubricates the contact area between the spheres, and drives the reorganization through minimization of the interfacial energy of the swollen polymer network. This reorganization process yields patchy particles whose patch arrangement is uniform for up to five patches. For particles with more patches, we find that the patch orientation depends on the degree of phase separation between the spheres and the monomer. This enables the synthesis of patchy particles with unprecedented patch arrangements. We demonstrate the broad applicability of this recycling strategy for making patchy particles as well as clusters of spheres by varying the swelling ratio, swelling solvent, surfactant concentration, and swelling time. PMID:27014995

  20. Production of lightweight aggregates from washing aggregate sludge and fly ash

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    manufactured with 75%:25% and 50%:50% proportions of washing aggregate sludge:fly ash, heated at different temperatures and dwell times, were expanded LWAs (BI > 0). They showed the lowest loose bulk density, the lowest dry and apparent particle density, the lowest water absorption and the highest compressive strength. The possible applications of sintered pellets, taking into consideration compressive strength and water absorption values, could be similar to those of Arlita G3 (insulation, geotechnical applications, gardening and/or horticulture) and/or Arlita F3 (prefabricated lightweight structures and insulation lightweight concretes), two varieties of the most widely marketed LWAs in Spain. References - Benbow, J., September 1987. Mineral in fire protection construction support market. Industrial Minerals, 61-73. - Bethanis, S., Cheeseman, C.R., Sollars, C.J., 2004. Effect of sintering temperature on the properties and leaching of incinerator bottom ash. Waste Management and Research 22 (4), 255-264. - De' Gennaro, R., Cappelletti, P., Cerri, G., De' Gennaro, M., Dondi, M., Langella, A., 2004. Zeolitic tuffs as raw materials for lightweight aggregates. Applied Clay Science 25 (1-2), 71-81. - Fakhfakh, E., Hajjaji, W., Medhioub, M., Rocha, F., López-Galindo, A., Setti, M.,Kooli, F., Zargouni, F., Jamoussi, F., 2007. Effects of sand addition on production of lightweight aggregates from Tunisian smectite-rich clayey rocks. Applied Clay Science 35, 228-237. - UNE-EN-13055-1, 2003. Lightweight aggregates - lightweight aggregates for concrete, mortar and grout. - Yasuda, Y., 1991. Sewage-sludge utilization in Tokyo. Water Science and Technology 23 (10-12), 1743-1752.

  1. A Method of Data Aggregation for Wearable Sensor Systems.

    PubMed

    Shen, Bo; Fu, Jun-Song

    2016-01-01

    Data aggregation has been considered as an effective way to decrease the data to be transferred in sensor networks. Particularly for wearable sensor systems, smaller battery has less energy, which makes energy conservation in data transmission more important. Nevertheless, wearable sensor systems usually have features like frequently dynamic changes of topologies and data over a large range, of which current aggregating methods can't adapt to the demand. In this paper, we study the system composed of many wearable devices with sensors, such as the network of a tactical unit, and introduce an energy consumption-balanced method of data aggregation, named LDA-RT. In the proposed method, we develop a query algorithm based on the idea of 'happened-before' to construct a dynamic and energy-balancing routing tree. We also present a distributed data aggregating and sorting algorithm to execute top-k query and decrease the data that must be transferred among wearable devices. Combining these algorithms, LDA-RT tries to balance the energy consumptions for prolonging the lifetime of wearable sensor systems. Results of evaluation indicate that LDA-RT performs well in constructing routing trees and energy balances. It also outperforms the filter-based top-k monitoring approach in energy consumption, load balance, and the network's lifetime, especially for highly dynamic data sources. PMID:27347953

  2. A Method of Data Aggregation for Wearable Sensor Systems

    PubMed Central

    Shen, Bo; Fu, Jun-Song

    2016-01-01

    Data aggregation has been considered as an effective way to decrease the data to be transferred in sensor networks. Particularly for wearable sensor systems, smaller battery has less energy, which makes energy conservation in data transmission more important. Nevertheless, wearable sensor systems usually have features like frequently dynamic changes of topologies and data over a large range, of which current aggregating methods can’t adapt to the demand. In this paper, we study the system composed of many wearable devices with sensors, such as the network of a tactical unit, and introduce an energy consumption-balanced method of data aggregation, named LDA-RT. In the proposed method, we develop a query algorithm based on the idea of ‘happened-before’ to construct a dynamic and energy-balancing routing tree. We also present a distributed data aggregating and sorting algorithm to execute top-k query and decrease the data that must be transferred among wearable devices. Combining these algorithms, LDA-RT tries to balance the energy consumptions for prolonging the lifetime of wearable sensor systems. Results of evaluation indicate that LDA-RT performs well in constructing routing trees and energy balances. It also outperforms the filter-based top-k monitoring approach in energy consumption, load balance, and the network’s lifetime, especially for highly dynamic data sources. PMID:27347953

  3. Legal but lethal: functional protein aggregation at the verge of toxicity

    PubMed Central

    Falsone, Angelika; Falsone, S. Fabio

    2015-01-01

    Many neurodegenerative disorders are linked to irreversible protein aggregation, a process that usually comes along with toxicity and serious cellular damage. However, it is emerging that protein aggregation can also serve for physiological purposes, as impressively shown for prions. While the aggregation of this protein family was initially considered exclusively toxic in mammalians organisms, it is now almost clear that many other proteins adopt prion-like attributes to rationally polymerize into higher order complexes with organized physiologic roles. This implies that cells can tolerate at least in some measure the accumulation of inherently dangerous protein aggregates for functional profit. This review summarizes currently known strategies that living organisms adopt to preserve beneficial aggregation, and to prevent the catastrophic accumulation of toxic aggregates that frequently accompany neurodegeneration. PMID:25741240

  4. Structure and flow of dense suspensions of protein fractal aggregates in comparison with microgels.

    PubMed

    Inthavong, Walailuk; Kharlamova, Anna; Chassenieux, Christophe; Nicolai, Taco

    2016-03-14

    Solutions of the globular whey protein β-lactoglobulin (β-lg) were heated at different protein concentrations leading to the formation of polydisperse fractal aggregates with different average sizes. The structure of the solutions was analyzed with light scattering as a function of the protein concentration. The osmotic compressibility and the dynamic correlation length decreased with increasing concentration and became independent of the aggregate size in dense suspensions. The results obtained for different aggregate sizes could be superimposed after normalizing the concentration with the overlap concentration. Dense suspensions of fractal protein aggregates are strongly interpenetrated and can be visualized as an ensemble of fractal 'blobs'. The viscosity of the heated β-lg solutions increased extremely sharply above 80 g L(-1) and diverged at 98 g L(-1), mainly due to the sharply increasing aggregate size. At a fixed aggregate size, the viscosity increased initially exponentially with increasing concentration and then diverged. The increase was stronger when the aggregates were larger, but the dependence of the viscosity on the aggregate size was weaker than that of the osmotic compressibility and the dynamic correlation length. The concentration dependence of the viscosity of solutions of fractal β-lg aggregates is much stronger than that of homogeneous β-lg microgels. The behavior of fractal aggregates formed by whey protein isolates was similar. PMID:26864954

  5. Kinetic regime of dithiothreitol-induced aggregation of bovine serum albumin.

    PubMed

    Borzova, Vera A; Markossian, Kira A; Kara, Dmitriy A; Kurganov, Boris

    2015-09-01

    A search for agents, which are capable of effectively suppressing protein aggregation, and elaboration of the appropriate test systems, are among important problems of modern biochemistry and biotechnology. One such test system is based on dithiothreitol (DTT)-induced aggregation of bovine serum albumin (BSA). Study of the kinetics of DTT-induced aggregation of BSA by asymmetric flow field flow fractionation showed that a decrease in the portion of the non-aggregated protein in time followed the exponential law, the rate constant of the first order remaining unchanged at varying protein concentration (0.1M Na-phosphate buffer, pH 7.0; 45 °C). The obtained results indicate that the rate-limiting stage of the general aggregation process is that of unfolding of the protein molecule. When studying the kinetics of DTT-induced aggregation of BSA by dynamic light scattering, we proposed to use parameter K(LS) as a measure of the initial rate of aggregation. Parameter K(LS) corresponds to the initial slope of the dependence of (I-I0)(0.5) on time (I0 and I are the initial and current values of the light scattering intensity, respectively). The K(LS) value has been applied to estimate anti-aggregation activity of chemical chaperones (arginine, its derivatives and proline). PMID:26116389

  6. Progress in Initiator Modeling

    SciTech Connect

    Hrousis, C A; Christensen, J S

    2009-05-04

    There is great interest in applying magnetohydrodynamic (MHD) simulation techniques to the designs of electrical high explosive (HE) initiators, for the purpose of better understanding a design's sensitivities, optimizing its performance, and/or predicting its useful lifetime. Two MHD-capable LLNL codes, CALE and ALE3D, are being used to simulate the process of ohmic heating, vaporization, and plasma formation in the bridge of an initiator, be it an exploding bridgewire (EBW), exploding bridgefoil (EBF) or slapper type initiator. The initiation of the HE is simulated using Tarver Ignition & Growth reactive flow models. 1-D, 2-D and 3-D models have been constructed and studied. The models provide some intuitive explanation of the initiation process and are useful for evaluating the potential impact of identified aging mechanisms (such as the growth of intermetallic compounds or powder sintering). The end product of this work is a simulation capability for evaluating margin in proposed, modified or aged initiation system designs.

  7. Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations.

    PubMed

    Raffaini, Giuseppina; Mazzaglia, Antonino; Ganazzoli, Fabio

    2015-01-01

    Amphiphilically modified cyclodextrins may form various supramolecular aggregates. Here we report a theoretical study of the aggregation of a few amphiphilic cyclodextrins carrying hydrophobic thioalkyl groups and hydrophilic ethylene glycol moieties at opposite rims, focusing on the initial nucleation stage in an apolar solvent and in water. The study is based on atomistic molecular dynamics methods with a "bottom up" approach that can provide important information about the initial aggregates of few molecules. The focus is on the interaction pattern of amphiphilic cyclodextrin (aCD), which may interact by mutual inclusion of the substituent groups in the hydrophobic cavity of neighbouring molecules or by dispersion interactions at their lateral surface. We suggest that these aggregates can also form the nucleation stage of larger systems as well as the building blocks of micelles, vesicle, membranes, or generally nanoparticles thus opening new perspectives in the design of aggregates correlating their structures with the pharmaceutical properties. PMID:26734094

  8. Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

    PubMed Central

    Mazzaglia, Antonino; Ganazzoli, Fabio

    2015-01-01

    Summary Amphiphilically modified cyclodextrins may form various supramolecular aggregates. Here we report a theoretical study of the aggregation of a few amphiphilic cyclodextrins carrying hydrophobic thioalkyl groups and hydrophilic ethylene glycol moieties at opposite rims, focusing on the initial nucleation stage in an apolar solvent and in water. The study is based on atomistic molecular dynamics methods with a “bottom up” approach that can provide important information about the initial aggregates of few molecules. The focus is on the interaction pattern of amphiphilic cyclodextrin (aCD), which may interact by mutual inclusion of the substituent groups in the hydrophobic cavity of neighbouring molecules or by dispersion interactions at their lateral surface. We suggest that these aggregates can also form the nucleation stage of larger systems as well as the building blocks of micelles, vesicle, membranes, or generally nanoparticles thus opening new perspectives in the design of aggregates correlating their structures with the pharmaceutical properties. PMID:26734094

  9. Tunable Nanosupramolecular Aggregates Mediated by Host-Guest Complexation.

    PubMed

    Zhang, Wen; Zhang, Ying-Ming; Li, Sheng-Hua; Cui, Yong-Liang; Yu, Jie; Liu, Yu

    2016-09-12

    Nanosupramolecular assemblies with controlled topological features have inventive applications in fundamental studies and material manufacturing. Herein, a variety of morphologically interesting aggregates have been constructed using the supramolecular modulation with bipyridinium-modified diphenylalanine derivative (BP-FF). Benefiting from the high binding affinity of bipyridinium group with four different macrocyclic receptors, namely cucurbit[7]uril, cucurbit[8]uril, pillar[5]arene, and tetrasulfonated crown ether, we have succeeded in tuning the topological aggregates of BP-FF from fine nanofibers to nanorods, octahedron-like nanostructure, helical nanowires, and rectangular nanosheets without any tedious chemical modification. This supramolecular approach may provide us a powerful method to construct well-defined nanostructures with different morphologies that can be conveniently controlled by facile host-guest interactions. PMID:27527684

  10. Compressive strength and resistance to chloride ion penetration and carbonation of recycled aggregate concrete with varying amount of fly ash and fine recycled aggregate.

    PubMed

    Sim, Jongsung; Park, Cheolwoo

    2011-11-01

    Construction and demolition waste has been dramatically increased in the last decade, and social and environmental concerns on the recycling have consequently been increased. Recent technology has greatly improved the recycling process for waste concrete. This study investigates the fundamental characteristics of concrete using recycled concrete aggregate (RCA) for its application to structural concrete members. The specimens used 100% coarse RCA, various replacement levels of natural aggregate with fine RCA, and several levels of fly ash addition. Compressive strength of mortar and concrete which used RCA gradually decreased as the amount of the recycled materials increased. Regardless of curing conditions and fly ash addition, the 28 days strength of the recycled aggregate concrete was greater than the design strength, 40 MPa, with a complete replacement of coarse aggregate and a replacement level of natural fine aggregate by fine RCA up to 60%. The recycled aggregate concrete achieved sufficient resistance to the chloride ion penetration. The measured carbonation depth did not indicate a clear relationship to the fine RCA replacement ratio but the recycled aggregate concrete could also attain adequate carbonation resistance. Based on the results from the experimental investigations, it is believed that the recycled aggregate concrete can be successfully applied to structural concrete members. PMID:21784626

  11. Mesoscale Simulation of Asphaltene Aggregation.

    PubMed

    Wang, Jiang; Ferguson, Andrew L

    2016-08-18

    Asphaltenes constitute a heavy aromatic crude oil fraction with a propensity to aggregate and precipitate out of solution during petroleum processing. Aggregation is thought to proceed according to the Yen-Mullins hierarchy, but the molecular mechanisms underlying mesoscopic assembly remain poorly understood. By combining coarse-grained molecular models parametrized using all-atom data with high-performance GPU hardware, we have performed molecular dynamics simulations of the aggregation of hundreds of asphaltenes over microsecond time scales. Our simulations reveal a hierarchical self-assembly mechanism consistent with the Yen-Mullins model, but the details are sensitive and depend on asphaltene chemistry and environment. At low concentrations asphaltenes exist predominantly as dispersed monomers. Upon increasing concentration, we first observe parallel stacking into 1D rod-like nanoaggregates, followed by the formation of clusters of nanoaggregates associated by offset, T-shaped, and edge-edge stacking. Asphaltenes possessing long aliphatic side chains cannot form nanoaggregate clusters due to steric repulsions between their aliphatic coronae. At very high concentrations, we observe a porous percolating network of rod-like nanoaggregates suspended in a sea of interpenetrating aliphatic side chains with a fractal dimension of ∼2. The lifetime of the rod-like aggregates is described by an exponential distribution reflecting a dynamic equilibrium between coagulation and fragmentation. PMID:27455391

  12. RAGG - R EPISODIC AGGREGATION PACKAGE

    EPA Science Inventory

    The RAGG package is an R implementation of the CMAQ episodic model aggregation method developed by Constella Group and the Environmental Protection Agency. RAGG is a tool to provide climatological seasonal and annual deposition of sulphur and nitrogen for multimedia management. ...

  13. Aggregation of Environmental Model Data for Decision Support

    NASA Astrophysics Data System (ADS)

    Alpert, J. C.

    2013-12-01

    Weather forecasts and warnings must be prepared and then delivered so as to reach their intended audience in good time to enable effective decision-making. An effort to mitigate these difficulties was studied at a Workshop, 'Sustaining National Meteorological Services - Strengthening WMO Regional and Global Centers' convened, June , 2013, by the World Bank, WMO and the US National Weather Service (NWS). The skill and accuracy of atmospheric forecasts from deterministic models have increased and there are now ensembles of such models that improve decisions to protect life, property and commerce. The NWS production of numerical weather prediction products result in model output from global and high resolution regional ensemble forecasts. Ensembles are constructed by changing the initial conditions to make a 'cloud' of forecasts that attempt to span the space of possible atmospheric realizations which can quantify not only the most likely forecast, but also the uncertainty. This has led to an unprecedented increase in data production and information content from higher resolution, multi-model output and secondary calculations. One difficulty is to obtain the needed subset of data required to estimate the probability of events, and report the information. The calibration required to reliably estimate the probability of events, and honing of threshold adjustments to reduce false alarms for decision makers is also needed. To meet the future needs of the ever-broadening user community and address these issues on a national and international basis, the weather service implemented the NOAA Operational Model Archive and Distribution System (NOMADS). NOMADS provides real-time and retrospective format independent access to climate, ocean and weather model data and delivers high availability content services as part of NOAA's official real time data dissemination at its new NCWCP web operations center. An important aspect of the server's abilities is to aggregate the matrix of

  14. An Aggregation Advisor for Ligand Discovery.

    PubMed

    Irwin, John J; Duan, Da; Torosyan, Hayarpi; Doak, Allison K; Ziebart, Kristin T; Sterling, Teague; Tumanian, Gurgen; Shoichet, Brian K

    2015-09-10

    Colloidal aggregation of organic molecules is the dominant mechanism for artifactual inhibition of proteins, and controls against it are widely deployed. Notwithstanding an increasingly detailed understanding of this phenomenon, a method to reliably predict aggregation has remained elusive. Correspondingly, active molecules that act via aggregation continue to be found in early discovery campaigns and remain common in the literature. Over the past decade, over 12 thousand aggregating organic molecules have been identified, potentially enabling a precedent-based approach to match known aggregators with new molecules that may be expected to aggregate and lead to artifacts. We investigate an approach that uses lipophilicity, affinity, and similarity to known aggregators to advise on the likelihood that a candidate compound is an aggregator. In prospective experimental testing, five of seven new molecules with Tanimoto coefficients (Tc's) between 0.95 and 0.99 to known aggregators aggregated at relevant concentrations. Ten of 19 with Tc's between 0.94 and 0.90 and three of seven with Tc's between 0.89 and 0.85 also aggregated. Another three of the predicted compounds aggregated at higher concentrations. This method finds that 61 827 or 5.1% of the ligands acting in the 0.1 to 10 μM range in the medicinal chemistry literature are at least 85% similar to a known aggregator with these physical properties and may aggregate at relevant concentrations. Intriguingly, only 0.73% of all drug-like commercially available compounds resemble the known aggregators, suggesting that colloidal aggregators are enriched in the literature. As a percentage of the literature, aggregator-like compounds have increased 9-fold since 1995, partly reflecting the advent of high-throughput and virtual screens against molecular targets. Emerging from this study is an aggregator advisor database and tool ( http://advisor.bkslab.org ), free to the community, that may help distinguish between

  15. Identification of aggregates for Tennessee bituminous surface courses

    NASA Astrophysics Data System (ADS)

    Sauter, Heather Jean

    Tennessee road construction is a major venue for federal and state spending. Tax dollars each year go to the maintenance and construction of roads. One aspect of highway construction that affects the public is the safety of its state roads. There are many factors that affect the safety of a given road. One factor that was focused on in this research was the polish resistance capabilities of aggregates. Several pre-evaluation methods have been used in the laboratory to predict what will happen in a field situation. A new pre-evaluation method was invented that utilized AASHTO T 304 procedure upscaled to accommodate surface bituminous aggregates. This new method, called the Tennessee Terminal Textural Condition Method (T3CM), was approved by Tennessee Department of Transportation to be used as a pre-evaluation method on bituminous surface courses. It was proven to be operator insensitive, repeatable, and an accurate indication of particle shape and texture. Further research was needed to correlate pre-evaluation methods to the current field method, ASTM E 274-85 Locked Wheel Skid Trailer. In this research, twenty-five in-place bituminous projects and eight source evaluations were investigated. The information gathered would further validate the T3CM and find the pre-evaluation method that best predicted the field method. In addition, new sources of aggregates for bituminous surface courses were revealed. The results of this research have shown T3CM to be highly repeatable with an overall coefficient of variation of 0.26% for an eight sample repeatability test. It was the best correlated pre-evaluation method with the locked wheel skid trailer method giving an R2 value of 0.3946 and a Pearson coefficient of 0.710. Being able to predict field performance of aggregates prior to construction is a powerful tool capable of saving time, money, labor, and possibly lives.

  16. Modelling of strongly coupled particle growth and aggregation

    NASA Astrophysics Data System (ADS)

    Gruy, F.; Touboul, E.

    2013-02-01

    The mathematical modelling of the dynamics of particle suspension is based on the population balance equation (PBE). PBE is an integro-differential equation for the population density that is a function of time t, space coordinates and internal parameters. Usually, the particle is characterized by a unique parameter, e.g. the matter volume v. PBE consists of several terms: for instance, the growth rate and the aggregation rate. So, the growth rate is a function of v and t. In classical modelling, the growth and the aggregation are independently considered, i.e. they are not coupled. However, current applications occur where the growth and the aggregation are coupled, i.e. the change of the particle volume with time is depending on its initial value v0, that in turn is related to an aggregation event. As a consequence, the dynamics of the suspension does not obey the classical Von Smoluchowski equation. This paper revisits this problem by proposing a new modelling by using a bivariate PBE (with two internal variables: v and v0) and by solving the PBE by means of a numerical method and Monte Carlo simulations. This is applied to a physicochemical system with a simple growth law and a constant aggregation kernel.

  17. Cometary nucleus as an aggregate of planetesimals

    SciTech Connect

    Yamamoto, T.; Kozasa, T.

    1988-09-01

    The present treatment of the properties of extant, primordial solar nebula-generated planetesimals and their aggregates, with a view to cometary origins, takes Greenberg et al.'s (1984) suggested formation of a small-mass planetesimal by the nonhomologous sedimentation of grains into account. It is noted that the mass of a planetesimal formed by gravitational instability of the dust layer is related to the total number of comets, and it is shown that the planetesimal's initial mass is 4 to 7 orders-of-magnitude smaller than that estimated by assuming complete grain sedimentation. The presence of a cometary cloud beyond the planetary region but closer than the Oort cloud is hypothesized. 47 references.

  18. The chemical composition of mineral trioxide aggregate

    PubMed Central

    Camilleri, Josette

    2008-01-01

    Mineral trioxide aggregate (MTA) is composed of Portland cement, with 4:1 addition of bismuth oxide added so that the material can be detected on a radiograph. The cement is made up of calcium, silicon and aluminium. The main constituent phases are tricalcium and dicalcium silicate and tricalcium aluminate. There are two commercial forms of MTA, namely the grey and the white. The difference between the grey and the white materials is the presence of iron in the grey material, which makes up the phase tetracalcium alumino-ferrite. This phase is absent in white MTA. Hydration of MTA occurs in two stages. The initial reaction between tricalcium aluminate and water in the presence of calcium sulphate results in the production of ettringite. Tricalcium and dicalcium silicate react with water to produce calcium silicate hydrate and calcium hydroxide, which is leached out of the cement with time. PMID:20351970

  19. Construction Technology.

    ERIC Educational Resources Information Center

    Barnes, James L.

    This curriculum guide is designed to assist junior high school industrial arts teachers in planning new courses and revising existing courses in construction technology. Addressed in the individual units of the guide are the following topics: basic types of construction and the impact of construction on society, preconstruction, personnel…

  20. Electrochemical construction

    DOEpatents

    Einstein, Harry; Grimes, Patrick G.

    1983-08-23

    An electrochemical cell construction features a novel co-extruded plastic electrode in an interleaved construction with a novel integral separator-spacer. Also featured is a leak and impact resistant construction for preventing the spill of corrosive materials in the event of rupture.

  1. Construction Package No. 2. Final Earthwork and Roadwork (RADL Item 7-28)

    SciTech Connect

    Not Available

    1980-07-01

    The final earthwork, aggregate surfacing, roadwork and paving for the Barstow Solar Pilot Plant are presented. The work consisted of applying weed killer to surfaces to be paved, constructing bituminous pavements, restoring existing compacted aggregate base roadways, and stripping and removing existing grade from the core area for compacted aggregate surfacing.

  2. Effects of Aggregation on Blood Sedimentation and Conductivity

    PubMed Central

    Zhbanov, Alexander; Yang, Sung

    2015-01-01

    The erythrocyte sedimentation rate (ESR) test has been used for over a century. The Westergren method is routinely used in a variety of clinics. However, the mechanism of erythrocyte sedimentation remains unclear, and the 60 min required for the test seems excessive. We investigated the effects of cell aggregation during blood sedimentation and electrical conductivity at different hematocrits. A sample of blood was drop cast into a small chamber with two planar electrodes placed on the bottom. The measured blood conductivity increased slightly during the first minute and decreased thereafter. We explored various methods of enhancing or retarding the erythrocyte aggregation. Using experimental measurements and theoretical calculations, we show that the initial increase in blood conductivity was indeed caused by aggregation, while the subsequent decrease in conductivity resulted from the deposition of erythrocytes. We present a method for calculating blood conductivity based on effective medium theory. Erythrocytes are modeled as conducting spheroids surrounded by a thin insulating membrane. A digital camera was used to investigate the erythrocyte sedimentation behavior and the distribution of the cell volume fraction in a capillary tube. Experimental observations and theoretical estimations of the settling velocity are provided. We experimentally demonstrate that the disaggregated cells settle much slower than the aggregated cells. We show that our method of measuring the electrical conductivity credibly reflected the ESR. The method was very sensitive to the initial stage of aggregation and sedimentation, while the sedimentation curve for the Westergren ESR test has a very mild slope in the initial time. We tested our method for rapid estimation of the Westergren ESR. We show a correlation between our method of measuring changes in blood conductivity and standard Westergren ESR method. In the future, our method could be examined as a potential means of accelerating

  3. Buckets: Aggregative, Intelligent Agents for Publishing

    NASA Technical Reports Server (NTRS)

    Nelson, Michael L.; Maly, Kurt; Shen, Stewart N. T.; Zubair, Mohammad

    1998-01-01

    Buckets are an aggregative, intelligent construct for publishing in digital libraries. The goal of research projects is to produce information. This information is often instantiated in several forms, differentiated by semantic types (report, software, video, datasets, etc.). A given semantic type can be further differentiated by syntactic representations as well (PostScript version, PDF version, Word version, etc.). Although the information was created together and subtle relationships can exist between them, different semantic instantiations are generally segregated along currently obsolete media boundaries. Reports are placed in report archives, software might go into a software archive, but most of the data and supporting materials are likely to be kept in informal personal archives or discarded altogether. Buckets provide an archive-independent container construct in which all related semantic and syntactic data types and objects can be logically grouped together, archived, and manipulated as a single object. Furthermore, buckets are active archival objects and can communicate with each other, people, or arbitrary network services.

  4. Aggregation of metallochlorophylls - Examination by spectroscopy

    NASA Technical Reports Server (NTRS)

    Boucher, L. J.; Katz, J. J.

    1969-01-01

    Nuclear magnetic resonance measurements determine which metallochlorophylls, besides magnesium-containing chlorophylls, possess coordination aggregation properties. Infrared spectroscopy reveals that only zinc pheophytin and zinc methyl pheophorbide showed significant coordination aggregation, whereas divalent nickel and copper did not.

  5. Oligomeric baroeffect and gas aggregation states

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1992-01-01

    The baroeffect is analyzed to include a gas that aggregates into higher-order polymers or oligomers. The resulting pressure change is found to vary independently of the molecular weight of the gas components and to depend only on the aggregation or oligomeric order of the gas. With increasing aggregation, diffusive slip velocities are found to increase. The calculations are extended to include general counterdiffusion of two distinct aggregation states (k-, j-mer) for the gas, and the pressure change is derived as a function that is independent of both molecular weight and the absolute aggregation. The only parameter that determines the baroeffect is the ratio of aggregated states, beta = k/j. For gases that reversibly aggregate, possible oscillatory behavior and complex dynamics for pressure are discussed. Gas aggregation may play a role for low-temperature crystal-growth conditions in which vapor concentrations of one (or more) species are high.

  6. Markov Modeling with Soft Aggregation for Safety and Decision Analysis

    SciTech Connect

    COOPER,J. ARLIN

    1999-09-01

    Sensitivity measures for soil aggregation, for developing dependence methodology, for constructing early alert logic, for tracking trends, for relating the Markov model to other (e.g., Reason) models, for developing and demonstrating rudimentary laptop software, and for developing an input/output display methodology.

  7. Aggregation risk prediction for antibodies and its application to biotherapeutic development

    PubMed Central

    Obrezanova, Olga; Arnell, Andreas; de la Cuesta, Ramón Gómez; Berthelot, Maud E; Gallagher, Thomas RA; Zurdo, Jesús; Stallwood, Yvette

    2015-01-01

    Aggregation is a common problem affecting biopharmaceutical development that can have a significant effect on the quality of the product, as well as the safety to patients, particularly because of the increased risk of immune reactions. Here, we describe a new high-throughput screening algorithm developed to classify antibody molecules based on their propensity to aggregate. The tool, constructed and validated on experimental aggregation data for over 500 antibodies, is able to discern molecules with a high aggregation propensity as defined by experimental criteria relevant to bioprocessing and manufacturing of these molecules. Furthermore, we show how this tool can be combined with other computational approaches during early drug development to select molecules with reduced risk of aggregation and optimal developability properties. PMID:25760769

  8. Protein aggregation in salt solutions

    PubMed Central

    Kastelic, Miha; Kalyuzhnyi, Yurij V.; Hribar-Lee, Barbara; Dill, Ken A.; Vlachy, Vojko

    2015-01-01

    Protein aggregation is broadly important in diseases and in formulations of biological drugs. Here, we develop a theoretical model for reversible protein–protein aggregation in salt solutions. We treat proteins as hard spheres having square-well-energy binding sites, using Wertheim’s thermodynamic perturbation theory. The necessary condition required for such modeling to be realistic is that proteins in solution during the experiment remain in their compact form. Within this limitation our model gives accurate liquid–liquid coexistence curves for lysozyme and γ IIIa-crystallin solutions in respective buffers. It provides good fits to the cloud-point curves of lysozyme in buffer–salt mixtures as a function of the type and concentration of salt. It than predicts full coexistence curves, osmotic compressibilities, and second virial coefficients under such conditions. This treatment may also be relevant to protein crystallization. PMID:25964322

  9. Low-Velocity Aggregate Collisions Simulating Planetary Ring Dynamics

    NASA Astrophysics Data System (ADS)

    Dove, A.; Colwell, J. E.; Bradley, E. T.; Vamos, C.

    2012-12-01

    Proto-planetary and planetary ring system evolution is driven by collisions between small particles and aggregates that may be composed of dust, water ice, or a combination of materials. In these collisional systems, impacts between objects can occur at very low velocities, much less than 1 m/s. Low-velocity impacts can have competing effects: at the lowest velocities, collisions may play a critical role in growth into larger aggregates; at slightly higher velocities, collisions can cause break-up and release of material. In the Saturnian ring system, for instance, particles are excited to such "higher" velocities (10's of cm/s) in regions where density waves enhance particle concentrations. These conditions are present in the A ring, and it has been hypothesized that collisions have an additional effect of modifying the spectral properties of the ring particles, which are composed of a mix of ice and dust (Nicholson et al., 2008). This modification may occur when collisions cause ejection of material with different spectral characteristics, or by breaking particles apart to reveal more pristine interiors. We have designed and built an apparatus to simulate low-velocity collisions between aggregates in a laboratory vacuum environment. In our experiment, two aggregates are launched towards each other; the resulting impact velocities are controlled by the initial spring launch velocity, the masses of the aggregates, and timing of the collisions. Initially, we use lunar regolith simulant to create the aggregates; the simulant can be packed to different densities to control the mass and porosity of the impactors. We also create aggregates that are mixtures of materials, including icy components. A high-speed digital video camera is used to record the impacts to observe the behavior of both impactors and the resulting ejecta material. We observe over a range of velocities to identify the conditions under which aggregates shed only some material from the surface, or

  10. The sensitivity of convective aggregation to diabatic processes in idealized radiative-convective equilibrium simulations

    NASA Astrophysics Data System (ADS)

    Holloway, C. E.; Woolnough, S. J.

    2016-03-01

    Idealized explicit convection simulations of the Met Office Unified Model exhibit spontaneous self-aggregation in radiative-convective equilibrium, as seen in other models in previous studies. This self-aggregation is linked to feedbacks between radiation, surface fluxes, and convection, and the organization is intimately related to the evolution of the column water vapor field. Analysis of the budget of the spatial variance of column-integrated frozen moist static energy (MSE), following Wing and Emanuel (2014), reveals that the direct radiative feedback (including significant cloud longwave effects) is dominant in both the initial development of self-aggregation and the maintenance of an aggregated state. A low-level circulation at intermediate stages of aggregation does appear to transport MSE from drier to moister regions, but this circulation is mostly balanced by other advective effects of opposite sign and is forced by horizontal anomalies of convective heating (not radiation). Sensitivity studies with either fixed prescribed radiative cooling, fixed prescribed surface fluxes, or both do not show full self-aggregation from homogeneous initial conditions, though fixed surface fluxes do not disaggregate an initialized aggregated state. A sensitivity study in which rain evaporation is turned off shows more rapid self-aggregation, while a run with this change plus fixed radiative cooling still shows strong self-aggregation, supporting a "moisture-memory" effect found in Muller and Bony (2015). Interestingly, self-aggregation occurs even in simulations with sea surface temperatures (SSTs) of 295 and 290 K, with direct radiative feedbacks dominating the budget of MSE variance, in contrast to results in some previous studies.

  11. Surface properties of heat-induced soluble soy protein aggregates of different molecular masses.

    PubMed

    Guo, Fengxian; Xiong, Youling L; Qin, Fang; Jian, Huajun; Huang, Xiaolin; Chen, Jie

    2015-02-01

    Suspensions (2% and 5%, w/v) of soy protein isolate (SPI) were heated at 80, 90, or 100 °C for different time periods to produce soluble aggregates of different molecular sizes to investigate the relationship between particle size and surface properties (emulsions and foams). Soluble aggregates generated in these model systems were characterized by gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Heat treatment increased surface hydrophobicity, induced SPI aggregation via hydrophobic interaction and disulfide bonds, and formed soluble aggregates of different sizes. Heating of 5% SPI always promoted large-size aggregate (LA; >1000 kDa) formation irrespective of temperature, whereas the aggregate size distribution in 2% SPI was temperature dependent: the LA fraction progressively rose with temperature (80→90→100 °C), corresponding to the attenuation of medium-size aggregates (MA; 670 to 1000 kDa) initially abundant at 80 °C. Heated SPI with abundant LA (>50%) promoted foam stability. LA also exhibited excellent emulsifying activity and stabilized emulsions by promoting the formation of small oil droplets covered with a thick interfacial protein layer. However, despite a similar influence on emulsion stability, MA enhanced foaming capacity but were less capable of stabilizing emulsions than LA. The functionality variation between heated SPI samples is clearly related to the distribution of aggregates that differ in molecular size and surface activity. The findings may encourage further research to develop functional SPI aggregates for various commercial applications. PMID:25586667

  12. Monte Carlo simulation of the heterotypic aggregation kinetics of platelets and neutrophils.

    PubMed

    Laurenzi, I J; Diamond, S L

    1999-09-01

    The heterotypic aggregation of cell mixtures or colloidal particles such as proteins occurs in a variety of settings such as thrombosis, immunology, cell separations, and diagnostics. Using the set of population balance equations (PBEs) to predict dynamic aggregate size and composition distributions is not feasible. The stochastic algorithm of Gillespie for chemical reactions (. J. Comput. Phys. 22:403-434) was reformulated to simulate the kinetic behavior of aggregating systems. The resulting Monte Carlo (MC) algorithm permits exact calculation of the decay rates of monomers and the temporally evolving distribution of sizes and compositions of the aggregates. Moreover, it permits calculation of all moments of these distributions. Using this method, we explored the heterotypic aggregation of fully activated platelets and neutrophils in a linear shear flow of shear rate G = 335 s(-1). At plasma concentrations, the half-lives of homotypically aggregating platelet and neutrophil singlets were 8.5 and 2.4 s, respectively. However, for heterotypic aggregation, the half-lives for platelets and neutrophils decreased to 2.0 and 0.11 s, respectively, demonstrating that flowing neutrophils accelerate capture of platelets and growth of aggregates. The required number of calculations per time step of the MC algorithm was typically a small fraction of Omega(1/2), where Omega is the initial number of particles in the system, making this the fastest MC method available. The speed of the algorithm makes feasible the deconvolution of kernels for general biological heterotypic aggregation processes. PMID:10465782

  13. Aggregation of intrinsically disordered fibrinogen as the influence of backbone conformation.

    PubMed

    Naeem, Aabgeena; Bhat, Sheraz Ahmad; Iram, Afshin; Khan, Rizwan Hasan

    2016-08-01

    Fib having intrinsically disordered αC domains is involved in coagulation cascade and thrombosis. Fib molecules forms prefibrillar oligomers at 30%, and associate in 40 and 50% TFE to proceed α to β transition, suggesting the formation of an intermolecular β-structure. AFM images confirmed the nature of Fib aggregates at 40 and 50% TFE to be prefibrillar and fibrillar respectively. These aggregates possess high thioflavin T fluorescence with a shifted Congo red absorbance. Kinetics of Fib aggregation data at 50% TFE supports nucleation-dependent polymerization mechanism. At 60 and 70% TFE, no aggregation was observed. The inhibition of protein aggregation appears due to weakening of the hydrophobic interactions that were initially stabilizing the intermolecular β-sheet structure in the protein aggregation. The loss of hydrophobic contacts seems to favor the formation of intramolecular hydrogen bonds over intermolecular hydrogen bonds leading to helix formation. To conclude, protein aggregation is accompanied by the formation of β-sheet conformation, and induction of non-native helical segments in the protein inhibits aggregation. The discrepancy of the secondary structures on aggregation is proposed to stem from the disparity in the nature of the hydrogen bonds and packing of hydrophobic residues of the side chains in the β-sheet and α-helix conformation. PMID:27150313

  14. Propagation of dysbindin-1B aggregates: exosome-mediated transmission of neurotoxic deposits.

    PubMed

    Zhu, C-Y; Shen, Y; Xu, Q

    2015-04-16

    Given the detection of aggregated deposits in chronic mental diseases (CMD), the disturbance of proteostasis in those diseases is receiving increasing attention. The study of aggregated proteins can contribute to our understanding of the chronic and progressive condition of such diseases. Dysbindin, encoded by the schizophrenia susceptibility gene DTNBP1, has been reported to co-aggregate with DISC1. However, there has been no evidence to date on the aggregation tendency of dysbindin. Therefore, we investigated the isoform-specific aggregation of dysbindin. We found that dysbindin-1B aggregated into cell-invasive deposits in mice. Because of the efficient propagation of dysbindin-1B, we further studied the mechanism of propagation and identified it as exosome-mediated transmission of the aggregates. In addition, aggregates of dysbindin-1B were toxic. Through exosome-mediated propagation, the deposits of dysbindin-1B exerted toxic effects on recipient neurons a long distance away from the initial aggregation site in mice brain. The rapid long distance propagation of neurotoxic deposits of dysbindin-1B in affected neuronal circuitry indicates a possible mechanism for the progressive deterioration of neurons and cognitive function in CMD. PMID:25704251

  15. Aggregated Authentication (AMAC) Using Universal Hash Functions

    NASA Astrophysics Data System (ADS)

    Znaidi, Wassim; Minier, Marine; Lauradoux, Cédric

    Aggregation is a very important issue to reduce the energy consumption in Wireless Sensors Networks (WSNs). There is currently a lack of cryptographic primitives for authentication of aggregated data. The theoretical background for Aggregated Message Authentication Codes (AMACs) has been proposed by Chan and Castelluccia at ISIT 08.

  16. 28 CFR 2.5 - Sentence aggregation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 1 2010-07-01 2010-07-01 false Sentence aggregation. 2.5 Section 2.5 Judicial Administration DEPARTMENT OF JUSTICE PAROLE, RELEASE, SUPERVISION AND RECOMMITMENT OF PRISONERS... aggregation. When multiple sentences are aggregated by the Bureau of Prisons pursuant to 18 U.S.C. 4161...

  17. Cytotoxic effects of aggregated nanomaterials.

    PubMed

    Soto, Karla; Garza, K M; Murr, L E

    2007-05-01

    This study deals with cytotoxicity assays performed on an array of commercially manufactured inorganic nanoparticulate materials, including Ag, TiO(2), Fe(2)O(3), Al(2)O(3), ZrO(2), Si(3)N(4), naturally occurring mineral chrysotile asbestos and carbonaceous nanoparticulate materials such as multiwall carbon nanotube aggregates and black carbon aggregates. The nanomaterials were characterized by TEM, as the primary particles, aggregates or long fiber dimensions ranged from 2nm to 20microm. Cytotoxicological assays of these nanomaterials were performed utilizing a murine alveolar macrophage cell line and human macrophage and epithelial lung cell lines as comparators. The nanoparticulate materials exhibited varying degrees of cytoxicity for all cell lines and the general trends were similar for both the murine and human macrophage cell lines. These findings suggest that representative cytotoxic responses for humans might be obtained by nanoparticulate exposures to simple murine macrophage cell line assays. Moreover, these results illustrate the utility in performing rapid in vitro assays for cytotoxicity assessments of nanoparticulate materials as a general inquiry of potential respiratory health risks in humans. PMID:17275430

  18. Aggregation of Heterogeneously Charged Colloids.

    PubMed

    Dempster, Joshua M; Olvera de la Cruz, Monica

    2016-06-28

    Patchy colloids are attractive as programmable building blocks for metamaterials. Inverse patchy colloids, in which a charged surface is decorated with patches of the opposite charge, are additionally noteworthy as models for heterogeneously charged biological materials such as proteins. We study the phases and aggregation behavior of a single charged patch in an oppositely charged colloid with a single-site model. This single-patch inverse patchy colloid model shows a large number of phases when varying patch size. For large patch sizes we find ferroelectric crystals, while small patch sizes produce cross-linked gels. Intermediate values produce monodisperse clusters and unusual worm structures that preserve finite ratios of area to volume. The polarization observed at large patch sizes is robust under extreme disorder in patch size and shape. We examine phase-temperature dependence and coexistence curves and find that large patch sizes produce polarized liquids, in contrast to mean-field predictions. Finally, we introduce small numbers of unpatched charged colloids. These can either suppress or encourage aggregation depending on their concentration and the size of the patches on the patched colloids. These effects can be exploited to control aggregation and to measure effective patch size. PMID:27253725

  19. Aggregation and Aggregate Carbon in a Forested Southeastern Coastal Plain Spodosol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil aggregation is influenced by the soil environment and is a factor in soil carbon sequestration. Sandy Coastal Plain soils often do not have the clay to promote aggregation nor have been considered soils with high levels of aggregation. This study was conducted to examine the aggregate morpholog...

  20. Bio-/Chemosensors and Imaging with Aggregation-Induced Emission Luminogens.

    PubMed

    Zhan, Chi; You, Xue; Zhang, Guanxin; Zhang, Deqing

    2016-08-01

    Aggregation-induced emission (AIE) luminogens show abnormal fluorescent behavior; they are non-emissive in solution, but they become strongly emissive after aggregation. Sensing and imaging are the major applications of AIE luminogens. By properly manipulating the aggregation and deaggregation of AIE molecules, various bio-/chemosensors have been developed. Moreover, AIE molecules with targeting groups have been devised for imaging of organelles and cancer cells. In this account, we report our recent work on the application of AIE luminogens for the construction of bio-/chemosensors and imaging. PMID:27427427

  1. Constructive Fun.

    ERIC Educational Resources Information Center

    Simanek, Donald E.

    1994-01-01

    Compares and reviews currently available brands of steel construction sets that are useful to physics teachers for building demonstrations, prototypes of mechanisms, robotics, and remote control devices. (ZWH)

  2. Research Initiatives

    Cancer.gov

    This page provides detailed information about currently funded RFA initiatives both led by DCCPS, and those led by other NIH Institutes and Centers (I/Cs) that include DCCPS as a partner. Each initiative includes a table of funded grants and a map that shows the location of funded institutions.

  3. [AGGREGATION OF METABOLICALLY DEPLETED HUMAN ERYTHROCYTES].

    PubMed

    Sheremet'ev, Yu A; Popovicheva, A N; Rogozin, M M; Levin, G Ya

    2016-01-01

    An aggregation of erythrocytes in autologous plasma after blood storage for 14 days at 4 °C was studied using photometry and light microscopy. The decrease of ATP content, the formation of echinocytes and spheroechinocytes, the decrease of rouleaux form of erythrocyte aggregation were observed during the storage. On the other hand the aggregates of echinocytes were formed in the stored blood. The addition of plasma from the fresh blood didn't restore the normal discocytic shape and aggregation of erythrocytes in the stored blood. The possible mechanisms of erythrocytes and echinocytes aggregation are discussed. PMID:27220249

  4. [Lysophosphatidic acid and human erythrocyte aggregation].

    PubMed

    Sheremet'ev, Iu A; Popovicheva, A N; Levin, G Ia

    2014-01-01

    The effects of lysophosphatidic acid on the morphology and aggregation of human erythrocytes has been studied. Morphology of erythrocytes and their aggregates were studied by light microscopy. It has been shown that lysophosphatidic acid changes the shape of red blood cells: diskocyte become echinocytes. Aggregation of red blood cells (rouleaux) was significantly reduced in autoplasma. At the same time there is a strong aggregation of echinocytes. This was accompanied by the formation of microvesicles. Adding normal plasma to echinocytes restores shape and aggregation of red blood cells consisting of "rouleaux". A possible mechanism of action of lysophosphatidic acid on erythrocytes is discussed. PMID:25509147

  5. Construction Cluster Skills Standards.

    ERIC Educational Resources Information Center

    DePaul Univ., Chicago, IL. Built Environment Partnership.

    Twelve construction cluster skill standards and associated benchmarks were developed as part of a federally funded school-to-work initiative that included the following parties: the Chicago Public Schools; City Colleges of Chicago; and business, labor, and community organizations. The standards, which include core academic, generic workplace…

  6. Automation of aggregate characterization using laser profiling and digital image analysis

    NASA Astrophysics Data System (ADS)

    Kim, Hyoungkwan

    2002-08-01

    Particle morphological properties such as size, shape, angularity, and texture are key properties that are frequently used to characterize aggregates. The characteristics of aggregates are crucial to the strength, durability, and serviceability of the structure in which they are used. Thus, it is important to select aggregates that have proper characteristics for each specific application. Use of improper aggregate can cause rapid deterioration or even failure of the structure. The current standard aggregate test methods are generally labor-intensive, time-consuming, and subject to human errors. Moreover, important properties of aggregates may not be captured by the standard methods due to a lack of an objective way of quantifying critical aggregate properties. Increased quality expectations of products along with recent technological advances in information technology are motivating new developments to provide fast and accurate aggregate characterization. The resulting information can enable a real time quality control of aggregate production as well as lead to better design and construction methods of portland cement concrete and hot mix asphalt. This dissertation presents a system to measure various morphological characteristics of construction aggregates effectively. Automatic measurement of various particle properties is of great interest because it has the potential to solve such problems in manual measurements as subjectivity, labor intensity, and slow speed. The main efforts of this research are placed on three-dimensional (3D) laser profiling, particle segmentation algorithms, particle measurement algorithms, and generalized particle descriptors. First, true 3D data of aggregate particles obtained by laser profiling are transformed into digital images. Second, a segmentation algorithm and a particle measurement algorithm are developed to separate particles and process each particle data individually with the aid of various kinds of digital image

  7. COMMERCIAL DEMONSTRATION OF THE MANUFACTURED AGGREGATE PROCESSING TECHNOLOGY UTILIZING SPRAY DRYER ASH

    SciTech Connect

    Roy Scandrol

    2003-04-01

    Universal Aggregates, LLC proposes to design, construct and operate a lightweight aggregate manufacturing plant at the Birchwood Power Facility in King George, Virginia. The installation and start-up expenses for the Birchwood Aggregate Facility are $19.5 million. The DOE share is $7.2 million (37%) and the Universal Aggregates share is $12.3 (63%). The project team consists of CONSOL Energy Inc., P.J. Dick, Inc., SynAggs, LLC, and Universal Aggregates, LLC. The Birchwood Facility will transform 115,000 tons per year of spray dryer by-products that are currently being disposed of in an offsite landfill into 167,000 tons of a useful product, lightweight aggregates that can be used to manufacture lightweight aggregates that can be used to manufacture lightweight and medium weight masonry blocks. In addition to the environmental benefits, the Birchwood Facility will create eight (8) manufacturing jobs plus additional employment in the local trucking industry to deliver the aggregate to customers or reagents to the facility. A successful demonstration would lead to additional lightweight aggregate manufacturing facilities in the United States. There are currently twenty-one (21) spray dryer facilities operating in the United States that produce an adequate amount of spray dryer by-product to economically justify the installation of a lightweight aggregate manufacturing facility. Industry sources believe that as additional scrubbing is required, dry flue gas desulfurization (FGD) technologies will be the technology of choice. Letters from potential lightweight aggregate customers indicate that there is a market for the product once the commercialization barriers are eliminated by this demonstration project.

  8. COMMERCIAL DEMONSTRATION OF THE MANUFACTURED AGGREGATE PROCESSING TECHNOLOGY UTILIZING SPRAY DRYER ASH

    SciTech Connect

    Roy Scandrol

    2003-10-01

    Universal Aggregates, LLC proposes to design, construct and operate a lightweight aggregate manufacturing plant at the Birchwood Power Facility in King George, Virginia. The installation and start-up expenses for the Birchwood Aggregate Facility are $19.5 million. The DOE share is $7.2 million (37%) and the Universal Aggregates share is $12.3 (63%). The project team consists of CONSOL Energy Inc., P.J. Dick, Inc., SynAggs, LLC, and Universal Aggregates, LLC. The Birchwood Facility will transform 115,000 tons per year of spray dryer by-products that are currently being disposed of in an offsite landfill into 167,000 tons of a useful product, lightweight aggregates that can be used to manufacture lightweight aggregates that can be used to manufacture lightweight and medium weight masonry blocks. In addition to the environmental benefits, the Birchwood Facility will create nine (9) manufacturing jobs plus additional employment in the local trucking industry to deliver the aggregate to customers or reagents to the facility. A successful demonstration would lead to additional lightweight aggregate manufacturing facilities in the United States. There are currently twenty-one (21) spray dryer facilities operating in the United States that produce an adequate amount of spray dryer by-product to economically justify the installation of a lightweight aggregate manufacturing facility. Industry sources believe that as additional scrubbing is required, dry FGD technologies will be the technology of choice. Letters from potential lightweight aggregate customers indicate that there is a market for the product once the commercialization barriers are eliminated by this demonstration project.

  9. Microwave extinction characteristics of nanoparticle aggregates

    NASA Astrophysics Data System (ADS)

    Wu, Y. P.; Cheng, J. X.; Liu, X. X.; Wang, H. X.; Zhao, F. T.; Wen, W. W.

    2016-07-01

    Structure of nanoparticle aggregates plays an important role in microwave extinction capacity. The diffusion-limited aggregation model (DLA) for fractal growth is utilized to explore the possible structures of nanoparticle aggregates by computer simulation. Based on the discrete dipole approximation (DDA) method, the microwave extinction performance by different nano-carborundum aggregates is numerically analyzed. The effects of the particle quantity, original diameter, fractal structure, as well as orientation on microwave extinction are investigated, and also the extinction characteristics of aggregates are compared with the spherical nanoparticle in the same volume. Numerical results give out that proper aggregation of nanoparticle is beneficial to microwave extinction capacity, and the microwave extinction cross section by aggregated granules is better than that of the spherical solid one in the same volume.

  10. Simulation of J-aggregate microcavity photoluminescence

    NASA Astrophysics Data System (ADS)

    Michetti, Paolo; La Rocca, Giuseppe C.

    2008-05-01

    We have developed a model in order to account for the photoexcitation dynamics of J-aggregate films and strongly coupled J-aggregate microcavities. The J aggregates are described as a disordered Frenkel exciton system in which relaxation occurs due to the presence of a thermal bath of molecular vibrations. The correspondence between the photophysics in J-aggregate films and that in J-aggregate microcavities is obtained by introducing a model polariton wave function mixing cavity photon modes and J-aggregate super-radiant excitons. With the same description of the material properties, we have calculated both absorption and luminescence spectra for the J-aggregate film and the photoluminescence of strongly coupled organic microcavities. The model is able to account for the fast relaxation dynamics in organic microcavities following nonresonant pumping and explains the temperature dependence of the ratio between the upper polariton and the lower polariton luminescence.

  11. Initial condition of stochastic self-assembly

    NASA Astrophysics Data System (ADS)

    Davis, Jason K.; Sindi, Suzanne S.

    2016-02-01

    The formation of a stable protein aggregate is regarded as the rate limiting step in the establishment of prion diseases. In these systems, once aggregates reach a critical size the growth process accelerates and thus the waiting time until the appearance of the first critically sized aggregate is a key determinant of disease onset. In addition to prion diseases, aggregation and nucleation is a central step of many physical, chemical, and biological process. Previous studies have examined the first-arrival time at a critical nucleus size during homogeneous self-assembly under the assumption that at time t =0 the system was in the all-monomer state. However, in order to compare to in vivo biological experiments where protein constituents inherited by a newly born cell likely contain intermediate aggregates, other possibilities must be considered. We consider one such possibility by conditioning the unique ergodic size distribution on subcritical aggregate sizes; this least-informed distribution is then used as an initial condition. We make the claim that this initial condition carries fewer assumptions than an all-monomer one and verify that it can yield significantly different averaged waiting times relative to the all-monomer condition under various models of assembly.

  12. Initial condition of stochastic self-assembly.

    PubMed

    Davis, Jason K; Sindi, Suzanne S

    2016-02-01

    The formation of a stable protein aggregate is regarded as the rate limiting step in the establishment of prion diseases. In these systems, once aggregates reach a critical size the growth process accelerates and thus the waiting time until the appearance of the first critically sized aggregate is a key determinant of disease onset. In addition to prion diseases, aggregation and nucleation is a central step of many physical, chemical, and biological process. Previous studies have examined the first-arrival time at a critical nucleus size during homogeneous self-assembly under the assumption that at time t=0 the system was in the all-monomer state. However, in order to compare to in vivo biological experiments where protein constituents inherited by a newly born cell likely contain intermediate aggregates, other possibilities must be considered. We consider one such possibility by conditioning the unique ergodic size distribution on subcritical aggregate sizes; this least-informed distribution is then used as an initial condition. We make the claim that this initial condition carries fewer assumptions than an all-monomer one and verify that it can yield significantly different averaged waiting times relative to the all-monomer condition under various models of assembly. PMID:26986290

  13. Sustainable management and supply of natural and recycled aggregates in a medium-size integrated plant.

    PubMed

    Faleschini, Flora; Zanini, Mariano Angelo; Pellegrino, Carlo; Pasinato, Stefano

    2016-03-01

    The consumption of natural aggregates in civil engineering applications can cause severe environmental impacts on a regional scale, depleting the stock of bulk resources within a territory. Several methods can improve the environmental sustainability of the whole aggregates' supply process, including natural and recycled aggregates' productive chains, for instance promoting the use of recycled aggregates (RA). However, when quarrying and recycling activities are considered as stand-alone processes, also the RA supply chain may not be as sustainable as expected, due to the high environmental loads associated to transportation, if high distances from the production to the use sites are involved. This work gives some insights on the environmental impact assessment of the aggregates' industry in the Italian context, through a comparative assessment of the environmental loads of natural and recycled aggregates' productive chains. An integrated plant for the extraction of virgin aggregates and recycling of construction and demolition waste (C&DW) was analyzed as significant case study, with the aim to identify the influence of sustainable solutions on the overall emissions of the facility. A Life Cycle Assessment (LCA) approach was used, using site-specific data and paying particular attention on transportation-related impacts, land use, avoided landfill and non-renewable resources preservation. From this work it was possible to evaluate the influence of transportation and PV energy use on the overall environmental emissions of natural and recycled aggregates' productive chains. PMID:26810029

  14. Examination of Ataxin-3 (atx-3) Aggregation by Structural Mass Spectrometry Techniques: A Rationale for Expedited Aggregation upon Polyglutamine (polyQ) Expansion*

    PubMed Central

    Scarff, Charlotte A.; Almeida, Bruno; Fraga, Joana; Macedo-Ribeiro, Sandra; Radford, Sheena E.; Ashcroft, Alison E.

    2015-01-01

    Expansion of polyglutamine stretches leads to the formation of polyglutamine-containing neuronal aggregates and neuronal death in nine diseases for which there currently are no treatments or cures. This is largely due to a lack in understanding of the mechanisms by which expanded polyglutamine regions contribute to aggregation and disease. To complicate matters further, several of the polyglutamine-disease related proteins, including ataxin-3, have a multistage aggregation mechanism in which flanking domain self-assembly precedes polyglutamine aggregation yet is influenced by polyglutamine expansion. How polyglutamine expansion influences flanking domain aggregation is poorly understood. Here, we use a combination of mass spectrometry and biophysical approaches to investigate this issue for ataxin-3. We show that the conformational dynamics of the flanking Josephin domain in ataxin-3 with an expanded polyglutamine tract are altered in comparison to those exhibited by its nonexpanded counterpart, specifically within the aggregation-prone region of the Josephin domain (amino acid residues 73–96). Expansion thus exposes this region more frequently in ataxin-3 containing an expanded polyglutamine tract, providing a molecular explanation of why aggregation is accelerated upon polyglutamine expansion. Here, harnessing the power of ion mobility spectrometry-mass spectrometry, oligomeric species formed during aggregation are characterized and a model for oligomer growth proposed. The results suggest that a conformational change occurs at the dimer level that initiates self-assembly. New insights into ataxin-3 fibril architecture are also described, revealing the region of the Josephin domain involved in protofibril formation and demonstrating that polyglutamine aggregation proceeds as a distinct second step after protofibril formation without requiring structural rearrangement of the protofibril core. Overall, the results enable the effect of polyglutamine expansion on

  15. Preparing Synthetic Aβ in Different Aggregation States

    PubMed Central

    Stine, W. Blaine; Jungbauer, Lisa; Yu, Chunjiang; LaDu, Mary Jo

    2013-01-01

    This chapter outlines protocols that produce homogenous preparations of oligomeric and fibrillar amyloid -β peptide (Aβ). While there are several isoforms of this peptide, the 42 amino acid form is the focus because of its genetic and pathological link to Alzheimer’s disease (AD). Past decades of AD research highlight the dependence of Aβ42 function on its structural assembly state. Biochemical, cellular and in vivo studies of Aβ42 usually begin with purified peptide obtained by chemical synthesis or recombinant expression. The initial steps to solubilize and prepare these purified dry peptide stocks are critical to controlling the structural assembly of Aβ. To develop homogenous Aβ42 assemblies, we initially monomerize the peptide, erasing any “structural history” that could seed aggregation, by using a strong solvent. It is this starting material that has allowed us to define and optimize conditions that consistently produce homogenous solutions of soluble oligomeric and fibrillar Aβ42 assemblies. These preparations have been developed and characterized by using atomic force microscopy (AFM) to identify the structurally discrete species formed by Aβ42 under specific solution conditions. These preparations have been used extensively to demonstrate a variety of functional differences between oligomeric and fibrillar Aβ42. We also present a protocol for fluorescently labeling oligomeric Aβ42 that does not affect structure, as measured by AFM, or function, as measured by a cellular uptake assay. These reagents are critical experimental tools that allow for defining specific structure/function connections. PMID:20967580

  16. Construction Technologies.

    ERIC Educational Resources Information Center

    Columbus State Community Coll., OH.

    This document contains materials developed for and about the construction technologies tech prep program of the South-Western City Schools in Ohio. Part 1 begins with a map of the program, which begins with a construction technologies program in grades 11 and 12 that leads to entry-level employment or one of five 2-year programs at a community…

  17. Construction Management.

    ERIC Educational Resources Information Center

    Abbott, James F.

    This article provides a detailed discussion of a team approach to building that involves a construction manager, an architect, and a contractor. Bidding methods are outlined; the major components in construction management -- value engineering and fast track scheduling -- and the use of performance specifications are discussed. The construction…

  18. Photoinduced charge separation reactions of J-aggregates coated on silver nanoparticles.

    SciTech Connect

    Hranisavljevic, J.; Dimitrijevic, N. M.; Wurtz, G. A.; Wiederrecht, G. P.; Chemistry

    2002-05-01

    The photochemistry of cyanine J-aggregates on the surface of colloidal Ag nanoparticles is reported. The photochemistry is initiated through ultrafast photoexcitation of the plasmon band in Ag nanoparticles, producing an enhanced near-field that interacts with the J-aggregate monolayer. Through transient absorption spectroscopy, we show that photoexcitation of the plasmon in Ag nanoparticles leads to exciton dynamics that differ strongly from J-aggregates alone or for J-aggregate monolayers on bulk metal surfaces. Specifically, charge-separated states with a lifetime of 300 ps between the J-aggregate and Ag colloid are formed. The reduction of the Ag nanoparticles is shown to be a multielectron process.

  19. Integrating service-life modeling and life-cycle assessment for recycled-aggregate concrete

    NASA Astrophysics Data System (ADS)

    Bergman, Todd Lee

    The development and implementation of one-dimensional (a) analytical and (b) numerical service-life models for chloride-induced corrosion of reinforced concrete containing both recycled-aggregates and supplementary cementitious materials (SCMs) are presented in this work. Both the analytical and numerical models account for initial chloride contamination levels due to previous applications. The effects of aggregate type (e.g., virgin, recycled aggregate, recycled mortar), aggregate replacement ratio, severity of chloride contamination levels, severity of in-service chloride exposure, reinforcement cover depth, SCM type (e.g., fly ash, slag, slice fume, metakaolin), and SCM replacement ratio on the expected service life of recycled-aggregate reinforced concrete were investigated. Results illustrated trends between concrete mixes and life cycle costs, which were employed to make conclusions on the trade-offs presented by cost, sustainability, and service life.

  20. Specification aggregate quarry expansion: a case study demonstrating sustainable management of natural aggregate resources

    USGS Publications Warehouse

    Langer, William H.; Tucker, M.L.

    2003-01-01

    Many countries, provinces, territories, or states in the European Union, Australia, Canada, the United States, and elsewhere have begun implementing sustainability programs, but most of those programs stop short of sustainable management of aggregate resources. Sustainable practices do not always have to be conducted under the title of sustainability. This case study describes how Lafarge, a large multinational construction materials supplier, implemented the principles of sustainability even though there was an absence of existing local government policies or procedures addressing sustainable resource management. Jefferson County, Colorado, USA, is one of three counties in the six-county Denver, Colorado, region that has potentially available sources of crushed stone. Crushed stone comprises 30 percent of the aggregate produced in the area and plays a major role in regional aggregate resource needs. Jefferson County is home to four of the five crushed stone operations in the Denver region. Lafarge operates one of those four quarries. Lafarge recently proposed to expand its reserves by exchanging company-owned land for existing dedicated open space land adjacent to their quarry but owned by Jefferson County. A similar proposal submitted about 10 years earlier had been denied. Contrary to the earlier proposal, which was predicated on public relations, the new proposal was predicated on public trust. Although not explicitly managed under the moniker of sustainability, Lafarge used basic management principles that embody the tenets of sustainability. To achieve the goals of sustainable aggregate management where no governmental policies existed, Lafarge not only assumed their role of being a responsible corporate and environmental member of the community, but also assumed the role of facilitator to encourage and enable other stakeholders to responsibly resolve legitimate concerns regarding the Lafarge quarry proposal. Lafarge successfully presented an enlightened

  1. Inhomogeneous diffusion-limited aggregation

    NASA Technical Reports Server (NTRS)

    Selinger, Robin Blumberg; Nittmann, Johann; Stanley, H. E.

    1989-01-01

    It is demonstrated here that inhomogeneous diffusion-limited aggregation (DLA) model can be used to simulate viscous fingering in a medium with inhomogeneous permeability and homogeneous porosity. The medium consists of a pipe-pore square-lattice network in which all pores have equal volume and the pipes have negligible volume. It is shown that fluctuations in a DLA-based growth process may be tuned by noise reduction, and that fluctuations in the velocity of the moving interface are multiplicative in form.

  2. Magnetically shaped cell aggregates: from granular to contractile materials.

    PubMed

    Frasca, G; Du, V; Bacri, J-C; Gazeau, F; Gay, C; Wilhelm, C

    2014-07-28

    In recent decades, significant advances have been made in the description and modelling of tissue morphogenesis. By contrast, the initial steps leading to the formation of a tissue structure, through cell-cell adhesion, have so far been described only for small numbers of interacting cells. Here, through the use of remote magnetic forces, we succeeded at creating cell aggregates of half million cells, instantaneously and for several cell types, not only those known to form spheroids. This magnetic compaction gives access to the cell elasticity, found in the range of 800 Pa. The magnetic force can be removed at any time, allowing the cell mass to evolve spontaneously thereafter. The dynamics of contraction of these cell aggregates just after their formation (or, in contrast, their spreading for non-interacting monocyte cells) provides direct information on cell-cell interactions and allows retrieving the adhesion energy, in between 0.05 and 2 mJ m(-2), depending on the cell type tested, and in the case of cohesive aggregates. Thus, we show, by probing a large number of cell types, that cell aggregates behave like complex materials, undergoing a transition from a wet granular to contractile network, and that this transition is controlled by cell-cell interactions. PMID:24710948

  3. The Thioredoxin System Protects Ribosomes against Stress-induced Aggregation

    PubMed Central

    Rand, Jonathan D.; Grant, Chris M.

    2006-01-01

    We previously showed that thioredoxins are required for dithiothreitol (DTT) tolerance, suggesting they maintain redox homeostasis in response to both oxidative and reductive stress conditions. In this present study, we screened the complete set of viable deletion strains in Saccharomyces cerevisiae for sensitivity to DTT to identify cell functions involved in resistance to reductive stress. We identified 195 mutants, whose gene products are localized throughout the cell. DTT-sensitive mutants were distributed among most major biological processes, but they particularly affected gene expression, metabolism, and the secretory pathway. Strikingly, a mutant lacking TSA1, encoding a peroxiredoxin, showed a similar sensitivity to DTT as a thioredoxin mutant. Epistasis analysis indicated that thioredoxins function upstream of Tsa1 in providing tolerance to DTT. Our data show that the chaperone function of Tsa1, rather than its peroxidase function, is required for this activity. Cells lacking TSA1 were found to accumulate aggregated proteins, and this was exacerbated by exposure to DTT. Analysis of the protein aggregates revealed that they are predominantly composed of ribosomal proteins. Furthermore, aggregation was found to correlate with an inhibition of translation initiation. We propose that Tsa1 normally functions to chaperone misassembled ribosomal proteins, preventing the toxicity that arises from their aggregation. PMID:16251355

  4. Recovery of MSWI and soil washing residues as concrete aggregates.

    PubMed

    Sorlini, Sabrina; Abbà, Alessandro; Collivignarelli, Carlo

    2011-02-01

    The aim of the present work was to study if municipal solid waste incinerator (MSWI) residues and aggregates derived from contaminated soil washing could be used as alternative aggregates for concrete production. Initially, chemical, physical and geometric characteristics (according to UNI EN 12620) of municipal solid waste incineration bottom ashes and some contaminated soils were evaluated; moreover, the pollutants release was evaluated by means of leaching tests. The results showed that the reuse of pre-treated MSWI bottom ash and washed soil is possible, either from technical or environmental point of view, while it is not possible for the raw wastes. Then, the natural aggregate was partially and totally replaced with these recycled aggregates for the production of concrete mixtures that were characterized by conventional mechanical and leaching tests. Good results were obtained using the same dosage of a high resistance cement (42.5R calcareous Portland cement instead of 32.5R); the concrete mixture containing 400 kg/m(3) of washed bottom ash and high resistance cement was classified as structural concrete (C25/30 class). Regarding the pollutants leaching, all concrete mixtures respected the limit values according to the Italian regulation. PMID:20537523

  5. Tracking Hypoxic Signaling within Encapsulated Cell Aggregates

    PubMed Central

    Skiles, Matthew L.; Sahai, Suchit; Blanchette, James O.

    2011-01-01

    nutrients, notably oxygen, is therefore reduced and limited by diffusion. This reduced oxygen availability may especially impact β-cells whose insulin secretory function is highly dependent on oxygen11-13. Capsule composition and geometry will also impact diffusion rates and lengths for oxygen. Therefore, we also describe a technique for identifying hypoxic cells within our PEG capsules. Infection of the cells with a recombinant adenovirus allows for a fluorescent signal to be produced when intracellular hypoxia-inducible factor (HIF) pathways are activated14. As HIFs are the primary regulators of the transcriptional response to hypoxia, they represent an ideal target marker for detection of hypoxic signaling15. This approach allows for easy and rapid detection of hypoxic cells. Briefly, the adenovirus has the sequence for a red fluorescent protein (Ds Red DR from Clontech) under the control of a hypoxia-responsive element (HRE) trimer. Stabilization of HIF-1 by low oxygen conditions will drive transcription of the fluorescent protein (Figure 1). Additional details on the construction of this virus have been published previously15. The virus is stored in 10% glycerol at -80° C as many 150 μL aliquots in 1.5 mL centrifuge tubes at a concentration of 3.4 x 1010 pfu/mL. Previous studies in our lab have shown that MIN6 cells encapsulated as aggregates maintain their viability throughout 4 weeks of culture in 20% oxygen. MIN6 aggregates cultured at 2 or 1% oxygen showed both signs of necrotic cells (still about 85-90% viable) by staining with ethidium bromide as well as morphological changes relative to cells in 20% oxygen. The smooth spherical shape of the aggregates displayed at 20% was lost and aggregates appeared more like disorganized groups of cells. While the low oxygen stress does not cause a pronounced drop in viability, it is clearly impacting MIN6 aggregation and function as measured by glucose-stimulated insulin secretion15. Western blot analysis of encapsulated

  6. Tracking hypoxic signaling within encapsulated cell aggregates.

    PubMed

    Skiles, Matthew L; Sahai, Suchit; Blanchette, James O

    2011-01-01

    , is therefore reduced and limited by diffusion. This reduced oxygen availability may especially impact β-cells whose insulin secretory function is highly dependent on oxygen. Capsule composition and geometry will also impact diffusion rates and lengths for oxygen. Therefore, we also describe a technique for identifying hypoxic cells within our PEG capsules. Infection of the cells with a recombinant adenovirus allows for a fluorescent signal to be produced when intracellular hypoxia-inducible factor (HIF) pathways are activated. As HIFs are the primary regulators of the transcriptional response to hypoxia, they represent an ideal target marker for detection of hypoxic signaling. This approach allows for easy and rapid detection of hypoxic cells. Briefly, the adenovirus has the sequence for a red fluorescent protein (Ds Red DR from Clontech) under the control of a hypoxia-responsive element (HRE) trimer. Stabilization of HIF-1 by low oxygen conditions will drive transcription of the fluorescent protein (Figure 1). Additional details on the construction of this virus have been published previously. The virus is stored in 10% glycerol at -80° C as many 150 μL aliquots in 1.5 mL centrifuge tubes at a concentration of 3.4 x 10(10) pfu/mL. Previous studies in our lab have shown that MIN6 cells encapsulated as aggregates maintain their viability throughout 4 weeks of culture in 20% oxygen. MIN6 aggregates cultured at 2 or 1% oxygen showed both signs of necrotic cells (still about 85-90% viable) by staining with ethidium bromide as well as morphological changes relative to cells in 20% oxygen. The smooth spherical shape of the aggregates displayed at 20% was lost and aggregates appeared more like disorganized groups of cells. While the low oxygen stress does not cause a pronounced drop in viability, it is clearly impacting MIN6 aggregation and function as measured by glucose-stimulated insulin secretion. Western blot analysis of encapsulated cells in 20% and 1% oxygen also

  7. Investigating the mechanisms leading to protein aggregation

    NASA Astrophysics Data System (ADS)

    McNamara, Ruth; McManus, Jennifer J.

    2014-03-01

    The formation of protein aggregates is a feature of several diseases and is a problem during the manufacture of biopharmaceutical and protein based food products. During processing, stability may become compromised leading to the condensation of proteins to form non-native aggregates. The aim of this work is to induce aggregation on model proteins by the imposition of a particular stress to evaluate the extent of aggregation and to assess the degree of structural change to the protein. Aggregation of two proteins, lysozyme and bovine serum albumin has been induced by several mechanisms. Using various techniques (electrophoresis, HPLC, spectroscopic analysis, and microscopic techniques) both the level of aggregation extent of protein unfolding has been investigated for a range of solution conditions. Our results show that the amount of aggregation depends strongly on the mechanism by which non-native aggregation proceeds, and within each mechanism, solution conditions are an important factor. With the exception of aggregation by self-association (which is concentration dependent), the appearance of aggregation is driven by structural changes induced by the applied stress (heat, chemical denaturant, oxidation or contact with a surface). Author would like to acknowledge support from Science Foundation Ireland (SFI), National University of Maynooth John and Pat Hume Scholarship.

  8. Applications of aggregation theory to sustainability assessment

    DOE PAGESBeta

    Pollesch, N.; Dale, V. H.

    2015-04-01

    In order to aid in transition towards operations that promote sustainability goals, researchers and stakeholders use sustainability assessments. Although assessments take various forms, many utilize diverse sets of indicators that can number anywhere from two to over 2000. Indices, composite indicators, or aggregate values are used to simplify high dimensional and complex data sets and to clarify assessment results. Although the choice of aggregation function is a key component in the development of the assessment, there are few examples to be found in literature to guide appropriate aggregation function selection. This paper develops a connection between the mathematical study ofmore » aggregation functions and sustainability assessment in order to aid in providing criteria for aggregation function selection. Relevant mathematical properties of aggregation functions are presented and interpreted. Lastly, we provide cases of these properties and their relation to previous sustainability assessment research. Examples show that mathematical aggregation properties can be used to address the topics of compensatory behavior and weak versus strong sustainability, aggregation of data under varying units of measurements, multiple site multiple indicator aggregation, and the determination of error bounds in aggregate output for normalized and non-normalized indicator measures.« less

  9. Applications of aggregation theory to sustainability assessment

    SciTech Connect

    Pollesch, N.; Dale, V. H.

    2015-04-01

    In order to aid in transition towards operations that promote sustainability goals, researchers and stakeholders use sustainability assessments. Although assessments take various forms, many utilize diverse sets of indicators that can number anywhere from two to over 2000. Indices, composite indicators, or aggregate values are used to simplify high dimensional and complex data sets and to clarify assessment results. Although the choice of aggregation function is a key component in the development of the assessment, there are few examples to be found in literature to guide appropriate aggregation function selection. This paper develops a connection between the mathematical study of aggregation functions and sustainability assessment in order to aid in providing criteria for aggregation function selection. Relevant mathematical properties of aggregation functions are presented and interpreted. Lastly, we provide cases of these properties and their relation to previous sustainability assessment research. Examples show that mathematical aggregation properties can be used to address the topics of compensatory behavior and weak versus strong sustainability, aggregation of data under varying units of measurements, multiple site multiple indicator aggregation, and the determination of error bounds in aggregate output for normalized and non-normalized indicator measures.

  10. Flow cytometric analysis of circulating platelet-monocyte aggregates in whole blood: methodological considerations.

    PubMed

    Harding, Scott A; Din, Jehangir N; Sarma, Jaydeep; Jessop, Alasdair; Weatherall, Mark; Fox, Keith A A; Newby, David E

    2007-08-01

    Platelet-monocyte aggregates are increasingly being used to quantify platelet activation. The variables that influence platelet-monocyte aggregates have not been well defined. We sought to determine the effect of blood collection, handling and processing techniques on detected levels of platelet-monocyte aggregates using a flow cytometric assay. Whole blood was labelled with anti-CD14-PE and anti-CD42a-FITC. Thereafter, samples were fixed and red cells lysed. Analysis was performed with the flow cytometer initially triggering on light scatter and then on FL-2 to identify CD14-PE positive monocytes. Platelet-monocyte aggregates were defined as monocytes positive for CD42a. The effect of collection, handling and processing techniques on this assay were assessed. Anticoagulation with heparin (20.1 +/- 2.0%), PPACK (16.8 +/- 1.9%), sodium citrate (12.3 +/- 1.6%) and EDTA (9.5 +/- 1.0%) resulted in markedly different levels of platelet-monocyte aggregation (P < 0.0001). Platelet-monocyte aggregation was higher in samples obtained from intravenous cannulae compared to those obtained by venepuncture (20.9 +/- 3.9% vs.13.8 +/- 2.4%, P = 0.03). For every 10 minutes of delay prior to processing platelet-monocyte aggregates increased by 2.8% (P = 0.0001) in PPACK anticoagulated blood and 1.7% (P = 0.01) in citrate anticoagulated blood. Erythrocyte lysis together with fixation does not affect platelet-monocyte aggregation. Platelet-monocyte aggregates remained stable over 24 hours when fixed and stored at 4 degrees C. Multiple handling and processing factors may affect platelet-monocyte aggregation. We recommend the measurement of platelet-monocyte aggregates on samples collected by direct venepuncture, using a direct thrombin inhibitor as the anticoagulant and minimising the time delay before sample fixation. PMID:17721630

  11. Chemical-mineralogical characterisation of coarse recycled concrete aggregate

    SciTech Connect

    Limbachiya, M.C. . E-mail: m.limbachiya@kingston.ac.uk; Marrocchino, E.; Koulouris, A.

    2007-07-01

    The construction industry is now putting greater emphasis than ever before on increasing recycling and promoting more sustainable waste management practices. In keeping with this approach, many sectors of the industry have actively sought to encourage the use of recycled concrete aggregate (RCA) as an alternative to primary aggregates in concrete production. The results of a laboratory experimental programme aimed at establishing chemical and mineralogical characteristics of coarse RCA and its likely influence on concrete performance are reported in this paper. Commercially produced coarse RCA and natural aggregates (16-4 mm size fraction) were tested. Results of X-ray fluorescence (XRF) analyses showed that original source of RCA had a negligible effect on the major elements and a comparable chemical composition between recycled and natural aggregates. X-ray diffraction (XRD) analyses results indicated the presence of calcite, portlandite and minor peaks of muscovite/illite in recycled aggregates, although they were directly proportioned to their original composition. The influence of 30%, 50%, and 100% coarse RCA on the chemical composition of equal design strength concrete has been established, and its suitability for use in a concrete application has been assessed. In this work, coarse RCA was used as a direct replacement for natural gravel in concrete production. Test results indicated that up to 30% coarse RCA had no effect on the main three oxides (SiO{sub 2}, Al{sub 2}O{sub 3} and CaO) of concrete, but thereafter there was a marginal decrease in SiO{sub 2} and increase in Al{sub 2}O{sub 3} and CaO contents with increase in RCA content in the mix, reflecting the original constituent's composition.

  12. Aggregation of liposomes in presence of La3+ : A study of the fractal dimension

    NASA Astrophysics Data System (ADS)

    Sabín, Juan; Prieto, Gerardo; Ruso, Juan M.; Messina, Paula; Sarmiento, Félix

    2007-07-01

    A study of the fractal dimension of the aggregation of three different types of large unilamellar vesicles, formed by egg yolk phosphatidylcholine (EYPC), dimyristoyl-phosphocholine (DMPC), and dipalmitoyl-phosphocholine (DPPC), in the presence of La3+ , is presented. Aggregate liposome fractal dimensions were calculated by two methods, aggregation kinetics, using the approaches diffusion-limited cluster aggregation (DLCA) and reaction-limited cluster aggregation (RLCA) and angle-scattering light dispersion. Electrophoretic measurements show a similar variation of the zeta potential ( ζ potential) for EYPC and DPPC, with a small increase of initial positive values. However, the ζ potential of DMPC changes from a initial negative value to near zero with increasing La3+ concentration. The evolution of the aggregate sizes was followed by light scattering. DPPC and DMPC show a RLCA regimen growth at low La3+ concentrations and a DLCA regimen at higher concentrations. In the case of EYPC, the final size of aggregation strongly depends on La3+ concentration. The calculated fractal dimension is in the range 1.8 to 2.1.

  13. Protein aggregates in Huntington's disease.

    PubMed

    Arrasate, Montserrat; Finkbeiner, Steven

    2012-11-01

    Huntington's disease (HD) is an incurable neurodegenerative disease characterized by abnormal motor movements, personality changes, and early death. HD is caused by a mutation in the IT-15 gene that expands abnormally the number of CAG nucleotide repeats. As a result, the translated protein huntingtin contains disease-causing expansions of glutamines (polyQ) that make it prone to misfold and aggregate. While the gene and mutations that cause HD are known, the mechanisms underlying HD pathogenesis are not. Here we will review the state of knowledge of HD, focusing especially on a hallmark pathological feature-intracellular aggregates of mutant Htt called inclusion bodies (IBs). We will describe the role of IBs in the disease. We speculate that IB formation could be just one component of a broader coping response triggered by misfolded Htt whose efficacy may depend on the extent to which it clears toxic forms of mutant Htt. We will describe how IB formation might be regulated and which factors could determine different coping responses in different subsets of neurons. A differential regulation of IB formation as a function of the cellular context could, eventually, explain part of the neuronal vulnerability observed in HD. PMID:22200539

  14. Mesoscale simulation of asphaltene aggregation

    NASA Astrophysics Data System (ADS)

    Wang, Jiang; Ferguson, Andrew

    Asphaltenes constitute a heavy aromatic crude oil fraction that can aggregate and precipitate out of solution. Association is thought to proceed hierarchically according to the Yen-Mullins model, but the molecular mechanisms and pathways remain poorly understood. In this study, we perform molecular dynamics simulations of the aggregation of hundreds of asphaltenes over microseconds using the coarse-grained Martini force field. We identified a hierarchical self-assembly mechanism consistent with Yen-Mullins model, but the details of which are strongly dependent on asphaltene molecular structure. Monomeric asphaltenes first self-assemble into 1-D rod-like nanoaggregates, followed by the formation of clusters of nanoaggregates. At high concentrations, asphaltenes with short aliphatic side chains assemble into a percolating network with the binding of 1-D rods. Conversely, molecules with more and longer side chains cannot efficiently stack, producing a fractal network of 1-D rods suspended in a sea of interpenetrating aliphatic side chains. Our results provide the first molecularly-detailed validation of the full Yen-Mullins hierarchy, and are in good agreement with recent computational and experimental studies. ACS Petroleum Research Fund.

  15. Sectoral shifts and aggregate unemployment

    SciTech Connect

    Loungani, P.

    1986-01-01

    Some recent research has taken the view that sectoral or industry-specific shocks significantly affect aggregate unemployment by increasing the amount of inter-industry labor reallocation required. The empirical evidence for this view rests on the finding that during the 1950s - and again during the 1970s - there was a positive correlation between aggregate unemployment and the dispersion of employment growth rates. This thesis demonstrates that this correlation arises largely because oil price shocks affect both unemployment and the dispersion of employment growth. Once the dispersion due to oil shocks is accounted for, the residual dispersion in employment has very low explanatory power for unemployment. Since the dispersion index does not measure pure sectoral shifts, an alternate measure of dispersion is developed that serves as a better proxy for the amount of inter-industry labor reallocation required each period. Estimates using this measure suggest that, during the 1950s, temporary increases in the relative price of oil were responsible for generating the observed correlation. On the other hand, sectoral shifts were important during the 1970s; in particular, the 1973 oil price increase has had significant reallocative effects on the economy. This contention is subjected to further tests by looking at the time-series behavior of employment in durable-goods industries and also by following the inter-industry movements of workers over time through the use of panel data.

  16. Attracted diffusion-limited aggregation.

    PubMed

    Rahbari, S H Ebrahimnazhad; Saberi, A A

    2012-07-01

    In this paper we present results of extensive Monte Carlo simulations of diffusion-limited aggregation (DLA) with a seed placed on an attractive plane as a simple model in connection with the electrical double layers. We compute the fractal dimension of the aggregated patterns as a function of the attraction strength α. For the patterns grown in both two and three dimensions, the fractal dimension shows a significant dependence on the attraction strength for small values of α and approaches that of the ordinary two-dimensional (2D) DLA in the limit of large α. For the nonattracting case with α = 1, our results in three dimensions reproduce the patterns of 3D ordinary DLA, while in two dimensions our model leads to the formation of a compact cluster with dimension 2. For intermediate α, the 3D clusters have a quasi-2D structure with a fractal dimension very close to that of the ordinary 2D DLA. This allows one to control the morphology of a growing cluster by tuning a single external parameter α. PMID:23005417

  17. Attracted diffusion-limited aggregation

    NASA Astrophysics Data System (ADS)

    Rahbari, S. H. Ebrahimnazhad; Saberi, A. A.

    2012-07-01

    In this paper we present results of extensive Monte Carlo simulations of diffusion-limited aggregation (DLA) with a seed placed on an attractive plane as a simple model in connection with the electrical double layers. We compute the fractal dimension of the aggregated patterns as a function of the attraction strength α. For the patterns grown in both two and three dimensions, the fractal dimension shows a significant dependence on the attraction strength for small values of α and approaches that of the ordinary two-dimensional (2D) DLA in the limit of large α. For the nonattracting case with α=1, our results in three dimensions reproduce the patterns of 3D ordinary DLA, while in two dimensions our model leads to the formation of a compact cluster with dimension 2. For intermediate α, the 3D clusters have a quasi-2D structure with a fractal dimension very close to that of the ordinary 2D DLA. This allows one to control the morphology of a growing cluster by tuning a single external parameter α.

  18. Non-local models for the formation of hepatocyte-stellate cell aggregates.

    PubMed

    Green, J E F; Waters, S L; Whiteley, J P; Edelstein-Keshet, L; Shakesheff, K M; Byrne, H M

    2010-11-01

    Liver cell aggregates may be grown in vitro by co-culturing hepatocytes with stellate cells. This method results in more rapid aggregation than hepatocyte-only culture, and appears to enhance cell viability and the expression of markers of liver-specific functions. We consider the early stages of aggregate formation, and develop a new mathematical model to investigate two alternative hypotheses (based on evidence in the experimental literature) for the role of stellate cells in promoting aggregate formation. Under Hypothesis 1, each population produces a chemical signal which affects the other, and enhanced aggregation is due to chemotaxis. Hypothesis 2 asserts that the interaction between the two cell types is by direct physical contact: the stellates extend long cellular processes which pull the hepatocytes into the aggregates. Under both hypotheses, hepatocytes are attracted to a chemical they themselves produce, and the cells can experience repulsive forces due to overcrowding. We formulate non-local (integro-partial differential) equations to describe the densities of cells, which are coupled to reaction-diffusion equations for the chemical concentrations. The behaviour of the model under each hypothesis is studied using a combination of linear stability analysis and numerical simulations. Our results show how the initial rate of aggregation depends upon the cell seeding ratio, and how the distribution of cells within aggregates depends on the relative strengths of attraction and repulsion between the cell types. Guided by our results, we suggest experiments which could be performed to distinguish between the two hypotheses. PMID:20709085

  19. Model simulations of particle aggregation effect on colloid exchange between streams and streambeds.

    PubMed

    Areepitak, Trachu; Ren, Jianhong

    2011-07-01

    Colloids found in natural streams have large reactive surface areas, which makes them significant absorbents and carriers for pollutants. Stream-subsurface exchange plays a critical role in regulating the transport of colloids and contaminants in natural streams. Previous process-based multiphase exchange models were developed without consideration of colloid-colloid interaction. However, many studies have indicated that aggregation is a significant process and needs to be considered in stream process analysis. Herein, a new colloid exchange model was developed by including particle aggregation in addition to colloid settling and filtration. Self-preserving size distribution concepts and classical aggregation theory were employed to model the aggregation process. Model simulations indicate that under conditions of low filtration and high degree of particle-particle interaction, aggregation could either decrease or increase the amount of colloids retained in streambeds, depending on the initial particle size. Thus, two possible cases may occur including enhanced colloid deposition and facilitated colloid transport. Also, when the aggregation rate is high and filtration increases, more particles are retained by bed sediments due to filtration, and fewer are aggregated, which reduces the extent of aggregation effect on colloid deposition. The work presented here will contribute to a better understanding and prediction of colloid transport phenomena in natural streams. PMID:21627165

  20. Describing Myxococcus xanthus Aggregation Using Ostwald Ripening Equations for Thin Liquid Films

    PubMed Central

    Bahar, Fatmagül; Pratt-Szeliga, Philip C.; Angus, Stuart; Guo, Jiaye; Welch, Roy D.

    2014-01-01

    When starved, a swarm of millions of Myxococcus xanthus cells coordinate their movement from outward swarming to inward coalescence. The cells then execute a synchronous program of multicellular development, arranging themselves into dome shaped aggregates. Over the course of development, about half of the initial aggregates disappear, while others persist and mature into fruiting bodies. This work seeks to develop a quantitative model for aggregation that accurately simulates which will disappear and which will persist. We analyzed time-lapse movies of M. xanthus development, modeled aggregation using the equations that describe Ostwald ripening of droplets in thin liquid films, and predicted the disappearance and persistence of aggregates with an average accuracy of 85%. We then experimentally validated a prediction that is fundamental to this model by tracking individual fluorescent cells as they moved between aggregates and demonstrating that cell movement towards and away from aggregates correlates with aggregate disappearance. Describing development through this model may limit the number and type of molecular genetic signals needed to complete M. xanthus development, and it provides numerous additional testable predictions. PMID:25231319

  1. Synthesis of several membrane proteins during developmental aggregation in Myxococcus xanthus.

    PubMed

    Orndorff, P E; Dworkin, M

    1982-01-01

    We have examined the pattern of synthesis of several membrane proteins during the aggregation phase of development in Myxococcus xanthus. Development was initiated by plating vegetative cells on polycarbonate filters placed on top of an agar medium that supported fruiting body formation. At various times during aggregation a filter was removed, the cells were pulse-labeled with [35S]methionine, and the membrane proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The rate of synthesis of numerous individual proteins changed during aggregation; we concentrated on six whose pattern of synthesis was greatly altered during aggregation. The rate of synthesis of five of the six proteins increased considerably during aggregation; that of the remaining protein was curtailed and appeared to be regulated by nutrient conditions. Three of the five major membrane proteins that increased during aggregation had a unique pattern of synthesis that was displayed only under conditions that are are required for development - high cell density, nutrient depletion, and a solid (agar) surface. The remaining two proteins were not unique to development; the appearance of one protein could be induced under conditions of high cell density, whereas the other could be induced by placing the cells on a solid agar surface. All of the five major proteins that appeared during development did so during the preaggregation stage, and the synthesis of four of the five proteins appeared to be curtailed late in aggregation. The synthesis of the remaining protein continued throughout aggregation. PMID:6798022

  2. Asphaltene Aggregation and Fouling Behavior

    NASA Astrophysics Data System (ADS)

    Derakhshesh, Marzie

    This thesis explored the properties of asphaltene nano-aggregates in crude oil and toluene based solutions and fouling at process furnace temperatures, and the links between these two phenomena. The link between stability of asphaltenes at ambient conditions and fouling at the conditions of a delayed coker furnace, at over 450 °C, was examined by blending crude oil with an aliphatic diluent in different ratios. The stability of the blends were measured using a S-value analyzer, then fouling rates were measured on electrically heated stainless steel 316 wires in an autoclave reactor. The less stable the blend, the greater the rate and extent of fouling. The most severe fouling occurred with the unstable asphaltenes. SEM imaging of the foulant illustrates very different textures, with the structure becoming more porous with lower stability. Under cross-polarized light, the coke shows the presence of mesophase in the foulant layer. These data suggest a correlation between the fouling rate at high temperature furnace conditions and the stability index of the crude oil. Three organic polysulfides were introduced to the crude oil to examine their effect on fouling. The polysulfides are able to reduce coking and carbon monoxide generation in steam crackers. The fouling results demonstrated that polysulfide with more sulfur content increased the amount of corrosion-fouling of the wire. Various additives, solvents, ultrasound, and heat were employed to attempt to completely disaggregate the asphaltene nano-aggregates in solution at room temperature. The primary analytical technique used to monitor the nano-aggregation state of the asphaltenes in solution was the UV-visible spectroscopy. The results indicate that stronger solvents, such as pyridine and quinoline, combined with ionic liquids yield a slight reduction in the apparent absorbance at longer wavelengths, indicative of a decrease in the nano-aggregate size although the magnitude of the decrease is not significant

  3. Full counting statistics of laser excited Rydberg aggregates in a one-dimensional geometry.

    PubMed

    Schempp, H; Günter, G; Robert-de-Saint-Vincent, M; Hofmann, C S; Breyel, D; Komnik, A; Schönleber, D W; Gärttner, M; Evers, J; Whitlock, S; Weidemüller, M

    2014-01-10

    We experimentally study the full counting statistics of few-body Rydberg aggregates excited from a quasi-one-dimensional atomic gas. We measure asymmetric excitation spectra and increased second and third order statistical moments of the Rydberg number distribution, from which we determine the average aggregate size. Estimating rates for different excitation processes we conclude that the aggregates grow sequentially around an initial grain. Direct comparison with numerical simulations confirms this conclusion and reveals the presence of liquidlike spatial correlations. Our findings demonstrate the importance of dephasing in strongly correlated Rydberg gases and introduce a way to study spatial correlations in interacting many-body quantum systems without imaging. PMID:24483893

  4. Formation and Growth of Stacking Fault Tetrahedra in Ni via Vacancy Aggregation Mechanism

    SciTech Connect

    Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke; Bei, Hongbin; Zhang, Yanwen; Wang, Lumin; Weber, William J.

    2015-12-29

    Using molecular dynamics simulations, the formation and growth of stacking fault tetrahedra (SFT) are captured by vacancy cluster diffusion and aggregation mechanisms in Ni. The vacancytetrahedron acts as a nucleation point for SFT formation. Simulations show that perfect SFT can grow to the next size perfect SFT via a vacancy aggregation mechanism. The stopping and range of ions in matter (SRIM) calculations and transmission electron microscopy (TEM) observations reveal that SFT can form farther away from the initial cascade-event locations, indicating the operation of diffusion-based vacancy-aggregation mechanism.

  5. Constructing Phylogenies.

    ERIC Educational Resources Information Center

    Bilardello, Nicholas; Valdes, Linda

    1998-01-01

    Introduces a method for constructing phylogenies using molecular traits and elementary graph theory. Discusses analyzing molecular data and using weighted graphs, minimum-weight spanning trees, and rooted cube phylogenies to display the data. (DDR)

  6. Construction Administration.

    ERIC Educational Resources Information Center

    Barley, John McKim, II

    1986-01-01

    Successful completion of a construction project requires the efforts of a team composed of the owner, architect, and contractor. A preconstruction conference can clarify the roles of the team as specified in the design contract. (MLF)

  7. Worldwide construction

    SciTech Connect

    Williamson, M.

    1994-10-17

    The paper lists major construction projects in worldwide processing and pipelining, showing capacities, contractors, estimated costs, and time of construction. The lists are divided into refineries, petrochemical plants, sulfur recovery units, gas processing plants, pipelines, and related fuel facilities. This last classification includes cogeneration plants, coal liquefaction and gasification plants, biomass power plants, geothermal power plants, integrated coal gasification combined-cycle power plants, and a coal briquetting plant.

  8. Space Construction

    NASA Technical Reports Server (NTRS)

    Hagaman, Jane A. (Editor)

    1987-01-01

    The purpose was to present to the aerospace community an in-depth review of Experimental Assembly of Structures on EVA (EASE)/Assembly Concept for Construction of Erectable Space Structures (ACCESS) space flight experiments and to present the status of activities regarding future space flight experiments and accompanying technology developments that will demonstrate the capability of on-orbit construction required for the Space Station.

  9. Effects of soil aggregates on debris-flow mobilization: Results from ring-shear experiments

    USGS Publications Warehouse

    Iverson, Neal R.; Mann, Janet E.; Iverson, Richard M.

    2010-01-01

    Rates and styles of landslide motion are sensitive to pore-water pressure changes caused by changes in soil porosity accompanying shear deformation. Soil may either contract or dilate upon shearing, depending upon whether its initial porosity is greater or less, respectively, than a critical-state porosity attained after sufficiently high strain. We observed complications in this behavior, however, during rate-controlled (0.02 m s−1) ring-shear experiments conducted on naturally aggregated dense loamy sand at low confining stresses (10.6 and 40 kPa). The aggregated soil first dilated and then contracted to porosities less than initial values, whereas the same soil with its aggregates destroyed monotonically dilated. We infer that aggregates persisted initially during shear and caused dilation before their eventual breakdown enabled net contraction. An implication of this contraction, demonstrated in experiments in which initial soil porosity was varied, is that the value of porosity distinguishing initially contractive from dilative behavior can be significantly larger than the critical-state porosity, which develops only after disaggregation ceases at high strains. In addition, post-dilative contraction may produce excess pore pressures, thereby reducing frictional strength and facilitating debris-flow mobilization. We infer that results of triaxial tests, which generally produce strains at least a factor of ∼ 4 smaller than those we observed at the inception of post-dilative contraction, do not allow soil contraction to be ruled out as a mechanism for debris-flow mobilization in dense soils containing aggregates.

  10. Aggregation server for grid-integrated vehicles

    SciTech Connect

    Kempton, Willett

    2015-05-26

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

  11. Multiscale simulation of red blood cell aggregation

    NASA Astrophysics Data System (ADS)

    Bagchi, P.; Popel, A. S.

    2004-11-01

    In humans and other mammals, aggregation of red blood cells (RBC) is a major determinant to blood viscosity in microcirculation under physiological and pathological conditions. Elevated levels of aggregation are often related to cardiovascular diseases, bacterial infection, diabetes, and obesity. Aggregation is a multiscale phenomenon that is governed by the molecular bond formation between adjacent cells, morphological and rheological properties of the cells, and the motion of the extra-cellular fluid in which the cells circulate. We have developed a simulation technique using front tracking methods for multiple fluids that includes the multiscale characteristics of aggregation. We will report the first-ever direct computer simulation of aggregation of deformable cells in shear flows. We will present results on the effect of shear rate, strength of the cross-bridging bonds, and the cell rheological properties on the rolling motion, deformation and subsequent breakage of an aggregate.

  12. A dimension map for molecular aggregates.

    PubMed

    Jian, Cuiying; Tang, Tian; Bhattacharjee, Subir

    2015-05-01

    A pair of gyradius ratios, defined from the principal radii of gyration, are used to generate a dimension map that describes the geometry of molecular aggregates in water and in organic solvents. Molecular dynamics simulations were performed on the aggregation of representative biomolecules and polyaromatic compounds to demonstrate application of the dimension map. It was shown that molecular aggregate data on the dimension map were bounded by two boundary curves, and that the map could be separated into three regions representing three groups of structures: one-dimensional rod-like structures; two-dimensional planar structures or short-cylinder-like structures; and three-dimensional sphere-like structures. Examining the location of the aggregates on the dimension map and how the location changes with solvent type and solute material parameter provides a simple yet effective way to infer the aggregation manner and to study solubility and mechanism of aggregation. PMID:25768393

  13. A survey of natural aggregate properties and characteristics important in remote sensing and airborne geophysics

    USGS Publications Warehouse

    Knepper, D.H., Jr.; Langer, W.H.; Miller, S.

    1995-01-01

    Natural aggregate is vital to the construction industry. Although natural aggregate is a high volume/low value commodity that is abundant, new sources are becoming increasingly difficult to find and develop because of rigid industry specifications, political considerations, development and transportation costs, and environmental concerns. There are two primary sources of natural aggregate: (1) exposed or near-surface bedrock that can be crushed, and (2) deposits of sand and gravel. Remote sensing and airborne geophysics detect surface and near-surface phenomena, and may be useful for detecting and mapping potential aggregate sources; however, before a methodology for applying these techniques can be developed, it is necessary to understand the type, distribution, physical properties, and characteristics of natural aggregate deposits. The distribution of potential aggregate sources is closely tied to local geologic history. Conventional exploration for natural aggregate deposits has been largely a ground-based operation, although aerial photographs and topographic maps have been extensively used to target possible deposits. Today, the exploration process also considers factors such as the availability of the land, space and water supply for processing, political and environmental factors, and distance from the market; exploration and planning cannot be separated. There are many physical properties and characteristics by which to judge aggregate material for specific applications; most of these properties and characteristics pertain only to individual aggregate particles. The application of remote sensing and airborne geophysical measurements to detecting and mapping potential aggregate sources, however, is based on intrinsic bulk physical properties and extrinsic characteristics of the deposits that can be directly measured, mathematically derived from measurement, or interpreted with remote sensing and geophysical data. ?? 1995 Oxford UniversityPress.

  14. Leaching assessment of concrete made of recycled coarse aggregate: physical and environmental characterisation of aggregates and hardened concrete.

    PubMed

    Galvín, A P; Agrela, F; Ayuso, J; Beltrán, M G; Barbudo, A

    2014-09-01

    Each year, millions of tonnes of waste are generated worldwide, partially through the construction and demolition of buildings. Recycling the resulting waste could reduce the amount of materials that need to be manufactured. Accordingly, the present work has analysed the potential reuse of construction waste in concrete manufacturing by replacing the natural aggregate with recycled concrete coarse aggregate. However, incorporating alternative materials in concrete manufacturing may increase the pollutant potential of the product, presenting an environmental risk via ground water contamination. The present work has tested two types of concrete batches that were manufactured with different replacement percentages. The experimental procedure analyses not only the effect of the portion of recycled aggregate on the physical properties of concrete but also on the leaching behaviour as indicative of the contamination degree. Thus, parameters such as slump, density, porosity and absorption of hardened concrete, were studied. Leaching behaviour was evaluated based on the availability test performed to three aggregates (raw materials of the concrete batches) and on the diffusion test performed to all concrete. From an environmental point of view, the question of whether the cumulative amount of heavy metals that are released by diffusion reaches the availability threshold was answered. The analysis of concentration levels allowed the establishment of different groups of metals according to the observed behaviour, the analysis of the role of pH and the identification of the main release mechanisms. Finally, through a statistical analysis, physical parameters and diffusion data were interrelated. It allowed estimating the relevance of porosity, density and absorption of hardened concrete on diffusion release of the metals in study. PMID:24889792

  15. Nanoarchitectonics of Molecular Aggregates: Science and Technology

    SciTech Connect

    Ramanathan, Nathan Muruganathan; Hong, Kunlun; Ji, Dr. Qingmin; Hill, Dr. Jonathan P; Ariga, Katsuhiko; Yusuke, Yonamine

    2014-01-01

    The field of making, studying and using molecular aggregates, in which the individual molecules (monomers) are arranged in a regular fashion, has come a long way. Taking control over the aggregation of small molecules and polymers in bulk, on surfaces and at interfaces pose a considerable challenge for their utilization in modern high tech applications. In this review we provide a detailed insight into recent trends in molecular aggregates from the perspectives of nanoarchitectonics.

  16. Diffusion Limited Aggregation: Algorithm optimization revisited

    NASA Astrophysics Data System (ADS)

    Braga, F. L.; Ribeiro, M. S.

    2011-08-01

    The Diffusion Limited Aggregation (DLA) model developed by Witten and Sander in 1978 is useful in modeling a large class of growth phenomena with local dependence. Besides its simplicity this aggregation model has a complex behavior that can be observed at the patterns generated. We propose on this work a brief review of some important proprieties of this model and present an algorithm to simulate a DLA aggregates that simpler and efficient compared to others found in the literature.

  17. Immunogenicity of therapeutic proteins: Influence of aggregation

    PubMed Central

    Derrick, Jeremy P.; Dearman, Rebecca J.; Kimber, Ian

    2014-01-01

    The elicitation of anti-drug antibodies (ADA) against biotherapeutics can have detrimental effects on drug safety, efficacy, and pharmacokinetics. The immunogenicity of biotherapeutics is, therefore, an important issue. There is evidence that protein aggregation can result in enhanced immunogenicity; however, the precise immunological and biochemical mechanisms responsible are poorly defined. In the context of biotherapeutic drug development and safety assessment, understanding the mechanisms underlying aggregate immunogenicity is of considerable interest. This review provides an overview of the phenomenon of protein aggregation, the production of unwanted aggregates during bioprocessing, and how the immune response to aggregated protein differs from that provoked by non-aggregated protein. Of particular interest is the nature of the interaction of aggregates with the immune system and how subsequent ADA responses are induced. Pathways considered here include ‘classical’ activation of the immune system involving antigen presenting cells and, alternatively, the breakdown of B-cell tolerance. Additionally, methods available to screen for aggregation and immunogenicity will be described. With an increased understanding of aggregation-enhanced immune responses, it may be possible to develop improved manufacturing and screening processes to avoid, or at least reduce, the problems associated with ADA. PMID:23919460

  18. A competitive aggregation model for flash nanoprecipitation.

    PubMed

    Cheng, Janine Chungyin; Vigil, R D; Fox, R O

    2010-11-15

    Flash NanoPrecipitation (FNP) is a novel approach for producing functional nanoparticles stabilized by amphiphilic block copolymers. FNP involves the rapid mixing of a hydrophobic active (organic) and an amphiphilic di-block copolymer with a non-solvent (water) and subsequent co-precipitation of nanoparticles composed of both the organic and copolymer. During this process, the particle size distribution (PSD) is frozen and stabilized by the hydrophilic portion of the amphiphilic di-block copolymer residing on the particle surface. That is, the particle growth is kinetically arrested and thus a narrow PSD can be attained. To model the co-precipitation process, a bivariate population balance equation (PBE) has been formulated to account for the competitive aggregation of the organic and copolymer versus pure organic-organic or copolymer-copolymer aggregation. Aggregation rate kernels have been derived to account for the major aggregation events: free coupling, unimer insertion, and aggregate fusion. The resulting PBE is solved both by direct integration and by using the conditional quadrature method of moments (CQMOM). By solving the competitive aggregation model under well-mixed conditions, it is demonstrated that the PSD is controlled primarily by the copolymer-copolymer aggregation process and that the energy barrier to aggregate fusion plays a key role in determining the PSD. It is also shown that the characteristic aggregation times are smaller than the turbulent mixing time so that the FNP process is always mixing limited. PMID:20800847

  19. Deterministic aggregation kinetics of superparamagnetic colloidal particles

    NASA Astrophysics Data System (ADS)

    Reynolds, Colin P.; Klop, Kira E.; Lavergne, François A.; Morrow, Sarah M.; Aarts, Dirk G. A. L.; Dullens, Roel P. A.

    2015-12-01

    We study the irreversible aggregation kinetics of superparamagnetic colloidal particles in two dimensions in the presence of an in-plane magnetic field at low packing fractions. Optical microscopy and image analysis techniques are used to follow the aggregation process and in particular study the packing fraction and field dependence of the mean cluster size. We compare these to the theoretically predicted scalings for diffusion limited and deterministic aggregation. It is shown that the aggregation kinetics for our experimental system is consistent with a deterministic mechanism, which thus shows that the contribution of diffusion is negligible.

  20. Neuronal aggregates: formation, clearance and spreading

    PubMed Central

    Lim, Junghyun; Yue, Zhenyu

    2015-01-01

    Summary Proteostasis is maintained by multiple cellular pathways, including protein synthesis, quality control and degradation. An imbalance of neuronal proteostasis, associated with protein misfolding and aggregation, leads to proteinopathies or neurodegeneration. While genetic variations and protein modifications contribute to aggregate formation, components of the proteostasis network dictate the fate of protein aggregates. Here we provide an overview of proteostasis pathways and their interplay (particularly autophagy) with the metabolism of disease-related proteins. We review recent studies on neuronal activity-mediated regulation of proteostasis and transcellular propagation of protein aggregates in the nervous system. Targeting proteostasis pathways therapeutically remains an attractive but challenging task. PMID:25710535

  1. Optimization and comparison of two different 3D culture methods to prepare cell aggregates as a bioink for organ printing.

    PubMed

    Imani, Rana; Hojjati Emami, Shahriar; Fakhrzadeh, Hossein; Baheiraei, Nafiseh; Sharifi, Ali M

    2012-04-01

    The ultimate goal of tissue engineering is to design and fabricate functional human tissues that are similar to natural cells and are capable of regeneration. Preparation of cell aggregates is one of the important steps in 3D tissue engineering technology, particularly in organ printing. Two simple methods, hanging drop (HD) and conical tube (CT) were utilized to prepare cell aggregates. The size and viability of the aggregates obtained at different initial cell densities and pre-culture duration were compared. The proliferative ability of the cell aggregates and their ability to spread in culture plates were also investigated. In both methods, the optimum average size of the aggregates was less than 500 microm. CT aggregates were smaller than HD aggregates. 5,000 cells per drop HD aggregates showed a marked ability to attach and spread on the culture surface. The proliferative ability reduced when the initial cell density was increased. Comparing these methods, we found that the HD method having better size controlling ability as well as enhanced ability to maintain higher rates of viability, spreading, and proliferation. In conclusion, smaller HD aggregates might be a suitable choice as building blocks for making bioink particles in bioprinting technique. PMID:23173303

  2. Collisional Aggregation Due to Turbulence

    NASA Astrophysics Data System (ADS)

    Pumir, Alain; Wilkinson, Michael

    2016-03-01

    Collisions between particles suspended in a fluid play an important role in many physical processes. As an example, collisions of microscopic water droplets in clouds are a necessary step in the production of macroscopic raindrops. Collisions of dust grains are also conjectured to be important for planet formation in the gas surrounding young stars and to play a role in the dynamics of sand storms. In these processes, collisions are favored by fast turbulent motions. Here we review recent advances in the understanding of collisional aggregation due to turbulence. We discuss the role of fractal clustering of particles and caustic singularities of their velocities. We also discuss limitations of the Smoluchowski equation for modeling such processes. These advances lead to a semiquantitative understanding on the influence of turbulence on collision rates and point to deficiencies in the current understanding of rainfall and planet formation.

  3. Swarms: Optimum aggregations of spacecraft

    NASA Technical Reports Server (NTRS)

    Mayer, H. L.

    1980-01-01

    Swarms are aggregations of spacecraft or elements of a space system which are cooperative in function, but physically isolated or only loosely connected. For some missions the swarm configuration may be optimum compared to a group of completely independent spacecraft or a complex rigidly integrated spacecraft or space platform. General features of swarms are induced by considering an ensemble of 26 swarms, examples ranging from Earth centered swarms for commercial application to swarms for exploring minor planets. A concept for a low altitude swarm as a substitute for a space platform is proposed and a preliminary design studied. The salient design feature is the web of tethers holding the 30 km swarm in a rigid two dimensional array in the orbital plane. A mathematical discussion and tutorial in tether technology and in some aspects of the distribution of services (mass, energy, and information to swarm elements) are included.

  4. Aggregate Remote Memory Copy Interface

    2006-02-23

    The purpose of the Aggregate Remote Memory Copy (ARMCI) library is to provide a general- purpose, efficient, and Widely portable remote memory access (RMA) operations (one-sided communication) optimized for Contiguous and noncontiguous (strided, scatter/gather, I/O vector) data transfers. In addition, ARMCI includes a set of atomic and mutual exclusion operations. The development ARMCI is driven by the need to support the global-addres space communication model in context of distributed regular or irregular distributed data structures,more » communication libraries, and compilers. ARMCI is a standalone system that could be used to support user-level libraries and applications that use MPI or PVM.« less

  5. Morphological classification of nanoceramic aggregates

    NASA Astrophysics Data System (ADS)

    Crosta, Giovanni F.; Kang, Bongwoo; Ospina, Carolina; Sung, Changmo

    2005-01-01

    Aluminum silicate nanoaggregates grown at near-room temperature on an organic template under a variety of experimental conditions have been imaged by transmission electron microscopy. Images have been automatically classified by an algorithm based on "spectrum enhancement", multivariate statistics and supervised optimization. Spectrum enhancement consists of subtracting, in the log scale, a known function of wavenumber from the angle averaged power spectral density of the image. Enhanced spectra of each image, after polynomial interpolation, have been regarded as morphological descriptors and as such submitted to principal components analysis nested with a multiobjective parameter optimization algorithm. The latter has maximized pairwise discrimination between classes of materials. The role of the organic template and of a reaction parameter on aggregate morphology has been assessed at two magnification scales. Classification results have also been related to crystal structure data derived from selected area electron diffraction patterns.

  6. Colloidal aggregation in polymer blends.

    PubMed

    Benhamou, M; Ridouane, H; Hachem, E-K; Derouiche, A; Rahmoune, M

    2005-06-22

    We consider here a low-density assembly of colloidal particles immersed in a critical polymer mixture of two chemically incompatible polymers. We assume that, close to the critical point of the free mixture, the colloids prefer to be surrounded by one polymer (critical adsorption). As result, one is assisted to a reversible colloidal aggregation in the nonpreferred phase, due the existence of a long-range attractive Casimir force between particles. This aggregation is a phase transition driving the colloidal system from dilute to dense phases, as the usual gas-liquid transition. We are interested in a quantitative investigation of the phase diagram of the immersed colloids. We suppose that the positions of particles are disordered, and the disorder is quenched and follows a Gaussian distribution. To apprehend the problem, use is made of the standard phi(4) theory, where the field phi represents the composition fluctuation (order parameter), combined with the standard cumulant method. First, we derive the expression of the effective free energy of colloids and show that this is of Flory-Huggins type. Second, we find that the interaction parameter u between colloids is simply a linear combination of the isotherm compressibility and specific heat of the free mixture. Third, with the help of the derived effective free energy, we determine the complete shape of the phase diagram (binodal and spinodal) in the (Psi,u) plane, with Psi as the volume fraction of immersed colloids. The continuous "gas-liquid" transition occurs at some critical point K of coordinates (Psi(c) = 0.5,u(c) = 2). Finally, we emphasize that the present work is a natural extension of that, relative to simple liquid mixtures incorporating colloids. PMID:16035822

  7. Detergent-mediated protein aggregation

    PubMed Central

    Neale, Chris; Ghanei, Hamed; Holyoake, John; Bishop, Russell E.; Privé, Gilbert G.; Pomès, Régis

    2016-01-01

    Because detergents are commonly used to solvate membrane proteins for structural evaluation, much attention has been devoted to assessing the conformational bias imparted by detergent micelles in comparison to the native environment of the lipid bilayer. Here, we conduct six 500-ns simulations of a system with >600,000 atoms to investigate the spontaneous self assembly of dodecylphosphocholine detergent around multiple molecules of the integral membrane protein PagP. This detergent formed equatorial micelles in which acyl chains surround the protein’s hydrophobic belt, confirming existing models of the detergent solvation of membrane proteins. In addition, unexpectedly, the extracellular and periplasmic apical surfaces of PagP interacted with the headgroups of detergents in other micelles 85 and 60% of the time, respectively, forming complexes that were stable for hundreds of nanoseconds. In some cases, an apical surface of one molecule of PagP interacted with an equatorial micelle surrounding another molecule of PagP. In other cases, the apical surfaces of two molecules of PagP simultaneously bound a neat detergent micelle. In these ways, detergents mediated the non-specific aggregation of folded PagP. These simulation results are consistent with dynamic light scattering experiments, which show that, at detergent concentrations ≥600 mM, PagP induces the formation of large scattering species that are likely to contain many copies of the PagP protein. Together, these simulation and experimental results point to a potentially generic mechanism of detergent-mediated protein aggregation. PMID:23466535

  8. Self-Templated Nucleation in Peptide and Protein Aggregation

    NASA Astrophysics Data System (ADS)

    Auer, Stefan; Dobson, Christopher M.; Vendruscolo, Michele; Maritan, Amos

    2008-12-01

    Peptides and proteins exhibit a common tendency to assemble into highly ordered fibrillar aggregates, whose formation proceeds in a nucleation-dependent manner that is often preceded by the formation of oligomeric assemblies. This process has received much attention because disordered oligomeric aggregates have been associated with neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease. Here we describe a self-templated nucleation mechanism that determines the transition between the initial condensation of polypeptide chains into disordered assemblies and their reordering into fibrillar structures. The results that we present show that at the molecular level this transition is due to the ability of polypeptide chains to reorder within oligomers into fibrillar assemblies whose surfaces act as templates that stabilize the disordered assemblies.

  9. DURABILITY EVALUATION AND PRODUCTION OF MANUFACTURED AGGREGATES FROM COAL COMBUSTION BY-PRODUCTS

    SciTech Connect

    M. M. Wu

    2005-02-01

    Under the cooperative agreement with DOE, the Research and Development Department of CONSOL Energy (CONSOL R&D), teamed with Universal Aggregates, LLC, to conduct a systematic study of the durability of aggregates manufactured using a variety of flue gas desulfurization (FGD), fluidized-bed combustion (FBC) and fly ash specimens with different chemical and physical properties and under different freeze/thaw, wet/dry and long-term natural weathering conditions. The objectives of the study are to establish the relationships among the durability and characteristics of FGD material, FBC ash and fly ash, and to identify the causes of durability problems, and, ultimately, to increase the utilization of FGD material, FBC ash and fly ash as a construction material. Manufactured aggregates made from FGD material, FBC ash and fly ash, and products made from those manufactured aggregates were used in the study. The project is divided into the following activities: sample collection and characterization; characterization and preparation of manufactured aggregates; determination of durability characteristics of manufactured aggregates; preparation and determination of durability characteristics of manufactured aggregate products; and data evaluation and reporting.

  10. Lysozyme-mediated aggregation and lysis of the periodontal microorganism Capnocytophaga gingivalis 2010.

    PubMed

    Iacono, V J; Zove, S M; Grossbard, B L; Pollock, J J; Fine, D H; Greene, L S

    1985-02-01

    The ability of lysozyme to aggregate and lyse the gram-negative capnophilic periodontal microorganism Capnocytophaga gingivalis 2010 was monitored optically at 540 nm. Both hen egg white and chromatographically purified human lysozymes had significant but similar aggregation potentials for both logarithmic- and stationary-phase bacteria. In general, an increase in enzyme concentration resulted in a graded increase in both the initial and maximum changes in turbidity which occurred during the reaction period. The greatest change in turbidity occurred within the initial minutes of interaction of lysozyme and the cells, and the extent of aggregation paralleled a rapid depletion of lysozyme by the suspensions during the first minute of its incubation with the bacteria. Interestingly, the muramidase inhibitors N-acetyl-D-glucosamine and histamine did not block aggregation, whereas maleylation of lysozyme completely inhibited its aggregating ability. Demaleylation, however, restored aggregation activity comparable to the native enzyme, indicating that maleylated lysozyme retained its integrity and that aggregation was primarily dependent on charge. The addition of up to physiological concentrations of NaHCO3 and NaCl to cell aggregates resulted in varying degrees of deaggregation and lysis. Surprisingly, ultrastructural analysis of lysozyme-treated cells revealed morphological changes with or without the addition of salt. Damage appeared to occur at the blunted polar end of the cells where there was a large spherical outpouching bordered by a damaged cell envelope. Damaged cells uniformly contained dense granular cytoplasmic debris. In effect, the cationic enzyme lysed C. gingivalis 2010, which was not apparent in the spectrophotometric assay. The paradoxical finding that during bacterial aggregation there was lysis may be of significance to the further elucidation of lysozyme's antibacterial role in the gingival sulcus. PMID:3967924

  11. Protein structural and surface water rearrangement constitute major events in the earliest aggregation stages of tau

    PubMed Central

    Pavlova, Anna; Cheng, Chi-Yuan; Kinnebrew, Maia; Lew, John; Dahlquist, Frederick W.; Han, Songi

    2016-01-01

    Protein aggregation plays a critical role in the pathogenesis of neurodegenerative diseases, and the mechanism of its progression is poorly understood. Here, we examine the structural and dynamic characteristics of transiently evolving protein aggregates under ambient conditions by directly probing protein surface water diffusivity, local protein segment dynamics, and interprotein packing as a function of aggregation time, along the third repeat domain and C terminus of Δtau187 spanning residues 255–441 of the longest isoform of human tau. These measurements were achieved with a set of highly sensitive magnetic resonance tools that rely on site-specific electron spin labeling of Δtau187. Within minutes of initiated aggregation, the majority of Δtau187 that is initially homogeneously hydrated undergoes structural transformations to form partially structured aggregation intermediates. This is reflected in the dispersion of surface water dynamics that is distinct around the third repeat domain, found to be embedded in an intertau interface, from that of the solvent-exposed C terminus. Over the course of hours and in a rate-limiting process, a majority of these aggregation intermediates proceed to convert into stable β-sheet structured species and maintain their stacking order without exchanging their subunits. The population of β-sheet structured species is >5% within 5 min of aggregation and gradually grows to 50–70% within the early stages of fibril formation, while they mostly anneal block-wisely to form elongated fibrils. Our findings suggest that the formation of dynamic aggregation intermediates constitutes a major event occurring in the earliest stages of tau aggregation that precedes, and likely facilitates, fibril formation and growth. PMID:26712030

  12. Beam-induced graphitic carbon cage transformation from sumanene aggregates

    SciTech Connect

    Fujita, Jun-ichi Tachi, Masashi; Murakami, Katsuhisa; Sakurai, Hidehiro; Morita, Yuki; Higashibayashi, Shuhei; Takeguchi, Masaki

    2014-01-27

    We found that electron-beam irradiation of sumanene aggregates strongly enhanced their transformation into a graphitic carbon cage, having a diameter of about 20 nm. The threshold electron dose was about 32 mC/cm{sup 2} at 200 keV, but the transformation is still induced at 20 keV. The transformation sequence suggested that the cage was constructed accompanied by the dynamical movement of the transiently linked sumanene molecules in order to pile up inside the shell. Thus, bond excitation in the sumanene molecules rather than a knock-on of carbon atoms seems to be the main cause of the cage transformation.

  13. Orbital construction demonstration study

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A conceptual design and program plan for an Orbital Construction Demonstration Article (OCDA) was developed that can be used for evaluating and establishing practical large structural assembly operations. A flight plan for initial placement and continued utility is presented as a basic for an entirely new shuttle payload line-item having great future potential benefit for space applications. The OCDA is a three-axis stabilized platform in low-earth orbit with many structural nodals for mounting large construction and fabrication equipments. This equipment would be used to explore methods for constructing the large structures for future missions. The OCDA would be supported at regular intervals by the shuttle. Construction experiments and consumables resupply are performed during shuttle visit periods. A 250 kw solar array provides sufficient power to support the shuttle while attached to the OCDA and to run construction experiments at the same time. Wide band communications with a Telemetry and Data Relay Satellite compatible high gain antenna can be used between shuttle revisits to perform remote controlled, TV assisted construction experiments.

  14. Responsive Microgrooves for Formation of Harvestable Tissue Constructs

    PubMed Central

    Tekin, Halil; Ozaydin-Ince, Gozde; Tsinman, Tonia; Gleason, Karen K.; Langer, Robert; Khademhosseini, Ali; Demirel, Melik C.

    2011-01-01

    Given its biocompatibility, elasticity and gas permeability, poly(dimethylsiloxane) (PDMS) is widely used to fabricate microgrooves and microfluidic devices for three dimensional (3D) cell culture studies. However, conformal coating of complex PDMS devices prepared by standard microfabrication techniques with desired chemical functionality is challenging. This study describes the conformal coating of PDMS microgrooves with Poly(N-isopropylacrylamide) (PNIPAAm) by using initiated chemical vapor deposition (iCVD). These microgrooves guided the formation of tissue constructs from NIH-3T3 fibroblasts that could be retrieved by the temperature dependent swelling property and hydrophilicity change of the PNIPAAm. The thickness of swollen PNIPAAm films at 24 °C was approximately three times greater than at 37 °C. Furthermore, PNIPAAm coated microgroove surfaces exhibit increased hydrophilicity at 24 °C (contact angle θ = 30° ± 2) compared to 37 °C (θ = 50° ± 1). Thus PNIPAAm film on the microgrooves exhibits responsive swelling with higher hydrophilicity at room temperature which could be used to retrieve tissue constructs. The resulting tissue constructs were the same size as the grooves and could be used as modules in tissue fabrication. Given its ability to form and retrieve cell aggregates and its integration with standard microfabrication, PNIPAAm coated PDMS templates may become useful for 3D cell culture applications in tissue engineering and drug discovery. PMID:21449596

  15. Experimental Studies on the Aggregation Properties of Dust in Planet-Forming Regions

    NASA Astrophysics Data System (ADS)

    Heißelmann, D.; Blum, J.; Fraser, H. J.

    2007-08-01

    To investigate the initial stage of planet formation, we built a setup for collision experiments with millimeter-sized, highly porous and well characterized dust aggregates. The experiments, which were successfully conducted at ambient temperature during ESA's 45th Parabolic Flight Campaign, are the first in a series of at least three parabolic flight campaigns. The recent experiment probed the sticking and collision behavior of dust aggregates (composed of 1.5 μm-sized monodisperse SiO2 grains) from which planetesimals and cometary nuclei are considered to have formed. In the parabolic flights, pairs of fragile dust aggregates were collided under microgravity conditions at relative velocities between 25 cm s-1 and 40 cm s-1 using a set of pistons driven at constant acceleration. Additionally, fragile aggregates were impacted on a dusty target screen, simulating protoplanetary collisions with larger bodies. The collision events happened at random impact angle and were recorded by a high-speed, high-resolution digital camera. The majority of both the particle-target and aggregate-aggregate collisions showed a quasi-elastic rebounding behavior. Whereas 10% of the particle-target collisions resulted in sticking (of sub-millimeter-sized fragments only), the other key effect in 10% of the aggregate-aggregate collisions was fragmentation. The measured coefficient of restitution for the bouncing collisions indicates that the residual translational energy is 5% of the primal energy of the aggregates' motion for central collisions and increases with increasing impact parameter. The next parabolic flight campaign will be conducted during July 2007.We will repeat previous experiments at low temperatures (140 - 220K) simulating the conditions at 1.5 - 5AU in the solar nebula. Should the experiments be successful, first results on the temperature dependence of the collision behavior of dust aggregates will be presented.

  16. SCB initiator

    DOEpatents

    Bickes, Jr., Robert W.; Renlund, Anita M.; Stanton, Philip L.

    1994-01-01

    A detonator for high explosives initiated by mechanical impact includes a cylindrical barrel, a layer of flyer material mechanically covering the barrel at one end, and a semiconductor bridge ignitor including a pair of electrically conductive pads connected by a semiconductor bridge. The bridge is in operational contact with the layer, whereby ignition of said bridge forces a portion of the layer through the barrel to detonate the explosive. Input means are provided for igniting the semiconductor bridge ignitor.

  17. SCB initiator

    DOEpatents

    Bickes Jr., Robert W.; Renlund, Anita M.; Stanton, Philip L.

    1994-11-01

    A detonator for high explosives initiated by mechanical impact includes a cylindrical barrel, a layer of flyer material mechanically covering the barrel at one end, and a semiconductor bridge ignitor including a pair of electrically conductive pads connected by a semiconductor bridge. The bridge is in operational contact with the layer, whereby ignition of said bridge forces a portion of the layer through the barrel to detonate the explosive. Input means are provided for igniting the semiconductor bridge ignitor.

  18. Inhibition of Rho-Associated Protein Kinase Increases the Angiogenic Potential of Mesenchymal Stem Cell Aggregates via Paracrine Effects.

    PubMed

    Hong, Soyoung; Lee, Jae Yeon; Hwang, Changmo; Shin, Jennifer H; Park, Yongdoo

    2016-02-01

    The aggregation of multiple cells, such as mesenchymal condensation, is an important biological process in skeletal muscle development, osteogenesis, and adipogenesis. Due to limited in vivo study model systems, a simple and effective in vitro three-dimensional (3D) aggregation system is required to study the mechanisms of multicellular aggregation and its applications. We first generated controlled mesenchymal stem cell (MSC) aggregates using a bioprinting technique to monitor their aggregation and sprouting. We induced the angiogenic potential of the MSCs through chemical inhibition of the Rho/Rho-associated protein kinase (ROCK) pathway, which led to hairy sprouting in the aggregates. The angiogenic potential of this 3D construct was then tested by subcutaneously implanting the Matrigel with 3D MSC aggregates in a rat. Treatment of 3D MSCs with the ROCK inhibitor, Y27632, increased their angiogenic activity in vivo. The gene expressions and histological staining indicated that angiogenesis and neovascularization were mainly regulated by the paracrine factors secreted from human 3D MSC constructs. Our results demonstrate the enhancement of the angiogenic potential of the MSC constructs through the secretion of vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) by the inhibition of the Rho/ROCK pathway. PMID:26592750

  19. Impact of Particle Aggregation on Nanoparticle Reactivity

    NASA Astrophysics Data System (ADS)

    Jassby, David

    2011-12-01

    The prevalence of nanoparticles in the environment is expected to grow in the coming years due to their increasing pervasiveness in consumer and industrial applications. Once released into the environment, nanoparticles encounter conditions of pH, salinity, UV light, and other solution conditions that may alter their surface characteristics and lead to aggregation. The unique properties that make nanoparticles desirable are a direct consequence of their size and increased surface area. Therefore, it is critical to recognize how aggregation alters the reactive properties of nanomaterials, if we wish to understand how these properties are going to behave once released into the environment. The size and structure of nanoparticle aggregates depend on surrounding conditions, including hydrodynamic ones. Depending on these conditions, aggregates can be large or small, tightly packed or loosely bound. Characterizing and measuring these changes to aggregate morphology is important to understanding the impact of aggregation on nanoparticle reactive properties. Examples of decreased reactivity due to aggregation include the case where tightly packed aggregates have fewer available surface sites compared to loosely packed ones; also, photocatalytic particles embedded in the center of large aggregates will experience less light when compared to particles embedded in small aggregates. However, aggregation also results in an increase in solid-solid interfaces between nanoparticles. This can result in increased energy transfer between neighboring particles, surface passivation, and altered surface tension. These phenomena can lead to an increase in reactivity. The goal of this thesis is to examine the impacts of aggregation on the reactivity of a select group of nanomaterials. Additionally, we examined how aggregation impacts the removal efficiency of fullerene nanoparticles using membrane filtration. The materials we selected to study include ZnS---a metal chalcogenide

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    Changes in soil utilization significantly affect aggregate stability and aggregate-associated soil organic carbon (SOC). A field investigation and indoor analysis were conducted in order to study the soil aggregate stability and organic carbon distribution in the water-stable aggregates (WSA) of the bare land (BL), grassland (GL), shrubland (SL), and woodland (WL) in a typical karst gorge region. The results indicated that the BL, GL, SL, and WL were dominated by particles with sizes > 5 mm under dry sieving treatment, and that the soil aggregate contents of various sizes decreased as the particle size decreased. In addition, the BL, GL, SL, and WL were predominantly comprised of WSA < 0.25 mm under wet sieving treatment, and that the WSA contents initially increased, then decreased, and then increased again as the particle size decreased. Furthermore, at a soil depth of 0-60 cm, the mean weight diameter (MWD), geometrical mean diameter (GMD), and fractal dimensions (D) of the dry aggregates and water-stable aggregates in the different types of land were ranked, in descending order, as WL > GL > SL > BL. The contents of WSA > 0.25 mm, MWD and GMD increased significantly, in that order, and the percentage of aggregate destruction (PAD) and fractal dimensions decreased significantly as the soil aggregate stability improved. The results of this study indicated that, as the SOC contents increased after vegetation restoration, the average SOC content of WL was 2.35, 1.37, and 1.26 times greater than that in the BL, GL, and SL, respectively. The total SOC and SOC associated in WSA of various sizes were the highest at a soil depth of 0-20 cm. In addition, the SOC contents of the WSA increased as the soil aggregate sizes decreased. The SOC contents of the WSA < 0.25 mm were highest except in the bare land, and the SOC contents of the aggregates < 0.25 mm, which ranged from 18.85 to 41.08 %, comprised the majority of the total aggregate SOC contents. The woodland and

  1. Growth of volcanic ash aggregates in the presence of liquid water and ice: an experimental approach

    NASA Astrophysics Data System (ADS)

    Van Eaton, Alexa R.; Muirhead, James D.; Wilson, Colin J. N.; Cimarelli, Corrado

    2012-11-01

    Key processes influencing the aggregation of volcanic ash and hydrometeors are examined with an experimental method employing vibratory pan aggregation. Mechanisms of aggregation in the presence of hail and ice pellets, liquid water (≤30 wt%), and mixed water phases are investigated at temperatures of 18 and -20 °C. The experimentally generated aggregates, examined in hand sample, impregnated thin sections, SEM imagery, and X-ray microtomography, closely match natural examples from phreatomagmatic phases of the 27 ka Oruanui and 2010 Eyjafjallajökull eruptions. Laser diffraction particle size analysis of parent ash and aggregates is also used to calculate the first experimentally derived aggregation coefficients that account for changing liquid water contents and subzero temperatures. These indicate that dry conditions (<5-10 wt% liquid) promote strongly size selective collection of sub-63 μm particles into aggregates (given by aggregation coefficients >1). In contrast, liquid-saturated conditions (>15-20 wt% liquid) promote less size selective processes. Crystalline ice was also capable of preferentially selecting volcanic ash <31 μm under liquid-free conditions in a two-stage process of electrostatic attraction followed by ice sintering. However, this did not accumulate more than a monolayer of ash at the ice surface. These quantitative relationships may be used to predict the timescales and characteristics of aggregation, such as aggregate size spectra, densities, and constituent particle size characteristics, when the initial size distribution and water content of a volcanic cloud are known. The presence of an irregularly shaped, millimeter-scale vacuole at the center of natural aggregates was also replicated during interaction of ash and melting ice pellets, followed by sublimation. Fine-grained rims were formed by adding moist aggregates to a dry mixture of sub-31 μm ash, which adhered by electrostatic forces and sparse liquid bridges. From this, we

  2. Compaction, Fusion, and Functional Activation of Three-Dimensional Human Mesenchymal Stem Cell Aggregate

    PubMed Central

    Tsai, Ang-Chen; Liu, Yijun; Yuan, Xuegang

    2015-01-01

    Human mesenchymal stem cells (hMSCs) are primary candidates in cell therapy and tissue engineering and are being tested in clinical trials for a wide range of diseases. Originally isolated and expanded as plastic adherent cells, hMSCs have intriguing properties of in vitro self-assembly into three-dimensional (3D) aggregates that improve a range of biological properties, including multilineage potential, secretion of therapeutic factors, and resistance against ischemic condition. While cell–cell contacts and cell–extracellular matrix interactions mediate 3D cell aggregation, the adaptive changes of hMSC cytoskeleton during self-assembly and associated metabolic reconfiguration may also influence aggregate properties and functional activation. In this study, we investigated the role of actin in regulating 3D hMSC aggregate compaction, fusion, spreading and functional activation. Individual hMSC aggregates with controlled initial cell number were formed by seeding a known number of hMSCs (500, 2000, and 5000 cells/well) in multi-well plates of an ultra-low adherent surface to form multicellular aggregates in individual wells. To assess the influence of actin-mediated contractility on hMSC aggregation and properties, actin modulators, including cytochalasin D (cytoD), nocodazole, lysophosphatidic acid (LPA), and Y-27632, were added at different stages of aggregation and their impacts on hMSC aggregate compaction and apoptosis were monitored. The results suggest that actin-mediated contractility influences hMSC aggregation, compaction, fusion, and spreading on adherent surface. Formation of multi-cellular aggregates significantly upregulated caspase 3/7 expression, expression of C-X-C chemokine receptor type 4 (CXCR-4), cell migration, secretion of prostaglandin E2 (PGE-2) and interleukin 6 (IL-6), and resistance to in vitro ischemic stress. The functional enhancement, however, is dependent on caspase activation, because treatment with Q-VD-OPh, a pan

  3. Inhibition of platelet-aggregating activity in thrombotic thrombocytopenic purpura plasma by normal adult immunoglobulin G.

    PubMed Central

    Lian, E C; Mui, P T; Siddiqui, F A; Chiu, A Y; Chiu, L L

    1984-01-01

    Plasma from patients with thrombotic thrombocytopenic purpura (TTP) caused the aggregation of autologous and homologous platelets, and effect which was inhibited by normal plasma. IgG purified from seven normal adults at a concentration of 0.7 mg/ml completely inhibited the platelet aggregation induced by plasma obtained from two TTP patients with active disease. The inhibition of platelet aggregation by human adult IgG was concentration dependent, and the inhibitory activity of human IgG was neutralized by rabbit antihuman IgG. Fab fragments inhibited the TTP plasma-induced platelet aggregation as well as intact IgG, whereas Fc fragments had no effect. Platelet aggregation caused by ADP, collagen, epinephrine, or thrombin was not affected by purified human IgG. The prior incubation of IgG with TTP plasma caused a significantly greater reduction of platelet aggregation by TTP plasma than that of IgG and platelet suspension, suggesting that the IgG inhibits TTP plasma-induced platelet aggregation through direct interaction with platelet aggregating factor in TTP plasma. IgG obtained initially from five infants and young children under the age of 4 yr did not possess any inhibitory activity. When one of the children reached 3 yr of age, his IgG inhibited the aggregation induced by one TTP plasma, but not that caused by another plasma. The IgG procured from the same boy at 4 yr of age inhibited the aggregation induced by both TTP plasmas. The IgG purified from the TTP plasma during active disease failed to inhibit the aggregation caused by the same plasma. After recovery, however, the IgG effectively inhibited aggregation. These observations suggest that platelet-aggregating factors present in the TTP plasma are heterogeneous in nature and that the IgG present in the normal adult plasma, which inhibits the TTP plasma-induced platelet aggregation, may be partially responsible for the success of plasma infusion therapy in TTP. Images PMID:6538207

  4. Aqueous Self-Sorting in Extended Supramolecular Aggregates

    PubMed Central

    Rest, Christina; Mayoral, María José; Fernández, Gustavo

    2013-01-01

    Self-organization and self-sorting processes are responsible for the regulation and control of the vast majority of biological processes that eventually sustain life on our planet. Attempts to unveil the complexity of these systems have been devoted to the investigation of the binding processes between artificial molecules, complexes or aggregates within multicomponent mixtures, which has facilitated the emergence of the field of self-sorting in the last decade. Since, artificial systems involving discrete supramolecular structures, extended supramolecular aggregates or gel-phase materials in organic solvents or—to a lesser extent—in water have been investigated. In this review, we have collected diverse strategies employed in recent years to construct extended supramolecular aggregates in water upon self-sorting of small synthetic molecules. We have made particular emphasis on co-assembly processes in binary mixtures leading to supramolecular structures of remarkable complexity and the influence of different external variables such as solvent and concentration to direct recognition or discrimination processes between these species. The comprehension of such recognition phenomena will be crucial for the organization and evolution of complex matter. PMID:23344056

  5. Use of recycled fine aggregate in concretes with durable requirements.

    PubMed

    Zega, Claudio Javier; Di Maio, Angel Antonio

    2011-11-01

    The use of construction waste materials as aggregates for concrete production is highly attractive compared to the use of non-renewable natural resources, promoting environmental protection and allowing the development of a new raw material. Several countries have recommendations for the use of recycled coarse aggregate in structural concrete, whereas the use of the fine fraction is limited because it may produce significant changes in some properties of concrete. However, during the last decade the use of recycled fine aggregates (RFA) has achieved a great international interest, mainly because of economic implications related to the shortage of natural sands suitable for the production of concrete, besides to allow an integral use of this type of waste. In this study, the durable behaviour of structural concretes made with different percentage of RFA (0%, 20%, and 30%) is evaluated. Different properties related to the durability of concretes such as absorption, sorptivity, water penetration under pressure, and carbonation are determined. In addition, the results of compressive strength, static modulus of elasticity and drying shrinkage are presented. The obtained results indicate that the recycled concretes have a suitable resistant and durable behaviour, according to the limits indicated by different international codes for structural concrete. PMID:21775123

  6. Worldwide construction

    SciTech Connect

    Radler, M.

    1998-04-13

    Tables list major construction projects for refineries, petrochemical plants, sulfur plants, natural gas processing plants, and gas and oil pipelines. Data are compiled by country, company name, project type, added capacity, status of the project, expected completion date, contractor and contract type. Gas processes include LPG recovery, cryogenic separation, turboexpanders, LNG, liquefaction, desulfurization, NGL recovery, dehydration, hydrogen plants, and fractionators.

  7. Metal Construction

    NASA Technical Reports Server (NTRS)

    Verduzio, Rodolfo

    1922-01-01

    The future development of aerial navigation is closely connected with the condition of obtaining airplanes of great stability and sufficient strength. Different construction materials such as wood, aluminum, iron, and alloys are examined to determine which materials or combination of materials provides a greater coefficient of safety.

  8. Constructive Criticism.

    ERIC Educational Resources Information Center

    Lieberfeld, Lawrence

    1982-01-01

    Many crucial questions need to be answered before a college embarks on a construction project and makes a substantial financial commitment. Computer modeling techniques can be used to make even complex project feasibility analyses. Available from Peat, Marwick, Mitchell & Co., 345 Park Avenue, New York, NY 10154. (MSE)

  9. Abstract Constructions.

    ERIC Educational Resources Information Center

    Pietropola, Anne

    1998-01-01

    Describes a lesson designed to culminate a year of eighth-grade art classes in which students explore elements of design and space by creating 3-D abstract constructions. Outlines the process of using foam board and markers to create various shapes and optical effects. (DSK)

  10. 24 CFR 58.32 - Project aggregation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... other activities and actions. (See 40 CFR 1508.25(a)). (2) Consider reasonable alternative courses of... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Project aggregation. 58.32 Section... Environmental Review Process: Documentation, Range of Activities, Project Aggregation and Classification §...

  11. 24 CFR 58.32 - Project aggregation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... other activities and actions. (See 40 CFR 1508.25(a)). (2) Consider reasonable alternative courses of... 24 Housing and Urban Development 1 2011-04-01 2011-04-01 false Project aggregation. 58.32 Section... Environmental Review Process: Documentation, Range of Activities, Project Aggregation and Classification §...

  12. 24 CFR 58.32 - Project aggregation.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... other activities and actions. (See 40 CFR 1508.25(a)). (2) Consider reasonable alternative courses of... 24 Housing and Urban Development 1 2014-04-01 2014-04-01 false Project aggregation. 58.32 Section... Environmental Review Process: Documentation, Range of Activities, Project Aggregation and Classification §...

  13. 24 CFR 58.32 - Project aggregation.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... other activities and actions. (See 40 CFR 1508.25(a)). (2) Consider reasonable alternative courses of... 24 Housing and Urban Development 1 2012-04-01 2012-04-01 false Project aggregation. 58.32 Section... Environmental Review Process: Documentation, Range of Activities, Project Aggregation and Classification §...

  14. 7 CFR 1.6 - Aggregating requests.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 1 2010-01-01 2010-01-01 false Aggregating requests. 1.6 Section 1.6 Agriculture Office of the Secretary of Agriculture ADMINISTRATIVE REGULATIONS Official Records § 1.6 Aggregating requests. When an agency reasonably believes that a requester, or a group of requesters acting in...

  15. 7 CFR 1.6 - Aggregating requests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 1 2013-01-01 2013-01-01 false Aggregating requests. 1.6 Section 1.6 Agriculture Office of the Secretary of Agriculture ADMINISTRATIVE REGULATIONS Official Records § 1.6 Aggregating requests. When an agency reasonably believes that a requester, or a group of requesters acting in...

  16. Streaming instability of aggregating slime mold amoebae

    NASA Astrophysics Data System (ADS)

    Levine, Herbert; Reynolds, William

    1991-05-01

    We propose a new model of aggregation in the cellular slime mold D. Discoideum. Our approach couples the excitable signaling system to amoeba chemotaxis; the resultant system of equations is tractable to analytical and numerical approaches. Using our model, we derive the existence of a streaming instability for the concentric target aggregation pattern.

  17. Biomass round bales infield aggregation logistic scenarios

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biomass bales often need to be aggregated (collected into groups and transported) to a field-edge stack for temporary storage for feedlots or processing facilities. Aggregating the bales with the least total distance involved is a goal of producers and bale handlers. Several logistics scenarios for ...

  18. 24 CFR 50.21 - Aggregation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Aggregation. 50.21 Section 50.21 Housing and Urban Development Office of the Secretary, Department of Housing and Urban Development... Aggregation. Activities which are geographically related and are logical parts of a composite of...

  19. 42 CFR 411.106 - Aggregation rules.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 2 2010-10-01 2010-10-01 false Aggregation rules. 411.106 Section 411.106 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICARE PROGRAM... Under Group Health Plans: General Provisions § 411.106 Aggregation rules. The following rules apply...

  20. Teaching Aggregate Demand and Supply Models

    ERIC Educational Resources Information Center

    Wells, Graeme

    2010-01-01

    The author analyzes the inflation-targeting model that underlies recent textbook expositions of the aggregate demand-aggregate supply approach used in introductory courses in macroeconomics. He shows how numerical simulations of a model with inflation inertia can be used as a tool to help students understand adjustments in response to demand and…

  1. Utilization of power plant bottom ash as aggregates in fiber-reinforced cellular concrete.

    PubMed

    Lee, H K; Kim, H K; Hwang, E A

    2010-02-01

    Recently, millions tons of bottom ash wastes from thermoelectric power plants have been disposed of in landfills and coastal areas, regardless of its recycling possibility in construction fields. Fiber-reinforced cellular concrete (FRCC) of low density and of high strength may be attainable through the addition of bottom ash due to its relatively high strength. This paper focuses on evaluating the feasibility of utilizing bottom ash of thermoelectric power plant wastes as aggregates in FRCC. The flow characteristics of cement mortar with bottom ash aggregates and the effect of aggregate type and size on concrete density and compressive strength were investigated. In addition, the effects of adding steel and polypropylene fibers for improving the strength of concrete were also investigated. The results from this study suggest that bottom ash can be applied as a construction material which may not only improve the compressive strength of FRCC significantly but also reduce problems related to bottom ash waste. PMID:19910181

  2. The implication of input data aggregation on upscaling of soil organic carbon changes - a case study with CENTURY model

    NASA Astrophysics Data System (ADS)

    Grosz, Balázs; Dechow, Rene; Ewert, Frank; Gaiser, Thomas; Hoffmann, Holger; Zhao, Gang

    2015-04-01

    Soil organic carbon models which have been extensively tested and calibrated for field scale applications in the past are now increasingly used for larger scale estimations. In large scale applications, recent data availability and limited computational capacity requires adequate aggregation of the model input and model initialization. Method and level of driver aggregation in up scaling studies are sources of uncertainty and might bias the aggregated model outcome. The suitability of up scaled model results using aggregated driving data depends on both the sensitivity of the model on these model drivers and the scale of interest describing the desired aggregation level of the model output. The implications of driver aggregation schemes have been examined in a scaling exercise within the joint research project MACSUR (Modelling European Agriculture with Climate Change for Food Security). In this study, meteorological driving data and data on soil properties on several aggregation levels have been used to calculate the soil organic carbon change of agricultural land use in North Rhine-Westphalia with the bio-geo-chemical model CENTURY. The model couples processes determining crop growth, soil organic matter and nutrient dynamics. In the aggregation study meteorological data and soil properties from a NUTS 2 region in Germany (North Rhine-Westphalia) from 1980 to 2010 were prepared on 6 aggregation levels corresponding to grid cells in 1x1km, 10x10km, 25x25km, 50x50km, 100x100km resolution and spatial means on federate state level. Upscaling exercises have been conducted by combining several aggregation levels of soil properties and weather data. Results show that the aggregation of meteorological data has little impact on modeled soil organic carbon changes although model uncertainty increases slightly with decreasing scale of interest from NUTS 2 (federal state) level to smaller grid cell size. Contrary, the aggregation of soil properties result in high uncertainty

  3. 5. VIEW SHOWING HORSE MESA DAM UNDER CONSTRUCTION. THREE PENSTOCKS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. VIEW SHOWING HORSE MESA DAM UNDER CONSTRUCTION. THREE PENSTOCKS ARE AT CENTER AND CONCRETE TOWER LINES. AGGREGATE OPERATION IS VISIBLE ABOVE CONSTRUCTION SITE July 22, 1926 - Horse Mesa Dam, Salt River, 65 miles East of Phoenix, Phoenix, Maricopa County, AZ

  4. Therapeutic Protein Aggregation: Mechanisms, Design, and Control

    PubMed Central

    Roberts, Christopher J.

    2014-01-01

    While it is well known that proteins are only marginally stable in their folded states, it is often less well appreciated that most proteins are inherently aggregation-prone in their unfolded or partially unfolded states, and the resulting aggregates can be extremely stable and long-lived. For therapeutic proteins, aggregates are a significant risk factor for deleterious immune responses in patients, and can form via a variety of mechanisms. Controlling aggregation using a mechanistic approach may allow improved design of therapeutic protein stability, as a complement to existing design strategies that target desired protein structures and function. Recent results highlight the importance of balancing protein environment with the inherent aggregation propensities of polypeptide chains. PMID:24908382

  5. Formation of Tethers from Spreading Cellular Aggregates.

    PubMed

    Beaune, Grégory; Winnik, Françoise M; Brochard-Wyart, Françoise

    2015-12-01

    Membrane tubes are commonly extruded from cells and vesicles when a point-like force is applied on the membrane. We report here the unexpected formation of membrane tubes from lymph node cancer prostate (LNCaP) cell aggregates in the absence of external applied forces. The spreading of LNCaP aggregates deposited on adhesive glass substrates coated with fibronectin is very limited because cell-cell adhesion is stronger than cell-substrate adhesion. Some cells on the aggregate periphery are very motile and try to escape from the aggregate, leading to the formation of membrane tubes. Tethered networks and exchange of cargos between cells were observed as well. Growth of the tubes is followed by either tube retraction or tube rupture. Hence, even very cohesive cells are successful in escaping aggregates, which may lead to epithelial mesenchymal transition and tumor metastasis. We interpret the dynamics of formation and retraction of tubes in the framework of membrane mechanics. PMID:26509898

  6. Aggregation of sodium alkylbenzenesulfonates in aqueous solution

    SciTech Connect

    Magid, L.J.; Shaver, R.J.; Gulari, E.; Bedwell, B.; Alkhafaji, S.

    1981-01-01

    The surfactant 6 phenyl C/sub 12/SNa forms small spherical micelles in aqueous solution, having an aggregation number of 20 to 30 and a fractional charge of 0.45. These micelles are hydrated to the extent of approximately 18 moles H/sub 2/O per moles of surfactant. A second larger aggregate is also present in 6 phenyl C/sub 12/SNa solutions; its importance increases with solution age. Addition of NaCl causes both aggregates to apparently increase modestly in size. The surfactant 8 phenyl C/sub 16/SNa also contains both aggregates in its solutions; the larger one is relatively more important here. The larger aggregate does not correspond to dispersed bits of a liquid crystalline mesophase.

  7. Protein aggregates stimulate macropinocytosis facilitating their propagation.

    PubMed

    Yerbury, Justin J

    2016-03-01

    Temporal and spatial patterns of pathological changes such as loss of neurons and presence of pathological protein aggregates are characteristic of neurodegenerative diseases such as Amyotrophic Lateral Sclerosis, Frontotemporal Dementia, Alzheimer's disease and Parkinson's disease. These patterns are consistent with the propagation of protein misfolding and aggregation reminiscent of the prion diseases. There is a surge of evidence that suggests that large protein aggregates of a range of proteins are able to enter cells via macropinocytosis. Our recent work suggests that this process is activated by the binding of aggregates to the neuron cell surface. The current review considers the potential role of cell surface receptors in the triggering of macropinocytosis by protein aggregates and the possibility of utilizing macropinocytosis pathways as a therapeutic target. PMID:26963158

  8. Imbibition kinetics of spherical colloidal aggregates.

    PubMed

    Debacker, A; Makarchuk, S; Lootens, D; Hébraud, P

    2014-07-11

    The imbibition kinetics of a millimeter-sized aggregate of 300 nm diameter colloidal particles by a wetting pure solvent is studied. Three successive regimes are observed. First, the imbibition proceeds by compressing the air inside the aggregate. Next, the solvent stops when the pressure of the compressed air is equal to the excess of capillary pressure at the meniscus of the wetting solvent in the porous aggregate. The interface is pinned and the aggregate slowly degases up to the point where the pressure of the entrapped air stops decreasing and is controlled by the capillary pressure. Finally, the imbibition starts again at a constant excess of pressure, smaller than the capillary pressure but larger than the one of the atmosphere. This last stage leads to the complete infiltration of the aggregate. PMID:25062241

  9. [The equation for platelet aggregation rate].

    PubMed

    Vrzheshch, P V; Verkhusha, V V; Varfolomeev, S D

    1990-01-01

    A platelet aggregation model in shear flow taking into account the kinetics of intercellular fibrinogen bond formation limited by aggregated platelets rotation time was considered. For this consideration the average duration of platelets interaction in flow with shear rate value G is shown to be pi/4G. One fibrinogen bond is sufficient to form a solid aggregate between two platelets. The equation for single platelets disappearance rate concerned with intercellular fibrinogen bond formation, stochastic character of bond distribution in collided platelets and hydrodynamically controlled interaction time was obtained. The Hill's approximation for the obtained aggregation rate dependences was suggested and appropriate constants were determined. The qualitative criterion of platelets aggregating systems behavior was introduced. PMID:2245229

  10. Excited-state dynamics of astaxanthin aggregates

    NASA Astrophysics Data System (ADS)

    Fuciman, Marcel; Durchan, Milan; Šlouf, Václav; Keşan, Gürkan; Polívka, Tomáš

    2013-05-01

    Astaxanthin forms three types of aggregates in hydrated dimethyl sulfoxide (DMSO). In DMSO/water ratio of 1:1, a red-shifted J-aggregate with maximum at 570 nm is generated, while a ratio of 1:9 produces blue-shifted H-aggregates with peaks at 386 nm (H1) and 460 nm (H2). Monomeric astaxanthin in DMSO has an S1 lifetime of 5.3 ps, but a long-lived (33 ps) S∗ signal was also identified. Aggregation changes the S1 lifetimes to 17 ps (H1), 30 ps (H2), and 14 ps (J). Triplet state of astaxanthin, most likely generated via singlet homofission, was observed in H1 and H2 aggregates.

  11. NUMERICAL MODELING OF THE COAGULATION AND POROSITY EVOLUTION OF DUST AGGREGATES

    SciTech Connect

    Okuzumi, Satoshi; Sakagami, Masa-aki; Tanaka, Hidekazu

    2009-12-20

    Porosity evolution of dust aggregates is crucial in understanding dust evolution in protoplanetary disks. In this study, we present useful tools to study the coagulation and porosity evolution of dust aggregates. First, we present a new numerical method for simulating dust coagulation and porosity evolution as an extension of the conventional Smoluchowski equation. This method follows the evolution of the mean porosity for each aggregate mass simultaneously with the evolution of the mass distribution function. This method reproduces the results of previous Monte Carlo simulations with much less computational expense. Second, we propose a new collision model for porous dust aggregates on the basis of our N-body experiments on aggregate collisions. As the first step, we focus on 'hit-and-stick' collisions, which involve neither compression nor fragmentation of aggregates. We first obtain empirical data on porosity changes between the classical limits of ballistic cluster-cluster and particle-cluster aggregation. Using the data, we construct a recipe for the porosity change due to general hit-and-stick collisions as well as formulae for the aerodynamical and collisional cross sections. Our collision model is thus more realistic than a previous model of Ormel et al. based on the classical aggregation limits only. Simple coagulation simulations using the extended Smoluchowski method show that our collision model explains the fractal dimensions of porous aggregates observed in a full N-body simulation and a laboratory experiment. By contrast, similar simulations using the collision model of Ormel et al. result in much less porous aggregates, meaning that this model underestimates the porosity increase upon unequal-sized collisions. Besides, we discover that aggregates at the high-mass end of the distribution can have a considerably small aerodynamical cross section per unit mass compared with aggregates of lower masses. This occurs when aggregates drift under uniform

  12. Soil aggregate stability: comparison of field and laboratory data

    NASA Astrophysics Data System (ADS)

    Graf, Frank

    2014-05-01

    Eco-engineering first and foremost, aims at stabilising soil and slopes in order to protect humans and infrastructure from potential damages caused by soil failure, usually due to heavy rainstorms. Whereas the technical constructions are well-defined and their protective effects in general calculable, this is rarely the case for biological measures. Furthermore, unlike engineering structures which are immediately useable and operative after their completion, the effects of plants are developing as a function of time. Within this scope, soil aggregation processes play a decisive role in in the re-colonisation process and the re-establishing of a protective vegetation cover. The strength of soil aggregates is not only critical to the stability of slopes but plays a key role in ecosystem functioning in general as it affects water, gas and nutrient fluxes and storage influencing the activity and growth of living organisms. Not by chance, therefore, soil aggregate stability has been proposed as an indicator reflecting multiple aspects allowing extensive information on ecosystem status to be gathered in a relatively short time, in particular in respect of protecting slopes from erosion and shallow mass movements. Various methods and approaches have been used to quantify soil aggregate stability but the lack of standardisation complicates the comparison of different investigations. From this perspective we investigated soil samples from the field as well as samples artificially prepared in the laboratory using the same soil material and testing procedure. The field samples were collected at two sites in the landslide area of Dallenwil-Wirzweli in Central Switzerland, once in a gully recently affected by erosion and landslide processes bare of vegetation (control site) and once in a re-stabilised gully with 25 year old eco-engineering measures dominated by Alnus incana (re-vegetated site). The laboratory samples were prepared with the soil from the control site. Two

  13. Classification and Characterization of Therapeutic Antibody Aggregates

    PubMed Central

    Joubert, Marisa K.; Luo, Quanzhou; Nashed-Samuel, Yasser; Wypych, Jette; Narhi, Linda O.

    2011-01-01

    A host of diverse stress techniques was applied to a monoclonal antibody (IgG2) to yield protein particles with varying attributes and morphologies. Aggregated solutions were evaluated for percent aggregation, particle counts, size distribution, morphology, changes in secondary and tertiary structure, surface hydrophobicity, metal content, and reversibility. Chemical modifications were also identified in a separate report (Luo, Q., Joubert, M. K., Stevenson, R., Narhi, L. O., and Wypych, J. (2011) J. Biol. Chem. 286, 25134–25144). Aggregates were categorized into seven discrete classes, based on the traits described. Several additional molecules (from the IgG1 and IgG2 subtypes as well as intravenous IgG) were stressed and found to be defined with the same classification system. The mechanism of protein aggregation and the type of aggregate formed depends on the nature of the stress applied. Different IgG molecules appear to aggregate by a similar mechanism under the same applied stress. Aggregates created by harsh mechanical stress showed the largest number of subvisible particles, and the class generated by thermal stress displayed the largest number of visible particles. Most classes showed a disruption of the higher order structure, with the degree of disorder depending on the stress process. Particles in all classes (except thermal stress) were at least partially reversible upon dilution in pH 5 buffer. High copper content was detected in isolated metal-catalyzed aggregates, a stress previously shown to produce immunogenic aggregates. In conclusion, protein aggregates can be a very heterogeneous population, whose qualities are the result of the type of stress that was experienced. PMID:21454532

  14. Amoeboid olivine aggregates from CH carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Krot, Alexander N.; Park, Changkun; Nagashima, Kazuhide

    2014-08-01

    Amoeboid olivine aggregates (AOAs) in CH carbonaceous chondrites are texturally and mineralogically similar to those in other carbonaceous chondrite groups. They show no evidence for alteration and thermal metamorphism in an asteroidal setting and consist of nearly pure forsterite (Fa<3; in wt%, CaO = 0.1-0.8, Cr2O3 = 0.04-0.48; MnO < 0.5), anorthite, Al-diopside (in wt%, Al2O3 = 0.7-8.1; TiO2 < 1), Fe,Ni-metal, spinel, and, occasionally, low-Ca pyroxene (Fs1Wo2-3), and calcium-aluminum-rich inclusions (CAIs). The CAIs inside AOAs are composed of hibonite, grossite, melilite (Åk13-44), spinel, perovskite, Al,Ti-diopside (in wt%, Al2O3 up to 19.6; TiO2 up to 13.9), and anorthite. The CH AOAs, including CAIs within AOAs, have isotopically uniform 16O-rich compositions (average Δ17O = -23.4 ± 2.3‰, 2SD) and on a three-isotope oxygen diagram plot along ∼slope-1 line. The only exception is a low-Ca pyroxene-bearing AOA 1-103 that shows a range of Δ17O values, from -24‰ to -13‰. Melilite, grossite, and hibonite in four CAIs within AOAs show no evidence for radiogenic 26Mg excess (δ26Mg). In contrast, anorthite in five out of six AOAs measured has δ26Mg corresponding to the inferred initial 26Al/27Al ratio of (4.3 ± 0.7) × 10-5, (4.2 ± 0.6) × 10-5, (4.0 ± 0.3) × 10-5, (1.7 ± 0.2) × 10-5, and (3.0 ± 2.6) × 10-6. Anorthite in another AOA shows no resolvable δ26Mg excess; an upper limit on the initial 26Al/27Al ratio is 5 × 10-6. We infer that CH AOAs formed by gas-solid condensation and aggregation of the solar nebula condensates (forsterite and Fe,Ni-metal) mixed with the previously formed CAIs. Subsequently they experienced thermal annealing and possibly melting to a small degree in a 16O-rich gaseous reservoir during a brief epoch of CAI formation. The low-Ca pyroxene-bearing AOA 1-103 may have experienced incomplete melting and isotope exchange in an 16O-poor gaseous reservoir. The lack of resolvable δ26Mg excess in melilite, grossite, and

  15. Platelet-collagen adhesion enhances platelet aggregation induced by binding of VWF to platelets

    SciTech Connect

    Laduca, F.M.; Bell, W.R.; Bettigole, R.E. State Univ. of New York, Buffalo )

    1987-11-01

    Ristocetin-induced platelet aggregation (RIPA) was evaluated in the presence of platelet-collagen adhesion. RIPA of normal donor platelet-rich plasma (PRP) demonstrated a primary wave of aggregation mediated by the binding of von Willebrand factor (VWF) to platelets and a secondary aggregation wave, due to a platelet-release reaction, initiated by VWF-platelet binding and inhibitable by acetylsalicylic acid (ASA). An enhanced RIPA was observed in PRP samples to which collagen had been previously added. These subthreshold concentrations of collagen, which by themselves were insufficient to induce aggregation, caused measurable platelet-collagen adhesion. Subthreshold collagen did not cause microplatelet aggregation, platelet release of ({sup 3}H)serotonin, or alter the dose-responsive binding of {sup 125}I-labeled VWF to platelets, which occurred with increasing ristocetin concentrations. However, ASA inhibition of the platelet release reaction prevented collagen-enhanced RIPA. These results demonstrate that platelet-collagen adhesion altered the platelet-release reaction induced by the binding of VWF to platelets causing a platelet-release reaction at a level of VWF-platelet binding not normally initiating a secondary aggregation. These findings suggest that platelet-collagen adhesion enhances platelet function mediated by VWF.

  16. Electrochemical Growth of Ag Junctions and Diffusion Limited Aggregate (DLA) Fractal Simulation

    NASA Astrophysics Data System (ADS)

    Olson, Zak; Tuppan, Sam; Kim, Woo-Joong; Seattle University Team

    2015-03-01

    We attempt construction of a single atom connection between two copper wires. By applying a DC voltage across the wires when immersed in a silver nitrate solution, we deposit silver until a junction is formed. The deposited silver forms a fractal structure that can be simulated with a diffusion limited aggregation model.

  17. The fractal aggregation of asphaltenes.

    PubMed

    Hoepfner, Michael P; Fávero, Cláudio Vilas Bôas; Haji-Akbari, Nasim; Fogler, H Scott

    2013-07-16

    This paper discusses time-resolved small-angle neutron scattering results that were used to investigate asphaltene structure and stability with and without a precipitant added in both crude oil and model oil. A novel approach was used to isolate the scattering from asphaltenes that are insoluble and in the process of aggregating from those that are soluble. It was found that both soluble and insoluble asphaltenes form fractal clusters in crude oil and the fractal dimension of the insoluble asphaltene clusters is higher than that of the soluble clusters. Adding heptane also increases the size of soluble asphaltene clusters without modifying the fractal dimension. Understanding the process of insoluble asphaltenes forming fractals with higher fractal dimensions will potentially reveal the microscopic asphaltene destabilization mechanism (i.e., how a precipitant modifies asphaltene-asphaltene interactions). It was concluded that because of the polydisperse nature of asphaltenes, no well-defined asphaltene phase stability envelope exists and small amounts of asphaltenes precipitated even at dilute precipitant concentrations. Asphaltenes that are stable in a crude oil-precipitant mixture are dispersed on the nanometer length scale. An asphaltene precipitation mechanism is proposed that is consistent with the experimental findings. Additionally, it was found that the heptane-insoluble asphaltene fraction is the dominant source of small-angle scattering in crude oil and the previously unobtainable asphaltene solubility at low heptane concentrations was measured. PMID:23808932

  18. Anisotropic diffusion-limited aggregation.

    PubMed

    Popescu, M N; Hentschel, H G E; Family, F

    2004-06-01

    Using stochastic conformal mappings, we study the effects of anisotropic perturbations on diffusion-limited aggregation (DLA) in two dimensions. The harmonic measure of the growth probability for DLA can be conformally mapped onto a constant measure on a unit circle. Here we map m preferred directions for growth to a distribution on the unit circle, which is a periodic function with m peaks in [-pi,pi) such that the angular width sigma of the peak defines the "strength" of anisotropy kappa= sigma(-1) along any of the m chosen directions. The two parameters (m,kappa) map out a parameter space of perturbations that allows a continuous transition from DLA (for small enough kappa ) to m needlelike fingers as kappa--> infinity. We show that at fixed m the effective fractal dimension of the clusters D(m,kappa) obtained from mass-radius scaling decreases with increasing kappa from D(DLA) approximately 1.71 to a value bounded from below by D(min) = 3 / 2. Scaling arguments suggest a specific form for the dependence of the fractal dimension D(m,kappa) on kappa for large kappa which compares favorably with numerical results. PMID:15244564

  19. Aggregate Models of Climate Change

    NASA Astrophysics Data System (ADS)

    Hooss, G.; Voss, R.; Hasselmann, K.; Maier-Reimer, E.; Joos, F.

    Integrated assessment of climate change generally requires the evaluation of many transient scenario simulations of century-timescale changes in atmospheric compo- sition and climate, desirably with the accuracy of state-of-the-art three-dimensional (3D) coupled atmosphere-ocean general circulation models (GCMs). Such multi- scenario GCM computations are possible through appropriate representation of the models in aggregate forms. For this purpose, we developed Nonlinear Impulse- response projections of 3D models of the global (oceanic and terrestrial) Carbon cycle and the atmosphere-ocean Climate System (NICCS). For higher CO2 forcing, appli- cability is extended beyond the linear response domain through explicit treatment of dominant nonlinear effects. The climate change module was furthermore augmented with spatial patterns of change in some of the most impact-relevant fields. Applied to three long-term CO2 emission scenarios, the model demonstrates (a) the minor rela- tive role of the terrestrial carbon sink through CO2 fertilization, and (b) the necessity to reduce fossil carbon emissions to a very small fraction of today's rates within the next few decades if a major climate change is to be avoided.

  20. Biomass Growth and Clogging in Porous Media: From Microscale and Mesoscale Observations in Silicon Pore Imaging Elements to the Modeling of Aggregates in Network Models Using Material Mechanics

    NASA Astrophysics Data System (ADS)

    Dupin, H. J.; Mccarty, P. L.; Kitanidis, P. K.

    2002-05-01

    An apparatus for non-destructive continuous visualization of biological growth and clogging in porous media has been constructed. Silicon Pore Imaging Elements (micromodels featuring two-dimensional pore networks) were seeded with mixed cultures. A feed solution was then continuously forced through the SPIEs. Subsequently, several forms of biomass developped simultaneously: aggregates, biofilms and filaments ressembling mycellia. Clogging appeared mostly related to the presence of aggregates along preferential flow paths. Due to clogging, mesocale flow paths were modified, and flow was reversed in channels. A novel numerical model was then developped to investigate bioclogging of two-dimensional pore networks by aggregates. Each pore (channel) is seeded with initial biomass that consumes an electron donor and an electron acceptor according to dual Monod kinetics. Biomass is modeled as a continuous uniform isotropic hyperelastic material, whose expansion and deformation are governed by material mechanics stress-strain relations, unlike traditional approaches that use ad hoc empirical schemes. The Stokes flow, the advection-diffusion- reaction mass transport, and the biomass deformation partial differential equations are solved using finite elements. Simple networks are investigated to identify phenomena of interest: four channels of different width operating in parallel to study the effect of local heterogeneity; a periodic network to quantify the effects of distance from the injection point on clogging and substrate utilization; and square lattice 5 x 5 random width networks. Although square-lattice random-width networks are deemed better approximations of porous media, the simpler networks exhibit all the phenomena of interest, with the added advantage of these phenomena being decoupled. Results of numerical simulations for different network types under various boundary conditions show that aggregates have a far greater potential than biofilms to clog a porous

  1. Construction measurements

    SciTech Connect

    Barry, B.A.

    1988-01-01

    This text/reference on construction measurements contains material concerning electronic surveying and remote sensing. New to this edition is coverage of the GPS satellite positioning system, electronic distance measurement (EDM), laser sweep, calculator techniques, radial surveying and tracking, Loran-C, inertial navigation surveying, 3-point resection, computer software, and electronic fieldbooks. It covers the difference of elevation, angle measurements and directions, coordinate surveying and layout, offshore measurements, and random field and office techniques.

  2. Soluble forms of polyQ-expanded huntingtin rather than large aggregates cause endoplasmic reticulum stress

    NASA Astrophysics Data System (ADS)

    Leitman, Julia; Ulrich Hartl, F.; Lederkremer, Gerardo Z.

    2013-11-01

    In Huntington’s disease, as in other neurodegenerative diseases, it was initially thought that insoluble protein aggregates are the toxic species. However, growing evidence implicates soluble oligomeric polyglutamine-expanded huntingtin in cytotoxicity. Here we show that pathogenic huntingtin inhibits endoplasmic reticulum (ER)-associated degradation and induces ER stress before its aggregation into visible inclusions. All three branches of the unfolded protein response are activated. ER stress can be compensated by overexpression of p97/VCP, suggesting its sequestration by pathogenic huntingtin as a main cause. Stress correlates with the presence of huntingtin oligomers and is independent of continual huntingtin synthesis. Stress levels, measured in striatal neurons, are stabilized but only slowly subside on huntingtin aggregation into inclusions. Our results can be explained by the constant conversion of huntingtin monomers to toxic oligomers; large aggregates sequester the former, precluding further conversion, whereas pre-existing toxic oligomers are only gradually depleted.

  3. Virtual Screening for Dipeptide Aggregation: Toward Predictive Tools for Peptide Self-Assembly.

    PubMed

    Frederix, Pim W J M; Ulijn, Rein V; Hunt, Neil T; Tuttle, Tell

    2011-10-01

    Several short peptide sequences are known to self-assemble into supramolecular nanostructures with interesting properties. In this study, coarse-grained molecular dynamics is employed to rapidly screen all 400 dipeptide combinations and predict their ability to aggregate as a potential precursor to their self-assembly. The simulation protocol and scoring method proposed allows a rapid determination of whether a given peptide sequence is likely to aggregate (an indicator for the ability to self-assemble) under aqueous conditions. Systems that show strong aggregation tendencies in the initial screening are selected for longer simulations, which result in good agreement with the known self-assembly or aggregation of dipeptides reported in the literature. Our extended simulations of the diphenylalanine system show that the coarse-grain model is able to reproduce salient features of nanoscale systems and provide insight into the self-assembly process for this system. PMID:23795243

  4. Virtual Screening for Dipeptide Aggregation: Toward Predictive Tools for Peptide Self-Assembly

    PubMed Central

    2011-01-01

    Several short peptide sequences are known to self-assemble into supramolecular nanostructures with interesting properties. In this study, coarse-grained molecular dynamics is employed to rapidly screen all 400 dipeptide combinations and predict their ability to aggregate as a potential precursor to their self-assembly. The simulation protocol and scoring method proposed allows a rapid determination of whether a given peptide sequence is likely to aggregate (an indicator for the ability to self-assemble) under aqueous conditions. Systems that show strong aggregation tendencies in the initial screening are selected for longer simulations, which result in good agreement with the known self-assembly or aggregation of dipeptides reported in the literature. Our extended simulations of the diphenylalanine system show that the coarse-grain model is able to reproduce salient features of nanoscale systems and provide insight into the self-assembly process for this system. PMID:23795243

  5. Reverse engineering an amyloid aggregation pathway with dimensional analysis and scaling

    NASA Astrophysics Data System (ADS)

    Bailey, J.; Potter, K. J.; Verchere, C. B.; Edelstein-Keshet, L.; Coombs, D.

    2011-12-01

    Human islet amyloid polypeptide (hIAPP) is a cytotoxic protein that aggregates into oligomers and fibrils that kill pancreatic β-cells. Here we analyze hIAPP aggregation in vitro, measured via thioflavin-T fluorescence. We use mass-action kinetics and scaling analysis to reconstruct the aggregation pathway, and find that the initiation step requires four hIAPP monomers. After this step, monomers join the nucleus in pairs, until the first stable nucleus (of size approximately 20 monomers) is formed. This nucleus then elongates by successive addition of single monomers. We find that the best-fit of our data is achieved when we include a secondary fibril-dependent nucleation pathway in the reaction scheme. We predict how interventions that change rates of fibril elongation or nucleation rates affect the accumulation of potentially cytotoxic oligomer species. Our results demonstrate the power of scaling analysis in reverse engineering biochemical aggregation pathways.

  6. Unusual sintering behavior of porous chromatographic zirconia produced by polymerization-induced colloid aggregation

    SciTech Connect

    Lorenzano-Porras, C.F.; Reeder, D.H.; Annen, M.J.; Carr, P.W.; McCormick, A.V.

    1995-08-01

    The effects of sintering temperature and duration on the pore structure of chromatographic zirconia particles produced by the controlled polymerization-induced aggregation of 1,000 {angstrom} colloids are studied with an eye toward optimally strengthening the aggregates and eliminating small pores while preserving large pores. Nitrogen adsorption and mercury porosimetry are used to estimate the surface area, pore volume, and pore size distribution. Pulsed field gradient NMR measurements of solvent diffusion are used to estimate the diffusion tortuosity of the pore space. Initially of course, the pore volume and surface area decrease significantly, the decrease being more pronounced at higher temperatures. With prolonged sintering, the pore size, pore volume, and surface area change much more slowly, but the diffusion tortuosity seems to be minimized at a sintering temperature and time at which pores are allowed to redistribute so as to optimize large pores. The aggregates synthesized by this aggregation method apparently produce metastable large pores which are not easily collapsed.

  7. Aggregation process of paramagnetic particles in fluid in the magnetic field.

    PubMed

    Pei, Ning; Cheng, Xiaoye; Huang, Zheyong; Wang, Xiang; Yang, Kai; Wang, Ye; Gong, Yongyong

    2016-07-01

    Magnetic targeting is a promising therapeutic strategy for localizing systemically delivered magnetic responsive drugs or cells to target tissue, but excessive aggregation of magnetic particles could result in vascular embolization. To analyze the reason for embolization, the attractive process of magnetic particles in magnetic field (MF) was studied in this paper by analyzing the form of the aggregated paramagnetic particles while the particle suspension flowed through a tube, which served as a model of blood vessels. The effects of magnetic flux density and fluid velocity on the formation of aggregated paramagnetic particles were investigated. The number of large aggregated clusters dramatically increased with increment in the magnetic flux density and decreased with increment in the fluid velocity. The analysis of accumulative process demonstrates the MF around initially attracted particles was focused, which induced the formation of clusters and increased the possibility of embolism. Bioelectromagnetics. 37:323-330, 2016. © 2016 Wiley Periodicals, Inc. PMID:27126920

  8. Neighborhood Supported Model Level Fuzzy Aggregation for Moving Object Segmentation.

    PubMed

    Chiranjeevi, Pojala; Sengupta, Somnath

    2014-02-01

    We propose a new algorithm for moving object detection in the presence of challenging dynamic background conditions. We use a set of fuzzy aggregated multifeature similarity measures applied on multiple models corresponding to multimodal backgrounds. The algorithm is enriched with a neighborhood-supported model initialization strategy for faster convergence. A model level fuzzy aggregation measure driven background model maintenance ensures more robustness. Similarity functions are evaluated between the corresponding elements of the current feature vector and the model feature vectors. Concepts from Sugeno and Choquet integrals are incorporated in our algorithm to compute fuzzy similarities from the ordered similarity function values for each model. Model updating and the foreground/background classification decision is based on the set of fuzzy integrals. Our proposed algorithm is shown to outperform other multi-model background subtraction algorithms. The proposed approach completely avoids explicit offline training to initialize background model and can be initialized with moving objects also. The feature space uses a combination of intensity and statistical texture features for better object localization and robustness. Our qualitative and quantitative studies illustrate the mitigation of varieties of challenging situations by our approach. PMID:24235250

  9. Can intra-aggregate pore structures affect the aggregate's effectiveness in protecting carbon?

    SciTech Connect

    Ananyeva, K; Wang, W; Smucker, A J.M.; Rivers, M L; Kravchenko, A N

    2012-11-15

    Aggregates are known to provide physical protection to soil organic matter shielding it from rapid decomposition. Spatial arrangement and size distribution of intra-aggregate pores play an important role in this process. This study examined relationships between intra-aggregate pores measured using X-ray computed micro-tomography images and concentrations of total C in 4–6 mm macro-aggregates from two contrasting land use and management practices, namely, conventionally tilled and managed row crop agricultural system (CT) and native succession vegetation converted from tilled agricultural land in 1989 (NS). Previous analyses of these aggregates indicated that small (<15 μm) and large (>100 μm) pores prevail in NS aggregates while medium (30–90 μm) pores are more abundant in CT aggregates (Kravchenko et al., 2011; Wang et al., 2012). We hypothesized that these differences in pore size distributions affect the ability of macro-aggregates to protect C. The results of this study supported this hypothesis. Consistent with greater heterogeneity of pore distributions within NS aggregates we observed higher total C and greater intra-aggregate C variability in NS as compared with CT aggregates. Total C concentrations and intra-aggregate C standard deviations were negatively correlated with fractions of medium sized pores, indicating that presence of such pores was associated with lower but more homogeneously distributed total C. While total C was positively correlated with presence of small and large pores. The results suggest that because of their pore structure NS macro-aggregates provide more effective physical protection to C than CT aggregates.

  10. Role of p53 isoforms and aggregations in cancer.

    PubMed

    Kim, SeJin; An, Seong Soo A

    2016-06-01

    p53 is a master regulatory protein that is involved in diverse cellular metabolic processes such as apoptosis, DNA repair, and cell cycle arrest. The protective function of p53 (in its homotetrameric form) as a tumor suppressor is lost in more than 50% of human cancers.Despite considerable experimental evidence suggesting the presence of multiple p53 states, it has been difficult to correlate the status of p53 with cancer response to treatments and clinical outcomes, which suggest the importance of complex but essential p53 regulatory pathways.Recent studies have indicated that the expression pattern of p53 isoforms may play a crucial role in regulating normal and cancer cell fates in response to diverse stresses. The human TP53 gene encodes at least 12 p53 isoforms, which are produced in normal tissue through alternative initiation of translation, usage of alternative promoters, and alternative splicing. Furthermore, some researchers have suggested that the formation of mutant p53 aggregates may be associated with cancer pathogenesis due to loss-of function (LoF), dominant-negative (DN), and gain-of function (GoF) effects.As different isoforms or the aggregation state of p53 may influence tumorigenesis, this review aims to examine the correlation of p53 isoforms and aggregation with cancer. PMID:27368003

  11. Aggregated Myocilin Induces Russell Bodies and Causes Apoptosis

    PubMed Central

    Yam, Gary Hin-Fai; Gaplovska-Kysela, Katarina; Zuber, Christian; Roth, Jürgen

    2007-01-01

    Primary open-angle glaucoma with elevated intraocular pressure is a leading cause of blindness worldwide. Mutations of myocilin are known to play a critical role in the manifestation of the disease. Misfolded mutant myocilin forms secretion-incompetent intracellular aggregates. The block of myocilin secretion was proposed to alter the extracellular matrix environment of the trabecular meshwork, with subsequent impediment of aqueous humor outflow leading to elevated intraocular pressure. However, the molecular pathogenesis of myocilin-caused glaucoma is poorly defined. In this study, we show that heteromeric complexes composed of wild-type and mutant myocilin were retained in the rough endoplasmic reticulum, aggregating to form inclusion bodies typical of Russell bodies. The presence of myocilin aggregates induced the unfolded protein response proteins BiP and phosphorylated endoplasmic reticulum-localized eukaryotic initiation factor-2α kinase (PERK) with the subsequent activation of caspases 12 and 3 and expression of C/EBP homologous protein (CHOP)/GADD153, leading to apoptosis. Our findings identify endoplasmic reticulum stress-induced apoptosis as a pathway to explain the reduction of trabecular meshwork cells in patients with myocilin-caused glaucoma. As a consequence, the phagocytotic capacity of the remaining trabecular meshwork cell population would be insufficient for effective cleaning of aqueous humor, constituting a major pathogenetic factor for the development of increased intraocular pressure in primary open-angle glaucoma. PMID:17200186

  12. Laboratory-scale sodium-carbonate aggregate concrete interactions. [LMFBR

    SciTech Connect

    Westrich, H.R.; Stockman, H.W.; Suo-Anttila, A.

    1983-09-01

    A series of laboratory-scale experiments was made at 600/sup 0/C to identify the important heat-producing chemical reactions between sodium and carbonate aggregate concretes. Reactions between sodium and carbonate aggregate were found to be responsible for the bulk of heat production in sodium-concrete tests. Exothermic reactions were initiated at 580+-30/sup 0/C for limestone and dolostone aggregates as well as for hydrated limestone concrete, and at 540+-10/sup 0/C for dehydrated limestone concrete, but were ill-defined for dolostone concrete. Major reaction products included CaO, MgO, Na/sub 2/CO/sub 3/, Na/sub 2/O, NaOH, and elemental carbon. Sodium hydroxide, which forms when water is released from cement phases, causes slow erosion of the concrete with little heat production. The time-temperature profiles of these experiments have been modeled with a simplified version of the SLAM computer code, which has allowed derivation of chemical reaction rate coefficients.

  13. Aggregation, lipid exchange, and metastable phases of dimyristoylphosphatidylethanolamine vesicles.

    PubMed

    Pryor, C; Bridge, M; Loew, L M

    1985-04-23

    A new fluorescent lipid analogue, bimanephosphatidylcholine, has been synthesized for use in lipid bilayers. This probe is well suited as an energy-transfer donor with N-(7-nitro-2,1,3-benzoxadiazol-4-yl)phosphatidylethanolamine as the acceptor. Dimyristoylphosphatidylethanolamine vesicles are prepared by sonication at pH 9 and characterized by electron microscopy and other methods. Resonance energy transfer between separately labeled donor and acceptor vesicles is monitored during HCl-induced aggregation to determine the kinetics of lipid randomization. Light scattering is also monitored to measure the kinetics of aggregation. The light scattering shows a marked reversal with NaOH while the energy transfer does not, indicating lipid exchange during a reversibly aggregated state; the extent of energy transfer suggests that only lipids in the outer monolayers exchange. The gel to liquid-crystalline phase transition temperature in HCl-treated vesicles is found to be 47 degrees C with diphenylhexatriene. The initial sonicated dispersion does not show a sharp phase transition. In vesicles labeled with both donor and acceptor probes, a small, irreversible increase in energy transfer is obtained upon lowering and then restoring the pH. These results suggest a metastable phase in the sonicated vesicles containing a randomized distribution of lipid and probes within the bilayers; the thermodynamically favored phase, whose formation is triggered by the pH shock, contains domains within which the probe lipids are more highly concentrated. PMID:3995010

  14. Role of p53 isoforms and aggregations in cancer

    PubMed Central

    Kim, SeJin; An, Seong Soo A.

    2016-01-01

    Abstract p53 is a master regulatory protein that is involved in diverse cellular metabolic processes such as apoptosis, DNA repair, and cell cycle arrest. The protective function of p53 (in its homotetrameric form) as a tumor suppressor is lost in more than 50% of human cancers. Despite considerable experimental evidence suggesting the presence of multiple p53 states, it has been difficult to correlate the status of p53 with cancer response to treatments and clinical outcomes, which suggest the importance of complex but essential p53 regulatory pathways. Recent studies have indicated that the expression pattern of p53 isoforms may play a crucial role in regulating normal and cancer cell fates in response to diverse stresses. The human TP53 gene encodes at least 12 p53 isoforms, which are produced in normal tissue through alternative initiation of translation, usage of alternative promoters, and alternative splicing. Furthermore, some researchers have suggested that the formation of mutant p53 aggregates may be associated with cancer pathogenesis due to loss-of function (LoF), dominant-negative (DN), and gain-of function (GoF) effects. As different isoforms or the aggregation state of p53 may influence tumorigenesis, this review aims to examine the correlation of p53 isoforms and aggregation with cancer. PMID:27368003

  15. Scaling in the aggregation dynamics of a magnetorheological fluid.

    PubMed

    Domínguez-García, P; Melle, Sonia; Pastor, J M; Rubio, M A

    2007-11-01

    We present experimental results on the aggregation dynamics of a magnetorheological fluid, namely, an aqueous suspension of micrometer-sized superparamagnetic particles, under the action of a constant uniaxial magnetic field using video microscopy and image analysis. We find a scaling behavior in several variables describing the aggregation kinetics. The data agree well with the Family-Vicsek scaling ansatz for diffusion-limited cluster-cluster aggregation. The kinetic exponents z and z' are obtained from the temporal evolution of the mean cluster size S(t) and the number of clusters N(t), respectively. The crossover exponent Delta is calculated in two ways: first, from the initial slope of the scaling function; second, from the evolution of the nonaggregated particles, n1(t). We report on results of Brownian two-dimensional dynamics simulations and compare the results with the experiments. Finally, we discuss the differences obtained between the kinetic exponents in terms of the variation in the crossover exponent and relate this behavior to the physical interpretation of the crossover exponent. PMID:18233655

  16. Three Genes Which Affect Founding of Aggregations in Polysphondylium Pallidum

    PubMed Central

    Francis, D.; Shaffer, A.; Smoyer, K.

    1991-01-01

    PN6024 is an extraordinary mutant strain of the cellular slime mold Polysphondylium pallidum, characterized by having defects in many unlinked genes. New strains with altered development appeared spontaneously as aberrant clones of PN6024. Genetic crosses using the macrocyst sexual cycle were used to show that PN6030 (a clone like PN6024 in phenotype) carries mutations at two loci, emm and hge, whereas PN6031 (a clone of altered morphology) carries in addition a mutation at a third locus, mgt. hge and possibly mgt are linked to the mating type locus mat. The relatively high frequency of recombination between mat and hge is strong evidence that meiosis precedes macrocyst germination. The mutant genes themselves are of interest. A major effect of the emm-1 mutation is to remove the requirement for light to trigger aggregation. hge-1 greatly reduces the frequency of aggregation, whereas mgt-1 greatly increases it under standard conditions. None of these mutations interrupts later development leading to stalks and spore cells. It is hypothesized that all three genes act on steps immediately preceding the differentiation of the founder cells which initiate aggregation. PMID:1874416

  17. Experimental volcanic ash aggregation: Internal structuring of accretionary lapilli and the role of liquid bonding

    NASA Astrophysics Data System (ADS)

    Mueller, Sebastian B.; Kueppers, Ulrich; Ayris, Paul M.; Jacob, Michael; Dingwell, Donald B.

    2016-01-01

    Explosive volcanic eruptions can release vast quantities of pyroclastic material into Earth's atmosphere, including volcanic ash, particles with diameters less than two millimeters. Ash particles can cluster together to form aggregates, in some cases reaching up to several centimeters in size. Aggregation alters ash transport and settling behavior compared to un-aggregated particles, influencing ash distribution and deposit stratigraphy. Accretionary lapilli, the most commonly preserved type of aggregates within the geologic record, can exhibit complex internal stratigraphy. The processes involved in the formation and preservation of these aggregates remain poorly constrained quantitatively. In this study, we simulate the variable gas-particle flow conditions which may be encountered within eruption plumes and pyroclastic density currents via laboratory experiments using the ProCell Lab System® of Glatt Ingenieurtechnik GmbH. In this apparatus, solid particles are set into motion in a fluidized bed over a range of well-controlled boundary conditions (particle concentration, air flow rate, gas temperature, humidity, liquid composition). Experiments were conducted with soda-lime glass beads and natural volcanic ash particles under a range of experimental conditions. Both glass beads and volcanic ash exhibited the capacity for aggregation, but stable aggregates could only be produced when materials were coated with high but volcanically-relevant concentrations of NaCl. The growth and structure of aggregates was dependent on the initial granulometry, while the rate of aggregate formation increased exponentially with increasing relative humidity (12-45% RH), before overwetting promoted mud droplet formation. Notably, by use of a broad granulometry, we generated spherical, internally structured aggregates similar to some accretionary pellets found in volcanic deposits. Adaptation of a powder-technology model offers an explanation for the origin of natural accretionary

  18. Local aggregation characteristics of microscale blood flows

    NASA Astrophysics Data System (ADS)

    Kaliviotis, Efstathios; Sherwood, Joseph M.; Dusting, Jonathan; Balabani, Stavroula

    2015-11-01

    Erythrocyte aggregation (EA) is an important aspect of microvascular flows affecting blood flow and viscosity. Microscale blood flows have been studied extensively in recent years using computational and microfluidic based approaches. However, the relationship between the local structural characteristics of blood and the velocity field has not been quantified. We report simultaneous measurements of the local velocity, aggregation and haematocrit distributions of human erythrocytes flowing in a microchannel. EA was induced using Dextran and flows were imaged using brightfield microscopy. Local aggregation characteristics were investigated using statistical and edge-detection image processing techniques while velocity profiles were obtained using PIV algorithms. Aggregation intensity was found to strongly correlate with local variations in velocity in both the central and wall regions of the channel. The edge detection method showed that near the side wall large aggregates are associated with high local velocities and low local shear rates. In the central region large aggregates occurred in regions of low velocity and high erythrocyte concentration. The results demonstrate the combined effect of haematocrit and velocity distributions on local aggregation characteristics.

  19. Osmolyte Induced Changes in Peptide Conformational Ensemble Correlate with Slower Amyloid Aggregation: A Coarse-Grained Simulation Study.

    PubMed

    Sukenik, Shahar; Sapir, Liel; Harries, Daniel

    2015-12-01

    Stabilizing osmolytes are known to impact the process of amyloid aggregation, often altering aggregation kinetics. Recent evidence further suggests that osmolytes modify the peptide conformational dynamics, as well as change the physical characteristics of assembling amyloid fibrils. To resolve how these variations emerge on the molecular level, we simulated the initial aggregation steps of an amyloid-forming peptide in the presence and absence of the osmolyte sorbitol, a naturally occurring polyol. To this end, a coarse-grained force field was extended and implemented to access larger aggregate sizes and longer time scales. The force field optimization procedure placed emphasis on calibrating the solution thermodynamics of sorbitol, the aggregating peptide in its monomeric form, and the interaction of both of these components with each other and with water. Our simulations show a difference in aggregation kinetics and structural parameters in the presence of sorbitol compared to water, which qualitatively agree well with our experimentally resolved aggregation kinetics of the same peptide. The kinetic changes induced by sorbitol can be traced in our simulations to changes in monomer conformations resulting from osmolyte presence. These translate into changes in peptide conformations within the aggregated clusters and into differences in rates of monomer nucleation and of association to formed fibrils. We find that, compared to pure water as solvent, the presence of sorbitol induces formation of more aggregates each containing fewer peptides, with an increased tendency toward parallel interpeptide contacts. PMID:26587669

  20. Modulating non-native aggregation and electrostatic protein-protein interactions with computationally designed single-point mutations.

    PubMed

    O'Brien, C J; Blanco, M A; Costanzo, J A; Enterline, M; Fernandez, E J; Robinson, A S; Roberts, C J

    2016-06-01

    Non-native protein aggregation is a ubiquitous challenge in the production, storage and administration of protein-based biotherapeutics. This study focuses on altering electrostatic protein-protein interactions as a strategy to modulate aggregation propensity in terms of temperature-dependent aggregation rates, using single-charge variants of human γ-D crystallin. Molecular models were combined to predict amino acid substitutions that would modulate protein-protein interactions with minimal effects on conformational stability. Experimental protein-protein interactions were quantified by the Kirkwood-Buff integrals (G22) from laser scattering, and G22 showed semi-quantitative agreement with model predictions. Experimental initial-rates for aggregation showed that increased (decreased) repulsive interactions led to significantly increased (decreased) aggregation resistance, even based solely on single-point mutations. However, in the case of a particular amino acid (E17), the aggregation mechanism was altered by substitution with R or K, and this greatly mitigated improvements in aggregation resistance. The results illustrate that predictions based on native protein-protein interactions can provide a useful design target for engineering aggregation resistance; however, this approach needs to be balanced with consideration of how mutations can impact aggregation mechanisms. PMID:27160179

  1. Exciton dynamics in perturbed vibronic molecular aggregates

    PubMed Central

    Brüning, C.; Wehner, J.; Hausner, J.; Wenzel, M.; Engel, V.

    2015-01-01

    A site specific perturbation of a photo-excited molecular aggregate can lead to a localization of excitonic energy. We investigate this localization dynamics for laser-prepared excited states. Changing the parameters of the electric field significantly influences the exciton localization which offers the possibility for a selective control of this process. This is demonstrated for aggregates possessing a single vibrational degree of freedom per monomer unit. It is shown that the effects identified for the molecular dimer can be generalized to larger aggregates with a high density of vibronic states. PMID:26798840

  2. On aggregation in spatial econometric modelling

    NASA Astrophysics Data System (ADS)

    Paelinck, Jean H. P.

    The spatial aggregation problem - also termed the modifiable areal unit problem - has attracted regular attention in spatial statistics and econometrics. In this study econometric aggregation analysis is used to investigate the formal composition of meso-areal parameters given micro-areal underlying relations with spatial dependence. Impact on stochastic terms (possible meso-areal spatial autocorrelation) is also studied. Finally consequences for meso-areal estimation are derived, the general finding having been that spatial aggregation leads to meso-region specific parameter values, with the estimation problems this implies.

  3. Aggregation of ice crystals in cirrus

    NASA Technical Reports Server (NTRS)

    Kajikawa, Masahiro; Heymsfield, Andrew J.

    1989-01-01

    Results are given from analysis of the aggregation of thick plate, columnar, and bullet rosette ice crystals in cirrus. Data were obtained from PMS 2D-C images, oil coated slides, and aircraft meteorological measurements. Crystal size ranged from 100 to 900 microns in temperatures from -30 to -45 C. The results indicate that the ratio of the sizes of aggregating crystals and the difference of their terminal velocities are important in aggregation. The collection efficiency was calculated for the thick plate crystals from the same data.

  4. Directional sensing and streaming in Dictyostelium aggregation

    NASA Astrophysics Data System (ADS)

    Almeida, Sofia; Dilão, Rui

    2016-05-01

    We merge the Kessler-Levine simple discrete model for Dictyostelium cyclic adenosine monophosphate (cAMP) production and diffusion with the Dilão-Hauser directional sensing aggregation mechanism. The resulting compound model describes all the known transient patterns that emerge during Dictyostelium aggregation, which include the spontaneous formation of cAMP self-sustained target and spiral waves and streaming. We show that the streaming patterns depend on the speed of the amoebae, on the relaxation time for the production of cAMP, on the cAMP degradation rate, and on directional sensing. Moreover, we show that different signaling centers emerge during Dictyostelium aggregation.

  5. Antiplatelet aggregation principles from Ephemerantha lonchophylla.

    PubMed

    Chen, C C; Huang, Y L; Teng, C M

    2000-05-01

    Bioactivity-directed separation led to the identification of four compounds, viz. denbinobin (1), 3,7-dihydroxy-2,4-dimethoxyphenanthrene (2), 3-methylgigantol (3), and erianthridin (4) from the ethanolic extract of Ephemerantha lonchophylla. Antiplatelet tests were carried out using 4 different aggregation inducers, viz. arachidonic acid (AA), thrombin, collagen and platelet activating factor (PAF). The results indicated that only compounds 2, 3, and 4 exhibited generally significant anti-aggregation activities with that against AA-induced aggregation being most effective. Estimated IC50, values in this regard for 2, 3, and 4 were 24 microM, 30 microM and 9 microM, respectively. PMID:10865460

  6. Exciton dynamics in perturbed vibronic molecular aggregates.

    PubMed

    Brüning, C; Wehner, J; Hausner, J; Wenzel, M; Engel, V

    2016-07-01

    A site specific perturbation of a photo-excited molecular aggregate can lead to a localization of excitonic energy. We investigate this localization dynamics for laser-prepared excited states. Changing the parameters of the electric field significantly influences the exciton localization which offers the possibility for a selective control of this process. This is demonstrated for aggregates possessing a single vibrational degree of freedom per monomer unit. It is shown that the effects identified for the molecular dimer can be generalized to larger aggregates with a high density of vibronic states. PMID:26798840

  7. Creep of dry clinopyroxene aggregates

    NASA Astrophysics Data System (ADS)

    Bystricky, Misha; Mackwell, Stephen

    2001-01-01

    We have determined diffusional and dislocation creep rheologies for clinopyroxenite Ca1.0Mg0.8Fe0.2Si2O6 under dry conditions by deforming natural and hot-pressed samples at confining pressures of 300-430 MPa and temperatures of 1100°-1250°C with the oxygen fugacity buffered by either nickel-nickel oxide or iron-wüstite powders. The coarse-grained natural Sleaford Bay clinopyroxenite yielded a stress exponent of n = 4.7 ± 0.2 and an activation energy for creep of Q = 760 ± 40 kJ mol-1, consistent with deformation in the dislocation creep regime. The strength of the natural clinopyroxenite is consistent with previous high-temperature measurements of dislocation creep behavior of Sleaford Bay clinopyroxenite by Kirby and Kronenberg [1984] and Boland and Tullis [1986]. Fine-grained clinopyroxenite was prepared from ground powders of the natural clinopyroxenite. Hot-pressed samples were deformed under similar conditions to the natural samples. Mixed-mode deformation behavior was observed, with diffusional creep (n = 1) at lower differential stresses and dislocation creep (with n and Q similar to those of the natural samples) at higher differential stresses. Within the dislocation creep field the predried hot-pressed samples generally yielded creep rates that were about an order of magnitude faster than the natural samples. Thus, even at the highest differential stresses, a component of strain accommodation by grain boundary diffusion was present in the hot-pressed samples. Optical and electron microscope investigations of the deformation microstructures of the natural and hot-pressed samples show evidence for mechanical twinning and activation of dislocation slip systems. When extrapolated to geological conditions expected in the deep crust and upper mantle on Earth and other terrestrial planets, the strength of dry single-phase clinopyroxene aggregates is very high, exceeding that of dry olivine-rich rocks.

  8. The Feasibility of Palm Kernel Shell as a Replacement for Coarse Aggregate in Lightweight Concrete

    NASA Astrophysics Data System (ADS)

    Itam, Zarina; Beddu, Salmia; Liyana Mohd Kamal, Nur; Ashraful Alam, Md; Issa Ayash, Usama

    2016-03-01

    Implementing sustainable materials into the construction industry is fast becoming a trend nowadays. Palm Kernel Shell is a by-product of Malaysia’s palm oil industry, generating waste as much as 4 million tons per annum. As a means of producing a sustainable, environmental-friendly, and affordable alternative in the lightweight concrete industry, the exploration of the potential of Palm Kernel Shell to be used as an aggregate replacement was conducted which may give a positive impact to the Malaysian construction industry as well as worldwide concrete usage. This research investigates the feasibility of PKS as an aggregate replacement in lightweight concrete in terms of compressive strength, slump test, water absorption, and density. Results indicate that by using PKS for aggregate replacement, it increases the water absorption but decreases the concrete workability and strength. Results however, fall into the range acceptable for lightweight aggregates, hence it can be concluded that there is potential to use PKS as aggregate replacement for lightweight concrete.

  9. The homophilic adhesion molecule sidekick-1 contributes to augmented podocyte aggregation in HIV-associated nephropathy.

    PubMed

    Kaufman, Lewis; Yang, Guozhe; Hayashi, Kayo; Ashby, James R; Huang, Li; Ross, Michael J; Klotman, Mary E; Klotman, Paul E

    2007-05-01

    The collapsing glomerulopathy of HIV-associated nephropathy (HIVAN) is characterized by podocyte dedifferentiation and proliferation. In affected glomeruli, proliferating podocytes adhere in aggregates to form glomerular pseudocrescents and fill an enlarged Bowman's space. Previously, we reported that sidekick-1 (sdk-1), an adhesion molecule of the immunoglobulin superfamily, was highly up-regulated in HIV-1 transgenic podocytes. In the current work, we explore how sdk-1 overexpression contributes to HIVAN pathogenesis. Murine podocytes infected with HIV-1 virus expressed significantly more sdk-1 than control-infected cells. Podocytes stably transfected with an sdk-1 expression construct grew in large aggregates with a simplified morphology characterized by a disorganized actin cytoskeleton, changes similar to podocytes in HIVAN. In contrast to controls, HIV-1 infected podocytes adhered to stably transfected sdk-1 podocyte aggregates in mixing studies. Furthermore, substrate-released cell sheets of wild-type podocytes were readily dissociated by mechanical stress, whereas HIV-1 podocytes remained in aggregates. The number of HIV-1 podocyte aggregates was significantly reduced in cells expressing a short hairpin RNA (shRNA) construct specific for sdk-1 compared with cells expressing control shRNA. Finally, in a HIVAN mouse model, sdk-1 protein was detected in podocytes in collapsed glomerular tufts and in glomerular pseudocrescents. These findings suggest that sdk-1 is an important mediator of cellular adhesion in HIV-infected podocytes and may contribute to podocyte clustering that is characteristic of pseudocrescent formation in HIVAN. PMID:17307840

  10. Metal concentrations in aggregate interiors, exteriors, whole aggregates, and bulk of Costa Rican soils

    SciTech Connect

    Wilcke, W.; Kretzschmar, S.; Bundt, M.; Zech, W.

    1999-10-01

    In many temperate soils the preferential weathering and leaching of aggregate surfaces and the nonaggregated material between aggregates depletes geogenic metals. It also shifts metals from strongly to more weakly bound metal forms. Deposited metals are sorbed preferentially on aggregate surfaces and between aggregates. The authors examined whether preferential desilication under tropical climate causes an enrichment in the aggregate exteriors in oxidic forms of metals. They also studied where deposited metals are bound in these soils. Aggregates (2--20 mm) were selected manually from the A horizons of eight Oxisols, six Andisols, two Mollisols, and two Inceptisols in Costa Rica. All samples were fractionated into interior and exterior portions and treated with a seven-step sequence to extract Al, Cd, Cu, Fe, Mn, Pb, and Zn. Total concentrations of all metals except Zn were higher in the aggregate exteriors than in the interiors. The average Cd and Pb concentrations in easily extractable fractions were significantly higher in the aggregate exteriors. There were no significant differences in metal partitioning between interiors and exteriors except for Pb, which had higher proportions in extractable forms with NH{sub 2}OH {center{underscore}dot} HCl {gt} NH{sub 4} - acetate, pH 6.0 {gt} EDTA in the exteriors. There were few significant differences in metal concentrations and partitioning between bulk soil and whole aggregates. The results may be explained by (i) preferential desilication of the aggregate exteriors and (ii) preferential sorption of deposited heavy metals mainly in easily extractable forms.

  11. The Social Amoeba Dictyostelium discoideum Is Highly Resistant to Polyglutamine Aggregation.

    PubMed

    Santarriaga, Stephanie; Petersen, Amber; Ndukwe, Kelechi; Brandt, Anthony; Gerges, Nashaat; Bruns Scaglione, Jamie; Scaglione, Kenneth Matthew

    2015-10-16

    The expression, misfolding, and aggregation of long repetitive amino acid tracts are a major contributing factor in a number of neurodegenerative diseases, including C9ORF72 amyotrophic lateral sclerosis/frontotemporal dementia, fragile X tremor ataxia syndrome, myotonic dystrophy type 1, spinocerebellar ataxia type 8, and the nine polyglutamine diseases. Protein aggregation is a hallmark of each of these diseases. In model organisms, including yeast, worms, flies, mice, rats, and human cells, expression of proteins with the long repetitive amino acid tracts associated with these diseases recapitulates the protein aggregation that occurs in human disease. Here we show that the model organism Dictyostelium discoideum has evolved to normally encode long polyglutamine tracts and express these proteins in a soluble form. We also show that Dictyostelium has the capacity to suppress aggregation of a polyglutamine-expanded Huntingtin construct that aggregates in other model organisms tested. Together, these data identify Dictyostelium as a novel model organism with the capacity to suppress aggregation of proteins with long polyglutamine tracts. PMID:26330554

  12. Rhizosphere Compaction: Modeling a Bed of Multiple Aggregates Using X-Ray Micro-Tomography Information

    NASA Astrophysics Data System (ADS)

    Aravena, J. E.; Berli, M.; Tyler, S. W.

    2010-12-01

    The rhizosphere is the thin layer of soil that surrounds the roots. Its properties are different from the bulk, thus it is a critical environmental interface that controls water, nutrient and solute transport from the soil to the biosphere. At the aggregate scale, natural root-induced compaction may be surprisingly beneficial for the plants, as it increases contact areas between the aggregates and, contrary to traditional thinking, increases the hydraulic conductivity. We study the combined effect of compaction in a bed of multiple soil aggregates, before and after compaction for (a) a micro-balloon-induced compacted sample and (b) a natural root-induced compacted sample. Numerical models were constructed using X-ray micro-tomography (XMT) images to build the finite element meshes; the soil hydraulic properties (porosity and air-entry pressure), used to populate the models of the beds of aggregates, were estimated using XMT information, as the consolidation of the aggregates, due to the compaction results in a variable distribution of inter- and intra-aggregate porosity. The results show that root-induced compaction can be very beneficial for the plant, as it increases the hydraulic conductivity of the system. Thus, roots are able to extract more water than prior to compaction. The numerical modeling results were compared with a new theoretical hydraulic conductivity model.

  13. Remote sensing and airborne geophysics in the assessment of natural aggregate resources

    USGS Publications Warehouse

    Knepper, D.H., Jr.; Langer, W.H.; Miller, S.H.

    1994-01-01

    Natural aggregate made from crushed stone and deposits of sand and gravel is a vital element of the construction industry in the United States. Although natural aggregate is a high volume/low value commodity that is relatively abundant, new sources of aggregate are becoming increasingly difficult to find and develop because of rigid industry specifications, political considerations, development and transporation costs, and environmental concerns, especially in urban growth centers where much of the aggregate is used. As the demand for natural aggregate increases in response to urban growth and the repair and expansion of the national infrastructure, new sources of natural aggregate will be required. The USGS has recognized the necessity of developing the capability to assess the potential for natural aggregate sources on Federal lands; at present, no methodology exists for systematically describing and evaluating potential sources of natural aggregate. Because remote sensing and airborne geophysics can detect surface and nearsurface phenomena, these tools may useful for detecting and mapping potential sources of natural aggregate; however, before a methodology for applying these tools can be developed, it is necessary to understand the type, distribution, physical properties, and characteristics of natural aggregate deposits, as well as the problems that will be encountered in assessing their potential value. There are two primary sources of natural aggregate: (1) exposed or near-surface igneous, metamorphic, and sedimentary bedrock that can be crushed, and (2) deposits of sand and gravel that may be used directly or crushed and sized to meet specifications. In any particular area, the availability of bedrock suitable for crushing is a function of the geologic history of the area - the processes that formed, deformed, eroded and exposed the bedrock. Deposits of sand and gravel are primarily surficial deposits formed by the erosion, transportation by water and ice

  14. Openness initiative

    SciTech Connect

    Duncan, S.S.

    1995-12-31

    Although antinuclear campaigns seem to be effective, public communication and education efforts on low-level radioactive waste have mixed results. Attempts at public information programs on low-level radioactive waste still focus on influencing public opinion. A question then is: {open_quotes}Is it preferable to have a program focus on public education that will empower individuals to make informed decisions rather than trying to influence them in their decisions?{close_quotes} To address this question, a case study with both quantitative and qualitative data will be used. The Ohio Low-Level Radioactive Waste Education Program has a goal to provide people with information they want/need to make their own decisions. The program initiated its efforts by conducting a statewide survey to determine information needed by people and where they turned for that information. This presentation reports data from the survey and then explores the program development process in which programs were designed and presented using the information. Pre and post data from the programs reveal attitude and knowledge shifts.

  15. Silt-clay aggregates on Mars

    NASA Technical Reports Server (NTRS)

    Greeley, R.

    1979-01-01

    Viking observations suggest abundant silt and clay particles on Mars. It is proposed that some of these particles agglomerate to form sand size aggregates that are redeposited as sandlike features such as drifts and dunes. Although the binding for the aggregates could include salt cementation or other mechanisms, electrostatic bonding is considered to be a primary force holding the aggregates together. Various laboratory experiments conducted since the 19th century, and as reported here for simulated Martian conditions, show that both the magnitude and sign of electrical charges on windblown particles are functions of particle velocity, shape and composition, atmospheric pressure, atmospheric composition and other factors. Electrical charges have been measured for saltating particles in the wind tunnel and in the field, on the surfaces of sand dunes, and within dust clouds on earth. Similar, and perhaps even greater, charges are proposed to occur on Mars, which could form aggregates of silt and clay size particles

  16. Acid soluble, pepsin resistant platelet aggregating material

    SciTech Connect

    Schneider, M.D.

    1982-08-31

    Disclosed is an acid soluble, pepsin resistant, platelet aggregating material isolated from equine arterial tissue by extraction with dilute aqueous acid. The method of isolation and use to control bleeding are described. 4 figs.

  17. EFFECT OF AGGREGATION ON VIBRIO CHOLERA INACTIVATION

    EPA Science Inventory

    Extensive research has shown that microorganisms exhibit increased resistance due to clumping, aggregation, particle association or modification of antecedent growth conditions. uring the course of investigating a major waterborne V. Cholerae outbreak in Peru, U.S. EPA investigat...

  18. Active matter model of Myxococcus xanthus aggregation

    NASA Astrophysics Data System (ADS)

    Patch, Adam; Bahar, Fatmagul; Liu, Guannan; Thutupalli, Shashi; Welch, Roy; Yllanes, David; Shaevitz, Joshua; Marchetti, M. Cristina

    Myxococcus xanthus is a soil-dwelling bacterium that exhibits several fascinating collective behaviors including streaming, swarming, and generation of fruiting bodies. A striking feature of M. xanthus is that it periodically reverses its motility direction. The first stage of fruiting body formation is characterized by the aggregation of cells on a surface into round mesoscopic structures. Experiments have shown that this aggregation relies heavily on regulation of the reversal rate and local mechanical interactions, suggesting motility-induced phase separation may play an important role. We have adapted self-propelled particle models to include cell reversal and motility suppression resulting from sporulation observed in aggregates. Using 2D molecular dynamics simulations, we map the phase behavior in the space of Péclet number and local density and examine the kinetics of aggregation for comparison to experiments.

  19. Quicklime application instantly increases soil aggregate stability

    NASA Astrophysics Data System (ADS)

    Keiblinger, Katharina M.; Bauer, Lisa M.; Deltedesco, Evi; Holawe, Franz; Unterfrauner, Hans; Zehetner, Franz; Peticzka, Robert

    2016-01-01

    Agricultural intensification, especially enhanced mechanisation of soil management, can lead to the deterioration of soil structure and to compaction. A possible amelioration strategy is the application of (structural) lime. In this study, we tested the effect of two different liming materials, ie limestone (CaCO3) and quicklime (CaO), on soil aggregate stability in a 3-month greenhouse pot experiment with three agricultural soils. The liming materials were applied in the form of pulverised additives at a rate of 2 000 kg ha-1. Our results show a significant and instantaneous increase of stable aggregates after quicklime application whereas no effects were observed for limestone. Quicklime application seems to improve aggregate stability more efficiently in soils with high clay content and cation exchange capacity. In conclusion, quicklime application may be a feasible strategy for rapid improvement of aggregate stability of fine textured agricultural soils.

  20. Aggregated Gas Molecules: Toxic to Protein?

    PubMed Central

    Zhang, Meng; Zuo, Guanghong; Chen, Jixiu; Gao, Yi; Fang, Haiping

    2013-01-01

    The biological toxicity of high levels of breathing gases has been known for centuries, but the mechanism remains elusive. Earlier work mainly focused on the influences of dispersed gas molecules dissolved in water on biomolecules. However, recent studies confirmed the existence of aggregated gas molecules at the water-solid interface. In this paper, we have investigated the binding preference of aggregated gas molecules on proteins with molecular dynamics simulations, using nitrogen (N2) gas and the Src-homology 3 (SH3) domain as the model system. Aggregated N2 molecules were strongly bound by the active sites of the SH3 domain, which could impair the activity of the protein. In contrast, dispersed N2 molecules did not specifically interact with the SH3 domain. These observations extend our understanding of the possible toxicity of aggregates of gas molecules in the function of proteins. PMID:23588597

  1. Protein aggregation and misfolding: good or evil?

    NASA Astrophysics Data System (ADS)

    Pastore, Annalisa; Temussi, Pierandrea

    2012-06-01

    Protein aggregation and misfolding have important implications in an increasing number of fields ranging from medicine to biology to nanotechnology and material science. The interest in understanding this field has accordingly increased steadily over the last two decades. During this time the number of publications that have been dedicated to protein aggregation has increased exponentially, tackling the problem from several different and sometime contradictory perspectives. This review is meant to summarize some of the highlights that come from these studies and introduce this topical issue on the subject. The factors that make a protein aggregate and the cellular strategies that defend from aggregation are discussed together with the perspectives that the accumulated knowledge may open.

  2. Diffusion-limited aggregation on curved surfaces

    NASA Astrophysics Data System (ADS)

    Choi, J.; Crowdy, D.; Bazant, M. Z.

    2010-08-01

    We develop a general theory of transport-limited aggregation phenomena occurring on curved surfaces, based on stochastic iterated conformal maps and conformal projections to the complex plane. To illustrate the theory, we use stereographic projections to simulate diffusion-limited aggregation (DLA) on surfaces of constant Gaussian curvature, including the sphere (K>0) and the pseudo-sphere (K<0), which approximate "bumps" and "saddles" in smooth surfaces, respectively. Although the curvature affects the global morphology of the aggregates, the fractal dimension (in the curved metric) is remarkably insensitive to curvature, as long as the particle size is much smaller than the radius of curvature. We conjecture that all aggregates grown by conformally invariant transport on curved surfaces have the same fractal dimension as DLA in the plane. Our simulations suggest, however, that the multifractal dimensions increase from hyperbolic (K<0) to elliptic (K>0) geometry, which we attribute to curvature-dependent screening of tip branching.

  3. Aggregation behavior of illite using light scattering

    SciTech Connect

    Derrendinger, L.; Sposito, G.

    1995-12-01

    Stable environmental particles can be at the origin of facilitated transport of metals and organic compounds, especially contaminants. We investigated the destabilization (aggregation) kinetics of both a reference and a soil clay mineral: Imt-1 (Silver Hill) illite and Hanford soil illite, respectively. Dynamic and static light scattering was used to follow the aggregation kinetics and infer the structure of the resulting clusters. Kinetics curves showed exponential and power-law shapes, corresponding respectively to reaction-limited and diffusion-limited regimes. The fractal dimension of the clusters showed no observable change with the change of aggregation regime, its value always being between 2.10 and 2.25 ({plus_minus}0.12). The change in aggregation regime for Na-illite (or ccc) was measured to be 45 mol.m{sup -3}.

  4. Aggregation of β-amyloid fragments

    NASA Astrophysics Data System (ADS)

    Meinke, Jan H.; Hansmann, Ulrich H. E.

    2007-01-01

    The authors study the folding and aggregation of six chains of the β-amyloid fragment 16-22 using Monte Carlo simulations. While the isolated fragment prefers a helical form at room temperature, in the system of six interacting fragments one observes both parallel and antiparallel β sheets below a crossover temperature Tx≈420K. The antiparallel sheets have lower energy and are therefore more stable. Above the nucleation temperature the aggregate quickly dissolves into widely separated, weakly interacting chains.

  5. Modeling Protein Aggregate Assembly and Structure

    NASA Astrophysics Data System (ADS)

    Guo, Jun-tao; Hall, Carol K.; Xu, Ying; Wetzel, Ronald

    One might say that "protein science" got its start in the domestic arts, built around the abilities of proteins to aggregate in response to environmental stresses such as heating (boiled eggs), heating and cooling (gelatin), and pH (cheese). Characterization of proteins in the late nineteenth century likewise focused on the ability of proteins to precipitate in response to certain salts and to aggregate in response to heating. Investigations by Chick and Martin (Chick and Martin, 1910) showed that the inactivating response of proteins to heat or solvent treatment is a two-step process involving separate denaturation and precipitation steps. Monitoring the coagulation and flocculation responses of proteins to heat and other stresses remained a major approach to understanding protein structure for decades, with solubility, or susceptibility to aggregation, serving as a kind of benchmark against which results of other methods, such as viscosity, chemical susceptibility, immune activity, crystallizability, and susceptibility to proteolysis, were compared (Mirsky and Pauling, 1936;Wu, 1931). Toward the middle of the last century, protein aggregation studies were largely left behind, as improved methods allowed elucidation of the primary sequence of proteins, reversible unfolding studies, and ultimately high-resolution structures. Curiously, the field of protein science, and in particular protein folding, is now gravitating back to a closer look at protein aggregation and protein aggregates. Unfortunately, the means developed during the second half of the twentieth century for studying native, globular proteins have not proved immediately amenable to the study of aggregate structures. Great progress is being made, however, to modify classical methods, including NMR and X-ray diffraction, as well as to develop newer techniques, that together should continue to expand our picture of aggregate structure (Kheterpal and Wetzel, 2006; Wetzel, 1999).

  6. Polyglutamine protein aggregation and toxicity are linked to the cellular stress response.

    PubMed

    Cowan, K J; Diamond, M I; Welch, W J

    2003-06-15

    Chronic exposure of cells to expanded polyglutamine proteins results in eventual cell demise. We constructed mouse cell lines expressing either the full-length androgen receptor (AR), or truncated forms of AR containing 25 or 65 glutamines to study the cellular consequences of chronic low-level exposure to these proteins. Expression of the polyglutamine-expanded truncated AR protein, but not the full-length expanded protein, resulted in the formation of cytoplasmic and nuclear aggregates and eventual cell death. Nuclear aggregates preferentially stained positive for heat shock protein (hsp)72, a sensitive indicator of a cellular stress response. Biochemical studies revealed that the presence of nuclear aggregates correlated with activation of the c-jun NH2-terminal kinase (JNK). Different metabolic insults, including heat shock treatment, and exposure to sodium arsenite or menadione, proved more toxic to those cells expressing the polyglutamine-expanded truncated protein than to cells expressing the non-expanded form. Cells containing cytoplasmic polyglutamine-protein aggregates exhibited a delayed expression of hsp72 after heat shock. Once expressed, hsp72 failed to localize normally and instead was sequestered within the protein aggregates. This was accompanied by an inability of the aggregate-containing cells to cease their stress response as evidenced by the continued presence of activated JNK. Finally, activation of the cellular stress response increased the overall extent of polyglutamine protein aggregation, especially within the nucleus. Inclusion of a JNK inhibitor reduced this stress-dependent increase in nuclear aggregates. Abnormal stress responses may contribute to enhanced cell vulnerability in cells expressing polyglutamine-expanded proteins and may increase the propensity of such cells to form cytoplasmic and nuclear inclusions. PMID:12783846

  7. Soil aggregation and slope stability related to soil density, root length, and mycorrhiza

    NASA Astrophysics Data System (ADS)

    Graf, Frank; Frei, Martin

    2013-04-01

    Eco-engineering measures combine the use of living plants and inert mechanical constructions to protect slopes against erosion and shallow mass movement. Whereas in geotechnical engineering several performance standards and guidelines for structural safety and serviceability of construction exist, there is a lack of comparable tools in the field of ecological restoration. Various indicators have been proposed, including the fractal dimension of soil particle size distribution, microbiological parameters, and soil aggregate stability. We present results of an soil aggregate stability investigation and compare them with literature data of the angle of internal friction ?' which is conventionally used in slope stability analysis and soil failure calculation. Aggregate stability tests were performed with samples of differently treated moraine, including soil at low (~15.5 kN/m³) and high (~19.0 kN/m³) dry unit weight, soil planted with Alnus incana (White Alder) as well as the combination of soil planted with alder and inoculated with the mycorrhizal fungus Melanogaster variegatus s.l. After a 20 weeks growth period in a greenhouse, a total of 100 samples was tested and evaluated. Positive correlations were found between the soil aggregate stability and the three variables dry unit weight, root length per soil volume, and degree of mycorrhization. Based on robust statistics it turned out that dry unit weight and mycorrhization degree were strongest correlated with soil aggregate stability. Compared to the non-inoculated control plants, mycorrhized White Alder produced significantly more roots and higher soil aggregate stability. Furthermore, the combined biological effect of plant roots and mycorrhizal mycelia on aggregate stability on soil with low density (~15.5 kN/m³) was comparable to the compaction effect of the pure soil from 15.5 to ~19.0 kN/m³. Literature data on the effect of vegetation on the angle of internal friction ?' of the same moraine showed

  8. Growth hormone aggregates in the rat adenohypophysis

    NASA Technical Reports Server (NTRS)

    Farrington, M.; Hymer, W. C.

    1990-01-01

    Although it has been known for some time that GH aggregates are contained within the rat anterior pituitary gland, the role that they might play in pituitary function is unknown. The present study examines this issue using the technique of Western blotting, which permitted visualization of 11 GH variants with apparent mol wt ranging from 14-88K. Electroelution of the higher mol wt variants from gels followed by their chemical reduction with beta-mercaptoethanol increased GH immunoassayability by about 5-fold. With the blot procedure we found 1) that GH aggregates greater than 44K were associated with a 40,000 x g sedimentable fraction; 2) that GH aggregates were not present in glands from thyroidectomized rats, but were in glands from the thyroidectomized rats injected with T4; 3) that GH aggregates were uniquely associated with a heavily granulated somatotroph subpopulation isolated by density gradient centrifugation; and 4) that high mol wt GH forms were released from the dense somatotrophs in culture, since treatment of the culture medium with beta-mercaptoethanol increased GH immunoassayability by about 5-fold. Taken together, the results show that high mol wt GH aggregates are contained in secretory granules of certain somatotrophs and are also released in aggregate form from these cells in vitro.

  9. An energy landscape approach to protein aggregation

    NASA Astrophysics Data System (ADS)

    Buell, Alexander; Knowles, Tuomas

    2012-02-01

    Protein aggregation into ordered fibrillar structures is the hallmark of a class of diseases, the most prominent examples of which are Alzheimer's and Parkinson's disease. Recent results (e.g. Baldwin et al. J. Am. Chem. Soc. 2011) suggest that the aggregated state of a protein is in many cases thermodynamically more stable than the soluble state. Therefore the solubility of proteins in a cellular context appears to be to a large extent under kinetic control. Here, we first present a conceptual framework for the description of protein aggregation ( see AK Buell et al., Phys. Rev. Lett. 2010) that is an extension to the generally accepted energy landscape model for protein folding. Then we apply this model to analyse and interpret a large set of experimental data on the kinetics of protein aggregation, acquired mainly with a novel biosensing approach (see TPJK Knowles et al, Proc. Nat. Acad. Sc. 2007). We show how for example the effect of sequence modifications on the kinetics and thermodynamics of human lysozyme aggregation can be understood and quantified (see AK Buell et al., J. Am. Chem. Soc. 2011). These results have important implications for therapeutic strategies against protein aggregation disorders, in this case lysozyme systemic amyloidosis.

  10. Influence of Phenylalanine on Carotenoid Aggregation

    NASA Astrophysics Data System (ADS)

    Lu, L.; Ni, X.; Luo, X.

    2015-01-01

    The carotenoids lutein and β-carotene form, in 1:1 ethanol-water mixtures H-aggregates, of different strengths. The effects of phenylalanine on these aggregates were recorded by UV-Vis absorption, steady-state fluorescence, and Raman spectra. The H-aggregate of lutein was characterized by a large 78 nm blue shift in the absorption spectra, confirming the strong coupling between hydroxyl groups of adjacent molecules. The 15 nm blue shift in the β-carotene mixture also indicates that it was assembled by weak coupling between polyenes. After adding phenylalanine, the reducing absorption strength of the aggregates of lutein and reappearance of vibrational substructure indicate that the hydroxyl and amino groups of phenylalanine may coordinate to lutein and disaggregate the H-aggregates. However, phenylalanine had no effect on aggregates of β-carotene. The Raman spectra show three bands of carotenoids whose intensities decreased with increasing phenylalanine concentration. The frequency of ν1 corresponding to the length of the conjugated region was more sensitive to the solution of lutein. This coordination of phenylalanine to lutein could increase the length of the conjugated region. In addition, phenylalanine significantly affected the excited electronic states of carotenoids, which were crucial in the energy transfer from carotenoids to chlorophyll a in vivo.

  11. Simulations of kinetically irreversible protein aggregate structure.

    PubMed Central

    Patro, S Y; Przybycien, T M

    1994-01-01

    We have simulated the structure of kinetically irreversible protein aggregates in two-dimensional space using a lattice-based Monte-Carlo routine. Our model specifically accounts for the intermolecular interactions between hydrophobic and hydrophilic protein surfaces and a polar solvent. The simulations provide information about the aggregate density, the types of inter-monomer contacts and solvent content within the aggregates, the type and extent of solvent exposed perimeter, and the short- and long-range order all as a function of (i) the extent of monomer hydrophobic surface area and its distribution on the model protein surface and (ii) the magnitude of the hydrophobic-hydrophobic contact energy. An increase in the extent of monomer hydrophobic surface area resulted in increased aggregate densities with concomitant decreased system free energies. These effects are accompanied by increases in the number of hydrophobic-hydrophobic contacts and decreases in the solvent-exposed hydrophobic surface area of the aggregates. Grouping monomer hydrophobic surfaces in a single contiguous stretch resulted in lower aggregate densities and lower short range order. More favorable hydrophobic-hydrophobic contact energies produced structures with higher densities but the number of unfavorable protein-protein contacts was also observed to increase; greater configurational entropy produced the opposite effect. Properties predicted by our model are in good qualitative agreement with available experimental observations. Images FIGURE 6 FIGURE 13 PMID:8061184

  12. Experimental testing of hot mix asphalt mixture made of recycled aggregates.

    PubMed

    Rafi, Muhammad Masood; Qadir, Adnan; Siddiqui, Salman Hameed

    2011-12-01

    The migration of population towards big cities generates rapid construction activities. These activities not only put pressure on natural resources but also produce construction, renovation and demolition waste. There is an urgent need to find out ways to handle this waste owing to growing environmental concerns. This can reduce pressure on natural resources as well. This paper presents the results of experimental studies which were carried out on hot mix asphalt mixture samples. These samples were manufactured by adding recycled aggregates (RA) with natural crushed stone aggregates (CSA). Three levels of addition of RA were considered in the presented studies. RA were obtained from both the concrete waste of construction, renovation and demolition activities and reclaimed asphalt pavement. Separate samples were manufactured with the coarse and fine aggregate fractions of both types of RA. Samples made with CSA were used as control specimens. The samples were prepared and tested using the Marshall method. The performance of the samples was investigated in terms of density-void and stability/flow analysis and was compared with the performance criteria as given by National Highway Authority for wearing course material in Pakistan. Based on this data optimum asphalt contents were determined. All the samples made by adding up to 50% RA conform to the specification requirements of wearing course material as given by National Highway Authority in terms of optimum asphalt contents, voids in mineral aggregates and stability/flow. A statistical analysis of variation of these samples confirmed that addition is also possible statistically. PMID:20483876

  13. Effects of tau domain-specific antibodies and intravenous immunoglobulin on tau aggregation and aggregate degradation.

    PubMed

    Esteves-Villanueva, Jose O; Trzeciakiewicz, Hanna; Loeffler, David A; Martić, Sanela

    2015-01-20

    Tau pathology, including neurofibrillary tangles, develops in Alzheimer's disease (AD). The aggregation and hyperphosphorylation of tau are potential therapeutic targets for AD. Administration of anti-tau antibodies reduces tau pathology in transgenic "tauopathy" mice; however, the optimal tau epitopes and conformations to target are unclear. Also unknown is whether intravenous immunoglobulin (IVIG) products, currently being evaluated in AD trials, exert effects on pathological tau. This study examined the effects of anti-tau antibodies targeting different tau epitopes and the IVIG Gammagard on tau aggregation and preformed tau aggregates. Tau aggregation was assessed by transmission electron microscopy and fluorescence spectroscopy, and the binding affinity of the anti-tau antibodies for tau was evaluated by enzyme-linked immunosorbent assays. Antibodies used were anti-tau 1-150 ("D-8"), anti-tau 259-266 ("Paired-262"), anti-tau 341-360 ("A-10"), and anti-tau 404-441 ("Tau-46"), which bind to tau's N-terminus, microtubule binding domain (MBD) repeat sequences R1 and R4, and the C-terminus, respectively. The antibodies Paired-262 and A-10, but not D-8 and Tau-46, reduced tau fibrillization and degraded preformed tau aggregates, whereas the IVIG reduced tau aggregation but did not alter preformed aggregates. The binding affinities of the antibodies for the epitope for which they were specific did not appear to be related to their effects on tau aggregation. These results confirm that antibody binding to tau's MBD repeat sequences may inhibit tau aggregation and indicate that such antibodies may also degrade preformed tau aggregates. In the presence of anti-tau antibodies, the resulting tau morphologies were antigen-dependent. The results also suggested the possibility of different pathways regulating antibody-mediated inhibition of tau aggregation and antibody-mediated degradation of preformed tau aggregates. PMID:25545358

  14. Crushed aggregates for roads and their properties for frost protection

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Elena; Willy Danielsen, Svein

    2015-04-01

    Crushed aggregates for roads and their properties for frost protection Elena Kuznetsova, NTNU and Svein Willy Danielsen, SINTEF With natural (fluvial, glaciofluvial) sand/gravel resources being rapidly depleted in many countries, the last decade has seen a significant trend towards using more alternative materials for construction purpose. In Norway the development and implementation of crushed aggregate technology has been the most important way to get around the problem with increased resource scarcity. Today Norway is one the European countries with the highest percentage of crushed/manufactured aggregates. A crushed product will reveal a different particle size distribution, a sharper, more angular particle shape, and not least - a significantly different mineral composition. The latter may often be characterised by more polymineral composition, and it will also much more depend on the local bedrock. When handled with care and knowledge, these differences can give the user a lot of new opportunities relating to materials design. Norwegian road construction practice has changed significantly during the last 40 years due to the replacement of gravel by crushed rock materials in the granular layers of the pavements. The use of non-processed rock materials from blasting was allowed in the subbase layer until 2012. This was a reason for a lot of problems with frost heaving due to inhomogeneity of this material, and in practice it was difficult to control the size of large stones. Since 2012 there is a requirement that rock materials for use in the subbase layer shall be crushed (Handbook N200, 2014). During the spring 2014 The Norwegian Public Roads Administration introduced a new handbook with requirements for roads construction in Norway, including new specifications for the frost protection layer. When pavements are constructed over moist and/or frost susceptible soils in cold and humid environments, the frost protection layer also becomes a very important part

  15. EUROANDRILL Initiative

    NASA Astrophysics Data System (ADS)

    Florindo, Fabio; Steering Committee, Euroandrill

    2010-05-01

    EuroANDRILL is a new initiative to create a European network with the goal to increase future involvement of European countries in the ANDRILL [ANtarctic geological DRILLing] Programme. Antarctica has been heavily glaciated for approximately 34 million years, but its ice sheets have fluctuated considerably and are one of the major driving forces for changes in climate throughout the Cenozoic Era. The spatial scale and temporal pattern of these fluctuations is subject to considerable debate. Understanding the response of large ice masses to climatic forcing is of vital importance because ice volume variations drive global sea level changes and also alter the capacity of ice sheets and sea-ice to act as major heat sinks/insulators. It is particularly important to assess the stability of the cryosphere in the face of rising CO2 levels, as modelling of the climate shift from a warm, vegetated Antarctica to a cold, ice-covered state 34 million years ago suggests a powerful greenhouse gas influence. As Antarctica is the major driver of Earth's climate and sea level, much effort has been expended in deriving models of its behaviour. Some of these models have been successfully validated against modern conditions. EuroANDRILL will provide a coherent, integrated platform for European leadership and involvement in the international ANDRILL programme. The coordination and networking provided by EuroANDRILL will seek to expand participation by European nations, institutions, and individual scientists in the study of the geologic history of the polar regions and their paleoclimatic significance. During the IPY, ANDRILL has been a highly visible and successful programme. This programme seeks to expand on this legacy beyond the IPY and make these contributions sustainable in the European Research Area through networking of research projects and future planning efforts, which establish Europe as a key player in future polar sediment and rock drilling. EuroANDRILL is set up under

  16. PUMP CONSTRUCTION

    DOEpatents

    Strickland, G.; Horn, F.L.; White, H.T.

    1960-09-27

    A pump which utilizes the fluid being pumped through it as its lubricating fluid is described. This is achieved by means of an improved bearing construction in a pump of the enclosed or canned rotor type. At the outlet end of the pump, adjacent to an impeller mechanism, there is a bypass which conveys some of the pumped fluid to a chamber at the inlet end of the pump. After this chamber becomes full, the pumped fluid passes through fixed orifices in the top of the chamber and exerts a thrust on the inlet end of the pump rotor. Lubrication of the rotor shaft is accomplished by passing the pumped fluid through a bypass at the outlet end of the rotor shaft. This bypass conveys Pumped fluid to a cooling means and then to grooves on the surface of the rotor shait, thus lubricating the shaft.

  17. Volcanic Glasses: Construction Materials

    NASA Astrophysics Data System (ADS)

    Moskowitz, Samuel E.

    1998-01-01

    Natural glass is the product of rapidly cooled molten rock. Two natural sources of the melt are volcanic eruption and meteoritic impact. Pure glass is an amorphous aggregate. Volcanic glass is a material that could be utilized in the construction of extraterrestrial outposts. Pumice and perlite are volcanic glasses currently used in the building industry. Samples of natural volcanic glass found in the lunar regolith were returned to Earth as part of the Apollo and Luna programs. An alpha proton X-ray spectrometer onboard the Pathfinder recently examined martian rocks located in the vicinity of the lander craft. Preliminary results of chemical composition by weight of SiO2 50-55%, Al203 11-13%, K20 1-2%, Na20 2-5%, CaO 4-6%, MgO 3-7%, FeO 12-14%, S03 2-5%, and MnO <1% were given for two rocks. Parenthetically, the values for K and Mn were perhaps too high, and the analysis was based on X-ray data only. The appreciable amount of silica already found on Mars and empirical evidence to support the hypothesis that the planet once had water sufficient to rapidly cool magma imply the possibility of discovering natural glass of volcanic origin in subsequent missions.

  18. Microdrill Initiative - Initial Market Evaluation

    SciTech Connect

    Spears & Associates, Inc

    2003-07-01

    The U.S. Department of Energy (DOE) is launching a major research and development initiative to create a small, fast, inexpensive and environmentally friendly rig for drilling 5000 feet boreholes to investigate potential oil and gas reservoirs. DOE wishes to get input from petroleum industry operators, service companies and equipment suppliers on the operation and application of this coiled-tubing-based drilling unit. To that end, DOE has asked Spears & Associates, Inc. (SAI) to prepare a special state-of-the-market report and assist during a DOE-sponsored project-scoping workshop in Albuquerque near the end of April 2003. The scope of the project is four-fold: (1) Evaluate the history, status and future of demand for very small bore-hole drilling; (2) Measure the market for coiled tubing drilling and describe the state-of-the-art; (3) Identify companies and individuals who should have an interest in micro drilling and invite them to the DOE workshop; and (4) Participate in 3 concurrent workshop sessions, record and evaluate participant comments and report workshop conclusions.

  19. Constructing populations in biobanking.

    PubMed

    Tupasela, Aaro; Snell, Karoliina; Cañada, Jose A

    2015-01-01

    This article poses the question of whether biobanking practices and standards are giving rise to the construction of populations from which various biobanking initiatives increasingly draw on for legitimacy? We argue that although recent biobanking policies encourage various forms of engagement with publics to ensure legitimacy, different biobanks conceptualize their engagement strategies very differently. We suggest that biobanks undertake a broad range of different strategies with regard to engagement. We argue that these different approaches to engagement strategies are contributing to the construction of populations, whereby specific nationalities, communities, societies, patient groups and political systems become imbued or bio-objectified with particular characteristics, such as compliant, distant, positive, commercialized or authoritarian. This bio-objectification process is problematic in relation to policy aspirations ascribed to biobanking engagement since it gives rise to reified notions of different populations. PMID:26194269

  20. Studying Microbial Mat Functioning Amidst "Unexpected Diversity": Methodological Approaches and Initial Results from Metatranscriptomes of Mats Over Diel cycles, iTags from Long Term Manipulations, and Biogeochemical Cycling in Simplified Microbial Mats Constructed from Cultures

    NASA Astrophysics Data System (ADS)

    Bebout, B.; Bebout, L. E.; Detweiler, A. M.; Everroad, R. C.; Lee, J.; Pett-Ridge, J.; Weber, P. K.

    2014-12-01

    Microbial mats are famously amongst the most diverse microbial ecosystems on Earth, inhabiting some of the most inclement environments known, including hypersaline, dry, hot, cold, nutrient poor, and high UV environments. The high microbial diversity of microbial mats makes studies of microbial ecology notably difficult. To address this challenge, we have been using a combination of metagenomics, metatranscriptomics, iTags and culture-based simplified microbial mats to study biogeochemical cycling (H2 production, N2 fixation, and fermentation) in microbial mats collected from Elkhorn Slough, Monterey Bay, California. Metatranscriptomes of microbial mats incubated over a diel cycle have revealed that a number of gene systems activate only during the day in Cyanobacteria, while the remaining appear to be constitutive. The dominant cyanobacterium in the mat (Microcoleus chthonoplastes) expresses several pathways for nitrogen scavenging undocumented in cultured strains, as well as the expression of two starch storage and utilization cycles. Community composition shifts in response to long term manipulations of mats were assessed using iTags. Changes in community diversity were observed as hydrogen fluxes increased in response to a lowering of sulfate concentrations. To produce simplified microbial mats, we have isolated members of 13 of the 15 top taxa from our iTag libraries into culture. Simplified microbial mats and simple co-cultures and consortia constructed from these isolates reproduce many of the natural patterns of biogeochemical cycling in the parent natural microbial mats, but against a background of far lower overall diversity, simplifying studies of changes in gene expression (over the short term), interactions between community members, and community composition changes (over the longer term), in response to environmental forcing.